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  • 1.
    Akram, Nadeem
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Imaging of ion transmission through glass capillariesManuscript (preprint) (Other academic)
    Abstract [en]

    We present a technique which is successfully used to directly observe the charge patches formed on a single glass capillary walls. This is done by imaging the emitted visible photons emitted from 4.5 keV Ar1+-ions -interaction with the inner capillary walls, using a high resolution digital camera. Simultaneously, the ions transmitted through the capillary are detected. The number of emitted photons decreases with the increase in the tilt angle of the capillary. The time evolution of emitted photons has revealed that the charge patches formed by charging-up the capillary walls change their location during ion transmission.

  • 2.
    Akram, Nadeem
    et al.
    Stockholm University, Faculty of Science, Department of Physics. COMSATS Institute of Information Technology, Pakistan.
    Zhang, Hongqiang
    Stockholm University, Faculty of Science, Department of Physics.
    Soroka, I. L.
    Stockholm University, Faculty of Science, Department of Physics.
    Trautmann, C.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Transmission of slow highly charged ions through rectangular nanocapillaries2014In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 488, 132043- p.Article in journal (Refereed)
    Abstract [en]

    Transmission of slow highly charged ions through rectangular nanocapillaries in phlogopite mica is studied. The transmission profiles have rhombic pattern at tilt angles within the geometrical opening angle of the capillaries. The time evolution of ion transmission reveals certain features contributing to the tailored transmission profiles.

  • 3.
    Akram, Nadeem
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Zhang, Hongqiang
    Stockholm University, Faculty of Science, Department of Physics.
    Soroka, Inna Leonidovna
    Stockholm University, Faculty of Science, Department of Physics.
    Trautmann, Christina
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Transmission of highly charged ions through phlogopite-mica nanocapillaries of rectangular cross-sectionIn: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455Article in journal (Refereed)
    Abstract [en]

    We measured the transmission of Ne7+ ions through nanocapillaries of rectangular cross-section produced by chemical etching of ion tracks in phlogopite mica. The two dimensional transmitted profiles are rhombic for tilt angles within the geometrical opening angle given by the aspect ratio of the short side of the rectangular cross section of the capillaries. The transmission depends on the incident charge indicating that the rhombic shape is due to the image charge of uncharged rectangular capillaries. Above a critical charge deposition, the rhombic shape tends to be smeared out. Ions are also transmitted at angles larger than the geometrical opening angle giving evidence for the guiding effect.

  • 4.
    Akram, Nadeem
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Zhang, Hongqiang
    Stockholm University, Faculty of Science, Department of Physics.
    Werner, Udo
    Beyer, André
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Transmission of slow highly charged ions through ultra-thin carbon nano-sheets2011In: Proceedings of 3rd Int. Conf. on “Current developments in Atomic, Molecular, Optical and Nano Physics”, 2011Conference paper (Refereed)
    Abstract [en]

    Transmission properties of slow highly charged ions through nanometer thick foils are discussed.  We also report on the measurement of the energy loss and the charge states of 46.2 keV Ne10+-ions and 11.7 keV Ne3+-ions transmitted through ultra-thin carbon nano-sheets. The sheets had a thickness of 1.2 nm (single molecular layer) and 3.6 nm (three molecular layers). The measured energy loss of the transmitted ions is considerably smaller than the calculated energy loss by SRIM but it is in agreement with energy loss calculated using the Firsov model. The majority of the transmitted ions retain their initial charge state (up to 98%) contrary to prediction by the classical over-the-barrier model. The results suggest that the energy loss of slow highly charged ions in such thin sheets is only due to the electronic excitations, without charge exchange inside the target.

  • 5.
    Ali, Safdar
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Mahmood, Sultan
    Stockholm University, Faculty of Science, Department of Physics.
    Orban, Istvan
    Stockholm University, Faculty of Science, Department of Physics.
    Tashenov, Stanislav
    Stockholm University, Faculty of Science, Department of Physics.
    Li, Y. M.
    Wu, Z.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Electron-ion recombination of H- and He-like sulfur2011In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 44, no 22, 225203- p.Article in journal (Refereed)
    Abstract [en]

    Electron-ion recombination of sulfur ions with electrons in the energy range of 1.6-3 keV was studied at the Stockholm Refrigerated Electron Beam Ion Trap. We obtained the KLn dielectronic recombination (DR) cross sections up to n = 5 for H-like and He-like sulfur ions by observing the x-rays from the trapped ions. A fully relativistic distorted wave approximation method was used for calculating the DR cross sections, while the resonance energies were obtained with a multiconfiguration Dirac-Fock approach using the GRASP II code. The calculations agree with the experimental results within the experimental error bars. Additionally, the obtained total DR resonance strengths were used to check the behaviour of a scaling formula for low-Z, He-like iso-electronic sequence (Watanabe et al 2001 J. Phys. B: At. Mol. Opt. Phys. 34 5095).

  • 6.
    Ali, Safdar
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Mahmood, Sultan
    Stockholm University, Faculty of Science, Department of Physics.
    Orban, Istvan
    Stockholm University, Faculty of Science, Department of Physics.
    Tashenov, Stanislav
    Stockholm University, Faculty of Science, Department of Physics.
    Li, Y. M.
    Wu, Z.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Photo-recombination studies at R-EBIT with a Labview control and data = quisition system2011In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 6, C01016- p.Article in journal (Refereed)
    Abstract [en]

    Equipment at the Stockholm Refrigerated Electron Beam Ion Trap (R-EBIT) was developed for photo-recombination studies. A LabView-based event mode data acquisition and R-EBIT control system was implemented. The energies of KLL dielectronic recombination resonances in Li- to C-like argon ions were determined and compared with theoretical calculations performed using a distorted wave approximation. The theoretical and experimental peak positions for Li-, Be-, and C-like argon ions agree within the error bars. For B-like argon we observe an energy shift of 9 eV between the experimentally obtained peak position and the calculated result.

  • 7.
    Ali, Safdar
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Orban, Istvan
    Stockholm University, Faculty of Science, Department of Physics.
    Mahmood, Sultan
    Stockholm University, Faculty of Science, Department of Physics.
    Altun, Zikri
    Glans, Peter
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Electron-ion recombination rate coefficients for C II forming C I2012In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 753, no 2, 132- p.Article in journal (Refereed)
    Abstract [en]

    We have determined absolute dielectronic recombination rate coefficients for C II, using the CRYRING heavy-ions storage ring. The resonances due to 2s-2p (∆n = 0) core excitations are detected in the center-of-mass energy range of 0-15 eV. The experimental results are compared with intermediate coupling AUTOSTRUCTURE calculations. Plasma rate coefficients are obtained from the DR spectrum by convoluting it with a Maxwell-Boltzmann energy distribution for temperatures in the range of 103-106 K. The derived temperature dependent plasma recombination rate coefficients are presented graphically to compare with the theoretical data available in literature and parameterized by using a fit formula for convenient use in plasma modelling codes. In the temperature range of 103-2×104 K, our experimental results show that previous calculations severely underestimate the plasma rate coefficients and also our AUTOSTRUCTURE calculation does not reproduce the experimental plasma rate coefficients well. Above 2×104 K the agreement between the experimental and theoretical rate coefficients is much better, and the deviations are smaller than the estimated uncertainties.

  • 8.
    Ali, Safdar
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Orban, Istvan
    Stockholm University, Faculty of Science, Department of Physics.
    Mahmood, Sultan
    Stockholm University, Faculty of Science, Department of Physics.
    Loch, S. D.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Experimental recombination rate coefficients of Be-like Frecombining into B-like FManuscript (preprint) (Other academic)
    Abstract [en]

    Recombination spectra of F VI forming F V have been investigated with high-energy resolution, using the CRYRING heavy-ion storage ring. The absolute recombination rate coefficients are derived in the center-of-mass energy range of 0-25 eV. The experimental results are compared with intermediate coupling AUTOSTRUCTURE calculations for 2s-2p (∆n=0) core excitation and show a very good agreement in the resonance energy positions and intensities. Trielectronic recombination with 2s2-2p2 transitions are clearly identified in the spectrum.  Metastable ion contributions are considered and found negligible. The energy dependent recombination spectra are convoluted with Maxwell-Boltzmann energy distribution in the 10-106 K temperature range. The resulting temperature dependent rate coefficients are compared with theoretical results from literature. In the 103-104 K range the calculated data significantly underestimates the plasma recombination rate coefficients. Above ~105 K, our AUTOSTRUCTURE results and plasma rate coefficients from Colgan et al. (2003) show an agreement better than 20% with the experimental results.

  • 9. Bergström, I
    et al.
    Björkhage, Mikael
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Blaum, K
    Bluhrne, H
    Fritioff, Tomas
    Stockholm University, Faculty of Science, Department of Physics.
    Nagy, Szilard
    Stockholm University, Faculty of Science, Department of Physics.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    High-precision Mass Measurements of Hydrogen-Like 24Mg11+ and 26Mg11+ ions in a Pening Trap2002In: European Physical Journal D: Atomic, Molecular and Optical Physics, ISSN 1434-6060, E-ISSN 1434-6079, Vol. 22, no 1, 41-45 p.Article in journal (Refereed)
    Abstract [en]

    For the determination of the bound-electron g factor in hydrogen-like heavy ions the mass of the ion is needed at a relative uncertainty of at least 1 ppb. With the SMILETRAP Penning trap mass spectrometer at the Manne Siegbahn Laboratory in Stockholm several mass measurements of ions with even-even nuclei at this level of precision have been performed so far, exploiting the fact that the mass precision increases linearly with the ion charge. Measurements of masses of the hydrogen-like ions of the two Mg-isotopes 24Mg and 26Mg are reported. The masses of the hydrogen-like ions are 23.979011054(14) u and 25.976562354(34) u, corresponding to the atomic masses 23.985041690(14) u and 25.982592986(34) u, respectively. The possibility to use these two isotopes for the first observation of an isotope effect in the bound-electron g factor in hydrogen-like heavy ions is discussed.

  • 10. Cariatore, N. D.
    et al.
    Otranto, S.
    Wolff, W.
    Luna, H.
    Turco, F.
    Fregenal, D.
    Bernardi, G.
    Suárez, S.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Water fragmentation induced by ion impact: Fragment-ion-energy determination at different Z(P)/v regimes2017In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 408, 198-202 p.Article in journal (Refereed)
    Abstract [en]

    This work focuses on the energy distributions of positive water ionic fragments produced by ion impact at MeV impact energies. An improved Coulomb explosion model coupled to a classical trajectory Monte Carlo simulation is used to provide energy centroids of the fragments for the dissociation channels resulting from the removal of two to five electrons from the water molecule. This model explicitly includes the post-collisional interaction of the projectile with the resulting ionic fragments affecting their kinetic energy release spectra especially at low impact energies. Theoretical data are benchmarked against recent data collected for 220 keV Xe22+ + H2O collisions which corresponds to a large Zp/v collision parameter. To extend our tests to the low Zp/v regime, fragment species as a function of emission energy and time-of-flight were recorded in 3 MeV Li3+ collisions by using an electrostatic spectrometer and a time-of-flight mass spectrometer, respectively. Present experimental data reveals the existence of multiple-ionization processes leading to charge state up to 4+.

  • 11.
    Fogle, M.
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Badnell, N.R.
    Glans, P.
    Loch, S.D.
    Madzunkov, S.
    Pindzola, M.S.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Electron-ion recombination of Be-like C, N, and O2005In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 442, no 2, 757-766 p.Article in journal (Refereed)
    Abstract [en]

    The absolute total recombination reaction rate coefficients for Be-like C, N, and O have been measured using the CRYRING storage ring and compared with the results from distorted-wave theory. For the theory results, it is found that shifts to NIST energy values for the core excited energies of the recombining system are not sufficient to accurately match all of the resonance positions and heights at lower energies. These theory results represent the quality of most archived theory DR data. The accurate calculation of these low energy resonances still presents a significant challenge to theory. In addition, trielectronic recombination resonances, associated with the formation of triply excited states during recombination, have been observed in the total recombination reaction rate coefficient spectra of and . Finally, we construct a dielectronic recombination Maxwellian rate coefficient from the experimental results for low n resonances, and from the theoretical results for high n resonances. In the case of , the trielectronic recombination resonances have a strong influence on the low temperature Maxwellian rate coefficient. Our best hybrid Maxwellian rate coefficient is compared with archived distorted-wave theory data, and is found to be in reasonable agreement, even at the low temperatures.

  • 12.
    Fritioff, Tomas
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Bergström, Ingmar
    Nagy, Sz
    Stockholm University, Faculty of Science, Department of Physics.
    Solders, Andreas
    Stockholm University, Faculty of Science, Department of Physics.
    Suhonen, Markus
    Stockholm University, Faculty of Science, Department of Physics.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Precise measurements of ionic masses for QED tests2006In: International Journal of Mass Spectrometry, ISSN 1387-3806, E-ISSN 1873-2798, Vol. 251, no 2-3, 281-285 p.Article in journal (Refereed)
    Abstract [en]

    The Penning trap mass spectrometer SMILETRAP is designed for precision mass measurements using the merits of highly charged ions. In this paper we describe the feature of SMILETRAP and give examples of mass measurements involving , , and ions. These emphasize the importance of accurate masses of hydrogen-like and lithium-like ions that are required in the evaluation of g-factor measurements of electrons bound to even–even nuclei and test of QED effects. Highly precise mass measurements can also be used for testing atomic structure calculations and determining atomic binding energies. Relevance of such measurements throughout the periodic system is discussed.

  • 13.
    Gudmundsson, Magnus
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Fischer, D.
    Stockholm University, Faculty of Science, Department of Physics.
    Haag, N.
    Stockholm University, Faculty of Science, Department of Physics.
    Johansson, H. A. B.
    Stockholm University, Faculty of Science, Department of Physics.
    Misra, Deepankar
    Stockholm University, Faculty of Science, Department of Physics.
    Reinhed, Peter
    Stockholm University, Faculty of Science, Department of Physics.
    Schmidt-Boecking, H.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Schoeffler, M.
    Stochkel, K.
    Schmidt, Henning T.
    Stockholm University, Faculty of Science, Department of Physics.
    Cederquist, Henrik
    Stockholm University, Faculty of Science, Department of Physics.
    Angular scattering in fast ion-atom electron transfer collisions: projectile wave diffraction and Thomas mechanisms2010In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 43, no 18, 185209- p.Article in journal (Refereed)
    Abstract [en]

    We report experimental angular differential cross sections for double-electron capture in He2+ + He collisions and single-electron capture in H+ + He collisions for the 1.3-12.5 MeV kinetic energy range. In all cases, the total cross sections are dominated by forward scattering peaks in d sigma/d Omega. The shapes and widths (but not the magnitudes) of these peaks are very similar for all energies and for capture of one or two electrons corresponding also to our measured linear increases in the transverse momentum transfers with increasing projectile velocities. These observations may be ascribed to diffraction limitations which are connected to electron transfer probabilities P(b) which are significant in limited regions of b only. For the H+ + He single-electron capture we observe two additional maxima in the angular differential cross sections. We conclude that while the secondary maxima at similar to 0.5 mrad probably have large contributions from the Thomas proton-electron-nucleus scattering mechanism, the third maxima at similar to 0.75 mrad are most likely mainly due to projectile de Broglie wave diffraction.

  • 14.
    Hobein, Matthias
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Liu, Yanfang
    Stockholm University, Faculty of Science, Department of Physics.
    Solders, Andreas
    Stockholm University, Faculty of Science, Department of Physics.
    Suhonen, Markus
    Stockholm University, Faculty of Science, Department of Physics.
    Kamalou, Omar
    Stockholm University, Faculty of Science, Department of Physics.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    A compact time-resolving pepperpot emittance meter for low-energy highly charged ions2011In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T144, 014062- p.Article in journal (Refereed)
    Abstract [en]

    An emittance meter for pulsed, low-energy ion beams was developed. Based on the pepperpot method, the device is compact and portable. It has been installed at the S-EBIT Laboratory at AlbaNova, Stockholm University, to measure the emittance of highly charged ions extracted from the electron beam ion trap R-EBIT and the cooling trap of the high-precision Penning trap mass spectrometer SMILETRAP II. Using a fast delay-line anode detector, the emittance and time-of-flight of the extracted ions can be measured simultaneously. In this paper, design and data processing system are described and preliminary results are presented.

  • 15.
    Hobein, Matthias
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Liu, Yuwen
    Stockholm University, Faculty of Science, Department of Physics.
    Solders, Andreas
    Stockholm University, Faculty of Science, Department of Physics.
    Suhonen, Markus
    Stockholm University, Faculty of Science, Department of Physics.
    Kamalou, Omar
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    A compact time-resolving pepperpot emittance meter for low energy highly-charged ionsIn: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896Article in journal (Refereed)
  • 16.
    Hobein, Matthias
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Orban, Istvan
    Stockholm University, Faculty of Science, Department of Physics.
    Böhm, Stefanie
    Stockholm University, Faculty of Science, Department of Physics.
    Solders, Andreas
    Stockholm University, Faculty of Science, Department of Physics.
    Suhonen, Markus
    Stockholm University, Faculty of Science, Department of Physics.
    Fritioff, T.
    Stockholm University, Faculty of Science, Department of Physics.
    Tashenov, Stanislav
    Stockholm University, Faculty of Science, Department of Physics.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Optimization of the Stockholm R-EBIT for the production and extraction of highly charged ions2010In: Journal of Instrumentation, ISSN 1748-0221, Vol. 5, no C11003Article in journal (Refereed)
    Abstract [en]

    We describe a refrigerated EBIT (R-EBIT) commissioned at the AlbaNova Research Center at Stockholm University. As an innovative solution, the superconducting magnet and the trapping drift tubes of the R-EBIT are cooled to a temperature of 4 K by a set of two cooling heads connected to helium compressors. This dry, i.e. liquid helium and liquid nitrogen free, system is easily operated and creates highly charged ions at a fraction of the cost of traditional liquid-cooled systems. A pulsed and continuous gas injection system was developed to feed neutral particles into the electron beam in the trap region. This improves significantly the highly charged ion production and R-EBIT performance. Fast extraction of ions from the R-EBIT yields very short ( < 100 ns), charge-separated ion bunches which can be either analysed using a straight time-of-flight section or sent to experimental beam lines following selection in a bending magnet. An emittance meter was used to measure the emittance of the ions extracted from the R-EBIT. The extracted ions were also re-trapped in a cylindrical Penning trap and properties of the re-trapped ions have been measured using the emittance meter. Results of these measurements are reported in this publication.

  • 17.
    Hobein, Matthias
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Solders, Andreas
    Stockholm University, Faculty of Science, Department of Physics.
    Liu, Yuwen
    Stockholm University, Faculty of Science, Department of Physics.
    Ketelaer, J.
    Suhonen Linné, Markus
    Stockholm University, Faculty of Science, Department of Physics.
    Marx, G.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    SMILETRAP II2011In: Hyperfine Interactions, ISSN 0304-3843, E-ISSN 1572-9540, Vol. 199, no 1-3, 141-150 p.Article in journal (Refereed)
    Abstract [en]

    The new Penning trap mass spectrometer SMILETRAP II has been set up at the AlbaNova Research Center, Stockholm. Based on the former spectrometer SMILETRAP I, it uses the merits of highly-charged ions to achieve high precision in the mass measurements. Various improvements over the SMILETRAP I setup will allow to routinely perform mass measurements with relative uncertainties of 10−10 and below. In this paper we will discuss the limitations of SMILETRAP I and present the corresponding improvements of SMILETRAP II. An overview on the SMILETRAP II setup is given.

  • 18.
    Hobein, Matthias
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Solders, Andreas
    Stockholm University, Faculty of Science, Department of Physics.
    Suhonen, Markus
    Stockholm University, Faculty of Science, Department of Physics.
    Liu, Yuwen
    Kamalou, Omar
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Re-trapping and cooling of highly-charged2009In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 163, 012109- p.Article in journal (Refereed)
    Abstract [en]

    Presently, a trapping system for cooling highly-charged ions (HCI) is being set up at AlbaNova at Stockholm University. The experiment aims at production of low temperature (emittance) HCI at very low energy. HCI are extracted from the new Stockholm EBIT (S-EBIT) before evaporative cooling is applied in a Penning trap. In the future the cooled ions will be injected into the precision trap of the high-precision mass spectrometer SMILETRAP II. In first tests the emittance of trapped ions was measured and it was shown that highly and low-charged ions could be simultaneously stored

  • 19.
    Hobein, Matthias
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Solders, Andreas
    Stockholm University, Faculty of Science, Department of Physics.
    Suhonen, Markus
    Stockholm University, Faculty of Science, Department of Physics.
    Liu, Yuwen
    Stockholm University, Faculty of Science, Department of Physics.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Evaporative Cooling and Coherent Axial Oscillations of Highly Charged Ions in a Penning Trap2011In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 106, no 1, 013002- p.Article in journal (Refereed)
    Abstract [en]

    Externally, in an electron beam ion trap, generated Ar16+ ions were retrapped in a Penning trap and evaporatively cooled in their axial motion. The cooling was observed by a novel extraction technique based on the excitation of a coherent axial oscillation which yields short ion bunches of well-defined energies. The initial temperature of the ion cloud was decreased by a factor of more than 140 within 1 s, while the phase-space density of the coldest extracted ion pulses was increased by a factor of up to about 9.

  • 20. Hoshino, Masamitsu
    et al.
    Kambara, Tadashi
    Kanai, Yasuyuki
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Yamazaki, Yasunori
    Multielectron processes in close collisions of slow Neq+ (q=1-9) ions with Ar atoms2007In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 75, no 3, 32722- p.Article in journal (Refereed)
    Abstract [en]

    We have studied the multielectron processes in close collisions between slow Neq+ ions (q=1-9, energies of 5 and 14 keV) and Ar atoms through measurements of the charge-state correlations between 27 degrees scattered and 70 degrees recoiling ions. At the selected scattering angle, the internuclear distance of the closest approach at 35 keV is comparable to the L-shell radius of Ar atoms. A drastic difference between low-charged (q=1-3) and highly charged (q=7-9) Ne ions was found. For example, the most probable channel for the Ne7+ projectile is three-electron capture accompanied with two-electron loss whereas for the Ne+ projectile pure double ionization was found most probable. As a general trend, the mean charges of the both ions and the mean number of captured electrons increase almost linearly with incident charge q, while the mean number of ejected electrons from the system is independent of q at both 5 and 14 keV. We also measured the charge state distributions of the Ar recoil ions as function of the Neq+ (q=3, 5, and 7) energies between 5 and 63 keV, which corresponds to distances of closest approach between 0.6 a.u. and 0.17 a.u. We found that the charge of the Ar ions increases at internuclear distances less than 0.32 a.u.

  • 21. Lestinsky, M.
    et al.
    Andrianov, V.
    Aurand, B.
    Bagnoud, V.
    Bernhardt, D.
    Beyer, H.
    Bishop, S.
    Blaum, K.
    Bleile, A.
    Borovik, At.
    Bosch, F.
    Bostock, C. J.
    Brandau, C.
    Braeuning-Demian, A.
    Bray, I.
    Davinson, T.
    Ebinger, B.
    Echler, A.
    Egelhof, P.
    Ehresmann, A.
    Engström, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    Enss, C.
    Ferreira, N.
    Fischer, D.
    Fleischmann, A.
    Foerster, E.
    Fritzsche, S.
    Geithner, R.
    Geyer, S.
    Glorius, J.
    Goebel, K.
    Gorda, O.
    Goullon, J.
    Grabitz, P.
    Grisenti, R.
    Gumberidze, A.
    Hagmann, S.
    Heil, M.
    Heinz, A.
    Herfurth, F.
    Hess, R.
    Hillenbrand, P. -M.
    Hubele, R.
    Indelicato, P.
    Källberg, Anders
    Stockholm University, Faculty of Science, Department of Physics.
    Kester, O.
    Kiselev, O.
    Knie, A.
    Kozhuharov, C.
    Kraft-Bermuth, S.
    Kuehl, T.
    Lane, G.
    Litvinov, Yu. A.
    Liesen, D.
    Ma, X. W.
    Maertin, R.
    Moshammer, R.
    Mueller, A.
    Namba, S.
    Neumeyer, P.
    Nilsson, T.
    Noertershaeuser, W.
    Paulus, G.
    Petridis, N.
    Reed, M.
    Reifarth, R.
    Reiss, P.
    Rothhardt, J.
    Sanchez, R.
    Sanjari, M. S.
    Schippers, S.
    Schmidt, Henning T.
    Stockholm University, Faculty of Science, Department of Physics.
    Schneider, D.
    Scholz, P.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Schulz, M.
    Shabaev, V.
    Simonsson, Ansgar
    Stockholm University, Faculty of Science, Department of Physics.
    Sjöholm, Johannes
    Skeppstedt, Örjan
    Stockholm Univ, Fysikum, S-10691 Stockholm, Sweden.
    Sonnabend, K.
    Spillmann, U.
    Stiebing, K.
    Steck, M.
    Stohlker, T.
    Surzhykov, A.
    Torilov, S.
    Trabert, E.
    Trassinelli, M.
    Trotsenko, S.
    Tu, X. L.
    Uschmann, I.
    Walker, P. M.
    Weber, G.
    Winters, D. F. A.
    Woods, P. J.
    Zhao, H. Y.
    Zhang, Y. H.
    Physics book: CRYRING@ESR2016In: The European Physical Journal Special Topics, ISSN 1951-6355, E-ISSN 1951-6401, Vol. 225, no 5, 797-882 p.Article, review/survey (Refereed)
    Abstract [en]

    The exploration of the unique properties of stored and cooled beams of highly-charged ions as provided by heavy-ion storage rings has opened novel and fascinating research opportunities in the realm of atomic and nuclear physics research. Since the late 1980s, pioneering work has been performed at the CRYRING at Stockholm (Abrahamsson et al. 1993) and at the Test Storage Ring (TSR) at Heidelberg (Baumann et al. 1988). For the heaviest ions in the highest charge-states, a real quantum jump was achieved in the early 1990s by the commissioning of the Experimental Storage Ring (ESR) at GSI Helmholtzzentrum für Schwerionenforschung (GSI) in Darmstadt (Franzke 1987) where challenging experiments on the electron dynamics in the strong field regime as well as nuclear physics studies on exotic nuclei and at the borderline to atomic physics were performed. Meanwhile also at Lanzhou a heavy-ion storage ring has been taken in operation, exploiting the unique research opportunities in particular for medium-heavy ions and exotic nuclei (Xia et al. 2002).

  • 22.
    Liu, Yuwen
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Hobein, Matthias
    Stockholm University, Faculty of Science, Department of Physics.
    Solders, Andreas
    Stockholm University, Faculty of Science, Department of Physics.
    Suhonen, Markus
    Stockholm University, Faculty of Science, Department of Physics.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Improved temperature regulation of Penning trap mass spectrometers2010In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 294, no 1, 28-32 p.Article in journal (Refereed)
    Abstract [en]

    In order to reach relative uncertainties in mass measurements with Penning traps of 10-10 or better, the temperature variation of the trap and surrounding materials must be kept below 10 mK. Temperature variations induce a shift in the measured ion cyclotron frequency because of non-zero, temperature dependent magnetic susceptibilities of the construction materials. In this paper we report of a new temperature regulation system recently installed at SMILETRAP II that manages to keep the temperature fixed at the set point with a standard deviation of only 2.6 mK. −10 or better, the temperature variation of the trap and surrounding.

  • 23.
    Mahmood, Sultan
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Ali, Safdar
    Stockholm University, Faculty of Science, Department of Physics.
    Orban, Istvan
    Stockholm University, Faculty of Science, Department of Physics.
    Tashenov, Stanislav
    Stockholm University, Faculty of Science, Department of Physics.
    Lindroth, Eva
    Stockholm University, Faculty of Science, Department of Physics.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Recombination and electron impact excitation rate coefficients for S XV AND S XVI2012In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 754, no 2, 86- p.Article in journal (Refereed)
    Abstract [en]

    Recombination and electron impact excitation of S14+ and S15+ ions was measured at the Stockholm refrigerated electron beam ion trap. The collision energy range was 1.4-3 keV, where we covered the KLL, KLM, KLN, and KLO dielectronic recombination resonances resulting in S13+ and S14+ ions. The recombination rates were obtained by detecting the charge state distribution with a newly developed time-of-flight technique. Resonance energies and cross sections calculated within the relativistic many-body perturbation theory for S15+ agree well with the experimental data. The temperature dependent rate coefficients have been extracted from the measured rates and compared with calculations from literature used for studies of collisionally ionized astrophysical plasmas. A good agreement for S15+ was obtained, while the plasma rates for S14+ were 23% lower than the so far published values. In addition to the time-of-flight spectra, the x-ray spectra, produced mainly by photo-recombination and excitation, have been also collected. The combination of these two measurements allowed us to separate the photo-recombination and the excitation spectra, and the excitation rate coefficients for summed intensities with known fractions of S14+ and S15+ ions were extracted.

  • 24.
    Mahmood, Sultan
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Orban, Istvan
    Stockholm University, Faculty of Science, Department of Physics.
    Ali, Safdar
    Stockholm University, Faculty of Science, Department of Physics.
    Glans, P.
    Bleda, E. A.
    Altun, Z.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    RECOMBINATION RATE COEFFICIENTS OF BORON-LIKE Ne2013In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 771, no 2, 78- p.Article in journal (Refereed)
    Abstract [en]

    Recombination of Ne5+ was measured in a merged-beam type experiment at the heavy-ion storage ring CRYRING. In the collision energy range 0-110 eV resonances due to 2s(2)2p -> 2s2p(2) (Delta n=0) and 2s(2)2p -> 2s(2)3l (Delta n=1), core excitations were observed. The experimentally derived rate coefficients agree well with the calculations obtained using AUTOSTRUCTURE. At low energies, recombination is dominated by resonances belonging to the spin-forbidden 2s2p(2)(P-4(J))nl series. The energy-dependent rate coefficients were convoluted with a Maxwell-Boltzmann electron energy distribution to obtain plasma recombination rate coefficients. The data from the literature deviate from the measured results at low temperature.

  • 25.
    Misra, Deepankar
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Schmidt, Henning Thordal
    Stockholm University, Faculty of Science, Department of Physics.
    Gudmundsson, Magnus
    Stockholm University, Faculty of Science, Department of Physics.
    Fischer, Daniel
    Max-Planck Institut, Heidelberg.
    Haag, Nicole
    Stockholm University, Faculty of Science, Department of Physics.
    Johansson, Henrik A B
    Stockholm University, Faculty of Science, Department of Physics.
    Källberg, Anders
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Najjari, B
    Max-Planck Institut, Heidelberg.
    Reinhed, Peter
    Stockholm University, Faculty of Science, Department of Physics.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Schöffler, Marcus
    Frankfurt University.
    Simonsson, Ansgar
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Voitkiv, A B
    Max-Planck Institut, Heidelberg.
    Cederquist, Henrik
    Stockholm University, Faculty of Science, Department of Physics.
    Two-Center Double-Capture Interference in Fast He2++H2 Collisions2009In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 102, no 15, 153201- p.Article in journal (Refereed)
    Abstract [en]

    We report the first observation of Young-type interference effects in a two-electron transfer process. These effects change strongly as the projectile velocity changes in fast (1.2 and 2.0 MeV) He^{2+}-H_2 collisions as manifested in strong variations of the double-electron capture rates with the H_2 orientation. This is consistent with fully quantum mechanical calculations, which ignore sequential electron transfer, and a simple projectile de Broglie wave picture assuming that two-electron transfer probabilities are higher in collisions where the projectile passes close to either one of the H_2 nuclei.

  • 26.
    Mohamed, T.
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Andler, Guillermo
    Stockholm University, Faculty of Science, Department of Physics, The Manne Siegbahn Laboratory.
    Fogle, M.
    Stockholm University, Faculty of Science, Department of Physics.
    Justiniano, E.
    Madzunkov, S.
    Stockholm University, Faculty of Science, Department of Physics.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Effects of polarization on laser-induced electron-ion recombination2011In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 83, no 3, 032702- p.Article in journal (Refereed)
    Abstract [en]

    The polarization dependence of laser-induced radiative recombination (LIR) to D(+) ions was investigated in the electron cooler of the CRYRING storage ring. The LIR gain as a function of wavelength into n = 3 principal quantum states of deuterium was measured at laser beam polarization angles of 0 degrees and 90 degrees with respect to the direction of the motional electric field in the interaction region. For the case of the polarization vector parallel to the external field, there is a double-peak structure in the gain curve that indicates a polarization effect in the LIR process. The two polarization directions also reveal a different width for the respective gain curves, giving additional evidence for the polarization effect, clearly seen by the behavior of a defined polarization parameter. The obtained polarization effect indicates a high sensitivity in recombination processes to external fields.

  • 27.
    Mohamed, Tarek
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Beni Suef University, Egypt.
    Andler, Guillermo
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    A linear optical trap with active medium for experiments with high power laser pulses2015In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 86, no 2, 23113Article in journal (Refereed)
    Abstract [en]

    A linear optical trap for circulating high power laser pulses and tuning these pulses to high repetition frequency of several tens of MHz has been developed. A ns excimer pumped dye laser pulse has been injected with help of a Wollaston prism and a synchronized Pockels cell into an optical trap formed by two highly reflecting mirrors in a linear configuration. The test was done at lambda = 580 nm, but the optical trap can be used without limitations in a broad band of optical wavelengths (400-700 nm). Power considerations give an increase of the efficiency of the optical trap of about 7 times compared to single passage of the laser pulse through the experimental section. The time structure of the trapped laser pulses can be controlled by changing the distance between the two high reflecting mirrors. The efficiency of the optical trap strongly depends upon optical losses. To compensate the optical losses, an amplifying cell was introduced, and the efficiency was about 60 times higher than that by single passage of the laser pulse through the experimental section. (C) 2015 AIP Publishing LLC.

  • 28.
    Mohamed, Tarek
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Beni Suef University, Egypt.
    Andler, Guillermo
    Stockholm University, Faculty of Science, Department of Physics.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    A seeded dye laser cavity for intracavity experiments2015In: Laser physics, ISSN 1054-660X, E-ISSN 1555-6611, Vol. 25, no 9, 095801Article in journal (Refereed)
    Abstract [en]

    A seeded dye laser cavity, synchronously pumped by the 2nd harmonic of the Nd:YAG laser has been designed and experimentally tested. The used seed signal was the well defined narrow linewidth output laser signal (Delta lambda = 0.013 nm) from the excimer-dye laser system. Energy considerations showed that the intracavity laser energy, that can be used for an experimental section inside the cavity, can reach an efficiency of 20% of the pumping energy. The wavelength and linewidth are fully controlled by the wavelength and linewidth of the seeding laser.

  • 29.
    Nagy, Sz
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Fritioff, T
    Stockholm University, Faculty of Science, Department of Physics.
    Bergström, I
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Blaum, K
    Stockholm University, Faculty of Science, Department of Physics.
    Suhonen, M
    Stockholm University, Faculty of Science, Department of Physics.
    Schuch, R
    Stockholm University, Faculty of Science, Department of Physics.
    High-precision mass measurements for fundamental applications using highly-charged ions with SMILETRAP2007In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 58, 109-112 p.Article in journal (Refereed)
    Abstract [en]

    The Penning trap mass spectrometer SMILETRAP takes advantage of highly-charged ions for high-accuracy mass measurements. In this paper recent mass measurements on Li and Ca ions are presented and their impact on fundamental applications discussed, especially the need for accurate mass values of hydrogen-like and lithium-like ions in the evaluation of the electron g-factor measurements in highly-charged ions is emphasized. Such experiments aim to test bound state quantum electrodynamics. Here the ionic mass is a key ingredient, which can be the limiting factor for the final precision.

  • 30.
    Nagy, Sz.
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Fritioff, T.
    Suhonen, M.
    Stockholm University, Faculty of Science, Department of Physics.
    Schuch, R.
    Stockholm University, Faculty of Science, Department of Physics.
    Blaum, K.
    Björkhage, M.
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Bergström, I.
    New Mass Value for 7Li2006In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 96, no 16, 163004- p.Article in journal (Refereed)
  • 31.
    Orban, Istvan
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Altun, Zikri
    Department of Physics, Marmara University, 81040 Istanbul, Turkey.
    Källberg, Anders
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Simonsson, Ansgar
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Andler, Guillermo
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Paál, Andreas
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Blom, Mikael
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Löfgren, Patrik
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Trotsenko, Sergiy
    GSI Gesellschaft für Schwerionenforschung, 64291 Darmstadt, Germany.
    Böhm, Sebastian
    Stockholm University, Faculty of Science, Department of Physics.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Experimental dielectronic recombination rate coefficientsfor Na-like S VI and Na-like Ar VIII2009In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 498, 909-914 p.Article in journal (Refereed)
    Abstract [en]

    Aims. Absolute recombination rate coefficients for two astrophysically relevant Na-like ions are presented.Methods. Recombination rate coefficients of S vi and Ar viii are determined from merged-beam type experiments at the CRYRINGelectron cooler. Calculated rate coefficients are used to account for recombination into states that are field-ionized and therefore notdetected in the experiment.Results. Dielectronic recombination rate coefficients were obtained over an energy range covering Δ n = 0 core excitations. ForNa-like Ar a measurement was also performed over the Δn = 1 type of resonances. In the low-energy part of the Ar viii spectrum,enhancements of more than one order of magnitude are observed as compared to the calculated radiative recombination. The plasmarecombination rate coefficients of the two Na-like ions are compared with calculated results from the literature. In the 103−104 Krange, large discrepancies are observed between calculated plasma rate coefficients and our data. At higher temperatures, above105 K, in the case of both ions our data is 30% higher than two calculated plasma rate coefficients, other data from the literaturehaving even lower values.Conclusions. Discrepancies below 104 K show that at such temperatures even state-of-the-art calculations yield plasma rate coefficientsthat have large uncertainties. The main reason for these uncertainties are the contributions from low-energy resonances, whichare difficult to calculate accurately.

  • 32.
    Orban, Istvan
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Böhm, Sebastian
    Stockholm University, Faculty of Science, Department of Physics.
    Loch, Stuart D.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Recombination rate coefficients of Be-like neon2008In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 489, no 2, 829-835 p.Article in journal (Refereed)
    Abstract [en]

    Aims. Merged-beam and plasma recombination rate coefficients for Be-likeNe vii were extracted from results of a merged-beam typeexperiment.Methods. The cryring heavy-ion storage ring was used to determine merged-beam recombination rate coefficients for Be-likeNe6+.Recombined Ne5+ ions were separated from the stored beam in the first dipole magnet following the electron-ion interaction region.Field-ionization at this dipole magnet prevented detection of recombination into states with the principal quantum number n > ncutoff =23. To account for the field-ionization effects, results obtained with autostructure calculations were used for recombinationchannels above ncutoff. The merged-beam recombination rate coefficients were then convoluted with Maxwellian electron energydistributions in the 103−3 × 106 K temperature region, to obtain plasma recombination rate coefficients.Results. Good agreement was found between the experimentally derived rate coefficient spectrum and results of the autostructurecalculation. At low energies, several strong dielectronic recombination resonances belonging to the spin-forbidden 2s2p(3PJ)nl seriesdominate the merged-beam spectrum. Recombination through these states dominates at low-temperatures, e.g. at 103 K recombinationthrough these resonances is more than one order of magnitude higher than the radiative recombination rate coefficient. Most data fromthe literature significantly underestimate the low-temperature plasma rate coefficients below 104 K, with only two calculations showingrate coefficients comparable to our results.Strong contributions from trielectronic recombination were found in the merged-beam spectrum of Be-like Ne, associated with doubleexcitation of the Be-likeNe core, during the attachment of the free electron. Calculated trielectronic recombination resonance positionsagree with experimental peaks, however compared to the experiment, the calculation underestimates the strength of trielectronicrecombination.

  • 33.
    Orban, Istvan
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Böhm, Sebastian
    Stockholm University, Faculty of Science, Department of Physics.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    DIELECTRONIC RECOMBINATION OF Na-LIKE S AND Na-LIKE Ar IN THE PRESENCE OF EXTERNAL FIELDS2009In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 694, no 1, 354-358 p.Article in journal (Refereed)
    Abstract [en]

    Recombination rate coefficients for two astrophysically relevant Na-like ions, S5+ and Ar7+, were derived frommeasurements at the electron cooler device of the CRYRING heavy-ion storage ring. Additionally, the enhancementof dielectronic recombination (DR) by external fields was studied for these ions. Motional electric fields wereinduced over the electron–ion interaction region by tilting the magnetic field that guides the electrons on thetrajectory of the circulating ions. Field ionization at the dipole magnet prevented the detection of ions recombinedinto high Rydberg states. By comparing integrated areas of the recombination spectra over the field-affected range,enhancement factors of up to 1.9 and 2 were observed in the case of S5+ and Ar7+, for the maximum appliedfields of ∼184 V cm−1 and ∼172 V cm−1, respectively. Saturation was not reached and at higher fields even higherenhancements are to be expected. Plasma DR rate coefficients were obtained from the experimental spectra recordedat different field strengths. For the highest applied fields, increasing enhancement of the plasma DR rates was foundwith higher temperatures, reaching up to ∼42% and ∼73% at 106 K, in the case of S5+ and Ar7+, respectively.

  • 34.
    Orban, Istvan
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Glans, P.
    Altun, Z.
    Lindroth, Eva
    Stockholm University, Faculty of Science, Department of Physics.
    Källberg, Anders
    Stockholm University, Faculty of Science, Department of Physics, The Manne Siegbahn Laboratory.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Determination of the recombination rate coefficients for Na-like Si IV forming Mg-like Si III2006In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 459, no 1, 291-296 p.Article in journal (Refereed)
    Abstract [en]

    Aims. Absolute, total recombination rate coefficients for Si iv were determined using the CRYRING heavy-ion storage ring.Calculated rate coefficients were used to estimate recombination into states that could not be detected in the experiment becauseof field ionization. Total, as well as separate, radiative and dielectronic plasma recombination rate coefficients were determined.Methods. Stored ions were merged with an expanded electron beam in the electron cooler section of the storage ring. Recombined ionswere separated from the stored ion beam in the first dipole magnet after the electron cooler and were detected with unity efficiency.The absolute radiative and dielectronic recombination rate coefficients were obtained over a center-of-mass energy range of 0−20 eV,covering Δn = 0 core excitations up to the 3s → 3d series limit. The results of an intermediate coupling autostructure calculationwere compared with the experiment. The theoretical results were also used to estimate the contribution to dielectronic recombinationby high Rydberg states, which were not detected because of field ionization. The spectra were convoluted with Maxwell-Boltzmannenergy distributions in the 103−106 K temperature range.Results. The resulting plasma recombination rate coefficients are presented and compared with theoretical results frequently usedfor plasma modeling. In the 103−104 K range, a significant underestimation of the calculated dielectronic recombination plasma ratecoefficients was observed. Above 3 × 104 K, the agreement between our dielectronic recombination plasma rate coefficients and twoof the previously published rate coefficients is better than 20%.Conclusions. The observed differences between the experimental and calculated recombination rate coefficients at low temperaturesreflect the need for benchmarking experiments. Our experimentally-derived rate coefficients can guide the development of bettertheoretical models and lead to more accurately-calculated rate coefficients.

  • 35.
    Orban, Istvan
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Lindroth, Eva
    Stockholm University, Faculty of Science, Department of Physics.
    Glans, Peter
    Department of Engineering, Physics and Mathematics, Mid Sweden University.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Spectroscopic study of doubly excited states in Mg-likeSi using dielectronic recombination2007In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 40, no 5, 1063-1080 p.Article in journal (Refereed)
    Abstract [en]

    We present calculated and experimentally derived electron–ion recombinationrate coefficients for Na-like Si IV, recombining into Mg-like Si III, andprovide accurate spectroscopic data for doubly excited states located above theionization threshold of Si III. The experimental recombination rate coefficientswere measured in a merged-beam-type experiment at the heavy-ion storagering CRYRING at the Manne Siegbahn Laboratory in Stockholm. Changing theelectron–ion relative energy from 0 to 20 eV we covered the energy region fromthe first to the third ionization threshold. We find that even for the low-chargedSi2+ ion, a relativistic many-body perturbation theory calculation is necessary,to describe the recombination rate coefficients in the low-energy region, up to1.5 eV, satisfactorily. Doubly excited states, forbidden to form in LS coupling,are responsible for the most prominent dielectronic recombination resonances atlow energies and contribute with 40% to the strength. Several wide resonancesgive rise to a plateau-like formation in the recombination spectrum. A broaderenergy range, up to 6.7 eV, was covered with a non-relativistic many-bodycalculation. This range contains, in addition to 3pn resonances, severalresonances of the type 3dn, with the LS-forbidden 3d2 3F states giving riseto a strong, isolated peak at 2.976 eV. The NIST database lists eleven doublyexcited states of Si III with energy positions deviating considerably from ourdetermination. Since the listed lines are also not fully matching those with thelargest fluorescence yields it must be concluded that they are misidentified.

  • 36.
    Orban, Istvan
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Loch, S. D.
    Glans, P.
    Böhm, S.
    Stockholm University, Faculty of Science, Department of Physics.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Effects of spin-forbidden resonances on the recombination of Be-like Si and Be-like Ne2011In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T144, 014035- p.Article in journal (Refereed)
    Abstract [en]

    Recombination through doubly excited states that can be formed only through spin-flip of the excited electrons can give very strong contributions to the recombination rate of Be-like ions. We demonstrate this, in this paper, with the electron-ion recombination spectra of Be-like Ne(6+) and Be-like Si(10+), recently measured at the CRYRING storage ring. These resonances have significant effects on the plasma rate coefficients. We show that neglect or imprecise calculation of these resonances is responsible for large spreads observed between various theoretical results from the literature.

  • 37.
    Orban, Istvan
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Loch, Stuart D
    Department of Physics, Auburn University, Auburn, 36849 Alabama, USA.
    Böhm, Sebastian
    Stockholm University, Faculty of Science, Department of Physics.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Recombination rate coefficients of Be-like Si2010In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 721, no 2, 1603-1607 p.Article in journal (Refereed)
    Abstract [en]

    Recombination rate coefficients for Be-like Si10+ recombining into B-like Si9+ are derived froma measurement at an electron cooler device. The recombination spectrum shows strong contributionsfrom trielectronic recombination. Below 100 meV several very strong resonances associatedwith a spin-flip of the excited electron dominate the spectrum and also dominate thelow-temperature plasma recombination rate coefficents. Calculated rate coefficients are used toestimate the metastable fraction of the ion beam in the experiment and are also used to estimatethe amount of recombined ions that were not detected in the experiment, because of fieldionization. The resonant plasma rate coefficients corrected for the experimental field ionizationare in good agreement with calculated results by Gu (2003) and with AUTOSTRUCTURE calculations.All other calculations significantly underestimate the plasma rate coefficients at lowtemperatures.

  • 38.
    Orban, Istvan
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Tashenov, Stanislav
    Stockholm University, Faculty of Science, Department of Physics.
    Ferro, Fabrizio
    Stockholm University, Faculty of Science, Department of Physics.
    Lindroth, Eva
    Stockholm University, Faculty of Science, Department of Physics.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Charge-state Selected Detection of Photons from Electron-Ion Interactions in an EBIT2009In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114Article in journal (Refereed)
    Abstract [en]

    A new approach provides charge-state selective recombination rate coefficients from TOF spectraof highly charged ions extracted from an EBIT. Experimentally derived dielectronic recombinationspectra are compared with results of relativistic many body perturbation theory calculations. Electronimpact excitation rate coefficients are also obtained from the experiment through the separationof the DR contribution in the X-ray spectra. The combination of TOF and X-ray measurementsoffers a powerful tool for the simultaneous extraction of atomic quantities for several charge states.

  • 39. Qian, Li-Bing
    et al.
    Li, Peng-Fei
    Jin, Bo
    Jin, Ding-Kun
    Song, Guang-Yin
    Zhang, Qi
    Wei, Long
    Niu, Ben
    Wan, Cheng-Liang
    Zhou, Chun-Lin
    Mueller, Arnold Milenko
    Dobeli, Max
    Song, Zhang-Yong
    Yang, Zhi-Hu
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Zhang, Hong-Qiang
    Chen, Xi-Meng
    Transmission of electrons through the conical glass capillary with the grounded conducting outer surface2017In: Wuli xuebao, ISSN 1000-3290, Vol. 66, no 12, 124101Article in journal (Refereed)
    Abstract [zh]

    The transmission of 1.5 keV-electrons through a conical glass capillary is reported. This study aims to understand the so-called guiding effect for the negatively charged particles (e.g. electrons). The guiding mechanism is understood quite well with positively charged particles in particular highly charged ions, but not clear with electrons, i. e., even the basic scheme mediated by the existence of negative charge patches to guide the electrons is still somewhat controversial.. The study of the charging-up dynamics causing the electrons transport inside the capillary will shed light on this issue. In order to perform this, a data acquisition system has been setup to follow the time evolution of the two-dimensional angular distribution of the transmitted electrons. The electrons are detected by the multi-channel plate (MCP) detector with a phosphor screen. The image from the phosphor screen is recorded by a charge-coupled device camera. The timing signals for the detected events are extracted from the back stack of the MCP detector and recorded by the data acquisition system, synchronized with the acquired images. The electron beam has a size of 0.5 mm x 0.5 mm and a divergence of less than 0.35.. The inner diameter of the straight part of the capillary is 1.2 mm and the exit diameter is 225 mu m. A small conducting aperture of 0.3 mm in diameter is placed at the entrance of the capillary. Two-dimensional angular distribution of the transmitted electrons through conical glass capillary and its time evolution are measured. The results show that the transmission rate decreases and reaches to a constant value for the completely discharged glass capillary with time going by. The centroid of the angular distribution moves to an asymptotic value while the width remains unchanged. These transmission characteristics are different from those indicated in our previous work (2016 Acta Phys: Si n: 65 204103). The difference originates from the different manipulations of the capillary outer surface. A conducting layer is coated on the outer surface of the capillary and grounded in this work. This isolates various discharge/charge channels and forms a new stable discharge channel. The transmission rate as a function of the tilt angle shows that the allowed transmission occurs at the tilt angle limited by the geometrical factors, i. e., the geometrical opening angle given by the aspect ratio as well as the beam divergence. The transmission characteristics suggest that most likely there are formed no negative patches to facilitate the electron transmission through the glass capillary at this selected beam energy. It is different from that of highly charged ions, where the formation of the charge patches prohibits the close collisions between the following ions and guides them out of the capillary.

  • 40. Rodriguez, D.
    et al.
    Blaum, K.
    Noertershaeuser, W.
    Ahammed, M.
    Algora, A.
    Audi, G.
    Aysto, J.
    Beck, D.
    Bender, M.
    Billowes, J.
    Block, M.
    Boehm, C.
    Bollen, G.
    Brodeur, M.
    Brunner, T.
    Bushaw, B. A.
    Cakirli, R. B.
    Campbell, P.
    Cano-Ott, D.
    Cortes, G.
    Crespo Lopez-Urrutia, J. R.
    Das, P.
    Dax, A.
    De, A.
    Delheij, P.
    Dickel, T.
    Dilling, J.
    Eberhardt, K.
    Eliseev, S.
    Ettenauer, S.
    Flanagan, K. T.
    Ferrer, R.
    Garcia-Ramos, J. -E
    Gartzke, E.
    Geissel, H.
    George, S.
    Geppert, C.
    Gomez-Hornillos, M. B.
    Gusev, Y.
    Habs, D.
    Heenen, P. -H
    Heinz, S.
    Herfurth, F.
    Herlert, A.
    Hobein, Matthias
    Stockholm University, Faculty of Science, Department of Physics.
    Huber, G.
    Huyse, M.
    Jesch, C.
    Jokinen, A.
    Kester, O.
    Ketelaer, J.
    Kolhinen, V.
    Koudriavtsev, I.
    Kowalska, M.
    Kraemer, J.
    Kreim, S.
    Krieger, A.
    Kuehl, T.
    Lallena, A. M.
    Lapierre, A.
    Le Blanc, F.
    Litvinov, Y. A.
    Lunney, D.
    Martinez, T.
    Marx, G.
    Matos, M.
    Minaya-Ramirez, E.
    Moore, I.
    Nagy, S.
    Naimi, S.
    Neidherr, D.
    Nesterenko, D.
    Neyens, G.
    Novikov, Y. N.
    Petrick, M.
    Plass, W. R.
    Popov, A.
    Quint, W.
    Ray, A.
    Reinhard, P. -G
    Repp, J.
    Roux, C.
    Rubio, B.
    Sanchez, R.
    Schabinger, B.
    Scheidenberger, C.
    Schneider, D.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Schwarz, S.
    Schweikhard, L.
    Seliverstov, M.
    Solders, Andreas
    Stockholm University, Faculty of Science, Department of Physics.
    Suhonen, Markus
    Stockholm University, Faculty of Science, Department of Physics.
    Szerypo, J.
    Tain, J. L.
    Thirolf, P. G.
    Ullrich, J.
    Van Duppen, P.
    Vasiliev, A.
    Vorobjev, G.
    Weber, C.
    Wendt, K.
    Winkler, M.
    Yordanov, D.
    Ziegler, F.
    MATS and LaSpec: High-precision experiments using ion traps and lasers at FAIR2010In: The European physical journal. Special topics, ISSN 1951-6355, Vol. 183, 1-123 p.Article, review/survey (Refereed)
    Abstract [en]

    Nuclear ground state properties including mass, charge radii, spins and moments can be determined by applying atomic physics techniques such as Penning-trap based mass spectrometry and laser spectroscopy. The MATS and LaSpec setups at the low-energy beamline at FAIR will allow us to extend the knowledge of these properties further into the region far from stability. The mass and its inherent connection with the nuclear binding energy is a fundamental property of a nuclide, a unique ""fingerprint"". Thus, precise mass values are important for a variety of applications, ranging from nuclear-structure studies like the investigation of shell closures and the onset of deformation, tests of nuclear mass models and mass formulas, to tests of the weak interaction and of the Standard Model. The required relative accuracy ranges from 10(-5) to below 10(-8) for radionuclides, which most often have half-lives well below 1 s. Substantial progress in Penning trap mass spectrometry has made this method a prime choice for precision measurements on rare isotopes. The technique has the potential to provide high accuracy and sensitivity even for very short-lived nuclides. Furthermore, ion traps can be used for precision decay studies and offer advantages over existing methods. With MATS (Precision Measurements of very short-lived nuclei using an Advanced Trapping System for highly-charged ions) at FAIR we aim to apply several techniques to very short-lived radionuclides: High-accuracy mass measurements, in-trap conversion electron and alpha spectroscopy, and trap-assisted spectroscopy. The experimental setup of MATS is a unique combination of an electron beam ion trap for charge breeding, ion traps for beam preparation, and a high-precision Penning trap system for mass measurements and decay studies. For the mass measurements, MATS offers both a high accuracy and a high sensitivity. A relative mass uncertainty of 10(-9) can be reached by employing highly-charged ions and a non-destructive Fourier-Transform Ion-Cyclotron-Resonance (FT-ICR) detection technique on single stored ions. This accuracy limit is important for fundamental interaction tests, but also allows for the study of the fine structure of the nuclear mass surface with unprecedented accuracy, whenever required. The use of the FT-ICR technique provides true single ion sensitivity. This is essential to access isotopes that are produced with minimum rates which are very often the most interesting ones. Instead of pushing for highest accuracy, the high charge state of the ions can also be used to reduce the storage time of the ions, hence making measurements on even shorter-lived isotopes possible. Decay studies in ion traps will become possible with MATS. Novel spectroscopic tools for in-trap high-resolution conversion-electron and charged-particle spectroscopy from carrier-free sources will be developed, aiming e. g. at the measurements of quadrupole moments and E0 strengths. With the possibility of both high-accuracy mass measurements of the shortest-lived isotopes and decay studies, the high sensitivity and accuracy potential of MATS is ideally suited for the study of very exotic nuclides that will only be produced at the FAIR facility. Laser spectroscopy of radioactive isotopes and isomers is an efficient and model-independent approach for the determination of nuclear ground and isomeric state properties. Hyperfine structures and isotope shifts in electronic transitions exhibit readily accessible information on the nuclear spin, magnetic dipole and electric quadrupole moments as well as root-mean-square charge radii. The dependencies of the hyperfine splitting and isotope shift on the nuclear moments and mean square nuclear charge radii are well known and the theoretical framework for the extraction of nuclear parameters is well established. These extracted parameters provide fundamental information on the structure of nuclei at the limits of stability. Vital information on both bulk and valence nuclear properties are derived and an exceptional sensitivity to changes in nuclear deformation is achieved. Laser spectroscopy provides the only mechanism for such studies in exotic systems and uniquely facilitates these studies in a model-independent manner. The accuracy of laser-spectroscopic-determined nuclear properties is very high. Requirements concerning production rates are moderate; collinear spectroscopy has been performed with production rates as few as 100 ions per second and laser-desorption resonance ionization mass spectroscopy (combined with beta-delayed neutron detection) has been achieved with rates of only a few atoms per second. This Technical Design Report describes a new Penning trap mass spectrometry setup as well as a number of complementary experimental devices for laser spectroscopy, which will provide a complete system with respect to the physics and isotopes that can be studied. Since MATS and LaSpec require high-quality low-energy beams, the two collaborations have a common beamline to stop the radioactive beam of in-flight produced isotopes and prepare them in a suitable way for transfer to the MATS and LaSpec setups, respectively.

  • 41.
    Schmidt, Henning
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Fischer, Daniel
    Stockholm University, Faculty of Science, Department of Physics.
    Berenyi, Zoltan
    Stockholm University, Faculty of Science, Department of Physics.
    Cocke, Charles Lewis
    Gudmundsson, Magnus
    Stockholm University, Faculty of Science, Department of Physics.
    Haag, Nicole
    Stockholm University, Faculty of Science, Department of Physics.
    Johansson, Henrik A. B.
    Stockholm University, Faculty of Science, Department of Physics.
    Källberg, Anders
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Levin, Sergey B.
    Reinhed, Peter
    Stockholm University, Faculty of Science, Department of Physics.
    Sassenberg, Ulf
    Stockholm University, Faculty of Science, Department of Physics.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Simonsson, Ansgar
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Stöchkel, Kristian
    Cederquist, Henrik
    Stockholm University, Faculty of Science, Department of Physics.
    Evidence of Wave-Particle Duality for Single Fast Hydrogen Atoms2008In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 101, no 8, 083201- p.Article in journal (Refereed)
    Abstract [en]

    We report the direct observation of interference effects in a Young's double-slit experiment where the interfering waves are two spatially separated components of the de Broglie wave of single 1.3 MeV hydrogen atoms formed close to either target nucleus in H+ + H2 electron-transfer collisions. Quantum interference strongly influences the results even though the hydrogen atoms have a de Broglie wavelength, \lambda_dB, as small as 25 fm.

  • 42.
    Schuch, R.
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Bergström, I.
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Fritioff, T.
    Stockholm University, Faculty of Science, Department of Physics.
    Solders, A.
    Stockholm University, Faculty of Science, Department of Physics.
    Suhonen, M.
    Stockholm University, Faculty of Science, Department of Physics.
    Nagy, Sz.
    Stockholm University, Faculty of Science, Department of Physics.
    Precise Atomic Masses for Fundamental Physics Determined at SMILETRAP2008In: Advances in Quantum Chemistry, ISSN 0065-3276, E-ISSN 2162-8815, Vol. 53, 67-81 p.Article in journal (Refereed)
    Abstract [en]

    In this paper we describe the features of the SMILETRAP Penning trap mass spectrometer and give examples of recently performed precision mass measurements. SMILETRAP is designed for precision mass measurements using the merits of highly-charged ions. We emphasize here the importance of accurate masses of hydrogen-like and lithium-like ions for the evaluation of g-factor measurements of electrons bound to even–even nuclei and test quantum electrodynamics (QED). For these experiments the ion masses of 40Ca17+ and 40Ca19+ were measured at SMILETRAP with 5×10−10 precision. Highly precise mass measurements can also be used for testing atomic structure calculations and determination of atomic and nuclear binding energies. Some Q-values are of fundamental interest, for example, the beta-decay of tritium and the double beta-decay with no neutrinos of several nuclei, in particular 76Ge. These decays are related to properties of the electron neutrino mass and whether this neutrino is a Majorana particle. The reason that Penning traps are so reliable for the determinations of accurate decay Q-values is due to the fact that systematic errors to a great deal cancel in the mass difference between the two atoms defining the Q-value. In this paper we report the most accurate Q-values of these two beta decays namely 18589.8(12) eV for the tritium decay, and 2038.997(46) keV for the neutrinoless double beta-decay of 76Ge.

  • 43.
    Schuch, Reinhold
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Bergström, Ingmar
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Blaum, K.
    Johannes Gutenberg-University Mainz.
    Fritioff, Tomas
    Stockholm University, Faculty of Science, Department of Physics.
    Solders, Andreas
    Stockholm University, Faculty of Science, Department of Physics.
    Suhonen, Markus
    Stockholm University, Faculty of Science, Department of Physics.
    Nagy, Szilárd
    Stockholm University, Faculty of Science, Department of Physics.
    Q value related mass determinations using a Penning trap2007In: Hyperfine Interactions, ISSN 0304-3843, E-ISSN 1572-9540, Vol. 173, no 1-3, 73-83 p.Article in journal (Refereed)
    Abstract [en]

    We report here about measurements of reaction and decay Q values by precise determination of pairs of atomic masses. These were performed with the Penning trap mass spectrometer SMILETRAP. Measurements with Penning traps give reliable and accurate masses, in particular Q values, due to the fact that certain systematic errors to a great deal cancel in the mass difference between the two atoms defining the Q value. Some Q values that are of fundamental interest will be discussed here, for example, a new Q value for the 6Li (n,γ) 7Li reaction, for the β-decay of tritium, related to properties of the electron neutrino mass, and for the neutrino-less double β-decay of 76Ge, related to the question of whether the neutrino is a Majorana particle or not. In case of the latter two we report the most accurate Q values, namely 18,589.8(12) eV for the tritium decay and 2,038.997(46) keV for the neutrino-less double β-decay of 76Ge.

  • 44.
    Schuch, Reinhold
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Johansson, A.
    Kumar, R.T.
    Stockholm University, Faculty of Science, Department of Physics.
    Sahana, M.B.
    Stockholm University, Faculty of Science, Department of Physics.
    Skog, Patrik
    Stockholm University, Faculty of Science, Department of Physics.
    Soroka, I.L.
    Stockholm University, Faculty of Science, Department of Physics.
    Vikor, György
    Stockholm University, Faculty of Science, Department of Physics.
    Zhang, Hongqiang
    Stockholm University, Faculty of Science, Department of Physics.
    Guiding of highly charged ions through insulating nanocapillaries2008In: Canadian journal of physics (Print), ISSN 0008-4204, E-ISSN 1208-6045, Vol. 86, no 1, 327-330 p.Article in journal (Refereed)
    Abstract [en]

    The guiding of highly charged ions through nanocapillaries in different insulating materials, such as polyethylene terephthalate, SiO<sub>2</sub>, and Al<sub>2</sub>O<sub>3</sub> has been investigated by our group, using 7 keV Ne<sup>7+</sup> ions. We find transmission of ions incident at angles larger than the angle given by the capillary aspect ratio in all these materials. The measured angular distributions, however, vary with the membrane material. In this report we compare the experimental findings with the different membranes.

  • 45.
    Skog, Patrik
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Zhang, Hongqiang
    Stockholm University, Faculty of Science, Department of Physics.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Evidence of Sequentially Formed Charge Patches Guiding Ions through Nanocapillaries2008In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 101, no 22, 223202- p.Article in journal (Refereed)
    Abstract [en]

    We investigated the time evolution of the dynamically shifting distribution of 7 keV Ne7+ ions guided through nanocapillaries in SiO2. We present evidence for a small number of charge patches, formed sequentially in the charging-up process, guiding the ions. We show that the charge patches are distributed along the whole length of the capillaries and that they are maintained in the equilibrium state of transmission. The interpretations are supported by model calculations.

  • 46.
    Solders, Andreas
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Bergström, Ingmar
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Nagy, Szilard
    Stockholm University, Faculty of Science, Department of Physics.
    Suhonen, Markus
    Stockholm University, Faculty of Science, Department of Physics.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Determination of the proton mass from a measurement of the cyclotron frequencies of D+ and H2+ in a Penning trap2008In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 78, no 1, 2514-2520 p.Article in journal (Refereed)
    Abstract [en]

    We determine the cyclotron frequency ratio of H2+ and D+, applying the two-pulse Ramsey-excitation technique in the Penning-trap mass spectrometer SMILETRAP. The final result, based on probing more than 100 000 ions, is a frequency ratio of 0.999 231 659 33(17). Using a value of the D+ mass recently measured by the Seattle group, we obtain so far the most precise experimental H2+ mass value of 2.015 101 497 16(34) u. From this value a proton mass value of 1.007 276 466 95(18) u (0.18 ppb relative uncertainty) could be derived, in good agreement with the value of 1.007 276 466 89(14) u published by Van Dyck et al.

  • 47. Stoehlker, Th.
    et al.
    Bagnoud, V.
    Blaum, K.
    Blazevic, A.
    Braeuning-Demian, A.
    Durante, M.
    Herfurth, F.
    Lestinsky, M.
    Litvinov, Y.
    Neff, S.
    Pleskac, R.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Schippers, S.
    Severin, D.
    Tauschwitz, A.
    Trautmann, C.
    Varentsov, D.
    Widmann, E.
    APPA at FAIR: From fundamental to applied research2015In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 235, 680-685 p.Article in journal (Refereed)
    Abstract [en]

    FAIR with its intense beams of ions and antiprotons provides outstanding and worldwide unique experimental conditions for extreme matter research in atomic and plasma physics and for application oriented research in biophysics, medical physics and materials science. The associated research programs comprise interaction of matter with highest electromagnetic fields, properties of plasmas and of solid matter under extreme pressure, density, and temperature conditions, simulation of galactic cosmic radiation, research in nanoscience and charged particle radiotherapy. A broad variety of APPA-dedicated facilities including experimental stations, storage rings, and traps, equipped with most sophisticated instrumentation will allow the APPA community to tackle new challenges. The worldwide most intense source of slow antiprotons will expand the scope of APPA related research to the exciting field of antimatter.

  • 48. Stoehlker, Thomas
    et al.
    Litvinov, Yuri A.
    Bagnoud, Vincent
    Bechstedt, Ulf
    Dimopoulou, Christina
    Dolinskii, Alexei
    Geppert, Christopher
    Hagmann, Siegbert
    Katayama, Takeshi
    Kuehl, Thomas
    Maier, Rudolf
    Noertershaeuser, Wilfried
    Prasuhn, Dieter
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Steck, Markus
    Stockhorst, Hans
    SPARC experiments at the high-energy storage ring2013In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T156Article in journal (Refereed)
    Abstract [en]

    The physics program of the SPARC collaboration at the Facility for Antiproton and Ion Research (FAIR) focuses on the study of collision phenomena in strong and even extreme electromagnetic fields and on the fundamental interactions between electrons and heavy nuclei up to bare uranium. Here we give a short overview on the challenging physics opportunities of the high-energy storage ring at FAIR for future experiments with heavy-ion beams at relativistic energies with particular emphasis on the basic beam properties to be expected.

  • 49. Stoehlker, Thomas
    et al.
    Litvinov, Yuri A.
    Braeuning-Demian, Angela
    Lestinsky, Michael
    Herfurth, Frank
    Maier, Rudolf
    Prasuhn, Dieter
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Steck, Markus
    SPARC collaboration: new strategy for storage ring physics at FAIR2014In: Hyperfine interactions, 2014, Vol. 227, no 1-3, 45-53 p.Conference paper (Refereed)
    Abstract [en]

    SPARC collaboration at FAIR pursues the worldwide unique research program by utilizing storage ring and trapping facilities for highly-charged heavy ions. The main focus is laid on the exploration of the physics at strong, ultra-short electromagnetic fields including the fundamental interactions between electrons and heavy nuclei as well as on the experiments at the border between nuclear and atomic physics. Very recently SPARC worked out a realization scheme for experiments with highly-charged heavy-ions at relativistic energies in the High-Energy Storage Ring HESR and at very low-energies at the CRYRING coupled to the present ESR. Both facilities provide unprecedented physics opportunities already at the very early stage of FAIR operation. The installation of CRYRING, dedicated Low-energy Storage Ring (LSR) for FLAIR, may even enable a much earlier realisation of the physics program of FLAIR with slow anti-protons.

  • 50.
    Suhonen, Markus
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Hobein, Matthias
    Stockholm University, Faculty of Science, Department of Physics.
    Liu, Yuwen
    Lanzhou University, School of Nuclear Science and Technology.
    Solders, Andreas
    Stockholm University, Faculty of Science, Department of Physics.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    First observation of evaporative cooling of highly charged ions in a Penning trap resolved by their coherent axial oscillationsManuscript (preprint) (Other academic)
    Abstract [en]

    We have trapped and stored Ar16+ ions in a cylindrical Penning trap and managed to evaporatively cool the ion clouds axial motion to thermal temperature. The stored ion cloud is excited axially by fast switching of the trap potentials whereafter the cloud starts to oscillate coherently. The cooling is observed from the time of flight resolved peaks originating from the oscillations while lowering the trap potential slowly. The peaks widths decrease with increased storage time.

12 1 - 50 of 64
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