Abstract: A method of mass analysis and a mass spectrometer are provided wherein a batch of ions is accumulated in a mass analyzer; the batch of ions accumulated in the mass analyzer is detected using image current detection to provide a detected signal; the number of ions in the batch of ions accumulated in the mass analyzer is controlled using an algorithm based on a previous detected signal obtained using image current detection from a previous batch of ions accumulated in the mass analyzer; wherein one or more parameters of the algorithm are adjusted based on a measurement of ion current or charge obtained using an independent detector located outside of the mass analyzer.

Abstract: A multi-reflection mass spectrometer comprising two ion-optical mirrors, each mirror elongated generally along a drift direction (Y), each mirror opposing the other in an X direction and having a space therebetween, the X direction being orthogonal to Y; the mass spectrometer further comprising one or more compensation electrodes each electrode being located in or adjacent the space extending between the opposing mirrors; the compensation electrodes being configured and electrically biased in use so as to produce, in at least a portion of the space extending between the mirrors, an electrical potential offset which: (i) varies as a function of the distance along the drift length, and/or; (ii) has a different extent in the X direction as a function of the distance along the drift length. In a preferred embodiment the period of ion oscillation between the mirrors is not substantially constant along the whole of the drift length.

Abstract: A method and apparatus of compensating a magnetic field inhomogeneity in a dynamically harmonized FT-ICR cell is presented, based on adding of extra electrodes into the cell, the extra electrodes being shaped in such a way that the averaged electric field created by these electrodes produces a counter force to the forces caused by the inhomogeneous magnetic field on the cycling ions.

Abstract: A method of isolating 99Mo produced using a (n,?) reaction according to example embodiments may include vaporizing a source compound containing 98Mo and 99Mo. The vaporized source compound may be ionized to form ions containing 98Mo and 99Mo. The ions may be separated to isolate the ions containing 99Mo. The isolated ions containing 99Mo may be collected with a collector. Accordingly, the isolated 99Mo may have a relatively high specific radioactivity and, in turn, may be used to produce the diagnostic radioisotope, 99mTc, through radioactive decay.

Abstract: In one embodiment, a substrate processing apparatus, includes: a chamber; a first electrode disposed in the chamber; a second electrode disposed in the chamber to face the first electrode, and to hold a substrate; an RF power supply to apply an RF voltage with a frequency of 50 MHz or more to the second electrode; and a pulse power supply to repeatedly apply a voltage waveform including a negative voltage pulse and a positive voltage pulse of which delay time from the negative voltage pulse is 50 nano-seconds or less to the second electrode while superposing on the RF voltage.

Abstract: The invention relates to embodiments of high-resolution time-of-flight (TOF) mass spectrometers with special reflectors. The invention provides reflectors with ideal energy and solid angle focusing, based on Cassini ion traps, and proposes that a section of the flight path of the TOF mass spectrometers takes the form of a Cassini reflector. It is particularly favorable to make the ions fly through this Cassini reflector in a TOF mass spectrometer at relatively low energies, with kinetic energies of below one or two kiloelectronvolts. This results in a long, mass-dispersive passage time in addition to the time of flight of the other flight paths, without increasing the energy spread, angular spread or temporal distribution width of ions of the same mass. It is also possible to place several Cassini reflectors in series in order to extend the mass-dispersive time of flight. Several TOF mass spectrometers for axial as well as orthogonal ion injection with Cassini reflectors are presented.

Abstract: An ion guide for mass spectrometry comprising an electrode arrangement of at least two electrodes, at least one of which is an RF electrode, arranged adjacent to each other but spaced apart on a planar surface of a dielectric material and arranged at a distance from an ion flow path, wherein a portion of the dielectric surface is exposed between an adjacent pair of the spaced apart electrodes and wherein at least one electrode of said adjacent pair of electrodes is arranged to overhang the exposed portion of surface between them such that there is no direct line of sight from the ion flow path to the exposed portion of dielectric surface. The device enables RF guiding of ions accompanied by much reduced charging-up of dielectric surfaces and reduced amount of collisions of neutral species with electrodes.

Abstract: A field terminator includes a plurality of electrode plates positioned around a guide axis at a radial distance therefrom. The plates generate a quadrupole DC field such that a polarity on each plate is opposite to a polarity on the plates adjacent thereto. The plates may be positioned at an axial end of a quadrupole ion guide such as a mass filter. In addition to an RF field, the ion guide may generate a quadrupole DC field. The DC field of the plates may be opposite in polarity to that of the ion guide.

Abstract: This invention describes an ion mobility spectrometer and operational methods for chemical analysis. The ion mobility spectrometer allows for continuous operation and rapid temperature control to reach designed operational conditions, as well as analysis under a temperature gradient.

Abstract: Systems and methods are provided for correcting uniform detector saturation. In one method, a mass analyzer analyzes N extractions of an ion beam. A nonzero amplitude from an ADC detector subsystem is counted as one ion, producing a count of one for each ion of each sub-spectrum. The ADC amplitudes and counts of the N sub-spectra are summed, producing a spectrum that includes a summed ADC amplitude and a total count for each ion of the spectrum. A probability that the total count arises from single ions hitting the detector is calculated. For each ion of the spectrum where the probability exceeds a threshold value, an amplitude response is calculated, producing amplitude responses for ions found to be single ions hitting the detector. Amplitude responses are combined, producing a combined amplitude response. The total count is dynamically corrected using the combined amplitude response and the summed ADC amplitude.

Abstract: Method for operating a mass spectrometer includes supplying a quantity of ions to an ion detector. The ion detector can include a conversion dynode operating in a first polarity and an electron multiplier. The method further includes adjusting the gain of the electron multiplier to determine a first set of calibration parameters, and calculating a second set of calibration parameters for the electron multiplier from the first set of calibration parameters. The second set of calibration parameters are for a second polarity of the conversion dynode. The method can further include configuring the ion detector to operate at the second polarity based on the second set of calibration parameters, and supplying ions of the second polarity to the mass spectrometer, and detecting an ion at a particular mass to charge ratio using the ion detector.

Abstract: A method of ion imaging is disclosed comprising scanning a sample and acquiring first mass spectral data related to a first pixel location at a first spatial resolution and determining whether or not the first mass spectral data satisfies a condition. If it is determined that the first mass spectral data does satisfy the condition then the first mass spectral data is stored, recorded or prioritized. If it is determined that the first mass spectral data does not satisfy the condition then the first mass spectral data is discarded or downgraded. Scanning of the sample then continues at the first spatial resolution and further mass spectral data related to further pixel locations is acquired.

Abstract: An ion guiding device is disclosed comprising a first ion guide which is conjoined with a second ion guide. Ions are urged across a radial pseudo-potential barrier which separates the two guiding regions by a DC potential gradient. Ions may be transferred from an ion guide which has a relatively large cross-sectional profile to an ion guide which has a relatively small cross-sectional profile in order to improve the subsequent ion confinement of the ions.

Abstract: According to one embodiments, an ion source connected with a vacuum-exhausted downstream apparatus is provided. The ion source includes a vacuum chamber which is vacuum-exhausted, a target which is set in the vacuum chamber and generates ions by irradiation of a laser beam, a transportation unit which transports the ions generated by the target to the downstream apparatus, and a vacuum sealing unit which seals the transportation unit so as to separate vacuum-conditions of the vacuum chamber side and the downstream apparatus side before exchanging the target set in the vacuum chamber.

Abstract: To control of an irradiation installation, a particle beam is generated with a beam intensity, and a beam quality of the particle beam is monitored with a beam monitoring device. One of several adjustable measurement ranges is selected, wherein the measurement range of the beam monitoring device is set depending on the beam intensity of the particle beam and/or depending on a particle count to be applied.

Abstract: A method and a device increases (e.g., uniformly) the internal energy of ions, in order to remove water shells or adducts, to decompose clusters or molecular agglomerations, to unfold large folded ions, or to prepare ions for fragmentation with high yield. The ions can be heated at a gas pressure of a few hectopascal viscously dragged through a tube comprising on-axis RF fields with strong axial field components. The ions are introduced, as usual together with entraining gas, into a vacuum system of a mass spectrometer through a small hole or capillary, and are driven by the gas flow through the tube with the RF fields. The RF fields decelerate and re-accelerate the ions, which travel through the tube, in rapid succession mainly in forward and backward direction, thus causing high numbers of collisions with the gas molecules and heating up the ions in a uniform manner.

Abstract: An ionization chamber with spatial distribution electrode for monitor hadron beam currents used for therapeutic treatment. Ionization chamber comprises humidity control, environmental sensing and real-time correction thereof. A flexible hermetic seal provide for ambient pressure equalization. X-Y electrode planes measure Gaussian distribution of incident particle beam. Methods described herein are suitable to fabricate highly accurate, low scattering electrodes with high spatial resolutions.

Abstract: This invention describes an apparatus and method with a combined primary electrospray and secondary electrospray ionization source used to enhance ionization efficiency. The solid phase as well as liquid phase sampling, ionization, and detection is described.

Abstract: A method of operating a gas-filled collision cell in a mass spectrometer is provided. The collision cell has a longitudinal axis. Ions are caused to enter the collision cell. A trapping field is generated within the collision cell so as to trap the ions within a trapping volume of the collision cell, the trapping volume being defined by the trapping field and extending along the longitudinal axis. Trapped ions are processed in the collision cell and a DC potential gradient is provided, using an electrode arrangement, resulting in a non-zero electric field at all points along the axial length of the trapping volume so as to cause processed ions to exit the collision cell. The electric field along the axial length of the trapping volume has a standard deviation that is no greater than its mean value.

Abstract: A method includes determining a highest peak of an optical spectrum waveform contained within a wavelength window having a fixed wavelength range, the wavelength window having a beginning wavelength value and an ending wavelength value, and iteratively modifying the beginning and ending wavelength values, within the fixed wavelength range, to shift the wavelength window so the highest peak is centered at a first position within the wavelength window. The method may further include determining a second highest peak of the optical spectrum waveform and iteratively expanding or contracting the optical spectrum waveform, while maintaining the highest peak centered at the first position, to locate the second highest peak at a predetermined position within the wavelength window. The method may be used for window calibration to enable repeatable and precise harmonic analysis of optical spectra, such as Raman spectra.

Abstract: A detector for gas chromatography using two or more ionization sources within a single body to separately provide ionization energy to a column gas eluent to provide electrical discharge to two or more collecting electrodes provides improved selectivity and may be so used. Use is made of combined bias/collecting electrodes or of sets of separated bias and collecting electrodes. The use of multiple ionization sources permits generation of multiple detector outputs from within a common body and of a common constituent flow. The ionization sources and any applicable discharge gas and dopant may be selected based on desired selectivity.

Abstract: A system and method for acquisition of mass spectrometry data is configured to provide a stream of charged particles (e.g., from an analytical volume). A primary mass spectrometer (e.g., time-of-flight mass spectrometer) may be used to separate charged particles of the stream of charged particles based on their mass-to-charge ratio and detect the charged particles in a mass-to-charge spectrum. A stream of precursor ions having a selected mass range may be diverted from the stream of charged particles for fragmentation to provide fragment ions (e.g., fragment ions from the analytical volume). The fragment ions may be provided to a second mass spectrometer for analysis of the fragment ions (e.g., during the same time as the time-of-flight mass spectrometer is separating and detecting charged particles of the stream of charged particles based on their mass-to-charge ratio).

Abstract: A method and apparatus for tandem mass spectrometry is disclosed. Precursor ions are fragmented and the fragments are accumulated in parallel, by converting an incoming stream of ions from an ion source (10) into a time separated sequence of multiple precursor ions which are then assigned to their own particular channel of a multi compartment collision cell (40). In this manner, precursor ion species, being allocated to their own dedicated fragmentation cell chambers (41, 42 . . . 43) within the fragmentation cell (40), can then be captured and fragmented by that dedicated fragmentation chamber at optimum energy and/or fragmentation conditions.

Abstract: A data acquisition system and method are described that may be used with various spectrometers. The data acquisition system may include an ion detector, an initial processing module, and a spectra processing module. The initial processing module is provided for processing the ion detection signals and for supplying processed signals to the spectra processing module. The spectra processing module generates spectra from the processed signals and supplies the generated spectra to an external processor for post-processing. The spectra processing module may include an ion statistics filter and/or a peak histogram filtering circuit.

Abstract: An apparatus includes an electrostatic ion trap and electronics configured to measure parameters of the ion trap and configured to adjust ion trap settings based on the measured parameters. A method of tuning the electrostatic ion trap includes, under automatic electronic control, measuring parameters of the ion trap and adjusting ion trap settings based on the measured parameters.

Abstract: There is provided a transfer device (30) that transfers ionized substances in a first direction. The transfer device (30) includes a drift tube (50) and the drift tube (50) includes electrode plates (71) and (72) constructing an outer wall and a plurality of ring electrodes (60, 61, 62) disposed inside the tube. The ring electrodes (60) forms a first AC electric field for linear driving that causes the ionized substances to travel in the first direction that is the axial direction. The electrode plates (71) and (72) form an asymmetric second AC electric field that deflects the direction of travel of the ionized substances.

Abstract: An ion guiding device is disclosed comprising a first ion guide which is conjoined with a second ion guide. Ions are urged across a radial pseudo-potential barrier which separates the two guiding regions by a DC potential gradient. Ions may be transferred from an ion guide which has a relatively large cross-sectional profile to an ion guide which has a relatively small cross-sectional profile in order to improve the subsequent ion confinement of the ions.

Abstract: Methods and systems for performing mass spectrometry of analytes labeled with isobaric tags are provided herein. In accordance with various aspects of the applicants' teachings, the methods and systems can enable enhanced discrimination between an analyte of interest and one or more interfering species when using isobaric tagging techniques.

Abstract: An electrostatic trap such as an orbitrap is disclosed, with an electrode structure. An electrostatic trapping field of the form U?(r, ?, z) is generated to trap ions within the trap so that they undergo isochronous oscillations. The trapping field U?(r, ?, z) is the result of a perturbation W to an ideal field U(r, ?, z) which, for example, is hyperlogarithmic in the case of an orbitrap. The perturbation W may be introduced in various ways, such as by distorting the geometry of the trap so that it no longer follows an equipotential of the ideal field U(r, ?, z), or by adding a distortion field (either electric or magnetic). The magnitude of the perturbation is such that at least some of the trapped ions have an absolute phase spread of more than zero but less than 2 ? radians over an ion detection period Tm.

Abstract: A method and apparatus are disclosed for improving ion mobility spectrometry by using a fast and spatially wide ion gate based on local RF field barrier opposed to a switching DC field. The improvement accelerates the ion mobility analysis and improves charge throughput and dynamic range of the IMS. The invention is particularly suited for rapid dual gas chromatography. In one important embodiment, the accelerated IMS is coupled to a multi-reflecting time-of-flight mass spectrometer with a fast encoded orthogonal acceleration. There are described methods of comprehensive and orthogonal separation in multiple analytical dimensions.

Abstract: A mass spectrometer is disclosed comprising a first quadrupole rod set mass filter, a collision cell, an ion mobility spectrometer or separator, an ion guide or collision cell arranged downstream of the ion mobility spectrometer or separator, a second quadrupole rod set mass filter and an ion detector.

Abstract: There is provided a mass spectrometry apparatus comprising: an ion source arranged in a substantially horizontal orientation and from which a quantity of ions may be sourced, an ion filter device arranged for receiving a stream of ions for filtering thereof; and, an ion guide arranged so as to guide ions sourced from the ion source toward the ion filter device. The ion source and the ion filter device are arranged relative to one another so that the profile of the apparatus is reduced so as to minimize the effective footprint of the apparatus.

Abstract: A method for determining origins of food products, and more specifically for determining geographic and/or biological origin of food products containing alcohols or sugars includes preparing an alcohol sample from a product in question, removing exchangeable hydrogen/deuterium atoms from alcohol molecules of the sample, determining the isotopic composition of non-exchangeable hydrogen/deuterium atoms from sample alcohol, and analyzing results for adulteration or determination of product origin. In addition, alcohol ?13C and ?18O isotopic values, along with ?18O isotopic value of the product water are used for the analysis. Products containing sugar are also subjected to tightly controlled fermentation.

Abstract: An apparatus for a mass spectrometer comprises: a set of four rod electrodes defining an ion occupation volume therebetween having entrance and exit ends, at least one of the rod electrodes having a slot passing therethrough; first and second ion optics disposed adjacent to the entrance and exit ends, respectively; a voltage supply system; and at least one supplemental electrode disposed at least partially within the at least one slot, wherein the voltage supply system is configured so as to supply a radio-frequency (RF) voltage, a direct-current (DC) filtering voltage and an oscillatory dipole resonant ejection voltage across members of the set of rod electrodes and so at to supply a secondary ion-trapping RF voltage and a secondary DC filtering voltage to the at least one supplemental electrode and to supply DC voltages across the rod electrodes and each of the first and second ion optics.

Abstract: The present invention provides a radio frequency (RF) power supply in a mass spectrometer. The power supply provides an RF signal to electrodes of a storage device to create a trapping field. The RF field is usually collapsed prior to ion ejection. In an illustrative embodiment the RF power supply includes a RF signal supply; a coil arranged to receive the signal provided by the RF signal supply and to provide an output RF signal for supply to electrodes of an ion storage device; and a shunt including a switch operative to switch between a first open position and a second closed position in which the shunt shorts the coil output.

Abstract: A mass spectrometer is disclosed comprising a quadrupole rod set ion trap wherein a potential field is created at the exit of the ion trap which decreases with increasing radius in one radial direction. Ions within the on trap are mass selectively excited in a radial direction. Ions which have been excited in the radial direction experience a potential field which no longer confines the ions axially within the ion trap but which instead acts to extract the ions and hence causes the ions to be ejected axially from the ion trap.

Abstract: The present invention is concerned with an ion analysis apparatus comprising an ion guide having an ion optical axis extending from an ion inlet to an ion outlet, the ion guide being configured to guide ions from the ion inlet to the ion outlet along the ion optical axis, wherein the ion guide comprises at least one extraction region located between the ion inlet and the ion outlet, the at least one extraction region being configured to extract ions moving along the ion optical axis of the ion guide in an extraction direction, the extraction direction being substantially orthogonal to the ion optical axis of the ion guide, wherein the apparatus includes ion radial confinement means that in use confine the ions in the radial direction within the ion guide.

Abstract: A linear ion trap is disclosed wherein an asymmetric voltage waveform is applied to electrodes forming the ion trap which causes ions to become radially separated according to their differential ion mobility. An axial potential barrier is arranged at the exit of the ion trap such that ions having a first differential ion mobility and a first radial displacement are retained axially within the ion trap but ions having a second differential ion mobility and a second radial displacement are ejected axially from the ion trap.

Abstract: LC/MS data generated by an LC/MS system is analyzed to determine groupings of ions associated with originating molecules. Ions are grouped initially according to retention time, for example, using retention time or chromatographic peaks in mass chromatograms. After initial groupings are determined based on retention time, ion peak shapes are compared to determine whether ions should be excluded. Ions having peak shapes not matching other ions, or alternatively a reference peak shape, are excluded from the group.

Abstract: The present invention provides a timing device, especially a timing device for use in mass spectrometers, for example TOF mass spectrometers, for processing trigger signal data containing a trigger signal indicating the occurrence of a trigger event, the timing device having: a trigger signal deserializer configured to receive trigger signal data containing a trigger signal indicating the occurrence of a trigger event as serial data and to output the trigger signal data as parallel data, and wherein suitably the timing device has a processing means configured to process trigger signal data outputted by the trigger signal deserializer as parallel data.

Abstract: Systems and methods for automatic gain control in mass spectrometers are disclosed. An exemplary system may include a mass spectrometer, comprising a lens configured to receive a supply of ions, and a mass analyzer. The mass analyzer may include an ion trap for trapping the supplied ions. The mass analyzer may also include an ion detector for detecting ions that exit the ion trap. The lens may focus the ions non-uniformly based on mass of the ions to compensate for space charge effects reflected in a measurement output of the mass spectrometer. An exemplary method may include focusing an ion beam into a mass analyzer. The method may also include obtaining a mass spectrum and identifying a space charge characteristic based on the mass spectrum. The method may further include defocusing the lens based on the identified space charge characteristic, wherein defocusing the lens is configured to divert lighter ions away from the entrance aperture.

Abstract: An annular ion guide is disclosed comprising inner and outer electrodes. Ions are confined within an annular ion guiding region by RF or pseudo-potential barriers in both an outward and inward radial direction.

Abstract: An ion guide is disclosed comprising a plurality of axial groupings of electrodes, wherein each axial grouping of electrodes comprises a ring or annular electrode which has been radially segmented into a plurality of electrode segments.

Abstract: A tandem mass spectrometer and method are described. Precursor ions are generated in an ion source (10) and an ion injector (21, 23) injects ions towards a downstream ion guide (50, 60) via a single or multi reflection TOF device (30) that separates ions into packets in accordance with their m/z. A single pass ion gate (40) in the path of the precursor ions between the ion injector (21, 23) and the ion guide (50, 60) is controlled so that only a subset of precursor ion packets, containing precursor ions of interest, is allowed onward transmission to the ion guide (50, 60). A high resolution mass spectrometer (70) is provided for analysis of those ions, or their fragments, which have been allowed passage through the ion gate (40). The technique permits multiple m/z ranges to be selected from a wise mass range of precursors, with optional fragmentation of one or more of the chosen ion species.

Abstract: In order to solve a problem in a mass spectrometry that a distribution of an emitted ion and a substance distribution on the measurement object surface are different from each other, which is due to a shaded portion of a irregular surface which falls under a shadow of primary beam, a primary ion optical system of the present apparatus includes a deflection unit configured to deflect the primary ion in such a manner that the primary ion intersects a flight space of the secondary ion in the course of flight.

Abstract: A method is provided comprising accumulating ions in a first ion trap at a first time; transmitting a first plurality of ions out of the first ion trap through a timed-ion selector; applying a pulsed DC voltage to the timed-ion selector; transmitting the first portion of selected ions into a second ion trap at a second time; retaining a second plurality of ions in the first ion trap at the second time; transmitting the first portion of selected ions out of the second ion trap at a third time; transmitting the second plurality of ions out of the first ion trap through a timed-ion selector; applying a pulsed DC voltage to the timed-ion selector transmitting a second portion of selected ions into the second ion trap at a fourth time; and transmitting the second portion of selected ions out of the second trap.

Abstract: An ion trap includes a containment region for containing ions, and a plurality of electrodes positioned on a regular polyhedral structure encompassing the containment region. An electrode is positioned on each vertex of the encompassing structure and at least one of the polygonal surfaces includes additional electrodes configured to form a plurality of quadrupoles on the surface. Alternating RF voltage is applied to the plurality of electrodes, so that directly neighboring electrodes are of equal amplitude and opposite polarity at any point in time. This configuration on the polyhedral structure forms a potential barrier for repelling the ions from each of the regular polygonal surfaces and containing them in the trap. Mass selective filters can be formed from the quadrupoles for parallel mass analysis in different m/z windows. Application of a small DC potential to a plate electrode outside the quadrupoles preferentially depletes single charged ions for enhanced signal-to-noise analysis.

Abstract: A method and apparatus for high resolution separation of ions based on their high field and low-field mobility properties is described. An elongate ion separation channel is defined by a plurality of channel walls. First and second channel walls have first and second spaced ion separation electrode assemblies respectively. A power supply applies a periodic asymmetric potential to one or both of the electrode assemblies so as to generate a periodically asymmetric electric field in the channel for ion mobility separation. The channel walls define an ion separation channel of substantially helical shape.

Abstract: The present invention relates to inductively coupled plasma mass spectrometry (ICPMS) in which a collision cell is employed to selectively remove unwanted artefact ions from an ion beam by causing them to interact with a reagent gas. The present invention provides a first evacuated chamber (6) at high vacuum located between an expansion chamber (3) and a second evacuated chamber (20) containing the collision cell (24). The first evacuated chamber (6) includes a first ion optical device (17). The collision cell (24) contains a second ion optical device (25). The provision of the first evacuated chamber (5) reduces the gas load on the collision cell (24), by minimising the residual pressure within the collision cell (24) that is attributable to the gas load from the plasma source (1). This serves to minimise the formation, or re-formation, of unwanted artefact ions in the collision cell (24).

Abstract: A mass filter apparatus for filtering a beam of ions is described. The apparatus comprises an ion beam source and first and second mass filter stages in series to receive the ion beam. A vacuum system maintains the first and second filter stages at substantially the same operating pressure, below 10?3 torr. The first mass filter stage transmits only ions having a sub-range of mass-to-charge ratios including a selected mass-to-charge ratio. The second filter transmits only ions of the selected mass-to-charge ratio. The second mass filter can achieve high accuracy detection without being subjected to problems such as build-up of material on quadrupole rods, resulting in a distorted electric field close to the rods. The first mass filter acts as a coarse filter, typically transmitting 1% of ions received from the ion source. Thus, the detection accuracy and lifetime of mass spectrometers embodying this invention are greatly improved. A mass filter apparatus for filtering a beam of ions is described.