Burn condition, helium particle confinement and exhaust efficiency

Reiter, D.; Wolf, G.H.; Kever, H.

doi:10.1088/0029-5515/30/10/012

Cited by 167 publications

(128 citation statements)

References 17 publications

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“…For W the effect of radiation is much more important than the dilution due to the large cooling factor. For more details of the evaluation of the ignition curves, confer to [38]. The scheme used in the present work corresponds to case 4 in section 3 of [38].…”

Section: Implications On Operation Of a Fusion Reactormentioning

confidence: 99%

Calculation and experimental test of the cooling factor of tungsten

Pütterich¹,

Neu²,

Dux³

et al. 2010

Nucl. Fusion

218

196

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Abstract. The cooling factor of W is evaluated using state of the art data for line radiation and an ionization balance which has been benchmarked with experiment. For the calculation of line radiation, level-resolved calculations were performed with the Cowan code to obtain the electronic structure and excitation cross sections (plane-wave Born approximation). The data were processed by a collisional radiative model to obtain electron density dependent emissions. These data were then combined with the radiative power derived from recombination rates and Bremsstrahlung to obtain the total cooling factor. The effect of uncertainties in the recombination rates on the cooling factor were studied and were identified to be of secondary importance. The new cooling factor is benchmarked, by comparisons of the line radiation to spectral measurements as well as to a direct measurement of the cooling factor. Additionally, a less detailed calculation using a configuration averaged model was performed. It was used to benchmark the level-resolved calculations and to improve the prediction on radiation power from line radiation for ionization stages which are computationally challenging. The obtained values for the cooling factor validate older predictions from literature. Its ingredients and the absolute value are consistent with the existing experimental results regarding the value itself, the spectral distibution of emissions and the ionization equilibrium. A table of the cooling factor versus electron temperature is provided. Finally, the cooling factor is used to investigate the operational window of a fusion reactor with W as intrinsic impurity. The minimum value of ¤ ¦ ¥ § © , for which a thermonuclear burn is possible, is increased by 20% for a W concentration of " !

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Section: Implications On Operation Of a Fusion Reactormentioning

confidence: 99%

Calculation and experimental test of the cooling factor of tungsten

Pütterich¹,

Neu²,

Dux³

et al. 2010

Nucl. Fusion

218

196

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“…The transport of helium from the core to the pumping plenum is commonly characterized by two figures of merit : a) the ratio of helium particle residence time to the energy confinement time, τ * He /τ E [229], and b) the ratio of the helium fraction in the exhaust gas to the main plasma helium fraction or helium enrichment factor, η He,exh . The requirements for reliable ITER fusion performance as well as results showing values of τ * He /τ E within that needed for the reference ITER ELMy H-mode regime (τ * He /τ E < 5-10), are included in the ITER Physics Basis [18].…”

Section: Helium Exhaust and Noble Gas Impurity Enrichmentmentioning

confidence: 99%

Chapter 4: Power and particle control

Divertor¹,

Database²,

Editors³

1999

Nucl. Fusion

282

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Abstract.Progress, since the ITER Physics Basis publication, in understanding the processes that will determine the properties of the plasma edge and its interaction with material elements in ITER is described. Experimental areas where significant progress has taken place are : energy transport in the SOL in particular of the anomalous transport scaling, particle transport in the SOL that plays a major role in the interaction of diverted plasmas with the main chamber material elements, ELM energy deposition on material elements and the transport mechanism for the ELM energy from the main plasma to the plasma facing components, the physics of plasma detachment and neutral dynamics including the edge density profile structure and the control of plasma particle content and He removal, the erosion of low and high Z materials in fusion devices, their transport to the core plasma and their migration at the plasma edge including the formation of mixed materials, the processes determining the size and location of the retention of tritium in fusion devices and methods to remove it and the processes determining the efficiency of the various fuelling methods as well as their development towards the ITER requirements. This experimental progress has been accompanied by the development of modelling tools for the physical processes at the edge plasma and plasma-materials interaction and the further validation of these models by comparing their predictions with the new experimental results. Progress in the modelling development and validation has been mostly concentrated in the following areas : refinement of the predictions for ITER with plasma edge modelling codes by inclusion of detailed geometrical features of the divertor and the introduction of physical effects, which can play a 2 major role in determining the divertor parameters at the divertor for ITER conditions such as hydrogen radiation transport and neutral-neutral collisions, modelling of the ion orbits at the plasma edge, which can play a role in determining power deposition at the divertor target, models for plasma-materials and plasma dynamics interaction during ELMs and disruptions, models for the transport of impurities at the plasma edge to describe the core contamination by impurities and the migration of eroded materials at the edge plasma and its associated tritium retention and models for the turbulent processes that determine the anomalous transport of energy and particles across the SOL. The implications for the expected performance of the reference regimes in ITER, the operation of the ITER device and the lifetime of the plasma facing materials are discussed. Introduction.This chapter outlines the significant progress achieved since the ITER Physics Basis in understanding basic scrape-off layer (SOL) and divertor processes in a tokamak. The interaction of plasma with first-wall surfaces will have considerable impact on the performance of fusion plasmas, the lifetime of plasma facing components, and the retention of tritium in next step Burning Plasma E...

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“…In addition, pumping is essential for helium ash removal from a fusion reactor such as ITER [1,2]. Adequate exhaust of helium ash for ITER requires the following criteria to be satisfied [2]:…”

Section: Introductionmentioning

confidence: 99%

Effects of divertor geometry and chemical sputtering on impurity behaviour and plasma performance in JET

et al. 2000

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Abstract. The effects of increased geometrical closure on the behaviour of the recycling and intrinsic impurities are investigated in JET Mark I, Mark IIA and Mark IIGB pumped divertors. Increasing the divertor closure leads to a significant improvement in exhaust for both deuterium and recycling impurities. However, the impurity enrichment in the exhaust gases remains unchanged due to a simultaneous increase in deuterium and impurity compression in the divertor. A comparison is made for helium, neon and argon under different plasma conditions. In addition, the operation of the Mark II and Mark IIGB divertors has shown that Z eff is reduced with the improved divertor closure in the L mode discharges, although no obvious changes in the Z eff values have been observed in the ELMy H modes. The divertor target surface temperature has a strong influence on intrinsic carbon production. The carbon source in the Mark II and Mark IIGB divertors is significantly higher than that in the Mark I divertor, which is attributed to enhanced chemical sputtering at the increased divertor tile temperature of the Mark II and Mark IIGB divertors (related to the divertor cooling system), as opposed to the increased closure. The consequences of this elevated yield for plasmas under different operation conditions are discussed, and further evidence, obtained from a specific wall/divertor temperature reduction experiment, is presented. The effect of the divertor screening on the chemically produced impurities is investigated using the EDGE2D/NIMBUS/DIVIMP codes for the different recycling regimes and comparisons are made with experimental observations from the Mark I, Mark IIA and Mark IIAP divertors taking into account the change in chemical sputtering yield due to the different tile temperatures of these divertors.

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Burn condition, helium particle confinement and exhaust efficiency

Cited by 167 publications

References 17 publications

Calculation and experimental test of the cooling factor of tungsten

Calculation and experimental test of the cooling factor of tungsten

Chapter 4: Power and particle control

Effects of divertor geometry and chemical sputtering on impurity behaviour and plasma performance in JET

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