Figure 7
The longitudinal phase space of a 1.0 GeV electron bunch with no initial chirp (a) before and (b–d) after it travels through the three beamline set-ups with differing values of \(R_{56}\). (a) The bunch has an initial length of 0.3 \(\upmu \text {m}\) (1 fs). (b) After travelling through the 11.5 m beamline with \(R_{56}={0.00}\,\text{mm}\) the bunch length has increased to 10 \(\upmu \text {m}\) (34 fs) at the beamline end (undulator entrance) because of divergence-driven lengthening. (c) The chicane-like set-up (\(R_{56}={0.20}\,\text{mm}\)) causes the bunch to develop a positive chirp. (d) The dogleg-like set-up (\(R_{56}=-{0.22}\,\text{mm}\)) causes the bunch to develop a negative chirp. All plots use the same scale and bunch lengths values are root-mean-squared (r.m.s.).
