Abstract: A spiral tool path is formed by determining a plurality of relatively low-curvature nested contours that are internal to the boundary of the pocket to be formed, and spiraling between the contours. The spiral tool path includes an orbit that extends from proximate a first one of the contours that extends around a center of the pocket to be formed to proximate a second one of the contours that also extends around the center. The orbit is arranged so that as a ray originating from proximate the center pivots about the center to travel in a first direction along the entire orbit, for a section of the ray extending between the first and second contours, the percentage of the section that extends between the orbit and the first contour continually decreases and the percentage of the section that extend between the orbit and the second contour continually increases.

Abstract: Identification of migratory animals, such as adult fish and the like, by means of implanted coded tags, with tag coding involving one or more higher atomic numbered chemical elements in stable, solid form (elements with atomic numbers 40-42, 44-53, 55-60 and 62-83), the elements being identified in the live animal by selective X-ray irradiation of the implanted tag and spectral analysis of the fluorescent X-ray radiation emitted by the tag. Rapid analysis of the fluorescent X-ray radiation to identify the coding element(s) with a high level of confidence is obtained by use of high intensity irradiation and controlled masking to essentially confine the irradiation to only the tag and the animal tissue immediately surrounding the tag and thereby improve the signal-to-noise ratio of the fluorescent X-ray radiation emitted by the coding element(s).