Development of a low-energy and high-current pulsed neutral beam injector with a washer-gun plasma source for high-beta plasma experiments

Journal Article · Wed Aug 15 04:00:00 EDT 2012 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.4744960· OSTI ID:22093701

Ii, Toru ^[1]; Gi, Keii; Umezawa, Toshiyuki; Inomoto, Michiaki; Ono, Yasushi ^[2]; Asai, Tomohiko ^[3]

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1. Graduate School of Engineering, The University of Tokyo, Tokyo 113-8656 (Japan)
2. Graduate School of Frontier Sciences, The University of Tokyo, Chiba 277-8561 (Japan)
3. College of Science and Technology, Nihon University, Tokyo 101-8308 (Japan)

We have developed a novel and economical neutral-beam injection system by employing a washer-gun plasma source. It provides a low-cost and maintenance-free ion beam, thus eliminating the need for the filaments and water-cooling systems employed conventionally. In our primary experiments, the washer gun produced a source plasma with an electron temperature of approximately 5 eV and an electron density of 5 Multiplication-Sign 10{sup 17} m{sup -3}, i.e., conditions suitable for ion-beam extraction. The dependence of the extracted beam current on the acceleration voltage is consistent with space-charge current limitation, because the observed current density is almost proportional to the 3/2 power of the acceleration voltage below approximately 8 kV. By optimizing plasma formation, we successfully achieved beam extraction of up to 40 A at 15 kV and a pulse length in excess of 0.25 ms. Its low-voltage and high-current pulsed-beam properties enable us to apply this high-power neutral beam injection into a high-beta compact torus plasma characterized by a low magnetic field.

• OSTI ID: 22093701
• Journal Information: Review of Scientific Instruments, Journal Name: Review of Scientific Instruments Journal Issue: 8 Vol. 83; ISSN 0034-6748; ISSN RSINAK
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
ACCELERATION
BEAM CURRENTS
BEAM EXTRACTION
COMPACT TORUS
COOLING SYSTEMS
CURRENT DENSITY
ELECTRON DENSITY
ELECTRON TEMPERATURE
HIGH-BETA PLASMA
ION BEAMS
ION TEMPERATURE
MAGNETIC FIELDS
PLASMA BEAM INJECTION
PLASMA DENSITY
PLASMA GUNS
SPACE CHARGE
TOKAMAK DEVICES