プラズマ利用加速器

その実験的研究の現状

抄録

Plasma based particle accelerators have potentiality to produce much higher gradient of acceleration fields compared with the one in the conventional accelerators, if the high power laser and the plasma are combined together. The accelerators can be divided into major three categories, depending on the accleration principle: 1) Potential acceleration, 2) Cross field acceleration (CFA) or VpxB acceleration, and 3) Synchronized acceleration. In the potential acceleration, the energy of the particles is decided by the potential difference between two points, even in the travelling wave frame, and this system is a “limited acceleration” scheme. The cross field acceleration is the mechanism which is newly found in the plasma, and is possible to have higher acceleration efficiency. The charged particles are accelerated very efficiently along the wave front, but across the static magnetic field. The particle energy is decided mainly by the wave width and this is an “unlimited acceleration” scheme. The VpxB accelerator and the Surfatron are typical examples of this scheme. The energy in the synchronized acceleration is proportional to the acceleration duration with a power of α which is less than unity. This is a “quasi-limited acceleration” scheme. The synchrotron and the cyclotron are typical examples. The present status of the experimental investigations on the advanced accelerators with plasma, and some of them without plasma, are reviewed, including new accelerators which use new accelertion principle such as the cross field acceleration.