WO1998054752A1

WO1998054752A1 - A gas detector of quadrupole type

Info

Publication number: WO1998054752A1
Application number: PCT/SE1998/001039
Authority: WO
Inventors: Staffan Jonsson
Original assignee: Staffan Jonsson
Priority date: 1997-05-29
Filing date: 1998-05-29
Publication date: 1998-12-03
Also published as: AU7794598A; SE9702053D0

Abstract

The components of a gas detector of quadrupole type, such as shielding layers, collector, electrical through-connections, rods, etc., are minimized by being integrated into two ceramic blocks (1, 10) having intermediate rods (12) and through-connections and are joined by glass forming a compact unit. A bottom block (10) comprises a thicker base plate (16) having no recesses or holes, thereon a collector plate, including a shielding, and on the top a lens plate (18) including a shielding layer. The two latter plates have a set of similarly located holes (19, 20), through which the electrically conducting rods (12) for the quadrupoles pass with some play. The rods (12) are only at their end surfaces in contact with the other components such as at their lower ends to the base plate, where it is electrically connected to a conductor pattern. The lens plate (100) has additional holes for letting through ions between the rods (12). A top block (1) operates as input lens, ion chamber lens and ion chamber and has holes for letting through ions. The lower flat surface of the top blocks is directly secured to top end surfaces of the quadrupole rods (12). Between the blocks are in addition electrical connection rods provided. All plates are ceramic type and their different electric functions are provided by electrical conductor patterns on the surfaces thereof. The different parts are attached to each other by means of different types of glass joints also forming an isolation between electrically conducting regions. The play of the respective holes (19, 20) allows an accurate and simple positioning of the quadrupole rods when assembling the detector.

Description

A GAS DETECTOR OF QUADRUPOLE TYPE TECHNICAL FIELD

The present invention relates to a gas detector of the quadrupole type. BACKGROUND Conventionally constructed quadrupole detectors for determining gases or ions contain a lot of individual mechanical parts such as various attachment means, i.e. screws, nuts, washers, spot welding, etc. and are assembled in a mechanically complicated way. This can negatively influence the mechanical stability of such quadrupole detectors and increase their physical size, what in turn influences a number of o functional characteristics of such detectors.

U.S. patent 5,401 ,962 for Ferran discloses the basic construction of a quadrupole gas detector having a mechanical construction according to the discussion above comprising metal rods projecting from an electrically conducting base plate. U.S. patent

5,596,193 for Chutjian et al. discloses a quadrupole detector which has both upper and s lower, not electrically conducting retainer plates of insulator material capable of being precisely machined such as a glass or ceramic, for retaining the metal rods. The quadrupole rods are mounted in positioning cavities in the positioning plates, these cavities defining the positions of the quadrupole rods. The retainer plates are secured in positions apart from each other by separate support rods. These patents are incorporated o herein by reference.

SUMMARY

It is an object of the invention to provide a quadrupole detector which has a good mechanical stability and which can be assembled in a reliable and rather simple way.

Thus, in a quadrupole as described hereinafter the different parts of the quadrupole 5 detector are minimized and integrated, such as shielding layers, collector, electrical through-connections, rods, etc. The different parts are assembled to form two ceramic blocks having intermediate rods and through-connections. Substantially all the parts are bonded to each other by means of glass to form a compact unit, which can be called a fusioned miniature quadrupole. The two blocks are attached to each other only by the o intermediate rods which all have different electric functions and no support rods are provided for retaining the blocks at each other.

The fusioned miniature quadrupole is constructed of circular ceramic plates all having the same diameter, which all in addition have a simple configuration and comprise suitably placed, small circular holes having typical diameters of between 0.8 and 1 5 millimetre. The ceramic plates are coated with different thin-film and thick-film layers of e.g. gold, silver, silver/platinum, glass. Metallic, electrically conducting elements such as the rods and through-connections are integrated, attached and sealed to the ceramic parts using different types of glass joints.

The fusioned quadrupole detector has substantially the following construction. A

CONFIRMATION COPY bottom assembly or bottom block comprises a thick base ceramic plate having no recesses or holes intended for the quadrupole rods. On top of the base plate is another ceramic plate, a collector plate, located having layers acting as a lower shielding and a collector, and on top of this plate is a ceramic lens plate having a lower shielding layer provided. The two latter plates, the collector plate and the lens plate, have sets of identically located holes, in which the electrically conducting rods, the quadrupole rods, are placed with some play in order to form the quadrupoles. The rods are in electrical contact with conducting patterns on the surface of the base plate. The lens plate has additional holes for letting ions through between the quadrupole rods up to the collector. A top assembly o or top block comprising ceramic plates attached to each other acts as an input lens, an ion chamber lens and an ion chamber and has holes located in the same way as the holes of the lower lens plate. Between the bottom and top assemblies in addition three electrical connection rods for electrically connecting filaments and two rods for electrically connecting an ion chamber are provided. All plates are ceramic type whereas their s different electrical functions are essentially produced by various electrical conductor patterns and electrically conducting areas and regions located on their surfaces. The rods and the different plates are attached to each other by means of glass by arranging material suitable to form glass joints on the corresponding joining positions, such as between the plates in each block a glass layer or glass joint layer. The all of the components are o permanently attached by heating the assembly in an oven, making the glass material flow and wet opposite surfaces.

A conventional gas detector of quadrupole type, as generally described, comprises at its inlet an ion chamber and an input plate having at least one inlet opening. Each inlet opening opens into a channel between quadrupole rods, which are electrically conducting 5 and are supplied with suitable electric voltages and are located to form an electric quadrupole configuration. Further the gas detector comprises a lens device, a collector and a base plate. However, in order to allow an easy and very accurate positioning of the quadrupole rods, when the components of the detector are being assembled, at least at one of the ends of the quadrupole rods is attached with only the end surface of this end to 0 a substantially flat surface of a plate included in the gas detector, in an abutting mode end surface - flat surface. Preferably the quadrupole rods are attached in this way at their two ends. This arrangement allows an assembly of the detector not requiring accurate holes in any of the other components of the detector for guiding and positioning the quadrupole rods. Such accurately made holes in for instance two plates of the device will add a 5 considerable amount to the manufacturing cost of the detector. Instead a very accurate jig can be used in the assembly process, the jig being used for producing many detectors. After assembling the detector using the jig, the various components are permanently attached to each other by a heating process using glass joint material at suitable locations between the components. The lens device may be constituted by a lens plate and the collector a collector plate. The lens plate and the collector plate then have holes through which the quadrupole rods pass and these holes have diameters larger than diameters of the respective quadrupole rods. A play thus exists between inner walls of the holes and the exterior surfaces of the respective quadrupole rods what allows, when mounting the gas detector, that the quadrupole rods can be moved somewhat in order to be accurately positioned, in a way that is substantially unaffected by the exact location of said holes.

Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the methods, processes, instrumentalities and combinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

While the novel features of the invention are set forth with particularly in the appended claims, a complete understanding of the invention, both as to organization and content, and of the above and other features thereof may be gained from and the invention will be better appreciated from a consideration of the following detailed description of non-limiting embodiments presented hereinbelow with reference to the accompanying drawings, in which: Fig. 1 is an exploded perspective view of a bottom block in a gas detector of the quadrupole type constructed of ceramic plates and conducting patterns,

Fig. 2a is a partial sectional view of an electrical contacting area on a base plate for a quadrupole rod,

Fig. 2b is a partial sectional view of an electrical contacting region for an electrical through-connection to a lower shielding layer located below a collector plate,

Fig. 2c is a partial sectional view of the region at a hole passing through the base plate and having an electrical contacting area for connection to an electrical shielding layer around an electric pin intended for electrical connection with a collector,

Fig. 2d is a view from above of the base plate having an electrically conducting contact layer placed thereon,

Fig. 3 is a plan view of a glass layer arranged on top of the contact layer which is located on the base plate,

Fig. 4a is a partial sectional view of the region at a hole passing through the collector plate and enclosing an electrical through-connection to the collector, Fig. 4b is a plan view of a bottom, electrical shielding layer located below the collector plate and on top of the glass layer shown in Fig. 3,

Fig. 5a is a plan view in a larger scale of the region at an electrical contact for connection to a collector pattern,

Fig. 5b is a plan view of the collector pattern arranged on top of the collector plate, Fig. 6a is a plan view of a glass layer arranged on top of the collector pattern on the collector plate,

Fig. 6b is a plan view in a larger scale of a region of the glass layer in Fig. 6a at an electrical connection between a collector connection area and a collector connection pin,

Fig. 7a is a plan view in a larger scale of a region in a top shielding layer at the electrical connection between the collector connection area and the collector connection pin,

Fig. 7b is a partial sectional view of the region shown in Fig. 7a, Fig. 7c is a plan view of a top shielding layer, placed on top of the glass layer shown in Fig. 6a and located on the collector plate,

Fig. 8 is a plan view of a glass layer for attaching a support ring,

Fig. 9 is a perspective exploded view of a top block in the gas detector,

Fig. 10 is a plan view of a bottom glass layer in the top block, Fig. 11a is a partial sectional view of a region in an electrically conducting layer arranged below an input plate at the top end of an ion chamber pin,

Fig. l ib is a partial sectional view of a region in the electrically conducting layer below the input plate at the top end of another ion chamber pin,

Fig. l ie is a plan view of the electrically conducting layer located below the input plate,

Fig. 12a is a partial sectional view of a region in an electrically conducting layer arranged on top of the input plate at a connection area for electrical connection of an ion chamber,

Fig. 12b is a plan view of the electrically conducting layer located on top of the input plate,

Fig. 13 is a plan view of a glass pattern arranged on top of the conducting layer in Fig. 12b,

Fig. 14a is a perspective view of a reflector,

Fig. 14b is a partial sectional view of the region at a slotted opening of the ion chamber,

Fig. 14c is a view from above of the top block,

Fig. 15a is a side view of the gas detector, and

Fig. 15b is a sectional view taken along the line A-A in Fig. 15a.

DETAILED DESCRIPTION An embodiment of a gas quadrupole detector will be described in detail hereinafter.

Some details of the quadrupole detector are conventional and will therefore only be mentioned without being described in detail, see for these details in particular the above- cited U.S. patent 5,401 ,962 for Ferran. In this patent a detector is disclosed which functionally is close to that described herein. The function of the quadrupole detector is described in detail in this patent, from which also the functions of the details described herein below readily appears. Some similar details are also described in the above-cited U.S. patent 5,596,193 for Chutjian et al.

The quadrupole detector, which has a miniature size, see Fig. 15a, consists of a number of circular, basically electrically isolating ceramic plates having circular holes for electrical through-connections and electrically conducting rods. The ceramic plates form two blocks having large surfaces facing each other. The two blocks are located at a distance of each other, a top block 1 and a bottom block 10. Between the blocks extends a plurality of circular-cylindrical rods located perpendicularly between and mechanically and electrically connecting the ceramic blocks. The rods are secured to the top block and the bottom block and maintain them at accurately defined positions in relation to each other, in particular at definite distance of each other. The circular ceramic plates which all have the same exterior diameter and are components of the ceramic blocks, are at their surfaces coated with different thin-film and thick-film layers of e.g. gold, silver, platinum, glass.

The bottom ceramic block 10 is a laminated package consisting of three circular ceramic plates having layers coated on their surfaces: A base plate 16 including associated layers 16b, 16c; A collector plate 17 including associated layers 17a, 17b, 17c, the layer 17a being coated on the bottom side of the collector plate and the two other layers on the top side thereof; A lens plate 18 including associated layers 18a and 18b, the layer 18a being coated on the bottom side of the lens plate and the layer 18b on the top side thereof.

The quadrupole array consists of sixteen cylindrical quadrupole rods 12, which connect the bottom and top ceramic blocks 10, 1 and are precision mounted extending perpendicularly to the large surfaces of the blocks and the coating layers thereof. The quadrupole rods thus extend very accurately in parallel to each other and their positions in relation to each other are very accurately defined. The quadrupole rods 12 are at least partly of electrically conducting material and can be made of metal, e.g. stainless steel, titanium, or of ceramic material coated with an electrically conducting surface layer of a suitable material, e.g. gold. In a preferred embodiment the diameter of the rods are about one millimetre and their length about 20 millimetres.

The sixteen quadrupole rods 12 in the quadrupole array form nine square elements 14, i.e. they constitute corners in nine squares placed next to each other, see Fig. 2d, neighbouring rods being shared by neighbouring square elements 14. In the centre of each square element 14 a channel 15 is formed, the centre of each such channel 15 having equally large distances to the rods 12 included in the corresponding square element 14. Such a square element 14 including four rods and a channel 15 constitute a quadrupole element. Sixteen rods in rows of four including four rods in each row thus form nine quadrupole elements. The ceramic bottom assembly 10, see Fig. 1 , is, as has been indicated above, constructed of a ceramic circular base plate 16, a ceramic circular collector plate 17 and a ceramic circular lens plate 18 all having the same radii. The rods 12, which form the quadrupole array, rest with their lower flat ends on the top surface of the base plate 16

5 and pass through circular holes 19 in the collector plate 17 and circular holes 20 in the lens plate 18, the quadrupole rods being electrically isolated from electrically conducting layers on the collector plate and the lens plate. The holes 19 and 20 in the collector and lens plates letting the quadrupole rods 12 through have a diameter which is slightly larger than the diameter of these rods, e.g. with a play of between 10 and 50 μm, so that these ιo plates do not mechanically contact or touch the quadrupole rods. The top surface of the lens plate 18 is along all of its circular periphery enclosed by an annular mounting block 21 of metal, which continues into or is part of an annular mounting element 22 of metal. The bottom surface of the mounting block is by means of glass joints attached to the top surface of the lens plate 18 along a circular ring extending along the periphery of the is latter one. The mounting element 22 can be welded to other encapsulation, not shown, of the quadrupole detector, this encapsulation being made of stainless steel. The quadrupole rods 12 have their flat top end surfaces abutting and secured to the lower surface of the top block 100, see also Fig. 15a.

Cylindrical rods 3, 4, 5 of metal constitute electrical connection elements for

20 electrical connection to filaments, see the description hereinafter in conjunction with Fig. 14c, which filaments are located on the top surface of the input plate 100 in the top ceramic block 1. The filament rods 3, 4, 5 extend in parallel to the quadrupole rods 12 and pass through the base plate 16 in circular cylindrical holes 23a, 24a, 25a in which they are attached by means of glass joints. The same rods 3, 4, 5 pass through holes 23b,

2524b, 25b in the collector plate 17 and through holes 23c, 24c, 25c in the lens plate 18. The filament rods 3, 4, 5 are electrically isolated from the electrically conducting layers, which are applied between the ceramic plates 16, 17, 18 included in the bottom ceramic block 10.

Ion chamber pins or rods 8, 9, also of metal, constitute electrical conductors for

30 electrical connection of layers in the top ceramic block 1. The ion chamber pins 8 and 9 also extend in parallel to the quadrupole rods 12 and are electrically isolated from electrically conducting layers in the bottom ceramic block 10 and pass through holes 8a and 9a in the base plate 16, through holes 8b and 9b in the collector plate 17 and through holes 8c and 9c in the lens plate 18. The ion chamber pins 8 and 9 are attached by means

35 of glass joints in the connection holes 8a and 9a in the base plate 16.

Fig. 2d and Fig. 3 show layers 16b and 16c respectively, which are arranged on the top surface of the base plate 16. The base plate 16 has no holes in its central portion and no recesses there but present a flat, smooth top surface for mechanical contact with and electrical connection to the lower ends of the quadrupole rods 12, see more hereinafter. The top surface of the base plate 16 is first coated with an electrically conducting layer 16b and on top of this layer with an electrically isolating glass layer or glass joint layer 16c. The electrically conducting layer 16b has as its main components a thin-film layer of gold and its different areas are denoted by 30, 31, 32, 33. The first thin-film area 30 constitutes conductors for electrical connection with eight of the quadrupole rods 12, which are included in the quadrupole array, whereas the second thin-film area 31 constitutes conductors for electrical connection with the remaining eight rods 12, which are included in the quadrupole array. The conductors are configured in such a way, that in a square element 14 of four neighbouring rods 12 two rods 12, which are located diagonally in relation to each other, are connected to the same conducting area 30 and the remaining two rods to the second conducting area 31. Two rods 12, which are located diagonally in relation to each other in a square primary element 14, can thus be supplied with a first voltage and the remaining two rods with a second voltage in order to form an electrostatic quadrupole field. The areas 30 and 31 have thus each eight circular connection areas 34, against which one of the end surfaces of the cylindrical rods 12 faces and with which they are in mechanical and electrical contact.

The thin-film area 32 included in the electrically conducting layer 16b, see Fig. 2b, has an exterior, substantially rectangular outline and constitutes a connection area for electrical through-connection to a bottom shielding layer 17a for the collector plate 17 in the bottom ceramic block 10. The thin-film area 33 around the hole 45 which passes through the base plate 16 constitutes a contact area for an electrical shielding layer around an electrical through-connection pin 54, not shown, intended to be placed in the hole 45, see also Fig. 2c, for electrical connection to the collector 17.

The areas 30 and 31 are, as has already been mentioned above, essentially produced by means of thin-film methods using gold and comprise the contact areas 34, conductor paths between and from these areas up to narrow circular rings 41a, 42a around through- connection holes 41 , 42, see hereinafter. At the centre of each one of the circular contact areas 34 for contacting quadrupole rods 12 regions of a circular and annular thick-film layer 35 of silver is applied, see Fig. 2a. Around each such circular silver area 35 is a thick-film region 36 of glass having the shape of a circular ring applied, which is included in a next applied layer 16c, see Figs. 1, 3 and 2a, so that a glass ring area 36 is located at least above part of the gold layer of the contact areas 34. The annular glass areas 36 attach the quadrupole rods 12 to the top surface of the base plate 16 and fix the rods to the electrical contact areas, which are constituted by the silver areas 35 and the gold areas 34 included in the respective conductive pattern 30 and 31. A permanent fixing is obtained when fusing the miniature quadrupole, i.e. when it, after placing all plates, layers and rods next to and in each other respectively at the intended positions, is heated to a suitably high temperature in order to melt glass in glass joints, so that it joins the different parts of the quadrupole detector. Fig. 2b shows a similar arrangement at a contact area 32 for through-connection to the bottom shielding layer 17a below the collector plate 17 in the bottom ceramic block 10. The contact area 32 comprises a thin-film gold area 32a, which encloses a circular through-connection hole 40 in the base plate 16 and is prolonged, so that it connects to a conducting area 37 of the same kind, which is simultaneously applied to the top portion of the inner wall of the through-connection hole 40, so that a connection pin, not shown, can be applied from the lower side of the base plate, see more below, for electrical contact with the conducting area 37 of the inner wall of the hole. A silver area 38 of thick-film type is applied on top of the rectangular gold area 32 on the top surface of the base plate and also encloses the hole 40. This silver area 38 is surrounded by a thick-film area 39 of glass as above.

A through-connection hole 41 passing through the base plate 16 for the first conductor pattern 30 connected to the rods 12 and a diametrically opposite through- connection hole 42 for the second conductor pattern 31 are coated with gold on the inner walls of the cylindrical holes, so that a connection pin, not shown, can be applied from the bottom surface of the base plate 16. The through-connection holes 41 and 42 are surrounded by narrow circular rings 41a, 42a of thin-film gold, which are in connection with the wall material in the holes 41 , 42 and which each through a conductor path included in the area 30 and 31 respectively is connected to these areas, whereby an electrical conductor path is obtained from the connection pins, not shown, in the holes 41, 42 to the two groups of quadrupole rods 12. The narrow circular rings 41a, 42a are, in the same way as for other holes, surrounded by a glass joint area having the shape of circular rings 43 and 44 respectively, see Fig. 3.

The through-connection hole 45 for connection to the collector is surrounded by the circular, annular thin-film gold area 33 and is coated with a gold layer 53 also on its cylindrical wall surface, see Fig. 2c, so that this gold layer is connected to the area 33 and also to a similar annular thin-film gold area 33a on the bottom side of the base plate 16. These gold layers 33, 33a, 53 also form part of a shielding layer surrounding the electrical connection with the collector. This connection is constituted by a metallic connection pin 54, which is coated with an electrically isolating thick-film layer of glass 55 and projects from below in through the base plate 16. The collector connection pin 54 and the shielding layer 53 in the through-connection hole 45 will thereby be electrically isolated from each other owing to the glass layer 55. Outside the annular gold area 33 a glass joint area having the shape of a circular ring 49 is provided, see also Fig. 3. The holes 24a, 25a, 23a extending through the base plate 16 for the rods 4, 5, 3 for connecting to the filaments in the top block 1 are surrounded by a glass joint area having the shape of circular rings 50, 51, 52. Around these holes no thin-film gold areas are provided.

The remaining part 56 of the glass layer 16c, i.e. that portion, which does not form complete circular rings surrounding holes and does not form electrical connection areas, consists of a dotted or patterned pattern of hexagons. The function of these dotted glass joints are previously described in the published International patent application WO 95/28623. The glass joint layer 16c is otherwise a substantially complete circular layer

5 having the same exterior diameter as the ceramic plates 16, 17, 18.

The bottom surface of the collector plate 17 is coated with an electrically conducting layer 17a, the main component of which is a thin-film layer of gold, see Figs. 1 and 4b. The conducting layer 17a is the bottom shielding layer mentioned above for the collector plate 17, has the same exterior diameter as the ceramic plates 16, 17, 18 and is an ιo approximately completely covering layer except holes around the quadrupole rods 12, the ion chamber pins 8, 9 and the filament rods 3, 4, 5, which holes all have larger diameters than the corresponding rods. Further a hole is arranged in the shielding layer 17 around the shielding connection pin, not shown, which extends through the hole 40 in the base plate 16 having a continuation in the shape of a concentric hole 40a having the is same diameter in the collector plate 17. Another circular hole in the shielding layer 17a surrounds a circular ring 45c of the same layer 17a, which is located around a collector pin through-connection hole 45 a, which is a continuation of the through-connection hole 45 in the base plate 16. Also holes 46 are provided, which surround the top end of connection pins, not shown, which pins are in connection with the conducting areas 30,

2031 on the top side of the base plate, which give the quadrupole rods the correct electrical potential and which pins pass through the holes 41 , 42 in the base plate 16 in contact with electrically conducting circular rings around these holes. Also these holes 46 have a larger diameter than the corresponding connection pins.

With the contact area 32, which is included in the contact layer 16b for the base

25 plate 16 and surrounds the shielding through-connection hole 40 in the base plate 16, is an opposite region 57 associated having the same outline, for connection between the electrical shielding connection pin, not shown, and the bottom shielding layer 17a through the gold area 37 on the walls in the hole 40, the thin-film area 32a surrounding the hole in the base plate and the thick-film silver area 38 located thereon, which has a direct

30 contact with the area 57 in the shielding layer 17a. The area 57 is thus located around the hole 40a in the shielding plate 17.

The through-connection hole 45 in the base plate 16 for the collector pin 54 has a continuation in the cylindrical hole 45a through the collector plate 17, which holes thus are concentric. The cylindrical hole 45a in the collector plate 17 is coated with a gold

35 layer 45f on its sidewalls, see Fig. 4a. The contact area 45b around the hole 45a is constructed of a circular, annular gold layer 45c of thin-film type, which is in contact with the gold layer 45f on the sidewalls of the hole, and it is further constructed of an annular thick-film area 45d of silver located on top of the annular gold layer 45c for connecting to the opposite contact area 33 in the conducting layer 16b which is located around the hole 45 in the base plate 16. The contact area 45 is enclosed by the circular ring 49 of glass in the glass joint layer 16c, see Figs. 2c and 3. The annular contact area 45b is electrically isolated from the other portions of the conducting bottom shielding layer 17a. s The shielding layer 17a is thus electrically isolated from the conducting layer or connection layer 16b of the base plate by the glass layer 16c. The rods 12, the filament pins 3, 4, 5 and the ion chamber pins 8 and 9 are electrically isolated from the shielding layer 17a. The holes in this conducting layer around the corresponding through- connection holes 19, 23b, 24b, 25b, 8b and 9b in the collector plate 17 have a somewhat o larger diameter than their respective through-connection holes in the collector plate 17, as has been mentioned above.

The top side of the collector plate 17 is coated with two layers, a conducting collector layer 17b, see Fig. 5b, and an intermediate glass layer 17c located thereon, see Fig. 6. The collector layer 17b comprises as a main component a thin-film layer of gold. s The collector layer has nine circular collector areas 58, which are connected to each other. Centred in the channel 15 of each square element 14 of the quadrupole is such a collector area 58 located. The collector areas 58 are electrically connected to each other by electrical conductor paths in the collector layer 17b and they are in addition, through a conductor path in the same layer, connected to a contact area 59, which consists of half a 0 circular ring, for transferring the collector current, collected by the collector areas, to an opposite contact area 60 on the bottom side of a conducting layer 18a located directly under the lens plate 18, see Fig. 7c. This contact area 59 and another isolated contact area 61 in the same collector layer 17b as well as contact areas 60, 60a and 62 in the electrically conducting layer 18a located on top thereof consist of a gold layer area 5 having a layer of thick-film silver located thereon. Thus, the circular area 60a in the top conducting layer 18a is constituted of thin-film gold having a concentric area 60b of thick-film silver located thereon, see Fig. 7b. The contact area 61 in the collector layer 17b surrounds the hole 40a for the shielding connection pin in the collector plate 17 and has an opposite contact area 62 in the conducting top layer 18a, which is coated on the 0 bottom surface of the lens plate 18, for contacting this conducting layer, which is also called the top shielding layer 18a.

The glass joint layer 17c, Fig. 6a, is arranged as an intermediate layer between the collector layer 17b and the top shielding layer 18a. A glass ring 63 in the glass layer 17c, see also Fig. 6b, constitutes a hermetic seal around the through-connection of the

35 collector connection pin 54. The glass joint ring 63 also covers a circular, annular area included in the area 60a and extending along the periphery, see Figs. 7b and 7c. The glass ring 63 surrounds and thus does not cover the thick-film silver area 60b, see also Fig. 7c. The top end surface of the collector pin 54 rests on both an outer circular ring of the glass joint area 63a and on the centrally located area 60b of silver. The top end surface of the collector pin 54 is attached by means of a glass joint to the glass joint ring 63a and the silver area 60b constitutes an electrical connection with the nine collector areas 58. The collector current can in this way be conducted through the collector pin 54 to the bottom side of the base plate 16 surrounded by an electrical shielding layer, which prevents current leakage to the ceramic block.

The contact area 62, which forms a part of the main area of the top shielding layer 18a, is surrounded by a hermetically sealing glass area 62a, see Fig. 6a. The through- connection holes 23c, 24c, 25c, 8c and 9c for filament rods and ion chamber pins respectively are enclosed by circular and annular hermetic glass joint areas 64, see also Fig. 6a. The remaining part of the glass layer 17c is as above constituted by a dotted pattern of hexagons and the glass layer 17c is a substantially complete layer having the same exterior diameter as the ceramic plates 16, 17, 18, which is only interrupted by holes and circular, annular areas around different holes and connection areas.

Lens holes 65 in the lens plate 18 allow, see Fig. 1, that ions which propagate through a channel 15 in a square quadrupole element 14 reach the collector area at the top side 58 of the collector plate 17, see Fig. 5b. Corresponding openings 65a and 65b are provided in the electrically conducting layer 18a, i.e. the shielding layer, in the intermediate layer 17c, which is located between the shielding layer 18a and the collector layer 17b. However, the shielding layer 18a can be in electrical contact with electrically conducting coatings, not shown, of the inner walls of the ion channel holes 65 of the lens plate 18. There may also be electrically conducting areas, not shown, around these holes on the top surface of the lens plate, requiring an additional electrically conducting pattern to be printed on the top side of the lens plate. By supplying such extra shielding of the ion channel holes 65 there will be no bare ceramic surfaces near the path of the ions which will avoid the risk of charge surfaces being formed by the ions on electrically nonconducting surfaces. Furthermore holes are arranged in the shielding layer 18a and the collector layer 17b for the quadrupole rods 12, the holes in the electrically conducting shielding layer being larger than the outer diameter of the rods, so that any electrical contact between the quadrupole rods and the shielding layer 18a is avoided. A bonding or joining layer 18b consists only of a glass joint area 75 designed as a circular ring extending along the periphery, see Figs. 1 and 8, on the top side of the lens plate 18. To this glass joint area is the bottom side of the mounting block 21 attached by means of a glass joint, see Fig. 1.

The top ceramic block 1, see Fig. 9, consists of an input plate 100 having a conducting layer 100b directly applied to the bottom surface of the input plate 100 and on this layer a glass layer 100a, which thus is the lowest layer in the top block. A conducting layer 100c and thereon a glass layer lOOd are coated on the top surface of the input plate 100. The input plate 100 has circular holes 165, which allow a free passage of ions, which are displaced downwards through a channel 15 in each square element 14 up to the collector area 58 on the top surface of the collector plate 17. The corresponding openings denoted by 165a are provided in the glass layer 100a, see Fig. 10, by 165b in the conducting layer 100b, see Fig. 11 , and by 165c in the conducting layer 100c, see Fig. 12. Through-connection holes 123, 124, 125 form a passage for the circular filament pins 3, 4, 5. The opening diameter around the filament rods 3, 4, 5 in the conducting layers 100b and 100c are somewhat larger than the diameter of the through-connection holes 123, 124, 125 in the input plate 100.

The ion chamber pin 8 rests with its top end surface on a contact area 102, see Figs, l ie, 11a. On the ceramic surface of the input plate 100 a gold layer area 102a is coated. A silver layer 102b forms a contact area for connection to the end surface of the ion chamber pin 8. The layer 102b is surrounded by a circular, annular glass joint area 102c, see Figs. 10 and 11a.

The other ion chamber pin 9 passes through the through-connection hole 90 to the top edge thereof. The inner wall of the circular through-connection hole 90 is coated with a thin-film layer of gold 90a, see Fig. l ib. On top of the layer 90a a thick-film silver layer 90b is located, which forms a contact surface for connection with the ion chamber 9. The gold layer 90a has electrical connection with the layer 100c, see Fig. 12b. The ion chamber pin 8 allows, that the conducting layer 100b on the bottom surface of the input plate 100 can be supplied with a voltage and the ion chamber pin 9 allows that the conducting layer 100c on the top surface of the input plate 100 can be supplied with a second voltage, which is different from the voltage, which is applied to the conducting layer 100b.

The filament pins 3, 4, 5 are somewhat higher than the surface of the top surface of the input plate 100. Between the filament pins 3 and 4 and between pins 4 and 5 two filaments 130, 131 of e.g. tungsten or iridium are arranged, see Fig. 14c. In the space between a filament and the peripheral edge of the input plate 100 two reflectors 132, 133 are provided, see Figs. 14c and 14a. The reflectors 132, 133 are bonded or joined to the top side of the input plate 100 by means of glass joint areas 126 and 127, see Fig. 13. An ion chamber 140, see Fig. 14c, is produced of a metal or ceramic material and is bonded to the top side of the input plate 100 by means of the glass joint area 128, see Fig. 13. The ion chamber 140 has electrical connection through a contact area 129, see Fig. 12a. A thin-film layer 129 is coated with a thick-film layer 129b of silver. The layer 129b forms a contact area for connection with an edge element 140a folded out from the ion chamber 140, see Fig. 14c. The layer 129b is surrounded by the glass joint 128. The ion chamber 140, see Fig. 14b is provided with a number of slotted openings 141.

The electrically conducting layer 100b located directly under the input plate 100 has holes corresponding to the quadrupole rods 12 and having a larger diameter than them, so that there will be no risk of making the quadrupole rods contact the conducting layer. The glass layer 100a located under the conducting layer 100b and facing the bottom block 10 consists of circular rings 166 corresponding to quadrupole rods 12, these rings having about the same exterior diameter as the rods and being used to secure the quadrupole rods to the input plate 100. In addition the glass layer 100a contains the ring 102c mentioned above but no more areas.

When manufacturing the gas detector as described above first the ceramic plates are produced. Then the various coating layers are applied to the respective plates. The bottom block 10 is then assembled by placing the three plates 16, 17, 18 on top of each other and thereupon the mounting ring 21 , 22. The rods are placed in their respective holes in the bottom block. Since there is a play for at least the holes associated with the quadrupole rods, a jig is used for keeping the rods at accurate positions. The top block with associated devices are placed on the top of the respective rods, the filament rods 3, 4, 5 passing into their respective holes 123, 124, 125 in the input plate 100. The other rods, the quadrupole rods 12 and the ion chamber pins 8, 9 will rest with their top ends on the underside of the input plate 100. The quadrupole rods define the distance between the bottom and top blocks. The assembly is then heated in an oven making the glass joint layers melt and attach the various components to each other. Finally, the fused device is allowed to cool and the jig maintaining the quadrupole rods 12 in their accurately defined positions during the heating operation is removed. While specific embodiments of the invention have been illustrated and described herein, it is realized that numerous additional advantages, modifications and changes will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative devices and illustrated examples shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. It is therefore to be understood that the appended claims are intended to cover all such modifications and changes as fall within a true spirit and scope of the invention.

Claims

1. A gas detector of quadrupole type, comprising at its inlet an ion chamber, an input plate having at least one inlet opening, each inlet opening leading to a channel between quadrupole rods, which have ends with end surfaces, are electrically conducting, are supplied with electric voltages and are located to form an electric quadrupole configuration, the gas detector further comprising a lens device, a collector and a base plate, characterized in that the quadrupole rods at least at one of the ends are with only the end surface of this end attached to a substantially flat surface of a plate included in the gas detector.

2. A gas detector according to claim 1, characterized by an electrically isolating joint layer attaching the end surface of the least one end to the substantially flat surface.

3. A gas detector according to any of claims 1 - 2, characterized in that the substantially flat surface is a surface of the input plate or of the base plate.

4. A gas detector according to any of claims 1 - 3, characterized in that the end surfaces of lower ends of the quadrupole rods are attached to a surface of the base plate, the surface carrying an electrically conducting layer which is patterned for electrical connection with the rods.

5. A gas detector according to any of claims 1 - 4, characterized in that the lens device and/or the collector are constituted by electrically isolating plates having surfaces carrying electrically conducting layers.

6. A gas detector according to any of claims 1 - 5, characterized in that the lens device is constituted by a lens plate which is electrically isolating and the collector is constituted by a collector plate which is electrically isolating, the lens plate and the collector plate having surfaces carrying electrically conducting layers and the lens plate and the collector plate being arranged tightly and/or directly at each other with surfaces contacting each other.

7. A gas detector according to any of claims 1 - 6, characterized in that the collector is constituted by a collector plate which is electrically isolating, the collector plate having a surface carrying an electrically conducting layer, the base plate and the collector plate being arranged tightly and/or directly at each other with surfaces contacting each other.

8. A gas detector according to any of claims 1 - 7, characterized in that the lens device is constituted by a lens plate and/or the collector is constituted by a collector plate, the lens plate and/or the collector plate having holes through which the quadrupole rods pass, the holes having diameters larger than diameters of the respective quadrupole rods, so that there is a play between inner walls of the holes and the exterior surfaces of the respective quadrupole rods allowing the quadrupole rods to be accurately positioned when mounting the gas detector, substantially unaffected by the exact location of the holes.

9. A gas detector according to any of claims 1 - 8, characterized in that the end surfaces of upper ends of the quadrupole rods are attached to a surface of the input plate.

10. A gas detector of quadrupole type, comprising at its inlet an ion chamber, an input plate having at least one inlet opening, each inlet opening leading to a channel between quadrupole rods, which have ends with end surfaces, are electrically conducting, are supplied with electric voltages and are located to form an electric quadrupole configuration, the gas detector further comprising a lens device, a collector and a base plate, characterized in that the lens device is constituted by a lens plate which is electrically isolating and the collector is constituted by a collector plate which is electrically isolating, the lens plate and the collector plate having surfaces carrying electrically conducting layers and the lens plate and the collector plate being arranged tightly and/or directly at each other with surfaces contacting each other, and/or that the base plate is electrically isolating and the collector is constituted by a collector plate which is electrically isolating, the base plate and the collector plate having surfaces carrying electrically conducting layers and the base plate and the collector plate being arranged tightly and/or directly at each other with surfaces contacting each other.

11. A gas detector of quadrupole type, comprising at its inlet an ion chamber, an input plate having at least one inlet opening, each inlet opening leading to a channel between quadrupole rods, which have ends with end surfaces, are electrically conducting, are supplied with electric voltages and are located to form an electric quadrupole configuration, the gas detector further comprising a lens device, a collector and a base plate, characterized in that the input plate and/or the lens device and/or the collector is constituted by an electrically isolating plate having a surface carrying an electrically conducting layer for providing different electrical functions, in particular lens functions, collector functions and shielding functions.

12. A gas detector of quadrupole type, comprising at its inlet an ion chamber, an input plate having at least one inlet opening, each inlet opening leading to a channel between quadrupole rods, which have ends with end surfaces, are electrically conducting, are supplied with electric voltages and are located to form an electric quadrupole configuration, the gas detector further comprising a lens device, a collector and a base plate, characterized in that lower end surfaces of the quadrupole rods are engaged with the base plate carrying an electrically conducting layer which is patterned for electrical connection with the rods.

13. A gas detector of quadrupole type, comprising at its inlet an ion chamber, an input plate having at least one inlet opening, each inlet opening leading to a channel between quadrupole rods, which have ends with end surfaces, are electrically conducting, are supplied with electric voltages and are located to form an electric quadrupole configuration, the gas detector further comprising a lens device, a collector and a base plate, characterized in that the lens device and/or the collector is constituted by an electrically conducting, patterned layer arranged on a surface of an electrically isolating plate.