Electron beam ion trap

Electron beam ion trap (or its acronym EBIT) is used in physics to denote an electromagnetic bottle that produces and confines highly charged ions. It was invented by R. Marrs [Levine et al, 1988] and M. Levine at LLNL.

An EBIT uses an electron beam focused by means of a powerful magnetic field to ionize (see Ionization) by repeated electron impact atoms injected into the apparatus to very high charge states. The vacuum device requires intense electron beam currents of tens up to hundreds of milliamps accelerated by means of high voltages (up to 200,000 V) applied to special electrodes. The positive ions produced in the region where the atoms intercep the electron beam are tighly confined in their motion by the strong attraction exerted by the negative charges flowing in the electron beam. Therefore, their paths orbit around the electron beam crossing it frequently, thus giving rise to further collisions and continued ionization. To keep their motion restricted in the direction of the electron beam axis, trapping electrodes carrying positive voltages with respect to the central electrode are used. The resulting ion trap can hold the ions for many seconds and minutes, and conditions for reaching the highest charge states, up to bare uranium (U⁹²⁺) are achieved in this way. To avoid spoiling the produced ions by collisions with neutral atoms from which they can capture electrons, the vacuum in the apparatus is usually maintained at UHV levels, with typical pressure values of only 10^-12 torr, (or ~10⁻¹⁰ pascal).

EBITs are used to investigate the fundamental properties of highly charged ions e. g. by photon spectroscopy in particular in the context of relativistic atomic structure theory and quantum electrodynamics (QED). Their suitability to prepare and reproduce in a microscopic volume the conditions of high temperature astrophysical plasmas and magnetic confinement fusion plasmas make them very appropriate research tools. Other fields include the study of their interactions with surfaces and possible applications to microlithography.

Footnotes

References

* Levine, M. A., et al., "The Electron Beam Ion Tr
T22, p. 157 (1988).

* Roscoe E. Marrs, Peter Beiersdorfer, and Dieter Schneider, Physics Today, 27 (October 1994)(Description of the Electron Beam Ion Trap)

* R. E. Marrs, M. A. Levine, D. A. Knapp, J. R. Henderson, Phys. Rev. Lett. 60, 1715 (1988)(First EBIT atomic spectroscopy measurement)

* R. E. Marrs, S. R. Elliott, D. A. Knapp, Phys. Rev. Lett. 72, 4082 (1994)(Production of bare uranium)

* Observation of Visible and UV Magnettic Dipole Transitions in Highly-Charged Xenon and Barium, C. A. Morgan et al., Phys. Rev. Lett. 74, 1716 (1995)

* Nanoscale modification of silicon surfaces via Coulomb explosion, H. P. Cheng, J. D. Gillaspy, Phys. Rev. B 55, 2628 (1997)

* Masked ion beam lithography with highly charged ions, J. D. Gillaspy, D. C. Parks, L. P. Ratliff,Journal of Vacuum Science and Technology B, 16, 3294 (1998)

* A new versatile electron-beam ion trap, F. J. Currell, et al., Journal of the Physical Society of Japan 65, 3186 (1996)

* H. F. Beyer, H.-J. Kluge, V. P. Shevelko, in: "X-ray Radiation of Highly Charged Ions", Springer Series on Atoms and Plasmas, Springer Verlag, Berlin-Heidelberg 1997

External links

* [http://physics.nist.gov/MajResFac/EBIT/intro.html A brief introfuction to EBIT]
* [http://physci.llnl.gov/Research/EBIT/ Original EBIT]
* [http://physics.nist.gov/MajResFac/EBIT/intro.html#140 A list of EBIT facilities]
* [http://physics.nist.gov/MajResFac/EBIT/ebit.html Introduction to EBIT]