Utilities 14 October 2008

1. Utilities14 October 2008 Martin Nordby, Gordon Bowden

2. Contents • Overview of services to camera • Operating parameters for services • Routing of utility lines • Facility design overview • Current issues

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 Relief valve return Nitrogen gas purge Cryostat vacuum Compressed air Valve Box vacuum Cryogen

4. Cryogenic System Operating Parameters • Cryogenic cooling • Closed-loop temperature control of cryo plate and cold plate • Nominal temperature: -140oC • 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 -145oC: 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. 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 – DT • 2700 W total capacity = 2400 W of pump heat + 300 W electronics heat • Minimum flow rate: 1 gpm

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. 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. Routing of Services to the Camera

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

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 Nitrogen gas purge Compressed air Relief valve return Cryogen Valve Box vacuum Cryostat vacuum

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. Open Issues • Cryo cooling technology • Cryo system design details • Transfer line design, routing, and installation