TCS Chiller Performance Review Phil Willems Nov. 17, 2004 LIGO R&D

Design Requirements Laser temperature: around room temperature, ±.5K Flow rates: Device Max power dissipated Flow requirement Source of requirement Carbon dioxide laser 80W ½ gpm Access Laser Co. Laser power supply 40W ‘cool to the touch’ AOM 30W 250 ml/min IntraAction, Inc. AOM driver TBD Noise: acoustic and EMI must be under ambient at nearest sensitive device (optical lever system) Monitoring and control from control room using EPICS Leak tight and robust LIGO R&D

Commissioning Timeline Device was installed on 2K Y arm Oct. 27-29 Device was commissioned from Oct. 29 to Nov. 8. Commissioning paused after overheating incident Nov. 6-7. Forensics from Nov. 8 to today. LIGO R&D

Installation Site chilled water delivered to chiller from over 100 feet away through uninsulated copper pipe This may account for some temperature issues and surges during control valve operation Site chilled water and TCS table water pipes interlaid and touching Insulation of TCS table supply pipe required for temperature stability Prototype control electronics not plug and play Control software implemented but not safety interlocks LIGO R&D

Commissioning Submerged thermistor failed after 2 days (Nov. 1) Thermistor was fine; problem later traced to bad solder joint outside chiller Short term solution was to glue another thermistor to pipe leaving chiller Laser power stabilized without AOM on (Nov. 3-5) Laser power unstable with AOM on (Nov. 5) Chiller noise performance verified (Nov. 6-7) http://blue.ligo-wa.caltech.edu/ilog/pub/ilog.cgi?group=detector&date_to_view=11/07/2004&anchor_to_scroll_to=2004:11:07:22:32:32-robert LIGO R&D

Overheating Incident After noise test, chiller was switched on to run overnight Apparently, one or both pumps failed to switch on System ran at very high temperature for about 1-2 days Much damage and corrosion to the chiller Thermistors on TCS table showed no overheating, no flow to table- TCS table not affected LIGO R&D

Why a Chiller Is Not a Boiler LIGO R&D

Overheating Incident Analyzed Without submerged thermistor operating, no way to monitor chiller reservoir temperature Without software interlocks programmed, system could not power down safely had the submerged thermistor worked Had system been fully operational before running unattended chiller would have safely shut itself down Why did pump fail to start? LHO reports that all Rio pumps studied failed to start 100% of the time LIGO R&D

Forensics Chiller disassembled, analyzed, and rebuilt Now it runs well even with the AOM on (for 30 minutes at least…) Rio 1100 pumps tested for reliability One pump tested by hand- 200 starts without failure One pump tested by robot- robot itself not 100% reliable, but pump starts ~15,000 times without failure Rio 2100 pump known to fail at LHO now under test Coolant corrosion tests Chloramine T not compatible with chiller components under accelerated aging test Propylene glycol and sodium hydroxide are compatible LIGO R&D

Chiller Performance After Rebuild LIGO R&D

Final Results Compared to Requirements Temperature of chiller and laser held to within .5K, as required Flow rate is 1.3GPM, as required Acoustic and electromagnetic noise is below ambient, as required Operation fully controlled and monitored from the control room, as required System is not yet robust to failure modes Design not fully implemented, software interlocks missing when needed New safeties can be added without change to conceptual design LIGO R&D

Are the Design Requirements Good Enough? The TCS laser stability is unverified even though the TCS chiller meets requirements. Laser power and coolant temperature fluctuations are frequently correlated. Is .5K temperature stability sufficient? Is 1.3GPM flow sufficient? Recommend that no more TCS chillers be installed until reconditioned prototype performance is verified. New chiller parts will replace boiled parts Software interlocks will be fully implemented Hardware interlocks under consideration Plan new commissioning effort Nov. 29-Dec. 3. LIGO R&D