Download or read book DETAILED MEASUREMENTS OF THE ELECTRON CYCLOTRON CURRENT DRIVE EFFICIENCY ON DIIID written by and published by . This book was released on 2002 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: Electron cyclotron current drive (ECCD) experiments on the DIII-D tokamak are solidifying the physics basis for localized, off-axis current drive, the goal being to validate a predictive model for ECCD. The ECCD profiles are determined from the magnetic field pitch angles measured by motional Stark effect (MSE) polarimetry. The measured ECCD switches from the co to the counter direction as the toroidal injection angle is varied with a profile width that is in accordance with ray tracing calculations. Tests of electron trapping in low beta plasmas show that the ECCD efficiency decreases rapidly as the deposition is moved off-axis and towards the outboard side of the plasma, but the detrimental effects of electron trapping on the current drive are greatly reduced in high beta plasmas. Overall, the measured ECCD is in good agreement with theoretical calculations using a quasilinear Fokker-Planck code over a wide range of injection angles and plasma parameters.
Download or read book PHYSICS OF ELECTRON CYCLOTRON CURRENT DRIVE ON DIII D written by and published by . This book was released on 2002 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: OAK A271 PHYSICS OF ELECTRON CYCLOTRON CURRENT DRIVE ON DIII-D. Recent experiments on the DIII-D tokamak have focused on determining the effect of trapped particles on the electron cyclotron current drive (ECCD) efficiency. The measured ECCD efficiency increases as the deposition location is moved towards the inboard midplane or towards smaller minor radius for both co and counter injection. The measured ECCD efficiency also increases with increasing electron density and/or temperature. The experimental ECCD is compared to both the linear theory (Toray-GA) as well as a quasilinear Fokker-Planck model (CQL3D). The experimental ECCD is found to be in better agreement with the more complete Fokker-Planck calculation, especially for cases of high rf power density and/or loop voltage.
Download or read book PHYSICS OF ELCTRON CYCLOTRON CURRENT DRIVE ON DIII D written by and published by . This book was released on 2002 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt: OAK A271 PHYSICS OF ELCTRON CYCLOTRON CURRENT DRIVE ON DIII-D. Recent experiments on the DIII-D tokamak have focused on determining the effect of trapped particles on the electron cyclotron current drive (ECCD) efficiency. The measured ECCD efficiency increases as the deposition location is moved towards the inboard midplane or towards smaller minor radius for both co and counter injection. The measured ECCD efficiency also increases with increasing electron density and/or temperature. The experimental ECCD is compared to both the linear theory (Toray-GA) as well as a quasilinear Fokker-Planck model (CQL3D). The experimental ECCD is found to be in better agreement with the more complete Fokker-Planck calculation, especially for cases of high rf power density and/or loop voltage. The narrow width of the measured ECCD profile is consistent with only low levels of radial transport for the current carrying electrons.
Download or read book Modeling of Electron Cyclotron Current Drive Experiments on DIII D written by and published by . This book was released on 1999 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Electron Cyclotron Current Drive (ECCD) is considered a leading candidate for current profile control in Advanced Tokamak (AT) operation. Localized ECCD has been clearly demonstrated in recent proof-of-principle experiments on DIII-D. The measured ECCD efficiency near the magnetic axis agrees well with standard theoretical predictions. However, for off-axis current drive the normalized experimental efficiency does not decrease with minor radius as expected from the standard theory; the observed reduction of ECCD efficiency due to trapped electron effects in the off-axis cases is smaller than theoretical predictions. The standard approach of modeling ECCD in tokamaks has been based on the bounce-average calculations, which assume the bounce frequency is much larger than the effective collision frequency for trapped electrons at all energies. The assumption is clearly invalid at low energies. Finite collisionality will effectively reduce the trapped electron fraction, hence, increase current drive efficiency. Here, a velocity-space connection formula is proposed to estimate the collisionality effect on electron cyclotron current drive efficiency. The collisionality correction gives modest improvement in agreement between theoretical and recent DIII-D experimental results.
Download or read book Electron Cyclotron Emission And Electron Cyclotron Heating Ec12 Proceedings Of The 12th Joint Workshop written by Gerardo Giruzzi and published by World Scientific. This book was released on 2003-02-21 with total page 613 pages. Available in PDF, EPUB and Kindle. Book excerpt: The 12th Joint Workshop on Electron Cyclotron Emission and Electron Cyclotron Resonance Heating (EC-12) was held in Aix-en-Provence (France) from May 13 to 16, 2002. This workshop was concerned with the interaction of electromagnetic waves and hot plasmas, a subject of great importance in the framework of research on controlled thermonuclear fusion. Using as a fuel a mixture of deuterium and tritium, which can be extracted from sea water, this is a very promising way to develop an intrinsically safe reactor. The workshop gathered approximately one hundred specialists in the production, use and theory of millimetre waves for heating and diagnostics of fusion plasmas.
Download or read book Current Profile Modification with Electron Cyclotron Current Drive in the DIII D Tokamak written by and published by . This book was released on 1998 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proof-of-principle experiments on the suitability of electron cyclotron current drive (ECCD) for active current profile control are reported. Experiments with second harmonic extraordinary mode absorption at power levels near 1 MW have demonstrated ability to modify the current profile. This modification is manifested in changes in the internal inductance and the time at which sawteeth appear. Measurements of the local current density and internal loop voltage using high resolution motional Stark effect spectroscopy to half of the minor radius in discharges with localized deposition clearly demonstrate localized off-axis ECCD at the predicted location. Comparison with theory indicates the detrimental effect of trapped electrons on the current drive efficiency is less than predicted. Modification of the theory for finite collisionality is the leading candidate to explain the observations.
Download or read book Comparison Between the Electron Cyclotron Current Drive Experiments on DIII D and Predictions for T 10 written by and published by . This book was released on 1990 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: Electron cyclotron current drive has been demonstrated on the DIII-D tokamak in an experiment in which (approximately)1 MW of microwave power generated (approximately)50 kA of non-inductive current. The rf-generated portion was about 15% of the total current. On the T-10 tokamak, more than 3 MW of microwave power will be available for current generation, providing the possibility that all the plasma current could be maintained by this method. Fokker-Planck calculations using the code CQL3D and ray tracing calculations using TORAY have been performed to model both experiments. For DIII-D the agreement between the calculations and measurements is good, producing confidence in the validity of the computational models. The same calculations using the T-10 geometry predict that for n{sub e}(0) (approximately) 1.8 x 1013 cm−3, and T{sub e}(0) (approximately) 7 keV, 1.2 MW, that is, the power available from only three gyrotrons, could generate as much as 150 kA of non-inductive current. Parameter space scans in which temperature, density and resonance location were varied have been performed to indicate the current drive expected under different experimental conditions. The residual dc electric field was considered in the DIII-D analysis because of its nonlinear effect on the electron distribution, which complicates the interpretation of the results. A 110 GHz ECH system is being installed on DIII-D. Initial operations, planned for late 1991, will use four gyrotrons with 500 kW each and 10 second output pulses. Injection will be from the low field side from launchers which can be steered to heat at the desired location. These launchers, two of which are presently installed, are set at 20 degrees to the radial and rf current drive studies are planned for the initial operation. 8 refs., 10 figs.
Download or read book Electron Cyclotron Current Drive in DIII D written by and published by . This book was released on 1999 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: Clear measurements of the localized current density driven by electron cyclotron waves have been made on the DIII-D tokamak. Direct evidence of the current drive is seen on the internal magnetic field measurements by motional Stark effect spectroscopy. Comparison with theoretical calculations in the collisionless limit shows the experimental current drive exceeds the predictions by a substantial amount for currents driven near the half radius. In all cases the experimental current density profile is broader than the predicted one.
Download or read book ELECTRON CYCLOTRON CURRENT DRIVE IN DIII D written by and published by . This book was released on 2003 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: A271 ELECTRON CYCLOTRON CURRENT DRIVE IN DIII-D: EXPERIMENT AND THEORY. Experiments on the DIII-D tokamak in which the measured off-axis electron cyclotron current drive has been compared systematically to theory over a broad range of parameters have shown that the Fokker-Planck code CQL3D provides an excellent model of the relevant current drive physics. This physics understanding has been critical in optimizing the application of ECCD to high performance discharges, supporting such applications as suppression of neoclassical tearing modes and control and sustainment of the current profile.
Download or read book Electron Cyclotron Emission And Electron Cyclotron Resonance Heating Ec 15 Proceedings Of The 15th Joint Workshop With Cd rom written by John Lohr and published by World Scientific. This book was released on 2009-04-15 with total page 583 pages. Available in PDF, EPUB and Kindle. Book excerpt: These proceedings present the latest results in electron cyclotron emission, heating and current drive, with an emphasis on the physics and technology of Electron Cyclotron Emission, Electron Cyclotron Heating and Electron Cyclotron Current Drive applied to magnetic fusion research. The field is a key element in the development of fusion power and the ITER project now under construction.
Download or read book Proceedings of the Fifteenth Joint Workshop on Electron Cyclotron Emission and Electron Cyclotron Resonance Heating written by John Lohr and published by World Scientific. This book was released on 2009 with total page 583 pages. Available in PDF, EPUB and Kindle. Book excerpt: These proceedings present the latest results in electron cyclotron emission, heating and current drive, with an emphasis on the physics and technology of Electron Cyclotron Emission, Electron Cyclotron Heating and Electron Cyclotron Current Drive applied to magnetic fusion research. The field is a key element in the development of fusion power and the ITER project now under construction.
Download or read book Modeling of Trapped Electron Effects on Electron Cyclotron Current Drive for Recent DIII D Experiments written by and published by . This book was released on 1999 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: Owing to its potential capability of generating localized non-inductive current, especially off-axis, Electron Cyclotron Current Drive (ECCD) is considered a leading candidate for current profile control in achieving Advanced Tokamak (AT) operation. In recent DIII-D proof-of-principle experiments [1], localized off-axis ECCD has been clearly demonstrated for first time. The measured current drive efficiency near the magnetic axis agrees well with predictions of the bounce-averaged Fokker-Planck theory [2,3]. However, the off-axis current drive efficiency was observed to exceed the theoretical results, which predict significant degradation of the current drive efficiency due to trapped electron effects. The theoretical calculations have been based on an assumption that the effective collision frequency is much smaller than the bounce frequency such that the trapped electrons are allowed to complete the banana orbit at all energies. The assumption might be justified in reactor-grade tokamak plasmas, in which the electron temperature is sufficiently high or the velocity of resonant electrons is much larger than the thermal velocity, so that the influence of collisionality on current drive efficiency can be neglected. For off-axis deposition in the present-day experiments, the effect of high density and low temperature is to reduce the current drive efficiency, but the increasing collisionality reduces the trapping of current-carrying electrons, leading to compensating increases in the current drive efficiency. In this work, we use the adjoint function formulation [4] to examine collisionality effects on the current drive efficiency.
Download or read book Fusion Physics written by MITSURU KIKUCHI and published by International Atomic Energy. This book was released on 2002-01-01 with total page 1158 pages. Available in PDF, EPUB and Kindle. Book excerpt: Humans do not live by bread alone. Physically we are puny creatures with limited prowess, but with unlimited dreams. We see a mountain and want to move it to carve out a path for ourselves. We see a river and want to tame it so that it irrigates our fields. We see a star and want to fly to its planets to secure a future for our progeny. For all this, we need a genie who will do our bidding at a flip of our fingers. Energy is such a genie. Modern humans need energy and lots of it to live a life of comfort. In fact, the quality of life in different regions of the world can be directly correlated with the per capita use of energy [1.1–1.5]. In this regard, the human development index (HDI) of various countries based on various reports by the United Nations Development Programme (UNDP) [1.6] (Fig. 1.1), which is a parameter measuring the quality of life in a given part of the world, is directly determined by the amount of per capita electricity consumption. Most of the developing world (~5 billion people) is crawling up the UN curve of HDI versus per capita electricity consumption, from abysmally low values of today towards the average of the whole world and eventually towards the average of the developed world. This translates into a massive energy hunger for the globe as a whole. It has been estimated that by the year 2050, the global electricity demand will go up by a factor of up to 3 in a high growth scenario [1.7–1.9]. The requirements beyond 2050 go up even higher.
Download or read book Current Drive with Fast Waves Electron Cyclotron Waves and Neutral Injection in the DIII D Tokamak written by and published by . This book was released on 1992 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: Current drive experiments have been performed on the DIII-D tokamak using fast waves, electron cyclotron waves, and neutral injection. Fast wave experiments were performed using a 4-strap antenna with 1 MW of power at 60 MHz. These experiments showed effective heating of electrons, with a global heating efficiency equivalent to that of neutral injection even when the single pass damping was calculated to be as small as 5%. The damping was probably due to the effect of multiple passes of the wave through the plasma. Fast wave current drive experiments were performed with a toroidally directional phasing of the antenna straps. Currents driven by fast wave current drive (FWCD) in the direction of the main plasma current of up to 100 kA were found, not including a calculated 40 kA of bootstrap current. Experiments with FWCD in the counter current direction showed little current drive. In both cases, changes in the sawtooth behavior and the internal inductance qualitatively support the measurement of FWCD. Experiments on electron cyclotron current drive have shown that 100 kA of current can be driven by 1 MW of power at 60 GHz. Calculations with a Fokker-Planck code show that electron cyclotron current drive (ECCD) can be well predicted when the effects of electron trapping and of the residual electric field are included. Experiments on driving current with neutral injection showed that effective current drive could be obtained and discharges with full current drive were demonstrated. Interestingly, all of these methods of current drive had about the same efficiency, 0.015 x 102° MA/MW/m2.
Download or read book Electron Cyclotron Current Drive Experiments on DIII D written by and published by . This book was released on 1990 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: Electron Cyclotron Current Drive (ECCD) experiments on the DIII-D tokamak have been performed using 60 GHz waves launched from the high field side of the torus. Preliminary analysis indicates rf driven currents between 50 and 100 kA in discharges with total plasma currents between 200 and 500 kA. These are the first ECCD experiments with strong first pass absorption, localized deposition of the rf power, and [tau]{sub E} much longer than the slowing-down time of the rf generated current carriers. The experimentally measured profiles for T{sub e}, [eta]{sub e} and Z{sub eff} are used as input for a 1D transport code and a multiply-ray, 3D ray tracing code. Comparisons with theory and assessment of the influence of the residual electric field, using a Fokker-Planck code, are in progress. The ECH power levels were between 1 and 1.5 MW with pulse lengths of about 500 msec. ECCD experiments worldwide are motivated by issues relating to the physics and technical advantages of the use of high frequency rf waves to drive localized currents. ECCD is accomplished by preferentially heating electrons moving in one toroidal direction, reducing their collisionality and thereby producing a non-inductively driven toroidal current. 6 refs., 4 figs.
Download or read book Modification of the Current Profile in DIII D by Off Axis Electron Cyclotron Current Drive written by and published by . This book was released on 1999 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: Localized non-inductive currents due to electron cyclotron wave absorption have been measured on the DIII-D tokamak. Clear evidence of the non-inductive currents is seen on the internal magnetic field measurements by motional Stark effect spectroscopy. The magnitude and location of the non-inductive current is evaluated by comparing the total and Ohmic current profiles of discharges with and without electron cyclotron wave power. The measured current agrees with Fokker-Planck calculations near the magnetic axis, but exceeds the predicted value as the location of the current drive is moved to the half radius.
