Measurement of the Total Energy Radiated by 150-GeV Electrons in a Ge Crystal

We have measured the radiation emitted by 150-GeV $e^{-}$ incident along the $〈110〉$ axis of Ge crystals. The on-axis total radiated energy is 25 times larger than for nonaligned directions for 0.4-mm-thick Ge. The distribution of the radiated energy versus the angle of the electron beam yields a half-width much larger than the channeling critical angle. The on-axis results confirm the predictions of the crystal-assisted radiation theory. The Born approximation to the coherent bremsstrahlung fits the data at large angles.