Ionization chamber for ion beams and method for monitoring the intensity of an ion beam
First Claim
1. An ionisation chamber for ion beams (1) having a chamber housing (2), a beam inlet window (3), a chamber volume (5) filled with counting gas, a high-voltage anode (6) and a high-voltage cathode (7) wherein:
- the ionisation chamber (8) is constructed sandwich-like, from flat large-surface-area structures of the above-mentioned components, which are aligned orthogonally relative to the axis of the ion beam, wherein a centrally arranged large-surface-area orthogonally aligned flat counting anode (9) is surrounded on both sides by a large-surface-area flat high-voltage cathode (7) comprising two parallel cathode surfaces (10), and the chamber housing (2) comprises a housing frame (11) which frames a virtually square ionisation chamber volume (12);
wherein a beam inlet window (3) and a beam outlet window (4) are mounted gas-impermeably and electrically conductively on the housing frame (11) in orthogonal alignment with the ion beam (1), the beam inlet window (3) and the beam outlet window (4) being metallised on the side facing the ionisation chamber volume (12) and the counting anode (9) and the high-voltage cathode (7) consisting of mesh comprising metal-coated plastics fibres and being mounted in frames (20) which are supported against the housing frame (11) in an electrically insulated manner, with electrically insulating spacing elements (21) defining the spacing between the counting anode (9) and the high-voltage cathode (7).
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Accused Products
Abstract
The invention relates to an ionization chamber for ion beams and to a method of monitoring the intensity of an ion therapy beam by way of such an ionization chamber. For that purpose, the ionization chamber includes a chamber housing, a beam inlet window and a beam outlet window, a chamber volume filled with counting gas, a high-voltage anode and a high-voltage cathode, wherein the ionization chamber is constructed flat and sandwich-like from plate-shaped large-surface-area structures of the above-mentioned components, which are aligned orthogonally relative to the axis of the ion beam, and a centrally arranged large-surface-area orthogonally aligned plate-shaped counting anode is surrounded on both sides by a large-surface-area plate-shaped high-voltage cathode consisting of two parallel cathode plates, and the chamber housing consists of a housing frame, which frames a square ionization chamber volume, and on which frame the beam inlet window and the beam outlet window are mounted gas-impermeably.
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Citations
16 Claims
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1. An ionisation chamber for ion beams (1) having a chamber housing (2), a beam inlet window (3), a chamber volume (5) filled with counting gas, a high-voltage anode (6) and a high-voltage cathode (7) wherein:
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the ionisation chamber (8) is constructed sandwich-like, from flat large-surface-area structures of the above-mentioned components, which are aligned orthogonally relative to the axis of the ion beam, wherein a centrally arranged large-surface-area orthogonally aligned flat counting anode (9) is surrounded on both sides by a large-surface-area flat high-voltage cathode (7) comprising two parallel cathode surfaces (10), and the chamber housing (2) comprises a housing frame (11) which frames a virtually square ionisation chamber volume (12);
wherein a beam inlet window (3) and a beam outlet window (4) are mounted gas-impermeably and electrically conductively on the housing frame (11) in orthogonal alignment with the ion beam (1), the beam inlet window (3) and the beam outlet window (4) being metallised on the side facing the ionisation chamber volume (12) and the counting anode (9) and the high-voltage cathode (7) consisting of mesh comprising metal-coated plastics fibres and being mounted in frames (20) which are supported against the housing frame (11) in an electrically insulated manner, with electrically insulating spacing elements (21) defining the spacing between the counting anode (9) and the high-voltage cathode (7). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method of monitoring the intensity of a heavy ion beam by means of ionisation chambers according to the following method steps:
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a) measurement of the intensity dose of an irradiation volume element of a planned irradiation raster for an irradiation layer by means of a first ionisation chamber (22);
b) monitoring of the measured value of the intensity dose of an irradiation volume element by a second ionisation chamber (23) arranged in tandem behind the first ionisation chamber;
c) comparison of the measured value of the first ionisation chamber with the monitoring value of the second ionisation chamber and clearance for the irradiation of the next irradiation volume element of a planned irradiation raster of an irradiation layer when the two irradiation intensity values match within a predetermined desired value range;
d) emergency switch-off of the radiation treatment when the predetermined desired value range is exceeded and readjustment of the intensity when it falls short of the predetermined desired value range;
e) repetition of the steps for the subsequent planned irradiation layers until the target volume to be irradiated has been fully scanned; and
f) integration of all the measured radiation doses of the monitoring values in a third ionisation chamber (24), which is arranged in tandem behind the first and second ionisation chambers, in order to monitor the total radiation to which a target volume is subjected during a treatment cycle. - View Dependent Claims (14, 15, 16)
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Specification