A Bigger and Better Lightsource

The year was 1982. Brookhaven National Laboratory (BNL) in Upton, New York was celebrating a milestone at its newest facility: the National Synchrotron Light Source (NSLS) had achieved its first light. It might sound insignificant, like a baby’s first sneeze or the first time a pair of newlyweds ate a donut together. But this was a moment that scientists had been building toward for over four years. Batches of electrons rushed through the accelerator at almost the speed of light. Gigantic magnets bent the path of these electrons into a circle, forcing them to lose energy in the form of x-rays. Beamlines directed these x-rays into a detector, towards a brighter future with more science and stuff. Bottles popped, confetti rippled, crowds roared.

It was a whole different world back then,” said Richard Greene, a technician who helped to build some of the first beam lines at the NSLS. “We always cracked a bottle of champagne for every beam line.”

But in 2013, BNL entered into a new era of synchrotron radiation. The lab began phasing out the NSLS, which until then had attracted researchers from all around the world, for a bigger and brighter facility: the NSLS-II. The NSLS-II, which celebrated its own first light in 2014, is currently considered one of the world’s most advanced synchrotrons, producing x-rays up to 10,000 times brighter than the NSLS. The new facility is almost half a mile in circumference—nearly five times the circumference of the NSLS. And while the concept of synchrotrons—bunches of electrons propelled by magnets travelling around and around in giant circles—might seem abstract, the consequences of the research done at these sorts of facilities is monumental, affecting everything from technology to human health.

Before the development of synchrotron light sources in the 60s, synchrotron radiation was seen as a nuisance in the scientific community. At that time, particle accelerators were primarily used to study collision between certain particles and synchrotron radiation caused an undesired loss of energy. When scientists realized that they could use this radiation to do different experiments, they began extracting the radiation, running synchrotron experiments parasitic to these big colliders. The NSLS was one of the first particle accelerators dedicated solely to creating synchrotron light for experimentation purposes. Currently there are seven operational synchrotron facilities in the United States, all running at different energies and used for different experiments.

Click here for a map of the seven synchrotrons in the US

“The principle of a synchrotron is that when electrons go around a bend, they lose energy in the form of synchrotron light, which is basically high powered x rays,” said Robert Rainer, one of the lead operators at the NSLS-II. “Those are the x rays that people come here to use.”

Rainer explained that in the light source, everything begins with the electron gun, which generates electron beams and feeds them into the linear accelerator (LINAC). The electrons must travel in a vacuum so they don’t encounter any resistance. Electromagnets and microwave radio frequency fields are used to accelerate the electrons—the electrons ride the radio frequency field like surfers riding a wave in the ocean. The electrons then enter the booster ring, where they are accelerated to approximately 99.9 percent the speed of light, before they are injected into the storage ring. In the storage ring, they’re steered using an array of magnets. In the photos below, the blue magnets are dipole magnets, which bend the motion of the electrons. The yellow magnets are quadrupoles, which focus and defocus the path of the electrons, and the red and orange magnets are sextupoles, which take outlying electrons and bring them into a closer path. The smaller magnets, which are also dipoles, are corrector magnets.  These magnets keep the beam in line. As the electrons go around turns in the storage ring and lose energy in the form of synchrotron radiation, they are given more energy in the form of radio frequency cavities. The synchrotron radiation lost in this process is directed down a beamline and used for experiments.

According to Timur Shaftan, an accelerator physicist at NSLS-II, in the early 2000s scientists came to the realization that the NSLS was becoming too old—other machines were providing brighter and more intense x-rays to enable more exciting experiments. So scientists decided to construct a new light source, the NSLS-II, which would support more beamlines equipped in a much better way.

“It’s a different level of science now,” Shaftan said. “Once you have a better source of light you can see much clearer, you can see many more details and have a look at those phenomena that nature hid for us.”

The NSLS-II is considered the first optimized third-generation synchrotron in the United States. Third-generation light sources are lightsources which  can support insertion devices like wiggler magnets and undulators. These insertion devices are magnetic structures that produce extremely bright and focused synchrotron radiation by forcing the electron beam in the storage ring to perform wiggles, or undulations, as they pass through the device. One of the most exciting details of the NSLS-II is its small source size, also known as its small emittance, bright x-rays. The x-rays produced by the NSLS-II are coherent, similar to the light in a laser. Unlike a regular lightbulb, which produces many waves and spreads light everywhere, lasers produce a very small spot of light with just one wave. Yong Chu, who is the lead physicist at the X-ray Nanoprobe Beamline at the NSLS-II, explained that because the x-rays are so much brighter, you can do work that couldn’t be done at other places.

“Because our source size is so small we can jam pack much more photons in a small area so we can get much better sensitivity when making measurements,” Chu said.

Peter Siddons had been working at the NSLS since 1985. He is now the head of the detector development group at the NSLS-II. Siddons explained that the new synchrotron makes a lot of new things possible. One of these things is the spacial resolution of measurements done. At the NSLS, scientists could focus the x-ray beam into a 10 micrometer spot. At the NSLS-II, scientists are hoping to focus it down to one nanometer.

“The job of this group is to come up with bigger and better detectors to suit the increased capability of the NSLS-II,” he said. This will allow scientists to study a broad range of samples like minerals, rocks, machinery, biological samples and disease tissue.

There are four main types of experiments that are done at synchrotron light sources: diffraction, scattering, microscopy and spectroscopy. Topics ranging from the proteins in your body, to the soil you walk on, to the batteries in your phone and the chips in your computer are being explored at these facilities.

Microscopy, or imaging, was the first area of application since the discovery of x-rays. One thing that microscopy can look at is drug transport within the human body. Rather than swallowing or injecting a drug, scientists can allocate the drug to a nanoparticle which will travel around until it finds the spot the drug needs to be released. By using synchrotron radiation to explore this method, scientists could significantly improve the aim or focus of drug treatments.

Spectroscopy, which is often associated with microscopy, is another major area of work being done at synchrotrons. Juergen Thieme, the lead physicist at the Submicron Resolution X-ray Spectrocopy Beamline at NSLS-II, explained that spectroscopy, which excites the atoms in a material, is about understanding the chemistry of a sample. An example he gave was clay particles.

“Clay particles are everywhere in the environment,” Thieme said. “Using spectroscopy you can understand better how toxicants are confined and cannot be transported into ground water and how nutrients are spread out when you put them on the soil in your home garden.”

Scattering looks at how amorphous materials scatter x-rays to determine its structure, how it’s made and how it changes based on certain conditions such as high pressure or high temperature. Chu explained that x-ray scattering can be used to test out materials that might be used in airplanes or spaceships to determine how they’ll hold up. This allows scientists to understand how certain materials fail and how to design better materials.

Diffraction uses x-rays to determine the structure of atoms within a crystal by determining how the atoms interact with incoming light. One major use of diffraction is in protein crystallography, where scientists study the structure of proteins to understand what they look like and how they perform.

Vivian Stojanoff is a protein crystallographer who was hired by BNL in 2000 to manage and direct one of the protein crystallography beamlines at the NSLS. When the NSLS closed, she became in charge of coordinating the user program during the construction of the protein crystallography beamlines. Stojanoff explained that the fact that scientists have now identified the genes for ovarian cancer and breast cancer, the progress being made in the research for Alzheimer’s and the development of medicines for osteoporosis were all made possible with the use of synchrotron radiation.

“One of thing we have been seeing since the late 90s is an explosion in the new molecular structures of proteins and enzymes. All the new medicines we see, new vaccines, new treatments for many diseases, are a result of all the structural work that has been done at synchrotrons,” she said.

Having a coherent light source, like the one at NSLS-II, is important when doing experiments in diffraction and scattering because it allows scientists to know that the patterns they are picking up in their detectors are all coming from their samples, and not from the light source. But one downside, Stojanoff explained, is that even though it will allow scientists to look at many more samples and to study the dynamics of the molecules, the source size is so brilliant and strong that it will destroy samples. Scientists will have to learn how to do the data collection with the new light source.

“It’s opening whole new areas of study that we have not had before,” Stojanoff said.

Jean Jordan-Sweet is an IBM researcher who had worked at the NSLS for 34 years. Jordan-Sweet uses diffraction to enable newer generations of computer chips to get made. Jordan-Sweet said that she thinks that the new technologies offered at the NSLS-II will be very useful and she is interested in learning to use coherent light to do measurements.

“There’s a lot of opportunity for us to really investigate what other kinds of measurements we can use to understand chips and the materials that go into making them,” she added.

Scientists and technicians who feel sad about the passing of BNL’s first light source can feel comforted knowing that its successor is considered the newest and most advanced light source in the world. For now. Though the NSLS-II is only running six project beamlines at the moment, BNL is expecting both the number of beamlines and the user base for these beamlines to grow exponentially. When asked their favorite aspects about working at Brookhaven, everyone agreed that it’s the mixture of different people and ideas from around the world and the sense of community that working at such a facility fosters.

“People from different very different fields are constantly helping each other out with their research,” Rainer said. “Being on the forefront of science and being involved in such a collaborative effort are my favorite things about working here.”

NSLS from Ali Sundermier on Vimeo.


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