Measurements of the neutron source strength at DIII-D

Heidbrink, W. W.; Taylor, P.L.; Phillips, J. A.

doi:10.1063/1.1147646

Cited by 52 publications

(59 citation statements)

References 10 publications

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“…The measured jump agrees with the expected jump within the 15% uncertainty in the absolute calibration of the neutron detector. 31 Overall, the systematic uncertainty appears comparable to the random uncertainty.…”

Section: Resultssupporting

confidence: 48%

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Accurate measurements of the pitch-angle scattering of beam ions

Heidbrink

2002

Physics of Plasmas

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The pitch-angle scattering rate of a dilute population of 75 keV deuterium ions is measured in a well-diagnosed, relatively quiet, magnetically-confined deuterium plasma. Neutral particle diagnostics detect the fast-ion density in velocity space following a short 10 ms pulse of injected beam ions. The data are compared to the classical theory of diffusion in velocity space caused by many, small-angle, Coulomb-scattering events. Within uncertainties of Շ15%, the data confirm the classical theory.

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Section: Resultssupporting

confidence: 48%

“…31 Under these conditions, beam-plasma reactions are calculated to constitute over 95% of the total neutron rate. Since the slowing down time of the beam ions is long compared to the beam pulse duration, the neutron rate rises nearly linearly during each 10 ms beam pulse ͑Fig.…”

Section: Experimental Techniquementioning

confidence: 99%

Accurate measurements of the pitch-angle scattering of beam ions

Heidbrink

2002

Physics of Plasmas

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“…As discussed extensively in [16], these different instruments weight the fast-ion distribution function differently in velocity space. A plastic scintillator that is cross-calibrated to an absolutely calibrated fission counter measures the volumeaveraged 2.5 MeV neutron rate [17]. In these plasmas, the neutron rate is dominated by beam-plasma reactions.…”

Section: Plasma Conditions and Diagnosticsmentioning

confidence: 99%

Central flattening of the fast-ion profile in reversed-shear DIII-D discharges

et al. 2008

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Neutral beam injection into a plasma with negative central shear produces a rich spectrum of toroidicity-induced and reversed-shear Alfvén eigenmodes in the DIII-D tokamak. The application of fast-ion D α (FIDA) spectroscopy shows that the central fast-ion profile is flattened in the inner half of the discharge. Neutron and equilibrium measurements corroborate the FIDA data. The temporal evolution of the current profile is also strongly modified. Studies in similar discharges show that flattening of the profile correlates with the mode amplitude and that both types of Alfvén modes correlate with fast-ion transport. Calculations by the ORBIT code do not explain the observed fast-ion transport for the measured mode amplitudes, however. Possible explanations for the discrepancy are considered.

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“…14 Conditions with multiple unstable AEs occur both in L-mode plasmas during the current ramp 6,14,25 and in H-mode steady-state scenario plasmas with elevated q profiles. 26,27 Fast-ion diagnostics include the volume-averaged neutron rate, 28 which is dominated by beam-plasma reactions in the L-mode plasmas, FIDA diagnostics with oblique sightlines, 29 and solid-state neutral-particle analyzers (NPA) operated in current mode 30 (Fig. 2).…”

Section: Critical Gradient Behaviormentioning

confidence: 99%

Fast-ion transport by Alfvén eigenmodes above a critical gradient threshold

et al. 2017

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Experiments on the DIII-D tokamak have identified how multiple simultaneous Alfvén eigenmodes (AEs) lead to overlapping wave-particle resonances and stochastic fast-ion transport in fusion grade plasmas [C. S. Collins et al., Phys. Rev. Lett. 116, 095001 (2016)]. The behavior results in a sudden increase in fast-ion transport at a threshold that is well above the linear stability threshold for Alfvén instability. A novel beam modulation technique [W. W. Heidbrink et al., Nucl. Fusion 56, 112011 (2016)], in conjunction with an array of fast-ion diagnostics, probes the transport by measuring the fast-ion flux in different phase-space volumes. Well above the threshold, simulations that utilize the measured mode amplitudes and structures predict a hollow fast-ion profile that resembles the profile measured by fast-ion Dα spectroscopy; the modelling also successfully reproduces the temporal response of neutral-particle signals to beam modulation. The use of different modulated sources probes the details of phase-space transport by populating different regions in phase space and by altering the amplitude of the AEs. Both effects modulate the phase-space flows.

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Measurements of the neutron source strength at DIII-D

Cited by 52 publications

References 10 publications

Accurate measurements of the pitch-angle scattering of beam ions

Accurate measurements of the pitch-angle scattering of beam ions

Central flattening of the fast-ion profile in reversed-shear DIII-D discharges

Fast-ion transport by Alfvén eigenmodes above a critical gradient threshold

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