Solid State and Optics Seminar

Friday, February 17, 2006

1:00 p.m.

408 Becton

"Superconducting Tunnel Junction X-ray Spectrometers for Synchrotron Science"
or
"The Chemistry of Dilute Samples"

Dr. Stephan Friedrich
Lawrence Livermore National Laboratory,
Advanced Detector Group

Abstract

Superconducting tunnel junctions (STJ) are attractive X-ray detectors for synchrotron science, because they combine the high energy resolution of cryogenic detector technologies with the high count rate capabilities of athermal devices. STJs consist of two superconducting electrodes separated by a thin insulating tunnel barrier, and infer X-ray energies from the increase in tunneling current upon photon absorption. The Advanced Detector Group is developing STJ spectrometers based on arrays of Nb-Al-AlOx-Al-Nb STJ arrays. They have achieved an energy resolution below 10 eV FWHM for X-ray energies below 1 keV, and can be operated at count rates of ~30,000 counts/s per pixel. These spectrometers are operated at at the Advanced Light Source synchrotron at Lawrence Berkeley Lab to measure chemical speciation of dilute metals by fluorescence-detector absorption spectroscopy. We will describe the performance of the instrument in applications from biophysics to material science. We will also outline future developments that are desirable to increase the sensitivity and the user-friendliness of the instrument and make STJ detector technology available to the wider science community.

Host: Dan Prober