[Dsg-halla_gem] [EXTERNAL] SBS gas distribution rack moved to EEL/125; help setting up?

Wed Sep 29 00:53:45 EDT 2021

For 75/25 Ar/CO2 the scale factor would be ~1.18 X the listed flow, so a bit higher, but maybe not a big deal especially at these little flow amounts.

As for mixing having variable timing, IIRC we see this most often on ones not in a temperature controlled environment, e.g. on the gas pad or mixing into tanks outside.

I can dig up some plots from some of our systems for comparison if you'd like.

________________________________
From: Jack Segal <segal at jlab.org>
Sent: Wednesday, September 29, 2021 12:00 AM
To: Brian Eng <beng at jlab.org>; jboyd at jlab.org <jboyd at jlab.org>
Cc: dsg-halla_gem at jlab.org <dsg-halla_gem at jlab.org>
Subject: Re: [Dsg-halla_gem] [EXTERNAL] SBS gas distribution rack moved to EEL/125; help setting up?

They are flowing Nitrogen at the moment, I guess. While we are talking about GEMs, in the hall we have switched to the old FPP (Focal Plane Polarimeter, Straw Tubes) mixing system. I have set the controller to mix Ar/CO2 75/25. Just a note, they have been using 75/25 this whole time and want to use 75/25 in the future. I'm seeing some curious behavior with the mass flow controllers. I have never seen this. The MFCs keep a buffer tank between 12 and 15 PSIG. The cycling frequency is varying, meaning the gas flow is varying radically. This is in the hall for the BigBite detectors. Do you see this on the MFCs? The time scale varies and is on the order of a few hours, or so. It is not consistent. I would include an EPICS archiver plot, but it is late and I am too tired. Tomorrow is another day.

-----------------------------------------------------------------------
John(Jack) Segal
Halls A and C Spectrometer Support Manager
Thomas Jefferson National Accelerator Facility
12000 Jefferson Avenue
Suite 12
Newport News, VA 23606-4486
Phone: (757) 269-7242
Cell: (757) 320-9977

________________________________
From: Brian Eng <beng at jlab.org>
Sent: Tuesday, September 28, 2021 3:45 PM
To: Jack Segal <segal at jlab.org>; jboyd at jlab.org <jboyd at jlab.org>
Cc: dsg-halla_gem at jlab.org <dsg-halla_gem at jlab.org>
Subject: Re: [Dsg-halla_gem] [EXTERNAL] SBS gas distribution rack moved to EEL/125; help setting up?

The flow through the system (rotameters and flow meters) should be multiplied by ~1.1375 to account for the fact that the gas being flown is 70/30 Ar/CO2

So the actual flow will be higher than indicated by the readouts.

________________________________
From: Dsg-halla_gem <dsg-halla_gem-bounces at jlab.org> on behalf of Jack Segal <segal at jlab.org>
Sent: Tuesday, September 28, 2021 1:22 PM
To: jboyd at jlab.org <jboyd at jlab.org>
Cc: dsg-halla_gem at jlab.org <dsg-halla_gem at jlab.org>
Subject: Re: [Dsg-halla_gem] [EXTERNAL] SBS gas distribution rack moved to EEL/125; help setting up?

   I turned off all the flow meters. Turned them on a section at a time. I think you
are just using a lot of gas. I'm not sure how accurate those visual meters are at
low flow. Also, they are calibrated for air. You are using Ar/CO2.
   What is the make and model of the visual flow meters?

On 9/28/2021 12:46 PM, Jack Segal wrote:
> Isolate the GEMs and restart flow one at a time.
>
> Sent from my iPhone
>
>> On Sep 28, 2021, at 11:39 AM, jboyd at jlab.org wrote:
>>
>> To all,
>>
>> Anu and I set up the gas distribution from the gas cylinders, to through
>> the gas rack, and onto the GEM layers. We have been flushing and flowing
>> gas. It seems that the gas loss rate is a bit more than what we would
>> expect given the flow rates that we have set. We are losing about a bottle
>> a day for our 8 layers of GEMs. We expect that 1 bottle should be about 3+
>> days.
>>
>> Therefore, we are suspecting a leak somewhere, perhaps on the gas
>> distribution rack. I checked around the gas cylinders and the connection
>> manifold and couldn't find any leaks (I did find one but I was able to
>> fix/seal it).
>>
>> What should we do about getting the setup of the gas rack and possibly the
>> cylinder/manifold setup leak tested and checked?
>>
>> Thank you for the help.
>>
>> Best,
>>
>> John
>>
>>> Hi Brad,
>>>
>>> We discussed the SBS gas distribution in our meeting today. I will
>>> schedule a time to come over and install a Raspberry Pi in area for
>>> monitoring.
>>>
>>> It looks like the rack accessory box has been relocated from the Hall to
>>> EEL 125, George is scheduling to connect the gas flow sensor chassis
>>> channels to the appropriate flow meters.
>>>
>>> After these steps are completed, I'll send an email so Kondo's group can
>>> connect their detector gas lines to the output side of the gas flow sensor
>>> chassis and hook up the premix bottle to the regulator input.
>>>
>>>
>>>
>>> Regards,
>>> Marc McMullen
>>> Sr. Instrumentation Designer
>>> Detector Support Group
>>> (757) 269-7738
>>>
>>> From: Brad Sawatzky<mailto:brads at jlab.org>
>>> Sent: Tuesday, September 21, 2021 10:51 PM
>>> To: Kondo Gnanvo<mailto:kagnanvo at jlab.org>; John
>>> Boyd<mailto:jboyd at jlab.org>; Rathnayake, Anuruddha
>>> (adr4zs)<mailto:adr4zs at virginia.edu>; Marc
>>> Mcmullen<mailto:mcmullen at jlab.org>
>>> Cc: dsg-halla_gem at jlab.org<mailto:dsg-halla_gem at jlab.org>; Jack
>>> Segal<mailto:segal at jlab.org>
>>> Subject: [EXTERNAL] SBS gas distribution rack moved to EEL/125; help
>>> setting up?
>>>
>>> Hi Marc, et al,
>>>
>>> The SBS GEM gas distribution rack was recently moved to EEL/125.
>>> That is where the SBS GEM layers are being stored and worked on.
>>>
>>> Marc, can your group support the GEM group in completing the setup
>>> of that gas system so they can start flowing gas to the layers in
>>> EEL/125?  It will need to be reconnected to the network, some gas line
>>> 'jumpers' need to be run between the two sides of the rack, and lines
>>> need to be run from the rack to the GEM modules themselves.  (I believe
>>> Jack fixed the issue with i2c multiplexing in that rack.)
>>>
>>> I also moved a large spool of 1/4" poly into EEL/125 so fresh gas lines
>>> can be run.  General consensus is to position the rack in the most
>>> convenient location in EEL/125 and run (relatively short) gas lines of
>>> the needed length to the individual GEM modules.  We will cut a set of
>>> new (longer) gas lines for the final setup in the Hall in a couple
>>> months.
>>>
>>> I'll be out of town for about a week, but I've discussed this with John
>>> Boyd and Anuruddha, and they are generally in either EEL/125 or /126.
>>>
>>> -- Brad
>>>
>>> --
>>> Brad Sawatzky (he/him), PhD <brads at jlab.org> -<>- Jefferson Lab/ Hall
>>> C/C111
>>> Ph: 757-269-5947  -<>-  Fax: 757-269-5235  -<>- Pager: brads-page at jlab.org
>>> The most exciting phrase to hear in science, the one that heralds new
>>>   discoveries, is not "Eureka!" but "That's funny..."   -- Isaac Asimov
>>>
>>>
>>
>>

--
John(Jack) Segal
Halls A and C Spectrometer Support Manager
Thomas Jefferson National Accelerator Facility
12000 Jefferson Avenue
Suite 12
Newport News, VA 23606-4486
Phone: (757) 269-7242
Cell: (757) 320-9977
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