Electron multipliers having tapered channels

Claim 1

A channel plate electron multiplier, comprising a thin plate having two major faces and a plurality of closely spaced substantially identical channels interconnecting said two major faces, the axes of said channels being parallel to each other and a major part of each of said channels having a cross-section which is gradually tapered from an input aperture of one cross-section to an exit aperture of smaller cross-section, the ratio of the cross-sectional area of said input aperture to the cross-sectional area of said exit aperture being no less than five, the ratio between the axial distance spacing said input aperture from said exit aperture to the smallest linear dimension of said input aperture being no greater than three, the surfaces of said channels being resistive and secondary emissive at leas over said gradually tapered major part, and an electrostatic field controlling conductive structure adjacent to and extending across said input aperture for flattening any fringing electrostatic field generated within said channels to the extent that substantially all equipotential surfaces within said channels intersect with the surfaces of said tapered major part at an angle not less than fifty degrees nor greater than seventy-five degrees, in order that a major portion of secondary emitted electrons are thereby attracted back toward and collide with the secondary emissive surface of said tapered major part at a point closer to said exit aperture without crossing to and colliding with the opposite side of said tapered major part.