Silicon drift detector – the key to new experiments

Structural Characterization of DNA-Templated Silver Nanoclusters by Energy Dispersive Spectroscopy

Here, a novel method of structural determination for DNA-templated silver nanoclusters (DNA-AgNCs) is introduced. This technique uses energy dispersive spectroscopy (EDS) coupled with a scanning electron microscope (SEM) to analyze a monodisperse solution of nucleic acid-based structures. Exploiting the consistent number of phosphate atoms in each structure, we determine the average number of silver atoms that make up the DNA-AgNCs. Proper sample preparation and fine-tuning of the SEM/EDS system settings were combined to achieve highly repeatable data.

Strategies and limitations for fluorescence detection of XAFS at high flux beamlines

The issue of detecting the XAFS signal from dilute samples is discussed in detail with the aim of making best use of high flux beamlines that provide up to 10(13) photons s(-1). Various detection methods are compared, including filters with slits, solid state detectors, crystal analyzers and combinations of these. These comparisons rely on simulations that use experimentally determined parameters. It is found that inelastic scattering places a fundamental limit on detection, and that it is important to take proper account of the polarization dependence of the signals. The combination of a filter-slit system with a solid state detector is a promising approach. With an optimized system good performance can be obtained even if the total count rate is limited to 10(7) Hz. Detection schemes with better energy resolution can help at the largest dilutions if their collection efficiency and count rate limits can be improved.

Performance of a four-element Si drift detector for X-ray absorption fine-structure spectroscopy: resolution, maximum count rate, and dead-time correction with incorporation into the ATHENA data analysis software

The performance of a four-element Si drift detector for energy-dispersive fluorescence-yield X-ray absorption fine-structure measurements is reported, operating at the National Institute of Standards and Technology beamline X23A2 at the National Synchrotron Light Source. The detector can acquire X-ray absorption fine-structure spectra with a throughput exceeding 4 x 10(5) counts per second per detector element (>1.6 x 10(6) total counts per second summed over all four channels). At this count rate the resolution at 6 keV is approximately 220 eV, which adequately resolves the Mn Kalpha and Kbeta fluorescence lines. Accurate dead-time correction is demonstrated, and it has been incorporated into the ATHENA data analysis program. To maintain counting efficiency and high signal to background, it is suggested that the incoming count rate should not exceed approximately 70% of the maximum throughput.