6533b826fe1ef96bd1283d73

RESEARCH PRODUCT

Oscillations of ECR ion source beam current along the beam transport of the JYFL K-130 cyclotron

subject

description

A versatile measurement system has been developed to study the temporal characteristics of ion beams in millisecond time scale. The system is composed of data acquisition hardware and LabVIEW based measurement and analysis program. The measurement system and ion beam current oscillation results measured with a 14 GHz AECR-U type ion source at University of Jyv"askyl"a, Department of Physics (JYFL), are presented. It is shown that the ion beams exhibit periodic current fluctuations at frequencies from 100 Hz to 1.5 kHz with amplitudes ranging from 1 to 65 percent of the average beam current. It is argued that these oscillations originate from the ion source plasma since their characteristics depend on the ion source tuning. It is shown that increasing the ion source solenoid magnetic field increases the relative oscillation amplitude. Increasing the ion source extraction voltage has the opposite effect. The beam current oscillations were measured along the low energy beam transport (LEBT) connecting the ion source to the JYFL K-130 cyclotron as well as in the following high energy beamline. It is shown that the beam current oscillations originating from the ion source are preserved during the LEBT but are not observed after the cyclotron. The transmission efficiency from the ion source through the cyclotron was measured with two beams of comparable beam currents but different oscillation frequency and amplitude, corresponding with the two cases typically seen when the ion source is tuned for high charge state production. The transmission of the LEBT remained unaltered but the cyclotron performance was affected by the varying oscillation characteristics.