We report theoretical studies of an ef ficient accumulation of 225 Ra atoms in a magneto-optical trap (MOT) from an atomic beam. The number of atoms in the trap is limited due to the large leakage into metastable D states from the cooling transition and the loss mechanism from collisions with the background gases and with other elements in the atomic beam. We propose a setup consisting of an ef ficient Zeeman slower, an optical atomic beam de flector, and an EggMOT, which provides a large capture velocity, e.g. the Zeeman slower capture velocity of 581 ms 1 and the MOT capture velocity of 46 ms 1 . Furthermore, the pure slow atomic beam produced by the optical atomic beam de flector can maximize the number of trapped atoms and their lifetime in a ultra high vacuum chamber by minimizing the collisional loss. Our proposed setup allows for the search for a permanent electric dipole moment based on laser-cooled and trapped radium atoms with improved sensitivity.
Laser cooling and trapping of heavy alkaline-earth element barium have been demonstrated for the first time ever. For any possible cycling transition in barium that could provide strong cooling forces, the excited state has a very large branching probability to metastable states. Additional lasers are thus needed to bring the atoms back in to the cooling cycle. In this work barium atoms were efficiently collected in a magneto-optical trap (MOT) by large optical forces from the strong 6s2 1S0 – 6s6p 1P1 transition. Trapping of barium has been achieved using up to seven lasers simultaneously. The properties of the barium MOT were characterized. The efficiency of capturing an atom from a thermal atomic beam into the MOT is 0.4(1) %. The developed scheme is very efficient for collecting atoms. Loss rate mechanisms from the trap were studied by observing the decay of the trap population. Typical lifetimes of the MOT cloud are on the order of one second and are limited mainly due to insufficient repumping of metastable states. The range of velocities from which barium atoms can be captured into the MOT is about 30 m/s. Different laser transitions were employed for repumping barium atoms from the 6s5d 3D1 and the 6s5d 3D2 states. They lead to similar trap populations and lifetimes. The temperature of the cold atomic barium cloud was determined to about 5 mK. Atomic properties of the 5d2 3F2 state were studied with trapped atoms, in particular it's lifetime was determined as 160(10) s. This work has shown a possible scheme to trap atoms with a leaky cooling cycle. Since atoms with such properties are the majority of the elements in the periodic table, the number of optically trapable elements can be significantly enlarged. Of particular high interest is radium, which is chemical homologue to barium. The interest in radium stems from it's high sensitivity to possible nuclear and electron permanent electric dipole moments (EDM's). An EDM violates parity as well as time reversal and is therefore of fundamental importance. Searches for such EDM's are among the main research goals of the recently commissioned TRImP facility at KVI.
Optical trapping techniques are an efficient way to probe limited quantities of rare isotopes. In order to achieve the highest possible measurement precision, it is critical to optimize the optical trapping efficiency. This work presents the development of a three-dimensional semi-classical Monte Carlo simulation of the optical trapping process and its application to optimizing the optical trapping efficiency of Radium for use in the search of the permanent electric dipole moment of
225Ra. The simulation includes an effusive-oven atomic beam source, transverse cooling and Zeeman slowing of an atomic beam, a three-dimensional magneto-optical trap, and additional processes such as collisions with residual gas molecules. We benchmark the simulation against a well-characterized
88Sr optical trap before applying it to the
225Ra optical trap. The simulation reproduces the relative gains in optical trapping efficiency measured in both the
88Sr and
225Ra optical traps. The measured and simulated values of the overall optical trapping efficiencies for
88Sr are in agreement; however, they differ by a factor of
30 for
225Ra. Studies of several potential imperfections in the apparatus or systematic effects, such as atomic beam source misalignment and laser frequency noise, show only limited effects on the simulated trapping efficiency for
225Ra. We rule out any one systematic effect as the sole cause of the discrepancy between the simulated and measured
225Ra optical trapping efficiencies; but, we do expect that a combination of systematic effects contribute to this discrepancy. The accurate relative gains predicted by the simulation prove that it is useful for testing planned upgrades to the apparatus.
We have demonstrated Zeeman slowing and capture of neutral 225Ra and 226Ra atoms in a magneto-optical trap. The intercombination transition 1S0-->3P1 is the only quasicycling transition in radium and was used for laser-cooling and trapping. Repumping along the 3D1-->1P1 transition extended the lifetime of the trap from milliseconds to seconds. Room-temperature blackbody radiation was demonstrated to provide repumping from the metastable 3P0 level. We measured the isotope shift and hyperfine splittings on the 3D1-->1P1 transition with the laser-cooled atoms, and set a limit on the lifetime of the 3D1 level based on the measured blackbody repumping rate. Laser-cooled and trapped radium is an attractive system for studying fundamental symmetries.
We describe an experimental setup for producing a large cold erbium (Er) sample in a narrow-line magneto-optical trap (MOT) in a simple and efficient way. We implement a pair of angled slowing beams with respect to the Zeeman slower axis, and further slow down atoms exiting from the Zeeman slower. The second-stage slowing beams enable the narrow-line MOT to trap atoms exiting from the Zeeman slower with higher velocity. This scheme is particularly useful when the Zeeman slower is at low optical power without the conventional transverse cooling between an oven and a Zeeman slower, in which case we significantly improve the loading efficiency into the MOT and are able to trap more than
108 atoms in the narrow-line MOT of
166Er. This work highlights our implementation, which greatly simplifies laser cooling and trapping of Er atoms and also should benefit other similar elements.
Laser cooling and trapping of the heavy alkaline-earth-metal element barium has been achieved based on the strong $6{s}^{2}\text{ }{^{1}S}_{0}\text{\ensuremath{-}}6s6p\text{ }{^{1}P}_{1}$ transition. The excited state decays to a large fraction into metastable
D states. Two schemes were implemented where three additional laser-driven transitions provide closed cooling cycles. This results in a fraction of 50(20)% of the trapped atoms in one of the metastable states. A total efficiency of $0.4(1)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2}$ for slowing a thermal atomic beam and capturing atoms into a magneto-optical trap was obtained. Trap lifetimes of more than 1.5 s were observed. They are shortened at high laser intensities by three photon photoionization losses. The developed scheme can be transferred to other systems with large leakage from the cooling transition, such as Ra which is interesting for sensitive fundamental symmetry research.