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Surface Characterization Of Nb Samples Electropolished Together With Real Superconducting Rf Accelerator Cavities
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Book Synopsis Surface Characterization of Nb Samples Electropolished Together with Real Superconducting Rf Accelerator Cavities by :
Download or read book Surface Characterization of Nb Samples Electropolished Together with Real Superconducting Rf Accelerator Cavities written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Here, we report the results of surface characterizations of niobium (Nb) samples electropolished together with a single cell superconducting radio-frequency accelerator cavity. These witness samples were located in three regions of the cavity, namely at the equator, the iris and the beam-pipe. Auger electron spectroscopy (AES) was utilized to probe the chemical composition of the topmost four atomic layers. Scanning electron microscopy with energy dispersive X-ray for elemental analysis (SEM/EDX) was used to observe the surface topography and chemical composition at the micrometer scale. A few atomic layers of sulfur (S) were found covering the samples non-uniformly. Niobium oxide granules with a sharp geometry were observed on every sample. Some Nb-O granules appeared to also contain sulfur.
Book Synopsis Surface Characterization of Nb Samples Electro-polished Together With Real Superconducting Radio-frequency Accelerator Cavities by :
Download or read book Surface Characterization of Nb Samples Electro-polished Together With Real Superconducting Radio-frequency Accelerator Cavities written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We report the results of surface characterizations of niobium (Nb) samples electropolished together with a single cell superconducting radio-frequency accelerator cavity. These witness samples were located in three regions of the cavity, namely at the equator, the iris and the beam-pipe. Auger electron spectroscopy (AES) was utilized to probe the chemical composition of the topmost four atomic layers. Scanning electron microscopy with energy dispersive X-ray for elemental analysis (SEM/EDX) was used to observe the surface topography and chemical composition at the micrometer scale. A few atomic layers of sulfur (S) were found covering the samples non-uniformly. Niobium oxide granules with a sharp geometry were observed on every sample. Some Nb-O granules appeared to also contain sulfur.
Book Synopsis Surface Characterization of Impurities in Superconducting Niobium for Radio Frequency (RF) Cavities Used in Particle Accelerators by : Prateek Maheshwari
Download or read book Surface Characterization of Impurities in Superconducting Niobium for Radio Frequency (RF) Cavities Used in Particle Accelerators written by Prateek Maheshwari and published by . This book was released on 2012 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Surface Characterization of Niobium Samples Electro-Polished Together with Real Cavities by :
Download or read book Surface Characterization of Niobium Samples Electro-Polished Together with Real Cavities written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We report the results of surface characterizations of niobium samples electropolished together with single cell cavities. These witness samples were located in three regions of the cavity, namely at the equator, the iris and the beam-pipe. Auger electron spectroscopy (AES) was utilized to probe the chemical composition of the topmost four atomic layers. Scanning electron microscopy with energy dispersive x-ray for elemental analysis (SEM/EDX) was used to observe the surface topography and chemical composition at the micrometer scale. A few atomic layers of sulphur (S) were found covering the samples non-uniformly. Niobium oxide granules with a sharp geometry were observed on every sample. Some Nb-O granules appeared to also contain sulphur.
Book Synopsis Surface Characterization of Niobium for Superconducting RF Cavities by : Cao Chaoyue
Download or read book Surface Characterization of Niobium for Superconducting RF Cavities written by Cao Chaoyue and published by . This book was released on 2014 with total page 210 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Methodology for the Characterization of Surface Treated High Purity Niobium by : Santosh Chetri
Download or read book Methodology for the Characterization of Surface Treated High Purity Niobium written by Santosh Chetri and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: High-purity niobium is the material of choice for making superconducting radio-frequency cavities for the modern particle accelerator. While making the cavities from the Nb sheet, it goes through a series of processes including chemical and thermal treatments. These treatments affect the microstructural as well as magnetic properties of niobium. In order to optimize the efficiency of Nb cavities, various treatments have been explored. During the last decade, surface modification through impurity diffusion has been extensively explored and found that the quality factor of Nb cavities can be enhanced by impurity diffusion to the niobium surface. The surface treatments that are found to enhance the quality factor include high-temperature nitrogen doping, low-temperature nitrogen infusion, and most recently mid-temperature furnace baking. Even though these treatments have been shown to improve cavity performance, the fundamental understanding of the phenomenon is very limited, and each treatment has its own drawbacks. During the operation of Nb cavities, the oscillating electromagnetic field penetrates the Nb surface only to the 40-200 nm depth. Hence, the cavity performance is dependent largely on the condition of this layer. Thus, a detailed understanding of the effect of different treatments on the Nb surface is essential.Cutting a Nb cavity for the characterization of its surface after different treatments is economically not viable and the characterizing tools are also limited for the cut-out samples. Based on the characterization techniques, the requirements for sample shape and size vary, for example, microscopy, x-ray photoelectron spectroscopy, ellipsometry et cetera require flat samples whereas magnetization measurements are best made using cylindrical samples. Hence, using a coupon sample characterization turns out to be a cost-effective way of probing the effect of different processing steps. In this thesis, I have used surface-characterizing tools such as scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), and magnetization to explore the effect of some of the recent cavity treatments on the microstructure, chemistry, and magnetic properties of high purity Nb surface. The goal is to construct a coupon-based methodology to explore the effect of different processing treatments.
Book Synopsis Buffered Electropolishing - A New Way for Achieving Extremely Smooth Surface Finish on Nb SRF Cavities to be Used in Particle Accelerators by :
Download or read book Buffered Electropolishing - A New Way for Achieving Extremely Smooth Surface Finish on Nb SRF Cavities to be Used in Particle Accelerators written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Future accelerators require unprecedented cavity performance, which is strongly influenced by interior surface nano-smoothness. Electropolishing (EP) is the technique of choice to be developed for high-field superconducting radio frequency (SRF) cavities. Electrochemical impedance spectroscopy (EIS) and related techniques point to the electropolishing mechanism of Nb in a sulphuric and hydrofluoric acid electrolyte controlled by a compact surface salt film under F- diffusion-limited mass transport control. These and other findings are guiding a systematic characterization to form the basis for cavities process optimization.
Book Synopsis Fastest Electropolishing Technique on Niobium for Particle Accelerators by :
Download or read book Fastest Electropolishing Technique on Niobium for Particle Accelerators written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Field emission on the inner surfaces of niobium (Nb) superconducting radio frequency (SRF) cavities is still one of the major obstacles for reaching high accelerating gradients for SRF community. Our previous experimental results [1] seemed to imply that the threshold of field emission was related to the thickness of Nb surface oxide layers. In this contribution, a more detailed study on the influences of the surface oxide layers on the field emission on Nb surfaces will be reported. By anodization technique, the thickness of the surface pentoxide layer was artificially fabricated from 3nm up to 460nm. A home-made scanning field emission microscope (SFEM) was employed to perform the scans on the surfaces. Emitters were characterized using a scanning electron microscope together with an energy dispersive x-ray analyzer. The experimental results could be understood by a simple model calculation based on classic electromagnetic theory as shown in Ref. 1. Possibly implications for Nb SRF cavity applications from this study will be discussed.
Book Synopsis Enhanced Field Emission Studies on Niobium Surfaces Relevant to High Field Superconducting Radio-Frequency Devices by :
Download or read book Enhanced Field Emission Studies on Niobium Surfaces Relevant to High Field Superconducting Radio-Frequency Devices written by and published by . This book was released on 2002 with total page 135 pages. Available in PDF, EPUB and Kindle. Book excerpt: Enhanced field emission (EFE) presents the main impediment to higher acceleration gradients in superconducting niobium (Nb) radiofrequency cavities for particle accelerators. The strength, number and sources of EFE sites strongly depend on surface preparation and handling. The main objective of this thesis project is to systematically investigate the sources of EFE from Nb, to evaluate the best available surface preparation techniques with respect to resulting field emission, and to establish an optimized process to minimize or eliminate EFE. To achieve these goals, a scanning field emission microscope (SFEM) was designed and built as an extension to an existing commercial scanning electron microscope (SEM). In the SFEM chamber of ultra high vacuum, a sample is moved laterally in a raster pattern under a high voltage anode tip for EFE detection and localization. The sample is then transferred under vacuum to the SEM chamber equipped with an energy-dispersive x-ray spectrometer for individual emitting site characterization. Compared to other systems built for similar purposes, this apparatus has low cost and maintenance, high operational flexibility, considerably bigger scan area, as well as reliable performance. EFE sources from planar Nb have been studied after various surface preparation, including chemical etching and electropolishing, combined with ultrasonic or high-pressure water rinse. Emitters have been identified, analyzed and the preparation process has been examined and improved based on EFE results. As a result, field-emission-free or near field-emission-free surfaces at 1̃40 MV/m have been consistently achieved with the above techniques. Characterization on the remaining emitters leads to the conclusion that no evidence of intrinsic emitters, id est, no fundamental electric field limit induced by EFE, has been observed up to 1̃40 MV/m. Chemically etched and electropolished Nb are compared and no significant difference is observed up to 1̃40 MV/m. To address concerns on the effect of natural air drying process on EFE, a comparative study was conducted on Nb and the results showed insignificant difference under the experimental conditions. Nb thin films deposited on Cu present a possible alternative to bulk Nb in superconducting cavities. The EFE performance of a preliminary energetically deposited Nb thin film sample are presented.
Book Synopsis Roughness Analysis of Variously Polished Niobium Surfaces by :
Download or read book Roughness Analysis of Variously Polished Niobium Surfaces written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Niobium superconducting radio frequency (SRF) cavities have gained widespread use in accelerator systems. It has been shown that surface roughness is a determining factor in the cavities' effi ciency and maximum accelerating potential achievable through this technology. Irregularities in the surface can lead to spot heating, undesirable local electrical fi eld enhancement and electron multipacting. Surface quality is typically ensured through the use of acid etching in a Buffered Chemical Polish (BCP) bath and electropolishing (EP). In this study, the effects of these techniques on surface morphology have been investigated in depth. The surface of niobium samples polished using different combinations of these techniques has been characterized through atomic force microscopy (AFM) and stylus profi lometry across a range of length scales. The surface morphology was analyzed using spectral techniques to determine roughness and characteristic dimensions. Experimentation has shown that this method is a valuable tool that provides quantitative information about surface roughness at different length scales. It has demonstrated that light BCP pretreatment and lower electrolyte temperature favors a smoother electropolish. These results will allow for the design of a superior polishing process for niobium SRF cavities and therefore increased accelerator operating effi ciency and power.
Download or read book Surface Study of Nb written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Deposition of thin niobium (Nb) films on copper (Cu) cavities, using an electron cyclotron resonance (ECR) plasma appears to be an attractive alternative technique for fabricating superconducting radio frequency cavities to be used in particle accelerators. The performance of these Nb/Cu cavities is expected to depend on the surface characteristics of the Nb films. In this paper, we report on an investigation of the influence of deposition energy on surface morphology, microstructure, and chemical composition of Nb films deposited on small Cu disks employing a metallographic optical microscope, a 3-D profilometer, a scanning electron microscope, and a dynamic secondary ion mass spectrometer. The results will be compared with those obtained on Nb surfaces treated by buffered chemical polishing, electropolishing, and buffered electropolishing. Possible implications from this study for Nb deposition on real Cu cavities will be discussed.
Book Synopsis Integrated Surface Topography Characterization of Variously Polished Niobium for Superconducting Particle Accelerators by :
Download or read book Integrated Surface Topography Characterization of Variously Polished Niobium for Superconducting Particle Accelerators written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: As superconducting niobium radio-frequency (SRF) cavities approach fundamental material limits, there is increased interest in understanding the details of topographical influences on realized performance limitations. Micro-and nano-roughness are implicated in both direct geometrical field enhancements as well as complications of the composition of the 50 nm surface layer in which the super-currents flow. Interior surface chemical polishing (BCP/EP) to remove mechanical damage leaves surface topography, including pits and protrusions of varying sharpness. These may promote RF magnetic field entry, locally quenching superconductivity, so as to degrade cavity performance. A more incisive analysis of surface topography than the widely-used average roughness is needed. In this study, a power spectral density (PSD) approach based on Fourier analysis of surface topography data acquired by both stylus profilometry and atomic force microscopy (AFM) is being used to distinguish the scale-dependent smoothing effects. The topographical evolution of the Nb surface as a function of different steps of EP is reported, resulting in a novel qualitative and quantitative description of Nb surface topography.
Book Synopsis Surface Polishing of Niobium for Superconducting Radio Frequency (SRF) Cavity Application by : Liang Zhao (Ph. D.)
Download or read book Surface Polishing of Niobium for Superconducting Radio Frequency (SRF) Cavity Application written by Liang Zhao (Ph. D.) and published by . This book was released on 2015 with total page 237 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Research and Development for Electropolishing of Nb for ILC Accelerator Cavities by :
Download or read book Research and Development for Electropolishing of Nb for ILC Accelerator Cavities written by and published by . This book was released on 2009 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objectives of this project are to 1, Expand the scientific and technological understanding of the effect of post-treatment (electropolish, buffered chemical polish, low-temperature baking) on the surface of niobium; 2, Relate the knowledge to the performance of niobium superconducting radiofrequency accelerator cavities; and, 3, Thereby design and demonstrate an electropolish process that can be applied to complete cavities.
Book Synopsis RF Superconductivity for Accelerators by : Hasan Padamsee
Download or read book RF Superconductivity for Accelerators written by Hasan Padamsee and published by John Wiley & Sons. This book was released on 2008-02-26 with total page 548 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book introduces some of the key ideas of this exciting field, using a pedagogic approach, and presents a comprehensive overview of the field. It is divided into four parts. The first part introduces the basic concepts of microwave cavities for particle acceleration. The second part is devoted to the observed behavior of superconducting cavities. In the third part,general issues connected with beam-cavity interaction and the related issues for the critical components are covered. The final part discusses applications of superconducting cavities to frontier accelerators of the future, drawing heavily on the examples that are in their most advanced stage. Each part of the book ends in a Problems section to illustrate and amplify text material as well as draw on example applications of superconducting cavities to existing and future accelerators.
Book Synopsis Surface Polishing of Niobium for Superconducting Radio Frequency (SRF) Cavity Applications by :
Download or read book Surface Polishing of Niobium for Superconducting Radio Frequency (SRF) Cavity Applications written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Niobium cavities are important components in modern particle accelerators based on superconducting radio frequency (SRF) technology. The interior of SRF cavities are cleaned and polished in order to produce high accelerating field and low power dissipation on the cavity wall. Current polishing methods, buffered chemical polishing (BCP) and electro-polishing (EP), have their advantages and limitations. We seek to improve current methods and explore laser polishing (LP) as a greener alternative of chemical methods. The topography and removal rate of BCP at different conditions (duration, temperature, sample orientation, flow rate) was studied with optical microscopy, scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). Differential etching on different crystal orientations is the main contributor to fine grain niobium BCP topography, with gas evolution playing a secondary role. The surface of single crystal and bi-crystal niobium is smooth even after heavy BCP. The topography of fine grain niobium depends on total removal. The removal rate increases with temperature and surface acid flow rate within the rage of 0~20 °C, with chemical reaction being the possible dominate rate control mechanism. Surface flow helps to regulate temperature and avoid gas accumulation on the surface. The effect of surface flow rate on niobium EP was studied with optical microscopy, atomic force microscopy (AFM), and power spectral density (PSD) analysis. Within the range of 0~3.7 cm/s, no significant difference was found on the removal rate and the macro roughness. Possible improvement on the micro roughness with increased surface flow rate was observed. The effect of fluence and pulse accumulation on niobium topography during LP was studied with optical microscopy, SEM, AFM, and PSD analysis. Polishing on micro scale was achieved within fluence range of 0.57~0.90 J/cm2, with pulse accumulation adjusted accordingly. Larger area treatment was proved possible by overlapping laser tracks at proper ratio. Comparison of topography and PSD indicates that LP smooths the surface in a way similar to EP. The optimized LP parameters were applied to different types of niobium surfaces representing different stages in cavity fabrication. LP reduces the sharpness on rough surfaces effectively, while doing no harm to smooth surfaces. Secondary ion mass spectrometer (SIMS) analysis showed that LP reduces the oxide layer slightly and no contamination occurred from LP. EBSD showed no significant change on crystal structure after LP.
Book Synopsis Nanostructural Features Degrading the Performance of Superconducting Radio Frequency Niobium Cavities Revealed by Transmission Electron Microscopy and Electron Energy Loss Spectroscopy by :
Download or read book Nanostructural Features Degrading the Performance of Superconducting Radio Frequency Niobium Cavities Revealed by Transmission Electron Microscopy and Electron Energy Loss Spectroscopy written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanoscale defect structure within the magnetic penetration depth of ~100 nm is key to the performance limitations of niobium superconducting radio frequency cavities. Using a unique combination of advanced thermometry during cavity RF measurements, and TEM structural and compositional characterization of the samples extracted from cavity walls, we discover the existence of nanoscale hydrides in electropolished cavities limited by the high field Q slope, and show the decreased hydride formation in the electropolished cavity after 120°C baking. Furthermore, we demonstrate that adding 800°C hydrogen degassing followed by light buffered chemical polishing restores the hydride formation to the pre-120°C bake level. We also show absence of niobium oxides along the grain boundaries and the modifications of the surface oxide upon 120°C bake.
