<html><body><div style="font-family: times new roman,new york,times,serif; font-size: 12pt; color: #000000"><div>Hi Marco,<br></div><div><br data-mce-bogus="1"></div><div>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.<br data-mce-bogus="1"></div><div><br data-mce-bogus="1"></div><div>To hopefully clarify the plots, attached are three individual plots for each signal. Each plot has its y-axis unique to the signal.<br data-mce-bogus="1"></div><div><br data-mce-bogus="1"></div><div>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.<br data-mce-bogus="1"></div><div><br data-mce-bogus="1"></div><div>Best regards,<br data-mce-bogus="1"></div><div>Tyler<br data-mce-bogus="1"></div><div><br></div><div><br style="color: rgb(0, 0, 255);" data-mce-style="color: #0000ff;"></div><hr id="zwchr" data-marker="__DIVIDER__"><div data-marker="__HEADERS__"><b>From: </b>"Mirazita Marco" <Marco.Mirazita@lnf.infn.it><br><b>To: </b>"George Jacobs" <jacobsg@jlab.org><br><b>Cc: </b>"Tyler Lemon" <tlemon@jlab.org>, "dsg-rich" <dsg-rich@jlab.org><br><b>Sent: </b>Wednesday, April 11, 2018 10:40:50 AM<br><b>Subject: </b>Re: [Dsg-rich] RICH N2 Flow instablility<br></div><div><br></div><div data-marker="__QUOTED_TEXT__">Hi all,<br>it seems that the drop in the nitrogen flow occurred this morning didn't <br>produce any appreciable effect in the humidity inside the RICH, see the <br>attached strip chart.<br>Besides, that, I agree with George that the low N2 flow should produce <br>an alarm because it is a potentially dangerous event, but there is no <br>reason to turn off the detector.<br>I have a couple of question on the plots Tyler sent this morning, <br>though:<br>- The first plot shows very different flows between the two supply <br>lines. In the second plot the two flows are basically the same over <br>several days. I also checked the online strip chart and the two flows <br>are the same. Is there anything wrong in the first plot?<br>- In the first plot, the B_DET_FTC_INTLK_FLOW (I guess it is the flow in <br>the forward tagger) at some point goes negative, which is an unphysical <br>value. Could it be that the problem was just in the readout system?<br><br>Marco<br><br><br><br>Il 2018-04-11 14:58 George Jacobs ha scritto:<br>> This is just for general knowledge.<br>> <br>> --- The purpose of an interlock is to either;<br>> #1 Protect from something "bad"<br>> or<br>> #2 Prevent something "bad"<br>> <br>> Now for the obvious question, What does the LOW N2 flow interlock<br>> either, #1 Protect? or #2 Prevent? Nothing I can determine, but it did<br>> turn off the detector for no real reason and perhaps ruin the data<br>> from that run.<br>> <br>> --- The purpose of an alarm is to warn and or inform the shift/oncall<br>> persons to investigate and/or troubleshoot. In this particular<br>> situation, perhaps an alarm would be more useful than an interlock.<br>> <br>> IMO, interlocks which do not protect or prevent bad things are self<br>> defeating. This case is a good example. However, a properly set up<br>> alarm would be my preference if it were my experiment.<br>> <br>> Cheers,<br>> George<br>> <br>> On 04/11/2018 08:30 AM, Tyler Lemon wrote:<br>> <br>>> Hello George,<br>>> <br>>> This morning, RICH interlocks tripped on low N2 flow as noted in<br>>> logbook entry 3558672 (https://logbooks.jlab.org/entry/3558672 [2]).<br>>> <br>>> <br>>> Looking at the flow history, it shows that the nitrogen flow dropped<br>>> from 20 slm to 15 slm in about ten minutes. About ten minutes later,<br>>> the flow had increased again to 20 slm, but has been unstable in<br>>> comparison to before the drop in flow. We checked other detector's<br>>> nitrogen flows and the only other we saw this on was the<br>>> FT-calorimeter.<br>>> <br>>> Attached is a plot of the two RICH N2 flows and one FT-calorimeter<br>>> N2 flow. The main point of the plot is to show the three nitrogen<br>>> flows all showed the same flow patterns, so the plots are tiled to<br>>> show all three signals. The Y-axis is for the blue RICH N2 flow #2.<br>>> The FT-calorimeter's flow is significantly less, on the order of<br>>> ~250 sccm, but its flow still show the same drop and instability.<br>>> <br>>> What would cause this change in flow? Could it be caused by Hall B's<br>>> nitrogen dewar being refilled?<br>>> <br>>> Best regards,<br>>> <br>>> Tyler<br>>> <br>>> _______________________________________________<br>>> Dsg-rich mailing list<br>>> Dsg-rich@jlab.org<br>>> https://mailman.jlab.org/mailman/listinfo/dsg-rich [1]<br>> <br>> --<br>> <br>> George Jacobs<br>> Jefferson Lab (TJNAF)<br>> STE 12<br>> 12000 Jefferson Ave.<br>> Newport News, VA 23606<br>> <br>> (office) 757-269-7115<br>> <br>> (cell) 757-876-0480<br>> <br>> (email) jacobsg@jlab.org<br>> <br>> (website) https://userweb.jlab.org/~jacobsg [3]<br>> <br>> <br>> <br>> Links:<br>> ------<br>> [1] https://mailman.jlab.org/mailman/listinfo/dsg-rich<br>> [2] https://logbooks.jlab.org/entry/3558672<br>> [3] https://userweb.jlab.org/~jacobsg<br>> <br>> _______________________________________________<br>> Dsg-rich mailing list<br>> Dsg-rich@jlab.org<br>> https://mailman.jlab.org/mailman/listinfo/dsg-rich<br></div></div></body></html>