Bragg Scattering Experiments with Laser-Cooled Be^+ Ions in a Penning Trap.
Abstract
We have observed Bragg scattering of near resonant laser light (313 nm) from approximately spherical plasmas with greater than 10^5 laser-cooled ^9Be^+ ions in a Penning trap.footnote J. N. Tan, et al., Phys. Rev. Lett. 75, 4198 (1995). With densities near 4×10^8 cm-3 and temperatures less than 5 mK the ions are strongly coupled (Γ>400). During some of the laser-cooling periods, the Bragg scattering patterns indicate the formation of a crystal with a size greater than 10-20 inter-ion spacings. We use the time dependence of the Bragg scattered light to strobe our camera synchronously with the plasma rotation. In this way we obtain a Laue pattern of dots and a precise measure of the plasma rotation frequency. With 2×10^5 trapped ions, the Bragg scattering patterns are consistent with a bcc lattice. Some preferred crystal orientations are observed. For example, bcc crystals are frequently formed with a 4-fold symmetry axis aligned with the laser beam (along the trap B field). Recently we have been able to stack many loads to obtain a few million trapped ions. Results with these larger clouds and a new camera system will be presented.
- Publication:
-
APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- November 1996
- Bibcode:
- 1996APS..DPP..9R19B