Ion detecting apparatus and methods

• US 7,268,347 B1
• Filed: 03/14/2005
• Issued: 09/11/2007
• Est. Priority Date: 01/25/2002
• Status: Expired due to Fees

• Current Assignee: Interlink Electronics Incorporated
• Original Assignee: KWJ Engineering, Inc. (Interlink Electronics Incorporated)
• Inventors: Blanchard, William C.
• Primary Examiner(s): Kim; Robert
• Assistant Examiner(s): SMITH, JOHNNIE L
• Application Number:
  US11/080,090
• Time in Patent Office: 911 Days
• Field of Search: 250/287, 250/282, 250/286, 250/288
• US Class Current: 250/292
• CPC Class Codes: H01J 49/025 Detectors specially adapted to particle spectrometers data acquisition H01J49/0036; detectors per se G01T, e.g. G01T1/28, G01T1/29
• CPC Class Codes: H01J 49/40 Time-of-flight spectrometers H01J49/36 takes precedence

Abstract

Ion injection in a drift tube apparatus for mobility spectrometry was accomplished without conventional ion shutters such as the Bradbury-Nielson or similar designs common to such drift tubes. Instead ions were passed between the ion source and drift region by using time-dependent electric field gradients that act as ion barriers between ordinary drift rings. Benefits of this design are simplicity and mechanical robustness. This ion injection technique dynamically accumulates the ions created between shutter grid pulses, as does the Bradbury-Nielson method. The invention provides not only structural improvements to the well known apparatus, but also provides inventive methods for operating a drift tube apparatus in achieve maximum analyte injection efficiency and improving ion detection sensitivity. Improving ion detection sensitivity of drift tubes has practical experimental application. Incorporation of the inventive apparatus into a smoke detector is a further practical application of the invention.

Claims

1. A smoke detector comprising an ion barrier mobility spectrometer apparatus having a sensor wherein said sensor operates to sense a reduction in the quantity of free reactant ions being carried along an electric field created by said ion barrier mobility spectrometer apparatus.

2. A smoke detector comprising:

a voltage gradient and an electric field ion barrier;

said smoke detector further communicating with a reactant ion source for introducing reactant ions into said smoke detector, wherein said reactant ions accumulate at said ion barrier, said ion barrier being located at a point prior to said voltage gradient;

a sensor for sensing a reduction in the amplitude of an electronic signal, the reduction in signal being caused by a reduction in the quantity of the reactant ions reaching said sensor, said sensor being located at a downstream end of said voltage gradient wherein the introduction of smoke at said ion barrier reacts with reactant ions accumulated at said ion barrier thereby reducing the amount of free reactant ions and wherein upon eliminating said ion barrier a remaining quantity of free reactant ions travel along said gradient to said sensor to be registered as an electronic signal; and

an alarm, said alarm being activated when a reduction in the amplitude of the electronic signal is sensed.

3. The smoke detector as recited in claim 2, wherein the introduction of increasing concentrations of smoke causes the amplitude of the detected signal to further decrease.

4. A smoke detector comprising an electric field ion barrier, said ion barrier accumulating reactant ions and smoke to create ionized smoke and free reactant ions, said smoke detector pulsing said ionized smoke and free reactant ions toward a sensor to create an electronic signal, the amplification of said signal being determined by the quantity of free reactant ions.

5. The smoke detector as recited in claim 4, wherein the introduction of increasing concentrations of smoke causes the amplitude of the detected signal to further decrease.

6. A smoke detector comprising an ion barrier mobility spectrometer (IBMS), said IBMS being operatively connected to control electronics, said control electronics creating an electric field ion barrier within said IBMS, said ion barrier accumulating reactant ions and smoke to create ionized smoke and free reactant ions, said IBMS further comprising a sensor for sensing a change in pulse amplitude resulting from a reduced reactant ion presence, said control electronics activating an alarm in response to the change in pulse amplitude being indicated by said IBMS.

7. The smoke detector as recited in claim 6, wherein said alarm is an audible alarm.

8. The smoke detector as recited in claim 6, wherein said reactant ions are charged water clusters.

9. A method of detecting smoke, the method comprising:

(a) creating an electric field ion barrier;

(b) introducing a plurality of reactant ions to said ion barrier, said reactant ions accumulating at said ion barrier;

(c) wherein the introduction of smoke to said ion barrier and reactant ions causes ionized smoke to occur, thereby reducing the number of free reactant ions at said ion barrier;

(d) deactivating said ion barrier to allow the ionized smoke and free reactant ions to travel along an electric field gradient;

(e) sensing a reduction in the amount of reactant ions upon said traveling reactant ions reaching a sensor; and

(f) activating an alarm in response to a reduction in the amount of reactant ions indicated by said sensor.