Method for acquiring an image formed using proton radiation

Abstract

The invention relates to a method for acquiring images formed using proton radiation. The essence of the invention consists in performing a preliminary check to establish a match between the parameters of the proton beam generated by a first magneto-optical system and the parameters of a second magneto-optical system, which requires: removing a converter from the first recording system and installing a detector of proton radiation in the Fourier plane of the second magneto-optical system instead of a collimator, where the converter and the collimator are returned to their previous positions before the start of the check; changing the angle of inclination of the phase ellipse of the proton beam generated by the first magneto-optical system in the vertical and horizontal planes while passing the beam through the examination zone and through the second magneto-optical system; recording signals from the detector installed in the Fourier plane; and determining the size of the beam in both planes, where the parameters of the proton beam are parameters matched to the parameters of the second magneto-optical system when the size of the beam is minimal, and the examination is performed using the beam with matched parameters. The quality of the recorded proton images is thus improved.

Description

Technical Field

[0001] This disclosure relates to the field of proton radiation imaging, and in particular to methods for acquiring images formed using proton radiation, which can be used, for example, to study high-speed processes, to examine the behavior of objects, and to determine the structure of said objects under shock wave loads. Background Technology

[0002] Existing techniques are known for methods of acquiring images of high-speed processes formed by proton radiation, for example, at accelerators provided at BNL (Brookhaven National Laboratory, Brookhaven, USA) ["THE PROTON RADIOGRAPHY CONCEPT" H.-J. Ziock, KJ et al. – LA-UR-98-1368] or at LANL (Los Alamos National Laboratory, Los Alamos, USA) ["A narrow-gap ion chamber for beam motion correction in protonradiography experiments"; LJSchultza, et al. – Nuclear Instruments and Methods in Physics Research, A 508 (2003), 220–226]. These methods involve: forming a proton beam generated by a magneto-optical system (MOS); passing the beam through an inspection zone; and acquiring digital images using recording systems positioned upstream and downstream of the inspection zone. As the beam passes over the object being inspected, an image is acquired in the focusing plane of the second MOS (Motion Spectrometer). This eliminates the influence of secondary particles on the image and ensures that protons scattered on the object plane are focused onto a scintillator (image plane) located several meters away. The MOS includes a magnetic lens and a collimator. The second document describes a recording system installed downstream of the inspection area, comprising a transducer (scintillator) that converts proton radiation into visible light, mirrors, optical lenses, and a digital camera. Information regarding the distribution of protons within the beam up to the object being inspected is recorded using an ion chamber divided into four quadrants, upon which the position of the proton beam center is calculated.

[0003] One of the known drawbacks of this method is the fact that the MOS that forms the proton beam in the inspection region provides a proton beam output with a fixed width, while the size of the inspection region may change during the experiment. This leads to inefficient use of the number of protons and a decrease in the quality of the proton image.

[0004] According to patent RU2573178 (published January 20, 2016), there is a known method for acquiring an image formed using proton radiation. This method partially eliminates the shortcomings of prior art solutions. To ensure efficient utilization of protons and improve the quality of the proton image, the method defined in this patent document involves introducing a proton beam into at least one magneto-optical channel, varying the width of the proton beam by different values, and forming a proton beam with phase parameters corresponding to the parameters of the examination region and the MOS parameters using a first MOS; then, the beam is directed to the entrance of a proton imaging complex (PRGC), and the examination region is ray-tested by alternately passing proton strings of different widths; subsequently, the passed proton beam is directed to a second MOS, the second MOS comprising at least two lens systems of different apertures, each group having an aperture corresponding to a proton beam of a certain width, and the lens groups being sequentially placed in a magneto-optical channel. The lens systems form a proton image of the examination region on their image plane.

[0005] Existing technology also discloses adjustments to the MOS to ensure protons are focused onto the image plane, thereby improving the quality of the proton image. Currently, PRGC primarily uses so-called "-1" optics, which consist of four quadrupole lenses symmetrically positioned relative to their intermediate plane, with the collimator positioned within the intermediate plane of the four quadrupole lenses. Other magneto-optical arrangements also exist ["DESIGN AND OPERATION OF A PROTON MICROSCOPE FORRADIOGRAPHY, AT 800MEV", T. Mottershead, D. Barlow et al, Proceedings of the 2003 Particle Accelerator Conference, 2003]. All arrangements used in proton radiography experiments have a so-called Fourier plane (FP), in which the proton beam is redistributed according to the scattering angle: the displacement of a proton relative to the central axis within a specific plane is proportional to the scattering angle of the proton in the object being examined and is independent of the proton's position within the object plane. In other words, protons are "distinguished" (or classified) in the FP according to their scattering angle. Due to this characteristic, and by placing collimators of different diameters in the FP [Flash radiography with 24GeV / c protons, CLMorris et al, JOURNAL OF APPLIED PHYSICS 109, 104905 (2011)], the MOS can be adjusted. When collimators of different diameters are installed in the FP, the form of the total transmittance changes. Therefore, by selecting the collimator of the optimal diameter, the total transmittance can be obtained, minimizing the mass thickness recovery error of a specific object with a specific mass thickness. This makes the proton facility a versatile facility: the same facility can be used to study dust formation processes with characteristic mass thicknesses of hundreds of milligrams per square centimeter, while also studying objects with masses of several hundred grams per square centimeter. In the case of the "-1" optics, the FP is located in the intermediate plane; in other cases, the FP can be located elsewhere.

[0006] When processing images acquired using PRGC, it is assumed that the parameters of the proton beam from the accelerator and guided to PRGC are matched with those of the focusing MOS. This means that the tilt angle of the beam phase ellipse corresponds to the tilt angle of the MOS receiving phase ellipse. In this case, the transmittance of the MOS should remain constant throughout the entire field of view of the PRGC, depending only on the scattering angle of the object being examined. Furthermore, in FP, for a matched beam that is not scattered in the examination area (where the object is not mounted), its size, defined by the emissivity and the beam size in the object plane, should be minimal. However, during experiments, it was found that the beam was not completely blocked by collimators with diameters of 10 mm or 15 mm, because the beam size at the bottom significantly exceeded 15 mm, while the beam size calculated in FP was 5 mm to 10 mm at the bottom. Moreover, practice in proton radiography shows that the transmittance of the MOS varies in different regions of the field of view, resulting in a positive image observed in one region and a negative image (the image of the object is darker or brighter than the background) in another. This means that in a collimator-equipped FP, the proton coordinates are dependent on their coordinates in the object plane (ideally, the proton coordinates in an FP should depend only on the proton scattering angle). This clearly indicates a proton beam mismatch with the MOS. This beam mismatch leads to difficulties in restoring the total transmittance, making beam control in the FP crucial.

[0007] A known method exists for acquiring images generated using proton radiation from the U-70 synchronous phase machine and PRGC installed in the town of Protvino [“Proton radiographic complex with 70 GeV accelerator provided in the SSC IHEP (State Scientific Center–Institute for High Energy Physics)”, Yu.M. Antipov et al, IHEP Preprint 2009-14, 2009]. This method is considered the closest prior art and includes the following operations: forming a proton beam generated by a first MOS and passing it through an inspection zone; passing the proton beam that has passed through the inspection zone through a second MOS; acquiring digital images of the beam before and after passing through the inspection zone using a first recording system and a second recording system; restoring the acquired images to a single viewpoint, and pixel-wise segmenting the second image into a first image to obtain an image of the inspection zone. Each recording system includes a converter (scintillator) for converting proton radiation into visible light, a mirror, and a digital camera (CCD array). The first MOS is installed at the accelerator output, upstream of the PRGC input. The beam, after passing through the inspection area, is obtained within the focusing plane of the second focusing MOS. This eliminates the influence of secondary particles on the image and ensures that protons scattered in the object plane are focused onto the scintillator. The MOS includes a magnetic lens and a collimator. Summary of the Invention

[0008] One problem to be solved in related technologies is obtaining high-quality images of the inspection area.

[0009] The technical results to be achieved using the proposed method are as follows:

[0010] Improve the quality of the recorded proton images to ensure the accuracy of their processing.

[0011] To address this problem and achieve the specified technical result, a method for acquiring an image formed using proton radiation is claimed. The method includes: passing a proton beam formed using a first magneto-optical system (MOS) through an inspection region; passing the proton beam, after passing through the inspection region, through a second MOS, the second MOS including a quadrupole lens and a collimator located in a Fourier plane; acquiring digital images before and after the proton beam passes through the inspection region using two recording systems, each of the two recording systems including a converter that converts the proton radiation into protons recorded by a CCD matrix; and subsequently processing the acquired digital images to obtain an image of the inspection region. The method is characterized by performing a preliminary check to establish parameters of the proton beam generated by the first magneto-optical system. Matching the parameters of the second magneto-optical system requires: removing the converter from the first recording system and installing a proton radiation detector in the Fourier plane of the second magneto-optical system in place of the collimator, wherein the converter and collimator are returned to their previous positions before the inspection begins; changing the tilt angle of the phase ellipse of the proton beam generated by the first magneto-optical system in the vertical and horizontal planes so that the beam passes through the inspection area and through the second magneto-optical system; recording the signal from the detector installed in the Fourier plane; and determining the size of the beam in the two planes, wherein the parameters of the proton beam are matched with the parameters of the second magneto-optical system when the beam size is minimized, and using the beam with the matched parameters for inspection.

[0012] The matching between the proton beam and the MOS ensures that the tilt angle of the beam phase ellipse corresponds to the tilt angle of the MOS receiving phase ellipse, and in this case, the transmittance of the MOS remains virtually constant throughout the entire field of view of the PRGC. Attached Figure Description

[0013] Figure 1 A schematic diagram of the ion-guided portion is shown, which illustrates the content to be protected by the present invention, wherein: 1 is the plane of the object, 2 is the image plane, 3 is the Fourier plane, 4 is the proton radiation detector (scintillator), 5 is the rotating mirror, 6 is the information output window, and 7 is the recording device. Detailed Implementation

[0014] To test the practical applicability of the proposed method, the U-70 synchronous phase machine, which is in operation in the town of Protvino, was studied [News and Problems of Fundamental Physics, No.1(5), 2009, pp.32-42].

[0015] The first MOS, forming the proton beam, is installed at the output of the synchronous phase machine. Next, the PRGC is placed, comprising a chamber for accommodating the object to be examined, a second proton focusing MOS, and two recording systems designed to record the proton image. The first recording system (not shown) is installed before the object is placed and includes a mirror and a scintillator (LSO) that converts proton radiation into protons recorded by a CCD matrix, which, along with lenses, is included in the recording device of the first system. Downstream of the chamber containing the object, a second MOS is installed. The second MOS includes a magnetic quadrupole lens, adjusted according to the calculated energy of the proton beam, and provides focusing of protons from the object plane to the image plane. The currently widely used conventional "-1" optics are used as the MOS, forming an image of the object placed in the object plane at a 1:1 scale in the image plane. The MOS includes four magnetic quadrupole lenses arranged symmetrically relative to the FP, in which a collimator is installed. After the second MOS is placed, the second recording system is positioned, which includes a rotating mirror and a scintillation converter, as well as appropriate recording devices: a lens and a CCD array. For verification, aiming to establish matching between the proton beam and the second MOS, a scintillator is installed within the ion guide plate in the FP located in the middle of the second MOS. This scintillator is configured to be replaced by a collimator before the experiment. The rotating mirror is placed at a short distance from the scintillator, and outputs light through a transparent window to provide external information to the recording devices (lens + CCD matrix).

[0016] Industrial applicability

[0017] Before conducting experiments on the object under inspection, a check was performed to establish a match between the proton beam and the second MOS. For this purpose, the converter was removed from the first recording system, and a proton radiation detector, i.e., a scintillator 4, was installed in the PF3 of the second MOS instead of a collimator. The proton beam passes through the inspection area and the second MOS by changing the tilt angle of the phase ellipse of the proton beam formed by the first MOS in the vertical and horizontal planes. With the aid of a rotating mirror 5 placed next to the scintillator 4 in the second MOS, information is output through the output window 6, and the image is recorded using the recording device 7. The scale of the proton image is recovered based on markings previously applied to the scintillator 4. The dimensions of the beam in the horizontal and vertical planes (e.g., width at half height) are numerically estimated. The parameters of the proton beam are matched to the parameters of the second MOS when the size of the proton beam in the FP is minimized. Furthermore, by installing a converter in the first recording system and replacing the scintillator 4 with a collimator in the second MOS, a proton beam with selected parameters formed using the first MOS passes through the inspection region. Two recording systems are then used to acquire digital images before and after the beam has passed through the inspection region, and the acquired digital images are processed to obtain an image of the inspection region. During processing, the transmittance is recovered.

[0018] The proposed method based on the U-70 "-1" optics provides better images and simplifies their processing by improving the accuracy of transmittance recovery and the sharpness of the acquired images.

Claims

1. A method for acquiring an image formed using proton radiation, the method comprising: The proton beam formed using the first magneto-optical system is passed through the inspection area; The proton beam that has passed through the inspection area is passed through a second magneto-optical system, the second magneto-optical system including a quadrupole lens and a collimator located in the Fourier plane; digital images are acquired before the proton beam passes through the inspection area and after the proton beam has passed through the inspection area by using two recording systems, each of the two recording systems including a converter that converts proton radiation into protons recorded by a CCD matrix; The acquired digital image is then processed to obtain an image of the inspection area; the method is characterized by performing a preliminary check to establish a match between the parameters of the proton beam generated by the first magneto-optical system and the parameters of the second magneto-optical system, the matching requiring the removal of a converter from the first recording system and the installation of a proton radiation detector in the Fourier plane of the second magneto-optical system instead of a collimator, wherein the converter and the collimator are returned to their previous positions before the inspection begins; the proton beam is made to pass through the inspection area and through the second magneto-optical system by changing the tilt angle of the phase ellipse of the proton beam generated by the first magneto-optical system in the vertical and horizontal planes; the signal from the detector installed in the Fourier plane is recorded; and the size of the proton beam in the two planes is determined, wherein when the size of the proton beam is minimized, the parameters of the proton beam are parameters that match the parameters of the second magneto-optical system, and the inspection is performed using a proton beam with matching parameters.

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