Probing local electron temperature and density inside a sheared flow stabilized Z-pinch using portable optical...

Area of Science:

• Plasma Physics
• Fusion Energy Research
• Advanced Diagnostics

Background:

• High electron temperature (≳1 keV) and moderate density (mid 10¹⁶ cm^-3) plasmas are crucial for fusion energy concepts.
• Optical Thomson scattering is a key diagnostic for measuring plasma parameters like electron temperature and density.
• Existing Thomson scattering techniques face challenges in unconventional plasma regimes.

Purpose of the Study:

• To report the first optical Thomson scattering measurements in a high electron temperature and moderate density plasma.
• To develop and validate a diagnostic for Advanced Research Projects Agency-Energy-supported fusion energy concepts.
• To analyze plasma parameters in an unconventional regime between tokamaks and laser-produced plasmas.

Main Methods:

• Utilized an 8 J, 532 nm, 1.5 ns laser for Thomson scattering measurements.
• Employed a diagnostic capable of measuring electron density from 5 × 10¹⁷ to 10¹⁹ cm^-3 and electron temperatures from tens of eV to several keV.
• Deployed the diagnostic on the sheared flow stabilized Z-pinch machine (FuZE) at Zap Energy, targeting measurements 20 cm from the central electrode.

Main Results:

• Successfully performed optical Thomson scattering measurements in the specified plasma regime.
• Determined electron density was consistently below 5 × 10¹⁶ cm^-3 during measurements.
• Observed inferred electron temperatures ranging from 167 ± 16 eV to 700 ± 85 eV over a 1.6 cm region in a sample shot.

Conclusions:

• The developed optical Thomson scattering diagnostic is effective for characterizing high-temperature, moderate-density plasmas.
• The findings provide critical data for fusion energy concepts, particularly in challenging plasma regimes.
• The study highlights the adaptability of Thomson scattering for diverse plasma conditions relevant to fusion energy development.