CS229250B1 - Electric quadruipole for transport of charged particles - Google Patents

Abstract

The invention relates to an electric quadrupole for transporting charged particles over an arbitrary distance. The essence of the device according to the invention lies in the fact that the electrodes are arranged in the shape of a four-turn helix, while the cavity defined by the helix forms a rectangular space, the value of the ratio of the helix pitch to the radius of the cross-sectional area of the working space is given by the relation 6 < j < /40. / , where L is the pitch of the helix, r is the radius of the cross-section of the working space, V is the voltage with which the transported particles were accelerated, and V is the voltage on the quadrupole electrodes. Furthermore, the center of this electrostatic quadrupole can be curved in the longitudinal direction, with the radius of curvature being equal to at least 10 times the radius of the cross-section of the working space. The electric quadrupole can be used for the effective transport of an ion beam over any distance, e.g. when injecting ions into charged particle accelerators, in mass separators, etc.

Description

The invention relates to an electric quadrupole for transporting charged particles over any distance.

The prior art methods for transporting charged particles over long distances compared to the focal lengths of ion-optical elements employ a series of electric or magnetic lenses, the arrangement and parameters of which are usually selected such that the object-image imaging condition is filled several times along the transport axis. This achieves high-quality lossless ion transfer within the acceptance of the ion-optical device. The disadvantage of this method is the relative complexity of the equipment required and its large transverse dimensions, especially when using magnetic elements.

These drawbacks are resolved electrically by the quadrupole of the invention, which consists of four voltage electrodes, the cross section of which is preferably circular or rectangular.

The principle of the device according to the invention consists in that the electrodes are arranged in the shape of a four-way helix, wherein the helical cavity delimits the working space, the value of the helix to radius ratio at the cross section of the working space is given by. r is the cross-sectional radius of the working space, is the voltage by which the transported particles were accelerated, V _Q is the voltage at the quadrupole electrodes. Further, the center line of the electrostatic quadrupole may be curved in the longitudinal direction, the radius of curvature being out of the order of at least 10 times the radius of the cross-section of the working space.

229 250

The quadrupole electrodes according to the invention, which consist of a conductor of a simple, eg circular or rectangular cross-section, are subjected to alternating voltages of alternating polarity. transported particles. According to the analytical calculations, the maximum stabilizing effect can be expected in the following relations between the radius of the cross-section of the working space r, the helix L, the potential at quadrupol + V _Q electrodes and the voltage V, which accelerated the transported particles:

L = H r

In this case, the expected acceptance of S. quadrupol is equal to:

S with 200 r / mm. Rad; mm /.

The axis of the electric quadrupol may not be completely straight.

The permissible radius of curvature of the axis at which the reduction in acceptance is not yet substantial is of the order of 1.10 r. Reducing the radius of curvature below this value will lead to a reduction in quadrupol acceptance.

Main advantages of electr. The quadrupol for long-range accelerated ion transport according to the present invention consists in its simplicity, small transverse dimensions due to the compactness of the structure, and in that neither the acceptance nor any of these advantages is dependent on the length of the quadrupol, The quadrupol may be curved within certain limits.

The electrical quadrupole of the invention is shown in elevation in Fig. 1, while Fig. 2 is a cross-sectional view of the line A-A perpendicular to the longitudinal dimension of the quadrupol.

The quadrupole according to the invention shown in front view in FIG. 1 consists of four electrodes 1, which are arranged in the shape of a four-way helix, in the cavity of which there is a working space

229 250

Giant. 2 is a cross-sectional view of the quadrupole in the plane A-A perpendicular to its longitudinal dimension where its four electrodes J define the cavity forming the working space

The electrical quadrupole can be used to efficiently transport a charged particle beam over any distance (e.g., when injecting ions into charged particle accelerators, mass separators, etc.).

Example

An electric quadrupol according to the invention was produced, whose geometric parameters are: r = 5.5 mm, L = 77 mm, the diameter of the conductor from which the electrodes are made is equal to 5 mm. For transported proton energy of 30 keV and electrode voltage V _Q = 4.5 kV, the calculated acceptance is 1100 mm.mrad.

Claims (2)

SUBJECT OF THE INVENTION 229 250 An electrically quadrupole for transporting charged particles comprising four voltage electrodes, the cross-section of which is preferably circular or rectangular, characterized in that the electrodes (1) are arranged in the form of a four-screw helix, the helical cavity delimiting a working space (2). The ratio of helix pitch to the working area cross-section radius is given by 6 <. where L is the helix pitch, r is the working area cross-sectional radius, V., is the voltage with which the transported particles were accelerated, and V _Q is the voltage to the quedrupole electrodes. An electric quadrupole according to claim 1, characterized in that its center line is curved, wherein the radius of curvature is of the order of at least 10 times the radius of the cross-section of the working space (2).