Three-dimensional equilibrium in quadrupole symmetric tandem mirrors in the paraxial limit (reduced MHD)

Equilibrium in quadrupole symmetric mirrors is fully three dimensional; however, because axial scale lengths are long compared with radial scale lengths (equivalently weak curvature) it is possible to reduce the complexity of the equations by expanding in the appropriate smallness parameter. Such a procedure leads to set of reduced MHD equations. The general theory will be presented, numerical results discussed, modifications due to finite Larmor radius will be added, and an analytic solution for sharp boundary pressure models will be developed

Status report on Corsica modeling for current drive scenario development

This milestone report covers the progress and status of Corsica modeling for DIII-D experiments over the past year, since our previous report in September, 1995. During this time, we have concentrated on improvements to the code in support of our ability to do self-consistent, predictive modeling of DIII-D discharges. Our interest is in obtaining a tool, benchmarked with experimental data, for developing advanced tokamak operations scenarios including simulation and analysis of high performance negative central shear (NCS) discharges and control of the current profile evolution. Our major focus has been on installing and improving the neutral beam current drive mode in Corsica; this element is critical to modeling the evolution of DIII-D discharges. The NFREYA neutral beam deposition code was installed (starting with a version consistent with GA`s ONETWO code) and the capability for following particle orbits, including the effects of drifts, was added for determining the current driven by neutral beam -injection. In addition, improved methods for more easily integrating experimental profile measurements into the code operation and for calculating Z{sub eff} either from models or from impurity density measurements have been added. We have recently begun to turn on various transport models in our simulation of discharge evolution. We have concentrated on the NCS configuration and have simulated the evolution of two different high neutron reactivity discharges; an NCS discharge with L-mode edge and a single- null, weak NCS discharge from the JET/ITER/DIII-D equivalent shape experiments. Corsica simulation results for these discharges were presented at the EPS meeting in Kiev, Ukraine in June, 1996

Model dependence of single-energy fits to pion photoproduction data

Model dependence of multipole analysis has been explored through energy-dependent and single-energy fits to pion photoproduction data. The MAID energy-dependent solution has been used as input for an event generator producing realistic pseudo data. These were fitted using the SAID parametrization approach to determine single-energy and energy-dependent solutions over a range of lab photon energies from 200 to 1200 MeV. The resulting solutions were found to be consistent with the input amplitudes from MAID. Fits with a $\chi$-squared per datum of unity or less were generally achieved. We discuss energy regions where consistent results are expected, and explore the sensitivity of fits to the number of included single- and double-polarization observables. The influence of Watson's theorem is examined in detail.Comment: 12 pages, 8 figure

Experimental vertical stability studies for ITER performance and design

Operating experimental devices have provided key inputs to the design process for ITER axisymmetric control. In particular, experiments have quantified controllability and robustness requirements in the presence of realistic noise and disturbance environments, which are difficult or impossible to characterize with modelling and simulation alone. This kind of information is particularly critical for ITER vertical control, which poses the highest demands on poloidal field system performance, since the consequences of loss of vertical control can be severe. This work describes results of multi-machine studies performed under a joint ITPA experiment (MDC-13) on fundamental vertical control performance and controllability limits. We present experimental results from Alcator C-Mod, DIII-D, NSTX, TCV and JET, along with analysis of these data to provide vertical control performance guidance to ITER. Useful metrics to quantify this control performance include the stability margin and maximum controllable vertical displacement. Theoretical analysis of the maximum controllable vertical displacement suggests effective approaches to improving performance in terms of this metric, with implications for ITER design modifications. Typical levels of noise in the vertical position measurement and several common disturbances which can challenge the vertical control loop are assessed and analysed.United States Department of Energy (DE-FC02-04ER54698, DEAC52- 07NA27344, and DE-FG02-04ER54235

Ion-cyclotron instability in magnetic mirrors

This report reviews the role of ion-cyclotron frequency instability in magnetic mirrors. The modes discussed here are loss-cone or anisotropy driven. The discussion includes quasilinear theory, explosive instabilities of 3-wave interaction and non-linear Landau damping, and saturation due to non-linear orbits. (JDH

Ion microstability in tandem mirrors

The formalism describing ion-cyclotron modes in mirror traps will be developed. Emphasis will be placed on the effects of finite axial boundaries on the normal modes of the system. Wave properties are a composite picture of: positive energy waves (plasma oscillation, shear Alfven and drift waves), negative energy waves (ion Bernstein waves in a loss-cone media), positive dissipation (electron Landau damping, outgoing waves), and negative dissipation (ion cyclotron damping in a loss-cone and anisotropic temperature medium). Stability boundaries in this bounded media is affected by scale lengths along the magnetic field; first, because they determine the widths of the resonances, and second, because they restrict the parallel structure of the modes

TEBASCO user's guide

TEBASCO is a Tandem mirror Equilibrium and BAllooning Stability COde. TEBASCO allows you to compute tandem-mirror MHD equilibria and to analyze both the flute-averaged and ballooning-mode stability of these equilibria. This stability analysis is directed toward the computation of marginal stability boundaries. Users of TEBASCO require a binary output file from the EFFI code which describes the vacuum magnetic field. In making this EFFI file the user will have defined a system of units for lengths (e.g., meters) and magnetic field (e.g., Tesla). In TEBASCO, all magnetic field strengths are normalized to the vacuum center-cell midplane value, and times are defined in units of the time for an Alfven wave in this field to transit one EFFI unit of length