Technology for Polarization Measurement

Hinds and Oak Ridge Nat’l Lab collaborate to introduce 2-MGEM OPTAF System

July 8th, 2008

ITU Taps Hinds Instruments And Oak Ridge National Labs For Advanced Technique To Characterize TRISO Fuel


The 2-MGEM Optical Anisotropy Factor Measurement System is faster, more repeatable and collects more data than previous measurement techniques


Hillsboro, Oregon, July 8, 2008 – Hinds Instruments, a leading global supplier of photoelastic modulators (PEMs), today announced the Institute for Transuranium Elements (ITU), in Karlsruhe, Germany, and part of the European Commission's Joint Research Centre, has installed Hinds Instruments' Two Modulator Generalized Ellipsometry Microscope (2-MGEM) Optical Anisotropy Factor Measurement System to help characterize cross sections of tristructural isotropic (TRISO) nuclear fuel particles. The instrument is a significant breakthrough; it is faster, more accurate and collects considerably more data than previous optical anisotropy measurement techniques. The 2-MGEM is a joint effort between Oak Ridge National Laboratory (ORNL) and Hinds Instruments; ORNL created the design using Hinds Instruments' core PEM technology. The instrument is patented by ORNL (U.S. Patent No. 5956147) and licensed by Hinds Instruments from UT-Battelle, LLC, management and operating contractor of ORNL, under Patent License Agreement No. 972.

"The 2-MGEM is a microscope-based, 2-PEM ellipsometer that is optimized to measure the linear diattenuation of pyrocarbon layers within a TRISO nuclear fuel particle," said Doug Mark, technical sales engineer with Hinds Instruments. "Specifically, the ITU wanted to characterize the degree of preferred orientation of crystallites in the polycrystalline pyrolytic carbon coatings. Excessive crystallographic anisotropy leads to unwanted anisotropic dimensional changes during irradiation that can cause the TRISO particles to fail."

"The 2-MGEM is a vast improvement over previous optical anisotropy measurement techniques,” said Dr. Gerald E. Jellison, a senior scientist in the Materials Science and Technology Division at ORNL. "For the first time, there's an exceptionally repeatable, sensitive and accurate way to characterize the linear diattenuation of pyrocarbon layers. (N.B. The diattenuation is directly related to the optical anisotropy factor (OPTAF) commonly used by TRISO fuel developers.) The 2-MGEM typically measures optical diattenuation to an accuracy of ±0.001 and the preferred direction of the crystallites to an accuracy of better than ±2° with a spatial resolution of better than 5 µm."

"Following an open market call, the ITU has ordered a 2-MGEM for its TRISO nuclear fuel program. Through the allocation of the market, it is recognized that the 2-MGEM is offering today's best solution to measure optical anisotropy,” Jellison continued. “Because Hinds Instruments had the license to the core technology, we asked Hinds to contact the ITU to set up the contract. They delivered a quality, commercialized system appropriate for use with nuclear material, where the sample is completely enclosed in a glove box. As per the ITU’s specifications, the Hinds Instruments 2-MGEM is a compact, turnkey instrument complete with an intuitive user interface. Furthermore, its data correlates well with ORNL's prototype version – exactly the level of accuracy and repeatability we were looking for."

The Hinds Instruments 2-MGEM is easily adapted to a wide range of demanding measurement applications. Its dual-PEM design is capable of measuring all 16 Mueller Matrix elements, from which diattenuation, retardation, direction of principal axis, circular diattenuation and depolarization can be determined. PEMs can be used at ultraviolet, visible and near infrared wavelengths. The company also offers a complete selection of detectors, polarizers, PEM options and demodulators to detect the small levels of ellipsometric polarization change that can occur.

Hinds Instruments is the world leader in developing and supplying polarization modulation components (or photoelastic modulators) for a broad range of applications. With 30+ years of polarization modulation experience, Hinds Instruments PEMs are proven tools for laboratory and research applications. PEMs operate on principles of resonance (20-84 kHz), require low power and have no moving parts. Hinds’ family of products includes modulators, optical choppers, Stokes polarimeters and birefringence measurement systems. For more information, please contact Hinds Instruments .

Back to News page