Electron multiplier and method of manufacturing dynodes

Claim 1

IN A PHOTOSENSITIVE PICKUP TUBE COMPRISING A FLAT TARGET ADAPTED TO OPERATE AT A RELATIVELY LOW VOLTAGE WITH RESPECT TO GROUND, A HEAT RADIATING ELECTRON GUN FOR DIRECTING ELECTRONS TO ONE FACE OF SAID TARGET, A PORTION OF SAID ELECTRONS RETURNING TOWARDS SAID GUN, AN ELECTRON MULTIPLIER HAVING A FIRST DYNODE ADJACENT TO SAID ELECTRON GUN AND IN THE PATH OF SAID RETURNING ELECTRONS, SAID MULTIPLIER BEING ADAPTED TO OPERATE AT A RELATIVELY HIGH VOLTAGE WITH RESPECT TO GROUND, WHEREBY SAID RETURNING ELECTRONS DIRECTLY IMPINGE ON A SURFACE OF SAID FIRST DYNODE WITH APPRECIABLE VELOCITY AND ARE DEFLECTED TO AN ADJACENT DYNODE, THE IMPROVEMENT CHARACTERIZED IN THAT: (A) SAID FIRST DYNODE COMPRISES A COMPOSITE STRUCTURE CONSISTING OF A BASE METAL SELECTED FROM THE GROUP CONSISTING OF SILVER, INDIUM AND NICKEL, A LAYER OF CHROMIUM ON SAID BASE METAL HAVING A THICKNESS OF FROM ABOUT 100 ANGSTROM UNITS TO ABOUT 200 ANGSTROM UNITS, AND A LAYER OF MAGNESIUM OXIDE ON SAID LAYER OF CHROMIUM, SAID MAGNESIUM OXIDE LAYER BEING DIRECTLY EXPOSED TO SAID RETURNING ELECTRONS, (B) SAID MAGNESIUM OXIDE LAYER HAVING A THICKNESS RELATED TO THE VOLTAGE DIFFERENCE BETWEEN SAID TARGET AND SAID MULTIPLIER WITHIN THE RANGE OF FROM 300 VOLTS TO 600 VOLTS, SAID THICKNESS OF SAID MAGNESIUM OXIDE LAYER BEING ABOUT 75 ANGSTROM UNITS WHEN SAID VOLTAGE DIFFERENCE IS ABOUT 300 VOLTS AND INCREASING SUBSTANTIALLY LINEARLY WITH INCREASE IN VOLTAGE TO A VALUE OF ABOUT 150 ANGSTROM UNITS WHEN SAID VOLTAGE DIFFERENCE IS ABOUT 600 VOLTS, (C) WHEREBY SAID FIRST DYNODE IS CHARACTERIZED BY OPTIMUM GAIN AND IS FREE FROM ADVERSE EFFECTS FROM THE HEAT OF SAID ELECTRON GUN.

Claim 3

THE METHOD OF MANUFACTURING A DYNODE ELECTRODE FOR USE IN AN ELECTRON TUBE HAVING A PHOTOCATHODE INCLUDING CESIUM, COMPRISING THE STEPS OF DEPOSITING IN A VACUUM A LAYER OF MATERIAL ON A SUBSTRATE BY EVAPORATION, DEPOSITIONG MAGNESIUM ONLY, ON SAID LAYER BY EVAPORATION WHILE MAINTAINING SAID VACUUM, OXIDIZING SAID MAGNESIUM, AND HYDROGEN FIRING SAID DYNODE FOR ELIMINATING CESIUM ATTRACTING CONTAMINANTS FROM SAID DYNODE.

Claim 4

THE METHOD OF MANUFACTURING A DYNODE ELECTRODE FOR USE IN AN ELECTRON TUBE HAVING A PHOTOCATHODE INCLUDING CESIUM, COMPRISING THE STEPS OF DEPOSITING IN A VACUUM A LAYER OF MATERIAL ON A SUBSTRATE BY EVAPORATION, DEPOSITIONG MAGNESIUM ONLY, ON SAID LAYER BY EVAPORATION WHILE MAINTAINING SAID VACUUM, OXIDIZING SAID MAGNESIUM, AND HYDROGEN FIRING SAID DYNODE FOR ELIMINATING CESIUM ATTRACTING CONTAMINANTS FROM SAID DYNODE.