Characterizing the emittance contribution due to rotated quadrupoles and canonical angular momentum using the quadrupole scan technique in electron accelerators

Abstract

Standard emittance measurement techniques for bright electron beams are either insensitive to the emittance due to correlated effects like misaligned quadrupoles or a nonzero axial magnetic field at the cathode, or are unable to differentiate that emittance from the beam’s intrinsic emittance corresponding to the beam’s actual entropy. We describe a technique based on the standard quadrupole scan, in which the beam correlations leading to emittance growth can be directly measured, and the emittance from these correlations can be found for special cases.