RF Performance of Ingot Niobium Cavities of Medium-Low Purity

Conference · Tue Dec 01 04:00:00 EST 2015

OSTI ID:1645109

Ciovati, Gianluigi ^[1]; Dhakal, Pashupati ^[1]; Kneisel, Peter ^[1]; Myneni, Ganapati Rao ^[1]; Spradlin, Joshua K. ^[1]

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1. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)

Superconducting radio-frequency cavities made of ingot niobium with residual resistivity ratio (RRR) greater than 250 have proven to have similar or better performance than fine-grain Nb cavities of the same purity, after standard processing. The high purity requirement contributes to the high cost of the material. As superconducting accelerators operating in continuous-wave typically require cavities to operate at moderate accelerating gradients, using lower purity material could be advantageous not only to reduce cost but also to achieve higher Q0-values, because of the well-known dependence of the BCS-surface resistance on mean free path. In this contribution we present the results from cryogenic RF tests of 1.3-1.5 GHz single-cell cavities made of ingot Nb of medium (RRR=100-150) and low (RRR=60) purity from different suppliers. Cavities made of medium-purity ingots routinely achieved peak surface magnetic field values greater than 70 mT with Q0-values above 1.5·1010 at 2 K. The performance of cavities made of low-purity ingots were affected by significant pitting of the surface after chemical etching.

• 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: 1645109
• Report Number(s): JLAB-ACC-15-2186; DOE/OR/23177-3622
• Country of Publication: United States
• Language: English