A QUADRUPOLE ION-TRAP WITH CYLINDRICAL GEOMETRY OPERATED IN THE MASS-SELECTIVE INSTABILITY MODE

A cylindrical geometry ion trap is used to record mass spectra in the mass-selective instability mode. The geometry of the cylindrical ion t rap has been optimized to maximize the quadrupole held component relat ive to the higher-order field content through held calculations using the Poisson/Superfish code and through experimental variation of the e lectrode structure. The results correspond well with predictions of th e calculations. The trap has been used to record mass spectra with bet ter than unit mass resolution, high sensitivity, and a mass/charge ran ge of similar to 600 Th. Multistage (MS3) experiments have been perfor med, and the Mathieu stability region has been experimentally mapped. The performance of this device compares satisfactorily with that of th e hyperbolic ion trap.