There aren’t many people in the world who can say of themselves that they have walked the whole length of the ILC’s accelerator tunnels and stood in the detector cavern looking up at the ILC detector. In fact, there’s probably only one person in the world who has done all this: Benno List. He is the hub of the integration team at DESY, which has spent the last years collecting and putting together all available Computer-Aided Design (or CAD) models of the ILC’s accelerator systems and their components, and combining it with a symbolic three-dimensional visualisation of the actual accelerator layout (the “lattice”). These models come from engineers working in universities and laboratories around the world. And mind you, there are different CAD systems and different designs for the individual systems as well. The goal of this exercise: put together a three-dimensional virtual ILC that you can actually walk through, provided you are at DESY and willing to wear 3D glasses with funny antennae that capture your movements, so you can duck under the beampipe and peer into cryomodules as realistically as that is possible for a machine that does not exist yet.
As much fun as that is, there’s a serious purpose behind it. Combining all accelerator systems in their detailed models can highlight faults, missing stretches of accelerator, space problems, crossing systems or pieces of tunnel wall sticking out.
Take for example the muon shield between main linac and beam delivery system. It’s essential for the detectors’ efficiency because it catches stray muons from the linac tunnel and stops them mingling with the particles from the interactions, it’s just not a very complicated piece of engineering. This means that it was always there in every drawing, but the CAD systems had simply put return beamlines and magnets through what will eventually be a five-metre thick wall of magnetised iron. During the Baseline Technical Review meeting last October at DESY, this problem was identified with the help of the integrated 3D model, which led to a complete redesign of how the transfer lines to and from the damping rings are arranged with respect to the main linac and the particle sources.
Having all varieties of designs also allows the experts to play around. For example, there’s one stretch of tunnel that’s in the Kamaboko configuration, Benno List can switch from one cavern design to the next and can also tune the level of precision for magnets and cryomodules – from big colourful blobs to detailed pieces of engineering down to the last screw. “It also works the other way round,” says List. “When the CERN experts started to lay out the European tunnel design, we already had the complete the magnet configuration. So we sent the lattice details to the civil engineers at CERN and they created the perfect tunnel around it.”
The ILC is not the first accelerator that has gone through this virtual creation process – DESY’s IPP group also has the complete European XFEL in its system. The head of the team, Lars Hagge, says that seeing one’s project in 3D also has a non-negligible psychological effect. “Accelerator physicists and engineers know their area of expertise extremely well, and they are happy with excel sheets and CAD models. But when they enter our virtual-reality room and explore their components in their full context, some so far hidden challenges or tiny details may suddenly become clearly obvious,” he says. People often leave with new ideas for resolving complexity in interfaces or for optimising installation procedures. . “This leads to updated designs, whereby the tool turns into a process,” says Hagge.
When new designs become available, the team adds them – the recently designed remote handling proposal from China, for example. However, they consider the current status mature and complete enough to create a full 5-minute flythrough movie of the ILC. Again, it’s not fun only: “The systems experts can see their system in the big picture without having to come to DESY,” says Hagge. For education – or fun – the movie will of course be featured in ILC NewsLine.