A klystron tube makes use of speedcontrolled streams of electrons that pass through a resonating cavity. It focuses on the needs of students who take up the subject at undergraduate and postgraduate levels selection from microwave and radar engineering book. The first reflex klystron is believed to be the one designed in 1940 by robert sutton of the signal. To study the characteristics of the reflex klystron tube and to determine its electronic tuning range. It was used as a local oscillator in some radar receivers and a modulator in microwave transmitters the 1950s and 1960s, but is now obsolete, replaced by semiconductor microwave devices. The buncher needs to be critically matched to the rf source at the working frequency. Jan 16, 2017 a klystron is a specialized linearbeam vacuum tube, invented in 1937 by american electrical engineers russell and sigurd varian, which is used as an amplifier for high radio frequencies, from uhf up into the microwave range. When the bunching process occurs the electrons lose kinetic energy. What are the limitations of conventional tubes at microwave frequencies. Velocity modulation, power output and efficiency, electronic admittance, mode patterns. Microwave engineering reflex klystron tutorialspoint.
Cavity of a repeller klystron another tube based on velocity modulation, and used to generate microwave energy, is the reflex klystron repeller klystron. Other articles where twocavity klystron is discussed. A reflex klystron is a specialized low power vacuum tube used to produce oscillations at microwave frequency. Typical operational problems with a klystron input drive power is too low and klystron is not saturated although this is required if the tube is included in a feedback loop reduced output power, efficiency, and increased output power amplitude jitter wrong cathode filament current wrong perveance. Now, let us see bunching process and the modes and reflex klystron, this vertical axis. Increasing klystron efficiency using com and bac tuning and application to the 5045 klystron aaron jensen, andy haase, erik jongewaard, mark kemp and jeff neilson technology and innovation directorate slac national accelerator laboratory menlo park, ca, usa, 94025 abstract. Reflex klystron consists of an electron gun, a cathode filament, an anode cavity, and an electrode at the cathode potential. What is a klystron amplifier, types, differences and their.
The bunching parameters measure deviations of the multiplicity distribution from a poisson distribution, since for this distribution. Determine the amplification process in helix traveling wave tube twt. What are the performance characteristics of a klystron amplifier. The reflex klystron is a singlecavity klystron that overcomes the disadvantages of the. As shown electron beam is generated by electron gun which passes through the space between input cavity i. Determine the beam current density in multi cavity klystron amplifiers 11. Which is impossible and not feasible to use other components for this purpose. Microwave engineering cavity klystron for the generation and amplification of microwaves, there is a need of some special tubes called as microwave tubes. Revathi klystron power supply reflex klystron isolator frequency meter detector mount c. The reflex klystron contains a reflector plate, referred to as the. Reflex klystron oscillators ieee xplore a reflex klystron oscillator. The dependence of the peak ac breakdown voltage v b ac on the dspacing of planeparallel gaps has been investigated by hackam and altcheh 53, 66 for a range of materials, including aluminium, copper, nickel, niobium and sterling silver.
Now, let us see bunching process and the modes and reflex klystron, this vertical axis represent the distance from the cavity gap towards the repeller plate, and this. The loss of kinetic energy is thus transferred to the cavity to conserve total power. Klystron tube article about klystron tube by the free. From each mode and the band of frequencies over which the circuit can be tuned. A method to achieve spatial bunching on the double frequency of the induced energy spread in an optical klystron is described. This microwave generator, is a klystron that works on reflections and oscillations in a single cavity, which has a variable frequency.
In wikipedia it says that, the electrons are fired into one end of the tube by an electron gun. Important question and answers on reflex klystron with. Slow wave structures, traveling wave tube, amplification process, wave modes, gain considerations. The process can be repeated by including more cavities, until considerable amplification takes place, or until the increased space charge within the bunches prevents tighter bunching. The reflex klystron contains a reflector plate, referred to as the repeller, instead of the output cavity used in other types of klystrons. Two cavity klystron amplifier is not lownoise device. The klystron was invented at stanford university in 1937 and originally used as the oscillator in radar receivers during world war ii. This klystron is totally dissimilar from cavity klystron because it has a single cavity and used for modulation otherwise demodulation. And that time is t d at time t d all electrons bunched at the center of cavity gap. If the power delivered by bunching process by the bunched electrons to cavity is greater. Its principle of operation is velocity and current modulation. Microwave engineering kg reddy college of engineering. Reflex klystron free download as powerpoint presentation. Reflex klystron working free download as powerpoint presentation.
How are oscillations produced in a reflex klystron. A klystron is a specialized linearbeam vacuum tube, invented in 1937 by american electrical engineers russell and sigurd varian, which is used as an amplifier for high radio frequencies, from uhf up into the microwave range. Reflex klystron telecommunications engineering mechanics. In statistics as applied in particular in particle physics, when fluctuations of some observables are measured, it is convenient to transform the multiplicity distribution to the bunching parameters. Microwave and radar engineering presents the essential features of microwave and radar engineering. Knowing the maximum voltage of two adjacent modes, mode number can be computed using the relation prepared by m. Uncorrelated particle production leads to the poisson statistics, thus deviations of the bunching parameters from the poisson values mean correlations between particles and.
The reflex klystron also known as a sutton tube after one of its inventors, robert sutton was a low power klystron tube with a single cavity, which functioned as an oscillator. A carbon nanotube cold cathode is employed to produce the required beam current. Construction a reflex klystron consists of an electron gun, a cavity with a pair of grids and a repeller plate as shown in the above diagram. In this klystron, a single pair of grids does the functions of both the buncher and the catcher grids. Rv latham, in high voltage vacuum insulation, 1995. Pdf injectionbunching section design of a submillimetric. The design of the injection and bunching section for a submillimetric klystron is described in this paper. So, this is how electrons move in this reflex klystron tube. The reflex klystron another tube based on velocity modulation, and used to generate microwave energy, is the reflex klystron figure 29. The reflex klystron operates in a different mode for each additional cycle that the electrons remain in the repeller field. How is tuning achieved in reflex klystron oscillators. A reflex klystron is an obsolete type in which the electron beam was reflected back. Mode 1 is obtained when the repeller voltage produces an electron transit time of 34 cycle. The reflex klystron has been the most used source of microwave power in laboratory applications.
Operative principles comsol conference 2015 grenoble multiphysics design of a klystron buncher dc beam from gun modulated beam. These electron c to d are confined to focused spokes and terminated to the alternate node. In this article, well learn about the twocavity klystron s unique build and the concept of electron bunching. It was found that, as with the dc experiments, there is a clear transition between the smallgap and largegap behaviour, being particularly marked with.
Microwave engineering cavity klystron tutorialspoint. Klystron multi cavity klystron, reflex klystron, working. The name of this klystron is taken due to its reflex act of electron beam. My apologies for the long answer but this is a complicated bit of technology and needs an appreciation of the physics behind it. A reflex klystron consists of an electron gun, a cavity with a pair of grids and a repeller plate as shown in the above diagram. Inspire your inbox sign up for daily fun facts about this day in history, updates, and special offers. The dependence of these characteristics on the beam current, beam voltage, re flector voltage, load, and other klystron design factors. Additional cavities serve to velocitymodulate the electron beam and produce an increase in the energy available at the output.
The reflex version of the klystron, perfected at sperry and. Electrons in a klystron are accelerated to a controlled speed by the application of several hundred volts. Sep 27, 2017 in this video, i have explained reflex klystron with following points 1. The rf signal to be amplified is coupled to input cavity. Slacpub16466 increasing klystron efficiency using com.
Second order bunching in an optical klystron sciencedirect. As shown in the given diagram it is composed of heater, cathode, focusing electrodes and repeller anode. A small hole in the broad wall of the waveguide is provided, through which output coupling pin of klystron tube enters into the waveguide. So, this is how oscillations are sustained in the reflex klystron by to and fro movement of electrons from cavity to repeller space. There are many practical devices, such as magnetrons, klystrons, vacuum switches and high voltage electronic rectifiers 103107, where it is necessary to use the insulating capability of vacuum for holding off timedependent voltages.
I have a doubt on how exactly a reflex klystron worksas an rf source. Characteristics of a reflectiontype microwave modulator. Explain the bunching process of a twocavity klystron and derive the expression for. What is a klystron amplifier, types, differences and their applications. Bunching occurs in the drift space, from the cavity to the vicinity of the repeller and back to resonator. In the output catcher cavity, each bunch enters the cavity at the time in the cycle. After the focusing electrodes there is a cavity resonator which encircles the glass envelope. Archived from the original pdf on september 24, 2015. In this video, i have explained reflex klystron with following points 1. A microwave source of surprising range and endurance george caryotakis stanford linear accelerator center, stanford university, stanford ca 94309 abstract this year marks the 60th anniversary of the birth of the klystron at stanford university. Klystrons are basically specialized tubes used as amplifiers and oscillators at microwave frequency range. This name is given by the name of its inventor robert sutton, it allow the passage of electron beam through a single resonant cavity. A reflex klystron achieves the same bunching by causing the beam to reverse. Mar 24, 2016 working of reflex klystron oscillator.
Criteria necessary to construct such a second order buncher and the phase space evolution are presented. The velocities of electrons emitted from the cathode are modulated to produce a densitymodulated electron beam. In order to generate microwave frequencies we need amplifiers or oscillators,in this video we will learn how a reflex klystron oscillator works in. The electronic tuning range of the reflex klystron is usually referred to as the variation in frequency between half power pointsthe points in the oscillating mode where the power output is half the maximum output in the mode. What are the assumptions for calculation of rf power in reflex klystron. Reflexklystron oscillators ieee xplore a reflexklystron oscillator.
Thus all these velocity modulated electrons are bunched together. To understand the operation of a reflex klystron i think you need to start with a basic understanding of a tuned circuit made up from a capacitor c and inductor l. It was used as a local oscillator in some radar receivers and a modulator in microwave transmitters the 1950s and 1960s, but is now obsolete, replaced by semiconductor. Dhanalakshmi college of engineering department of ece ec6701 rf and microwave engineering unit 4 part a 1. Reflex klystron used as a lowpower microwave oscillator 2. 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. From each mode and the band of frequencies over which the circuit can be. Pdf optimization of micromachined reflex klystrons for operation. Now understand the concept of reflex klystron in microwave engineering in details through following questions and answers. Reflex klystron working, oscillator and applegate diagram. This places an upper limit on the efficiency of the device.
The reflex klystron is an oscillator with a built in feedback mechanism. Understand the velocity modulation process and power output in reflex klystron 12. The main difference between two cavity reflex klystron amplifier. Another tube based on velocity modulation, and used to generate microwave energy, is the reflex klystron figure 29. Dhanalakshmi college of engineering department of ece. Increasing klystron efficiency using com and bac tuning and application to the 5045 klystron aaron jensen, andy haase, erik jongewaard, mark kemp and jeff neilson. As a result the bunch of electrons will be formed near the buncher cavity. It focuses on the needs of students who take up the subject at undergraduate and postgraduate levels of electronics and communications engineering courses. This type of klystron is mostly used for the purpose of amplification of microwave length of frequencies. The speed of electrons will be controlled by the bunching cavities so that they can enter in bunches at. Klystron power supply, klystron tube, isolator, frequency meter, variable attenuator, detector mount, waveguide stand, vswr meter and bnc cable. It is known by this name due to its reflex action of electron beam. All these components are enclosed in a glass envelope.
Fmt has studied using simulation codes the resonant bunching process which gives rise to high current densities 0. The bunching parameters measure deviations of the multiplicity distribution from a poisson distribution. The reflex klystron makes use of velocity modulation to transform a continuous electron beam into. And this is how the bunching process occurs in the klystron tube. Bunching process bunching process is called phase focusing effect. Explain the bunching process of a twocavity klystron and derive the expression for bunching parameter. Modern semiconductor technology has effectively replaced the reflex klystron in most applications. Bunching of electrons is clearly visible in the central region. The difference between reflex and twomulti cavity klystron is that, reflex klystron uses single cavity for modulationdemodulation. Klystrons, velocity modulation process, bunching process, output power and beam loading. Slacpub16466 increasing klystron efficiency using com and. This type of a klystron is called a reflex klystron because of the reflex action of the electron beam. A klystron is a specialized linearbeam vacuum tube, invented in 1937 by american electrical.
Klystron amplifiers are used in a variety of industries, including satellite systems, television broadcasting, radar, particle accelerators, and in the medical field. In klystron, each cavity operates independently and there is no mutual coupling. To study the mode characteristics of the reflex klystron tube and to determine its electronic tuning range. In this klystron, a single pair of grids does the functions of both the buncher and the. In order to generate microwave frequencies we need amplifiers or oscillators, in this video we will learn how a reflex klystron oscillator works in. Following are the benefits or advantages of klystron.