Progress of MCP-PMT R&D LIU Shulin Institute of High energy Physics, Chinese Academy of Science On behalf of the Workgroup On January 13~14 For The 3rd JUNO Pre- Collaboration Meeting

Outline Objective The final technical index technical solution corresponding 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.itemtechnical index 1Type of photocathodebiaklali 2323 quantum efficiency Spectral response range （ nm ） >35% 300nm~650 nm 4545 Dimension photocathode coverage 20 inch sphere ≥95% 6Collection Efficiency (CE)>85% 7878 Gain P/V >10 7 >2 9DARK CURRENT<10nA 8” PMT; 11resistance to compression>10MPa 12lifetime20years

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 shell approaches: 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 ： SiO 2 ：~80%； B 2 O 3 ：~13%；Al 2 O 3 :~3%；Na 2 O:~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 + Kovar One 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 line C ） 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#) 29% MCP resistance(MΩ): A: MCP1: 83 MCP2:110 B: MCP1’: 74 MCP2’ 100 Dark current : anode1 and 2: ～ Signal 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!