Pixel Cooling Upgrade (2013) 1 December 20081Hans Postema - CERN

Cooling Pipes The currently installed cooling pipes are virtually impossible to replace People ask: “Is this really the case” Please have a look at the following slides 1 December 20082Hans Postema - CERN

Empty YB0 – far left 1 December 20083Hans Postema - CERN

YB0 – fully cabled 1 December 20084Hans Postema - CERN

YB0 - numbers Tracker cooling pipes below all the cables HB: 180 cables, 180 optical fiber cables EB: 1600 cables, 180 optical fiber cables Tracker: 3000 cables, 640 Optical fiber cables 9 month plus, installation time Removing and reinstalling ~10 year old EB cables is inviting trouble 1 December 20085Hans Postema - CERN

Re-use of installed pipes The currently installed pipes are OD=14 and OD=16 mm copper pipes with a wall of 1 mm Cannot be used for 2 phase CO2 cooling without special precaution But can be used when the system design takes care that pressures remain below a limit Avoiding 100+ bar pressures is also advantageous for detector design 1 December 20086Hans Postema - CERN

Storage tank The system contains a cooled storage tank When system is inoperative, all liquid is condensed in the tank, all warm components are filled with gas (Standard for cryogenic systems) A very similar system is used for the CDF COT flange cooling, same concept, different fluid, different temperature. See next slide 1 December 20087Hans Postema - CERN

CDF – COT endplate cooling Courtesy Richard Schmitt FNAL 1 December 20088Hans Postema - CERN

Which pressures Strong request for detector operation with coolant at +15 C. Avoids condensation during the installation and testing phase. For this a safety valve setting at 57 bar, corresponding to +20 C seems acceptable. Normal operation is below 0 degree C, which corresponds to 35 bar 1 December 20089Hans Postema - CERN

Operation modes Normal operation, system cooled by commercial chiller, CO2 temperatures between 0 and -20 C, pressures 35 to 20 bar Testing during installation, system cooled by chilled water, temperature +15 C, pressure 50 bar Storage during shutdown, cooled by standard CERN chilled water system, temp +5 C, 40 bar 1 December Hans Postema - CERN

CERN safety First contact with CERN safety (preliminary) Pipe-work to be tested at 1.25x maximum operating pressure 1.25 x 57 bar = 71 bar Safety valve set at 57 bar CO2 charge will not be vented as long as the tank remains below +20 degrees C 1 December Hans Postema - CERN

Copper pipe Installed pipes are “soft” copper 16x1 mm Material tested by S. Sgobba – CERN UTS 217 Mpa, elastic limit 0.5% 106 Mpa Stress during pressure testing 55 Mpa Safety factor of ~2 during pressure testing! Situation seems rather comfortable All this TBC by CERN safety 1 December Hans Postema - CERN