Development of a multiwire proportional chamber as an area sensitive detector for X-ray protein crystallography

The prototype of an area sensitive multiwire proportional chamber operated in series with a spherical drift chamber was investigated for its applicability to protein crystallography, employing 14.4 keV (λ=0.86 A ̊) γ-radiation of ⁵⁷Co Mössbauer sources. The 10 cm long spherical drift field, in this case, provides high efficiency in order to compensate for the small primary intensity of Mössbauer sources. The detector system was tested with different gas mixtures. The improvement of the spatial resolution with increasing xenon content is demonstrated using the 603 reflection of a myoglobin crystal. The addition of xenon to the counter gas is shown to be necessary for protein crystallography with short wavelengths. The background is sufficiently low for Mössbauer experiments, due to good energy discrimination at the anode (≤0.003 counts/(min×mm²)).