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S30XL-LESA/LDMX
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We observed that there was a new channel that had high noise after installation. It was not there during test with the source. Could be dust or a real pin hole
PLOTS OF SOURCE TESTING AND THE BASELINE RUN FROM MONDAY AT 180V
10:10
Module fully installed but powered off. Out sensor is ~177cm from the exit window.
Mike setting up electron gun; some tuning is needed on the beam line since last experiment ran at 60MeV instead of 120MeV.
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11:10
Linac back again.
10Hz, 120MeV, ~fC (estimation)
180V bias, see a ~10uA leakage current. This doesn't chance when beam goes on/off.
We observe large, ~400ADC, sample to sample shifts when using external trigger.
When beam is turned off we still see ~100ADC sample to sample shifts.
Everything looks ok with software trigger with beam on/off.
We turned off the RF equipment (X- and S) in the tunnel and that brought the noise back to 35-40ADC. Looks like there was some interference. There are many things that are exposed: 5m long power, incl. bias, wires running along floor, devboard on floor 1m below beam line and ~1m from dump. This only happened on external trigger and due to time constraints we decided to go on with our program and forget about timing in.
PLOTS OF SHIFTS FOR THE DIFFERENT CONDITIONS
11:30Operation:36
Starting radiation program. There was no way we could measure anything below ~1pC so we start the program from there.
Foil thickness = 5:
I(pC)\Bias (V) | 180 | 250 | 350 | 400 | 450 | 500 |
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0.001 | x | x | x | x | x | x |
0.01 | x |
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0.1 | x |
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1.0 | x |
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10.0 | x |
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100 | x |
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| x |
highest possible | x |
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Runs taken, all at 6 foils:
Time | Bunch charge (pC) | ADC1 | Bias (V) | Ileak (uA) | Baseline | Baseline 180V | Comment |
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~11:00 | ?~0.001 | - | 180 | 10 | links | links |
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11:36 | 1.0 | 0.002 | 180 | 17 |
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| 1.0 | 0.002 | 250 | 22 |
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| 1.0 | 0.002 | 350 | 22 |
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| 1 | 0.002 | 400 | 38 |
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| 1 | 0.002 | 500 | 21 |
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12:00 | 10 | 0.01 | 180 | 6 |
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| 10 | 0.01 | 350 | 7 |
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| 10 | 0.01 | 500 | 50 |
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| 100 | 0.135 | 180 | 7 |
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| 100 | 0.135 | 250 | 6 |
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| 100 | 0.135 | 350 | 14 |
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11:36
Everything looks ok for 1pC setting.
12:00
At 10pC and 500V we observed a channel with x3 higher noise in the "weird" apv chip which looked like a pinhole candidate. However, after cycling the bias it went away.
We observe a previously unseen step in the noise from 30 to 35 ADC in the middle of both working APV25. This step was turning on over a couple of channels. Not sure what this is.
12:15
Continue to 100pC and 180V.
Here we see a drastic change and what looks like many shorts has developed across the sensors. We don't see any case where the channel get a larger noise but they all go down to a level of about 20ADC.
The step in noise also become worse.
12:30
At 100pC and 350V.
Here we see a large increase in number of channels that are "shorted".
Interesting it seems like the behavior depends very sharply on the bias voltage setting. If we go to 210V the shorts are less pronounced but spike up above 215.
We don't see any real changes on the leakage current.
Since we'd like to keep some channels alive we stop at this point.Time: 25x7min=175mins
IP address: 172.27.244.72
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