Cryogenic testing of the 2.1 GHz five-cell superconducting RF cavity with a photonic band gap coupler cell

• Published in: Applied physics letters 2016-05, Vol.108 (22)
• Main Authors: Arsenyev, Sergey A., Temkin, Richard J., Haynes, W. Brian, Shchegolkov, Dmitry Yu, Simakov, Evgenya I., Tajima, Tsuyoshi, Boulware, Chase H., Grimm, Terrence L., Rogacki, Adam R.
• Format: Article
• Language: English
• Subjects: BEAM CURRENTS; CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; CRYOGENICS; DAMPING; GHZ RANGE; INSTABILITY; LIGHT SOURCES; LINEAR ACCELERATORS; NIOBIUM; PARTICLE ACCELERATORS; RADIOWAVE RADIATION; SUPERCONDUCTING CAVITY RESONATORS; TESTING
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.4953204

We present results from cryogenic tests of the multi-cell superconducting radio frequency (SRF) cavity with a photonic band gap (PBG) coupler cell. Achieving high average beam currents is particularly desirable for future light sources and particle colliders based on SRF energy-recovery-linacs (ERLs). Beam current in ERLs is limited by the beam break-up instability, caused by parasitic higher order modes (HOMs) interacting with the beam in accelerating cavities. A PBG cell incorporated in an accelerating cavity can reduce the negative effect of HOMs by providing a frequency selective damping mechanism, thus allowing significantly higher beam currents. The multi-cell cavity was designed and fabricated of niobium. Two cryogenic (vertical) tests were conducted. The high unloaded Q-factor was demonstrated at a temperature of 4.2 K at accelerating gradients up to 3 MV/m. The measured value of the unloaded Q-factor was 1.55 × 10{sup 8}, in agreement with prediction.