Ion source

Details Ion source Ion source

1998-09-30

2001-04-17

Arroyo, Teresa M. (Department: 2881)

Radiant energy

Ion generation

Electron bombardment type

C250S42300F

Reexamination Certificate

active

06218672

ABSTRACT:

FIELD OF THE INVENTION
The present invention relations to an ion source, and more particularly to a device which generates ions using a beam of generated electrons.
BACKGROUND
An ion source utilizes an electron gun to generate electrons, which ionize neutral atoms and molecules. There are various apparatus, such as a mass spectrometer, which require an ion source. In a mass spectrometer, the ion source is used to ionize a gas which consists of neutral particles so that the ions of the gas can be analyzed. The electron-ionization source which has been generally used for mass spectrometers is the Nier source. Referring to
FIGS. 1 and 2
there is shown diagrams of two views of a typical Nier source
10
. The Nier source
10
comprises a chamber
12
having a front wall
14
and a back wall
16
. A gas inlet passage
18
extends through the back wall
16
to allow a gas to be ionized to enter the chamber
12
. An exit slit
20
is in the front wall
14
of the chamber
12
. An electron source filament
22
is in the chamber adjacent the side wall
24
of the chamber
12
. The filament
20
is connected to a source of electricity (not shown) for heating the filament
20
. An accelerator plate
26
is adjacent but spaced from the outer surface of the front wall
14
of the chamber
12
. The accelerator plate
26
has a slit
28
therethrough which is aligned with the exit slit
20
in the front wall
14
of the chamber
12
.
In the operation of the Nier ion source
10
, a gas of the sample material passes through the gas inlet passage
18
into the chamber
12
. The filament
20
is heated so as to emit electrons. The electrons from the filament
20
pass transversely across the chamber
12
and across the flow of the gas. The electrons bombard the gas so that ions are generated by the electron impact. These ions are drawn through the exit slit
20
in the front wall
14
of the chamber
12
by the accelerator plate
26
. The ions then pass through the slit
28
in the accelerator plate
26
and flow into a mass spectrometer (not shown). In the Nier ion source
10
, ionization takes place only in the area of the gas which is traversed by the electron beam so that the amount of ions generated is relatively small. Also, the ions are generated only over an area defined by the length and width of the exit slit
20
. These ions must then be focused onto the entrance of a quadrupole mass spectrometer, which is typically a small circular aperture. Therefore, additional focusing plates are required to ensure that all of the ions generated enter the mass spectrometer.
SUMMARY OF THE INVENTION
An ion source includes an electron generating chamber and a ionization chamber adjacent the electron generating chamber. A gas inlet opens into the ionization chamber and an opening extends between the ionization chamber and the electron generating chamber. The electron generating chamber has an outlet opening therein. The gas inlet, opening between the ionization chamber and electron generating chamber and the outlet opening are all along a common axis. The electron generating chamber has therein means for generating electrons completely around the axis and means for directing the electrons radially toward the axis. Also in the electron generating chamber is means for deflecting the radial flow of electrons longitudinally along the axis and into the ionization chamber. At the outlet opening is means for attracting the ions toward and through the outlet opening.


REFERENCES:
patent: 3731089 (1973-05-01), Elliott
patent: 4159423 (1979-06-01), Kambara
patent: 5101105 (1992-03-01), Fenselau et al.

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