Method for assessment of ion beam distribution for tandem electrostatic accelerator at irradiation sample

FIELD: electricity.

SUBSTANCE: method includes removal of residue gas particles ionised by the beam in question in the capacitor electric field, formation of the removed ionised particles in a ribbon beam by means of a slot, deviation of the ribbon beam particles by the capacitor electric field depending on their energy and formation of two-dimensional image of the ion beam in question by means of its delivery to the electro-optical converter consisting of an amplifier based on microchannel plates and luminophor-coated plate and further registration of the optical image by means of a camera-recorder. The optical axis of the camera-recorder is positioned against the display of the beam cross-section image sensor. A test geometrical figure is applied to the sensor display and compared to the reference geometrical figure included into a programmed algorithm of the calculating machine, thereafter adjustment of the camera-recorder is continued till shapes of the test and reference figures coincide.

EFFECT: improving accuracy in assessment of the ion beam distribution.

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The invention relates to accelerators for low and medium energy for various purposes and, in particular, to electrostatic accelerators.

There is a method of estimating the transverse charge distribution in beams of charged particles [RF Patent of Russia №1392645 "Method of measuring the transverse charge distribution in beams of charged particles". Priority from 30.08.1988], including removing ionized investigated by the beam particles and residual gas in the electric field of the capacitor, forming the extracted ionized particles in the ribbon beam through the gap, the deviation of the electric field of the capacitor ionized particles of the ribbon beam, depending on their energy, the formation of two-dimensional image of the cross section of the investigated ion beam, by applying the extracted ribbon beam in the electro-optical Converter, consisting of an amplifier microchannel plate and covered with a phosphor plate, the registration of optical images by using video cameras.

The disadvantage of this method is the relatively low accuracy of estimation of the distribution of the ion beam due to the fixed location of the optical axis of the camera in the center of the screen of the image sensor section of the beam and preset lens with a field of view covering the entire screen of the image sensor brings the I beam, that at small cross-section dimensions of the beam degrades the resolution of the system, and also due to the lack of validation of the accuracy of positioning the camera in front of the screen of the image sensor section of the beam, which may lead to the distortion of the received data.

The technical result is to avoid this drawback, namely to increase the accuracy of the estimated distribution of the ion beam.

To achieve the technical result in the method of estimating the distribution of the ion beam Stripping electrostatic accelerator at the irradiated sample, comprising removing ionized investigated by the beam particles and residual gas in the electric field of the capacitor, forming the extracted ionized particles in the ribbon beam through the gap, the deviation of the electric field of the capacitor ionized particles of the ribbon beam, depending on their energy, the formation of two-dimensional image of the cross section of the investigated ion beam, by applying the extracted ribbon beam in the electro-optical Converter, consisting of an amplifier microchannel plate and covered with a phosphor plate, the registration of optical images using a video camera, features:

- the optical axis of the camera position relative to the screen of the image sensor section puck is;

- the focal length of the camcorder lens to adjust in accordance with the position and size of the ion beam;

- on the screen of the sensor to represent the test geometry;

to start the alignment position of the cameras;

standard geometric figure, embodied in a software algorithm in a computer to compare the test with a geometric figure drawn on the screen of the image sensor section of the beam;

- continue to align the camera to the matching of the shapes of the reference and test geometric shapes.

Technical essence and the principle of the method are explained with the help of the device represented in figure 1-3, with the following symbols: 1 - video; 2 computing machine; 3 - display computing machine; 4 - the image of the cross section of the beam; 5 - ionization sensor image of the cross section of the beam; 6 - plane plates extracts the capacitor of the image sensor section of the beam; 7 - screen image sensor cross-section of the beam.

Figure 1 shows the elements of the system estimate the distribution of the ion beam Stripping electrostatic accelerator at the irradiated sample, figure 2 - illustration of the positioning of the camera and change the focal length of the lens to make full use of the matrix camera and resolution enhancement techniques with the system estimate the distribution of the ion beam, where as in the field of view of the video camera 1 full screen sensor 7; b - in the field of view only the image of the cross section of the beam 4; figure 3 - illustration of the distortion of the recorded image of the cross section of the beam, where : a is the correct position of the camera, the optical axis of the camera perpendicular to the plane of the plates extracts the capacitor sensor 6; b - incorrect position of the camera, the optical axis of the camera not perpendicular to the plane of the plates extracts the capacitor sensor; comparing the obtained image, the distorted image shown by the dotted line.

The way to estimate the distribution of the ion beam Stripping electrostatic accelerator at the irradiated sample includes: extracting ionized residual gas particles in the electric field of the capacitor, forming the extracted ionized particles in a ribbon beam, the deflection electric field of ionized particles ribbon beam depending on their energy and the formation of two-dimensional image of the cross section of the investigated ion beam.

Forming a two-dimensional image of the cross section of the investigated ion beam is carried out by feeding the extracted ribbon beam in the electro-optical Converter, consisting of an amplifier microchannel plate and covered with a phosphor plate.

The resulting distribution is of the cross-section analyzed ion beam is converted into a visible image, which is recorded by a video camera 1.

The optical axis of the camera 1 is positioned relative to the screen of the image sensor section of the beam 7. The focal length of the camcorder lens 1 is set in accordance with the position and size of the investigated ion beam.

On the screen of the sensor depict the test geometry. Reference geometry inherent in the software algorithm computing machine 2, is compared with the test geometrical figure drawn on the screen of the image sensor section of the beam 7.

Continue the alignment of the video camera 1 to the matching of the shapes of the reference and test geometric shapes.

Irradiation of various materials with high-energy ions require strictly controlled and kept at a given level, the main parameters of the ion beam irradiation process.

High requirements to the parameters of the ion beam when performing exposures due to the fact that in the further processing of the irradiated material is divided into parts, each of which must have the minimum possible variance properties from the specified requirements. Thus, dispersion of the energy of accelerated ions when conducting rapid simulation studies of reactor materials should not exceed ±0.5%, and the uneven density distribution of particles over the area of the di sample should not exceed ±10%.

On the path of formation and acceleration of ion beams has many of the ion-optical systems, which affect the output parameters of accelerated ion beams, such as intensity, spatial position and energy. For these reasons, it is necessary to choose the optimal modes of all of the ion-optical systems tract acceleration of ions that provide the desired level settings of the accelerated beams, and maintain them at a specified level during the entire cycle of irradiation samples.

Work to maintain at a given level parameters of the ion beam is substantially complicated by the fact that the process of irradiation of the samples, depending on the specific conditions according to the intensity of the ion beam, can last from a few seconds to days. Interruption of the beam after the start of irradiation is not allowed, so for continuous control of its parameters it is necessary to use non-destructive methods.

An example of a specific implementation can serve as a way to estimate the distribution of the ion beam irradiated on the sample, based on the Stripping electrostatic accelerator EGP-15 IPPE. The residual gas is air. The voltage on the plates extracts capacitor of about 7.5 kV. Geometrical dimensions of the ribbon beam, max: 50×1 mm in size forming a slit). The formation of a double room is REGO image of the cross section of the investigated ion beam is carried out by feeding the extracted ribbon beam amplifier based on a microchannel plate of size 64×42 mm The phosphor ZnS converts the stream of charged particles in the optical image, which is registered analogue black-and-white video camera with a resolution of 600 TVL. Camcorder lens Varifocal.

The optical axis of the camera position relative to the screen of the image sensor section of the beam, the focal length of the camcorder lens is set in accordance with the position and size of the ion beam on the screen of the sensor caused the test geometric shape: rectangle (frame around the screen of the image sensor section of the beam). Then make a comparison test geometric shapes with a reference geometric shape in the form of rectangle.

Computer: PentiumD/2.8 GHz/2 GB of RAM. Software: modified [2].

The position and size of the ion beam: the position is changed in the process of setting accelerator, the shape of a circle or ellipse with dimensions on the axes within 3-10 mm

Alignment of the camera to achieve the absence of distortion of the cross section of the beam, which increases the accuracy of the estimates of the distribution of the ion beam.

Sources of information

1. RF patent for the invention №1462521. Ionization sensor density distribution of the charged particle beam in cross-section. Priority from 08.12.1986.

2. Artemyev, A.N., The'ev N.A., Matushkin ST and other Sirovatka television information on the geometric parameters of the ionizing beam. // Proceedings of the 13th International conference on Electrostatic accelerators of charged particles". Obninsk, may 2000 - Obninsk: jist GS RF IPPE. - P. 246-248.

The way to estimate the distribution of the ion beam Stripping electrostatic accelerator at the irradiated sample, comprising removing ionized investigated by the beam particles and residual gas in the electric field of the capacitor, forming the extracted ionized particles in the ribbon beam through the gap, the deviation of the electric field of the capacitor ionized particles of the ribbon beam, depending on their energy, the formation of two-dimensional image of the cross section of the investigated ion beam, by applying the extracted ribbon beam in the electro-optical Converter, consisting of an amplifier microchannel plate and covered with a phosphor plate, the registration of optical images using a camera, wherein the optical axis of the camera position relative to the screen of the image sensor section beam, the focal length of the camcorder lens is set in accordance with the position and size of the ion beam on the screen of the sensor test is applied geometric figure, begin the alignment position of the camera, reference geometry inherent in the software algorithm computing machine compared to test a geometric figure, plotted on the screen of the image sensor section of the beam, and continue to align the camera to the matching of the shapes of the reference and test of geometric shapes.