PMT gain check at Indiana University. Test setup inside dark box LED white paper PMT # JT0298...
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Transcript of PMT gain check at Indiana University. Test setup inside dark box LED white paper PMT # JT0298...
![Page 1: PMT gain check at Indiana University. Test setup inside dark box LED white paper PMT # JT0298 channel #2 (per HPK numbering) OTHER CHANNELS MASKED WITH.](https://reader036.fdocument.org/reader036/viewer/2022082821/5697bfc51a28abf838ca6d89/html5/thumbnails/1.jpg)
PMT gain check at Indiana University
![Page 2: PMT gain check at Indiana University. Test setup inside dark box LED white paper PMT # JT0298 channel #2 (per HPK numbering) OTHER CHANNELS MASKED WITH.](https://reader036.fdocument.org/reader036/viewer/2022082821/5697bfc51a28abf838ca6d89/html5/thumbnails/2.jpg)
Test setup inside dark box
LED
whi
te p
aper
PMT # JT0298channel #2 (per HPK numbering)
OTHER CHANNELS MASKED WITH BLACK TAPE
oscilloscope
pulser
trigger in
C.R.T. Proto Pogo Pin HVB
Direct connection of anode to MMCX/cable, with 10 kΩ bleeder resistor to ground.Scope’s voltage integral / 49.75 Ω is PMT charge.
The setup Integrate charge in fixed gate, triggered by pulser that fires LED.No discriminator / no cuts. No external amplifiers.
production front board
![Page 3: PMT gain check at Indiana University. Test setup inside dark box LED white paper PMT # JT0298 channel #2 (per HPK numbering) OTHER CHANNELS MASKED WITH.](https://reader036.fdocument.org/reader036/viewer/2022082821/5697bfc51a28abf838ca6d89/html5/thumbnails/3.jpg)
integration gate 7.5 ns
blue trace is PMT charge (since t = 209 ns)
purple histogram is charge at end of the gate interval
↑ 80fC
Typical results The LED is slow of course (~3ns width), but it is cheap
![Page 4: PMT gain check at Indiana University. Test setup inside dark box LED white paper PMT # JT0298 channel #2 (per HPK numbering) OTHER CHANNELS MASKED WITH.](https://reader036.fdocument.org/reader036/viewer/2022082821/5697bfc51a28abf838ca6d89/html5/thumbnails/4.jpg)
↑ 80fC
Typical single event with signal
![Page 5: PMT gain check at Indiana University. Test setup inside dark box LED white paper PMT # JT0298 channel #2 (per HPK numbering) OTHER CHANNELS MASKED WITH.](https://reader036.fdocument.org/reader036/viewer/2022082821/5697bfc51a28abf838ca6d89/html5/thumbnails/5.jpg)
A few more details in case you want to know…• Scope set to 800 MHz bandwidth limit, 2 mV/div• Sampling at 20 GS/s (integral = 150 sample points sum)• Interpolation between sample points is turned off. (Worry is, this might
cause some unknown error in the integral.)• LED pulser rate 500 Hz• From look at single-shot acquisitions, even at very low amplitude such
that only a few % of events are not pedestal, there is a sizeable fraction of double-pulse events. Either this is afterpulsing in the PMT, or a characteristic of my LED source. In latter case, my results are contaminated with 2-photon events. Probably it doesn’t make a big difference, but this needs to be considered.
• It is useful to note that math trace does not saturate to screen display limits. As long as ADC (ch1 display) does not saturate, all the data of that event is good. I adjust ch1 gain V/div so that it very rarely saturates.
![Page 6: PMT gain check at Indiana University. Test setup inside dark box LED white paper PMT # JT0298 channel #2 (per HPK numbering) OTHER CHANNELS MASKED WITH.](https://reader036.fdocument.org/reader036/viewer/2022082821/5697bfc51a28abf838ca6d89/html5/thumbnails/6.jpg)
↑ 80fC
A double pulse event – they are not extremely rare…
![Page 7: PMT gain check at Indiana University. Test setup inside dark box LED white paper PMT # JT0298 channel #2 (per HPK numbering) OTHER CHANNELS MASKED WITH.](https://reader036.fdocument.org/reader036/viewer/2022082821/5697bfc51a28abf838ca6d89/html5/thumbnails/7.jpg)
3150 V
Old results for reference – suffers from binning artifacts
![Page 8: PMT gain check at Indiana University. Test setup inside dark box LED white paper PMT # JT0298 channel #2 (per HPK numbering) OTHER CHANNELS MASKED WITH.](https://reader036.fdocument.org/reader036/viewer/2022082821/5697bfc51a28abf838ca6d89/html5/thumbnails/8.jpg)
3150 V
Old results for reference – suffers from binning artifacts
![Page 9: PMT gain check at Indiana University. Test setup inside dark box LED white paper PMT # JT0298 channel #2 (per HPK numbering) OTHER CHANNELS MASKED WITH.](https://reader036.fdocument.org/reader036/viewer/2022082821/5697bfc51a28abf838ca6d89/html5/thumbnails/9.jpg)
3200 V
Improved analysis:• Integer waveform data stored from scope• Integer sum for charge• Binned as integer (here bin=charge/4)• As before, then fit pedestal and subtract it,
see next slide
But, fewer events here (0.5 vs. 7.5M…)
pedestal σ = 4.13 fC
![Page 10: PMT gain check at Indiana University. Test setup inside dark box LED white paper PMT # JT0298 channel #2 (per HPK numbering) OTHER CHANNELS MASKED WITH.](https://reader036.fdocument.org/reader036/viewer/2022082821/5697bfc51a28abf838ca6d89/html5/thumbnails/10.jpg)
3200 V
61900 hits (12%, I should lower LED intensity…)
mean 65.6 fC (410 k electrons)