A lead shielding for a betatron in an X-ray generator is provided that includes at least four shielding parts of which two are semi-cylindrical and provided with recesses in the envelope surfaces thereof. The semi-cylindrical shielding parts are arranged in corresponding recesses of the remaining shielding parts by means of the envelope surfaces thereof, such that the recesses in the envelope surfaces form air channels between the semi-cylindrical shielding parts and the remaining shielding parts.