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PMT Test @ Univ. of Tokyo

Yasuko HISAMATSUICEPP, The University of Tokyo

MEG　 VRVS meeting Jan. 20th, 2004

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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.)

• 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 HISAMATSU Jan. 20th, 2004 MEG VRVS Meeting

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PMT Test @ Univ. of Tokyo• Set up

PMT (Al Strip Type)

TB0094 TB0102 TB0286 TB0302

(now being analized…)

TB0284 TB0568 PMT

PMT

Alpha source(241Am )

LED

Liq. Xe

5.5MeV alpha peak

ADC channel

Yasuko HISAMATSU Jan. 20th, 2004 MEG VRVS Meeting

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Condition and Procedure

• alpha source : ~200Hz, • LED pulse height: 500p.e. ~ 12000p.e. per event

pulse shape: ~10nsecrate: 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 Jan. 20th, 2004 MEG VRVS Meeting

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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 HISAMATSU Jan. 20th, 2004 MEG VRVS Meeting

Ratio of alpha peak with LED ON to one with LED OFF

Number of photoelectrons from LED per second

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For instance…TB03025*e^5 gainpeak (LED ON)/peak (LED OFF)

1*e^6 gainpeak (LED ON)/peak (LED OFF)

1*e^6 gain(peak/sigma @LED ON)/(peak/sigma @LED OFF)

10^7p.e. per sec

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Result

5*e5gain

TB0094 TB0102

TB0268 TB0302

X: number of photoelectrons per second from LED

Y: alpha peak (@LED ON) / alpha peak (@LED OFF)

Yasuko HISAMATSU Jan. 20th, 2004 MEG VRVS Meeting

?

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Result

TB0268

TB0094 TB0102

TB0302

1*e6gainX: number of photoelectrons per second from LED

Y: alpha peak (@LED ON) / alpha peak (@LED OFF)

Yasuko HISAMATSU Jan. 20th, 2004 MEG VRVS Meeting

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Result

TB0302

TB0094TB0102

TB0268

1e6gainX: number of photoelectrons per second from LED

Y: (peak/sigma @LED ON) / (peak/sigma @LED OFF)

Yasuko HISAMATSU Jan. 20th, 2004 MEG VRVS Meeting

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Schedule

DAQ• Jan. 21-22 2PMTs• Jan. 27-28 2PMTs

• 10 PMTs will be tested and analized before the meeting at PSI.

Yasuko HISAMATSU Jan. 20th, 2004 MEG VRVS Meeting

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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 HISAMATSU Jan. 20th, 2004 MEG 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.