Abstract: An improved apparatus and method for plasma source mass spectrometry, the apparatus comprising: means (16) for generating a plasma (15) at substantially atmospheric pressure in a gas; means (4) for introducing a sample to the plasma wherein the sample is ionized to form sample ions (17); means (19, 23) for transmitting the ions from the plasma into an evacuated chamber (24); a mass filter (26) disposed within the evacuated chamber; a substantially non-multiplying ion detector (58) comprising an ion collector (59), the detector being responsive to the charge of at least some of the sample ions which pass through the mass filter; and means for inhibiting the response of the detector to electrically neutral particles. Typically the detector comprises a suppressor (63) and means (64) for negatively biassing the suppressor with respect to the collector, and also a shield (61) disposed to shield the suppressor from the neutral particles.

Abstract: There is disclosed a double-focusing mass spectrometer in which ions are generated from a sample in a microwave-induced or inductively-coupled plasma (3). Ions are sampled from the plasma (3) through an aperture in a sampling cone (19) and pass through a skimmer cone (28) and several electrostatic lenses (30,33) to the entrance slit of the mass analyzer. The sampling cone (19) and skimmer cone (28) are maintained by a power supply (40) at a potential approximately equal to the accelerating potential required by the mass analyzer. It is found that the plasma potential may be maintained at such a value that a substantial proportion of the ions generated in the plasma (3) have energies lying within the energy passband of the mass analyzer, so that a high sensitivity, high resolution mass spectrometer especially suitable for the elemental analysis of solid or liquid samples is provided.

Abstract: The invention comprises a mass spectrometer wherein a sample is ionized in a plasma (14), especially an inductively-coupled or microwave-induced plasma. Ions are sampled from the plasma (14) through an orifice (16) in a sampling member (15), a second orifice (37) in a hollow tapered member (19) and a third orifice (53) in a tubular electrode (43). The hollow tapered member (19) comprises a portion (35) both externally and internally tapered with an interior included angle greater than 60.degree., and preferably a shorter externally tapered portion (38) with an external included angle of less than 60.degree.. A tubular extraction electrode 43, preferably comprising a conical end-portion (47) , is disposed within the member (19) for efficiently transmitting the ions into a mass analyzer.

Abstract: The invention comprises a mass spectrometer adapted for the determination of isotopic ratios which has several ion-collecting means disposed along its mass focal plane. Separate current amplifier means are provided for each ion collecting means and comprise an electrometer amplifying element, and an input resistor disposed in an inner box, itself disposed within a sealed evacuated housing. Means are provided for cooling the amplifier element to a temperature substantially below 20.degree. C. Means are provided for maintaining the temperature of at least the input resistor substantially constant. Cooling the amplifier element, typically to between 0.degree. and 5.degree. C., results in an unexpected reduction in low frequency noise which allows the time required to determine an isotope ratio to be reduced, thereby substantially increasing sample throughout.

Abstract: There is provided a mass spectrometer adapted for the elemental analysis of a sample, especially a solid sample, comprising a glow discharge ion source which yields ions characteristic of the elements in the sample. The background spectrum produced by such a mass spectrometer is substantially reduced by cooling the ion source below 20.degree. C., and preferably below -100.degree. C., thereby increasing the sensitivity and the accuracy of the spectrometer. The cooling of the ion source is preferably accomplished by flowing liquid nitrogen through a heat exchanger disposed in good thermal contact with it.