Focus
Lowering the Barrier to Using Synchrotron Radiation
F
rom the start there were researchers who recognized that the intense beam of photons generated by flinging charged particles saound a synchrotron ring could be put to good use as an analytical tool. In one of the first experiments, performed nearly 35 years ago at the then National Bureau of Standards (now National Institute of Standards and Technology) physicists evaluated synchrotron radiation as a fundamental standard of flux for far-UV light (1) Despite its potential, chemical analysis by synchrotron radiation traditionally has been limited to special communities, such as protein crystallographers, and expert researchers with ties to a national laboratory. "There are high-energy barriers to doing [synchrotron radiation research]," says Stanford University geochemist Gordon Brown. "You have to devote your life and the lives of your graduate students to doing it." However, several efforts are being made to expand the use of synchrotron radiation as a new generation of light sources opens up for operation. Efforts include bringing in new communities, such as environmental and semiconductor researchers, and improving accessibility to the national laboratories that run the synchrotron light sources. In addition, some synchrotron scientists are providing their expertise for running samples for nonexperts. There are even serious pro-
Learning about access
Synchrotron radiation describes photons over a range of wavelengths, from high-energy X-rays to far-IR. The photons are produced when electrons or positrons are accelerated to near-light speed and forced by powerful magnets to travel in a circular path. The resulting radiation is very bright, highly collimated, and linearly polarized. The light comes in rapid, stroboscopic pulses. Moreover the spectrum is continuous providing a tunable light source A host of analytical techniques benefit from synchrotron light, and most of them use X-rays (2). Some techniques, such as extended X-ray absorption fine structure (EXAFS) for identifying nearest atomic neighbors to a central element, can only be run practically with synchrotron radiation. As the brightness of synchrotron sources has grown, researchers have been able to collect data on smaller samples that measure only micrometers in size. Synchrotron light sources are major financial investments. They require construction of a particle accelerator and a high-vacuum storage ring. The United States' newest, and currently the world's most powerful, synchrotron is Argonne National Laboratory's 7.5-GeV Advanced Photon Source (APS), which will cost taxpayers $467 million. The costs, however don't end there. Construction of the instrumentation or beamlines that manipulate the photons for various experiments
New applications and better techniques lead researchers to envision more routine analytical uses posals to build new light sources as dedicated service laboratories. Proponents of these efforts face many obstacles. Foremost is obtaining sufficient funding and providing an atmosphere that will encourage more scientists to use analytical methods based on synchrotron radiation.
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Focus runs tens of millions of dollars. For example, Brown says that two new beamlines being built at APS for environmental, soil, and geologic research will cost $15 million,financedlargely by the Keck Foundation, National Science Foundation, and the Department of Energy (DOE). Some beamlines on APS may cost as much as $50 million. As a result, most beamlines are being built by consortia that share costs; the beamlines Brown described are being constructed by the Consortium for Advanced Radiation Sources which has 140 researchers as members. Other beamlines have been underwritten by private companies to perform a mix of publishable and proprietary research. To reconcile the public investment in the photons with the secretive nature of proprietary research, the national laboratories charge companies the full cost of providing the light for these experiments. Companies are charged around $100 per hour at the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory, says senior scientist Jerome Hastings. Membership to one of these beamline consortia is the best way to gain time at a synchrotron. Nevertheless, "general users" can also access lines. Under the national lab rules, 25% of the operating time on these beamlines is reserved for outside researchers. In addition, there are also DOE-built beamlines open 75% or more of the time for general users. General access to beamlines is controlled by competitive, peer-reviewed proposals. It was at NSLS that national laboratories and DOE learned what accessibility meant. NSLS, one of the first of the second-generation light sources, began full operation in the early 1980s. First-generation light sources had piggy-backed synchrotron radiation with other applications, but the second-generation sources were fully dedicated to synchrotron light. As such, says Roland Hirsch of DOE's Office of Health and Environmental Research, NSLS was designed in consultation with the user community. Yet ,dmits Hirsch rniiny
factors limited access According to researchers who have conducted studies at NSLS, initial visitors to the facility had to overcome an absence of laboratory and office space, a crowded beamlinefloor,one-of-a-kind 256 A
Come on in: An inside view of the Advanced Photon Source prior to beamline construction. (Courtesy of Argonne National Laboratory.)
equipment and software that did not always operate well, as much as half a day to re-tune beamline systems, a light source that was out of commission or running poorly, and difficulty in finding knowledgeable staff. "There was not much of a concept of service," says Richard Harlow, a synchrotron researcher with DuPont. Harlow argues that much of the problem was caused by the federal government underfunding the NSLS operating budget. DOE has recently addressed some of the problems through a special funding initiative to upgrade facilities. NSLS and other light sources have used the monies to build visitor laboratories and offices, says Hirsch. In fact, laboratory facilities have improved to the point where researchers at the Stanford Synchrotron Radiation Laboratory (SSRL) were able to analyze radioactive actinide samples in support of DOE's laboratory cleanup. In addition, computer facilities and appropriate algorithms have been established so that researchers can at least know whether they have collected a useful data set. Funds are also being spent on improvements in some of the general user beamlines and in the light source. "All synchrotron light sources emphasize accessibility," says Hirsch. Operating funds for light sources are still tight, however, and how these monies are being spent seems to vary among light sources. NSLS has adopted the slogan
Analytical Chemistry News & Features, April 1, 1996
"our light is always on," referring to their more than 200 days of beam time in 1995. "We've never held a user captive to running time," says Hastings. SSRL, on the other hand, ran 150 days last year. That laboratory has committed more of its funds to support staff, says Brown. However, SSRL plans to use this year's $4 million in special scientific facilities money to increase its running time to 180 days. Meanwhile, synchrotron users are demanding better access and service at light sources. Last December, industrial users met at NSLS to air concerns and complaints. The meeting, co-chaired by Harlow and Hastings, appears to be the first step to an industrial synchrotron users group. "We are trying to change the way that industrial users work with national laboratories," says Harlow. Hastings says that synchrotron light sources such as NSLS are "struggling with the dilemma" of balancing the need for service basic research In particular, industry users need to make their synchrotron visits more productive. Traditional chemical and oil companies were among the groups well represented when NSLS began operation. Most of these companies found NSLS because of a researcher within the firm who knew something of synchrotron techniques or had a professional connection with a synchrotron expert, says Harlow. Studies have focused on characterizing ac-
the spot intensity data and phase angles searchers collecting data on large biologiback to their labs. There they can refine cal structures and with smaller, less perthe structure using commercially availfect crystals, says Westbrook. able software. However, warns WestThe addition of APS should also help brook, even this new service is "not a with access time for particular types of black box." beamlines that are oversubscribed. DOE, Nevertheless, a synchrotron crystallog- says Hirsch, plans to keep all of its synraphy service could become quite popular. chrotron light sources open. "All of them do things that you couldn't do at home." "Almost every month Science or Nature has a feature article with a structure done One group that would like more access with synchrotron radiation," Hirsch is environmental scientists. Environmenpoints out. Oliver calculates that a crystal tal studies are probably the fastest growthat requires 14 days on a standard rotat- ing application of synchrotron light, as More businesslike measured by demand for beam time, says Many of the lessons about access and ser- ing anode X-ray spectrometer to generate enough Bragg diffraction data will take Brown. In a report just released, a workvice learned at NSLS have been incorpojust 0.3 s at APS. "In principle you can do shop of environmental scientists conrated into the design of APS, a third15 to 20 crystals a day," he says. More cluded that "the number of available syngeneration light source featuring adchrotron beamlines for molecular-scale envanced magnet and optics designs. "APS is likely, the time will be taken up by remore user-focused," says Procter & Gamble's Joel Oliver. He heads the Industrial Macromolecular Crystallography Association, a consortium of 12 major pharmaceutical companies building two beamlines at APS. At APS, each sector on the synchrotron storage ring, which provides two beamline ports, has an associated office or laboratory. Beamline floor space is huge. Harlow says that DuPont, together with Northwestern University and Dow Chemical, is funding six experimental stations, each with its own "hutch" the size of a oneor two-car garage (see photo). In fact, DuPont paid for an extra eight feet in height on one hutch, which will house a working polymer spinning line for real-time experiments. "The science that is going to from this machine is incredible like handing laser in the days of only light bulbs " There are also plans to have support personnel available and beamlines set up for nonexpert users. Edwin Westbrook, director of the structural biology center at APS, says his group is developing an X-ray crystallography line for protein chemists who "don't know which way a Fourier transform goes and don't care." As planned, a technician will help these novices mount and flash-freeze a crystal to 100 K. A graphical on-line computer tutorial will then guide the visiting scientist Figure 1 . Up close and detailed: A false-color synchrotron X-ray through the data collection and the subfluorescence map of Cr distribution within a hyperaccumulating plant. sequent data analysis New computer algo- Top spectra show oxidation states using X-ray absorption near-edge structure spectroscopy. rithms will heto calculate the important tive catalysts, analyzing high-temperature superconductors, and determining the orientation of polymerfiberswith X-ray microscopy. Now, as companies downsize, the dollars, and even the researchers to conduct synchrotron studies, are disappearing. Some industries that have traditionally funded beamlines have stopped supporting those lines; others have transferred their lines or are selling time to help defray costs.
phase angles necessary to solve a structure Visiting researchers can then e-mail
Although the plants were exposed to Cr(VI), all of the Cr that localized in the cells (see bottom sketch) is the less toxic Cr(lll). This suggests a detoxification mechanism. (Figure courtesy of Paul Bertsch and Douglas Hunter.)
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Focus ports achieving detection limits of 3 x 108 commodate as many as 46 beamlines. atoms/cm2. Advanced Photon Source, Argonne Part of the trial is to determine whether National Synchrotron Light Source, National laboratory, ,L. This stirdsimilar results can be obtained at both Brookhaven NationalLaboratory,NY. generation 7-GeV light source that prolight sources. If all goes well, the plan is to vides hard X-rays begins operating Two storage rings, vacuum-UV, and get an "analytical provider" to run the this year. The beam is so intense that X-ray offer more than 80 beamlines. samples for the manufacturers. "Industry radiation damage may limit some exApproximately 20% of the beamlines has faith in service providers; if they want periments. Around 40 beamlines were built by the laboratory and are something, they can pay for it," says Pitypically more accessible to general us- (about half of the potential beamlines) anetta. On the other hand, national labs are in development by collaborative ers than lines built by consortia. NSLS "do the best they can," and throwing teams. Many lines are three to five is in operation most of the year. money at them doesn't necessarily help, years from full operation. he adds. Stanford Synchrotron Radiation Laboratory, ,tanford Linear Acceleration Cornell High-Energy gynchrotrot Indeed, all the private industry synCenter, CA. Second-generation 3.0-GeV Source, Cornell University, NY. A para- chrotron users complained to some desynchrotron with 25 experimental stasitic synchrotron, technically firstgree about working with DOE. The contions. Some beamlines, such as the generation, but at 5 GeV it has features tract language for running proprietary reX-ray absorption spectroscopy staequivalent to those of third-generasearch at light sources is not as "crisp" as tion, are oversubscribed. SSRL prides tion systems. CHESS has 11 experiwhat private companies are accustomed itself on providing staff support. mental stations, all owned by the lab, to, says Oliver, but it is something that the and is considered a research facility. members of his consortium have indiAdvanced Light Source, Lawrence cated they can "live with." Berkeley National Laboratory, Berkeley, Aladdin, University of WisconsinCA. A third-generatton 1.9-GeV synchro- Madison, WI. A 1-GeV storage ring with tron, the light source is optimized for 26 beamlines and 3 others in developFull service soft X-rays. ALS began running in 1993 ment, it operates like national laboratoIn principle, a commercial analytical serand at the start of this year had 12 beam- ries with beamlines built by consortia vice could be established on one of the lines in operation. The facility can acof researchers. beamlines. That hasn't happened, but there is some nibbling at the edges. Paul Bertsch, an environmental geovironmental research is currently However, there are obstacles to routine chemist with the University of Georgia's Savannah River Ecology Laboratory saturated." The authors expect that desynchrotron environmental analysis. The (SREL, Aiken, SC), says that he has been mand for beam time in this area will douworkshop report noted that improvements ble in the next three years. New environ- in the detectors used in synchrotrons wiil be approached for collaborative synchrotron research efforts. As a member of a remental science beamlines being built at needed to analyze the typically dilute and search team working at NSLS, Bertsch anSSRL and APS wiil not meet the increased complex environmental samples. In addidemand, concludes the report (3). tion, methods have not progressed to the alyzes samples via X-ray microprobe and EXAFS. point where general users can easily run The report's authors expect that synsamples or, even more important, analyze In 1994, SREL established the Adchrotron techniques will play a major role the data, says Brown. vanced Center for Environmental Sciin providing information on the chemiences with DOE and state of Georgia supcal form or speciation of metal contamiA novel solution to the problem of acnants, determining the spatial distribution cessibility has been created to serve semi- port. The center provides environmental researchers with state-of-the-art facilities of contaminants in samples, and elucidatconductor chip manufacturers based in and, as part of the center, Bertsch's group ing the environmental chemistry at surCalifornia. A consortium of these compafaces or within microorganisms and nies, led by Hewlett Packard and Sema- provides access to NSLS. Fees charged to outsiders are calculated to break even plants. Applications include measuring As tech, has negotiated to run at both SSRL and help Bertsch's group maintain a fulland Se contamination at Superfund sites; and the nearby Advanced Light Source. time beamline scientist at NSLS. mapping the uptake, distribution, and That way these high-technology compaciation of Se and Cr in metal-concentratnies will have rapid access to synchrotron Dale Sayers, a physicist at North Caroing or hyperaccumulating plants (Figure analysis all year long. This plan is curlina State University, says that he, too, 1) ; and investigating the in situ reducrently in the trial stages hopes to offer analytical synchrotron sertion of carcinogenic Cr(VD to CrdID SvnStanford Uni- vices. He is negotiating with NSLS, where chrotron-based methods such as X-rav he heads one of the beamlines, and with versity electrical engineer Piero Pianetta. absomtion spectrosconv when detected in The consortium is exploring a new tech- Lawrence Berkeley Laboratory, which opthe fluorescence mode work even with erates the third-generation Advanced nique total X-ray reflection fluorescence Light Source. wet samples and offer detection limits at (TXRF) for determining contaminants in a r n n n r i 1 fl n n m r»r 1 fT~5 lVJ fnr tmanv pnvi Sayers, however, has a more audasemiconductors TXRF sends in X-rays at ronmentally important very low angles to look at small areas on cious plan. He heads the North Carolina Open for business: Major U.S. synchrotron light sources
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the surface of silicon wafers Pianetta reAnalytical Chemistry News & Features, April 1, 1996
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Storage Ring and Technology Advanced Resources (NC STAR) project, an effort to build an NSLS-sized synchrotron ring dedicated to applied research and technology. According to Sayers, the NC STAR plan would need around $200 million to construct a light source that could provide as many as 60 beamlines. The approximately $10 million in estimated annual operating costs would come from user fees set on a break-even basis he says. Sayers envisions that NC STAR would not be tied to DOE, so it would have a "simpler policy and cost structure." In fact, he reports that recently NC STAR got very close to gaining federal funding as a technology transfer project before a "window of opportunity" closed. The project still has strong support from the university and the state, according to Sayers. He reports that similar efforts to fund service-oriented light sources are under review in Japan and Germany. "Both have shown the case " he argues "There is lots of market out there " Creating analytical synchrotron services, whether at a national laboratory or in a new facility, is only the beginning. Synchrotron researchers still need to develop standard methods supported by QA/QC data that will show businesses and regulatory agencies the value of these techniques, says Sayers. In the end, the degree to which synchrotron techniques become routine analytical tools will depend on finding the money to develop the service beamlines and to support sufficient staff. Given the potential demand, there may be room for analytical services at national laboratories and in projects such as NC STAR. "Synchrotron light sources are an investment in the future of the country," argues Brown. "To build these incredible resources and not have the wisdom to support them would be utter stupidity " Alan Newman
References (1) Madden, R. P.; Codling, K. Phys Rev. Lett. 1963,10, 516. (2) Noble, D.Anal. Chem. 1993, 65,949 A. (3) Molecular Environment Science: Speciation, Reactivity, and Mobility of Environmental Contaminants. An Assessment of Research Opportunities and the Need for Synchrotron Radiation Facilities; National Technical Information Service: Springfield, VA, 1995.
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