Method and apparatus for X-ray irradiation having improved throughput and dose uniformity ratio
The present invention is related to a method and apparatus of radiation processing of a product package in a device having a radiation source, a collimator having a variable aperture, and a turntable, said radiation processing resulting in a point in the product package where the dose is minimal (D min point) and a point in said product package where the dose is maximal (D max point) comprising the steps of: determining a first value of the collimator aperture, by increasing said aperture from a small value, where the D max point is located near the centre of the product package, up to a value where the D max point moves near to the centre of a small side of said package's rectangular horizontal cross-section; determining a second value of the collimator aperture, by further increasing the collimator aperture up to a point where the D min point moves from a point near the corner of the product package to the centre of said package; processing said package with radiation, the collimator aperture being kept at a constant value comprised between said first and said second value, the turntable being rotated at a variable speed.
1. A method of radiation processing of a product package o of essentially equal rectangular size in a device having a radiation source, a collimator having a variable aperture, and a turntable, said radiation processing resulting in a point in the product package where the dose is minimal (D min point) and a point in said product package where the dose is maximal (D max point) comprising the stops of:
determining a first value of the collimator aperture, by increasing said aperture from a small value, where the D max point is located near the centre of the product package, up to a value where the D max point moves near to the centre of a small side of said package's rectangular horizontal cross-section;
determining a second value of the collimator aperture, by further increasing the collimator aperture up to a point where the D min point moves from a point near the corner of the product package to the centre of said package;
processing said package with radiation, the collimator aperture being kept at a constant value comprised between said first and said second value, the turntable being rotated at a variable speed.
2. The method according to claim 1 , wherein the collimator aperture is selected as being said second value.
3. The method according to claim 1 , wherein said product package has a mean density between 0.4 and 0.8 g/cm 3 .
4. Apparatus for radiation processing of package of essentially equal rectangular size, comprising a radiation source, a collimator having a variable aperture, and a turntable, adapted for supporting one of said packages during said radiation processing, wherein said apparatus comprises a means for:
determining a first value of the collimator aperture, by increasing said aperture from a small value, where a D max point is located near tho centre of the product package, up to a value where the D max point moves near to the centre of a small side of said package's rectangular horizontal cross-section; and
determining a second value of the collimator aperture, by further increasing the collimator aperture up to a point where a D min point moves from a point near the corner of the product package to the centre of said package; and
wherein said collimator is adapted far adjusting its aperture to a value comprised between said first and second value, prior to irradiation of the package.
5. The apparatus according to claim 4 , wherein the ratio of collimator aperture over a distance d 1 from radiation so to front face of collimator is adjustable between 0.54 and 0.73.
6. The apparatus according to claim 4 , wherein the ratio of collimator aperture over a distance d 2 from radiation source to centre of turntable is adjustable between 0.11 and 0.16.
7. The apparatus according to claim 4 , wherein product packages having a mean density between 0.4 and 0.8 g/cm 3 are irradiated.