11 research outputs found
Investigation of the composition of the Luna 16 lunar sample
The concentrations of aluminum, manganese, sodium, chromium, iron, cobalt, and 12 rare earth elements were determined by neutron activation analysis using slow neutrons. Oxygen and silicon were determined using a fast neutron generator. Mossbauer spectroscopy was used to investigate iron compounds in Luna 16 regolith samples from the upper part of the core
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Electron Cyclotron Heating on the ISX-B Tokamak
One experiment on electron cyclotron heating on the Impurity Study Experiment (ISX-b) tokamak has been completed and a second experiment is in progress. In the first experiment, with a gyrotron producing 100 kW at 35 GHz, a heating efficiency greater than 60% was achieved. Unpolarized radiation was launched from the high field side of the tokamak, heating electrons at cyclotron resonance in the center of the plasma. From laser scattering and thermal emission at the second gyroharmonic, the electron temperature, initially 850 eV, increased to 1250 eV at the end of a 15-ms pulse. The second experiment is now in progress, with 180 kW at 28 GHz and a capability of 100-ms pulses. A comparison between polarized and unpolarized radiation, modification of the plasma current profile, and a critical comparison with theory are planned. In this paper, experiments on preionization at the upper hybrid resonance are reported. A plasma with an electron temperature of 10 eV was produced, which is not high enough to reduce impurity radiation. The resistive part of the loop voltage was reduced by preionization. Plans for an experiment to measure electric current induced by electron cyclotron heating are presented, along with a review of the theoretical basis of the current drive
DIII-D research advancing the physics basis for optimizing the tokamak approach to fusion energy
Funding Information: This material is based upon work supported by the US Department of Energy, Office of Science, Office of Fusion Energy Sciences, using the DIII-D National Fusion Facility, a DOE Office of Science user facility, under Awards DE-FC02-04ER54698 and DE-AC52-07NA27344. Publisher Copyright: © 2022 IAEA, Vienna.DIII-D physics research addresses critical challenges for the operation of ITER and the next generation of fusion energy devices. This is done through a focus on innovations to provide solutions for high performance long pulse operation, coupled with fundamental plasma physics understanding and model validation, to drive scenario development by integrating high performance core and boundary plasmas. Substantial increases in off-axis current drive efficiency from an innovative top launch system for EC power, and in pressure broadening for Alfven eigenmode control from a co-/counter-I p steerable off-axis neutral beam, all improve the prospects for optimization of future long pulse/steady state high performance tokamak operation. Fundamental studies into the modes that drive the evolution of the pedestal pressure profile and electron vs ion heat flux validate predictive models of pedestal recovery after ELMs. Understanding the physics mechanisms of ELM control and density pumpout by 3D magnetic perturbation fields leads to confident predictions for ITER and future devices. Validated modeling of high-Z shattered pellet injection for disruption mitigation, runaway electron dissipation, and techniques for disruption prediction and avoidance including machine learning, give confidence in handling disruptivity for future devices. For the non-nuclear phase of ITER, two actuators are identified to lower the L-H threshold power in hydrogen plasmas. With this physics understanding and suite of capabilities, a high poloidal beta optimized-core scenario with an internal transport barrier that projects nearly to Q = 10 in ITER at âŒ8 MA was coupled to a detached divertor, and a near super H-mode optimized-pedestal scenario with co-I p beam injection was coupled to a radiative divertor. The hybrid core scenario was achieved directly, without the need for anomalous current diffusion, using off-axis current drive actuators. Also, a controller to assess proximity to stability limits and regulate ÎČ N in the ITER baseline scenario, based on plasma response to probing 3D fields, was demonstrated. Finally, innovative tokamak operation using a negative triangularity shape showed many attractive features for future pilot plant operation.Peer reviewe