Characterization of REBCO-Coated Conductors under Cryogenic Electron Beam Irradiation

Основні поняття

The secondary electron yield (SEY) and electron-stimulated desorption (ESD) of REBCO-coated conductors were characterized under cryogenic electron beam irradiation, revealing their compatibility for use in particle accelerator beam screens.

Анотація

The study investigated the surface properties of two types of REBCO-coated conductors (REBCO-CCs), one deposited by pulsed laser deposition (PLD) and the other by reactive co-evaporation by deposition and reaction (RCE-DR), under cryogenic electron beam irradiation.
Key highlights:

SEM and EDS analyses confirmed the surface morphology and chemical composition of the REBCO coatings.
SEY measurements showed that the RCE-deposited sample could be conditioned to a maximum SEY of 1.2 after electron irradiation, while the PLD-deposited sample only reached 2.0.
ESD measurements revealed that the energy and dose dependencies of ESD for both REBCO-CC samples were comparable to technical-grade metals.
The electron conditioning behavior of the REBCO-CCs, in terms of decreasing SEY and ESD yields, was similar to that of technical-grade metals.
The results indicate the compatibility of REBCO-CCs for use in particle accelerator beam screens, where low SEY and ESD are required to mitigate electron cloud effects.

Статистика

The maximum SEY (δmax) of the RCE-deposited sample decreased from 1.65 to 1.2 after electron conditioning at 300 eV and 1 mC/mm^2 dose.
The maximum SEY (δmax) of the PLD-deposited sample decreased from 1.65 to 2.0 after electron conditioning at 300 eV and 4.5 mC/mm^2 dose.
The peak ESD yield (η_max) for H2 was 1.5x10^-4 molecules/e- for the RCE-deposited sample and 1.9x10^-4 molecules/e- for the PLD-deposited sample.

Цитати

"The SEY of the RCE-deposited sample decreased to a value of δmax = 1.2 at 1 mC/mm^2 electron dose, which is a value acceptable for many applications."
"Conversely, the PLD-deposited sample SEY only conditioned to δmax ≈ 2 at a 4.5 mC/mm^2 dose."

Ключові висновки, отримані з

Electron Beam Characterization of REBCO-Coated Conductors at Cryogenic Conditions

by Michal Haubn... о arxiv.org 10-02-2024

https://arxiv.org/pdf/2410.00770.pdf

Глибші Запити

How could the SEY of the PLD-deposited sample be further reduced to an acceptable level for accelerator applications?

To further reduce the Secondary Electron Yield (SEY) of the PLD-deposited sample to an acceptable level for accelerator applications, several strategies can be employed. One effective approach is to apply a post-deposition treatment that enhances the surface properties of the REBCO-coated conductor. This could include:

Surface Graphitization: Introducing a controlled layer of carbon on the surface can significantly lower the SEY. Carbon, when graphitized, exhibits a low SEY, which can help in achieving values below the critical threshold for multipacting. This can be achieved through techniques such as chemical vapor deposition (CVD) or physical vapor deposition (PVD) of carbon.

Electron Beam Conditioning: Further electron irradiation at optimized energies and doses can be employed to condition the surface. This process, known as beam scrubbing, can help in reducing the SEY by modifying the surface state and composition, particularly by promoting the formation of a graphitic layer from carbon contaminants.

Chemical Treatments: Utilizing chemical etching or passivation techniques can help in removing surface contaminants that contribute to a higher SEY. For instance, treatments that selectively remove oxides or hydroxides while preserving the underlying REBCO structure could be beneficial.

Layering with Low SEY Materials: Coating the REBCO surface with a thin layer of materials known for their low SEY, such as certain metal oxides or polymers, could also be a viable strategy. This would create a barrier that minimizes electron emission.

Optimizing Surface Roughness: Adjusting the deposition parameters to control the surface morphology can also influence the SEY. A smoother surface typically results in lower SEY values, so refining the PLD process to achieve a more uniform and less textured surface could be beneficial.

By implementing these strategies, the SEY of the PLD-deposited sample can be effectively reduced to meet the stringent requirements for accelerator applications, thereby mitigating the risk of electron cloud formation.

What other surface treatment or coating methods could be explored to improve the SEY and ESD properties of REBCO-CCs?

Several innovative surface treatment and coating methods can be explored to enhance the Secondary Electron Yield (SEY) and Electron Stimulated Desorption (ESD) properties of REBCO-coated conductors (REBCO-CCs):

Amorphous Carbon Coatings: Applying a thin layer of amorphous carbon can significantly reduce SEY. This material has been shown to exhibit low SEY values and can be deposited using techniques such as sputtering or CVD.

Metallic Coatings: Coating the REBCO-CCs with metals known for their low SEY, such as gold or silver, can provide a protective layer that minimizes electron emission. These coatings can be applied through electroplating or PVD methods.

Oxide Coatings: Certain metal oxides, such as titanium dioxide (TiO2) or aluminum oxide (Al2O3), can be deposited on the REBCO surface. These materials can provide a low SEY while also enhancing the chemical stability of the surface.

Self-Assembled Monolayers (SAMs): Utilizing SAMs can modify the surface chemistry at the molecular level, potentially leading to reduced SEY and ESD. These monolayers can be tailored to enhance electron absorption properties.

Plasma Treatments: Plasma treatment techniques can be employed to modify the surface characteristics of REBCO-CCs. This can include plasma cleaning to remove contaminants or plasma-enhanced chemical vapor deposition (PECVD) to deposit low-SEY materials.

Nanostructuring: Creating nanoscale features on the surface through techniques like nanoimprinting or lithography can alter the electron emission characteristics. This method can be used to engineer surfaces that inherently have lower SEY.

Hybrid Coatings: Combining different materials in a multilayer structure can optimize the surface properties. For example, a base layer of REBCO could be topped with a low-SEY material, followed by a protective layer to enhance durability.

By exploring these surface treatment and coating methods, the SEY and ESD properties of REBCO-CCs can be significantly improved, making them more suitable for high-performance applications in particle accelerators.

What are the potential implications of using REBCO-CCs in particle accelerator beam screens beyond mitigating electron cloud effects, such as on the overall accelerator performance and efficiency?

The integration of REBCO-coated conductors (REBCO-CCs) in particle accelerator beam screens presents several potential implications that extend beyond merely mitigating electron cloud effects. These implications can significantly enhance overall accelerator performance and efficiency:

Reduced Impedance: REBCO-CCs can lower the resistive-wall impedance in beam screens, which is crucial for maintaining beam stability. A lower impedance allows for better beam quality and reduced energy loss, leading to more efficient accelerator operation.

Improved Thermal Management: The high thermal conductivity of REBCO-CCs can enhance heat extraction from the beam screen, thereby improving the thermal management of superconducting magnets. This can lead to more stable operating conditions and reduced cooling requirements, ultimately enhancing the overall efficiency of the accelerator.

Enhanced Superconducting Performance: By operating at higher temperatures (around 50 K), REBCO-CCs can relax the stringent cryogenic requirements typically associated with superconducting magnets. This can lead to reduced operational costs and simplified cooling systems, making the accelerator more economically viable.

Increased Luminosity: The ability to maintain low SEY values and mitigate electron cloud formation can lead to increased luminosity in particle collisions. Higher luminosity is essential for achieving more significant experimental results in high-energy physics research.

Longer Operational Lifespan: The durability and stability of REBCO-CCs under operational conditions can lead to a longer lifespan for beam screens. This reduces maintenance needs and downtime, contributing to more efficient accelerator operation.

Versatility in Applications: The unique properties of REBCO-CCs make them suitable for various applications beyond beam screens, such as in RF cavities and other accelerator components. This versatility can lead to innovations in accelerator design and functionality.

Potential for Higher Energy Collisions: The enhanced performance characteristics of REBCO-CCs may enable the design of future accelerators capable of achieving higher energy collisions, which is vital for exploring new physics beyond the current capabilities of existing facilities.

In summary, the use of REBCO-CCs in particle accelerator beam screens can lead to significant improvements in performance, efficiency, and operational stability, paving the way for advancements in high-energy physics research and the development of next-generation accelerators.