ObjectiveIn strontium atomic optical clock experiments, hot atoms emitted from the Sr oven need to undergo precooling by a Zeeman decelerator and a transverse cooling device, which often results in a larger size for the optical clock system. To reduce the size of the optical clock system, we have integrated the Zeeman decelerator and transverse cooling device on the basis of ensuring the precooling effect.MethodsPreviously, we utilized 40 small magnets to design a permanent magnet array Zeeman decelerator with an overall length of 95 mm. By mounting three reflecting mirrors on the frame of the Zeeman decelerator, beam of 461 nm laser can create two pairs of mutually perpendicular transverse cooling beams across the cross-section of the decelerator, thereby achieving the integration of transverse cooling and the Zeeman decelerator. Furthermore, it was observed that at the axial magnetic field null point of the Zeeman decelerator, there exists a radial gradient magnetic field of approximately 27 G/cm. By installing reflecting mirrors at this location, a transverse cooling device based on a two-dimensional magneto-optical trap (2D MOT) can be constructed.Results and DiscussionsTo ensure the performance of the Zeeman deceleration, we simulated the motion of atoms within the Zeeman decelerator, calculated the proportion of low-speed atoms below 50 m/s, and compared it with experimental results. According to the simulation, transverse cooling can increase the proportion of low-speed atoms by a factor of 2.56. In the experiment, for hot atoms ejected from a Sr oven at 410 °C, the proportion of low-speed atoms was 0.5%. After the Zeeman deceleration process without transverse cooling, the proportion of low-speed atoms increased to 2.4%. Furthermore, after undergoing both Zeeman deceleration and transverse cooling processes, the proportion of low-speed atoms was further increased to 4.8%. This demonstrates that the 2D MOT-style transverse cooling device integrated within the decelerator can significantly enhance the effect of Zeeman deceleration.ConclusionsSince the transverse cooling device does not occupy separate space, we have reduced the size of the cold atomic beam source for strontium to 40 cm. Additionally, during the 560 ms loading period, the first cooling stage captured 8.0×10⁵⁸⁷Sr atoms. The design that integrates a 2D MOT-style transverse cooling device into the Zeeman decelerator is of significant importance for the realization of high-performance, compact strontium atomic optical clocks.