Channeling revisited

Possible uses of channeling at ISABELLE have been reported. Channeling is the phenomenon of coherent scattering of particles between the lattice planes in a crystal. Such a process is shown schematically but actually thousands of atoms are usually needed to bend a particle trajectory. The uses of channeling discussed include an internal beam profile device and an effective low density targeting device. The behavior exploited in these applications is that the particle, once within the channel (moving along the crystal principal axis), continues unscattered through the channel. That is, the crystal acts as if it were transparent to the particle, and in fact dE/dx losses are about half what they are for random orientation of path to crystal. Since the previous report appeared, an experiment has been done on channeling at FNAL with particles having energies of 35, 100, and 250 GeV. Pronounced channeling is seen at all energies with no evidence of particle scattering in the 2-cm-thick Ge crystal used, even at the lowest energy. Since the dechanneling length (average path length before a particle is scattered out of the channel) is theoretically proportional to the energy, one would expect that, if the dechanneling is >2 cm at 35 GeV, it should be >20 cm at the 400-GeV energies of ISABELLE. This experiment also produced other interesting results