Speaker
Description
Tungsten divertor is one of the most important plasma facing components in EAST device. However, it has complex structure and faces extreme work environment. Centralized thermal strain would cause leakages on some weak welding seams, which was harmful for divertor’s operation. To measure divertor’s thermal strain shall be a valued way to understand its service behavior and then optimize its design and manufacturing process. Fiber Bragg Graing (FBG) was a proven technique to measure temperature and strain in sensor field. Though no similar works have been done before, it was considered an appropriate and feasible method to measure thermal strain on such a high temperature and strong electromagnetic field work environment.
In this work, a heat-resistant bare FBG sensor system had been introduced to measure surface thermal strain of one EAST tungsten divertor module. Ten FBG sensors made in four optical fibers were included in this system. Among the ten FBGs, seven were used for strain measurement and three for strain compensation. A logical compensation method had been adopted to make the results more credible. Heating procedure had been divided into four stages: fast heating stage, slow heating stage, heat preservation stage and cooling stage. Two thermocouples had been used for a feed-back loop to control heating rate and to record temperature.
The strain measurement system had withstood as high as 210℃ temperature and finished the experiment successfully. Experiment results showed that three measurement areas were under tensile strain and four were under compressed strain. Detail strain values had been calculated approximately. The results also had been compared with the measurement results using electric resistance strain gauges. Through the comparison, major results on corresponding areas were found similar, which told that the measurement results were reliable to some extent. In general, areas under tensile strain were more possible to leak than areas under compressed strain. This experiment would be a meaningful reference for tungsten divertor’s optimization and maintenance.
| Eligible for student paper award? | Yes |
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