ISSN:
1089-7674
Source:
AIP Digital Archive
Topics:
Physics
Notes:
A dense pulsed electron beam (tr≤20 ns, Vb=200 V, ib≤2 A, nb/ne≤10%) is injected into a uniform magnetoplasma (ne=1−4×1010 cm−3, kTe≤0.5 eV, B0=90 G) to study wave–particle interactions that occur at the front of the beam on short-time scales during which the ions are regarded as fixed and immobile. Above a threshold beam density (nb/ne(approximately-greater-than)5%), the beam front is observed using optical diagnostics to rapidly erode due to beam scattering and energetic tail production, and broaden into a warm front that propagates slower than its injected speed. Using radio-frequency (RF) antennas, the beam is observed to bunch due to the streaming beam–plasma instability and create a ballistic beam mode (fB=nfpe), which collapses into broadband electrostatic turbulence during the onset of beam scattering. A low-frequency electrostatic wave mode (fpi〈fLF〈fpe) is also detected that is coupled to the scattering process. These measurements show that rich beam–plasma phenomena occur in this electron time-scale regime, which are not adequately addressed by current plasma theory.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.870601
