Spectrum, temporal structure, and fluctuations in a high-gain free-electron laser starting from noise

Abstract

We study the time structure, the frequency composition, and the shot to shot fluctuations of the radiation emitted by a free-electron laser starting from shot noise in the electron beam longitudinal distribution, taking into account slippage and finite bunch length effects. We find a very difkrent behavior when the bunch length, Eg, is much longer than the cooperation length, E"or of the order of a few 8,. The field evolution is dominated by slippage eÃects in both cases, and shows the presence of superradiant spikes.

The free-electron laser FLASH

“…The SASE process was first described by Kondratenko and Saldin [15] , theoretically explored in the early 1980s and later by many groups [16][17][18][19][20][21][22][23] .…”

Finite pulse effects in self-amplified-spontaneous-emission

“…The phase Oi is introduced via (3) where ku = 21r I Au and Au is the undulator period. Figure 1 illustrates the coordinates ( and 8(i.…”

“…The theory of SASE in the linear regime has been treated before for the case of an infinitely long, uniform electron beam [1,2]. Recently, Bonifacio et al [3] have presented a theory of SASE for a finite, top-hat density profile with a vanishing electron's energy spread. In this paper, we extend the theory to a general density profile including the effects of electron's energy spread, diffraction and the betatron oscillation.…”

Statistical correlations and intensity spiking in the SASE FEL

“…The theory of high-gain single-pass free-electron lasers has been developing since the late 1970's [6][7][8][9]. Because SASE starts from the shot noise in the electron beam, a proper theory requires a statistical treatment of the output radiation [10][11][12][13][14][15][16][17][18][19][20].…”

“…Average properties of the output were studied in [10][11][12][13][14][15][16] and fluctuations were considered in [17][18][19][20]. The spiking of the output radiation (see Fig.…”