Siemens Aktiengesellschaft

Siemens Energy & Automation, Inc.

Leybold Inficon, Inc.

Applied Automation, Inc.

Duane P Littlejohn

Robert W Arnold

Fritz H Schlereth

Thomas Knudsen

James E Phillips

W Peter Schubert

A mass spectrometer (MS) which uses the Fourier transform ion cyclotron resonance (FTICR) technique to determine the mass of ions. The MS is prepared with a surface that guarantees that a particle striking the surface will have at least one contact with the cathode and will most likely be re-pumped before escaping into the vacuum chamber volume.

Automatic background ejection (ABE)

Triode ion pump

A method for forming the seat in a pulsed sampling valve used in a FTICR MS. The valve has a ceramic ball that closes against the seat to thereby seal the passageway that is used for introduction of sample into the FTICR MS vacuum chamber. The material from which the seat is formed is chosen to withstand relatively high operating temperatures and a precise deburred hole is drilled in that material. The pre-load spring exerts a force against the ball when the valve is assembled. The force initially exceeds the yield strength of the seat material to deform the material to form the seat.

Method for forming a seat in a pulsed sampling valve

A quantity of electrons that will be used in the ionization event in an FTICR MS is preprogrammed. When the number of electrons produced reaches that number, the electron beam is turned off. This approach assures that the same number of electrons are used for every measurement and eliminates the variations due to fundamental characteristics of the electron sourcere and the variations in temperature due to changing ambient conditions.

Programmed electron flux

A relay control for an ion pump used in a FTICR MS. When it is desired to admit new sample gas into the vacuum system, the high voltage that powers the ion pump is removed from the pump electrode by opening the normally closed relay contact. A normally open contact relay contact is then closed to ground the pump electrode and discharge any stray capacity. The sample valve is opened momentarily to admit new sample gas and after the ions are formed and trapped in the ion cell in the vacuum system the pump is restarted.

Ion pump relay control

During operation of a FTICR MS the time after the opening of the pulsed valve sample gas inlet system that the peak of sample gas pressure occurs in the vacuum chamber is determined by measuring the amplitude of the ion pump current. The FTICR MS then uses that time and the known period of time for which a source of electrons used for an ionization event is energized to energize the electron source so that the known period of time includes the peak of vacuum chamber sample gas pressure. This allows ions to be created during the peak of the sample gas pressure to thereby obtain the maximum sensitivity during measurements.

Precision pressure monitor

The closure of a leak valve in a pulsed mass spectrometer is controlled to thereby substantially extend the life of the valve. An actuator responds to a pulse to open the valve. At the end of the open period the element that closes the valve seat is allowed to travel a substantial distance from the open position of the element to the nearly closed position of the element. The pulse amplitude is then controlled so that the time for the element to travel the remaining distance to valve seat closure is extended in time. The pulse amplitude can also be controlled so that the valve will never close except under fault conditions where power is lost or in a non-operating mode.

Pulsed mass spectrometer leak valve with controlled energy closure

A molecular spectrometer is provided that performs Fourier analysis utilizing the discrete Fourier Transform on a digitized time domain waveform that relates to the composition of a sample. Digitized reference waveforms are employed to permit the instrument to limit its analysis to frequencies of interest and thereby increase the rapidity of the analysis. Data at differing frequencies can be resolved at independent resolutions, and the instrument can analyze spectroscopic data in real time.

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Manlius, NY, United States of America

Duane P Littlejohn