System and method for trace detection using dual ionization sources

Abstract

A dual source ionizer includes a first ionization source and a second ionization source. The first ionization source is configured to generate a first electric field. The first electric field has a first field strength that is insufficient to form NOx− ions. The second ionization source is configured to generate a second electric field. The second electric field has a second field strength that is sufficient to form ozone and the NOx− ions.

1 . A dual source ionizer comprising:
 a first ionization source configured to generate a first electric field, the first electric field having a first field strength insufficient to form NO x   −  ions; and   a second ionization source configured to generate a second electric field, the second electric field having a second field strength sufficient to form ozone and the NO x   −  ions.   
     
     
         2 . The dual source ionizer of  claim 1  further comprising a controller configured to disable said second ionization source for a period of time while said first ionization source is enabled. 
     
     
         3 . The dual source ionizer of  claim 1  wherein said first ionization source comprises a radioactive ionization source. 
     
     
         4 . The dual source ionizer of  claim 1  wherein the first ionization source comprises a photoionization source. 
     
     
         5 . The dual source ionizer of  claim 1  wherein the first ionization source comprises an X-ray source. 
     
     
         6 . The dual source ionizer of  claim 1  wherein the first field strength is no greater than 10 megavolts per meter, and wherein the first electric field is generated in a volume having a pressure of substantially 1 atmosphere. 
     
     
         7 . The dual source ionizer of  claim 1  wherein the second ionization source comprises an electrical discharge radiation source. 
     
     
         8 . The dual source ionizer of  claim 1  wherein the second field strength is at least 12.5 megavolts per meter, and wherein the second electric field is generated in a volume having a pressure of substantially 1atmosphere. 
     
     
         9 . A method of ionizing a gas, the method comprising:
 ionizing the gas using a first ionization source configured to generate one of the group consisting of a low-strength electric field and no electric field;   enabling a second ionization source for a duration; and   ionizing the gas using the second ionization source configured to generate a high-strength electric field.   
     
     
         10 . The method of  claim 9 , wherein ionizing the gas using the first ionization source is carried out over a scan duration that is determined according to a vaporization time of a chemical substance sample. 
     
     
         11 . The method of  claim 9 , wherein the duration the second ionization source is enabled is a portion of the scan duration. 
     
     
         12 . The method of  claim 9  further comprising disabling the first ionization source before enabling the second ionization source. 
     
     
         13 . The method of  claim 9  further comprising performing spectrometry on ions of the gas to screen for a target chemical substance. 
     
     
         14 . The method of  claim 13 , wherein performing spectrometry comprises performing mass spectrometry. 
     
     
         15 . The method of  claim 13 , wherein performing spectrometry further comprises screening for a nitrate-based explosive and for a non-nitrate-based explosive. 
     
     
         16 . A trace detection system comprising:
 a chamber configured to contain a gas composed of at least vapor of a chemical substance sample;   a first ionization source configured to generate a low-strength electric field in said volume to ionize the gas;   a second ionization source configured to generate a high-strength electric field in said volume to ionize the gas; and   a switch configured to enable said second ionization source for a portion of a scan duration and to disable said second ionization source.   
     
     
         17 . The trace detection system of  claim 16  further comprising a spectrometer configured to screen ions of the gas for a nitrate-based explosive and for non-nitrate-based explosives. 
     
     
         18 . The trace detection system of  claim 17 , wherein said chamber comprises a first chamber within which said first ionization source operates, and a second volume, distinct from said first volume, within which said second ionization source operates. 
     
     
         19 . The trace detection system of  claim 18 , wherein said spectrometer is further configured to screen ions from said first volume for the nitrate-based explosives, and to screen ions from said second volume for the non-nitrate-based explosives. 
     
     
         20 . The trace detection system of  claim 16 , wherein said low-strength electric field is configured to:
 liberate a free electron from a molecule of the gas; and   accelerate the free electron to a first kinetic energy level, the first kinetic energy level insufficient to break chemical bonds of diatomic oxygen.   
     
     
         21 . (canceled)