Accelerator tube electrode for focusing a beam of charged particles

Claim 2

An electrode for use in an accelerator tube, said electrode comprising a conductive member adapted to be attached to said tube and havinG a centrally located aperture for permitting the passage of charged particles therethrough; said conductive member being shaped such that the displacement of the surface thereof from the principal plane of said conductive member at fixed radial distances from the center of said aperture varies sinusoidally and has amplitudes which vary as an increasing function of the value of said radial distance when said radial distance is less than a preselected value.

Claim 3

An electrode in accordance with claim 1 wherein said sinusoidal variation is such that said displacement in a full circle about said aperture is equivalent to two or more wavelengths and the amplitude of said displacement varies substantially as the square of the value of said radial distance when said radial distance is less than said preselected value.

Claim 4

An electrode in accordance with claim 2 wherein said displacement is equivalent to two wavelengths and said preselected value is approximately twice the value of the radius of said centrally located aperture.

Claim 5

An electrode in accordance with claim 1 wherein said displacement can be expressed in a cylindrical coordinate system having its origin at the center of said aperture substantially by the expression Delta z kr2 cos n theta wherein r is the radial distance from said center, theta is the angular position about said center, k is a constant, n is a whole number greater than one, and Delta z is the displacement in a direction substantially parallel to the direction of travel of said particles.

Claim 6

An electrode in accordance with claim 1 wherein said displacement is such as to form a first pair of protrusions being oppositely disposed with respect to said aperture and protruding in the direction of travel of said particles; and a second pair of protrusions intermediate said first pair of protrusions, said second pair of protrusions being oppositely disposed with respect to said aperture and protruding in a direction opposite to the direction of travel of said particles.

Claim 7

An electrode in accordance with claim 5 wherein said first and said second pairs of protrusions are symmetrically disposed about said aperture.

Claim 8

An electrode in accordance with claim 1 wherein said electrode is formed in a cup-shaped configuration.

Claim 9

An accelerator tube for accelerating charged particles passing therethrough, said tube utilizing electrodes in accordance with claim 1, wherein said tube comprises one or more first sections, each said first sections including a set of said electrodes substantially identically oriented with respect to each other for producing a converging lens effect with respect to said charged particles in a first plane and a diverging lens effect with respect to said charged particles in a second plane; and one or more second sections, each said second sections including a set of electrodes substantially orthogonally oriented with respect to the set of electrodes of said first sections for producing a diverging lens effect with respect to said charged particles in said first plane and a converging lens effect in said second plane with respect to said charged particles; said electrodes in each said first and said second sections being spaced at specified distances from each other to form a plurality of spaced equipotential surfaces along the length of said tube.

Claim 10

An accelerator tube in accordance with claim 8 wherein said first and said second sections are alternately positioned along the length of said tube.

Claim 11

An accelerator tube in accordance with claim 8 and further including one or more further sections, each said further section including a set of electrodes which produce substantially no converging or diverging lens effects in either said first or said second planes.

Claim 12

An accelerator tube in accordance with claim 10 wherein said further sections are positioned at the entrance and exit end portions of said tube and said first and second sections are positiOned in the central portion of said tube.

Claim 13

An accelerator tube utilizing electrodes in accordance with claim 1 wherein said electrodes are positioned along the length of said tube and each successive electrode is oriented at an angle less than 90* from its adjacent preceding electrode.

Claim 14

An accelerator tube in accordance with claim 12 wherein said angles between each adjacent pairs of said electrodes are equal.

Claim 15

A system for accelerating charged particles utilizing an accelerator tube in accordance with claim 8 wherein said accelerator tube comprises one said first section mounted at or near the entrance end of said tube to produce a converging lens effect with respect to said charged particles in a first plane and a diverging lens effect with respect to said charged particles in a second plane; and one said second section mounted at or near the exit end of said tube to produce a diverging lens effect with respect to said charged particles in said first plane and a converging lens effect in said second plane; said system further includes a source mounted at the entrance end of said tube for providing a flared input beam of charged particles; whereby an accelerated output flared beam of said charged particles is produced at the exit of said accelerator tube.

Claim 16

A processing system utilizing an accelerating system in accordance with claim 14 and further including means for supplying material to be processed by the impingement of charged particles thereon; and means for moving said processing material into the path of said output flared beam of charged particles whereby said material is processed by the impingement of said charged particles thereon.