Superconducting DC and RF properties of ingot Niobium used in SRF cavity fabrication

Conference · Sun Jan 01 04:00:00 EST 2012

OSTI ID:1996013

Myneni, Ganapati; Dhakal, Pashupati; Ciovati, Gianluigi

Bulk niobium (Nb) has been the material of choice for the superconducting radiofrequency (SRF) cavity used in particle accelerator because of its highest transition temperature (Tc) and highest lower critical field (Hc1~ 190 mT) among the elemental type-II superconductors. The overall performance of these SRF cavities is measured by its quality factor, Q0 as a function of the accelerating gradient, Eacc. Higher Q0 for the reduction of cryogenic loss and higher Eacc for the use of high energy accelerators are desired. SRF cavities fabricated from ingot niobium have become a viable alternative to standard high-purity fine-grain Nb for the fabrication of high-performing SRF cavities with the possibility of significant cost reduction. In this contribution, we present the results on DC, low-frequency and RF measurements of Nb rods machined from ingots with different impurity concentrations, provided by CBMM, Brazil. The rods have been subjected to different treatments typically applied to SRF cavities. In addition, single-cell cavities are being fabricated from the same ingot material and initial results on one of them showed high Q0-values at 2 K up to peak surface magnetic fields of about 110 mT. Residual resistance values below 5 n have been consistently achieved on this cavity. A new induction furnace was commissioned for the heat treatment of these single-cells, which allows avoiding subsequent chemical etching of the cavity surface.

• Research Organization: Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP)
• DOE Contract Number: AC05-06OR23177
• OSTI ID: 1996013
• Report Number(s): JLAB-ACC-11-1541; DOE/OR/23177-7019
• Country of Publication: United States
• Language: English