An improved oxygen diffusion model to explain the effect of low-temperature baking on high field losses in niobium superconducting cavities

Journal Article · Sat Jul 01 04:00:00 EDT 2006 · Applied Physics Letters

DOI:https://doi.org/10.1063/1.2220059· OSTI ID:850150

Ciovati, Gianluigi

Radio-frequency (RF) superconducting cavities made of high purity niobium are widely used to accelerate charged particle beams in particle accelerators. The major limitation to achieve RF field values approaching the theoretical limit for niobium is represented by ''anomalous'' losses which degrade the quality factor of the cavities starting at peak surface magnetic fields of about 100 mT, in absence of field emission. These high field losses are often referred to as ''Q-drop''. It has been observed that the Q-drop is drastically reduced by baking the cavities at 120 C for about 48 h under ultrahigh vacuum. An improved oxygen diffusion model for the niobium-oxide system is proposed to explain the benefit of the low-temperature baking on the Q-drop in niobium superconducting rf cavities. The model shows that baking at 120 C for 48 h allows oxygen to diffuse away from the surface, and therefore increasing the lower critical field towards the value for pure niobium.

• Research Organization: TJNAF (Thomas Jefferson National Accelerator Facility, Newport News, VA)
• Sponsoring Organization: USDOE Office of Energy Research (ER)
• DOE Contract Number: AC05-84ER40150
• OSTI ID: 850150
• Report Number(s): JLAB-ACC-05-404; DOE/ER/40150-3571
• Journal Information: Applied Physics Letters, Journal Name: Applied Physics Letters Journal Issue: 02 Vol. 89
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
ACCELERATORS
BAKING
CAVITIES
CHARGED PARTICLES
CRITICAL FIELD
DIFFUSION
FIELD EMISSION
MAGNETIC FIELDS
NIOBIUM
OXYGEN
QUALITY FACTOR