Download or read book X ray Imaging of Superconducting Radio Frequency Cavities written by Susan Elizabeth Musser and published by . This book was released on 2006 with total page 426 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Superconducting Radiofrequency Technology for Accelerators written by Hasan Padamsee and published by John Wiley & Sons. This book was released on 2023-03-06 with total page 405 pages. Available in PDF, EPUB and Kindle. Book excerpt: Superconducting Radiofrequency Technology for Accelerators Single source reference enabling readers to understand and master state-of-the-art accelerator technology Superconducting Radiofrequency Technology for Accelerators provides a quick yet thorough overview of the key technologies for current and future accelerators, including those projected to enable breakthrough developments in materials science, nuclear and astrophysics, high energy physics, neutrino research and quantum computing. The work is divided into three sections. The first part provides a review of RF superconductivity basics, the second covers new techniques such as nitrogen doping, nitrogen infusion, oxide-free niobium, new surface treatments, and magnetic flux expulsion, high field Q slope, complemented by discussions of the physics of the improvements stemming from diagnostic techniques and surface analysis as well as from theory. The third part reviews the on-going applications of RF superconductivity in already operational facilities and those under construction such as light sources, proton accelerators, neutron and neutrino sources, ion accelerators, and crab cavity facilities. The third part discusses planned accelerator projects such as the International Linear Collider, the Future Circular Collider, the Chinese Electron Positron Collider, and the Proton Improvement Plan-III facility at Fermilab as well as exciting new developments in quantum computing using superconducting niobium cavities. Written by the leading expert in the field of radiofrequency superconductivity, Superconducting Radiofrequency Technology for Accelerators covers other sample topics such as: Fabrication and processing on Nb-based SRF structures, covering cavity fabrication, preparation, and a decade of progress in the field SRF physics, covering zero DC resistance, the Meissner effect, surface resistance and surface impedance in RF fields, and non-local response of supercurrent N-doping and residual resistance, covering trapped DC flux losses, hydride losses, and tunneling measurements Theories for anti-Q-slope, covering the Xiao theory, the Gurevich theory, non-equilibrium superconductivity, and two fluid model based on weak defects Superconducting Radiofrequency Technology for Accelerators is an essential reference for high energy physicists, power engineers, and electrical engineers who want to understand the latest developments of accelerator technology and be able to harness it to further research interest and practical applications.

Download or read book ELECTRON TUNNELING STUDIES OF MATERIALS FOR SUPERCONDUCTING RADIO FREQUENCY APPLICATIONS written by Eric Lechner and published by . This book was released on 2019 with total page 115 pages. Available in PDF, EPUB and Kindle. Book excerpt: Radio frequency (RF) cavities are the foundational infrastructure which facilitates much of the fundamental research conducted in high energy particle physics. These RF cavities utilize their unique shape to produce resonant electromagnetic fields used to accelerate charged particles. Beside their core role in fundamental physics research, RF cavities have found application in other disciplines including material science, chemistry and biology which take advantage of their unique light sources. Industry has been keen on taking advantage of accelerator technology for a multitude of applications. Particle accelerators like the one found at Jefferson Lab's Continuous Electron Beam Accelerator Facility must produce stable beams of high energy particles which is an incredibly costly endeavor to pursue. With the gargantuan size of these facilities, the cost of high-quality beam production is a matter of great importance. The quest to find highly efficient RF cavities has resulted in the widespread use of superconducting radio frequency (SRF) cavities which are the most efficient resonators that exploit a superconductor's incredibly low AC surface resistance. While metals like Cu are up to the demanding job of RF cavity particle acceleration, their efficiency at transferring RF power to the particle beam is low when they are compared with SRF Nb cavities. Nb is the standard material for all SRF cavity technology particularly for its reproducibly low surface resistance, comparatively high transition temperature and thermodynamic critical field. Using superconducting Nb is not without its drawbacks. Keeping hundreds of Nb cavities in their superconducting state under extreme RF conditions is quite a daunting task. It requires the normal state not nucleate during operation. This is achieved by producing high-quality cavities with as few defects and impurities as possible while also keeping the cavities at low temperature, usually 2K. Again, due to the sheer scale of the facilities, hundred million-dollar cryogenic plants are required to handle the heat loads during SRF cavity operation. This means even small increases in maximum accelerating gradients or decrease in cavity surface resistance results in a sizably reduced operation cost. Considerable effort has been put forth to increase the efficiency of Nb cavities toward and even beyond the theoretical maximum accelerating gradients and quality factor for a clean superconductor. Recently, a new method to produce high quality factor cavities has emerged that involves nitrogen doping the cavity. The mechanism by which N doping causes the improvement is still not well understood, but the experimental research described in this dissertation shines some light into the mechanisms behind such a drastic improvement. These insights are universal for all superconductors and may prove useful for SRF cavities beyond Nb. With Nb approaching its fundamental limits, new materials are being proposed to increase the performance of future SRF cavities which MgB2 finds itself among. MgB2 is a two-band superconductor that possesses many properties that are very attractive for the next generation of SRF cavities. One of the most important properties is MgB2's comparatively large critical temperature which in part predicts it will have a lower surface resistance than Nb at higher operating temperatures. Such behavior of MgB2 may unlock the possibility of using cryocoolers instead of costly liquid helium plants for large scale industrial use. This dissertation starts with an introduction to superconductivity, its theory, and application to SRF cavities as well as the open questions that can be addressed in Nb and the next generation of SRF materials. A description of the experimental techniques of scanning tunneling microscopy, X-ray photoelectron spectroscopy, and atomic force microscopy is presented. Our experimental investigation into Nb SRF cavity cutouts starts with a discussion of the material's limitations for SRF applications with an emphasis on the proximity effect which arises at the surface of this material due to its myriad of naturally forming oxides. The results of our scanning tunneling microscopy measurements for typically prepared Nb and nitrogen doped Nb follows and comparisons are made which show that the surface oxides are fundamentally different between these samples likely resulting in the profound enhancement of the cavity's quality factor. Experimental investigation into the native oxide of hot spot nitrogen doped Nb shows a degraded oxide and superconducting properties as compared with the cold spot. The dissertation continues with a brief introduction to MgB2, followed by our scanning tunneling and electron tunneling insights into MgB2. The dissertation is concluded with a summary of our investigations and broader impact of our research on the SRF community.

Download or read book Use of Simple X ray Measurement in the Performance Analysis of Cryogenic RF Accelerator Cavities written by and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: X-ray emission by radiofrequency (RF) resonant cavities has long been known to accelerator health physicists as a potentially serious source of radiation exposure. The authors points out the danger of klystrons and microwave cavities by stating that the radiation source term is erratic and may be unpredictable depending on microscopic surface conditions which change with time. He also states the x-ray output is a rapidly increasing function of RF input power. At Jefferson Lab, the RF cavities used to accelerate the electron beam employ superconducting technology. X-rays are emitted at high cavity gradients, and measurements of cavity x-rays are valuable for health physics purposes and provide a useful diagnostic tool for assessing cavity performance. The quality factor (Q) for superconducting RF resonant cavities used at Jefferson Lab, is typically 5 x 109 for the nominal design gradient of 5 MVm−1. This large value for Q follows from the small resistive loss in superconducting technology. The operating frequency is 1,497 MHz. In the absence of beam, the input power for a cavity is typically 750 W and the corresponding dissipated power is 2.6 W. At 5 MWm−1, the input power is 3 kW fully beam loaded. At higher gradients, performance degradation tends to occur due to the onset of electron field emission from defects in the cavity.

Download or read book Superconducting Properties of Niobium Radio frequency Cavities written by Gianluigi Ciovati and published by LAP Lambert Academic Publishing. This book was released on 2012 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: Superconducting radio-frequency (SRF) cavities are used to increase the energy of a charged particle beam in particle accelerators throughout the world. Bulk niobium is the material of choice to fabricate SRF cavities and their performance at cryogenic temperatures is characterized by a non-linearity of the surface resistance as a function of the RF field, in absence of field emission, which limits the operational accelerating gradient. This book presents the results on the investigation of such non-linearity in cavities which received different surface and bulk treatments as well as cavities made of single-crystal niobium. The experimental methods include measurements of the surface impedance as a function of temperature, of the quality factor as a function of the RF field below 4.2 K, and the excitation of different resonant modes. A thermometry system was used to better characterize the loss mechanisms. This book consists of the author's PhD dissertation at Old Dominion University (ODU) under the supervision of Prof. Colm T. Whelan of ODU and Dr. Peter Kneisel of Jefferson Lab. This book should be useful to students or young researchers in the field of SRF for accelerators.

Download or read book Development of Ultra High Gradient and High Q sub 0 Superconducting Radio Frequency Cavities written by and published by . This book was released on 2013 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: We report on the recent progress at Jefferson Lab in developing ultra high gradient and high Q0 superconducting radio frequency (SRF) cavities for future SRF based machines. A new 1300 MHz 9-cell prototype cavity is being fabricated. This cavity has an optimized shape in terms of the ratio of the peak surface field (both magnetic and electric) to the acceleration gradient, hence the name low surface field (LSF) shape. The goal of the effort is to demonstrate an acceleration gradient of 50 MV/m with Q0 of 101° at 2 K in a 9-cell SRF cavity. Fine-grain niobium material is used. Conventional forming, machining and electron beam welding method are used for cavity fabrication. New techniques are adopted to ensure repeatable, accurate and inexpensive fabrication of components and the full assembly. The completed cavity is to be first mechanically polished to a mirror-finish, a newly acquired in-house capability at JLab, followed by the proven ILC-style processing recipe established already at JLab. In parallel, new single-cell cavities made from large-grain niobium material are made to further advance the cavity treatment and processing procedures, aiming for the demonstration of an acceleration gradient of 50 MV/m with Q0 of 2-101° at 2K.

Download or read book Compact Superconducting Radio frequency Accelerators and Innovative RF Systems written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We will present several new technical and design breakthroughs that enable the creation of a new class of compact linear electron accelerators for industrial purposes. Use of Superconducting Radio-Frequency (SRF) cavities allow accelerators less than 1.5 M in length to create electron beams beyond 10 MeV and with average beam powers measured in 10's of KW. These machines can have the capability to vary the output energy dynamically to produce brehmstrahlung x-rays of varying spectral coverage for applications such as rapid scanning of moving cargo for security purposes. Such compact accelerators will also be cost effective for many existing and new industrial applications. Examples include radiation crosslinking of plastics and rubbers, creation of pure materials with surface properties radically altered from the bulk, modification of bulk or surface optical properties of materials, sterilization of medical instruments animal solid or liquid waste, and destruction of organic compounds in industrial waste water effluents. Small enough to be located on a mobile platform, such accelerators will enable new remediation methods for chemical and biological spills and/or in-situ crosslinking of materials. We will describe one current design under development at Fermilab including plans for prototype and value-engineering to reduce costs. We will also describe development of new nano-structured field-emitter arrays as sources of electrons, new methods for fabricating and cooling superconducting RF cavities, and a new novel RF power source based on magnetrons with full phase and amplitude control.

Download or read book Superconducting Radio frequency Technology written by and published by . This book was released on 1997 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A large number of diagnostic methods have been developed during the last two decades to gain insight in limiting phenomena occurring in superconducting rf cavities during operation. Temperature mapping in subcooled and superfluid helium and x-ray mapping have successfully been applied to understand and subsequently prevent or eliminate loss mechanisms present in these devices. Newer techniques specific to problems such as rf window arcing are under development. This paper reviews various diagnostic techniques and discusses the impact of their application on progress made in SRF technology.

Download or read book Superconducting Radio frequency Cavities Made from Medium and Low purity Niobium Ingots written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Superconducting radio-frequency cavities made of ingot niobium with residual resistivity ratio (RRR) greater than 250 have proven to have similar or better performance than fine-grain Nb cavities of the same purity, after standard processing. The high purity requirement contributes to the high cost of the material. As superconducting accelerators operating in continuous-wave typically require cavities to operate at moderate accelerating gradients, using lower purity material could be advantageous not only to reduce cost but also to achieve higher Q0-values. In this contribution we present the results from cryogenic RF tests of 1.3-1.5 GHz single-cell cavities made of ingot Nb of medium (RRR = 100-150) and low (RRR = 60) purity from different suppliers. Cavities made of medium-purity ingots routinely achieved peak surface magnetic field values greater than 70 mT with an average Q0-value of 2 × 1010 at 2 K after standard processing treatments. As a result, the performances of cavities made of low-purity ingots were affected by significant pitting of the surface after chemical etching.

Download or read book Effect of Microscopic Defects on Superconducting Properties of High Purity Niobium Used for SRF Cavities written by Mingmin Wang and published by . This book was released on 2020 with total page 193 pages. Available in PDF, EPUB and Kindle. Book excerpt: High purity niobium has been used to fabricate superconducting radio-frequency (SRF) cavities for linear particle accelerator applications for decades due to its high critical temperature (9.3 K) and critical magnetic field. Great progress has been made in achieving high accelerating gradients and quality factors (a measure of efficiency). However, the performance of Nb cavities still suffers from the variability of the material such that high quality factors and accelerating gradients cannot be consistently produced.Trapped magnetic flux is well known for causing significant radio-frequency losses. Both local flux penetration and flux trapping indicate the local suppression of superconductivity. Magnetic flux from both unshielded earth field and thermoelectric currents can be trapped when a cavity is cooled through its superconducting transition temperature. Microstructural defects including hydrogen, grain boundaries, and dislocations are possible causes for flux trapping. However, the details of magnetic flux trapping mechanisms and conditions that enable it are still not clear. Research on this topic has been very active in the SRF community. Cavity studies on flux expulsion after different heat treatments and cooldown procedures have been performed in recent years, but the study of flux trapping mechanisms at the microscopic level is still lacking.In order to study the effect of microscopic defects on flux trapping, single crystal and bicrystal samples were designed with strategically chosen tensile axes to intentionally introduce defects by a 5% tensile strain. Magneto-Optical (MO) Imaging was used to visualize locations where magnetic flux was trapped, and the dislocation substructures were studied using Electron Channeling Contrast Imaging (ECCI).The results show that high angle grain boundaries (HAGB) and low angle grain boundaries (LAGBs) have different flux penetration behaviors. LAGBS could be hydrogen segregation sites leading to precipitation of normal conducting hydrides along LAGBs at ~100-130 K during cooling. In hydrogen contaminated single-crystal samples, large hydride scars (locations where a hydride formed and then dissolved during heating) were observed both at the LAGBs and within the grain after MO cooling; however, only hydrides at the LAGBs appeared to cause premature flux penetration. Flux trapping related to LAGBs could still be observed after the heat treatment removed most of the hydrogen. By contrast, the flux penetration along a HAGB could be turned off by heat treatment that removed hydrogen and restored by reintroducing hydrogen into the sample. This work suggests that HAGBs are not as effective at causing flux penetration or trapping as hydrides and LAGBs.Some deformed bi-crystal samples show correlations between a larger amount of deformation or a higher density of dislocations and more trapped flux. Deformation led to the development of dislocation substructures; however, the effect of dislocation arrangements on flux penetration could not be observed in the current work. Further study with flux measurement techniques of a higher resolution and sensitivity is necessary to understand what kinds of dislocation substructures are most likely to cause flux penetration.

Download or read book New Results of Development on High Efficiency High Gradient Superconducting Rf Cavities written by and published by . This book was released on 2015 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: We report on the latest results of development on high-efficiency high-gradient superconducting radio frequency (SRF) cavities. Several 1-cell cavities made of large-grain niobium (Nb) were built, processed and tested. Two of these cavities are of the Low Surface Field (LSF) shape. Series of tests were carried out following controlled thermal cycling. Experiments toward zero-field cooling were carried out. The best experimentally achieved results are Eacc = 41 MV/m at Q0 = 6.5×1010 at 1.4 K by a 1-cell 1.3 GHz large-grain Nb TTF shape cavity and Eacc = 49 MV/m at Q0 = 1.5×1010 at 1.8 K by a 1-cell 1.5 GHz large-grain Nb CEBAF upgrade low-loss shape cavity.

Download or read book Production of Seamless Superconducting Radio Frequency Cavities from Ultra fine Grained Niobium Phase II Final Report written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The positron and electron linacs of the International Linear Collider (ILC) will require over 14,000, nine-cell, one meter length, superconducting radio frequency (SRF) cavities [ILC Reference Design Report, 2007]. Manufacturing on this scale will benefit from more efficient fabrication methods. The current methods of fabricating SRF cavities involve deep drawing of the halves of each of the elliptical cells and joining them by high-vacuum, electron beam welding, with at least 19 circumferential welds per cavity. The welding is costly and has undesirable effects on the cavity surfaces, including grain-scale surface roughening at the weld seams. Hydroforming of seamless tubes avoids welding, but hydroforming of coarse-grained seamless tubes results in strain-induced surface roughening. Surface roughness limits accelerating fields, because asperities prematurely exceed the critical magnetic field and become normal conducting. This project explored the technical and economic feasibility of an improved processing method for seamless tubes for hydroforming. Severe deformation of bulk material was first used to produce a fine structure, followed by extrusion and flow-forming methods of tube making. Extrusion of the randomly oriented, fine-grained bulk material proceeded under largely steady-state conditions, and resulted in a uniform structure, which was found to be finer and more crystallographically random than standard (high purity) RRR niobium sheet metal. A 165 mm diameter billet of RRR grade niobium was processed into five, 150 mm I.D. tubes, each over 1.8 m in length, to meet the dimensions used by the DESY ILC hydroforming machine. Mechanical properties met specifications. Costs of prototype tube production were approximately twice the price of RRR niobium sheet, and are expected to be comparable with economies of scale. Hydroforming and superconducting testing will be pursued in subsequent collaborations with DESY and Fermilab. SRF Cavities are used to construct particle accelerators for high-energy physics research, as well as for lower energy particle accelerators, and Free Electron Lasers. These machines have applications in the fields of basic science, industrial processing, medical diagnostics, pharmaceutical research and weapons systems. The scientific community and the general public will benefit from the implementation of this technology since lower production costs will increase the availability of SRF particle accelerators.

Download or read book Insights to Superconducting Radio Frequency Cavity Processing from First Principles Calculations and Spectroscopic Techniques written by and published by . This book was released on 2013 with total page 127 pages. Available in PDF, EPUB and Kindle. Book excerpt: Insights to the fundamental processes that occur during the manufacturing of niobium superconducting radio-frequency (SRF) cavities are provided via analyses of density functional theory calculations and Raman, infrared, and nuclear magnetic resonance (NMR) spectra. I show that during electropolishing fluorine is bound and released by the reaction of the acid components in the solution: HF + H2SO4 - HFSO3 + H2O. This result implies that new recipes can possibly be developed on the principle of controlled release of fluorine by a chemical reaction. I also show that NMR or Raman spectroscopy can be used to monitor the free fluorine when polishing with the standard electropolishing recipe. Density functional theory was applied to calculate the properties of common processing impurities - hydrogen, oxygen, nitrogen, and carbon - in the niobium. These impurities lower the superconducting transition temperature of niobium, and hydride precipitates are at best weakly superconducting. I modeled several of the niobium hydride phases relevant to SRF cavities, and explain the phase changes in the niobium hydrogen system based on the charge transfer between niobium and hydrogen and the strain field inside of the niobium. I also present evidence for a niobium lattice vacancy serving as a nucleation center for hydride phase formation. In considering the other chemical impurities in niobium, I show that the absorption of oxygen into a niobium lattice vacancy is preferred over the absorption of hydrogen, which indicates that oxygen can block these phase nucleation centers. I also show that dissolved oxygen atoms can trap dissolved hydrogen atoms to prevent niobium hydride phase formation. Nitrogen and carbon were studied in less depth, but behaved similarly to oxygen. Based on these results and a literature survey, I propose a mechanism for the success of the low-temperature anneal applied to niobium SRF cavities. Finally, I present the beginning of a model to describe magnetic impurities in niobium SRF cavities, which can cause a loss of local superconductivity. I calculated magnetic configurations of niobium hydrides and oxides, and show that stoichiometric hydride and oxide structures are nonmagnetic, but defective oxide structures retain local magnetic moments.

Download or read book Superconducting Thin Films for the Enhancement of Superconducting Radio Frequency Accelerator Cavities written by Matthew C. Burton and published by . This book was released on 2017 with total page 151 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bulk niobium (Nb) superconducting radio frequency (SRF) cavities are currently the preferred method for acceleration of charged particles at accelerating facilities around the world. However, bulk Nb cavities have poor thermal conductance, impose material and design restrictions on other components of a particle accelerator, have low reproducibility and are approaching the fundamental material-dependent accelerating field limit of approximately 50MV/m. Since the SRF phenomena occurs at surfaces within a shallow depth of ~1 μm, a proposed solution to this problem has been to utilize thin film technology to deposit superconducting thin films on the interior of cavities to engineer the active SRF surface in order to achieve cavities with enhanced properties and performance. Two proposed thin film applications for SRF cavities are: 1) Nb thin films coated on bulk cavities made of suitable castable metals (such as copper or aluminum) and 2) multilayer films designed to increase the accelerating gradient and performance of SRF cavities. While Nb thin films on copper (Cu) cavities have been attempted in the past using DC magnetron sputtering (DCMS), such cavities have never performed at the bulk Nb level. However, new energetic condensation techniques for film deposition, such as High Power Impulse Magnetron Sputtering (HiPIMS), offer the opportunity to create suitably thick Nb films with improved density, microstructure and adhesion compared to traditional DCMS. Clearly use of such novel technique requires fundamental studies to assess surface evolution and growth modes during deposition and resulting microstructure and surface morphology and the correlation with RF superconducting properties. Here we present detailed structure-property correlative research studies done on Nb/Cu thin films and NbN- and NbTiN-based multilayers made using HiPIMS and DCMS, respectively.

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.

Download or read book Handbook of Superconductivity written by David A. Cardwell and published by CRC Press. This book was released on 2022-07-05 with total page 472 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the first of three volumes of the extensively revised and updated second edition of the Handbook of Superconductivity. The past twenty years have seen rapid progress in superconducting materials, which exhibit one of the most remarkable physical states of matter ever to be discovered. Superconductivity brings quantum mechanics to the scale of the everyday world where a single, coherent quantum state may extend over a distance of metres, or even kilometres, depending on the size of a coil or length of superconducting wire. Viable applications of superconductors rely fundamentally on an understanding of this intriguing phenomena and the availability of a range of materials with bespoke properties to meet practical needs. This first volume covers the fundamentals of superconductivity and the various classes of superconducting materials, which sets the context and background for Volumes 2 and 3. Key Features: Covers the depth and breadth of the field Includes contributions from leading academics and industry professionals across the world Provides hands-on guidance to the manufacturing and processing technologies A comprehensive reference, this handbook is suitable for both graduate students and practitioners in experimental physics, materials science and multiple engineering disciplines, including electronic and electrical, chemical, mechanical, metallurgy and others.

Download or read book Strong Meissner Screening Change in Superconducting Radio Frequency Cavities Due to Mild Baking written by and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: