First Results from a Search for Magnetic Monopoles by a Detector Utilizing the Drell Mechanism and the Penning Effect

A search for massive moving magnetic monopoles has been performed with a combined detector of proportional chambers and scintillation counters. Mixed gas of helium and 10% methane was used for the proportional chambers, because ionizations occur by the Drell mechanism and the Penning effect. No candidate for the monopole was obtained during 150 days of live time. The upper flux limit of 7.2×${10}^{-13\mathrm{}}$ ${\mathrm{cm}}^{-2\mathrm{}}$ ${\mathrm{sr}}^{-1\mathrm{}}$ ${\mathrm{s}}^{-1\mathrm{}}$ for monopoles is obtained for the velocity range from $\sim 3\times {10}^{-4\mathrm{}}c$ to $1c$ at a 90% confidence level.