Optimal Design Of The Zeeman Slower Based On Permanent Magnets

As an efficient slower,the Zeeman slower is an important part of atomic physics experiments,such as cold atomic optical lattice clocks and quantum degenerate gases,which require continuous,high-flux and low-speed atomic beams.Nowadays,optical lattice clocks are developing toward the miniaturization,which requires the experimental apparatus with low-power consumption,small size,and light weight.The traditional Zeeman slower based on the current-carrying coils suffering from high-power consumption and a complicated water-cooling system,limits the progress towards the miniaturization of optical lattice clocks.Therefore,the permanent magnetic Zeeman slower with no electric power has become a research hotspot recently.To realize a miniaturized Zeeman slower applying to ytterbium optical clocks,permanent magnetic Zeeman slowers are designed and optimized in this thesis.Firstly,this thesis introduces the principle of Zeeman slower and the experimental process of atomic laser cooling,and the discussion about trapping conditions of the blue magneto-optical trap(MOT)follows.Secondly,the experimental parameters of the Zeeman slower with permanent magnets are calculated and analyzed.In order to obtain a stable atomic deceleration process and a small-size Zeeman slower,the effective coefficient?and the saturation parameters s₀ need to be set as 0.75 and 2,combined with the?^-light.Under the above parameters,the Zeeman slower based on permanent magnets with a capture speed of 220 m/s and a length of 10 cm,10%of the total atoms could be cooling below 10 m/s,which can satisfy the experiment demand of ytterbium optical clocks.Thirdly,this thesis proposes three types of miniaturized permanent magnetic Zeeman slower models for ytterbium atoms,including transverse-field,longitudinal-field and ring-shaped structure.Furthermore,the structural parameters of the transverse-field and longitudinal-filed Zeeman slower are optimized and the reliable design schemes of these two types of Zeeman slower are given.These design schemes could realize the 2-D adjustment of the Zeeman magnetic field by changing the radial and axial positions of the magnets.Finally,this thesis has developed a miniaturized transverse-field Zeeman slower with a size of110 mm×100 mm×30 mm,and a miniaturized longitudinal-field Zeeman slower with a size of 120 mm×130 mm×130 mm,respectively.These two apparatus utilizes the principle of spiral amplification so that the radial adjustment accuracy of the permanent magnets can reach0.01 mm.Meanwhile the adjustment accuracy of the axial position is 0.1 mm.During the preliminary magnetic field measurement,the result slightly deviates from the theoretical expectation that is limited to the assembly and machining errors and the performance difference of the permanent magnets.However,after finely optimizing and adjusting the axial and radial positions of the permanent magnets,the distributions of the magnetic field generated by these two apparatus based on permanent magnets are consistent with the theoretical expectation,which fully reflects the high degree of adjustability and fault tolerance of this design.In the magneto-optical trap cooling experiment,the Zeeman magnetic field distribution could be optimized according to the fluorescence signal of atoms,so that more atoms are loaded into the magneto-optical trap.In this thesis,the optimal design of the miniaturization of the Zeeman slower based on permanent magnets would lay the foundation for the development of portable optical clocks and space-borne clocks.