Kharkiv Institute of Physics and Technology

The luminescence properties of stable chloride double perovskites Cs2BIInCl6, where BI is 4 at.% Ag, 6 at.% Na, doped with Sb³⁺ and Er³⁺ were investigated for the first time in the 250‐1600 nm region and revealed significant potential for advanced application. We employed XPS and ToF‐SIMS for chemical analyses, while SEM, XRD, and Raman spectroscopy provided insights into the morphology, crystal structure, and vibrational characteristics of the samples. The crystal structures of Cs2Ag0.292Na0.708InCl6, Cs2Ag0.285Na0.715In0.971Er0.029Cl6, Cs2Ag0.16Na0.84In0.893Er0.017Sb0.09Cl6 were examined using single‐crystal methods. The excited Sb³⁺ ions emitted blue light at 450 nm due to electronic absorption at sub‐band gap levels, facilitating energy transfer to Er³⁺ ions. Notably, the Er³⁺ emitted radiation at 1540 nm, a wavelength particularly useful for optical communication applications. Additionally, emissions at 525 nm, 552 nm, 665 nm, and 805 nm were observed, corresponding to f‐f transitions of Er³⁺ ions. These compelling results were supported with calculations based on the Modified Crystal Field Theory, explaining the effects of varying concentrations of Sb³⁺ and Er³⁺ on the crystal structure and luminescent properties. By using the synthesized materials, we successfully developed an LED prototype that utilized a UV chip (320 nm) combined with the Cs2Ag0.4Na0.6In0.9Er0.01Sb0.09Cl6 powder as a stable and effective luminophore for possible application in optoelectronics.

A synthetic Mirnov coil array diagnostic for non-axisymmetric magnetic configurations is presented and used to study the capabilities of the poloidal array of single-axis coils and the two helical arrays of tri-axial coils installed in the TJ-II stellarator. This tool integrates the plasma currents induced by Alfvén-like perturbations of the electric potential inside the plasma and provides the induced magnetic field oscillations anywhere outside of it. The simulated signals can then be analyzed in the same manner as the experimental ones, and a scan on the radial position and width of the potential perturbation is conducted to find the limiting values that produce identifiable signals. We find that core-localized (ρ ≲ 0.5) modes are indistinguishable from one another and that the identification of low-n, low-m modes is often subject to off-by-one errors. We also determine the optimal polarization basis in which to analyze the tri-axial coil signals and address the diagnostic performance when resolving components of gap modes. In addition, selected cases have been analyzed with a simplified plasma response model, showing that plasma shielding of the mode currents may further deteriorate the accuracy of the mode identification method. We conclude with the analysis of an experimental case taken from the TJ-II database to illustrate the usefulness of this synthetic diagnostic.

The propagation and absorption of the slow waves in the plasma of the Joint European Torus (JET) tokamak have been investigated by ray tracing. The study aims to obtain a qualitative notion of the penetration into the plasma and absorption of the slow wave excited by the A2 ITER-like antenna. The slow waves are radiated by antennas in the ion cyclotron resonance frequency inverted minority heating or mode conversion heating regimes. It has been discovered that the rays propagate in the toroidal direction over a significant distance, up to 6 × 10 ³ cm, from the antenna. Spreading in the peripheral plasma, mainly between the separatrix and the wall, they slowly shift in the poloidal direction and can reach the divertor region. The change in equilibrium of the JET tokamak has a strong influence on both the propagation and absorption of slow waves. Absorption of the slow waves is caused by ion–electron collisions and Landau damping. In the minority heating regimes, the slow waves are strongly damped in the cyclotron resonance of minority ions even at very low minority density.

Elastic scattering of protons on , , , and nuclei is analyzed in the framework of the Born approximation and an optical model for energies of 150 to 320 MeV. Analytical expressions for the scattering amplitudes, differential cross sections and polarization observables are obtained both in the Born approximation and within an optical model approach. The differences between outcomes of these approaches are discussed.

Effects of nanoparticles (NPs) on properties of the ionization region (IR) of a gas aggregation source (GAS) plasma and the properties of the sheath near the target are investigated using a global (volume averaged) model. The case where the GAS is operating in argon with copper target is considered. It is shown that with increasing the nanoparticle charge density, taking place at an increase of the NP size or the NP density, the densities of thermal electrons and argon ions slightly decrease, while the temperature of thermal electrons becomes larger. The voltage drop in the IR increases when the NP charge density becomes larger, to increase the power transferred to thermal electrons at an enhancement of the power losses in collisions with NPs and argon and copper atoms. For a fixed voltage applied to the target, the increase of the voltage drop in the IR is accompanied by a decrease of the voltage drop in the sheath near the target and, consequently, by a decrease of the sheath size, voltage drop in the sheath, energies with which ions bombard the target, sputtering yields and, as a result, by decreasing the densities of copper ions and copper atoms. It is shown that the absolute value of the charge of negatively charged NPs increases with increasing the NP density because of the growth of thermal electron temperature. Comparing the rates describing the deposition of copper ions and copper atoms on NPs, it is found that the growth of relatively large NPs (⩾10 nm) in the IR is due to the deposition of Cu ions on the surface of NPs, not Cu atoms. The results of our simulations are in good agreement with the available experimental data on the effect of NPs on magnetron plasma properties.

The drift trajectories of untrapped (passing, circulating) and trapped particles have been analyzed in the axisymmetric tokamaks with circular and elliptic magnetic surfaces for arbitrary aspect ratios and elongation. Analytical expressions for the drift deflections and orbit-widths of plasma particles are derived using the self-consistent collisionless drift-kinetic equation for plasma particles in a tokamak with circular magnetic surfaces. The computational results demonstrate that the direction of toroidal magnetic drift of plasma particles is significantly influenced by the sign of their charge, the direction of their parallel velocity relative to the equilibrium magnetic field, and the particle's initial (starting) position on the magnetic surface. In the case of elongated tokamaks, the existence of the usual t-trapped particles and two groups of d-trapped particles on the elliptic magnetic surfaces is examined.

Neoclassical tearing modes (NTMs) have been identified as the most deleterious perturbations in high-performance plasmas at Mega Amp Spherical Tokamak Upgrade (MAST-U). They produce magnetic islands that flatten the electron temperature profile and enhance the fast-ion transport. Understanding the NTM-induced losses can reveal paths to mitigate them, thus increasing the energy available to heat up the plasma. The MAST-U fast-ion loss detector (FILD) is equipped with a high-resolution camera and a high-speed camera that simultaneously measure the fast-ion losses in MAST-U. The combination of both systems makes it possible to infer the velocity-space of the losses fluctuating at the frequency of the NTMs. The FILDSIM code is used to infer the velocity space of the fast-ion losses from the strike position in a scintillator plate. Eulerian video magnification is employed to identify the losses that oscillate at the frequencies of the NTMs. NTMs produce fast-ion losses across a broad range of velocity space, with pitch angles ranging from 35∘ to 54∘. Non-linear interactions between the fast-ion orbits and different magnetic islands have been observed. The lost fast-ion orbits meet the stringent conditions that makes it possible to measure these effects.

Lepton flavor universality in rare b → s transitions is tested for the first time using B s 0 meson decays. The measurements are performed using p p collision data collected by the LHCb experiment between 2011 and 2018, corresponding to a total integrated luminosity of 9 fb − 1 . Branching fraction ratios between the B s 0 → ϕ e + e − and B s 0 → ϕ μ + μ − decays are measured in three regions of dilepton mass squared, q 2 , with 0.1 < q 2 < 1.1 , 1.1 < q 2 < 6.0 , and 15 < q 2 < 19 GeV 2 / c 4 . The results agree with the standard model expectation of lepton flavor universality. © 2025 CERN, for the LHCb Collaboration 2025 CERN

Diffusion coefficient usually decreases when friction increases. We analyze the opposite behavior in the paradigmatic system consisting of an inertial Brownian particle moving in a symmetric spatially periodic potential and driven by an unbiased time periodic force. For tailored parameter set in strong dissipation regime the particle spreading can be giantly amplified: if the friction is twice as large then the diffusion grows up to five orders of magnitude. The mechanism lying behind this effect is related to bifurcation of periodic orbits oscillating around the potential maximum and their symmetric displacement towards the adjacent potential minima when the friction coefficient increases. On the other hand, in the weak dissipation regime, where the increase of diffusion vs friction is also observed, the effect is induced by a non-monotonic change of population of the running orbits. However, in this regime the enhancement of diffusion is much smaller.

For successfully heating plasma with waves in the ion cyclotron range of frequencies (ICRFs), mitigating impurity production is just as crucial as maximizing power coupling, especially in high-Z environments (Urbanczyk et al 2021 Nucl. Mater. Energy 26 100925). ICRF can effectively deposit energy on ions, modify turbulence-driven transport, and enhance fusion reaction efficiency, but only when its power coupling has minimal impact on impurity production. To do so, one must rely on a toroidal array of at least three active elements excited with appropriate phasing and power ratio to reduce the currents induced on the antenna frame below levels critical for physical sputtering. In contrast to classic two-strap antennas, which are optimized for dipole phasing with equal power on both straps, three-strap antennas in ASDEX Upgrade (AUG)—but also four-strap antennas in JET, Alcator C-Mod, SPARC and ITER—offer the possibility to act also on the power ratio between the central and outer straps. With optimal settings, impurity production can be reduced substantially, making the ICRF compatible with the high-Z wall (Bobkov et al 2017 Plasma Phys. Control. Fusion 59 014022). This paper explores the characteristics of the AUG three-strap antennas in terms of impurity production, as well as the key role of plasma composition in this process. Numerical simulations were performed using SSWICH and Petra-M (finite element codes) to quantify impurity production and compare with experimental results. Energies of ions falling on antenna limiters (measured with probes) are well predicted by both codes. These tools are then used to further describe the source of the impurity, namely the gross erosion of tungsten from an ICRF antenna, for different plasma mixtures. Results are also compared to spectroscopy data. Ultimately, we show that deleterious effects of the ICRF on plasma surface interactions will be weaker in plasmas containing larger fractions of highly ionized heavier low-Z impurity, which is typically relevant for experiments relying on impurity seeding.

The experiments carried out in hydrogen at the TOMAS facility show the possibility of controlling plasma parameters such as temperature and electron density in a combined electron cyclotron resonance and radio frequency (ECR+RF) discharge. A maximum plasma density of up to ≈6 × 10¹⁶ m⁻³ and electron temperature of up to 35 eV are observed in the combined ECR+RF discharge. The propagation of RF waves in hydrogen plasma under a weak magnetic field is analyzed. Depending on RF frequency and experimental conditions, such as radial distribution of plasma density and magnetic field, there can be several cases: only the slow wave can propagate, simultaneously slow and fast waves can propagate, or only the fast wave can propagate. The injection of additional RF power into the ECR discharge allows us to change the flux of neutral particles and their distribution function. Even the injection of small RF power of ≈ 0.26 kW relative to microwave power of ≈ 1.7 kW leads to an increase in the hydrogen flux by a factor of ∼2.5. At RF power PRF ≈ 1.57 kW, the H⁰ flux increases by a factor of ∼9.3. The ability to control the fluxes and energies of particles leaving the plasma volume is important to approach the conditions necessary to study plasma–surface interactions in wall conditioning and fusion edge plasmas.

A bstract The first measurement of ϕ (1020) meson production in fixed-target p Ne collisions at $\sqrt{s_{NN}}$ s NN = 68 . 5 GeV is presented. The ϕ (1020) mesons are reconstructed in their K ⁺ K − decay in a data sample consisting of proton collisions on neon nuclei at rest, corresponding to an integrated luminosity of 21 . 7 ± 1 . 4 nb − 1 , collected by the LHCb detector at CERN. The ϕ (1020) production cross-section in the centre-of-mass rapidity range of − 1 . 8 < y * < 0 and transverse momentum range of 800 < p T < 6500 MeV/ c is found to be σ = 182 . 7 ± 2 . 7 (stat.) ± 14 . 1 (syst) μ b/nucleon. A double-differential measurement of the cross-section is also provided in four regions of rapidity and six regions of transverse momentum of the ϕ (1020) meson and compared with the predictions from Pythia and EPOS4, which are found to underestimate the experimental values.

A bstract A measurement of the CP -violating parameters in ${B}_s^0\boldsymbol{\to}{D}_s^{\mp }{K}^{\pm}$ B s 0 → D s ∓ K ± decays is reported, based on the analysis of proton-proton collision data collected by the LHCb experiment corresponding to an integrated luminosity of 6 fb − 1 at a centre-of-mass energy of 13 TeV. The measured parameters are obtained with a decay-time dependent analysis yielding C f = 0.791 ± 0.061 ± 0.022, ${A}_f^{\Delta \Gamma}$ A f ∆ Γ = −0.051 ± 0.134 ± 0.058, ${A}_{\overline{f}}^{\Delta \Gamma}$ A f ¯ ∆ Γ = −0.303 ± 0.125 ± 0.055, S f = −0.571 ± 0.084 ± 0.023 and ${S}_{\overline{f}}$ S f ¯ = −0.503 ± 0.084 ± 0.025, where the first uncertainty is statistical and the second systematic. This corresponds to CP violation in the interference between mixing and decay of about 8.6 σ . Together with the value of the ${B}_s^0$ B s 0 mixing phase −2 β s , these parameters are used to obtain a measurement of the CKM angle γ equal to (74 ± 12)° modulo 180°, where the uncertainty contains both statistical and systematic contributions. This result is combined with the previous LHCb measurement in this channel using 3 fb − 1 resulting in a determination of $\gamma ={\left({81}_{-11}^{+12}\right)}^{\circ }$ γ = 81 − 11 + 12 ∘ .

A bstract An analysis of the flavour oscillations of the charmed neutral meson is presented. The ratio of D ⁰ → K ⁺ π − and D ⁰ → K − π ⁺ decay rates is measured as a function of the decay time of the D ⁰ meson and compared with the charge-conjugated system to search for charge-parity violation. The meson flavour at production is double-tagged by the charges of the muon and pion in the preceding $\overline{B}\to {D}^{\ast }{(2010)}^{+}{\mu}^{-}X$ B ¯ → D ∗ 2010 + μ − X and D ∗ (2010) ⁺ → D ⁰ π ⁺ decays, respectively. These decays are selected from proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 5.4 fb − 1 . The flavour oscillation parameters, relating to the differences in mass and width of the mass eigenstates, are found to be y ′ = (5.8 ± 1.6) × 10 − 3 and ( x ′) ² = (0.0 ± 1.2) × 10 − 4 . No evidence for charge-parity violation is seen either in the flavour oscillations or in the decay, where the direct charge-parity asymmetry is measured to be A D = (2.3 ± 1.7) %.

The C P asymmetry and branching fraction of the Cabibbo-Kobayashi-Maskawa-suppressed decay B + → J / ψ π + are precisely measured relative to the favored decay B + → J / ψ K + using a sample of proton-proton collision data corresponding to an integrated luminosity of 5.4 fb − 1 recorded at a center-of-mass energy of 13 TeV during 2016–2018. The results of the C P asymmetry difference and branching fraction ratio are Δ A C P ≡ A C P ( B + → J / ψ π + ) − A C P ( B + → J / ψ K + ) = ( 1.29 ± 0.49 ± 0.08 ) × 10 − 2 , R π / K ≡ [ B ( B + → J / ψ π + ) / B ( B + → J / ψ K + ) ] = ( 3.852 ± 0.022 ± 0.018 ) × 10 − 2 , where the first uncertainties are statistical and the second are systematic. A combination with previous LHCb results based on data collected at 7 and 8 TeV in 2011 and 2012 yields Δ A C P = ( 1.42 ± 0.43 ± 0.08 ) × 10 − 2 and R π / K = ( 3.846 ± 0.018 ± 0.018 ) × 10 − 2 . The combined Δ A C P value deviates from zero by 3.2 standard deviations, providing the first evidence for direct C P violation in the amplitudes of beauty decays to charmonium final states. © 2025 CERN, for the LHCb Collaboration 2025 CERN

An amplitude analysis of B − → D − D 0 K S 0 decays is performed using proton-proton collision data, corresponding to an integrated luminosity of 9 fb − 1 , collected with the LHCb detector at center-of-mass energies of 7, 8, and 13 TeV. A resonant structure of spin-parity 0 + is observed in the D 0 K S 0 invariant-mass spectrum with a significance of 5.3 σ . The mass and width of the state, modeled with a Breit-Wigner line shape, are determined to be 2883 ± 11 ± 8 MeV / c 2 and 87 − 47 + 22 ± 17 MeV , respectively, where the first uncertainties are statistical and the second systematic. These properties and the quark content are consistent with those of the open-charm tetraquark candidate T c s 0 * ( 2870 ) 0 observed previously in the D + K − final state of the B − → D − D + K − decay. This result confirms the existence of the T c s 0 * ( 2870 ) 0 state in a new decay mode. The T c s 1 * ( 2900 ) 0 state, reported in the B − → D − D + K − decay, is also searched for in the D 0 K S 0 invariant-mass spectrum of the B − → D − D 0 K S 0 decay, without finding evidence for it. © 2025 CERN, for the LHCb Collaboration 2025 CERN

We report the first experimental detection of a zero-frequency fluctuation that is pumped by an Alfvén mode in a magnetically confined plasma. Core-localized Alfvén modes of frequency inside the toroidicity-induced gap (and its harmonics) exhibit three-wave coupling interactions with a zero-frequency fluctuation. The observation of the zero-frequency fluctuation is consistent with theoretical and numerical predictions of zonal modes pumped by Alfvén modes, and is correlated with an increase in the deep core ion temperature, temperature gradient, confinement factor H 89 , P , and a reduction in the main ion heat diffusivity. Despite the energetic particle transport induced by the Alfvén eigenmodes, the generation of a zero-frequency fluctuation that can suppress the turbulence leads to an overall improvement of confinement. Published by the American Physical Society 2025

Plasma production in stellarators with ion cyclotron heating is complementary to the widely used electron cyclotron heating (ECRH). The prospective light ion minority scenario developed and tried on Uragan-2M and Large Helical Device (LHD) stellarators had been reexamined at LHD. The distinctive feature of this attempt is that the parameters of plasma produced are better than before and are comparable with those of plasma produced by the ECRH. This new possibility of ion cyclotron heating, if it becomes practical, motivates rethinking of the role of ion cyclotron heating in stellarator machines.