An ion gate and its control method

Abstract

The present invention provides an ion gate and a control method therefor. The ion gate includes an ion gate fixed frame, an ion gate IG-A, an insulating ring, an ion gate IG-B, and a pressure plate. By reasonably configuring the physical positions and plate potentials of the TP-type ion gate, a closing electric field component with an ion-blocking effect is selected to be formed, thereby improving the closing efficiency of the ion gate. The control power supply is taken from high voltage without the need for an additional auxiliary power supply. The ion gate adopts a TP-type structure and uses rectangular grids instead of parallel grids. Two control signals, namely an opening signal and a closing signal, are respectively used for ion control, effectively compressing the thickness of the ion subgroup passing through the ion gate, eliminating the influence of the clearing area of the traditional BN gate in the closed state, and improving the resolution of ion detection. Without increasing the system complexity, the main performance indexes of the IMS instrument are improved in the traditional TP-type ion gate structure, bringing good benefits.

Description

Technical Field

[0001] The present invention relates to the field of ion mobility spectrometers, and particularly to an ion gate and a control method thereof. Background Art

[0002] Migration time ion mobility spectrometry (IMS) is a pulsed ion packet separation and detection technique similar to time-of-flight mass spectrometry. The ion number density of the ion packet injected into the ion migration region directly determines the sensitivity of ion mobility spectrometry detection.

[0003] The resolution R of ion mobility spectrometry = Td / W 0.5 , where Td is the time of the ion peak emergence position; W 0.5 is the full width at half maximum, that is, the peak width at half of the peak height. With the emergence position unchanged, the narrower the ion peak, the higher the resolution.

[0004] The ion gate in the IMS drift tube is usually made by etching wire grids or metal analogs. They are usually located between the reaction region and the drift region, running through the internal cross-section of the drift tube. By using the voltage difference between adjacent wires, an electric field is established across the cross-section of the drift tube. Ions moving in a drift tube with a drift electric field of 150 - 450 V / cm will encounter a gate electric field that is ≧ 2.5 times the drift electric field and be attracted to the wire surface. The collision of ions on the gate wires causes the ions to be neutralized, and the neutral products follow the unidirectional drift gas flow, pass through the ionization source, and are then discharged.

[0005] When the electric field between the wire grids is eliminated, the ions will pass through the grid holes under the action of the drift electric field and enter the drift region, and at this time, the migration spectrometry measurement begins. In this case, the voltages of all wires in the gate are the same and are in the voltage gradient of the drift tube. When passing through the gate, some ions will be absorbed by the wires, but most will pass through the grid of the ion gate. After 100 - 600 μs, the electric field of the wires in the grid returns to the set value, and the ions are again blocked from entering the drift region.

[0006] In ion migration technology, there are mainly two designs for ion gates. All gate wires are arranged in the same plane, and the electrodes are divided into two groups and arranged alternately, which is called the BN-type ion gate, that is, Bradbury Neilson. The closing electric field direction of the BN-type ion gate is perpendicular to the drift electric field direction; the other is called the TP-type ion gate, that is, Tyndall-Powell. This gate consists of parallel wires placed on two planes respectively to form a grid, and the two planes are separated by an insulator with a thickness of 0.01 - 1 mm. When the device is assembled and aligned, looking from the direction of ion drift, the grid wires look parallel and in a staggered form, just like the BN-type ion gate. Due to the different grid spacing widths and insulator sheet thicknesses of the TP-type ion gate, the closing electric field direction and the drift electric field direction will form a certain angle. The existence of this angle will form an electric field component that accelerates or hinders ion drift, so it is less used in practical applications.

[0007] A TP-type ion gate disclosed in the prior art is formed by stacking two independent metal grid sheets without using an independent support mechanism. It needs to be assembled during the assembly of the drift tube, which is not convenient for production process control. Only when the overall test is carried out after the drift tube is produced can it be determined whether the ion gate reaches the designed technical state; Li Haiyang designed an ion gate control method for automatically enriching ions in the ionization region, thereby improving the detection sensitivity of ion mobility spectrometry. This method is based on the Bradbury-Neilsen type ion gate and can be achieved only by controlling the voltage waveform of the ion gate without special modification of the ion migration tube. However, whether the technology of this literature is applicable to the TP-type ion gate has not been studied; Dr. You designed a multi-ion gate migration tube and a multi-ion gate compression control method, which can change its working mode by adjusting the working voltage of the ion gate, weaken the influence of the emptying area in the closed state of the ion gate, and at the same time increase the density of ions per unit volume by compressing the ion cluster, improving the sensitivity and resolution of the ion mobility spectrometry instrument. This method uses a grid on each side of the BN-type ion gate and two sets of power supply modules from 5V to 200V, and up to 4 field effect transistors for control, increasing the complexity and cost of the ion gate structure and control circuit. Summary of the Invention

[0008] In order to solve the above problems, the present invention proposes an ion gate and its control method, specifically related to the manufacture and control of the Tyndall-Powell type ion gate in an ion mobility spectrometer.

[0009] The technical solution of the present invention is as follows:

[0010] An ion gate assembly includes an ion gate fixed frame, ion gate IG-A, an insulating ring, ion gate IG-B, and a pressure plate;

[0011] The ion gate fixed frame is annular, with an inner circular cavity axially provided in the middle. The diameter matches the inner diameter of the drift tube, and air guide grooves and air inlet holes for passing air flow are provided on the outer diameter.

[0012] The ion gates IG-A and IG-B include criss-crossing grids provided on the frame. The ion gates IG-A and IG-B are arranged in parallel in the ion gate fixed frame, such that the grid positions of the two ion gates are staggered, doubling the grid density. The ion control grid is in the shape of a rectangular sieve hole.

[0013] The insulating ring is provided between the frames of the ion gates IG-A and IG-B; the pressure plate fixes the ion gates IG-A and IG-B to the ion gate fixed frame.

[0014] The ion gate IG-A is on the side close to the ion source and is connected to a control electrode with a low potential. The ion gate IG-B is on the side close to the ion receiving electrode and is connected to a control electrode with a high potential. The electric field passes through the ion gate fixed frame and the criss-crossing grids.

[0015] One end face of the ion gate fixed frame is provided with 6 - 8 mounting holes, with wire thread inserts embedded, and also 2 - 4 positioning holes are provided; the pressure plate is an annular component, with 6 - 8 mounting holes provided on the ring. The mounting holes are designed as counterbored holes, and the screw head is completely sunk into the hole. The pressure plate also has 2 - 4 positioning holes.

[0016] The opening signal controls the opening time and the length of the opening time of the ion gate, and the closing signal controls the closing time of the ion gate, eliminating the influence of the clearance area near the ion gate IG-B in the closed state.

[0017] On one side of the first opto-isolator U1, the diode input terminal is connected to the power supply VCC terminal through the connector JK2, the diode output terminal is connected to the closing control terminal through the connector JK3, one output terminal is connected to the pin 1 of the first diode bridge DB1, and the other output terminal is connected to the pin 2 of the first diode bridge DB1.

[0018] On one side of the second opto-isolator U2, the diode input terminal is connected to the power supply VCC terminal through the connector JK2, the diode output terminal is connected to the opening control terminal through the connector JK1, one output terminal is connected to the pin 1 of the second diode bridge DB2, and the other output terminal is connected to the pin 2 of the second diode bridge DB2.

[0019] Pin 4 of the second diode bridge DB2 is connected to one end of the resistor RG5 and also to the ion gate IG-A. Pin 3 is connected to LD2. The conduction of the second opto-isolator U2 ultimately causes the diode bridge DB2 to short-circuit, forcing the voltage across RG2 to be zero, thus achieving the door-opening operation. One end of pin 3 of the first diode bridge DB1 is connected to the other end of the resistor RG5 and also to one end of the resistors RG1 and RG2. Pin 4 is connected to the resistor RG2, the capacitor CG1, the ion gate IG-B, and LD2. LD1 is also connected to the other end of the resistor RG1 and the other end of the capacitor CG1. The other end of the resistor RG1 is connected to the resistor RG2. The conduction of the first opto-isolator U1 ultimately causes the diode bridge DB1 to be connected, and the capacitor CG1 is connected to the loop of the resistors RG1 and RG5, thus achieving the door-closing operation.

[0020] Further, the insulating ring has the same outer diameter as the ion gate and the same inner diameter as the drift tube. There are 6 - 8 holes for inserting screws corresponding to the ion gate and 2 - 4 positioning holes distributed on the ring.

[0021] Further, the ion gates IG-A and IG-B have a thickness of 150um - 500um, a longitudinal grid spacing of 200 - 2000um, and a grid bar width of 50 - 300um. The transverse grid spacing is 3 - 6mm, and the grid bar width is 50 - 300um. Finally, a grid of rectangular grid holes is formed, and the grid holes account for 40 - 80% of the cross-sectional area of the drift tube.

[0022] The present invention also relates to an ion gate control method, which is based on the above ion gate assembly and is carried out as follows:

[0023] Upon receiving the door-opening signal, the door-opening control terminal outputs a low level at time T1. The voltage on the ion gate grid changes from Voff to Vopen, and the ion gate opens. Ions enter the drift region. The door-opening time lasts until T2. At time T2, the door-opening signal of the ion gate is cancelled. After a delay and waiting until time T3, a dead time is left between the door-opening and door-closing controls. At time T_{3}, the door-closing control terminal outputs a low level, and the first opto-isolator U1 is turned on. The ion gate closing capacitor CG1 is connected to the ion gate IG-A, and a reverse closing voltage is quickly established on the ion gate IG-A. This voltage eliminates the ions in the clearing area near the ion gate IG-A, making the ion peak narrower.

[0024] Further, the radial component of the closing electric field is always opposite to the drift electric field. By adjusting the size S of the mesh holes and the thickness of the insulating sheet between the two grid electrode sheets, the intensity of the radial component of the closing electric field is controlled. The voltage applied to the grid electrode changes the magnitude of the closing electric field. By forming a reverse closing electric field, the influence of the clearing area near the ion gate IG-A in the closed state is eliminated.

[0025] Furthermore, the ion gate control is achieved by reversing the diode bridge to adapt to the drift tube in positive mode, negative mode, or positive-negative mode switching; the first opto-isolator U1 and the second opto-isolator U2 are used as the switching devices for opening and closing the gate.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] The present invention adopts an overall modular manufacturing process. The ion gate is pre-assembled, and after being formed and tested qualified, it is installed into the drift tube. By reasonably configuring the physical position and plate potential of the TP type ion gate, a closing electric field component with an ion blocking effect is selected to improve the closing efficiency of the ion gate. The control power supply is taken from high voltage without the need for an additional auxiliary power supply. The ion gate uses a rectangular grid instead of a parallel grid; two control signals for opening and closing are respectively used for ion control, effectively compressing the thickness of the particle swarm passing through the ion gate, eliminating the influence of the traditional BN gate clearing area in the closed state, improving the sensitivity and resolution of ion detection, and achieving the main performance indicators of the IMS instrument in the traditional TP type ion gate structure without increasing the system complexity, bringing good benefits. Brief Description of the Drawings

[0028] Figure 1 is the exploded view of the ion gate of the present invention;

[0029] Figure 2 is the first three-dimensional view of the assembled ion gate of the present invention;

[0030] Figure 3 is the second three-dimensional view of the assembled ion gate of the present invention;

[0031] Figure 4 is the sectional view of the assembled ion gate of the present invention;

[0032] Figure 5 is the control circuit diagram of the ion gate of the present invention;

[0033] Figure 6 is the closing electric field and drift electric field during the control process of the present invention;

[0034] Figure 7 is the timing diagram of the control signal of the present invention;

[0035] Figure 8 is the comparison between the conventional ion peak shape and the ion peak shape diagram of the present invention. Detailed Embodiments

[0036] To more clearly illustrate the prior art solutions of the present invention, the following will further introduce the present invention in conjunction with the accompanying drawings and specific embodiments. Obviously, the following descriptions are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings and embodiments can be obtained based on these drawings and embodiments.

[0037] The ion gate assembly composed of overlapping grid-shaped metal sheets in this embodiment includes an ion gate fixed frame 2, an ion gate IG-B, an insulating ring 3, an ion gate IG-A, and a pressure plate 1. Figure 1 is the exploded view of the assembly sequence of the ion gate assembly, which is stacked in the order from left to right in Figure 1 . Adjust the symmetry of the grid holes of the ion gates IG-B and IG-A, and connect the ion gate fixed frame 2 and the pressure plate 1 with 8 screws to form the ion gate assembly. Figures 2 - 4 is the three-dimensional view after assembly.

[0038] Among them, the ion gate fixed frame 2 is machined or injection-molded from an electrically insulating material. An inner circle is axially opened in the middle, and its diameter matches the inner diameter of the drift tube. The inner diameter of the fixed frame 2 constitutes a part of the ionization region of the drift tube; air guide grooves and air inlet holes for passing air are opened on the outer diameter, 8 mounting holes are opened on one end face, wire thread inserts are embedded, and 4 positioning holes are also opened.

[0039] As Figure 3 shown, the ion gates IG-A and IG-B are processed from corrosion-resistant metal sheets and have longitudinal grid meshes. The grid mesh positions of the two ion gates are staggered, and the grid density doubles after overlapping installation. Its remarkable feature is that strengthening grids are added horizontally. After assembly, the shape of the ion control grid mesh is a rectangular sieve hole. The ion gate grid electrode changes from parallel lines to a rectangular sieve hole, increasing the strength of the grid mesh and significantly reducing the voltage required to close the door. After the two electrodes are bent, they are parallel to the radial direction and can be connected to the circuit board through elastic electrode contacts.

[0040] As Figure 1 shown, the insulating ring 3 is a concentric ring cut from an electrically insulating film, having the same outer diameter as the ion gate and the same inner diameter as the drift tube. 8 holes for inserting screws corresponding to the ion gate and 4 positioning holes are distributed on the ring; adjusting the thickness of the insulating ring can change the radial component of the closing electric field and control the closing effect of the ion gate.

[0041] As Figure 1 、 3 shown, the pressure plate 1 is an annular assembly machined or injection-molded from an electrically insulating material. 8 mounting holes are provided on the ring, and the mounting holes are designed as counterbore holes so that the screw heads are completely sunk into the holes to avoid the fastening screws protruding from the end face. The pressure plate also has 4 positioning holes.

[0042] The ion gate fixed frame and the pressure plate are made of PEEK material; the insulating ring 3 is made of a 200um polytetrafluoroethylene thin film material.

[0043] The ion gate is processed from a 150um thick 316 stainless steel sheet; the longitudinal grid spacing is 800um, the grid bar width is 200um, the transverse grid spacing is 6mm, the grid bar width is 200um, IG-A is provided with 4 transverse grids, IG-B is provided with 3 transverse grids, and finally a grid of rectangular grid holes is formed, and the grid holes account for 60% of the total cross-sectional area.

[0044] Figure 5 Among them, the connectors JK1, JK2, and JK3 are connected to the control circuit, VCC is the control voltage, 3.3V or 5V; G-open is the door opening control terminal, G-close is the door closing control terminal; the electrical node LD1 is connected to the high potential side of the drift power supply, and the electrical node LD2 is connected to the low potential side of the drift power supply; the electrical node B is connected to the ion gate grid IG-B, and the electrical node A is connected to the ion gate grid IG-A;

[0045] One side diode input terminal of the first opto-isolator U1 is connected to the power supply VCC terminal through the connector JK2, the diode output terminal is connected to the G-close control terminal through the connector JK3, one side output terminal is connected to the pin 1 of the first diode bridge DB1, and the other side output terminal is connected to the pin 2 of the first diode bridge DB1.

[0046] One side diode input terminal of the second opto-isolator U2 is connected to the power supply VCC terminal through the connector JK2, the diode output terminal is connected to the G-open control terminal through the connector JK1, one side output terminal is connected to the pin 1 of the second diode bridge DB2, and the other side output terminal is connected to the pin 2 of the second diode bridge DB2.

[0047] The pin 4 of the second diode bridge DB2 is connected to one end of the resistor RG5 and also to the ion gate IG-A, the pin 3 is connected to LD2, and the conduction of the second opto-isolator U2 finally causes the diode bridge DB2 to short-circuit, forcing the voltage across RG2 to be zero, realizing the door opening operation; one end of the pin 3 of the first diode bridge DB1 is connected to the other end of the resistor RG5 and also to one end of the resistor RG1 and the resistor RG, the pin 4 is connected to the resistor RG2, the capacitor CG1, the ion gate IG-B, and LD2; LD1 is also connected to the other end of the resistor RG1 and the other end of the capacitor CG1, and the other end of the resistor RG1 is connected to the resistor RG2; the conduction of the first opto-isolator U1 finally causes the diode bridge DB1 to turn on, and the capacitor CG1 is connected to the RG1, RG5 loop, realizing the door closing operation.

[0048] In this embodiment, optoelectronic isolation devices U2 and U1 are used as the switching devices for opening and closing the door. The selected models of U1 and U2 are TLP-127. The control power supply of the ion gate is taken from the high-voltage circuit. The current inputs from LD1 and outputs from LD2. The energy required for closing the door is provided by the energy storage of the closing capacitor CG1, whose capacity is selected as 223 / 500V. The stored voltage is the closing voltage plus the additional voltage. The closing voltage is provided by the resistor RG2 with a resistance value of 1M, and the additional voltage is provided by the resistor RG1 with a resistance value of 350K. The ion gate control uses diode bridges DB1 and DB2 for commutation, and the selected model is MD4S. The described ion gate can adapt to the drift tube in the positive mode, negative mode, or alternating switching between positive and negative modes.

[0049] In this embodiment, the ion gates are electrically staggered. It means that the ion gate IG-B is arranged closer to the ion source side in space, and the control electrode connected to the low potential electrically. It means that the ion gate IG-A is arranged closer to the ion receiving electrode side in space, and the control electrode connected to the high potential electrically. The ion gate control signal is generated by a computer program. The opening signal is connected to G-open, and the closing signal is connected to G-close. The computer output is low-level effective. As Figure 6 、 7 shown, for the TP-type ion gate arranged in this structure, the radial component Eg of the closing electric field is always opposite to the drift electric field E, enhancing the closing effect. By adjusting the size S of the mesh and the thickness d of the insulating sheet 3 between the two grid electrodes, the intensity of the radial component Eg of the closing electric field can be effectively controlled. At the same time, the voltage applied to the grid electrode can change the magnitude of the closing electric field Eg. The magnitude of the closing electric field Eg is adjusted by RG2. Due to the formation of the reverse closing electric field Eg, the influence of the clearance area near the ion gate IG-A in the closed state is eliminated.

[0050] The control timing diagram of this embodiment is as Figure 7 shown. At time T1, G-open outputs a low level, the optocoupler U2 is turned on, and the resistor RG2 is short-circuited by the diode bridge DB2. The voltage on the ion gate grid changes from Voff to Vopen, and the ion gate opens. Ions enter the drift region. The opening time lasts until T2. At time T2, the ion gate opening signal is cancelled, and it waits until time T3 after a delay, leaving a dead time between the opening and closing controls. At time T3, G-close outputs a low level, the first optoelectronic isolation device U1 is turned on, the ion gate closing capacitor CG1 is connected to the ion gate IG-A, and a reverse closing voltage Vclose is quickly established on IG-A. This voltage eliminates the ions in the clearance area near the ion gate IG-A, making the ion peak narrower and improving the resolution of the ion mobility spectrometry.

[0051] Figure 8 For the comparison between the ion spectrum diagram without using the closing control and the ion spectrum diagram after using the closing control, by Figure 8It can be seen that:

[0052] When controlling in the conventional door opening and closing manner, that is, only using G-open to control the ion gate, the door is opened at time T1 and closed at time T2. The control method is as shown in the upper curve of Figure 6 . At this time, due to the influence of the closing clearing area, the number of ions passing through the ion gate becomes larger, the ion peak is high and wide, and the resolution is low. See the left peak pattern in Figure 7 . According to the general resolution calculation method, R = Td / W 0.5 . The resolution is approximately R = 8.5 ms / 1 ms = 8.5.

[0053] Using the method of the present invention, after closing the ion gate at time T2 using G-open, start the G-close closing control at time T3. The control method is as shown in the lower curve of Figure 6 . At this time, the amplitude of the obtained ion peak becomes smaller, but the ion peak width becomes narrower, effectively improving the resolution of the IMS instrument. The resolution is approximately R = 8.5 ms / 0.3 ms = 28, and the resolution is increased by about 3 times.

[0054] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An ion gate assembly, characterized in that: It includes an ion gate fixed frame, ion gate IG-A, an insulating ring, ion gate IG-B, and a pressure plate; The ion gate fixed frame is annular, with an inner circular cavity axially provided in the middle. Its diameter matches the inner diameter of the drift tube, and air guiding grooves and air inlet holes for passing air flow are provided on the outer diameter; Ion gate IG-A and ion gate IG-B include criss-crossing grids provided on the frame. Ion gate IG-A and ion gate IG-B are parallelly arranged in the ion gate fixed frame, such that the grid positions of the two ion gates are staggered, doubling the grid density. The ion control grid is in the shape of a rectangular sieve hole; The insulating ring is provided between the frames of ion gate IG-A and ion gate IG-B; the pressure plate fixes ion gate IG-A and ion gate IG-B to the ion gate fixed frame; Ion gate IG-A is on the side close to the ion source and is connected to a control electrode with a low potential. Ion gate IG-B is on the side close to the ion receiving electrode and is connected to a control electrode with a high potential. The electric field passes through the ion gate fixed frame and the criss-crossing grids; One end face of the ion gate fixed frame has 6 - 8 mounting holes, with wire screw inserts embedded, and also has 2 - 4 positioning holes; the pressure plate is an annular component, with 6 - 8 mounting holes provided on the ring. The mounting holes are designed as counterbore holes, and the screw head is completely sunk into the hole. The pressure plate also has 2 - 4 positioning holes; The opening signal controls the opening time and the length of the opening time of the ion gate, and the closing signal controls the closing time of the ion gate, eliminating the influence of the empty area near ion gate IG-B in the closed state; One side diode input end of the first opto-isolator U1 is connected to the power supply VCC end through the connector JK2, the diode output end is connected to the closing control end through the connector JK3, one side output end is connected to the pin 1 of the first diode bridge DB1, and the other side output end is connected to the pin 2 of the first diode bridge DB1; One side diode input end of the second opto-isolator U2 is connected to the power supply VCC end through the connector JK2, the diode output end is connected to the opening control end through the connector JK1, one side output end is connected to the pin 1 of the second diode bridge DB2, and the other side output end is connected to the pin 2 of the second diode bridge DB2; The pin 4 of the second diode bridge DB2 is connected to one end of the resistor RG5, and is also connected to ion gate IG-A. The pin 3 is connected to LD2. The conduction of the second opto-isolator U2 ultimately causes the diode bridge DB2 to short-circuit, forcing the voltage across RG2 to be zero, realizing the opening operation; one end of the pin 3 of the first diode bridge DB1 is connected to the other end of the resistor RG5, and is also connected to one end of the resistor RG1 and the resistor RG2. The pin 4 is connected to the resistor RG2, the capacitor CG1, ion gate IG-B, and LD2; LD1 is also connected to the other end of the resistor RG1 and the other end of the capacitor CG1. The other end of the resistor RG1 is connected to the resistor RG2. The conduction of the first opto-isolator U1 ultimately causes the diode bridge DB1 to connect, and the capacitor CG1 is connected to the loop of the resistor RG1 and the resistor RG⑤, realizing the closing operation.

2. The ion gate assembly according to claim 1, wherein The insulating ring has the same outer diameter as the ion gate and the same inner diameter as the drift tube. There are 6 - 8 holes for inserting screws corresponding to the ion gate and 2 - 4 positioning holes distributed on the ring.

3. The ion gate assembly according to claim 1, wherein The ion gates IG-A and IG-B have a thickness of 150 μm - 500 μm, a longitudinal grid spacing of 200 - 2000 μm, and a grid bar width of 50 - 300 μm; a transverse grid spacing of 3 - 6 mm, and a grid bar width of 50 - 300 μm; finally, a grid of rectangular grid holes is formed, and the grid holes account for 40 - 80% of the cross-sectional area of the drift tube.

4. An ion gate control method, characterized in that, Based on the ion gate assembly according to any one of claims 1 - 3, proceed as follows: Receive an open door signal. At time T1, the output of the open door control terminal is at a low level, the voltage on the ion gate grid changes from Voff to Vopen, the ion gate opens, and ions enter the drift region. The open door time lasts until T2. At time T2, the open door signal of the ion gate is cancelled, and after a delay until time T3, a dead time is left between the open door and close door controls. At time T3, the output of the close door control terminal is at a low level, the first opto-isolator U1 is turned on, the ion gate closing capacitor CG1 is connected to the ion gate IG-A, and a reverse closing voltage is quickly established on the ion gate IG-A. This voltage eliminates the ions in the clearing area near the ion gate IG-A, making the ion peak narrower. The radial component of the closing electric field is always opposite to the drift electric field. By adjusting the size S of the mesh holes and the thickness of the insulating sheet between the two grid electrode sheets, the intensity of the radial component of the closing electric field is controlled; the voltage applied to the grid electrode changes the size of the closing electric field, and by forming a reverse closing electric field, the influence of the clearing area near the ion gate IG-A in the closed state is eliminated.

5. The ion gate control method according to claim 4, wherein: The ion gate control is through a diode bridge commutation to adapt to a drift tube in positive mode, negative mode, or positive-negative mode switching; the first opto-isolator U1 and the second opto-isolator U2 are used as the switching devices for opening and closing the door.

6. The ion gate control method according to claim 4, wherein: ​

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