Jill Mary Marshall

US Patent:

53609760, Nov 1, 1994

Filed:

Aug 25, 1992

Appl. No.:

7/935039

Inventors:

David T. Young - San Antonio TX
Jill A. Marshall - San Antonio TX
Emile A. Schweikert - Bryan TX
Melvin A. Park - Alexandria VA

Assignee:

Southwest Research Institute - San Antonio TX

International Classification:

H01J 4904

US Classification:

250287

Abstract:

A portable time of flight mass spectrometer using plasma desorption sample ionization. The sample is deposited onto a sample surface by condensing a sample gas stream onto the surface. While the instrument is evacuated, the sample surface is cooled and a sample gas stream is injected into the instrument near the sample surface causing a portion of the gas stream to condense on the sample surface and the remainder to be removed by the evacuation pump. A mass spectrometer having a linear geometry is disclosed. A reflective geometry is also disclosed wherein the flight path length is maximized by placing the fission source between the sample surface and a single detector. A collector surface for receiving start signal-generating fission fragments is sized to insure equal collection of start signal fragments and sample ionizing fragments. An area on the sample surface which is occluded by the fission source is compensated for by appropriate sizing of the fission source and the collector surface.

US Patent:

54632200, Oct 31, 1995

Filed:

Oct 28, 1994

Appl. No.:

8/331210

Inventors:

David T. Young - San Antonio TX
Jill A. Marshall - San Antonio TX
Emile A. Schweikert - Bryan TX
Melvin A. Park - Alexandria VA

Assignee:

Southwest Research Institute - San Antonio TX

International Classification:

H01J 4904

US Classification:

250288

Abstract:

A portable time of flight mass spectrometer using plasma desorption sample ionization. The sample is deposited onto a sample surface by condensing a sample gas stream onto the surface. While the instrument is evacuated, the sample surface is cooled and a sample gas stream is injected into the instrument near the sample surface causing a portion of the gas stream to condense on the sample surface and the remainder to be removed by the evacuation pump. A mass spectrometer having a linear geometry is disclosed. A reflective geometry is also disclosed wherein the flight path length is maximized by placing the fission source between the sample surface and a single detector. A collector surface for receiving start signal-generating fission fragments is sized to insure equal collection of start signal fragments and sample ionizing fragments. An area on the sample surface which is occluded by the fission source is compensated for by appropriate sizing of the fission source and the collector surface.