This eliminates springfinger contact problems associated with inductiveslug tuners. To study the characteristics of the reflex klystron tube and to determine its electronic tuning range. A klystron in which there is at least one cavity between the input and output cavities, each of which remodulates the beam so that electrons are more closely bunched. A cw klystron operating at 476 mhz has been developed jointly by slac and varian associates. Electrons in a klystron are accelerated to a controlled speed by the application of several hundred volts. In the reflex klystron, the electron beam passes through a single resonant cavity. The heater boils off electrons when heated and the electrons are ejected from the cathode and accelerate towards the anode due to the high dc potential. The klystron was the first embodiment of the velocity modulation principle. Two cavity klystron amplifier full circuit explanation. Design and analysis of rf section and beam wave interaction for c. In this problem the gain of a klystron is proportional to the cavity shunt resistance r sh, while bandwidth proportional to the cavity 1q 0, so that r sh q 0 is a useful figure of merit in describing the effect of the each cavity on the gainbandwidth product of overall amplifier. The two cavity klystron in figure 27a and b may be used either as an oscillator or an amplifier.
The following figure depicts an example of multicavity klystron amplifier. Design study of rf section and cavities for cepc 650 mhz klystron. It also utilizes a collector element at the end of the electron stream. A klystron is a microwave vacuum tube using cavity resonators to produce velocity modulation of the electron beam and produce amplification. Multicavity klystron article about multicavity klystron by. Reflex klystron the analysis of a reflex klystron is similar to that of a twocavity klystron to some extent and is subjected to the following approximations.
Microwave electronics because of the presence of the electron beam, this amplifier periodic structure can propagate both a growing wave and a decaying wave in the direction of electron flow. Secondly, the solidstate switch protects the klystron against arc damage. The gain of both waves can be determined from the prototype of the periodic structure shown in fig. Firstly, as we know that klystrons are used as amplifiers for microwave frequency and conventional vaccum tubes cant be used due to interelectrode capacitance and lead inductance effect,but though microwave signals can be amplified by klystrons is there any limitation to. The reflex klystron is mostly used as a microwave oscillator. The two cavity klystron utilizes an electron source heater, an anode, and a cathode like a conventional vacuum tube.
The difference between reflex and twomulti cavity klystron is that, reflex klystron uses single cavity for modulationdemodulation. Jul 31, 2018 the two cavity klystron utilizes an electron source heater, an anode, and a cathode like a conventional vacuum tube. The electrons are fired into one end of the tube by an electron gun. Although a small deviation has been found in tuning. The simplest klystron tube is the two cavity klystron. The catcher grids are placed along the beam at a point where the bunches are fully formed. They propagate in free space freely means that attenuation in free space is. When switch on the circuit, the electrons starts emitting from the cathode. Diagram of a twocavity klystron, used as an amplifier and rf signal source at microwave frequencies, and also as an oscillator.
It is known by this name due to its reflex action of electron beam. Modeling and design of the thz klystron cavity, bunching grid, repeller and output structure based on silicon technology are. The klystron was the first significantly powerful source of radio waves in the microwave range. Microwave engineering reflex klystron tutorialspoint. Klystron, including the reflex and multicavity klystron. Microwave engineering ece questions and answers page 2. After the electron gun there are two focusing electrodes used to keep the electron beam in the center around the glass envelope. F input signal to the buncher cavity with the help of loop coupling. Microwave engineering cavity klystron tutorialspoint. By lowering the qs of the cavities and by introducing intermediate cavities, wider bandwidth operation can be achieved.
These will set up a field in the third cavity, which produces more concentrated bunches and. With the signal applied in the first cavity, we get weak bunches in the second cavity. 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. It was invented by the brothers russell and sigurd varian at stanford university. Additional cavities serve to velocitymodulate the electron beam and produce an increase in the energy available at the output. The multi cavity klystron consist of a glass envelope in which there is an electron gun composed of heater and cathode. Electrically, the operation of the planar triode is much more complicated at microwave frequencies than at low fre. The reflex klystron contains a reflector plate, referred to as the repeller, instead of the output cavity used in other types of klystrons. Suppression of thirdorder intermodulation in a klystron. Caryotakis, performance of a 150mw sband klystron, aip conf. Slacpub16466 increasing klystron efficiency using com. The velocities of electrons emitted from the cathode are modulated to produce a densitymodulated electron beam. Multicavity klystron amplifiers nippon electric co. On this channel you can get educational video tutorials of all subjects for diploma and engineering electronics students.
Phase space plot of particles for bac design klystron. Multicavity klystron article about multicavity klystron. Firstly, as we know that klystrons are used as amplifiers for microwave frequency and conventional vaccum tubes cant be used due to interelectrode capacitance and lead. A simple resonant circuit which consists of a capacitor and an inductive loop can be compared with this cavity resonator. Microwave engineering ece questions and answers this is the electronics and communication engineering questions and answers section on microwave communication with explanation for various interview, competitive examination and entrance test. Their prototype was completed and demonstrated successfully on august 30, 1937. Other articles where twocavity klystron is discussed.
Design study on the high power klystron for komac hyeokjung kwon1, kangok lee1, hansung kim2, minjoon park2, moonsung chun2, kiehyung chung2, seungjeong noh3 1 korea accelerator and plasma research association, chonan 330825, korea 2dept. The feedback path provides energy of the proper delay and phase relationship to sustain oscillations. Main parameters for bt258a and bt258b rf frequency. Klystron, thermionic electron tube that generates or amplifies microwaves by controlling the speed of a stream of electrons. The twocavity klystron is a widely used microwave amplifier operated by the principles of. Amplification of such two cavity klystron is low and hence multi cavity klystrons are used. A three cavity klystron is illustrated in figure 28. Slacpub16466 increasing klystron efficiency using com and.
A klystron is a specialized linearbeam vacuum tube evacuated electron tube the name klystron comes from the stem form. Klystron tube article about klystron tube by the free. The configuration shown in the figure is correct for oscillator operation. This requires a combination of bandwidth and short group delay within the klystron. The klystron was invented at stanford university in 1937 and originally used as the oscillator in radar receivers during world war ii. The following figure depicts an example of multi cavity klystron amplifier. This section will explain the basic operation of the most widely used microwave tubes, including klystrons, travelingwave tubes, backwardwave oscillators, magnetrons, and crossedfield amplifiers.
Therefore, two cavity klystrons are generally used for fixedfrequency applications. The function of the catcher grids is to absorb energy from the electron beam. An electron in the gap of the input cavity at z 0 is subject to the velocity modulation fig. Bb4c6c from alamys library of millions of high resolution stock photos, illustrations and vectors. The klystron with internal or external feedback built in its design can function as oscillator. Dielectric tuning of klystron cavities springerlink. The l3403 klystron is a fourcavity, modulating anode, pulsed klystron amplifier which can be mechanically tuned to amply any frequency within the range from 400 to 450 mhz. Functional and schematic diagram of a twocavity klystron. A new cold cathode klystron oscillator in the thz range is presented. The two cavity reflex klystron is a widely used microwave amplifier operated. The basic two cavity klystron klystrons are velocitymodulated tubes that are used in radar and communications equipment as oscillators and amplifiers.
These electrons move at a uniform speed towards the anode until they are attracted by it. Introduction to the twocavity klystron amplifier technical. Bunching occurs in the drift space, from the cavity to the vicinity of the repeller and back to resonator. It is different from the two or multi cavity klystron because it uses a single cavity for modulation or demodulation. Klystrons make use of the transittime effect by varying the velocity of an electron beam in much the same manner as the previously discussed velocitymodulation process. The vacuum tube consists of a cathode, which is heated by a filament. Diode drive cavity idler cavities output cavity collector guidefield solenoid. This process continues the transfer of enegy takes place again near the third cavity. In this tube there are two microwave cavity resonators, the catcher and the buncher. The frequency of operation of a klystron is set by the sizes of the input and output cavities. If, on the other hand, free charges are present in the gun volume, the value of c 1 will be changed from the value. F output from the cavity with the help of loop coupling. The location is determined by the transit time of the bunches at the. It is given the name reflex klystron because of its reflex action of electron beam.
An rf signal consisting of an arbitrary number of drive tones, each of independent amplitude and phase, is applied to the input cavity of the klystron. I am reading two cavity klystrons but not able to understand at all. Download download reflex klystron operation pdf read online read online reflex klystron operation pdf. A klystron is a specialized linearbeam vacuum tube, invented in 1937 by american electrical. The invention of the cavity magnetron and its introduction into canada and the usa. The same method has been applied to tuning measurement of a diode pulsed klystron, e3712.
A klystron is basically a vacuum tube with input and output structures replaced with resonant cavities known as buncher cavity and catcher cavity. Phase space plot of particles for com design klystron. Klystron amplification, power output, and efficiency can be greatly improved by the addition of intermediate cavities between the input and output cavities of the basic klystron. The electron beam first passes through a cavity to which the input signal is applied. Typical phase space plot of particles in klystron interaction simulation. The klystron is the ubiquitous source of rf power in accelerators today. In font of cavity resonator a huge crowed of electrons assembles and excites cavity, the oscillation it the cavity takes place and hence we get the r. There are two cavities known as buncher and catcher cavity. Vidyalankar group of educational institutes 1,312 views 8.
After passing through the resonant cavity they are reflected by a negatively charged reflector electrode for another pass through the cavity, where they are then collected. Jun 02, 2014 i am reading two cavity klystrons but not able to understand at all. Klystron multi cavity klystron, reflex klystron, working. A klystron tube makes use of speedcontrolled streams of electrons that pass through a resonating cavity. Klystron vs magnetrondifference between klystron,magnetron. The second cavity was tuned to lower frequency and penultimate cavity to higher frequency than the center frequency for a better efficiency also. Microwave tubes perform the same functions of generation and amplification in the microwave portion of the frequency spectrum that vacuum tubes perform at lower frequencies. 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 figure, where they are acted upon by a radiofrequency field, which causes a bunchingup effect. Reflex klystron telecommunications engineering mechanics. The klystron amplifier comprises an input cavity a plurality of intermediate cavities and an output cavity. The unique set of characteristics of this tube were strongly guided by requirements of the fast feedback necessary to prevent oscillations of the storage ring beams caused by the detuned accelerating cavity. Since all intermediate cavities in a multicavity klystron operate in the same manner, a representative three cavity klystron will be discussed. Tuning measurement of multicavity klystrons in diode mode. The introduction of a high permittivity, lowloss, dielectric material into a klystron cavity provides a means of obtaining large tuning ranges with low power loss.
Difference between two cavity klystron and reflex klystron. Reflex klystron consists of an electron gun, a cathode filament, an anode cavity, and an electrode at the cathode potential. Since all intermediate cavities in a multicavity klystron operate in the same manner, a. Furthermore, no contact is required between the dielectric tuner and the cavity wall. The entire drifttube assembly, the three cavities, and the collector plate of the three cavity klystron are operated at ground potential for. The electron gun emits the electron beam, which passes through the gap in the anode cavity.
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