Precision High Voltage Platform for Accelerators and Ion Mass Analysis

In nuclear physics experiments, high voltage platforms are fundamental both for initial acceleration of ions and for mass spectrometers of exotic nuclei. These devices require a well defined beam energy, that poses challenging requests to high voltage design, rising the question of which electrode design rules are necessary for a stable voltage operation, since tolerable energy rms relative fluctuation are in the 10 -5 order. Dependence of mass resolution from several platform component perfomance is discussed, including the ion source specifications, the ion beam emittance and the platform voltage stability, related to ripple from power supplies, and to microdischarges, whose possibility is to be suppressed with accurate electrode and acceleration tube design. In the example of the High Resolution Mass Spectrometer under construction in Legnaro, a comparatively moderate voltage V p ? 120 kV together with a reduced energy spread (and emittance) in the injection line gives the desired mass resolution of 1 : 20000, as shown by theory and simulation; some platform features are also described.