Performance of fast-ion loss diagnostic on EAST

Area of Science:

• Fusion energy research
• Plasma physics diagnostics

Background:

• The EAST tokamak utilizes a scintillator-based detector for fast-ion loss measurements.
• Previous systems offered good energy and pitch resolution but required complementary high temporal resolution measurements.

Purpose of the Study:

• To develop fast photomultiplier tube systems for high temporal resolution fast-ion loss diagnostics.
• To investigate and mitigate interference from X-rays produced by energetic electrons on scintillator-based detectors.

Main Methods:

• Installation of a scintillator-based detector on the EAST tokamak.
• Development of fast photomultiplier tube systems to complement CCD camera imaging.
• Utilizing a rotatable platform for measurements in normal and reverse magnetic fields.
• Studying the effects of runaway and lower hybrid wave-accelerated electrons on detector signals.

Main Results:

• Fast photomultiplier tube systems provide complementary high temporal resolution data.
• Prompt beam-ion losses can be measured in both normal and reverse magnetic fields.
• X-ray interference from thick-target bremsstrahlung caused by energetic electrons was identified as a significant factor.

Conclusions:

• The developed systems enhance fast-ion loss diagnostics on EAST.
• Understanding and accounting for X-ray interference is crucial for accurate measurements.
• The detector is capable of measuring prompt losses under various magnetic field configurations.