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Power Dependence Of The Rf Surface Resistance Of Mgb2 Superconductor
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Book Synopsis Power Dependence of the RF Surface Resistance of MgB2 Superconductor by :
Download or read book Power Dependence of the RF Surface Resistance of MgB2 Superconductor written by and published by . This book was released on 2005 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnesium diboride (MgB2) is a superconducting material that has a transition temperature (T{sub c}) of (almost equal to)40 K, which is (almost equal to)30 K higher than niobium (Nb) that has been used for most superconducting RF cavities in the past decades. Last year, it was demonstrated that the RF surface resistance of MgB2 can be lower than Nb at 4 K. One of the problems with other high-T{sub c} materials such as YBCO was its rapid increase in RF surface resistance with higher surface magnetic fields. Recently, we have shown that MgB2 shows little increase in the surface resistance up to (almost equal to)120 Oe, equivalent of an accelerating field of (almost equal to)3 MV/m. The highest field tested was limited by available power. This result is encouraging and has made us consider fabrication of a cavity coated with MgB2 and test it. Also, there is a potential that this material has a higher critical magnetic field that enables the cavity to run at a higher gradient than Nb cavities in addition to the possibility of operation at higher temperatures.
Book Synopsis Applied Superconductivity by : Paul Seidel
Download or read book Applied Superconductivity written by Paul Seidel and published by John Wiley & Sons. This book was released on 2015-01-29 with total page 1334 pages. Available in PDF, EPUB and Kindle. Book excerpt: This wide-ranging presentation of applied superconductivity, from fundamentals and materials right up to the details of many applications, is an essential reference for physicists and engineers in academic research as well as in industry. Readers looking for a comprehensive overview on basic effects related to superconductivity and superconducting materials will expand their knowledge and understanding of both low and high Tc superconductors with respect to their application. Technology, preparation and characterization are covered for bulk, single crystals, thins fi lms as well as electronic devices, wires and tapes. The main benefit of this work lies in its broad coverage of significant applications in magnets, power engineering, electronics, sensors and quantum metrology. The reader will find information on superconducting magnets for diverse applications like particle physics, fusion research, medicine, and biomagnetism as well as materials processing. SQUIDs and their usage in medicine or geophysics are thoroughly covered, as are superconducting radiation and particle detectors, aspects on superconductor digital electronics, leading readers to quantum computing and new devices.
Book Synopsis Tests on MgB2 for Application to SRF Cavities by :
Download or read book Tests on MgB2 for Application to SRF Cavities written by and published by . This book was released on 2006 with total page 77901 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnesium diboride (MgB2) has a transition temperature (Tc) of ~40 K, i.e., about four times higher than niobium (Nb). The studies in the last three years have shown that it could have about one order of magnitude less RF surface resistance (Rs) than Nb and seems much less power dependent compared to high-Tc materials such as YBCO. In this paper we will present results on the dependence of Rs on surface magnetic fields and possibly the critical RF surface magnetic field.
Book Synopsis MgB2 for Application to RF Cavities for Accelerators by :
Download or read book MgB2 for Application to RF Cavities for Accelerators written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnesium diboride (MgB2) has a transition temperature (T{sub c}) of (almost equal to)40 K, i.e., about 4 times as high as that of niobium (Nb). We have been evaluating MgB2 as a candidate material for radio-frequency (RF) cavities for future particle accelerators. Studies in the last 3 years have shown that it could have about one order of magnitude less RF surface resistance (Rs) than Nb at 4 K.A power dependence test using a 6 GHz TE011 mode cavity has shown little power dependence up to (almost equal to)12 mT (120 Oe), limited by available power, compared to other high-Tc materials such as YBCO. A recent study showed, however, that the power dependence of Rs is dependent on the coating method. A film made with on-axis pulsed laser deposition (PLD) has showed rapid increase in Rs compared to the film deposited by reactive evaporation method. This paper shows these results as well as future plans.
Book Synopsis On the Rf Surface Resistance of the Perovskite Superconductors at 3 GHz by :
Download or read book On the Rf Surface Resistance of the Perovskite Superconductors at 3 GHz written by and published by . This book was released on 1987 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The rf surface resistance is measured for Y1Ba2Cu3O-- samples fabricated in different laboratories by exposing them to the rf field of a niobium cavity at 3 GHz in a temperature range from 4.2 to 300 K. The rf surface resistance of the best sample decreases sharply at the transition temperature from typically 0.2 .cap omega. at 100 K by more than two orders of magnitude. The residual losses measured at 4.2 K in the superconducting host cavity are strongly dependent on the purity of the sample. The observed dependence of the residual losses on the rf field level is attributed to the granular structure of the superconductor. Rf magnetic fields of up to 1800 A/m have been achieved in pulsed operation. This field corresponds to a surface current density of 1.3 . 106 A/cm2. The low residual losses indicate that less than 1% of the conduction electrons of the perovskite superconductors remain unpaired.
Book Synopsis A New First-Principles Calculation of Field-Dependent RF Surface Impedance of BCS Superconductor by :
Download or read book A New First-Principles Calculation of Field-Dependent RF Surface Impedance of BCS Superconductor written by and published by . This book was released on 2014 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: There is a need to understand the intrinsic limit of radiofrequency (RF) surface impedance that determines the performance of superconducting RF cavities in particle accelerators. Here we present a field-dependent derivation of Mattis-Bardeen theory of the RF surface impedance of BCS superconductors based on the shifted density of states resulting from coherently moving Cooper pairs. Our theoretical prediction of the effective BCS RF surface resistance (Rs) of niobium as a function of peak surface magnetic field amplitude agrees well with recently reported record low loss resonant cavity measurements from JLab and FNAL with carefully, yet differently, prepared niobium material. The surprising reduction in resistance with increasing field is explained to be an intrinsic effect.
Book Synopsis Application of Superconducting Magnesium Diboride (MgB2) in Superconducting Radio Frequency Cavities by : Teng Tan
Download or read book Application of Superconducting Magnesium Diboride (MgB2) in Superconducting Radio Frequency Cavities written by Teng Tan and published by . This book was released on 2015 with total page 159 pages. Available in PDF, EPUB and Kindle. Book excerpt: The superconductivity in magnesium diboride (MgB2) was discovered in 2001. As a BCS superconductor, MgB2 has a record-high Tc of 39 K, high Jc of > 107 A/cm2 and no weak link behavior across the grain boundary. All these superior properties endorsed that MgB2 would have great potential in both power applications and electronic devices. In the past 15 years, MgB2 based power cables, microwave devices, and commercial MRI machines emerged and the next frontier are superconducting radio frequency (SRF) cavities. SRF cavities are one of the leading accelerator technologies. In SRF cavities, applied microwave power generates electrical fields that accelerate particle beams. Compared with other accelerator techniques, SRF cavity accelerators feature low loss, high acceleration gradients and the ability to accelerate continuous particle beams. However, current SRF cavities are made from high-purity bulk niobium and work at 2 K in superfluid helium. The construction and operational cost of SRF cavity accelerators are very expensive. The demand for SRF cavity accelerators has been growing rapidly in the past decade. Therefore, a lot of effort has been devoted to the enhancement of the performance and the reduction of cost of SRF cavities. In 2010, an acceleration gradient of over 50 MV/m has been reported for a Nb-based SRF cavity. The magnetic field at the inner surface of such a cavity is ~ 1700 Oe, which is close to the thermodynamic critical field of Nb. Therefore, new materials and technologies are required to raise the acceleration gradient of future SRF cavity accelerators. Among all the proposed approaches, using MgB2 thin films to coat the inner surface of SRF cavities is one of the promising tactics with the potential to raise both the acceleration gradient and the operation temperature of SRF cavity accelerators. In this work, I present my study on MgB2 thin films for their application in SRF cavities. C-epitaxial MgB2 thin films grown on SiC(0001) substrates showed Tc > 41 K and Jc > 107 A/cm2, which is superior to bulk MgB2 samples. Polycrystalline MgB2 thin films grown on metal substrates showed similar Tc and Jc compared with bulk samples, indicating MgB2 is suitable for coating a metal cavity. Large c-pitaxial MgB2 thin films were grown on 2-inch diameter c-sapphire wafers, showing our technique is capable of depositing large area samples. The lower critical field (Hc1) of MgB2 thin films was measured as well as it is know that bulk MgB2 has a small Hc1 and would suffer from vortex penetration at low magnetic fields. The penetrating magnetic vortices would result in loss in an applied RF field. However, due to the geometry barrier, thin film MgB2 would have a higher Hc1 than the bulk material. In my experiments, the Hc1 of MgB2 thin films increased with decreasing film thickness. At 5 K, a 100 nm epitaxial MgB2 thin film showed enhanced Hc1 ~ 1880 Oe, which is higher than Hc1 of Nb at 2 K. This showed that MgB2 coated SRF cavities have the potential to work at higher magnetic fields and higher temperature. Because the magnetic field distribution in the thin film Hc1 measurement is different from the magnetic field in a real SRF cavity, a few Nb ellipsoids were machined and coated with MgB2. The ellipsoid only has a magnetic field outside its surface and can serve as an inverse SRF cavity in the vortex penetration measurement. In the experiments, vortices penetrate into the bulk Nb ellipsoid at a magnetic field 400 Oe lower than the vortex penetration field of MgB2 coated Nb ellipsoids. This result confirmed our prediction that MgB2 coated SRF cavities could work at higher magnetic fields, thus producing higher acceleration gradients. In the last part of this thesis, I discussed how I used the dielectric resonator technique to measure the surface resistance (Rs) and Tc of MgB2 thin films. While the sensitivity of this technique was not high enough to lead to reliable Rs values, it can still serve for the determination of Tc for large area samples that are too bulky for other measurement systems.
Book Synopsis Tests on MgB2 for Application to SRF Cavities by : L. Phillips
Download or read book Tests on MgB2 for Application to SRF Cavities written by L. Phillips and published by . This book was released on 2006 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnesium diboride (MgB{sub 2}) has a transition temperature (T{sub c}) of {approx} 40 K, i.e., about 4 times higher than niobium (Nb). Studies in the last 3 years have shown that it could have about one order of magnitude less RF surface resistance (R{sub s}) than Nb at 4 K and seems to have much less power dependence than high-T{sub c} materials such as YBCO. However, it was also found that it will depend on the way you deposit the film. The result from on-axis pulsed laser deposition (PLD) showed rapid increase in R{sub s} with higher surface magnetic fields compared to the film deposited with reactive evaporation method.
Book Synopsis Dependence of Trapped-flux-induced Surface Resistance of a Large-grain Nb Superconducting Radio-frequency Cavity on Spatial Temperature Gradient During Cooldown Through [math Display by :
Download or read book Dependence of Trapped-flux-induced Surface Resistance of a Large-grain Nb Superconducting Radio-frequency Cavity on Spatial Temperature Gradient During Cooldown Through [math Display written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent studies by Romanenko et al. revealed that cooling down a superconducting cavity under a large spatial temperature gradient decreases the amount of trapped flux and leads to reduction of the residual surface resistance. In the present paper, the flux expulsion ratio and the trapped-flux-induced surface resistance of a large-grain cavity cooled down under a spatial temperature gradient up to 80K/m are studied under various applied magnetic fields from 5E-6 T to 2E-5 T. We show the flux expulsion ratio improves as the spatial temperature gradient increases, independent of the applied magnetic field: our results supports and enforces the previous studies. We then analyze all RF measurement results obtained under different applied magnetic fields together by plotting the trapped- flux-induced surface resistance normalized by the applied magnetic field as a function of the spatial temperature gradient. All the data can be fitted by a single curve, which defines an empirical formula for the trapped- flux-induced surface resistance as a function of the spatial temperature gradient and applied magnetic field. The formula can fit not only the present results but also those obtained by Romanenko et al. previously. Furthermore, the sensitivity rfl of surface resistance from trapped magnetic flux of fine-grain and large-grain niobium cavities and the origin of dT/ds dependence of Rfl/Ba are also discussed.
Book Synopsis Superconducting Surface Impedance Under Radiofrequency Field by :
Download or read book Superconducting Surface Impedance Under Radiofrequency Field written by and published by . This book was released on 2013 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: Based on BCS theory with moving Cooper pairs, the electron states distribution at 0K and the probability of electron occupation with finite temperature have been derived and applied to anomalous skin effect theory to obtain the surface impedance of a superconductor under radiofrequency (RF) field. We present the numerical results for Nb and compare these with representative RF field-dependent effective surface resistance measurements from a 1.5 GHz resonant structure.
Book Synopsis RF Properties of High Temperature Superconductors by :
Download or read book RF Properties of High Temperature Superconductors written by and published by . This book was released on 1990 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: A description of cavities used in the study of the microwave properties of the high-temperature superconductors is followed by a lumped-circuit analysis of the coupling of transmission lines and resonators. The frequency dependence of the reflected and transmitted microwave power and the character of transient cavity response are analyzed. Techniques are discussed for the introduction of samples of the high-temperature superconductors into microwave cavities. Following a discussion of sample surface impedance and sample geometry factor, the connection between surface resistance and cavity Q is examined as well as the connection between cavity frequency shift and surface reactance. Measurement techniques that utilize reflected or transmitted power or transient response are described. 35 refs., 1 fig.
Book Synopsis Proceedings of the Eighth Workshop on RF Superconductivity by : 1997 Abano Terme Workshop on RF Superconductivity
Download or read book Proceedings of the Eighth Workshop on RF Superconductivity written by 1997 Abano Terme Workshop on RF Superconductivity and published by . This book was released on 1997 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Dependence of Surface Resistance on Field Level in Pure Superconductors by : Jürgen Halbritter
Download or read book Dependence of Surface Resistance on Field Level in Pure Superconductors written by Jürgen Halbritter and published by . This book was released on 1970 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Proceedings of the Eight Workshop on RF Superconductivity Vol. II by :
Download or read book Proceedings of the Eight Workshop on RF Superconductivity Vol. II written by and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Measurements of the Rf Surface Resistance of High- Tc Superconductors by :
Download or read book Measurements of the Rf Surface Resistance of High- Tc Superconductors written by and published by . This book was released on 1990 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental program is being conducted to assess the applicability of high-{Tc} superconductors for use in high power rf and microwave devices. The program involves the measurement of the rf surface resistance of high-{Tc} samples at frequencies between 0.15 and 40 GHz and rf surface magnetic fields as high as 640 gauss. Polycrystalline samples were found to have surface resistances which increase monotonically with rf-field amplitude, saturating at high field at a few percent of the normal-state surface resistance just above {Tc}. 13 refs., 2 figs., 1 tab.
Book Synopsis Superconducting DC and RF Properties of Ingot Niobium by :
Download or read book Superconducting DC and RF Properties of Ingot Niobium written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The thermal conductivity, DC magnetization and penetration depth of large-grain niobium hollow cylindrical rods fabricated from ingots, manufactured by CBMM subjected to chemical and heat treatment were measured. The results confirm the influence of chemical and heat-treatment processes on the superconducting properties, with no significant dependence on the impurity concentrations in the original ingots. Furthermore, RF properties, such as the surface resistance and quench field of the niobium rods were measured using a TE011 cavity. The hollow niobium rod is the center conductor of this cavity, converting it to a coaxial cavity. The quench field is limited by the critical heat flux through the rods' cooling channel.
Book Synopsis RF Superconductivity by : Hasan Padamsee
Download or read book RF Superconductivity written by Hasan Padamsee and published by John Wiley & Sons. This book was released on 2009-03-30 with total page 464 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the second book to RF Superconducting, written by one of the leading experts. The book provides fast and up-to-date access to the latest advances in the key technology for future accelerators. Experts as well as newcomers to the field will benefit from the discussion of progress in the basic science, technology as well as recent and forthcoming applications. Researchers in accelerator physics will also find much that is relevant to their discipline.
