1. Radiation Hardness of new generation of plastic scintillators
R. Erasmus, H.Jivan, S.Liao, M.Madhuku, L.Maphanga, B.Mellado, C.Pelwan, G.Peters, K.Sekonya, E.Sideras-Haddad
University of the Witwatersrand/iThemba Labs

2. Scope
Currently ATLAS and CMS are testing a new generation of plastic scintillators for some Phase-2 upgrades
These studies are very relevant to new hadronic calorimeters including the LHeC and even the FCC hh detector
Not only assessing the changes in transmittance and light yield, but also understanding the nature of the radation damage
Survey of formation of radicals and changes in the polymer base with various techniques from material sciences
Need to understand if slow chemical reactions as a result of damage is an issue

3. Plastic Scintillators Investigated
Three polyvinyl toluene based scintillators obtained from ELJEN Technology were investigated. Got samples used now at the ATLAS Tile Calorimeter, referred to as the “Dubna” samples
(Top left) The EJ208 and EJ200 scintillators
(Bottom left) The EJ260 scintillator

4. Sample preparation
250 μm thick samples were prepared by Mr. Gerrard Peters.
10mm wide sections of each sample were cut using a low speed saw

5. Sample preparation
These sections were then cut to ~0.5mm thickness using a diamond wire saw

6. Sample preparation
The samples were then mounted to a holder using carbon tape and a fine polishing process was followed using a complementary polishing direction.

7. Proton Irradiation at iThemba LABS
Tandem accelerator
Extraction line
Injection line
Irradiation experiments were conducted at iThemba LABS.
A beam of 6 MeV protons was provided by the tandem accelerator.
The beam current was measured using a faraday cup.
Radiation doses of kilo Gray, 164 kilo Gray and ~1.5 Mega Gray were administered to various samples of each scintillator grade.
Line used for radiation

8. Microscope to monitor beam position
Chamber containing scintillator sample
Microscope to monitor beam position
Quadruple magnets for beam focusing

9. Beam located by observing scintillation of diamond
Diamond and ceramic used to locate beam
Beam located by observing scintillation of diamond

10. Irradiation of scintillator sample with maximum defocusing and scanning (in x and y) of beam. Achieved irradiation over a surface of 3mm x 3mm.

11. Transmission Experiments
Light transmission experiments were conducted using the Varian Cary Spectrophotometer
Transmission over UV and visible wavelength range ( nm)
A tungsten lamp source and diffraction grating is used in order to increment light over this range
Transmission of light in each irradiated scintillator sample as well as the un-irradiated samples were measured relative to transmission in air.

12. Transmission spectra of various un-irradiated scintillator grades through either face
Preliminary

13. Transmission spectra of various 40 Mega Gray irradiated scintillator grades through either face
Preliminary

14. Preliminary
Increased transmission could be a result of the destruction of some specie that absorbs in this region.
5% loss
7.5% loss
9.5% loss

15. 1.5% loss
3.5% loss
5% loss

16. 4% loss
3.5% loss
7% loss

17. Raman Spectroscopy
Raman spectroscopy was conducted using the Horiba Jobin-Yvon Raman spectrographs.
A 515 nm excitation laser was used.
Spectra were obtained for the un-irradiated and highest dose irradiated samples of each scintillator grade.

18. Results of Raman Spectroscopy for EJ200 sample
(C-H)
(C-C) aromatic ring
(C-C) aliphatic
CH3 or CH2
(=(C-H))
(C-C) aliphatic
(C=C)

19. -Y X Z Light yield studies with Sr90 lab at CERN
0,5 MeV electrons are emitted from the Sr90 source and impinge the scintillator from above it ( along z direction)
The source is scanned along x and -y and the PMT signal is registered for each position
Added piece to here
Used the new holder set-up, as above.
Fibers fit into the grooves on either side of the scintillator.
To ensure that the fibers did not move, we added a piece of plastic to the bottom end and fastened it with aluminium tape.

20. Light yield of EJ208 samples
Unirradiated
~1 Kilo Gray
~ 100 Kilo Gray
~1 Mega Gray

21. Preliminary Conclusions
Assessing radiation hardness of new generation of plastic scintillators
Radiating thin plastics with 6 MeV protons at iThemba-Gauteng
Have resummed a second radiation campaign to re-do radiation of all samples
Plan to redo analysis of all samples to improve systematics and ensure robustness of measurement
Preliminary studies with first round of radiation are very encouraging. This includes studies of light transmittance, light yield and Raman scattering.
Will have definitive statement this year
Trying to add Bycron samples