Abstract:
Apparatuses and method are provided. For example, in one embodiment, a ring electrode includes a plurality of sub-rings adapted to provide an electric field inside a spectrometer. The sub-rings have an internal sub-ring radius. There is a ring insulator between adjacent sub-rings. Each said ring insulator has substantially the same internal radius as the sub-rings. In another embodiment, a method is provided for insertion of the ring electrode inside the spectrometer.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    Embodiments of the present invention generally relate to ion spectrometers, and more specifically to, a system, method, and apparatus for greater control over an ion spectrometer drift chamber. 
         [0003]    2. Description of the Related Art 
         [0004]    Ion mobility spectrometers have many applications, including security applications where the ion mobility spectrometer is used to search for unwanted substances (e.g., to identify explosives, narcotics, and other contraband). 
         [0005]    Some prior art ion spectrometers acquire a sample by wiping a woven or non-woven fabric trap across a surface that is to be tested for molecules of interest. Other prior art ion spectrometers create a stream of gas adjacent the surface to be tested for the molecules of interest or rely upon an existing stream of gas. 
         [0006]      FIG. 1  depicts a typical prior art ion mobility spectrometer  100 . The ion spectrometer  100  includes a housing  102  (also known as a “bottle”  100 ); a gas inlet  106  (for receipt of a dopant (i.e., air in combination with ammonia and/or methylene chloride); a semi-permeable membrane  104 ; an inlet tube  118 ; an ionization chamber  114 ; radioactive source  116 ; electrodes  122 ,  124 ,  126 ,  128 ,  130 , and  132 ; a drift region  112 ; an anode screen grid  134 ; an anode  136 ; and a gas exhaust  110 . 
         [0007]    When there is a chemical that needs to be identified, a sample of the chemical is taken. For example, a swab is wiped on an object containing the questionable chemical. The swab is placed against the semi-permeable membrane  104 . The swab is then heated and the chemical(s) (e.g., explosives, narcotics, and the like) are turned into a vapor. The vapor permeates the membrane  104  while the membrane  104  helps to keep out contaminants (e.g., water). 
         [0008]    An inlet tube  106  provides an inert gas (which includes air and a dopant (i.e., ammonia and/or methylene chloride)), which forces the vapor towards an ionization chamber  114 . While in the ionization chamber  114 , the vapor is exposed to a radioactive material  116  (i.e., nickel  63  or tritium). The radioactive material  116  bombards the vapor molecules with beta-particles and creates ions (i.e., charged molecules) from the vapor molecules. 
         [0009]    A population of the ions builds up in the ionization chamber  114 . An ion grid  120  separates the charged molecules from the drift region  112 . The drift region  112  also includes a plurality of field-defining electrodes  122 ,  124 ,  126 ,  128 ,  130 , and  132 ; and an anode screen grid  134  at the end of the drift chamber opposite the ionization chamber  114 . Electrode  122  also includes a perforated ion grid  120  that, at the appropriate time, allows ions to pass through the perforations. 
         [0010]    Electrodes  122 ,  124 ,  126 ,  128 ,  130 , and  132  are each shaped like a disk. Because of their shape, electrodes  122 ,  124 ,  126 ,  128 ,  130 , and  132  are referred to herein as “disk electrodes.” “Disk shaped” as used herein is generally defined as a shape similar to a circular plate having a hole therethrough. The disk shape of the electrodes protrudes into the drift region  112  and has spaces there-between. 
         [0011]    During manufacture of a spectrometer unwanted substances (e.g., cutting oil) can remain in the spectrometer. These unwanted substances often collect in the spaces between the disk shaped electrodes. In addition, after the spectrometer has analyzed a substance of interest, the analyzed substance of interest is no longer needed in the spectrometer and is considered an unwanted substance with respect to tests performed on subsequent substances of interest. The spaces between the disk shaped electrodes provide areas where the unwanted substances are trapped in the drift region. A “contaminant” as used herein is generally defined as any unwanted substance. 
         [0012]    The impedance of the flow of ions can cause multiple problems. For example, during fabrication of the ion spectrometer, the spectrometer must be “burned in.” The length of time for the burn in process is, in part, dependant upon the shape and configuration of the electrodes. The duration of the burn in time slows the manufacturing process. Other examples, a longer time to flush ions out of corners formed between the electrodes  122 ,  124 ,  126 ,  128 ,  130 , and  132 ; and a non-uniform electric field (e.g., eddy currents) produced in the drift region  112 . 
         [0013]    After the ions have built up in the ionization chamber  114 , a voltage is varied at the G1 electrode  122  to accelerate the ions through the ion grid  120  and into the drift region  112 . The ions strike the anode  136  (also know as the collector electrode). 
         [0014]    The anode  136  is coupled to an amplifier (not shown). The amplifier amplifies signals (i.e., ion currents) received by the anode  136 . When a change in ion current is detected, the time that respective ions take to travel through the drift region  112  is measured. Larger ions move through the drift region  112  slower than smaller ions. The time taken to travel through the drift region  112  is used to derive the identity of the ions. 
         [0015]    As the ions are analyzed, they are flushed out of the drift region  112  through a gas exhaust  110  and into a pump (not shown) and dryer (also not shown) for recycling of the dopant. 
         [0016]    There is a need in the art for an improved electrode configuration that avoids the shortcomings and drawbacks of prior art systems and methodologies (e.g., which allows a shorter burn in time; a more uniform electric field; and easier flushing of contaminants). 
       SUMMARY 
       [0017]    These and other deficiencies of the prior art are addressed by embodiments of the present invention, which generally relates to ion spectrometers, and more specifically to, apparatuses for greater control over an ion spectrometer drift chamber. 
         [0018]    In one embodiment, a ring electrode includes a plurality of sub-ring shaped electrodes (hereinafter referred to as “sub-rings”) adapted to provide an electric field inside a spectrometer. The sub-rings have an internal radius. There is a ring insulator between adjacent sub-rings. Each ring insulator has substantially the same internal radius as the sub-rings. 
         [0019]    In another embodiment, a spectrometer is provided which includes a housing. The housing has a first end and a second end. Inside the housing are a substance of interest inlet (e.g., a membrane inlet), at least one gas inlet, a plurality of electrical contacts, an ionization source, and ring electrode, and an anode. The substance of interest inlet is adapted to receive molecules. The gas inlet is adapted to receive air and a dopant. The ionization source is adapted to create ions; and is in communication with the substance of interest inlet and in proximity to the first end. The anode is adapted to collect ions and is in proximity to the second end. The ring electrode in the housing includes a plurality of sub-rings adapted to provide an electric field inside the spectrometer. The sub-rings have an internal radius and a ring insulator between adjacent sub-rings. Each ring insulator has substantially the same internal radius as the sub-rings. The apparatus utilizes a gas exhaust in the housing for expelling contaminants and/or ions. 
         [0020]    Other embodiments are also provided in which computer-readable mediums, apparatuses and systems perform similar features recited by the above methods. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
           [0022]      FIG. 1  is a prior art ion spectrometer. 
           [0023]      FIG. 2  is an embodiment of an exemplary ring electrode in accordance with aspects disclosed herein. 
           [0024]      FIG. 3  depicts a cross-sectional view of an exemplary embodiment of a ring. 
           [0025]      FIG. 4  depicts a cross-sectional view of an embodiment of an exemplary ion spectrometer, which utilizes the exemplary ring electrode disclosed in  FIG. 2 . 
       
    
    
       [0026]    To facilitate understanding, identical reference numerals have been used, wherever possible, to designate identical elements that are common to the figures. 
       DETAILED DESCRIPTION 
       [0027]    In the following description, numerous specific details are set forth to provide a more thorough understanding of the invention. As will be apparent to those skilled in the art, however, various changes using different configurations may be made without departing from the scope of the invention. In other instances, well-known features have not been described in order to avoid obscuring the invention. Thus, the invention is not considered limited to the particular illustrative embodiments shown in the specification and all such alternate embodiments are intended to be included in the scope of the appended claims. For example, aspects of this disclosure depict and describe the inlet that receives vapors from a substance of interest as a membrane inlet. However, those depictions and descriptions are for illustrative purposes. 
         [0028]      FIG. 2  is an embodiment of an exemplary ring electrode  200  in accordance with aspects disclosed herein. The ring electrode  200  includes a plurality of individual sub-ring shaped electrodes (“sub-rings”)  204 ; and individual ring insulators  202 . The ring insulators  202  separate adjacent sub-rings  204 . The ring insulators  202  and sub-rings  204  have substantially the same internal diameter (also referred to herein as an “internal radius”). As a result, the interior surface of the ring electrode  200  is substantially smooth. One of the technical effects of the substantially smooth interior surface is that the likelihood of contaminants being trapped between the sub-rings  204  is significantly diminished. Because there is little or no space between the sub-rings  204 , the time required to flush unwanted gases and contaminates (also referred to herein as the “clear-down time”) is decreased. 
         [0029]    The ring insulators  202  are made of any non-conductive material able to withstand temperatures within the spectrometer (e.g., ceramic, glass, quartz, or high temperature resistant plastic). 
         [0030]    Although  FIG. 2  depicts the ring electrode  200  having 5 sub-rings  204  and  6  ring insulators  202  there-between that depiction is for illustrative purposes only. It is appreciated that more or less sub-rings  204  and ring insulators  202  can be used in accordance with this disclosure. For example, about 4 to about 9 sub-rings  204  (and ring insulators  202  there-between) can be used. Increasing the number of sub-rings  204  increases resolution and sensitivity of the spectrometer. 
         [0031]      FIG. 3  depicts a cross-sectional view of an exemplary embodiment of a single sub-ring electrode  300 . The sub-ring electrode  300  has an internal radius (“r”)  302 , a width (“w”)  304 , and an external radius (“R”)  306 . A ring as used herein is generally defined as a solid having a volume calculated using Equation 1 below. 
         [0000]      Volume of Ring=π( R   2   −r   2 ) w   Equation (1) 
         [0032]    where (R−r) is a number smaller than w. To provide the ring electrode  200  with a substantially smooth interior surface, the sub-rings  204  have the same internal radius r as the ring insulators  202 . 
         [0033]      FIG. 4  depicts a cross-sectional view of an embodiment of an exemplary ion spectrometer  400 , which utilizes the exemplary ring electrode disclosed in  FIG. 2 . The spectrometer  400  includes housing  402 , a membrane  404 , an ionization region  406 , a ring electrode  200 , electrical contacts  408 , a membrane gas inlet  410 , an anode electrical wire  412 , a drift gas inlet  414 , a perforated ion grid  418 , a perforated anode grid  420 , anode  422 , and an exhaust gas outlet  416 . 
         [0034]    The ion spectrometer  400  includes a housing  402 . The membrane gas inlet  410  is a conduit that allows air and a dopant (e.g., ammonia and/or methylene chloride) into the housing  402 . The membrane gas with substances of interest (e.g., explosives or narcotics) that have permeated the membrane  404  pass into the ionization region  406 . The membrane gas inlet  410  allows the air and dopant to force vapors of a substance to enter the ionization region  406  for subsequent testing. 
         [0035]    The drift gas inlet  414  is a conduit that also allows air and the dopant (e.g., ammonia and/or methylene chloride) into the housing  402 . However, the injection of air and dopant, via the drift gas inlet  414 , is done so on an opposite end of the housing  402  (i.e., for injection of air and dopant past the anode screen grid  420  and into the drift region). 
         [0036]    When a substance of interest (e.g., explosives, narcotics, and the like) is placed against a heated semi-permeable membrane  404  (e.g., via a swab), the chemical(s) is turned into a vapor. The vapor permeates the membrane  404  while the membrane  404  helps to keep out contaminants (e.g., water). 
         [0037]    Air and dopant, provided via the first drift gas inlet  410 , forces the vapor towards the ionization chamber  406 . While in the ionization chamber  406 , the vapor is ionized (e.g., ionization is induced either electrically or by a radioactive material (e.g., nickel  63  or tritium)). 
         [0038]    A population of the ions builds up in the ionization chamber  406 . An applied voltage pushes the ions through the ion grid  418  and into the drift region. 
         [0039]    The ring electrode (e.g., ring electrode  200 ) is located inside the housing  402  to provide an electrical field inside the drift region. As such, the drift region is a single unobstructed cavity (i.e., the entire interior of the ring electrode). After the ions have been ionized in the ionization region, the voltage at  418  is varied to allow the flow of ions through the drift region. The electrical contacts  408  contact the sub-rings  204  that form the ring electrode  200  and allow the voltages to pass to each respective sub-ring  204  in the ring electrode  200 . 
         [0040]    Ring insulators  202  prevent physical and electrical contact between the sub-rings  204 . In addition, the ring insulators  202  have substantially the same interior diameter (and radius about a central longitudinal axis) as that of the sub-rings  204 , which decreases the likelihood of substances being trapped between the sub-rings  204 . 
         [0041]    The charged ring electrode  200  accelerates the ions towards the anode  422 . The anode  422  collects the ions for subsequent analysis by a computer. 
         [0042]    As the ions are collected, the drift region is flushed of the analyzed gas and ions, via the exhaust gas outlet  416 . Because the area upon which the gases are expelled is unobstructed, the drift region can be flushed in a shorter time-span than if disk shaped electrodes were used. Some of the additional benefits of the ring electrode (i.e., the unobstructed interior of the ring electrode and drift region) are a shorter burn in time (i.e., a time-span shorter than a configuration that uses disk shaped electrodes or electrodes that protrude into the drift region) during construction of the spectrometer  400 ; and a more uniform electrical field (e.g., no eddy currents). 
         [0043]    Although the ion spectrometer  100  utilizes a disk shaped electrodes, the ion spectrometer  100  can be modified or retrofitted (i.e., by removal of the disk shaped electrodes) to utilize ring electrode  200 . 
         [0044]    While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.