The Concept of a Linac Driven by a Traveling Laser Focus

Here we describe a Linac, driven by a Traveling Laser Focus (TLF), arranged with the help of a special deflecting device. This Linac has an accelerating structure, which is open from one side. The laser radiation is focused from this side onto a spot with minimal transverse dimensions. This spot is moved by a fast deflecting device in synchronism with the instantaneous position of the charged particles, thereby providing an accelerating field mostly in the region where the accelerating particles are located. The method described allows a reduction of the power required for creating the accelerating gradient which is desired proportional to the number of resolved spots of the deflecting device (typically a hundred). The same number gives the shortening of the illumination time for any point on the structure. All this gives the possibility for a gradient up to 100 GeV/m with present day techniques. The systems for the laser beam sweeping, the emittances requirements, the electro-focusing system, the accelerating structure, the final focusing system, the injection system and some tolerances are considered in this connection. As applicable to the Linear Collider, the resulting luminosity is estimated made to be in the range of 10 10 33 34 2 1 − − − cm s at the energy about 1TeV. This requires a laser flash energy of about 5 Joules at a moderate repetition rate f =100 Hz. The considerations made indicate, that the system of the type proposed makes a TLF driven Linac a realistic possibility.