Jackson, Alabama -- 6/17/2005 -- The paper industry is one step closer to saving millions of dollars each year. An innovative laser ultrasonic sensor designed and built by a team of scientists from the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) and the Institute of Paper Science and Technology at the Georgia Institute of Technology (IPST at Georgia Tech), was recently successfully tested at a mill making copy paper in Jackson, Alabama.

The two-week test was conducted in February at the mill owned by Boise Cascade. "I didn't see anything that would preclude us from considering a Beta trial and would suggest that the Alpha test equipment worked remarkably well for serial #1, hand constructed equipment", said Kevin Rucker, Director of Product Development for Boise Cascade. "Boise Cascade's engineers considered the trial to be quite successful, and are hopeful that a six-month trial will be conducted at the same mill," added Paul Ridgway, an engineer at Berkeley Lab who has worked on the project since its inception.

The sensor measures a paper's bending stiffness and shear rigidity - two fundamental properties and hallmarks of paper quality - as it speeds through a production web. By doing so, it can ensure that the optimum amount of raw material is used to make the paper, which could reduce the consumption of trees and chemicals and save the U.S. industry approximately $200 million in energy costs and up to $300 million in fiber costs each year.

Emmanuel Lafond, lead scientist for IPST at GT said, "We have cleared another hurdle toward commercialization of a technology that has the potential to save a significant amount of raw materials and energy while producing the same surface area of paper".

Eight years in the making, the sensor was funded by the Department of Energy's Office of Industrial Technologies as part of a partnership to improve the energy efficiency of several industries. Under this program, the American Forest and Paper Association created Agenda 2020, which outlines ways in which the forest products industry can improve industry competitiveness and environmental performance by using the tools of technology. Papermaking is a highly energy intensive process and is an obvious candidate for energy conservation technologies.

To gauge paper quality today, a 15 to 30-ton paper roll is manufactured, and a few samples are obtained from the end of the roll and analyzed for their mechanical properties. In the case of copy paper, bending stiffness or flexural rigidity are very important. If the samples don't meet certain specifications, the entire roll is recycled into pulp or sold as an inferior grade. To avoid this costly mistake, manufacturers often over-engineer the paper and use more pulp than necessary to ensure the final product isn't substandard.

This method consumes more raw material and energy than necessary, so the Georgia Tech and Berkeley Lab team developed a sensor that tracks papers' flexibility on the fly, in real time. Specifically, the sensor measures the time it takes ultrasonic shock waves to propagate from a laser-induced excitation point on the moving paper to a detection point several millimeters away. The velocity at which the ultrasound waves travel from the excitation point through the paper to the detection point is related to two elastic properties, bending stiffness and out-of-plane shear rigidity.

The laser ultrasonic sensor conducts these measurements without touching the paper, an important advantage given that the paper moves at approximately 45 miles per hour through the paper machine and the slightest contact can break the sheet and cause costly machine downtime, or mar the paper. The recent trial is believed to use the highest sample speed ever reported for a commercial application of laser ultrasonics.

Dr. Jim Frederick, Director of IPST said, "We have a problem attracting young engineers to the paper industry. If they understood the difference that they could make, and the cool technologies that they could work with, I think we would have much less trouble in recruiting students to our program. Laser ultrasonics and millions of dollars at stake - that is pretty cool!"

The next step in the project is to work with Boise Cascade to link the sensor with sophisticated feedback controls that maintain the paper's stiffness while it's being manufactured. ABB Corporation, which participated in the recent trial, is also likely to participate in this phase. "We are thrilled to work with very talented engineers from ABB and Boise Cascade to make this sensor an energy-saving and a commercial success." says Lafond, "so that Boise Cascade and other paper companies will be able to benefit from it".

"Our technology will enable this real-time feedback control," says Ridgway. "And the successful mill trial shows we are one step closer to realizing it." The mill trial is the latest in a string of successful real-world tests. In 2001, researchers from both labs (Ridgway, Habeger, Lafond, Jackson, Russo) conducted a pilot-scale test of the laser ultrasonic sensor at Mead Paper Company's research center in Chillicothe , Ohio .

This test first demonstrated that the sensor's sophisticated hardware can successfully perform at high speeds and under the harsher conditions of an industrial environment, as compared to a laboratory.

In the sensor, a detection beam from a commercially available interferometer is directed toward a rotating mirror. The spinning mirror reflects the beam onto the paper as it courses along the production belt. Because both the beam and the paper are moving at the same speed, the detection beam remains fixed on the same point on the paper during their brief contact. Next, an optical encoder determines when the detection beam is perpendicular to the paper, at which time a circuit fires a pulsed laser. This five-nanosecond pulse causes a microscopic thermal ablation of the paper, which is too small to visibly mar the paper but strong enough to send ultrasonic shock waves through the sheet. The waves propagate until they reach the detection beam. Because the laser is synchronized to fire only when the detection beam is perpendicular to the paper, the distance between the excitation point and detection point is known, and the waves' speed is calculated and bending stiffness and shear rigidity computed.

For more information, please contact:

Paul Ridgway at: Tel (1) 510 486-7363, plridgway@lbl.gov or,

Emmanuel Lafond at: Tel (1) 404 894-3707, emmanuel.lafond@ipst.gatech.edu