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Transmission of slow highly charged ions through nano-structures
Stockholm University, Faculty of Science, Department of Physics. (Atomic Physics)
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is based on experimental investigations of transmitting slow highly charged ions through nano-structures of various cross-sections. Transmission through rhombic and rectangular nanocapillaries in muscovite and phlogopite mica, respectively, is used to study the guiding and shaping of highly charged ion beams. The two-dimensional angular distributions of the transmitted ions reveal that slow highly charged ion beams are tailored into rectangular and rhombic shapes after passing through the capillaries of rhombic and rectangular cross-sections, respectively. These transmission profiles are maintained for tilt angles within the geometrical opening angle of the capillaries. The ‘incident charge-dependent’ time evolution of the transmission profiles indicates that the tailored shape comes from the image force experienced by the traversing ions and the deposited charge by the incident ions moves the transmission profiles towards higher observation angles with respect to the beam direction. Transmission is also observed for tilt angles larger than the geometrical opening of the capillaries and evidence of charging-up of capillary walls was seen. Other incident charge-dependent features including the increase in angular width and shift of transmitted angular distributions were also observed. Starting from initially charged capillaries, it was found that the deposited charge must be distributed uniformly along the capillary walls to maintain the tailored rhombic shape through rectangular capillaries.

In this thesis, a technique is presented which is successfully employed to investigate directly the formation of charge patches on the walls of a glass capillary by imaging the visible photons emitted due to impact of ions on the walls. These tapered glass capillaries were applied in biological studies of cell damage by ion impact and the technique provides a new way to directly observe the development of ion-guiding in these capillaries. With the help of this technique the mechanism of ion-guiding can be controlled and optimized.

We also review the transmission characteristics of slow highly charged ions through nanometer thick foils and present the results of transmission of slow highly charged ions through ultra-thin carbon nano-sheets of molecular layer thickness. The observed energy loss is smaller than the calculated one using SRIM and agrees rather well with the Firsov model. The transmitted ions also keep their initial charge state up to 98% in a complete contradiction to the electron capture rate predicted by the classical over-the-barrier model. The results suggest that the energy loss of slow highly charged ions in such thin sheets is due to the electronic excitations, without charge exchange inside the target.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University , 2012. , 73 p.
Keyword [en]
Highly charged ions, nano-structures, nanocapillaries, ion-guiding
National Category
Physical Sciences
Research subject
Physics
Identifiers
URN: urn:nbn:se:su:diva-75470ISBN: 978-91-7447-514-2 (print)OAI: oai:DiVA.org:su-75470DiVA: diva2:516767
Public defence
2012-05-24, FA31, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 2: Submitted. Paper 3: Submitted. Paper 4: Accepted. Paper 5: Submitted.

Available from: 2012-05-02 Created: 2012-04-19 Last updated: 2012-04-23Bibliographically approved
List of papers
1. Imaging of ion transmission through glass capillaries
Open this publication in new window or tab >>Imaging of ion transmission through glass capillaries
(English)Manuscript (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.

National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-75610 (URN)
Available from: 2012-04-23 Created: 2012-04-23 Last updated: 2012-04-23Bibliographically approved
2. Transmission of highly charged ions through phlogopite-mica nanocapillaries of rectangular cross-section
Open this publication in new window or tab >>Transmission of highly charged ions through phlogopite-mica nanocapillaries of rectangular cross-section
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(English)In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455Article in journal (Refereed) Submitted
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.

National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-75619 (URN)
Available from: 2012-04-23 Created: 2012-04-23 Last updated: 2017-12-07Bibliographically approved
3. Transmission of highly charged ions through mica nanocapillaries of rhombic cross section
Open this publication in new window or tab >>Transmission of highly charged ions through mica nanocapillaries of rhombic cross section
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(English)In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622Article in journal (Refereed) Submitted
Abstract [en]

The angular distributions of Ne7+-ions transmitted at various kinetic energies of 7 – 70 keV through muscovite mica nanocapillaries of rhombic cross section are measured. It is found that the transmitted ion beams form a rectangular shape at tilt angles, small compared to as given by the aspect ratio, i.e., the capillary geometrical opening angle. This shape is retained for all ion energies, but its size changes. The time evolution of the transmitted angular distributions shows that the characteristic profile occurs instantaneously and remains in the stationary state of the transmission, whereas it shifts with the increase of the accumulated incident charge. At tilt angles of the capillaries larger than their aspect ratio, the shape in the transmission profile gets distorted from the rectangle by the deposited charge. Combined with trajectory simulations we show the observed shaping effect is due to the image force seen by the ions, overplayed with a deflection by deposited charge, on the capillary walls.

National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-75618 (URN)
Available from: 2012-04-23 Created: 2012-04-23 Last updated: 2017-12-07Bibliographically approved
4. Tailoring of keV-ion beams by image charge when transmitting through rhombic and rectangular shaped nanocapillaries
Open this publication in new window or tab >>Tailoring of keV-ion beams by image charge when transmitting through rhombic and rectangular shaped nanocapillaries
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(English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114Article in journal (Refereed) Accepted
Abstract [en]

We report on an unexpected effect of tailoring transmission profiles of Ne7+-ions through nanocapillaries of rhombic and rectangular cross sections in mica. We find that capillaries of rhombic cross section produce rectangular shaped ion transmission profiles and, vice versa, capillaries of rectangular geometry give a rhombic beam shape. This shaping effect only occurs for transmitted ions and is absent for the small fraction of neutralized particles. The experimental findings and simulations of the projectile trajectories give clear evidence that the observed effect is due to the image forces experienced by the transmitting ions. This novel beam shaping mechanism suggests application for guiding, focusing, and shaping of ion beams.

National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-75616 (URN)
Available from: 2012-04-23 Created: 2012-04-23 Last updated: 2017-12-07Bibliographically approved
5. Transmission of slow highly charged ions through ultra-thin carbon nano-sheets
Open this publication in new window or tab >>Transmission of slow highly charged ions through ultra-thin carbon nano-sheets
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2011 (English)In: Proceedings of 3rd Int. Conf. on “Current developments in Atomic, Molecular, Optical and Nano Physics”, 2011Conference paper, Published 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.

National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-75613 (URN)
Conference
Current developments in Atomic, Molecular, Optical and Nano Physics, 14-16 Dec, 2011, Delhi, India
Note

Submitted as Springer’s book chapter for Proceedings of 3rd Int. Conf. on “Current developments in Atomic, Molecular, Optical and Nano Physics”, 14-16 Dec, 2011, Delhi, India

Available from: 2012-04-23 Created: 2012-04-23 Last updated: 2012-04-23Bibliographically approved
6. The new Stockholm Electron Beam Ion Trap (S-EBIT)
Open this publication in new window or tab >>The new Stockholm Electron Beam Ion Trap (S-EBIT)
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2010 (English)In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 5, C12018- p.Article in journal (Refereed) Published
Abstract [en]

A new laboratory for highly charged ions is being built up at Stockholm University. A fully refrigerated electron beam ion trap (R-EBIT, 3 T magnet, 30 keV electron energy) was installed. It was used for spectroscopic studies, ion cooling experiments, electron ion collisions, and highly-charged ion surface studies. Here we report on an upgrade of this EBIT to a ``Super EBIT'' (S-EBIT, 4 T magnet, 260 keV electron energy). The high-voltage trapping system, the ion injection as well as the extraction scheme of S-EBIT and the LabView based operational system of S-EBIT are described.

National Category
Atom and Molecular Physics and Optics
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-57786 (URN)10.1088/1748-0221/5/12/C12018 (DOI)
Conference
International Symposium on Electron Beam Ion Sources and Traps (EBIST), Stockholm University, April 7th - 10th, 2010
Available from: 2011-05-19 Created: 2011-05-19 Last updated: 2017-12-11Bibliographically approved

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