1. A radiation generating apparatus comprising:
a radiation tube having a cathode for emitting an electron and an anode for generating radiation by impingement thereon of
the electron emitted from said cathode;
a housing container filled with an insulating liquid, and containing said radiation tube; and
a mechanism in which a voltage for allowing the insulating liquid to flow is applied between said cathode and said anode in
a state where said cathode does not emit any electron.