Electron temperature and density characterization using L-shell spectroscopy of laser irradiated buried iron layer targets

Shahzad, Mohammed; Tallents, G. J.; Steel, A. B.; Hobbs, L. M. R.; Hoarty, D. J.; Dunn, James P.

doi:10.1063/1.4892263

Cited by 5 publications

(1 citation statement)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Short pulse lasers have been used to heat materials to hundreds of eVs at near solid densities [1][2][3][4][5][6][7][8][9][10][11][12]. Xray emission measurements, at such stellar-relevant conditions, may provide insight into existing disagreements between solar models and observations [13][14][15][16][17][18][19][20][21] by testing the validity of theoretical opacity models.…”

Section: Introductionmentioning

confidence: 99%

An automated design process for short pulse laser driven opacity experiments

Martin

London

Goluoglu

et al. 2018

High Energy Density Physics

View full text Add to dashboard Cite

Stellar-relevant conditions can be reached by heating a buried layer target with a short pulse laser. Previous design studies of iron buried layer targets found that plasma conditions are dominantly controlled by the laser energy while the accuracy of the inferred opacity is limited by tamper emission and optical depth effects. We developed a process to simultaneously optimize laser and target parameters to meet a variety of design goals. We explored two sets of design cases: a set focused on conditions relevant to the upper radiative zone of the sun (electron temperatures of 200 to 400 eV and densities greater than 1/10 of solid density) and a set focused on reaching temperatures consistent with deep within the radiative zone of the sun (500 to 1000 eV) at a fixed density. We found optimized designs for iron targets and determined that the appropriate dopant, for inferring plasma conditions, depends on the goal temperature: magnesium for up to 300 eV, aluminum for 300 to 500 eV, and sulfur for 500 to 1000 eV. The optimal laser energy and buried layer thickness increase with goal temperature. The accuracy of the inferred opacity is limited to between 11 % and 31 %, depending on the design. Overall, short pulse laser heated iron experiments reaching stellar-relevant conditions have been designed with consideration of minimizing tamper emission and optical depth effects while meeting plasma condition and x-ray emission goals.implementing an automated process to systemically explore a broad range of laser and target parameters and find optimized designs therein. This allows us to determine globally optimized designs for specific goals, such as plasma temperature and density. We used the process to find optimized designs of buried iron sulfide (FeS 2 ) targets. The choice of iron sulfide is motivated by experiments at Atomic Weapons Establishment's Orion Laser Facility, which were originally proposed to use 0.3 µm iron sulfide sandwiched between two 3 µm layers of parylene-N. 1 The experiments were planned to use a 0.53 µm wavelength laser beam with a pulse length of 0.5 ps [34], focused to 20 -50 µm diameters [8], and laser energies up to 100 J [34]. We explored two sets of design cases using the automated process. The first set focused on the range of plasma conditions relevant to the upper radiative zone of the sun: T = 200 eV, T = 300 eV, and T = 400 eV, each with ρ > 1/10 of solid density. The second set focused on reaching higher plasma temperatures, relevant to deep within the radiative zone of the sun, at a fixed density: T = 500 eV, T = 750 eV, and T = 1000 eV, each with ρ = 4.2 g/cm 3 . The designs for both sets may be valuable for investigating how iron opacity scales with temperature. In this paper, we discuss the automated design process and its application to these six design cases.

show abstract

Section: Introductionmentioning

confidence: 99%

An automated design process for short pulse laser driven opacity experiments

Martin

London

Goluoglu

et al. 2018

High Energy Density Physics

View full text Add to dashboard Cite

show abstract

Diagnosis of energy transport in iron buried layer targets using an extreme ultraviolet laser

et al. 2015

View full text Add to dashboard Cite

We demonstrate the use of extreme ultra-violet (EUV) laboratory lasers in probing energy transport in laser irradiated solid targets. EUV transmission through targets containing a thin layer of iron (50 nm) encased in plastic (CH) after irradiation by a short pulse (35 fs) laser focussed to irradiances 3 × 1016 Wcm−2 is measured. Heating of the iron layer gives rise to a rapid decrease in EUV opacity and an increase in the transmission of the 13.9 nm laser radiation as the iron ionizes to Fe5+ and above where the ion ionisation energy is greater than the EUV probe photon energy (89 eV). A one dimensional hydrodynamic fluid code HYADES has been used to simulate the temporal variation in EUV transmission (wavelength 13.9 nm) using IMP opacity values for the iron layer and the simulated transmissions are compared to measured transmission values. When a deliberate pre-pulse is used to preform an expanding plastic plasma, it is found that radiation is important in the heating of the iron layer while for pre-pulse free irradiation, radiation transport is not significant.

show abstract