Instrumentation and Detectors
High-precision beam profile measurement with a microchannel-plate detector in the high magnetic field of the WISArD experiment
S. Lecanuet, X. Fléchard, P. Alfaurt et al. (+23 more)
We present the development and characterization of a compact low-energy ion beam diagnostic for the WISArD (Weak Interaction Studies with $\mathrm{^{32}Ar}$ Decay) experiment at ISOLDE/CERN. The microchannel plate (MCP) detector, which is configured in a Z-stack and has a resistive position sensitive anode, was tested with both stable and radioactive beams. This work focuses on the image reconstruction method, which corrects the pincushion distortion inherent to the square-shaped resistive anode, and investigates the influence of the
magnetic field on the detector performance. Our results demonstrate that the detector achieves beam profile measurements with sub-millimeter accuracy, while coping with the spatial and high-
magnetic field (4 T) constraints of the experiment. These capabilities meet the precision requirements of the WISArD experiment for extracting the modified beta-
neutrino angular correlation coefficient, ã$_{\beta\nu}$, with an uncertainty of 0.1%.
Read the full abstract ▾
All authors S. Lecanuet, X. Fléchard, P. Alfaurt, P. Ascher, D. Atanasov, B. Blank, L. Daudin, H. DePreaumont, M. Gerbaux, J. Giovinazzo, S. Grévy, G. Guignard, J. Ha, C. Knapen, S. Lechner, A. Lépine, J. Lory, J. Perronnel, M. Pomorski, M. Roche, C. Roumegou, N. Severijns, Y. Son, S. Vanlangendonck, M. Versteegen, D. Zakoucky
Applied Physics · Cross-listed from cond-mat.mtrl-sci
Molecular Beam Epitaxy of Al$\mathrm{_{1-x}}$Sc$\mathrm{_{x}}$N Nanowires: Towards Group-III Nitride Piezoelectric Nanogenerators with Enhanced Response
Adriano Notarangelo, Rudeesun Songmuang, Mostafa Saleh et al. (+10 more)
We study the molecular beam epitaxy of self-assembled Al$\mathrm{_{1-x}}$Sc$\mathrm{_{x}}$N nanowires on conductive TiN layers and demonstrate their application in piezoelectric nanogenerators. Wurtzite Al$\mathrm{_{1-x}}$Sc$\mathrm{_{x}}$N nanowires with uniform Sc incorporation are grown across a wide composition range (0<x<0.35). At substrate temperatures below 700 $^\circ{}$C, these nanowires exhibit an inversely tapered morphology, whereas higher temperatures favor the nucleation of additional branches due to a phase separation of Al$\mathrm{_{1-x}}$Sc$\mathrm{_{x}}$N into wurtzite AlN and rock-salt ScN. Phase-pure Al$\mathrm{_{1-x}}$Sc$\mathrm{_{x}}$N nanowires are integrated into vertical nanogenerators, where the metallic TiN substrate serves as bottom electrode. The fabricated
polymer-nanowire composite devices achieve effective piezoelectric charge coefficients of up to 8.5 pC N$^{-1}$ at x=0.32, thus exceeding the piezoelectric response of bulk AlN by nearly a factor of two. Although the charge response remains lower compared to Al$\mathrm{_{1-x}}$Sc$\mathrm{_{x}}$N thin films, the reduced effective dielectric permittivity of the nanowire-
polymer composites compensates the reduction in piezoelectric charge coefficient, eventually yielding a higher voltage response and comparable energy harvesting efficiency. Finally, effective medium modeling reveals that the device architecture is the primary factor limiting performance, providing general design principles for highly efficient nanowire-based piezoelectric energy harvesters.
Read the full abstract ▾
All authors Adriano Notarangelo, Rudeesun Songmuang, Mostafa Saleh, Natthawadi Buatip, Ileana Florea, Philippe Vennéguès, Aidan F. Campbell, Hans Tornatzky, Jonas Lähnemann, Thomas Auzelle, Lutz Geelhaar, Oliver Brandt, Philipp M. John
Chemical Physics · Cross-listed from cond-mat.soft
Divergent Impact Charging of Polymer Particles
Simon Jantač and Holger Grosshans
When a particle contacts a surface of another material, it is commonly believed that the particle acquires an impact charge that scales inversely with its pre-impact charge and whose polarity is set by the materials. We show that this belief holds for conductive particles but fails for
polymers. For
polymers, the impact charge increases linearly with the particle's pre-impact charge. Its polarity is not determined by the materials but by the pre-impact particle charge relative to a divergence point at which the net charge transfer reverses. We attribute this divergence to the attraction of surrounding ions to the particle surface. These attracted ions carry polarity opposite to that of the particle, and their amount scales with the particle charge. They transfer to the opposing surface during contact, thereby defining the impact charge. We propose a phenomenological model for the divergent impact charge arising from this mechanism. Finally, we reexamine previous measurements and show that they support this mechanism.
Read the full abstract ▾
Instrumentation and Detectors
Cross-correlation on a single channel for resistance noise measurements
Tim Thyzel
Cross-correlation is an established tool to reduce the background in resistance noise measurements. However, the conventional method requires the amplifier, demodulator and digitizer channels to be duplicated, increasing the cost and complexity of the measurement
circuit. We propose an alternating-current technique that allows cross-correlation with only a single channel by modulating the device under test with two carrier frequencies simultaneously. Using multiple software-based demodulators, we show that this method produces accurate amplitude measurements and noise spectra. The signal-to-noise-ratio is improved by 7 decibel for standard parameters. Longer measurement durations increase this improvement, which makes the new technique a true cross-correlation method.
Read the full abstract ▾
Applied Physics
All-Optically Controlled Memristive Reservoir Computing Capable of Bipolar and Parallel Coding
Lingxiang Hu, Dian Jiao, Kexuan Wang et al. (+7 more)
Physical reservoir computing (RC) utilizes the intrinsic dynamical
evolution of physical systems for efficient data processing. Emerging optoelectronic RC platforms,such as light-driven memristors, merge the benefits of electronic and photonic computation. However, conventional designs are often limited by the unipolar photoresponse of optoelectronic devices, which restricts reservoir state diversity and reduces computational accuracy. To overcome these limitations, we introduce an all-optically controlled RC system employing an
oxide memristor array that demonstrates exceptional uniformity and stability. The memristive devices exhibit wavelength-dependent bipolar photoresponse, originating from light-induced dynamic
evolution of oxygen vacancies. Tuning the power density and irradiation mode of dual-wavelength light pulses enables dynamic control of photocurrent relaxation and nonlinearity. By leveraging these unique device properties, we develop bipolar and parallel coding strategies to significantly enrich reservoir dynamics and enhance nonlinear mapping capability. In word recognition and time-series prediction tasks, the bipolar coding demonstrates markedly improved accuracy compared to unipolar coding. The parallel coding supports multi-source signal fusion within a single reservoir, maintaining high computational accuracy while significantly reducing hardware consumption. This work provides a high-performance approach to physical RC, paving the way for intelligent edge computing.
Read the full abstract ▾
All authors Lingxiang Hu, Dian Jiao, Kexuan Wang, Peihong Cheng, Jingrui Wang, Li Zhang, Athanasios V. Vasilakos, Yang Chai, Zhizhen Ye, Fei Zhuge
Medical Physics · Cross-listed from cs.CV
Deep-Learning Atlas Registration for Melanoma Brain Metastases: Preserving Pathology While Enabling Cohort-Level Analyses
Nanna E. Wielenberg, Ilinca Popp, Oliver Blanck et al. (+6 more)
Melanoma
brain metastases (MBM) are common and spatially heterogeneous lesions, complicating cohort-level analyses due to anatomical variability and differing MRI protocols. We propose a fully differentiable, deep-learning-based deformable registration framework that aligns individual pathological
brains to a common atlas while preserving metastatic tissue without requiring lesion masks or preprocessing. Missing anatomical correspondences caused by metastases are handled through a forward-model similarity metric based on distance-transformed anatomical labels, combined with a volume-preserving regularization term to ensure deformation plausibility. Registration performance was evaluated using Dice coefficient (DSC), Hausdorff distance (HD), average symmetric surface distance (ASSD), and Jacobian-based measures. The method was applied to 209 MBM patients from three centres, enabling standardized mapping of metastases to anatomical, arterial, and perfusion atlases. The framework achieved high registration accuracy across
datasets (DSC 0.89-0.92, HD 6.79-7.60 mm, ASSD 0.63-0.77 mm) while preserving metastatic volumes. Spatial analysis demonstrated significant over-representation of MBM in the cerebral cortex and putamen, under-representation in white matter, and consistent localization near the gray-white matter junction. No arterial territory showed increased metastasis frequency after volume correction. This approach enables robust atlas registration of pathological
brain MRI without lesion masks and supports reproducible multi-centre analyses. Applied to MBM, it confirms and refines known spatial predilections, particularly preferential seeding near the gray-white matter junction and cortical regions. The publicly available implementation facilitates reproducible research and extension to other
brain tumours and neurological pathologies.
Read the full abstract ▾
All authors Nanna E. Wielenberg, Ilinca Popp, Oliver Blanck, Lucas Zander, Jan C. Peeken, Stephanie E. Combs, Anca-Ligia Grosu, Dimos Baltas, Tobias Fechter
Instrumentation and Detectors
Simulation Study for Particle Identification with the dRICH of the ePIC Experiment at the EIC
Tiziano Boasso, Chatterjee Chandradoy, Dalla Torre Silvia et al. (+24 more)
The dual-radiator Imaging Cherenkov detector (dRICH) is a key component of the forward particle identification system for the ePIC experiment at the Electron-Ion
Collider (EIC). This study evaluates the dRICH performance using Geant4 simulations in the context of the global ePIC simulation stack, focusing on the optimization of the aerogel radiator and the impact of sensor noise. We compare two aerogel configurations: the initial design (n=1.019) and the current default (n=1.026). The latter, characterized by improved optical properties and a higher refractive index, demonstrates enhanced $\pi-K$ separation at high momenta, effectively extending the operational overlap with the $\mathrm{C_2F_6}$ gas radiator. Additionally, the study investigates the impact of Silicon Photomultiplier (SiPM) dark noise, showing that a 300 kHz noise rate per channel leads to a moderate reduction (approximately 1.5 GeV/c) in the $3\sigma$ separation threshold. These results validate the current dRICH design and quantify the purity levels achievable for both radiators under expected experimental conditions.
Read the full abstract ▾
All authors Tiziano Boasso, Chatterjee Chandradoy, Dalla Torre Silvia, Martin Anna, Tessarotto Fulvio, Agarwala Jinky, Contalbrigo Marco, Polizzi Lorenzo, Occhiuto Luisa, Del Caro Annalisa, Nagorna Tetiana, Osipenko Mikhail, Vallarino Simone, Farokhi Fateme, Kiselev Alexander, Bhadauria Rohit Singh, Ghosh Tapasi, Nunez Cynthia, Pecar Connor, George Nebin, Rajan Adithyan, Samuel Deepak, Jangid Rohit, Kumar Ramandeep, Laishram Girdish, Tanvi Tanya, Thakur Meenu
Medical Physics
Ultrasound-Guided Real-Time Spinal Motion Visualization for Spinal Instability Assessment
Feng Li, Yuan Bi, Tianyu Song et al. (+2 more)
Purpose: Spinal instability is a widespread condition that causes pain, fatigue, and restricted mobility, profoundly affecting patients' quality of life. In clinical practice, the gold standard for diagnosis is dynamic X-ray imaging. However, X-ray provides only 2D motion information, while 3D modalities such as computed
tomography (CT) or cone beam computed
tomography (CBCT) cannot efficiently capture motion. Therefore, there is a need for a system capable of visualizing real-time 3D spinal motion while minimizing radiation exposure. Methods: We propose ultrasound as an auxiliary modality for 3D spine visualization. Due to acoustic limitations, ultrasound captures only the superficial spinal surface. Therefore, the partially compounded ultrasound volume is registered to preoperative 3D imaging. In this study, CBCT provides the neutral spine configuration, while robotic ultrasound acquisition is performed at maximal spinal bending. A kinematic model is applied to the CBCT-derived spine model for coarse registration, followed by ICP for fine registration, with kinematic parameters optimized based on the registration results. Real-time ultrasound motion tracking is then used to estimate continuous 3D spinal motion by interpolating between the neutral and maximally bent states. Results: The pipeline was evaluated on a bendable 3D-printed lumbar spine phantom. The registration error was $1.941 \pm 0.199$ mm and the interpolated spinal motion error was $2.01 \pm 0.309$ mm (median). Conclusion: The proposed robotic ultrasound framework enables radiation-reduced, real-time 3D visualization of spinal motion, offering a promising 3D alternative to conventional dynamic X-ray imaging for assessing spinal instability.
Read the full abstract ▾
All authors Feng Li, Yuan Bi, Tianyu Song, Zhongliang Jiang, Nassir Navab
Atomic Physics · Cross-listed from quant-ph
Quantum logic control and entanglement in hybrid atom-molecule arrays
Chi Zhang, Sara Murciano, Nathanan Tantivasadakarn et al. (+1 more)
Polar molecules, with their rich internal structure, offer immense potential for fundamental physics,
quantum technology, and controlled chemistry. However, their utilization is currently limited because of slow and imperfect state detection and weak dipolar interaction, limiting fast and large-scale
entanglement generation. We propose and analyze a scheme for
quantum logic control and measurement-based state preparation in a hybrid platform of polar molecules and neutral atoms. The method leverages fast, high-fidelity atom-molecule gates and high-fidelity atomic ancilla measurements to overcome the common challenges in molecule-only platforms, while preserving their diverse structural advantages. The proposed atom-molecule controlled-phase gate is based on resonant dipole-dipole exchange between a molecular rotational transition and an atomic Rydberg transition, rendering it three orders of magnitude faster than any direct molecule-molecule entangling gate. We further study several applications of our scheme including the preparation of molecular GHZ states for
quantum enhanced precision measurements, the preparation of exotic molecular qudit states with topological order, and measurement-altered criticality. Our scheme is applicable to any polar molecule. It expands the paradigm of
quantum logic control and paves the way to large-scale molecular entangled states. More generally, it highlights a concrete hybrid
quantum system in which each
qubit is utilized in an optimal way and where the measurement-based approach can yield a significant advantage in near-term devices.
Read the full abstract ▾
All authors Chi Zhang, Sara Murciano, Nathanan Tantivasadakarn, Ran Finkelstein
Atomic Physics
Sympathetic cooling of charged particles in Penning traps using electron cyclotron radiation
Jost Herkenhoff, Jonathan Notter and Klaus Blaum
We present a new technique for cooling arbitrary charged particles in a Penning trap by utilizing self-cooled electrons stored in a separate, macroscopically distant Penning trap as the cooling medium. The electrons decay predominantly to their motional ground state by emission of cyclotron radiation, which results in extremely low temperatures in the realm of single-digit
quantum numbers in the motional degrees of freedom of the sympathetically cooled particle species. This opens up an exciting new frontier of tests of fundamental physics in Penning traps. This article provides a conceptual overview as well as a
quantum-mechanical description of the involved cooling dynamics. The first implementation of this technique is currently being realized at the dedicated ELCOTRAP experiment at the Max Planck Institute for
Nuclear Physics, which introduces special features for a quick iterative technical development cycle. Its current status, first results from commissioning, and future prospects will be presented.
Read the full abstract ▾
Atomic Physics · Cross-listed from cond-mat.quant-gas
Shift of the Bose-Einstein condensation transition in the presence of a second atomic species
Pedro M. Gaspar, Vanderlei S. Bagnato and Patricia C. M. Castilho
Atomic interactions play an important role in the properties of ultracold atomic gases. In single component bosonic systems, its effect is already present at the critical point for the Bose-Einstein condensate phase transition by shifting it to lower temperatures as a consequence of effective repulsion between the atoms. When considering atomic bosonic mixtures, interesting effects arise from the competition between intra- and interspecies interactions such as the miscible-immiscible phase transition and the particular case of self-bounded
quantum droplets. In such a scenario, it is natural to expect that these interactions will also affect the critical point of each species composing the mixture. In this paper, we obtain analytical expressions for the critical temperature shift of the phase transition to a Bose-Einstein condensate in the presence of a second species. We treat differently the cases in with the second species is above or below its own critical temperature and apply the obtained relations to the case of a $^{23}$Na-$^{39}$K bosonic mixture which can be realized in current running experimental setups. Our findings can be easily extended to other atomic mixtures trapped by arbitrary conservative traps.
Read the full abstract ▾
Fluid Dynamics
On the rheoscopic measurement of turbulent decay in wall-bounded flows
Tao Liu, Victoria Nicolazo-Crach, Ramiro Godoy-Diana et al. (+2 more)
Quench experiments where the flow passes from a fully turbulent state to a laminar state by an abrupt decrease in the flow Reynolds number ($Re$) have been extensively studied in the literature to quantify the turbulent-laminar transition process in wall-bounded flows. Measurements have been classically made using rheoscopic fluid visualisations, which make turbulent coherent structures easily identifiable, allowing for quantification of the
evolution of a turbulent fraction – the percentage of a given observation window where
turbulence is deemed active by the presence of coherent structures, such as streamwise
vortices called rolls, and modulations of the streamwise velocity fluctuations called streaks. Decay characteristic times of these structures have therefore been extensively measured. However, owing to the nature of visualization based techniques, only a single decay time is typically extracted, whereas measurements of the velocity field can reveal distinct decay times associated with different velocity or kinetic energy components. As a result, the physical meaning of the decay time inferred from visualization alone is not straightforward. The goal of the present paper is to perform such a comparison quantitatively, using particle image velocimetry (PIV) measurements and rheoscopic fluid visualisations in the same setup: a Couette-Poiseuille experiment. We observe via PIV different characteristic times of decay for streamwise (streaks) and spanwise (rolls) velocity fluctuations. We show that the characteristic time of decay of the turbulent fraction observed by visualisation is close to the decay of the streaks.
Read the full abstract ▾
All authors Tao Liu, Victoria Nicolazo-Crach, Ramiro Godoy-Diana, José Eduardo Wesfreid, Benoît Semin
Optics
The Refractive Index of Gallium Antimonide
Ulrich Galander, Nicolas Huwyler, Mirela Encheva et al. (+2 more)
Gallium antimonide (GaSb) is a key material for near- and mid-infrared photonics, enabling high-performance
laser architectures and detectors. Design and simulation of such devices depend on accurate optical material data, especially the complex refractive index $n^*_{\text{GaSb}} = n_{\text{GaSb}} +ik_{\text{GaSb}}$, consisting of the real part $n_{\text{GaSb}}$ (refractive index) and the imaginary part $k_{\text{GaSb}}$ (extinction coefficient). However, GaSb refractive index values are based either on theoretical models, typically informed by legacy experimental data, or on experimental measurements without quantified uncertainties. This limits their reliability for state-of-the-art devices. Here, we present measurement results of $n^*_{\text{GaSb}}$ in the near- to mid-infrared range from \SIrange{1}{3.1}{\micro \metre} with a relative uncertainty <\num{7.8e-5} for $n_{\text{GaSb}}$, and <\num{2.0e-3} for $k_{\text{GaSb}}$. As a side result of our method, we also report $n_{\text{AlAsSb}}$ for aluminium arsenide antimonide ($\mathrm{AlAs_{0.08}Sb_{0.92}}$) with a relative uncertainty <\num{3.9e-4}. Our results are based on two complementary measurements on a GaSb/AlAsSb-based heteroepitaxial structure under controlled environmental conditions: photometric transmission and layer-thickness analysis by cross-sectional scanning electron microscopy. We simultaneously retrieve the refractive indices of the two materials by fitting a Sellmeier equation and a theoretical dispersion model by Djurišić et al.~\cite{djurisic_modeling_2000}. The uncertainties of $n^*_{\text{GaSb}}$ and $n_{\text{AlAsSb}}$ are quantified using a Monte Carlo-based approach. Our results provide accurate complex refractive index values for GaSb, which are vital to advance photonics-related technologies in the near- and mid infrared spectral region.
Read the full abstract ▾
All authors Ulrich Galander, Nicolas Huwyler, Mirela Encheva, Matthias Golling, Oliver H. Heckl
Instrumentation and Detectors
R&D Efforts in Cherenkov Imaging Technologies for Particle Identification in Future Experiments
Chandradoy Chatterjee
Cherenkov imaging detectors will continue to play a central role for particle identification in future particle and
nuclear physics experiments. Growing demands on momentum coverage, timing precision, radiation tolerance, and sustainability have driven extensive R&D in detector concepts, radiator materials, and
photon sensors. This article reviews recent efforts, focusing on experiments leading advances in sensor technology, radiator materials, and the exploitation of Cherenkov
photon timing to push PID limits, while highlighting synergies across experiments in addressing common challenges.
Read the full abstract ▾
Optics · Cross-listed from cond-mat.mes-hall
Subcycle videography of lightwave-driven Landau-Zener-Majorana transitions in graphene
Vincent Eggers, Giacomo Inzani, Manuel Meierhofer et al. (+14 more)
Strong light fields have unlocked previously unthinkable possibilities to tailor coherent electron trajectories, engineer band structures and shape emergent phases of matter all-optically. Unravelling the underlying
quantum mechanisms requires a visualisation of the lightwave-driven electron motion directly in the band structure. While photoelectron momentum microscopy has imaged optically excited electrons averaged over many cycles of light, actual subcycle band-structure videography has been limited to small electron momenta. Yet lightwave-driven elementary processes in
quantum materials often occur throughout momentum space. Here, we introduce attosecond-precision, subcycle band-structure videography covering the entire first Brillouin zone (BZ) and visualize one of the most fundamental but notoriously elusive strong-field processes: non-adiabatic Landau-Zener-Majorana (LZM) tunnelling. The interplay of field-driven acceleration within the Dirac-like band structure of
graphene and periodic LZM interband tunnelling manifest in a coherent displacement and distortion of the momentum distribution at the BZ edge. The extremely non-thermal electron distributions also allow us to disentangle competing scattering processes and assess their impact on coherent electronic control through electron redistribution and thermalization. Our panoramic view of strong-field-driven electron motion in
quantum materials lays the foundation for a microscopic understanding of some of the most discussed light-driven phenomena in condensed matter physics.
Read the full abstract ▾
All authors Vincent Eggers, Giacomo Inzani, Manuel Meierhofer, Lasse Münster, Jakob Helml, Robert Wallauer, Sarah Zajusch, Suguru Ito, Leon Machtl, Hao Yin, Christian Kumpf, François C. Bocquet, Changhua Bao, Jens Güdde, F. Stefan Tautz, Rupert Huber, Ulrich Höfer
Instrumentation and Detectors
Sub-eV uncertainties on gamma-ray energies using a magnetic microcalorimeter - Potential new reference energies
Matias Rodrigues, Mostafa L. Zahir, Martin Loidl et al. (+6 more)
We present new measurements of 27 gamma-ray energies ranging from 14 keV to 136 keV, obtained using
magnetic microcalorimeters for energy-dispersive spectrometry. The spectrometer has eight pixels and achieves a high energy resolution between 15 eV and 30 eV across the entire energy range. It faces a cryogenic source sampler with four movable sources, each containing a mixture of radionuclides, including $^{169}\mathrm{Yb}$ and $^{57}\mathrm{Co}$. Four gamma-ray lines from $^{169}\mathrm{Yb}$and one from 57Co were used to calibrate the spectrometer and correct for its non-linearity in the energy range 14 keV - 130 keV. The gamma-ray energies, emitted through the decay of $^{57}\mathrm{Co}$, $^{109}\mathrm{Cd}$, $^{133}\mathrm{Ba}$, $^{153}\mathrm{Gd}$, $^{154}\mathrm{Eu}$, $^{155}\mathrm{Eu}$, $^{169}\mathrm{Yb}$, $^{170}\mathrm{Tm}$, $^{210}\mathrm{Pb}$, $^{239}\mathrm{Np}$, $^{241}\mathrm{Am}$ and $^{243}\mathrm{Am}$, have been reassessed. This work significantly reduces the uncertainties upon previously reported gamma energies obtained by energy-dispersive spectrometry using
semiconductor detectors: the lowest absolute uncertainty achieved is 0.13 eV at 105.3 keV, which corresponds to a relative uncertainty of 1.3 ppm. With respect to the available literature, among the 27 measured gamma-ray lines, the uncertainties of 10 energies were reduced by a factor of 5, while those of 4 additional energies were reduced by more than one order of magnitude.
Read the full abstract ▾
All authors Matias Rodrigues, Mostafa L. Zahir, Martin Loidl, Lucille Chambon, Quentin Drenne, Michael Müller, Sebastian Kempf, Etienne Nigron, Ferid Haddad
Computational Physics
Estimating Full Path Lengths and Kinetics from Partial Path Transition Interface Sampling Simulations
Wouter Vervust, Elias Wils, Sina Safaei et al. (+2 more)
Assessing the time scale of biological processes using molecular dynamics (MD) simulations with sufficient statistical accuracy is a challenging task, as processes are often rare and/or slow events, which may extend largely beyond the time scale of what is accessible with modern day high performance computational infrastructure. Recently, the replica exchange partial path transition interface sampling (REPPTIS)
algorithm was developed to study rare and slow events involving metastable states along their reactive pathways. REPPTIS is a path sampling method where paths are cut short to reduce the computational cost, while combining this with the efficiency offered by replica exchange between the partial path ensembles. However, REPPTIS still lacks a formalism to extract time-dependent properties, such as mean first passage times, fluxes, and rates, from the short partial paths. In this work, we introduce a Markov state model (MSM) framework to estimate full path lengths and kinetic properties from the overlapping partial paths generated by REPPTIS. The framework results in newly derived closed formulas for the REPPTIS crossing probability, mean first passage times (MFPTs), flux, and rate constant. Our approach is then validated using simulations of Brownian and Langevin particles on a series of one-dimensional potential energy profiles as well as the dissociation of KCl in solution, demonstrating that REPPTIS accurately reproduces the exact kinetics
benchmark. The MSM framework is further applied to the trypsin-benzamidine complex to compute the dissociation rate as a test case of a biological system, albeit the computed rate underestimates the experimental value. In conclusion, our MSM framework equips REPPTIS simulations with a robust theoretical and practical foundation for extracting kinetic information from computationally efficient partial paths.
Read the full abstract ▾
All authors Wouter Vervust, Elias Wils, Sina Safaei, Daniel T. Zhang, An Ghysels
Fluid Dynamics · Cross-listed from cond-mat.soft
Nanoscale Electroviscous Lift Force
Hao Zhang, Zaicheng Zhang, Thomas Guérin et al. (+1 more)
About forty years ago, it was predicted that a charged particle, moving parallel to a charged wall in an electrolyte, should experience a lift force that, contrarily to electrostatic forces, is not screened at large distances. Up to now, such electroviscous lift force has not been directly measured. Here, we use Atomic Force Microscopy to directly measure the electroviscous lift force and quantify its dependency with the distance to the wall, the translation velocity or the particle's size. Observing that existing theories exhibit large discrepancies with our experimental observations, we develop an analytical approach combining lubrication theory to a previously introduced formalism for small screening length. The experimentally observed lift forces are in good agreement with our theoretical predictions and reveal, for the first time, a saturation of the lift force for increasing velocities. Altogether, our results characterize, through direct measurements and analytical approach, the properties of electroviscous forces between charged particles in viscous electrolytes in non-
equilibrium conditions.
Read the full abstract ▾
All authors Hao Zhang, Zaicheng Zhang, Thomas Guérin, Abdelhamid Maali
Atomic Physics · Cross-listed from quant-ph
Towards Trapped-Ion Thermometry Using Cavity-Based EIT
Abhijit Kundu, Vijay Bhatt and Arijit Sharma
We present a technique for measuring ion temperature using cavity-based electromagnetically induced transparency (EIT) applicable for cavity QED systems. This method enables efficient extraction of the ion's
phonon occupation number following sub-Doppler cooling close to the motional ground state. The proposed method requires operation in the resolved-sideband regime, where individual motional states can be selectively addressed for all relevant transitions either by selecting appropriate energy levels for the three-level system or by employing strong confinement with high secular frequencies ($\sim 10 MHz$). It relies on monitoring the cavity probe transmission while scanning the probe
laser frequency to establish cavity-induced EIT using a control beam, thereby significantly simplifying the measurement procedure. We establish a theoretical model that demonstrates the influence of the thermal state of the trapped ion vis-à-vis the EIT linewidth measured. We show through numerical simulations how the cavity-induced EIT transmission may be used as a thermometry tool to deduce the ion temperature as well as its motional state in the sub-Doppler cooling regime, even for systems that are in the weak coupling regime.
Read the full abstract ▾
Plasma Physics
Quantitative 3D non-linear simulations of shattered pellet injection in ASDEX Upgrade using JOREK
W. Tang, M. Hoelzl, P. Heinrich et al. (+16 more)
Shattered pellet injection (SPI) as primary mitigation method for major disruptions in ITER has a large parameter space available for optimization including the total amount of injected material, the size of the individual pellet fragments, the material composition, and the timing of multiple injections. This flexibility needs to be exploited to simultaneously minimize thermal heat loads, electromagnetic vessel forces, and formation of relativistic electrons and their impacts on
plasma facing components. In this article, we apply 3D non-linear magnetohydrodynamic modelling to SPI experiments in the ASDEX Upgrade tokamak, going beyond our previous work [Tang et al Nucl. Fusion 65 116003 (2025)] by resolving some discrepancies between simulations and experiment and thus opening the path to quantitative model validation and experiment interpretation. The key element that enables the transition from merely qualitative comparisons to quantitatively reliable predictions of the thermal quench duration and the radiation fraction is the incorporation of a simplified treatment of parallel heat-flux limiting. The work increases the confidence of matching the key processes of disruption mitigation with this high fidelity modelling in view of predictive studies for ITER.
Read the full abstract ▾
All authors W. Tang, M. Hoelzl, P. Heinrich, D. Hu, F. J. Artola, P. de Marne, M. Dibon, M. Dunne, O. Ficker, P. Halldestam, S. Jachmich, M. Lehnen, E. Nardon, G. Papp, A. Patel, U. Sheikh, the ASDEX Upgrade Team, the EUROfusion Tokamak Exploitation Team, the JOREK Team
Physics and Society
Forecasting emergency department visits in the reference hospital of the Balearic Islands: the role of tourist and weather data
Paride Crisafulli, Angel del Río Mangada, Juan José Segura Sampedro et al. (+3 more)
Accurate
forecasting of patient arrivals at emergency departments (EDs) is vital for efficient resource allocation and high-quality patient care. In this study we investigate the relevance of exogenous variables, namely tourism, weather, calendar and demographic variables, in
forecasting ED visits in the reference hospital in Palma de Mallorca, a city with significant seasonal population fluctuations due to tourism. Using a machine learning approach, we develop a model that predicts ED visits based solely on these exogenous variables. We test different machine learning
algorithms (random forests, support vector machines, and feedforward neural networks) with different combinations of input variables and compare their symmetric mean average percentage errors (SMAPEs). Our findings reveal that calendar information, resident, and tourist population data are statistically significant for the accuracy of the predictions, while the addition of weather data does not provide any further improvement. Comparison of non-time-series with time-series prediction models reveals that the latter provide better accuracy for short prediction horizons (e.g. shorter than a week). Furthermore, time-series models become less or equally accurate to models relying only on exogenous variables for long prediction horizons (e.g. fortnight or month). Our study highlights the importance of carefully selecting predictive variables to ensure short- and long-term, robust and reliable forecasts. This demonstrates that, despite their lower complexity, non-time-series models with well-chosen input variables can be as effective as time-series models when predicting for long time horizons.
Read the full abstract ▾
All authors Paride Crisafulli, Angel del Río Mangada, Juan José Segura Sampedro, Claudio R. Mirasso, Raúl Toral, Tobias Galla
Medical Physics
A Wavefield Correlation Approach to Improve Sound Speed Estimation in Ultrasound Autofocusing
Louise Zhuang, Samuel Beuret, Ben Frey et al. (+4 more)
In pulse-echo ultrasound, aberration often degrades image quality when beamforming does not account for wavefront distortions. To address this issue, local sound speed
estimators have been developed in the past decade for distributed aberration correction. Recently, methods based on iterative optimization have improved sound speed accuracy with respect to earlier approaches. However, the accuracy of these newer methods is limited by media with reverberation clutter and by the straight-ray model of wave propagation. To address these challenges, we propose using wavefield correlation (WFC) beamforming when performing sound speed optimization. WFC, an ultrasound adaptation of reverse time migration, correlates simulated forward-propagated transmit wavefields and backwards-propagated receive wavefields in order to reconstruct images. This process more accurately models wave propagation in heterogeneous media and can decrease diffuse clutter due to its spatiotemporal matched filtering effect. We implement herein a WFC beamformer using an auto-differentiation software and estimate the sound speed map by optimizing a regularized common-midpoint phase focusing criterion using gradient descent. This approach is compared to a previous method relying on delay and sum (DAS) with straight-ray time delay calculations on a variety of simulated, phantom, and in vivo data with large sound speed variations and clutter. Results show that using WFC decreases sound speed estimation error, leading to improvements in resolution and contrast in the corrected image. In particular, these promising results have potential to improve pulse-echo imaging for challenging clinical scenarios.
Read the full abstract ▾
All authors Louise Zhuang, Samuel Beuret, Ben Frey, Saachi Munot, Walter Simson, Dongwoon Hyun, Jeremy J. Dahl
Plasma Physics
Resonant Excitation of Surface Plasmon for Wakefield Acceleration by Beating GW Lasers on Smooth Cylindrical Surface
Bifeng Lei, Hao Zhang, Alexandre Bonatto et al. (+5 more)
We present a theoretical and numerical study of resonant surface-plasmon (SP) excitation driven by the beating of two co-propagating
laser pulses on a smooth cylindrical
plasma-
vacuum interface. Analytical expressions for the SP dispersion relation, field amplitude,
geometric coupling factor, and resonance conditions are derived and validated by fully three-dimensional particle-in-
cell simulations. We reveal that
curvature-induced
geometric effects can substantially modify the SP dispersion and enable resonant matching by
laser beat waves. This is inaccessible in planar geometries or with a single
laser. Under matched resonance conditions, a high-amplitude SP-based wakefield can be generated by a few gigawatt
lasers, placing this mechanism within reach of state-of-the-art fibre
lasers. It therefore opens a route toward portable
laser-driven
plasma wakefield accelerators.
Read the full abstract ▾
All authors Bifeng Lei, Hao Zhang, Alexandre Bonatto, Bin Liu, Javier Resta-Lopez, Matt Zepf, Guoxing Xia, Carsten Welsch
Applied Physics
Model-based upscaling of vanadium redox flow battery systems: engineering challenges and solutions
B. Sziffer and V. Jozsa
Large-scale energy storage has become an inevitable solution for integrating stochastically available renewable energy sources into the electric grid. Vanadium redox flow batteries offer a viable option among other technologies, due to their long lifetime and independently scalable output power and capacity. The electrolyte temperature should be maintained within the range of 5-40 Celsius for safe operation; therefore, a thermal management system is necessary, which affects battery efficiency. The study presents a detailed, containerized battery model with a hybrid thermal management system that considers thermal radiation and real ambient temperatures. A total of 180 configurations were investigated in 10 cases, ranging from 4 to 400 kW, with 18 different discharging current-
cell number ratios in each case, including multistack arrangements. Current-dependent ohmic losses influence the electric efficiency, which increases from a minimum of 68% to 89% in low-current configurations. However, the net system efficiency ranges between 43% and 66% due to the self-consumption of pumps, the inverter, and the thermal management system. In addition to the detailed efficiency analysis, a comprehensive investigation of thermal processes is provided in terms of the current-
cell number ratio and output power, which is crucial for designing thermal management systems and sizing batteries.
Read the full abstract ▾
Applied Physics · Cross-listed from quant-ph
Design and Operation of Wafer-Scale Packages Containing >500 Superconducting Qubits
Oscar W. Kennedy, Waqas Ahmad, Robert Armstrong et al. (+14 more)
Packages capable of supporting large arrays of high-coherence superconducting
qubits are vital for the realisation of fault-tolerant
quantum computers and the necessary high-throughput metrology required to optimise fabrication and manufacturing processes. We present a wafer-scale packaging architecture supporting over 500
qubits on a single 3-inch die. The package is engineered to suppress parasitic RF modes, and to mitigate material loss through simulation-informed design while managing differential thermal contraction to ensure robust operation at millikelvin temperatures. System-level heat-load calculations from a large wiring payload show this package may be operated in commercial dilution refrigerators. Measurements of the
qubits loaded into the package show median $T_1$, $T_{2e} \sim 100~\mu$s ($\sim$100
qubits) alongside readout with median fidelity of 97.5% (54
qubits) and a median
qubit temperature of 36 mK (54
qubits). These results validate the performance of these packages and demonstrate that large-scale integration can be achieved without compromising device performance. Finally, we highlight the utility of these packages as a tool for high throughput feedback on
qubit figures of merit over large sample sizes, allowing identification of performance outliers in the tails of the coherence distribution, a critical capability for informing fabrication and manufacture of high-quality
quantum qubits and
quantum processors.
Read the full abstract ▾
All authors Oscar W. Kennedy, Waqas Ahmad, Robert Armstrong, Amir Awawdeh, Anirban Bose, Kevin G. Crawford, Sergey Danilin, William D. David, Hamid El Maazouz, Darren J. Hayton, George B. Long, Alexey Lyapin, Scott A. Manifold, Kowsar Shahbazi, Ryan Wesley, Evan Wong, Connor D. Shelly
Fluid Dynamics
Stokes flows in a sessile hemispherical drop due to evaporation and surface tension gradient
Peter Lebedev-Stepanov
Viscous hydrodynamic flow in a small, slowly evaporating, sessile hemispherical droplet with a pinned contact line is considered. Analytical solutions are obtained for the Deegan outward flow, which is responsible for the coffee ring effect, as well as the Marangoni flow excited by a surface tension gradient. It is assumed that the surface tension gradient may be caused by anisotropic cooling of droplet surface or other factors, such as nonuniform illumination of an optically active surfactant. Two main types of boundary conditions, no-slip and full-slip, are considered in describing the flow-substrate interaction. It is shown that under the no-slip condition, there is a rigid relationship between the evaporation rate and the surface tension gradient, which imposes strict requirements on the temperature regime inside the droplet. This result offers a new
vision of the critical Marangoni number, which describes the threshold for the transition of an evaporating droplet from capillary flow to developed Marangoni convection. The results of this work may attract the
attention of experimenters to the study of the sensitivity of viscous flow in an evaporating droplet to the
liquid-substrate boundary conditions, especially if the system under consideration passes into the Marangoni regime, when the no-slip condition changes to a partial or full slip condition due to the increase in viscous shear stress near the substrate.
Read the full abstract ▾
Accelerator Physics
Demonstration of ultra-low emittance beams in a kHz laser wakefield accelerator and application to electron diffraction
J. Monzac, S. Smartsev, J. Huijts et al. (+12 more)
We present a compact, cost-effective method for measuring the emittance of kHz-repetition-rate
laser-wakefield accelerated electron beams using a permanent solenoid. The measured normalized emittance, $\epsilon_n = 124\,\mathrm{nm \cdot rad}$ ($\simeq 0.04 \pi\,\mathrm{mm \cdot mrad}$) at $2.7\,$MeV, is comparable to that of ultra-low emittance radiofrequency guns used for electron diffraction. Leveraging this low emittance, we successfully applied the electron beam to electron diffraction. We demonstrate diffraction images obtained from a single-
crystal silicon nanomembrane sample, clearly resolving diffraction peaks across multiple orders.
Read the full abstract ▾
All authors J. Monzac, S. Smartsev, J. Huijts, A. Vernier, I. A. Andriyash, V. Tomkus, V. Girdauskas, G. Raciukaitis, M. Mackeviciute, V. Stankevic, A. Cavagna, J. Kaur, A. Kalouguine, R. Lopez-Martens, J. Faure
Applied Physics
Electro-thermal quench in metal-insulated nested REBCO coils for magnets over 40 T
Anang Dadhich, Philippe Fazilleau and Enric Pardo
Superconducting high field magnets have the capability to generate over 40 T, with multiple existing practical applications globally. However, at such high
magnetic fields, these magnets are prone to rapid electrothermal quench which can affect the continuous operation of such magnets. A nested stack configuration, with multiple HTS inserts inside a LTS outsert, can be used for better thermal stability and compact design. We have performed detailed multiphysics quench analysis of such a nested stack high field magnet design under SuperEMFL project using our in-house software, which considers screening currents. Through various case studies, we have identified various weak spots in such a magnet, where thermal quench can be the most detrimental for magnet operation, and various ways are suggested to overcome this important issue.
Read the full abstract ▾
Computational Physics
T-matrix scattering formalism for electron-beam spectroscopy
P. Elli Stamatopoulou, Ulrich Hohenester and Carsten Rockstuhl
Advanced computational tools that describe the interaction of electrons with structured nanophotonic devices are crucial for theoretical predictions, specific design tasks, and the interpretation of experimental results. These tools open the door to a systematic exploration of light-matter interactions in complex photonic environments and support the development of next-generation nanophotonic platforms. Here, we report on the implementation of electron-beam spectroscopy in a T-
matrix-based scattering formulation. Such a framework is quite versatile in predicting the electromagnetic response of complex photonic materials composed of periodically or aperiodically arranged individual scatterers. By extending this formalism to describe interactions with fast electrons, we provide a fast and accurate numerical tool for simulating cathodoluminescence (CL) and electron energy-loss spectroscopy (EELS) measurements. The desired functionalities are implemented in treams_ebeam, an extension of the existing software suite treams for electromagnetic scattering computations, available at https://github.com/tfp-photonics/treams_ebeam. We demonstrate the implementation details on a carefully selected set of problems, including single scatterers of various shapes and materials, a periodic chain of elliptical nanodisks, and a finite cluster of nanospheres arranged in a two-dimensional (2D)
lattice. By uniting fast-electron physics with advanced scattering theory, our framework unlocks new possibilities for designing, understanding, and engineering next-generation nanoscale light-matter interactions.
Read the full abstract ▾
Optics
Torus-Projected Electromagnetic Wormholes Enabled by Anisotropic Singularity Reconstruction of Metamaterials
Junke Liao, Wen Xiao, Yixiao Ge et al. (+1 more)
Transformation optics uses coordinate mappings to emulate curved geometries and control electromagnetic fields. However, existing approaches primarily focus on
geometric deformation while offering limited control over the global
topology of the resulting optical space. Here we introduce a
torus projection combined with a conformal mapping to construct a wormhole-like virtual optical geometry, providing a controllable route to manipulate virtual space
topology within transformation optics. By tuning a single
torus parameter, the virtual-space refractive index switches between isotropic and anisotropic forms, driving a transition from a disconnected horn-
torus geometry to a connected ring-
torus geometry in virtual space. In physical space, this virtual-space
topology transition gives rise to switchable black-hole-like trapping, field redistribution, and geometry-controlled wave responses. Our results demonstrate how refractive-index anisotropy governs singularity structure and
topology in transformation optics, while also suggesting practical functionalities including beam splitting, absorbing-like switching, and
curvature-assisted focusing.
Read the full abstract ▾
All authors Junke Liao, Wen Xiao, Yixiao Ge, Huanyang Chen