1. Status of the ETL 9125FLB Photomultiplier Tubes Steve Bache UNC-Wilmington

2. Parameters Hall D Pair Spectrometer requires 20 PMT’s (16 for detector, 4 spare) 45 out of ~3000 I have checked so far – *Visual inspection – *Working High Voltage – Signal width – *Rise time – Noise – Coincidence related to possible ion feedback *highest importance

3. Visual Inspection All PMT’s had “frosty” front window

4. Set-up -High voltage was applied to 4 PMT’s at a time in a covered, black box -No additional source and scintillator are attached -Used oscilloscope for all timing measurements -Checked coincidence rate at lowest threshold, also on scalars

5. Set up

6. Signal Width Rise Time Noise

7. Working High Voltage HV required for average signal ~10mV High Voltage (kV) # of PMT’s

8. Signal Widths Full signal widths (in ns) Width (ns) # of PMT’s

9. Rise Time Rise time from 10% to 90% Rise Time (ns) # of PMT’s

10. Noise Amplitude Noise between signals Noise (mV) # of PMT’s

11. Coincidence Rates Coincidence proportions at lowest threshold Related to ionic feedback, i.e. air leakage Coincidence / Total count # of PMT’s

12. Initial Conclusions: Consistent rise time (~2ns) working HV ~1.15kV Signal width~12 ns Out of 45 tested, found one with no signal and 1 unusable due to noise Original experiment was designed for Cherenkov radiation (few photoelectron detection) Frosty PMT front window Require positive HV Next: Develop a streamlined procedure for testing up to 16 PMT’s at a time, more results