Simulation of the collisional cooling effect for binary and ternary buffergas mixtures in a quadrupole ion trap mass spectrometer

Simulation of the collisional cooling effect using binary and ternary buffe r gas mixtures in the ion trap mass spectrometer was performed using the SI MION 6.0 program, in which a 3D collision model was used to describe the io n-buffer gas collisions. Computation of the ion kinetic energy based on the Langevin theory under various conditions was used to account for the effec ts of mixed buffer gases on ion-collisional cooling. The addition of small amounts (8-9%) of one or two heavier target gases (nitrogen, argon or SF6) to the 1 mtorr helium buffer gas in the ion trap can greatly improve the co llisional cooling effects. The kinetic energy of ions can be reduced to clo se to 0 eV. Although the use of ternary buffer gas mixtures can also effect ively improve the collisional cooling effects, the use of binary buffer gas mixtures is the better choice due to convenience and lower cost in real io n trap applications.