ES350590A1 - Automatic goniometer with high resolving power - Google Patents

Abstract

An automatic goniometer used in studies utilizing small angle X-ray diffraction comprises a pivoting arm 3 Fig. 1 a radiation detector 7 carried by the arm, a counting system associated with the detector, a fixed sample carrier 20 centred on the axis of rotation 15 of the arm, means for pivoting the arm comprising micrometer screw 21 driven by a step by step motor 32 Fig.2 the end of said screw acting on a bearing member 23 of arcuate form, the centre O of the arc being on the longitudinal axis of the arm 3 the member 23 being fixed to one side of the arm by a rod which is on a radius of the arc and substantially perpendicular to the longitudinal axis, the arm being pivoted automatically by an electronic circuit in a series of steps, a series of counts being accomplished at each step. The motor 32 is preferably started by a pulse formed in the electronic circuit which closes its supply circuit and is stopped by means of a cam e.g. 34 which actuates a micro-switch 33 to open the circuit. The distance between the axis 15 and the arc centre O is preferably such that the rotation of the arm 3 by an exact decimal fraction of a degree corresponds to an advance of one revolution of the screw 21. The fluctuations with time of the incident X-ray beam from tube 8 are compensated for by adjusting the duration of e.g. count e.g. by means of a monitor detector 11 which functions with a constant number of counts, the stopping of the monitor count functioning to stop the count of the main detector 7. The angular position of the arm is monitored by means of cam 38 and micro-switch 37 which is arranged to deliver a pulse to a counting system just before the stopping of the motor 32. The same counting system also registers the pulses for starting the motor 32 and is arranged to deliver an alarm signal when a starting pulse is not followed by a stopping pulse.