Attempt to generate x-ray beam carrying orbital angular momentum in Photon Factory

We have tried to generate x-ray beam carrying orbital angular momentum (vortex beam) at BL-16A in Photon Factory. The beam profile of 2nd harmonic radiation from helical undulator was measured, and that was explained by the calculated one of the vortex beam. Hence, it is expected to succeed in generating the vortex beam. We also elucidated that the simulated diffraction pattern with vortex beam is distinct from that with usual coherent beam. Hence the diffraction is an appropriate technique to evaluate the orbital angular momentum of x-ray beam. However, the orbital angular momentum could not be detected in this diffraction experiment.