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
scanned during a period when the outside temperature was stable. The pulse-to-pulse amplitude
stability over 2 seconds is 0.06% rms, measured at the PAD, as shown in Figure 7.59.
Phase [ ° S−band]
1
0.8
0.6
0.4
0.2
0
0 5 10
Time [sec]
15 20
200
150
100
50
0.071 ° rms
0
0.2 0.4 0.6 0.8 1
Phase [ ° S−band]
Figure 7.58 Pulse-to-pulse phase variations, and histogram, measured at PAD of a single klystron
shows 0.07-degree S-band rms variation over 17 seconds.
RF Amplitude [arb. units]
sigma = 0.06%
Time [klystron pulses]
Figure 7.59 Pulse-to-pulse relative amplitude variations measured at the PAD of a single klystron
shows 0.06% rms variation over 2 sec (horizontal axis is in 1/30-sec ticks).
Analysis of the performance of the present linac shows that individual SLAC klystrons, when
selected for superior stability, can meet LCLS pulse-to-pulse jitter tolerances over a short (~2 sec)
time scale. Some improvements are planned for the rf distribution and control system. These will
facilitate beam-based feedback control to be applied to the LCLS linac sections. Phase and
amplitude control of individual klystrons will be implemented for parts of the linac as well as
global sector controls. The phase gymnastics for PEP II injection need to be decoupled from the
7-84 ♦ A C C E L E R A T O R