Ion Trap with Elongated Electrodes

Abstract

An ion trap 1 comprises one ejection electrode 2 for ion trapping having an opening 4, through which ions in the ion trap 1 can be ejected in an ejection direction E and further electrodes 3 for ion trapping, wherein the ejection electrode 2 and the further electrodes 3 are elongated in a longitudinal direction L. The angle α between the longitudinal direction L and the ejection direction E is nearly 90°. The ion trap 1 comprises a primary winding 5 connected to an RF power supply 6, a secondary winding 7 coupling with the primary winding 5 for transforming the RF voltage of the RF power supply 6 supplying the transformed RF signals to the ejection electrode 2 and secondary windings 7′ coupling with the primary winding 5 for transforming the RF voltage of the RF power supply 6 supplying the transformed RF signals to the further electrodes 3. The ion trap 1 comprises a first DC supply 8, a second DC supply 9 and a controller 50, which is applying in a time period a first DC voltage provided by first DC supply 8 via the secondary winding 7 to the ejection electrode 2 to pull ions in the ion trap to the opening 4 of the ejection electrode 2 and a second DC voltage provided by the second DC supply 9 via the secondary windings 7′ to the at least 70% of the further electrodes 3 to push ions in the ion trap to the opening 4 of the ejection electrode 2.

1 . An ion trap comprising:
 an ejection electrode for ion trapping having an opening, through which ions in the ion trap can be ejected in an ejection direction E;   electrodes for ion trapping a primary winding connected to an RF power supply;   a secondary winding coupling with the primary winding for transforming the RF voltage of the RF power supply and supplying the transformed RF signals to the ejection electrode;   secondary windings coupling with the primary winding for transforming the RF voltage of the RF power supply and supplying the transformed RF signals to the further electrodes;   a first DC supply;   a second DC supply; and   a controller,   
       wherein the ejection electrode and the further electrodes are elongated in a longitudinal direction L, 
       the angle α between the longitudinal direction L and the ejection direction E deviates from 90° not more than 15°, 
       the controller is configured for applying in a time period a first DC voltage provided by first DC supply via the secondary winding to the ejection electrode to pull ions in the ion trap to the opening of the ejection electrode and a second DC voltage provided by the second DC supply via the secondary windings to the at least 70% of the further electrodes to push ions in the ion trap to the opening of the ejection electrode. 
     
     
         2 . The ion trap according to  claim 1 , wherein the ion trap is comprising  3  further electrodes. 
     
     
         3 . The ion trap according to  claim 1 , wherein the ion trap is comprising  5  further electrodes. 
     
     
         4 . The ion trap according to  claim 1 , wherein the ion trap is comprising  7  further electrodes. 
     
     
         5 . The ion trap according to  claim 1 , wherein the ion trap is a curved ion trap. 
     
     
         6 . The ion trap according to  claim 1 , wherein the angle α between the longitudinal direction L and the ejection direction E deviates from 90° not more than 7°, preferably not more than 3°. 
     
     
         7 . The ion trap according to  claim 1 , wherein the controller is applying in the time period the second DC voltage provided by the second DC supply via the secondary windings to the at least 80% of the further electrodes to push ions in the ion trap to the opening of the ejection electrode. 
     
     
         8 . The ion trap according to  claim 7 , wherein the controller is applying in the time period the second DC voltage provided by the second DC supply via the secondary windings to all further electrodes to push ions in the ion trap to the opening of the ejection electrode. 
     
     
         9 . The ion trap according to  claim 1 , wherein the control is applying at the same time a first DC voltage provided by first DC supply via the secondary winding to the ejection electrode to pull ions in the ion trap to the opening of the ejection electrode and a second DC voltage provided the second DC supply via the secondary windings to the at least 70% of the further electrodes to push ions in the ion trap to the opening of the ejection electrode 
     
     
         10 . The ion trap according to  claim 1 , wherein voltage difference between the first DC voltage applied to the ejection electrode and the second DC voltage applied to the further electrodes is between 50 V and 800 V, preferably between 100 V and 600 V and particular preferably between 200 V and 400 V. 
     
     
         11 . The ion trap according to  claim 1 , wherein the ion trap is comprising a focusing lens, which is arranged for the ejected ions downstream of the of the opening of the ejection electrode and is focusing the ejected ions. 
     
     
         12 . The ion trap according to  claim 11 , wherein the focusing lens has an opening into which the ejected ions are directed which is larger than the opening of the ejection electrode. 
     
     
         13 . The ion trap according to  claim 11 , wherein the focusing lens is an electrostatic lens to which a DC voltage is applied, so that the voltage difference between the DC voltage of the focusing lens and the first DC voltage of the ejection electrode is between 250 V and 1,500 V, preferably between 400 V and 1,000 V and particular preferably between 600 V and 800 V. 
     
     
         14 . The ion trap according to  claim 11 , wherein the focusing lens is an electrostatic lens to which a DC voltage is applied and the ratio of the voltage difference between the DC voltage of the focusing lens and the first DC voltage of the ejection electrode and the voltage difference between the DC voltage applied to the ejection electrode and the DC voltage applied to the further electrodes is between 1.5 and 6, preferably between 2.0 and 4 and particular preferably between 2.2 and 3. 
     
     
         15 . The ion trap according to  claim 11 , wherein the ion trap is comprising an acceleration lens, which is arranged for the ejected ions downstream of the focusing lens. 
     
     
         16 . The ion trap according to  claim 15 , wherein the acceleration lens has an opening into which the ejected ions are directed which is smaller than the opening of focusing lens. 
     
     
         17 . The ion trap according to  claim 15 , wherein the acceleration lens is an electrostatic lens to which a DC voltage is applied, so that the voltage difference between the DC voltage of the acceleration lens and the DC voltage of the focusing lens is between 800 V and 5,000 V, preferably between 1,500 V and 3,500 V and particular preferably between 2,000 V and 2,700 V. 
     
     
         18 . The ion trap according to  claim 15 , wherein the acceleration lens is an electrostatic lens to which a DC voltage is applied, and ratio of the voltage difference between the voltage difference between the DC voltage of the acceleration lens and the first DC voltage of the ejection electrode and the voltage difference between the first DC voltage applied to the ejection electrode and the second DC voltage applied to the further electrodes is between 2 and 12, preferably between 4 and 9 and particular preferably between 5 and 7. 
     
     
         19 . The ion trap according to  claim 15 , wherein the acceleration lens is an electrostatic lens to which a DC voltage is applied, and ratio of the voltage difference between the first DC voltage applied to the ejection electrode and the second DC voltage applied to the further electrodes and the voltage difference between the voltage difference between the DC voltage of the acceleration lens and the second DC voltage applied to the further electrodes and is between 0.05 and 0.4, preferably between 0.1 and 0.25 and particular preferably between 0.12 and 0.2. 
     
     
         20 . The ion trap according to  claim 1 , wherein the secondary winding supplying the transformed signal to the ejection electrode and the secondary winding supplying the transformed signal to one of the further electrodes are a pair of secondary windings connected in series. 
     
     
         21 . The ion trap according to  claim 1 , wherein the secondary windings supplying the transformed signal to two of the further electrodes are a pair of secondary windings connected in series. 
     
     
         22 . The ion trap according to  claim 1  at least one of  claims 1  to  21 , wherein by tapping RF signals from the RF supply of the ejection electrode and further electrodes of the ion trap further components of a mass spectrometer, in particular a HCD cell or a transport multipole, are supplied with a RF voltage, wherein preferably an inductance divider is used. 
     
     
         23 . Method of ejecting ions from an ion trap, which is comprising one ejection electrode and further electrodes elongated in a longitudinal direction L for ion trapping, wherein the ejection electrode comprising an opening, through which ions in the ion trap can be ejected in an ejection direction E, wherein an angle α between the longitudinal direction L and the ejection direction E deviates from 90° not more than 15°, wherein RF voltage is supplied to the ion trap by a primary winding connected to an RF power supply, a secondary winding coupling with the primary winding transforming the RF voltage of the RF power supply and supplying the transformed RF voltages to the ejection electrode and secondary windings coupling with the primary winding transforming the RF voltage of the RF power supply and supplying the transformed RF voltages to the further electrodes, a first DC supply and a second DC supply, comprising the steps:
 switching off the RF voltage supplied to the one ejection electrode and the further electrodes of the ion trap; and 
 applying in a time period a first DC voltage via secondary winding provided by the first DC supply to the ejection electrode to pull ions in the ion trap to the opening of the ejection electrode and a second DC voltage provided by the second DC supply via the secondary windings to the at least 70% of the further electrodes to push ions in the ion trap to the opening of the ejection electrode.