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Instrumentation development for physics with antiproton beams
Stockholm University, Faculty of Science, Department of Physics. (Nuclear Physics)
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: urn:nbn:se:su:diva-94925ISBN: 978-91-7447-728-3 (print)OAI: oai:DiVA.org:su-94925DiVA: diva2:656885
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
List of papers
1. The response of lead-tungstate scintillators (PWO) to photons with energies in the range 13 MeV-64 MeV
Open this publication in new window or tab >>The response of lead-tungstate scintillators (PWO) to photons with energies in the range 13 MeV-64 MeV
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2012 (English)In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 679, 36-43 p.Article in journal (Refereed) Published
Abstract [en]

The response of a matrix of 25 lead tungstate (PWO) scintillator detectors, operated at -25 degrees C, to photons in the range 13 MeV-64 MeV has been measured at the tagged-photon facility at MAX-lab, Lund. The tapered PWO crystals, each with a length of 200 mm and a cross-section of 24.4 x 24.4 mm(2) in the front end, read out by 19 mm photomultiplier tubes, were arranged in a 5 x 5 matrix. The response was measured for photons directed towards the centre of the central crystal as well as for photons directed towards the corner of the central crystal, where four crystals meet. The obtained energy resolution surpasses what has been published so far and is close to the limit given by Poisson statistics and escaped energy. For photons directed towards the centre(corner) of the central crystal the relative energy resolution, defined as (FWHM/2.35)/E-gamma, decreases from 7.3%(11.0%) at E-gamma = 13 MeV to 3.3%(3.6%) at E-gamma = 64 MeV. The reconstructed point of impact of a photon in this energy range is determined with an uncertainty (one standard deviation) of 7.3 +/- 0.1 mm.

Keyword
Lead tungstate, PWO scintillators, Electromagnetic calorimeter, PANDA, Tagged photons
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-80026 (URN)10.1016/j.nima.2012.03.030 (DOI)000304503400007 ()
Note

AuthorCount:15;

Available from: 2012-09-12 Created: 2012-09-12 Last updated: 2017-12-07Bibliographically approved
2. Exploring vacuum phototriodes for photon calorimetry
Open this publication in new window or tab >>Exploring vacuum phototriodes for photon calorimetry
(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:nbn:se:su:diva-94924 (URN)
Available from: 2013-10-17 Created: 2013-10-17 Last updated: 2013-10-17
3. Polarization of a stored beam by spin filtering
Open this publication in new window or tab >>Polarization of a stored beam by spin filtering
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2012 (English)In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 718, no 1, 64-69 p.Article in journal (Refereed) Published
Abstract [en]

The PAX Collaboration has successfully performed a spin-filtering experiment with protons at the COSY-ring. The measurement allowed the determination of the spin-dependent polarizing cross section, that compares well with the theoretical prediction from the nucleon-nucleon potential. The test confirms that spin-filtering can be adopted as a method to polarize a stored beam and that the present interpretation of the mechanism in terms of the proton-proton interaction is correct. The outcome of the experiment is of utmost importance in view of the possible application of the method to polarize a beam of stored antiprotons.

Keyword
Polarized beams, Storage rings, Antiprotons
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-85529 (URN)10.1016/j.physletb.2012.10.030 (DOI)000311816400010 ()
Note

AuthorCount:72;

Available from: 2013-01-10 Created: 2013-01-08 Last updated: 2017-12-06Bibliographically approved

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