Skip to comments.Sandia Imagists Overcome Maelstrom Obscuring Z Machine's Drive Force
Posted on 11/11/2004 1:12:47 PM PST by tricky_k_1972
Albuquerque NM (SPX) Nov 11, 2004 Peering into the center of Sandia National Laboratory's Z machine as it fires had been a feat unachievable for a decade. Other than a nuclear bomb, Z is the most powerful generator of X-rays on the planet. Last year, its central mechanism, called a Z-pinch, fused isotopes of hydrogen to create nuclear fusion.
Now, by inserting a pretty, two-inch-long crystal that reflects at only a single frequency into the hellish center of Z as it fires, researchers have been able to visually filter out the bedlam of more than 99 percent of the energies generated.
By shining the energy from a relatively weak laser beam through the machine and reflecting it off the crystal to a detector, the researchers have emerged with a series of pictures of the machine's key process - the dissolution of a wire cage (about the size of a spool of thread) into ionized gas particles.
By viewing the dissolution nanosecond by nanosecond, Z experimentalists can see more rapidly and accurately how to improve the final output.
These alterations will achieve still more powerful outputs for weapons studies and, eventually, controlled nuclear fusion that could produce unlimited energy from seawater.
The results will be the subject of an invited talk by Sinars at the upcoming American Physical Society's Division of Plasma Physics meeting in Savannah, Ga., Nov. 15-19.
Ignoring unwanted suitors
The imaging process works because the crystal reflects only at a single wavelength. All other wavelengths, like unwanted suitors, are ignored.
By bouncing the energy of a relatively weak laser beam of the same wavelength through the machine and off the crystal, researchers have emerged with a series of pictures resembling dental X-rays of the wire cage's dissolution into ionized gas particles.
(The particles, contracted by a huge magnetic field, must be arranged to strike the central axis of the vanishing cage as simultaneously as possible to generate maximum X-rays; these already have been used to fuse pellets of deuterium.)
But how did Sinars' team do it?
Real "crystal power"
Expanding on work by Sergei Pikuz and Tanya Shelkovenko of the Lebedev Institute in Moscow and Cornell mentor David Hammer, who each had worked on far smaller machines, Sinars realized that while the Z machine released huge energies over tens of nanoseconds, it did so in a wide frequency band.
He imagined shining X-rays generated by a relatively weak but single-frequency laser beam through the wire array as it crumbled. The image generated would be reflected by a crystal functioning in only that same frequency, spherically curved for better focus on a carefully placed external detector.
Almost all of Z's energies would be eliminated from the image because they would not be reflected by the crystal - as eerie a phenomenom as a vampire's absent image in horror-movie mirrors - thus leaving the laser-generated image as unblotched as a dental X-ray.
The laser's energies - though only one-millionth as energetic as Z's total output - would dominate in that one band, and from it, Sinars' team would create images of the wire cage's dissolution.
"Until our work, virtually every diagnostic on the Z facility simply measured the luminous self-emission from the z-pinch mass as it assembled on-axis and radiated," says Sinars. "We now have been able to observe plasma stages at any point in the process, not just the final stage when the plasma is radiating x rays."
The images provide quantifiable information about where the plasma mass is located, whether instabilities exist at any moment, what the wavelength and amplitude of such instabilities are, and where these instabilities are spatially correlated over large distances.
Like finding a grain of sand in a sand pile
Says Sandia Pulsed Power Sciences Center director Jeff Quintenz, "That Dan can extract such detailed images from that maelstrom environment using such a small amount of energy is more than impressive. It's like being able to find a grain of sand in a sand pile, or a single voice in a crowded coliseum."
Says Cornell physics professor David Hammer, Chair of the American Physical Society's Plasma Physics division, "Dan has extended backlighting work done elsewhere, but done so in the most extremely difficult environment. His implementation had to be novel to make it work. His work contributes major understanding of the critical dynamics of the Z-pinch."
What the Sinars group saw
The images showed that wires at the center of the high-energy machine do not uniformly disintegrate, as was once thought. Current passing through the wires at first heats and melts them as expected, but only a portion of the metal becomes plasma.
Because plasma is so much more conductive than the heated liquid metal "cores," much of the electrical current is diverted from heating the wires and instead flows in the tenuous plasma surrounding the dense wire cores.
The plasma - continually swept inward toward the center by the magnetic forces acting on the array - is replenished with material from the dense wire cores. The dense cores persist for relatively extended periods of time, eventually burn through, and only then are swept inward.
"The non-simultaneous arrival of the mass on the axis is believed to be the limiting factor on the peak radiation power achievable using wire-array z-pinches, so it is critical for us to understand exactly how the wire array mass assembles on the axis," says Sinars.
"This information is critical to improving our still-primitive understanding of why z-pinches work as well as they do."
Z produces one to two million joules of X-rays in 100 to 200 terawatt bursts. The crystals reflect at either 6.648 or 2.015 angstroms.
Still more creativity from a red state. Whowouldathunkit?
Sounds a tad like a solid state laser for xrays. Pretty cool. Make one heck of a missile interceptor in space. Use the same system to generate it's own power via fusion.
The number of PhDs and advanced degrees is enormous compared to the poulation. You have Sandia, Los Alamos, the VLA and one or two other major scientific research facilities.
Sounds like Huntsville.
But I thought all the intellectuals, artists, and "Big Thinkers" were in the blue states, I'm so confused (/sarcasm).
I try to give people some reason to go to the web site that I pick this stuff up from, after all they pay for their site and it's content, besides you might find something else there you like.
Don't forget Phillips National Lab (also on K.A.F.B.). Now why they didn't just incorporate it into Sandia when they moved here I don't know.
And when it goes awry, instant black hole, is it? No, wait a minute, that was a conversation with Art Bell....
These are big steps. But compared to the total task they are small. The number of such big steps is nearly uncountable up to this point and there is probably at least as much to go. Commercial fusion power is proceeding by such steps of genius and creativity and technical excellence and inspiration. If funding were bumped up 10X would it go 10X faster? Probably not, but it might go appreciably faster. It might go fast enough to save us from the energy disaster that looms in the not too distant future.
Let's hope this research leads to some of THESE for our troops...
"Aye...it's called a 'DiLithium Crystal'"...
Gene Roddenberry strikes again!
I love science
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.