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R. K. Fisher

Bio: R. K. Fisher is an academic researcher from General Atomics. The author has contributed to research in topics: Alpha particle & Tokamak Fusion Test Reactor. The author has an hindex of 22, co-authored 56 publications receiving 1743 citations.


Papers
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Journal ArticleDOI
TL;DR: In this paper, the authors describe the requirements for high reliability in the systems (diagnostics) that provide the measurements in the ITER environment, which is similar to those made on the present-day large tokamaks while the specification of the measurements will be more stringent.
Abstract: In order to support the operation of ITER and the planned experimental programme an extensive set of plasma and first wall measurements will be required. The number and type of required measurements will be similar to those made on the present-day large tokamaks while the specification of the measurements—time and spatial resolutions, etc—will in some cases be more stringent. Many of the measurements will be used in the real time control of the plasma driving a requirement for very high reliability in the systems (diagnostics) that provide the measurements. The implementation of diagnostic systems on ITER is a substantial challenge. Because of the harsh environment (high levels of neutron and gamma fluxes, neutron heating, particle bombardment) diagnostic system selection and design has to cope with a range of phenomena not previously encountered in diagnostic design. Extensive design and R&D is needed to prepare the systems. In some cases the environmental difficulties are so severe that new diagnostic techniques are required. a Author to whom any correspondence should be addressed.

309 citations

Journal ArticleDOI
J. D. Strachan, H. Adler, P. Alling, C. Ancher, H. Anderson, J.L. Anderson, D. Ashcroft, Cris W. Barnes, G. Barnes, S. H. Batha, M. G. Bell, R.E. Bell, Manfred Bitter, W. R. Blanchard, N. L. Bretz, Robert Budny, C.E. Bush, R. Camp, M. Caorlin, S. Cauffman, Z. Chang, Chio-Zong Cheng, J. Collins, G. Coward, D. S. Darrow, J. DeLooper, H.H. Duong, L. Dudek, R. Durst, P. C. Efthimion, D.R. Ernst, R. K. Fisher, R. J. Fonck, E.D. Fredrickson, N. Fromm, Guoyong Fu, Harold P. Furth, C. Gentile, N. N. Gorelenkov, B. Grek, L. R. Grisham, Gregory W. Hammett, G. R. Hanson, R. J. Hawryluk, William Heidbrink, H. W. Herrmann, K. W. Hill, J. Hosea, H. Hsuan, A.C. Janos, D. L. Jassby, F. C. Jobes, David W. Johnson, L. C. Johnson, J. H. Kamperschroer, H.W. Kugel, N. T. Lam, P. H. LaMarche, Michael Loughlin, B.P. LeBlanc, M. Leonard, Fred Levinton, J. Machuzak, D.K. Mansfield, A. Martin, E. Mazzucato, Richard Majeski, E.S. Marmar, J.M. McChesney, B. McCormack, D.C. McCune, K. M. McGuire, G. R. McKee, Dale Meade, S. S. Medley, D. R. Mikkelsen, D. Mueller, M. Murakami, A. Nagy, Raffi Nazikian, R. Newman, Takeo Nishitani, M. Norris, T. O’Connor, M. Oldaker, Masaki Osakabe, D. K. Owens, Hyeon K. Park, W. Park, S.F. Paul, G. Pearson, E. Perry, M. P. Petrov, C. K. Phillips, S. Pitcher, A. T. Ramsey, David A Rasmussen, M. H. Redi, D. W. Roberts, J. H. Rogers, R. Rossmassler, A. L. Roquemore, E. Ruskov, S.A. Sabbagh, Mamiko Sasao, G. Schilling, J.F. Schivell, G. L. Schmidt, S. D. Scott, R. Sissingh, C.H. Skinner, Joseph Snipes, J. E. Stevens, T. Stevenson, B. C. Stratton, E. J. Synakowski, William Tang, G. Taylor, J. L. Terry, M. E. Thompson, M. Tuszewski, C. Vannoy, A. von Halle, S. von Goeler, D. Voorhees, R. T. Walters, R. M. Wieland, John B Wilgen, M. Williams, James R. Wilson, K. L. Wong, G. A. Wurden, Masaaki Yamada, Kenneth M. Young, M. C. Zarnstorff, S. J. Zweben1 
TL;DR: The measured loss rate of energetic alpha particles agreed with the approximately 5% losses expected from alpha particles which are born on unconfined orbits.
Abstract: Peak fusion power production of 6.2 ± 0.4 MW has been achieved in TFTR plasmas heated by deuterium and tritium neutral beams at a total power of 29.5 MW. These plasmas have an inferred central fusion alpha particle density of 1.2 x 1017 m ₋3 without the appearance of either disruptive magnetohydrodynamics events or detectable changes in Alfven wave activity. The measured loss rate of energetic alpha particles agreed with the approximately 5% losses expected from alpha particles which are born on unconfined orbits.

122 citations

Journal ArticleDOI
TL;DR: In this article, neutral beam injection into reversed magnetic shear DIII-D and ASDEX upgrade plasmas produces a variety of Alfvenic activity including toroidicity-induced Alfven eigenmodes (RSAEs) and reversed shear Alfven (RSE) during discharge current ramp phase when incomplete current penetration results in a high central safety factor and increased drive due to multiple higher order resonances.
Abstract: Neutral beam injection into reversed magnetic shear DIII-D and ASDEX Upgrade plasmas produces a variety of Alfvenic activity including toroidicity-induced Alfven eigenmodes and reversed shear Alfven eigenmodes (RSAEs) These modes are studied during the discharge current ramp phase when incomplete current penetration results in a high central safety factor and increased drive due to multiple higher order resonances Scans of injected 80 keV neutral beam power on DIII-D showed a transition from classical to AE dominated fast ion transport and, as previously found, discharges with strong AE activity exhibit a deficit in neutron emission relative to classical predictions By keeping beam power constant and delaying injection during the current ramp, AE activity was reduced or eliminated and a significant improvement in fast ion confinement observed Similarly, experiments in ASDEX Upgrade using early 60 keV neutral beam injection drove multiple unstable RSAEs Periods of strong RSAE activity are accompanied

105 citations

Journal ArticleDOI
R. J. Hawryluk, S. H. Batha, W. Blanchard1, Michael A. Beer1, M. G. Bell1, R. E. Bell1, Herbert L Berk1, S. Bernabei1, M. Bitter1, Boris Breizman1, Norton Bretz2, R. Budny2, C.E. Bush2, James D. Callen3, R. Camp2, S. Cauffman2, Z. Chang2, Chio-Zong Cheng2, D. S. Darrow2, R. O. Dendy2, William Dorland1, H.H. Duong4, P. C. Efthimion5, Darin Ernst5, Nathaniel J. Fisch, R. K. Fisher, R.J. Fonck3, E.D. Fredrickson, Guoyong Fu, Harold P. Furth, N. N. Gorelenkov, B. Grek2, L. R. Grisham2, G. W. Hammett2, Gregory R. Hanson2, H. W. Herrmann2, M. C. Herrmann2, K. W. Hill2, J.T. Hogan2, J. C. Hosea2, Wayne A Houlberg2, M. H. Hughes6, R. A. Hulse3, D. L. Jassby3, F. C. Jobes3, D. W. Johnson3, R. Kaita3, S. Kaye3, J. S. Kim3, Michael W Kissick3, A. V. Krasilnikov, H. Kugel7, A. Kumar7, B.P. LeBlanc, Fred Levinton, C. Ludescher4, R. P. Majeski4, J. Manickam4, D. K. Mansfield4, E. Mazzucato4, J. McChesney4, D.C. McCune, K. M. McGuire, Dale Meade, S. S. Medley, R. Mika, D. R. Mikkelsen, S. V. Mirnov, D. Mueller8, A. Nagy8, Gerald Navratil8, Raffi Nazikian, M. Okabayashi, Hyeon K. Park, W. Park, S.F. Paul, G. Pearson, M. P. Petrov, C. K. Phillips6, M. Phillips6, A. T. Ramsey, M. H. Redi, G. Rewoldt, S.N. Reznik, A. L. Roquemore8, J. Rogers8, E. Ruskov8, S.A. Sabbagh8, Mamiko Sasao9, G. Schilling, J.F. Schivell, G. L. Schmidt, S. D. Scott, I. Semenov, C. H. Skinner10, T. Stevenson10, B. C. Stratton10, J. D. Strachan10, W. Stodiek10, E.J. Synakowski10, H. Takahashi10, W. Tang10, G. Taylor10, M. E. Thompson10, S. von Goeler10, A. von Halle10, R. T. Walters10, Robert White10, R. M. Wieland10, M. Williams10, J. R. Wilson10, K. L. Wong10, G. A. Wurden10, Masaaki Yamada, V. Yavorski, Kenneth M. Young11, Leonid E. Zakharov11, M. C. Zarnstorff11, Stewart Zweben11 
TL;DR: Hawryluk et al. as mentioned in this paper described the Tokamak Fusion Test Reactor (TFTR) experiments on high-temperature plasmas, that culminated in the study of deuterium-to-tritium D-T Plasmas containing significant populations of energetic alpha particles, spanned over two decades from conception to completion.
Abstract: The Tokamak Fusion Test Reactor (TFTR) (R. J. Hawryluk, to be published in Rev. Mod. Phys.) experiments on high-temperature plasmas, that culminated in the study of deuterium–tritium D–T plasmas containing significant populations of energetic alpha particles, spanned over two decades from conception to completion. During the design of TFTR, the key physics issues were magnetohydrodynamic (MHD) equilibrium and stability, plasma energy transport, impurity effects, and plasma reactivity. Energetic particle physics was given less attention during this phase because, in part, of the necessity to address the issues that would create the conditions for the study of energetic particles and also the lack of diagnostics to study the energetic particles in detail. The worldwide tokamak program including the contributions from TFTR made substantial progress during the past two decades in addressing the fundamental issues affecting the performance of high-temperature plasmas and the behavior of energetic particles. The progress has been the result of the construction of new facilities, which enabled the production of high-temperature well-confined plasmas, development of sophisticated diagnostic techniques to study both the background plasma and the resulting energetic fusion products, and computational techniques to both interpret the experimental results and to predict the outcome of experiments.

84 citations

Journal ArticleDOI
R. J. Hawryluk, H. Adler, P. Alling, C. Ancher, H. Anderson, J.L. Anderson, D. Ashcroft, Cris W. Barnes, G. Barnes, S. H. Batha, M. G. Bell, R.E. Bell, Manfred Bitter, W. R. Blanchard, N. L. Bretz, R.V. Budny, C.E. Bush, R. Camp, M. Caorlin, S. Cauffman, Z. Chang, Chio-Zong Cheng, J. Collins, G. Coward, D. S. Darrow, J. DeLooper, H.H. Duong, L. Dudek, R. Durst, P. C. Efthimion, D.R. Ernst, R. K. Fisher, R. J. Fonck, E.D. Fredrickson, N. Fromm, Guoyong Fu, Harold P. Furth, C. Gentile, N. N. Gorelenkov, B. Grek, L. R. Grisham, Gregory W. Hammett, G. R. Hanson, William Heidbrink, H. W. Herrmann, K. W. Hill, J. Hosea, H. Hsuan, A.C. Janos, D. L. Jassby, F. C. Jobes, David W. Johnson, L. C. Johnson, J. H. Kamperschroer, H.W. Kugel, N. T. Lam, P. H. LaMarche, Michael Loughlin, B.P. LeBlanc, M. Leonard, Fred Levinton, J. Machuzak, D.K. Mansfield, A. Martin, E. Mazzucato, Richard Majeski, E.S. Marmar, J.M. McChesney, B. McCormack, D.C. McCune, K. M. McGuire, G. R. McKee, Dale Meade, S. S. Medley, D. R. Mikkelsen, D. Mueller, M. Murakami, A. Nagy, Raffi Nazikian, R. Newman, Takeo Nishitani, M. Norris, T. O’Connor, M. Oldaker, Masaki Osakabe, D. K. Owens, Hyeon K. Park, W. Park, S.F. Paul, G. Pearson, E. Perry, M. P. Petrov, C. K. Phillips, S. Pitcher, A. T. Ramsey, David A Rasmussen, M. H. Redi, D. W. Roberts, J. H. Rogers, R. Rossmassler, A. L. Roquemore, E. Ruskov, S.A. Sabbagh, Mamiko Sasao, G. Schilling, J.F. Schivell, G. L. Schmidt, S. D. Scott, R. Sissingh, C.H. Skinner, Joseph Snipes, J. E. Stevens, T. Stevenson, B. C. Stratton, J. D. Strachan, E. J. Synakowski, William Tang, G. Taylor, J.L. Terry, M. E. Thompson, M. Tuszewski, C. Vannoy, A. von Halle, S. von Goeler, D. Voorhees, R. T. Walters, R. M. Wieland, John B Wilgen, M. Williams, James R. Wilson, K. L. Wong, G. A. Wurden, Masaaki Yamada, Kenneth M. Young, M. C. Zarnstorff, Stewart Zweben 
TL;DR: Improvements in confinement associated with the use of tritium and possibly heating of electrons by α-particles are indicated.
Abstract: The Tokamak Fusion Test Reactor (TFTR) has performed initial high-power experiments with the plasma fueled by deuterium and tritium to nominally equal densities. Compared to pure deuterium plasmas, the energy stored in the electron and ions increased by ~20%. These increases indicate improvements in confinement associated with the use of tritium and possibly heating of electrons by α-particles.

77 citations


Cited by
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Journal ArticleDOI
TL;DR: In this paper, an approach to fusion that relies on either electron conduction (direct drive) or x rays (indirect drive) for energy transport to drive an implosion is presented.
Abstract: Inertial confinement fusion (ICF) is an approach to fusion that relies on the inertia of the fuel mass to provide confinement. To achieve conditions under which inertial confinement is sufficient for efficient thermonuclear burn, a capsule (generally a spherical shell) containing thermonuclear fuel is compressed in an implosion process to conditions of high density and temperature. ICF capsules rely on either electron conduction (direct drive) or x rays (indirect drive) for energy transport to drive an implosion. In direct drive, the laser beams (or charged particle beams) are aimed directly at a target. The laser energy is transferred to electrons by means of inverse bremsstrahlung or a variety of plasma collective processes. In indirect drive, the driver energy (from laser beams or ion beams) is first absorbed in a high‐Z enclosure (a hohlraum), which surrounds the capsule. The material heated by the driver emits x rays, which drive the capsule implosion. For optimally designed targets, 70%–80% of the d...

2,121 citations

Journal ArticleDOI
TL;DR: The ITER Physics Basis as mentioned in this paper presents and evaluates the physics rules and methodologies for plasma performance projections, which provide the basis for the design of a tokamak burning plasma device whose goal is to demonstrate the scientific and technological feasibility of fusion energy for peaceful purposes.
Abstract: The ITER Physics Basis presents and evaluates the physics rules and methodologies for plasma performance projections, which provide the basis for the design of a tokamak burning plasma device whose goal is to demonstrate the scientific and technological feasibility of fusion energy for peaceful purposes. This Chapter summarizes the physics basis for burning plasma projections, which is developed in detail by the ITER Physics Expert Groups in subsequent chapters. To set context, the design guidelines and requirements established in the report of ITER Special Working Group 1 are presented, as are the specifics of the tokamak design developed in the Final Design Report of the ITER Engineering Design Activities, which exemplifies burning tokamak plasma experiments. The behaviour of a tokamak plasma is determined by the interaction of many diverse physics processes, all of which bear on projections for both a burning plasma experiment and an eventual tokamak reactor. Key processes summarized here are energy and particle confinement and the H-mode power threshold; MHD stability, including pressure and density limits, neoclassical islands, error fields, disruptions, sawteeth, and ELMs; power and particle exhaust, involving divertor power dispersal, helium exhaust, fuelling and density control, H-mode edge transition region, erosion of plasma facing components, tritium retention; energetic particle physics; auxiliary power physics; and the physics of plasma diagnostics. Summaries of projection methodologies, together with estimates of their attendant uncertainties, are presented in each of these areas. Since each physics element has its own scaling properties, an integrated experimental demonstration of the balance between the combined processes which obtains in a reactor plasma is inaccessible to contemporary experimental facilities: it requires a reactor scale device. It is argued, moreover, that a burning plasma experiment can be sufficiently flexible to permit operation in a steady state mode, with non-inductive plasma current drive, as well as in a pulsed mode where current is inductively driven. Overall, the ITER Physics Basis can support a range of candidate designs for a tokamak burning plasma facility. For each design, there will remain a significant uncertainty in the projected performance, but the projection methodologies outlined here do suffice to specify the major parameters of such a facility and form the basis for assuring that its phased operation will return sufficient information to design a prototype commercial fusion power reactor, thus fulfilling the goal of the ITER project.

1,025 citations

Journal ArticleDOI
TL;DR: The understanding and predictive capability of transport physics and plasma confinement is reviewed from the perspective of achieving reactor-scale burning plasmas in the ITER tokamak, for both core and edge plasma regions.
Abstract: The understanding and predictive capability of transport physics and plasma confinement is reviewed from the perspective of achieving reactor-scale burning plasmas in the ITER tokamak, for both core and edge plasma regions. Very considerable progress has been made in understanding, controlling and predicting tokamak transport across a wide variety of plasma conditions and regimes since the publication of the ITER Physics Basis (IPB) document (1999 Nucl. Fusion 39 2137-2664). Major areas of progress considered here follow. (1) Substantial improvement in the physics content, capability and reliability of transport simulation and modelling codes, leading to much increased theory/experiment interaction as these codes are increasingly used to interpret and predict experiment. (2) Remarkable progress has been made in developing and understanding regimes of improved core confinement. Internal transport barriers and other forms of reduced core transport are now routinely obtained in all the leading tokamak devices worldwide. (3) The importance of controlling the H-mode edge pedestal is now generally recognized. Substantial progress has been made in extending high confinement H-mode operation to the Greenwald density, the demonstration of Type I ELM mitigation and control techniques and systematic explanation of Type I ELM stability. Theory-based predictive capability has also shown progress by integrating the plasma and neutral transport with MHD stability. (4) Transport projections to ITER are now made using three complementary approaches: empirical or global scaling, theory-based transport modelling and dimensionless parameter scaling (previously, empirical scaling was the dominant approach). For the ITER base case or the reference scenario of conventional ELMy H-mode operation, all three techniques predict that ITER will have sufficient confinement to meet its design target of Q = 10 operation, within similar uncertainties.

798 citations

Journal ArticleDOI
TL;DR: The NUBEAM module as mentioned in this paper is a comprehensive computational model for Neutral Beam Injection (NBI) in tokamaks, which is used to compute power deposition, driven current, momentum transfer, fueling, and other profiles.

636 citations

Journal ArticleDOI
TL;DR: A review of the progress accomplished since the redaction of the first ITER Physics Basis (1999 Nucl Fusion 39 2137-664) in the field of energetic ion physics and its possible impact on burning plasma regimes is presented in this paper.
Abstract: This chapter reviews the progress accomplished since the redaction of the first ITER Physics Basis (1999 Nucl Fusion 39 2137-664) in the field of energetic ion physics and its possible impact on burning plasma regimes New schemes to create energetic ions simulating the fusion-produced alphas are introduced, accessing experimental conditions of direct relevance for burning plasmas, in terms of the Alfvenic Mach number and of the normalised pressure gradient of the energetic ions, though orbit characteristics and size cannot always match those of ITER Based on the experimental and theoretical knowledge of the effects of the toroidal magnetic field ripple on direct fast ion losses, ferritic inserts in ITER are expected to provide a significant reduction of ripple alpha losses in reversed shear configurations The nonlinear fast ion interaction with kink and tearing modes is qualitatively understood, but quantitative predictions are missing, particularly for the stabilisation of sawteeth by fast particles that can trigger neoclassical tearing modes A large database on the linear stability properties of the modes interacting with energetic ions, such as the Alfven eigenmode has been constructed Comparisons between theoretical predictions and experimental measurements of mode structures and drive/damping rates approach a satisfactory degree of consistency, though systematic measurements and theory comparisons of damping and drive of intermediate and high mode numbers, the most relevant for ITER, still need to be performed The nonlinear behaviour of Alfven eigenmodes close to marginal stability is well characterized theoretically and experimentally, which gives the opportunity to extract some information on the particle phase space distribution from the measured instability spectral features Much less data exists for strongly unstable scenarios, characterised by nonlinear dynamical processes leading to energetic ion redistribution and losses, and identified in nonlinear numerical simulations of Alfven eigenmodes and energetic particle modes Comparisons with theoretical and numerical analyses are needed to assess the potential implications of these regimes on burning plasma scenarios, including in the presence of a large number of modes simultaneously driven unstable by the fast ions

519 citations