Proton induced radiation damage studies on plastic scintillators for the Tile calorimeter of the atlas detector

1.3.
 
Presentation of chapters 
In chapter 2, an overview of the Tile calorimeter is given with focus on how 
plastic scintillators are used to generate a signal in the detector. The scintillation 
mechanism and radiation damage mechanisms are discussed in chapter 3. 
Chapter 4 describes the experimental procedures followed for inducing radiation 
damage in thin plastic scintillator samples using 6 MeV protons, and describes 
the analysis techniques used for assessing this damage. The results of this study 
are presented in chapter 5, with conclusions summarised in chapter 6.

---

5 
2
 
The Tile Calorimeter of the ATLAS detector 
The ATLAS detector [5] is a general purpose detector at the Large Hadron 
collider of CERN. It spans a length of 42 m, a diameter of 25 m and weighs a 
heavy 7000 tons. Proton bunches are accelerated within the 27 km long LHC 
tunnels and two beams are sent towards each other, which collide at the 
interaction point at the centre of the detector. Various particl e fragments result 
from the collisions and interact with the various detector layers.
The ATLAS detector contains four main components which each play a 
significant role in reconstructing the original collision in order for new physics 
to be probed. These are the inner detector, the calorimeters, the muon 
spectrometer and the magnetic system. A schematic representation of the ATLAS 
detector is shown in Figure 2-1.  
Figure 2-1: A computer generated image of the ATLAS detector [ATLAS Experiment © 
2013 CERN] 
The Inner Detector (ID) is situated closest to the beam pipe . It consists of three 
sub-detectors; the Pixel detector, the Semi-Conductor Tracker (SCT) and the 
Transition Radiation Tracker (TRT), and is surrounded by a superconducting 

---

6 
solenoid magnet which generates a 2 Tesla magnetic field. The ID is used for 
measuring the tracks of charged particles that emerge from th e collisions. The 
tracks are curved due to the influence of the magnetic field , enabling their 
momenta to be determined.
Surrounding the ID concentrically are the Electromagnetic Calorimeters and the 
Tile Calorimeter, hadronic end-cap and forward calorimeters. The Calorimeters 
are based on “Sampling Calorimeter” technologies and are used to measure the 
energy of both charged and neutral particles. The calorimeters are designed to 
contain all electromagnetic and hadronic showers developing within them, and 
only neutrinos and muons manage to exit from these layers.
The Muon spectrometer surrounds the calorimeters and operates within a 
magnetic field generated by eight toroidal magnets. The Muon spectrometer 
measures the tracks of muons as they are bent by th is magnetic field. Neutrino’s 
pass through ATLAS undetected.
A schematic of how the different particles interact through a wedge in the ATLAS 
detector is shown in Figure 2-2. A more detailed description of how each sublayer 
works in order to detect or track particles is provided in Appendix A. 
The interactions of the various particles, resulting from the collision, with the 
different detector layers generate a huge amount of data. The ATLAS detector 
therefore incorporates a trigger and data acquisition (DAQ) system in order to 
only record events containing physics potential. T his three level system uses