Generation of radiation by intense plasma and e.m. undulators

This program involves the generation of short wavelength optical radiation by intense plasma and e.m. undulators. In this concept a relativistic electron beam is wiggled by either the oscillating electric field of an intense plasma wave, or by a laser beam causing it to radiate. For both types of undulators the designed parameters are aw > 0.1, N ∼ 100 and λw = 100 μm for plasma wave or 10.6 μm for laser light. This progress report describes the work to-date on generating such intense short wavelength undulators. We have successfully generated up to 200 GW of CO2 radiation in a 200 ps long pulse. A uniform plasma source, Θ-pinch, has been constructed and it's density diagnosed using holographic interferometry. Using about 20 GW of laser radiation at two frequencies, 10.27 μm and 9.56 μm, relativistic plasma wave has been excited using the ''beat wave'' technique. The amplitude of this plasma wave has been inferred to be n1/n0 approx-lt 1%. The plasma wave width is thought to be about 2--3 wavelengths. A 1.5 MeV, 9 GHz linac has been procurred using funds from another contract and diagnosed. The electron beam emittance as it exits a 6 μm thick mylar foil, which separates the high vacuum linac structure from the plasma, has been measured to be about 50 π mm mrad. The key problem areas have been identified. These are: (1) damage to certain optical components in the laser chain because of stimulated Brillouin scattering in the plasma, (2) small scale random deflection of the electron beam by the magnetic field trapped inside the Θ-pinch plasma, and (3) poor focusability of the electron beam due to emittance blow-up due to foil scattering. 6 figs