The Scattering of Protons by Protons near 30 Mev, Photographic Method

The scattering of 29.4-Mev protons by hydrogen gas at one atmosphere pressure has been studied with the beam of the Berkeley linear accelerator. The beam, collimated to a diameter of $\frac{1}{16}$ in., passes through the gas and constitutes a line source of scattered protons. The scattering angle of the scattered protons is measured directly in the emulsion of $50\mu$ Ilford C-2 emulsions. Measurements of the range of the scattered protons was made on a fraction of the tracks. From range-energy relations established in the magnetic field of the 184-in. cyclotron for the emulsions used, the primary energy of the protons before scattering was found to be 29.4±0.1 Mev. Protons were observed in the angular range $10°<~{\theta }_{\mathrm{lab}}<~80°$; two independent sets of scattering data in the angular region greater or less than 45° are thus obtained; a valuable internal check on observational errors or background or impurity effects is thus possible. No statistically significant difference in the two regions was observed. 10,934 tracks have been tabulated; this results in the statistical error approximately matching systematic errors such as those due to tolerance of plate geometry, observational error, etc. Cross sections obtained are absolute; the beam is measured by absorption in a Faraday cup and charge integration on a low leakage condenser. The most significant result of these experiments is the apparent absence of expected repulsive $P$ wave and of $D$ wave effects.