Transverse and longitudinal emittance measurements in the ELSA linac

The ELSA RF linac photoinjector has been designed to deliver high-brightness electron beams. The present paper deals with the transverse and longitudinal emittance measurements, at different locations along the ELSA beam line, and the analysis of their variations as a function of the photoinjector parameters: magnetic field generated by the anode focusing lens, bunch charge and pulse duration. While transverse emittance has been already studied in other similar installations, there has been little study of the electron beam longitudinal dynamics. Experimental results are presented and compared to simulation-code expectations. For 2.0 nC, 85 A electron bunches, a normalized rms emittance of 2 π mm mrad and a brightness of 4.5 × 1013 A/(πm rad)2 at the linac exit have been measured as well as less than 10 keV rms energy spread (or less than 0.1% at 16.5 MeV).