CN204424202U - Graphite cake ionization chamber - Google Patents
Graphite cake ionization chamber Download PDFInfo
- Publication number
- CN204424202U CN204424202U CN201520145577.1U CN201520145577U CN204424202U CN 204424202 U CN204424202 U CN 204424202U CN 201520145577 U CN201520145577 U CN 201520145577U CN 204424202 U CN204424202 U CN 204424202U
- Authority
- CN
- China
- Prior art keywords
- ionization chamber
- wall
- graphite
- insulate
- connection bar
- 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.)
- Withdrawn - After Issue
Links
Landscapes
- Measurement Of Radiation (AREA)
Abstract
The utility model relates to a kind of graphite cake ionization chamber, and described graphite cake ionization chamber comprises: outer wall, and described outer wall is round pie, and material is graphite; Passive electrode, be flake, material is graphite, is positioned at described outer wall, and insulate with described outer wall; Electrode connection bar, material is graphite, is connected with described passive electrode, and insulate with described outer wall; First protected level, is socketed in outside described Electrode connection bar, and insulate with described Electrode connection bar; Second protected level, is connected with described first protected level, is socketed in outside described Electrode connection bar, and insulate with described Electrode connection bar; High compression ring, is connected with described outer wall.Graphite cake ionization chamber of the present utility model, machining and assembly precision high, be easy to Modeling Calculation.Improve stability and the accuracy of benchmark reproduction value.
Description
Technical field
The utility model relates to a kind of graphite cake ionization chamber, particularly relates to a kind of graphite cake ionization chamber.
Background technology
Air kerma is the summation of the initial kinetic energy of the whole charged ionizing particle that uncharged ionizing particle discharges in the air of unit mass, is that one of most important physical quantity is learned in ionising radiation metering.Air kerma is also the Research foundation of absorbed dose and dose equivalent, and through value conversion, absorbed dose and the dose equivalent value of application can be traced to the source to Kerma benchmark.It is the existing legality measurement system of China that air kerma passes system, and the dose measurement device for the treatment of for radiation-caused disease, radiation protection and environmental monitoring is all traced to the source to air kerma benchmark.Accurate reproduction air kerma value is one of important symbol of national ionising radiation scientific research level.And the measurement of air kerma needs to use ionization chamber.
Utility model content
The purpose of this utility model is the defect for prior art, and provide a kind of graphite cake ionization chamber, mechanical precision is high, improves the precision that air kerma calculates.
For achieving the above object, the utility model provides a kind of graphite cake ionization chamber, and described graphite cake ionization chamber comprises:
Outer wall, described outer wall is round pie, and material is graphite;
Passive electrode, be flake, material is graphite, is positioned at described outer wall, and insulate with described outer wall;
Electrode connection bar, material is graphite, is connected with described passive electrode, and insulate with described outer wall;
First protected level, is socketed in outside described Electrode connection bar, and insulate with described Electrode connection bar;
Second protected level, is connected with described first protected level, is socketed in outside described Electrode connection bar, and insulate with described Electrode connection bar;
High compression ring, is connected with described outer wall.
Further, described passive electrode insulate to connect by insulation draw-in groove and described outer wall and establishes.
Further, described Electrode connection bar insulate to connect by the first insulation division and described outer wall, the first protected level and the second protected level and establishes.
Further, described outer wall insulate to connect by the second insulation division and described first protected level and establishes.
Further, described high compression ring insulate to connect by the 3rd insulation division and described first protected level and establishes.
Further, described graphite cake ionization chamber also comprises HV Terminal, is connected with described high compression ring.
Graphite cake ionization chamber of the present utility model, machining and assembly precision high, be easy to Modeling Calculation.Improve stability and the accuracy of benchmark reproduction value.
Accompanying drawing explanation
Figure 1A is the front view of the utility model graphite cake ionization chamber;
Figure 1B is the end view of the utility model graphite cake ionization chamber;
Fig. 2 is volt-ampere characteristic curve figure.
Embodiment
Below by drawings and Examples, the technical solution of the utility model is described in further detail.
60the development of Co gamma-rays air kerma ionization chamber achieves and utilizes nominal volume for 10cm
3ball-cylindrical cavity ionization chamber to the measurement of air kerma.
Compared with ball-cylindrical cavity ionization chamber, cake ionization chamber has the advantages such as more easily processing, and it is measuring unit with cake type ionization chamber that the utility model provides a set of
60co gamma-rays air kerma measurement mechanism, high-pressure stage and the collector of this cake ionization chamber all adopt graphite material, and device is operated in 50TBq
60in Co irradiation field, and weak current acquisition system is adopted to obtain current signal.Each physical parameter of method obtaining means adopting experiment and illiteracy snap gauge to intend combining and correction term.
When Kerma refers to uncharged ionizing particle and matter interaction, in unit mass material, be transferred to secondary charged particle initial kinetic energy summation, all charged particles that bremstrahlen energy and medium quadratic effect comprising ionizing particle produce are as the energy of auger electrons.Suppose that uncharged particle be the initial kinetic energy sum of all charged particles discharged in the medium of dm (units/kg) in quality is dE
tr(unit J), then Kerma K can as given a definition:
Wherein the unit of K is Jkg
-1; Special gray(Gy) by name (Gy).
Photon directly can not cause ionization, and causes ionization by the secondary electron that photoelectric effect, Compton scattering and pair effect etc. produce.When secondary electron is through air, can have an effect with the orbital electron of air Atom, the part or all of energy of loss itself, makes air Atom ionize or excite, form electronics and cation pair, experimentally by can obtain the radiation dose of photon to the measurement of ionization current.When Bragg-Gray aperture theory supposition gas cavity size is much smaller than the range of secondary electron, the ionization of the secondary electron that photon produces in the cavities can be ignored; The introducing of cavity does not change fluence and the spectral distribution of secondary electron; In material around cavity, radiation field is equally distributed.The material developments close with air effective atomic number such as graphite need be adopted to ionize locular wall, with As soon as possible Promising Policy aperture theory condition, carry out air kerma measurement.
For cavity ionization chamber, the formula of reproduction air kerma K is as follows:
Wherein Q is for being that (unit is kgm to ρ in density
-3) and volume be that (unit is m to V
3) dry air in produce given birth to total electrical charge, unit is C; The average electrical of W/e required for the ion pair of generation a pair unit charge is from merit, and unit is JC
-1; G is the share not being collected the energy that pole is collected because bremstrahlen is used up; (μ
tr/ ρ)
a,cfor the mass energy transfer coefficient ratio of air and graphite, relevant to ionization chamber graphite material; s
c,afor the stopping-power ratio of graphite and air, relevant to ionization chamber graphite material and geometry; Π k
ibe comprise the various correction terms relevant to ionization chamber geometry, measuring condition etc.
Figure 1A is the front view of the utility model graphite cake ionization chamber; Figure 1B is the end view of the utility model graphite cake ionization chamber; as shown in the figure, the utility model graphite cake ionization chamber specifically comprises: outer wall 1, passive electrode 2, Electrode connection bar 3, first protected level 4, second protected level 5 and high compression ring 6.
Outer wall 1 is round pie, and material is graphite.Passive electrode 2 is flake, and material is also graphite, is positioned at outer wall 1, and insulate with outer wall 1.Electrode connection bar 3, material is graphite, is connected with passive electrode 2, and insulate with outer wall 1.First protected level 4 is socketed in outside Electrode connection bar 3, and insulate with Electrode connection bar 3.Second protected level 5 is connected with the first protected level 4, is socketed in outside Electrode connection bar 3, and insulate with Electrode connection bar 3.High compression ring 6 is connected with outer wall 1.
Concrete, passive electrode 2 insulate to connect by insulation draw-in groove 7 and outer wall 1 and establishes.Electrode connection bar 3 insulate to connect with outer wall 1, first protected level 4 and the second protected level 5 by the first insulation division 81 and establishes.Outer wall 1 insulate to connect by the second insulation division 82 and the first protected level 4 and establishes.High compression ring 6 insulate to connect by the 3rd insulation division 83 and the first protected level 4 and establishes.
In addition, the utility model graphite cake ionization chamber also comprises HV Terminal 9, is connected with high compression ring 6.
The material of ionization chamber outer wall 1, passive electrode 2, Electrode connection bar 3 adopts monoblock density to be 1.85gcm
-3graphite, to ensure the even density of various piece.Again as shown in Figure 1, the outer wall 1 of ionization chamber is made up of cylindrical box and upper cover, and passive electrode 2 is for being positioned at central authorities and the cylindrical sheets insulated with ionization chamber outer wall 1.The main geometric parameters row of ionization chamber in Table 1.
Table 1
| Geometric parameter | Numerical value |
| External diameter (mm) | 50.955 |
| Internal diameter (mm) | 45.115 |
| Upper cover thickness (mm) | 2.753 |
| Interior height (mm) | 5.208 |
| Passive electrode diameter (mm) | 40.948 |
| Passive electrode thickness (mm) | 0.966 |
| Draw-in groove and Electrode connection rod volume (mm 3) | 71.3 |
| Cavity volume (mm 3) | 6981.6 |
Support section is made up of three parts.Foremost is high compression ring 6 made of copper, Electrode connection bar 3 and outer wall 1 part, high compression ring 6 has gold-plated copper HV Terminal 9, is connected by scolding tin with high-voltage power-line.
During measurement, add positive high voltage or negative high voltage and passive electrode 2 by high compression ring 6 at ionization chamber outer wall 1 and form ionizing electric field, derive passive electrode electric current by Electrode connection bar 3 from outer wall 1 circular hole.
Insulation draw-in groove 7, first insulation division 81, second insulation division 82, the 3rd insulation division 83 for material be the insulating material of PTFE material.First protected level 4, second protected level 5 plays the effect of signal shielding.Finally, signaling interface partial design is become the Q9 base of standard, by Q9 connector sending out signals.
Graphite cake ionization chamber pair
60the gamma-ray response of Co.Weak current measuring system is taken into account industrial computer by electrometer, temperature humidity air pressure and is formed.Control electrometer to realize bias adjustment and automatic measurement by the system controlling software of Labview programming, and charge measurement and current measurement two kinds of measurement patterns can be realized.Temperature humidity barometer is connected with industrial computer by RS232, directly reads environmental parameter, and the correction of temperature humidity air pressure for electric current.Electrometer and temperature humidity barometer are all traced to the source to correlate values National primary standard.
In measuring process, ionization chamber active centre is apart from source container external diaphragm front surface 430mm, wafer thickness 3.4mm, source active centre is apart from source container external diaphragm front surface 555mm (drawing nominal value), the front surface in the geometrical center to center source in source is 11.25mm, and the distance of the geometrical center to center ionization chamber active centre (fiducial value reproduction measurement point) in source is 999.25mm.
In measuring process, electrometer selects 200nC range.Be illustrated in figure 2 volt-ampere characteristic curve figure, in figure, abscissa is by being added high pressure, and ordinate is the ionization current measured, and blocks in figure in 27V-30V scope.Determine that polarizing voltage is 150V, now curent change ± 50V, curent change is less than 0.4%.By software programming, the correction of real time temperature barometric pressure humidity is carried out to measured value in measurement.
The physical parameter of graphite cake ionization chamber experiment measuring of the present utility model and correction term are concluded in table 2.In table 2, first is classified as physical parameter and correction term, comprise and measure electric current, atmospheric density, ionization chamber volume, ionization merit, compound modifying factor, handle modifying factor and field uniformity modifying factor, provide corresponding value respectively at secondary series, comprise type A standard uncertainty and type B standard uncertainty in tertial uncertainty.Category-A uncertainty comes from statistical computation; Category-B uncertainty comes from tracing to the source of measuring instrument, or from adopted method of measurement, hereafter subitem is listed the list of references of occurrence and method of measurement.Calculated by side and root method, the Composite Seismogram of whole 7 physical parameters and correction term is 0.17%.
Atmospheric density ρ selects BIPM recommendation, namely temperature 0 DEG C, under pressure 101.325kPa, and the density 1.2930kgm of dry air
-3, uncertainty is with the assessment of category-B method, and its value is 0.01%.
Wherein temperature correction factor:
k
T＝(273.15+T)/293.15 (3-1)
Air pressure modifying factor:
k
P＝101.325/P (3-2)
In above-mentioned formula, T is temperature, and unit is DEG C, and P is atmospheric pressure, and unit is kPa.Humidity is 0.9970 by the correction factor being adapted to dry gas.Under the utility model measuring system is directly adapted to the status of criterion measurement electric current, therefore the correction of temperature and air pressure humidity is not included in correction factor, in order to avoid double counting.
The ionization merit producing a pair ion pair in dry air selects CCRI (I) recommendation 33.97JC
-1.By W/e and S
c,auncertainty COMPREHENSIVE CALCULATING, (W/e) S
c,auncertainty is with the assessment of category-B method, and its value is 0.11%.
Compound modifying factor k
sagain be combined before not measured from ion and electronics and do not collect through collector and measure.Obtaining computing formula by Boag method is:
I
U/I
U/n＝1+(n-1)A/U+(n
2-1)m
2(g/U
2)I
U(3-1)
k
s＝1+Α/U+m
2(g/U
2)I
U(3-2)
The constant that A relies on ionization chamber type in formula, I
uthe ionization current measured when be operating voltage being U, I
u/nthe ionization current measured when be operating voltage being U/n, g is the factor relevant with ionization chamber physical dimension, m
2for the physical quantity relevant to the mobility of negative ions.
The utility model employing changes current value when voltage is U and U/n by change source and ionization chamber distance, draws I
u/ I
u/n-I
ufigure, draws A/U and m from slope and intercept
2(g/U
2), then draw compound modifying factor according to formula 3-2.The utility model is chosen n=3 (U=150V, U/n=50V) and is calculated compound modifying factor k with n=5 (U=150V, U/n=30V) two kinds of conditions
sbe 1.0009, category-A uncertainty is 0.004%, determines this correction term with ARPANSA Same Way, and its category-B uncertainty is 0.05%.
Handle correction k
stfrom the scattering item that ionization chamber support section brings.Handle correction value is obtained by the support section placing size material identical relative to ionization chamber Central Symmetry place at ionization chamber support section.Testing the handle correction value obtained is 0.9976, and uncertainty is with type A evaluation, and its value is 0.06%.
Field uniformity correction by 1 PTW model be TW31014, volume is 0.015cm
3ionization chamber record, measuring respectively in ionization chamber central plane is the average current value of 2.1cm 4 with ionization chamber centre distance, compared with the current value of cake ionization chamber center.Record field uniformity correction factor k
rnbe 1.0016, uncertainty is with type A evaluation, and its value is 0.09%.
Table 2: the physical parameter of graphite cake ionization chamber experiment measuring and correction term
Adopt Monte Carlo method to carry out analog computation to the graphite cake ionization chamber that this work is developed, physical parameter and the correction term of acquisition are listed in table 3.The category-A uncertainty of 5 physical parameters and correction term is the statistical error that illiteracy snap gauge is intended providing, the value that category-B uncertainty adopts the article of identical calculations method to provide with reference to NRC.Obtained the Composite Seismogram of each analog parameter and correction term by side and root method, the Composite Seismogram of 5 physical parameters and correction term is 0.17%.
The utility model monte carlo method program thereby is EGSnrc, calculates each physical parameter and correction term by different subprogram.By the g program computation bremstrahlen factor in EGSnrc, during calculating, the graphite material density of cake ionization chamber used is 1.85gcm
-3.By air kerma relative value and 1.85gcm under DOSRZnrc subprogram in EGSnrc respectively mock standard situation
-3graphite material Kerma relative value, the two ratio is the mass energy transfer coefficient ratio (μ of air and graphite
tr/ ρ)
a,c.By the stopping-power ratio of SPRRZnrc process simulation ionization chamber wall material in EGSnrc and specified material (the utility model select the status of criterion under air), this analogy method can not provide the absolute value of stopping power.Wall modifying factor k
wallcalculating select CAVRZnrc subprogram, in its compute type select " Aatt and Ascat " option.Axial uniformity correction records the ratio of absorption of air dosage by ionization chamber under DOSRZnrc simulation parallel beam incidence and 100cm far point source condition of incidence.The simulation of stopping-power ratio, k
wallsimulation and the simulation of axial uniformity all need to carry out modeling to cake ionization chamber.
Table 3: graphite cake ionization chamber covers physical parameter and the correction term that snap gauge intends acquisition
Same measurement point in radiation field, is adapted to the measurement result of cake ionization chamber on the same day through the half-life, with the country based on ball-cylindrical cavity ionization chamber
60co gamma-rays air kerma standard apparatus measurement result is compared, and the ratio of the former with the latter is 0.9987.Calculate the method for comparison uncertainty with reference to international comparison report, after removing same source partial uncertainty, the combined standard uncertainty of this ratio is 0.23%.The relevant parameter of stream oriented device absolute measurement is listed in table 4, and because of two ionization chamber volumes and structure difference, part correction term value difference is larger.The wall modifying factor K of cake ionization chamber
wallbe 1.0011, be less than 1.0186 of ball-columnar ionization room, illustrate that the design of patty ionization chamber can make wall effect reduce.Because cake ionization chamber design feature makes it be greater than ball-columnar ionization room by irradiation solid angle, therefore analyze its axial uniformity parameters k
anbeing greater than ball-columnar ionization room, confirming this supposition by comparing in table.
Table 4: cake ionization chamber compares with ball-columnar ionization room
The utility model, from the design of different structure ionization chamber, by the development of cake ionization chamber, achieves
60the absolute measurement of Co gamma-rays air kerma.This work reappear air kerma value with
60the ratio of Co gamma-rays air kerma National primary standard is 0.9987, and combined standard uncertainty is 0.23%.Institute's development ionization chamber adopts full graphite pied geometry, machining and assembly precision high, be also easy to Monte Carlo Modeling Calculation, reduce the uncertainty of correction term.This ionization chamber will form ionization chamber group with existing benchmark, to improve stability and the accuracy of benchmark reproduction value.In addition, for this cover cake ionization chamber devises anti-Water ball, this cake ionization chamber is made to may be used for ionization method absolute measurement
60co gamma-rays water absorbent amount, related work also achieves good result.
Above-described embodiment; the purpose of this utility model, technical scheme and beneficial effect are further described; be understood that; the foregoing is only embodiment of the present utility model; and be not used in restriction protection range of the present utility model; all within spirit of the present utility model and principle, any amendment made, equivalent replacement, improvement etc., all should be included within protection range of the present utility model.
Claims (6)
1. a graphite cake ionization chamber, is characterized in that, described graphite cake ionization chamber comprises:
Outer wall, described outer wall is round pie, and material is graphite;
Passive electrode, be flake, material is graphite, is positioned at described outer wall, and insulate with described outer wall;
Electrode connection bar, material is graphite, is connected with described passive electrode, and insulate with described outer wall;
First protected level, is socketed in outside described Electrode connection bar, and insulate with described Electrode connection bar;
Second protected level, is connected with described first protected level, is socketed in outside described Electrode connection bar, and insulate with described Electrode connection bar;
High compression ring, is connected with described outer wall.
2. graphite cake ionization chamber according to claim 1, is characterized in that, described passive electrode insulate to connect by insulation draw-in groove and described outer wall and establishes.
3. graphite cake ionization chamber according to claim 1, is characterized in that, described Electrode connection bar insulate to connect by the first insulation division and described outer wall, the first protected level and the second protected level and establishes.
4. graphite cake ionization chamber according to claim 1, is characterized in that, described outer wall insulate to connect by the second insulation division and described first protected level and establishes.
5. graphite cake ionization chamber according to claim 1, is characterized in that, described high compression ring insulate to connect by the 3rd insulation division and described first protected level and establishes.
6. graphite cake ionization chamber according to claim 1, is characterized in that, described graphite cake ionization chamber also comprises HV Terminal, is connected with described high compression ring.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201520145577.1U CN204424202U (en) | 2015-03-13 | 2015-03-13 | Graphite cake ionization chamber |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201520145577.1U CN204424202U (en) | 2015-03-13 | 2015-03-13 | Graphite cake ionization chamber |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN204424202U true CN204424202U (en) | 2015-06-24 |
Family
ID=53474548
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201520145577.1U Withdrawn - After Issue CN204424202U (en) | 2015-03-13 | 2015-03-13 | Graphite cake ionization chamber |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN204424202U (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104681390A (en) * | 2015-03-13 | 2015-06-03 | 中国计量科学研究院 | Graphite round-cake ionization chamber |
-
2015
- 2015-03-13 CN CN201520145577.1U patent/CN204424202U/en not_active Withdrawn - After Issue
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104681390A (en) * | 2015-03-13 | 2015-06-03 | 中国计量科学研究院 | Graphite round-cake ionization chamber |
| CN104681390B (en) * | 2015-03-13 | 2017-12-01 | 中国计量科学研究院 | Graphite cake ionisation chamber |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN102879794B (en) | A kind of device for reappearing air kerma in radioactive source radiation field | |
| CN104681390A (en) | Graphite round-cake ionization chamber | |
| Tölli et al. | A two-dose-rate method for general recombination correction for liquid ionization chambers in pulsed beams | |
| KR101751330B1 (en) | Device and method for measuring an energy particle beam | |
| CN104319222A (en) | Standard high-pressure ionization chamber and manufacturing method thereof | |
| CN103311086B (en) | Multi-layer cavity ionization chamber | |
| CN204424202U (en) | Graphite cake ionization chamber | |
| CN203787385U (en) | Multilayer high air pressure ionization chamber suitable for detecting high-dose-rate radiation fields | |
| Bouet et al. | R2D2 spherical TPC: first energy resolution results | |
| Weiping et al. | A thin float glass MRPC for the outer region of CBM-TOF wall | |
| CN103472475A (en) | Transmission-type monitoring ionization chamber suitable for low-energy X-ray measurement | |
| CN209387885U (en) | It is a kind of for pulse X, the plane ionization chamber of gamma-rays dosage measurement | |
| CN202495420U (en) | Multi-layer cavity ionization chamber | |
| CN115793014A (en) | Laminated ionization chamber equipment with internal calibration function | |
| CN202661630U (en) | Transmission type monitoring ionization chamber suitable for measurement of low-energy X-rays | |
| CN204067298U (en) | A kind of radiation detector ionization chamber | |
| CN109444948B (en) | Ionization chamber for absolute measurement of air kerma | |
| Vahabi et al. | Design, fabrication and characterization of a windowless extrapolation chamber for low-energy X-rays: Experimental and Monte Carlo results | |
| CN208384129U (en) | A kind of Flouride-resistani acid phesphatase hyperbar honeycomb grid ionization chamber | |
| CN108459342A (en) | A kind of Flouride-resistani acid phesphatase hyperbar honeycomb grid ionization chamber and manufacturing method | |
| JP2002014171A (en) | HIGH-PERFORMANCE He-3 COUNTER FOR NEUTRON | |
| Khalil | Evaluation of the Characteristics of Ionization Chambers Used for Commissioning in High Dose Rate Linacs | |
| Ruonan et al. | Key comparison BIPM. RI (I)-K7 of the air-kerma standards of the NMIJ, Japan and the NIM in mammography x-rays | |
| CN115019987A (en) | Method and system for determining compensation voltage of intermediate range detector and storage medium | |
| Minniti et al. | Comparison of the air kerma standards for 137Cs and 60Co gamma-ray beams between the IAEA and the NIST |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| AV01 | Patent right actively abandoned |
Granted publication date: 20150624 Effective date of abandoning: 20171201 |
|
| AV01 | Patent right actively abandoned |