Abstract: The invention comprises methods and apparatus for the mass spectrometric determination of the isotopic composition of an element comprised in an analysis gas (that is, a gas comprising the element in elemental form or in the form of a simple compound, e.g., nitrogen or carbon dioxide). First and second flows of a carrier gas (e.g., helium) are simultaneously passed into the mass spectrometer, and samples of analysis gas and a reference gas are respectively introduced into the first and second flows during selected time intervals. The time intervals are selected so that mass spectrometric measurements are made on the analysis gas samples in the absence of any signal from the reference gas samples, and v.v. A preferred embodiment comprises a gas chroatograph through which a sample containing the element is passed, and conversion means to convert the eluting sample into the analysis gas.

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.

Abstract: The invention provides a sample valve adapted to produce a sample of any one of a plurality of fluid streams for an analytical instrument (especially a mass spectrometer). It comprises a stationary plate member in which are formed a plurality of inlet ports. A sampling head is mounted from a drive shaft which is rotated to select one of the inlet ports. A sample of the fluid flowing through the selected inlet is taken by a narrow-bore pipe and is transferred via a rotary shaft sealing means to a stationary output member. Excess gas from the selected inlet port passes inside a sleeve member in the sampling head and into a purging chamber adjacent to the exterior of the sealing means, thereby minimizing contamination of the sample through a leak in the sealing means.

Abstract: An apparatus adapted for the analysis of a surface of a sample and comprising: means for stimulating a region of said surface to emit charged particles; means for moving a light reflecting means in a substantially rectilinear fashion along an optical axis of a microscope to a position where it reflects an image of said region to said microscope; and means for moving an extraction electrode in a substantially rectilinear fashion in a direction substantially parallel to, or coincident with, said optical axis to a position where said charged particles pass through an aperture in said extraction electrode to a charged particle analyzer. The invention allows both the direction of extraction of charged particles, and the direction along which said surface is viewed, to be coincident and perpendicular to said surface.

Abstract: The invention provides a mass spectrometer capable of detecting both positive and negative ions. Positive ions emerging from the mass analyzer strike a conversion electrode to release secondary electrons which pass through an annular electrode to strike a phosphor, releasing photons. Negative ions strike the surface of the annular electrode to release secondary electrons which also strike the phosphor, releasing photons. The photons are detected with a conventional photomultiplier. The electrodes are biased and disposed so that both positive ions and negative ions may be detected without changing the potentials applied to them.

Abstract: The invention provides a mass spectrometer for the analysis of a sample dissolved in a fluid, and in particular a spectrometer for the analysis of high molecular weight compounds in the eluent of a liquid chromatograph. The fluid to be analyzed is at least partly vaporized and sprayed into the cathode dark space of a glow discharge. Ions characteristic of the sample are extracted from the discharge and subsequently mass analyzed. conveniently, spraying into the cathode dark space is achieved by making the cathode electrode of the discharge comprise the spraying means through which the fluid is sprayed. Little fragmentation of the high mass ions is caused by the process, and the invention extends the range of compounds which can be analyzed in comparison with similar prior art thermospray type mass spectrometers.

Abstract: A method of time-of-flight mass spectrometry adapted for the analysis of ions up to a required mass limit comprises the following sequences of events:(a) producing, during a first time interval, a pulse of charged particles,(b) directing said charged particles towards the entrance of a mass analyzer;(c) recording the times-of-flight of said charged particles after they pass through said mass analyzer;(d) closing a gating means, which is disposed in the path of said charged particles between said source and said mass analyzer, after a second time interval which, measured from the start of said first time interval, is sufficient for substantially all of said charged particles having mass less than or substantially equal to said mass limit to travel from said source to and through said gating means;(e) keeping said gating means closed until the end of a third time interval which, measured from the start of said first time interval, is at least as long as the time taken for substantially the most massive of said

Abstract: The invention provides a charged-particle energy analyzer of the cylindrical mirror type (2,9,10) which incorporates beam shaping means (5,6) at one, or preferably both, ends. The beam shaping means to convert a substantially parallel beam of charged particles to an annular beam which diverges at the optimum entrance angle of the CMA, and v.v. They enable the CMA to operate efficiently with parallel input and output beams of circular cross section, and allow it to be efficiently combined with a mass analyzer, especially a quadrupole mass analyzer (31,32) to provide a compact energy-filtered mass spectrometer particularly suitable for secondary ion mass spectrometry.

Abstract: The invention provides a mass spectrometer adapted for the elemental analysis of a sample in which ions are formed from the sample in an inductively coupled plasma (ICP). The flame of the plasma (14) is directed against the front surface (30) of a cone (19), and ions are sampled from the plasma through a hole (16) in the apex of the cone. In order to reduce the intensity of the background mass spectra, the rear surface (32) of the inside of the cone is polished to a surface finish of 5 microns or better, at least in the vicinity of the hole.

Abstract: There is provided an electron spectrometer operable to produce an image of an electron emitting surface, said spectrometer comprising in sequence:(a) means for causing electrons to be emitted from said surface;(b) a first electrostatic lens system arranged to project at least some of said electrons onto a first diffraction plane as a Fourier transform of an electron image of at least a part of said surface;(c) a torroidal capacitor type electrostatic energy analyzer having an object plane and conjugate thereto a first image plane, said analyzer being disposed with said object plane coincident with said first diffraction plane and being arranged to project electrons of said Fourier transform as an energy dispersed Fourier transform in said first image plane;(d) energy selection means for transmitting electrons of said energy dispersed Fourier transform having energies only within a selected range; and(e) a second electrostatic lens system arranged to receive electrons transmitted by said energy selection means

Abstract: The invention provides a wide range pressure gauge comprising a thermal-conductivity gauge and a high-vacuum total or partial pressure gauge such as a hot-cathode ionization gauge or a residual gas mass spectrometer, mounted from a common flange. In order to allow the use of a filament (3) shorter than those conventionally used in thermal conductivity pressure gauges, means (49-54) are provided to maintain the filament temperature substantially constant over its entire pressure range. Pressure is measured by means (51, 52, 56-58) adapted to measure the power dissipated in the filament (3).

Abstract: The invention comprises apparatus capable of unambiguous determination of the length and diameter of fibrous particles, especially asbestos fibres, based on near-forward scattering of light by fibres aligned in a hydrodynamically focused gas flow. Three portions of scattered light are detected, two portions perpendicular to the fibre axis and one aligned with it, from which length and diameter can be independently determined. This independence is achieved by allowing only selected parts of the light scattered within certain selected ranges of angles to reach each detector. A two-detector instrument capable of accurate determination of fibre diameter is also described.

Abstract: The invention relates to a mass spectrometer having a magnetic sector analyzer in which the magnetic field is developed neither by a permanent magnet nor by an electromagnet having the conventional ferromagnetic core. In particular, the spectrometer has a magnetic sector analyzer through which ions of a mass-to-charge ratio selected by said analyzer may travel along a substantially circular trajectory disposed in a first plane, said analyzer comprising at least two electrical conductor portions of substantially circular arcuate form, respectively of greater and smaller radius than said circular trajectory and disposed on radially opposite sides of a curved plane which is aligned with said circular trajectory and perpendicular to said first plane, and wherein substantially all of the magnetic flux generated by the passage of electrical current through said conductor portions passes only through non-ferromagnetic materials.

Abstract: There is provided a mass spectrometer having at least three analyser sectors of the electrostatic or magnetic types, at least one sector being of the electrostatic type and at least one further sector being of the magnetic type. The spectrometer includes a focusing sector array having at least three analyzer sectors, the sectors of the array being dimensioned and positioned so as to cooperate to form a velocity- and direction- focused image. The sectors of the array are dimensioned and positioned as to form no velocity focused image within the array. One sector of said array is disposed adjacent to and between two sectors of the other type.

Abstract: A mass spectrometer having a thermospray ion source, suitable for the analysis of liquid samples is disclosed. The source comprises a strongly heated atomizing nozzle (4) through which the sample is pumped into a spray chamber (5, 11), and an aperture in a cone (26), through which the ions pass through an electrostatic lens (15, 16, 17) into a region (23) in which a mass analyzer is situated. Electrode means (27, 45) generate a repulsive electrostatic field which improves the efficiency of the transmission of ions through the hole in the cone (26). The electrode is situated downstream of the hole in cone (26). By further increasing the potential on the electrode (27, 45) the nature of the ions passing through the hole in the cone (26) can be changed from largely adduct and cluster ions formed by association of solvent molecules with sample ions in the thermospray to largely pseudomolecular sample ions similar to those formed by conventional chemical ionization.

Abstract: The invention comprises a compact substantially frictionless positioning device for guiding the motion of an object accurately along one or two axes. The object is supported on a pair of parallel motion solid hinges disposed either side of the axis of motion, each hinge comprising two flexible arms disposed in one plane. Springs are provided at one end of each hinge arm to permit the movement of the object along the axis and to restore it to its rest position when the displacing force is removed. Preferably the hinge arms and the springs are of rectangular cross-section to confine the motion of the object to one plane without the need for additional guides. The displacing force may conveniently be provided by an electromagnetic drive motor, the stator of which may be mounted on a further double parallel motion solid hinge assembly to minimize the change in the center of gravity which would otherwise occur when the object is displaced.

Abstract: A charged particle energy spectrometer, typically an electron spectrometer, comprising an electrostatic dispersive charged particle analyzer, e.g. a substantially hemispherical sector analyzer (1,6), and a detector means comprising a plurality of charged particle detectors (26-28) is described. Fringing fields at the exit of the analyzer are corrected by a fringing field corrector plate (7) containing a plurality of apertures (20, 22, 23) each aligned with one channel of the detector means. Exit beam defining slits (21, 24, 25) in a plate (12) situated in the exit focal plane of the analyzer may optionally be provided. Each aperture (20, 22, 23) is preferably the same size and shape as the single aperture used to achieve optimum correction of the fringing fields in a conventional spectrometer having a single channel detector. One or more position sensitive detectors may be used in place of some or all of the detectors (26-28).

Abstract: The invention consists of a mass spectrometer having a sample insertion probe on which a reference compound and an unknown sample can be simultaneously introduced without mixing into a field ionization or ion or neutral particle bombardment ion source. An insulated support is mounted by a parallel hinge on the end of the probe shaft. Two or more separated segments or emitter wires, one carrying the unknown sample, another carrying an appropriate reference compound, are mounted on a base member which is fitted to the support. A drive shaft, concentric with the outer probe shaft, has an eccentric peg on the end, which engages with a cam on the support, so that rotation of the drive shaft results in an oscillating motion of the segments or emitters, alternately positioning them in the optimum position for ionization. A spectrum of the sample or the reference compound can be obtained when required by selecting the appropriate position of the drive shaft.

Abstract: A molecular or atomic beam source for use in molecular beam epitaxy comprises a hollow cylindrical crucible, preferably made of boron nitride, which is heated by an electric current passed through a plurality of very thin elongate metal strips disposed outside of and spaced apart from said crucible and mounted parallel to its axis. In order to maintain the strips in the correct position irrespective of temperature, they may be mounted on springs at each end, but preferably they are made in self supporting pairs linked at the open end of the crucible and mounted on brackets at the other end. The thin strips can be made self supporting by folding along lines parallel to their long axis in a variety of ways. They are arranged to present a large surface area to the crucible which ensures efficient heating and increases the maximum operating temperature of the source.

Abstract: This invention relates to a method of operating quadrupole mass spectrometers with only an RF potential applied to the filter rods so that the spectrometer operates to pass all ions above a particular value of m/e. In practice, spectrometers operated in this way usually show a marked loss in transmission efficiency for ions of high m/e when operated with an RF potential low enough to pass ions of m/e<10, and the invention overcomes this defect by providing a method of switching the RF potential between two or more values at which ions of different ranges of m/e values are efficiently transmitted, and combining the output signals at each value to give a resultant signal more accurately proportional to the number of ions formed in the source of the spectrometer, irrespective of their m/e values. The invention can be used to improve the accuracy of total pressure measurement using a conventional residual gas analyzing mass spectrometer, eliminating the need for additional pressure gauges.