SI24520A - The device for measuring the incident direction of the gamma rays - Google Patents

Abstract

The method and the concrete implementation of the device for measuring the incident direction of the gamma rays are presented. The optimized shape of the lead cross-sight, to which four scintillation detectors are attached, allows a uniform determination of the incident direction of gamma radiation based solely on the comparison of the counting speeds from all four detectors. The approach is particularly suitable for use in a hand-held measuring instrument for field work in the scenario of searching for a lost source of radiation.

Description

DEVICE FOR MEASURING THE DIRECT DIRECTION OF GAMES BEAMS

The invention belongs to the technical field of radiation measurement, more specifically it is a gauge of the incident direction of gamma rays.

1. Demonstration of a technical problem

In some industrial process control methods (bulk thickness, suspension density, weld control, level gauges in containers), medicine (imaging and radiotherapy devices), some physico-chemical analytical methods and radiation sterilization devices, sources are used. gamma rays with activities up to several Tbq (several trillion radioactive decays per second). When, for technical or human reasons, such a strong source of radiation is lost, the latter pose a risk of serious injury to persons moving near an unprotected source.

When looking for a blank source, detecting the general proximity of a source is relatively easy with radiation dose rate gauges, where in the sense of the 'hot-cold' instrument, information is obtained about the distance from the source.

It complicates the determination of the microlocation when the person seeking the source may be exposed to dangerously high radiation dose rates and cannot see the source with the naked eye. Usually, the geometry of the immediate surroundings (overgrown terrain in the natural environment, or with walls, furniture and objects limited urban environment) makes it difficult to look at the source and often also unpredictably partially obscures the radiation, making it difficult to interpret the signal from dose-only instruments. velocity independent of the angle of incidence of radiation.

An instrument that would also measure (or, most of all, or even just) the intrusion • ·

In such circumstances, radiation is much more useful because it shows the user the direction from which radiation is coming, while not being significantly sensitive to partial shading due to nearby objects. Field experience shows that, in a typical source search scenario, several times the dose rate for the operator is achievable if he or she knows the downward direction of radiation when determining the microlocation.

2. State of the art

Among the known gamma rays with pronounced angular sensitivity, we recognize some key implementation concepts.

The first concept is collimating and operates in such a way that the radiation meter is either inserted into a sleeve of absorbent material or has an absorbent honeycomb attached to one of the boundary surfaces, which limits the sensitivity to incidence from a large part of the spatial angle, except for the selected incident direction [US3011057, US3936646, US5021667, EP0090594A1, EP0212416A1, US 5448073 A]. In the current scenario, the disadvantage of these approaches is that such a device had to be rotated in different directions of the room, observing at which orientation of the device the signal was greatest. From the latter, we can roughly deduce the direction from which radiation is coming.

The second group of approaches are i.e. Compton cameras [US4857737, US5175434], based on multiple gamma ray scattering and using the computational methods [US5841141, US5861627], reconstruct the western direction of radiation from a large number of measured detections. Typically, a heavier construction is required, less suitable for installation in a hand held field instrument, and measurement of the deposited energy of the gamma ray beam is required, which increases the requirements for the signal acquisition chain.

A third approach is a one-shot or multi-hole camera derivative with a locally sensitive flat-panel detector [US8389943 B2, US6628984 Β2], which suffer from poor detection efficiency and relatively complex signal capture electronics. A special example is space-encoded telescopic systems • · · • · · · ·

-3Shield [EP 0920643 lon1] which improve detection efficiency but still require a spatially resolved detector element and careful analog signal processing.

Our proposed solution goes towards a small number of sensors with simple signal capture requirements, which can be achieved at the expense of innovative sensor geometry.

3. Description of the solution to the problem with the implementation example

The sensor part of the device is, in principle, based on geometry, as shown in Figure 1.

The sought radiation source 1 is a strain of gamma rays 2, some of which reach the sensitive detection portion 3 of the object of the present invention. The latter detection part is composed of at least four independent gamma ray detector elements 4 and may further have an additional passive shade 5. The system geometry is designed to illuminate from two to four detector elements simultaneously for any incident direction of the gamma 2 rays. This is achieved by means of a sensor part 3, which is formed by intersection of the first, second and third geometric planes, which are perpendicular to each other, and two of the detection elements 4 are entirely on one side of the first geometric plane and the remaining two on the other hand. At the same time there is one detection element from the one mentioned on one side of the other geometric plane and one on the other side of the other geometric plane. At the same time there is one detection element on one side of the third geometric plane and one detection element on its other side. The passive shade 5 consists mainly of a panel with one ridge outgrowth on each of the two major boundary surfaces.

Since these elements 4, depending on the incident angle, are differently shaded by the incident rays (each of them can be shadowed by the other detection elements 4 and the passive shading 5), we can uniquely deduce from the individual signals from the detection elements the direction from which radiation 2 falls, since at the same time interval more gamma 2 beams are detected in more illuminated elements.Electric signals from all • · · · ·

-4Detection elements are captured and processed in process part 6, followed by the conversion of the measured quantities into the estimate of the incident angle of radiation. The latter angle is shown geometrically on screen 7, where the horizontal and vertical positions of the drawn badges represent the azimuthal and elevation parameters of the incident direction.

For the sake of clearer user perception, in some embodiments, the timing of the incident beam direction of gamma 2 can be conveniently realized in processing unit 6 so that the averaging time is dynamically adjusted with respect to the statistical uncertainty of the signal and the average weighting is calculated from the counting speeds of the individual detection elements.

For design reasons, an embodiment is particularly suitable with the combination of four non-hygroscopic solid scintillation detectors coupled to semiconductor optoelectric converters and a passive shading of dense material such as lead. For the basic determination of the angle, it is sufficient to measure and compare the count velocities in each of the detection elements, which is performed in the integrated electronics 6 and the process part.

Claims (4)

A gamma ray incident beam detector assembly, characterized in that it • includes four gamma ray detector elements (4) (4). 2) and, in addition, a passive shade (5) which, depending on the incident direction of said gamma rays, shades to a certain extent the incident of said gamma rays on said detector elements, • intersected by the first, second and third geometric planes, which are perpendicular to the pair , • two of the above-mentioned detection elements are entirely on one side of the first geometric plane, and the remaining two of the detection elements are entirely on the other side of the first geometric plane, • exactly one detection element of the ones mentioned is completely on one side of the second geometric plane, and exactly one detection element from those mentioned entirely on the other side of the second geometric plane, • exactly one detection element from the mentioned ones completely on one side of the third geometric plane and exactly one detection element from the mentioned ones completely on the other side of the third geometric plane, • mentioned passively the shade (5) comprises a panel lying such that the first geometric plane divides it into two thin plates and having plate two ridges, one of which is on the first side of the first geometric plane and divided by the second geometric plane into two narrower ridges and the second outgrowth on the other side of the first geometric plane and divided by the third geometric plane into two narrower ridges. • · · · · -62. An apparatus comprising a detector assembly according to claim 1, characterized in that, in a built-in electronic processing unit (6), the incident direction of the gamma rays (2) is determined by computational comparison of the signals from said detection elements (4). Apparatus according to claim 2, characterized in that, in calculating the incident beam direction, the gamma (2) averages the estimate of the incident beam direction by adjusting the average weight with respect to the statistical uncertainty of the signal and the weight calculated from the counting speeds of the individual detection elements. Apparatus according to claim 2, characterized in that the estimated azimuthal and elevation angle of the incident beams presents the gamma in the horizontal and vertical position of the displayed badges on the graphical screen (7).