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An all-solid-state microsecond pulsed power system has been tested in this paper. It can produce larger than 50 kV and microsecond-range pulses continuously for more than 9 × 104 shots into a resistive load at a repetition rate of 10 pps. The whole device has accumulatively operated more than 15 000 pulses at 100 Hz and 3 × 105 pulses at 10 Hz. This all-solid-state pulsed power system consists of a repetitive power supply, a four-stage Marx generator, a pulse forming network, and a resistive load. The repetitive power supply of the pulsed power system is calculated and analyzed first, followed by the introduction of the Marx generator and the three-section anti-resonance network. A polymer box of sodium chloride solution is applied as a resistive load with an impedance of 200 Ω. Repetitive experiments showed that this system is able to operate stably at 100 Hz repetition rate without failure. [ABSTRACT FROM AUTHOR]

An X-band Cerenkov-type high power microwave (HPM) oscillator driven by a sheet electron beam is proposed and designed in this paper. In order to improve the efficiency of simulation optimization, a research method is proposed in which the large caliber coaxial Cerenkov-type HPM oscillator is taken as an initial model, which is equivalent to that of the planar slow-wave structure (SWS) by using the similarity between the planar SWS and the large caliber coaxial SWS. In addition, the effectiveness of the equivalent method is verified from the geometric structure, the field distribution of the operating mode, dispersion characteristics, and the preliminary particle simulation results of two devices. Based on the results of an X-band large caliber coaxial Cerenkov-type HPM oscillator, an X-band Cerenkov-type HPM oscillator driven by a sheet electron beam is investigated by the 3D particle-in-cell code. The simulation results show that the power conversion efficiency can reach 26.1% at the frequency of 11.9 GHz with the output power of 0.3 GW, while the sheet electron beam has the energy of 486 kV and it carries the current of 2.4 kA conducted by the magnetic field of 2.5 T. [ABSTRACT FROM AUTHOR]

A carbon fiber array cathode (CFAC) was presented and tested in a magnetically insulated transmission line oscillator (MILO) in earlier papers; however, the performance of this cathode was not as good as the traditional polymer velvet cathode, and the nonuniform fibers' distribution on the cathode surface was postulated as the culprit for this. In this paper, this CFAC has been carefully reprocessed, and the performance is improved (efficiency increases from ∼12% to ∼16%) and reaches a level that is as good as the velvet cathode, which means that this CFAC provides a promising substitute for the polymer velvet cathode in MILO. [ABSTRACT FROM AUTHOR]

A novel Ku-band coaxial transit-time oscillator (TTO) with Pierce-like cathode is proposed in this paper. TTO has the characteristics of low space-charge effect and short interaction distance. Combining with these features, we design a novel Pierce-like cathode to lower the demand for the guiding magnetic field. The guiding magnetic field intensity is reduced to about 0.32T by loading the Pierce-like cathode, but the magnetic field intensity is not a stable value, it fluctuates at 0.32T because of the properties of permanent magnet. To achieve the light and small goals of TTO, we design a novel permanent magnet structure with NdFeB. Based on the research, the typical simulation result is that when the diode voltage is 440kV, the beam current is 11kA, the guiding magnetic field is about 0.32T, the device can output 1.46GW microwave pulse at 14.2GHz. The power conversion efficiency is about 30%. [ABSTRACT FROM AUTHOR]

The high power pulse generators have been widely used in high power microwave generation and plasma physics research. In this paper, a novel compact solid-state high power pulse generator is studied, numerically and experimentally. The generator is mainly composed of the primary energy supply, the magnetic pulse compressor, the Blumlein type low-impedance pulse forming network, and the square waveform pulse transformer. Especially, design considerations for a solid-state high power pulse generator are proposed. Experimental results show that pulses with a peak power of 2 GW, a duration of 150 ns, and a repetitive rate of 10 Hz are continuously achieved on a dummy load. The dimension is Φ60 × 210 cm2, and the average power density reaches ∼5 W/L. Experimental results show reasonable agreement with numerical analysis. [ABSTRACT FROM AUTHOR]

The method for calculating the dispersion relations of the slow-wave structures (SWSs) with arbitrary geometrical structures is studied in detail by using the Fourier series expansion. In addition, dispersive characteristics and longitudinal resonance properties of the SWSs with the cosinusoidal, trapezoidal, and rectangular corrugations are analyzed by numerical calculation. Based on the above discussion, a comparison on an L-band coaxial relativistic backward wave oscillator (BWO) and an L-band coaxial BWO with a coaxial extractor is investigated in detail with particle-in-cell KARAT code (V. P. Tarakanov, Berkeley Research Associates, Inc., 1992). Furthermore, experiments are carried out at the TORCH-01 accelerator under the low guiding magnetic field. At diode voltage of 647 kV, beam current of 9.3 kA, and guiding magnetic field strength of 0.75 T, the microwave is generated with power of 1.07 GW, mode of TM01, and frequency of 1.61 GHz. That is the first experimental report of the L-band BWO. [ABSTRACT FROM AUTHOR]

Radial transit time oscillator (RTTO) can be relied on to generate effective coherent electromagnetic radiation in the millimeter wave domain. In this paper, the preliminary experimental research on a Ka-band RTTO is reported for the first time. In experiments, the radial electron beam emitted from the knife edge of the disk cathode is guided by the radial magnetic field. The bombardment trace on the nylon target verifies the emission and transportation uniformity of the radial e-beam. When the diode voltage is 410 kV, the beam current is 7.8 kA, and the magnetic field is 0.6 T, the RTTO can output microwaves with the power of 320 MW and the frequency of 31.35 GHz. As the diode voltage increases from 350 kV to 430 kV, the output microwave power will grow accordingly. Taking the ohmic loss into consideration, the experimental results are in agreement with the simulation ones. [ABSTRACT FROM AUTHOR]

The initial experimental results of an L-band relativistic backward wave oscillator with a coaxial slow-wave structure are presented. The asymmetric-mode-competition mechanism in the device is investigated theoretically and experimentally. It is shown that the diode voltage, guiding-magnetic field, and concentricity play a key role in the suppression and excitation of the asymmetric-mode (coaxial quasi-TE11 mode). In the experiments, the asymmetric-mode with a frequency of 2.05 GHz is suppressed and excited, which is in good agreement with the theoretical results. [ABSTRACT FROM AUTHOR]

The radial transit time oscillator (RTTO) is promising to realize high power output of millimeter-waves. Although the radial structure can enhance the power capacity, less cavities and small radial dimension make it difficult to improve the power capacity in RTTOs, especially in the extraction cavity. A one-gap extraction cavity in the Ka-band RTTO is proposed in this paper to improve the power capacity. Without electrons, taking the TM011 cavity as an example, the radial reversal resonant electric field can intersect with radial electrons. By choosing the sizes of the cavity, the synchronization of the electrons and the electric field can be realized to achieve effective energy exchange. In particle-in-cell simulation, the RTTO with the TM011 extraction cavity can output 1.0 GW high power microwaves (HPMs) at 31.2 GHz, and the beam-wave conversion efficiency is 31.6%. The maximum electric field in the TM011 cavity is only 800 kV/cm, which is less than one third that in the TM010 extraction cavities. In addition, the TM012 extraction cavity is employed to improve the efficiency to 35.4%. At the same time, because of the increase in the output power, the maximum radial electric field in the TM012 cavity increases to 850 kV/cm. Therefore, the one-gap extraction cavity can realize multiple energy exchanges to get high beam-wave conversion efficiency and enhance the power capacity in the extraction cavity significantly. [ABSTRACT FROM AUTHOR]

High power coherent electromagnetic radiation of a millimeter waveband is a tough research topic of plasma physics. In axial millimeter wave electromagnetic radiation devices, low power capacity and mode competition limited the output power. The radial structure is a promising candidate to realize high power millimeter wave radiation. Structural characteristics of a radial Ka-band high power millimeter wave transit time oscillator (TTO) are studied in this paper. Analysis without an electron beam indicates that if the average radius of radial cavities is increased, the mode of the stimulated field will not change, the power capacity will be improved, and the quality factor due to ohmic loss will remain unchanged. Particle-in-cell simulation proves that, for radial millimeter wave TTO, increasing the radius of the cathode and keeping sizes of the other parts unchanged, the output power will be increased, the efficiency will remain the same, and electric field growth will be slower than that in axial devices. Besides, taking ohmic loss into consideration, the efficiency will increase to a stable value. Therefore, by this method, high power coherent electromagnetic radiation in a millimeter wave can be realized. [ABSTRACT FROM AUTHOR]

A solid-state quasi-square pulse Marx generator has been designed, constructed, and tested in this paper. The spark gap switches of a typical Marx generator have been replaced by a fractional-turn ratio saturable pulse transformer (FRSPT), and a three-section anti-resonance network has taken the role of pulse forming module in this quasi-square Marx generator. For the switches, thyristors are used as the primary switches and the FRSPT is used as the pulse modulating switch. The experimental results show that if the charge voltage is about 1000 V, the output quasi-square pulse has an amplitude of 18.5 kV and a pulse width of 3.15 μs, and the experimental results verify the feasibility of the concept of an all-solid-state quasi-square square pulse Marx generator based on an FRSPT and anti-resonance network. [ABSTRACT FROM AUTHOR]

This paper presents both numerical and experimental studies of a repetitive S-band long-pulse relativistic backward-wave oscillator. The dispersion relation curve of the main slow-wave structure is given by the numerical calculation. Experimental results show that a 1 GW microwaves with pulse duration of about 100 ns (full width of half magnitude) under 10 Hz repetitive operation mode are obtained. The microwave frequency is 3.6 GHz with the dominant mode of TM01, and power conversion efficiency is about 20%. The single pulse energy is about 100 J. The experimental results are in good agreement with the simulation ones. By analyzing the experimental phenomenon, we obtain the conclusion that the explosive emission on the surface of the electrodynamics structure in intense radio frequency field mainly leads to the earlier unexpected termination of microwave output. [ABSTRACT FROM AUTHOR]

A high efficient relativistic backward wave oscillator with coaxial nonuniform slow-wave structures (SWSs) and depth-tunable extractor is presented. The physical mechanism to increase the power efficiency is investigated theoretically and experimentally. It is shown that the nonuniform SWSs, the guiding magnetic field distribution, and the coaxial extractor depth play key roles in the enhancement of the beam-wave power conversion efficiency. The experimental results show that a 1.609 GHz, 2.3 GW microwave can be generated when the diode voltage is 890 kV and the beam current is 7.7 kA. The corresponding power efficiency reaches 33.6%. [ABSTRACT FROM AUTHOR]