[Dsg-mvt] suggestions for the MVT gas system priorities and plan for this summer and fall?

[Mac Mestayer]

Hello George and Volker;

First, thanks to George for a very enlightening discussion of
some of the relevant facts to consider.

Here are a few comments:

1- the barrel and forward micromegas detectors are said to require
15 l/hr (each) in operation.  At 30 l/hr one cylinder (850 liters)
of pre-mixed Ar/C4H10 lasts for 30 hrs.  So, we would be paying at most 
$240/day for MM gas.

The reason I say "at most" is because I suspect that the relatively
high flow rate they request is to prevent aging which is much less in
the low-radiation environment of the clean room.

Now, this is assuming that we can commission with Ar/C4H10, which I
think is true.

In the hall during beam operation, the detectors will need 15 l/hr of
Ar/C4H10 and about 20 l/hr of an Argon/C4H10/CF4 mixture.  Since this
is very expensive in pre-mix form and since we cannot have C4H10 bottles
in the hall, this gas supply should be done properly in the gas shed.

My suggestions:

1- save the one-time labor to certify a temporary flammable-gas mixing
system and go with pre-mix Ar/C4F10 for the EEL commissioning, and

2- use flow rates considerably smaller than 15 l/hr (on this, consult
with Stephan and Franck), and

3- for the engineering run, do the full design, certify and build of
a combined Ar/C4H10 and Ar/C4H10/CF4 in the gas shed.


 				regards, Mac

"mestayer at jlab.org", (757)-269-7252