A device for measuring high-energy short-pulse X-ray energy spectrum and spectrum interpretation method thereof

Abstract

The present invention relates to a device for measuring energy spectra based on the transmission-absorption method and a spectrum interpretation method thereof. This invention aims to solve the problem in the prior art that when a stacked filter arrangement is used for energy spectrum measurement, the energy spectrum measuring device cannot easily obtain an accurate relationship between the energy deposition of the absorber and the energy of the incident photon. Existing spectrum interpretation methods have several problems. The accuracy of the initial energy spectrum required by the iterative method, the perturbation method, and the expected maximum method will greatly affect the solution effect. The singular value decomposition method cannot provide a solution that conforms to the actual situation when the measurement error is large and the energy range to be solved is large. The present invention provides a device for measuring the energy spectrum of high-energy, short-pulse X-rays and a spectrum interpretation method thereof. The device adopts an array filter-absorber arrangement, making it easy to calculate the relationship between the energy deposition of the absorber and the energy of the incident photon. Furthermore, the spectrum interpretation method provides an energy spectrum interpretation method based on Tikhonov regularization, which can obtain more precise energy spectrum results by merging multiple sets of solutions and making corresponding corrections.

Description

Technical Field

[0001] The present invention relates to a device for measuring energy spectrum based on a transmission-absorption method and a spectrum interpretation method thereof, and relates to a device for measuring high-energy short-pulse width X-ray energy spectrum and a spectrum interpretation method thereof. Background Art

[0002] The energy spectrum is the primary indicator of the radiation characteristics of a radiation source. Energy spectrum measurement techniques for high-energy, short-pulse X-rays have important applications in fields such as flash photography. Currently, the main feasible energy spectrum measurement techniques include absorption, Compton scattering, filter-fluorescence, multichannel analysis, and bent-crystal Bragg diffraction. Of these, absorption is the simplest, most cost-effective, and applicable over a wide energy range.

[0003] Energy spectrum measurement devices based on absorption methods typically use a radiation fluence detector (PIN diode) or a thermoluminescent dosimeter (hereinafter referred to as a dosimeter) as the absorption material, combined with different absorption filter combinations to obtain a series of radiation source transmission intensities. Combined with the energy deposition of photons in different energy ranges in the dosimeter, a linear equation system can be constructed with the energy spectrum data as the vector to be solved. PIN diodes easily saturate under experimental conditions with high radiation dose rates, preventing effective measurement signals. Therefore, they must be placed far from the radiation source, significantly increasing the size of the measurement device. Dosimeters do not have this limitation and can be placed closer to the radiation source. However, current absorption spectrum measurement devices using dosimeters typically employ a stacked arrangement, with filters and dosimeters stacked alternately. This results in a complex attenuation process for radiation reaching the rearmost dosimeter, making it difficult to accurately determine the relationship between the energy deposition of the dosimeter and the incident photon energy. Furthermore, the linear equation system obtained by the absorption method often exhibits highly ill-conditioned characteristics. Existing spectrum solution methods include direct inversion, iterative methods, perturbation methods, expectation maximum methods, and singular value decomposition. The direct inversion method is difficult to implement when the system of equations is highly ill-conditioned; the iterative method, perturbation method and expected maximum method require the provision of an initial energy spectrum, and the accuracy of the initial energy spectrum will greatly affect the solution effect; the singular value decomposition method still cannot give a solution that conforms to the actual situation when the measurement error is large and there are many energy segments to be solved. Summary of the Invention

[0004] The present invention aims to address the difficulty of measuring energy spectra using the stacked filter arrangement absorption method. The energy spectrum measurement device cannot accurately determine the relationship between the energy deposition of the absorber and the energy of the incident photon. Furthermore, existing spectrum decomposition methods have several problems, such as the difficulty in implementing direct inversion; the accuracy of the initial energy spectrum required by iterative methods, perturbation methods, and expected maximum methods, which greatly affects the solution effect; and the inability of the singular value decomposition method to provide a solution that conforms to actual conditions when the measurement error is large and the energy range to be solved is large. The present invention provides a device for measuring the energy spectrum of high-energy, short-pulse X-rays and a spectrum decomposition method thereof.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a device for measuring high-energy, short-pulse-width X-ray energy spectra, comprising a thermoluminescent dose sheet loading box, a metal foil, and a filter cover;

[0007] The front surface of the thermoluminescent dose sheet loading box is provided with a dose sheet placement slot group, the dose sheet placement slot group is at least four and is arranged in n×n rows, where n is an integer greater than or equal to 2; the dose sheet placement slot group includes a plurality of dose sheet placement slots;

[0008] The front surface of the metal foil is provided with a filter and a blank area, the thermoluminescent dose sheet loading box is fixed to the rear surface of the metal foil, and the front surface of the thermoluminescent dose sheet loading box faces the rear surface of the metal foil, a+1=n 2 , the filter discs and blank areas correspond to the positions and sizes of the dosage disc placement slots respectively; the types of the filter discs are the same as the number of the filter discs;

[0009] The filter cover is provided with a first through hole running through the front and back, and a plurality of barriers are provided in the first through hole for dividing the first through hole into a plurality of sub-areas; the metal foil is fixed to the rear surface of the filter cover, and each filter and blank area are respectively located in each sub-area, and the filter and blank area are respectively adapted to the corresponding sub-area.

[0010] In a second aspect, the present invention further provides a spectrum interpretation method for an apparatus for measuring a high-energy short-pulse X-ray energy spectrum, comprising the following steps:

[0011] S1, using at least two energy bands to divide different E, where E is a vector composed of equivalent monoenergetic photon energies in each energy band of the energy spectrum;

[0012] S2, use simulation software to obtain the response matrix R corresponding to E;

[0013] S3, solve the linear equations corresponding to different E by the following method, and obtain the solution I corresponding to different E:

[0014] Solve the following linear system using the Tychonov regularization method with nonnegative solution constraints:

[0015] R 11 I1+R 12 I2+R 13 I3+…+R 1(n-1) I n-1 +R 1n I n =D1

[0016] R 21 I1+R 22 I2+R23 I3+…+R 2(n-1) I n-1 +R 2n I n =D2

[0017] R 31 I1+R 32 I2+R 33 I3+…+R 3(n-1) I n-1 +R 3n I n =D3

[0018] …

[0019] R i1 I1+R i2 I2+R i3 I3+…+R ij I j ++…+R i(n-1) I n-1 +R in I n =D i

[0020] …

[0021] R n1 I1+R n2 I2+R n3 I3+…+R n(n-1) I n-1 +R nn I n =D n

[0022] Among them, R ij is the photon energy E of the dose plate after the i-th filter j The response is in rad / photon; I j is the photon energy E j The corresponding number of photons; i = 1, 2, ..., n, j = 1, 2, ..., n; n is the number of dose tablets; D i is the average absorbed dose value of the dose sheet after the i-th filter;

[0023] S4, merging the parts of the solutions obtained in step S3 divided according to the preset fineness to obtain a final energy spectrum solution.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. This invention proposes a device for measuring the energy spectrum of high-energy, short-pulse X-rays. This device utilizes an arrayed filter-absorber arrangement, simplifying the photon transmission and absorption path and making the relationship between absorber energy deposition and incident photon energy easy to calculate. The filter cover utilizes a corresponding blocking structure to reduce scattering and crosstalk. Using this device, an accurate relationship between absorber energy deposition and incident photon energy can be easily determined.

[0026] 2. In the present invention, when the thermoluminescent dose sheet loading box, metal foil and filter cover are connected, screws are only provided at three corners, which can determine the angular position relationship between the thermoluminescent dose sheet loading box, metal foil and filter cover.

[0027] 3. In the present invention, a filter combination with a smaller condition number of the calculated response matrix is ​​selected under the premise of comprehensively considering the measured energy spectrum range and energy band division, filter material cost, processing difficulty, and processing accuracy.

[0028] 4. The present invention also proposes a spectrum decomposition method for a device for measuring the energy spectrum of high-energy short-pulse X-rays, and provides a spectrum decomposition method based on Tikhonov regularization. It can obtain more precise energy spectrum results by merging multiple groups of solutions, thus solving several problems existing in existing spectrum decomposition methods.

[0029] 5. The present invention also corrects the number of photons in the final energy spectrum solution obtained by comparing the simulation results and the measured results of the dose sheet energy deposition, so as to obtain more accurate values ​​of the number of photons in each energy band. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 A schematic diagram of an embodiment of a device for measuring high-energy, short-pulse X-ray energy spectrum according to the present invention;

[0032] Figure 2 for Figure 1 Exploded diagram;

[0033] Figure 3 for Figure 1 Schematic diagram of the structure of the medium-dose thermoluminescent tablet loading box;

[0034] Figure 4 for Figure 1 Schematic diagram of the structure of the metal foil;

[0035] Figure 5 for Figure 1 Schematic diagram of the structure of the middle filter cover.

[0036] Among them: 1-thermoluminescent dose sheet loading box, 2-metal foil, 3-filter cover, 4-dose sheet placement slot group, 5-dose sheet placement slot, 6-filter, 7-block, 8-sub-area, 9-second through hole, 10-third through hole, 11-threaded hole, 12-blank area, 13-screw. DETAILED DESCRIPTION

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0038] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0039] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not require further definition or explanation in subsequent drawings.

[0040] In the description of the embodiments of the present invention, it should be noted that if the terms "upper," "lower," "horizontal," "inner," etc. appear, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the inventive product is typically placed when in use. These terms are merely for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first," "second," etc. are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0041] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0042] In the description of the embodiments of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0043] The present invention is described in further detail below with reference to the accompanying drawings:

[0044] The present invention provides a device for measuring the energy spectrum of high-energy, short-pulse X-rays using the absorption method of thermoluminescent dose sheets. The device adopts an array filter-absorber arrangement, which makes the relationship between the energy deposition of the absorber and the energy of the incident photons easy to calculate, and reduces the influence of scattering and crosstalk through the corresponding structure. Secondly, a simple evaluation method for selecting the thickness of the filter is provided. Finally, a spectrum solution method based on Tychonoff regularization is provided, which can obtain more detailed energy spectrum results by merging multiple groups of solutions. By comparing the simulation results of the dose sheet energy deposition with the measured results, a more accurate value of the number of photons in each energy range can be obtained.

[0045] See also Figures 1 to 5 As shown, an embodiment of the present invention discloses a device for measuring the energy spectrum of high-energy, short-pulse X-rays. The device comprises a three-layer structure: a thermoluminescent dosimeter cartridge 1, a metal foil 2, and a filter cover 3. The metal foil 2 is provided with three second through-holes 9, the filter cover 3 is provided with three third through-holes 10, and the thermoluminescent dosimeter cartridge 1 is provided with three threaded holes 11. The positions of the second through-holes 9, third through-holes 10, and threaded holes 11 correspond to each other. The thermoluminescent dosimeter cartridge 1, metal foil 2, and filter cover 3 are fastened together from front to back using three screws 13 threaded through the third through-holes 10, second through-holes 9, and threaded holes 11, respectively. One corner is not provided with a screw 13 to maintain the angular positional relationship between the three components. The metal foil 2 is bonded to the filter cover 3, and the bonding area corresponds to the outer surface of the barrier 7 on the filter cover 3.

[0046] like Figure 3As shown, the front surface of the thermoluminescent dosing tablet loading box 1 is provided with a dosing tablet placement slot group 4. There are at least four dosing tablet placement slots 4 arranged in n×n rows, where n is an integer greater than or equal to 2. The specific number can be adjusted according to experimental needs. The dosing tablet placement slot group 4 includes several dosing tablet placement slots 5. Dosing tablets are placed in corresponding dosing tablet placement slots 5 in the thermoluminescent dosing tablet loading box 1. As a preferred embodiment, the dosing tablets are CTLD-1000 LiF (Mg, Cu, P) dosing tablets with a diameter of 4.5 mm and a thickness of 0.8 mm. The dosing tablet placement slots 5 are shaped to match the shape of the dosing tablets. In this embodiment, the dosing tablet placement slots 5 are circular. The diameter of the circular dosing tablet placement slots 5 should match the diameter of the dosing tablets used. In general, it is slightly larger than the dosing tablet diameter by 0.1 mm. The depth of the circular dosing tablet placement slots 5 matches the thickness of the dosing tablets. The distance from the bottom of the dosing tablet placement slot 5 to the corresponding surface of the metal foil after assembly is slightly larger than the thickness of the dosing tablet by 0.1 mm. In this embodiment, the device uses four dosing sheets to form a dosing sheet group. Specifically, each dosing sheet placement slot group 4 includes four dosing sheet placement slots, which are used to measure energy deposition behind the same filter 6. The depth of the dosing sheet placement slots should be consistent with the thickness of the dosing sheet. The distance from the bottom of the dosing sheet placement slot group 4 to the corresponding surface of the metal foil after assembly is slightly less than the thickness of the dosing sheet by 0.4 mm. This ensures that the dosing sheet does not shift within the thermoluminescent dosing sheet loading box 1. The thermoluminescent dosing sheet loading box 1 can be made of platinum, providing daily storage, transportation, and annealing capabilities for the dosing sheets.

[0047] The front surface of the metal foil 2 is provided with a filter 6 and a blank area 12. The thermoluminescent dose sheet loading box 1 is fixed to the rear surface of the metal foil 2. The front surface of the thermoluminescent dose sheet loading box 1 faces the rear surface of the metal foil 2. a+1=n 2 , the filter disc 6 and the blank area 12 correspond to the position and size of the dosage disc placement slot group 4 respectively, and the type of the filter disc 6 is the same as the number of the filter disc 6. Figure 4 Filters 6 are attached to the front surface of the metal foil 2 at positions corresponding to the dosing plate placement slots 4. In this embodiment, the device utilizes 15 different filters 6 arranged in a tiled array. The blank area 12 utilizes the metal foil 2 itself as the thinnest filter in the entire 4×4 filter array.

[0048] The filter cover 3 is provided with a first through hole running through the front and back. A plurality of blocks 7 are provided within the first through hole to divide the first through hole into a plurality of sub-areas 8. The size of the filter 6 matches the size of the blocks 7 within the metal foil 2, ensuring that the area where the dosage sheet placement slot 5 is located can be completely covered. The metal foil 2 is fixed to the rear surface of the filter cover 3. Each filter 6 and blank area 12 is located within each sub-area 8, and the filter 6 and blank area 12 are respectively adapted to the corresponding sub-area 8. Figure 5As shown, the filter cover 3 is used to secure the filter array to the thermoluminescent dosimeter cartridge 1. Furthermore, the structure surrounding the barrier 7 on the filter cover 3 blocks scattered photons during the experiment, improving the rationality of the photons collected by the measurement device. Furthermore, the barrier 7 prevents photon crosstalk. In this embodiment, the filter cover 3 is made of lead and can be lengthened to function as a photon collection and collimation system.

[0049] During actual measurement, the device should face the radiation source with the filter cover 3. If measuring point source radiation, the device should be placed in an area where the radiation energy decays with the square of the distance.

[0050] When a photon vertically penetrates a filter 6, its intensity satisfies the exponential decay:

[0051] I / I0 = exp[-(μ / ρ)x] (1)

[0052] Where I0 is the incident light photon density, I is the transmitted light photon density, μ / ρ is the mass attenuation coefficient (cm 2 / g), x is the surface density of the material (g / cm 2 ). The choice of the filter combination of the device is the combination of μ / ρ and x in formula (1). Similarly, after a photon vertically penetrates a layer of absorbing material, the energy deposition on the absorbing material satisfies:

[0053] E / E0 = 1 - exp[-(μ en / ρ)x] (2)

[0054] Where E0 is the incident photon energy (keV), E is the deposition energy on the absorbing material (keV), and μ en / ρ is the mass energy absorption coefficient (cm 2 / g), x is the surface density of the material (g / cm 2 The main material (LiF) and shape of the dose sheet used in the device determine μ in formula (2). en / ρ and x.

[0055] Formula (1) and formula (2) can be used to analytically express the response of the dose sheet after different filters 6 to different photon energies:

[0056] R = (1.6×10 -11 )·E0·exp[-(μ / ρ1)x1]·{1-exp[-(μ en / ρ2)x2]} / (ρ2V) (3)

[0057] Where R is an element of the response matrix, is the dose response (rad / photon), μ / ρ1 (cm 2 / g) is the mass attenuation coefficient of the filter corresponding to the photon energy E0 (keV), x1 (g / cm 2 ) is the surface density of the filter, μ en / ρ2(cm 2 / g) is the mass energy absorption coefficient of the main material of the dose sheet LiF corresponding to the photon energy E0 (keV), x2 (g / cm 2 ) is the surface density of LiF, ρ2(g / cm 3 ) is the density of LiF, V (cm 3 ) is the volume of the dosage tablet.

[0058] When the device is actually measuring, 16 sets of dose tablets will give 16 different absorbed dose values, which are recorded as D1~D 16 Assuming that the equivalent monoenergetic photon energy of each energy segment of the energy spectrum is determined in advance as E, and the corresponding energy spectrum to be solved is I (the lengths of E and I are both equal to 16 to meet the completeness of the equation system), the linear equation system to be solved can be expressed as:

[0059] R 11 I1+R 12 I2+R 13 I3+…+R 1(n-1) I n-1 +R 1n I n =D1

[0060] R 21 I1+R 22 I2+R 23 I3+…+R 2(n-1) I n-1 +R 2n I n =D2

[0061] R 31 I1+R 32 I2+R 33 I3+…+R 3(n-1) I n-1 +R 3n I n =D3

[0062] …

[0063] R i1 I1+R i2 I2+R i3 I3+…+R ij I j ++…+R i(n-1) I n-1 +R in I n =D i

[0064] …

[0065] R n1 I1+R n2 I2+R n3 I3+…+R n(n-1) I n-1 +R nn I n =D n

[0066] Right now:

[0067] RI = D (4)

[0068] Among them, R ij (rad / photon) is the photon energy E of the dose plate after the i-th filter j Response, I j is the photon energy E j The corresponding number of photons, D i The average absorbed dose value of the dose plate after the i-th filter.

[0069] The response matrix R of the device is determined by the filter combination, and its pathological degree directly determines the difficulty of solving the linear equation group (4). After the material and thickness of the filter 6 are determined, the response matrix R of the device is determined by formula (3) and the existing μ / ρ and μ en The device's response matrix can be quickly and easily derived from the ρ / ρ data (see the NIST (National Institute of Standards and Technology) database). Considering the energy spectrum and energy bands being measured, filter material cost, manufacturing difficulty, and precision, the filter combination corresponding to the matrix R with the lowest condition number is optimal.

[0070] The energy spectrum solution and photon number correction are performed in the following ways:

[0071] Since both formula (1) and formula (2) are based on some specific idealized assumptions, they have certain limitations. Formula (3) only gives a rough estimate of the matrix R, and the pathological nature of the matrix R requires extremely precise data. Therefore, formula (3) can also be used only in the process of selecting filter combinations. When solving the energy spectrum, Monte Carlo simulation software (such as MCNP, Geant4) is used to calculate the response of the dose sheet to different photon energies after different filters under the condition consistent with the experimental settings.

[0072] The energy spectrum is solved by using the Tikhonov regularization method with non-negative solution constraints, that is, when using the least squares method with non-negative solution constraints to solve I in the linear equation system (4), the cost function is used:

[0073] J = ||RI - D|| 2 + λ·||I|| 2 (5)

[0074] Where λ is the regularization parameter. For a highly discrete energy spectrum, such as a fluorescence spectrum, λ should be a small value, such as 0.1; for a more continuous energy spectrum, such as a bremsstrahlung spectrum, λ should be a large value, such as 0.4.

[0075] For a set of experimentally measured absorbed dose values ​​D, a set of corresponding energy spectrum solutions can be obtained by specifying the equivalent monoenergetic photon energy E for each energy band of the energy spectrum. Using multiple energy bands with different E values ​​can yield multiple energy spectrum solutions. By combining the more refined energy bands from multiple solutions, a more refined energy spectrum can be ultimately obtained. For example, when measuring an X-ray energy spectrum with a terminal energy less than 140 keV, 16 sets of absorbed dose values ​​are obtained. Two energy bands are used: E1 = [5, 10, 15, 20, 25, 30, 35, 40, 50, 60, 70, 80, 90, 100, 120, 140] keV and E2 = [10, 20, 35, 50, 55, 60, 65, 70, 75, 80, 90, 100, 120, 130, 135, 140] keV. Two energy spectrum solutions are then obtained using their corresponding response matrices R. Then, the 5-50 keV part of the former energy spectrum solution and the 55-140 keV part of the latter energy spectrum solution are selected and merged into the final energy spectrum solution.

[0076] Combining multiple energy spectrum solutions can produce a more refined energy spectrum shape, but this may result in a deviation in the number of photons in the energy spectrum solution. This can be corrected using Monte Carlo simulation. The solved energy spectrum shape is used as a photon particle source to simulate the energy deposition on each dose group in the experimental scenario. This is then compared with the measured dose results. The number of photons in the combined energy spectrum can be corrected based on the proportional relationship.

[0077] The following is a specific embodiment of the present invention using the above-mentioned device and spectrum interpretation method:

[0078] The laboratory used the aforementioned energy spectrum measurement device and spectrum decomposition method to measure the radiation spectrum of a rod-pinch diode. Rod-pinch diodes are often used as loads in X-ray flash photography. In the experiment, the radiation source was nearly spherical, less than 1 mm in size, and produced photon energies as high as 130 keV. The radiation pulse had a half-width of only ~20 ns, making it a typical submillimeter-level high-energy pulsed X-ray point source.

[0079] The steps for setting up the energy spectrum measurement device before the experiment are as follows:

[0080] (1) It is estimated that the maximum photon energy in the laboratory does not exceed 200 keV;

[0081] (2) Select the energy spectrum band E = [5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 120, 130, 150, 175, 200] keV;

[0082] (3) Purchase a batch of filters of different thicknesses and materials and measure their thickness using a thickness gauge;

[0083] (3) Calculate the condition number of the response matrix R corresponding to several sets of filter combinations using formula (3);

[0084] (4) Select the filter combination corresponding to the smaller condition number: metal foil 2 is 0.1mm aluminum, filter 6 material and thickness are: aluminum thickness 0.5, 1, 2, 5, 10mm; iron thickness 0.5, 2, 3, 7, 10mm; copper thickness 0.5, 2, 4, 8, 10mm;

[0085] (5) Paste the filter 6 onto the metal foil 2;

[0086] (6) Paste the metal foil 2 onto the filter cover 3 , with the pasting area being the corresponding surface of the outer periphery of the filter cover 3 .

[0087] The measurement steps are as follows:

[0088] (7) placing the dosage sheet in the thermoluminescent dosage sheet loading box 1 for annealing;

[0089] (8) Read and record the average background value of the dose tablet;

[0090] (9) Assemble the metal foil 2 and the filter cover 3 on the thermoluminescent dose sheet loading box 1;

[0091] (10) Place the energy spectrum measurement device directly above the point source, with the dose sheet 40 cm away from the point source;

[0092] (11) The rod pinch diode discharges and generates X-ray radiation;

[0093] (12) Open the filter cover 3;

[0094] (13) Read and record the absorbed dose data of the dose tablets, take the average of the readings of the four dose tablets in the same group, and subtract the background to obtain 16 absorbed dose values ​​D1~D 16 .

[0095] The steps for decomposing the spectrum are as follows:

[0096] (14) Monte Carlo simulation software Geant4 was used to calculate the response matrix R under the experimental situation;

[0097] (15) The energy spectrum is solved using the energy band E = [5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 120, 130, 150, 175, 200] keV and its corresponding response matrix. The Tikhonov regularization method with non-negative solution constraint is used, and the regularization parameter λ = 0.4;

[0098] (16) After solving, it was found that the terminal energy of the actual energy spectrum is between 130 and 150 keV;

[0099] (17) Select energy spectrum energy band E1 = [5, 10, 15, 20, 25, 30, 35, 40, 50, 60, 70, 80, 90, 100, 120, 140] keV, E2 = [10, 20, 35, 50, 55, 60, 65, 70, 75, 80, 90, 100, 120, 130, 135, 140] keV;

[0100] (18) Repeat step (14);

[0101] (19) The energy spectrum is divided into E1, E2 and its corresponding response matrix to solve the energy spectrum. The Tikhonov regularization method with non-negative solution constraint is used, and the regularization parameter λ = 0.4;

[0102] (20) Merging the 5-50 keV part of the energy spectrum solution corresponding to E1 and the 55-140 keV part of the energy spectrum solution corresponding to E2 to obtain the energy spectrum;

[0103] (21) The solved energy spectrum shape is used as the photon particle source, and Geant4 is used to simulate the energy deposition on each dose group in the experimental scenario;

[0104] (22) The simulation results of the dose sheet energy deposition were compared with the measured results. It was found that under the photon energy distribution conditions corresponding to the energy spectrum, the average number of photons required to achieve the measured dose results for each group was 1.2 times the number of photons corresponding to the energy spectrum obtained in step (20);

[0105] (23) Correct the vertical axis value of the energy spectrum obtained in step (20) (×1.2) to obtain the final energy spectrum result.

[0106] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A device for measuring the energy spectrum of high-energy, short-pulse X-rays, characterized by: It comprises a thermoluminescent dose sheet loading box (1), a metal foil (2) and a filter sheet cover (3); The front surface of the thermoluminescent dosage sheet loading box (1) is provided with a dosage sheet placement slot group (4), and the dosage sheet placement slot group (4) is at least four and is arranged in a n × n Column settings, n is an integer greater than or equal to 2; the dosage tablet placement slot group (4) includes a plurality of dosage tablet placement slots (5); The front surface of the metal foil (2) is provided with a The thermoluminescent dose sheet loading box (1) is fixed to the rear surface of the metal foil (2), and the front surface of the thermoluminescent dose sheet loading box (1) faces the rear surface of the metal foil (2). a +1 = n 2 , the filter discs (6) and the blank areas (12) correspond to the positions and sizes of the dosage disc placement slot groups (4) respectively; the types of the filter discs (6) are the same as the number of the filter discs (6); a The filter disc combination formed by the filter discs (6) is determined in the following manner: Sx, the condition number of the response matrix corresponding to multiple filter combinations is calculated by the following formula: R = (1.6×10 -11 )· E 0·exp[-( μ / ρ 1) x 1]·{1-exp[-( μ en / ρ 2) x 2]} / ( ρ 2 V ) in R is the dose sheet response, in rad / photon; μ / ρ 1 is the photon energy corresponding to the filter E 0 mass attenuation coefficient, μ / ρ The unit of 1 is cm 2 / g, E The unit of 0 is keV; x 1 is the surface density of the filter, in g / cm 2 ; μ en / ρ 2 is the photon energy corresponding to the main material of the dose sheet LiF E 0 mass energy absorption coefficient, μ en / ρ The unit of 2 is cm 2 / g; x 2 is the surface density of the dose sheet material, in g / cm 2 ; ρ 2 is the density of the dose tablet material, in g / cm 3 ; V is the volume of the dosage tablet in cm 3 ; Sy, select the filter combination corresponding to the minimum condition number; The filter cover (3) is provided with a first through hole extending from front to back, and a plurality of blocks (7) are provided in the first through hole for dividing the first through hole into a plurality of sub-areas (8); the metal foil (2) is fixed to the rear surface of the filter cover (3), and each filter (6) and blank area (12) is respectively located in each sub-area (8), and the filter (6) and blank area (12) are respectively adapted to the corresponding sub-area (8).

2. The device for measuring high-energy short-pulse X-ray energy spectrum according to claim 1, characterized in that: The metal foil (2) is provided with three second through holes (9), the filter cover (3) is provided with three third through holes (10), and the thermoluminescent dosage sheet loading box (1) is provided with three threaded holes (11); The positions of the second through hole (9), the third through hole (10) and the threaded hole (11) correspond one to one; The thermoluminescent dose sheet loading box (1), the metal foil (2) and the filter cover (3) are connected by three screws (13), and the screws (13) are located in the second through hole (9), the third through hole (10) and the threaded hole (11).

3. The device for measuring high-energy short-pulse X-ray energy spectrum according to claim 1 or 2, characterized in that: The thermoluminescent dose sheet loading box (1) and the filter sheet cover (3) are both in the shape of a rectangular parallelepiped, and the metal foil (2) is in the shape of a square; The second through holes (9) are respectively located at three corners of the metal foil (2).

4. The device for measuring high-energy short-pulse X-ray energy spectrum according to claim 3, characterized in that: n = 4, there are four dosage tablet placement slots (5).

5. The device for measuring high-energy short-pulse X-ray energy spectrum according to claim 4, characterized in that: The filter cover (3) is made of lead material, and the thermoluminescent dose sheet loading box (1) is made of platinum material.

6. A spectrum interpretation method for a device for measuring high-energy short-pulse X-ray energy spectrum, based on the device for measuring high-energy short-pulse X-ray energy spectrum according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1, use at least two energy segments to divide different E , E is a vector composed of the equivalent monoenergetic photon energies of each energy band of the energy spectrum; S2, obtained using simulation software E The corresponding response matrix R ; S3, solve different E The corresponding linear equations give different E The corresponding solution I : Solve the following linear system using the Tychonov regularization method with nonnegative solution constraints: R 11 I 1 + R 12 I 2 + R 13 I 3 + … + R 1(n-1) I n-1 + R 1n I n = D 1 R 21 I 1 + R 22 I 2 + R 23 I 3 + … + R 2(n-1) I n-1 + R 2n I n = D 2 R 31 I 1 + R 32 I 2 + R 33 I 3 + … + R 3(n-1) I n-1 + R 3n I n = D 3 … R i1 I 1 + R i2 I 2 + R i3 I 3 + … + R ij I j + +… + R i(n-1) I n-1 + R in I n = D i … R n1 I 1 + R n2 I 2 + R n3 I 3 + … + R n(n-1) I n-1 + R nn I n = D n in, R ij For dose tablets i Photon energy after filter E j The response is in rad / photon; I j Photon energy E j The corresponding number of photons; i = 1, 2, …, n , j = 1, 2, …, n ; n is the number of dosage tablets; D i For the i The average absorbed dose value of the dose sheet after the filter; S4, merging the parts of the solutions obtained in step S3 divided according to the preset fineness to obtain a final energy spectrum solution.

7. The spectrum interpretation method according to claim 6, characterized in that: The method further includes step S5 of correcting the number of photons in the final energy spectrum solution obtained in step S4 using a Monte Carlo simulation method.

8. The spectrum interpretation method according to claim 7, wherein: In step S3, the following system of equations is solved using the Tychonov regularization method with non-negative solution constraints: RI = D Specifically: Solve using the least squares method with non-negative solution constraints I When , use the cost function: J = || RI - D || 2 + λ·|| I || 2 Among them, λ is the regularization parameter.

9. The spectrum interpretation method according to claim 8, characterized in that: Specifically, step S5 is to use the energy spectrum shape corresponding to the final energy spectrum solution as the photon particle source, simulate the energy deposition on each dose piece group in the experimental scenario, compare it with the measured dose result, and correct the number of photons in the final energy spectrum solution through the proportional relationship.

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