Donald P. Umstadter

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Using interferometry, we investigate the dynamics of interaction of a relativistically intense 4-TW, 400-fs laser pulse with a He gas jet. We observe a stable plasma channel 1 mm long and less than 30 microm in diameter, with a radial gradient of electron density approximately 5 x 10(22) cm(-4) and with an on-axis electron density approximately ten times(More)
We report the generation of MeV x rays using an undulator and accelerator that are both driven by the same 100-terawatt laser system. The laser pulse driving the accelerator and the scattering laser pulse are independently optimized to generate a high energy electron beam (>200  MeV) and maximize the output x-ray brightness. The total x-ray photon number(More)
The maximum achievable photon energy of compact, conventional, Compton-scattering X-ray sources is currently limited by the maximum permissible field gradient of conventional electron accelerators.1,2 An alternative compact Compton X-ray source architecture with no such limitation is based instead on a high-field-gradient laser–wakefield accelerator.3–6 In(More)
Timeand space-resolved extreme ultraviolet spectra of carbon plasmas, created with 100-fs laser pulses, are obtained with the novel technique of picosecond jitter-free streak-camera averaging. Spectroscopic diagnostics indicate electron densities and temperatures evolving from 1023 to 1021 cm23 and 80 to 50 eV, respectively, implying less than one particle(More)
Gamma-ray photons with energy >9  MeV were produced when second-harmonic-generated laser light (3 eV) inverse-Compton-scattered from a counterpropagating relativistic (~450  MeV) laser-wakefield-accelerated electron beam. Two laser pulses from the same laser system were used: one to accelerate electrons and one to scatter. Since the two pulses play very(More)
We demonstrate that a beam of x-ray radiation can be generated by simply focusing a single high-intensity laser pulse into a gas jet. A millimeter-scale laser-produced plasma creates, accelerates, and wiggles an ultrashort and relativistic electron bunch. As they propagate in the ion channel produced in the wake of the laser pulse, the accelerated electrons(More)
A novel laser-plasma-based source of relativistic electrons is described. It involves a combination of orthogonally directed laser beams, which are focused in a plasma. One beam excites a wakefield electron plasma wave. Another locally alters the trajectory of some of the electrons in such a way that they can be accelerated and trapped by the wave. With(More)
An on-axis plasma density depression channel was observed during and after the passage of a relativistically and ponderomotively self-guided laser pulse through a plasma. Optical interferometry was used to produce time-resolved plasma density distributions, revealing the formation of a plasma waveguide. These results were complemented by the guiding of a(More)