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Cryogenics for SuperB IR Magnets

This project aims to design a cryogenic system for the SuperB IR Magnets to ensure reliable and safe operations. The proposed solution involves bundling the magnets into separate cryostats and cooling them with pressurized He II. This design allows for sufficient travel of magnets while cold, permits warm beam tubes, and allows for independent warmup/cooldown of IR magnets.

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Cryogenics for SuperB IR Magnets

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  1. Cryogenics for SuperB IR Magnets J. G. Weisend II SLAC National Accelerator Lab

  2. Top Level Design Goals • Operate magnets reliably and safely. Allow safe operations during off normal conditions such as: quench, venting and vacuum failures • Meet space requirements • Use excess capacity of existing Babar cryoplant for cooling • Provide for sufficient travel of magnets while cold to allow access to vertex detector • Permit warm beam tubes • Allow warmup / cooldown of IR magnets independent of central solenoid

  3. Proposed Solution • Bundle magnets into 2 separate cryostats (QD0H,QD0L, Q5,S1) and (QF1H,QF1L, S2) and bath cool with pressurized He II (1.9 K, 1 Bar) • Advantages: • Larger combined cryostats allows room for 80 K thermal shield, MLI and lower heat leaks • Piping is simpler than trying to force flow cool individual magnets • 1.9 K operation allows for higher performance magnets either now or in the future • Pressurized He II eliminates boiling inside the magnet bath – heat transfer done via internal convection (no net mass flow) • Can be connected to existing BaBar refrigerator

  4. Proposed Solution • Advantages: • Significant experience with He II systems at other labs – CERN, FNAL, Jlab, DESY • Adds to He II cryogenic experience at Super B home institution (Italy) • Disadvantages: • More complicated & expensive feedbox • Possible leaks into subatmospheric piping – can be addressed by good QA program • Design alternatives are: • Distributed HE II HX - more heat transfer but results in 2 phase flow in cryostats • Boiling He bath at 4.2 K

  5. He IIInternal Convection Vn Q Vs TH TL • No net mass flow • Extremely effective heat transfer mechanism

  6. Insert 3D Model

  7. Vertex Detector Access Scheme

  8. Cooling Limits & Estimated Heat Loads • Available cooling from refrigerator at 1.9 K: ~ 3.5 g/s ~ 77 W • Internal Convection Heat Transfer Limit per side assuming a 2.5 “ ID line – 24 W • Estimated Heat loads per side: • Conduction - 16 W (assumes 8 supports @ 2 W each) • Thermal radiation ~ 2 W • LDI/DT – TBD • Ionizing radiation - TBD

  9. Next Steps • Finish conceptual design including: • Iterate with magnet design – more detailed design of supports • Finalize connections to BaBar refrigerator • More detailed safety analysis • More detailed heat leak analysis including LdI/dt and ionizing radiation load (if any) • Description of operating modes • Layout of control system – make use of existing Babar cryocontrols? • Conceptual design review (Summer 2010) • Detailed design work • Preliminary and Final design reviews (Start in late fall 2010) • Construction and commissioning

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