Abstract: A mass spectrometry method in which an improved field comprising two or more trapping fields having substantially identical spatial form is established and at least one parameter of the improved field is changed to excite selected trapped ions sequentially, for example for detection. The improved field can also include a supplemental field of different spatial form. The changing improved field can sequentially eject selected ones of the trapped ions from the improved field for detection (or other purposes). An improved field comprising two quadrupole trapping fields can be established in a region defined by the ring and end electrodes of a three-dimensional quadrupole ion trap, and the amplitude of an RF (and/or DC) component (and/or the frequency of the RF component) of one or both trapping fields can be changed to sequentially excite trapped ions.

Abstract: A mass spectrometry method in which notch-filtered noise is applied to an ion trap to resonate all ions except selected parent ions out of the region of the trapping field. Preferably, the trapping field is a quadrupole trapping field defined by a ring electrode and a pair of end electrodes positioned symmetrically along a z-axis, and the filtered noise is applied to the ring electrode (rather than to the end electrodes) to eject unwanted ions in radial directions (toward the ring electrode) rather than toward a detector mounted along the z-axis. Application of the filtered noise to the trap in this manner can significantly increase the operating lifetime of such an ion detector. Also preferably, the trapping field has a DC component selected so that the trapping field has both a high frequency and low frequency cutoff, and is incapable of trapping ions with resonant frequency below the low frequency cutoff or above the high frequency cutoff.

Abstract: A mass spectrometry method in which one or more high power supplemental AC voltage signals and one or more low power supplemental AC voltage signals are applied to an ion trap. The frequency of each supplemental AC voltage is selected to match a resonance frequency of an ion having a desired mass-to-charge ratio. The low power supplemental voltage signals are applied for the purpose of dissociating specific ions (i.e., parent ions) within the trap, and the high power supplemental voltage signals are applied to resonate products of the dissociation process (i.e., daughter ions) so that they can be detected. In one class of embodiments, the high power voltage signals resonate daughter ions out from the trap for detection by an external detector.

Abstract: A method for generating a filtered noise signal, which includes the steps of generating a broadband signal having optimized (reduced or minimized) dynamic range, and filtering the broadband signal in a notch filter to generate a broadband signal whose frequency-amplitude spectrum has one or more notches (the "filtered noise" signal). In preferred embodiments, the filtered noise signal is a voltage signal suitable for application to an ion trap during a mass spectrometry operation. The invention enables rapid generation of different filtered noise signals (for use in different mass spectrometry experiments) by filtering a single, optimized broadband signal using a set of different notch filters, each having a simple, easily implementable design.

Abstract: A mass spectrometry method in which a trapping field signal (such as a three-dimensional quadrupole trapping field signal or other multipole trapping field signal) set to store ions of interest is superimposed with a notch-filtered broadband ("filtered noise") signal, and ions are formed or injected in the resulting combined field. The filtered noise signal resonates all ions (except selected ones of the ions) from the combined field, so that only selected ones of the ions remain trapped in the combined field. The combined filtered noise and trapping field signal (the "combined signal") is then changed to excite the trapped ions sequentially, so that the excited ions can be detected sequentially. The invention can be applied to perform an (MS).sup.n or CI, or combined CI/(MS).sup.n, mass spectrometry operation.

Abstract: A mass spectrometry method in which a supplemental AC voltage signal having at least one high power frequency component, and at least one low power frequency component, is applied to an ion trap. Each high power component has an amplitude sufficiently large to eject one or more selected ions from the trap, by resonantly exciting the ions. Each low power component has an amplitude sufficient to induce dissociation (or reaction) of one or more selected ions, but insufficient to resonate the ions for detection. The frequency (or band of frequencies) of each high and low power frequency component is selected to match a resonance frequency of ions having a desired mass-to-charge ratio. Each low power component is applied for the purpose of inducing dissociation or reaction of specific trapped ions, which may be parent, daughter, reagent, or product ions, and each high power component is applied to eject undesired products of each such dissociation or reaction process from the trap.

Abstract: A mass spectrometry method in which notch-filtered noise is applied to an ion trap to resonate all ions except selected reagent ions out of the region of the trapping field. Preferably, the trapping field is a quadrupole trapping field defined by a ring electrode and a pair of end electrodes positioned symmetrically along a z-axis, and the filtered noise is applied to the ring electrode to eject unwanted ions in radial directions rather than toward a detector mounted along the z-axis. Also preferably, the trapping field has a DC component selected so that the trapping field has both a high frequency and low frequency cutoff, and is incapable of trapping ions with resonant frequency below the low frequency cutoff or above the high frequency cutoff. Application of the filtered noise signal to such a trapping field is functionally equivalent to filtration of the trapped ions through a notched bandpass filter having such high and low frequency cutoffs.

Abstract: A method for performing mass analysis with dynamic mass resolution, in which a time-varying notch filtered broadband voltage signal (sometimes denoted as a time-varying "filtered noise" signal) is applied to a quadrupole mass filter. The time-varying filtered noise signal can consist of a rapid sequence of static (time-invariant) filtered noise signals, each defining a notch having a selected width and center location. The invention facilitates performance of mass analysis over a wide range of ion mass-to-charge ratios ("mass ranges") with adequate mass resolution. By appropriately choosing the width of each notch in the applied time-varying filtered noise, mass analysis can be performed with substantially constant mass separation over a wide mass range.

Abstract: A feed-forward amplifier utilizes frequency dependent delay elements to cancel the effects of phase dispersion in the amplifier to amplify a broadband, high-frequency signal with low distortion.

Abstract: A MMIC variable slope gain-equalizer varies the conductance of depletion mode Schottky gate FETs to controllably insert frequency dependent resonant members in a modified bridged-T configuration. Resistors connected from circuit input port to output port define the arms of the "T" and a T-node to which a first frequency dependent resonant member is connected in series with a first FET. A second FET and a second frequency dependent resonant member are each connected in series between the circuit ports, bridging the T. Preferably a third frequency dependent resonant member is series connected with the second frequency dependent member. Each frequency dependent resonant member resonates at about the highest frequency of interest, typically about 18 GHz. When the first FET is on and the second FET off, maximum attenuation at lower frequencies is inserted into the circuit, and when the first FET is off and the second FET on, minimum attenuation is inserted at lower frequencies.

Abstract: An improved method for assembling a travelling wave tube (TWT) including the step of forming a heat stripe along the barrel of the TWT to reduce the diameter of the barrel and create an interference fit between the barrel and internal components of the TWT.

Abstract: A MMIC variable att4enuator uses depletion mode Schottky gate FETS as variable conductance devices in a ".pi." configuration to vary attenuation as a function of a DC control voltage. Attenuation is flat within .+-.1 dB, VSWR is .ltoreq.2:1 throughout the operating frequency and control voltage range, and about 12 dB variable attenuation is provided. The ".pi." is formed by FETs in shunt to ground between attenuator input and output, and by a FET in series between input and output. Resistors and an inductor connected in parallel with the series FET extend attenuator bandwidth to 20 GHZ and improve attenuation linearity versus control voltage. A resistor in series with each shunt FET also improves linearity. The typically 0 to +3 VDC control voltage is applied to the FET gates and drain/source leads permitting attenuation control with a single control voltage.