NIST Light Source Illuminates Plasma Of Experimental Reactor

Source:

http://www.sciencedaily.com/releases/2007/10/071011161327.htm

Science Daily — Using a device that can turn a tiny piece of laboratory space into an ion cloud as hot as those found in a nuclear fusion reactor, physicists at the National Institute of Standards and Technology are helping to develop one of the most exotic “yardsticks” on earth, an instrument to monitor conditions in the plasma of an experimental fusion reactor. Their measurement tool also is used in incandescent light bulbs–it’s the element tungsten.
The intended beneficiary of this research is ITER, a multinational project to build the world’s most advanced fusion test reactor. ITER, now under construction in Cadarache, France, will operate at high power in near-steady-state conditions, incorporate essential fusion energy technologies and demonstrate safe operation of a fusion power system. It will be a tokamak machine, in which a hot—250 million degrees Celsius—plasma of hydrogen isotope ions, magnetically confined in a huge toroidal shape, will fuse to form helium nuclei and generate considerable amounts of energy, much the same way energy is generated in the sun.
One major issue is how to measure accurately the temperature and density of the plasma, both of which must reach critical values to maintain the fusion process. Any conventional instrument would be incinerated almost instantly. The usual solution would be to use spectroscopy: monitor the amount and wavelengths of light emitted by the process to deduce the state of the plasma. But light comes from electrons as they change their energies, and at tokamak temperatures the hydrogen and helium nuclei are completely ionized -- no electrons left. The answer is to look at a heavier element, one not completely ionized at 250 million degrees, and the handy one is tungsten. The metal with the highest melting point, tungsten is used for critical structures in the walls of the tokamak torus, so some tungsten atoms always are present in the plasma.
To gather accurate data on the spectrum of highly ionized tungsten, as it would be in the tokamak, NIST physicists use an electron beam ion trap (EBIT), a laboratory instrument which uses a tightly focused electron beam to create, trap and probe highly charged ions. An ion sample in the EBIT is tiny—a glowing thread about the width of a human hair and two to three centimeters long -- but within that area the EBIT can produce particle collisions with similar energies to those that occur in a fusion plasma or a star.
In a pair of papers,* the NIST researchers uncovered previously unrecognized features of the tungsten spectrum, effects only seen at the extreme temperatures that produce highly charged ions. The NIST team has reported several previously unknown spectral lines for tungsten atoms with 39 to 47 of their 74 electrons removed. One particularly significant discovery was that an anomalously strong spectral line that appears at about the energies of an ITER tokamak is in fact a superposition of two different lines that result from electron interactions that, under more conventional plasma conditions, are too insignificant to show up.
Team member John Gillaspy observes, “That’s part of the fascination of these highly charged ions. Things become very strange and bizarre. Things that are normally weak become amplified, and some of the rules of thumb and scaling laws that you learned in graduate school break down when you get into this regime.” The team has proposed a possible new fusion plasma diagnostic based on their measurements of the superimposed lines and supporting theoretical and computational analyses.
Articles: * Yu. Ralchenko. Density dependence of the forbidden lines in Ni-like tungsten. J. Phys. B: At. Mol. Opt. Phys. 40 (2007) F175-F180
Yu. Ralchenko, J. Reader, J.M. Pomeroy, J.N. Tan and J.D. Gillaspy. Spectra of W(39+)-W(47+) in the 12-20 nm region observed with an EBIT light source. J. Phys. B: At. Mol. Opt.Phys. 40 (2007) 3861-3875.
Note: This story has been adapted from material provided by National Institute of Standards and Technology.

Fausto Intilla
www.oloscience.com

Not Just Science Fiction: 'Electromagnetic Wormhole' Possible, Say Mathematicians

Source:

http://www.sciencedaily.com/releases/2007/10/071012160144.htm

Science Daily — The team of mathematicians that first created the mathematics behind the "invisibility cloak" announced by physicists last October has now shown that the same technology could be used to generate an "electromagnetic wormhole."

In the study, which is to appear in the Oct. 12 issue of Physical Review Letters, Allan Greenleaf, professor of mathematics at the University of Rochester, and his coauthors lay out a variation on the theme of cloaking. Their results open the possibility of building a sort of invisible tunnel between two points in space.
"Imagine wrapping Harry Potter's invisibility cloak around a tube," says Greenleaf. "If the material is designed according to our specifications, you could pass an object into one end, watch it disappear as it traveled the length of the tunnel, and then see it reappear out the other end."
Current technology can create objects invisible only to microwave radiation, but the mathematical theory allows for the wormhole effect for electromagnetic waves of all frequencies. With this in mind, Greenleaf and his coauthors propose several possible applications. Endoscopic surgeries where the surgeon is guided by MRI imaging are problematical because the intense magnetic fields generated by the MRI scanner affect the surgeon's tools, and the tools can distort the MRI images. Greenleaf says, however, that passing the tools through an EM wormhole could effectively hide them from the fields, allowing only their tips to be "visible" at work.
To create cloaking technology, Greenleaf and his collaborators use theoretical mathematics to design a device to guide the electromagnetic waves in a useful way. Researchers could then use these blueprints to create layers of specially engineered, light-bending, composite materials called metamaterials.
Last year, David R. Smith, professor of electrical and computer engineering at Duke's Pratt School, and his coauthors engineered an invisibility device as a disk, which allowed microwaves to pass around it. Greenleaf and his coauthors have now employed more elaborate geometry to specify exactly what properties are demanded of a wormhole's metamaterial in order to create the "invisible tunnel" effect. They also calculated what additional optical effects would occur if the inside of the wormhole was coated with a variety of hypothetical metamaterials.
Assuming that your vision was limited to the few frequencies at which the wormhole operates, looking in one end, you'd see a distorted view out the other end, according the simulations by Greenleaf and his coauthors. Depending on the length of the tube and how often the light bounced around inside, you might see just a fisheye view out the other end, or you might see an Escher-like jumble.
Greenleaf and his coauthors speculated on one use of the electromagnetic wormhole that sounds like something out of science fiction. If the metamaterials making up the tube were able to bend all wavelengths of visible light, they could be used to make a 3D television display. Imagine thousands of thin wormholes sticking up out of a box like a tuft of long grass in a vase. The wormholes themselves would be invisible, but their ends could transmit light carried up from below. It would be as if thousands of pixels were simply floating in the air.
But that idea, Greenleaf concedes, is a very long way off. Even though the mathematics now says that it's possible, it's up to engineers to apply these results to create a working prototype.
Greenleaf's coauthors are Matti Lassas, professor of mathematics at the Helsinki University of Technology; Yaroslav Kurylev, professor of mathematics at the University College, London; and Gunther Uhlmann, Walker Family Endowed Professor of Mathematics at the University of Washington.
Note: This story has been adapted from material provided by University of Rochester.

Fausto Intilla

www.oloscience.com

Understanding The Big Bang: Relativistic Heavy Ion Collider Aids Search For Quark-gluon Plasma

Source:

http://www.sciencedaily.com/releases/2007/09/070925171721.htm

Science Daily — A large scale STAR experiment is currently under way at Brookhaven National Laboratory, with the Sun Grid Compute Utility from Sun's Network.com delivering large-scale computing power and related resources on a utility basis as the project requires.

An acronym for Solenoidal Tracker At RHIC -- the laboratory's Relativistic Heavy Ion Collider -- STAR tracks the thousands of particles produced by ion collisions at RHIC, searching for signs of something called the quark-gluon plasma (QGP), a form of matter that is believed to have last existed just after the Big Bang, at the dawn of the universe.
The goal of STAR is to bring about a better understanding of the universe in its earliest stages, by making it possible for scientists to better understand the nature of the QGP. The STAR experiment is a massive collaboration of 570 scientists and engineers representing 60 institutions in 12 countries. The STAR detector captures images at a rate of about 100 per second and has accumulated several hundred million images so far in the course of the experiment.
As the size of the collaboration and the scope of its work continue to grow, so does the challenge of having the computing power and data processing resources to carry out that work efficiently.
Due to the computing and data intensive nature of the project, the Sun Grid Compute Utility has become a part of the STAR distributed computing strategy to allows such computations to be done at a faster rate, leaving more time for physicists' to analyze the large datasets.
"A scientist will look at the initial analysis and then go on to look at the details, which requires even larger data samples," explains Jerome Lauret, RHIC/ STAR Software and Computing Project Leader, "so the more scientists that are involved, the greater the scope of the data and dataset challenge."
Sun Grid Compute Utility has proven useful on the computing side of the equation, as a resource for the simulations of design, collisions, and other models that are essential to the research conducted by the experiment's physics working groups.
Sun™ Grid has also supported simulations associated with ongoing research related to upgrades of the STARdetector -- upgrades that will allow further advances in the experimental physics of heavy ion collisions.
Note: This story has been adapted from material provided by Sun Microsystems.

Fausto Intilla

www.oloscience.com