DETECTOR PROTECTION METHOD FOR PROTECTING FLAT DETECTORS FOR ELECTROMAGNETIC RADIATION AND/OR PARTICLE RADIATION, AND DETECTOR PROTECTION ASSEMBLY

Abstract

A method and assembly for protecting flat detectors for electromagnetic radiation and/or particle radiation from excessive local intensities in an experiment to be conducted. Multiple absorbers are intelligently positioned in front of sections of a detector area, and further disclosing a detector protection arrangement for protecting area detectors for electromagnetic radiation and/or particle radiation from excessive local intensities.

Claims

1. A detector protection method for protecting area detectors for electromagnetic radiation and/or particle radiation from excessive local intensities in an experiment to be conducted, wherein multiple absorbers are positioned in front of sections of a detector area, the detector protection method comprising the steps of: 1. preparatory configuration: a. setting a threshold value I.sub.lim for the intensity at a point of the detector area, in accordance with the expected intensity maxima based on the experiment to be performed and the necessary intensity I.sub.x, required for conducting the experiment, of the primary beam used for the measurement and in accordance with the maximum intensity to be tolerated by the detector; b. loading magazines with or providing magazines having absorbers of different shapes and sizes, selected in accordance with the type of experiment to be conducted; 2. determining a position pattern of the absorbers; 3. computer-assisted automatic placing of the absorbers on an absorber carrier on the basis of the position pattern; and 4. checking the positions of the placed absorbers and conducting the measurement.

2. The detector protection method according to claim 1, wherein determining a position pattern of the absorbers in step 2 comprises: a. measuring the sample with strongly reduced intensity I.sub.1 of the primary beam; b. identifying the points where the threshold I.sub.lim on the detector surface has been exceeded and from this creating a binary image B1 with the positions of these points; c. determining contiguous areas X in B1 and their size, shape and distribution; d. selecting the number and shape of the required absorbers; and e. generating a list L corresponding to the position pattern of positions, shapes and orientations of the absorbers to be placed according to the position pattern.

3. The detector protection method according to claim 1, wherein for the computer-assisted automatic placing of the absorbers on the absorber carrier in step 3 the following is carried out on the basis of a list L corresponding to the position pattern: a. an assignment of the selected absorbers to magazines of the detector arrangement; b. determining the order of placement of the absorbers; and c. moving the absorbers onto the absorber carrier.

4. The detector protection method according to claim 2, wherein the verification of the positions of the placed absorbers in step 4 comprises: a. creating and evaluating a binary image at greatly reduced intensity I.sub.1 after completion of the positioning step 3c, wherein in the presence of points with exceeding of the threshold value I.sub.lim in the binary image step 4b will be the next step, otherwise further go on to step 4e; b. checking and, if necessary, correcting the absorber list L according to step 2c to 2e; c. repeating step 3—computer-assisted automatic placement of the absorbers based on a corrected absorber list L1; d. repeating step 4a until threshold I.sub.lim is not exceeded at any point in the binary image; e. checking the placed absorbers by creating a binary image at higher intensity I.sub.2, where I.sub.1<1.sub.2<I.sub.x, and steps 4b to 4d are repeated if there are points where the threshold value I.sub.lim is exceeded; and f. repeating step 4d until the intensity l.sub.x required for the measurement is reached.

5. The detector protection method according to claim 2, wherein in step 2d the selection of the number and shape of the required absorbers is performed with the following conditions: i. all areas X are completely covered by an absorber; ii minimizing the coverage of the areas outside of areas X; and iii. minimizing the number of absorbers to be used.

6. The detector protection method according to claim 3, wherein the determination of a placement order of the absorbers in step 3b is carried out under the condition that the paths to be covered for the positioning include as few changes of direction as possible and are as short as possible.

7. The detector protection method according to claim 3, wherein the displacement of the absorbers on the absorber carrier in step 3c is carried out taking into account the avoidance of collisions with already placed absorbers and taking into account the following conditions: i minimizing changes in direction and length of the paths to be covered for positioning; and ii. taking into account the geometrical parameters of the experimental setup.

8. The detector protection method according to claim 3, wherein a further step 5 is processed:

5. modifying the position pattern of the placed absorbers when the detector position is changed, wherein the following is carried out for this purpose: a. recalculation of the absorber list L from the position changes, in accordance with the geometric parameters of the experimental setup; b. computer-assisted automatic changing of the position pattern by shifting the absorbers on the absorber carrier on the basis of list L and/or, if appropriate, replacement by absorbers of a different shape stored in the magazine, wherein these changes are carried out in accordance with steps 3b and 3c; and c. checking the positions according to step 4.

9. A detector protection arrangement for protecting area detectors for electromagnetic radiation and/or particle radiation from excessive local intensities, wherein absorbers can be positioned in front of sections of a detector area, wherein the positioning can be carried out by means of a computer-assisted method executed on a computer unit with a computer program in accordance with detector protection methods according to claim 1, wherein the detector protection arrangement comprises the following components: thin planar absorber carrier made of a material with sufficiently high transparency for the radiation measured in the detector; and absorbers consisting of bodies of highly absorbing material for the radiation present and magazines for absorbers and X-Y positioning arm for the displacement of the absorbers on the absorber carrier.

10. The detector protection arrangement according to claim 9, wherein the detector protection arrangement further comprises at least one of: absorber manipulator mounted on the X-Y positioning arm, stepper motor mounted on the absorber manipulator and having a freely rotatable axis, the manipulator axis, perpendicular to the detector, on which a manipulator holder is mounted by means of which the absorber can be displaced, and a holder for absorber carrier and X-Y positioning arm, which optionally allows direct attachment to the detector or free positioning in space.

Description

[0070] The following description of the invention is based on a particularly preferred example of an embodiment. However, this is not intended to limit the scope of protection.

[0071] In the particularly preferred embodiment, the method comprises the following steps:

[0072] 1. Configuration: [0073] a. determination of a threshold value I.sub.lim for the intensity at a point on the detector surface, taking into account the expected intensity maxima based on the experiment to be performed and the intensity I.sub.x of the primary beam used for the measurement required to perform the experiment, as well as the maximum intensity that can be tolerated by the detector; [0074] b. loading of magazines with absorbers of various shapes and sizes, selected according to the type of experiment to be conducted;

[0075] 2. determination of a position pattern of the absorbers: [0076] a. measuring the sample with highly reduced intensity of the primary beam I.sub.1; [0077] b. identification of the points where the threshold value I.sub.lim was exceeded on the detector surface and from this creating a binary image B1 with the positions of these points; [0078] c. determination of contiguous areas X in B1 and their size, shape and distribution: [0079] d. selection of the number and shape of the required absorbers with the conditions: [0080] i. all areas X are completely covered by an absorber; [0081] ii. Minimize overlap of areas outside of areas X; [0082] iii. Minimizing the number of absorbers to be used; [0083] e. preparation of a list L of positions, shapes and orientations of the absorbers to be placed for the position pattern;

[0084] 3. computer-assisted automatic placement of the absorbers on an absorber carrier based on list L [0085] a. assignment of the selected absorbers to the magazines of the apparatus according to the invention; [0086] b. determination of a placement sequence of the absorbers under the condition that the paths to be covered for positioning involve as few changes of direction as possible and are as short as possible; [0087] c. moving the absorbers on the absorber carrier according to known algorithms, taking into account the avoidance of collisions with already placed absorbers and observing the conditions: [0088] i. minimization of changes in direction and length of travel required for positioning; [0089] ii. consideration of the geometric parameters of the experimental setup;

[0090] 4. checking the positions of the placed absorbers: [0091] a. creation and evaluation of a binary image with strongly reduced intensity I.sub.1 after completion of positioning step 3c; in the presence of points with exceeding threshold I.sub.lim in the binary image step 4b will follow, otherwise step 4e will be the next step; [0092] b. review and, if necessary, correct absorber list L according to steps 2c to 2e; [0093] c. repeat step 3—computer-assisted automatic placement of absorbers using the corrected absorber list L1; [0094] d. repeat step 4a until threshold I.sub.lim is not exceeded at any point in the binary image; [0095] e. checking the set absorbers by creating a binary image at higher intensity I.sub.2, where I.sub.1<1.sub.2<I.sub.x; repeating steps 4b to 4d in the presence of points exceeding the threshold I.sub.lim; [0096] f. repeat step 4d up to the intensity required for the measurement 1.sub.x;

[0097] 5. modification of the position pattern of the set absorbers when the detector position is changed: [0098] a. recalculation of the absorber list L from the position changes taking into account the geometrical parameters of the experimental setup; [0099] b. computer-aided automatic change of the position pattern by shifting the absorbers on the absorber carrier using list L and/or, if necessary, replacement by absorbers of a different shape stored in the magazine, these changes being made in accordance with steps 3b and 3c; [0100] c. check the positions according to step 4.

[0101] The device for conducting the method, which is also in accordance with the invention, can be described as follows, whereby this represents preferred embodiments and is not necessarily to be regarded as limiting the scope of protection of the invention:

[0102] The device for protecting area detectors from locally elevated intensities of measured radiation may include, in particular, the following components: [0103] thin planar absorber carrier made of a material with sufficiently high transparency for the radiation measured in the detector. Preferred for X-ray detectors are carbon-based materials (composite carbons, glassy carbons), plastics (Kapton, PEEK) and A1, other suitable materials are other metals (steels), semiconductors (Si), insulators (LiF, NaF, boron nitride, boron carbide, borides), oxides (sapphire, quartz, boron oxide, borosilicate). These semiconductors, insulators and oxides can also be used for absorber carriers for electromagnetic radiation in the infrared (IR), visible (Vis) and ultraviolet (UV) regions. The thickness of the absorber carrier is between 0.05 m and 5 mm, height and width are determined by the dimensions of the detector area (typically between 10×10 mm.sup.2 and 1000×1000 mm.sup.2). [0104] Absorbers consisting of bodies of highly absorbing material for the radiation at hand, having a defined thickness (0.5 to 20 mm) perpendicularly and a predetermined shape parallel to the detector plane. The highly absorbing materials are mounted on magnets of smaller dimensions in the detector plane and are held in a stable position by counter magnets located on the other side of the absorber carrier. The shapes of the absorbers are optionally circles, ellipses, crescents and rectangles with dimensions between 1 and 50 mm. For X-ray absorbers, heavy metals (W, Ta, Pb, Bi) are preferably used. For special applications other materials (especially elementary metals and semiconductors) can be used, the choice of which depends on the wavelength of the radiation and the position of the X-ray absorption edges in the material. For IR, Vis and UV radiation, highly absorbing materials made of easily machinable metals (A1, steels) with highly absorbing coatings (black emitters) are preferred. [0105] Magazines for absorbers located along one or more sides of the absorber carrier. The magazines allow insertion and initial placement of absorbers at specified positions of the absorber carrier. [0106] X-Y positioning arm for moving the absorbers on the absorber carrier. The X-Y positioning arm allows the movement of the absorber manipulator along two axes in the detector plane via stepper motors. The position accuracy is smaller than the size of a single detector dot. Optical or magnetic length encoders can optionally be used to control the position and ensure position accuracy. The position of the absorbers can optionally also be checked via a camera on the absorber carrier or on the X-Y positioning arm. [0107] Absorber manipulator mounted on the X-Y positioning arm. [0108] Stepper motor mounted on the absorber manipulator, which has a freely rotatable axis, the manipulator axis, perpendicular to the detector, on which a manipulator holder is mounted, with which the absorber can be moved. [0109] Bracket for absorber carrier and X-Y positioning arm, allowing either direct attachment to the detector or free positioning in the room. [0110] Electronic control unit for controlling the motor movements of the X-Y positioning arm and absorber manipulator, the control unit preferably including a small computer or microcontroller for calculating the movements. [0111] In a preferred embodiment, when circular absorbers are used (with radii between R.sub.min and R.sub.max), the manipulator is formed by a rod holder on which two axially parallel round rods are eccentrically mounted, the round rods having a radius r between 1 and 5 mm and being made of metal, preferably stainless steel, have distances ≥r+R.sub.max from the manipulator axis and a maximum pick-up angle α≤140° is ensured by a distance d=2(r+R.sub.min)−sin(α/2) of the round rods, wherein the movement of the absorbers is performed as follows: [0112] i) Moving the manipulator towards the absorber until it is touched by both round bars; [0113] ii) Rotation of the manipulator holder around the center of the absorber axis until the round bars are positioned in the opposite direction to the intended traverse; [0114] iii) movement of the X-Y positioning arm with absorber in the same direction up to the desired final position where changes of direction are realized by rotations of the manipulator holder around the center of the absorber axis, and [0115] iv) after reaching the target position, final movement of the X-Y positioning arm to a position in which the experiment to be performed is not disturbed by the X-Y positioning arm, avoiding contact with already placed absorbers.

[0116] In this embodiment, it is possible to detect the contact of the round bars with the absorbers by means of an electrical measurement and thus to determine the position of the absorbers. In an alternative embodiment, when non-circular absorbers are used, an alternative version of absorber manipulator may be used that allows fixed gripping of absorbers. For this purpose, for example, a motorized or electromagnetically displaceable third rod can be mounted. on the manipulator rod, which can be moved towards the circular rods, thus allowing gripping of absorbers.

[0117] In another embodiment, the manipulator holder has a device which is positioned centrally above the absorber and which lifts the absorber electromagnetically or by means of negative pressure generated by a pump, whereby the absorbers can be lifted off the absorber holder by 0.1 to 2 mm and transported. The counter magnet is magnetically carried along.

[0118] Further embodiments include manipulator holders in which motorized, electromagnetic or compressed air driven vertical movements can be used to insert a molded part, e.g. pyramid, cross, hexagon, into a corresponding mating mold mounted on the absorber and subsequently rotate and move it over the absorbers,

[0119] The manipulator bars with different - and d can be interchanged to cover different ranges of radii R.sub.min and R ..sub.max

[0120] The invention to react to the changing load situation of the detector during and due to the measurement by repositioning the absorbers and to do this automatically and not “manually” is also new and inventive in itself.

[0121] In particular, it is a computer-aided or computer-assisted method that autonomously and automatically protects an area detector from excessive local radiation intensities by detecting areas at risk, deriving a course of action from this, creating a protection pattern, placing protective absorbers based on this pattern, and verifying the results of this course of action. In the method according to the invention for protecting area detectors for electromagnetic radiation or particle beams, in particular 2D X-ray detectors, against excessive local intensities at multiple positions on the detector, the device autonomously detects areas with excessive intensity and covers them with absorbers. The selection of the absorbers from a set of different basic shapes and their sequential placement is done autonomously without any intervention by the user.

[0122] FIG. 1 shows an example (not necessarily limiting the scope of protection) of a device for the protection of area detectors, consisting of a holder H, an absorber carrier AT, absorbers A, X-Y positioning arm XYP and absorber manipulator M.

[0123] FIG. 2 shows a detailed drawing of the manipulator M with manipulator holder MH, manipulator axis MA, round rods MR and an absorber A held on the absorber carrier AT by magnets AM as an example (not necessarily to be regarded as limiting the protected area).