ION FUNNEL DEMO

Ion Funnel - Octopole Ion Guide - Digital Ion Trap

This demonstration includes three examples.

In the first example, we study the ion funnel performance. This Demo shows how ions of different m/z (100 ions in each group) travel trough the funnel and then are transmitted into a 3D ion trap.

It is interesting to note here that all ions of 50 Da are lost, about 10% of 150 Da ions are trapped at the RF traps near the exit aperture of the ion funnel, and very low number of ions are trapped in a the ion trap. This is not surprising result, because the trapping efficiency of a 3D trap with direct injection of ions is very low and shows substantial mass discrimination.

In the second example, we include an additional field in the exit of the octopole ion guide. This field has a uniform potential distribution, which can be implemented in practice by a resistive coating of a part of the octopole rods. With a potential of 5V this field produces a potential well at the rear part of the ion guide, where ions are trapped and accumulated.

The third example demonstrates a pulsed injection of ions into the ion trap.

Ions are collected for 10 ms and then injected into the trap by switching the offset voltage. There is no filed in the trap at this stage. The RF field is turned on when ions reach the center of the trap. This method, known as the “Fast RF start-up”, has been invented by researches in Shimadzu Research Laboratory (SRL), Manchester, UK. Now days, Shimadzu Co uses this patented technology in commercial ion trap instruments.

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Last updated 26/12/2019