Experimental Study On Zeeman Slower And Magneto-optical Trap Capture Of Cesium Atom

Over the past 30 years,many remarkable achievements have been made in the basic and applied research of laser cooling technology,both in some basic physical research,such as the basic properties of Bose-einstein condensation(BEC),and in practical applications,such as atomic clocks and interferometers.In recent years,many important breakthroughs have been made in laser cooling of alkali metal cesium atoms,because cesium atom has precise microwave transition frequency,it has important applications in frequency scale,metrology and high-precision positioning.Moreover,cesium atoms have very complex collision characteristics and abundant Feshbach resonance,which are widely used in the studies of ultracoled collisions,three-body Effimov physics and quantum multibody physics.The most basic of these applications is to capture enough cesium atom samples in MOT.In this paper,a differential two-stage vacuum device is used to reduce the velocity of cesium atoms ejected from a high temperature source to a high vacuum MOT chamber by zeeman slower,at the same time the temperature of cesium atom samples in the MOT is reduced by laser cooling technology.It provided enough samples of cold atoms for subsequent Raman sideband cooling and evaporative cooling and laid the foundation for the realization of a BEC of cesium atoms.Main work of this paper is to design a two-stage vacuum device with zeeman slower to cool and capture enough samples of cesium atoms with a magneto-optical trap and reduce the temperature to about a few dozen microkelvin,and then to reduce the temperature of the cesium atoms to 5.5?k with optical molasses cooling technology.It is beneficial to the realization of Raman sideband cooling and evaporative cooling.Mainly summarized as the following three parts:1.Design the experimental vacuum system and calculate the system each part of the vacuum degree.The difference of pressure between thevacuum at the source and the vacuum in the MOT chamber was maintained at1~2 orders of magnitude by using zeeman slower.In addition,a cooling device with TEC temperature control is designed to cool the stainless steel tube connected to the cesium source oven,so that most of the heated cesium atoms condense into the inner wall of the stainless steel vacuum tube,maintaining the vacuum at the source at 10-8 Pa,even up to 10-9 Pa.2.The relation curve between the magnitude of zeeman slower magnetic field and its position is calculated and measured theoretically.The best deceleration effect is obtained by optimizing the parameters of the zeeman slower and the slower laser,and the velocity of the cesium atom after passing through the zeeman slower is calculated.3.The MOT is used to cool and capture the low-speed cesium atoms passing through the zeeman slower.The effects of experimental parameters such as laser intensity and frequency detuning of trap laser and repump laser on MOT loading rate were studied.A large number of ultracold cesium atom samples were captured by MOT in ultra-high vacuum chamber by optimizing relevant parameters.Then the atoms were cooled by optical molasses and the sample was cooled below the doppler limit by largely detuned cooling laser,and the temperature of the sample was measured by time of flight at 5.5 ?k.