Status of the ETL 9125FLB Photomultiplier Tubes

Steve BacheUNC-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

RiseTime

Noise

Working High Voltage• HV required for average signal ~10mV

High Voltage (kV)

# ofPMT’s

Signal Widths

• Full signal widths (in ns)

Width (ns)

# ofPMT’s

Rise Time

• Rise time from 10% to 90%

Rise Time (ns)

# ofPMT’s

Noise Amplitude• Noise between signals

Noise (mV)

# ofPMT’s

Coincidence Rates• Coincidence proportions at lowest threshold• Related to ionic feedback, i.e. air leakage

Coincidence / Total count

# ofPMT’s

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