Reactions with radioactive beams and development of scintillator-based detector systems

Alexander Knyazev

    Research output: ThesisDoctoral Thesis (compilation)

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    Abstract

    An experiment on elastic scattering of 15 C on 208 Pb at an energy of 65 MeV
    was performed at ISOLDE (CERN) exploiting the advantages of the ISOL te-
    chinique. The measurement showed in increase of the reaction cross section to
    3035 mb with respect to 12 C, confirming the results obtained at 80 MeV/u. Mea-
    surements to characterise and develop detector modules for the CALIFA setup
    was performed for the R 3 B experiment at FAIR. Light output characteristics of
    478 detector modules of the CALIFA Barrel section were measured as a part
    this work in order to investigate the correlation between resolution and non-
    uniformity. For this set of crystals the average resolution was found to be 5.2%
    (FWHM) at E γ = 1275 keV. Further investigations also done in this work show
    that the inhomogeneity in the Tl dopant distribution contributes ∼0.5%, and
    the noise in the read-out chain with .0.1% to that number. The most important
    contribution to variations in the resolution was found to be from non-uniform
    light collection due to the geometry of the modules. The APD light read-out
    sensors were also investigated and found to be stable below 24.8 ◦ C using a gain
    correction algorithm. Energy add-back and light cross-talk were investigated.
    It was found that a closest-neighbor add-back algorithm recovers 14.7% of the
    events for E γ = 662 keV and 65% of the events for E γ = 1460 keV, while the
    light cross-talk contributes .0.03% to the photo peak. The attenuation length
    of the emission light of the scintillators was also determined and found to be
    34.6 ± 4.5 cm. In addition the micro facet distribution for a polished and a
    lapped sample was measured using atomic force microscopy to produce look-up
    tables for GEANT4 simulations of light transport. Simulations of light output
    non-uniformity were performed for different configurations of lapped surfaces
    of a CALIFA detector module. The simulations reproduced the general trend
    of the measurement where the non-uniformity decreased with increasing lapped
    area, although the exact values for the non-uniformity were not reproduced. A
    sensitivity test for the simulated light-output non-uniformity with respect to
    different input parameters was also performed. The non-uniformity was found
    to be most sensitive to the reflectivity of the reflector foil while the sensitivity
    to the other parameters was less prominent.
    Original languageEnglish
    Awarding Institution
    Supervisors/Advisors
    • Cederkäll, Joakim, Supervisor
    • Golubev, Pavel, Assistant supervisor
    Publisher
    ISBN (Print)978-91-7895-594-7
    ISBN (electronic) 978-91-7895-595-4
    Publication statusPublished - 2020

    Bibliographical note

    Defence details

    Date: 2020-10-30

    Time: 09:00

    Place: Rydbergsalen, Fysiska Institutionen, Lund. Join via zoom: https://lu-se.zoom.us/j/65808666704?pwd=ZEhyZlc0ZW02TURET05PK0g3dDBGUT09

    External reviewer(s)

    Name: Tegnér Per-Erik

    Title: Professor

    Affiliation: Stockholms universitet

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    Subject classification (UKÄ)

    • Subatomic Physics

    Free keywords

    • Nuclear physics
    • Reactions
    • Detectors
    • SImulation
    • Light transport simulation
    • Calorimetry
    • Fysicumarkivet A:2020:Knyazev

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