2-D measurements of plasma electron density using coherence imaging with a pixelated phase mask

2-D measurements of plasma electron density using coherence imaging with a pixelated phase mask

2-D measurements of plasma electron density using coherence imaging with a pixelated phase mask 150 150 Mathew
UKAEA-CCFE-PR(21)40

2-D measurements of plasma electron density using coherence imaging with a pixelated phase mask

In this paper, the pixelated phase mask (PPM) method of interferometry is applied to coherence imag-ing (CI) — a family of passive, narrowband spectro-polarimetric imaging techniques for diagnosing plasmas. Compared to designs using a linear phase mask, PPM is more compact, rugged and has a higher spatial resolution (averaged across both image dimensions). A single-delay instrument design is introduced as well as a multi-delay design which uses both pixelated and linear phase masks. Thedesigns are demonstrated with measurements of electron density n_e, via the Stark broadening of the Hγ line at 434.0 nm, made on the Magnum-PSI linear plasma experiment. Comparison of the Abel-inverted multi-delay CI results with Thomson scattering measurements shows good agreement across the 5×10^19 < n_e < 8×10^20 m^−3 range. The neutral temperature estimates of≈3 eV simultaneously inferred from this CI data matches previous spectroscopic studies. For the single-delay CI results, Doppler broadening causes systematic error for n_e < 10^20 m−3.

Collection:
Journals
Journal:
Review of Scientific Instruments
Publisher:
AIP (American Institute of Physics)