SU1011032A1 - Ion accelerating tube - Google Patents

Abstract

1. ION ACCELERATING TUBE, containing equipotential baffles with diaphragms on the ion-optical axis of the accelerator tube, on which magnets with gaps for the ion guide are attached, characterized in that, in order to increase the intensity of the accelerated flow, each magnet is made multi-gap with alternating polar poles and enclosed in an electrically conductive shield with holes for accommodating the ion guide, in the middle part of which an additional diaphragm is mounted. 2. A tube of pop, 1, characterized in that, in order to increase its radiation safety, the x i ion line is provided with a shield of radiation protective material. (L garden to

Description

The invention relates to a technique for producing accelerated ion beams in a vacuum, and can be used in accelerator technology, electronic engineering, and solid state physics. A known ion accelerator tube containing concentric, flat electrodes made of magnetic material, magnetized in the direction perpendicular to the plane of the electrode. In this tube due to the effect of magnetic fields in the near-electrode region, the electron load in the tube increases, and its electrical strength increases and, as a result, increases the flow rate is accelerated by ions and the radiation hazard of the tube is reduced. The disadvantage of this accelerator tube is that electrons produced as a result of ionizing the residual gas with an ion beam or stripping negative ions when accelerating negative IONS in the tube can be accelerated to significant energy determined by the electric potential at the place of their origin, t . up to the maximum ion energy. The intensity of the electron current generated in this way is determined by the tube length, the pressure and composition of the gas in it, the energy, the mass, and the charge of the accelerated ions. In accelerators of ionic elements, for example, for ionic immobilization, in industrial semiconductor devices, the required intensities of ionic: fluxes can reach tens of milliamperes, and accelerating voltages 1-2 MB, under unfavorable conditions (pressure, type of accelerated ions) the electron load in the tube can be comparable with the current of accelerated ions. In this case, it is necessary to see that some of the accelerated electron flux will be planted on the electrodes, which can reduce the electrical strength of the tube and makes it impossible to localize high penetrating power. The known ion accelerator tube contains permanent magnets attached to the electrodes with POLAR tips that create an alternating direction transverse to the ion-optical axis and distributed inside the tube along an axis of several hundred kilovolts. In this tube, the magnetic field of the permanent magnets is sufficient to deflect the accelerated electrons to the electrodes of the tube and only slightly deflects the ions. Since the direction of the magnetic flux changes along the tube axis, the ions, when moving in the tube, oscillate in a plane perpendicular to the direction of the ion-optical axis, with an amplitude of several millimeters and a wavelength equal to the distance between the magnets. The disadvantages of the accelerator tube are that: 1) the deviation of the accelerated electrons to the electrodes of the tube leads to a decrease in its electrical strength and significantly limits the magnitude of the accelerated current of ions; 2) the very large maximum electron energy, determined by the maximum potential difference between the nearest unidirectional magnets, increases its radiation hazard; 3) The low gas conductivity of the tube, determined by its length and the size of the hole in the ring magnet, makes it difficult to pump the tube out; 4) the restriction on the magnitude of the magnetic field, due to the permissible deviation of the ion beam, makes it impossible to localize the x-rays and install the local radiation protection. Closest to the invention is an ion accelerator tube containing equipotential baffles having gas conductivity, such as louvre, with holes in the ion-optical axis, in which magnets with gaps are strengthened. The drawbacks of this tube are similar to those indicated above, except for item 3, since there are no fundamental limitations on gas, it has no new conductivity. The disadvantage is also the presence of a diaphragm, which is a source of secondary electrons (secondary ion-electron emission from the edges of the diaphragm), the number of which increases with increasing accelerated ion current. Thus, the diaphragm limits the magnitude of the accelerated current of the ions, and the radiation hazard during the operation of the tube, caused by bombers310

Its electrode electrodes (x-rays) are significant.

The aim of the invention is to increase the intensity of the accelerated flow and increase the radiation safety of the tube.

The goal is achieved by the fact that in an ion accelerator tube containing equipotential partitions with diaphragms on the ion-optical axis of the accelerator tube, on which magnets with gaps for the ion guide are fixed, each magnet is made multi-gap with alternating polarity of pole tips and enclosed in an electrically conductive shield openings for placement of the ion guide, in the middle part of which a diaphragm is mounted.

In addition, the ion guide is equipped with a screen of radiation-shielding material.

At the same time, the magnetic field strength in the gaps of the magnet is much higher than in the prototype and can reach (tenths of tesla, which is ten times more than in the prototype.

Fig, 1 shows a multi-gap magnet; Figure 2 shows the displacement of the ion trajectory at the site of the magnet; Figs. 3 and 4 show accelerator tubes, embodiments.

A three-gap, six-pole magnet 1 consists of two symmetric W-shaped elements, each of which has three pole tips of alternating polarity, with pole tips forming a gap having a different polarity. The magnet 1 is enclosed in a screen 2 of electrically conductive material with entry windows. And the output of the beam is 0. and Ojj, between which the ion conduit 3 is located, in the central part of which is placed the diaphragm 4, the ion conductor 3 is surrounded by an additional screen 5 of radiation-protective material. The threaded ring 6 serves to fasten the magnet with accompanying elements on the equipotential partitions 7 that partition the accelerator tube (Figs. 3 and 4).

In the three-gap magnet (Fig. 1), the magnetic fields in all the gaps are uniform and the same in absolute value, and their direction alternates. Extreme pole tips2

wives are symmetrical with respect to the central pole tip, which is twice as long

along the ion-optical axis of the tube. The cumulative effect of magnetic fields on the ion of the beam manifests itself in the displacement of the ion trajectory at the location of the magnet. For proton with energy

200 keV with the passage of the gaps of the magnet with a field of 0.05 tons and the geometry (Fig.2) (,, 5 cm, 8 cm), the magnitude of the displacement S is 0.6 mm. Electrons with the same energy are deflected to the ion duct 3 (1.5 cm E), the resulting x-ray radiation is mainly absorbed by the screen 5 from the radiation-shielding material. As

ion acceleration, the value of S decreases with, and the maximum electron energy remains unchanged, in the given example, 200 keV. In order to avoid the possible release of electrons from the ion guide

due to the joint action on them

electric and magnetic fields is desirable to 1 - (.1,5-2) a (figure 1). Due to collisions of ions of a beam with atoms (molecules)

of residual gas, and also due to the effect of various kinds of aberrations, some of the ions go beyond the boundary of the formed beam, forming a so-called fur coat. Iona fur coats

may cause secondary electron emission from the end of the screen 2 and the ion guide 3, which is undesirable because it causes an additional electronic load in the tube. To remove the specified t

ions from the beam to the center; Part of the ion guide is introduced by the diaphragm 4, the emission of electrons from the diaphragm into the accelerating tube is impossible, since it is in the equipotential region and in the magnetic field of the central gap, which suppresses the emission of electrons, Unlike the prototype, in the region of ion acceleration of ion-optical tube axis and the beam axis coincide, which contributes to an improvement in the beam quality k, respectively, to a decrease in ion loss. Since the maximum displacement of ions in the ion. the wire is very small (the displacement for heavy ions will be even smaller than for protons), then the correction for the specified displacement when the aperture is set in the ion guide can be ignored. On fig.Z and 4 shows the options usko5101

tube tubes with three-gap magnets located in the equipotential; The arrows indicate the directions of the flow of gas flows through the equipotential partitions, which are opaque to accelerated electrons.

The accelerator tube works as follows. After pumping out the vacuum

Accelerator system of direct action, of which the accelerator tube is a part, turns on the ion source. After the required operating mode of the source is reached, the power elements of the accelerator ion-optical system are turned on, by means of which the beam is pre-formed and the voltage is raised directly on the accelerator tube. as conditions for optimal formation and acceleration of the beam are achieved using magnetically

The separator beam is cleaned of impurity ions and directed to the irradiated sample.

Compared to the prototype, in this ion accelerator tube, the energy of electrons deflected by the magnetic field is halved, their X-ray interaction with the ion conductor is absorbed by a shield of radiation-protective material covering the ion conductor. Radiation hazard

the tubes are drastically reduced, which is essential when placing accelerators of the megavolt range in industrial premises. Po., Compared with the prototype with an increase

The intensity of the accelerated ion beam is several times that the radiation hazard is reduced by several orders of magnitude. nova radiation arising from

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Claims (2)

1. ION ACCELERATING TUBE, containing equipotential baffles with diaphragms on the ion-optical axis of the accelerating tube, on which magnets with gaps for the ion guide are mounted, characterized in that, in order to increase the accelerated flux intensity, each magnet is multi-gap with alternating polarity of the pole tips and enclosed in an electrically conductive screen with holes for placing an ion conductor, in the middle of which an additional diaphragm is installed. 2. A tube according to π, 1, characterized in that, in order to increase its radiation safety, the ion guide is equipped with a screen of radiation-protective material.