[Dsg-rtpc] [EXTERNAL] Gas fittings for the BONuS12 DMS

[Brian Eng]

While I'm not sure the FS range of the absolute ones off hand, I'm pretty sure they're 1000 Torr units, in which case MKS recommends the lowest pressure for reading to be 0.5 Torr and the lowest pressure to control to be 5 Torr.

We can probably use lower values since we have fairly stable temperature and flow, but definitely not down to a 0.01 Torr level.

> On Jan 5, 2020, at 12:06 PM, Sebastian Kuhn <kuhn at jlab.org> wrote:
> 
> Hi Carlos,
> 
> thanks so much for checking this. So, it looks like we MAY have the necessary hardware for either solution. However, does someone have the specs for the “Model 226 mks”? I suspect the resolution/accuracy will be much worse than ideal (0.01 Torr) or even  0.1 Torr, given the range of 200 Torr. (Does anybody know the resolution for this as well as for the 2 differential pressure meters we already have in the gas panel - MKS AA01 if I’m not mistaken?)
> 
> As you guessed, using ABSOLUTE pressure measurements to “dead-reckon” the differential pressure between the RTPC and the 4He buffer is likely to be even worse - the accuracy of these absolute pressure meters is probably not (much) better than 1 Torr. 
> 
> Happy New Year - Sebastian
> 
>> On Jan 5, 2020, at 11:40 AM, Carlos Ayerbe Gayoso <gayoso at jlab.org> wrote:
>> 
>> Hallo Sebastian, 
>> 
>> sorry for the late answer, I was driving back to NN from Georgia. I went to the EEL today to find the differential sensor (picture attached (left) ), so it is available. Also, there is the absolute pressure sensor.
>> 
>> I wonder if we can (or is desirable) determine the differential pressure between the buffer and the drift volume with the information we already have from the panel. 
>> 
>> As far I know, we have differential pressure from the He volume and since we have the absolute pressure from the hall, we can determine absolute He pressure (don't we?). Then we have absolute from the RTPC, so the differential is just the difference from both. Probably the accuracy is not so good, I don't know.
>> 
>> Cheers
>> 
>> -Carlos
>> 
>> From: Sebastian Kuhn <kuhn at jlab.org>
>> Sent: Saturday, January 4, 2020 9:38 AM
>> To: Carlos Ayerbe Gayoso <gayoso at jlab.org>
>> Cc: dsg-rtpc at jlab.org <dsg-rtpc at jlab.org>; JIWAN POUDEL <jpoud001 at odu.edu>; Bob Miller <rmiller at jlab.org>; Mohammad Hattawy <mohammad.hattawy at gmail.com>; Nathan Baltzell <nbaltzel at odu.edu>; Narbe Kalantarians <narbe at jlab.org>
>> Subject: Re: [Dsg-rtpc] [EXTERNAL] Gas fittings for the BONuS12 DMS
>>  
>> Hi Carlos,
>> 
>> I’m wondering whether that diff pressure sensor is not already used - we changed the sensor for the 4He buffer volume to measure the differential pressure with the surrounding air, so there are already 2 diff press sensors “in service” in the panel as of now. If there is one more in the EEL, would you know where to look for it? 
>> 
>> Alternatively, we could (with minimal rerouting) use THAT diff press. sensor to connect it to the RTPC witness line instead of leaving it open to air. That would minimize the amount of work required, no more additional sensors needed (lowering hardware and software cost), and we still would have the full information by comparing the absolute pressure in the RTPC with the absolute pressure measured in the Hall, while having the highest sensitivity where it counts - the differential pressure across the ground foil. How does that sound?
>> 
>> - Sebastian
>> 
>>> On Jan 3, 2020, at 6:45 PM, Carlos Ayerbe Gayoso <gayoso at jlab.org> wrote:
>>> 
>>> Hello All and Happy New Year,
>>> 
>>> there is a differential pressure sensor available (the original one used in the panel), BUT I don't know if it is enough accurate. There are two Honeywell 19C015PA4K pressure transducer available, but they were discarded due to the accuracy. 
>>> 
>>> The differential is still at EEL, the transducer are at W&M.
>>> 
>>> Cheers
>>> 
>>> -Carlos
>>> From: Sebastian Kuhn <kuhn at jlab.org>
>>> Sent: Friday, January 3, 2020 2:34 PM
>>> To: dsg-rtpc at jlab.org <dsg-rtpc at jlab.org>
>>> Cc: JIWAN POUDEL <jpoud001 at odu.edu>; Bob Miller <rmiller at jlab.org>; Mohammad Hattawy <mohammad.hattawy at gmail.com>; Nathan Baltzell <nbaltzel at odu.edu>; Carlos Ayerbe Gayoso <gayoso at jlab.org>; Narbe Kalantarians <narbe at jlab.org>
>>> Subject: Re: [Dsg-rtpc] [EXTERNAL] Gas fittings for the BONuS12 DMS
>>>  
>>> Dear Brian,
>>> 
>>> I realize that this is very late in the game. I agree that if we can’t get it done in time, we will (have to) live with the present arrangement. The reason that I would prefer a differential pressure meter (as opposed to dead-reckoning with absolute pressure measurements) is that the this pressure difference between RTPC and 4He buffer is directly relevant for the strain on the thin ground foil, as well as potentially the leak rate from the detector.
>>> 
>>> I am cc’ing Narbe and Carlos in case they are aware of any still existing differential pressure meters that we could use; in any case, to be useful, the meter should have the following parameters:
>>> 
>>> 1) Sensitivity/accuracy: Ideally about 0.013*10^-3 atm or 0.005 iwc or 0.0002 psi or 0.01 Torr (can be a bit less accurate)
>>> 2) Range: At least +/-1.3*10^-3 atm or 0.5 iwc or 0.02 psi or 1 Torr (it doesn’t hurt if it is more, obviously, as long as it is sensitive enough).
>>> I believe these specs are compatible with the differential pressure sensor we are presently using for the RTPC - DMS sensor PDT332 (MKS226A).
>>> 
>>> - Sebastian
>>> 
>>> 
>>> > On Jan 3, 2020, at 1:58 PM, Brian Eng <beng at jlab.org> wrote:
>>> > 
>>> > Hi Sebastian,
>>> > 
>>> > Regarding this point, The Hall B Gas System already has a sensor/PV that is reading the absolute pressure in the Hall itself (i.e. ambient). This can be used to convert any absolute pressure to a relative one.
>>> > 
>>> > So we already have enough sensors that we could calculate this value (DP between RTPC & He Buffer), but I don't know what kind of accuracy/speed you require.
>>> > 
>>> > If you require something with higher accuracy we would need to know what pressure range you expected to see if there is any sensors available in-hand that would work. The lead-time on these is long enough that we wouldn't get it in time for the experiment.
>>> > 
>>> >> On Jan 3, 2020, at 11:58 AM, Sebastian Kuhn <kuhn at jlab.org> wrote:
>>> >> 
>>> >> 2) Is there a possibility to add one more item to the gas panel? (rather belated, I know - my apologies) I realized that we really would like to be able to measure the differential pressure between the 4He gas buffer volume  (orange in the gas  panel design drawings) and the RTPC (green). This would
>>> >> a) close the loop so we have both absolute and relative pressure for all relevant parts of the system
>>> >> b) allow us to monitor (and alarm on) any pressure differential between the RTPC and the buffer volume that exceeds the (rather limited) safety margin for the thin ground foil between the two.
>>> > 
>>> > _______________________________________________
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>> 
>> <20200105_111737.jpg>
> 
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