Power deposition on the DIII-D inner wall limiter

ITER will use the shaped inner column as startup/rampdown limiter. An exploratory experiment was performed in DIII-D using a similarly shaped inner wall limiter, looking for evidence of a short fall-off feature, λshort, near the last closed flux surface. Measurements were made on the high field side (HFS) using infrared thermography and a Langmuir swing-probe. In some cases clear evidence was found for a narrow feature λshort∼ρpolD+∼ a few mm. The ratio q||0short/q||0long was mostly between 0.1 and 0.6. Measurements made on the low field side and bottom side showed little clear indication of any narrow feature.