Gas electron multiplier detector

1. A mass spectrometer comprising a Gas Electron Multiplier ion detector, wherein said ion detector comprises a first gas electron multiplier stage and one or more counter electrodes arranged adjacent said first gas electron multiplier stage.

2. A mass spectrometer as claimed in claim 1 , further comprising a device arranged and adapted either:

(a) to maintain said ion detector at a pressure selected from the group consisting of: (i)<1000 mbar; (ii)<100 mbar; (iii)<10 mbar; (iv)<1 mbar; (v)<0.1 mbar; (vi)<0.01 mbar; (vii)<0.001 mbar; (viii)<0.0001 mbar; and (ix)<0.00001 mbar; or

(b) to maintain said ion detector in a mode of operation at a pressure selected from the group consisting of: (i)>1000 mbar; (ii)>100 mbar; (iii)>10 mbar; (iv)>1 mbar; (v)>0.1 mbar; (vi)>0.01 mbar; (vii)>0.001 mbar; and (viii)>0.0001 mbar; or

(c) to maintain said ion detector in a mode of operation at a pressure selected from the group consisting of: (i) 0.0001-0.001 mbar; (ii) 0.001-0.01 mbar; (iii) 0.01-0.1 mbar; (iv) 0.1-1 mbar; (v) 1-10 mbar; (vi) 10-100 mbar; and (vii) 100-1000 mbar.

3. A mass spectrometer as claimed in claim 1 , wherein said ion detector is arranged and adapted to detect ions having an energy selected from the group consisting of: (i)<1 eV; (ii) 1-5 eV; (iii) 5-10 eV; (iv) 10-15 eV; (v) 15-20 eV; (vi) 20-25 eV; (vii) 25-30 eV; (viii) 30-35 eV; (ix) 35-40 eV; (x) 40-45 eV; (xi) 45-50 eV; (xii) 50-55 eV; (xiii) 55-60 eV; (xiv) 60-65 eV; (xv) 65-70 eV; (xvi) 70-75 eV; (xvii) 75-80 eV; (xviii) 80-85 eV; (xix) 85-90 eV; (xx) 90-95 eV; (xxi) 95-100 eV; (xxii) 100-105 eV; (xxiii) 105-110 eV; (xxiv) 110-115 eV; (xxv) 115-120 eV; (xxvi) 120-125 eV; (xxvii) 125-130 eV; (xxviii) 130-135 eV; (xxix) 135-140 eV; (xxx) 140-145 eV; (xxxi) 145-150 eV; (xxxii) 150-155 eV; (xxxiii) 155-160 eV; (xxxiv) 160-165 eV; (xxxv) 165-170 eV; (xxxvi) 170-175 eV; (xxxvii) 175-180 eV; (xxxviii) 180-185 eV; (xxxix) 185-190 eV; (xl) 190-195 eV; (xli) 195-200 eV; and (xlii)>200 eV.

4. A mass spectrometer as claimed in claim 1 , wherein said ion detector comprises a first foil layer, or a first substrate.

5. A mass spectrometer as claimed in claim 4 , wherein 0-5%, 5-10%, 10-15%, 15-20%, 20-25%, 25-30%, 30-35%, 35-40%, 40-45%, 45-50%, 50-55%, 55-60%, 60-65%, 65-70%, 70-75%, 75-80%, 80-85%, 85-90%, 90-95% or 95-100% of an upper or lower surface of said first foil layer, said first substrate or said first gas electron multiplier stage comprises a first surface layer or coating which is either:

(i) arranged and adapted to enhance the yield of secondary ions or electrons; or

(ii) a photocathode layer which is arranged and adapted to receive photons and to release photoelectrons.

6. A mass spectrometer as claimed in claim 4 , wherein said ion detector comprises a second foil layer, a second substrate or a second gas electron multiplier stage.

7. A mass spectrometer as claimed in claim 6 , wherein 0-5%, 5-10%, 10-15%, 15-20%, 20-25%, 25-30%, 30-35%, 35-40%, 40-45%, 45-50%, 50-55%, 55-60%, 60-65%, 65-70%, 70-75%, 75-80%, 80-85%, 85-90%, 90-95% or 95-100% of an upper or lower surface of said second foil layer, said second substrate or said second gas electron multiplier stage comprises a second surface layer or coating which is either:

(i) arranged and adapted to enhance the yield of secondary ions or electrons; or

(ii) a photocathode layer which is arranged and adapted to receive photons and to release photoelectrons.

8. A mass spectrometer as claimed in claim 6 , wherein said ion detector comprises a third foil layer, a third substrate, or a third gas electron multiplier stage.

9. A mass spectrometer as claimed in claim 8 , wherein 0-5%, 5-10%, 10-15%, 15-20%, 20-25%, 25-30%, 30-35%, 35-40%, 40-45%, 45-50%, 50-55%, 55-60%, 60-65%, 65-70%, 70-75%, 75-80%, 80-85%, 85-90%, 90-95% or 95-100% of an upper or lower surface of said third foil layer, said third substrate or said third gas electron multiplier stage comprises a third surface layer or coating which is either:

(i) arranged and adapted to enhance the yield of secondary ions or electrons; or

(ii) a photocathode layer which is arranged and adapted to receive photons and to release photoelectrons.

10. A mass spectrometer as claimed in claim 8 , wherein said ion detector comprises a fourth foil layer, a fourth substrate or a fourth gas electron multiplier stage.

11. A mass spectrometer as claimed in claim 10 , wherein 0-5%, 5-10%, 10-15%, 15-20%, 20-25%, 25-30%, 30-35%, 35-40%, 40-45%, 45-50%, 50-55%, 55-60%, 60-65%, 65-70%, 70-75%, 75-80%, 80-85%, 85-90%, 90-95% or 95-100% of an upper or lower surface of said fourth foil layer, said fourth substrate or said fourth gas electron multiplier stage comprises a fourth surface layer or coating which is either:

(i) arranged and adapted to enhance the yield of secondary ions or electrons; or

(ii) a photocathode layer which is arranged and adapted to receive photons and to release photoelectrons.

12. A mass spectrometer as claimed in claim 4 , wherein said ion detector comprises one or more electrodes, counter electrodes or cathodes arranged either:

(i) facing or opposed to said first foil layer, said first substrate or said first gas electron multiplier stage; or

(ii) in a drift or input region of said ion detector; or

(iii) to receive analyte cations and to release secondary electrons or secondary anions or secondary cations.

13. A mass spectrometer as claimed in claim 12 , wherein said one or more electrodes, counter electrodes or cathodes comprise:

(i) one or more planar electrodes; or

(ii) one or more grid or mesh electrodes; or

(iii) one or more electrodes having one or more apertures through which ions or analyte cations may be transmitted in use.

14. A mass spectrometer as claimed in claim 1 , wherein said ion detector has a gain selected from the group consisting of: (i)<10; (ii) 10-100; (iii) 100-1000, (iv) 10 3 -10 4 ; (v) 10 4 -10 5 ; (vi) 10 5 -10 6 ; (vii) 10 6 -10 7 ; and (viii)>10 7 .

15. A method of mass spectrometry comprising:

using a Gas Electron Multiplier ion detector to detect ions, wherein said ion detector comprises a first gas electron multiplier stage and one or more counter electrodes arranged adjacent said first gas electron multiplier stage.