Friday, March 30, 2012

Zr gasket provides new window at high d

For crystalline systems with structure at high d-spacings 7-10 Å, including many magnetic systems, it has been so far necessary to use detectors in a low-angle geometry, with concurrent loss in resolution. Another possibility has been to use the bandwidth choppers to use very long wavelength neutrons to probe this structure with increased resolution. However, the substantial attenuation of the gasket and pressure vessel has made this unfeasible.

Xiaojia Chen has used IDT time to successfully test a pure Zr gasket in place of the more conventional TiZr alloys. The low absorption cross-section of Zr (0.185 barn at 2200m/s) versus Ti (6.09 barn at 2200m/s) means that a much stronger sample signal is accessible with the new gaskets. These measurements use a vertical geometry with the beam entering and exiting through the gasket and both detectors at 90 degrees. Testing has shown that the resulting data shows sharp strong Bragg peaks on very low backgrounds.

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