November 21, 2013 — Stanford's Fermi Gamma-ray Large Area Space Telescope Detects Most Energetic Gamma-ray Burst On Record
(Story by Bjorn Carey. Reprinted from Stanford Report, November 21, 2013)
Animation showing high-energy gamma-
When the core of a massive star collapses,
This past April, an incredibly bright flash of light burst from near the constellation Leo. Originating billions of light years away, this explosion of light, called a gamma ray burst, has now been confirmed as the brightest gamma ray burst ever observed. Astronomers around the world were able to view the blast in unprecedented detail and observe several aspects of the event for the first time ever. The data could lead to a rewrite of standard theories of how gamma ray bursts work.
The blast, named GRB 130427A, was observed by several space- and ground-based telescopes, and the data was analyzed by dozens of astronomers around the world. The Fermi Gamma-ray Space Telescope was the first to detect the event, and it quickly began monitoring the flood of radiation using its Large Area Telescope (LAT), whose principal investigator is Peter Michelson, a physics professor at Stanford and the SLAC National Accelerator Laboratory. Michelson leads the international collaboration that built and operates the LAT.
Fermi's quick action, allowing the LAT to record nearly the entire event, yielded incredible data that revealed previously unknown aspects of the mechanisms involved in a gamma ray burst. The findings are reported in a series of papers published by the journal Science at the Science Express website on Nov. 21.
A special cosmic event
Several features of GRB 130427A combined to make it of particular interest to astronomers. First, its light traveled 3.6 billion years before arriving at Earth, about one-third the travel time for light from typical bursts. The record-setting 20 hours that the LAT observed gamma rays was longer than any other observed GRB. And, in addition to being the brightest GRB ever witnessed, it was also one of the most energetic. "When that happens, we start seeing features that we were not able to observe before," said Nicola Omodei, a research associate at Stanford's Hansen Experimental Physics Laboratory who led LAT data analysis for one of the Science papers. "Especially because it was very bright, you can uncover features that were not predicted by the standard models."
The leading theory explaining long gamma ray bursts such as GRB 130427A posits that they are created during the most energetic explosions in the cosmos, which occur when a very massive star collapses on itself. These explosions erupt a jet of elementary particles traveling at close to the speed of light. Within the jet, pressure, temperature and density are not uniform, creating internal shock waves that move inward and outward as faster regions within the jet collide with slower ones. As the jet travels outward, it collides with the interstellar medium to create additional shock waves, called "external shocks." Although details are not well understood, particles are accelerated at the shock front and, at the same time, interact with the surrounding electromagnetic fields. This causes particles to lose part of their energy emitting photons, through a process known as synchrotron radiation. The balance between the gain in energy from acceleration by the shock and the loss of energy due to synchrotron radiation dictates the maximum energy of the photons that can be emitted by such a system. The highest energy photons among these are classified as gamma rays and are detected by the LAT.
An unexpected observation
The observations of GRB 130427A, however, didn't quite match energy levels predicted by these models. For instance, the telescopes detected more photons, and more high-energy gamma rays, than theoretical models would predict for a burst of this magnitude. In particular, a few of these high-energy events are so energetic that they cannot be produced via existing models of synchrotron radiation from shock-accelerated particles. Additionally, the prevailing thought was that the brightest flashes were driven by the explosion's internal shock waves, but the evidence indicates that these photons were created externally. "It's like having a blanket that's too short. You pull it up to your chin and uncover your toes," Omodei said. "With our standard model, if you try to explain the pulse, you will fail to explain the energy."
The new observations don't rule out the existing model, but researchers will need to either amend portions of it or adopt a new theory altogether to account for these characteristics, said Giacomo Vianello, a postdoctoral scholar in Michelson's group and a co-author who performed LAT data analysis and interpretation on three of the Science papers. The microphysics of how particles are accelerated involves a certain amount of well-thought assumptions, and these assumptions therefore get built into the theoretical models used to predict the behavior of cosmic events. The assumptions are necessary in part because these events cannot be recreated in laboratory settings, he said, which highlights the critical role that observations play in the fine-tuning of fundamental physics theories.
"The really cool thing about this GRB is that because the exploding matter was traveling at the speed of light, we were able to observe relativistic shocks," Vianello said. "We cannot make a relativistic shock in the lab, so we really don't know what happens in it, and this is one of the main unknown assumptions in the model. These observations challenge the models and can lead us to a better understanding of physics."
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November 6, 2013 — A Particle Accelerator on a Silicon Chip
(Story by Mike Ross. Reprinted from Stanford Report, September 27, 2013)
A nanofabricated chip of fused silica just
The nanoscale patterns of SLAC and
Members of the Accelerator on a Chip
In an advance that could dramatically shrink particle accelerators for science and medicine, researchers used a laser to accelerate electrons at a rate 10 times higher than conventional technology in a nanostructured glass chip smaller than a grain of rice. The achievement was reported today in the journal Nature by a team including scientists from the U.S. Department of Energy's SLAC National Accelerator Laboratory and Stanford University.
"We still have a number of challenges before this technology becomes practical for real-world use, but eventually it would substantially reduce the size and cost of future high-energy particle colliders for exploring the world of fundamental particles and forces," said Joel England, the SLAC physicist who led the experiments. "It could also help enable compact accelerators and X-ray devices for security scanning, medical therapy and imaging, and research in biology and materials science."
Because it employs commercial lasers and low-cost, mass-production techniques, the researchers believe it will set the stage for new generations of "tabletop" accelerators. At its full potential, the new "accelerator on a chip" could match the accelerating power of SLAC's 2-mile-long linear accelerator in just 100 feet, and deliver a million more electron pulses per second. This initial demonstration achieved an acceleration gradient, or amount of energy gained per length of the accelerator, of 300 million electronvolts per meter. That's roughly 10 times the acceleration provided by the current SLAC linear accelerator. "Our ultimate goal for this structure is one billion electronvolts per meter, and we're already one-third of the way in our first experiment," said Stanford applied physics Professor Robert Byer, the principal investigator for this research.
Today's accelerators use microwaves to boost the energy of electrons. Researchers have been looking for more economical alternatives, and this new technique, which uses ultrafast lasers to drive the accelerator, is a leading candidate. Particles are generally accelerated in two stages. First they are boosted to nearly the speed of light. Then any additional acceleration increases their energy, but not their speed; this is the challenging part.
In the accelerator-on-a-chip experiments, electrons are first accelerated to near light-speed in a conventional accelerator. Then they are focused into a tiny, half-micron-high channel within a glass chip just half a millimeter long. The channel had earlier been patterned with precisely spaced nanoscale ridges. Infrared laser light shining on the pattern generates electrical fields that interact with the electrons in the channel to boost their energy. (View animation for more detail.)
Turning the accelerator on a chip into a full-fledged tabletop accelerator will require a more compact way to get the electrons up to speed before they enter the device. A collaborating research group in Germany, led by Peter Hommelhoff at Friedrich Alexander University and the Max Planck Institute of Quantum Optics, has been looking for such a solution. It simultaneously reports in Physical Review Letters its success in using a laser to accelerate lower-energy electrons.
Applications for these new particle accelerators would go well beyond particle physics research. Byer said laser accelerators could drive compact X-ray free-electron lasers, comparable to SLAC's Linac Coherent Light Source, that are all-purpose tools for a wide range of research. Another possible application is small, portable X-ray sources to improve medical care for people injured in combat, as well as to provide more affordable medical imaging for hospitals and laboratories. That's one of the goals of the Defense Advanced Research Projects Agency's Advanced X-Ray Integrated Sources program, which partially funded this research. Primary funding for this research is from the U.S. Department of Energy Office of Science.
The study's lead authors were Stanford graduate students Edgar Peralta and Ken Soong. Peralta created the patterned fused silica chips in the Stanford Nanofabrication Facility. Soong implemented the high-precision laser optics for the experiment at SLAC's Next Linear Collider Test Accelerator. Additional contributors included researchers from the University of California-Los Angeles and Tech-X Corp. in Boulder, Colo.
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September 1, 2013 — Sarah Church succeeds Peter Michelson as HEPL Director
An official "Sarach Church HEPL Director" cake
On September 1, 2013, physics professor Sarah Church became the new Director of HEPL. Professor Church is the eleventh person to oversee and direct the lab's activities during its 58-year history, beginning in 1951 when the lab was officially founded as the Stanford "High Energy Physics Lab" (also abbreviated HEPL). In 1990, the lab was renamed the" W.W. Hansen Experimental Physics Lab," honoring pioneering physicist and engineer, William W. Hansen.
The directorship of HEPL is a rotating position among the faculty members whose research programs are administered by HEPL. Having just completed his four-year term as HEPL Director, Professor Peter Michelson is keeping busy as Chairman of the Physics Department, as well as Principal Investigator of the NASA-funded Fermi Gamma-ray Large-Area Space Telescope program.
Professor Church, who heads the Church Group that builds instrumentation at centimeter and millimeter wavelengths to study the early universe, has kindly agreed to take the helm of HEPL for the next three-four years.
To commemorate this transition in HEPL leadership, an informal ceremony was held following the monthly HEPL Administrative Committee meeting on September 9, 2013, which was chaired by Professor Church. Refreshments were served, including a cake welcoming the new director, and all HEPL faculty and staff were invited to attend.
You can read more about the colorful history of HEPL and its previous directors on the About HEPL page of this web site.
January 29, 2013 — Fermi LAT Physicist, Roger Romani, wins 2013 Rossi Prize
(Reprinted from Stanford News: The Dish, January 29, 2013)
Stanford physics Professor, Roger W. Romani, will share the 2013 Rossi Prize with Alice Harding of NASA's Goddard Space Flight Center. The prize is being awarded to them by the American Astronomical Society for establishing a theoretical framework for understanding gamma-ray pulsars.
Gamma-ray pulsars are unusual cosmic objects: They are the remnants of massive stars that have exploded as supernovae and are now rapidly spinning neutron stars that emit gamma-ray photons and sometimes (but not always) radio photons. By elucidating the theoretical behavior of these irregular objects, Harding and Romani made possible many of the observations made with the Fermi Gamma-ray Space Telescope.
"While pulsars were discovered nearly 50 years ago via their radio emissions, it turns out that the radio pulses are just an energetically insignificant echo of the particle accelerators blasting away in these exotic stars' magnetospheres," said Romani. "Fermi, by detecting gamma rays from over 100 of these neutron stars, has revealed to us the heart of the pulsar machine."
"I am thrilled that Roger W. Romani's many contributions to our understanding of pulsars have been acknowledged in this way," said ROGER BLANDFORD, a physics professor at Stanford and the SLAC National Accelerator Laboratory and the 2013 winner of Britain's Royal Astronomical Society's highest honor, the Gold Medal.
"They have provided the essential connection between the basic theory of these fascinating objects and what we actually observe. This, in turn, has enabled the great discoveries made using Fermi," Blandford added.
The prize is awarded annually by the American Astronomical Society's High-Energy Astrophysics Division to recognize significant contributions in high-energy astrophysics. The award is named in honor of Bruno Rossi, an authority on cosmic ray physics and a pioneer in the field of X-ray astronomy.
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January 14, 2013 —Roger Blandford Receives Royal Astronomical Society's Top Honor
Britain’s Royal Astronomical Society has named Stanford University Physics Professor Roger Blandford as the 2013 winner of the Society’s highest honor, the Gold Medal. Blandford directs the Kavli Institute for Particle Astrophysics and Cosmology, which is jointly run by Stanford and SLAC National Accelerator Laboratory, and is a professor of particle physics and astrophysics at SLAC.
Up to two Gold Medals are presented annually, one for extraordinary lifetime achievement in astronomy and another for the same in geophysics. Blandford was selected to receive the 2013 astronomy medal on the basis of “his varied and inspirational contributions to theoretical astrophysics, as well as his service to the astrophysics research community at an international level.”
The accompanying citation calls out Blandford’s many contributions to theoretical astrophysics, including work that helped decipher the high-energy processes powering supermassive black holes in the centers of galaxies and lay the groundwork for the current model of cosmic jets. He has also studied relativistic effects in neutron stars and binary systems, the extraction of energy from black holes and the analysis of gravitational lensing, “an important tool for probing the nature of the as yet unidentified dark matter found throughout the universe,” the citation stated.
Also cited are less tangible qualities that have earned Blandford the respect of his colleagues and a leadership role in the field, including fellowships in the Royal Society and the American Academy of Arts and Sciences and memberships in the National Academy of Sciences and the American Astronomical Society. Blandford served as chair of Astro2010: The Astronomy and Astrophysics Decadal Survey, which provided valuable guidance for the future path of astrophysics research in the United States and worldwide.
“I am overwhelmed but delighted by this quite unexpected recognition,” Blandford said. “It makes me realize just how fortunate I am to be working at a time of great discovery in astrophysics and cosmology and to be grateful to my wonderful teachers, collaborators and students."
David MacFarlane, director of SLAC’s Particle Physics and Astrophysics Directorate, added his congratulations. “This is a wonderful and very appropriate recognition of Roger's research contributions and leadership in the astrophysics community, including his establishment at Stanford and SLAC of KIPAC as a world-leading institution in particle astrophysics and cosmology.”
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June 4, 2012 — Underground Search for Neutrino Properties Unveils First Results
Scientists studying neutrinos have found with the highest degree of sensitivity yet that these mysterious particles behave like other elementary particles at the quantum level. The results shed light on the mass and other properties of the neutrino and prove the effectiveness of a new instrument that will yield even greater discoveries in this area.
Photo of the Enriched Xenon Observatory
The Enriched Xenon Observatory 200
The Enriched Xenon Observatory 200 (EXO-200), an international collaboration led by Stanford University and the U.S. Department of Energy's (DOE) SLAC National Accelerator Laboratory, has begun one of the most sensitive searches ever for a mysterious mechanism called "neutrinoless double-beta decay" in which two neutrinos, acting as particle and antiparticle, do not emerge from the nucleus.
If this decay were observed, it would signal that neutrinos have a different quantum structure than other elementary particles. EXO-200, which is capable of detecting decays that happen, on average, only once every 1025 years (1 quadrillion times the age of the universe), did not observe this decay, which constitutes the strongest evidence yet that neutrinos behave like other particles.
"The result could only have been more exciting if we'd been hit by a stroke of luck and detected neutrinoless double-beta decay," said Giorgio Gratta, a professor of physics at Stanford University and spokesperson for EXO-200. "In the region where double-beta decay was expected, the detector recorded only one event. That means the background activity is very low and the detector is very sensitive. It's great news to say that we see nothing!"
EXO-200 has been able to all but rule out a previous, highly controversial result claiming to have detected the decay, and they've also been able to narrow down the mass of the neutrino to less than 140- to 380-thousandths of an electronvolt (the unit of mass used in particle physics). For comparison, the minuscule electron has a mass of roughly 500,000 electronvolts.
At the heart of EXO-200 is a thin-walled cylinder made of extremely pure copper. It is full of about 200 kilograms (about 440 pounds) of liquid xenon and buried 2,150 feet deep at the DOE's Waste Isolation Pilot Plant (WIPP), a New Mexico salt bed where low-level radioactive waste is stored. The xenon—in particular the isotope xenon-136, which makes up the lion's share of the xenon in EXO-200—is one of the few substances that can theoretically undergo the decay. Constructing the experiment of exceedingly pure materials and locating it underground ensured that all other traces of radioactivity and cosmic radiation are eliminated or kept at a minimum.
EXO-200 will take data for a few more years and in the future, the team hopes to expand the technique to a several-ton version that would be even more sensitive at observing the nearly imperceptible physical processes that have been theorized.
EXO is a collaboration that involves scientists from SLAC, Stanford, the University of Alabama, Universität Bern, Caltech, Carleton University, Colorado State University, University of Illinois Urbana-Champaign, Indiana University, UC Irvine, ITEP (Moscow), Laurentian University, the University of Maryland, the University of Massachusetts – Amherst, the University of Seoul and the Technische Universität München. This research was supported by DOE and NSF in the United States, NSERC in Canada, SNF in Switzerland and RFBR in Russia. This research used resources of the National Energy Research Scientific Computing Center (NERSC).
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May 13, 2012 — Restoring sight to the blind with a new photovoltaic retinal prosthesis
(Excerpted from a story by Jonathan Rabinovitz in the online newsletter, Inside Stanford Medicine.)
Biophysicist Daniel Palanker and team members from his lab recently published an article entitled: Photovoltaic retinal prosthesis with high pixel density in the June 2012 issue of the journal Nature Photonics.
In this article, the Palanker Group demonstrates, in both normal and degenerate rat retinas, a photovoltaic subretinal prosthesis in which the silicon photodiodes in each pixel receive power and data through pulsed near-infrared illumination.
Using tiny solar-panel-like cells surgically placed underneath the retina, scientists in HEPL's Palanker Lab, in collaboration with researchers from the Stanford Schools of Engineering and Medicine, have devised a system that may someday restore sight to people who have lost vision because of certain types of degenerative eye diseases.
This device — a new type of retinal prosthesis — involves a specially designed pair of goggles, which are equipped with a miniature camera and a pocket PC that is designed to process the visual data stream.The resulting images would be displayed on a liquid crystal microdisplay embedded in the goggles, similar to what's used in video goggles for gaming. Unlike the regular video goggles, though, the images would be beamed from the LCD using laser pulses of near-infrared light to a photovoltaic silicon chip — one-third as thin as a strand of hair — implanted beneath the retina.
Electric currents from the photodiodes on the chip would then trigger signals in the retina, which then flow to the brain, enabling a patient to regain vision.
Having demonstrated the viability of this technique using rat retinas to assess the photodiode arrays in vitro, as reported in the June 2012 Nature Photonics article, the Palanker Group is now testing the system in live rats, taking both physiological and behavioral measurements, and are hoping to find a sponsor to support tests in humans.
“It works like the solar panels on your roof, converting light into electric current,” said Daniel Palanker, PhD, associate professor of ophthalmology and the paper’s senior author. “But instead of the current flowing to your refrigerator, it flows into your retina.”
In addition to be a member of the HEPL research faculty, Palanker is also a member of the interdisciplinary Stanford research program, Bio-X. The study’s co-first authors are Keith Mathieson, PhD, a visiting scholar in Palanker’s lab, and James Loudin, PhD, a postdoctoral scholar. Palanker and Loudin jointly conceived and designed the prosthesis system and the photovoltaic arrays.
There are several other retinal prostheses being developed, and at least two of them are in clinical trials. A device made by the Los Angeles-based company Second Sight was approved in April for use in Europe, and another prosthesis-maker, a German company called Retina Implant AG, announced earlier this month results from its clinical testing in Europe.
But, unlike these other devices — which require coils, cables or antennas inside the eye to deliver power and information to the retinal implant — the Stanford device uses near-infrared light to transmit images, thereby avoiding any need for wires and cables, and making the device thin and easily implantable.
View San Francisco ABC Channel 7 News Story, Restoring Sight with a Tiny Chip, June 26, 2012
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August 19, 2011 — New method developed by HEPL's Solar Research Group detects emerging sunspots deep inside the sun
The first clear detection of emerging sunspot regions prior to any indication of the region in magnetograms was publishe today in the journal, Science.
Sunspots, dark features in the solar photosphere with strong magnetic field, have been observed for more than 400 years. They are the most visible components of regions where solar flares and coronal mass ejections (CMEs) occur, and these eruptive events may cause power outages and interruptions of telecommunication and navigation services on the Earth. Although it is widely believed that sunspot regions are generated in the deep solar interior, the detection of these regions before they emerge from the convection zone into the photosphere has remained undetected until now.
Movie showing the detected
KQED QUEST - Journey into the Sun
May 4, 2011 — Gravity Probe B Announces Final Experimental Results in Press/Media Event at NASA HQ
After 31 years of research and development, 10 years of flight preparation, a 1.5 year flight mission and 5 years of data analysis,the GP-B team has arrived at the final experimental results for this landmark test of Einstein’s 1916 general theory of relativity.
Graph of the results for each gyroscope
Click to view PRL paper (left) and
The results have been published in Physical Review Letters, Volume 106, Number 221101, 31 May 2011. Here is the abstract of the paper:
Gravity Probe B, launched 20 April 2004, is a space experiment testing two fundamental predictions of Einstein's theory of General Relativity (GR), the geodetic and frame-dragging effects, by means of cryogenic gyroscopes in Earth orbit. Data collection started 28 August 2004 and ended 14 August 2005. Analysis of the data from all four gyroscopes results in a geodetic drift rate of -6,601.8±18.3 mas/yr and a frame-dragging drift rate of -37:2±7.2 mas/yr, to be compared with the GR predictions of -6,606.1 mas/yr and -39.2 mas/yr, respectively ('mas' is milliarc-second; 1 mas= 4.848 X10-9 radians or 2.778 X10-7 degrees).
These experimental results are in agreement with Einstein's theoretical predictions of the geodetic effect with a 0.28% margin of error and the frame-dragging effect with a19% margin of error.
The PRL paper was accompanied by a Physics Viewpoint article written by Clifford Will, Professor of Physics at Washington University and Chairman of the GP-B Science Advisory Committee. The Viewpoint article is entitled Finally, Results from Graivty Probe B.
You can view/download thePhysics Viewpoint article, as well as the GP-B PRL paper from the American Physical Society website at: http://physics.aps.org/articles/v4/43
You can also download and view a PDF copy of th PRL paper in the GR-QC section of arXiv at: http://arxiv.org/abs/1105.3456
On May 4th, in a press and media event at NASA Headquarters, GP-B Principal Investigator, Francis Everitt announced the final results, and four other panelists discusssed various aspects of the program, its many accomplishments and the significance of the results to physicists and the scientific community at large.
This event, which was televised live on NASA TV and streamed live from the NASA TV website, featured a panel of five presenters:
The panel presentations were followed by a Question and Answer session for members of the press and media and others present in the NASA auditorium, as well as press and media representatives linked-in from other NASA centers.
For more information, see the following:
February, 2011 — HEPL's Igor Moskalenko and Stanford Professors Mark Brongersma and Juan Santiago Selected as 2010 APS Fellows
Story from Stanford Report, February 8, 2011
2010 Stanford APS Fellows.
From left: Igor Moskalenko,
Mark Brongersma and Juan
Santiago. (Photos courtesty
Stanford News Service)
Three Stanford scientists have been named fellows of the American Physical Society (APS), an honor bestowed upon members of the association by their peers. The APS was founded in 1889, and is dedicated to the advancement of physics.
The Stanford scholars join more than 200 other newly elected fellows chosen after extensive review. The total number of APS Fellows who may be elected in a given year is limited to one-half of 1 percent of the total APS membership.
The fellows are:
Igor Moskalenko, senior research scientist in the Hansen Experimental Physics Laboratory and the Kavli Institute for Particle Astrophysics and Cosmology. Moskalenko was nominated by the division of astrophysics and selected for his seminal contributions to gamma-ray astronomy, for making self-consistent computations of high-energy charged particle and gamma radiations from the galaxy and for making such calculations accessible to the astrophysics community world-wide. Moskalenko is part of the team working on the Large Area Telescope, which is the principal instrument on the Fermi Gamma Ray Space Telescope spacecraft launched in 2008. This project has increased knowledge of a number of cosmic phenomena, including pulsars, binary stars, galaxies, supernovas and cosmic rays.
Mark Brongersma, associate professor of materials science and engineering. Brongersma was nominated by the division of laser science and selected for pioneering contributions and seminal works on plasmonics and silicon nanophotonics. Brongersma’s research is focused on building and characterizing nanoscale electronic and optical devices. His work could lead to advances in semiconductors, telecommunications, chemistry and biology. Brongersma received a 2007 Walter J. Gores Award for Excellence in Teaching, the university’s highest teaching honor.
Juan Santiago, professor of mechanical engineering and director of the Stanford Microfluidics Laboratory. Santiago was nominated by the division of fluid dynamics and selected for insightful and manifold contributions to microfluidics, including novel measurement methods, characterization and explanation of electrically driven flow instabilities, and studies and engineering applications of electrically driven flows for pumps, separations and sample preparation. His work could be applied to genetic analysis, drug discovery, bioweapon detection, drug delivery and power generation. Santiago received one of the 2003 Presidential Early Career Awards for Scientists and Engineers, the nation’s highest honor for professionals at the outset of their independent research careers.
For more information, see:
January 12, 2011 — Fermi Large Area Telescope Team Awarded Rossi Prize
Story by Shawne Workman, SLAC Today
Group photo at the Fermi
LAT Collaboration meeting
in September, 2009.
(Photo: Fermi LAT
On Wednesday, January 12, 2011, SLAC and Stanford astrophysicist and HEPL Director, Peter Michelson, and UC Santa Cruz particle astrophysicist Bill Atwood received word that they and the entire Fermi Gamma-ray Space Telescope, Large Area Telescope team have received the 2011 Bruno Rossi Prize.
Each year, the High Energy Astrophysics Division (HEAD) of the American Astronomical Society awards the Rossi Prize for recent original research in high-energy astrophysics. AAS HEAD leaders sent Atwood and Michelson word of the honor by e-mail:
The 2011 Rossi prize is awarded to Bill Atwood, Peter Michelson, and the Fermi Gamma-Ray Space Telescope/LAT team for enabling, through the development of the Large Area Telescope, new insights into neutron stars, supernova remnants, cosmic rays, binary systems, active galactic nuclei, and gamma-ray bursts.
"Both Bill and I are gratified that we were named in the citation for the award," Michelson wrote in e-mail. "However, as we said in an e-mail message to the Fermi LAT Collaboration: ... we are both keenly aware of the myriad contributions made by members of the collaboration that includes scientists, engineers and technicians, and by the community at large. It was the team work and effort that has made the Fermi Mission and the Large Area Telescope the success we are now enjoying."
The prize, named in honor of cosmic ray researcher Bruno Rossi, is awarded "for a significant contribution to High Energy Astrophysics, with particular emphasis on recent, original work," according to the HEAD website. It includes a cash award, citation and an invitation for the recipient to give a lecture, often a plenary talk at the January meeting of the American Astronomical Society. Potential awardees are nominated by HEAD members each fall; final selection is made by the HEAD executive committee.
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Palanker Group's Laser Cataract Surgery Technique is Cover Story in November 17, 2010 Issue of Science Translational Medicine
Excerpted from a story by Jonathan Rabinovitz, Inside Stanford Medicine, November 17, 2010
A colorized image of a
cut made in a porcine
lens with a femto-
Imagine trying to cut by hand a perfect circle roughly one-third the size of a penny. Then consider that instead of a sheet of paper, you’re working with a scalpel and a thin, elastic, transparent layer of tissue, which both offers resistance and tears easily. And, by the way, you’re doing it inside someone’s eye, and a slip could result in a serious impairment to vision.
This standard step in cataract surgery — the removal of a disc from the capsule surrounding the eye’s lens, a procedure known as capsulorhexis — is one of the few aspects of the operation that has yet to be enhanced by technology, but new developments in guided lasers could soon eliminate the need for such manual dexterity. A paper from Stanford University School of Medicine, published as the Nov. 17, 2010 cover story in Science Translational Medicine, presents clinical findings about how one new system for femtosecond laser-assisted cataract surgery is not only safe but also cuts circles in lens capsules that are 12 times more precise than those achieved by the traditional method, as well as leaving edges that are twice as strong in the remaining capsule, which serves as a pocket in which the surgeon places the plastic replacement lens.
“The results were much better in a number of ways — increasing safety, improving precision and reproducibility, and standardizing the procedure,” said Daniel Palanker, PhD, associate professor of ophthalmology, who is the lead author of the paper. “Many medical residents are fearful of doing capsulorhexis, and it can be challenging to learn. This new approach could make this procedure less dependent on surgical skill and allow for greater consistency.” The senior author is William Culbertson, MD, professor of ophthalmology at the Bascom Palmer Eye Institute at the University of Miami.
of lens capsule extraction
by manual capsulorhexis
(Row A) are not as close
to being perfect circles
and less uniform than
those from laser
capsulotomy (Row B)
Image courtesy of
While the technology to perform this new approach — called a capsulotomy instead of capsulorhexis — is being developed by a number of private companies, this paper focuses on a specific system being produced by OpticaMedica Corp. of Santa Clara, Calif., which funded the study. Palanker, Culbertson and five other co-authors have equity stakes in the company; the remaining seven co-authors are company employees.
Cataract surgery is the most commonly performed surgery in the nation, with more than 1.5 million of these procedures done annually. The operation is necessary when a cloud forms in the eye’s lens, causing blurred and double vision and sensitivity to light and glare, among other symptoms.
“This will undoubtedly affect millions of people, as cataracts are so common,” said Palanker, though he expects that it will take time for the new procedure to be adopted. At present, the new procedure takes longer than the current standard, and it would cost more, with Medicare unlikely to cover it in the immediate future. “But there will be people who elect to have it done the new way if they can afford it. There are competitors coming out with related systems. This is what’s exciting. This technology is going to be picked up in the clinic.”
The other Stanford co- author is Mark Blumenkranz, MD, professor and chair of ophthalmology. Information about the Department of Ophthalmology, which also supported the work, is available at http://ophthalmology.stanford.edu/.
Read the full story:
For more information, see:
Femtosecond Laser–Assisted Cataract Surgery with Integrated Optical Coherence Tomography. D. V. Palanker, M. S. Blumenkranz, D. Andersen, M. Wiltberger, G. Marcellino, P. Gooding, D. Angeley, G. Schuele, B. Woodley, M. Simoneau, N. J. Friedman, B. Seibel, J. Batlle, R. Feliz, J. Talamo, W. Culbertson,. Science Translational Medicine 2, 58ra85 (2010).
March 2010 — Francis Everitt and Sir Roger Penrose Awarded 2010 Trotter Prize; Delivered Trotter Lectures at Texas A&M University
On Thursday, March 11, 2010, two physicists—Francis Everitt, Principal Investigator for the HEPL Gravity Probe B Program and Sir Roger Penrose from Oxford—were jointly awarded the ninth annual Trotter Prize at Texas A&M University. The annual Trotter event includes both a cash prize to the recipient(s) and an endowed public lecture series.
The Trotter Prize in Information, Complexity and Inference is awarded annually for pioneering contributions to the understanding of the role of information, complexity and inference in illuminating the mechanisms and wonder of nature.
The Trotter Lecture seeks to reveal connections between science and religion, often viewed in academia as non-overlapping, if not rival, worldviews. For this year’s Trotter Lecture, both Everitt and Penrose spoke on this topic. Everitt’s talk, entitled “Mystery in Science, Reason in Religion,” explored how mystery and moral discipline permeate both science and religion and how reason affects each in the context of Christian faith. Penrose’s talk, entitled “ Did the Universe Have a Beginning?” explored the philosophical implications of conformal cyclic cosmology (CCC), which Penrose offers as an alternative scheme to the prevailing Big Bang theory.
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EXO Takes Clean to an Extreme
Excerpted from a story by Lauren Knoche, Symmetry magazine
The triangular metal gadget
is an "APD Spider." It con-
nects EXO's light sensors—
the golden circles with
electronics that allow
scientists to read out the
from the experiment's
detector. Photo courtesy of
the EXO Collaboration.
Some particle physics experiments require an extraordinary degree of cleanliness and quiet. How far will they go to achieve this? Try etching tools with acid, setting up shop in a deep salt bed, putting equipment on stilts, and choreographing a 2100-kilometer truck ride so not a moment would be lost.
Just before midnight on November 3, 2009, a large truck loaded with 40 tons of cargo pulled away from the Stanford University campus. It carried the last shipment of laboratory equipment from Stanford to New Mexico for a high-energy physics experiment that will begin taking data this year.
Moving complicated experimental equipment is always a delicate process, but in this case the task was more challenging than usual. The experiment, called the Enriched Xenon Observatory 200, or EXO-200, is designed to look for an ultra-rare phenomenon that could reveal key secrets about the nature of the neutrino. This process is so rare that detecting just a few signals over the course of a year would be a triumph. Scientists have no hope of seeing these faint signals unless they eliminate every possible source of background radiation that could get in the way. Yet sources of radiation are everywhere—from cosmic ray particles that rain down from space to materials as common as copper, everyday tools, ordinary rocks, even the human body.
It had taken the 70 scientists and engineers of the EXO collaboration six years to design and assemble their detector—a tank that would hold 200 kilograms of liquid xenon cooled to a very low temperature and heavily shielded by onion-like layers of components. A fanatic degree of cleanliness prevailed at every step. Most of the components were not only assembled in clean rooms, but also shipped in those same clean rooms, shielded and sealed against contamination. Even so, the team choreographed and practiced every move to make sure those containers spent as little time as possible in the open air.
February 11, 2010 — Stanford Helioseismic and Magnetic Imager (HMI) Launches on NASA SDO Satellite
SDO Satellite launches on 11 Feb 2010
at 10:23AM EST. (42-second video;
Photo Credit: Pat Corkery, U.L.A.)
At 10:23 AM EST on Thursday, February 11, 2010,NASA's Solar Dynamic Observatory (SDO) lifted off from Cape Canaveral, FL aboard a United Launch Alliance Atlas V rocket in a picture-perfect launch. One of the three instruments on board the SDO is the Helioseismic and Magnetic Imager (HMI) developed collaboratively by the Stanford Solar Physics Group here in the HEPL lab and the Lockheed Martin Solar and Astrophysics Laboratory (LMSAL) in Palo Alto, CA.
Click on the launch photo thumbnail to the right to view a short video of the launch.
SDO is the first mission to be launched under NASA's new Living with a Star Program. It is designed to help scientists study the solar atmosphere and better understand the causes of solar variability and its effects on space weather. Specifically, the observatory will perform various measurements to help characterize the interior of the Sun, the Sun's magnetic field, the hot plasma of the solar corona and the extreme ultraviolet radiation that creates the ionosphere surrounding Earth and other planets.
The SDO satellite houses three scientific instruments:
The HMI instrument on a
test bench at NASA's
Goddard Space Flight
Center. (Click to view
HMI produces data to determine the interior sources and mechanisms of solar variability and how the physical processes inside the Sun are related to surface magnetic field and activity. It also produces data to enable estimates of the coronal magnetic field for studies of variability in the extended solar atmosphere which is where the Earth is. Solar variability that affects the Earth is called “space weather.”
The primary goal of the HMI investigation is to study the origin of solar variability and to characterize and understand the Sun’s interior and magnetic activity. Because of the turbulence in the convection zone near the surface, the Sun is figuratively ringing like a bell. By studying these oscillations of the visible surface of the Sun, considerable insight can be gained into the processes inside. In effect the solar turbulence is analogous to earthquakes. In a manner similar to the way seismologists can learn about the interior of the Earth by studying the waves generated in an earthquake, HMI’s helioseismologists will learn about the structure, temperature and flows in the solar interior.
HMI is a new and improved version of the Michelson Doppler Imager (MDI) instrument on the Solar and Heliospheric Observatory (SOHO). SOHO is a joint project of the European Space Agency and NASA. MDI was developed starting in 1988 by the same collaboration between Stanford and Lockheed Martin teams that developed HMI. SOHO/MDI was launched in December 1995. It is still operating well and has completed helioseismic and magnetic field observations of the Sun for all of solar cycle 23 and the beginning of cycle 24. HMI will continue these important measurements from space into the next solar cycle. It will observe the full solar disk in the Fe I absorption line at 6173Å with a resolution of 1 arc-second. Moreover, HMI will be able to measure the direction of the magnetic field, something MDI couldn't do!
The goal of SDO is to understand—striving towards a predictive capability—the solar variations that influence life on Earth and humanity’s technological systems. The mission seeks to determine how the Sun’s magnetic field is generated and structured, and how this stored magnetic energy is converted and released into the heliosphere and geospace in the form of solar wind, energetic particles, and variations in the solar irradiance. SDO is the most advanced spacecraft ever designed to study the Sun and its dynamic behavior. SDO will provide better quality, more comprehensive science data faster than any NASA spacecraft currently studying the Sun and its processes. SDO will unlock the secrets of how our nearest star sustains life on Earth and how it affects the planets of our solar system and beyond.
Following are a number of links for more information about the SDO program and the HMI Instrument:
December 17, 2009 — Dark Matter Search: Latest CDMS-II Results
Scientists believe that most of the matter in the universe neither emits nor absorbs light, but rather is "dark matter" which provides the gravitational scaffolding that caused normal matter to coalesce into the galaxies we see today. Particle physics theories suggest that dark matter may be composed of Weakly Interacting Massive Particles (WIMPs), with masses comparable to, or perhaps heavier than, the masses of atomic nuclei. Although such WIMPs would rarely interact with normal matter, they could occasionally scatter from an atomic nucleus like billiard balls, leaving a small amount of energy that might be detectable under the right conditions.
The Cryogenic Dark Matter Search (CDMS) experiment, located a half-mile underground at the Soudan mine in northern Minnesota, uses 30 detectors made of germanium and silicon in an attempt to detect such WIMP scatters.CDMS has been searching for dark matter at Soudan since 2003, and until now, the data have not yielded evidence for WIMPs, but there is good cause for optimism....
At 2:00 Pm on Thursday, December 17, 2009, scientists from the CDMS program announced the latest research findings in two simultaneous presentations—one in California and one in Illinois. The California presentation was given at Stanford's SLAC National Accelerator Laboratory by Southern Methodist University physicist and CDMS analysis coordinator, Jodi Cooley. The Illinois presentation was given by Lauren Hsu at the Fermi National Accelerator Laboratory in Batavia, Ill.
The essence of these presentations is that the recently completed analysis of the latest CDMS-II data set, collected in 2007-08, shows two events that have characteristics consistent with those expected from WIMPs. However, with only two such events detected, there is a ~25% chance that they could be due to background particles, rather than WIMPs, so this result cannot be deemed statistically significant. With the current detector setup, at least five events would have to have been detected in order to allay any seeds of doubt. But, rather than running the current dectector system for many more years, the CDMS team is taking advantage of new detector developments and, most important, trippling the number of detectors used in hopes of significantly increasing the number of events detected from these elusive particles.
Both the Cooley and Hsu presentations were videotaped and now can be viewed in various web video formats via links on the U.C. Berkeley CDMS web site (http://cdms.berkeley.edu). Likewise, PDF copies of the presentation slides and a summary of the latest results are available for downloading from this site.
See also, the December 2009 Web edition of Symmetry Breaking, a joint publication of SLAC and Fermilab.
November 2, 2009 — Fermi Telescope Celebrates First Year's Results with Cosmic Reflection Concert
Reflecting on cosmology
and the story of the universe
Image by Pierre Schwob
(Click thumbnail to enlarge)
The 2009 Fermi International Science Symposium will be held in Washington, D.C. , Nov. 2-5, 2009, looking back on the first year of spectacular results from the Fermi Gamma-ray Space Telescope (formerly known as GLAST).
An extraordinary highlight of this symposium will be a live public concert on Nov. 2nd at the John F. Kennedy Center for the Performing Arts in Washington, D.C. This concert, produced and sponsored by Pierre Schwob, founder and CEO of Classical Archives in Palo Alto, Ca., will feature two works by composer Nolan Gasser (Stanford Ph.D. in Musicology, 2001)—GLAST Prelude, Op.12, for brass quintet and the World Premiere of Cosmic Reflection: A Narrated Symphony, Op.15.
September, 2009 — Peter Michelson succeeds Blas Cabrera as HEPL Director
HEPL Director Transition Ceremony.
Following a luncheon featuring Chinese
cuisine, GP-B Principal Investigator,
Francis Everitt (left), reads the fortune
cookie messages for outgoing HEPL
Director, Blas Cabrera (center), and for
incoming director, Peter Michelson (right).
(Click on the thumbnail above to view
On September 1, 2009, physics professor Peter Michelson became the new Director of HEPL. Professor Michelson is the tenth person to oversee and direct the lab's activities during its 58-year history, beginning in 1951 when the lab was officially founded as the Stanford "High Energy Physics Lab" (also abbreviated HEPL). In 1990, the lab was renamed the" W.W. Hansen Experimental Physics Lab," honoring pioneering physicist and engineer, William W. Hansen.
Over the years, the directorship of HEPL has evolved into a three-year, rotating position among the faculty members whose research programs are administered by HEPL. Having just completed his term as HEPL Director, Professor Blas Cabrera is now looking forward to devoting more time to his research on the search for cryogenic dark matter and weakly interactive massive particles (WIMPs). Professor Michelson, who is Principal Investigator of the NASA-funded Fermi Gamma-ray Large-Area Space Telescope program, has kindly agreed to take the helm of HEPL for the next three years.
To commemorate this transition in HEPL leadership, a brief ceremony was held on August 24, 2009 in the Physics/Astrophysics main conference room. The highlight of the ceremony came when Professor Francis Everitt, Principal Investigator of the Gravity Probe B program, picked out two fortune cookies—one for the outgoing HEPL director and one for the incoming HEPL director—and read them aloud. Both fortunes were uncannily apt for their respective recipients.
You can read more about the colorful history of HEPL and its previous directors on the About HEPL page of this web site.
August 2009 —Fermi Gamma-ray Space Telescope results prominently featured in 8/14 issue of AAAS Science
Pulsars in our Galaxy newly
discovered by the Fermi LAT
Telescop. Image: NASA/U.S.
DOE/Fermi LAT Collaboration
/Sonoma State University/
Aurore Simonnet. (Click to
view larger cover image.)
The extraordinary results of the Fermi Gamma-ray Large Area Telescope in detecting and thereby confirming the predicted presence of gamma-ray pulsars in our galaxy was the cover story in the August 14, 2009 issue of Science, the journal of the American Association for the Advancement of Science (AAAS). In addition to the cover story article about the detection of 16 " gamma-ray-only" pulsars, the issue contains two related research reports, as well as an Astronomy Perspectives overview article by astronomer, Jules Halpern of Columbia University.
Following are abbreviated abstracts of the cover story article and the two related research reports, which follow each other sequentially beginning on page 840 of the issue.
Cover article (p. 840): Detection of 16 Gamma-Ray Pulsars Through Blind Frequency Searches Using the Fermi LAT.
Research Report (p. 845 ): Detection of High-Energy Gamma-Ray Emission from the Globular Cluster 47 Tucanae with Fermi.
Research Report (p.848): A Population of Gamma-Ray Millisecond Pulsars Seen with the Fermi Large Area Telescope.
For more information, see:
June/July, 2009 — Gravity Probe B Data Analysis Update
Significantly improved GP-B results from
December 2008. Both the geodetic and
frame-dragging effects are clearly visible
in the data for all 4 gyros. (Click on the
thumbnail above to view full-sized image.)
In a series of five HEPL Seminars, members of the Gravity Probe B (GP-B) science team have been detailing the progress they have made over the past three and a half years in analyzing the data from this landmark physics experiment. Four ultra-precise gyroscopes and a telescope in an earth-orbiting satellite are used to measure two effects predicted by Einstein's 1916 general theory of relativity—1) the geodetic effect (the warping of earth's local spacetime due to earth's mass) and 2) the frame-dragging effect (the twisting of earth's local spacetime due to earth's rotation).
The latest progress shows a tenfold improvement over the preliminary experimental results announced at the American Physical Society annual meeting in April 2007. At that time, only the larger, geodetic effect was clearly visible in the data. Over the past two years, the GP-B data analysis team has made significant progress in understanding and modeling three Newtonian effects, all due to patch potentials on the gyroscope rotor and housing surfaces. The latest results, based upon treatment of 1) damped polhode motion, 2) misalignment torques and 3) roll-polhode resonance torques, clearly show both frame-dragging and geodetic precession in all four gyroscopes (see figure above left).
The GP-B data analysis history reads like a detective story, with the last chapter still in-work. The data analysis described above was performed using orbit-by-orbit modeling of gyroscope orientation (97-minute intervals). The team is now developing 2-second processing of the science data, resulting in about a 3,000-fold increase in the number of data points that have to be processed.This increased computational load will be handled with parallel processing, using a computer cluster in Stanford's Aeronautics and Astronautics Department. The GP-B data analysis will conclude next spring, with final results to be announced next summer or early fall.
For more information see:
May 2009 — NASA's Fermi Telescope Measures Spectrum of Electrons and Positrons; Celebratory 'Cosmic Reflection' Concert
The Large Area Telescope (LAT) onFermi
detects gamma-rays by tracking the
electrons positrons they produce after
striking layers of tungsten. This ability also
makes the LAT an excellent tool for
exploring high-energy cosmic rays.
Credit: NASA/Goddard Space Flight Center
Conceptual Image Lab. (Click to enlarge.)
There was much excitement at the recent American Physical Society meeting in Denver, May 2-5, 2009 about recent results from the Fermi Gamma-ray Space telescope A number of talks were given by collaboration members on many topics, including gamma-ray bursts, active galaxies, pulsars, and diffuse radiation. However, the result that received the most attention was the Fermi LAT measurement of the spectrum of electrons and positrons from 20 GeV to 1 TeV, reported on in talks by Alex Moiseev and Luca Latronico. This result received much attention, not only from the meeting attendees, but also from the science news media. An APS online Viewpoint article highlighted this important result, and Science, Nature, New Scientist, Discover Magazine, Sky and Telescope and Science News have all published stories as well.
Within hours of the cosmic-ray electron/positron result being published by Physical Review Letters, there were several new appears appearing in the online astrophysics archives offering various interpretations of these results in the context of the earlier Pamela results. These interpretations generally fell into two camps: either nearby pulsar(s) injecting primary positrons (and electrons) or dark matter decays or annihilations. The Fermi team is just beginning to understand the results, and there is much work ahead. The possibility of finding new physics cannot be ignored, and thus the theoretical physics community is eagerly anticipating more results and information from the Fermi group in the future.
The Fermi international science team, including members from Stanford and NASA, will be holding a symposium in Washington DC the first week in November 2009. On November 2, 2009, Stanford alumnus and composer, Nolan Gasser's newest composition, 'Cosmic Reflection,' will debut at the Kennedy Center for the Performing Arts as part of a free public event, celebrating the success of missions like Fermi, which explore the nature of the universe and provide possible answers to fundamental questions of physics and basic science. Gasser's composition will be performed by the Boston University Symphony. The American Brass Quintet will also be performing at the event, and there will be a short lecture about the early Fermi science results.
For more information, see:
April 28, 2009 — Bob Byer Awarded the Frederic Ives Medal/Jarus W. Quinn Endowment by the OSA
On April 28, 2009, the Optical Society of America (OSA) announced the 2009 recipients of 17 prestigious awards and medals for outstanding achievements in the field of optics. Among the recipients of this year's awards was Robert Byer, Stanford's William R. Kenan Jr. Professor of Applied Physics.
Byer was awarded the Frederic Ives Medal/Quinn Prize, the highest award bestowed by the Optical Society of America, for his pioneering contributions to optical science and the commercial development of optical technologies, and for wide-ranging leadership activities within the optics community.
"OSA is honored to recognize these leaders in the field of optics," said Elizabeth Rogan, OSA executive director. "These recipients have demonstrated tremendous ingenuity and have proved themselves to be invaluable to the understanding of optics and photonics. OSA congratulates them on their outstanding achievements."
Byer has conducted research and taught classes in lasers and nonlinear optics at Stanford since 1969. Byer will receive his award at the society's annual meeting in October in San Jose.
Fore more information see:
February 19, 2009 - NASA's Fermi Telescope Sees Most Extreme Gamma-ray Blast Yet
On Sept. 17, 31.7 hours after GRB 080916C
exploded, the Gamma-Ray Burst Optical/Near-
Infrared Detector (GROND) on the 2.2m
Max Planck Telescope at the European
Southern Observatory, La Silla, Chile, began
acquiring images of the blasts fading
afterglow (circled). Credit: MPE/GROND
(Click to view enlarged photo.)
The first gamma-ray burst to be seen in high-resolution from NASA's Fermi Gamma-ray Space Telescope is one for the record books. The blast had the greatest total energy, the fastest motions and the highest-energy initial emissions ever seen.
"We were waiting for this one," said Peter Michelson, the principal investigator on Fermi's Large Area Telescope at Stanford University. "Burst emissions at these energies are still poorly understood, and Fermi is giving us the tools to understand them."
Gamma-ray bursts are the universe's most luminous explosions. Astronomers believe most occur when exotic massive stars run out of nuclear fuel. As a star's core collapses into a black hole, jets of material -- powered by processes not yet fully understood -- blast outward at nearly the speed of light. The jets bore all the way through the collapsing star and continue into space, where they interact with gas previously shed by the star and generate bright afterglows that fade with time.
This explosion, designated GRB 080916C, occurred at 7:13 p.m. EDT on Sept. 15, in the constellation Carina. Fermi's other instrument, the Gamma-ray Burst Monitor, simultaneously recorded the event. Together, the two instruments provide a view of the blast's initial, or prompt, gamma-ray emission from energies between 3,000 to more than 5 billion times that of visible light.
NASA provides a movie that compresses about 8 minutes of Fermi LAT observations of GRB 080916C into 6 seconds. Colored dots represent gamma rays of different energies. Visible light has energy between about 2 and 3 electron volts (eV). The blue dots represent lower-energy gamma rays (less than 100 million eV); green, moderate energies (100 million to 1 billion eV); and red, the highest energies (more than 1 billion eV). Credit: NASA/DOE/Fermi LAT Collaboration.
View video at: http://www.nasa.gov/mov/314162main_GRB080916C_LAT_600.mov.
For more information, see:
January 5, 2009 - CDMS Leading the Search for Dark Matter in the Form of WIMPs
Project manager Dan Bauer from Fermilab
holds one tower of detectors as Vuk Mandic,
now at the University of Minnesota, examines
them. (Photo courtesy of Fermilab. Click to
view enlorged photo. )
In the January 13, 2009 issue of Physical Review Letters, the CDMS (Cryogenic Dark Matter Search) Collaboration has published the latest results from its search for WIMPs (weakly interactive massive particles). These elusive particles are curently favored as the essence of dark matter, which scientists believe accounts for 83% of all matter in the universe. Data for this experiment was collected at the Soudan Underground Laboratory (CDMS II), located 2,400 ft undergournd in the Soudan Mine in Minnesota, using an arragy of five detector towers, each containing a vertical stack of six solid-state detector discs, cooled with liquid helium to a cryogenic temperature of ~40 mK. The results from this experiment have achieved the best sensitivity to date for dark matter WIMPs with masses above 4 GeV/c2 and have set new upper limits on the spin-independent interaction of WIMPs and nucleons. Full Story...
January 7, 2009 - Fermi Gamma Ray Space Telescope Discovers Slew of New Pulsars
by Kelen Tuttle, SLAC Today
The Fermi Telescope has found 12 previously unknown
pulsars (orange). It also detected gamma-ray emissions
from known radio pulsars (magenta, cyan) and from known
or suspected gamma-ray pulsars (green). (Image courtesy
of NASA/Fermi/LAT Collaboration. Click to enlarge.)
Four months into its mission, the Fermi Gamma-ray Space Telescope has discovered 12 never-before-seen pulsars and observed gamma-ray pulses from 18 others, shedding new insight on the high-energy universe.
"I am very happy to welcome you all to a new era in pulsar physics," Roger Romani said at a press conference held yesterday at the American Astronomical Society meeting in Long Beach, California. Romani is a researcher in the Kavli Institute for Particle Astrophysics and Cosmology at SLAC National Accelerator Laboratory and Stanford University. "We know of 1800 pulsars, but until Fermi we saw only little wisps of energy from all but a handful of them. Now, for dozens of pulsars, we're seeing the actual power of these machines."
In the past, most pulsars–rapidly spinning neutron stars that emit energy in narrow beams–were observed only in radio waves. Yet, as the FGST data reveals, this radio-wave emission is extremely weak compared to the pulsars' flashes of gamma-rays.
The 12 newly discovered pulsars offer insight into the mechanism behind the gamma-ray emissions. The data show that the classic understanding of emission, whereby gamma rays are created in the same location as radio waves, is mistaken. Researchers now theorize that the radio beams form near the neutron star's surface, while the gamma rays form far above.
FGST is also shedding light on pulsars as they near the end of their lifecycles. Over the past few months, the telescope found seven very old and relatively rare pulsars that are thought to have gravitationally attracted additional stellar matter from companion stars, causing them to increase in mass and spin much faster. These "millisecond" pulsars spin hundreds of times faster than their younger siblings, with their surfaces moving at up to a tenth of the speed of light. They also have magnetic fields 10,000 times lower and are thought to be 10,000 times older than previously discovered pulsars.
With the observation of these millisecond pulsars, Romani said, "we're really seeing the history of pulsars." Alice Harding of the NASA-Goddard Space Flight Center added: "This is the tip-of-the-iceberg. We'll probably be discovering a lot more."
Researchers announced these findings at the American Astronomical Society meeting this week in Long Beach, California, and at the Texas Symposium on Relativistic Astrophysics last December in Vancouver, Canada. More information can be found in a NASA press release issued yesterday and in a recent Science News article by Ron Cowen.
For more information, see:
August 26, 2008 - GLAST Observatory Renamed for Fermi, Reveals Entire Gamma-Ray Sky
The U.S. Department of Energy (DOE) and NASA announced today that the Gamma-Ray Large Area Space Telescope (GLAST) has revealed its first all-sky map in gamma rays. The onboard Large Area Telescope's (LAT) all-sky image—which shows the glowing gas of the Milky Way, blinking pulsars and a flaring galaxy billions of light-years away—was created using only 95 hours of "first light" observations, compared with past missions which took years to produce a similar image. Scientists expect the telescope will discover many new pulsars in our own galaxy, reveal powerful processes near super-massive black holes at the cores of thousands of active galaxies and enable a search for signs of new physical laws.
The NASA mission was made possible by collaboration with many U.S. and international partners. As part of its support for particle physics research, DOE contributed funding to the LAT—the primary instrument on GLAST—and DOE's Stanford Linear Accelerator Center (SLAC) managed the LAT construction. SLAC also played a key role in assembling the instrument and now plays the central role in LAT science operations, data processing and making scientific data available to collaborators for analysis.
"The DOE-NASA collaboration on this new observatory has been very successful and shows what can be accomplished when we work together," said Dennis Kovar, DOE Associate Director of Science for High Energy Physics. "We look forward to the scientific discoveries it will enable in both particle physics and astrophysics."
NASA also announced today that GLAST has been renamed the Fermi Gamma-ray Space Telescope. The new name honors Prof. Enrico Fermi (1901-1954), a pioneer in high-energy physics. "Enrico Fermi was the first person to suggest how cosmic particles could be accelerated to high speeds," said Paul Hertz, chief scientist for the Science Mission Directorate at NASA Headquarters in Washington, D.C. "His theory provides the foundation for understanding the powerful phenomena his namesake telescope will discover."
For two months following the mission's June 11, 2008 launch, scientists tested and calibrated its two instruments, the LAT and the GLAST Burst Monitor (GBM). "What impressed me the most is that everything went by the book," said Peter Michelson, LAT principal investigator at Stanford University, Calif. "We're elated." The LAT has already verified sources found by other gamma-ray detectors—and discovered more.
The all-sky image shows gas and dust in the plane of the Milky Way glowing in gamma rays due to collisions with accelerated nuclei called cosmic rays. The famous Crab Nebula and Vela pulsars also shine brightly at these wavelengths. These fast-spinning neutron stars, which form when massive stars die, were originally discovered by their radio emissions. The image's third pulsar, named Geminga and located in Gemini, is not a radio source. It was discovered by an earlier gamma-ray satellite. The Fermi Gamma-ray Space Telescope is expected to discover many more radio-quiet pulsars, providing key information about how these exotic objects work.
A fourth bright spot in the LAT image lies some 7.1 billion light-years away, far beyond our galaxy. This is 3C 454.3 in Pegasus, a type of active galaxy called a blazar. It's now undergoing a flaring episode that makes it especially bright.
The LAT scans the entire sky every three hours when operating in survey mode, which will occupy most of the telescope's observing time during the first year of operations. These fast snapshots will let scientists monitor rapidly changing sources.
The LAT instrument detects photons with energies ranging from 20 million electronvolts to over 300 billion electronvolts. The high end of this range, which corresponds to energies more than 5 million times greater than dental X-rays, is little explored.
The spacecraft's secondary instrument, the GBM, spotted 31 gamma-ray bursts in its first month of operation. These high-energy blasts occur when massive stars die and when orbiting neutron stars spiral together and merge.
The GBM is sensitive to lower energy range gamma rays (8000 to 30 million electronvolts) than LAT. Bursts seen by both instruments will provide an unprecedented look across a broad gamma-ray spectrum, enabling scientists to peer into the processes powering these events.
NASA's Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy, along with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.
Date Issued: August 26, 2008 (SLAC Today)
Relevant Web URLs:
August 2008 - Palanker Research Group Develops Pulsed Electron Avalanche Knife (PEAK)
Discharge on cylindrical microelectrode in
saline driven by microsecond burst of pulses.
Daniel Palanker's research group at HEPL and the Stanford Medical School have developed electrosurgical technology called Pulsed Electron Avalanche Knife (PEAK). Stanford's Office of Technology Licensing licensed it to a local startup company called PEAK Surgical Inc. They recently received FDA approval for this device, and performed their first 30-40 human cases during the last couple weeks. Feedback from surgeons is exceptionally good, so this device has a potential to become a new standard of care in surgery. In contrast to conventional electrosurgery, based on continuous radiofrequency waveforms applied via large electrodes, PEAK uses microsecond pulses and micrometers-thin blade electrodes to excise tissue with cellular precision. Not only the cuts are more precise and narrow, but also, due to the very low collateral thermal damage produced by PEAK technology, the tissue heals faster, and with much less scarring and other defects, than after traditional electrosurgery.
For more information see:
August 2008 —Professor Robert Byer Wins 2009 IEEE Photonics Award
ROBERT L. BYER, HEPL faculty member, professor of applied physics and director of the Ginzton Laboratory, has won the 2009 IEEE Photonics Award. Byer, the William R. Kenan Jr. Professor, was cited for "seminal contributions to nonlinear optics and solid-state lasers for commercial applications
June 11, 2008 — NASA's GLAST Launch Successful
image courtesy of
CAPE CANAVERAL AIR FORCE STATION, Fla. -- NASA's Gamma-ray Large Area Space Telescope, or GLAST, successfully launched aboard a Delta II rocket from Cape Canaveral Air Force Station in Florida at 12:05 p.m. EDT Wednesday, 6/11/08..
The GLAST observatory separated from the second stage of the Delta II at 1:20 p.m. and the flight computer immediately began powering up the components necessary to control the satellite. Twelve minutes after separating from the launch vehicle, both GLAST solar arrays were deployed. The arrays immediately began producing the power necessary to maintain the satellite and instruments. The operations team continues to check out the spacecraft subsystems.
"The entire GLAST Team is elated the observatory is now on-orbit and all systems continue to operate as planned," said GLAST program manager Kevin Grady of NASA's Goddard Space Flight Center in Greenbelt, Md.
After a 75-minute flight, the GLAST spacecraft was deployed into low Earth orbit. It will begin to transmit initial instrument data after about three weeks. The telescope will explore the most extreme environments in the universe, searching for signs of new laws of physics and investigating what composes mysterious dark matter. It will seek explanations for how black holes accelerate immense jets of material to nearly light speed, and look for clues to crack the mysteries behind powerful explosions known as gamma-ray bursts.
"After a 60-day checkout and initial calibration period, we'll begin science operations," said Steve Ritz, GLAST project scientist at Goddard. "GLAST soon will be telling scientists about many new objects to study, and this information will be available on the internet for the world to see."
NASA's GLAST mission is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy, along with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the U.S.
—NASA Press Release 6/11/08
For more information about the GLAST mission, please visit:
March 2008 — Crystal bells stay silent as physicists look for dark matter
Closeup of a CDMS detector,
made of crystal germanium.
Credit: Fermilab. (Click to
view enlarged photo.)
U.S. experiment retakes the lead in competitive race
Batavia, Ill.--Scientists of the Cryogenic Dark Matter Search experiment today announced that they have regained the lead in the worldwide race to find the particles that make up dark matter. The CDMS experiment, conducted a half-mile underground in a mine in Soudan, Minn., again sets the world’s best constraints on the properties of dark matter candidates.
“With our new result we are leapfrogging the competition,” said Blas Cabrera of Stanford University, co-spokesperson of the CDMS experiment, for which the Department of Energy’s Fermi National Accelerator Laboratory hosts the project management. “We have achieved the world’s most stringent limits on how often dark matter particles interact with ordinary matter and how heavy they are, in particular in the theoretically favored mass range of more than 40 times the proton mass. Our experiment is now sensitive enough to hear WIMPs even if they ring the ‘bells’ of our crystal germanium detector only twice a year. So far, we have heard nothing.”
January 30, 2008 — On the frontiers of science for decades, a storied building is soon to be razed
BY DAN STOBER, Stanford Report
Panoramic photo of the HEPL Lab building
taken in November 2007, prior to demolition.
Photo by Bob Kahn (Click to enlarge.)
From the obituary desk: The HEPL building, 58 years old, a Stanford baby boomer born in 1949 in the aftermath of World War II, a child prodigy that produced the world's first full-scale linear accelerator when only a year old and won the Nobel Prize for physics at age 12, has passed on. Despite a certain gangly appearance, it was loved by its extended family of researchers for its utilitarian qualities. There were several causes for its passing (old and in the way, in essence), but the final blow was delivered by heavy-duty construction equipment.
HEPL Directors: Sandy
Fetter, Blas Cabrera,
Mason Yearian & Bob Byer.
Photo by Linda Cicero
(Click to enlarge.)
On November 7, 2007, a gala party was held in honor of sixty years of research in this historic building 04-250, aka "HEPL North." The event was part celebration, part wake to say "goodbye" to the building that had been home to numerous collaborative research projects for over 60 years. Alan J. Keith played the bagpipes and marched through the gutted laboratories during this pre-demolition party, which brought together many former and current researchers for an afternoon of reminiscing.
It was built nearly six decades ago with science in mind. Long and skinny with a wide-open interior, the no-fuss structure was an experimenter's delight, a sort of high-end tinkerer's garage stretched out over several blocks—a perfect space for a linear accelerator pushing a beam of electrons at extremely high speeds. It was made of cinder block and concrete, in some places several feet thick. Sunlight came into the building from rows of identical windows high up on the walls. One employee described the architectural style as "old."
"I'll miss it," said Bob Byer, a professor of applied physics who was director of HEPL from 1997 to 2006. "It has character, it has a rhythm, it has a design that is pleasing. We've replaced it with buildings that have a scale larger than humans."
" Working in an old building had its advantages," said Blas Cabrera, who followed Byer as HEPL director: "We always found it very useful because nobody cared if you punched a hole in the wall."
Now, the bulldozers are circling, and if all goes as planned, an elder statesman of Stanford research structures will be torn down and hauled away this week. The HEPL building (originally the High-Energy Physics Laboratory, now the Hansen Experimental Physics Laboratory) will be put to rest with as much recycling as possible.
October 31, 2007 — Physicists chase Einstein’s equivalence principle down a hole
Physicist Mark Kasevich works in a 25-foot pit beneath the Varian Building in search of Albert Einstein. Or more specifically, Kasevich is searching for proof that Einstein got it right in 1907 when he formulated his equivalence principle, declaring in effect that the tug of gravity is indistinguishable from the force that pushes you back into your seat in a rapidly accelerating Porsche.
If Einstein was right, the equivalence principle also requires that "objects should fall at the same rate under gravity, regardless of their composition, regardless of their mass," said Jason Hogan, one of Kasevich's graduate students. Their team is now installing the esoteric equipment designed to test that prediction by tossing up a handful of rubidium atoms—some slightly heavier than others—and watching them fall to the bottom of the pit.