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[Sandia Lab News]

Vol. 56, No. 16                August 6, 2004
[Sandia National Laboratories]

Albuquerque, New Mexico 87185-0165    ||   Livermore, California 94550-0969
Tonopah, Nevada; Nevada Test Site; Amarillo, Texas

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SAR to the rescue: Search and rescue group uses Sandia synthetic aperture radar to save stranded hiker Real New Age crystal: Sandia's John Reno fabricates the best terahertz crystals in US US-Russian accord seeks global use of nuclear energy



SAR to the rescue: Search and rescue group uses Sandia synthetic aperture radar to save stranded hiker

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By Chris Burroughs

A Sandia radar, originally developed for military surveillance and reconnaissance applications, is helping a local volunteer search and rescue group save lives. The Rapid Terrain Visualization (RTV) precision mapping synthetic aperture radar (SAR) was used for the first time last November by the Albuquerque Mountain Rescue Council (AMRC) to help find and rescue a hiker stranded in the dark in the Sandia Mountains.

It all started with a conversation between Dale Dubbert of SAR Sensor Technologies Dept. 2345, a former rescue council volunteer, and Steve Attaway (9134), long-time group member.

"We talked about Sandia's capabilities to do precision terrain maps and realized that this technology could be useful in search and rescue missions," Dale says. "It had the potential of providing detailed information about terrain where searches are underway, including heights, location

of crevices and cliffs, and even different types of vegetation." The RTV mapping system uses interfero- metric synthetic aperture radar (IFSAR). Two antennae offset in elevation aboard a moving aircraft allow the measurement of target height, as well as east-west and north-south position like conventional SAR. This produces a 3-D map that shows terrain details.

The IFSAR maps have an absolute height accuracy of less than two meters and a relative accuracy of less than one meter. "This is an order of magnitude precision improvement over the standard USGS topographical maps generally used in search and rescue missions," Dale says.

No other mapping system in the world achieves this level of accuracy combined with a high area coverage rate and real-time processing, says Dale. The IFSAR can map day or night and through cloud cover.

It was Dale who provided the map data of the Sandias, obtained while the RTV SAR was installed on a deHavilland DHC-7 Army aircraft. He gave the council a CD of the maps last year.

A few months later, on a chilly November evening, the search and rescue group used the precision maps for the first time.

Steve says he got a call just before sundown telling him that a hiker was lost in the Sandia Mountains, and his help was needed for a rescue.

After collecting additional information on the hiker's location, he took a few minutes to create detailed RTV SAR maps. He zoomed in on the area where the man was believed to be and printed out color maps of the location.

Steve then went to the Sandia tram, located on the west side of the Sandia Mountains where the rescuers were gathering, and took the tram up to the peak.

"The hiker was climbing the mountain using the tram cables as a guide for off-trail hiking," Steve says. "He apparently became lost while attempting to follow the tram towers and used his cell phone to call for help. We spotted him from the tram as he waved his flashlight so we would notice him. But seeing him and getting to him were two different things."

The terrain in the area where the hiker was lost is extremely rugged. Members of the rescue group are experts in using compasses, GPS, and topographic maps, but even for them the terrain was difficult to navigate.

AMRC President Bill Scherzinger (9123), who also participated in the rescue mission, says that's when the crew turned to the RTV SAR maps for help.

"The detail available helped us make our way to the man," Bill says. "The maps were color-coded for height and gave estimates of ground roughness. They also distinguished individual rock formations - known to the rock climbers in our group - that are not seen on the topographic maps."

The initial plan was to have rescuers ride the tram to the top of the mountain and then hike down to the stranded hiker's location. However, when they determined that the man was not near the bottom of the canyon, but instead at the top of a ridge called Dragon's Tail, plans changed. The hiker was 100 feet down from the top in a narrow slot that was impossible to access without technical rock climbing. "Using the RTV SAR maps to help us plan the rescue, we sent one team to nearby Echo Canyon to better determine the exact location of the hiker. A second team went along the treacherous ridgeline of Dragon's Tail. The first team made voice contact with the man from the bottom of the bluffs at about 3 a.m.," Bill says.

The second team rappelled to the hiker at 6 a.m., following a ridgeline that was one of the most difficult and risky routes the rescue group ever attempted. Another four-hour hike using climbing gear and ropes was necessary to bring the man to safety. The entire rescue took more than 12 hours.

"There's no doubt that if we didn't have the RTV SAR maps, reaching the stranded hiker would have been even more difficult than it was," Bill says. "The 3-D detail of SAR maps saved us time while we were planning our route. We expect to continue to use the RTV SAR in future rescue missions where it seems like it will help the most." -- Chris Burroughs

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Real New Age crystal: Sandia's John Reno fabricates the best terahertz crystals in US

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By Neal Singer

The relatively unexplored terahertz frequency range - higher than microwaves, lower than the far infrared - has long intrigued researchers. Lasers and detectors in the THz frequency regime have wide-ranging applications in spectroscopy, astronomy, medical and other types of imaging, and in remote sensing. They are expected to be useful in chemical sensing systems for the detection of molecular absorption lines associated with trace gases.

While lasers with detectors already exist to send and receive signals from that realm, commercial lasers weigh hundreds of pounds, contain long fragile glass tubes, and cost a lot of money, says Jerry Simmons, Manager of Sandia's Semiconductor Materials & Device Sciences Department (1123).

What's wanted are lightweight, inexpensive, robust devices. Such devices are now appearing. Their generating sources are semiconductor crystal films. Perhaps surprisingly, the very best crystal films for terahertz work in the US are made on a 10-year-old molecular beam epitaxy machine in Sandia's aging Compound Semiconductor Research Lab.

Credit, many agree, goes to the expert hand of John Reno (1123).

Sandia is the best and (until very recently, through a transfer of Sandia technology) the only place in the US to grow a crystal film that can be made into such lasers and sensors.

One difference between the older, clunkier lasers and modern attempts at penetrating the terahertz range are obvious. Instead of requiring the space of a table top, THz lasers from crystals grown by John are smaller than a cubic millimeter.

Achieving a laser that operates close to room temperature is still an issue. Currently the highest operating temperature - 130K - has been achieved by Professor Qing Hu at MIT, using crystals grown at Sandia. While the required cooling system for this device is bigger than a cubic millimeter, the overall size is still small compared to the older lasers.

Mike Wanke (1743) at Sandia is developing a terahertz semiconductor laser that should be easier and cheaper to maintain than the MIT version. Aided by tiny thermoelectric coolers, it should operate in higher ambient temperatures.

In addition to growing the best THz laser crystals, John grows another type of crystal structure - one of such ultrahigh purity that, at temperatures of 1 K and below, electrons can travel up to 0.1 millimeter in the crystal without scattering. Only four places in the world have successfully grown these structures.

Because only two of these places are in the US, John's ultrapure semiconductor layers are in high demand at universities and "are a centerpiece of the resources being assembled at Sandia's Center for Integrated Nanotechnologies," says Neal Shinn, CINT User Program Manager. John's materials already play key roles in several CINT collaborations.

This material also is being used to develop revolutionary THz detectors, in work again led by Mike Wanke. According to Mike, "Having a grower who can create the structures required for either the lasers or the detectors is incredibly rare, but one able to grow both is amazing." All these gadgets, which weigh almost nothing and whose materials cost will be trivial when scaled up to mass production, use crystals fabricated by John Reno.

"What's wanted is a solid-state source that is reliable, depends on semiconductor technology, and delivers a reasonable amount of power," says Mark Lee (1123). He says that except for people John has taught, "John Reno is the only grower of semiconductor material in the US who has grown terahertz crystals that work."

What's needed, says Mark, is several milliwatts in continuous output. "John's output of 30 milliwatts at 2.5 terahertz is an order of magnitude higher than any other at that frequency," he says.

How does John achieve this on his aging MBE machine?

"It's not the machine, it's the skill of the person operating it," says Mark. There are, he says, a half-dozen molecular beam epitaxy growers in the US who could deliver as good or a bit better high-purity material.

"Of the other two things that really matter, one is precision in layer thicknesses; equally important is alloy precision. John has been tuning his machine for years." Nobody in the US does it better, he says.

To see bearded John at work in his lair - gowned, booted, gloved, masked, and capped, facing a 10-foot-long, seven-foot-high, molecular beam epitaxy machine - is a stirring sight. John is as suited as any armored knight facing a dragon.

On his commands, the MBE's black electrical wires, thin silver tubes delivering nitrogen, thick cylindrical cooling pumps, and still-larger arm of an electron beam gun all work together to deposit atoms, atomic layer by structured atomic layer.

John's position is so central that in the strange deck of cards called the Tarot, whose face cards are claimed to represent archetypical human situations - the Hanged Man, the Empress, the Huntsman and so on - John might be a new archetypal entity . . . . the Crystal Grower.

But not, obviously, of the glitzy kind hawked by merchants in Santa Fe. THz sources based on semiconductor crystals have been achieved at very few other sites in the world - among them, the Cavendish Lab in England and the University of Neuchatel in Switzerland.

Each crystal for terahertz lasers takes approximately 17 hours to grow and is composed of 175 "steps," so-called because the declining energies at each step resemble a set of stairs going downhill. Indeed, this type of semiconductor laser is called a "quantum cascade laser," since the electrons act like water as they "cascade" down the steps, emitting a THz photon at each one. These steps consist of about 10 layers built of different thicknesses and materials, each composed of five to 35 atomic layers. John can grow one crystal each day.

The amount of care resembles that taken by a Japanese blacksmith forging a classical samurai ceremonial sword, rearranging and elongating his material's crystal domains by continual refolding. "The process has to remain the same, whether after five hours or 17 hours, or the quantum levels [of the materials] change," says John. The work requires the opening and closing of precise shutters, he says. To do this, he heats and boils off potentially dangerous materials like arsenic, gallium, aluminum, and indium at roughly 1,100 degrees C, and allows them to coalesce as a crystal film on a mirror-smooth gallium arsenide substrate, 625 microns thick, at nearly 600 degrees C. The work must be accurate down to the atom.

"Some sites are gallium surrounded by four arsenic; or an arsenic surrounded by four gallium," John says. "Different metals are different distances apart." A deposited atom has to have time to find a home before being barraged by new atoms, he says. "They need to be given the right amount of energy to move on this hot surface."

John sees himself as facing two challenges. One is the chemical/mechanical challenge to put what he wants into, say, four atomic layers. The second challenge is the precise growth that will produce the desired output. For that, he says, he relies on researchers to provide him with a working set of specifications to build to.

The specifications are in, and more are on their way. -- Neal Singer

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US-Russian accord seeks global use of nuclear energy

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By Ken Frazier

Sandia announced Monday that representatives of seven DOE national labs, including Sandia, and nine Russian scientific nuclear organizations have developed a joint document that advocates greater global use of nuclear energy.

Sandia President and Labs Director C. Paul Robinson was elected chairman of the seven US representatives. "These meetings were held to explore alternative research and development paths to meet growing energy needs," Paul says. "We found considerable common ground on ways to achieve future energy needs, with use of advanced nuclear systems."

US and Russian representatives developed the document July 19-21 at the International Atomic Energy Agency headquarters in Vienna, Austria. The meeting was a follow up to the address by Russian President Putin to the Millennium Summit in September 2000, the Bush-Putin Summit in 2002, and the speech by President Bush at the National Defense University in February 2004. On each of these occasions the idea was advanced that nuclear power should play an appropriate role in the energy mix in the 21st century while providing protection against proliferation.

The document says the participants believe that of all current or imminently developable energy technologies, only nuclear power is capable of meeting the growing world demand for safe, clean, plentiful, and economically viable sources of electricity, fresh water, and hydrogen.

"The time has come to develop a comprehensive and realistic plan to ensure the development and deployment of nuclear energy," the joint document says. "It must preserve access to nuclear energy sources for all countries of the world, and in parallel, reduce the risks of nuclear arms proliferation, nuclear terrorism, and hazardous impacts on environment and population health."

"With government encouragement and the right regulatory and economic conditions, nuclear energy could supply a substantial part of US and Russian energy needs and 30-40 percent of the world electricity demand by 2050," the document says.

In addition to providing a virtually limitless supply of secure and reliable energy, greater use of nuclear energy would greatly reduce the risk of nuclear weapon proliferation and nuclear terrorism and reduce the worldwide amount of carbon emissions, the directors said.

US, Russian signers of the document

Representatives in the American delegation were Paul, Hermann Grunder, director, Argonne National Laboratory; Paul Kearns, director, Idaho National Engineering and Environmental Laboratory; Michael Anastasio, director, Lawrence Livermore National Laboratory; Pete Nanos, director, Los Alamos National Laboratory; Jeffrey Wadsworth, director, Oak Ridge Laboratories, and Leonard Peters, director, Pacific Northwest National Laboratory.

The Russian delegates were Evgeny Velikhov, president, RRC "Kurchatov Institute"; Antoly Zrodnikov, director general, Leypunsky Institute for Physic and Power Engineering, RF Federal Agency on Atomic Energy; Leonid Bolshov, director, Nuclear Safety Institute, Russian Academy of Sciences; Alexander Vatulin, director, Bochvar Russian Research Institute of Nonorganic Materials, RF Federal Agency on Atomic Energy; Boris Gabaraev, director, Dollejal Research and Development Institute of Power Engineering, RF Federal Agency on Atomic Energy; Alexey Grachev, director, Research Institute of Nuclear Reactors, RF Federal Agency on Atomic Energy; Yury Dragunov, director, general designer, Experimental Design Bureau Hydropress, RF Federal Agency on Atomic Energy; Vital Kostin, director, principal designer, Afrikantov Experimental Design Bureau of Mashine Building, RF Federal Agency on Atomic Energy; Alexander Rimsky-Korsakov, director general, Research and Production Association Khlopin Radium Institute, RF Federal Agency on Atomic Energy.

All of the delegates signed the joint document, which will be submitted to their respective governments for consideration. -- Ken Frazier


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Last modified: August 5, 2004

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