Quadrupole mass spectrometer having resolution variation capability

Claim 2

A variable resolution system for a quadrupole mass spectrometer comprising an ionization chamber, an ion detector and a quadrupole structure having four electrodes extending between said detector and chamber; said electrodes being symmetrically disposed with respect to the axis thereof; means for electrically connecting alternate ones of said electrodes together to form two electrode pairs; said electrode pairs having direct current potentials of an opposite polarity applied thereto; wherein the improvement comprises: a variable d.c. source for supplying a d.c. voltage of a magnitude U to said electrodes of said quadrupole structure, a high frequency sinusoidal voltage source for supplying a high frequency voltage of variable amplitude V to said electrodes, and means for varying the d.c. voltage U and the amplitude V of the high frequency voltage in a manner satisfying the relationship U Alpha MV K, where Alpha M denotes a critical U/V ratio at the limit of stable spectrometer response, and K denotes a constant determining the peak width Delta m of a mass spectrum determined by said spectrometer; whereby all the mass peaks of the spectrum are characterized by a substantially identical shape.

Claim 3

A variable resolution system for a quadrupole mass spectrometer comprising an ionization chamber, an ion detector and a quadrupole structure having four electrodes extending between said detector and chamber; said electrodes being symmetrically disposed with respect to the axis thereof; means for electrically connecting alternate ones of said electrodes together to form two electrode pairs; said electrode pairs having direct current potentials of an opposite polarity applied thereto; wherein the improvement comprises: a source of high frequency sinusoidal voltage of variable amplitude V; means for producing a d.c. voltage proportional to the amplitude V of the high frequency voltage; variable resistor means forming a voltage divider for said d.c. voltage and for providing a second d.c. voltage of a value Alpha MV, where Alpha M denotes a critical U/V ratio at the limit of stable spectrometer response; means for biasing said second d.c. voltage of magnitude Alpha MV with a third d.c. voltage of magnitude -K, where K denotes a constant which determines the peak width Delta m of a mass spectrum; and means for applying the high frequency voltage and the resultant d.c. voltage of magnitude Alpha MV-K to said electrodes of said quadrupole structure.

Claim 4

A variable resolution system for a quadrupole mass spectrometer comprising an ionization chamber, an ion detector and a quadrupole structure having four electrodes extending between said detector and chamber; said electrodes being symmetrically disposed with respect to the axis thereof; means for electrically connecting alternate ones of said electrodes together to form two electrode pairs; said electrode pairs having direct current potentials of an opposite polarity applied thereto; wherein the improvement comprises: a source of high frequency sinusoidal voltage of variable amplitude V; means for producing a d.c. voltage proportional to the amplitude V of the high frequency voltage; variable resistor means forming a voltage divider for said d.c. voltage and for providing a second d.c. voltage of a value Alpha MV, where Alpha M denotes a critical U/V ratio at the limit of stable spectrometer response; means for biasing said second d.c. voltage of magnitude Alpha MV with a third d.c. voltage of magnitude -K, where K denotes a constant which determines the peak width Delta m of a mass spectrum; and means for applying the high frequency voltage and the resultant d.c. voltage of magnitude Alpha MV-K to said electrodes of said quadrupole structure.

Claim 5

A variable resolution system for a quadrupole mass spectrometer comprising an ionization chamber, an ion detector and a quadrupole structure having four electrodes extending between said detector and chamber; said electrodes being symmetrically disposed with respect to the axis thereof; means for electrically connecting alternate ones of said electrodes together to form two electrode pairs; said electrode pairs having direct current potentials of an opposite polarity applied thereto; wherein the improvement comprises: a source of high frequency sinusoidal voltage of variable amplitude V for application to said electrodes of said quadrupole structure; means for generating a d.c. voltage U for connection to said electrodes which remains at a constant value of H for values of V, wherein O<V < or = K/ Alpha M-H and which varies in accordance with the equation U Alpha MV-K for a value of V in excess of K/ Alpha M-H, where Alpha M denotes a critical U/V ratio at the limit of stable sPectrometer response and K denotes a constant determining the peak width Delta m of a mass spectrum determined by said spectrometer; means for varying the parameter K to vary peak width; and means for varying the parameter H to establish said parameter H at a value smaller than the peak value of the stable spectral response for atomic hydrogen.

Claim 6

A variable resolution system for a quadrupole mass spectrometer comprising an ionization chamber, an ion detector and a quadrupole structure having four electrodes extending between said detector and chamber; said electrodes being symmetrically disposed with respect to the axis thereof; means for electrically connecting alternate ones of said electrodes together to form two electrode pairs; said electrode pairs having direct current potentials of an opposite polarity applied thereto; wherein the improvement comprises: a source of high frequency sinusoidal voltage of variable amplitude V for application to said electrodes of said quadrupole structure; means for generating a d.c. voltage U for connection to said electrodes which remains at a constant value of H for values of V, wherein O<V < or = K/ Alpha M-H and which varies in accordance with the equation U Alpha MV-K for a value of V in excess of K/ Alpha M-H, where Alpha M denotes a critical U/V ratio at the limit of stable sPectrometer response and K denotes a constant determining the peak width Delta m of a mass spectrum determined by said spectrometer; means for varying the parameter K to vary peak width; and means for varying the parameter H to establish said parameter H at a value smaller than the peak value of the stable spectral response for atomic hydrogen.

Claim 7

A variable resolution system for a quadrupole mass spectrometer comprising an ionization chamber, an ion detector and a quadrupole structure having four electrodes extending between said detector and chamber; said electrodes being symmetrically disposed with respect to the axis thereof; means for electrically connecting alternate ones of said electrodes together to form two electrode pairs; said electrode pairs having direct current potentials of an opposite polarity applied thereto; wherein the improvement comprises: a source of high frequency sinusoidal voltage of the variable amplitude V; means for generating a d.c. voltage proportional to the amplitude V of said high frequency voltage; voltage divider means for deriving, by voltage division of said d.c. voltage, a second d.c. voltage of a value Alpha MV, where Alpha M denotes a critical U/V ratio at the limit of stable spectrometer response, means for biasing said second d.c. voltage with a third d.c. voltage of a value K, where K denotes a parameter that determines the peak width Delta m of a spectrum; means for rendering said biased d.c. voltage Alpha MV - K equal to a null output for a value of V between zero and K/ Alpha M; means for comparing the output from said rendering means with a constant voltage H and choosing the greater of the two as its output U, the value of H being chosen less than the peak value of the stable spectral response for atomic hydrogen and means for applying said output U and said high frequency voltage to the electrodes of the quadrupole structure.

Claim 8

A variable resolution system for a quadrupole mass spectrometer comprising an ionization chamber, an ion detector and a quadrupole structure having four electrodes extending between said detector and chamber; said electrodes being symmetrically disposed with respect to the axis thereof; means for electrically connecting alternate ones of said electrodes together to form two electrode pairs; said electrode pairs having direct current potentials of an opposite polarity applied thereto; wherein the improvement comprises: a source of high frequency sinusoidal voltage of the variable amplitude V; means for generating a d.c. voltage proportional to the amplitude V of said high frequency voltage; voltage divider means for deriving, by voltage division of said d.c. voltage, a second d.c. voltage of a value Alpha MV, where Alpha M denotes a critical U/V ratio at the limit of stable spectrometer response, means for biasing said second d.c. voltage with a third d.c. voltage of a value K, where K denotes a parameter that determines the peak width Delta m of a spectrum; means for rendering said biased d.c. voltage Alpha MV - K equal to a null output for a value of V between zero and K/ Alpha M; means for comparing the output from said rendering means with a constant voltage H and choosing the greater of the two as its output U, the value of H being chosen less than the peak value of the stable spectral response for atomic hydrogen and means for applying said output U and said high frequency voltage to the electrodes of the quadrupole structure.

Claim 9

A variable resolution system according to claim 4, further including means for varying the magnitude of the voltage H.