Existing underground facilities are scattered throughout the world. The principal ones are discussed in this section in geographical order, from west to east, starting from Europe. In developing this material, the committee drew from the results of two recent comprehensive surveys of underground laboratories.1
Boulby Underground Laboratory (U.K.)
Boulby Underground Laboratory was developed as an underground laboratory in 1988 in an active potash mine on the northeast coast of England.
• Its principal research space is at a depth of 1,000 m.
• Access is through a vertical shaft, and the salt environment of the surrounding rock limits the cavities’ width and height to about 5 m. A clean area of
1 A. Bettini. 2011. Underground laboratories. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 626: S64-S68. E. Coccia. 2010. Underground laboratories: Cosmic silence, loud science. Journal of Physics Conference Series 203: 012023.
approximately 1,500 m2 is available for experiments. There is potential for expansion.
• The flux of neutrons with energies greater than 0.5 MeV is 1.7 × 10−2 m−2s−1; the muon flux is 4.5 × 10−2 m−2s−1.
• A building on the surface (200 m2) hosts laboratories for computing, electronics, and chemistry, offices, a conference room, changing rooms, mess rooms, a mechanical workshop, and storage and construction rooms. About 30 scientists work at the laboratory.
• The scientific program is focused on dark matter search: ZEPLIN II and ZEPLIN III, both based on two phases of Xe, and DRIFT II, which is in the research and development phase. In addition to the physics program, there are low radioactivity measurements and geophysics research.
Laboratorio Subterráneo de Canfranc (Spain)
The underground laboratory at Canfranc, Spain, was created beneath the Pyrenees mountains in the 1980s by the Nuclear and High-Energy Physics Department of Saragossa University and expanded in 2005, after the excavation of a road tunnel. It is managed by a consortium of the Ministry for Education and Science, the Government of Aragon, and the University of Saragossa.
• The maximum rock coverage is 850 m.
• The access is horizontal, via a road tunnel.
• The available underground space consists of Hall A, measuring 40 × 15 × 12(h) m3, Hall B, measuring 15 × 10 × 8(h) m3, a clean room of 45 m2, and service facilities in a 215 m2 space.
• The muon flux is between 2 × 10−3 and 4 × 10−3 m−2s−1, depending upon the location, while the neutron flux is 2 × 10−2 m−2s−1. The Rn activity in the air is 50-80 Bq/m3 with a ventilation of 11,000 m3/h—that is, one lab volume in 40 min.
• The surface building contains headquarters, administration, a library, a meeting room, offices, laboratories, storage and a mechanical workshop, safety structures, and management, for a total of approximately 1,500 m2.
• The scientific program, developed with the advice of an international scientific committee, includes the following experiments: on dark matter searches, ANAIS (looking for an annual modulation with NaI crystals) and ROSEBUD (developing scintillation bolometers in the frame of Eureka), and on double-beta decay, NEXT (with 100 kg of enriched Xe). Two other projects are ancillary to experiments in other laboratories: BiPo for the
neutrinoless double-beta decay project SuperNEMO and SUPERKGD (SK) for material screening in view of a possible addition of Gd into the SK water. A new hall to host an underground accelerator facility dedicated to nuclear astrophysics is under design. A special facility is dedicated to other low-radioactivity measurements.
Laboratoire Souterrain de Modane (France)
The Laboratoire Souterrain de Modane (LSM) is operated jointly by the Institut National de Physique Nucléaire et de Physique des Particules (CNRS/IN2P3) and the Commissariat à l’Energie Atomique/Direction des Sciences de la Matière (CEA/DSM) of the Centre National de la Recherche Scientifique. The excavation of the Laboratory started in 1979 and was completed in 1982.
• The vertical direction of the rock measures 1,700 m.
• Horizontal access is provided through a connection to the Fréjus roadway tunnel.
• The main hall volume is 30 × 10 × 11(h) m3, the gamma hall has an area of 70 m2, and two smaller halls have 18 m2 and 21 m2 areas, for a total of 400 m2.
• The muon flux is 4.7 × 10−5 m−2s−1. The neutron flux is 5.6 × 10−2 m−2s−1. Low radon activity in the air, 15 Bq/m3, is obtained by intaking fresh air at the rate of 1.5 lab volumes per hour. An “antiradon factory” produces 150 m3 per hour of air with 10 mBq/m3.
• A surface building hosts outreach facilities, offices, technical laboratories, and sleeping rooms. The user community is about 200, with scientists from 31 institutions in seven countries. On-site support personnel typically consist of eight technicians and engineers and one postdoc.
• The scientific program, developed with the advice of an international scientific committee, includes the following experiments: NEMO 3 (double-beta decay), EDELWEISS (dark matter), and a low-radioactivity counting facility.
• A 60,000 m3 extension of the lab has been proposed (Ulisse project) to take advantage of the opportunity presented by the construction of a new tunnel approved by the French and Italian governments to increase the safety conditions of traffic in the tunnel. Two large halls are foreseen: hall A, 24 × 100 m2, and hall B, 18 × 50 m2. An extremely low background environment will be obtained in hall B by surrounding its central volume with a water shield and by artificially producing an atmosphere with very low Rn content (0.1 mBq/m3).
Laboratori Nazionali del Gran Sasso (Italy)
The Laboratori Nazionali del Gran Sasso (LNGS) is a national laboratory of Italy’s Istituto Nazionale di Fisica Nucleare (INFN). The construction started in 1982 and was completed by 1987.
• The vertical rock overburden is 1,400 m.
• Access is horizontal, through a freeway.
• The underground laboratory consists of three main halls, A, B and C, each with dimensions of about 100 × 20 × 18(h) m3, plus ancillary tunnels that provide space for services and small-scale experiments. The total area is 17,300 m2, and the total volume 180,000 m3.
• Muon flux is 3 × 10−4 m−2s−1; neutron flux is 3.78 × 10 2 m−2s−1, and measured radon in the air is 50-120 Bq/m3. The ventilation system provides one lab volume of fresh air every 3.5 h.
• Services hosted on the surface campus include offices, a mechanical workshop, storage facilities, a chemical laboratory, an electronic workshop, an assembly hall, computer and networking facilities, a library, a canteen, sleeping quarters, conference rooms, and headquarters for administration.
• The scientific user community consists of 752 scientists from 26 countries. Personnel (physicists, engineers, technicians, administration) include a permanent staff of 76 and about 20 nonpermanent positions.
• LNGS is operated as an international laboratory. An international scientific committee, appointed by INFN, advises the director. The rich experimental program includes the CERN to Gran Sasso neutrino beam experiments OPERA and ICARUS; dark matter search, with LIBRA, CRESST2, XENON, and WARP; neutrinoless double-beta decay, with COBRA, CUORE, and GERDA; solar neutrinos (and geoneutrinos) experiments with BOREXINO; supernova neutrinos studies with LVD; and nuclear astrophysics experiments with LUNA2. A special facility is dedicated to low-radioactivity measurements. The laboratory also supports several experiments on geology, biology, and environmental issues. Two 90-m-long tunnels were built for two Michelson interferometers for geology studies.
Centre for Underground Physics in Pyhäsalmi (Finland)
• Hosted in a working mine. Access is both via shaft and via an inclined tunnel.
• Several cavities that are no longer being mined are available for use as laboratory space at different depths down to 980 m, for a total area of more than 1,000 m2. Presently the mine works at depths between 1,000 m and 1,400 m.
• The principal experiment on-site is the EMMA experiment, an array of cosmic ray detectors currently being installed 75 m underground and designed to study energetic cosmic rays. Small lab and office space is available in a surface building and a guesthouse is also available.
• The personnel consist of about three people on-site and three in Oulu University.
Solotvina Underground Laboratory (Ukraine)
This laboratory was constructed in a salt mine in 1984 by the Lepton Physics Department (LPD) of the Institute for Nuclear Research, under the Ukrainian National Academy of Sciences.
• The lab is 430 m deep in salt (≈1,000 m.w.e.).
• Access is vertical by the mine cage and depends on the timetable of the mine.
• The laboratory space is divided into a main hall, 25 × 18 × 8(h) m3, and four chambers 6 × 6 × 3(h) m3. The total area is approximately 1,000 m2.
• The muon flux is 1.7 × 10−2 m−2 s−1. The neutron flux is 2.7 × 10−2 m−2 s−1. Radon concentration in air is 33 Bq/m3.
• On the surface, three living rooms are available for visiting researchers. Staff consists of 14 technicians and engineers. Typically, about 11 researchers and Ph.D. students from LPD work in the laboratory.
• The main subject of the scientific program is on double-beta decay, preparing a new 116Cd experiment using 1-2 kg 116CdWO4 higher quality crystal scintillators and developing R&D projects on scintillators and for the SuperNEMO project.
Baksan Neutrino Observatory (Russia)
The Baksan Neutrino Observatory laboratory is operated by the Institute for Nuclear Research of the Russian Academy of Sciences. It is the oldest underground facility in the world built specifically for scientific research. It is placed under Mount Andyrchi in the Caucasus.
• The access is horizontal via two dedicated tunnels, with train transportation.
• In this lab the muon flux is 3 × 10−5 m−2s−1. The neutron flux (with energies greater than 1 MeV) is 1.4 × 10 3 m−2s−1. The Rn activity is 40 Bq/m3 with a fresh air input of 60,000 m3/h.
• Personnel providing all necessary services (heating station, water supply system, first aid medical help, transportation, safety and so on) live in a new village, called Neutrino. The staff who are directly engaged in research number 50 to 60.
• A large hall, 24 × 24 × 16 m3 in volume, 300 m deep, hosts the Baksan Underground Scintillation Telescope. The telescope has been ready to observe neutrinos from galactic supernovas since 1978. Another hall, 60 × 10 × 12 m3 at a vertical depth of 2,100 m, hosts the Soviet-American Gallium Experiment’s gallium germanium neutrino telescope. Low-background chambers with volumes from 100 m3 to 300 m3 are used for R&D on dark matter and neutrinoless double-beta decay search as well as for gravitational wave search and for some geophysics measurements.
India-Based Neutrino Observatory (India)
The India-based Neutrino Observatory (INO) is a project under development to create an underground laboratory in southern India.
• Two main underground cavities are foreseen: Lab 1 with a volume of 26 × 135 × 25(h) m3 and Lab 2 with 53.4 × 12.5 × 8.6(h) m3 plus connection tunnels and services. Access will be horizontal through a dedicated 2-km tunnel. On the surface the facility is planned to have a 1,400 m2 building for administration, offices, shops, and the like; a 2,750 m2 building with lecture hall and guesthouse; and a residential complex with 20 units. A support staff of 50 to 100 is expected.
• The main experiment foreseen for INO is ICAL, a 50-kT magnetized iron tracking calorimeter for atmospheric and very-long-baseline accelerator neutrinos. It will occupy only a fraction of Lab 1.
Kamioka Observatory (Japan)
The Kamioka Observatory is operated by the Institute for Cosmic Ray Research, University of Tokyo. It was established in 1983.
• The vertical coverage is 1,000 m.
• Access is horizontal by car, with no interference from mining activity.
• The measured muon flux is 3 × 10 3 m−2s−1; thermal neutron flux is 8 × 10−2 m−2s1, and nonthermal neutron flux is 11 × 10 2 m−2s−1. The ventilation is 3,000 m3/h. Buildings for offices and computer facilities are available on the surface. On-site staff consists of 19 scientists, 3 technical support staff, and 4 administrators. The average number of scientific users is more than 200.
• The underground structures and related scientific activities are as follows:
— Hall SK (50 m diameter) hosting Super-Kamiokande, the largest experiment underground. It is the target of the T2K experiment and is a third-generation neutrino oscillation experiment on an intense off-axis beam of muon neutrinos (vμ) produced at the J-PARC accelerator facility 295 km from the Super-K detector.
— Clean room (10 × 5 m2) with XMASS prototype;
— Hall 40 (L-shape, 40 × 4 m arms) hosting the purification tower for XMASS and the NEWAGE experiment on dark matter;
— Hall 100 (L-shape, 100 × 4 m arms) with CLIO, a prototype gravitational antenna (to be terminated in 2013);
— The new Hall A (15 × 21 m2) hosting XMASS 800 kg;
— The new Hall B (6 × 11 m2) hosting CANDLE on double-beta decay;
— In the same mountain, the Kamioka liquid scintillator antineutrino detector (KamLAND experiment) is operated by the Neutrino Centre, Tohoku University. It studies neutrino oscillation by measuring antineutrinos from the commercial power reactors surrounding the site; and
— The underground large cryogenic gravitational antenna LCGT, which has baseline lengths of 3 × 3 km, has been recently approved.
Further enlargements are under development to accommodate more experiments.
China Deep Underground Science and Engineering Laboratory/China JinPing Deep Underground Laboratory
Recently, the China Deep Underground Science and Engineering Laboratory (CDUSEL), designed to be the world’s deepest, and possibly its largest, underground laboratory, was launched in China.2 The facility plans to take advantage of infrastructure being developed by the Ertan Hydropower Development Company (EHDC), which is installing a series of 21 hydroelectric power stations on
2 Qian, Yue. 2010. “Status and prospects of China JinPing Deep Underground Laboratory (CJPL) and China Dark Matter Experiment (CDEX).” Presentation at the TeV Particle Astrophysics 2010 Conference, Paris, France, July.
the Yalong River in central China. A system of tunnels 17.5 km long will cut a big U-turn in the river, under 4,193-m-tall JinPing mountain.
• The future underground laboratory will have a maximum vertical rock overburden of 2,500 m and a greater than 1,500 m overburden in 70 percent of the directions.
• The access will be horizontal, from two sides.
• Two small experimental halls 5 × 5 × 30 m3 are under construction. The final size of the laboratory has not been made public, although it has been reported that the laboratory will be designed as an international facility, open to the world community.
• Measurements of the muon flux (expected to be very low, on the order of 20 m −2y −1), the neutron flux and radon concentration in the air will be performed shortly. A working group, including scientists and engineers from major Chinese institutions and universities, as well as EHDC, has been established to further develop plans for this facility.
Sudbury Neutrino Observatory Laboratory (Canada)
The Sudbury Neutrino Observatory was excavated in the 1990s in an operating nickel mine. The original SNO cavity, a 200 m2 area, is now being freed for further experimental activity. To this original space, new structures have been added to form a new laboratory, the SNOLAB, whose main features are reported here.
• The vertical coverage is 2,000 m under a flat surface.
• The access is vertical, through the shaft of the working mine, and is available daily.
• Space underground consists of a main hall 18 × 15 × 15-19.5(h) m3, a service hall of about 180 m2, and a number of narrow volumes called “ladder labs.” The volume for a further structure, called the “cryopit,” has also been excavated. This hall is designed to cope with the safety issues surrounding large volumes of cryogenic fluids. The total area is 7,215 m2, of which 3,055 m2 is available for experiments. The total volume is 46,648 m3, of which 29,555 m3 is available for experiments.
• Measured muon flux is 3 × 10−6 m−2s−1, thermal neutron flux is 4.7 × 10−2 m−2s−1, and fast neutron flux is 4.6 × 10−2 m−2s−1. The air has a relatively high
radon count, 120 Bq/m3. The ventilation in the smaller lab spaces provides 10 air changes per hour, in the larger ones 5 air changes per hour.
• All of the laboratory will be clean, maintained at Class 1500.
• On the surface, a 3,159-m2 building will host a clean room, laboratories, staging and assembly areas, office space for 60 users, meeting rooms, control rooms, an IT server room, an emergency generator, a high-speed network link off-site, both surface and underground high-speed network links, safety structures, and management. Staff will consist of 30 full-time people.
• The scientific program includes the PICASSO experiment, searching for dark matter (2 kg) using the superheated bubbles technique, which is running. A new instrument for neutrino research, SNO+, is to be hosted in the former SNO cavity and is based on liquid scintillator for low-energy solar neutrinos, geoneutrinos, and double-beta decay, by dissolving 150Nd in the liquid. Dark matter searches include DEAP/CLEAN with noble liquids, which is operating with a prototype, and the installation of superCDMS with bolometers. More letters of intent for possible future experiments are expected to be reviewed by the facility’s experimental advisory committee.
Soudan Underground Laboratory (United States)
The underground structure is hosted in the Soudan Underground Mine state park. The laboratory coexists with a historic state park, which offers mine tours to the public and to school groups. There is no active mining.
• The vertical overburden is 700 m of rock.
• The access is vertical via a two-compartment, slightly angled shaft. Diameters in excess of 1 m and lengths in excess of 10 m pose a problem. Access outside normal park operating hours is possible.
• The muon flux is 2 × 10−3 m−2s−1. The neutron interaction rates are approximately 10 kg−1d−1 (from low-energy uranium and thorium) or 0.01 kg−1d−1 (muons generated in the rock). The radon concentration is seasonal, varying from 300 Bq/m3 in the winter to 700 Bq/m3 in the summer. The mine has natural ventilation, about 550 m3/h at the laboratories’ level. This results in a complete air change every 110 minutes.
• The main facility on the surface is a building of approximately 650 m2 with offices, kitchen, and sanitary facilities. The laboratory has a staff of nine, including secretarial and accounting assistance and network and computer maintenance personnel. There are currently 265 scientific users of the facility.
• The scientific facility includes the Soudan lab (20 × 7 × 10(h) m3), which hosts the dark matter experiment CDMSII and a low-background counting facility that currently occupies 5 × 5 × 3 m3 and will expand to 25 × 14 × 14(h) m3, if funded; and the MINOS lab, which occupies 35 × 16 × 14(h) m3 and is expected to run a few years more with a 2-year decommissioning period at the conclusion, and a high-purity copper fabrication facility that occupies 4 × 6 × 3(h) m3.
Special-Purposes Laboratories (United States)
Two special-purpose underground research laboratories have been developed in the United States. The Waste Isolation Pilot Plant (WIPP) in bedded salt, at Carlsbad, New Mexico, evolved from an underground laboratory to a full-scale facility and has been used since 1998 as a permanent disposal repository for intermediate (long-lived) radioactive waste. An underground laboratory at Yucca Mountain, Nevada, in volcanic tuff at a depth of 300 m, was developed and used for research into high-level waste disposal until 2010, when a plan for the construction of a permanent repository at the site was submitted to the U.S. Nuclear Regulatory Commission. As with WIPP, the intent is to develop a permanent repository at the site.
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