CN111025372A - Cerium-doped yttrium aluminate scintillation crystal radiation detector with exit surface matched with lens set - Google Patents
Cerium-doped yttrium aluminate scintillation crystal radiation detector with exit surface matched with lens set Download PDFInfo
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- CN111025372A CN111025372A CN201911195176.6A CN201911195176A CN111025372A CN 111025372 A CN111025372 A CN 111025372A CN 201911195176 A CN201911195176 A CN 201911195176A CN 111025372 A CN111025372 A CN 111025372A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/16—Measuring radiation intensity
- G01T1/20—Measuring radiation intensity with scintillation detectors
- G01T1/202—Measuring radiation intensity with scintillation detectors the detector being a crystal
- G01T1/2023—Selection of materials
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/16—Measuring radiation intensity
- G01T1/20—Measuring radiation intensity with scintillation detectors
- G01T1/208—Circuits specially adapted for scintillation detectors, e.g. for the photo-multiplier section
Abstract
The invention relates to a scintillation crystal radiation detector with a special light-emitting surface matched with a lens group, which constructs the matched lens group with wide angle and large depth of field, increases the collection efficiency of a light sensor on scintillation light and improves energy resolution, takes the matching of the specific parameter design of the scintillation crystal with the emergent wave band of the scintillation crystal into consideration, can increase an incident light sensor for focusing and collecting the scintillation light, improves the energy resolution, correspondingly designs the shape of the light-emitting surface of the scintillation crystal matched with the lens group, further improves the measurement efficiency and the measurement precision, and particularly can further improve the detection performance when developing a high-performance detector.
Description
Technical Field
The present invention relates to the measurement of nuclear or X-ray radiation, and in particular to the measurement of X-ray radiation, gamma-ray radiation, corpuscular radiation or cosmic radiation, and in particular to scintillation detectors in which the scintillator is a crystal in the measurement of the intensity of the radiation.
Background
Radiation measurement has played an important role in many fields, such as nuclear power plant and thermal power plant radiation measurement, continuous measurement of radiation dose at a measurement site; industrial and civil buildings, building decoration, building material production and manufacture, and radioactivity measurement of various building materials; geological exploration, geological prospecting and mine radiation measurement; the system is used for a ray security inspection passage door, and can provide help for customs, airport, border inspection and security inspection of important meeting places; radiation measurement and radiation therapy (CT, PET, ray knife, etc.) used in medical treatment both need to be used for diagnosis and treatment by measuring radiation intensity, and radiation measurement has been widely used in radioactive places such as radioactivity monitoring, industrial nondestructive inspection, treatment and diagnosis in hospitals, isotope application, waste recovery, etc., and radiation measurement monitors radiation on one hand to prevent radiation from causing harm, and plays a role in monitoring and calculating diagnosis and treatment on the other hand.
Radiation detection is the most fundamental research field of radiation measurement, the basic principle of radiation detectors is that radiation detection is performed by using an ionization excitation effect or other physical or chemical changes caused by radiation in gas, liquid or solid, the known types of detectors include gas detectors, scintillation detectors and semiconductor detectors, the gas detectors are complex in structure and the semiconductor detectors are not ideal in detection efficiency, the scintillation detectors are the most commonly used detectors at present, the scintillation detectors are strictly classified into liquid scintillation detectors and solid scintillation detectors, the liquid scintillation detectors are much less portable than the solid scintillation detectors, and the liquid scintillation detectors are basically used for laboratory research, and the solid detectors for measuring radiation by using scintillation crystals are the most researched detector types in the field.
A typical structure of a conventional scintillation crystal radiation measuring apparatus is shown in fig. 1, in which a scintillation crystal is used as a detection crystal, a reflective layer is disposed on a surface facing an emission source and around the surface, and the remaining surface is an excited light emitting surface, and the excited light emitting surface is connected to a photosensor (typically, a photomultiplier tube, for example) through an optical coupling structure, and the photosensor photomultiplier tube is respectively connected to a high voltage divider and a preamplifier; the input high voltage is loaded on the photomultiplier through the high voltage divider, and the output signal is processed by the preamplifier, the linear amplifier and the multi-channel analyzer in sequence to form the final output signal. Such detectors using scintillation crystals have also been well studied by those skilled in the art because of their ease of use and simplicity of construction to provide the most widely used detectors.
At present, how to further improve the energy resolution and the time resolution of the detector is a technical bottleneck for developing a high-performance detector.
In order to further improve the performance of the detector, the applicant's technical team develops an external light guide idea in a creative way, the conventional technical idea usually does not aim at the light path between the scintillation light emitting surface of the crystal and the light sensor, and usually focuses on how to avoid the damage of rays to the light sensor, and the light path needs to be changed, or when the light is connected by using an optical fiber, a corresponding lens is arranged for transmitting light to the optical fiber so as to perform light guiding and focusing, and a corresponding lens unit is arranged when imaging is needed. As is well known, the design of a lens assembly with multiple lens combinations is very complex, and a technical bias lies in that, in general, a person skilled in the art considers that designing a lens assembly for improving the corresponding efficiency of a detector in a limited space is irrevocable, even if the lens assembly is improved and arranged in a few existing technologies, only a simple description is provided, and no practical lens assembly design parameters are given, so that the applicant team can find several groups of lens assembly design schemes (planning multiple groups of patent layouts on research results) which break through the conventional effect and are applicable to a detector system in a large amount of irregular experimental data and form a detection system on the basis of the lens assembly design schemes, wherein the scheme is a detection system based on one of the design schemes, and other schemes are filed for another application.
On the basis of improving the detection efficiency of the detector by using the lens group, the technical team of the applicant further researches and discovers the technical thought dead angle in the prior art, the prior art generally uses an external reflecting film and an external antireflection film to improve the emergence efficiency and the emergence time of scintillation light, but actually ignores that the scintillation crystal is also a part of an important light guide assembly, particularly after the team of the applicant proposes a latest scheme for guiding the scintillation light by using the lens group, the influence of the scintillation crystal on the light emergence efficiency becomes an important factor which can be considered, and the technical team of the applicant proposes the matching relationship between the shape of the emergence surface of the scintillator and the lens group through further breakthrough design, so that the energy resolution and the time resolution of the detector can be further improved.
It should be noted that, after more than three years of research in this field, the technical team of the applicant has arrived at a plurality of technical achievements, and in order to avoid the prior art that may become the later application or the conflicting application, the technical achievements are purposely proposed to be applied on the same day and combined with different techniques to form a patent layout, the prior art mentioned in the corresponding background art is not necessarily the one that has been disclosed to the public, and some of the prior art that is not disclosed when the technical team of the applicant researches the corresponding technique, so neither the prior art mentioned in the background art nor the claimed prior art can be taken as the evidence that the related art has been known to the public, and can not be the evidence of common knowledge.
Disclosure of Invention
Aiming at the problems and bottlenecks existing in the prior art, the invention provides a cerium-doped yttrium aluminate scintillation crystal radiation detector with an emergent surface matched with a lens group, and mainly aims to provide a structure capable of further improving the light collection rate when a high-performance radiation detector is developed so as to improve the detection efficiency and precision.
In order to achieve the purpose, the invention is realized by the following technical scheme:
the utility model provides a mix cerium yttrium aluminate scintillation crystal radiation detector with lens group complex emergent face, includes scintillation crystal, photosensor, preamplification circuit and multichannel analysis appearance, and the scintillation crystal surface is provided with reflector layer and anti-reflection coating, and the reflector layer setting is on the surface except that the scintillation emergent face, and the anti-reflection coating sets up at the scintillation emergent face, the scintillation crystal is for mixing cerium yttrium aluminate crystal, and scintillation crystal and photosensor setting are provided with multichannel analysis appearance, its characterized in that outside the casing in the encapsulation casing: a lens group matched with the waveband of the scintillation light of the cerium-doped yttrium aluminate crystal is arranged between the scintillation light emitting surface and the optical sensor, and the scintillation light emitting surface is provided with an aspheric convex structure matched with the waveband of the scintillation light of the cerium-doped yttrium aluminate crystal;
further, the main body of the scintillation crystal except for the scintillation light emergent surface is a cylindrical structure, the axis of the cylindrical structure coincides with the optical axis of the lens group and the central axis of the light receiving surface of the optical sensor, the lens group sequentially comprises a first lens, a second lens, a third lens, a fourth lens and a fifth lens along the scintillation light emergent direction, the two side surfaces of each lens are aspheric surfaces, and the following aspheric surface equation is satisfied:
y＝(x2/R)/(1+(1－(k+1)(x2/R2))1/2+A4x4+A6x6+A8x8+A10x10+A12x12+A14x14+A16x16，
wherein R is a radius of curvature (length in mm in absolute value) on the central axis, k is a conic coefficient, A4, A6, A8, A10, A12, A14, A16 are aspherical coefficients,
the values are as follows:
wherein N-R columns in the lens surface columns represent the object side surface of the Nth lens, and N-L represents the image side surface of the Nth lens;
the convex shape of the glittering light emitting surface satisfies the following aspheric surface formula:
y＝(x2/R)/(1+(1－(k+1)(x2/R2))1/2+A4x4+A6x6+A8x8+A10x10+A12x12+A14x14+A16x16，
wherein, R is the curvature radius (the length unit of the absolute value is mm) on the central axis, k is the cone coefficient, A4, A6, A8, A10, A12, A14 and A16 are aspheric coefficients, and the values are as follows:
R＝-0.87，k＝-2.92212，A4＝0.61403，A6＝0.02233，A8＝0.02111，A10＝-0.01808，A12＝0.00387，A14＝0.00039，A16＝-0.00015；
further, the light sensor is a silicon photomultiplier;
further, the focal lengths of the first to fifth lenses are respectively 2.04mm, -3.83mm, 239.14mm, 1.82mm, -1.60 mm;
further, the thicknesses of the first to fifth lenses are respectively: 0.43mm, 0.21mm, 0.21mm, 0.48mm, 0.27 mm.
Further, a distance between an object side surface of the first lens and the scintillator light exit surface is greater than 0.8 mm;
further, the object side surface of the first lens is larger than the area of the scintillator light exit surface by 20%.
Compared with the prior art, the invention has the advantages that:
1) the invention breaks through the traditional technical thought, overcomes the inherent defects that the data volume is too large and is difficult to select and optimize when the lens group is designed aiming at the main emergent wave band of the scintillation crystal, constructs the matched wide-angle and large-depth-of-field lens group, increases the collection efficiency of the optical sensor to the scintillation light and improves the energy resolution, and the specific parameter design considers the matching with the emergent wave band of the scintillation crystal, can increase the incident light sensor after focusing and collecting the scintillation light, improves the energy resolution, correspondingly improves the measurement efficiency and the measurement precision, and can further improve the detection performance especially when developing a high-performance detector;
2) the radiation detector in the prior art usually considers the external reflection and the permeability increase of the scintillator, and rarely starts from the shape and the performance of the scintillation crystal, the invention initiatively provides the conception of optimizing the shape of the light emergent surface of the scintillation crystal, an optical light guide structure is formed by the emergent end of the scintillator, the specific shape design considers the matching with the emergent wave band of the scintillation crystal, the emergent probability of emergent light which is totally reflected and is emergent for the first time in the prior art can be increased, the measurement efficiency and the measurement precision are improved, when the radiation detector is matched with a lens set, the improvement is particularly obvious, and the detection performance can be further improved when a high-performance detector is developed.
Drawings
FIG. 1 is a schematic diagram of a prior art radiation detector;
FIG. 2 is a schematic view of a radiation detector of the present invention;
FIG. 3 is a schematic diagram of the lens geometry and the lens exit face of the present invention (the relative size relationship is not considered in the figure);
in the figure: r: a radioactive source L: lens group S1: scintillation crystal light exit surface S2: scintillation crystal light reflection surface S3: light-receiving surface 1 of photomultiplier: scintillation crystal 2: the optical sensor 3: internal circuit 4: the detector packaging shell 5: external power supply and circuit, L1-L5: first to fifth lenses.
Detailed Description
The present invention is further explained with reference to the accompanying drawings, as shown in fig. 2, a cerium-doped yttrium aluminate scintillation crystal radiation detector with an emitting surface matched with a lens group comprises a scintillation crystal 1, a light sensor 2, a preamplifier circuit and a plurality of analyzers 3 and 5, wherein the surface of the scintillation crystal is provided with a light reflecting layer and an antireflection layer, the light reflecting layer is arranged on a surface S2 except for the scintillation light emitting surface, the antireflection layer is arranged on the scintillation light emitting surface S1, the scintillation crystal is a cerium-doped yttrium aluminate crystal, the scintillation crystal 1 and the light sensor 3 are arranged in a packaging shell 4, the plurality of analyzers are arranged outside the shell, and a lens group L matched with the waveband of scintillation light of the cerium-doped yttrium aluminate crystal is arranged between the scintillation light emitting surface S2 and the light sensor 3.
The cerium-doped yttrium aluminate is one of conventional scintillation crystals known in the prior art, low-energy visible photons generated inside the crystals are distributed isotropically, when the visible photons generated inside the crystals reach the tail end scintillation light emitting surface S1, the emission angle range is large, the energy resolution of a detector is affected, in order to improve the collection rate of high-angle photons of the detector and improve the energy resolution of the detector, a lens group design with a large amount of data is carried out around the wavelength of cerium-doped yttrium aluminate scintillation light, and practical tests and performance comparison are carried out to obtain the aspheric shape lens group shown in FIG. 3, of course, FIG. 3 is only a schematic diagram and does not represent absolute distance and relative size relations, and as known in the art, the aspheric relation takes the intersection point of an aspheric surface and an axis as an origin, only the aspheric coordinates of the scintillation light emitting surface are shown in FIG. 3, and the y axis of a coordinate system formed by other aspheric relations does not have the relationship with the aspheric surface of the scintillation light emitting The y-axes of the coordinates of (a) are coincident, and the actual aspheric parameters satisfy the following relations:
the main body of the scintillation crystal except for the scintillation light emergent surface is of a cylindrical structure, the axis of the cylindrical structure coincides with the optical axis of the lens group and the central axis of the light receiving surface of the optical sensor, the lens group sequentially comprises a first lens L1, a second lens L2, a third lens L3, a fourth lens L4 and a fifth lens L5 along the scintillation light emergent direction, the two side surfaces of each lens are aspheric surfaces, and the following aspheric surface equations are satisfied:
y＝(x2/R)/(1+(1－(k+1)(x2/R2))1/2+A4x4+A6x6+A8x8+A10x10+A12x12+A14x14+A16x16，
wherein R is a radius of curvature (length in mm in absolute value) on the central axis, k is a conic coefficient, A4, A6, A8, A10, A12, A14, A16 are aspherical coefficients,
the values are as follows:
wherein N-R columns in the lens surface columns represent the object side surface of the Nth lens, and N-L represents the image side surface of the Nth lens;
the convex shape of the glittering light emitting surface satisfies the following aspheric surface formula:
y＝(x2/R)/(1+(1－(k+1)(x2/R2))1/2+A4x4+A6x6+A8x8+A10x10+A12x12+A14x14+A16x16，
wherein, R is the curvature radius (the length unit of the absolute value is mm) on the central axis, k is the cone coefficient, A4, A6, A8, A10, A12, A14 and A16 are aspheric coefficients, and the values are as follows:
R＝-0.87，k＝-2.92212，A4＝0.61403，A6＝0.02233，A8＝0.02111，A10＝-0.01808，A12＝0.00387，A14＝0.00039，A16＝-0.00015。
the focal lengths of the first lens, the second lens, the third lens and the fourth lens are respectively 2.04mm, -3.83mm, 239.14mm, 1.82mm, -1.60mm, and the thicknesses are respectively 0.43mm, 0.21mm, 0.21mm, 0.48mm and 0.27 mm.
The light sensor used in this experiment was a photomultiplier tube, but other light sensors known to those skilled in the art may be used.
In combination with the emitting angle of the aspheric surface, the distance between the object-side surface of the first lens and the scintillation light emitting surface is inconsistent with the traditional experience, performance improvement within 0.8mm is not obvious through experiments, performance improvement is realized after the distance is larger than 0.8mm, the object-side surface of the first lens needs to be large enough to cover the emitting range of the emitting light, when the distance is larger than 0.8mm, the area of the object-side surface of the first lens is larger than the area of the scintillation light emitting surface by at least 20% to completely receive the emitted scintillation light, only the shape is illustrated in fig. 3, and no drawing is performed according to the actual relative size.
It should be noted that, the aspheric formula is a known formula for lens design, and the difficulty lies in specific aspheric parameter design, after the parameters of the aspheric formula are disclosed, the conventional manufacturing technology in the prior art can easily implement the aspheric processing, and the specific processing manner is not described again.
Through comparison of a large amount of experimental data, the average data of the design comparison experiment of the invention is as follows, when other conditions are the same, the design of the lens group and the light emitting surface of the invention is not adopted, the detected number of the coincident events is reduced by more than 10%, and the arrangement of the visible lens group and the crystal light emitting surface can effectively improve the energy resolution of the system.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
Claims (7)
1. The utility model provides a scintillation crystal radiation detector with special play plain noodles with battery of lens complex, includes scintillation crystal, photosensor, preamplification circuit and multichannel analysis appearance, the scintillation crystal surface is provided with reflector layer and antireflection layer, and the reflector layer sets up on the surface except scintillation light emergence face, and antireflection layer sets up at scintillation light emergence face, the scintillation crystal is cerium-doped yttrium aluminate crystal, and scintillation crystal and photosensor setting are provided with multichannel analysis appearance, its characterized in that outside the casing in the encapsulation casing: a lens group matched with the wave band of the scintillation light of the cerium-doped yttrium aluminate crystal is arranged between the scintillation light emitting surface and the optical sensor, and the scintillation light emitting surface is provided with an aspheric surface convex structure matched with the wave band of the scintillation light of the cerium-doped yttrium aluminate crystal.
2. The radiation detector of claim 1, wherein:
the main part of scintillation crystal except that scintillation light outgoing face is the cylinder structure, and the axis of cylinder and the optical axis of battery of lens and the central axis coincidence of the light receiving surface of light sensor, the battery of lens includes first lens, second lens, third lens, fourth lens and fifth lens along scintillation light outgoing direction in proper order, and the both sides surface of each lens is the aspheric surface to satisfy following aspheric surface equation:
y＝(x2/R)/（1+（1－(k+1) (x2/R2)）1/2+A4x4+A6x6+A8x8+A10x10+A12x12+A14x14+A16x16，
wherein R is a radius of curvature (length in mm in absolute value) on the central axis, k is a conic coefficient, A4, A6, A8, A10, A12, A14, A16 are aspherical coefficients,
the values are as follows:
Wherein N-R in the lens surface column represents an object side surface of the Nth lens, and N-L represents an image side surface of the Nth lens;
the convex shape of the glittering light emitting surface satisfies the following aspheric surface formula:
y＝(x2/R)/（1+（1－(k+1) (x2/R2)）1/2+A4x4+A6x6+A8x8+A10x10+A12x12+A14x14+A16x16，
wherein, R is the curvature radius (the length unit of the absolute value is mm) on the central axis, k is the cone coefficient, A4, A6, A8, A10, A12, A14 and A16 are aspheric coefficients, and the values are as follows:
R=-0.87，k=-2.92212，A4=0.61403，A6=0.02233，A8=0.02111，A10=-0.01808，A12=0.00387，A14=0.00039，A16=-0.00015。
3. the radiation detector of claim 1, wherein: the light sensor is a silicon photomultiplier.
4. The radiation detector of claim 1, wherein: the focal lengths of the first lens, the second lens, the third lens and the fourth lens are respectively 2.04mm, -3.83mm, 239.14mm, 1.82mm and-1.60 mm.
5. The radiation detector of claim 1, wherein: the thicknesses of the first to fifth lenses are respectively as follows: 0.43mm, 0.21mm, 0.21mm, 0.48mm, 0.27 mm.
6. The radiation detector of claim 1, wherein: the distance between the object side surface of the first lens and the scintillation light exit surface is more than 0.8 mm.
7. The radiation detector of claim 1, wherein: the object side surface of the first lens is larger than the area of the scintillation light exit surface by 20%.
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