Excitation of Oscillations Between the Ion Cyclotron and Electron Plasma Frequency in an Ion-Beam Generated Plasma
Description
A helium ion beam propagating near the axis of a grounded metal cylinder with grounded grids at its ends penetrates neutral helium gas and generates a beam-plasma column. The beam-plasma is radially confined by a homogeneous magnetic field aligned parallel to the axis of the metal cylinder. The length of the plasma column, i.e. the distance between the two grids, is variable up to 100 cm and the diameter of the metal cylinder is 20 cm, whereas the beam diameter is about 2 cm. With neutral gas pressures in the range of about 104 Torr, beam energies of about 10 keV, beam currents of a few milliamperes and magnetic fields of some thousand gauss, oscillations with radial field amplitudes up to a few volts per centimeter in the megacycle range together with their lower ''harmonics'' are picked up by probes. The oscillation spectrum is more or less continuous, having apparent peaks at the ''harmonic'' frequencies. Oscillation amplitude measurements carried out along the plasma column with a movable probe, giving something like a standing wave envelope, and interference measurements between a fixed and a movable probe indicate phase velocities greater than the beam velocity. According to the dispersion diagram of a cold cylindrical beam-plasma these oscillations belong to a wave propagating between the fast cyclotron wave and the ω-k-plane, i.e. to the electron plasma wave. Since this wave is stable in an infinitely long system, it is assumed that it be coupled to the unstable space charge wave by the axial boundary conditions of the finite beam plasma. This yields the desired instability and also a quantitative representation of the observed frequency spectrum. (author)
Additional details
Publishing Information
- Publisher
- IAEA
- Imprint Place
- Vienna (International Atomic Energy Agency (IAEA))
- Imprint Title
- Plasma Physics and Controlled Nuclear Fusion Research. Proceedings of the Third International Conference on Plasma Physics and Controlled Nuclear Fusion Research. Vol. II
- Imprint Pagination
- 852 p.
- Journal Series
- Proceedings Series
- Journal Page Range
- p. 785-792
- ISSN
- 0074-1884
Conference
- Title
- 3. international conference on plasma physics and controlled nuclear fusion research
- Dates
- 1-7 Aug 1968
- Place
- Novosibirsk, USSR (Russian Federation)
INIS
- Country of Publication
- International Atomic Energy Agency (IAEA)
- Country of Input or Organization
- International Atomic Energy Agency (IAEA)
- INIS RN
- 44064152
- Subject category
- S70: PLASMA PHYSICS AND FUSION TECHNOLOGY;
- Resource subtype / Literary indicator
- Conference
- Quality check status
- Yes
- Descriptors DEI
- AMPLITUDES; BEAM CURRENTS; BOUNDARY CONDITIONS; CYCLOTRONS; CYLINDERS; DISPERSION RELATIONS; ELECTRON PLASMA WAVES; ELECTRONS; EXCITATION; HARMONICS; HELIUM IONS; INTERFERENCE; ION BEAMS; KEV RANGE; LANGMUIR FREQUENCY; MAGNETIC FIELDS; PHASE VELOCITY; PLASMA INSTABILITY; SPACE CHARGE; STANDING WAVES;
- Descriptors DEC
- ACCELERATORS; BEAMS; CHARGED PARTICLES; CURRENTS; CYCLIC ACCELERATORS; ELEMENTARY PARTICLES; ENERGY RANGE; ENERGY-LEVEL TRANSITIONS; FERMIONS; INSTABILITY; IONS; LEPTONS; OSCILLATIONS; PLASMA WAVES; VELOCITY;
Optional Information
- Lead record
- 61a4m-c8n42
- Notes
- 6 refs., 6 figs. Imprint:In two volumes
- Secondary number(s)
- IAEA-CN--24/L-9