Mass spectrometer tube

Claim 1

A MASS SPECTROMETER TUBE OF THE TYPE IN WHICH IONS RESULTING FROM THE ELECTRON BEAM OF A CATHODE IN AN ION SOURCE ARE DIRECTED IN THE FORM OF A BEAM OF IONS THROUGH A SORTING SPACE, IN WHICH A HIGH FREQUENCY ALTERNATING FIELD OF VARIABLE FREQUENCY IS PRESENT ON A PLURALITY OF SORTING ELECTRODES SO THAT ONLY IONS HAVING A MASS CORRESPONDING TO A GIVEN FREQUENCY CAN REACH A TARGET ELECTRODE, THE CURRENT OF WHICH SERVES AS A MEASUREMENT OF THE PARTIAL PRESSURE OF THIS GIVEN IONIC MASS IN THE GIVEN MIXTURE; THE IMPROVEMENT COMPRISING A CYLINDRICAL ANODE ELEMENT POSITIONED ADJACENT THE ION SOURCE AND HAVING A CENTRAL AXIS PARALLEL TO THE DIRECTED ION BEAM, A CYLINDRICAL EXIT ELEMENT OF SMALLER DIAMETER THAN AND CONCENTRIC WITH SAID CYLINDRICAL ANODE ELEMENT, SAID CYLINDRICAL EXIT ELEMENT EXTENDING BEYOND SAID CYLINDRICAL ANODE ELEMENT IN THE DIRECTION OF THE TARGET ELECTRODE, AN ENTRANCE GRID ELECTRODE POSITIONED AT THE END OF SAID CYLINDRICAL ANODE ELEMENT FACING THE ION SOURCE, AN EXIT GRID ELECTRODE POSITIONED AT THE END OF SAID CYLINDRICAL EXIT ELEMENT FACING THE TARGET ELECTRODE, A CONDUCTIVE TUBULAR SCREENING PART ENCLOSING THE TARGET ELECTRODE AND EXTENDING INTO THE SORTING SPACE SO AS TO OVERLAP AT LEAST ONE SORTING GRID THEREIN, AND MEANS FOR ESTABLISHING THE SAME POTENTIAL ON SAID CYLINDRICAL ANODE ELEMENT AS ON SAID CYLINDRICAL EXIT ELEMENT.