Non-statistical population distributions for hydrogen beams in fusion plasmas

Marchuk, O.; Ralchenko, Yu.; Schultz, David

doi:10.1088/0741-3335/54/9/095010

Cited by 28 publications

(43 citation statements)

References 48 publications

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“…This allows us to only consider transitions between different energy levels. However, this assumption has been shown 26 to break down when the electron density is less than 10 14 cm À3 . In this regime, the following collisional radiative model can overestimate the D-a emission by about 20%-25%.…”

Section: Appendix: Collisional Radiative Modelmentioning

confidence: 99%

Action-angle formulation of generalized, orbit-based, fast-ion diagnostic weight functions

Stagner

Heidbrink

2017

Physics of Plasmas

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Due to the usually complicated and anisotropic nature of the fast-ion distribution function, diagnostic velocity-space weight functions, which indicate the sensitivity of a diagnostic to different fast-ion velocities, are used to facilitate the analysis of experimental data. Additionally, when velocity-space weight functions are discretized, a linear equation relating the fast-ion density and the expected diagnostic signal is formed. In a technique known as velocity-space tomography, many measurements can be combined to create an ill-conditioned system of linear equations that can be solved using various computational methods. However, when velocity-space weight functions (which by definition ignore spatial dependencies) are used, velocity-space tomography is restricted, both by the accuracy of its forward model and also by the availability of spatially overlapping diagnostic measurements. In this work, we extend velocity-space weight functions to a full 6D generalized coordinate system and then show how to reduce them to a 3D orbit-space without loss of generality using an action-angle formulation. Furthermore, we show how diagnostic orbit-weight functions can be used to infer the full fast-ion distribution function, i.e., orbit tomography. In depth derivations of orbit weight functions for the neutron, neutral particle analyzer, and fast-ion D-α diagnostics are also shown.

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Section: Appendix: Collisional Radiative Modelmentioning

confidence: 99%

Action-angle formulation of generalized, orbit-based, fast-ion diagnostic weight functions

Stagner

Heidbrink

2017

Physics of Plasmas

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“…Thus, knowing the local density, these ratios are obtained from atomic model based relative intensity curves for an attenuated beam [27]. Although ratios from another model have been considered [28], it was found that the standard deviation of the differences between measured and predicted values of |B Z 2 + B φ 2 | 1/2 and ϕ are slightly larger for the latter ratios, hence the ratios from [27] are used here. Note: the -and + intensities, I − and I + respectively, are allowed to differ by a few percent as asymmetries can arise from beam divergence and beam width effects [17].…”

Section: Spectrum Fittingmentioning

confidence: 99%

A Spectrally Resolved Motional Stark Effect Diagnostic for the TJ‐II Stellarator

McCarthy¹,

Panadero

Löpez‐Fraguas³

et al. 2015

Contrib. Plasma Phys.

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A spectrally resolved motional stark effect (MSE) diagnostic has been implemented for the TJ-II stellarator to quantify the magnitude and pitch of components of the magnetic field created in this magnetic confinement device. The system includes a compact diagnostic neutral beam injector (DNBI) that provides a short pulse of accelerated neutral hydrogen atoms with an e −1 beam radius of 2.1 cm to stimulate the Doppler-displaced Balmer Hα emissions, which are the basis for this diagnostic. Measurement of the wavelength separation of the Stark splitting of the Hα spectrum, as well as of the relative line intensities of its components, allow the local magnitude and direction of the internal magnetic field components to be measured at 10 positions across the plasma. The use of a DNBI extends such measurements to the electron cyclotron resonance (ECR) heated phases of plasmas while also overcoming the need for the complicated inversion techniques that are required when such measurements are performed with a heating neutral beam injector (NBI). Moreover, the use of the shot-to-shot technique with reproducible discharges further simplifies fits to the MSE spectra as nearby impurity spectral emission lines can be eliminated or significantly reduced. After outlining the principles of this technique and the diagnostic set-up, magnetic field measurements made during ECR or NBI heating phases are reported for a range of magnetic configurations and are compared with vacuum magnetic field estimates in order to evaluate the capabilities and limitations of this diagnostic for the TJ-II.

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“…A new general method was developed in Refs. [17,18] and is brieÀy described here. The major dif¿culty in calculation of collisional characteristics is due to presence of two independent quantization axis.…”

Section: Atomic Data For Mse and Bes Diagnosticsmentioning

confidence: 99%

Atomic data for beam-stimulated plasma spectroscopy in fusion plasmas

Marchuk¹,

Ralchenko²,

Schultz³

et al. 2013

AIP Conference Proceedings

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Articles you may be interested inDevelopment of the charge exchange recombination spectroscopy and the beam emission spectroscopy on the EAST tokamaka) Rev. Sci. Instrum. 85, 11E428 (2014); 10.1063/1.4890408 Charge exchange recombination spectroscopy on fusion devices AIP Conf. Approaches to confined alpha diagnostics on ITER Rev. Sci. Instrum. 75, 3556 (2004); 10.1063/1.1787915 70 keV neutral hydrogen beam injector with energy recovery for application in thermonuclear fusion research Rev. Abstract.Injection of high energy atoms into a con¿ned plasma volume is an established diagnostic technique in fusion research. This method strongly depends on the quality of atomic data for chargeexchange recombination spectroscopy (CXRS), motional Stark effect (MSE) and beam-emission spectroscopy (BES). We present some examples of atomic data for CXRS and review the current status of collisional data for parabolic states of hydrogen atoms that are used for accurate MSE modeling. It is shown that the collisional data require knowledge of the excitation density matrix including the off-diagonal matrix elements. The new datasets for transitions between parabolic states are used in an extended collisional-radiative model. The ratios between the σ -and π-components and the beam-emission rate coef¿cients are calculated in a quasi-steady state approximation. Good agreement with the experimental data from JET is found which points out to strong deviations from the statistical distribution for magnetic sublevels.

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Non-statistical population distributions for hydrogen beams in fusion plasmas

Cited by 28 publications

References 48 publications

Action-angle formulation of generalized, orbit-based, fast-ion diagnostic weight functions

Action-angle formulation of generalized, orbit-based, fast-ion diagnostic weight functions

A Spectrally Resolved Motional Stark Effect Diagnostic for the TJ‐II Stellarator

Atomic data for beam-stimulated plasma spectroscopy in fusion plasmas

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