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

Standard emittance measurement techniques for bright electron beams are eit her 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 corres ponding to the beam's actual entropy. We describe a technique based on the standard quadrupole scan, in which the beam correlations leading to emittan ce growth can be directly measured, and the emittance from these correlatio ns can be found for special cases. (C) 1999 American Institute of Physics. [S0034-6748(99)02603-9].