Klystron vs. Magnetron: Key Differences Explained

This article compares and contrasts the klystron and magnetron, two important types of vacuum tubes. We’ll explore their basic principles, characteristics, and key differences.

Klystron

A klystron is a vacuum tube where the traditional input and output structures are replaced with resonant cavities, specifically a buncher cavity and a catcher cavity.

Image alt: Two cavity Klystron

Typically, a klystron functions as an amplifier. However, with the inclusion of internal or external feedback in its design, it can also operate as an oscillator. There are two primary types of klystrons: two or multi-cavity klystrons and reflex klystrons.

Klystron Characteristics:

• Frequency of operation: 4 to 200 GHz
• Bandwidth: +/- 30 MHz (for Delta(V R ) of +/- 10 Volt)
• Power: 1 mW to 2.5 Watt
• Practical efficiency: 10 to 20 %
• Tuning Range: 5 GHz @ 2 Watt, 30 GHz @ 10 mWatt

Magnetron

A magnetron differs significantly from a standard vacuum tube. In a magnetron, an external magnetic field forces the electron beam to follow a spiral path from the cathode to the anode.

Image alt: magnetron

Magnetrons are designed to operate exclusively as oscillators. These devices are tunable, meaning the output frequency can be adjusted by changing the resonant frequency of the cavity.

There are two primary methods for tuning a magnetron:

• Electronic Tuning: Achieved by generating variable reactance using the electron beam.
• Mechanical Tuning: Achieved by inserting mechanical devices, such as rods or rings, into the resonator cavities to alter the inductance of the resonant circuit.

Magnetron Characteristics:

• Fixed tube magnetron: Provides 600 Watt CW power @ 2.45GHz
• Peak power: Up to 40 MWatt with DC voltage of 50 KV @ 10GHz
• Average power: 800 KWatt
• Duty Cycle: 0.1 %
• Efficiency: 40 to 80 %

Klystron vs. Magnetron: Key Differences