1. Neutron Beam Test for Measuring Quenching Factor of CsI(Tl) Crystal
Qian Yue
IHEP, Beijing

2. The Experimental Setup
2H + 2H → 3He + n ( Pulsed Deuteron Beam)
We get 8MeV pulsed neutron beam

3. The Energy Calibration of System
109Cd, 133Ba X-ray Sources
109Cd: keV
133Ba: keV 81.keV

4. FADC Current Signal Shape
For different X-ray energy, it should use different integration time bin.

5. Q-bin for Different Energy
We can see from the pictures that when the integration time is long enough, the Q value will increase at a constant speed.

6. Energy Spectra for Different X-ray Sources
22.1keV keV keV

7. Energy Calibration Equation
Y- Energy X- Channels of Photoelectron Peak

8. Two Methods We Used to Process Our Data
Background Subtraction
PSD & <t>
PSD = Qpart/Qtotal <t> = (Ni × Ti)/ Ni

9. 1 Background Subtraction
This is the background TOF spectrum and signal TOF spectrum. We can use the numbers of recoiled proton of the background spectrum to normalize and to get the numbers and spectrum of the recoiled nuclei.

10. Signal Spectra of CsI(Tl)
This is the energy spectrum of recoiled nuclei including nuclei of H,C,Cs and Al(a) and energy spectrum of recoiled proton(b).

11. Spectra Fitted for Different Angles

12. 2 PSD Method
Use the cuts(PSD,tbar and TOF) to get the real recoiled signal of CsI(Tl) crystal.

13. Q , PSD, <t> for degree 95

14. For degree 50(Scattering Plot)

15. Degree 50 (Q, PSD, <t>)

16. The Results of Two Methods
Here is the results for two different methods

17. The Ratio of Two Methods
Here ratio = Qpsd/Qbg_sub

18. Check of Our Result
Test our result using the cross section data of 8MeV n beam scattering off by Cs and I nuclei.
  Area/ t×r2

19. The Quenching Factor

20. The Block Diagram of Single Photoelectron Measurement
We change the voltage supplied to the LED to change its lighting intensity. 20 layer of thin Teflon have been used to attenuate the light arrived to photo cathode of PMT.

21. The Result of Single Photoelectron(37ch/per pe)

22. Summary: We have gotten the quenching factor of 7keV recoiled energy.
For our system, we can get 3.7 pe/keV.
The energy limit of PSD method is less than 2keV in our experiment.