CN212180609U

CN212180609U - Optical window assembly and spectrometer

Info

Publication number: CN212180609U
Application number: CN202020698179.3U
Authority: CN
Inventors: J·拉斯坎普; T·沃尔夫
Original assignee: Thermo Fisher Scientific Bremen GmbH
Current assignee: Thermo Fisher Scientific Bremen GmbH
Priority date: 2020-03-09
Filing date: 2020-04-30
Publication date: 2020-12-18
Anticipated expiration: 2030-04-30
Also published as: DE202020101270U1

Abstract

The utility model relates to an optical window sub-assembly (10), it is used with the plasma chamber of spectrum appearance together, and include: a frame member comprising at least one optical window (131); a first housing part (11) comprising at least one first opening; a second housing component comprising at least one second opening; a first guide member and a second guide member (15). The first housing component and the second housing component collectively define a chamber for receiving the frame component such that the at least one optical window, the at least one first opening, and the at least one second opening are aligned. The chamber can be opened or closed by a movement (A; B) of the guide member relative to the housing member. The guide members may be connected by a handle (16). The optical window assembly allows for simple and quick replacement of the transparent element without the need for special tools. The utility model discloses still relate to a spectrum appearance.

Description

Optical window assembly and spectrometer

Technical Field

The present invention relates to an optical window assembly for use with a plasma chamber, in particular a plasma chamber of a spectrometer, such as an inductively coupled plasma mass spectrometer (ICP-MS) or an inductively coupled plasma optical emission spectrometer (ICP-OES).

Background

It is well known to use plasma sources in spectrometers, such as emission spectrometers and mass spectrometers. A plasma source, such as an Inductively Coupled Plasma (ICP) source, generates a plasma in which atoms and molecules can be ionized. Extremely high temperatures may occur in such plasmas, such as temperatures of 8,000K or even 10,000K. For example, by

(Thermo Fisher

) Produced Thermo Scientific^TM iCAP^TMThe 7000ICP-OES analyzer system has a plasma chamber with a plasma torch housed therein. When the plasma torch is housed in the plasma chamber, the plasma chamber is commonly referred to as a torch box.

In optical emission spectrometers, light generated by a plasma in the presence of an analyte is analyzed. In mass spectrometers that do not typically analyze light generated by the plasma, there may still be a need to observe the plasma and/or capture light emitted by the plasma. To this end, one or more viewing ports may be arranged in the spectrometer. Axial and/or radial viewing ports may be provided to allow axial and/or radial viewing of the plasma. Such viewing ports, which may also be referred to as optical windows, are typically enclosed by transparent elements to contain heat and control airflow. However, such transparent elements, which are usually composed of heat-resistant glass plates, may become dirty during use due to deposits from the plasma. This reduces the effectiveness of the viewing port. Although the transparent element can be replaced in some spectrometer models, this is often difficult and requires skilled technicians.

SUMMERY OF THE UTILITY MODEL

The present invention seeks to solve this problem by providing an optical window assembly for use in a plasma chamber which allows the transparent element to be simply and quickly replaced without the need for special tools. The present invention additionally seeks to provide an optical window assembly which allows for simple and fast sealing of the assembly.

Accordingly, the present invention provides an optical window assembly for use with a plasma chamber of a spectrometer, the optical window assembly comprising:

-a frame part comprising at least one optical window,

a first housing part comprising at least one first opening,

a second housing part comprising at least one second opening,

-a first guide member, and

-a second guide member for guiding the second guide member,

wherein the first housing part and the second housing part are arranged to together define a chamber for accommodating the frame part such that the at least one optical window, the at least one first opening and the at least one second opening are aligned, and

wherein the first housing part and the second housing part are movably connected to the guide part such that when the guide part is moved in a first direction relative to the housing parts, the second housing part is moved away from the first housing part to allow the frame part to be removed from the chamber, and when the guide part is moved in a second direction opposite to the first direction relative to the housing parts, the second housing part is moved towards the first housing part, thereby pressing the housing parts against the frame part.

By providing a frame member containing at least one optical window and housing the frame member in a housing having two portions that can be removed, the frame member can be easily removed when necessary and the optical window can be cleaned or replaced. By providing a mechanism that can close the housing and press the housing parts against the frame part, a good sealing and thus a good control of heat and air flow can be obtained.

Since the relative movement of the guide parts opens the housing and separates the housing parts, the removal of the frame part can be achieved without special tools and without expert knowledge. Thus, maintenance of the optical window assembly is significantly simplified.

In an embodiment, the frame part is substantially planar, while the first direction is substantially in the plane of the frame part and the second direction is also in the plane of the frame part. In such embodiments, the relative movement of the guide member in the first and second directions may be substantially in the plane of the frame member or substantially parallel to the frame member.

Preferably, each guide member has a longitudinal direction and comprises a set of first slots for receiving the projections of the first housing member and a set of second slots for receiving the projections of the second housing member, wherein the first slots extend substantially parallel to the longitudinal direction and wherein the second slots extend at an acute angle to the longitudinal direction. That is, the protrusion of the housing component engages the slot in the guide component. When the guide member moves relative to the housing member, the projection is guided by the slot, thereby determining the movement of the housing member. Since the first slot extends substantially parallel to the longitudinal direction of the guide member, the first housing part is only movable in the longitudinal direction relative to the guide member. However, the second slot extends at a non-zero angle with respect to the longitudinal direction, causing the second housing part to move not only in the longitudinal direction, but also in a direction substantially perpendicular to the longitudinal direction, causing the housing parts to move away from or towards each other.

While the second slots may be substantially straight with a constant non-zero angle, it is preferred that the second slots have a varying angle. That is, the second slot may not have a non-zero angle over its entire length with respect to the longitudinal direction of the guide member. This results, for example, in a non-zero angle and thus a vertical movement during a first part of the closing movement, and in a zero angle and thus no vertical movement of the second housing part during a second part of the closing movement of the guide part relative to the housing.

In a preferred embodiment, the second slot may further comprise a ridge defining the closed position. That is, such small ridges in the second slot may define a minimum distance between the housing components. Thus, the ridge may define a boundary between two portions of the slot having different angles.

Preferably, the projections comprise rollers or other rotating parts, as the rotating parts reduce friction. However, in some embodiments, fixed pins may be used instead of rollers.

The guide members may be located on respective opposite sides of the housing member and the projections may extend from those sides of the housing member.

The guide members are preferably connected by a handle member. Such a handle member enables the two guide members to be operated in a single movement while providing convenience to the user. The guide member preferably has an extension to which the handle member is attached. The extension is preferably shaped in such a way that: the handle member is spaced from the housing member so that, in use, the handle member does not interfere with the frame member when the handle member is removed from the housing.

In an advantageous embodiment, the frame part comprises two optical windows, while the first housing part comprises two first openings and the second housing part also comprises two second openings. In use, each of the optical windows is aligned with the first and second openings. Embodiments having three or more optical windows, a first opening and a second opening are also contemplated.

At least one optical window is preferably provided with a transparent element for sealingly closing the optical window, a sealing element and an elastic element. The transparent member may comprise quartz glass.

The optical window assembly may further comprise at least one first additional sealing element and at least one second additional sealing element for sealing the frame member to the first and second housing parts, respectively.

The frame member may be provided with a frame handle for inserting and removing the frame member into and from the chamber. The frame handle may be constituted by a substantially flat portion of the frame part extending substantially in the longitudinal direction of the frame part. The frame handle may be slightly inclined relative to the plane of the frame member to facilitate handling. In addition, the frame handle may be provided with transverse ribs and/or slots to further facilitate handling by the user.

The optical window assembly according to the present invention may further comprise at least one tube connector for movably connecting the chamber to an optical tube extending into the plasma chamber, e.g. a so-called periscope. At least one tube connector may extend from the second housing part, in particular from a side facing away from the chamber, for holding the frame part.

The present invention further provides a spectrometer comprising an optical window assembly as described above. For example, the spectrometer may be a mass spectrometer or an optical emission spectrometer. A mass spectrometer according to the present invention may further comprise one or more torches, a plasma chamber, multipole ion optics and at least one ion detector.

Drawings

Fig. 1 schematically illustrates a perspective view of an optical window assembly according to the present invention when closed.

Fig. 2 schematically shows a perspective view of the optical window assembly of fig. 1 when opened.

Fig. 3 schematically shows a detail of the mechanism of fig. 1 and 2 in an enlarged view.

Fig. 4 schematically illustrates an exploded view of a frame member of the optical window assembly of fig. 1 and 2.

Fig. 5 schematically shows an exploded view of the optical window assembly of fig. 1 and 2.

Figure 6 schematically illustrates the mounting of an optical window assembly according to the present invention between a torch cartridge and a polychromator.

Detailed Description

It is an object of the present invention to provide an optical window assembly for use with a plasma chamber of a spectrometer, in particular an ICP (inductively coupled plasma) spectrometer, such as an ICP-MS (mass spectrometer) or ICP-OES (optical emission spectrometer).

Only exemplary embodiments of an optical window assembly for use with a plasma chamber of a spectrometer are schematically depicted in fig. 1 and 2, wherein the optical window assembly is shown in a closed state in fig. 1 and in an open state in fig. 2. The optical window assembly 10 according to the present invention depicted in fig. 1 and 2 includes: a frame member 13 including two optical windows 131; a first housing part 11 comprising two first openings 111; and a second housing part 12 including two second openings (121 in fig. 5).

The combination of the optical window 131, the first opening 111, and the second opening 121 constitutes an observation port for observing plasma in the plasma chamber. Typically, optical window assembly 10 will be mounted on top of a plasma chamber (e.g., a torch box) in which a plasma is generated. The tube holder 128 is aligned with the first opening 111 and the second opening (121 in fig. 5) and is arranged to receive an optical viewing tube, for example a so-called periscope. The tube holder 128 is arranged in such a manner: the optical sight tube may slide relative to the tube holder so that the second housing part 12 may be moved up and down while the optical sight tube is in place, as will be explained in more detail below.

In the illustrated embodiment, there are two viewing ports that allow, for example, axial and radial viewing of the plasma. However, the present invention is not limited to two view ports, and may be equally applied to a plasma chamber having a single view port or three or more view ports.

An example of an ICP plasma chamber suitable for use with the optical window assembly of the present invention is described in uk patent application No. 1905069.9 (seemer fly-seoul technology) filed on day 10, 4/2019.

The optical window assembly of fig. 1 and 2 is further shown to include a first guide member 14 and a second guide member 15. In the illustrated embodiment, the first guide member 14 is arranged on a first side of the

housing parts

11 and 12, while the second guide member 15 is arranged on an opposite second side of the housing parts. In this way, the housing part is held between the guide parts. The housing part is movably connected to the guide part, as will be explained in more detail later, in particular with reference to fig. 3. The limiting member 17 extends over the top surface of the first housing member 11 and over the side edges of the

guide members

14 and 15 so as to define the relative distance of the guide members and limit the guide members during their movement.

In the illustrated embodiment, the first housing part 11 and the second housing part 12 together define a chamber for accommodating the frame part 13. As illustrated in fig. 1, this chamber may be closed at its longitudinal sides and kept open at its two ends. In some embodiments,

housing components

11 and 12 may be substantially flat, without side walls, to accommodate frame component 13 without providing a partially closed chamber.

The first housing part 11, the second housing part 12 and the frame part 13 are arranged such that the optical window 131 of the frame part, the first opening 111 of the first housing part and the second opening 121 of the second housing part are aligned when the frame part 13 is accommodated between the housing parts (see also fig. 5).

The

guide members

14 and 15 are connected by a handle 16 which allows both guide members to be moved simultaneously. To provide a convenient location for the handle 16, the

guide members

14 and 15 have

extensions

141 and 151, respectively, which in the illustrated embodiment allow the handle to be positioned below the frame member 13 so that the handle 16 does not interfere when the frame member is removed from or placed into the optical window assembly, as will be explained below. Furthermore, the

extensions

141 and 151 are shaped in such a way: there is sufficient space between the frame handle 133 of the frame member 13 and the handle 16 to accommodate the fingers of the operator.

The first housing part 11 and the second housing part 12 are supported by

guide parts

14 and 15 such that the guide parts can move in a first direction a and an opposite second direction B relative to the housing parts, both directions being substantially in the plane of the frame part 13.

When the guide member is moved in the first direction a (leftward in fig. 1 and 2), the second housing member 12 is moved away from the first housing member 11 in a third direction C substantially perpendicular to the first direction a. In the example of fig. 1, this means that when the

guide members

14 and 15 are moved to the left, the second housing member 12 is moved downward. In contrast, when the

guide members

14 and 15 are moved in the second direction B (rightward in fig. 1 and 2) opposite to the first direction a, the second housing member 12 is moved in the fourth direction D (upward in fig. 1 and 2) perpendicular to both the first direction a and the second direction B. This movement in the third and fourth directions C, D is achieved by the cooperation of the slots and the projections, which will also be explained with reference to fig. 3.

It should be noted that the movement of the

guide members

14 and 15 relative to the

housing members

11 and 12 is facilitated since the

housing members

11 and 12 are prevented from moving in the first direction a and the second direction B. In the embodiment shown, the first or upper housing part 11 is provided with a threaded hole 117 for fixedly connecting the first housing part to another structure above the optical window assembly (see also fig. 6). Further, openings 115 are provided in the first housing part 11 to accommodate pins (125 in fig. 5) extending from the second housing part 12 towards the first housing part 11 and serving to limit the relative movement of the housing parts to movement in directions C and D (i.e. movement of the housing parts is limited to up and down movement in the illustrated embodiment).

As can be seen in fig. 1 and 2, the

guide members

14 and 15 are each provided with two first slots 21 and two second slots 22 (in fig. 5, the first slots of the guide members 14 are also illustrated). The tab 112 extends from the first housing part 11 into the first slot 21, while the tab 122 extends from the second housing part 12 into the second slot 22. It should be noted that the

projections

112 and 122 are preferably rotatable to reduce friction and may be rollers each having an integral axis.

It can be seen that the first slot 21 extends substantially along the longitudinal axis of the

guide members

14 and 15, while the second slot 22 extends at an acute angle relative to the longitudinal axis. When the protrusion (or roller) 112 of the first housing part 11 extends into the first slot, the relative movement of the

guide members

14 and 15 will keep the relative vertical position of the first housing part 11 unchanged. When the guide member is moved in direction a, a protrusion (or roller) 122 of the second housing part 12 extending into the second slot 22 will move the second housing part 12 away from the first housing part 11 in the third direction C. In the embodiment shown, this movement of the second housing part 12 is substantially perpendicular to the direction a, i.e. downwards. Thus, when the

guide members

14 and 15 are moved in direction a, the chamber formed by the

housing members

11 and 12 is opened, for example by pulling on a handle 16 connecting the guide members. As a result, the frame member 13 can be taken out for cleaning or replacement.

Similarly, when the

guide members

14 and 15 are moved in direction B, for example by pushing on the handle 16 to which the guide members are connected, the chamber formed by the

housing members

11 and 12 is closed when the second housing member 12 is moved upwards in direction D.

An exemplary embodiment of the second slot 22 is shown in more detail in fig. 3. The roller 122 is shown extending into the slot 22. The lower inner surface of slot 22 is shown as having two portions separated by a point 23. The main portion 24 has a rising slope towards the point 23. If the roller 122 moves from the main inclined portion 24 to the second inclined portion 25 via point 23, the roller moves first upwards and reaches its highest point at point 23. When the optical window assembly is closed, roller 122 is positioned on non-tilt portion 25. The point 23 at which the slope of the slot 22 changes may be referred to as a ridge.

In some embodiments, the main angled portion 24 has a varying slope, such as a steeper slope toward the right in fig. 3, to provide a faster initial closing movement.

It should be noted that the present invention is not limited to two first slots and two second slots. In some embodiments, three or more first and/or second slots may be provided.

In fig. 4, the frame part 13 and the various parts that can be mounted on the frame part are shown. A transparent element 136, preferably made of quartz glass, is fitted in the openings constituting the optical window 131 and rests on the ridges in these openings. The transparent element 136 may be sealed to the ridges in the frame part 13 by a frame seal 135.

On the other side of the transparent element 136, a wire spring 137 may be accommodated. These wire springs 137 may be curved wire frames as shown that may be pressed against the transparent element 136 while resting against the locking edge 132 provided in the optical window opening 131.

A first seal 138 may be received around the optical window at the top side of the frame member to seal to the first housing member (11 in fig. 1), while a second seal 139 may be received around the optical window at the bottom side of the frame member 13 to seal to the second housing member (12 in fig. 1). The first and

second seals

138 and 139 may be received in appropriate grooves in the frame members.

It will be appreciated that when the

shell parts

11 and 12 are moved together, as explained with reference to fig. 1 and 2, a good sealing of the frame part 13 to the

shell parts

11 and 12 can be obtained. The optical window assembly provides a hermetic seal. It can be seen that any higher relative pressure at the top side of the frame part 13 will press the transparent element 136 against the frame seal 135, thereby improving the seal. Indeed, there is typically a low pressure in the plasma chamber, which may be mounted below the optical window assembly (see, e.g., fig. 5), creating a high relative pressure above the optical window assembly.

Thus, the optical window assembly of the present invention not only allows for easy maintenance of the transparent element of the optical window, but also provides effective sealing to the plasma chamber, particularly to one or more optical sight tubes (e.g., periscopes) of the plasma chamber.

The frame member 13 of fig. 4 is also provided with a frame handle 133, which is shown extending from the frame member in the longitudinal direction. The frame handle is provided with ribs to facilitate handling by the operator. Furthermore, the frame handle 133 does not extend straight, but at an acute angle of between 15 ° and 30 ° relative to the plane of the frame part, again for ease of handling.

The frame member 13 is shown with a single cut-out angle 130 that is used to define the only position of the frame member 13 between the housing members. At least the second housing part has matching interior angles (120 in fig. 5) in the space forming the chamber for accommodating the frame part. Due to the corners 130 of the frame part and the mating corners 120 of the housing parts, it is not possible to assemble the frame part upside down, thereby preventing any accidental incorrect use of the frame part.

An exploded view of the embodiment of fig. 1 and 2 is shown in fig. 5. The optical window assembly 10 of fig. 5 also contains a first housing part 11, a second housing part 12, a frame part 13, and guide

parts

14 and 15 connected by a handle 16, which is fixed by screws 161. The limiting member 17 may be positioned to limit the movement of the

guide members

14 and 15. The upper seal 118 is shown fitting in a groove 119 in the first housing part 11 and is used to seal the optical window assembly to other parts, for example other parts of a spectrometer, such as a polychromator.

The second housing component 12 is shown with pins 125 that fit into openings 115 in the first housing component 11 to define the relative movement of the housing components. The combination of the openings 115 and the pins 125 allow the housing components to move vertically relative to each other while preventing any other movement. The tubular holder 128 allows the second housing part 12 to move vertically relative to the optical sight tube (7 in fig. 6). Push-fit gas fitting 127 allows gas to be drawn from or into the optical window assembly.

So-called spherical heads 129 are provided on either side of the second housing part 12 to lock the second housing part in at least one position, for example a fully closed position of the housing and/or a fully open position of the housing. A spherical head 129 comprising a small metal or plastic ball resiliently held in the mounting tube may fit into a suitable opening in the guide member.

The guide member 15 is shown as being provided with a first slot 21 and a second slot 22. The first slot 21 is arranged for receiving a first tab 112 connected with the first housing part 11. Similarly, the second slot 22 is arranged for receiving a second tab 122 connected with the second housing component 12. The projection 112 may be a roller, which may be connected to the first housing part 11 using a nut 113 and a ring 114. The tab 122 may be connected to the second housing component 12 in a similar manner.

Fig. 6 schematically shows an optical arrangement comprising an optical window assembly according to the present invention. The only exemplary arrangement 1 of fig. 6, not drawn to scale, is shown to include a polychromator 3, a plasma chamber 5 and an optical window assembly 10. The optical window assembly is shown to include a first housing part 11 and a second housing part 12 with a frame member (13 in fig. 5) received therebetween. Frame member frame handle 133 is shown extending from optical window assembly 10 (handle 16 is not shown in fig. 6 to simplify the drawing). An optical sight tube 7 extends from the plasma chamber 5 up into the optical window assembly 10 and bridges the gap 6 between the plasma chamber 5 and the optical window assembly 10. The optical viewing tube 7 is slidably received in a tube holder (128 in fig. 1, 2 and 5) such that the second or lower housing component 12 of the optical window assembly 10 can be moved down into the space 6 to allow the frame component 13 to be removed, as explained with reference to fig. 1 and 2.

In the embodiment shown, optical window assembly 10 is attached to polychromator 3. In particular, the first or upper housing part 11 can be screwed to the polychromator 3 at an interface S constituted by the bottom surface of the polychromator 3 and the top surface of the first or upper housing part 11. To this end, threaded holes (117 in fig. 5) may be provided in both the top surface of the first housing member 11 and the bottom surface of the polychromator 3. Since the polychromat is securely mounted in a housing or stand (not shown) containing the optical arrangement 1, the first or upper housing part 11 will remain in position when the guide member (14 and 15 in fig. 5) is pulled in the first direction a (to the left in fig. 6). Since the second or lower housing part 12 is slidably connected to the first or upper housing part 11 by means of the pins 125 and the corresponding openings 115, the second housing part 12 cannot be moved in the first direction a, but only in the third (or downward) direction C (see also fig. 2), which is achieved by the second slots of the guide members. Similarly, when the guide member is pushed in the second direction B (to the right in fig. 6), the second housing part 12 can only move in the fourth (or upward) direction D (see also fig. 2).

It will be appreciated that the invention works equally well when the device 3 is not a polychromator but another device that is fixed in position. Conversely, in some embodiments of the invention, the second or lower housing component may be fixed while the first or upper housing component is movable.

A spectrometer, e.g., a mass spectrometer, according to the present invention may include an optical window assembly, a plasma chamber, a multipole assembly, and at least one detector according to the present invention. In the case of an optical spectrometer, the multipole assembly may be omitted.

Although the invention has been described with reference to embodiments having a single frame member, embodiments having two or more frame members, each having at least one optical window, are contemplated. Such frame parts may be arranged in parallel in a single housing or in a corresponding plurality of housings.

Accordingly, it will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that many additions and modifications may be made without departing from the scope of the invention as defined in the appending claims.

Claims

1. An optical window assembly (10) for use with a plasma chamber of a spectrometer, the optical window assembly comprising:

a frame part (13) comprising at least one optical window (131),

a first housing part (11) comprising at least one first opening (111),

a second housing part (12) comprising at least one second opening (121),

a first guide member (14), and

a second guide member (15),

wherein the first housing part (11) and the second housing part (12) are arranged to jointly define a chamber for accommodating the frame part (13) such that the at least one optical window (131), the at least one first opening (111) and the at least one second opening (121) are aligned, and

wherein the first housing part (11) and the second housing part (12) are movably connected to the first guide part (14) and the second guide part (15), such that when the first and second guide members are moved in a first direction (A) relative to the first and second housing parts, the second housing part is moved away from the first housing part to allow the frame part to be removed from the chamber, and the second housing part moves towards the first housing part when the first and second guide parts move in a second direction (B) opposite to the first direction relative to the first and second housing parts, thereby pressing the first and second housing parts against the frame part.

2. Optical window assembly according to claim 1, wherein the frame part (13) is planar, wherein the first direction (a) is in the plane of the frame part, and wherein the second direction (B) is also in the plane of the frame part.

3. Optical window assembly according to claim 1 or 2, characterized in that each guiding member (14, 15) has a longitudinal direction and comprises a set of first slots (21) for accommodating first protrusions (112) of the first housing part (11) and a set of second slots (22) for accommodating second protrusions (122) of the second housing part (12), wherein the first slots (21) extend parallel to the longitudinal direction, and wherein the second slots (22) extend at an acute angle with respect to the longitudinal direction.

4. The optical window assembly of claim 3, wherein the second slot (22) has a varying angle.

5. The optical window assembly of claim 3, wherein the first and second protrusions comprise rollers.

6. The optical window assembly of claim 3, wherein the first and second guide members are located on respective opposite sides of the first and second housing parts (11, 12), and wherein the first and second protrusions extend from those sides of the first and second housing parts.

7. Optical window assembly according to claim 1 or 2, characterized in that the first guide member (14) and the second guide member (15) are connected by a handle member (16).

8. Optical window assembly according to claim 1 or 2, characterized in that the frame part (13) comprises two optical windows (131), wherein the first housing part (11) comprises two first openings (111), and wherein the second housing part (12) comprises two second openings (121).

9. Optical window assembly according to claim 1 or 2, characterized in that the at least one optical window (131) is provided with a transparent element (136), a sealing element (135) and an elastic element (137) for sealingly closing the optical window.

10. The optical window assembly of claim 9, wherein the transparent element (136) comprises quartz glass.

11. The optical window assembly according to claim 9, further comprising at least one first additional sealing element (138) and at least one second additional sealing element (139) for sealing the frame member (13) to the first housing member (11) and the second housing member (12), respectively.

12. Optical window assembly according to claim 1 or 2, characterized in that the frame part (13) is provided with a frame handle (133) for inserting and removing the frame part into and from the chamber.

13. The optical window assembly of claim 1 or 2, further comprising at least one tube connector (128) for movably connecting the chamber to an optical viewing tube (7).

14. The optical window assembly according to claim 4, wherein the second slot (22) comprises a ridge (23) defining a locking position.

15. Spectrometer, characterized in that it comprises an optical window assembly (10) according to any one of the preceding claims.

16. The spectrometer according to claim 15, wherein the spectrometer further comprises a plasma chamber (5) containing an inductively coupled plasma source.

17. The spectrometer of claim 15, wherein the spectrometer is a mass spectrometer or an optical emission spectrometer.