X-ray or gamma ray systems or devices – Specific application – Absorption
Patent
1998-09-02
2000-07-25
Porta, David P.
X-ray or gamma ray systems or devices
Specific application
Absorption
378 86, 378 87, 378 89, G01B 1502
Patent
active
060944706
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to a method of determining the density profile of a plate-shaped material.
BACKGROUND ART
Danish Patent Application No. 0723/94 discloses a method of determining the density profile of plate-shaped materials by way of a measuring of Compton-scattered radiation from small partial volumes in the material. During the measuring, a predetermined angular relation is maintained between the incident and the scattered radiation, and the scattered radiation is adjusted by a simultaneous measuring of the incident radiation intensity and the attenuation in the entire plate-shaped material. However, such a measuring method only makes allowance for singly scattered radiation.
It is known from the article "The characterisation of multiple scattering in Compton profile measurements" by T. Pitkanen in Nuclear Instruments and Methods i Physics Research A257 (1987) pp 384-390 that multiple scattered radiation is rather important in connection with relatively thick plates.
BRIEF DESCRIPTION OF THE INVENTION
The object of the invention is therefore to provide a method of determining the density profile of a plate-shaped material, said method being more accurate than hitherto known.
A method of the above type is according to the invention characterized by compensating for multiple scattered radiation in each partial volume. The resulting measuring method is far more accurate than hitherto known, especially in connection with relatively thick plates.
According to a particularly advantageous embodiment, the multiple scattered radiation is compensated for by said radiation being reduced by the measured radiation, as the multiple scattered radiation can be found on the basis of some parameter values provided by way of a calibration measur- ing.
BRIEF DESCRIPTION OF THE DRAWING
The invention is explained in greater detail below with reference to the accompanying drawing, in which
FIG. 1 illustrates how the measured intensity of the scattered radiation is composed of several values,
FIG. 2 shows a measuring arrangement wherein an additional detector is coupled between the X-ray source and the plate-shaped material,
FIG. 3 shows an arrangement of two plate-shaped materials arranged at a mutual distance, and
FIG. 4 shows an example of how one of the parameter values .beta. varies versus the height of the plate material.
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows how the measured intensity of the scattered radiation is composed of contributions from the considered partial volume at P and contributions from multiple scattered radiation either in the plate-shaped material M itself, where scattered radiation from the entire length AB can cause a renewed scattering from the length CD in a direction towards the detector F, or via a collimator where scattered radiation from the length AB meets the wall of said collimator and is scattered towards the detector F.
The intensity of the multiple scattered radiation is not correlated with the density of the partial volume at P, but almost unambiguously correlated with the surface weight .rho. of the plate-shaped material M, where .rho. is the average density and t is the thickness.
The latter has been confirmed by simulation calculations performed by the known Monte-Carlo-method. For the present measuring geometry with a narrow incident beam and a strong collimation in front of the detector for scattered radiation and an optical thickness of .mu..multidot..rho.p.multidot.t.ltoreq.1, where .mu. is the absorption coefficient, the intensity of multiple scattered radiation I.sub.MS can be approximately expressed by .mu..multidot..rho..multidot.t(1-.alpha..multidot..mu..rho.t)(1) and the parameters .alpha. and .beta. depend on the actual measuring geometry (the extent of the beam, the visual field of and the distance to the collimator and the detector etc. Furthermore, .beta. depends on the position of P of the actual partial volume, from which singly scattered radiation is to be measured. When the location P.sub.1 is considered outside the p
REFERENCES:
patent: 4123654 (1978-10-01), Reiss et al.
patent: 4228351 (1980-10-01), Snow et al.
patent: 4380817 (1983-04-01), Harding et al.
patent: 5313511 (1994-05-01), Annis et al.
patent: 5970116 (1999-10-01), Ducholm et al.
Nuclear Instruments and Methods . . . , T. Pitkanen et al, "The Characterisation of Multiple Scattering . . . ", pp. 384-390, 1987.
Hobden Pamela R.
Porta David P.
Wesser & Dueholm
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