The radius at which a component is spinning at the end of the period of centrifugation. For a component sedimented from a dilute suspension, it can be equated with radius of rotation at the bottom of the centrifuge tube.
Sources:
PAC, 1994, 66, 897. 'Quantities and units for centrifugation in the clinical laboratory (IUPAC Recommendations 1994)' on page 901 (https://doi.org/10.1351/pac199466040897)
PAC, 1996, 68, 957. 'Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)' on page 965 (https://doi.org/10.1351/pac199668040957)