STUDY OF A FRAGMENTATION REACTION BY THIN-TARGET RECOIL TECHNIQUES PRODUCTION OF Na$sup 24$ FROM BISMUTH BY 2.9-Gev PROTONS

The angular distribution of Na/sup 24/ nuclei produced by bombardment of thin bismuth targets with 2.9-Bev protons was measured. The forward-to-backward ratio in the laborator system was found to be 1.52 plus or minus 0.06. Differential range curves for the Na nuclei were obtained at angles of 15, 90, and 165 deg , with respect to the beam direction. The mean energy of emission at 90 deg is 47 Mev with a full width at half-maximum of 40 Mev. The mean is only 60% of the energy expected from Coulomb repulsion. Velocity spectra at 15 and 165 deg are nearly identical to the 90 deg spectrum linearly shifted by approximately 10% to higher and lower velocities, respectively. From the analysis of the angular distribution and the range data, it is concluded that there is no moving system in which both the angular distribution and velocity spectra of the Na/sup 24/ nuclei are symmetric about the direction perpendicular to the beam. This indicates that this typical fragmentation product is produced by a direct (rapid) process and not by the usual fast nucleonic cascade followed by a slower de-excitation step. (auth)