Method for producing a supported scintillator for particle radiation, and supported scintillator

Abstract

The invention relates to a method for producing a supported scintillator for particle radiation, and to a supported scintillator. The supported scintillator comprises, as a substrate, a plastics film and a layer of scintillator powder which is adhesively bonded to the substrate. In the method according to the invention, the scintillator powder is applied in excess to an adhesive layer on the plastics film while the plastics film is caused to vibrate with vibrations at ultrasonic frequency. The scintillator powder is then pressed on, after which non-adhering scintillator powder is removed. The supported scintillator has a transmission of τ ≥ 0.99.

Description

[0001] Designation

[0002] Method for producing a supported scintillator for particle radiation and supported scintillator

[0003] Technical field

[0004] The invention relates to a method for producing a supported scintillator for particle radiation and a supported scintillator, such as one used, for example, in proton therapy of tumors.

[0005] State of the art

[0006] Scintillators for the detection of particle radiation, e.g. for creating a beam profile, are known from the prior art.

[0007] The beam profile of a particle beam depicts the intensity distribution in a cross-section, usually perpendicular to the beam. In medical applications, and elsewhere, the beam profile of a particle beam must meet parameters predetermined by the specific application. These parameters include, for example, the beam diameter, the intensity distribution within the beam profile, and the beam profile itself.

[0008] A scintillator is a material that emits ultraviolet or visible light when excited by ionizing radiation (X-rays or gamma rays) or energetic particles (such as electrons, protons, neutrons, or ions). Scintillators absorb the energy of an incident particle when struck and subsequently scintillate, meaning they re-emit the absorbed energy in the form of light.

[0009] To detect particle radiation, in addition to the scintillator itself, a device is always required with which the amount of light emitted by the scintillator can be quantitatively measured with advantageous spatial resolution. CCD cameras, for example, are suitable for this purpose.

[0010] In the article 1 by C. Simon et al. (Scintillating Screens Investigations with proton beams at 30 keV and 3 MeV, Proceedings of IBIC2016, Barcelona, ​​Spain, MOPG79, pp. 1-4) examples of the use of scintillators for the detection of proton radiation are described.

[0011] Particle beams within the meaning of the invention are electron-Z-positron beams, proton beams, neutron beams, ion beams and all particle beams such as alpha radiation.

[0012] In medical applications, but not only there, it is advantageous to be able to determine parameters of a particle beam without significantly altering the particle beam itself.

[0013] Task

[0014] The object of the present invention is to provide a method for producing a supported scintillator for particle radiation and a supported scintillator with which the beam profile of a particle beam can be detected with negligible attenuation of the same in the energy range greater than 3 MeV for protons, and in addition, the production is associated with low costs and the method is simplified.

[0015] The problem is solved by the method according to claim 1 and according to the supported scintillator according to claim 2.

[0016] The inventive method for producing a supported scintillator for particle radiation comprises at least the steps listed below.

[0017] In the first step, a., a carrier in the form of a plastic film with an adhesive layer on one side is provided. The plastic film is made of an organic or inorganic material with a transmission T that, for a given thickness d of the plastic film with adhesive layer, for a proton beam in an energy range from 3 MeV upwards, with perpendicular passage through the film, is given by: with l Q= original intensity of the proton beam, / (d) = intensity of the proton beam after passing a distance d (= the thickness of the plastic film) through the plastic film, and = absorption coefficient of the material from which the film is made, advantageously approximately equal to 1 and at least T > 0.999. This means that the absorption of a proton beam at energies greater than 3 MeV is at the detection limit when the intensity is determined using an ionization chamber or similar device, and thus the absorption is negligible. The energy range of the application is limited to 100 MeV. Below 3 MeV, the absorption may be greater depending on the material, i.e.,The transmission is lower, and at low energies (below a few hundred keV) it can be very high or even complete. This does not preclude the use of a supported scintillator according to the invention for beam characterization in these energy ranges, but it may prohibit the supported scintillator from remaining in the beam during an application. However, allowing the supported scintillator to remain in the beam during an application, at proton beam energies above 3 MeV, is an advantage of a supported scintillator according to the invention, where the transmission condition for the entire supported scintillator is T > 0.99. The scintillator powder contributes to attenuation or leads to a slightly lower transmission.

[0018] Materials that meet this condition at manageable thicknesses of the plastic films made from them include, for example, polyimides, polyolefins such as polyethylene and polypropylene, polystyrene, polyesters such as polyethylene terephthalate, polyurethanes and others.

[0019] The material of the plastic film should advantageously be largely radiation-hard, or sufficiently radiation-hard for the intended application, or not age too quickly. This condition can be verified in practice if no data for a specific material can be found in the prior art. For the materials mentioned above, a sufficient thickness of the plastic film to ensure very low and negligible attenuation (absorption) of the proton beam upon passage through the material lies in a range between 1 pm and 50 pm. The sufficient thickness can be determined, if necessary, by measuring the absorption or transmission for proton beams of 3 MeV and above.

[0020] According to the invention, the plastic film is provided on one side with an adhesive layer. The adhesive, together with the plastic film, should exhibit the particle beam absorption properties described above. The adhesive is preferably a physically setting adhesive, in particular a solvent-based wet adhesive or a dispersion adhesive, which can be applied uniformly with a layer thickness in the range of 5 pm to 500 pm, particularly in the range of 10 pm to 100 pm. Such adhesives are known from the prior art and are commercially available, as are suitable plastic films already provided with a suitable adhesive layer. Otherwise, the plastic film is coated with the adhesive in the intended layer thickness (see above) and then prepared for the subsequent steps of the process.The thickness of the adhesive layer essentially determines the resulting layer thickness of an applied scintillator powder.

[0021] In a second step, b., a scintillator in powder form is provided. The scintillator powder has particle sizes ranging from 1 nm to 20 pm. Scintillators used include, for example, those from the group: yttrium oxide (Y₂O₃), zinc sulfide (ZnS), and Nal:TI. + , Csl:TI + , CdW04, Bi4GesOi2, doped Lu2SiOs, Lu2(ix)Y2xSiOs, doped Gd2O2S, LU3AI5O12, NaYF4, doped Srh, doped CsBa2ls, doped ZnGa2O4, doped NaGdF4, PbW04, doped Y2SiOs, perovskite nanocrystals from the group: CsPb halide, Rb2Cu halide, Cs2NaTb halide and others, in consideration.

[0022] The scintillator powder is then applied to the adhesive layer, in excess and in an amount sufficient to visibly cover the entire adhesive layer. Excess means that the applied quantity (or volume) of scintillator powder is significantly greater than the quantity (or volume) that the adhesive layer can absorb. The excess amount can thus be determined by the thickness and area of ​​the adhesive layer. Homogenization of the scintillator layer on the adhesive layer is achieved by vibrating the plastic film, along with the adhesive layer and the applied scintillator powder, at frequencies ranging from 20 kHz to 1 GHz. Advantageously, this vibration occurs during the application of the scintillator powder.The vibration is advantageously achieved in a device that transmits ultrasonic vibrations to a sample carrier, as is the case with devices commonly referred to as ultrasonic baths. (It should be noted, however, that this process is carried out dry.) The plastic film is advantageously already arranged on the sample carrier of the ultrasonic device, which may, for example, be in the form of a tray belonging to the device, before the scintillator powder is applied.

[0023] To compact the adhesive and ensure good contact between the adhesive and scintillator powder, the powder is then pressed in a fourth step. This is done, for example, in a closed-loop press, such as a screw press, or manually with rams (press jaws).

[0024] The thickness of the scintillator powder layer is determined almost entirely by the thickness of the adhesive layer. The adhesive absorbs most of the scintillator powder when pressed into place. Only negligible amounts adhere to the adhesive layer. Depending on the adhesive, the final thickness may also be slightly influenced by the adhesive's volume loss during curing and, to a very small extent, by the volume of the scintillator powder.

[0025] Only after this step is excess scintillator powder removed in a final step. This can be done, for example, by shaking, also using transmitted ultrasonic vibrations, blowing off, or similar methods.

[0026] The supported scintillator produced according to the invention comprises a plastic film as a carrier and exhibits a transmission Tf of T > 0.99 at an energy of 3 MeV and above, and a total thickness of 6 pm to 550 pm. A scintillator layer made of scintillator powder is bonded to the plastic film. The sufficient transmission can be easily verified by measurements familiar to those skilled in the art, such as those using ionization chambers.

[0027] With a supported scintillator according to the invention, beam profiles of a proton beam with an energy of 3 MeV or higher can be advantageously determined without the determination itself no longer describing or changing the remaining beam (the beam after passing through the scintillator), i.e., there is a negligible attenuation (absorption) of the beam, given by a transmission of at least T > 0.99.

[0028] Furthermore, the scintillator according to the invention is easy and inexpensive to produce.

[0029] Example of implementation

[0030] The invention will be explained in more detail using an exemplary embodiment.

[0031] In the exemplary embodiment of a method according to the invention for the production of supported scintillators, the plastic film is made of polyimide with a thickness of 25 pm and an area of ​​8 cm². 2The scintillator powder in the exemplary embodiment is Y₂O₃ with a particle size distribution ranging from 1 pm to 10 pm. The plastic film is coated with an adhesive layer, the adhesive being a silicone-based adhesive with a thickness of 35 pm. The scintillator powder is sprinkled in excess onto the adhesive layer on the plastic film, while the plastic film is simultaneously vibrated with ultrasonic vibration at a frequency of 35 kHz. Sufficient scintillator powder is applied to visibly cover the entire film. The scintillator powder is then pressed onto the adhesive layer using a stamp whose surface area is large enough to cover the entire surface of the plastic film. This is done manually with a stamp (press jaw). Finally, the excess scintillator powder that does not adhere to the adhesive layer is shaken off.In this exemplary embodiment, this is again achieved using ultrasonic vibrations. The supported scintillator in this embodiment is a polyimide film carrier with a thickness of 25 pm and an area of ​​8 cm². 2 In the above embodiment of the inventive method, a scintillator layer is applied to the substrate, which adheres to the substrate by means of an adhesive layer made of silicone-based adhesive. The supported scintillator has a layer thickness of 60 pm.

[0032] The supported scintillator of the exemplary embodiment shows a transmission T of approximately 1, an attenuation of the beam is below the detection limit.

[0033] As shown, the invention advantageously combines a cost-effective, simple and time-saving manufacturing process.

Claims

Patent claims 1. A method for producing a supported scintillator for particle radiation, comprising at least the steps of: a. providing a support in the form of a plastic film with an adhesive layer on one side; b. providing a scintillator in powder form, wherein the scintillator powder has particle sizes in the range of 1 nm to 20 pm; c. applying the scintillator powder to the adhesive layer and vibrating the support with the scintillator powder applied to the adhesive at a frequency in the range of 20 kHz to 1 GHz, and wherein the scintillator powder is applied in excess; d. pressing down the scintillator powder and subsequently e. removing any non-adherent scintillator powder; and wherein the plastic film with the adhesive layer and scintillator powder has a transmission T of T > 0.99 at energies above 3 MeV.

2. Supported scintillator; characterized in that the support is formed from a plastic film and a scintillator powder is arranged on one side of the support in an adhesive layer with a layer thickness of 5 pm to 500 pm, in particular from 10 pm to 100 pm, and the supported scintillator has a transmission of T > 0.99 at energies of a proton beam from 3 MeV.

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