Measurements of Thermal Conductivity and Kapitza Conductance of Niobium for SRF Cavities for Various Treatments

• Published in: IEEE transactions on applied superconductivity Vol. 17; no. 2; pp. 1310 - 1313
• Main Authors: Aizaz, A., Bauer, P., Grimm, T.L., Wright, N.T., Antoine, C.Z.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: New York, NY IEEE 01.06.2007; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Acceleration; Accelerators; Applied sciences; Capacitive sensors; Conductance; Conducting materials; Conductivity measurement; Electrical engineering. Electrical power engineering; Electronics; Electrostatic, collective, and linear accelerators; Exact sciences and technology; Experimental methods and instrumentation for elementary-particle and nuclear physics; Heat transfer; Holes; Kapitza conductance; Materials; Niobium; Nuclear physics; Particle accelerators; phonon peak; Phonons; Physics; plastic deformations; Plastics; superconducting accelerator cavities; Superconducting materials; Superconductivity; surface treatment; Thermal conductivity; Conducting material; Radio wave; Annealing; Heat treatment; Phonon; Material selection; Linear accelerator; Plastic deformation; Radiofrequency; super- conducting materials; Surface treatment; Kapitza conductance; Cavity; plastic deformations; Charged particle; niobium; Linear colliders; phonon peak; Thermal conductivity; Yield strength; superconducting accelerator cavities; Low temperature
• ISSN: 1051-8223; 1558-2515
• DOI: 10.1109/TASC.2007.897855

Niobium is the material of choice for making the superconducting radio frequency cavities used in present-day accelerators for the acceleration of charged particles. In order to achieve high accelerating gradients for future accelerators such as the linear collider, thermal limitations in Nb cavities play an important role. The effects of plastic deformations due to applied strains on thermal conductivity of Nb in phonon transmission regime as well as on its Kapitza conductance have been studied. The study reveals absence of the phonon peak due to applied strains beyond the elastic limits of the Nb metal as well as reduced Kapitza conductance. This resulted in almost 80% reduction in thermal conductivity of the niobium at 2 K. Low temperature annealing did not recover the phonon peak as was seen before the application of plastic deformations.