P R O T O N I N D U C E D R A D I A T I O N D A M A G E
S T U D I E S O N P L A S T I C S C I N T I L L A T O R S
F O R T H E T I L E C A L O R I M E T E R O F T H E
A T L A S D E T E C T O R
Harshna Jivan
Supersior: Bruce Mellado
Co-supervisor: Elias Sideras-Haddad
A Dissertation submitted to the Faculty of Science, University of the
Witwatersrand, Johannesburg, in fulfilment of the requirements for the
degree of Master of Science.
Johannesburg, 2016
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Declaration
I declare that this Dissertation is my own, unaided work. It is being submitted for
the Degree of Master of Science at the University of the Witwatersrand,
Johannesburg. It has not been submitted before for any degree or examination at
any other University.
_____________________
8
th
day of August 2016 in Johannesburg.
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Abstract
Plastic scintillators play a key role in reconstructing the energy and tracks of hadronic
particles that impinge the Tile Calorimeter of the ATLAS detector as a result of high
energy particle collisions generated by the Large Hadron Collider of CERN. In the
detector, plastic scintillators are exposed to harsh radiation environments and are
therefore susceptible to radiation damage.
The radiation damage effects to the optical properties and structural damage were studied
for PVT based commercial scintillators EJ200, EJ208, EJ260 and BC408, as well as PS
based UPS923A and scintillators manufactured for the Tile Calorimeter. Samples of
dimensions 5x5x0.3 mm were subjected to irradiation using 6 MeV protons to doses of
approximately 0.8 MGy, 8 MGy, 25 MGy and 25 MGy using the 6 MV tandem
accelerator of iThemba LABS.
Results show that damage leads to a reduced light output and loss in transmission
character. Structural damage to the polymer base and the formation of free
radicals occur for doses ≥ 8 MGy leading to reduced scintillation in the base and
re-absorption of scintillation light respectively. Scintillators containing a larger
Stokes shift, i.e. EJ260 and EJ208 exhibit the most radiation hardness. EJ208 is
recommended as a candidate to be considered for the replacement of Gap
scintillators in the TileCal for the 2018 upgrade.
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