Re: MuCap tel conf or not - status of both tpc's

[Claude Petitjean <claude.petitjean@psi.ch>]

Dear friends,

since tomorrow is for me not good for a teleconference, I give
you here an account of the status of both tpc's:

1) Gatchina tpc
===============

as you already know from Anatoly's report (see run 9 prep. e-log),
the Gatchina crew was quite successful to tune their tpc in
protium gas up to 5.8 kV without drawing large dark currents and
including the Sr90 Beta source radiating into the tpc volume.
On his last day, Volodja tried in 10 bar protium to reach
6.0 kV, but the tpc sparked at this voltage.

The 4-track picture in the report probably shows a Beta near
or at the Bragg peak - not a MIP (min. ionizing particle).
To study MIP's one needs to trigger a Beta at the exit and
look for correlated signals at the entrance of the tpc. This
shall be done in future studies.

The pulses (about 200 Hz/wire) seen without source are of
course not nice. Anatoly believes they come from edge regions.
He calls it "Micropulsing" and will study the problem on other
chambers back in Gatchina. At present it is not clear how
serious the problem is for routine operation in the beam
and how the situation can be improved in the future.

Another serious problem is the leak in the big valve from the
tpc volume to the turbo pump (2.2 liters/day at 10 bar). It fills
the turbo volume within one day to dangerous pressures and the
turbo volume needs therefore to be pumped frequently. On
Anatoly's request we have taken down the protium pressure in
the tpc to 1.2 bar and tightly closed the turbo volume. This
should be a reasonably safe standby mode.

Anatoly et al. will discuss the situation with Alexei before
making plans how to go on. One suggestion was to continue work
already in July.

2) PSI tpc
==========

 From Nov-04 - March-05 our tpc was totally overhauled and
equipped with new cathode planes, and all bad anode wires were
replaced by new ones.

As in the past, we are tuning up our tpc on a much slower
pace as compared with the Gatchina procedure. So far, we have
successfully finished tuning the tpc in 10 bar Nitrogen up to
6.25 kV (no dark currents). Then, a few weeks ago, we have
reduced the Nitrogen pressure to 5 bar (where the tpc shows
very similar characteristics as in 10 bar protium), and
we have started to run the voltage up again.

If successful, we will in June switch to operate the tpc in
10 bar protium. In July, we hope to get the tpc fully
operational - provided that no unexpected major problems occur.

With best wishes, yours

Claude

Peter Kammel wrote:
> Dear friends,
> 
> Please share your opinions whether we should have a telconf tomorrow.
> Illinois status: we are working but have no special issues to report
> tomorrow. Conc the moisture sensor I could talk with Bernhard off-line
> and we would inform you on the outcome per e-mail.
> 
> Another issue is the status of TPC2 tests before Valodja left, but that
> could also be reported by Francoise and Claude in an email.
> 
> With best regards
> 
> Peter