GB516785A - Improvements in or relating to electron multipliers - Google Patents

Abstract

516,785. Electron multipliers. BAIRD TELEVISION, Ltd. (Fernseh Akt.-Ges.). July 7, 1938, No. 20162. [Class 39 (i)] An electron multiplier comprises an electron permeable secondary emitting electrode, means for causing an electron stream to strike the electrode, and for controlling it immediately after it has passed the electrode, and an output electrode for collecting the controlled electron stream, the controlling means being so disposed in relation to the secondary emitting electrode, that electrons emitted from the latter must deviate from the previous general direction of the stream in order to pass through the controlling means to the output electrode. The electron beam from a thermionic or photoelectric cathode 2 is multiplied at the electrodes 3. The low-velocity electrons emitted by the last electrode 3<1> are diverted by the field of electrodes 4, 5, 7 to the control electrode 4; the fast electrons which have passed through the electrode 3<1> continue to a collecting electrode 6, which may be cup-shaped, or coated with carbon, or screened bv other electrodes, so that no secondary electrons escape from it. The electrode 4, which may be carbon or chromic oxide coated to prevent secondary emission, modulates the beam before it passes to the permeable secondary electron emitting electrodes 5, and output electrode 6. The electrode 6 and say, one of the electrodes 5 may be connected. The first electrode 5 may be set at angle of 45‹ and be impermeable, so that the beam then travels parallel to its original direction and strikes the further electrodes 5, 7, which are set parallel to the electrodes 3. A second controlling electrode may be placed before the electrodes 3. When the cathode is photo-electric and the device is used for television, the electrode 4 may be used to impose the carrier frequency, and the second modulating electrode may impress synchronizing impulse on the signal.