M. A. Levine

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.

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.

Evaporative cooling of highly charged ions in EBIT: An experimental realization

Both the total number and trapping lifetime of near‐neon‐like gold ions held in an electron beam ion trap have been greatly increased by a process of ‘evaporative cooling.’ A continuous flow of low‐charge‐state ions into the trap cools the high‐charge‐state ions in the trap. Preliminary experimental results using titanium ions as a coolant are presented.

EBIT: Electron beam ion trap

An electron Beam Ion Trap (EBIT) has been built as an instrument for in situ studies of atomic physics. Based on the EBIS concept, EBIT incorporates several novel features including ion cooling using light ions and plasma instability control using a short trap length. To understand the operation of EBIT, measurements have been made of the electron beam behavior. The radius of the beam is observed to follow Herrmann Theory during compression. The electron beam displays an energy dispersion that is larger than theory. However, this energy dispersion is only about 15% of the electron temperature in the trap due to the adiabatic compression of the beam.

Dielectronic recombination measurements of highly‐charged heliumlike and neonlike ions using an electron beam ion trap

The electron beam ion trap (EBIT) at LLNL is a unique device designed to measure the interactions of electrons with highly‐charged ions. We describe three methods used at EBIT to directly measure the dielectronic recombination (DR) process: (1) The intensity of the stabilizing X rays is measured as a function of electron beam energy; (2) The ions remaining in a particular ionization state are counted after the electron beam has been held at a fixed electron energy for a fixed time; and (3) High‐resolution spectroscopy is used to resolve individual DR satellite lines. In our discussions, we concentrate on the KLL resonances of the heliumlike target ions (V21+ to Ba54+), and the LMM resonances of the neonlike target ions (Xe44+ to Th80+).

Computer predictions of ‘‘evaporative’’ cooling of highly charged ions in EBIT

Evaporative cooling has been used successfully in EBIT to extend the containment time for neon‐like gold to several hours. This paper discusses a theoretical basis for evaporative cooling. Also included is an assessment of the processes which affect the temperature and number balance of the trapped and coolant ions in EBIT, and how the basic operating parameters affect these processes. Results of computer calculations using nitrogen as a coolant are presented and compared with an approximate analytic solution.