Present: M. Bosteels , L. Feld, S. Grohmann, G. Hallewell, R. Hammarstrom, S.
Ilie, J. Inigo-Golfin, A. Onnela, B. Pirollet, H. Postema, A. Smith and M. Wilhelmsson.
 

1. Primary Cooling Sytems and Integration with the Experiments
Mats introduced several members of his group, B. Pirollet who is responsible
for the primary cooling plants, J. Inigo-Golfin from the design office and S.
Grohmann from the specialised cooling firm, ILK Dresden. The last will be
present at CERN for a year, partly supported by ST-CV, ATLAS and CMS, and
these experiments were encouraged to use him as a consultant. Mats gave an
overview of ST-CV and its mandate. He presented the current layout of the CMS
cooling circuits with one cooling circuit per subdetector in the USC. It was
recognised that subdetectors with common requirements should be supplied from
a common circuit. Closest contact had been made with CMS ECAL. All of the
cooling tower tenders will be sent out this year with construction foreseen to
start in 2000. The water chillers and the surface and pit pipework will be
tendered in 1999 for construction in 2000-2002. Lastly, the underground
cooling stations will go for tender in 2000 for construction in 2001-2003.
ST-CV must be closely involved in the design of the detector cooling plants to
achieve standardisation of components and controls such that maintenance can
be included in a standard service contract. ST-CV will be able to assist with
the design and installation of the pipework between the USC’s and the UX’s as
well as some of the UX pipework.

2. Status of Phase I test preparations
Michel announced that the uniphase plant was already running. He then
presented the evaporative circuit constructed using some of the Marseille
system’s components. He had provided a pump which would enable the circuit to
be used with C4F10 and this could be bypassed to allow the circuit to be used
with C3F8. Although the liquid arrives at room temperature at the evaporator,
he had added a heat exchanger to cool it via the return gas. Evaporation takes
place via an expansion valve instead of the ruby orifice or capilliary which
will be used on the actual detector.  Three pixel staves were available but
the University of Geneva might be able to supply a further ten staves. The
present circuit would be upgraded by adding a pressure regulator at the input
to the evaporator to provide better control and the ability to work at
different input pressures. Although this could be used to simulate loads at
different heights, he felt there would still be a need to carry out tests with
real height differences as the return pressure to the pump was important.
There would be about 500 W cooling power available with C4F10 and about 2 KW
with C3F8.
Antti presented the first results from the uniphase tests on a 1 m long ladder
with a simulated heat load. The cooling tubes were of 2 mm outer diameter and
1.86 mm inner diameter. The results implied that the water tests had been
carried out with laminar flow and the fluorocarbon tests with turbulent flow.
Similar performance in terms of temperature difference could be achieved by
fluorocarbon circulation with a in/out pressure difference five times higher
than for water. Tests would continue on parallel circuits and vibration
measurements. Samples of the ATLAS TRT units were needed for testing.

3.  Status of preparations for irradiation tests
Sorin announced that tests at PSI Villigen would start around 15 September
using thermal neutrons from the SINQ spallation source and Co60 gammas. He had
received polypropylene vials capable of withstanding 120C for the neutron
tests and had 4 st. steel bottles 20cm high and 15cm in diameter for the gamma
tests. The measurements would be free of charge. Test with Co60 were possible
also at ENEA Casaccia and 6 st. steel bottles had been prepared.  It might
also be possible to have fast neutron activation via the TRIGA or TAPIRO
reactors but this can only be confirmed after agreement has been reached with
ENEA after 7 September.
6 Kg of Flouoroinert FC72 (C6F14) had been provide free of charge by 3M and 6
Kg of PFG 5040 (C4F10) had been provided free of charge by O. Ullaland of TA2.
Both samples had been analysed and found suitable for the tests.  Sorin
finished by listing the status of the various pieces of analysis equipment
which will be needed for the measurements on the irradiated samples.

4. Phase II tests - where, when and how many.
Michel explained the need to have bigger cooling circuits to cool full scale
prototypes and presented a possible circuit for uniphase cooling at -25C with
2 KW capacity. Robert later pointed out that his plans would require  about 5
KW capacity and Michel said that this would only require using a larger pump
which would involve only a small increase in the price of the system which had
been estimated at 20-25 KCHF. Michel’s circuit had a pump working at 6 bar for
fluorocarbons. The pump would probably have ceramic-ceramic contacts to
provide sealing. A heater would allow control of the input temperature to the
cooler/condenser. The final system would be likely to require a pump capable
of working in a magnetic field. Control would be via a PLC. Mats pointed out
that there had been a recent report on PLC standardisation for the LHC
machine.  It was believed that the recommended standard would be capable of
connection to both Siemens and Telemechanique devices. Greg was concerned that
the ATLAS silicon group(s) had not been involved in the discussions on the PLC
for the cooling system Michel had just presented, as uniphase flouoroinert was
their fall-back solution in case of problems with the evaporative systems.
Eric Perrin had been contacted by Hans but had said that his group did not
wish to get involved in the phase II tests at the moment.  Although it had
been agreed by those concerned that the uniphase II tests did not require a
full height difference and hence could be carried out in B186, the evaporative
tests  would require the full height because of uncertainty concerning the
return pressure. It became obvious that there was a need for a meeting devoted
solely to Phase II and that this should include representation from the ATLAS
and CMS slow controls groups (+ ALICE and LHCb?) as there were major
differences in what those present believed the phase II tests should include
regarding control of detector electronics power and HV.
Robert presented his planned cooling circuit for the CMS forward silicon
tracker Phase II tests. He wished to have 2 loops at -25C, each requiring
cooling power of 300 W on the feed lines and 800 W on the detectors and
electronics with an additional 1200 W being used to test cooling of power
cables via the return lines. This would require a total cooling power of 5 KW.
 

5.   Next meeting

The next CCG meeting is arranged for Wednesday 23 September at 09h00 in B40
R-B10.  This meeting will be devoted to the Phase II tests and will have a
larger circle of attendees than usual.

It was agreed that Eric Perrin be asked to give a report on the work carried
out at the U. of Geneva at a later meeting. Graham Stevenson will be contacted
once more for the problems associated with irradiated fluorocarbons and might
also give a presentation at a future meeting.

 
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