TEMPERATURE-DEPENDENCE OF PLANAR CHANNELING RADIATION IN SILICON, GERMANIUM, AND BERYLLIUM BETWEEN 12 AND 330 K

The temperature dependence of planar channeling radiation of 62.8 MeV electrons has been studied for silicon, germanium, and beryllium. The measurements have been performed using an uncollimated low-emittance c w beam from the superconducting electron linac S-DALINAC at the Techni sche Hochschule Darmstadt. Energies and linewidths of transitions betw een transverse bound states have been determined in the energy range b etween 40 and 230 keV for silicon and beryllium at temperatures betwee n 12 and 330 K, and for germanium between 12 and 223 K. From the shift of the transition energies with temperature the mean thermal vibratio nal amplitudes of the atoms transverse to the channeling planes rue de termined by comparison with calculations using the many-beam;formalism . Within experimental errors no directional dependence of the vibratio ns is observed. For silicon a Debye temperature of (535.2+/-8.5) K at 12 K and (519.0+/-10.8) K at 300 K has been derived. For germanium an increase from (232.7+/-12.8) K at 12 K to (292.0+/-16.4) K at 223 K is observed. Planar channeling radiation spectra from a beryllium crysta l taken at 12, 220, and 300 K have been analyzed the same way yielding a Debye temperature of (1060+/-50) K.