Extreme ultraviolet interferometry of laser plasma material between the critical and ablation surfaces

TY - JOUR

T1 - Extreme ultraviolet interferometry of laser plasma material between the critical and ablation surfaces

AU - Gartside, L. M. R.

AU - Tallents, G. J.

AU - Rossall, A. K.

AU - Wagenaars, E.

AU - Whittaker, D. S.

AU - Kozlova, M.

AU - Nejdl, J.

AU - Sawicka, M.

AU - Polan, J.

AU - Kalal, M.

AU - Rus, B.

PY - 2011/6

Y1 - 2011/6

N2 - Interferometric probing using an extreme ultraviolet (EUV) laser has measured both transmission and phase information through laser-irradiated plastic (parylene-N C8H8) targets (thickness 350 nm). Unusually, the probe beam is incident longitudinally in approximately the same direction as the incident optical laser. Agreement of the experimental interferometry results has been obtained with two-dimensional radiation hydrodynamic code (h2d) simulations of EUV (21.2 nm) probe transmissions and phase shifts. We show that the transmission of the EUV probe beam provides a measure of the rate of target ablation, as ablated plasma becomes close to transparent when the photon energy is less than the ionization energy of the predominate ion species. Here C3+ ions with ionization energy 64.5 eV are transparent, while lower carbon ionization stages, present in the unablated target and close to the ablation surface, absorb the 58.5 eV photons. Similarly, we show that refractive indices eta below the solid parylene-N (eta(solid) = 0.946) and expected plasma values are produced in the warm dense plasma created by laser irradiation due to bound-free absorption in C+. (C) 2011 Elsevier B.V. All rights reserved.

AB - Interferometric probing using an extreme ultraviolet (EUV) laser has measured both transmission and phase information through laser-irradiated plastic (parylene-N C8H8) targets (thickness 350 nm). Unusually, the probe beam is incident longitudinally in approximately the same direction as the incident optical laser. Agreement of the experimental interferometry results has been obtained with two-dimensional radiation hydrodynamic code (h2d) simulations of EUV (21.2 nm) probe transmissions and phase shifts. We show that the transmission of the EUV probe beam provides a measure of the rate of target ablation, as ablated plasma becomes close to transparent when the photon energy is less than the ionization energy of the predominate ion species. Here C3+ ions with ionization energy 64.5 eV are transparent, while lower carbon ionization stages, present in the unablated target and close to the ablation surface, absorb the 58.5 eV photons. Similarly, we show that refractive indices eta below the solid parylene-N (eta(solid) = 0.946) and expected plasma values are produced in the warm dense plasma created by laser irradiation due to bound-free absorption in C+. (C) 2011 Elsevier B.V. All rights reserved.

KW - Extreme ultraviolet lasers

KW - Interferometry

KW - Radiation-hydrodynamics

KW - Transmission

KW - X-RAY LASERS

KW - ANOMALOUS-DISPERSION

KW - GENERATION

KW - PARAMETERS

KW - SCATTERING

KW - TRANSPORT

KW - OPACITY

UR - http://www.scopus.com/inward/record.url?scp=79953063573&partnerID=8YFLogxK

U2 - 10.1016/j.hedp.2011.03.003

DO - 10.1016/j.hedp.2011.03.003

M3 - Article

SN - 1574-1818

VL - 7

SP - 91

EP - 97

JO - HIGH ENERGY DENSITY PHYSICS

JF - HIGH ENERGY DENSITY PHYSICS

IS - 2

ER -