Speaker
Y. Sakai
(Department of Energy Sciences, Tokyo Institute of Technology)
Description
Y. Sakai, A. Nakayama, T. Kikuchi (1), J. Hasegawa, M. Nakajima, and K. Horioka
Department of Energy Sciences, Tokyo Institute of Technology,
Nagatsuta 4259, Midori-ku, Yokohama, 226-8502, Japan
(1) Department of Electrical Engineering, Nagaoka University of Technology, 1603-1 Kamitomioka, Niigata 940-2188, Japan
Heavy ion beams are expected to be potential drivers for high-energy density physics and heavy ion inertial fusion. For the heavy ion inertial fusion, we need to increase the beam power more than TW level by the acceleration and the bunch compression. Processes of longitudinal beam manipulation and bunch compression are essential to increase the beam power particularly at the final stage of the accelerator. However, in the compression stage, space-charge effects may degrade the beam focus-ability seriously.
When the beam bunch is modulated quasi-statically, such as the beam bunching in conventional RF accelerator, emittance growth should be suppressed at a minimum level. In contrast, in the stage of final bunching, a dynamical space-charge effect may induce significant emittance growth. Furthermore, the beam coupling in transverse and longitudinal directions by the space charge effect may cause unpredictable emittance growth during the final bunching. So we intend to investigate the space-charge induced dissipation processes using a compact simulator.
We have made a compact bunching simulator based on electron beams. The device consists of an electron gun, an induction voltage modulator, and a solenoidal transport line. For applying the modulation voltage, we use an induction modulator composed of five units with induction adder configuration, which can apply arbitrarily waveforms for the bunch compression. In our experiment, the beam bunch is compressed during the drift in the transport line in which the transverse motion is suppressed by the longitudinal field. Then we expect that all of the dissipation processes are reflected in the compression ratios of the beam current.
We compare influence factors for the compression ratios and discuss the condition for the evaluation of dynamical space charge and/or collective effects on the bunch compression, based on the experimental results and a simplified particle transport simulation [1]. As the results indicated that the initial beam brightness should be higher than the present level, we are now planning to increase the brightness of beam source with pulsed thermionic emission. We are also planning to investigate the beam compression ratios as a function of the beam parameters and the transport distance.
[1] Y. Sakai, A.Nakayama, M.Nakajima, T.Kikuchi and K.Horioka;
Physics and Application of Plasmas based on Pulsed Power Technology,
NIFS-Proc. (to be published)
Primary author
Y. Sakai
(Department of Energy Sciences, Tokyo Institute of Technology)
