Development of a magnetic field monitoring system for the JAERI AVF cyclotron

Okumura, Susumu; Arakawa, Kazuo; Fukuda, Mitsuhiro; Nakamura, Yoshiteru; Yokota, Wataru; Ishimoto, Takayuki; Kurashima, Satoshi; Ishibori, Ikuo; Nara, Takayuki; Agematsu, Takashi; Nakajima, Tsukasa*

In the JAERI AVF cyclotron, unstable phenomena, such as beam intensity decrease, were observed. We found that an increase in temperature of the iron body of the magnet induced the drift of the magnetic field. Stabilization of the iron body temperature was achieved. We have developed a nuclear magnetic resonance (NMR) magnetometer with an accuracy of the order of 10 to measure the stability of the cyclotron magnetic field with a large gradient by using a pair of correction coils to reduce the field gradient and by eliminating the effect of the RF.