Dispersion of low-frequency waves in the plasma of a neutralized ion beam

Journal Article · Tue May 01 04:00:00 EDT 1979 · Sov. J. Plasma Phys. (Engl. Transl.); (United States)

OSTI ID:5785295

Virko, V F; Kirichenko, G S

Experiments have been carried out on the region of transparency for low-frequency electrostatic waves in the cylindrical plasma column represented by an electron-neutralized ion beam. The wave frequencies of interest are in the range ..omega../sub O/ivery-much-less-than..omega..very-much-less-than..omega../sub Oe/, where ..omega../sub O/e,e are the ion and electron plasma frequencies. In the actual experiments, a beam of potassium ions with an energy approx.100 eV and a current approx.1 mA (an ion density approx.10/sup 8/ cm/sup -3/), neutralized by electrons at a temperature approx.0.5 eV, propagates in a conducting chamber 36 cm long and 10 cm in diameter at a residual gas pressure approx.10/sup -5/ torr. The results show that there are three regions corresponding to transmission of an external modulation signal along the plasma column: two space-charge waves of the ion-acoustic type, which propagate at phase velocities V/sub O/+..delta..v (V/sub O/ is the velocity of the ion beam, and ..delta..v is the velocity of the ion-acoustic waves), and a low-frequency electron wave, which propagates at a velocity higher than the electron thermal velocity. The interference of the three waves leads to a characteristic distribution of the alternating field along the beam. The ion-acoustic wave dispersion in the ion-beam plasma is manifested over a broad range of kd/sub e/ (k is the wave number and d/sub e/ is the Debye length in terms of the electron temperature). The finite radial dimension of the plasma column is taken into account. The imposition of a weak magnetic field transverse to the beam, which magnetizes the electrons, leads to an instability involving the spatial growth of a slow ion-acoustic wave. On the other hand, at magnetic fields such that the average electron gyroradius approaches the debye length, such a field suppresses the propagation of electron waves along the beam. The experimental results are interpreted using linear theory.

• Research Organization: Institute of Nuclear Research, Academy of Sciences of the Ukrainian SSR, Kiev
• OSTI ID: 5785295
• Journal Information: Sov. J. Plasma Phys. (Engl. Transl.); (United States), Journal Name: Sov. J. Plasma Phys. (Engl. Transl.); (United States) Vol. 5:3; ISSN SJPPD
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700108* -- Fusion Energy-- Plasma Research-- Wave Phenomena
BEAM-PLASMA SYSTEMS
BEAMS
DISPERSION RELATIONS
ELECTROSTATIC PROBES
INSTABILITY
ION ACOUSTIC WAVES
ION BEAMS
ION WAVES
PLASMA INSTABILITY
PLASMA MICROINSTABILITIES
PLASMA WAVES
PROBES
SPACE CHARGE