[Halld-cal] [Revised Logentry] FCAL HV scan

[Colin Gleason]

To add to this, you can currently see some bases exhibiting this behavior
in the FCAL with their standard production settings. Example: col=13 row=23
(-17,-7). It is set to HV=1749V for standard production running but can
only hold 1620-1640V and has been like this for some time (see attached
strip chart blue line). Its current is also reading a max value of 15mA.
This base will need to be swapped out during the next access. The tan line
is a base at the center of the FCAL set to 1794V and you can see the HV is
very stable. The dip you see at the right is during the HV testing today
when the setpoints were changed.

-Colin

On Mon, Nov 19, 2018 at 1:48 PM Colin Gleason <gleasonc609 at gmail.com> wrote:

> Hi Ashot,
>
> I do not think you will need to run at 1800V. Most of the FCAL is
> calibrated properly (we know the inner and outer layers need to be
> calibrated) and when new HV set points are determined it's unlikely that a
> lot of new channels will need to be set to 1800V. The bases that are
> exhibiting this behavior all have high currents being drawn from them. The
> max value we can see on EPICS is 15mA, but it's likely the current being
> drawn is higher than this. We have been aware of this for some time now and
> are taking steps to address it. If for some reason a base can not hold the
> HV at which you want, it can be replaced with a spare. Since we've seen the
> failure rate of bases dying decrease this run period, we plan on removing
> more bases with large current draw in the future.
>
> -Colin
>
> On Mon, Nov 19, 2018 at 12:23 PM <gasparan at jlab.org> wrote:
>
>>
>>   Hi Sasha,
>>
>>  a very good test. It looks like we may have serious problems if we need
>>  to set 1800 V range.
>>  We will need to have more information (gains, electronic noise, ...)
>>  before making some decision.
>>
>>  Thanks,
>>  Ashot
>>
>>
>> >
>> > Logentry Text:
>> > --
>> > FCAL readout: RAW mode (mode 10)
>> >
>> > Use violet LED, 500 Hz
>> >
>> > 1500 V
>> > ----------
>> >
>> > Run  51604,  130 K events,  17 V
>> > Run  51605,  122 K events,  22 V
>> >
>> > 1550 V
>> > ---------
>> >
>> > Run 51606,  120 K events, 17 V
>> > Run 51607,  120 K events,  22 V
>> >
>> > 1600 V
>> > ----------
>> >
>> > Run 51608, 17 V
>> > Run 51609,  22 V
>> >
>> > 1650 V
>> > ----------
>> >
>> > Run 51610, 17 V
>> > Run 51611, 22 V
>> >
>> > 1700 V
>> > ----------
>> >
>> > Problems with setting HV on channel (22,22 ;  -8,-8)
>> >
>> > Run 51612,  17 V
>> > Run 51613,  22 V
>> >
>> >
>> > 1750 V
>> > ----------
>> >
>> > Not able to set this voltage on the following channels:
>> > Channel, Read back voltage
>> >
>> > (1, 31) 1610 V
>> > (7, 46) 1601
>> > (13, 23) 1618
>> > (13, 47) 1651
>> > (20, 26) 1600
>> > (22, 22) 1607
>> > (25, 26) 1620
>> > (29,7) 1640
>> > (33,47) 1609
>> > (35, 37) 1630
>> > (44, 30) 1590
>> > (41, 39) 1660
>> > (44, 30) 1590
>> > (47, 38) 1625
>> > (49, 31) 1612
>> >
>> > Run 51614,  17 V
>> > Run 51615,  22 V
>> >
>> > 1800 V
>> > ---------
>> >
>> > Cannot set HVs on 41 channels
>> >
>> > Run 51616,  17 V
>> > Run 51617,  22 V
>> >
>> >
>> >
>> >
>> >
>> >
>> > ---
>> >
>> > This is a plain text email for clients that cannot display HTML.  The
>> full
>> > logentry can be found online at
>> >
>> https://logbooks.jlab.org/entry/3628470_______________________________________________
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>>
>>
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>
>
> --
> Colin Gleason
> Postdoctoral Fellow
> Indiana University
> Department of Physics
>


-- 
Colin Gleason
Postdoctoral Fellow
Indiana University
Department of Physics
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