An edge fast-ion D-alpha system installed at ASDEX Upgrade

Vuuren, A. Jansen van; Geiger, B.; Jacobsen, A. S.; Cavedon, M.; Dux, R.; Köhnlein, H.

doi:10.1063/1.5121588

Cited by 9 publications

(13 citation statements)

References 25 publications

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“…Another important experimental case included in this analysis is the stationary phase at 1.9 s of the discharge #35681, with B t = −2.5 T, I p = 0.6 MA, P heat = 7.5 MW, δ = 0.24, Γ D = 0.14 × 10 22 e/s. This experiment aimed at studying the effect of ELMs on the fast-ion densities at the plasma edge using a new edge FIDA spectrometer installed at AUG [68]. From a modeling perspective it is particularly interesting for two reasons: first, in the experiment tangential NBI sources were used, obtaining a strongly off-axis power deposition, and second, the edge FIDA spectrometer is capable of measuring the intensity of the edge D-alpha line simultaneously with the FIDA radiation, which allows the determination of the background density of neutrals.…”

Section: Comparison With Experimental Measurements and Ipb98(y2) Scal...mentioning

confidence: 99%

Validation of a full-plasma integrated modeling approach on ASDEX Upgrade

et al. 2021

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In this work we present the extensive validation of a refined version of the integrated model based on engineering parameters (IMEP) introduced in reference (Luda et al 2020 Nucl. Fusion 60 036023). The modeling workflow is now fully automated, computationally faster thanks to the reduced radial resolution of the TGLF calculation, and it includes the modeling of the toroidal rotation, which was still taken from experimental measurements in our previous work. The updated model maintains the same accuracy as its previous version when tested on the cases presented in the initial publication. The confined plasma, from the magnetic axis to the separatrix, is simulated without using any experimental information from profiles measurements, and the inputs of IMEP are the same engineering parameters used when programming a plasma discharge. The model validation database consists of 50 ASDEX Upgrade (AUG) stationary (over a few energy confinement time) H-mode phases, which largely cover the entire AUG operational domain. The prediction of IMEP is compared with experimental measurements and with scaling laws, such as the IPB98(y,2), the ITPA20-IL, and AUG specific regressions. This modeling framework has proven to be very accurate over the entire set of 50 cases, with a significantly lower mean relative error with respect to each of the scaling laws considered, accurately reproducing the change in pedestal and core confinement caused by a change in plasma current, heating power, fueling rate, triangularity, magnetic field, NBI voltage (i.e. the effect of a change in the core particle source), and heating mix (e.g. correctly predicting the effect on confinement caused by a change in T e/T i). Plasma confinement is correctly described by IMEP also for two particular operating regimes, such as the ITER baseline scenario, and the QCE regime (quasi continuous exhaust, also referred as type-II and small ELMs). This work clearly demonstrates the power of this approach in pulling out physics mechanisms to interpret subtle interdependencies and that a 1D integrated model can reproduce experimental results over very large parameter variations with a higher accuracy than any statistical regression. This approach has therefore the potential to improve the prediction of the fusion performance in future tokamak reactors.

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Section: Comparison With Experimental Measurements and Ipb98(y2) Scal...mentioning

confidence: 99%

Validation of a full-plasma integrated modeling approach on ASDEX Upgrade

et al. 2021

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“…The simulation of passive FIDA and NPA fluxes has gained increasing attention in recent years since it turned out that FIDA and NPA signals can be significantly affected by passive contributions [21,22]. In addition, charge exchange of fast ions has been identified as an significant loss mechanism for instance at the TCV tokamak and the corresponding passive FIDA signal provides a direct measure to probe these losses [23].…”

Section: Passive Simulations -Cold Neutralsmentioning

confidence: 99%

“…As Ref. [29] published by [21]: A dedicated edge-FIDA diagnostic system has been installed at ASDEX Upgrade which observes particularly strong passive FIDA signals during off-axis NBI injection. Fig.…”

Section: Validation Using Balmer Alpha Spectroscopy Diagnosticsmentioning

confidence: 99%

Progress in modelling fast-ion D-alpha spectra and neutral particle analyzer fluxes using FIDASIM

Geiger

Stagner

Heidbrink

et al. 2020

Plasma Phys. Control. Fusion

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FIDASIM is a code that models signals produced by charge-exchange reactions between neutrals and ions (both fast and thermal) in magnetically confined plasmas. With the ion distribution function as input, the code predicts the efflux to a neutral particle analyzer (NPA) diagnostic and the photon radiance of Balmer-alpha light to a fast-ion D α (FIDA) diagnostic, in addition to many other related quantities. A new, parallelized version of the Monte Carlo code FIDASIM has been developed in Fortan90 that is substantially faster than the original IDL version. Modified algorithms include more accurate treatments of the time dependent collisional-radiative equations that describe neutral energy levels, of the cloud of "halo" neutrals that surround the injected neutral beam, and of finite Larmor radius effects. Enhanced physics capabilities include modeling "passive" signals from cold edge neutrals, the ability to treat general three-dimensional magnetic confinement configurations, and calculations of diagnostic-specific weight functions that enable tomographic reconstructions of the fast-ion distribution function. Neutral beam attenuation, beam emission, and fast-ion birth profiles are also modelled. The new algorithms have been successfully validated against experimental data and new features have been tested through benchmarks between two independently developed versions of the code.

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“…This is the biggest challenge in resolving main ion properties and is assessed via forward modelling of the spectra, as will be explained in detail in subsection 4.1. The edge main ion CXRS at AUG uses the two new edge FIDA spectrometers [11]. The two spectrometers have a dispersion relation of 0.015 (0.021) nm/pixel and a time resolution of 1.3 (3.1) ms with a simultaneous imaging of 11 (19) channels.…”

Section: Diagnostic Setupmentioning

confidence: 99%

“…The edge main ion CXRS at AUG uses the two new edge FIDA spectrometers [11]. The two spectrometers have a dispersion relation of 0.015 (0.021) nm/pixel and a time resolution of 1.3 (3.1) ms with a simultaneous imaging of 11 (19) channels.…”

Section: Wavelength [Nm]mentioning

confidence: 99%

Feasibility study for an edge main ion charge exchange recombination spectroscopy system at ASDEX Upgrade

Cano-Megias¹,

Viezzer²,

Vuuren³

et al. 2019

J. Inst.

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A feasibility study for a new edge main ion charge exchange recombination spectroscopy (CXRS) system at the ASDEX Upgrade tokamak has been carried out. This diagnostic uses the new edge fast-ion Dα (FIDA) spectrometers and the optical heads of the existing edge CXRS systems. Standard CXRS resolved temperature and rotation profiles rely on the observation of impurity emission lines. The complexity of the photoemission processes and the fact that the measured ions represent the majority bulk plasma ions (here deuterium) make the interpretation of the main ion spectra in comparison more challenging. At the plasma edge, the diagnostic capabilities in terms of temporal and spatial resolution are extremely demanding. The difficulties in the interpretation of the main ion spectra are overcome by comprehensive fitting and forward modelling of the beam halo (which introduces a major challenge) using a collisional radiative model, as described in [S.R. Haskey, JINST 12 (2017) C10013]. In this work, the diagnostic set up and the sensitivity of the main ion spectra to changes in plasma parameters have been characterized. The tools and techniques necessary for a correct interpretation of the spectra are also discussed. In addition to the halo effect, corrections due to atomic physics effects which could affect the splitting and broadening of the spectral Dα line and lead to misinterpretation of the spectra are evaluated. The first measurements of the edge main ion diagnostic are also presented.

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An edge fast-ion D-alpha system installed at ASDEX Upgrade

Cited by 9 publications

References 25 publications

Validation of a full-plasma integrated modeling approach on ASDEX Upgrade

Validation of a full-plasma integrated modeling approach on ASDEX Upgrade

Progress in modelling fast-ion D-alpha spectra and neutral particle analyzer fluxes using FIDASIM

Feasibility study for an edge main ion charge exchange recombination spectroscopy system at ASDEX Upgrade

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