CN109444948A - A kind of ionisation chamber for air kerma absolute measurement - Google Patents
A kind of ionisation chamber for air kerma absolute measurement Download PDFInfo
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- 229910001080 W alloy Inorganic materials 0.000 claims description 8
- 239000011133 lead Substances 0.000 claims description 3
- 229910000978 Pb alloy Inorganic materials 0.000 claims description 2
- 229910001256 stainless steel alloy Inorganic materials 0.000 claims description 2
- 229910000831 Steel Inorganic materials 0.000 claims 1
- 239000010959 steel Substances 0.000 claims 1
- 230000005855 radiation Effects 0.000 description 13
- 230000005684 electric field Effects 0.000 description 7
- 239000011810 insulating material Substances 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 239000004696 Poly ether ether ketone Substances 0.000 description 4
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- 230000000149 penetrating effect Effects 0.000 description 2
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 2
- 239000010937 tungsten Substances 0.000 description 2
- 229910052721 tungsten Inorganic materials 0.000 description 2
- 229910000881 Cu alloy Inorganic materials 0.000 description 1
- 229910000737 Duralumin Inorganic materials 0.000 description 1
- -1 Ether ketone Chemical class 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 239000004411 aluminium Substances 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 235000010210 aluminium Nutrition 0.000 description 1
- 230000003471 anti-radiation Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- SBYXRAKIOMOBFF-UHFFFAOYSA-N copper tungsten Chemical compound [Cu].[W] SBYXRAKIOMOBFF-UHFFFAOYSA-N 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- RTZKZFJDLAIYFH-UHFFFAOYSA-N ether Substances CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 1
- 239000003063 flame retardant Substances 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T7/00—Details of radiation-measuring instruments
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Abstract
本发明提供一种可用于60～350kV范围内的X射线比释动能绝对测量的电离室，包括：屏蔽外壳；入射光阑，设置在屏蔽外壳的一个侧壁上；出口，设置在屏蔽外壳的与入射光阑相对的另一个侧壁上；高压极，设置在屏蔽外壳内，位于入射光阑与出口的中心点连线的一侧；保护极，设置在屏蔽外壳内，位于入射光阑与出口的中心点连线的与高压极相对的另一侧，与高压极平行，保护极内设置有通孔；收集极，设置于保护极的通孔内，收集极与保护极之间设置有间隙，并且收集极的上表面与保护极的上表面处于同一平面上；保护环，设置在高压极的周缘与保护极的周缘之间，包括多个层叠的保护环单元，将与入射光阑和出口对应的位置设置为可使X射线通过。
The invention provides an ionization chamber that can be used for absolute measurement of X-ray kerma energy in the range of 60-350kV, comprising: a shielding shell; an incident aperture, which is arranged on one side wall of the shielding shell; On the other side wall opposite to the entrance aperture; the high-voltage electrode is arranged in the shielding casing and is located on the side of the line connecting the entrance aperture and the center point of the exit; the protection electrode is arranged in the shielding casing and is located between the incident aperture and the exit. The other side of the line connecting the center point of the outlet opposite to the high voltage electrode is parallel to the high voltage electrode, and a through hole is arranged in the protection electrode; the collector electrode is arranged in the through hole of the protection electrode, and a gap, and the upper surface of the collector electrode and the upper surface of the guard electrode are on the same plane; the guard ring, which is arranged between the periphery of the high-voltage electrode and the periphery of the guard electrode, includes a plurality of stacked guard ring units, which will be connected with the incident aperture. The position corresponding to the exit is set so that X-rays can pass through.
Description
Technical field
The present invention relates to the fields of ionising radiation metering, in particular to a kind of to be used for X-ray air kerma absolute measuring
The ionisation chamber of amount.
Background technique
With the development of science and technology with social progress, Nuclear Science and Technology are increasingly applied in national economy
Various industries.At the same time, nuclear safety and ionising radiation are accompanied safely, expansion and accuracy of measurement to actinometry range
Raising propose requirements at the higher level.
The application of research and the radiation of radiation safety all be unable to do without the metering of electric radiation amount.Need various amount of radiation units
The characteristic of radiation source is characterized, the property of radiation field is described, the transmitting of energy and is shone when measuring coupled radiation and convection heat transfer
The variation degree and rule of interior of articles.Exposure is exactly to describe the amount of radiation field.Exposure is once to characterize X, gamma-ray
Intensity, X, gamma-ray dosage correlation run practical amount be by based on air kerma multiplied by corresponding conversion coefficient
It obtains.Air kerma and numerous practical amounts associated there are to carry out the works such as radiation protection, radiation environmental monitoring
The basis of work.
Derived quantity of the Kerma as the International System of Units, proper noun Gy, dimension J/kg, No. ICRU60 report
Be defined as follows to Kerma: all times that interaction is released occur in the air of dm mass for uncharged particle
The initial kinetic energy summation dEtr of grade electronics is divided by dm.Free-air ionization chamber is all made of in existing calibration laboratory as air ratio
The measuring device for releasing kinetic energy, for the absolute measurement of air kerma, and as Laboratory X-ray dosage primary mark
It is quasi-.But existing free-air ionization chamber's measurement X-ray energy is up to 250kV, there are no for more than 250kV energy
X-ray measurement capability, be unable to satisfy the requirement of existing X-ray air kerma canonical measure energy range.
Summary of the invention
The X that cannot achieve for existing air kerma absolute measurement device to energy range in 250kV~350kV is penetrated
Line carries out the problem of air kerma measurement, and it is freely empty that the present invention provides a kind of X-ray that can be used for 60~350kV gamut
Gas ionisation chamber.
The present invention provides a kind of ionisation chamber of X-ray Kerma absolute measurement that can be used within the scope of 60~350kV, packet
It includes:
Shield shell；
Incident diaphragm is arranged on a side wall of shielding shell；
Outlet is arranged on another side wall opposite with incident diaphragm of shielding shell；
High-pressure stage, setting is in shielding shell, positioned at the side of the central point line of incident diaphragm and outlet；
Protect pole, setting shielding shell in, positioned at incident diaphragm with outlet central point line it is opposite with high-pressure stage
The other side, it is parallel with high-pressure stage, protection extremely in is provided with through-hole；
Collector is set in the through-hole of protection pole, is provided with gap between collector and protection pole, and collector
The upper surface of upper surface and protection pole is in the same plane；
Protection ring is arranged between the periphery of high-pressure stage and the periphery of protection pole, the protection ring element including multiple stackings,
Position corresponding with incident diaphragm and outlet is configured such that X-ray passes through.
In some embodiments, shielding shell is made of lead, stainless steel and aluminium alloy, and incident diaphragm is by tungsten alloy system
At high-pressure stage, protection pole, collector and protection ring are all made of aluminium alloy.Particularly, shielding shell to be includes stainless steel layer-
Lead layer-stainless steel layer multilayered structure, more particularly, the side wall that incident diaphragm is arranged includes stainless steel layer-lead layer-stainless steel
The multilayered structure of layer-aluminium alloy layer.In some embodiments, stainless steel layer is with a thickness of at least 3mm, and lead layer is with a thickness of at least
10mm, aluminium alloy layer is with a thickness of at least 3mm.
In some embodiments, shielding shell is cuboid, and incident diaphragm and outlet are circle, high-pressure stage, protection pole
With collection extremely rectangular slab, the extremely internal through-hole of protection is rectangle.
In some embodiments, the diameter of incident diaphragm is adjustable, particularly, can adjust between 5-60mm,
For example, 10,20 or 50mm.
In some embodiments, protecting the gap between pole and collector is 3mm to 8mm, is 5mm particularly.
In some embodiments, protect the upper level difference of pole and collector less than 20 μm, particularly, less than 10 μ
M, and/or the surface smoothness of pole and collector is protected less than 10 μm, particularly, less than 5 μm.
In some embodiments, the surface smoothness of high-pressure stage is less than 10 μm, particularly, less than 5 μm.
In some embodiments, the surface smoothness of protection ring is less than 10 μm, particularly, less than 5 μm.
In some embodiments, on the central point line direction of incident diaphragm and outlet, the size of high-pressure stage is greater than
600mm is less than 720mm, and the size of pole is protected to be greater than 600mm, is less than 720mm, and the size of collector is greater than 120mm, is less than
180mm；The central point line perpendicular to incident diaphragm and outlet and be parallel to high-pressure stage direction on, the size of high-pressure stage is big
In 500mm, it is less than 620mm, the size of pole is protected to be greater than 500mm, be less than 620mm, the size of collector is greater than 450mm, is less than
510mm。
In some embodiments, the thickness of high-pressure stage is greater than 80mm, is less than 120mm, and the thickness of pole is protected to be greater than 80mm,
Less than 120mm, the thickness of collector is greater than 15mm, is less than 30mm.
In some embodiments, the distance between high-pressure stage and protection pole are greater than 450mm, are less than 520mm.
In some embodiments, attenuation length is 400 to 460mm.
In some embodiments, the outer edge alignment of high-pressure stage, protection pole and protection ring.
In some embodiments, each protection ring element is sheet annular, and protecting the Ring Width of ring element is 10-
20mm, protecting the height of ring element is 10-20mm, and the spacing between adjacent guard rings unit is less than 2mm.
In some embodiments, the diameter of outlet is 1.5-2.5 times of incident diaphragm.
In some embodiments, protection ring is arranged through-hole in position corresponding with incident diaphragm and outlet or reserves sky
Gap.Particularly, it is greater than the straight of incident diaphragm in the diameter of through-hole of position corresponding with incident diaphragm setting or the height in gap
Diameter, in position corresponding with outlet, the diameter of the through-hole of setting or the height in gap are less than the diameter of outlet.
The present invention can be realized it is following the utility model has the advantages that
Compared to previous free-air ionization chamber, the present invention by the shape of each component, material, size in ionisation chamber with
And the combination of positional relationship, provide it is a kind of can be used in bigger energy measurement range, can especially meet 250kV~350kV
The ionisation chamber of X-ray air kerma absolute measurement demand in range；
Since free-air ionization chamber of the invention has higher machining accuracy, introduced uncertainty is smaller, surveys
It is more accurate to measure；
Free-air ionization chamber of the invention uses the design of iris diaphgram, can make to measure sensitive volume in a certain range
Interior variation can carry out the measurement definite value of air kerma more flexiblely.
Live definite value can be carried out to X-ray Reference radiation field using free-air ionization chamber of the invention, solved
The quantity demand of 250kV~350kV X-ray air kerma.
Detailed description of the invention
By the description made for the present invention of below with reference to attached drawing, those skilled in the art will manage more fully hereinafter
Solve other objects and advantages of the present invention.
Fig. 1 shows the structural profile illustration of free-air ionization chamber according to an embodiment of the invention.
Fig. 2 shows the structural profile illustrations of diaphragm according to an embodiment of the invention.
Fig. 3 shows the structural upright schematic diagram of free-air ionization chamber according to an embodiment of the invention.
Appended drawing reference meaning in figure is as follows:
1: shielding shell
2: incident diaphragm
3: outlet
4: high-pressure stage
5: protection pole
6: collector
7: the gap between collector and protection pole
8: protection ring
81: protection ring element
9: collecting region
10: measurement volume
201: penetrating X-ray
202: X-ray is used in measurement
203: scattered x-ray
210: stainless steel
220: tungsten alloy
All attached drawings are only illustrative purpose, wherein what the number of each component, size etc. were not limit the invention in any way
Embodiment.
Specific embodiment
Below with reference to the embodiments and with reference to the accompanying drawing the technical solutions of the present invention will be further described.Illustrating
In book, the same or similar drawing reference numeral indicates the same or similar component.
In the following detailed description, for convenient for explain, elaborate many concrete details with provide to present disclosure implement
The comprehensive understanding of example.It should be apparent, however, that one or more embodiments without these specific details can also be by reality
It applies.In other cases, well known construction and device is diagrammatically embodied to simplify attached drawing.
The present invention provides a kind of ionisation chamber of X-ray Kerma absolute measurement that can be used within the scope of 60~350kV, figure
1 shows the structural schematic diagram of free-air ionization chamber according to an embodiment of the invention, which includes:
Shield shell 1；
Incident diaphragm 2 is arranged on a side wall of shielding shell 1；
Outlet 3 is arranged on another side wall opposite with incident diaphragm 2 of shielding shell 1；
High-pressure stage 4, setting is in shielding shell 1, positioned at the side of incident diaphragm 2 and the central point line of outlet 3；
Pole 5 is protected, setting is in shielding shell 1, positioned at incident diaphragm 2 and the central point line of outlet 3 and high-pressure stage 4
The opposite other side, it is parallel with high-pressure stage 4, it protects in pole 5 and is provided with through-hole；
Collector 6 is set in the through-hole of protection pole 5, is provided with gap 7 between collector 6 and protection pole 5, and receive
The upper surface of collector 6 and the upper surface of protection pole 5 are in the same plane；
Protection ring 8 is arranged between the periphery of high-pressure stage 4 and the periphery of protection pole 5, the protection ring list including multiple stackings
Member 81 will be configured such that X-ray passes through with incident diaphragm 2 and 3 corresponding positions of outlet.
Wherein, the space formed between collector 6 and high-pressure stage 4 is collecting region 9, is formed by high-pressure stage 4 and collector 6
The electric field in the region that electric field line determines collects ionizing particle, length of the length and width in the region substantially with collector 6
Degree and equivalent width.The intersection in the region that collecting region 9 and the X-ray for entering incident diaphragm are passed through is measurement volume 10.In this hair
Under the conditions of each size of components, material employed in bright etc., the existing charged particle equilibrium condition in volume 10 that measures makes institute
The ionization current of measurement can be corresponding with the generation of required air kerma, so as to penetrate for the X within the scope of 60~350kV
Line Kerma absolute measurement.
In some embodiments, shielding shell is made of lead, stainless steel and aluminium, and incident diaphragm is made of tungsten alloy, high
Pressure pole, protection pole, collector and protection ring are made of aluminium alloy.In order to which shield effectiveness is better achieved, shielding shell is to include
Stainless steel layer-lead layer-stainless steel layer multilayered structure, since X-ray incidence side needs better shield effectiveness, setting
The side wall (i.e. X-ray thus incident side) of incident diaphragm includes that stainless steel layer-lead layer-stainless steel layer-aluminium alloy layer is more
Layer structure.In some embodiments, stainless steel layer is with a thickness of at least 3mm, and lead layer is with a thickness of at least 10mm, aluminium alloy layer thickness
It is at least 3mm.In some embodiments, stainless steel layer is with a thickness of at least 5mm, and lead layer is with a thickness of at least 20mm, aluminium alloy layer
With a thickness of at least 5mm.Particularly, the side wall that incident diaphragm is arranged includes stainless steel layer (5mm)-lead layer (30mm)-stainless steel layer
(5mm)-aluminium alloy layer (5mm), other side walls include stainless steel layer (5mm)-lead layer (15mm)-stainless steel layer (5mm).
In some embodiments, shielding shell is cuboid.Length direction is the path direction that X-ray passes through.
The material of incident diaphragm is tungsten alloy, and structure needs high precision to process, in some embodiments, incident light
Door screen is circle.The diameter of incident diaphragm can be set to it is adjustable, so as to so that measurement sensitive volume in a certain range
Variation, can carry out the measurement definite value of air kerma more flexiblely.Particularly, the diameter of incident diaphragm can be in 5-
It is adjusted between 60mm, for example, 10,20 or 50mm.Fig. 2 shows the structures of diaphragm according to an embodiment of the invention to show
It is intended to, wherein coating stainless steel material 210 in diaphragm periphery and front end, diaphragm is made of tungsten alloy 220.X-ray passes through light
Can penetrate or scatter when late, such as penetrate X-ray 201 and scattered x-ray 203, and the X-ray without penetrating or scattering be can
For the X-ray of measurement, such as measurement X-ray 202.
Each diaphragm of free-air ionization chamber need to arrange in pairs or groups corresponding tungsten plug (plug made of tungsten alloy), and tungsten plug is solid
Construction, it is ensured that it can completely fill in diaphragm mouth, and diaphragm mouth is blocked completely.
It is arranged between the outlet with incident diaphragm opposite side and incident diaphragm and forms the path passed through for X-ray,
In some embodiments, it exports as circle, particularly, the diameter of outlet is 1.5-2.5 times of incident diaphragm, thus formation one
A coniform region passed through for X-ray.
In some embodiments, high-pressure stage, protection pole and collector are rectangular slab.Collector, protection pole and high pressure
The parallel-plate electrode that spacing distance is d is collectively formed in pole；Apply polarizing voltage on high-pressure stage, and pole and collector is protected to keep
It is grounded (virtual earth), to generate electric field between the electrodes.Spacing distance d according to collector, protection pole and high-pressure stage size and
Selection, influence of the spacing distance d to measurement is embodied in some modifying factors, real although theoretically seeing that d is the bigger the better
In the case of border, the modifying factor of the bigger generation of d is bigger, and the volume of entire instrument and quality are also difficult to ensure.In some realities
It applies in scheme, the distance between high-pressure stage and protection pole are greater than 450mm.The general spacing distance is no more than 520mm.In some realities
It applies in scheme, the distance between high-pressure stage and protection pole are 460-500mm, for example, about 480mm.
Collector is set in the extremely internal through-hole of protection, is provided with gap between collector and protection pole, and collect
The upper surface of pole and the upper surface of protection pole are in the same plane.Collector and the coplanarity of protection pole there are certain requirements,
Protect the upper level of pole and collector almost the same, specifically, the upper level difference of the two is less than 20 μm, particularly,
Less than 10 μm, more particularly, less than 5 μm.The bad uniformity that will affect electric field of coplanarity, the uniformity of electric field is bad to be introduced
Modifying factor becomes larger.
In some embodiments, the extremely internal through-hole of protection is rectangle, and collector is also rectangle, protects pole and collector
Between maintain constant gap, the width in gap is 3mm to 8mm, is 5mm particularly.On the one hand the width in gap will affect
The uniformity of electric field, gap is bigger, and uniformity is poorer；On the other hand, the width in gap will affect the size of collecting region, relief width
Degree is too small, will cause collector and the induced current between pole is protected to increase, this electric current will avoid.
Collector and protection pole can also be collectively referenced as collection-protection pole.
Distortion of the protection ring to reduce electric field is arranged between the periphery of high-pressure stage and the periphery of protection pole, including more
The protection ring element of a stacking, and position corresponding with incident diaphragm and outlet is arranged to X-ray can be made to pass through.
In some embodiments, each protection ring element is sheet annular, for example, by duralumin, hard alumin ium alloy strip straight-flanked ring group
At as shown in Figure 3.The Ring Width for protecting ring element is 10-20mm, and protecting the height of ring element is 10-20mm, adjacent protection
Spacing between ring element is less than 2mm, particularly, is less than 1.2mm.In order to be conducive to keep field uniformity, in some implementations
In scheme, protection ring is made of at least 25 protection ring elements.Particularly, protection ring is made of 30 protection ring elements, each
The Ring Width of a protection ring element is 15mm, is highly 15mm, the gap between adjacent guard rings unit is about 1mm.Protection
The length and width of ring element extremely determine according to high-pressure stage and protection, can respectively with high-pressure stage and protect pole size in the corresponding direction
Equally, so that the outer edge alignment of high-pressure stage, protection pole and protection ring.
In some embodiments, through-hole is arranged in position corresponding with incident diaphragm and outlet in protection ring.Particularly, exist
The diameter of the through-hole of position setting corresponding with incident diaphragm is greater than the diameter of incident diaphragm, is arranged in position corresponding with outlet
The diameter of through-hole be less than the diameter of outlet, thus with incident diaphragm and exporting be collectively formed one it is coniform for X-ray
By region.
In some embodiments, protection ring reserves gap in position corresponding with incident diaphragm and outlet, such as passes through
Thickness, gap, the number etc. of adjustment protection ring element make protection ring X can be made to penetrate in position corresponding with incident diaphragm and outlet
Line passes through, as shown in Figure 3.Particularly, the height in the gap of position corresponding with incident diaphragm setting is greater than incident diaphragm
Diameter, in position corresponding with outlet, the height in the gap of setting is less than the diameter of outlet.
In order to be conducive to keep field uniformity, the surface of any of protection ring, collector, protection pole, high-pressure stage is flat
Whole degree is less than 10 μm, particularly, less than 5 μm, more particularly, less than 2 μm.
In some embodiments, less than 2 μm, collector is total to protection pole for collector and the surface smoothness of protection pole
Face property is better than 5 μm.
Ionisation chamber provided by the invention is realized by shape, material, size and the positional relationship etc. of each component of selection
The X-ray air kerma absolute measurement demand within the scope of 250kV~350kV can be met under finite size, device is total
Weight about 600kg.
In some embodiments, in the central point line direction (hereinafter also referred to a axis direction) of incident diaphragm and outlet
On, the size of high-pressure stage is greater than 600mm, is less than 720mm, protects the size of pole to be greater than 600mm, is less than 720mm, the ruler of collector
It is very little to be greater than 120mm, it is less than 180mm；In the central point line perpendicular to incident diaphragm and outlet and it is parallel to the direction of high-pressure stage
In (hereinafter also referred to b axis direction), the size of high-pressure stage is greater than 500mm, is less than 620mm, and the size of pole is protected to be greater than 500mm,
Less than 620mm, the size of collector is greater than 450mm, is less than 510mm.Particularly, size of the high-pressure stage in a axis direction is greater than
Size in b axis direction, protection pole are greater than the size in b axis direction in the size in a axis direction, and collector is in the axis side a
Upward size is less than the size in b axis direction.
In some embodiments, at the same time perpendicular on the direction (hereinafter also referred to c-axis direction) of a axis and b axis, high pressure
The thickness of pole is greater than 80mm, is less than 120mm, protects the thickness of pole to be greater than 80mm, is less than 120mm, the thickness of collector is greater than
15mm is less than 30mm.If pole plate is too thick to generate deformation because of self weight, it is difficult to long-term to keep measurement stability.
Plane locating for diaphragm front surface is parallel with b axis, and plane locating for diaphragm front surface and collector are in its b axis direction
Heart imaging plane is parallel, and the distance between two planes are also referred to as attenuation of air length or attenuation length.In some embodiments
In, it is about 430mm particularly that attenuation length, which is 400 to 460mm,.
In some embodiments, bracket is set in shielding shell, and high-pressure stage, protection pole, collector and protection ring are logical
It crosses and is fixed on the bracket and is arranged on required position.The fixed each component of insulating materials can be used, insulating materials can be poly-
Object adhesive is closed, resistivity is generally greater than 1012Ω/cm is particularly higher than 1014Ω/cm, it is, for example, possible to use PEEK (polyethers
Ether ketone, English name polyetheretherketone), resistivity is up to 1016Ω/cm.PEEK has resistance to positive high temperature 260
Degree, mechanical performance is excellent, self-lubrication is good, chemicals-resistant burn into is fire-retardant, peel resistance, wearability, the superpower machine such as anti-radiation
Tool performance.PEEK can be used in all insulating materials in the total of ionisation chamber.
It, can by the technology in order to realize that good flatness and coplanarity, the present invention use numerical controlled machinery processing technology
To meet requirement of the present invention to surface smoothness, particularly, surface smoothness is up to μm rank.
Embodiment
Ionization cell structure in embodiment is as shown in figure 3, shielding shell is cuboid, and pole plate is rectangle, and use is following
Material preparation:
Diaphragm: tungsten-copper alloy
Electrode plate: aluminium alloy 6063
Shell: stainless steel 304 lead-sheathing is shielded, wall where diaphragm is pressed outside ionisation chamber to interior including following layers: stainless steel
Layer (5mm)-lead layer (30mm)-stainless steel layer (5mm)-aluminium alloy layer (5mm)；Remaining wall includes following layers: stainless steel layer
(5mm)-lead layer (15mm)-stainless steel layer (5mm).
Diaphragm is circle, and diameter is variable, and for surface smoothness within 0.5 μm, structure is as shown in Figure 2.
Outlet is circle, and diameter is variable, and diameter is 2 times or so of diaphragm diameter.
It is fixed between pole plate and shell by insulating materials PEEK-450G.
The major parameter for influencing free-air ionization chamber includes: incident diaphragm diameter, attenuation of air length, collection-protection
Electrode spacing d between pole and high-pressure stage, the geometric dimension etc. of collector, specific value is as shown in table 1.Diaphragm diameter is designed as
Greater than the diameter of x-ray source, in order to change the measurement volume of X-ray, free-air ionization chamber point in free-air ionization chamber
Not She Ji 3 kinds of different-diameter sizes diaphragm.
The major parameter (mm) of 1 free-air ionization chamber of table
| Device parameter | Numerical value |
| Diaphragm diameter | 10、20、50 |
| Diaphragm tungsten alloy thickness | 25 |
| Interpolar distance d | 481 |
| Collector a shaft size | 150 |
| Collector b shaft size | 480 |
| Collector c-axis size | 20 |
| Protect pole a shaft size | 660 |
| Protect pole b shaft size | 560 |
| Protect pole c-axis size | 100 |
| Gap between collector and protection pole | 5 |
| High-pressure stage a shaft size | 660 |
| High-pressure stage b shaft size | 560 |
| High-pressure stage c-axis size | 100 |
| Attenuation length | 430 |
Frame structure is dug out by machining at the pole plate back side of free-air ionization chamber, with enhance whole rigidity with
Stability.
Collector is made with protection pole of aluminium alloy.Collector and the surface smoothness of protection pole are respectively less than 2 μm, collector
It is better than 5 μm with the coplanarity of protection pole, that is, the upper level of protection pole and collector difference is no more than 5 μm.Collector passes through
High insulating materials is fixed in the rectangular through-hole at protection pole center of inside, is not connect mutually between collector and the geometry for protecting pole
Touching, and the gap of each interplanar is maintained at 5mm between collector and protection pole.Collection-protection pole and high-pressure stage pass through height
Insulating materials is fixed, and interpolar distance d between the two is kept.
It protects and has been evenly arranged protection ring between the periphery of pole and the periphery of high-pressure stage, protection ring is made of aluminium alloy, table
Surface evenness is less than 5 μm.Protection ring is made of 30 protection ring elements in the present embodiment, and protection ring element is flat strip shaped rectangle
Ring, it is highly 15mm that the Ring Width of each, which is 15mm, and protecting the gap between ring element is 1mm, protects ring element in a
The size of axis and b axis is identical as protection pole and high-pressure stage.
The ionisation chamber of the present embodiment can be used for the X-ray Kerma absolute measurement within the scope of 60~350kV.
Although in conjunction with attached drawing, the present invention is described, and embodiment disclosed in attached drawing is intended to reality of the invention
The mode of applying illustrates, and should not be understood as to a kind of limitation of the invention.
It will be appreciated by the skilled addressee that in the case where the principle and spirit without departing substantially from present general inventive concept,
These embodiments can be made a change, the scope of the present invention is limited with claim and their equivalent.
Claims (10)
1. a kind of ionisation chamber for the X-ray Kerma absolute measurement that can be used within the scope of 60~350kV, comprising:
Shield shell；
Incident diaphragm is arranged on a side wall of shielding shell；
Outlet is arranged on another side wall opposite with incident diaphragm of shielding shell；
High-pressure stage, setting is in shielding shell, positioned at the side of the central point line of incident diaphragm and outlet；
Protect pole, setting in shielding shell, positioned at incident diaphragm with outlet central point line it is opposite with high-pressure stage another
Side, it is parallel with high-pressure stage, through-hole is provided in protection extremely；
Collector is set in the through-hole of protection pole, is provided with gap, and the upper table of collector between collector and protection pole
The upper surface in face and protection pole is in the same plane；
Protection ring, the periphery of high-pressure stage is set and protect pole periphery between, the protection ring element including multiple stackings will be with
The corresponding position of incident diaphragm and outlet is configured such that X-ray passes through.
2. ionisation chamber according to claim 1, wherein shielding shell is made of lead, stainless steel and aluminium alloy, incident diaphragm
It is made of tungsten alloy, high-pressure stage, protection pole, collector and protection ring are made of aluminium alloy, and particularly, shielding shell to be includes not
Become rusty steel layer-lead layer-stainless steel layer multilayered structure, and more particularly, the side wall that incident diaphragm is arranged includes stainless steel layer-lead layer-
Stainless steel layer-aluminium alloy layer multilayered structure, also, stainless steel layer, with a thickness of at least 3mm, lead layer is with a thickness of at least 10mm, aluminium
Alloy layer thickness is at least 3mm.
3. ionisation chamber according to claim 1 or 2, wherein shielding shell is cuboid, incident diaphragm and outlet are circle,
High-pressure stage, protection pole and collection extremely rectangular slab, the extremely internal through-hole of protection is rectangle.
4. ionisation chamber according to claim 1 or 2, wherein the diameter of incident diaphragm is adjustable, it particularly, can be in 5-
It is adjusted between 60mm, for example, 10,20 or 50mim；Particularly, the diameter of outlet is 1.5-2.5 times of incident diaphragm.
5. ionisation chamber according to claim 1 or 2, wherein the gap between protection pole and collector is 3mm to 8mm, it is special
It not, is 5mm；
And/or
The upper level difference of pole and collector is protected less than 20 μm, particularly, less than 10 μm；
And/or
Protect the surface smoothness of pole and collector less than 10 μm, particularly, less than 5 μ μm.
6. ionisation chamber according to claim 1 or 2, wherein the surface smoothness of high-pressure stage and/or protection ring is less than 10 μm,
Particularly, less than 5 μm.
7. ionisation chamber according to claim 1 or 2, wherein on the central point line direction of incident diaphragm and outlet, it is high
It presses the size of pole to be greater than 600mm, is less than 720mm, protect the size of pole to be greater than 600mm, be less than 720mm, the size of collector is big
In 120mm, it is less than 180mm；
The central point line perpendicular to incident diaphragm and outlet and be parallel to high-pressure stage direction on, the size of high-pressure stage is greater than
500mm is less than 620mm, and the size of pole is protected to be greater than 500mm, is less than 620mm, and the size of collector is greater than 450mm, is less than
510mm；
The thickness of high-pressure stage is greater than 80mm, is less than 120mm, protects the thickness of pole to be greater than 80mm, is less than 120mm, the thickness of collector
Degree is greater than 15mm, is less than 30mm；
The distance between high-pressure stage and protection pole are greater than 450mm, are less than 520mm；
And/or
Attenuation length is 400 to 460mm.
8. ionisation chamber according to claim 7 protects the annular of ring element wherein each protection ring element is sheet annular
Width is 10-20mm, and protecting the height of ring element is 10-20mm, and the spacing between adjacent guard rings unit is less than 2mm.
9. ionisation chamber according to claim 1 or 2, wherein the outer edge alignment of high-pressure stage, protection pole and protection ring.
10. ionisation chamber according to claim 1 or 2, wherein protection ring is set in position corresponding with incident diaphragm and outlet
It sets through-hole or reserves gap, particularly, the diameter of the through-hole of setting or the height in gap are big in position corresponding with incident diaphragm
In the diameter of incident diaphragm, in position corresponding with outlet, the diameter of the through-hole of setting or the height in gap are less than the straight of outlet
Diameter.
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| CN201811653869.0A CN109444948B (en) | 2018-12-29 | 2018-12-29 | Ionization chamber for absolute measurement of air kerma |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111487662A (en) * | 2020-06-02 | 2020-08-04 | 中国计量科学研究院 | Free air ionization chamber and air kerma measuring method |
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