Light Transport and Detection with VLPCs D. Dutta TUNL/ Duke University MEP group.
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Transcript of Light Transport and Detection with VLPCs D. Dutta TUNL/ Duke University MEP group.
Light Transport and Detection with VLPCs
D. Dutta TUNL/ Duke University
MEP group
Current Cell Design
Current Design for Light Transport
C. R. Brome et al., PRC 63, 055502 (2001)
Visible Light Photon Counters
VLPC's are arsenic doped silicon diodes,designed to convert single photons in to many thousands of electrons with high quantum efficiency
Detects single photons Operate at a few degrees Kelvin Quantum efficiency ~80% Insensitive to magnetic fields High gain ~40 000 electrons per converted photon
Visible Light Photon Counters
Excellent individual photoelectron resolution SVX Readout (ADC Counts) of Cassette A (T=8.2K, V=7V)
0
100
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400
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600
40 60 80 100 120 140 160 180 200Integrated Charge
Low gain dispersion ~0.13 p.e.
0
200
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1000
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1400
0 10 20 30 40 50 60 70 80
Gain (in Thousands)
Fre
qu
en
cy
Visible Light Photon Counters
Ideal operating temperature ~ 6.5 K
S. Takeuchi et al., Appl. Phys. Lett, 74, 1063 (1999)
High gain ~ 20,000- 60,000
VLPC Applications
Extensively used in Scintillating Fiber Trackers @ Fermilab
Fermilab has 10+ yrs of experience and expertise
VLPC Applications
Alternative Cell Design
d
Studies by nEDM Collaborators
Wavelength shifting fiber based detector was tested by the Doyle group for their neutron traps.
D. N. McKinsey et al., NIM A 516,475 (2004)
QRCeSYFN Sll att /1/)1(
detector of eff. quantum
coating ofty reflectivi
fiber oflength
fiberfor eff. conv.
fiberby covered surface offraction
eff. converv. TPB
yieldphoton EUV
Q
R
l
C
S
F
Y
Studies by nEDM Collaborators
D. N. McKinsey et al., NIM A 516,475 (2004)
But acrylic tube based light transport detected ~5.5 p.e. in the neutron lifetime measurement cell , due to more complicated & less efficient optics. => optics is 3% efficient not 31%
P. R. Huffman et al., Nature 403, 62 (2000).C. R. Brome et al., PRC 63, 055502 (2001).
Comparison with Current Design
QRCeYFTN Sll
Acrylicatt /1/
detector of eff. quantum
coating ofty reflectivi
fiber oflength
fiberfor eff. conv.
Acrylic of eff.sport light tran
fiberby covered surface offraction
eff. converv. TPB
yieldphoton EUV
Q
R
l
C
T
S
F
Y
Acrylic
old new
(1-S) = 0.88 S = 0.8
2.4 m 8.5 m
~ 1.1
~ 0.17
0.19 0.85 ~ 4.5 ~ 4
0.25 0.88 ~ 3.5
-- 0.7 ~ 0.7 ~ 0.4
net
Optics 0.4 0.8 ~ 2.0
Expected Performance
Acrylic tube+ PMT Acrylic tube+ WLSfiber+ VLPC
# of photonscollected in cryo cell
Efficiency of transport to detector
Quantum Eff.
# of photo-electrons
N 0.4* N /4
3% 80%
20% 80%
0.064*N 0.006*N
Relevant Studies by nEDM Collaborators
The Doyle group also attempted to test wavelength shifting fiber based detector with VLPCs instead of PMTs.
J. S. Butterworth et al., Private Communication
“Failed to get the pre-amp board working, it was too noisy.” - James Butterworth
VLPC, wavelength shifting fiber, pre-amplifier board and biasing circuit borrowed from Fermilab.
New Readout MethodUse a ultra low-noise amplification scheme developed for single photon counting experiments
J. Kim et al., Appl. Phys. Lett, 70, 2852 (1997) S. Takeuchi et al., Appl. Phys. Lett, 74, 1063 (1999)
Pros & Cons
• Shorter pathlength from cell to detector
• No breaks in the light guide.
• lower backgrounds
• lower noise
• Discrimination of gammas with afterpulses may not be feasible
Cost Estimates
• VLPC + Readout: $3000/channel x 16 channels = $48,000
• Temperature controller+ Fiber + Misc: $2,000
Cost per cell : $50,000 Net cost: $100,000
Test Setup at Duke
Status of the Duke Project
Dewar, dTPB coated acrylic, Am source, WLS fiber, VLPC chips have been obtained.
The low noise readout circuit is being built. Special order cold amplifier from NFE Japan has arrived.
Mary Kidd ( 1st yr Grad student) worked on designing parts of the Duke test setup last summer. Alan Ye will take over the project as the he-3 relaxation study at Duke wraps up.
A trip to Fermilab, to learn on their test setup and to get WLS fiberspliced to clear fiber, is being planned ( delayed due to broken cryostat at Fermilab, waiting for repairs.)
241
Fermilab Test Setup
10 60s2 ms s
VLPC biasCryostat
PreamplifierBoard
Preamppower
HP 8112APulse Generator
LED
VLPC
Delay
Gate
input
LeCroy2249A
Transformer
PC
ITC4
Background
SignalHP 8112APulse Generator
LED zz
Conclusions
10 60s2 ms s
• WLS Fiber + VLPC based cell maybe more efficient in transporting and detecting scintillation light.
• New design needs to be tested and must be proven
• Tests under way at Duke should help decide.