CN203498075U - Micro-flow-rate deuterium and helium gas separation device - Google Patents

Abstract

The utility model relates to a device for separating deuterium and helium gas with a micro-flow rate, which is characterized in that it includes a shell (2), which is a T-shaped channel structure with double openings, and the T-shaped channel structure inside the shell (2) is A refrigerator (1) is packaged in the vertical direction of the housing (2), a condensation plate (4) is provided in the horizontal direction of the T shape in the housing (2), a baffle (5) is provided at the port, and an upper radiation screen (6) is provided at the upper end ), the baffle (5) is connected to the primary cold head of the refrigerator (1), the condensation plate (4) is connected to the secondary cold head, and the lower radiation shield (3) is set on the refrigerator (1). The condensation plate (4) adopts a multi-piece non-linear conduction structure, and a temperature control component (7) is arranged on the condensation plate (4). The utility model has the advantage that the deuterium gas in the passed micro-flow residual gas is condensed by the low-temperature condensation plate, and does not generate adsorption to the helium gas so as to achieve the purpose of separating the deuterium and helium mixed gas.

Description

A device for separating micro-flow deuterium and helium gas

technical field

The invention belongs to a micro-flow gas separation device, in particular to a deuterium-helium mixed gas separation device in the technical field of nuclear fusion device vacuum leak detection.

Background technique

Strict real-time leak detection is required in the operation of modern tokamak fusion devices. Since the mass numbers of the tracer gas helium used in vacuum leak detection and the experimental working gas deuterium are very close, the general-purpose helium mass spectrometer leak detector cannot distinguish between the two. The flow rate of deuterium in the residual gas of the vacuum chamber of the tokamak device is generally 10 ^-5 -10 ^-8 Pa.m ³ S ^-1 , under such a background, it will be extremely difficult to detect tiny vacuum leaks of the device with a helium leak detector. In order to improve the sensitivity of the leak detection system, selective pumping and compression sampling techniques are required to suppress the hydrogen isotope background in the residual gas of the tokamak device. Cryogenic pumping is a possible selective pumping method. At present, commercial cryopumps mainly use the method of coating adsorbents to realize the pumping of low-mass gases (H ₂ , He). This pump also has a certain pumping speed for helium, and cannot separate deuterium and helium. . Based on the above reasons, a low-temperature condensation device without adsorbent is designed, using the characteristics that helium and deuterium have different boiling points (deuterium: 23.6K, helium: 4.2K), and the control device is at a certain temperature to condense deuterium And helium does not condense, and the separation of deuterium and helium mixed gas is realized to improve the sensitivity of the vacuum leak detection system of the tokamak device.

Contents of the invention

The object of the present invention is to provide a device for separating deuterium and helium gas with micro-flow, which can improve the sensitivity of helium mass spectrometry leak detection under the background of deuterium gas in a tokamak device.

The present invention is realized in this way, a device for separating deuterium and helium gas with micro-flow, which includes a shell, the shell is a T-shaped channel structure with double openings, a refrigerator is packaged in the vertical direction of the T-shaped inside the shell, and the inside of the shell is The T-shaped horizontal direction is equipped with a condensation plate, the port is equipped with a baffle, and the upper end is equipped with an upper radiation screen. The baffle is connected to the primary cold head of the refrigerator, the condensation plate is connected to the secondary cold head, and the lower radiation screen is set. on the refrigerator.

The condensation plate adopts a multi-piece non-linear conduction structure, and a temperature control component is arranged on the condensation plate.

The advantage of the present invention is that the deuterium gas in the passing micro-flow residual gas is condensed by the low-temperature condensation plate, and the helium gas is not adsorbed so as to achieve the purpose of separating the deuterium-helium mixed gas.

Description of drawings

Fig. 1 is a kind of microflow deuterium provided by the present invention, the device schematic diagram of helium gas separation;

Figure 2 is a schematic diagram of the structure of the condensation plate.

In the figure: 1 refrigerator, 2 shell, 3 lower radiation screen, 4 condensation plate, 5 baffle plate, 6 upper radiation screen, 7 temperature control components.

Detailed ways

The present invention is described in detail below in conjunction with accompanying drawing and embodiment:

As shown in Figures 1 and 2, a device for separating deuterium and helium gas at a micro-flow rate includes a housing 2, a refrigerator 1, a radiation shield, a baffle 5, a condensation plate 4, and a temperature control assembly 7; the housing 2 It is a double-opening T-shaped channel structure, and the airflow is introduced from the air inlet. Its diameter is a double-opening T-shaped channel structure shell 2 of ￠150, and the horizontal direction is the air inlet and outlet. It can be connected with other pipes or vacuum The system is connected in series. Pass through the baffle plate 5 and the condensation plate 4 in turn, and flow out from the gas outlet. The baffle plate 5 is connected with the primary cold head of the refrigerator 1, and the condensation plate 4 is connected with the secondary cold head. The condensing plate adopts a multi-piece non-linear conduction structure, and the gas flow can pass through and be condensed. A temperature control point is installed on the condensing plate 4, and a heating assembly is configured so that the temperature of the condensing plate can be precisely controlled. The condensation plate 4 is not coated with adsorbent, and in the range of 6K-16K, the deuterium gas in the passing gas flow is condensed, but the helium gas is not condensed.

The cold source adopts a 4.2K refrigerator 1, and the cold head is packaged in the vertical direction of the T shape in the shell 2, and its first stage is used as a cold source for the lower radiation screen 3, the upper radiation screen 6 and the baffle plate 5, providing a temperature of 77K. The second stage is used as the cold source of the low-temperature condensation plate 4, and the minimum temperature is 5K.

The condensation plate 4 is composed of 5 parallel bright nickel-plated oxygen-free copper plates with a diameter of ￠120 and a thickness of 2 mm, which are installed side by side on the heat transfer plate, with a total area of 1130 cm ² . The heat transfer plate is located in the T-shaped horizontal mid-plane and is in direct contact with the secondary cold head. A number of ￠3 air holes are opened on the copper plate, and the air holes of every two plates are staggered to form a non-linear conduction structure. Since the gas is a micro-flow rate, the influence of the conductance on the airflow is not considered. The design of multi-piece staggered holes is used to increase the contact probability of deuterium gas with the condensation plate and improve the condensation efficiency.

In order to prevent the condensing plate from being subjected to direct heat radiation from the outside, the condensing plate is surrounded by a radiation screen, and a baffle 5 is added in front of the radiation screen at the air inlet end. The baffle adopts a louver structure and can pre-cool the pumped gas at the same time.

For the convenience of assembly, the radiation screen adopts a two-level connection design, that is, it is designed as an upper and lower radiation screen, and the upper radiation screen 6 is installed and fixed with the lower radiation screen 3 by screws.

A temperature control point (temperature sensor and heating component) is installed on the edge of the first condensing plate (closest to the cold head), and the temperature of the low-temperature condensing plate 4 is accurately collected and controlled by a temperature controller. The accuracy of the temperature sensor is 0.1K, and the temperature difference between the nearest and the farthest condensation plate is less than 1K. After setting a certain temperature for the condensing plate, the temperature controller can maintain the temperature of the condensing plate stable by adjusting the output power of the heating component. The temperature adjustment range of the condensation plate is: 5K-30K, and the temperature range in which the deuterium gas can effectively condense but the helium gas does not condense is: 6K-16K.

In a specific embodiment, the inlet and outlet ends of the device for deuterium and helium gas separation at micro-flow are respectively connected in series with a vacuum chamber of the same caliber, and a vacuum gauge, a high-resolution quadrupole mass spectrometer and a flow meter are installed on the vacuum chamber tool. The vacuum chamber at the outlet end is connected to a molecular pump for auxiliary pumping.

The temperature of the condensation plate is set to 10K, and a mixed gas sample with a deuterium-helium ratio of 10:1 is introduced from the vacuum chamber at the inlet end, the gas sample is pre-cooled through the baffle plate, and then passed through the condensation plate. Every time it passes through a condensing plate, some deuterium gas will be condensed. Since the vacuum chamber at the outlet end is evacuated by the molecular pump, the gas sample passing through the condensation plate will move toward the vacuum chamber at the outlet end. The measurement results show that after passing through the device, the ratio of deuterium to helium in the sample becomes about 1:1, and the helium flow rate does not decrease, which realizes the effective condensation of deuterium in the mixed gas.

In another embodiment, the vacuum chamber at the inlet end is connected to the vacuum chamber of the tokamak device, and the front stage of the molecular pump at the outlet end is connected with a helium leak detector. Set the temperature of the condensing plate to 10K, and the background signal of the leak detector with a mass number of 4 (deuterium and helium mixed gas) in the residual gas introduced by the tokamak device is obtained from 2.7×10 ^-7 Pa.m ³ S ^{- 1} is reduced to 2.2×10 ^-8 Pa.m ³ S ^-1 , which means that the sensitivity of the helium leak detector is increased by an order of magnitude.

Claims (2)

1. the device of a micrometeor deuterium, helium gas separation, it is characterized in that: it comprises housing (2), housing (2) is the T word channel architecture of two openings, the vertical direction of the interior T font of housing (2) is packaged with refrigerator (1), in the horizontal direction of the interior T font of housing (2), be provided with cold plate (4), port is provided with baffle (5), upper end is provided with radiation screen (6), baffle (5) is connected with the one-level cold head of refrigerator (1), cold plate (4) is connected with secondary cold head, and lower radiation screen (3) is sleeved on refrigerator (1).

2. the device of a kind of micrometeor deuterium as claimed in claim 1, helium gas separation, is characterized in that: described cold plate (4) adopts multi-disc non-rectilinear conductance structure, and cold plate (4) is provided with temperature-controlling component (7).

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