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

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

The Energy Calibration of System 109Cd, 133Ba X-ray Sources 109Cd: 22.1 keV 133Ba: 30.9 keV 81.keV

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

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.

Energy Spectra for Different X-ray Sources 22.1keV 30.9keV 88.1keV

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

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

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.

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).

Spectra Fitted for Different Angles

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

Q , PSD, <t> for degree 95

For degree 50(Scattering Plot)

Degree 50 (Q, PSD, <t>)

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

The Ratio of Two Methods Here ratio = Qpsd/Qbg_sub

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

The Quenching Factor

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.

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

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.