Engineering topics

Burk, David

Publications and source records attributed to Burk, David.

3 records

DOE OSTI2024

Improving Nb 3 Sn cavity performance using centrifugal barrel polishing

Abstract In this study we will show a new method of polishing for Nb 3 Sn cavities known as centrifugal barrel polishing (CBP). Using this method, Nb 3 Sn coated samples are polished to a surface roughness comparable to a traditional Nb cavity after electropolishing. We also investigate different methods of cleaning the Nb 3 Sn surface after CBP to remove residual abrasive particles. The polished Nb 3 Sn surface is analyzed using confocal laser microscopy, and scanning electron microscopy is used to image the surface and measure the surface roughness after polishing. Transmission electron microscopy is also used for high resolution analysis of the surface after polishing. Finally, we show that CBP can improve the performance of a Nb 3 Sn superconducting radiofrequency cavity.

43 PARTICLE ACCELERATORS↗

DOE OSTI2023

Latest Development of Electropolishing Optimization for 650 MHz Cavity

Electropolishing (EP) of 1.3 GHz niobium (Nb) superconducting RF cavities is conducted to achieve a desired smooth and contaminant-free surface that yields good RF performance. Achieving a smooth surface of a large-sized elliptical cavity with the standard EP conditions was found to be challenging. This work aimed to conduct a systematic parametric EP study to understand the effects of various EP parameters on the surface of 650 MHz cavities used in PIP-II linac. Parameters optimized in this study provided a smooth surface of the cavities. The electropolished cavities met the baseline requirement of field gradient and qualified for further surface treatment to improve the cavity quality factor.

43 PARTICLE ACCELERATORS↗

DOE OSTI2023

Improving Nb3Sn Cavity Performance Using Centrifugal Barrel Polishing

Nb3Sn superconducting radiofrequency (SRF) cavities have been an ongoing research topic for many years motivated by the potential for higher accelerating gradients and quality factors compared to niobium SRF cavities. The highest performing Nb3Sn cavities are manufactured using tin vapor-diffusion coating, which creates a Nb3Sn film with a surface roughness of around 100-200 nm. This is thought to be one of the limiting factors for the accelerating gradient of Nb3Sn cavities due to enhancement of magnetic field near sharp surface features. To smooth Nb3Sn SRF cavities, we have developed a mechanical polishing procedure which uses centrifugal barrel polishing to smooth the surface followed by a secondary tin coating step to repair the surface. We show that the accelerating field of a Nb3Sn SRF cavity is improved by applying this procedure. We also investigate the quench mechanism of the polished cavity by utilizing temperature mapping to measure which regions of the cavity e xperience heating during RF operation. We then cut samples from these regions and analyze the film microstructure and chemical composition in 3D using EDS and EBSD measurements together with a focused ion-beam (FIB) tomography technique.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗