Electron channeling radiation from diamond

A series of channeling-radiation experiments for incident electrons of 16.9, 30.5, and 54.5 MeV has been performed, using a type-IIa natural diamond 23 μm thick. Channeling-radiation transition energies calculated with the standard (Hartree-Fock) potential are in good agreement with the observed results for the (100) and (110) planes as well as for the 〈100〉 axis at all energies, but are in error for the (111) plane. Corrections to the (111) potential due to anisotropic electron distributions which are based upon x-ray-diffraction data result in calculated transition energies that are in better agreement with the observed data; an empirical (111) potential yields calculated transition energies which are in even better agreement with the data. Calculated linewidths are considerably narrower than the observed values; this disagreement probably results from incoherent scattering by crystal defects having an average spacing of approximately 1 μm. The transition energies are shown to scale as ${\gamma }^{5/3}$ for transitions involving states that are localized close to the atomic planes and as ${\gamma }^2$ for those localized close to the midplane regions. Free-state populations are shown to increase relative to bound-state populations with incident electron-beam energy. Channeling radiation has been shown to constitute a practical source of x-ray photons utilizable at many existing accelerators.