Stability and Constructive Aspects

BACK

The dimensional stability of the accelerators and beamlines, required to operate an electron beam with micrometric dimensions and light beams focused at nanometers, demand high performance buildings and facilities.

The most important aspects are the stability of the floor against differential settlements and deformations; the isolation of vibrations from the external environment and the mitigation of the vibrations generated by the components of the facilities; and the thermal stability of the environments and components.

Moreover, it is necessary to provide the facilities with a good grounding system, capable of ensuring the safety of the people and preserve the integrity of the equipment, as well as reduce electromagnetic noise levels that interfere with the performance of instrumentation and components.

STABILITY IN NUMBERS

The maximum differential strain across the surface of the building is at most 2.5mm per year.

Temperature control with maximum variation of $\pm$ 0.1°C at the Storage Ring Tunnel.

Foundation

The foundation of the building will be divided into two fully independent structures.

The first, consisting of 910 piles with diameters between 40 centimeters and one meter, with average depth of 18 meters, will be fully connected by beams, whose function is to support the structure of the building.

The second foundation will support the floor of the experimental hall and the shielding of the accelerators. Besides the role of supporting the floor and the equipment, it has the function of preventing differential settlements and propagation of vibrations, whether generated internally or externally.

The foundation is composed of a layer of 2.85 meter deep modified soil obtained from the local soil removal, followed by mixing with cement and reapplication of thin layers with high degree of compression. The process gives greater resistance (specified 2 MPa) and rigidity, reducing the vibration propagated through the ground.

In the region of the shielding of the accelerators, the modified layer of soil will be supported in 1322 piles, with 40 cm in diameter and 15 meters long. The piles will be of CFA (Continuous Flight Auger) type, which gives great constructive uniformity to the foundation.

Critical Floor

The Critical Floor is the floor of the accelerators and beamlines that presents the best possible performance in terms of stability and transmission of vibrations.

Supported on a 15 cm thick layer of CTCR (Cement Treated Crushed Rock), which coats the modified soil, the floor of accelerators will be made of 90 cm thick reinforced concrete. Its construction will be performed in 20 segments, with a two meters wide gap between each of them. The profile of this cement will provide the concrete with a very low shrinkage. The concreting of the gaps is carried out after the segments reach most of the shrinkage, to obtain a monolithic structure without the occurrence of cracks.

The floor for the beamlines will be 60 cm thick and connected to the accelerator floor by means of transfer bars. Between the segments, special expansion joints will allow the circulation devices, without premature wear or unwanted vibrations. Both the accelerator and the beamline floor will be separated from the rest of the building floors by rubber floor joints. Thus, the total separation between the experimental area and the rest of the building will be guaranteed.

Building

The structure of the building will be made of cast-in-place reinforced concrete and all its floors, including the ground floor, will also be built in reinforced concrete slabs. Thus, the structure will present great rigidity, reducing the transmission of vibration from the action of the wind, the movement of people and the operation of equipment and facilities.

The roofing will be in aluminium conical seam panels with insulation for low thermal transmittance, ensuring the highly stable temperature control required by the environment.

The majority of the inner walls will be dry-walls filled with glass wool. The external walls of the building will be glass wall protected from the sun by brises-soleil.

Electrical Installations

Given the need for high availability of the accelerators, the two medium voltage substations planned for this building operate with redundant circuits. The electrical feeders, cabinets and transformers are duplicated, allowing continued operation in the event of failure of one of them.

To meet the expectations of power quality demanded by sources of the accelerators, the project includes four UPS sets configured for N + 1 redundancy with power of 900 + 300 KVA each. These devices suppress the momentary fluctuations of the power grid.

Cold Water

The production of cold water is intended for the air conditioning system, the hydraulic cooling systems and heat stabilization systems and components of the beamlines, laboratories and accelerators. Through 10 chillers with condensation by air, part of the produced water will be used directly in air-conditioning equipment, while a second portion will be directed to thermal stabilization circuits. The third part will be stored in thermal storage tanks for use in peak periods (more expensive electricity), allowing the economy of electric power through the shutdown of equipment.

Thermal Stabilization

Eight closed circuits using ultrapure water as a circulating medium included in the project. They are formed by an automatic pressurization system which allows the system pressure to be kept constant by varying the flow as it is demanded. This circuit is important for the stability of the temperature control systems of the various components and allows the rational use of energy. The pumping systems use a computerized control mechanism that uses algorithms capable of determining the most efficient configuration for each operating situation. To avoid the generation of vibrations by the liquid flow in these circuits, the pipes are oversized in order to obtain low speeds.

Grounding

The grounding system of this building has two main purposes: the protection and safety of people and equipment, both in case of lightning and for fault situations in equipment and facilities; and the proper functioning of equipment and scientific instrumentation within an environment with the presence of high-power electronic systems that operate on radio frequency, pulsed systems and strong electromagnetic fields. The project is designed with a grounding resistance of 1.2 Ohms.

In addition to the traditional captors system, electrical interconnection of all hardware will be used in frame structures, floors and concrete piles. On the ground, a grid with 4.5 km of copper wire will be connected to the reinforcement of the piles. Finally, grounding system is also composed of a large ring formed by copper wires connected to grounding rods distributed on the perimeter of the terrain and electrically connected to the network under the buildings.

Liquid Nitrogen

For the consumption of 18,000 liters of liquid nitrogen per day for the operation of 40 beamlines, two cryogenic tanks with a capacity of 60,000 liters each will be installed. This capacity will gradually be achieved with the installation of tanks with increasing capacities, appropriate to the expected consumption for each step and assuring the rational use of this material.