Review of the Frontier Workshop and Q-slope results

Conference · Tue Sep 20 04:00:00 EDT 2005

OSTI ID:850211

Ciovati, Gianluigi

Over the last few years, significant progress has been made to produce field emission free niobium surfaces. Nowadays, the major limitation towards achieving the critical field in radio-frequency (rf) superconducting cavities made of bulk niobium of high purity is represented by the so-called ''high field Q-slope'' or ''Q-drop''. This phenomenon is characterized by a sharp decrease of the cavity quality factor, in absence of field emission, starting at a peak surface magnetic field of the order of 100 mT. It has been observed that these losses are usually reduced by a low-temperature ''in-situ'' baking, typically at 100-120 C for 24-48 h. Several models have been proposed to explain the high field Q-slope and many experiments have been conducted in different laboratories to validate such models. A three-day workshop was held in Argonne in September 2004 to present and discuss experimental and theoretical results on the present limitations of superconducting rf cavities. In this paper, we will focus on the high field Q-slope by reviewing the results presented at the workshop along with other experimental data. In order to explain the Q-drop and the baking effect we will discuss an improved version of the oxygen diffusion model.

• Research Organization: TJNAF (Thomas Jefferson National Accelerator Facility, Newport News, VA)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-84ER40150
• OSTI ID: 850211
• Report Number(s): JLAB-ACC-05-416; DOE/ER/40150-3586
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
BAKING
CRITICAL FIELD
DIFFUSION
FIELD EMISSION
MAGNETIC FIELDS
NIOBIUM
QUALITY FACTOR
SUPERCONDUCTING CAVITY RESONATORS