[Dsg-ltcc] LTCC S5 Status - 05 Feb 2018

[Maurizio Ungaro]

Hi George,

Do you think the 2.1 limit can be increased or is it too dangerous?
It seems to me that c4f10 in the bubbler may be "the" main cause of gas losses. Please correct if I'm wrong.

The scale stayed at 71 for almost 3 days. This indicates a leak rate of 0.3 Kg / day, which is what was predicted, however I believe the box performs even better than this since David patched a couple of places.

Results on the gas on the data coming soon, I apologize it's taking so long.

Thanks,
Mauri





> On Feb 5, 2018, at 10:48 AM, George Jacobs <jacobsg at jlab.org> wrote:
> 
> Hi Mauri,
> 
> Current Status -From the pressure strip chart, it looks as if the detector has been full since around noon on 29 Jan.  The best way to determine the detector fill is from the detector monitor or event plots.
> 
> Gas Usage - From the gas supply remaining as indicated by the scale readout, usage since 30 Jan is 3 kg or 0.5 kg per day
> 
> The detector pressure is limited to 2.1"wc by the bubblers, ambient pressure changes or transients are a significant factor in gas loss.
> 
> I have attached the strip chart showing the detector pressure and ambient pressure history.
> 
> Blue line is gas pressure at the bottom of the detector.
> Brown line show pressure at the bubbler.
> Green line is ambient pressure.
> 
> 22 Jan - gas flow started @ 0.5 slm
> 29 Jan - Detector volume indicates it is FULL
> 29 Jan - gas flow reduced to 0.1 slm
> 30 Jan - gas flow reduced to 0.065 slm (65 sccm)
> 31 Jan - Gas supply programmed to shut off when pressure reaches 2.02"wc and turn back on when it falls to 1.95"wc
> 
> <LTCC-S5-Press-05Feb2018-2.png>
> 
> Detector pressure rises and falls as ambient pressure changes. Ambient pressure changes are significant when compared with detector pressure.
> 
> When ambient pressure decreases, detector differential pressure increases. When the detector pressure exceeds 2.1"wc, gas is lost out the bubbler. This gas loss is significant.
> 
> When ambient pressure increases, detector differential pressure decreases. The magnitude of the pressure decrease follows that of the ambient pressure change and is countered by the gas flow. Current gas flow is set at 65 sccm, the minimum flow the mass flow controllers can achieve. A higher flow would help minimize the magnitude of the pressure decrease. A higher flow would also increase gas usage or loss out the bubbler, during an ambient pressure decrease.
> 
> Determining the maintenance gas flow rate is a balancing act. Increasing the gas flow would minimize the detector pressure decrease during ambient pressure transients, but would also increase gas usage or loss rate. A good reason to increase gas flow would be to verify proper detector operation at the current flow rate.
> 
> Everything looks good from what the pressure strip chart shows. Has anyone looked at the events from beam as yet?
> 
> George
> 
> -- 
> 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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