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Lab News -- September 29, 2006

September 29, 2006

LabNews 09/29/2006PDF (650KB)

Secretary Chertoff dedicates new NISAC facility

By Stephanie Holinka

Department of Homeland Security Secretary Michael Chertoff dedicated the National Infrastructure Simulation and Analysis Center (NISAC) at Sandia on Sept. 18. NISAC is a program that integrates the laboratories’ expertise in modeling and simulation of complex systems to examine both natural and manmade infrastructure national security issues.

The center is a partnership between Sandia and Los Alamos national labs and is managed by the Department of Homeland Security’s Preparedness Directorate.

Secretary Chertoff affirmed the need for NISAC, insisting that “people who have to make decisions need accessible and reliable information.” He praised the “willingness of the Labs to adapt to 21st-century challenges and step forward” to address the types of problems that may someday face our nation.

Chertoff was joined by Sen. Pete Domenici, R-N.M, Rep. Heather Wilson, R-N.M., and Rep. Steve Pearce, R-N.M., as they dedicated the first DHS-funded facility at Sandia. They received an overview of NISAC’s technical contributions to the nation’s homeland security efforts and demonstrations of several technologies.

Proposal predates 9/11, Katrina

Domenici proposed NISAC in 1999, before policymakers fully appreciated the need for such a facility. “I was a salesman selling NISAC to a country that didn't want to accept NISAC,” Domenici said.

John Mitchiner, manager of System Engineering and Analysis Business Area Dept. 6320 says NISAC’s mission is “to help make US infrastructures more resilient to disruption.”

Before 9/11 and before Hurricane Katrina, the idea of having some of the nation’s best and brightest examine bad things that hadn’t happened yet seemed odd. Domenici found initial funding for the program. When it began to bear fruit, Homeland Security provided additional funding.

In remarks at the ribbon-cutting, Sandia Senior VP and Deputy Labs Director for Integrated Technologies and Systems Al Romig took note of the increasing importance of Sandia’s relationship with DHS. He said the Labs is “energized” by the opportunity to continue the tradition of exceptional service to the nation as it confronts the security challenges of the 21st century.

Al said the NISAC facility is evidence of an evolving partnership between NNSA and DHS, adding that it is especially gratifying for the national laboratories to see the interagency cooperation blossom and bear fruit.

Building has collaborative workspaces

The $7 million, 24,000-square-foot building provides facilities for individuals, teams, and distributed collaboration for some 110 people, and includes a visualization space where modeling results and simulations can be displayed for cooperative analysis and technical development. The building was designed with significant input from its occupants and has incorporated collaborative workspaces to encourage groups to interact more frequently.

NISAC employs experts from a variety of disciplines; it includes computer modelers, economists, and civil engineers. They examine scenarios of disruption from a variety of viewpoints, offering their results to those who may respond to future real events.

Theresa Brown at Sandia and her LANL counterpart Jim Smith serve as program managers at their respective labs.

NISAC aids decision makers in preparedness, consequence and risk analysis, policy analysis, investment and mitigation planning, education and training, and provides near real-time assistance to crisis-response organizations.

Because the US supports one of the world’s highest standards of living, it relies heavily on interconnected systems for distribution of energy, transportation of food and other goods, and information. When this flow is disrupted in one area of the country, surprising consequences can result. NISAC provides multidisciplinary consequence analysis of infrastructure disruption, which allows decision makers to have more robust information before they make critical infrastructure decisions during natural disasters or after a terrorist event. -- Stephanie Holinka

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Phase diagram of water revised by Sandia researchers

By Neal Singer

Two Sandia researchers have significantly altered the theoretical diagram universally used by scientists to chart the phases of water. The new model also expands the known range of water’s electrical conductivity under extreme temperatures and pressures.

“We were trying to understand conditions at [Sandia’s] Z [accelerator] when its flash goes through water,” says Thomas Mattsson (1674), a theoretical physicist, “but the problems are so advanced that they hopscotched to another branch of science and apply to the outside world to a high degree.”

The intent of Thomas and Mike Desjarlais (also 1674) was to produce more accurate information on the changing state of water in Sandia’s Z machine as its extreme amperage passes through a water bath insulating Z’s transmission lines, as well as through water switches placed along those lines to first restrain and then transmit Z’s electrical pulse.

The researchers first found the standard water-phase diagram out of whack when, on Sandia’s Thunderbird supercomputer, they ran an advanced quantum molecular simulation program able to include “warm” electrons instead of unrealistic cold ones, says Mike.

The work showed that phase boundaries for “metallic water” — water with its electrons able to migrate like a metal’s — should be lowered from 7,000 kelvin and 250 gigapascals to 4,000 K and 100 GPa.

This new range — far beyond that which Z routinely enters — is nevertheless useful because it is sure to revise astronomers’ calculations of the strength of the magnetic cores of gas-giant planets like Neptune. Because the characteristics of Neptune’s interior water partly lie in this electrically conducting sector, the water probably contributes to a magnetic field formerly thought to be generated only by the planet’s core.

Diagram confirmed experimentally

The new calculations agree with experimental measurements in research led by physicist Peter Celliers of Lawrence Livermore National Laboratory.

The computational work, paid for by Sandia’s internal Laboratory Directed Research and Development program, is part of a broad front of research to understand conditions that will prevail when the current upgrade of Z to ZR is completed in July ’07. With new giant capacitors around Z’s circular rim replacing ones 20 years old, the expected amperage sent through the machine’s 36 “spokes” to a target placed at its hub is expected to rise from 20 million to 26 million amps.

A key question for Sandia designers is to determine what characteristics of water can be expected as greater amounts of electricity pour through the machine’s switches. These switches not only rely on water’s insulating properties to momentarily restrain the current but, in water’s ionized state, to pass the pulse forward at a time interval reduced from micro- to nanoseconds.

So much electricity passing through water vaporizes it, causing pressures to rise in surrounding regions as the shock wave travels outward. But how much is the increase? How big a transmitting cavity does the ionized region form to transmit what amounts to a giant spark? And what are the best sizes for these channels, and for the switches themselves, to optimize the transmission of electrical pulses in future upgrades?

“The concern was that ZR or its successors might go beyond the ability of a water switch

to function and carry the current we want it to carry,” says Keith Matzen, director of Sandia’s Pulsed Power Sciences Center (1600). “The

concern is that more efficient, larger machines may run into a limit and their switches not meet design requirements. So the question is, how does a water switch really work from first principles?”

Understanding water’s phases

One aspect of this knowledge is to model water to get a finer understanding of its phases, he says.

The molecular modeling code, VASP (Vienna Ab-initio Simulation Package), based on density functional theory (DFT), was written in Austria and initially used at Sandia by Peter Feibelman (1114). Mike extended it to model electrical conductivity and Thomas developed a model for ionic conductivity based on calculations of hydrogen diffusion. An accurate description of water requires this combined treatment of electronic and ionic conductivity.

The adaptation of VASP to high-energy-density physics (HEDP) work at Sandia was motivated by earlier experimental measurements of the conductivity of exploding wires by Alan DeSilva at the University of Maryland. DeSilva found a considerable disparity between his data and theoretical models of materials in the region of phase space called warm dense matter. Mike’s early VASP conductivity calculations immediately resolved the discrepancy. In recent years, a team of Sandia researchers has been extending one of Sandia’s own DFT codes (Socorro) to go beyond the capabilities of VASP for HEDP applications.

“Mike was the first to pioneer this capability for warm dense matter,” says Tom Mehlhorn, manager of 1674, “and Thomas has come on to be a near-perfect complement as the work enters more complex areas.”

Information vital for ZR

Sandia’s ability to calculate electrical properties and phase diagrams “has rapidly progressed from simple metals like aluminum for Z’s flyer plates — a critical breakthrough by Mike, the need for which was driven by experimental-theoretical discrepancies,” says Tom, “to alloys like stainless steel for Z’s wire arrays and ZR’s structural conductors (with Thomas’ help), and now to water, with Thomas leading the way. This six-year history gives us a unique ability to model the extreme conditions of high-energy-density environments.”

As it turns out, the newly discovered regime will not adversely affect Sandia’s water switches on ZR. But water switches not yet designed for future upgrades may require the more accurate understanding of the phases of water discovered by the Sandia researchers, says Larry Warne (1152).

Because of Z’s success in provoking fusion neutrons from deuterium pellets, it is thought of as a possible (if dark-horse) contender in the race for high-yield controlled nuclear fusion, which would provide essentially unlimited power to humanity.

Compression of Z’s amperage in time is the cause of its huge power, equivalent to 50 times the electrical production of all the generating plants on Earth for a few nanoseconds.

The work on water phases was initially published July 7 in Physical Review Letters and most recently reported at the 12th International Workshop on the Physics of Non-Ideal Plasmas, held in Darmstadt, Germany, Sept. 4-8. -- Neal Singer

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Sandia LDRI sensor continues to monitor space shuttle missions

By Michael Padilla

During each of the three space shuttle flights since the Columbia disaster, the Sandia Laser Dynamic Range Imager (LDRI) sensor has been used to help ensure that the shuttle’s thermal protection system is intact before the spacecraft returns to earth.

During the latest Atlantis mission nearly two dozen Sandians served as the ground station team at NASA’s Johnson Space Center near Houston, Texas.

During the flight while preparing for reentry, astronauts saw several unidentified objects floating in space nearby. Mission control decided to do a quick inspection of the shuttle’s skin using NASA’s in-house video camera.

“In the spirit of doing everything possible to aid the NASA screeners, the Sandia ground station team processed the NASA data and provided them with improved, high-quality imagery that helped NASA make the decision to return the shuttle to earth,” says team member Mark Heying (2624).

On flight day two after liftoff, the LDRI sensor is used in a series of multiple pass scans of the leading edges of both wings of the shuttle and of the nose cap. Approximately three hours of video is acquired. The operation is repeated just before the shuttle returns to earth, in case the shuttle was impacted by micrometeorites or space debris while on orbit. The sensor generates images of 720 by 480 pixels, at 30 Hz, which are transmitted to the Space Center.

The Sandia team staffed four workstations, which captured the down-linked data and provided various types of products for the NASA screening teams. The first product, called level 1, is the imagery corrected for transmission line artifacts incurred, and for fixed pattern noise, which is called flat field correction.

When the level 1 images are delivered to NASA, the total number of frames is reduced by a factor of four, Mark says. This is to help the screeners avoid information overload, while ensuring that full inspection coverage is maintained.

Another ground station product is generated by registering multiple contiguous frames together into a single sharpened image. This high-quality, low-noise imagery is closely examined by NASA screeners for artifacts that did not exist on the shuttle before lift off. If any potential defects are found, an “area of interest” is declared and a request goes out to the Sandia team for a detailed report.

By using a set of in-house processing tools, workstation operators can quickly generate a report that details the length, width, and depth of the specified object, says Mark. The team can also generate a 3-D point cloud image, which can be rotated and examined from numerous angles and zoom settings.

Since the first return-to-flight mission the Sandia team has applied multiple lessons learned to improve the quality of the imagery products and the speed at which they are delivered.

“We have also created several tools to aid NASA that go above and beyond the original requirements,” says Mark. “These tools include real-time documentation of acquisition events, and web-based graphical representation of scan coverage.”

New next-generation software is in the works to improve the operator interface, and to speed the delivery of processed imagery even further.

“This mission was another example of the dedication and willingness of the Sandia team to do everything possible to help NASA complete the construction of the International Space Station in a timely and safe manner,” says Mark.

The Sandia ground station team includes: Tom Casaus, Dennis Clingan, Mark Heying, Joel Jordan, Bob Nellums, Todd Pitts, Gus Rodriguez, Jose Rodriguez, John Sandusky, Richard Taplin (all 2624) Erik Fosshage (12343), Steve Gradoville (2661), Simon Hathaway (2623), David Karelitz (4326), Steve Lebien (5919), Cristina Montoya (4341), Eric Ollila (2623), Megan Slinkard (2661), and Patricia Tempel (2622). Other support personnel include: Bob Habbit (2624), Dan Talbert (5413), and Larry Dalton (2622). -- Michael Padilla

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