Possibility of plasma density diagnostics using Langmuir-wave-caused dips observed in dense laser plasmas

Abstract

A systematic study of the Langmuir-wave-caused dips (L dips) observed in profiles of the Al Ly γ line emitted from laser irradiated sandwich targets indicates that these fine spectral features can be used as a tool for density diagnostics in intermediately coupled plasmas. The spectroscopic data required for a reliable identification of L dips were collected by a vertical-geometry Johann spectrometer providing high spectral and spatial resolution. The electron densities deduced from the evolution of the L dips along the laser target axis compare well with those derived from hydrosimulations and from measurements of the line widths and shifts.

Review of Langmuir-Wave-Caused Dips and Charge-Exchange-Caused Dips in Spectral Lines from Plasmas and their Applications

“…The experiment was performed at the nanosecond Nd:glass laser facility at LULI. A single laser beam with an intensity of 2 × 10 14 W/cm 2 was focused onto a structured target; an Al strip sandwiched between magnesium substrate [7,8]. The Al plasma was well confined and the transverse emission was optimized.…”

“…Later, the X-dips were observed in laser-produced plasmas characterized by a high electron density 10 22 -3 × 10 22 cm −3 [15,20]. The setup was implemented at the laser facility LULI using the same nanosecond laser at 10 14 W/cm 2 and the same high-resolution Vertical-geometry Johann Spectrometer (R = 8,000) as in the experiments devoted to the observation of L-dips [7,8]. The targets used for the observation of X-dips were aluminum carbide Al 4 C 3 strips inserted in carbon substrate.…”

Two-plasmon decay instability’s signature in spectral lines and spectroscopic measurements of charge exchange rate in a femtosecond laser-driven cluster-based plasma

“…Studies of dips in spectral line profiles from plasmas emerged as a new area of fundamental and applied research within the field of atomic processes in plasmas (APiPs) at the time of the first APiP conference in 1977. In the intervening decades they were recognized as an important plasma diagnostic tool [12][13][14][15][16][17][18][19][20][21] and later also as a source of fundamental reference data on charge exchange [22][23][24][25][26].…”

“…Previous experimental studies of L-dips [18,19,21] and of X-dips [25,26] in laser-produced plasmas were limited to just two spectral lines (mostly Ly γ and in one case Ly α ) of just one radiating ion: Al XIII (see also review [30]). In distinction, the present study has several very important novel features/results as follows.…”