Документ взят из кэша поисковой машины. Адрес оригинального документа : http://antares.sinp.msu.ru/docs/MAM%202011%20-%20Volodya.pdf Дата изменения: Mon Dec 16 17:03:27 2013 Дата индексирования: Thu Feb 27 20:26:52 2014 Кодировка:

Afterpulses measurements for the ANTARES PMT
Vladimir Kulikovskiy INFN Genova / SINP MSU 07/06/2011

Afterpulses measerements, V.Kulikovskiy, INFN Genova / SINP MSU

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Spurious pulses

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Afterpulses type 1.
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1a due to escaped e1b due to escaped

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2) afterpulse type 2. Due to ionization. 3) late pulse, due to e- reflection 4) pre-pulse, photo-effect on the dynode
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Afterpulses measerements, V.Kulikovskiy, INFN Genova / SINP MSU


Setup
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Laser length - 439nm SPE mode (1hit/100) Laser and PMT pulses in coincidence 1GHz digitizer 16µs after laser sync out Trigger to the channel0, because external trigger has 70MHz Logic unit & digitizer =0.67ns

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PMT light
Sync out

Discrim.

CAEN V1731

Laser HP PLP10 ( 440 nm)
Afterpulses measerements, V.Kulikovskiy, INFN Genova / SINP MSU 03/10


Signal

Pulse integration: from Tl-5ns till Tr+10ns Tl and Tr are times where threshold of 10mV is passed Tl Tr

2p.e. contribution is negligible. Left distortion due to integration systematic error for the small hits? Or low charge of the prepulses?

Afterpulses measerements, V.Kulikovskiy, INFN Genova / SINP MSU

04/10


Pre-pulses & late pulses.
Hit time since beginning of the frame

28% + 2.5% =1.2ns

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Random noise plateau Two estimations of the delayed pulses
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Afterpulses measerements, V.Kulikovskiy, INFN Genova / SINP MSU


Afterpulses type 1
NB: afterpulse has always a main pulse before (main pulse + afterpulse). Prepulse and delayed pulse ­ are the "main" pulses (one pulse only).

main pulse

afterpulse

1.0%.

Afterpulses measerements, V.Kulikovskiy, INFN Genova / SINP MSU

06/10


Afterpulse type 2

0.8%

0.1% type 2 after-pulses with charge 6

GRB files analysis of pulses with charge 6. 0.1% of them have charge 6 It is in consistency with the assumption: "high charge pulses are mostly due to the afterpulses".

Afterpulses measerements, V.Kulikovskiy, INFN Genova / SINP MSU

07/10


Dark current spectrum (no laser)
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Comparison to the Saclay measurements with the bare PMT 1/3 p.e. threshold for the discriminator 25ns charge integration 10ns dead time for the token to another ARS 1.3kHz
2.5% (33Hz) 0.25% 0.05% dark noise have a pulse before

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Afterpulses measerements, V.Kulikovskiy, INFN Genova / SINP MSU

08/10


Conclusions
Pre-pulses Delayed pulses Afterpulses t1 Afterpulses t2
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<<1% 2.5%(28%) 1.0% 0.8%

Setup was improved (better time sampling, problem of the first hit time jitter solved). Measurements with a µ-metal cage could decrease number of delayed pulses... Successful comparison with a Saclay measurements on the dark current. Afterpulses give an explanation for the hits with an high charge observed in ANTARES. Paper with description in the CDS: ANTARES-OPMO-2011-002.

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Crosscheck with another laboratory is WELCOME! Include TTF from slide 5 to MC ­ see Aart's talk tomorrow.
Afterpulses measerements, V.Kulikovskiy, INFN Genova / SINP MSU 09/10

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Afterpulses measerements, V.Kulikovskiy, INFN Genova / SINP MSU

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