ADVANTAGES OF A 4-VALVE PULSE TUBE CRYOCOOLER FOR HIGH T-C SENSOR OPERATION

In this contribution the results of our recent research on a special f our-valve pulse tube cryocooler will be presented. We have performed c ontrol volume analysis in order to get information about the cooling p ower, the coefficient of performance and fundamental limitations of th e ideal principle as a function of temperature, pressure ratio and the gas used for operation. High speed resistance thermometry at a protot ype machine was used for measuring the temperature at the hot end and at the cold end of the pulse tube during operation for comparison with the predictions of theory. We will discuss a comparison about the pos sibility for continuous operation of a high-T-c SQUID gradiometer for biomagnetic applications on our prototype cryocooler and on a Gifford- McMahon cryocooler using the results of noise measurements recorded du ring cryocooler operation. (C) 1997 Published by Elsevier Science Ltd.