Measurement of multi-pulsed electron beams emittance

The emittance of multi-pulsed electron beams was experimentally measured using pepper pot and thus the corresponding brightness was calculated. Different from using fluorescent screen as the recorder of beam divergence angle, a quartz foil was used to record the information through Cerenkov radiation, which is generated by the interaction of electron beamlets and the quartz foil. The phenomenon of beam rotation in magnetic field was observed in the experiment, and the integrated brightness of double-pulsed and four-pulsed beams were measured. For the electron beam of about 600 kV, the divergence of beamlets was below 2 degree when the magnetic field at the pepper plate was lower than 2.7 mT. The calculated brightnesses of the double-pulsed and four-pulsed beams were 4.14 x 108 A/(m · rad)2 and 7.5 x 107 A/(m · rad)2 respectively. The difference may be due to the movement of cathode plasma. (authors)