A barrel-shaped plastic scintillation counter with Multi-Pixel Photon Counter (MPPC) readout has been developed and operated in the first WASA-FRS experimental campaign at GSI. The detector was used to measure charged particles emitted from reactions induced by a 2.5 GeV proton beam incident on a carbon target, providing particle identification in combination with momentum reconstruction in a 1 T magnetic field. The performance of this detector, particularly its response to energy deposition and time resolution, was systematically investigated as a function of count rate and total number of irradiating protons. A time resolution of 45-75 ps ($σ$), depending on the energy deposition, was achieved. Stable performance was maintained under high-rate conditions up to 1.35 MHz per single counter, with no significant degradation in either signal amplitude or timing response. Radiation-induced damage to the MPPCs was observed primarily as a reduction in signal amplitude, with approximately $35\%$ decrease at an estimated 1 MeV neutron-equivalent fluence of $2.4 \times 10^{10}$ cm$^{-2}$.
The nuclear charge radius plays a vital role in determining the equation of state of isospin asymmetric nuclear matter. Based on the correlation between the differences in charge radii of mirror-partner nuclei and the slope parameter ($L$) of symmetry energy at the nuclear saturation density, an analysis of the calibrated slope parameter $L$ was performed in finite nuclei. In this study, relativistic and non-relativistic energy density functionals were employed to constrain the nuclear symmetry energy through the available databases of the mirror-pair nuclei $^{36}$Ca-$^{36}$S, $^{38}$Ca-$^{38}$Ar, and $^{54}$Ni-$^{54}$Fe. The deduced nuclear symmetry energy was located in the range 29.89-31.85 MeV, and $L$ of the symmetry energy essentially covered the range 22.50-51.55 MeV at the saturation density. Moreover, the extracted $L_s$ at the sensitivity density $ρ_{s}=0.10~\mathrm{fm}^{-3}$ was located in the interval range 30.52-39.76 MeV.
Background: Nuclear transfer reactions are a useful tool to study the structure of a nucleus. For reactions involving weekly bound nuclei, breakup effects can play significant role and theoretical calculations can be computational expensive in such cases. Purpose: To utilize the Lagrange-mesh and R-matrix methods for nuclear transfer reactions. Methods: We use the adiabatic distorted wave approximation (ADWA) method which can approximately treats the breakup effects in a simpler manner. In our approach, we apply the R-matrix method combining it with the Lagrange-mesh method, which is known to provide the fast and accurate computations. Results: As a test case, we calculate the angular distribution of the cross sections for the 54Fe(d, p)55Fe reaction, where deuteron breakup effects play important role. Conclusions: We show that these methods work well in the ADWA framework, and we look forward to applying these methods in coupled channel calculations.
We present the results of a National Science Foundation (NSF) Project Scoping Workshop, the purpose of which was to assess the current status of calculations for the nuclear matrix elements governing neutrinoless double-beta decay and determine if more work on them is required. After reviewing important recent progress in the application of effective field theory, lattice quantum chromodynamics, and ab initio nuclear-structure theory to double-beta decay, we discuss the state of the art in nuclear-physics uncertainty quantification and then construct a road map for work in all these areas to fully complement the increasingly sensitive experiments in operation and under development. The road map contains specific projects in theoretical and computational physics as well as an uncertainty-quantification plan that employs Bayesian Model Mixing and an analysis of correlations between double-beta-decay rates and other observables. The goal of this program is a set of accurate and precise matrix elements, in all nuclei of interest to experimentalists, delivered together with carefully assessed uncertainties. Such calculations will allow crisp conclusions from the observation or non-observation of neutrinoless double-beta decay, no matter what new physics is at play.
Special high-protein foods suitable for diabetics must be treated to ensure the complete absence of microorganisms and bacteria. It is also important to achieve that this treatment does not change the nutritional value of the product. Among the new decontamination technologies, low-energy electron-beam treatment has proven to be an effective technique for inactivating bacteria with minimal impact on food quality. The paper aims to analyze the influence of low-energy electron-beam irradiation on the microbiological properties and nutritional value of high-protein foods.
Bojan Rankovic, Nikolina Nikolic, Slobodan Masic
et al.
The distribution of the absorbed dose within the irradiated product is a complex function of the product density and homogeneity, the position and shape of the radiation source, as well as the design of the irradiator. In this paper, detailed mapping of absorbed radiation doses in products of different density: gauze, plastic, and soil, is performed. Positions of minimum and maximum absorbed radiation dose were determined, and the homogeneity of irradiation of products was calculated using the ethanol-monochlorobenzene oscillotitrator dosimetry system.
We give a brief overview of recent theoretical and experimental results on the chiral magnetic effect and spin polarization effect in heavy-ion collisions. We present updated experimental results for the chiral magnetic effect and related phenomena. The time evolution of the magnetic fields in different models is discussed. The newly developed quantum kinetic theory for massive fermions is reviewed. We present theoretical and experimental results for the polarization of $Λ$ hyperons and the $ρ_{00}$ value of vector mesons.
Within the Bayesian statistical framework we infer the incompressibility $K_0$, skewness $J_0$ and kurtosis $Z_0$ parameters of symmetric nuclear matter (SNM) at its saturation density $ρ_0$ using the constraining bands on the pressure in cold SNM in the density range of 1.3$ρ_0$ to 4.5$ρ_0$ from transport model analyses of kaon production and nuclear collective flow in relativistic heavy-ion collisions. As the default option assuming the $K_0$, $J_0$ and $Z_0$ have Gaussian prior probability distribution functions (PDFs) with the means and variances of $235\pm 30$, $-200\pm 200$ and $-146\pm 1728$ MeV, their posterior most probable values are narrowed down to 192$^{+12}_{-16}$ MeV, -180$^{+100}_{-110}$ MeV and 200$^{+250}_{-250}$ at 68\% confidence level, respectively. The results are largely independent of the prior PDFs of $J_0$ and $Z_0$ used. However, if one adopts the strong belief that the incompressibility $K_0$ has a uniform prior PDF within its absolute boundary of 220-260 MeV as one can find easily in the literature, the posterior most probable values of $K_0$, $J_0$ and $Z_0$ shift to $K_0=220^{+6}_{-0}$ MeV, $J_0=-390^{+60}_{-70}$ MeV and $Z_0=600^{+200}_{-200}$ MeV, respectively. While the posterior PDFs of the SNM EOS parameters depend somewhat on the prior PDF of $K_0$ used, the results from using different prior PDFs are qualitatively consistent. The uncertainties of all three parameters are significantly reduced especially for the $J_0$ and $Z_0$ parameters compared to their current values.
We describe the Bayesian Analysis of Nuclear Dynamics (BAND) framework, a cyberinfrastructure that we are developing which will unify the treatment of nuclear models, experimental data, and associated uncertainties. We overview the statistical principles and nuclear-physics contexts underlying the BAND toolset, with an emphasis on Bayesian methodology's ability to leverage insight from multiple models. In order to facilitate understanding of these tools we provide a simple and accessible example of the BAND framework's application. Four case studies are presented to highlight how elements of the framework will enable progress on complex, far-ranging problems in nuclear physics. By collecting notation and terminology, providing illustrative examples, and giving an overview of the associated techniques, this paper aims to open paths through which the nuclear physics and statistics communities can contribute to and build upon the BAND framework.
The strange quark plays a unique role in QCD, reflecting its intermediate mass between the light and heavy quarks. In recent years, remarkable progress has been made in the spectroscopy of baryons with strangeness. Many new features of the strange baryon spectrum have been revealed by accurate experimental data with novel techniques, as well as systematic developments of theoretical framework to describe hadron resonances. The basic properties of strange baryons, namely, the pole positions, spin and parity, and decay branching ratios, are being determined accurately. As a consequence, the Particle Data Group have added new entries in the particle listings, such as the $Λ(1380)$ and the $Ω(2012)$. The developments of the spectroscopy stimulate intensive discussion on the exotic internal structure of strange baryons beyond the ordinary three-quark configuration. In this review, we introduce the basics of QCD, the scattering theory, and the exotic internal structure of hadrons, emphasizing the importance of the pole positions of the scattering amplitude for the characterization of hadron resonances. We then summarize the current status of selected strange baryon resonances; $Λ(1405)$, $Λ(1670)$, $Ξ(1620)$, $Ξ(1690)$, and $Ω(2012)$, from theoretical and experimental viewpoints.
The mean-field approximation based on effective interactions or density functionals plays a pivotal role in the description of finite quantum many-body systems that are too large to be treated by ab initio methods. Some examples are strongly interacting medium and heavy mass atomic nuclei and mesoscopic condensed matter systems. In this approach, the linear Schrodinger equation for the exact many-body wave function is mapped onto a non-linear density-dependent one-body potential problem. This approximation, not only provides computationally very simple solutions even for systems with many particles, but due to the non-linearity, it also allows for obtaining solutions that break essential symmetries of the system, often connected with phase transitions. In this way, additional correlations are subsumed in the system. However, the mean-field approach suffers from the drawback that the corresponding wave functions do not have sharp quantum numbers and, therefore, many results cannot be compared directly with experimental data. In this article, we discuss general group-theory techniques to restore the broken symmetries, and provide detailed expressions on the restoration of translational, rotational, spin, isospin, parity and gauge symmetries, where the latter corresponds to the restoration of the particle number. In order to avoid the numerical complexity of exact projection techniques, various approximation methods available in the literature are examined. Applications of the projection methods are presented for simple nuclear models, realistic calculations in relatively small configuration spaces, nuclear energy density functional theory, as well as in other mesoscopic systems. Further, unresolved problems in the application of the symmetry restoration methods to the energy density functional theories are highlighted in the present work.
High-energy scattering processes, such as deep inelastic scattering (DIS) and quasielastic (QE) scattering provide a wealth of information about the structure of atomic nuclei. The remarkable discovery of the empirical linear relationship between the slope of the European Muon Collaboration (EMC) effect in DIS and the short-range-correlation (SRC) scaling factors $a_2$ in QE kinematics is naturally explained in terms of scale separation in effective field theory. This explanation has powerful consequences, allowing us to calculate and predict SRC scaling factors from ab initio low-energy nuclear theory. We present ab initio calculations of SRC scaling factors for a nucleus $A$ relative to the deuteron $a_2(A/d)$ and relative to $^3\rm He$ $a_2(A/^3\rm He)$ in light and medium-mass nuclei. Our framework further predicts that the EMC effect and SRC scaling factors have minimal or negligible isovector corrections.
In this paper, the application of three-component gas mixtures as a working gas in Geiger-Mueller tubes was considered. In addition to the noble and quenching gas, an electronegative gas is used, at the same time, as the third component of gas mixture. This paper is mostly experimental. The experiments are carried out on the enlarged Geiger-Mueller counter tube model. By applying the similarity law for electric discharges in gases on the model and commercial Geiger-Mueller counting tubes, the model was verified. The obtained results showed that a small percentage of SF6 gas, in the working gas, stabilize operating point of Geiger-Mueller counter tubes and reduce dead time. <br><br><font color="red"><b> This article has been corrected. Link to the correction <u><a href="http://dx.doi.org/10.2298/NTRP1804417E">10.2298/NTRP1804417E</a><u></b></font>
LiF is an alkali halide that is commonly used in radiation dosimetry utilizing its well-known thermoluminescence property. Pure LiF has very limited use in radiation dosimetry since the density and types of the internal traps are limited. For that reason, LiF is usually doped with different elements such as Mg and Ti in (TLD-100) to enhance its thermoluminescence properties and to be suitable for dosimetry applications. In this work we used ball milling as an alternative to dopants (impurities) to induce structure defects (e.g. dislocation) that will play the major role in thermoluminescence process similar to defectsecaused by dopants. The dislocation density of 1 h ball milled pristine LiF was evaluated at the MCX beamline of the Italian Synchrotron ELETTRA. A ball milled LiF was then compressed in the form of chips, then annealed for 1 h at 600?C to get rid of low temperature dislocations. The annealed samples showed linear response in the range 50-300 Gy. Fading investigation showed that the integral thermoluminescence intensity almost stabilizes after 12 days from the first irradiation. Results indicate that ball milling is a new promising technique to produce thermoluminescence dosimeters without using any kind of dopants.
The effects of radiation damage in silicon photomultipliers (SiPMs) from gamma rays have been measured and compared with the damage produced by neutrons. Several types of MPPCs from Hamamatsu were exposed to gamma rays and neutrons at the Solid State Gamma Ray Irradiation Facility (SSGRIF) at Brookhaven National Lab and the Institute for Nuclear Research (Atomki) in Debrecen, Hungary. The gamma ray exposures ranged from 1 krad to 1 Mrad and the neutron exposures ranged from 10$^8$ n/cm$^2$ to 10$^{12}$ n/cm$^2$. The main effect of gamma ray damage is an increase in the noise and leakage current in the irradiated devices, similar to what is seen from neutron damage, but the level of damage is considerably less at comparable high levels of exposure. In addition, the damage from gamma rays saturates after a few hundred krad, while the damage from neutrons shows no sign of saturation, suggestive of different damage mechanisms in the two cases. The change in optical absorption in the window material of the SiPMs due to radiation was also measured. This study was carried out in order to evaluate the use of SiPMs for particle physics applications with moderate levels of radiation exposures.
Resonance is a general phenomenon which can happen in classic or quantum systems. An unbound many-body quantum system can undergo a self-resonant process. It has long been a challenge how to describe unbound many-body quantum systems in resonances. In this paper, we develop a novel first-principles method that is capable of describing resonant quantum systems. We exploit, for the first time, the advanced in-medium similarity renormalization group (IMSRG) in the complex-energy Gamow-Berggren representation with resonance and non-resonant continuum. The ab initio Gamow IMSRG has broad applications, such as, to the electromagnetic-interaction systems of atoms, molecules or quantum dots, and strong-interaction atomic nuclei. In the present work, we apply the method to loosely bound or unbound nuclear systems. Carbon and oxygen isotopes have been investigated with an optimized chiral effective field theory potential. The resonant states observed in neutron-rich 22O and 24O are well reproduced. The loose halo structure of the Borromean nucleus 22C is clearly seen by the density calculation, in which the continuum s-waves play a crucial role. Further, we predict low-lying resonant excited states in 22C. This method provides rigorous and tractable theoretical calculations for weakly-bound or unbound open quantum systems.
We present an up-to-date global analysis of data coming from neutrino oscillation and non-oscillation experiments, as available in April 2018, within the standard framework including three massive and mixed neutrinos. We discuss in detail the status of the three-neutrino (3nu) mass-mixing parameters, both known and unknown. Concerning the latter, we find that: normal ordering (NO) is favored over inverted ordering (IO) at 3sigma level; the Dirac CP phase is constrained within ~15% (~9%) uncertainty in NO (IO) around nearly-maximal CP-violating values; the octant of the largest mixing angle and the absolute neutrino masses remain undetermined. We briefly comment on other unknowns related to theoretical and experimental uncertainties (within 3nu) or possible new states and interactions (beyond 3nu).
Marija Radmilovic-Radjenovic, Petar Belicev, Branislav Radjenovic
Electron field emission limiting the accelerating gradient in superconducting cavities remains the dominant setback in cavity production. The need to understand and control the field emission has become increasingly important because of the prospect of using high-gradient structures in linear colliders. Since building an accelerator structure is a complicated and costly process, elimination of unnecessary steps has priority. In this paper an analysis of the influence of the enhanced field emission in superconducting radio frequency cavity together with modal field calculations by using COMSOL finite elements package has been presented. The obtained results reveal that the electric field required for the field emission is generated in the cavity irises. The imperfection of the cavity surface leading to very high fields is modelled by a simple cone. The estimated value of the enhancement factor for the cone tip of around 4 is in a good agreement with the data found in the literature. In addition, from the slopes and the intercepts of the Fowler-Nordheim plots, a dependence of the enhancement factor and the effective area on the work function has been estimated.
This study presents the determination of fuel rejuvenation times in a D-T fusion breeder reactor fuelled with a mixture of natUO2 and ThO2 for multi-reuse of nuclear fuels in CANDU-37 reactors. To determine the effect of thorium on the fuel enrichment and rejuvenation times, neutronic analyses are performed by increasing the percentage of ThO2 in the fuel mixture from 10 to 35. The time-dependent neutronic calculations are carried out in three stages. In the first stage, which is the fuel enrichment or rejuvenation process in the fusion breeder reactor, the subcritical calculations of the fusion breeder reactor fuelled with the fuel mixtures are performed by using the MCNPX 2.7/CINDER under a fusion neutron wall loading of 1 MWm-2, corresponding to neutron flux of 4.444?1013 cm-2s-1 (energy of every fusion neutron is 14.1 MeV). In the second stage, which is the thermal reactor analysis, the fuel rods enriched at the end of the first stage are placed in the CANDU-37 reactor, and the critical calculations of this reactor are performed by using MCNPX 2.7 and MONTEBURNS codes separately. The numerical results show that the neutronic values obtained from both codes are very near each other. The third stage is the two-year cooling process of CANDU spent fuels. The values obtained by numerical calculations show that this fusion breeder reactor is self-sufficient in terms of tritium and has a high performance in terms of energy multiplication as well as fuel rejuvenation and thorium utilization.