Abstract: A method and apparatus for generating an accurate, stable phase shift (b) in a sinusoidal signal employs fast analog multiplication to implement the trigonometric relationship sin(&ohgr;t+b)=sin(&ohgr;t)cos(b)+cos(&ohgr;t) sin(b). Cos(&ohgr;t) is generated by accurately shifting a signal sin(&ohgr;t) through 90° C. using a delay line, for example. Sin(b) and cos(b) are dc signals generated by digital to analog conversion, using a demanded phase shift (b) whose sine and cosine are obtained from look-up tables. A controller for controlling a phase shift in an rf cavity is also disclosed and operates on the basis of the same trigonometrical principle. The amplitude of the signals in the rf cavity is also controllable; fast analog multipliers are again employed to scale the signal amplitude to a nominal fixed value such as 1 volt.

Abstract: A compact high energy photoelectron injector integrates the photocathode directly into a multicell linear accelerator with no drift space between the injection and the linac. High electron beam brightness is achieved by accelerating a tightly focused electron beam in an integrated, multi-cell, X-band rf linear accelerator (linac). The photoelectron linac employs a Plane-Wave-Transformer (PWT) design which provides strong cell-to-cell coupling, easing manufacturing tolerances and costs.

Abstract: A high power adjustable rf coupling loop which is used to interface a transmission line to a resonant cavity is described. The coupling loop is made entirely of metallic parts and therefore is ideal for high power rf applications. Contrary to all existing loops it does not require water cooling Among the unique features of this loop is the fact that it is adjustable. Subsequently the combined impedance of the loop and cavity can be adjusted to match perfectly with the line impedance rendering almost zero reflected power.

Abstract: A device for use in a linear accelerator operable to accelerate charged particles along a beam axis. The device includes a first end section, a second end section, and a transition section interposed between the first and second end sections. The sections are coupled together to form a plurality of accelerating cavities aligned along the beam axis. The first and second sections are configured to operate in a fixed collective resonant mode and the transition section is tunable such that resonant modes of the transition section may be tuned to lie at generally the same frequency as the resonant mode of the first and second sections.

Abstract: The specification describes a method and apparatus for electron beam lithography wherein a Wehnelt electron gun is modified to improve the uniformity of the electron beam. A mesh grid is applied to the Wehnelt aperture and the mesh grid functions as a multiple secondary emitter to produce a uniform beam flux over a wide area. The grid voltage of the modified gun is substantially lower than in a conventional Wehnelt gun, i.e. less than 100 volts, which can be switched conveniently and economically using semiconductor drive circuits.

Abstract: This device allows the variation of the coupling between two points in an RF circuit in a very simple way while maintaining the RF phase relationship and varying the relative magnitude of the RF fields. The device is characterized by a simple mechanical control of coupling value, that has negligible effect on the phase shift across the device. This is achieved by the simple rotation of the polarisation of a TE111 mode inside a cylindrical cavity. Such a device does not contain resistive elements, and the sliding mechanical surfaces are free from high RF currents. This device finds an application in standing wave linear accelerators, where it is desirable to vary the relative RF field in one set of cavities with respect to another, in order that the accelerator can operate successfully over a wide range of energies.

Abstract: Systems and methods for reducing dark current levels in a standing wave linear accelerator without sacrificing operating performance are described. In a radiation mode, the standing wave linear accelerator is operated to produce a pulsed therapeutic photon beam having a characteristic pulse width. In an electron mode, the standing wave linear accelerator is operated to produce a pulsed therapeutic electron beam having a characteristic pulse width that is shorter than the characteristic pulse width of the therapeutic photon beam. In some embodiments, assuming a uniform dark current level, the dark current level may be reduced in proportion with the beam pulse width reduction in the electron mode of operation. A system for implementing this therapeutic beam generation method also is described.

Abstract: A standing wave particle beam accelerator in which the electric fields in one side coupling cavity are switched by inserting two probes of selected diameter to provide different upstream and downstream electric field coupling to adjacent coupled accelerator cavities.

Abstract: A new radio frequency (rf) linear accelerator (linac) is disclosed in this invention. The rf linac includes a plurality of resonators each includes an inductor circuit L(k), k=1,2,3, . . . , n′ where n′ is a second integer, wherein the inductor circuit connected to at least two electrodes E(j′), j′=1,2,3, . . . (n−1), for applying an accelerating rf voltage thereto. The rf linac further includes a plurality sets of transverse focusing lenses, represented by Lenses(j), where j=1,2,3, . . . n, and n is an integer, for guiding and focusing an ion beam. Each of the electrodes E(j′) disposed between and aligned with two sets of the transverse focusing lenses Lenses(J′) and Lenses(J′+1), j′=1,2,3, . . . (n−1), as a linear array. In a preferred embodiment, at least two of the adjacent electrodes E(j′) and E(j′+1) are connected to a same inductor circuit L(k).

Abstract: An industrial X-ray/electron beam source includes an accelerator having a) a coaxial cavity b) an electron gun for emitting an electron beam to be accelerated, c) at least one deflection magnet positioned outside of the cavity, and d) a radio frequency power supply means for supplying power of a radio frequency to the cavity to induce TM010 mode as an accelerating mode in the cavity; and a beam irradiator having a two-dimensional scanning magnet which deflects accelerated beam by the accelerator, an extracting window for extracting the deflected electron beam to be irradiated to an object, and means for guiding the deflected beam toward a center of the extracting window in a radial direction. The source is advantageous in that the electron beams do not intersect inside the cavity, which can reduce beam loss, and that beams or X-rays are irradiated to the object spatially uniformly.

Abstract: A method and apparatus for generating an accurate, table phase shift (b) in a sinusoidal signal employs fast analog multiplication to implement the trigonometric relationship sin(&ohgr;t+b)=sin(&ohgr;t)cos(b)+cos(&ohgr;t)sin(b). Cos (&ohgr;t) is generated by accurately shifting a signal sin(&ohgr;t) through 90° using a delay line, for example. Sin(b) and cos(b) are dc signals generated by digital to analogue conversion, using a demanded phase shift (b) whose sine and cosine are obtained from look-up tables. A controller for controlling a phase shift in an rf cavity is also disclosed and operates on the basis of the same trigonometrical principle. The amplitude of the signals in the rf cavity is also controllable; fast analogue multipliers are again employed to scale the signal amplitude to a nominal fixed value such as 1 volt.

Abstract: A standing wave accelerator structure that has both inline coupling cavities and side coupling cavities combined into one structure. Additionally, the invention uses a prebunching (re-entrant) cavity, excited electrically or magnetically, through apertures between a first accelerating cavity and the prebunching cavity.

Abstract: A dielectric-wall linear accelerator is improved by a high-voltage, fast rise-time switch that includes a pair of electrodes between which are laminated alternating layers of isolated conductors and insulators. A high voltage is placed between the electrodes sufficient to stress the voltage breakdown of the insulator on command. A light trigger, such as a laser, is focused along at least one line along the edge surface of the laminated alternating layers of isolated conductors and insulators extending between the electrodes. The laser is energized to initiate a surface breakdown by a fluence of photons, thus causing the electrical switch to close very promptly. Such insulators and lasers are incorporated in a dielectric wall linear accelerator with Blumlein modules, and phasing is controlled by adjusting the length of fiber optic cables that carry the laser light to the insulator surface.

Abstract: There is provided a high-performance magnetic core with a high &mgr;′Qf-value for an RF accelerating. The strip wound magnetic core has a thin strip of nanocrystalline soft magnetic alloy, whose bcc solid solution with an average grain size less than 100 nm has a volume fraction more than 50% of the whole structure of the alloy, and around which an interlayer insulation film at least on one side thereof. A gap is formed in at least a part of a magnetic path of the magnetic core. Stack cores formed by arranging in series a plurality of the magnetic cores are oppositely installed via a high-voltage gap, making it possible to provide an excellent RF accelerating cavity.