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Dear Peter and Claude,
As it was decided at the November meeting at
PSI, a second TPC detector should be constructed ,
so that both TPCs could be replaceable during the physics runs. We all understand how
important is this task
for relayable performance of our
experiment.
Here we present a tentative plan on how to achieve
this goal.
1. Cylindrical
Al-vessel with Al-flanges.
Claude has already ordered
this vessel at the PSI workshop using the existing design.
The promise is to produce it in
April. Then it should be transported to PNPI.( May )
2. Outer
flanges.
These steel flanges
should be produced at PNPI . They should fit exactly the existing
Al-flanges.
Claude will provide
the old drawings of the flanges. It would be nice to have these flanges ready
also in May.
3.
Be-window
There is already a design of such window at PNPI and
preliminary agreement with a company to produce these
windows. This will be a sphere of 50 mm in diameter and
with 0.5 mm thickness.
These
windows might be fabricated only in Summer. We shall try to accelerate
this process.
4.
QUESTION
Should we forsee also changing the window for Be in the first TPC? For
safety reasons and also to
gain in the muon stop rate.
Or maybe
it would be better to build the whole big flanges also for
the first TPC,thus solving t in addition
the
existing problem with gas leaks?
5. 30 kV HV
input connector
Fortunately, it is available at PNPI.
6 .
7 kV HV and multi-pin input connectors
Same type as
used in the present TPC but with modified fixation in the flange
body to allow the safe heating.
We would
ask our US colleagues to provide these connectors. It is an urgent
task.
7.
TPC wire chambers
PNPI will
construct all the chambers (PC2 and TPC) as well as everything else inside the
TPC detector
so that this
detector could be assembled and tested at PNPI.
A new
technology for strip depositing on the glass frames has been tested recently
with very optimistic results.
We are going
to use this technology to build the TPC planes.
8. Testing the TPC detector at
PNPI
The
ideal goal would be testing the TPC detector under real conditions ,that is
using heating,
gas
circulation/purification system ,gas analysis etc.
The main
problem here is that so far we have no free-of-oil for-vacuum
pumping.
We shall
try to buy such pump . We may have money for this,though it is quite
expensive.
Unfortunately, we
are not sure that this can be done by
Summer.
In this case the TPC
detector can be tested at PNPI only with nitrogen
9.
How to disconnect the TPC detector from the vacuum system.
To replace
one TPC detector by another,we should have possibility to
disconnect it from the vacuum system.
How to do this?
Just to cut the tube and put there the flanges? In this case the air will
enter the TPC during these
manipulations. Or
to put in addition the valves closing the TPC? It would be much
better, but how expensive?
This problem
should be discussed with Claude.
CONCLUSIONS
In principle, there is a non-zero chance to build
the new TPC by the next run in August 2003, though this will require
big efforts, especially at PNPI.
In this planning we believe that the
central Al-vessel will be built at PSI in April.
It is urgent to understand the situation
with the 7 kV and multi-pin connectors , as this might appear to be a
critical
point for the time scale of the whole
project.
Please, give me your comments. In particular, on
the connectors and on the point 4 of this mail.
With best regards Alexey
P.S. I have prepared also a
report on the gas circulating system and on our plans to have highly
depleted
protium. I
shall send it to you next week after additional discussions with PNPI experts.
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