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Exploring vacuum phototriodes for photon calorimetry
Stockholm University, Faculty of Science, Department of Physics. (Instrumentation physics)
Stockholm University, Faculty of Science, Department of Physics. (Instrumentation physics)
(English)Manuscript (preprint) (Other academic)
Abstract [en]

In this work properties of a vacuum phototriode (VPT) and preamplifier unit designed for the electromagneticcalorimeter of the PANDA experiment being built at FAIR are investigated. With the use of leadtungstate and lanthanum bromide scintillators the VPT properties are studied at low photon energies, fromtens of keV in the lanthanum bromide measurements and between 10 MeV and 60 MeV in the lead tungstatemeasurements. At these energies the noise of the VPT unit can be expected to influence its performancesignificantly. It is shown that the noise contribution to the measured energy resolution, under optimal conditions,is consistent with a fluctuation of (one standard deviation) approximately 200 electrons at the VPTanode. For a lead tungstate crystal this is equivalent to a noise of 1.2 MeV. For lanthanum bromide thismakes it possible to use VPTs for gamma ray spectroscopy above a few hundreds of keV without noticableeffects on the energy resolution compared to measurements with a standard photomultiplier. The gain sensitivityto rate is shown to be small. The gain changes by less than 1.5 % for a rate of 2105 s−1 comparedto low rates.

National Category
Accelerator Physics and Instrumentation
Identifiers
URN: urn:nbn:se:su:diva-94924OAI: oai:DiVA.org:su-94924DiVA: diva2:656864
Available from: 2013-10-17 Created: 2013-10-17 Last updated: 2013-10-17
In thesis
1. Instrumentation development for physics with antiproton beams
Open this publication in new window or tab >>Instrumentation development for physics with antiproton beams
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis summarises work done in the preparation for the PANDA (antiproton ANnihilations at DArmstadt) experiment, that will be built at the HESR (High Energy Storage Ring) at FAIR (Facility for Antiproton and Ion Research) and for the PAX (Polarised Antiproton eXperiment) experiment proposed for the HESR.

For PANDA, characteristics of the electromagnetic calorimeter have been measured at the tagged photon beam facility at the MAX IV laboratory for 61 photon energies in the range 12-63 MeV. The tested detector array consisted of 5×5 PbWO4 (lead tungstate) crystals designed for the forward end-cap. The array was cooled to -25 °C and read out with either conventional photomultiplier tubes or vacuum phototriodes (VPTs), the photo-sensor proposed for the forward end-cap. The measured relative energy resolution with photomultiplier tubes, σ/E, (for example 6 % at 20 MeV) is well within the limits of the PANDA requirements. In tests with VPTs the lower signal-to-noise ratio deteriorates the resolution to a level suggesting that VPTs should not be used in PANDA.

For PAX, the analysing power with respect to the neutron in pd → ppn, with a transversely polarised proton beam with energy 49.3 MeV, has been measured. Data was taken at the COSY storage ring, Forschungszentrum Jülich, during an experiment in which the PAX collaboration successfully polarised a stored proton beam by spin filtering. In the measurement the beam was scattered of a deuterium cluster-jet target and the scattered protons were detected in the two silicon tracking telescopes of the ANKE detector system. The measured analysing power is compared to the predictions by chiral effective field theory at next-to-next-to-leading order by interpolating on a precalculated grid and using the sampling method.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2013. 118 p.
National Category
Accelerator Physics and Instrumentation
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-94925 (URN)978-91-7447-728-3 (ISBN)
Public defence
2013-11-18, Lecture hall FA32 , AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 09:30 (English)
Opponent
Supervisors
Note

At the time of the doctoral defence the following paper was unpublished and had a status as follows: Paper 2: Manuscript.

Available from: 2013-10-26 Created: 2013-10-17 Last updated: 2014-02-04Bibliographically approved

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