Cosmic Neutron Research Articles

NATURAL OR ARTIFICIAL TRITIUM IN RIVERS – THE ASSESSMENT USING SYMMETRICAL INDEX

Tritium, hydrogen isotope, with a half-life of 12.3 years, is produced in two ways: naturally and artificially. Naturally, tritium is generated through the interaction of cosmic radiation protons and neutrons with gases in the upper atmosphere. Artificially, tritium origins from the atmospheric nuclear tests, production from nuclear reactors, future fusion reactors, fuel reprocessing plants, heavy water production facilities and commercial production for medical diagnostics, radiopharmaceuticals, luminous paints. Elevated concentrations of tritium in the environment are of great public concern. Considering the fact that nuclear power plants are located on rivers, knowing the activity concentration of this isotope in rivers is of great importance. This work presents the results for tritium determination in Danube and Sava River in Belgrade, Serbia. The origin of tritium was estimated using a mathematical parameter, symmetrical index.

Effects of soil moisture variations on the neutron spectra measured above ground: feasibility of a soil moisture monitor system based on neutron moderating cylinders

Mapping the soil moisture is a key activity in water management and sustainable agriculture, especially in regions characterised by fragile agri-food systems and water scarcity. Cosmic Ray Neutron Sensors (CRNS) is a contactless nuclear technology used for estimating soil moisture (SM) content on a 20–30 m scale at the landscape level. Very interestingly, this corresponds to the so-called intermediate scale gap between the local probes, operating on the meter scale, and the satellite-based technologies, working on the kilometre scale and above. In state-of-art CRNS, the cosmic neutrons degraded by the soil are simply counted by a slightly moderated thermal neutron counter. After a calibration procedure, the SM is inferred by combining this count rate with environmental parameters: the atmospheric pressure, temperature and the air humidity. As the SM affects not only the environmental neutron fluence rate but also its energy distribution, this study was organised in such a way to understand if a CRNS with spectrometric capabilities could provide improved information on the SM distribution. To this aim, an environmental neutron spectrometer was designed by extending the Bonner Spheres to a more sensitive system made of moderating cylinders embedding long BF3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ _3 $$\\end{document} proportional counters, the Moderating Cylinders Spectrometer (MCS). Relying on literature environmental neutron spectra, corresponding to different SM values in a standardised soil, the count rates in the MCS were calculated for different values of SM. To simulate various counting scenarios, these count rates were associated to different levels of “realistic” uncertainties and unfolded by means of the FRUIT code. The resulting neutron spectra are compared to the literature ones, allowing at estimating the resolving power of the spectrometer in terms of SM.

Calibration of the W-PIE neutron spectrometer at CERF reference facility.

The W-PIE is a cosmic neutron spectrometer used for environmental measurements, developed by Politecnico di Milano. The instrument is based on the Artkis M800 thermal neutron detector and works as a 4-channel spectrometer for detecting neutrons in the energy range of 0.01eV-1GeV. After the spectrometer had been calibrated in some monoenergetic neutron fields at the PIAF facility of PTB, the instrument was tested in the neutron field generated at the CERF facility, whose spectrum fairly resembles the cosmic one. This measurement is a precious tool for predicting the performance of the instrument in a realistic situation.

The JUNO water Cherenkov detector system

The Jiangmen Underground Neutrino Observatory (JUNO) is a 20 kton liquid scintillator detector with the primary physics goal of the neutrino mass ordering determination. The detector will be built in a laboratory 650-m underground. The pool is filled with 34 kton ultrapure water outside the central detector as a water Cherenkov detector for cosmic muon detection. 2400 MCP-PMTs detect the water Cherenkov light produced by cosmic muons. The inner surface of the water veto is covered with a Tyvek reflector to increase the light collection efficiency. A water system is used for water purification and circulation to maintain high water quality for optimal detector performance. A set of radon removal equipment will be integrated with the water system to reduce the radon-induced background in the central detector. Based on prototype studies, the radon concentration in water could be reduced to less than 10 mBq/m3. The cosmic muon detection efficiency of the water Cherenkov detector can reach 99.5%. With this veto system, the cosmic muon-induced fast neutron background can also be reduced to the level of about ∼0.1/day level.

Global dose distributions of neutrons and gamma-rays on the Moon

Dose assessment on the lunar surface is important for future long-term crewed activity. In addition to the major radiation of energetic charged particles from galactic cosmic rays (GCRs), neutrons and gamma-rays are generated by nuclear interactions of space radiation with the Moon’s surface materials, as well as natural radioactive nuclides. We obtained neutron and gamma-ray ambient dose distributions on the Moon using Geant4 Monte Carlo simulations combined with the Kaguya gamma-ray spectrometer measurement dataset from February 10 to May 28, 2009. The neutron and gamma-ray dose rates varied in the ranges of 58.7–71.5 mSv/year and 3.33–3.76 mSv/year, respectively, depending on the lunar geological features. The lunar neutron dose was high in the basalt-rich mare, where the iron- and titanium-rich regions are present, due to their large average atomic mass. As expected, the lunar gamma-ray dose map was similar to the distribution of natural radioactive elements (238U, 232Th, and 40K), although the GCR-induced secondary gamma-ray dose was significant at ~ 3.4 mSv/year. The lunar secondary dose contribution resulted in an additional dose of 12–15% to the primary GCR particles. Global dose distributions on the lunar surface will help identify better locations for long-term stays and suggest radiation protection strategies for future crewed missions.

Cosmic Muon Rates and Neutron Background in a Backpack Radiation Detection System

Radiation detection systems for security applications are often equipped with neutron sensors and required to promptly respond with an alarm if the neutron flux exceeds the background level. As the ambient neutron flux is essentially caused by cosmic radiation, this background could be evaluated by assessing the rate of muons crossing the gamma-ray detector which is comprised in such systems anyway. A study performed with a commercial Backpack Radiation Detection System (BRD) demonstrates the feasibility of this approach, supposed the gamma spectrometer is capable of discriminating muon signals from energetic events caused by the gamma-ray cascades following neutron captures. This requires a dynamic range exceeding the usual 3-4 MeV. The instrument used provided standard spectroscopy up to 10 MeV and facilitated charge-loss compensated spectroscopy up to 1 GeV, which allowed a separate assessment of normal gamma events (< 3 MeV), neutron-capture gamma events (3-7 MeV), and muon events (> 10 MeV). In this case, the rate of neutron-capture gamma events can be used as a neutron indicator on its own, while the muon rate signals the ambient neutron background level.

Cosmic neutrons at ground: new spectral measurements at 3480 m a.s.l. and benchmarking of the cascade component as a function of the elevation at around 45° geomagnetic latitude

Within the INFN-based project SAMADHA, environment neutron spectrum measurements were performed at 3480 m a.s.l. on the Italian western Alps. An extended range Bonner Sphere Spectrometer was used, that was especially designed to operate unattended and to discriminate genuine neutron events from spurious ones. In addition to the measurements of neutron fluence rate, its energy distribution and the related ambient dose equivalent, as well as the arrival time distribution of the events were also studied. The high-energy component of the neutron fluence rate was compared to literature data measured with the same technique at similar latitudes as a function of the elevation, in turn being fitted with an exponential curve and compared to the results from EXPACS code. As the cascade component is not influenced by the materials surrounding the measurement site, this curve can be regarded as “universal” at the studied latitudes.

Verification of Estimated Cosmic Neutron Intensities Using a Portable Neutron Monitoring System in Antarctica

Many ongoing studies for predicting the production rates of cosmogenic nuclides, forecasting changes of atmospheric compositions and climate, assessing the cosmic-radiation exposure of aircraft crew, and the effects on precise electronic devices use numerical models that estimate cosmic-radiation intensities in the atmosphere. Periodic verifications of those models are desirable to be performed for assuring the reliability of the study outcomes. Here, we investigated an application of a portable neutron-monitoring system composed of an extended-energy-range neutron monitor and a small data logger for monitoring of cosmic-neutron intensities in a polar region. As a result of measurements in the east Antarctica region covering a wide range of altitudes (from 30 m to 3762 m) and comparisons with the model calculations performed with an analytical model based on comprehensive Monte Carlo simulations (PARMA), it was demonstrated that the portable neutron-monitoring system could be effectively applied for periodic verification of cosmic-neutron intensities that would improve the reliability of related studies.

IDREAM: industrial Detector of REactor Antineutrinos for Monitoring at Kalinin nuclear power plant

The paper is devoted to the description of the iDREAM detector and its systems. iDREAM is a prototype detector designed to demonstrate the feasibility of antineutrino detectors for remote reactor monitoring and safeguard purposes. Antineutrinos are detected with a 1 ton liquid scintillator via inverse beta decay on protons. In order to suppress cosmic muons, gamma and neutron background, the detector is housed in a dedicated shielding. The detector is installed at the Kalinin nuclear power plant (Russia), 20 m from the 3 GWth reactor core.

Calibration of a large-size wide-range neutron spectrometer

Over the last year, Politecnico di Milano has developed the W-PIE, a cosmic neutron spectrometer employed for environmental measurements. The W-PIE is based on the Artkis M800 thermal neutron detector and works as a 4-channel spectrometer for detecting neutrons in the energy range 0.01eV – 1GeV. In this paper, the calibration of the instrument in monoenergetic neutron fields at the PIAF facility of PTB is discussed. These measurements were intended to calibrate the detector and validate the response functions. Despite obtaining satisfactory results in terms of fluence and dose calculations, the irradiation in the monoenergetic fields suggested that the detector sensitivity to fast neutrons was greater than expected by the calculated response functions. This discrepancy was investigated and a reasonable explanation for it was proposed.

Evaluation of cosmogenic production of 39Ar and 42Ar for rare-event physics using underground argon

Underground argon (UAr) with lower cosmogenic activities of 39Ar and 42Ar has been planned as a detector in detecting scintillation light and charge collection using time projection chambers for dark matter searches and as a veto detector in suppressing backgrounds for neutrinoless double beta decay (0νββ) experiments. Long-lived radioactive isotopes, 39Ar and 42Ar, can also be produced on the surface when UAr is pumped out from a deep well. Understanding the production of long-lived isotopes in Ar is important for utilizing UAr for dark matter and 0νββ experiments in terms of its production, transportation, and storage. Ar exposure to cosmic rays at sea-level is simulated using Geant4 for a given cosmic ray muon, neutron, and proton energy spectrum. We report the simulated cosmogenic production rates of 39Ar, 42Ar, and other long-lived isotopes at sea-level from fast neutrons, high energy muons, and high energy protons. Total production rates of 938.53/kgArday and 5.81 × 10−3/kgArday for 39Ar and 42Ar are found from our simulation. Utilizing these production rates, we set a time limit of 954 days constrained by the production of 39Ar for UAr to be on the surface before it compromises the sensitivity for a dark matter experiment. Similarly, a time limit of 1702 days constrained by the production of 42Ar is found for a 0νββ experiment.

Genetic algorithm-based optimization of a target for the production of atmospheric-like neutrons via 100 MeV proton beam

This paper presents the optimization of a white neutron target for 100 MeV proton beam to produce a fast neutron spectrum shape similar to that of the atmospheric neutron at ground level. The neutron target consists of 0.5 mm-thick discs consecutively placed in front of a cooling water channel. A sensitivity analysis is performed with different materials to assimilate resulting neutron spectrum with the ground-level cosmic ray-induced neutron spectrum by applying the genetic algorithm (GA). Optimization of the spectrum is conducted in consideration of neutron impact to semiconductor devices. To reconstruct a target-generated neutron spectrum, parametrization on neutron generation and stopping power by target material and position is configured. The loss function in the GA is defined to evaluate similarity between the target neutron spectrum and the atmospheric neutron spectrum. The GA is modeled with a package of consecutive discs as a gene for optimization, and the length and material of target for each disc are decided throughout generations. As a result, the target is configured with six different materials, with approximately half of the weighted deviation of atmospheric neutrons being compared with any other single-solid neutron target. The GA-based optimization process shown here suggests further use for designing targets with other incident proton energies or neutron spectra for various applications.

COSMOGENIC14CO FOR ASSESSING THE OH-BASED SELF-CLEANING CAPACITY OF THE TROPOSPHERE

ABSTRACTAn application of radiocarbon (14C) in atmospheric chemistry is reviewed.14C produced by cosmic neutrons immediately forms14CO, which reacts with hydroxyl radicals (OH) to14CO2. By this the distribution and seasonality (the lifetime of14CO is ∼1 month) of the pivotal atmospheric oxidant OH can be established.14CO measurement is a complex but unique application which benefitted enormously from the realization of AMS, bearing in mind that14CO abundance is of the order of merely 10 molecules per cm3not only provides14CO an independent measure for the OH based self-cleansing capacity of the troposphere, but also enabled detection of14C production due to high energy solar protons in 1989. Although its production takes place throughout the atmosphere and does not have the character of a point source, transport processes in the atmosphere affect the distribution of14CO. Vertical mixing in the troposphere renders gradients in its production rate less critical, but considerable meridional gradients exist. One question has remained open, namely confirmation of calculated14C production by direct measurement. A new sampling method is proposed. The conclusions are a guide to future work on14CO in relation to OH and atmospheric transport.

Radio-Electronic Modules and Radiation Monitoring Systems based on Diamond Detectors

An overview of the current state and promising areas of application of semiconductor diamond detectors for creating radio-electronic monitoring systems for ionizing studies based on them is given. The main attention is paid to the creation of multifunctional space radiation monitoring systems that combine a set of diamond detectors and hardware and software tools that provide diagnostics of dose and spectrometric characteristics of various types of radiation. The data on the developed and manufactured samples of blocks and on-board control systems for cosmic and ionizing radiation are presented. The overview shows that diamond ionizing radiation detectors (IRD) are actively used in the creation of radio-electronic devices and monitoring systems for ionizing and cosmic radiation. The use of diamond IRD in combination with the developed design and technological solutions, hardware and software principles for the construction of such devices make it possible to create samples of on-board onboard avionics for separate measurement of the parameters of cosmic radiation and neutron fluxes, gamma radiation, characterized by small dimensions, high speed, hardness to radiation, mechanical and temperature influences. Multifunctional systems for ionizing radiation detection based on diamond detectors use the accumulated experience of successful development and application of discrete diamond IRD allowed us to start creating multifunctional modules and radiation monitoring systems (RMS) based on them. Theыыыыыы creation of such devices allows us to practically demonstrate the traditional advantages of discrete DIRD (high speed, the highest radiation hardness, high resistance to mechanical and thermal influences) in on-board equipment with smaller mass dimensions. The main structural and technological solutions that ensure the creation and effective functioning of RMS based on diamond IRD are the following: (1) separation the IR flow into energy sub-bands; (2) the use of software and hardware processing of data received from the IRD; (3) using a multi-detector system. Further development of research and development in these areas, in addition to solving the target tasks of radio-electronic instrumentation, will stimulate technological progress in various areas of solid-state electronics, including materials science and physics of wide-band semiconductors, the development of an experimental and technological base for the synthesis of diamond bulk crystals and multilayer structures, the creation of new technologies for ion-plasma processing of semiconductors, and a number of others.

An innovative neutron spectrometer for soil moisture measurements

Soil moisture is a crucial variable in evaluating soil properties and its interaction with the atmosphere, yet none of the techniques currently employed is fully adequate for evaluating the water content in soil over an area of hectares and depth of tens of centimeters. In recent times, it has been shown how the water content over this volume can be accurately assessed measuring changes in the epithermal flux of cosmic neutrons, which is extremely sensitive to the moderation caused by hydrogen. The instruments employed for neutron flux measurements are usually neutron counters, covered with moderator coatings for enhancing their sensitivity in the epithermal energy range. On the other hand, the worldwide shortage of {}^{3}He caused a considerable increase in the costs associated with the manufacturing of proportional counters based on this gas, which were widely employed for their great sensitivity and noise rejection capability. In this work, we developed a {}^{3}He-free neutron spectrometer for performing these measurements, which detects neutrons in the energy range from 0.01 ev to 1 GeV. The reconstruction of the energy spectrum allows a more accurate evaluation of the epithermal neutron flux and provides other information which improves the quality of soil moisture measurements. Irradiations performed with neutron sources of {}^{241}Am and AmBe allowed to evaluate the spectrometric capability of the instrument, whereas the measurements of cosmic neutrons were employed to assess its sensitivity to cosmic radiation. The sensitivity of the instrument is slightly less than the one of the neutron counters currently employed, yet the access to the spectrometric information should provide greater accuracy in the epithermal flux measurements.

Radioactive background for ProtoDUNE detector

The Deep Underground Neutrino Experiment (DUNE) is a leading-edge, international experiment for neutrino science and proton decay studies. This experiment is looking for answers regarding several fundamental questions about the nature of matter and the evolution of the universe: origin of matter, unification of forces, physics of black holes. Two far detector prototypes using two distinct technologies have been developed at CERN. The prototypes are testing and validating the liquid argon time projection chamber technology (LArTPC). In neutrino physics, as well as in any experiment with rare interaction rate, the good knowledge of the radioactive backgrounds is important to the success of the study.Muons and neutrons represent the main sources of background for this kind of experiments. In this paper, we have considered two sources of neutrons: cosmic neutrons and neutrons coming from the accelerating tunnel. Also, cosmic muons are taken into account. The contribution of these particles to the production of radioactive isotopes inside the active volume of the detector in comparison to the one corresponding to muons is shown. Also, simulations of nuclear reactions for the processes of interest for investigating the radioactive background due to the lack of measurements or insufficient experimental data are presented. Most of the results presented in this paper will be of interest for the future underground DUNE experiment.

Spectroscopic study of the effect of low dose fast neutrons on the hemoglobin structure

Cosmic rays, nuclear accidents, and neutron therapy could be sources for exposure to low-dose fast neutrons. However, the study of low dose effects needs sentient techniques to detect slight alteration happen by this low dose. Herein, the effects of low-dose fast neutrons on the structure of hemoglobin (Hb) using spectroscopic techniques, namely, Fourier transform infrared (FTIR), Raman, and ultraviolet–visible (UV–Vis) spectroscopic. Forty (20 control/20 irradiated) female Wistar rats were used in this work. The irradiated rats were irradiated to low-dose at a total dose of 10 mGy from a fast neutron source (241Am-Be, 0.2 mGy/h). Multivariate analyses were applied to differentiate between the control and irradiated rats’ Raman spectra. The erythrocytes samples were isolated from whole blood to explore the Hb structure. FTIR results revealed changes in the ν(S-H) bond of α-104 and β-93 cysteines by low-dose fast neutrons. Raman spectra showed changes in the spin state and oxidation state of the iron atom of the Hb. Besides, deformation in methine C-H was recorded. UV–Vis spectroscopy disclosed that the irradiated rats might be more susceptive to oxidation than control rats. The study deduced that the low dose fast neutron could cause tiny Hb structure changes by indirect effects. Besides, the spectroscopic techniques showed a potent ability to reveal tiny changes in the Hb structure that happened by a low dose of fast neutrons.

The Role of Strong Gravity and the Nuclear Equation of State on Neutron-star Common-envelope Accretion

Abstract Common-envelope evolution is important in the formation of neutron star binaries within the isolated binary formation channel. As a neutron star inspirals within the envelope of a primary massive star, it accretes and spins up. Because neutron stars are in the strong-gravity regime, they have a substantial relativistic mass deficit, i.e., their gravitational mass is less than their baryonic mass. This effect causes some fraction of the accreted baryonic mass to convert into neutron star binding energy. The relativistic mass deficit also depends on the nuclear equation of state, since more compact neutron stars will have larger binding energies. We model the mass growth and spin-up of neutron stars inspiraling within common-envelope environments and quantify how different initial binary conditions and hadronic equations of state affect the post-common-envelope neutron star’s mass and spin. From these models, we find that neutron star mass growth is suppressed by ≈15%–30%. We also find that for a given amount of accreted baryonic mass, more compact neutron stars will spin-up faster while gaining less gravitational mass, and vice versa. This work demonstrates that a neutron star’s strong gravity and nuclear microphysics plays a role in neutron-star-common-envelope evolution, in addition to the macroscopic astrophysics of the envelope. Strong gravity and the nuclear equation of state may thus affect both the population properties of neutron star binaries and the cosmic double neutron star merger rate.

БИОЛОГИЧЕСКАЯ ЭФФЕКТИВНОСТЬ БЫСТРЫХ НЕЙТРОНОВ И УСКОРЕННЫХ МНОГОЗАРЯДНЫХ ИОНОВ ДЛЯ ПОСТРОЕНИЯ НОВОЙ ЗАВИСИМОСТИ КОЭФФИЦИЕНТОВ КАЧЕСТВА КОСМИЧЕСКИХ ИЗЛУЧЕНИЙ ОТ ЛИНЕЙНОЙ ПЕРЕДАЧИ ЭНЕРГИИ

The authors review recent experimental data about relative biological effectiveness (RBE) of low absorbed doses (0.01–0.5 Gy) from fast neutrons and accelerated multicharged ions currently accepted as career limits for cosmonauts from the standpoint of late effects risk mitigation. According to the new radiobiological findings, literary maximum values of the RBEM coefficients for low doses and dose rates are increased two or three times for late cytogenetic effects; benign cell transformation and tumor risks; lifetime reduction; disorders in the brain cortex neurons and damages to organs; lenticular opacity and cataract. The analysis-based revision of the quality coefficients – linear energy transfer (LET) relationship leads to a considerable increase of equivalent doses received from galactic cosmic rays and fast neutrons, and calculated total radiation risk over cosmonaut's lifetime.

Effect of low-dose fast neutrons on the protein components of peripheral blood mononuclear cells of whole-body irradiated Wistar rats.

The immune system is exposed to extremely low doses of neutrons under different circumstances, such as through exposure to cosmic rays, nuclear accidents, and neutron therapy. Peripheral blood mononuclear cells (PBMCs) are the primary immune cells that exhibit selective immune responses. Changes in the functions of the protein components of PBMC can be induced by structural modifications of these proteins themselves. Herein, we have investigated the effect of low-dose fast neutrons on PBMC proteins at 0, 2, 4, and 8days post-whole body irradiation. 64 Wistar rats were used in this study of which, 32 were exposed to fast neutrons at a total dose of 10mGy (241Am-Be, 0.2mGy/h), and the other 32 were used as controls. Blood samples were drawn, and PBMCs were isolated from whole blood. Fourier transform infrared (FTIR) spectroscopy and fluorescence spectroscopy were used to estimate the changes in the proteins of PBMCs. An alkaline comet assay was performed to assess DNA damage. Hierarchical cluster analysis (HCA) and principal components analysis (PCA) were utilized to discriminate between irradiated and non-irradiated samples. FTIR and fluorescence spectra of the tested samples revealed alterations in the amides and tryptophan, and therefore protein structure at time intervals of 2 and 4days post-irradiation. No changes were recorded in samples tested at time intervals of 0 and 8days post-irradiation. The FTIR band intensities of the PBMC proteins of the irradiated samples decreased slightly and were statistically significant. Curve fitting of the amide I band in the FTIR spectra showed changes in the secondary structure of the proteins. At 2days post-irradiation, fluorescence spectra of the tested samples revealed decreases in the band tryptophan. The comet assay revealed low levels of DNA damage. In conclusion, low-dose fast neutrons can affect the proteins of PBMC.