Difference between revisions of "BEC"
(→Overview) |
|||
| Line 6: | Line 6: | ||
==Overview== | ==Overview== | ||
| − | |||
| − | |||
| − | |||
| − | The experiment takes place in a G-10 cell, coaxially inside the bore of a 4 T deep superconducting anti-Helmholtz magnetic trap and thermally anchored to a dilution refrigerator. 4He* is excited via RF discharge with an efficiency of 10^{-5} from a 4He buffer gas and cooled to the refrigerator temperature by collisions with the remaining buffer gas. The buffer gas is cryo-pumped to a charcoal sorb, leaving ,math>\sim 10^{11} ^4</math>He* atoms trapped in the magnetic field. The atom cloud is then evaporatively cooled to 1 mK by surface-induced evaporation and transferred to a tightly confining superconducting quadrupole-Ioffe configuration trap to prevent Majorana losses. Further evaporative cooling using a RF knife leads to the creation of a BEC at a temperature of 5 uK with approximately 10^6 atoms remaining. | + | Despite innumerable experimental advances, research with degenerate Bose and Fermi gases has remained limited to only a handful of atomic species since its inception due to the field's reliance on laser pre-cooling as the first step towards quantum degeneracy. Developmening new cooling methods applicable to a wider range of atoms and also to molecules is thus important for taking full advantage of scientific opportunities in new areas. |
| + | |||
| + | ==Metastable Helium BEC== | ||
| + | [[File:BEC_cell.jpg|300px|left|The G-10 cell and trapping magnets.]] | ||
| + | We have utilized buffer-gas methods to demonstrate Bose-Einstein condensation of 4He* without the use of laser pre-cooling. These methods are readily extendable to any paramagnetic species with typical collisional parameters that allow for efficient evaporative cooling, significantly extending the scope of ultracold atom/molecule research. The experiment takes place in a G-10 cell, coaxially inside the bore of a 4 T deep superconducting anti-Helmholtz magnetic trap and thermally anchored to a dilution refrigerator. 4He* is excited via RF discharge with an efficiency of 10^{-5} from a 4He buffer gas and cooled to the refrigerator temperature by collisions with the remaining buffer gas. The buffer gas is cryo-pumped to a charcoal sorb, leaving ,math>\sim 10^{11} ^4</math>He* atoms trapped in the magnetic field. The atom cloud is then evaporatively cooled to 1 mK by surface-induced evaporation and transferred to a tightly confining superconducting quadrupole-Ioffe configuration trap to prevent Majorana losses. Further evaporative cooling using a RF knife leads to the creation of a BEC at a temperature of 5 uK with approximately 10^6 atoms remaining. | ||
[[File:He_BEC_formation.jpg|400px|right|Phase-contrast images of 4He* in 1 ms TOF, showing BEC formation. (a) a thermal cloud slightly above Tc. (b) onset of BEC. (c) a nearly pure BEC after further evaporative cooling.]] | [[File:He_BEC_formation.jpg|400px|right|Phase-contrast images of 4He* in 1 ms TOF, showing BEC formation. (a) a thermal cloud slightly above Tc. (b) onset of BEC. (c) a nearly pure BEC after further evaporative cooling.]] | ||
Atoms are detected in time-of-flight using phase-contrast imaging. | Atoms are detected in time-of-flight using phase-contrast imaging. | ||
| + | ==Two-body collisions in Thulium and Erbium== | ||
Since producing our 4He* BEC we have been investigating two-body atom-atom collisional properties of the "submerged-shell" rare-earth atoms Thulium and Erbium. Previous research in our lab indicated that the submerged-shell nature of these atoms gives rise to strong suppression of inelastic processes during atom-helium collisions. Similar suppression of inelastic collisions in atom-atom collisions would permit efficient evaporative cooling and make these atoms excellent candidates for new quantum degenerate gases, accessible using our new buffer-gas BEC approach. | Since producing our 4He* BEC we have been investigating two-body atom-atom collisional properties of the "submerged-shell" rare-earth atoms Thulium and Erbium. Previous research in our lab indicated that the submerged-shell nature of these atoms gives rise to strong suppression of inelastic processes during atom-helium collisions. Similar suppression of inelastic collisions in atom-atom collisions would permit efficient evaporative cooling and make these atoms excellent candidates for new quantum degenerate gases, accessible using our new buffer-gas BEC approach. | ||
Revision as of 11:08, 29 July 2009
Contents
Buffer-Gas BEC project
People
- Charlie Doret
- Colin Connolly
- Yat Shan Au
Overview
Despite innumerable experimental advances, research with degenerate Bose and Fermi gases has remained limited to only a handful of atomic species since its inception due to the field's reliance on laser pre-cooling as the first step towards quantum degeneracy. Developmening new cooling methods applicable to a wider range of atoms and also to molecules is thus important for taking full advantage of scientific opportunities in new areas.
Metastable Helium BEC
We have utilized buffer-gas methods to demonstrate Bose-Einstein condensation of 4He* without the use of laser pre-cooling. These methods are readily extendable to any paramagnetic species with typical collisional parameters that allow for efficient evaporative cooling, significantly extending the scope of ultracold atom/molecule research. The experiment takes place in a G-10 cell, coaxially inside the bore of a 4 T deep superconducting anti-Helmholtz magnetic trap and thermally anchored to a dilution refrigerator. 4He* is excited via RF discharge with an efficiency of 10^{-5} from a 4He buffer gas and cooled to the refrigerator temperature by collisions with the remaining buffer gas. The buffer gas is cryo-pumped to a charcoal sorb, leaving ,math>\sim 10^{11} ^4</math>He* atoms trapped in the magnetic field. The atom cloud is then evaporatively cooled to 1 mK by surface-induced evaporation and transferred to a tightly confining superconducting quadrupole-Ioffe configuration trap to prevent Majorana losses. Further evaporative cooling using a RF knife leads to the creation of a BEC at a temperature of 5 uK with approximately 10^6 atoms remaining.
Atoms are detected in time-of-flight using phase-contrast imaging.
Two-body collisions in Thulium and Erbium
Since producing our 4He* BEC we have been investigating two-body atom-atom collisional properties of the "submerged-shell" rare-earth atoms Thulium and Erbium. Previous research in our lab indicated that the submerged-shell nature of these atoms gives rise to strong suppression of inelastic processes during atom-helium collisions. Similar suppression of inelastic collisions in atom-atom collisions would permit efficient evaporative cooling and make these atoms excellent candidates for new quantum degenerate gases, accessible using our new buffer-gas BEC approach.
