Download or read book High harmonic Fast Wave Heating and Current Drive Results for Deuterium H mode Plasmas in the National Spherical Torus Experiment written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A critical research goal for the spherical torus (ST) program is to initiate, ramp-up, and sustain a discharge without using the central solenoid. Simulations of non-solenoidal plasma scenarios in the National Spherical Torus Experiment (NSTX) [1] predict that high-harmonic fast wave (HHFW) heating and current drive (CD) [2] can play an important roll in enabling fully non-inductive (fNI ≈ 1) ST operation. The NSTX fNI ≈ 1 strategy requires 5-6 MW of HHFW power (PRF) to be coupled into a non-inductively generated discharge [3] with a plasma current, Ip ≈ 250-350 kA, driving the plasma into an HHFW H-mode with Ip ≈ 500 kA, a level where 90 keV deuterium neutral beam injection (NBI) can heat the plasma and provide additional CD. The initial approach on NSTX has been to heat Ip ≈ 300 kA, inductively heated, deuterium plasmas with CD phased HHFW power [2], in order to drive the plasma into an H-mode with fNI ≈ 1.
Download or read book Exploration of High Harmonic Fast Wave Heating on the National Spherical Torus Experiment written by J. R. Wilson and published by . This book was released on with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Generation Of High Non inductive Plasma Current Fraction H mode Discharges By High harmonic Last Wave Heating In The National Spherical Torus Experiment written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 1.4 MW of 30 MHz high-harmonic fast wave (HHFW) heating, with current drive antenna phasing, has generated a Ip = 300kA, BT (0) = 0.55T deuterium H-mode plasma in the National Spherical Torus Experiment that has a non-inductive plasma current fraction, fNI = 0.7-1. Seventy-five percent of the non-inductive current was generated inside an internal transport barrier that formed at a normalized minor radius, r/a ≈ 0.4 . Three quarters of the non-inductive current was bootstrap current and the remaining non-inductive current was generated directly by HHFW power inside r/a ≈ 0.2.
Download or read book Advances in High harmonic Fast Wave Physics in the National Spherical Torus Experiment written by and published by . This book was released on 2009 with total page 91 pages. Available in PDF, EPUB and Kindle. Book excerpt: Improved core high-harmonic fast wave (HHFW) heating at longer wavelengths and during start-up and plasma current ramp-up, has now been obtained by lowering the edge density with lithium wall conditioning, thereby moving the critical density for perpendicular fast-wave propagation away from the vessel wall. Lithium conditioning allowed significant HHFW core electron heating of deuterium neutral beam injection (NBI) fuelled H-mode plasmas to be observed for the first time. Large edge localized modes were observed immediately after the termination of rf power. Visible and infrared camera images show that fast wave interactions can deposit considerable rf energy on the outboard divertor. HHFW-generated parametric decay instabilities were observed to heat ions in the plasma edge and may be the cause for a measured drag on edge toroidal rotation during HHFW heating. A significant enhancement in neutron rate and fast-ion profile were measured in NBI-fuelled plasmas when HHFW heating was applied. __________________________________________________
Download or read book High Harmonic Fast Wave Driven H mode Plasmas on NSTX written by R. E. Bell and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The launch of High-Harmonic Fast Waves (HHFW) routinely provides auxiliary power to NSTX plasmas, where it is used to heat electrons and pursue drive current. H-mode transitions have been observed in deuterium discharges, where only HHFW and ohmic heating, and no neutral beam injection (NBI), were applied to the plasma. The usual H-mode signatures are observed. A drop of the Da light marks the start of a stored energy increase, which can double the energy content. These H-mode plasmas also have the expected kinetic profile signatures with steep edge density and electron temperature pedestal. Similar to its NBI driven counterpart--also observed on NSTX-- the HHFW H mode have density profiles that features ''ears'' in the peripheral region. These plasmas are likely candidates for long pulse operation because of the combination of bootstrap current, associated with H-mode kinetic profiles, and active current drive, which can be generated with HHFW power.
Download or read book The National Spherical Torus Experiment NSTX Research Program and Progress Towards High Beta Long PulseOperating Scenarios written by E. J. Synakowski and published by . This book was released on 2002 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Wave Heating and Current Drive in Plasmas written by Victor L. Granatstein and published by CRC Press. This book was released on 1985 with total page 524 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book High Performance Plasmas on the National Spherical Torus Experiment written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Long Pulse High Performance Plasma Scenario Development for the National Spherical Torus Experiment written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The National Spherical Torus Experiment [Ono et al., Nucl. Fusion, 44, 452 (2004)] is targeting long pulse high performance, noninductive sustained operations at low aspect ratio, and the demonstration of nonsolenoidal startup and current rampup. The modeling of these plasmas provides a framework for experimental planning and identifies the tools to access these regimes. Simulations based on neutral beam injection (NBI)-heated plasmas are made to understand the impact of various modifications and identify the requirements for (1) high elongation and triangularity, (2) density control to optimize the current drive, (3) plasma rotation and/or feedback stabilization to operate above the no-wall limit, and (4) electron Bernstein waves (EBW) for off-axis heating/current drive (H/CD). Integrated scenarios are constructed to provide the transport evolution and H/CD source modeling, supported by rf and stability analyses. Important factors include the energy confinement, Zeff, early heating/H mode, broadening of the NBI-driven current profile, and maintaining q(0) and qmin>1.0. Simulations show that noninductive sustained plasmas can be reached at IP=800 kA, BT=0.5 T, 2.5, N5, 15%, fNI=92%, and q(0)>1.0 with NBI H/CD, density control, and similar global energy confinement to experiments. The noninductive sustained high plasmas can be reached at IP=1.0 MA, BT=0.35 T, 2.5, N9, 43%, fNI=100%, and q(0)>1.5 with NBI H/CD and 3.0 MW of EBW H/CD, density control, and 25% higher global energy confinement than experiments. A scenario for nonsolenoidal plasma current rampup is developed using high harmonic fast wave H/CD in the early low IP and low Te phase, followed by NBI H/CD to continue the current ramp, reaching a maximum of 480 kA after 3.4 s.
Download or read book High harmonic Fast wave Heating in NSTX written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: High-Harmonic Fast-Wave (HHFW), a radio-frequency technique scenario applicable to high-beta plasmas, has been selected as one of the main auxiliary heating systems on the National Spherical Torus Experiment (NSTX). The HHFW antenna assembly comprises 12 toroidally adjacent current elements, extending poloidally and centered on the equatorial plane. This paper reviews experimental results obtained with a symmetrical (vacuum) launching spectrum with k= 14 m(superscript ''-1'') at a frequency of 30 MHz. We describe results obtained when HHFW power is applied to helium and deuterium plasmas, during the plasma-current flattop period of the discharge. Application of 1.8-MW HHFW pulse to MHD quiescent plasmas resulted in strong electron heating, during which the central electron temperature T(subscript ''eo'') more than doubled from approximately 0.5 keV to 1.15 keV. In deuterium plasmas, HHFW heating was found less efficient, with a central electron temperature increase of the order of 40% during a 1.8-MW HHFW pulse, from approximately 400 eV to approximately 550 eV. (At HHFW power of 2.4 MW, central electron temperature increased by 60%, reaching 0.625 keV.) HHFW heating in presence of MHD activity is also discussed. A short neutral-beam pulse was applied to permit charge-exchange recombination spectroscopy (CHERS) measurement of the impurity ion temperature T(subscript ''i''). Preliminary CHERS analysis show that ion temperature approximately equals electron temperature during HHFW heating. Of special interest are deuterium discharges, where the application of HHFW power was done during the current ramp-up. We observe the creation of large density gradients in the edge region. In the latter case, the density rose spontaneously to n (subscript ''eo'') less than or equal to 8 x 10 (superscript ''13'') cm (superscript ''-3'').
Download or read book Initial Physics Results From the National Spherical Torus Experiment written by S. M. Kaye and published by . This book was released on 2001 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Exploration of High Harmonic Fast Wave Heating on the National Spherical Torus Experiment written by J. R. Wilson and published by . This book was released on with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The National Spherical Torus Experiment NSTX Research Programme and Progress Towards High Beta Long Pulse Operating Scenarios written by and published by . This book was released on 2004 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Radio Frequency Power in Plasmas written by Tak K. Mau and published by American Institute of Physics. This book was released on 2001-11-09 with total page 568 pages. Available in PDF, EPUB and Kindle. Book excerpt: This proceedings volume includes the most recent research advances in the application of RF power in plasmas, mainly in fusion science. Most papers deal with plasma heating and current drive, profile control, and stabilization using RF techniques, with some on RF sources and launchers. New and exciting results from all major tokamak experiments, and from theory and modeling are included. There is also a paper on RFplasma application in space propulsion by an active NASA astronaut. This book is a valuable reference for the RF researchers in fusion and other disciplines.
Download or read book Physics Results from the National Spherical Torus Experiment written by and published by . This book was released on 2000 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Simulations Towards the Achievement of Non inductive Current Ramp up and Sustainment in the National Spherical Torus Experiment Upgrade written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the goals of the National Spherical Torus Experiment Upgrade (NSTX-U) (Menard et al 2012 Nucl. Fusion 52 083015) is the demonstration of fully non-inductive start-up, current ramp-up and sustainment. This work discusses predictive simulations where the available heating and current drive systems are combined to maximize the non-inductive current and minimize the solenoidal contribution. Radio-frequency waves at harmonics higher than the ion cyclotron resonance (high-harmonic fast waves (HHFW)) and neutral beam injection are used to ramp the plasma current non-inductively starting from an initial Ohmic plasma. An interesting synergy is observed in the simulations between the HHFW and electron cyclotron (EC) wave heating. Furthermore, time-dependent simulations indicate that, depending on the phasing of the HHFW antenna, EC wave heating can significantly increase the effectiveness of the radio-frequency power, by heating the electrons and increasing the current drive efficiency, thus relaxing the requirements on the level of HHFW power that needs to be absorbed in the core plasma to drive the same amount of fast-wave current.
Download or read book New Capabilities and Results for the National Spherical Torus Experiment written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The National Spherical Torus Experiment (NSTX) produces plasmas with toroidal aspect ratio as low as 1.25, which can be heated by up to 6 MW High-Harmonic Fast Waves and up to 7 MW of deuterium Neutral Beam Injection. Using new poloidal fields coils, plasmas with cross-section elongation up to 2.7, triangularity 0.8, plasma currents Ip up to 1.5 MA and normalized currents Ip/a·BT up to 7.5 MA/m·T have been achieved. A significant extension of the plasma pulse length, to 1.5 s at a plasma current of 0.7 MA, has been achieved by exploiting the bootstrap and NBI-driven currents to reduce the dissipation of poloidal flux. Inductive plasma startup has been supplemented by Coaxial Helicity Injection (CHI) and the production of persistent current on closed flux surfaces by CHI has now been demonstrated in NSTX. The plasma response to magnetic field perturbations with toroidal mode numbers n = 1 or 3 and the effects on the plasma rotation have been investigated using three pairs of coils outside the vacuum vessel. Recent studies of both MHD stability and of transport benefitted from improved diagnostics, including measurements of the internal poloidal field using the motional Stark effect (MSE). In plasmas with a region of reversed magnetic shear in the core, now confirmed by the MSE data, improved electron confinement has been observed.
