Pedestal and Er profile evolution during an edge localized mode cycle at ASDEX Upgrade

The upgrade of the edge charge exchange recombination spectroscopy diagnostic at ASDEX Upgrade has enabled highly spatially resolved me asurements of the impurity ion dynamics during an edge-localized mode cycle ( ELM ) with unprecedented temp oral resolution, i.e. 65 μ s. The increase of transport during an ELM induces a relaxation of the ion, electron edge gradients in impurity density and fl ows. Detailed characterization of the recovery of the edge temperature gradients reveals a difference in the ion and electron channe l: the maximum ion temperature gradient T i is re-established on similar timescales as n e , which is faster than the recovery of T e .Afterthe clamping of the maximum gradient, T i and T e at the pedestal top continue to rise up to the next ELM while n e stays constant which means that the temperatur e pedestal and the resu lting pedestal pressure widen until the next ELM. The edge radial electric fi eld E r at the ELM crash is found to reduce to typical L-mode values and its ma ximum recovers to its pre-ELM conditions on a similar time scale as for n e and T i . Within the uncertainties, the measurements of E r align with their neoclassical predictions E r,neo for most of the ELM cycle, thus indicating that E r is dominated by collisional processes. However, between 2 and 4 ms af ter the ELM crash, other contributions to E B ́ fl ow, e.g. zonal fl ows or ion orbit effects, could not be excluded within the uncertainties.European Commission (EUROfusion 633053

Experimental conditions to suppress edge localised modes by magnetic perturbations in the ASDEX Upgrade tokamak

Access conditions for full suppression of Edge Localised Modes (ELMs) by Magnetic Perturbations (MP) in low density high confinement mode (H-mode) plasmas are studied in the ASDEX Upgrade tokamak. The main empirical requirements for full ELM suppression in our experiments are: 1. The poloidal spectrum of the MP must be aligned for best plasma response from weakly stable kink-modes, which amplify the perturbation, 2. The plasma edge density must be below a critical value, $3.3 \times 10^{19}$~m$^{-3}$. The edge collisionality is in the range $\nu^*_i = 0.15-0.42$ (ions) and $\nu^*_e = 0.15-0.25$ (electrons). However, our data does not show that the edge collisionality is the critical parameter that governs access to ELM suppression. 3. The pedestal pressure must be kept sufficiently low to avoid destabilisation of small ELMs. This requirement implies a systematic reduction of pedestal pressure of typically 30\% compared to unmitigated ELMy H-mode in otherwise similar plasmas. 4. The edge safety factor $q_{95}$ lies within a certain window. Within the range probed so far, $q_{95}=3.5-4.2$, one such window, $q_{95}=3.57-3.95$ has been identified. Within the range of plasma rotation encountered so far, no apparent threshold of plasma rotation for ELM suppression is found. This includes cases with large cross field electron flow in the entire pedestal region, for which two-fluid MHD models predict that the resistive plasma response to the applied MP is shielded

A novel two-stage kinetic model for surface DBD simulations in air

In this work, a novel 0D model for the evaluation of O-3 and NO2 produced by a surface dielectric barrier discharge (SDBD) in a closed environment is presented. The model is composed by two coupled sub-models, a discharge sub-model and an afterglow one. The first one, simulating the discharge regime and consequently including electron impact reactions, aims to calculate the production rates of a set of key species (atomic oxygen, excited states of molecular oxygen and molecular nitrogen). These latter are the input of the afterglow sub-model, that simulates the afterglow regime. We introduce a methodology to relate the production rates of the above mentioned species to the input power of the SDBD reactor. The simulation results are validated by a comparison with experimental data from absorption spectroscopy. The experimental measurements are carried out as follows. First, the discharge is turned on until the NO2 number density reaches steady state. Then, the discharge is turned off for several minutes. Finally, the discharge is turned on again to observe the effects of the NO2 concentration on ozone dynamics. The entire process is done without opening the box. The system operating in all the above-listed conditions is simulated for three different levels of input power

The role of radial electric field and neoclassical transport in the establishment and sustainment of the edge transport barrier in the ASDEX Upgrade tokamak

EUROfusion Consortium 63305

Dynamics of the pedestal transport during edge localized mode cycles at ASDEX Upgrade

The dynamic behaviour of the ion and electron energy, particle and momentum transport measured during type-I edge localized mode (ELM) cycles at ASDEX Upgrade is presented. Fast measurements of the ion and electron temperature profiles revelead that the ion and electron energy transport recover on different timescales, with the electrons recovering on a slower timescale (Cavedon et al 2017 Plasma Phys. Control. Fusion 59 105007). The dominant mechanism for the additional energy transport in the electron channel that could cause the delay in the electron temperature gradient (VTe) recovery is attributed to the depletion of energy caused by the ELM. The local sources and sinks for the electron channel in the steep gradient region are much smaller compared to the energy flux arriving from the pedestal top, indicating that the core plasma may dictate the local dynamics of the VTe recovery during the ELM cycle. A model for the edge momentum transport based on toroidal torque balance that takes into account the existence of poloidal impurity asymmetries has been developed. The analysis of the profile evolution during the ELM cycle shows that the model captures the dynamics of the rotation both before the ELM crash and during the recovery phase.European Commission (Euratom) Grant agreement No. 633053H2020 Marie-Sklodowska Curie programme (grant agreement No. 708257)European Union’s Horizon 2020 (grant agreement No. 805162

Qualification and implementation of line ratio spectroscopy on helium as plasma edge diagnostic at ASDEX Upgrade

A new thermal helium beam diagnostic has been implemented as plasma edge diagnostic at the ASDEX Upgrade (AUG) tokamak. The helium beam is built to measure the electron density ne and temperature Te simultaneously with high spatial and temporal resolution in order to investigate steady-state as well as fast transport processes in the plasma edge region. For the thermal helium beam emission line ratio spectroscopy, neutral helium is locally injected into the plasma by a piezo valve. This enabled the measurement of the line resolved emission intensities of seven He i lines for different plasma scenarios in AUG. The different line ratios can be used together with a collisional-radiative model (CRM) to reconstruct the underlying electron temperature and density. Ratios from the same spin species are used for the electron density reconstruction, whereas spin mixed ratios are sensitive to electron temperature changes. The different line ratios as well as different CRMs are tested for their suitability for diagnostic applications. Furthermore their consistency in calculating identical parameters is validated and the resulting profiles are compared to other available diagnostics at AUG.EUROfusion Consortium 633053US Department of Energy DE-SC00013911 and DE-SC001421

Detecting bubbles in exotic nuclei

The occurrence of a bubble, due to an inversion of s$_{1/2}$ state with the state usually located above, is investigated. Proton bubbles in neutron-rich Argon isotopes are optimal candidates. Pairing effects which can play against the bubble formation are evaluated. They cannot prevent bubble formation in very neutron-rich argon isotopes such as $^{68}$Ar. This pleads for a measurement of the charge density of neutron-rich argon isotopes in the forthcoming years, with the advent of electron scattering experiments in next generation exotic beam facilities such as FAIR or RIBF.Comment: 6 pages, 5 figures, to be published in Nucl. Phys.

Epidemiology of simultaneous medullary and papillary thyroid carcinomas (MTC/PTC): An Italian multicenter study

Background: The concomitant presence of papillary thyroid cancer (PTC) and medullary TC (MTC) is rare. In this multicentric study, we documented the epidemiological characteristics, disease conditions and clinical outcome of patients with simultaneous MTC/PTC. Methods: We collected data of patients with concomitant MTC/PTC at 14 Italian referral centers. Results: In total, 183 patients were enrolled. Diagnosis was mostly based on cytological examination (n = 58, 32%). At diagnosis, in the majority of cases, both PTC (n = 142, 78%) and MTC (n = 100, 54%) were at stage I. However, more cases of stage II\u2013IV were reported with MTC (stage IV: n = 27, 15%) compared with PTC (n = 9, 5%). Information on survival was available for 165 patients: 109 patients (66%) were disease-free for both PTC and MTC at the last follow-up. Six patients died from MTC. Median time to progression was 123 months (95% confidence interval (CI): 89.3\u2013156.7 months). Overall, 45% of patients were disease-free after >10 years from diagnosis (125 months); this figure was 72.5% for PTC and 51.1% for MTC. Conclusions: When MTC and PTC are concurrent, the priority should be given to the management of MTC since this entity appears associated with the most severe impact on prognosis