Reduction of Raman scattering and fluorescence from anvils in high pressure Raman scattering.

We describe a new design and use of a high pressure anvil cell that significantly reduces the Raman scattering and fluorescence from the anvils in high pressure Raman scattering experiments. The approach is particularly useful in Raman scattering studies of opaque, weakly scattering samples. The effectiveness of the technique is illustrated with measurements of two-magnon Raman scattering in LaCuO.

Development of new apertures for coherent X-ray experiments.

When one performs a coherent small-angle X-ray scattering experiment, the incident beam must be spatially filtered by slits on a length scale smaller than the transverse coherence length of the source which is typically around 10 microm. The Fraunhofer diffraction pattern of the slit is one of the important sources of background in these experiments. New slits which minimize this parasitic background have been designed and tested.

Concentration fluctuations in the binary mixture hexane-nitrobenzene with static and dynamic x-ray scattering.

We report on a small-angle x-ray scattering study of the hexane-nitrobenzene binary fluid mixture near its critical point. The use of an ultrabright x-ray undulator synchrotron source enabled us to measure the temperature dependence of the static structure factor with unprecedented contrast, and the large coherent flux of this source provided a probe for the fluctuation dynamics via the x-ray photon correlation spectroscopy technique. We find that the intensity and correlation lengths diverge with the expected three-dimensional Ising critical exponents, and the dynamical correlation function decays exponentially with correlation times as small as 250 micros.

Bridge for measurement of low resistance.

A simple four-terminal bridge of low power dissipation and high resolution is used to measure small resistances at low temperatures.