  Crystals with small thickness along the beam exhibit top performance for
steering particle beams through planar channeling. For such crystals, the
effect of nuclear dechanneling plays an important role because it affects their
efficiency. We addressed the problem through experimental work carried out with
400 GeV/c protons at fixed-target facilities of CERN-SPS. The dependence of
efficiency vs. curvature radius has been investigated and compared favourably
to the results of modeling. A realistic estimate of the performance of a
crystal designed for LHC energy including nuclear dechanneling has been
achieved.
