P. G. Burkhalter

X‐ray spectra from a gas‐puff z‐pinch device

X‐ray emission was used to diagnose the plasma formation in a gas‐puff pulsed‐discharge device. X‐ray pinhole images were collected simultaneously with x‐ray spectra from Ar and Kr gases. X rays were emitted from z‐pinched regions (50–100 μm in diameter) along a collinear track formed by the plasma implosion of a hollow gas jet. Spectral analysis indicated Ar plasma formation with electron densities of ∼2×1021 cm−3. The Ar plasma temperature was ∼1 keV, based on a collisional‐radiative transport model. Li‐like satellite lines were classified in Ar XVI with atomic structure calculations. The Kr x‐ray spectrum (6–8‐A region) was dominated by Ne‐like Kr XXVII lines. New spectral transitions were classified in Na‐like Kr XXVI and F‐like Kr XXVIII. The wavelength calibrations in the Kr spectrum were obtained from exploded‐Al‐wire plasma generated in coincidence with the plasma implosion formed in the puff gas.

X‐ray line spectra from exploded‐wire arrays

Temperatures and densities were determined from the plasma formed by implosion at the center of symmetrical exploded‐wire arrays. Temperatures of 500–725 eV were found from line ratios in Al and Si spectra using various plasma models. The recombination temperatures for these elements were 500–550 eV. Higher implosion plasma temperatures of 1.5–2 keV were found in Ti and Fe data. The densities were ∼1×1020 electrons/cm3 for the spatially integrated implosion region. Intense emitting regions of ∼500 μm to ∼1.5 mm in size were observed in densitometer contours of Al‐plasma pinhole camera x‐ray images.

Spectra of Mo xxx, xxxi, and xxxii from a laser-produced plasma*

Spectra of highly charged Mo ions generated in a laser-produced plasma were observed from 10 to 190 A with a 3 m grazing- incidence spectrograph. Line identifications in Mo xxx–xxxii were made with the help of relativistic Hartree–Fock calculations. In Mo xxxi (Mg-like) the 3s21S0–3s 3p1P1 resonance line was found to be at 115.944 A. In Mo xxxii (Na-like) the 3s2S1/2–3p2P3/2,1/2 resonance lines are at 127.814 and 176.62 A. These values support the recent identifications of these lines in the Princeton ST tokamak by Hinnov. The density-sensitive 3p2P3/2–3d2D5/2 transition in Mo xxxii is at 126.937 A. At shorter wavelengths, the 3s–4p transitions of Mo xxxii are at 14.384 and 14.565 A.

Spectra of Mo xiii–xviii from a laser-produced plasma and a low-inductance vacuum spark

The spectrum of Mo from 20 to 90 A was obtained with a laser-produced plasma and a low-inductance vacuum spark. Wavelengths and line identifications were determined for transitions of the type 3d–4p and 3d–4f in Mo xiii–xvi and for 3p–3d type transitions in Mo xvi–xviii. The line identifications were obtained with the aid of relativistically corrected Hartree-Fock calculations. Energy-level diagrams are given for the 3d84p and 3d84f configurations of Mo xvi.

X‐ray spectral line coincidences between fluorine K‐ and transition‐metal L‐series lines

X‐ray spectroscopy was performed in the 12–15‐A region, recording L‐series lines from selected laser‐irradiated transition metals. Line coincidences and near coincidences were identified between Cr, Mn, Fe, and Ni L spectra, and F viii and F ix K‐shell lines. Wavelengths were determined to accuracies of 1–3 mA and will be utilized in selecting potential pumping candidates in future x‐ray lasing schemes. High‐resolution x‐ray spectra were collected under controlled illumination and target conditions, using 1.05‐ and 0.527‐μm laser excitation with the KMS CHROMA laser. Laser intensity varied from 1.2–2.5×1014 W/cm2 in 200‐ps pulses. Three groups of x‐ray spectra were collected with highly dispersive x‐ray crystals at wave bands centered at 12.643, 13.781, and 14.458 A, corresponding to H‐ and He‐like lines from fluorine. Two specially designed flat crystal spectrographs employing camera shutters were used with pairs of beryl and thallium acid phthalate (TAP) crystals. The spectra from potential lasant and p...

A high‐resolution x‐ray diagnostic technique using simultaneous diffraction from several planes of acid phthalate crystals

An x‐ray diagnostic tool was developed for acquiring and interpreting high‐resolution spectra for hot‐plasma emission from selected elements. A convex, curved potassium acid phthalate (KAP) crystal was used to collect spectral data from an exploded‐A1‐wire plasma over a wide exposure latitude with the 001, 002, and the 013 planes simultaneously diffracting. The curved‐crystal diffraction efficiencies were calculated for these three planes in KAP and evaluated with x‐ray line intensities derived from the experimental A1 data. The crystal efficiencies were also computed for two other commonly used acid phthalate crystals rubidium acid phthalate (RAP) and thallium acid phthalate (TAP), to compare with KAP crystals. The calculated efficiencies for the first‐order diffraction in KAP, RAP, and TAP agreed with available experimental data.

Transitions in highly ionized Sn spectra from a laser-produced plasma*

A laser-produced spectrum of highly stripped Sn atoms in the xuv region of 10–60 A was recorded with a grating spectrograph. Atomic SCF calculations were used to identify as many as six ionization states from observations of resonance transitions to the M shell. Multiplets in the Sn spectrum belonging to the Ni I and Co I isoelectronic sequences were identified by atomic-structure calculations.

Laser-produced x-ray spectra of the fluorine isoelectronic sequence for Zn, Ge, and Se †

The transitions 2p5-2p43s and 2p5-2p43d in fluorine-like Zn, Ge, and Se have been measured in laser-produced x-ray spectra. The experimental spectral data agree well with ab initio atomic structure calculations based on Hartree-Fock wave functions. Classifications of the F i-like lines in these spectra are based on isoelectronic extrapolations and theoretical calculations.

L-series satellite spectra in Ti xii and Fe xvi

Transitions in Na-like Ti and Fe ions, which appears as satellites to 2p-3s and 2p-3d transitions in Ne-like ions, were studied. The soft x-ray spectra produced by a focused-laser source and a vacuum-spark device were obtained with the same grazing-incidence spectrograph. Atomic structure calculations agreed with the observed 2p-3s spectral patterns and made possible line identifications in Ti xii and Fe xvi.

X‐ray line emission and plasma conditions in exploded Fe wires

Single‐wire Fe spectra collected from two different exploded‐wire generators (Gamble II and Owl II) were analyzed to determined the ionization stages produced in the plasmas. The temperature for the hot‐plasma pinches for both generators was 1.4±0.2 keV at which an abundance of Fe XXIV transitions is produced. The Fe K spectra from exploded wires are basically similar to those produced in the pinched plasma generated randomly in the vacuum spark; however, the exploded wires have lower plasma temperatures than the hottest pinches produced in the vacuum spark. A detailed interpretation of the Fe L spectra formed in the exploded wires permitted line and ionization stage identifications in the 7–12‐A region. Such spectroscopic data is useful for analysis of complex Fe spectra generated in multitemperature plasma devices like Tokamaks.