First-Principles Density Limit Scaling in Tokamaks Based on Edge Turbulent Transport and Implications for ITER.

A first-principles scaling law, based on turbulent transport considerations, and a multimachine database of density limit discharges from the ASDEX Upgrade, JET, and TCV tokamaks, show that the increase of the boundary turbulent transport with the plasma collisionality sets the maximum density achievable in tokamaks. This scaling law shows a strong dependence on the heating power, therefore predicting for ITER a significantly larger safety margin than the Greenwald empirical scaling [Greenwald et al., Nucl.

RNA Sequencing of Seedlings after Non-Thermal Plasma-Seed Treatment Reveals Upregulation in Plant Stress and Defense Pathways.

Not all agricultural practices are sustainable; however, non-thermal plasma treatment of seeds may be an eco-friendly alternative to improve macroscopic plant growth parameters. Despite the numerous successful results of plasma-seed treatments reported in the literature, there is a large gap in our understanding of how non-thermal plasma treatments affect seeds, especially due to the plethora of physical, chemical, and biological variables. This study uses RNA sequencing to characterize the changes in gene transcription in (L.

Magnetic control of tokamak plasmas through deep reinforcement learning.

Nuclear fusion using magnetic confinement, in particular in the tokamak configuration, is a promising path towards sustainable energy. A core challenge is to shape and maintain a high-temperature plasma within the tokamak vessel. This requires high-dimensional, high-frequency, closed-loop control using magnetic actuator coils, further complicated by the diverse requirements across a wide range of plasma configurations.

Application of Copper Thermal Spraying for Electrical Joints between Superconducting NbSn Cables.

This manuscript reports on the application of copper thermal spraying in the manufacturing process of an electrical connection between NbSn cables for superconducting magnets of fusion reactors. The joint is realized through diffusion bonding of the sprayed coating of the two cables. The main requirement for such a connection is its electrical resistance, which must be below 1 nΩ at B = 8 T, I = 63.

An In Situ FTIR Study of DBD Plasma Parameters for Accelerated Germination of Seeds.

Current agricultural practices are not sustainable; however, the non-thermal plasma treatment of seeds may be an eco-friendly alternative to alter macroscopic plant growth parameters. Despite numerous successful results of plasma-seed treatments reported in the literature, the plasma-treatment parameters required to improve plant growth remain elusive due to the plethora of physical, chemical, and biological variables. In this study, we investigate the optimal conditions in our surface dielectric barrier discharge (SDBD) setup, using a parametric study, and attempt to understand relevant species in the plasma treatment using in situ Fourier transform infrared (FTIR) absorption spectroscopy.

Graphene Confers Ultralow Friction on Nanogear Cogs.

Friction-induced energy dissipation impedes the performance of nanomechanical devices. Nevertheless, the application of graphene is known to modulate frictional dissipation by inducing local strain. This work reports on the nanomechanics of graphene conformed on different textured silicon surfaces that mimic the cogs of a nanoscale gear.

Low-energy electron beam has severe impact on seedling development compared to cold atmospheric pressure plasma.

Sprouts are germinated seeds that are often consumed due to their high nutritional content and health benefits. However, the conditions for germination strongly support the proliferation of present bacteria, including foodborne pathogens. Since sprouts are consumed raw or minimally processed, they are frequently linked to cases of food poisoning.

Development of an 11-channel multi wavelength imaging diagnostic for divertor plasmas in MAST Upgrade.

Divertor detachment and alternative divertor magnetic geometries are predicted to be promising approaches to handle the power exhaust of future fusion devices. In order to understand the detachment process caused by volumetric losses in alternative divertor magnetic geometries, a Multi-Wavelength Imaging (MWI) diagnostic has recently been designed and built for the Mega Amp Spherical Tokamak Upgrade. The MWI diagnostic will simultaneously capture 11 spectrally filtered images of the visible light emitted from divertor plasmas and provide crucial knowledge for the interpretation of observations and modeling efforts.

A fast-reciprocating probe array for two-dimensional measurements in the divertor region of the Tokamak à configuration variable.

A detailed description of the construction and commissioning of the fast-moving reciprocating divertor Langmuir probe array on the Tokamak à Configuration Variable (TCV) is presented. A horizontal array of 24 Langmuir probes (12 Mach probes) combined with a fast vertical movement provides unprecedented two-dimensional measurements of the plasma properties across the entire divertor outer leg volume and up to the X-point. The L-shape probe arm has to be very compact to minimize plasma perturbations and, at the same time, has to house 24 coaxial transmission lines, withstand time-averaged heat fluxes of up to ≈30 MW/m and accelerations of up to 8 g, and be resilient to violent plasma disruptions.

Determining 1D fast-ion velocity distribution functions from ion cyclotron emission data using deep neural networks.

The relationship between simulated ion cyclotron emission (ICE) signals s and the corresponding 1D velocity distribution function fv of the fast ions triggering the ICE is modeled using a two-layer deep neural network. The network architecture (number of layers and number of computational nodes in each layer) and hyperparameters (learning rate and number of learning iterations) are fine-tuned using a bottom-up approach based on cross-validation. Thus, the optimal mapping gs;θ of the neural network in terms of the number of nodes, the number of layers, and the values of the hyperparameters, where θ is the learned model parameters, is determined by comparing many different configurations of the network on the same training and test set and choosing the best one based on its average test error.

Development and first operation of a cavity ring down spectroscopy diagnostic in the negative ion source SPIDER.

The neutral beam injectors of the ITER experiment will rely on negative ion sources to produce 16.7 MW beams of H/D particles accelerated at 1 MeV. The prototype of these sources was built and is currently operated in the SPIDER (Source for the Production of Ions of Deuterium Extracted from a Radio frequency plasma) experiment, part of the Neutral Beam Test Facility of Consorzio RFX, Padua.

Transition between Instability and Seeded Self-Modulation of a Relativistic Particle Bunch in Plasma.

We use a relativistic ionization front to provide various initial transverse wakefield amplitudes for the self-modulation of a long proton bunch in plasma. We show experimentally that, with sufficient initial amplitude [≥(4.1±0.

Methods to determine the radiated power in SPI-mitigated disruptions in JET.

This paper presents techniques for evaluating the radiated power in JET disruptions. Disrupting plasmas are shown to have non-axisymmetric radiation profiles, motivating the re-evaluation of the standard techniques for calculating the total radiated power at JET using bolometry. Four single-channel bolometers at different toroidal locations are exploited to quantify the radiation asymmetry.

Real-time feedback control of the impurity emission front in tokamak divertor plasmas.

In magnetic confinement thermonuclear fusion the exhaust of heat and particles from the core remains a major challenge. Heat and particles leaving the core are transported via open magnetic field lines to a region of the reactor wall, called the divertor. Unabated, the heat and particle fluxes may become intolerable and damage the divertor.

Proton Bunch Self-Modulation in Plasma with Density Gradient.

We study experimentally the effect of linear plasma density gradients on the self-modulation of a 400 GeV proton bunch. Results show that a positive or negative gradient increases or decreases the number of microbunches and the relative charge per microbunch observed after 10 m of plasma. The measured modulation frequency also increases or decreases.

Persistent random walks of charged particles across magnetic field lines.

We investigate the time evolution of the mean location and variance of a charged particle subject to random collisions that are Poisson distributed. The particle moves on a plane and is subject to a magnetic field applied perpendicular to the plane, so it is constrained to move in circles in the absence of collisions. We develop a procedure that yields analytic expressions of the mean and variance.

Fibronectin/thermo-responsive polymer scaffold as a dynamic ex vivo niche for mesenchymal stem cells.

In this paper, we created a dynamic adhesive environment (DAE) for adipose tissue-derived mesenchymal stem cells (ADMSCs) cultured on smart thermo-responsive substrates, i.e., poly (N-isopropyl acrylamide) (PNIPAM), via introducing periodic changes in the culture temperature.

Manufacturing, installation, commissioning, and first results with the 3D low-temperature co-fired ceramic high-frequency magnetic sensors on the Tokamak à Configuration Variable.

Innovative high-frequency magnetic sensors have been designed and manufactured in-house for installation on the Tokamak à Configuration Variable (TCV), which are now routinely operational during the TCV experimental campaigns. These sensors combine the Low Temperature Co-fired Ceramic (LTCC) and the classical thick-film technologies and are in various aspects similar to the majority of the in-vessel inductive magnetic sensors foreseen for ITER (around 450 out of the 505 currently being procured are of the LTCC-1D type). The TCV LTCC-3D magnetic sensors provide measurements in the frequency range up to 1 MHz of the perturbations to the wall-aligned toroidal (δB), vertical (δB), and radial (δB) magnetic field components.

Establishing multiple osteogenic differentiation pathways of mesenchymal stem cells through different scaffold configurations.

Mimicking the complex organization of the extracellular matrix (ECM), especially its structure and dimensionality, is necessary to produce living tissues from stem cells. In compliance with a previously established role of nanofiber organization for the osteogenic differentiation of stem cells, here we used hybrid fibrinogen/poly(l-lactide-ε-caprolactone) (FBG/PLCL) nanofibers arranged in aligned and honeycomb configurations, to recapitulate the highly oriented ECM of the cortical bone and the sponge-like (i.e.

Cathodoluminescent screen imaging system for seeded blob detection in toroidal plasma experiment.

We designed and built a diagnostic based on a cathodoluminescent screen for the detection of turbulent plasma structures with high spatial resolution. The screen is coated with a low threshold energy cathodoluminescent powder that emits light when exposed to a plasma. The emitted light is imaged with a fast frame camera combined with an image intensifier and an optical bandpass filter.

Identification of an Optimized Heating and Fast Ion Generation Scheme for the Wendelstein 7-X Stellarator.

A Doppler shifted resonance minority species ion cyclotron range of frequency (ICRF) scheme for heating neutral beam ions has been identified and optimized for the Wendelstein 7-X stellarator. Compared with more conventional methods, the synergetic scheme increases the normalized core collisional power transfer to the background plasma, and induces larger concentrations of energetic ions. Simulations in the intricate 3D magnetic stellarator geometry reveal an energetic distribution function that is only weakly anisotropic, and is thus relevant to fast ion and alpha particle driven Alfvén eigenmode experimental preparation.

Update of ion-optical system of neutral beam of Tokamak à Configuration Variable.

An injector of fast deuterium atoms for plasma heating was designed and installed at the Tokamak à Configuration Variable (TCV). The neutral beam can deliver 1 MW power to the plasma in 2 s pulses. An ion beam of the injector is formed by a triode multislit ion-optical system with spherical electrodes which provide ballistic focusing.

MANTIS: A real-time quantitative multispectral imaging system for fusion plasmas.

This work presents a novel, real-time capable, 10-channel Multispectral Advanced Narrowband Tokamak Imaging System installed on the TCV tokamak, MANTIS. Software and hardware requirements are presented together with the complete system architecture. The image quality of the system is assessed with emphasis on effects resulting from the narrowband interference filters.