Abstract: A DC conductive, low RF/microwave loss titanium oxide ceramic provides, at room temperature, a bulk DC resistivity of less than 1×1011 ohm-meters and an RF loss tangent of less than 2×10?4 at 7.5 GHz and less than 2×10?5 at 650 MHz. The resistivity is reduced by oxygen vacancies and associated Ti3+ and/or Ti4+ centers created by sintering in an atmosphere containing only between 0.01% and 0.1% oxygen. The reduced resistivity prevents DC charge buildup, while the low loss tangent provides good RF/microwave transparency and low losses. The ceramic is suitable for forming RF windows, electron gun cathode insulators, dielectrics, and other components. An exemplary Mg2TiO4—MgTiO3 embodiment includes mixing, grinding, pre-sintering in air, and pressing 99.95% pure MgO and TiO2 powders, re-sintering in air at 1400° C.-1500° C. to reduce porosity, and sintering at 1350° C.-1450° C. for 4 hours in an 0.05% oxygen and 99.05% nitrogen atmosphere.

Abstract: The luminance of a transmission mode X-ray scintillator diamond plate is dominated by induced defect centers having an excited state lifetime less than 10 msec, and in embodiments less than 1 msec, 100 usec, 10 used, 1 used, 100 nsec, or even 50 nsec, thereby providing enhanced X-ray luminance response and an X-ray flux dynamic range that is linear with X-ray flux on a log-log scale over at least three orders of magnitude. The diamond plate can be a single crystal having a dislocation density of less than 104 per square centimeter, and having surfaces that are ion milled instead of mechanically polished. The defect centers can be SiV centers induced by silicon doping during CVD diamond formation, and/or NV0 centers formed by nitrogen doping followed by applying electron beam irradiation of the diamond plate and annealing.

Abstract: An electromagnetic mechanical pulser implements a transverse wave metallic comb stripline TWMCS kicker having inwardly opposing teeth that retards a phase velocity of an RF traveling wave to match the kinetic velocity of a continuous electron beam, causing the beam to oscillate before being chopped into pulses by an aperture. The RF phase velocity is substantially independent of RF frequency and amplitude, thereby enabling independent tuning of the electron pulse widths and repetition rate. The TWMCS further comprises an electron pulse picker (EPP) that applies a pulsed transverse electric field across the TWMCS to deflect electrons out of the beam, allowing only selected electrons and/or groups of electrons to pass through. The EPP pulses can be synchronized with the RF traveling wave and/or with a pumping trigger of a transverse electron microscope (TEM), for example to obtain dynamic TEM images in real time.

Abstract: An electromagnetic mechanical pulser implements a transverse wave metallic comb stripline TWMCS kicker having inwardly opposing teeth structured to retard a phase velocity of an RF traveling wave propagated therethrough to match the kinetic velocity of a continuous electron beam simultaneously propagated therethrough. The kicker imposes transverse oscillations onto the beam, which is subsequently chopped into pulses by an aperture. The RF phase velocity is substantially independent of RF frequency and amplitude, thereby enabling independent tuning of the electron pulse widths and repetition rate. The exterior surface of the kicker is conductive, thereby avoiding electron charging. In embodiments, various elements of the kicker and/or aperture can be mechanically varied to provide further tuning of the pulsed electron beam. A divergence suppression section can include a mirror TWMCS and/or magnetic quadrupoles.

Abstract: A method of preparing a diamond crystal substrate for epitaxial deposition thereupon of a delta doping layer includes preparing an atomically smooth, undamaged diamond crystal substrate surface, which can be in the (100) plane, by polishing the surface and then etching the surface to remove subsurface damage caused by the polishing. The polishing can include a rough polish, for example in the (010) direction, followed by a fine polish, for example in the (011) direction, that removes the polishing tracks from the rough polishing. After etching the polished face can have a roughness Sa of less than 0.3 nm. An inductively coupled reactive ion etcher can apply the etching at a homogeneous etch rate using an appropriate gas mixture such as using argon and chlorine to remove between 0.1 and 10 microns of material from the polished surface.

Abstract: A technique for controlling and compensating the energy spread of a charged particle beam is provided. This technique is based on a passive dielectric-loaded structure that redistributes the energy within the bunch by means of the wakefield generated in the structure. Cylindrical and planar structure configurations are provided and also means for electrical and mechanical tuning to optimize performance. The instant abstract is neither intended to define the invention disclosed in this specification nor intended to limit the scope of the invention in any way.

Abstract: An ElectroMagnetic-Mechanical Pulser (“EMMP”) generates electron pulses at a continuously tunable rate between 100 MHz and 20-50 GHz, with energies up to 0.5 MeV, duty cycles up to 20%, and pulse widths between 100 fs and 10 ps. A dielectric-filled Traveling Wave Transmission Stripline (“TWTS”) that is terminated by an impedance-matching load such as a 50 ohm load imposes a transverse modulation on a continuous electron beam. The dielectric is configured such that the phase velocity of RF propagated through the TWTS matches a desired electron energy, which can be between 100 and 500 keV, thereby transferring electromagnetic energy to the electrons. The beam is then chopped into pulses by an adjustable aperture. Pulse dispersion arising from the modulation is minimized by a suppressing section that includes a mirror demodulating TWTS, so that the spatial and temporal coherence of the pulses is substantially identical to the input beam.

Abstract: An apparatus and method for creating nanometric delta doped layers in epitaxial diamond includes providing a dummy gas load with gas impedance equivalent to the reactor, and switching gas supplied between the reactor and the gas dummy load without stopping either flow, thereby enabling rapid flow and rapid gas switching without turbulence. An atomically smooth, undamaged substrate can be prepared, preferably in the (100) plane, by etching the surface after polishing to remove subsurface damage. A gas phase chemical getter reactant such as hydrogen disulfide can be used to suppress incorporation of residual boron into the intrinsic layers. Embodiments can produce interfaces between doped and mobile layers that provide at least 100 cm2/Vsec carrier mobility and 1013 cm?2 sheet carrier concentration.

Abstract: 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.

Abstract: The present invention provides a technique for constructing compact, high gradient magnetic lenses for charged particle beam focusing. Methods for adjusting the focusing strength of the lenses are provided, based on thermal control, mechanical motion of the magnetic chips within the yoke. The present invention is a method for designing and fabricating permanent magnet focusing elements that are compact, simple to construct, and having a large, adjustable focusing strength. Applications include beamlines for THz radiation sources, free electron lasers, wakefield accelerators and any other charged particle devices that require a compact beamline.

Abstract: An ElectroMagnetic-Mechanical Pulser can generate electron pulses at rates up to 50 GHz, energies up to 1 MeV, duty cycles up to 10%, and pulse widths between 100 fs and 10 ps. A modulating Transverse Deflecting Cavity (“TDC”) imposes a transverse modulation on a continuous electron beam, which is then chopped into pulses by an adjustable Chopping Collimating Aperture. Pulse dispersion due to the modulating TDC is minimized by a suppressing section comprising a plurality of additional TDC's and/or magnetic quadrupoles. In embodiments the suppression section includes a magnetic quadrupole and a TDC followed by four additional magnetic quadrupoles. The TDC's can be single-cell or triple-cell. A fundamental frequency of at least one TDC can be tuned by literally or virtually adjusting its volume. TDC's can be filled with vacuum, air, or a dielectric or ferroelectric material. Embodiments are easily switchable between passive, continuous mode and active pulsed mode.

Abstract: A dielectric loaded accelerator for accelerating charged particles, such as electrons, ions and/or protons, is described herein. The dielectric loaded accelerator accelerates charged particles along a longitudinal axis and towards an outlet of the accelerator. The dielectric loaded accelerator accelerates the charged particles using oscillating electromagnetic fields that propagate within the accelerator according to an electromagnetic mode. The dielectric loaded accelerator described herein includes an electromagnetic mode with a phase velocity that increases towards the outlet of the accelerator and matches a velocity of the charged particles being accelerated along the longitudinal axis of the accelerator. By matching the phase velocity of the oscillating electromagnetic fields to the velocity of the charged particles, the accelerator reduces phase slippage between the fields and the charged particles and, therefore, efficiently accelerates charged particle towards the outlet.

Abstract: A technique for producing a coherent beam of hard X-rays is provided. This technique is based on a short wavelength undulator that uses the fields of an electromagnetic wave to deflect a relativistic electron beam along a sinusoidal trajectory in order to cause it to emit X-rays. The undulator consists of a slow-wave structure that is energized by a second counterpropagating electron beam. Cylindrical and planar structure configurations are provided and also a mechanism for electrical and mechanical tuning to allow control over the wavelength of the emitted X-ray beam.

Abstract: An active device is provided that is energized by an optical source and uses an active paramagnetic medium to transfer this energy to a resonant circuit enabling new classes of electronic components.