Our team has been examining several architectures for short-wavelength, coherent light
sources. We are presently exploring the use and role of advanced, high-peak power lasers for both
accelerating the electrons and generating a compact light source with the same laser. Our overall
goal is to devise light sources that are more accessible by industry and in smaller laboratory
settings. Although we cannot and do not want to compete directly with sources such as third-generation
light sources or that of national-laboratory-based free-electron lasers, we have several
interesting schemes that could bring useful and more coherent, short-wavelength light source to
more researchers. Here, we present and discuss several results of recent simulations and our future
steps for such dissemination.
We perform a series of single-pass, one-D free-electron laser simulations based on an electron
beam from a standard linear accelerator coupled with a so-called laser undulator, a specialized device
that is more compact than a standard undulator based on magnetic materials. The longitudinal field
profiles of such lasers undulators are intriguing as one must and can tailor the profile for the needs of
creating the virtual undulator. We present and discuss several results of recent simulations and our future
steps.
We present a summary of our team’s recent efforts in developing adaptive, artificial
intelligence-inspired techniques specifically to address several control challenges that arise in
machines/systems including those in particle accelerator systems. These techniques can readily be
adapted to other systems such as lasers, beamline optics, etc… We are not at all suggesting that we
create an autonomous system, but create a system with an intelligent control system, that can
continually use operational data to improve itself and combines both traditional and advanced
techniques. We believe that the system performance and reliability can be increased based on our
findings. Another related point is that the controls sub-system of an overall system is usually not
the heart of the system architecture or design process. More bluntly, often times all of the
peripheral systems are considered as secondary to the main system components in the architecture
design process because it is assumed that the controls system will be able to “fix” challenges
found later with the sub-systems for overall system operation. We will show that this is not always
the case and that it took an intelligent control application to overcome a sub-system’s challenges.
We will provide a recent example of such a “fix” with a standard controller and with an artificial
intelligence-inspired controller. A final related point to be covered is that of system adaptation for
requirements not original to a system’s original design.
We propose a scheme for bright, sub-100-femtosecond x-ray radiation generation using small-angle Thomson scattering. Coupling high-brightness electron bunches with high-power ultrafast laser pulses, radiation with photon energies of 8- to 40-keV can be generated with pulse duration comparable to that of the incoming laser pulse with peak spectral brightness of approximately 1020 photons s-1 mm-2 mrad-2 per 10(superscript -3 bandwidth, close to those of the third-generation synchrotron light sources. The scheme is scalable to shorter pulse duration and high peak brightness, depending on the performance of the laser system.
Over the last few years, there has been a growing interest in self-amplified spontaneous emission (SASE) free-electron lasers (FELs) as a means for achieving a fourth-generation light source. In order to correctly and easily simulate the many configurations that have been suggested, such as multi- segmented wigglers and the method of high-gain harmonic generation, we have developed a robust three-dimensional code. The specifics of the code, the comparison to the linear theory as well as future plans will be presented.
Stephen Milton, N. Arnold, Christa Benson, S. Berg, William Berg, Sandra Biedron, Y. Chae, E. Crosbie, G. Decker, B. Deriy, Roger Dejus, Pat Hartog, R. Dortwegt, M. Erdmann, Zhirong Huang, H. Friedsam, Henry Freund, J. Galayda, Efim Gluskin, G. Goeppner, A. Grelick, J. Jones, Y. Kang, Kwang Kim, S. Kim, Kim Kinoshita, B. Lill, John Lewellen, Alex Lumpkin, G. Markovich, Oleg Makarov, E. Moog, A. Nassiri, V. Ogurtsov, S. Pasky, J. Power, Brian Tieman, Emil Trakhtenberg, Gil Travish, I. Vasserman, Nikolai Vinokurov, D. Walters, Jin Wang, Xi Wang, Bingxin Yang, Shenglan Xu
KEYWORDS: Free electron lasers, Diagnostics, Light sources, Electron beams, Ultraviolet radiation, Vacuum ultraviolet, X-rays, Medium wave, S band, Copper
Construction of a single-pass free-electron laser (FEL) based on the self-amplified spontaneous emission (SASE) mode of operation is nearing completion at the Advanced Photon Source (APS) with initial experiments imminent. The APS SASE FEL is a proof-of-principle fourth-generation light source. As of January 1999 the undulator hall, end-station building, necessary transfer lines, electron and optical diagnostics, injectors, and initial undulators have been constructed and, with the exception of the undulators, installed. All preliminary code development and simulations have also been completed. The undulator hall is now ready to accept first beam for characterization of the output radiation. It is the project goal to push towards full FEL saturation, initially in the visible, but ultimately to UV and VUV, wavelengths.
Preliminary calculations using the computer code PARMELA indicate that it is possible to achieve peak currents on the order of 1 kA using a thermionic-cathode rf gun and ballistic bunch compression. In contrast to traditional magnetic bunching schemes, ballistic bunch compression uses a series of rf cavities to modify the energy profile of the beam and properly chosen drifts to allow the bunching to occur naturally. The method, suitably modified, should also be directly applicable to photo injector rf guns. Present work is focusing on simultaneously compressing the bunch while reducing the emittance of the electron beam. At present, the calculated normalized rms emittance is in the neighborhood of 6.8 (pi) mrad with apeak current of 0.88 kA, and a peak bunch charge of 0.28 nC from a thermionic-cathode gun.
The injector system of the advanced photon source (APS) consists of a linac capable of producing 450-MeV positrons or greater than 650-MeV electrons, a positron accumulator ring (PAR), and a booster synchrotron designed to accelerate particles to 7 GeV. There are long periods of time when these machines are not required for filling the main storage ring and instead can be used for synchrotron radiation research. We describe here an extension of the linac beam transport called the low-energy undulator test line (LEUTL). The LEUTL will have a twofold purpose. The first is to fully characterize innovative, future generation undulators, some of which may prove difficult or impossible to measure by traditional techniques. Perhaps the most intriguing and exciting use of the LEUTL, however, will be in the planned investigation and generation of coherent radiation at wavelengths below 100 nm. This is due to the use of the high quality electron beam generated from a thermionic microwave gun.
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