Performance of large electron energy filter in large volume plasma device

Area of Science:

• Plasma Physics
• Fusion Energy Research
• Applied Electromagnetics

Background:

• Controlling energetic electrons and plasma temperature profiles is crucial for various plasma applications.
• Existing methods often struggle to independently modify electron temperature gradients without affecting plasma density.
• The Large Volume Plasma Device (LVPD) requires advanced diagnostics and control mechanisms for specific experimental objectives.

Purpose of the Study:

• To design and implement an in-house Electron Energy Filter (EEF) within the LVPD.
• To remove remnant primary ionizing energetic electrons and non-thermal electrons from the plasma.
• To introduce controllable radial gradients in plasma electron temperature while preserving plasma density profiles.

Main Methods:

• Utilized a custom-designed Electron Energy Filter (EEF) comprising 19 independent coils forming a variable aspect ratio solenoid.
• Generated a transverse magnetic field (B(x) ~ 100 G) superimposed on the ambient axial field (B(z) ~ 6.2 G) of the LVPD.
• Analyzed plasma characteristics in distinct source, EEF, and target regions, measuring electron density (n(e)) and temperature (T(e)).

Main Results:

• Successfully eliminated detectable energetic electrons in the target plasma region (n(e) ~ 2 × 10^11 cm^-3, T(e) ~ 2 eV).
• Established controllable radial gradients in electron temperature with scale lengths ranging from 50 to 600 cm by adjusting the EEF magnetic field.
• Observed that the EEF magnetic field influences transverse electron transport, particularly enhancing transport due to plasma turbulence.

Conclusions:

• The designed Electron Energy Filter (EEF) is effective in removing energetic electrons and controlling electron temperature gradients in the LVPD.
• The EEF allows for independent manipulation of electron temperature profiles without significantly altering plasma density.
• The study highlights the role of magnetic field-dependent electron transport and plasma turbulence in the EEF's performance.