X-ray tube for producing a high-efficiency beam and especially a pencil beam

Claim 1

An x-ray tube for producing an x-ray beam having only slightly divergent walls, wherein said x-ray tube comprises an anode provided with a rectilinear bore having internal walls constituting an anode target, said bore having a longitudinal axis along which the beam of x-radiation is emitted, and walls which are parallel, said bore having an axial length greater than its largest cross sectional dimension, and a cathode positioned outside said bore for generating an electron beam of small divergence which is directed towards the bore, and wherein said electron beam enters a first end of the bore substantially along the axis of said bore in such manner as to bombard said walls of said bore at a small angle of incidence with respect to the generatrix of said bore and over a bombardment length which is at least an order of magnitude greater than the largest cross section dimension of said bore, the difference between the axial length of said bore and said bombardmant length being at least an order of magnitude greater than the largest cross sectional dimension of said bore, and positioned more remote from said cathode than said bombardment length, in order to produce at least one x-ray beam containing a high percentage of the total x-radiation, said x-ray beam being intended to emerge from one end of said bore.