Environmental neutrons originate from two sources: cosmic rays and natural radioactivity. They are in equilibrium with media and are therefore sensitive to many geophysical or Sun–Earth–Moon ...phenomena in accordance with the source of production. A history and some results obtained with the neutron technique are overviewed and discussed. The electron–neutron detectors (en-detectors) were developed at INR RAS in the framework of the PRISMA project to study Extensive Air Shower (EAS) hadronic component through thermalized neutrons. By continuous monitoring of neutron background with the en-detectors we have found interesting variation effects in the environmental thermal neutron flux, caused by geophysical phenomena. As shown, environmental thermal neutron flux could serve as a useful instrument to study cosmic rays, geophysical phenomena and many other applications.
Interest to study neutrons produced in Extensive Air Showers (EAS) is rising last years. History and recent publications on this subject are overviewed and estimated. Advantages of the method to ...study hadronic component being the main EAS component, as well as perspectives of the method are shown using ENDA-LHAASO project as an example.
Environmental fluxes of thermal neutrons originate from two sources: cosmic rays and natural radioactivity. Owing to a long lifetime of free neutrons, they are able to propagate over rather long ...distances in surrounding media prior to undergoing absorption, provided that these media do not contain elements that have large cross sections for neutron capture. The real lifetime of free neutrons and distances that they travel are determined by the properties of the medium with which they are in a dynamical equilibrium. At rather large depths under the ground, natural radioactivity associated with
reactions on light nuclei of the Earth’s crust is the main source of neutrons. Radioactive gaseous radon, especially its long-lived isotope
, which is able to migrate over significant distances (several tens of meters in soil and several kilometers in the Earth’s atmosphere) plays a great role in this process. This means that the changes in the medium that are caused by various geophysical processes or by Moon–Solar–Earth phenomena should also be reflected in the neutron flux escaping from the Earth’s crust. The present article gives a brief survey of studies devoted to this subject and a discussion on them.
Recent results obtained in the LHAASO experiment are discussed. The Km2A array, which is one of the constituents of this experiment and is designed to detect extensive air showers, is shown to be a ...unique instrument for gamma-ray astronomy owing to its outstanding characteristics. Using only the operating half of this array, PeVatrons (natural particle accelerators to energies of 10
15
eV or more) have already been discovered in our Galaxy, many new astrophysical gamma-ray sources have been detected, the energy spectra of emitted gamma-ray photons have been measured, and, what is particularly important, their arrival directions have been determined with an accuracy as high as 0.05°, i.e., their sources have been localized with such an accuracy. This already allows some conclusions about the nature of PeVatrons, i.e., about the possible cosmic-ray acceleration mechanisms, to be drawn.
Primary cosmic ray energy spectrum around and above 1 PeV is of great interest due to its non-power-law behavior (“knee”) in PeV region found many years ago using the indirect EAS (Extensive Air ...Shower) method. The method is based on secondary particles measuring on Earth’s surface under a thick atmosphere. Traditionally, people use detectors sensitive to ionization produced mostly by secondary electromagnetic component and therefore any found changes in EAS size spectrum correspond to secondary components, which have to be recalculated to primary spectrum. Recently some new “knees” were claimed by high altitude experiments: at ∼45 TeV for all-particle spectrum (HAWC), for primary protons and helium: at ∼400 TeV (Tibet ASγ) and at ∼700 TeV (ARGO-YBJ) thus widening the “knee” region from ∼0.045 to 5 PeV. The natural explanation of such a strange spectrum behavior in a wide energy range could be found in the EAS phenomenological approach to the knee problem.
The gamma-ray background problem is known to be acute in any low-background underground experiment. The variations of this background depend on many parameters and should be taken into account when ...interpreting the results of experiments combined under the term “underground physics”. This paper is devoted to studying the long-term variations of the gamma-ray background in an underground laboratory with a scintillation detector based on a CsI crystal. Our studies have revealed a new effect in underground physics—a delayed nonlinear pumping effect for the gamma-ray background in an underground room that can lead to a significant rise of this background at an anomalously low atmospheric pressure.
The electron–neutron detector array (ENDA) is being created in China within the large high-altitude air shower observatory (LHAASO) project. The concept of the array is to simultaneously record the ...electromagnetic and hadronic components of extensive air showers (EAS) with EN detectors. To estimate the number of hadrons in an EAS, the array detectors record secondary thermal neutrons delayed relative to the shower front. Some of the delayed pulses are created by the simultaneous passage of several charged particles through the scintillator (the signal from one particle lies below the detection threshold) and by the photomultiplier noise. We propose a neutron pulse separation method for EN detectors using convolutional neural networks and make a comparison with the baseline method being currently applied at the installation.
As a part of the high-altitude LHAASO project, ENDA (Electron Neutron Detector Array) is being created in China. The ENDA concept consists in simultaneous registration of the electromagnetic and ...thermal neutron components (being a part of hadronic component) of the EAS. The article provides a brief overview of analytical and ML (Machine Learning) methods for shower and primary particle parameters’ reconstruction for simulation of the data. Also, methods for estimation the uncertainty of such reconstruction are presented.
Some unexpected sporadic increases of an environmental radioactive background have been recorded at mountain level at Baksan Neutrino Observatory (BNO, 1700 m above sea level) using electron-neutron ...detectors (en-detectors), which could be explained by radioactive aerosol enhancements. The large area inorganic scintillator en-detectors developed for cosmic ray study are continuously monitoring environmental thermal neutron fluxes at various geophysical conditions. Application of the pulse shape discrimination method allows us to select and separately measure both thermal neutrons and radioactive beta-decay nuclides being products of radon decays in air (mostly Rn-222 and Rn-220). There are two en-detector setups running now at BNO, one deep underground while another one at surface. Both installations had recorded some strange sporadic increases of radioactive nuclides in air. In this paper, we present results and the most probable explanation of the significant increases joint by radioactive aerosols production but caused by different reasons: Baksan river floods or nearby underground experiment with powerful Cr-51 radioactive source.
•High mountain river flow level, flood and waterfall can increase nearby charged aerosol concentration.•Radon and its progenies above mountain rivers attracting by charged aerosols make them radioactive.•Intensive radioactive source can be a reason of radioactive aerosol concentration enhancement in underground laboratories.
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