STUDIES OF ENERGY RECOVERY LINACS AT ... - CASA
STUDIES OF ENERGY RECOVERY LINACS AT ... - CASA
STUDIES OF ENERGY RECOVERY LINACS AT ... - CASA
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TABLE 3.1: Design system parameters of the 10 kW FEL Upgrade.<br />
Parameter Design Value<br />
Beam energy at undulator 80-210 MeV<br />
Average beam current 10 mA<br />
Bunch charge 135 pC<br />
Bunch repetition rate up to 74.85 MHz<br />
Normalized emittance (rms) 13 mm-mrad<br />
Bunch length at undulator (rms) 200 fs<br />
Peak Current 270 A<br />
FEL extraction efficiency 1%<br />
∆E/E before undulator (rms) 0.5%<br />
∆E/E after undulator (full) 10%<br />
CW FEL power 10 kW<br />
displayed in Fig. 3.1. The primary system parameters (design values) are listed in<br />
Table 3.1.<br />
Because the experimental measurements described in Chapters 5, 6 and 7 were<br />
performed with the Driver, this chapter presents the required conditions for lasing,<br />
from the standpoint of the electron beam, and how these conditions are satisfied in<br />
the FEL Driver.<br />
Reduced to its primary objective, the Driver must generate a short bunch (high<br />
peak current) at the undulator and energy compress and energy recover the large<br />
longitudinal phase space of the spent electron beam following the undulator [49].<br />
The injector is designed to generate a long bunch with low momentum spread.<br />
The objective of the Driver is to rotate the longitudinal phase space 90 ◦ to create<br />
a short bunch at the undulator. Following the undulator, the longitudinal phase<br />
space must be rotated back by 90 ◦ to energy compress the beam which has ac-<br />
quired a large momentum spread. These longitudinal phase space manipulations<br />
are achieved by accelerating the bunches off-crest through the linac to impart a<br />
phase-energy correlation. Rotation of the phase space to an upright ellipse at the<br />
undulator is accomplished with a proper choice of the momentum compaction (the<br />
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