EDM B-Field Issues
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Transcript of EDM B-Field Issues
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EDM B-Field Issues
• EDM B-field Specifications• R&D Projects• Hardware Requirements
– What’s available– What’s needed
B. Filippone
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n-EDM Specifications3/28/03 pre-Proposal vs NSAC Sub-
comm.
• 10-3 homogeneity (@ B ~ 1mG) required over large volume and with large “penetrations”
(Any change for dn < 10-28 e-cm?)
• (1/B)dB/dt < 10-6/s via mag. shielding to minimize fluctuations and allow operation of SQUID sensors
(Need 10x better shielding for dn < 10-28 e-cm)
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B-field and Shielding
Superconducting Shield
Cos Magnet
~2.3 m
Plus external multilayermu-metal shield (to reduce local fields)
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Magnetic Shielding• EDM Apparatus at Low T (< 1 K)
– Superconducting shield is innermost shield in 3/28/03 pre-proposal
• But SC shield never used in previous EDM experiments
– Trapped flux may vary randomly giving increased B-field noise
– Anecdotal info [J. Eisenstein (CIT)] also not good
– Standard Ferromagnetic shielding (mu-metal) performs poorly at low T• With from 50,000 at 300K to < 10,000 at 4K
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• Discussed last time several advanced materials– Cryoperm10
• ( from 25,000 at 300K to 75,000 at 4K)
– Metglas• Amorphous metal• Very large un-annealed (>200,000) • Very small magnetostriction
– Small loss in under mechanical stress
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R&D Efforts
• Study & test low T behavior of promising ferromagnetic materials – Tests to 4K at CIT, to < 1K at UIUC
• Build ~ ¼ scale prototypes – Including Superconducting shield,
penetrations and Cos coil
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R&D Hardware
• 3-axis Hall Probe (at CIT)
• Cryogenic Hall probe
• Fluxgate magnetometer
• LHe and Transfer line
• Cryoperm & Metglas prototypes
• Mu metal and/or 3-axis Helmholtz to limit environmental fields
• 4K & 1K Dewar (at CIT & UIUC)
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¼ scale prototype from Amuneal ~ 2k$
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Comes in50mm x .02mm x 2,700,000mm
Rolls have one at Caltech ~ 1k$
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Wide Mouth DewarBorrowed from Jim Eisenstein (CIT)
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8 inch clear bore
20 cm
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Larger Bore Dewar also Available
200 cm
30 cm
20 cm
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R&D plans
• M. Cheung (summer student), T. Ito, BWF
• Order/assemble hardware 6-7/03
• 77K Ferromagnetic tests by 9/03
• 4K Ferromagnetic tests by 12/03
• 1K tests @ UIUC in spring 04