A beam line ion implanter includes an ion source configured to generate an ion beam, a scanner configured to scan the ion beam to produce a scanned ion beam having trajectories which diverge from a scan origin, and a focusing element having a focusing field positioned upstream of the scanner configured to focus the ion beam to a focal point at the scan origin. A method of ion beam tuning includes generating an ion beam, focusing the ion beam to a focal point positioned at a scan origin, and scanning the ion beam to produce a scanned ion beam having trajectories which diverge from the scan origin.