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Preliminary Results From Single Crystal And Very Large Crystal Niobium Cavities
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Book Synopsis Preliminary Results from Single Crystal and Very Large Crystal Niobium Cavities by :
Download or read book Preliminary Results from Single Crystal and Very Large Crystal Niobium Cavities written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We have fabricated and tested several single cell cavities using material from very large grain niobium ingots. In one case the central grain exceeded 7 inches in diameter and this was used to fabricate two 2.2 GHz cavities. This activity had a dual purpose: to investigate the influence of grain boundaries on the often observed Q-drop at gradients E[sub acc]> 20 MV/m in the absence of field emission, and to study the possibility of using ingot material for cavity fabrication without going through the expensive rolling process. The sheets for these cavities were cut from the ingot by wire electro-discharge machining (EDM) and subsequently formed into half-cells by deep drawing. The following fabrication steps were standard: machining of weld recesses, electron beam welding of beam pipes onto the half cells and final equator weld to join both half cell/beam pipe subunits. The cavities showed heavy Q-disease caused by the EDM. After hydrogen degassing at 800 C for 3 hrs in UHV and about 200 [micro]m total removals from the inner surface by BCP 1:1:1, the cavities showed promising results, however, the Q-drop was still present. In the two cavities made from large grain material accelerating gradients of 30 MV/m have been reached. After ''in-situ'' baking the Q-drop disappeared. The smaller cavities made from single crystal material showed very low residual resistances and accelerating gradients up to E[sub acc] = 45 MV/m were reached (one of the highest ever achieved), corresponding to a peak surface magnetic fields (B[sub p]) of 160 mT. In one rf test at 2 K, a B[sub p] = 185 mT was reached for few hundred milliseconds, close to the theoretical critical field of this material.
Book Synopsis Performance of Large Grain and Single Crystal Niobium Cavities by :
Download or read book Performance of Large Grain and Single Crystal Niobium Cavities written by and published by . This book was released on 2006 with total page 114013 pages. Available in PDF, EPUB and Kindle. Book excerpt: We have fabricated and tested several single and one multi-cell cavity made from large grain niobium of four different ingots. Two cavities at a frequency of ~ 2.2 GHz were made from single crystal sheets. Large grain material was used for four single cell cavities of the HG â and OC shapes, a 7-cell cavity of the HG â shape â all resonating at 1500 MHz â and an ILC_LL single cell cavity at 1300 MHz. We began to explore also different chemical polishing baths such as a 1:1:1 and a 1:1:2 buffered solution and explored the change of cavity performance as a function of material removal. The results from these preliminary investigations are reported in this contribution.
Book Synopsis Development of Large Grain/Single Crystal Niobium Cavity Technology at Jefferson Lab by : Peter Kneisel
Download or read book Development of Large Grain/Single Crystal Niobium Cavity Technology at Jefferson Lab written by Peter Kneisel and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Approximately two years ago we started to develop high performance niobium accelerating cavities based on large grain or single crystal high purity niobium. We have fabricated and tested 15 single cell cavities of various shapes and frequencies between 1300 MHz and 2300 MHz using material from a total of 9 different very large grain niobium ingots from four niobium suppliers. The materials differed not only in grain sizes, but also in RRR? value and in the amount of Ta contained in the material. In one ingot supplied by CBMM the central grain exceeded 7 inches in diameter and this was used to fabricate two 2.2 GHz cavities. A single crystal 1300 MHz mono-cell cavity was also produced at DESY by rolling out a single crystal to the size required for this cavity. It was sent to Jlab for surface treatment and testing. In addition, we have fabricated three 7-cell cavities: two of the Jlab high gradient (HG) shape and one of the ILC Low Loss shape. Two 9-cell TESLA shape cavities are presently in fabrication at Jlab and are close to completion.
Book Synopsis Single Crystal - Large Grain Niobium Technology by : Ganapati Rao Myneni
Download or read book Single Crystal - Large Grain Niobium Technology written by Ganapati Rao Myneni and published by AIP Conference Proceedings / H. This book was released on 2007-08-30 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt: SRF Technology based accelerators, FEL’s, and ERL’s, are becoming common worldwide. Several new frontier technologies and applications are expected to be evolving in coming years as the cost of SRF technology comes. Terra Hertz (THz) Science could benefit from these advances, and many applications are likely to be developed in the fields of medical imaging, material science, pharmaceuticals, communications etc.
Book Synopsis Investigations of Residual Stresses and Mechanical Properties of Single Crystal Niobium for SRF Cavities by :
Download or read book Investigations of Residual Stresses and Mechanical Properties of Single Crystal Niobium for SRF Cavities written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This work investigates properties of large grained, high purity niobium with respect to the forming of superconducting radio frequency (SRF) cavities from such large grained sheets. The yield stresses were examined using tensile specimens that were essentially single crystals in orientations evenly distributed in the standard projection triangle. No distinct yield anisotropy was found, however, vacuum annealing increased the yield strength by a factor 2.3. The deep drawing forming operation of the half cells raises the issues of elastic shape changes after the release of the forming tool (springback) and residual stresses, both of which are indicated to be negligible. This is a consequence of the low yield stress (
Book Synopsis PROGRESS ON LARGE GRAIN AND SINGLE GRAIN NIOBIUM by :
Download or read book PROGRESS ON LARGE GRAIN AND SINGLE GRAIN NIOBIUM written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Large grain and single crystal niobium has been proposed several years ago as an alternative material to poly-crystalline niobium for superconducting cavities, exhibiting potential advantages such as ¿stream-lined¿ procedures, reduced costs and better reproducibility in performance. Several major laboratories have investigated the use of large grain and single crystal material in the past years and the niobium producing industry has responded in providing ingot material with enlarged grain sizes. Besides a large number of single cell and multi-cell cavities from large grain niobium, several single crystal cavities have been fabricated and tested with good performances. This contribution will review the progress since the SRF workshop in 2005 in material processing and handling and in cavity performances.
Book Synopsis Investigating Single Crystal Plasticity of Niobium with a Dislocation Mechanics-based Model by : Eureka Pai Kulyadi
Download or read book Investigating Single Crystal Plasticity of Niobium with a Dislocation Mechanics-based Model written by Eureka Pai Kulyadi and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: One suggested method to manufacture superconducting radio frequency (SRF) cavities, which are used as driving units in particle accelerators, is the deep-drawing of Niobium (Nb) disks that were cut from large-grained ingots. This is a promising and cost-effective alternative to the current industry standard of deep-drawing rolled poly-crystalline sheets. It is essential to understand the sources of the observed variability in the performance of cavities fabricated by either process in order to define the most suitable fabrication route.Cavity performance is hampered by material defects such as dislocations or crystallite boundaries that can arise and evolve during deformation processes involved in the mechanical shaping of the cavity (mostly by deep-drawing). Such defects can trap magnetic flux causing significant radio frequency (RF) losses leading to reduced performance. Understanding dislocation mechanics in Nb based on deformation experiments allows predictive modeling to enable informed design strategies for optimal cavity fabrication and improved performance.Crystal plasticity (CP) modeling is a powerful and well-established computational materials science tool to investigate mechanical structure-property relations in crystalline materials. A dislocation mechanics-based constitutive description of plastic deformation in body-centered cubic (BCC) metals is used to formulate a CP model for Nb. Uniaxial tension experiments on several Nb single crystals cut from a large-grained ingot disk were conducted at several different strain rates. The specific selection of grains and the in-plane orientation of deformation samples cut from those grains were based on the active slip systems anticipated from SCHMID factor calculations. The results from these specifically designed deformation experiments are used to validate the model.Simulations and corresponding deformation experiments exhibit notable discrepancies in terms of the stress-strain response and lattice reorientation. These discrepancies are rationalized by considering the effect of a distribution in pre-existing dislocation densities across the possible slip systems, which entails a significant variability in the resulting slip system activity and associated crystal reorientation and strain hardening behavior. An exhaustive numerical study probing thousands of initial dislocation density distributions could be condensed into inverse pole figure (IPF) maps that chart the range of crystallographic tensile directions for which stable outcomes can be expected despite a given variability in the pre-existing dislocation density distribution. Consequently, it becomes clear that while single-crystal experiments can be a useful guide toward the development and testing of dislocation mechanics-based models, care must be exercised as to not expect a one-to-one matching between any specific experiment and its corresponding simulation, since the exact values and distribution of pre-existing dislocations in the sample is generally unknown (and likely unknowable).
Book Synopsis Performance of Single Crystal Niobium Cavities by :
Download or read book Performance of Single Crystal Niobium Cavities written by and published by . This book was released on 2008 with total page 45205 pages. Available in PDF, EPUB and Kindle. Book excerpt: We have fabricated and tested a total of six single cell niobium cavities, made from single crystal, high purity niobium. Two of the three cavities of the TESLA shape (1300 MHz) were made from Heraeus niobium by extending a smaller single crystal by rolling and annealing steps; the third cavity was made by spinning from CBMM material. The three other cavities of the scaled "Low Loss" (LL) shape (two) and "High Gradient" (HG) shape (one) resonated at 2.3 GHz and were fabricated from "as received" single crystals, both from Heraeus and CBMM niobium. After appropriate surface treatments by buffered chemical polishing and electropolishing most cavities performed quite nicely and peak surface magnetic fields of ~ 160 mT or above corresponding to accelerating gradients between 38 MV/m and 45 MV/m were reached. This paper reports about the performance of these cavities.
Book Synopsis Single Crystal and Large Grain Niobium Research at Michigan State University by :
Download or read book Single Crystal and Large Grain Niobium Research at Michigan State University written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: As Superconducting Radio Frequency (SRF) technology is used in more accelerator designs, research has focused on increasing the efficiency of these accelerators by pushing gradients and investigating cast reduction options. Today, most SRF structures are fabricated from high purity niobium. Over years of research, a material specification has been derived that defines a uniaxial, fine gain structure for SRF cavity fabrication. Most recently a push has been made to investigate the merits of using single or large grain niobium as a possible alternative to fine grain niobium. Michigan State University (MSU), in collaboration with Fermi National Accelerator Laboratory (FNAL) and Thomas Jefferson National Accelerator Facility (JLAB), is researching large grain niobium via cavity fabrication processes end testing, as well as exploring materials science issues associated with recrystallization and heat transfer. Single-cell 1.3 GHz (Beta=0.081) cavities made from both fine end large grain niobium were compared both in terms of fabrication procedures and performance. Two 7-cell cavities are currently being fabricated.
Book Synopsis PRELIMINARY RESULTS ON "POLARIZED" BUFFERED CHEMICAL POLISHING OF A LARGE GRAIN NIOBIUM CAVITY. by :
Download or read book PRELIMINARY RESULTS ON "POLARIZED" BUFFERED CHEMICAL POLISHING OF A LARGE GRAIN NIOBIUM CAVITY. written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In order to further understand the relation between the high-field Q-drop and the native oxide layer on the surface of SRF niobium cavities, we tried to alter the oxidation of niobium by applying a small voltage between a large-grain niobium cavity and a niobium rod inserted in the center, during buffered chemical polishing (BCP). The cavity RF test results at 1.7 K and 2.0 K did not show any major difference in the Q-drop behavior, compared to a standard BCP treatment. In one case, dark gray regions were visible inside the cavity and were responsible for additional losses, as seen with temperature maps. In order to better understand the electrochemical process occurring during the "polarized" BCP treatment, measurements of the polarization curve have been made on a cylindrical niobium sample, with a cylindrical niobium rod in the center.
Book Synopsis Single Crystal and Polycrystalline Niobium and OFE Copper for SRF Cavities Applications by : Jean-François Croteau
Download or read book Single Crystal and Polycrystalline Niobium and OFE Copper for SRF Cavities Applications written by Jean-François Croteau and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Manufacturing of superconducting radiofrequency (SRF) cavities with high performances is paramount to increase the collision energy in new particle accelerators. The use of high-speed sheet forming techniques, such as electro-hydraulic forming, can be beneficial, but requires a detailed understanding of the mechanical properties of the materials being deformed and the consequence on their microstructure. This thesis focuses on the characterization of high-purity niobium single crystals, polycrystalline niobium sheets, and polycrystalline OFE copper sheets. The results from this study are separated in two parts. In Part I, the characterization of niobium single crystals focused on the mechanical properties in tension and compression at strain rates of 10-4 to 103 s-1 and on the microstructure (analyzed using SEM, EBSD, TEM, and nanoindentation) of the deformed specimens. The effect of crystal orientation, strain rate, and loading direction on the mechanical properties, the crystal rotation, and the dislocation substructures are presented. In Part II, the forming limit diagram (FLD) of polycrystalline niobium sheets and OFE copper sheets were measured at a quasi-static strain rate. The FLDs of those materials should provide important data for manufacturers using conventional techniques, such as deep-drawing and spinning. The second part also presents the mechanical properties of electron beam (EB) welded polycrystalline niobium sheets and OFE copper sheets deformed in tension and compression at strain rates of 10-3 to 103 s-1.
Book Synopsis PERFORMANCES OF HIGH PURITY NIOBIUM CAVITIES WITH DIFFERENT GRAIN SIZES. by :
Download or read book PERFORMANCES OF HIGH PURITY NIOBIUM CAVITIES WITH DIFFERENT GRAIN SIZES. written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Grain boundaries have for some time been suspected of influencing the performance of RF cavities made from high purity niobium by limiting the temperature dependent BCS surface resistance to a residual resistance because of impurity segregation and by causing field limitations due to flux penetration. We have carried out a comparative study of the RF behavior of 2.2 GHz TM010 cavities of identical shape, fabricated from single crystal niobium, niobium of grain sizes of the order of several cm2 and standard poly-crystalline material. All the cavities were treated with buffered chemical polishing (BCP), post-purified at 1250 C and ''in-situ'' baked at 120 C. This contribution reports about the results of the measurements of the temperature dependence of the surface resistance Rs(T) and the Q0 vs. Eacc behavior at 2 K. From the analysis of the Rs(T) data at low RF fields material parameters such as gap value, mean free path and residual resistance could be extracted. The dependence of the Q-value on RF field was analyzed with respect to the medium field Q-slope, ''Q-drop'' at high fields and the ''quench'' fields. The best performance resulted in a breakdown field of (almost equal to) 165 mT, corresponding to an accelerating gradient of Eacc (almost equal to) 38 MV/m.
Book Synopsis Preliminary Results from Prototype Niobium Cavities for The JLab Ampere-Class FEL. by :
Download or read book Preliminary Results from Prototype Niobium Cavities for The JLab Ampere-Class FEL. written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In a previous paper the cavity [1] design for an Ampere-class cryomodule was introduced. We have since fabricated a 1500 MHz version of a single cell cavity with waveguide couplers for HOM and fundamental power, attached to one end of the cavity, a 5-cell cavity made from large grain niobium without couplers and. a 750 MHz single cell cavity without endgroups to get some information about obtainable Q-values, gradients and multipacting behavior at lower frequency. This contribution reports on the various tests of these cavities.
Book Synopsis Physical and Mechanical Properties of Single and Large Crystal High-RRR Niobium by : Ganapati Myneni
Download or read book Physical and Mechanical Properties of Single and Large Crystal High-RRR Niobium written by Ganapati Myneni and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: High RRR bulk niobium SRF cavities are the building blocks of the latest and future particle accelerators, free electron lasers (FEL's) and energy recovery linacs (ERL's.). These cavities are fabricated from high purity (RRR) poly crystalline niobium sheets via deep drawing, e-beam welding and surface treatment to obtain high accelerating gradients and quality factors. However, the starting bulk RRR niobium properties are not yet optimized with respect to both cost reduction and achievement of ultimate performance. A major limitation in achieving the highest performance can possibly be attributed to imperfections at or near the grain boundaries. Recently, at Jefferson Lab single/large grain RRR niobium cavities are developed using customized RRR ingots with optimized amounts of impurities such as Tantalum and minimizing the interstitial contents (O, C, N and H).
Book Synopsis PERFORMANCES OF HIGH PURITY NIOBIUM CAVITIES WITH DIFFERENT GRAIN SIZES. by : Ganapati Myneni
Download or read book PERFORMANCES OF HIGH PURITY NIOBIUM CAVITIES WITH DIFFERENT GRAIN SIZES. written by Ganapati Myneni and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Grain boundaries have for some time been suspected of influencing the performance of RF cavities made from high purity niobium by limiting the temperature dependent BCS surface resistance to a residual resistance because of impurity segregation and by causing field limitations due to flux penetration. We have carried out a comparative study of the RF behavior of 2.2 GHz TM{sub 010} cavities of identical shape, fabricated from single crystal niobium, niobium of grain sizes of the order of several cm{sup 2} and standard poly-crystalline material. All the cavities were treated with buffered chemical polishing (BCP), post-purified at 1250?C and?in-situ? baked at 120 C. This contribution reports about the results of the measurements of the temperature dependence of the surface resistance Rs(T) and the Q0 vs. Eacc behavior at 2 K. From the analysis of the Rs(T) data at low RF fields material parameters such as gap value, mean free path and residual resistance could be extracted. The dependence of the Q-value on RF field was analyzed with respect to the medium field Q-slope, Q-drop at high fields and the quench fields. The best performance resulted in a breakdown field of {approx}165 mT, corresponding to an accelerating gradient of E{sub acc} {approx} 38 MV/m.
Book Synopsis Mechanical Properties of Niobium Radio-frequency Cavities by :
Download or read book Mechanical Properties of Niobium Radio-frequency Cavities written by and published by . This book was released on 2015 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: Radio-frequency cavities made of bulk niobium are one of the components used in modern particle accelerators. The mechanical stability is an important aspect of cavity design, which typically relies on finite-element analysis simulations using material properties from tensile tests on sample. This contribution presents the results of strain and resonant frequency measurements as a function of a uniform pressure up to 722 kPa, applied to single-cell niobium cavities with different crystallographic structure, purity and treatments. In addition, burst tests of high-purity multi-cell cavities with different crystallographic structure have been conducted up to the tensile strength of the material. Finite-element analysis of the single-cell cavity geometry is in good agreement with the observed behavior in the elastic regime assuming a Young's modulus value of 88.5 GPa and a Poisson's ratio of 0.4, regardless of crystallographic structure, purity or treatment. However, the measured yield strength and tensile strength depend on crystallographic structure, material purity and treatment. In particular, the results from this study show that the mechanical properties of niobium cavities with large crystals are comparable to those of cavities made of fine-grain niobium.
Download or read book Development of Large Grain written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Approximately two years ago we started to develop high performance niobium accelerating cavities based on large grain or single crystal high purity niobium. We have fabricated and tested 15 single cell cavities of various shapes and frequencies between 1300 MHz and 2300 MHz using material from a total of 9 different very large grain niobium ingots from four niobium suppliers. The materials differed not only in grain sizes, but also in RRR? value and in the amount of Ta contained in the material. In one ingot supplied by CBMM the central grain exceeded 7 inches in diameter and this was used to fabricate two 2.2 GHz cavities. A single crystal 1300 MHz mono-cell cavity was also produced at DESY by rolling out a single crystal to the size required for this cavity. It was sent to Jlab for surface treatment and testing. In addition, we have fabricated three 7-cell cavities: two of the Jlab high gradient (HG) shape and one of the ILC Low Loss shape. Two 9-cell TESLA shape cavities are presently in fabrication at Jlab and are close to completion.
