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Distinguishing photon-arrival time and position is crucial for advancing quantum technology. However, capturing spatial and temporal information efficiently remains challenging. Here, we present a novel photon-detection technique to achieve a significantly more efficient measurement of frequency-entangled biphoton than conventional photon detectors. We utilize a delay-line-anode single-photon detector (DLD), which consists of a position-sensitive delay line anode sensor behind a microchannel plate. Biphotons are obtained from the decay of biexcitons in the copper chloride semiconductor crystal. Two DLDs are coupled with a grating spectrometer exit to measure the joint spectral distributions of the biphoton. The resulting non-scanning process requires only a few minutes to obtain a temporally and spectrally resolved image, which is much quicker than the conventional biphoton frequency measurement. Our technique paves the way for all experiments in multi-mode quantum science requiring coincidence measurement.

Contrast variation small-angle neutron scattering (CV-SANS) is a powerful tool to evaluate the structure of multi-component systems by decomposing scattering intensities $I$ measured with different scattering contrasts into partial scattering functions $S$ of self- and cross-correlations between components. The measured $I$ contains a measurement error, $\Delta I$, and $\Delta I$ results in an uncertainty of partial scattering functions, $\Delta S$. However, the error propagation from $\Delta I$ to $\Delta S$ has not been quantitatively clarified. In this work, we have established deterministic and statistical approaches to determine $\Delta S$ from $\Delta I$. We have applied the two methods to experimental SANS data of polyrotaxane solutions with different contrasts, and have successfully estimated the errors of $S$. The quantitative error estimation of $S$ offers us a strategy to optimize the combination of scattering contrasts to minimize error propagation.

In the process of tunnel excavation, advance geological prediction technology has become indispensable for safe, economical, and efficient tunnel construction. Although traditional methods such as drilling and geological analysis are effective, they typically involve destructive processes, carry high risks, and incur significant costs. In contrast, non-destructive geophysical exploration offers a more convenient and economical alternative. However, the accuracy and precision of these non-destructive methods can be severely compromised by complex geological structures and environmental noise. To address these challenges effectively, a novel approach using frequency domain full waveform inversion, based on a penalty method and Sobolev space regularization, has been proposed to enhance the performance of non-destructive predictions. The proposed method constructs a soft-constrained optimization problem by restructuring the misfit function into a combination of data misfit and wave equation drive terms to enhance convexity. Additionally, it semi-extends the search space to both the wavefield and the model parameters to mitigate the strong nonlinearity of the optimization, facilitating high-resolution inversion. Furthermore, a Sobolev space regularization algorithm is introduced to flexibly adjust the regularization path, addressing issues related to noise and artefacts to enhance the robustness of the algorithm. We evaluated the modified full waveform inversion with several tunnel fault models by comparing the results of the enhanced method with those of traditional least squares-based Tikhonov regularization and total variation regularization full waveform inversion methods. The verification results confirm the superior capabilities of the proposed method as expected., Comment: 60 pages, 21 figures

A single-celled amoeba can solve the traveling salesman problem through its shape-changing dynamics. In this paper, we examine roles of several elements in a previously proposed computational model of the solution-search process of amoeba and three modifications towards enhancing the solution-search preformance. We find that appropriate modifications can indeed significantly improve the quality of solutions. It is also found that a condition associated with the volume conservation can also be modified in contrast to the naive belief that it is indispensable for the solution-search ability of amoeba. A proposed modified model shows much better performance., Comment: 13 pages, 2 figures

In this study, we propose a design methodology for a piezoelectric energy-harvesting device optimized for maximal power generation at a designated frequency using topology optimization. The proposed methodology is adapted to the design of a unimorph-type piezoelectric energy harvester, wherein a piezoelectric film is affixed to a singular side of a silicon cantilever beam. Both the substrate and the piezoelectric film components undergo concurrent optimization. Constraints are imposed to ensure that the resultant design is amenable to microfabrication, with specific emphasis on the etchability of piezoelectric energy harvesters. Several numerical examples are provided to validate the efficacy of the proposed method. The results show that the proposed method yields optimized substrate and piezoelectric designs with an enhanced electromechanical coupling coefficient, while allowing the eigenfrequency of the device and the minimum output voltage to be set to the desired values. Furthermore, the proposed method can provide solutions that satisfy the cross-sectional shape, substrate-dependent, and minimum output voltage constraints. The solutions obtained by the proposed method are manufacturable in the field of microfabrication., Comment: 52 pages, 11 figures

Recent progress in high-power pulsed neutron sources has stimulated the development of the Bragg-dip and Bragg-edge analysis methods using a two-dimensional neutron detector with high temporal resolution to resolve the neutron energy by the time-of-flight method. The delay-line current-biased kinetic-inductance detector (CB-KID) is a two-dimensional superconducting sensor with a high temporal resolution and multi-hit capability. We demonstrate that the delay-line CB-KID with a $^{10}$B neutron conversion layer can be applied to high-spatial-resolution neutron transmission imaging and spectroscopy up to 100\,eV. Dip structures in the transmission spectrum induced by Bragg diffraction and nuclear resonance absorption in YbSn$_3$ single crystals. We successfully drew the orientation mapping of YbSn$_3$ crystals based on the analysis of observed Bragg-dip positions in the transmission spectrum., Comment: 18 pages, 6 figures

Chirality-induced spin selectivity (CISS) has been extensively studied over the past two decades. While current-induced spin polarization in chiral molecules is widely recognized as the fundamental principle of the CISS, only a few studies have been reported on bias-current-free CISS, where there is no bias electric current in chiral molecules. Recent studies on the chirality-induced exchange bias and current-in-plane magnetoresistance (CIP-MR) effects using chiral molecule/ferromagnet bilayer systems indicate that chiral molecules at the interface possess thermally driven broken-time-reversal symmetry, which induces bias-current-free CISS, i.e. a spontaneous effective magnetic field in the system. In this paper, we briefly review CISS-related phenomena in terms of the symmetry and discuss the mechanism of bias-current-free CISS. We also discuss the possibility of the linear magnetoelectric effect of chiral molecules, which arises from the spin polarization at the edges of molecules with metallic contacts, and its potential impact on the observed CISS phenomena.

We have performed a powder neutron diffraction study on CsO$_2$, where the unpaired electron with $s=1/2$ in the $\pi^*$ orbital of the O$_2^-$ ion is responsible for the magnetism. The magnetic reflections 0 $\frac{1}{2}$ 0 and 0 $\frac{1}{2}$ 1 were observed below the N\'{e}el temperature of about 10 K. An antiferromagnetic structure with a propagation vector of (0 ,$\frac{1}{2}$, 0) and magnetic moments parallel to the $a$-axis is the most plausible. The magnitude of the ordered moment is about 0.2 $\mu_B$, which is considered to be strongly suppressed due to the one-dimensionality of the system. We propose a possible $\pi^*$ orbital order that can explain the obtained magnetic structure, and discuss its relation to the one-dimensionality.

We propose two machine-learning methods based on neural networks, which we respectively call the phase-classification method and the temperature-identification method, for detecting different types of phase transitions in the XXZ models without prior knowledge of their critical temperatures. The XXZ models have exchange couplings which are anisotropic in the spin space where the strength is represented by a parameter $\Delta(>0)$. The models exhibit the second-order phase transition when $\Delta>1$, whereas the Berezinskii-Kosterlitz-Thouless (BKT) phase transition when $\Delta<1$. In the phase-classification method, the neural network is trained using spin or vortex configurations of well-known classical spin models other than the XXZ models, e.g., the Ising models and the XY models, to classify those of the XXZ models to corresponding phases. We demonstrate that the trained neural network successfully detects the phase transitions for both $\Delta>1$ and $\Delta<1$, and the evaluated critical temperatures coincide well with those evaluated by conventional numerical calculations. In the temperature-identification method, on the other hand, the neural network is trained so as to identify temperatures at which the input spin or vortex configurations are generated by the Monte Carlo thermalization. The critical temperatures are evaluated by analyzing the optimized weight matrix, which coincide with the result of numerical calculation for the second-order phase transition in the Ising-like XXZ model with $\Delta=1.05$ but cannot be determined uniquely for the BKT transition in the XY-like XXZ model with $\Delta=0.95$., Comment: 17 pages, 12 figures

In the realm of music information retrieval, similarity-based retrieval and auto-tagging serve as essential components. Given the limitations and non-scalability of human supervision signals, it becomes crucial for models to learn from alternative sources to enhance their performance. Self-supervised learning, which exclusively relies on learning signals derived from music audio data, has demonstrated its efficacy in the context of auto-tagging. In this study, we propose a model that builds on the self-supervised learning approach to address the similarity-based retrieval challenge by introducing our method of metric learning with a self-supervised auxiliary loss. Furthermore, diverging from conventional self-supervised learning methodologies, we discovered the advantages of concurrently training the model with both self-supervision and supervision signals, without freezing pre-trained models. We also found that refraining from employing augmentation during the fine-tuning phase yields better results. Our experimental results confirm that the proposed methodology enhances retrieval and tagging performance metrics in two distinct scenarios: one where human-annotated tags are consistently available for all music tracks, and another where such tags are accessible only for a subset of tracks., Comment: 11 pages

We present the transfer of the spatially variant polarization of topologically structured light to the spatial spin texture in a semiconductor quantum well. The electron spin texture, which is a circular pattern with repeating spin-up and spin-down states whose repetition rate is determined by the topological charge, is directly excited by a vector vortex beam with a spatial helicity structure. The generated spin texture efficiently evolves into a helical spin wave pattern owing to the spin-orbit effective magnetic fields in the persistent spin helix state by controlling the spatial wave number of the excited spin mode. By tuning the repetition length and azimuthal angle, we simultaneously generate helical spin waves with opposite phases by a single beam., Comment: 6 pages, 4 figures

Secret sharing schemes for classical secrets can be classified into classical secret sharing schemes and quantum secret sharing schemes. Classical secret sharing has been known to be able to distribute some shares before a given secret. On the other hand, quantum mechanics extends the capabilities of secret sharing beyond those of classical secret sharing. We propose quantum secret sharing with the capabilities in designing of access structures more flexibly and realizing higher efficiency beyond those of classical secret sharing, that can distribute some shares before a given secret., Comment: 11 pages, 1 figure, 1 table. Publisher's open access PDF. Results unchanged. This research was in part presented at QCrypt 2022, Taipei City, Taiwan, August 29-September 2, 2022

In this paper, stress-constrained topology optimization is applied to the design of compliant displacement magnification mechanisms. By formulating the objective function based on the concept of effective energy, it is not necessary to place artificial spring components at the boundaries of the output and input ports as in previous methods. This makes it possible to design mechanisms that do not receive a reaction force at the output port, such as sensors. Furthermore, by imposing a constraint on the maximum stress evaluated in terms of the p-norm of the von Mises equivalent stress, problems such as stress concentration can be avoided. Several numerical examples of displacement magnification mechanisms are provided to demonstrate the effectiveness of the proposed method., Comment: 38 pages, 23 figures

Carbon is an essential element for the existence and evolution of life on Earth. Its abundance in Earth's crust and mantle (the Bulk Silicate Earth, BSE) is surprisingly high given that carbon is strongly siderophile (metal-loving) at low pressures and temperatures, and hence should have segregated almost completely into Earth's core during accretion. Estimates of the concentration of carbon in the BSE lie in the range 100-260 ppm and are much higher than expected based on simple models of core-mantle differentiation. Here we show through experiments at the putative conditions of Earth's core formation (49-71 GPa and 3600-4000 K) that carbon is significantly less siderophile at these conditions than at the low pressures ($\leq$13 GPa) and temperatures ($\leq$2500 K) of previous large volume press studies, but at least an order of magnitude more siderophile than proposed recently based on an experimental approach that is similar to ours. Using our new data along with previously published results, we derive a new parameterization of the pressure-temperature dependence of the metal-silicate partitioning of carbon. We apply this parameterization in a model that combines planet formation and core-mantle differentiation that is based on astrophysical N-body accretion simulations. Because differentiated planetesimals were almost completely depleted in carbon due to sublimation at high temperatures, almost all carbon in the BSE was added by the accretion of fully-oxidized carbonaceous chondrite material from the outer solar system. Carbon is added to the mantle continuously throughout accretion and its concentration reaches values within the BSE range (e.g. 140$\pm$40 ppm) at the end of accretion. The corresponding final core and bulk Earth carbon concentrations are 1270$\pm$300 ppm and 495$\pm$125 ppm respectively., Comment: Supplementary material included in pdf

We report chirality-induced current-in-plane magnetoresistance (CIP-MR) in chiral molecule/ferromagnetic metal bilayer at room temperature. The previously reported chiralityinduced current-perpendicular-to-plane magnetoresistance (CPP-MR) originates from the chiral induced spin-selectivity (CISS) effect that needs charge-current passing through the molecule. In contrast, the observed CIP-MR in the present study requires no bias charge current through the molecule. The temperature dependence of CIP-MR suggests thermally induced spin-polarization in the chiral molecules is the key for the observed MR., Comment: 11 pages, 4 figures

Neutron imaging is one of the most powerful tools for nondestructive inspection owing to the unique characteristics of neutron beams, such as high permeability for many heavy metals, high sensitivity for certain light elements, and isotope selectivity owing to a specific nuclear reaction between an isotope and neutrons. In this study, we employed a superconducting detector, current-biased kinetic-inductance detector (CB-KID) for neutron imaging using a pulsed neutron source. We employed the delay-line method, and high spatial resolution imaging with only four reading channels was achieved. We also performed wavelength-resolved neutron imaging by the time-of-flight method for the pulsed neutron source. We obtained the neutron transmission images of a Gd-Al alloy sample, inside which single crystals of GdAl3 were grown, using the delay-line CB-KID. Single crystals were well imaged, in both shapes and distributions, throughout the Al-Gd alloy. We identified Gd nuclei via neutron transmissions that exhibited characteristic suppression above the neutron wavelength of 0.03 nm. In addition, the ^{155}Gd resonance dip, a dip structure of the transmission caused by the nuclear reaction between an isotope and neutrons, was observed even when the number of events was summed over a limited area of 15 X 12 um^2. Gd selective imaging was performed using the resonance dip of ^{155}Gd, and it showed clear Gd distribution even with a limited neutron wavelength range of 1 pm., Comment: 7 pages, 6 figures, Accepted in Journal of IEEE transactions of Applied Superconductivity

Fourier transform spectroscopy with classical interferometry corresponds to the measurement of a single-photon intensity spectrum from the viewpoint of the particle nature of light. In contrast, the Fourier transform of two-photon quantum interference patterns provides the intensity spectrum of the two photons as a function of the sum or difference frequency of the constituent photons. This unique feature of quantum interferometric spectroscopy offers a different type of spectral information from the classical measurement and may prove useful for nonlinear spectroscopy with two-photon emission. Here, we report the first experimental demonstration of two-photon quantum interference of photon pairs emitted via biexcitons in the semiconductor CuCl. Besides applying Fourier transform to quantum interference patterns, we reconstruct the intensity spectrum of the biexciton luminescence in the two-photon sum or difference frequency. We discuss the connection between the reconstructed spectra and exciton states in CuCl as well as the capability of quantum interferometry in solid-state spectroscopy., Comment: 12 pages,4 figures

Chirality in organic molecules has attracted considerable attention in the fields of chemistry, biology, and spintronics. This paper reports on perpendicular magnetization hysteresis loops of a multilayer consisting of ultrathin Fe (001), chiral phthalocyanine molecule ((P)- or (M)-PbPc-DTBPh), and MgO (001). We find a chirality-dependent shift of the hysteresis loop. Unlike the previously reported bias current induced phenomena, the result shows a chirality-induced effective magnetic field in the phthalocyanine molecule in the absence of a bias current in the system. This study opens up a new direction in the emerging field of chiral molecular spintronics.

We demonstrate that a machine learning technique with a simple feedforward neural network can sensitively detect two successive phase transitions associated with the Berezinskii-Kosterlitz-Thouless (BKT) phase in q-state clock models simultaneously by analyzing the weight matrix components connecting the hidden and output layers. We find that the method requires only a data set of the raw spatial spin configurations for the learning procedure. This data set is generated by Monte-Carlo thermalizations at selected temperatures. Neither prior knowledge of, for example, the transition temperatures, number of phases, and order parameters nor processed data sets of, for example, the vortex configurations, histograms of spin orientations, and correlation functions produced from the original spin-configuration data are needed, in contrast with most of previously proposed machine learning methods based on supervised learning. Our neural network evaluates the transition temperatures as T_2/J=0.921 and T_1/J=0.410 for the paramagnetic-to-BKT transition and BKT-to-ferromagnetic transition in the eight-state clock model on a square lattice. Both critical temperatures agree well with those evaluated in the previous numerical studies., Comment: 11pages, 9 figures

We have investigated the low-temperature magnetism of sodium superoxide (NaO$_{2}$), in which spin, orbital, and lattice degrees of freedom are closely entangled. The magnetic susceptibility shows anomalies at $T_{1}=220$ K and $T_{2}=190$ K, which correspond well to the structural phase transition temperatures, and a sudden decrease below $T_{3}=34$ K. At 4.2 K, the magnetization shows a clear stepwise anomaly around 30 T with a large hysteresis. In addition, the muon spin relaxation experiments indicate no magnetic phase transition down to $T=0.3$ K. The inelastic neutron scattering spectrum exhibits magnetic excitation with a finite energy gap. These results confirm that the ground state of NaO$_{2}$ is a spin-singlet state. To understand this ground state in NaO$_{2}$, we performed Raman scattering experiments. All the Raman-active libration modes expected for the marcasite phase below $T_{2}$ are observed. Furthermore, we find that several new peaks appear below $T_{3}$. This directly evidences the low crystal symmetry, namely, the presence of the phase transition at $T_{3}$. We conclude the singlet-ground state of NaO$_{2}$ due to the spin-Peierls instability., Comment: 6 pages, 3 figures

The mid-infrared range is an important spectrum range where materials exhibit a characteristic response corresponding to their molecular structure. A free-electron laser (FEL) is a promising candidate for a high-power light source with wavelength tunability to investigate the nonlinear response of materials. Although the self-amplification spontaneous emission (SASE) scheme is not usually adopted in the mid-infrared wavelength range, it may have advantages such as layout simplicity, the possibility of producing a single pulse, and scalability to a short-wavelength facility. To demonstrate the operation of a mid-infrared SASE FEL system in an energy recovery linac (ERL) layout, we constructed an SASE FEL setup in cERL, a test facility of the superconducting linac with the ERL configuration. Despite the adverse circumstance of space charge effects due to the given boundary condition of the facility, we successfully established the beam condition at the undulators, and observed FEL emission at a wavelength of 20 $\mu$m. The results show that the layout of cERL has the potential for serving as a mid-infrared light source., Comment: 18 pages, 35 figures

Samples were examined using a superconducting (Nb) neutron imaging system employing a delay-line technique which in previous studies was shown to have high spatial resolution. We found excellent correspondence between neutron transmission and scanning electron microscope (SEM) images of Gd islands with sizes between 15 and 130 micrometer which were thermally-sprayed onto a Si substrate. Neutron transmission images could be used to identify tiny voids in a thermally-sprayed continuous Gd2O3 film on a Si substrate which could not be seen in SEM images. We also found that neutron transmission images revealed pattern formations, mosaic features and co-existing dendritic phases in Wood's metal samples with constituent elements Bi, Pb, Sn and Cd. These results demonstrate the merits of the current-biased kinetic inductance detector (CB-KID) system for practical studies in materials science. Moreover, we found that operating the detector at a more optimal temperature (7.9 K) appreciably improved the effective detection efficiency when compared to previous studies conducted at 4 K. This is because the effective size of hot-spots in the superconducting meanderline planes increases with temperature, which makes particle detections more likely., Comment: 19 pages, 6 figures

We previously proposed a method to detect neutrons by using a current-biased kinetic inductance detector (CB-KID), where neutrons are converted into charged particles using a 10B conversion layer. The charged particles are detected based on local changes in kinetic inductance of X and Y superconducting meanderlines under a modest DC bias current. The system uses a delay-line method to locate the positions of neutron-10B reactions by acquiring the four arrival timestamps of signals that propagate from hot spots created by a passing charged particle to the end electrodes of the meanderlines. Unlike conventional multi-pixel imaging systems, the CB-KID system performs high spatial resolution imaging over a 15 mm x 15 mm sensitive area using only four channel readouts. Given the large sensitive area, it is important to check the spatial homogeneity and linearity of detected neutron positions when imaging with CB-KID. To this end we imaged a pattern of 10B dot absorbers with a precise dot pitch to investigate the spatial homogeneity of the detector. We confirmed the spatial homogeneity of detected dot positions based on the distribution of measured dot pitches across the sensitive area of the detector. We demonstrate potential applications of the system by taking a clear transmission image of tiny metallic screws and nuts and a ladybug. The image was useful for characterizing the ladybug noninvasively. Detection efficiencies were low when the detector was operated at 4 K, so we plan to explore raising the operating temperature towards the critical temperature of the detector as a means to improve counting rates.

A potassium-ion electret, which is a key element of vibration-powered microelectromechanical generators, can store negative charge almost permanently. However, the mechanism by which this negative charge is stored is still unclear. We theoretically study the atomic and electronic structures of amorphous silica (a-SiO2) with and without potassium atoms using first-principles molecular-dynamics calculations. Our calculations show that a fivefold-coordinated Si atom with five Si-O bonds (an SiO5 structure) is the characteristic local structure of a-SiO2 with potassium atomsm, which becomes negatively charged and remains so even after removal of the potassium atoms. These results indicate that this SiO5 structure is the physical origin of the robust negative charge observed in potassium-ion electrets. We also find that the SiO5 structure has a Raman peak at 1000cm-1., Comment: 5 pages, 4 figures

We propose a scalable readout interface for superconducting nanowire single-photon detector (SSPD) arrays, which we call the AQFP/RSFQ interface. This interface is composed of adiabatic quantum-flux-parametron (AQFP) and rapid single-flux-quantum (RSFQ) logic families. The AQFP part reads out the spatial information of an SSPD array via a single cable, and the RSFQ part reads out the temporal information via a single cable. The hybrid interface has high temporal resolution owing to low timing jitter in the operation of the RSFQ part. In addition, the hybrid interface achieves high circuit scalability because of low supply current in the operation of the AQFP part. Therefore, the hybrid interface is suitable for handling many-pixel SSPD arrays. We demonstrate a four-pixel SSPD array using the hybrid interface as proof of concept. The measurement results show that the hybrid interface can read out all of the pixels with a low error rate and low timing jitter., Comment: 10 pages, 6 figures

Two numerical algorithms are proposed for computing an interval matrix containing the matrix gamma function. In 2014, the author presented algorithms for enclosing all the eigenvalues and basis of invariant subspaces of $A \in \mathbb{C}^{n \times n}$. As byproducts of these algorithms, we can obtain interval matrices containing small matrices whose spectrums are included in that of $A$. In this paper, we interpret the interval matrices containing the basis and small matrices as a result of verified block diagonalization (VBD), and establish a new framework for enclosing matrix functions using the VBD. To achieve enclosure for the gamma function of the small matrices, we derive computable perturbation bounds. We can apply these bounds if input matrices satisfy conditions. We incorporate matrix argument reductions (ARs) to force the input matrices to satisfy the conditions, and develop theories for accelerating the ARs. The first algorithm uses the VBD based on a numerical spectral decomposition, and involves only cubic complexity under an assumption. The second algorithm adopts the VBD based on a numerical Jordan decomposition, and is applicable even for defective matrices. Numerical results show efficiency and robustness of the algorithms.

Neutron imaging is one of the key technologies for non-destructive transmission testing. Recent progress in the development of intensive neutron sources allows us to perform energy-resolved neutron imaging with high spatial resolution. Substantial efforts have been devoted to developing a high spatial and temporal resolution neutron imager. We have been developing a neutron imager aiming at conducting high spatial and temporal resolution imaging based on a delay-line neutron detector, called the current-biased kinetic-inductance detector, with a conversion layer $^{10}$B. The detector allowed us to obtain a neutron transmission image with four signal readout lines. Herein, we expanded the sensor active area, and improved the spatial resolution of the detector. We examined the capability of high spatial resolution neutron imaging over the sensor active area of 15 $\times$ 15 mm$^2$ for various samples, including biological and metal ones. We also demonstrated an energy-resolved neutron image in which stainless-steel specimens were discriminating of other specimens with the aid of the Bragg edge transmission., Comment: 17 pages, 6 figures

The Energy Recovery Linac (ERL) paradigm offers the promise to generate intense electron beams of superior quality with extremely small six-dimensional phase space for many applications in the physical sciences, materials science, chemistry, health, information technology and security. Helmholtz-Zentrum Berlin started in 2010 an intensive R\&D programme to address the challenges related to the ERL as driver for future light sources by setting up the bERLinPro (Berlin ERL Project) ERL with 50 MeV beam energy and high average current. The project is close to reach its major milestone in 2020, acceleration and recovery of a high brightness electron beam. The goal of bERLinProCamp 2019 was to discuss scientific opportunities for bERLinPro 2020+. bERLinProCamp 2019 was held on Tue, 17.09.2019 at Helmholtz-Zentrum Berlin, Berlin, Germany. This paper summarizes the main themes and output of the workshop.

Advanced driver assistance and automated driving systems rely on risk estimation modules to predict and avoid dangerous situations. Current methods use expensive sensor setups and complex processing pipeline, limiting their availability and robustness. To address these issues, we introduce a novel deep learning based action recognition framework for classifying dangerous lane change behavior in short video clips captured by a monocular camera. We designed a deep spatiotemporal classification network that uses pre-trained state-of-the-art instance segmentation network Mask R-CNN as its spatial feature extractor for this task. The Long-Short Term Memory (LSTM) and shallower final classification layers of the proposed method were trained on a semi-naturalistic lane change dataset with annotated risk labels. A comprehensive comparison of state-of-the-art feature extractors was carried out to find the best network layout and training strategy. The best result, with a 0.937 AUC score, was obtained with the proposed network. Our code and trained models are available open-source., Comment: 8 pages, 3 figures, 1 table. The code is open-source

Accelerator-based terahertz (THz) radiation has been expected to realize a high-power broadband source. Employing a low-emittance and short-bunch electron beam at a high repetition rate, a scheme of coherent diffraction-radiation in an optical cavity layout is proposed. The scheme's stimulated radiation process between bunches can greatly enhance the efficiency of the radiation emission. We performed an experiment with a superconducting linac constructed as an energy recovery linac (ERL) test facility. The electron beam passes through small holes in the cavity mirrors without being destroyed. A sharp THz resonance signal, which indicates broadband stimulated radiation correlated with beam deceleration, was observed while scanning the round-trip length of the cavity. This observation proves the efficient beam-to-radiation energy conversion due to the stimulated radiation process., Comment: 13 pages , 20 figures

At the Ibaraki Neutron Medical Research Center, an accelerator-based neutron source for iBNCT (Ibaraki - Boron Neutron Capture Therapy) is being developed using an 8-MeV proton linac and a beryllium-based neutron production target. The proton linac consists of an RFQ and a DTL, which is almost the same as the front part of J-PARC linac. However, here only one high-power klystron is used as the RF source to drive the two cavities, which have quite different Q-values and responses. From June 2016, a cPCI based digital feedback system was applied to the iBNCT accelerator. It serves not only as a controller for the feedback of acceleration fields, but also as a smart operator for the auto-tuning of the two cavities in the meantime, especially during the RF startup process to the full power. The details will be described in this report., Comment: Poster presented at LLRF Workshop 2017 (LLRF2017, arXiv:1803.07677)

With a low emittance and short-bunch electron beam at a high repetition rate realized by a superconducting linac, stimulated excitation of an optical cavity at the terahertz spectrum range has been shown. The electron beam passed through small holes in the cavity mirrors without being destroyed. A sharp resonance structure which indicated wide-band stimulated emission via coherent diffraction radiation was observed while scanning the round-trip length of the cavity.

Alkali superoxide CsO2 is one of candidates for the spin-1/2 one-dimensional (1D) antiferromagnet, which may be sequentially caused by an ordering of the pi-orbital of O2- molecule below TS ~ 70 K. Here, we report on the magnetism in powder CsO2 and high-magnetic field magnetization measurements in pulsed-magnetic fields of up to 60 T. We obtained the low temperature phase diagram around the antiferromagnetic ordering temperature TN = 9.6 K under the magnetic field. At 1.3 K, remarkable up-turn curvature in the magnetization around a saturation field of ~ 60 T is found, which corresponds to the spin-1/2. We will compare it with the theoretical calculation., Comment: 11 pages, 3 figures

We revisit the 2d Navier--Stokes equations on the periodic $\beta$-plane, with the Coriolis parameter varying as $\beta y$, and obtain bounds on the number of determining modes and nodes of the flow. The number of modes {and nodes} scale as $cG_0^{1/2} + c'(M/\beta)^{1/2}$ and $cG_0^{2/3} + c'(M/\beta)^{1/2}$ respectively, where the Grashof number $G_0=|f_v|_{L^2}^{}/(\mu^2\kappa_0^2)$ and $M$ involves higher derivatives of the forcing $f_v$. For large $\beta$ (strong rotation), this results in fewer degrees of freedom than the classical (non-rotating) bound that scales as $cG_0$., Comment: 15 pages

Realization of a short bunch beam by manipulating the longitudinal phase space distribution with a finite longitudinal dispersion following an off-crest accelera- tion is a widely used technique. The technique was applied in a compact test accelerator of an energy-recovery linac scheme for compressing the bunch length at the return loop. A diagnostic system utilizing coherent transition radiation was developed for the beam tuning and for estimating the bunch length. By scanning the beam parameters, we experimentally found the best condition for the bunch compression. The RMS bunch length of 250+-50 fs was obtained at a bunch charge of 2 pC. This result confirmed the design and the tuning pro- cedure of the bunch compression operation for the future energy-recovery linac (ERL).

Evidence of the $K^+\to\mu^+\nu\bar\nu\nu$ decay was searched for using E949 experimental data with an exposure of $1.70\times 10^{12}$ stopped kaons. The data sample is dominated by the backgrond process $K^+\to\mu^+\nu_\mu\gamma$. An upper limit on the decay rate $\Gamma(K^+\to\mu^+\nu\bar\nu\nu)< 2.4\times 10^{-6}\Gamma(K^+\to all)$ at 90% confidence level was set assuming the Standard Model muon spectrum. The data are presented in such a way as to allow calculation of rates for any assumed $\mu^+$ spectrum., Comment: 7 pages, 5 figures

We introduce new clustering coefficients for weighted networks. They are continuous and robust against edge weight changes. Recently, generalized clustering coefficients for weighted and directed networks have been proposed. These generalizations have a common property, that their values are not continuous. They are sensitive with edge weight changes, especially at zero weight. With these generalizations, if vanishingly low weights of edges are truncated to weight zero for some reason, the coefficient value may change significantly from the original value. It is preferable that small changes of edge weights cause small changes of coefficient value. We call this property the continuity of generalized clustering coefficients. Our new coefficients admit this property. In the past, few studies have focused on the continuity of generalized clustering coefficients. In experiments, we performed comparative assessments of existing and our generalizations. In the case of a real world network dataset (C. Elegans Neural network), after adding random edge weight errors, though the value of one discontinuous generalization was changed about 436%, the value of proposed one was only changed 0.2%., Comment: 29 pages, 14 figures

Evidence of a heavy neutrino, $\nu_H$, in the $K^+\to\mu^+\nu_H$ decays was sought using the E949 experimental data with an exposure of $1.70\times 10^{12}$ stopped kaons. With the major background from the radiative $K^+\to\mu^+\nu_\mu\gamma$ decay understood and suppressed, upper limits (90% C.L.) on the neutrino mixing matrix element between muon and heavy neutrino, $|U_{\mu H}|^2$, were set at the level of $10^{-7}$ to $10^{-9}$ for the heavy neutrino mass region 175 to 300 MeV/$c^2$., Comment: 14 pages, 13 figures; accepted by Physical Review D

Our toolchain for accelerating application called Courier-FPGA, is designed for utilize the processing power of CPU-FPGA platforms for software programmers and non-expert users. It automatically gathers runtime information of library functions from a running target binary, and constructs the function call graph including input-output data. Then, it uses corresponding predefined hardware modules if these are ready for FPGA and prepares software functions on CPU by using Pipeline Generator. The Pipeline Generator builds a pipeline control program by using Intel Threading Building Block to run both hardware modules and software functions in parallel. Finally, Courier-FPGA dynamically replaces the original functions in the binary and accelerates it by using the built pipeline. Courier-FPGA performs these acceleration processes without user intervention, source code tweaks or re-compilations of the binary. We describe the technical details of this mixed software hardware pipeline on CPU-FPGA platforms in this paper. In our case study, Courier-FPGA was used to accelerate a corner detection using the Harris-Stephens method application binary on the Zynq platform. A series of functions were off-loaded, and speed up 15.36 times was achieved by using the built pipeline., Comment: Presented at First International Workshop on FPGAs for Software Programmers (FSP 2014) (arXiv:1408.4423)

The magnetic noise spectra induced by direct-current (dc) current flowing through a micron-scale ferromagnetic wire have been investigated. We have observed the noise spectra with a resonance frequency. Under the application of the magnetic field in the plane, the magnetic field dependences of the resonance frequency and amplitude were well interpreted by the analytical calculation based on the stochastic model. The noise spectra are attributable to the resistance oscillation reflecting the uniform magnetization precession which is produced by the Joule heating due to the dc current., Comment: 24 pages, 7 figures

Spin-polarized radio frequency (RF) currents and RF-Oersted fields resonantly excite a magnetic vortex core confined in a micron-scale soft magnetic disk. In this study, we measured the rectifying voltage spectra caused by the anisotropic magnetoresistance oscillation due to the gyration of the vortex with different polarity and chirality. The measured spectra are presented such that we can determine the vortex properties and strength of the spin torques and Oersted field accurately and directly through analytical calculation., Comment: 39 pages,1 table, 10 figures

Quantum interference incorporating spatially asymmetric potential profiles is realized experimentally to manipulate a magnetic domain wall (DW) into a single multilayered wire whose spacer has a thickness gradient for generating asymmetrical interlayer exchange coupling from side to side. We demonstrate experimentally how to guide a DW in a micron-scale ferromagnetic wire without reflection symmetry of the interlayer exchange coupling. This is the ratcheting of a DW in a form of ratchet potential using quantum interference. The experimental results can be described well by numerical simulations considering spatially asymmetric potential profiles due to quantum interference.

Experiment E949 at Brookhaven National Laboratory has observed three new events consistent with the decay K+ => pi+,nu,nubar in the pion momentum region 140 < P_pi < 199 MeV/c in an exposure of 1.71e12 stopped kaons with an estimated total background of 0.93+-0.17(stat.)+0.32-0.24(syst.) events. This brings the total number of observed K+ => pi+,nu,nubar events to seven. Combining this observation with previous results, assuming the pion spectrum predicted by the standard model, results in a branching ratio of (1.73+1.15-1.05)e-10. An interpretation of the results for alternative models of the decay K^ => pi+,nothing is also presented., Comment: Submitted to Phys.Rev. D

An anomalous Hall effect and rectification of a Hall voltage are observed by applying a radio-frequency (rf) current through a single-layered ferromagnetic wire located on a coplanar waveguide. The components of the magnetization precession, both in and perpendicular to the plane, can be detected via the Hall voltage rectification of the rf current by incorporating an additional direct (dc) current. In this paper, we propose a phenomenological model, which describes the time-dependent anisotropic magnetoresistance and time-dependent planer Hall effect. The nonlinearity of the spin dynamics accompanied by spin-waves as functions of rf and dc currents is also studied, as well as those of the magnitude and orientation of the external magnetic field., Comment: 42 pages, 5 figures, submitted

Laser acceleration promises innovation in particle beam therapy of cancer where an ultra-compact accelerator system for cancer beam therapy can become affordable to a broad range of patients. This is not feasible without the introduction of a technology that is radically different from the conventional accelerator-based approach. The laser acceleration method provides many enhanced capabilities for the radiation oncologist. It reduces the overall system size and weight by more than one order of magnitude. The characteristics of the particle beams (protons) make them suitable for a class of therapy that might not be possible with the conventional accelerator, such as the ease for changing pulse intensity, the focus spread, the pinpointedness, and the dose delivery in general. A compact, uncluttered system allows a PET device to be located in the vicinity of the patient in concert with the compact gantry. The radiation oncologist may be able to irradiate a localized tumor by scanning with a pencil-like particle beam while ascertaining the actual dosage in the patient with an improved in-beam PET verification of auto-radioactivation induced by the beam therapy. This should yield an unprecedented flexibility in the feedback radiotherapy by the radiation oncologist. Laser accelerated radiotherapy has a unique niche in a current world of high energy accelerator using synchrotron or cyclotron., Comment: 26 pages, 8 figures, 2 tables, 69 references. International Symposium on Laser-Driven Relativistic Plasmas Applied for Science, Industry and Medicine, Kyoto, Japan, 17-20 September (2007)

The rectifying effect of radio-frequency (RF) current is highly sensitive in terms of the spatial spin distribution and dynamics. It emerged that an additional spin wave mode was stimulated by the direct-current (DC) current and that this spin wave was detectable via rectification of the RF current. A phenomenological model to describe the time-dependent anisotropic magnetoresistance or time-dependent planer Hall effect is proposed and found to correlate well to the experimental results. The nonlinear spin dynamics accompanying additional spin waves are studied as functions of the RF and DC currents, the external magnetic field, and the applied field direction., Comment: 19 pages, 4 figures

The broadband ferromagnetic resonance measurement using the rectifying effect of Ni81Fe19 wire has been investigated. One wire is deposited on the center strip line of the coplanar waveguide (CPW) and the other one deposited between two strip lines of CPW. The method is based on the detection of the magnetoresistance oscillation due to the magnetization dynamics induced by the radio frequency field. The magnetic field dependences of the resonance frequency and the rectification spectrum are presented and analytically interpreted on the standpoint of a uniform magnetization precession model., Comment: 33pages, 8 figures. submitted

Experimental results of rectification of a constant wave radio frequency (RF) current flowing in a single-layered ferromagnetic wire are presented. We show that a detailed external magnetic field dependence of the RF current induced a direct-current voltage spectrum. The mechanism of the rectification is discussed in a term of the spin transfer torque, and the rectification is closely related to resonant spin wave excitation with the assistant of the spin-polarized RF current. The micromagnetic simulation taking into account the spin transfer torque provides strong evidence which supports the generation of spin wave excitation by the RF current., Comment: 29 page, 7 figures

We report the rectifying effect of a constant-wave radio frequency (RF) current by a magnetic domain wall (DW) on a single-layered ferromagnetic wire. A direct-current (DC) voltage is generated by the spin torque diode effect, which is a consequence of magnetoresistance oscillation due to the resonant spin wave excitation induced by the spin-polarized RF current. The DC voltage spectrum strongly depends on the internal spin structure in the DW, which corresponds to the magnetic fingerprint of the spin structure in the ferromagnetic wire., Comment: 18 pages, 4 figures

We report the rectification of a constant wave radio frequency (RF) current by using a single-layer magnetic nanowire; a direct-current voltage is resonantly generated when the RF current flows through the nanowire. The mechanism of the rectification is discussed in terms of the spin torque diode effect reported for magnetic tunnel junction devices and the rectification is shown to be direct attributable to resonant spin wave excitation by the RF current., Comment: 20 Pages, 4 figures, submitted