GB1297501A - - Google Patents

Abstract

1297501 Discharge apparatus HORIZONS Inc 2 Jan 1970 [8 Jan 1969] 271/70 Heading H1D [Also in Divisions B6 and C7] An X-ray image intensifier comprises a laminar arrangement of means for absorbing X-rays, and means for transforming the resulting photc electrons into either secondary electrons or charged particles which are multiplied and accelerated towards an electron- and/or charged particle-sensitive receptor 16. In the arrangement shown an electrode 12 adjoins an insulating film 14, e.g. of plastics material, supporting the receptor layer 16. Electrode 10 may be a thin sheet of Al or may also act as the X-ray absorber in which case it should contain a high proportion of elements having an atomic number higher than Ag, e.g. Pb, Bi, U, Th and their compounds, which may be dispersed in a partially conducting plastics film to act as an electrode and a multiplying structure. A separate multiplication layer 18 is preferably provided and may act in either the Geiger-Muller or secondary emission mode. For the G-M mode the layer 18 contains a gas, e.g. A or N, with a quenching gas such as alcohol, methane or a halogen, confined by insulating spacers 22 which are not necessarily hermetic seals since electrode 12 may be a metallic surface in a cassette which can be filled with the gas at a pressure of a few mm. up to atmospheric. The region 18 may be a porous film, open mesh, a grid, or a layer containing a large number of channels formed by anodic etching (see Division C7) or by a photo-resist etching process (see Division B6). The electrode 10 is positive for the G-M mode and negative for the secondary emission mode. For the latter mode the channels are lined with a compound of high atomic number to act as an X-ray absorber and with secondary emitting material, e.g. alkali metals or alkaline earth metals. The channels retain the resolution of the incident X-ray pattern. In alternative embodiments (Figs. 2, 3 or 4, not shown) an additional electrode is provided above the layer 16 to provide what is in effect a voltage divider circuit. A power source connects the additional electrode to either or both of electrodes 10 and 12, depending on the insulating properties of the layer 14. In a further alternative embodiment (Fig. 5, not shown), the electrode 12 is provided on the opposite side of the insulating layer 14. Examples of suitable receptor layer compositions are given.