Modelling of 3D fields due to ferritic inserts and test blanket modules in toroidal geometry at ITER

Computations in toroidal geometry are systematically performed for the plasma response to 3D magnetic perturbations produced by ferritic inserts (FIs) and test blanket modules (TBMs) for four ITER plasma scenarios: the 15 MA baseline, the 12.5 MA hybrid, the 9 MA steady state, and the 7.5 MA half-field helium plasma. Due to the broad toroidal spectrum of the FI and TBM fields, the plasma response for all the n = 1-6 field components are computed and compared. The plasma response is found to be weak for the high-n (n > 4) components. The response is not globally sensitive to the toroidal plasma flow speed, as long as the latter is not reduced by an order of magnitude. This is essentially due to the strong screening effect occurring at a finite flow, as predicted for ITER plasmas. The ITER error field correction coils (EFCC) are used to compensate the n = 1 field errors produced by FIs and TBMs for the baseline scenario for the purpose of avoiding mode locking. It is found that the middle row of the EFCC, with a suitable toroidal phase for the coil current, can provide the best correction of these field errors, according to various optimisation criteria. On the other hand, even without correction, it is predicted that these n = 1 field errors will not cause substantial flow damping for the 15 MA baseline scenario

Mental health by gender-specific occupational groups : Profiles, risks and dominance of predictors

Background: We defined gender-specific profiles of mental ill-health for the main occupational groups using three outcomes; antidepressant use, sickness absence (SA) due to depression, and suicides. We also examined which occupational groups had the highest risk of the outcomes, and compared the importance of their predictors. Methods: From a random register cohort of Finnish working age population, individuals in the six largest occupational groups in 2004 for men and women were included (N = 414 357). We used register data to define the first antidepressant purchase (i.e. use), the first long-term SA spell for depression, and suicide between Jan 1st 2005 and Dec 31st 2014. We assessed the risk of each outcome by occupational group with logistic regression models, and used dominance analysis to compare the relative importance of predictors. Results: In all six occupational groups for women, the prevalence of antidepressant use and SA for depression was higher than in the men's occupational groups. The opposite was observed for suicides. The risk of antidepressant use was lower, but the risk of suicide was 2-times higher among men in low vs. high-skilled occupations. Among women, a lower skill-level was associated with a higher risk of SA due to depression. Gender was the most important predictor of all outcomes. Limitations: We lacked information on history of medication use or health problems prior to follow-up. Conclusions: Gendered occupational status was an underlying factor explaining distinctive mental health profiles in the working population. Occupational class-dependent behavioural patterns related to mental health existed among men.Peer reviewe

Modelling of the effect of ELMs on fuel retention at the bulk W divertor of JET

Effect of ELMs on fuel retention at the bulk W target of JET ITER-Like Wall was studied with multi-scale calculations. Plasma input parameters were taken from ELMy H-mode plasma experiment. The energetic intra-ELM fuel particles get implanted and create near-surface defects up to depths of few tens of nm, which act as the main fuel trapping sites during ELMs. Clustering of implantation-induced vacancies were found to take place. The incoming flux of inter-ELM plasma particles increases the different filling levels of trapped fuel in defects. The temperature increase of the W target during the pulse increases the fuel detrapping rate. The inter-ELM fuel particle flux refills the partially emptied trapping sites and fills new sites. This leads to a competing effect on the retention and release rates of the implanted particles. At high temperatures the main retention appeared in larger vacancy clusters due to increased clustering rate

ASCOT orbit-following simulations of ion cyclotron heating with synthetic fast ion loss diagnostic: a first application to ASDEX Upgrade

The orbit-following Monte Carlo code ASCOT interfaced with the radiofrequency Monte Carlo library RFOF can simulate radiofrequency heating of ion populations using wave solutions from full-wave solvers such as TORIC. It is applied to the fundamental mode ion cyclotron resonant heating of hydrogen and 2nd harmonic frequency heating of neutral beam injected deuterium in ASDEX Upgrade discharge #33147 to validate the model against fast ion loss detector (FILD) measurements. In addition, for FILD signal simulations requiring enhanced resolution or scanning the effect of various perturbations such as magnetohydrodynamic phenomena near the plasma edge, a two-stage simulation scheme is presented where the fast ion population is first created by a full ASCOT-RFOF ion cyclotron heating simulation, and the resulting distribution is then used as an input to ASCOT's distribution-sampling marker source module for more efficient simulation of the ICRH ion wall load and FILD signal. A satisfactory agreement with the experimentally observed FILD signal is found.</p

Effect of plasma response on the fast ion losses due to ELM control coils in ITER

Mitigating edge localized modes (ELMs) with resonant magnetic perturbations (RMPs) can increase energetic particle losses and resulting wall loads, which have previously been studied in the vacuum approximation. This paper presents recent results of fusion alpha and NBI ion losses in the ITER baseline scenario modelled with the Monte Carlo orbit following code ASCOT in a realistic magnetic field including the effect of the plasma response. The response was found to reduce alpha particle losses but increase NBI losses, with up to 4.2% of the injected power being lost. Additionally, some of the load in the divertor was found to be shifted away from the target plates toward the divertor dome

Conceptual design of the DEMO neutral beam injectors: Main developments and R&D achievements

The objectives of the nuclear fusion power plant DEMO, to be built after the ITER experimental reactor, are usually understood to lie somewhere between those of ITER and a 'first of a kind' commercial plant. Hence, in DEMO the issues related to efficiency and RAMI (reliability, availability, maintainability and inspectability) are among the most important drivers for the design, as the cost of the electricity produced by this power plant will strongly depend on these aspects. In the framework of the EUROfusion Work Package Heating and Current Drive within the Power Plant Physics and Development activities, a conceptual design of the neutral beam injector (NBI) for the DEMO fusion reactor has been developed by Consorzio RFX in collaboration with other European research institutes. In order to improve efficiency and RAMI aspects, several innovative solutions have been introduced in comparison to the ITER NBI, mainly regarding the beam source, neutralizer and vacuum pumping systems

Dynamic modelling of local fuel inventory and desorption in the whole tokamak vacuum vessel for auto-consistent plasma-wall interaction simulations

An extension of the SolEdge2D-EIRENE code package, named D-WEE, has been developed to add the dynamics of thermal desorption of hydrogen isotopes from the surface of plasma facing materials. To achieve this purpose, D-WEE models hydrogen isotopes implantation, transport and retention in those materials. Before launching autoconsistent simulation (with feedback of D-WEE on SolEdge2D-EIRENE), D-WEE has to be initialised to ensure a realistic wall behaviour in terms of dynamics (pumping or fuelling areas) and fuel content. A methodology based on modelling is introduced to perform such initialisation. A synthetic plasma pulse is built from consecutive SolEdge2D-EIRENE simulations. This synthetic pulse is used as a plasma background for the D-WEE module. A sequence of plasma pulses is simulated with D-WEE to model a tokamak operation. This simulation enables to extract at a desired time during a pulse the local fuel inventory and the local desorption flux density which could be used as initial condition for coupled plasma-wall simulations. To assess the relevance of the dynamic retention behaviour obtained in the simulation, a confrontation to post-pulse experimental pressure measurement is performed. Such confrontation reveals a qualitative agreement between the temporal pressure drop obtained in the simulation and the one observed experimentally. The simulated dynamic retention during the consecutive pulses is also studied.Peer reviewe