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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8-in 10-in

13-in

20-inHamamatsu

R5912 R7081 R8055R3600-02

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 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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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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