• T. Iwashita, T. Adachi, T. Arai, Y. Arakida, M. Hasimoto, H. Someya, K. Takayama, M. Wake
  KEK, Ibaraki
• T.S. Dixit
  SAMEER, Mumbai
• K. Mochiki, T. Sano
  Tokyo City University, Tokyo

The KEK-DA (Digital Accelerator) is a modification of the KEK 500 MeV booster*, in which an induction acceleration system is employed. It has an ability to accelerate arbitrary ions with their possible charge states**. An outline of the acceleration scenario is described and a necessary control system fully integrating the induction acceleration system is given in details. The KEK-DA is a rapid cycle synchrotron operating at 10 Hz; the accelerating pulse voltage must be dynamically varied in time to follow the ramping magnetic field. A novel technique combining the pulse density control and intermittent operation of acceleration cells is required. The intelligent gate control system which uses 1 GHz digital signal processors (DSPs) has been designed. Construction of the KEK-DA is in the final stage; installation of the induction cells and the power supplies are done. The whole system including gate control system is demonstrated with high voltage outputs,long-term stability of the system through a heat run is examined. Also a future plan which replaces DSPs by FPGA (Field Programmable Gate Array)is discussed.

* K.Takayama et al., JOURNAL OF APPLIED PHYSICS 101, 063304 (2007).
** K.Takayama et al., "KEK Digital Accelerator for Material and Biological Sciences" in this conference.

• K. Takayama, T. Adachi, T. Arai, Y. Arakida, M. Hasimoto, T. Iwashita, E. Kadokura, M. Kawai, T. Kawakubo, K. Koyama, T. Kubo, T. Kubo, H. Nakanishi, K. Okamura, H. Someya, A. Takagi, M. Wake
  KEK, Ibaraki
• T. Kikuchi, T. Yoshii
  Nagaoka University of Technology, Nagaoka, Niigata
• K.W. Leo
  Sokendai, Ibaraki
• K. Mochiki, T. Sano
  Tokyo City University, Tokyo
• M. Okamura
  RBRC, Upton, Long Island, New York
• K. Okazaki
  Nippon Advanced Technology Co. Ltd., Ibaraki-prefecture
• H. Tanaka
  Iwate university, Morioka, Iwate

A novel circular accelerator capable of accelerating any ions from an extremely low energy to relativistic energy is discussed. A digital accelerator (DA)* is based on the induction synchrotron concept, which had been demonstrated in 2006. All ions are captured and accelerated with pulse voltages generated by induction acceleration cell (IAC). The IAC is energized by the switching power supply, in which power solid-state conductors are employed as switching elements and their tuning on/off is maneuvered by gate signals digitally manipulated from the circulating signal of an ion beam. Acceleration synchronized with the revolution of the ion beam is always guaranteed. The concept is realized by renovating the KEK 500 MeV booster into the DA, introducing a laser ablation ion source. Ion energy of 85-140 MeV/au and intensity of 10⁺⁹ - 10⁺¹⁰ /sec are estimated and these ions will be delivered without any large-scale injector. Companion papers** will discuss more details of instruments of DA. Applications for innovative material sciences and life sciences will be briefly introduced as well as the outline of DA.

*K. Takayam, J. of Appl. Phys. 101 (2007) 063304.
**K.Takayama "Ion source and LEBT", T.Adachi "Injection and extraction system", T.Iwashita "Induction acceleration system" in this conference.

• K. Takayama, T. Adachi, T. Arai, Y. Arakida, M. Hasimoto, T. Kawakubo, K. Koyama, T. Kubo, T. Kubo, H. Nakanishi, A. Takagi, K. Zhang
  KEK, Ibaraki
• T. Kikuchi
  Nagaoka University of Technology, Nagaoka, Niigata
• K.W. Leo
  Sokendai, Ibaraki
• K. Okazaki
  Nippon Advanced Technology Co. Ltd., Ibaraki-prefecture

KEK digital accelerator (DA) capable of accelerating all species of ion* is an induction synchrotron employing no large scale injectors. At the beginning of its operation, Ar ions from the ECR ion source (ECRIS) embedded in the 200 kV high voltage terminal (HVT) are directly injected into KEK-DA though the low energy BT line (LEBT). The permanent magnet ECRIS was assembled at KEK. Its characteristics such as a charge-state spectrum, emittance, and intensity are presented. The 200 kV HVT has been also assembled at KEK. Its voltage stability in the pulse mode operation, where a plasma of 1 msec is created by x-band microwaves at 10 Hz, is discussed. The LEBT consists of the Eintzel lens, momentum analyzer, B magnets with edge focusing, electrostatic chopper**, and a combination of Q magnets. In the upper LEBT from the ion extraction hall to the entrance of the analyzer, possible charge-state ions are contaminated in the space-charge limit and beam focusing is realized through the Eintzel lens and tandem acceleration gaps. In the lower LEBT from the analyzer to the KEK-DA injection point, the lattice has been optimized so as to meet optics matching at the injection point.

*K. Takayama, J. of Appl. Phys. 101 063304(2007), "KEK digital accelerator for material and biological sciences" in this conference
**T.Adachi, "Injection and extraction system" in this conference

• K. Okabe, R. Nakano, Y. Niwa, I. Sakai
  University of Fukui, Faculty of Engineering, Fukui
• Y. Arakida
  KEK, Ibaraki
• M. Inoue, Y. Ishi, Y. Kuriyama, J.-B. Lagrange, Y. Mori, T. Planche, T. Uesugi, E. Yamakawa
  KURRI, Osaka

In Kyoto University Research Reactor Institute (KURRI), the FFAG accelerator for accelerator driven sub-critical reactor (ADSR) system has been constructed and world's first ADSR experiments have started in March 2009. In order to upgrade beam intensity, multiturn charge exchange injection system for scaling FFAG accelerator is being studied. The 11MeV H^- beam is injected from linac and is accelerated up to 100MeV in FFAG main ring. In this presentation, the detail of injection system is described and feasibility of such a low energy H^- injection system is discussed.