The Design and Performance of the Dual-Function Spectrodiffractometer and Automatic Programmer

Abstract

A new concept in a dual-function diffractometer-spectrometer has been developed. With this new concept, it is unnecessary to disassemble any part of the instrument when changing from diffraction to air-helium spectroscopic applications and vice versa. Therefore, the alignment of the instrument is not disturbed and changeover is accomplished in a matter of seconds. The diffractoraeter is the standard biplane diffractometer, having an angular range of −55 to +164° 20 and a full 360° ω. Without interfering with the entire angular range of the diffractometer, the spectrometer section allows an angular range to 154° 2θ, This uninterrupted freedom of angular motion for both functions is accomplished by the design concept of using different frames of reference for the 0-180° 2θ plane of the diffractometer and the 0-180° 2θ plane of the spectrometer. In one case, the motion of 16 toward higher positive angles is counterclockwise and in the other case, it is clockwise. The frames of reference are displaced by 96°. The helium attachment for low-atomic-mimber elements ensures complete replacement of the air with helium in a flushing time of 15 sec. After changing samples, the helium atmosphere returns to equilibrium within 5 sec. A ten station programmer also has been developed, enabling one to automatically program oscillating scans and stepped scans of diffraction profiles as well as sequential emission analyses. The angular position is programmed in increments of 0.01° and is reproducible within 0.005°. During the sequential mode of operation, 20 is driven to the next position at a rate of 40 deg/min. In addition, stepping increments as small as 1/120° and scanning speeds of ⅛, ¼, ½, 1, and 2 deg/min are available. In all of the above modes of operation, data are collected and printed as a function of preset time, preset count, or angular position. In this paper, typical performance characteristics and applications are presented.