  In this paper, we present a detailed analysis of the effects of quadrupole
components in radiofrequency (RF) photoinjectors, which could occur either in
the RF cavity or in the gun solenoid, and their compensation using a skew
quadrupole corrector. The analysis is generalized to the case in which the
correction cannot be applied at the same location as the quadrupole. A
practical guide to setting the corrector to eliminate correlation in the x-y
space is discussed. Particle tracking simulations and measurements of emittance
and beam matrix elements obtained at the UCLA Pegasus photoinjector are
presented to validate the analysis.
