Multilayer crystal, detector and multilayer crystal bonding method

Abstract

The application provides a multilayer crystal, a detector and a multilayer crystal bonding method. In the multilayer crystal, the matrix of at least two crystals is the same, and the crystals are doped differently. The multilayer crystal bonding method comprises the following steps: polishing the contact surface of two adjacent scintillation crystals in the multilayer crystal by using a polishing liquid; removing the polishing liquid on the contact surface of the scintillation crystal; making the polished contact surfaces of the adjacent scintillation crystals correspond to each other and heating; applying pressure to the scintillation crystals to strengthen the connection between the molecules on the contact surface of the scintillation crystals; and cooling. The multilayer crystal provided by the application adopts the same type of crystal materials which are doped differently, the coupling interface of the adjacent crystals will not reflect and refract, and the transmission efficiency of visible photons is improved.

Description

Technical Field

[0001] This application relates to the field of detectors, and more specifically, to a multilayer crystal, a detector, and a method for bonding multilayer crystals. Background Technology

[0002] The ability of a high-energy photon detector to resolve the energy, time, and spatial information of high-energy photons directly determines the imaging quality of the detection system. The working principle of a high-energy photon detector is as follows: First, high-energy photons interact with a scintillation crystal to convert them into visible light photons. These visible light photons are then incident on a photoelectric conversion device coupled to the scintillation crystal. The photoelectric conversion device converts the incident visible light into an electrical signal, which is then output and acquired by an electronics system matched to the photoelectric conversion device. Finally, using software algorithms, the time, energy, and position information of the high-energy photons can be calculated from the digital signal.

[0003] For example, the Positron Emission Tomography (PET) system uses a scintillation crystal to convert gamma photons into visible light signals. Then, a photoelectric conversion device coupled to the scintillation crystal converts the visible light signals into electrical signals. The electrical signals are then sampled to obtain digital signals for signal processing, thereby obtaining information such as the time, energy, and spatial location of the gamma photons.

[0004] In traditional multilayer crystal detectors, different types of crystal materials are used for each layer, and the layers are coupled together using materials such as optical adhesives. Because different types of crystal materials have different refractive indices, scintillation photons will be reflected and refracted at the crystal coupling interfaces, reducing the transmission efficiency of visible photons and affecting the detection of depth information of incident rays within the crystal. This leads to a decrease in image quality and produces the depth of interaction (DOI).

[0005] The DOI effect causes trailing in the reconstructed image and reduces the spatial resolution of the image, especially at the edges of the field of view, where the impact is more pronounced. Summary of the Invention

[0006] This application proposes a multilayer crystal detector to address the problem of reflection and refraction at the scintillation crystal coupling interface affecting image quality.

[0007] According to one aspect of this application, a multilayer crystal is provided, comprising: at least two crystal layers, wherein each layer of the multilayer crystal is bonded to each other, and the matrix types of the at least two crystal layers are the same but the doping types are different.

[0008] According to some embodiments, there is a coupling interface between two adjacent crystal layers, and each coupling interface is formed by crystal bonding, so that the two adjacent crystal layers are bonded together.

[0009] According to some embodiments, after the contact surfaces of two adjacent crystal layers are polished, the root mean square roughness value in the range of 10 μm is less than 1.0 nm.

[0010] According to some embodiments, each layer of the scintillation crystal in the multilayer crystal uses the same type of matrix, including LSO, LYSO, LuAG, LuAP, or GAGG.

[0011] According to some embodiments, the doping of each layer of the multilayer crystal includes: luminescent ions and / or cations.

[0012] According to some embodiments, the luminescent ions include Ce, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb.

[0013] According to some embodiments, the cations include Sc, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Ca, Li, Mg, Zn, and Cu.

[0014] According to some embodiments, the molar percentage of the luminescent ions or the cations to the matrix is ​​between 0.001% and 1%.

[0015] According to some embodiments, there is a coupling interface between two adjacent crystal layers, and each coupling interface is coupled with an optical coupling agent with the same refractive index as the crystal, so that no photon reflection or refraction occurs at each coupling interface.

[0016] According to some embodiments, each layer of the crystal includes a plurality of scintillation crystals arranged in a matrix, and each of the scintillation crystals in at least one layer of the crystal uses the same matrix, but at least a portion of the scintillation crystals in the at least one layer of the crystal are doped differently.

[0017] According to some embodiments, each layer of the crystal comprises a plurality of scintillation crystals arranged in a matrix, and adjacent scintillation crystals in each layer are coupled by an opaque material, crystal bonding, or an optical coupling agent with the same refractive index.

[0018] According to one aspect of this application, a detector is provided, the detector comprising a multilayer crystal as described above, the detector further comprising a photoelectric converter coupled to the multilayer crystal.

[0019] According to some embodiments, the detector further includes a light guide, through which the multilayer crystal and the photoelectric converter are coupled.

[0020] According to one aspect of this application, a multilayer crystal bonding method is proposed, comprising the following steps: polishing the contact surfaces of two adjacent scintillation crystals in a multilayer crystal using a polishing slurry; removing the polishing slurry from the contact surfaces of the scintillation crystals; bringing the polished contact surfaces of the adjacent scintillation crystals into contact and heating them; applying pressure to the scintillation crystals to strengthen the intermolecular connections at the contact surfaces of the scintillation crystals; and cooling the scintillation crystals.

[0021] According to some embodiments, after the contact surfaces of two adjacent scintillation crystals are polished, the root mean square roughness value of the polished contact surfaces of the scintillation crystals is less than 1.0 nm in the range of 10 μm.

[0022] According to some embodiments, the heating temperature is between 1000 degrees and 1800 degrees.

[0023] According to some embodiments, the pressure applied to the scintillation crystal is less than 100 MPa.

[0024] According to some exemplary embodiments of this application, a multilayer crystal and detector are proposed. The multilayer crystal and detector use the same type of crystal material with different doping, and adjacent crystals are bonded together using a bonding technique. This prevents reflection and refraction at the coupling interface of adjacent crystals, improving the transmission efficiency of visible photons. This helps to determine the deposition location of high-energy rays using information such as the amplitude, decay time, and peak wavelength of the detected scintillation pulses, thereby achieving the acquisition of depth effect information.

[0025] According to some embodiments, adjacent crystals of a multilayer crystal are coupled using an optical coupling agent with the same refractive index as the crystal material, so that the coupling interface between adjacent crystals does not reflect or refract, thereby improving the transmission efficiency of visible photons. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0027] Figure 1a A side view of a multilayer crystal according to an example embodiment of this application is shown.

[0028] Figure 1b A perspective view of a multilayer crystal according to an example embodiment of this application is shown.

[0029] Figure 1c A schematic diagram of the coupling interface of a multilayer crystal according to an example embodiment of this application is shown.

[0030] Figure 2a A side view of a detector according to an example embodiment of this application is shown.

[0031] Figure 2b A perspective view of a detector according to an example embodiment of this application is shown.

[0032] Figure 2c This diagram illustrates the coupling interface of a multilayer crystal in a detector according to an example embodiment of this application.

[0033] Figure 3 A flowchart of a crystal bonding method according to an example embodiment of this application is shown.

[0034] Figure 4a The X-ray excitation emission spectrum of LSO:Ce,Pr doped is shown.

[0035] Figure 4b The X-ray excitation emission spectrum of LSO:Ce,Nd doped is shown.

[0036] Figure 4c The X-ray excitation emission spectrum of LSO:Ce,Eu doped is shown.

[0037] Figure 4d The X-ray excitation emission spectrum of LSO:Ce,Tb doped is shown.

[0038] Figure 4e The X-ray excitation emission spectrum of LSO:Ce,Dy doped is shown.

[0039] Figure 4f The X-ray excitation emission spectrum of LSO:Ce,Yb doped is shown. Detailed Implementation

[0040] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided so that this application will be thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted.

[0041] The described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a full understanding of embodiments of this disclosure. However, those skilled in the art will recognize that the technical solutions of this disclosure can be practiced without one or more of these specific details, or other methods, components, materials, apparatus, or operations may be employed. In these cases, well-known structures, methods, apparatuses, implementations, materials, or operations will not be shown or described in detail.

[0042] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0043] The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0044] The specific embodiments according to this application will now be described in detail with reference to the accompanying drawings.

[0045] Figure 1a A side view of a multilayer crystal according to an example embodiment of this application is shown. Figure 1b A perspective view of a multilayer crystal according to an example embodiment of this application is shown. Figure 1c A schematic diagram of the coupling interface of a multilayer crystal according to an example embodiment of this application is shown.

[0046] like Figure 1a and Figure 1b The multilayer crystal shown comprises four crystal layers, each consisting of several matrix-coupled scintillation crystals. For example, Figure 1c As shown, crystal layer 1 and crystal layer 2 are coupled through coupling interface 1, crystal layer 2 and crystal layer 3 are coupled through coupling interface 2, and crystal layer 3 and crystal layer 4 are coupled through coupling interface 3.

[0047] Multilayer crystals utilize scintillation crystals to convert high-energy photons into visible light signals, and then use photoelectric converters coupled to the scintillation crystals to convert the visible light signals into electrical signals. According to some example embodiments of this application, the multilayer crystal comprises scintillation crystals of the same type but with different doping. Since the scintillation crystals use the same type of crystal material, a small amount of doping does not change their refractive index.

[0048] According to some embodiments, each crystal layer in a multilayer crystal uses the same type of matrix, wherein the matrix includes lutetium silicate (LSO), yttrium lutetium silicate (LYSO), bismuth silicate (BSO), lutetium aluminum garnet (LuAG), lutetium aluminum perovskite (LuAP), or gadolinium aluminum gallium garnet (GAGG).

[0049] For example, crystal layer 1, crystal layer 2, crystal layer 3 and crystal layer 4 use the same matrix, all of which is LYSO.

[0050] According to some example embodiments of this application, each crystal layer in a multilayer crystal employs different doping. For example, crystal layer 1, crystal layer 2, crystal layer 3, and crystal layer 4 employ different doping methods, with each crystal layer using a doping scheme including one or more luminescent ions and / or cations.

[0051] According to some embodiments, the luminescent ions include cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), and ytterbium (Yb).

[0052] According to some embodiments, the cations include scandium (Sc), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), calcium (Ca), lithium (Li), magnesium (Mg), zinc (Zn), and copper (Cu).

[0053] For example, crystal layer 1 is based on LYSO and includes doping with one luminescent ion, Ce; crystal layer 2 is based on LYSO and includes doping with two luminescent ions, Ce and Pr; crystal layer 3 is based on LYSO and includes doping with one luminescent ion, Ce, and one cation, Sc; crystal layer 4 is based on LYSO and includes doping with two cations, Sc and La.

[0054] For example, crystal layer 1 is based on GAGG matrix and includes doping with one luminescent ion, Ce; crystal layer 2 is based on GAGG matrix and includes doping with two luminescent ions, Nd and Pm, and one cation, Sc; crystal layer 3 is based on GAGG matrix and includes doping with two luminescent ions, Sm and Eu, and two cations, Pr and Nd; crystal layer 4 is based on GAGG matrix and includes doping with three cations, Er, Tm, and Yb.

[0055] Those skilled in the art should note that, in the embodiments of this application, "a small amount" refers to the molar percentage of luminescent ions or cations to the matrix being between 0.001% and 1%. Depending on the specific embodiment, the specific value of "a small amount" can be any value within this range. For example, in the first LYSO matrix layer, 0.1% molar percentage of luminescent ions Ce is doped; in the second LYSO matrix layer, 0.2% molar percentage of luminescent ions Ce and 0.3% molar percentage of luminescent ions Pr are doped; and in the third LYSO matrix layer, 0.3% molar percentage of cation Sc and 0.4% molar percentage of cation La are doped.

[0056] Those skilled in the art should understand that in the embodiments of this application, "multilayer" refers to a crystal with at least two layers. The four layers in the above embodiments are merely examples and not limitations. The specific number of layers can be determined comprehensively based on the energy of high-energy photons and the actual detection resolution requirements, and will not be elaborated here.

[0057] According to some embodiments of this application, each scintillation crystal in at least one layer of crystal uses the same type of matrix, but at least a portion of the scintillation crystals in that layer of crystal use different doping. The type of matrix and the type and content of doping can be the same as in the above embodiments, and will not be repeated here.

[0058] According to some exemplary embodiments of this application, the coupling interfaces between adjacent crystal layers in a multilayer crystal are formed by crystal bonding, thereby bonding the adjacent crystal layers together. The bonding method between two adjacent scintillation crystals within the same layer can be selected as needed. For example, in some detector applications, the sides of two adjacent scintillation crystals within the same layer need to be wrapped or coated with an opaque material to prevent visible light from entering other crystals; while in some special detector applications, the sides of two scintillation crystals within the same layer may also need to be bonded using a transparent crystal bonding method. The method for bonding two adjacent scintillation crystals is shown in Figure 2.

[0059] According to some example embodiments of this application, each layer of crystal uses the same type of crystal material with different doping. By performing a small amount of doping on the crystal material and using bonding technology between adjacent crystals, the coupling interface between adjacent crystals will not emit or refract. This not only improves the transmission efficiency of visible photons, but also enables the control of the amplitude, attenuation time and peak wavelength of the scintillation pulse of digital signals used for signal processing.

[0060] According to some exemplary embodiments of this application, the coupling interfaces between adjacent crystal layers in a multilayer crystal are coupled using an optical coupling agent with the same refractive index, thereby forming a bond between the adjacent crystal layers. The bonding method between two adjacent crystals within the same layer can be selected as needed. For example, in some detector applications, the sides of two adjacent crystals within the same layer need to be wrapped or coated with an opaque material to prevent visible light from entering other crystals; while for some special detector applications, the sides of two crystals within the same layer may also need to use a transparent crystal bonding method. Of course, the sides of two crystals within the same layer can also be coupled using an optical coupling agent with the same refractive index.

[0061] According to some example embodiments of this application, each layer of crystal uses the same type of crystal material with different doping, and the coupling interface between adjacent crystals is coupled with an optical coupling agent with the same refractive index, so that gamma photons will not be reflected or refracted at the coupling interface, which can improve the transmission efficiency of visible photons.

[0062] Figure 2a A side view of a detector according to an example embodiment of this application is shown. Figure 2b A perspective view of a detector according to an example embodiment of this application is shown. Figure 2c This diagram illustrates the coupling interface of a multilayer crystal in a detector according to an example embodiment of this application.

[0063] like Figure 2a and Figure 2b The multilayer crystal detector shown includes the multilayer crystal as described in the embodiment of Figure 1 and a photoelectric converter coupled to the multilayer crystal. The multilayer crystal includes four crystal layers. Each crystal layer can be coupled in the manner described in the embodiment of Figure 1. Different coupling methods can also be selected between crystal layer 4 and the photoelectric converter, such as coupling with a couplant, coupling with a photoconductor, or bonding.

[0064] according to Figures 2a-2cThe illustrated embodiment proposes a detector with multilayer crystals. The multilayer crystals in the detector are made of the same type of scintillation crystal material but with different doping. Adjacent scintillation crystals are coupled using bonding technology or an optical coupling agent with the same refractive index as the scintillation crystal material. This prevents reflection and refraction at the coupling interface of adjacent scintillation crystals, improving the transmission efficiency of visible photons. This facilitates the determination of gamma-ray deposition locations using information such as the amplitude, decay time, and peak wavelength of the detected scintillation pulses, thereby enabling the acquisition of depth effect information.

[0065] Figure 3 A flowchart illustrating a crystal bonding method according to an example embodiment of this application is shown. Referring below... Figure 3 This application provides a detailed description of a crystal bonding method according to an example embodiment.

[0066] In step S301, the contact surface of two adjacent scintillation crystals in the multilayer crystal is polished using polishing fluid, so that the root mean square roughness (RMS) value of the polished contact surface of the two scintillation crystals is less than 1.0 nm in the range of 10 μm.

[0067] In step S303, the polishing fluid on the contact surfaces of two adjacent scintillation crystals is removed.

[0068] According to some embodiments, two adjacent scintillation crystals that have completed the surface treatment in step S301 are placed in deionized water for ultrasonic cleaning to remove the polishing liquid remaining on the surface of the scintillation crystals.

[0069] In step S305, the polished contact surfaces of two adjacent scintillation crystals are brought into contact and heated.

[0070] According to some embodiments, the coupling surfaces of the two scintillation crystals processed in step S303 are brought into contact according to the designed array shape and heated to a certain temperature. For example, the temperature is heated to 1300 degrees to 1800 degrees.

[0071] According to some embodiments, the heating time can be determined based on the bonding strength. Different heating times will result in different coupling strengths, which is easily understood by those skilled in the art based on the teachings of this application, and will not be elaborated further here.

[0072] In step S307, pressure is applied to two adjacent scintillation crystals to strengthen the intermolecular connections at the contact surfaces of the scintillation crystals.

[0073] According to some embodiments, a pressure of less than 100 MPa is applied to the two scintillation crystals after the treatment in step S305 to enhance the intermolecular connection at the contact surface of the two scintillation crystals.

[0074] According to some embodiments, before applying pressure to the two scintillation crystals in step S307, an optical coupling agent with the same refractive index is first placed on the contact surface of the two scintillation crystals, and then pressure is applied to the two crystals to strengthen the intermolecular connection at the contact surface of the two scintillation crystals.

[0075] In step S309, the scintillation crystal is cooled, thus forming a bonded scintillation crystal.

[0076] According to some embodiments, cooling can be achieved through self-cooling at room temperature, or through water cooling or air cooling at room temperature, etc., which will not be elaborated here.

[0077] Figures 4a-4f X-ray excitation emission spectra of scintillation crystals with different doping according to embodiments of this application are shown. The different doping scintillation crystals include LSO:Dy, LSO:Tb, LSO:Eu, LSO:Pr, LSO:Nd, and LSO:Yb.

[0078] Taking LSO:Yb as an example, it means that the scintillation crystal matrix is ​​LSO and Yb is used as the doping agent. Other doping schemes are represented in the same way and will not be described in detail here.

[0079] After ultraviolet irradiation, different doping schemes exhibit varying degrees of color depth, increasing in intensity in the order of LSO:Dy, LSO:Tb, LSO:Eu, LSO:Pr, LSO:Nd, and LSO:Yb. This demonstrates that different doping schemes affect the peak wavelength, light output, and decay time of the scintillation crystal, thus providing more comprehensive front-end measurement information for obtaining the response depth of multilayer crystals.

[0080] Figure 4a The X-ray excitation emission spectrum of LSO:Ce,Pr doped is shown. Figure 4b The X-ray excitation emission spectrum of LSO:Ce,Nd doped is shown. Figure 4c The X-ray excitation emission spectrum of LSO:Ce,Eu doped is shown. Figure 4d The X-ray excitation emission spectrum of LSO:Ce,Tb doped is shown. Figure 4e The X-ray excitation emission spectrum of LSO:Ce,Dy doped is shown. Figure 4f The X-ray excitation emission spectrum of LSO:Ce,Yb doped is shown.

[0081] Taking LSO:Ce,Pr as an example, it means that the scintillation crystal matrix is ​​LSO and doped with both Ce and Pr. Other doping schemes are represented in the same way and will not be described in detail here.

[0082] Depend on Figures 4a-4fAs shown, due to the doping of other luminescent ions and / or cations, the wavelength information of the scintillation emission of the scintillation crystal is enriched. Among them, the newly added emission peaks of LSO:Ce,Pr are 464 nm, 509 nm, 545 nm, 614 nm, 738 nm and 772 nm; the newly added emission peaks of LSO:Ce,Nd are 544 nm, 608 nm and 774 nm; the newly added emission peaks of LSO:Ce,Eu are 540 nm, 608 nm and 778 nm; the newly added emission peaks of LSO:Ce,Tb are 383 nm, 415 nm, 435 nm, 545 nm, 768 nm, 827 nm and 872 nm; the newly added emission peaks of LSO:Ce,Dy are 481 nm, 539 nm, 573 nm and 782 nm; and the newly added emission peaks of LSO:Ce,Yb are 536 nm, 606 nm and 776 nm. The newly added peak wavelength characteristics can be used as a basis for judging DOI information.

[0083] While this application provides the operational steps of the methods described in the above embodiments or flowcharts, the methods may include more or fewer operational steps based on conventional or non-inventive methods. For steps where there is no logically necessary causal relationship, the execution order of these steps is not limited to the execution order provided in the embodiments of this application.

[0084] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0085] According to some exemplary embodiments of this application, a multilayer crystal and detector are proposed. The multilayer crystal uses scintillation crystal materials of the same type but with different doping, and adjacent scintillation crystals are bonded together using a bonding technique. This prevents reflection and refraction at the coupling interface of adjacent scintillation crystals, improving the transmission efficiency of visible photons. This helps to determine the deposition location of high-energy rays using information such as the amplitude, decay time, and peak wavelength of the detected scintillation pulses, thereby achieving the acquisition of depth effect information.

[0086] According to some embodiments, adjacent scintillation crystals of a multilayer crystal detector are coupled using an optical coupling agent with the same refractive index as the scintillation crystal material, so that the coupling interface between adjacent scintillation crystals does not reflect or refract, thereby improving the transmission efficiency of visible photons.

[0087] The embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this application. Furthermore, any changes or modifications made by those skilled in the art based on the ideas of this application, and on the specific implementation methods and application scope of this application, are all within the scope of protection of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A multilayer crystal, characterized in that, Each layer in the multilayer crystal is bonded to each other, and at least two layers of the crystal have the same matrix type but different doping. The doping of each layer of the multilayer crystal includes: luminescent ions.

2. The multilayer crystal according to claim 1, characterized in that, There is a coupling interface between two adjacent crystal layers, and each coupling interface is formed by crystal bonding, so that the two adjacent crystal layers are bonded together.

3. The multilayer crystal according to claim 2, characterized in that, After the contact surfaces of two adjacent crystal layers are polished, the root mean square roughness value in the range of 10 μm is less than 1.0 nm.

4. The multilayer crystal according to claim 1, characterized in that, Each layer of the multilayer crystal uses the same type of matrix, including LSO, LYSO, LuAG, LuAP, or GAGG.

5. The multilayer crystal according to claim 1, characterized in that, The doping of each layer of the multilayer crystal further includes cations.

6. The multilayer crystal according to claim 5, characterized in that, The luminescent ions include Ce, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb.

7. The multilayer crystal according to claim 5, characterized in that, The cations include Sc, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Ca, Li, Mg, Zn, and Cu.

8. The multilayer crystal according to claim 5, characterized in that, The molar percentage of the luminescent ions or the cations to the matrix is ​​between 0.001% and 1%.

9. The multilayer crystal according to claim 1, characterized in that, There is a coupling interface between two adjacent crystal layers. Each coupling interface is coupled with an optical coupling agent with the same refractive index as the crystal, so that no photon reflection or refraction occurs at each coupling interface.

10. The multilayer crystal according to claim 1, characterized in that, Each layer of the crystal comprises a plurality of scintillation crystals arranged in a matrix, wherein each scintillation crystal in at least one layer of the crystal uses the same matrix, but at least a portion of the scintillation crystals in the at least one layer of the crystal are doped differently.

11. The multilayer crystal according to claim 1, characterized in that, Each layer of the crystal comprises a plurality of scintillation crystals arranged in a matrix, and adjacent scintillation crystals in each layer are coupled by an opaque material, crystal bonding, or an optical coupling agent with the same refractive index.

12. A detector, characterized in that, The detector includes a multilayer crystal as described in any one of claims 1-11, and the detector further includes a photoelectric converter coupled to the multilayer crystal.

13. The detector according to claim 12, characterized in that, The detector also includes a light guide, through which the multilayer crystal and the photoelectric converter are coupled.

14. A method for bonding multilayer crystals, characterized in that, Includes the following steps: The contact surfaces of two adjacent scintillation crystals in a multilayer crystal are polished using a polishing slurry. At least two layers of the crystal have the same matrix type but different doping. The doping of each layer of the multilayer crystal includes: luminescent ions. Remove the polishing fluid from the contact surfaces of the scintillation crystal; The polished contact surfaces of adjacent scintillation crystals are brought into contact and heated. Pressure is applied to the scintillation crystal to enhance the intermolecular connections at the contact surfaces of the scintillation crystal; Cool the scintillation crystal.

15. The multilayer crystal bonding method according to claim 14, characterized in that, After the contact surfaces of two adjacent scintillation crystals are polished, the root mean square roughness value of the polished contact surfaces of the scintillation crystals is less than 1.0 nm in the range of 10 μm.

16. The multilayer crystal bonding method according to claim 14, characterized in that, The heating temperature is between 1000 degrees and 1800 degrees.

17. The multilayer crystal bonding method according to claim 14, characterized in that, The pressure applied to the scintillation crystal is less than 100 MPa.

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