O'Brien Wl

A simple variable line space grating monochromator for synchrotron light source beamlines

Abstract In this paper, we present and analyze an improved spectrometer design that has evolved from studies of the focal properties of transmission gratings in converging ligid beams. This design uses a variable line space grating at a fixed angle of incidence to focus the diffracted light in one dimension, producing resolutions in excess of 1000 over a large wavelength region. Attractive features of this concept include high throughout, simple wavelenght scanning, simple optical elements (plane gratings and plane and toroidal mirrors), and relatively inexpensive realizations. After presenting a mathematical analysis of the primary design features, we discuss implementations of this design both as a spectrometer and as two versions of beamline monochromators. Design parameters for the two monochromators will be given.

Novel techniques for characterizing detector materials using pulsed infrared synchrotron radiation

The VUV ring at the National Synchrotron Light Source (NSLS, Brookhaven national Laboratory) is a source of nanosecond-duration, high-brightness, broadband IR pulses. The authors are developing several measurement techniques for characterizing Hg1-xCdxTe and other IR detector materials using this source. For example, the broadband IR pulses can be used to study transient photoconductive decay at various photon energies near the bandgap. A particularly novel technique they have developed is far-infrared photoinduced nanosecond spectroscopy (FIR-PINS). In this all-optical (contactless) measurement, a short laser pulse generates photocarriers which are subsequently sensed by a far-infrared pulse from the synchrotron. Spectroscopic analysis of the far-infrared yields the free carrier plasma frequency, providing information on the photocarrier density. By varying the delay time of the far-infrared pulse (relative to the laser pulse), the photocarrier relaxation is determined with nanosecond resolution. In addition to being contactless, the technique offers other potential advantages over electrical measurements. Results for MBE-grown Hg1-xCdxTe are presented.

A soft‐x‐ray‐emission investigation of cobalt implanted silicon crystals

The Si L2,3 emission spectra of silicon crystals implanted with Co at doses of (1–8) × 1017 Co/cm2 have been examined using soft‐x‐ray‐emission (SXE) spectroscopy. At the lowest dose, the spectra are little modified from that of crystalline Si, indicating that only a small fraction of Si is in the form of silicides within the probe depth of SXE spectroscopy. For higher doses and implant profiles with Co extending to the surface, there is clear evidence for ordered CoSi2 combined with richer Co phases, but little evidence for pure Si or for ordered regions of CoSi.