Analysis of dust collecting tapes with laser ablation mass spectroscopy for assessing PFC slag management experiments on DIII-D

A dust collection performed after the DIII-D FY24 campaign suggests the capability to distinguish isotopically enriched B11 powder from background boron on double-sided copper tapes mounted on scanning electron microscopy stubs. The main purpose of this collection was to assess the tape technique as an analysis method for future Plasma Facing Component dust and debris (aka “PFC slag”) accumulation management experiments. This collection also provides a clean case to compare with after such an experiment since the last B11 powder injection occurred over a month before the campaign end. A total of 100 copper tapes collected material at various toroidal and poloidal locations, including 60 tapes used to create radial profiles across the lower divertor at two toroidal locations. Glow discharge boronizations introduced natural B using diborane gas about every six weeks during the campaign, and the impurity powder dropper (IPD) injected enriched B11 powder during several experiments. No natural B was injected from the IPD. Laser ablation mass spectroscopy (LAMS) measurements of the tapes on the divertors record B11 isotopic abundances at 82-83%, a 2-3% enrichment above the natural abundance (~80% B11). Initial scans suggest a higher B enrichment near the strike point region on the nose tile. Enriched B clumps (>90% B11) are observed on the tapes on the far outer shelf.

This research is supported by the U.S. Department of Energy under Awards DE-SC0023378, DE-FC02-04ER54698, DE-AC05-00OR22725, DE-AC02-09CH11466.