[Dsg-mvt] MVT Mixing System Testing

[Amrit Yegneswaran]

marc thanks for the detailed info.
as you say we'll discuss the matter in detail on wed.
check  the power to the MFC .
i agree with the suggestion that the MVT group should proceed with the 
pre-mixed system, while george, brian and you debug the mixing system.
amrit

On 12/8/2017 1:09 PM, Marc McMullen wrote:
> Hi Amrit,
>
> On 12/6 the Saclay MVT gas controls started with demanding mixed gas 
> from the Hall B gas controls, which was setup in automatic mode. This 
> started the flow of Ar and C4H10 from the MVT mixing system. That 
> evening MVT staff observed fluctuations in flow from the C4H10 mass 
> flow controllers. We checked it out  and noticed fluctuations in C4H10 
> supply, and odd behavior from the mfcs such as: reporting significant 
> flow, with the internal valve closed. extremely slow response to  
> change in flow commands.  These issues have only been observed with 
> the C4H10 mfcs. We spent most of the day yesterday troubleshooting the 
> Mix 2 C4H10 mfc. The last part of the day we operated the mfc using 
> the software provided by MKS and performed the "zeroing" procedure a 
> couple of times to correct a flow offset. During this part of the 
> procedure the gas supply is mechanically valved off and the mfc is 
> isolated as much as the valve panel will allow. Generally, this 
> produces a small flow value (0, +/-  < 1 unit), close to zero. As I 
> observed the flow, I noted that the flow was all over the place for a 
> long time before it settled at a point where I thought it was ready to 
> complete the procedure. However once I opened the manual gas valve the 
> offset returned. This morning I noted that it was back in the "normal" 
> range, so that offset flow number must take a while to bleed off.
>
> In any case, we will start a rigorous testing procedure on the spare, 
> using a normal gas type (maybe compressed air) in a controlled 
> environment on Monday. Once we are sure that it works, we will have it 
> installed and perform those tests on the mixing system, first using 
> Argon and then finally C4H10. I should have a full report completed 
> for the next DSG status meeting on Wednesday.
>
> We have informed the MVT group to use the 2 premix bottles they have 
> on the target gas pad for data taking. We have ordered 10 bottles of  
> premix, and it has been signed and ordered by procurement.
>