SPHE test of replaced PMTs

To account for possible changes over time in our lab test setup for single photoelectron gain measurements (i.e., a new Caen V792 QDC, etc.), a brand new never used before PMT has been measured again and compared with a similar measurement from a year ago. Both old and new gain values (2.71 and 2.87 million) are reasonably close to each other and reflect the uncertainty of the measurement.

PMT FA0367 : brand new
Initially measured: June 2020
Old gain: 2.71     New gain: 2.87

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Next, 4 replaced PMTs have been re-measured. The first 2 PMTs were originnaly measured with Caen V792 QDC in 2017 and used in TOF-II. The next 2 PMTS were orginnally measured with Caen V256 QDC in 2012 and used in the original TOF. By the way, they were on the same scintillator bar.

PMT WA0440 : TOF-N-20
Initially measured: October 2017
Old gain: 4.22     New gain: 3.20

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PMT WA0462 : TOF-S-21
Initially measured: October 2017
Old gain: 3.12     New gain: 1.84

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PMT ZQ2603 : TOF-DW-24
Initially measured: Novermber 2012
Old gain: 3.79     New gain: 1.89

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PMT ZQ2635 : TOF-U-24
Initially measured: Novermber 2012
Old gain: 3.62     New gain: 1.35

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Summary

Old PMT	Position	Original gain	Current gain			New PMT	Original gain
WA0440	N-20	4.22	3.20			FA0400	6.00
WA0462	S-21	3.12	1.84			FA0283	7.48
ZQ2603	DW-24	3.79	1.89			FA0396	5.77
ZQ2635	U-24	3.62	1.35			FA0398	7.16

19 remaining spare PMTs are in the range of gains 2.5-5.5 mln, including 11 ones which are below 3.5 mln.