Deep Underground Laboratories Research Articles

Protracted Exposure to a Sub-background Radiation Environment Negatively Impacts the Anhydrobiotic Recovery of Desiccated Yeast Sentinels.

Experiments that examine the impacts of subnatural background radiation exposure provide a unique approach to studying the biological effects of low-dose radiation. These experiments often need to be conducted in deep underground laboratories in order to filter surface-level cosmic radiation. This presents some logistical challenges in experimental design and necessitates a model organism with minimal maintenance. As such, desiccated yeast ( Saccharomyces cerevisiae ) is an ideal model system for these investigations. This study aimed to determine the impact of prolonged sub-background radiation exposure in anhydrobiotic (desiccated) yeast at SNOLAB in Sudbury, Ontario, Canada. Two yeast strains were used: a normal wild type and an isogenic recombinational repair-deficient rad51 knockout strain ( rad51 Δ). Desiccated yeast samples were stored in the normal background surface control laboratory (68.0 nGy h -1 ) and in the sub-background environment within SNOLAB (10.1 nGy h -1 ) for up to 48 wk. Post-rehydration survival, growth rate, and metabolic activity were assessed at multiple time points. Survival in the sub-background environment was significantly reduced by a factor of 1.39 and 2.67 in the wild type and rad51 ∆ strains, respectively. Post-rehydration metabolic activity measured via alamarBlue reduction remained unchanged in the wild type strain but was 26% lower in the sub-background rad51 ∆ strain. These results demonstrate that removing natural background radiation negatively impacts the survival and metabolism of desiccated yeast, highlighting the potential importance of natural radiation exposure in maintaining homeostasis of living organisms.

Sub-background radiation exposure at the LNGS underground laboratory: dosimetric characterization of the external and underground facilities

Radiobiological studies conducted in Deep Underground Laboratories allow to improve the knowledge of the biological effects induced by ionizing radiation at low doses/dose rates. At the Gran Sasso National Laboratory of the Italian Institute of Nuclear Physics we can study the possible differences in behavior between parallel biological systems, one maintained in a Reference-Radiation Environment (RRE, external) and the other maintained in an extremely Low-Radiation Environment (LRE, underground), in the absence of pressure changes, the RRE and LRE laboratories being at the same altitude. For these investigations, it is mandatory to evaluate the dose rate values at RRE and LRE. The aim of our work is to provide a comprehensive dosimetric analysis for external and underground laboratories. Measurements of the different low Linear Energy Transfer (LET) components at RRE and LRE were performed using different detectors. Gamma dose rates were 31 nSv/h at RRE and 27 nSv/h at LRE respectively. The muon dose rate was 47 nSv/h at RRE and negligible at LRE (less than pGy/h). Dosimetric measurements were also carried out to characterize the devices used to modulate the gamma dose rate, namely, a gamma source irradiator (to increase the dose rate by about 90 nSv/h) and shields (of iron at LRE and lead at RRE). Using the iron shield at LRE a dose reduction factor of about 20, compared to the RRE, was obtained for the low LET components; inside the lead shield at RRE the gamma component was negligible compared to the muonic component. Radon activity concentrations were approximately of 20 Bq/m3 at both LRE and RRE. The intrinsic contribution of radioactivity in the experimental set up was of 0.25 nGy/h, as evaluated with a GEANT4-simulation, using as input the measured activity concentrations. GEANT4 simulations were also performed to calculate the neutron dose rate at RRE, yielding a value of 1.4 nGy/h, much larger than that at LRE (which is less than pGy/h). In conclusion, RRE and LRE are currently characterized and equipped to perform radiobiological studies aimed at understanding the involvement of the different low LET components in determining the response of biological systems.

Overview of DISCOVER22 experiment in the framework of INFN-LNGS Cosmic Silence activity: challenges and improvements in underground radiobiology

One of the most intriguing and still pending questions in radiobiology is to understand whether and how natural environmental background radiation has shaped Life over millions of years of evolution on Earth. Deep Underground Laboratories (DULs) represent the ideal below-background exposure facilities where to address such a question. Among the few worldwide DULs, INFN-Laboratorio Nazionale del Gran Sasso (LNGS) is one of the largest in terms of size and infrastructure. Designed and built to host neutrino and dark matter experiments, since the 1990 s the LNGS has been one of the first DULs to systematically host radiobiology experiments. Here we present the DISCOVER22 (DNA Damage and Immune System Cooperation in VEry low Radiation environment 2022) experiment recently started at LNGS. DISCOVER22 aims at investigating how the low radiation background modulates the Immune System (IS) response in in vitro and in vivo models. Underground radiobiology experiments are particularly complex and tricky to design and perform. In these studies, the accurate characterization of exposure scenarios is mandatory, but a challenging aspect is to understand how the very few ionizing tracks in the ultra-Low Radiation Environment (LRE) interact with the living matter in space and time in order to trigger different biological responses. In this Perspective, we describe these challenges and how we address them through a microdosimetric and a radiobiological approaches. We aim at linking physical microdosimetric measurements and the corresponding biological radiation responses by using radiation biophysical models that could shed light on many as yet unresolved questions.

The deep underground Bellotti Ion Beam Facility—status and perspectives

For more than three decades, accelerators are in use in the underground laboratories of the Laboratori Nazionali del Gran Sasso (LNGS), located in central Italy. The LUNA Collaboration has exploited the potential of the site’s low cosmic ray background to achieve important and often groundbreaking results in the field of nuclear astrophysics. This long success story stimulated the installation of accelerators in deep underground laboratories also in other countries, including the USA and China. Recently, LNGS took a major step forward with the activation of the Bellotti Ion Beam Facility, which will provide ion beams to the scientific community for research not only in nuclear astrophysics, but in all fields that can benefit from the low cosmic ray background conditions of the underground site.

Design of a mobile neutron spectrometer for the Laboratori Nazionali del Gran Sasso (LNGS)

Environmental neutrons are a source of background for rare event searches (e.g., dark matter direct detection and neutrinoless double beta decay experiments) taking place in deep underground laboratories. The overwhelming majority of these neutrons are produced in the cavern walls by means of intrinsic radioactivity of the rock and concrete. Their flux and spectrum depend on time and location. Precise knowledge of this background is necessary to devise sufficient shielding and veto mechanisms, improving the sensitivity of the neutron-susceptible underground experiments. In this report, we present the design and the expected performance of a mobile neutron detector for the LNGS underground laboratory. The detector is based on capture-gated spectroscopy technique and comprises essentially a stack of plastic scintillator bars wrapped with gadolinium foils. The extensive simulation studies demonstrate that the detector will be capable of measuring ambient neutrons at low flux levels (∼10-6 n/cm2/s) at LNGS, where the ambient gamma flux is by about 5 orders of magnitude larger.

Progress in biological and medical research in the deep underground: an update.

As the growing population of individuals residing or working in deep underground spaces for prolonged periods, it has become imperative to understand the influence of factors in the deep underground environment (DUGE) on living systems. Heping Xie has conceptualized the concept of deep underground medicine to identify factors in the DUGE that can have either detrimental or beneficial effects on human health. Over the past few years, an increasing number of studies have explored the molecular mechanisms that underlie the biological impacts of factors in the DUGE on model organisms and humans. Here, we present a summary of the present landscape of biological and medical research conducted in deep underground laboratories and propose promising avenues for future investigations in this field. Most research demonstrates that low background radiation can trigger a stress response and affect the growth, organelles, oxidative stress, defense capacity, and metabolism of cells. Studies show that residing and/or working in the DUGE has detrimental effects on human health. Employees working in deep mines suffer from intense discomfort caused by high temperature and humidity, which increase with depth, and experience fatigue and sleep disturbance. The negative impacts of the DUGE on human health may be induced by changes in the metabolism of specific amino acids; however, the cellular pathways remain to be elucidated. Biological and medical research must continue in deep underground laboratories and mines to guarantee the safe probing of uncharted depths as humans utilize the deep underground space.

A new ultra low-level HPGe activity counting setup in the Felsenkeller shallow-underground laboratory

A new ultra low-level counting setup has been installed in the shallow-underground laboratory Felsenkeller in Dresden, Germany. It includes a high-purity germanium detector (HPGe) of 163% relative efficiency within passive and active shields. The passive shield consists of 45 m rock overburden (140 meters water equivalent), 40 cm of low-activity concrete, and a lead and copper castle enclosed by an anti-radon box. The passive shielding alone is found to reduce the background rate to rates comparable to other shallow-underground laboratories. An additional active veto is given by five large plastic scintillation panels surrounding the setup. It further reduces the background rate by more than one order of magnitude down to 116(1) kg−1d−1 in an energy interval of [40 keV;2700 keV]. This low background rate is unprecedented for shallow-underground laboratories and close to deep underground laboratories.

Exploring the frontiers of deep underground sciences and engineering—China Yunlong Lake Laboratory is striving to be the best

AbstractThis paper introduces the establishment of deep underground infrastructure for science and engineering research. First, the representative deep underground research laboratories and facilities in the world and their functions were summarized and reviewed. Then, the plan and service target of China Yulong Lake Laboratory were proposed for the storage of resources and energy, as well as the sealing of hazardous waste in deep underground space. On this basis, this paper reveals how the facility addresses its key scientific issue on “The law of fluid matter migration in deep underground space” and engineering significance. Finally, the construction progress of the facility components was demonstrated in details. As is hoped, this paper would provide useful reference to the deep underground research community; meanwhile, international collaboration on deep underground research is highly welcome.

The effect of neutrons on the background of HPGe detectors operating deep underground

The background of a High Purity Germanium (HPGe) detector measured in a deep underground laboratory was investigated analytically and by Monte Carlo simulations using the GEANT4 toolkit. Contributions of different background sources to the experimental γ-ray background were determined. Namely, contribution of radionuclides in materials of the detector and around the detector, neutrons produced by (α, n) reactions due to presence of radionuclides in rock and concrete and by spontaneous fission of mainly 238U, and finally, cosmic rays with neutron generation. The simulation, including radionuclides in the material, was in a good agreement with the experiment. At the same time, neutron and muon induced spectra were simulated. The radiation coming from the presence of members of the 238U, and 232Th decay series, and 40K in the detector parts and the laboratory walls contribute to the continuum of the experimental spectrum at the level of around 94%. According to simulations, the contribution of muon events to the experimental energy spectrum was below 1% and it was confirmed that muon induced spectra are about three orders of magnitude lower than the experimental one. The comparison of integral count rates of the experimental spectrum with the simulated spectrum induced by neutrons showed that about 6% of the measured background continuum originated from neutron reactions. Fast neutrons contributed more to the background (at around 65%) than thermal neutrons. Despite only a 6% share of neutron contributions in the total γ-ray background, they contributed mainly to the lower continuum of the spectrum up to 250 keV, which is a region of interest for potential low mass weakly interacting massive particle (WIMP) dark matter interactions. In addition, they interact with the detector and the shield by inelastic scattering and induce unwanted γ-rays. Neutron capture, elastic and inelastic scattering were simulated separately as well. It was found that inelastic scattering is the major contributor to the spectrum induced by neutrons. The effect of neutrons on the background of the HPGe detector operating underground, such as Obelix, is manifested mainly by their contribution to the continuum up to 1 MeV, especially in the lower part up to 500 keV. Thus, neutrons are an important background component in deep underground laboratories, too. Possible detector optimization is also discussed.

Reduced Environmental Dose Rates Are Responsible for the Increased Susceptibility to Radiation-Induced DNA Damage in Larval Neuroblasts of Drosophila Grown inside the LNGS Underground Laboratory.

A large amount of evidence from radiobiology studies carried out in Deep Underground Laboratories support the view that environmental radiation may trigger biological mechanisms that enable both simple and complex organisms to cope with genotoxic stress. In line with this, here we show that the reduced radiation background of the LNGS underground laboratory renders Drosophila neuroblasts more sensitive to ionizing radiation-induced (but not to spontaneous) DNA breaks compared to fruit flies kept at the external reference laboratory. Interestingly, we demonstrate that the ionizing radiation sensitivity of flies kept at the LNGS underground laboratory is rescued by increasing the underground gamma dose rate to levels comparable to the low-LET reference one. This finding provides the first direct evidence that the modulation of the DNA damage response in a complex multicellular organism is indeed dependent on the environmental dose rate.

Studies of the Earth shielding effect to direct dark matter searches at the China Jinping Underground Laboratory

Dark matter direct detection experiments mostly operate at deep underground laboratories. It is necessary to consider shielding effect of the Earth, especially for dark matter particles interacting with a large cross section. We analyzed and simulated the Earth shielding effect for dark matter at the China Jinping Underground Laboratory (CJPL) with a simulation package, CJPL Earth Shielding Simulation code (CJPL\_ESS), which is applicable to other underground locations. The further constraints on the $\chi$-N cross section exclusion regions are derived based on the studies with CDEX experiment data.

Callio Lab – the deep underground research centre in Finland, Europe

Pyhäsalmi, in the Town of Pyhäjärvi, hosts one of the northernmost deep underground laboratories in Europe, the Callio Lab. Its origins are in underground physics (Centre for Underground Physics in Pyhäsalmi, CUPP), but gradually it has turned into a multi- and transdisciplinary research environment utilising both the surface and underground. Besides research, the infrastructure is open for business and innovation under the Callio – Mine for Business. The pre-investment for an underground pumped-hydro storage facility to be built at the area utilising the existing tunnel network for construction has been made. This investment ensures the existing and future utilisation of the underground and surface facilities.

Science in Underground Laboratories and DULIA-Bio

This paper reports a brief introduction to Deep Underground Laboratories (DULs) and the connection they have with research on biology in extreme environments and the effect of radiation in life. Presently, there are 14 DULs in operation worldwide. Although the main research activity in these infrastructures concerns the search for rare events in astroparticle physics and neutrino physics, DULs offer a unique opportunity to undertake experiments in astrobiology and biology in extreme environments. This is the main motivation of Deep Underground Laboratory Integrated Activity in biology (DULIA-bio) 2019 Workshop, which was held at the Gran Sasso (Italy) underground laboratory. This paper aims to give an introduction to the subject of the Workshop by reviewing the main features of DULs.

Underground Radiobiology: A Perspective at Gran Sasso National Laboratory.

Scientific community and institutions (e. g., ICRP) consider that the Linear No-Threshold (LNT) model, which extrapolates stochastic risk at low dose/low dose rate from the risk at moderate/high doses, provides a prudent basis for practical purposes of radiological protection. However, biological low dose/dose rate responses that challenge the LNT model have been highlighted and important dowels came from radiobiology studies conducted in Deep Underground Laboratories (DULs). These extreme ultra-low radiation environments are ideal locations to conduct below-background radiobiology experiments, interesting from basic and applied science. The INFN Gran Sasso National Laboratory (LNGS) (Italy) is the site where most of the underground radiobiological data has been collected so far and where the first in vivo underground experiment was carried out using Drosophila melanogaster as model organism. Presently, many DULs around the world have implemented dedicated programs, meetings and proposals. The general message coming from studies conducted in DULs using protozoan, bacteria, mammalian cells and organisms (flies, worms, fishes) is that environmental radiation may trigger biological mechanisms that can increase the capability to cope against stress. However, several issues are still open, among them: the role of the quality of the radiation spectrum in modulating the biological response, the dependence on the biological endpoint and on the model system considered, the overall effect at organism level (detrimental or beneficial). At LNGS, we recently launched the RENOIR experiment aimed at improving knowledge on the environmental radiation spectrum and to investigate the specific role of the gamma component on the biological response of Drosophila melanogaster.

Cross section of the 13C(α,n)16O reaction at low energies

The 13C(α, n)16O reaction is the main neutron source for the s-process in low mass AGB stars. Although several direct measurements have been performed, no dataset reaches the Gamow window (140-250 keV) due to the the exponential drop of the cross section σ(E) with decreasing energy. The reaction rate becomes so low that the strong cosmic background would become predominant.In order to measure the 13C(α, n)16O cross section at low energies, a double effort has been performed, namely to suppress the background in the setup and to keep under control the target modification under an intense stable beam provided by the LUNA accelerator (100-200 µA). These measurements were carried out in deep underground laboratories of Laboratori Nazionali del Gran Sasso (LNGS) in the framework of the LUNA experiment. Preliminary results are reported in this contribution.

The ANDES Deep Underground Laboratory

Deep Underground Laboratories (DUL) provide a unique environment to address some key questions in basic and applied science. A penetrating radiation due to cosmic rays is present at ground level at a rate of a few hundred particles per square meter per second. Moving deep underground with more than 1000m of overburden allows a reduction of this flux by 5 to 8 orders of magnitude. Frontier experiments in search for dark matter or neutrino properties can be designed and operated in DUL thanks to this background reduction. The ANDES DUL is foreseen to be built at the same time as the Agua Negra tunnel planned between the Argentine province of San Juan and the Chilean region of Coquimbo. It is designed to be a world class deep and large laboratory, operated by an international consortium.

Considerations on Underground Laboratories

Deep Underground Laboratories are multidisciplinary infrastructures to carry out research on rare events, such as neutrino interactions, proton decay, and dark matter, on geophysics, general relativity, and biology. There are 12 such infrastructures deployed in the north hemisphere. Three new Laboratories are underway, two in the south hemisphere. In the paper some characteristics of the Underground Laboratories are discussed. Synergy between Laboratories is reviewed.

SABRE and the Stawell Underground Physics Laboratory Dark Matter Research at the Australian National University

The direct detection of dark matter is a key problem in astroparticle physics that generally requires the use of deep-underground laboratories for a low-background environment where the rare signals from dark matter interactions can be observed. This work reports on the Stawell Underground Physics Laboratory – currently under construction and the first such laboratory in the Southern Hemisphere – and the associated research program. A particular focus will be given to ANU’s contribution to SABRE, a NaI:Tl dark matter, direct detection experiment that aims to confirm or refute the long-standing DAMA result. Preliminary measurements of the NaI:Tl quenching factor and characterisation of the SABRE liquid scintillator veto are reported.

A record of changes in the Gran Sasso groundwater before, during and after the 2016 Amatrice earthquake, central Italy

We performed continuous recordings (May 2015 – January 2017) of hydraulic pressure and electrical conductivity of groundwater in the 190 m-long horizontal S13 borehole drilled next to the deep underground laboratories of Gran Sasso (LNGS-INFN), located in the core of the Gran Sasso carbonate aquifer (central Italy) at a distance of about 39 km south-eastward from the 24 August 2016 Amatrice earthquake (6.0 Mw) epicenter. Using a 3-channel, 24-bit ADC we achieved a sampling rate of groundwater physical properties up to 50 Hz for each channel. We focused on the analysis of data recorded before, during and after the Amatrice earthquake, describing and discussing in detail the evidence for significant hydraulic pressure and electrical conductivity anomalies recorded before the main shock. We identified unambiguous signals in the hydraulic pressure data starting on 19 August, i.e. five days before the 24 August mainshock. A more careful analysis allowed us to detect the inception of a weak change up to 40 days before the Amatrice earthquake and a significant variation in the electrical conductivity data about 60 days before. The data revealed highly dynamic aquifer behaviour associated with the uprising of geogas probably related to the preparation stage of the Amatrice earthquake.

Fruit Flies Provide New Insights in Low-Radiation Background Biology at the INFN Underground Gran Sasso National Laboratory (LNGS).

Deep underground laboratories (DULs) were originally created to host particle, astroparticle or nuclear physics experiments requiring a low-background environment with vastly reduced levels of cosmic-ray particle interference. More recently, the range of science projects requiring an underground experiment site has greatly expanded, thus leading to the recognition of DULs as truly multidisciplinary science sites that host important studies in several fields, including geology, geophysics, climate and environmental sciences, technology/instrumentation development and biology. So far, underground biology experiments are ongoing or planned in a few of the currently operating DULs. Among these DULs is the Gran Sasso National Laboratory (LNGS), where the majority of radiobiological data have been collected. Here we provide a summary of the current scenario of DULs around the world, as well as the specific features of the LNGS and a summary of the results we obtained so far, together with other findings collected in different underground laboratories. In particular, we focus on the recent results from our studies of Drosophila melanogaster, which provide the first evidence of the influence of the radiation environment on life span, fertility and response to genotoxic stress at the organism level. Given the increasing interest in this field and the establishment of new projects, it is possible that in the near future more DULs will serve as sites of radiobiology experiments, thus providing further relevant biological information at extremely low-dose-rate radiation. Underground experiments can be nicely complemented with above-ground studies at increasing dose rate. A systematic study performed in different exposure scenarios provides a potential opportunity to address important radiation protection questions, such as the dose/dose-rate relationship for cancer and non-cancer risk, the possible existence of dose/dose-rate threshold(s) for different biological systems and/or end points and the possible role of radiation quality in triggering the biological response.