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Fusion Science and Technology
Latest News
First astatine-labeled compound shipped in the U.S.
The Department of Energy’s National Isotope Development Center (NIDC) on March 31 announced the successful long-distance shipment in the United States of a biologically active compound labeled with the medical radioisotope astatine-211 (At-211). Because previous shipments have included only the “bare” isotope, the NIDC has described the development as “unleashing medical innovation.”
C. L. Fiore, D. R. Ernst, J. E. Rice, K. Zhurovich, N. Basse, P. T. Bonoli, M. J. Greenwald, E. S. Marmar, S. J. Wukitch
Fusion Science and Technology | Volume 51 | Number 3 | April 2007 | Pages 303-316
Technical Paper | Alcator C-Mod Tokamak | doi.org/10.13182/FST07-A1424
Articles are hosted by Taylor and Francis Online.
Internal transport barriers (ITBs) marked by steep density and pressure profiles and reduction of core transport are obtained in Alcator C-Mod. Transient single barriers are observed at the back-transition from H- to L-mode and also when pellet injection is accompanied by ion cyclotron resonance frequency (ICRF) power. Double barriers are induced with injection of off-axis ICRF power deposition. These also arise spontaneously in ohmic H-mode plasmas when the H-mode lasts for several energy confinement times. C-Mod provides a unique platform for studying such discharges: The ions and electrons are tightly coupled by collisions with Ti/Te = 1, and the plasma has no internal particle or momentum sources. ITB plasmas with average pressure greater than 1 atm have been obtained. To form an ITB, particle and thermal flux are reduced in the barrier region, allowing the neoclassical pinch to peak the density while maintaining the central temperature. Gyrokinetic simulation suggests that long-wavelength drift wave turbulence in the core is marginally stable at the ITB onset, but steepening of the density profile destabilizes trapped electron modes (TEMs) inside the barrier. The TEM ultimately drives sufficient outgoing particle flux to balance the inward pinch and halt further density rise, which allows control of particle and impurity peaking.