1. Effect of small (2G) external B-field on standard PMT for magnetic moment experiment Chunyang Ding and Zhanpei Fang

2. Photomultiplier tube (PMT) background PMTs used to detect small light pulses through photoelectric effect and signal amplification. However, very sensitive to external magnetic fields – we require fields of significant (55G) strength inside solenoid, producing <2G field on outside. Varying shielding methods (Lee 192 ) Schematic of PMT. Magnetic field most affects circled portion. (Remø)

3. Goal: test effect of magnetic field in z-axis on PMT yield rate PMT B-Field PMT Z-Axis X-Axis Y-Axis Coordinate System:

4. Motivation: Conduct tests to confirm possible ranges of B-field that PMT can withstand without damage or large yield reduction in magnetic moment experiment. Proposed Magnet Design (Nick): Copper Scintillator (Top) Solenoid PMT Note that solenoid extends beyond the CRMD in both directions. Given our knowledge of solenoids, we can determine the B-field lines to be along z-axis at an 18 degree angle to the PMT.

5. Pre-experiment setup Testing of solenoid’s B-Field at various currents using radial Hall Effect probe.

6. Experimental setup Control B-Field Test DAQ See detail: DAQ Solenoid DC Power Supply (<4A) A + - Each plate tested at different B-fields against control plate for 10 minutes. Results normalized using control plate (Converted into percent loss/gain)

7. Experimental setup (photographs)

8. Results For small B-field (<3 G), we found small variations in counting rate yield. Channel counts PMT0PMT1PMT2PMT3 CurrentGRateG G G None0.001.00.0010101 0.10.750.971.10.990.50.990.9051.02 0.21.900.931.80.971.3311.7681 0.33.100.9 2.980.962.6351.02 0.44.400.8540.933.260.93.5371 0.1-1.400.98-1.220.98-1.11.01-1.1151.01 0.2-2.300.97-2.10.98-2.010.99-1.9741.02 0.3-3.700.89 -2.950.96-2.8381.01 0.4-4.400.850.93 -3.860.94-3.7881 0.5-5.500.78 0.6-6.500.72

9. Comparison chart (single channel rate) Lee

10. Conclusion Z-Axis X-Axis Y-Axis PMT ? ? Limited scope: only z-axis measured Basic covering on PMTs No significant effect on rate of coincidence counts – possibly removing thermal noise? Shows preliminary confirmation that magnet experiment can proceed – more data may be needed for full PMT mapping.