Ken Takayama

Compact solid-State switched pulsed power and its applications

Power semiconductor devices, such as insulated-gate bipolar transistors, metal-oxide-semiconductor field-effect transistors, and static-induction thyristors, are used in different kinds of pulsed power generators developed for different applications. In addition, the semiconductor opening switch is found to have very effective applications in pulsed power generation by inductive energy storage. Semiconductor switches have greatly extended the scales of pulsed power parameters, especially in repetition rate and lifetime. They have also enabled new areas of pulsed power applications, such as accelerators, flue-gas treatment, and gas lasers.

First result of the KEK X-band free electron laser in the ion channel guiding regime

Abstract Recent experimental results are reported for an induction-driven X-band FEL, with ion channel guiding inside the wiggler. Power in excess of 10 MW at 9.4 GHz, has been observed with a beam energy of 750 keV and a current of 520 A. Maximum gain is 22 dB/m, with no saturation after 15 wiggler periods. A self-amplified spontaneous power of 4 kW was also measured. Data for the detuning curve, field evolution and current transmission are presented and discussed.

Superbunch Hadron Colliders

A novel concept of a high luminosity hadron collider is proposed. This would be a typical application of an induction synchrotron being newly developed. Extremely long bunches, referred to as superbunches, are generated by a multibunch stacking method employing barrier buckets at the injection into the collider and are accelerated with a step voltage induced in the induction gaps. Superbunches intersect with each other, yielding a luminosity of more than 10(35) cm(-2) sec(-1). A combination of vertical crossing and horizontal crossing must be employed in order to avoid any significant beam-beam tune shift.

X-band prebunched FEL amplifier

Abstract We have designed and constructed a prebunched FEL amplifier consisting of a prebuncher and a standard FEL. Microwave power saturation with a short wiggler length has been realized by a prebunched beam. We have also examined microwave phase evolutions. It has been demonstrated the adjustable range of the output microwave phase by changing the input microwave phase is restricted within a narrow band due to spontaneous emission radiated by the prebunched beam.

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.

Magnetic core characteristics for high rep-rate induction modulator

Typical magnetic materials are experimentally characterized. Particularly our efforts are concentrated on deriving a core-loss scaling in operation region with minor B–H loops for highly repetitive voltage modulators. The core losses are evaluated as functions of magnetization rate and flux swing using semiempirical equations based on magnetization models. A prototype induction module has been successfully operated up to 1 MHz and the loss values are adapted well to the core-loss criterion.

Experimental results on the 1.5 MeV ion-channel guided X-band free-electron laser

Abstract Experiments on the ion-channel guided X-band free-electron laser amplifier (IXFEL) generated peak microwave power exceeding 100 MW at 9.4 GHz with a gain of 21 dB/m. Saturation in the evolution curve has been achieved and a frequency spread of 0.9% was observed. The amplified microwaves were separated from the driving beam line and extracted without breakdown.

Ion‐channel guided x‐band free‐electron laser amplifier

All aspects of the ion‐channel guided x‐band free‐electron laser amplifier which has been developed at KEK are described in detail. Amplification experiments (1,3) were performed at two different beam energy of 0.8 MeV and 1.5 MeV. At 9.4 GHz, a peak power of 25 MW with a gain of 18 dB/m and 100 MW with a gain of 21 dB/m have been demonstrated in each experiment. In the 1.5 MeV experiment, saturation in the evolution curve has been achieved and a frequency spread of 0.9% was observed. The amplified microwave was separated from the driving beam line and extracted without break‐down.

1.5 MeV ion‐channel guided X‐band free‐electron laser amplifier

Recent experiments on the Ion‐Channel Guided X‐band Free‐Electron Laser Amplifier (IXFEL) generated peak microwave power exceeding 100 MW at 9.4 GHz with a gain of 21 dB/m(1). Saturation in the evolution curve has been achieved and a frequency spread of 0.9% was observed. The amplified microwave was separated from the driving beam line and extracted without break‐down. Details of the experiments are presented here.

A solid-state Marx generator driven Einzel lens chopper

A new type of pulse chopper called an Einzel lens chopper is described. An Einzel lens placed immediately after an electron cyclotron resonance ion source is driven by high-voltage pulses generated by a newly developed solid-state Marx generator. A rectangular negative barrier pulse-voltage is controlled in time, and the barrier pulse is turned on only when a beam pulse is required. The results of successful experiments are reported herein.