[Dsg-ltcc] stop gas flow?

[Maurizio Ungaro]

Thanks George.

Mauri

> On Mar 12, 2018, at 10:05 AM, George Jacobs <jacobsg at jlab.org> wrote:
> 
> Hi All,
> 
> IMO, the only way to reduce gas loss due to ambient pressure changes is to lower the pressure inside the detector. That will increase the magnitude of pressure transient required to vent gas out the bubbler. Therefor, I have reduced the pressure setpoint for gas flow from 1.8"wc to 1.4"wc. That will increase the delta from where the gas flow stops and where the gas is relieved out the bubbler. Once the pressure in the detector falls to this value, we should check the window shape to see if it can be set lower.
> 
> This pressure setpoint will need reset to 1.8"wc prior to resuming detector operation. Once the detector gas volume gas been refilled to 1.8"wc, we can calculate gas usage during this period to determine how effective this change was in saving gas.
> 
> George
> 
> On 3/9/2018 3:27 PM, Stepan Stepanyan wrote:
>> Hi George,
>> 
>> OK, thank you.
>> 
>> Stepan
>> 
>> On 3/9/18 3:19 PM, George Jacobs wrote:
>>> Hi Stepan,
>>> 
>>> The only way to keep the window inflated is to flow gas. We could switch to N2 to maintain sufficient pressure to maintain window shape. But, that may result in an increase is gas C4F10 loss during during N2 flow operation and again during the later "topping off" process. Since we have not done this before, there is no reference to point to. It does add an additional layer of complexity to the activity.
>>> 
>>> George
>>> 
>>> On 3/9/2018 2:54 PM, Stepan Stepanyan wrote:
>>>> George,
>>>> 
>>>> Thanks for the details. Yes, it seems not much can be saved, but anything we can save is a plus. 
>>>> Of course we cannot allow window come down on mirrors. In that respect, is there a option to reduce the loss?
>>>> 
>>>> Regards, Stepan
>>>> 
>>>> 
>>>>> On Mar 9, 2018, at 2:23 PM, George Jacobs <jacobsg at jlab.org <mailto:jacobsg at jlab.org>> wrote:
>>>>> 
>>>>> Ho Mauri,
>>>>> 
>>>>> An additional 2 weeks of running  will result in a decrease of ~7 kg gas from the supply tank, assuming 0.5kg per day usage.
>>>>> 
>>>>> Currently, ~56 kg C4F10 remains in the supply tank. This is a 112 day supply assuming 0.5 kg per day usage.
>>>>> 
>>>>> So, if we do nothing, in 2 weeks there will be ~49 kg C4F10 remaining in the tank. No change in detector pressure. Same as now.
>>>>> 
>>>>>  If we do turn it off, there will be ~56 kg remaining in the tank when we restart flow. Detector pressure and fill will be reduced due to gas leakage and the loss from ambient pressure changes during the outage. The detector will need to be "topped off" once we turn the gas back on. This will require X amount of gas. Since X is unknown, but most likely X < 7 kg and most definitely X > 0, the amount of gas saved will definitely be < 7kg. So, we do not know how much gas  this will actually save. Once gas flow is restarted, it may require 1-2 days to refill. My only real concern is if the window deflates to the point were it contacts and applies pressure to the mirrors. That would be bad
>>>>> 
>>>>> I do not see much of a savings or advantage in turning it off. But, that's not my call, it's yours. We can turn gas flow off if you want it off. Let me know what you decide. We will need to turn the gas off at the supply tank.
>>>>> 
>>>>> Cheers,
>>>>> George
>>>>> 
>>>>> On 3/9/2018 11:03 AM, Maurizio Ungaro wrote:
>>>>>> Hi George,
>>>>>> 
>>>>>> We'll have a downtime in accelerator that may run for a couple of weeks.
>>>>>> 
>>>>>> In the spirit of saving as much gas as possible, what are our options?
>>>>>> 
>>>>>> Thanks,
>>>>>> Mauri
>>>>>> 
>>>>> 
>>>>> -- 
>>>>> 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 <mailto:jacobsg at jlab.org>
>>>>> 
>>>>> (website) https://userweb.jlab.org/~jacobsg <https://userweb.jlab.org/%7Ejacobsg>
>>> 
>>> -- 
>>> 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 <mailto:jacobsg at jlab.org>
>>> 
>>> (website) https://userweb.jlab.org/~jacobsg <https://userweb.jlab.org/%7Ejacobsg>
> 
> -- 
> 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 <mailto:jacobsg at jlab.org>
> 
> (website) https://userweb.jlab.org/~jacobsg <https://userweb.jlab.org/~jacobsg>
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