LHC, the Large Hadron Collider at CERN in Geneva, is the largest and most complex machine ever built by humans. While CERN is known as a user of AM for prototyping, only recently did the center start to look at AM for the actual production of parts. One of these parts is a set of 3D printed cooling pipes for the new scintillating fiber tracker, or LHCb SciFi Tracker. The highly specialized component was produced by 3D Systems, using DMP metal powder bed fusion 3D printing technology, and won the 2019 LHCb Industry Award.
The LHC is now in the midst of getting an upgrade during the so-called long shutdown period. The LHC Run 2 ended a year ago. The LHCb experiment has since been largely dismantled and an almost completely new detector is now under construction. LHCb stands for “Large Hadron Collider beauty” experiment. It is essentially a point along the 27 kilometers long accelerator where hadrons (“large” particles) collide and generate billions of much smaller, subatomic, particles (namely the “beauty Quarks” but many others as well). The LHCb captures the data relative to the collision to try to understand what happened, right after the Big Bang, when the Universe was born.
A new LHCb will be inaugurated in 2021. Almost all LHCb’s sub-detectors will be replaced or upgraded during the ongoing LHC shut down and the newly upgraded detectors will profit from the most recent technological developments. These, of course, include metal 3D printing. LHCb physicists and engineers have been assisted in their effort by several firms that have collaborated closely with LHCb. Their contributions were crucial to ensure the successful upgrade of the experiment.
The LHCb collaboration selected this year four of these companies, 3D Systems, Automation NV, LETI-3S and SOMACIS for the LHCb Industry Awards, and presented awards to these at a special ceremony which took place during the plenary collaboration meeting taking place at CERN.
3D Systems received the award for producing a set of thin 3D printed titanium bars with embedded cooling channels for the SciFi Tracker of the LHCb Detector. The challenge was to realize cooling pipes with a very complex shape in a tight space, very thin walls for thermal conductance, combined with very tight mechanical tolerances (50 microns flatness). These had to be divided into subsections to minimize the effect of different thermal expansion coefficients and needed to feature an effective “gluing” surface.
The scintillating-fiber tracker, SciFi, will be placed behind the dipole magnet of LHCb (see image above). The magnet is used to slow down the particles after a collision. By evaluating the trajectory of this slow-down, which varies depending on the particle’s size/energy (at this level it’s basically the same thing), a very powerful computer is able to identify each different particle. In the SciFi component, the scintillating fibres emit light when a particle interacts with them and the tiny amount of emitted light is collected by silicon photomultipliers (SiPM) that convert it to electrical signals. The SiPMs are operated at low temperatures, about -40°C, and are therefore attached to the cooling bars (as seen in the image below).