Dynamic Operation of a 4 K Pulse Tube Cryocooler with Inverter Compressors

Abstract

This paper introduces the concept of operating a 4 K pulse tube cryocooler using an inverterdriven compressor. The cryocooler is a Cryomech model PT410. By adjusting the power frequency of the inverter compressor from 46 to 70 Hz, the cryocooler can offer 22 W to 43 W at 45K on the first stage and 0.5 W to 1.1 W at 4.2 K on the 2nd stage; for this range, the compressor input power changes from 5.0 kW to 8.6 kW. Dynamic operation of the 4 K pulse tube cryocooler has been successfully demonstrated using a liquid helium cryostat. The compressor controller maintained the desired cryostat temperature by adjusting the power frequency to reduce the cooling capacity of the pulse tube cooler at 4 K, and resulted in less compressor input power.