Accelerate particles, a matter of Stability.

ALBA is a 3rd generation Synchrotron Light facility located in Cerdanyola del Vallès, Barcelona, being the newest particle source in the Mediterranean area.

ALBA is a complex of electron accelerators to produce Synchrotron Light, which allows the visualization of the atomic structure of matter as well as the study of its properties.?

The 3 GeV electron beam energy at ALBA is achieved by combining a Linear Accelerator (LINAC) and a low-emittance, full-energy BOOSTER placed in the same tunnel as the STORAGE RING. ALBA's 270-meter perimeter has 17 straight sections, all of which are available for the installation of insertion devices to fulfill wide range of beam lines for experiments by the User’s Community.

We are going to take a look at how the facilities of the Spanish synchrotron light source particle accelerator are and how a potential design improvement that was present from the origin of the facility has been improved through Engineering.

This is a success story that I want to tell you about.

Some years ago I started an Engineering project, necessary for the institution where I was developing my work. Alba Synchrotron Light Source.

In this type of scientific facilities, obtaining the necessary stability in various fields of Engineering is an essential condition to carry out the high-level research that is developed there.

How is stability achieved in this type of scientific facility?

Stability understood as?

The property of a body to remain in stable equilibrium or to return to that state after suffering a disturbance.

Mechanical Stability,

It is obtained with the structural design of the building that acts as a container for the particle accelerator and allows the accelerator to be isolated from the outside world.

With different solutions, such as the manufacture of a critical concrete slab (more than one meter thick and approximately 90 meters in diameter, more than 6000 m3 of concrete) where the tunnel it is hold, in this case with a positive elevation.

The walls of the tunnel act as nerves to stiffen the entire set since they are born from the critical slab itself as if they were wings of a beam, finally the ceiling is located, also made of concrete, 1 meter thick, with which it is achieved the circular tunnel shape.

The more than 15,000 tons that the whole weighs, are supported on a gravel bed about two meters deep.

Despite all this effort to isolate the vibrations from the outside world, which could affect the operation of the accelerator, this is not fully achieved, and electron orbit correction systems are needed to adjust the position and avoid losses of beam, which you might even assume, even stopping the particle accelerator.

You have to understand the accelerator as a tool with extreme sensitivity, to understand this point, consider that several of the earthquakes suffered in other parts of the world, such as, for example: Chile earthquake.

The earthquakes in Chile in recent years were detected in the accelerator of particles starting some hours after the earthquake occurred, detected by the action of the fast electron orbit correction control. This system together with others, perform the control and correction of the orbit of the electrons.

Earthquakes in Chile in recent years were detected in the accelerator of particles starting some hours after the earthquake occurred.

Electrical Stability,

In Europe, every day, there are alterations in the electrical network that last more than 10 milliseconds,

The facility has an electrical management system, which allows to guarantee a constant and stable frequency output, giving an exceptional response, in order to thus, supply in a stable way the more than 500 direct current power supplies that supply the necessary and stable energy to the more than 600 magnets that the particle accelerator has to carry out the rotation of the electrons, orbit correction, stabilization of the beam, etc.

More than 600 magnets that the particle accelerator has to carry out the rotation of the electrons.

Spain high voltage net, ALBA Synchrotron is connected to a devoted transformer 220/25 kV of 20 MVA in an own property substation. In case of power supply failure, except for non-preferential loads, there are standby diesel generators linked to uninterrupted power supplies (static and dynamic) ready and 24/365 available.

Up to four 4 different levels of power supply continuity are present in the facility: non-preferential, preferential, critical and clean (perfect sinusoidal wave).

Thermal stability,

The entire building is covered by a dome that resembles the shape of a snail and creates an open space into which 240.000 m3/h of air treated at 23o ± 1oC is introduced by an HVAC system, which operates 24 hours a day, 365 days a year, to achieve adiabatic protection around the tunnel, avoiding temperature changes caused by the environment.

The construction of the building lacks access to the outside such as windows, to avoid influences due to solar radiation.

An open space into which 240.000 m3/h of air treated at 23o ± 1oC during all the year.

Inside the tunnel and the linear accelerator (LINAC), the heat generated by the activity of the magnets is dissipated in two ways, the first, through treated air (23 ± 0.2oC), by equipment of HVAC air conditioning with adjustable nozzles.

Deionized water circuits:

The second through a deionized water cooling system, which circulates treated water (23 ± 0.2oC), inside the magnet coils.

Proposed Solution.

It is in the thermal stability, where the study has been carried out, which has allowed to achieve the necessary stability in the Storage Ring.

I attach a summary of the technical detail, (also links that I have shared in the publications section of my profile), the project solves one of the biggest design problems since the commissioning of the installation.

The solution has gone through the following phases,

Diagnosing the problem: Aspiration pressure drop and thermal instabillities

As a result of the problems detected during the cooling operation, it was discovered that the Storage ring had less pressure on the pump suction than the rest of the circuits, which could affect the operation.

Storage ring had less pressure on the pump suction than the rest of the circuits

Identified in an excessive pressure drop in the mixing valve that must achieve an output of 23oC of cold water towards the components of the Storage Ring, with an accuracy of ± 0.2oC

Exploring different solutions: new valve size.

Increased valve size from current DN150 to DN200.

Validity of the hypotheses

Check the validity of the solution by modelling it in CFD Fluid Simulation (SW), checking that the configured solution allows us to solve the problem of excessive pressure drop and at the same time allows us stability in the outlet temperature, lost due to the opening of a valve of bypass that helped us to give greater pressure, but penalizing the thermal stability.

Check the validity of the solution by modelling it in CFD Fluid Simulation (SW)

The technical presentations that I share with you explore the best solution that has allowed us to solve for the next few years the serious problem of stability in the cooling temperature of the electron Storage ring.

End Task

Once the installation, start-up and commissioning have been carried out, we have gone from the initial 0.85 bar, to 1.65 bar thanks to the configuration of the new valve.

Regarding thermal stability, by being able to close the bypass that penalized the temperature, the variation is no longer a problem, returning to recover the thermal stability of the system.

we have gone from the initial 0.85 bar, to 1.65 bar thanks to the configuration of the new valve.

Acknowledgement.

I am glad that finally, after more than two years of work, with the collaboration of @Marcos Quispe and @ José Ferrer (engineering division), my partners was able to complete the project in the installation of the valve and its components, giving the results that were expected and that they were foreseen applying the accumulated experience and the simulations that I carried out, using SolidWorks Flow Simulation.

I wish you many years of success Synchrotron Alba.