Measurements of the total cross section differences a-j.(^Ca)-a^C^^Ca) and o-pC^^Ca) -(TTi^^Cd) are reported for positive and negative pions. Optical-model calculations are used to extract values of the rms neutron radius difference for each isotope pair. For ^Ca-^^Ca the deduced radius difference agrees with the results of recent cK-particle and proton scattering experiments but is smaller than values predicted from Hartree-Fock calculations.
An experiment using a plasma gun as a source to inject a high-velocity jet of plasma into a picket fence magnetic confinement system is described. The results show that a plasma jet having 5 × 1013 deuterons/cm3 and a mean directed kinetic energy of 1 kev/deuteron is able to traverse a 2-kg magnetic barrier displacing the field completely in its path, i.e., traveling as a β = 1 plasma. Some focusing of the plasma jet occurs during the penetration which increases its density. If the plasma is injected into a higher field it mixes with the field and penetrates as a β < 1 plasma. These two phenomena combine so that the idealized sudden stopping of a given beam at a critical magnetic field (Bc2 > 12πρV2) is not observed. For fields <2000 gauss the plasma jet opens the entrance cusp for ≈ 3 μsec; a biconical diamagnetic region with β = 1 builds up within the picket fence volume and then decays with a time constant of 50 μsec. This indicates that some irreversible process does occur, trapping plasma within the magnetic confining field.
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