From M.I.T.: “New solar-cell design based on dots and wires”

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MIT researchers improve efficiency of quantum-dot photovoltaic system by adding a forest of nanowires.

March 25, 2013
David L. Chandler

“Using exotic particles called quantum dots as the basis for a photovoltaic cell is not a new idea, but attempts to make such devices have not yet achieved sufficiently high efficiency in converting sunlight to power. A new wrinkle added by a team of researchers at MIT — embedding the quantum dots within a forest of nanowires — promises to provide a significant boost.”

Scanning Electron Microscope images show an array of zinc-oxide nanowires (top) and a cross-section of a photovoltaic cell made from the nano wires, interspersed with quantum dots made of lead sulfide (dark areas). A layer of gold at the top (light band) and a layer of indium-tin-oxide at the bottom (lighter area) form the two electrodes of the solar cell.
Images courtesy of Jean, et al/Advanced Materials

See the full article here.

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From Fermilab- “Frontier Science Result: MINOS Does matter matter for neutrino flavor?”

Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

Friday, March 15, 2013
Zeynep Isvan, Brookhaven National Laboratory

“The NuMI (Neutrinos at the Main Injector) beam is generated here at Fermilab and points toward the Soudan Underground Laboratory in Soudan, Minn. The MINOS collaboration detects this beam of neutrinos in its journey twice: once at Fermilab right after it is generated and once at Soudan Lab after the neutrinos have traveled 450 miles through the Earth’s crust. At its generation, the beam is made up of muon-flavored neutrinos (neutrinos come in three flavors: electron, muon, and tau). After traveling such a long distance, some of the neutrinos change flavor, primarily into and a few into electron neutrinos. This phenomenon of flavor change is called neutrino oscillation. By counting the number (and measuring the energy) of muon neutrinos before and after travel, MINOS can measure parameters that govern neutrino oscillations.

By combining its neutrino and antineutrino data sets, MINOS has constrained the non-standard interaction parameter εμτ, finding that the results are consistent with εμτ=0, shown by the gray line. The angle θ and the parameter Δm2 relate to the relative masses of the neutrinos and to how quantum mechanically “mixed” the flavors are.

The presence of matter in the neutrino path may also have an impact on flavor change. If it does, the flavor count after travel would be altered. Some of these interactions are expected from the tiny number of oscillation-generated electron neutrinos, but extra interactions of muon or tau neutrinos with the Earth are non-standard and are thus called non-standard interactions, or NSI for short. (The Earth is made up of regular matter—electrons, protons and neutrons—and not of matter in muon or tau flavors.)

Because of its magnetized detectors, MINOS remains the most suitable experiment to further investigate NSI. Starting this spring, MINOS+ will collect data in a complementary energy regime. This will allow for a more precise determination of the impact of NSI in neutrino flavor change.”

See the full article here.

Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics.

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From PPPL: “Rajesh Maingi adds a new strategic dimension to fusion and plasma physics research”

March 14, 2013
John Greenwald

“Physicist Rajesh Maingi remembers nearly everything. Results of experiments he did 20 years ago play back instantly in his mind, as do his credit card and bank account numbers.

Rajesh Maingi. (Photo credit: Elle Starkman )

Maingi brings his expertise to the new position of manager of edge physics and plasma-facing components at the U.S. Department of Energy’s Princeton Plasma Physics Laboratory (PPPL). The recently created post calls for coordinating all Laboratory research on the volatile edge of the plasma, which must be carefully controlled for fusion to take place, and on the crucial boundary between the plasma and the interior surfaces of a tokamak.

Tokamak

At PPPL

The strategic position adds a new dimension to research at PPPL. ‘We’ve decided to pull all our activities in this area together and plan how to use them to make an impact in the fusion community and the world,’ said Michael Zarnstorff, deputy director for research at the Laboratory. ‘Rajesh is well-known around the world, particularly in tokamak physics. He has experience and perspective and strategic vision, and we see him as a great opportunity for the Lab.’”

See the full article here.

Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University.

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From CERN: “Still making tracks: Eighty Years of the Positron”

March 15, 2013
Kelly Ann Izlar

“Eighty years ago today, the journal Physical Review published a paper by physicist Carl Anderson announcing the discovery of the positron.

The positron is the antimatter counterpart of the electron. The two particles have identical masses but opposite charges. When an electron and a positron interact, they annihilate in a burst of energy, producing two gamma rays.

LEP at CERN

In the early 1930s, Anderson and his mentor, Robert Millikan, were using a cloud chamber to measure high-energy cosmic rays.

A cloud chamber’s sealed cavity contains a supersaturated vapour, usually water or alcohol, which condenses around ion trails left behind by fast-moving charged particles, allowing them to be seen as they pass through. Physicists can deduce the charge of a particle from the way it curves when the chamber is subjected to a magnetic field.

In August of 1932, Anderson photographed the track of a high-energy particle with a mass about the same as an electron’s but with a positive charge. By measuring both the energy the particle lost in crossing a lead plate within the chamber and the length of the track on the other side of the lead, he determined an upper limit for the particle’s mass. He found it to be of the same order of magnitude as the electron’s mass.

Anderson had observed a new kind of particle, which he named the positron. It was soon to be identified as the first antiparticle, the antielectron.”

Meet CERN in a variety of places:

Cern Courier

THE FOUR MAJOR PROJECT COLLABORATIONS

ATLAS

ALICE

CMS

LHCb

LHC

Quantum Diaries

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From Berkeley Lab: “Building the Massive Simulation Sets Essential to Planck Results”

Berkeley Lab

Using NERSC supercomputers, Berkeley Lab scientists generate thousands of simulations to analyze the flood of data from the Planck mission

March 14, 2013
Paul Preuss

“To make the most precise measurement yet of the cosmic microwave background (CMB) – the remnant radiation from the big bang – the European Space Agency’s (ESA’s) Planck satellite mission has been collecting trillions of observations of the sky since the summer of 2009. On March 21, 2013, ESA and NASA, a major partner in Planck, will release preliminary cosmology results based on Planck’s first 15 months of data. The results have required the intense creative efforts of a large international collaboration, with significant participation by the U.S. Planck Team based at NASA’s Jet Propulsion Laboratory (JPL).

From left, Reijo Keskitalo, Aaron Collier, Julian Borrill, and Ted Kisner of the Computational Cosmology Center with some of the many thousands of simulations for Planck Full Focal Plane 6. (Photo by Roy Kaltschmidt)

‘NERSC supports the entire international Planck effort,’ says Julian Borrill of the Computational Research Division (CRD) , who cofounded C3 in 2007 to bring together scientists from CRD and the Lab’s Physics Division. ‘Planck was given an unprecedented multi-year allocation of computational resources in a 2007 agreement between DOE and NASA, which has so far amounted to tens of millions of hours of massively parallel processing, plus the necessary data-storage and data-transfer resources.’

JPL’s Charles Lawrence, Planck Project Scientist and leader of the U.S. team, says that ‘without the exemplary interagency cooperation between NASA and DOE, Planck would not be doing the science it’s doing today.’”

See the full article here.

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

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FRom PPPL: "A fast new method for measuring hard-to-diagnose 3D plasmas in fusion facilities"

March 12, 2013
John Greenwald

“Scientists at the U.S. Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) and the National Institute for Fusion Science (NIFS) in Japan have developed a rapid method for meeting a key challenge for fusion science. The challenge has been to simulate the diagnostic measurement of plasmas produced by twisting, or 3D, magnetic fields in fusion facilities. While such fields characterize facilities called stellarators, otherwise symmetric, or 2D, facilities such as tokamaks also can benefit from 3D fields.

A cutaway view of the ITER Project Tokamak reactor.

Researchers led by PPPL physicist Sam Lazerson have now created a computer code that simulates the required diagnostics, and have validated the code on the Large Helical Device stellarator in Japan. Called ‘Diagno v2.0,’ the new program utilizes information from previous codes that simulate 3D plasmas without the diagnostic measurements. The addition of this new capability could, with further refinement, enable physicists to predict the outcome of 3D plasma experiments with a high degree of accuracy.

A simulated plasma in the Large Helical Device showing the thin blue saddle coils that researchers used to make diagnostic measurements with the new computer code. (Photo credit: Graphic by Sam Lazerson)

Lazerson and co-authors Satoru Sakakibara and Yasuhiro Suzuki of NIFS have published their paper online in the February issue of Plasma Physics and Controlled Fusion http://dx.doi.org/10.1088/0741-3335/55/2/025014. The journal also is using a Lazerson graphic of a simulated plasma on the cover of its print edition. “

See the full article here.

Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University.

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From Symmetry: “Spin”

Objects as large as a planet or as small as a photon can have the property of spin. Spin is also the reason we can watch movies in 3D.

March 07, 2013
Jim Pivarski, Fermilab

“Spin is the amount of rotation an object has, taking into account its mass and shape. This is also known as an object’s angular momentum.

All objects have some amount of angular momentum. A spinning coin has a little angular momentum; the moon orbiting the earth has a lot. Like energy, angular momentum is a conserved quantity: The total amount is constant, though it can flow from one object to another. When a spinning figure skater contracts her arms and rotates faster, her angular momentum is unchanged because a narrow object rotating quickly has the same angular momentum as a wide object rotating slowly.

Particles, as far as we know, are infinitesimal points of zero size. Yet they have measurable amounts of angular momentum. Does the concept of rotation even make sense for a featureless speck? Angular momentum seems to be a more foundational concept than rotation itself.

The angular momentum, or spin, of a single particle is restricted in strange ways. It can have only an integer value, and not all values are allowed for all particles. Electrons and quarks (particles of matter) can have a spin of –1 or +1; photons (particles of light) can have a spin of –2 or +2; and Higgs bosons must have a spin of 0.

Though particle spins are tiny, they have an impact on our everyday world. The spin property of photons allows us to create 3D movies. A movie theater simultaneously projects two images, one with positive-spin photons and the other with negative-spin photons. One side of a pair of 3D glasses filters out the positive-spin photons, and the other filters out the negative-spin photons. We therefore see one image with each eye. Our brains combine them to create the illusion of depth.

It is a fortunate accident of biology that humans have as many eyes as photons have spin states.”

Symmetry is a joint Fermilab/SLAC publication.

From Berkeley Lab: “Long Predicted Atomic Collapse State Observed in Graphene”

Berkeley Lab

Berkeley Lab researchers recreate elusive phenomenon with artificial nuclei

March 07, 2013
Lynn Yarris

“The first experimental observation of a quantum mechanical phenomenon that was predicted nearly 70 years ago holds important implications for the future of graphene-based electronic devices. Working with microscopic artificial atomic nuclei fabricated on graphene, a collaboration of researchers led by scientists with the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley have imaged the “atomic collapse” states theorized to occur around super-large atomic nuclei.

An artificial atomic nucleus made up of five charged calcium dimers is centered in an atomic-collapse electron cloud. (Image courtesy of Michael Crommie)

‘Atomic collapse is one of the holy grails of graphene research, as well as a holy grail of atomic and nuclear physics,’ says Michael Crommie, a physicist who holds joint appointments with Berkeley Lab’s Materials Sciences Division and UC Berkeley’s Physics Department. ‘While this work represents a very nice confirmation of basic relativistic quantum mechanics predictions made many decades ago, it is also highly relevant for future nanoscale devices where electrical charge is concentrated into very small areas.’”

Michael Crommie is a physicist who holds joint appointments with Berkeley Lab’s Materials Sciences Division and UC Berkeley’s Physics Department. (Photo by Roy Kaltschmidt)

See the full article here.

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

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From Berkeley Lab: “Searching for the Solar System’s Chemical Recipe”

Berkeley Lab

Berkeley Lab’s Chemical Dynamics Beamline points to why isotope ratios in interplanetary dust and meteorites differ from Earth’s

February 20, 2013
Paul Preuss

“By studying the origins of different isotope ratios among the elements that make up today’s smorgasbord of planets, moons, comets, asteroids, and interplanetary ice and dust, Mark Thiemens and his colleagues hope to learn how our solar system evolved. Thiemens, Dean of the Division of Physical Sciences at the University of California, San Diego, has worked on this problem for over three decades.

The protosun evolved in a hot nebula of infalling gas and dust that formed an accretion disk (green) of surrounding matter. Visible and ultraviolet light poured from the sun, irradiating abundant clouds of carbon monoxide, hydrogen sulfide, and other chemicals. Temperatures near the sun were hot enough to melt silicates and other minerals, forming the chondrules found in early meteoroids (dashed black circles). Beyond the “snowline” (dashed white curves), water, methane, and other compounds condensed to ice. Numerous chemical reactions contributed to the isotopic ratios seen in relics of the early solar system today.

In recent years his team has found the Chemical Dynamics Beamline of the Advanced Light Source (ALS) at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) to be an invaluable tool for examining how photochemistry determines the basic ingredients in the solar system recipe.

‘Mark and his colleagues Subrata Chakraborty and Teresa Jackson wanted to know if photochemistry could explain some of the differences in isotope ratios between Earth and what’s found in meteorites and interplanetary dust particles,’ says Musahid (Musa) Ahmed of Berkeley Lab’s Chemical Sciences Division, a scientist at the Chemical Dynamics Beamline who works with the UC San Diego team. ‘They needed a source of ultraviolet light powerful enough to dissociate gas molecules like carbon monoxide, hydrogen sulfide, and nitrogen. That’s us: our beamline basically provides information about gas-phase photodynamics.’”

At this point, I direct you to the full article. There is a lot going on here.

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

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From Berkeley Lab: “Searching for the Solar System’s Chemical Recipe”

Berkeley Lab

Berkeley Lab’s Chemical Dynamics Beamline points to why isotope ratios in interplanetary dust and meteorites differ from Earth’s

February 20, 2013
Paul Preuss

The protosun evolved in a hot nebula of infalling gas and dust that formed an accretion disk (green) of surrounding matter. Visible and ultraviolet light poured from the sun, irradiating abundant clouds of carbon monoxide, hydrogen sulfide, and other chemicals. Temperatures near the sun were hot enough to melt silicates and other minerals, forming the chondrules found in early meteoroids (dashed black circles). Beyond the “snowline” (dashed white curves), water, methane, and other compounds condensed to ice. Numerous chemical reactions contributed to the isotopic ratios seen in relics of the early solar system today. No image credit.

“By studying the origins of different isotope ratios among the elements that make up today’s smorgasbord of planets, moons, comets, asteroids, and interplanetary ice and dust, Mark Thiemens and his colleagues hope to learn how our solar system evolved. Thiemens, Dean of the Division of Physical Sciences at the University of California, San Diego, has worked on this problem for over three decades.

In recent years his team has found the Chemical Dynamics Beamline of the Advanced Light Source (ALS) at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) to be an invaluable tool for examining how photochemistry determines the basic ingredients in the solar system recipe.

‘Mark and his colleagues Subrata Chakraborty and Teresa Jackson wanted to know if photochemistry could explain some of the differences in isotope ratios between Earth and what’s found in meteorites and interplanetary dust particles,’ says Musahid (Musa) Ahmed of Berkeley Lab’s Chemical Sciences Division, a scientist at the Chemical Dynamics Beamline who works with the UC San Diego team. ‘They needed a source of ultraviolet light powerful enough to dissociate gas molecules like carbon monoxide, hydrogen sulfide, and nitrogen. That’s us: our beamline basically provides information about gas-phase photodynamics.’”

See the full article here.

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

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