Incorporating Beam Attenuation Calculations into an Integrated Data Analysis Model for Ion Effective Charge

Nornberg, M. D.; Hartog, D. J. Den; Reusch, L. M.

doi:10.1080/15361055.2017.1387008

Cited by 4 publications

(3 citation statements)

References 25 publications

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“…Here, we choose logarithmic priors for p(E 0,wall ) and p(n 0,wall ) to avoid a bias toward high amplitudes [36,37]. Since equation ( 2) is linear with respect to n z , the profile of each charge state for given D and v can be solved analytically.…”

Section: Priormentioning

confidence: 99%

Non-parametric inference of impurity transport coefficients in the ASDEX Upgrade tokamak

Nishizawa¹,

Dux²,

McDermott³

et al. 2022

Nucl. Fusion

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We present a non-parametric inference of impurity transport coefficients by using charge exchange recombination spectroscopy measurements of Ne X, Ne VIII, O VIII, and C VI lines. Due to their close atomic numbers, neon, oxygen and carbon impurity ions are assumed to have the same diffusion coefficient D and convection velocity v. In order to reduce a large computational cost, which a non- parametric approach typically entails, we have derived an analytical steady state solution for impurity profiles for given background plasma parameters and transport coefficients. Since the ratio of v to D only describes the equilibrated profile of the sum of all impurity charge states, steady-state measurements can still decouple D and v if different charge states are simultaneously observed. We have formulated a non-parametric analysis framework based on the Bayesian probability theory and conducted transport coefficient measurements for a Type III ELMy H-mode plasma at ASDEX Upgrade. The charge exchange reactions with the background neutrals, which are known to affect the impurity charge state balance, are taken into account by introducing additional free parameters. While D at the pedestal is close to the neoclassical level (<1 m/s2), a large diffusion coefficient and a strong outward pinch are inferred right inside the pedestal top.

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Section: Priormentioning

confidence: 99%

Non-parametric inference of impurity transport coefficients in the ASDEX Upgrade tokamak

Nishizawa¹,

Dux²,

McDermott³

et al. 2022

Nucl. Fusion

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show abstract

“…In this analysis, each element of θ is allowed to vary many orders of magnitude. To avoid biasing distribution toward higher orders of magnitude [19,20], the following prior distributions are used:…”

Section: ϵ and D δ Spectroscopy For A Uniform Plasma Slab Using Bayes...mentioning

confidence: 99%

Bayesian inference of particle source and sink in a closed-divertor using Balmer line spectroscopy

Nishizawa

Cavedon

Reimold

et al. 2020

Plasma Phys. Control. Fusion

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A new analysis technique for Balmer line spectroscopy that enables recombination rate (particle sink) and ionization rate (particle source) inference in a closed divertor configuration is reported. Bayesian inference is employed to systematically utilize all available information from multiple Balmer lines and constrain parameter ranges by using prior knowledge about plasmas. While a closed-divertor facilitates detachment, neutral plugging typically leads to large spatial variations in plasma parameters. A forward model is developed to take into account non-uniformity in the plasma parameters and applied to test data generated by divertor plasma simulations. It is shown that the forward model robustly provides particle source and sink inference over a wide parameter range. In addition, the precision improves as more Balmer lines are resolved simultaneously. The new analysis technique is also applied to an L-mode ASDEX Upgrade plasma in the high-recycling regime. The inferred quantities and their profiles are consistent with the expectations of a high-recycling divertor plasma. The further insight into the detachment physics will be provided by using this new analysis technique.

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“…Development of a forward model for CHERS data is currently underway, starting with a self-consistent calculation of the neutral beam attenuation (necessary for inferring impurity density measurements from CHERS data). 40 This model uses the same impurity density profiles used in the SXR forward model and atomic cross sections to predict the neutral beam density as it traverses the plasma and is attenuated by ion collisions. The model is combined with experimental data from beam Doppler-shift spectra and shine-through particle flux to determine the local neutral beam particle density.…”

Section: Ida Measurement Of Z Eff On Mstmentioning

confidence: 99%

Using integrated data analysis to extend measurement capability (invited)

Reusch

Nornberg

Goetz

et al. 2018

Review of Scientific Instruments

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The analysis approach called integrated data analysis (IDA) provides a means to exploit all information present in multiple streams of raw data to produce the best inference of a plasma parameter. This contrasts with the typical approach in which information (data) from a single diagnostic is used to measure a given parameter, e.g., visible bremsstrahlung → Z eff. Data from a given diagnostic usually contain information on many parameters. For example, a Thomson scattering diagnostic is sensitive to bremsstrahlung and line emission in addition to electron temperature. This background light is typically subtracted off and discarded but could be used to improve knowledge of Z eff. IDA encourages explicit awareness of such information and provides the quantitative framework to exploit it. This gives IDA the ability to increase spatial and temporal resolution, increase precision and accuracy of inferences, and measure plasma parameters that are difficult or impossible to measure using single diagnostic techniques. One example is the measurement of Z eff on Madison symmetric torus using IDA since no single diagnostic can provide a robust measurement. As we enter the burning plasma era, application of IDA will be critical to the measurement of certain parameters, as diagnostic access in the harsh fusion environment will be extremely limited.

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Incorporating Beam Attenuation Calculations into an Integrated Data Analysis Model for Ion Effective Charge

Cited by 4 publications

References 25 publications

Non-parametric inference of impurity transport coefficients in the ASDEX Upgrade tokamak

Non-parametric inference of impurity transport coefficients in the ASDEX Upgrade tokamak

Bayesian inference of particle source and sink in a closed-divertor using Balmer line spectroscopy

Using integrated data analysis to extend measurement capability (invited)

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