Novel radiochromic membrane calibration device and use method

Abstract

The invention relates to a novel radiochromic diaphragm calibration device and a use method, which are suitable for application of a high-beam-density particle accelerator. The device comprises a metal foil for scattering a particle beam, an RCF calibration bracket, an RCF sample to be detected and a detector for detecting the flow intensity of a particle flow. The RCF calibration support is of a plane-arc curved surface composite structure, a metal foil is fixed to the front plane and used for scattering particle beams, a clamping groove with a marked angle is formed in the arc curved surface and used for containing a to-be-measured RCF sample, and a notch is reserved at the position of a specific angle and used for a detector to measure the flow intensity of scattering particles. The beam intensity is reduced through Rutherford scattering of the metal foil, theoretical calculation is combined with actual measurement data comparison of a detector, a correction coefficient is obtained, and accurate dose calibration of the RCF sample is achieved. By adjusting the material, the thickness and the irradiation time of the metal foil, the wide-range calibration from 10Gy to 10000 Gy is realized. The method is not limited by too high flow intensity of the accelerator, and has the advantages of high flow intensity adaptability, high calibration efficiency, flexibility in use, large dynamic range, adjustable measuring range and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of particle acceleration and nuclear detection, and in particular to a device for calibrating absolute radiation dose of a radiochromic diaphragm and a method for using the device. Background Art

[0002] In laser ion acceleration research, the measurement of proton energy spectrum is crucial to understanding the physical process of laser-target interaction. Radiochromic film (RCF) is widely used for radiation dose measurement of various radiations. Its color changes immediately, permanently, and significantly after irradiation. By stacking RCF stacks, proton angular distribution information of discrete energies can be obtained. However, this method cannot directly provide continuous energy spectrum information. Instead, it is necessary to scan the irradiated RCF and evaluate its degree of discoloration by the obtained optical density (OD). The OD is then converted into irradiation dose (Dose), and then into deposited energy. Since the total deposited energy on each RCF is the superposition of the energy deposited on the RCF by protons of different energies, the proton energy spectrum needs to be obtained by inverse solution.

[0003] The process of converting OD to Dose is also called RCF calibration, and many RCF calibration results have been obtained in the past. However, as manufacturers introduce new RCFs, the properties of new batches of films change. To use these new films for dose measurement, these new films need to be recalibrated. Currently, RCF calibration is primarily performed using accelerator particle sources. However, the particle beam densities of many existing accelerators are higher than the desired calibration density. Therefore, existing RCF calibration methods have certain limitations when applied to the beam current densities of accelerator particle sources. Summary of the Invention

[0004] Based on this, it is necessary to provide a new type of radiation color film calibration device and its use method for application in particle sources with high beam density.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A novel radiation-chromic film calibration device includes a metal foil, an RCF calibration bracket, an RCF sample to be measured, and a detector. The RCF calibration bracket adopts a plane-arc surface composite structure, mainly including a front plane, an arc surface, and a bilaterally symmetrical side plane for sealing and connecting the two. The front plane is adhered with a metal foil for reducing beam intensity and scattering the incident particle beam. The arc surface is provided with a slot with an angle marked. The RCF sample to be measured is fixed in the slot in a manner of completely fitting the arc surface, and a notch is left at a specific angle of the arc surface. The slot position corresponding to the notch also forms a sample notch. A detector for detecting particle beam intensity is placed behind the notch. The two side planes are used to shield stray scattered signals, which include signals caused by scattering at other angles and scattering from the chamber wall. The horizontal center line of the RCF sample to be measured and the horizontal center axis of the sensitive surface of the detector are both located in the horizontal reference plane where the center of the accelerator particle source is located.

[0007] The metal foil, made of materials including but not limited to gold, silver, copper, and aluminum, is used to reduce the particle beam intensity through Rutherford scattering. By varying the metal foil's material, thickness, or particle beam irradiation time, the irradiation dose range on the RCF sample under test can be adjusted. The metal foil's material and thickness determine the energy of the particles after Rutherford scattering, and thus the particle dose deposited on the RCF sample after deducting energy losses. The accelerator particle beam's intensity is generally fixed, so the irradiation time determines the total number of particles before irradiation.

[0008] Furthermore, the thickness of the metal foil ranges from 1 nanometer to 10,000 nanometers.

[0009] The material of the RCF calibration bracket includes but is not limited to aluminum alloy, titanium alloy and stainless steel.

[0010] The RCF samples to be tested are films that exhibit different degrees of discoloration depending on the radiation dose, including but not limited to HD-v2, MD-v3, and EBT3.

[0011] The types of detectors include but are not limited to Faraday cups, gold-silicon surface detectors, and scintillator detectors.

[0012] The present invention also provides a method for using the calibration device, which specifically includes the following steps:

[0013] S1: Stick the metal foil (1) flatly on the front surface of the RCF calibration bracket (2);

[0014] S2: Cut the RCF sample (3) to fit the size of the curved slot of the RCF calibration bracket (2) and insert it into the curved slot. Leave a notch at a specific angle of the curved surface. Cut a through hole at the corresponding notch position of the RCF sample (3) to be tested. Place the detector (4) behind the notch position to ensure that the particles can pass through the notch and enter the detector (4).

[0015] S3: Fix the RCF calibration bracket (2) at the beam outlet of the particle beam generated by the accelerator particle source through a hook or a translation stage, and adjust the position of the RCF calibration bracket (2) so that the particle beam is vertically incident on the metal foil (1);

[0016] S4: According to the experimental requirements, select the accelerator particle source type, set the beam energy, flux and irradiation time;

[0017] S5: Start the accelerator and make the particle beam vertically incident on the metal foil (1), causing Rutherford scattering. The scattered particles enter the RCF calibration bracket (2) and deposit a dose on the RCF sample to be measured (3). At the same time, some particles pass through the gap and are recorded by the detector (4);

[0018] S6: By calculating the Rutherford scattering cross section of the particle and the metal at a specific scattering angle, the number of particles falling in that direction is obtained by combining the particle beam intensity, and the number of particles passing through the gap measured in real time by the detector (4) is compared with it to obtain the correction coefficient;

[0019] S7: After the irradiation is completed, the RCF sample to be tested is taken out and stored away from light for a certain period of time before scanning and analysis;

[0020] S8: replacing the RCF sample (3) to be tested, changing the material, thickness or particle beam irradiation time of the metal foil (1), and expanding the calibration dose range;

[0021] S9: The optical density values ​​(OD) at different angles of the RCF sample (3) to be tested obtained by scanning are matched with the calculated values ​​of the irradiation dose (Dose) at the corresponding angles, and an OD-Dose curve is established to achieve calibration of the batch of RCF samples (3) to be tested.

[0022] Furthermore, in step S3, the accelerator particle source is an electron source, a proton source or a photon source.

[0023] Furthermore, in step S7, the dark-proof storage time is 24-72 hours, preferably 48 hours.

[0024] Compared with the general RCF calibration technology, the beneficial effects of the present invention are as follows:

[0025] 1. Not limited by excessive accelerator current intensity. The accelerator beam current intensity can be reduced by approximately 4 to 5 orders of magnitude through Rutherford scattering, thus meeting the RCF calibration dose requirements.

[0026] 2. Large dynamic range and adjustable range. The present invention changes the irradiation dose range on the RCF by changing the material and thickness of the metal foil, the sample irradiation time, etc., and can achieve calibration of the irradiation dose from 10Gy to 10,000Gy.

[0027] 3. High calibration efficiency and flexible use. The metal foil and the RCF sample to be measured are fixed on the RCF calibration bracket. They can be placed at any position on the accelerator beam line using a translation stage or hook. After irradiation, they can be removed. A single irradiation can cover a continuous range of doses, improving calibration efficiency from one irradiation experiment per dose value to only two to three irradiation experiments, greatly shortening calibration time. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention, the following briefly introduces the drawings required for implementation.

[0029] Figure 1 This is a structural diagram of a novel radiochromic film calibration device according to the present invention;

[0030] Figure 2 It is a scanning diagram of the experimental sample of the HDv2 type RCF calibration experiment with three different irradiation times in the embodiment. DETAILED DESCRIPTION

[0031] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. The embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0032] Figure 1 The present invention is a schematic diagram of the principle of a novel radiation dose calibration device for a radiochromic film.

[0033] See also Figure 1In this embodiment of the RCF irradiation dose calibration device, the metal foil 1 for scattering the proton beam is a 2μm-thick gold foil, the RCF calibration bracket 2 is constructed of aluminum alloy, the irradiated RCF sample 3 to be tested is an HDv2 model, and the detector 4 for detecting the actual particle count is a gold-silicon surface detector. The gold foil is positioned in the accelerator proton source beam path, directly in front of the RCF calibration bracket. Protons scattered by the gold foil enter the curved slot of the RCF calibration bracket, which holds the HDv2 model. A notch (30°±1°) is left on one side of the RCF calibration bracket at a 30° angle to the incident direction. The gold-silicon surface detector is placed therein to detect the actual proton count at 30°. This is then compared with the proton count calculated using the Rutherford scattering cross section on the other side (-30°), thereby generating a correction factor (≈1).

[0034] In this embodiment, the RCF calibration bracket on which the HDv2 sample is placed is located on the accelerator beam line. The proton beam emitted by the accelerator beam line serves as the experimental irradiation source and is incident on the gold foil surface at a 90° angle. After being irradiated, the HDv2 sample at different angles of the RCF calibration bracket will produce color changes that depend on the radiation dose. The radiation dose can be calculated based on the back-Rutherford scattering process after the proton beam bombards the gold foil, that is, the number of protons = scattering cross section × proton beam intensity × gold mass density × receiving angle × irradiation time, where the scattering cross section is related to the scattering angle, and the receiving angle is related to the irradiation distance, that is, the distance from the proton beam incident point to the HDv2 sample. Since the HDv2 sample is placed in the arc-shaped curved slot of the RCF calibration bracket, the irradiation distance is the radius of the arc. For example, based on the size of the accelerator beam line target room flange, the radius of the arc bracket is set to 68 cm, and the accelerator 2-MeV proton beam line intensity is 10 11 / s, then after 5 minutes of irradiation, the doses on the stent at 25° and 45° from the beam center are 200 and 20 Gy, respectively. By further extending or shortening the irradiation time, we can extend the total irradiation dose range to 10–10,000 Gy within three irradiation experiments, meeting the dose requirements for HDv2 calibration. By scanning the irradiated HDv2 samples to obtain OD values ​​at different angles and correlating them with the calculated dose values ​​at those angles, we can generate an OD-Dose curve, enabling calibration of the entire batch of HDv2s.

[0035] Figure 2Shown are scans of experimental samples from three HDv2 RCF calibration experiments, irradiated for 310, 1503, and 2700 seconds, respectively. The HDv2 samples exhibit dose-dependent color changes at different scattering angles. Because the number of protons increases with irradiation time, the color change deepens for HDv2 samples at the same angle. If samples with scattering angles between 25° and 43° were analyzed for each irradiation, the dose ranges covered were 21–207 Gy, 103–1006 Gy, and 185–1807 Gy, respectively. The total dose for the three irradiations ranged from 21 to 1807 Gy, corresponding to an OD range of 0.03 to 0.53.

[0036] The above embodiments are only a part of the embodiments of the present invention. This article uses this example to illustrate the principles and implementation methods of the invention. The description of the above embodiments is only used to help understand the method and core concept of the present invention. For different particle sources and different types of radiochromic film, the required irradiation dose can be obtained through the design of the present invention. At the same time, for those skilled in the art, according to the concept of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A new type of radiation color film calibration device, characterized in that: The invention comprises a metal foil (1), an RCF calibration bracket (2), an RCF sample to be measured (3) and a detector (4), wherein the RCF calibration bracket (2) adopts a plane-arc-shaped surface composite structure, mainly comprising a front plane, an arc-shaped surface and a symmetrical side plane for sealing and connecting the two, the front plane is pasted with the metal foil (1) for reducing beam intensity and scattering incident particle beams, the arc-shaped surface is provided with a slot with an angle marked, the RCF sample to be measured (3) is fixed in the slot in a manner of being completely fitted with the arc-shaped surface, and a notch is left at a specific angle of the arc-shaped surface, the slot position corresponding to the notch also forms a sample notch, a detector (4) for detecting particle beam intensity is placed behind the notch, and the two side planes are used to shield stray scattered signals; the horizontal center line of the RCF sample to be measured (3) and the horizontal center axis of the sensitive surface of the detector (4) are both located in the horizontal reference plane where the center of the accelerator particle source is located.

2. A novel radiochromic film calibration device according to claim 1, characterized in that: The metal foil (1) is made of gold, silver, copper or aluminum.

3. A novel radiochromic film calibration device as claimed in claim 2, characterized in that: The thickness of the metal foil (1) is 1 nanometer to 10,000 nanometers.

4. A novel radiochromic film calibration device according to claim 1, characterized in that: The RCF calibration bracket (2) is made of aluminum alloy, titanium alloy or stainless steel.

5. The novel radiochromic film calibration device according to claim 1, characterized in that: The RCF samples (3) to be tested are films that show different degrees of discoloration depending on the radiation dose, including HD-v2 type, MD-v3 type, and EBT3 type radiation-discoloration films.

6. A novel radiochromic film calibration device as claimed in claim 1, characterized in that: The detector (4) is a Faraday cup, a gold-silicon surface detector or a scintillator detector.

7. A method for using the novel radiochromic film calibration device according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1: Stick the metal foil (1) flatly on the front surface of the RCF calibration bracket (2); S2: Cut the RCF sample (3) to be tested into a size that fits the arc-shaped slot of the RCF calibration bracket (2), cut a through hole at the position of the notch of the detector (4) corresponding to the RCF sample (3) to be tested to ensure that particles can pass through and enter the detector (4), and insert the RCF sample (3) to be tested into the arc-shaped slot; S3: Fix the RCF calibration bracket (2) at the beam outlet of the particle beam generated by the accelerator particle source through a hook or a translation stage, adjust the position of the RCF calibration bracket (2) so that the particle beam is incident vertically on the metal foil (1), and place the detector (4) behind the notch; S4: According to the experimental requirements, select the accelerator particle source type, set the beam energy, flux and irradiation time; S5: Start the accelerator and make the particle beam vertically incident on the metal foil (1), causing Rutherford scattering. The scattered particles enter the RCF calibration bracket (2) and deposit a dose on the RCF sample to be measured (3). At the same time, some particles pass through the gap and are recorded by the detector (4); S6: By calculating the Rutherford scattering cross section of the particle and the metal at a specific scattering angle, the number of particles falling in that direction is obtained by combining the particle beam intensity, and the number of particles passing through the gap measured in real time by the detector (4) is compared with it to obtain the correction coefficient; S7: After the irradiation is completed, the RCF sample to be tested is taken out and stored away from light for a certain period of time before scanning and analysis; S8: replacing the RCF sample (3) to be tested, changing the material, thickness or particle beam irradiation time of the metal foil (1), and expanding the calibration dose range; S9: The optical density values ​​(OD) at different angles of the RCF sample (3) to be tested obtained by scanning are matched with the calculated values ​​of the irradiation dose (Dose) at the corresponding angles, and an OD-Dose curve is established to achieve calibration of the batch of RCF samples (3) to be tested.

8. The method for using the novel radiochromic film calibration device according to claim 7, characterized in that: The accelerator particle source includes but is not limited to an electron source, a proton source and a photon source.

9. The method for using the novel radiochromic film calibration device according to claim 7, characterized in that: In step S7, the storage time in the dark is 24-72 hours.

10. The method for using the novel radiochromic film calibration device according to claim 9, characterized in that: In step S7, the storage time in the dark is 48 hours.

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