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Nanoscale chemical and structural investigation of Mg-doped GaN nanowires using EDS and WDS on SEM
No full textSemiconductors are the basis of many of today's technical products and therefore an important foundation of our modern economy. One material that is currently the subject of intensive research is doped gallium nitride (GaN), which has outstanding properties, particularly in the form of nanowire structures. For the chemical and structural characterization of such semiconductor nanowires, analyses using EDS and WDS were carried out on a FESEM in this work. The results show that strictly controlled analytical conditions, in particular low primary energy (here 4 keV), are crucial for analysis with high spatial resolution. Only by supplementing the EDS with WDS was it possible to determine both the structure of the nanowires and the trace element content of the dopant Mg (800 ppm). This example proves that advanced analytical questions, in which both high spatial and high spectral resolution are important, can only be solved by using WDS in addition to EDS on SEM
Development of correlated FIB-ToF-SIMS and SEM-AM methods for the search for, and characterisation of, enriched uranium particles
No full textAs part of a global initiative to detect and monitor uranium use in nuclear facilities, the International Atomic Energy Agency (IAEA) collects environmental samples from various countries and analyses them for the presence of man-modified uranium and other nuclear fuel cycle materials. For example, highly enriched uranium can be associated with undeclared nuclear material or activities, making its detection critical for nuclear non-proliferation efforts. The paper presents an advanced analytical workflow that combines automated mineralogy, FIB ToF-SIMS (focussed ion beam-time of flight secondary ion mass spectrometry), and LG SIMS (large geometry secondary ion mass spectrometry) to efficiently identify and characterise uranium-containing particles in field samples. This integrated workflow automates time-consuming aspects of particle analysis, significantly improving the speed and precision of detecting uranium. It also provides detailed, complementary data on particle morphology and the chemical elements associated with each particle. The approach was shown to effectively identify and characterise particles containing enriched uranium, offering an in-depth understanding of the material's composition. The workflow's efficiency and precision make it a potentially valuable tool for nuclear material monitoring and non-proliferation efforts
Calculation of the magnetic field and its modal analysis in the port plug cavity of the ITER ICRF antenna
No full textThe ITER Ion Cyclotron Range of Frequencies (ICRF) antenna plug and the vacuum vessel port form an electromagnetic cavity that can exhibit resonances of the coaxial type within the range of frequencies relevant for ion cyclotron heating (between 40 and 55 MHz). At resonance (~47.5 MHz), and for specific phasing, large electric fields and Radio Frequency (RF) losses can occur. This work focuses on the calculation of the magnetic field and its modal analysis in the port-plug cavity, an important step in the assessment of the resonant effects. The approach consists of several steps. First, a detailed model of the antenna is imported into the TOPICA (TOrino Polytechnic Ion Cyclotron Antenna) code [1], meshed, and run with several plasma density profiles. Subsequently, the electric surface current is reconstructed from the TOPICA code outputs on the inner conductor of the antenna plug, and the magnetic field in the gap around the plug is calculated from the values of the surface current. Furthermore, the cavity model is simulated using electromagnetic software CST Microwave Studio (MWS) [2] to calculate the cavity eigenmodes. The magnetic field is then expanded into a series of cavity eigenmodes previously obtained and expansion coefficients are determined. In the next step, the modal expansion of the cavity fields at the reference plane can be used to excite the lossy cavity with the corresponding forward wave spectrum, enabling the subsequent evaluation of magnetic fields and RF losses in the cavity [3]
Recent Progress in ICRF Experiments on the Experimental Advanced Superconducting Tokamak (EAST)
No full textIon Cyclotron Range of Frequency (ICRF) heating is a major auxiliary heating method used on the Experimental Advanced Superconducting Tokamak (EAST). This paper summarizes recent progress in ICRF experiments on EAST, including the upgrade of ICRF heating systems, improvements in ICRF coupling and core RF power absorption, and ICRF heating schemes. Furthermore, ICRF application in multiphysics studies is also discussed, including ICRF-induced Alfvén instabilities, sawtooth control, turbulence suppression, Ion Cyclotron Wall Conditioning (ICWC), and demonstration of good efficiency of ICRF for plasma heating in dominant RF-electron-heated plasmas relevant for ITER. These results demonstrate significant advances in ICRF performance and provide insights into wave–plasma interactions. They offer valuable guidance for improving heating efficiency and plasma control in next-generation fusion devices
40 years of ICRF Physics on the JET Tokamak: Highlights and Lessons Learned for Future Facilities
No full textDuring its 40-year operational period (1983–2023), the Joint European Torus (JET) made significant contributions to the advancement of knowledge in the field of ion cyclotron range of frequencies (ICRF) physics in magnetically confined plasmas. The unique combination of large size, flexible auxiliary systems, and tritium-handling capabilities of JET provided an unparalleled environment for reactor-relevant investigations. The studies furthered the understanding of wave-particle interactions and fast ion dynamics. Furthermore, they explored the interplay between ICRF heating and key plasma phenomena, including current drive, rotation, and impurity transport. Notable achievements included the stabilisation of sawtooth oscillations, the characterisation of alpha-like fast ion behaviour, and the development of impurity control strategies. These achievements contributed to the validation of advanced ICRF heating schemes. Collectively, the results offer valuable lessons that directly inform the design and operation of ITER and other next-generation fusion devices
Real-time estimates of the ICRF single-pass absorption for ITER
No full textEstimating the single-pass absorption (SPA) of a given Ion Cyclotron Resonance Heating (ICRH) scenario as function of the plasma and the radio-frequency (RF) wave properties requires a multispecies hot plasma wave solver. Even in 1D and using truncated finite Larmor radius expansion for the plasma dielectric response, the simulations cannot be done much faster than in a couple of seconds. In ITER, it is envisaged to estimate the single-pass absorption of the ICRF waves in real-time to take preventive actions in case of poor absorption for avoiding increased plasma-wall interaction and enhanced heat loads on the plasma facing components. This work proposes a potential solution based on pre-calculated look-up tables of the ICRF single-pass absorption that can be interpolated in real-time by the Advanced Protection System (APS) and by the Plasma Control System (PCS) in ITER [1,2,
The foundational value of quantum computing for classical fluids
No full textQuantum algorithms for classical physics problems expose new patterns of quantum information flow as compared to the many-body Schrödinger equation. As a result, besides their potential practical applications, they also offer a valuable theoretical and computational framework to elucidate the foundations of quantum mechanics, particularly the practical value of the many-body Schrödinger equation in the limit of large number of particles, on the order of the Avogadro number. This idea is illustrated by means of a concrete example, the block-encoded Carleman embedding of the lattice Boltzmann (LB) formulation of fluid dynamics (CLB hereafter)
Distance to the globular cluster M 3 from the infrared surface brightness technique applied to RR Lyrae stars
No full textContext. The infrared surface brightness (IRSB) technique is a specific application of the Baade-Wesselink method. Given proper calibration, well-covered optical and near-infrared photometry, as well as radial velocity curves, it allows the estimation of distances to individual pulsating stars and the determination of their mean radii. Even though it is observationally demanding, it offers a way of distance determination to systems of pulsating stars that is independent of period-luminosity relations. The technique is fully empirical and does not depend on stellar atmosphere models.
Aims. The goal of the work is to test the precision of distance determinations to individual RR Lyrae stars and to their host system as a whole using the IRSB technique for a relatively distant globular cluster M 3 (NGC 5272). We also determined the mean radii and period-radius relations for these stars in order to compare them with the existing theoretical predictions and empirical estimations for the field stars from the solar neighborhood.
Methods. We used the data available in the literature and the calibration of the IRSB technique based on the RR Lyrae stars from the solar neighborhood we published previously in order to determine distances to 14 RR Lyrae stars in the globular cluster M 3. We applied the IRSB technique, as previously presented in our work for RR Lyraes, from the solar vicinity with an extra determination and implementation of phase shifts between observables due to the phase incoherence of data gathered at different epochs. We studied the impact of the selection of the fitting procedure (bisector vs. the least-squares fit) on the results. We applied five different empirical surface brightness-color relations from the literature in the analysis.
Results. We obtained a mean distance to M 3 of rM3 = (10.07 ± 0.19 ± 0.29) kpc, which corresponds to a distance modulus μM3 = (15.015 ± 0.041 ± 0.063) mag and a 7% scatter of individual stellar distances for 14 RR Lyrae stars in M 3. We obtained a very good agreement between the two fitting techniques; the bisector proved to be a biased estimator, while the least-squares fit yielded slightly larger uncertainties. We also determined mean stellar radii for pulsators in the sample with a precision of 0.5% and obtained excellent agreement with a theoretical prediction of the period-radius relation for RRab stars available in the literature
An angular dispersion-free resonant metasurface for quantum photon pair generation
No full textMetasurfaces supporting high quality factor resonances have shown the ability to enhance spontaneous parametric down-conversion (SPDC) process and are therefore seen as a promising platform for entangled quantum photon pair generation. We propose a high quality (Q) factor flat-band optical metasurface for efficient quantum light generation via SPDC. The structure consisting of periodic GaAs nano-resonators on SiO2 was numerically optimised to realise a metasurface that is dispersionless along the Γ–Y axis near the telecommunications band (∼1550 nm). Our simulations show that the metasurface hosts two quasi–bound-states-in-the-continuum (q-BIC) modes with quality factors exceeding 109; the intentional merging of the BICs results in high-Q (>105) across a finite in-plane wave-vector range. This combination of angle-independent resonance frequency with persistently high Q mitigates the off-Γ degradation typical of symmetry-broken q-BICs. The design increases the optical density of states and allows for efficient collection of the generated photons using a high numerical aperture. It is anticipated that the resulting devices could be used for both quantum photon pair generation and for classical nonlinear second-harmonic generation. Our results demonstrate flat-band, high-Q metasurfaces that can be fabricated as a compact route to on-chip nonlinear and quantum photonics
The ALMA survey to Resolve exoKuiper belt Substructures (ARKS)
No full textContext. Debris disks – collisionally sustained belts of dust and sometimes gas around main sequence stars – are remnants of planet formation processes and are found in systems ≳10 Myr old. Millimeter-wavelength observations are particularly important, as the grains probed by these observations are not strongly affected by radiation pressure and stellar winds, allowing them to probe the dynamics of large bodies producing dust. The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) is analyzing high-resolution observations of 24 debris disks to enable the characterization of debris disk substructures across a large sample for the first time.
Aims. For the most highly inclined disks, it is possible to recover the vertical structure of the disk. We aim to model and analyze the most highly inclined systems in the ARKS sample in order to uniformly extract the vertical dust distributions for a sample of well-resolved debris disks.
Methods. We employed both parametric and nonparametric methods to constrain the vertical dust distributions for the most highly inclined ARKS targets.
Results. We find a broad range of aspect ratios, revealing a wide diversity in vertical structure, with a range of best-fit parametric values of 0.0026 ≤ hHWHM ≤ 0.193 and a median best-fit value of hHWHM = 0.021. The results obtained by nonparametric modeling are generally consistent with the parametric modeling results. We find that five of the 13 disks are consistent with having total disk masses less than that of Neptune (17 M⊕), assuming stirring by internal processes (self-stirring and collisional and frictional damping). Furthermore, most systems show a significant preference for a Lorentzian vertical profile rather than a Gaussian