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
wakefield. Atomic Force Microscope measurements [63] of surface roughness gives results in
agreement with the second case, p/δ = 500
Figure 4.9 LCLS undulator wake potential including the resistive and roughness wakefields. The
roughness wakefields include both the inductive model Eq. (4.31) and the synchronous
mode Eq. (4.32), assuming a 1 nC electron bunch, a bump height of 100 nm, and a
bump length of 5 µm (solid line) or 50 µm (dashed line). The resistive wall wakefield
dominates the dashed curve. The head of the bunch is at the right hand side of the
graph.
Figure 4.10 Effect of wakefields on the temporal radiation power profile at the undulator exit:
Dotted line: no wakefields; dashed line: “long bump case”; solid line: short “bump
case”. The head of the bunch is at the right hand side of the graph. The simulation
includes micro-tapering to offset the energy loss from spontaneous radiation.
F E L P H Y S I C S♦ 4-21