JP2003068245A - Time-of-flight mass spectrograph having quantitative energy correcting function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a time-of-flight mass spectrograph to measure both kinetic energy and mass of an ion concurrently and to perform quantitative energy correction, by deflecting the orbit of the ion with a static electric field and measuring the orbit of the ion after the deflection with a position-sensing type ion detector. SOLUTION: Two plate electrodes are set in parallel with each other inclined 45 degrees toward the orbit of an ion beam, and the orbit of the ion beam is deflected 90 degrees away by the static electric field generated between the two plate electrodes. Since the deflected orbit of the ion depends on the kinetic energy of the ion, the kinetic energy of the ion is determined by measuring the detected position of the ion with the position-sensing type ion detector. Furthermore, when the mass of the ion is calculated from the flight time of the ion, the drift of the flight time is corrected on the basis of the kinetic energy, and the quantitative energy correction is performed.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a time-of-flight mass spectrometer having an energy correcting function. 2. Description of the Related Art Time-of-flight mass spectrometers are used for identifying single ions one by one. However, since the mass is calculated from the time of flight from the emission of ions to the detection of the ions, all types of mass spectrometers are used. If the kinetic energy of the ions is not constant, the flight time varies, and the mass cannot be measured accurately. However, it is difficult to make the kinetic energy of all ions completely constant in actual measurement,
A time-of-flight mass analyzer having an energy correction function such as an electrostatic reflection type or an electrostatic deflection type is used. [0003] These conventional time-of-flight mass spectrometers having an energy correcting function reduce the flight distance of fast ions by reflecting or deflecting ions, thereby increasing the flight distance of fast ions. Thus, the flight time of ions is converged. However, such a correction is qualitative and has a sufficient energy correction function when the variation in kinetic energy is small, but there is a drawback that correction cannot be performed in principle when the variation in kinetic energy is large. Also, the magnitude of the kinetic energy shift cannot be known. [0004] The present invention is directed to an ion having a large variation in kinetic energy.
The purpose is to make accurate corrections. According to the present invention, the trajectory of an ion beam is changed by an electrostatic field generated between two plate electrodes provided at an angle of 45 degrees with respect to the trajectory of a pulsed ion beam. By deflecting 90 degrees and detecting the deflected ions with a position-sensitive ion detector, the kinetic energy and flight time of both ions are simultaneously measured, and the mass of the ion is calculated from the measured kinetic energy and flight time. Is the most important feature. FIG. 1 is an explanatory view of an embodiment of the apparatus according to the present invention. Two plate electrodes 1 and 2 are placed in parallel in a vacuum vessel, and two large and small holes 3 and 4 are formed in one plate electrode 1 as shown in FIG. A single ion detector 5 having a function of measuring the incident position is attached to the large hole 4. At this time, as shown in the cross-sectional view of FIG. 3, the detection surface of the position-sensitive ion detector 5 is made to be the same plane as the plate electrode 1. As shown in FIG. 1, the plate electrode 1 is grounded, and a voltage is applied to the plate electrode 2 to generate a uniform electrostatic field between the electrodes. At this time, a voltage having the same polarity as the ions, such as a positive voltage for the positive ion beam and a negative voltage for the negative ion beam, is applied to the plate electrode 2. In addition, the plate electrodes 1 and 2
It is necessary to generate a uniform electric field between
The flat plate electrode 9 having a hole at the center as shown in FIG.
And 2 are arranged in parallel with each other and connected by a resistor 10 to generate a uniform electric field. This is a method similar to that of a conventional reflection-type mass analyzer or the like. [0009] To a small hole 3 opened in the plate electrode 1,
The plate electrode 1 is irradiated with an ion beam at an angle of 45 degrees. Here, the ion source 6 may be any one that emits a pulsed ion beam having a narrow peak width. Ions passing through the small holes 3 are deflected by 90 degrees by the electric field generated between the electrodes, and enter the position-sensitive ion detector 5 through the orbit shown in FIG. Since the detection position of the ions is determined by the kinetic energy of the ions before entering the small hole 3, the kinetic energy of the ion beam can be measured from the incident position by using Equation 1. [0010] Further, by measuring the time of flight from the time of emission from the ion source 6 to the time of detection by the position-sensitive ion detector 5, the mass of the ions whose energy variation is quantitatively corrected from the equation (2) is calculated. The ratio between M and charge q can be calculated. ## EQU2 ## The symbols in the above equations 1 and 2 are shown in FIG.
As shown in F, F is the kinetic energy of the ion, M is the mass of the ion, q is the charge of the ion, L is the flight distance of the ion from the ion source 1 through the small hole 2 of the plate electrode 2, and d is the plate. The distance between the electrodes 1 and 5, X is the distance from the small hole 2 to the ion detection position, t is the flight time of the ions from the ion source 6 to the position-sensitive ion detector, and V is the plate electrode 5 for deflecting the ions. Is the voltage to be applied. Further, e in Equation 1 is the elementary charge. The embodiment of FIG. 6 combines the analyzer of the present invention with a linear mass analyzer in order to detect particles that have become neutral due to the decomposition of clusters during flight.
In this embodiment, a hole 12 is formed at a position 11 on the linear trajectory of the beam before deflection on the plate electrode 2, and a single ion detector 13 is mounted behind the hole. By doing so, neutral particles that are not deflected can be detected without being missed. Although the energy correction of the particles detected by the linear single ion detector 13 cannot basically be performed, when the cluster ions are decomposed, the position-sensitive detector 5 is used.
Identification is possible by estimating the kinetic energy of neutral particles from the kinetic energy of the ions detected in step (1). As described above, the time-of-flight mass analyzer having a quantitative energy correction function of the present invention measures both the detection position of ions deflected by an electrostatic field and the time of flight. In addition, both the kinetic energy and the mass of the ion can be measured simultaneously, and at the same time, the quantitative correction of the mass from the value of the kinetic energy was enabled.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram showing a method of implementing a time-of-flight mass spectrometer having an energy correction function. (Example 1) FIG. 2 is an explanatory view showing the shape of a plate electrode 1. FIG. FIG. 3 is an explanatory view showing a mounting position of a position-sensitive ion detector 5; FIG. 4 is an explanatory diagram showing how to attach an electrode 9 for generating a uniform electrostatic field between the plate electrodes 1 and 2; FIG. 5 is an explanatory diagram showing symbols in Expressions 1 and 2. FIG. 6 is an explanatory diagram showing an implementation method in which a linear mass analyzer 13 is combined. (Explanation 2) [Description of symbols] 1 Plate electrode with a hole 2 Plate electrode 3 Small hole 4 for capturing ions 4 Large hole 5 for mounting position-sensitive ion detector 5 Position-sensitive ion detector 6 Ion source 7 Orbit of ion beam 8 Constant voltage source 9 Plate electrode with a hole at the center for generating uniform electrostatic field 10 Resistor 11 Orbit of neutral particles 12 Hole 13 through which neutral particles pass 13 Single ion detector

Claims (1)

Claims: 1. An orbit of an ion beam is set to 90 degrees by an electrostatic field generated between two electrodes, wherein two plate electrodes are installed in parallel at an angle of 45 degrees with respect to the orbit of the ion beam. Deflection degrees. Since the trajectory of the deflected ion varies depending on the kinetic energy of the ion, the kinetic energy of the ion is determined by measuring the detected position with a position-sensitive ion detector, and then calculating the mass of the ion from the time of flight. A time-of-flight mass spectrometer characterized in that a time-of-flight deviation is corrected from the value of, and a quantitative energy correction is performed.