Technion, Haifa
Franck and Hertz in 1914 were the first to demonstrate that free electrons can be decelerated by mercury atoms in discrete energy quanta. In 1930 Latyscheff and Leipunsky have demonstrated the inverse effect namely; free electrons can be accelerated by energy stored in the mercury atoms (collision of the second kind). It was only in 1958 that Townes has used multiple collisions between photons and excited atoms to amplify radiation (MASER & LASER). In 1995 Schachter suggested to use excited atoms for coherently accelerate particles. The results of a proof-of-principle experiment (2006) demonstrating the PASER scheme are reported here. Performed at the BNL-ATF, the essence of the experiment is to inject a 45MeV density modulated beam into an excited CO2 gas mixture. Resonance is insured by having the beam bunched by its interaction with a high-power CO2 laser pulse within a wiggler. The electrons experienced 0.15% relative change in their kinetic energy, in less than 40cm long interaction region. The experimental results indicate that a fraction of these electrons have gained 200keV each, implying that such an electron has undergone 2,000,000 collisions of the second kind.
Stanford University, Stanford, Califormia
SLAC, Menlo Park, California
There has been continued interest in the development of dielectric-loaded wakefield structures that can be used to accelerate particle beams. The present search for materials able to withstand very intense RF fields has renewed this interest. Recent experiments at the Argonne Wakefield Accelerator have generated short RF pulses with accelerating fields in excess of 80 MV/m. These experiments used ceramic-lined cylindrical waveguides, operating at frequencies between 10 and 15 GHz. Other important experiments, at different RF frequencies and using planar or cylindrical geometries, have been carried out at various other facilities. A number of new experiments are planned in the near future to explore the capabilities of this class of structures. This presentation will provide an up-to-date survey of the activities in this area of research.