Download or read book Study of H mode Threshold Conditions in DIII D written by and published by . This book was released on 1996 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Studies have been conducted in DIII-D to determine the dependence of the power threshold P{sub lh} for the transition to the H-mode regime and the threshold P{sub hl} for the transition from H-mode to L-mode as functions of external parameters. There is a value of the line-averaged density n{sub e} at which P{sub lh} has a minimum and P{sub lh} tends to increase for lower and higher values of n{sub e}. Experiments conducted to separate the effect of the neutral density n0 from the plasma density n{sub e} give evidence of a strong coupling between n0 and n{sub e}. The separate effect of neutrals on the transition has not been determined. Coordinated experiments with JET made in the ITER shape show that P{sub lh} increases approximately as S{sup 0.5} where S is the plasma surface area. For these discharges, the power threshold in DIII-D was high by normal standards, thus suggesting that effects other than plasma size may have affected the experiment. Studies of H-L transitions have been initiated and hysteresis of order 40% has been observed. Studies have also been done of the dependence of the L-H transition on local edge parameters. Characterization of the edge within a few ms prior to the transition shows that the range of edge temperatures at which the transition has been observed is more restrictive than the range of densities at which it occurs. These results suggest that some temperature function is important for controlling the transition.
Download or read book Experimental Survey of the L H Transition Conditions in the DIII D Tokamak written by and published by . This book was released on 1994 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present the global analysis of a recent survey of the H-mode power threshold in DIII-D using D{sup o} --> D NBI after boronization of the vacuum vessel. Single parameter scans of B{sub T}, I{sub p}, density, and plasma shape have been carried out on the DIII-D tokamak for neutral beam heated single-null and double-null diverted plasmas. In single-null discharges, the power threshold is found to increase approximately linearly with B{sub T} and n{sub e} but remains independent of I{sub p}. In double-null discharges, the power threshold is found to be approximately independent of both B{sub T} and n{sub e}. Various shape parameters such as plasma-wall gaps had only a weak effect on the power threshold. Imbalancing the double null configuration resulted in a large increase in the threshold power.
Download or read book A 0 D Scaling Approach to the DIII D L H Power Threshold in the Presence of Resonant Magnetic Perturbations written by Michael Hanson and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: We report a DIII-D database study of the H-mode power threshold over a wide range of plasma conditions and in the presence of resonant magnetic perturbations (RMPs). This database consisting of global (i.e. averaged) quantities is first compared to the 2008 ITPA database and the resulting L-H power scaling [38]. Since ELM control is critical for ITER, and applied 3D fields will likely be present prior to the transition into the H-mode, this study is important for assessing the impact of RMP ELM suppression on the L-H power threshold. The L-H transition has been studied extensively and is dependent on the physical and magnetic divertor geometry, shear flows, and drifts, among other parameters, some of which are altered by RMP fields. In order to understand the effects of RMPs on the L-H threshold, we attempt to make a robust empirical model, using only DIII-D data, that includes magnitudes and the toroidal modes of various resonant and non-resonant 3D fields. In addition, we assess the validity of previous assumptions about fast ion losses, as well as the usefulness of 0-D database regressions for extrapolation to ITER. Results from this database study show the standard 0-D parameters to be insufficient for capturing the complex L-H transition physics at a level high enough to provide an extrapolation to ITER with reasonable certainty.
Download or read book Study of the Conditions for Spontaneous H mode Transitions in DIII D written by and published by . This book was released on 1996 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: A series of scaling studies attempting to correlate the H(high)-mode power threshold (P{sub TH}) with global parameters have been conducted. Data from these discharges is also being used to look for dependence of P{sub TH} on local edge parameters and to test theories of the transition. Boronization and better operational techniques have resulted in lower power thresholds and weaker density scaling. Neon impurity injection experiments show that radiation also plays a role in determining P{sub TH}. A low density threshold for the L(low)-H(high) transition has been linked with the locked mode low density limit, and can be reduced with the use of an error field correcting coil. Highly developed edge diagnostics, with spatial resolution as low as 5 mm, are used to evaluate how the power threshold depends on local edge conditions. Preliminary analysis of local edge conditions for parameter scans of n{sub e}, B{sub T}, and I{sub p} in single-null discharges, and the X-point imbalance in double-null discharges-show that, just before the transition to H-mode, the edge temperatures near the separatrix are approximately constant at 100
Download or read book written by and published by . This book was released on 1976 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Tokamaks written by John Wesson and published by Oxford University Press. This book was released on 2011-10-13 with total page 828 pages. Available in PDF, EPUB and Kindle. Book excerpt: The tokamak is the principal tool in controlled fusion research. This book acts as an introduction to the subject and a basic reference for theory, definitions, equations, and experimental results. The fourth edition has been completely revised, describing their development of tokamaks to the point of producing significant fusion power.
Download or read book The Back Transition and Hysteresis Effects in DIII D written by and published by . This book was released on 1997 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: The back transition from H-mode to L-mode has been studied on DIII-D as a part of the investigation of the L-H transition power threshold scaling. Based on a density-dependent scaling for the H-mode power threshold, ITER will require substantial hysteresis in this parameter to remain in H-mode as n{sub e} rises. Defining the hysteresis in terms of the ratio of sustaining to threshold power, P{sub HL}/P{sub LH} may need to be as small as 50% for ITER. Operation of DIII-D at injection powers slightly above the H-mode threshold results in an oscillatory behavior with multiple forward-backward transitions in the course of a discharge. These discharges represent a unique system for studying various control parameters that may influence the H↔L state transition. Careful analysis of the power flow through the edge gives values for the sustaining power which are well below the corresponding threshold powers (P{sub HL}/P{sub LH} = 35--70%), indicating substantial hysteresis can be achieved in this parameter. Studies of other control parameter candidates such as edge temperature during the back transitions are less clear: the amount of hysteresis seen in these parameters, if any, is primarily dependent on the nature (ELMing, ELM-free) of the parent H-state.
Download or read book H mode Threshold Power Scaling and The gradient B Drift Effect written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the largest influences on the H-mode power threshold (P[sub TH]) is the direction of the ion[gradient]B drift relative to the X-point location, where factors of 2--3 increase in P[sub TH] are observed for the ion[gradient]B drift away from the X-point. It is proposed that the threshold power scaling observed in single-null configurations with the ion[gradient]B drift toward the X-point location (P[sub TH][approximately] nB, where n is the plasma density, and B is the toroidal field) is due to the scaling of the magnitude of the[gradient]B drift effect. Hinton and later Hinton and Stebler have modeled this effect as neoclassical cross field fluxes of both heat and particles driven by poloidal temperature gradients on the open field lines in the scrape-off layer (SOL). The[gradient]B drift effect influences the power threshold by affecting the edge conditions needed for the L-H transition. It is not essential for the L-H transition itself since transitions are observed with either direction of B. Predictions of this model include saturation of the B scaling of P[sub TH] at high field, 1/B scaling of P[sub TH] with reverse B, and no B scaling of P[sub TH] in balanced double-null configurations. This last prediction is consistent with the observed scaling of p[sub TH] in double-null plasma sin DIII-D.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fusion Energy written by and published by . This book was released on 1997 with total page 962 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Energy Research Abstracts written by and published by . This book was released on 1994-05 with total page 438 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book JET DIII D Size Scaling of the H mode Power Threshold written by and published by . This book was released on 1995 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: Previous scaling results indicate that the H-mode power threshold increases nearly linearly with the line averaged density, {bar n}{sub e}, and the toroidal field, B{sub t}. The power threshold was measured in similar, ITER-like, discharges in JET and DIII-D, at the same {bar n}{sub e} and B{sub t} in order to determine the size scaling of the power threshold. The results indicate a size scaling proportional to the surface area, S{sup 0.5}, which is weaker than the linear surface area dependence previously assumed.
Download or read book Fusion Energy 1996 written by International Atomic Energy Agency and published by Fusion Energy 1996. This book was released on 1997 with total page 954 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proceedings of the Sixteenth International Conference, formerly called the International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Montreal, 7-11 October 1996. The papers presented reflect the excellent progress achieved since the last conference in Seville 1994. Among many other achievements, the Tokamak Fusion Test Reactor has produced over 10 MW of fusion power, the JT-60U experiment has demonstrated plasma conditions equivalent to breakeven, the reversed shear mode has been demonstrated, low aspect ratio tokamaks have produced promising results and plans have been drawn up for powerful new inertial confinement fusion experiments.
Download or read book Overview of H mode Studies in DIII D written by and published by . This book was released on 1994 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: A major portion of the DIII-D program includes studies of the L-H transition, of the VH-mode, of particle transport and control and of the power-handling capability of a diverter. Significant progress has been made in all of these areas and the purpose of this paper is to summarize the major results obtained during the last two years. An increased understanding of the origin of improved confinement in H-mode and in VH-mode discharges has been obtained, good impurity control has been achieved in several operating scenarios, studies of helium transport provide encouraging results from the point of view of reactor design, an actively pumped diverter chamber has controlled the density in H-mode discharges and a radiative diverter is a promising technique for controlling the heat flux from the main plasma.
Download or read book Fusion Science and Technology written by and published by . This book was released on 2008 with total page 512 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Critical Edge Parameters for H mode Transition in DIII D written by and published by . This book was released on 1997 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Measurements in DIII-D of edge ion and electron temperatures (T{sub i} and T{sub e}) just prior to the transition to H-mode are presented. A fitting model based on a hyperbolic tangent function is used in the analysis. The edge temperatures are observed to increase during the L-phase with the application of auxiliary heating. The temperature rise is small if the H-mode power threshold is close to the Ohmic power level in the absence of auxiliary heating and is large if the H-mode threshold is well above the Ohmic power level. The edge temperatures just prior to the transition are approximately proportional to the toroidal magnetic field Bt for the field either in the reversed or forward direction. However, for the reversed magnetic field, the temperatures are at least a factor of two higher than for the forward direction.
Download or read book Final Report of the Committee on a Strategic Plan for U S Burning Plasma Research written by National Academies of Sciences, Engineering, and Medicine and published by National Academies Press. This book was released on 2019-05-31 with total page 341 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fusion offers the prospect of virtually unlimited energy. The United States and many nations around the world have made enormous progress toward achieving fusion energy. With ITER scheduled to go online within a decade and demonstrate controlled fusion ten years later, now is the right time for the United States to develop plans to benefit from its investment in burning plasma research and take steps to develop fusion electricity for the nation's future energy needs. At the request of the Department of Energy, the National Academies of Sciences, Engineering, and Medicine organized a committee to develop a strategic plan for U.S. fusion research. The final report's two main recommendations are: (1) The United States should remain an ITER partner as the most cost-effective way to gain experience with a burning plasma at the scale of a power plant. (2) The United States should start a national program of accompanying research and technology leading to the construction of a compact pilot plant that produces electricity from fusion at the lowest possible capital cost.
