Temperature and phase-space density of a cold atom cloud in a quadrupole magnetic trap

Abstract

We present studies on the modifications in temperature, number density and phase-space density when a laser cooled atom cloud from the optical molasses is trapped in a quadrupole magnetic trap. Theoretically it is shown that for a given temperature and size of the cloud from the molasses, the phase-space density in the magnetic trap first increases with magnetic field gradient and then decreases with it, after attaining a maximum value at an optimum value of magnetic field gradient. The experimentally measured variation in phase-space density in the magnetic trap with the magnetic field gradient has shown the similar trend. However, the experimentally measured values of number density and phase-space density are much lower than their theoretically predicted values. This is attributed to the higher experimentally observed temperature in the magnetic trap than the theoretically predicted temperature. Nevertheless, these studies can be useful to set a higher phase-space density in the trap by setting the optimum value of field gradient of the quadrupole magnetic trap.

Magnetically-Trapped Molecules Efficiently Loaded from a Molecular MOT

“…When the trap is maintained approximately at its switch-on gradient for the duration of trapping (referred to as the low-gradient case), so that only molecules in the most strongly-trapped states are retained, we load ≈ 40% of the molecules from the |N P = 1 − state in the MOT into the MQT. In this low-gradient case, only slight heating (to T trap ≈ 90 µK) is expected based on an analytic expression for the energy imparted by the switch-on of the MQT [36]; we confirm this expectation in numerical simulations including the effect of gravity. Experimentally, we detect no substantial heating of the molecules by the trap.…”

A toroidal trap for cold ${}^{87}{Rb}$ atoms using an rf-dressed quadrupole trap

“…The experiments have been performed on a double magneto-optical trap (double-MOT) setup [24][25][26] in which a vapour chamber MOT (VC-MOT) of 87 Rb atoms is formed in a chamber at pressure of ∼ 1×10 −8 mbar and an ultra-high vacuum MOT (UHV-MOT) is formed in a glass cell at pressure of ∼ 5×10 −11 mbar . The schematic of the setup is shown in Fig.…”

“…The experiments have been performed on a double magnetooptical trap (double-MOT) setup [24][25][26]. The schematic of the setup is shown in figure 3.…”