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
The parameters of Table 7.14 are chosen such that the relative ISR emittance growth is 0.3%
(‘slice’ emittance growth). This incoherent energy spread is generated through a random process
and therefore cannot be corrected. Unlike most other dilution effects in the LCLS accelerator,
here the ‘slice’ emittance is increased, and so the growth is held to a very small level. The energy
in BC1 is too low for this effect to be important.
7.4.2.4 Coherent Synchrotron Radiation (CSR)
Introduction
The effects of CSR have been described in Section 7.4.1 pertaining to the BC1 design. The
BC2 compression-stage is also a 4-dipole chicane and the bunch is linearly compressed from
195 µm to 22 µm. Calculations of the CSR-induced emittance dilution have been made using the
DESY TraFiC4 code [22] and Elegant [10] (see below, “CSR Calculations with a Transient
Model”). The slice emittance is, however, almost unchanged.
Shielding is, however, not practical for BC2 since a full vacuum chamber height of