Speaker
Description
A layer-short occurred in a bending magnet of the J-PARC Main Ring (MR) in May 2024. Its location and cause could not be identified from the external appearance of the magnet. Identifying the layer-short location by non-destructive methods before destructive investigation is important because information related to the cause may be lost during coil disassembly and cutting. The layer-short location was first estimated from the resistance to the layer-short point, calculated from the voltage and current measured while energizing individual coil layers or combinations of layers. The insulation around the estimated region was then removed, and a local temperature rise was observed during energization. Field scans were subsequently performed to further narrow down the layer-short region, followed by coil cutting. Through the series of investigations, the location, extent, and condition of the layer-short have been clarified to some extent. The results also showed that the actual layer-short region was close to the location estimated from the resistance measurement, indicating the usefulness of the resistance-based estimation method. However, the cause of the layer-short has not yet been identified. The investigation is ongoing, and this presentation will report the progress of the investigation and the current understanding of the layer-short in the J-PARC MR bending magnet.