Implementation of an impurity diagnostic suite on the Pegasus-III experiment

Sanchez, Cuauhtemoc Rodriguez; Bongard, Michael W.; Diem, Stephanie J.; Goetz, John A.; Nornberg, Mark D.; Reusch, Joshua A.; Tierney, Timothy N.; Sontag, Aaron C.

doi:10.1063/5.0219339

Implementation of an impurity diagnostic suite on the Pegasus-III experiment

Journal Article · Mon Aug 12 00:00:00 EDT 2024 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/5.0219339· OSTI ID:2453877

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University of Wisconsin-Madison, WI (United States); University of Wisconsin-Madison
University of Wisconsin-Madison, WI (United States)

A suite of diagnostics used to assess impurity content and dynamics has been updated, upgraded, and installed on the Pegasus-III Experiment. Typical plasma parameters during local helicity injection start-up are τ_shot ~10 ms, n_e ~ 1 × 10¹⁹ m^–3, and T_e ~ 50 eV. The deployed diagnostics are compatible with this modest temperature and density regime and provide species identification, source localization, and estimation of radiation losses. Impurity species are determined by recording time-evolving, single line-of-sight spectra at 1.25 kfps using a SPRED (Survey, Poor Resolution, Extended Domain) vacuum ultraviolet spectrometer. SPRED is equipped with 450 g/mm grating, giving a spectral resolution of 0.33 nm and a spectral range from ~10 to 110 nm, useful to identify light impurity species in this temperature and density range. An absolutely calibrated spectrometer that collects light from the plasma at R_tan = 15.9 cm and Δt ≥ 2 ms is used as a visible survey spectrometer and for continuum measurements. The radiated power from the plasma is estimated with a photodiode-based diagnostic. Two 16-channel absolute extreme ultraviolet diode arrays are placed behind pinhole apertures, resulting in 32 lines of sight at Z = 0, with a spatial resolution of 2–3 cm and a time response of 60 kHz. A photometrically calibrated collinear D_α/near infrared filtered photodiode-based system measures the D_α emission and around 1040 nm. All these instruments have been designed to suppress electromagnetic interference from megawatt-class switching power supplies.

View Accepted Manuscript (DOE)

Research Organization:: University of Wisconsin-Madison, WI (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Fusion Energy Sciences (FES)

Grant/Contract Number:: SC0019008

OSTI ID:: 2453877

Journal Information:: Review of Scientific Instruments, Journal Name: Review of Scientific Instruments Journal Issue: 8 Vol. 95; ISSN 0034-6748

Publisher:: American Institute of Physics (AIP)Copyright Statement

Country of Publication:: United States

Language:: English

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