BS EN 12543-2-2008 pdf download.Non-destructive testing Characteristics of focal spots in industrial X-ray systems for use in nondestructive testing Part 2: Pinhole camera radiographic method.
This BS EN 12543-2 specifies a method for the measurement of focal spot dimensions above 0,2 mm of X-ray systems up to and including 500 kV tube voltage by means of the pinhole camera radiographic method, The voltage applied for this measurement is restricted to 200 kV for visual film evaluation.
The image quality and the resolution of X-ray images depend highly on the characteristics of the focal spot, in particular the size and the two dimensional intensity distribution.
For the characterisation of commercial X-ray tube types (i.e. for advertising or trade) the specific values of Table A.1 are used.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
EN 462-5, Non-destructive testing — Image quality of radiographs — Part 5: Image quality indicators (duplex wire t).pe), determination of image unsharpness value
EN 584-1, Non-destructive testing — Industrial radiographic film — Part 1: Classification of film systems for industrial radiography
EN 12543-1:1999, Non-destructive testing — Characteristics of focal spots in industrial X-ray systems for use in non-destructive testing — Part 1: Scanning method
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
focal spot
X-ray emitting area on the anode of the X-ray tube as seen from the measuring device
[EN 12543-1:1999]
4 Test equipment
4.1 Essential characteristics of the pinhole
Radiographic films or digital radiographic detectors can be used, provided sensitivity, dynamic range and detector unsharpness allow capturing of the full spatial size of the focal spot image without detector saturation. The maximum allowed detector unsharpness is given by the geometrical unsharpness UG of the pin hole and is calculated according to:
uG=P(1+n/m) (1)
The detector unsharpness shall be determined with the duplex wire IQI according to EN 462-5. For correct quantitative measurements the minimum projected length and width of the focal spot image should be covered always by at least 20 detector pixels. The signal-to-noise ratio of the focal spot image (ratio of the maximum intensity value inside the focal spot and the standard deviation of the background signal outside) should be at least 50. The maximum intensity inside the focal spot should be above 50%, but lower than 100% of the maximum linear detector output value to achieve an image with good contrast.
Imaging plates systems (Computed Radiography. CR) or digital detector arrays (e.g. based on CCD-, a-Si- or
CMOS-detectors coupled to an X-ray fluorescent screen, direct converting detectors or image intensifiers with
CCD cameras) may be used as digital image detectors.
If radiographic film is used as image detector. it shall meet the requirements of the film system class C 6 or better according to EN 584-1 and shall be used without screens. The film shall be exposed to give a maximum optical density between 1.5 and 2,5. For reference measurements, the film can be digitised with a maximum pixel size, which fulfils the requirements of the above unsharpness conchtions, and evaluated according to 5.1.
4.5 Loading factors
The X-ray tube voltage shall be 75 % of the nominal tube voltage, but not more than 200 kV for visual film evaluation. For digital evaluation the maximum voltage is limited by the need that the background intensity is lower than half of the maximum intensity inside the focal spot. The X-ray tube current shall be the maximum applicable tube current at the selected voltage.
5 Measurement and determination of the focal spot size
5.1 Measurement
The grey scale image of the radiation detector shall be proportional to the X-ray dose. It shall be evaluated to measure the dimensions of the focal spot. The area of all pixels of the focal spot image with grey values higher than 10% of the maximum value (of a 3×3 pixel median filtered image to suppress outliers) above background intensity are used to represent the area of the focal spot (see Figure 4). An isodose contour plot at 10% of the maximum intensity (see Figure 6 in EN 12543-1:1999) may also be used to indicate the area of the focal spot. The focal spot size is determined by the extent of the focal spot area in x and y-direction divided by the magnification factor (n/rn) of the pinhole camera.
If radiographic film is used as an image detector, it is evaluated visually using an illuminator with a uniform luminance of 2000 cd/rn2 to 3000 cd/rn2. The visual evaluation shall be carried Out using an X5 or X10.BS EN 12543-2-2008 pdf download.