Knowing the paths that cables take also means knowing the machine to which they belong. Emanuel Hüsler, Head of the Electrical Installations Section at the Paul Scherrer Institute PSI, guides us through the complex electrical network of SLS 2.0 and thereby through the entire upgrade.
Network cables, high-voltage cables, supply cables, power cables, fibre optic cables – the cables installed in recent months by the Electrical Installations Section, headed by Emanuel Hüsler, come in a wide variety of shapes and colours. Research at the Swiss Light Source SLS at PSI has been on hold since the end of September 2023: The SLS 2.0 upgrade is in full swing and will allow the refurbished facility to produce even more brilliant synchrotron light for scientific experiments, starting in 2025. As part of this upgrade, Hüsler and his team have already laid 30,000 cables, whose total length of 504 kilometres would theoretically allow someone to abseil from the International Space Station (ISS) to Earth.
A strict numbering scheme ensures that the many cables do not end up as a hopeless tangle of wires. Each cable is recorded in layouts of the system as well as in lists; each is labelled and installed chronologically under raised floors, in rails or in cabinets. “Our professional pride dictates meticulous workmanship, which is also helpful later on, when the system goes into operation,” says Hüsler.
The qualified electrician takes major projects like the SLS upgrade in his stride. He joined PSI as group leader in 2007, having previously gathered many years of experience in industry and trained as a Swiss certified electrician (advanced diploma). In 2014, he took over as Head of the Electrical Installations Section, which is part of the PSI Centre for Accelerator Science and Engineering.
Hüsler gained important experience in the wiring of complex large-scale facilities through PROSCAN, the ongoing project to expand proton therapy for the treatment of cancer, as well as the construction of SwissFEL, which was inaugurated in 2016: “These tasks gave us the necessary expertise to move forward with the SLS upgrade and connect the technical teams and their systems.” Fourteen teams are now working on SLS 2.0 in parallel, each with different requirements and approaches.
But how does one plan the wiring for such a huge and complex system which is constantly being modified and refined throughout the construction phase? Hüsler’s answer: by being well organised, having a motivated team, being willing to improvise and keeping track of everything.
From the outline to the details
Hüsler and his team of 45 began planning the major project back in 2019, four years before the synchrotron light of the SLS was switched off for the upgrade, in the autumn of 2023. “This preparatory phase gave us the necessary head start to establish an overview and place our first orders for materials.” They kept going back to the various technical teams to find out the latest status of their equipment, the stages of its construction and their individual needs.
The Building Technology Engineering Group, for example, without which the highly complex conversion would be impossible; the Magnets Section, which is responsible for planning, measuring the properties of and installing the 1000 or so magnets, each the size of a wagon wheel, needed for the completely refurbished SLS electron storage ring; and the IT Department, which is integrating the facility into the PSI network. What connects all these different units is the cables, and that means: Emanuel Hüsler and his team. “In addition to high-voltage cables for maintaining the vacuum inside the ring, we also have to plan everyday things like light switches, thousands of temperature sensors and loudspeakers for safety announcements.”
Once the initial outline plans had been drawn up, it was soon time to get down to the specifics. Such as what type of shielding each particular cable would need. Shielding isolates the electromagnetic fields generated by the flow of current, which would interfere with sensitive sensors or other signals.
It was particularly important to determine the maximum length of each cable so as to avoid latency – a delay in the signal. The length of the cables is particularly important for the diagnostics team, for example, which measures the size and position of the electron beam. This is because the electrons race inside the storage ring at almost the speed of light, and in order to adjust this beam of charged particles, signal transmission needs to be instantaneous. “If there was any delay, we would constantly trail behind the electron bunch, whenever we wanted to use the magnets to realign it,” says Emanuel Hüsler. “That’s why we use the shortest possible paths and standardised cable lengths – in close consultation with the diagnostics team.”
45 tonnes of old cables were dismantled and sent for recycling.
670 electronic racks were installed and wired up. These yellow, red and grey cabinets in the SLS hall house the control units.
210 kilometres of network cables: These cables with the characteristic latching tab are used in a home setting to connect your PC to an internet router. At the SLS, they connect the different control units, for example.
42 kilometres of multi-mode optical fibre cables: These fibre optic cables are used for high-speed transmission of information using light (carried by optical fibres) and are mainly used to cover short distances.
20 kilometres of single-mode optical fibre cables: Like multi-mode optical fibre cables, except that the single-mode version can cover longer distances.
39 kilometres of RF cables: Radio frequency (RF) cables are used at the SLS for the Beam Position Monitor (BPM) – the sensors that monitor the path of the electron beam as it travels inside the storage ring.
70 kilometres of DC cables for magnets: These supply direct current (DC) to the electromagnets.
20 kilometres of various AC supply cables: This type of cable will be familiar, for example, as the means of supplying power to your printer at home. AC stands for alternating current, the type of power supplied by a conventional electrical socket.
24 kilometres of cables for the vacuum system: A high vacuum must be maintained in the storage ring to prevent the electrons inside it from being lost through collisions with gas molecules. The vacuum pumps are powered by electricity, and electrically operated sensors monitor the vacuum in the ring.
25 kilometres of high-voltage cables for vacuum pumps: Some of the vacuum pumps require a high voltage supply, i.e. voltages above one kilovolt.
54 kilometres of cables for front ends: At the SLS, the term “front end” refers to the sections connecting the synchrotron beam junctions around the electron storage ring with the sites where the scientific experiments are carried out.
The connecting element
In theory, the SLS electronics follows a simple pattern. At its heart are the control units, spread across 670 yellow, red and grey electronic racks within the electron storage ring. These colourful units – designed by the technical units and built by the Electrical Installations team – determine the number of cables entering and leaving the storage ring.
The Controls and Control Systems groups record the interaction between the various control units in the form of diagrams, and electrical specialists then connect the units. The appropriate interaction is governed by the harmony of input and feedback: “To create the vacuum, for example, cables have to go into the electron storage ring. To control it, cables have to come out. And all this happens through countless control units.” The safety of the people working here must always be considered, too: every cable must be properly insulated, measured and documented, and everything must be earthed.
Underneath the raised floors of the electronic racks, countless kilometres of numbered cables are installed to connect the many small units into a single system. Everything has been designed, drawn and built step by step – and sometimes discarded again.
“That’s just the way things are in a large-scale project like this,” says Emanuel Hüsler. “You go to a lot of trouble, you wire everything up neatly and tidily, everything is working perfectly – and then you have to take it all down again because some new piece of equipment has been added.”
Working overtime was unfortunately also part of the job. “I owe my team a huge compliment for getting everything done on time,” says Emanuel Hüsler. “It took a great deal of flexibility and commitment, from everyone.”
Meanwhile, the next large project is already under way at PSI: the proton accelerator facility is due for a major upgrade, called IMPACT, which is planned to start in 2025. Hüsler and his team have already been planning the cabling there for quite some time.
