In Lund, Sweden, the European Spallation Source, the most powerful neutron source in the world, is being built. The ZHAW played a key role in the development of the machine protection and personal safety systems for this plant. The large-scale research facility is used to study material properties and processes at the atomic level in fields ranging from medicine, renewable energy and environmental technology to quantum computing. In 2025, the facility is expected to generate neutrons for the first time.
Construction of the European Spallation Source (ESS) in Lund, Sweden, started in 2014. The research facility is a European Research Infrastructure Consortium (ERIC), which includes Sweden and Switzerland as well as eleven other European countries. In addition to the ZHAW, the Paul Scherrer Institute (PSI) is also significantly involved in the development of the ESS in Switzerland. The plant is currently under commissioning. In 2025, the large-scale research facility is expected to generate spallation neutrons for the first time. Scientists from many different research fields hope that the very intense and pulsed neutron beam will enable more efficient research into material properties. Applications range from the optimization of hard drives and the investigation of structures in quantum computing to the further development of solar cells and the breakdown of molecular structures. "Neutron physics is very interesting for scientists who want to learn about material structure. Neutrons penetrate denser materials better than X-rays, for example. This makes it possible to study the internal structures of objects," explains Christian Hilbes. The ZHAW researcher is deputy director of the Institute for Applied Mathematics and Physics (IAMP) and conducts research in the field of safety-critical systems. "Our task in setting up the ESS was, on the one hand, to develop the concepts for the machine protection system and, on the other, to implement specific subsystems of it. We also supported ESS in the development of various personnel safety systems," says Hilbes.
Proton beam must stop within the shortest possible time
The 600-meter-long proton accelerator and the adjacent rotating neutron source were developed specifically for the ESS. Many of the accelerator's components are elaborately realized one-offs. If the beam strongly changes properties such as expansion or direction, the protons can hit these components, which react to them, for example with a rapid aging process. Misdirection of the jet can even cause a hole in the jet pipe. "The consequences of this are damage that can possibly lead to a long shutdown of the plant, which should be avoided at all costs," explains Christian Hilbes. The Machine Protection system has the task of reacting before damage to the equipment occurs. To do this, the system monitors countless parameters that are measured along the entire accelerator. If the parameters exceed specified tolerances, a beam shutdown is performed within a very short time.
A fast interlock system as a central element of ESS Machine Protection
The challenge for the ZHAW team, which consisted of ten researchers from IAMP, was to develop a concept for the ESS on how to build the Machine Protection system with all its subsystems. "Here, we have supported ESS with our broad know-how from the very beginning," says Christian Hilbes. Some of the events that can occur at the accelerator must be responded to extremely quickly. For this category of events, the ZHAW team has developed the so-called Fast Beam Interlock System (FBIS). "The very specific requirements for the FBIS meant that this system had to be developed from scratch. "There was no commercially available system that would have met the requirements; only technical models at other accelerators on which to build," Hilbes classifies. "The FBIS must react within a few 10 to 100 microseconds and do so during 24 hours a day, if possible without generating false shutdowns," explains Martin Rejzek, deputy head of the Safety Critical Systems research area and responsible for the specification and development of the complete FBIS and its integration into the ESS architecture at the ESS project.
In total, the IAMP team, supported by researchers from the Institute for Embedded Systems (InES) and two Swiss companies - IOxOS Technologies and Sotronik GmbH - developed and produced 593 hardware units and implemented the software running on them. One example illustrates how demanding this task was: "The FBIS is used, for example, when a beam current monitor measures an unexpected beam intensity. The FBIS then has to decide whether or not to switch off the beam," explains Rejzek. The beam current monitors as well as their evaluation system were developed with the focus on beam optimization and not machine protection. The challenge now was to integrate these systems into FBIS and thus into the ESS Machine Protection concept in such a way that high reliability is achieved despite the overall complexity of the Machine Protection system. "All in all, we had to integrate several hundred input signals into FBIS, some of them from very different systems," says Martin Rejzek, summarizing the complex task.
Participation in protection concept for ESS personnel
The ZHAW team was also significantly involved in the design, realization and verification of various Personnel Safety systems of the ESS. "Since it is a matter of personal protection, primarily protection against radiation, very strict specifications from the authorities must be observed for this area," explains Christian Hilbes. This includes release regulations, for example on the question of when a person is allowed to be in which area. ZHAW supported ESS in the conception, development and validation of various personnel safety systems. From the ZHAW side, Joanna Weng, who has great expertise in the field of functional safety assessment, has been primarily involved in this.
Surprising challenge for the ZHAW team
The ZHAW researchers had to deal with seemingly mundane issues in addition to the numerous challenges involved in realizing such a novel machine protection system. "Participating in the construction of a large-scale European research facility is not something that happens every day at a university of applied sciences like the ZHAW. From the non-trivial logistics from Switzerland to Sweden to contractual and financial issues, we were involved in many areas and processes in addition to our development work, with which we had little contact as researchers before," Christian Hilbes sums it up. One thing is certain: "For the entire team and the ZHAW, this was an extraordinary and challenging project, the dimension and character of which was a completely new experience for us as a university."
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