1 PMT Univ. of Tokyo Yasuko HISAMATSU ICEPP, The University of Tokyo MEG VRVS meeting Jan. 20th, 2004

2 PMT Output Deterioration During the pi0 beam output from some PMTs reduced by 20-30% when beam was ON. (The background was estimated to be ~ 1.5*10^6p.e.) Similar change was observed under the background simulated using LED pulses -> The Deterioration of old type PMT output due to the high rate background. ・ Output from Al Strip Type PMT (new type) needs to be tested under the high rate background. Yasuko HISAMATSUJan. 20 th, 2004MEG VRVS Meeting

3 PMT Univ. of Tokyo Set up PMT (Al Strip Type) TB0094 TB0102 TB0286 TB0302 (now being analized…) TB0284 TB0568 PMT Alpha source( 241 Am ) LED Liq. Xe 5.5MeV alpha peak ADC channel Yasuko HISAMATSUJan. 20 th, 2004MEG VRVS Meeting

4 Condition and Procedure alpha source : ~200Hz, LEDpulse height:500p.e. ~ 12000p.e. per event pulse shape: ~10nsec rate: 100Hz ~ 10KHz Trigger: alpha self trigger (veto by LED driver pulse) Procedure Pedestal Run & Gain calibration using LED Alpha LED OFF Alpha LED ON (LED : high rate background) -Change LED Pulse height, rate and PMT gain Yasuko HISAMATSUJan. 20 th, 2004MEG VRVS Meeting

5 Condition and Procedure DAQ: -Alpha run with LED OFF -Alpha run with LED ON The cause of the change in PMT output –Breeder current ? –Deterioration of photocathode? Low gain run Peak/Sigma (gain independent) The change in PMT output? Yasuko HISAMATSUJan. 20 th, 2004MEG VRVS Meeting Ratio of alpha peak with LED ON to one with LED OFF Number of photoelectrons from LED per second

6 For instance…TB0302 5*e^5 gain peak (LED ON)/peak (LED OFF) 1*e^6 gain peak (LED ON)/peak (LED OFF) 1*e^6 gain ON)/ OFF) 10^7p.e. per sec

7 Result 5*e5gain TB0094TB0102 TB0268TB0302 X: number of photoelectrons per second from LED Y: alpha peak ON) / alpha peak OFF) Yasuko HISAMATSUJan. 20 th, 2004MEG VRVS Meeting ?

8 Result TB0268 TB0094 TB0102 TB0302 1*e6gain X: number of photoelectrons per second from LED Y: alpha peak ON) / alpha peak OFF) Yasuko HISAMATSUJan. 20 th, 2004MEG VRVS Meeting

9 Result TB0302 TB0094 TB0102 TB0268 1e6gain X: number of photoelectrons per second from LED Y: ON) / OFF) Yasuko HISAMATSUJan. 20 th, 2004MEG VRVS Meeting

10 Schedule DAQ Jan PMTs Jan PMTs 10 PMTs will be tested and analized before the meeting at PSI. Yasuko HISAMATSUJan. 20 th, 2004MEG VRVS Meeting

11 Summary 4 Al Strip Type PMTs (new type) have been tested under the high rate background environment at the university of Tokyo. So far, for the 4 PMTs, the stability of PMT output is better than 10% under the background up to 10^7 p.e. per sec. No output deterioration so far under background of ~1.5 *10^6p.e. In order to confirm the stability of PMT performance under the high rate background, additional 6PMTs are going to be tested. The more precise analysis is now going on. Yasuko HISAMATSUJan. 20 th, 2004MEG VRVS Meeting Additional Comments: Of the 4 PMTs, the HV of 2 PMTs tripped frequently. The cause of this HV trip is now being investigated.