Apparatus and method for pulsed mode charge detection mass spectrometry

A method of operating a charge detection mass spectrometer including an electrostatic linear ion trap (ELIT) having a charge detection cylinder positioned between front and rear ion mirrors and an ion trap spaced apart from the front ion mirror, the method comprising:

• generating ions from a sample,
• storing the generated ions in the ion trap,
• controlling the ion trap to release at least some of the stored ions therefrom and travel toward and into the ELIT via the front ion mirror,
• after controlling the ion trap to release stored ions, controlling the rear ion mirror to a reflection state in which the rear ion mirror reflects ions entering therein from the charge detection cylinder back through the charge detection cylinder and toward the front ion mirror, and
• after controlling the rear ion mirror to the reflection state thereof, controlling the front ion mirror to a reflection state in which the front ion mirror reflects ions entering therein from the charge detection cylinder back through the charge detection cylinder and toward the rear ion mirror to trap in the ELIT at least one of the ions released from the ion trap such that the trapped at least one ion oscillates between the front and rear ion mirrors each time passing through and inducing a corresponding charge on the charge detection cylinder,
• wherein a range of mass-to-charge ratios of ions trappable within the ELIT is a function of a distance between the ion trap and the ELIT and on internal axial dimensions of the ELIT.

A charge detection mass spectrometer, comprising:

• an ion source configured to generate ions from a sample,
• an ion trap configured to receive and store the generated ions therein and to selectively release stored ions therefrom,
• an electrostatic linear ion trap (ELIT) spaced apart from the ion trap, the ELIT including first and second ion mirrors and a charge detection cylinder positioned therebetween, and
• means for selectively controlling the ion trap to release at least some of the stored ions therefrom to travel toward and into the ELIT, and for controlling the first and second ion mirrors in a manner which traps in the ELIT at least one of the ions traveling therein and causes the trapped at least one ion to oscillate back and forth between the first and second ion mirrors each time passing through and inducing a corresponding charge on the charge detection cylinder, wherein the first ion mirror faces the ion trap, an ion exit of the ion trap is spaced apart by a first distance from a first end of the charge detection cylinder facing the first ion mirror, and a length of the charge detection cylinder between the first end thereof and a second end of the charge detection cylinder facing the second ion mirror defines a second distance, the first and second distances selected to define a range of mass-to-charge ratio values of ions trappable within the ELIT.

A method of operating a charge detection mass spectrometer including an electrostatic linear ion trap (ELIT) having a charge detection cylinder positioned between front and rear ion mirrors and an ion trap spaced apart from the front ion mirror, the method comprising:

• generating ions from a sample,
• storing the generated ions in the ion trap,
• controlling the ion trap to release at least some of the stored ions therefrom and travel toward and into the ELIT via the front ion mirror,
• at a first delay time after controlling the ion trap to release stored ions, controlling the rear ion mirror to a reflection state in which the rear ion mirror reflects ions entering therein from the charge detection cylinder back through the charge detection cylinder and toward the front ion mirror, and
• at a second delay time after controlling the rear ion mirror to the reflection state thereof, controlling the front ion mirror to a reflection state in which the front ion mirror reflects ions entering therein from the charge detection cylinder back through the charge detection cylinder and toward the rear ion mirror to trap in the ELIT at least one of the ions released from the ion trap such that the trapped at least one ion oscillates between the front and rear ion mirrors each time passing through and inducing a corresponding charge on the charge detection cylinder,
• wherein minimum and maximum mass-to-charge ratio values of ions trappable within the ELIT is proportional to a sum of the first and second delay times.