The possibility of producing femtosecond x-rays through Thomson scattering high power laser beams off laser wakefield gnerated relativistic electron beams is discussed. The electron beams are produced with either a self-modulated laser wakefield accelerator (SM-LWFA) or through a standard laser wakefield accelerator (LWFA) with optical injection. For a SM-LWFA (LWFA) produced electron beam, a broad (narrow) energy distribution is assumed, resulting in X-ray spectra that are broadband (monochromatic). Designs are presented for 3-100 fs x-ray pulses and the expected flux and brightness of these sources are compared.

The basic principles and design of radiation sources (transition radiation, Cerenkov radiation, radiation from periodic structures, etc.) and radiation-based diagnostics will be discussed, with emphasis on radiation from ultra-short electron bunches. Ultra-short electron bunches have the potential to produce high peak flux radiation sources that cover wavelength regimes where sources are currently not widely available (coherent THz/IR) as well as ultrashort X-ray pulses (3-100 fs). While radiation from the electron bunch contains the full signature of the electron beam and/or medium it has travelled through, the deconvolution of a single property of interest can be difficult due to a large number of contributing properties. The experimental implementation of novel solutions to this problem will be described for beams from 30 MeV to 30 GeV, including fluctuational interferometry, source imaging, phase matched cone angles and laser-based techniques, which utilize optical transition radiation, wiggler and Cerenkov radiation, and Thomson scattering. These novel diagnostic methods have the potential to resolve fs bunch durations, slice emittance on fs scales, etc. The advantages and novel features of these techniques will be discussed.

Spontaneous radiation emitted from relativistic electrons undergoing betatron motion in a plasma focusing channel is analyzed and application to plasma wakefield accelerator experiments and to the ion channel laser (ICL) are discussed. Important similarities and differences between a free electron laser (FEL) and an ICL are delineated. It is shown that the frequency of spontaneous radiation is a strong function of the betatron strength parameter alpha_beta, which plays a similar role to that of the wiggler strength parameter in a conventional FEL. For alpha_beta > 1, radiation is emitted in numerous harmonics. Furthermore, alpha_beta is proportional to the amplitude of the betatron orbit, which varies for every electron in the beam. The radiation spectrum emitted from an electron beam is calculated by averaging the single electron spectrum over the electron distribution. This leads to a frequency broadening of the radiation spectrum, which places serious limits on the possibility of realizing an ICL.

The effect of asymmetric laser pulses on electron yield from a laser wakefield accelerator has been experimentally studied using > 10^19 cm^-3 plasmas and a 10 TW, > 45 fs, Ti:Al_2O_3 laser. Laser pulse shape was controlled through non-linear chirp with a grating pair compressor. Pulses (76 fs FWHM) with a steep rise and positive chirp were found to significantly enhance the electron yield compared to pulses with a gentle rise and negative chirp. Theory and simulation show that fast rising pulses can generate larger amplitude wakes that seed the growth of the self-modulation instability and that frequency chirp is of minimal importance for the experimental parameters.

The transverse dynamics of a 28.5 GeV electron beam propagating in a 1.4 m long, 0-2 x 10^14 cm^-3 plasma are studied experimentally in the underdense or blow-out regime. The transverse component of the wake field excited by the short electron bunch focuses the bunch, which experiences multiple betatron oscillations as the plasma density is increased. The spot size variations are observed using optical transition radiation and Cherenkov radiation. In this regime, the behavoir of the spot size as a function of the plasma density is well described by a simple beam envelope model. Dynamic changes of the beam envelope are observed by time resolving the Cherenkov light.