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Beam parameters - 150um beam spot

Operation

Log book

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.

10:30
Beam E=119.3MeV, 50pC at gun, 10Hz
Start with 0 foils in order to search for the beam on the insertable phosphor screen.
The Phosphor screen is at ~75cm from exit window.
We use the measured voltage on the toroid located downstream of the spectrometer magnet: "ADC1".
At this point ADC1=0.06V which is ~40pC according to Mike.

10:37
Move in foils one by one and observe beam spot on phosphor screen. Picture and extracted spot size at each thickness can be seen below.

We should check if we can extract the beam spot size on the Be window from this data and ask Mike if it's consistent with his experience.

10:49
Lower bunch charge.
Insert 6 foils.
Still possible to see the beam on the phosphor screen but barely.
Mike estimates this to be order of 1fC/bunch.

10:55
Trying to time in readout using external trigger. Observe strange very large signals that went away after restart of daq. The disconnected APV got occassional hits at 0 ADC? This seemed to happen a few times even after we disabled it in the configuration. Is that possible even? We kept it disabled as it screwed up the scale.
We stepped through the latency setting from 130->5 with no sign of signal.
The linac had tripped so we don't know if we could have seen anything.

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. This only happened on external trigger and due to time constraints we decided to go on with our program and forget about timing in.

11:30

OperationOperation plan:

• Start with 5 foils (or maximum) and lowest current available to time in detector readout
• 10Hz beam for each setting of beam intensity, foil thickness and bias voltage (5 min each)
• Run baseline (1000k events at 100Hz) and save to file for each setting (2min)
• Total time would be about 7mins/setting
• Going from 5 foils to 0 foils changes e/strip with a factor of 2

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