H. S. Margolis

The Oxford electron‐beam ion trap: A device for spectroscopy of highly charged ions

An electron‐beam ion trap (EBIT) has just been completed in the Clarendon Laboratory, Oxford. The design is similar to the devices installed at the Lawrence Livermore National Laboratory. It is intended that the Oxford EBIT will be used for x‐ray and UV spectroscopy of hydrogenic and helium‐like ions, laser resonance spectroscopy of hydrogenic ions and measurements of dielectronic recombination cross sections, in order to test current understanding of simple highly charged ions.

Studies of magnetic dipole transitions in highly charged argon and barium using an electron beam ion trap

Using the Oxford electron beam ion trap (EBIT), we have studied a number of magnetic-dipole fine-structure transitions in highly charged argon and barium, which lie in the visible and near-UV region of the spectrum. Our wavelength measurements, with uncertainties of between 7 and 20 ppm, are the most accurate yet reported using an EBIT as a spectroscopic source of ions, and provide a useful test of atomic structure calculations for many-electron systems. The argon transitions studied are also of astrophysical interest. Finally, we present the first studies of the polarization of a visible transition from a highly charged ion trapped in an EBIT.

A design study for a super‐EBIT/EBIS without magnetic fielda)

A super‐EBIT may be defined by its ability to ionize even hydrogenlike uranium, requiring an electron energy well above 140 keV. The first super‐EBIT has been put into operation at Livermore, operating with electron energies up to 200 keV, the second one is in progress in Tokyo, aiming at 300 keV. A distinctive advantage may be obtained by raising the electron energy from 200–300 to 500 keV, thus reducing the radiative recombination of hydrogenlike heavy ions such as U91+ and increasing their relative abundance by an order of magnitude.

Laser spectroscopy of the 1s22s2p 3P2-3P1 transition in beryllium-like argon using the Oxford EBIT

A study of the 1s22s2p 3P2-3P1 fine-structure transition in beryllium-like argon is planned on the Oxford electron beam ion trap (EBIT), using laser-induced resonance. This transition wavelength was measured previously as 594.373(4) nm, which is accessible using a dye laser. The ions are produced and excited in the EBIT and are confined during laser irradiation using the magnetic trapping mode. The 3P2 level population is depleted by the laser and by subsequently monitoring the emitted fluorescence a laser resonance signal can be obtained.

Laser spectroscopy using the Oxford electron beam ion trap

The utility of an electron beam ion trap (EBIT) as a source of highly charged ions for laser spectroscopy is discussed, with a view to measuring the 2s Lamb shift in a medium-Z hydrogenlike ion. Such an experiment could shed light on a small but systematic discrepancy between previous measurements and theory.

Determination of the number of ions in the Oxford electron beam ion trap

Abstract In order to determine absolute numbers of ions trapped in the Oxford electron beam ion trap (EBIT), the efficiency of a lithium-drifted silicon X-ray detector has been characterized over the energy range 1.5–15 keV using the Oxford scanning proton microprobe. Preliminary results for the number densities of neon-like barium and highly charged argon ions are presented.

Laser spectroscopy of the 2s lamb shift in hydrogen-like silicon using an electron beam ion trap

We describe progress towards a precision measurement of the 2s Lamb shift in hydrogen-like silicon. This will use the Oxford electron beam ion trap (EBIT) as a source of highly charged ions for laser spectroscopy. We have successfully trapped silicon ions in the EBIT, and are determining the optimum operating conditions required to maximize the number of Si13+ ions. The laser system required for the experiment is currently under development; the first stage of this work involves locking a frequency-stabilized laser operating at 734 nm to a high-finesse enhancement cavity.

Recent research using the Oxford electron beam ion trap

An overview is given of the current spectroscopic effort on the Oxford electron beam ion trap. Recent results from three different experiments are discussed: a precision measurement of the 1s2s3S1–1s2p3P2 transition in helium-like neon by VUV emission spectroscopy, a measurement of the two-electron contribution to the ground state energy of helium-like argon using absorption edge spectroscopy, and a study of the lifetime of the 1s22s2p3P2 level in beryllium-like argon.

Studies of the ionization balance in an electron beam ion trap

The evolution of the ion charge state balance in an electron beam ion trap has been studied using a computer program which models the atomic processes occurring within the trap. The predictions of this modelling code have been compared with experimentally-determined charge state distributions. Results are presented here for highly charged nickel.