High speed measurements of neutral beam turn-on and impact of beam modulation on measurements of ion density

Journal Article · Wed Oct 15 00:00:00 EDT 2014 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.4896514· OSTI ID:22305924

Grisham, L. ^[1]; Burrell, K. H.; Crowley, B.; Scoville, J. T. ^[2]

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1. Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States)
2. General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States)

Modulation of neutral beams on tokamaks is performed routinely, enabling background rejection for active spectroscopic diagnostics, and control of injected power and torque. We find that there exists an anomalous initial transient in the beam neutrals delivered to the tokamak that is not accounted for by the accelerator voltage and power supply current. Measurements of the charge-exchange and beam photoemission on the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] at high speed (200 μs) reveal that the energy of the beam neutrals is constant, but the density of beam neutrals displays dramatic variation in the first 2–3 ms following beam turn-on. The impact of this beam density variation on inferred ion densities and impurity transport is presented, with suggested means to correct for the anomalous transient.

• OSTI ID: 22305924
• Journal Information: Review of Scientific Instruments, Vol. 85, Issue 10; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
• Country of Publication: United States
• Language: English

Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ACCELERATORS
CHARGE EXCHANGE
DOUBLET-3 DEVICE
ELECTRIC POTENTIAL
ION DENSITY
MODULATION
NEUTRAL PARTICLES
PARTICLE BEAMS
PHOTOEMISSION
POWER SUPPLIES
SPECTROSCOPY
TORQUE