[Sbs_gems] [EXTERNAL] RE: GEM HV scan with new resistors

[Gnanvo, Kondo (kg6cq)]

Hi Holly,
Sorry but I am missing something,
What does the 14% occupancy means and how does that compare with the other layers? Why is 14% occupancy an issue for you. I am just not up to date with the details I want to understand

My point about the scan not needed alignment is that it is a relative measurement, everything kept equal when doing the HV scan at some point whatever you define by efficiency no longer depends on HV and that all that matter. But you are right that if there are other concerns related to the alignment, it needs to be looked at.

I seem to remember that when I tested this layer back at UVa, it was operating at lower gain (for same HV setting) compared to the first two that were initially in BB, that is why I am asking for HV scan, I believe that to keep everything  equal the nominal voltage for this layer will have to be higher than the other 2 U-V layers but only the HV scan will tell.

You can skip half of the data point. Whether to stay below 3653 in my view depends on what you are seeing with the HV scan. I don’t think there are magic numbers like that. Each module has its optimal setting.

Best regards
Kondo

From: Sbs_gems <sbs_gems-bounces at jlab.org> On Behalf Of Holly Szumila-Vance
Sent: Friday, November 19, 2021 4:09 PM
To: sbs_gems at jlab.org
Subject: [Sbs_gems] GEM HV scan with new resistors

Hi Kondo, Nilanga, all,

I realize the voltage scan doesn’t need good alignment, but right now the alignment was showing the new HV layer with about 14% occupancy, which is why I brought up the point about making sure alignment will be somewhat ready. Andrew says it will be, so we should be able to see in real time if we are getting plateaus.

The HV scan we completed previously consisted of running:
3385 (3800 equiv)
3430 (3850 equiv)
3475 (3900 equiv)
3519 (3950 equiv)
3564 (4000 equiv)
3608 (4050 equiv)
3653 (4100 equiv)
3697 (4150 equiv)
3720 (4175 equiv)

Can we reduce some of these points? Should we stay below 3653V or some other limit? These values correspond to the divider before modification.

Thanks,
Holly

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