Fast rise time, high sensitivity MCP ion detector for low-energy ion spectroscopy

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Abstract
A two-stage MCP ion detector for steady ion currents of the order of some pA and ion pulses of a pulse width between 10 and 500 ns is described. Detector current gain for Ne+ and H2+ ions at an energy of 0.1 to 4 keV was found to be dependent on ion energy and species. In pulse current mode, linearity is maintained up to an output charge density of 1.9 nC cm-2; the detector rise time is below 3.5 ns. For the first time an MCP ion detector is used at an ambient gas pressure of 10-3 Pa to investigate ions emitted by a transient gas discharge. With an appropriate operating voltage the detector operated without degradation of performance for at least 500 hours. First measurements of ion species, ion-energy distribution function, ion current density and pulse shape of the axial ion pulse of a pseudospark discharge were performed.