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Why does magnetron work at high DC voltage ?

A magnetron, commonly used in microwave ovens to generate microwaves for cooking, operates at high direct current (DC) voltage for several reasons related to its structure and the physics involved in electron motion within the device.

  1. Electron Acceleration: The fundamental principle behind the operation of a magnetron is the generation of microwaves through the acceleration of electrons in a magnetic field. In a magnetron, a high DC voltage is applied to a cathode, creating an electron cloud. The electrons are then accelerated towards an anode within a resonant cavity.
  2. Cyclotron Resonance: The magnetic field within the resonant cavity causes the accelerated electrons to move in circular or helical paths due to cyclotron resonance. The high DC voltage ensures that the electrons gain sufficient kinetic energy to follow these circular paths at a high velocity.
  3. Frequency of Oscillation: The oscillation frequency of the electrons in the magnetic field is determined by the combination of the magnetic field strength and the applied voltage. To generate microwaves at the desired frequency (typically in the gigahertz range), a high DC voltage is necessary to achieve the required electron velocities and resonant conditions.
  4. Output Power: Higher DC voltages lead to increased electron velocities, resulting in higher output power of the microwaves generated by the magnetron. This is crucial for the efficient and effective cooking of food in microwave ovens.
  5. Sputtering of Cathode Material: The high DC voltage assists in sputtering cathode material, typically made of a material like tungsten. Sputtering is the process by which electrons bombard the cathode, causing it to release electrons and ions. This release of electrons contributes to the formation of the electron cloud needed for further acceleration.

It’s important to note that the design of a magnetron is optimized for specific voltage ranges, and exceeding these ranges can lead to undesirable consequences, such as reduced efficiency or damage to the device. Therefore, the choice of a high DC voltage is a careful balance to ensure optimal magnetron performance for microwave generation in applications like cooking.

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