Cryocooled Biomagnetometer

DESCRIPTION (provided by applicant): We propose to study and determine the feasibility of developing a novel approach for a cryocooled multichannel large biomagnetic system. Mechanical refrigeration is the only technique capable of providing the economical gains involved in cooling large biomagnetic systems. The proposed design would make these systems more economically attractive to run and maintain as well as reducing the logistics associated with constant handling of liquid helium. Biomagnetometers insta llations based on SQUID operation have always required liquid cryogens to operate. Typically this operation can run a cost in the range from 0.5 - 2.5 million dollars depending on the type of system and number of detection channels. Thus a typical MEG i nstallation will consume 20,000 - 40,000 of liquid helium annually. While the economics of liquid helium have not been a major inhibitor to the diffusion of biomagnetic instrumentation in the past, scarcity and increasing costs could change that. Mechanic al closed cycle refrigerators has become an alternative to the use of liquid cryogens. These include reduction of operating costs, use in remote locations, and operation in non-vertical orientations, avoiding interruptions in cryogen deliveries, safety, an d the convenience of not having to transfer every few days. There are two main obstacles to using closed cycle refrigeration with SQUIDs. The first is the mechanical movement that (ultimately) causes the detection coils to move in the Earth's magnetic fiel d. The second is the magnetic signature due to the moving parts of the cryocooler's cold head and compressor. The proposed design could significantly increase the market for large biomagnetometer systems not only in the US but also especially in European a nd Asian countries because of the lack of foreign helium gas source causing the associated costs to be twice the US costs. In addition, a helium shortage is developing due to increasing demand in industrial.