Search Results

Advanced search parameters have been applied.
open access

Where Next with SRF?

Description: RF superconductivity (SRF) has become, over the last ~20 years, the technology of choice to produce RF cavities for particle accelerators. This occurred because of improvements in material and processing techniques as well as the understanding and remediation of practical limitations in SRF cavities. This development effort span ~40 years and Nb has been the material of choice for SRF cavity production. As the performances of SRF Nb cavities are approaching what are considered to be theoretical… more
Date: June 1, 2013
Creator: Ciovati, Gianluigi
Partner: UNT Libraries Government Documents Department
open access

HIGH FIELD Q-SLOPE AND THE BAKING EFFECT

Description: The performance of SRF cavities made of bulk Nb at high fields (peak surface magnetic field greater than about 90 mT) is characterized by exponentially increasing RF losses (high-field Q-slope), in the absence of field emission, which are often mitigated by a low temperature (100-140 °C, 12-48h) baking. In this contribution, recent experimental results and phenomenological models to explain this effect will be briefly reviewed. New experimental results on the high-field Q-slope will be presente… more
Date: November 1, 2009
Creator: Ciovati, Gianluigi
Partner: UNT Libraries Government Documents Department
open access

Study of Etching Pits in a Large-grain Single Cell Bulk Niobium Cavity

Description: Performance of SRF cavities are limited by non-linear localized effects. The variation of local material characters between "hot" and "cold" spots is thus of intense interest. Such locations were identified in a BCP-etched large-grain single-cell cavity and removed for examination by high resolution electron microscopy (SEM), electron-back scattering diffraction microscopy (EBSD), optical microscopy, and 3D profilometry. Pits with clearly discernable crystal facets were observed in both "hotspo… more
Date: November 1, 2009
Creator: Zhao, Xin; Ciovati, Gianluigi; Reece, Charles E. & Wu, Andy T.
Partner: UNT Libraries Government Documents Department
open access

Analysis Of Post-Wet-Chemistry Heat Treatment Effects On Nb SRF Surface Resistance

Description: Most of the current research in superconducting radio frequency (SRF) cavities is focused on ways to reduce the construction and operating cost of SRF-based accelerators as well as on the development of new or improved cavity processing techniques. The increase in quality factors is the result of the reduction of the surface resistance of the materials. A recent test on a 1.5 GHz single cell cavity made from ingot niobium of medium purity and heat treated at 1400 {degrees}C in a ultra-high vacu… more
Date: February 1, 2014
Creator: Dhakal, Pashupati; Ciovati, Gianluigi; Kneisel, Peter K. & Myneni, Ganapati Rao
Partner: UNT Libraries Government Documents Department
open access

Performance of 3-cell Seamless Niobium cavities

Description: In the last several months we have surface treated and cryogenically tested three TESLA-type 3-cell cavities, which had been manufactured at DESY as seamless assemblies by hydroforming. The cavities were completed at JLab with beam tube/flange assemblies. All three cavities performed very well after they had been post-purified with titanium at 1250C for 3 hrs. The cavities, two of which consisted of an end cell and 2 center cells and one was a center cell assembly, achieved gradients of Eacc = … more
Date: November 1, 2009
Creator: Kneisel, Peter K.; Ciovati, Gianluigi; Jelezov, I.; Singer, W. & Singer, X.
Partner: UNT Libraries Government Documents Department
open access

Lorentz force detuning analysis of the Spallation Neutron Source (SNS) accelerating cavities.

Description: The Spallation Neutron Source (SNS) project incorporates a superconducting radio-frequency (SRF) accelerator for the final section of the pulsed mode linac. Cavities with geometrical {beta} values of {beta}=0.61 and {beta}=0.81 are utilized in the SRF section, and are constructed out of thin-walled niobium with stiffener rings welded between the cells near the iris. The welded titanium helium vessel and tuner assembly restrains the cavity beam tubes. Cavities with {beta} values less than one ha… more
Date: January 1, 2001
Creator: Mitchell, Russell R.; Matsumoto, Kay Yuri; Ciovati, Gianluigi; Davis, Kirk; Macha, Kurt & Sundelin, Ronald M.
Partner: UNT Libraries Government Documents Department
open access

Characterization of ingot material for SRF cavity production

Description: In recent years, large-grain/single-crystal niobium has become a viable alternative to the standard fine grain (ASTM grain size>6), high purity (RRR ) niobium for the fabrication of high-performance SRF cavities for particle accelerators. In this contribution we present the results of a systematic study of the superconducting properties of samples obtained from four Niobium ingots (from CBMM, Brazil) of different purity. Measurements of bulk magnetization, surface pinning, critical temperature … more
Date: November 1, 2009
Creator: Mondal, Jayanta; Ciovati, Gianluigi; Kneisel, Peter K.; Myneni, Ganapati Rao & Mittal, K. C.
Partner: UNT Libraries Government Documents Department
open access

Results from Point Contact Tunnelling Spectroscopy and Atomic Layer Deposition

Description: We have shown previously that magnetic niobium oxides can influence the superconducting density of states at the surface of cavity-grade niobium coupons. We will present recent results obtained by Point Contact Tunneling spectroscopy (PCT) on coupons removed from hot and cold spots in a niobium cavity, as well as a comparative study of magnetic oxides on mild baked/unbaked electropolished coupons. We will also describe recent results obtained from coated cavities, ALD films properties and new m… more
Date: November 1, 2009
Creator: Proslier, Th.; Zasadzinski, J.; Ciovati, Gianluigi; Kneisel, Peter K.; Elam, J. W.; Norem, J. et al.
Partner: UNT Libraries Government Documents Department
open access

Surface Treatments of Nb by Buffered Electropolishing

Description: Buffered electropolishing (BEP) is a Nb surface treatment technique developed at Jefferson Lab1. Experimental results obtained from flat Nb samples show2-4 that BEP can produce a surface finish much smoother than that produced by the conventional electropolishing (EP), while Nb removal rate can be as high as 4.67 μm/min. This new technique has been applied to the treatments of Nb SRF single cell cavity employing a vertical polishing system5 constructed at JLab as well as a horizontal polishing … more
Date: November 1, 2009
Creator: Wu, Andy T.; Rimmer, Robert A.; Ciovati, Gianluigi; Manus, Robert L.; Reece, Charles E.; Williams, J. S. et al.
Partner: UNT Libraries Government Documents Department
open access

Superconducting Prototype Cavities for the Spallation Neutron Source (SNS) Project

Description: The Spallation Neutron Source project includes a superconducting linac section in the energy range from 192 MeV to 1000 MeV. For this energy range two types of cavities are needed with geometrical beta - values of beta = 0.61 and beta = 0.81. An aggressive cavity prototyping program is being pursued at Jlab, which calls for fabricating and testing of four beta = 0.61 cavities and two beta = 0.81 cavities. Both types consist of six cells made from high purity niobium and feature one HOM coupler … more
Date: June 1, 2001
Creator: Kneisel, Peter; Brawley, John; Bundy, Richard; Ciovati, Gianluigi; Macha, Kurt; Machie, Danny et al.
Partner: UNT Libraries Government Documents Department
Back to Top of Screen