By Neal Singer
The ingenious system called adaptive optics, known for its computer control of subdivided, individually angled mirrors, is an efficient but expensive way to correct distortions in laser beams. The mirrors automatically adjust until an undistorted beam is obtained in a way formerly thought unachievable by a single large mirror.
Now a Sandia tool that efficiently but inexpensively uses a single mirror to achieve some of the same effects has received a US patent, issued June 12.
The Sandia device, which resembles an inexpensive vise similar to those bolted to many home workshop benches, functions as a kind of poor man’s adaptive optics. It corrects optical distortions simply through pressure that changes the convexity or concavity of a single reflecting surface.
“We can’t compensate for small-scale aberrations,” says principal investigator Jens Schwarz (1672), “but certain large-scale beam distortions are correctable with this tool.”
The method already has improved the beam quality of Sandia’s huge Z-Beamlet laser, which can now fire every two hours instead of every four because the device precorrects for distortions caused by heat, Jens says.
Similar beam corrections, of course, can be achieved with tens to hundreds of thousands of dollars through traditional adaptive optics. Many small reflecting mirrors controlled by a computer can adjust in milliseconds to correct beam distortions reported by sensors farther down the line.
But for the overwhelming majority of laser users who do not need such fine control, deformation of a single mirror through convex or concave deformation applied through only a single actuator may be the ticket, especially when the price is expected to be only a few thousand dollars.
Commercial interest in the inexpensive device already has been expressed.
A reverse use of the technique could deliberately focus the beam to interrogate points of distant interest. This use would detect chemical or biological agents introduced at battlefields many miles away, a technique called laser-induced fluorescence spectroscopy. “Because the mirror can change the focus of a laser beam quickly and rapidly, a laser beam could interrogate molecules at a variety of distances and the results would be visible through backscattered light,” Jens says.
Coping with beam distortions
Distortions happen when new energies are injected in the lasing system to create more powerful beams. These injections are achieved by racks of lamps that flare briefly, like old-fashioned photographer’s flashbulbs, sending an energy pulse into the laser medium of doped glass in which the beam is forming.
When the laser beam traverses the doped glass, it stimulates the material to release energy that adds to the beam’s strength, an effect known as gain. But the exterior of the doped glass — closer to the flashlamps — is unavoidably heated more than its interior. This modifies its refractive index, focusing the beam to a point some meters away instead of allowing it to continue to infinity.
Rather than alter the flashlamps or gain medium, Jens, with the aid of Marc Ramsey and Daniel Headley (both also 1672), used a single flexible mirror to precorrect for the distortion to take place later in the beam’s passage.
The motivation for the work, Jens says, is that “It’s customary to use a static concave mirror — or a combination of appropriate lenses — and hope it’s correcting well for distortions in the lensing system you have. But rather than buy a succession of lenses or mirrors, we thought: Let’s see if we can do the job more simply and inexpensively by using only one mirror with a flexible focal length.”
The corrective effect is achieved by placing a flat mirror between two concentric rings of different sizes, one stationary and the other free. A screwdriver turned either by fingertips or by motor (the motor raises the price) applies a force to the free ring and bends the mirror a few microns, changing its focal length. The orientation of the large and small rings determines whether the distortion is concave or convex.
The method has been shown to work over a wide range of laser beam energies ranging from 30 millijoules to 500 joules.
Descriptions of the work and its applications have been published in the February 2006 Applied Physics B: Lasers and Optics and the November 2006 Optics Express. Other authors in addition to Jens, Marc, and Daniel include Ian Smith (1672) and John Porter (1670).
The device, listed as a “Variable Focal Length Deformable Mirror,” will issue as US Patent No. 7,229,178. -- Neal Singer
Casa Angelica, a home for developmentally disabled children and young adults in Albuquerque’s South Valley, is the site of an innovative Sandia water treatment system known as “in tank filtration,” designed to remove arsenic from drinking water.
“The Sisters who own and operate Casa Angelica are always proactive — whether it’s taking our young people into the community or, like now, trying a new method of arsenic water removal from our well water,” says Casa Angelica Administrator Louise Turner. “We are excited about being able to help Sandia with this research.”
A program for developmentally disabled young people
Directed by the Canossian Daughters of Charity, Casa Angelica provides a family-centered program for 16 developmentally disabled young people. It is located on 15 grass-landscaped acres and has a facility featuring family rooms, a light/sound therapy room, and playground area. There is also a pool where the children and young adults, who all use wheelchairs, receive therapy four afternoons a week.
The Sandia project is an experiment to help small water systems, like that used by Casa Angelica, inexpensively and easily lower arsenic levels to meet new Environmental Protection Agency standards. The revised regulations, which went into effect in January 2006, reduce the maximum arsenic water contaminant level from 50 to 10 micrograms per liter.
Casa Angelica’s water comes from a well that has naturally occurring arsenic levels of 15 micrograms per liter. Lowering the arsenic concentration to meet the new 10 microgram per liter standard is readily attainable with commercially available arsenic adsorption media, says Sandia researcher Brian Dwyer (6316).
He and his colleagues at Sandia chose the Casa Angelica water system from about 20 systems in New Mexico as a research site because of its small size and relatively low levels of arsenic. The Casa Angelica well currently provides drinking and bathing water to 16 medically fragile children and young adults who live there, 50 staff, and the Canossian Daughters of Charity, who own and operate the facility. It is also used for grounds irrigation.
The “in-tank filtration” technology uses a small pump to continuously circulate stored drinking water through a small vessel containing commercially available arsenic adsorption media. Conventional systems remove arsenic in a single filter pass that requires the filter vessel to be sized based on peak water demand.
Sandia system continuously recirculates water
In contrast, the Sandia technology continuously recirculates water from the community storage tank through a much smaller filter vessel and back into the storage tank thereby removing most arsenic during off-peak water usage. This results in a gradual lowering of the entire storage tank arsenic concentration, providing the ballast capacity to meet peak demand with a very small treatment unit, which translates into a significant cost savings for the small water systems.
The New Mexico Environmental Department (NMED) Drinking Water Bureau has identified roughly 100 small, predominantly rural water systems that exceed the new arsenic standard. In the past the only water treatment these small water systems have conducted is chlorination (disinfection). Systems exceeding the new 10 micrograms per liter of arsenic must now install and operate a treatment system for the first time.
Casa Angelica, like many of the small water suppliers, obtained an extension to install the modifications necessary to bring their water into arsenic compliance.
“I want to assure everyone that Casa Angelica’s water is in no way dangerous,” Brian says. “We just want to make sure it meets the new standards.”
The Sandia treatment system, which was designed and built at the Labs and recently installed at the agency, will be used until later this year when Casa Angelica is expected to be connected to the City of Albuquerque water system. Then all water for drinking, bathing, and the therapeutic pool will be supplied by the city. Well water will continue to be used as the irrigation source for the lands.
The Casa Angelica arsenic research is sponsored by the Arsenic Water Technology Partnership, a consortium of Sandia, the Awwa Research Foundation (AwwaRF), and WERC, a consortium for Environmental Education and Technology Development. US Sen. Pete Domenici, R-N.M., secured funding for the project through DOE when he was chairman of the Senate Energy and Water Development and Appropriations Subcommittee.
Other experimental arsenic removal sites in New Mexico that have been part of the program are in Soccoro, Anthony, Jemez, and Rio Rancho. -- Chris Burroughs
By Neal Singer
In 2007, only one research team in the nation received the Federal Laboratory Consortium’s Interagency Partnership Award for Excellence in transferring federal technology to the commercial marketplace.
Larry Schneider (1650), R. Kevin Howard, Michael Dinallo, and Steve Glover (all 1653) won for their team’s work in creating a commercially viable technique capable of spotting potential short circuits in airplanes before their misfirings cause damage, thus reducing risks of catastrophic in-flight failures.
The PASD (pulse arrested spark discharge) technique was developed largely through a partnership with the Federal Aviation Administration. The technique, proven after years of development and testing at Sandia, was transferred last year to the private sector.
Wrote DOE Secretary of Energy Samuel Bodman, “PASD is the world’s first wiring diagnostic tool that can detect and locate a broad range of aircraft defects, such as breached insulation, chafing, and small insulation cracks, and because of this detection will save lives.”
Sandia VP Rick Stulen: “This is a perfect example of innovation stemming from the intersection of world-class science and engineering capabilities at Sandia that I’m eager to stimulate further throughout our technical communities. Congratulations [Larry and your team] on an extraordinary accomplishment.”
Says Larry, “The final step was finding the right commercial partner. Astronics Advanced Electronics Systems recognized PASD’s capabilities and then brought to bear their significant expertise to field a system within months. PASD’s first use in a National Transportation Safety Board accident investigation yielded exceptional results. ArcSafe® [the commercial name for PASD and other test technology] is just now coming to market, but its future looks very bright.”
Sandia also had three winners in the more populated but still selective “Award for Excellence in Technology Transfer” category. Those selected also received a congratulatory letter from Bodman.
Craig Smith (8529) and Ernest Friedman-Hill (8964) were winners for “Jess® – the Rule Engine for the Java™ Platform.” The program is a tool for building intelligent software that can be repeatedly applied as an expert system to difficult or ill-defined systems when rote computation won’t do. It has been applied to problems in technology, insurance, and financial services, as well as in academic artificial intelligence research, and has been licensed to hundreds of academic institutions.
Nathan Golden (9104), Tom Anderson), Bill Camp (ret.), Art Hale (4600), and Mark Allen (5434) won for Novint’s 3-D haptic technology software that adds interactive, realistic virtual touch capabilities to human-computer interactions. Among the uses might be medical applications, remote vehicle or robotic control, military applications, and video games. Users are said to feel realistic weight, shape, texture, dimension, dynamics, and force effects.
An improved solar design won an award for David King, Paul Smith (9104), James Gee, Mark Allen (5434), and Jeffrey Nelson (6337). The breakthrough photovoltaic cell design and fabrication process for Advent Solar moves current-carrying electrical circuits from the front surface of the cell, where they unavoidably block sunlight, to the back surface where the backside wiring carries the current away. In addition to being more efficient, the advance — which uses a laser to drill holes through a silicon substrate and form conductive channels from front to rear surfaces — is said to lower costs by eliminating front-to-back assembly. And the design is aesthetically pleasing, a quality not often mentioned in connection with Sandia advances.
National winners were culled from a field of more than 250 federal laboratories, research centers, and facilities represented by the FLC.
In regional victories, Sandia itself won a Mid-Continent Region Award for overall achievement.
The “Athena Radar-Responsive Tag Sensor” garnered an Outstanding Technology Development Award. In Outstanding Partnerships, the University Alliance program and the Sandia Science and Technology Park were winners.
Sandia’s “Computational Analysis Tools for Goodyear Assurance Tires — Featuring Triple-Tred Technology” received an honorable mention.
Organized in 1974, the Federal Laboratory Consortium for Technology Transfer serves as a loose nationwide network of federal laboratories that provides a forum to develop strategies for linking laboratory mission technologies with the marketplace. -- Neal Singer