Abstract
The High Energy Accelerator Research Organization KEK digital accelerator (KEK-DA) is a renovation of the KEK 500 MeV booster proton synchrotron, which was shut down in 2006. The existing 40 MeV drift tube linac and rf cavities have been replaced by an electron cyclotron resonance (ECR) ion source embedded in a 200 kV high-voltage terminal and induction acceleration cells, respectively. A DA is, in principle, capable of accelerating any species of ion in all possible charge states. The KEK-DA is characterized by specific accelerator components such as a permanent magnet X-band ECR ion source, a low-energy transport line, an electrostatic injection kicker, an extraction septum magnet operated in air, combined-function main magnets, and an induction acceleration system. The induction acceleration method, integrating modern pulse power technology and state-of-art digital control, is crucial for the rapid-cycle KEK-DA. The key issues of beam dynamics associated with low-energy injection of heavy ions are beam loss caused by electron capture and stripping as results of the interaction with residual gas molecules and the closed orbit distortion resulting from relatively high remanent fields in the bending magnets. Attractive applications of this accelerator in materials and biological sciences are discussed.
Highlights
The High Energy Accelerator Research Organization KEK digital accelerator (DA) is a renovation of the former 500 MeV rapid-cycle proton synchrotron
The existing 40 MeV drift tube linac and rf cavities have been replaced by an electron cyclotron resonance (ECR) ion source embedded in a 200 kV high-voltage terminal and induction acceleration cells, respectively
The KEK-DA is characterized by specific accelerator components such as a permanent magnet X-band ECR ion source, a low-energy transport line, an electrostatic injection kicker, an extraction septum magnet operated in air, combined-function main magnets, and an induction acceleration system
Summary
The High Energy Accelerator Research Organization KEK digital accelerator (DA) is a renovation of the former 500 MeV rapid-cycle proton synchrotron (a booster for the KEK 12 GeV PS). A crucial feature of the IS is that voltage timing is controlled by an intelligent gate controller of solid-state switching elements, based on signals picked up at the bunch monitor This operational performance allows acceleration of ions from extremely low velocity and is a reason why the DA does not require a large injector accelerator. The main alterations are listed as follows: (i) construction of an electron cyclotron resonance (ECR) ion source and a 200 kV high-voltage terminal; (ii) rearrangement of the low-energy beam transport (LEBT); (iii) introduction of an electrostatic chopper for injection pulse shaping and an electrostatic kicker for injection; (iv) replacement of the existing rf cavities by induction cells; (v) a change in the repetition frequency of the accelerator ring The position of the horn antenna aperture is optimized for matching
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