  Thermal emittance and quantum efficiency (QE) are key figures of merit of
photocathodes, and their uniformity is critical to high-performance
photoinjectors. Several QE mapping technologies have been successfully
developed; however, there is still a dearth of information on thermal emittance
maps. This is because of the extremely time-consuming procedure to gather
measurements by scanning a small beam across the cathode with fine steps. To
simplify the mapping procedure, and to reduce the time required to take
measurements, we propose a new method that requires only a single scan of the
solenoid current to simultaneously obtain thermal emittance and QE distribution
by using a pattern beam with multiple beamlets. In this paper, its feasibility
has been confirmed by both beam dynamics simulation and theoretical analysis.
The method has been successfully demonstrated in a proof-of-principle
experiment using an L-band radiofrequency photoinjector with a cesium telluride
cathode. In the experiment, seven beamlets were generated from a microlens
array system and their corresponding thermal emittance and QE varied from 0.93
to 1.14 $\mu$m/mm and from 4.6 to 8.7%, respectively. We also discuss the
limitations and future improvements of the method in this paper.
