A relay control for an ion pump used in a FTICR MS. When it is desired to admit new sample gas into the vacuum system, the high voltage that powers the ion pump is removed from the pump electrode by opening the normally closed relay contact. A normally open contact relay contact is then closed to ground the pump electrodes and discharge any stray capacity. The sample valve is opened momentarily to admit new sample gas and after the ions are formed and trapped in the ion cell in the vacuum system the pump is restarted.