RADIAL ION-TRANSPORT DUE TO RESISTIVE-WALL DESTABILIZATION IN FOURIER-TRANSFORM MASS-SPECTROMETRY

Destabilization of coherent magnetron motion due to loss of ion energy in resistive external circuit elements is found to result in radial ion transport and ultimately ion loss from the trapped-ion cell of Fourier transform mass spectrometers. In contrast to random-walk diffusion and drift in radial electric fields, the resistive-wall destabilization mechanism described here does not involve collisions and is therefore independent of system pressure. Instead the mechanism prevails when large ion populations exhibit a significant degree of coherent magnetron motion. In this work a simple model to describe the transport effect is derived and is found to relate the rate of transport directly to ion number, external circuit resistance, and applied trapping potential. Experimental data for ions formed by electron ionization are acquired and found to support the model. Under certain conditions ion loss is shown to occur within a few hundred milliseconds which has important implications for quantitative Fourier transform mass spectrometry experiments that include lengthy collisional stabilization or reaction delays.