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Book The National Spherical Torus Experiment NSTX Research Program and Progress Towards High Beta Long PulseOperating Scenarios

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:

Book The National Spherical Torus Experiment NSTX Research Program and Progress Towards High Beta Long PulseOperating Scenarios

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:

Book Recent Physics Results from NSTX

Download or read book Recent Physics Results from NSTX written by R. E. Bell and published by . This book was released on 2006 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: The National Spherical Torus Experiment (NSTX) has made considerable progress in advancing the scientific understanding of high performance long-pulse plasmas needed for ITER and future low-aspect-ratio Spherical Torus (ST) devices. Plasma durations up to 1.6s (5 current redistribution times) have been achieved at plasma currents of 0.7 MA with non-inductive current fractions above 65% while achieving {beta}{sub T} and {beta}{sub N} values of 16% and 5.7 (%mT/MA), respectively. Newly available Motional Stark Effect data has allowed systematic study and validation of current drive sources and improved the understanding of ''hybrid''-like scenarios. In MHD research, six mid-plane ex-vessel radial field coils have been utilized to infer and correct intrinsic error fields, provide rotation control, and actively stabilize the n=1 resistive wall mode at ITER-relevant low plasma rotation values. In transport and turbulence, the low aspect ratio and wide range of achievable {beta} in NSTX provide unique data for confinement scaling studies. A new high-k scattering diagnostic is investigating turbulent density fluctuations with wavenumbers extending from ion to electron gyro-scales. In the area of energetic particle research, cyclic neutron rate drops have been associated with the destabilization of multiple large Toroidal Alfven Eigenmodes (TAEs) similar to the ''sea-of-TAE'' modes predicted for ITER. Three wave coupling processes between energetic particle modes and TAEs have also been observed for the first time. In boundary physics, advanced shape control has been utilized to study the role of magnetic balance in H-mode access and ELM stability. Peak divertor heat flux has been reduced by a factor of 5 using an H-mode compatible radiative divertor, and Lithium conditioning has demonstrated particle pumping and improved thermal confinement. Finally, non-solenoidal plasma start-up research is particularly important for the ST, and Coaxial Helicity Injection has now produced 160kA plasma currents on closed magnetic flux surfaces.

Book Progress Towards High Performance Plasmas in the National Spherical Torus Experiment NSTX

Download or read book Progress Towards High Performance Plasmas in the National Spherical Torus Experiment NSTX written by and published by . This book was released on 2006 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: The major objective of the National Spherical Torus Experiment (NSTX) is to understand basic toroidal confinement physics at low aspect ratio and high [beta]{sub T} in order to advance the spherical torus (ST) concept. In order to do this, NSTX utilizes up to 7.5 MW of neutral beam injection, up to 6 MW of high harmonic fast waves (HHFWs), and it operates with plasma currents up to 1.5 MA and elongations of up to 2.6 at a toroidal field up to 0.45 T. New facility, and diagnostic and modeling capabilities developed over the past two years have enabled the NSTX research team to make significant progress towards establishing this physics basis for future ST devices. Improvements in plasma control have led to more routine operation at high elongation and high [beta]{sub T} (up to ≈ 40%) lasting for many energy confinement times. [beta]{sub T} can be limited by either internal or external modes. The installation of an active error field (EF) correction coil pair has expanded the operating regime at low density and has allowed for initial resonant EF amplification experiments. The determination of the confinement and transport properties of NSTX plasmas has benefited greatly from the implementation of higher spatial resolution kinetic diagnostics. The parametric variation of confinement is similar to that at conventional aspect ratio but with values enhanced relative to those determined from conventional aspect ratio scalings and with a [beta]{sub T} dependence. The transport is highly dependent on details of both the flow and magnetic shear. Core turbulence was measured for the first time in an ST through correlation reflectometry. Non-inductive start-up has been explored using PF-only and transient co-axial helicity injection techniques, resulting in up to 140 kA of toroidal current generated by the latter technique. Calculated bootstrap and beam-driven currents have sustained up to 60% of the flat-top plasma current in NBI discharges. Studies of HHFW absorption have indicated parametric decay of the wave and associated edge thermal ion heating. Energetic particle modes, most notably toroidal Alfven eigenmodes and fishbone-like modes result in fast particle losses, and these instabilities may affect fast ion confinement on devices such as ITER. Finally, a variety of techniques has been developed for fueling and power and particle control.

Book Progress Towards High Performance Steady State Spherical Torus

Download or read book Progress Towards High Performance Steady State Spherical Torus written by and published by . This book was released on 2004 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: Research on the spherical torus (or spherical tokamak) (ST) is being pursued to explore the scientific benefits of modifying the field line structure from that in more moderate aspect ratio devices, such as the conventional tokamak. The ST experiments are being conducted in various US research facilities including the MA-class National Spherical Torus Experiment (NSTX) at Princeton, and three medium sized ST research facilities: PEGASUS at University of Wisconsin, HIT-II at University of Washington, and CDX-U at Princeton. In the context of the fusion energy development path being formulated in the US, an ST-based Component Test Facility (CTF) and, ultimately a Demo device, are being discussed. For these, it is essential to develop high performance, steady-state operational scenarios. The relevant scientific issues are energy confinement, MHD stability at high beta ([beta]), non-inductive sustainment, Ohmic-solenoid-free start-up, and power and particle handling. In the confinement area, the NSTX experiments have shown that the confinement can be up to 50% better than the ITER-98-pby2 H-mode scaling, consistent with the requirements for an ST-based CTF and Demo. In NSTX, CTF-relevant average toroidal beta values [beta]{sub T} of up to 35% with a near unity central [beta]{sub T} have been obtained. NSTX will be exploring advanced regimes where [beta]{sub T} up to 40% can be sustained through active stabilization of resistive wall modes. To date, the most successful technique for non-inductive sustainment in NSTX is the high beta poloidal regime, where discharges with a high non-inductive fraction (≈60% bootstrap current+NBI current drive) were sustained over the resistive skin time. Research on radio-frequency (RF) based heating and current drive utilizing high harmonic fastwave and electron Bernstein wave is also pursued on NSTX, PEGASUS, and CDX-U. For non-inductive start-up, the coaxial helicity injection, developed in HIT/HIT-II, has been adopted on NSTX to test the method up to I{sub P} ≈500 kA. In parallel, start-up using a RF current drive and only external poloidal field coils are being developed on NSTX. The area of power and particle handling is expected to be challenging because of the higher power density expected in the ST relative to that in conventional aspect-ratio tokamaks. Due to its promise for power and particle handling, liquid lithium is being studied in CDX-U as a potential plasma-facing surface for a fusion reactor.

Book Fusi n Nuclear

Download or read book Fusi n Nuclear written by and published by . This book was released on 2004-12 with total page 504 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Progress Towards Steady State on NSTX

Download or read book Progress Towards Steady State on NSTX written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In order to reduce recirculating power fraction to acceptable levels, the spherical torus concept relies on the simultaneous achievement of high toroidal [beta] and high bootstrap fraction in steady state. In the last year, as a result of plasma control system improvements, the achievable plasma elongation on the National Spherical Torus Experiment (NSTX) has been raised from [kappa] [approx] 2.1 to [kappa] [approx] 2.6--approximately a 25% increase. This increase in elongation has lead to a doubling increase in the toroidal [beta] for long-pulse discharges. The increase in [beta] is associated with an increase in plasma current at nearly fixed poloidal [beta], which enables higher [beta][sub t] with nearly constant bootstrap fraction. As a result, for the first time in a spherical torus, a discharge with a plasma current of 1 MA has been sustained for 1 second. Data is presented from NSTX correlating the increase in performance with increased plasma shaping capability. In addition to improved shaping, H-modes induced during the current ramp phase of the plasma discharge have been used to reduce flux consumption during and to delay the onset of MHD instabilities. A modeled integrated scenario, which has 100% non-inductive current drive with very high toroidal [beta], will also be presented. The NSTX poloidal field coils are currently being modified to produce the plasma shape which is required for this scenario, which requires high triangularity ([delta] [approx] 0.8) at elevated elongation ([kappa] [approx] 2.5). The other main requirement for steady state on NSTX is the ability to drive a fraction of the total plasma current with radio-frequency waves. The results of High Harmonic Fast Wave heating and current drive studies as well as electron Bernstein Wave emission studies will be presented.

Book Engineering Overview of the National Spherical Torus Experiment NSTX

Download or read book Engineering Overview of the National Spherical Torus Experiment NSTX written by and published by . This book was released on 1997 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The National Spherical Torus Experiment (NSTX) Project will provide a national facility for the study of plasma confinement, heating, and current drive in a low-aspect-ratio, spherical torus (ST) configuration. The ST configuration is an alternate confinement concept which is characterized by high beta, high elongation, high bootstrap fraction, and low toroidal magnetic field compared to conventional tokamaks. The NSTX is the next-step ST experiment following smaller experiments such as the Princeton Plasma Physics Laboratory CDX-U (Current Drive Experiment-Upgrade), the START (Small Tight Aspect Ratio Tokamak) at Culham Laboratory, UK, and the HIT (Helicity Injected Tokamak) at the University of Washington, and it is smaller in scale to the MAST (Meg-Amp Spherical Tokamak) machine now under construction at Culham. This paper provides a description of the NSTX mission and gives an overview of the main engineering features of the design of the machine and facility and discusses some of the key design solutions.

Book Recent Progress on the National Spherical Torus Experiment NSTX

Download or read book Recent Progress on the National Spherical Torus Experiment NSTX written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Exploration of Spherical Torus Physics in the NSTX Device

Download or read book Exploration of Spherical Torus Physics in the NSTX Device written by and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The National Spherical Torus Experiment (NSTX) is being built at the Princeton Plasma Physics Laboratory to test the fusion physics principles for the Spherical Torus (ST) concept at the MA level. The NSTX nominal plasma parameters are R 0 = 85 cm, a = 67 cm, R/a greater than or equal to 1.26, B {sub T} = 3 kG, I {sub p} = 1 MA, q 95 = 14, elongation [kappa] less than or equal to 2.2, triangularity [delta] less than or equal to 0.5, and plasma pulse length of up to 5 sec. The plasma heating/current drive (CD) tools are High Harmonic Fast Wave (HHFW) (6 MW, 5 sec), Neutral Beam Injection (NBI) (5 MW, 80 keV, 5 sec), and Coaxial Helicity Injection (CHI). Theoretical calculations predict that NSTX should provide exciting possibilities for exploring a number of important new physics regimes including very high plasma beta, naturally high plasma elongation, high bootstrap current fraction, absolute magnetic well, and high pressure driven sheared flow. In addition, the NSTX program plans to explore fully noninductive plasma start-up, as well as a dispersive scrape-off layer for heat and particle flux handling.

Book Directory of Graduate Research

Download or read book Directory of Graduate Research written by American Chemical Society. Committee on Professional Training and published by . This book was released on 2005 with total page 1932 pages. Available in PDF, EPUB and Kindle. Book excerpt: Faculties, publications and doctoral theses in departments or divisions of chemistry, chemical engineering, biochemistry and pharmaceutical and/or medicinal chemistry at universities in the United States and Canada.

Book Overview of Results from the National Spherical Torus Experiment NSTX

Download or read book Overview of Results from the National Spherical Torus Experiment NSTX written by and published by . This book was released on 2009 with total page 45 pages. Available in PDF, EPUB and Kindle. Book excerpt: The mission of NSTX is the demonstration of the physics basis required to extrapolate to the next steps for the spherical torus (ST), such as a plasma facing component test facility (NHTX) or an ST based component test facility (ST-CTF), and to support ITER. Key issues for the ST are transport, and steady state high [beta] operation. To better understand electron transport, a new high-k scattering diagnostic was used extensively to investigate electron gyro-scale fluctuations with varying electron temperature gradient scale-length. Results from n = 3 braking studies confirm the flow shear dependence of ion transport. New results from electron Bernstein wave emission measurements from plasmas with lithium wall coating applied indicate transmission efficiencies near 70% in H-mode as a result of reduced collisionality. Improved coupling of High Harmonic Fast-Waves has been achieved by reducing the edge density relative to the critical density for surface wave coupling. In order to achieve high bootstrap fraction, future ST designs envision running at very high elongation. Plasmas have been maintained on NSTX at very low internal inductance l{sub i} H"0.4 with strong shaping ([kappa] H"2.7, [delta] H"0.8) with [beta]{sub N} approaching the with-wall beta limit for several energy confinement times. By operating at lower collisionality in this regime, NSTX has achieved record non-inductive current drive fraction f{sub NI} H"71%. Instabilities driven by super-Alfvenic ions are an important issue for all burning plasmas, including ITER. Fast ions from NBI on NSTX are super-Alfvenic. Linear TAE thresholds and appreciable fast-ion loss during multi-mode bursts are measured and these results are compared to theory. RWM/RFA feedback combined with n = 3 error field control was used on NSTX to maintain plasma rotation with [beta] above the no-wall limit. The impact of n> 1 error fields on stability is a important result for ITER. Other highlights are: results of lithium coating experiments, momentum confinement studies, scrape-off layer width scaling, demonstration of divertor heat load mitigation in strongly shaped plasmas, and coupling of CHI plasmas to OH ramp-up. These results advance the ST towards next step fusion energy devices such as NHTX and ST-CTF.