Internal Surface Roughness Research Articles

Measurements on two Nb superconductive RF cavities

The r-f properties of two Nb cavities tuned to 270 Mc/s were measured. The two mechanically identical cavities were of the capacity-loaded coaxial type and were made of sirtered Nb 99.98% pure. One was unannealed and the other annealed at 1200 deg C for 1 hour. The quality factor Q was measured by the 3 db method up to a currert of 8 ma. In the unannealed cavity the Q was independert of current. In the annealed cavity the Q decreased with increasing current. Internal and external stresses and surface roughness are thought to have a harmful influence on the quality factor. (H.D.R.)

Measurements on a MIS-11 set of the roughness of internal surfaces

Measurements on a MIS-11 set of the roughness of internal surfaces

Attenuation and permeability of ferromagnetic waveguides between 9000 and 9675 Mc/s

Measurements of the attenuations produced by air-filled rectangular waveguides of nickel, mild steel, Mumetal, Radiometal and Rhometal have been made in the frequency range 9000–9675 Mc/s. The permeabilities of the materials have been determined from these measurements and a knowledge of the roughness and resistivity of each waveguide internal surface. The effects of temperature on the h.f. permeabilities have also been studied, and some qualitative results are included on the effect of superimposing a steady magnetic field on the h.f. one.

Attenuation in nickel and mild-steel waveguides at 9375 Mc/s

Measurements of the attenuations produced by air-filled waveguides of nickel and mild steel have been made at a frequency of 9 375 Mc/s. It is shown that the permeability of a ferromagnetic material can be determined from such measurements provided the roughness of the waveguide internal surfaces can be estimated with reasonable certainty. It is found that mild-steel waveguides with machined internal surfaces give attenuations as high as 3.79 db/m, and the figure of 3 is deduced for the permeability of commercially-pure-nickel drawn waveguide.