Poloidally asymmetric impurity-ion emission has been observed in high-density discharges of the Alcator Tokamak. The sense of the asymmetry reverses when the direction of the toroidal field is reversed, and all observed dependence of the strength of the asymmetry upon proton density and safety factor are consistent with the explanation that the gradient and curvature drifts of the highly collisional impurity ions cause the asymmetry. Thus the asymmetry implies that the drift is a major impurity transport process at high densities.

It is known that an internal tokamak disruption leads to a current profile which is flattened inside the surface when the safety factor equals unity. It is shown that such a profile can lead to $m=2\mathrm{}$ magnetic islands which grow to fill a substantial part of the tokamak cross section in a time consistent with the observation of a major disruption.

Instabilities in a triple-plasma device which produces counterstreaming ion beams are investigated. We observed a new type of standing oscillations whose wavelength is given by $\frac{D}{n}$, where $D$ is the distance between boundaries and $n$ is an integer. The phase velocity and the critical beam velocity are compared with theory.

It is shown that the positions of the peaks in the angle-resolved photoemission spectra from a Cu(111) surface for $h\nu =11.6-40.8\mathrm{}$ eV are predicted reasonably well by the initial-state band structure and a single-plane-wave final state, but the strengths of the peaks are described by atomiclike dipole selection rules.

We have used complementary sets of normal and superconducting probes to study the nonequilibrium region near phase-slip centers in narrow superconducting strips. An exponentially decaying branch imbalance potential, ${\mu }_Q$, is observed and the decay length, the quasiparticle diffusion length, is measured directly and compared to the phase-slip resistance.

A strong resonance effect has been observed for the first time in photoemission: This happens on a metallic nickel (100) surface when the photon energy is close to that of the $3p$ energy level. The effect is interpreted as the autionization of an excited quasidiscrete atomic configuration into a continuum of excitations with two holes in the $3d$ shell.

The oxidation rate of nickel has been measured in the vicinity of its Curie temperature. The results reveal a large difference in the oxidation kinetics, manifested as a change in activation energy of ∼ 1 eV/atom, between the paramagnetic and ferromagnetic phases of nickel. The observed modifications of the kinetics are qualitatively consistent with recent theoretical predictions by Suhl.

Pseudorapidity distributions for proton-nucleus interactions are presented. The data cover twelve nuclei ranging from carbon to uranium and three incident proton momenta, 50, 100, and 200 GeV/c.

The inclusive production of antiprotons and $\Lambda \text{'}\mathrm{s}$ in $e^{+}{e}^{-}$ annihilation has been measured as a function of the c.m. energy in the range 3.7-7.6 GeV. We find that the baryon cross section has a behavior different from the total hadronic production. Our results show a rapid rise in the ratio $\frac{{\sigma }_{\overline{p}}}{{\sigma }_{\mu \mu }}$ between 4.4 and 5 GeV, consistent with what would be expected from charmed baryon production. $\overline{\Lambda }$ production is 10-15% of $\overline{p}$ production at all energies.

We suggest that both two-body and many-body bound states of a charmed baryon and nucleons should exist. Estimates indicate binding in the ${}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ state of $C_{1}N$ ($I=\frac{3}{2}$) and $\mathrm{SN}$ ($I=1\mathrm{}$). We further estimate the binding energy of $C_0$, $C_1$ in various finite nuclei.

The results of hydrogen profile measurements on samples prepared by the same methods used for these materials when making ultracold-neutron (UCN) storage bottles show that the surface hydrogen is sufficient to account for the bulk of the anomalous shortening of UCN storage times.

The diamagnetic Zeeman effect has been isolated by observing energy shifts of the $6s6p{}_{}{}^1{}_{}{}^{}{P}_1_{}^{\circ }{}_{}{}^{}-6\mathrm{sns}$ ${}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ Rydberg series in laser-excited Ba in magnetic fields of 20-40 kG. Perturbation of this series by the $5d7d{}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ level reduces the shift below the hydrogenic value for $n=18\mathrm{}$. Magnetically induced mixing between the $6sns{}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ and $6snd{}_{}{}^1{}_{}{}^{}D_2^{}{}_{}{}^{}$ series causes both an enhancement in intensity of the higher members of the ${}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ series and deviations of the shifts from the hydrogenic values.

Lithium atoms in high Rydberg states, excited in an atomic beam by pulsed electron impact, are passed through a target gas and detected following electric-field state selection. Cross sections obtained from time-of-flight spectra are virtually independent of the principal quantum number and in numerical agreement with calculations for deflection of the core ion alone. This deflection has also been observed directly. These results suggest a new method for very-low-energy ion-atom scattering experiments.

Measurements of the $g$ factor for a series of bound, $5snd$ $J=2\mathrm{}$ states in Sr, in the region of an avoided crossing between ${}_{}{}^1{}_{}{}^{}D_2^{}{}_{}{}^{}$ and ${}_{}{}^3{}_{}{}^{}D_2^{}{}_{}{}^{}$ Rydberg series, show a variation which is in agreement with the prediction of multichannel quantum-defect theory. The $g$ factor was measured by multiphonon ionization spectroscopy. The dependence of ionization signal on laser polarization was also studied.

We report a new Doppler-free rephasing effect, the tri-level echo, which we use to study Ar-Na collisional relaxation of several $3{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}-n{}_{}{}^2{}_{}{}^{}D_{\frac{3}{2}}^{}{}_{}{}^{}$ superpositions in atomic Na. Three excitation pulses are required: The first resonantly excites a selected state, while the others resonantly couple this state with a higher-lying state. This sequence produces a delayed rephasing on the resonance transition which radiates strongly; the radiated intensity monitors relaxation in the higher-lying stepwise-excited state.

Compression of neon-filled glass microballoons irradiated by a four-beam laser system has been measured directly by Stark broadening, opacity broadening, and spatial profiles of ${\mathrm{Ne}}^{+9\mathrm{}}$ x-ray lines. For an 8.6-atm fill pressure and a 0.2-TW, 40-psec laser pulse, the measured compressed neon density was 0.26 g/${\mathrm{cm}}^3$ and the product $\rho R$ was 2.5 × ${10}^{-4\mathrm{}}$ ${\mathrm{g}/\mathrm{c}\mathrm{m}}^2$.

The absorption of intense laser light is found to be reduced when targets are irradiated by 1.06-μ m light with long pulse widths (150-400 ps) and large focal spots (100-250 μm). Estimates of Brillouin scatter which account for the finite heat capacity of the underdense plasma predict this reduction. Spectra of the back-reflected light show red shifts indicative of Brillouin scattering.

Parylene and tungsten-glass disks have been irradiated with a 1.06-μm laser at fluxes of ${10}^{13}$-${10}^{15}$ ${\mathrm{W}/\mathrm{c}\mathrm{m}}^2$. Analysis of the experimental results indicates that the laser-plasma interaction was characterized by critical surface steepening, rippling and/or filamentation, polarization-dependent scattering, and efficient generation of superthermal electrons. These effects were significantly stronger in the tungsten-glass experiments.

The Fokker-Planck kinetic equation for suprathermal electrons which are confined in a spherical plasma by the sheath potential and collide with colder denser electrons and ions is investigated. In the region where the collisional mean free path, $\lambda$, is longer than the spatial scale length, $L$, the kinetic equation is reduced by averaging it along an orbit between reflections by the sheath. The electrons are seen to diffuse in impact parameter relative to the plasma core while slowing down in velocity. The resulting heat flow scales as $\left(\frac{L}{\lambda }\right)n_{\mathrm{sth}}m{v_{\mathrm{sth}}}^3$.

The small magnetic perturbations accompanying drift waves are shown to produce microscopic, fluctuating magnetic island structures and to enhance radial electron heat transport in tokamaks. The "magnetic-flutter"-induced electron heat-conduction coefficient is found to be ${{\chi }_e}^{\delta }\simeq \frac{3}{16} (\nu +\gamma ){\delta }^2$, where $\delta$ is the magnetic island width, $\nu$ is the electron-ion collision frequency, and $\gamma$ is the drift-wave growth rate, or inverse island correlation time.