Fig. 1. (a) The diagrammatic sketch for the potassium isotope separation machine. Atoms are emitted from a heated oven, collimated by the light in the 2D region, and pumped by L₁ and L₂. A curved magnet array deflects atoms with the right magnetic moment, and finally, atoms are imaged by the probe laser L_p. (b) Enlarged view of the 2D region where the particles are collimated. (c) The ⁴⁰K fluorescence we took in the detection area. The top and bottom images were taken by the camera, and the y-axis and z-axis represent the positions of the pixels in the photo. The top one has no light in the 2D region, and the bottom one has 2D transverse cooling.

Fig. 2. (a) The trajectories of particles after exiting the oven. θ represents the divergence angle at which the particle velocity deviates from the main axial direction. (b) The numerical results of ⁴⁰K enhancement versus the laser frequency. The total intensity of the 2D laser is 280 mW/cm² and the oven temperature is 600 K. Square markers result from numerical simulation and the red line is the Gaussian fitting curve. (c) The numerical results of ⁴⁰K enhancement versus the total intensity of the 2D laser. The laser detuning is 5 MHz and the oven temperature is 600 K. Square markers result from numerical simulation and the red line is the fitting curve with the function y = A × I /(I + I_s). (d) The divergence angle of the particle beam leaves the 2D region with (red) and without (blue) transverse cooling. The laser detuning is 5 MHz, the total intensity of the 2D laser is 280 mW/cm², and the oven temperature is 600 K. The green dotted line represents 0.38°, with only particles having a divergence angle less than this value likely to enter the detection region.

Fig. 3. (a) The ⁴⁰K signal versus the laser frequency at different temperatures ranging from 220°C to 300°C with a total intensity of 260 mW/cm². The curve represents the Gaussian fitting. (b) The ⁴⁰K signal versus the laser intensity with detuning of 5 MHz. The curve is the fitting curve with the function y = A × I / (I + I_s).

Fig. 4. (a) The enriched abundance of ⁴⁰K at different temperatures (black triangle) and the gain from 2D transverse cooling (red square). (b) The suppression ratios for both ³⁹K and ⁴¹K.