Present: M. Bosteels , L. Feld, R. Gregory, R. Hammarstrom, M. Hatch, A.
Onnela, H. Postema and A. Smith.
Apologies had been received from G. Hallewell, S. Ilie and A. Placci, but Greg
arrived as the meeting was closing.

1. The minutes of the previous meeting were accepted.

2.  Draft Program for irradiation tests
Sorin was visiting PSI which is why he was unable to attend. PSI was willing
to have tests carried out on their facilities with both neutron and gamma
irradiation being available. Sorin had gone to get details of the type of
containers which could be used, and to try to arrive at a schedule. It was
likely that there would be no charge for the use of their facilities. He had
also made contact with ENEA and might also make some tests there.
Sorin had obtained 6 Kg of FC 72 (C6F14) which he planned to use for the first
tests. Only after testing the pure fluoroinert, would “dirty” samples be
tested e.g. with disolved air.  The apparatus needed for the tests was being
assembled and some parts were undergoing maintenance.

3. Update on Phase I tests
Antti reported that the liquid cooling unit was not yet fully assembled but
most of it had been running for more than a week. He would use it at 20C but
it could also be used at -25C if there was a wish to do so. Geneva University
also had a system in operation. Michael said that the C4F10 (& C3F8) tests
would start after the system delivered from Marseilles had been reassembled.
Hans confirmed that CMS was only interested in liquid cooling at present and
that this applied to all detectors including the pixels.
Alasdair asked about the availability of test pieces for the phase I tests but
it appeared that few elements were being prepared especially for this.
Mark wished to see the goals of the Phase I tests for ATLAS written in a
concise form. Mark would ask Greg and Geoff Tappern to define this. It was
recalled that one of the earlier CCG meetings had spent a long time discussing
Tapio’s written criteria for Phase I and II.
The needs of CMS for Phase I were considered to be understood.

4. Phase II tests
In the absence of Greg, and given the lack of interest from CMS and ALICE in
the gas refrigerants, it was decided to limit the discussion to liquid
cooling.
Robert Hammarstrom wished to have tests carried out at -20C with a cooling
circuit having feed lines of 20-30 m length. These would have to be properly
insulated and equiped with isolation valves etc. He would prepare 2 half discs
to be tested. A complete disc would comsume 700 W and he expected that an
equivalent heat load would be provided by the supply piping. Thus he would
need a minimum of 1.4 KW cooling power.
CMS plans to use only stainless steel piping as they consider that aluminium
tubes would provide the same amount of material owing to the need for greater
pipe thickness. Al tubes are also more difficult to bend and weld than st. st.
It was suggested that the CCG makes a recommendation that all cooling pipes be
in st. st.
ATLAS and CMS are both interested in supporting Phase II liquid cooling tests.
At the same time, both wish to study the possibility of cable cooling using
the return flow. The refrigeration plant used for -20C cooling will also be
able to be used for cooling tests around ambient temperature.
Although no great interest was expressed at the meeting for under pressure
systems, it was pointed out that the ATLAS liquid Argon electronics group and
the Tile calorimeter group wish to have an under pressure system.
It was agreed that Hans for CMS, and Michael and Greg for ATLAS, would
investigate within their respective experiments what has to be tested in Phase
II. The information wanted includes the number of modules to be tested in
parallel, their power dissipation, size and orientation.

5.   Next meeting
Greg arrived while discussion was taking place on the timing of a smaller
meeting to cover the gas refrigerant Phase II tests. This meeting was then
arranged for 7th July and would involve only a subgroup of those present.

The next CCG meeting is provisionally arranged for Tuesday 18 August at 14h00
in B40 R-C10.  This will be confirmed or cancelled nearer the time.
 
 
 

Notes from the meeting of 9-7-98 between Greg Hallewell, Mark Hatch, Hans
Postema and Alasdair Smith

Phase I

Greg believed that both C3F8 and C4F10 should be tested in Phase I.  RAL is
producing test structures for these tests. The question was posed as to
whether C3F8 would work with the larger diameter tubes needed for C4F10.  This
has to be checked but it was felt that flattened tubes would not work because
of the increased pressure. The ATLAS SET was planning to use evaporative
cooling and, like the pixels, would use 4 mm diameter tubing which could also
be used for liquid cooling. These detectors planned to use 0.2 mm Aluminium
piping. It was pointed out that, as mentioned in the above minutes, CMS would
use stainless steel throughout as being easier to bend and to
weld/braise/solder and that most members of the CCG were also in favour of
st. steel.
Regarding the induced radioactivity in fluoroinerts, Alasdair reported that G.
Stevenson did not reckon this to pose a problem for leaks in the cavern, where
the activation of the air had to be taken into account and was more of a
problem. It was not known whether there would be a problem if the compressors
were on the surface.

Phase II

The ATLAS pixels and SET are the only candidates for evaporative cooling. The
pixels would have 5 cooling circuits each with an input and output reservoir.
Greg planned to test controls software already in phase I and tests would
include shutting off power to a stave or staves and observing the behaviour ot
their temperatures.
 

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