[Dsg-mvt] Fwd: Fwd: MVT and FTT gas system

[Marc McMullen]

Hi Bob,

I can meet you at the counting house at 9:15.

Marc


On 1/2/2018 8:01 AM, Bob Miller wrote:
>
> Hi Marc,
>
> Let's meet this morning to go over the plans for this system. Let me 
> know when  you are available and we can meet in the counting house.
>
> Thanks,
>
> Bob
>
>
>
> -------- Forwarded Message --------
> Subject: 	Fwd: MVT and FTT gas system
> Date: 	Sat, 23 Dec 2017 07:44:41 -0500 (EST)
> From: 	Robert Miller <rmiller at jlab.org>
> To: 	Marc McMullen <mcmullen at jlab.org>
> CC: 	Brian Eng <beng at jlab.org>
>
>
>
> Hi Marc,
>
> It may be time to use the drift chamber buffer tanks on level 3 for the MVT system.  Will the isobutane mixing system work at 100 sccm?  Does the CF4 system mix properly?
>
> If the isobutane system will work at 100 sccm then we just tee in the DC buffer tank to the supply to the MVT, then batch fill the system based on pressure, probably 10-30 psi.  We may need a solenoid valve in front of the MFC to stop the flow between fills.  We will put a manual valve to the buffer tank so we can isolate it during argon purges.  We can do the same for the CF4 system if necessary.
>
> Please think about this and give me a call on Tuesday to discuss the system.
>
> Thanks
> Bob
>
> 238-8338 home
> 822-9586 cell
>
>
>
>
>
> ----- Forwarded Message -----
> From: "Aune Stephan"<stephan.aune at cea.fr>
> To: "burkert"<burkert at jlab.org>, "Bob Miller"<rmiller at jlab.org>,gotra at jlab.org, "Raffaella De Vita"<Raffaella.Devita at ge.infn.it>
> Cc: "SABATIE Franck"<Franck.Sabatie at cea.fr>, "DEFURNE Maxime"<Maxime.Defurne at cea.fr>
> Sent: Friday, December 22, 2017 10:15:58 AM
> Subject: MVT and FTT gas system
>
> Dear All,
>
> The mixing system for MVT, and FTT, is not yet operational and it seems it will not be ready for the January run.
> The fact that the system was put outside, without our consent, has lead to condensation and failure of the isobutene flowmeters.Two flowmeters have therefore to be changed and there is ~6 to 8 week delay.
> Also the setup outside must be done properly, and thoroughly tested, in order to avoid condensation again, or over pressure if the isobutene is heated too much.
>
> This means the mixing system will likely not be operational before ~ February, potentially March. Some premix gas, 10 cylinders, have been ordered but they might not arrive before mid-January.
>
> During the first December engineering run we have taken data in MVT with only two bottles of premixed gas, by closing them and opening them only before data taking, because if the very limited amount.
>
> This is not at all a stable way of having Micromegas detectors functioning. Indeed when gas flow is stopped, lines and detectors outgas and time is needed before having the good mixture inside again.
> Our detectors have a high ratio surface/volume (small drift), thus they have outgassed (surface) and need stable gas configuration.
>
> In fact we have two detectors showing signs of troubleshooting, one  entire layer of micromegas and one forward disk, and it is likely that the issue is due to "bad gas" mixture with HV on.
>
> Since the barrel detectors are sealed, the repair is not an easy task and needs at minimum replacement of drift Kapton window. At this stage, and considering the damage already done to the SVT, jeopardizing the central tracking capabilities, we have decided that we cannot take risk of further damage to the MVT:
>
> Therefore, if there is no stable gas configuration (either enough supply of premix or a fully operational gas mixing system),  we will not allow the MVT to be turned on.
>
>
> As it is JLab's responsibility to provide this gas to Hall B, we urge you to take the necessary steps towards establishing proper gas distribution as soon as possible.
>
> When Maxime is back at JLab after Xmas break, he will make a full presentation summarizing what has been observed so far during these first three weeks of engineering run.
>
>
> Best regards,
> Stephan, Franck, Maxime

-- 
Marc McMullen
Detector Support Group
757-269-7738

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mailman.jlab.org/pipermail/dsg-mvt/attachments/20180102/cc9447a7/attachment.html>