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Fast Ion Orbits In Spherical Tokamaks
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Book Synopsis Fast Ion Orbits in Spherical Tokamaks by :
Download or read book Fast Ion Orbits in Spherical Tokamaks written by and published by . This book was released on 1995 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: In a spherical tokamak, the 1/R variation of the toroidal field is extreme, and for a given value of the safety factor a relatively low average toroidal field can be used, together with large plasma current and large plasma minor radius and elongation. The poloidal and toroidal fields are then of similar size. In consequence, the orbits of fast ions depart considerably from the guiding center orbits because of gyromotion in the small magnetic fields in the low field side.
Book Synopsis Wave Driven Fast Ion Loss in the National Spherical Torus Experiment by :
Download or read book Wave Driven Fast Ion Loss in the National Spherical Torus Experiment written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Spherical tokamaks, with their relatively low toroidal field, extend fast-ion-driven instability physics to parameter ranges not normally accessed in conventional tokamaks. The low field means that both the fast-ion Larmor radius normalized to the plasma minor radius and the ratio of the fast-ion velocity to the Alfven speed are relatively large. The large Larmor radius of the ions enhances their interaction with instability modes, influencing the structure of the unstable mode spectrum. The relatively large fast-ion velocity allows for a larger population of fast ions to be in resonance with the mode, increasing the drive. It is therefore an important goal of the present proof-of-principle spherical tokamaks to evaluate the role of fast-ion-driven instabilities in fast-ion confinement. This paper presents the first observations of fast-ion losses resulting from toroidal Alfven eigenmodes and a new, fishbone-like, energetic particle mode.
Book Synopsis Fast Ion Non-adiabaticity in Spherical Tokamaks by : V. Yavorskij
Download or read book Fast Ion Non-adiabaticity in Spherical Tokamaks written by V. Yavorskij and published by . This book was released on 2002 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Fast Ion Non-adiabaticity in Spherical Tokamaks by :
Download or read book Fast Ion Non-adiabaticity in Spherical Tokamaks written by and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Transport processes of fast ions in axisymmetric low-aspect-ratio spherical torus (ST) plasmas are investigated, which are induced by the non-conservation of the magnetic moment [mu]. The reason for non-conservation of [mu] of fast ions in ST's is the relatively large adiabaticity parameter epsilon typically exceeding the value 0.1 (epsilon = ratio of ion gyroradius to the gradient scale length of the magnetic field). Both analytical and numerical evaluations of the magnitude of nonadiabatic variations of [mu] are performed. Nonadiabaticity effects are shown to be most significant for fast ions for which the bounce oscillations are in resonance with the gyromotion, i.e., for ions with omega(subscript)B - lomega(subscript)b = 0, where omega(subscript)B and omega(subscript)b represent the bounce-averaged gyrofrequency and the bounce frequency, respectively, and l is an integer. The critical threshold of the adiabaticity parameter, epsilon(subscript)cr, to be exceeded for the transition to stochastic behavior of fast ions in axisymmetric ST's is inspected. Nonadiabatic variations of [mu] are shown to lead to collisionless transformation of trapped orbits into circulating ones and vice versa. For the case of strong nonadiabaticity, epsilon> epsilon(subscript)cr, we assess the transport coefficients describing intense collisionless pitch-angle diffusion, whereas, in the case of weak nonadiabaticity, epsilon> epsilon(subscript)cr, the more substantial coefficients of enhanced collisional radial diffusion and convection of fast ions gyrating resonantly with the bounce oscillations are estimated.
Book Synopsis Orbital Effects on Pitch Angle Diffusion of Injected Fast-ion Beams in Tokamaks by : Joseph J. Wleklinski
Download or read book Orbital Effects on Pitch Angle Diffusion of Injected Fast-ion Beams in Tokamaks written by Joseph J. Wleklinski and published by . This book was released on 2005 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt: The effects of ion orbits on pitch angle scattering of fast ion beam injection are investigated here for the magnetic equilibrium of the ITER tokamak. Two methods are used to calculate distributions in the presence of orbits, one applying boundary conditions a posteriori and one a priori. In both cases an orbit average of the Fokker-Planck equation is taken, yielding a solution in velocity space variables velocity and pitch angle. In the first case, conditions in the form of a linear combination of co, counter, and trapped distributions or fluxes are matched at the orbit transition value of pitch angle so that several distributions combine to form a solution. In the second case, an overall distribution is found which obeys boundary conditions derived from the trapped and passing regime essential behavior. Ultimately, both methods yield distributions which are essentially equivalent in character.
Book Synopsis A Description of the Full Particle Orbit Following SPIRAL Code for Simulating Fast-ion Experiments in Tokamaks by :
Download or read book A Description of the Full Particle Orbit Following SPIRAL Code for Simulating Fast-ion Experiments in Tokamaks written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The numerical methods used in the full particle-orbit following SPIRAL code are described and a number of physics studies performed with the code are presented to illustrate its capabilities. The SPIRAL code is a test-particle code and is a powerful numerical tool to interpret and plan fast-ion experiments in Tokamaks. Gyro-orbit effects are important for fast ions in low-field machines such as NSTX and to a lesser extent in DIII-D.A number of physics studies are interlaced between the description of the code to illustrate its capabilities. Results on heat loads generated by a localized error-field on the DIII-D wall are compared to measurements. The enhanced Triton losses caused by the same localized error-field are calculated and compared to measured neutron signals. MHD activity such as tearing modes and Toroidicity-induced Alfven Eigenmodes (TAEs) have a profound effect on the fast-ion content of Tokamak plasmas and SPIRAL can calculate the effects of MHD activity on the confined and lost fast-ion population as illustrated for a burst of TAE activity in NSTX. The interaction between Ion Cyclotron Range of Frequency (ICRF) heating and fast ions depends solely on the gyro-motion of the fast ions and is captured exactly in the SPIRAL code. A calculation of ICRF absorption on beam ions in ITER is presented. The effects of high harmonic fast wave heating on the beam-ion slowing-down distribution in NSTX is also studied.
Book Synopsis Applications of Fast Wave in Spherical Tokamaks by :
Download or read book Applications of Fast Wave in Spherical Tokamaks written by and published by . This book was released on 1997 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: In spherical tokamaks (ST), the magnetic field strength varies over a wide range across the plasma, and at high betas it deviates significantly from the 1/R dependence of conventional tokamaks. This, together with the high density expected in ST, poses challenging problems for RF heating and current drive. In this paper, the authors investigate the various possible applications of fast waves (FW) in ST. The adjoint technique of calculating current drive is implemented in the raytracing code CURRAY. The applicability of high harmonic and subharmonic FW to steady state ST is considered. They find that high harmonic FW tends to be totally absorbed before reaching the core and may be considered a candidate for off axis current drive while the subharmonic FW tends to be absorbed mainly in the core region and may be considered for central current drive. A difficult problem is the maintenance of current at the startup stage. In the bootstrap ramp-up scenario, the current ramp-up is mainly provided by the bootstrap current. Under this condition, the role of rf becomes mainly the sustainment of plasma through electron heating. Using a slab full-wave code SEMAL, the authors find that the ion-ion-hybrid mode conversion scheme is a promising candidate. The effect of possible existence of edge Alfven resonance and high harmonic cyclotron resonance is investigated and regimes of minimization of edge heating identified.
Book Synopsis Dynamics of fast ions in tokamaks by : Per Helander
Download or read book Dynamics of fast ions in tokamaks written by Per Helander and published by . This book was released on 1994 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Fast Ion Confinement in the Reversed-field Pinch by : Benjamin F. Hudson
Download or read book Fast Ion Confinement in the Reversed-field Pinch written by Benjamin F. Hudson and published by . This book was released on 2006 with total page 262 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Energetic Particles in Tokamak Plasmas by : Sergei Sharapov
Download or read book Energetic Particles in Tokamak Plasmas written by Sergei Sharapov and published by CRC Press. This book was released on 2021-04-02 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt: The study of energetic particles in magnetic fusion plasmas is key to the development of next-generation "burning" plasma fusion experiments, such as the International Thermonuclear Experimental Reactor (ITER) and the Demonstration Power Station (DEMO). This book provides a comprehensive introduction and analysis of the experimental data on how fast ions behave in fusion-grade plasmas, featuring the latest ground-breaking results from world-leading machines such as the Joint European Torus (JET) and the Mega Ampere Spherical Tokamak (MAST). It also details Alfvenic instabilities, driven by energetic ions, which can cause enhanced transport of energetic ions. MHD spectroscopy of plasma via observed Alfvenic waves called "Alfvén spectroscopy" is introduced and several applications are presented. This book will be of interest to graduate students, researchers, and academics studying fusion plasma physics. Features: Provides a comprehensive overview of the field in one cohesive text, with the main physics phenomena explained qualitatively first. Authored by an authority in the field, who draws on his extensive experience of working with energetic particles in tokamak plasmas. Is suitable for extrapolating energetic particle phenomena in fusion to other plasma types, such as solar and space plasmas.
Book Synopsis Resonance and Synergy Effects on Fast Ion Transport in Tokamaks by : Majid Khan
Download or read book Resonance and Synergy Effects on Fast Ion Transport in Tokamaks written by Majid Khan and published by LAP Lambert Academic Publishing. This book was released on 2012 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt: One of today's most challenging issues in energy physics and engineering is the utilization of nuclear fusion power which can provide a lasting energy supply on earth. In the context of designing and developing magnetic confinement fusion reactors, the behavior of high-energetic ions in tokamaks deserves careful examination in theory, experiments and simulations since these ions play a crucial role in achieving and sustaining favorable fusion conditions in the fuel plasma. Thus a burning deuterium (D)-tritium (T) plasma tends to become self-heated by fusion born alphas. Therefore the behavior of energetic alpha particles in a D-T fusion reactor, i.e. their transport and losses as well as their impact on plasma stability must be well understood. In this book we examine the trajectories and diffusion properties of fast alpha particles in a tokamak reactor. For that we employ an orbit following code using a symplectic integration algorithm which allows for accurate calculations of the ion trajectories over long time periods, even in the presence of magnetic and electric field perturbations. The investigations presented in the book are of scientific importance to fusion research.
Book Synopsis Diamagnetic Fishbone Mode Associated with Circulating Fast Ions in Spherical Tokamaks by : Ya. I. Kolesnichenko
Download or read book Diamagnetic Fishbone Mode Associated with Circulating Fast Ions in Spherical Tokamaks written by Ya. I. Kolesnichenko and published by . This book was released on 2001 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Fast-ion Studies in the National Spherical Torus Experiment by : Deyong Liu
Download or read book Fast-ion Studies in the National Spherical Torus Experiment written by Deyong Liu and published by . This book was released on 2009 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: An extensive set of fast-ion diagnostics, including neutron detectors, a E//B type neutral particle analyzer (NPA) and the newly built four-chord solid state neutral particle analyzer array (SSNPA) and a 16-channel Fast-ion D-alpha (FIDA) diagnostic, provides a good test-bed to study fast ion physics in the National Spherical Torus Experiment (NSTX). During combined neutral beam injection (NBI) and High-Harmonic Fast-Wave (HHFW) heating, the acceleration of fast ions is evident in all fast ion diagnostics. The neutron rate is about three times larger during the HHFW heating. A fast-ion tail above the beam injection is observed in the NPA, SSNPA and FIDA diagnostics. It is also shown that the accelerated fast ions observed by the NPA and SSNPA diagnostics mainly come from passive charge exchange reactions at the edge due to the NPA/SSNPA localization in phase space. The spatial profile of accelerated fast ions that is measured by the FIDA diagnostic is much broader than in conventional tokamaks because of the multiple resonance layers and large orbits in NSTX. The fast-ion distribution function calculated by the CQL3D Fokker-Planck code differs from the measured spatial profile, presumably because the current version of CQL3D uses a zero-banana-width model. In addition, the effects of bursting instabilities on the fast ion distribution in neutral beam heated plasmas are examined. Fishbone events generally have a minor effect on the fast ion distribution and no clear correlation is observed in the NPA and SSNPA diagnostics. However, sawteeth or the combinations of fishbones and CAEs always cause neutron rate drops up to 25% and bursts at outer chords of the SSNPA, which indicate fast ion loss. It is also observed that high energy fast ions respond earlier than low energy fast ions.
Book Synopsis Heating by Collisional Slowing of Fast Ions in Non-circular Tokamaks by :
Download or read book Heating by Collisional Slowing of Fast Ions in Non-circular Tokamaks written by and published by . This book was released on 1980 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Plasma heating by energetic, charged fusion-products is a crucial issue for obtaining fusion reactors conditions. The evolution of alpha particle density, momentum, kinetic energy and heat flux is important in the study of start-up and ignition scenarios as well as in steady-state operation. Since fast ions have large banana-width guiding-center orbits in tokamaks, the usual locally-defined particle distribution function loses its usefulness. Accordingly, the fast ion collisional slowing-down problem has been formulated to describe these orbits in an axisymmetric, non-circular tokamak.
Book Synopsis Experimental Fast-ion Transport Studies on the Mega-Amp Spherical Tokamak by : Owen Matthew Jones
Download or read book Experimental Fast-ion Transport Studies on the Mega-Amp Spherical Tokamak written by Owen Matthew Jones and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Nuclear Fusion written by and published by . This book was released on 2006 with total page 1144 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Effects of Resonant Magnetic Perturbations on Fast Ion Confinement in the Mega Amp Spherical Tokamak by :
Download or read book The Effects of Resonant Magnetic Perturbations on Fast Ion Confinement in the Mega Amp Spherical Tokamak written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
