CN102109605B - Method for measuring energy of accelerator - Google Patents
Method for measuring energy of accelerator Download PDFInfo
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- CN102109605B CN102109605B CN 200910243772 CN200910243772A CN102109605B CN 102109605 B CN102109605 B CN 102109605B CN 200910243772 CN200910243772 CN 200910243772 CN 200910243772 A CN200910243772 A CN 200910243772A CN 102109605 B CN102109605 B CN 102109605B
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Abstract
The invention discloses a method for measuring the energy of an accelerator, comprising the following steps: a measuring step for measuring a measurement curve that an attenuation multiple of an X ray from an accelerator is changed along with the thickness of a shielding material; and a comparing step for comparing the measurement curve with a reference curve to determine the energy of the X ray from the accelerator. The method can accurately judge the actual energy of the X ray beam from the electronic accelerator. The method is not limited from the restriction condition of the accelerator, and has the characteristics of low cost, simple operation, vivid data, high precision and small error caused by artificial factor. The method is not only suitable for the quality control of the production, debugging and check of the accelerator in the nuclear technology but also capable of guiding the operator to debug the accelerator precisely.
Description
Technical field
The present invention relates to a kind of method of measuring accelerator energy, the mensuration of the X ray energy that produces especially for accelerator in the Application of Nuclear Technology field.
Background technology
In the Application of Nuclear Technology field, determine that the energy of the X-ray beam that accelerator is launched is extremely important, in the energy test of industrial accelerator, measuring method commonly used is Steel material half-value layer method, that is: at present
select a fixed position at the accelerator beam direction, the perpendicular fasciculus flow path direction is placed respectively the steel plate of some same thickness, detector is placed on the position near steel plate, when relatively not adding any steel plate by the signal of measuring the detector of X ray after through different effectively steel plate thickness, the serial ratio of detector signal does not fit to curve, extrapolate again corresponding steel plate half value thickness by curve, half-value layer refers to that original X-ray beam dose rate decays to two/for the moment thickness of required certain material (as steel plate), then compare with a cover half-value layer reference data (as the table E13 in U.S. NCRP51 report), remove to judge by comparison half-value layer value the accelerator energy that produces X ray.
There are many shortcomings in said method:
1, the reference frame of judgement energy is more rough: only use half-value layer more rough as energy criterion, because same energy-ray can be hardened in shielding material, have first, a plurality of half-value layer numerical value such as when second and balance, half-value layer is not unique, but corresponding scope, therefore there is the overlapping region in the corresponding half-value layer scope of ray that is more or less the same of energy and is difficult to distinguish, and namely the energy resolving power is undesirable.For example: when the steel half-value layer that measures was 23mm, the method was difficult to be judged as YES 4MV or the accelerator of 6MV.
2, the method is mainly derived from as the reference data of energy judgement the data that provide under medical accelerator wide beam condition, for the industrial accelerator under fan-shaped narrow beam, little launched field condition and not exclusively applicable.
3, because the method is totally more spacious, the parameters such as geometric layout propose are strict with in test, and in fact when detector during near shielding slab small variable in distance can will bring larger impact to measurement result.
Summary of the invention
The purpose of this invention is to provide more X ray ENERGY METHOD under Measurement accuracy and different limit bundle conditions that the judgement electron accelerator produces of another kind.
According to an aspect of the present invention, the invention provides a kind of method of measuring accelerator energy, the method comprises the steps: measuring process: the attenuation multiple of the X ray that the measurement accelerator sends is with the measurement curve of shielding material variation in thickness, comparison step: measurement curve and the reference curve that will record compare, and determine thus the energy of the X ray that accelerator sends.
The method is not subjected to accelerator limit bundle condition restriction, and cost is low, simple to operate, data are directly perceived, precision is high, the error of being brought by human factor is very little, not only can be widely used in the quality control in the production, debugging, examination of all kinds of accelerators in the Application of Nuclear Technology field, but also can the guiding work personnel carry out the accurate debugging of accelerator.
Description of drawings
Fig. 1 covers for utilizing the normative reference KD curve (shielding material: steel) that snap gauge is intended 2.5～4MV accelerator of software for calculation acquisition;
Fig. 2 is KD curve method energy measurement method schematic diagram;
Fig. 3 is according to KD curve method testing scheme schematic diagram provided by the invention;
Fig. 4 is the reference KD curve of cone-beam 5.0-7.5MV accelerator according to an embodiment of the invention.
Fig. 5-9 are according to the several embodiments of the present invention measurement result.
Figure 10 is schematic diagram, shows the 3MV accelerator energy with the variation tendency of electron gun high voltage adjusting, and accelerator energy raises with the electron gun high pressure and reduces, and the energy variation scope is about 0.8MV.
Figure 11 is schematic diagram, shows the variation tendency that the 3MV accelerator energy is regulated with the magnetron pulse electric current, and accelerator energy raises with the magnetron pulse electric current, and the energy variation scope is about 0.3MV.
Embodiment
Following examples are used for explanation the present invention, but are not used for limiting the scope of the invention.
The method of measuring according to an embodiment of the invention accelerator energy comprises: measuring process: the attenuation multiple of the X ray that the measurement accelerator sends is with the measurement curve of shielding material variation in thickness, and comparison step: measurement curve and the reference curve that will record compare, and determine thus the energy of the X ray that accelerator sends.
The attenuation multiple of X ray is with the measurement curve of shielding material variation in thickness, i.e. KD curve is the attenuation multiple change curve after X ray passes through the shielding material of different-thickness.Here shielding material can comprise the various inorganic and organic materials such as tungsten, steel, lead, aluminium, water, crystal.
At first intend software for calculation (for example GEANT 4) and calculate with covering snap gauge, only to have provided (1.0-12) MV energy bite be the reference KD curve of 0.5MV according to using needs in the present invention.As shown in Figure 1, (2.5～4MV) KD curve, corresponding energy is by the KD attenuation characteristic of slit X ray out in the steel shielding material after 2.5MV, 3.0MV, 3.5MV and 4.0MV accelerator electronic target respectively to provide the portion of energy section in Fig. 1.
Here adopt Geant4 process simulation monoenergetic electrons to practice shooting, then obtain forward direction 5 degree with interior power spectrum, as the power spectrum of each energy, the angle that obtains simultaneously X ray distributes.Wherein target material and size can be determined according to the design parameter of accelerator.Table 1 is corresponding target material and size in this method analog computation.
The corresponding target material of the various energy of table 1 and size
| Energy (MV) | Target thickness (mm) | Target diameter (mm) | Target material |
| 1.0-1.5 | 1.0 | 5.0 | Tungsten |
| 2.0-4.0 | 2.0 | 5.0 | Tungsten |
| 4.5-12.0 | 2.5 | 5.0 | Tungsten |
(1) obtain the curve with reference to KD
Set up by testing scheme shown in Figure 3 and cover the snap gauge type, analogy model comprises four parts: source item, solid structure, geometric arrangement, dosage statistics.Wherein the solid structure mainly is comprised of accelerator shielding structure, steel plate and ground three parts, and wherein steel plate thickness and variation provide according to testing scheme, and simulating ground is to consider to have concrete ground area scattering situation in test.In accelerator structure, the outlet shielding is the principal element that affects result, therefore need to carry out analog computation according to different outlet shielding construction models.Fig. 4 has provided the analog computation KD reference curve of 5-7.5MV conical outlet accelerator.
Arranging of analog prober, should use detector active region size to be consistent with actual measurement, for example Unidos ionization chamber probe detection face size is: (5mm * the 20mm of W * H).The physical quantity of statistics is energy deposition, requires the statistics photon number at least more than 1000.
(2) set up testing scheme
Set up a cover experiment test scheme, main consideration shielding steel plate size, steel plate variable thickness, relative geometry are put the problems such as distance, consider that simultaneously testing scheme is simple and convenient in implementation process, the measuring error that causes is as far as possible little, guarantees that with reference to KD curve and measurement KD curve be to obtain under the same terms.Through considering fully and comparing, we obtain more excellent testing scheme, as shown in Figure 3.In scheme
■ select the length of side be square body in (20～100) cm scope as shielding steel plate 4, thickness does not wait from 0～20cm;
■ dose fluctuations monitoring detector 3, the variation of Real-Time Monitoring accelerator output dose is used for revising the accelerator dose fluctuations to the impact of measurement result; It is placed on accelerator outlet main beam, and namely on 0 of X ray degree direction line 8, in a single day the position is determined just to maintain static, until whole test job is completed;
The layout of ■ relative geometry position is also the key factor that affects measurement result.
In measuring process, accelerator target spot 1 is relative fixing with dose detector 5 positions, and spacing L remains on (1.0～2.0) m scope, and guarantees that detector 5 is on the accelerating tube axis, namely on 0 of X ray degree direction line 8;
The distance of the surface 9 of shielding steel plate 4 (perpendicular to the plane of the paper of Fig. 3) and dose detector 5 is greater than 20cm;
0 degree direction line 8 of surface 9 and the X ray of shielding steel plate 4 keeps vertical, and the center line of shielding steel plate 4 (being the center line of thickness direction or the normal of surperficial 9 center) is spent direction line 8 with 0 of X ray and overlapped;
As shown in Figure 3, during test, shielding steel plate 4 is placed on testing jig 6, and this testing jig 6 is placed on ground 7;
(3) test concrete grammar
The first step: do not add shielding steel plate 4, directly read the reading D of dose detector 5
0Reading D with dose fluctuations monitoring detector 3
0m
Second step: adding a thickness in distance target spot 1L-D position is d
1 Shielding steel plate 4, obtain respectively the reading D of dose detector 5 and dose fluctuations monitoring detector 3
1And D
1m
The 3rd step: increase progressively respectively the thickness of shielding steel plate 4, record one group of corresponding dose value D by dose detector 5 and dose fluctuations monitoring detector 3 respectively
2, D
3, D
4And D
2m, D
3m, D
4m
The 4th step: by formula K
i=(D
0/ D
i) (D
im/ D
0m) calculate corresponding a certain thickness d
iThe attenuation multiple K of steel plate
i, curve plotting in EXCEL table then, and provide the measuring error line, attenuation multiple K is with the change curve of steel plate thickness D as shown in Figure 2, i.e. the measurement KD curve map of corresponding a certain energy accelerator.
In the situation that dose fluctuations is little, accuracy requirement is not high or satisfy actual requirement, can be without dose fluctuations monitoring detector 3, this moment K
i=D
0/ D
i
Utilize in the present invention and cover card program (as GEANT 4) when carrying out analog computation, can fully according to accelerator geometry to be measured, shielding material, detector and these solid positioned opposite situations, obtain the normative reference KD curve of corresponding certain shielding material decay of accelerator X ray of a cover different-energy; Then carry out actinometry according to the geometrical solution of simulate given fully, directly obtain one group and measure the KD data, then curve plotting in EXCEL table, and provide the measuring error line, the normative reference curve that obtains with above illiteracy card again compares and simple analysis, just can judge more exactly the actual energy of the X-ray beam that this electron accelerator launches.
Adopt the KD curve method, judge the method for accelerator energy by measuring the attenuation change characteristic (KD variation relation) of X-ray beam in shielding material that the different-energy electron accelerator launches, can be applied to the X ray energy measurement that the electron accelerator under various limit bundle conditions is launched.The method cost is low, simple to operate, data are directly perceived, precision is high, the error of being brought by human factor is very little, not only can be widely used in the quality control in the production, debugging, examination of all kinds of accelerators in the Application of Nuclear Technology field, but also can differentiate the subtle change of accelerator energy, thereby the guiding work personnel carry out the accurate debugging of accelerator.
As shown in Fig. 5-9, adopt method provided by the invention, the narrow beam accelerator that respectively energy is nominally 2.5MV, 3.0MV, 4.0MV, 6.0MV, 9.0MV carries out the energy test result, and shielding material adopts steel plate.
Fig. 5 is that a station symbol claims 2.5MV accelerator energy measurement result, the actual 2.6MV that is judged as; Fig. 6 is that a station symbol claims 3.0MV accelerator energy measurement result, the actual 3.0MV that is judged as; Fig. 7 is that a station symbol claims 4.0MV accelerator energy measurement result, the actual 4.9MV that is judged as; Fig. 8 is that a station symbol claims 6.0MV accelerator energy measurement result, and reality only reaches 6.2MV; Fig. 9 is that a station symbol claims 9.0MV accelerator energy measurement result, the actual 9.0MV that is judged as.
Accelerator can change energy and the dosage of its output X ray by regulating its electron gun high pressure and magnetron pulse electric current.Therefore use the inventive method and implement the monitoring accelerator energy with the variation tendency of electron gun high pressure and magnetron pulse electric current, as shown in Figure 10 and Figure 11.
Figure 10 is schematic diagram, shows the 3MV accelerator energy with the variation tendency of electron gun high voltage adjusting, and accelerator energy raises with the electron gun high pressure and reduces, and the energy variation scope is about 0.8MV;
Figure 11 is schematic diagram, shows the variation tendency that the 3MV accelerator energy is regulated with the magnetron pulse electric current, and accelerator energy raises with the magnetron pulse electric current, and the energy variation scope is about 0.3MV.
In above-described embodiment, only having provided as required the 1.0-12MV energy bite is the reference KD curve of 0.5MV, actual in using needs, covers card and can also continue the expend energy scope.Require the statistics photon number at least more than 1000 when in addition, the dosage in covering the calculating of snap gauge plan is added up.
The variation of dose fluctuations monitoring detector Real-Time Monitoring accelerator output dose is used for revising the accelerator dose fluctuations to the impact of measurement result; In measuring process, it is placed on accelerator outlet main beam, namely on 0 of X ray degree direction line 8, the position is in case determine just to maintain static.
In above-mentioned experiment test scheme, the accelerator target spot is relative fixing with the dose detector position, and spacing L can remain on 0.5～12.0m, in the scope of preferred 1.0～2.5m; Shielding steel plate outside surface can be greater than 10cm apart from dose detector.
The above results shows, measuring method of the present invention can not only simply and exactly be measured accelerator energy, as produce, debugging and the quality control checked and accepted, but also can differentiate the subtle change of accelerator energy, thereby the guiding work personnel carry out the accurate debugging of accelerator.
In the above-described embodiments, adopt illiteracy card program to obtain reference curve by analog computation, as selection, also can obtain reference curve by measurement with the accelerator of known parameters, perhaps adopt alternate manner well known in the art to obtain reference curve.
Claims (8)
1. a method of measuring accelerator energy, comprise the steps:
Measuring process: measure the attenuation multiple of the X ray that accelerator sends with the measurement curve of shielding material variation in thickness,
Comparison step: measurement curve and the reference curve that will record compare, and determine thus the energy of the X ray that accelerator sends,
Described measuring process comprises:
Shielding material never, the thickness that is shielding material is zero, beginning increases the thickness of shielding material successively, and measure the dosage of the X ray there is no shielding material and pass the dosage of X ray of the shielding material of different-thickness, and measure simultaneously directly the dosage of the X ray that sends from accelerator, by the dosage of the X ray that directly sends from accelerator, revise the dosage of the X ray of the shielding material that passes different-thickness that records
Wherein in measuring process, the spacing that the target spot of accelerator and being used for is measured between the dose detector of x-ray dose is 0.5～12.0m,
Wherein in measuring process, the spacing between described dose detector and described shielding material is greater than 10cm,
Wherein in measuring process, the dose fluctuations monitoring detector is placed on accelerator outlet main beam, and when there is no shielding material, the reading of dose fluctuations monitoring detector is not D
om, the reading of dose fluctuations monitoring detector is D when increasing progressively the thickness of shielding material the i time
im, described attenuation multiple by with D
im/ D
omMultiply each other and be corrected, i equals 1,2, the positive integer of 3....
2. the method for measurement accelerator energy according to claim 1, wherein
Reference curve obtains in the following way: cover the card program by utilization the X ray that the accelerator of different-energy sends is carried out analog computation, obtain the attenuation multiple of X ray of accelerator of different-energy with the calculated curve of shielding material variation in thickness, this calculated curve is as reference curve.
3. the method for measurement accelerator energy according to claim 1, wherein shielding material is that the length of side is the plate of the general square shape in 20～100cm scope.
4. the method for measurement accelerator energy according to claim 1, wherein in measuring process, the spacing that the target spot of accelerator and being used for is measured between the dose detector of x-ray dose is 1.0～2.5m.
5. the method for according to claim 1 or 4 described measurement accelerator energies, wherein in measuring process, the spacing between described dose detector and described shielding material is greater than 20cm.
6. the method for measurement accelerator energy according to claim 1, wherein in measuring process, roughly be in 0 degree direction line of X ray for the dose detector of measuring x-ray dose.
7. the method for measurement accelerator energy according to claim 3,0 degree direction line almost parallel of the normal to a surface direction of wherein said plate and X ray.
8. the method for measurement accelerator energy according to claim 7, the normal of the center on the surface of wherein said plate roughly overlaps with 0 degree direction line of X ray.
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| CN103645494B (en) * | 2011-12-30 | 2016-04-06 | 同方威视技术股份有限公司 | Measure the method for the energy of accelerator beam |
| CN104459754A (en) * | 2014-12-18 | 2015-03-25 | 清华大学 | Online measurement method of X-ray energy of accelerator of container inspection system |
| CN112485821B (en) * | 2020-11-19 | 2022-09-30 | 上海束能辐照技术有限公司 | Method for rapidly measuring beam energy of electron accelerator |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5434417A (en) * | 1993-11-05 | 1995-07-18 | The Regents Of The University Of California | High resolution energy-sensitive digital X-ray |
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|---|---|---|---|---|
| FR2626432B1 (en) * | 1988-01-25 | 1995-10-13 | Commissariat Energie Atomique | X-RAY TOMOGRAPHY APPARATUS |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5434417A (en) * | 1993-11-05 | 1995-07-18 | The Regents Of The University Of California | High resolution energy-sensitive digital X-ray |
Non-Patent Citations (3)
| Title |
|---|
| 严慧勇.窄束X射线半价层测量法标定电子直线加速器的能量.《原子能科学技术》.2003,第37卷(第4期), * |
| 朱国平等.一种精确测量加速器能量的新方法.《全国第七届核监测学术研讨会论文集》.2009, * |
| 石成玉等.半价层法测量电子束能量的模拟计算和分析.《原子能科学技术》.2001,第35卷(第6期), * |
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Effective date of registration: 20190320 Address after: 101500 No. 18 Garden Road, Miyun Economic Development Zone, Beijing Co-patentee after: Nuctech Company Limited Patentee after: Tongfang Weishi Technology (Beijing) Co., Ltd. Address before: 100084 Beijing city Haidian District Shuangqing Road with Party building A block 2 layer Patentee before: Nuctech Company Limited |