High-frequency instantaneous shut-off device for ion trap

Abstract

The present invention instantaneously attenuates and cuts off a high-frequency voltage when ions are emitted from an ion trap, without placing a load on a high-frequency circuit. In addition, by instantaneously attenuating and cutting off the high-frequency voltage when ions are ejected from the ion trap, the resolution of mass measurement in a mass measurement device in a subsequent stage is increased compared with conventional technology. Provided is a high-frequency voltage shut-off device for an ion trap, comprising: a high-frequency circuit that generates a high-frequency voltage and is configured to include a first coil; an ion trap unit that traps ions in accordance with the high-frequency voltage generated by the high-frequency circuit; a second coil that is coupled to the first coil so as to be capable of absorbing electromagnetic energy generated by the first coil; a shunt circuit that includes a shunt switch that operates so as to release electrical energy accumulated in the second coil; and a control unit that operates the shunt switch at the time when the ions trapped by the ion trap unit are ejected.

Description

High-frequency instantaneous shutoff device for ion traps

[0001] The present invention relates to a radio frequency instantaneous shutoff device for an ion trap.

[0002] A time-of-flight nuclear mass measuring device measures the mass of an unknown target ion (atomic nucleus) by multiplying the mass of the reference ion by the square of the ratio of the flight time of the unknown target ion in a flight tube to the flight time of a known reference ion in a flight tube.

[0003] The ion trap system accumulates and cools sample ions in the ion trap space before injecting them into the flight tube of the nuclear mass spectrometer, and then injects them as ion bunches with a predetermined pulse width at a predetermined timing.

[0004] To improve the resolution and precision of nuclear mass measurements, it is necessary to keep the energy spread and spatial emittance (variation in position and direction) of the ion bunch as small as possible and to inject the ion bunch into the flight tube as a high-intensity ion pulse with a narrow pulse width.

[0005] However, in a configuration in which ions are trapped by applying a radio-frequency voltage to sample ions, the mass resolution of the sample ions is limited if the radio-frequency electric field is not blocked at the time the sample ions are ejected into the flight tube.

[0006] In other words, if the RF voltage is not shut off immediately after the ion bunch is injected into the flight tube, the sample ions will be deflected or undergo unnecessary acceleration and deceleration, which will limit the mass resolution of the sample ions.

[0007] Furthermore, simply stopping the driving source of the high-frequency voltage leaves ripples corresponding to the Q value of the high-frequency resonant circuit remaining for a long time, which limits the mass resolution of the sample ions.

[0008] 2 of Non-Patent Document 1 describes a technique in which a shunt circuit, in which a diode and a MOSFET (metal-oxide semiconductor field-effect transistor) are connected in series, is electrically connected to both terminals and the center tap of the secondary coil of a transformer in a resonant circuit, and the secondary coil is short-circuited by driving the transistor (MOSFET) in response to a control signal, thereby attenuating and stopping the high-frequency voltage signal generated in the resonant circuit in the minimum amount of time.

[0009] 2 of Non-Patent Document 2 describes a technique in which a shunt circuit is electrically connected to both terminals of the primary coil and the secondary coil of a transformer in a resonant circuit, and the primary coil and secondary coil are short-circuited by turning on a switching element of the shunt circuit, thereby attenuating and stopping the high-frequency voltage signal generated in the resonant circuit in the minimum amount of time.

[0010] Furthermore, the following patent documents 1, 2 and 3 describe the following inventions.

[0011] Patent Document 1 (JP 2005-166369 A) describes an invention in which the inductance, capacitance and effective resistance of the inductor, capacitor and resistor of a resonant circuit are set to values ​​that satisfy the critical damping condition, in order to improve the resolution of ion analysis by quickly attenuating the high-frequency voltage after the high-frequency voltage is stopped.

[0012] Patent Document 2 (Japanese Patent Publication No. 6249023) describes an invention in which a shunt circuit is formed by connecting in series an LC parallel resonant circuit having a first inductor and an LC parallel resonant circuit having a second inductor.

[0013] Patent document 3 (Japanese Patent Publication No. 6681845) describes an invention in which a high-frequency signal from an antenna input to a common terminal is guided to the common terminal and then to a ground terminal via an inductor and a switching element of a shunt circuit connected to the common terminal.

[0014] Review of Scientific Instruments 88, 123107 (2017); doi: 10.1063 / 1.4996911International Journal of Mass Spectrometry 394

[0015] (2016) 1-8 JP 2005-166369 A JP 6249023 A JP 6681845 A

[0016] According to the circuit configurations shown in Non-Patent Documents 1 and 2, a switching element such as a transistor is electrically connected to a coil that constitutes a high-frequency resonant circuit, and therefore the switching element itself becomes a load on the high-frequency circuit, making it difficult to obtain a stable high-frequency high voltage for ion trapping.

[0017] An object of the present invention is to instantly attenuate and cut off the radio frequency voltage at the time when ions are ejected from the ion trap without imposing a load on the radio frequency circuit.

[0018] Another object of the present invention is to improve the resolution and accuracy of mass measurement in the subsequent mass measurement device compared to conventional techniques by instantly attenuating and cutting off the radio frequency voltage at the time ions are ejected from the ion trap.

[0019] The first aspect is a device for blocking a radio frequency voltage for an ion trap, comprising: a radio frequency voltage generation circuit that generates a radio frequency voltage and that includes a first coil; an ion trap section that traps ions in response to the radio frequency voltage generated by the radio frequency voltage generation circuit; a second coil that is coupled to the first coil so as to be able to absorb electromagnetic energy generated by the first coil; a shunt circuit that includes a shunt switch that operates to release electrical energy stored in the second coil; and a control section that operates the shunt switch at a timing to eject ions trapped in the ion trap section.

[0020] In a second aspect, in the first aspect, the ion trap section has an ion injection port connected to an ion analysis section, and the control section operates the shunt switch at the timing when ions captured in the ion trap section are injected into the ion analysis section through the ion injection port.

[0021] A third aspect is the device for cutting off a high frequency voltage for an ion trap according to the second aspect, wherein the ion analysis unit is an ion mass analysis unit.

[0022] A fourth aspect is the device for blocking a radio frequency voltage for an ion trap, wherein the ion trap section is configured to alternately eject reference ions and ions whose masses are to be measured from the ion ejection port, and the control section operates the shunt switch at the timing when the reference ions and ions whose masses are to be measured are alternately ejected from the ion ejection port.

[0023] A fifth aspect is the device for cutting off a radio frequency voltage for an ion trap according to the first aspect, wherein the shunt circuit is configured so that both ends of the second coil are short-circuited in response to operation of the shunt switch.

[0024] A sixth aspect is a device for blocking high-frequency voltage for an ion trap, in which the first coil in the first aspect is partially or entirely surrounded by a material capable of absorbing electromagnetic energy generated by the first coil.

[0025] A seventh aspect is the device for cutting off a radio frequency voltage for an ion trap according to the first aspect, wherein the second coil is wound around the first coil.

[0026] An eighth aspect is the device for cutting off a radio frequency voltage for an ion trap according to the first aspect, wherein the first coil is a toroidal coil.

[0027] A ninth aspect is a device for blocking high-frequency voltage for an ion trap according to the seventh or eighth aspect, wherein the first coil and the second coil are partially or entirely surrounded by a material capable of absorbing electromagnetic energy generated by the first coil and the second coil.

[0028] A tenth aspect is a device for cutting off a radio frequency voltage for an ion trap, comprising a first coil, a second coil wound around the first coil, and a shunt switch that short-circuits both ends of the second coil.

[0029] An eleventh aspect is the tenth aspect, wherein the first coil is a toroidal coil;

[0030] The second coil is wound around the first coil and serves as a cutoff device for the high frequency voltage for the ion trap.

[0031] A twelfth aspect is a device for blocking high-frequency voltage for an ion trap according to the tenth or eleventh aspect, wherein the first coil and the second coil are partially or entirely surrounded by a material capable of absorbing electromagnetic energy generated by the first coil and the second coil.

[0032] According to the first to twelfth aspects, the radio frequency voltage can be instantly attenuated and cut off at the time when ions are ejected from the ion trap, without imposing a load on the radio frequency circuit.

[0033] Furthermore, by instantly attenuating and cutting off the radio frequency voltage at the time when ions are ejected from the ion trap, the resolution and accuracy of mass measurement in the subsequent mass measurement device are improved compared to the prior art.

[0034] FIG. 1 is a diagram showing the overall configuration of a radio frequency instantaneous shutoff device for an ion trap according to an embodiment. FIG. 2A is a diagram showing the configuration of the ion trap section. FIG. 2B is a diagram showing cross sections of a reference ion trap section and a mass measurement target ion trap section. FIG. 2C is a perspective view showing the configuration of a flat section. FIG. 2D is a cross-sectional view of the flat section taken along the line A-A. FIG. 3 is a diagram used to explain an ion mass analysis section. FIG. 4 is a diagram showing an example configuration of a radio frequency voltage generation circuit and a shunt circuit. FIG. 5 is a diagram used to explain an ion trap section. FIG. 6 is a diagram explaining the control performed by a radio frequency voltage control section, a switch control section, and an injection voltage control section. FIG. 7A is a perspective view showing an example configuration of a coil unit consisting of a first coil and a second coil. FIG. 7B is a cross-sectional view showing an example configuration of a coil unit consisting of a first coil and a second coil. FIG. 7C is a cross-sectional view showing an example configuration of a coil unit consisting of a first coil and a second coil. FIG. 8 is a diagram showing an example of a coil unit. 9A and 9B are graphs showing the mass measurement results of the conventional technique and the embodiment, respectively.

[0035] Hereinafter, an embodiment of a radio frequency instantaneous cutoff device for an ion trap according to the present invention will be described with reference to the drawings.

[0036] FIG. 1 is a diagram showing the overall configuration of a high-frequency instantaneous cutoff device 1 for an ion trap according to an embodiment.

[0037] (Overall structure)

[0038] The ion trap high frequency instantaneous cutoff device 1 is mainly composed of an ion trap section 100 , an ion mass analysis section 200 , a voltage generation and application section 300 , and a control section 400 .

[0039] The ion trap section 100 is configured to include an ion trap space 100A in which reference ions 10 and ions 11 to be measured for mass measurement are trapped in response to a radio frequency voltage V20 generated by a radio frequency voltage generating circuit 320 and applied to the electrodes of the ion trap section 10, and an ejection port 101 for ejecting the reference ions 10 and ions 11 to be measured for mass measurement, which have been trapped and cooled in the ion trap space 100A, as ion bunches with a predetermined pulse width (preferably, a pulse width as short as possible) at a predetermined timing toward the flight tube 210 of the ion mass analysis section 200.

[0040] Reference ions 10 and mass measurement target ions 11 are introduced into the ion trap section 100 from the outside. The reference ions 10 and mass measurement target ions 11 present in the ion trap section 100 are cooled by a collision gas such as helium. The reference ions 10 and mass measurement target ions 11 lose kinetic energy through collisions with the collision gas and are accumulated in the ion trap section 100.

[0041] The ion mass analysis section 200 is configured to include a flight tube 210 for causing the reference ions 10 and the ions 11 to fly back and forth multiple times after being ejected from the ejection port 101, a detector 220 for detecting the time of flight of the reference ions 10 and the ions 11 to be measured, which are ejected from the flight tube 210 at predetermined timings, and a measurement processing section 230 for measuring the mass of the atomic nucleus of the ions 11 to be measured, which have an unknown mass, in accordance with the time of flight detected by the detector 220.

[0042] The voltage generation and application unit 300 includes a transport voltage generation and application unit 310 that generates a transport voltage V10 for transporting the reference ions 10 and the mass measurement target ions 11 into the ion trap space 100A at predetermined timings and applies the voltage to each electrode of the ion trap unit 100; a radio frequency voltage generation circuit 320 that generates a radio frequency voltage V20 for trapping the reference ions 10 and the mass measurement target ions 11 in the ion trap space 100A; a second coil 372 that couples to the first coil 321 of the radio frequency voltage generation circuit 320 so as to be able to absorb electromagnetic energy generated by the first coil 321; and a shunt that operates to release electrical energy stored in the second coil 372. the reference ions 10 and the ions 11 to be mass measured are injected into the flight tube 210, causing them to fly back and forth multiple times, and a flight voltage generation and application unit 350 which generates a flight voltage V50 for introducing the reference ions 10 and the ions 11 to be mass measured in the flight tube 210 into the detector 220 at a predetermined timing, and applies the flight voltage V50 to the corresponding electrodes 211A, 212A.

[0043] The control unit 400 is composed of a transport voltage control unit 410 that controls the generation and application of a transport voltage V10, a radio frequency voltage control unit 420 that controls the generation and application of a radio frequency voltage V20, a switch control unit 430 that operates the shunt switch 371 at the timing when the reference ion 10 and the mass measurement target ion 11 captured in the ion trap unit 100 are ejected from the ejection port 101, an ejection voltage control unit 440 that controls the generation and application of an ejection voltage V40, and a flight voltage control unit 450 that controls the generation and application of a flight voltage V50.

[0044] (Ion trap section 100)

[0045] FIG. 2A shows the configuration of the ion trap section 100 .

[0046] The ion trap section 100 is configured to include a flat section 110, a reference ion trap section 120, and a mass measurement target ion trap section 130, which are arranged symmetrically in the figure with respect to the flat section 110. Hereinafter, in Figures 2A, 2B, 2C, and 2D, the left-to-right direction of the paper in Figure 2A is defined as the "transport direction," and the depth direction of the paper in Figure 2A is defined as the "width direction."

[0047] In the reference ion trap section 120, a plurality of electrodes 121, 122, and 123 to which DC transport voltages V, V, and V are applied, respectively, are arranged along the transport direction (horizontal direction in the drawing). The electrodes 121, 122, and 123 are sequentially arranged from the left in the drawing toward the flat section 110 in the center.

[0048] Similarly, in the trap section 130 for ions to be mass measured, multiple electrodes 131, 132, and 133 to which DC transport voltages V14, V15, and V16 are applied, respectively, are arranged along the transport direction (left-right direction in the figure). The electrodes 131, 132, and 133 are arranged in sequence from the right in the figure toward the flat section 110 in the center. Note that the electrodes 131, 132, and 133 are shown as representatives in the figure. In an actual system, a large number of electrodes are arranged continuously with small gaps between them along the longitudinal direction of the trap section 130 for ions to be mass measured. The same is true for the trap section 120 for reference ions.

[0049] Reference ions 10 are introduced into the reference ion trap section 120 from a reference ion supply source (not shown). Ions 11 to be measured for mass measurement are introduced into the mass measurement target ion trap section 130 from a mass measurement target ion supply source (not shown).

[0050] 2B shows cross sections of the reference ion trap section 120 and the mass measurement target ion trap section 130. The reference ion trap section 120 includes electrodes 120A and 120B arranged vertically in the figure, and electrodes 120C and 120D arranged horizontally in the figure. Reference ions 10 are transported toward the flat section 110 within the space surrounded by the electrodes 120A, 120B, 120C, and 120D. Opposite phase AC voltages +V30 and −V30 are applied to adjacent electrodes (e.g., electrodes 120A and 120C) among the electrodes 120A, 120B, 120C, and 120D. By applying opposite phase AC voltages +V30 and −V30 to adjacent electrodes (e.g., electrodes 120A and 120C) among the electrodes 120A, 120B, 120C, and 120D, the reference ions 10 are held in a direction perpendicular to the transport direction of the reference ion trap section 120.

[0051] Similarly, the mass measurement target ion 11 is transported toward the flat section 110 within the space surrounded by the plates 130A, 130B, 130C, and 130D that make up the trapping section 130 for ions to be measured. Similarly, by applying opposite phase AC voltages +V30 and −V30 to adjacent electrodes (e.g., electrodes 130A and 130C) among the electrodes 130A, 130B, 130C, and 130D, the mass measurement target ion 11 is held in a direction perpendicular to the transport direction of the trapping section 130 for ions to be measured.

[0052] FIG. 2C is a perspective view showing the configuration of the flat portion 110.

[0053] FIG. 2D is a cross-sectional view of the flat portion 110 taken along line AA of FIG. 2A.

[0054] The flat portion 110 is configured to include opposing substrates 110A and 110B.

[0055] An injection port 101 is formed in the center of the substrate 110A of the flat portion 110.

[0056] A plurality of electrodes 111A, 112A, 113A, and 114A to which DC transport voltages V17, V18, and V19 and an ejection voltage V40 (-V42), respectively, are applied are arranged along the transport direction on the substrate 110A of the flat section 110. On the substrate 110A of the flat section 110, the electrodes 111A, 112A, 113A, and 114A (central portion) are sequentially arranged from the reference ion trap section 120 and the mass measurement target ion trap section 130 side toward the center.

[0057] Similarly, a plurality of electrodes 111B, 112B, 113B, and 114B to which DC transport voltages V, V, and V and an ejection voltage V (+V) are respectively applied are arranged along the transport direction on the substrate 110B of the flat section 110. On the substrate 110B of the flat section 110, the electrodes 111B, 112B, 113B, and 114B (central portion) are sequentially arranged from the reference ion trap section 120 and the mass measurement target ion trap section 130 side toward the center.

[0058] An ion trap space 100A is defined between the substrates 110A and 110B of the flat section 110. Electrodes 115A and 116A to which an AC high-frequency voltage V is applied are arranged symmetrically in the width direction on the substrate 110A of the flat section 110, sandwiching electrodes 111A, 112A, 113A, and 114A therebetween.

[0059] Similarly, electrodes 115B and 116B to which an AC high-frequency voltage V is applied are arranged symmetrically in the width direction across electrodes 111B, 112B, 113B, and 114B on substrate 110B of flat section 110. As described above, high-frequency voltage V is applied to each of electrodes 115A, 116A, 115B, and 116B, and the phases of each of electrodes 115A, 116A, 115B, and 116B are the same.

[0060] By applying a negative ejection voltage −V42 and a positive ejection voltage +V42 to electrodes 114A and 114B at the center of the flat section 110, respectively, the positive reference ions 10 or mass measurement target ions 11 stored in the ion trap space 100A are ejected from the ejection port 101 toward the ion mass analysis section 200.

[0061] The control of transporting the reference ions 10 and the mass measurement target ions 11 from the reference ion trap section 120 and the mass measurement target ion trap section 130 to the flat section 110 will be described later.

[0062] (Ion mass analysis unit 200)

[0063] As shown in FIG. 3A, the flight tube 210 of the ion mass analysis section 200 is composed of an entrance mirror 211 and an exit mirror 212 as a pair of electrostatic ion mirrors for reciprocating the reference ions 10 and the ions 11 to be mass-measured, and a connecting section 213 connecting the entrance mirror 211 and the exit mirror 212.

[0064] The entrance side mirror 211 and the exit side mirror 212 are each composed of a number of annular electrodes, and by applying a predetermined voltage to each annular electrode, the flight states of the reference ions 10 and the mass measurement target ions 11 are controlled. For the sake of simplicity, the annular electrode 211A of the entrance side mirror 211 closest to the exit port 101 and the annular electrode 212A of the exit side mirror 212 closest to the detector 220 are shown here.

[0065] The detector 220 can be configured to include an element, such as a secondary electron multiplier, that can amplify collisions of incident charged particles (reference ions 10, mass measurement target ions 11) and detect them with high precision. The detector 220 emits secondary electrons in response to the reference ions 10 and mass measurement target ions 11 colliding with a metal or ceramic surface, and outputs an ion detection signal.

[0066] The ion detection signal output from the detector 220 is correlated with the ion detection time and is measured and processed by the measurement processing unit 230 .

[0067] The measurement processing unit 230 can be configured by a computer.

[0068] The mass m of the mass measurement target ion 11 is calculated by the following equation (1) using the flight time t of the mass measurement target ion 11, the mass m of the reference ion 10 (known value), and the flight time t of the reference ion 10.

[0069] m1=m0(t1 / t0)^2...(1)

[0070] In equation (1), "^2" means squared.

[0071] The measurement processing unit 230 statistically processes the distribution of the time of flight t of the ions 11 to be mass-measured and the distribution of the time of flight t of the reference ions 10 to calculate the mass m of the ions 11 to be mass-measured. The time of flight t and t are on the order of a dozen milliseconds.

[0072] (Voltage generation and application unit 300)

[0073] 1 , 2A, 2B, 2C, and 2D, the transport voltage generation and application unit 310 generates DC transport voltages V11, V12, V13, V14, V15, V16, V17, V18, and V19 (collectively referred to as V10) in response to a control signal output from the transport voltage control unit 410 of the control unit 400, and applies these voltages to the electrodes 121, 122, and 123 of the reference ion trap unit 120, the electrodes 131, 132, and 133 of the mass measurement target ion trap unit 130, and the electrodes 111 (111A and 111B), 112 (112A and 112B), and 113 (113A and 113B) of the flat unit 110, respectively.

[0074] In addition, the transportation voltage generation / application unit 310 generates AC voltages +V30 and -V30 in response to a control signal output from the transportation voltage control unit 410 of the control unit 400, and applies these voltages to each of the opposing electrodes among the electrodes 120A, 120B, 120C, 120D, 130A, 130B, 130C, and 130D.

[0075] Furthermore, the ejection voltage generation and application unit 340 generates DC ejection pulse voltages −V42, +V42 (collectively referred to as V40) in accordance with a control signal output from an ejection voltage control unit 440 of the control unit 400, and applies these voltages to the electrodes 114A, 114B at the center of the flat portion 110, respectively.

[0076] Furthermore, flight voltage generation and application unit 350 generates DC flight voltages V51 and V52 (collectively referred to as V50) in response to control signals output from control unit 400 and flight voltage control unit 450, and applies these voltages to ring electrode 211A on entrance mirror 211 and ring electrode 212A on exit mirror 212. Note that in the drawing, ring electrodes 211A and 212A are shown as representatives. In an actual system, flight tube 210 is divided into multiple ring electrodes along its length, and electrostatic potential and pulse potential are applied to each of the ring electrodes.

[0077] FIG. 4 shows an example of the configuration of the high-frequency voltage generating circuit 320 and the shunt circuit 370.

[0078] The high-frequency voltage generating circuit 320 is configured as an LC parallel high-frequency resonant circuit. The high-frequency voltage generating circuit 320 includes an oscillator 322 that generates and outputs a high-frequency voltage signal, a high-frequency voltage generation command switch 323 that turns on / off the generation of the high-frequency voltage signal generated and output by the oscillator 322 in response to a control signal (on / off logic signal) output from an external high-frequency voltage control unit 420, an amplifier 325 that amplifies the high-frequency voltage signal output from the oscillator 322 and applies it to a primary coil 311 of a downstream transformer 326, a first coil 321 configured as a secondary coil of the transformer 326, and a variable capacitor 324 connected in parallel to the first coil 321. As described below, a second coil 372 of a shunt circuit 370 is wound around a core 410 of the transformer 326 together with the first coil 321. The oscillator 322 can be configured as a function generator.

[0079] When the high frequency voltage generation command switch 323 is turned on, a high frequency voltage V20 is generated by parallel resonance of the first coil 321 and the capacitor 324. For example, a high frequency voltage V20 having a frequency of 2 to 5 MHz and an amplitude of 400 Vpp to 900 Vpp is generated.

[0080] When the high frequency voltage generation command switch 323 is turned off, the generation of the high frequency voltage V20 is stopped.

[0081] The inductance and capacitance of the first coil 321 and capacitor 323 are set to values ​​that satisfy the equations for the conditions of parallel resonance.

[0082] A terminal 321A on one end of the first coil 321 is electrically connected to the electrodes 115A, 116A, 115B, and 116B of the flat portion 110 as an output terminal for the high frequency voltage V20.

[0083] The shunt circuit 370 is configured as a closed circuit in which a second coil 372 and a shunt switch 371 are connected in series. The shunt switch 371 is turned on / off depending on a control signal (an on / off logic signal) output from an external switch control unit 430. When the shunt switch 371 is turned off to the open side, a terminal 372A on one side of the second coil 372 and a terminal 372B on the other side are open.

[0084] When the shunt switch 371 is turned on to the closed side, a terminal 372A on one side of the second coil 372 and a terminal 372B on the other side are short-circuited.

[0085] The inductance of the first coil 321 and the inductance of the second coil 372 are typically set to, for example, 20 μH and 5 μH, respectively.

[0086] (Control unit 400)

[0087] The control performed by the control unit 400 will be described below.

[0088] (Transportation of reference ions 10 and mass measurement target ions 11 to the flat section 110)

[0089] FIG. 5A is a diagram corresponding to FIG. 2A and shows the configuration of the ion trap section 100. In FIG.

[0090] Figures 5(B1), 5(B2), 5(B3), and 5(B4) are diagrams showing the potentials during ion transport control corresponding to each part in Figure 5(A), and explain the control content performed by the transport voltage control unit 410.

[0091] 5(B1), transport voltages V14, V15, V16, V17, V18, and V19, which decrease sequentially in the order of V14, V15, V16, V17, V18, and V19, are applied to electrodes 131, 132, and 133 in the trapping section 130 for ions to be mass measured, and to electrodes 111, 112, and 113 in the flat section 110. Furthermore, ejection voltages (trapping voltages) V41 and V41 (e.g., 0 V), which are lower than V19 but have the same magnitude, are applied to electrodes 114A and 114B in the flat section 110.

[0092] As a result, the ions 11 to be measured by mass measurement are transported from the trapping section 130 for ions to be measured by mass measurement to the flat section 110, where they are accumulated and cooled in the ion trapping space 100A of the flat section 110 without being ejected.

[0093] On the other hand, transport voltages V11, V12, and V13 are applied to the electrodes 121, 122, and 123 of the reference ion trapping section 120, respectively, so that V12 is lower than V11 and V13 is higher than V12. As a result, the reference ions 10 are accumulated in the reference ion trapping section 120 without being transported to the flat section 110.

[0094] 5(B2), transport voltages V14, V15, and V16 are applied to electrodes 131, 132, and 133 of the trapping section 130 for ions whose masses are to be measured, respectively, so that V15 is lower than V14 and V16 is higher than V15. Furthermore, ejection voltages -V42 and +V42 of opposite polarities are applied to electrodes 114A and 114B of the flat section 110, respectively.

[0095] As a result, the transport of the mass measurement target ions 11 to the flat section 110 stops, and the mass measurement target ions 11 that have been accumulated and cooled in the ion trap space 100 A of the flat section 110 are ejected from the ejection port 101 .

[0096] 5(B3), transport voltages V11, V12, V13, V17, V18, and V19, which decrease sequentially in the order of V11, V12, V13, V17, V18, and V19, are applied to the electrodes 121, 122, and 123 of the reference ion trap section 120 and the electrodes 111, 112, and 113 of the flat section 110. Furthermore, ejection voltages (trapping voltages) V41 and V41 (e.g., 0 V), which are lower than V19 but have the same magnitude as V19, are applied to the electrodes 114A and 114B of the flat section 110.

[0097] As a result, the reference ions 10 are transported from the reference ion trap section 120 to the flat section 110, and are accumulated and cooled in the ion trap space 100A of the flat section 110 without being ejected.

[0098] 5(B4), transport voltages V11, V12, and V13 are applied to the electrodes 121, 122, and 123 of the reference ion trap section 120, respectively, so that V12 is lower than V11 and V13 is higher than V12. Furthermore, ejection voltages -V42 and +V42 of opposite polarities are applied to the electrodes 114A and 114B of the flat section 110, respectively.

[0099] As a result, the transport of the reference ions 10 to the flat section 110 stops, and the reference ions 10 that have been accumulated and cooled in the ion trap space 100 A of the flat section 110 are ejected from the ejection port 101 .

[0100] Next, the control performed by the flight voltage control unit 450 will be described.

[0101] 3(B1), 3(B2), 3(B3), and 3(B4) are diagrams showing the potentials during flight control corresponding to the various parts of the flight tube 210 shown in FIG. 3(A).

[0102] 3(B1), when the reference ions 10 and the mass measurement target ions 11 are accumulated and cooled in the flat section 110, the flight voltage V51 of the annular electrode 211A is higher than the voltage of the flat section 110 and is also higher than the voltage of the connecting section 213. In addition, the flight voltage V52 of the annular electrode 212A is also high.

[0103] 3(B2), the flight voltage V51 applied to the annular electrode 211A is reduced when the reference ion 10 or the ion 11 to be measured is ejected from the ejection port 101. As a result, the potential is gradually reduced from the flat portion 110 to the entrance-side mirror 211, and the reference ion 10 or the ion 11 to be measured ejected from the ejection port 101 is accelerated from the ejection port 101 toward the entrance-side mirror 211 and the connecting portion 213. The reference ion 10 or the ion 11 to be measured is also decelerated from the connecting portion 213 toward the exit-side mirror 212, and its direction is reversed by the exit-side mirror 212.

[0104] 3(B3), a high voltage is again applied to the flight voltage V51 of the annular electrode 211A before the reference ion 10 or the mass measurement target ion 11 returns to the exit 101. As a result, the direction of the reference ion 10 or the mass measurement target ion 11 is reversed by the entrance side mirror 211.

[0105] Thereafter, the reference ions 10 or the ions 11 to be subjected to mass measurement fly back and forth within the flight tube 210 multiple times.

[0106] 3(B4), when the reference ion 10 or the mass measurement ion 11 has made a predetermined number of round trips within the flight tube 210, the flight voltage V52 of the annular electrode 212A is reduced. As a result, the reference ion 10 or the mass measurement ion 11 passes through the end of the exit mirror 212 without being inverted by the exit mirror 212, and is guided to the detector 220.

[0107] Next, the control contents performed by the high frequency voltage control section 420, the switch control section 430, and the injection voltage control section 440 will be described with reference to FIG.

[0108] FIG. 6A shows the change over time in the waveform of the high frequency voltage V20 applied to the electrodes 115A, 116A, 115B, and 116B of the flat portion 110.

[0109] FIG. 6B shows the on / off changes of the high frequency voltage generation command switch 323 over time.

[0110] FIG. 6C shows the change over time between the off and on states of the shunt switch 371.

[0111] 6D and 6E show the change over time of the ejection voltage V40 applied to the electrodes 114B and 114A of the flat portion 110, respectively.

[0112] (Ion cooling and storage)

[0113] As shown in Fig. 6B, the high-frequency voltage generation command switch 323 is turned on until time t. As shown in Fig. 6C, the shunt switch 371 is turned off until time t. Therefore, the high-frequency voltage V is applied to the electrodes 115A, 116A, 115B, and 116B of the flat portion 110 until time t.

[0114] 6(D) and 6(E), until time t1, ejection voltages (trapping voltages) V41 and V41 (e.g., 0 V) ​​of the same magnitude are applied to the electrodes 114B and 114A of the flat section 110. Therefore, until time t1, the reference ions 10 or the ions 11 to be measured in mass are accumulated and cooled in the ion trap space 100A of the flat section 110 without being ejected.

[0115] (When high frequency voltage is cut off)

[0116] 6B, at time t1, the high frequency voltage generation switch 323 is turned off, thereby stopping the generation of the high frequency voltage V20.

[0117] Furthermore, as shown in FIG. 6C, when time t1 is reached, the shunt switch 371 is turned on.

[0118] Therefore, the electromagnetic energy generated in the first coil 321 is absorbed by the second coil 372. The electromagnetic energy stored in the second coil 372 is then instantly released from the second coil 372 by the current circulating through the shunt circuit 370. As a result, the high-frequency signal is attenuated and blocked as much as possible, as shown by C in Fig. 6A.

[0119] (When ions are emitted)

[0120] As shown in Figures 6(D) and (E) , at time t2, when a predetermined time Δt (several microseconds) has elapsed since time t1, ejection voltages +V42 (e.g., +100 V) and -V42 (e.g., +100 V) of opposite polarities are applied to the electrodes 114B and 114A of the flat portion 110, respectively.

[0121] Therefore, the reference ions 10 or the ions 11 to be mass-measured are ejected from the ejection port 101 with the high-frequency voltage V20 completely shut off.

[0122] According to the embodiment, the radio frequency voltage V20 can be instantaneously shut off when an ion bunch of the reference ions 10 or the ions 11 to be mass measured is injected into the flight tube 210. This prevents the radio frequency voltage from remaining applied immediately after injection, preventing the reference ions 10 or the ions 11 to be mass measured from being deflected or from undergoing unnecessary acceleration or deceleration. Furthermore, no ripple corresponding to the Q value of the radio frequency voltage generation circuit 320 remains. This makes it possible to suppress a decrease in the mass resolution of the ions 11 to be mass measured.

[0123] Furthermore, the second coil 372 (shunt circuit 370) can instantly attenuate and cut off the radio frequency voltage V20 at the moment when the reference ion 10 or the mass measurement target ion 11 is ejected without imposing a load on the radio frequency voltage generation circuit 320. This allows the radio frequency voltage generation circuit 320 to obtain a stable high frequency high voltage for ion trapping.

[0124] 7A and 7B show an example of the configuration of a coil unit 400 including a first coil 321 and a second coil 372. Fig. 7A is a plan view, and Fig. 7B is a cross-sectional view.

[0125] The coil unit 400 is composed of a toroidal core 410, a primary coil 311 wound around the toroidal core 410, a first coil 321 as a secondary coil wound around the toroidal core 410, a second coil 372 wound around the first coil 321, and an electromagnetic energy absorbing material 420 that surrounds the entire primary coil 311, the first coil (secondary coil) 321, and the second coil 372.

[0126] Here, the toroidal core 410 is made of a ferromagnetic material that has low loss and high magnetic permeability, and allows a magnetic field to pass through more easily than through air, such as silicon steel plate, permalloy, or ferrite.

[0127] The electromagnetic energy absorbing material 420 is made of a material capable of absorbing the electromagnetic energy generated by the first coil 321 and the second coil 372, such as aluminum foil.

[0128] It is also possible to partially cover the first coil 321 and the second coil 372 with the electromagnetic energy absorbing material 420 .

[0129] In FIG. 7A, the high-frequency voltage generating circuit 320 is configured such that the output voltage of the amplifier 325 is applied to the primary coil 311, but the primary coil 311 may be omitted and the output voltage of the amplifier 325 may be applied directly to the first coil 321.

[0130] A variation of the coil unit 400 shown in FIG. 7A is shown in FIG. 7C.

[0131] That is, the coil unit 400 is composed of a toroidal core 410, a first coil 321 wound around the toroidal core 410, a second coil 372 wound around the first coil 321, and an electromagnetic energy absorbing material 420 that surrounds the entire first coil 321 and second coil 372.

[0132] Furthermore, the coil unit 400 does not necessarily have to be toroidal, and can be formed into any shape. For example, the coil unit 400 may be formed by winding the first coil 321 around a rod-shaped core, and then winding the second coil 372 around the first coil 321.

[0133] Furthermore, the coil unit 400 does not necessarily have to be an iron core type, but may be an air core type.

[0134] Fig. 8 shows an example of the coil unit 400. The effects of the present invention are not limited to the case where a toroidal coil transformer as exemplified in Fig. 7A, Fig. 7B, and Fig. 7C is used, but can also be achieved by using an air-core coil transformer as exemplified in Fig. 8.

[0135] The coil unit 400 is composed of a bobbin 411 molded from a resin material, a primary coil 311 wound around the bobbin 411, a first coil 321 as a secondary coil wound around a toroidal core 410, an insulating material 430 covering the first coil 321, and a second coil 372 wound around the first coil 321.

[0136] (Effects of the embodiment)

[0137] The measurement processing unit 230 statistically processes the distribution of the flight times t 1 of the ions 11 to be mass-measured and the distribution of the flight times t 0 of the reference ions 10 to calculate the mass m 1 of the ions 11 to be mass-measured.

[0138] Here, with conventional technology, if drift occurs due to voltage fluctuations, temperature fluctuations, etc. in various parts while measuring the times of flight t0 and t1, systematic errors may occur, and the precision and accuracy of mass measurement may decrease.

[0139] However, in the measurement method of this embodiment, the reference ions 10 and the mass measurement target ions 11 fly alternately, so that the measurement of the flight times t0 and t1 is performed in a cycle of, for example, several tens of milliseconds without a large time difference compared to the conventional technique, and therefore it is possible to suppress a decrease in the precision and accuracy of mass measurement due to the influence of drift.

[0140] In addition, the flight times t0 and t1 of the reference ion 10 and the mass measurement target ion 11 are on the order of

[0141] is, for example, about 10-15 milliseconds, making it possible to measure short-lived nuclei with a lifetime of 0.1 seconds or less and heavy nuclei.

[0142] Moreover, according to the embodiment, the radio frequency voltage V20 is instantaneously shut off every time the reference ions 10 or the ions 11 to be mass-measured are injected into the flight tube 210. This prevents a decrease in the mass resolution and accuracy of the ions 11 to be mass-measured.

[0143] Therefore, according to the embodiment, it is possible to dramatically improve the precision, accuracy and resolution of mass measurement of ions of short-lived nuclei and heavy nuclei.

[0144] 9A and 9B show the results of mass measurement using the conventional technology and the embodiment, respectively. The horizontal axis of each of Fig. 9A and 9B represents the time Δt [μs] from the end of the radio frequency signal to the extraction of ions, and the vertical axis represents the relative difference [ppm] from the true mass of the ions 11 to be measured. In this experiment, 139Xe and 105Mo, whose true masses are known in advance, were used as the ions 11 to be measured.

[0145] As can be seen from FIG. 9A, in a conventional ion mass analysis system not equipped with a shunt circuit 370, the radio frequency voltage cannot be cut off instantaneously, and the radio frequency voltage remains applied for a while even immediately after the ions 11 to be measured for mass measurement are ejected. Depending on the time Δt from the cessation of the radio frequency signal to the ejection of the ions, the measured mass of the ions 11 to be measured for mass measurement may deviate from the true value, resulting in large variations in the measured mass for each time Δt.

[0146] In contrast to this, in the ion mass analysis system of this embodiment equipped with the shunt circuit 370 shown in FIG. 9B, the radio frequency voltage can be instantaneously cut off, and the radio frequency voltage is not applied immediately after ejection. Therefore, regardless of the length of the time Δt from the cessation of the radio frequency signal to the ejection of ions, the measured mass of the ions 11 to be measured matches or nearly matches the true value, and there is no variation in the measured mass for each time Δt.

[0147] Therefore, according to this embodiment, it can be evaluated that the precision, accuracy and resolution of mass measurement of ions of short-lived nuclei and heavy nuclei are improved compared to the prior art.

[0148] In this embodiment, the flight tube 210 of the ion mass analysis unit 200 is configured as a multi-reflection type.

[0149] However, any time-of-flight measurement method and configuration may be used for the flight tube 210. That is, the time-of-flight measurement method and configuration of the flight tube 210 may be an open-circuit multiple reflection type, a linear type, a reflector (single reflection) type, an open-circuit or closed-circuit track type, or the like.

[0150] In the embodiment, the case where the system is applied to eject ions trapped in the ion trap unit 100 into the ion mass analysis unit 200 has been described.

[0151] However, the component to which the ions trapped in the ion trap unit 100 are ejected does not necessarily have to be an ion mass analysis unit, but can be applied to a system in which the ions trapped in the ion trap unit 100 are ejected toward an ion analysis unit configured for any purpose other than mass analysis, such as composition analysis.

[0152] The disclosure of Japanese Patent Application No. 2024-99947, filed on June 20, 2024, is incorporated herein by reference in its entirety.

[0153] REFERENCE SIGNS LIST 1 Ion trap high frequency instantaneous cutoff device 100 Ion trap section 200 Ion mass analysis section 300 Voltage generation and application section 400 Control section 320 High frequency voltage generation circuit 321 First coil 370 Shunt circuit 371 Shunt switch 372 Second coil

Claims

1. A device for cutting off a high frequency voltage for an ion trap, comprising: a high frequency circuit that generates a high frequency voltage and includes a first coil; an ion trap section that traps ions in response to the high frequency voltage generated by the high frequency circuit; a second coil that is coupled to the first coil so as to be able to absorb electromagnetic energy generated by the first coil; a shunt circuit that includes a shunt switch that operates to release electrical energy stored in the second coil; and a control section that operates the shunt switch at the timing to eject ions trapped in the ion trap section.

2. The ion trap radio frequency voltage cut-off device according to claim 1, wherein the ion trap section has an ion injection port connected to an ion analysis section, and the control section operates the shunt switch at the timing when ions trapped in the ion trap section are injected into the ion analysis section through the ion injection port.

3. The device for cutting off a high frequency voltage for an ion trap according to claim 2, wherein the ion analysis section is an ion mass analysis section.

4. The ion trap radio frequency voltage cut-off device according to claim 3, wherein the ion trap section is configured to alternately eject reference ions and ions whose masses are to be measured from the ion ejection port, and the control section operates the shunt switch at the timing when the reference ions and ions whose masses are to be measured are alternately ejected from the ion ejection port.

5. The ion trap radio frequency voltage cutoff device according to claim 1, wherein the shunt circuit is configured so that both ends of the second coil are short-circuited in response to operation of the shunt switch.

6. The device for blocking high frequency voltage for an ion trap according to claim 1, wherein the first coil is partially or entirely surrounded by a material capable of absorbing electromagnetic energy generated by the first coil.

7. The device for cutting off a high frequency voltage for an ion trap according to claim 1, wherein the second coil is wound around the first coil.

8. The device for cutting off a radio frequency voltage for an ion trap according to claim 7, wherein the first coil is a toroidal coil.

9. The device for blocking high frequency voltage for an ion trap according to claim 7 or 8, wherein the first coil and the second coil are partially or entirely surrounded by a material capable of absorbing electromagnetic energy generated by the first coil and the second coil.

10. A radio frequency voltage cut-off device for an ion trap, comprising: a first coil; a second coil wound around the first coil; and a shunt switch that short-circuits both ends of the second coil.

11. The device for cutting off a radio frequency voltage for an ion trap according to claim 10, wherein the first coil is a toroidal coil, and the second coil is wound around the first coil.

12. The device for blocking high frequency voltage for an ion trap according to claim 10 or 11, wherein the first coil and the second coil are partially or entirely surrounded by a material capable of absorbing electromagnetic energy generated by the first coil and the second coil.

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