Exciting Atomic Physics
This is a material edited from the presentation of the
Electron Beam Ion Trap at Lawrence Livermore National Laboratory
captured and edited for teaching purposes by
AUTHOR: David Knapp
EBIT - The Electron Beam Ion Trap
Project Leader: Dieter H. G. Schneider (firstname.lastname@example.org)
An Electron Beam Ion Trap (EBIT) is a device that produces,
traps, and excites very highly charged
ions. We have two EBITs at the Lawrence Livermore National
Laboratory, called EBIT and
Super-EBIT. With these devices,
we have performed a wide range of physics experiments. The ions
can either be observed in the trap itself or extracted from the
trap for external experiments.
Experiments with highly charged ions are at the leading edge of
physics research in several areas today. These ions
are used to study relativity, quantum electrodynamics, plasma physics,
and surface physics.
Recently, we produced bare uranium
(U92+) in the lab using Super-EBIT, the first time this feat has
been accomplished without the use of high-energy particle accelerators.
has been built at NIST
in Gaithersburg, MD.
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 invented at the Lawrence Livermore
National Laboratory by Mort Levine and Ross Marrs. Here is a nice
artist's concept of the EBIT. It was 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. In this country, EBISes
have been built at Kansas
State, Brookhaven National Laboratory, Cornell
University, and (in collaboration with our group) at LBL.
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. EBIT, therefore, allows us to study an otherwise
inaccessible domain in which the potential energy of an ion is
comparable to its kinetic energy.
An EBIT consists of a high-current-density electron beam (up to
5000 A/cm^2) passing through a series of three drift tubes. Ions
are trapped radially by the space charge of the electron beam
itself, and axially by voltages applied to the end drift
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 neonlike
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+, a uranium
nucleus with no electrons around it).
To find out about experiments done with the EBITs, go back to the
EBIT Introduction .
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