Measurement of Longitudinal Channeling Radiation with the Ucsb-Cfels Electrostatic Accelerator.

Longitudinal channeling radiation(LCR) was measured with unprecedented accuracy for electrons of several MeV energy. The electrons are channeled in a 5mu m thick silicon crystal along the < 100> axis. Also, the Weiszacker-Williams method of virtual quanta is used for the first time to predict the LCR spectrum. By applying calculated and measured properties of the channeled electrons, it is shown that the LCR spectrum has a fine structure due to interaction between the transverse channeling states and the crystal's longitudinal periodicity. The fine structure has not been measured previously. Evidence of the fine structure is presented here. It is shown that the measured spectra agrees well with the theory.