Performance assessment of a tightly baffled, long-legged divertor configuration in TCV with SOLPS-ITER

Numerical simulations explore the possibility to test the tightly baffled, long-legged divertor (TBLLD) concept in a future upgrade of the Tokamak \`a configuration variable (TCV). The SOLPS-ITER code package is used to compare the exhaust performance of several TBLLD configurations with existing unbaffled and baffled TCV configurations. The TBLLDs feature a range of radial gaps between the separatrix and the outer leg side walls. All considered TBLLDs are predicted to lead to a denser and colder plasma in front of the targets and improve the power handling by factors of 2-3 compared to the present, baffled divertor and by up to a factor of 12 compared to the original, unbaffled configuration. The improved TBLLD performance is mainly due to a better neutral confinement with improved plasma-neutral interactions in the divertor region. Both power handling capability and neutral confinement increases when reducing the radial gap. The core compatibility of TBLLDs with nitrogen seeding is also evaluated and the detachment window with acceptable core pollution for the proposed TBLLDs is explored, showing a reduction of required upstream impurity concentration up to 18% to achieve the detachment with thinner radial gap

Validation of SOLPS-ITER Simulations against the TCV-X21 Reference Case

This paper presents a quantitative validation of SOLPS-ITER simulations against the TCV-X21 reference case and provides insights into the neutral dynamics and ionization source distribution in this scenario. TCV-X21 is a well-diagnosed diverted L-mode sheath-limited plasma scenario in both toroidal field directions, designed specifically for the validation of turbulence codes [D.S. Oliveira, T. Body, et al 2022 Nucl. Fusion 62 096001]. Despite the optimization to reduce the impact of the neutral dynamics, the absence of neutrals in previous turbulence simulations of TCV-X21 was identified as a possible explanation for the disagreements with the experimental data in the divertor region. This motivates the present study with SOLPS-ITER that includes kinetic neutral dynamics via EIRENE. Five new observables are added to the extensive, publicly available TCV-X21 dataset. These are three deuterium Balmer lines in the divertor and neutral pressure in the common and private flux regions. The quantitative agreement metric is combined with the conjugate gradient method to approach the SOLPS-ITER input parameters that return the best overall agreement with the experiment. A proof-of-principle of this method results in a modest improvement in the level-of-agreement; shortcomings of the method and how to improve it are discussed. Alternatively, a scan of the particle and heat diffusion coefficients shows an improvement of 10.4% beyond the agreement level achieved by the gradient method. The result is found for an increased transport coefficient compared to what is usually used for TCV L-mode plasmas, suggesting the need for accurate self-consistent turbulence models for predictive boundary simulations. The simulations indicate that ~65% of the total ionization occurs in the SOL, motivating the inclusion of neutrals in future turbulence simulations towards improved agreement with the experiment

First Ex-Vivo Validation of a Radioguided Surgery Technique with beta- Radiation

Purpose: A radio-guided surgery technique with beta- -emitting radio-tracers was suggested to overcome the effect of the large penetration of gamma radiation. The feasibility studies in the case of brain tumors and abdominal neuro-endocrine tumors were based on simulations starting from PET images with several underlying assumptions. This paper reports, as proof-of-principle of this technique, an ex-vivo test on a meningioma patient. This test allowed to validate the whole chain, from the evaluation of the SUV of the tumor, to the assumptions on the bio-distribution and the signal detection. Methods: A patient affected by meningioma was administered 300 MBq of 90Y-DOTATOC. Several samples extracted from the meningioma and the nearby Dura Mater were analyzed with a beta- probe designed specifically for this radio-guided surgery technique. The observed signals were compared both with the evaluation from the histology and with the Monte Carlo simulation. Results: we obtained a large signal on the bulk tumor (105 cps) and a significant signal on residuals of $\sim$0.2 ml (28 cps). We also show that simulations predict correctly the observed yields and this allows us to estimate that the healthy tissues would return negligible signals (~1 cps). This test also demonstrated that the exposure of the medical staff is negligible and that among the biological wastes only urine has a significant activity. Conclusions: This proof-of-principle test on a patient assessed that the technique is feasible with negligible background to medical personnel and confirmed that the expectations obtained with Monte Carlo simulations starting from diagnostic PET images are correct.Comment: 17 pages, 4 Figs, Accepted by Physica Medic

SOLPS-ITER validation with TCV L-mode discharges editors-pick

This work presents a quantitative test of SOLPS-ITER simulations against tokamak a configuration variable (TCV) L-mode experiments. These simulations account for drifts, currents, kinetic neutrals, and carbon impurities providing the most complete edge transport simulations for TCV to date. The comparison is performed on nominally identical discharges carried out to assess the effectiveness of TCV's divertor baffles in the framework of the European Plasma Exhaust program and employs numerous edge diagnostics providing a detailed code-experiment benchmark for TCV. The simulations show a qualitative consistency, but the quantitative differences remain, which are assessed herein. It is found that, for a given separatrix density, the simulations most notably yield a colder, and denser, divertor state with a higher divertor neutral pressure than measured

Reduction in benefits of total flux expansion on divertor detachment due to parallel flows

The Super-X divertor (SXD) is an alternative divertor configuration leveraging total flux expansion at the outer strike point (OSP). Key features for the attractiveness of the SXD are facilitated detachment access and control, as predicted by the extended 2-point model (2PM). However, parallel flows are not consistently included in the 2PM. In this work, the 2PM is refined to overcome this limitation: the role of total flux expansion on the pressure balance is made explicit, by including the effect of parallel flows. In consequence, the effect of total flux expansion on detachment access and control is weakened, compared to predictions of the 2PM. This new model partially explains discrepancies between the 2PM and experiments performed on TCV, in ohmic L-mode scenarios, where in core density ramps in lower single-null (SN) configuration, the impact of the OSP major radius Rt on the CIII emission front movement in the divertor outer leg - used as a proxy for the plasma temperature - is substantially weaker than 2PM predictions; and in OSP sweeps in lower and upper SN configurations, with a constant core density, the peak parallel particle flux density at the OSP is almost independent of Rt, while the 2PM predicts a linear dependence. Finally, analytical and numerical modelling of parallel flows in the divertor is presented, to support the argument. It is shown that an increase in total flux expansion can favour supersonic flows at the OSP. Parallel flows are also shown to be relevant by analysing SOLPS-ITER simulations of TCV

A Web-based spatial decision supporting system for land management and soil conservation

Abstract. Today it is evident that there are many contrasting demands on our landscape (e.g. food security, more sustainable agriculture, higher income in rural areas, etc.) as well as many land degradation problems. It has been proved that providing operational answers to these demands and problems is extremely difficult. Here we aim to demonstrate that a spatial decision support system based on geospatial cyberinfrastructure (GCI) can address all of the above, so producing a smart system for supporting decision making for agriculture, forestry, and urban planning with respect to the landscape. In this paper, we discuss methods and results of a special kind of GCI architecture, one that is highly focused on land management and soil conservation. The system allows us to obtain dynamic, multidisciplinary, multiscale, and multifunctional answers to agriculture, forestry, and urban planning issues through the Web. The system has been applied to and tested in an area of about 20 000 ha in the south of Italy, within the framework of a European LIFE+ project (SOILCONSWEB). The paper reports – as a case study – results from two different applications dealing with agriculture (olive growth tool) and environmental protection (soil capability to protect groundwater). Developed with the help of end users, the system is starting to be adopted by local communities. The system indirectly explores a change of paradigm for soil and landscape scientists. Indeed, the potential benefit is shown of overcoming current disciplinary fragmentation over landscape issues by offering – through a smart Web-based system – truly integrated geospatial knowledge that may be directly and freely used by any end user (www.landconsultingweb.eu). This may help bridge the last very important divide between scientists working on the landscape and end users

Comparison of detachment in Ohmic plasmas with positive and negative triangularity

Detachment is investigated using core density ramps for lower single null Ohmic L-mode plasmas across a wide range of upper, lower, and total triangularity ($\delta$) in the TCV tokamak. It is universally found that detachment is more difficult to access with negative triangularity (NT) shaping. The outer divertor leg of discharges with $\delta\approx -0.3$ could not be cooled below 5 eV using core density ramps alone. The behavior of the upstream plasma and geometrical divertor effects (e.g. a reduced connection length at negative lower triangularity) do not fully explain the challenges of detaching NT plasmas. Langmuir probe measurements of the target heat flux widths ($\lambda_q$) remained constant within 30% across an upper triangularity scan, while the spreading factor $S$ was found to be lower by up to 50% in NT, indicating a generally lower integral SOL width. An interesting pattern has been observed in the particle balance where the line-averaged core density was typically higher in NT discharges for a given fuelling rate. Conversely, the divertor neutral pressure and integrated particle content were typically lower for the same line-averaged density. This indicates that NT plasmas may be closer to the sheath-limited regime than their PT counterparts, which could explain why NT is more challenging to detach