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Semi-Transparent Cathode PMT having Enhanced Sensitivity

IP.com Disclosure Number: IPCOM000044774D
Original Publication Date: 1984-Aug-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Wallace, SE: AUTHOR [+2]

Abstract

This article describes semi-transparent cathode photomultiplier tubes (PMTs) which achieve enhanced sensitivity without using external optics. The internal or inner surface of the end window, which serves as a support for a layer of semi-transparent photocathode material, is not flat but rather consists of an array of pyramids or cones or pointed rods. The surface geometry enhances the sensitivity of the PMT due to increased light absorption by the photocathode material and to an antenna effect.

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Semi-Transparent Cathode PMT having Enhanced Sensitivity

This article describes semi-transparent cathode photomultiplier tubes (PMTs) which achieve enhanced sensitivity without using external optics. The internal or inner surface of the end window, which serves as a support for a layer of semi- transparent photocathode material, is not flat but rather consists of an array of pyramids or cones or pointed rods. The surface geometry enhances the sensitivity of the PMT due to increased light absorption by the photocathode material and to an antenna effect.

Referring to Fig. 1, a photomultiplier tube 10 includes an end window 12 having a conventional flat outer surface. Conventionally, the inner surface of the end window 12 would also be flat and would provide a planar support for a layer of photocathode material. In the photo- multiplier tube disclosed herein, the inner surface of the window 12 consists of an array of cones or pyramids or pointed rods 14 upon which a layer 16 of photocathode material is deposited. The non- planar geometry of the inner surface improves the sensitivity of the photomultiplier tube to produce a greater current flow from the cathode to a first dynode 18 for a given level of impinging light.

There are several reasons why the non-planar geometry is believed to improve sensitivity. Light entering the tube 10 along an axis 20 undergoes total internal reflection in the cones or pyramids. This increases the probability that the light will be ab...