The valve timing effect on cooling power of 4K Gifford-McMahon cryocooler

The valve timing effect on cooling power of a Gifford-McMahon cryocooler was studied theoretically and experimentally. In this paper we describe first the theoretical refrigeration efficiency assuming an ideal gas and argue that the Carnot efficiency can be achieved if the valve timing is optimized. Then we describe an experimental cryocooler fabricated to demonstrate an effect that can control the valve timing freely and report the results of the experiment using this equipment. The experiment demonstrated that the refrigeration efficiency can be enhanced by about 35%.