ANALYSIS ON DESIGNING A NONMAGNETIC AND NONMETALLIC MINIATURE COAXIAL PULSE TUBE CRYOCOOLER

The main source of interference signals of a pulse tube cryocooler（PTC） system were analyzed in detail. The practicable solutions for minimizing them were found. Then a nonmagnetic and nonmetallic miniature pulse tube cryocooler was designed and fabricated. The biggest obstacles for cooling highly sensitive high-Tc SQUID by a miniature PCT was the electromagnetic interference and the induced eddy currents from the magnetic or metallic materials in a PTC system. All the magnetic or metallic ones in a PTC were gaven place to nonmagnetic, non-metallic and electronically insulating ones, so that the EMI and eddy currents from them could be mininized. The objective was supplying a nonmagnetic and nonmetallic PTC for the low-noise cooling of highly magnetic flux sensitive high-Tc superconductors including high-Tc SQUIDs.