Abstract: The purpose of the off-axis electron gun is to generate a beam of electrons and to deflect the beam onto the axis of a device which utilizes the beam. The off-axis electron gun includes an arcuate wire electron emitting source subtending an azimuthal angle of up to 125.degree., a non-intercepting azimuthally asymmetric focussing and deflecting electrode located at and around the electron source, and an anode plate with a beam exit hole. The non-intercepting electrode has an arcuate slot subtending a predetermined angle at a predetermined radius from the beam axis in which the arcuate wire electron source is mounted in electrical isolation from the electrode. The deflecting section of the electrode is azimuthally asymmetric in shape such that when selected voltages are applied between the wire source, the focussing and deflecting sections of the non-intercepting electrode and the anode, an electric field is produced which directs the electrons towards the axis, focusses the beam and deflects it onto the axis.

Abstract: The beam deflection system includes two dipole magnets for deflecting a charged particle beam in a deflection plane. The first magnet bends the beam in a path having a radius .rho..sub.1 and a deflection angle .theta..sub.1 greater than 180.degree.. The first magnet has an effective exit edge at an angle (90.degree.-.eta..sub.1) with respect to the beam path. The second magnet further bends the beam in a path having a radius .rho..sub.2 and a deflection angle .theta..sub.2 where 225.degree..ltoreq.(.theta..sub.1 +.theta..sub.2).ltoreq.280.degree.. The effective entry edge of the second magnet is at an angle of (90.degree.-.eta..sub.2) to the beam path. In the usual practical case the effective interior edges of the two magnets are roughly parallel, that is, .eta..sub.1 .perspectiveto.-.eta..sub.2 and the doubly achromatic properties are obtained to first order when the angles satisfy the following formula:.eta..sub.1 .apprxeq.-.eta..sub.22.eta..sub.2 .apprxeq..theta..sub.2 -(.theta..sub.1 -180.degree.

Abstract: A two reference cavity structure for tracking the frequency of a high power liquid cooled cavity structure, consisting of two low power cavities tuned to frequencies slightly above and slightly below the resonant frequency of the high power structure. Each of the cavities has a first and a second section, with the first sections maintained at a first temperature and the second sections maintained at a second temperature such that the reference cavities track the frequency shifts in the high power structure caused by temperature differentials between regions of that high power structure. The first section of each reference cavity may have a cylindrical outer wall and a first end wall whose temperature is governed by the temperature of the liquid coolant before it enters the high power structure.