Hard X-Ray telescope up for final NASA review; project will be led by Caltech's Fiona Harrison

PASADENA, Calif.--If all goes well with a technical study approved by NASA for this year, an innovative telescope should be orbiting Earth by the end of the decade and taking the first focused high-energy X-ray pictures of matter falling into black holes and shooting out of exploding stars. Not only will the telescope be 1,000 times more capable of finding new black holes than anything previously launched into space, but it will also give us an unprecedented look at the origins of the heavy elements we're all made of.

Named the Nuclear Spectroscopic Telescope Array--or NuSTAR, for short--the project has just been pegged by NASA for detailed study in the competitive Small Explorer Program (SMEX), which seeks out new technologies and new proposals for space missions that can be launched at low cost. NASA announced earlier this week that an unrelated mission called the Interstellar Boundary Explorer will be launched by 2008, and that NuSTAR will be given an up-or-down decision by next year for launch in 2009.

According to California Institute of Technology astrophysicist Fiona Harrison, the principal investigator of the NuSTAR project, an April high-altitude balloon flight in New Mexico should help to demonstrate whether the advanced sensors invented and built at Caltech are ready for space.

The balloon phase of the project sports the intuitive acronym HEFT (for High-Energy Focusing Telescope), and will mark the first time that focused pictures at "hard X-ray" wavelengths will have been returned from high altitudes. In fact, the HEFT data from the balloon is expected to be superior to any data returned so far from satellites at high X-ray energies.

NuSTAR will be much better than the balloon experiment, Harrison explains, because it's necessary to get above Earth's atmosphere for extended periods to get a good view of the X-ray sky. NuSTAR will orbit Earth at an altitude of about 300 miles or so for at least three years.

The reason that the new technology will be superior to that employed by existing X-ray satellites for certain observations is that high-energy, or hard, X rays, tend to penetrate the gas and dust of galaxies much better than the soft X rays observed by NuSTAR's forerunners. Thus, NuSTAR will get the first focused hard X-ray images for three basic science goals:

--The taking of a census of black holes at all scales. NuSTAR will not only count them, but will also measure the "accretion rate" at which material has fallen into them over time, and the rate supermassive black holes have grown.

--The detecting and measuring of radioactive stuff in recently exploded stars. These remnants of supernovae will provide a better idea of how elements are formed in supernova explosions and then mixed in the interstellar medium, which is the space between stars. NuSTAR will be especially good at observing the decay of titanium to calcium, which tends to be produced in the region of a supernova where material either is ejected forever from the explosion or falls back inward to form a compact remnant of some sort. NuSTAR will thus be an especially good probe of this region, and the data returned will contribute directly to NASA's "Cycles of Matter and Energy" program.

--The observing and imaging of the highly energetic jets that stream out of certain black holes at nearly the speed of light. Coupled with observations from the Gamma-Ray Large-Area Space Telescope (GLAST), NuSTAR will provide data to help scientists explain this still-enigmatic but powerful phenomenon.

The technical difficulties of obtaining hard X-ray images has been overcome with groundbreaking work in various Caltech labs, including that of famed inventor Carver Mead, who is the Moore Professor of Engineering and Applied Science, Emeritus, at Caltech. Both HEFT and NuSTAR will rely on an array of coaligned conical mirrors that will focus X rays from about 20 to 100 kilo-electron-volts on a pixel detector made of cadmium zinc telluride. The sensor is segmented into squares of about half a millimeter each, and these will take thousands of individual readings of X-ray photons and turn them into electronic signals.

"With this mission, we'll open the hard X-ray frontier and look at things never seen before," says Harrison, who is an associate professor of physics and astronomy at Caltech.

In addition to Caltech, the other participating organizations and universities are the Jet Propulsion Laboratory (managed by Caltech for NASA), Columbia University, the Stanford Linear Accelerator (SLAC), the Lawrence Livermore National Laboratory, Sonoma State University, the University of California at Santa Cruz, and the Danish Space Research Institute. NuSTAR's spacecraft will be built by General Dynamics Spectrum Astro.

JPL handles project management, the metrology system, and the extensible mast, and is involved in the mission's science. The mast is based on a previous JPL mission, the Shuttle Radar Topography Mission.

The selected proposals were among 29 SMEX and eight mission-of-opportunity proposals submitted to NASA in May 2003. They were in response to an Explorer Program Announcement of Opportunity issued in February 2003. NASA selected six proposals in November 2003 for detailed feasibility studies.

The Explorer Program is designed to provide frequent, low-cost access to space for physics and astronomy missions with small to mid-sized spacecraft. NASA has successfully launched six SMEX missions since 1992. The missions include the Reuven Ramaty High Energy Solar Spectroscopic Imager, launched in February 2002, and the Galaxy Evolution Explorer, launched in April 2003 and led by Caltech physics professor Chris Martin.

NASA's Goddard Space Flight Center, Greenbelt, Md., manages the Explorer Program for the Science Mission Directorate.

 

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RT

Retired Caltech Physicist Robert Walker Dies; Worked on Manhattan Project as Grad Student

PASADENA, Calif.-Robert Walker, a retired physics professor at the California Institute of Technology, died January 4 in New Mexico. A graduate student who worked on the Manhattan Project during World War II, he was 85 years old at the time of his death.

Born June 29, 1919, in St. Louis, Walker earned his bachelor's degree at the University of Chicago and was a doctoral student at Cornell University when he joined the effort to produce the atomic bomb. While on the Manhattan Project he worked both at Los Alamos and the University of Chicago. He finished his doctorate in physics in 1948, and after an additional year at Cornell as a postdoctoral researcher he was hired as an assistant professor at Caltech.

Walker became an associate professor in 1953 and a full professor in 1959. During his time on the faculty he served as executive officer for physics. He retired in 1981 and moved to the Santa Fe area.

Walker's specialty was experimental high-energy physics, and for many years he worked on the Caltech synchrotron, first as one of the co-developers with colleagues Robert V. Langmuir and Bruce Rule, and as a researcher for the accelerator's entire 30-year lifetime. For many years, he was also the principal investigator of Caltech's contract with the Department of Energy and its predecessors to do experimental and theoretical research in elementary particle physics.

According to Charles Peck, a professor emeritus of physics at Caltech who earned his doctorate under Walker's tutelage, Walker's collaborative research utilizing the synchrotron helped lay the foundation work that led to what is now known as the Standard Model of elementary particle physics. In particular, Peck said, Walker's work involved pion photoproduction (in which a proton or neutron is bombarded with a high-energy photon which converts into a pi meson). His research was also useful to his longtime Caltech colleague Richard Feynman in his theoretical studies of the underlying mechanisms of particles.

"Bob was also a superb teacher," Peck said. "He taught a course in the mathematical methods of physics, and also courses in quantum mechanics and particle phenomena."

Walker also co-wrote a textbook, Mathematical Methods of Physics, with Jon Mathews.

After retiring from Caltech, Walker built harpsichords at his home near Santa Fe, Peck said.

He is survived by two children, Robert Craig Walker and Jan Walker Roenisch.

 

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Robert Tindol
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Physicists at Caltech, UT Austin ReportBose-Einstein Condensation of Cold Excitons

PASADENA, Calif.-Bose-Einstein condensates are enigmatic states of matter in which huge numbers of particles occupy the same quantum state and, for all intents and purposes, lose their individual identity. Predicted long ago by Albert Einstein and Satyendranath Bose, these bizarre condensates have recently become one of the hottest topics in physics research worldwide.

Now, physicists at the California Institute of Technology and the University of Texas at Austin have created a sustained Bose-Einstein condensate of excitons, unusual particles that inhabit solid semiconductor materials. By contrast, most recent work on the phenomenon has focused on supercooled dilute gases, in which the freely circulating atoms of the gas are reduced to a temperature where they all fall into the lowest-energy quantum state. The new Caltech-UT Austin results are being published this week in the journal Nature.

According to Jim Eisenstein, who is the Roshek Professor of Physics at Caltech and co-lead author of the paper, exciton condensation was first predicted over 40 years ago but has remained undiscovered until now because the excitons usually decay in about a billionth of a second. In this new work, the researchers created stable excitons, which consist of an electron in one layer of a sandwich-like semiconductor structure bound to a positively charged "hole" in an adjacent layer. A hole is the vacancy created when an electron is removed from a material.

Bound together, the electron and hole form a "boson," a type of particle that does not mind crowding together with other similar bosons into the same quantum state. The other type of particle in the universe, "fermions," include individual protons and electrons and neutrons. Only one fermion is allowed to occupy a given quantum state.

The picture is complex, but if one imagines two layers of material, one containing some electrons, the other completely empty, the results are somewhat easier to visualize. Begin by transferring half of the electrons from the full layer to the empty one. The resulting situation is equivalent to a layer of electrons in parallel with a layer of holes. And because the electron has a negative charge, the taking away of an electron means that the hole in which it once existed has a positive charge.

The difficult thing about the procedure is that the layers have to be positioned just right and a large magnetic field has to be applied just right in order to avoid swamping the subtle binding of the electron and hole by other forces in the system. The magnetic field is also essential for stabilizing the excitons and preventing their decay.

Eisenstein says that the simplest experiment consists of sending electrical currents through the two layers in opposite directions. The "smoking gun" for exciton condensation is the absence of the ubiquitous sideways force experienced by charged particles moving in magnetic fields. Excitons, which have no net charge, should not feel such a force.

One mystery that remains is the tendency of the excitons to dump a small amount of energy when they move. "We find that, as we go toward lower temperatures, energy dissipation does become smaller and smaller," Eisenstein says. "But we expected no energy dissipation at all.

"Therefore, this is not really an ideal superfluid--so far it is at best a bad one."

The other author of the paper is Allan MacDonald, who holds the Sid W. Richardson Foundation Regents Chair in physics at UT Austin and is a specialist in theoretical condensed matter physics.

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Robert Tindol
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Internet Speed Quadrupled by International Team During 2004 Bandwidth Challenge

PITTSBURGH, Pa.--For the second consecutive year, the "High Energy Physics" team of physicists, computer scientists, and network engineers have won the Supercomputing Bandwidth Challenge with a sustained data transfer of 101 gigabits per second (Gbps) between Pittsburgh and Los Angeles. This is more than four times faster than last year's record of 23.2 gigabits per second, which was set by the same team.

The team hopes this new demonstration will encourage scientists and engineers in many sectors of society to develop and deploy a new generation of revolutionary Internet applications.

The international team is led by the California Institute of Technology and includes as partners the Stanford Linear Accelerator Center (SLAC), Fermilab, CERN, the University of Florida, the University of Manchester, University College London (UCL) and the organization UKLight, Rio de Janeiro State University (UERJ), the state universities of São Paulo (USP and UNESP), the Kyungpook National University, and the Korea Institute of Science and Technology Information (KISTI). The group's "High-Speed TeraByte Transfers for Physics" record data transfer speed is equivalent to downloading three full DVD movies per second, or transmitting all of the content of the Library of Congress in 15 minutes, and it corresponds to approximately 5% of the rate that all forms of digital content were produced on Earth during the test.

The new mark, according to Bandwidth Challenge (BWC) sponsor Wesley Kaplow, vice president of engineering and operations for Qwest Government Services exceeded the sum of all the throughput marks submitted in the present and previous years by other BWC entrants. The extraordinary achieved bandwidth was made possible in part through the use of the FAST TCP protocol developed by Professor Steven Low and his Caltech Netlab team. It was achieved through the use of seven 10 Gbps links to Cisco 7600 and 6500 series switch-routers provided by Cisco Systems at the Caltech Center for Advanced Computing (CACR) booth, and three 10 Gbps links to the SLAC/Fermilab booth. The external network connections included four dedicated wavelengths of National LambdaRail, between the SC2004 show floor in Pittsburgh and Los Angeles (two waves), Chicago, and Jacksonville, as well as three 10 Gbps connections across the Scinet network infrastructure at SC2004 with Qwest-provided wavelengths to the Internet2 Abilene Network (two 10 Gbps links), the TeraGrid (three 10 Gbps links) and ESnet. 10 gigabit ethernet (10 GbE) interfaces provided by S2io were used on servers running FAST at the Caltech/CACR booth, and interfaces from Chelsio equipped with transport offload engines (TOE) running standard TCP were used at the SLAC/FNAL booth. During the test, the network links over both the Abilene and National Lambda Rail networks were shown to operate successfully at up to 99 percent of full capacity.

The Bandwidth Challenge allowed the scientists and engineers involved to preview the globally distributed grid system that is now being developed in the US and Europe in preparation for the next generation of high-energy physics experiments at CERN's Large Hadron Collider (LHC), scheduled to begin operation in 2007. Physicists at the LHC will search for the Higgs particles thought to be responsible for mass in the universe and for supersymmetry and other fundamentally new phenomena bearing on the nature of matter and spacetime, in an energy range made accessible by the LHC for the first time.

The largest physics collaborations at the LHC, the Compact Muon Solenoid (CMS), and the Toroidal Large Hadron Collider Apparatus (ATLAS), each encompass more than 2000 physicists and engineers from 160 universities and laboratories spread around the globe. In order to fully exploit the potential for scientific discoveries, many petabytes of data will have to be processed, distributed, and analyzed. The key to discovery is the analysis phase, where individual physicists and small groups repeatedly access, and sometimes extract and transport, terabyte-scale data samples on demand, in order to optimally select the rare "signals" of new physics from potentially overwhelming "backgrounds" from already-understood particle interactions. This data will be drawn from major facilities at CERN in Switzerland, at Fermilab and the Brookhaven lab in the U.S., and at other laboratories and computing centers around the world, where the accumulated stored data will amount to many tens of petabytes in the early years of LHC operation, rising to the exabyte range within the coming decade.

Future optical networks, incorporating multiple 10 Gbps links, are the foundation of the grid system that will drive the scientific discoveries. A "hybrid" network integrating both traditional switching and routing of packets, and dynamically constructed optical paths to support the largest data flows, is a central part of the near-term future vision that the scientific community has adopted to meet the challenges of data intensive science in many fields. By demonstrating that many 10 Gbps wavelengths can be used efficiently over continental and transoceanic distances (often in both directions simultaneously), the high-energy physics team showed that this vision of a worldwide dynamic grid supporting many-terabyte and larger data transactions is practical.

While the SC2004 100+ Gbps demonstration required a major effort by the teams involved and their sponsors, in partnership with major research and education network organizations in the United States, Europe, Latin America, and Asia Pacific, it is expected that networking on this scale in support of largest science projects (such as the LHC) will be commonplace within the next three to five years.

The network has been deployed through exceptional support by Cisco Systems, Hewlett Packard, Newisys, S2io, Chelsio, Sun Microsystems, and Boston Ltd., as well as the staffs of National LambdaRail, Qwest, the Internet2 Abilene Network, the Consortium for Education Network Initiatives in California (CENIC), ESnet, the TeraGrid, the AmericasPATH network (AMPATH), the National Education and Research Network of Brazil (RNP) and the GIGA project, as well as ANSP/FAPESP in Brazil, KAIST in Korea, UKERNA in the UK, and the Starlight international peering point in Chicago. The international connections included the LHCNet OC-192 link between Chicago and CERN at Geneva, the CHEPREO OC-48 link between Abilene (Atlanta), Florida International University in Miami, and São Paulo, as well as an OC-12 link between Rio de Janeiro, Madrid, Géant, and Abilene (New York). The APII-TransPAC links to Korea also were used with good occupancy. The throughputs to and from Latin America and Korea represented a significant step up in scale, which the team members hope will be the beginning of a trend toward the widespread use of 10 Gbps-scale network links on DWDM optical networks interlinking different world regions in support of science by the time the LHC begins operation in 2007. The demonstration and the developments leading up to it were made possible through the strong support of the U.S. Department of Energy and the National Science Foundation, in cooperation with the agencies of the international partners.

As part of the demonstration, a distributed analysis of simulated LHC physics data was done using the Grid-enabled Analysis Environment (GAE), developed at Caltech for the LHC and many other major particle physics experiments, as part of the Particle Physics Data Grid, the Grid Physics Network and the International Virtual Data Grid Laboratory (GriPhyN/iVDGL), and Open Science Grid projects. This involved the transfer of data to CERN, Florida, Fermilab, Caltech, UC San Diego, and Brazil for processing by clusters of computers, and finally aggregating the results back to the show floor to create a dynamic visual display of quantities of interest to the physicists. In another part of the demonstration, file servers at the SLAC/FNAL booth in London and Manchester also were used for disk-to-disk transfers from Pittsburgh to England. This gave physicists valuable experience in the use of the large, distributed datasets and to the computational resources connected by fast networks, on the scale required at the start of the LHC physics program.

The team used the MonALISA (MONitoring Agents using a Large Integrated Services Architecture) system developed at Caltech to monitor and display the real-time data for all the network links used in the demonstration. MonALISA (http://monalisa.caltech.edu) is a highly scalable set of autonomous, self-describing, agent-based subsystems which are able to collaborate and cooperate in performing a wide range of monitoring tasks for networks and grid systems as well as the scientific applications themselves. Detailed results for the network traffic on all the links used are available at http://boson.cacr.caltech.edu:8888/.

Multi-gigabit/second end-to-end network performance will lead to new models for how research and business is performed. Scientists will be empowered to form virtual organizations on a planetary scale, sharing in a flexible way their collective computing and data resources. In particular, this is vital for projects on the frontiers of science and engineering, in "data intensive" fields such as particle physics, astronomy, bioinformatics, global climate modeling, geosciences, fusion, and neutron science.

Harvey Newman, professor of physics at Caltech and head of the team, said, "This is a breakthrough for the development of global networks and grids, as well as inter-regional cooperation in science projects at the high-energy frontier. We demonstrated that multiple links of various bandwidths, up to the 10 gigabit-per-second range, can be used effectively over long distances.

"This is a common theme that will drive many fields of data-intensive science, where the network needs are foreseen to rise from tens of gigabits per second to the terabit-per-second range within the next five to 10 years," Newman continued. "In a broader sense, this demonstration paves the way for more flexible, efficient sharing of data and collaborative work by scientists in many countries, which could be a key factor enabling the next round of physics discoveries at the high energy frontier. There are also profound implications for how we could integrate information sharing and on-demand audiovisual collaboration in our daily lives, with a scale and quality previously unimaginable."

Les Cottrell, assistant director of SLAC's computer services, said: "The smooth interworking of 10GE interfaces from multiple vendors, the ability to successfully fill 10 gigabit-per-second paths both on local area networks (LANs), cross-country and intercontinentally, the ability to transmit greater than 10Gbits/second from a single host, and the ability of TCP offload engines (TOE) to reduce CPU utilization, all illustrate the emerging maturity of the 10Gigabit/second Ethernet market. The current limitations are not in the network but rather in the servers at the ends of the links, and their buses."

Further technical information about the demonstration may be found at http://ultralight.caltech.edu/sc2004 and http://www-iepm.slac.stanford.edu/monitoring/bulk/sc2004/hiperf.html A longer version of the release including information on the participating organizations may be found at http://ultralight.caltech.edu/sc2004/BandwidthRecord

 

New Home for Astronomers

PASADENA, Calif. - For almost 100 years, Caltech has been at the forefront of astronomy and astrophysics, pioneering research that has led to greater understanding of the earth, the solar system, and the Universe. Now the Institute is about to help its world-renowned astronomers and other investigators continue their groundbreaking discoveries well into the 21st century.

Thanks to a lead gift from Charles H. Cahill and Aniko Dér Cahill, plus support from the Sherman Fairchild Foundation and other Institute friends, Caltech will soon begin construction of an estimated 100,000-square-foot facility that will provide a much needed collective and collaborative home for its astronomers, instrument builders, and theorists who now work in numerous buildings on campus.

With an imposing view of the southern facade of Caltech with the San Gabriel Mountains beyond, the new $50 million Cahill Center for Astronomy and Astrophysics will be located on the south side of California Boulevard, between the Institute's athletic facilities on the south and the rest of the campus on the north. Internationally recognized architect Thom Mayne and his firm, Morphosis, based in Santa Monica, CA, have been chosen to design what promises to be a visually impressive structure and a facility that will be extremely functional.

The recipient of 52 awards from the American Institute of Architects, Mayne has designed both consumer products and buildings, including the striking new Caltrans District 7 headquarters in downtown Los Angeles. Mayne will design a structure for Caltech that will complement the aesthetics of the campus and the surrounding neighborhood while meeting the practical needs of scientists.

Plans call for the Cahill Center to be composed of five floors, two of them underground. The building will contain space for offices, laboratories, remote observing rooms, conference rooms, a library, an auditorium, and classrooms. The design is expected to be completed by the spring.

"An institution conducting cutting-edge research in astronomy and astrophysics should have a facility that advances those investigations," said Caltech president David Baltimore. "Thom Mayne and Morphosis is an exciting choice that will provide the campus and Pasadena with a highly visible icon. By bringing investigators together from across campus, the center will engender the kinds of collaborations that are Caltech's hallmark, and which lead to breakthrough discoveries."

Since the time of George Ellery Hale, Caltech astronomers have been housed in the elegant Robinson building, opened in 1932 and distinguished by its rooftop astronomical dome. Generations of occupants have discovered remarkable phenomena, including the cosmological nature of quasars, the incredibly bright beacons in the sky indicating the presence of very distant galaxies, millisecond pulsars, and brown dwarfs, also known as "failed stars." This year alone, Caltech astronomers found the largest object orbiting the sun since the discovery of Pluto in 1930, and the most distant galaxy in the Universe.

Over the years, the Institute's astronomy program has increased in size, overfilling the Robinson building, so that other astrophysical programs began to occupy neighboring physics laboratories. Despite their many successes, Caltech astronomers and astrophysicists have been limited by the physical separation between research groups. "Pulling together the division's many activities in astronomy and astrophysics to achieve optimal synergy has been our goal for some time," says Tom Tombrello, chair of the Division of Physics, Mathematics and Astronomy. "The Cahill Center is an essential step in this progression and, naturally, a top priority for us. We greatly appreciate the gift by the Cahills and other Caltech friends that will help us tackle some of the remaining questions in astronomy."

Caltech's observing facilities, which span almost the entire electromagnetic spectrum, are unmatched by any other institution in the world. Its optical observatories stretch from the Palomar Observatory, which includes the famous 200-inch telescope built in the 1930's, to the twin 10-meter Keck telescopes on Mauna Kea. A recently proposed Thirty Meter Telescope is now being designed. To this impressive list of world-leading optical telescopes is added the nation's largest millimeter wave radio interferometer, and submillimeter wave single dish. The list goes on, including balloon-borne and land-based cosmic background detection facilities, an ultraviolet sky survey satellite, European Space Agency satellites and NASA satellites, and an airborne telescope.

"The Cahill Center will enable the inventors of all these devices to be brought together under one roof, no doubt fostering exciting new discoveries," says Tombrello. "Caltech is known worldwide for its leadership in astronomy. It's the unique quality of Caltech's education that promotes these discoveries, which will help improve our understanding of the Universe."

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Manhattan Project Physicist Robert Bacher Dies

PASADENA, Calif.-Robert Fox Bacher, a renowned California Institute of Technology physicist who headed the experimental physics division at Los Alamos Laboratory during the Manhattan Project, died Thursday, November 18, in Montecito, California. He was 99.

Bacher was affiliated with MIT's Radiation Laboratory when the Manhattan Project began, and took a leave of absence to head the experimental physics division and, once the bomb-production phase began, the bomb physics division. After the war he became one of the first members of the U.S. Atomic Energy Commission, and also served on the President's Science Advisory Committee during the Eisenhower Administration.

A close associate of former Caltech president Lee DuBridge while both were at MIT, Bacher joined the Caltech faculty in 1949, three years after DuBridge became president. Bacher remained at Caltech for the remainder of his career, serving as chairman of the physics, math, and astronomy division from 1949 to 1962, as provost from 1962 to 1969, and as vice president and provost from 1969 to 1970. He took emeritus status in 1976.

His colleague Robert Christy, also a former provost and emeritus professor of physics at Caltech who worked on the Manhattan Project, said that, next to Robert Andrews Millikan, Bacher was the person most important to the early growth of Caltech's reputation in physics and astronomy. "He was responsible for building Caltech physics after the war, and for making Caltech physics what it is today," Christy said.

Born August 31, 1905, in Loudonville, Ohio, Bacher earned his bachelor's degree from the University of Michigan in 1926 and his doctorate in 1930. He first came to Caltech in 1930 for a one-year appointment as a National Research Council Fellow, and afterward held postdoctoral positions at MIT and the University of Michigan before joining the faculty at Columbia University in 1934. He moved to the Cornell University physics department in 1935, where he became a full professor of physics and director of the Laboratory of Nuclear Studies. He was affiliated with MIT's Radiation Laboratory and the Manhattan Project at Los Alamos from 1940 to 1945, while on the Cornell faculty.

As chairman of the Caltech Division of Physics, Mathematics, and Astronomy, Bacher shaped the program in the burgeoning field of high-energy physics, and was responsible for bringing both Richard Feynman and Murray Gell-Mann to Caltech. He also initiated the program in radio astronomy with the creation of the Owens Valley Radio Observatory, which to this day is one of the leading radio astronomy facilities in the world.

Bacher was president of the American Physical Society in 1964, president of the International Union of Pure and Applied Physics from 1969 to 1972, and winner of the President's Medal for Merit in 1946. In addition, he was a member of the U.S. delegation to the nuclear test ban negotiations in 1958, and a member at various times of committees and panels for the State Department, Department of Defense, the Atomic Energy Commission, and the National Academy of Sciences.

Bacher's wife of 64 years, Jean Dow Bacher, died in 1994. He is survived by a son, Andrew Dow Bacher of Bloomington, Indiana; a daughter, Martha Bacher Eaton of Santa Barbara; and two grandchildren.

Writer: 
Robert Tindol
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Laser Points to the Future at Palomar

PALOMAR MOUNTAIN, Calif. — The Hale Telescope on Palomar Mountain has been gathering light from the depths of the universe for 55 years. It finally sent some back early last week as a team of astronomers from the California Institute of Technology, the Jet Propulsion Laboratory and the University of Chicago created an artificial star by propagating a 4-watt laser beam out from the Hale Telescope and up into the night sky.

The laser was propagated as the first step in a program to expand the fraction of sky available to the technique known as adaptive optics. Adaptive optics allows astronomers to correct for the fuzzy images produced by earth's moving atmosphere, giving them a view that often surpasses those of smaller telescopes based in space.

"We have been steadily improving adaptive optics using bright natural guide stars at Palomar. As a result, the system routinely corrects for atmospheric distortions. Now we will be able to go to the next step," says Richard Dekany, associate director for development at Caltech Optical Observatories. Currently astronomers at Palomar can use the adaptive-optics technique only if a moderately bright star is sufficiently close to their object of interest. The adaptive-optics system uses the star as a source by which astronomers monitor and correct for the distortions produced by earth's atmosphere.

Employing the laser will allow astronomers to place an artificial corrective guide star wherever they see fit. To do so, they shine a narrow sodium laser beam up through the atmosphere. At an altitude of about 60 miles, the laser beam makes a small amount of sodium gas glow. The reflected glow from the glowing gas serves as the artificial guide star for the adaptive-optics system. The laser beam is too faint to be seen except by observers very close to the telescope, and the guide star it creates is even fainter. It can't be seen with the unaided eye, yet it is bright enough to allow astronomers to make their adaptive-optics corrections.

The Palomar Observatory currently employs the world's fastest astronomical adaptive optics system on its 200-inch Hale Telescope. It is able to correct for changes in the atmosphere 2,000 times per second. Astronomers from Caltech, JPL, and Cornell University have exploited this system to discover brown dwarf companions to stars, study the weather on a moon of Saturn, and see the shapes of asteroids.

"This is an important achievement that brings us one step closer to our goal," says Mitchell Troy, the adaptive optics group lead and Palomar adaptive optics task manager at the Jet Propulsion Laboratory. The goal, achieving adaptive-optics correction using the laser guide star, is expected next year. This will place Palomar in elite company as just the third observatory worldwide to deploy a laser guide system. This laser will greatly expand the science performed at Palomar and pave the way for future projects on telescopes that have not yet been built.

"This is a terrific technical achievement which not only opens up a bold and exciting scientific future for the venerable 200-inch telescope, but also demonstrates the next step on a path toward future large telescopes such as the Thirty Meter Telescope, " says Richard Ellis, Steele Family Professor of Astronomy and director of the Caltech Optical Observatories. "The next generation of large telescopes requires sodium laser guide-star adaptive-optics of the type being demonstrated at Palomar Observatory," he adds.

Currently in the design phase, the Thirty Meter Telescope (TMT) will eventually deliver images at visible and infrared wavelengths 12 times sharper than those of the Hubble Space Telescope. The TMT project is a collaboration between Caltech and the Associated Universities for Research in Astronomy, the Association of Canadian Universities for Research in Astronomy, and the University of California.

The Caltech adaptive optics team is made up of Richard Dekany (team leader) and Viswa Velur, Rich Goeden, Bob Weber, and Khanh Bui. Professor Edward Kibblewhite, University of Chicago, built the Chicago sum-frequency laser used in this project. The JPL Palomar adaptive optics team includes Mitchell Troy (team leader), Gary Brack, Steve Guiwits, Dean Palmer, Jennifer Roberts, Fang Shi, Thang Trinh, Tuan Truong and Kent Wallace. Installation of the laser at the Hale Telescope was overseen by Andrew Pickles, Robert Thicksten, and Hal Petrie of Palomar Observatory, and supported by Merle Sweet, John Henning, and Steve Einer.

The Palomar adaptive optics instrument was built and continues to be supported by the Jet Propulsion Laboratory as part of a Caltech-JPL collaboration.

Support for the adaptive-optics research at Caltech's Palomar Observatory comes from the Gordon and Betty Moore Foundation, the Oschin Family Foundation, and the National Science Foundation Center for Adaptive Optics.

Writer: 
Jill Perry
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CBI Reveals Motion in the Remotest Seeds of Galaxy Clusters in the Very Early Universe

PASADENA, Calif.--Cosmologists from the California Institute of Technology have used observations probing back to the remote epoch of the universe when atoms were first forming to detect movements among the seeds that gave rise to clusters of galaxies. The new results show the motion of primordial matter on its way to forming galaxy clusters and superclusters. The observations were obtained with an instrument high in the Chilean Andes known as the Cosmic Background Imager (CBI), and they provide new confidence in the accuracy of the standard model of the early universe in which rapid inflation occurred a brief instant after the Big Bang.

The novel feature of these polarization observations is that they reveal directly the seeds of galaxy clusters and their motions as they proceeded to form the first clusters of galaxies.

Reporting in the October 7 online edition of Science Express, Caltech's Rawn Professor of Astronomy, and principal investigator on the CBI project, Anthony Readhead and his team say the new polarization results provide strong support for the standard model of the universe as a place in which dark matter and dark energy are much more prevalent than everyday matter as we know it, which poses a major problem for physics. A companion paper describing early polarization observations with the CBI has been submitted to the Astrophysical Journal.

The cosmic background observed by the CBI originates from the era just 400,000 years after the Big Bang and provides a wealth of information on the nature of the universe. At this remote epoch none of the familiar structures of the universe existed--there were no galaxies, stars, or planets. Instead there were only tiny density fluctuations, and these were the seeds out of which galaxies and stars formed under the hand of gravity.

Instruments prior to the CBI had detected fluctuations on large angular scales, corresponding to masses much larger than superclusters of galaxies. The high resolution of the CBI allowed the seeds of the structures we observe around us in the universe today to be observed for the first time in January 2000.

The expanding universe cooled and by 400,000 years after the Big Bang it was cool enough for electrons and protons to combine to form atoms. Prior to this time photons could not travel far before colliding with an electron, and the universe was like a dense fog, but at this point the universe became transparent and since that time the photons have streamed freely across the universe to reach our telescopes today, 13.8 billion years later. Thus observations of the microwave background provide a snapshot of the universe as it was just 400,000 years after the Big Bang--long before the formation of the first galaxies, stars, and planets.

The new data were collected by the CBI between September 2002 and May 2004, and cover four patches of sky, encompassing a total area three hundred times the size of the moon and showing fine details only a fraction of the size of the moon. The new results are based on a property of light called polarization. This is a property that can be demonstrated easily with a pair of polarizing sunglasses. If one looks at light reflected off a pond through such sunglasses and then rotates the sunglasses, one sees the reflected light varying in brightness. This is because the reflected light is polarized, and the polarizing sunglasses only transmit light whose polarization is properly aligned with the glasses. The CBI likewise picks out the polarized light, and it is the details of this light that reveal the motion of the seeds of galaxy clusters.

In the total intensity we see a series of peaks and valleys, where the peaks are successive harmonics of a fundamental "tone." In the polarized emission we also see a series of peaks and valleys, but the peaks in the polarized emission coincide with the valleys in the total intensity, and vice versa. In other words, the polarized emission is exactly out of step with the total intensity. This property of the polarized emission being out of step with the total intensity indicates that the polarized emission arises from the motion of the material.

The first detection of polarized emission by the Degree Angular Scale Interferometer (DASI), the sister project of the CBI, in 2002 provided dramatic evidence of motion in the early universe, as did the measurements by the Wilkinson Microwave Anisotropy Probe (WMAP) in 2003. The CBI results announced today significantly augment these earlier findings by demonstrating directly, and on the small scales corresponding to galaxy clusters, that the polarized emission is out of step with the total intensity.

Other data on the cosmic microwave background polarization were released just two weeks ago by the DASI team, whose three years of results show further compelling evidence that the polarization is indeed due to the cosmic background and is not contaminated by radiation from the Milky Way. The results of these two sister projects therefore complement each other beautifully, as was the intention of Readhead and John Carlstrom, the principal investigator of DASI and a coauthor on the CBI paper, when they planned these two instruments a decade ago.

According to Readhead, "Physics has no satisfactory explanation for the dark energy which dominates the universe. This problem presents the most serious challenge to fundamental physics since the quantum and relativistic revolutions of a century ago. The successes of these polarization experiments give confidence in our ability to probe fine details of the polarized cosmic background, which will eventually throw light on the nature of this dark energy."

"The success of these polarization experiments has opened a new window for exploring the universe which may allow us to probe the first instants of the universe through observations of gravitational waves from the epoch of inflation," says Carlstrom.

The analysis of the CBI data is carried out in collaboration with groups at the National Radio Astronomy Observatory (NRAO) and at the Canadian Institute for Theoretical Astrophysics (CITA).

"This is truly an exciting time in cosmological research, with a remarkable convergence of theory and observation, a universe full of mysteries such as dark matter and dark energy, and a fantastic array of new technology--there is tremendous potential for fundamental discoveries here" says Steve Myers of the NRAO, a coauthor and key member of the CBI team from its inception.

According to Richard Bond, director of CITA and a coauthor of the paper, "As a theorist in the early eighties, when we were first showing that the magnitude of the cosmic microwave background polarization would likely be a factor of a hundred down in power from the minute temperature variations that were themselves a heroic effort to discover, it seemed wishful thinking that even in some far distant future such minute signals would be revealed. With these polarization detections, the wished-for has become reality, thanks to remarkable technological advances in experiments such as CBI. It has been our privilege at CITA to be fully engaged as members of the CBI team in unveiling these signals and interpreting their cosmological significance for what has emerged as the standard model of cosmic structure formation and evolution."

The next step for Readhead and his CBI team will be to refine these polarization observations significantly by taking more data, and to test whether or not the polarized emission is exactly out of step with the total intensity with the goal of finding some clues to the nature of the dark matter and dark energy.

The CBI is a microwave telescope array comprising 13 separate antennas, each about three feet in diameter and operating in 10 frequency channels, set up in concert so that the entire instruments acts as a set of 780 interferometers. The CBI is located at Llano de Chajnantor, a high plateau in Chile at 16,800 feet, making it by far the most sophisticated scientific instrument ever used at such high altitudes. The telescope is so high, in fact, that members of the scientific team must each carry bottled oxygen to do the work.

The upgrade of the CBI to polarization capability was supported by a generous grant from the Kavli Operating Institute, and the project is also the grateful recipient of continuing support from Barbara and Stanley Rawn Jr. The CBI is also supported by the National Science Foundation, the California Institute of Technology, and the Canadian Institute for Advanced Research, and has also received generous support from Maxine and Ronald Linde, Cecil and Sally Drinkward, and the Kavli Institute for Cosmological Physics at the University of Chicago.

In addition to the scientists mentioned above, today's Science Express paper is coauthored by C. Contaldi and J. L. Sievers of CITA, J.K. Cartwright and S. Padin, both of Caltech and the University of Chicago; B. S. Mason and M. Pospieszalski of the NRAO; C. Achermann, P. Altamirano, L. Bronfman, S. Casassus, and J. May all of the University of Chile; C. Dickinson, J. Kovac, T. J. Pearson, and M. Shepherd of Caltech; W. L. Holzapfel of UC Berkeley; E. M. Leitch and C. Pryke of the University of Chicago; D. Pogosyan of the University of Toronto and the University of Alberta; and R. Bustos, R. Reeves, and S. Torres of the University of Concepción, Chile.

 

Writer: 
Robert Tindol
Writer: 

David Politzer Wins Nobel Prize in Physics

PASADENA, Calif.--Hugh David Politzer has won the 2004 Nobel Prize in physics for work he began as a graduate student on how the elementary particles known as quarks are bound together to form the protons and neutrons of atomic nuclei. The announcement was made today by the Royal Swedish Academy of Sciences.

Politzer, a professor of theoretical physics at the California Institute of Technology, shares the prize with David Gross and Frank Wilczek. The key discovery celebrated by today's prize was made in 1973, when Politzer, a Harvard University graduate student at the time, and two physicists working independently from Politzer at Princeton University--Gross and his graduate student Wilczek--theorized that quarks actually become bound more tightly the farther they get from each other.

This discovery has been known for 31 years as "asymptotic freedom," and is often described by physics professors to their students with the analogy of a rubber band increasing in tightness as it is pulled apart. Asymptotic freedom established quantum chromodynamics (QCD) as the correct theory of the strong force, one of the four fundamental forces of nature.

Caltech president David Baltimore, himself a Nobel laureate, said he was pleased that another Caltech faculty member has joined the list of the Institute's Nobel recipients. "It's wonderful that David was acknowledged for something that was so far back in his career," Baltimore said. "It shows what young people can do if they think differently."

Politzer joined the Caltech faculty as a visiting associate in 1975, the year after finishing his Harvard Ph.D. in physics and three years after publishing his work on asymptotic freedom. He earned tenure in 1976, became a full professor in 1979, and served as head of the physics department (executive officer, in Caltech parlance) from 1986 to 1988.

A native of New York City, Politzer earned his bachelor's degree from the University of Michigan in 1969. The paper that inaugurated his Nobel Prize-winning work, titled "Reliable Perturbative Results for Strong Interactions?" appeared in the journal Physical Review Letters in 1973 and was Politzer's first published article. Politzer's initial foray into the public limelight came in 1989, when he was recruited to play physicist Robert Serber in the movie Fat Man and Little Boy, which recounted the story of the Manhattan Project and starred Paul Newman as the hard-driving project leader Gen. Leslie Groves. The director of the film, Roland Joffe, had been recruiting career physicists to play some of the roles, and he settled on Politzer, whose academic specialty was quite similar to that of the man he would play.

Politzer, who did not even own a television, later told a reporter from Caltech's internal publication On Campus that he had been reluctant to take the part, but had relented after Joffe convinced him that the "role would not require too much in the way of time or talent." During his two weeks on the set, Politzer warmed up to the project and began discussing nuclear defense policy with Paul Newman, with whom he shared a memorable dinner of spaghetti and salad--the latter dressed with "Newman's Own," of course.

Today's award brings to 31 the total number of prizes won by 30 Caltech faculty and alumni through the years (Linus Pauling won awards in both chemistry and peace). Founded in 1891, Caltech is located on a 124-acre campus in Pasadena. The Institute also manages the nearby Jet Propulsion Laboratory and operates eight other off-campus astronomical, seismological, and marine biology facilities. Caltech has an enrollment of some 2,000 students, more than half of whom are in graduate studies, and a faculty of about 280 professorial members and 65 research members, and some 560 postdoctoral scholars. Caltech employs a staff of more than 2,600 on campus and 5,100 at JPL.

U.S. News &World Report consistently ranks Caltech's undergraduate and graduate programs as being among the nation's best. The average SAT score of members of recent incoming freshman classes has consistently been at 1500.

Four Crafoord Prizes have been awarded to faculty members and alumni. Forty-seven Caltech faculty members and alumni have received the National Medal of Science; and nine alumni (two of whom are also trustees; and one is also a faculty member), two additional trustees, and one additional faculty member have won the National Medal of Technology. Since 1958, 14 faculty members have received the annual California Scientist of the Year award. On the Caltech faculty there are 78 fellows of the American Academy of Arts and Sciences; and on the faculty and Board of Trustees, 71 members of the National Academy of Sciences and 43 members of the National Academy of Engineering.

Caltech has more than 21,000 alumni.

 

The following information was written by Caltech's MacArthur Professor of Theoretical Physics John Preskill, a colleague of Politzer's. Preskill prepared the text upon learning that Politzer had won the Nobel Prize, and sent it from England this morning:

Of the four fundamental forces--the others besides the strong nuclear force are electromagnetism, the weak nuclear force (responsible for the decay of radioactive nuclei), and gravitation--the strong force was by far the most poorly understood in the early 1970s. It had been suggested in 1964 by Caltech physicist Murray Gell-Mann that protons and neutrons contain more elementary objects, which he called quarks.

Yet isolated quarks are never seen, indicating that the quarks are permanently bound together by powerful nuclear forces. Meanwhile, studies of high-energy collisions between electrons and protons performed at the Stanford Linear Accelerator Center (SLAC) had probed the internal structure of the proton, and Caltech's Richard Feynman had suggested in 1969 that the results of these experiments could be explained if quarks inside a proton are nearly free, not subject to any force. Feynman's suggestion, together with the observation that quarks are unable to escape from nuclear particles, posed a deep puzzle: how could nuclear forces be both strong enough to account for the permanent confinement of quarks and weak enough to account for the SLAC experiments?

The discovery of asymptotic freedom provided a highly satisfying resolution of this puzzle. The calculations of Gross, Wilczek, and Politzer showed that in quantum chromodynamics (QCD), quarks are held together strongly when separated by a distance comparable to the size of a proton, explaining quark confinement. Yet for the smaller separations explored in the high-energy SLAC experiments, the attraction is weaker, supporting Feynman's proposal.

Before this development, many physicists had anticipated that understanding the strong nuclear force would require revolutionary new concepts. But surprisingly, QCD has a remarkable mathematical similarity to quantum electrodynamics (QED), the theory that successfully explains electromagnetic phenomena. In QED the force between two electrically charged particles is mediated by the exchange of a photon (a particle of light) between the two particles; in QCD, the quarks carry a different kind of charge, called "color," and the force between two colored particles is mediated by the exchange of a "gluon" between the particles.

The crucial difference between the two theories is that while the photons of QED carry no charge of their own, the gluons of QCD are themselves colored particles. A quark is surrounded by a sea of "virtual" gluons that arise due to quantum fluctuations, and the color of the virtual gluons enhances the quark's own color. A probe coming closer and closer to the quark is influenced less and less by the virtual gluons, so that the effective color charge of the quark seems to weaken; this is asymptotic freedom.

Gross, Wilczek, and Politzer used pencil and paper to perform their breakthrough calculation. In 1973, the methods they needed were newly developed and fraught with subtleties. Today, the calculation is routinely assigned to physics graduate students as a homework exercise.

QCD predicts that the strength of the force between quarks changes with distance in a particular calculable way that has been well confirmed in experiments studying high-energy collisions of elementary particles. The theory makes other detailed predictions, such as the masses of various strongly interacting nuclear particles, which can be extracted only through large-scale numerical computations performed using supercomputers; these too are in satisfying agreement with experiment.

Because QCD, the theory of the strong nuclear force, turned out to be so similar to QED and to the theory of the weak nuclear force, it became possible after the discovery of asymptotic freedom to conceive of unified theories that incorporate all three forces into a common framework. Such theories have been proposed, but still await experimental confirmation. A further challenge, being pursued by many physicists today, is to achieve an even broader unification theory that encompasses the gravitational force as well.

Writer: 
RT

Caltech Physicists Achieve Measurement on a Single Magnetic Domain Wall

PASADENA, Calif.--Physicists for several years have been predicting a new age of semiconductor devices that operate by subtle changes in the orientation of electron spins. Known as "spintronics," the field relies on an intricate knowledge of the magnetic properties of materials and of how magnetic moments can be manipulated.

Now, scientists at the California Institute of Technology have developed a novel method of measuring the resistance of "domain walls," which are the nanoscale boundaries separating areas of a magnetized material that possess different magnetic alignments, or a "twist" of magnetic spins. Reporting in the September 2 issue of the journal Nature, Caltech physicists Hongxing Tang, Michael Roukes, and their colleagues show that their approach leads to an unparalleled precision in isolating, manipulating, and trapping domain walls one by one.

The authors have been able to trap individual domain walls between electrical probes for periods longer than a week. During that time, they are able to carry out extremely sensitive electrical measurements to identify the tiny amounts of resistance generated by this trapped single magnetic domain wall.

"We have demonstrated how a single magnetic domain wall can be monitored as it is made to traverse a patterned array of electrical probes in a microdevice made from single-crystal manganese-doped gallium arsenide," says Professor Roukes. Manganese- doped gallium arsenide belongs to a new class of ferromagnetic semiconductors that isexpected to have great potential for new spintronics devices.

This work also resolves an issue that has puzzled scientists for some time, according to Tang. Many physicists have thought that domain walls were a natural barrier to electron transport and that they cause positive resistance--in other words, the magnetic moments with different alignments created a natural opposition to the flow of charge from one side of the wall to the other. However, the new results show that the resistance is actually negative, which can be attributed to quantum effects in the locale of the domain wall itself. The very fact that the resistance is negative means that electrons can flow more easily under certain conditions, manifesting quantum mechanical origin in this novel phenomenon.

"We are certain that both this result and our new measurement methodology will be of interest to those working on future semiconductor devices based on spintronics," Tang says.

Understanding the dynamics of magnetic domain walls is crucial for magnetic storage devices such as magnetic hard drives, and for future magnetic memories. The methods have the potential to significantly alter the theoretical and experimental research for some time to come.

The work has been made possible through the Caltech team's earlier discovery of a phenomenon dubbed the "giant planar Hall effect." To reach the ultra-high resolution required to resolve the resistance of a domain wall, the authors advance a nanofabrication process for precise alignments of materials at the microscopic level and deploy an innovative way of manipulating domain walls.

"Using these advances, we have made careful measurements on many devices having domain walls of varying lengths and thicknesses," says Roukes. "All show negative resistance at the domain wall."

In addition to being a professor of physics, applied physics, and bioengineering at Caltech, Roukes is also founding director of Caltech's new Kavli Nanoscience Institute. Dr. Hongxing Tang is a senior research scientist at Caltech. Other authors of the paper are Sotiris Masmanidis, a Caltech graduate student in applied physics, and Roland Kawakami and Prof. David Awschalom, both of the UC Santa Barbara department of physics.

Writer: 
Robert Tindol

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