An improved apparatus for the study of disintegrations produced by high -energy particles accelerated in a cyclotron has been constructed. The instrument employs the photographic method of detecting charged particles, and allows the numbers and energy of the scattered and disintegration products to be determined— at any angle with respect to the primary beam, in the interval from 15 to 165°— as a result of a single exposure. By means of a slit system, the spread in energy of the deuteron beam from the Liverpool cyclotron has been reduced to 60 keV, and the angular divergence of the beam to ± 1/3°. ‘Targets’ composed of gases or thin foils have been used. The Q-values of the resulting nuclear reactions which lead to the emission of protons and α-particles can, in the refined conditions provided by the instrument, be determined to within ± 0.03 MeV; separate proton groups with a difference of energy of 0.08 MeV can be resolved.