An integrating photometer for X-ray crystal analysis

Abstract

The measurement of the relative intensities of reflection of X-rays from lattice planes of a crystal is of vital importance in modern structure analysis, but it presents a problem often difficult of solution. The use of the ionisation spectrometer is laborious and sometimes impossible, at any rate for the small crystals which may be the only ones available; while photographic methods cannot usually be applied to records in which the distribution of energy over area varies considerably from one spot to another. A new principle of photographic photometry was suggested by Astbury to overcome the difficulty and to make it possible to obtain, as a single observation, a measure of the integrated energy corresponding to narrow beam of radiation, not necessarily of uniform distribution, falling on to a photographic plate. Briefly the method involves the reproduction of the photograph by the bichromated gelatin process as a thin membrane whose thickness diminishes with increasing opacity of the original; this membrane is then used as an obstacle to a beam of α-particles penetrating the tissue is found to measure the energy which formed the spot on the original record.