In one embodiment, an x-ray tube 15 can be used closer to a sample. An angle A.sub.1 between an anode axis 02 and an electron-beam axis 01 can be 10 and 80 and an angle A.sub.2 between the anode axis 02 and an x-ray axis 03 can be 10 and 80. In another embodiment, a cap 20 on an anode 12 can block x-rays emitted in undesired directions. The cap 20 can include an internal cavity 24, an electron-beam hole 21, an anode hole 22, and an x-ray hole 23. In another embodiment, an electrical connection between an x-ray tube 15 and a power supply 18 can be reliable and easy to manufacture. The anode 12 can include a hole 31 at an end of the anode 12 sized and shaped for insertion of an electrical connector 32.

Three dimensional beam forming X-ray source includes an electron beam generator (EBG) to generate an electron beam. A target element is disposed a predetermined distance from the EBG and positioned to intercept the electron beam. The target element is responsive to the electron beam to generate X-ray radiation. A beam former is disposed proximate to the target element and comprised of a material which interacts with the X-ray radiation to form an X-ray beam. An EBG control system controls at least one of a beam pattern and a direction of the X-ray beam by selectively varying a location where the electron beam intersects the target element to control an interaction of the X-ray radiation with the beam-former.

Some embodiments include an x-ray system, comprising: a vacuum enclosure; a plurality of electron sources disposed within the vacuum enclosure; an anode including at least one target with a plurality of focal spots disposed in a planar array within the vacuum enclosure, each focal spot configured to generate an x-ray beam in response to an electron beam from a corresponding one of the electron sources; a plurality of first collimators disposed within the vacuum enclosure, each first collimator associated with a corresponding one of the focal spots and configured to collimate the x-ray beam of the corresponding focal spot; and a second collimator integrated with a housing of the vacuum enclosure or external to the vacuum enclosure, the second collimator configured to collimate each of the x-ray beams.

This specification describes an anode for an X-ray tube with multiple channels, where each channel defines an electron aperture through which electrons from a source pass to strike a target and a collimating aperture through which X-rays produced at the target pass out of the anode as a collimated beam. At least a portion of the walls of each channel are lined with an electron absorbing material for absorbing any electrons straying from a predefined trajectory. The electron absorbing material has a low atomic number, high melting point and is stable in vacuum. Graphite may be used as the electron absorbing material.

A shield around an x-ray tube, a voltage multiplier, or both can improve the manufacturing process by allowing testing earlier in the process and by providing a holder for liquid potting material. The shield can also improve voltage standoff. A shielded x-ray tube can be electrically coupled to a shielded power supply.

An x-ray source includes an optical communications link to provide a galvanically isolated communication between a system controller and a gun controller. In specific examples, the link is provided through one or more fibers. In addition, the gun controller is preferably remote programmed by the system controller during startup. This addresses the problem of reprogramming a processor in a hard to access location/environment. A watchdog timer is also useful for the gun digital processor of the gun controller.

A transmission-target x-ray tube can include an x-ray window mounted on a window-housing. The window-housing can be made of a high density material (e.g. 12 g/cm.sup.3) with a high atomic number (e.g. 45), and can include an aperture with an increasing-inner-diameter region, with a smaller diameter closer to the electron-emitter and a larger diameter closer to the window-mount, for blocking x-rays and electrons. An example angle in the increasing-inner-diameter region is between 15 degrees and 35 degrees. The x-ray tube can further comprise a window-cap. The x-ray window can be sandwiched between the window-housing and the window-cap. The window-cap can be made of a high density material (e.g. 12 g/cm.sup.3) with a high atomic number (e.g. 45) for blocking x-rays in undesirable directions, and can include an aperture for allowing x-rays to transmit in desirable directions.

An X-ray tube includes: a cathode assembly that emits electrons; an anode that receives the electrons and generates X-rays; an envelope that is a case having the cathode assembly and the anode accommodated therein; a first shielding portion that shields the X-rays between the envelope and the cathode assembly on a reference line that connects a center of a point where the electrons are generated and a center of a point where the X-rays are generated; and a second shielding portion that shields the X-rays between the envelope and the cathode assembly in a direction perpendicular to the reference line from the center of the electron generation point.

An X-ray tube includes: an envelope that is a case; a cathode assembly that emits electrons in the envelope; and an anode including a first member of which at least a portion extends to the outside of the envelope, a second member that is provided in a direction perpendicular to a central axis of the first member, comes into contact with the first member, and has a higher X-ray shielding performance than the first member, and a target that receives the electrons emitted from the cathode assembly and generates X-rays.