Abstract:
In this talk I will present use of the Maia detector at CHESS to obtain large-area, full spectrum x-ray absorption near edge structure (XANES) maps. The Maia is a 384-pixel energy-resolving detector system designed for large solid angle and high-speed operation. It's large, ~1.3sr solid angle is obtained with 384 individual 1-mm2 detector elements arranged in an annular array, allowing operation in backscattering geometry with a sample to detector distance of 10mm. Parallel detection enables high count rates at low dead time, allowing for fast scanning with typical dwell times of about 1 ms. I will also discuss the application of this new capability to study iron chemistry in geological samples formed by a meteorite impact on Earth. Figure 1a shows an iron ?XRF map of a thin section taken from an impact melt-bearing rock sample from the Mistastin lake impact structure (northern Labrador, Canada). The map was collected at the bending magnet F3 beamline of CHESS in focused beam mode using a single-bounce monocapillary optic. XANES mapping, from 7.05 to 7.3keV, was performed on the entire 3.6 x 5.5mm2 area (see Fig. 1a, green box) with 0.5eV energy steps in the near-edge region. With an integration time of 15 milliseconds per pixel and a spatial resolution of 40 ?m, the entire XANES image stack was produced in less than 8 hours (with a count rate of 160 kcps).p