1. Utilities 14 October 2008 Martin Nordby, Gordon Bowden

2. LSST Camera Systems Integration 2 Contents Overview of services to camera Operating parameters for services Routing of utility lines Facility design overview Current issues

3. LSST Camera Systems Integration 3 Services to the Camera Heat extraction and environmental control –Cryogenic system –Cryogen vapor return –Purge system –Fluorinert cooling system Operations and control –Compressed air –Cryostat backing vacuum –Valve box backing vacuum –Power –Alarm signals out –Data and control fiber lines Cryostat vacuumValve Box vacuum Relief valve return Compressed air Nitrogen gas purge Cryogen

4. LSST Camera Systems Integration 4 Cryogenic System Operating Parameters Cryogenic cooling –Closed-loop temperature control of cryo plate and cold plate –Nominal temperature: -140 o C –Total capacity: 1400 W FEE process heat: 600 W (cryo plate) Cryo plate heat leaks: 16 W (cryo plate) IR heat load: 98 W (cryo plate) RCC process heat: 400 W (cold plate) Cold plate heat leaks: 36 W (cold plate) Transfer line losses: 250 W –Minimum flow rate: 1 kg/sec Cryogen properties –Cryogen: refrigerant R124 –Design mass flow rate: 1 kg/sec –Design volumetric flow rate: 8.65 gpm –Specific weight: 1.84 –Viscosity at -145 o C: 0.012 kg-m/s (compare with water: 0.001 kg-m/s) Flow configuration –Elevation difference: 93 ft (28 m) –Total circuit length: 712 ft (217 m) –Max pressure head: 87 psi –Total line losses: 95 psi Cold Plate Cryo Plate

5. LSST Camera Systems Integration 5 Camera Utilities Operating Parameters (1) Cryogen relief valve –Purpose Exhaust of vaporized R124 refrigerant during cool-down, line purging, or over-pressure condition Prevents venting to dome air –Design parameters Must handle 1 kg/sec flow rate at 100:1 expansion ratio, with < 2 atm back-pressure Insulated to prevent condensation Lines will run warm during normal operation Nitrogen gas purge –Purpose Temperature and humidity control of Camera and Utility Trunk volumes Preserve clean environment in the Camera volume Supply for emergency back-fill of cryostat vacuum volume –Design parameters Minimum 260 STP-liter capacity at 30 psi min pressure, for emergency back-fill Closed-loop temperature controlled flow with re-heaters Nominal temperature: dome temperature Minimum flow rate: 2 L/sec of 30 psi nitrogen Fluorinert –Purpose Closed-loop temperature control of support electronics crates in the Utility Trunk –Design parameters Nominal temperature: dome temperature –  T 2700 W total capacity = 2400 W of pump heat + 300 W electronics heat Minimum flow rate: 1 gpm

6. LSST Camera Systems Integration 6 Camera Utilities Operating Parameters (2) Compressed air –Purpose Power source for pneumatically-operated remote shut-off valves for cryogenic and fluorinert systems –Design parameters Filtered, oil-free air ~75 psi minimum pressure Minimum flow rate: 2 L/sec of 75 psi air Cryostat backing vacuum –Purpose Pumps down the cryostat from ambient, using roughing pumps on the ground Provides mechanical backing vacuum for turbo-pumps during normal operation Valve box backing vacuum –Purpose Pumps down the valve box to prepare it for cool-down Independent of cryostat system, allowing the cryostat to stay cold while the camera is being de-/re-mounted from/to the telescope

7. LSST Camera Systems Integration 7 Camera Utilities Operating Parameters (3) Data and control fiber lines –62 fiber lines, total Science data lines: 25 pairs of optical fibers Guider, WFS data lines: 4 pairs of optical fibers Control lines: 2 pair of optical fibers Alarm –Direct copper lines for camera protection circuits –Provide hardware enable/disable signals Power –6 kW on-camera capacity; 120V single phase (2x margin) Cryostat electronics: 950 W Support electronics: 250 Pumps: 2400 W

8. LSST Camera Systems Integration 8 Routing of Services to the Camera

9. LSST Camera Systems Integration 9 Routing of Camera Utility and Service Lines test/staging mirror coating data control office cable wrap platform lift shaft telescope pier entry mech. clean room white room camera utilities Suite of camera maintenance rooms on east side of service & ops building Approximate routing of utility runs from camera on telescope: On telescope mount & rotator to camera 76’+34’ To camera utility room - 281’ +10% for indirect routing = 310’ (location of Polycold units) From camera utility room to: - clean room - 30’ - white room - 50’ - test/staging area - 80’ Elevation drape Flex Line 20’+5’ margin From elevation drape to azimuth wrap 40’ Azimuth drape Flex Line 50’+20’margin Through enclosure to S&O building 10’+ 40’ In building to camera utility equipment 30’ Section through Enclosure & Support Building (showing routing of camera coolant lines) Elevation drape to spider 55' Spider Length (custom pipe) 12‘ + 2x2’ Flex Camera Cable Rotator (flex line) 30’ + Wrap to Camera (flex line) 9' Flex line: 50 + 20 + 25 + 4 + 30 = 129’ Hard line: 30 + 50 + 40 + 76 =196’ Flex Hard

10. LSST Camera Systems Integration 10 Ground Facility All camera utilities and service lines are routed to the Utility Room –All support hardware for camera operations is located in the Utility room –This includes UPS’, SDS and process controllers Total power estimate –66 kW needed 51 kW for 3 Polycold units 4.5 kW for pumps 2.4 kW to camera for pumps 1.2 kW to camera for power 1 kW facility electronics 3.9 kW miscellaneous –We may be able to go to 2 Polycold units…. All systems assumed to be water cooled, using facility chilled water Cryostat vacuumValve Box vacuum Relief valve return Compressed air Nitrogen gas purge Cryogen

11. LSST Camera Systems Integration 11 Camera Utilities Reliability and Fault Tolerance Redundancy/single-point failures –No moving parts or valves in the cryostat Fluid flow channels are in parallel We have not investigated whether these 3 parallel channels are 2-for-3 redundant –Valve box contains valves and flow instrumentation—this is presumably where problems would occur This is in a separate vacuum The valve box can be dis-assembled in situ, but it is not yet clear if we can do this on the telescope –Ground facility includes redundancy of critical components Polycolds: 2-for-3 redundancy Cryo pumps: either 1-for-2 redundancy or a “cold” spare ready for turn-on Servicing and repair concepts

12. LSST Camera Systems Integration 12 Open Issues Cryo cooling technology Cryo system design details Transfer line design, routing, and installation