Spectroscopic study of anode plasmas in a microsecond electron beam diode

Journal Article · Sat Aug 01 04:00:00 EDT 1987 · IEEE Trans. Plasma Sci.; (United States)

DOI:https://doi.org/10.1109/TPS.1987.4316721· OSTI ID:6023065

Cuneo, M E; Gilgenbach, R M; Brake, M L

Experiments have been performed to investigate the visible emissions (370-600 nm) from long-pulse electron-beam-driven carbon anode plasmas, and to correlate the spectroscopic evidence for ions with deviations of the diode current and voltage from Child-Langmuir behavior. Electron beams had peak voltages of -0.8 MV, current densities approaching 10/sup 3/ A/cm/sup 2/, and pulselengths of about 1 ..mu..s. Diode closure resulted in three phases of the beam/plasma evolution. In stage I the deposited electron dose was smaller than that required for anode plasma optical emission (less than or equal to250 J/gr). No deviations of the diode operation from conventional Child-Langmuir scaling were observed. In stage II, the electron dose was large enough for anode plasma formation before shorting (less than or equal to350 J/gr), and low-intensity optical emission was primarily from CII and CIII. During stage II, two types of non-Child-Langmuir diode behavior occurred due to the presence of an anode plasma. An anomalous voltage peaking behavior occurred at an average dose of 740 J/gr, at about 80 percent of the diode shorting time. The diode impedance was constant during this voltage peaking behavior, contrary to the impedance collapse expected from Child-Langmuir behavior in a closing diode. This voltage peaking was accompanied by an increase in continuum emission, particularly at shorter wavelengths. A bipolar impedance level was occasionally observed before voltage peaking, at an average dose of 4120 J/gr, at about 66 percent of the predicted shorting time. During stage III, an intense vacuum arc mode, the cathode plasma shorted the anode-cathode (A-K) gap, resulting in intense optical emission from CI through CIV on noncrowbarred pulses, and from CII, C/sub 2/, CH, and H on crowbarred pulses.

• Research Organization: Intense Energy Beam Interaction Lab., Dept. of Nuclear Engineering, Univ. of Michigan, Ann Arbor, MI 48109-2104
• OSTI ID: 6023065
• Journal Information: IEEE Trans. Plasma Sci.; (United States), Journal Name: IEEE Trans. Plasma Sci.; (United States) Vol. PS-15:4; ISSN ITPSB
• Country of Publication: United States
• Language: English

Related Subjects

640301 -- Atomic
Molecular & Chemical Physics-- Beams & their Reactions
640304* -- Atomic
Molecular & Chemical Physics-- Collision Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
74 ATOMIC AND MOLECULAR PHYSICS
BEAMS
CARBON IONS
CHARGED PARTICLES
CURRENTS
DIODE TUBES
ELECTRIC ARCS
ELECTRIC CURRENTS
ELECTRIC DISCHARGES
ELECTRICAL PUMPING
ELECTRON BEAM ION SOURCES
ELECTRON BEAM PUMPING
ELECTRON BEAMS
ELECTRON TUBES
ION SOURCES
IONS
LEPTON BEAMS
PARTICLE BEAMS
PLASMA
PLASMA PRODUCTION
PLASMA WAVES
PUMPING
SCALING LAWS
SPECTRA
THERMIONIC DIODES
THERMIONIC TUBES
VISIBLE SPECTRA