Preliminary Proton/Electron Mass Ratio using a Compensated Quadring Penning Trap

A new type of compensated Penning trap with the ring electrode split into equal quadrants allows intense unshifted ion cyclotron resonances to be synchronously detected with very small relative linewidths ( 2×{}10^-9). By measuring the cyclotron frequencies of both protons and electrons in the same magnetic field (5 T) and the same trapping volume (10^-7 cm³), a preliminary value of the mass ratio mₚmₑ=1836.15300(25) is obtained with an accuracy that is more than four times greater than any previous direct measurement.