Gas cluster ion beam surface treatments for reducing field emission and breakdown of electrodes and SRF cavities

Swenson, D.; Wu, Andy; Degenkolb, E. O.; Insepov, Z.

doi:10.1016/j.nimb.2007.04.277

Cited by 7 publications

(2 citation statements)

References 15 publications

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“…It is well known that the surface state of a cavity plays an important role in achieving the required performance. The rough surface and surface contaminants that remain after the surface treatment of a cavity degrade its performance because of magnetic field enhancement and field emission [4][5][6]. Electropolishing (EP), which is used to smoothen a surface by anodic dissolution in an electrolyte under mass transport control [7,8], was found to be a promising technique for the final surface treatment of Nb SRF cavities [9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Effort towards symmetric removal and surface smoothening of 1.3-GHz niobium single-cell cavity in vertical electropolishing using a unique cathode

Chouhan

Kato

Nii

et al. 2017

Phys. Rev. Accel. Beams

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A detailed study on vertical electropolishing (VEP) of a 1.3-GHz single-cell niobium coupon cavity, which contains six coupons and four viewports at different positions, is reported. The cavity was vertically electropolished using a conventional rod and three types of unique cathodes named as Ninja cathodes, which were designed to have four retractable blades made of either an insulator or a metal or a combination of both. This study reveals the effect of the cathodes and their rotation speed on uniformity in removal thickness and surface morphology at different positions inside the cavity. Removal thickness was measured at several positions of the cavity using an ultrasonic thickness gauge and the surface features of the coupons were examined by an optical microscope and a surface profiler. The Ninja cathode with partial metallic blades was found to be effective not only in reducing asymmetric removal, which is one of the major problems in VEP and might be caused by the accumulation of hydrogen (H 2) gas bubbles on the top iris of the cavity, but also in yielding a smooth surface of the entire cavity. A higher rotation speed of the Ninja cathode prevents bubble accumulation on the upper iris, and might result in a viscous layer of similar thickness in the cavity cell. Moreover, a higher electric field at the equator owing to the proximity of partial metallic blades to the equator surface resulted in a smooth surface. The effects of H 2 gas bubbles and stirring were also observed in lab EP experiments.

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Section: Introductionmentioning

confidence: 99%

Effort towards symmetric removal and surface smoothening of 1.3-GHz niobium single-cell cavity in vertical electropolishing using a unique cathode

Chouhan

Kato

Nii

et al. 2017

Phys. Rev. Accel. Beams

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“…Recent experiments [1][2][3][4] have shown that the gas cluster ion beam (GCIB) technique is a highly desirable tool for treating Nb surfaces to reduce field emission. In order to use this new technique in an optimized fashion, it is important to understand what kind of effects this new tool has on the treated Nb surfaces.…”

Section: Introductionmentioning

confidence: 99%

Modification on surface oxide layer structure and surface morphology of niobium by gas cluster ion beam treatments

Swenson

Insepov

2010

Phys. Rev. ST Accel. Beams

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Recently, it was demonstrated that significant reductions in field emission on Nb surfaces could be achieved by means of a new surface treatment technique called gas cluster ion beam (GCIB). Further study as shown in this paper revealed that GCIB treatments could modify surface irregularities and remove surface asperities leading to a smoother surface finish as demonstrated through measurements using a 3D profilometer, an atomic force microscope, and a scanning electron microscope. These experimental observations were supported by computer simulation via atomistic molecular dynamics and a phenomenological surface dynamics. Measurements employing a secondary ion mass spectrometry found that GCIB could also alter Nb surface oxide layer structure. Possible implications of the experimental results on the performance of Nb superconducting radio frequency cavities treated by GCIB will be discussed. First experimental results on Nb single cell superconducting radio frequency cavities treated by GCIB will be reported.

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Thin Films

Colligon¹,

Vishnyakov²

2020

Surface and Interface Science

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Gas cluster ion beam surface treatments for reducing field emission and breakdown of electrodes and SRF cavities

Cited by 7 publications

References 15 publications

Effort towards symmetric removal and surface smoothening of 1.3-GHz niobium single-cell cavity in vertical electropolishing using a unique cathode

Effort towards symmetric removal and surface smoothening of 1.3-GHz niobium single-cell cavity in vertical electropolishing using a unique cathode

Modification on surface oxide layer structure and surface morphology of niobium by gas cluster ion beam treatments

Thin Films

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