The European XFEL at DESY, Germany, will be a brilliant light source for a broad range of fundamental research in all areas of science – but it is also the first great mass production of the so-called TESLA technology. This particle accelerating technology was developed by DESY together with its collaborators within the TESLA project and has now been transferred into industrial mass production to build the European XFEL. This is the first time that accelerator modules based on the superconducting radio frequency TESLA technology, are completely mass-produced in industry. And even though such a challenging industrial production is already needed for the European XFEL, this is not the end of the line. After all, the European XFEL’s big brother is the International Linear Collider, and they share the TESLA technology. The ILC community is thus watching the construction of the European XFEL very closely.
“The ILC’s mission is to provide an accelerator and the infrastructure for experiments that can explore the structure of matter and the universe with unprecedented precision.” This statement by Brian Foster, European Director in the LCC, encompasses the three key goals of the ILC: Measuring the newly discovered Higgs boson with high precision, understanding the properties of the top quark, and searching for new particles beyond known physics. The Higgs boson was discovered at the Large Hadron Collider (LHC) at CERN in 2012, and with it the last part of an established theory could be finally proven. The top quark, on the other hand, may not be a new discovery but the particle itself still raises a lot of questions; and finally there is always the physics beyond what is known – or in this case the search for new particles.
The big question now is if a machine like the ILC is actually needed given that we already have the LHC. The world community answers with a clear ‘Yes, it is.’. To show the importance for the community hundreds of physicists explain why they need the ILC in short videos – see here to find out more about the #mylinearcollider campaign. The ILC and LHC will be like a pan and a pot. It is possible to cook a meal with just one of the two, but for a greater variety of meals having both is essential. So the community is convinced that both machines are needed to fully understand the Higgs boson and other particles our universe has.
A machine such as the ILC needs a great global effort to be brought into existence. To make this happen every possible source of information and knowledge is needed. This is where the European XFEL enters the stage. In the scope of the ILC, the European XFEL acts as a prototype for technical design, project planning and construction phase. Both machines basically use the same TESLA technology for acceleration of the particles.
At DESY Nick Walker, a physicist and Global Coordinator for ILC Accelerator Design & Integration, has his eyes on the XFEL production. In his 20 years working for DESY at the machine group he has mostly worked on the TESLA project and its successor, the ILC. Right now he is projecting the numbers learnt from the European XFEL production into the ILC frame. For example he compares the performance of the superconducting TESLA cavities, the power drivers for the particles in the accelerator: “The overall approach to module production, from niobium sheets to accelerator modules, for the ILC is fundamentally taken from XFEL,” he says. The European XFEL will have 800 such superconducting cavities in 100 accelerator modules, while the ILC will have 16 000 cavities in about 2000 accelerator modules. The cavity and module production for the European XFEL was the first real industrial production for these specific parts of an accelerator and of course the ILC will handle it nearly the same way. “The cavities are a great success. Although we are a tad shy of the ILC goals they confirm the choice for the used recipe,” Walker stresses. And with 80 percent of the cavities reaching a gradient (the accelerating strength) of 33 megavolts/metre(MV/m) at the current status of the XFEL production together with an ILC goal of 90 percent at 35MV/m, this is a potential achievable goal for the ILC.
The cavity production is not the only influence the ILC can carry over to their project. Many other aspects of the project are very helpful for the further planning and designing of the whole ILC project. “The ILC cost estimates are effectively projections of the known XFEL costs, which puts ILC on solid ground,” is another benefit of the European XFEL which Walker emphasises. For an international project of this scope not all contributions from participants are financial. Some ‘in-kind contributions’ have to be handled differently. For these in-kind contributions the European XFEL has some well-functioning examples: the Institute of Nuclear Physics Polish Academy of Science (IF-PAN) sent a team of 27 skilled physicists, engineers and software engineers to DESY to provide needed manpower for the whole project duration. This team runs the important cavity and module test facility AMTF at DESY. Another example of those contributions is the accelerator module assembly which takes place in Saclay, near Paris, France. The modules are finished on the grounds of the Commissariat à l’Énergie Atomique et aux Énergies Alternatives (CEA) and then sent to Germany for testing and installation into the accelerator. Here not only industrial manpower, but also laboratory space was offered and used in the production. The LAL laboratory in Orsay, France, has a similar story: they are responsible for testing and conditioning the so-called high-power couplers – another key component of the technology. Those two are just examples for the different kinds of contributions from many laboratories to the European XFEL construction (for further contributions see here). For the ILC these contributions could be scattered all around the globe – which means good planning and identifying possible problems is the key to success.
The European XFEL has started the first industrial mass production of cavities and accelerator modules. For all the scientists involved in this project this is a completely new situation. And as with everything new in life one has to learn how to do it well. And even this learning curve along the production and construction of the European XFEL will be beneficial for the ILC: the community can learn where more attention is needed or further development of parts or other design plans could be included. All these details give the ILC an opportunity which no other project this size has.
Even after the production phase during the installation, commissioning and finally operation of the European XFEL, the ILC community will still be there and watching intensely. Here the European XFEL will give the ILC community invaluable experience for all the needed steps to build a machine in this global scale with the same set of technology behind it. The installation of the ILC will by nearly 20 times larger, and this is a real challenge on manpower, logistics and planning. So it is important to learn everything possible from the European XFEL which will help the ILC to be prepared.
Of course, Nick Walker and his colleagues in the ILC community will keep a close eye on the European XFEL project: “No doubt lessons will be learnt here [at XFEL] that will influence the ILC design.”