[Dsg-rich] RICH N2 Flow instablility

Wed Apr 11 10:56:33 EDT 2018

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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