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 6.17 also shows the new radiation shielding separating the injector vault from the
linac housing. The injector personnel protection system is designed to allow access to the injector
when the linac is operating (including 50-GeV beams), but electron beams in the injector cannot
be run when the main linac is in permitted access. (See Section 6.7, Radiation Protection Issues.)
Turning off the first MS bend magnet allows independent operation of the injector and main
linac. In this situation, a spectrometer dipole in the aisle just beyond the main linac bends the
injector beam into a beam dump, while the main linac supplies beam to the Research Yard (End
Station A, etc.).
A schematic layout (not to scale) showing only the principal beamline elements is shown in
Figure 6.18. The diagnostics are discussed in Section 6.5.2, Standard Beamline Diagnostics.
Because of the unique nature of the LCLS photoinjector, there is also the need for several state-
of-the art diagnostics. These are described in Secs. 6.5.3, Slice Emittance, and 6.5.4, Temporal
Pulse Shape.
The rf distribution system is also shown in Figure 6.18. UnSLEDed klystrons will be used to
improve the phase and amplitude stability. The accelerating sections will operate at about 25
MeV/m (see Section 6.6, PARMELA Simulations). The electron beam energy increment, E in
units of MeV, in a standard SLAC 3-m section installed in the 3-km linac, is
E[ MeV] = 10 P[MW] , (6.10)
where P is the klystron rf power at the klystron in units of MW. Thus the gun and each of the
two 3-m sections require their own 5045 klystron. The rf deflector will also require a separate
klystron. This arrangement will allow the rf phase and amplitude for the rf gun, the two sections,
and the rf deflector to be controlled independently using low-power controls.
6-40 ♦ I NJECTOR