Abstract: An end portion (14a) of a center conductor (14) of a coaxial cable (16) protrudes transversely into a tubular waveguide (10) near an end thereof. A piston (22) having a stepped inner wall (24) closes the end of the waveguide (10). The inner wall (24) is formed with two or more steps (24a,24b,24c) which protrude axially into the waveguide (10) by different distances (L1,L2,L3), reducing the return loss and extending the bandwidth of the coaxial cable-to-waveguide transition.

Abstract: A traveling-wave tube (10) has a confined-flow periodic permanent magnet focusing arrangement (26) in which either the first magnet (60f) or the third magnet (60t) from the electron gun (12) has an extent or axial thickness along the electron stream path which is one-half that of the remaining magnets in the arrangement, thereby providing a scalar magnetic potential of essentially zero on the electron gun pole piece (46), thereby eliminating the field reversal at the cathode (14). This enables a magnetic field to be provided in the region of the electron gun between the gun pole piece (46) and a location behind the cathode due solely to the magnetic field leaking through the gun pole piece aperture (50). The axial magnetic field within the electron gun (12) may be tailored or fine tuned, by varying the size of the aperture (50) in the gun pole piece (46).

Abstract: Ion pump (10) has feedthrough (33) for electrical connection to anode post (32) within the pumping chamber. Opening (36) in the pumping chamber wall receives a portion of insulator (42). The insulator (42) has a flange (48) which is of larger diameter than the opening (36) so that sputtered cathode material cannot directly disposit on the outer and upper surfaces of the flange (48).

Abstract: An improved pole piece structure for periodic-permanent-magnet focused traveling wave tubes is disclosed. In one embodiment, the pole pieces have two fold symmetry and the magnets are arranged about the tube axis in a pattern with two-fold symmetry. This structure accommodates the input or output waveguides while maintaining the symmetry of the magnet placement. This allows the electron beam to remain centered on the tube axis and, therefore, minimizes beam interception. Circuit heating is reduced and the power handling margin of the tube is increased in comparison to conventional TWT structures. In another embodiment, a triangular pole piece configuration is employed, eliminating displacement of the magnets at the coupler and sever cavities and providing a third cooling channel.

Abstract: Seal (40) between travelling-wave tube electrodes (32 and 34) includes an inner hermetic seal ring (50) for providing vacuum sealing and an outer ring (52) which shares the mechanical stresses due to changes in temperature.

Abstract: A dual-mode electron gun for a traveling-wave tube is disclosed which selectively generates an electron beam of two different cross-sectional areas. The electron gun includes radially inner and annular control grids as well as a shadow grid disposed between the cathode and the control grids along the electron beam path. The shadow grid is provided with a suppressor ring which precludes electron emission from an annular portion of the cathode immediately radially outwardly of the cathode region over which the inner control grid projects, thereby eliminating generation of a spurious beam portion radially outwardly from the desired smaller cross-section beam.

Abstract: A cathode/grid assembly for effecting a dual power mode electron gun for use with a traveling wave tube. The conventional "shadow grid" is both electrically and mechanically isolated from the cathode. A variable voltage source is connected to the shadow grid to bias it slightly above or slightly below the cathode potential, depending on the power mode. The electron emitting surface area of the cathode is the same in both modes. By changing the bias on the shadow grid, the transverse beam temperature may be increased to compensate for the reduced space charge density of the low power mode. Thus, the diameter of the low power beam is substantially the same as the diameter of the high power beam. This ensures good beam transmission and high electron beam rf interaction in the low power mode.

Abstract: Electron beam microfabrication apparatus has spherically concave photocathode pattern 40 which when excited produces patterned electron beam 48 which is accelerated by electrode 44 and magnetically focused by magnet 58 to impinge as a demagnified patterned field 60 on a photoresist carrying semiconductor wafer 36 mounted of wafer holder 34.

Abstract: Radial electron flow in an elongated electron gun is achieved from a unipotential, planar cathode by locating the cathode with respect to the gun axis and with respect to a cylindrical divergent anode lens so that the lens focal line lies on the gun axis. The effect of the accelerating field on the distortion of the radial flow is reduced by employing a deep anode grid to reduce the penetration of the accelerating field into the anode drift region.