Future Synchrotron Radiation Sources
Sources of synchrotron radiation (also called synchrotron light) and their associated research facilities have experienced a spectacular growth in number, performance, and breadth of application in the past two to three decades. In 1978 there were eleven electron storage rings used as light sources. Three of these were small rings, all below 500 mega-electron volts (MeV), dedicated to this purpose; the others, with energy up to 5 giga-electron volts (GeV), were used parasitically during the operation of the ring for high energy physics research. In addition, at that time synchrotron radiation from nine cyclic electron synchrotrons, with energy up to 5 GeV, was also used parasitically. At present no cyclic synchrotrons are used, while about 50 electron storage rings are in operation around the world as fully dedicated light sources for basic and applied research in a wide variety of fields. Among these fields are structural molecular biology, molecular environmental science, materials, analytic chemistry, microfabrication, archaeometry and medical diagnostics. These rings span electron energies from a few hundred MeV to 8 GeV. Several facilities serve 2000 or more users on 30-60 simultaneously operational experimental stations. The largest rings are more than 1 km in circumference, cost about US$1B to build and have annual budgets of about US$100M. This growth is due to the remarkable properties of synchrotron radiation, including its high intensity, brightness and stability; wide spectral range extending from the infra-red to hard x-rays; variable polarization; pulsed time structure; and high vacuum environment. The ever-expanding user community and the increasing number of applications are fueling a continued growth in the number of facilities around the world. In the past few years new types of light sources have been proposed based on linear accelerators. Linac-based sources now being pursued include the free-electron laser (FEL) and energy recovery linac (ERL). In some respects (e.g., coherence, peak brightness, sub-picosecond pulse duration) these sources will far exceed the performance of storage-ring-based sources. As a consequence, they will open entirely new experimental opportunities. In particular, scientific interest is growing in the short pulse lengths that linacs can provide, making it possible to study chemical reactions and biological processes on the femtosecond time scale. The high peak brightness and peak power of the FEL also makes it possible to create and probe novel states of matter such as warm dense matter. It may also make it possible to determine the structure of proteins using single molecules as targets rather than crystal arrays. Depending on the linac energy, these sources can reach photon energies of 10 keV or higher. The reasons that linacs can deliver higher performance than rings, particularly high peak brightness and short pulse length, are given below. Short pulses can also be obtained in other ways. At the Advanced Light Source at LBNL a femtosecond laser has been used to slice out part of the longer electron bunch to provide short pulses of x-rays. Such a facility could operate at high repetition rate with natural synchronization with the laser, facilitating pump-probe experiments. Also, a project called the Sub-Picosecond Photon Source (SPPS) is in construction at SLAC using a magnetic compressor in the linac to produce an 80 femtosecond electron beam which, when passed through an undulator at the end of the linac, will generate 80 femtosecond x-ray pulses. The figure shows how these sources compare in peak brightness and pulse length with conventional storage ring beams, ERLs and FELs. We can thus discern some broad trends for new sources. One is making more synchrotron radiation available, including regions in which there are no present facilities. Another is the focus on high performance intermediate energy facilities. A third is the use of linac-based sources to achieve shorter pulses and higher brightness and peak power than storage rings can provide.
- Research Organization:
- SLAC National Accelerator Lab., Menlo Park, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (US)
- DOE Contract Number:
- AC03-76SF00515
- OSTI ID:
- 813270
- Report Number(s):
- SLAC-PUB-10006; TRN: US0303824
- Resource Relation:
- Other Information: PBD: 9 Jul 2003
- Country of Publication:
- United States
- Language:
- English
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ADVANCED LIGHT SOURCE
CHEMICAL REACTIONS
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ENERGY FACILITIES
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FREE ELECTRON LASERS
HIGH ENERGY PHYSICS
LIGHT SOURCES
LINEAR ACCELERATORS
MOLECULAR BIOLOGY
PEAK LOAD
STANFORD LINEAR ACCELERATOR CENTER
STORAGE RINGS
SYNCHROTRON RADIATION
SYNCHROTRON RADIATION SOURCES
SYNCHROTRONS
WIGGLER MAGNETS