review of high quantum efficiency large area
TRANSCRIPT
Review of High Quantum Efficiency Large
Area Photomultiplier Tubes
Jinping Solar Neutrino Workshop,
LBNL, June 2014
Jianglai Liu
Shanghai Jiao Tong University
2014/6/10
Disclaimer: I am not personally involved in most of the work
presented here. This is a review with publically available info.
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KamLAND Daya Bay
MILAGRO
For large scale and photon-hungry experiments, large area
photomultipliers are still by far the most economical and
mature technology
PMTs and Large Detectors
JUNO
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Photocathode
Quantum efficiency = probability of a photon converted to a electron in
the vacuum (free from the cathode)
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Photocathode materials
Many options: Bialkali is a popular type (QE curve matches the LS and
NaI emission spectrum) and its low thermal noise, Sb-Rb-Cs/Sb-K-
Cs/Sb-Na-Cs
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Impurity reduce electron escape depth
~10-20 atom layersAnti-reflective layer
Ways to enhance QE
Enhance e escape
length (some experts
argue 99.9% is
sufficient)
10-20 atomic layer
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Coating on the glass
Likely to be difficult for large PMTs with stringent chemical compatibility
requirements
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Winston cone
• Smart optical “trap”
• Considered for
LBNE to enhance
the light collection
• Simulation with
water indicate 50%
gain
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Recent development (commercial)
• Photonics reported similar high QE PMTs as well
• Improvements likely lie within the points Mirzoyan et al. stressed
Hamamatsu
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• 10”-20” considered by
LBNE
• Hamamatsu high QE
versions available.
• Not aware if ET and
Photonics high QE
version available for
large area
10”
20” 12”
8”
Top commercial candidates
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Dimensions of R7081 (Hamamatsu datasheet)
Quantum efficiency of a SBA and a standard R7081 (Hamamatsu internal communication)
Hamamatsu Super BiAlkali (SBA) photomultipliers
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• IceCube (A. Karle)
• NEMO (E. Leonora)QE SBA increase @ 410 nm [%]
SBA PMT 1 37.7
SBA PMT 2 32.1
SBA PMT 3 39.7
SBA PMT 4 36.1
Two groups have consistent results: QE up 30-40%, dark noise up (<2 kHz to 3
kHz), afterpulsing worsen (4%->11%)
R7081-02 (10-in)
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Brack et al., NIMA 712 p162-173 (2013)
• The dark noise shows a similar trend.
• The afterpulse does not appear to change
between the normal and HQE version.
R11780 (12-in)
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• HyperK collaboration is making good progress on the 20-in
PMTs (Y. Suda, TIPP’14)
• Clearly the HQE version of the 20” PMTs are
better than the old SK tubes.
• The collaboration is also working on alternative
hybrid PMT solution.
R3600 (20-in)
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Aside from mysterious cathode alchemy, usual complaints about
are
• limited incident angle coverage
• complicated dynode structure (expensive)
• low PE collection efficiency (70%)
Several promising alternatives
• Hybrid photo-diode (HPD)
• MCP-PMT
Alternative approach
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E. Lorenz and D. Ferenc
Quasar370, used
in Lake Baikal
underwater
neutrino telescope
in 90th (B. K.
Lubsandorzhiev)
Hybrid phototubes with luminescent screen
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• Replace the dynode with an avalanch diode
• Pros:
• No dynode so simpler structure = cheaper
• High first stage gain = best SPE resolution
• Shoft drift length = good timing
• Cons:
• HV high (8 kV)
• Preamp needed since the gain is ~105
Y. Suda, TIPP’14
5 mm (target
20 mm)
Hybrid APD-PMT
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20-in HPD prototype with 5 mm AD
• HPD timing and SPE response very good compared to regular PMTs
• HyperK expects to decide photon sensor technology by 2016
20-in HPD
Y. Suda, TIPP’14
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Other HPD examples
QUPID, Katsushi Arisaka, H. Wang
Less metal materials from dynodes and stems less
radioactivity, critical for DM searches
Not widely used in DM experiments yet.
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Used in MAGIC II
M. Teshima
GaAsP emerges as a strong HQE cathode material, but expensive
and not available for large area
HPD with very high QE: GaAsP cathode
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Transmission and reflective photocathode
• Cathode: can we make use of the reflective PE as well?
• Dynode structure is a blockage to the photoelectrons
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• Effort led by Y. F. Wang, a collaboration between IHEP and commercial
companies in China
• One photosensor option for the JUNO Experiment.
New type of MCP-PMT
S. Qian, NDIP2011
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Operating at 2 kV, with 105 gain
Multichannel plates
Commercially available in
imaging/vision business
S. L. Liu,
TIPP’14
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8-in test results
• Much progress in the past a
couple of years
• Results of MCP-PMT is
encouraging
• The collaboration will make a
decision on the photosensor
technology in not-to-far future
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Summary
• HQE crucial for large scale experiments:
• more lights more physics potential
• brings the cost down
• Commercial HQE option, Hamamatsu in particular, are
available and mature. QE of ~35% consistently reported
for 10”-20” tubes
• There are strong incentives for alternative hybrid PMTs
(HyperK, JUNO). Such products might be available in few
years time scale.
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