Radiochemical activation techniques were used to study the behavior of projectile fragments formed in the interaction of 0.9A and 1.8A GeV ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ ions within thick Cu targets. Two identical 1 cm thick Cu disks were irradiated with separations between the disks of 0, 10, and 20 cm, respectively. The results show an enhancement in the formation of light mass (A<30) radioactive residues in the second disk relative to the first in the contact configuration for both projectile energies. This enhancement decreases for increasing distance between the Cu disks. While our results with 0.9A GeV projectiles can be explained within the framework of conventional nuclear physics, the data at 1.8A GeV demand that either secondaries of Z=1, neutrons and/or pions are emitted with surprisingly large transverse momenta, or that some projectile fragments have large interaction cross sections but decay in flight (τ∼${10}^{\mathrm{-}10}$ s).

• Received 31 August 1987

DOI:https://doi.org/10.1103/PhysRevC.38.1658