Investigation of thermal emittance measurement in RF photoinjector

A new method for the measurement of the thermal emittance in the RF photoinjector is introduced. The measurement are affected mainly by three factors which are the RF effect, the space charge effect and the error of measurement. According to the theory of emittance growth in the RF photoinjector and the simulation, a new method to eliminate the RF effect is proposed for the thermal emittance measurement in RF photoinjector. Error of measurements is not included, and the space charge effect is also ignored on the condition of the low charge operation mode. (authors)