Abstract
Continuous developments in additive manufacturing (AM) technology are opening up opportunities in novel machining, and improving design alternatives for modern particle accelerator components. One of the most critical, complex, and delicate accelerator elements to manufacture and assemble is the radio frequency quadrupole (RFQ) linear accelerator, which is used as an injector for all large modern proton and ion accelerator systems. For this reason, the RFQ has been selected by a wide European collaboration participating in the AM developments of the I.FAST (Innovation Fostering in Accelerator Science and Technology) Horizon 2020 project. The RFQ is as an excellent candidate to show how sophisticated pure copper accelerator components can be manufactured by AM and how their functionalities can be boosted by this evolving technology. To show the feasibility of the AM process, a prototype RFQ section has been designed, corresponding to one-quarter of a 750 MHz 4-vane RFQ, which was optimised for production with state-of-the-art laser powder bed fusion (L-PBF) technology, and then manufactured in pure copper. To the best of the authors’ knowledge, this is the first RFQ section manufactured in the world by AM. Subsequently, geometrical precision and surface roughness of the prototype were measured. The results obtained are encouraging and confirm the feasibility of AM manufactured high-tech accelerator components. It has been also confirmed that the RFQ geometry, particularly the critical electrode modulation and the complex cooling channels, can be successfully realised thanks to the opportunities provided by the AM technology. Further prototypes will aim to improve surface roughness and to test vacuum properties. In parallel, laboratory measurements will start to test and improve the voltage holding properties of AM manufactured electrode samples.
Highlights
This is an internal CERN publication and does not necessarily reflect the views of the CERN management
Joint multidisciplinary effort proved that a pure-copper Radio Frequency Quadrupole (RFQ) prototype can be successfully manufactured with Additive Manufacturing (AM) technology, and is, to the best knowledge of authors, the first AM manufactured RFQ in the world
Thanks to dedicated teamwork, the concepts on how to improve RFQ design and manufacturing features offered by the state-of-art Laser Powder Bed Fusion (L-PBF) technology were described in this paper
Summary
RFQ is a component of particle accelerators featuring strict technical requirements for its successful field service. LPBF is the most promising AM process for pure copper RFQ, thanks to the fact that a) high relative density and high electrical conductivity can be achieved, and b) build-up of complex-shaped parts is possible with a minimum wall thickness of 400 microns and a layer thickness of 30 microns. These challenging material properties can be attained by deploying a short wavelength laser because the absorptivity level of the pure copper is very low within the commonly used infrared L-PBF systems and significantly increases in the green wavelength. In the case of the proofof-concept, to ensure that all residual manufacturing powder is eliminated, the prototype was cleaned with pressurized air and in an ultrasonic bath
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