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PMT Test @ Univ. of Tokyo

PMT Test @ Univ. of Tokyo. Yasuko HISAMATSU. ICEPP,. MEG Collaboration meeting Feb. 10th, 2004. PMT Output Deterioration. During the pi0 beam test @PSI, output from some PMTs reduced by 20-30% when beam was ON. (The background was estimated to be ~ 1.5*10^6p.e. per sec)

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PMT Test @ Univ. of Tokyo

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  1. PMT Test @ Univ. of Tokyo Yasuko HISAMATSU ICEPP, MEGCollaboration meeting Feb. 10th, 2004

  2. PMT Output Deterioration • During the pi0 beam test @PSI, output from some PMTs reduced by 20-30% when beam was ON. (The background was estimated to be ~ 1.5*10^6p.e. per sec) • 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, 10^6 ~ 10^8 p.e. per sec . Yasuko HISAMATSU MEG Collaboration Meeting @ PSI February 2004

  3. PMT Test @ Univ. of Tokyo PMT (Al Strip Type) TB0094 TB0102 TB0239 TB0268 TB0284 TB0302 TB0415 TB0439 TB0568 • Set up Liq. Xe PMT 5.5MeV alpha peak Alpha source(241Am ) LED PMT ADC channel Yasuko HISAMATSU MEG Collaboration Meeting @PSI February 2004

  4. PMT Test facility @Univ. of Tokyo Purification system Chamber Inside alpha source LED Xe tank Liq.Xe chamber PMT

  5. Condition and Procedure • alpha source : ~200Hz, • LED pulse 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 Run @ LED OFF • Alpha Run @ LED ON (LED : high rate background) • -Change LED Pulse height, rate and PMT gain Yasuko HISAMATSU MEG Collaboration Meeting @PSI February 2004

  6. 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? The change in PMT output? Low gain run Peak/Sigma (gain independent) Yasuko HISAMATSU MEG Collaboration Meeting @PSI February 2004

  7. Thermal neutron background estimation • Condition of the estimation • 16 n/cm^2/sec (MEG TN022) • From all direction • 6*10^5 photons ( : ~9MeV gamma ) are generated in LP MC 5.2 * 10^6 p.e. /PMT/sec @LP • Scaled to the final detector (surface area) 3.2 * 10^7 p.e./PMT/sec @final detector = 5.0 *10^-6 A @10^6gain PMTs were tested under the background of 10^6 ~ 10^8 p.e./sec

  8. For instance…TB0415 5*e^5 gain peak (LED ON)/peak (LED OFF) 1*e^6 gain peak (LED ON)/peak (LED OFF) 10^7p.e. per sec 1*e^6 gain (peak/sigma @LED ON)/ (peak/sigma @LED OFF)

  9. Result X: number of photoelectrons per second from LED Y: alpha peak (@LED ON) / alpha peak (@LED OFF) TB0094 TB0302 TB0568 TB0102 TB0284 TB0439 5*e5gain TB0268 TB0415 TB0239 Yasuko HISAMATSU MEG Collaboration Meeting @PSI February 2004

  10. Result X: number of photoelectrons per second from LED Y: alpha peak (@LED ON) / alpha peak (@LED OFF) 1*e6gain TB0094 TB0302 TB0568 TB0102 TB0284 TB0439 TB0268 TB0415 TB0239 Yasuko HISAMATSU MEG Collaboration Meeting @PSI February 2004

  11. Result X: number of photoelectrons per second from LED Y: (peak/sigma @LED ON) / (peak/sigma @LED OFF) 5*e5gain TB0094 TB0302 TB0568 TB0102 TB0284 TB0439 TB0268 TB0415 TB0239 Yasuko HISAMATSU MEG Collaboration Meeting @PSI February 2004

  12. Result X: number of photoelectrons per second from LED Y: (peak/sigma @LED ON) / (peak/sigma @LED OFF) 1*e6gain TB0094 TB0302 TB0568 TB0439 TB0102 TB0284 TB0268 TB0415 TB0239 Yasuko HISAMATSU MEG Collaboration Meeting @PSI February 2004

  13. X: event number Y: ADC count PMT Output vs Elapsed Time TB0239 1*10^6gain Background 1.33*10^8pe/sec 5*10^5gain Background: 8.32*10^7pe/sec ~10sec ~20sec • DAQ started 2 ~ 10 sec after the LED had been turned on. • Stable output up to 5*10^7 photoelectrons/sec Yasuko HISAMATSU MEG Collaboration Meeting @PSI February 2004

  14. Summary • 9 Al Strip Type PMTs (new type) have been tested under the high rate background environment at the university of Tokyo. • So far, for the 9 PMTs, the stability of PMT output is better than 10% under the background up to 10^7 p.e. per sec. • For the 8 PMTs out of 9 PMTs, no output deterioration under background of ~1.5*10^6p.e. per sec. • For a PMT, TB0239, the output deterioration due to the breeder circuit was found under the background of ~1.9 * 10 ^6p.e. per sec. • The background number of photoelectrons should be suppressed to 10*6 p.e./sec. • Necessary to suppress thermal neutrons to 1/10. • Neutron background measurements @piE5 using LP is recommended. Yasuko HISAMATSU MEG Collaboration Meeting @PSI February 2004

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