Company News, 2008-09-08, 10:00 AM
Special stainless steels help simulate the Big Bang: ThyssenKrupp Nirosta supplies materials for the world’s largest particle accelerator
What is the universe made of? How did it come about, and how come we exist? Scientists have no clear answers to these questions. But that could soon change. One of the world’s most renowned nuclear research organizations – CERN (Conseil Européen pour la Recherche Nucléaire) in Geneva – is currently building the largest particle accelerator in the world: The LHC (Large Hadron Collider) is a machine that can simulate the “Big Bang”. Researchers use the term Big Bang to describe the beginning of the universe, when matter was created by the interplay of elementary particles and energy. The LHC will be able to create conditions similar to those thought to have occurred only a few moments after the Big Bang, and therefore may help clear up the still unsolved questions. The researchers are entering new territory with this unprecedented scientific experiment and hope to obtain key findings about the origin of the universe. ThyssenKrupp Nirosta has supplied two special high-alloy stainless steels for the two billion euro project. They are capable of meeting the extremely high demands imposed by the 27 kilometer circular tunnel that has been built over a period of roughly ten years 100 meters beneath the Jura Mountains, crossing the border between Switzerland and France twice. The preparations for the tests have already begun and the commissioning of the LHC is scheduled for mid September, the official inauguration for October.
“There has never been a project of this scale before,” explains Professor Lucio Rossi, physicist and group leader accelerator technology at CERN. “We can hardly wait for it to start.” The special accelerator works as follows: Protons – the building blocks of atoms – are accelerated to the speed of light in opposite directions in two separate circular vacuum pipes. They collide repeatedly at four crossing points where several huge detectors are located. High-frequency electric fields ensure that the particles pick up more and more energy on their journey through the machine until they reach the final section of the complex, the LHC.
So-called quadrupole magnets, consisting of four magnetic poles, act as magnetic lenses, focusing the particle beam alternately in horizontal and vertical direction and keeping it on a predetermined “flight path”. “The special arrangement of different kinds of magnets limits the oscillations of the particles around this path,” explains Dr. Theodor Tortschanoff, a physicist at CERN responsible for the construction of the magnets. “This means they cannot hit the walls of the vacuum chamber, which would signify their loss for the experiment.” For the LHC’s roughly 500 quadrupole magnets ThyssenKrupp Nirosta supplied 860 tons of the material Nirosta 4375, a manganese-containing non-magnetizable austenitic stainless steel (X2 Cr Mn Ni N 20-9-7), from which the parts of the pretensioning rings were later manufactured. Dr. Alfred Otto, Executive Board member for Strategic Product Development of ThyssenKrupp Nirosta: “The material has very special physical properties, which are also fulfilled near absolute zero – i.e. at minus 271 degrees Celsius.” The extremely low magnetic conductivity and high strength of the material ensure that it does not itself become magnetized and can withstand the strong forces in the magnet coil. Dr. Detlef Krischel is a senior manager at ACCEL Instruments GmbH in Bergisch-Gladbach and responsible for the magnet projects: “The high quality of this special material was essential for the smooth production of the magnets and for their outstanding mechanical and magnetic properties.”
But without another important material from ThyssenKrupp Nirosta the particles in the LHC would not be able to circulate. To keep the particles on track the magnets with their superconducting coils have to be cooled to 271 degrees Celsius. This is done by means of a ring main running parallel to the magnets which supplies them with liquid helium for cooling. It is the low temperature which makes the magnet coils superconducting and allows the particles to be accelerated to the speed of light without any energy loss. The ring main is made of Nirosta 4307 stainless steel, a chrome-nickel steel (X2 Cr Ni 18-9) which remains tough and resistant to cracking even at very low temperatures. ThyssenKrupp Nirosta supplied 450 tons of this material to the stainless steel fabricator Butting, who used it to manufacture approximately 120 kilometers of pipe in four different sizes. Jörg Pollmann, a member of the Butting sales team: “This scientific project was a particular challenge, but one we enjoyed meeting. The material from ThyssenKrupp Nirosta was the perfect choice for this premium pipe.”
The protons have reached their highest energy level: The two particle streams cross in the four LHC detectors and collide, releasing unprecedented particle energies at a level which would be impossible with a rigid target. At the four collision points the huge detectors measure the new particles created during the collision and their properties. These are then filtered and analyzed. The particle beams circulate for around ten hours with decreasing intensity before new beams are injected and accelerated. “We don’t know whether we will be able to confirm existing theories with these experiments,” says Professor Rossi. “But even if something totally unexpected emerges, that too would push our knowledge forward.” The scientists from the 20 member countries of CERN hope the unique machine and the experiments will provide deeper insights into the fundamental building blocks of the universe.