Download or read book Ultra high Quality Factors in Superconducting Niobium Cavities in Ambient Magnetic Fields Up to 190 MG written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Ambient magnetic field, if trapped in the penetration depth, leads to the residual resistance and therefore sets the limit for the achievable quality factors in superconducting niobium resonators for particle accelerators. Here, we show that a complete expulsion of the magnetic flux can be performed and leads to: (1) record quality factors Q> 2 x 1011 up to accelerating gradient of 22 MV/m; (2) Q ~ 3 x 1010 at 2 K and 16 MV/m in up to 190 mG magnetic fields. This is achieved by large thermal gradients at the normal/superconducting phase front during the cooldown. Our findings open up a way to ultra-high quality factors at low temperatures and show an alternative to the sophisticated magnetic shielding implemented in modern superconducting accelerators.
Download or read book Superconducting Properties of Niobium Films written by Wayne R. Hudson and published by . This book was released on 1971 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Studies of Superconducting Cavities for Heavy Ion Accelerators written by Peter Hutson Ceperley and published by . This book was released on 1972 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Investigation of the Superconducting Properties of Niobium Radio frequency Cavities written by Gianluigi Ciovati and published by . This book was released on 2005 with total page 398 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book High Gradient Superconducting Niobium Cavities written by and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Superconducting niobium cavities used in particle accelerators are limited in their rf performance by two phenomena: quench field levels below the theoretical limit of the material caused by defects, and field emission loading resulting from artificial contamination of the superconducting surfaces during surface treatment and assembly procedures. In recent years, the community involved in SRF technology developments has successfully improved cavity performances by applying advanced surface treatment methods such as chemical polishing, electropolishing, tumbling, high temperature heat treatment, high pressure rinsing, ''in situ'' high peak power processing, and clean room assembly procedures. In addition, improvements in the material properties such as thermal conductivity by ''solid state'' gettering'' and very strict QA methods, both in material inspection and during cavity fabrication, have resulted in cavity performance levels of E{sub acc} up to 40 MV/m in monocells and gradients in the vicinity of 30 MV/m in multicell structures at Q-values of (almost equal to) 101° at a temperature of 2K. More recently the fabrication of ''seamless'' cavities by spinning is being pursued with encouraging results. This process eliminates electron beam welds, which sometimes are the causes of performance degradations.
Download or read book Preliminary Studies of Electric and Magnetic Field Effects in Superconducting Niobium Cavities written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Superconducting cavities made from high purity niobium with RRR> 200 often show pronounced features in the Q vs. E[sub acc] dependence such as a peak at low gradients, a B[sup 2]-slope at intermediate fields and a steep degradation of Q-values (''Q-drop'') at gradients above E[sub acc][approx] 20 MV/m without field emission loading. Whereas the B[sup 2]-slope is in line with ''global'' heating[2] there are still different models to explain the observed ''Q-drop''. The model of ref.[1] is based on magnetic field enhancements at grain boundaries in the equator weld region of the cavity and local heating. These grain boundaries become normal conducting, when their critical magnetic field is reached and contribute gradually to the losses in the cavity as long as they are thermally stable. The model proposed in ref.[2] is based on effects taking place in the metal-oxide interface on the niobium surface. The major contribution to the RF absorption is coming from interface tunnel exchange between electronic states of superconducting Nb with their energy gap and localized states of the dielectric Nb[sub 2]O[sub 5]. An experimental program was started at JLab to settle the mechanisms behind B[sup 2]-slope and the Q-drop. A modified CEBAF single cell cavity is excited in either TM[sub 010] or TE[sub 011] modes and the Q vs. E[sub acc] dependences are measured as a function of various surface treatments such as BCP, electropolishing, high temperature heat treatment and ''in-situ'' baking. In addition, a special two-cell cavity was designed, which allows the excitation of the 0- and[pi]-modes of the TM[sub 010] passband, which ''scan'' different areas of the cavity surface with high electric and magnetic fields, respectively. This contribution reports about the design and first measurements with both types of cavities.
Download or read book High gradient Pulsed Operation of Superconducting Niobium Cavities written by and published by . This book was released on 1984 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Tests performed on several Niobium TM010 cavities at frequencies of about 2856 MHz using a high-power, pulsed method indicate that, at the end of the charging pulse, peak surface magnetic fields of up to approx. 1300 Oe, corresponding to a peak surface electric field of approx. 68 MV/m, can be reached at 4.2°K without appreciable average losses. Further studies of the properties of superconductors under pulsed operation might shed light on fundamental properties of rf superconductivity, as well as lead to the possibility of applying the pulse method to the operation of high-gradient linear colliders. 7 references, 30 figures, 2 tables.
Download or read book Superconductors at the Nanoscale written by Roger Wördenweber and published by Walter de Gruyter GmbH & Co KG. This book was released on 2017-09-11 with total page 590 pages. Available in PDF, EPUB and Kindle. Book excerpt: By covering theory, design, and fabrication of nanostructured superconducting materials, this monograph is an invaluable resource for research and development. Examples are energy saving solutions, healthcare, and communication technologies. Key ingredients are nanopatterned materials which help to improve the superconducting critical parameters and performance of superconducting devices, and lead to novel functionalities. Contents Tutorial on nanostructured superconductors Imaging vortices in superconductors: from the atomic scale to macroscopic distances Probing vortex dynamics on a single vortex level by scanning ac-susceptibility microscopy STM studies of vortex cores in strongly confined nanoscale superconductors Type-1.5 superconductivity Direct visualization of vortex patterns in superconductors with competing vortex-vortex interactions Vortex dynamics in nanofabricated chemical solution deposition high-temperature superconducting films Artificial pinning sites and their applications Vortices at microwave frequencies Physics and operation of superconducting single-photon devices Josephson and charging effect in mesoscopic superconducting devices NanoSQUIDs: Basics & recent advances Bi2Sr2CaCu2O8 intrinsic Josephson junction stacks as emitters of terahertz radiation| Interference phenomena in superconductor-ferromagnet hybrids Spin-orbit interactions, spin currents, and magnetization dynamics in superconductor/ferromagnet hybrids Superconductor/ferromagnet hybrids
Download or read book High Q0 in Superconducting Niobium Cavities written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
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:
Download or read book High Gradient Superconducting Niobium Cavities written by Peter Kneisel and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Progress on the Development of a Superconducting Connection for Niobium Cavities written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The availability of a superconducting connection between adjacent niobium radio-frequency (RF) cavities with the capability to carry up to 30 mT of the magnetic flux would be particularly of great benefit to layouts of long accelerators like the International Linear Collider (ILC). It would shorten the distances between structures and therefore the total length of an accelerator with the associated cost reductions. In addition, the superconducting connection would be ideal for a superstructure - two multi-cell cavities connected through a half wavelength long beam pipe providing the coupling. Two single-cell niobium cavities have been designed with Nb-1Zr flanges welded to one of the irises to allow a connection between them with a niobium gasket. A transition to the normal-conducting state of the connection due to the applied RF field causes a reduction of the cavities' quality factor. The cavity design will be presented in this contribution along with possible choices of materials for the joint.
Download or read book Thermal Transport and Thermal magnetic Breakdown in Superconducting Cavities Made of High Thermal Conductivity Niobium written by Kathleen Rempel Krafft and published by . This book was released on 1983 with total page 408 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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:
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 Transient High field Behavior of Niobium Superconducting Cavities written by and published by . This book was released on 1983 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Tests have been performed on the breakdown behavior of a TM010 mode, S-band niobium cavity at low temperatures. Unloaded Q's of 9 x 107 at 4.2 K and of 7 x 109 at 1.35 K were measured during several tests performed using pulses long enough for the cavity to reach steady state. The breakdown field at 1.35 K was increased from 15 to 20 MV/m by processing the cavity at room temperature using 1 MW, 2.5 .mu.s pulses. The response of the cavity at 4.2 K to 1 MW, 2.5.mu.s pulses was also tested in several cool-downs. In these tests the cavity was heavily overcoupled to lower its time constant to a value of 0.80 times the RF pulse length of 2.5 .mu.s. This condition maximizes the energy transfer from the klystron source to the cavity. Measurements made during these experiments clearly indicated that fields of about 50 MV/m were being reached in the cavity without breakdown.
