eReport

May 2007

The 2007 Magnetics Conference Proceedings Are Now Available For Purchase
For those of you who were unable to attend the 2007 Magnetics Conference, you can still stay up-to-date on the most recent industry advancements by purchasing the conference proceedings now available on CD-ROM.

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Podcasts are available for 9 presentations & are included with each CD-ROM purchase. For a complete list of podcast presentations visit www.magneticsmagazine.com.

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To order email Julie Williams or call 800 803 9488, ext.117.

Photo Credit: Hahn-Meitner Institute

The Hahn-Meitner Institute in Berlin has contracted with the National High Magnetic Field Laboratory and Florida State University to build an $8.7-million hybrid magnet for “neutron scattering” experiments.

When finished in 2011, the new, high-field magnet, which is based on the Magnet Lab’s Series-Connected Hybrid concept, will be housed at the Berlin Neutron Scattering Center. The magnet will produce a magnetic field between 25 tesla and 30 tesla, more than half a million times stronger than the Earth’s magnetic field. It will be the world’s strongest magnet for neutron experiments, eclipsing the 15-tesla system presently at the Hahn-Meitner Institute (HMI).

The Magnet Lab’s Magneti Science & Technology division has been working with Hahn-Meitner since the summer of 2005 and has recently completed a design study. The results of that study were strong enough to convince the review committee of the German Helmholtz Association and the Federal Ministry of Education and Research that the investment in the new technology was worth the cost.

“Part of the challenge in science is figuring out how to maximize resources,” said Mark Bird, interim director of the Magnet Science & Technology division. “We can’t always afford to bring the tools and techniques to the magnets; sometimes we have to bring the magnets to the tools to advance the science.”

The lab’s Series-Connected Hybrid combines copper-coil “resistive” magnet technology in the magnet’s interior with a superconducting magnet, cooled with liquid helium, on the exterior. The copper-coil insert is powered by an electrical current, while the superconducting outsert conducts electricity without resistance as long as it is kept colder than 450° below zero Fahrenheit. By combining the power supplies of these two technologies, engineers can produce extremely high magnetic fields using one-third of the power required by traditional magnets.

The version that Magnet Lab engineers will build for HMI is different in that its bore, or experimental space, will be conical to allow neutrons to be scattered through large angles. It also will be horizontal, as opposed to the traditional vertical bore of most high-field magnets. These modifications make the magnet well suited for neutron scattering experiments, which are among the best methods for probing atoms to better understand the structure of materials.

“With this major piece of equipment, Hahn-Meitner Institute itself becomes a magnet, pulling in researchers from around the world to Berlin,” said Thomas Rachel, parliamentary state secretary of the Federal Ministry of Education and Research.

Neutrons are remarkable probes of phenomena within solids. With this new magnet, scientists from around the world will be able to carry out experiments that aren’t currently possible. Presently, one of the greatest challenges in condensed matter physics is to develop a comprehensive theory describing high-temperature superconductors. The combination of neutrons and high magnetic fields will allow scientists to study the normal state of high-temperature superconductors in the low-temperature limit. In addition, it will be possible to probe hydrogen structure in both biological and hydrogen-storage materials.

The project is funded primarily through the German Federal Ministry for Education and Research. In addition to the $8.7-million magnet, the Germans are putting $14.4 million into infrastructure, such as cooling and current supplies, needed to run a high-field magnet. The agreement will be administered by the Florida State University Magnet Research and Development Co., a not-for-profit direct support organization of the magnet lab.

The announcement comes just six months after the National Science Foundation awarded the Magnet Lab an $11.7 million grant to build a 36-tesla Series Connected Hybrid, expected to come online in 2011, for the Tallahassee facility. Together with Johns Hopkins University, the lab also is conducting a NSF-funded engineering design of a split-gap Series-Connected Hybrid for the Spallation Neutron Source, a neutron facility in Oak Ridge, Tenn.

The first sector of CERN’s Large Hadron Collider (LHC) to be cooled down has reached a temperature of 1.9 K (-271°C), which is colder than deep outer space. Although just one-eighth of the LHC ring, this sector is the world’s largest superconducting installation. The entire 27-kilometre LHC ring needs to be cooled down to this temperature in order for the superconducting magnets, which guide and focus the proton beams, to remain in a superconductive state. Such a state allows the current to flow without resistance, creating a dense, powerful magnetic field in relatively small magnets. Guiding the two proton beams as they travel nearly the speed of light, curving around the accelerator ring and focusing them at the collision points is no easy task. A total of 1,650 main magnets need to be operated in a superconductive state, which presents a huge technical challenge.

"This is the first major step in the technical validation of a full-scale portion of the LHC," said LHC project leader Lyndon Evans.

There are three parts to the cool down process, with many tests and intense checking in between. During the first phase, the sector is cooled down to 80°K, slightly above the temperature of liquid nitrogen. At this temperature the material will have seen 90 percent of the final thermal contraction, a 3-millimeter per meter shrinkage of steel structures. Each of the eight sectors is about 3.3 kilometers long, which means shrinkage of 9.9 meters. To deal with this amount of shrinkage, specific places have been designed to compensate for it, including expansion bellows for piping elements and cabling with some slack. Tests are done to make sure no hardware breaks as the machinery is cooled.

The second phase brings the sector to 4.5°K using enormous refrigerators. Each sector has its own refrigerator and each of the main magnets is filled with liquid helium, the coolant of choice for the LHC because it is the only element to be in a liquid state at such a low temperature.

The final phase requires a sophisticated pumping system to help bring the pressure down on the boiling Helium and cool the magnets to 1.9°K. To achieve a pressure of 15 millibars, the system uses both hydrodynamic centrifugal compressors operating at low temperature and positive-displacement compressors operating at room temperature. Cooling down to 1.9°K provides greater efficiency for the superconducting material and helium's cooling capacity. At this low temperature helium becomes superfluid, flowing with virtually no viscosity and allowing greater heat transfer capacity.

"It's exciting because for more than 10 years people have been designing, building and testing separately each part of this sector and now we have a chance to test it all together for the first time," said Serge Claudet, head of the Cryogenic Operation Team.

As the number of toys with magnets increases, so is the number of serious injuries to children. The US Consumer Product Safety Commission (CPSC) is aware of hundreds of complaints that magnets have fallen out of various toys and at least 33 cases where children swallowed loose magnets and required emergency surgery. In addition, a 20-month-old boy from Seattle, Wash. died.

Of the 33 cases, the children ranged in age from 10 months to 11 years, the majority were older than three, and the majority were boys. All of the injuries led to hospital stays, which ranged from three to 19 days. In nearly all cases reviewed by CPSC, children had suffered intestinal perforations.

Within the past year, the CPSC has conducted five recalls with more than eight million products containing magnets that could come loose and fall out of the product. In the fall of 2006, the CPSC alerted parents to the emerging hazard of magnets. Even so, children continue to be treated in emergency rooms across the country for complications due to ingesting magnets or toy components with magnets.

If two or more magnets, two or more magnet components, or a magnet and another metal object are swallowed separately, they can attract to one another through intestinal walls. When this happens, parents and physicians may think that the materials will pass through the child. But with magnets this is often not the case. The magnets become trapped in the body and can twist or pinch the intestine, causing holes, blockage and infection in the intestine or blood poisoning. All of which can lead to death.

The CPSC is working with manufacturers, the toy industry and other stakeholders to protect children from the dangers of magnets. New voluntary standards requirements were approved on March 15th. In addition, the voluntary standards group will continue to consider additional requirements during the next year.

In the meantime, the CPSC is working to help those in the medical community better understand the hazard and how to properly diagnose it.

Freezing Magnets with Magnets

A "spin liquid" is a very unique, dynamic material in which each spin – the tiny magnetic field carried by an electron – is not frozen into place, producing clearly defined magnetic regions. Instead, the spins are free to change orientation. Because of this, external magnetic fields applied to spin liquids may produce changes that extreme temperatures and pressures cannot.

Jason Gardner, a scientist at the US Department of Energy's Brookhaven National Laboratory and the National Institute of Standards and Technology, has been able to freeze a spin liquid by applying a magnetic field. This liquid-to-solid transition (like water to ice) allowed Gardner and his colleagues to reveal an unusual property of a spin liquid system, a property that may hold the key to understanding this unusual magnetic state and how it could be used to better understand superconductivity.

"Regular liquids are expected to crystallize at low temperatures," Gardner said. "A spin liquid should too, but the system I'm studying remains a liquid down to temperatures close to absolute zero, the coldest temperature possible."

Spin liquids are found in several magnetic materials, including high-temperature superconducting materials, however Gardner studies this exotic magnetic state in materials that exhibit geometrical frustration. This occurs when the geometry of the material's atomic lattice and the magnetic interactions within the material are incompatible. In his most recent study, he examined an insulating material consisting of the elements terbium (Tb), titanium (Ti) and oxygen (O). Abbreviated Tb2Ti2O7, this material remains in a spin liquid state at extreme low temperatures, but begins to crystallize under extremely high pressure (100,000 times atmospheric pressure) and now, as Gardner and his group have discovered, under magnetic fields.

"Tb2Ti2O7 is a bit of a mystery in frustrated magnetism," Gardner said. "It remains very dynamic down to 17 milli-Kelvin (absolute zero is 0°Kelvin), but theory states that it should freeze at temperatures 1,000 times higher. Fully understanding this magnet will bring new insight into other dynamic systems, not only spin liquids."

Gardner also explained the "neutron spin echo technique," a new area of research in frustrated magnetism. This technique uses neutrons to measure the slow motions of atoms, molecules and magnetic spins on very short timescales, as small as nanoseconds (billionths of a second) and even picoseconds (trillionths of a second). It works by measuring the very subtle change in speed of a neutron as it interacts with matter. It has been applied to problems in biology, chemistry and physics including how oil and water interact and how polymer chains vibrate.

"The neutron spin echo facility at the Center for Neutron Research at NIST is unique in the Americas," Gardner said. "In collaboration with Georg Ehlers at the Spallation Neutron Source at Oak Ridge National Laboratory, we have been doing some great work on the slow dynamics in frustrated magnets."

IBM Milestone Brings MRI Technology to the Nanoscale

IBM BRINGS MRI TECH TO THE NANOSCALE: The cantilever force sensor at the heart of IBM’s “nano-MRI” microscope measures just twelve hundredths of a millimeter in length and a tiny one ten-thousandth of a millimeter thick. IBM scientists have used this nano-MRI to visualize structures at resolution 60,000 times better than current magnetic resonance imaging technology allows. This technique brings MRI capability to the nanoscale level for the first time and represents a major milestone in the quest to build a microscope that could "see" individual atoms in three dimensions. With further development, applications could include understanding how individual proteins interact with drugs for discovery and development, and analyzing computer circuits only a few atoms wide.

Achievement marks significant advance toward the imaging of molecular structures

IBM’s researchers at its Almaden Research Center have demonstrated magnetic resonance imaging (MRI) techniques to visualize nanoscale objects. This technique brings MRI capability to the nanoscale level for the first time and represents a major milestone in the quest to build a microscope that could "see" individual atoms in three dimensions.

Using Magnetic Resonance Force Microscopy (MRFM), IBM researchers have demonstrated two-dimensional imaging of objects as small as 90 nanometers, a key advancement on the path of 3D imaging at the atomic scale. Such imaging could ultimately provide a better understanding of how proteins function, which in turn may lead to more efficient drug discovery and development.

“Our ultimate goal is to perform three-dimensional imaging of complex structures such as molecules with atomic resolution,” said Dan Rugar, manager, Nanoscale Studies, IBM Research. “This would allow scientists to study the atomic structures of molecules, such as proteins, which would represent a huge breakthrough in structural molecular biology."

MRFM offers imaging sensitivity that is 60,000 times better than current magnetic resonance imaging (MRI) technology. MRFM uses what is known as force detection to overcome the sensitivity limitations of conventional MRI to view structures that would otherwise be too small to be detected.

To achieve this, the research team developed specialized magnetic tips for their microscope, optimizing their ability to manipulate and detect the very weak magnetism of atomic nuclei. Conventional medical MRI typically operates on a scale at least 1,000 times coarser - even the most specialized MRI microscopy is limited to about 3 micrometers, or 3,000 nanometers.

This achievement could eventually have major impact on the study of materials, ranging from proteins and pharmaceuticals to integrated circuits, for which a detailed understanding of the atomic structure is essential. Knowing the exact location of specific atoms within tiny nanoelectronic structures, for example, would enhance designers' insight into manufacture and performance. The ability to directly image the detailed atomic structure of proteins would aid the development of new drugs.

For more than a decade, IBM researchers have been making pioneering advancements in MRFM. With this latest achievement, the team is now able to make images with as few as 10 3 atoms as opposed to the 10 8 atoms required to make an image with today’s MRI technology. This improved sensitivity extends MRI into the nanometer realm. (The nanometer realm is typically considered to be at dimensions below 100 nanometers; a nanometer is a billionth of a meter, the length spanned by about 5 to10 atoms.)

IBM Research has a distinguished history in developing microscopes for nanoscale imaging and science. Gerd Binnig and Heinrich Rohrer of IBM's Zurich Research Laboratory received the 1986 Nobel Prize in Physics for their invention of the scanning tunneling microscope, which can image individual atoms on electrically conducting surfaces.

The report on this work, “Nuclear magnetic resonance imaging with 90-nm resolution,” by H. J. Mamin 1, M. Poggio 1,2, C. L. Degen 1 and D. Rugar 1 at IBM Research Division 1, Almaden Research Center, San Jose, California and the Center for Probing the Nanoscale, Stanford University 2 will appear in the April 22 issue of Nature Nanotechnology.

Oxford Instruments NanoScience has recently launched three new products that have received a positive response from the physical sciences research market for these products.

Oxford Instruments NanoScience supports the growing need for alternative cryogenic solutions that overcome the operational difficulties associated with the supply of liquid helium. The company has implemented a number of breakthrough technologies to provide greater user benefits in its next generation of products.

The Integra AC helium recondensing systems offers ultimate performance in low temperature and high magnetic field with significant savings in helium running cost. In cases where the characteristics of conventional liquid helium driven systems are preferred, the low temperature research scientist can now achieve the best of two worlds:

• Ultimate performance in low temperature and high magnetic field sample environments
• Significantly reduced He running costs and higher levels of equipment utilization

The Integra AC systems incorporate a high performance low vibration pulse tube refrigerator to significantly reduce helium loss during low temperature insert and superconducting magnet operation. The systems are designed to accommodate upgradeable modular components to cater for future changes in experimental program. The return on investment in relation to the saving in liquid helium running costs and greater utilization of equipment more that justify the installation of the Integra AC in most cryogenic laboratories.

The Triton DR Cryofree dilution refrigerator, features technology that eliminates the use of conventional pumping system to provide greater user convenience and productivity. This is a revolution in dilution refrigerator technology for pump-free Cryofree mK temperatures.

The key features and benefits of this new product are:

• Utilizes patented & completely self-contained cryogenic gas cycle for leak free reliable operation
• Incorporates a low vibration pulse tube refrigerator with convenient to use air or water cooled compressor
• No external pumping system required enabling a compact system footprint
• Self diagnostic computer control with versatile LabVIEW user interface
• Incorporating FemtoPowerÒ thermometry system for accurate temperature control
• Compatible with Oxford Instruments Cryofree magnet options

The 16 T Active Shield Cryofree Magnet, enables efficient use of valuable lab space through significant reduction of stray magnetic field.

Active shielding of the stray magnetic field of the16 T Cryofree magnet provides a 15 times reduction in the 5 Gauss stray field volume. This impressive performance is achieved in a compact and convenient to use package to provide greater access to high magnetic field in the typical laboratory environment. The system is equipped with a closed cycle refrigerator to eliminate the need for liquid cryogens to cool the superconducting magnet.

The Triton DR Cryofree dilution refrigerator and ActiveShield Cryofree magnets expand the Oxford Instruments family of Cryofree products providing optimum integration of low temperature / high magnetic field sample environments. Oxford Instruments can now offer the most extensive range of modular elements, covering room temperature to less than 50 mK with or without magnetic field up to 16T. The range features versatile low temperature inserts, configurable to suit specific applications, which interface with fully compatible superconducting magnet units. All of these elements are operated entirely without the need to supply liquid cryogens thereby providing convenient and efficient measurement platforms.

Rapid-fire Pulse Brings Sandia Z Method Closer to Goal of High-Yield Fusion Reactor

From Siberia: Sandia researcher Bill Fowler tests circuits on an LTD device able to produce large electrical impulses rapidly and repeatedly. (Photo by Randy Montoya)

Revolutionary circuit fires thousands of times without flaw

An electrical circuit that should carry enough power to produce the long-sought goal of controlled high-yield nuclear fusion and, equally important, do it every 10 seconds, has undergone extensive preliminary experiments and computer simulations at Sandia National Laboratories’ Z machine facility.

Z, when it fires, is already the largest producer of X-rays on Earth and has been used to produce fusion neutrons. But rapid bursts are necessary for future generating plants to produce electrical power from seawater. This had not been thought achievable till now.

How does it work?

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 that pace up 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 National Laboratories’ 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 enclose a continuous fusion reaction from which to draw power.

The 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.

“This is the most significant advance in primary power generation in many decades,” says Keith Matzen, director of Sandia’s Pulsed Power Center.

The new 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.

Rick Stulen, Sandia vice president for Science, Technology and Research Foundations, said,“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.”

The large-cherry-lifesaver path to nuclear 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 in Sandia’s Technical Area 4 has fired 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, Sandia 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, who supervised the tests at the Siberian site, are performing without flaw.

“This is an amazing achievement,” says Sandia Vice President Gerry Yonas, a former leader at Z and of Sandia’s Advanced Concepts Group.

Advantages of the new technology

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, 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 machine’s original microsecond pulse.

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 previously possible.

The subsets are then linked in series to add voltages.

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.

To confirm the new Z concept would take $35 million over five to seven years to build a test bed with 100 cavities. If successful, future generations of Z-like facilities would be constructed with LTDs.

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 Matzen. “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, and encouraged by Sandia managers Rick Spielman and Ken Struve; the work was led at Sandia and Tomsk by Sandia researcher Mike Mazarakis; testing at Sandia was by Bill Fowler and Robin Sharpe; the Z-IFE fusion energy program at Sandia was initiated and is managed by Craig Olson.

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 2007.

Sandia has filed a patent application on a high-power pulsed-power accelerator invented by William Stygar that can use an LTD as the primary power generator to replace the conventional Marx generator.

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