photo-cathode

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Schematic of Liquid Argon Purity Monitor (PrM)
photo-cathode
-HV cathode
ground grid
RD
RD
cathode signal
RD 50 MW
RD
field rings
RD
quartz fiber
RD
Qanode/Qcathode e-tdrift/t
RD
RD
20 cm
RD
RD
RD
RD
RD
anode signal
RD
RD
RD
anode grid
R 110 MW
HV anode
anode
liquid argon
photodiode signal
quartz fiber
photodiode
light pulser
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ICARUS PURITY MONITOR
field rings
anode grid
ground grid
anode
photo-cathode (gold - Lab 7)
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anode signal
photodiode
cathode signal
tdrift 150 ms, Qanode/Qcathode 1
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anode signal
cathode signal
a 2.8 millisecond drift, Qanode/Qcathode 0.4
() () peaks need some correction for cathode
signal rise-time
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This plot shows signals at 1.5 ms, 1.8 ms and 2.8
ms drift-times taken with an amplifier/integrator
with longer decay time. To achieve such long
drift-times, the drift-field is lower than
required for optimal transmission across the
cathode-grid and this needs to be accounted for
in calculating effective lifetimes. The
efficiencies are 80, 65 and 50 respectively
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a plot of long drift times from another run a
week later with fresh argon. An alternative way
to calculate lifetimes would be to use just the
anode signals at different drift times, making
appropriate compensation for the different
transmission efficiencies as the drift field
changes at fixed cathode fields.
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Credits F. Cavanna, F. Arneodo et al. at LNGS
for loan of PrM E. Hahn for production of
photocathodes (TCD) W. Jaskierny for HV and
readout electronics (SSD) C. Kendziora and PAB
group for assembly of cryogenic system (MSD) J.
Krider for understanding and development of PrM
(TCD) T. Tope for design of cryogenic system
(MSD)
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