8
Free Electron Lasers
8.1 FEL history
143 In this chapter we will continue to build upon the results of
8.2 SR from bends,
the previous chapters — particularly Chapter 3 (Synchrotron
wigglers and
Radiation) and Chapter 7 (Light Sources) — and will discuss
undulators
144 the present reigning champion among the X-ray light sources:
8.3 Basics of FEL
the free electron laser.
operation
147
We will begin with a brief, historical introduction. Then,
8.4 FEL types
150 we will recall the properties of radiation from a sequence of
8.5 Microbunching and bends, wigglers and undulators, and then discuss how their
gain
152 radiation spectra compare. Next, we will follow up on un8.6 FEL designs and
dulator resonance conditions and microbunching. Finally, we
properties
157 will discuss the precise physical meaning and exact defini8.7 Beyond the
tion of the undulator parameter K, which was introduced in
fourth-generation
earlier chapters as a qualitative factor.
light sources
160
Following this introduction of basic FEL concepts, we will
discuss FEL designs and parameters, as well as possible future advances in the evolution of FEL technology.
8.1 FEL history
The FEL concept, as well as the term itself, was suggested by
John Madey in the early 1970s during his work at Stanford
University. His research benefited from the earlier work by
Hanz Motz who, in 1953, built an undulator (which was proposed in Vitaly Ginzburg’s 1947 theoretical paper, wherein
the undulator was described as a device generating electromagnetic radiation via relativistic electrons).
In 1971, John Madey wrote his first FEL-related published
journal entry on the subject of stimulated emissions of radiation in a periodic magnetic field. This was shortly followed
by a patent on FEL filed in 1972 — but that’s a whole ‘nother
story. The FEL created by Madey used a 43 MeV electron
beam to create radiation with wavelengths of 3.4 μm in a 5 m
helical undulator, with a 3.2 cm period and a field of 0.24 T.
Following this pioneering work, many FELs have been
created all around the world — their wavelengths gradually shortening as the technology matured. The most modern FELs have recently reached the Angstrom range, creating
unsurpassed possibilities for discovery science, bio-medical
studies and technology-aimed research.
143
DOI: 10.1201/b18696-8
Free Electron Lasers
8.1 FEL history
143 In this chapter we will continue to build upon the results of
8.2 SR from bends,
the previous chapters — particularly Chapter 3 (Synchrotron
wigglers and
Radiation) and Chapter 7 (Light Sources) — and will discuss
undulators
144 the present reigning champion among the X-ray light sources:
8.3 Basics of FEL
the free electron laser.
operation
147
We will begin with a brief, historical introduction. Then,
8.4 FEL types
150 we will recall the properties of radiation from a sequence of
8.5 Microbunching and bends, wigglers and undulators, and then discuss how their
gain
152 radiation spectra compare. Next, we will follow up on un8.6 FEL designs and
dulator resonance conditions and microbunching. Finally, we
properties
157 will discuss the precise physical meaning and exact defini8.7 Beyond the
tion of the undulator parameter K, which was introduced in
fourth-generation
earlier chapters as a qualitative factor.
light sources
160
Following this introduction of basic FEL concepts, we will
discuss FEL designs and parameters, as well as possible future advances in the evolution of FEL technology.
8.1 FEL history
The FEL concept, as well as the term itself, was suggested by
John Madey in the early 1970s during his work at Stanford
University. His research benefited from the earlier work by
Hanz Motz who, in 1953, built an undulator (which was proposed in Vitaly Ginzburg’s 1947 theoretical paper, wherein
the undulator was described as a device generating electromagnetic radiation via relativistic electrons).
In 1971, John Madey wrote his first FEL-related published
journal entry on the subject of stimulated emissions of radiation in a periodic magnetic field. This was shortly followed
by a patent on FEL filed in 1972 — but that’s a whole ‘nother
story. The FEL created by Madey used a 43 MeV electron
beam to create radiation with wavelengths of 3.4 μm in a 5 m
helical undulator, with a 3.2 cm period and a field of 0.24 T.
Following this pioneering work, many FELs have been
created all around the world — their wavelengths gradually shortening as the technology matured. The most modern FELs have recently reached the Angstrom range, creating
unsurpassed possibilities for discovery science, bio-medical
studies and technology-aimed research.
143
DOI: 10.1201/b18696-8