Brighter than the Sun
Consulting engineer: UMA Group, Saskatoon officeThe UMA Group is overseeing the largest science project undertaken in Canada in 30 years, building the giant microscope known as the Canadian Light Sour...
Consulting engineer: UMA Group, Saskatoon office
The UMA Group is overseeing the largest science project undertaken in Canada in 30 years, building the giant microscope known as the Canadian Light Source at the University of Saskatchewan in Saskatoon.
The project is to build a synchrotron — a football-field sized apparatus which produces the brightest light possible, billions of times more intense than the sun, and in beams the width of a human hair. Scientists and researchers all over the world are relying more and more on this special light, and yet Canada is the only G7 country which until now has no synchrotron of its own and relies on having to send researchers elsewhere.
The literature from the Canadian Light Source likens synchrotron light to that from pulsars — supermassive stars that are collapsing under their own gravity. Electrons caught in this ferocious pull and spin of gravity are constantly forced to change direction as they whirl around the collapsed star, and as they do so, they give off streams of highly energetic photons — synchrotron light. Similarly, the synchrotron light source generator works by using powerful magnets and radio frequency waves to accelerate electrons to nearly the speed of light. The infrared, ultraviolet and X-ray light is shone down beamlines to end-station small laboratories where the scientists can select different parts of the spectrum for their experiments.
Synchrotron light is extremely useful to scientists because it covers the full range of the light spectrum, from infrared to X-ray wavelengths. It allows matter to be seen at the subatomic level, which means scientists using it can “see,” for example, even into living cells and molecules and watch how they react. The applications are myriad. In the health sciences the technology can help researchers develop drugs and vaccines, investigate the effect of pollutants on the natural world, or manufacture biomedical implants. In industry, synchrotron light can be used for etching microchips for powerful computers, developing new materials, manufacturing microscopic machines as small as the eye on a needle, and developing ultra thin coatings and lubricants.
With financial support from several levels of government and the largest grant ever from the Canada Foundation for Innovation, the $173.5 million synchrotron in Saskatoon is under construction and due to start operations by the end of 2003. The Saskatoon office of UMA Group of Vancouver is overall program and construction manager for the total project, as well as responsible for the civil, structural, mechanical and electrical engineering for the building. The firm is also providing consulting engineering services to support the Canadian Light Source designers and engineers on the technical systems. A Danish company, Danfysik A/S, recently won an $8 million contract to design and build one of those systems, the booster ring.
Building a synchrotron
The new facilities are being built adjacent to an existing building housing the Saskatchewan Accelerator Laboratory, taking advantage of the existing linear accelerator in its basement. Inside the new 9,000-m2 steel-clad building is the main experimental hall at grade. It contains the massive booster and storage rings, which are enclosed in a concrete tunnel. The hall’s floor plate is 84 metres x 83 metres. The roof trusses weigh 6,700 tonnes each and are up to 9 metres deep in order to achieve the clear span. Offices and laboratories are on a mezzanine, and there are also wet and dry labs, clean rooms, and a 750-m2 service basement.
The existing linear accelerator is the “gun” that starts off the process. It fires a steady stream of electrons that pass through a linear accelerator or “linac” that increases their speed to 99.99986 per cent of the speed of light. They now carry about 300 million electron volts of energy. From this basement site the electron beam travels 8 metres up a newly constructed transfer tunnel into the booster ring at grade in the new main experimental hall. The booster ring uses magnetic fields to force the electrons to travel in a circle (much like the electrons in pulsars), and radio waves are used to ramp the energy up to 2.9 gigaelectron volts (GeV). The booster ring then feeds into the storage ring, a many-sided doughnut of 170 metres circumference. The tube is maintained under vacuum as free as possible of air or other stray atoms that could deflect the electron beam, while computer controlled magnets keep the beam absolutely true. This is a third generation synchrotron, which means the electrons also pass through devices known as “wigglers” and “undulators” that bend the path of the charged particles many times in short distances and thus make the light seven times more intense. Finally, the electrons pass through a set of bending magnets connected to each “beamline” to be delivered to each experimental station.
Engineering such a complex and unique building obviously involved some challenges. Barry Hawkins, project manager with UMA, describes them as follows:
Structure: “A difficult issue was minimizing the transfer of vibrations (caused by wind loads, an overhead bridge crane, mechanical pumps, traffic, etc.) from the structure to the experimental stations. If you picture a beamline with a length of 30 metres from the extraction point to the experimental target, the lever effect is induced, which amplifies any vibrations along that length. That makes controlling the beam very difficult and costly.”
To mitigate the vibration effects, the facility is built on over 700 cast-in-place concrete piles. As well, the building structure, experimental hall floor slab and booster floor slab are physically isolated from each other.
Power: the synchrotron will have a total electrical load of 10MW, increasing to 12MW in the future. Since the existing accelerator used only 2MW, the university substation is having a major upgrade in order to provide the new service. The engineers and suppliers have decided that harmonics will not be a problem, although space has been allotted for installing corrective equipment if it is needed.
HVAC: as with vibrations, Hawkins says, the objective is to maintain a very stable environment within the experimental hall since variations in ambient air temperatures can affect the stability of the beam.
Within the booster and storage ring enclosures the temperature has to be 25C, controlled to +/- 0.1C accuracy. To achieve this, heat has to be removed from the magnets, power supplies and other equipment, and this is done through a precise and reliable closed loop low conductivity water system with heat exchangers and pumps. The system removes a total of 8 MW of energy which is rejected through outdoor closed circuit fluid coolers.
The main experimental hall HVAC system maintains temperature control at 22-23C for the beamline work areas. It consists of dual central station, variable speed air handlers each supplying a maximum of 31.4 cubic metres/sec of conditioned air to the space via ducting. Variable air volume terminal units with reheat coils use a portion of the 8MW of heat removed from the technical components of the synchrotron. Free cooling with outside air is used as much as possible.
To ensure that equipment vibrations are not transferred onto the main experimental hall floor slab, the air handlers are located within the roof truss areas, and other rotating equipment such as pumps and compressors are located on floors slabs that are physically isolated from the main hall floor slab. Vibration isolators and inertia pads are also provided for the equipment.
Besides the unusual technical nature of this project, UMA has to manage the efforts and programs of many different parties and sometimes deal with conflicting interests. They find the web site at www.cls.usask.ca is useful for keeping all the parties informed and dealing with equipment suppliers from around the world. Transferring knowledge is also a big part of the job, says Hawkins, and UMA enjoys the fact that the science community likes to share knowledge. It was advice from vi
sitors from a similar site in Germany that led to the decision to split the floor slabs to help mitigate the vibration effects.
Indeed UMA has become a seasoned expert in large-scale scientific projects, having helped manage the TRIUMF ISAC, high energy physics laboratory built in Vancouver in 1996, plus the TRIUMF KAON PDS Study in 1990, the Free Electron Laser Laboratory expansion at Duke University in Durham, N.C. and the AHI project for the University of Hawaii. With the Canadian Light Source project, which is expected to generate $35 million annually by drawing commercial and industrial researchers from around the world, UMA is helping Canada stay in the vanguard of scientific and technological advance.–BL
Client: University of Saskatchewan
UMA project team leaders: Barry Hawkins, (project manager), Martin Heikoop, P.Eng. (construction manager), Nizar Dhanani, P.Eng. (design manager). Peter Hooge P.Eng. (mechanical), Edwin Klassen and Harbans Aulakh (electrical)
Architect: AODBT Architects
Graphics courtesy: University of Saskatoon/CLS