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Basic info - Mode Characteristics of Reflex Klystron

Raaghavan Krishnamurthy
Written by Raaghavan Krishnamurthy. Posted in Engineering on 07 October 2009.
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1. What is klystron?

A klystron is a specialized linear-beam vacuum tube (evacuated electron tube). Klystrons are used as amplifiers at microwave and radio frequencies to produce both low-power reference signals for superheterodyne radar receivers and to produce high-power carrier waves for communications and the driving force for modern particle accelerators.

2. What are the advantages of klystron amplifiers?

Klystron amplifiers have the advantage (over the magnetron) of coherently amplifying a reference signal so its output may be precisely controlled in amplitude, frequency and phase.

3. What is Traveling-Wave Tube ?

The traveling-wave tube (twt) is a high-gain, low-noise, wide-bandwidth microwave amplifier. It is capable of gains greater than 40 dB with bandwidths exceeding an octave. (A bandwidth of 1 octave is one in which the upper frequency is twice the lower frequency.). The twt is primarily a voltage amplifier.

4. What is Backward-Wave Oscillator ?

The backward-wave oscillator (bwo) is a microwave-frequency, velocity-modulated tube that operates on the same principle as the twt. However, a traveling wave that moves from the electron gun end of the tube toward the collector is not used in the bwo. Instead, the bwo extracts energy from the electron. beam by using a backward wave that travels from the collector toward the electron gun (cathode).

5. What is magnetron?

The magnetronis a self-contained microwave oscillator that operates differently from the linear-beam tubes, such as the twt and the klystron.. crossed-electron and magnetic fields are used in the magnetron to produce the high-power output required in radar and communications equipment.

6. State the law of motion of electron in an electric field.

The law governing the motion of an electron in an electric field (E field) states: The force exerted by an electric field on an electron is proportional to the strength of the field. Electrons tend to move from a point of negative potential toward a positive potential

7. State the law of motion of an electron in a magnetic field.

The law of motion of an electron in a magnetic field (H field) states: The force exerted on an electron in a magnetic field is at right angles to both the field and the path of the electron. The direction of the force is such that the electron trajectories are clockwise when viewed in the direction of the magnetic field.

8.What is negative-resistance magnetron oscillator?

A negative-resistance magnetron oscillator is operated by a static negative resistance between its electrodes. This oscillator has a frequency equal to the frequency of the tuned circuit connected to the tube.

9. What is an electron-resonance magnetron oscillator?

An electron-resonance magnetron oscillator is operated by the electron transit time required for electrons to travel from cathode to plate. This oscillator is capable of generating very large peak power outputs at frequencies in the thousands of megahertz.

10. What is the primary difference in construction between the basic magnetron and the negative-resistance magnetron?

The negative-resistance magnetron has a split plate.

11. Why is the negative-resistance magnetron often operated with reduced filament voltage?

To reduce the effects of filament bombardment.

12. How are the input and output directional couplers in a twt connected to the helix?

The directional couplers are not physically connected to the helix.

13. What relationship must exist between the electron beam and the traveling wave for bunching to occur in the electron beam of a twt?

The traveling wave must have a forward velocity equal to or less than the speed of the electrons in the beam

14.What is the primary use of the twt?

Voltage amplification.

15.The magnet surrounding the body of a twt serves what purpose?

Used to focus the electrons into a tight beam.

16.What serves as a grid in a magnetron?

A magnetic field serves as a grid in a magnetron.

17. A cylindrical copper block with resonant cavities around the circumference is used as what component of a magnetron?

Anode or plate.

18.What controls the output frequency of a magnetron?

The resonant cavities controls the output frequency of a magnetron.

19.What element in the magnetron causes the curved path of electron flow?

The permanent magnet in the magnetron causes the curved path of electron flow.

20. What is the term used to identify the amount of field strength required to cause the electrons to just miss the plate and return to the filament in a circular orbit?

The critical value of field strength.

21. What can be added to the basic two-cavity klystron to increase the amount   of  velocity modulation and the power output?

Intermediate cavities between the input and output cavities.

22.How is a beam of electrons velocity-modulated?

By alternately speeding up or slowing down the electrons.

23.The cavities of a multicavity klystron are tuned to slightly different frequencies in what method of tuning?

Stagger tuning.  

24.In a multicavity klystron, tuning all the cavities to the same frequency has what effect on the bandwidth of the tube?
The bandwidth decreases.

25. What will be the effect upon an electron traveling in the opposite direction to the lines of force in an electrostatic field?

The electron will be accelerated.

26. How is the electron beam of a three-cavity klystron accelerated toward the drift tube?

A large negative pulse is applied to the cathode.


Raaghavan Krishnamurthy

Author: Raaghavan Krishnamurthy

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Trying to be a good boy and also help others whenever possible.... should stick to my motto "Never Give up..... Life is beautiful... Enjoy the life"...
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