Ion chamber array with reduced dead space

In X-ray detection apparatus of the type comprising a plurality of substantially planar, parallel anodes and cathodes disposed in an ionizable detecting medium, voltage supply means coupled to said anodes and cathodes for maintaining said anodes positive with respect to said cathodes and including electric current flow measuring means coupled to said anodes, and vessel means enclosing said anodes, cathodes and detecting medium, said vessel means including a thin window substantially transparent to X-ray radiation and oriented substantially perpendicular to said anodes and cathodes, said window being maintained positive with respect to said cathodes, the improvement wherein electric field distribution in said medium between said window and said parallel anodes and cathodes is configured to permit collection on said anodes of electrons and ions produced by interactions between X-ray photons and said medium, said improvement comprising:

• a thin layer of dielectric material having a major surface disposed on an inner major surface of said window;
• a thin electrode having a major surface disposed on the major surface of said dielectric layer opposite said window;
• and
• means coupled to said thin electrode for maintaining said electrode substantially at the potential of said cathodes such that electrons in said medium between said electrode and said parallel anodes and cathodes tend to flow to said anodes.

In an X-ray detector of the type comprising a plurality of substantially planar, parallel anodes and cathodes disposed in an ionizable detecting medium, means adapted to apply an electric field between said cathodes and said anodes so that said anodes can be maintained positive with respect to said cathodes, and vessel means enclosing said anodes, cathodes and detecting medium, said vessel means including a thin window substantially transparent to X-ray radiation and oriented perpendicular to said anodes and said cathodes, said window adapted to be maintained positive with respect to said cathodes, the improvement wherein electric field distribution in said medium between said window and said parallel anodes and cathodes is adapted to be configured to permit collection on said anodes of electrons and ions produced by interactions between X-ray photons and said medium, said improvement comprising:

• a thin layer of dielectric material having a major surface disposed on an inner major surface of said window;
• and
• a thin electrode having a major surface disposed on the major surface of said dielectric layer opposite said window, said electrode being adapted to be maintained substantially at the potential of said cathodes such that electrons in said medium between said electrode and said parallel anodes and cathodes tend to flow to said anodes, and said anodes being adapted to be connected to electric current measuring means.