The Realization Of²³Na-⁴⁰K Degenerative Experiment Device,the Magnetic Transfer Technology And The Bec Of²³Na Atom

Bose-Einstein Condensation (BEC) is a kind of unique quantum mechanical transition process and a new state of matter. The realization of BEC is an important milestone in the study of cold atom. The implementation of BEC can not only improve the measurement accuracy of physical constants. But also it is the key technology of the frontier such as quantum information storage, optical information transmission, quantum logic operation and microstructure etching. While the BEC of23Na atom has not yet achieved in our country, this paper mainly focuses on the study of the realization of the BEC of23Na. The specific work and achievements are as follows:First of all, in order to avoid the heat effect caused by the collision between the impurity atoms in the background and the cold atoms, at the same time, in order to cut off the relatively high temperature environment outside, the cold atom experiment must be carried out in a vacuum environment. And it has different vacuum degree requirements in different experimental stage. The laser cooling requires vacuum degree of the level of10-7Pa, while the evaporation cooling requires higher vacuum degree, which is the level of10-9Pa. However the higher vacuum degree needs the more difficulties and the higher cost. We design and build the ultra-high vacuum experimental system with double cavity structure. We use the difference to maintain pressure difference. At the same time, double cavity structure can optimize the optical channel.Secondly, because of the use of the double cavity structure, it needs transfer the atoms between the two cavities. In order to avoid the adverse effects such as the loss of a large number of atoms, the heating of the cold atoms and the change of the size of the atom cloud in the transfer process, we use the technology of the atom magnetic field transfer. Finally, we successfully achieve the high efficiency of the cold atoms with the rational design of the parameters such as the structure and turns of the coil and the magnetic field gradient. Finally, through the following three steps:(1) we use the Zeeman slower to pre-reduce. The atoms reduce to the speed of30m/s.(2) we use laser cooling including Doppler cooling and Polarization gradient cooling in the magneto-optical trap (MOT).The cold atom cloud is cooled to the level of200μK.(3) we use the RF evaporative cooling in the scientific cavity (Science cavity) and the cold atom cloud cooled to the level of20μK. Then we use the evaporation cooling in the optical trap (Science cavity) and the cold atom cloud reaches the quantum phase transition temperature. At last, we got the BEC of the23Na.