OBSERVATION OF HIGH DEFLECTION EFFICIENCY AND NARROW ENERGY-LOSS DISTRIBUTIONS FOR 450 GEV PROTONS CHANNELED IN A BENT SILICON CRYSTAL

A 450 GeV proton beam has been deflected by various angles from 1 to 1 1 mrad using planar channeling in a (111) silicon crystal which was me chanically bent to achieve the desired beam deflection. High deflectio n efficiencies of up to 50% have been measured, in good agreement with present theoretical estimates. It is shown that bent crystals are als o a unique tool for measurements of energy loss and straggling of chan neled particles, without any influence from random particles: Selectin g protons which are deflected by increasing angles corresponds to decr easing the transverse energy at the crystal entrance. With this techni que energy loss and straggling was measured for protons channeled in t he wide and narrow (111) planes in silicon for the first time.