Abstract:
A photomultiplier tube includes a photocathode and a primary dynode having input and output apertures. A field isolating mesh is positioned at the input aperture of the primary dynode to facilitate the collection of electrons from the photocathode of the photomultiplier to the primary dynode while simultaneously electrostatically shielding secondary emission electrons from the field of the photocathode. The field isolating mesh has a central opening that is dimensioned to maximize the throughput of photoelectrons from the photocathode to the primary dynode while providing effective field isolation in the vicinity of the primary dynode. The central opening in the field isolation mesh provides the further advantage of permitting uniform deposition of photo-emissive materials on the surface of the dynode during manufacture. In an alternative embodiment, the field isolating mesh of the primary dynode is formed in two segments. The first segment is disposed in the input aperture of the primary dynode and the second segment is disposed in offset, spaced parallel relation to the first segment. The photomultiplier according to the disclosed invention provides a significant improvement in electron collection efficiency, pulse height resolution, and magnetic sensitivity compared to known photomultiplier tubes of otherwise similar construction.
Abstract:
This invention relates to a photomultiplier tube including: a photocathode PK with a semi-transparent photo-sensitive layer provided to emit an electron flux towards the inside of the tube, focusing optics comprising a first dynode D1, concave on the side of the photocathode PK, and several Rajkman dynodes D3, . . . , D8 located on each side of a plane called the dynodes plane DP. According to the invention, the focusing optics also includes a second dynode D2 concave on the side of the re-emitting surface of the first dynode D1, the angle between the plane of the dynodes DP and the center line of the tube exceeding 45°, the concave side of the first Rajkman dynode D3 facing the re-emitting surface of the second dynode D2.