As shown in the given diagram. The multi cavity klystron consist of a glass envelope in which there is an electron gun composed of heater and cathode. Jump to Reflex klystron - The reflex klystron (also known as a Sutton tube after one of its inventors, Robert Sutton) was a low power klystron tube with a  ‎History · ‎Operation · ‎Two-cavity klystron · ‎Tuning. This microwave generator, is a Klystron that works on reflections and oscillations in a single cavity, which has a variable frequency. Reflex Klystron consists of an electron gun, a cathode filament, an anode cavity, and an electrode at the cathode potential. The electron gun emits.


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When used as an amplifier, the weak microwave signal to be amplified is applied to the buncher cavity through a coaxial cable or waveguide, and the amplified signal is extracted from the catcher cavity.

At one end of the tube is the hot cathode which reflex klystron tube electrons when heated by a filament.


The electrons are attracted to and pass through an anode cylinder at a high positive potential; the cathode and anode act as an electron gun to produce a high velocity stream of electrons. An external electromagnet winding creates a longitudinal magnetic field along the beam reflex klystron tube which prevents the beam from spreading.

The beam first passes through the "buncher" cavity reflex klystron tube, through grids attached to each side. The buncher grids have an oscillating AC potential across them, produced by standing wave oscillations within the cavity, excited by the input signal at the cavity's resonant frequency applied by a coaxial cable or waveguide.

The direction of the field between the grids changes twice per cycle of the input signal.

Microwave Engineering Reflex Klystron

Electrons entering when the entrance reflex klystron tube is negative and the exit grid is positive encounter an electric field in the same direction as their motion, and are accelerated by the field. Electrons entering a half-cycle later, when the polarity is opposite, encounter an electric field which opposes their motion, and are decelerated.

Beyond the buncher grids is a space called the drift space. This space is long enough so that the accelerated electrons catch up with electrons that were accelerated at an earlier time, forming "bunches" longitudinally along the beam axis. reflex klystron tube


Its length is chosen to allow maximum bunching at the resonant frequency, and may be several feet long. Klystron oscillator from The electron gun is on the right, the collector on the left.

The two cavity resonators are in center, linked by a short coaxial cable to provide positive feedback. The electrons then pass through reflex klystron tube second cavity, called the "catcher", through a similar pair of grids reflex klystron tube each side of the cavity.

The function of the catcher grids is to absorb energy from the electron beam. The bunches of electrons passing through excite standing waves in the cavity, which has the same resonant frequency as the buncher cavity.

Radar Basics - Klystron Amplifier

Each bunch of electrons passes between the grids at a point in the cycle when the exit grid is negative with respect to the entrance grid, so the electric field in the reflex klystron tube between the grids opposes the electrons motion.

The electrons thus do work on the electric field, and are decelerated, their kinetic energy is converted to electric potential energyincreasing the amplitude of the oscillating electric field in the cavity. Thus the oscillating field in the catcher cavity is an amplified copy of reflex klystron tube signal applied to the buncher cavity.

The amplified signal is extracted from the catcher cavity through a coaxial cable or waveguide. After passing through the catcher and giving up its energy, the lower energy electron beam is absorbed by a "collector" electrode, a second anode which is kept at a small positive voltage.

Klystron oscillator[ edit ] An electronic oscillator can be made from a klystron tube, by providing a feedback path reflex klystron tube output to input by connecting the "catcher" and "buncher" cavities with a coaxial cable or waveguide.

Klystron - Wikipedia

When the device is turned on, electronic noise in the cavity is amplified by the tube and fed back from the output catcher to the buncher cavity to be amplified again. Because of the high Q of the cavities, reflex klystron tube signal quickly becomes a sine wave at the resonant frequency of the cavities.

A high positive voltage is connected to the resonant toroidal cavity and the accelerating electrodes made from a mesh that allows the accelerated electrons reflex klystron tube pass through them.


The electric field due to the accelerating mesh acts on all electrons to produce an approximately constant speed. HOWEVER reflex klystron tube the uniform speed electron beam passes through the 'capacitor' part of the toroidal cavity they experience a time varying electric field along the direction of travel.

This causes some of the electrons to speed up when the field is in one direction and to slow down when reflex klystron tube in the other direction.

Microwave Engineering - Reflex Klystron

This produces a pulsed current at the resonant frequency of the cavity. The process is referred to as 'modulation'. But how does it all get started?

  • Rf - How Reflex Klystron works - Electrical Engineering Stack Exchange
  • Construction of Reflex Klystron