Radiation from Ag high energy density Z-pinch plasmas and applications to lasing

Abstract

International audienceSilver (Ag) wire arrays were recently introduced as efficient x-ray radiators and have been shown to create L-shell plasmas that have the highest electron temperature (>1.8 keV) observed on the Zebra generator so far and upwards of 30 kJ of energy output. In this paper, results of single planar wire arrays and double planar wire arrays of Ag and mixed Ag and Al that were tested on the UNR Zebra generator are presented and compared. To further understand how L-shell Ag plasma evolves in time, a time-gated x-ray spectrometer was designed and fielded, which has a spectral range of approximately 3.5–5.0 Å. With this, L-shell Ag as well as cold Lα and Lβ Ag lines was captured and analyzed along with photoconducting diode (PCD) signals (>0.8 keV). Along with PCD signals, other signals, such as filtered XRD (>0.2 keV) and Si-diodes (SiD) (>9 keV), are analyzed covering a broad range of energies from a few eV to greater than 53 keV. The observation and analysis of cold Lα and Lβ lines show possible correlations with electron beams and SiD signals. Recently, an interesting issue regarding these Ag plasmas is whether lasing occurs in the Ne-like soft x-ray range, and if so, at what gains? To help answer this question, a non-local thermodynamic equilibrium (LTE) kinetic model was utilized to calculate theoretical lasing gains. It is shown that the Ag L-shell plasma conditions produced on the Zebra generator at 1.7 maximum current may be adequate to produce gains as high as 6 cm−1 for various 3p → 3s transitions. Other potential lasing transitions, including higher Rydberg states, are also included in detail. The overall importance of Ag wire arrays and plasmas is discussed

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

“…Although the fits we achieved between our modeling calculations and the measured spectrum are far from perfect, our modeling suggests an electron density on the order of 8×10 20 cm −3 -although this density is only poorly constrained by the opacity affecting the relative intensity of the Lyα lines-and an electron temperature of approximately 1.6 keV. The standard error for our modeling has been previously reported as an order of magnitude for electron density and around 10% for electron temperature (Weller et al 2014). In the present case, we double the uncertainty for the temperature because of the uncertainty in the intensity of the Lyα lines due to opacity effects.…”

Radiation Transport in Z-Pinches

“…It is a subject of more recent and ongoing work [40]- [42]. L-shell spectral lines more frequently overlap than those of the K-shell and exhibit considerably more complex patterns [40,.…”

“…Plasma diagnostics using these lines have not reached the level of maturity of their K-shell counterparts. The recent development of L-shell diagnostics includes the possibility of laser action from Ne-like ions [42].…”

Temporal characteristics and radiative properties of uniform Mo and combined with Al triple planar wire arrays

“…The ratio of Al2 (Lyα: 2p 2 P 1/2,3/2 → 1s 2 S 1/2 ) to Al1 (Heα: 1s2p 1 P 1 → 1s 2 1 S 0 ) is used to estimate T e with an uncertainty of ± 10%. Usually, the electron density is estimated by the ratio of Al1 and inter-combination line Al1' (IC: 1s2p 3 P 1 -1s 2 1 S 0 ) with an estimated uncertainty within an order of magnitude, however here the intensity of the Al1' is too low and the electron density 10 20 cm -3 is used (electron densities on the order of 10 19 -10 20 cm -3 are common for university scale generators, see for example Ref [13,14]). Frame 4, 5 ns later, which corresponds just before the main implosion and re-emergence of background, shows a K-shell Al T e of 430 eV.…”