The deuterium inventory in ASDEX Upgrade

Mayer, M.; Rohde, V.; Ramos, Gustavo; Vainonen-Ahlgren, E.; Likonen, J.; Herrmann, A.; Neu, R.

doi:10.1088/0029-5515/47/11/024

Cited by 25 publications

(24 citation statements)

References 34 publications

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“…In the deposits on the inner divertor the D/C ratio was about 0.2 and the overall D retention estimated from these data is about 4% (34 g) of the total amount injected [12]. In AUG the long-term D retention for different campaigns obtained with surface analysis is about 3-4% of the D input [13]. The long-term D retention fraction evaluated from integrated gas balance ($10-20%) for various devices is larger than the D retention deduced from the post-mortem analysis of tiles [12].…”

Section: Discussionmentioning

confidence: 81%

Post-mortem measurements of fuel retention at JET with MKII-SRP divertor

Likonen

Coad

Hole

et al. 2009

Journal of Nuclear Materials

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Section: Discussionmentioning

confidence: 81%

Post-mortem measurements of fuel retention at JET with MKII-SRP divertor

Likonen

Coad

Hole

et al. 2009

Journal of Nuclear Materials

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“…Post-campaign analysis of C and B layers on PFC surfaces as well as D retention measurements allowed the characterisation of fuel retention over the C ¢ W PFC transition [4] [5]. Figure 1 shows a large reduction of C deposition in the inner divertor after W coating of the outer limiters, identifying these limiters as a dominant C source.…”

Section: Campaign Integrated Deposited Layers and Fuel Retentionmentioning

confidence: 99%

Non-boronized compared with boronized operation of ASDEX Upgrade with full-tungsten plasma facing components

Kallenbach¹,

Dux²,

Mayer³

et al. 2009

Nucl. Fusion

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112

114

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Abstract. After completion of the tungsten coating of all plasma facing components, ASDEX Upgrade has been operated without boronization for 1 1/2 experimental campaigns. This has allowed the study of fuel retention under conditions of relatively low D co-deposition with low-Z impurities as well as the operational space of a full-tungsten device for the unfavourable condition of a relatively high intrinsic impurity level. Restrictions in operation were caused by central accumulation of tungsten in combination with density peaking, resulting in H-L backtransitions induced by too low separatrix power flux. Most important control parameters have been found to be the central heating power, as delivered predominantly by ECRH, and the ELM frequency, most easily controlled by gas puffing. Generally, ELMs exhibit a positive impact, with the effect of impurity flushing out of the pedestal region overbalancing the ELM induced W source. The restrictions of plasma operation in the unboronized W machine occured predominantly under low or medium power conditions. Under medium-high power conditions, stable operation with virtually no difference between boronized and unboronized discharges was achieved. Due to the reduced intrinsic radiation with boronization and the limited power handling capability of VPS coated divertor tiles ( 10 MW/m 2 ), boronized operation at high heating powers was possible only with radiative cooling. To enable this, a previously developed feedback system using (thermo-)electric current measurements as approximate sensor for the divertor power flux was introduced into the standard AUG operation. To avoid the problems with reduced ELM frequency due to core plasma radiation, nitrogen was selected as radiating species since its radiative characteristic peaks at lower electron temperatures in comparison to Ne and Ar, favouring SOL and divertor radiative losses. Nitrogen seeding resulted not only in the desired divertor power load reduction, but also in improved energy confinement, as well as in smaller ELMs.

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“…Assuming both He and D are implanted into Mo at the same rate He is more likely to nucleate, forming a gas and distorting the lattice [50,16]. In order to ascertain whether the He discharges with no retention had reached an equilibrium, 5 discharges were run sequentially with approximately the same characteristics.…”

Section: Effect Of Boron Layersmentioning

confidence: 99%

Hydrogenic retention with high-Z plasma facing surfaces in Alcator C-Mod

et al. 2009

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Abstract. The retention of deuterium (D) fuel in the Alcator C-Mod tokamak is studied using a new 'static' gas balance method. C-Mod solely employs high-Z molybdenum (Mo) and tungsten (W) for its plasma-facing materials, with intermittent application of thin boron (B) films. The primarily Mo surfaces are found to retain large fractions, ~20-50%, of the D 2 gas fuelled per quiescent discharge, regardless if the Mo surfaces are cleaned of, or partially covered by, B films. Several experiments and calculations show that it is improbable that B is retaining significant fractions of the fuel. Rather, the retention is occurring in Mo and W surfaces through ion bombardment, implantation and diffusion to trap sites. Roughly 1% D of incident ion fluence, D , to surfaces is retained, and with no indication of the retention rate decreasing after 25 s of integrated plasma exposure. The magnitude of retention is significantly larger than extrapolated from the results of laboratory studies for either Mo or W. The high levels of D/Mo in the near surface, measured directly post-campaign (~ .01) in tiles and inferred from gas balance, are consistent with trapping sites for fuel retention in the Mo being created, or expanded, by high D atom densities in the near surface which arise as a result of high incident ion fluxes. Differences between C-Mod and laboratory retention results may be due to such factors as the multiply-ionized B ions incident on the surface directly creating traps, the condition of the Mo (impurities, annealing), and the high flux densities in the C-Mod divertor which are similar to ITER, but 10-100x those used in laboratory studies. Disruptions produce rapid heating of the surfaces, releasing the trapped hydrogenic species into the vessel for recovery. The measurements of the large amount of gas released in disruptions are consistent with the analysis of tiles removed from the vessel post-campaign -the campaign-integrated retention is very low, of order 1000x less than observed in a single, non-disruptive discharge.

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The deuterium inventory in ASDEX Upgrade

Cited by 25 publications

References 34 publications

Post-mortem measurements of fuel retention at JET with MKII-SRP divertor

Post-mortem measurements of fuel retention at JET with MKII-SRP divertor

Non-boronized compared with boronized operation of ASDEX Upgrade with full-tungsten plasma facing components

Hydrogenic retention with high-Z plasma facing surfaces in Alcator C-Mod

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