D. D. Dietrich

The use of an electron beam ion trap in the study of highly charged ions

The Electron Beam Ion Trap (EBIT) is a relatively new tool for the study of highly charged ions. Its development has led to a variety of new experimental opportunities; measurements have been performed with EBITs using techniques impossible with conventional ion sources or storage rings. In this paper, I will highlight the various experimental techniques we have developed and the results we have obtained using the EBIT and higher-energy Super-EBIT built at the Lawrence Livermore National Laboratory.

Time and space resolved vacuum‐ultraviolet spectroscopy of an argon gas‐puff Z pinch

Time and radially resolved vacuum‐ultraviolet spectra from an argon gas‐puff Z pinch have been obtained using a grazing incidence spectrometer with gated microchannel plates curved to the Rowland circle. Most of the 50–300‐A radiation is emitted from a dense core (r≊0.4 mm, ne≳1019 cm−3, Te≊150 eV) which forms when the plasma assembles on the axis.

Spectroscopic studies of an argon plasma produced in a relativistic electron beam gas puff Z pinch

The spectra of argon ions emitted from a plasma created by discharging a 3‐TW relativistic electron beam generator through an argon gas column are reported. New lines have been classified for 2s 2pn–2pn+1 transition arrays in Ar XI–XV and energy levels have been derived for lithiumlike argon XVI. The effects of mass motion Doppler shifts on the spectra have been measured and systematic shifts of transition energies with charge state are observed in the data.

Transitions in Na-like and Mg-like ions of In, Sb, I, and Cs

The spectra of highly charged ions of the elements In, Sb, I, and Cs have been recorded by using a 3-m grazing-incidence spectrograph at the University of Rochester’s Laboratory for Laser Energetics. Transitions in the Na i and Mg i isoelectronic sequences have been identified. Wavelengths in the range 7–100 A were measured to an accuracy of ± 0.02 A, and energy levels were derived from the measured wavelengths.

Soft-x-ray spectra of krypton xxiv–xxvii in gas puff Z-pinch plasmas

The spectra of krypton ions produced by the magnetic implosion of a krypton gas cylinder in the wavelength range from 10 to 250 A have been observed. Lines from highly ionized krypton ions from Kr xxiv to Kr xxvii have been identified by isoelectronic sequence extrapolation and compared with ab initio relativistic calculations. Energy levels are derived for Kr xxvi.

A differential measurement of the ground state Lamb shift in hydrogenic germanium, Ge31+

Abstract The 1s-2p Lyman α transitions in hydrogenic germanium, Ge31+, have been observed in fourth order of diffraction from a beam-foil light source, simultaneously with the n = 2 to n = 4 Balmer β transitions observed in first order of diffraction. This enables a measurement of the Lyman α wavelengths using the Balmer β wavelengths as a calibration. The results are presented, along with a discussion of the experimental errors, and further work which should improve the accuracy with which the Lyman α. wavelengths can be determined.

Active Detection of Shielded SNM With 60-keV Neutrons

Fissile materials, e.g., 235U and 239Pu, can be detected non-invasively by active neutron interrogation. A unique characteristic of fissile material exposed to neutrons is the prompt emission of high-energy (E > 1 MeV) fission neutrons. One promising mode of operation subjects the object to a beam of low-energy (E < 1 MeV) neutrons, generated by a proton beam impinging on a Li target. The emergence of high-energy secondary neutrons then clearly indicates the presence of fissile material. Our interrogation system comprises a low-dose 60-keV neutron generator (5 times 106/s ), and a 1 m2 array of scintillators for high-energy neutron detection. Preliminary experimental results demonstrate the detectability of small quantities (376 g) of 235U shielded by steel (200 g/cm2) or plywood (30 g/cm2), with a typical measurement time of 1 min.

Photographic Response to X-Ray Irradiation III: Photographic Linearization of Beam-Foil Spectra

In this paper models for the relation of specular density to incident (x-ray) intensity with uncertainties are applied to experimental data, indicating methods for the correction of additional effects. Linearization and error calculations are simplified by double linear interpolation, and the effect of this is quantified. Relative first-order intensities are determined directly. Secondary linearization or calculation for higher-order lines gives correction factors that yield absolute and relative higher-order intensity ratios. The effects of energy and angle on linearization are included. Densitometry uncertainty is estimated and quantified.

Beam foil spectroscopy of n = 3 to n = 2 transitions in highly stripped heavy ions

The spectroscopy of very highly ionized atoms provides an important testing ground for multi-electron atomic theory. We report preliminary experimental results on the n = 3 ..-->.. 2 spectra of Bi/sup +73/ and A/sup +69/ obtained at the GSI UNILAC accelerator. 19 refs., 4 figs.

Precision X-ray spectroscopy on 8.5 MeVamu heavy ions

A new experimental capability has been developed at the Lawrence Berkeley Laboratory Super-HILAC to investigate questions relating to high resolution atomic spectroscopy. A key element of these measurements is a dual arm Johann spectrometer. The ion beam passes inside the Rowland circle of two curved crystals which are mounted such that diffracted X-rays have equal and opposite linear Doppler shifts. The X-ray lines are detected with high speed X-ray film mounted on the Rowland circle. The beam-crystal geometry is arranged so a spectral range θB ~ 30°–70° is detected. The spectrometer efficiency is high with useful exposures obtained with only 10 mC of beam. A wavelength calibration is obtained by simultaneously exposing the film with diffracted K and L X-rays from an X-ray tube. X-ray lines from the beam are slanted, with respect to the calibration lines, due to Doppler shifts arising from X-rays incident on the crystal at angles other than perpendicular to the diffraction plane. The slope of these lines provides an independent determination of the beam velocity, which is used to correct for the transverse Doppler shift. Typical results are presented.