Status of the ETL 9125 FLB Photomultiplier Tubes

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

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

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

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

Set up

Signal Width Rise Time Noise

Working High Voltage • HV required for average signal ~10 m. V # of PMT’s High Voltage (k. V)

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

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

Noise Amplitude • Noise between signals # of PMT’s Noise (m. V)

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

Initial Conclusions: • Original experiment was • Consistent rise time designed for Cherenkov (~2 ns) radiation (few • working HV ~1. 15 k. V photoelectron • Signal width~12 ns detection) • Out of 45 tested, found one with no signal and 1 • Frosty PMT front window unusable due to noise • Require positive HV Next: Develop a streamlined procedure for testing up to 16 PMT’s at a time, more results