Energy loss of low energy protons channeling in silicon crystals

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Abstract
Experimental energy loss measurements were made for protons of energy 0.5 to 1.6 MeV channeling through 1 μm thick silicon targets along the (110), (11l), and (211) axial directions, and the {l00}, {110}, (1ll}, and (211) planar directions. These data have a precision of ±5% and are presented graphically along with an extensive summary of other data in the literature. The new data cover a wider range of channels than has previously been examined with protons and are in agreement with the helium data of Eisen et 01.' A standard theory of energy loss is summarized and ampli- tied, and straggling is calculated theoretically. Local electron densities for various channels in silicon are extracted from plane and row averaged Thomas Fermi potentials via v ▿2 V = 4 πρ, and are used in the theoretical energy loss and straggling equations. The results agree with the experimental data to within 5%. The need for more precise measure-ments in order to make a decisive test of the theory is discussed.