A simulation study of a windowless gas stripping room in an E//B neutral particle analyzer

TL;DR

This study uses simulations to analyze a windowless gas stripping chamber in a neutral particle analyzer, optimizing pressure conditions for maximum efficiency in particle detection.

Contribution

It introduces a simulation-based approach combining pressure distribution analysis and particle tracking to optimize a windowless gas stripping chamber in NPA devices.

Findings

Optimal pressure of 240 Pa for maximum efficiency.

Pressure distribution insights from Fluent and MolFlow+ simulations.

Enhanced understanding of charge state tracking in GEANT4.

Abstract

Neutral Particle Analyzer (NPA) is one of the crucial diagnostic devices on Tokamak facilities. Stripping unit is one of the main parts of the NPA. A windowless gas stripping room with two differential pipes is adopted in a parallel direction of electric and magnetic fields (E//B) NPA. The pressure distributions in the stripping chamber are simulated by Ansys Fluent together with MolFlow+. Based on the pressure distributions extracted from the simulation, the stripping efficiency of the E//B NPA is studied with GEANT4. The hadron reaction physics is modified to track the charge state of each particle in a cross section base method in GEANT4. The transmission rates ($R$) and the stripping efficiencies $f_{+1}$ are examined for the particle energy ranging from 20 to 200 keV at the input pressure ($P_0$) ranging from 20 to 400 Pa. According to the combined global efficiency, $R \times f_{+1}$, $P_0$ = 240 Pa is obtained as the optimum pressure for the maximum global efficiency in the incident energy range investigated.