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

Tatsuhiko Sato, Y. Iwamoto, S. Hashimoto et al.

Shiyi Liu, Bei Liu, I. Ivanov et al.

Vortex states of photons or electrons are a novel and promising experimental tool across atomic, nuclear, and particle physics. Various experimental schemes to generate high-energy vortex particles have been proposed. However, diagnosing the characteristics of vortex states at high energies remains a significant challenge, as traditional low-energy detection schemes become impractical for high-energy vortex particles due to their extremely short de Broglie wavelength. We recently proposed a novel experimental detection scheme based on a mechanism called"superkick"that is free from many drawbacks of the traditional methods and can reveal the vortex phase characteristics. In this paper, we present a complete theoretical framework for calculating the superkick effect in elastic electron scattering and systematically investigate the impact of various factors on its visibility. In particular, we argue that the vortex phase can be identified either by detecting the two scattered electrons in coincidence or by analyzing the characteristic azimuthal asymmetry in individual final particles.

T. Bikbaev, M. Khlopov, A. Mayorov

Within the framework of the XHe hypothesis, the positive results of the DAMA/NaI and DAMA/LIBRA experiments on the direct search for dark matter particles can be explained by the annual modulation of the radiative capture of dark atoms into low-energy bound states with sodium nuclei. Since this effect is not observed in other underground WIMP (weakly interacting massive particle) search experiments, it is necessary to explain these results by investigating the possibility of the existence of low-energy bound states between dark atoms and the nuclei of matter. Numerical modeling is used to solve this problem, since the study of the XHe–nucleus system is a three-body problem and leaves no possibility of an analytical solution. To understand the key properties and patterns underlying the interaction of dark atoms with the nuclei of baryonic matter, we develop the quantum mechanical description of such an interaction. In the numerical quantum mechanical model presented, takes into account the effects of quantum physics, self-consistent electromagnetic interaction, and nuclear attraction. This approach allows us to obtain a numerical model of the interaction between the dark atom and the nucleus of matter and interpret the results of direct experiments on the underground search for dark matter, within the framework of the dark atom hypothesis. Thus, in this paper, for the first time, steps are taken towards a consistent quantum mechanical description of the interaction of dark atoms, with unshielded nuclear attraction, with the nuclei of atoms of matter. The total effective interaction potential of the OHe–Na system has therefore been restored, the shape of which allows for the preservation of the integrity and stability of the dark atom, which is an essential requirement for confirming the validity of the OHe hypothesis.

Zhilong Pan, Wenhui Huang, Chuanxiang Tang et al.

In low and medium energy electron storage rings, intrabeam scattering (IBS) is a significant collective effect that can lead to an increase in equilibrium emittance, thereby diminishing the light source’s flux. Typically, the bunch length of the electron beam in storage rings is considered constant around the ring circumference. However, in the concept of steady-state microbunching storage rings, the bunch length can vary significantly around the ring in an effort to achieve high coherence in the longitudinal dimension. In this paper, we have extended the Bjorken and Mtingwa (B-M) model to accommodate this requirement, making it versatile enough to be used for arbitrary planar storage rings. Additionally, this paper addresses the simplification of equilibrium emittance calculations involving IBS through certain approximations, making it possible to directly calculate equilibrium emittance by a formula rather than conventional iteration method. This method reveals the physical relationship between equilibrium emittance and the IBS growth rates, and also allows for the IBS effect optimization of the ring lattice by directly using equilibrium emittance as the optimization target rather than the IBS growth rate.

F. D. Amaro, R. Antonietti, E. Baracchini et al.

Dark matter, which is considered to account for approximately the 27% of the Universe's energy-mass content, remains an open issue in modern particle physics along with its composition. The CYGNO Experiment aims to exploit an innovative approach applied to the direct detection search of low energy nuclear recoils possibly induced by cold particle-like dark matter candidates. CYGNO employs a directional detector based on a Time Projection Chamber (TPC) filled with a He:CF$_{4}$ gas mixture and equipped with an optical readout. Currently, the CYGNO Collaboration is constructing the detector demonstrator, CYGNO-04, in Hall F at Laboratori Nazionali del Gran Sasso (LNGS). This 0.4 m$^3$ detector has the goal of proving the scalability of the technology and assessing the physics and radiopurity capabilities. Given the low radioactivity requirements, especially in internal components such as field cage and cathode, the reduction of material while keeping the correct electrical behavior is paramount. In this paper, we present the validation of several internal components, mainly focusing on the field cage material and support structure. The tests included geometrical asymmetries in the electric field response, collection efficiency as well as measurement of known physical quantities. A preferred configuration is found with a structure based on Nylon material which supports a PET or Kapton sheet with copper strips deposited on.

D. Poenaru, R. Gherghescu

In 1980 A. Sǎndulescu, D.N. Poenaru from Bucharest, Romania and Walter Greiner from Frankfurt am Main, Germany, published an article in which cluster radioactivity was predicted. For years latter (1984) H.J. Rose and J.A. Jones from Oxford University reported the first experimental evidence of 14 C radioactivity of 223 Ra. Extensive calculations have been published by D.N. Poenaru et al. in 1986 and 1991 in Atomic Data and Nuclear Data Tables. A very useful review of experimental results was published by R. Bonetti and A. Guglielmetti from Milano, Italy in Romanian Reports in Physics 59 (2007) 301-310. In this article we compare the measured Q-values and half-lives with predictions within the Analytical Super-Asymmetric Fission (ASAF) model. Cluster radioactivity (spontaneous emission of particles larger than 4 He) is a rare phenomenon in a large background of alpha decay. For some very heavy nuclei it is possible to observe cluster radioactivity comparable or even stronger than alpha decay.

M. Bikchurina, I. P. Asanov, T. Bykov et al.

Chang-Hao Fang, Yi-Ke Shu, Shin-Ted Lin et al.

Diverse searches for direct dark matter (DM) in effective electromagnetic and leptophilic interactions resulting from new physics, as well as Weakly Interacting Massive Particles (WIMPs) with unconventional electronic recoils, are intensively pursued. Low-energy backgrounds from radioactive $\gamma$ rays via Compton scattering and photon coherent scattering are unavoidable in terrestrial detectors. The interpretation of dark matter experimental data is dependent on a better knowledge of the background in the low-energy region. We provide a 2.3% measurement of atomic Compton scattering in the low momentum transfer range of 180 eV/c to 25 keV/c, using a 10-g germanium detector bombarded by a $^{137}\mathrm{Cs}$ source with a 7.2 m-Curie radioactivity and the scatter photon collected by a cylindrical NaI[Tl] detector. The ability to detect Compton scattering's doubly differential cross section (DDCS) gives a special test for clearly identifying the kinematic restraints in atomic many-body systems, notably the Livermore model. Additionally, a low-energy-background comparison is made between coherent photon scattering and Compton scattering replacing the scattering function of ${GEANT4}$@software, which uses a completely relativistic impulse approximation (RIA) together with Multi-Configuration Dirac-Fock (MCDF) wavefunctions. For the purpose of investigating sub-GeV mass and electronic-recoil dark matter theories, signatures including low energy backgrounds via high energy $\gamma$ rays in germanium targets are discussed.

A. Šagátová

This university textbook provides the first part of basic knowledge in nuclear physics and technology. It focuses on the correct understanding of the problematics of radioactivity of atomic nuclei. The textbook describes the structure and forces of atomic nuclei with background in standard model of elementary particles. It discusses the radioactive decay law as well as the activation of atomic nuclei. It offers the overview of stabilisation of radioactive nuclei via radioactive decay, gamma emission or spontaneous fission. At the end of individual chapters, students will find exercises for practicing their correct understanding of the discussed topics: the atomic nuclei, the radioactivity and the radioactive decays. All exercises are based on real examples with actual parameters of nuclei. The correct answers to problems can be found in the rear part of the textbook. The textbook also responds to the recent methods and knowledge in the field of nuclear physics and encourages the students to use the global databases involving latest results of world leading research centres in nuclear physics and technology. The textbook is primary dedicated to the students of nuclear power engineering and nuclear technology, but it can also enrich students of other study fields of natural science and technology, as well as the employees in the nuclear power engineering with a different background than nuclear.

Serge F. Timashev

The present study demonstrates that the mechanism of initiation of low-energy nuclear chemical processes under conditions of low-temperature non-equilibrium deuterium and protium-containing glow discharge plasma is similar to the previously studied cumulative mechanism of initiation of nuclear processes in the collision of relativistic particles (protons) with target atomic nuclei. This process results in the formation of high-energy products that significantly exceed the kinematically resolved region in the pulse space for two-particle collisions “nucleus–target’s nucleus.” The cumulative effect in this case is associated with the initiation of non-nucleonic metastable excitations in nuclear matter during relativistic collisions leading to the formation of a group of quarks from different nucleons within the nucleus. In low-energy nuclear chemical processes, the initiation of quark-cumulative processes in nuclear matter occurs through interaction of nuclei with electrons with high kinetic energies on a chemical scale, typically Ee ~ 3–5 eV. Experiments and available literature data suggest that the metastable excitations of nuclear matter containing three “free” quarks during such collisions are associated with quark-cumulative effects, leading to the radioactive α- and β-decay of elements. This phenomenon is observed during laser ablation of metals in aqueous media containing radioactive elements and in the artificial radioactivity of initially non-radioactive isotopes in cathodes exposed to low-temperature non-equilibrium deuterium- and protium-containing plasma flows during glow discharge.

Jingke Xu, P. Barbeau, Ziqing Hong

Detection of low-energy nuclear recoil events plays a central role in searches for weakly interacting massive particle (WIMP) dark matter interactions with atomic matter and studies of coherent neutrino scatters. Precise nuclear recoil calibration data allow the responses of these dark matter and neutrino detectors to be characterized and enable in situ evaluation of an experiment's sensitivity to anticipated signals. This article reviews the common methods for detection of nuclear recoil events and the wide variety of techniques that have been developed to calibrate detector response to nuclear recoils. We summarize the main experimental factors that are critical for accurate nuclear recoil calibrations, investigate mitigation strategies for different backgrounds and biases, and discuss how the presentation of calibration results can facilitate comparison between experiments. Lastly, we discuss the challenges for future nuclear recoil calibration efforts and the physics opportunities they may enable. Expected final online publication date for the Annual Review of Nuclear and Particle Science, Volume 73 is September 2023. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Zuhair, Luthfi Wahid, Dwijayanto Andika Putra R. et al.

Thorium, in this case, 232Th has a higher thermal neutron capture cross-section than 238U, which means that more fertile isotopes can be transmuted and could lead to higher fissile isotope 233U. In addition, 233U has a good performance in the thermal spectrum. Theoretically, a nuclear reactor using thorium fuel can also last longer than one using uranium fuel. The use of TRISO duplex fuel is predicted to produce better neutronic behavior in a pebble bed reactor. This work aims to study the kinetic parameters of a pebble bed reactor with TRISO duplex fuel. The configuration of the TRISO duplex fuel pebble consists of an inner region filled with UO2 TRISO particles and an outer region filled with ThO2 TRISO particles surrounded by a graphite matrix of fuel pebble. Three configurations with volume fraction of UO2-ThO2 were considered in this study: 80-20 %, 75-25 %, and 70-30 %. The HTR-10 reactor was chosen as a reactor model because its geometry and material specifications are known. A series of calculations were conducted using the Monte Carlo transport code MCNP6 and ENDF/B-VII.1 nuclear data library. The calculation results were then analyzed to investigate the effect of UO2 and ThO2 compositions in TRISO duplex fuel on the kinetic parameters of the pebble bed reactor with various TRISO packing fractions of 1-50 %. It can be concluded that the utilization of TRISO duplex fuel in a pebble bed reactor could significantly affect the core multiplication factor and kinetic parameters caused by an increase in Th content. On the other hand, the TRISO packing fraction is taking part in neutron moderation since a lower packing fraction means higher moderation for fueled pebble.

Lam Hui, Austin Joyce, Ilia Komissarov et al.

Abstract We derive soft theorems for theories in which time symmetries — symmetries that involve the transformation of time, an example of which are Lorentz boosts — are spontaneously broken. The soft theorems involve unequal-time correlation functions with the insertion of a soft Goldstone in the far past. Explicit checks are provided for several examples, including the effective theory of a relativistic superfluid and the effective field theory of inflation. We discuss how in certain cases these unequal-time identities capture information at the level of observables that cannot be seen purely in terms of equal-time correlators of the field alone. We also discuss when it is possible to phrase these soft theorems as identities involving equal-time correlators.

Alexandre Landry, Robert J. van den Hoogen

A complete perturbation theory suitable for teleparallel gravity is developed. The proposed perturbation scheme takes into account perturbations of the coframe, the metric, and the spin-connection, while ensuring that the resulting perturbed system continues to describe a teleparallel gravity situation. The resulting perturbation scheme can be transformed to one in which perturbations all take place within the co-frame. A covariant definition of a teleparallel Minkowski geometry is proposed. We compute the perturbed field equations for <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>f</mi><mo>(</mo><mi>T</mi><mo>)</mo></mrow></semantics></math></inline-formula> teleparallel gravity and discuss the stability of the teleparallel Minkowski geometry within <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>f</mi><mo>(</mo><mi>T</mi><mo>)</mo></mrow></semantics></math></inline-formula> teleparallel gravity.

C.U. Schuster, E. Wolfrum, T. Görler et al.

Gas puff modulation experiments are performed at ASDEX Upgrade in L-mode, EDA H-mode and quasi-continuous exhaust discharges. Plasma density and temperatures are measured and their temporal development is analyzed simultaneously, revealing that both heat and particle transport are strongly influenced by the modulation. As a consequence, the particle transport coefficients are underdetermined. In the transport modelling, the pedestal cannot be treated as a single region, but the pedestal foot must be allowed to increase its transport with gas puff modulation independently. The analysis of the temporal behaviours of the heat and particle diffusivities shows that they are strongly correlated. Considering the heat diffusivity as a proxy for the particle diffusivity, allows interpretation of the density evolution: a pinch is not required for any of the discharges. An analysis with the gyrokinetic turbulence code GENE identifies dominant instabilities and reproduces several experimentally found trends. Despite all uncertainties concerning particle transport, one can expect a future reactor featuring a weak edge density gradient even with purely diffusive transport.

R. Kohale, S. Dhoble, V. Chopra

Fundamentals of Nuclear Physics gives elementary understanding of nuclear and particle physics. The textbook offers an overview of the subject, providing students with a basic understanding about 1) the atomic structure and the nucleus, 2) equipment such as particle detectors, particle accelerators, and nuclear reactors, 3) radioactivity, and 4) elementary particles. Each chapter provides fundamental theoretical and experimental knowledge required for students to strengthen their concepts. Other key features of the book include: - Structured chapters designed for easy reading and stimulating interest for learners - Sophisticated figures - Thoroughly solved equations - Bibliographic references for further reading - Updated information about different types of nuclear reactors - Information about nuclear astrophysics Fundamentals of Nuclear Physics is suitable for introductory undergraduate courses in nuclear physics as well as more innovative courses geared towards nuclear engineering.

F. Sabatié, H. Moutarde

The Institute for Research into the Fundamental Laws of the Universe (IRFU) at the French Atomic Energy and Alternative Energies Commission (CEA) was created in 1992 by bringing together the scientific and technological components of entities dedicated to particle physics, nuclear physics, and astrophysics. The embodiment of a visionary scheme at a time when the links between the infinitely small and the infinitely large were less common and less obvious than they are today, IRFU federates seven physical and technical departments through shared methods, instrumental technologies, and scientific questioning:

Amy L. Anderson, Graham L. O'Donnell, J. Piekarewicz

Reduced basis methods provide a powerful framework for building efficient and accurate emulators. Although widely applied in many fields to simplify complex models, reduced basis methods have only been recently introduced into nuclear physics. In this letter we build an emulator to study the single-particle structure of atomic nuclei. By scaling a suitable mean-field Hamiltonian, a “universal” reduced basis is constructed capable of accurately and efficiently reproduce the entire single-particle spectrum of a variety of nuclei. Indeed, the reduced basis model reproduces both ground- and excited-state energies as well as the associated wave-functions with remarkable accuracy. Our results bode well for more demanding applications that use Bayesian optimization to calibrate nuclear energy density functionals.

HE Yihai;WANG Gang;KUANG Bo;LUO Yuejian;WU Xiaoli

External reactor vessel cooling (ERVC) is one of the important severe accident mitigation strategies to achieve in-vessel retention(IVR) of melt core debris under severe accident conditions. Referring to the IVR-ERVC conditions for the prototypical pressure vessel lower head wall of elliptic-shaped, a critical heat flux (CHF) test campaign was, in the paper, carried out upon a full-sized thick test block section which was installed in a one-dimensional full height natural circulation test loop. Eighteen groups of heating rods with independent power control were inserted into the test block. Eight experimental measuring points were evenly distributed on the heating wall of the test block along the inclination angle, and the heating power shapes of each experimental measuring point were determined according to the Theofanous’ power shaping principle. Thermocouples were arranged near the heating wall and on all sides of the test block to obtain the temperature information during heating and CHF occurring. CHF data as well as their distribution along ellipticalshaped outer wall of test block were obtained. Meanwhile, preliminary evidence of typical CHF triggering mechanism on downwardfacing curved heating wall was deduced through the visual observations during the test. The visual observations show that when the evaporative drying area of the liquid film under the vapor block is large enough, it is difficult to cool the heating wall of test block. The wall temperature rises rapidly, and CHF occurs. Furthermore, effects of inlet subcooling, flooding water level, flow resistance and natural circulation flow rate, as well as the gap size of ERVC channels on CHF limits are experimentally studied. Test results show that, CHF increases with the increase of the inclination angle of heating wall, the increase of inlet subcooling can significantly increase CHF. Increasing the inlet subcooling can reduce the liquid temperature in the twophase boundary layer and effectively delay the evaporation of the liquid film, so as to improve the CHF. In the base cases and inlet subcooling cases, the relative decrease of CHF occurs in the uppermost section of the heating wall, which is called “exit phenomenon”. The CHF of the heating wall increases slightly with the increase of liquid level. While the change of natural circulation flow resistance and flow rate in a certain range has a rather limited impact on CHF. According to the CHF triggering mechanism, the flow rate change is not large enough to cause the instability and fracture of vapor block and the near wall flow structure does not change significantly, so the impact is limited. The influence of the change of gap size of ERVC channel on CHF is quite complicated. It seems that the relative relationship between the gap size and the thickness of twophase boundary layer, as well as the streamline constraints of the flow channel wall on the vapor phase both have influence on the CHF quantity and distribution.

J. Klusoň

Abstract We study string theory with momentum living on de Sitter space. We argue that consistency of the theory implies that the global momentum can be defined on de Sitter space. Then we perform careful canonical analysis and we we also show that this presumption leads to the string with deformed dispersion relation.