A method for controlling a density distribution of electrons provided by an electron source for use in hard X-ray, soft X-ray and/or extreme ultraviolet generation, the method comprising generating a plurality of electrons from a pattern of ultracold excited atoms using an ionization laser inside a cavity, wherein the electrons have a density distribution determined by at least one of the patterns of excited atoms and the ionization laser, and accelerating the electrons out of the cavity using a non-static acceleration profile, wherein the acceleration profile controls the density distribution of the electrons as they exit the cavity.

Disclosed below are representative embodiments of methods, apparatus, and systems for generating electrons. For example, certain embodiments comprise a charge gating diamond QED based electron source, which can be suspended within the RF cavity of an electron injection system in a superconducting radiofrequency (SRF) electron accelerator. Embodiments of the disclosed technology are capable of producing low temperature (cold) electron beams, where temperature refers to the transverse energy in the extracted electron beam (or beam emittance). Embodiments of the disclosed technology can also exhibit enhanced charge replenishment capabilities by virtue of the material selected to suspend the electron source within the RF cavity of the electron injection system.

A linear accelerator is operated by emitting charged particles from a particle source and accelerating the particles in an accelerator by wayof a high-frequency alternating field in such a way that pulses of charged particles are generated. A high-frequency power is periodically supplied by way of high-frequency pulses to the accelerator in order to generate the high-frequency alternating field. A particle stream emitted by the particle source is varied during a HF pulse length of the high-frequency pulse in such a way that the pulse formed during the HF pulse length has at least two sub-pulses with different mean energies per particle. There is also described a linear accelerator that carries out the method and a material-discriminating radioscopy device with a linear accelerator of this kind.

An electron accelerator is provided. The electron accelerator comprises a resonant cavity comprising a hollow closed conductor, an electron source configured to inject a beam of electrons, and an RF system. The electron accelerator further comprises a magnet unit, comprising a deflecting magnet. The deflecting magnet is configured to generate a magnetic field in a deflecting chamber in fluid communication with the resonant cavity by a deflecting window. The magnetic field is configured to deflect an electron beam emerging out of the resonant cavity through the deflecting window along a first radial trajectory in the mid-plane (Pm) and to redirect the electron beam into the resonant cavity through the deflecting window towards the central axis along a second radial trajectory. The deflecting magnet is composed of first and second permanent magnets positioned on either side of the mid-plane (Pm).

A resonant apparatus such as a resonant waveguide module in an RF particle accelerator includes an unbrazed joint that provides a reliable vacuum seal and RF contact between resonators with precisely controlled internal geometry. The joint can be disassembled and reassembled without degradation. Hard, stainless steel end faces include knife edges pressed into a copper central component, such as a gasket. The knife edges extend the waveguide interiors without gaps or interruptions. The central component serves as a coupling iris or other functional component of the resonant apparatus, thereby allowing the central component to have substantial dimensions that inhibit mechanical distortions thereof. The waveguides and knife edges can be copper plated. Embodiments include embedded passages and/or recesses used for cooling, radiation shielding, magnetic focusing coils, and/or electron optics element formed by permanent magnets.

Methods for generating a multiple-energy X-ray pulse. A beam of electrons is generated with an electron gun and modulated prior to injection into an accelerating structure to achieve at least a first and specified beam current amplitude over the course of respective beam current temporal profiles. A radio frequency field is applied to the accelerating structure with a specified RF field amplitude and a specified RF temporal profile. The first and second specified beam current amplitudes are injected serially, each after a specified delay, in such a manner as to achieve at least two distinct endpoint energies of electrons accelerated within the accelerating structure during a course of a single RF-pulse. The beam of electrons is accelerated by the radio frequency field within the accelerating structure to produce accelerated electrons which impinge upon a target for generating Bremsstrahlung X-rays.

An apparatus for generating high frequency electromagnetic radiation includes a whispering gallery mode resonator, coupled to an output waveguide through a coupling aperture. The resonator has a guiding surface, and supports a whispering gallery electromagnetic eigenmode. An electron source is configured to generate a velocity vector-modulated electron beam, where each electron in the velocity vector-modulated electron beam travels substantially perpendicular to the guiding surface, while interacting with the whispering gallery electromagnetic eigenmode in the whispering gallery mode resonator, generating high frequency electromagnetic radiation in the output waveguide.

A photocathode comprises a substrate in which a cavity is formed and a film of material disposed on the substrate. The film of material comprises an electron emitting surface configured to emit electrons when illuminated by a beam of radiation. The electron emitting surface is on an opposite side of the film of material from the cavity.

A particle accelerator comprising a waveguide comprising a series of acceleration cells. The series of acceleration cells comprise an input acceleration cell configured to accelerate a beam of electrons along the central axis of the cells. A source of electrons is configured to input a beam of electrons into the input acceleration cell and a magnet arrangement is configured to prevent electrons that have deviated from the beam of electrons from hitting the source of electrons.

An annular apparatus is provided for generating accelerated electrons, wherein ions from a glow discharge plasma may be accelerated onto the surface of an annular second cathode and electrons emitted by the annular second cathode may be accelerated towards an annular electron exit window by a second electrical voltage applied between the annular second cathode and an annular second anode, wherein a housing is designed as a first cathode; a first anode comprises a number of wire-like electrodes which extend completely or partially through an annular evacuable space, and wherein a second reservoir contains a hydrocarbon-containing compound which may be admitted into the evacuable space through the at least one first inlet.