Ion beam measurement with a high-temperature superconductor SQUID and current comparator

A noninvasive and potentially absolute method is described for the real-time measurement of ion or electron beams in the range 1 /spl mu/A-10 mA. The principle of the superconducting current comparator, which is well established in liquid-helium-temperature applications, is realized with high-temperature superconductor (HTS) components, and shown to be capable of sufficient sensitivity and accuracy for the proposed application. Particular attention is paid to the optimization of coupling between the current comparator and the HTS SQUID detector. The advantages to be gained by suitable patterning of the outer superconducting coating to achieve gradiometric detection are described. No serious problems were encountered during trial operation of the SQUID with an argon-ion magnetron plasma source.