Performance of extraction kicker magnet in a rapid cycling synchrotron

Installation of the kicker magnets in the extraction section of the rapid cycling synchrotron in the J-PARC facility has been completed. They succeeded in extracting the proton beam accelerated up to 3 GeV in the first commissioning with beam. The operation parameters of the kicker system agreed well with the parameters, which were estimated from the magnetic field measurement and the current test of each power supply. The distribution of the integrated magnetic field is flat enough to meet the beam requirements. The beam based measurement of the flattop of the magnetic field was performed with the beam position monitors. Although a ringing structure was observed, which exceeded the specified limit, the degree of the flattop distortion could be corrected by the timing adjustment of the output current. The stability of the power supply is on the order of ±0.2%, which is sufficient to achieve stable beam extraction. The rise time of the output current largely depends on the gas pressure in the thyratrons. Dependence of the rise time on the gas pressure was strictly measured and the number of unwanted prefires could be reduced.