MXP (Manipulator eXPeriment)

The MXP testbed is used for the production of RF breakdowns in controlled condition.

Arcs can limit the operating voltage of the ICRF system and, when they occur, can release a large amount of energy and damage the components.

It is therefore important to understand how arcs are triggered and how they can be detected. The control parameters are the following:

• geometry and material of the electrodes where the arcs are produced.
• voltage (up to 100kV)
• residual gas pressure
  
  
  

Principle of operation

MXP is basically a transmission line open at one side and short-circuited at the other side, building a 3λ/4 resonator, powered by one of the ASDEX Upgrade ICRF generators. The resulting high voltage at the open end can be controlled and increased until a RF breakdown occurs.

The system is equipped with a full set of cameras, voltage and power probes to measure the electrical characteristics at the moment of the discharge and with a high temporal resolution (in the nanosecond range).

This very flexible testbed has allowed different teams from Europe to study several aspects of arcs and arc detection. We give some example of the results obtained in the following section.