Experimental studies of the microwave properties of 8. 6 gHz superconducting niobium, niobium--tantalum, and tantalum cavities
Measurements on the surface impedance of superconducting Nb, Ta and on Nb(30%)--Ta(70%) alloy are reported. The surface resistance and the change of surface reactance were measured from 1.3K up to their respective transition temperatures and compared with computer calculations based on the Mattis-Bardeen expressions. The reduced energy gaps were found to be 3.70 +- 0.02 for Nb, 3.55 +- 0.02 for Ta, and 3.61 +- 0.03 for the Nb--Ta alloy. The electron mean free paths were 500 AA 1500 AA, and 70 AA respectively. Penetration depth measurements show that the temperature dependence of the energy gap is described by the BCS theory rather than the cosine gap. Unloaded Q values of 1 x 10/sup 10/ for Nb, 5 x 10/sup 7/ for Ta, and 2 x 10/sup 8/ for Nb--Ta were achieved. Peak rf magnetic field strengths of 104 Oe in a Ta cavity and 35 Oe in a Nb--Ta cavity were attained. The influence of trapped magnetic flux on the microwave surface resistance and reactance of niobium is reported.
- OSTI ID:
- 7212026
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
SUPERCONDUCTING CAVITY RESONATORS
PERFORMANCE TESTING
BCS THEORY
ENERGY GAP
MAGNETIC FIELDS
MATHEMATICAL MODELS
MICROWAVE RADIATION
NIOBIUM
NIOBIUM ALLOYS
QUALITY FACTOR
SURFACE PROPERTIES
TANTALUM
TANTALUM BASE ALLOYS
ALLOYS
CAVITY RESONATORS
ELECTROMAGNETIC RADIATION
ELEMENTS
METALS
RADIATIONS
REFRACTORY METALS
SUPERCONDUCTING DEVICES
TANTALUM ALLOYS
TESTING
TRANSITION ELEMENTS
420201* - Engineering- Cryogenic Equipment & Devices