Patent ID: 8410433

Claim:
A mass spectrometer arrangement having a detection system ( 12 ) and comprising: a cathode configuration ( 6 ) for emitting electrons ( 21 ); a reaction zone ( 3 ) having an entrance opening ( 14 ) for a supply of neutral particles ( 20 ), the reaction zone being operatively connected to the cathode configuration ( 6 ) for ionization of the neutral particles ( 20 ) in an effective region of the reaction zone to form ions ( 22 ); an ion extraction system ( 4 ) communicating with the effective region of the reaction zone ( 3 ); guidance means ( 1 , 10 , 11 ) for guidance of the ions ( 22 ) to the detection system ( 12 ) within the mass spectrometer arrangement; evacuation means for evacuation of the mass spectrometer arrangement; the cathode configuration ( 6 ) comprising a field emission cathode with an emitter surface ( 7 ) and, at a short distance from the emitter surface ( 7 ), an extraction grid ( 9 ) for extraction of electrons ( 21 ) away from the emitter surface, the extraction grid substantially covering the emitter surface ( 7 ), and the emitter surface ( 7 ) at least partly encompassing a hollow volume ( 13 ) to create a tubular structure around the hollow volume ( 13 ), wherein the emitter surface ( 7 ) is a surface which has been subjected to etching to thereby form a rough surface.