Abstract: A method for ion activation in an ion guide that comprises a first section and a second section, the second section having a longitudinal axis, the method comprising steps of: receiving ions into the first section of the ion guide at a trajectory that is offset from the longitudinal axis; applying a DC potential gradient in the first section along a dimension that is at a non-zero angle to the longitudinal axis to direct the ions towards the second section and to cause ion activation; and applying an RF field in the second section of the ion guide to confine the ions to the ion guide.

Abstract: Provided herein are methods and systems for controlling the number of ions in a batch of ions accumulated in an ion trap. The ion trap comprises one or more detection electrodes configured to detect image current signals from ions accumulated within the ion trap. An ion or group of ions passed to the ion trap is caused to impact upon one or more of the detection electrode(s) of the ion trap so as to provide a detected signal. An ion current or charge of the ion or group of ions is determined from the detected signal, and the determined ion current or charge of the ion or group of ions is used to control the number of ions in a batch of ions subsequently accumulated in the ion trap.