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Book Superconducting Cavities from High Thermal Conductivity Niobium for CEBAF

Download or read book Superconducting Cavities from High Thermal Conductivity Niobium for CEBAF written by and published by . This book was released on 1991 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Continuous Electron Beam Accelerator Facility (CEBAF) is presently under construction in Newport News, VA. The accelerator consists of approximately 169 meters of 5-cell niobium cavities made from high thermal conductivity niobium with RRR values> 250. Cavities have been manufactured of material from three different suppliers. The material properties like thermal conductivity, residual resistivity and tensile behavior are compared. Results on the performance of these cavities in the presence of high rf fields are reported. Q(sub)0 values as high as 10^10 at 2 K and accelerating gradient of E> 14 MV/m have been achieved.

Book Performance of Superconducting Cavities for CEBAF

Download or read book Performance of Superconducting Cavities for CEBAF written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Continuous Electron Beam Accelerator Facility (CEBAF) is presently under construction in Newport News, Virginia. The accelerator consists of [approx]160 meters of 5-cell niobium cavities manufactured from high thermal conductivity niobium with RRR values> 250. After an initial six-month period of first article manufacturing at a rate of 3 cavities per month, the full production rate of 12 cavities per month was reached in October 1990. These cavities are chemically treated at CEBAF, assembled into hermetically sealed cavity pairs and tested in a vertical configuration prior to installation into the accelerator. The performance of all cavities received from the manufacturer and tested at CEBAF has exceeded CEBAF's design criteria for Q value> 2.4 x 10[sup 9] at 2 K and an accelerating gradient E[sub acc]> 5 MV/m. Q[sub 0] values as high as 10[sup 10] and accelerating gradients of E[sub acc] [ge] 18 MV/m have been achieved.

Book Thermal Transport and Thermal magnetic Breakdown in Superconducting Cavities Made of High Thermal Conductivity Niobium

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:

Book High Gradient Superconducting Niobium Cavities

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.

Book Q Degradation in Superconducting Niobium Cavities May 1991

Download or read book Q Degradation in Superconducting Niobium Cavities May 1991 written by Kenji Saito and published by . This book was released on 1991 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Superconducting Niobium Cavities with High Gradients August 1992

Download or read book Superconducting Niobium Cavities with High Gradients August 1992 written by Peter Kneisel and published by . This book was released on 1992 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Advances in Cryogenic Engineering

Download or read book Advances in Cryogenic Engineering written by Peter Kittel and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 1973 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Hyatt Regency Hotel, Columbus, Ohio was the venue for the 1995 Cryogenic Engineering Conference. The meeting was held jointly with the International Cryogenic Materials Conference. Jim Peeples, of CVI, Inc., was conference chairman. Columbus is the home of the Battelle Memorial Institute, a pioneer in cryogenic materials development; the home of CVI, Inc., and Lake Shore Cryotronics, Inc., two leading manufacturers of cryogenic equipment; and it is the home of Ohio State University, where research on liquid helium has long been conducted. The program consisted of 315 CEC papers, nearly the same number as for CEC-91. This was the second largest number of papers ever submitted to the CEC. Of these, 252 papers are published here, in Volume 41 of Advances in Cryogenic Engineering. Once again the volume is published in two books. This volume includes a number of photographs taken during the awards lunch on July 20, 1995. Photographs have often been taken during the conferences, but they have never been used. The pictures are of the awardees, the conference chairs, and the organizers. They are distributed through out the books on pages that would otherwise have been blank. The pictures can be found on the following pages: 28, 232, 334, 536, 640, 826, 990, 1032, 1202, 1462,1682,1888, and 1994.

Book Energy Research Abstracts

Download or read book Energy Research Abstracts written by and published by . This book was released on 1993 with total page 724 pages. Available in PDF, EPUB and Kindle. Book excerpt: Semiannual, with semiannual and annual indexes. References to all scientific and technical literature coming from DOE, its laboratories, energy centers, and contractors. Includes all works deriving from DOE, other related government-sponsored information, and foreign nonnuclear information. Arranged under 39 categories, e.g., Biomedical sciences, basic studies; Biomedical sciences, applied studies; Health and safety; and Fusion energy. Entry gives bibliographical information and abstract. Corporate, author, subject, report number indexes.

Book Transient High field Behavior of Niobium Superconducting Cavities

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.

Book Effect of Low Temperature Baking on Niobium Cavities

Download or read book Effect of Low Temperature Baking on Niobium Cavities written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A low temperature (100 C-150 C) ''in situ'' baking under ultra-high vacuum has been successfully applied as final preparation of niobium RF cavities by several laboratories over the last few years. The benefits reported consist mainly of an improvement of the cavity quality factor and a recovery from the so-called ''Q-drop'' without field emission at high field. A series of experiments with a CEBAF single cell cavity have been carried out at Jefferson Lab to carefully investigate the effect of baking at progressively higher temperatures for a fixed time on all the relevant material parameters. Measurements of the cavity quality factor in the temperature range 1.37K-280K and resonant frequency shift between 6K-9.3K provide information about the surface resistance, energy gap, penetration depth and mean free path. The experimental data have been analyzed with the complete BCS theory of superconductivity using a modified version of the computer code originally written by J. Halbritter [1] . Small niobium samples inserted in the cavity during its surface preparation were analyzed with respect to their hydrogen content with a Nuclear Reaction Analysis (NRA). The single cell cavity has been tested at three different temperatures before and after baking to gain some insight on thermal conductivity and Kapitza resistance and the data are compared with different models. This paper describes the results from these experiments and comments on the existing models to explain the effect of baking on the performance of niobium RF cavities.

Book Intense Microwave and Particle Beams II

Download or read book Intense Microwave and Particle Beams II written by Howard E. Brandt and published by . This book was released on 1991 with total page 678 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book High Q0 in Superconducting Niobium Cavities

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:

Book Effect of Microscopic Defects on Superconducting Properties of High Purity Niobium Used for SRF Cavities

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.