A position-sensitive detector for neutron powder diffraction

Abstract

A linear position-sensitive detector has been constructed with an array of three proportional counters and installed on the neutron powder diffractometer at the University of Missouri Research Reactor. The event position is determined by the charge division method using digital arithmetic. Consideration has been given to the corrections necessary to account for the differences in detection efficiency, solid angle, dead time and resolution for different points along the detector, caused by the finite thickness and tangential orientation of the detectors. An important feature of the instrument is an oscillating radial collimator with high transmission placed between the sample and detector which enables the system to have low background and a high signal-to-noise ratio. By considering the angular rate of accumulating data, the peak intensity per channel and the resolution of a Bragg diffraction peak, the enchancement factor for the positionsensitive detector is estimated to be about 50 compared to a single detector with a step scan. This allows experiments to be performed with better statistics, better resolution and smaller samples, and enables marginal experiments to be worthwhile. A number of structures have been refined with this detector using Rietveld analysis including a new rareearth-transition-metal phase whose structure has been solved from the powder diffraction data.

Structural, Magnetic, and Thermal Properties of La1−tCatCrO3−δ

“…of wavelength 147.66 pm. Intensities were measured by an array of five 600 mm position sensitive 3 He detectors Phase pure sample of La 1Ϫt Ca t CrO 3 , 0.00 Յ t Յ 0.30, were obtained after a second heating in air at 1473 K. The distri-(PSD), covering 20Њ in 2⌰ (23). A complete diagram, from 2⌰ ϭ 5Њ to 105Њ, was obtained by moving the detector unit bution of Ca and La over the A site is random, as indicated by small half-widths of the Bragg reflections and lacking in five steps.…”

Lithium-ion cell based on orthorhombic LiMnO2

“…The raw data, collected with a positionsensitive detector, were corrected for the detector geometry according to the procedures of Ref. [8].…”

The Structure of Yttrium Cobaltate from Neutron Diffraction

“…A list of the first 23 corrected peak positions was made (excluding the silicon peaks). Four of these peaks corresponded to Y O ; the remaining peaks were indexed Neutron diffraction data were collected at the wavelength of 1.4873 A s on the PSD-II diffractometer at the University of Missouri Research Reactor (4). The finely ground sample was packed into a 3 mm quartz capillary, and the capillary was mounted in a displex closed cycle refrigerator.…”