Near-infrared spectroscopy for burning plasma diagnostic applications

Abstract

Ultraviolet and visible (UV-VIS, 200-750 nm) atomic spectroscopy of neutral and ionized fuel species (H, D, T, and Li) and impurities (e.g., He, Be, C, and W) is a key element of plasma control and diagnosis on International Thermonuclear Experimental Reactor and future magnetically confined burning plasma experiments (BPXs). Spectroscopic diagnostic implementation and performance issues that arise in the BPX harsh nuclear environment in the UV-VIS range, e.g., degradation of first mirror reflectivity under charge-exchange atom bombardment (erosion) and impurity deposition, permanent and dynamic loss of window, and optical fiber transmission under intense neutron and gamma-ray fluxes, are either absent or not as severe in the near-infrared (NIR, 750-2000 nm) range. An initial survey of NIR diagnostic applications has been undertaken on the National Spherical Torus Experiment. It is demonstrated that NIR spectroscopy can be used for machine protection and plasma control applications, as well as contribute to plasma performance evaluation and physics studies. Emission intensity estimates demonstrate that NIR measurements are possible in the BPX plasma operating parameter range. Complications in the NIR range due to the parasitic background emissions are expected to occur at very high plasma densities, low impurity densities, and at high plasma-facing component temperatures.

Broad‐Band Time‐Resolved Near Infrared Spectroscopy in the TJ‐II Stellarator

“…To the best of our knowledge, only a few experimental studies in the NIR region have been yet performed: In NSTX tokamak [2] it is limited to wavelengths below 1100 nm where a silicon-based CCD detector was used in the experimental set-up. To the best of our knowledge, only a few experimental studies in the NIR region have been yet performed: In NSTX tokamak [2] it is limited to wavelengths below 1100 nm where a silicon-based CCD detector was used in the experimental set-up.…”

“…The plasma emission in the Near Infrared (NIR) spectral region (loosely defined here as covering the spectral range from 750 nm to 1650 nm) has been only marginally studied to date in magnetic confinement fusion devices. To the best of our knowledge, only a few experimental studies in the NIR region have been yet performed: In NSTX tokamak [2] it is limited to wavelengths below 1100 nm where a silicon-based CCD detector was used in the experimental set-up. In the JET tokamak [3], the system combines a standard Indium Gallium Arsenide (InGaAs) 256 pixel linear array and two extended photodiodes for Paschen α line (1875 nm) studies.…”

Kinetics of highly excited states in Ar17+charge exchange recombination fusion plasma spectroscopy

“…The spectroscopic diagnostics of plasmas in fusion devices make use of different techniques and cover the wavelength range from x-ray [1] through visible [2] to infrared [3]. The methods of plasma spectroscopy have been refined over several decades and are widely implemented in the current and planned magnetic fusion experiments.…”

Enhanced visible and near-infrared capabilities of the JET mirror-linked divertor spectroscopy system

“…r Extending the near-infrared spectral coverage to 1875 nm r Increasing the time resolution of Balmer series and Be line intensity spatially resolved measurements up to ∼500 μs r Increasing the wavelength window for dedicated Balmer series measurements Spectroscopy in the near-infrared range offers the potential of increased tolerance to the degradation of optics under a harsh burning plasma environment, 3 but plasma emission in the 1000-1875 nm range is poorly characterized at present.…”