EDM B-Field Issues

• EDM B-field Specifications• R&D Projects• Hardware Requirements

– What’s available– What’s needed

B. Filippone

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)

B-field and Shielding

Superconducting Shield

Cos Magnet

~2.3 m

Plus external multilayermu-metal shield (to reduce local fields)

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

• 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

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

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)

¼ scale prototype from Amuneal ~ 2k$

Comes in50mm x .02mm x 2,700,000mm

Rolls have one at Caltech ~ 1k$

Wide Mouth DewarBorrowed from Jim Eisenstein (CIT)

8 inch clear bore

20 cm

Larger Bore Dewar also Available

200 cm

30 cm

20 cm

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