Review of High Quantum Efficiency Large Area Photomultiplier Tubes - - PowerPoint PPT Presentation

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 2

8-in 10-in 13-in 20-in

Hamamatsu

R5912 R7081 R8055 R3600-02 R7250

Large area photomultiplier family

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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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They worked with commercial companies to improve the technology.

Ways to enhance QE?

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Impurity reduce electron escape depth ~10-20 atom layers

Anti-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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Prototypes

20-in 8-in

• 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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