Gas path system applied to vacuum photoelectron spectroscopy workstation

Abstract

The utility model relates to the technical field of vacuum photoelectron spectroscopy work stations, and discloses a gas path system applied to a vacuum photoelectron spectroscopy work station, which comprises a base, a turbo molecular pump, a rotary vane vacuum pump, a connecting pipe, an adsorption pipe, an adsorption trap and a rapid sample introduction chamber, the turbo molecular pump is connected with the sliding vane rotary vacuum pump through a connecting pipe, an adsorption pipe is arranged in the middle of the connecting pipe, an adsorption trap is arranged in the adsorption pipe, an adsorbent is stored in the adsorption trap, and a rapid sample introduction chamber is detachably mounted at the top of the turbo molecular pump. The adsorption pipe is composed of the pipe cover, the pipe body and the sealing gasket, one end of the pipe cover is hinged to the pipe body, the other end of the pipe cover is connected with the pipe body through the two sets of bolts and nuts, when the adsorbent is replaced, only the two sets of bolts and nuts need to be screwed off, the sealing gasket is taken down, and the adsorption trap in the clamping groove needs to be replaced without moving the pump body or detaching the adsorption pipe. The replacement process is simple, and the replacement speed is high.

Description

Technical Field

[0001] The utility model relates to the field of vacuum photoelectron spectrum workstations, and more specifically, to a gas path system applied to vacuum photoelectron spectrum workstations. Background Art

[0002] The vacuum photoelectron spectroscopy workstation is an experimental device used to study the surface structure and electronic properties of materials. It uses high-energy electron beams to interact with materials to generate photoelectrons. By analyzing the energy distribution of these photoelectrons, the energy level structure, chemical bond information, elemental composition, etc. of the material can be obtained. The workstation usually includes a vacuum chamber, an electron source, an energy analyzer, a detector, and a control and measurement system. The vacuum chamber has a gas path system to maintain a certain vacuum degree and reduce the loss of signal intensity due to collisions between photoelectrons and residual gas molecules during movement. The vacuum chamber includes a fast injection chamber, a sample preparation chamber, and an analysis chamber. The fast injection chamber generally uses a turbomolecular pump group with a rotary vane vacuum pump as the front stage as the main pump, and an adsorption trap is set between the two pumps to prevent oil return.

[0003] An adsorption tube equipped with an adsorption trap is flange-connected between the two pumps of a conventional turbomolecular pump unit to prevent oil return. The adsorbent in the adsorption trap needs to be replaced regularly to ensure a good adsorption effect. However, the replacement process requires moving the pump unit and removing the adsorption tube, which is time-consuming and labor-intensive. Utility Model Content

[0004] The utility model provides a gas path system applied to a vacuum photoelectron spectrum workstation, which solves the technical problem of time-consuming and labor-intensive replacement of an adsorbent in an adsorption tube in the related technology.

[0005] According to one aspect of the utility model, a gas path system applied to a vacuum photoelectron spectroscopy workstation is provided, comprising a base, a turbomolecular pump, a rotary vane vacuum pump, a connecting pipe, an adsorption tube, an adsorption trap and a fast sample introduction chamber, wherein the turbomolecular pump and the rotary vane vacuum pump are both fixedly mounted on the base, the turbomolecular pump and the rotary vane vacuum pump are connected via a connecting pipe, an adsorption tube is arranged in the middle of the connecting pipe, an adsorption trap is arranged in the adsorption tube, an adsorbent is stored in the adsorption trap, and a fast sample introduction chamber is detachably mounted on the top of the turbomolecular pump;

[0006] The adsorption tube includes a tube body, a tube cover and a sealing gasket. The tube body has an inner cavity. The inner wall of the tube body is provided with a card slot. The adsorption trap is card-connected with the card slot. The outer ring of the tube body is provided with an installation groove. The installation groove is connected with the card slot. A sealing gasket is installed in the installation groove. One end of the tube cover is hinged to the tube body, and the other end of the tube cover is connected to the tube body by bolts and nuts.

[0007] Furthermore, the tube body includes a tube body, a hinged plate 1 and a fixed plate 1, the hinged plate 1 and the fixed plate 1 are respectively fixedly connected at both ends of the tube body, the tube cover includes a cover body, a hinged plate 2 and a fixed plate 2, the hinged plate 2 and the fixed plate 2 are respectively fixedly connected at both ends of the cover body, the hinged plate 1 is hinged to the hinged plate 2, the fixed plate 1 and the fixed plate 2 are connected by bolts and nuts, and the length of the fixed plate 2 is greater than the length of the fixed plate 1, so that the tube cover can be rotated by pushing the fixed plate 2.

[0008] Furthermore, the heights of the sealing gasket, the mounting groove and the pipe cover are consistent, and the height of the clamping groove is smaller than the height of the mounting groove.

[0009] Furthermore, both ends of the sealing gasket have outward protrusions, and the protrusions have guide surfaces and pressure surfaces. The guide surfaces are inclined inward in the direction close to the two ends of the sealing gasket, and the guide surfaces are in contact with the inner wall of the installation groove. One group of pressure surfaces corresponds to hinge plate two, and the other group of pressure surfaces corresponds to fixed plate two.

[0010] Furthermore, the adsorption trap comprises a storage box, which is engaged with the card slot, and a plurality of groups of sieve holes are passed through the top and the bottom of the storage box, and the adsorbent is stored in the storage box.

[0011] Furthermore, a rib is fixedly connected to the inner side wall of the storage box, thereby increasing the stability of the storage box and preventing the storage box from being deformed.

[0012] Furthermore, the storage box and the adsorption tube are coaxially arranged, and the axis direction of the adsorption tube is the vertical direction.

[0013] Furthermore, a bypass pipe is fixedly connected to one side of the connecting pipe, both ends of the bypass pipe are connected to the connecting pipe, and the adsorption pipe is located between the openings at both ends of the bypass pipe.

[0014] Furthermore, an oil vapor valve and an air valve are provided in the connecting pipe. The oil vapor valve is located between the upper opening of the bypass pipe and the adsorption pipe, and the air valve is located between the lower opening of the bypass pipe and the adsorption pipe. A quick air extraction valve is provided in the bypass pipe.

[0015] The beneficial effects of the utility model are:

[0016] 1. The adsorption tube of the utility model is composed of a tube cover, a tube body and a sealing gasket. One end of the tube cover is hinged to the tube body, and the other end of the tube cover is connected to the tube body through two sets of bolts and nuts. When replacing the adsorbent, it is only necessary to unscrew the two sets of bolts and nuts, remove the sealing gasket, and replace the adsorption trap in the card slot. There is no need to move the pump body or remove the adsorption tube. The replacement process is simple and the replacement speed is fast.

[0017] 2. The utility model is provided with a sealing gasket, which seals the gap between the tube cover and the tube body through the squeezing effect of the tube cover, thereby preventing the outside atmosphere from entering the connecting tube and affecting the vacuum degree inside the device.

[0018] 3. The utility model is provided with a bypass pipe, which greatly speeds up the efficiency of rough extraction in the initial stage, and is provided with an oil vapor valve, an air valve and a quick exhaust valve. Through the different opening and closing states of the three valves, different needs in the vacuum extraction process are met, the ineffective waste of the adsorbent is reduced, and the utilization rate of the adsorbent is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a front view cross-sectional schematic diagram of a gas path system applied to a vacuum photoelectron spectroscopy workstation provided by the utility model;

[0020] Figure 2 This is a schematic diagram of the overall structure of a gas path system applied to a vacuum photoelectron spectroscopy workstation provided by the utility model;

[0021] Figure 3 yes Figure 1 A magnified view of the structure at center A;

[0022] Figure 4 This is a three-dimensional structural schematic diagram of a tube cover and a tube body when they are opened in a gas path system of a vacuum photoelectron spectroscopy workstation provided by the utility model;

[0023] Figure 5 This is a three-dimensional structural schematic diagram of a sealing gasket in a gas path system used in a vacuum photoelectron spectroscopy workstation provided by the utility model;

[0024] Figure 6 The utility model provides a top view and cross-sectional schematic diagram of an adsorption tube and an adsorption trap in a gas path system used in a vacuum photoelectron spectroscopy workstation;

[0025] Figure 7 The utility model provides a three-dimensional structural cross-sectional schematic diagram of a storage box in a gas path system used in a vacuum photoelectron spectroscopy workstation.

[0026] Description of main symbols:

[0027] 1. Base; 2. Turbomolecular pump; 3. Rotary vane vacuum pump; 4. Connecting pipe; 41. Bypass pipe; 42. Oil vapor valve; 43. Air valve; 44. Quick exhaust valve; 5. Adsorption tube; 51. Tube body; 511. Tube body; 512. Hinge plate 1; 513. Fixed plate 1; 52. Tube cover; 521. Cover body; 522. Hinge plate 2; 523. Fixed plate 2; 53. Sealing gasket; 531. Protrusion; 532. Guide surface; 533. Pressure surface; 54. Inner cavity; 55. Card slot; 56. Mounting slot; 6. Adsorption trap; 61. Storage box; 62. Sieve hole; 63. Rib plate; 7. Quick sample injection chamber. DETAILED DESCRIPTION

[0028] The subject matter described herein will now be discussed with reference to example embodiments. It should be understood that the discussion of these embodiments is to enable those skilled in the art to better understand and implement the subject matter described herein. The functions and arrangements of the elements discussed may be changed without departing from the scope of protection of the present specification. Various examples may omit, replace or add various processes or components as needed. In addition, the features described relative to some examples may also be combined in other examples.

[0029] Embodiment 1:

[0030] like Figure 1-Figure 7 As shown, a gas path system applied to a vacuum photoelectron spectroscopy workstation includes a base 1, a turbomolecular pump 2, a rotary vane vacuum pump 3, a connecting pipe 4, an adsorption tube 5, an adsorption trap 6 and a fast injection chamber 7. The turbomolecular pump 2 and the rotary vane vacuum pump 3 are both fixed on the base 1, and the turbomolecular pump 2 and the rotary vane vacuum pump 3 are connected by a connecting pipe 4. An adsorption tube 5 is arranged in the middle of the connecting pipe 4, and an adsorption trap 6 is arranged in the adsorption tube 5. An adsorbent is stored in the adsorption trap 6. The fast injection chamber 7 is detachably installed on the top of the turbomolecular pump 2.

[0031] In this embodiment, the fast sampling chamber 7 is fixedly installed on the top of the turbomolecular pump 2 through a flange, one end of the connecting pipe 4 is connected to the exhaust pipe of the turbomolecular pump 2 through a flange, and the other end of the connecting pipe 4 is connected to the intake pipe of the rotary vane vacuum pump 3 through a flange. When the turbomolecular pump 2 absorbs non-rare gas, the collision between gas molecules is not an elastic collision, which will affect the performance of the turbomolecular pump 2. When evacuating, the rotary vane vacuum pump 3 first performs rough pumping to gradually reduce the air pressure in the fast sampling chamber 7 to the operating range of the turbomolecular pump 2, and then the turbomolecular pump 2 performs vacuuming.

[0032] The adsorption tube 5 includes a tube body 51, a tube cover 52 and a sealing gasket 53. The tube body 51 has an inner cavity 54. The inner wall of the tube body 51 is provided with a card slot 55. The adsorption trap 6 is card-engaged with the card slot 55. The outer ring of the tube body 51 is provided with a mounting groove 56. The mounting groove 56 is communicated with the card slot 55. The sealing gasket 53 is installed in the mounting groove 56. One end of the tube cover 52 is hinged to the tube body 51, and the other end of the tube cover 52 is connected to the tube body 51 by bolts and nuts.

[0033] In this embodiment, the tube body 51 is welded to the middle part of the connecting tube 4, and the inner cavity 54 of the tube body 51 is connected to the inside of the connecting tube 4. The bolts and nuts are unscrewed, the tube cover 52 is turned off, the sealing gasket 53 is taken out from the installation groove 56, and then the adsorption trap 6 is taken out from the card slot 55. The new adsorption trap 6 is replaced to complete the replacement of the adsorbent.

[0034] The tube body 51 includes a tube body 511, a hinged plate 512 and a fixed plate 513, which are fixedly connected at both ends of the tube body 511 respectively. The tube cover 52 includes a cover body 521, a hinged plate 522 and a fixed plate 523, which are fixedly connected at both ends of the cover body 521 respectively. The hinged plate 512 is hinged to the hinged plate 522, and the fixed plate 513 and the fixed plate 523 are connected by bolts and nuts. The length of the fixed plate 523 is greater than that of the fixed plate 513, so that the tube cover 52 can be rotated by pushing the fixed plate 523.

[0035] In this embodiment, the fixing plate 1 513 is penetrated by a through hole 1, the fixing plate 2 523 is penetrated by a through hole 2, the through hole 2 corresponds to the through hole 1, and the bolts are passed through the through hole 1 and the through hole 2.

[0036] The sealing gasket 53 , the mounting groove 56 and the pipe cover 52 have the same height, and the height of the clamping groove 55 is smaller than the height of the mounting groove 56 .

[0037] In this embodiment, the sealing gasket 53 installed in the installation groove 56 will cover the upper and lower edges of the adsorption trap 6. After the tube cover 52 is installed on the tube body 51 by means of bolts and nuts, the tube cover 52 presses the sealing gasket 53, and the sealing gasket 53 seals the upper and lower ends of the installation groove 56 to prevent the outside atmosphere from entering the inner cavity 54 through the gaps at the upper and lower ends of the installation groove 56.

[0038] Both ends of the sealing gasket 53 have outward protrusions 531, and the protrusions 531 have guide surfaces 532 and pressure surfaces 533. The guide surfaces 532 are inclined inwardly arranged in a direction close to the two ends of the sealing gasket 53, and the guide surfaces 532 are in contact with the inner wall of the mounting groove 56. One group of pressure surfaces 533 corresponds to the hinge plate 2 522, and the other group of pressure surfaces 533 corresponds to the fixed plate 2 523.

[0039] In this embodiment, when the tube cover 52 is installed on the tube body 51 by means of bolts and nuts, the hinge plate 522 squeezes the pressure surface 533 of one group of protrusions 531, and the fixed plate 523 squeezes the pressure surface 533 of the other group of protrusions 531. The guide surface 532 plays a guiding role so that the sealing gasket 53 can completely enter the installation groove 56, so that the two groups of guide surfaces 532 of the two groups of protrusions 531 are tightly fitted with the inner walls on both sides of the installation groove 56, thereby sealing the left and right ends of the installation groove 56 to prevent the outside atmosphere from entering the inner cavity 54 through the gaps at the left and right ends of the installation groove 56.

[0040] In this embodiment, there are two groups of bolts and nuts to ensure that when the pipe cover 52 is installed on the pipe body 51 through the bolts and nuts, the sealing gasket 53 is evenly stressed, thereby improving the sealing effect.

[0041] The adsorption trap 6 comprises a storage box 61 , which is engaged with the card slot 55 . A plurality of groups of sieve holes 62 are penetrated through the top and the bottom of the storage box 61 . Adsorbent is stored in the storage box 61 .

[0042] In this embodiment, the adsorbent is activated alumina with a particle size of 3 to 6 mm. The activated alumina has a good oil blocking effect and has a relatively low impact on the pumping speed of the pump. The aperture of the sieve hole 62 is smaller than the particle size of the activated alumina to prevent the activated alumina from leaking out of the sieve hole 62.

[0043] The inner wall of the storage box 61 is fixedly connected with a rib plate 63, so as to increase the stability of the storage box 61 and prevent the storage box 61 from being deformed.

[0044] In this embodiment, the rib plate 63 is in a circular ring shape and is fixedly connected to the middle of the inner wall of the storage box 61 to prevent the sealing gasket 53 from being squeezed during the connection between the tube cover 52 and the tube body 51, thereby squeezing the storage box 61 and deforming the storage box 61, affecting the sealing effect.

[0045] The storage box 61 is coaxially arranged with the adsorption tube 5 , and the axis direction of the adsorption tube 5 is the vertical direction.

[0046] In this embodiment, the upper and lower surfaces of the storage box 61 are parallel to the horizontal plane, and the activated alumina is spread flat inside the storage box 61. The oil vapor refluxed by the rotary vane vacuum pump 3 will be adsorbed by the activated alumina, and there will be no dead corners.

[0047] The present embodiment proposes a gas path system for a vacuum photoelectron spectroscopy workstation that is easy to replace the adsorbent. When replacing, unscrew the two sets of bolts and nuts, push the fixing plate 2 523 to rotate the tube cover 52, then take out the sealing gasket 53 from the installation groove 56, and then take out the adsorption trap 6 from the card slot 55, replace the new adsorption trap 6, and the adsorbent can be replaced. After the replacement is completed, the tube cover 52 is fixedly installed on the tube body 51 with bolts and nuts according to the reverse steps above to complete the sealing of the adsorption tube 5.

[0048] Embodiment 2:

[0049] like Figure 1 and Figure 2 As shown, this embodiment is a further improvement on the basis of Embodiment 1 in that a bypass pipe 41 is fixedly connected to one side of the connecting pipe 4 , both ends of the bypass pipe 41 are connected to the connecting pipe 4 , and the adsorption pipe 5 is located between the openings at both ends of the bypass pipe 41 .

[0050] In this embodiment, the bypass pipe 41 is U-shaped, the upper opening of the bypass pipe 41 is located above the adsorption tube 5, and the upper opening of the bypass pipe 41 is connected to the connecting pipe 4 between the rotary vane vacuum pump 3 and the adsorption tube 5, the lower opening of the bypass pipe 41 is located below the adsorption tube 5, and the lower opening of the bypass pipe 41 is connected to the connecting pipe 4 between the turbomolecular pump 2 and the adsorption tube 5. By adding the bypass pipe 41, the exhaust time can be shortened, so that the rapid injection chamber 7 can reach a vacuum state in a relatively short time.

[0051] An oil vapor valve 42 and an air valve 43 are provided in the connecting pipe 4. The oil vapor valve 42 is located between the upper opening of the bypass pipe 41 and the adsorption pipe 5. The air valve 43 is located between the lower opening of the bypass pipe 41 and the adsorption pipe 5. A quick air extraction valve 44 is provided in the bypass pipe 41.

[0052] In this embodiment, the oil vapor valve 42 and the air valve 43 are used to control whether the gas in the connecting pipe 4 passes through the adsorption pipe 5 , and the quick air extraction valve 44 is used to control the opening and closing of the bypass pipe 41 .

[0053] This embodiment proposes a vacuum extraction method. First, the oil vapor valve 42 and the air valve 43 are closed, the quick air extraction valve 44 is opened, and the rotary vane vacuum pump 3 is started to perform quick rough extraction. During this process, the air in the quick sampling chamber 7 is extracted by the rotary vane vacuum pump 3. The air can only be extracted from the bypass pipe 41 and will not enter the adsorption tube 5, so as to prevent humid air from entering the adsorption tube 5. The adsorbent absorbs the humid air and affects its oil blocking effect.

[0054] When the air pressure in the fast sampling chamber 7 is pumped to a lower level (lower than 10Pa), the oil vapor valve 42 and the air valve 43 are opened, the fast air extraction valve 44 is closed, and the turbomolecular pump 2 is started to complete the subsequent vacuuming. During this process, the air in the fast sampling chamber 7 is simultaneously extracted by the turbomolecular pump 2 and the rotary vane vacuum pump 3, and the air will pass through the adsorption tube 5 instead of the bypass pipe 41. At the same time, the rotary vane vacuum pump 3 generates heat during operation. The vaporized oil vapor in the rotary vane vacuum pump 3 will be adsorbed by the adsorbent in the storage box 61 when flowing through the adsorption tube 5, thereby preventing the oil vapor from entering the turbomolecular pump 2.

[0055] When the air pressure in the rapid injection chamber 7 reaches a certain level (less than 10 -3 Pa), close the oil vapor valve 42 and the air valve 43 to prevent the adsorbent from continuing to absorb a large amount of oil vapor, turn off the turbomolecular pump 2 and the rotary vane vacuum pump 3, and the vacuuming is completed.

[0056] The embodiment of the present embodiment is described above in conjunction with the accompanying drawings, but the present embodiment is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the enlightenment of the present embodiment, ordinary technicians in this field can also make many forms without departing from the purpose of the present embodiment and the scope of protection of the claims, all of which are within the protection of the present embodiment.

Claims

1. A gas path system used in a vacuum photoelectron spectroscopy workstation, It is characterized in that The invention comprises a base (1), a turbomolecular pump (2), a rotary vane vacuum pump (3), a connecting pipe (4), an adsorption tube (5), an adsorption trap (6) and a fast sample injection chamber (7); the turbomolecular pump (2) and the rotary vane vacuum pump (3) are both fixedly mounted on the base (1); the turbomolecular pump (2) and the rotary vane vacuum pump (3) are connected via the connecting pipe (4); an adsorption tube (5) is arranged in the middle of the connecting pipe (4); an adsorption trap (6) is arranged in the adsorption tube (5); an adsorbent is stored in the adsorption trap (6); and a fast sample injection chamber (7) is detachably mounted on the top of the turbomolecular pump (2); The adsorption tube (5) comprises a tube body (51), a tube cover (52) and a sealing gasket (53); the tube body (51) has an inner cavity (54); the inner wall of the tube body (51) is provided with a clamping groove (55); the adsorption trap (6) is clamped with the clamping groove (55); the outer ring of the tube body (51) is provided with a mounting groove (56); the mounting groove (56) is communicated with the clamping groove (55); a sealing gasket (53) is installed in the mounting groove (56); one end of the tube cover (52) is hinged to the tube body (51); and the other end of the tube cover (52) is connected to the tube body (51) through bolts and nuts.

2. A gas path system for a vacuum photoelectron spectroscopy workstation according to claim 1, It is characterized in that The tube body (51) comprises a tube body (511), a hinged plate 1 (512) and a fixed plate 1 (513), wherein the hinged plate 1 (512) and the fixed plate 1 (513) are respectively fixedly connected at two ends of the tube body (511), and the tube cover (52) comprises a cover body (521), a hinged plate 2 (522) and a fixed plate 2 (523), wherein the hinged plate 2 (522) and the fixed plate 2 (523) are respectively fixedly connected at two ends of the cover body (521), the hinged plate 1 (512) is hingedly connected to the hinged plate 2 (522), the fixed plate 1 (513) and the fixed plate 2 (523) are connected by bolts and nuts, and the length of the fixed plate 2 (523) is greater than the length of the fixed plate 1 (513).

3. The gas path system used in a vacuum photoelectron spectroscopy workstation according to claim 2, It is characterized in that The sealing gasket (53), the mounting groove (56) and the pipe cover (52) are all of the same height, and the height of the clamping groove (55) is smaller than the height of the mounting groove (56).

4. The gas path system used in a vacuum photoelectron spectroscopy workstation according to claim 3, It is characterized in that Both ends of the sealing gasket (53) have outward protrusions (531), and the protrusions (531) have guide surfaces (532) and pressure surfaces (533). The guide surfaces (532) are arranged inwardly and inclined in a direction close to the two ends of the sealing gasket (53). The guide surfaces (532) are in contact with the inner wall of the installation groove (56), one group of pressure surfaces (533) corresponds to the second hinge plate (522), and the other group of pressure surfaces (533) corresponds to the second fixed plate (523).

5. The gas path system used in a vacuum photoelectron spectroscopy workstation according to claim 4, It is characterized in that The adsorption trap (6) comprises a storage box (61), the storage box (61) is snap-connected with the card slot (55), a plurality of groups of sieve holes (62) are penetrated through the top and bottom of the storage box (61), and an adsorbent is stored in the storage box (61).

6. A gas path system for a vacuum photoelectron spectroscopy workstation according to claim 5, It is characterized in that The inner side wall of the storage box (61) is fixedly connected with a rib plate (63).

7. A gas path system for a vacuum photoelectron spectroscopy workstation according to claim 6, It is characterized in that The storage box (61) is coaxially arranged with the adsorption tube (5), and the axial direction of the adsorption tube (5) is the vertical direction.

8. The gas path system used in a vacuum photoelectron spectroscopy workstation according to claim 1, It is characterized in that A bypass pipe (41) is fixedly connected to one side of the connecting pipe (4), both ends of the bypass pipe (41) are in communication with the connecting pipe (4), and the adsorption pipe (5) is located between the openings at both ends of the bypass pipe (41).

9. The gas path system used in a vacuum photoelectron spectroscopy workstation according to claim 8, It is characterized in that An oil vapor valve (42) and an air valve (43) are arranged in the connecting pipe (4); the oil vapor valve (42) is located between the upper opening of the bypass pipe (41) and the adsorption pipe (5); the air valve (43) is located between the lower opening of the bypass pipe (41) and the adsorption pipe (5); and a quick air extraction valve (44) is arranged in the bypass pipe (41).

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