Klystron

From Wikinfo

A klystron is a specialized vacuum tube (evacuated electron tube) called a linear-beam tube. Klystrons are used as an oscillator or amplifier 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 linear accelerators. It has the advantage (over the magnetron) of coherently amplifying a reference signal and so its output may be precisely controlled in amplitude, frequency and phase.

Russell and Sigurd Varian of Stanford University are generally considered to be the inventors of the klystron. Their prototype was completed in August 1937. Upon publication in 1939, news of the klystron immediately influenced the work of US and UK researchers working on radar equipment.

In the two-chamber klystron, an electron beam from the cathode of an electron gun is injected into a resonant cavity. The beam is held together by a parallel magnetic field and is attracted through a connecting passage (called a drift tube) to a second resonant chamber containing a positively charged anode. While passing through the connecting chamber the electron beam is velocity modulated (periodically bunched) by the weaker RF signal. The electrons are attracted to a positive anode contained in a second resonant chamber. As the bunched electrons enter the second chamber they induce standing waves at the same frequency as input signal. The signal induced in the second chamber is much stronger than that in the first.

In the reflex klystron, a single toroidal resonant chamber surrounds a tubular chamber. The electrons are fired into one end of the tube by the accelerator grid of an electron gun. After passing by the resonant chamber they are reflected by a negatively charged repeller plate for another pass through the chamber.

In the multicavity klystron, multiple toroidal cavities surround a cylindrical acceleration tube.

These amplifiers are used to produce HF, VHF, UHF, and EHF signals where such high amplitude (power) is required that solid state devices (semi-conductors) remain inadequate. Klystrons can be found at work in radar, satellite and wideband high power communication (very common in television broadcast and EHF satellite terminals), and high-power physics (particle accelerators and experimental reactors).

See also: Magnetron, inductive output tube

External links

• http://www.tpub.com/neets/book11/45b.htm (two cavity klystron)
• http://www.tpub.com/neets/book11/45c.htm (multicavity klystron)
• http://www.tpub.com/neets/book11/45d.htm (reflex klystron)
• http://www2.slac.stanford.edu/vvc/accelerators/klystron.html (high power for linear accelerator)
• http://e2vtechnologies.com/introduction/prod_klystron_nojs.htm
• http://www.tpub.com/neets/book11/45d.htm

References

• Adapted from the Wikipedia article, "Klystron" http://en.wikipedia.org/wiki/Klystron, used under the GNU Free Documentation License