Simple method for calculating island widths

A simple method for calculating magnetic island widths has been developed. This method uses only that information obtained from integrating along the closed field line at the island center. Thus, this method is computationally less intensive than the usual method of producing surfaces of section of sufficient detail to locate and resolve the island separatrix. This method has been implemented numerically and used to analyze the buss work islands of ATF [Fusion Technol. 1 0, 179 (1986)]. In this case the method proves to be accurate to at least within 20% even though the islands are within a factor of 2 of overlapping.