An Analytical Model for Evaluation of the Properties of Metallic Coatings in RF Structures

Abstract

A simple analytic model based on the equations of the propagation matrices theory has been developed in order to evaluate the effective skin depth of coated metallic surfaces. With particular attention to the R&D of highly-performing accelerating structures, different thick coatings with excellent mechanical and electrical properties have been considered such as molybdenum and its oxides, p-doped SiC, and TiN. Calculations show that copper coated with a p-type SiC may exhibit an improved hardness and a higher thermal resistance. Combined with experimental tests, this study may support the identification of reliable multilayers capable of improving the higher power performance of radio-frequency (RF) structures in terms of the accelerating gradient in order to increase the resistance to the high thermal stress of structures made with copper.

Structural Evolution of MoO3 Thin Films Deposited on Copper Substrates upon Annealing: An X-ray Absorption Spectroscopy Study

“…MoO 3 is used in solar cells, batteries, and organic light-emitting diodes (OLEDs), and it is a promising material for protective coatings of accelerating radiofrequency (RF) cavities [5]. In fact, due to the low WF, the performance and the lifetime of a copper RF cavity are strongly affected by breakdown phenomena and thermal stress generated by electron emission from the surface [11]. A high WF conductive coating could be used to reduce these detrimental phenomena, extending the lifetime of the device and allowing it to operate at higher electric fields [1,5,11,12].…”

“…In fact, due to the low WF, the performance and the lifetime of a copper RF cavity are strongly affected by breakdown phenomena and thermal stress generated by electron emission from the surface [11]. A high WF conductive coating could be used to reduce these detrimental phenomena, extending the lifetime of the device and allowing it to operate at higher electric fields [1,5,11,12]. Hence, MoO 3 coating can significantly enhance the electronic and mechanical properties of copper-based devices via its high WF and relatively higher hardness, compared with copper [5,[13][14][15], without affecting the surface conductivity.…”

Materials and Breakdown Phenomena: Heterogeneous Molybdenum Metallic Films

“…Compared to Cu, the Mo conductivity is lower, however, the relatively high-conductivity of Mo metallic coatings and the higher Mo breakdown rate make its application in high-gradient accelerating structures an interesting and useful option [13][14][15]38]. Moreover, we show that, by using X-ray absorption spectroscopy, we can control the presence of insulating oxide phases and correlate the electronic properties with the conductivity properties of these films.…”