Douglas M. Patterson

Confinement time scaling in TEXT

Values of the total energy confinement time tau E are presented for ohmic hydrogen discharges on the TEXT Tokamak, spanning a range of chord-averaged densities of 2.0-8.5*1013 cm-3, plasma currents of 150-400 kA, and toroidal fields of 15-28 kG. At the higher densities tau E exhibits a saturation which corresponds well with a recently proposed scaling law (Goldston, 1984) in which the saturated value is given by an empirical expression for beam-heated limiter discharges with Ptot identical to POH. The relationship between this observed saturation and density-profile widths is addressed.

Interpretation of impurity confinement time measurements in Tokamaks

An analysis technique for interpreting impurity confinement time data is presented. If chord-averaged temporal evolutions of injected impurity spectra are employed in an impurity transport experiment, they are normally used to obtain impurity confinement times. The authors have established experimentally that this type of data often has characteristics which justify its use in conjunction with a simple analytical model to evaluate the constant diffusion coefficient and the constant convective velocity in an impurity transport flux which is the sum of diffusive and convective terms. Since this is often the goal of numerical simulation analysis, the technique may in some instances substitute for data-intensive numerical modelling.

Neutral beam diagnostics for Alcator C-Mod

A diagnostic neutral beam will be installed on Alcator C-Mod for measurement of ni, nz, Tz, vθ, vφ, and j. The beam will be used primarily for the study of thermal transport, Er in H-mode discharges, and to provide critical profile and turbulence data for tests of theoretically based models of turbulence and transport. The beam selected for this work was used on Texas Experimental Tokamak and is rated at 50 kV and 6 A of extracted current in hydrogen. It can produce beams of deuterium or helium as well. It is currently being reconfigured for installation on C-Mod. Capabilities for the intended measurements are described using simulations based on measured C-Mod profiles.

The TEXT data base

The TEXTDB data base organizes the analyzed experimental data from the TEXT experiment so as to aid in understanding the physics of a complete discharge. The data base was constructed using a commercial relational data base. The relational model provided a flexible structure for organizing data from many different diagnostics into a unified description of the plasma discharge.

Simulations of beam-emission spectroscopy on Alcator C-Mod (abstract)

An eight-channel beam-emission-spectroscopy (BES)1 system has been installed on the Alcator C-Mod tokamak, intended for use with a diagnostic neutral hydrogen beam (DNB). Capable of localized measurements from the plasma edge to the plasma core, the BES diagnostic collects light from the first Balmer transition (Hα) resultant from beam/plasma collisions. The Hα line splits into several components whose central wavelengths depend on the viewing geometry, the magnetic field, and the beam energy. This is due to the Doppler shifts from viewing the beam off perpendicular, the different velocities of the three mass components of the beam (H, H2, H3), and the large motional Stark effect. Optimal signal-to-noise requires collecting these components while attenuating all other emission: primarily bremsstrahlung and Dα radiation (from plasma D0/e− collisions). Tunable bandpass filters are thus required. A BES simulation code has been developed that calculates the brightnesses (bremsstrahlung, Dα, Hα) versus wavelen...