A 3D printed copper radio frequency (RFQ) quadrupole component for the Large Hadron Collider
CERN, or European Organization for Nuclear Research, is currently home to the world’s largest particle accelerator. Called the Large Hadron Collider (LHC), its purpose is to transmit energy to particles through electric or magnetic fields. Today we draw your attention to the LHC as it could for the first time include a 3D printed copper radiofrequency quadrupole. Specifically, it is a radiofrequency quadrupole linear accelerator (RFQ), one of the most difficult parts to design and assemble. For these reasons, Fraunhofer IWS, in collaboration with CERN, the Technical University of Riga and the Polytechnic University of Milan, has chosen additive manufacturing, or more precisely powder bed laser fusion, to produce it.
The partners are all part of the Horizon 2020 I.FAST (Innovation Fostering in Accelerator Science and Technology) project, which is funded by the European Union and aims to develop new designs of particle accelerators. With 49 partners, he hopes to accelerate innovation in a subject that can be quite difficult. It is in this context that metal additive manufacturing was used, a new concrete example of the technology’s potential.
Additive manufacturing to overcome assembly problems
According to project partners, the RFQ is traditionally made from highly conductive materials and alloys, via multi-axis milling of “Large scale forged prefabricated monobloc components”. Concretely, the RFQ integrates 4 modules assembled by furnace brazing. However, the latter generally releases residual stresses, which can lead to geometric deformations. Several heat treatments during machining are then necessary to maintain the quality level and ensure the correct functioning of the part. As you can imagine, all of these steps are time consuming, expensive, and inefficient. To remedy this, the project partners turned to additive manufacturing, in particular because of its ability to produce components in a single block, thus avoiding assembly steps and their constraints.
They explained, “Ultimately, complete segments comprising the four ‘vanes’ of the RFQ system could be built as a single piece, avoiding soldering and allowing the optimal fabrication of complex items such as internal cooling channels and external ports. Advances in FA equipment, design capability (including simulation tools), and manufacturing methodology itself open up entirely new avenues for RFQ design optimization and large-scale production, even using pure copper, which is considered a difficult material for the AM Process laser. This is because copper is a metal that will reflect laser light, so it will also reflect some of the energy needed to make the part.
An optimized radiofrequency quadrupole prototype
The partners have chosen laser fusion on a powder bed, more precisely on a TruPrint1000 machine, to meet all production constraints, particularly in terms of geometric precision, surface roughness and electrical conductivity. They reproduced a quarter of the radiofrequency quadrupole currently used by CERN. The 3D printed prototype is 95mm long and features the vane tip, internal surfaces, improved cooling channels and a redesigned internal structure. A honeycomb pattern was chosen during the design phase, which reduced the volume of material needed by 37% and the total weight by 21%. It took 16.5 printing hours to produce the prototype, which has a layer thickness of 30 microns and a height of 98.01 mm.
The teams concluded, “AM technology is uniquely suited to the required mechanical complexity of RFQs and offers significant design and optimization freedom to meet stringent manufacturing requirements that cannot be achieved by conventional technologies. It also paves the way for major improvements in tendering and possibly large-scale production, even using pure copper, which is a technologically demanding material. 3D printing could therefore have a significant impact in the manufacture of the particle accelerators of tomorrow! Learn more about the team’s work HERE.
* Cover photo credits: Christoph Wilsnack / Fraunhofer IWS
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