Coherent light generators – Free electron laser
Reexamination Certificate
2001-07-27
2004-12-14
Thomas, Tom (Department: 2815)
Coherent light generators
Free electron laser
C372S022000, C372S023000, C372S074000, C372S109000
Reexamination Certificate
active
06831933
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a modular system and method for implementing next generation light sources with Free Electron Lasers (FELs).
DESCRIPTION OF THE RELATED ART
The Advanced Photon Source (APS) at Argonne National Laboratory is a national synchrotron-radiation light source research facility. Utilizing high-brilliance x-ray beams from the APS, members of the international synchrotron-radiation research community carry out forefront basic and applied research in the fields of materials science; biological science; physics; chemistry; environmental, geophysical, and planetary science; and innovative x-ray instrumentation.
The Advanced Photon Source (APS) is a third-generation synchrotron radiation source that stores electrons in a storage ring. The third-generation synchrotron radiation sources are designed to have low beam emittance and many straight sections for insertion devices, undulator magnets. This makes for a bright beam of x-rays; however the x-ray pulses are long (10-100 picoseconds) and incoherent longitudinally and only partially coherent in the transverse dimension. This incoherence arises from the fact that this radiation is spontaneously, or randomly, emitted from the electrons.
The APS facility is comprised of three basic systems: the injection system, the storage ring system, and the experimental beamlines. The components of the injection system are listed according to the causal flow of electrons. The individual components of the injection system include the electron source, the linear accelerator (linac) system, low energy transport line from linac to the PAR, particle accumulator ring or PAR, low energy transport line from PAR to booster synchrotron, and the high energy transport line from booster synchrotron to storage ring. This system is similar to other synchrotron light source centers around the globe.
The beam acceleration and storage process begins at the electron gun (source). An electron bunch train ten (10) nanoseconds long are raised to an energy of 450 million electron volts (MeV) at up to thirty (30) pulses per second by a series of radio frequency (2856 MHz) accelerating structures in the linac. The PAR is used to accumulate and damp the pulse train into a single bunch suitable for injection into the booster synchrotron. The 368-m long, racetrack-shaped booster synchrotron raises electron energies at a rate of 32 keV per turn. The accelerating force is supplied by electrical fields within four 5-cell radio frequency (RF) cavities operating at 352 MHz, the same frequency used by the storage ring RF cavities. In 0.25 sec, electrons orbit the booster 200,000 times as their energy climbs to 7 billion electron volts (GeV). The electrons are then injected into the storage ring.
Electrons injected into the 1104-m circumference storage ring orbit the ring more than 271,000 times per second. The beam of electrons is steered and focused by 1097 powerful electromagnets as it travels within a closed system of 240 aluminum alloy vacuum chambers running through the magnet centers. The beam loses energy at a rate of about 6 MeV per turn as it emits synchrotron radiation. This energy loss is replaced by the storage ring 352-MHz RF systems.
The APS storage ring magnetic system is based upon the Chasman-Green lattice, a specialized magnetic lattice developed for synchrotron light sources. There are forty Chasman-Green sectors in all for a total length of 1104 m. Five sectors are used for either the RF systems or the beam injection system. The remaining 35 have two beamlines for extracting the x-rays to the experimental end stations. One beamline in each sector is used to extract the x-rays from bending magnets while the other is aligned with a straight section that houses a specialized magnet, either an undulator and a wiggler.
Although the Advanced Photon Source's x-rays are very useful to the user community with its long pulses and incoherent properties, there is a desire to produce and use significantly shorter, coherent, and, thus, laser-like pulses. Unfortunately, traditional lasers based upon atomic transitions do not permit us to produce such laser-like photons or radiation at the hard x-ray wavelengths. A need exists for a next generation synchrotron radiation (light) source that would provide better properties, more flexibility and more laser-like pulses than the Advanced Photon Source (APS) at Argonne National Laboratory.
A principal object of the present invention is to provide an improved, next-generation light source.
Another object of the present invention is to provide an improved method for implementing a next generation light source.
Another object of the present invention is to provide a modular next-generation light source that provides a coherent, laser-like, ultra-short wavelength radiation source.
Another object of the present invention is to provide a modular next-generation light source for use by a large user community of synchrotron radiation and laser sources with wavelength ranges extending from the vacuum ultraviolet (VUV) to the hard x-ray regime.
Another object of the present invention is to provide a harmonic-based, short-wavelength source that can provide a higher brightness and is more laser-like than existing sources.
Another object of the present invention is to provide a harmonic-based, short-wavelength source that can be achieved with a much lower electron beam energy than a FEL-based source using the fundamental radiation only.
Another object of the present invention is to provide a next-generation light source capable of producing pulses that have ultra-short pulse lengths exhibiting temporal coherence and transform-limited bandwidths unachievable by the existing third-generation sources.
Another object of the present invention is to provide a way to shift output pulse wavelengths originally derived from an input seed laser.
Another object of the present invention is to provide a next-generation light source and method for implementing a next generation synchrotron light source substantially without negative effect and that overcome some disadvantages of prior art arrangements.
SUMMARY OF THE INVENTION
In brief, a system and method for implementing a next generation synchrotron light source with Free Electron Lasers (FELs) are provided whereby the construction of a Free Electron Laser (FEL) is customized through the use of individual modules having specified characteristics. Such individual modules include lasers, electron guns, linear accelerators, magnetic bunch compressors, permanent magnet undulators and specialized optical arrangements. These individual modules are arranged to exploit the occurring fundamental and nonlinear harmonics generated in single-pass, high-gain Free Electron Laser (SP HG FEL) both of which can be used as the final product, or alternatively to be a coherent seed for another module.
In accordance with features of the invention, an improved method is provided for producing arbitrary wavelengths with a next generation synchrotron light source independent of a seed pulse wavelength. Ultra-short pulse lengths exhibiting full temporal coherence are produced through a three step process. The electron beam processing includes imprinting; upconverting or wavelength shifting; and reinforcing or strengthening.
In accordance with features of the invention, the modular FEL is designed and constructed to meet specific user requirements in the most cost-effective manner. The modular single-pass, high-gain Free Electron Laser (SP HG FEL) significantly reduces the size and cost of FEL machines, obtains the shortest wavelength, has the ability to tune the output wavelength, and retains the coherence quality of the seed laser.
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patent: 4835446 (1989-05-01), Nation et al.
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patent: 2002/0044573 (2002-04-01), Bennett
Biedron Sandra Gail
Freund Henry Philip
Milton Stephen Val
Pennington Joan
The University of Chicago
Thomas Tom
Warren Matthew E.
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