Search

Detached plasmas have been proposed as a means of distributing power losses uniformly on walls in ITER and other reactor scenarios. Ohmically and neutral beam injection (NBI) heated detached plasma studies are being carried out on TFTR in order to help determine the practicality of this concept. NBI heated detached plasmas with up to 8.5 MW of beam power have been maintained detached for up to 300 ms. A confinement related delay in the radiated power is observed at low beam power. H-mode-like events have been observed for several beam heated detached plasmas and radiative emissivities as high as 0.8 MW/m 3 have been realized. These results are especially of interest to ITER and other reactor design studies.

Quantitative spectroscopic measurements of Zeff, impurity densities and radiated power losses have been made for ohmically heated and neutral beam heated TFTR discharges at a plasma current of 2.2 MA and a toroidal field of 4.7 T. Variations in these quantities with line average plasma density (e) and beam power up to 5.6 MW are presented for discharges on a movable graphite limiter. A detailed discussion of the use of an impurity transport model to infer absolute impurity densities and radiative losses from line intensity and visible continuum measurements is given. These discharges were dominated by low-Z impurities, with carbon having a considerably higher density than oxygen, except in high e Ohmic discharges where the densities of carbon and oxygen were comparable. Metallic impurity concentrations and radiative losses were small, resulting in hollow radiated power profiles and fractions of the input power radiated being 30–50% for Ohmic heating and 30% or less for beam heating. Spectroscopic estimates of the radiated power were in good agreement with bolometrically measured values. Because of an increase in the carbon density, Zeff rose from 2.0 to 2.8 as the beam power increased from 0 to 5.6 MW, pointing to a potentially serious dilution of the neutron producing plasma ions with increasing beam power. Both the low-Z and the metallic impurity concentrations were approximately constant with minor radius, indicating no central impurity accumulation in these discharges.

Methods are discussed for reconstructing spatial distributions from two types of projection-in a direction tangential to a torus and in a cross-sectional plane. For a tangential projection the reconstruction is unambiguous. For cross-sectional projections one usually does not have enough information for an unambiguous reconstruction, unless strong simplifying assumptions are made. A method is given for fitting a spatial distribution to such projections. Tests of both methods are discussed. The fitting method for cross-sectional projections is compared with a Fourier-series method.

The event-to-event fluctuations of the rapidity distributions are analyzed for semi-inclusive data obtained from 205 GeV/ c and 303 GeV/ c proton-proton collisions observed at NAL. The results indicate the presence of clustering effects, with cluster sizes approximating those observed in the quasi-elastic events. The average cluster size appears to be independent of the multiplicity of the final state.

We have studied the properties of the inclusive pp → pX reation at 303 GeV c . Protons of momentum 1.4 GeV c or less are measured and identified by their ionization. We investigate the multiplicity distribution associated with those events having a small four-momentum transfer to the target proton. Under the assumption that this selection enhances or isolates the diffractive component of the interaction, we discuss the properties of the diffractive and nondiffractive components.

The properties of the diffractively excited system observed at low missing mass in the inclusive pp → pX reaction at 303 GeV c are presented. For diffraction excitation with | x | > 0.9, the cross section, σ D =(5.6±0.8) mb, the mean charged multiplicity depends on the mass of the diffractive system approximately at 〈 n c 〉 ≈ 0.6 M x + 2, and the slope of the momentum transfer distribution with | t | 2 is 7.5±0.8 GeV −2 .