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Advanced Tokamak Profile Evolution In Diii D
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Book Synopsis ADVANCED TOKAMAK PROFILE EVOLUTION IN DIII-D. by :
Download or read book ADVANCED TOKAMAK PROFILE EVOLUTION IN DIII-D. written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Using off-axis electron cyclotron current drive (ECCD), self-consistent integrated advanced tokamak operation has been demonstrated on DIII-D, combining high[beta] (>3%) at high q(q[sub min]> 2.0) with good energy confinement (H[sub 89][approx] 2.5) and high noninductive current fraction (f[sub BS][approx] 55%, f[sub NI][approx] 90%). Modification of the current profile by ECCD led to internal transport barrier formation even in the presence of type I edge localized modes. Improvements were observed in all transport channels, and increased peaking of profiles led to higher bootstrap current in the core. Separate experiments have shown the ability to maintain a nearly steady-state current profile for up to 1 s with q[sub min]> 1.5. Modeling indicates that this favorable current profile can be maintained indefinitely at a higher[beta][sub N] using tools available to the near-term DIII-D program. Modeling and simulation have become essential tools for the experimental program in interpreting the data and developing detail plans for new experiments.
Book Synopsis Current Profile Modeling to Extend the Duration of High Performance Advanced Tokamak Modes in DIII-D. by :
Download or read book Current Profile Modeling to Extend the Duration of High Performance Advanced Tokamak Modes in DIII-D. written by and published by . This book was released on 1998 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: In DIII-D, as in a number of tokamaks, high performance is obtained with various optimized magnetic shear configurations that exhibit internal transport barriers. Negative central shear (NCS) discharges are created transiently during the current ramp-up by auxiliary heating and current drive from neutral beam injection. Both q{sub min} and the radius at which it occurs, [rho]{sub qmin}, decrease with time as the Ohmic current diffuses inward. The q-profiles calculated using EFIT with external magnetic and Motional Stark Effect (MSE) measurements as constraints are comparable to those calculated with the Corsica code, a time-dependent, 2D equilibrium and 1D transport modeling code. Corsica is used to predict the temporal evolution of the current density from a combination of measured profiles, transport models and neoclassical resistivity. Using these predictive capabilities, the authors are exploring methods for increasing the duration and [rho]{sub qmin} of the NCS configuration by local control of the current density profile with simulations of the possible control available from the electron cyclotron heating and current drive system currently being upgraded on DIII-D. Their intention is not to do a detailed investigation of transport models but rather to provide a reasonable model of heat conductivity to be able to simulate effects of electron cyclotron heating (ECH) and current drive (ECCD) on confinement in NCS configurations. The authors adjust free parameters (c, c1 and c2) in the model to obtain a reasonable representation of the temporal evolution of electron and ion temperature profiles consistent with those measured in selected DIII-D shots. In all cases, they use the measured density profiles rather than self-consistently solve for particle sources and particle transport at this time.
Book Synopsis PROGRESS TOWARD SUSTAINED HIGH-PERFORMANCE ADVANCED TOKAMAK DISCHARGES IN DIII-D. by :
Download or read book PROGRESS TOWARD SUSTAINED HIGH-PERFORMANCE ADVANCED TOKAMAK DISCHARGES IN DIII-D. written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Key elements of a sustained advanced tokamak discharge in DIII-D are a large fraction of the total current from bootstrap current (f[sub BS]) and parameters that optimize the capability to use electron cyclotron current drive (ECCD) at[rho][approx] 0.5 to maintain the desired current profile[1-4]. Increased f[sub BS] results from increasing both the normalized beta ([beta][sub N]) and the minimum value of the safety factor (q[sub min]). Off-axis ECCD is, for the available gyrotron power, optimized at high[beta][sub N], high electron temperature (T[sub e]) and low electron density (n[sub e]). As previously reported[2-4], these required elements have been separately demonstrated: density control at high[beta][sub N] with n[sub e][le] 5 x 10[sup 19] m[sup -3] using divertor-region pumping, stability at high[beta], and off-axis ECCD at the theoretically predicted efficiency. This report summarizes recent work on optimizing and integrating these results through evaluation of the dependence of the beta limit on q[sub min] and q[sub 95], exploration of discharges with relatively high q[sub min], testing of feedback control of T[sub e] for control of the q profile evolution, and modification of the current profile time evolution when ECCD is applied.
Book Synopsis Current Profile Evolution During Fast Wave Current Drive on the DIII-D Tokamak by :
Download or read book Current Profile Evolution During Fast Wave Current Drive on the DIII-D Tokamak written by and published by . This book was released on 1995 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: The effect of co and counter fast wave current drive (FWCD) on the plasma current profile has been measured for neutral beam heated plasmas with reversed magnetic shear on the DIII-D tokamak. Although the response of the loop voltage profile was consistent with the application of co and counter FWCD, little difference was observed between the current profiles for the opposite directions of FWCD. The evolution of the current profile was successfully modeled using the ONETWO transport code. The simulation showed that the small difference between the current profiles for co and counter FWCD was mainly due to an offsetting change in the o@c current proffie. In addition, the time scale for the loop voltage to reach equilibrium (i.e., flatten) was found to be much longer than the FWCD pulse, which limited the ability of the current profile to fully respond to co or counter FWCD.
Book Synopsis Long Pulse Advanced Tokamak Discharges in the DIII-D Tokamak by :
Download or read book Long Pulse Advanced Tokamak Discharges in the DIII-D Tokamak written by and published by . This book was released on 2002 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the main goals for the DIII-D research program is to establish an advanced tokamak plasma with high bootstrap current fraction that can be sustained in-principle steady-state. Substantial progress has been made in several areas during the last year. The resistive wall mode stabilization has been done with spinning plasmas in which the plasma pressure has been extended well above the no-wall beta limit. The 3/2 neoclassical tearing mode has been stabilized by the injection of ECH into the magnetic islands, which drives current to substitute the missing bootstrap current. In these experiments either the plasma was moved or the toroidal field was changed to overlap the ECCD resonance with the location of the NTMs. Effective disruption mitigation has been obtained by massive noble gas injection into shots where disruptions were deliberately triggered. The massive gas puff causes a fast and clean current quench with essentially all the plasma energy radiated fairly uniformly to the vessel walls. The run-away electrons that are normally seen accompanying disruptions are suppressed by the large density of electrons still bound on the impurity nuclei. Major elements required to establish integrated, long-pulse, advanced tokamak operations have been achieved in DIII-D: [beta]{sub T} = 4.2%, [beta]{sub p} = 2, f{sub BS} = 65%, and [beta]{sub N}H9 = 10 for 600 ms (H"4[tau]{sub E}). The next challenge is to integrate the different elements, which will be the goal for the next five years when additional control will be available. Twelve resistive wall mode coils are scheduled to be installed in DIII-D during the summer of 2003. The future plans include upgrading the tokamak pulse length capability and increasing the ECH power, to control the current profile evolution.
Book Synopsis Advanced Tokamak Research on the DIII-D Tokamak by :
Download or read book Advanced Tokamak Research on the DIII-D Tokamak written by and published by . This book was released on 1994 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Modeling of Current Profile Evolution and Equilibria in Negative Central Shear Discharges in the DIII-D Experiment by :
Download or read book Modeling of Current Profile Evolution and Equilibria in Negative Central Shear Discharges in the DIII-D Experiment written by and published by . This book was released on 1996 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent DIII-D advanced tokamak experiments with negative central shear (NCS) have resulted in operation at high normalized [beta], [beta]{sub N}=[beta]/(I/aB), to 4.2, confinement enhancement factors to H=4 (H=[tau]{sub E}/[tau]ITER-89P), and record neutron rates for DIII-D to 2.4X1016 neutrons/sec. These data were obtained during high triangularity, single and double null diverted operation with peaked (L-mode) and broad (H-mode) pressure profiles. We are modeling the spatial and temporal current profile evolution for these discharges using Corsica, a predictive 1-1/2 D equilibrium and transport code. Current profile evolution is self-consistently determined by including current diffusion resulting from current drive due to early neutral beam injection during the ohmic current ramp-up phase of the discharge and the bootstrap current drive associated with pressure profile evolution.
Book Synopsis Study of Current Profile Evolution in Presence of Tearing Modes in DIII-D Hybrid Discharges by : L. Pearlstein
Download or read book Study of Current Profile Evolution in Presence of Tearing Modes in DIII-D Hybrid Discharges written by L. Pearlstein and published by . This book was released on 2004 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: An intermediate regime for tokamak operation has been obtained in DIII-D and in other tokamaks in which the inductive flux consumption is reduced and a broad current profile with the safety factor just above or near the sawtoothing limit is obtained and maintained. The DIII-D tokamak was operated in this regime near the no-wall b limit. High stability and good confinement was achieved at a desired level of q{sub 95} {approx} 3 to 4 for durations as long as 35{tau}{sub E}, three times the current-diffusion time. This regime offers the promise of achieving higher fusion gain and yield and/or longer burn duration for ITER.
Book Synopsis ADVANCED TOKAMAK OPERATION USING THE DIII-D PLASMA CONTROL SYSTEM. by :
Download or read book ADVANCED TOKAMAK OPERATION USING THE DIII-D PLASMA CONTROL SYSTEM. written by and published by . This book was released on 2002 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: A271 ADVANCED TOKAMAK OPERATION USING THE DIII-D PLASMA CONTROL SYSTEM. The principal focus of experimental operations in the DIII-D tokamak is the advanced tokamak (AT) regime to achieve, which requires highly integrated and flexible plasma control. In a high performance advanced tokamak, accurate regulation of the plasma boundary, internal profiles, pumping, fueling, and heating must be well coordinated with MHD control action to stabilize such instabilities as tearing modes and resistive wall modes. Sophisticated monitors of the operational regime must provide detection of off-normal conditions and trigger appropriate safety responses with acceptable levels of reliability. Many of these capabilities are presently implemented in the DIII-D plasma control system (PCS), and are now in frequent or routine operational use. The present work describes recent development, implementation, and operational experience with AT regime control elements for equilibrium control, MHD suppression, and off-normal event detection and response.
Book Synopsis SELF-CONSISTENT, INTEGRATED, ADVANCED TOKAMAK OPERATION ON DIII-D. by :
Download or read book SELF-CONSISTENT, INTEGRATED, ADVANCED TOKAMAK OPERATION ON DIII-D. written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent experiments on DIII-D have demonstrated the ability to sustain plasma conditions that integrate and sustain the key ingredients of Advanced Tokamak (AT) operation: high[beta] with q[sub min]” 1, good energy confinement, and high current drive efficiency. Utilizing off-axis ([rho]= 0.4) electron cyclotron current drive (ECCD) to modify the current density profile in a plasma operating near the no-wall ideal stability limit with q[sub min]> 2.0, plasmas with[beta]= 2.9% and 90% of the plasma current driven non-inductively have been sustained for nearly 2 s (limited only by the duration of the ECCD pulse). Separate experiments have demonstrated the ability to sustain a steady current density profile using ECCD for periods as long as 1 s with[beta]= 3.3% and> 90% of the current driven non-inductively.
Author :Federico Bribiesca Argomedo Publisher :Springer Science & Business Media ISBN 13 :3319019589 Total Pages :105 pages Book Rating :4.3/5 (19 download)
Book Synopsis Safety Factor Profile Control in a Tokamak by : Federico Bribiesca Argomedo
Download or read book Safety Factor Profile Control in a Tokamak written by Federico Bribiesca Argomedo and published by Springer Science & Business Media. This book was released on 2013-11-08 with total page 105 pages. Available in PDF, EPUB and Kindle. Book excerpt: Control of the Safety Factor Profile in a Tokamak uses Lyapunov techniques to address a challenging problem for which even the simplest physically relevant models are represented by nonlinear, time-dependent, partial differential equations (PDEs). This is because of the spatiotemporal dynamics of transport phenomena (magnetic flux, heat, densities, etc.) in the anisotropic plasma medium. Robustness considerations are ubiquitous in the analysis and control design since direct measurements on the magnetic flux are impossible (its estimation relies on virtual sensors) and large uncertainties remain in the coupling between the plasma particles and the radio-frequency waves (distributed inputs). The Brief begins with a presentation of the reference dynamical model and continues by developing a Lyapunov function for the discretized system (in a polytopic linear-parameter-varying formulation). The limitations of this finite-dimensional approach motivate new developments in the infinite-dimensional framework. The text then tackles the construction of an input-to-state-stability Lyapunov function for the infinite-dimensional system that handles the medium anisotropy and provides a common basis for analytical robustness results. This function is used as a control-Lyapunov function and allows the amplitude and nonlinear shape constraints in the control action to be dealt with. Finally, the Brief addresses important application- and implementation-specific concerns. In particular, the coupling of the PDE and the finite-dimensional subsystem representing the evolution of the boundary condition (magnetic coils) and the introduction of profile-reconstruction delays in the control loop (induced by solving a 2-D inverse problem for computing the magnetic flux) is analyzed. Simulation results are presented for various operation scenarios on Tore Supra (simulated with METIS) and on TCV (simulated with RAPTOR). Control of the Safety Factor Profile in a Tokamak will be of interest to both academic and industrially-based researchers interested in nuclear energy and plasma-containment control systems, and graduate students in nuclear and control engineering.
Book Synopsis OVERVIEW OF RECENT EXPERIMENTAL RESULTS FROM THE DIII-D ADVANCED TOKAMAK PROGRAM. by :
Download or read book OVERVIEW OF RECENT EXPERIMENTAL RESULTS FROM THE DIII-D ADVANCED TOKAMAK PROGRAM. written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: OAK A271 OVERVIEW OF RECENT EXPERIMENTAL RESULTS FROM THE DIII-D ADVANCED TOKAMAK PROGRAM. The DIII-D research program is developing the scientific basis for advanced tokamak (AT) modes of operation in order to enhance the attractiveness of the tokamak as an energy producing system. Since the last International Atomic Energy Agency (IAEA) meeting, they have made significant progress in developing the building blocks needed for AT operation: (1) they have doubled the magnetohydrodynamic (MHD) stable tokamak operating space through rotational stabilization of the resistive wall mode; (2) using this rotational stabilization, they have achieved[beta][sub N]H[sub 89][ge] 10 for 4[tau][sub E] limited by the neoclassical tearing mode; (3) using real-time feedback of the electron cyclotron current drive (ECCD) location, they have stabilized the (m, n)= (3,2) neoclassical tearing mode and then increased[beta][sub T] by 60%; (4) they have produced ECCD stabilization of the (2,1) neoclassical tearing mode in initial experiments; (5) they have made the first integrated AT demonstration discharges with current profile control using ECCD; (6) ECCD and electron cyclotron heating (ECH) have been used to control the pressure profile in high performance plasmas; and (7) they have demonstrated stationary tokamak operation for 6.5 s (36[tau][sub E]) at the same fusion gain parameter of[beta][sub N]H[sub 89]/q[sub 95][sup 2][approx] 0.4 as ITER but at much higher q[sub 95]= 4.2. The authors have developed general improvements applicable to conventional and advanced tokamak operating modes: (1) they have an existence proof of a mode of tokamak operation, quiescent H-mode, which has no pulsed, ELM heat load to the divertor and which can run for long periods of time (3.8 s or 25[tau][sub E]) with constant density and constant radiated power; (2) they have demonstrated real-time disruption detection and mitigation for vertical disruption events using high pressure gas jet injection of noble gases; (3) they have found that the heat and particle fluxes to the inner strike points of balanced, double-null divertors are much smaller than to the outer strike points. They have made detailed investigations of the edge pedestal and SOL: (1) Atomic physics and plasma physics both play significant roles in setting the width of the edge density barrier in H-mode; (2) ELM heat flux conducted to the divertor decreases as density increases; (3) Intermittent, bursty transport contributes to cross field particle transport in the scrape-off layer (SOL) of H-mode and, especially, L-mode plasmas.
Book Synopsis Advanced Tokamak Physics Experiments on DIII-D. by :
Download or read book Advanced Tokamak Physics Experiments on DIII-D. written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Significant reductions in the size and cost of a fusion power plant core can be realized if simultaneous improvements in the energy confinement time ([tau][sub E]) and the plasma pressure (or beta[beta][sub T]= 2[mu][sub 0] /B[sub T][sup 2]) can be achieved in steady-state conditions with high self driven bootstrap current fraction. In addition, effective power exhaust and impurity and particle control is required. Significant progress has been made in experimentally achieving regimes having the required performance in all of these aspects as well as in developing a theoretical understanding of the underlying physics. The authors have extended the duration of high performance ELMing H-mode plasmas with[beta][sub N] H[sub iop][approximately] 10 for 5[tau][sub E] ([approximately]1 s) and have demonstrated that core transport barriers can be sustained for the entire 5-s neutral beam duration in L-mode plasmas. Recent DIII-D work has advanced the understanding of improved confinement and internal transport barriers in terms of E x B shear stabilization of micro turbulence. With the aim of current profile control in discharges with negative central magnetic shear, they have demonstrated off-axis electron cyclotron current drive for the first time in a tokamak, finding an efficiency above theoretical expectations. MHD stability has been improved through shape optimization, wall stabilization, and modification of the pressure and current density profiles. Heat flux reduction and improved impurity and particle control have been realized through edge/divertor radiation and understanding and utilization of forced scrape off layer flow and divertor baffling.
Book Synopsis Scientific and Technical Aerospace Reports by :
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 704 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis ACHIEVING AND SUSTAINING STEADY-STATE ADVANCED TOKAMAK CONDITIONS ON DIII-D. by :
Download or read book ACHIEVING AND SUSTAINING STEADY-STATE ADVANCED TOKAMAK CONDITIONS ON DIII-D. written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent experiments on the DIII-D tokamak have demonstrated the feasibility of sustaining advanced tokamak conditions that combine high fusion power density ([beta]> 4%), high bootstrap current fraction (f[sub BS][approx] 65%), and high non-inductive current fractions (f[sub NI][approx] 85%) for several energy confinement times. The duration of such conditions is limited only by resistive relaxation of the current density profile. Modeling studies indicate that the application of off-axis ECCD will be able to maintain a favorable current density profile for several seconds.
Book Synopsis NEXT-GENERATION PLASMA CONTROL IN THE DIII-D TOKAMAK. by :
Download or read book NEXT-GENERATION PLASMA CONTROL IN THE DIII-D TOKAMAK. written by and published by . This book was released on 2002 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: OAK A271 NEXT-GENERATION PLASMA CONTROL IN THE DIII-D TOKAMAK. The advanced tokamak (AT) operating mode which is the principal focus of the DIII-D tokamak requires highly integrated and complex plasma control. Simultaneous high performance regulation of the plasma boundary and internal profiles requires multivariable control techniques to account for the highly coupled influences of equilibrium shape, profile, and stability control. This paper describes progress towards the DIII-D At mission goal through both significantly improved real-time computational hardware and control algorithm capability.
Book Synopsis CONTROL OF MHD STABILITY IN DIII-D ADVANCED TOKAMAK DISCHARGES. by : M. MURAKAMI
Download or read book CONTROL OF MHD STABILITY IN DIII-D ADVANCED TOKAMAK DISCHARGES. written by M. MURAKAMI and published by . This book was released on 2003 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt:
