  Long pulse operation of present and future magnetic fusion devices requires
sophisticated methods for protection of plasma facing components from
overheating. Typically, thermographic systems are being used to fulfill this
task. Steady state operation requires, however, autonomous operation of the
system and fully automatic detection of abnormal events. At Wendelstein 7-X
(W7-X), a large advanced stellarator, which aims at demonstrating the
capabilities of the stellarator line as a future fusion power plant,
significant efforts are being undertaken to develop a fully automatic system
based on thermographic diagnostics. In October 2018, the first divertor-based
experimental campaign has been finished. One of the goals of this operation
phase (named OP1.2) was to study the capabilities of the island divertor
concept using an uncooled test divertor made of fine-grain graphite tiles.
Throughout this campaign, it was possible to test the infrared imaging
diagnostic system, which will be used to protect the actively water-cooled
plasma facing components (PFCs) during the steady-state operation in the next
experimental campaign. An overview of the most relevant thermal events on the
PFCs that were detected in OP1.2 using this system are presented. This includes
events that limited operation during the campaign, like baffe hot spots and
divertor overloads, events that are potentially critical in steady state
operation like leading edges, events caused by the ECRH and NBI heating systems
and other events which are a common source of false alarms like surface layers.
The detected thermal events are now part of an important and extensive image
database which will be used to further automate the system by means of computer
vision and machine learning techniques in preparation for steady-state
operation, when the system must be able to detect dangerous events and protect
the machine in real-time.
