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Self Consistent Integrated Advanced Tokamak Operation On Diii D
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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.
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 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 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 HIGH PERFORMANCE ADVANCED TOKAMAK REGIMES FOR NEXT-STEP EXPERIMENTS. by :
Download or read book HIGH PERFORMANCE ADVANCED TOKAMAK REGIMES FOR NEXT-STEP EXPERIMENTS. written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: OAK-B135 Advanced Tokamak (AT) research in DIII-D seeks to provide a scientific basis for steady-state high performance operation in future devices. These regimes require high toroidal beta to maximize fusion output and poloidal beta to maximize the self-driven bootstrap current. Achieving these conditions requires integrated, simultaneous control of the current and pressure profiles, and active magnetohydrodynamic (MHD) stability control. The building blocks for AT operation are in hand. Resistive wall mode stabilization via plasma rotation and active feedback with non-axisymmetric coils allows routine operation above the no-wall beta limit. Neoclassical tearing modes are stabilized by active feedback control of localized electron cyclotron current drive (ECCD). Plasma shaping and profile control provide further improvements. Under these conditions, bootstrap supplies most of the current. Steady-state operation requires replacing the remaining Ohmic current, mostly located near the half-radius, with noninductive external sources. In DIII-D this current is provided by ECCD, and nearly stationary AT discharges have been sustained with little remaining Ohmic current. Fast wave current drive is being developed to control the central magnetic shear. Density control, with divertor cryopumps, of AT discharges with edge localized moding (ELMing) H-mode edges facilitates high current drive efficiency at reactor relevant collisionalities. A sophisticated plasma control system allows integrated control of these elements. Close coupling between modeling and experiment is key to understanding the separate elements, their complex nonlinear interactions, and their integration into self-consistent high performance scenarios. Progress on this development, and its implications for next-step devices, will be illustrated by results of recent experiment and simulation efforts.
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 2002 with total page 39 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}H9 e"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}H9/q952 H"0.4 as ITER but at much higher q95 = 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 Status of Advanced Tokamak Scenario Modeling with Off-Axis Electron Cyclotron Current Drive in DIII-D. by :
Download or read book Status of Advanced Tokamak Scenario Modeling with Off-Axis Electron Cyclotron Current Drive in 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: The status of modeling work focused on developing the advanced tokamak scenarios in DIII-D is discussed. The objectives of the work are two-fold: (1) to develop AT scenarios with ECCD using time-dependent transport simulations, coupled with heating and current drive models, consistent with MHD equilibrium and stability; and (2) to use time-dependent simulations to help plan experiments and to understand the key physics involved. Time-dependent simulations based on transport coefficients derived from experimentally achieved target discharges are used to perform AT scenario modeling. The modeling indicates off-axis ECCD with approximately 3 MW absorbed power can maintain high-performance discharges with q[sub min]> 1 for 5 to 10 s. The resultant equilibria are calculated to be stable to n= 1 pressure driven modes. The plasma is well into the second stability regime for high-n ballooning modes over a large part of the plasma volume. The role of continuous localized ECCD is studied for stabilizing m/n= 2/1 tearing modes. The progress towards validating current drive and transport models, consistent with experimental results, and developing self-consistent, integrated high performance AT scenarios is discussed.
Book Synopsis Shape Optimization for DIII-D Advanced Tokamak Plasmas by : C. E. Kessel
Download or read book Shape Optimization for DIII-D Advanced Tokamak Plasmas written by C. E. Kessel and published by . This book was released on 2003 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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:
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 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 Quiescent Double Barrier H-Mode Plasmas in the DIII-D Tokamak by :
Download or read book Quiescent Double Barrier H-Mode Plasmas in the DIII-D Tokamak written by and published by . This book was released on 2000 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: High confinement (H-mode) operation is the choice for next-step tokamak devices based either on conventional or advanced tokamak physics. This choice, however, comes at a significant cost for both the conventional and advanced tokamaks because of the effects of edge localized modes (ELMs). ELMs can produce significant erosion in the divertor and can affect the beta limit and reduced core transport regions needed for advanced tokamak operation. Experimental results from DIII-D this year have demonstrated a new operating regime, the quiescent H-mode regime, which solves these problems. We have achieved quiescent H-mode operation which is ELM-free and yet has good density and impurity control. In addition, we have demonstrated that an internal transport barrier can be produced and maintained inside the H-mode edge barrier for long periods of time (>3.5 seconds or>25 energy confinement times [tau]{sub E}), yielding a quiescent double barrier regime. By slowly ramping the input power, we have achieved [beta]{sub N} H89 = 7 for up to 5 times the [tau]{sub E} of 150 ms. The [beta]{sub N} H89 values of 7 substantially exceed the value of 4 routinely achieved in standard ELMing H-mode. The key factors in creating the quiescent H-mode operation are neutral beam injection in the direction opposite to the plasma current (counter injection) plus cryopumping to reduce the density. Density and impurity control in the quiescent H-mode is possible because of the presence of an edge magnetic hydrodynamic (MHD) oscillation, the edge harmonic oscillation, which enhances the edge particle transport while leaving the energy transport unaffected.
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 Results from the DIII-D Scientific Research Program by :
Download or read book Results from the DIII-D Scientific Research Program written by and published by . This book was released on 1998 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Franco-American Convention Relative to Double Taxation by : Emmet McCaffery
Download or read book The Franco-American Convention Relative to Double Taxation written by Emmet McCaffery and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 2002 with total page 7 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] ≈ 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} ≤ 5 x 1019 m−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 q95, 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 Development of Burning Plasma and Advanced Scenarios in the DIII-D Tokamak by : T. C. Luce
Download or read book Development of Burning Plasma and Advanced Scenarios in the DIII-D Tokamak written by T. C. Luce and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Significant progress in the development of burning plasma scenarios, steady-state scenarios at high fusion performance, and basic tokamak physics has been made by the DIII-D Team. Discharges similar to the ITER baseline scenario have demonstrated normalized fusion performance nearly 50% higher than required for Q = 10 in ITER, under stationary conditions. Discharges that extrapolate to Q {approx} 10 for longer than one hour in ITER at reduced current have also been demonstrated in DIII-D under stationary conditions. Proof of high fusion performance with full noninductive operation has been obtained. Underlying this work are studies validating approaches to confinement extrapolation, disruption avoidance and mitigation, tritium retention, ELM avoidance, and operation above the no-wall pressure limit. In addition, the unique capabilities of the DIII-D facility have advanced studies of the sawtooth instability with unprecedented time and space resolution, threshold behavior in the electron heat transport, and rotation in plasmas in the absence of external torque.
