Yoshio Arakida

All-ion accelerators: An injector-free synchrotron

A medium-energy synchrotron capable of accelerating all-ion species is proposed. The accelerator employs a strong focusing lattice for ion-beam guiding and induction acceleration for acceleration and longitudinal capture, which is driven by a switching power supply. All ions, including cluster ions in their possible and arbitrary charge state, are accelerated in a single accelerator. Since the switching power supply employing solid-state switching elements is energized by a trigger signal, which is generated from a bunch monitor signal produced by a circulating ion bunch, the induction acceleration always synchronizes with the bunch circulation. This feature enables the realization of an almost injector-free synchrotron.

Switching power supply for induction accelerators

A new particle acceleration method using pulsed induction cells was introduced in the super-bunch project at KEK. Unlike conventional RF acceleration, this acceleration method separates functions of acceleration and confinement. As a result, this acceleration method is capable of accelerating a very long bunch of beam or a wide mass range of particles. However, it is necessary to give a very fast pulsed- excitation to the magnetic material to induce an electric field to accelerate particles. Switching power supplies of high voltage output with very fast pulse-operation is one of the most important key technologies for this new acceleration method. Features of switching power supply developed for induction synchrotron is reported. The 31 kW MOSFET switch performed 1 MHz continuous operation with 15 nsec rise time.

Induction System for a Proton Bunch Acceleration in Synchrotron

Recently the first induction acceleration of a single proton bunch of 2.3E10ppp was demonstrated [1], where it was accelerated from 500MeV to 8GeV in 1.9sec in KEK-PS. This paper describes the induction system for a synchrotron and a beam confinement experiment as a second step of the proof-of principle (PoP) experiments of a “induction synchrotron” [2], where a proton beam with a bunch length of 500ns was longitudinally confined by the induction barriers for 500msec, is introduced..

A POP experiment scenario of induction synchrotron at the KEK 12 GeV-PS

A scenario for the first POP experiment and crucial issues of accelerator operation with induction acceleration are discussed.

R&D works on 1MHz power modulator for induction synchrotron

A proof of principle experiment of an Induction Synchrotron is scheduled in 2003 at the KEK 12GeV-PS. Proton bunches are accelerated with a 10kV of rectangular shaped induction voltage. An accelerating system consists of four induction cavities capable of individually generating a 2.5kV of output voltage. Each cavity is driven by a solid-state power modulator, which is operated at a revolution frequency of 600-800 kHz. The modulator circuit consists of MOS-FETs as switching element. Uniformity in the voltage waveform is crucial for the stable acceleration. Ringing in the voltage waveform caused by coupling of self-inductance of circuit and output capacitance of MOS-FETs deteriorates the uniformity. With the help of circuit analysis and simulation method of minimizing the self-inductance has been developed. Ratio of numbers of MOS-FETs in series and in parallel which defines the total output capacitance is also important to design the power modulator circuit. Power loss in MOS-FET is also important for stable operation of the power modulator. By the circuit analysis, it is also found that the output capacitance contributes to the power loss.

Induction Acceleration of a Single RF Bunch in the KEK PS

Results of the induction acceleration of a single RF bunch in the KEK PS are reported.

Design study of 1MHz induction cavity for induction synchrotron

An induction cavity was designed for the POP experiment of induction synchrotron using the KEK 12 GeV PS. It must be operated at a repetition rate of 667-882 kHz for acceleration from the injection energy to the flat-top energy. Design issues include handling of heat deposit, minimization of voltage droop and coupling impedance, and tolerable jitter. Its Q-value on the cavity assembled following the design was obtained from the longitudinal coupling impedance measurement. Effects of the droop in the acceleration voltage on the synchrotron motion, which has been estimated from the circuit parameter measurement on R, C, and L, was analysed from a longitudinal beam dynamics point of view. The effect of the droop is given by the square of phase delay.

Progress of 7-GeV SuperKEKB Injector Linac Upgrade and Commissioning

KEK injector linac is being upgraded for the SuperKEKB project, which aims at a 40-fold increase in luminosity over the previous project KEKB. SuperKEKB asymmetric electron and positron collider with its extremely high luminosity requires a high current, low emittance and low energy spread injection beam from the injector. Electron beams will be generated by a new type of RF gun, that will inject a much higher beam current to correspond to a large stored beam current and a short lifetime in the storage ring. The positron source is another major challenge that enhances the positron bunch intensity from 1 to 4 nC by increasing the positron capture efficiency, and the positron beam emittance is reduced by introducing a damping ring, followed by the bunch compressor and energy compressor. The recent status of the upgrade and beam commissioning is reported.

Acceleration scheme of the AIA and its control system

Acceleration scheme of All Ion Accelerator (AIA), one of the active applications of Induction Synchrotron (IS) is proposed with its beam simulation analysis. The KEK 500 MeV booster is going to be modified to KEK-AIA. Trigger system of the accelerator is described. A new type of acceleration cell for KEK-AIA is described.

Status of the induction acceleration system

A single proton bunch confined by the barrier voltage was accelerated by the induction step-voltage from 500MeV to 6GeV at the KEK 12-GeV proton synchrotron in March 2006. Various technical issues in the induction acceleration system, which have been faced in actual operation, are summarized.