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Re: Plans for the second TPC
Dear all,
I read Alexei's plans for the second tpc. I agree basically
with these plans which were formulated last December at PSI.
I have a number of comments as follows:
ad 1) The Alu vessel is indeed on order in the PSI workshop.
We will just make 32 holes for M10 screws - no special
hole of smaller size.
ad 2) The PSI construction drawings of both steel flanges are
underway to CERN. Besides the beam window, one should
also separate the evacuation tube from the back flange.
ad 4) Changing the window in PSI's tpc setup is unrealistic
this year. There is no time for reconstruction.
Conc. gas leaks: we have sealed all 50 pin connectors
with an epoxy-like material. This was successful, but
it must be rechecked, if it holds tight in the longterm.
This check will be done hopefully in one to two weeks
from now.
ad 5) We have reconstructed the outer part of the 30 kV plug
with protection resistor. It is now hv sealed with oil.
For the first time it does'nt spark anymore.
ad 6) The problem with welding the 50 pin plugs is, that it
must be done without stress. Andi Hofer has a lot of
expertise from the "POLDI" detector (He3 det. for SINQ).
One has to adjust the hole in the flange exactly to
the outer form of the plugs.
ad 8) Oil free pumping is absolutely essential. I have no
money for new pumps, but we could provide our old
turbo pump which was used for the muCF experiments.
This does'nt solve the problem of oil free fore-vacuum,
of course.
ad 9) The clear experience with our PC2 is, that flooding a
well formed chamber with Nitrogen and then evacuate
+ bake it, does not deteriorate the chamber. One can
very quickly reach again the design performance.
Exchanging the tpc vessels, means indeed that it has
to be flooded with Nitrogen. Buying another big 10 bar
to high vacuum valve would be simply too expensive
and delivery very long (about 1 year).
I hope this helps your planning! With best regards
Claude
Alexei Vorobyev wrote:
>
> 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.
>