The new method intended as a user method for measurement of the effective focal spot sizes of nano-, micro-, mini- and macro- (standard) focus tubes. For mini- and macro-focus tubes (>100µm) the method is similar to the user method of the annex in ASTM E1165 using the edges of a plate hole IQI.


For nano- and micro-focus tubes a multi hole (or disk) target is used for image capture, the evaluation is the same as above.
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The edge method is intended for field and lab applications where users need to observe the effective focal spot on a regular basis and other methods are non-practical.

Test target for nanofocus tubes and microfocus tubes (spot size < 100 μm)
The focal spot measurement shall be based on the measurement of the unsharpness of hole or disk test objects acquired with specified exposure geometries and parameter settings.
The hole or disk test objects shall consist of hole or disk structures with specified diameter and roundness - see picture in the posting above.
The disks shall be manufactured from highly attenuating materials such as, e.g., lead, (Pb), gold (Au), tungsten (W) or its alloys. The holes shall be manufactured in a plate of highly attenuating materials such as e.g. lead, (Pb), gold (Au), tungsten (W) or its alloys. The test objects shall be fixed on a supporting solid structure (plate) of a low attenuating material. The diameter of the holes or disks shall not deviate more than 5 % from the nominal value as indicated on the hole or disk test object. The roundness shall be specified by the manufacturer and be less than 5 % of the diameter.
Depending on the tube voltage, the minimum thickness of the metal layers (disks or plates) should be selected. The minimum thickness to be selected depends on the applied radiation voltage. The relative contrast should be ≥ 10 %. Any use of additional X-ray filtering should be avoided.
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Within the NanoXSpot project Kowotest developed a test phantom with different holes which are conform to this standard.

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The setup for focal spots >100µm and the evaluation is done as described in the annex of ASTM E1165.

Classification and result of focal spot size evaluation:
The focal spot shall be classified according to its measured size. The preferred values of focal spot sizes and dedicated classes are consistent with ISO 19232-5. The measured values shall be rounded up to the upper limit of the corresponding nominal focal spot values (SS) and focal spot class (FS) according the following tables:
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The values for width and length or horizontal and vertical dimension shall be provided separately.

The test report shall provide the following values:
a) reference to this document, i.e. ISO 32543-2:2026;
b) measured focal spot size values d for the different directions (X, Y) and tube parameters in mm or μm;
c) nominal focal spot size (SS) in μm for the different tube parameters;
d) focal spot class (FS) for the different tube parameters;
e) image file name of the spot measurement with the test object;
f) X-ray tube model and serial number;
g) parameters of the focal spot d measurements for the different directions (X, Y);
h) set-up parameters (Source-Object Distance [SOD = m], Object-Detector Distance [ODD = n], Magnification [M], anticipated focal spot size [dap]);
i) exposure parameters (e.g. kilovoltage, target current, magnification);
j) SNR in the measured image at maximum intensity;
k) CNR of the profile;
l) iSRbdetector in accordance with ISO 19232-5 or ASTM E2002;
m) detector brand, type and parameters;
n) optionally, estimated beam time hours (if available);
o) type of the test object and diameter certificate;
p) any deviations from the procedure and any unusual features observed;
q) date of the test;
r) name of organization and of the operator and operator’s signature.