However, the efficiency of these devices is usually limited to 1520% when a homogeneous slowwave structure is used. The bwos will be used by the national aeronautics and space administration as local oscillator sources in heterodyne receivers for lowbackground astronomy observations and remote sensing. A travelingwave tube twt, pronounced twit or travelingwave tube amplifier twta, pronounced tweeta is a specialized vacuum tube that is used in electronics to amplify radio frequency rf signals in the microwave range. Backward wave oscillator article about backward wave. Study of multiple beam backward wave oscillator based on. Terahertz backward wave oscillator circuits university of utah. Backward wave oscillator model for chorus generation is tested by cluster data chorus elements are formed for large excess over the linear generation threshold the. Backward wave oscillator basics, structure, working and. It generates oscillations traveling in an opposite direction to. The results of the experiments and modeling demonstrate that overmoded electrodynamic structures can be used to decrease internal electric. A backward wave oscillator bwo, also called carcinotron a trade name for tubes manufactured by csf, now thales or backward wave tube, is a vacuum tube that is used to generate microwaves up to. It is an oscillator with a wide electronic tuning range 9. Metamaterialbased multibeam backward wave oscillator. An analytical and numerical study of backward wave oscillator bwo in linear regime is presented to get an insight into the excitation of electromagnetic waves as a result of the interaction of the relativistic electron beam with a slow wave structure.
Backward wave oscillators bwos are otype, cerenkov radiation based, high power. Backward wave oscillator vs twtdifference between bwo and. This letter presents the theory describing the dispersion properties of such a waveguide and the linear beamwave interaction. Dispersion equation, gain, effects of nonsynchronism, space charge, and loss in a slow. Based on a numerical solution of the equations of the nonstationary nonlinear theory, we study chaotic selfoscillation regimes in a backwardwave oscillator. Their prototype was completed and demonstrated successfully on august.
A gyrobwo is an oscillator that functions analogously to a backward wave oscillator bwo. We have recently made some measurements of the voltage distribution along the slowwave circuit of our travellingwavetube analogue, operated as a. Index terms backwardwave oscillator bwo, highpower microwave hpm, overmoded. Chu2 1physics division, national center for theoretical sciences, hsinchu, taiwan 2department of physics, national tsing hua university, hsinchu 300, taiwan 3department of physics, national changhua university of education, changhua, taiwan. Metamaterialbased multibeam backward wave oscillator 1 hamide seidfaraji university of new mexico may 05, 2017. Relativistic backward wave oscillator how is relativistic backward wave oscillator abbreviated. The backtvardwave oscillator the operation of the backnardna,ve oscillator may be understood in terms of the coupling of the slow space charge wave and the backward circuit wave. Progress in theoretical design and numerical simulation of. Bwos generate microwaves from noise when the beam current exceeds the start current.
A 200 to 250 ghz version was designed and built figure 4 using aluminum metalization for crystalline quartz with no etching of the quartz. When the axial magnetic field is used in these devices to confine the electron beam satisfies the condition of cyclotron resonance there is a significant. A gyrotron backward wave oscillator gyrobwo with a helically corrugated interaction waveguide demonstrated its potential as a powerful microwave source with high ef. To enhance the bwo output power, many swss have been. An analytical and numerical study of backward wave oscillator bwo in linear regime is presented to get an insight into the excitation of electromagnetic waves as a result of the interaction of. However, 2d pic simulations cannot reveal the effect of asymmetric modes on beamwave interaction. Development of backward wave oscillators for terahertz. A multimode theory of the resonant backwardwave oscillator bwo with an electron beam inclined with respect to the surface of a periodic structurea clinotronis presented.
For a backwardwave opo,6,7 the forward components include a pump laser and a lowfrequency output wave, and the backward component is another lowfrequency. In order to investigate whether asymmetric mode competition needs to. Each source includes a submm wave bwo backeward wave oscillator tube and a specially designed permanent magnet. A conceptual design of a high efficiency sband backwardwave oscillator driven by a 500 kv, 5 ka electron beam has been developed and analyzed. Two examples of slowwave circuit characteristics are shown, in the. Backwardwave oscillators driven by high current relativistic electron beams are capable of producing high power coherent radiation in the ceentimeter and millimeter wavelength regimes. Linear theory of plasma filled backward wave oscillator. Theoretical and experimental investigations of the. Insight product company offers submm wave sources from 179 ghz to 1250 ghz. The effect of background plasma on the bwo instability is also presented. The linear and nonlinear theory of backwardwave oscillators bwos is developed taking into account reflection of the electromagnetic wave at the boundaries of the slow wave structure. Ccr is developing advanced backward wave oscillators bw0s operating from 300 ghz to more than 1 thz.
Utilizing a twosection slow wave structure, where the spatial period of the second section is larger than that of the first section, a bwo efficiency of greater than 50% was calculated. Backward wave oscillator how is backward wave oscillator. Unlike a forward phasematched distributedfeedback optical parametric oscillator, a backward oscillator of this type can have highthreshold gap modes at bragg resonance and lowthreshold detuned modes. The backwardwave oscillator the backwardwave oscillator bwo is a microwavefrequency, velocitymodulated tube that operates on the same principle as the twt. Most of the investigated overmoded relativistic backward wave oscillators rbwos are azimuthally symmetric. It is applied to explain the slipping stream, or diocotron, effect as a coupling of two surface waves of the electron beam, and to derive the start oscillation conditions of the mtype backward wave oscillator. For a backwardtraveling wave tube or a gyrotron backwardwave oscillator,4,5 the forward pump is an electron beam and the backward signal is a microwave. The gap between the cathode and the disc can be varied from 6 to 12 mm. The theory is basic to the understanding of the small signal behavior of crossed field electron devices. Design of terahertzwave transmission imaging system. The inital experimental results produced an 800 ghz signal as the secondharmonic frequency of the backwardwave oscillator.
Experimental studies of overmoded relativistic backward. Development of a 2 mw relativistic backward wave oscillator. Belonging to the travelingwave tube family, it is an oscillator with a wide electronic tuning range. This bwo is designed to operate at the frequency of 3451 ghz with. For weak chaos, arising via a perioddoubling cascade of selfmodulation for moderate values of the normalizedlength parameter, and for developed chaos, which corresponds to large values of this parameter, we. Highefficiency relativistic backwardwave oscillator. Enhancement of twto efficiency velocity tapering, depressed collectors basic characteristics and applications of nonrelativistic twtos. Sweep oscillator model 8690, operating and service manual, palo alto, u. As shown in the given diagram, the backward wave oscillator is made of tube in which heater, cathode, helix, feedback conductor and focusing electrodes and anode is located. It sustains the oscillations by propagating a traveling wave backwards against the beam.
Studies of relativistic backwardwave oscillator operation. It is an oscillator with a wide electronic tuning range. It was invented by the brothers russell and sigurd varian at stanford university. Pdf backward wave oscillator for high power generation at thz. The bwos or carcinotrons are also twt type of oscillators in which they interact with an em wave supported by the structure as shown in the figure. Find backwardwave oscillator related suppliers, manufacturers, products and specifications on globalspec a trusted source of backwardwave oscillator information. As we know slow wave structure is the heart of bwo. Backwardwave oscillator article about backwardwave. An electronic device which amplifies microwave signals simultaneously over a wide band of frequencies and in which the traveling wave produced is. Plasma oscillations and radio noise from the disturbed sun. The system software based on the oscilloscope is designed to control the object movement, and the capture and display of the continuous thz. Pdf the linear and nonlinear theory of backwardwave oscillators bwos is developed taking into account reflection of the electromagnetic wave at the.
X backward circuit wave is one whose group velocity or direction of energy flow is in the opposite direction from the phase velocity. Hummelt, high power microwave generation using an active metamaterial powered by an electron beam, ph. A coupled mode description of the backward wave oscillator and. An electron gun generates an electron beam that interacts with a slowwave structure. We derive a coupledwave theory for backward phasematched optical parametric amplifiers and oscillators in a dielectric modulated nonlinear optical material. This letter presents the theory describing the dispersion properties of such a waveguide and the linear beam wave interaction. Theory of backward distributedfeedback optical parametric. The waveguide cavity resonator is used for the input trigger known as buncher cavity resonator. Rise and fall time behavior of the gyrotron backwardwave oscillator k. They allow users to control frequency in a very wide band and with extremely high.
When electrons are moving through a slowwave structure, electron bunches form since there is a feedback mechanism and beam wave synchronism wave phase velocity and electron beam velocity must be close. The generated electromagnetic wave power has its group velocity dire. In a backward wave oscillator bwo or a traveling wave tube twt, the electric field traveling in the waveguide interacts with an electron beam grazing or piercing the electric field of a slow wave circuit and transfers energy from the beam to the circuit mode. Offered sources wide banded, reliable, small sized, powerful and easy to operate. In the electron gun, current is drawn from the cathode when the accelerator. The twt belongs to a category of linear beam tubes, such as the klystron, in which the radio wave is amplified by absorbing power from a. Pdf linear theory of plasma filled backward wave oscillator. Find out information about backward wave oscillator. The carcinotron is an mtype backwardwave oscillator in which the electron stream traverses the tube and interacts with the fields on the slowwave structure under conditions where the electric and magnetic fields are perpendicular to each other. In this video, i have explained backward wave oscillator with following topics. The theory of backwardwave interaction closely parallels that given for the travelingwave amplifier in section 10. A backward wave oscillator bwo, also called carcinotron a trade name for tubes manufactured by csf, now thales or backward wave tube, is a vacuum tube that is used to generate microwaves up to the terahertz range. Novel concepts for slow wave structures used in high power. An imaging system based on the transmission and reflection modes in the terahertz thz region is developed by using a backwardwave oscillator bwo as source, a golaycell as detector, and an oscilloscope as data acquisition unit.
A gyrotron backward wave oscillator gyrobwo with a helically corrugated interaction waveguide demonstrated its potential as a powerful microwave source with high efficiency and a wide frequency tuning range. Microwave sources based on backwardwave oscillators bwos driven by relativistic electron beams are capable of producing high power coherent radiation in the cm and mm wavelength region. The use of mtms for designing hpmgenerating veds has been reported in the literature. Osa theory of backward distributedfeedback optical.
Theory and simulations of a gyrotron backward wave. For a backwardwave opo,6,7 the forward components include a pump laser and a lowfrequency output wave, and the backward component is another lowfrequency output wave. A backward wave oscillator, also called carcinotron or backward wave tube, is a vacuum tube that is used to generate microwaves up to the terahertz range. In a backward wave oscillator bwo or a traveling wave tube twt, the electric field traveling in the waveguide interacts with an. Backwardwave oscillator based on veds, generates electron beams that interacts with a slowwave structuresws, is a kind of wonderfully and widely investigated sources at terahertz band2. When the electron beam is surrounded by an electromagnetic circuit, such as a helix, which supports a wave whose velocity is nearly equal to the phase velocity. Rise and fall time behavior of the gyrotron backwardwave. Relativistic backward wave oscillator listed as rbwo. The klystron was the first significantly powerful source of radio waves in the microwave range. It has a slow wave structure similar to a twt paralleling the beam, with the input microwave signal applied to the upstream end and the amplified output signal taken from the downstream end. Theory of multimode resonant backwardwave oscillator with.
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