High Frequency Electromagnetic Interference Reduction on the SQUID Attached in Pulse Tube Cryocooler

Measurements of the high frequency electromagnetic interference (emi) of a pulse tube cryocooler are made in atypical laboratory environment using laboratory-made current transformers. the inverter makes high frequency emiwhich could cause severe interference with squid operation inside the pulse tube cryocooler. by covering thepower lines, including a neutral line, of the valve motor with a copper mesh cover, as a ground line, one order decreasein the magnitude of the emi noise is successfully obtained. this paper describes an example to show how toobserve and reduce conducted high frequency noise currents in a precision experimental system.