Analysis of the outer divertor hot spot activity in the protection video camera recordings at JET Articles uri icon

publication date

  • February 2019

start page

  • 115

end page

  • 123

volume

  • 139

international standard serial number (ISSN)

  • 0920-3796

electronic international standard serial number (EISSN)

  • 1873-7196

abstract

  • Hot spots on the divertor tiles at JET result in overestimation of the tile surface temperature which causes unnecessary termination of pulses. However, the appearance of hot spots can also indicate the condition of the divertor tile surfaces. To analyse the behaviour of the hot spots in the outer divertor tiles of JET, a simple image processing algorithm is developed. The algorithm isolates areas of bright pixels in the camera image and compares them to previously identified hot spots. The activity of the hot spots is then linked to values of other signals and parameters in the same time intervals. The operation of the detection algorithm was studied in a limited pulse range with high hot spot activity on the divertor tiles 5, 6 and 7. This allowed us to optimise the values of the controlling parameters. Then, the wider applicability of the method has been demonstrated by the analysis of the hot spot behaviour in a whole experimental campaign.

keywords

  • jet; iter-like wall; plasma-wall interaction; image analysis