Electrostatic quadrupole array for focusing parallel beams of charged particles
AssigneeThe United States of America as represented by the United States Department of Energy
InventorJohn Brodowski
Life of this patent
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Abstract
An array of electrostatic quadrupoles, capable of providing strong electrostatic focusing simultaneously on multiple beams, is easily fabricated from a single array element comprising a support rod and multiple electrodes spaced at intervals along the rod. The rods are secured to four terminals which are isolated by only four insulators. This structure requires bias voltage to be supplied to only two terminals and eliminates the need for individual electrode bias and insulators, as well as increases life by eliminating beam plating of insulators.
Claims3
An array of elements forming a quadrupole of the type which applies a strong focusing force to a beam of charged particles, comprising:
- (a) four substantially identical elements, each comprising an electrically conductive support rod and an electrically conductive electrode, the electrode having a longitudinal axis and a cross-sectional area orthogonal to the longitudinal axis which is greater than the cross-sectional area of the rod, the electrode being mounted on and in electrical contact with the rod with the longitudinal axis of the electrode substantially orthogonal to the axis of the rod, the electrodes having planar faces at each end orthogonal to the longitudinal axis of the electrode, and the electrodes being mounted asymmetrically on the rods;
- (b) means for positioning the electrodes in a substantially square array to form a quadrupole with the axes of the electrodes being substantially parallel, the faces of the electrodes being aligned in two planes orthogonal to the longitudinal axes of the electrodes, the rods connected to one pair of opposite electrodes forming a first parallel pair and the rods connected to the other pair of opposite electrodes forming a second parallel pair, the first pair of rods being substantially orthogonal to the second pair and spaced from the second pair due to asymmetrical mounting of the electrodes, the rods being so positioned that no rod will obstruct the passage of a beam through the volume, defined by the quadrupole, wherein the beam may be exposed to strong focusing forces and so that a plan view of the array taken orthogonally to the longitudinal axes of the electrodes would show the sides of the square formed by said electrodes being at an angle of approximately 45 degrees with the rods, the positioning means further comprising:
- (b1) an insulator;
- and
- (b2) first and second conductive terminals, each terminal having two ends, the terminals being electrically and mechanically connected to the first and second pairs of rods respectively and being mechanically joined but electrically insulated at one end by the insulator, whereby the elements are held in position to form the quadrupoles and each of the pairs of opposite electrodes may be connected to sources of electrical potential so that they have opposite polarity.
Dependencies are inferred from the claim text.