Alpha radiation detector with an optical sensor for measuring the radon concentration in the ambient air

Description

[0001] The invention relates to an alpha radiation detector with an optical sensor for measuring the radon concentration in the ambient air. BACKGROUND OF THE INVENTION

[0002] Radon is a radioactive noble gas that forms as an intermediate product in the radioactive decay of radium, actinium, or thorium. It occurs naturally in certain rock formations, from where it can reach the Earth's surface. At the surface, it tends to accumulate in building basements, where it can sometimes reach high concentrations. All known isotopes of radon are radioactive and emit alpha (or beta) particles during decay. Because radon and its decay products (polonium, lead, and bismuth) are inhaled by humans along with the surrounding air, they are potentially hazardous to health.

[0003] There are various approaches to measuring radon concentration in ambient air. One of these utilizes the property of scintillators, i.e., materials that emit a light pulse upon contact with an alpha particle. The light pulses generated in this way are then detected by an optical sensor. The number and strength / intensity of the light pulses per unit of time are a measure of the radon concentration in the ambient air. All known radon detectors with an optical sensor are relatively complex in design, expensive, energy-intensive, and either very large, insufficiently sensitive, or slow to respond.

[0004] Various alpha detectors for measuring radon concentration in ambient air are known from CN 202 362 462 U, KR 2017 002 539 5 A, and US 5 489 780 A. Further alpha detectors are described in the publications: MCDONALD E. WRENN ET AL.: "DESIGN OF A CONTINUOUS DIGITAL-OUTPUT ENVIRONMENTAL RADON MONITOR", IEEE TRANSACTIONS ON NUCLEAR SCIENCE, February 1, 1975, pages 645-648, and YAMAMOTO S. ET AL.: "NUCLEAR SCIENCE SYMPOSIUM CONFERENCE RECORD", 2000, IEEE, article "Development of a continuous radon concentration monitoring system in underground soil", pages 6313-6316. However, the alpha radiation detectors known from the prior art are relatively complex in design and expensive to manufacture. KR 101 771 476 B1 further describes a radon detector with a housing that has a passage through which ambient air can enter the interior of the housing. TASK OF INVENTION

[0005] It is therefore an object of the present invention to create an alpha ray detector with an optical sensor that is significantly simpler in design, very small, very energy-efficient, very sensitive, fast and more cost-effective to manufacture.

[0006] This problem is solved according to the invention by the features specified in claim 1. Further embodiments of the invention are the subject of dependent claims.

[0007] According to the invention, an alpha radiation detector with an optical sensor for measuring the radon concentration in the ambient air is proposed, configured according to claim 1. Such an alpha radiation detector has a very simple design and can be manufactured in a very small, energy-efficient, and cost-effective manner.

[0008] The housing, and thus also the measuring chamber, of the radon detector according to the invention is preferably completely closed, i.e., it has no free opening. To nevertheless allow ambient air to enter the chamber, in the alpha-ray detector defined in claim 1, an annular area of ​​the housing is made of a material that is opaque to light but permeable to air / gas. The alpha-ray detector defined in claim 11 alternatively comprises a base with a passage that is sealed by the opaque but permeable to gas material. The material thickness, structure, and density of said material are selected such that no light, but sufficient ambient air, can enter the chamber. Furthermore, the material is preferably selected such that already decayed radon, i.e., polonium, lead, or bismuth, cannot penetrate the chamber from the outside.Since these subsequent decays of radon are ionized, they are bound by the material and therefore cannot penetrate the chamber.

[0009] The gas-permeable material of the housing wall could be, for example, felt, silicone, fabric, a plastic, a membrane, or another material with the aforementioned properties.

[0010] According to the invention, a second embodiment of an alpha-ray detector is also proposed, as defined in claim 11. In this case, the alpha-ray detector comprises a base with a passage that is sealed by a suitable material in a light-tight but gas-permeable manner. This material can optionally be located inside the passage, on the inside of the housing wall, and / or on the outside of the housing wall, so that the passage is sealed.

[0011] Both embodiments of the alpha-ray detector proposed here have a hood with an inner wall coated with a scintillation material. This scintillation material could be, for example, zinc sulfide, bismuth germanate, lead tungstate, lutetium oxyorthosilicate, sodium iodide, zinc sulfide, or cesium iodide.

[0012] The scintillation material is preferably a layer applied to the inner wall of the chamber.

[0013] Both embodiments of the alpha-ray detector according to the invention comprise a base on which a hood is arranged, which may, for example, have the shape of a dome. The chamber mentioned above is located inside the hood. In the first embodiment according to claim 1, the optical sensor is preferably arranged inside the chamber and preferably on the base.

[0014] The hood can, for example, be designed as part of a sphere. It can be hemispherical or pyramidal, for instance. However, it can also be cylindrical or angular, e.g., cuboid.

[0015] The optical sensor of the alpha ray detector according to claim 1 is preferably a photomultiplier, in particular a SiPM. The optical sensor is preferably arranged within the measuring chamber.

[0016] The base of the alpha detector according to claim 1 can, for example, be plate-shaped. It preferably consists of a printed circuit board material. This has the advantage that the evaluation electronics can be arranged directly on or below the base. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The invention is explained in more detail below with reference to the accompanying drawing. The drawing shows: Fig. 1 Figure 1 shows an alpha radiation or radon detector 1 with a multi-part housing 10, which includes a base 5 on which a hemispherical hood 2 is arranged. Inside the hood 2 is a chamber 9, which represents a measuring cell in which the radon concentration is measured.

[0018] The housing 10 of the radon detector 1 is completely closed, so that no light from the outside can penetrate into the chamber 9. However, an annular area 6 of the hood 2 is made of a material that is opaque to light but permeable to air / gas / radon, so that ambient air from the outside can penetrate into the chamber 9.

[0019] The air-permeable material can be, for example, felt, silicone, fabric, a plastic, or a membrane. The wall thickness and the material's structure / tightness are chosen so that it is opaque to the light present at the point of use, but allows sufficient exchange of ambient air within the chamber. The remaining hood 2 can be made of, for example, metal or plastic.

[0020] A scintillation material 3 is provided on the inner wall of the hood 2 and possibly also on the base 5. Upon contact with alpha radiation, this material generates light pulses that are then detected by the optical sensor 4. As mentioned earlier, radon decays into further decay products by emitting alpha particles. These decay products, such as polonium, then decay again, emitting alpha radiation. An alpha particle 7 is in Fig. 1The alpha particle 7 moves in the direction of the arrow and collides at point P with the scintillation material 3 located on the inner wall of the hood 2. This material then emits an optical light pulse 8, which is subsequently detected by the optical sensor 4. The scintillation material 3 is preferably a layer of zinc sulfide (ZnS:Cu, ZnS:Ag). Alternatively, other materials known from the prior art could also be used.

[0021] The base 5 comprises a printed circuit board on or beneath which evaluation electronics 11 can also be arranged. The optical sensor 4 is preferably a silicon photomultiplier. In the illustrated embodiment, the optical sensor 4 is located at the bottom of the chamber 9 on the base 5.

[0022] Optics for focusing the light pulses 8 may be provided, but are not required.

[0023] The measured radon concentration is preferably displayed on a screen (not shown). The radon detector 1 may also have one or more interfaces for peripheral devices, such as display units or computers.

Claims

1. Alpha radiation detector (1) for measuring the radon concentration in the ambient air, comprising: - a multi-part housing (10) with a base (5) on which a cover (2) is arranged, in which a chamber (9) is located, wherein the housing (10) is designed such that ambient air can enter the chamber (9) from the outside, and - an optical sensor (4); wherein the hood (2) has an inner wall provided with a scintillation material (3) which, upon impact with alpha particles (7), generates light pulses (8) that are detected by the optical sensor (4); characterised in that the hood (2) further comprises an annular region (6) made of a material that is opaque to light but permeable to air, so that ambient air can enter the chamber (9) from the outside.

2. Alpha radiation detector (1) according to claim 1, characterised in that the housing (10) has a housing wall that completely encloses the chamber (9).

3. Alpha radiation detector (1) according to claim 1, characterised in that the air-permeable material comprises felt, silicone, fabric, plastic or a membrane.

4. Alpha radiation detector (1) according to one of the preceding claims, characterised in that the scintillation material (3) comprises zinc sulphide, bismuth germanate, lead tungstate, lutetium oxyorthosilicate, sodium iodide or caesium iodide.

5. Alpha ray detector (1) according to claim 1, characterised in that the optical sensor (4) is arranged on the base (5) inside the chamber (9).

6. Alpha radiation detector (1) according to claim 1, characterised in that the cover (2) is part of a sphere.

7. Alpha radiation detector (1) according to one of the preceding claims, characterised in that the optical sensor (4) is a photomultiplier.

8. Alpha radiation detector (1) according to one of the preceding claims, characterised in that the optical sensor (4) is arranged in the chamber (9).

9. Alpha radiation detector (1) according to claim 1, characterised in that the base (5) is designed in the form of a plate.

10. Alpha radiation detector (1) according to claim 1, characterised in that the base (5) is made of a printed circuit board material.

11. Alpha radiation detector (1) for measuring the radon concentration in the ambient air, comprising - a multi-part housing (10) with a base (5) on which a cover (2) is arranged, in which a chamber (9) is located; wherein the housing (10) is designed such that ambient air can enter the chamber (9) from the outside, and - an optical sensor (4); wherein the hood (2) has an inner wall provided with a scintillation material (3) which, upon impact with alpha particles (7), generates light pulses (8) that are detected by the optical sensor (4); characterised in that - the base (5) is made of a printed circuit board material ; - evaluation electronics (21) are arranged on or under the base (5); - the optical sensor (4) is arranged on the base (5) inside the chamber (9) - the optical sensor (4) is a silicon photomultiplier; and - the base (5) has a passageway that is closed by an opaque but gas-permeable material (6), so that radon gas can enter the chamber (9) from the outside through the passageway (16) .