Ludwig, J. D. | Search NASA

DOE OSTI2022

Direct spectral measurements of midinfrared radiation from a laser wakefield accelerator

The formation of plasma waves during laser wakefield acceleration (LWFA) produces time-dependent frequency shifts in the driving laser pulse, extending its spectral content to the infrared. We present direct spectral measurements of multi-mJ infrared pulses from an LWFA. Experimental beam profile measurements and three-dimensional particle-in-cell simulations suggest high focusability of these pulses. Further, particle-in-cell simulations demonstrate that the measurement of side-scattered infrared radiation may serve as a diagnostic of plasma waves and the efficiency of spectral broadening during LWFA.

43 PARTICLE ACCELERATORS↗

DOE OSTI2019

Single shot high bandwidth laser plasma probe

Herein a novel scheme to probe a plasma's ion acoustic resonances in single shot high-bandwidth pump-probe experiments is proposed. Our design utilizes concepts similar to smoothing by spectral dispersion; however, we propose a method of applying the bandwidth to the probe that avoids the effects of angular dispersion. Theoretical modeling and fluid simulations of the interaction are presented and compared. The results show the possibility of recovering a plasma's full complex index of refraction in a single shot pump-probe experiment. This wavelength dependent refractive index is directly related to the plasma's particle distribution function and can be used to recover plasma parameters including electron and ion temperatures, electron density, and plasma flow velocity.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗