Heterostructures offer superior photocatalytic characteristics over their constituent counterparts due to their charge separation abilities. Here, we conduct a systematic study of a recently synthesized novel family of palladium-based pentagonal air-stable 2D monolayers, PdSe2, PdPSe, and PdPS, and their heterostructures using first-principles calculations for photocatalytic applications. Electronic band structure calculations reveal moderate bandgaps of 2.27 eV for PdSe2, 2.01 eV for PdPSe, and 2.25 eV for PdPS, indicating their suitability for photocatalytic water splitting. Moreover, to spatially separate and reduce the recombination possibility of photoinduced electron-hole pairs, we propose three van der Waals heterostructures: PdPSe/PdSe2, PdPS/PdSe2, PdPS/PdPS, with the corresponding bandgaps of 1.84 eV, 1.64 eV, and 1.65 eV, respectively. Based on work functions and the staggered band alignment of constituting monolayers, all three heterostructures are identified as type-II photocatalysts, which makes them notable photocatalyst. Additionally, band-edge potentials of PdPSe/PdSe2 and PdPS/PdSe2 confirm their suitability for overall water splitting via photocatalysis, whereas PdPS/PdPSe is suitable for oxygen evolution reactions only. The optical absorption spectra show the ability of each system to operate under a wide range of the spectrum, from visible light to high-energy (UV) regions. These characteristics make these systems valuable and attractive for photocatalytic applications.

The current worldwide energy and economical crisis has triggered the need for more sustainable technological solutions to implement energy-efficient next generation communication systems, which should also be commercially viable and cost-effective. Moreover, future terrestrial and satellite communications will bring a wide range of use cases, services, and environments with very different requirements and specifications to ful-fill in order to generate a smart digital, fully connected society. Designing new antennas for each single application is not feasible since it is very complex to meet the customer's demand in the short run, and antenna system solutions that are easily re-configurable to be re-used in diverse scenarios are needed. The combination of lenses with traditional phased array antennas (also known as dome antennas) is a promising way of mixing the advantages of both antenna technologies and optimizing the performance of our systems depending on the use case scenario. This article discusses the industrial and technical potential of using dome antennas implemented in different technologies for expected use cases and applications of future terrestrial and satellite communication systems.

In this article, we propose an innovative concept to realize flexible and cost-effective array antenna systems for next generation communication systems. The idea is to tailor the performance of an antenna array to different use case scenarios by applying a customized dielectric lens placed in front of the array. By combining a lens with an array, we can improve certain performance properties of the antenna system and adapt it for unique site locations and requirements. Moreover, the lens may also act as a radome, providing mechanical protection from environmental conditions. This study consists of exploring the possibilities of using a lens to increase the gain of the antenna in certain directions: scanning range close to broadside (from 0 degrees to 30 degrees), and extreme scanning ranges (from 60 degrees to 80 degrees).

This work deals with the effect of oil reclamation on the conduction mechanism and dielectric aspects of accelerated thermally aged transformer mineral oil. The reclamation is a treatment with Fuller's earth (FE) adsorbent to remove corrosive sulfur compounds and other contaminants formed during thermal aging. The properties of the oil are compared between different stages of the treatment. Corona (partial discharge) inception is identified by the optical fluorescent fiber technique. The results show an increased corona inception voltage after treatment. Dielectric response spectroscopy (DRS) showed a lower loss factor and electrical conductivity after treatment. The conduction mechanism is measured under uniform and nonuniform electric fields with variations in applied voltage magnitude. The conduction mechanism at a uniform electric field (low E) is studied using the polarity reversal technique to estimate the respective ionic motilities in the fluid. The apparent mobility of ions, conductivity, ionic radius, and concentration from the oil are found to reduce on reclamation. In addition, the conduction mechanism for a higher electric field is simulated by the current-voltage characteristic in nonuniform conditions and the slope determines the ionic mobility of the fluid.

Present work deals with accelerated electrical and thermal stress on transformer oil and its characteristic variation on Fuller's earth (FE) reclamation. The influence of carbon particles in the fluid, its role on thermal ageing characteristics can be understood by electrical characterization. Reclamation of insulation fluid extends the lifetime and reliability of the transformer over the year of operation. The average particle size of carbon particles on electrical breakdown are in the range of 644 nm. Dielectric response spectroscopy (DRS) which identifies the conductivity and relative permittivity variation with the effect multi-stress ageing. Conduction mechanism with higher electric field is simulated by current-voltage (IV) characteristics using non-uniform field configuration to derive the ionic mobility of the liquid. Dissolved decayed products and turbidity showed drastic enhancement with multi-stress ageing than the thermally aged specimen. Reclamation with fuller earth treatment removes the carbon traces and ageing by-products in the fluid regaining its relative dielectric performances. Rheological aspects with viscosity indicates the ageing by-products build and also its characteristic variation on the reclamation process.

In this paper, a lightweight spherical Luneburg lens with high performance is introduced for use in the frequency range 1 (FR1). The continuously varying refractive index profile of the lens is implemented using a quasi-isotropic partially metalized periodic structure. Much of the lens volume is made of foam, so the design is lightweight, making it applicable for low-band microwave frequency communication systems and, more specifically, 5G communications in FR1. The periodic structure allows a simple and low-cost layered construction with a quasi-isotropic response. This approach improves the scanning performance of the lens in all angular directions when compared to equivalent lens designs previously reported. Such a structure is an ideal candidate for high-gain multi-beam communication systems.

With the emergence of cyber-physical systems (CPSs) in utility systems like electricity, water, and gas networks, data collection has become more prevalent. While data collection in these systems has numerous advantages, it also raises concerns about privacy as it can potentially reveal sensitive information about users. To address this issue, we propose a Bayesian approach to control the adversarial inference and mitigate the physical-layer privacy problem in CPSs. Specifically, we develop a control strategy for the worst-case scenario where an adversary has perfect knowledge of the user’s control strategy. For finite state-space problems, we derive the fixed-point Bellman’s equation for an optimal stationary strategy and discuss a few practical approaches to solve it using optimization-based control design. Addressing the computational complexity, we propose a reinforcement learning approach based on the Actor-Critic architecture. To also support smart meter privacy research, we present a publicly accessible “Co-LivEn” dataset with comprehensive electrical measurements of appliances in a co-living household. Using this dataset, we benchmark the proposed reinforcement learning approach. The results demonstrate its effectiveness in reducing privacy leakage. Our work provides valuable insights and practical solutions for managing adversarial inference in cyber-physical systems, with a particular focus on enhancing privacy in smart meter applications.

The PION code has been integrated into the European Transport Solver (ETS) transport workflow, and we present the first application to model Ion Cyclotron Resonance Frequency (ICRF) heating scenarios in the next-step fusion reactor ITER. We present results of predictive, self-consistent and time-dependent simulations where the resonant ion concentration is varied to study its effects on the performance, with a special emphasis on the resulting bulk ion heating and thermal ion temperature. We focus on two ICRF heating schemes, i.e., fundamental H minority heating in a 4He plasma at 2.65 T/7.5 MA and a three-ion ICRF scheme consisting of fundamental 3He heating in a H-4He plasma at 3.3 T/ 8.8 MA. The H minority heating scenario is found to result in strong absorption by resonant H ions as compared to competing absorption mechanisms and dominant background electron heating for H concentrations up to 10%. The highest H absorption of ∼80% of the applied ICRF power and highest ion temperature of ∼15 keV are obtained with an H concentration of 10%. For the three-ion scheme in 85%:15% H:4He plasma, PION+ETS predicts 3He absorption in the range of 21–65% for 3He concentrations in the range of 0.01–0.20%, with the highest 3He absorption at a 3He concentration of 0.20%.

The energy system, including the electrical power system, is currently undergoing major changes to meet increased demands and climate target plans, and to stand against potential malicious activities and all sorts of disruptions. Specifically, the electrical power system is drastically changing with regards to consumption, production, transmission, control, monitoring, markets, and digitalization. Such a change, however, makes the power system an attractive and vulnerable target to all kinds of disruptive events and social-cyber-physical attacks since the system is crucial for the functioning of the society and economy. In this work, to act against such events and to study the future power system's susceptibility and resilience towards social-cyber-physical attacks, the Resilient Digital Sustainable Energy Transition (REDISET) project has shown the need for a new model that is able to describe the future electrical power system in a way that reflects the future reality. In this paper, existing power system models, the changing landscape of power systems, the drivers for a new model, the suggested model that comprises 7 building blocks instead of today's 3, and finally a direction of future related work are presented.

Experiments in various tokamaks and their analysis identify the fast ions (FI) generated by NBI and/or ICRF heating as one of the main causes of the observed improvement in core confinement: fast ions can reduce core microturbulence (mainly Ion-Temperature-Gradient (ITG) driven modes) either electrostatically or electromagnetically, or they can resonate with fishbones and high-frequency Alfvén modes, which in turn contribute in stabilizing ITG. In this perspective, we discuss recent experiments done on ASDEX Upgrade (AUG) where ICRF is the main actuator for FI generation for energies above 100 keV. Additionally, ICRF-FIs can substantially impact the MHD activity and its consequent effects on fast ion losses (FILs) and ion-cyclotron emission (ICE). We present dedicated AUG experiments with NBI-D further accelerated by ICRF.

This paper describes the first vertical electron cyclotron emission measurement of non-thermal electron distributions in the Tokamak & agrave; Configuration Variable. These measurements were conducted in runaway electron scenarios and in the presence of electron cyclotron current drive. Measured intensities of linearly polarized X- and O-mode radiation from fast electrons allow the analysis of the energy distribution. The measurements were made possible through the creation of an operational regime for the diagnostic that is free of thermal background radiation, in relaxed electron density operations. This operational regime notably enables the cross-calibration of the diagnostic system, relying on thermal plasma measurements and modeling with the ray-tracing code SPECE.

Efficient Electron Cyclotron Resonance Heating (ECRH) breakdown and pre-ionization can be achieved with fundamental X-mode, while higher harmonics can introduce excessive stray radiation. Fundamental heating however is characterized by a low cut-off density, introducing additional power absorption mechanisms in the plasma. A good knowledge of these mechanisms is necessary to use fundamental X-mode as an efficient pre-ionization method. Numerous experiments were performed on the TOroidally MAgnetized System (TOMAS) to study the power deposition for ECRH in helium. It is a facility designed to study plasma production, wall conditioning and plasma-surface interactions and is operated by LPP-ERM/KMS at the FZ-J & uuml;lich. The influence of the injected power P EC and the magnetic field B 0 on the absorption mechanisms is examined, in order to reduce stray radiation and improve the absorption efficiency. This will allow to determine the best scenarios for plasma start-up and pre-ionization.

To improve the plasma performance and control the density and plasma quality during the flat top phase, wall conditioning techniques are used in large fusion devices like W7-X and in JT60-SA. To study the performance of electron cyclotron wall conditioning, numerous experiments were performed on the TOroidally MAgnetized System, which is operated by LPP-ERM/KMS at the FZ-Jülich. It is a facility designed to study plasma production, wall conditioning, and plasma-surface interactions. The produced electron cyclotron resonance heating plasmas are characterized in various conditions by density and temperature measurements using a movable triple Langmuir probe in the horizontal and the vertical direction, complemented by video and spectroscopic data, to obtain a 2D extrapolation of the plasma parameters in the machine. A way to calibrate the triple Langmuir probe measurements is also investigated. These data can be used to determine the direction of the plasma drift in the vessel and identify the power absorption mechanisms. This will give more insight in the plasma behavior and improve the efficiency of wall conditioning and sample exposure experiments.

Electron Cyclotron Heating (ECH) at the fundamental resonance in X-mode is limited by a low cut-off density. Electromagnetic waves cannot propagate in the region between this cut-off and the Upper Hybrid Resonance (UHR) and cannot reach the Electron Cyclotron Resonance (ECR) position. Higher harmonic heating is hence preferred in nowadays ECH plasma heating scenarios to overcome this problem. However, if this evanescent region is small compared to the wavelength of the waves, additional power deposition mechanisms can occur to increase the plasma density. This includes collisional losses in the evanescent region, tunneling of the X-wave with resonant coupling at the ECR, and conversion to the Electron Bernstein Wave (EBW) with resonant coupling. Several ECH plasma production experiments were performed on the TOMAS device with simple toroidal magnetic field to identify these additional heating regimes and to study the influence of the heating power on the ECH plasma parameters and the power deposition. Density and temperature profiles were measured with Langmuir Probes. Measurements of the forwarded and reflected power allow to estimate the coupling efficiency. The results help to understand ECH plasma production for tokamak plasma breakdown assistance and Electron Cyclotron Wall Conditioning (ECWC).

During ion cyclotron resonance heating (ICRH) in fusion plasmas the fast magnetosonic wave transports wave energy to the plasma core, where it is transferred to both electrons, thermal ions and fast ions. The modelling of these processes requires a self-consistent treatment of the wave propagation and absorption, as well as the acceleration of fast ions by the wave. Here, a new self-consistent model is presented based on the FEMIC full wave solver [1] and the FOPPLER Fokker-Planck solver [2]. The use of optimised commercial wave solvers in FEMIC and a reduced 1D Fokker-Planck model make the model relatively fast and therefore suitable for e.g. the use in a transport solver.The novelty of this model, compared to other codes with 1D Fokker-Planck models, is the consistent description of Doppler physics in the FEMIC and FOPPLER codes. This description is of particular interest for scenarios with strong absorption around the ion-ion hybrid layer, like in 3-ion scenarios [3] and certain minority scenarios. Here we will present modelling of such scenarios, quantifying the impact of the Doppler shift, as well as characterising the non-linear effects associated with the acceleration of fast ions.

This work has been carried out within the framework of the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No 101052200 — EUROfusion). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Commission. Neither the European Union nor the European Commission can be held responsible for them.

References:[1] P. Vallejos et al., Nuclear Fusion 59, 076022 (2019)[2] L. Bähner et al., to be submitted (2024) [3] Y.O. Kazakov et al., Nuclear Fusion 55, 032001 (2015)

New generation of communication systems have the challenge of providing data in many diverse scenarios with very different hardware requirements. Here, we explore the potential advantages of combining array antennas with domes featuring lens functionality in some use cases. To reduce the computational cost of the lens design, we developed an efficient ray-tracing model. This model calculates radiation patterns while accounting for losses due to absorption and reflections. To demonstrate the potential of this approach, we present a lens designed to increase the gain from 60 degrees.

We propose the use of a generalized ray-tracing model to design geodesic lens array antennas. This model is capable of computing the radiation patterns and taking into account losses due to finite conductivity and surface roughness, which are essential when producing prototypes as single monolithic pieces. The ray-tracing model is used to design a modified Rinehart-Luneburg lens that shows very good agreement with simulations while significantly decreasing computation time. The profile of the lens is designed in such a way that it can be vertically stacked in an array and produced as a single piece. The lens array antenna is manufactured as a single monolithic piece using the laser powder-bed fusion technique. The tests of this prototype validate the use of additive manufacturing for geodesic lens antennas operating in V-band.

Fully metallic geodesic lens antennas are popular for millimeter-wave band applications due to their simplicity, robustness, and low loss. Here, we report the experimental results of a geodesic lens array antenna, which was specifically designed to be additive-manufactured in one single piece using laser powder-bed fusion (LPBF). LPBF in aluminum alloy AlSi10Mg is able to produce high conductivity and relatively low surface roughness, so the antenna is highly directive and efficient. In addition, LPBF increases the robustness of the design since the lens array is monolithic, i.e., the risks associated with the assembly, including misalignments and undesired air gaps between pieces, are totally eliminated.

Here, we propose a generalized ray-tracing (RT) model to accurately compute the radiation patterns and radiation efficiency of lossy non-rotationally symmetric geodesic lens antennas. The RT model uses geometrical optics to obtain the ray paths from the source to the aperture, ray tube theory to calculate the field amplitude distribution, and Kirchhoff's diffraction formula to compute the radiation pattern. Losses in geodesic lenses are mainly produced by the finite conductivity and roughness of the metallic plates. These losses are added to the calculation of the radiation pattern to estimate the radiation efficiency of the antenna. To demonstrate the accuracy of the proposed RT model, a geodesic half-Maxwell fish-eye lens is designed. Radiation patterns, scan losses, and radiation efficiency are calculated. These results agree well with those computed by full-wave simulations.

This article proposes a ray-tracing and physical-optics (RT-PO) model that allows for an accurate and time-efficient evaluation of planar Mikaelian lens antennas implemented by parallel plate waveguides (PPWs). With an intrinsic flat shape and axis-symmetry of refractive-index distribution characteristics, the planar Mikaelian lens antennas are easy to fabricate and integrate into standard planar feeds. A numerical computation of the ray paths based on Snell's law describes the phase of the electric field in the lens aperture, while the ray-tube power conservation theory is employed to evaluate the amplitude. The field equivalence principle is then used to calculate the far-field of the lens antenna. The information on far-field directivity, gain, and dielectric efficiency is further obtained, considering a small loss in the dielectric materials. Our approach is validated by comparing the results of a particular Mikaelian lens antenna with those computed using a commercial full-wave simulator, demonstrating high accuracy and a significant reduction in computation resources and times.

This paper proposes a combined ray-tracing and physical-optics model to analyze parallel-plate-waveguide lens antennas with a flat aperture. A family of rays is traced from the source to a set of target points on the lens radiating aperture, giving a description of the aperture electric field. On the basis of the physical-optics approximation, an equivalent magnetic current is then assumed and used to evaluate the far-field radiation characteristics in every direction. This numerical approach is validated by applying it to a particular planar Mikaelian lens antenna and comparing the results with those obtained using a commercial full-wave simulator.

In this contribution, we provide an experimental validation of a ray-tracing and physical-optics model for geodesic horn antennas. The proposed model employs a ray-tracing technique to obtain electric fields in the horn aperture and applies the field equivalence principle in physical optics to evaluate the three-dimensional radiation characteristics of the geodesic horn antennas. The numerical results agree well with the measurements in terms of radiation patterns in the uv-plane, the principal E- and H-plane patterns, and directivities.

This article describes a detailed procedure that allows for a time-efficient design of fully metallic geodesic H-plane horn antennas using an in-house ray-tracing method together with an optimization algorithm. With all the propagation in the air, geodesic H-plane horn antennas are of low loss and highly efficient. The proposed geodesic H-plane horn antennas provide a new degree of freedom, the height profile, to alleviate phase errors, realizing high gains and aperture efficiencies. Optimizations are implemented to design the height profile for a given target, enabled by the highly accurate and time-efficient in-house ray-tracing model. To demonstrate the correctness and versatility of the proposed design procedure, two prototypes are manufactured with computerized numerical control (CNC) machining and compared to their planar counterparts, with the aim of a high increased gain and aperture efficiency, respectively. The prototypes maintain good frequency stability from 26 to 33GHz, with sidelobe levels lower than -15dB and return loss better than 15dB. The first prototype improves the realized gain by over 5dB compared to the reference horn, while the second prototype achieves an aperture efficiency of around 65% within the operating frequency band.

We present a dual-polarized lens antenna for point-to-multipoint communications at sub-THz. The lens is constructed by a doubly-curved parallel plate following a geodesic lens shape equivalent to the Luneburg index profile. The polarization is changed by metallic screens patterned with complementary split resonant rings (CSRRs). These screens are integrated in the radiation aperture of the lens. Two lenses are stacked up, one for each polarization. Each lens is fed by 11 waveguide ports, providing beam steering or multiple beams. The antenna is fully metallic and hence, highly efficient. In the operating band from 115 GHz to 125 GHz, the simulation shows a realized gain of 20 dBi with a maximum scan loss of 0.6 dB up to 60 degrees, a cross-polarization discrimination around 20 dB, and an insertion loss smaller than 1.5 dB.

A double-layer lens consists of a pair of rotationally symmetric index profiles or geodesic lens shapes connected by a reflecting mirror partially covering their common periphery. Such a lens can provide a focus in each layer, and a wave travelling between the foci explores both layers. Here, we concentrate on the case with one layer being homogeneous or flat, and derive a general solution for the lens profiles by solving a Luneburg-like inverse problem with pre-specified foci inside or outside the lens, and different background indices in two layers. We demonstrate four examples of interest in ray-tracing plots. These lenses may find application in communications, sensing, and imaging from millimeter waves up to the optical bands.

Detecting and locating local degradations at an incipient stage is very important for mission-critical high-voltage rotating machines. One particular challenge in the existing testing techniques is that the characteristic of a local incipient defect is not prominent due to various factors such as averaging with the healthy remainder, attenuation in signal propagation, interference, and varied operating conditions. This paper proposes and investigates the frequency domain reflectometry (FDR) technique based on the scattering parameter measurement. The FDR result presents the object length, wave impedance, and reflections due to impedance discontinuity along the measured windings. Experiments were performed on two commercial coils with artificially created defects. These defects include turn-to-turn short, surface creepage, loose coils, insufficient end-winding spacing, and local overheating, which are commonly seen in practice. Two practical water pumps in the field were also selected for investigation. The study outcome shows that FDR can identify and locate structural and insulation degradation in both shielded and unshielded objects with good sensitivity. This makes FDR a complementary technique for machine fault diagnosis and aging assessment.

A novel differential laser-induced thermoelastic spectroscopy (D-LITES) was demonstrated. In D-LITES, one probe and one control laser beam with different modulation phases were combined to generate two quartz tuning fork (QTF) mechanical oscillations, which are π out of phase. The powers of the two lasers were adjusted to balance out the background noise. The differential signal was acquired by demodulating the QTF piezoelectric signal. The D-LITES sensor had a compact and cost-effective one-path configuration and was able to realize dual-gas detection. Carbon dioxide (CO2) and methane (CH4) were chosen as target gases to verify the D-LITES sensor performance. With the D-LITES technique, the background noise was greatly suppressed. The minimum detection limit (MDL) was improved by 9 times from 260 ppm to 29 ppm and 7.13 times from 0.385 ppm to 0.054 ppm for CO2 and CH4 detection, respectively.

A novel differential laser-induced thermoelastic spectroscopy (D-LITES) was demonstrated. In D-LITES, one probe and one control laser beam with different modulation phases were combined to generate two quartz tuning fork (QTF) mechanical oscillations, which are pi out of phase. The powers of the two lasers were adjusted to balance out the background noise. The differential signal was acquired by demodulating the QTF piezoelectric signal. The D-LITES sensor had a compact and cost-effective one-path configuration and was able to realize dualgas detection. Carbon dioxide (CO₂) and methane (CH₄) were chosen as target gases to verify the D-LITES sensor performance. With the D-LITES technique, the background noise was greatly suppressed. The minimum detection limit (MDL) was improved by 9 times from 260 ppm to 29 ppm and 7.13 times from 0.385 ppm to 0.054 ppm for CO₂ and CH₄ detection, respectively.

This presentation discusses a ray tracing model developed to determine the radiation pattern of geodesic lens antennas with non-rotationally symmetric footprints, where the geometry of the lens is defined using spline functions. The shape of this footprint and lens height profile can be modified by changing parameters in the defined functions. The code features a significant modification to work previously published by the authors to account for the non-rotationally symmetric design. The model runs significantly faster than commercially available software.

This paper discusses non-rotationally symmetric geodesic lens antennas. By defining the shape of the lens footprint, additional degrees of freedom are introduced into the design process, allowing for further tailoring of the electromagnetic performance of the lens while simultaneously reducing the volume occupied by the lens. An in-house ray-tracing model for geodesic lenses has been modified to analyze this class of lenses. Examples showing the effect of modifying the lens profile are presented, with a more detailed discussion on profile presenting improved side-lobe levels at the extreme ports. The examples presented operate at 30 GHz.

The study of discharge initiation by an Ion Cyclotron Range of Frequency (ICRF) antenna is of importance for operational scenarios at low magnetic field in e.g., ITER and Wendelstein 7-X. At low magnetic fields ohmic breakdown is difficult because of relatively short connection lengths and the electron cyclotron (EC) systems cannot assist because of a low-density cut-off. In that case ion cyclotron (IC) start-up, with waves in the Radio Frequency (RF) wavelength range, can be a good alternative solution. To explore in more detail the processes at play during the initial breakdown phase and to test measurement requirements, the diagnostic's capabilities of the TOMAS experimental device are being enlarged to allow for IC breakdown studies. A first set of IC breakdown experiments has been performed and data was taken by a newly installed spectrometer and a horizontal triple Langmuir probe. Limitations were found in pressure, ICRF power, and hydrogen concentration. Further diagnostic's upgrades and extensions of the experimental sessions will allow for a more complete study in support of modelling and experiments on other machines.

Graded dielectric media composites, with negative-index materials (MM), are of interest for various applications such as microwave graded-index (GRIN) lenses [ 1,2], wideband THz filtering [3], and enhanced energy harvesting [4]. Graded dielectric media with regular positive-index materials are also of importance in e.g. the field of biosensing. One example is mimicking of dielectric phantoms for the characterization of biological tissue's properties and response to electromagnetic radiation [5,6]. Our research is therefore of interest for applications within both general electromagnetics and biosensing due to its generality. In line with our previous work [7], in the present abstract we review TE-wave propagation in waveguide structures filled with dielectric composites graded along the direction of the waveguide (conveniently chosen to be z-direction). Using Maxwell's equations in a source-free (p = 0 and 7 = 0) inhomogeneous medium{Formula Method} for TE-waves (Ez = 0) in the z-direction along the waveguide structure filled with a non-magnetic (ii(r, a») = ii0) dielectric composite with graded permittivity along the z-direction (e(r, a») = e(z, a»)), the wave equation for the electric field reduces to a simple form V2E(r, a>) + fc2£r(z, a>)E(r, a>) = 0 where k2 = o»2£0lu0 and £r(z,a>) is the relative permittivity function. The longintudinal component of the magnetic field Hz(r,a>) satisfies the same differential equation, i.e. V2Hz(r,a>) + k2Er(z,a>)Hz(r,a>) = 0 . These wave equations have the form of the Klein-Gordon (or Schrôdinger) equation of quantum physics, and they offer readily available exact analytical solutions for a number of permittivity profiles of interest, such as the hyperbolic tangent profile or periodic (sinusoidal) profile and similar. As an example, for a circular waveguide, of radius r0 , filled with graded dielectric composite with the periodic permittivity function{Formula Method} where C {...} and S {...} are the even and odd Mathieu functions, and we otherwise use standard textbook notation.

In recent years, several researchers and research groups have proposed and studied a novel method of using gold nanoparticles (AuNPs) for radio frequency (RF) hyperthermia treatment of cancer. Such a method is occasionally described as a very promising new method for cancer treatment, without the side effects that are typical for other radiation treatments. It is well established that optical heating of AuNPs is caused by localized surface plasmon resonances. However, the physical mechanism behind RF heating of AuNP-fed biological tissue is a subject of some controversy. It is believed that the applied RF radiation drives the AuNPs into resonant oscillation, leading to relatively high dielectric losses, such that Joule and inductive heating is found to be negligible. In the present paper, we therefore perform an in-depth investigation of the parameter ranges and limitations that exist for the proposed methods of using AuNPs for RF hyperthermia treatment of cancer. Thereby, we show that a number of claims made so far about the potential of the proposed method are uncertain, and require further quantitative investigation.

We study TE-wave propagation in a circular waveguide with a graded transition from a lossy right-handed material (RHM) filling the left-hand half of the waveguide to the impedance-matched lossy left-handed material (LHM) filling the right-hand half of the waveguide. We obtain exact analytical solutions to Maxwell's equations and perform corresponding numerical simulations in COMSOL. An excellent agreement is obtained between the numerical simulations and analytical results. The presented method can model smooth realistic material transitions, where the interface width is an additional degree of freedom in the design of practical RHM-LHM interfaces.

A new H-mode regime at low density and low edge safety factor (q 95 = 3.2, with Ip = 3 MA) that combines high energy confinement, stationary conditions for density and radiation and small Edge Localized Modes (ELMs) have been found in JET with Be/W wall. Such a regime is achieved by operating without external gas puffing, leading to a decrease in the edge density and a substantial increase in rotation and ion temperature in both the pedestal and the core region. Transport modelling shows a reduction of the turbulence, which starts in the pedestal region and extends into the plasma core, and outward impurity convection, consistent with the improved energy confinement and the lack of W accumulation observed in those conditions. In addition, large type I ELMs, typically found in gas-fuelled plasmas, are replaced by smaller and more frequent ELMs, whose appearance is correlated with a substantial reduction of the pedestal density and its gradient. Pedestals in this operating regime are stable to peeling-ballooning modes, consistent with the lack of large ELMs. This is in contrast to results in unfuelled JET-C plasmas that typically operated at higher pedestal densities and developed low frequency, large type I ELMs, thus pointing to the low density as one of the critical parameters for accessing this small ELMs regime in JET. This small ELMs regime exhibits the same low pedestal collisionality ( nu e,ped & lowast;similar to 0.1 ) expected in ITER and operates at low q 95, thus making it different from other small ELMs regimes that are typically obtained at higher q 95 and higher pedestal collisionality. These features make this newly developed H-mode regime in JET with Be/W wall a valuable tool for exploring the underlying transport, the different mechanisms of turbulence stabilization, as well as the physics associated with the appearance of small ELMs in high-temperature plasmas at ITER relevant pedestal collisionality.

Runaway electrons (REs) are a concern for tokamak fusion reactors from discharge startup to termination. A sudden localized loss of a multi-megaampere RE beam can inflict severe damage to the first wall. Should a disruption occur, the existence of a RE seed may play a significant role in the formation of a RE beam and the magnitude of its current. The application of central electron cyclotron resonance heating (ECRH) in the Tokamak à Configuration Variable (TCV) reduces an existing RE seed population by up to three orders of magnitude within only a few hundred milliseconds. Applying ECRH before a disruption can also prevent the formation of a post-disruption RE beam in TCV where it would otherwise be expected. The RE expulsion rate and consequent RE current reduction are found to increase with applied ECRH power. Whereas central ECRH is effective in expelling REs, off-axis ECRH has a comparatively limited effect. A simple 0-D model for the evolution of the RE population is presented that explains how the effective ECRH-induced RE expulsion results from the combined effects of increased electron temperature and enhanced RE transport.

Polycrystalline (PC) and single crystal (SC) molybdenum mirrors were irradiated with 98Mo+, 1H+, 4He+, 11B+ and 184W+. Energies were chosen to impact the optically active region (up to 30 nm deep) of Mo mirrors. Some surfaces were coated by magnetron sputtering either with B or W films 4–65 nm thick. The overall objective was to simulate the neutron-induced damage and transmutation (H, He), and the impact of H, He, B, W on the optical performance of test mirrors, and on fuel retention. In parallel, a set of PC Mo mirrors irradiated with 1.6 MeV 98Mo3+ to a damage of 2 dpa and 20 dpa was installed in the JET tokamak for exposure during deuterium-tritium campaigns. Data from spectrophotometric, ion beam and microscopy techniques reveal: (i) the irradiation decreased specular reflectivity, whereby the differences between PC and SC in reflectivity are very small, (ii) He is retained in bubbles within 25–30 nm of the subsurface layer in all irradiated materials, (iii) W, either deposited or implanted, decreases reflectivity, but the strongest reflectivity degradation is caused by B deposition. Laboratory studies show the correlation of damage and H retention. Several cycles of W deposition and its removal from SC-Mo mirrors by plasma-assisted methods were also performed.

The geodesic Luneburg lens has been revisited as a suitable solution for applications requiring directive beams in the millimeter waveband. Among its advantages, its rotational symmetry and high efficiency stand out. However, one of its drawbacks is the need for a certain height to produce the desired focusing properties of the lens. Here, we propose a low-profile solution based on rotationally symmetric ridges that mimic, similar to geodesic lenses, the effective refractive index of a Luneburg lens. Moreover, we show that both rectangular and trapezoidal ridges perform similarly, opening the possibility for other manufacturing techniques. We demonstrate this concept with a prototype that is fully metallic and provides a scanning range of +/- 62 degrees over a broadband of operation, from 24 to 34 GHz. In this prototype, the height of the lens is 18 times more compact than the original Rinehart-Luneburg lens, allowing the lens to be vertically stacked, which is beneficial, for example, for producing linear arrays. This technique could be used to produce other type of lenses.

Tokamak à configuration variable (TCV), recently celebrating 30 years of near-continual operation, continues in its missions to advance outstanding key physics and operational scenario issues for ITER and the design of future power plants such as DEMO. The main machine heating systems and operational changes are first described. Then follow five sections: plasma scenarios. ITER Base-Line (IBL) discharges, triangularity studies together with X3 heating and N2 seeding. Edge localised mode suppression, with a high radiation region near the X-point is reported with N2 injection with and without divertor baffles in a snowflake configuration. Negative triangularity (NT) discharges attained record, albeit transient, βN ∼ 3 with lower turbulence, higher low-Z impurity transport, vertical stability and density limits and core transport better than the IBL. Positive triangularity L-Mode linear and saturated ohmic confinement confinement saturation, often-correlated with intrinsic toroidal rotation reversals, was probed for D, H and He working gases. H-mode confinement and pedestal studies were extended to low collisionality with electron cyclotron heating obtaining steady state electron iternal transport barrier with neutral beam heating (NBH), and NBH driven H-mode configurations with off-axis co-electron cyclotron current drive. Fast particle physics. The physics of disruptions, runaway electrons and fast ions (FIs) was developed using near-full current conversion at disruption with recombination thresholds characterised for impurity species (Ne, Ar, Kr). Different flushing gases (D2, H2) and pathways to trigger a benign disruption were explored. The 55 kV NBH II generated a rich Alfvénic spectrum modulating the FI fas ion loss detector signal. NT configurations showed less toroidal Alfvén excitation activity preferentially affecting higher FI pitch angles. Scrape-off layer and edge physics. gas puff imaging systems characterised turbulent plasma ejection for several advanced divertor configurations, including NT. Combined diagnostic array divertor state analysis in detachment conditions was compared to modelling revealing an importance for molecular processes. Divertor physics. Internal gas baffles diversified to include shorter/longer structures on the high and/or low field side to probe compressive efficiency. Divertor studies concentrated upon mitigating target power, facilitating detachment and increasing the radiated power fraction employing alternative divertor geometries, optimised X-point radiator regimes and long-legged configurations. Smaller-than-expected improvements with total flux expansion were better modelled when including parallel flows. Peak outer target heat flux reduction was achieved (>50%) for high flux-expansion geometries, maintaining core performance (H98 > 1). A reduction in target heat loads and facilitated detachment access at lower core densities is reported. Real-time control. TCV’s real-time control upgrades employed MIMO gas injector control of stable, robust, partial detachment and plasma β feedback control avoiding neoclassical tearing modes with plasma confinement changes. Machine-learning enhancements include trajectory tracking disruption proximity and avoidance as well as a first-of-its-kind reinforcement learning-based controller for the plasma equilibrium trained entirely on a free-boundary simulator. Finally, a short description of TCV’s immediate future plans will be given.

The primary objective of this thesis is to enhance the security of electricity supply by providing a holistic perspective and introducing a comprehensive framework for assessing power system health. This novel approach aims for a thorough evaluation of the system’s overall performance and well-being, using the physical dimensions of the security of supply as the foundation for a power system health index. 

After establishing the theoretical framework, relevant and available data is collected in order to analyze and understand the system’s performance. By analyzing outage statistics in Sweden, the research identifies specific trends and performance metrics that can be further investigated and segmented according to various criteria. The insights gained from this research can, in turn, be used to inform proactive maintenance strategies and capacity planning, ultimately mitigating the risks of outages and ensuring a more reliable electricity supply. 

Outage statistics are furthermore analyzed from the aspect of data quality, focusing on inconsistencies and missing values in the outage reports, i.e. unknown outage causes and unidentified faulty equipment. By carefully examining the data, noticeable gaps and deficiencies are revealed. Thus, a format for improving outage reporting using a database with 3 relations (outage summary, outage breakdown and customer breakdown) is proposed. In addition to a qualitative analysis of the data, various machine learning algorithms are explored and tested for their capability to predict the unknown values within the dataset, thereby offering a twofold solution: enhancing the accuracy of outage data and facilitating deeper, more accurate analytical capabilities. The findings and proposals within this work highlight the current challenges within outage data management and also lay the groundwork for a more comprehensive, data-driven approach in outage management and policy development. 

The health index has traditionally been devised and calculated for individual assets within a power system. This index provides vital details about an asset’s overall health and allows for a standardized comparison among various assets. However, the intricate nature of power systems poses significant challenges when trying to adapt this methodology for a broader, global power system health index. To tackle this obstacle, this paper proposes an innovative framework for evaluating power system health. The framework’s primary purpose is either to monitor the performance of a power system within a defined jurisdiction (such as a country, region, or utility) over time and identify trends/changes or to compare the performance across various jurisdictions. This paper further presents a comprehensive overview of key concepts that play a vital role in determining power system health. These include the driving factors, performance metrics, and associated costs, all of which are under the careful supervision of asset management. Special attention is given to the physical dimensions of the security of electricity supply, which represent the performance-based aspect of power system health and constitute the foundation for the power system health index. Each performance-based dimension is thoroughly reviewed, and a list of relevant key performance indicators is provided for every dimension. 

Data analysis plays a pivotal role in identifying patterns and relationships within data sets. By examining historical outage statistics in power systems, trends in system performance can be revealed, contributing to a better understanding of its behavior. Furthermore, by understanding the past performance of the power system, utility companies can make better decisions to enhance system reliability and resilience. This study investigates outage statistics in the Swedish power system from 2009 to 2019 and examines in depth the reporting mechanism. The data is clustered and analyzed according to three different criteria: voltage level of the breaking device, cause of the failure, and faulty equipment. Although the presented overview highlights key trends in system performance, the analysis has uncovered issues related to data quality and availability, such as missing values and inconsistencies that require further attention.

This study investigates outage statistics in the Swedish power system. More specifically, this paper delves into the critical analysis and enhancement of data quality, focusing on inconsistencies and missing values, i.e. unknown outage causes and unidentified faulty equipment. By carefully examining the data, noticeable gaps and deficiencies are revealed. Thus, a format for improving outage reporting using a database with 3 relations (outage summary, outage breakdown and customer breakdown) is proposed. In addition to a qualitative analysis of the data, various machine learning algorithms are explored and tested for their capability to predict the unknown values within the dataset, thereby offering a twofold solution: enhancing the accuracy of outage data and facilitating deeper, more accurate analytical capabilities. The findings and proposals within this work not only illuminate the current challenges within outage data management but also pave the way for more robust, data-driven decision-making in outage management and policy formation. 

This study investigates outage statistics in the Swedish power system. More specifically, this paper highlights the critical importance of addressing data quality issues such as inconsistencies and missing values, including unknown outage causes and unidentified faulty equipment. Existing research often overlooks the depth of these data quality challenges, leaving significant gaps in the reliability and utility of outage statistics. This paper reveals noticeable deficiencies in the current data and proposes a structured format for improving outage reporting through a database with three relations: outage summary, outage breakdown, and customer breakdown. To tackle these issues, a detailed qualitative analysis of the data is conducted, complemented by the exploration and testing of various machine learning algorithms. These algorithms are employed to predict unknown values within the dataset, thereby offering a twofold solution: enhancing the accuracy of outage data and enabling more precise analytical capabilities. Specifically, methods such as decision trees and random forests are utilized to address the data gaps. The findings and proposals within this work not only illuminate the current challenges in outage data management but also pave the way for more robust, data-driven decision-making in outage management and policy formation.

When simulating runaway electron dynamics in tokamak disruptions, fluid models with lower numerical cost are often preferred to more accurate kinetic models. The aim of this work is to compare fluid and kinetic simulations of a large variety of different disruption scenarios in ITER. We consider both non-activated and activated scenarios; for the latter, we derive and implement kinetic sources for the Compton scattering and tritium beta decay runaway electron generation mechanisms in our simulation tool Dream (Hoppe et al., Comput. Phys. Commun., vol. 268, 2021, 108098). To achieve a diverse set of disruption scenarios, Bayesian optimization is used to explore a range of massive material injection densities for deuterium and neon. The cost function is designed to distinguish between successful and unsuccessful disruption mitigation based on the runaway current, current quench time and transported fraction of the heat loss. In the non-activated scenarios, we find that fluid and kinetic disruption simulations can have significantly different runaway electron dynamics, due to an overestimation of the runaway seed by the fluid model. The primary cause of this is that the fluid hot-tail generation model neglects superthermal electron transport losses during the thermal quench. In the activated scenarios, the fluid and kinetic models give similar predictions, which can be explained by the significant influence of the activated sources on the runaway dynamics and the seed.

The increasing demand for higher data rates and capacity encompasses diverse applications in modern wireless systems. This necessitates addressing the limitations of conventional wireless systems, e.g. bandwidth constraints, efficiency issues, link budget limitations, and size and cost constraints. To achieve high data rates in the gigabit-per-second (Gbit/s), wider bandwidths in the gigahertz (GHz) range are required, leading to a transition to the microwave and millimeter wave (mm-wave) frequency band. However, this transition presents additional challenges, such as increased insertion- and free space path losses. All of these challenges are particularly critical in the Radio Frequency (RF) front-end, which comprises antennas along with other necessary RF elements, e.g. Power Amplifiers (PAs), that play a significant role in determining overall system performance. In this thesis, our research focuses on advancements in RF front-end efficiency— encompassing energy, spectral, size, and cost efficiency— to contribute to meeting the growing demands of next-generation communication systems. 

Phased array antennas are widely utilized in modern communication networks to enhance radiation characteristics such as gain and scan capability. Additionally, the direct-integration technique, which removes the need for any intermediate 50 Ω interface impedance, offers improvements in efficiency, size- and cost reduction. This thesis develops active direct-integrated phased array antenna (AIPAA) designs that utilize a combination of wide-scan phased array antennas and direct-integration technique. The presented designs advance the radiation performance through the phased array antenna, enhance the overall efficiency of the antenna and PAs combination via direct-integration, eliminate matching networks' losses through direct-integration, and remove RF switch elements by introducing a half-duplex array. The active integration approach employs an interdisciplinary co-design method to address complex interactions and mutual coupling in the proposed compact-size AIPAAs. In this thesis, the mutual interactions that can impact the system performance have been theoretically and practically discussed in our proposed coupling reduction approach. Besides, a seamless integration of filtering functionality, using proposed periodic structures, into a Vivaldi antenna is employed to design a high-selectivity filtering antenna with wide out-of-band suppression. These proposed designs and approaches help to enhance the performance by improving the spectral- and energy efficiencies, reducing the size, and minimizing costs.

Another approach in this thesis, utilizing irregularly partitioned phased arrays, offers a means to reduce the number of transmitter/receiver modules (system simplification) while maintaining functionality in next-generation wireless systems. An innovative fast-partitioning iterative optimization approach, introduced in the last part of the thesis, overcomes the computational cost/time of phased arrays' exact partitioning while resulting in satisfactory radiation characteristics over wide-scan coverage for large arrays.

This paper introduces a novel filtering approach that employs integrated periodic structures with a conventional Vivaldi antenna to achieve a fully integrated bandpass filtering antenna. The approach results in a wide out-of-band suppression, high passband selectivity, adjustable operational bandwidth, and low insertion loss. The proposed filtering approach maintains the original size of the conventional Vivaldi antenna (base antenna) without requiring additional modifications. To validate the approach, we present two filtering Vivaldi antennas: filtering antenna I (center frequency: 18GHz, fractional bandwidth: 21%, insertion loss: 0.32dB) and filtering antenna II (center frequency: 6.5GHz, fractional bandwidth: 12%, insertion loss: 0.6dB). Their wide out-of-band gain suppression (typically >= 15dB) covers the conventional Vivaldi antenna's frequency range (4-24GHz). A prototype of the filtering antenna I is manufactured. Its measurement results validate the proposed approach and show good agreement with the simulated reflection coefficient, realized gain, and radiation patterns. The features of the proposed filtering antenna approach, make it suitable for various applications requiring efficient frequency filtering.