Measurements of beam pulse induced mechanical strain inside the SNS* target module

Because several of the SNS targets have had a shorter lifetime than desired, a new target has been instrumented with strain sensors to further our understanding of the proton beam’s mechanical impact. The high radiation and electrically noisy environment led us to pick multi-mode fiber optical strain sensors over other types of strain sensors. Special care was taken to minimize the impact of the sensors on the target’s lifetime. We also placed accelerometers outside the target to try correlating the outside measurements with the internal measurements. Remote manipulators performed the final part of the installation, as even residual radiation is too high for humans to come close to the target’s final location. The initial set of optical sensors on the first instrumented target lasted just long enough to give us measurements from different proton beam intensities. A second set of more rad-hard sensors, installed in the following target, lasted much longer, to give us considerably more data. We are developing our own rad-hard, single-mode fiber optic sensors. This paper describes the design, installation, data-acquisition system, the results of the strain sensors, and future plans.