[Primexd] FCAL bad channel status

[Alexander Somov]

Thanks Colin,

This makes sense, let's look on the waveform of this channel
with an LED first.

Cheers,
        Sasha




On Thu, 29 Nov 2018, Colin Gleason wrote:

> Sasha,
>
> There is one dead base in the FCAL (x,y)=(-3,29), crate, slot, channel= 3
> BOT, 18, 12. I suggest we look at occupancies and waveforms in LED data to
> see if there are other suspicious channels prior to changing this base out.
> In my experience, it is not worth the effort to change one dead base on the
> edge of the FCAL. If it was from an inner block, things would be different.
> I also expect there is one bad fadc channel (this has been a known issue
> since before the spring 2018 run). Once we know the complete list of bad
> channels, we can check the signal and swap at bases as needed. In my
> experience, there is usually one or two cables that need to be repaired in
> addition to some bases that need to be changed.
>
> -Colin
>
> On Wed, Nov 28, 2018 at 1:08 PM Alexander Somov <somov at jlab.org> wrote:
>
>>
>> Hi,
>>
>> Yes, I agree with Matt, it is important to understand what's going on with
>> these bases
>>
>> Cheers,
>>        Sasha
>>
>>
>>
>>
>> On Wed, 28 Nov 2018, Shepherd, Matthew wrote:
>>
>>>
>>>> On Nov 28, 2018, at 11:38 AM, Colin Gleason <gleasonc at jlab.org> wrote:
>>>
>>>>  The base failure rate had dropped to less than 2 per week by the end
>> of the run, so we should be able to manage replacements through the rest of
>> the Fall run. I think Chris and Nick have been busy with installation, but
>> once that is complete we can get them to repair more bases for the spring.
>>>
>>> We should start targeting bases that have high current draw when HV is
>> on and set to operational value but normal current when HV is off.  These
>> are likely to be the same bases that have trouble holding HV at the highest
>> settings.  The symptoms are different from HV drop, but I believe the
>> suspected root cause (poor cleanliness QC by the manufacturer) is the same
>> and I think the documented repair will work.  Let's pull 3-5 of these and
>> have Nick and Chris rework them and see that the operating current is
>> reduced and HV is able to be set high.  If it is, we can gradually begin
>> working through those.
>>>
>>> Matt
>>>
>>>
>>
>
>
> -- 
> Colin Gleason
> Postdoctoral Fellow
> Indiana University
> Department of Physics
>