DEVELOPMENT OF A PORTABLE ION MOBILITY SPECTROMETER (IMS) - FINAL REPORT

• NCJ Number: 13146
• Author(s): S T FISHER; E J DOUGHERTY
• Date Published: 1973
• Length: 46 pages
• Grant Number(s): DAAD05-72-C-0146
• Corporate Author: US Dept of the Army
• Publication Format: Document

Annotation

PORTABLE ELECTRONIC INSTRUMENT IS CAPABLE OF DETECTING CHEMICALS WHOSE PRESENCE MAY BE LESS THAN ONE PART PER MILLION.

Abstract

THE VERSATILE IMS UNIT IS HOUSED IN A METAL SUITCASE. INCLUDED WITH THE UNIT ARE BOTH A.C. AND D.C. POWER OPTIONS. THE UNIT IS PROGRAMMED TO DETECT A WIDE VARIETY OF EFFLUVIA, INCLUDING EXPLOSIVE MATERIALS AND NARCOTICS. THE IMS OPERATES ON THE PRINCIPLE THAT IONIZED MOLECULES OF DIFFERENT CHEMICALS DRIFT IN AIR AT DIFFERENT VELOCITIES UNDER THE INFLUENCE OF AN ELECTROSTATIC FIELD. MOLECULES OF THE EFFLUENT ARE IONIZED BY A COMPLEX INTERACTION INVOLVING ELECTRONS FROM A RADIOACTIVE SOURCE, MOLECULES OF WATER VAPOR, OXYGEN, AND NITROGEN IN THE AIR, AND MOLECULES OF THE TRACE MATERIAL ITSELF. A 'SPECTRUM', REPRESENTING CONCENTRATIONS OF VARIOUS ION SPECIES AS A FUNCTION OF THEIR TIMES OF FLIGHT ACROSS A KNOWN DRIFT SPACE, IS DISPLAYED ON AN OSCILLOSCOPE. (AUTHOR ABSTRACT)