1. Large Area MCP-PMT and its Application at JUNO
Yifang Wang
For the MCP-PMT development group
Institute of High Energy Physics
NeuTel 2017, Venice

2. The JUNO Experiment Key Issue：How to get sE < 3%/√E  1200 PE/MeV ?
Vito’s talk
Yangjiang NPP
Taishan NPP
Daya Bay NPP
Huizhou NPP
Lufeng NPP
53 km
Hong Kong
Macau
Guang Zhou
Shen Zhen
Zhu Hai
2.5 h drive
Daya Bay
JUNO
20 kt LS
Previous site candidate
J. Phys. G 43: (2016) (arXiv: )
Talk by YFW at ICFA seminar 2008, Neutel 2011;
Key Issue：How to get sE < 3%/√E  1200 PE/MeV ?

3. How to Get Enough Photons
KamLAND
JUNO
Needed gain
Light yield
250 p.e./MeV
1200 p.e./MeV 5
Photocathode coverage
34%
75%
2.2
1.5g/l PPO
3-5g/l PPO
1.5
Attenuation length/R
15 m/16m
25m/35m
~ 0.8
PMT QE*CE
20%*60% ？
~ 2
Where to get a factor of 2 increase for
Quantum Efficiency(QE)* Collection Efficiency(CE) ?

4. New type of PMTs under-development in ~2009
Reflective photocathode by UC Davis, Higher QE
Dynode replaced by Scintillator/APD
Large Area picosecond photo detectors(LAPPD)
Hamamatsu Production：X-HPD， 8” and 13”; 18KV HV

5. High QE PMTs in ~ 2008 SBA/UBA/EBA/GaAsP Good enough QE for PMTs ?
35%/45%/55%/50%
Good enough QE for PMTs ?
Good enough for 20” PMTs ?
Good enough price ?
2018/6/17

6. Our Proposal: MCP-based PMTs
Advantages:
Higher QE: transmmissive photocathode at top + reflective photocathode at bottom
High CE: less shadowing effect
Easy for production: less manual operation and steps
Good MCP production capabilities in China
Disadvantages:
Higher cost ?
No one knows how to make it

7. First Attempt: A Prototype by 2011
Partnership with a research institute
Prototypes: signal barely seen, low gain, low QE, high noise, …
no hope for production, …
5” MCP-PMT
Spectral Response
300~ 650nm
Anode Dark Current
< 100nA
Cathode luminous sensitivity
> 50 uA/Lm
Gain
> 1.0*105

8. New Collaboration Established
1/3 MCP of the world
Setup groups
Design & simulation
Photocathode & metal film
MCP production & pre-processing
Glass bulb & low radioactive backgrounds
Other components
Assembly & vacuum sealing
Testing & evaluation
Setup roadmap
quit very soon
5”(8”)
Prototype
20”
Prototype
Production
Bylaws, management, …
Weekly phone meetings
Bi-monthly general meeting
Design
2009
2010~2013
2013~2015
2016~2019

9. Design and Simulation 8” and 20” PMTs Bulb Shape & MCP position
Voltage setting and optimization
Focusing field shape，location and voltage setting
Collection efficiency, timing, geomagnetic field effect, etc.
Collection efficiency

10. MCP Production & Pre-processing
MCP parameters: size, hole diameter & depth(detector type), bulk resistance,etc.
Surface treatment & electron cleaning
Electrode: depth, shape, materials, …
Low cost: production process, quality control, selection criteria, …
Microchannel Plate response Simulation

11. Photocathode Art: thin layers of K-Cs-Sb
Alkali source: materials, shape, evaporation process, etc.
Vacuum equipment: monitoring and control during production
Quality: consistency, uniformity, …
QE ~
Cathode current  QE

12. Glass bulb, Transition Section and Kovar
Skilled workers: manual blowing
Glass: hardness, thermal expansion, K free, water compatible, etc.
Oven, welding with Kovar, …
Low radioactive backgrounds: material, process, environment, …
Mechanical design and Shape optimization

13. MCP-PMT Assembly Process

14. Prototypes and Failures
After a few years with a lot of troubles, we start to get prototypes:
Photocathode, MCP assembly, vacuum sealing,…
Reasonable signals & good
properties
But major issues:
Gain of MCPs are not the same
cannot have two independent
MCPs giving output signals
CE very much dependent on
Incident angle
New focusing field
Too low CE
Surface treatment
Dead bodies

15. New Design & Improved CE
Horizontal collection surface: one output
New surface treatment of MCP: CE increased from ~60% to ~100%
Better than dynode which has a 10% loss due to the field mesh
Such MCP-PMT has a better CE but worse timing
Dynode: A mesh over the dynode, CE ~ 90%

16. Tests
Mechanical: Glass bulb under pressure, welding with Kovar, vacuum, compatibility with water, etc
MCP Aging
Collection efficiency: angular dependence
radioactive backgrounds
30% Gain  500 yrs
Angular response
Component
WT%
238U (Bq/kg)
232Th (Bq/kg)
40K (Bq/kg)
Glass bulb
89.48
0.87/0.78
0.38/0.34
0.2/0.18
Transition section
2.82
1.74/0.05
0.45/0.01
10.1/0.28
Others
7.7
Negligible
Total
100
~0.83
~0.35
~0.46
Requirement
0.93
0.30
0.96

17. Performance QE & uniformity Dark rate After pulse Min:24.5%; Max:29%
Average:26.5%

18. Main Difference with Hamamatsu
1ns
spread
6ns
spread
TTS at top
~90%
~100%
Relativity detection efficiency:
Hamamatsu R12860
MCP-PMT

19. reflection+ transmission
Performance Summary
Characteristics
unit
MCP-PMT（IHEP）
R12860(Hamamatsu)
Electron Multiplier --
MCP
Dynode
Photocathode mode
reflection+ transmission
transmission
Quantum Efficiency（400nm） %
26 (T), 30 (T+R)
30(T)
Relativity Detection Efficiency
~ 110%
~ 100%
P/V of SPE
＞ 3
TTS on the top point ns
~12 ~3
Rise time/ Fall time
R~2 , F~10
R~7 , F~17
Anode Dark Count Hz
~30K
After Pulse Time distribution us
4.5
4, 17
After Pulse Rate 3 10
Glass
Low-Potassium Glass
HARIO-32

20. PMT Purchasing of JUNO
Dec.16, 2015
Characteristics
unit
MCP-PMT（NNVC）
R12860（Hamamatsu）
Detection Efficiency (QE*CE*area) %
27%, > 24%
P/V of SPE
3.5, > 2.8
3, > 2.5
TTS on the top point ns
~12, < 15
2.7, < 3.5
Rise time/ Fall time
R~2, F~12
R~5,F~9
Anode Dark Count Hz
20K, < 30K
10K, < 50K
After Pulse Rate
1, <2
10, < 15
Radioactivity of glass
ppb
238U:50
232Th:50
40K: 20
238U:400
232Th:400
40K: 40
15k MCP-PMT (75%) from NNVT
5k Dynode(25%) from Hamamatzu
By Scaling PMT Spec for LS quantity to reach 6year 
Decision based on risk, price, performance merit for physics

21. Mass Production at NNVT

22. Pilot Production Production equipment all in hands
Training workers, tuning equipment
All parts in hand
A few hundreds of products
Gain vs HV
first batch by workers
CE*QE
Radioactivity of glass
P/V

23. Summary Driven by JUNO, we develop a new type of PMTs based on MCP
New design, new technology
Potentially better performance than PMTs based on Dynode
Its performance satisfied JUNO requirements
Based on a model to maximize Physics*Price/Risk, JUNO signed contract to purchase ¼ PMTs from Hamamatsu and ¾ from NNVT
Mass production started at NNVT & Hamamatsu for JUNO
We started from a wrong design but ended up a good product

24. PMT Selection Maximize: Sum(Scores*S*F)
Scale PMT Spec for LS quantity to reach 6year QE
Dark rate
Radioactivity
After pulsing
TTS
Unit Price
Safety factor(S)
Award fraction(F) x, 1-x
(PQE)A=(ε-27)×3.518
(PDN)A=(20-DN)×0.118
Maximize:
Sum(Scores*S*F)
30×(2.5-P)
（1-0.15x）, (1-0.15(1-x))