High Resolution LTS-SQUID Magnetometer
Abstract
Biological systems present a challenge to magnetic imaging Superconducting Quantum Interference Devices (SQUID). A field resolution of a few hundred fT/Hz^1/2 and spatial resolution of 0.1 to 0.3 mm are needed to image the magnetic fields produced by action and injury currents in isolated tissue. To achieve the highest field sensitivity with a 0.3 mm spatial resolution we designed and optimized a LTS thin-film SQUID with integrated pickuploops. The optimized configuration consists of a four turn pickuploop and a one turn balance coil forming an asymmetric gradiometer with a 3 mm baseline. A flux transformer couples the flux difference to a double loop SQUID sensor. The flux noise of the device is 2.3 microphi-naught/Hz^1/2 above 0.5 kHz, resulting in a field sensitivity of 130 fT/Hz^1/2. The SQUID chip is mounted in the vacuum space of a cryostat behind a 0.05 mm sapphire window resulting in a .07 mm spacing between a room temperature sample and the SQUID chip. Tests on a photolythographic wire pattern demonstrate a 0.3 mm spatial resolution. We are investigating biological and geophysical samples and initial results will be presented.
- Publication:
-
APS Southeastern Section Meeting Abstracts
- Pub Date:
- November 1998
- Bibcode:
- 1998APS..SES..EE10B