We present experimental results for Rayleigh-Bénard convection with rotation about a vertical axis at dimensionless rotation rates 0 ≤ Ω ≤ 250 and ǫ ≡ ∆T /∆Tc − 1 < ∼ 0.2. Critical Rayleigh numbers and wavenumbers agree with predictions of linear stability analysis. For Ω > ∼ 70 and small ǫ the patterns are cellular with local four-fold coordination and differ from the theoretically expected Küppers-Lortz-unstable state. Stable as well as intermittent defect-free square lattices exist over certain parameter ranges. Over other ranges defects dynamically disrupt the lattice but cellular flow and local four-fold coordination is maintained.

Electrons are bound to the surface of liquid helium by the image potential due to the induced polarization of the helium. The potential varies as the reciprocal of the distance of the electron from the surface so that the energy levels for the electron motion perpendicular to the surface are those of a one-dimensional hydrogen atom with very small charge. In order to make quantum logic elements (qubits) using the ground state and first excited state in this potential, individual electrons must be confined over microelectrodes which are individually connected to variable voltage sources so that the electron energy levels can be shifted in and out of resonance with applied microwave radiation. The electrodes consist of an array of gold columns, about 1.2 m tall and 200 nm in diameter, separated by 500 nm. These are grown by electroplating on the ends of leads deposited on a silicon substrate by e-beam lithography. The leads are covered by a dielectric layer and then a metal ground plane, so that the electric field from the leads is screened. We describe, here, our technique for fabricating this system and present the numerical computations of the electric fields from the electrodes.

We have developed a porous silicon (PS) diode that yields free-electron currents with energies &lt;0.1eV below 77 K. The power dissipated during emission is low so that pulses of electrons can be produced below 100 mK without raising the temperature of the system. Free electrons were generated in liquid He4 and He3 as well. The device was developed as a source of electrons for a quantum computing system using electrons on the surface of a dielectric film. The results suggest that a Poole-Frenkel type of mechanism accounts for the observed electric-field-enhanced conduction but the electron emission mechanism is not well understood in the present models of PS.