Gain and Quantum Efficiency of a Cold Photomultiplier
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Transcript of Gain and Quantum Efficiency of a Cold Photomultiplier
Gain and Quantum Efficiency of a Cold Photomultiplier
Hans-Otto MeyerIndiana University10/7/06
run a Hamamatsu R7725 @ 4 K
determine minimum heat load
measure quantum efficiency and gain vs T
… and vs frequency
The Plan
cold warm
R7725Monitor PM
thermometer
base part 1
opt. fiber
base part 2
light pulser
light splitter
Enclosure(evacuated, submersed in cryo-liquid)
existing at this time (9/27/06)
warmPM under testBurle 8850
Monitor(8575)
base
opt. fiber
light pulser
light splitter
data acquisition
Light source
pulse width: ~10 ns
λ = 467 nmLED (LITEON LTST-C150)
Splitter(imperfect splice in clear epoxy)
mounted LED
n-channelMosfet
setup
ne = 3.6 ne = 2.0
ne = 1.1 ne = 0.52
ne = 0.034ne = 0.10
red curve:
peak index
21
21
2
)(
1 2
),()(
k
xkxx
k
e ek
nkpxG
xx ,, 11 determined once and for all
ne (avg. number of photoelectrons) from
fitQuantum efficiency: from ne
PM gain: from peak locations
measure quantum efficiency
ne= 1.055gain ≡ 1.0
ne= 1.053gain ≡ 1.6
ne= 1.055gain ≡ 2.5
measure gain
changing PM HV:
gain changes, but ne stays the same
photoelectrons vs monitor signal
0.01
0.1
1
10
10 100 1000 10000
monitor centroid (channels)
ave
rag
e n
um
be
r o
f p
ho
toe
lect
ron
s
monitor
The monitor signal is proportional to the light emitted from the splitter
+HV signal
cold
warmlong leads
R7725 split base
How is performance affected?Ho to fix it?
Radiant heat transfer between concentric cylinders
length of cylinders L 0.2m Stephan Boiltzmann 5.67108
W
m2
K4
inner radius r1 0.025m
outer radius r2 0.035m
inner emissivity 1 0.8 inner temperature: varying T1 = T
outer emissivity 2 0.8 mass of inner cylinder (steel) Ms 0.3kg
outer temperature T2 4K
1 10 100 1 1030.01
0.1
1
10
100
1 103
cooling rate
T (K)
cool
ing
rate
(K
/hou
r)
1 10 100 1 1030
50
100
150
time for cool-down
final temperature (K)
tota
l tim
e (h
ours
)
T2
T
cooling
Project is on hold