Upgrades to the macro residual stress facilities are underway to achieve at least a 10-fold increase in measurement effectiveness. The upgrades include the installation of a PSD detector array, consisting of 7 vertically stacked position-sensitive detectors, an elastically bent, vertically focusing Si (331) monochromator, and installation of two dedicated stress mapping goniometers with associated new automation.

The PSD seven detector array was first installed in the summer of 1996 and currently the output of three of the seven detectors is in routine operation. While methods are being developed to make use of all seven detectors, the use of the middle three detectors have already significantly increased the data throughput while giving better sampling of diffracting grains.

The doubly focusing Si (331) monochromator was fabricated at the University of Missouri. A monochromator mount and shield was constructed at ORNL. Test results show a gain of 30% in neutron flux at the sample position as compared to the prior Be monochromator for neutrons of comparable wavelength. However, high angle diffraction peaks are narrower with the Si (331) monochromator, giving rise to more accurate determination of the peak position and hence the strains. For these reasons, the Si (331) monochromator has become the preferred choice for stress mapping. This monochromator represents a significant improvement over the Be monochromator used previously and offers potential for further gains when HFIRâs beam port is redesigned during beryllium reflector replacement.

Two dedicated neutron goniometers with sample mapping capabilities have been ordered along with new computer capabilities for data analysis. These instruments will provide the capability to more rapidly measure and map the stress fields inside relatively large solid objects with lateral dimensions of a few feet as well as to map phase and texture throughout specimens.

Remote operation of the stress mapping facility is being developed to improve user access to the facility as part of the DOE2000 program which aims to accelerate the ability of the DOE to accomplish its mission through advanced computing and collaboration technologies. The Materials Microcharacterization Collaboratory Pilot Project will provide internet access to instrument control and advanced tools for remote collaboration.