Search

The procedure for induction acceleration of a heavy ion beam of A/Q=4 in the KEK digital accelerator is reported. This paper discusses essential issues associated with induction acceleration of ion beams from low energies, including injection error, relatively large closed orbit distortion, and a fully predictive control method for the acceleration.

This paper reports the early beam commissioning of the KEK digital accelerator, which consists of novel accelerator components such as a permanent-magnet x-band electron cyclotron resonance ion source, an Einzel lens longitudinal chopper, an electrostatic injection kicker, and induction acceleration devices. The performance of the Einzel lens longitudinal chopper is described together with the results of beam commissioning, including the beam orbit correction, barrier bucket bunch capture, and induction acceleration.

The KEK digital accelerator (DA) is an alternative to high-voltage electrostatic accelerators and conventional cyclotrons and synchrotrons, which are commonly used as swift heavy ion beam drivers. Compared with conventional accelerators, KEK-DA is capable of delivering a wider variety of ion species with various energies, as a result of its intrinsic properties. It is expected to serve as a heavy ion beam factory for research in materials science. Plans for its utilization include unique application programs, such as laboratory-based space science using virtual cosmic rays, heavy-ion mutagenesis in microorganisms, deep ion implantation, and modification of materials, which may be categorized into systematic studies of the spatial and temporal evolution of the locally and highly excited states of materials.

A fast-cycling induction synchrotron was demonstrated. Ions with extremely low energies and mass-to-charge ratios ($A/Q$) in the range from 2 to 10 were injected, captured by barrier voltages, and accelerated to the end of the acceleration cycle of 50 ms by flat pulse voltages generated by pulse transformers referred to as induction cells. Induction acceleration in a wide dynamic frequency range of 56 kHz to 1 MHz was also demonstrated. This accelerator is expected as the next generation of a heavy ion driver for cancer therapy, where a large scale injector is not required. A wide variety of ions for ion energy implantation experiments needing novel materials will be delivered from this compact circular accelerator.