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Printed, Flexible and Rechargeable Battery Can Power Wearable Sensors

Nanoengineers at the University of California San Diego have developed the first printed battery that is flexible, stretchable and rechargeable. The zinc batteries could be used to power everything from wearable sensors to solar cells and other kinds of electronics. The work appears in the April 19, 2017 issue of Advanced Energy Materials.

Neutrons Provide the First Nanoscale Look at a Living Cell Membrane

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How X-Rays Helped to Solve Mystery of Floating Rocks

Experiments at Berkeley Lab's Advanced Light Source have helped scientists to solve a mystery of why some rocks can float for years in the ocean, traveling thousands of miles before sinking.

Special X-Ray Technique Allows Scientists to See 3-D Deformations

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Neptune: Neutralizer-Free Plasma Propulsion

The most established plasma propulsion concepts are gridded-ion thrusters that accelerate and emit a larger number of positively charged particles than those that are negatively charged. To enable the spacecraft to remain charge-neutral, a "neutralizer" is used to inject electrons to exactly balance the positive ion charge in the exhaust beam. However, the neutralizer requires additional power from the spacecraft and increases the size and weight of the propulsion system. Researchers are investigating how the radio-frequency self-bias effect can be used to remove the neutralizer altogether, and they report their work in this week's Physics of Plasmas.

Report Sheds New Insights on the Spin Dynamics of a Material Candidate for Low-Power Devices

In a report published in Nano LettersArgonne researchers reveal new insights into the properties of a magnetic insulator that is a candidate for low-power device applications; their insights form early stepping-stones towards developing high-speed, low-power electronics that use electron spin rather than charge to carry information.

Researchers Find Computer Code That Volkswagen Used to Cheat Emissions Tests

An international team of researchers has uncovered the mechanism that allowed Volkswagen to circumvent U.S. and European emission tests over at least six years before the Environmental Protection Agency put the company on notice in 2015 for violating the Clean Air Act. During a year-long investigation, researchers found code that allowed a car's onboard computer to determine that the vehicle was undergoing an emissions test.

Physicists Discover That Lithium Oxide on Tokamak Walls Can Improve Plasma Performance

A team of physicists has found that a coating of lithium oxide on the inside of fusion machines known as tokamaks can absorb as much deuterium as pure lithium can.

Scientists Perform First Basic Physics Simulation of Spontaneous Transition of the Edge of Fusion Plasma to Crucial High-Confinement Mode

PPPL physicists have simulated the spontaneous transition of turbulence at the edge of a fusion plasma to the high-confinement mode that sustains fusion reactions. The research was achieved with the extreme-scale plasma turbulence code XGC developed at PPPL in collaboration with a nationwide team.

Green Fleet Technology

New research at Penn State addresses the impact delivery trucks have on the environment by providing green solutions that keep costs down without sacrificing efficiency.


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Rensselaer Polytechnic Institute Graduates Urged to Embrace Change at 211th Commencement

Describing the dizzying pace of technological innovation, former United States Secretary of Energy Ernest J. Moniz urged graduates to "anticipate career change, welcome it, and manage it to your and your society's benefit" at the 211th Commencement at Rensselaer Polytechnic Institute (RPI) Saturday.

ORNL Welcomes Innovation Crossroads Entrepreneurial Research Fellows

Oak Ridge National Laboratory today welcomed the first cohort of innovators to join Innovation Crossroads, the Southeast region's first entrepreneurial research and development program based at a U.S. Department of Energy national laboratory.

Department of Energy Secretary Recognizes Argonne Scientists' Work to Fight Ebola, Cancer

Two groups of researchers at Argonne earned special awards from the office of the U.S. Secretary of Energy for addressing the global health challenges of Ebola and cancer.

Jefferson Science Associates, LLC Recognized for Leadership in Small Business Utilization

Jefferson Lab/Jefferson Science Associates has a long-standing commitment to doing business with and mentoring small businesses. That commitment and support received national recognition at the 16th Annual Dept. of Energy Small Business Forum and Expo held May 16-18, 2017 in Kansas City, Mo.

Rensselaer Polytechnic Institute President's Commencement Colloquy to Address "Criticality, Incisiveness, Creativity"

To kick off the Rensselaer Polytechnic Institute Commencement weekend, the annual President's Commencement Colloquy will take place on Friday, May 19, beginning at 3:30 p.m. The discussion, titled "Criticality, Incisiveness, Creativity," will include the Honorable Ernest J. Moniz, former Secretary of Energy, and the Honorable Roger W. Ferguson Jr., President and CEO of TIAA, and will be moderated by Rensselaer President Shirley Ann Jackson.

ORNL, University of Tennessee Launch New Doctoral Program in Data Science

The Tennessee Higher Education Commission has approved a new doctoral program in data science and engineering as part of the Bredesen Center for Interdisciplinary Research and Graduate Education.

SurfTec Receives $1.2 Million Energy Award to Develop Novel Coating

The Department of Energy has awarded $1.2 million to SurfTec LLC, a company affiliated with the U of A Technology Development Foundation, to continue developing a nanoparticle-based coating to replace lead-based journal bearings in the next generation of electric machines.

Ames Laboratory Scientist Inducted Into National Inventors Hall of Fame

Iver Anderson, senior metallurgist at Ames Laboratory, has been inducted into the National Inventors Hall of Fame.

DOE HPC4Mfg Program Funds 13 New Projects to Improve U.S. Energy Technologies Through High Performance Computing

A U.S. Department of Energy (DOE) program designed to spur the use of high performance supercomputers to advance U.S. manufacturing is funding 13 new industry projects for a total of $3.9 million.

Penn State Wind Energy Club Breezes to Victory in Collegiate Wind Competition

The Penn State Wind Energy Club breezed through the field at the U.S. Department of Energy Collegiate Wind Competition 2017 Technical Challenge, held April 20-22 at the National Wind Technology Center near Boulder, Colorado--earning its third overall victory in four years at the Collegiate Wind Competition.


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Casting a Wide Net

Designed molecules will provide positive impacts in energy production by selectively removing unwanted ions from complex solutions.

New Software Tools Streamline DNA Sequence Design-and-Build Process

Enhanced software tools will accelerate gene discovery and characterization, vital for new forms of fuel production.

The Ultrafast Interplay Between Molecules and Materials

Computer calculations by the Center for Solar Fuels, an Energy Frontier Research Center, shed light on nebulous interactions in semiconductors relevant to dye-sensitized solar cells.

Supercapacitors: WOODn't That Be Nice

Researchers at Nanostructures for Electrical Energy Storage, an Energy Frontier Research Center, take advantage of nature-made materials and structure for energy storage research.

Groundwater Flow Is Key for Modeling the Global Water Cycle

Water table depth and groundwater flow are vital to understanding the amount of water that plants transmit to the atmosphere.

Finding the Correct Path

A new computational technique greatly simplifies the complex reaction networks common to catalysis and combustion fields.

Opening Efficient Routes to Everyday Plastics

A new material from the Inorganometallic Catalyst Design Center, an Energy Frontier Research Center, facilitates the production of key industrial supplies.

Fight to the Top: Silver and Gold Compete for the Surface of a Bimetallic Solid

It's the classic plot of a buddy movie. Two struggling bodies team up to drive the plot and do good together. That same idea, when it comes to metals, could help scientists solve a big problem: the amount of energy consumed by making chemicals.

Saving Energy Through Light Control

New materials, designed by researchers at the Center for Excitonics, an Energy Frontier Research Center, can reduce energy consumption with the flip of a switch.

Teaching Perovskites to Swim

Scientists at the ANSER Energy Frontier Research Center designed a two-component layer protects a sunlight-harvesting device from water and heat.


Low-Energy RHIC Electron Cooling Gets Green Light, Literally

Article ID: 674439

Released: 2017-05-10 09:05:50

Source Newsroom: Brookhaven National Laboratory

  • Credit: Brookhaven National Laboratory

    Zhi Zhao, Michiko Minty, and Patrick Inacker wearing protective goggles with the tabletop housing the components that create the green fiber laser in the foreground. Team member Brian Sheehy, now retired, was not present for the photo.

  • Credit: Brookhaven National Laboratory

    The laser must stay precisely aligned as it zigzags through amplification and frequency-doubling components on this tabletop—anchored for stability to a 50-ton steel block buried deep underground. The beam then travels through a 27-meter-long vacuum transfer line to strike its electron-generating target inside a photocathode electron gun.

  • Credit: Brookhaven National Laboratory

    View of the high-power green laser during a test after it has been transported into the vacuum chamber, deflected off the photocathode, and finally deflected back out of the vacuum chamber, confirming proper alignment.

Aligning a sequence of amplifiers and mirrors with hair-thin precision on a tabletop anchored to a steel block deep underground, scientists at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory have produced a powerful green laser. The light—the highest average power green laser ever generated by a single fiber-based laser—will be crucial to experiments in nuclear physics at the Lab’s Relativistic Heavy Ion Collider (RHIC).

“When the green light strikes a target 27 meters downstream from this tabletop, it will generate pulses of electrons needed to cool the ion beams at RHIC to keep them colliding,” said Brookhaven physicist Zhi Zhao, who built the laser system and is lead author on a paper describing its attributes in Optics Express, a journal of the Optical Society of America. In addition to cooling ion beams at RHIC, such a high-power green laser could also have applications in materials processing, laser machining, and generating other lasers.

Using electrons to cool ion beams

High collision rates at RHIC generate reams of data for the 1,000 nuclear physicists who come to this DOE Office of Science User Facility to study the intricate details of the building blocks of matter. The collisions reduce the building blocks to their most primitive form—a soup of fundamental particles that mimics the conditions of the early universe. But as the ions circulate through RHIC’s 2.4-mile-circumference tunnels, they tend to heat up and spread apart, decreasing the chances that collisions will occur.

“Intra-beam scattering causes the ions to spread out and get lost, so the beam doesn’t survive,” said RHIC accelerator physicist Michiko Minty, a co-author on the paper and leader of the project to develop and integrate this laser into RHIC collider operations.

Heating is a particular problem when the ion beams are circulating at relatively low energies—in a range RHIC scientists are using to study interesting aspects of how the primordial soup transforms into more familiar protons and neutrons. So physicists at RHIC have been exploring ways to periodically inject a stream of relatively cool electrons to take away some of the ions’ heat.

“The whole point of electron cooling is to stop the spreading of the ion bunches to maximize the collision rate,” Minty said.

Electron cooling has been successful at other particle accelerators. But at RHIC physicists are exploring new strategies for generating electron beams at very high electron energies (billions of electron volts), which requires using linear radiofrequency acceleration of energetic bunches.

“We have to make bunches of electrons that overlap with the ion bunches, and the ion bunches repeat. So we want to generate a set of pulse trains of electrons that co-propagate with the ions so the energy of the ions can get transferred to the electrons, making the ion beam shrink,” Minty said.

The idea is to use pulses of a laser to strike a photo-emissive material—a material that emits electrons when struck with just the right wavelength, or color, of light—inside a photocathode electron gun. In the case of the photocathode installed in the electron gun at RHIC, the magic color is green.

(Infra)red light, green light, 1, 2, 3!

To make the green light, the Brookhaven team started with something invisible, an infrared (IR) “seed” laser at relatively low power. They send modulated pulses of that invisible IR light through a series of optical fibers to amplify the power.

As the light from an additional IR “pump” laser enters the fiber, it excites electrons in the material lining the fiber. When these electrons relax back to their “ground state,” they emit photons of light at the IR wavelength, perfectly in sync with the seed IR waves, gradually increasing the signal strength in multiple fiber amplifier stages.

Once the desired power is reached, the infrared laser strikes a “frequency-doubling” crystal.

“When two photons of infrared light strike the crystal, it emits one photon of a shorter wavelength,” Zhao explained. “Frequency doubling essentially cuts the wavelength in half, changing the IR input to green visible light.”

The green laser light then zigzags along pathways guided by mirrors on the tabletop through various optical components to optimize the net laser output.  These include multiple crystals used to convert short laser pulses into a train of multiple pulses (temporal shaping), a variety of lenses to produce the desired transverse profile of the laser pulses (spatial shaping), and so-called half-wave plates used to pass or reject passage of the laser beam to control the overall laser intensity. 

After this, the laser light is guided to a series of electrical optical modulators—“devices that chop out sections of the laser light to produce the desired sequence of laser pulses—a sequence which matches the structure of the ion beams to be cooled,” Minty explained.

The goal is to time the pulses to match to the frequency of the electron gun so the resulting electrons can be accelerated to perfectly match the accelerated ions circulating in RHIC.

“In the end it’s the velocity of the ion beam that ‘decides’ what we need, and everything has to be matched to that. We get a signal from the ion accelerating cavities that is used to generate the timing signals for the components generating the laser pulse structure,” Minty said.

Anchoring and testing the light

Fiber lasers are especially well suited for generating high-brightness electron bunches in photocathode electron injectors. The high surface-to-volume ratio of the fiber supports the generation and delivery of laser pulses at high repetition rate and high average laser power. Also, the dynamics of the laser light propagating through the fiber leads to excellent laser profiles, low variations in the laser’s position, and maintenance-free operation. Taken together these properties result in long-term operation of a highly stable laser, which is essential for the RHIC physics programs.

Two key factors the scientists need to control are the laser’s extinction ratio—the difference between the laser being on and off—and its stability.

“If you have light present when it’s not supposed to be there, you’ll get residual electrons, which can produce unwanted effects,” Minty said. “We’re aiming for a factor of 10-6, which means when we say it’s off it’s off, and only one in a million electrons will come through.”

For stability, the scientists need to ensure that the path of the light doesn’t deviate more than 10 microns from its starting point to the photocathode gun in the RHIC tunnel, even with all the amplification steps and zigzag pathways on the tabletop.

“Overall, the path is about 30 meters—3 meters on the tabletop with 40 mirrors creating the zigzag path and 27 meters in the transfer line,” said Zhao, standing inside the mobile trailer housing the laser outside the RHIC ring.  

“We stabilized the table by digging a big hole and burying a 50-ton steel block down at the level of Long Island’s water table, and drilled holes in the trailer to secure the laser table to that block,” Minty said. “You can jump up and down on the floor in here and the table won’t move,” she added, pointing out super stable posts that hold mirrors and other key components on the motion-isolated table. 

Also, the long evacuated pipes through which the laser travels are decoupled from multiple smaller optical tables between the trailer and the electron gun located inside the RHIC enclosure.  These tables house optics and mirrors with supports likewise designed for thermal and vibrational stability.

The team—which also included Brian Sheehy (recently retired) and a new addition, Patrick Inacker—has already achieved two significant milestones for the Low-Energy Electron Cooling Experiment. On March 9, 2017, they successfully transported an alignment laser through the entire laser transport system, followed on April 5 by the first successful transport using the green laser light. First tests of electron cooling are anticipated to begin during RHIC operations in late 2018 and early 2019.

This work was funded by the DOE Office of Science.

Brookhaven National Laboratory is supported by the Office of Science of the U.S. Department of Energy.  The Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time.  For more information, please visit science.energy.gov.