MEETING FOR VACUUM SYSTEM

MEETING FOR VACUUM SYSTEM (06/06/03)

Present: A. Jokinen, S. Meunier, I. Podadera, D. Porret

At the end, the layout will have to be discussed with the radioprotection group.
The nitrogen venting that was before the forepumps must be removed (we could put it in the turbopump).
At ISOLDE the forepumps have to be ALCATEL 2033H (30 m³/H) which is hermetic and doesn’t have leaks.
The RFQCB has to be very clean system, even manufacturers proposed at Jyväskylä to put membrane oil-free forepumps, to avoid some oil diffusion to the system.
David suggests to use pirani gauges for every turbomolecular pump.
If the pressure is not too good after the main pump (TP1), the other two pumps (TP2 and 3) would be affected.
It’s possible to work without HV valves but if some of turbopumps broke down all the system should be stopped. Better if these valves are controlled automatically.
The solution of taking the bypass directly of the existing ISOLDE system is more complicated from the point of view of control system.
Ari comments that the system won’t be vented very often.
A bypass would be necessary to prepump the cavity.

Final decision (after different proposals):

Use of only one forepump for all the 3 turbomolecular pumps and another forepump in a roughing line to bypass the system during the startup.
The procedure (pumping-down) will be studied.