No abstract

No abstract

A radial electric field can be imposed on the plasma column of a stellarator by means of a comparatively large, positively biased Langmuir probe. Measurements are presented which confirm the theoretical description of the resulting E × B rotation in terms of a leaky plasma capacitor; the leakage is caused most likely by resonant charge exchange collisions with neutral atoms. The plasma loss rate is changed in the rotating region; a decrease in loss rate by a factor 8 can be realized; too large a rotational velocity causes the loss rate to increase again. Comparisons are made with other experiments and theories. The experiments were carried out in highly ionized hydrogen and deuterium plasmas created by Ohmic heating in the B-3 stellarator, having electron temperatures of 3 to 5 eV, densities of 2 to 20 × 1012 cm−3, and confined in magnetic fields of 25 to 40 kG. An experimental justification for the interpretation of Langmuir probe characteristics under these conditions is given.

No abstract

External meson beams, ranging in energy from 135 Mev to 260 Mev for the ir~, and 135 Mev to 198 Mev for the 7r + , have been used for the measurement of total cross sections by an attenuation experiment using liquid hydrogen as well as CH2 and C as absorbers. Possible errors introduced by contamination of the ir + beam by protons have been eliminated by use of time-of-flight and pulse-height discrimination. The corrected cross sections for iT mesons in hydrogen rise from 47 mb at 133 Mev to a maximum of about 66 mb near 180 Mev and fall thereafter to 38 mb at 258 Mev, with typical uncertainties of ±5 percent. The cross sections for ir + mesons rise from 122 mb at 128 Mev to around 200 mb between 170 Mev and 196 Mev, with accuracy comparable to that for the ir~ mesons except for the very high energies where the beams are of low intensity. The ir + cross sections follow very well the curve representing three times the total ir~ cross section, indicating that in the measured energy range the dominant interaction between pion and nucleon occurs for total isobaric spin 7=f. Comparison of the ir~ cross section with (8/3)7rX 2 supports the idea that the particular angular momentum state /= §, L-1 (for /= f) is especially prominent in the scattering.The total cross sections for TT + and if~ mesons interacting with deuterium have also been measured by comparing the transmissions of D 2 0 and H2O cells. Within the accuracy, the TT + and x~ total cross sections are equal, consistent with the principle of charge symmetry. The total scattering cross section of deuterium is less than but of the same order of magnitude as the sum of the hydrogen cross sections for TT + and ir~. DEFLECTING MAGNET SCALE IN FEETFIG.