Development of a high pulse rate intense ion beam diode and investigations of the physics of beam formation

Thesis/Dissertation · Thu Dec 31 23:00:00 EST 1992

OSTI ID:7042383

Noonan, W A

Virtually all practical applications for intense ion beams require that the beam pulses be generated at high repetition rates. Until the work presented in this thesis, intense ion beam diodes have been able to pulse only a few times per hour at best. A magnetically insulated ion diode capable of producing intense ion beams at high pulse rates has been developed. This diode employs a magnetically confined anode plasma ion source. The high repetition rate pulsed power systems are based upon saturable magnetic switching. Proton beams of 75keV, 10-25A/cm[sup 2] and with 100 ns duration have been generated at 90 Hz in four pulse bursts. This diode can also operate at one pulse per minute indefinitely. This capability has been exploited to measure the relative density profile of electrons in the acceleration gap. The diode was backfilled with about 10[sup [minus]2] Torr of He, which was collisionally excited by energetic in the acceleration gap. When the excited He atoms radiatively decayed, the emitted light was measured with 2 ns time resolution and submillimeter space resolution and used to deduce the relative electron density profile. The diode was configured to produce 100 keV Ar[sup +] beams at up to 4 A/cm[sup 2]. The electron density profile peaked toward the center of the gap and dropped off significantly toward the anode and cathode. The absence of electron density near the physical cathode is evidence for diamagnetic drift of the virtual cathode. Several stages leading to the formation of the diodes virtual cathode and the ion beam were observed. The electron current takes many tens of nanoseconds from when the initial cathode emission to when their Child-Langmuir current is reached. The extent to which this limit is exceeded depends strongly on the configuration of the insulating magnetic field. The delay between when electrons are first observed in the gap spectroscopically and when the beam is formed is independent of the magnetic field configuration.

• Research Organization: Cornell Univ., Ithaca, NY (United States)
• OSTI ID: 7042383
• Country of Publication: United States
• Language: English

Related Subjects

661200* -- Techniques of General Use in Physics-- (1992-)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AMP BEAM CURRENTS
BEAM CURRENTS
BEAMS
CURRENTS
DIODE TUBES
ELECTRON DENSITY
ELECTRON TUBES
MAGNETIC FIELD CONFIGURATIONS
NUCLEON BEAMS
OPERATION
PARTICLE BEAMS
PROTON BEAMS
PULSES
THERMIONIC DIODES
THERMIONIC TUBES