Superconducting High-Resolution X-Ray Spectrometers for Chemical State Analysis of Dilute Samples

Conference · Tue Sep 02 04:00:00 EDT 2003

DOI:https://doi.org/10.1063/1.1757962· OSTI ID:15005013

Friedrich, S; Drury, O B; Funk, T; Sherrell, D; Yachandra, V K; Labov, S E; Cramer, S P

Cryogenic X-ray spectrometers operating at temperatures below 1 K combine high energy resolution with broadband efficiency for X-ray energies up to 10 keV. They offer advantages for chemical state analysis of dilute samples by fluorescence-detected X-ray absorption spectroscopy (XAS) in cases where conventional Ge or Si(Li) detectors lack energy resolution and grating spectrometers lack detection efficiency. We are developing soft X-ray spectrometers based on superconducting Nb-Al-AlOx-Al-Nb tunnel junction (STJ) technology. X-rays absorbed in one of the superconducting electrodes generate excess charge carriers in proportion to their energy, thereby producing a measurable temporary increase in tunneling current. For STJ operation at the synchrotron, we have designed a two-stage adiabatic demagnetization refrigerator (ADR) with a cold finger that holds a 3 x 3 array of STJs inside the UHV sample chamber at a temperature of {approx}0.1 K within {approx}15 mm of a room temperature sample. Our STJ spectrometer can have an energy resolution below 10 eV FWHM for X-ray energies up to 1 keV, and has total count rate capabilities above 100,000 counts/s. We will describe detector performance in synchrotron-based X-ray fluorescence experiments and demonstrate its use for XAS on a dilute metal site in a metalloprotein.

• Research Organization: Lawrence Livermore National Lab., CA (US)
• Sponsoring Organization: US Department of Energy (US)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 15005013
• Report Number(s): UCRL-JC-155314
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
59 BASIC BIOLOGICAL SCIENCES
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
99 GENERAL AND MISCELLANEOUS
ABSORPTION SPECTROSCOPY
ADIABATIC DEMAGNETIZATION
CHARGE CARRIERS
CHEMICAL STATE
ENERGY RESOLUTION
LI-DRIFTED SI DETECTORS
SPECTROMETERS
SYNCHROTRON RADIATION
X-RAY SPECTROMETERS