Multiconfiguration ionization source

Abstract

This is an ion-producing source having a distinct chemical ionization configuration and a distinct electron impact configuration. In this source, a hollow chamber including an ion source and a source of sample molecules receives a hollow, slidable cylindrical member having a chemical ionization chamber within it. Orifices in the chamber and the cylindrical member connect the chemical ionization source chamber to the electron source and to the sample molecule source when the cylindrical member is pulled to one position. When the cylindrical member is pulled to another position, the slidable cylindrical member and the inside walls of the chamber define the ionization region to which the electron source and the sample molecule source are directly connected. By moving the cylindrical member, the ionization source can be changed from a chemical ionization source to an electron impact source.

We claim: .[. 
     
       1.  A multiconfiguration multimode ionization source comprising: a vacuum tight envelope;   means mounted within said envelope and defining a chamber having a plurality of openings;   electron source means disposed exterior to the chamber for supplying electrons to the chamber, through a first of said openings;   sample inlet means for supplying a gaseous sample through a second of said openings for reaction with the electrons inside the chamber to create ions, said ions exiting through a third of said openings; and   aperture control means for changing the size of said first and third openings to change the pressure in the chamber, thereby to change the operating mode of the source from a first to a second ionization mode..]. .[.2. The apparatus of claim 1, wherein the first ionization mode is a chemical ionization mode and the second ionization mode is an electron impact ionization mode..]. .Iadd.3. An ionization source comprising:   a vacuum tight envelope;   a chamber having walls surrounding an internal cavity and mounted within the envelope, said chamber having a plurality of openings;   an electron source disposed exterior to the chamber for supplying electrons to the chamber through a first of said openings;   sample inlet means for supplying a gaseous sample for reaction with the electrons inside the chamber to create ions, said ions exiting through a second of said openings; and   aperture control means for cooperatively changing the size of the first and second openings for changing the pressure of the sample in the chamber. .Iaddend. .Iadd.4. An ionization source according to claim 3 wherein:   the aperture control means comprises a movable member within the chamber, said member having an electron opening smaller than said first opening and also having an ion opening smaller than said second opening; and in the operation of said ionization source,   said electrons from the source can pass through the electron opening and the first opening when said movable member is in the first position;   said ions in the cavity can pass through the ion opening and the second opening when the movable member is in the first position; and   said electrons can pass through only the first opening and said ions pass through only the second opening when the movable member is in a second   
     
     
        position. .Iaddend. .Iadd.5.  An ionization source according to claim 4 wherein the movable member comprises a hollow slidable cylinder having an ion exit and a handle end. .Iaddend. .Iadd.6. An ionization source according to claim 5 wherein there is provided: a bellows having a first end attached to the handle end of the cylinder and a second end attached to a wall of the vacuum tight envelope; and   a handle surrounded by the bellows, one end of said handle being attached to said handle end of the cylinder, the other end of the handle protruding through said vacuum tight envelope wall. .Iaddend. .Iadd.7. An ionization source according to claim 6 wherein an electron collector is provided opposite the electron source, and magnets are disposed adjacent the electron source and the electron collector to direct the electrons from the electron source. .Iaddend. .Iadd.8. An source according to claim 7 wherein an ion lens assembly is attached to one end of the chamber adjacent the electron source for focusing ions into a utilization device. .Iaddend. .Iadd.9. An ionization source according to claim 8 wherein a vernier adjustment screw is attached to said handle for making fine adjustments in the position of the cylinder for aligning the electron opening with the electron source. .Iaddend. .Iadd.10. An ionization source according to claim 5 further including ion repelling means comprising:   first and second repeller electrodes mounted in and electrically insulated from the hollow slidable cylinder; and   a connector connectable to a source of potential for making an electrical connection with the first repeller electrode when the slidable cylinder is in the first position and with the second repeller electrode when the slidable cylinder is in the second position. .Iaddend. .Iadd.11. An ionization source according to claim 10 wherein said ion opening is in the second repeller electrode..Iaddend.