A Liquid-helium-free superconducting coil system forming a flat minimum-magnetic-field distribution of an electron cyclotron resonance ion source

Yoshida, Kenichi; Nara, Takayuki; Saito, Yuichi; Yokota, Wataru

Recent studies about ECRIS have revealed that not only the maximum magnetic field (B) but also the minimum field(B) has effect on the production ability. A superconducting ECRIS which can change the B distribution with plural solenoids shows that a flat distribution of B (flat B) gives better performance in highly charged ion production than classical B. Superconducting device of conduction cooling type is useful, because a Lq-helium system needs a large quantity of Lq-helium to be supplied at after every quench. However, many refrigerators are necessary to keep low temperature against the heat through the current leads of a number of coils to form flat-B. Therefore, we have designed a coil configuration which can adjust B and flat-B with the minimum lead number of four. The flat-B is formed by three central coils connected one another between the mirror coils. There is another pair of coils to adjust B of the injection side keeping flat B unchanged.