RU-2861375-C1 - MULTICHANNEL COLLIMATOR

RU2861375C1RU 2861375 C1RU2861375 C1RU 2861375C1RU-2861375-C1

Abstract

FIELD: multichannel collimator. SUBSTANCE: invention can be used in devices for forming a gamma radiation beam for gamma radiography, including for pulsed gamma radiography of fast processes. The collimator is made of thin-walled elements forming a coaxial layered structure, forming, when assembled, through conical holes along the radiation path for the passage of direct radiation. Each thin-walled element is a solid body, the outer side, inner, and end surfaces of which are bounded by the lateral faces and bases of regular hexagonal truncated pyramids. The vertices of the complete regular hexagonal pyramids from which the truncated pyramids are formed have a common vertex. Straight grooves are made on the outer side and inner faces of each element along the radiation path. The grooves form the conical holes of the collimator and are formed by conical surfaces, the axes of which converge at one point, which is the focus of the collimator. EFFECT: increasing image contrast by effectively suppressing scattered radiation with minimal loss of information content. 4 cl, 4 dwg

Inventors

Baidarova Natalia Aleksandrovna
KOLESNIKOV ALEKSANDR VIKTOROVICH
Parkhomenko Valerii Petrovich
SELEMIR VIKTOR DMITRIEVICH
Fadeev Vladimir Vitalevich
FOMICHEV VADIM ALEKSEEVICH
Chekunov Oleg Viacheslavovich
SHAMRO OLEG ALEKSEEVICH

Dates

Publication Date: 20260505
Application Date: 20251105

Claims (6)

1. A multichannel collimator for pulse radiography, which consists of thin-walled elements made of a material with a high absorption coefficient of gamma radiation, forming a coaxial layered structure with the formation, when assembled, along the radiation path of through conical holes for the passage of straight-flight radiation, characterized in that each thin-walled element is a solid body, the outer lateral, inner and end surfaces of which are limited by the lateral faces and bases of regular hexagonal truncated pyramids in such a way that the apices of the full regular hexagonal pyramids from which the truncated pyramids are formed have a common apex, while on the outer lateral and inner faces of each element along the radiation path, rectilinear grooves are made, formed by conical surfaces, the axes of which converge at one point, which is the focus of the collimator, and when assembling the collimator, conical holes are formed from the grooves.
2. A multi-channel collimator according to paragraph 1, characterized in that the following relationship is used to determine the distance L between the centers of adjacent openings on the end surface of the collimator, which serves to input radiation:
where d is the diameter of the hole, θ=π/6 for the hexagonal arrangement of the holes in the collimator, β is the transparency coefficient of the collimator, and to determine the distance L H between the centers of adjacent holes on the end surface of the collimator, which serves to output radiation, the following relationship is used:
where f 0 is the distance from the radiation source to the end surface of the collimator used to input the radiation, H is the length of the collimator along the radiation path, and to determine the diameter d H of the holes on the end surface of the collimator used to output the radiation, the following relationship is used:
3. A multi-channel collimator according to paragraph 1, characterized in that the thin-walled elements are manufactured using the wire-cut electrical discharge method.
4. A multi-channel collimator according to paragraph 1, characterized in that the side surface of the collimator allows for the combination of identical collimators into a single structure by joining them along the side surfaces to form a honeycomb structure.

Description

Field of technology to which the invention relates A multichannel collimator is a gamma-ray radiographer, specifically a device that shapes a gamma-ray beam passing through a test object. It can be used in pulsed gamma-ray radiography of fast processes. State of the art The design of a gas-dynamic experiment for studying fast processes in optically dense media using shadow radiography includes a radiation source, a collimator limiting the irradiation field, a research object forming a multi-channel collimator that suppresses scattered radiation and is placed between the research object and the recorder, and a shadow image recorder [V.V. Klyuev et al. Industrial Radiation Introscopy. Moscow: Energoatomizdat, 1985]. When optically dense objects are illuminated with bremsstrahlung, the flux of primary quanta passing through the object and carrying information about the object of study is attenuated by 4-6 orders of magnitude. At the same time, both the object itself and the auxiliary experimental equipment (collimators, shielding, recorder) become a source of scattered radiation. Upon reaching the recording system, this radiation leads to a decrease in the image contrast of the details of the object under study, and, consequently, a decrease in the sensitivity of the gamma-ray method. Collimators of various designs are used to selectively reduce the level of scattered radiation reaching the recording system. The characteristic parameters of such collimators are: the size of the through channels d, the thickness Δ of the absorbing wall between the channels formed from a material with a high absorption coefficient of gamma radiation, the distance L between the centers of adjacent channels, the length of the collimator along the radiation path H, and the raster ratio focal length f 0 , collimator grating pitch h, the value of which is expressed through the sum of the channel size d and the thickness of the adjacent absorbing layer: The channels can be represented as capillary openings along the radiation path, thin plates, shells, segments, etc., through which direct-flight radiation passes, while absorbing layers between the channels serve to absorb scattered radiation. Thus, a periodic grating with a pitch h and a transparency for scattered radiation characterized by a transmittance coefficient β is formed. The multichannel collimator is designed to work with bremsstrahlung, a photon energy range from 1 to approximately 100 MeV. This energy range encompasses both hard X-rays and gamma radiation. Therefore, from here on, the terms bremsstrahlung, X-rays, and gamma are used to denote the energy ranges mentioned. A multichannel collimator for reducing the level of scattered radiation is known at the 20 MeV gamma-ray imaging facility DARHT (Los Alamos, USA). See [S.A. Watson et al. Design, fabrication and testing of a large anti-scatter grid for megavolt γ-ray imaging. Nuclear Science Symposium Conference Record, 2005 IEEE, vol. 2on]. The collimator is a layered structure made of a material with a high absorption coefficient of bremsstrahlung with the formation of through channels in the form of holes for the passage of straight-through radiation, diverging along conical guides along the radiation path. The layered structure is assembled from thin plates made from a mixture of tungsten powder and epoxy resin. The resulting grating is 450 mm in diameter, 400 mm thick, weighing approximately 1 ton, and contains approximately 135,000 holes with a diameter of 0.9 mm. Each plate is manufactured using powder casting using molding templates. The resulting blanks are carefully inspected for defects and then glued together into a stack. The collimator has a large raster ratio of r=H/d=480, which, according to available information obtained in real experiments, reduces background radiation by a factor of 84. The stack of thin plates is perforated with through-channels in the form of holes with a diameter of 0.9 mm, precisely replicating the structure of a fan-shaped beam of straight-through radiation, thereby allowing it to pass unimpeded through the collimator without generating secondary radiation. The disadvantage of the described device is the reduced absorption coefficient of bremsstrahlung due to the use of a mixture of tungsten powder with epoxy resin in the manufacture of the collimator, which reduced the average density of the blanks to 11.8 g/ cm3 compared to the density of pure tungsten of 19.3 g/ cm3 , and as is known, the higher the density of the material, the higher the absorption coefficient of bremsstrahlung. A collimator for hard X-ray radiation is also known [Patent No. 2706219 of the Russian Federation IPC H01J 35/14. Collimator for hard X-ray radiation. Yu. P. Kuropatkin et al. Published 11/15/2019. Bulletin No. 32]. In the known invention, the collimator body is formed by a set of plates of thickness d k made of a material with a high absorption coefficient of bremsstrahlung, for example, tantalum or tu