Stuttgart 2012 – wissenschaftliches Programm
Q 34.50: Poster
Dienstag, 13. März 2012, 16:30–19:00, Poster.I+II
Enhanced loading for ultracold Calcium ensembles — •Max Kahmann, Sebastian Kraft, Oliver Appel, Dennis Le Plat, and Uwe Sterr — Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig
For producing quantum degenerate 40Ca we use a two stage magneto-optical trap (MOT) and subsequent forced evaporative cooling in an optical dipole trap. The first “blue” MOT on the transition 1S0 – 1P1 is used to capture atoms efficiently from a beam generated by a Zeeman-slower and to precool the atoms to temperatures in the order of a few mK. The second “red” MOT on the transition 1S0 – 3P1 cools the atoms further to typically 15 µK and ensures good transfer to the dipole trap.
A limiting factor both in atom number and for a fast repetition rate is the transfer of atoms from the density limited “blue” to the “red” MOT. To avoid this limitation we remove the repumper during the “blue” MOT and thus let the atoms decay to the metastable 3P2 state. This state is trapped within the magnetic quadrupole field of the MOT. The atoms can then at the end of the MOT stage be repumped to the ground state via the 3D2 and the 3P1 states with a diode laser at 446 nm. To provide long and short term stability we use a reference cavity made from ultra low expansion (ULE) glass placed in a vacuum chamber with an additional internal heat shield. The compact design of this system allows for an simple and robust stabilization of the laser.
This loading scheme will enable us to work with less abundant isotopes as the fermionic 43Ca.