Radiant energy – Ionic separation or analysis – Ion beam pulsing means with detector synchronizing means
Patent
1994-03-21
1995-12-12
Berman, Jack I.
Radiant energy
Ionic separation or analysis
Ion beam pulsing means with detector synchronizing means
250289, 250288, H01J 4940
Patent
active
054752175
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to ion mobility spectrometry (IMS) equipment.
IMS equipment is increasingly used for the detection and location of gases and vapours of interest in ambient atmosphere. The principles of operation of such equipment are well known in the art and are described, for example, in "Plasma Chromatography" ed. T. W. Carr, Plenum Press (1984).
One disadvantage of the IMS technique is that water vapour and other contaminants present in the equipment can interfere with the detection of many vapours of interest. This has led to the practice of providing a flow of dry clean air within the equipment into which samples are introduced, the dry clean air flow being provided either from an external source, or, in the case of portable equipment, such as the applicants' CAM (RTM) chemical agent monitor, by means of an internal circulatory system including filters and driers. Such a system is described in US Pat. No. 4,317,995.
The need to provide a continuous flow of dry clean air has constrained miniaturisation of IMS equipment as continual operation of an electric fan or pump to maintain airflow in the circulatory loop calls for a power source far larger than would otherwise be necessary and considerably complicates the internal design and the manufacture of the equipment.
It is an object of the invention to at least partly obviate these drawbacks and thereby enable IMS equipment to be further miniaturised.
According to the present invention there is provided IMS equipment comprising a hermetically sealed compartment containing an IMS cell and a body of absorbent material, sample means for introducing a sample into the compartment via an inlet thereof, the IMS cell being arranged to detect or identify gases or vapours of interest present in the sample, water vapour or other interfering species introduced into or otherwise present within the compartment diffusing within the compartment and being absorbed by the body of absorbent material.
The invention also extends to IMS equipment comprising a hermetically sealed compartment containing an IMS cell and a body of absorbent material, into which compartment samples may be introduced to enable the detection or identification of gases or vapours of interest present in such samples, water vapour or other interfering species introduced into or otherwise present in the compartment diffusing within the compartment and being absorbed by the body of absorbent material, whereby a dry clean atmosphere may be maintained within the compartment.
IMS equipment in accordance with the invention, in which there is no requirement for a continuous flow of dry clean air, may be made smaller, simpler, less bulky and more rapidly operable than hitherto.
The invention may be carried into practice in a number of ways, and one specific embodiment will now be described with reference to the accompanying drawings, in which:
FIG. 1 is a diagrammatic representation of an IMS instrument in accordance with an embodiment of the present invention;
FIG. 2 is a cross-sectional view illustrating more specifically the construction and layout of part of a preferred embodiment of an IMS instrument;
FIG. 3 is a plan view of part of the embodiment of FIG. 2; and
FIG. 4 shows an end view of the embodiment of FIG. 2, looking in the direction of the arrow IV of FIG. 2, with the end closure removed.
Referring to FIG. 1, IMS equipment (shown here schematically) comprises a sealed case 10, within which is mounted an IMS cell assembly 12, a gauze-faced box 14, containing a body of molecular sieve material, and a dopant permeation source 16.
The IMS cell assembly 12 comprises an ionizing source 18, internally coated with a radioactive source material, typically Nickel-63, to ionise incoming vapour molecules; an electrode structure comprising a gate electrode 19 and a series of electrodes 20, to establish an electrostatic field along the length of the cell 12; and a collector electrode 22, connected to instrument signal processing and control circuitry 24, which in turn is connected, inter alia, t
REFERENCES:
patent: 3668382 (1972-06-01), Cohen et al.
patent: 4317995 (1982-03-01), Bradshaw et al.
patent: 5304796 (1994-04-01), Siefering et al.
PCT Written Opinion (PCT Rule 66).
PCT Notification of Transmittal of the Int'l Search Report on the Declaration.
Berman Jack I.
Graseby Dynamics Limited
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