Instrumentation and Detectors
Measurements of efficiency, timing and response to irradiation for direct detection of charged particles with SiPMs
F. Carnesecchi, B. Sabiu, B.R. Achari et al. (+47 more)
In this paper the efficiency of direct charged particle detection with different Silicon PhotoMultiplier (SiPM) sensors has been measured to be close to 100%. Time resolution of about 20 ps has also been confirmed for sensors with an active area of around 3x3 mm$^\text{2}$ and a single-
cell area of 40 $\mu$m$^\text{2}$. In addition, the SiPM performance after irradiation, in terms of timing response and dark count rate, has been evaluated for sensors with a 1x1 mm$^\text{2}$ area, demonstrating that SiPMs can maintain excellent timing capabilities and a low dark count rate when an appropriate threshold is applied to the signal.
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All authors F. Carnesecchi, B. Sabiu, B.R. Achari, N. Agrawal, A. Alici, P. Antonioli, S. Arcelli, C. Baldanza, F. Bellini, S. Bufalino, D. Cavazza, L. Cifarelli, G. Clai, M. Colocci, S. Durando, F. Ercolessi, G. Fabbri, D. Falchieri, C. Ferrero, A. Ficorella, U. Follo, M. Garbini, S. Geminiani, G. Gioachin, A. Gola, D. Hatzifotiadou, A. Khuntia, I. Lax, M. Maestrelli, A. Margotti, G. Malfattore, R. Nania, F. Noferini, L. Parellada-Monreal, M. Penna, O. Pinazza, R. Preghenella, M. Razza, R. Ricci, L. Rignanese, A. Rivetti, G. Romanenko, N. Rubini, E. Rovati, E. Scapparone, G. Scioli, S. Strazzi, S. Tomassini, C. Veri, A. Zichichi
Computational Physics
Integrated photonic multigrid solver for partial differential equations
Timoteo Lee, Frank Brückerhoff-Plückelmann, Jelle Dijkstra et al. (+2 more)
Solving partial differential equations is crucial to analysing and predicting complex, large-scale physical systems but pushes conventional high-performance computers to their limits. Application specific photonic processors are an exciting computing paradigm for building efficient, ultrafast hardware accelerators. Here, we investigate the synergy between multigrid based partial differential equations solvers and low latency photonic
matrix vector multipliers. We propose a mixed-precision photonic multigrid solver, that offloads the computationally demanding smoothening procedure to the optical domain. We test our approach on an integrated photonic accelerator operating at 2 GSPS solving a Poisson and Schrödinger equation. By offloading the smoothening operation to the photonic system, we can reduce the digital operation by more than 80%. Finally, we show that the photonic multigrid solver potentially reduces digital operations by up to 97 % in
lattice quantum chromodynamics (LQCD) calculations, enabling an order-of-magnitude gain in computational speed and efficiency.
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All authors Timoteo Lee, Frank Brückerhoff-Plückelmann, Jelle Dijkstra, Jan M. Pawlowski, Wolfram Pernice
Chemical Physics · Cross-listed from cond-mat.mtrl-sci
Polaronic-Distortion-Driven Enhancement of Excitonic Auger Recombination in ZnO Nanoparticles
Fuyong Hua, Zheng Zhang, Zhong Wang et al. (+5 more)
The surface effect and
quantum confinement render nanomaterials the optoelectronic properties more susceptible to nonradiative processes than their bulk counterparts. These nonradiative processes usually contain a series of interwoven and competing sub-processes, which are challenging to disentangle. Here, we investigate the structural origin of Auger recombination in ZnO nanoparticles using transient absorption spectroscopy and ultrafast electron diffraction. The photogenerated hot holes are captured by oxygen vacancies through an Auger mechanism, inducing significant local structural distortions around the oxygen vacancy and its neighboring zinc tetrahedron on a sub-picosecond timescale. The recombination of trapped holes accelerates the
lattice thermalization and stabilizes the formed small hole polarons. Subsequently, the recombination of localized polarons forms a confined
exciton-polaron complex that may account for the long-lived (>7 ns) visible luminescence observed in ZnO nanoparticles. Our findings are potentially applicable to other transition metal
oxide nanomaterials, bringing insights for the optimization of their functional properties.
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All authors Fuyong Hua, Zheng Zhang, Zhong Wang, Yang Liu, Changchang Gong, Chunlong Hu, Yinhua Zhou, Wenxi Liang
Medical Physics
Multiplexed Catheter-Integrated Pressure Sensing System for Endoluminal Interventions
Xiaotong Guo, Qindong Zheng, Jinshi Zhao et al. (+2 more)
Advances in flexible catheters pave the way for minimally invasive diagnosis and treatment of luminal organs and tubular structures through endoluminal interventions. A key challenge is in establishing non-constraining pressure monitoring at the interfaces between medical catheters and intraluminal anatomy exhibiting curvilinear contours, structural variability, and time-dependent physiological motion. This work presents a scalable and multi-purpose pressure sensing system for multidirectional monitoring of tissue interactions, establishing a robust solution for deploying diagnostic and therapeutic instruments in various types of endoluminal interventions. This approach provides an integrated system encompassing pressure sensors, catheters, and signal acquisition devices. A poly (vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) film is miniaturized and configured into a multiplexed piezoelectric-based pressure sensor, providing flexibility and scalability in conforming to medical catheters with curved surfaces. The catheter is fabricated with a cost-effective and highly scalable fiber drawing technology, establishing a means of fast prototyping catheters with bespoke structures for sensor integration and medical instrument integration. The system achieves enhanced pressure detection sensitivity and a comparable sensing range, compared with state-of-the-art catheter-integrated sensors. Through in-vitro phantom studies, the system performs precise multi-directional sensing within various clinical endoluminal scenarios, showing its potential in digitalizing tissue interactions during endoluminal interventions.
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All authors Xiaotong Guo, Qindong Zheng, Jinshi Zhao, Bing Li, Eric Morgan Yeatman
Atmospheric and Oceanic Physics · Cross-listed from astro-ph.EP
Onset of habitable conditions on the Hadean Earth set by feedback between tides and greenhouse forcing
Marijn R. van Dijk, Harrison Nicholls and Tim Lichtenberg
In the aftermath of the Moon-forming
giant impact, the Hadean Earth's mantle and surface crystallized from a global magma ocean blanketed by a dense volatile-rich atmosphere. While prior studies have explored the thermal
evolution of such early Earth scenarios under idealized, oxidizing conditions, the potential feedback between
tidal heating driven by Earth–Moon orbital forcing and variable redox scenarios have not yet been explored in detail. We investigate whether
tidal heating could have prolonged this early magma ocean phase and supported quasi-steady state epochs of global radiative
equilibrium: periods of thermal balance between outgoing radiation and interior heat flux. Using the $\texttt{PROTEUS}$ simulation framework, we simulate Earth's early
evolution under a range of plausible
tidal power densities, oxygen fugacities, and volatile inventories. Our results suggest that feedback between
tidal heating and atmospheric forcing can induce substantial variation in magma ocean lifetimes, from $\sim$30 Myr up to $\sim$500 Myr, sensitive to interior redox conditions. Global radiative
equilibrium epochs commonly arise across this range, lasting from $\sim$2 to $\sim$320 Myr, and typically occur from 24 Myr after the Moon-forming impact. Under oxidizing conditions, late-stage H$_2$O degassing promotes melt retention and sustained heating due to its significant contribution to greenhouse forcing. Weak tides increase the atmospheric abundance of H$_2$S and NH$_3$ and deplete CO. Therefore, the feedback between tides and atmospheric forcing induces a disequilibrium signature in the magma ocean atmosphere.
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Chemical Physics
Design, Assessment, and Application of Machine Learning Potential Energy Surfaces
Valerii Andreichev, Sena Aydin, Kai Töpfer et al. (+2 more)
Potential Energy Surfaces (PESs) are an indispensable tool to investigate, characterise and understand chemical and biological systems in the gas and condensed phases. Advances in Machine Learning (ML) methodologies have led to the development of Machine Learned Potential Energy Surfaces (ML-PES) which are now widely used to simulate such systems. The present work provides an overview of concepts, methodologies and recommendations for constructing and using ML-PESs. The choice of topics is focused on practical and recurrent issues to conceive and use such model. Application of the principles discussed are illustrated through two different systems of biomolecular importance: the non-reactive dynamics of the Alanine-Lysine-Alanine tripeptide in gas and solution phases, and double
proton transfer reactions in DNA base pairs.
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All authors Valerii Andreichev, Sena Aydin, Kai Töpfer, Markus Meuwly, Luis Itza Vazquez-Salazar
Computational Physics · Cross-listed from cond-mat.str-el
Exploring the limit of the Lattice-Bisognano-Wichmann form describing the Entanglement Hamiltonian: A quantum Monte Carlo study
Siyi Yang, Yi-Ming Ding and Zheng Yan
As a powerful theoretical construct, the
entanglement Hamiltonian (EH) encapsulates the essential
entanglement properties of a
quantum many-body system. From the EH, one can extract a variety of
entanglement quantities, such as
entanglement entropies, negativity, and the
entanglement spectrum. However, its general analytical form remains largely unknown. While the Bisognano-Wichmann
theorem gives an exact EH form for Lorentz-invariant field theories, its validity on
lattice systems is limited, especially when Lorentz invariance is absent. In this work, we propose a general scheme based on the
lattice-Bisognano-Wichmann (LBW) ansatz and multi-replica-trick
quantum Monte Carlo methods to numerically reconstruct the
entanglement Hamiltonian in two-dimensional systems and systematically explore its applicability to systems without translational invariance, going beyond the original scope of the
primordial Bisognano-Wichmann
theorem. Various
quantum phases–including gapped and gapless phases, critical points, and phases with either discrete or continuous
symmetry breaking–are investigated, demonstrating the versatility of our method in reconstructing
entanglement Hamiltonians. Furthermore, we find that when the
entanglement boundary of a system is ordinary (i.e., free from surface anomalies), the LBW ansatz provides an accurate approximation well beyond Lorentz-invariant cases. Our work thus establishes a general framework for investigating the analytical structure of
entanglement in the complex
quantum many-body systems.
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Physics and Society
Low-Cost Carriers in Aviation: Significance and Developments
Bruno Felipe de Oliveira and Alessandro V. M. Oliveira
This paper aims to discuss the impacts of low-cost airlines on the air transport
market and, in particular, to present the most recent findings from the specialized literature in this field. To this end, several papers published on the topic since 2015 were selected and analyzed. Based on this analysis, the main subjects addressed in the studies were categorized into five groups: (i) impacts of low-cost airlines on competing carriers; (ii) impacts on airports; (iii) general effects on air transport demand; (iv) effects on passengers' choice processes; and (v) broader effects on geographical regions.
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Instrumentation and Detectors
Performance of resistive MPGDs with pad readout coupled to VMM3a ASIC
D. Zavazieva, I. Ravinovich, L. Moleri et al. (+6 more)
We present a comparative study of three resistive Micro-Pattern Gaseous Detector (MPGD) technologies - Micromegas, RPWELL, and $\mu\mathrm{-RWELL}$ - with VMM3a based readout, using relativistic
muons and pions. The Micromegas and the RPWELL were operated in $\mathrm{Ar/CO_2/iC_4H_{10}}$ gas mixture, while the $\mu\mathrm{-RWELL}$ in $\mathrm{Ar/CO_2/CF_4}$ (greenhouse gas containing mixture). All detectors operated stably exceeding 96% efficiency. The usage of continuous readout enabled studies of detector electrical instabilities in- and off-beam at near breakdown voltages. Each technology has different advantages making it more suitable for various experimental conditions.
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All authors D. Zavazieva, I. Ravinovich, L. Moleri, M. Borysova, E. B. Shields, O. Arie, M. Kwok Lam Chu, L. Arazi, S. Bressler
Biological Physics
New avenues for characterizing individual mineralized collagen fibrils with transmission electron microscopy
Tatiana Kochetkova, Stephanie M. Ribet, Lilian M. Vogl et al. (+5 more)
Bone serves as a remarkable example of nature's architectured material with its unique blend of strength and toughness, all at a lightweight design. Given the hierarchical nature of these materials, it is essential to understand the governing mechanisms and organization of its constituents across length scales for bio-inspired structural design. Despite recent advances in transmission electron miscoscopy (TEM) that have allowed us to witness the fascinating arrangement of bone at micro-down to the nano-scale, we are still missing the details about the structural organization and mechanical properties of the main building blocks of bone – mineralized collagen fibrils (MCFs). Here, we propose a novel approach for extracting individual MCFs from nature's model material via a dropcasting procedure. By isolating the MCFs onto TEM-compatible substrates, we visualized the arrangement of organic and mineral phases within the individual MCFs at the nanoscale. Using a 4D-STEM approach, the orientation of individual mineral
crystals within the MCFs was examined. Furthermore, we conducted first-of-its-kind in situ tensile experiments, revealing exceptional tensile strains of at least 8%, demonstrating the intricate relationship between structural organization and the mechanical behavior of MCFs. The capabilities of TEM allow us to resolve MCF organization and composition down to the nanoscale level. This new knowledge of the ultrastructure of the bone-building blocks and the proposed sample extraction and in situ mechanical testing opens up new avenues for research into nature's inspired material design.
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All authors Tatiana Kochetkova, Stephanie M. Ribet, Lilian M. Vogl, Daniele Casari, Rohan Dhall, Philippe K. Zysset, Andrew M. Minor, Peter Schweizer
Optics
Encoding orbital angular momentum of light in space with optical catastrophes
Xiaoyan Zhou, John You En Chan, Chia-Te Chang et al. (+6 more)
Light beams carrying orbital angular momentum (OAM) possess an unbounded set of orthogonal modes, offering significant potential for optical communication and security. However, exploiting OAM beams in space has been hindered by the lack of a versatile design toolkit. Here, we demonstrate a strategy to tailor OAM across multiple transverse planes by shaping optical caustics leveraging on catastrophe theory. With complex-amplitude metasurfaces fabricated using two-
photon polymerization lithography, we construct these caustics to steer Poynting vectors and achieve arbitrary shapes of OAM beams. Interestingly, we use such an approach to realize hidden OAM along the propagation trajectory, where the intensity of the beam is spread out thus avoiding detection. The OAM of these beams can be intrinsic, which avoids OAM distortions arising from the mixing of intrinsic and extrinsic components. By exploiting this intrinsic nature of OAM, we demonstrate the detection of encoded information in optical encryption. Our approach provides a unique framework for dynamic control of OAM in space, with promising applications in optical trapping and sensing, high-capacity data storage, and optical information security.
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All authors Xiaoyan Zhou, John You En Chan, Chia-Te Chang, Zhenchao Liu, Wang Hao, Andrew Forbes, Cheng-Wei Qiu, Hongtao Wang, Joel K.W. Yang
Optics
Hyperentanglement in Nanophotonic Systems with Discrete Rotational Symmetry
Lior Fridman, Amit Kam, Amir Sivan et al. (+3 more)
We propose a scheme to generate hyperentanglement between
photons carrying angular momentum in nanophotonic systems with discrete rotational
symmetry. Coupling free-space
photons into surface plasmon polaritons by a polygonal-shaped grating restricts the basis of the generated near-field modes to a finite set, thus creating a new mechanism for spatial mode
entanglement. By encoding the incoming
photons with
spin and orbital angular momenta, we find that the system preserves the high-dimensional
Hilbert space, in contrast to rotationally symmetric nanophotonic platforms, where the inseparability of
spin and orbital degrees of freedom results in loss of information. We further show that by properly engineering the phase of the
photons to conform to the polygonal boundary conditions, we achieve a new scheme for generating hyperentangled states, utilizing both the vector-field nature of the nanophotonic modes and the finite basis of states in polygonal boundary conditions. Our approach paves the way for on-chip
quantum communication by expanding the
Hilbert space used in computation.
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All authors Lior Fridman, Amit Kam, Amir Sivan, Guy Sayer, Stav Lotan, Guy Bartal
Data Analysis and Statistics · Cross-listed from gr-qc
Reconstruction of Black Hole Ringdown Signals with Data Gaps using a Deep-Learning Framework
Jing-Qi Lai, Jia-Geng Jiao, Cai-Ying Shao et al. (+2 more)
We introduce DenoiseGapFiller (DGF), a deep-learning framework specifically designed to reconstruct gravitational-wave ringdown signals corrupted by data gaps and instrumental noise. DGF employs a dual-branch encoder-decoder architecture, which is fused via mixing layers and
Transformer-style blocks. Trained end-to-end on synthetic ringdown waveforms with gaps up to 20% of the segment length, DGF can achieve a mean waveform mismatch of 0.002. The residual amplitudes of the Time-domain shrink by roughly an order of magnitude and the power spectral density in the 0.01-1 Hz band is suppressed by 1-2 orders of magnitude, restoring the peak of quasi-normal mode(QNM) in the time-frequency representation around 0.01-0.1 Hz. The ability of the model to faithfully reconstruct the original signals, which implies milder penalties in the detection evidence and tighter credible regions for parameter estimation, lay a foundation for the following scientific work.
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All authors Jing-Qi Lai, Jia-Geng Jiao, Cai-Ying Shao, Jun-Xi Shi, Yu Tian
Atmospheric and Oceanic Physics
Global Kilometer-Scale Simulations with ARP-GEM2: Effect of Parameterized Convection and Calibration
Olivier Geoffroy and David Saint-Martin
The objective of this paper is twofold. First, it documents the second version of the global atmospheric model ARP-GEM and its calibration at kilometer-scale resolution. The model is currently able to run simulations at a resolution of up to 1.3 km. Second, this paper focus on multi-year global atmospheric simulations at a 2.6 km resolution with and without parameterized convection and associated calibration. Simulations without deep convection tend to be similar to those with infinite, or at least large, entrainment values. Consistently, entrainment and detrainment are used as primary drivers for the gradual reduction of convection as resolution increases. The results indicate that, with this hydrostatic model, parameterized convection still plays a significant role in the correct representation of the mean state at the kilometer scale. Additionally, they suggest some added value of high resolution in representing
climate variability. However, a compromise between the adequate representation of the mean state and variability is necessary, as both are differently favored by the degree of parameterized convection. Finally, it is likely that even higher resolutions are necessary to achieve an unequivocal added value.
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Biological Physics
Optimal Undulatory Swimming with Constrained Deformation and Actuation Intervals
Fumiya Tokoro, Hideki Takayama, Shinji Deguchi et al. (+2 more)
In nature, many unicellular organisms are able to swim with the help of beating filaments, where local energy input leads to cooperative undulatory beating motion. Here, we investigate by employing reinforcement learning how undulatory microswimmers modeled as a discretized bead-bend-spring filament actuated by torques which are constrained locally. We show that the competition between actively applied torques and intrinsic bending stiffness leads to various optimal beating patterns characterized by distinct frequencies, amplitudes, and wavelengths. Interestingly, the optimum solutions depend on the action interval, i.e.\ the time scale how fast the microswimmer can \rev{change the applied torques} based on its internal state. We show that optimized stiffness- and action-interval-dependent beating is realized by bang-bang solutions of the applied torques with distinct optimum time-periodicity and phase shift between consecutive joints, which we analyze in detail by a systematic study of possible bang-bang wave solution patterns of applied torques. Our work not only sheds light on how efficient beating patterns of biological microswimmers can emerge based on internal and local constraints, but also offers actuation policies for potential artificial elastic microswimmers.
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All authors Fumiya Tokoro, Hideki Takayama, Shinji Deguchi, Andreas Zöttl, Daiki Matsunaga
Applied Physics · Cross-listed from cond-mat.mtrl-sci
Gate Dielectric Engineering with an Ultrathin Silicon-oxide Interfacial Dipole Layer for Low-Leakage Oxide-Semiconductor Memories
Fabia F. Athena, Jonathan Hartanto, Matthias Passlack et al. (+11 more)
We demonstrate a gate dielectric engineering approach leveraging an ultrathin, atomic layer deposited (ALD) silicon
oxide interfacial layer (SiL) between the amorphous
oxide semiconductor (AOS) channel and the high-k gate dielectric. SiL positively shifts the threshold voltage (V$_T$) of AOS transistors, providing at least four distinct $V_T$ levels with a maximum increase of 500 mV. It achieves stable $V_T$ control without significantly degrading critical device parameters such as mobility, on-state current, all while keeping the process temperature below 225 $^{\circ}$C and requiring no additional heat treatment to activate the dipole. Positive-bias temperature instability tests at 85 $^{\circ}$C indicate a significant reduction in negative $V_{T}$ shifts for SiL-integrated devices, highlighting enhanced reliability. Incorporating this SiL gate stack into two-transistor gain-
cell (GC)
memory maintains a more stable storage node voltage ($V_{SN}$) (reduces $V_{SN}$ drop by 67%), by limiting unwanted charge losses. SiL-engineered GCs also reach retention times up to 10,000 s at room temperature and reduce standby leakage current by three orders of magnitude relative to baseline device, substantially lowering refresh energy consumption.
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All authors Fabia F. Athena, Jonathan Hartanto, Matthias Passlack, Jack C. Evans, Jimmy Qin, Didem Dede, Koustav Jana, Shuhan Liu, Tara Peña, Eric Pop, Greg Pitner, Iuliana P. Radu, Paul C. McIntyre, H.-S. Philip Wong
Applied Physics
Polarization-sensitive GeSn Mid-Infrared Membrane Photodetectors with Integrated Plasmonic Metasurface
Ziqiang Cai, Cédric Lemieux-Leduc, Mahmoud R. M. Atalla et al. (+4 more)
Germanium-Tin (GeSn)
semiconductors are promising for mid-infrared optoelectronics owing to their silicon compatibility, tunable bandgap, and potential for room-temperature operation. Released GeSn membranes provide an additional degree of freedom to extend the operation wavelength through epitaxial strain relaxation, while their transferability expands design flexibility. On the other hand, metasurfaces have become an effective strategy to engineer light–matter interaction, and their integration with photodetectors can enhance performance and introduce new functionalities. Here, we demonstrate a mid-infrared photodetector consisting of a transfer-printed Ge$_{0.89}$Sn$_{0.11}$ membrane integrated with an Au plasmonic metasurface. The photodetector exhibits a wavelength cutoff exceeding 3.0~$\mu$m with nearly fourfold increase in responsivity at 2.5~$\mu$m as compared to unreleased films, attributed to Fabry–Pérot resonance. Furthermore, the integration with an anisotropic metasurface yields detectors with strong polarization sensitivity, achieving a measured contrast ratio of $\sim$4:1 between orthogonal polarizations. Moreover, the operation wavelength of the photodetector can be selectively tuned by varying the
geometric scale of the metasurface. The experimental results show excellent agreement with simulations, confirming the effectiveness and versatility of this integrated metasurface–membrane design.
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All authors Ziqiang Cai, Cédric Lemieux-Leduc, Mahmoud R. M. Atalla, Luo Lu, Gérard Daligou, Simone Assali, Oussama Moutanabbir
Applied Physics · Cross-listed from cond-mat.mtrl-sci
Characterising Atomic-Scale Surface Disorder on 2D Materials Using Neutral Atoms
Chenyang Zhao, Sam M. Lambrick, Ke Wang et al. (+5 more)
Two-dimensional (2D) transition metal dichalcogenides (TMDs), such as MoS2, have the potential to be widely used in electronic devices and sensors due to their high carrier mobility and tunable band structure. In 2D TMD devices, surface and interface cleanness can critically impact the performance and reproducibility. Even sample surfaces prepared under ultra-high
vacuum (UHV) can be contaminated, causing disorder. On such samples, trace levels of submonolayer contamination remain largely overlooked, and conventional surface characterisation techniques have limited capability in detecting such adsorbates. Here, we apply scanning helium microscopy (SHeM), a non-destructive and ultra-sensitive technique, to investigate the surface cleanness of 2D MoS2. Our measurements reveal that even minute amounts of adventitious carbon induce atomic-scale disorder across MoS2 surfaces, leading to the disappearance of helium diffraction. By tracking helium reflectivity over time, we quantify the decay of surface order across different microscopic regions and find that flat areas are more susceptible to contamination than regions near edges. These findings highlight the fragility of surface order in 2D materials, even under UHV, and establish SHeM as a powerful tool for non-damaging microscopic 2D material cleanness characterisation. The approach offers a new route to wafer-scale characterisation of 2D material quality.
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All authors Chenyang Zhao, Sam M. Lambrick, Ke Wang, Shaoliang Guan, Aleksandar Radic, David J. Ward, Andrew P. Jardine, Boyao Liu
Plasma Physics
Nonlinear effects in light-ion stopping powers within real-time time-dependent density functional theory
Alina Kononov, Thomas W. Hentschel, Stephanie B. Hansen et al. (+1 more)
Electronic stopping power models describing fuel heating processes in inertial fusion energy concepts typically assume linear-response behavior through quadratic scaling with the projectile charge. We report the results of real-time time-dependent density functional theory (TDDFT) calculations indicating that even for low-Z ions, nonlinear processes modify stopping powers in warm dense matter by about 10% near and below the Bragg peak. By describing partial neutralization of slow ions, analytic effective charge models capture some qualitative aspects of the TDDFT results but do not always offer quantitative accuracy. Cases where the effective charge inferred from TDDFT exceeds the bare ion charge suggest that more complex nonlinear effects also contribute. These findings will inform future improvements to more efficient stopping power models.
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All authors Alina Kononov, Thomas W. Hentschel, Stephanie B. Hansen, Andrew D. Baczewski
Medical Physics · Cross-listed from eess.SY
High-Power Dual-Channel Field Chamber for High-Frequency Magnetic Neuromodulation
Xiaoyang Tian, Hui Wang, Boshuo Wang et al. (+10 more)
Several novel methods, including magnetogenetics and magnetoelectric stimulation, use high frequency alternating
magnetic fields to precisely manipulate neural activity. To quantify the behavioral effects of such interventions in a freely moving mouse, we developed a dual-channel
magnetic chamber, specifically designed for rate-sensitive magnetothermal-genetic stimulation, and adaptable for other uses of alternating
magnetic fields. Through an optimized coil design, the system allows independent control of two spatially orthogonal uniform
magnetic fields delivered at different frequencies within a 10 cm x 10 cm x 6 cm chamber. The two channels have nominal frequencies of 50 and 550 kHz with peak
magnetic field strengths of 88 and 12.5 mT, achieved with resonant coil drives having peak voltages of 1.6 and 1.8 kV and currents of 1.0 and 0.26 kA, respectively. Additionally, a
liquid cooling system enables
magnetic field generation for second-level duration, and an observation port and camera allow
video capture of the animal's behavior within the chamber. The system generates high-amplitude
magnetic fields across two widely separated frequency channels with negligible interference (< 1%). Relatively uniform
magnetic field distribution (+/-10% across 94% of the chamber volume) is maintained throughout the chamber, and temperature increase of the inner side of the coil enclosure during the operation is limited to < 0.35 {\deg}C/s to ensure in vivo safety. Using cobalt-doped and undoped iron
oxide nanoparticles, we demonstrate channel-specific heating rates of 3.5 {\deg}C/s and 1.5 {\deg}C/s, respectively, validating frequency-selectivity. Both channels can run continuously for four seconds stably.
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All authors Xiaoyang Tian, Hui Wang, Boshuo Wang, Jinshui Zhang, Dong Yan, Jeannette Ingabire, Samantha Coffler, Guillaume Duret, Quoc-Khanh Pham, Gang Bao, Jacob T. Robinson, Stefan M. Goetz, Angel V. Peterchev
Medical Physics
Magnetic Materials for Transcranial Magnetic Stimulation (TMS)
Max Koehler, Akshata Sangle and Stefan M. Goetz
Various coils for transcranial
magnetic stimulation (TMS) are widely available for clinical and research use. These coils are almost all designed as air coils, which require large levels of energy to achieve a given
magnetic flux density and in turn electric field strength, whereas in other sectors, such as power electronics or electrical machines,
magnetic materials have been used for a long time to achieve higher efficiencies. We tested the impact on the electric and
magnetic properties of different soft
magnetic materials, including various ferrite cores, laminated sheet materials of nonisotropic corn-oriented silicon-steel, non-oriented silicon-steel, as well as cobalt-iron, and soft
magnetic compound powder cores with insulated particles. Every material led to a reduction in coil current and voltage for the same target electric field strength. For the same field energy, every material yielded lower losses. Most common materials saturated already at very low currents. More material in thicker layers could shift the saturation point but at the cost of high weight. Due to their low saturation flux density, ferrites appear unsuitable for the high amplitude requirements of TMS. Laminated sheet materials and powder cores reduce the pulse energy, but the laminated sheet material adds more weight for the same effect than powder cores. Thus, appropriate
magnetic materials can reduce the required pulse energy. Saturation flux density is the most relevant parameter, whereas the permeability beyond a certain base level is practically irrelevant. Most importantly, the weight of a
magnetic-core coil may always be increased compared to an air coil for the same target field.
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