Strong suppression of nuclear-charge changing interactions for 18 TeV/c In ions channeled through a bent Si crystal

We present experimental results giving evidence for the strong reduction-a factor of more than 20-of nuclear-charge changing interactions for 18 TeV In49+ ions channeled through a silicon crystal bent to 7.5, 11.9 and 19.8 mrad. A very small fraction of the deflected ions suffer electromagnetic or nuclear interactions leading to proton loss while traversing the 60 mm long crystal, even though its thickness corresponds to about 0.13 nuclear interaction lengths for an amorphous material. By considering the deflected ions only, we show experimentally that the nuclear-charge pickup reaction believed to be induced by virtual photons is a short-range phenomenon.