Angular momentum measurement of the FNPL electron beam

In the flat beam experiment at Fermilab/NICADD Photoinjector Laboratory(FNPL), it is essential to have a nonvanishing longitudinal magnetic field on the photocathode. The canonical angular momentum of the electron beam generated by this magnetic field is an important parameter in understanding the round to flat beam transformation. In this paper, we report our measurements of the canonical angular momentum, which is directly related to the skew diagonal elements of the beam matrix before beam is made flat. The measurements of the other elements of the beam matrix are also reported.