Abstract: A method determines ion beam emittance, i.e., the beam current density based on position and angle, in a charged particle transport system. The emittance is determined from variations in the current measured in a slot Faraday or sample cup as a straight-edged mechanism traverses the beam upstream of the sample cup in a direction perpendicular to the orientation of the slot Faraday and the straight-edged mechanism, which also can be the direction in which the emittance is determined. An expression in terms of the beam current density can be determined for the derivative of the sample current with respect to position of the mechanism. Depending on the angular spread of the beam reaching the sample cup, the density can be determined directly from the derivative, or can be determined using a least squares analysis of the derivative over a range of mechanism positions.

Abstract: A method determines ion beam emittance, i.e., the beam current density based on position and angle, in a charged particle transport system. The emittance is determined from variations in the current measured in a slot Faraday or sample cup as a straight-edged mechanism traverses the beam upstream of the sample cup in a direction perpendicular to the orientation of the slot Faraday and the straight-edged mechanism, which also can be the direction in which the emittance is determined. An expression in terms of the beam current density can be determined for the derivative of the sample current with respect to position of the mechanism. Depending on the angular spread of the beam reaching the sample cup, the density can be determined directly from the derivative, or can be determined using a least squares analysis of the derivative over a range of mechanism positions.