SQUID NMR Signal

1
SQUID NMR Signal
Outline Overview of SQUIDs in EDM present
thinking - experimental design ideas -
expected signal, SQUIDs Update on SQUID NMR/MRI
progress Obstacles and Issues 15 month
plan - Final Design - Noise tests - NMR tests
on polarized 3He - High voltage tests
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Overview of SQUIDs in EDM present thinking
Experimental Design Ideas (big coils vs.
gradiometers)
Expected signal in 40x4 cm2 coil 13.5 m?0
coupling to SQUID 1 for 10-4 ?0. SNR 10
Expected signal in one gradiometer 10-19 Wb,
limit 2x10-19 Wb SNR 1/3 Definitely Need Array
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Overview of SQUIDs in EDM present thinking
Expected Signal, SQUIDs

• Clearly signal larger for big coil
• Vibration
• Gradiometer advantages
• Array of gradiometers
• (12x12 with 36mm baseline)
• Gradiometers AND big coils, big gradiometer?
• Modeling Requirements (Chen-Yu)
• Multiple SQUIDs? Coil position? Other designs,
  48x48 make grads wider?

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Update on SQUID NMR/MRI progress
Simultaneous measurements of biomagnetic signals
and anatomy
Volegov, et al., Mag. Resn. Med., 52, 467 (2004)
B0 60 G, Bm 5.5µT

• - Measurements through/in presence of metal
• Electronics for helping SQUIDs survive pulse,
  pulse sequences, cryoswitch already exists
• Systems/hardware in place for tests
• Understanding of NMR issues (transients, eddy
  currents etc.)

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Update on SQUID NMR/MRI progress
T2 Contrast Image at 12?T (First ever T2
contrast image at ?T fields)
Kraus, et al., Human Brain Mapping (2005)

Distortions due primarily to Bp inhomogeneities
Density Contrast image of Human Hand
Zotev, et al., 4EG08 ASC (2006)
7-channel ULF-MRI reconstructed using SENSE
(sensitivity encoding) approach
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Remaining Obstacles and Issues

• - Vibration noise
• Leakage current from HV electrodes
• Johnson noise mu metal inside superconducting
  shield, electrode material, sc shield material
• Eddy currents
• Other noise sources
• Feed-throughs
• Andrei/Steve discussion about RF shielding

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15 month plan
What needs to be done/ what we can offer
Modeling, final design of SQUIDs SQUID/pick-up
testing Noise testing (Johnson noise of materials
- easy at 4K, can be moved into dilution
refrigerator) NMR tests on 3He with SQUIDs HV
Test with SQUIDs NMR signal extraction
(experience with ULF-NMR, multiple component
analysis, NIH grant)
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15 month plan