2012.05.15 | RASMUS RØRBÆK
During spring, the final touches will be made in the basement below the Department of Physics and Astronomy to the actual construction of what will be one of the world’s best and most powerful particle accelerators – ASTRID2.
Once ‘she’ is up and running in the course of 2013, researchers from all over the world will be able to use the technology – known in research circles as synchrotron radiation – to gain new knowledge by studying things such as biomolecules and new materials in fields ranging from biology to nanotechnology and fundamental physics.
The accelerator will supersede the old ASTRID storage ring, which has attracted physicists, biologists and doctors from all over the world for two decades. This is because the technology at Aarhus University has provided the international science community with a unique opportunity to build up more knowledge and a basic understanding of the smallest components we are made of.
The new accelerator will be able to produce better and stronger X-rays, which will enable researchers to probe deeper into the microscopic world and see far more details. In other words, ASTRID2 will have a position in the absolute world elite when the facility is operating. By that time, the technology will be hidden behind concrete structures weighing several tons to protect the researchers from radiation.
Creating one of the world’s ultimate light sources is an extremely complicated and extensive task, but Director Søren Pape Møller hopes that the ring will be completed in the near future. This will make it possible to begin circulating electrons in the accelerator, and ASTRID2 will be capable of accelerating the electrons up to the speed of light during the course of autumn 2012.
In this photo report, he invites you into the basement where the facility is still being built to show you around while the accelerator mechanism is still visible to the naked eye.
Click on the images to see them in larger format.
The ASTRID2 accelerator has a circumference of 46 metres and is basically used as a lamp. However, where a lamp such as a pocket torch works by casting light in a way that makes it possible to see what we would otherwise run into, the ASTRID2 concept takes ‘lamps’ to completely new heights. ASTRID2 accelerates electrons to just below the speed of light, by which very intense short-wave light is emitted. The electrons are deflected from the main orbit by means of extremely strong magnets. Each time the electron beam is deflected at very high speeds, X-rays are emitted and these can be led from the facility itself to experimental stations.
When the radiation hits the test object, other particles are struck off the surface and are registered by different sensors. It is these particles that provide information about the object’s atomic composition and structure.
The accelerator works by using electric and magnetic fields to manipulate electrons into the ring. About 100 magnets are placed all the way round, each of which can affect the flow of electrons in different ways. Some are used to deflect the electrons around corners, while others focus and concentrate the density of the electrons in the ring. In combination, the magnets provide an opportunity for ASTRID2 to become one of the most brilliant sources of light in the world! When ASTRID2 is operating, the electrons are gathered in clusters that are accelerated by electric fields to almost the speed of light. X-rays can be drawn from these clusters towards a test set-up, partly by a deflection magnet as shown in this image.
There is nothing like watching it happening. This short animated film shows how the old ASTRID works.
ASTRID2 works in the same way, and the two accelerators will be linked to one large facility in future.
In this film, you can follow the electrons (red dots) all the way from acceleration to where the magnets ‘wrench’ the X-rays out to the test object. There is no sound in this clip, which takes 1 minute and 6 seconds.
A considerable number of the components in this image were designed by the researchers themselves. As the staff here say with a twinkle in their eye, “You can’t just run down to the local DIY store to buy any of this.” It is absolutely essential, for example, that ASTRID2’s ring is kept in a vacuum at all times. Specially manufactured gaskets and seals have therefore been used all the way round. If it was not for the vacuum, the electrons that are supposed to be accelerated up to the speed of light would collide with air molecules inside the ring and would thus be slowed down.
Once ASTRID2 is up and running, ionising radiation will be formed from the accelerator’s electrons. Several hundred tons of concrete have therefore been placed all the way round the facility. However, it will still be possible to stay within the concrete enclosure when the facility is not in use. ASTRID2’s very heavy ‘ball gown’ is made of specially built blocks each weighing a ton. They are constructed so they can be tightly stacked on top of each other. Once this stage of the work is completed, it will no longer be possible to see ASTRID2’s mechanical parts.
ASTRID2 consists of thousands of parts, including everything from kilometres of cables and leads to concrete blocks weighing several tons, and from extremely powerful magnets to special vacuum packs that keep the accelerator hermetically sealed.
Much of this was designed and built by employees at the department. Niels Hertel (right) and Henrik Juul (left) are two of the approximately forty members of staff at Aarhus University who have been working intensely on building ASTRID2 in recent years.
Work began in 2009, when the Ministry of Science, Technology and Innovation granted DKK 37 million to the new facility. Once the facility has been commissioned at Aarhus University, the total price for ASTRID2 will be more than DKK 50 million.
