Diffusion cloud chamber

Abstract

To provide a diffuse cloud chamber used to observe the trajectory of incoming charged particles that is simple in structure, facilitates easy handling, makes stable observation possible, and is inexpensive.SOLUTION: An observation surface is provided on a bottom portion of an observation tank 1. On the top of a cooling tank 2, a Peltier element 22 that transfers heat from an observation surface 14 downward and a cooling plate 25 that accepts the heat from it. In the lower part thereof, a coolant 26 whose top surface is in contact with the cooling plate 25 and cools the same and a lower heat insulating material 27 that insulates the coolant 26. The lower heat insulating material 27 is elastic and urges the coolant 26 against the cooling plate 25.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a cloud chamber, which is a device for detecting the tracks of charged particles using the condensation of vapor, and more particularly to a diffusion cloud chamber that creates a temperature gradient inside an observation chamber to create a supersaturated state. [Background technology]

[0002] In science experiments in schools and other educational institutions, cloud chambers, especially diffusion cloud chambers, which are easy to use, are used to observe the tracks of charged particles such as natural radiation. The principle of a cloud chamber is that when charged particles or radiation are injected into a supersaturated gas, which contains more vapor than the saturated vapor volume (the maximum amount of vapor a gas can contain), the gas molecules are ionized, and the ions act as condensation nuclei to form droplets. By shining light on this process and photographing it, the movement of the radiation can be seen as a line (the trajectory or track of the radiation).

[0003] A diffusion cloud chamber generates a temperature gradient (warm at the top and cold at the bottom) inside the cloud chamber to artificially create a supersaturated state. Specifically, water or alcohol is heated and evaporated at the top, while the bottom of the chamber is cooled to about -30°C using a cooling device. In this state, the vapor cools downward and becomes liquid, but a supersaturated region appears in between. Charged particles entering this region are observed.

[0004] A diffusion cloud chamber needs to be equipped with a powerful cooling means to create a low temperature of around -30°C, but considering its use in science experiments at educational institutions, it is desirable that the cooling means be simple in structure, easy to use, and inexpensive. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2007-232416 A Summary of the Invention [Problem to be solved by the invention]

[0006] To observe the radiation trajectory in a diffusion cloud chamber, the temperature of the bottom surface must be lowered to at least -30°C. Dry ice or liquid nitrogen has been used as a cooling method for this purpose, but it is not only time-consuming to prepare, but also difficult to consistently generate an appropriate temperature gradient. While some devices use ice packs capable of cooling down to -20°C, it is difficult to lower the temperature down to -30°C, making stable observations difficult.

[0007] To address these issues, Patent Document 1 uses a Peltier element, a thermoelectric element, as a cooling means. However, using a Peltier element to lower temperatures to below -30°C requires a large power supply and a large heat sink, resulting in problems such as increased size and cost of the equipment. A Peltier element generates heat on the heat dissipation side, which is the sum of the heat absorbed on the heat absorption side and the amount of power consumed. This heat must be dissipated into the outside air or other sources for cooling. To cool to below -30°C, a large amount of heat must be removed from the observation area of ​​the diffusion cloud chamber, requiring a powerful heat dissipation means, which inevitably requires a larger heat sink. Larger heat sinks also increase costs. Furthermore, transferring large amounts of heat requires a larger current consumption by the Peltier element, necessitating a larger power supply. Higher current consumption leads to larger heat sinks and higher power supply costs.

[0008] The present invention has been made to solve the above problems, and has as its object to provide an inexpensive diffusion cloud chamber that has a simple structure, is easy to handle, allows stable observation, and allows for stable observation. [Means for solving the problem]

[0009] The diffusion cloud chamber according to the present invention comprises: A diffusion cloud chamber comprising an observation tank for observing the tracks of incident charged particles, and a cooling tank located below the observation tank for cooling the observation tank, a steam generating means for generating steam is provided above the observation tank; The bottom of the observation tank is provided with an observation surface located approximately at the center thereof and a bottom plate surrounding the observation surface, a thermoelectric element located below the observation surface and in contact with the observation surface with a small thermal resistance, which transfers heat from above downward, an intermediate heat insulating material located below the bottom plate, and a cooling plate located below the thermoelectric element and in contact with the thermoelectric element with a small thermal resistance, which receives heat from the thermoelectric element, A cooling material whose upper surface is in contact with the cooling plate for cooling it, and a lower heat insulator positioned below the cooling material for insulating the cooling material, are provided below the cooling tank. The lower heat insulating material may be elastic and bias the cold material toward the cooling plate.

[0010] the thermoelectric element is approximately the same size as the observation surface and smaller than the cooling plate; The cooling plate is a plate-like plate without any irregularities (specifically, without fins), The cooling material has approximately the same size as the cooling plate and also has approximately the same size as the inner diameter of the cooling tank. The cooling plate and the cooling material are preferably large, and can fill the inner diameter of the observation chamber and / or the cooling chamber. [Effects of the Invention]

[0011] According to this invention, by combining the thermoelectric element and the cooling material, it is possible to provide a diffusion cloud chamber that is easier to handle than conventional cases where dry ice or liquid nitrogen is used, allows for more stable observation than when only conventional cooling materials are used, and is more inexpensive than when only conventional Peltier elements are used. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a perspective view of a diffusion cloud chamber according to an embodiment of the present invention; [Figure 2] FIG. 2 is a perspective view showing components of the diffusion cloud chamber. [Figure 3]FIG. 1 is a perspective view (photograph) showing the diffusion cloud chamber in use. [Figure 4] FIG. 2 is a cross-sectional perspective view of the diffusion cloud chamber cut in a vertical plane. [Figure 5] FIG. 2 is a cross-sectional view of the diffusion cloud chamber cut in a vertical plane. [Figure 6] FIG. 2 is an exploded perspective view showing the bottom plate of the observation chamber, the heat insulating material of the cooling chamber, the thermoelectric element, and the cooling plate of the diffusion cloud chamber. [Figure 7] FIG. 2 is a schematic cross-sectional view of the diffusion cloud chamber taken along a vertical plane. DETAILED DESCRIPTION OF THE INVENTION

[0013] An embodiment of the present invention will be described with reference to the drawings.

[0014] As can be seen from FIGS. 1 and 2, the diffusion cloud chamber according to the embodiment of the invention comprises an observation tank 1 for observing the trajectories of incident charged particles, a cooling tank 2 located below the observation tank 1 and including a cooling means 22 for cooling the observation tank 1, an LED lighting stand 3 for illuminating the interior of the observation tank 1, a control unit 4 that turns on and off the cooling means 22, the LED lighting stand 3, and the heater of the steam generating means 12 (described below), and a power supply unit 5 that supplies current to them. The cooling means 22 and the heater are connected to the control unit 4 by connection cables (electric wires) 21 and 41. The LED lighting stand 3 and the control unit 4 are connected by a cable (electric wire) not shown. A power cable 51 is connected to the control unit 4, and current is supplied from the power supply unit 5. A transparent upper cap 7 is attached to the top of the observation tank 1. A translucent lower cap 8 is attached to the bottom of the cooling tank 2. The LED unit 31 of the LED lighting stand 3 is a unit (such as an LED tape) consisting of multiple LEDs arranged in a line, and to make it easier to observe the generated fog, it does not illuminate the bottom plate of the observation tank 1, but only the generated fog.

[0015] Figure 3 shows the state of the diffusion cloud chamber with the cooling means 22 and LED lighting stand 3 turned on. The LED lighting stand 3 brightly illuminates the interior of the observation chamber 1, revealing the cooling and frosting that has occurred. Part of the side of the observation chamber 1 is made of transparent material (see symbol 1a in Figure 4). The cooling means 22 cools the lower part of the observation chamber 1 to approximately -30°C, creating a temperature gradient between the lower part and the upper part. When water or alcohol is heated and evaporated using the steam generating means 12 (described below), the vapor cools downward and becomes liquid, creating a supersaturated region. A radiation source 6 (e.g., uraninite, a natural mineral) is inserted through the radiation source insertion port 11 on the side of the observation chamber 1 near the supersaturated region. The trajectories of charged particles can then be observed within the observation area (above the cooling means 22) (see symbol A in Figure 7). The radiation source 6 is attached to the tip of a metal radiation source holding rod 61. When not in use, it is covered with a metal protective cap 62.

[0016] Next, the cross-sectional structure of the diffusion cloud chamber and its cooling method will be explained with reference to Figures 4 to 7. For ease of explanation, the dimensions of the elements in Figure 7 have been slightly exaggerated and do not match those in Figure 5. The arrows in Figure 7 indicate the flow of heat.

[0017] Steam generating means 12 that generates water or alcohol vapor is provided above the observation tank 1. The steam generating means 12 includes a sponge for soaking in water or alcohol and a heater for generating steam, and is provided inside the observation tank 1 so as to release steam into the interior of the observation tank 1.

[0018] An observation surface 14 is provided at approximately the center of the bottom of the observation tank 1, and an observation tank bottom plate 13 is provided to cover the area other than the observation surface 14. A black anodized aluminum seal 29 is used on the observation surface 14 to facilitate observation of the trajectories of charged particles and to enable efficient cooling. The surface of the observation tank bottom plate 13 is also black. From the perspective of cooling efficiency, it is preferable to make the observation surface 14, which corresponds to observation area A in Figure 7, as small as possible without interfering with observation.

[0019] The upper part of the cooling tank 2 is provided with thermoelectric elements (Peltier elements) 22U and 22L, which are positioned below the observation surface 14 and contact the observation surface 14 with low thermal resistance. These elements serve as cooling means 22, transferring heat downward. The two thermoelectric elements 22U and 22L are stacked. Furthermore, a heat insulating material (intermediate heat insulating material) 24 is positioned below the observation tank bottom plate 13, and a heat-dissipating aluminum plate (cooling plate) 25 is positioned below the thermoelectric element 22L, contacts the thermoelectric element 22L with low thermal resistance, and receives heat from the thermoelectric element 22L. Heat-dissipating silicone adhesive 23 is applied between the two thermoelectric elements 22U and 22L, and between the thermoelectric element 22L and the heat-dissipating aluminum plate 25, improving thermal conductivity between them. The heat insulating material 24 prevents excess heat from being absorbed from areas unrelated to the observation. Therefore, the thermal resistance between the observation chamber bottom plate 13 and the aluminum plate 25 for heat dissipation is large.

[0020] The bottom of the cooling tank 2 is provided with ice packs (refrigerants) 26, whose upper surface contacts a heat-dissipating aluminum plate 25 to cool it. Also, sponges 27U and 27L are located below the ice packs 26 and act as lower insulating materials to insulate the ice packs. The sponges 27U and 27L insulate the ice packs 26 from heat transfer from the lower cap 8 on the bottom of the cooling tank 2, and their elasticity presses (biases) the ice packs 26 toward the heat-dissipating aluminum plate 25. The ice packs 26 are capable of cooling to approximately -20°C. The size of the aluminum plate 25 and ice packs 26 is important, and they are designed to be as large as possible, specifically to fill the entire inner diameter of the observation tank 1. By enlarging them, heat transfer from the aluminum plate 25 to the ice packs 26 is facilitated, and the increased volume of the ice packs 26 increases the amount of heat they can absorb.

[0021] If the surface area of ​​the cooling plate that receives heat from thermoelectric element 22L is not large, it will not be possible to obtain a sufficient cooling effect. Normally, fins are used to increase the surface area, but in this cooling tank 2, the cooling plate must be flat because it uses ice insulation, and fins cannot be used (if fins are used, gaps and air layers will form between the ice insulation and the cooling plate, preventing efficient heat conduction). For this reason, aluminum, which has high thermal conductivity, is used as the cooling plate, and a flat aluminum plate 25 with an area several times larger than that of thermoelectric elements 22U and 22L is used. Ice pack 26 is a special product that is large enough to fully cover aluminum plate 25.

[0022] As shown in Figure 6, the observation tank bottom plate 13 is a disk with a diameter roughly equal to the inner diameter of the observation tank 1, and has a roughly square opening in its center that is slightly smaller than the thermoelectric elements 22U and 22L. The heat insulating material 24 located below the observation tank bottom plate 13 has the same shape as the observation tank bottom plate 13, but has a notch to accommodate the thermoelectric elements 22U and 22L. The observation tank bottom plate 13, the heat insulating material 24, and the heat dissipation aluminum plate 25 have four holes for assembly screws 28 that surround the thermoelectric elements 22U and 22L. The assembly screws 28 assemble the observation tank bottom plate 13, the heat insulating material 24, and the heat dissipation aluminum plate 25, and the thermoelectric elements 22U and 22L are tightly attached to the heat dissipation aluminum plate 25.

[0023] Next, the operation will be described. When the control unit 4 turns on the cooling means 22 and the LED lighting stand 3, the LED lights come on and the thermoelectric elements (Peltier elements) 22U and 22L are simultaneously activated. The current of the upper thermoelectric element 22U is set to be greater than the current of the lower thermoelectric element 22L. After about five minutes, the temperature of the upper part of the observation surface 14 of the observation tank 1 drops to approximately -30°C or below. The upper cap 7 is removed, and alcohol (isopropyl alcohol IPA) or absolute ethanol is thoroughly soaked into the sponge of the steam generating means 12, which is then evaporated by the heater of the steam generating means 12. As steam is generated by the action of the heater (not shown), the temperature difference between the upper and lower cooled observation surfaces 14 inside the observation tank 1 increases, resulting in a supercooled state. In this state, the radiation source 6 is placed near the observation surface 14. The upper cap 7 is then attached and observation is performed from above the observation tank 1.

[0024] The arrows in Figure 7 indicate the flow of heat. Thermoelectric elements (Peltier elements) 22U and 22L absorb heat from the observation surface 14, transfer it downward, and pass it on to the heat-dissipating aluminum plate 25. Because aluminum has high thermal conductivity, the heat is transferred to the entire aluminum plate 25 and absorbed by the ice pack 26 through its entire underside. The large contact area between the aluminum plate 25 and the ice pack 26 ensures efficient heat transfer. The contact area between the thermoelectric element 22L and the aluminum plate 25 is smaller, but the presence of heat-dissipating silicone adhesive 23 between them reduces thermal resistance, ensuring efficient heat transfer. Because heat insulation material 24 is present in areas other than the thermoelectric elements 22U and 22L, heat does not transfer from the observation chamber bottom plate 13; instead, heat is absorbed exclusively from the observation surface 14. This allows efficient cooling of only the observation area A corresponding to the observation surface 14. The ice pack 26 is insulated by the sponges 27U and 27L, and therefore absorbs heat mainly from the aluminum plate 25.

[0025] According to the embodiment of the invention, by making the aluminum plate 25 and the ice pack 26 as large as possible and by making the observation surface 14 as small as possible, it was possible to efficiently cool the observation area A. By providing the ice pack 26, a large heat sink was no longer necessary, allowing for miniaturization. Furthermore, power consumption was reduced to a fraction of that of a Peltier element alone. This also made it possible to reduce costs.

[0026] According to the embodiment of the invention, handling was easier than when dry ice or liquid nitrogen was used, and observation became more stable than when only ice packs were used.

[0027] In this invention, a general refrigerant capable of cooling to about -20°C is used as the cooling material (a refrigerant for lowering the temperature of an object by contact), but it is also possible to use a refrigerant made by mixing calcium chloride, magnesium chloride, sodium chloride, or the like with ice. The refrigerant is packed in a bag for easy handling. Moreover, it can be cooled in a general freezer. The above effect can be achieved by attaching this to a flat cooling plate 25.

[0028] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention described in the claims, and it goes without saying that these modifications are also included within the scope of the present invention. [Explanation of symbols]

[0029] 1 Observation tank 1a LED light transmission part 11 Radiation source insertion port 12 Steam generating means 13 Observation tank bottom plate 14 Observation surface (black anodized aluminum seal) 2 Cooling tank 21 Connection cable 22 Cooling means 22U Upper Peltier element (thermoelectric element) 22L Lower Peltier element (thermoelectric element) 23 Heat dissipating silicone adhesive 24 Insulation material (intermediate insulation material) 25 Aluminum plate for heat dissipation (cooling plate) 26 Ice packs (refrigerants) 27U Upper sponge (lower insulation) 27L Lower sponge (lower insulation) 28 Assembly screws 29 Black anodized aluminum seal 3 LED lighting stand 31 LED unit 4. Control Unit 41 Connection cable 51 Power cable 6 source 61 Source support rod 62 Protective cap 7 Top Cap 8 Bottom Cap A. Observation range

Claims

[Claim 1] A diffusion cloud chamber comprising an observation tank for observing the tracks of incident charged particles, and a cooling tank located below the observation tank for cooling the observation tank, a steam generating means for generating steam is provided above the observation tank; The bottom of the observation tank is provided with an observation surface located approximately at the center thereof and a bottom plate surrounding the observation surface, a thermoelectric element located below the observation surface and in contact with the observation surface with a small thermal resistance, which transfers heat from above downward, an intermediate heat insulating material located below the bottom plate, and a cooling plate located below the thermoelectric element and in contact with the thermoelectric element with a small thermal resistance, which receives heat from the thermoelectric element, a cooling material whose upper surface is in contact with the cooling plate and which cools the cooling plate; and a lower heat insulating material located below the cooling material and which insulates the cooling material, are provided in the lower part of the cooling tank; Diffusion cloud chamber characterized in that the lower heat insulating material has elasticity and urges the cooling material toward the cooling plate.

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