Abstract: An overmoded distributed interaction network is provided that generates high peak and average RF power amplification at high frequencies. A series of overmoded cavities are bounded by parallel or concentric grids that may be separated by metallic spacers adapted to function as a photonic bandgap circuit to suppress competing electromagnetic modes. The selected electromagnetic modes have wavelengths much shorter than the lateral dimension of the grids, allowing the beam-wave interaction to be distributed transversely for improved interaction efficiency. The grids may optionally be slotted and arranged to provide a serpentine traveling wave tube configuration.

Abstract: An active electronically steered cathode (AESC) applies one or more electromagnetic modes to an input cavity, similar to that used in an inductive output tube. The structure and superposition of these modes creates local electric field maxima, causing the electron emission site or sites to move or be distributed across the surface of the cathode. Changing the amplitude, phase, or frequency of the modes provides time-variable control of the electric field profile, thereby generating electronically steered electron beams. One embodiment employs a pair of orthogonal TM modes driven out of phase, causing the electric field maximum to rotate around an annular cathode, producing a helical beam. Slots in the control grid may be used to segment the helical beam into discrete bunches to provide additional density modulation.

Abstract: An apparatus and method of modulating an electron beam to induce a high degree of spatial bunching uses multiple control grids located in close proximity to an electron-emitting cathode. An RF field couples to the electron beam in the cathode-grid gap to induce velocity modulation. The electron beam then propagates through a first control grid, allowing the velocity modulation to induce spatial bunching. The electron beam then traverses a gap between the first grid and a second control grid and interacts with the RF field to induce further bunching of the beam. Simulations show that bunching factors of 50:1 may be achieved.

Abstract: An output circuit for a microwave tube is provided that has generally high interaction impedance for good efficiency, has high average power capability, and is physically large for a given operating frequency. The output circuit is designed to operate in conjunction with an off-axis, bunched electron beam. Electromagnetic fields are applied to the region in which the electron beam propagates to impart an azimuthal velocity to the bunched electron beam. The electron bunches then interact synchronously with a resonant output structure to excite radio-frequency modes from which energy can be extracted and applied to a load.

Abstract: An overmoded distributed interaction network is provided that generates high peak and average RF power amplification at high frequencies. A series of overmoded cavities are bounded by parallel or concentric grids that may be separated by metallic spacers adapted to function as a photonic bandgap circuit to suppress competing electromagnetic modes. The selected electromagnetic modes have wavelengths much shorter than the lateral dimension of the grids, allowing the beam-wave interaction to be distributed transversely for improved interaction efficiency. The grids may optionally be slotted and arranged to provide a serpentine traveling wave tube configuration.

Abstract: An apparatus and method of modulating an electron beam to induce a high degree of spatial bunching uses multiple control grids located in close proximity to an electron-emitting cathode. An RF field couples to the electron beam in the cathode-grid gap to induce velocity modulation. The electron beam then propagates through a first control grid, allowing the velocity modulation to induce spatial bunching. The electron beam then traverses a gap between the first grid and a second control grid and interacts with the RF field to induce further bunching of the beam. Simulations show that bunching factors of 50:1 may be achieved.

Abstract: An active electronically steered cathode (AESC) applies one or more electromagnetic modes to an input cavity, similar to that used in an inductive output tube. The structure and superposition of these modes creates local electric field maxima, causing the electron emission site or sites to move or be distributed across the surface of the cathode. Changing the amplitude, phase, or frequency of the modes provides time-variable control of the electric field profile, thereby generating electronically steered electron beams. One embodiment employs a pair of orthogonal TM modes driven out of phase, causing the electric field maximum to rotate around an annular cathode, producing a helical beam. Slots in the control grid may be used to segment the helical beam into discrete bunches to provide additional density modulation.

Abstract: A resonant cavity with a bowtie shape supports an electromagnetic field used to deflect the trajectory of an electron beam passing through the cavity. The short transit time of the beam across the gap maintains the cavity fields at near-optimal phase, improving interaction efficiency even for relatively low-energy beams. High interaction impedance ensures good drive-power-to-deflection conversion efficiency. The uniform field achieved across the gap enforces uniform deflection across the beam profile to maintain beam quality. Multiple bowtie cavities can be arranged to allow arbitrary two-dimensional deflections.

Abstract: An input circuit of a microwave amplification tube achieves improved instantaneous bandwidth. By directly coupling the transmission line carrying a modulating radio frequency signal to a control grid, a low-Q input circuit is created that increases the fractional bandwidth of the system. A resonant cavity may be used to generate a voltage across the gap between the cathode and the control grid. Alternative geometries are presented whereby the electron beam is emitted from a cathode connected either to the center conductor of the transmission line or to the outer conductor of the transmission line. Alternatively, the electric field of the radio-frequency signal propagating through the transmission line may be used to create a voltage across the gap between the cathode and the control grid without using a resonant cavity. Likewise, alternative geometries are presented by which the electron beam is emitted from a cathode connected either to the center conductor or to the outer conductor of the transmission line.

Abstract: A compact, reliable scanning electron-beam x-ray source achieves reduced complexity and cost. In particular, the x-ray source includes an electron beam that is propagated parallel to an x-ray target and is swept across the target in response to a moving magnetic cross field. Rather than scanning the beam by deflecting it about a single point, the point of deflection is translated along the target length, dramatically reducing the volume of the device. The magnetic cross field is translated along the target length using either mechanical systems to move permanent magnets, or electrical systems to energize an array of electromagnets.

Abstract: An electron beam amplification device provides trajectory modulation of an electron beam, and includes an electron gun, a modulator, an interceptor, an output circuit, and a collector. The electron gun produces an electron beam. The modulator receives an RF input signal and provides a corresponding electromagnetic field region that alters trajectory of the electron beam in correspondence with the RF input signal. The interceptor has at least one aperture oriented such that the electron beam transmits through the aperture when the electron beam altered by the modulator follows a particular transmission path and impacts upon the interceptor when the electron beam trajectory altered by the modulator follows a path other than the particular transmission path. The output circuit is arranged so that the electron beam transmitted through the interceptor aperture passes therethrough and produces an RF output signal. The collector recovers remaining energy of the electron beam after passing through the output circuit.

Abstract: A resonant cavity with a bowtie shape supports an electromagnetic field used to deflect the trajectory of an electron beam passing through the cavity. The short transit time of the beam across the gap maintains the cavity fields at near-optimal phase, improving interaction efficiency even for relatively low-energy beams. High interaction impedance ensures good drive-power-to-deflection conversion efficiency. The uniform field achieved across the gap enforces uniform deflection across the beam profile to maintain beam quality. Multiple bowtie cavities can be arranged to allow arbitrary two-dimensional deflections.

Abstract: An output circuit for a microwave tube is provided that has generally high interaction impedance for good efficiency, has high average power capability, and is physically large for a given operating frequency. The output circuit is designed to operate in conjunction with an off-axis, bunched electron beam. Electromagnetic fields are applied to the region in which the electron beam propagates to impart an azimuthal velocity to the bunched electron beam. The electron bunches then interact synchronously with a resonant output structure to excite radio-frequency modes from which energy can be extracted and applied to a load.

Abstract: A compact, reliable scanning electron-beam x-ray source achieves reduced complexity and cost. In particular, the x-ray source includes an electron beam that is propagated parallel to an x-ray target and is swept across the target in response to a moving magnetic cross field. Rather than scanning the beam by deflecting it about a single point, the point of deflection is translated along the target length, dramatically reducing the volume of the device. The magnetic cross field is translated along the target length using either mechanical systems to move permanent magnets, or electrical systems to energize an array of electromagnets.

Abstract: An input circuit of a microwave amplification tube achieves improved instantaneous bandwidth. By directly coupling the transmission line carrying a modulating radio frequency signal to a control grid, a low-Q input circuit is created that increases the fractional bandwidth of the system. A resonant cavity may be used to generate a voltage across the gap between the cathode and the control grid. Alternative geometries are presented whereby the electron beam is emitted from a cathode connected either to the center conductor of the transmission line or to the outer conductor of the transmission line. Alternatively, the electric field of the radio-frequency signal propagating through the transmission line may be used to create a voltage across the gap between the cathode and the control grid without using a resonant cavity. Likewise, alternative geometries are presented by which the electron beam is emitted from a cathode connected either to the center conductor or to the outer conductor of the transmission line.

Abstract: An electron beam amplification device provides trajectory modulation of an electron beam, and includes an electron gun, a modulator, an interceptor, an output circuit, and a collector. The electron gun produces an electron beam. The modulator receives an RF input signal and provides a corresponding electromagnetic field region that alters trajectory of the electron beam in correspondence with the RF input signal. The interceptor has at least one aperture oriented such that the electron beam transmits through the aperture when the electron beam altered by the modulator follows a particular transmission path and impacts upon the interceptor when the electron beam trajectory altered by the modulator follows a path other than the particular transmission path. The output circuit is arranged so that the electron beam transmitted through the interceptor aperture passes therethrough and produces an RF output signal. The collector recovers remaining energy of the electron beam after passing through the output circuit.