SEARCH FOR MULTIPLY CHARGED DIRAC MAGNETIC POLES

A 265 000-G pulsed magnetic field and plastic track detectors have been used in an attempt to extract and observe magnetic monopoles from manganese nodules formed on the floor of the Southern Ocean. Because of their low growth rate, these nodules compress a long period of possible monopole trapping (300000 years) into small volumes of material, making possible in this search an (area)×(time) factor of 3×1014 cm2-sec. The detector system has the merit of containing zero background, making possible a sensitivity such that any multiple of Dirac's original charge of up to 120 could have been detected. The absence of monopoles in the material searched sets new limits on the abundance of multiply-charged monopoles and of monopoles that are too massive (>3mproton) to have been produced in previously reported accelerator experiments. The results imply that at no energy up to at least 2×1017 eV are the primary cosmic rays dominantly composed of magnetic monopoles. © 1969 The American Physical Society.