Updates from April, 2016 Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 1:46 pm on April 4, 2016 Permalink | Reply
    Tags: , , ,   

    From LBL: “Construction Begins on Major Upgrade to World’s Brightest X-ray Laser” 

    Berkeley Logo

    Berkeley Lab

    April 4, 2016
    Glenn Roberts Jr.
    510-486-5582
    geroberts@lbl.gov

    1
    An electron beam travels through a niobium cavity, a key component of a future LCLS-II X-ray laser, in this illustration. Kept at minus 456 degrees Fahrenheit, these cavities will power a highly energetic electron beam that will create up to 1 million X-ray flashes per second. (Credit: SLAC National Accelerator Laboratory)

    Construction begins today on a major upgrade to a unique X-ray laser that will add a second X-ray laser beam that’s 10,000 times brighter, on average, than the first one and fires 8,000 times faster—up to a million pulses per second.

    Researchers at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) are contributing key components for the project, known as LCLS-II, that will greatly increase the power and capacity of the Linac Coherent Light Source (LCLS), a free-electron X-ray laser at the DOE’s SLAC National Accelerator Laboratory in Menlo Park, Calif.

    2
    A prototype LCLS-II undulator, which is designed to wiggle electrons, causing them to emit brilliant X-ray light, undergoes magnetic measurements at Berkeley Lab. (Credit: Roy Kaltschmidt/Berkeley Lab)

    3
    The powerful, toothlike rows of magnets (center) in this prototype device, called an undulator, can produce up to 7 tons of force. This undulator, designed for LCLS-II, an X-ray laser project, is needed to magnetically wiggle electrons, causing them to emit X-ray light. (Credit: Roy Kaltschmidt/Berkeley Lab)

    4
    Berkeley Lab’s Fernando Sannibale inspects the APEX (Advanced Photoinjector Experiment) that has served as a test electron gun and injector system for LCLS-II. (Credit: Roy Kaltschmidt/Berkeley Lab)

    The project, which is now formally approved by the DOE to start construction and is being funded by DOE’s Office of Science, will enable experiments that sharpen our view of how nature works on the atomic level and on ultrafast timescales.

    Like the existing facility, LCLS-II will use electrons accelerated to nearly the speed of light to generate beams of extremely bright X-ray laser light. The electrons fly through a series of magnets, called an undulator, that forces them to travel a zigzag path and give off energy in the form of X-rays. At present, electrons are accelerated in a copper structure that operates at room temperature and allows the generation of 120 X-ray laser pulses per second.

    For LCLS-II, crews will install a new accelerator that is called “superconducting” because its metal cavities, made of niobium, will conduct electricity with nearly zero loss when chilled to minus 456 degrees Fahrenheit. Accelerating electrons through a series of these cavities allows the generation of an almost continuous X-ray laser beam.

    To make the upgrade a reality, a nationwide collaboration has formed that includes SLAC, Berkeley Lab and three other national labs—Argonne, Fermilab and Jefferson Lab—and Cornell University, with each partner making key contributions to project planning as well as to component design, acquisition and construction.

    “We bring a lot of expertise to the LCLS-II collaboration,” said John Corlett, senior team leader for the LCLS-II effort at Berkeley Lab. “We were selected to provide critical technologies that generate the high-brightness and high-repetition-rate electron beam that is the first component in the superconducting accelerator chain, and the undulators that are the core of the free-electron laser X-ray source.

    “Additionally, we have lead roles in control of the superconducting cavities, and in modeling the electron beam to optimize the laser performance.”

    SLAC’s John Galayda, head of the LCLS-II project team, said, “We couldn’t do this without our collaborators. To bring all the components together and succeed, we need the expertise of all partners, their key infrastructure and the commitment of their best people.”

    When LCLS opened six years ago as a DOE Office of Science User Facility, it was the first light source of its kind—a unique X-ray microscope that uses the brightest and fastest X-ray pulses ever made to provide unprecedented details of the atomic world.

    Hundreds of scientists, including Berkeley Lab researchers, use LCLS each year to catch a glimpse of nature’s fundamental processes in unprecedented detail. Molecular movies reveal how chemical bonds form and break; ultrafast snapshots capture electric charges as they rapidly rearrange in materials and change their properties; and sharp 3-D images of disease-related proteins provide atomic-level details that could hold the key for discovering potential cures.

    The new X-ray laser will work in parallel with the existing one, with each occupying one-third of SLAC’s 2-mile-long linear accelerator (“linac”) tunnel. Together they will allow researchers to make observations over a wider energy range, capture detailed snapshots of rapid processes, probe delicate samples that are beyond the reach of other light sources and gather more data in less time, thus greatly increasing the number of experiments that can be performed at this pioneering facility.

    SLAC is now clearing out the first third of the linac to make room for the superconducting accelerator, which is scheduled to begin operations in early 2020.

    “LCLS-II will take X-ray science to the next level, opening the door to a whole new range of studies of the ultrafast and ultrasmall,” said LCLS Director Mike Dunne. “This will tremendously advance our ability to develop transformative technologies of the future, including novel electronics, life-saving drugs and innovative energy solutions.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    A U.S. Department of Energy National Laboratory Operated by the University of California

    University of California Seal

    DOE Seal

     
  • richardmitnick 8:00 am on March 31, 2016 Permalink | Reply
    Tags: , , , ,   

    From LBL: “Revealing the Fluctuations of Flexible DNA in 3-D” 

    Berkeley Logo

    Berkeley Lab

    March 30, 2016
    Glenn Roberts Jr.
    510-486-5582
    geroberts@lbl.gov

    `
    In a Berkeley Lab-led study, flexible double-helix DNA segments connected to gold nanoparticles are revealed from the 3-D density maps (purple and yellow) reconstructed from individual samples using a Berkeley Lab-developed technique called individual-particle electron tomography or IPET. Projections of the structures are shown in the background grid. (Credit: Berkeley Lab)

    An international team working at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) has captured the first high-resolution 3-D images from individual double-helix DNA segments attached at either end to gold nanoparticles. The images detail the flexible structure of the DNA segments, which appear as nanoscale jump ropes.

    This unique imaging capability, pioneered by Berkeley Lab scientists, could aid in the use of DNA segments as building blocks for molecular devices that function as nanoscale drug-delivery systems, markers for biological research, and components for computer memory and electronic devices. It could also lead to images of important disease-relevant proteins that have proven elusive for other imaging techniques, and of the assembly process that forms DNA from separate, individual strands.

    The shapes of the coiled DNA strands, which were sandwiched between polygon-shaped gold nanoparticles, were reconstructed in 3-D using a cutting-edge electron microscope technique coupled with a protein-staining process and sophisticated software that provided structural details to the scale of about 2 nanometers, or two billionths of a meter.

    “We had no idea about what the double-strand DNA would look like between the nanogold particles,” said Gang “Gary” Ren, a Berkeley Lab scientist who led the research. “This is the first time for directly visualizing an individual double-strand DNA segment in 3-D,” he said. The results were published in the March 30 edition of Nature Communications.

    The method developed by this team, called individual-particle electron tomography (IPET), had earlier captured the 3-D structure of a single protein that plays a key role in human cholesterol metabolism. By grabbing 2-D images of the same object from different angles, the technique allows researchers to assemble a 3-D image of that object. The team has also used the technique to uncover the fluctuation of another well-known flexible protein, human immunoglobulin 1, which plays a role in our immune system.


    Access mp4 video here .

    For this latest study of DNA nanostructures, Ren used an electron-beam study technique called cryo-electron microscopy (cryo-EM) to examine frozen DNA-nanogold samples, and used IPET to reconstruct 3-D images from samples stained with heavy metal salts. The team also used molecular simulation tools to test the natural shape variations, called “conformations,” in the samples, and compared these simulated shapes with observations.

    Ren explained that the naturally flexible dynamics of samples, like a man waving his arms, cannot be fully detailed by any method that uses an average of many observations.

    A popular way to view the nanoscale structural details of delicate biological samples is to form them into crystals and zap them with X-rays, though this does not preserve their natural shape and the DNA-nanogold samples in this study are incredibly challenging to crystallize. Other common research techniques may require a collection of thousands near-identical objects, viewed with an electron microscope, to compile a single, averaged 3-D structure. But this 3-D image may not adequately show the natural shape fluctuations of a given object.

    The samples in the latest experiment were formed from individual polygon gold nanostructures, measuring about 5 nanometers across, connected to single DNA-segment strands with 84 base pairs. Base pairs are basic chemical building blocks that give DNA its structure. Each individual DNA segment and gold nanoparticle naturally zipped together with a partner to form the double-stranded DNA segment with a gold particle at either end.


    Access mp4 video here .
    These views compare the various shape fluctuations obtained from different samples of the same type of double-helix DNA segment (DNA renderings in green, 3-D reconstructions in purple) connected to gold nanoparticles (yellow). (Credit: Berkeley Lab)

    The samples were flash-frozen to preserve their structure for study with cryo-EM imaging, and the distance between the two gold particles in individual samples varied from 20-30 nanometers based on different shapes observed in the DNA segments. Researchers used a cryo-electron microscope at Berkeley Lab’s Molecular Foundry for this study.

    They collected a series of tilted images of the stained objects, and reconstructed 14 electron-density maps that detailed the structure of individual samples using the IPET technique. They gathered a dozen conformations for the samples and found the DNA shape variations were consistent with those measured in the flash-frozen cryo-EM samples. The shapes were also consistent with samples studied using other electron-based imaging and X-ray scattering methods, and with computer simulations.

    While the 3-D reconstructions show the basic nanoscale structure of the samples, Ren said that the next step will be to work to improve the resolution to the sub-nanometer scale.

    3
    Gang Ren (standing) and Lei Zhang participated in a study at Berkeley Lab’s Molecular Foundry that produced 3-D reproductions of individual samples of double-helix DNA segments attached to gold nanoparticles. (Photo by Roy Kaltschmidt/Berkeley Lab)

    “Even in this current state we begin to see 3-D structures at 1- to 2-nanometer resolution,” he said. “Through better instrumentation and improved computational algorithms, it would be promising to push the resolution to that visualizing a single DNA helix within an individual protein.”

    The technique, he said, has already excited interest among some prominent pharmaceutical companies and nanotechnology researchers, and his science team already has dozens of related research projects in the pipeline.

    In future studies, researchers could attempt to improve the imaging resolution for complex structures that incorporate more DNA segments as a sort of “DNA origami,” Ren said. Researchers hope to build and better characterize nanoscale molecular devices using DNA segments that can, for example, store and deliver drugs to targeted areas in the body.

    “DNA is easy to program, synthesize and replicate, so it can be used as a special material to quickly self-assemble into nanostructures and to guide the operation of molecular-scale devices,” he said. “Our current study is just a proof of concept for imaging these kinds of molecular devices’ structures.”

    The Molecular Foundry is a DOE Office of Science User Facility.

    In addition to Berkeley Lab scientists, other researchers contributing to this study were from UC Berkeley, the Kavli Energy NanoSciences Institute at Berkeley Lab and UC Berkeley, and Xi’an Jiaotong University in China.

    This work was supported by the National Science Foundation, DOE Office of Basic Energy Sciences, National Institutes of Health, the National Natural Science Foundation of China, Xi’an Jiaotong University in China, and the Ministry of Science and Technology in China.

    View more about Gary Ren’s research group here.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    A U.S. Department of Energy National Laboratory Operated by the University of California

    University of California Seal

    DOE Seal

     
  • richardmitnick 7:40 am on March 31, 2016 Permalink | Reply
    Tags: , , Ee-Been Goh, , woman scientist   

    From LBL: “From Near-Dropout to PhD, Berkeley Lab Scientist Now at Forefront of Biofuels Revolution” 

    Berkeley Logo

    Berkeley Lab

    March 30, 2016
    Julie Chao
    (510) 486-6491
    JHChao@lbl.gov

    1
    Ee-Been Goh works with summer intern Joshua Borrajo in 2013. (Credit: Roy Kaltschmidt/Berkeley Lab)

    To see biochemist Ee-Been Goh in the lab today, figuring out how to rewire bacteria to produce biofuels, one would never guess she was once so uninterested in school that she barely made it through junior high.

    “My mom would say, ‘You used to be the worst in school—why would you want to go for more school?’” Goh said. “That was the joke when I was going into grad school.”

    Today Goh is a project scientist at the Joint BioEnergy Institute (JBEI), a Department of Energy Bioenergy Research Center led by Lawrence Berkeley National Laboratory (Berkeley Lab). She has been lead author on two important publications on methyl ketones, a compound found in blue cheese that has also turned out be one of the most promising and high-performing biofuels at JBEI.

    Her path into science is an object lesson she likes to share with the high school students she mentors through a JBEI summer program called Introductory College Level Experience in Microbiology (iCLEM). “I always tell the iCLEM kids how I was a terrible student in Singapore,” she said. “I was a tomboy, and I just loved goofing off on the streets and playing sports. I really hated school. I would’ve loved to have had a career in professional sports.”

    At the age of 14, her parents moved the entire family to Vancouver, largely for a better educational experience for Goh and her two sisters. Getting to do hands-on science activities in high school, such as animal dissections, sparked her interest in science. “When you do it yourself, you understand things a lot better than when you’re being bombarded with words on a board or an overhead projector,” she said. “That’s something that really caught on for me.”

    Likewise, she encourages students to take advantage of any opportunity they might have. “I think some of these students get really dejected when they don’t do well in school, and as you get more dejected, you just don’t want to put in any more effort,” she said. “That’s how I felt when I was a little kid. The most important thing for me is to fan their interest.”

    As an undergrad at the University of British Columbia, her opportunity was an internship in the microbiology lab of Julian Davies, a renowned scientist in the field of antibiotics and drug resistance. “He was retired and in his 70s, but he really loved science so he was still taking on undergrad students who liked to do research,” she said. “He was very hands-on and got very excited even with small results, and it got me excited too.”

    With encouragement from Davies, Goh decided to pursue an advanced career in science. She did her graduate work in microbiology at UC Davis, where her research focused on understanding how bacteria communicate with each other. This work in the basic sciences taught Goh useful research techniques, but she realized she wanted to pursue a career in the applied sciences.

    “With applied science it impacts more people and has broader reach,” she said. “People can take it and use it. That’s what science is about, right?”

    Landing a job at JBEI fit that requirement perfectly.

    From blue cheese to climate change

    “Many valuable commodity chemicals and fragrances are often derived from petroleum,” Goh said. “At JBEI we’re aiming not just to make biofuels but also to replace a lot of everyday products that come from that barrel of crude oil. We’re trying to do our part in slowing down climate change—that’s the ultimate goal.”

    The focus of her research has been methyl ketones, which are derived from fatty acids and show great promise for biodiesel fuels. Not only are methyl ketones a potential biodiesel, there is a market for these compounds as flavors and fragrances. Working with Harry Beller, director of Biofuels Pathways at JBEI, Goh’s research is aimed at engineering E. coli bacteria to produce methyl ketones as efficiently as possible.

    “Ee-Been has made significant scientific contributions to the development of new biofuels at JBEI,” Beller said. “Her two first-author publications on engineering and optimizing a novel methyl ketone pathway in E. coli have made a notable impact in the area of fatty acid-derived biofuels—medium-chain methyl ketones are among our best performing biofuels at JBEI.”

    Beller elaborated on what made Goh good at what she does: “Qualities that have helped Ee-Been be a successful scientist are her persistence and intelligent approach to troubleshooting. In biotechnology, as in many areas of science and technology, only a fraction of scientific avenues we follow lead to clear success. Ee-Been has the fortitude and ability to learn from things that didn’t work to eventually pursue things that do.”

    And although she occasionally likes to pull pranks in the lab—switching out medium-sized gloves for small ones is a perennial favorite—her JBEI colleagues have voted her “JBEI Citizen” for two consecutive years for “fostering a positive working environment through helping colleagues.”

    “Perhaps Ee-Been’s most lasting legacy at JBEI is all the people she has helped along the way,” Beller said. “She’s been very generous with her time, including ongoing involvement in the iCLEM summer internship program for economically disadvantaged high-school students.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    A U.S. Department of Energy National Laboratory Operated by the University of California

    University of California Seal

    DOE Seal

     
  • richardmitnick 5:16 pm on March 23, 2016 Permalink | Reply
    Tags: , , ,   

    From LBL: “Unlocking the Secrets of Gene Expression” 

    Berkeley Logo

    Berkeley Lab

    March 23, 2016
    Julie Chao (510) 486-6491
    JHChao@lbl.gov

    Your DNA governs more than just what color your eyes are and whether you can curl your tongue. Your genes contain instructions for making all your proteins, which your cells constantly need to keep you alive. But some key aspects of how that process works at the molecular level have been a bit of a mystery—until now.

    Using cryo-electron microscopy (cryo-EM), Lawrence Berkeley National Laboratory (Berkeley Lab) scientist Eva Nogales and her team have made a significant breakthrough in our understanding of how our molecular machinery finds the right DNA to copy, showing with unprecedented detail the role of a powerhouse transcription factor known as TFIID.

    1
    Berkeley Lab scientists Eva Nogales and Robert Louder at the electron microscope. (Credit: Roy Kaltschmidt/Berkeley Lab)

    This finding is important as it paves the way for scientists to understand and treat a host of malignancies. “Understanding this regulatory process in the cell is the only way to manipulate it or fix it when it goes bad,” said Nogales. “Gene expression is at the heart of many essential biological processes, from embryonic development to cancer. One day we’ll be able to manipulate these fundamental mechanisms, either to correct for expression of genes that should or should not be present or to take care of malignant states where the process has gone out of control.”

    Their study has been published online in the journal Nature in an article titled, Structure of promoter-bound TFIID and insight into human PIC assembly. The lead author is Robert Louder, a biophysics graduate student in Nogales’ lab, and other authors are Yuan He, José Ramón López-Blanco, Jie Fang, and Pablo Chacón.

    Nogales, a biophysicist who also has appointments at Howard Hughes Medical Institute and UC Berkeley, has been studying gene expression for 18 years. While she and her team have made several significant findings in recent years, she calls this the biggest breakthrough so far. “This is something that will go in biochemistry textbooks,” she said. “We now have the structure of the whole protein organization that is formed at the beginning of every gene. This is something no one has come close to doing because it is really very difficult to study by traditional methodologies.”

    2
    Cryo-EM model of the human transcription pre-initiation complex. (Credit: Robert Louder/Berkeley Lab )

    How genetic information flows in living organisms is referred to as the “central dogma of molecular biology.” Cells are constantly turning genes on and off in response to what’s happening in their environment, and to do that, the cell uses its DNA, the big library of genetic blueprints, finds the correct section, and makes a copy in the form of messenger RNA; the mRNA is then used to produce the needed protein.

    The problem with this “library” is that it has no page numbers or table of contents. However, markers are present in the form of specific DNA sequences (called core promoter motifs) to indicate where a gene starts and ends. So how does the polymerase, the enzyme that carries out the transcription, know where to start? “DNA is a huge, huge molecule. Out of this soup, you have to find where this gene starts, so the polymerase knows where to start copying,” Nogales said. “This transcription factor, TFIID, is the protein complex that does exactly that, by recognizing and binding to DNA core promoter regions.”

    What Nogales and her team have been able to do is to visualize, with unprecedented detail, TFIID bound to DNA as it recognizes the start, or promoter, region of a gene. They have also found how it serves as a sort of landing pad for all the molecular machinery that needs to assemble at this position—this is called the transcription pre-initiation complex (PIC). This PIC ultimately positions the polymerase so it can start transcribing.

    3
    TFIID (blue) as it contacts the DNA and recruits the polymerase (grey) for gene transcription. The start of the gene is shown with a flash of light. (Credit: Eva Nogales/Berkeley Lab)

    “TFIID has to do not only the binding of the DNA, recruitment, and serving as landing pad, it has to somehow do all that differently for different genes at any given point in the life of the organism,” Nogales said.

    Added Louder: “We have generated the first ever structural model of the full human TFIID-based PIC. Our model yields novel insights into human PIC assembly, including the role of TFIID in recruiting other components of the PIC to the promoter DNA and how the long observed conformational flexibility of TFIID plays a role in the regulation of transcription initiation.”

    Proteins have traditionally been studied using X-ray crystallography, but that technique has not been possible for this kind of research. “TFIID has not been accessible to protein crystallography because there’s not enough material to crystallize it, it has very flexible elements, and it is of a huge size,” Nogales said. “All of those things we can overcome through cryo-EM.”

    Cryo-EM, in which samples are imaged at cryogenic temperatures without need for dyes or fixatives, has been used since the 1980s in structural biology. With extensive computational analysis of the images researchers are able to obtain three-dimensional structures. However, cryo-EM has undergone a revolution in the last few years with the advent of new detectors—developed, in fact, at Berkeley Lab—that improve resolution and reduce the amount of data needed by up to a hundred-fold.

    “Many biological systems we had thought were impossible to study at high resolution have become accessible,” she said. “Now the resolution allows us to get atomic details. This is an area in which Berkeley Lab has been one of the leaders.”

    While this study has revealed important new insights into gene expression, Nogales notes that much work remains to be done. Next she plans to investigate how TFIID is able to recognize different sequences for different gene types and also how it is regulated by cofactors and activators.

    “We are just at the beginning,” she said. “This complex, TFIID, is very, very critical. Now we have broken barriers in the sense that we can start generating atomic models and get into details of how DNA is being bound.”

    This research was supported by the National Institutes of Health’s National Institute of General Medical Sciences and by the Spanish Ministry of Economy and Competitiveness. Computational work was carried out at the National Energy Research Scientific Computing Center (NERSC), a DOE Office of Science User Facility hosted at Berkeley Lab. Nogales is a Senior Faculty Scientist in Berkeley Lab’s Molecular Biophysics and Integrated Bioimaging Division; additional information on her lab can be found here.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    A U.S. Department of Energy National Laboratory Operated by the University of California

    University of California Seal

    DOE Seal

     
  • richardmitnick 4:24 pm on February 29, 2016 Permalink | Reply
    Tags: , ,   

    From LBL: “New Form of Electron-beam Imaging Can See Elements that are ‘Invisible’ to Common Methods” 

    Berkeley Logo

    Berkeley Lab

    February 29, 2016
    Glenn Roberts Jr. 510-486-5582
    geroberts@lbl.gov

    Electrons can extend our view of microscopic objects well beyond what’s possible with visible light—all the way to the atomic scale. A popular method in electron microscopy for looking at tough, resilient materials in atomic detail is called STEM, or scanning transmission electron microscopy, but the highly focused beam of electrons used in STEM can also easily destroy delicate samples.

    This is why using electrons to image biological or other organic compounds, such as chemical mixes that include lithium—a light metal that is a popular element in next-generation battery research—requires a very low electron dose.

    Scientists at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have developed a new imaging technique, tested on samples of nanoscale gold and carbon, that greatly improves images of light elements using fewer electrons.

    The newly demonstrated technique, dubbed MIDI-STEM, for matched illumination and detector interferometry STEM, combines STEM with an optical device called a phase plate that modifies the alternating peak-to-trough, wave-like properties (called the phase) of the electron beam.

    1
    In MIDI-STEM (right), developed at Berkeley Lab, an electron beam travels through a ringed “phase plate,” producing a high-resolution image (bottom right) that provides details about a sample containing a heavy element (gold) and light element (carbon). Details about the carbon are missing in an image (bottom left) of the sample using a conventional electron imaging technique (ADF-STEM). (Colin Ophus/Berkeley Lab, Nature Communications: 10.1038/ncomms10719)

    This phase plate modifies the electron beam in a way that allows subtle changes in a material to be measured, even revealing materials that would be invisible in traditional STEM imaging.

    Another electron-based method, which researchers use to determine the detailed structure of delicate, frozen biological samples, is called cryo-electron microscopy, or cryo-EM. While single-particle cryo-EM is a powerful tool—it was named as science journal Nature’s 2015 Method of the Year—it typically requires taking an average over many identical samples to be effective. Cryo-EM is generally not useful for studying samples with a mixture of heavy elements (for example, most types of metals) and light elements like oxygen and carbon.

    “The MIDI-STEM method provides hope for seeing structures with a mixture of heavy and light elements, even when they are bunched closely together,” said Colin Ophus, a project scientist at Berkeley Lab’s Molecular Foundry and lead author of a study, published Feb. 29 in Nature Communications, that details this method.

    If you take a heavy-element nanoparticle and add molecules to give it a specific function, conventional techniques don’t provide an easy, clear way to see the areas where the nanoparticle and added molecules meet.

    “How are they aligned? How are they oriented?” Ophus asked. “There are so many questions about these systems, and because there wasn’t a way to see them, we couldn’t directly answer them.”

    While traditional STEM is effective for “hard” samples that can stand up to intense electron beams, and cryo-EM can image biological samples, “We can do both at once” with the MIDI-STEM technique, said Peter Ercius, a Berkeley Lab staff scientist at the Molecular Foundry and co-author of the study.

    The phase plate in the MIDI-STEM technique allows a direct measure of the phase of electrons that are weakly scattered as they interact with light elements in the sample. These measurements are then used to construct so-called phase-contrast images of the elements. Without this phase information, the high-resolution images of these elements would not be possible.

    2
    This animated representation shows a Berkeley Lab-developed technique called MIDI-STEM (at right) and conventional STEM (at left) that does not use a ringed object called a phase plate. In MIDI-STEM, an interference pattern (bottom right) introduced by the phase plate (top right) interacts with the electron beam before it travels through a sample (the blue wave in the center). As the phase of the sample (the distance between the peaks and valleys of the blue wave) changes, the electrons passing through the sample are affected and can be measured as a pattern (bottom right). (Colin Ophus/Berkeley Lab)

    In this study, the researchers combined phase plate technology with one of the world’s highest resolution STEMs, at Berkeley Lab’s Molecular Foundry, and a high-speed electron detector.

    They produced images of samples of crystalline gold nanoparticles, which measured several nanometers across, and the superthin film of amorphous carbon that the particles sat on. They also performed computer simulations that validated what they saw in the experiment.

    The phase plate technology was developed as part of a Berkeley Lab Laboratory Directed Research and Development grant in collaboration with Ben McMorran at University of Oregon.

    The MIDI-STEM technique could prove particularly useful for directly viewing nanoscale objects with a mixture of heavy and light materials, such as some battery and energy-harvesting materials, that are otherwise difficult to view together at atomic resolution.

    It also might be useful in revealing new details about important two-dimensional proteins, called S-layer proteins, that could serve as foundations for engineered nanostructures but are challenging to study in atomic detail using other techniques.

    In the future, a faster, more sensitive electron detector could allow researchers to study even more delicate samples at improved resolution by exposing them to fewer electrons per image.

    “If you can lower the electron dose you can tilt beam-sensitive samples into many orientations and reconstruct the sample in 3-D, like a medical CT scan. There are also data issues that need to be addressed,” Ercius said, as faster detectors will generate huge amounts of data. Another goal is to make the technique more “plug-and-play,” so it is broadly accessible to other scientists.

    Berkeley Lab’s Molecular Foundry is a DOE Office of Science User Facility. Researchers from the University of Oregon, Gatan Inc. and Ulm University in Germany also participated in the study.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    A U.S. Department of Energy National Laboratory Operated by the University of California

    University of California Seal

    DOE Seal

     
  • richardmitnick 1:38 pm on February 23, 2016 Permalink | Reply
    Tags: , , ,   

    From LBL: “Berkeley Lab, UC Berkeley Scientists to Participate in New NASA Space Telescope Project” 

    Berkeley Logo

    Berkeley Lab

    February 18, 2016
    Glenn Roberts Jr. 510-486-5582
    geroberts@lbl.gov

    Scientists at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and UC Berkeley will play a role in an upcoming space telescope project, formally set in motion this week by NASA, that will explore the mysteries of the expanding universe and observe alien worlds circling distant suns, among other science aims.

    The Wide Field Infrared Survey Telescope (WFIRST) will launch into its six-year mission from Cape Canaveral, Fla., in the mid-2020s. NASA’s Agency Program Management Council made the decision to move forward with the WFIRST mission.

    NASA WFIRST New
    WFIRST

    Saul Perlmutter, a Berkeley Lab astrophysicist and UC Berkeley astrophysics professor who shared the 2011 Nobel Prize in Physics for his research team’s discovery that our universe is expanding at an accelerating rate, will lead a 29-member scientific team, from 15 institutions, that will plan for the use of WFIRST supernovae observations to explore “dark energy,” the presumed cause of this mysterious acceleration.

    Saul Perlmutter
    Saul Perlmutter

    Tracing the history of the universe to its so-called cosmic dawn, gaining new insight about star and galaxy formation and evolution, finding faint dwarf galaxies, studying distant objects through a light-bending phenomenon known as gravitational lensing, and surfacing new details from objects near the center of the Milky Way are also among WFIRST’s goals. The telescope will be NASA’s next major astrophysics observatory following the launch of the James Webb Space Telescope [JWST] in 2018.

    NASA Webb telescope annotated
    JWST

    “The question that was raised with the 2011 Nobel Prize is, ‘Why is the universe’s expansion accelerating?’” Perlmutter said. “With this new mission we get the chance to begin exploring the nature of dark energy.”


    Download mp4 video here .

    He added, “We think that this detailed expansion history is our current best shot as to getting a hint at which explanations for the accelerating expansion of the universe are true: If it’s dark energy, is it constant in time or changing over time? And if it’s not dark energy, are there revisions needed in [Albert] Einstein’s theory of general relativity”—a sort of rule book for spacetime and other fundamental physics—to best explain this acceleration?

    Perlmutter and other Berkeley Lab scientists co-led earlier proposals, dating back to 1999, for a space telescope designed to study dark energy. The core dark energy mission of the earlier proposals, and more, can now be accomplished with WFIRST, Perlmutter noted.

    WFIRST is a 2.4-meter telescope with a primary mirror the same size as that of the Hubble Space Telescope.

    NASA Hubble Telescope
    NASA/ESA Hubble

    It has a field of view that is 100 times larger than Hubble’s infrared instrument and will measure light from an estimated billion galaxies.

    WFIRST is expected to discover thousands of exoplanets—planets outside our solar system. It will be equipped with a device called a coronagraph that will record information about the chemistry of atmospheres for dozens of nearby exoplanets by blocking out light from their central stars, creating an artificial eclipse.

    “In addition to its exciting capabilities for dark energy and exoplanets, WFIRST will provide a treasure trove of exquisite data for all astronomers,” said Neil Gehrels, WFIRST project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md. “This mission will survey the universe to find the most interesting objects out there.”

    In measuring the shapes, positions and distances of millions of galaxies, WFIRST will provide fresh data on dark matter—the mysterious, unseen stuff that can be measured through its gravitational effects and makes up most of the universe’s matter.

    Perlmutter noted that while his research team has used the Hubble telescope to study tens of Type Ia supernovae, WFIRST will gather more detailed information for thousands of supernovae. This precision should allow scientists to categorize Type Ia supernovae into different subclasses, he said.

    The telescope’s dark energy mission will include three separate surveys:

    A Type Ia Supernovae Survey will focus on the subclass of exploding stars that emit light in a narrow range of peak brightness. Type Ia supernovae are often referred to as standard candles because their common brightness provides researchers with a standard gauge of their distance from us. This survey, which will be the focus of Perlmutter’s team, will calculate the distance and redshift of Type Ia supernovae. Redshift is a measure of how light is stretched to redder wavelengths as the universe stretches during light’s multi-billion-year trip from the supernovae to us.
    A High Latitude Spectroscopic Survey will determine changes in the concentration of galaxies throughout the history of the universe by precisely measuring the distance and position of galaxies.
    A High Latitude Imaging Survey will study galaxies and galaxy clusters and calculate the mass distribution of the universe in 3-D. This can be useful in understanding the effects of dark energy over time and the evolution of the universe’s large-scale structure.

    Perlmutter’s team, which has received approval for a five-year NASA grant, will work over the next few years to identify scientific requirements for the telescope’s instruments and to help guide the capabilities of the instrumentation. A dozen of these Science Investigation Teams were formalized in early January to explore different areas of WFIRST science, including two teams focusing on the supernova measurements of dark energy.

    “We have to understand the exact properties of the instruments and figure out how to get the most precise measurements,” said David Rubin of the Space Telescope Science Institute in Maryland, a member of the WFIRST science team led by Perlmutter. “We also will conduct overall survey planning, including studies of possible ties with other observatories’ observations.”

    Wendy Freedman, a fellow team member at University of Chicago, said it’s gratifying to see the space telescope project moving forward.

    “With WFIRST, we should be able to graph a beautiful history of the expansion of the universe in unprecedented detail,” Freedman said. “This will be one for the textbooks, for years to come.”

    The Berkeley Lab-led WFIRST Science Investigation Team will include scientists from the Carnegie Institution of Washington; California Institute of Technology; Florida State University; Harvard University; Las Cumbres Observatory Global Telescope Network Inc.; NASA Goddard Space Flight Center; Space Telescope Science Institute; Texas A&M University; University of Chicago; University of Pennsylvania; University of Pittsburgh; University of Texas, Austin; University of Washington; and Yale University.

    As a principal investigator of the team, Perlmutter will serve on a Formulation Science Working Group that will include lead investigators from all of the WFIRST science teams.

    WFIRST is managed at NASA’s Goddard Space Flight Center in Greenbelt, Md., with participation by the Jet Propulsion Laboratory in Pasadena, Calif.; the Space Telescope Science Institute in Baltimore; the Infrared Processing and Analysis Center in Pasadena; and a science team comprised of members from U.S. research institutions across the country.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    A U.S. Department of Energy National Laboratory Operated by the University of California

    University of California Seal

    DOE Seal

     
  • richardmitnick 9:35 pm on February 3, 2016 Permalink | Reply
    Tags: , , , Mosaic-3 camera,   

    From LBL: “New Galaxy-hunting Sky Camera Sees Redder Better” 

    Berkeley Logo

    Berkeley Lab

    February 2, 2016
    Glenn Roberts Jr. 510-486-5582

    A newly upgraded camera that incorporates light sensors developed at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) is now one of the best cameras on the planet for studying outer space at red wavelengths that are too red for the human eye to see.

    Very distant astronomical objects appear much redder when observed on Earth due to an effect known as redshift, so this sensitivity to red light enables the camera to detect objects many billions of light years away.

    The camera has begun its two-year mission to quickly survey the sky, amassing images of hundreds of millions of galaxies and stars.

    NOAO Mayall 4 m telescope exterior
    NOAO Mayall 4 m telescope interior
    The 4-meter Mayall telescope at Kitt Peak National Observatory near Tucson, AR, USA

    The rebuilt camera, dubbed Mosaic-3, was installed in October on the 4-meter Mayall telescope at Kitt Peak National Observatory near Tucson, Ariz. It will survey the northern sky at infrared wavelengths from 850 nanometers to 1 micron, a range known as the “z-band.”

    Mosaic-3 will capture images nearly twice as fast as its predecessor camera, and can see galaxies 10 times fainter than those detected in a previous survey called the Sloan Digital Sky Survey [SDSS].

    SDSS Telescope
    SDSS telescope at Apache Point, NM, USA

    Mosaic-3 is the product of a small collaboration of scientists and engineers at Berkeley Lab, Yale University, and the National Optical Astronomy Observatory (NOAO).

    It will help to scout out galaxies that can be targeted for further observations by DESI, the Dark Energy Spectroscopic Instrument, which is scheduled to be installed on the Mayall telescope in 2018.

    DESI Dark Energy Spectroscopic Instrument
    DESI

    DESI, which will be built by a Berkeley Lab-led collaboration, will produce a 3-D map of the universe out to a distance of 12 billion light years. By measuring the velocities of millions of galaxies and extremely bright and distant objects known as quasars, DESI will chronicle the expansion history of the universe to unprecedented precision. It will yield a better understanding of “dark energy,” a mysterious form of energy that is causing this universal expansion to accelerate.

    Mosaic-3’s primary mission is to carry out a survey of roughly one-eighth of the sky (5,500 square degrees). This survey, known as the Mayall z-Band Legacy Survey (MzLS), will span about 220 nights of observations this year and next, and all of the camera’s data will be immediately available to the public. During the remaining nights, Mosaic-3 will be available to astronomers for other research.

    The z-band survey is just one layer in the galaxy survey that is locating targets for DESI. Data from this survey are being combined with data from other telescopes to produce images of galaxies in many colors, and the combined data will be publicly released twice per year on the Legacy Survey website.

    The Mosaic-3 camera is an upgrade that brings new cutting-edge sensors developed at Berkeley Lab to an existing, decade-old camera at the Mayall Telescope. The cryostat (a device used to maintain a supercool temperature) from this camera was refurbished to incorporate the new light sensors, and the electronics were replaced.

    “We rebuilt the whole camera,” said Charles Baltay, a Yale physics professor who oversaw the university’s work on Mosaic-3. “We started in early February and delivered it in August—we had to hustle. At first, people said we couldn’t do it this fast.”

    He added, “Mosaic-3 can measure the same object in half the time compared to its predecessor. It allows us to do the target-selection survey in time—it moves it from impossible to comfortable.”

    The piece of glass used as Mosaic-3’s filter for gathering infrared light appears perfectly black to the naked eye but transmits 98 percent of the incoming infrared light at the wavelengths it is scanning.

    Berkeley Lab supplied the charge-coupled devices (CCDs) that capture light and the readout system that translates the light into images, and Yale was responsible for new mechanical components and software. David Rabinowitz at Yale oversaw the software development, working closely with NOAO astronomers and engineers.

    Mosaic-3 is equipped with four CCDs, each measuring about 6 square inches and containing 16 megapixels. Each pixel in the CCDs is about 100 times larger in area than a pixel in an iPhone 6 camera sensor, and each Mosaic-3 CCD is about 50 times larger in area than the iPhone 6 camera sensor.

    “It’s really the light-gathering power that matters,” said Armin Karcher, a Berkeley Lab design engineer who built a compact, flexible readout system for the camera.

    The large pixel size and overall CCD size are key in gathering light, and the 0.5-millimeter thickness of the CCDs helps the CCDs see deeper into the infrared wavelengths.

    Steve Holland, an engineer at Berkeley Lab who invented these red-sensitive CCDs, said he was already engaged in the design of similar CCDs for the DESI project when Mosaic-3 launched. “It was serendipitous,” he said.

    Christopher Bebek, who manages Berkeley Lab’s CCD group and served as the lab’s liaison on the Mosaic-3 project, added, “This was like a dress rehearsal for detectors and electronics for DESI.” An updated CCD design is now in production for DESI, which will require 20 of these CCDs for its spectrograph system.

    The Mosaic-3 instrument upgrade was funded by the U.S. Department of Energy Office of Science through the DESI project, and by NOAO. The DESI project is managed by the Lawrence Berkeley National Laboratory.

    For more information about DESI, go here.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    A U.S. Department of Energy National Laboratory Operated by the University of California

    University of California Seal

    DOE Seal

     
  • richardmitnick 1:12 pm on December 19, 2015 Permalink | Reply
    Tags: , ,   

    From LBL: “News Center Diamonds May Be the Key to Future NMR/MRI Technologies” 

    Berkeley Logo

    Berkeley Lab

    December 16, 2015
    Lynn Yarris (510) 486-5375

    Berkeley Lab/UC Berkeley Researchers Increase NMR/MRI Sensitivity through Hyperpolarization of Nuclei in Diamond

    1
    The research group of Alex Pines has recorded the first bulk room-temperature NMR hyperpolarization of carbon-13 nuclei in diamond in situ at arbitrary magnetic fields and crystal orientations. (Photo by Christophoros Vassiliou)

    Researchers with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley have demonstrated that diamonds may hold the key to the future for nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) technologies

    In a study led by Alexander Pines, a senior faculty scientist with Berkeley Lab’s Materials Sciences Division and UC Berkeley’s Glenn T. Seaborg Professor of Chemistry, researchers recorded the first bulk room-temperature NMR hyperpolarization ​of carbon-13 nuclei in diamond in situ at arbitrary magnetic fields and crystal orientations. The signal of the hyperpolarized carbon-13 spins showed an enhancement of NMR/MRI signal sensitivity by many orders of magnitude above what is ordinarily possible with conventional NMR/MRI magnets at room temperature. Furthermore, this hyperpolarization was achieved with microwaves, rather than relying on precise magnetic fields for hyperpolarization transfer.

    Pines is the corresponding author of a paper in Nature Communications describing this study. The paper is titled Room-temperature in situ nuclear spin hyperpolarization from optically pumped nitrogen vacancy centers in diamond.

    Jonathan King, a member of Pines’ research group is the lead author. Other co-authors are Keunhong Jeong, Christophoros Vassiliou, Chang Shin, Ralph Page, Claudia Avalos and Hai-Jing Wang.

    2
    (From left) Claudia Avalos, Keunhong Jeong and Jonathan King were part of a team led by Alex Pines that used microwaves to enhance NMR/MRI signal sensitivity many orders of magnitude above what is ordinarily possible with conventional NMR/MRI magnets at room temperature. (Photo by Roy Kaltschmidt)

    The authors report the observation of a bulk nuclear spin polarization of six-percent, which is an NMR signal enhancement of approximately 170,000 times over thermal equilibrium. The signal of the hyperpolarized spins was detected in situ with a standard NMR probe without the need for sample shuttling or precise crystal orientation. The authors believe this new hyperpolarization technique should enable orders of magnitude sensitivity enhancement for NMR studies of solids and liquids under ambient conditions.

    “Our results in this study represent an NMR signal enhancement equivalent to that achieved in the pioneering experiments of Lucio Frydman and coworkers at the Weizmann Institute of Science, but using microwave-induced dynamic nuclear hyperpolarization in diamonds without the need for precise control over magnetic field and crystal alignment,” Pines says. “Room-temperature hyperpolarized diamonds open the possibility of NMR/MRI polarization transfer to arbitrary samples from an inert, non-toxic and easily separated source, a long sought-after goal of contemporary NMR/MRI technologies.”

    “These results are an important contribution that adds to a growing arsenal of tools being developed by experts throughout the world, including leading laboratories in the US, Europe, Japan and Israel, for creating a more sensitive NMR/MRI signature at easily attainable conditions,” says Frydman, a professor of chemistry at thes Weizmann Institute of Science. which is located in Israel, near Tel Aviv. “Achieving this could open up a plethora of applications in physics, chemistry and biology.”

    The combination of chemical specificity and non-destructive nature has made NMR and MRI indispensable technologies for a broad range of fields, including chemistry, materials, biology and medicine. However, sensitivity issues have remained a persistent challenge. NMR/MRI signals are based on an intrinsic quantum property of electrons and atomic nuclei called spin. Electrons and nuclei can act like tiny bar magnets with a spin that is assigned a directional state of either “up” or “down.” NMR/MRI signals depend upon a majority of nuclear spins being polarized to point in one direction – the greater the polarization, the stronger the signal. Over several decades Pines and members of his research group have developed numerous ways to hyperpolarize the spins of atomic nuclei. Their focus over the past two years has been on diamond crystals and an impurity called a nitrogen-vacancy (NV) center, in which optical and spin degrees of freedom are coupled.

    3

    “An NV center is created when two adjacent carbon atoms in the lattice of a pure diamond crystal are removed from the lattice leaving two gaps, one of which is filled with a nitrogen atom, and one of which remains vacant,” Pines explains. “This leaves unbound electrons in the center between the nitrogen atom and a vacancy that give rise to unique and well-defined electron spin polarization states.”

    In earlier studies, Pines and his group demonstrated that a low-strength magnetic field could be used to transfer NV center electron spin polarization to nearby carbon-13 nuclei, resulting in hyperpolarized nuclei. This spin transference process – called dynamic nuclear polarization – had been used before to enhance NMR signals, but always in the presence of high-strength magnetic fields and cryogenic temperatures. Pines and his group eliminated these requirements by placing a permanent magnet near the diamond.

    “In our new study we’re using microwaves to match the energy between electrons and carbon-13 nuclei rather than a magnetic field, which removes some difficult restrictions on the strength and alignment of the magnetic field and makes our technique more easy to use,” says King. “Also, in our previous studies, we inferred the presence of nuclear polarization indirectly through optical measurements because we weren’t able to test if the bulk sample was polarized or just the nuclei that were very close to the NV centers. By eliminating the need for even a weak magnetic field, we’re now able to make direct measurements of the bulk sample with NMR.”

    In their Nature Communications paper, Pines, King and the other co-authors say that hyperpolarized diamonds, which can be efficiently integrated into existing fabrication techniques to create high surface area diamond devices, should provide a general platform for polarization transfer.

    “We envision highly enhanced NMR of liquids and solids using existing polarization transfer techniques, such as cross-polarization in solids and cross-relaxation in liquids, or direct dynamic nuclear polarization to outside nuclei from NV centers,” King says, noting that such transfer of polarization to solid surface and liquids had been previously demonstrated by the Pines group using laser polarized Xe-129. “Our hyperpolarization technique based on optically polarized NV centers is far more robust and efficient and should be applicable to arbitrary target molecules, including biological systems that must be maintained at near ambient conditions.”

    This research was supported by the DOE Office of Science.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    A U.S. Department of Energy National Laboratory Operated by the University of California

    University of California Seal

    DOE Seal

     
  • richardmitnick 1:10 pm on December 14, 2015 Permalink | Reply
    Tags: , , ,   

    From LBL: “New Results from World’s Most Sensitive Dark Matter Detector” 

    Berkeley Logo

    Berkeley Lab

    December 14, 2015
    Glenn Roberts Jr. 510-486-5582

    Berkeley Lab Scientists Participate in Mile-deep Experiment in Former South Dakota Gold Mine

    The Large Underground Xenon (LUX) dark matter experiment, which operates nearly a mile underground at the Sanford Underground Research Facility (SURF) in the Black Hills of South Dakota, has already proven itself to be the most sensitive detector in the hunt for dark matter, the unseen stuff believed to account for most of the matter in the universe. Now, a new set of calibration techniques employed by LUX scientists has again dramatically improved the detector’s sensitivity.

    1
    A view inside the LUX detector. (Photo by Matthew Kapust/Sanford Underground Research Facility)

    Researchers with LUX are looking for WIMPs, or weakly interacting massive particles, which are among the leading candidates for dark matter. “We have improved the sensitivity of LUX by more than a factor of 20 for low-mass dark matter particles, significantly enhancing our ability to look for WIMPs,” said Rick Gaitskell, professor of physics at Brown University and co-spokesperson for the LUX experiment. “It is vital that we continue to push the capabilities of our detector in the search for the elusive dark matter particles,” Gaitskell said.

    LUX improvements, coupled to advanced computer simulations at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory’s (Berkeley Lab) National Energy Research Scientific Computing Center (NERSC) and Brown University’s Center for Computation and Visualization (CCV), have allowed scientists to test additional particle models of dark matter that now can be excluded from the search. NERSC also stores large volumes of LUX data—measured in trillions of bytes, or terabytes—and Berkeley Lab has a growing role in the LUX collaboration.

    Scientists are confident that dark matter exists because the effects of its gravity can be seen in the rotation of galaxies and in the way light bends as it travels through the universe. Because WIMPs are thought to interact with other matter only on very rare occasions, they have yet to be detected directly.

    2
    The LUX dark matter detector is seen here during the assembly process in a surface laboratory in South Dakota. (Photo by Matthew Kapust/Sanford Underground Research Facility)

    “We have looked for dark matter particles during the experiment’s first three-month run, but are exploiting new calibration techniques better pinning down how they would appear to our detector,” said Alastair Currie of Imperial College London, a LUX researcher.

    “These calibrations have deepened our understanding of the response of xenon to dark matter, and to backgrounds. This allows us to search, with improved confidence, for particles that we hadn’t previously known would be visible to LUX.”

    The new research is described in a paper submitted to Physical Review Letters. The work reexamines data collected during LUX’s first three-month run in 2013 and helps to rule out the possibility of dark matter detections at low-mass ranges where other experiments had previously reported potential detections.

    3
    A view of the LUX detector during installation. (Photo by Matthew Kapust/Sanford Underground Research Facility)

    LUX consists of one-third ton of liquid xenon surrounded with sensitive light detectors. It is designed to identify the very rare occasions when a dark matter particle collides with a xenon atom inside the detector. When a collision happens, a xenon atom will recoil and emit a tiny flash of light, which is detected by LUX’s light sensors. The detector’s location at Sanford Lab beneath a mile of rock helps to shield it from cosmic rays and other radiation that would interfere with a dark matter signal.

    So far LUX hasn’t detected a dark matter signal, but its exquisite sensitivity has allowed scientists to all but rule out vast mass ranges where dark matter particles might exist. These new calibrations increase that sensitivity even further.

    One calibration technique used neutrons as stand-ins for dark matter particles. Bouncing neutrons off the xenon atoms allows scientists to quantify how the LUX detector responds to the recoiling process.

    “It is like a giant game of pool with a neutron as the cue ball and the xenon atoms as the stripes and solids,” Gaitskell said. “We can track the neutron to deduce the details of the xenon recoil, and calibrate the response of LUX better than anything previously possible.”

    The nature of the interaction between neutrons and xenon atoms is thought to be very similar to the interaction between dark matter and xenon. “It’s just that dark matter particles interact very much more weakly—about a million-million-million-million times more weakly,” Gaitskell said.

    The neutron experiments help to calibrate the detector for interactions with the xenon nucleus. But LUX scientists have also calibrated the detector’s response to the deposition of small amounts of energy by struck atomic electrons. That’s done by injecting tritiated methane—a radioactive gas—into the detector.

    “In a typical science run, most of what LUX sees are background electron recoil events,” said Carter Hall a University of Maryland professor. “Tritiated methane is a convenient source of similar events, and we’ve now studied hundreds of thousands of its decays in LUX. This gives us confidence that we won’t mistake these garden-variety events for dark matter.”

    Another radioactive gas, krypton, was injected to help scientists distinguish between signals produced by ambient radioactivity and a potential dark matter signal.

    “The krypton mixes uniformly in the liquid xenon and emits radiation with a known, specific energy, but then quickly decays away to a stable, non-radioactive form,” said Dan McKinsey, a UC Berkeley physics professor and co-spokesperson for LUX who is also an affiliate with Berkeley Lab. By precisely measuring the light and charge produced by this interaction, researchers can effectively filter out background events from their search.

    “And so the search continues,” McKinsey said. “LUX is once again in dark matter detection mode at Sanford Lab. The latest run began in late 2014 and is expected to continue until June 2016. This run will represent an increase in exposure of more than four times compared to our previous 2013 run. We will be very excited to see if any dark matter particles have shown themselves in the new data.”

    McKinsey, formerly at Yale University, joined UC Berkeley and Berkeley Lab in July, accompanied by members of his research team.

    The Sanford Lab is a South Dakota-owned facility. Homestake Mining Co. donated its gold mine in Lead to the South Dakota Science and Technology Authority (SDSTA), which reopened the facility in 2007 with $40 million in funding from the South Dakota State Legislature and a $70 million donation from philanthropist T. Denny Sanford. The U.S. Department of Energy (DOE) supports Sanford Lab’s operations.

    Kevin Lesko, who oversees SURF operations and leads the Dark Matter Research Group at Berkeley Lab, said, “It’s good to see that the experiments installed in SURF continue to produce world-leading results.”

    The LUX scientific collaboration, which is supported by the DOE and National Science Foundation (NSF), includes 19 research universities and national laboratories in the United States, the United Kingdom and Portugal.

    “The global search for dark matter aims to answer one of the biggest questions about the makeup of our universe. We’re proud to support the LUX collaboration and congratulate them on achieving an even greater level of sensitivity,” said Mike Headley, Executive Director of the SDSTA.

    Planning for the next-generation dark matter experiment at Sanford Lab is already under way. In late 2016 LUX will be decommissioned to make way for a new, much larger xenon detector, known as the LUX-ZEPLIN (LZ) experiment.

    LZ project
    LZ schematic

    LZ would have a 10-ton liquid xenon target, which will fit inside the same 72,000-gallon tank of pure water used by LUX. Berkeley Lab scientists will have major leadership roles in the LZ collaboration.

    “The innovations of the LUX experiment form the foundation for the LZ experiment, which is planned to achieve over 100 times the sensitivity of LUX. The LZ experiment is so sensitive that it should begin to detect a type of neutrino originating in the Sun that even Ray Davis’ Nobel Prize-winning experiment at the Homestake mine was unable to detect,” according to Harry Nelson of UC Santa Barbara, spokesperson for LZ.

    LUX is supported by the DOE Office of Science. NERSC is a DOE Office of Science User Facility.

    A version of this release and additional materials are available on the Sanford Lab site.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    A U.S. Department of Energy National Laboratory Operated by the University of California

    University of California Seal

    DOE Seal

     
  • richardmitnick 9:23 am on December 14, 2015 Permalink | Reply
    Tags: , , Total-Body PET Scanner   

    From LBL: “Berkeley Lab Scientists to Help Build World’s First Total-Body PET Scanner” 

    Berkeley Logo

    Berkeley Lab

    October 21, 2015
    Dan Krotz 510-486-4019

    1

    Scientists from the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have set out to help build the world’s first total-body positron emission tomography (PET) scanner, a medical imaging device that could change the way cancers and other diseases are diagnosed and treated.

    The project is a consortium led by a UC Davis research team and includes scientists from Berkeley Lab and the University of Pennsylvania. It’s supported by a recently announced five-year, $15.5 million Transformative Research Award from the National Institutes of Health.

    The consortium’s goal is to build a PET scanner that images the entire human body simultaneously, a big jump from today’s PET scanners that only scan 20-cm segments at a time. In addition to being able to diagnose and track the trajectory of a disease in a way not possible today, a total-body PET scanner would reduce a patient’s radiation dose by a factor of 40, or decrease scanning time from 20 minutes to just 30 seconds.

    Berkeley Lab’s contribution, led by William Moses of the Molecular Biophysics and Integrated Bioimaging Division, is to develop electronics that send data collected by the scanner’s detectors to a computer, which converts the data into a three-dimensional image of the patient. The new scanner will have half a million detectors, and the data from each detector must be electronically transmitted to a computer, so the task is incredibly complex.

    “We’re developing the electronic interface between the detectors and the computer algorithm—and the electronics for this scanner is an order of magnitude more complicated than what’s been done before,” says Moses. “But Berkeley Lab has a long history developing instrumentation for nuclear medical imaging, including PET scanners, and this project is another milestone in our research.”

    2
    Berkeley Lab’s William Moses. No image credit.

    Other Berkeley Lab scientists involved in the project are Qiyu Peng, who is assisting Moses on the electronic instrumentation; and Bill Jagust, a longtime user of PET imaging techniques for clinical neurology research, who serves on an advisory board of medical doctors for the project.

    PET scans are used to diagnose and track a variety of diseases by showing how organs and tissues are functioning in the body. Typically, a radioactive tracer that targets a metabolic process specific to a disease is given to a patient. The PET scanner then detects where the tracer collects in the body, effectively imaging the disease itself. For example, tracers that accumulate in tumors are used to diagnose, stage, and follow treatment for cancer.

    For several decades, Berkeley Lab scientists have specialized in developing advanced electronic instrumentation for PET scanners and other medical imaging technologies. This effort has evolved into Berkeley Lab’s OpenPET project, a resource led by Woon-Seng Choong that enables scientists to collaborate on electronics for research-focused PET scanners.

    The total-body PET scanner is the latest project in Berkeley Lab’s PET-related research, coming at a time when technology has advanced to the point that it‘s possible to efficiently process the data generated from the scanner’s half a million detectors.

    To appreciate some of the challenges faced by the Berkeley Lab scientists in developing state-of-the-art instrumentation for the new PET scanner, consider how PET scanners work: As the radiotracer concentrates in the body, positrons in the tracer decay and emit gamma rays in opposite directions. These two gamma rays are detected by detectors on opposite sides of they body. Scintillating crystals convert the radiation to light, and a photosensor converts the light into an electrical signal.

    The time difference between the detection of the two gamma rays is used to determine where the positron is located along a line, which indicates where the radiotracer accumulates in the body. In order for this to work, the electronic instrumentation must have a time resolution of about 300 picoseconds (a picosecond is one trillionth of a second).

    “The time resolution has to be exceptionally good. It’s a challenge to do this with one detector, and to do that with half a million detectors introduces new challenges in terms of reproducibility and stability,” says Moses. “Our role is to ensure the detectors, and their associated electronics, have the spatial and temporal resolution to work at a total-body scale.”

    The scientists hope to have a prototype developed in about two years.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    A U.S. Department of Energy National Laboratory Operated by the University of California

    University of California Seal

    DOE Seal

     
c
Compose new post
j
Next post/Next comment
k
Previous post/Previous comment
r
Reply
e
Edit
o
Show/Hide comments
t
Go to top
l
Go to login
h
Show/Hide help
shift + esc
Cancel
%d bloggers like this: