TY - CPAPER AU - Di Mitri, S. TI - On the Importance of Electron Beam Brightness in High Gain Free Electron Lasers J2 - Proc. of FEL2015 AB - Linear accelerators delivering high brightness electron beams are essential for driving short wavelength, high gain free-electron lasers (FELs). The FEL radiation output efficiency is often parametrized through the power gain length that relates FEL performance to the electron beam quality at the undulator. Experimental data and simulation results of existing and planned FEL facilities are used to explicit the relationship between the FEL output wavelength and the electron beam six-dimensional brightness*. Practical formulas are provided that show the dependence of the exponential gain length on the beam brightness**. PB - JACoW CY - Geneva, Switzerland SP - 227 EP - 232 KW - FEL KW - electron KW - emittance KW - undulator KW - brightness DA - 2015/12 PY - 2015 SN - 978-3-95450-134-2 DO - 10.18429/JACoW-FEL2015-MOP079 UR - http://accelconf.web.cern.ch/AccelConf/FEL2015/papers/mop079.pdf ER -