Pdf relativistic klystron amplifiers driven by modulated intense. It includes 161hq15963, a special investigation of chavez initiated in 1966 at the behest of the white house. The next step is to take useful power from the beam. These will set up a field in the third cavity, which produces more concentrated bunches and so on. Reflex klystron is also known as a sutton klystron. Their work was preceded by the description of velocity modulation by a. These will set up a field in the third cavity, which produces more concentrated bunches and. Understand the velocity modulation process and power output in reflex klystron 12. Two cavity klystron amplifiers working, amplification and applegate diagram by engineering funda duration.
In a multi cavity klystron each of the intermediate cavities, placed at a distance of the bunching parameter x of 1. Velocity modulation definition of velocity modulation at. Reflex klystron working, oscillator and applegate diagram. Why is pulse modulation required in reflex klystron. However, it is sometimes desirable to vary the klystron power output for a given bea. Determine the beam current density in multi cavity klystron amplifiers 11. The net effect of velocity modulation is to form a currentdensity modulated beam that varies at the same rate as the gridsignal frequency. To understand the impact of the current modulation in a klystron, we have to understand both the mechanism. Klystron is a vacuum tube that uses a microwave resonant cavity to produce a modulation change the velocity of the electron beam and lead to the reinforcement.
After the electron gun there are two focusing electrodes used to keep the electron beam in the center around the glass envelope. A 2cavity klystron amplifier has accelerating voltage volt and frequency 5 ghz and cavity gap 1 mm. The reflex klystron another tube based on velocity modulation, and used to generate microwave energy, is the reflex klystron figure 29. Microwave engineering cavity klystron for the generation and amplification of microwaves, there is a need of some special tubes called as microwave tubes. Klystrons velocity modulation tubes the klystron has been invented in late 30s by hansen and varian bros. Velocity modulation process in two cavity klystrons.
This name is given by the name of its inventor robert sutton, it allow the passage of electron beam through a single resonant cavity. Reflex klystron consists of an electron gun, a cathode filament, an anode cavity, and an electrode at the cathode potential. The difference between reflex and twomulti cavity klystron is that, reflex klystron uses single cavity for modulationdemodulation. Cavity of a repeller klystron another tube based on velocity modulation, and used to generate microwave energy, is the reflex klystron repeller klystron. The reflex klystron makes use of velocity modulation to transform a continuous electron beam into. Explain with schematic diagram the operation of reflex klystron oscillator. Now understand the concept of reflex klystron in microwave engineering in details through following questions and answers. The major difference between klystron and twt is that klystron cavities are replaced by structure of helix shape in twt. Although the planar tube isnt a velocitymodulated tube, it was included into this table for comparison purposes.
Even if magnetron structures were described since the twenties, more serious investigation on velocity modulated or vm tubes started around the second half of the thirties, to overcome the. The operation of reflex klystron is understood by some assumptions. Important question and answers on reflex klystron with. Klystron, thermionic electron tube that generates or amplifies microwaves by controlling the speed of a stream of electrons. Arsenjewaheil and oskar heil wife and husband in 1935, though the varians were probably unaware of the heils work. A klystron is a specialized linearbeam vacuum tube, invented in 1937 by american electrical. This electron beam induces a rf current in this field is opposite to the input cavity. Ultrawideband clusteredcavity klystron springerlink.
This resonant cavity is used to velocity modulate the electron beam and is very similar to the buncher and catcher cavities in the twocavity klystron. This amplitude modulation is generally used along with vswr measurements in slotted line technique. At microwave frequencies, however, the transit time or angle is large compared to the period of the microwave signal, and the potential between the cathode and the. Reflex klystron is a microwave device that works on principle of velocity modulation in addition to current modulation.
Velocity modulation, therefore, lends itself particularly to highfrequency tubes. Velocity modulation is the process that causes the velocity modulated electron and electron would be collected gradually. Electron emitted from the cathode are accelerated and passed through the positive. Hansen was instrumental in the development of the klystron and was cited by the varian brothers in their 1939 paper. They are velocitymodulated tubes that are used in radars as amplifiers or oscillators. Determine the amplification process in helix traveling wave tube twt. The two velocity modulated tubes described in the present chapter, the klystron. The buncher cavity velocity modulates the electron beam. Tv receiver conversion for velocity modulation, april 1951. Interaction in klystron occurs only at the gaps of resonant cavities. The klystron was the first embodiment of the velocity modulation principle. The electrons are originally accelerated to high velocity by a potential of several hundred volts and enter a narrow gap that forms part of a cavity resonator system see. The electron beam is velocity modulated when it first passes through the cavity. Microwave engineering cavity klystron tutorialspoint.
Electron velocity modulation by cavity gap voltage the electrons group in. All these velocity modulated electrons will be repelled back to the cavity by the repeller due to its negative potential. The variation in electron velocity in drift space is called velocity modulation. Unfortunately, however, the term velocity modulation has also gained acceptance in an entirely different sense, as the velocity modulated klystron tube. Klystron multi cavity klystron, reflex klystron, working. Reflex klystron or repeller klystron another tube based on velocity modulation, and used to generate microwave energy, is the reflex klystron repeller klystron.
Let us understand twt and klystron basics before we look into comparison between the two. The electrons that are accelerated by the cathode pulse are acted upon by rf fields developed across the input and middle cavities. How does the reflex klystron differ from amplifier klystron. Velocity modulation definition of velocity modulation by. The electron beam is modulated as it was in the other types of. Basic klystron rf power input rf drive rf power output energy modulation d v z,0, i 0 v z,0, i 1 modulate decelerate v c e z e z velocity bunching beamtube must not propagate the rf backward wave or the tube can oscillate. Pdf an overview is provided for the novel relativistic klystron amplifiers which are. With the signal applied in the first cavity, we get weak bunches in the second cavity.
The reflex klystron makes use of velocity modulation to transform a continuous electron beam into microwave power. The simplest klystron tube is the reflex klystron klystron. Oct 01, 2014 340 microwave linearbeam tubes 0 type chap. Horner kuper klystrons and microwave triodes volume 7 in the massachusetts institute of technology radiation laboratory series dover publications inc. Velocity modulation definition is modification of the velocity of a stream of electrons by imparting alternate accelerations and decelerations to the electrons in such a way that they are caused to bunch together with the result that each bunch causes a cycle of current as it passes an output electrode. This is a set of 5 fbi headquarters files on cesar chavez, founder of the united farm workers ufw union, from 196675. Klystron power supply, klystron tube, isolator, frequency meter, variable attenuator, detector mount, waveguide stand, vswr meter and bnc cable. The output of any klystron regardless of the number of cavities used is developed by velocity modulation of the electron beam. Klystron article about klystron by the free dictionary. The currentmodulated bunched electron beam in figure 26 is shown in various stages of formation and dispersion. Microwave engineering reflex klystron tutorialspoint.
Velocity modulation definition and meaning collins english. Comsol conference 2016 munich multiphysics design of a ghz klystron the analysis follows a multiphysics model approach, in order to prevent alterations of the electromagnetic em behavior, while exposing the device to these multiple physics factors. Klystrons back to main index go to the klystron index. Another tube based on velocity modulation, and used to generate microwave energy, is the reflex klystron repeller klystron. Note in figure that the resonator potential is common to the resonator cavity, the accelerating grid, and the entire body of the tube. To study the characteristics of the reflex klystron tube and to determine its electronic tuning range. Velocity modulation output cavity bandwidth performance cavity chain input. Arsenjewaheil and oskar heil wife and husband in 1935.
Klystrons chapter microwave and rf vacuum electronic. The reflex klystron contains a reflector plate, referred to as the repeller, instead of the output cavity used in other types of klystrons. The multi cavity klystron consist of a glass envelope in which there is an electron gun composed of heater and cathode. The following figure depicts an example of multicavity klystron amplifier. After being accelerated to a nonrelativistic energy in an electrostatic field, a thermoionic beam is velocity modulated crossing the gap of an rf cavity buncher excited by the rf input signal. Explain how velocity modulation creates density modulation in a klystron amplifier. In this video, i have explained reflex klystron with following points 1. The klystron power supply skps610 has built in modulation facilities of amplitude and frequency modulation. Question bank department of electronics and communication.
At higher frequencies and powers it is necessary to modulate the beam in some other way. Experiment4 study of the characteristics of the klystron tube. Amplification of such twocavity klystron is low and hence multicavity klystrons are used. Velocity modulation in klystron amplifier electronics. Other articles where twocavity klystron is discussed. Velocity modulation definition at, a free online dictionary with pronunciation, synonyms and translation. A microwave source of surprising range and endurance pdf. The klystron is the most widely diffused rf source in particle accelerators. B derive an expression for velocity modulation at the input cavity of klystron amplifier. It is known by this name due to its reflex action of electron beam. In the klystron this is achieved by velocity modulation.
In the floating drift klystron, electrons pass successively through the gaps of cavity resonators see figure 1. Draw a schematic diagram of 2cavity klystron amplifier and explain how amplification is achieved. Klystron tube article about klystron tube by the free. In a reflex klystron, a small modulation of the repeller voltage is more often employed to fix the emitted frequency to that of a microwave resonator by a phase locking loop technique. Velocity modulation occurs in the gap of the input resonator, the ultrahighfrequency field in the gap periodically accelerating half a cycle and decelerating half a cycle. Radar, accelerators, uhf television, satellite communications, millimeter wave transmitters. This microwave generator, is a klystron that works on reflections and oscillations in a single cavity, which has a variable frequency. Comsol conference 2015 grenoble multiphysics design of a klystron buncher the analysis follows a multiphysics model approach, in order to prevent alterations of the electromagnetic em behavior, while exposing the device to these multiple physics factors.