Design of solid state neutral particle analyzer array for National Spherical Torus Experiment-Upgrade

Area of Science:

• Plasma Physics
• Fusion Energy Research
• Diagnostic Technology

Background:

• Fast ions play a crucial role in heating and sustaining plasma in fusion devices.
• Accurate measurement of fast ion behavior is essential for understanding and controlling fusion plasmas.
• Existing diagnostics may have limitations in temporal resolution or energy discrimination for fast ions.

Purpose of the Study:

• To design and fabricate a new compact, multi-channel Solid State Neutral Particle Analyzer (SSNPA) diagnostic.
• To achieve fast temporal resolution and coarse energy information for fast ions in the NSTX-U.
• To differentiate between passing and trapped fast ions and monitor passive signals.

Main Methods:

• Utilizing silicon photodiode arrays in current mode with varying filter thicknesses.
• Employing vertically stacked arrays for fast temporal resolution (∼120 kHz bandwidth).
• Implementing 15 radial and 15 tangential sightlines intersecting neutral beams at specific major radii.
• Incorporating a dedicated photodiode array for monitoring passive charge-exchange signals.

Main Results:

• The SSNPA system is designed to provide energy information in three bands: >25 keV, >45 keV, and >65 keV.
• The diagnostic aims to separate the responses of passing and trapped fast ions.
• The system is capable of monitoring fast ion behavior with high temporal resolution.

Conclusions:

• The developed SSNPA diagnostic is a promising tool for fast ion research in the NSTX-U.
• This diagnostic advancement will enhance the understanding of fast ion physics in toroidal fusion devices.
• The SSNPA's multi-channel and multi-energy band capabilities offer significant advantages for plasma diagnostics.