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The groundbreaking work about the beat-wave acceleration of electrons by Tajima and Dawson (1979) within the field of two laser beams with different frequency needed some initial clarification. This was achieved by Joshi (Joshi et al. 1984, Joshi 2006). The merit to move this matter into the focus of interest was last but not least reached by Sessler (1985) when he initiated conferences by the American Institute of Physics (AIP) led by Channel (1982), Joshi, and Katsouleas (1985). The fact that an optical wave packet of an infinite symmetric plane wave cannot transfer optical energy into free electrons (Sessler 1985) was to be understood while laser acceleration of free electrons was known, e.g., from the Boreham experiment (Chapter 6.2). The advantage of the very high electric fields of laser pulses for accelerator application was very interesting, but the fields were directed into the wrong direction.
This book describes the basic ingredients of nonlinearities, the extremely high gradients of laser energy densities, the longitudinal field components of laser beams, and the extreme longitudinal “static” fields in double layers. These were well recognized in the earlier stages and were continued and studied with the beginning of the AIP conference (Joshi et al. 1985), but the entire breakthrough was possible only by Mourou’s discovery of the chirped pulse amplification (CPA) (Strickland et al. 1985), where the numerically predicted (Hora 1981) and finally measured (Sauerbrey 1996) ultrahigh acceleration of plasma blocks led to the large-scale step of physics developments (see Chapter 8).
It may be advantageous to first recognize several achievements of the laser-driven electron acceleration in this chapter with reference to the basic property of nonlinearity (Hora 1988; Evans 1988) and the clarification of asymmetries in wave packets (Scheid et al. 1989) before realizing and appreciating the next steps in Chapter 8.
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