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

Research output: ThesisDoctoral Thesis (compilation)

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.

Details

Authors
Organisations
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Subatomic Physics

Keywords

  • Nuclear physics, Reactions, Detectors, SImulation, Light transport simulation, Calorimetry
Original languageEnglish
Awarding Institution
Supervisors/Assistant supervisor
Publisher
  • Lund University
Print ISBNs978-91-7895-594-7
Electronic ISBNs978-91-7895-595-4
Publication statusPublished - 2020
Publication categoryResearch

Bibliographic 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 ---