Mode Converted Relativistic Backward Wave Oscillator

Abstract

Relativistic electron device is a device which generates high power electromagnetic radiation using relativistic electron beam. In our study, the electromagnetic pulse wave (0.5GW-10GHz for 30ns) is normally radiated by using relativistic backward wave oscillator (RBWO) in mildly relativistic regime under 500kV-5kA from relativistic electron device with pulsed magnet system (Max. 3.4Tesla) to focus on relativistic electron beam. Relativistic backward-wave oscillator (RBWO) with relativistic electron beam is capable of producing high-power coherent Cerenkov radiation in the centimeter and millimeter wavelength regimes. The RBWO is designed, fabricated and tested to be operated at 10GHz-Max. 0.5GW level. High power electromagnetic (HPEM) source such as the RBWO has the purpose of transmitting GW-level to specific target. This uses an azimuthally symmetric TM01 waveguide mode for the reason of the characteristic of slow wave structure to interact between relativistic electron beam and backward propagating electromagnetic wave and power capacity to optimize the efficiency. TM01 mode is a doughnut-shaped one with a boresight null due to the cancellation by azimuthally symmetric aperture electric field distribution. In order to focus high-power electromagnetic radiation at the object, it is necessary to be theoretically designed a mode converted antenna which can changes from the TM01 mode to the circularly polarized TE11 mode. The mode converted antenna to be completed on design and fabrication shows that the measured radiation pattern is well matched with the simulated one. In addition, we tested the power estimation of electromagnetic coupling effectiveness on electronic devices at near field range. Relativistic electron device including RBWO, pulsed magnet system and mode converted antenna needs a simultaneously synchronous remote control system with pulsed trigger switch because the discharge and charge characteristic times of respective component devices are different. The remote control system with the software of lab-view is designed, fabricated and tested through several analyses for respective component devices. The study to generate high-power THz radiation source has developed at recent. To increase the frequency of the THz range, some unique physical phenomena with characteristic features including high power THz oversized relativistic backward wave oscillator (RBWO) can be produced. We present an investigation of a coherent Cerenkov radiation (CCR) high power THz source with an oversized slow wave structure of rectangular type. We designed on the cylindrical waveguide structure of a large diameter (D/λ≈8) to generate the power of 0.3GW and to operate at 0.1 THz. The result theoretical design is well matched with the predicted results by a particle-in-cell simulation code, MAGIC 2D with finite difference time domain, CST code.