Calibration of the Latest Generation Superconducting Gravimeter iGrav-043 Using the Observatory Superconducting Gravimeter OSG-CT040 and the Comparisons of Their Characteristics at the Walferdange Underground Laboratory for Geodynamics, Luxembourg

In December 2019, the latest generation transportable superconducting gravimeter (SG) iGrav-043 purchased by the University of Bonn was installed in the Walferdange Underground Laboratory for Geodynamics (WULG) in the Grand Duchy of Luxembourg. In this paper, we estimate the calibration factor of the iGrav-043, which is essential for long-term gravity monitoring. We used simultaneously collected gravity data from the un-calibrated iGrav-043 and the calibrated Observatory superconducting gravimeter OSG-CT040 that operates continuously at WULG since 2002. The tidal analysis provides a simple way to transfer the calibration factor of one SG to the other. We then assess and compare tidal analyses, instrumental drifts and high frequency noises. After 20 years of continuous operation, the instrumental drift of the OSG-CT040 is almost zero. From 533 days of joint operation, we found that the instrumental drift of iGrav-043 exhibits a composite behavior: just after the setup and for two months a fast exponential decrease of 171 nm s−2, then a linear with a rate of 66 nm s−2 ± 10 nm s−2 per year. We suggest that a period of 3 months is sufficient for calibrating the iGrav. Accidental electrical power cuts triggered slight differences in the reaction and recovery of the OSG-CT040 and iGrav-043. However, it has been found that the long-term linear behavior of the drift was not affected.

Identification of neutron sources and background levels in the polyethylene room of the China Jinping Underground Laboratory

The neutron backgrounds induced by supplementary experimental materials can result in contaminations in rare event search experiments. To address this, we present the neutron background levels arising from ambient materials in the polyethylene room of the China Jinping Underground Laboratory; particularly, we compare simulated spectra with measured neutron spectra unfolded using a genetic algorithm. The genetic algorithm optimizes the continuity of the energy spectra and obtains a reasonable spectral result. A good agreement between the unfolded and simulated spectra is achieved. Moreover, estimated neutron background levels of representative ambient materials such as polyethylene, aluminum, and lead are obtained using an exposure time of 511.27 days via a 28 liter 0.5%-gadolinium-doped liquid scintillator detector. The identification of rare neutron sources can aid in background reduction in next-generation large-scale rare event experiments.

EXPERIMENTS AT MODANE UNDERGROUND LABORATORY OR THE SWAN SONG OF RADIOCARBON ß-COUNTING BY GAS PROPORTIONAL COUNTER

ABSTRACT In 1991, a 14C ß-counting installation with four proportional CO2 gas counters was tested at the Modane underground laboratory, 1700 m below the summit of Pointe du Fréjus, reducing the muon flux to 4 muons per square meter and per day. With cosmic radiation attenuated by a factor of 2.106, the background level of the counters was reduced by 65 to 85% while its variability was reduced by a factor of 30–80 depending on the type of counter. The dating limit of these counters extends to well beyond 60,000 years.

Finite Element Method-based geomechanical risk assessment of underground laboratory located in the deep copper mine

<p>Underground laboratories provide a unique environment for various industries and are a suitable place for developing new technologies for mining, geophysical surveys, radiation detection, as well as many other studies and measurements. Unfortunately, any operation in underground excavations is associated with exposure to many hazards not necessarily encountered in surface laboratories. One of the most dangerous events observed in underground conditions is the dynamic manifestation of rock mass pressure in form of rockburst, roof falls and mining tremors. Therefore, proper evaluation of geomechanical risk is a key element ensuring the safety of work in underground conditions. Finite Element Method-based numerical analysis is one of the tools which allow conducting a detailed geomechanical hazard assessment already at the object design stage. The results of such calculations may be the basis for the implementation of preventive measures before running up the underground facility.</p><p>Within this paper, the three-dimensional FEM-based numerical analysis of large-scale underground laboratory located in deep Polish copper mine was presented. The calculations were made with GTS NX software, which allowed determining the changes in the safety factor in surrounding of the analyzed area. Finally, the possibility of underground laboratory establishment, with respect to predicted stress and strain conditions, were determined.</p>

Investigations based on biaxial tiltmeter array and uniaxial hydrostatic levelling system at the Mont Terri rock laboratory

<p>In order to enable investigations and further comprehensive understanding of dynamical processes, it is clear one has to identify all relevant parameters and aim to record them all under best conditions concerning e.g. resolution, coverage in space, and in many cases on a multitude of scales in time. Obviously, it is also difficult to satisfy all these constrains in full. Especially scientific long-term observations often suffer the lack of necessary lasting commitment; secure funding, continual high quality maintenance, protected environment, or sufficient planning stability. Fortunately, the Swiss Mont Terri rock laboratory, with its history of now 25 years of forefront scientific expertise, a long-standing fruitful cooperation formed by the partners of the consortium and in consequence thereof state-of-the-art results obtained through 100 completed individual experiments and 45 additional experiments actually ongoing, ensures the conditions listed above.</p><p>Based on this favorable prospect, a now growing tiltmeter array is established at the underground laboratory. The instruments are embedded in several multidisciplinary experiments, dedicated to numerous, different scientific questions. Starting in April 2019, the first two platform tiltmeters became operational. Less than two years later, ten biaxial instruments are quasi-continuously monitoring deformation at various locations within the galleries and niches at Mont Terri. The envisioned, increasing spatial coverage of the network will facilitate geodetic observations of the underground rock laboratory as a whole and of its subregions as well.</p><p>Already in September 2012, a 50 m long hydrostatic levelling system (HLS) was installed along a gallery in the underground laboratory to detect displacements across an active geological fault zone. The combination of both, i.e. the uniaxial, integral deformations data provided by HLS together with the array of biaxial, point measurements acquired by the tiltmeters offers a unique concerted opportunity to achieve detailed deformation data in a large underground rock laboratory and to survey the associated dynamical processes occurring on timeframes covering seconds to decades.</p>

Empowering Underground Laboratories Network Usage in the Baltic Sea Region

<p>In the Baltic Sea region, there are world leading science organisations and industrial companies specialised in geophysics, geology and underground construction. There are also several highly interesting underground laboratories (ULs), research mines and test-sites,  that are not utilised to their full potential.</p><p>Six of these facilities cooperate within the Interreg Baltic Sea Region program funded project, Empowering Underground Laboratories Network Usage (EUL) [1]. Underground facilities have been established into existing or historical mines, research tunnel networks or as a dedicated underground laboratory for a specific purpose. The EUL project continues in 2021 the work of the Interreg funded Baltic Sea Underground Innovation Network (BSUIN) [2], that ended in December 2020. While the BSUIN project concentrated on characterising the underground facilities and operational settings, the EUL project works on testing, validation, and enhancing previously created practices, tools, and approaches. During the EUL project, the emphasis is put on identifying the global user segments of underground facilities, the effectiveness of marketing of ULs and created network, now known as European Underground Laboratories Association, and customer relations management from the first contact to the realisation of the project.</p><p>The underground laboratories participating in BSUIN and EUL projects are Callio Lab (Pyhäjärvi Finland), ÄSPÖ Hard Rock Laboratory (Oskarshamn, Sweden), Ruskela Mining Park (Ruskeala, Russia), Educational and research mine Reiche Zeche (Freiberg, Germany), Underground Low Background Laboratory of the Khlopin Radium Institute (St.Petersburg, Russia) and the Conceptual Lab development co-ordinated by KGHM Cuprum R&D centre (Poland).</p><p>One of the main objectives of EUL project is to test the developed business and service concepts for the established network of underground laboratories and for the individual laboratories. Testing ensures the functionality of laboratory service concepts and customer relationship management processes for commercial and non-commercial users.</p><p>Another main objective is to test and develop the web-based tool (WBT). Users from partner and associative organisations and underground laboratories (Uls) will test it from their perspectives. The feedback helps to steer the tool into the more user-friendly and more purposeful direction for the potential customers and the underground laboratory managers to use.</p><p>To reach new customers and understand different possible customer segments, a big data analysis of users of ULs world-wide will be conducted. Also marketing the network and underground laboratories will be tested and best marketing strategies identified.</p><p>Main target groups are the ULs, their users and potential customers (companies and researchers). Another target group is regional development agencies that will be informed about the business possibilities in ULs so that they can provide information to potential customers looking for business opportunities.</p><div> <p>In this paper, the EUL project's first outcomes will be discussed reflected to the BSUIN project. The BSUIN and EUL projects are funded by the Interreg Baltic Sea Region Progamme.</p> <p>[1] Empowering Underground Laboratories Network Usage, www.bsuin.eu, 18 Jan 2021</p> <p>[2] Baltic Sea Underground Innovation Network, www.bsuin.eu, 18 Jan 2021</p> </div>