PURPOSE: To reduce welding positions and reduce work processes by providing a reinforcing member inside the tube of an input window to prevent the deformation of the input window.
CONSTITUTION: An input window 3 is hermetically connected to the opening end of a bottomed cylindrical vacuum envelope 1, a reinforcing member 8 is provided inside this connection portion. This reinforcing member 8 is provided to prevent the deformation of the input window 3, it is circularly provided along inner faces of both the vacuum envelope 1 and the input window 3, its cross section is formed in a nearly triangular shape. In this case, the reinforcing member 8 is not hermetically connected to the input window 3. since a vacuum airtight connection section is provided at one position, the productivity such as the confirmation of the vacuum airtightness by the surface oxidation processing, welding process, and blowholes of the welding section is improved.
KUBO HIROSHI
SANO SATORU
