An X-ray window includes a primary and a secondary window element. In order to evaporate debris by ohmic heating, current flows through the secondary (upstream) window element. Meanwhile, electric charge originating from electron irradiation and/or depositing charged particles is to be drained off the secondary window element via a charge-drain layer. To prevent large debris particles from short-circuiting the secondary window element, the current for heating the window element flows through heating circuitry which is electrically insulated from the charge-drain layer.