Patent Publication Number: US-8981289-B2

Title: Ultraviolet diode and atomic mass analysis ionization source collecting device using ultraviolet diode and an MCP

Description:
TECHNICAL FIELD 
     The present invention relates to an electron gun for ionizing gaseous molecules in a mass analyzer and, more particularly, to a device for acquiring an ion source of a mass analyzer using an ultraviolet (UV) diode and a micro-channel plate (MCP), in which cold electrons are produced at room temperature using the UV diode and an MCP electron multiplier plate, and are applied to the mass analyzer, without using a thermionic emission method based on a high temperature and a high current. 
     BACKGROUND ART 
     In general, to separate molecular ions to analyze components according to the masses of the ions in a mass analyzer, first, a process of ionizing gaseous molecules is required. 
     A method of bombarding the gaseous molecules with an electron beam to produce the molecular ions is most frequently used. To produce the electron beam, a device for heating a filament at a high temperature to induce thermionic emission is most widely used. 
     The filament can be heated at a high temperature by causing a high current to flow to a high-temperature metal such as tungsten or rhenium. However, due to high power consumption, battery power is rapidly consumed in a portable mass analyzer, and a reaction to electron emission caused by a rise to a high temperature is slow. As such, it is difficult to control the electron emission in a mass analyzer that is suitable to produce a continuous output electron beam and requires pulse ionization within a short time. 
     DISCLOSURE 
     Technical Problem 
     Accordingly, the present invention is directed to a device for acquiring an ion source of a mass analyzer using an ultraviolet (UV) diode and a micro-channel plate (MCP), in which an MCP electron multiplier plate is used to produce a portable mass analyzer, UV photons emitted from the UV diode are applied to the front of the MCP electron multiplier plate and induce initial electron emission, the emitted electrons are amplified into an electron beam, and the electron beam in which an emission time thereof is accurately adjusted with a low temperature and low power is obtained. 
     Technical Solution 
     According to an aspect of the present invention, there is provided a device for acquiring an ion source of a mass analyzer using an ultraviolet (UV) diode and a micro-channel plate (MCP), in which electrons generated by UV photons are amplified into an electron beam using the UV diode and the MCP, the electron beam ionizes gaseous sample molecules to produce ions, and the ions are detected. The device includes: the UV diode emitting the UV using supplied power; an MCP electron multiplier plate causing the UV photons from the UV diode to induce initial electron emission and amplifying the emitted electrons into a large quantity of electron beam at a rear plate thereof; an electron beam focusing lens focusing the electron beam amplified through the MCP electron multiplier plate; an ion trap mass separator ionizing the gaseous sample molecules to produce ions using the electron beam injected by the electron beam focusing lens and trapping the ions in a given space; and an ion detector detecting the ions produced by the ion trap mass separator based on a mass spectrum. 
     Advantageous Effects 
     As described above, the device for acquiring an ion source of a mass analyzer using an ultraviolet (UV) diode and a micro-channel plate (MCP) can produce the electron beam for ionizing the gaseous sample molecules at a low temperature without using a high temperature and a high current, reduce a size, weight, and battery power consumption when applied to a small mass analyzer because only a necessary quantity of electron beam is produced at a necessary time, be applied to a portable mass analyzer. Further, a thin electron beam is emitted, and is thus focused with relative ease. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  shows an overall configuration of a device for acquiring an ion source of a mass analyzer using an ultraviolet (UV) diode and a micro-channel plate (MCP) in accordance with an embodiment of the present invention. 
         FIG. 2  shows a configuration of an MCP module shown in  FIG. 1 . 
     
    
    
     MODE FOR INVENTION 
     Hereinafter, exemplary embodiments of the present invention will be described in detail below with reference to the attached drawings. While the present invention is shown and described in connection with exemplary embodiments thereof, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention. 
     A device for acquiring an ion source of a mass analyzer using an ultraviolet (UV) diode and a micro-channel plate (MCP) in accordance with an embodiment of the present invention will be described below in detail with reference to the attached drawings. 
       FIG. 1  shows a configuration of a device for acquiring an ion source of a mass analyzer using a UV diode and an MCP in accordance with an embodiment of the present invention. The device includes a UV diode  110  emitting UV using supplied power, an MCP electron multiplier plate  120  causing the UV photons from the UV diode  110  to induce initial electron emission and amplifying the emitted electrons into a large quantity of electron beam at a rear plate thereof, an electron beam focusing lens  130  focusing the electron beam amplified when passing through the MCP electron multiplier plate  120 , an ion trap mass separator  140  ionizing gaseous sample molecules to produce ions using the electron beam injected by the electron beam focusing lens  130 , and an ion detector  150  detecting the ions produced by the ion trap mass separator  140  based on a mass spectrum. 
     Each component of the mass analyzer is operated in a vacuum chamber having a pressure of 10 −4  to 10 −10  Torr. 
     Here, the MCP electron multiplier plate  120  is configured so that the UV photons emitted from the UV diode  110  is applied to a front plate  121  thereof, and the electrons generated by the UV photons applied to the front plate  121  are amplified at a rear plate  122  thereof. 
     An operation of the ion source acquiring device configured in this way will be described below in greater detail with reference to  FIGS. 1 and 2 . 
     First, an MCP module causes the UV photons to induce the initial electron emission, and amplifies the emitted electrons into the electron beam. After the electron beam is focused by the electron beam focusing lens, the ion trap mass separator ionizes the gaseous sample molecules to produce ions, and the produced ions are detected by the ion detector. 
       FIG. 1  shows an overall configuration of a device for acquiring an ion source of a mass analyzer using a UV diode and an MCP in accordance with an embodiment of the present invention.  FIG. 2  shows a configuration of an MCP module shown in  FIG. 1 . The UV diode  110  applies a pulse signal of supplied power for emitting the UV based on the pulse signal of supplied power. 
     The UV emitted from the UV diode  110  is applied to the front plate  121  of the MCP electron multiplier plate, and induces the initial electron emission at the front plate  121 . 
     The initial electrons emitted in quantity by the UV are amplified into the electron beam when passing through the front and rear plates  121  and  122 , and the electron beam amplified at the rear plate  122  can be obtained. 
     As shown in  FIG. 2 , a negative voltage of −500 V to −2500 V is applied to the front plate  121 , and a negative voltage of −10 V to −500 V is applied to the rear plate  122 . Thereby, the electrons generated by the UV are highly amplified. 
     The electron beam amplified by the MCP electron multiplier plate  120  is focused in one direction by the electron beam focusing lens  130 , and is injected into the ion trap mass separator  140 . The electron beam ionizes the gaseous sample molecules. 
     Here, the ionization is adjusted by a UV emission time and UV intensity of the UV diode  110 . In detail, the ionization is adjusted by an on/off pulse signal of the power driving the UV diode  110 . When the on pulse signal is applied for a long time, a large quantity of UV is emitted. When the on pulse signal is applied for a short time, a small quantity of UV is emitted. 
     Further, the UV intensity of the UV diode  110  is adjusted by a value of current flowing to the UV diode. Thereby, a quantity of the emitted UV photons is adjusted. Thus, it is possible to accurately momentarily obtain an electron current which the mass analyzer requires for gas ionization. 
     To focus the UV emitted from the MCP module  110  or  120 , a negative voltage is applied to the electron beam focusing lens  130 , and is higher than that applied to the rear plate  122  of the MCP electron multiplier plate  120 . 
     The ion trap mass separator  140  ionizes the gaseous sample molecules to produce ions using the electron beam passing through the electron beam focusing lens  130 . The ion detector  150  detects the ions produced by the ion trap mass separator  140 , and the detected ions are converted into signals by a principle of the ion trap mass separator. 
     In this way, the device for acquiring an ion source of a mass analyzer using a UV diode and an MCP in accordance with an embodiment of the present invention can be applied to apparatuses using a low-temperature electron gun or beam required for a portable compact device, a low-power device, or a low-temperature device. 
     It will be apparent to those skilled in the art that various modifications can be made to the above-described exemplary embodiments of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention covers all such modifications provided they come within the scope of the appended claims and their equivalents.