HTc-SQUID beam current monitor at the RIBF

For the purpose of measuring the DC current of heavy-ion beams non-destructively at high resolution, we have developed a high critical temperature (HTc) superconducting quantum interference device (SQUID) beam current monitor for use in the radioactive isotope beam factory (RIBF) at RIKEN in Japan. Because of its low vibration, a pulse-tube refrigerator cools the HTc fabrications that include the SQUID in such a way that the size and the operational costs of the system are reduced. Last year,we significantly reinforced the magnetic shielding system. The new strong magnetic shielding system can attenuate the external AC magnetic noise by 10⁻¹⁰. With the aim of practical use in acceleration operation, we disassembled the prototype high-Tc SQUID current monitor (SQUID monitor), installed improved parts, and re-assembled it. Beginning this year, we have installed the SQUID monitor in the beam transport line in the RIBF. Here we describe the present details of the developed SQUID monitor system and the results of beam measurements. (author)