Penetration of the Field of a Bunched Beam through a Ceramic Vacuum Chamber with Metallic Coating

The penetration of the electro-magnetic field of a bunched beam through a ceramic vacuum chamber with a metallic coating on the inside is investigated. It is shown that the field will only penetrate the chamber if the thickness of the metallic coating is small as compared to the square of the skin depth in the metal, divided by the thickness of the ceramics. If, in addition, the chamber is surrounded by ferrite, as used in beam monitors, the field penetration is further reduced. The field outside of the chamber and the power losses in the metallic layer are calculated. It turns out that these losses can be larger by orders of magnitude than the, losses in a pure metallic vacuum chamber.