GB148184A - Improvements in electric discharge tubes - Google Patents

Abstract

148,184. Kossel, W. March 1, 1917, [Convention date]. Vacuum tubes; R÷ntgen-ray tubes. - In discharge apparatus, such as an amplifier or Rontgen-ray tube, the emission of electrons from an auxiliary cathode is produced bv the impact thereon of canal rays set up by the discharge in the tube between an anode and the main cathode, and the electrons are controlled by an electrostatic or electro-magnetic field. As shown in Fig. 7, the positive ions produced by the discharge between the anode A and the main cathode AK pass through the cathode as canal rays and impinge on the auxiliary cathode C, the discharge of electrons from which is controlled bv the difference of potential between the cathodes C, AK supplied by a battery B and a transformer I in the circuit containing current to be amplified &c. A telephone receiver T is coupled through a transformer II with the anode circuit. The auxiliary cathode C may be mounted behind, and insulated from an axial extension of the cathode AK, in which the canal rays are concentrated, or, as shown in Fig. 2, it may be mounted in a part AK<1> of larger diameter, which is screened from the canal rays by the axial extension D, the part AK<1> serving to set up a controlling electric field. The cathode C is preferably of material electropositive to the material of the cathode AK. In the arrangement shown in Fig. 3, which may be used in a tube containing gas at a pressure of a tenth of a millimetre of mercury, the positive ions are concentrated by means of a magnetic field. For this purpose the main cathode AK consists of two hollow cylinders of soft-iron forming the poles of a permanent magnet mounted inside or outside the tube, the cylinders being separated by a circular gap S surrounded by an annular anode A. The electron-emitting cathode C is in the form of a cylindrical rod preferably insulated from the cylinders. An electric field is produced between the cathodes AK, C. The parts X of the cylinders adjoining the gap may be of non-magnetic material and may be extended inwards as shown to concentrate the electrode field towards the cathode C. Two additional cathodes, protected from the canal rays, may be mounted around the cathode C and inside the cathodes AK. The electro-magnetic controlling field may be produced by a winding around the tube. The field of the magnet may be controlled by means of an adjustable shunt. According to the Specification as open to inspection under Sect. 91 (3) (a), the cathode C may be of the incandescent type, and the cathode AK, Fig. 7, has a number of perforations. This subject-matter does not appear in the Specification as accepted.