A cooling system for a cold-atom sensor, this system includes a two-dimensional cooling chamber, called the 2D chamber (Ch2D), kept under ultra-high vacuum and placed at least partially inside an integrating cylinder (IC) having a Z-axis, the integrating cylinder being configured to illuminate the 2D chamber with a first isotropic light (IL1), the 2D chamber comprising atoms to be cooled, a three-dimensional cooling chamber, called the 3D chamber (Ch3D), kept under ultra-high vacuum and joined to the 2D chamber by an aperture (Op) configured to allow the atoms to pass from the 2D chamber to the 3D chamber via movement substantially along the Z-axis, the 3D chamber being placed at least partially inside an integrating sphere (IS), the integrating sphere being configured to illuminate the 3D chamber with a second isotropic light (IL2).