- Email: [email protected]
The Gran Sasso Underground Laboratory
Nuclear Instruments and Methods in Physics Research A264 (1988) 1-4 North-Holland, Amsterdam
Section I. Large underground detectors THE GRAN SASSO UNDERGROUND LABORATORY E. BELLOTTI Laboratorio Nazionale del Gran Sasso, Universit6 degli Studi e Sezione INFN, Milano, Italy The Gran Sasso Underground Laboratory, located on a side of the road tunnel under the Gran Sasso Massif, not far from Rome, is nearly completed . The status of construction and outfitting of experimental halls is reported, as well as future plans to improve safety and available room for experiments . 1 . Introduction Laboratorio Nazionale del Gran Sasso is the national facility of INFN - the Italian agency for fundamental research in nuclear and subnuclear physics - for underground physics . The construction of this laboratory was proposed in 1981 by A. Zichichi, at that time president of INFN ; according to a first design, the laboratory consisted of a single large hall to be dedicated to an experiment on proton decay . A law was approved in February 1982, and a sum of 20 billion lire was allocated : one year later, the project was largely improved and the total budget was increased up to a total of 77 billions Italian lire [1] . Present underground experiments are located in mines, like IMB in USA and Kamiokande in Japan, or in caves along car tunnels under Alps like NUSEX in the Mt. Blanc and the French-German detector in the Frejus tunnel . Mines and caves were adapted to permit the installation of these detectors ; however, these facilities cannot really be called "laboratories" ; on the contrary, Gran Sasso was designed as a complete laboratory, with a diversified research program and general facilities . In that sense, Baksan in Soviet Union is the only operating laboratory for underground physics ; however, at least for groups from western countries, Gran Sasso is in a better geographical position . The laboratory has been realized under the responsibility of ANAS (the Italian authority for roads and highways), which depends on Ministry of Public Works ; two major Italian companies where engaged in this work : Cogefar S .p .A. for the excavation and SAEM (a group of firms) for most of the general installations . The laboratory is located on a side of the road tunnel under the Gran Sasso, along the highway connecting Rome to the Adriatic sea ; it is at about 150 km from the Rome International Airport and it is linked to the European network of highways. It is not far from L'Aquila, a small and beautiful town, seat of a university. 0168-9002/88/$03 .50 C Elsevier Science Publishers B .V . (North-Holland Physics Publishing Division)
Its geographical position is : 42' 27' N and 13' 34' E of Greenwich ; the altitude is - 960 m a.s .l . The rock overburden is - 3500 hg of water equivalent . At this depth, the muon flux is of the order of 1 tt/(m2 h) [2] . The rock, mainly limestone, has a low content of radioactive elements, if compared with Mt . Blanc granite ; measurements of gamma-ray and neutron fluxes have been carried out before the starting of the outfitting works [3]. New measurements are in progress or will start in a short time to take into account the effect of different materials introduced in the laboratory and to improve the quality of the neutron flux determination. The laboratory consists, at present, of an outside building, the internal halls and a few sheds at Campo Imperatore . Before giving a short description of the laboratory, it must be mentioned that other fields of research will be developed in the laboratory, beside the experiments which will be described by the other speakers in this same session . First of all, installation of a gravitational wave antenna is planned, which is presently under construction by the Rome group . Groups from L'Aquila, Rome and other universities are interested in carrying out measurements on geophysical phenomena (fault movements, assessment of the rock after the excavation, propagation of electromagnetic fields through the earth crust, etc.). Interest has been expressed also by people involved in radiation controls in having a laboratory where their detectors can be calibrated in the absence of a cosmic radiation background . 2. The outside building The offices, groups, 11/780
outside building hosts some administration a conference room, a few offices for external a computer room, where at present a VAX linked to INFNET (the INFN network of 1 . LARGE UNDERGROUND DETECTORS
E. Bellotti / The Gran Sasso underground laboratory
HIGHWAY-
Fig . 1 . General layout of the underground laboratories . computers) is installed, small laboratories and two large counting rooms . While this building is extremely useful at this stage of construction of the laboratory, in the near future it will be absolutely necessary to build new assembling halls and buildings for general services . 3. Installation at Campo Imperatore According to plans of INFN, in collaboration with CNR (National Council for Research) an extensive air shower detector will be installed at Campo Imperatore (2000 m a . s . L, 25 ° off the vertical from the underground laboratory) [4] . The installation will consist of about 30 small sheds, each one instrumented with a 10 mZ detector (liquid scintillator or plastic scintillator) to measure the electromagnetic component of showers, and a central building with a 200 mZ hadron and muon detector consisting of a sandwich of limited streamer tubes and passive material . These detectors will be distributed over an area of - 10 5 mz . The expected rate of events observed on the surface and in one of the underground detectors is of the order of 1 per day. During winter 1986-1987 a few detectors have been successfully tested .
tation by means of heavy lorries. A smaller tunnel will be used by cars. Three small galleries in the form of a triangle have been excavated in the northern part of the laboratory ; an interferometric system and other devices for geophysics measurements will be installed there. The total excavated volume is 180000 m3 . Halls A N and A s are 42 m long, 17 m wide and 17 m high ; hall B is 127 m long and has the same transversal dimensions as halls A ; hall C is 100 m long, 22 m wide and 20 m high ; the cross section has the typical shape of tunnels (figs . 2a and 2b) . In hall A s a hole has been excavated to house a few tanks where gallium will be recovered in case of an important damage in the main tanks ; in that way pollution of the laboratory with HCl will be avoided in case of an accident [5] . Similarly, in hall C an extra hole has been excavated to allow the installation of the dewar and, possibly, of the magnet of ICARUS. Major experiments will be installed as follows : LVD in hall A, north wing ; GALLEX, ,ß/3 decay in hall A, south wing ; MACRO in hall B ; and ICARUS in hall C . The position of the gravitational antenna has not yet been defined ; however, this antenna will be ready for installation in Gran Sasso in not less than two years from now .
4 . Underground laboratories The general layout of the underground laboratories is shown in fig . 1 . Four main halls, conventionally denoted by A N , A s , B and C, are connected by a large road, directly linked to the highway, to allow transpor-
5 . Status of works Excavation has been completed, with the exception of a very small and short gallery connecting the access
E. Bellotti / The Gran Sasso underground laboratory
a
IMM IBM
3
road between hall A and hall B and the car road ; this gallery has been excavated for safety purposes . The Gran Sasso massif is extremely rich in water ; its presence has probably been the major obstacle in excavation of the main tunnel where outflows of up to 60 atm have been encountered . This large amount of water is collected and sent to the public water supplies at the two sides of the tunnel ; therefore floors and walls of the laboratory were designed (fig . 3) in order to have complete separation between the laboratory environment and the drain parts where water for public supplies is collected, to avoid water pollution . 5.1 . Outfitting works
b
The outfitting works started in January dealing with the following main topics. - False walls in order to isolate halls from the rock . These walls are necessary because natural conditions are 6-7 ° C and 95% humidity ; thanks to them and to an air conditioning system it will be possible to mantain 20'C and 50-60% humidity. - Cranes . A 40 tons curved crane will be installed in each hall . - Distribution system for water, electric power and compressed air . Cables and tubes run along walls . At present, crane legs and rails have been assembled in hall A hall and B, and false walls are mounted in hall A. We expect to have hall A completed before the end of July . Hall B will follow with a few weeks of delay . Hall C will be finished later also because we intend to have a design of general services tailored to meet the liquid argon detector requirements . At a first stage, a few MW of electric power will be available in the laboratory, a fraction of which will be absorbed by general services. A plan to increase the total power to -- 10 MW is forecast . If a large magnet, like than one designed for ICARUS, is used, at least 15 MW will be needed . Such a large amount of power will require special equipment to condition the laboratory. Large amounts of water are in principle available even if some agreement with the public water supply management will be required . Of course, protections against power failures will be guaranteed by additional power supply systems . 5 .2. Ventilation
Fig. 2 . (a) Cross section of hall C. (1) Access tunnel, (2) emergency bypass, (3) hole for ICARUS. (b) Cross section of hall C . (1) Drain tubes (rä 300 mm), (2) PVC sheet .
Ventilation is one of the major problems in underground laboratories . At the moment a flow of 20000 m3 /h of fresh air (i.e . air from outside the highway tunnel) is available and, in case of need, 80000 m3 /h of air taken from the highway can be steered in a single hall. I. LARGE UNDERGROUND DETECTORS
4
E. Bellotti / The Gran Sasso underground laboratory
Fig. 3. Details of the draining system . (1) PVC sheet. 5.3 . Safety
Safety is probably the most complex problem in such a laboratory . Halls can be isolated by means of fire and pressure (5 kg/cm2) resistant doors. A general system of fire, dangerous and cryogenic gases detectors will be in operation. Information will be continuously sent to the outside building. 5.4. Data link
The internal laboratory will be linked to the external world through a 100 optical fiber cable and a few standard copper cables. The main cable, which will run along the car tunnel, has been constructed and it is presently being tested . Installation of this system will start next fall . 6. Future programs From the above description and from the following papers describing in detail specific experiments, it will be clear that the laboratory is insufficient in two respects : space for new experiments is completely missing, and the safety level has to be increased in order to achieve complete decoupling of the highway from the laboratory . A third law has been presented to our Parliament to obtain new funds of the order of 150 billion lire to
excavate a third small tunnel from the laboratory to Assergi (7 km tunnel) and two new halls; one of them will be probably dedicated to experiments using cryogenic techniques and the second one to special applications, to new experiments or to implement one of the detectors presently under construction. References
A. Zichichi, The Gran Sasso Project, Proc. of Physics and Astrophysics with a Multikiloton Modular Underground Detector, Rome (Oct . 29-31, 1981) p. 141 ; The Gran Sasso Laboratory, Invited Paper to ICOMAN 83 Meeting, Frascati (1983) ; The Gran Sasso Project, INFN/AE-82/1 (1982) . [2] R. Cardarelli et al ., Muon flux measurement in the Gran Sasso Laboratory, INFN/AE-86/11 (1986). [3] E. Bellotti et al ., INFN/TC-89-19 and references therein reported . [4] M. Aglietta et al ., Nuovo Cimento 9C (1986) 262; M. Aglietta et al ., EAS-TOP, The Muon-Hadron Detector System, Istituto di Cosmogeofisica, Torino (1987); M. Aglietta et al., Proc . NATO Workshop on High Energy Gamma-Ray Astronomy and Related Topics, Durham (1986) in press; M. Aglietta et al., The EAS-TOP Detector at the Gran Sasso, Results from the Test Modules, submitted to the 20th ICRC (1987) . L. Paoluzi, presented at this Workshop (Workshop on Non-Accelerator Particle Physics, Rochester, NY, 1987).
Section I. Large underground detectors THE GRAN SASSO UNDERGROUND LABORATORY E. BELLOTTI Laboratorio Nazionale del Gran Sasso, Universit6 degli Studi e Sezione INFN, Milano, Italy The Gran Sasso Underground Laboratory, located on a side of the road tunnel under the Gran Sasso Massif, not far from Rome, is nearly completed . The status of construction and outfitting of experimental halls is reported, as well as future plans to improve safety and available room for experiments . 1 . Introduction Laboratorio Nazionale del Gran Sasso is the national facility of INFN - the Italian agency for fundamental research in nuclear and subnuclear physics - for underground physics . The construction of this laboratory was proposed in 1981 by A. Zichichi, at that time president of INFN ; according to a first design, the laboratory consisted of a single large hall to be dedicated to an experiment on proton decay . A law was approved in February 1982, and a sum of 20 billion lire was allocated : one year later, the project was largely improved and the total budget was increased up to a total of 77 billions Italian lire [1] . Present underground experiments are located in mines, like IMB in USA and Kamiokande in Japan, or in caves along car tunnels under Alps like NUSEX in the Mt. Blanc and the French-German detector in the Frejus tunnel . Mines and caves were adapted to permit the installation of these detectors ; however, these facilities cannot really be called "laboratories" ; on the contrary, Gran Sasso was designed as a complete laboratory, with a diversified research program and general facilities . In that sense, Baksan in Soviet Union is the only operating laboratory for underground physics ; however, at least for groups from western countries, Gran Sasso is in a better geographical position . The laboratory has been realized under the responsibility of ANAS (the Italian authority for roads and highways), which depends on Ministry of Public Works ; two major Italian companies where engaged in this work : Cogefar S .p .A. for the excavation and SAEM (a group of firms) for most of the general installations . The laboratory is located on a side of the road tunnel under the Gran Sasso, along the highway connecting Rome to the Adriatic sea ; it is at about 150 km from the Rome International Airport and it is linked to the European network of highways. It is not far from L'Aquila, a small and beautiful town, seat of a university. 0168-9002/88/$03 .50 C Elsevier Science Publishers B .V . (North-Holland Physics Publishing Division)
Its geographical position is : 42' 27' N and 13' 34' E of Greenwich ; the altitude is - 960 m a.s .l . The rock overburden is - 3500 hg of water equivalent . At this depth, the muon flux is of the order of 1 tt/(m2 h) [2] . The rock, mainly limestone, has a low content of radioactive elements, if compared with Mt . Blanc granite ; measurements of gamma-ray and neutron fluxes have been carried out before the starting of the outfitting works [3]. New measurements are in progress or will start in a short time to take into account the effect of different materials introduced in the laboratory and to improve the quality of the neutron flux determination. The laboratory consists, at present, of an outside building, the internal halls and a few sheds at Campo Imperatore . Before giving a short description of the laboratory, it must be mentioned that other fields of research will be developed in the laboratory, beside the experiments which will be described by the other speakers in this same session . First of all, installation of a gravitational wave antenna is planned, which is presently under construction by the Rome group . Groups from L'Aquila, Rome and other universities are interested in carrying out measurements on geophysical phenomena (fault movements, assessment of the rock after the excavation, propagation of electromagnetic fields through the earth crust, etc.). Interest has been expressed also by people involved in radiation controls in having a laboratory where their detectors can be calibrated in the absence of a cosmic radiation background . 2. The outside building The offices, groups, 11/780
outside building hosts some administration a conference room, a few offices for external a computer room, where at present a VAX linked to INFNET (the INFN network of 1 . LARGE UNDERGROUND DETECTORS
E. Bellotti / The Gran Sasso underground laboratory
HIGHWAY-
Fig . 1 . General layout of the underground laboratories . computers) is installed, small laboratories and two large counting rooms . While this building is extremely useful at this stage of construction of the laboratory, in the near future it will be absolutely necessary to build new assembling halls and buildings for general services . 3. Installation at Campo Imperatore According to plans of INFN, in collaboration with CNR (National Council for Research) an extensive air shower detector will be installed at Campo Imperatore (2000 m a . s . L, 25 ° off the vertical from the underground laboratory) [4] . The installation will consist of about 30 small sheds, each one instrumented with a 10 mZ detector (liquid scintillator or plastic scintillator) to measure the electromagnetic component of showers, and a central building with a 200 mZ hadron and muon detector consisting of a sandwich of limited streamer tubes and passive material . These detectors will be distributed over an area of - 10 5 mz . The expected rate of events observed on the surface and in one of the underground detectors is of the order of 1 per day. During winter 1986-1987 a few detectors have been successfully tested .
tation by means of heavy lorries. A smaller tunnel will be used by cars. Three small galleries in the form of a triangle have been excavated in the northern part of the laboratory ; an interferometric system and other devices for geophysics measurements will be installed there. The total excavated volume is 180000 m3 . Halls A N and A s are 42 m long, 17 m wide and 17 m high ; hall B is 127 m long and has the same transversal dimensions as halls A ; hall C is 100 m long, 22 m wide and 20 m high ; the cross section has the typical shape of tunnels (figs . 2a and 2b) . In hall A s a hole has been excavated to house a few tanks where gallium will be recovered in case of an important damage in the main tanks ; in that way pollution of the laboratory with HCl will be avoided in case of an accident [5] . Similarly, in hall C an extra hole has been excavated to allow the installation of the dewar and, possibly, of the magnet of ICARUS. Major experiments will be installed as follows : LVD in hall A, north wing ; GALLEX, ,ß/3 decay in hall A, south wing ; MACRO in hall B ; and ICARUS in hall C . The position of the gravitational antenna has not yet been defined ; however, this antenna will be ready for installation in Gran Sasso in not less than two years from now .
4 . Underground laboratories The general layout of the underground laboratories is shown in fig . 1 . Four main halls, conventionally denoted by A N , A s , B and C, are connected by a large road, directly linked to the highway, to allow transpor-
5 . Status of works Excavation has been completed, with the exception of a very small and short gallery connecting the access
E. Bellotti / The Gran Sasso underground laboratory
a
IMM IBM
3
road between hall A and hall B and the car road ; this gallery has been excavated for safety purposes . The Gran Sasso massif is extremely rich in water ; its presence has probably been the major obstacle in excavation of the main tunnel where outflows of up to 60 atm have been encountered . This large amount of water is collected and sent to the public water supplies at the two sides of the tunnel ; therefore floors and walls of the laboratory were designed (fig . 3) in order to have complete separation between the laboratory environment and the drain parts where water for public supplies is collected, to avoid water pollution . 5.1 . Outfitting works
b
The outfitting works started in January dealing with the following main topics. - False walls in order to isolate halls from the rock . These walls are necessary because natural conditions are 6-7 ° C and 95% humidity ; thanks to them and to an air conditioning system it will be possible to mantain 20'C and 50-60% humidity. - Cranes . A 40 tons curved crane will be installed in each hall . - Distribution system for water, electric power and compressed air . Cables and tubes run along walls . At present, crane legs and rails have been assembled in hall A hall and B, and false walls are mounted in hall A. We expect to have hall A completed before the end of July . Hall B will follow with a few weeks of delay . Hall C will be finished later also because we intend to have a design of general services tailored to meet the liquid argon detector requirements . At a first stage, a few MW of electric power will be available in the laboratory, a fraction of which will be absorbed by general services. A plan to increase the total power to -- 10 MW is forecast . If a large magnet, like than one designed for ICARUS, is used, at least 15 MW will be needed . Such a large amount of power will require special equipment to condition the laboratory. Large amounts of water are in principle available even if some agreement with the public water supply management will be required . Of course, protections against power failures will be guaranteed by additional power supply systems . 5 .2. Ventilation
Fig. 2 . (a) Cross section of hall C. (1) Access tunnel, (2) emergency bypass, (3) hole for ICARUS. (b) Cross section of hall C . (1) Drain tubes (rä 300 mm), (2) PVC sheet .
Ventilation is one of the major problems in underground laboratories . At the moment a flow of 20000 m3 /h of fresh air (i.e . air from outside the highway tunnel) is available and, in case of need, 80000 m3 /h of air taken from the highway can be steered in a single hall. I. LARGE UNDERGROUND DETECTORS
4
E. Bellotti / The Gran Sasso underground laboratory
Fig. 3. Details of the draining system . (1) PVC sheet. 5.3 . Safety
Safety is probably the most complex problem in such a laboratory . Halls can be isolated by means of fire and pressure (5 kg/cm2) resistant doors. A general system of fire, dangerous and cryogenic gases detectors will be in operation. Information will be continuously sent to the outside building. 5.4. Data link
The internal laboratory will be linked to the external world through a 100 optical fiber cable and a few standard copper cables. The main cable, which will run along the car tunnel, has been constructed and it is presently being tested . Installation of this system will start next fall . 6. Future programs From the above description and from the following papers describing in detail specific experiments, it will be clear that the laboratory is insufficient in two respects : space for new experiments is completely missing, and the safety level has to be increased in order to achieve complete decoupling of the highway from the laboratory . A third law has been presented to our Parliament to obtain new funds of the order of 150 billion lire to
excavate a third small tunnel from the laboratory to Assergi (7 km tunnel) and two new halls; one of them will be probably dedicated to experiments using cryogenic techniques and the second one to special applications, to new experiments or to implement one of the detectors presently under construction. References
A. Zichichi, The Gran Sasso Project, Proc. of Physics and Astrophysics with a Multikiloton Modular Underground Detector, Rome (Oct . 29-31, 1981) p. 141 ; The Gran Sasso Laboratory, Invited Paper to ICOMAN 83 Meeting, Frascati (1983) ; The Gran Sasso Project, INFN/AE-82/1 (1982) . [2] R. Cardarelli et al ., Muon flux measurement in the Gran Sasso Laboratory, INFN/AE-86/11 (1986). [3] E. Bellotti et al ., INFN/TC-89-19 and references therein reported . [4] M. Aglietta et al ., Nuovo Cimento 9C (1986) 262; M. Aglietta et al ., EAS-TOP, The Muon-Hadron Detector System, Istituto di Cosmogeofisica, Torino (1987); M. Aglietta et al., Proc . NATO Workshop on High Energy Gamma-Ray Astronomy and Related Topics, Durham (1986) in press; M. Aglietta et al., The EAS-TOP Detector at the Gran Sasso, Results from the Test Modules, submitted to the 20th ICRC (1987) . L. Paoluzi, presented at this Workshop (Workshop on Non-Accelerator Particle Physics, Rochester, NY, 1987).