Bremsstrahlung Polarization Measurements for 1.0-Mev Electrons

With 1-Mev electrons incident on thin aluminum and gold targets, bremsstrahlung polarization as a function of photon energy for a 20-degree emission angle has been measured with a polarimeter that depends on the polarization sensitivity of the Compton process. The selection of energy intervals out of the continuous bremsstrahlung spectrum was accomplished by employing the polarimeter as a double crystal Compton spectrometer. The results show a polarization reversal in qualitative agreement with the Born approximation calculations of Gluckstern and Hull. With the gold target, the polarization reversal occurs at a lower photon energy than that predicted by the Born approximation theory. Such a shift in the reversal energy is obtained with the Born approximation theory for a lower initial electron energy.