JPH0746853Y2 - Differential exhaust system - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to a mass spectrometer in which an ion source is under atmospheric pressure,
Specifically, a high frequency inductively coupled plasma mass spectrometer (ICP-
MS), a liquid chromatograph mass spectrometer (LC-MS), a scanning electron microscope, and the like, and two differential vacuum systems for opening and closing the two spaces in a high vacuum state.

[Conventional technology]

A high-frequency inductively coupled plasma mass spectrometer, a liquid chromatograph mass spectrometer, and the like perform sample analysis under high vacuum. That is, conventionally, as shown in FIG. 1, the gate valve 5 is moved in the direction of the arrow to shut off the atmospheric pressure space 1 where the ion source is located and the space 4 such as the sample analysis chamber, and the space 4 such as the sample analysis chamber. Is evacuated by a pump such as an oil diffusion pump or a turbo molecular pump, and the space 1 and the first-stage vacuum region space 2 that were under atmospheric pressure are evacuated by a rotary pump to a vacuum state. Was further moved, and both spaces were communicated with each other by a hole 51 (described later) formed in the gate valve 5 to keep both spaces in an “open” state. Then, an operation of guiding the ionized sample from the space 1 to the space 4 such as the sample analysis chamber through the first stage vacuum region 2 was performed.

[Problems to be solved by the device]

As described above, when the gate valve 5 is moved after the space 4 such as the sample analysis chamber, the atmospheric pressure space 1 with the ion source, and the first stage vacuum region space 2 are set to a high vacuum state, the gate valve 5 and the first stage vacuum region space 2 are moved. Since there is a dead space 3 between and, the residual gas in the dead space 3 suddenly flows into the space 4 such as the sample analysis chamber in a high vacuum state. Therefore, there are problems that the pump load is suddenly changed, and troubles such as lowering the degree of vacuum are likely to occur. The present invention has been made to solve such a problem, and in the case of connecting both the space 4 such as the sample analysis chamber in a high vacuum state and the first stage vacuum region space 2 with the dead space 3, An object of the present invention is to provide a differential evacuation system capable of avoiding a sudden change in pump load due to such a decrease in vacuum degree or abrupt pressure change and smoothly shifting to an analysis state.

[Means for Solving the Problems]

That is, in order to solve the above problems, the present invention is directed to a differential exhaust system in which a space under atmospheric pressure, a first stage vacuum region space, and a high vacuum region space are sequentially connected, A dead space existing between the first-stage vacuum region space and the high-vacuum region space, the gate valve having a hole formed by opening the first-stage vacuum region space and the high-vacuum region space. The gate valve is provided with a small hole for communicating between the high vacuum region space and the space before the hole.

[Action]

When the differential evacuation system is used as the above means, when the space between the first-stage vacuum region space and the high-vacuum region space is shut off to make both spaces vacuum, the gate valve is moved a little and first the two vacuum chambers are passed through a small hole. Exhausts the dead space area. Then, the gate valve can be opened in a state in which both vacuum region spaces have a sufficiently high degree of vacuum, and a momentary drop in the degree of vacuum or a sudden change in the load on the vacuum pump is eliminated.

〔Example〕

Hereinafter, a specific embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic cross-sectional view of the vicinity of a gate valve installed between an atmospheric pressure space 1 having an ion source of a differential exhaust system of the present invention, a first stage vacuum region space 2 and a high vacuum region space 4 such as a sample analysis chamber. FIG. 2 is a front view of the gate valve 5 of FIG.

In this gate valve 5, a small hole 52 (orifice) is formed above a hole 51 that “opens” the high vacuum region space 4 and the first stage vacuum region space 2 of a normal sample analysis chamber. That is, in a system in which ions are sampled from the ion source in the space 1 under atmospheric pressure and introduced into the mass spectrometer, the space 1 with the ion source and the first stage vacuum region space 2 are evacuated by a rotary pump or the like, and the first stage region is exhausted. The region 2 is kept at a vacuum of about several Torr and the gate valve 5 is opened to maintain the degree of vacuum at which the mass spectrometer operates. In this system, when the gate valve 5 is opened, the dead space 3 between the first stage vacuum region space 2 and the gate valve 5 separating the high vacuum region space 4 such as the sample analysis chamber has a higher pressure than the space 4. Next, when the gate valve 5 is opened, the degree of vacuum in the space 4 is affected.

In order to increase the degree of vacuum in the dead space 3, the gate valve 2 is moved from the shut-off state shown in FIG. 3 to the state shown in FIG. 4 when the high vacuum region space 4 such as a sample analysis chamber is evacuated. The gas is exhausted in advance through the orifice 52 formed in the valve 5. Then, as shown in FIG. 5, after the dead space 3 is made to have a vacuum degree equal to or higher than that of the first stage vacuum region space 2, the gate valve 5 is completely opened.

In the differential evacuation system, in short, the gate valve 5 is preliminarily provided with a small hole 52 in addition to the hole 51 for opening the first stage vacuum region space 2 and the sample analysis space 4. By doing so, when the gate valve 5 moves, first, the exhaust of the dead space 3 region is performed through the orifice 52, and as a result, it becomes possible to open the gate valve 5 in a state where both spaces have a sufficiently high degree of vacuum. The instantaneous decrease in vacuum will not occur.

6 and 7 are views of a modified embodiment of the differential exhaust valve of the present invention. That is, as shown in these drawings, the hole 52 (orifice) is connected to the large hole 51 in the vertical direction (of course,
2) Even if it is a long hole 52 '(may be in the lateral direction)
A long hole 52 ″ may be used instead of 52, and the shape thereof does not matter.

[Effect of device]

Since the differential exhaust valve of the present invention has the structure described in detail above, there is no reduction in the degree of vacuum or sudden change in the load of the vacuum pump, which is caused by the presence of dead space near the gate valve. Also, it is possible to shorten the time required to open the gate valve and shift to a state in which the system operates after the first evacuation.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of the vicinity of a gate valve installed between the space where the ion source of the differential exhaust system of the present invention is located and the space such as a sample analysis chamber, and FIG. 2 is a front view of the gate valve, and FIG. The figure is a cross-sectional view of the gate valve completely closed and the two spaces are in a shut-off state. Fig. 4 is a cross-sectional view of the gate valve of the present invention when the dead space is exhausted by an orifice (orifice). FIG. 5 is a sectional view showing a state in which a space such as a sample analysis room and a space where an ion source is provided are opened, FIGS. 6 and 7
The figure is a diagram showing a modification of the gate valve. 1 ... Space with ion source, 2 ... First-stage vacuum area 3 ... Dead space, 4 ... Space for sample analysis chamber, etc. 5 ... Gate valve, 51 ... Gate valve hole 52 ... Hole (orifice)

Claims (1)

[Scope of utility model registration request] 1. A differential evacuation system in which a space under atmospheric pressure, a first-stage vacuum region space, and a high-vacuum region space are connected in sequence,
A gate valve having a hole to be opened by moving is provided between the first-stage vacuum region space and the high-vacuum region space, and is present between the first-stage vacuum region space and the gate valve. A differential exhaust system characterized in that a small hole for communicating between the dead space and the high vacuum region space prior to the hole is formed in the gate valve.