Beam driven instabilities in magnetized plasmas

Project: Research

Project Details


Electromagnetic radiation is another, broader, name for light, encompassing radio waves through to gamma rays. This proposal intends to investigate the ability of an electron beam gyrating in a fixed magnetic field to interact with an electromagnetic wave, in the microwave part of the spectrum. In certain conditions this interaction can be arranged so that the electrons slow down, and the energy they lose is conserved by an increase in the energy of the wave. This process is effectively LASER action. In particular the project will consider an electron beam where some electrons are very nearly travelling along the magnetic field lines and others are gyrating nearly perpendicularly to it. A new theoretical idea has been proposed as a result of astronomical observations which expects especially high growth rates to occur from this type of electron beam and potentially efficient conversion of the electron energy to wave energy. To evaluate this potential, and the validity of the theoretical idea, the project will conduct an experiment where such a beam will be produced by magnetic compression and the emissions from the beam will be observed for different values of the magnetic field and radiation field distributions. Measurements of the beam current, voltage position and velocity will be compared to the measurements of the amplitude and frequency of the microwave emissions. Theoretical research will also be undertaken to ensure the expected behaviour is compared accurately with the actually realisable experimental geometry. This combined approach of theoretical and experimental investigation will allow the project to compare the experimental results with the predictions of the theoretical model and also with the output of computational simulations, thereby establishing its validity and potential for applications.

Layman's description

Most of the visible matter in our universe is in the form of plasma and understanding its behaviour is of fundamental importance, as well as being useful in several applications such as the plasma processing of semiconductor chips used in very many modern devices including PCs and mobile telephones and in potential future energy generation via magnetic confinement fusion or inertial confinement fusion (laser fusion). Electron beams passing through plasmas can produce instabilities in the plasmas, which it is important to understand and control and this is the main aim of this research project.

Key findings

Theory, numerical modelling and laboratory experiments were used to understand the physical mechanism of certain types of electron beam driven instabilities in magnetized plasmas. It was established that the horseshoe instability is responsible for electromagnetic emissions observed when an electron beam is injected along a converging magnetic field in the presence of a tenuous plasma.


The outcomes from this research have impact on the understanding of natural planetary and astrophysical emissions, as well as understanding the mechanism of the growth of instabilities in laboratory plasmas used for research in magnetic confinement fusion and inertial confinement fusion.
Effective start/end date1/04/0630/09/09


  • EPSRC (Engineering and Physical Sciences Research Council): £295,079.00


  • plasma physics
  • plasma instabilities
  • plasma science
  • electron beams
  • plasmas
  • microwaves
  • mm-waves


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  • Electrons Make Waves

    Adrian Cross (Participant)

    Impact: Impact - for External PortalEconomic and commerce, Other