LCLS Conceptual Design Report - Stanford Synchrotron Radiation ...

L C L S C O N C E P T U A L D E S I G N R E P O R T
Figure 5.12 Power vs. undulator length for a 0.25-nC case, with an emittance of 0.3 µm-rad and a
peak current of 1.5 kA. No undulator wakefields have been included. The dashed line
assumes a constant value of emittance and current along the bunch. The effect of using
the longitudinal and transverse phase-space distribution produced in the gun-linaccompressor
system (solid line) is a reduction in output saturation power.
The distribution of power along the bunch obtained in the start-to-end simulation is shown in
Figure 5.13. The transverse displacement along the bunch and other effects produce a non-
uniform power distribution.
Figure 5.13 Power distribution at saturation (solid) along the electron bunch for the start-to-end
simulations for a charge of 0.25 nC. The dashed curve is the current profile in kilo-
Amperes. The head of the bunch is to the right.
5-16♦ F E L P A R A M E T E R S A N D P E R F O R M A N C E