Slide 1 D G Haase, EDM Meeting, 5/06 Refrigeration and Heat Budget for the EDM Cryostat David G. Haase Physics Department North Carolina State University

Slide 2 D G Haase, EDM Meeting, 5/06 Overview of the refrigeration Room temperature vacuum vessel Intermediate temperature shield –Cooled by vapor, LN or GM cooler Liquid helium at 4.2 K Pumped helium coldplate at 1.5 K DR or 3 He cooling at 0.25 < T < 0.5 K

Slide 3 D G Haase, EDM Meeting, 5/06 Target cooling powers 50 Watts at T intermediate (50 K) 3.6 Watts at 4.2 K (5 liters of LHe/hour) 1 Watt at 1.5 K 80 mWatts at T operating = 0.5 K

Slide 4 D G Haase, EDM Meeting, 5/06 Cooling power of dilution fridge

Slide 5 D G Haase, EDM Meeting, 5/06 Cooling power of dilution fridge 60 mW at T = 0.5 K (one fridge)

Slide 6 D G Haase, EDM Meeting, 5/06 Heat Sources Conduction from higher temperatures Infrared heating from higher temperatures Electrical heating P = I 2 R Mechanical heating from operations

Slide 7 D G Haase, EDM Meeting, 5/06 How you minimize heating to refrigerators? Heat sinking at higher temperatures Radiation shields at higher temperatures Low conductivity wiring and supports Use materials that cool readily Vacuum integrity

Slide 8 D G Haase, EDM Meeting, 5/06 How you minimize cooling times? Cooling time Problems - glasses Thermal boundary conductances - Kapitza resistance

Slide 9 D G Haase, EDM Meeting, 5/06 Budgetary Assumptions Two dilution refrigerators T operating = 0.5 K Wiring, radiation and support heat leaks at 0.1 mW /package No tax cuts or moving costs to next generation

Slide 10 D G Haase, EDM Meeting, 5/06 Proposed heat budget (operation, T = 0.5 K)

Slide 11 D G Haase, EDM Meeting, 5/06 Proposed heat budget (operation, T = 0.25 K)

Slide 12 D G Haase, EDM Meeting, 5/06 Other cryogenic issues Differential contraction Demountable vacuum seals Welds Temperature gradients Virtual heat leaks Superfluid leaks Pathologies - e.g., Taconis oscillations, blind tapped holes, bad brass, nuclear susceptibilities, superconducting transitions at the wrong spots, wrong cryo coax, poorly cleaned tubing and pinhole leaks,…

Slide 13 D G Haase, EDM Meeting, 5/06 Conclusion Follow the cryogenic advisories Please do not be offended by my questions to you Ask for help and advice on your designs Always think about the budget consequences

Slide 14 D G Haase, EDM Meeting, 5/06