In an electron tube having coaxial cylindrical electrodes and at least one cylindrical grid of pyrolytic graphite, the grid is joined to the upper portion of a central conducting mast by means of a bell which is also of pyrolytic graphite and fixed on the mast. Slits are cut at uniform intervals around the periphery of the bell in order to form resilient strips which serve to establish an electrical contact between the grid and the conducting mast.
A power amplifier valve with a grid is disclosed having improved reliability of operation and lifetime of the valve. A screen grid of a tetrode has a mesh grid with vertical or oblique rods in pyrolytic graphite. According to the invention, the rods are provided with a greater width at the bottom of the grid near the output of the valve where the high-frequency currents are greatest.
The electronic optical apparatus provided is such that the parts situated in the immediate vicinity of the beam, anode, screen placed inside the condenser block, screen formed from a tube and limiter diaphragms inside the deflection block, screen placed between the final focussing lens and the sample to be observed and the secondary electron collector electrode have their faces exposed to the electron beam formed from pyrolytic graphite.
An electron gun arrangement includes an electron gun having a longitudinal axis and including first and second electrodes longitudinally spaced apart for generating an electron beam in a longitudinal direction. A first support member supports the first electrode and includes a first slot arrangement presenting a first pair of surfaces longitudinally spaced apart. A second support member is longitudinally spaced apart from the first support member for supporting the second electrode and includes a second slot arrangement presenting a second pair of surfaces longitudinally spaced apart. The surface of the first pair of surfaces that is closer to the second support member constitutes a first clamping surface and the surface of the second pair of surfaces that is closer to the first support member constitutes a second clamping surface. Each of a plurality of spacer members made of electrically non-conductive material includes a first portion disposed in the first slot arrangement and abutting the first clamping surface and a second portion disposed in the second slot arrangement and abutting the second clamping surface for maintaining a distance in the longitudinal direction between the first and second clamping surfaces substantially constant and allowing movement between the respective support members in a direction transverse to the longitudinal axis due to differential thermal expansion.
In a controllable high-power electron tube in the form of a tetrode, the anode direct voltage is reduced to less than 10 kV with an anode efficiency of greater than 80%. The tube includes coaxially arranged electrodes including a cylindrical indirectly heated full walled matrix cathode containing BaO, a cylindrical control grid, a cylindrical screen grid and an anode, where the spacing between the control grid and the cathode and the spacing between the control grid and the screen grid is less than 1 mm. Such a tube can be used for achieving AM broadcast transmitters which are distinguished by a compact construction, the overall efficiency remaining largely unchanged.
