Related Experiment Video
Updated: Jun 19, 2026
07:17
Non-equilibrium Microwave Plasma for Efficient High Temperature Chemistry
Published on: August 1, 2017
Microwave window breakdown experiments and simulations on the UM/L-3 relativistic magnetron
B W Hoff1, P J Mardahl, R M Gilgenbach
1Department of Nuclear Engineering and Radiological Sciences, Plasma, Pulsed Power and Microwave Laboratory, University of Michigan, Ann Arbor, Michigan 48109, USA.
The Review of Scientific Instruments
|October 2, 2009
Summary
A new microwave window design for relativistic magnetrons significantly improved performance by preventing vacuum side breakdown. This enhancement allows for higher power output and longer pulse durations in magnetron devices.
Area of Science:
- Physics
- Electrical Engineering
- Plasma Science
Background:
- Relativistic magnetrons are crucial for high-power microwave generation.
- Vacuum side breakdown in microwave windows limits magnetron performance.
- Existing window configurations are susceptible to electron impact and secondary electron emission.
Purpose of the Study:
- To design and test a novel microwave window configuration for relativistic magnetrons.
- To mitigate vacuum side breakdown and enhance power handling capabilities.
- To investigate the underlying causes of window breakdown in previous designs.
Main Methods:
- Modified the UM/L-3 (6-vane, L-band) relativistic magnetron with a new window configuration.
- Incorporated vacuum-rated directional coupler waveguide segments and polycarbonate windows.
- Utilized simulations to analyze electron trajectories and secondary electron yield.
- Compared performance against a baseline configuration with acrylic windows.
Main Results:
- The new configuration eliminated vacuum side window breakdown at output powers exceeding 120+ MW.
- Achieved a threefold increase in measured microwave pulse duration and peak power compared to the baseline.
- Simulations identified anode block electron emission and secondary electron multiplication as key breakdown causes in the original design.
- Simulated electrons struck windows with a mean kinetic energy of 33 keV, predicting a 65% secondary electron yield.
Conclusions:
- The redesigned microwave window effectively prevents vacuum side breakdown in relativistic magnetrons.
- The improved design enables significantly higher power operation and extended pulse durations.
- Understanding electron dynamics and secondary emission is critical for optimizing magnetron window performance.
Related Concept Videos
01:28Standing Waves in a Cavity
A household microwave and lasers are examples of standing electromagnetic waves in a cavity. When two conducting metal plates are placed parallel at the nodal planes, it creates a cavity where standing waves are formed. The cavity between the two planes is analogous to a stretched string held at the points x = 0 and x = L. Here, the distance 'L' between the two planes must be an integer multiple of half of the wavelength. The wavelengths that satisfy this condition are given by:
01:15Transmission Electron Microscopy
In 1931, physicist Ernst Ruska—building on the idea that magnetic fields can direct an electron beam just as lenses can direct a beam of light in an optical microscope—developed the first prototype of the electron microscope. This development led to the development of the field of electron microscopy. In the transmission electron microscope (TEM), electrons are produced by a hot tungsten element and accelerated by a potential difference in an electron gun, which gives them up to 400 keV in...
01:19Thomson's e/m Experiment
In a beam of charged particles created by a heated cathode, the particles move at different speeds. However, many applications need a beam with uniform particle speeds. An arrangement known as a velocity selector uses electric and magnetic fields to pick particles with a particular speed from the beam.
A particle with charge q, speed v, and mass m enters an area from the top, where the magnetic and electric fields are perpendicular both to the particle's motion and to one another. The magnetic...
A particle with charge q, speed v, and mass m enters an area from the top, where the magnetic and electric fields are perpendicular both to the particle's motion and to one another. The magnetic...