Dependence of the linewidth of planar electron channeling radiation on the thickness of the diamond crystal

Measurements of (110) planar channeling radiation have been performed at the radiation source ELBE at electron energies of 14.6, 17, 30 and 34 MeV using diamond crystals of thickness 42.5, 102, 168 and 500 micrometers. The influence of different line-broadening mechanisms on the spectral shape of radiation from the 1 - 0 transition has been investigated. The analysis bases on fitting a convolution of the intrinsic Lorentz-like line shape with a Gaussian-like multiple-scattering distribution to the measured spectra. The asymmetry parameter involved relates to the standard deviation of the multiple-scattering angle under channeling condition. Its dependence on the crystal thickness at channeling was found to be weaker than for nonchanneled particles. The deduced coherence lengths show no significant dependence on the electron energy.