A MODIFIED QUADSCAN TECHNIQUE FOR EMITTANCE MEASUREMENT OF SPACE CHARGE DOMINATED BEAMS

The quadscan technique is one of the most commonly used methods for measuring emittances in photoinjectors at medium range energy in which the beam is not primarily space charge dominated. The space charge can nevertheless contribute strongly to the beam size evolution along the drift from the scanning quadrupole to the measurement screen. To take the space charge into account, we fit the beam sizes while solving the envelope equation for each quadrupole value. This algorithm is first applied to round beams and then extended to asymmetric beams. The benchmarking of this solver with the envelope equation tracker with PARMELA simulations is presented. The quadrupole scan algorithm including space charge correction for the round and not round beams is presented.