an improved klystron device is disclosed which has opposed electrostatic magnetic field generating members which are uniformly spaced along a longitudinal axis to form an electron beam chamber . the es magnetic field generating members produce a magnetic flux which confines an electron beam passing through the chamber when an alternating current is imposed upon the magnetic field generating members . an additional improvement includes a chamber formed from a single sheet of electron conductive metal having a ladder - like structure symmetrical about a longitudinal hinge which permits the structure to be folded about the hinge to form a suitable electron beam chamber .