Structure And Theory Of The Operation・・・・・・・・・・・9 - Canon E3730A Operating Instructions Manual

E3730A OPERATING INSTRUCTIONS
4. Structure and theory of operation
4.1 Theory of operation
A high-power klystron with multi cavities consists of an electron gun, interaction cavities for Radio
Frequency (RF), a collector, an output window and an ion pump. At the electron gun section, a heated
cathode emits electrons and high voltage which is applied between the cathode and an anode generates an
electron flow called an electron beam. The electron beam is focused by the electric field formed by the
cathode and the anode electrodes under the influence of the magnetic field formed by a focusing magnet.
Interaction section of RF consists of a drift tube and some cavities. When RF drive power is inputted into the
input cavity which locates near the electron gun section, amplified RF power is outputted from the output
cavity near the collector section. When RF drive is inputted into the input cavity, voltage is generated at the
gap of the input cavity. This voltage modulates the velocity of the electrons. The electrons go forward in the
drift tube and then density of the electrons is modulated by difference of the velocity. Resonant frequency of
the intermediate cavity is tuned to frequency of the density modulation. The electrons reach next cavity and
velocity is modulated further by voltage at the gap of the intermediate cavity. The electron beam has
ingredient of RF power much higher than the drive power consequently. The electron beam passes through
the output cavity finally and RF power of the modulated electron beam is outputted at this cavity. The
amplified RF power passes through the waveguide and is outputted to outside. The electron beam which
passed interaction cavities reaches collector section and the energy of the electrons is absorbed at this
section. A large amount of heat is generated in the collector caused by the energy of the electron beam.
Therefore, the collector needs to be cooled. According to amount of the loss, cooling method is selected to
air-cooled, water-cooled, evaporation-cooled and so on.
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