Virtual wall gas sampling for an ion mobility spectrometer

A gas sampling system, comprising:

• an ion mobility spectrometer having a sampling orifice through which a sampling gas flow passes in a sampling gas flow direction;
• and
• at least one sheet-like gas flow source that creates at least one sheet-like gas flow virtual wall that is different from the sampling gas flow and is beyond the sampling orifice, the at least one sheet-like gas flow virtual wall forming at least part of a boundary of an enclosed volume used for gas sampling, wherein a normal axis of the sheet-like gas flow is substantially perpendicular to the sampling gas flow direction and wherein a flow direction of the sheet-like gas flow is also substantially perpendicular to the sampling gas flow direction.

A gas sampling system, comprising:

• at least one source that produces at least one sheet-like air flow used to define an enclosed sample volume;
• and
• an orifice coupled to said enclosed sample volume, said orifice providing a partial vacuum to cause gas to flow in a sampled gas direction from within said enclosed sample volume to said orifice, wherein the sampled gas direction is substantially perpendicular to both a direction of flow of the sheet-like air flow and a normal axis to the sheet-like air flow.

A method of sampling gas, comprising:

• forming an enclosed volume around the gas using at least one virtual wall provided by a sheet-like air flow;
• and
• receiving a sampling gas flow moving in a sampling gas flow direction for sampling from within the enclosed volume, wherein a normal axis to the sheet-like air flow is substantially perpendicular to the sampling gas flow direction and wherein a direction of flow of the sheet-like air flow is also substantially perpendicular to the sampling gas flow direction.