He-like Satellites Research Articles

Observation of He-like Satellite Lines of the H-like Potassium K xix Emission

Abstract We present measurements of the H-like potassium (K xix) X-ray spectrum and its He-like (K xviii) satellite lines, which are situated in the wavelength region between 3.34 and 3.39 Å, which has been of interest for the detection of dark matter. The measurements were taken with a high-resolution X-ray spectrometer from targets irradiated by a long-pulse (2 ns) beam from the Orion laser facility. We obtain experimental wavelength values of dielectronic recombination satellite lines and show that the ratio of the Lyα lines and their dielectronic satellite lines can be used to estimate the electron temperature, which in our case was about 1.5 ± 0.3 keV.

K-shell X-ray spectroscopy of laser produced aluminum plasma

Optimization of a laser produced plasma (LPP) X-ray source has been performed by analyzing K-shell emission spectra of Al plasma at a laser intensity of 1013–1014W/cm2. The effect of varying the laser intensity on the emissivity of the K-shell resonance lines is studied and found to follow a power law, Ix=(IL)α with α=2.2, 2.3, 2.4 for Heβ, Heγ, Heδ respectively. The emission of these resonance lines has been found to be heavily anisotropic. A Python language based code has been developed to generate an intensity profile of K-shell spectral lines from the raw data. In theoretical calculations, the temperature is estimated by taking the ratio of the Li-like satellite (1s22p–1s2p3p) and the Heβ (1s2–1s3p) resonance line and the ratio of the He-like satellite (1s2p–2p2) and the Lyα (1s–2p) resonance line. To determine the plasma density, stark broadening of the Lyβ spectral line is used. Simulation was carried out using the FLYCHK code to generate a synthetic emission spectrum. The results obtained by FLYCHK are Te=160eV, Th=1keV, f=0.008, ne=5×1020cm-3 and the analytical model resulted Te=260–419eV and ne=3x1020cm-3.

Spatial structure analysis of direct-drive implosion cores at OMEGA using x-ray narrow-band core images

The spectroscopic analysis of x-ray narrow-band images and space-integrated x-ray line spectra from argon-doped deuterium-filled inertial confinement fusion implosion experiments yields information about the spatial profiles in the compressed core. We discuss the analysis of direct-drive implosion experiments at OMEGA, in which images were obtained with a multimonochromatic imaging instrument. The analysis method considers data based on the argon Heβ and Lyβ spectral features and their associated Li- and He-like satellites. The temperature gradient structure is investigated by using the sensitivity of the Lyβ∕Heβ emissivity ratio to the temperature.

Time- and space-resolved spectroscopy of dynamic hohlraum interiors

A dynamic hohlraum is created when an annular z-pinch plasma implodes onto a cylindrical 0.014 g/cc 6-mm-diameter CH 2 foam. The impact launches a radiating shock that propagates toward the axis at ∼350 μm/ns. The radiation trapped by the tungsten z-pinch plasma forms a ∼200 eV hohlraum that provides X-rays for indirect drive inertial confinement fusion capsule implosion experiments. We are developing the ability to diagnose the hohlraum interior using emission and absorption spectroscopy of Si atoms added as a tracer to the central portion of the foam. Time- and space-resolved Si spectra are recorded with an elliptical crystal spectrometer viewing the cylindrical hohlraum end-on. A rectangular aperture at the end of the hohlraum restricts the field of view so that the 1D spectrometer resolution corresponds approximately to the hohlraum radial direction. This enables distinguishing between spectra from the unshocked radiation-heated foam and from the shocked foam. Typical spectral lines observed include the Si Lyα with its He-like satellites and the He-like resonance sequence including Heα, Heβ, and Heγ, along with some of their associated Li-like satellites. Work is in progress to infer the hohlraum conditions using collisional–radiative modeling that accounts for the radiation environment and includes both opacity effects and detailed Stark broadening calculations. These 6-mm-scale radiation-heated plasmas might eventually also prove suitable for testing Stark broadening line profile calculations or for opacity measurements.

Generation of hot plasma at solid density by high-contrast ultra-short laser pulses

We have generated a high-density plasma by focusing frequency-doubled Ti-Sapphire laser pulses at λ=395 nm and a duration of 150 fs on flat solid targets at an intensity of ≈10 17 W/ cm 2 . Using solid Al targets tamped by a thin surface layer of MgO we measured the Al K-shell emission. The measured resonance lines ( Ly α, He α and He β ) and their Li-like and He-like satellites are extremely broad. In addition, we observed clear center of gravity red shifts of the main lines by using the cold K α line as a reference. The temporal duration of the K-shell emission, measured by an X-ray streak camera, is ≈2.5 ps. Analysis of the spectra yields an effective electron temperature of ≈300 eV and an electron density of ≈(7–10)×10 23 cm −3 . A very weak emission of cold Al K α indicates a low level of energy deposited by fast electrons in the solid. Essential for achieving these results is the suppression of early time expansion of the Al target by using both, a high-contrast laser pulse and a tamped target.

Isochoric Heating of Solid Aluminum by Ultrashort Laser Pulses Focused on a Tamped Target

We have studied the $K$-shell emission of an Al plasma which was generated by focusing a high contrast 150 fs laser pulse at a wavelength of 395 nm and intensity of $5\ifmmode\times\else\texttimes\fi{}{10}^{17}\mathrm{W}/{\mathrm{cm}}^{2}$ on a flat Al target tamped by a thin surface layer of MgO. The measured resonance lines ( ${\mathrm{Ly}}_{\ensuremath{\alpha}}$, ${\mathrm{He}}_{\ensuremath{\alpha}}$, and ${\mathrm{He}}_{\ensuremath{\beta}}$) and their Li-like and He-like satellites are extremely broadened and show a red polarization shift. Analysis of the ${\mathrm{Ly}}_{\ensuremath{\alpha}}$ and ${\mathrm{He}}_{\ensuremath{\beta}}$ satellites yields an electron temperature of $\ensuremath{\approx}300\mathrm{eV}$ and an electron density of $(5--10)\ifmmode\times\else\texttimes\fi{}{10}^{23}{\mathrm{cm}}^{\ensuremath{-}3}$.

Li- and He-like satellite emission from aluminium plasma produced by a 12 ps KrF laser

We present time-resolved measurements and calculations of Li- and He-like satellites in a 2000 AA aluminium plasma created with a 12 ps KrF laser at intensities of up to 1016 W cm2. The evolution of the plasma at early times following the laser beam is inferred from the ratio of two satellite lines which have the advantage of small optical thicknesses compared to resonance lines. Hydrodynamic simulations and time-dependent non-local thermodynamic equilibrium (non-LTE) calculations of the satellite intensity ratios compare favourably with experimental results for the incident laser intensities used.