ions are formed and trapped in the ion cell in the vacuum system the pump is restarted application_number US 17394498 A description referring now to fig3 there is shown a functional block diagram for the ion pump relay control circuit 30 of the present invention circuit 30 includes a source 32 of high voltage typically in the order of 6 5 kv that powers the ion pump 14 b the output of source 32 is connected through the series combination of a switch s 1 in the form of a normally closed nc relay and a resistor r 1 to junction 34 the nc relay s 1 delivers the voltage of source 32 to the ion pump 14 b junction 34 is connected to ground through the series combination of a resistor r 2 and a switch s 2 in the form of a normally open no relay the ion pump 14 b has stray capacitance cs which is shown in dashed lines in fig3 with switch s 1 normally closed and switch s 2 normally open the ion pump 14 b is energized and can continue to maintain the vacuum in the chamber 14 when it is desired to have a new sample gas enter into the chamber 14 the ion pump should be stopped and the stray capacitance cs should be discharged.