rods 201 u02dc 203 are disposed in a housing 401 having an arcuate shape with a radius of curvature that is substantially identical to the radius of curvature r it is emphasized that the arcuate shape of the collision cell 400 is merely illustrative and that other over shapes for the collision cell 400 are contemplated notably the collision cell 400 may comprise substantially u2018 straight u2019 rods disposed in a converging arrangement and as described for example in the referenced patent application to j l bertsch et al in accordance with the present teachings rod heating is reduced by reducing the reactive currents flowing in the rods 201 u02dc 303 caused by the rf drive voltages in a representative embodiment reduction of reactive current flow in the rods 201 u02dc 303 is effected by electrically connecting an inductor 402 at substantially the mid length of the rods 201 u02dc 203 and 301 u02dc 303 but not shown in fig4 as described more fully below the inductor 402 creates a parallel l c circuit with the stray capacitance of the rods 201 u02dc 303 an electrical loss effect is due to the series resistance of respective rods 201 u02dc 303 and the reactive current due to the stray capacitance the reactive current without the inductor is approximately i vpp xc assuming the reactance xc is much greater than the resistance of the rods xc gt gt r the rods 201 u02dc 303 can be approximated by a series of lumped element resistors and a capacitor in.