Abstract: Electron accelerator of the re-circulating type, having a resonant coaxial cavity presenting an outer cylindrical conductor of axis A and a coaxial inner cylindrical conductor, an electron gun for injecting electrons into the cavity following a radial direction and into a median plane of the cavity, an RF system capable of accelerating the injected electrons following a trajectory into the median plane which has the shape of a flower centered on the axis A, deflecting magnets disposed into the median plane externally to the cavity for redirecting electrons back towards the axis A. The RF system includes final power amplifiers, each amplifier being directly coupled to the cavity through its own individual inductive loop and each two of these loops being physically spaced apart from each other by an angle alpha, such that alpha is not an integer multiple of 90 degrees.

Abstract: Electron accelerator of the re-circulating type, having a resonant coaxial cavity presenting an outer cylindrical conductor of axis A and a coaxial inner cylindrical conductor, an electron gun for injecting electrons into the cavity following a radial direction and into a median plane of the cavity, an RF system capable of accelerating the injected electrons following a trajectory into the median plane which has the shape of a flower centered on the axis A, deflecting magnets disposed into the median plane externally to the cavity for redirecting electrons back towards the axis A. The RF system includes final power amplifiers, each amplifier being directly coupled to the cavity through its own individual inductive loop and each two of these loops being physically spaced apart from each other by an angle alpha, such that alpha is not an integer multiple of 90 degrees.

Abstract: A method for the production of extremely wide bandwidth THz radiation comprising: delivering an electron beam from a source to an undulator that does not deflect the angle or transversely move the electron beam; and optimizing the undulator to yield peak emission in the middle of the THz band (1 THz). These objectives are accomplished by magnetically bending the orbit of the incoming electron beam in the undulator according to the function x(z)=xo exp(?z2/2?2) and controlling the transverse magnetic field to be B(z)=B0(1?z2/?2)exp(?z2/2?2).

Abstract: In accordance with the invention, improved vacuum microtube devices are provided with arrangements for tunably spacing the gate and the cathode. Tuning can be effected by using an electrostaic or magnetic actuator to move the gate on a spring or a rail. Advantageously a feedback arrangement can be used to control the spacing. Magnetic reassembly components can be provided for facilitating release of tube components in fabrication.

Abstract: According to the present invention, there is provided a compact source of intense THz radiation comprising a short bunch, low energy particle beam source, an accelerator cavity and an electromagnetic wiggler. Application of state-of-the-art superconducting accelerating structures and beam recirculation allows such a THz radiation source to have a small footprint and high average intensity without the need of the larger equipment necessary to produce the large charge per bunch generally associated with the production of THz radiation. Consequently, low emittance electron beams can be used to produce emitted THz radiation of high average brilliance.

Abstract: An improved gridded microwave tube is provided, the tube containing a cold cathode, an anode, and a grid located between the anode and cathode. In one embodiment, the cold cathode has a refractory metal substrate and carbon nanotube emitters, the emitters having a diameter of 1 to 300 nm and a length of 0.05 to 100 &mgr;m. The grid-cathode spacing is 1 to 100 &mgr;m, the grid contains apertures having a maximum dimension of 0.5 to 100 &mgr;m, and the grid thickness is 0.5 to 100 &mgr;m. Emission from the cathode directly onto the grid material itself, which undesirably heats the grid, is reduced by either (a) the presence of a shadow mask between the grid and the emitters or (b) selective formation of the emitters in locations that correspond to the grid apertures. The microwave tube operates at a frequency of greater than 0.5 GHz, advantageously greater than 2 GHz.