Physical design and primary experimental results of imaging neutral particle analyzer on HL-2A tokamak

The imaging neutral particle analyzer (INPA) based on scintillator (ZnS(Ag)) is designed and used on HL 2A tokamak to investigate the distribution of energetic particles (EPs) and even their interactions with magnetohydrodynamic instabilities. The collimation system is composed of a pinhole of 3 mm in diameter and six circular carbon microcrystal diaphragms each with a thickness of 10 nm. The neutral particles escape from six definite positions in the neutral beam injection path and pass through the collimator system at a certain pitch angle, and the neutral particles become fast ions after passing through the carbon microcrystal diaphragm. The fast ions will hit the scintillator after a 180 degrees deflection by the edge magnetic field. The energy, pitch angle and birthplace can be calculated by the position and light intensity of the impact spots. The images of impact spots caused by long-lived mode are recorded by a high-speed camera through the fiber optic bundle. The longlived mode instabilities approve to be excited by the core EPs with energy value in a range of E similar to 12.5- 32 keV, pitch angle of upsilon(//)/upsilon similar to 0.86, and the birthplace in a range of R similar to 170.5-171.5 cm.