JPH03211441A - Molecular beam sampling device - Google Patents

Abstract

PURPOSE:To eliminate the delay in evacuation time by the pressure difference between adjacent chambers by providing an auxiliary discharge mechanism for discharging the interior of a 1st chamber with a 2nd evacuation system or 3rd evacuation system in addition to a 2nd throttling mechanism. CONSTITUTION:The 1st chamber 1 is subjected to auxiliary discharge by the auxiliary discharge mechanism 30 consisting of an auxiliary discharge pipe 31 and an auxiliary discharge valve 32 for discharging the interior thereof with the evacuation system 8 of the 2nd chamber 2 or the evacuation system 9 of the 3rd chamber 3 at the time of evacuation down to the ultimate pressure before the gas on a side to be detected is introduced into the molecular beam sampling device. The pressure difference between the 1st chamber 1 and the 2nd chamber 2 is decreased in this way and, therefore, the amt. of the gas leaking from the 1st chamber 1 to the 2nd chamber 2 through the 1st throttling mechanism 5 is decreased. The discharge time down to the ultimate pressure is thus shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a molecular beam sampling device, and particularly to a molecular beam sampling device suitable for shortening the time required to start measurement.

[Conventional technology]

In a molecular beam sampling device, before introducing the gas to be detected, the entire device must be evacuated to an ultimate pressure below the operating pressure of the detector.

FIG. 6 is a block diagram of a conventional molecular beam sampling device.

The molecular beam sampling apparatus shown in FIG. 6 is one example of the International Journal of Mass Spectrometry and Ion Processing.

Volume 60 (1984), pages 173 to 187 (In
International Journal of Mas
s 5pectroa+etryand Ion Pr
occesses, 60 (1984) pp, 173~
187), and the conventional molecular beam sampling device will be described below with reference to FIG.

Before introducing the gas to be detected into the molecular beam sampling device, the molecular beam sampling device is evacuated to the ultimate pressure. The operation will be described below. Each chamber is evacuated using its own vacuum evacuation system. That is, the gas in the first chamber 1 is evacuated by the first chamber evacuation system 7, the gas in the second chamber 2 is evacuated by the second chamber evacuation system 8, and the gas in the third chamber 3 is evacuated. The third chamber is evacuated using the vacuum evacuation system 9. At this time, the first chamber vacuum gauge 14 and the second chamber vacuum gauge 15 are provided to monitor the pressure in each chamber. A third chamber in which the pressure in the third chamber 3 measured by the third chamber vacuum gauge 16 is lower than the pressure at which the quadrupole mass spectrometer 10, which is a detector installed in the third chamber 3, can sufficiently operate. Confirm that the pressure reaches the ultimate pressure in step 3.

Next, the operation when analyzing the gas on the detection side using the molecular beam sampling device will be described. The gas to be detected passes through an orifice 4 with an extremely small hole and enters the first chamber 1.
will be introduced to. The first chamber 1 is evacuated by a first chamber vacuum evacuation system 7 so that the pressure in the first chamber 1 is sufficiently lower than the pressure in the area where the gas is present on the detection side. Therefore, the gas that has passed through the orifice 4 becomes a free jet within the first chamber 1.

Since the gas introduced at this time expands adiabatically, the temperature of the gas decreases significantly, and intermediate species that would normally be generated by reactions that easily decompose are also preserved.

Note that the pressure state of the first chamber 1 is measured by a first chamber vacuum gauge 14.

During this free jet, the gap 5 is moved through the gap moving mechanism 11.
is moved to an appropriate position and a part of the free jet is guided to the second chamber 2.

The inside of the second chamber 2 is evacuated by the second chamber evacuation system 8 so that the pressure is sufficiently lower than that of the first chamber 1, and the pressure state is measured by the second chamber vacuum gauge 15. ing.

The gas introduced into the second chamber 2 through the gap 5 expands and becomes a molecular beam in which gas molecules do not collide with each other.

This molecular beam becomes a molecular beam that is interrupted by a chopper 12 having a plurality of notches on a rotating disk. Also, at this time, a signal is output from the detector 19 for detecting when the molecular beam passes through the chopper 12, and is used for signal processing of the signal of the quadrupole mass spectrometer 10.

A portion of the intermittent molecular beam is introduced into the third chamber 3 through a collimator 6 provided on the wall of the third chamber 3. Third chamber 3
The interior of the chamber is evacuated to a pressure sufficient to operate the quadrupole mass spectrometer 10 by a third chamber vacuum evacuation system 9, and the pressure state is measured by a second chamber vacuum gauge 16.

Part of the intermittent molecular beam was taken into the quadrupole mass spectrometer 10 for analysis, and the rest passed through the quadrupole mass spectrometer ionization section 101 and was introduced into the third chamber 3. The light passes through the small hole 17 on the opposite side and is irradiated onto the second chamber molecular beam irradiation surface 18 . Solid line 20 indicates a molecular line.

[Problem to be solved by the invention]

In the above conventional technology, each chamber is evacuated to the ultimate pressure before the gas to be detected is introduced into the molecular beam sampling device using a vacuum evacuation system connected to each chamber. For example, the first chamber 1 is connected to the second chamber 2 via a gap 5, and the second chamber is connected to a collimator 6.
and communicates with the third chamber 3 through a small hole 17. When analyzing gas on the detection side with a molecular beam sampling device, different gas loads are applied to each chamber, and usually the first chamber 1, the second chamber 2, and the third chamber 3 are placed in the order of the load. In addition, gas molecules of the analyzed gas on the detection side will adhere to the wall surface of each chamber, and the amount is thought to be proportional to the gas load, and the first chamber 1. The second chamber 2 and then the third chamber 3. For this reason, when analyzing the gas on the test side using a carbon molecular beam sampling device and evacuating the molecular beam sampling device to the ultimate pressure of the device for the next analysis, it is necessary to Gas molecules adhering to the walls of each chamber will be released into the gas phase. Since the amount of gas released can be considered to be proportional to the amount of gas molecules attached to the wall surface, the first chamber 1. The second chamber 2 and the third chamber 3. Since the gas load is the highest in the first chamber 1, followed by the second chamber 2, and then the third chamber 3, the pressure in each chamber during the evacuation process becomes different, and the first chamber has the highest pressure. Room 1. The order is second chamber 2 and third chamber 3. Adjacent chambers create a pressure difference, and as mentioned above, the chambers are connected by small holes through which gas flows from the high pressure chamber to the low pressure chamber. This is a type of leak when viewed from the side of the room with lower pressure, and this leak is caused by the pressure difference between the lower pressure room and the higher pressure room due to the conductance defined by the small hole connecting these two chambers. This will continue until the pressure difference reaches

The time this leak continues will significantly lengthen the evacuation time for the device to reach its ultimate pressure, but this point has not been taken into consideration, resulting in the problem that it takes a long time to start measurement.

The purpose of the present invention is to eliminate delays in evacuation time caused by minute leaks caused by pressure differences between adjacent rooms;
An object of the present invention is to provide a molecular beam sampling device that can shorten the time before measurement.

[Means to solve the problem]

In order to achieve the above object, the configuration of the molecular beam sampling device according to the present invention is such that at least the gas on the detection side is
It includes a first throttle mechanism that causes the gas to be ejected from the side where it exists to a chamber with low pressure to form a free jet, and a first evacuation system that makes the pressure in the chamber lower than the gas pressure on the detected side. a first chamber adjacent to the first chamber, at least a second throttle mechanism that introduces the free jet formed by the first throttle mechanism to form a molecular beam; a second evacuation system for adjusting the molecular beam, a molecular beam intermittent mechanism that periodically intermittents the molecular beam formed by the second aperture mechanism, and means for detecting that the molecular beam has passed through the molecular beam intermittent mechanism. a second chamber adjacent to the second chamber, the small hole introducing at least a portion of the intermittent molecular beam formed in the second chamber; A molecular beam sampling device consisting of an analyzer for analyzing the components inside, a movement mechanism for adjusting the relative position of the analyzer and the molecular beam, and a third chamber equipped with a third vacuum exhaust system for adjusting the pressure inside the chamber. In addition to the second throttle mechanism, the first chamber is connected to a second evacuation system or a second evacuation system.

An auxiliary exhaust mechanism is provided for exhausting with a third vacuum exhaust system.

[Effect]

The working of the above technical means is as follows.

An auxiliary exhaust mechanism that evacuates the first chamber with the second chamber's vacuum exhaust system or the third chamber's vacuum exhaust system when evacuating the gas to be detected to the ultimate pressure before introducing it into the molecular beam sampling device. By performing auxiliary evacuation and reducing the pressure difference between the first and second chambers, the amount of gas leaking from the first chamber to the second chamber through the second throttling mechanism is significantly reduced. Pumping time is shortened.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a schematic configuration diagram of a molecular beam sampling apparatus according to an embodiment of the present invention.

In Figure 1, 1 is the first chamber, 2 is the second chamber, 3 is the third chamber, and 4 is the gas on the side to be detected that is ejected from the side where this gas is present to the first chamber 1 where the pressure is low. The orifice 5 associated with the first throttling mechanism that forms the free jet flows into the second chamber 2.
6 is a collimator having a small hole for introducing a part of the intermittent molecular beam formed in the second chamber; 7 is a collimator having a small hole for introducing a part of the intermittent molecular beam formed in the second chamber; a first chamber vacuum evacuation system that lowers the pressure inside the chamber than the gas pressure on the detected side;
8 is a second chamber vacuum exhaust system that adjusts the pressure inside the second chamber; 9
1 is a third chamber vacuum evacuation system that adjusts the pressure in the third chamber 3;
0. is a quadrupole mass spectrometer that analyzes the components of the molecular beam introduced into the third chamber 3, 101 is the ionization part of the quadrupole mass spectrometer, and 11 is the distance between the orifice 4 and the gap 5. 12 is a chopper related to a molecular beam intermittent mechanism that periodically interrupts the molecular beam formed in the gap 5; 13 is a chopper for adjusting the molecular beam between the quadrupole mass spectrometer 1o and the molecular beam; Quadrupole mass spectrometer movement mechanism for adjusting relative position, 14
15 is a first chamber vacuum gauge that measures the pressure state of the first chamber 1;
16 is a second chamber vacuum gauge that measures the pressure state of the second chamber 2;
19 is a second chamber vacuum gauge that measures the pressure state of the third chamber 3;
2 shows a detector which is a means for detecting that the molecular beam has passed through the chopper 12, and 20 indicates the molecular beam.

30 is an auxiliary exhaust mechanism that connects the first chamber 1 and the second chamber vacuum exhaust system 8.
It is composed of an auxiliary exhaust pipe 31 and an auxiliary exhaust valve 32 that communicate with each other.

The operation of this device will be explained below.

Before introducing the gas to be detected into the molecular beam sampling device, the device is evacuated to the ultimate pressure.

The first chamber 1 is evacuated by a first chamber evacuation system 7, the second chamber 2 is evacuated by a second chamber evacuation system 8, and the third chamber 3 is evacuated by a third chamber evacuation system 9. At this time, the auxiliary exhaust mechanism 30 is used. The method of operating the auxiliary exhaust mechanism 30 differs depending on the exhaust capacity of the first chamber vacuum exhaust system 7 and the second chamber vacuum exhaust system 8. The first chamber evacuation system 7 usually has a large gas load in the first chamber 1, so the evacuation speed is often higher or the same as that of the evacuation systems for other chambers, and the ultimate pressure is also the same. The operation of the auxiliary exhaust mechanism 30 will be described below in each case. Here, the auxiliary exhaust mechanism 30 is
It is composed of an auxiliary exhaust pipe 31 that connects the first chamber 1 and the second chamber evacuation system 8, and an auxiliary exhaust valve 32 provided in the middle of the auxiliary exhaust pipe 31.

(i) When the ultimate pressure of the first chamber evacuation system 7 is similar to that of other evacuation systems: In this case, only the pressure difference occurs due to the difference in gas load, so the auxiliary exhaust valve 32 is closed from the beginning of evacuation. Leave it open. In this way, the first chamber 1 is exhausted not only by the first chamber vacuum exhaust system 7 but also by the second chamber vacuum exhaust system 8, and the pressure in the first chamber 1 is exhausted only by the first chamber vacuum exhaust system 7. The pressure in the first chamber 1 is lower than that in the case where
The pressure difference between the auxiliary exhaust mechanism 3o and the second chamber 2 becomes much smaller than that in the case where the auxiliary exhaust mechanism 3o is not used, and almost no gas leaks into the second chamber 2 through the second throttle mechanism 5. Therefore, the evacuation time to reach the ultimate pressure of the device is significantly shortened.

(ii) When the ultimate pressure of the first chamber evacuation system 7 is higher than other evacuation systems: the auxiliary exhaust valve 32 is opened at the beginning of evacuation. The pressure in the first chamber 1 is measured with the first chamber vacuum gauge 14, and when the pressure in the first chamber 1 reaches the ultimate pressure determined by the first chamber vacuum evacuation system 7, the first chamber vacuum evacuation system 7 is switched to the first chamber. This is because the ultimate pressure of the first chamber evacuation system 7 is higher than that of the second chamber evacuation system 8, so the first chamber 1 is evacuated using the first chamber evacuation system 7. If this continues, the pressure in the first chamber 1 will be maintained close to the ultimate pressure determined by the first chamber evacuation system 7, and a large pressure difference will remain between the first chamber 1 and the second chamber 2. Due to this pressure difference, a slight recirculation from the first chamber 1 to the second chamber 2 continues through the second throttle mechanism 5, and the exhaust time is about the same as in the conventional case. Therefore, if the first chamber vacuum evacuation system 7 is disconnected as described above, the first chamber 1 will be evacuated by the second chamber vacuum evacuation system 8, and the first chamber 1 will be evacuated by the first chamber vacuum evacuation system 7. The pressure becomes lower than that of the exhaust, and the pressure difference between the first chamber 1 and the second chamber 2 becomes significantly smaller, and almost no leakage occurs from the first chamber 1 to the second chamber 2 through the throttle mechanism 5 of the second chamber. It disappears. Therefore, the evacuation time to reach the ultimate pressure of the device is significantly shortened. Further, this embodiment has a feature that the number of added parts is small and the device can be easily improved.

FIG. 2 is a block diagram of a molecular beam sampling device according to another embodiment of the present invention.

In FIG. 2, the first chamber 1 is connected to the second chamber 2 through an auxiliary exhaust mechanism 30. Here, the auxiliary exhaust mechanism 30 includes an auxiliary exhaust gate valve 33. The operation of this auxiliary exhaust gate valve 33 is the same as that of the auxiliary exhaust valve 32 of the auxiliary exhaust mechanism 30 in FIG. 1, and the description will be omitted to avoid duplication.

Even with this configuration, it is possible to significantly shorten the time required to evacuate the molecular beam sampling device to the ultimate pressure. Further, in this embodiment, it is sufficient to add the auxiliary exhaust gate valve 33 into the main body of the apparatus.

Another feature is that the exhaust piping system does not become complicated. It should be noted that in this embodiment, the auxiliary exhaust gate valve 33 has a gate valve valve part provided on the first chamber 1 side, but it may also be provided on the second chamber 2 side, or between the first chamber 1 and the first chamber 1. It may be provided in the partition wall of the two chambers 2.

FIG. 3 is a block diagram of a molecular beam sampling device according to another embodiment of the present invention.

In FIG. 3, the first chamber 1 is connected to a third vacuum evacuation system 9 through an auxiliary exhaust mechanism 30.
0 has the same configuration as that shown in FIG. 1, with a second auxiliary exhaust pipe 34 connecting the first chamber 1 and the third vacuum exhaust system 9, and a second auxiliary exhaust pipe 34 provided in the middle of this second auxiliary exhaust pipe 34. It consists of a valve 35.

The operation of the auxiliary exhaust valve 35 is the same as that of the auxiliary exhaust valve 32 of the first @ auxiliary exhaust mechanism 30, and will not be repeated. This mechanism can also significantly shorten the time required to evacuate the molecular beam sampling device to the ultimate pressure. In this embodiment, as in the embodiment shown in FIG.
It is characterized by the fact that the device can be easily improved since there are only a small number of parts to be added.

FIG. 4 is a block diagram of a molecular beam sampling device according to another embodiment of the present invention.

In Figure 4, 1 is the first chamber, 2 is the second chamber, 3 is the third chamber, and 4 is the gas on the detection side from the side where this gas is present to the first chamber 1 where the pressure is low. 5 is an orifice related to the first throttle mechanism that introduces the free jet into the second chamber 2 to form a molecular beam; 6 is a gap related to the second throttle mechanism that introduces the free jet into the second chamber 2 to form a molecular beam; 6 is the second chamber 10 is a quadrupole mass spectrometer that analyzes the components of the molecular beam introduced into the third chamber 3; The ionization section 11 of the quadrupole mass spectrometer sets the distance between the orifice 4 and the gap 5 to IIIm! 12 is a chopper related to a molecular beam intermittent mechanism that periodically interrupts the molecular beam formed in the gap 5; 13 is a chopper for controlling the relative position of the quadrupole mass spectrometer 1o and the molecular beam; *a quadrupole mass spectrometer moving mechanism; 14 is a first chamber vacuum gauge that measures the pressure state of the first chamber 1; 15 is a third chamber vacuum gauge that measures the pressure state of the second chamber 2; 16 is a third vacuum evacuation system 9 that measures the pressure state of the third chamber 3, and a molecular beam is connected to the chopper 12.
A detector 20 is a means for detecting the passage of a molecular beam.

50 is a general evacuation system that adjusts the pressure in the first chamber 1, the second chamber 2, and the third chamber 3.

The operation of this device will be explained below.

Before introducing the gas to be detected into the molecular beam sampling device, the device is evacuated to the ultimate pressure.

First room 1. Comprehensive vacuum evacuation system 5 for the second chamber 2 and third chamber 3
Exhaust at 0. At this time, the first chamber 1 is checked by the first chamber vacuum gauge 14.
While measuring the internal pressure in the second chamber 2 and the third chamber 3, the pressure in each chamber is adjusted by adjusting the conductance of the piping that connects the comprehensive vacuum exhaust system 50 and each chamber. Evacuate to prevent this from occurring. As a result, leaks that occur through the small holes connecting the chambers due to the pressure difference between adjacent chambers, which would cause a delay in evacuation time to reach the ultimate pressure of the device, can be suppressed. This shortens the evacuation time to reach the ultimate pressure of the device.

FIG. 5 is a block diagram of a molecular beam sampling device according to another embodiment of the present invention.

In Fig. 5, 1 is the first chamber, 2 is the second chamber, 3 is the third chamber, and 4 is the gas on the side to be detected that is ejected from the side where this gas is present to the first chamber 1 where the pressure is low. 40 is an orifice related to the first throttle mechanism that forms a free jet by introducing the free jet into the second chamber 2 to form a molecular beam; 6 is a variable throttle mechanism related to the second throttle mechanism that introduces the free jet into the second chamber 2 to form a molecular beam; a second variable aperture mechanism 7 having a small hole for introducing a portion of the intermittent molecular beam formed in the chamber;
A first chamber vacuum evacuation system 8 makes the pressure in the first chamber 1 lower than the gas pressure on the detection side; 8 is a quadrupole mass spectrometer 101 into which a third vacuum evacuation system 9 is introduced to analyze the components of the molecular beam; is the ionization part of the quadrupole mass spectrometer, 11 is the orifice 4
and a gap moving mechanism 12 for adjusting the distance between the variable aperture mechanism 40 and the variable aperture mechanism 40;
3 is a quadrupole mass spectrometer moving mechanism that adjusts the relative position of the quadrupole mass spectrometer 10 and the molecular beam; 14 is a first chamber vacuum gauge that measures the pressure state of the first chamber 1; and 15 is a , a third chamber vacuum gauge that measures the pressure state of the second chamber 2; 16, a third chamber vacuum gauge that measures the pressure state of the third chamber 3; and 19, a third chamber vacuum gauge that measures the pressure state of the second chamber 2; A detector 20 as a means for detecting a molecular beam.

The operation of this device will be explained below.

Before introducing the gas to be detected into the molecular beam sampling device, the device is evacuated to the ultimate pressure.

At this time, the first chamber 1 is evacuated by the first chamber vacuum evacuation system 7, the second chamber 2 is evacuated by the second chamber vacuum evacuation system 8, and the third chamber 3 is evacuated by the third chamber vacuum exhaust system 9. , a variable diaphragm mechanism 40 that connects the first chamber 1 and the second chamber 2, and the second chamber 2 and the third chamber 3.
The size of the hole of the second variable aperture mechanism 41 that communicates with the second variable aperture mechanism 41 is set to the maximum size, which is larger than that when the gas to be detected is analyzed using the molecular beam sampling device. In this case, gas can flow in more easily than in the case where the holes connecting the chambers are small, so that the pressure difference between the chambers is quickly reduced. For this reason, leakage that would occur through the small holes connecting the chambers due to the pressure difference between adjacent chambers, which would have caused a delay in evacuation time to reach the ultimate pressure of the device, can be suppressed. As a result, the evacuation time to reach the ultimate pressure of the device is shortened.

〔Effect of the invention〕

According to the present invention, when the device is evacuated to the ultimate pressure before introducing the gas to be detected into the molecular beam sampling device, the pressure difference between the first chamber and the second chamber is reduced by the auxiliary exhaust mechanism. I can do it. Therefore, the amount of gas leaking from the first chamber to the second chamber through the second throttle mechanism can be significantly reduced, and the evacuation time to reach the ultimate pressure can be significantly shortened.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a molecular beam sampling device according to one embodiment of the present invention, and FIGS. 2 to 5 are block diagrams of molecular beam sampling devices according to other embodiments of the present invention.
FIG. 6 is a block diagram of a conventional molecular beam sampling device.

Claims (1)

[Claims] 1. At least a first throttling mechanism that injects the gas on the detection side from the side where the gas is present to a low pressure chamber to form a free jet; a first chamber equipped with a first vacuum evacuation system that makes the gas pressure lower than the gas pressure on the detection side;
A chamber adjacent to the first chamber, at least a second throttle mechanism that introduces the free jet formed by the first throttle mechanism to form a molecular beam, and a second throttle mechanism that adjusts the pressure in the chamber. A vacuum pumping system, a molecular beam interrupting mechanism that periodically interrupts the molecular beam formed by the second aperture mechanism, and a means for detecting that the molecular beam has passed through the molecular beam interrupting mechanism. a second chamber, and a chamber adjacent to the second chamber,
At least a small hole that introduces a portion of the intermittent molecular beam formed in the second chamber, an analyzer that analyzes components in the introduced intermittent molecular beam, and a third chamber that adjusts the pressure inside the chamber. and a third chamber equipped with a vacuum evacuation system, the first chamber is evacuated by the second evacuation system or the third evacuation system other than the second aperture mechanism. A molecular beam sampling device characterized by being provided with an auxiliary exhaust mechanism for