阅读说明：本技术 多栅极测氡仪静电测量腔 (Electrostatic measurement cavity of multi-grid radon measuring instrument ) 是由 谭延亮 莫贻香 王璐薇 范钟凯 林芬 胡滔 袁红志 于 2021-07-27 设计创作，主要内容包括：多栅极测氡仪静电测量腔,包括圆柱形测量腔、塑料上盖、半导体探测器及复数个半球形金属网格栅极,圆柱形测量腔筒壁的下部对称设有第一阀门管道及第二阀门管道,半导体探测器固定安装在塑料上盖的中间位置,半球形金属栅极依次固定在塑料上盖上,半导体探测器处在最内侧的半球形金属栅极内,塑料上盖与圆柱形测量腔采用螺纹连接。通过圆柱形测量腔的直径为D-(1)和半导体探测器的直径为D-(0)设置复数个半球形金属栅极直径并计算圆柱形测量腔内各个半球形金属栅极上的电压。本发明提供的多栅极测氡仪静电测量腔通过优化调整超大测量腔腔壁与半球形金属栅极的大小及与电压的合适值,使得测量腔内电场尽可能相对均匀,从而提高静电场对带正电的～(218)Po的收集效率,提高静电收集法测氡仪探测灵敏度。(The multi-grid radon measuring instrument electrostatic measurement cavity comprises a cylindrical measurement cavity, a plastic upper cover, a semiconductor detector and a plurality of hemispherical metal grid electrodes, wherein a first valve pipeline and a second valve pipeline are symmetrically arranged at the lower part of the cylindrical measurement cavity cylinder wall, the semiconductor detector is fixedly arranged in the middle of the plastic upper cover, the hemispherical metal grid electrodes are sequentially fixed on the plastic upper cover, the semiconductor detector is positioned in the innermost hemispherical metal grid electrode, and the plastic upper cover is in threaded connection with the cylindrical measurement cavity. Diameter D through the cylindrical measuring chamber 1 And the diameter of the semiconductor detector is D 0 The diameters of a plurality of hemispherical metal grids are set and the voltage on each hemispherical metal grid in the cylindrical measurement cavity is calculated. The electrostatic measurement cavity of the multi-gate emanometer provided by the invention is formed by optimally adjusting the cavity wall of an oversized measurement cavity and hemispherical metalThe size of the grid and the proper value of the voltage enable the electric field in the measuring cavity to be relatively uniform as much as possible, thereby improving the electrostatic field to be positively charged 218 Po collection efficiency, and the detection sensitivity of the electrostatic collection radon detector is improved.)

1. The multi-grid radon measuring instrument electrostatic measurement cavity is characterized in that: the device comprises a cylindrical measurement cavity, a plastic upper cover, a semiconductor detector and n hemispherical metal grids, wherein n is the number of the arranged hemispherical metal grids, and the value is a positive integer;

the lower part of the cylindrical measuring cavity wall is symmetrically provided with a first valve pipeline and a second valve pipeline, a semiconductor detector is fixedly arranged in the middle of a plastic upper cover, n hemispherical metal grids are sequentially fixed on the plastic upper cover, the semiconductor detector is positioned in the innermost hemispherical metal grid, and the plastic upper cover is in threaded connection with the cylindrical measuring cavity;

wherein the diameter of the cylindrical measuring cavity is D₁Measuring the height H of the cavity as D₁2 +/-20%, and the diameter of the semiconductor detector is D₀The diameter from the most outside hemispherical metal grid to the most inside hemispherical metal grid is d₁、d₂ ......d_nThe calculation formula of the hemispherical metal gate diameter is as follows:

（1）

wherein D is₁、D₀The values of (a) are known.

2. The multi-gate radon meter electrostatic measurement chamber of claim 1, wherein: the calculation formula of the voltage on the hemispherical metal gate in the cylindrical measurement cavity during measurement is as follows:

（2）

u is a preset voltage of the inner wall of the cylindrical measuring cavity, k is a proportional coefficient between the adjusting measuring cavity and the grid, between the grid and the detector, the value range of k is 1.5-10, and a is the electric field intensity; the voltage of the first hemispherical metal gate at the outermost side isThe voltage of the second hemispherical metal gate is∙ ∙ ∙ ∙ ∙ ∙ in turn, the voltage between the nth hemispherical metal gate and the semiconductor detector is。

3. The multi-gate radon meter electrostatic measurement chamber of claim 1 or 2, wherein: the cylindrical measuring cavity is made of copper, and the n hemispherical metal grids are all grid grids.

4. The multi-gate radon meter electrostatic measurement chamber of claim 1 or 2, wherein: the adjustment range of the actual diameter of each hemispherical metal gate is d_n 20%, the actual voltage value of each hemispherical metal gate is adjusted to be U_n 20%。

Technical Field

The invention relates to a nuclear radiation measurement technology, in particular to an electrostatic measurement cavity of a multi-grid emanometer.

Background

Radon is the only natural radioactive inert gas in the natural world generated by the decay of radium and thorium, has been listed as an important carcinogen in the room by the international cancer research institute, and is the second leading cause of lung cancer. Radon measurement must be brought to our attention. Monitoring the radon concentration level in the room is an important means for people to evaluate the environment and control diseases. Radon is generated by decay²¹⁸Po，²¹⁸Po is radioactive and radon decays²¹⁸Po was found to be 88% positively charged ions, which upon inhalation, produced internal irradiation of the human respiratory system. There are many measurement methods for radon in air, and a static electricity collection method, an ionization chamber method, a scintillation chamber method, a double filter membrane method, an activated carbon method, a thermoluminescence method, a solid track etching method, and the like are commonly used. Among them, the electrostatic collection method is a radon measurement method which is widely used.

The working principle of the electrostatic collection radon measuring instrument is that a high-voltage electric field is arranged in a measuring cavity, air is pumped into the measuring cavity by an air pump through a drying tube and a filter membrane at a certain speed, after air pumping is finished,²²²rn decays to generate positively charged radon daughter²¹⁸Po, under the action of electrostatic field in measuring cavity, will be positively charged²¹⁸Po collects on the surface of the detector and the collected radon daughter²¹⁸The Po will decay further to produce alpha particles, the detected alpha particles are counted, and finally the radon concentration is determined according to the number of the detected alpha particles.

It has been proposed that positive charging can be effectively enhanced by adding a metal grid (mesh) within the electrostatic measurement chamber²¹⁸Efficiency of Po particle collection using a column as the measurement chamberWhen the voltage of the dome-shaped dome is 2000V and the voltage of the hemispherical grid is 1800V, the radon daughter collection efficiency is improved to 86.6% from 73.3%, and compared with the collection efficiency which is improved by 13.3% when the grid is not added.

However, the electric field optimization in the measurement cavity cannot be well completed by adding a metal grid in the oversized measurement cavity, simulation shows that the distribution of electric field lines in the oversized measurement cavity wall is not uniform, the distribution of the electric field lines between the measurement cavity wall and the hemispherical grid is dispersed, the distribution of the electric field lines between the hemispherical grid and the detector is dense, and the electric field cannot be uniformly distributed by simply changing the size and the voltage of the hemispherical grid. Therefore, how to determine the radius of the hemispherical metal grid and the magnitude of the voltage value to optimally design and improve the electric field in the ultra-large measurement cavity²¹⁸The collection efficiency of Po is a challenging task.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide an electrostatic measurement cavity of a multi-grid emanometer.

The technical scheme of the invention is as follows: the multi-grid radon measuring instrument electrostatic measurement cavity comprises a cylindrical measurement cavity, a plastic upper cover, a semiconductor detector and n hemispherical metal grids, wherein n is the number of the set hemispherical metal grids, and the value is a positive integer.

The lower part of the cylindrical measuring cavity cylinder wall is symmetrically provided with a first valve pipeline and a second valve pipeline, the semiconductor detector is fixedly arranged in the middle of the plastic upper cover, the n hemispherical metal grids are sequentially fixed on the plastic upper cover, the semiconductor detector is positioned in the innermost hemispherical metal grid, and the plastic upper cover is in threaded connection with the cylindrical measuring cavity.

Wherein the diameter of the cylindrical measuring cavity is D₁Measuring the height H of the cavity as D₁2 +/-20%, and the diameter of the semiconductor detector is D₀The diameter from the most outside hemispherical metal grid to the most inside hemispherical metal grid is d₁、d₂......d_nThe calculation formula of the hemispherical metal gate diameter is as follows:

（1）

wherein D is₁、D₀The values of (a) are known.

The further technical scheme of the invention is as follows: the calculation formula of the voltage on the hemispherical metal gate in the cylindrical measurement cavity during measurement is as follows:

（2）

u is a preset voltage of the inner wall of the cylindrical measuring cavity, k is a proportional coefficient between the adjusting measuring cavity and the grid, between the grid and the detector, the value range of k is 1.5-10, and a is the electric field intensity.

The voltage of the first hemispherical metal gate at the outermost side isThe voltage of the second hemispherical metal gate is∙ ∙ ∙ ∙ ∙ ∙ in turn, the voltage between the nth hemispherical metal gate and the semiconductor detector is。

The invention further adopts the technical scheme that: the cylindrical measuring cavity is made of copper, and the n hemispherical metal grids are all grid grids.

The further technical scheme of the invention is as follows: the adjustment range of the actual diameter of each hemispherical metal gate is d_n 20%, the actual voltage value of each hemispherical metal gate is adjusted to be U_n 20%。

Compared with the prior art, the invention has the following characteristics:

the electrostatic measurement cavity of the multi-gate radon measuring instrument provided by the invention has the advantages that the electric fields between the cavity wall of the measurement cavity and the outermost hemispherical metal grid, between the hemispherical metal grids and between the innermost hemispherical metal grid and the surface of the semiconductor detector are relatively uniform as much as possible by optimally adjusting the sizes of the cavity wall of the oversized measurement cavity and the hemispherical metal grid and the proper value of the voltage. When the electric field in the measuring chamber is relatively uniform and positively charged²¹⁸The average moving speed of Po ions in the measuring cavity is relatively high, and the collecting time is relatively short, so that the electrostatic field is improved to be positively charged²¹⁸Po collection efficiency, and the detection sensitivity of the electrostatic collection radon detector is improved.

The detailed structure of the present invention will be further described with reference to the accompanying drawings and the detailed description.

Drawings

FIG. 1 is a schematic structural diagram of the present invention.

Detailed Description

In the embodiment, as shown in the attached figure 1, the multi-grid radon measuring instrument electrostatic measurement cavity comprises a cylindrical measurement cavity 1, a plastic upper cover 2, a semiconductor detector 3 and four hemispherical metal grids 4.

The measuring device is characterized in that the cylindrical measuring cavity 1 is made of copper materials, a first valve pipeline 1-1 and a second valve pipeline 1-2 are symmetrically arranged at the lower portion of the wall of the cylindrical measuring cavity 1, a semiconductor detector 3 is fixedly installed in the middle of the plastic upper cover 2, four hemispherical metal grids 4 are sequentially fixed on the plastic upper cover 2, the semiconductor detector 3 is located in the innermost hemispherical metal grid, the plastic upper cover 2 is in threaded connection with the cylindrical measuring cavity 1, and the four hemispherical metal grids 4 are latticed so as to facilitate gas circulation.

Wherein the diameter of the cylindrical measuring chamber 1 is D₁Measuring the height H of the cavity as D₁2 +/-20%, the diameter of the semiconductor detector 3 is D₀The diameter from the most outside hemispherical metal gate to the most inside hemispherical metal gate 4 is d₁、d₂......d_nThe calculation formula of the hemispherical metal gate diameter is as follows:

（1）

in the formula (1), let D₁、D₀The values of (d) are known, and in this example, four hemispherical metal gates are designed in total from the outermost hemispherical metal gate to the innermost hemispherical metal gate 4, and the theoretical diameters d of the four hemispherical metal gates can be obtained from the above equation (1)₁、d₂、d₃、d₄The adjustment range of the actual diameter of the hemispherical metal gate is d_n 20%。

（3）

The embodiment also relates to the calculation of the voltage on the hemispherical metal gate 4 in the cylindrical measurement cavity 1 during measurement, and the calculation formula of the voltage is as follows:

（4）

in the formula (4), U is a voltage preset on the inner wall of the cylindrical measurement cavity 1.

Wherein the content of the first and second substances,the distance between the inner wall of the cylindrical measurement cavity 1 and the outermost first hemispherical metal grid is shown,the distance between the outermost first hemispherical metal gate and the second hemispherical metal gate is shown,the distance between the second hemispherical metal gate and the third hemispherical metal gate is shown,the distance between the third hemispherical metal gate and the innermost fourth hemispherical metal gate is shown,the distance between the innermost fourth hemispherical metal gate and the semiconductor detector 3 is shown.

Wherein the content of the first and second substances,the potential difference between the inner wall of the cylindrical measurement cavity 1 and the outermost first hemispherical metal gate is shown,the potential difference between the outermost first hemispherical metal gate and the second hemispherical metal gate is shown,the potential difference between the second hemispherical metal gate and the third hemispherical metal gate is shown,the potential difference between the third hemispherical metal gate and the innermost fourth hemispherical metal gate is shown,the potential difference between the innermost fourth hemispherical metal gate and the semiconductor detector 3 is shown.

K is the distance between the inner wall of the cylindrical measurement cavity 1 and the first hemispherical metal grid at the outermost side, between the first hemispherical metal grid at the outermost side and the second hemispherical metal grid, between the second hemispherical metal grid and the third hemispherical metal grid, and between the third hemispherical metal gridsThe proportionality coefficients between the electrode and the innermost fourth hemispherical metal grid and between the innermost fourth hemispherical metal grid and the semiconductor detector 3 are optimized to ensure that the electric field is relatively uniform as much as possible, the value range of k is 1.5-10,is the electric field strength.

By knowing that the outermost voltage U, k is a fixed value, it is possible to solve using equation (4)Then obtaining each potential difference, and finally calculating to obtain the theoretical voltage values U of the four hemispherical metal grids₁、U₂、U₃、U₄. Wherein the voltage of the first hemispherical metal gate at the outermost side isThe voltage of the second hemispherical metal gate isThe voltage of the third hemispherical metal gate isThe voltage of the innermost fourth hemispherical metal gate isThe actual voltage value of each hemispherical metal gate is adjusted within the range of U_n 20 percent. From the above, it can be known that the device can effectively determine the diameter of the metal grid in the measurement cavity and the voltage value on the metal grid, thereby improving the electrostatic field to be positively charged²¹⁸Po collection efficiency, and the detection sensitivity of the electrostatic collection radon detector is improved.