5 research outputs found
Concentrator of laser energy for thin vapour cloud production near a surface
A novel scheme is presented for production of a thin ( mm) uniform vapor
layer over a large surface area ( cm) by pulsed laser ablation of a
solid surface. Instead of dispersing the laser energy uniformly over the
surface, a modified Fabry-Perot interferometer is employed to concentrate the
laser energy in very narrow closely-spaced concentric rings. This approach may
be optimized to minimum total laser energy for the desired vapor density.
Furthermore, since the vapor is produced from a small fraction of the total
surface area, the local ablation depth is large, which minimized the fraction
of surface contamination in the vapor.
Key words: laser evaporation, thin gas layer formation.Comment: 8 pages, 2 figure
Vortex in a d-wave superconductor at low temperatures
A systematic perturbation theory is developed to describe the magnetic
field-induced subdominant - and -wave order parameters in the mixed
state of a -wave superconductor, enabling us to obtain, within
weak-coupling BCS theory, analytic results for the free energy of a d-wave
superconductor in an applied magnetic field H_{c1}\ltsim H\ll H_{c2} from
down to very low temperatures. Known results for a single isolated vortex
in the Ginzburg-Landau regime are recovered, and the behavior at low
temperatures for the subdominant component is shown to be qualitatively
different. In the case of subdominant pair component, superfluid
velocity gradients and an orbital Zeeman effect are shown to compete in
determining the vortex state, but for realistic field strengths the latter
appears to be irrelevant. On this basis, we argue that recent predictions of a
low-temperature phase transition in connection with recent thermal conductivity
measurements are unlikely to be correct.Comment: 20 RevTEX pages, 6 EPS figures; considerably expanded versio