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Electron Beam Ion Trap (EBIT)
What is EBIT?
An Electron Beam Ion Trap, or EBIT, is a device that makes and traps very highly charged ions by means of a high current density electron beam. The EBIT was developed at the Lawrence Livermore National Laboratory by Mort Levine and Ross Marrs. At left is an artist's concept of the EBIT. With this device we perform a wide range of physics experiments. The ions can either be observed in the trap itself or extracted from the trap for external experiments. We produced bare uranium (U92+) in the lab using Super-EBIT (a high energy modification to the origional EBIT). This was the first time this feat has been accomplished without the use of high-energy particle accelerators.
EBIT is an idea based upon the Electron Beam Ion Source (EBIS), a design for an ion source intended for use in atomic physics and as an injector into heavy-ion accelerators. Other EBITs exist now at NIST in Gaithersburg, MD., Oxford, England, Berlin, Germany and Tokyo, Japan.
The EBIT is the only ion source in the world that can create highly charged ions at rest. All other sources of highly charged ions involve accelerators that accelerate the ions to very high energies. Therefore EBIT allows us to study an otherwise inaccessible domain in which the potential energy of the ion is comparable to or exceeds its kinetic energy.
Experiments with highly charged ions are in the forefront of physics research in several areas today. These ions are used for studies in the areas of atomic, nuclear, plasma, astro and surface physics.
How EBIT works
EBIT consists of a high-current-density electron beam (up to 5000 A/cm2) passing through a series of three drift tubes. Ions are trapped radially by the charge of the electron beam itself, and axially by voltages applied to the end drift tubes.
The electron beam is magnetically compressed by a high magnetic field from a pair of superconducting Helmholtz coils. The electron beam energy in the trap is determined by the voltage applied to the central drift tube.
As electrons collide with the ions in the beam, they strip off electrons until the energy required to remove the next electron is higher than the beam energy. Our original EBIT is capable of an electron beam energy of about 30 keV, enough to make neon-like uranium (U82+, or a uranium atom with only 10 of the usual 92 electrons). We have built a high-energy EBIT, named Super-EBIT, with a floating electron gun, that can achieve an electron beam energy of 200 keV, enough to make bare uranium (U92+)