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Physical Review A

Trapping and cooling of potassium isotopes in a double-magneto-optical-trap apparatus

M. Prevedelli, F. S. Cataliotti, Eric Cornell, J. R. Ensher, C. Fort, Leonardo Ricci, Guglielmo Maria Tino, M. Inguscio

Published Jan 1, 1999• 38 citations
Publisher

Abstract

We report on the efficient operation of a double-magneto-optical-trap (MOT) apparatus for potassium isotopes. Mechanisms for the cooling and the transfer between the two MOTs are studied. A magnetic quadrupole trap has been loaded from the second MOT; density and temperature appear to be promising for starting runaway evaporative cooling.

DOI
10.1103/physreva.59.886

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We report on the efficient operation of a double-magneto-optical-trap (MOT) apparatus for potassium isotopes. Mechanisms for the cooling and the transfer between the two MOTs are studied. A magnetic quadrupole trap has been loaded from the second MOT; density and temperature appear to be promising for starting runaway evaporative cooling.
The main goal of this research is to cool potassium-41 atoms to ultracold temperatures (<10 μK) in order to study the spin dynamics of atom to atom interactions. However, our current goal is to finish constructing the apparatus that will allow us to confine and cool these atoms in three dimensions. This apparatus will cool and confine the potassium atoms in 3 steps. First, the atoms will be cooled and trapped in our 3D magneto-optical trap. This step of the experiment will cool the atoms near the Doppler-cooling limit, which for potassium atoms is 145 μK. Second, atoms will be loaded into a FORT (far off resonance trap) with an expected depth of 25 μK. In order to cool the atoms below the Doppler-cooling limit, we will use sub-Doppler cooling techniques. What is particularly unique about our experiment is that we plan to use an octupole magnetic field to achieve sub-Doppler cooling. In typical laser cooling experiments sub-Doppler temperatures are achieved when the quadrupole magnetic field is off, which leaves the atoms untrapped. Third, once the atoms have been loaded into the FORT one last cooling mechanism will be implemented. This mechanism is referred to as evaporative cooling and will cool the atoms below 10 μK.
We report the sub-Doppler deep-cooled three-dimensional magneto-optical trap (3D MOT) of the fermionic 40K and bosonic 39K isotopes of potassium loaded by a very compact 2D+ MOT with a novel optical design feature. The set-up is meant for studies on the quantum dynamics of a few fermionic and bosonic atoms in an optical dipole trap near and well within quantum degeneracy. The loading rate and atom numbers achieved in the compact simple set-up are comparable to those in the previous set-ups with more elaborate vacuum design. We attained relatively low temperatures of 34 and 30 µK for 39K and 40K after the sub-Doppler cooling process.
We report the magnetic trapping of metastable 3P2{}^{3}{P}_{2}3P2​ atomic strontium. Atoms are cooled in a magneto-optical trap (MOT) operating on the dipole-allowed ${}^{1}{S}_{0}{\ensuremath{-}}^{1}{P}_{1}$ transition at 461 nm. Decay via ${}^{1}{\stackrel{\ensuremath{\rightarrow}}{{P}_{1}}}^{1}{\stackrel{\ensuremath{\rightarrow}}{{D}_{2}}}^{3}{P}_{2}$ continuously loads a magnetic trap formed by the quadrupole magnetic field of the MOT. Over 108{10}^{8}108 atoms at a density of $8\ifmmode\times\else\texttimes\fi{}{10}^{9}{\mathrm{cm}}^{\ensuremath{-}3}$ and temperature of 1 mK are trapped. The atom temperature is significantly lower than what would be expected from the kinetic and potential energies of atoms as they are transferred from the MOT. This suggests the occurrence of thermalization and evaporative cooling in the magnetic trap.
We have built an apparatus for setting up a double magneto-optical trap (double MOT) which allows more than 10 Rb atoms to be loaded in 15 seconds. This compact system consists mainly of a stainless steel chamber and a homemade glass cell. The two chambers are spatially separated by a small diameter transfer tube for differential pumping. The stainless steel chamber is maintained at a pressure of 10 Torr, enabling fast capturing of background Rb atoms. The optically cooled atomic clouds are pushed by a laser beam towards the glass cell which is in a much higher vacuum. Under this condition, the glass cell provides a rather long life time for holding the atoms. After the atoms are loaded in the temporarily bright MOT, a semi-dark type MOT compression is employed to reach a spatial density of 1×10 atoms/cm. The compressed atom clouds are further cooled by polarization gradient cooling to a temperature of 30 μK. The high phase space density cloud is suitable for experiments related to ultracold atoms.
Abstract The optical tweezer experiment with neutral atoms is widely used for quantum information research. Here, we present a compact dual magneto-optical trap (MOT) setup for a two-species optical tweezer. Rubidium (Rb) atoms are directly captured using a vapor MOT, while potassium (K) atoms are collected via a 2-stage MOT. Both the quadratic and gradient magnetic fields required for the MOT and Zeeman slower are created by permanent magnets. With the help of the Zeeman slower, the K MOT loading efficiency is enhanced by a factor of three. After the MOT stage, we apply D 1 gray molasses to reduce the temperature of the K atoms to 9 μK. Using this apparatus, both Rb and K are loaded into the optical tweezer.