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Validation of Off-axis Neutral Beam Current Drive Physics in the DIII-D Tokamak
| Content Provider | Semantic Scholar |
|---|---|
| Author | Park, J. M. Murakami, Masakatsu Petty, Clinton Craig Heidbrink, William W. Zeeland, Michael Anthony Van Pace, D. C. Prater, R. Ferron, John R. Osborne, Thomas H. Holcomb, Christopher T. Jackson, Graham J. Petrie, Thomas W. Grierson, B. A. Murphy, Colin J. Suzuki, Toshishige |
| Copyright Year | 2012 |
| Abstract | DIII-D experiments on neutral beam current drive (NBCD) using the new tilted beamline have clearly demonstrated off-axis NBCD as expected from modeling, alleviating concerns of NBCD loss due to microturbulence. The local NBCD profile was measured in H-mode plasma and compared with modeling under a range of beam injection and discharge conditions. The full radial profile of NBCD measured by the magnetic pitch angles from the motional Stark effect (MSE) diagnostic shows a clear hollow NBCD with the peak NBCD location at ρ~0.45, which is in good agreement with the classical model calculation using the Monte-Carlo beam ion slowing down code, NUBEAM. Time evolution of the MSE signals is consistent with transport simulation with modeled current drive sources. The beam-stored energy estimated by equilibrium reconstruction and neutron data do not show any noticeable anomalous losses of NBCD and fast ions. The measured magnitude of off-axis NBCD is very sensitive to the toroidal magnetic field (BT) direction that modifies the alignment of the off-axis beam injection to the local helical pitch of the magnetic field lines. The NBCD profile for the BT direction in poor alignment shows substantially reduced NBCD (~45%) as well as inward shift of the peak NBCD location (Δρ~0.1). This dependency of the off-axis NBCD efficiency on the BT direction is crucial to optimum use of the off-axis beams not only for DIII-D but also for ITER. Detailed NB and Electron Cyclotron Heating (ECH) power scans to vary the ratio of beam injection energy to electron temperature (Eb/Te) at fixed β and vary β at fixed Eb/Te, around the anticipated ITER parameters, imply that ITER is not likely to suffer from loss of NBCD efficiency due to additional transport from microturbulence. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://www-naweb.iaea.org/napc/physics/FEC/FEC2012/papers/444_EXP213.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
