LLNL & Los Alamos National Laboratories

Phase Laser Systems provides engineering and developmental services to industry and government in order that our fundamental laser ranging technology may be customized for very specific applications.  Past and current development projects have produced products for use in many different and varied fields.  Automotive, geological, level, fuel combustion and fiber optics are examples of past and current developmental projects.

The following is an excerpt from a story in the September, 1996 issue of Sensors Magazine describing a joint project with Lawrence Livermore Laboratories and Los Alamos National Laboratories.  The full text of the article may be requested from Phase Laser Systems and is entitled “The Frequency Modulated Laser...Designing a Practical System”.

Photo: The Principles of frequency-modulated laser ranging are being evaluated as a way to monitor the movement of rock inside tunnels being constructed to house radioactive waste. (Photo courtesy of Los Alamos National Laboratories)

Measuring Deformities in Rock at High Temperatures

The U.S. Department of Engery’s Yucca Mountain Project, located ~100 miles north of Las Vegas, Nevada, is the proposed site for a high-level radioactive waste storage facility.  As part of the DOE’s evaluation of the site, Los Alamos National Laboratories is overseeing the construction of one primary and several smaller test tunnels beneath Yucca Mountain (see Photo).  The test tunnels are used for conducting experiments designed to determine the effects of heat on the mechanical and hydrological properties of the surrounding rock.

Because radioactive waste generates a large amount of heat, the scientists want to evaluate the impact of increased temperatures on the structural integrity of the tunnel and on opening in the rock. The data will help determine a suitable way to construct additional tunnels at the site.

Until recently, the expansion or contraction of the tunnel opening was measured with a tape extensometer.  The tape was attached to pins placed in the rock and measurements were taken. These devices are accurate to a fraction of a millimeter but are very time consuming to operate and require the services of a skilled technician.

Los Alamos scientists are evaluating the feasibility of replacing the tape extensometer with a frequency-modulated laser extensometer from Phase Laser Systems.  In addition to being more convenient to use, the laser would be an inexpensive way to measure rock movements down to 0.1mm resolution.

Lawrence Livermore National Laboratory is using the laser, paired with a multipoint extensometer, to measure deformities that occur in boreholes when the surrounding rock is exposed to high heat. Because these deformities must be monitored at several points within the boreholes, the laser system design had to satisfy tight space restrictions as well as heat and pressure within the hole.

For this application, the frequency-modulated laser was fiber-optically coupled on both the transmit and receive sides.  The sensor was then connected to an optical switch containing four separate optical channels.  Three of the optical cables were positioned to read targets at different depths in the borehole, and the fourth function as a reference to counteract potential long-term drift in the system.  By electronically controlling the position of the optical switch, one sensor became three, and all the electronics could be mounted well away from the area of environmental concern.