Calculation and experimental test of the cooling factor of tungsten

Pütterich

Review of Scientific Instruments

et al. 2016

Self Cite

The soft X-ray (SXR) emission provides valuable insight into processes happening inside of high-temperature plasmas. A standard method for deriving the local emissivity profiles of the plasma from the line-of-sight integrals measured by pinhole cameras is the tomographic inversion. Such an inversion is challenging due to its ill-conditioned nature and because the reconstructed profiles depend not only on the quality of the measurements, but also on the inversion algorithm used. This paper provides a detailed description of several tomography algorithms, which solve the inversion problem of Tikhonov regularization with linear computational complexity in the number of basis functions. The feasibility of combining these methods with the Minimum Fisher Information Regularization is demonstrated, and various statistical methods for the optimal choice of the regularization parameter are investigated with emphasis on their reliability and robustness. Finally, the accuracy and the capability of the methods are demonstrated by reconstructions of experimental SXR profiles, featuring poloidal asymmetric impurity distributions as measured at the ASDEX Upgrade tokamak.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Optimized tomography methods for plasma emissivity reconstruction at the ASDEX Upgrade tokamak

Pütterich

Review of Scientific Instruments

et al. 2016

Self Cite

“…Impurities with higher Z number like Ar and Kr radiate significantly up to high temperatures and can therefore be used as main plasma radiators. Tungsten radiates strongly up to about 10 keV [13]. The local radiation power density is given by the product L z · n 2 e · c z where n e is the electron density and c z the impurity concentration.…”

Section: Theoretical Background and Modelling: Coronal And Non-coronamentioning

confidence: 99%

Transport analysis of high radiation and high density plasmas in the ASDEX Upgrade tokamak

Casali¹,

Bernert²,

Dux³

et al. 2014

EPJ Web of Conferences

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Abstract. Future fusion reactors, foreseen in the "European road map" such as DEMO, will operate under more demanding conditions compared to present devices. They will require high divertor and core radiation by impurity seeding to reduce heat loads on divertor target plates. In addition, DEMO will have to work at high core densities to reach adequate fusion performance. The performance of fusion reactors depends on three essential parameters: temperature, density and energy confinement time. The latter characterizes the loss rate due to both radiation and transport processes. The DEMO foreseen scenarios described above were not investigated so far, but are now addressed at the ASDEX Upgrade tokamak. In this work we present the transport analysis of such scenarios. Plasma with high radiation by impurity seeding: transport analysis taking into account the radiation distribution shows no change in transport during impurity seeding. The observed confinement improvement is an effect of higher pedestal temperatures which extend to the core via stiffness. A non coronal radiation model was developed and compared to the bolometric measurements in order to provide a reliable radiation profile for transport calculations. High density plasmas with pellets: the analysis of kinetic profiles reveals a transient phase at the start of the pellet fuelling due to a slower density build up compared to the temperature decrease. The low particle diffusion can explain the confinement behaviour.

Eur. Phys. J. Spec. Top.

“…Radiation from excited tungsten ions leads to substantial plasma cooling which has to be well controlled in order to maintain the conditions for nuclear fusion. Thus, a comprehensive knowledge of atomic energy levels and collision cross sections is required for a thorough understanding of the spatial and temporal evolution of the tungsten charge states and emission spectra in fusion plasmas [174].…”

Section: Atomic Data For Fusion Energy Researchmentioning

confidence: 99%

“…TSR at HIE-ISOLDE will allow one to considerably extend the range of charge states up to about 50+ with the currently available charge breeder (REXEBIS) and possibly up to 72 + (Helike) with an upgraded charge breeder. Measurements of absolute rate coefficients for DR and, equally important, for electron-ion impact ionization will thus become possible for all the charge states of tungsten which are relevant for fusion plasma modeling [174]. The dashdotted curve is the calculated merged-beams rate coefficient for radiative recombination (RR) using a hydrogenic approximation.…”

Section: Atomic Data For Fusion Energy Researchmentioning

confidence: 99%

Storage ring at HIE-ISOLDE

Grieser

Litvinov

Raabe

et al. 2012

111

We propose to install a storage ring at an ISOL-type radioactive beam facility for the first time. Specifically, we intend to install the heavy-ion, low-energy ring TSR at the HIE-ISOLDE facility in CERN, Geneva. Such a facility will provide a capability for experiments with stored secondary beams that is unique in the world. The envisaged physics programme is rich and varied, spanning from investigations of nuclear groundstate properties and reaction studies of astrophysical relevance, to investigations with highly-charged ions and pure isomeric beams. The TSR can also be used to remove isobaric contaminants from stored ion beams and for systematic studies within the neutrino beam programme. In addition to experiments performed using beams recirculating within the ring, cooled beams can also be extracted and exploited by external spectrometers for high-precision measurements. The existing TSR, which is presently in operation at the Max-Planck Institute for Nuclear Physics in Heidelberg, is well-suited and can be employed for this purpose. The physics cases, technical details of the existing ring facility and of the beam requirements at HIE-ISOLDE, together with the cost, time and manpower estimates for the transfer, installation and commissioning of the TSR at ISOLDE are discussed in the present technical design report.