Radiation From Particles Moving in Small-Scale Magnetic Fields Created in Solid-Density Laser-Plasma Laboratory Experiments

Plasmas created by high-intensity lasers are often subject to the formation of kinetic-streaming instabilities, such as the Weibel instability, which lead to the spontaneous generation of high-amplitude, tangled magnetic fields. These fields typically exist on small spatial scales, i.e. "sub-Larmor scales". Radiation from charged particles moving through small-scale electromagnetic (EM) turbulence has spectral characteristics distinct from both synchrotron and cyclotron radiation, and it carries valuable information on the statistical properties of the EM field structure and evolution. Consequently, this radiation from laser-produced plasmas may offer insight into the underlying electromagnetic turbulence. Here we investigate the prospects for, and demonstrate the feasibility of, such direct radiative diagnostics for mildly relativistic, solid-density laser plasmas produced in lab experiments.Comment: 18 pages, 2 figures, (This version corrects numerous issues.

The theory of spectral evolution of the GRB prompt emission

We develop the theory of jitter radiation from GRB shocks containing small-scale magnetic fields and propagating at an angle with respect to the line of sight. We demonstrate that the spectra vary considerably: the low-energy photon index, $\alpha$, ranges from 0 to -1 as the apparent viewing angle goes from 0 to $\pi/2$. Thus, we interpret the hard-to-soft evolution and the correlation of $\alpha$ with the photon flux observed in GRBs as a combined effect of temporal variation of the viewing angle and relativistic aberration of an individual thin, instantaneously illuminated shell. The model predicts that about a quarter of time-resolved spectra should have hard spectra, violating the synchrotron $\alpha=-2/3$ line of death. The model also naturally explains why the peak of the distribution of $\alpha$ is at $\alpha\approx-1$. The presence of a low-energy break in the jitter spectrum at oblique angles also explains the appearance of a soft X-ray component in some GRBs and a relatively small number of them. We emphasize that our theory is based solely on the first principles and contains no {\it ad hoc} (phenomenological) assumptions.Comment: 5 pages, 3 figures, accepted to Ap

Modeling of liquid metal droplet deformation by laser impact

The method of sequential simulation of liquid metal droplet deformation by a laser pulse is considered. The first stage is the laser impact on a droplet. It was simulated using RALEF-2D code, based on the radiative gas dynamic model. The next stage is target deformation from a droplet to a disk. This part of simulation was carried out using OpenFOAM code where surface tension forces are taken into account. Good agreement with experimental results was obtained

Characterization of carbon contamination under ion and hot atom bombardment in a tin-plasma extreme ultraviolet light source

Molecular contamination of a grazing incidence collector for extreme ultraviolet (EUV) lithography was experimentally studied. A carbon film was found to have grown under irradiation from a pulsed tin plasma discharge. Our studies show that the film is chemically inert and has characteristics that are typical for a hydrogenated amorphous carbon film. It was experimentally observed that the film consists of carbon (~70 at. %), oxygen (~20 at. %) and hydrogen (bound to oxygen and carbon), along with a few at. % of tin. Most of the oxygen and hydrogen are most likely present as OH groups, chemically bound to carbon, indicating an important role for adsorbed water during the film formation process. It was observed that the film is predominantly sp3 hybridized carbon, as is typical for diamond-like carbon. The Raman spectra of the film, under 514 and 264 nm excitation, are typical for hydrogenated diamond-like carbon. Additionally, the lower etch rate and higher energy threshold in chemical ion sputtering in H2 plasma, compared to magnetron-sputtered carbon films, suggests that the film exhibits diamond-like carbon properties.Comment: 18 pages, 10 figure