1、Designation: E 1165 04Standard Test Method forMeasurement of Focal Spots of Industrial X-Ray Tubes byPinhole Imaging1This standard is issued under the fixed designation E 1165; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the ye
2、ar of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method provides instructions for determiningthe length and width dimensions of line focal spots in in
3、dustrialX-ray tubes (see Note 1). This determination is based on themeasurement of an image of a focal spot that has beenradiographically recorded with a “pinhole” projection/imagingtechnique.NOTE 1Line focal spots are associated with vacuum X-ray tubeswhose maximum voltage rating does not generally
4、 exceed 500 kV.1.2 This test method may not yield meaningful results onfocal spots whose nominal size is less than 0.3 mm 0.011 in.(See Note 2.)NOTE 2The X-ray tube manufacturer may be contacted for nominalfocal spot dimensions.1.3 This test method may also be used to determine thepresence or extent
5、 of focal spot damage or deterioration thatmay have occurred due to tube age, tube overloading, and thelike. This would entail the production of a focal spot radio-graph (with the pinhole method) and an evaluation of theresultant image for pitting, cracking, and the like.1.4 Values stated in SI unit
6、s are to be regarded as thestandard. Inch-pound units are provided for information only.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices
7、 and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E 999 Guide for Controlling the Quality of Industrial Ra-diographic Film Processing3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 actual focal spotthe X-ray pro
8、ducing area of thetarget as viewed from a position perpendicular to the targetsurface (see Fig. 2).3.1.2 effective focal spotthe X-ray producing area of thetarget as viewed from a position perpendicular to the tube axisin the center of the X-ray beam (see Fig. 2).3.1.3 line focal spota focal spot wh
9、ose projected pinholeimage consists primarily of two curved lines (see Fig. 3).4. Significance and Use4.1 One of the factors affecting the quality of a radiographicimage is geometric unsharpness. The degree of geometricunsharpness is dependent upon the focal size of the radiationsource, the distance
10、 between the source and the object to beradiographed, and the distance between the object to beradiographed and the film. This test method allows the user todetermine the focal size of the X-ray source and to use thisresult to establish source to object and object to film distancesappropriate for ma
11、intaining the desired degree of geometricunsharpness.5. Apparatus5.1 Pinhole DiaphragmThe pinhole diaphragm shall con-form to the design and material requirements of Table 1 andFig. 1.1This test method is under the jurisdiction of ASTM Committee E07 onNondestructive Testing and is the direct respons
12、ibility of Subcommittee E07.01 onRadiology (X and Gamma) Method.Current edition approved January 1, 2004. Published February 2004. Originallyapproved in 1987. Last previous edition approved in 2002 as E 1165 92 (2002).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact AS
13、TM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.FIG. 1 Pinhole Diaphragm Design1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United Stat
14、es.5.2 CameraThe pinhole camera assembly consists of thepinhole diaphragm, the shielding material to which it is affixed,and any mechanism that is used to hold the shield/diaphragm inposition (jigs, fixtures, brackets, and the like; see Fig. 4).5.3 FilmIndustrial type extra fine grain. No intensifyi
15、ngscreens are to be used. The film shall be processed inaccordance with Guide E 999.5.4 Image Measurement ApparatusThis apparatus is usedto measure the size of the image of the focal spot. Theapparatus shall be an optical comparator with built-in graticulewith 0.1 mm or .001 in., or both divisions a
16、nd magnification of53 to 103 (or equivalent).6. Procedure6.1 If possible, use a standard 91.44 cm 36 in. focal spotto film plane distance (FFD) for all exposures. If machinegeometry or accessibility limitations will not permit the use ofa 91.44 cm 36 in. FFD, use the maximum attainable FFD (inthese
17、instances adjust the relative distances between focal spot,pinhole, and film accordingly to suit the image enlargementfactors specified in Table 2). The distance between the focalspot and the pinhole is based on the nominal size of the focalspot being measured and the desired degree of image enlarge
18、-ment (see Fig. 5). The specified focal spot to pinhole distance(FHD) for the different nominal focal spot size ranges isprovided in Table 2. Position the pinhole such that it is within61 of the central axis of the X-ray beam. Fig. 6 illustrates atypical focal spot exposure arrangement.NOTE 3The acc
19、uracy of the pinhole system is highly dependent uponthe relative distances between (and alignment of) the focal spot, thepinhole, and the film. Accordingly, specially designed apparatus may beFIG. 2 Actual/Effective Focal SpotNOTE 1During the production of X-rays the electrons are accelerated from t
20、he filament to the target in two separate paths (see Sketch 1). Electronsemitted at the front of the filament travel primarily along Path A, and electrons emitted at the backside of the filament travel primarily along Path B. Notethat these two paths intersect at a certain point; this is the point a
21、t which the target is positioned. As a result, the pinhole picture of the focal spot showstwo lines that correspond with the intersections of Paths A and B at the target (see Sketch 2).FIG. 3 Line Focal SpotE1165042necessary in order to assure compliance with the above requirements. Fig.7 provides a
22、n example of a special collimator that can be used to ensureconformance with the 61 alignment tolerance. Some other standardsimpose very stringent alignment requirements and express these require-ments in terms of radial tolerances. These documents do not, however,address any means for assuring comp
23、liance with such tolerances. In orderto simplify the focal spot radiography technique and to improve theoverall practicality of the procedure, it is considered that a workablealignment tolerance, and a means of assuring conformance with thattolerance, is appropriate. Accordingly, this standard addre
24、sses tolerancesin angular terms and provides a method for assuring compliance withthese tolerances. This provides a practical means of meeting the precisionand bias requirements of Section 9.6.2 Position the film as illustrated in Fig. 6. The exposureidentification appearing on the film (by radiogra
25、phic imaging)TABLE 1 Pinhole Diaphragm Design Requirements (Dimension)ANOTE 1The pinhole diaphragm shall be made from one of the following materials:(1) An alloy of 90 % gold and 10 % platinum,(2) Tungsten,(3) Tungsten carbide,(4) Tungsten alloy,(5) Platinum and 10 % Iridium Alloy, or(6) Tantalum.No
26、minal Dimension ofFocal Spot, mm in.BNominal Diameter of DiaphragmOpening, mm in.Required “D” and “L” Dimensions, mm in.DL0.3 to 1.2 0.011 to 0.046 incl 0.030 0.0011 0.030 6 0.0050.0011 6 0.00020.075 6 0.0100.0029 6 0.00041.2 to 2.5 0.046 to 0.097 incl 0.075 0.0029 0.075 6 0.0050.0029 6 0.00020.350
27、6 0.0100.014 6 0.00042.5 0.097 0.100 0.0039 0.100 6 0.0050.00396 0.00020.500 6 0.0100.02 6 0.0004ASee Fig. 1.BNominal focal spot dimensions may be obtained from the X-ray tube manufacturer.FIG. 4 Pinhole Camera (Typical)TABLE 2 Image Enlargement FactorsNominal Focal SpotSize, mm in.EnlargementFactor
28、Distance BetweenFocalSpot and Pinhole(FHD), cm in.A0.3 to 1.2 0.011 to 0.046 incl 33 22.9 91.2 to 2.5 0.046 to 0.097 incl 23 30.5122.5 0.097 13 45.718AWhen using a technique that entails the use of enlargement factors and a91.44 cm 36 in. focal spot to film distance (FFD) is not possible (see 6.1),
29、thedistance between the focal spot and the pinhole (FHD) shall be adjusted to suit theactual focal spot to film distance (FFD) used (for example, if a 61 cm 24 in. FFDis used, the FHD shall be 15.25 cm 6 in. for 33 enlargement, 20.32 cm 8 in. for23 enlargement, and the like).E1165043should be X-ray
30、machine identity (that is, make and serialnumber), organization making the radiograph, and date ofexposure.6.3 Adjust the kilovoltage and milliamperage settings on theX-ray machine to that specified in Table 3.FFD = 91.44 cm 36 in.FHD = 22.86 cm 9 in. for 33 enlargement30.48 cm 12 in. for 23 enlarge
31、ment45.72 cm 18 in. for 13 enlargementNoteSee 6.1 and Table 1 if a 91.44 cm 36 in. FFD is not achievable.FIG. 5 Schematic of FHD/FFD RelationshipFIG. 6 Exposure Set-Up SchematicE11650446.4 Expose the film such that the density of the darkestportion of the focal spot image conforms to the limits spec
32、ifiedin Table 4. Density measurement shall be as illustrated in Fig.8. Density shall be controlled by exposure time only.6.5 Process the film in accordance with Guide E 999.6.6 Focal Spot Measurement:6.6.1 Back LightingBack lighting shall be such that thefocal spot image can be easily and comfortabl
33、y viewed.6.6.2 Place the magnification graticule (handheld opticalcomparator) in intimate contact with the film for the measure-ment determination. Determine an imaginary “box” that rep-resents the perceptible edges of the focal spot image (see Fig.9(a) for the extremities measurement.6.6.3 Measure
34、the focal spot image in two directions (seeFig. 9(b):6.6.3.1 Direction AParallel to the axis of the tube.6.6.3.2 Direction BPerpendicular to the axis of the tube.7. Calculation of Results7.1 Multiply the measured “A” direction dimension by acorrection factor of 0.7 to determine the actual “A” dimens
35、ion(see Notes 4 and 5). The measured “B” direction dimension isrepresentative of actual size.NOTE 4The need for the 0.7 fractional multiplier for correction of themeasured image length arises from the fact that the lengthwise distributionof energy in the focal spots of line-focus tubes tends to be p
36、eaked in thecenter and diminishes gradually to zero at the ends. Hence, the effectivelength, (that is, resultant effect on radiographic definition and film densitydistribution) cannot be stated as equal to the measured length.NOTE 5European standard EN 12543-2 describes a similar x-rayfocal spot mea
37、surement method (pin-hole method), but does not use the“0.7” correction factor described within this standard. EN 12543-2, at thetime of this revision, has a range of applications considered beyond thescope of E 1165. International users of these standards should be aware ofthis difference for their
38、 particular applications.7.2 If an image enlargement technique was used, divide the“A” and “B” direction measurements by the pertinent enlarge-ment factor to obtain actual focal spot size (see Fig. 5 and Table2).(a) Plan(b) FunctionFIG. 7 Alignment CollimatorTABLE 3 Test Voltage and CurrentkVp Ratin
39、gof X-RayMachineVoltage To Be Usedfor Focal SpotRadiographyCurrent To Be Usedfor Focal SpotRadiography#75 kV maximum rated voltage75 kV to 150 kV 75 kV 50 % of maximum permis-sible current at the testvoltage utilized150 kV 50 % of maximum ratedvoltageTABLE 4 Density Range for Darkest Area of Focal S
40、pot Image(See Fig. 8)TransmissionDensitometerAperture Diam-eter, mm in.For images whose minimumdimension is less than2 mm 0.078 in.For images whose minimumdimension is greater than2 mm 0.078 in.1 0.039 0.8 to 2.0 density 1.0 to 3.0 density2 0.078 0.5 to 1.8 density 1.0 to 3.6 densityE11650458. Repor
41、t8.1 A report documenting the focal spot size determinationshould include the machine model number and serial number,the X-ray tube serial number, the focal spot(s) that wasmeasured (some machines have dual focal spots), the set-upand exposure parameters (for example, kilovoltage, milliamps,enlargem
42、ent factor, and the like), date, name of organization,and estimated beam time hours (if available).9. Precision and Bias9.1 Conformance to the requirements specified herein willproduce results that are within the following tolerances:9.1.1 TechniqueThe technique requirements specifiedherein will pro
43、duce a focal spot image whose size is 65%ofthe actual effective focal spot size.9.1.2 MeasurementThe measurement requirements speci-fied herein will produce results that are within the tolerances:Nominal Focal Spot Size, mm in. Measurement Tolerances0.3 to 1.2 0.011 to 0.046 incl 630 %1.2 to 2.5 0.0
44、46 to 0.097 incl 625 %2.5 0.097 620 %10. Keywords10.1 focal spots; pinhole camera; pinhole imaging; X-ray;X-ray tubeNoteFor instances where the focal spot image is larger than the densitometer aperture, measure the density in several places to determine the darkest area.NoteFor instances where the f
45、ocal spot image is smaller than the densitometer aperture, center the focal spot image in the densitometer aperture area.FIG. 8 Focal Spot Density MeasurementE1165046ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin thi
46、s standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be
47、 reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresp
48、onsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, We
49、st Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).(a) Imaginary “Box” That Represents the Perceptible Edges of the Focal Spot Image(b) Measurement DirectionFIG. 9 Focal Spot ImageE1165047
