GB527209A - Braun tube arrangement - Google Patents

Abstract

527,209. Cathode-ray tubes. RADIOAKT-GES. D. S. LOEWE. April 4, 1939, No. 10463. Convention date, April 5, 1938. [Class 39 (i)] In apparatus of the kind in which the electron stream from a cathode 6 of large area is focused at a first cross-over point in the aperture of a diaphragm 1 and means are provided for electron-optically reproducing the aperture on a luminescent screen 5, a diaphragm 8 having an aperture greater than that of the diaphragm 1 is mounted near the latter on the cathode side and is electrically connected therewith preferably by means of a metal ring having a larger diameter than both the apertures. The diaphragm 1 consists of a thick metal disc with a conical recess and the aperture is made in a thin sheet of platinum welded to the rear of the disc. The main lens consists of a tube 2, which has a lower potential than the diaphragm, and a tube 3 at the potential of the anode 4 and preferably integral therewith. The diameter of the tube 3 is approximately half that of the tube 2 and extends for about half its length therein. A diaphragm 14 is mounted in the tube 2 and has an aperture such that the cone determined by it amounts to 80-90 per cent. of that determined by the tube 3. The diaphragm is positioned so as not to interfere with the lens field and the screen effect is increased the further it is spaced from the diaphragm 1. Preferably smoothing elements consisting of a high resistance 10 and small condenser are connected in the leads to the tube 2, and a transformer 12 may be provided for superposing alternating potentials on the constant potential of the electrode. The preconcentrating system comprises an electrode 7, the aperture of which is somewhat larger than the cross-section of the beam traversing it ; and the control electrode 15 is in the form of a mesh grid supported in a diaphragm the aperture of which is equal to or only slightly larger than the emitting surface of the cathode. In a modification, Fig. 2 (not shown) the diaphragm 8 is replaced by an apertured diaphragm which is raised to a potential which is positive by a few hundred volts relative to the diaphragm 1. This diaphragm has an aperture of approximately 1 mm. diameter and it is spaced from the diaphragm 1 approximately the same distance.