Generation of combination of RF and axial DC electric fields in an RF-only multipole
First Claim
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1. An RF-only multipole, comprising:
- at least four elongated rods held in spaced apart, mutually parallel relation, the rods defining an interior region through which ions are transmitted along the major axis of the multipole, each rod having a spiral resistive path disposed around a rod body and traversing at least a portion of the length of the rod;
a radio-frequency voltage source, coupled to each rod, for establishing an RF-only field that radially confines the ions; and
a direct current voltage source, for respectively applying first and second direct current voltages to first and second locations on the resistive path of each rod to generate an axial direct current field that propels the ions along the major axis.
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Abstract
An RF-only multipole includes a spiral resistive path formed around each multipole rod body. RF voltages are applied to the rod body and resistive path, and DC voltages are applied to the resistive path, to create a radially confining RF field and an axial DC field that assists in propelling ions through the multipole interior along the longitudinal axis thereof. In one implementation, the resistive path takes the form of a wire of resistive material, such as nichrome, which is laid down in the groove defined between threads formed on the rod body. The RF-only multipole of the invention avoids the need to use auxiliary rods or similar supplemental structures to generate the axial DC field.
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Citations
22 Claims
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1. An RF-only multipole, comprising:
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at least four elongated rods held in spaced apart, mutually parallel relation, the rods defining an interior region through which ions are transmitted along the major axis of the multipole, each rod having a spiral resistive path disposed around a rod body and traversing at least a portion of the length of the rod; a radio-frequency voltage source, coupled to each rod, for establishing an RF-only field that radially confines the ions; and a direct current voltage source, for respectively applying first and second direct current voltages to first and second locations on the resistive path of each rod to generate an axial direct current field that propels the ions along the major axis. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 19, 20)
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9. A mass spectrometer system, comprising:
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an ion source for generating ions; a mass analyzer for analyzing the mass-to-charge ratio of at least a portion of the ions; and an RF-only ion guide for transferring ions along a segment of an ion path extending between the ion source and the mass analyzer, the ion guide comprising; at least four elongated rods held in spaced apart, mutually parallel relation, the rods defining an interior region through which ions are transmitted along the major axis of the multipole, each rod having a spiral resistive path disposed around a rod body and traversing at least a portion of the length of the rod; a radio-frequency voltage source, coupled to each rod, for establishing an RF-only field that radially confines the ions; and a direct current voltage source, for respectively applying first and second direct current voltages to first and second locations on the resistive path of each rod to generate an axial direct current field that propels the ions along the major axis. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 21, 22)
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Specification