A prototype of a highly sensitive cryogenic current comparator with a HTS SQUID andHTS magnetic shield

Abstract

A highly sensitive cryogenic current comparator (CCC) for the measurement of theintensity of faint beams, such as a radioisotope beam, was developed for the RIKEN RIbeam factory project. This monitor is composed of a high-temperature superconducting(HTS) magnetic shield and an HTS current sensor including an HTS superconductingquantum interference device (SQUID), which are cooled by a low-vibration pulse-tuberefrigerator. Both the HTS magnetic shield and the HTS current sensor based onBi2–Sr2–Ca2–Cu3–Ox (Bi-2223) were fabricated by dip-coating on a 99.9% MgO ceramic substrate.Recently, a prototype of the HTS SQUID CCC system was completed and wecarried out the first measurements using DC ion beams in the current range of0.5–20 µA, which were produced by the ECR (electron cyclotron resonance) ion source in the CNSexperimental hall. After the measurement was successfully carried out in the CNS, weinstalled the system into the beam transport line of the RIKEN Ring Cyclotron (RRC) tomeasure the current of the high-energy heavy-ion beam which has a bunchedmicrostructure. In this paper, we describe the performance and the present status of theprototype of the HTS SQUID CCC system and the results of the ion beam measurement.