D. A. Vogel

High‐resolution x‐ray spectrometer for an electron beam ion trap

A high‐throughput von Hamos‐type Bragg crystal spectrometer is described that is operated with the Livermore electron beam ion trap. The spectrometer is employed to measure high‐resolution x‐ray spectra from highly charged heliumlike and neonlike ions. Data from heliumlike Ti20+ and Fe24+ and from neonlike Au69+ are presented to demonstrate the utility of the new instrument.

X-ray measurement of the ionization balance in an electron beam ion trap

Abstract The charge-state abundances of bare, hydrogen-, helium-, lithium-, and beryllium-like iron in the Livermore electron beam ion trap have been measured with uncertainties ranging from 3 to 15% by monitoring the emitted X rays. The ionization balance is determined in two ways: (1) by observing radiative recombination photons with a solid-state detector, and (2) by observing line radiation with a Bragg crystal spectrometer. The results are in good agreement with an ionization balance model.

High‐pressure position‐sensitive proportional counter

A gas‐filled position‐sensitive proportional counter was constructed for the detection and analysis of x rays in the 8–20 keV range. The detector’s active volume is 9.5×3×0.4 cm3. Based on an earlier design, the cathode incorporates a 160‐ns delay line, etched using printed‐circuit techniques. The detector operates at an 80‐psig gas pressure and achieves a spatial resolution as low as 80 μm and linearity better than 25 μm. The counting efficiency ranges from 80% at 8 keV to 37% at 20 keV. The new detector allowed efficient recording of high‐resolution spectra of the K emission lines from heliumlike Ge30+ and Kr34+.

Electron impact excitation cross section measurements of highly charged heliumlike and lithiumlike ions

The relative cross sections for electron impact excitation of the heliumlike forbidden line z, intercombination lines y and x, and the resonance line w, together with the associated lithiumlike satellites line q, r, t, u, and v have been measured for Ti, V, Cr, Mn, and Fe on the Livermore electron beam ion trap. The measurements were made near the threshold for excitation of the heliumlike transitions where no other processes can contribute to the excitation of the lines. The uncertainties in the measurements are up to 15% for the heliumlike transitions and between 14 and 27% for the lithiumlike transitions. After normalizing the relative results to theoretical radiative recombination cross sections, we find good agreement with results from a distorted‐wave calculation.

Spectroscopy and atomic physics in EBIT and SuperEBIT

An overview is given of x‐ray measurements in progress on the Livermore electron beam ion trap facilities. The measurements include detailed investigations of the satellite spectrum of heliumlike krypton Kr34+ for diagnostic applications in future tokamak fusion reactors, precise measurements of the 2‐2 transition energies in neonlike U82+ through lithiumlike U89+ to test the predictions of QED theory, and investigations of line formation by innershell ionization and non‐resonant electron capture for the development of line diagnostics applicable to non‐equilibrium plasmas.

Inner-shell ionization of lithium-like chromium ions

We have used high-resolution x-ray spectroscopy to investigate inner-shell ionization of Cr21+ ions by electron impact using the Electron Beam Ion Trap at Lawrence Livermore Laboratory. Our measurements indicate that inner-shell ionization enhances the intensity of the radiative transition 1s2s3S1→1s21S0.

Dielectronic recombination into Rydberg levels of lithiumlike titanium

To characterize line formation near threshold for electron-impact excitation, dielectronic capture into high-n levels in lithiumlike Ti19+ ions has been studied with high-resolution x-ray spectroscopy on the Livermore electron beam ion trap. The process is shown to result in satellite lines which are virtually indistinguishable from their dipole-allowed heliumlike parent lines. High-n satellite lines are absent from dipole-forbidden heliumlike lines.