Patent ID: 6515408
Filing Date: 2003-02-04
Classification: H01J

Abstract:
Ion beam apparatus comprising:an analysing magnet including a flight tube for receiving and conveying through the magnet a beam of ions, the magnet being operable to generate a substantially uniform magnetic field in the flight tube to deflect beam ions according to their mass/charge ratio in a dispersion plane perpendicular to the direction of said uniform magnetic field; and a thermionic electron source inside the flight tube, arranged adjacent and outside a nominal cross section of a beam of ions travelling through the magnet and extending along a nominal flight path of a beam travelling through the magnet, the thermionic electron source being further arranged such that the projection of the thermionic electron source on the dispersion plane and the nominal projection o n the dispersion plane of an ion beam travelling through the magnet overlap at a plurality of positions along the nominal flight path of the beam.