Open AccessFeature PaperArticle
Red and Green Laser Powder Bed Fusion of Pure Copper in Combination with Chemical Post-Processing for RF Cavity Fabrication
by
Michael Mayerhofer, Stefan Brenner, Marcel Dickmann, Michael Doppler, Samira Gruber, Ricardo Helm, Elena Lopez, Verena Maier, Johannes Mitteneder, Carsten Neukirchen, Vesna Nedeljkovic-Groha, Bernd Reinarz, Michael Schuch, Lukas Stepien and Günther Dollinger
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Abstract
Linear particle accelerators (Linacs) are primarily composed of radio frequency cavities (cavities). Compared to traditional manufacturing, Laser Powder Bed Fusion (L-PBF) holds the potential to fabricate cavities in a single piece, enhancing Linac performance and significantly reducing investment costs. However, the question of
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Linear particle accelerators (Linacs) are primarily composed of radio frequency cavities (cavities). Compared to traditional manufacturing, Laser Powder Bed Fusion (L-PBF) holds the potential to fabricate cavities in a single piece, enhancing Linac performance and significantly reducing investment costs. However, the question of whether red or green laser PBF yields superior results for pure copper remains a subject of ongoing debate. Eight 4.2 GHz single-cell cavities (SCs) were manufactured from pure copper using both red and green PBF (SCs R and SCs G). Subsequently, the surface roughness of the SCs was reduced through a chemical post-processing method (Hirtisation) and annealed at 460 °C to maximize their quality factor (
). The geometric accuracy of the printed SCs was evaluated using optical methods and resonant frequency (
) measurements. Surface conductivity was determined by measuring the quality factor (
) of the SCs. Laser scanning microscopy was utilized for surface roughness characterization. The impact of annealing was quantified using Energy-Dispersive X-ray Spectroscopy and Electron Backscatter Diffraction to evaluate chemical surface properties and grain size. Both the SCs R and SCs G achieved the necessary geometric accuracy and thus
precision. The SCs R achieved a 95%
after a material removal of 40 µm. The SCs G achieved an approximately 80%
after maximum material removal of 160 µm. Annealing increased the
by an average of about 5%. The additive manufacturing process is at least equivalent to conventional manufacturing for producing cavities in the low-gradient range. The presented cavities justify the first high-gradient tests.
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