US3471691A

US3471691A - Plug-in detachable electrode structures for mass spectrometers

Info

Publication number: US3471691A
Application number: US622781A
Authority: US
Inventors: David E Gielow; Duane P Littlejohn
Original assignee: Varian Associates Inc
Current assignee: Varian Medical Systems Inc
Priority date: 1967-03-13
Filing date: 1967-03-13
Publication date: 1969-10-07
Anticipated expiration: 1986-10-07

Description

Oct. 7, 1969 ow ET AL 3,471,691

PLUG-IN DETACHABLE ELECTRODE STRUCTURES FOR MASS SPECTROMETERS Fil'ed March 13, 1967 FIG. 2

v INVENTORS- DAVID E. GIELOW DUANE P. TLEJOHN il? TORNEY United States Patent 3,471,691 PLUG-IN DETACHABLE ELECTRODE STRUC- TURES FOR MASS SPECTROMETERS David E. Gielow, Los Altos, and" Duane P. Littlejohn,

Santa Clara, Calif., assignors ito Varian Associates,

Palo Alto, Calif., a corporation of California Filed Mar. 13, 1967, Ser; No. 622,781 Int. Cl. B01d 59/44 U.S. Cl. 25041.9 5 Claims ABSTRACT OF THE DISCLOSURE Electrode structures for mass spectrometers are disclosed which include plug-in connector assemblies located inside the vacuum envelope of the mass spectrometer. Leads to the various electrodes inside the vacuum envelope of the mass spectrometer are brought through the envelope by means of feedthrough insulator assemblies. Once inside, the leads are connected to one half of a plug-in multiconnector assembly. One or more of the various electrode structures of the mass spectrometer, such as the ion source, mass analyzer, and ion detector, have a set of electrical leads which are connected to the other half of the plug-in multiconnector assembly. The plugged in mass spectrometer electrode structures are supported inside the vacuum envelope in such a way that they can be readily detached from their supports and replaced by merely unfastening a few screws or the like and unplugging the electrode structure.

In one embodiment, a plug-in electrode structure for an ion cyclotron resonance mass spectrometer is provided. In another embodiment, a plug-in ion source for cycloidal or magnetic sector type mass spectrometers is provided. Such plug-in mass spectrometer electrode structures greatly facilitate cleaning, replacement, and interchange of the various mass spectrometer parts.

DESCRIPTION OF THE PRIOR ART Heretofore, mass spectrometers have been built wherein the various electrode structures of the mass analyzer, ion source, and ion detector were mounted from a flange assembly. The flange assembly was bolted to a mating flange assembly around a post in the vacuum envelope. The various elements and electrode structures could be removed from the vacuum envelope for cleaning, replacement or interchange by unbolting the flange and withdrawing the dependent electrode structures. However, the multitude of electrical leads to the various separate components included no take apart connecting means such that to replace an ion source, for example, the leads would have to be unscrewed or cut and new leads made up for the replacement unit. Moreover, the separate units were mounted by means of screws and the like to their supporting struc ture such that removal of the units was time consuming and tedious. This resulted in substantial down-time for the spectrometer which it is desired to avoid.

SUMMARY OF THE PRESENT INVENTION The principal object of the present invention is the provision of an improved mass spectrometer.

One feature of the present invention is the provision, in a mass spectrometer, of a plug-in type electrical connector assembly located inside the vacuum envelope of the spectrometer for making connections to various electrode structures of the spectrometer, whereby cleaning, replacement, and interchange of the various electrode structures of the spectrometer are facilitated.

Another feature of the present invention is the same as the preceding feature wherein one half of the electrical connector assembly is fixedly mounted to a vacuum flange assembly and the other half of the electrical connector is fixedly secured to a detachable electrode structure.

3,471,691 Patented Oct. 7, 1969 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of an electrode structure for an ion cyclotron resonance mass spectrometer incorporating features of the present invention, and FIG. 2 is an exploded view, partly in section, of an ion source electrode structure for a mass spectrometer incorporating features of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, there is shown an electrode structure for an ion cyclotron resonance mass spectrometer. Such a spectrometer is described and claimed in 00- pending US. patent application, Ser. No. 456,173 filed May 17, 1965 and assigned to the same assignee as the present invention. Such a spectrometer is also marketed by Varian Associates, of Palo Alto, Calif., under the trademark, Syrotron.

The electrode structure 1 comprises a generally hollow elongated rectangular structure formed by a plurality of rectangular metallic plates, various ones of which are insulated from each other. Various different operating potentials are applied to the various plates, in use. The structure is separated into three portions for performing different functions.

A first electrode structure portion 2 comprises the ion source for ionizing gaseous substances which find their way into the source region. Ions which are formed in the source region 2 are projected axially of the structure 1 into a second region 3 which forms the mass analyzer structure.

In the mass analyzer region 3 a radio frequency electric field is applied to the ions at right angles to the direction of a static magnetic field B. When the RF electric field is at the cyclotron resonance frequency for the ions in the magnetic field B, energy is absorbed from the RF electric field. This absorption is detected to provide a resonance spectrum. At resonance, the ions expand their orbits and are collected in the analyzer region 3. Nonresonant ions pass through the analyzer region 3 to an ion detector electrode structure 4.

In the ion collector structure 4, the ions are collected on the surrounding walls of the collector.

The cyclotron resonance electrode structure 1 is disposed, in use, within an evacuated vacuum envelope at about 10" torr. The electrode structure 1 is carried from a flanged separable portion of the vacuum envelope 5 via a pair of support rods 6 and 7. Insulator assemblies 8 support the electrode structure 1 from the support rods 6 and 7.

The support rods 6 and 7 are segmented at 9 to form a take-apart joint such that the electrode structure 1 may be detached from the separable portion of the vacuum envelope 5. The take-apart joints 9 comprise a pair of solid rods 11 which are affixed inside the hollow support rods 6 and 7 on one side of the joint 9. The rods 11 slide into the hollow interior of the hollow rods 6' and 7 on the other side of joint 9. A pair of set screws 12, when tightened down against the solid rods 11, serve to lock the two support rod segments together.

Electrical leads 15, for applying the various operating electrical potentials to the various ones of the electrodes of the electrode structure 1, pass into the vacuum envelope through a feed-through insulator assembly 17 in the separable portion of the vacuum envelope 5. A multiconductor plug-in type electrical connector assembly 18 is disposed intermediate the length of the electrical leads 15.

A first half 19 of the plug-in connector 18, in this case the receptacle part, is fixedly secured to the first segments of the support rods 6' and 7' via insulative ears 21. The various leads 15 are connected to various ones of the sockets in the first half 19 of the plug-in connector 18. A second half 22 of the connector 18 is fixedly secured to the detachable segments of the support rods 6 and 7 via insulative ears 23. The final segments of the electrical leads, which terminate on the various electrodes, are connected to various ones of the pins 24 which plug into the various sockets in the receptacle 19.

The advantages of the separable envelope portion with detachable electrode structure 1 is that, the envelope may be separated, the electrode structure 1 may be interchanged with a second electrode structure 1 in a few minutes and the new unit reassembled into the spectrometer. Such rapid interchange is desired in case a dilferent electrode structure 1 is desired in order to perform different experiments or measurements. A rapid interchange is also desired in case of a failure of one of its components, such as the ion source 2. Rapid interchange is desired for exchanging a clean electrode structure 1 for one which has become dirty. All such interchanges reduce the down-time of the spectrometer.

Referring now to FIG. 2, there is shown an ion source electrode structure for a mass spectrometer, which may be of the magnetic sector or cycloidal type. An ion source electrode structure 31 is fixedly secured to a first half 32 of a multiconductor plug-in connector assembly 33. The second half 34 of the connector assembly 33 also comprises a feed-through insulator assembly. The second half 34 of the connector 33, which in this case is the receptacle half, is sealed in a gas-tight manner at its periphery to a metallic bellows 35, as of stainless steel. The bellows 35 is in turn sealed to a flange 36 such that the flange 36, bellows 35 and connector receptacle 34 forms a removable portion of the vacuum envelope 37 of the mass spectrometer.

Electrical leads 38, which serve to apply the various operating electrical potentials to the various electrodes within the ion source 31, are connected to sockets 39 of the receptacle 34. The various leads 38 terminate on the various electrodes within the ion source 31. The segments of such leads 38 which are inside the vacuum envelo e 37 are connected to the pins 41 of the first half 32 of the connector assembly 33. The pins 41 are plugged into the sockets 39 of the receptacle to connect together the segments of the leads 38.

The ion source 31 projects a beam of ions 45 through a slit 46 in an electrode structure 47. The electrode structure 47 includes an aligning tube 48 of hollow rectangular shape which projects toward the source 31 and which surrounds the source 31. The end of the tube 48 is provided with an aligning shoulder at 49 to receive a rectangular shoulder 51 on the first half of the connector 32 to which the ion source 31 is mounted. Alternatively, the aligning shoulder 51 may be placed directly on the ion source 31. These mating shoulders assure proper alignment of the ion source 31 upon interchange of source 31. The flexible bellows 35 permits relative movement between the support structure for the ion source 31 and its aligning

structure

48 and 49 such that the source 31 may be properly seated and registered with respect to the aligning structure 48.

The ion source 31 is replaced, due to a failure or the like, merely by unbolting the flange 36 and withdrawing the ion source 31 and connector 33. The old source is then unplugged and a new source plugged into the receptacle 34. The flange 36 is then reassembled and after evacuation the spectrometer is both in operation. Thus,

the plug-in ion source 31 greatly reduces the downtime of the spectrometer and permits use of inexpensive throwaway type ion sources 31.

Although, in both embodiments of FIGS. 1 and 2, the male part of the plug-in connector has been disclosed as being fixedly secured to the detachable electrode structure, this is not a requirement. The receptacle part of the connector may just as well be aflixed to the detachable electrode structure.

Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description and as shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In a mass spectrometer apparatus, means forming a vacuum envelope to be evacuated in use and having a detachable portion, means forming electrode structures to be disposed in said vacuum envelope for analyzing the mass of substances in the gaseous state introduced into the region of said electrode structures, mean forming a plurality of electrical leads for applying various operating potentials to various ones of said electrode structures within said envelope, said detachable portion of said vacuum envelope having a hermetically sealed multiple conductor feedthrough insulator assembly for passing said electrical leads through said vacuum envelope, the improvement comprising, means forming a multiple conductor plug-in type electrical connector assembly at least partially disposed inside said vacuum envelope for connecting segments of said electrical leads together inside said vacuum envelope, said electrical connector means comprising first and second mating connector parts, said first connector part being fixedly mounted to said separable portion of said vacuum envelope, at least a portion of said electrode structures being detachably mounted to said separable portion of said vacuum envelope, and said second connector part of said electrical connector being fixedly mounted to said detachably mounted electrode structure.

2. The apparatus of claim 1 wherein said detachably mounted electrode structure includes an ion source.

3. The apparatus of claim 1 wherein the mass spectrometer is a cyclotron mass spectrometer, and said detachable electrode structure comprises an ion source, a mass analyzer, and an ion detector.

4. The apparatus of claim 1 wherein said detachable electrode structure comprises an ion source and said first connector part is hermetically sealed to said leads to form said feed-through insulator assembly.

5. The apparatus of claim 4 including, means forming a gas tight bellows sealing said first connector part to the remaining portion of said removable vacuum envelope portion, and said ion source including, indexing means for registration with structure inside said envelope, whereby said bellows will permit relative movement between said ion source and said separable portion of said vacuum envelope to attain proper alignment of said ion source within said envelope.

References Cited UNITED STATES PATENTS 5/1953 Clark et al. 313-237 X 8/1966 Briggs 250-4196 OTHER REFERENCES RALPH G. NILSON, Primary Examiner A. L. BIRCH, Assistant Examiner US. Cl. X.R. 313237