CN109444948B - Ionization chamber for absolute measurement of air kerma - Google Patents
Ionization chamber for absolute measurement of air kerma Download PDFInfo
- Publication number
- CN109444948B CN109444948B CN201811653869.0A CN201811653869A CN109444948B CN 109444948 B CN109444948 B CN 109444948B CN 201811653869 A CN201811653869 A CN 201811653869A CN 109444948 B CN109444948 B CN 109444948B
- Authority
- CN
- China
- Prior art keywords
- electrode
- collector
- diaphragm
- guard
- less
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 238000005259 measurement Methods 0.000 title claims abstract description 29
- 230000001681 protective effect Effects 0.000 claims abstract description 22
- 239000010935 stainless steel Substances 0.000 claims description 27
- 229910001220 stainless steel Inorganic materials 0.000 claims description 26
- 229910000838 Al alloy Inorganic materials 0.000 claims description 16
- 239000011800 void material Substances 0.000 claims description 8
- 230000005855 radiation Effects 0.000 description 13
- 230000005684 electric field Effects 0.000 description 8
- 229910001080 W alloy Inorganic materials 0.000 description 7
- 239000000463 material Substances 0.000 description 6
- 239000004696 Poly ether ether ketone Substances 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 4
- 239000011810 insulating material Substances 0.000 description 4
- 229920002530 polyetherether ketone Polymers 0.000 description 4
- JUPQTSLXMOCDHR-UHFFFAOYSA-N benzene-1,4-diol;bis(4-fluorophenyl)methanone Chemical compound OC1=CC=C(O)C=C1.C1=CC(F)=CC=C1C(=O)C1=CC=C(F)C=C1 JUPQTSLXMOCDHR-UHFFFAOYSA-N 0.000 description 3
- 238000012937 correction Methods 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 3
- 229910052721 tungsten Inorganic materials 0.000 description 3
- 239000010937 tungsten Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 2
- 230000005865 ionizing radiation Effects 0.000 description 2
- 238000003754 machining Methods 0.000 description 2
- 230000000149 penetrating effect Effects 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229910000881 Cu alloy Inorganic materials 0.000 description 1
- 229910000978 Pb alloy Inorganic materials 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 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
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- SBYXRAKIOMOBFF-UHFFFAOYSA-N copper tungsten Chemical compound [Cu].[W] SBYXRAKIOMOBFF-UHFFFAOYSA-N 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000012774 insulation material Substances 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 229910001256 stainless steel alloy Inorganic materials 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T7/00—Details of radiation-measuring instruments
Landscapes
- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- General Physics & Mathematics (AREA)
- High Energy & Nuclear Physics (AREA)
- Molecular Biology (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Measurement Of Radiation (AREA)
Abstract
The invention provides an ionization chamber for absolute measurement of X-ray kerma energy in the range of 60-350 kV, comprising: a shielding housing; an incident diaphragm disposed on one side wall of the shield case; an outlet provided on the other side wall of the shield case opposite to the incident diaphragm; the high-voltage pole is arranged in the shielding shell and is positioned at one side of a connecting line of the center point of the incident diaphragm and the outlet; the protective electrode is arranged in the shielding shell, is positioned on the other side of the connecting line of the central point of the incident diaphragm and the outlet, which is opposite to the high-voltage electrode, is parallel to the high-voltage electrode, and is internally provided with a through hole; the collector is arranged in the through hole of the protective electrode, a gap is arranged between the collector and the protective electrode, and the upper surface of the collector and the upper surface of the protective electrode are positioned on the same plane; the protection ring is arranged between the periphery of the high-voltage pole and the periphery of the protection pole, and comprises a plurality of laminated protection ring units, and positions corresponding to the incident diaphragm and the outlet are arranged to enable X-rays to pass through.
Description
Technical Field
The invention relates to the field of ionizing radiation metering, in particular to an ionization chamber for absolute measurement of X-ray air kerma.
Background
With the development of science and technology and the progress of society, nuclear science and technology are increasingly widely applied to various industries in national lives. At the same time, nuclear safety is accompanied by ionizing radiation safety, and higher requirements are put on expansion of radiation measurement range and improvement of measurement accuracy.
Both the investigation of radiation safety and the application of radiation are independent of the metering of the amount of electrical radiation. Various units of radiation are required to characterize the radiation source, describe the nature of the radiation field, measure the energy transfer as the radiation interacts with the substance and the degree and regularity of the change inside the illuminated object. The dose is the dose describing the radiation field. The irradiation quantity is used for representing the intensity of X-rays and gamma-rays, and the dose-related operation practical quantity of the X-rays and the gamma-rays is obtained by multiplying corresponding conversion coefficients by taking air kerma as a basis. Air kerma and the numerous practical quantities associated with it are the basis for performing radiation protection, radiation environment monitoring, etc.
The derived quantity of the kerma is the international unit system, the proper noun is Gy, the dimension is J/kg, and the report number ICRU is as follows: the sum dEtr of the initial kinetic energies of all secondary electrons released by the uncharged particles interacting in the air of dm mass is divided by dm. The free air ionization chamber is used as a measuring device of air kerma in the existing calibration laboratory and is used for absolute measurement of the air kerma and is used as a laboratory X-ray dose primary standard. However, the maximum energy of the X-ray measured by the existing free air ionization chamber is 250kV, and the requirement of the energy range of the existing X-ray air kerma standard measurement cannot be met because the X-ray measuring capability exceeding the energy of 250kV is not provided.
Disclosure of Invention
Aiming at the problem that the existing absolute measuring device for the air kerma can not realize the air kerma measurement of the X-rays with the energy range of 250kV to 350kV, the invention provides the free air ionization chamber for the X-rays with the full range of 60 kV to 350 kV.
The invention provides an ionization chamber for absolute measurement of X-ray kerma energy in the range of 60-350 kV, comprising:
A shielding housing;
an incident diaphragm disposed on one side wall of the shield case;
An outlet provided on the other side wall of the shield case opposite to the incident diaphragm;
The high-voltage pole is arranged in the shielding shell and is positioned at one side of a connecting line of the center point of the incident diaphragm and the outlet;
The protective electrode is arranged in the shielding shell, is positioned on the other side of the connecting line of the central point of the incident diaphragm and the outlet, which is opposite to the high-voltage electrode, is parallel to the high-voltage electrode, and is internally provided with a through hole;
The collector is arranged in the through hole of the protective electrode, a gap is arranged between the collector and the protective electrode, and the upper surface of the collector and the upper surface of the protective electrode are positioned on the same plane;
The protection ring is arranged between the periphery of the high-voltage pole and the periphery of the protection pole, and comprises a plurality of laminated protection ring units, and positions corresponding to the incident diaphragm and the outlet are arranged to enable X-rays to pass through.
In some embodiments, the shielding enclosure is made of lead, stainless steel, and aluminum alloy, the incident diaphragm is made of tungsten alloy, and the high voltage pole, the guard pole, the collector pole, and the guard ring are all made of aluminum alloy. In particular, the shield case is a multilayer structure including a stainless steel layer-a lead layer-a stainless steel layer, and more particularly, a side wall provided with the incident diaphragm includes a multilayer structure including a stainless steel layer-a lead layer-a stainless steel layer-an aluminum alloy layer. In some embodiments, the stainless steel layer has a thickness of at least 3mm, the lead layer has a thickness of at least 10mm, and the aluminum alloy layer has a thickness of at least 3mm.
In some embodiments, the shielding enclosure is a cuboid, the entrance aperture and the exit are circular, the high voltage pole, the guard pole and the collector are rectangular plates, and the through holes inside the guard pole are rectangular.
In some embodiments, the diameter of the entrance stop may be adjustable, in particular, between 5 and 60mm, for example 10, 20 or 50mm.
In some embodiments, the gap between the guard and collector is 3mm to 8mm, in particular 5mm.
In some embodiments, the upper surface height difference of the guard and collector is less than 20 μm, in particular less than 10 μm, and/or the surface flatness of the guard and collector is less than 10 μm, in particular less than 5 μm.
In some embodiments, the high voltage electrode has a surface flatness of less than 10 μm, in particular, less than 5 μm.
In some embodiments, the guard ring has a surface flatness of less than 10 μm, in particular less than 5 μm.
In some embodiments, the dimension of the high voltage electrode is greater than 600mm, less than 720mm, the dimension of the guard electrode is greater than 600mm, less than 720mm, the dimension of the collector electrode is greater than 120mm, less than 180mm in the direction of the line of the center point of the incident diaphragm and the outlet; in the direction perpendicular to the line of the central point of the incident diaphragm and the outlet and parallel to the high-voltage pole, the size of the high-voltage pole is more than 500mm and less than 620mm, the size of the protection pole is more than 500mm and less than 620mm, and the size of the collector pole is more than 450mm and less than 510mm.
In some embodiments, the thickness of the high voltage electrode is greater than 80mm, less than 120mm, the thickness of the guard electrode is greater than 80mm, less than 120mm, and the thickness of the collector electrode is greater than 15mm, less than 30mm.
In some embodiments, the distance between the high voltage pole and the guard pole is greater than 450mm and less than 520mm.
In some embodiments, the decay length is 400 to 460mm.
In some embodiments, the high voltage pole, the guard pole, and the outer edge of the guard ring are aligned.
In some embodiments, each guard ring unit is a sheet-like ring, the guard ring unit has a ring width of 10-20mm, the guard ring unit has a height of 10-20mm, and the spacing between adjacent guard ring units is less than 2mm.
In some embodiments, the diameter of the exit is 1.5-2.5 times the diameter of the entrance stop.
In some embodiments, the guard ring is provided with a through hole or a void at a position corresponding to the entrance diaphragm and the exit. In particular, the diameter of the through hole or the height of the void provided at the position corresponding to the entrance diaphragm is larger than the diameter of the entrance diaphragm, and the diameter of the through hole or the height of the void provided at the position corresponding to the exit is smaller than the diameter of the exit.
The invention can realize the following beneficial effects:
compared with the prior free air ionization chamber, the ionization chamber provided by the invention can be used for a larger energy measurement range by combining the shape, the material, the size and the position relation of each component in the ionization chamber, and particularly can meet the absolute measurement requirement of the X-ray air kerma in the range of 250 kV-350 kV;
the free air ionization chamber has higher processing precision, so that the introduced uncertainty is smaller, and the measurement is more accurate;
the free air ionization chamber adopts the design of the iris diaphragm, so that the measurement sensitivity volume can be changed within a certain range, and the measurement constant value of the air kerma can be more flexibly carried out.
The free air ionization chamber can be used for carrying out on-site value setting on an X-ray reference radiation field, and the magnitude requirement of 250 kV-350 kV X-ray air kerma can be met.
Drawings
Other objects and advantages of the present invention will become more fully apparent to those having ordinary skill in the art from the following description of the invention with reference to the accompanying drawings.
Fig. 1 shows a schematic cross-sectional view of a free air ionization chamber according to one embodiment of the present invention.
Fig. 2 shows a schematic structural cross-section of a diaphragm according to an embodiment of the invention.
Fig. 3 shows a schematic structural perspective view of a free air ionization chamber according to one embodiment of the present invention.
The reference numerals in the figures have the following meanings:
1: shielding shell
2: Incident diaphragm
3: An outlet
4: High voltage pole
5: Protective electrode
6: Collector electrode
7: Gap between collector and guard
8: Protection ring
81: Guard ring unit
9: Collecting zone
10: Measuring volume
201: Penetrating X-rays
202: X-ray for measurement
203: Scattered X-rays
210: Stainless steel
220: Tungsten alloy
All figures are for illustrative purposes only, and the number, size, etc. of the various components are not intended to limit embodiments of the present invention in any way.
Detailed Description
The technical scheme of the invention is further specifically described below through examples and with reference to the accompanying drawings. In the specification, the same or similar reference numerals denote the same or similar components.
In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the present disclosure. It may be evident, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are shown in the drawings in order to simplify the drawings.
The invention provides an ionization chamber which can be used for absolute measurement of X-ray kerma in the range of 60-350 kV, fig. 1 shows a schematic structural diagram of a free air ionization chamber according to one embodiment of the invention, the ionization chamber comprising:
A shield case 1;
an incident diaphragm 2 disposed on one side wall of the shield case 1;
an outlet 3 provided on the other side wall of the shield case 1 opposite to the entrance diaphragm 2;
The high-voltage electrode 4 is arranged in the shielding shell 1 and is positioned at one side of a connecting line of the central points of the incident diaphragm 2 and the outlet 3;
The protection electrode 5 is arranged in the shielding shell 1, is positioned on the other side of the connecting line of the central points of the incidence diaphragm 2 and the outlet 3, which is opposite to the high-voltage electrode 4, is parallel to the high-voltage electrode 4, and a through hole is arranged in the protection electrode 5;
The collector 6 is arranged in the through hole of the guard electrode 5, a gap 7 is arranged between the collector 6 and the guard electrode 5, and the upper surface of the collector 6 and the upper surface of the guard electrode 5 are positioned on the same plane;
The guard ring 8 is provided between the periphery of the high-voltage electrode 4 and the periphery of the guard electrode 5, and includes a plurality of stacked guard ring units 81, and positions corresponding to the entrance diaphragm 2 and the exit 3 are provided so as to allow X-rays to pass therethrough.
Wherein the space formed between the collector 6 and the high voltage electrode 4 is a collecting area 9, and the electric field in the area defined by the electric field lines formed by the high voltage electrode 4 and the collector 6 can collect ionized particles, and the length and width of the area are approximately consistent with those of the collector 6. The intersection of the collection area 9 with the area through which the X-rays entering the entrance diaphragm pass is the measurement volume 10. Under the conditions of the sizes, materials and the like of the components adopted in the invention, the balance condition of the charged particles in the measurement volume 10 enables the measured ionization current to correspond to the required air kerma generation, so that the method can be used for absolute measurement of the X-ray kerma in the range of 60-350 kV.
In some embodiments, the shielding enclosure is made of lead, stainless steel, and aluminum, the incident diaphragm is made of tungsten alloy, and the high voltage pole, the guard pole, the collector, and the guard ring are made of aluminum alloy. In order to achieve a better shielding effect, the shielding case is a multilayer structure including a stainless steel layer-a lead layer-a stainless steel layer, and since a better shielding effect is required on the side on which the X-rays are incident, a multilayer structure including a stainless steel layer-a lead layer-a stainless steel layer-an aluminum alloy layer is provided on the side wall of the incident diaphragm (i.e., the side on which the X-rays are incident). In some embodiments, the stainless steel layer has a thickness of at least 3mm, the lead layer has a thickness of at least 10mm, and the aluminum alloy layer has a thickness of at least 3mm. In some embodiments, the stainless steel layer has a thickness of at least 5mm, the lead layer has a thickness of at least 20mm, and the aluminum alloy layer has a thickness of at least 5mm. In particular, the side wall provided with the incident diaphragm comprises a stainless steel layer (5 mm) -a lead layer (30 mm) -a stainless steel layer (5 mm) -an aluminum alloy layer (5 mm), and the other side wall comprises a stainless steel layer (5 mm) -a lead layer (15 mm) -a stainless steel layer (5 mm).
In some embodiments, the shielding enclosure is a cuboid. The longitudinal direction is the direction of the path of the X-rays.
The material of the incident diaphragm is tungsten alloy, and the structure of the incident diaphragm needs high-precision processing, and in some embodiments, the incident diaphragm is circular. The diameter of the incident diaphragm can be set to be adjustable, so that the measurement sensitive volume can be changed within a certain range, and the measurement constant value of the air kerma can be more flexibly carried out. In particular, the diameter of the entrance diaphragm can be adjusted between 5 and 60mm, for example 10, 20 or 50mm. Fig. 2 shows a schematic structural view of an aperture according to an embodiment of the invention, wherein the aperture is made of tungsten alloy 220, coated with stainless steel material 210 at both the outer periphery and the front end of the aperture. The X-rays pass through the diaphragm and penetrate or scatter, such as penetrating X-rays 201 and scattering X-rays 203, whereas the X-rays that are not penetrated or scattered are X-rays that can be used for measurement, such as measuring X-rays 202.
Each diaphragm of the free air ionization chamber is matched with a corresponding tungsten plug (a plug made of tungsten alloy), and the tungsten plug is of a solid structure, so that the tungsten plug can be completely plugged into a diaphragm opening, and the diaphragm opening is completely plugged.
The exit opening, which is arranged on the side opposite the entrance diaphragm, forms a path for the X-rays to pass through, and in some embodiments is circular, in particular the exit opening has a diameter of 1.5 to 2.5 times that of the entrance diaphragm, so that a cone-shaped region for the X-rays to pass through is formed.
In some embodiments, the high voltage electrode, the guard electrode, and the collector electrode are rectangular plates. The collector, the guard electrode and the high-voltage electrode form parallel plate electrodes with a spacing distance d together; a polarizing voltage is applied to the high voltage electrode while the guard electrode and collector electrode remain grounded (virtual ground), thereby generating an electric field between the electrodes. The distance d is selected according to the sizes of the collector, the guard and the high-voltage poles, and the influence of the distance d on measurement is reflected on some correction factors, and although the larger d is better in theory, in practical situations, the larger d generates the larger correction factor, and the volume and the quality of the whole instrument are difficult to ensure. In some embodiments, the distance between the high voltage pole and the guard pole is greater than 450mm. Typically the separation distance does not exceed 520mm. In some embodiments, the distance between the high voltage pole and the guard pole is 460-500mm, for example about 480mm.
The collector is arranged in the through hole in the protective electrode, a gap is arranged between the collector and the protective electrode, and the upper surface of the collector and the upper surface of the protective electrode are positioned on the same plane. There is a requirement for the coplanarity of the collector and the guard to be substantially uniform in height over the upper surfaces of the guard and collector, in particular the difference in height over the upper surfaces of the guard and collector being less than 20 μm, in particular less than 10 μm, more in particular less than 5 μm. Poor coplanarity can affect the uniformity of the electric field, which can introduce a correction factor that becomes large.
In some embodiments, the through-holes inside the guard electrode are rectangular, the collector electrode is also rectangular, and a constant gap is maintained between the guard electrode and the collector electrode, the width of the gap being 3mm to 8mm, in particular 5mm. On one hand, the width of the gap can influence the uniformity of the electric field, and the larger the gap is, the worse the uniformity is; on the other hand, the width of the gap affects the size of the collector region, and too small a gap width can cause an increase in the induced current between the collector and guard electrodes, which is to be avoided.
The collector and guard may also be collectively referred to as a collector-guard.
The guard ring is provided between the periphery of the high-voltage electrode and the periphery of the guard electrode to reduce distortion of an electric field, includes a plurality of stacked guard ring units, and is provided at positions corresponding to the incident diaphragm and the exit so as to allow X-rays to pass therethrough.
In some embodiments, each guard ring unit is a sheet-like ring, e.g., composed of a hard aluminum alloy strip-like rectangular ring, as shown in fig. 3. The guard ring units have a ring width of 10-20mm, a height of 10-20mm, and a spacing between adjacent guard ring units is less than 2mm, particularly less than 1.2mm. To facilitate maintaining electric field uniformity, in some embodiments, the guard ring is comprised of at least 25 guard ring units. In particular, the guard ring is composed of 30 guard ring units, each guard ring unit having an annular width of 15mm and a height of 15mm, and a gap between adjacent guard ring units is about 1mm. The length and width of the guard ring unit are determined according to the high voltage pole and the guard pole, and may be the same as the sizes of the high voltage pole and the guard pole in the respective directions, respectively, so that the outer edges of the high voltage pole, the guard pole and the guard ring are aligned.
In some embodiments, the guard ring is provided with through holes at positions corresponding to the entrance diaphragm and the exit. In particular, the diameter of the through hole arranged at the position corresponding to the incident diaphragm is larger than that of the incident diaphragm, and the diameter of the through hole arranged at the position corresponding to the outlet is smaller than that of the outlet, so that a cone-shaped area through which X-rays can pass is formed together with the incident diaphragm and the outlet.
In some embodiments, the guard ring is spaced apart at locations corresponding to the entrance aperture and exit, for example, by adjusting the thickness, spacing, number, etc. of guard ring elements such that the guard ring passes X-rays at locations corresponding to the entrance aperture and exit, as shown in fig. 3. In particular, the height of the void provided at the position corresponding to the entrance diaphragm is larger than the diameter of the entrance diaphragm, and the height of the void provided at the position corresponding to the exit is smaller than the diameter of the exit.
To facilitate maintaining electric field uniformity, the surface flatness of any of the guard ring, collector, guard electrode, and high voltage electrode is less than 10 μm, specifically less than 5 μm, and more specifically less than 2 μm.
In some embodiments, the collector and guard have a surface flatness of less than 2 μm and a coplanarity of the collector and guard of better than 5 μm.
The ionization chamber provided by the invention can meet the absolute measurement requirement of the X-ray air kerma in the range of 250 kV-350 kV under the limited size by selecting the shape, the materials, the size, the position relation and the like of each component, and the total weight of the device is about 600kg.
In some embodiments, the dimension of the high voltage pole in the direction of the center point line of the incident diaphragm and the outlet (hereinafter also referred to as a-axis direction) is greater than 600mm, less than 720mm, the dimension of the guard pole is greater than 600mm, less than 720mm, the dimension of the collector pole is greater than 120mm, less than 180mm; in a direction perpendicular to the line connecting the center point of the incident diaphragm and the outlet and parallel to the high-voltage pole (hereinafter also referred to as b-axis direction), the size of the high-voltage pole is greater than 500mm, less than 620mm, the size of the guard pole is greater than 500mm, less than 620mm, and the size of the collector pole is greater than 450mm, less than 510mm. In particular, the dimension of the high voltage pole in the a-axis direction is larger than the dimension in the b-axis direction, the dimension of the guard pole in the a-axis direction is larger than the dimension in the b-axis direction, and the dimension of the collector pole in the a-axis direction is smaller than the dimension in the b-axis direction.
In some embodiments, the thickness of the high voltage pole is greater than 80mm, less than 120mm, the thickness of the guard pole is greater than 80mm, less than 120mm, and the thickness of the collector pole is greater than 15mm, less than 30mm in a direction perpendicular to both the a-axis and the b-axis (hereinafter also referred to as the c-axis direction). If the polar plate is too thick, deformation is generated due to dead weight, and the stability of measurement is difficult to maintain for a long time.
The plane of the front surface of the diaphragm is parallel to the b axis, the plane of the front surface of the diaphragm is parallel to the central mirror plane of the collector in the direction of the b axis, and the distance between the two planes is also called the air attenuation length or the attenuation length. In some embodiments, the decay length is 400 to 460mm, specifically, about 430mm.
In some embodiments, a bracket is provided within the shield enclosure, and the high voltage pole, guard pole, collector pole, and guard ring are positioned in a desired location by being secured to the bracket. The components may be fixed using an insulating material, which may be a polymeric adhesive, having a resistivity generally higher than 10 12 Ω/cm, in particular higher than 10 14 Ω/cm, for example PEEK (polyetheretherketone, english name polyethetherketone) may be used, the resistivity of which may reach 10 16 Ω/cm. PEEK has super-strong mechanical properties of 260 ℃ resistance, excellent mechanical properties, good self-lubricating property, chemical corrosion resistance, flame retardance, peeling resistance, wear resistance, radiation resistance and the like. PEEK can be used for all insulating materials in the entire structure of the ionization chamber.
In order to realize good flatness and coplanarity, the invention adopts a numerical control machining technology, and the technology can meet the requirement of the invention on the flatness of the surface, in particular, the flatness of the surface can reach the mu m level.
Examples
The ionization chamber structure in the embodiment is shown in fig. 3, the shielding shell is cuboid, the polar plates are rectangular, and the ionization chamber structure is prepared from the following materials:
A diaphragm: tungsten copper alloy
Electrode plate: aluminum alloy 6063
A shielding shell: the stainless steel 304 is coated with lead, and the wall of the diaphragm comprises the following layers from the outside to the inside of the ionization chamber: stainless steel layer (5 mm) -lead layer (30 mm) -stainless steel layer (5 mm) -aluminum alloy layer (5 mm); the remaining walls comprise the following layers: stainless steel layer (5 mm) -lead layer (15 mm) -stainless steel layer (5 mm).
The diaphragm is circular, the diameter is variable, the surface flatness is within 0.5 μm, and the structure is shown in figure 2.
The outlet is circular, the diameter is changeable, and the diameter is about 2 times of the diameter of the diaphragm.
The polar plate and the shell are fixed by insulating material PEEK-450G.
The main parameters affecting the free air ionization chamber include: the specific values of the incident diaphragm diameter, the air attenuation length, the electrode spacing d between the collector-guard electrode and the high-voltage electrode, the geometry of the collector, etc. are shown in table 1. The diaphragm diameter is designed to be larger than the diameter of the X-ray source, and 3 diaphragms with different diameter sizes are respectively designed in the free air ionization chamber in order to change the measurement volume of X-rays.
TABLE 1 Main parameters (mm) of free air ionization chamber
| Device parameters | Numerical value |
| Diameter of diaphragm | 10、20、50 |
| Diaphragm tungsten alloy thickness | 25 |
| Distance d between poles | 481 |
| Collector a-axis dimension | 150 |
| Collector b-axis dimension | 480 |
| Collector c-axis dimension | 20 |
| Protection pole a-axis dimension | 660 |
| Guard pole b-axis dimension | 560 |
| C-axis dimension of guard pole | 100 |
| Gap between collector and guard | 5 |
| High voltage pole a-axis dimension | 660 |
| High voltage pole b-axis dimension | 560 |
| High voltage pole c-axis dimension | 100 |
| Attenuation length | 430 |
The frame structure is drawn out on the back of the polar plate of the free air ionization chamber through machining so as to enhance the integral rigidity and stability.
The collector and the guard are made of an aluminum alloy. The surface flatness of the collector and the guard electrode is less than 2 μm, and the coplanarity of the collector and the guard electrode is better than 5 μm, i.e. the heights of the upper surfaces of the guard electrode and the collector are not more than 5 μm. The collector is fixed in a rectangular through hole at the center of the inside of the guard electrode by a high insulating material, the geometric structures of the collector and the guard electrode are not contacted with each other, and the gap between each plane between the collector and the guard electrode is kept at 5mm. The collecting-protecting electrode and the high-voltage electrode are fixed by high-insulation materials, and the interelectrode distance d between the collecting-protecting electrode and the high-voltage electrode is kept.
Guard rings are uniformly arranged between the periphery of the guard electrode and the periphery of the high-voltage electrode, and are made of aluminum alloy, and the surface flatness of the guard rings is smaller than 5 mu m. In this embodiment, the guard ring is composed of 30 guard ring units, each of which is a rectangular flat bar-shaped ring, the width of the ring is 15mm, the height is 15mm, the gap between the guard ring units is 1mm, and the dimensions of the guard ring units on the a-axis and the b-axis are the same as those of the guard electrode and the high-voltage electrode.
The ionization chamber of the embodiment can be used for absolute measurement of the X-ray kerma in the range of 60-350 kV.
Although the present invention has been described with reference to the accompanying drawings, the examples disclosed in the drawings are intended to illustrate embodiments of the invention and are not to be construed as limiting the invention.
It would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the general inventive concept, the scope of which is defined in the claims and their equivalents.
Claims (3)
1. An ionization chamber usable for absolute measurement of X-ray kerma in the range of 60-350 kV, comprising:
A shielding housing;
an incident diaphragm disposed on one side wall of the shield case;
An outlet provided on the other side wall of the shield case opposite to the incident diaphragm;
The high-voltage pole is arranged in the shielding shell and is positioned at one side of a connecting line of the center point of the incident diaphragm and the outlet;
The protective electrode is arranged in the shielding shell, is positioned on the other side of the connecting line of the central point of the incident diaphragm and the outlet, which is opposite to the high-voltage electrode, is parallel to the high-voltage electrode, and is internally provided with a through hole;
The collector is arranged in the through hole of the protective electrode, a gap is arranged between the collector and the protective electrode, and the upper surface of the collector and the upper surface of the protective electrode are positioned on the same plane;
a protective ring provided between the periphery of the high-voltage electrode and the periphery of the protective electrode, including a plurality of laminated protective ring units, the positions corresponding to the incident diaphragm and the exit being set so as to allow the X-rays to pass therethrough;
The side wall of the incidence diaphragm comprises a multilayer structure of a stainless steel layer, a lead layer, a stainless steel layer and an aluminum alloy layer, wherein the thickness of the stainless steel layer is at least 3mm, the thickness of the lead layer is at least 10mm, and the thickness of the aluminum alloy layer is at least 3mm;
the shielding shell is cuboid, the incident diaphragm and the outlet are round, the high-voltage electrode, the protection electrode and the collecting electrode are rectangular plates, and the through holes in the protection electrode are rectangular;
wherein the diameter of the entrance diaphragm can be adjusted between 5 and 60 mm;
Wherein the gap between the guard electrode and the collector electrode is 3mm to 8mm and,
The height difference between the upper surfaces of the guard electrode and the collector electrode is less than 20 mu m;
And
The surface flatness of the guard electrode and the collector electrode is less than 10 mu m;
Wherein the surface flatness of the high voltage electrode and/or the guard ring is less than 10 μm;
The size of the high-voltage electrode is larger than 600mm and smaller than 720mm, the size of the protective electrode is larger than 600mm and smaller than 720mm, and the size of the collector electrode is larger than 120mm and smaller than 180mm in the direction of the connecting line of the central point of the incident diaphragm and the outlet;
In the direction perpendicular to the line of the central point of the incident diaphragm and the outlet and parallel to the high-voltage pole, the size of the high-voltage pole is more than 500mm and less than 620mm, the size of the protection pole is more than 500mm and less than 620mm, and the size of the collector pole is more than 450mm and less than 510mm;
the thickness of the high-voltage electrode is more than 80mm and less than 120mm, the thickness of the protective electrode is more than 80mm and less than 120mm, and the thickness of the collector electrode is more than 15mm and less than 30mm;
the distance between the high-voltage electrode and the protective electrode is more than 450mm and less than 520mm;
And
Attenuation length is 400 to 460mm;
wherein each guard ring unit is in a sheet shape, the annular width of the guard ring unit is 10-20mm, the height of the guard ring unit is 10-20mm, and the interval between adjacent guard ring units is less than 2mm.
2. The ionization chamber of claim 1 wherein the outer edges of the high voltage electrode, guard electrode, and guard ring are aligned.
3. The ionization chamber according to claim 1 or 2, wherein the guard ring is provided with a through hole or a void at a position corresponding to the entrance diaphragm and the exit, a diameter of the through hole or a height of the void at a position corresponding to the entrance diaphragm is larger than a diameter of the entrance diaphragm, and a diameter of the through hole or a height of the void at a position corresponding to the exit is smaller than a diameter of the exit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201811653869.0A CN109444948B (en) | 2018-12-29 | 2018-12-29 | Ionization chamber for absolute measurement of air kerma |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201811653869.0A CN109444948B (en) | 2018-12-29 | 2018-12-29 | Ionization chamber for absolute measurement of air kerma |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN109444948A CN109444948A (en) | 2019-03-08 |
| CN109444948B true CN109444948B (en) | 2024-05-14 |
Family
ID=65542512
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201811653869.0A Active CN109444948B (en) | 2018-12-29 | 2018-12-29 | Ionization chamber for absolute measurement of air kerma |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN109444948B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111487662B (en) * | 2020-06-02 | 2022-04-29 | 中国计量科学研究院 | Free air ionization chamber and air kerma measuring method |
Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH09292468A (en) * | 1996-04-26 | 1997-11-11 | Toshiba Corp | Ionization chamber |
| WO2006005246A1 (en) * | 2004-07-14 | 2006-01-19 | Southwest Technology & Engineering Institute Of China | A measuring device for the shortwavelength x ray diffraction and a method thereof |
| CN105022079A (en) * | 2015-07-03 | 2015-11-04 | 中国计量科学研究院 | Ionization chamber system |
| CN106376165A (en) * | 2016-09-22 | 2017-02-01 | 中国原子能科学研究院 | Portable X-ray irradiation device for field calibration |
| CN206057592U (en) * | 2016-09-22 | 2017-03-29 | 中国原子能科学研究院 | For the variable scattering chamber gamma-rays irradiation unit that X, gamma-radiation doser are calibrated |
| CN106646584A (en) * | 2016-10-28 | 2017-05-10 | 中国计量科学研究院 | Shielding box |
| CN207817220U (en) * | 2018-02-09 | 2018-09-04 | 湖南省核工业中心实验室 | A kind of ionisation chamber |
| CN209606622U (en) * | 2018-12-29 | 2019-11-08 | 中国原子能科学研究院 | A kind of ionisation chamber for the X-ray Kerma absolute measurement that can be used within the scope of 60~350kV |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9885675B2 (en) * | 2015-05-20 | 2018-02-06 | Canon Kabushiki Kaisha | Ionizing radiation detection apparatus |
| CN112074067A (en) * | 2020-08-05 | 2020-12-11 | 中国原子能科学研究院 | Portable X-ray irradiation device for field calibration |
-
2018
- 2018-12-29 CN CN201811653869.0A patent/CN109444948B/en active Active
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH09292468A (en) * | 1996-04-26 | 1997-11-11 | Toshiba Corp | Ionization chamber |
| WO2006005246A1 (en) * | 2004-07-14 | 2006-01-19 | Southwest Technology & Engineering Institute Of China | A measuring device for the shortwavelength x ray diffraction and a method thereof |
| CN105022079A (en) * | 2015-07-03 | 2015-11-04 | 中国计量科学研究院 | Ionization chamber system |
| CN106376165A (en) * | 2016-09-22 | 2017-02-01 | 中国原子能科学研究院 | Portable X-ray irradiation device for field calibration |
| CN206057592U (en) * | 2016-09-22 | 2017-03-29 | 中国原子能科学研究院 | For the variable scattering chamber gamma-rays irradiation unit that X, gamma-radiation doser are calibrated |
| CN106646584A (en) * | 2016-10-28 | 2017-05-10 | 中国计量科学研究院 | Shielding box |
| CN207817220U (en) * | 2018-02-09 | 2018-09-04 | 湖南省核工业中心实验室 | A kind of ionisation chamber |
| CN209606622U (en) * | 2018-12-29 | 2019-11-08 | 中国原子能科学研究院 | A kind of ionisation chamber for the X-ray Kerma absolute measurement that can be used within the scope of 60~350kV |
Non-Patent Citations (8)
| Title |
|---|
| Comparison of the NIST and BIPM air-kerma standards for measurements in the low-energy X-ray range;BURNS D T;Journal of reasearch of the National Institute of standards and technology;第104卷(第2期);全文 * |
| Correction factors for the INER-improved free-air ionization chambers calculated with the Monte Carlo method;LIN U T;Applied radiation and isotopes;第64卷(第5期);全文 * |
| Free-air ionization chambers;BURNS D T;Metrologia;第46卷(第2期);全文 * |
| National promary standard for the unit of air kerma, air kerma rate, exposure, exposure rate, and X- and gamma-ray energy flux;OBORIN A V;Measurement Techniques;第55卷(第8期);第2页表格2至第4页第1段 * |
| Plate separation requirements for standard free-air ionization chambers;ATTIX F H;Radiology;第63卷(第6期);全文 * |
| X射线空气比释动能基准装置辐射场均匀野的研究;段小娟;吴金杰;王培玮;谢希成;马柯帆;中国计量;20121231(003);全文 * |
| 余继利 ; 吴金杰 ; 方方 ; 李论 ; 王培玮 ; 杨杨.低能自由空气电离室空气衰减修正因子的研究.第十八届全国核电子学与核探测技术学术年会.2016,全文. * |
| 吴金杰 ; 杨元第 ; 王培玮.用于低能X射线绝对测量的自由空气电离室.第七届全国核仪器及其应用学术会议暨全国第五届核反应堆用核仪器学术会议.2009,全文. * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN109444948A (en) | 2019-03-08 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Burns et al. | Free-air ionization chambers | |
| Bressan et al. | Beam tests of the gas electron multiplier | |
| Brandenburg et al. | An electromagnetic calorimeter for the small angle regions of the Collider Detector at Fermilab | |
| CN109444948B (en) | Ionization chamber for absolute measurement of air kerma | |
| Johns et al. | Currents induced in the dielectrics of ionization chambers through the action of high-energy radiation | |
| Dado et al. | A new high gain thin gap detector for the OPAL hadron calorimeter | |
| KR20120052350A (en) | Device and method for measuring an energy particle beam | |
| CZ280494B6 (en) | Apparatus for detection and localization of neutral particles | |
| CN111880212B (en) | Surface tritium concentration detector | |
| Galaktionov et al. | The parallel plate chamber as a detector for fast, radiation resistive calorimetry | |
| CN209606622U (en) | A kind of ionisation chamber for the X-ray Kerma absolute measurement that can be used within the scope of 60~350kV | |
| CN110927770B (en) | Device and method for measuring particle source air kerma | |
| Mohammadi et al. | Free-air ionization chamber, FAC-IR-300, designed for medium energy X-ray dosimetry | |
| US8481957B2 (en) | Ionizing radiation detector | |
| JP4671153B2 (en) | Open window ionization chamber | |
| Zhong et al. | Monte Carlo numerical simulation and experimental study of polyimide under monochromatic steady-state X-ray radiation | |
| CN214704019U (en) | Multilayer fast fission chamber for measuring fission cross section of wide energy region | |
| Bacak et al. | A compact multi-plate fission chamber for the simultaneous measurement of 233U capture and fission cross-sections | |
| CN112558138B (en) | Proton fluence rate measuring device and system | |
| Badura et al. | Pestov Spark Counter prototype development for the CERN-LHC ALICE experiment | |
| Dölling et al. | Beam diagnostics for the proton therapy facility PROSCAN | |
| Sochor et al. | Characterization of the new free-air primary standard for medium-energy X-rays at CMI | |
| Rocco | Development of a gaseous photon detector for Cherenkov imaging applications | |
| Henry et al. | The Canadian standard free-air chamber for medium quality x-rays | |
| Biswas | R&D of gas filled detectors for High Energy Physics experiments |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |