PandaX 实验中的电子学概述 郭国栋

Outline Introduction Original scheme Improved scheme PMT base design in PandaX I and PandaX II Decoupler design in PandaX I and PandaX II 2

Introduction 3 A liquid Xenon dark matter experiment in China Jinping underground lab In Stage I, the top PMT array has 143 Hamamatsu 1’’ R PMTs, the bottom array has 37 Hamamatsu 3’’ R11410-MOD PMTs In Stage II, the top PMT array will have 55 Hamamatsu 3’’ R MOD PMTs, and the bottom array will be the same

PMT system cabling scheme 4

Electronics and data acquisition system 5

Test Diagram for PMT base electronics 6 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

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

Ideal S1 and S2 signal 8

Outline Introduction Original scheme Improved scheme PMT base design in PandaX I and PandaX II Decoupler design in PandaX I and PandaX II 9

Original Scheme 10 inside

Actual S1 and S2 signal 11

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

Pspice Simulation -- Transient 13 Simulate the S2 waveform distortion when Cd changesThe S2 waveform distortion in real circuit test

Outline Introduction Original scheme Improved scheme PMT base design in PandaX I and PandaX II Decoupler design in PandaX I and PandaX II 14

Improved scheme 15 inside

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

Pspice Simulation -- Transient 17 Simulate the S2 waveform distortion when Cd changesThe S2 waveform in real circuit test

The reflection in S1 signal 18

Outline Introduction Original scheme Improved scheme PMT base design in PandaX I and PandaX II Decoupler design in PandaX I and PandaX II 19

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

PMT base in PandaX II 21 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 800V for 1’’ PMT, 1500V for 3’’ PMT, while the voltage rating for multi-pin feedthrough is 500V. With GND in the middle, both –HV and +HV drops to around 800V, 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 S1 and S2 waveform

Outline Introduction Original scheme Improved scheme PMT base design in PandaX I and PandaX II Decoupler design in PandaX I and PandaX II 22

Decoupler in PandaX I 23 Each module has 4 boards, each board has 12 channels The +HV is supplied through 4 DB25 connectors Extra cables are required for connection between the connectors and the boards A similar design following Daya Bay Experiment

Decoupler in PandaX II 24 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

Thank you ！ 25