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

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

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) 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: Advantages: Larger combined cryostats allows room for 80 K thermal shield, MLI and lower heat leaks 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 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 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) 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 Can be connected to existing BaBar refrigerator

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

He II Internal Convection No net mass flow No net mass flow Extremely effective heat transfer mechanism Extremely effective heat transfer mechanism Q VnVn VsVs THTH TLTL

Insert 3D Model

Vertex Detector Access Scheme

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

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