8.6.3 FEL radiation properties
Due to the coherent nature of radiation, FELs can provide
peak brilliance of around 8–10 orders of magnitudes larger
than that of storage ring light sources (see Fig. 8.19).
158 unifying physics of accelerators, lasers and plasma
8.6.2 FEL and laser comparison
It can be useful to compare the properties and features of
FELs and lasers side by side — see Table 8.1. Amongst many
similarities, the most notable difference is in their theoretical
foundations: while the laser is a purely quantum device, an
FEL is entirely classical.
TABLE 8.1
FEL and laser comparison
LASER
FEL
Characteristics
Source of narrow, monochromatic
and coherent light beams
Source of narrow, monochromatic
and coherent light beams
Configurations
Oscillator or amplifier
Oscillator or amplifier
First demonstration 1960
1977
Laser media
Solids, liquids, gases
Vacuum with electron beam
in periodic magnetic field
Energy storage
Potential energy of electrons
Kinetic energy of electrons
Energy pump
Light or applied electric current
Electron accelerator
Theoretical basis
Quantum mechanics
Relativistic mechanics
and electrodynamics
Wavelength
definition
Energy levels of laser medium
Electron energy, magnetic
field strength and period
8.6.3 FEL radiation properties
Due to the coherent nature of radiation, FELs can provide
peak brilliance of around 8–10 orders of magnitudes larger
than that of storage ring light sources (see Fig. 8.19).
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FIGURE 8.19
Peak brilliance (left) and temporal resolution (right) of typical FEL
in comparison with third-generation SR sources.
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