Bulletin of the American Physical Society
51st Annual Meeting of the APS Division of Plasma Physics
Volume 54, Number 15
Monday–Friday, November 2–6, 2009; Atlanta, Georgia
Session CM9: Mini-Conference on Innovative Magnetic Mirror Concepts and Applications II |
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Chair: E. Bick Hooper, Lawrence Livermore National Laboratory Room: The Learning Center |
Monday, November 2, 2009 2:00PM - 2:30PM |
CM9.00001: Vortex Confinement of Plasmas in Axially Symmetric Mirrors Alexei Beklemishev, Peter Bagryansky, Maxim Chaschin, Elena Soldatkina Efforts to optimize operation of the Gas Dynamic Trap with variation of plasma rotation led to discovery of a new way of efficient plasma confinement. Its nature is similar to confinement of material in the dead zone of a vortex flow. It is achieved by applying voltage to the limiters and the endplates of the device, thus creating shear-flow layer, which surrounds the core of the discharge. In this regime the gas-dynamic stabilization is shown to be unnecessary, as the confinement is excellent even with straight field lines in the expanders. While the axisymmetric equilibrium remains unstable, there appears a new dynamic state of confinement with approximate axial symmetry and low convective losses. The needed power consumption is a fraction of parallel ion losses (30kW), while the theoretical scaling predicts the scheme to work even at fusion temperatures. The talk will contain simplified analytic theory of the nonlinear dissipative saturation of the m=1 mode in the presence of the externally-driven vortex flow, and the two-dimensional drift-ordered MHD simulation of the vortex confinement in the GDT. [Preview Abstract] |
Monday, November 2, 2009 2:30PM - 3:00PM |
CM9.00002: The Design of anchor divertor of GAMMA10 Isao Katanuma, Kotaro Yagi, Yosuke Nakashima, Masayuki Yoshikawa, Makoto Ichimura, Tsuyoshi Imai The plan that one of the anchor mirror cells, which was installed for the flute interchange mode stability, is replaced by an axisymmetric divertor mirror cell is in progress. The main object of the divertor mirror is to simulate the ITER divertor physics. Then the scenario on the effective evacuation of core plasma in the divertor mirror cell to the magnetic null region is required in order to obtain a high power plasma flow outside the divertor mirror cell region. We are designing the divertor mirror coil system in GAMMA10 and estimating the plasma parameter in the divertor system and radial energy loss flux outside the magnetic null. The MHD stability is determined with help of the kinetic analysis of flute mode by taking into account the ion FLR, magnetic field line curvature and plasma compressibility. The stored energy is calculated by the bounce-averaged Fokker-Planck code. The radial evacuation of hot ions is estimated by the reduced MHD simulation taking into account the flute-like electrostatic potential fluctuations. [Preview Abstract] |
Monday, November 2, 2009 3:00PM - 3:15PM |
CM9.00003: Trapped Particle Instability in Kinetic Stabilized Tandem Mirror Herbert Berk, Jane Pratt The kinetic stabilizer tandem mirror (KSTM) devised by R. F. Post (J. Fus. Energy 2007) is an innovative concept devised to stabilize a symmetric tandem mirror machines using a concept devised by D. Ryutov (Proc. of Course and Workshop, Varenna, Italy, 1987) and empirically verified in the Gas Dynamic Trap (Ivanov, et. al. Trans. Fusion Technology 39, 127, 2001). The KSTM uses the momentum flux of unconfined particles that only sample the outer end regions of the mirror where there is very favorable field line curvature. Charged ion beams at relatively low energy are externally injected into the ends and reflected out from the ends. MHD stability with a power drain less than the fusion power production can be achieved. We examine the effect of fast growing trapped particle instability (Berk et. al. Sov J. Plasma Phys. 1983) on the overall stability. In this case stability is very sensitive to the electron connection between the stabilizer and end plug. [Preview Abstract] |
Monday, November 2, 2009 3:15PM - 3:30PM |
CM9.00004: The TASKA, TDF, and TASKA-M Fusion Neutron Materials Test Facilities John Santarius, Gerald Kulcinski This talk will summarize key features of three conceptual fusion neutron test facilities designed in the early 1980s: TASKA,$^1$ TDF,$^2$ and TASKA-M.$^3$ Motivated by the accessibility and maintainability of cylindrical geometry, these magnetic-mirror designs possess a simple central cell, as in a fusion neutron test facility based on the gas dynamic trap (GDT).$^4$ The TASKA-M design, like today's GDT designs, included the injection of neutral beams into the central cell to create a sloshing-ion distribution that gives density peaks near the materials test modules. In TASKA and TDF, the minimum-B end-cell designs contained thermal barriers, regions of low electrostatic potential to reduce electron flow between central cell and end cells. Thermal barriers improve performance but require more complicated input power systems, and their physics basis is less well established than that of simple mirrors. For TASKA-M, a more conservative design, minimum-B end cells provided MHD stability, but thermal barriers and an end-plug potential peak were absent. [1] B. Badger, et al., UW FTI Report UWFDM-500 (1982). [2] T.H. Batzer, et al., LLNL Report UCID-19328 (1983). [3] B. Badger, al., UW FTI Report UWFDM-600 (1984). [4]~P.A. Bagryanski, et al., {\it Fus. Eng. Design} {\bf 70}, 13 (2004). [Preview Abstract] |
Monday, November 2, 2009 3:30PM - 3:45PM |
CM9.00005: Minimum B mirror with expander aimed for transmutation and energy production Olov {\AA}gren, V.E. Moiseenko, Klaus Noack, Anders Hagnest{\aa}l A comparatively simple fusion driven fission device may be developed for industrial transmutation and energy production from spent nuclear waste [1-2]. This opportunity stems from the large fission to fusion power production ratio, $P_{fis}$/$P_{fus} \quad \approx $150, in a subcritical fusion device surrounded by a fission mantle with the neutron multiplicity $k_{eff }$=0.96. Power production is predicted if the electron temperature exceeds 700 eV. The expanders may improve the electron temperature by a formation of an ambipolar potential. Theoretical studies include RF heating, magnetic coil designs, fission mantle kinetics and some basic plasma investigations. A 20 m long mirror with a 40 cm plasma radius could be sufficient for a electric power production of 500 MW. [1] S. Taczanowski, ``Premises for development of fusion-fission hybrid systems'' in IAEA-RC-870.3, TWG-FR/132, Chennai, India 15 -- 19 January 2007. [2] O. {\AA}gren, V.E. Moiseenko, A. Hagnest{\aa}l, ``The straight field line mirror concept and applications'', Problems of atomic science and technology \textbf{6}. \textit{Series: }Plasma Physics, 8 (2008). [Preview Abstract] |
Monday, November 2, 2009 3:45PM - 4:00PM |
CM9.00006: Gas Dynamic Trap Neutron Source (DTNS) -- applications and development path A.W. Molvik, T.C. Simonen, D.D. Ryutov The successes in the Gas Dynamic Trap at the Budker Institute of Nuclear Physics -- stable operation to $\beta \sim $60{\%}, T$_{e}$ increasing with neutral beam power to $>$200 eV, and classical behavior of hot ions (Ivanov and Beklemishev, this conf.) -- motivate building a DTNS. The DTNS provides $\sim $2 MW/m$^{2}$neutron flux, and 20 l irradiated volume (in a 2.5 cm thick annulus) to enable aggressive programs in fusion materials development, tritium-breeding blankets (which do not have to breed initially because the DTNS burns less than 200 g/yr of T), and hybrid fission blankets. The major issue is steady-state operation of a configuration that has been demonstrated during 5 ms pulses. The known issues are all engineering: cooling components impinged by beams, pumping the gas and regenerating the pumps. Possible plasma physics issues, such as drift waves, are expected to have slow growth times enabling suppression or saturation at low levels. [Preview Abstract] |
Monday, November 2, 2009 4:00PM - 4:15PM |
CM9.00007: Investigations of axisymmetric mirror boundary conditions using Reconnection Scaling Experiment T.P. Intrator, R.J. Oberto, T.D. Olson Axisymmetric magnetic mirrors such the Gas Dynamic Trap (GDT) concept do not need complex and expensive minimum B magnetic coil structures to enhance MHD stability. GDTs and related mirror designs typically contain a large end loss region region of flared and expanding magnetic field lines between a mirror coil and an end cell with radial and axial end walls. This end loss region can furnish pressure weighted good curvature field line forces that stabilize MHD behavior, and also provide electrostatic sheaths that confine electron heat loss. Investigations of axial boundary conditions will be useful to determine how and why MHD stability can be enhanced, and how to improve confinement of electron heat flux. The Reconnection Scaling Experiment (RSX) has been used to for a wide range of conditions in an MHD relevant experiment. We have demonstrated a continuous range of adjustability between line tied (fixed) and non line tied (free) axial boundary conditions. [Preview Abstract] |
Monday, November 2, 2009 4:15PM - 4:30PM |
CM9.00008: MHD-Stabilization of Axisymmetric Mirror Systems Using Pulsed ECRH R.F. Post A method of MHD-stabilizing axisymmetric mirror systems, demonstrated in the Gas Dynamic Trap [1] and analyzed by Ryutov [2] employs low pressure plasma on expanding field lines outside the mirrors. Methods of creating such plasmas have been analyzed [3]. This paper studies another technique: Pulsed ECRH in regions of positive curvature. The ansatz: If the repetition time is shorter than the MHD growth time, and if their time-averaged amplitude is exceeds that required by the theory the system will be stable. The calculations confirm the ansatz. Applications include axisymmetric tandem mirror and multiple-mirror systems. In the latter it might perform the functions of MHD-stabilization and of biasing cell-loss probabilities inwardly. Post and Li [4] showed that such biasing leads to confinement times that increase exponentially with the number of cells, rather than linearly, as occurs with symmetric losses. Prepared by LLNL under Contract DE-AC52-07NA27344. [1] P. A. Bagryansky, et. al., Trans. Fusion Tech. \textbf{35}, 79 (1999) [2] D. D. Ryutov, Proc. of Course and Workshop, Varenna, Italy, Vol II, 791 (1987) [3] R. F. Post, Trans. Fusion Tech., \textbf{39}, 25 (2001) [4] R. F. Post and X. Z. Li, Nuc. Fusion, \textbf{21}, 135 (1981). [Preview Abstract] |
Monday, November 2, 2009 4:30PM - 4:45PM |
CM9.00009: Alpha-Channeling in Mirror Machines Andrey Zhmoginov, Nathaniel Fisch Linear magnetic trap is an attractive concept for fusion research and plasma applications due to its relative engineering simplicity and high-beta operation. Application of the alpha-channeling technique to mirror machines can benefit this concept by efficiently redirecting alpha particle energy to fuel ion heating or sustaining plasma confinement, thus increasing the effective fusion reactivity. To identify waves suitable for alpha-channeling a rough optimization of the energy extraction rate with respect to the wave parameters is performed. After the optimal regime is identified, the systematic search for modes with similar parameters in mirror plasmas is performed by assuming quasi-longitudinal, or quasi-transverse wave propagation. As a result, modes suitable for alpha particle energy extraction are identified in several device designs including the LAPD experiment. Under a proper choice of the tandem mirror device parameters, the predicted modes are expected to feed ICRH waves in the device plugs, thus redirecting the extracted energy to sustaining the plasma confinement. [Preview Abstract] |
Monday, November 2, 2009 4:45PM - 5:00PM |
CM9.00010: Alpha channeling using stationary waves in a centrifugal mirro Abraham Fetterman, Nathaniel Fisch In a mirror with supersonic rotation, charged fusion products might interact with radio-frequency waves to maintain the rotation against drag forces. Magnetic ripples that are stationary in the lab frame can match the cyclotron frequency in the particle frame, allowing resonant interaction without requiring power input. We examine the feasibility of using these waves in a fusion device with a deuterium-tritium plasma. [Preview Abstract] |
Monday, November 2, 2009 5:00PM - 5:15PM |
CM9.00011: Proposed Thomson scattering measurements on the Gas Dynamic Trap Harry McLean, Daniel Den Hartog We describe a proposed short-term collaborative experimental investigation of electron temperature on the Gas Dynamic Trap (GDT) experiment at the Budker Institute in Novosibirsk, Russia using the double-pulse multipoint Thomson scattering diagnostic from the decommissioned SSPX spheromak at Lawrence Livermore National Laboratory. Electron temperature is a critical parameter in the gas dynamic trap (GDT) since fast-ion energy losses are governed by electron drag, which decreases with increased electron temperature. Higher fast-ion densities lead to higher neutron production in fusion neutron sources based on the GDT concept. Expected plasma conditions and measurement capabilities will be compared. Suitable experimental campaigns will be presented. This work performed under the auspices of the U.S. DoE by LLNL under Contract DE-AC52-07NA27344. [Preview Abstract] |
Monday, November 2, 2009 5:15PM - 5:30PM |
CM9.00012: Extension of XGC kinetic simulation codes to magnetic mirror configurations G. Bateman, A.Y. Pankin, A.H. Kritz, T. Rafiq, G.Y. Park, S. Ku, C.S. Chang, W. Horton, J. Pratt The XGC codes, developed to simulate the edge regions of tokamak plasmas, are modified to carry out kinetic simulations of axisymmetric magnetic mirror configurations. The XGC codes are particle in cell kinetic codes that include a virtual sheath condition where magnetic field lines run into end plates. The XGC1 code is a fully five dimensional kinetic code that is used to investigate turbulence, while the faster XGC0 code uses the axisymmetric average electrostatic potential in order to simulate charged particle drifts, losses and collisional effects. Kinetic electron computations, neutral beam injection, atomic physics and the effects of thermal neutrals are included in the XGC codes. Changes are being made to allow the XGC codes to accept mirror equilibria and to run without a toroidal magnetic field component. The XGC0 code will be used to compute particle dynamics, electrostatic potentials, and moments of the distribution functions including plasma flows in mirror configurations. \newline [1] C.S. Chang, S. Ku, H. Weitzner, Phys. Plasmas {\bf 11} (2004) 2649 [Preview Abstract] |
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