Patent ID: 6198798
Filing Date: 2001-03-06
Classification: H01J

Abstract:
A parallax-free X-ray imager in which a parallel X-ray beam is directed to a crystal so as to generate a conical X-ray beam for illuminating an entrance window of said X-ray imager, said X-ray imager comprising a vessel containing an ionizing gas for generating primary electrons in response to impingement of said conical X-ray beam within said ionizing gas through said entrance window, said X-ray imager further comprising, within said vessel:a spherical conversion volume chamber associated with said entrance window, said conversion volume chamber comprising first and second parallel electrodes for generating, in operations electrical equipotential surfaces of spherical shape and corresponding radial electric field lines within said spherical conversion volume chamber, said electrical equipotential surfaces of spherical shape being each centered at a common center focal point substantially corresponding to the location of the crystal so as to allow any primary electron generated within said spherical conversion volume chamber to drift substantially along said radial field lines;a third electrode disposed substantially parallel to said second electrode and forming therewith a gas electron multiplier structure, said gas electron multiplier structure comprising at least one matrix of electric field condensing areas, distributed within a solid surface, for generating a local electric field amplitude enhancement sufficient to generate in said gas an electron avalanche from one of said primary electrons, and said gas electron multiplier thereby operating as an amplifier of given gain for said primary electrons; anda signal readout electrode comprising an array of elementary electrodes, said signal readout electrode being disposed on a wall of said vessel in parallel with said third electrode;and further comprising, outside of said vessel:electrical bias means, connected to said first, second and third electrodes, for supplying voltage potentials sufficient to provide drift of said primary electrons within said spherical conversion volume chamber and to multiply corresponding drifted primary electrons through said avalanche phenomenon within said gas electron multiplier structure; anddetection means, connected to said readout electrode, for providing a bi-dimensional readout of the position of any generated avalanche phenomenon provided by said gas electron multiplier structure without substantial parallax.