Resistive glass structures used to shape electric fields in analytical instruments

Abstract

A reflectron lens for a time-of-flight mass spectrometer is disclosed. The reflectron lens includes a glass tube having a conductive surface along the length of the tube. The conductive surface has an electrical resistance gradient along its length. The electrical resistance gradient provides an electric field interior to the tube that varies in strength along the length of the tube when an electric potential is applied to opposing ends of the tube. A mass spectrometer incorporating the reflectron lens, a method of making the reflectron lens, and an apparatus for removing lead from the surface of a lead silicate glass tube are also disclosed.

1 . A reflectron lens comprising a glass tube having a conductive surface along the length of said tube, said conductive surface having an electrical resistance gradient along said length, whereby said tube provides an electric field interior to the tube that varies in strength along the length of the tube when an electric potential is applied to opposing ends of the tube.  
   
   
       2 . The reflectron lens set forth in  claim 1  wherein the electrical resistance gradient changes linearly along the length of the tube.  
   
   
       3 . The reflectron lens set forth in  claim 1  wherein the electrical resistance gradient changes in steps along the length of the tube.  
   
   
       4 . The reflectron lens set forth in  claim 1  wherein the electrical resistance gradient changes nonlinearly along the length of the tube.  
   
   
       5 . A mass spectrometer comprising: 
 a flight tube;    a source of ions;    an ion detector;    a reflectron lens; and    a voltage supply electrically connected to opposing ends of said reflectron lens;    wherein said reflectron lens is formed of a glass tube having a conductive surface extending along the length of the glass tube and said conductive surface has a electrical resistance gradient along said length, whereby said reflectron lens provides an electric field interior thereto that varies in strength along the length of said lens.    
   
   
       6 . The mass spectrometer set forth in  claim 5  wherein the electrical resistance gradient changes linearly along the length of the glass tube.  
   
   
       7 . The mass spectrometer set forth in  claim 5  wherein the electrical resistance gradient changes in steps along the length of the glass tube.  
   
   
       8 . The mass spectrometer set forth in  claim 5  wherein the electrical resistance gradient changes nonlinearly along the length of the glass tube.  
   
   
       9 . A method of preparing a glass tube for use as a reflectron lens comprising the steps of: 
 providing a glass tube wherein the glass contains a lead compound;    immersing a portion of said glass tube in a solution that removes lead from the surface of the glass tube;    holding said portion of the glass tube in the solution for a time sufficient to remove lead from the surface of the immersed portion of said glass tube; and then    chemically reducing the surface of the glass tube to form an electrically resistive layer on the surface of the glass tube, whereby the electrical resistance of the portion held in the acidic solution is lower than the electrical resistance of the other portion of the glass tube.    
   
   
       10 . The method set forth in  claim 9  wherein the step of providing the glass tube comprises the step of providing a lead silicate glass tube.  
   
   
       11 . The method set forth in  claim 9  wherein before said chemically reducing step, performing the further steps of immersing a second portion of said glass tube in the lead-removal solution and holding said second portion in the solution for a time sufficient to remove lead from the surface of the immersed second portion of the glass tube.  
   
   
       12 . The method set forth in  claim 9  wherein the lead removal solution comprises an acidic solution.  
   
   
       13 . The method set forth in  claim 9  wherein the step of holding the portion of the glass tube in the lead removal solution comprises the step of moving the glass tube into the solution at a speed selected to provide removal of lead in a linear manner along the length of the glass tube.  
   
   
       14 . Apparatus for removing lead from the surface of a lead silicate glass tube comprising: 
 a tank for holding liquid solution containing a lead removal ingredient;    means for holding a lead silicate glass tube; and    means operably connected to said holding means for moving the lead silicate glass tube into and out of said tank.    
   
   
       15 . The apparatus set forth in  claim 14  wherein the means for moving the lead silicate glass tube comprises: 
 a slider mechanism operably connected to said holding means;    a support stand for mounting said slider mechanism; and    drive means for activating said slider mechanism.    
   
   
       16 . The apparatus set forth in  claim 15  wherein the drive means comprises: 
 a stepper motor mounted on said support stand, said stepper motor having a drive shaft;    a second drive shaft mounted on said support stand independently of said stepper motor and coupled to said slider mechanism; and    transmission means for coupling the drive shaft of said stepper motor to said second drive.