Patent GB-1189628-A (GB)
Title: Travelling Wave-Tubes.
Inventor: PUTZ JOHN LEWIS
IPC: H01J23/50
Filed: 1968-07-25
Abstract: 1,189,628. Travelling-wave tubes; attenuation equalizers. VARIAN ASSOCIATES. 25 July, 1968, No. 35580/68. Headings H1D and H1W. In a discharge tube, e.g. a travelling wave tube, in which an electron beam interacts with a slow-wave structure, the means for coupling one end of the slow-wave structure to an external circuit defines a space within which is disposed an attenuator formed by a dielectric body supporting an elongate conductor, whereby, by choice of the resonance frequency of the elongate conductor, it may be arranged that the variation of attenuation corresponds to the variation of gain of the tube, such that a flat gain-frequency characteristic of the tube is obtained. As shown, the helical slow-wave structure 16 is coupled to the rectangular output waveguide 17 by a coaxial coupling 19, attenuation being provided by two probes 30 and 31 which are both transversely off-set from the waveguide axis, as shown, and also axially displaced from one another (Fig. 1, not shown). Each probe is a quartz tube bearing a conductive stripe 34 in the form of a helix with an axially extending end portion. The resonant frequency of the stripe is primarily determined by its length and by the spacing of the turns of the helix; the bandwidth by the stripe conductivity; and the coupling to the electromagnetic wave by the projection into the guide of the linear end portion of the stripe, which extends parallel to the electric field of the dominant waveguide mode, and the projection of which into the guide is adjustable by screws 36. The conductive stripe, which may in alternative arrangements be borne by a dielectric rod, or by the interior surface of the quartz tube, may be a film of silver, platinum alloy, or carbon. In an alternative embodiment a single dielectric tube is used, bearing two conductive strips wound as a bifilar helix (Fig. 5, not shown). 1,189,636. Refining photo-sensitive particles. XEROX CORP. 24 Oct., 1967 [27 Oct., 1966], No. 48212/67. Heading H1K. [Also in Divisions C4, C7 and G2] Electrically photo-sensitive particles for use in the photo-electrophoretic process of Specification 1,124,625 are refined by simultaneously exposing to coloured light and subjecting to an electric field a suspension of the particles in an insulating liquid so that particles not sensitive to the coloured light and particles sensitive thereto are separated, and the particles not having the required specific sensitivity or lack of sensitivity are discarded. A dispersion in an insulating liquid of red-sensitive cyan particles may be coated on a conductive transparent electrode in the form of a drum 20, contacted with an electrode drum 21 having an insulating paper surface 25 and simultaneously exposed to blue and/or green light so that particles sensitive thereto are transferred to surface 25 and discarded, remoistened with a spray 35, contacted with a drum 22 similar to drum 21 and simultaneously exposed to red light so that the particles attracted thereto are transferred to drum 22 and collected for use, the particles not transferred being discarded. Magenta and yellow particles sensitive to green and blue light respectively may be refined similarly. In an alternative refining apparatus, the conductive transparent electrode is in the form of a plate. The examples describe the refining of metal-free phthalocyanine, 1-(4<SP>1</SP>- methyl - 5<SP>1</SP> - chloroazobenzene - 2<SP>1</SP> - sulphonic acid) - 2 - hydroxy - 3 - naphthoic acid, and N - 2<SP>11</SP> - pyridyl - 8,13 - dioxodinaphtho - (1,2 - 2<SP>1</SP>,3<SP>1</SP>) - furan - 6 - carboxamide.