LASER WAKEFIELD ACCELERATOR
In 1979, Tajima and Dawson suggested that the use of intense short-pulse laser (or beat of two lasers) under appropriate conditions can lead to a well-structured relativistic plasma wave that propagates near the speed of light in the wake of the laser pulse. This longitudinal plasma wave can accelerate charged particles to high energies at a rate as high as 1GeV/cm, some thousand fold higher than the highest existing accelerator field. Until the late '80's due mainly to the lack of intense and short-pulse lasers theoretical investigations have been carried out. (See Publications #65, 67, 68, 76, 77, 79, 89, 91, 98, 108, 114, and 129) The invention of the chirped pulse amplification method (G. Mourou, et al. 1985) combined with the development of high-fluence solid-state laser media in late '80's lead to the emergence of what is now called "table-top terawatt (T3) lasers", since they are compact enough to sit on top of a table and yet able to deliver TW or more. This coincided with the end of Tajima's decade old involvement with the SSC accelerator physics (at the demise of SSC in 1993 ). This emergence of laser technology and its application to wakefield generation, in contrast to the event of SSC shutdown may be best captured in the latest book "The Future of Accelerated Physics" [Editor: Tajima (1996)]. The Physics Department was awarded the first US Department of Energy research grant on laser wakefield excitation. The University of Texas at Austin experimental effort led by Mike Downer (see his web page "Femtosecond Spectroscopy") developed an in-house Ti-Sapphire T3 laser, femtosecond resolution detection techniques based on laser pulse interferometry, and detected a laser wakefield of about 10 GeV/m (work was cited in Science Jan. 5, 1996). Theoretical support of these experiments: see D. Fisher and Tajima's web page movie (Fisher) and Publications #192, 206, 227, 236, and 237. Tajima was instrumental in raising the consciousness of the importance of and elevating the research in this science and related T3 laser (optical) science in our Department and led the effort to formulate the vision for the future direction in this science. He also played the leading role in the community effort to promote this science. For this he was elected to the Advisory Board Member of the Center for Ultrafast Optical Science of the University of Michigan, as an Affiliated Faculty Member of the Lawrence Berkeley Laboratory of the University of California, and as a Member of the Commission on Advanced Photon Research of the Science and Technology Agency of Japan. Some of his recent community service and leadership include: Chairman and Organizer of the Tamura Symposium on Accelerator Physics (1994); co-organizer of the First Michigan Workshop on Laser Wakefield Acceleration (1995); Organizer and Presider of the Symposium on Short-Pulse Lasers and Wakefield at American Physical Society (1995); pioneering work and advocacy cited in Physics Today (Jan. 1995), The Washington Post (Sept. 1995), Science (Jan. 1996), etc. are only the more publicized ones among the strong interest in the wide scientific communities. An effort to apply laser wakefield to medical physics is also under way.