Development of atomic beam probe for tokamaks

• ABP is newly developed diagnostic.
• Unique measurement method for the determination of plasma edge current variations caused by different transient events such as ELMs.
• The design process has been fruitfully supported by the physically motivated computer simulations.
• Li-BES system has been modified accordingly to the needs of the ABP.

The concept and development of a new detection method for light alkali ions stemming from diagnostic beams installed on medium size tokamak is described. The method allows us the simultaneous measurement of plasma density fluctuations and fast variations in poloidal magnetic field, therefore one can infer the fast changes in edge plasma current. The concept has been worked out and the whole design process has been done at Wigner RCP. The test detector with appropriate mechanics and electronics is already installed on COMPASS tokamak. General ion trajectory calculation code (ABPIons) has also been developed. Detailed calculations show the possibility of reconstruction of edge plasma current density profile changes with high temporal resolution, and the possibility of density profile reconstruction with better spatial resolution compared to standard Li-BES measurement, this is important for pedestal studies.