Outline Introduction Original scheme Improved scheme PMT base

Outline • Introduction • Original scheme • Improved scheme • PMT base design in Panda. X I and Panda. X II • Decoupler design in Panda. X I and Panda. X II 2

Introduction • A liquid Xenon dark matter experiment in China Jinping underground lab • In Stage I, the top PMT array has 143 Hamamatsu 1’’ R 8520 -406 PMTs, the bottom array has 37 Hamamatsu 3’’ R 11410 -MOD PMTs • In Stage II, the top PMT array will have 55 Hamamatsu 3’’ R 11410 MOD PMTs, and the bottom array will be the same 3

PMT system cabling scheme 4

Electronics and data acquisition system 5

Test Diagram for PMT base electronics Single cable – The +HV and signal share one cable, Which requires a decoupler to separate the signal from the +HV Two cables – The –HV and signal use separate cables 6

Schematic for PMT base electronics inside Here the PMT base (voltage divider) and the decoupler are integrated together 7

Ideal S 1 and S 2 signal 8

Outline • Introduction • Original scheme • Improved scheme • PMT base design in Panda. X I and Panda. X II • Decoupler design in Panda. X I and Panda. X II 9

Original Scheme inside 10

Actual S 1 and S 2 signal 11

Pspice Simulation -- AC To study the impact of the capacitance of Cd on the bandwidth of the circuit 12

Pspice Simulation -- Transient Simulate the S 2 waveform distortion when Cd changes The S 2 waveform distortion in real circuit test 13

Outline • Introduction • Original scheme • Improved scheme • PMT base design in Panda. X I and Panda. X II • Decoupler design in Panda. X I and Panda. X II 14

Improved scheme inside 15

Pspice Simulation -- AC To study the impact of the capacitance of Cd on the bandwidth of the circuit 16

Pspice Simulation -- Transient Simulate the S 2 waveform distortion when Cd changes The S 2 waveform in real circuit test 17

The reflection in S 1 signal 18

Outline • Introduction • Original scheme • Improved scheme • PMT base design in Panda. X I and Panda. X II • Decoupler design in Panda. X I and Panda. X II 19

PMT base in Panda. X I 1’’ PMT 3’’ PMT The photocathode of both 1’’ and 3’’ PMTs are connected to GND 20

PMT base in Panda. X II The 1’’ PMT base remains the unchanged, except that the resistance is fivefold. The 3’’ PMT base has major changes. The GND is moved from photocathode to dynode 5, with photocathode connected to –HV and anode to +HV. • • • The HV is about 800 V for 1’’ PMT, 1500 V for 3’’ PMT, while the voltage rating for multi-pin feedthrough is 500 V. With GND in the middle, both –HV and +HV drops to around 800 V, greatly reducing the chance of sparking in liquid Xenon. All 3’’ PMT share a fixed –HV supply, while each uses a individual +HV supply to allow gain calibration. The number of cables connected to the feedthroughs remain almost unchanged The bench test gives good S 1 and S 2 waveform 21

Outline • Introduction • Original scheme • Improved scheme • PMT base design in Panda. X I and Panda. X II • Decoupler design in Panda. X I and Panda. X II 22

Decoupler in Panda. X I A similar design following Daya Bay Experiment • Each module has 4 boards, each board has 12 channels • The +HV is supplied through 4 DB 25 connectors • Extra cables are required for connection between the connectors and the boards 23

Decoupler in Panda. X II • The schematic remains unchanged • Each module has 12 channels with separate PCB boards • The +HV for each channel is provided through SHV connector for robustness • The dimension of the metal box is designed to allow the BNC and SHV connectors soldered directly to the PCB board without extra cables 24

Thank you！ 25