Progress of MCP-PMT R&D

LIU ShulinInstitute of High energy

Physics, Chinese Academy of Science

On behalf of the Workgroup On January 13~14 For The 3rd JUNO Pre-

Collaboration Meeting

OutlineObjective The final technical indextechnical solutioncorresponding technological approaches obtained results of 8’’ MCP-PMT(31#)Next plan

Objective • JUNO Requirements: – Large detector: >10 kt LS– Energy resolution: 2%/E 2500 p.e./MeV 3 %/E 1100 p.e./MeV

• Ongoing R&D:– Low cost, large area , high QE, low background , high

photocathode coverage , resistance to compression and high reliability “PMT”

• New type of PMT 20” UBA/SBA photocathode PMT is also a possibility

The final technical index No. item technical index

1 Type of photocathode biaklali

23

quantum efficiencySpectral response

range （ nm ）

>35%300nm~650nm

45

Dimensionphotocathode coverage

20 inch sphere≥95%

6 Collection Efficiency (CE) >85%

78

GainP/V

>107

>29 DARK CURRENT <10nA

10 TTS <10ns@ 8” PMT; <20ns@20’’PMT

11 resistance to compression >10MPa

12 lifetime 20years

technical solution

Our Plan:（ 1 ） Low background and low expansion coefficient glass

shell

（ 2 ） High photon detection efficiency photocathode

（ 3 ） Single photoelectron detection system

（ 4 ） Reliability Engineering

corresponding technological approaches:

（ 1 ） 20’’ glass sphere shellapproaches: GG-17 glass formula （ Pyrex ） + Low radioactive background raw materials + artificial fine blowing process + intermediate sealing glass + Kovar

（ 1.1 ） GG-17 glass formula and performance

a) Our GG-17 glass the chemical composition ：

SiO2 ： ~80% ； B2O3 ： ~13% ； Al2O3:~3% ；Na2O:~4%

b) expansion coefficient :(33±1)×10-7/℃; c) index of refraction:1.47 d) transmittance

(1.2) Low radioactive background raw materials

(1.3) artificial fine blowing process

Inspection and acceptance

(1.4) intermediate sealing glass + KovarOne section

Three sections

Mul-section

20’’ GG-17 Glass shell with kovar

stress measurements

Superb water pressure-resistance

1MPa 24h OK

（ 2 ） High photon detection efficiency photocathode

（ 2.1 ） Using transmission photocathode + reflection photocathode

~ 4π viewing angle!

（ 2.2 ） Antireflection film for transmission photocathode

As=73% (n=2.4,d=30nm)

（ 3 ） Single photoelectron detection system

(3.1) design of focusing electrode lets most of photoelectron enter the surface of MCP

For 8’’ MCP-PMT Good design of focusing electrode + appropriate distribution of voltage can ensure 95% photoelectrons enter the surface of MCP

For 20’’ MCP-PMT

NO focusing electrode

Good design of focusing electrode + appropriate distribution of voltage can ensure 98% photoelectrons enter the surface of MCP

(3.2) excellent detector of MCPs

(3.3) no ringing of anode

A ） Metal mesh+ anode plate B ） microstrip lineC ） The conical anode

Signal variation of The anode before and after improvement

before improvement

after improvement

Voltage of each MCP is 800V ， gap: 250 μm ， Vg=50V ， voltage of anode is 300V

obtained results of 8’’ MCP-PMT(31#)

QE @410nm: 29%MCP resistance(MΩ): A: MCP1: 83 MCP2:110 B: MCP1’: 74 MCP2’ 100Dark current : anode1 and 2: ～ 3nA@2210VSignal of dark noise :

Single photoelectron PHD

Uniformity of QE

Gain ~voltage of MCPs

A Group

B Group

Next plan

（ 1 ） Continuous Improvement QE（ 2 ） Optimization process of MCP outgas（ 3 ） R&D of 20’’MCP-PMT （ 4 ） Study on the Reliability

Thanks for your attention!Any comment and suggestion are welcomed!