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Title: Power combination of a self-coherent high power microwave source

Abstract

In our previous work, generating two phase-locked high power microwaves (HPMs) in a single self-coherent HPM device has been demonstrated. In this paper, after optimizing the structure of the previous self-coherent source, we design a power combiner with a folded phase-adjustment waveguide to realize power combination between its two sub-sources. Further particle-in-cell simulation of the combined source shows that when the diode voltage is 687 kV and the axial magnetic field is 0.8 T, a combined output microwave with 3.59 GW and 9.72 GHz is generated. The impedance of the combined device is 36 Ω and the total power conversion efficiency is 28%.

Authors:
; ; ; ;  [1]
  1. College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha 410073 (China)
Publication Date:
OSTI Identifier:
22493774
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 22; Journal Issue: 9; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; EFFICIENCY; ELECTRIC POTENTIAL; ENERGY CONVERSION; GHZ RANGE; MAGNETIC FIELDS; MICROWAVE RADIATION; OPTIMIZATION; PLASMA SIMULATION; WAVEGUIDES

Citation Formats

Yan, Xiaolu, E-mail: yanxl-dut@163.com, Zhang, Xiaoping, Li, Yangmei, Dang, Fangchao, and Zhang, Jun. Power combination of a self-coherent high power microwave source. United States: N. p., 2015. Web. doi:10.1063/1.4930112.
Yan, Xiaolu, E-mail: yanxl-dut@163.com, Zhang, Xiaoping, Li, Yangmei, Dang, Fangchao, & Zhang, Jun. Power combination of a self-coherent high power microwave source. United States. doi:10.1063/1.4930112.
Yan, Xiaolu, E-mail: yanxl-dut@163.com, Zhang, Xiaoping, Li, Yangmei, Dang, Fangchao, and Zhang, Jun. Tue . "Power combination of a self-coherent high power microwave source". United States. doi:10.1063/1.4930112.
@article{osti_22493774,
title = {Power combination of a self-coherent high power microwave source},
author = {Yan, Xiaolu, E-mail: yanxl-dut@163.com and Zhang, Xiaoping and Li, Yangmei and Dang, Fangchao and Zhang, Jun},
abstractNote = {In our previous work, generating two phase-locked high power microwaves (HPMs) in a single self-coherent HPM device has been demonstrated. In this paper, after optimizing the structure of the previous self-coherent source, we design a power combiner with a folded phase-adjustment waveguide to realize power combination between its two sub-sources. Further particle-in-cell simulation of the combined source shows that when the diode voltage is 687 kV and the axial magnetic field is 0.8 T, a combined output microwave with 3.59 GW and 9.72 GHz is generated. The impedance of the combined device is 36 Ω and the total power conversion efficiency is 28%.},
doi = {10.1063/1.4930112},
journal = {Physics of Plasmas},
number = 9,
volume = 22,
place = {United States},
year = {Tue Sep 15 00:00:00 EDT 2015},
month = {Tue Sep 15 00:00:00 EDT 2015}
}
  • In this paper, a compact self-coherent high power microwave source based on dual beams is presented. It consists of a two-cavity triaxial klystron amplifier (TKA) (noted as the outer sub-source below) and a multiwave Cerenkov generators (noted as the inner sub-source) inserted in the TKA's inner conductor. These two sub-sources share a common cathode and the magnetic field. The injected signals to the outer sub-source are leakage microwaves from the inner sub-source through the anode-cathode gap (A-K gap). Particle-in-cell simulation shows that when the diode voltage is 687 kV and the axial magnetic field is 0.8 T, two microwaves with power ofmore » 1.02 GW and 2.65 GW and the same frequency of 9.72 GHz are generated in the inner and the outer sub-source, respectively; the corresponding power efficiencies are 24% and 31%. Two sub-sources reach the phase locking at 23 ns with a phase difference fluctuation within ±3°. The fast and stable phase locking in the voltage ranging from 665 kV to 709 kV further suggests that the proposed source is promising for coherent power combination and to export a higher power of combined microwaves.« less
  • The new coaxial high power microwave source based on dual beams has demonstrated two phase-locked output microwave beams generated by its two sub-sources. In order to achieve a single higher output power, we present a three-port waveguide-based power combiner to combine the two microwave beams. Particle-in-cell simulation results show that when the diode voltage is 675 kV and the guiding magnetic field is 0.8 T, a combined microwave with an average power of about 4.0 GW and a frequency of 9.74 GHz is generated; the corresponding power conversion efficiency is 29%. The combination effect of the combiner is further validated in the diodemore » voltage range from 675 kV to 755 kV as well as in the pulse regime. The simulations indicate that the maximum surface axial electric field strength of the electrodynamic structure is 720 kV/cm, which is relatively low corresponding to an output power of 4.0 GW. The stable combined output suggests the probability of long-pulse operation for the combined source.« less
  • This paper presents an explanation of the influence of a microwave falling edge on high-power microwave pulse combination. Through particle-in-cell simulations, we discover that the falling edge is the driving factor that limits the output power of the combined pulses. We demonstrate that the space charge field, which accumulates to become comparable to the E-field at the falling edge of the former pulse, will trap the electrons in the gas layer and decrease its energy to attain a high ionization rate. Hence, avalanche discharge, caused by trapped electrons, makes the plasma density to approach the critical density and cuts offmore » the latter microwave pulse. An X-band combination experiment is conducted with different pulse intervals. This experiment confirms that the high density plasma induced by the falling edge can cut off the latter pulse, and that the time required for plasma recombination in the transmission channel is several microseconds. To ensure a high output power for combined pulses, the latter pulse should be moved ahead of the falling edge of the former one, and consequently, a beat wave with high peak power becomes the output by adding two pulses with normal amplitudes.« less
  • The formation of an oscillating virtual cathode by a relativistic electron beam and the subsequent generation of coherent microwaves are investigated. If the electron beam is of high quality, the microwaves excited in a cylindrical waveguide are found to occupy a very narrow band (..delta omega../..omega..approx.5%) primarily in a single transverse magnetic mode. Furthermore, the efficiency of microwave production is demonstrated in our computer simulations to be as high as 20%. It is also shown quantitatively that the efficiency decreases monotonically as the mean scattering angle of the electron beam increases.
  • The optical guiding of an intense electromagnetic wave is demonstrated with the use of high power microwaves in a preformed plasma density channel. The high power microwaves make a duct into the overdense area by the ponderomotive force in a preformed density channel and are guided along the duct to remain within it. The parametric dependencies are investigated to be compared with the results obtained from numerical calculation, showing fairly good coincidence. {copyright} {ital 1996 The American Physical Society.}