Source: http://patents.com/us-9831077.html
Timestamp: 2018-08-20 03:38:43
Document Index: 218221678

Matched Legal Cases: ['Application No. 2015', 'Application No. 2016', 'art 41', 'art 41', 'art 41', 'art 41', 'art 42']

US Patent # 9,831,077. Method for analyzing evolved gas and evolved gas analyzer - Patents.com
United States Patent 9,831,077
Method for analyzing evolved gas and evolved gas analyzer
Disclosed herein is an evolved gas analyzer and a method for analyzing evolved gas, the apparatus enhancing detection accuracy for gas component without providing the apparatus in a large size. The apparatus includes a heating unit evolving a gas component by heating a sample, a detecting means detecting the gas component, a gas channel connecting the heating unit to the detecting means, the gas channel through which mixed gas of the gas component and carrier gas flows, wherein the gas channel includes a branching channel being open to outside and including a discharge flow rate controlling device, and a flow rate control device controlling the discharge flow rate controlling device based on a detection signal received from the detecting means so as to control the detection signal to be within a predetermined range.
Akiyama; Hideyuki (Tokyo, JP), Watanabe; Masafumi (Tokyo, JP), Maruoka; Kantaro (Tokyo, JP)
Family ID: 1000002977404
15/356,580
US 20170148616 A1 May 25, 2017
Nov 20, 2015 [JP] 2015-227371
Sep 6, 2016 [JP] 2016-173396
Current CPC Class: H01J 49/0422 (20130101); H01J 49/10 (20130101); G01N 30/7206 (20130101)
Current International Class: G01N 27/62 (20060101); H01J 49/04 (20060101); H01J 49/10 (20060101); G01N 30/72 (20060101); G01N 1/38 (20060101)
Field of Search: ;250/281,282,287,288,423R,424,425
4814612 March 1989 Vestal
4883958 November 1989 Vestal
7928370 April 2011 Amirav
8866075 October 2014 Sato
2008/0128615 June 2008 Yamada
2012/0326022 December 2012 Kumano
2013/0277547 October 2013 Sato
2001-28251 Jan 2001 JP
2012-202887 Oct 2012 JP
1. An evolved gas analyzer comprising: a heating unit evolving a gas component by heating a sample, a detecting means detecting the gas component evolved by the heating unit, and a gas channel making connection between the heating unit and the detecting means in which mixed gas of the gas component and carrier gas, carrying the gas component to the detecting means, flows, wherein the gas channel comprises a branching channel open to outside, the branching channel comprises a discharge flow rate controlling device, adjusting flow rate of the mixed gas discharged to outside, and the evolved gas analyzer further comprises a flow rate control device controlling the discharge flow rate controlling device based on a detection signal from the detecting means so as to bring the detection signal to be within a given range.
2. The apparatus of claim 1, further comprising a heat retaining unit, heating or retaining heat of the gas channel or the branching channel.
3. The apparatus of claim 1, further comprising: a forced discharge unit, discharging the mixed gas flowing in the branching channel by force, on a discharge side of the branching channel.
4. The apparatus of claim 1, wherein an angle between a first axis of the gas channel at a point of contact with the branching channel and a second axis of the branching channel at a point of contact with the gas channel is between 30 to 60 degrees and the branching channel discharges naturally.
5. The apparatus of claim 2, wherein an angle between a first axis of the gas channel at a point of contact with the branching channel and a second axis of the branching channel at a point of contact with the gas channel is between 30 to 60 degrees and the branching channel discharges naturally.
6. The apparatus of claim 1, further comprising a heating control device maintaining the heating unit at a certain temperature, wherein the detecting means is a mass spectrometer.
7. The apparatus of claim 2, further comprising a heating control device maintaining the heating unit at a certain temperature, wherein the detecting means is a mass spectrometer.
8. The apparatus of claim 3, further comprising a heating control device maintaining the heating unit at a certain temperature, wherein the detecting means is a mass spectrometer.
9. The apparatus of claim 4, further comprising a heating control device maintaining the heating unit at a certain temperature, wherein the detecting means is a mass spectrometer.
10. The apparatus of claim 5, further comprising a heating control device maintaining the heating unit at a certain temperature, wherein the detecting means is a mass spectrometer.
11. The apparatus of claim 1, wherein the detecting means is a mass spectrometer, the evolved gas analyzer further comprises an ion source between the gas channel and the mass spectrometer, ionizing the gas component of the mixed gas, and the flow rate control device controls the discharge flow rate controlling device to increase the discharge flow rate of the mixed gas when a detection signal from the detecting means is outside the given range.
12. The apparatus of claim 2, wherein the detecting means is a mass spectrometer, the evolved gas analyzer further comprises an ion source between the gas channel and the mass spectrometer, ionizing the gas component of the mixed gas, and the flow rate control device controls the discharge flow rate controlling device to increase the discharge flow rate of the mixed gas when a detection signal from the detecting means is outside the given range.
13. The apparatus of claim 3, wherein the detecting means is a mass spectrometer, the evolved gas analyzer further comprises an ion source between the gas channel and the mass spectrometer, ionizing the gas component of the mixed gas, and the flow rate control device controls the discharge flow rate controlling device to increase the discharge flow rate of the mixed gas when a detection signal from the detecting means is outside the given range.
14. The apparatus of claim 4, wherein the detecting means is a mass spectrometer, the evolved gas analyzer further comprises an ion source between the gas channel and the mass spectrometer, ionizing the gas component of the mixed gas, and the flow rate control device controls the discharge flow rate controlling device to increase the discharge flow rate of the mixed gas when a detection signal from the detecting means is outside the given range.
15. The apparatus of claim 5, wherein the detecting means is a mass spectrometer, the evolved gas analyzer further comprises an ion source between the gas channel and the mass spectrometer, ionizing the gas component of the mixed gas, and the flow rate control device controls the discharge flow rate controlling device to increase the discharge flow rate of the mixed gas when a detection signal from the detecting means is outside the given range.
16. The apparatus of claim 6, wherein the evolved gas analyzer further comprises an ion source between the gas channel and the mass spectrometer, ionizing the gas component of the mixed gas, and the flow rate control device controls the discharge flow rate controlling device to increase the discharge flow rate of the mixed gas when a detection signal from the detecting means is outside the given range.
17. The apparatus of claim 7, wherein the evolved gas analyzer further comprises an ion source between the gas channel and the mass spectrometer, ionizing the gas component of the mixed gas, and the flow rate control device controls the discharge flow rate controlling device to increase the discharge flow rate of the mixed gas when a detection signal from the detecting means is outside the given range.
18. The apparatus of claim 8, wherein the evolved gas analyzer further comprises an ion source between the gas channel and the mass spectrometer, ionizing the gas component of the mixed gas, and the flow rate control device controls the discharge flow rate controlling device to increase the discharge flow rate of the mixed gas when a detection signal from the detecting means is outside the given range.
19. The apparatus of claim 9, wherein the evolved gas analyzer further comprises an ion source between the gas channel and the mass spectrometer, ionizing the gas component of the mixed gas, and the flow rate control device controls the discharge flow rate controlling device to increase the discharge flow rate of the mixed gas when a detection signal from the detecting means is outside the given range.
20. The apparatus of claim 10, wherein the evolved gas analyzer further comprises an ion source between the gas channel and the mass spectrometer, ionizing the gas component of the mixed gas, and the flow rate control device controls the discharge flow rate controlling device to increase the discharge flow rate of the mixed gas when a detection signal from the detecting means is outside the given range.
21. A method for analyzing evolved gas, comprising: generating mixed gas by mixing a gas component evolved by heating a sample with carrier gas, introducing the mixed gas into a detecting means through a gas channel, detecting the gas component with the detecting means, and discharging a portion of the mixed gas to outside from a branching channel installed on the gas channel and open to outside based on a detection signal from the detecting means so as to bring the detection signal to be within a given range.
This application claims the benefit of Japanese Patent Application No. 2015-227371, filed Nov. 20, 2015, and Japanese Patent Application No. 2016-173396, filed Sep. 6, 2016, which are hereby incorporated by reference in their entirety into this application.
In addition, in the evolved gas analysis, the evolved gas component flows with carrier gas such as nitrogen gas, etc. so as to be introduced into a detecting means. However, when a plurality of gas components are evolved, gas density is too high. Therefore, the gas density exceeds a detection range of a detecting means and thus, a detection signal is overly scaled, whereby the measurement is inaccurate.
Therefore, technology of increasing flow rate of the carrier gas that is mixed with the gas component to dilute the gas component so as to reduce the gas density, when the detection signal of the detecting means exceeds the detection range are disclosed in Patent Documents 1 and 2.
(Patent Document 1) Japanese Patent Application Publication No. 2001-28251 (Patent Document 2) Japanese Patent Application Publication No. 2012-202887
However, in case of the Patent Documents 1 and 2, when the gas density is high, it is desired to increase the supply of carrier gas in order to increase flow rate of carrier gas, whereby it results in a large size of the entire apparatus and in an increase of costs.
In addition, when using a mass spectrometer as the detecting means, the gas component is ionized at the front thereof. However, in case of the gas component including an accessory substance, which is not the measurement target, when a plurality of gas components are evolved, a plurality of accessory substances are also ionized. Therefore, substances of the measurement targets are insufficiently ionized, and thus, the detection signal of the measurement target is degraded (ion-suppression). In this case, it is inappropriate to use Patent Documents 1 and 2.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the related art, and an object of the present invention is to provide an evolved gas analyzer and a method for analyzing evolved gas, the apparatus enhancing detection accuracy for the gas component without providing the entire apparatus in a large size.
In order to accomplish the above object, the present invention provides an evolved gas analyzer including: a heating unit evolving a gas component by heating a sample, a detecting means detecting the gas component evolved by the heating unit, and a gas channel making connection between the heating unit and the detecting means in which mixed gas of the gas component and carrier gas, carrying the gas component to the detecting means, flows, wherein the gas channel comprises a gas discharge channel open to outside, the gas discharge channel comprises a discharge flow rate adjusting device, adjusting flow rate of the mixed gas discharged to outside, and the evolved gas analyzer further comprises a flow rate control unit controlling the discharge flow rate adjusting device based on a detection signal from the detecting means so as to bring the detection signal to be within a given range
According to the evolved gas analyzer, when a plurality of the gas components are evolved, the gas density is too high. The flow rate of the mixed gas discharged from the branching channel to the outside is increased, and the flow rate of the mixed gas introduced from the gas channel into the detecting means is decreased. Therefore, it is possible to avoid that the gas density exceed the detection range of the detecting means and thus, the detection signal is overly scaled, whereby the measurement is inaccurate.
Here, the flow rate of the mixed gas discharged from the branching channel to the outside is controlled without increasing flow rate of the carrier gas. Therefore, detection accuracy for the gas component may be enhanced without increasing supply of the carrier gas, and without providing the entire apparatus in a large size.
The evolved gas analyzer may include heat retaining unit heating or retaining heat of the gas channel or the branching channel.
According to the evolved gas analyzer, it is possible to prevent the gas component, which is evolved in the heating unit, being cooled, condensed, and trapped at the gas channel or at the inner wall of the branching channel. Therefore, the trapped gas component is not vaporized and is not measured by the detecting means, whereby it is possible to avoid that the measurement is performed for a long time, thus degrading work efficiency. Alternatively, it is possible to prevent the gas component, which is condensed and vaporized, from influencing the next measurement.
The evolved gas analyzer may include a forced discharge unit discharging the mixed gas flowing through the branching channel by force, the forced discharge unit being provided at a discharge side of the branching channel.
According to the evolved gas analyzer, the mixed gas is forced to be discharged, and air pressure of the gas channel and of the branching channel is reduced, whereby the trapped gas component is prevented from flowing backward to the detecting means. Therefore, the trapped gas component is not vaporized and is not measured by the detecting means, whereby it is possible to avoid that the measurement is performed for a long time, thus degrading work efficiency. Alternatively, it is possible to prevent the gas component, which is condensed and revaporized, from influencing the next measurement.
An angle of a first axis of the gas channel and a second axis of the branching channel may be within a range of 30 to 60 degree angles at a contact point of the gas channel and the branching channel, and the mixed gas may be naturally discharged through the branching channel.
According to the evolved gas analyzer, when the mixed gas is naturally discharged through the branching channel, the mixed gas flowing from upstream of the gas channel does not rapidly change the direction of the mixed gas at the branching channel. Therefore, turbulence is avoided at the branching channel, whereby the mixed gas may be smoothly discharged from the branching channel. In addition, the height of the branching channel is low and thus, space is reduced, in comparison with the case that the angle of the first axis and the second axis is a range of .theta.>60 degree angles (for example, 90 degree angles).
In addition, when the mixed gas is naturally discharged through the branching channel, the forced discharge unit discharging the mixed gas by force is not provided at the branching channel or at a discharge side of the branching channel. Alternatively, an inlet hole such as a duct, etc. may be provided away from the discharge side of the branching channel. In this case, while operating the duct, flow rate of the mixed gas from the branching channel is set.
The evolved gas analyzer may include a heating control device maintaining the heating unit at a predetermined temperature. The detecting means may be a mass spectrometer.
According to the evolved gas analyzer, the temperature of the heating unit is simply controlled and thus, the measurement is performed for a short time in comparison with a chromatograph, etc. performing detection by changing the temperature of the heating unit.
The evolved gas analyzer may include an ion source provided between the gas channel and a mass spectrometer, the ion source ionizing the gas component of the mixed gas. The detecting means may be the mass spectrometer, and the flow rate control device may control the discharge flow rate controlling device to increase the flow rate of the mixed gas discharged to the outside, when the detection signal received from the detecting means is less than the predetermined range.
When using a mass spectrometer as the detecting means, the gas component is ionized at the ion source, which is placed in front of the detecting means. However, when a plurality of gas components are evolved, a plurality of accessory substances are also ionized. Therefore, substances of the measurement targets are insufficiently ionized, and thus, the detection signal of the measurement target is degraded, which means that ion-suppression occurs, thereby reducing the detection signal.
According to the evolved gas analyzer, in case of the ion-suppression, the flow rate control device determines the peak intensity of the detection signal is less than a threshold value. Next, the flow rate control device controls the discharge flow rate controlling device to increase the flow rate of the mixed gas discharged to the outside. Therefore, the flow rate of the mixed gas introduced into the ion source is reduced, and the ionization of the accessory substances and the degradation of the detection signal are prevented, whereby the detection accuracy for the gas component may be enhanced.
According to another aspect, there is provided a method for analyzing evolved gas, the method including: generating mixed gas by mixing carrier gas and a gas component evolved by heating a sample; introducing the mixed gas into a detecting means through a gas channel; detecting the gas component by using the detecting means; and discharging a portion of the mixed gas from a branching channel open to outside based on a detection signal received from the detecting means so as to control the detection signal to be within a predetermined range, the branching channel being provided with the gas channel.
According to the described above, detection accuracy for the gas component can be enhanced without providing the entire apparatus in a large size.
FIG. 7 is a view showing a gas channel and heat retaining unit of a branching channel;
FIG. 8 is a view showing a forced discharge unit of the branching channel; and
FIG. 9 is a view showing a gas channel and heat retaining unit according to another exemplary embodiment of the present invention.
In addition, for example, when the sample holder 20 is moved on a movement rail 204L by a stepping motor, etc. controlled by the computer 210, the sample holder 20 may be automatically moved into or from the heating furnace 10.
The heating block 14 surrounds the heating chamber 12, and the heat retaining jacket 16 surrounds the heating block 14. The heating block 14 is made of aluminum, and is heated by electricity from a pair of heating unit heaters 14a extending from the heating furnace 10 to outside in a direction of the axis O as shown in FIG. 4.
In addition, a gas channel 41 communicates with a cross section on the opposite side (right side of FIG. 3) of an opening side of the heating chamber 12. Mixed gas M of the carrier gas C and a gas component G evolved by the heating furnace 10 (heating chamber 12) flows through the gas channel 41.
The sample holder 20 includes a stage 22 moving on the movement rail 204L attached to an inner upper surface of the attaching unit 204; a bracket 24c attached on the stage 22 and extending in a vertical direction; insulators 24b and 26 attached to a front surface (left side of FIG. 3) of the bracket 24c; a sample holding unit 24a extending from the bracket 24c in a direction of the axis O in the heating chamber 12; a sample heater 27 provided just below the sample holding unit 24a; and a sample plate 28 provided on an upper surface of the sample holding unit 24a above the sample heater 27, the sample plate on which the sample is placed.
In addition, an upper portion of the bracket 24c has a semicircular shape and a lower portion of the bracket has a rectangular shape. Referring to FIG. 2, the insulator 24b has a substantially cylinder shape, and is provided at a front surface of an upper portion of the bracket 24c. An electrode 27a of the sample heater 27 penetrates the insulator 24b, and protrudes to an outside of the gas evolving unit. The insulator 26 has a rectangular shape, and is provided at the front surface of the bracket 24c. The insulator 26 is located lower than the insulator 24b. In addition, the insulator 26 is not provided at a lower portion of the bracket 24c, and a front surface of the lower portion of the bracket 24c is exposed to form a contact surface 24f.
The cooling unit 30 faces the bracket 24c of the sample holder 20, and is located at an outside of the heating furnace 10 (left side of the heating furnace 10 in FIG. 3). The cooling unit 30 includes a cooling block 32 having a concave portion 32r that has a rectangular shape; cooling fins 34 connected to a lower surface of the cooling block 32; and a pneumatic cooling fan 36 connected to a lower surface of the cooling fins 34, and blowing air to the cooling fins 34.
In addition, when the sample holder 20 moves in a direction of the axis O on the movement rail 204L toward a left side of FIG. 3, and comes out of the heating furnace 10, the contact surface 24f of the bracket 24c is positioned at the concave portion 32r of the cooling block 32 by being in contact with the concave portion. Consequently, as heat of the bracket 24c is removed by the cooling block 32, the sample holder 20 (particularly, the sample holding unit 24a) is cooled.
The gas channel 41 may have a straight line shape extending in a direction of axis O from the heating chamber 12 connected with the gas channel to the end part 41e. Alternatively, depending on a positional relationship with the heating chamber 12 or with the ion source 50, the gas channel 41 may have a various curved shape, a line shape having an angle to the axis O, etc.
In addition, according to the exemplary embodiment of the present invention, the gas channel 41 has a diameter about 2 mm, and the branch chamber 41M and the branching channel 42 have respective diameters about 1.5 mm. In addition, a ratio (split ratio) of flow rates from the gas channel 41 to the end part 41e, and flow rates branched to the branching channel 42 is determined by a flow resistance. The mixed gas M may flow more through the branching channel 42. In addition, the split ratio is controlled by adjusting an opening ratio of the mass flow controller 42a.
In addition, the inner diameter of the branching channel 42 is determined to provide that the sum of cross sectional areas of the gas channel being in contact with the ion source and the branching channel is less than a cross sectional area of the gas channel positioned just before the branching channel. In addition, the inner diameter of the branching channel 42 is determined to avoid the flow rate of the mixed gas from being reaching the speed of sound at any position of the gas channel being in contact with the ion source and the branching channel. It is desired that the inner diameter of the branching channel is 50.about.90% of the inner diameter of the gas channel 41 positioned just before the contact potion P (referring to FIG. 9).
As shown in FIGS. 3 and 4, the ion source 50 includes an ionizer housing unit 53; an ionizer heat retaining unit 54 surrounding the ionizer housing unit 53; a discharge needle 56; and a staying unit 55 fixing the discharge needle 56. The ionizer housing unit 53 has a plate shape, and a surface of the plate is parallel to the axis O. A small hole 53C penetrates the center of the surface of the plate. In addition, the end part 41e of the gas channel 41 passes through the ionizer housing unit 53, and faces a side wall of the small hole 53C. In the meantime, the discharge needle 56 extends in a direction perpendicular to the axis O, and faces the small hole 53C.
In addition, the ion source 50 is contained in the ionizer heat retaining unit 54.
In addition, as shown in FIGS. 6A and 6B, according to the exemplary embodiment of the present invention, the stage 22 moves the sample holder 20 in the direction of axis O between predetermined two positions (a discharging position which is located at the outside of the heating furnace 10 where the sample plate 28 is discharged as shown in FIG. 6A, and a measuring position at which the gas component is measured is located in the heating furnace 10 where the sample plate 28 is received therein as shown in FIG. 6B).
Therefore, the sample and the sample plate 28 are supplied on or removed from the sample holder at the discharging position of FIG. 6A. Here, the contact surface 24f of the bracket 24c is in contact with the concave portion (contact portion) 32r of the cooling block 32. Therefore, heat of the bracket 24c is cooled by the cooling block 32, and thus the sample holder 20 is cooled.
According to the exemplary embodiment of the present invention, as shown in FIGS. 3 and 4, the gas channel 41 includes a branching channel 42 opened to the outside. An opening ratio of a mass flow controller 42a attached to the branching channel 42 is controlled to adjust flow rate of the mixed gas M discharged from the branching channel 42 to the outside, and to adjust flow rate of the mixed gas M introduced from the gas channel 41 into the ion source 50.
Therefore, when a plurality of gas components are evolved and thus, gas density is too high, the flow rate of the mixed gas M discharged from the branching channel 42 to the outside is increased, and the flow rate of the mixed gas M introduced from the gas channel 41 into the ion source 50 is decreased. Therefore, it is possible to avoid that the gas density exceeds the detection range of the mass spectrometer 110, whereby the detection signal is overly scaled and the measurement is inaccurate.
Here, the flow rate of the mixed gas discharged from the branching channel 42 to the outside is controlled without increasing flow rate of the carrier gas. Therefore, detection accuracy for the gas component may be enhanced without increasing supply of the carrier gas, and without providing the entire apparatus in a large size.
In addition, when using the mass spectrometer as the detecting means, the gas component is ionized at the front thereof, which is the ion source 50. However, when the plurality of gas components are evolved, accessory substances are ionized. Thus, ion-suppression occurs, and the detection signal is degraded.
Therefore, in case of the ion-suppression, the flow rate control device 216 determines the peak intensity of the detection signal of the mass spectrometer 110 received from the detection signal determining unit 214 is less than a threshold value. Next, the flow rate control device 216 transmits a control signal to the mass flow controller 42a to increase the opening ratio. Therefore, the flow rate of the mixed gas M introduced into the ion source 50 is reduced, and the ionization of the accessory substances and the degradation of the detection signal are prevented, whereby the detection accuracy for the gas component may be enhanced.
In addition, it is difficult to determine whether or not the ion-suppression occurs by only obtaining the peak intensity of the detection signal. Also, the measurement target may have a low content of the gas component. Therefore, it is required to determine whether or not ion-suppression occurs due to high content of a concomitant, etc. that is not the measurement target. The determination is performed by a user or the flow rate control device 216 based on a table storing that whether or not ion-suppression occurs at each sample or at each gas component.
In addition, the flow rate control device 216 generates a control signal to increase the flow rate of the mixed gas M discharged from the branching channel 42 to the outside, when the peak intensity of the detection signal exceeds the threshold value (overly scaled) or is less than the threshold value (when determining that ion-suppression occurs).
In this case, for example, the table stores that whether or not ion-suppression occurs at each gas component, and the flow rate control device 216 determines the ion-suppression based on the table. When determining that ion-suppression occurs, a control signal for increasing the opening ratio is transmitted to the mass flow controller 42a. In addition, whenever the measurement is conducted the user input whether the measurement causes ion-suppression or not, using an input unit (select button, etc.) of the computer 210. The flow rate control device 216 compares the peak intensity of the detection signal with the threshold value based on the input signal, and transmits a control signal for increasing the opening ratio to the mass flow controller 42a.
In addition, when the measurement target is phtalates and the accessory substance is additive agent of phthalate, etc., ion-suppression occurs.
In addition, the gas component evolved in the heating furnace 10 may be cooled, condensed, and trapped at the gas channel 41 located close to the branch chamber 41M and at an inner wall of the branching channel 42, and next, may be vaporized and measured in the ion source 50. In this case, a long period is required for measurement, thus work efficiency is degraded. In addition, the gas component, which is condensed and vaporized, may influence the next measurement.
Therefore, as shown in FIG. 7, heat retaining unit 41H and 42H may be provided to heat or retain the heat of the perimeter of at least one of the gas channel 41 located close to the branch chamber 41M and the branching channel 42. Therefore, it is possible to prevent the gas component being trapped at the gas channel 41 or at the inner wall of the branching channel 42.
In addition, referring to FIG. 7, the heat retaining part 41H is a coil heater heating the perimeter of the gas channel 41 located close to the branch chamber 41M, and the heat retaining part 42H is a coil heater heating the perimeter of the branching channel 42 located close to the branch chamber 41M.
In addition, the heat retaining unit 41H and 42H are not limited to heaters, and may be an insulator, etc. that can prevent coagulation of the gas component. In addition, it is possible to provide at least one of the heat retaining unit 41H and 42H, or both.
In the meantime, when the gas component (mixed gas) is heated by the heat retaining unit 41H and 42H, the mixed gas discharged from the branching channel 42 and flowing through the mass flow controller 42a starts to have high temperature. Therefore, a heating resisting type mass flow controller 42a may be required.
Therefore, as shown in FIG. 8, instead of providing the heat retaining unit 41H and 42H, a discharge pump (forced discharge unit) 42p may be provided at the branching channel 42, which is closer to the outgoing side than the mass flow controller (42a). By this, the air pressure in the gas channel 41 located close to the branch chamber 41M and the branching channel 42 is lowered from discharging the mixed gas M flowing through the branching channel 42 by force through this, so the trapped gas component is prevented from flowing back to the ion source 50.
In addition, as shown in FIG. 9, at a contact point P (contact portion) of the gas channel 41 and the branching channel 42 that are located around the branch chamber 41M, an angle .theta. of a first axis AX1 (an axis of the gas channel 41) and a second axis AX2 (an axis of the branching channel 42) is within a range of 30 to 60 degree angles. The mixed gas is naturally discharged through the branching channel 42.
According to the described above, when the mixed gas is naturally discharged through the branching channel 42, the mixed gas M flowing from upstream of the gas channel 41 does not rapidly change the direction of the mixed gas at the branching channel 42. Therefore, turbulence is avoided at the branching channel 42, whereby the mixed gas may be smoothly discharged from the branching channel 42. In addition, the height of the branching channel 42 is low and thus, the space is reduced, in comparison with the case that the angle of the first axis and the second axis is a range of .theta.>60 degree angles (for example, 90 degree angles). In addition, when the angle of the first axis and the second axis is a range of .theta.<30 degree angles, the turbulence may be avoided. However, the branching channel 42 is almost horizontal, such that sufficient space is required therefor. In addition, when the branching channel 42 is long, the gas component may be trapped in the branching channel 42. Moreover, it is difficult to heat the branching channel 42. Therefore, the angle .theta. of the first axis and the second axis is equal to or greater than 30 degree angles.
Here, the branching channel 42 of FIG. 9 is provided to enter the housing unit of FIG. 3.
In addition, flow rate of the mixed gas at an introduction side the branching channel 42 having the angle .theta. of the first axis and the second axis at the range of 30 to 60 degree angles may be, for example, 0.5.about.2 ml/min, without being limited thereto.
In addition, the contact potion P is an intersection point of the center-lines of the gas channel 41 and of the branching channel 42. In addition, at the contact potion P, when the angle .theta. of the first axis AX1 and the second axis AX2 is a range of 30 to 60 degree angles, an angle of an axis of the gas channel 41 and an axis of the branching channel 42 that are located downstream of the contact potion P may be beyond the range of 30 to 60 degree angles.
In addition, "the branching channel discharges naturally" means not providing a device changing the flow rate in the branching channel 42 (a discharge pump 42p of FIG. 8, etc.) at the branching channel 42, which is closer to the outgoing side than the mass flow controller (42a).
In addition, the contact potion P is located at a position of the gas channel 41 in which flow of gas is uniform.
Components, shapes, configurations, etc. of the gas channel 41, the branching channel 42, and the splitter 40 are not limited to the exemplary embodiments. In addition, the detecting means is not limited to the mass spectrometer.
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