Hasil untuk "Nuclear and particle physics. Atomic energy. Radioactivity"

Ling-Zheng Xia, Lixin Xu, Wei-Jia Li

Abstract Fractonic phases of matter, a class of states in which collective excitations with constrained mobility exist, were originally discovered in the study of quantum error-correcting codes in solvable lattice spin models such as Haah’s code and the X-cube model. Recently, they have also drawn the attention of the high-energy physics community due to the UV/IR mixing that arises when coarse-graining these lattice models. In this work, we consider a (3+1)-dimensional holographic model of fractonic solids and investigate the low-energy collective dynamics systematically. By computing the quasinormal modes of black holes, we obtain all the hydrodynamic excitations on the boundary, including two acoustic phonons, a longitudinal diffusive mode, and a subdiffusive collective mode with the dispersion ω ~ – ik 4. In addition, it is found that the latter remains gapless when translational symmetry is explicitly broken. These results suggest that the subdiffusive mode is inherently protected by the crystal-dipole symmetry in solids and is qualitatively unaffected by broken spacetime symmetries.

Mahendra Rajaram More, Prashant Singh, Mayank Shukla et al.

Radioisotope-based neutron sources are employed in a myriad of industrial applications, but they are not well suited for applications that require controlled neutron irradiation and may create the safety issues and logistical complications. In contrast, accelerator-based neutron sources based on the T (d, n)α and D (d, n) 3He reactions, known as D-T and D-D generators respectively, generate quasi-monoenergetic neutrons with neutron energy of 14.1 and 2.45 MeV, respectively, and neutron production can be controlled electronically. This article describes in-house development of sealed D-T neutron source as an alternative to more commonly used 252Cf or 241Am-Be neutron sources. The development of neutron generator requires development of various important sub-components such as Titanium hydride target, solid state gas reservoir, acceleration column and HV supply, etc. The development of suitable thin film using thermal vapor deposition techniques was carried out and used for deuterium/tritium deposition. Similarly, high deuterium storage in a solid reservoir is very crucial for the long life of the neutron generator. Therefore, we have chosen titanium metal due to its good sorption-desorption characteristics. The neutron yield of the generator is 3 × 107 n/s in D-T mode. These neutron generators are widely used as calibration standards for detector calibrations and dosimetry applications. Such generators are now accessible in a range of configurations and are becoming suitable for a variety of other applications such as mining, oil exploration, and elemental characterization of materials.

LIU Zhan, HE Gaokui, LIU Haifeng

High purity germanium detectors play an increasingly significant role in particle physics and astrophysics, particularly in low-background radiation measurement experiments, due to their exceptional energy resolution, high detection efficiency. These detectors are especially critical in the search for rare events, such as neutrinoless double-beta decay (0vββ) and direct detection of dark matter, as they operate effectively under extremely low-background conditions. To fully leverage the advantages of HPGe detectors, a specifically tailored front-end readout system was required to minimize the contribution of electronic noise from the system itself. This noise minimization is critical to ensure that weak event signals from inside the detector are not obscured by the system’s inherent noise. In this paper, the design of a multi-channel, low-noise charge-sensitive amplifier (CSA) optimized for use with coaxial HPGe detectors was proposed, particularly those with large input capacitance. Large-capacitance detectors tend to introduce significant input noise, which degrades the overall energy resolution of the system. Therefore, higher standards are necessary for the noise performance of front-end electronics in such systems to preserve the excellent resolution that HPGe detectors can achieve. In multi-stage amplification systems, the noise performance is primarily influenced by the first amplification stage, where the noise characteristics of the input transistor play a crucial role. To address this, the input transistor was designed using an optimized noise model, iterative simulations, and a specially engineered layout structure to ensure low noise. However, larger transistor sizes can lead to gate leakage currents, which can alter the baseline of the amplifier output. To address this issue, a low-noise CSA circuit with a feedback resistor module for leakage current compensation was developed. This resistor feedback module mitigates sensitivity to power supply variations, temperature changes, and process deviations, and can compensate for leakage currents up to several micro amperes. Importantly, the circuit is self-biased, eliminating the need for external bias to adjust the feedback resistance value. The proposed amplifier demonstrated a rise time of less than 50 ns when used with a detector capacitance of 10 pF, and no oscillations were observed under these conditions. At low temperatures, the amplifier exhibits outstanding noise performance, with a noise level as low as 5.6 electrons. Additionally, it provides an output conversion gain of 5 mV/fC, a linearity deviation of only 0.15%, and a low static power consumption of 12.5 milliwatts. The performance achieved is sufficient for gamma-ray spectroscopy and pulse shape analysis using coaxial high purity germanium detectors.

J. Dobaczewski, B. C. Backes, R. P. de Groote et al.

Electromagnetic interactions serve as essential probes for studying and testing our understanding of the atomic nucleus, as they reveal emergent properties across the nuclear chart. We analyse their corresponding observables, which relate to charge and current distributions in nuclei expressed through their multipole components. We focus on theoretical results obtained within nuclear density functional theory (DFT) to derive self-consistent, symmetry-restored nuclear wave functions along with their spectroscopic multipole moments. We demonstrate how these compare with experimental data. We also discuss potential improvements in the formulation of magnetic dipole operators by including two-body meson-exchange contributions. Discussions of exotic symmetry-breaking moments emphasise their importance for understanding fine details of fundamental nuclear interactions. Detailed derivations are provided in the accompanying Supplemental Material.

N. Tsoulfanidis, S. Landsberger

Vijay Shankar, N. Bisai, Shrish Raj et al.

We present an improved model for the study of edge biasing in a tokamak plasma that incorporates electron and ion mobility contributions. The non-ambipolar nature of the drifts due to the electron/ion mobility terms influences the space charge separation due to edge biasing and affects plasma dynamics in the edge and SOL regions in a significant manner. In contrast to earlier studies, the present model enables simulation studies at higher biasing voltages. The inclusion of mobility enhances/decreases the effect of negative/positive biasing. The radial profiles of plasma density, electron temperature, radial electric field, and its shear for positive as well as negative biasing are investigated as a function of mobility.

Cong Li, Liang Gao, Udo von Toussaint et al.

This comment examines a recent study claiming the observation of deuterium (D) supersaturated surface layer (SSL) in tungsten samples exposed to D plasma in the PISCES-A plasma device at ion energies as low as 45 eV/D (Nishijima et al 2023 Nucl. Fusion 63 126003). Applying SDTrimSP simulations and recalling the previous study on SSL formation, herein we want to emphasize that the proposed model in the mentioned paper relies on a number of strong assumptions and that many of the observations made can be more easily rationalized by the presence of impurities. The present comment will be conducive to avoid some possible misunderstanding on the SSL formation mechanism.

ZOU Hang1,2, CHEN Ying3, ZHANG Qian4, CAO Wei4, ZHANG Jinchao5, LIANG Liang6, SONG Peitao7, LIU Jie1,2

The purpose of this study is to investigate the impact of neutron anisotropic scattering on critical experimental setups and to develop a MOC (method of characteristic) program capable of handling anisotropic scattering, along with a high-performance heterogeneous parallel algorithm for high-order scattering transport calculations. In the initial stages, the physical calculations of the critical experimental setup were analyzed, revealing that neutron anisotropic scattering can significantly affect the calculation results, particularly when a thicker water reflector is present. Building upon the P1 anisotropic scattering MOC, a specialized MOC program was developed to address this issue. To validate the accuracy of the newly developed program for critical experimental simulations, the researchers selected the LCT011 critical experimental benchmark for neutronic calculations. A comprehensive comparison was performed between the results obtained from the MOC program and a Monte Carlo program, serving as a benchmark for verification. One notable challenge encountered during the study was the substantial increase in computation time and memory consumption caused by the presence of anisotropic sources. This created a significant memory burden, especially on heterogeneous systems. Consequently, the researchers conducted a thorough performance analysis of the high-order scattering transport solver employed in the program. The numerical results obtained from the study showcase that the MOC program achieves comparable accuracy to the Monte Carlo program under conditions involving high-order scattering computations. Furthermore, the researchers observed that the developed program exhibited remarkable computational efficiency, making it a promising alternative to the Monte Carlo method. By effectively addressing the impact of neutron anisotropic scattering and providing accurate results with enhanced computational efficiency, the developed MOC program holds great potential for advancing critical experimental simulations. This research significantly contributes to the field of physical calculations by offering a reliable and efficient solution for handling anisotropic scattering in high-order transport calculations. In conclusion, this study presents the purposeful investigation of neutron anisotropic scattering in critical experimental setups, resulting in the development of a specialized MOC program and a high-performance heterogeneous parallel algorithm. The validation process, conducted using the LCT011 critical experimental benchmark, confirms the accuracy of the program. The performance analysis showcases the computational efficiency of the developed program, thus establishing its viability for critical experimental simulations involving anisotropic scattering effects. This research underscores the importance of accurate neutron anisotropic scattering calculations and offers an innovative solution to address the associated challenges in the field of reactor core physical calculations.

Chunjian Zhang

In relativistic heavy-ion collisions, the extractions of properties of quark-gluon plasma (QGP) are hindered by a limited understanding of its initial conditions, where the nuclear structure of the colliding ions play a significant role. In these proceedings, we present the first quantitative demonstration using ``collective flow assisted nuclear shape imaging" method to extract the quadrupole deformation and triaxiality from $^{238}$U using data from the Relativistic Heavy Ion Collider (RHIC). We achieve this by comparing bulk observables in $^{238}$U+$^{238}$U collisions with nearly spherical $^{197}$Au+$^{197}$Au collisions. A similar comparative measurement performed in collisions of $^{96}$Ru+$^{96}$Ru and $^{96}$Zr+$^{96}$Zr, suggests the presence of moderate quadrupole deformation of $^{96}$Ru, large octupole deformation of $^{96}$Zr, as well as an apparent neutron skin difference between these two species. The prospect of this nuclear shape imaging method as a novel tool for the study of nuclear structure is also elaborated.

The ATLAS collaboration, G. Aad, B. Abbott et al.

Abstract This paper presents a search for hypothetical massive, charged, long-lived particles with the ATLAS detector at the LHC using an integrated luminosity of 139 fb −1 of proton–proton collisions at s $$ \sqrt{s} $$ = 13 TeV. These particles are expected to move significantly slower than the speed of light and should be identifiable by their high transverse momenta and anomalously large specific ionisation losses, dE/dx. Trajectories reconstructed solely by the inner tracking system and a dE/dx measurement in the pixel detector layers provide sensitivity to particles with lifetimes down to O $$ \mathcal{O} $$ (1) ns with a mass, measured using the Bethe–Bloch relation, ranging from 100 GeV to 3 TeV. Interpretations for pair-production of R-hadrons, charginos and staus in scenarios of supersymmetry compatible with these particles being long-lived are presented, with mass limits extending considerably beyond those from previous searches in broad ranges of lifetime.

Enzo Canonero, Alessandra Rosalba Brazzale, Glen Cowan

Abstract We present improved methods for calculating confidence intervals and p values in situations where standard asymptotic approaches fail due to small sample sizes. We apply these techniques to a specific class of statistical model that can incorporate uncertainties in parameters that themselves represent uncertainties (informally, “errors on errors”) called the Gamma Variance Model. This model contains fixed parameters, generically denoted by $$\varepsilon $$ ε , that represent the relative uncertainties in estimates of standard deviations of Gaussian distributed measurements. If the $$\varepsilon $$ ε parameters are small, one can construct confidence intervals and p values using standard asymptotic methods. This is formally similar to the familiar situation of a large data sample, in which estimators for all adjustable parameters have Gaussian distributions. Here we address the important case where the $$\varepsilon $$ ε parameters are not small and as a consequence the first-order asymptotic distributions do not represent a good approximation. We investigate improved test statistics based on the technology of higher-order asymptotics (modified likelihood root and Bartlett correction). The effective application of higher-order corrections removes an important computational barrier to the use of the Gamma Variance Model.

I. Noureen, Ali Raza, S. A. Mardan

Abstract In this article, cracking technique is developed for spherically symmetric compact sources in the framework of f(R, T) gravity, where R denotes Ricci scalar and T stands for trace of energy momentum tensor. The characteristics of a star with anisotropic pressure stresses are investigated by utilizing the Tolman–Kuchowicz spacetime solutions. Modified field equations are developed for a particular model i.e., $$f(R,T)=R+2\gamma T$$ f ( R , T ) = R + 2 γ T , where $$\gamma $$ γ is constant, that are further used to develop expressions for matter density, radial and tangential pressures. A generalized form of the Tolman Oppenheimer Volkoff (TOV) equation is developed for the modified field equations. The consequence of the local density perturbation scheme, as presented by Biswas et al. (Eur Phys J C 80:175, 2020) is considered. The mathematical framework for cracking has been tested on five realistic stars namely, Vela X-1, Cen X-3, SMC X-1, PSR J1614-2230 and PSR J1903+327. The graph of forces distribution of these stars have been observed to check the stability regions. The results of cracking/overturning for various values of the parameters involved in this model are observed by checking the instability regions in the form intervals.

Yasushi Muraki, Shoichi Shibata, Hisanori Takamaru et al.

Muons produced by cosmic rays above the atmosphere provide valuable information on the intensity of cosmic rays and variations in the upper atmosphere. Since 1970, the Nagoya University Cosmic Ray Laboratory has been observing the muon intensity using a multi-directional cosmic ray telescope with two layers of 36 plastic scintillators of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>1</mn><mspace width="4pt"></mspace><msup><mi mathvariant="normal">m</mi><mn>2</mn></msup></mrow></semantics></math></inline-formula> each, which measure the muon intensity in different incident directions. The energy of an incident proton that produces a muon incident from a vertical direction is over 11.5 GV. This paper analyzes vertical muon intensities obtained over 48 years from 1970 to 2018 using methods that differ from the East–West method. As a result, a new periodicity of (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>125</mn><mo>±</mo><mn>45</mn></mrow></semantics></math></inline-formula>) days and a new periodicity of (4–16) days were found. The latter appears only in winter time, so it may be caused by a synoptic-scale disturbance associated with the arrival of the Siberian cold air mass. On the other hand, the former periodicity may be related to solar dynamo activity. In 1984, the Solar Maximum Mission’s Gamma Ray Spectrometers reported a periodicity of about (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>154</mn><mo>±</mo><mn>10</mn></mrow></semantics></math></inline-formula>) days in the flux of solar gamma rays. The (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>125</mn><mo>±</mo><mn>45</mn></mrow></semantics></math></inline-formula>)-day periodicity found here is most likely related to solar dynamo activity, since the intensity of cosmic rays around 11.5 GV is affected by the magnetic field induced by the Sun. However, this (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>125</mn><mo>±</mo><mn>45</mn></mrow></semantics></math></inline-formula>)-day periodicity differs from the report measured by the GRS instrument in a point that it also appears during periods of low solar activity. Furthermore, it has not appeared often during lower solar activity since 1992. This information is important for future investigation of the origin of this periodicity.

Martin J. Savage

Future quantum computers are anticipated to be able to perform simulations of quantum many-body systems and quantum field theories that lie beyond the capabilities of classical computation. This will lead to new insights and predictions for systems ranging from dense non-equilibrium matter, to low-energy nuclear structure and reactions, to high-energy collisions. I present an overview of digital quantum simulations in nuclear physics, with select examples relevant for studies of quark matter.

Ya. D. Krivenko-Emetov

A two-component van der Waals gas model is proposed to describe the hadronic stages of the evolution of a nuclear fireball in the cooling stage. At the first stage of hadronization, when mesons dominate, a two-component meson model ($π^0$ and $π^+$ -mesons) with an effective two-particle interaction potential of a rectangular well is proposed. At the late-stage hadronization, when almost all mesons have decayed, a two-component nucleon model of protons and neutrons is proposed with the corresponding effective rectangular nucleon potential. The saddle point method has been applied for analytical calculations of the partition function. This made it possible to uniformly obtain analytical expressions for both the pressure and density, taking into account the finite dimensions of the system, and the analytical expressions for chemical potentials. It is assumed that the proposed models and derived formulas can be used to analyze experimental data connected to the quantitative characteristics of the particle yields of different types in the final state from the hadronic stages of the evolution of a nuclear fireball, as well as to determine the critical parameters of the system in high-energy nucleus-nucleus collisions.

G. Gallina, Y. Guan, F. Retiere et al.

Abstract Liquid xenon time projection chambers are promising detectors to search for neutrinoless double beta decay (0 $$\nu \beta \beta $$ ν β β ), due to their response uniformity, monolithic sensitive volume, scalability to large target masses, and suitability for extremely low background operations. The nEXO collaboration has designed a tonne-scale time projection chamber that aims to search for 0 $$\nu \beta \beta $$ ν β β of $$^{136}$$ 136 Xe with projected half-life sensitivity of $$1.35\times 10^{28}$$ 1.35 × 10 28  yr. To reach this sensitivity, the design goal for nEXO is $$\le $$ ≤ 1% energy resolution at the decay Q-value ( $$2458.07\pm 0.31$$ 2458.07 ± 0.31  keV). Reaching this resolution requires the efficient collection of both the ionization and scintillation produced in the detector. The nEXO design employs Silicon Photo-Multipliers (SiPMs) to detect the vacuum ultra-violet, 175 nm scintillation light of liquid xenon. This paper reports on the characterization of the newest vacuum ultra-violet sensitive Fondazione Bruno Kessler VUVHD3 SiPMs specifically designed for nEXO, as well as new measurements on new test samples of previously characterised Hamamatsu VUV4 Multi Pixel Photon Counters (MPPCs). Various SiPM and MPPC parameters, such as dark noise, gain, direct crosstalk, correlated avalanches and photon detection efficiency were measured as a function of the applied over voltage and wavelength at liquid xenon temperature (163 K). The results from this study are used to provide updated estimates of the achievable energy resolution at the decay Q-value for the nEXO design.

HAN Jinyu;HE Wen;ZHAO Chenru;BO Hanliang

In the two-phase flow system, the flow pattern affects the frictional resistance and heat transfer characteristics of the system. Accurate identification of different flow patterns is of great significance to the calculation of twophase flow. For the gasliquid flow in narrow channels, especially the flow pattern and flow pattern transition criterion in rectangular narrow channels, some researchers have done some experimental studies. For the study of flow pattern in narrow rectangular channels, the classification of flow patterns is basically consistent with that in conventional rectangular channels, including bubbly flow, slug flow, churn flow and annular flow. However, the performance of existing flow pattern transition criteria for twophase flow in narrow rectangular channels still needs further and comprehensive assessments. In this paper, a parameter representing the success rate of boundary separation of bubblyslug flow transition was introduced to quantitatively evaluate the performances of five typical bubbly-slug flow transition criteria and experimental data reported by 10 previous researchers, covering channel sizes ranging from 0.6 mm to 30 mm. Results show that the success rate of boundary separation of the Jones & Zuber criterion, Taitel criterion, MishimaIshii criterion and Xu criterion in predicting the experimental data varies from 61.86% to 98.10%. The variation mainly attributes to the assumption of constant critical void fraction in these criterions, since analyzing shows that the critical void fraction of flow pattern transition is related to the channel geometry. Although the HibikiMishima criterion considers the effect of channel size on the critical void fraction, the bubbly diameter (Db) is also needed in this model, which is difficult to obtain. The influence of channel size on the flow transition was quantitatively analyzed based on a dimensionless parameter of confinement number (Co). Finally, the flow pattern transition function (f(k)) was correlated with Co, and a new flow pattern transition criterion of bubbly-slug flows in narrow channel considering the physical properties of working fluid and the size of flow channel with higher accuracy and wider application range was established, which predicts the experimental data with success rates of boundary separation of 83.78% to 98.10% within the range of 0.486 57≤Co≤1.471 04, 0.016 m/s≤jg≤6.758 m/s, and 0.058 m/s≤jf≤5.059 m/s. The conclusions of this paper can provide references for the design and optimization of reactor heat exchanger components and compact heat exchangers.

Malte Storm, Florian Döring, Shashidhara Marathe et al.

Full-field transmission X-ray microscopy (TXM) is a very potent high-resolution X-ray imaging technique. However, it is challenging to achieve fast acquisitions because of the limited efficiency of the optics. Using a broader energy bandwidth, for example using a multilayer monochromator, directly increases the flux in the experiment. The advantage of more counts needs to be weighed against a deterioration in achievable resolution because focusing optics show chromatic aberrations. This study presents theoretical considerations of how much the resolution is affected by an increase in bandwidth as well as measurements at different energy bandwidths (ΔE/E = 0.013%, 0.27%, 0.63%) and the impact on achievable resolution. It is shown that using a multilayer monochromator instead of a classical silicon double-crystal monochromator can increase the flux by an order of magnitude with only a limited effect on the resolution.

Damiano Anselmi

We review the concept of purely virtual particle and its uses in quantum gravity, primordial cosmology and collider physics. The fake particle, or "fakeon", which mediates interactions without appearing among the incoming and outgoing states, can be introduced by means of a new diagrammatics. The renormalization coincides with the one of the parent Euclidean diagrammatics, while unitarity follows from spectral optical identities, which can be derived by means of algebraic operations. The classical limit of a theory of physical particles and fakeons is described by an ordinary Lagrangian plus Hermitian, micro acausal and micro nonlocal self-interactions. Quantum gravity propagates the graviton, a massive scalar field (the inflaton) and a massive spin-2 fakeon, and leads to a constrained primordial cosmology, which predicts the tensor-to-scalar ratio $r$ in the window $0.4\lesssim 1000r\lesssim 3.5$. The interpretation of inflation as a cosmic RG flow allows us to calculate the perturbation spectra to high orders in the presence of the Weyl squared term. In models of new physics beyond the standard model, fakeons evade various phenomenological bounds, because they are less constrained than normal particles. The resummation of self-energies reveals that it is impossible to get too close to the fakeon peak. The related peak uncertainty, equal to the fakeon width divided by 2, is expected to be observable.

M. Rosner, D. Beck, P. Fierlinger et al.

We report the design and performance of a non-magnetic drift stable optically pumped cesium magnetometer with a measured sensitivity of 35 fT at 200 s integration time and stability below 50 fT between 70 s and 600 s. To our knowledge this is the most stable magnetic field measurement to date. The sensor is based on the nonlinear magneto-optical rotation effect: in a Bell-Bloom configuration a higher order polarization moment (alignment) of Cs atoms is created with a pump laser beam in an anti-relaxation coated Pyrex cell under vacuum, filled with Cs vapor at room temperature. The polarization plane of light passing through the cell is modulated due the precession of the atoms in an external magnetic field of 2.1 muT, used to optically determine the Larmor precession frequency. Operation is based on a sequence of optical pumping and observation of freely precessing spins at a repetition rate of 8 Hz. This free precession decay readout scheme separates optical pumping and probing and thus ensures a systematically highly clean measurement. Due to the residual offset of the sensor of < 15 pT together with the cross-talk free operation of adjacent sensors, this device is uniquely suitable for a variety of experiments in low-energy particle physics with extreme precision, here as highly stable and systematically clean reference probe in search for time-reversal symmetry violating electric dipole moments.