JPS61259449A - Double convergence mass spectrograph - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an improvement of the double convergence mass spectrometer described in Japanese Patent Publication No. 57-31261. Regarding excellent mass spectrometers.

[Prior Art] Recently, there has been a strong desire to analyze high-mass molecules in applied fields such as biochemistry. This is due to advances in ionization methods such as -order ion bombardment or high-speed atom bombardment.
This is because even ions of high-mass molecules exceeding z = 10,000 can now be produced relatively easily. In order to analyze such high-mass molecular ions, an extremely large mass spectrometer is required, but large mass spectrometers are extremely expensive and cannot be easily used by anyone.

Therefore, there is a need for a mass spectrometer that is relatively small and capable of performing high-quality analysis, and the following ideas have been made, for example.

That is, by using the electric field E and uniform fan-shaped magnetic field of a conventional commercially available mass spectrometer as shown in Fig. 7(b), we can calculate the rotation radius rm of the ion beam in the magnetic field as shown in Fig. 7(b). This is a method of increasing the measurement mass range by about 4 times by increasing the rotation angle by about 2 times and decreasing the rotation angle φm by about 172 times. In FIG. 7, S represents an ion source and D represents an ion detector.

[Problems to be solved by the invention] Although this method does expand the measurement mass range, the ion trajectory becomes longer because φm becomes smaller, and higher-order aberrations increase due to the vertical spread of the ion beam. There is also a tendency for resolution to decrease, and this tendency has been thought to be inevitable.

Table 1 shows a general example of the conventional device shown in Fig. 7 (1)) (φm = 35°, φe = 70', re /r
m = 0.643), -th order aberration coefficient AX,
Ay.

Aβ and second-order aberration coefficient A (XCX + A (X8t A
66t A”ly.

The values of Ays and Asβ are shown.

When the practically required resolution is 50,000 and the width of the ion beam at the ion source is around r m/300, it is desirable that the second-order aberration coefficient is at least smaller than 0.8 to 1.0. However, if we take this value into consideration and look at the second-order aberration coefficients in Table 1, we will see that the apparatus shown in Table 1 cannot provide a satisfactory resolution.

By the way, the inventor first arranged a quadrupole electrostatic lens QL between the N field E and the 1i field H, which gives the ion beam a divergent property in the horizontal direction and a convergent property in the vertical direction. A double convergence mass spectrometer featuring
It was proposed as No.-31261.

This proposed device has, for example, φe=70′ to 95°, φm
=65.8°~74. de, re/rm = 1.27~
1.357, all secondary aberrations can be reduced and high sensitivity and high resolution can be obtained. In this proposed device, the comb φm is reduced to about 172 times (rm@2) as described above (specifically, 30°≦φm≦50', 0
．． If a method of expanding the measurement mass range (in the range of approximately 4≦re/rm≦0.8) is applied, it is fully expected that higher-order aberrations will increase and resolution will decrease.

The present invention has been made in view of the above-mentioned points, and the φm and r e/r m of the proposed device are set to 30°≦φm.
The purpose is to provide conditions in which the resolution does not deteriorate even if the measurement mass range is expanded by setting the range to be ≦50° and 0.4≦r e/r m≦0.8.

[Means for solving the problem] In order to achieve this object, the double focusing mass spectrometer according to the present invention is arranged between an electric field and a magnetic field, and provides divergence in the lateral direction of the ion beam. In a double-focusing mass spectrometer equipped with a quadrupole electrostatic lens that provides convergence in the longitudinal direction of the ion beam, the rotation angle of the ion beam in the magnetic field is φm, and the radius of rotation of the ion beam in the magnetic field is rm. , the radius of rotation of the ion beam in the electric field is re, the strength of the quadrupole electrostatic lens is Qk, the effective length of the quadrupole electrostatic lens in the ion beam direction is Qj, the convex curvature of the input end face of the magnetic field is ρ', and the output When the convex curvature on the end face is ρ'', 30°≦φm≦50' 0.4≦re/ r m≦0.8 0.35≦Qk2Qjr6≦1°O rm , /p' 10rm , /, o''< 0.

[Embodiment] FIG. 1 is a diagram showing the configuration of an apparatus showing an embodiment of the present invention. The ion source has an ionization chamber 2 and a plurality of slits 3S,
The accelerated ion beam IB is taken out from the slit 4. This IB is a cylindrical electric field5. The ions enter a uniform fan-shaped magnetic field 7 through a quadrupole electrostatic lens 6, undergo dispersion according to the mass-to-charge ratio, and those with a specific mass-to-charge ratio enter the ion detector 8 and are detected. Ru. Above 1@7
is configured so that its magnetic field strength can be repeatedly swept by a power source (not shown). Therefore, the mass-to-charge ratio of ions passing through the magnetic field 7 changes with the sweep, and a mass spectrum signal is obtained from the detector 8. Incidentally, the entrance and exit surfaces of the magnetic field 7 are set at angles ε' and ε" such that the ion beam enters and exits obliquely, and the entrance and exit end faces are given curvature radii of ρ' and ρ". ing.

FIG. 2 is a cross-sectional view taken along the line AA of the quadrupole electrostatic lens 6 and a diagram showing the configuration of a power source 9 for applying a potential to the quadrupole electrostatic lens 6. The quadrupole electrostatic lens 6 consists of four cylindrical electrodes, which are arranged symmetrically at 90° intervals around the ion beam path O.
When analyzing positive ions, a positive potential is applied to opposing electrodes Py in a direction perpendicular to the orbital plane of the ions (y direction), and a positive potential is applied to opposing electrodes Py in the radial direction (X direction) of the ion beam. A negative potential is applied to Px. Therefore, positive ions receive a force in the convergence direction in the y direction, and a force in the divergence direction in the x direction.

Table 2 shows 62 examples (*) of the proposed device and five design examples ((1) to (5)) with appropriate dimensions for the device according to the present invention.

(Left below) Table 2 The undefined symbols used in Table 2 are as follows.

Qk: Strength of the electrostatic quadrupole lens Q12: Length of the electrostatic quadrupole lens je': Distance between the main slit and the electric field 1IIl'' Distance between the collector slit and the magnetic field deq:
Distance dqm between the electric field and the quadrupole electrostatic lens: Distance between the quadrupole electrostatic lens and the magnetic field Note that the lengths in Table 2 are all normalized using the design example of the proposed device (the radius of rotation of the magnetic field rm in the ladle is 1). Qk is normalized by the acceleration voltage of the ion beam.

In the design examples (1) to (5) above, the second-order aberration coefficients are all 1, which is much smaller than 1;
It can be seen that a high resolution that could not be achieved with the conventional device shown in the table can be obtained.

By the way, although the numerical value of Qk 2Qj re is shown in Table 2, the inventor of the present application believes that this value represents the second-order aberration and the 1~transmission of ions.

We found that there is a close connection with Aβ (the smaller the size, the better the transmission).

Figure 3 shows how the sum of the absolute values of the secondary aberration coefficients I and Ay, Aβ, and the sum of the absolute values of A'' and Δβ change depending on the value of Qkz(1re) for the above design example (1). The results of the investigation are shown in Figures 4 and 5 for the above design example (4).
, (5) are similarly investigated.

Usually, if the value of (■) exceeds 4 to 5, practically sufficient resolution cannot be obtained, so it is necessary to keep it below this value. Furthermore, Ay
If the sum of the absolute values of and 8β exceeds 10, the sensitivity is sufficient) q
Therefore, it is necessary to keep it below that level. Looking at Figures 3 to 5 based on these two conditions, we can see that from the condition (■), Qk+! It is necessary to set QJ2re in the range of 0.35 to 1.0, and also considering the sensitivity,
Qk2Qjre needs to be set in the range of 0.4 to 0.9.

Along with the value of Qk2Qere mentioned above, the curvatures ρ′ and ρ
''.In the above design examples (1) to (5), vi
Although the output end face of the i-field does not have a curvature, based on the conditions discovered by the inventor, in such a case, it is necessary to give the input end face a negative curvature (in the direction in which the end face is concave). It is necessary. In reality, the curvature is approximately equivalent whether it is applied to the input end face of the magnetic field or to the output end face, so rm/ρ'+r
It is necessary to consider it as a value of m, /ρ''.

Figure 6 shows rm/ρ′+rm/ for the above design example (1).
Given several values of ρ'', the results of investigating what value the sum of the absolute values of the second-order aberration coefficients takes depending on the values are shown.Based on this figure, the value of ■ is 4 to 4. Considering that it is not possible to obtain a practically sufficient resolution when the value exceeds 5, at least rm/ρ'+r is required to suppress the value of
It is necessary for m/ρ〃 to take a negative value, and furthermore, rm, /l:)' rm, /ρ'' can be set in the range of -0.3 to -1.5. desirable.

Furthermore, in the present invention, since the rotation angle of the magnetic field becomes smaller, it is inevitable that the convergence effect of the magnetic field becomes weaker.
As shown in the design example of the proposed device in the table (*), simply adding an inclination (ε') of -15° to the magnetic field input end face would increase the distance between the magnetic field and the ion detector, which would be a problem as a practical device. . Therefore, the magnetic field output end face also tilts ε
') must be set at -15° or more. Incidentally, if the inclination is increased too much, the aberration becomes large, so the practical limit for both ε' and ε'' is about -30'.

[Effects of the Invention] As detailed above, according to the present invention, the ion beam is disposed between an electric field and a magnetic field, and provides divergence in the lateral direction of the ion beam, and convergence in the longitudinal direction of the ion beam. In a double focusing mass spectrometer equipped with a quadrupole electrostatic lens, φm is set to 30°≦φm≦50°, re/rm
Even if a mass spectrometer with a wide measurement mass range is obtained by setting r e/r m in the range of 0.4≦re/r m≦0.8, a device with high resolution can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an embodiment of the present invention, and Fig. 2 is a sectional view taken along line A-A of a quadrupole electrostatic lens and a diagram showing the configuration of a power supply for applying a potential to the lens. Fig. 3 Figures 5 to 5 show Qk'' for design examples (1), (4), and (5).
A diagram showing the results of investigating how the sum of the absolute values of the quadratic aberration coefficients I, Ay, Aβ, AV, and 8β changes depending on the value of Qj re. Figure 6 is a design example. (1)
Give some values of rm/ρ′+rm/ρ” for
FIG. 7 is a diagram illustrating a conventional apparatus, which shows the results of examining what value the sum I of the absolute values of the secondary aberration coefficients takes depending on the value. 1: Ion source 2: Ionization chamber 3.4 Nislit 5: Cylindrical electric field 6: Quadrupole electrostatic lens

Claims (1)

[Claims] A quadrupole electrostatic lens is arranged between an electric field and a magnetic field, and is provided with a quadrupole electrostatic lens that provides divergence in the lateral direction of the ion beam and convergence in the longitudinal direction of the ion beam. In a double focusing mass spectrometer, the rotation angle of the ion beam in the magnetic field is φm, the radius of rotation of the ion beam in the magnetic field is rm, and the radius of rotation of the ion beam in the electric field is re.
, the strength of the quadrupole electrostatic lens is Qk, the effective length of the quadrupole electrostatic lens in the ion beam direction is Ql, the convex curvature on the input end face of the magnetic field is ρ', and the convex curvature on the output end face is ρ''. 30°≦φm≦50° 0.4≦re/rm≦0.8 0.35≦Qk^2Qlre≦1.0 rm/ρ′+rm/ρ″<0 Features: Double convergence mass spectrometer.