By Neal Singer
An automobile engine that fired one cylinder and then waited hours before firing again wouldn’t take a car very far.
Similarly, a machine to provide humanity unlimited electrical energy from cheap, abundant seawater can’t fire once and quit for the day. It must deliver energy to fuse pellets of hydrogen every 10 seconds and keep up that pace for millions of shots between maintenance — a kind of an internal combustion engine for nuclear fusion. That’s so, at least, for the fusion method at Sandia’s Z machine and elsewhere known as inertial confinement.
But, unable to produce fusion except episodically, the method has been overshadowed by the technique called magnetic confinement — a method that uses a magnetic field to confine a continuous fusion reaction from which to draw power.
Now an electrical circuit emerging from the technological hills may change the balance between these systems. Tagged as “revolutionary” by ordinarily conservative researchers, it may close the gap between the two methods.
The circuit is easily able to fire every 10.2 seconds in brief, powerful bursts.
Arranged modularly, a collection of these circuits could deliver enough power to cause high-yield fusion releases — that is, more power emitted than inserted — from hydrogen pellet targets every few seconds, a basic requirement for a nuclear fusion-fueled electrical generating plant.
The system, called a linear transformer driver (LTD), was created by researchers at the Institute of High Current Electronics in Tomsk, Russia, in collaboration with colleagues at Sandia.
“This is the most significant advance in primary power generation since the invention of the Marx generator, my staff and I believe,” says Keith Matzen, director of Pulsed Power Center 1600. Marx generators are giant capacitors used to store and discharge Z’s 20 million amps of electrical current. They were invented in 1924.
The cherry-lifesaver path to fusion
The circuit — a switch tightly coupled to two capacitors — is about the size of a shoebox and is termed a “brick.” When bricks are tightly packed in groups of 20 and electrically connected in parallel in a circular container resembling a large cherry lifesaver, the aggregate, or “cavity” as the physicists would have it, can transmit a current of 0.5 megamperes at 100 kilovolts.
A test cavity has fired in Sandia’s Tech Area 4 without flaw more than 11,000 times.
Because the cavities are modular, they can be stacked like donuts on a metal prong called a stalk. Arranged in a suitable configuration, they could generate 60 megamperes and six megavolts of electrical power, enough (theoretically) to generate high-yield nuclear fusion within the parameters necessary to run an electrical power plant.
“This is a revolutionary advance,” says Craig Olson (1640), senior scientist and manager of the pulsed power inertial fusion energy program.
The next-generation cavity model, now being tested in Tomsk, transmits 1.0 megamperes at the same voltage and with the same rapidity. Five such units have been built; four have been purchased by Sandia and one by the University of Michigan. The units cost $160,000 each. They too, according to Sandia scientist and project leader Mike Mazarakis (1671), who supervised the tests at the Siberian site, are performing without flaw.
Says Rick Stulen (1000), Sandia VP for Science, Technology, and Research Foundations, “This new technology not only represents a remarkable technical advance but also demonstrates the strong engagement of Sandia’s scientists and engineers in the international community.”
“This is an amazing achievement,” says VP Gerry Yonas, a former leader at Z and of the Labs’ Advanced Concepts Group.
Happily for Sandia accountants but sadly to those who love the widely distributed arcs-and-sparks photo of Z firing by Sandia photographer Randy Montoya (3651), the new switch eliminates the need for the hundreds of thousands of gallons of insulating water and oil carried by the present Z structure. It was over the surface of that water that the electrical arcing of Z became a phenomenon as much appreciated by graphic artists as it was loathed by engineers (who saw it as wasted energy). Also gone will be much of Z’s intricate switching. All were needed to shorten to nanoseconds the microsecond pulse produced by Marx generators.
Advantages of the new technology
The linear transformer driver produces its 100-nanosecond pulse from the get-go. It works so well because its design lowers inductances that ordinarily slow electrical transmission.
It does this in part by eliminating the huge plates and extensive wiring in the current Z machine, all of which generate magnetic fields. In the new system, each brick has almost no wiring. Two capacitors about the size of small thermos bottles are tightly linked to a switch the size of a lunchbox. There is little opportunity to generate magnetic fields that slow the passage of current.
Further, linking the bricks in parallel in a cavity not only adds currents, but decreases inductances to levels significantly less than that of Marx generators.
The subsets are then linked in series to add voltage.
This allows a very powerful machine to fire very rapidly, with only a thin layer of oil bathing the rings and rows of switches.
The LTD technology is 50 percent more efficient than current Z machine firings, in terms of the ratio of useful energy out to energy in. Z is currently 15 percent efficient to its load (already a very high efficiency among possible fusion machines).
There is, however, a small matter of cost.
Funding for Z historically has been for defense purposes: Its experiments are used to generate data for simulations on supercomputers that help maintain the strength, effectiveness, and safety of the US nuclear deterrent. Even without its rapid repetition capability, a powerful LTD machine would better simulate conditions created by nuclear weapons, so that data from the laboratory-created explosion of Z firing could be used with greater certainty in computer simulations regarding nuclear weapons. The US has refrained from actual testing of nuclear weapons for 15 years.
But fired repeatedly, the machine could well be the fusion machine that could form the basis of an electrical generating plant only two decades away. Progress in this arena might eventually require funding from DOE’s energy arm.
$35 million and five years
To confirm the new Z concept would take $35 million over five to seven years to build a test bed with 100 cavities.
Funding thus far has come from two US congressional initiatives through DOE-NNSA Defense Programs, Sandia’s internal Laboratory Directed Research and Development monies, and Sandia’s Inertial Confinement Fusion program.
“It’s like building a tinker toy,” says Keith. “We think we need 60 megamperes to make large fusion yields. But though our simulations show it can be done, we won’t know for certain until we actually build it.”
The device was designed by Tomsk pulsed-power head Alexander Kim with the switch developed by Boris Kovalchuk. Its speed-up from a microsecond to 100 nanosecond firing was urged by Sandia manager Dillon McDaniel (1650), and encouraged by Sandia managers Rick Spielman (1676) and Ken Struve (1671). The work was led at Sandia and Tomsk by Sandia researcher Mike Mazarakis (1671). Testing at Sandia was by Bill Fowler (1671) and Robin Sharpe (1676). The Z-IFE fusion energy program at Sandia was initiated and is managed by Craig Olson (1640).
Sandia has filed a patent application on a high-power pulsed-power accelerator invented by William Stygar (1671) that can use an LTD as the primary power generator to replace the conventional Marx generator.
Recent results on LTD development will be presented at the IEEE International Pulsed Power Conference and the IEEE Symposium on Fusion Engineering to be held in Albuquerque in June. -- Neal Singer
By John German
There’s a new product on the shelves of local hardware stores. Among the household cleaners is a bright green box emblazoned with a catchy promise: “Stops Mold Cold!”
On the back of the box, in tiny black letters, appears this: “New technology originally developed and patented by Sandia National Laboratories.”
The product is Mold Control 500, distributed by Scott’s Liquid Gold of Denver, Colo., and now available in Home Depot, Wal-Mart, True Value, Ace Hardware, and other home improvement stores across the country.
For around $30, a box of MC 500, dispensed as a foam, treats 500 square feet of mildew- and mold-contaminated surface area indoors or outdoors, according to the information on the box.
Mold and anthrax
The product is based on Sandia’s decontamination formulation (a.k.a. decon foam), which has become a widely stockpiled first responder tool for cleanup following a terrorist attack involving either chemical or biological warfare agents. It is best known for its role in helping remediate anthrax-contaminated buildings in Washington, D.C., and New York in 2001 (see “Sandia’s decon formulation: You’ve come a long way, baby” on page 5).
The formulation — which employs the active chemical ingredients of toothpastes and hair conditioners — kills fungi such as molds in much the same way it kills anthrax, says Mark Tucker (6327), who leads the Sandia team that has developed, improved, and tested the formulation during the last 10 years.
Mold growths form films over their surfaces that, like the shells of anthrax spores, are difficult to penetrate. Mold spores also are able to survive extreme temperatures and low humidity and can remain dormant indefinitely.
When used as a foam, the decon formulation expands to fill space and thus gets into corners and other hard-to-reach places, and it sticks to walls and ceilings and remains there, giving the chemistry time to do its work.
The decon formulation’s surfactants poke holes in the mold’s film, and its mild oxidizing components kill the fungal organisms beneath, its developers believe.
“This is pretty exciting,” says Mark. “Mold remediation wasn’t what we set out to do, but it is effective at killing most micro-organisms, so it’s good to find uses beyond our original intent — especially uses that might improve public health.”
Two companies hold Sandia licenses to market and distribute products based on the formulation: Modec, Inc., of Denver and Intelagard, Inc., of Broomfield, Colo. Scott’s Liquid Gold has an arrangement with Modec to sell Mold Control 500 in retail markets.
“Mold control is an up-and-coming issue,” says Modec President Brian Kalamanka. “We felt there was an excellent niche for this.”
Scott’s existing relationships with several large retail chains helped get the product on store shelves, he says. (The company also distributes wood care and air freshener products, and a subsidiary company, Neoteric Cosmetics, makes and markets skin care products.)
“It’s nearly impossible to break into the large retail markets,” he says. “Those types of connections are very valuable.”
Thousands of stores
Jeff Hinkle, Scott’s senior VP for marketing, says developing the packaging and arranging
for retail distribution of MC 500, important details for the success of any product, took nearly two years.
With EPA approval newly in hand, shipping to retail outlets began in the fall. Many stores began stocking MC 500 in November, and the product is expected to reach thousands of stores this spring, says Hinkle.
During the decontamination formulation’s 10-year project life, project leader Mark Tucker (6327) and others have transformed the original chemistry into one of Sandia’s top technology transfer success stories.
Sandia’s two licensees, Modec, Inc., and Intelagard, Inc., have sold thousands of gallons of the formulation to municipal and state governments, the first responder community, and the US military, among other users.
Over the years it has brought in nearly $300,000 in royalty earnings, according to Craig Tyner, manager of Licensing and Intellectual Property Management Dept. 9104. It also has the distinction of being among a very few Sandia technologies to be made available in the consumer retail market.
Its development began in 1997, funded initially by DOE’s Chemical and Biological National Security Program. Other funding contributors over the years have included the DoD and Sandia’s internal Laboratory Directed Research and Development program. It has earned two patents, and several more are pending.
The formulation also has been among Sandia’s top publicity earners. It first hit the public scene in 1998 when former Sandia chemical engineer Maher Tadros, after presenting its chemistry at a technical conference, got a two-sentence write-up about the foam in an Atlanta newspaper. Its availability and use attracted hundreds of media mentions, including a 1998 spread in the New York Times’ science section.
The formulation is best known for its role in helping clean up contaminated buildings following a series of mailings of anthrax powder to recipients in Washington, D.C., New York, and Florida in 2001. It was staged in the Middle East in 2003 as part of Operation Iraqi Freedom and has played a role there in helping clean up hazardous chemical sites.
Tests at Sandia and Kansas State University in 2004 demonstrated the formulation’s effectiveness for killing the virus that causes severe acute respiratory syndrome (SARS), suggesting its use also might blunt the spread of other viruses such as the Norwalk (cruise ship) virus, avian influenza (bird flu), and the common flu.
The formulation now is being discussed as a potential solution to at least a dozen problems, among them ridding citrus crops of canker (an annual several hundred million dollar setback to Florida citrus growers), hospital sanitization, meth lab cleanup, mold remediation in commercial buildings, and cleaning out agricultural pesticide sprayers in an environmentally benign way.
By Nigel Hey
Sandia’s determination to do big things with tiny technology is evident across the Labs. It has spawned an unprecedented cross-disciplinary surge of interest, attracting new talent in a number of disciplines, from mechanical engineering to microbiology.
At the micro scale, Sandia has pioneered a number of microelectromechanical systems (MEMS) innovations. At the nano scale, as researchers expand their understanding of the science and learn to take advantage of nano’s unique properties, the opportunities for innovation are limitless: increased energy efficiency, improved healthcare, and enhanced national security are only the beginning.
The technical community is fairly well agreed that, with time, micro- and nano-scale devices will revolutionize engineering, and that the manufacture of micro-scale devices will be transformed by nano-scale assembly. For now, though, progress in developing complex MEMS devices has been slow, slower than early champions may have hoped or anticipated. To date, the most successful MEMS innovations have been relatively simple devices
like mass-produced accelerometers for airbag sensors, inkjet printer heads, and digital mirrors for video projection. In the case of more complex systems with multiple components, unexpected and little-understood problems of reliability begin to appear.
Using modeling and simulation tools originally developed for Sandia’s weapons-related work, Labs researches have begun to speed up MEMS development by learning more about the unusual nature of micro-engineered mechanisms and devising ways of turning their peculiarities into assets. Building on this promising approach, continued advances in modeling and simulation are revealing ever more about the world at the nano scale. The latest modeling and simulation results — where nano-scale physical effects can be formulated to describe more general aspects of MEMS systems — are generating a high level of enthusiasm among researches.
A different world
One of the great discoveries of engineering at the micro and nano scales is that the world down there is quite, quite different from the world we can see and touch. Sandia researchers are discovering that if we don’t learn to operate in that realm — and essentially that means that engineers and physicists will need to cooperate more closely than ever — then the full potential of MEMS technology will most likely remain beyond our grasp.
In other words, one cannot scale down confidently from macro-dimensional assumptions when the final product is measured in micrometers rather than fractions of an inch. When they attempt to apply traditional methods at such small scales, engineers may find themselves face-to-face with the unexpected — a host of situations in which the experiences of designing in the macro world can no longer provide all the answers.
Because many of the old assumptions don’t work and the new ones are much more complex, micro-scale engineering is likely to reap great dividends from the growing interest in modeling and simulation, while relying less on conventional engineering problem solving.
“We are moving from the early, relatively unenlightened days of ‘making macro solutions smaller’ to doing things a new way, through micro-scale-enabled solutions,” wrote Art Ratzel, director of Engineering Sciences Center 1500, in the March 2007 issue of Mechanical Engineering,
flagship magazine of the American Society of Mechanical Engineers. “Engineering at the micro scale introduces an appreciation of the complex physics at the feature scales of the devices. It demands the appreciation of a ground-up approach to design and problem solving.
“While MEMS has not yet lived up to the optimism of the 1990s, enhanced understanding of scale-dependent physics is helping us to make progress toward the buoyant expectations voiced during those times.”
‘A lot of new things to do’
As a result, emphasis on computerized design support is increasing dramatically, and modern mechanical engineers are becoming software experts, some arguing that, since MEMS production is an automated two-month process, model-based design verification should be completed before fabrication begins.
“It’s exciting that you can review the design and check out the 3-D solid model before it’s actually made,” says Channy Wong, manager of Applied Mechanics Development Dept. 1526. “You predict the performance, evaluate the responses from different design variations and analyze the results. Applying modeling and simulation allow us to conduct concurrent engineering and optimize the design, reducing cost significantly.
“There are a lot of new things to do,” he adds. “I think that’s the most exciting thing about working in the micro and nano world. Science and engineering can be very different at that length scale.”
Lessons learned: the 1995 micro engine experience
Interest in modeling and simulation blossomed as the result of lessons learned with the Sandia micro engine, an early MEMS product initially developed in 1995. The basic design was simple, and the first micro engines were built under stringent clean room conditions, but proved to be only somewhat reliable. After 477,000 cycles, an electron microscope image clearly showed the reason — accumulation of debris detached from rubbing surfaces. The Sandia development team, conceding they had insufficient understanding of the wear mechanisms, accelerated the Labs’ research into micro-scale science — and engineering. The “build-and-test” approach, which was relatively expensive, was supplemented with discovery experiments, model development, and computational simulation. This shed new light onto the mechanisms that were causing imprecise precision control and lateral instability (“clamping”), as well as wear.
Since the micro engine experiments, researchers in Sandia’s micro-scale modeling and simulation community in 1000, 2000, and 8000 have been occupied with forensics (asking what went wrong?), exploration (can modeling and simulation help ensure that a component will perform up to expectations?), and improved performance (can modeling and simulation suggest better operation and perhaps improved design?). Their next step is to bring about micro-scale-enabled engineering solutions — ultimately a transformation in component design — through shared innovation by individuals specializing in components, engineering, and microelectronics.
Down the rabbit hole
Some engineers compare moving from macro to micro to nano to Alice’s trip down the rabbit hole. Physical models must change, sometimes drastically, as length scales shrink. For example, at the world down there gravity is more easily overcome by adhesion; friction models break down; solids melt at lower temperatures; a tiny moving “front” of changing temperature must be described as a quantum effect — as a spreading cloud of ballistic phonons.
Such effects are especially important in polycrystalline silicon (including structures made with Sandia’s SUMMiT® V process), which have several levels and have geometry features of 1 to 10 micro-meters and grains of 10s to 100s of micrometers.
The fledgling MEMS industry has a limited knowledge of materials physics at micrometer size, and currently commercialized devices are designed for specialized purposes. Partly for this reason, they do not have a broad user base, and therefore have not generated industry standards or the design and process software that would be built based on those industry standards. However, this may change as Sandia’s materials science, engineering, and computer sciences organizations develop engineering systems that, while designed for their own use, could migrate into the private sector and revitalize the pace of invention.
While Sandia is seeing a major effort to harness nanoscience for the improvement of esoteric applications such as micromachines, big benefits for everyday products also are visualized by Jim Redmond, manager of Strategic Initiatives Dept. 1525. Jim calls this “the connection of nano-scale phenomena to the engineering of macro-scale solutions for the world we live in, like lighter, stronger, more robust materials.”
“For example, carbon black is a ‘nano material’ that has been used for years to enhance the performance of tires, a product we’re all familiar with,” he says. “This benefit was determined by trial and error. With modern computing and production tools, we ought to be able to engineer similar improvements for many products.”
“As these new perspectives evolve into reality, a new breed of engineer is also coming into existence,” says Art in Mechanical Engineering. “In fact, the line among the computer scientist, the materials
scientist, and the engineer is becoming blurred and indistinct. Mechanical engineering cannot help but benefit from this exciting new horizon. MEMS is here to stay, and it will transform the future.” -- Nigel Hey
The physics of the “normal” world, the macro world we live in every day, begins to break down in odd and unanticipated ways at the micro and nano scale. For example, many surface interaction models depend on a statistical description of the asperity heights — that is, points of roughness — for high-contact forces, since the real contact area increases with load as asperities are flattened and more come into contact. But with light contact, only the outlier asperities are engaged. Thus, at the macro scale, where a surface will have many contacting asperities, the real contact area varies directly with load — the heavier the package, the harder it is to slide along a counter top. But at the micro scale, unfamiliar effects can increase static friction (stiction, the force required to get an object moving), as a result of the interaction between single asperities.
Understanding the effect of asperities is vital, because asperity points are an artifact of MEMS fabrication. MEMS structures are built from depositing and etching away polysilicon at selected areas using a multilayer, multistage photolithographic process. Each deposition and etching process exposes a new surface which, when examined with an electron microscope, can be seen to include a large number of unwanted rough points, or asperities, which project at various heights above the “real” part of that surface. In the macro world, the effect of these asperities gives rise to an averaging-out notion of “slick” or “rough” surfaces and thence to the idea of sliding friction, the force that resists relative motion between two bodies in contact. On the micro scale, friction behavior depends on discrete contacts because each asperity is relatively large and a small number of them will interact and produce effects of their own — for example breaking off and generating debris. The physics of friction at the nano scale is not completely understood. This is still an active area of research.
Computational simulation of a Sandia-designed micro-scale thermal actuator provides another example of how size affects how things work. In this device, electrical current passes through four mechanical legs, causing them to expand and displace a shuttle with a reciprocating motion. Remarkably, conventional methods predict the beam temperature at 750 kelvin, whereas Sandia’s “non-continuum” calculation, using nano-scale data, puts it at a more accurate 900 K. With some materials, this could make the difference between melting and not melting. -- Nigel Hey