Fig. 1. Layout of symmetrical snake device

Fig. 2. Flow chart of snake device design by particle swarm optimization

Fig. 3. Change of particle swarm distribution with the progress of algorithm iteration

Fig. 4. Change of fitness with the number of iterations

Fig. 5. Comparison of the betatron functions in the snake device when the solenoid is turned on and turned off

Fig. 6. Distribution of the components of the stable spin direction (n axis) along the ring

Fig. 7. Comparison of spin transparency characteristics of ±I snake and ±L snake devices

Fig. 8. Comparison of dynamic aperture when snake is turned on and off