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The TOSCA Site at the CERN NGS

The planned location of the experiment is at 1858 m from the proton target. Due to the -5.6% slope of the beam, its underground depth is already 151 m at this location (see Figure 1). On the surface, the site corresponds to an unoccupied plot of land of around 3000  area, which belongs to the Geneva airport. According to our studies this plot is sufficiently large to house the necessary infrastructure for the TOSCA experiment.

  
Figure 6: The layout of the underground cavern (top view) with the access shaft on the left and the TOSCA experiment with open magnet on the right

  
Figure 7: The cross section of the underground cavern. The MEP50 magnet in open position is depicted at the centre.

The basic elements of the site infrastructure are:

• An underground cavern housing the experiment, its electronic counting house, a manipulation area for detector equipment and a service room for ventilation, cooling and electrical supplies (see Figures 6 and 7)
• A 140 m deep shaft of 10 m diameter comprising a 9x3 material shaft, cables trays and conducts as well as a pressurised personnel access zone with 2 elevators and a staircase.
• Several surface buildings: a hall for material access and manipulation, a building for cooling and ventilation equipment, 2 buildings for electrical power conversion and supplies, an office building housing the control room of the experiment and a building for detector gas supplies (see Figure 8).

  
Figure 8: The layout of the surface site showing the central hall for material access with the access shaft, surrounded by various infrastructure buildings.

The outer dimensions of the TOSCA experiment are essentially defined by the spectrometer magnet MEP50 and by the muon detection system. The MEP50 magnet is a classical magnet, presently in use by the NOMAD experiment and previously used by the UA1 experiment. Table 3 summarises the main characteristics of the spectrometer magnet. The magnet will be operated at maximum field. It requires sizeable cooling and electricity infrastructures. The proximity of existing buildings near the site and a tight construction height limit due to the proximity of the airport runway exclude the installation of cooling towers or power pylons in the area. Therefore the cooling water for the magnet as well as the electrical power will be transported from the LEP-PA8 site in a surface trench of about 1.2 km length. After the termination of LEP running sufficient cooling power and electrical power will be available at LEP-PA8 and the NGS time planning does not interfere with the LHC planning in this respect.

  
Table 3: Characteristics of the MEP50 magnet

More detailed information on the design, cost and planning of the site are being written in a forthcoming report [12]. Concerning the time planning for the construction of the site, approximately 3 years starting from the approval date are necessary. The complete cost estimate of the TOSCA site amounts to approximately 41 MCHF. It includes: civil engineering, surface buildings, the trench to LEP-PA8, cooling, ventilation, electricity, cranes, lifts, access control, fire detection, gas detection and supplies for detector gas.

Operation in Fast Extraction No Title Muon Flux at the