[Dsg-rich] RICH N2 Flow instablility

Wed Apr 11 11:04:47 EDT 2018

Thank you for the clarification.
Marco

Il 2018-04-11 16:56 Tyler Lemon ha scritto:
> Hi Marco,
> 
> In answer to your questions: for that first plot, the signals were
> tiled and the three signals do not have the same y-axis. This is why
> they appear to not be the same value.
> 
> To hopefully clarify the plots, attached are three individual plots
> for each signal. Each plot has its y-axis unique to the signal.
> 
> If you were to overlay the three plots, just as they appear in the
> images, the result would be the same as the first plot.
> 
> Best regards,
> 
> Tyler
> 
> -------------------------
> 
> FROM: "Mirazita Marco" <Marco.Mirazita at lnf.infn.it>
> TO: "George Jacobs" <jacobsg at jlab.org>
> CC: "Tyler Lemon" <tlemon at jlab.org>, "dsg-rich" <dsg-rich at jlab.org>
> SENT: Wednesday, April 11, 2018 10:40:50 AM
> SUBJECT: Re: [Dsg-rich] RICH N2 Flow instablility
> 
> Hi all,
> it seems that the drop in the nitrogen flow occurred this morning
> didn't
> produce any appreciable effect in the humidity inside the RICH, see
> the
> attached strip chart.
> Besides, that, I agree with George that the low N2 flow should produce
> 
> an alarm because it is a potentially dangerous event, but there is no
> reason to turn off the detector.
> I have a couple of question on the plots Tyler sent this morning,
> though:
> - The first plot shows very different flows between the two supply
> lines. In the second plot the two flows are basically the same over
> several days. I also checked the online strip chart and the two flows
> are the same. Is there anything wrong in the first plot?
> - In the first plot, the B_DET_FTC_INTLK_FLOW (I guess it is the flow
> in
> the forward tagger) at some point goes negative, which is an
> unphysical
> value. Could it be that the problem was just in the readout system?
> 
> Marco
> 
> Il 2018-04-11 14:58 George Jacobs ha scritto:
>> This is just for general knowledge.
>> 
>> --- The purpose of an interlock is to either;
>> #1 Protect from something "bad"
>> or
>> #2 Prevent something "bad"
>> 
>> Now for the obvious question, What does the LOW N2 flow interlock
>> either, #1 Protect? or #2 Prevent? Nothing I can determine, but it
> did
>> turn off the detector for no real reason and perhaps ruin the data
>> from that run.
>> 
>> --- The purpose of an alarm is to warn and or inform the
> shift/oncall
>> persons to investigate and/or troubleshoot. In this particular
>> situation, perhaps an alarm would be more useful than an interlock.
>> 
>> IMO, interlocks which do not protect or prevent bad things are self
>> defeating. This case is a good example. However, a properly set up
>> alarm would be my preference if it were my experiment.
>> 
>> Cheers,
>> George
>> 
>> On 04/11/2018 08:30 AM, Tyler Lemon wrote:
>> 
>>> Hello George,
>>> 
>>> This morning, RICH interlocks tripped on low N2 flow as noted in
>>> logbook entry 3558672 (https://logbooks.jlab.org/entry/3558672
> [2]).
>>> 
>>> 
>>> Looking at the flow history, it shows that the nitrogen flow
> dropped
>>> from 20 slm to 15 slm in about ten minutes. About ten minutes
> later,
>>> the flow had increased again to 20 slm, but has been unstable in
>>> comparison to before the drop in flow. We checked other detector's
>>> nitrogen flows and the only other we saw this on was the
>>> FT-calorimeter.
>>> 
>>> Attached is a plot of the two RICH N2 flows and one FT-calorimeter
>>> N2 flow. The main point of the plot is to show the three nitrogen
>>> flows all showed the same flow patterns, so the plots are tiled to
>>> show all three signals. The Y-axis is for the blue RICH N2 flow #2.
>>> The FT-calorimeter's flow is significantly less, on the order of
>>> ~250 sccm, but its flow still show the same drop and instability.
>>> 
>>> What would cause this change in flow? Could it be caused by Hall
> B's
>>> nitrogen dewar being refilled?
>>> 
>>> Best regards,
>>> 
>>> Tyler
>>> 
>>> _______________________________________________
>>> Dsg-rich mailing list
>>> Dsg-rich at jlab.org
>>> https://mailman.jlab.org/mailman/listinfo/dsg-rich [1]
>> 
>> --
>> 
>> George Jacobs
>> Jefferson Lab (TJNAF)
>> STE 12
>> 12000 Jefferson Ave.
>> Newport News, VA 23606
>> 
>> (office) 757-269-7115
>> 
>> (cell) 757-876-0480
>> 
>> (email) jacobsg at jlab.org
>> 
>> (website) https://userweb.jlab.org/~jacobsg [3]
>> 
>> 
>> 
>> Links:
>> ------
>> [1] https://mailman.jlab.org/mailman/listinfo/dsg-rich
>> [2] https://logbooks.jlab.org/entry/3558672
>> [3] https://userweb.jlab.org/~jacobsg
>> 
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