Berkeley Laboratory researchers have demonstrated a novel superconducting gradiometer that helps to reduce ambient magnetic field noise generated by relatively distant sources in favor of tiny magnetic signals generated by a local source. This is another step toward the operation of SQUID-based instruments in an unshielded environment: for example, for the detection of magnetic signals produced by the human heart or brain.
The asymmetric gradiometer consists of a thin film of YBa2Cu3O7-x (YBCO) patterned to form two interconnected loops, one much bigger than the other. The smaller loop is inductively coupled to a high-transition-temperature (high-TC) magnetometer. The dimensions of the gradiometer are carefully chosen so that a uniform magnetic field induces no response from the magnetometer. On the other hand, application of a magnetic field that varies spatially along the length of the gradiometer produces a response that is proportional to the gradient. Tests show that uniform magnetic fields in any direction are reduced by at least a factor of 1000. The device involves a single layer of YBCO, and should be relatively inexpensive to manufacture, even with baselines sufficiently long for medical applications.
The most likely applications are in biomagnetism: for example, magnetocardiology and magnetoencephalography. Other potential applications are in nondestructive evaluation of materials.
This work was done by John Clarke and colleagues at Ernest Orlando Lawrence Berkeley National Laboratory. Patents are pending on this invention. Berkeley Lab seeks partners for licensing and/or collaborative development and commercialization of this new technology. For further information, contact Steve Hunter, Technology Transfer Department, Berkeley National Laboratory, 1 Cyclotron Rd., MS 90-1070, Berkeley, CA 94720; (510) 486-5366; fax: (510) 486-6457;