RU204393U1 - Device for measuring the spatial characteristics of ionizing radiation beams - Google Patents

Abstract

The utility model relates to accelerator technology and can be used to measure the parameters of ionizing radiation beams: transverse dimensions, shape, transverse profiles, position, divergence, emittance. The device contains scanning elements, clamps, holders, an energy-dispersive X-ray detector, and a linear translator. The scanning elements are made L-shaped and fixed with clamps in holders connected by means of hinged joints with guides, which are also attached to the base with hinged joints, in addition, the device additionally contains a motorized drive that controls the scanning elements. The proposed utility model makes it possible to measure in a simple way the characteristics of ionizing radiation beams: transverse dimensions, transverse profiles, position in space, divergence, emittance.

Description

The utility model refers to accelerator technology and can be used to measure the parameters of ionizing radiation beams: transverse dimensions, shape, transverse profiles, position, divergence, emittance.

Due to the low cost and simplicity of design, wire meshes, wire scanners, and slot scanners are widely used for measuring the profiles of beams of charged and neutral particles.

The known "Method for measuring the parameters of a beam of charged particles" (SU No. 1684829, publ. 15.10.1991). The patent describes a device containing a mask in which slits are made at a certain angle. The measurement of the profiles of the beam of charged particles by the described method occurs when plotting the dependence of the current of the beam passing through the system of slits on its position. The disadvantage of such a system is the high thermal load to which the mask is subjected, which imposes a limitation on the value of the beam current.

The patent entitled "Device for measuring the current density of beams of charged particles" (US No. 3600580A, publ. 17.08.1971) describes a wire scanner designed to measure the transverse profiles of beams of charged particles of high intensity. The base of the scanner is 0.25 mm beryllium wire. The main feature of the device is the high speed of movement of the wire (about 6 m / s) in the direction perpendicular to the beam axis and the fact that the movement of the wire during profile scanning is carried out due to inertia. In the course of scanning, the current generated by the interaction of the investigated beam of charged particles with the scanning wire is measured. The disadvantages of such a device include the complexity of measuring the profiles of beams of charged particles at various points along the beam axis, since in this case it will be necessary to install several such scanners (which is not always possible due to the limitations imposed on the overall dimensions of the device) or the installation of several wires, each of which will have to separately process the signal (which complicates the measurement system).

Also known is the technical solution described in the patent entitled "Monitor for accurate measurement of vertical and horizontal profiles of beams" (US No. 20050068048A1, publ. 03/31/2005). The device is designed to measure a pair of transverse profiles (in mutually perpendicular directions) of a particle beam simultaneously in two places along the beam axis. The possibility of such measurements is provided by rotating four helicoidal wires in the region of the beam passage. In the course of measurements, the dependence of the secondary electron current on the scanner rotation angle is recorded. The disadvantages of such a device include a possible change in the shape of thin wires during scanning, which will distort the measured dependence, as well as the difficulty of increasing the number of points along the axis of the beam in which scanning is performed. In addition, problems can arise when shaping the wires to the desired shape.

Known device (Cutler RI, Mohr JK, Whittaker JK, Yoder NR A high resulution wire scanner beam profile monitor with a microprocessor data acquisition system // IEEE Transactions on Nuclear Science, 1983, Vol. NS-30, No. 4, P. 2213-2215), in which the measurement of a pair of transverse profiles of a beam of charged particles is determined from the secondary electron emission current generated by the interaction of the beam particles with an L-shaped wire. The disadvantages of such a device include the ability to measure profiles only at one point in space and the complexity of signal separation when using several wires in the device.

Known device (Ross MC, Seeman JT, Bong E., Hendrickson L., McCormick D., Sanchez-Chopitea L. Wire scanners for beam size and emittance measurements at the SLC // Conference Record of the 1991 IEEE Particle Accelerator Conference, San Francisco, CA, USA, 1991, vol. 2, pp. 1201–1203) to determine the beam profiles using a photomultiplier tube, the intensity of bremsstrahlung generated in the L-shaped wires is recorded. The disadvantages of such a device include the impossibility of separating signals from different wires and the fact that the bremsstrahlung of relativistic particles is directed predominantly along their velocity; therefore, detectors recording bremsstrahlung radiation have to be installed as close as possible to the beam axis (which can be hindered by the design features of the vacuum system ).

The closest design to the proposed utility model is the device described in the patent "X-ray fluorescent wire scanner of ionizing radiation beam profiles" (RU No. 182076 U1, publ. 07.08.2018). The device consists of a holder, clamps, scanning wires, a linear translator and an energy-dispersive X-ray detector. Measurement of the characteristics of the beam of ionizing radiation in this device is carried out by moving a set of wires of different materials in the direction perpendicular to the axis of the beam. In this case, the energy dispersive detector registers the intensity of the characteristic X-ray radiation generated in the wires, depending on their position. The disadvantages of such a device include the ability to measure the characteristics of the beam in only one plane, which does not allow determining the shape of beams with an asymmetric cross section and their real position in space, as well as the impossibility of changing the position of the wires relative to each other during operation, which significantly complicates the measurements. in the case when the characteristics of the beams change significantly over time.

The general disadvantages of analogs and the prototype include the impossibility of increasing the number of scanning elements without complicating the design of the data acquisition system, as well as the impossibility of simultaneously measuring the main characteristics of the ionizing radiation beam (size, shape, trajectory, divergence, emittance).

The problem to be solved by the proposed technical solution is to create a device that allows simultaneously in two mutually perpendicular planes to measure transverse dimensions, transverse profiles, positions, divergences, emittance of ionizing radiation beams (beams of charged and neutral particles) of any shape according to the characteristics of X-ray radiation, formed in the scanning elements under the action of beams.

The problem is solved with the help of the proposed device for measuring the spatial characteristics of ionizing radiation beams, including scanning elements, clamps, holders, an energy dispersive X-ray detector, a linear translator, and the scanning elements are L-shaped and fixed with clamps in holders connected by means of articulated joints with guides, which are also attached to the base with hinged joints, in addition, the device additionally contains a motorized drive that controls the scanning elements.

The proposed device differs from the one described in the prototype in that the scanning elements made of different materials have an L-shape, as well as the presence of hinged joints and a motorized drive, allowing you to change the position of the scanning elements relative to each other. The L-shaped shape of the scanning elements makes it possible to determine the transverse profiles and dimensions of the ionizing radiation beams corresponding to two mutually perpendicular planes (directions), which makes it possible to evaluate the shape of the beam. In the described prototype, the beam characteristics are measured in only one plane, which makes it possible to use the prototype only when working with axisymmetric beams (round). The presence of articulated joints and a motorized drive allows during measurements to change the distance between the scanning elements and their position relative to each other, which makes it possible to quickly select the optimal measurement geometry when changing the spatial parameters of the ionizing radiation beam, and also provides the ability to carry out measurements at different points located along beam axis, thereby increasing the accuracy of determining its characteristics.

The advantage of the proposed utility model lies in the possibility of simultaneous (in one pass) in two mutually perpendicular planes measuring the transverse profiles of ionizing radiation beams of any shape in different places along the beam axis, where the L-shaped scanning elements are installed, by registering the spectra of the characteristic radiation of the scanning elements, made of different materials, using only one energy-dispersive X-ray detector of X-ray radiation, as well as the ability to determine the position (trajectory), dimensions, divergence, shape and emittance of a beam of ionizing radiation of any shape from the results of measurements.

The technical result consists in the simultaneous measurement of the characteristics of beams of ionizing radiation of any shape: transverse dimensions, transverse profiles, shape, position, divergence, emittance, in two mutually perpendicular planes. This is achieved by placing in several places along the axis of the beam L-shaped scanning elements made of different materials and fixed in holders, the position of which can be changed relative to each other. Holders with scanning elements are mounted on a linear translator capable of simultaneously moving all scanning elements in a direction transverse to the beam axis. The parameters of the beams are determined from the spectra of characteristic X-ray radiation generated by the interaction of the ionizing radiation beam with the scanning elements and recorded by the energy-dispersive X-ray detector.

The utility model is illustrated by a drawing.

FIG. 1 - General view of the proposed utility model

FIG. 2 - General view of the holder with a fixed scanning element

FIG. 3 - Adjustment of the position of the scanning elements using a motorized drive

FIG. 4 - Image of the holder with the attached scanning element

FIG. 5 - Spectra of X-ray radiation generated in scanning elements under the action of a beam

FIG. 6 - Transverse profiles of the ionizing radiation beam measured using the proposed utility model

FIG. 7 - Dependence of the size and shape of the beam on the distance, measured using the proposed utility model

The device (Fig. 1) consists of scanning elements 1, clamps 2, holders 3, energy dispersive X-ray detector 4, guides 5, articulated joints 6 and 8, base 7, motorized drive 9 and linear translator 10.

Scanning elements 1 with clamps 2 are attached to holders 3 (Fig. 2). Scanning elements 1 have an L-shaped shape and can be made or have coatings of various materials with values of characteristic X-ray radiation that do not coincide with each other, which will make it possible to separate the signals from each scanning element 1, recorded by the energy-dispersive X-ray detector 4. Length of each scanning element 1 should ensure the possibility of its fastening by means of clamps 2 in the holder 3, and the thickness should be significantly less than the transverse dimensions of the ionizing radiation beam. Holders 3 are interconnected by means of guides 5 and articulated joints 6. Guides 5 with holders 3 installed on them are attached to the base 7 using articulated joints 8. Articulated joints 6 and 8 allow you to change the relative position of the scanning elements 1 in the holders 3 relative to each other keeping their parallelism (Fig. 3). The position of the holders 3 relative to each other and the angle between the guides 5 and the beam axis is controlled using a motorized drive 9. The base 7 is mounted on a linear translator 10, which ensures the movement of the entire device as a whole in a direction perpendicular to the intended beam axis (directions of the device movement are shown by an arrow in Fig. 1 and 4). An energy-dispersive X-ray detector 4 is used to measure the X-ray spectra (Fig. 5) generated by the interaction of the ionizing radiation beam with the scanning elements 1.

Measurement of the beam characteristics (scanning) using the proposed device is as follows: the assembled device (Fig. 1) is placed on the section of the beam channel, where it is required to measure the characteristics of the ionizing radiation beam. Using a motorized drive 9, the angle between the guides 5 and the beam axis is adjusted (the device at the maximum tilt angles of the guides 5 is shown in Figs. 3a and 3c; Fig. 3b shows the case when the guides 5 are parallel to the beam axis). The angle between the guides 5 and the axis of the ionizing radiation beam determines the distance between the scanning elements 1, measured along the axis of the beam. Further, using the linear translator 10, the holders 3 with the fixed scanning elements 1 are simultaneously displaced in the direction perpendicular to the assumed axis of the beam (as shown by the arrow in Fig. 1) with a predetermined step. In this case, the scanning elements 1 sequentially or simultaneously intersect the beam. Due to the L-shaped shape, the intersection of the beam by the scanning element 1 occurs in two mutually perpendicular planes (Fig. 4). When the beam of ionizing radiation interacts with the scanning elements 1, characteristic X-rays are formed, the spectrum of which at each step of the translator 10 is recorded by an energy-dispersive X-ray detector 4. The energy-dispersive X-ray detector 4 should provide the possibility of measuring spectra in the energy range of characteristic X-rays emitted by each scanning element 1. In scanning time, the dependence of the intensity of the characteristic X-ray radiation on the position of the holders 3 with scanning elements 1 is measured (Fig. 6). This dependence contains the transverse profiles (transverse flux density distributions) of the ionizing radiation beam, measured in two mutually perpendicular planes at the location of a particular scanning element 1. Since the scanning elements 1 are made of different materials, their characteristic radiation has different energies, which makes it possible to separate the signals from each of the scanning elements 1 in the recorded spectra, even in the case of their simultaneous interaction with the beam. The dependences of the characteristic radiation intensity on the coordinate of the holder 3 (or translator 10) obtained for each scanning element 1 make it possible to determine the transverse beam profiles at the locations of the scanning elements 1. Thus, using the utility model in one pass, one can obtain data on the transverse beam profiles measured in mutually perpendicular directions, at different points (the number of these points is determined by the number of scanning elements 1) located along the beam axis. From the measured profiles, it is possible to determine how the size and shape of the ionizing radiation beam change, which makes it possible to calculate the divergence and emittance of the beam. Also, the measured profiles make it possible to establish the real position of the beam relative to the assumed axis.

The proposed device may additionally contain an unlimited number of scanning elements 1 located at any distance, made of various materials. Also, the device allows you to make measurements both in vacuum and at atmospheric pressure. The requirement for the pressure of residual gases in the region of beam propagation is determined by the parameters of this beam (energy and type of particles), and not by the features of the utility model. In the case of measurements at atmospheric pressure, it is necessary to take into account that low-energy X-rays are absorbed in air, which imposes a limitation on the choice of material for the manufacture of scanning elements.

An example of how the device works.

Па. В процессе измерений электромеханический линейный транслятор 10 перемещал все элементы устройства, закрепленные на основании 7, перпендикулярно оси пучка с шагом 0.1 мм. На каждом шаге энергодисперсионный рентгеновский детектор 4 регистрировал спектр характеристического рентгеновского излучения, образующегося в сканирующих элементах 1 (примеры спектров представлены на Фиг. 5). После сканирования строились зависимости интенсивности излучения каждого сканирующего элемента 1 от координаты положения держателя 3. Данные зависимости (Фиг. 6) содержат два пика, соответствующие поперечным профилям пучка, измеренным во взаимно перпендикулярных плоскостях (направлениях), и позволяют определить поперечные размеры пучка

и

и его координаты в местах расположения каждого сканирующего элемента 1. Горизонтальная

и вертикальная

координаты пучка могут быть определены по формулам:The proposed utility model was used to determine the position, shape, size, divergence, and emittance of electron beams with an energy of 10–50 keV, a current of about 1 μA, and a minimum size of about 0.3 mm. As scanning elements 1, we used metal wires 0.1 mm thick, made of titanium, copper, tungsten and platinum, fixed on duralumin holders 3 with screw clamps 2. Using a motorized drive 9, an angle was set between the guides 5 and the assumed beam axis, at which in the process of scanning, the overlap of the beam by scanning elements 1 occurred in turn. To measure the spectra of characteristic X-ray radiation generated in the scanning elements 1 under the action of the beam, we used a semiconductor silicon energy-dispersive X-ray detector 4, capable of measuring emission spectra in the energy range 1–20 keV with a resolution of 130 eV. All elements of the device were placed in a vacuum chamber in which the residual gas pressure was maintained

Pa. In the course of measurements, electromechanical linear translator 10 moved all elements of the device, fixed on base 7, perpendicular to the beam axis with a step of 0.1 mm. At each step, the energy-dispersive X-ray detector 4 recorded the spectrum of characteristic X-rays generated in the scanning elements 1 (examples of the spectra are shown in Fig. 5). After scanning, the dependences of the radiation intensity of each scanning element 1 on the coordinate of the holder position 3 were plotted. These dependences (Fig. 6) contain two peaks corresponding to the transverse beam profiles measured in mutually perpendicular planes (directions), and make it possible to determine the transverse dimensions of the beam

and

and its coordinates at the locations of each scanning element 1. Horizontal

and vertical

beam coordinates can be determined by the formulas:

,

,

,

,

– горизонтальная координата пучка ,Where

- horizontal coordinate of the beam,

и

– положение максимумов пиков интенсивности характеристического рентгеновского излучения (Фиг. 6),

and

- the position of the maxima of the intensity peaks of the characteristic X-ray radiation (Fig. 6),

– вертикальная координата пучка,

- vertical coordinate of the beam,

и

– константы, определяемые при юстировке устройства.

and

- constants determined when adjusting the device.

и

пучка строят зависимости (Фиг. 6), полученные в результате фитирования по формулам:Based on measured dimensions

and

beam dependences are plotted (Fig. 6), obtained as a result of fitting according to the formulas:

,

,

и

– размеры пучка,Where

and

- beam dimensions,

– координата вдоль оси пучка,

- coordinate along the beam axis,

и

– минимальные размеры пучка,

and

- the minimum size of the beam,

,

и

– параметры фитирования.

,

and

- fitting parameters.

The fitting results (Fig. 7) make it possible to determine how the dimensions and shape of the beam change, as well as to calculate the divergences and emittances:

,

,

,

,

,

,

и

– эмиттансы пучка,Where

and

- beam emittances,

и

– расходимости пучка,

and

- beam divergence,

и

– минимальные размеры пучка,

and

- the minimum size of the beam,

и

– параметры фитирования.

and

- fitting parameters.

Application of the proposed device is possible in accelerators of charged particles of low and high energies; in electron, proton and ion microscopes; in systems of electronic and ionic lithography; in ion implantation installations; in systems containing sources of neutral atoms, molecules, X-ray and gamma radiation, and in other devices that use beams of ionizing radiation. The proposed utility model makes it possible to measure in a simple way the characteristics of ionizing radiation beams: transverse dimensions, transverse profiles, position in space, divergence, emittance.

Claims (1)

A device for measuring the spatial characteristics of ionizing radiation beams, containing scanning elements, clamps, holders, an energy-dispersive X-ray detector, a linear translator, characterized in that the scanning elements are L-shaped and fixed with clips in holders connected by means of hinged joints with guides, which are also attached to the base by hinged joints, in addition, the device additionally contains a motorized drive that controls the scanning elements.

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