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  • From: videbaek <videbaek AT bnl.gov>
  • To: "Visser, Gerard" <gvisser AT indiana.edu>
  • Cc: Star-fst L <star-fst-l AT lists.bnl.gov>
  • Subject: Re: [Star-fst-l] FST Latency Adjusted
  • Date: Mon, 29 May 2023 16:45:00 -0400

Hi,

The APV chips are really much more radiation hardened as they were desing and used for LHC.
Too, I do not recall we ever have seen such shifts with APV chips for either IST or FST last year. I might be wrong,. Zhenyu can you confirm if we have seen such behavior ever before


best Flemming





On 2023-05-29 16:06, Visser, Gerard wrote:
hi Ziyue,
It is also possible, of course, that the max timebin plot is just
generally unstable i.e. not that it moved in response to a particular
beam incident. That _might_​ be the case, we should watch out for
the possibility. (If it is like that, probably adjustments each time
it changes is not the right approach, though I can't say for sure.)

* Gerard

-------------------------

From: Ziyue Zhang <zzhan70 AT uic.edu>
Sent: Monday, May 29, 2023 3:36 PM
To: Visser, Gerard <gvisser AT indiana.edu>
Cc: Star-fst L <star-fst-l AT lists.bnl.gov>
Subject: Re: [Star-fst-l] FST Latency Adjusted

Hello Gerard,

Thank you for bringing up your concern. A minor clarification, I
should have used the word "accident"...

You are absolutely correct, I forgot the power cycle step; that will
be on my top list next time.

In the case of the current situation, this is my naive understanding:
since there was already a trip on every channel, and during the 1-2
days, the shift crews have turned on and off the FST multiple times,
so they should effectively have gone over power cycle... I checked the
Max Time Bin plots yesterday late afternoon, and noticed this issue,
but there was no beam, so I checked again this morning and made the
adjustment based on the plot in this morning's PHYS runs.

Sincerely,
Ziyue

On Mon, May 29, 2023, 12:11 Visser, Gerard <gvisser AT indiana.edu>
wrote:

Dear Ziyue,
Thanks, this sounds good. (I didn't look at plots right now,
sorry, but I trust you see the correct effects.)
However I am concerned by the statement " New APVs need
adjustment found, which is most likely caused by the "FST not off
during beam dump" incident yesterday":

* It should be basically impossible to have any lasting effect of
this sort from any beam incident. I'd expect if there is a lasting
effect, it would be in the nature of total failure or of an increase
in noise level.
* On the other hand though, the hardware _might at any time get
into a "upset" condition_, where some internal states are incorrect
and this might (not unlikely) be caused by beam conditions. It would
go back to normal upon a power cycling of everything.
* ==> If you think something shifted or is acting abnormally, power
cycle!
* If you readjusted something to make it normal instead, I suggest
power cycle and check things, and if necessary make adjustments
(maybe contrary to prior adjustments.

Sincerely,

Gerard

-------------------------

From: Star-fst-l <star-fst-l-bounces AT lists.bnl.gov> on behalf of
Ziyue Zhang <zzhan70 AT uic.edu>
Sent: Monday, May 29, 2023 11:40 AM
To: Star-fst L <star-fst-l AT lists.bnl.gov>
Subject: [Star-fst-l] FST Latency Adjusted

Dear all,
The FST APV latency has been adjusted. Details can be found here
[1].
Best regards,
Ziyue


Links:
------
[1] https://drupal.star.bnl.gov/STAR/blog/zyzhang/FST-Operation-Log-May-10-July-4-2023
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--
Flemming Videbaek
senior scientist, emeritus
videbaek @ bnl.gov
Brookhaven National Lab
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