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Proton-induced degradation of vacuum ultraviolet (VUV) transmittance of LiF and MgF(2) was measured for 85- and 600-MeV protons for a fluence up to 2.8 x 10(13)p/cm(2). Transmittances were measured from 105 to 210 nm. When the irradiation level for a given material is expressed in terms of absorbed energy per unit of volume of crystal, 85- and 600-MeV protons produce the same degradation. MgF(2) is substantially more radiation resistant than LiF in the VUV. Irradiation of LiF with 1.8 x 10(13)p/cm(2) at 85 MeV changed the transmittance of the hydrogen Lyman-alpha line at 121.6 nm from 55 to 23%. The corresponding change for MgF(2) was from 52 to 42% for 2.8 x 10(13)p/cm(2).

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The (P, n) reaction cross sections were measured to+4% for 3to 5.5-MeV protons on Sn and on natural Sn and In. Analyses with a conventional optical-model potential were made in the energy regions where the (p, n) cross sections are nearly equal to the total absorption cross sections. These analyses show that the energy dependence in the real well is about three times greater for 5to 10-MeV protons than it is for 10to 61-MeV protons. The best-fit potential for 3to 5.5-MeV protons on the Sn isotopes has a surface absorptive layer about half as thick as at 10 MeV. The In strength functions are fitted by increasing both the width and depth of the imaginary part of this potential by about 25%. The Q value for ' Sn(P, n)' Sb was found to be -3465 +7 keV.