Ion Trapping

A method of gas-assisted trapping of ions in a target ion trap of an ion trapping assembly comprising a series of volumes arranged such that ions can traverse from one volume to the next, the volumes including the target ion trap, the method comprising:

• filling at least the volume corresponding to the target ion trap with gas;
• applying potentials to the ion trapping assembly such that (i) the potential rises at either end of the target ion trap, thereby forming a potential well in the target ion trap, (ii) any of the one or more gas-filled volumes adjacent the target ion trap are at a higher potential than the target ion trap, and (iii) potential barriers are formed at either end of the ion trapping assembly;
• and
• introducing ions into the ion trapping assembly where they are subsequently reflected by the potential barriers at either end of the ion trapping assembly, thereby traversing the target ion trap repeatedly to settle in the potential well as their energy decreases.

An ion trapping assembly comprising:

• a series of volumes arranged such that ions can traverse from one volume to the next, wherein some of the volumes are adapted to be filled with gas, and wherein the series of volumes include a target ion trap;
• electrodes arranged to carry potentials;
• and
• a controller arranged to set potentials on the electrodes such that (i) the potential rises at either end of the target ion trap, thereby forming a potential well in the target ion trap, (ii) the one or more volumes adapted to be filled with gas adjacent the target ion trap are at a higher potential than the target ion trap, and (iii) potential barriers are formed at either end of the ion trapping assembly.