JPH0351053B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention comprises an ion source and a focusing ion mirror, in which ions of different masses and energies depart from a starting point almost simultaneously, and an ion collector is located at the end point. A time-of-flight mass spectrometer that flies over a flight section, in which the flight time between the starting position and the ion collector does not depend on ion energy, and the ions are three-dimensionally focused from the starting position to the ion collector. This relates to a type in which an ion mirror refracts the flight path several times.

In a time-of-flight mass spectrometer, ions with the same energy but different masses pass through the same distance at different speeds, and are sequentially transferred to an ion collector or an ion-SEV (Sekunda¨r-Elektronen-
They are separated from each other by reaching the Vervielfacher (secondary electron multiplier). It is important that all ions leave the starting point of the flight section at the same time.

Special equipment of time-of-flight mass spectrometer (Figure 1)
was proposed in the specification of the Union of Soviet Socialist Republics Patent No. 198034 [BAMamyrin]
et al., Zh.Tekh.Fiz., Volume 41 (1971), page 1498 - Soviet Physics - Technical Physics (Sov.Phys.-Tech.Phys.), Volume 16 (1972)
), p. 1177]. The device does not require that the ion energy be the same for all ions. That is, the ion is deflected approximately 180° by the electrostatic mirror after a distance (L) traveled, so that the ion must return the same distance before being recorded by the ion-SEV adjacent to the ion source. .
It is important here that ions with higher energy penetrate deeper into the ion mirror formed from the grating plate. The ions therefore have to travel a longer distance overall than ions with lower energies. Of course, there will be significant ion flow loss, but due to the suitable potential distribution in the ion mirror,
The flight time of the ion to SEV does not depend on the energy of the ion, but only on the mass of the ion.

Since the mass separability of a time-of-flight mass spectrometer is proportional to the length of flight time, it is desirable to make this interval large. When using the Mamillin ion mirror, ie when the length of the structure is utilized in a double manner, the system quickly becomes elongated, and in this system the diameters of the ion collector and the ion mirror must also be larger. At least the ion collector can be made smaller by introducing focusing elements, for example electrostatic unipotential lenses, but even then the diameter of the ion mirror is still large.

It is an object of the present invention to further improve a time-of-flight mass spectrometer of the type described above, avoiding the drawbacks of the known technology, reducing losses in the ion flow and increasing the resolution capacity with a simple and space-saving construction. It is to obtain.

This object is achieved according to the invention by the features specified in claim 1. In the time-of-flight mass spectrometer according to the invention, a beam path that is bent several degrees is important. Repeated bends or refractions of these flight sections result in a series connection of multiple (simple) time-of-flight mass spectrometers with ion mirrors. The flight range is extended with relatively little equipment outlay and the resolvability of the overall system is improved with the same ion pulse time. By using N such ion mirrors (reflectance 100%), the structural length can be utilized not only twice but (N+1) times.
In this case, the number N of ion mirrors may be an even number or an odd number.

In time-of-flight mass spectrometers, on the other hand, mass resolving power increases as the ion pulse time decreases. On the other hand, as the ion pulse time decreases, the ion intensity decreases. The present invention allows high mass resolution and high strength to be combined in the following manner. That is, instead of the immediately preceding pulsed ion source used in the time-of-flight mass spectrometer of Mamilin et al., a flight section of length D is provided between the ion source and the start of the flight section (length L). (See Figure 2). Thus, at the beginning of the ion pulse, the ion source emits ions of low energy, and then the ions acquire progressively higher energy and thus increasing velocity. When properly selected or controlled, the fast ions catch up with the slower departing ions at point E each time. A significantly shorter ion pulse is therefore generated here without loss of ion flow, but with an increased energy width. In particle accelerator technology, this process is called ion bunching.

The pulse time at the catch-up point E is D・△U
, where ΔU is the inevitable energy width that the ions have when they leave the ion source at a given time. In order to make the pulse time at catch-up point E as short as possible, D is chosen as small as possible. In certain cases, this catch-up effect can be omitted, for example if the ion generation is limited to short moments, ie in this case D=O is chosen.

In time-of-flight mass spectrometers of the type described in FIGS. 1 and 2, the ion flux diameter increases with the flight length of the ions. To counter this effect, a focusing lens may be inserted in the beam path to reduce the beam diameter at the ion collector.

According to the invention, the ion mirror itself is used very advantageously as the focusing element. For this reason, the ion mirror is not constructed from parallel metal nets forming a specific potential plane in each case, as is conventional. Rather, the ion mirror has a series of aperture stops, tubes, etc., which are at various potentials. Such ion mirrors, which use reflection as well as Moöllenstedt-filter lenses using transmission, exhibit a focusing effect, as can be shown by numerical calculations. Additionally, an ion mirror consisting of a focusing aperture diaphragm eliminates the losses of the ion beam that are inevitable when the ion flux passes through conventional nets.

The invention will now be explained in detail with reference to the embodiments shown in the drawings.

The device shown in FIG. 1 corresponds to the document mentioned at the beginning (by Marimin et al.). A time-of-flight mass spectrometer, generally designated 10, has an ion source 12 as well as an ion flux controller 14, as shown schematically, and the ion flux is refracted by an ion mirror 16 having a grating plate 18. and guided to an ion collector (SEV) 20.

As can be seen from FIG. 2, part of the time-of-flight mass spectrometer according to the invention is quite outwardly similar to the device shown in FIG. In this case, the same elements are indicated by the same symbols. The mass spectrometer 10 has an ion source 12 with an ion flux controller 14, and the ion flux is guided by an ion mirror 16 to an ion collector (SEV) 20.

Figures 3 and 4 show ion mirrors R1, R consisting of aperture stops or tubes that bend the optical path.
How can the 2nd class interact directly with each other (3rd class)?
(Figure 4) or in a circle (Figure 4). In this case, the i-th mirror should generally be tilted or adjustable to deflect the ion flux to the center of the next (i+l)-th mirror. This can be done electrostatically or electromagnetically under electrical control. That is, in the case of FIG. 3, the mirrors on the two planes and are arranged linearly and parallel to each other so that the ion flux is reflected back and forth within one cross section and reaches the ion collector 20. .
In the embodiment of FIG. 4, the two planes and the ion mirrors R1, R2, etc. are each arranged on a circle, so that the corresponding envelope surface can be cylindrical or conical. good. In this case, too, a substantially parallel arrangement of all ion mirrors is possible by interposing a compressed electrode 22 that is deflected approximately toward the center of the entire device each time it passes through the ion flux.

It is clear that the device according to FIGS. 3 and 4 uses a structural length approximately corresponding to L as (N+1) ion sections using N ion mirrors.

However, according to the apparatus shown in FIG. 5, the ion beam is passed between two ion mirrors R1 and R2.
It can also be reciprocated several times. In this case, the ion cloud is placed within this interval (≒L) between both mirror and mirror R.
Means must be taken to make it enter between R1 and R2 and eject again.

In the apparatus of FIG. 5, the ion mirror potential, instead of being applied continuously, can be pulsed by a suitable control device. For example, mirror R2 is first grounded in front of the ion cloud, ie is not present as such, and mirror R2 reflects the ions. The ion cloud returned by mirror R2 is then reflected by mirror R1, which was switched on during this time. Mirror R1
After passing through the section between R2 and R2 N times, when the ions reach the mirror R2 for the (N+1)th time by electrical control, R2 is grounded, that is, it is configured not to exist. Therefore, the ions are ejected and reach the ion-SEV20.

In the device according to FIG. 6, mirrors R1, R2, etc. are used which are electrically tilted for a short time, in which the potential distribution is such that the ion flux is reflected at a different angle than its previous angle. Controlled for a short time. 1st collector (ion-
SEV) records medium-height resolved time-of-flight mass spectra. By briefly tilting mirror R1, the ion flux reaches mirror R2. Mirror R2 is tilted such that it directs the ion beam to mirror R3 during the passage of the ion cloud. Subsequently, mirror R2 is moved back and the ion cloud is reflected back and forth N times between mirrors R2 and R3 until a brief rotation of mirror R directs the ion flux to the second collector A2, thus: Here, ion masses in a small range that were not confirmed from the mass spectrum recorded by the first collector A1 are recorded with high mass resolution.

Such a beam tilting can be implemented according to the invention by an additional tilting mechanism, not shown, for example electrostatic or magnetic.

In time-of-flight mass meters, on the other hand,
As the ion pulse length decreases, the mass resolving power increases. A high mass resolving power is achieved by providing a further flight section D of length D between the ion source and the flight section (length L) (see Figures 5 and 6) with high intensity. This can be achieved by doing so. Now, at the beginning of the ion pulse, the ion source
By ejecting ions of lower energy than at subsequent points in time, by appropriate design or control, the faster ions can overtake the slower, earlier departing ions at point E, respectively. Therefore,
Very short ion pulses with relatively large energy widths are then generated without loss of ion flow. In particle accelerator technology, such a process is called ion bunching.

In the embodiments of FIGS. 5 and 6, measures are taken to achieve the ion bunching.
For this reason, it is important that higher energy ions departing later from the overtaking point E (Fig. 5) or E1 (Fig. 6) behind the ion source 12 enter the orbit first. It is designed and controlled to catch up with ions of the same mass, but of lower energy. Ion mirror R consisting of an aperture diaphragm, tube, etc. (not shown)
1, R2, etc. are "bunched" to the second catch-up point E2 in ion collector A1 (or the Nth catch-up point E _N of ion collector A2).
It has a focusing effect so that the ions are incident. This device is based on the section D provided in front (between the ion source 14 and the first catch-up point E1), and the total flight time of the subsequent section L depends only on the mass of the ions, but not on the ion energy. This ensures that no short ion pulses occur, thus minimizing the number of ions of only one mass in the collector. It is also possible to configure the first catch-up point to be located at a position of the ion collectors A1, A2 that is a distance D behind the ion source.

All the features and advantages of the invention, including the structural parts, spatial arrangement and process steps, are apparent from the claims, the detailed description and the drawings, both on their own and in various combinations. are also important to the invention.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an example of a known technique, FIG. 2 is a schematic diagram of an embodiment according to the present invention, FIG. 3 is a schematic perspective view of an embodiment according to the present invention, and FIG. 4
The figure is a schematic perspective view of one embodiment according to the present invention,
FIG. 5 is a schematic diagram of an embodiment according to the present invention,
And FIG. 6 is a schematic diagram of one embodiment according to the present invention. 16, R1, R2, etc...Ion mirror, S...
Starting point, A...Ion collector, E...Catching up point, ,...Plane, 22...Compression electrode.

Claims (1)

[Claims] 1. A device comprising an ion source and a focusing ion mirror, in which ions with different masses and energies depart from a starting point at almost the same time and fly over a fixed flight section in which an ion collector is placed at the end point. A time-of-flight mass spectrometer is a type of time-of-flight mass spectrometer in which ions are In the type in which the mirror refracts the flight section several times, each ion mirror (R1, R2
time-of-flight mass spectrometers characterized in that they have aperture diaphragms or tubes which are loaded with different potentials (such as ) and which form approximately spherical equipotential lines. 2 the aperture diaphragm or tube is closed by a grid at a position where the ions no longer reach;
A time-of-flight mass spectrometer according to claim 1. 3. The time-of-flight mass spectrometer according to claim 1 or 2, wherein the three-dimensional focal length of the ion mirrors (R1, R2, etc.) is half the distance between them. 4. The time-of-flight mass spectrometer according to any one of claims 1 to 3, wherein the aperture stop or tube on the entrance side or exit side of the ion mirror is connected as a single lens. 5. In an ion mirror that reflects the ion flight trajectory by itself, the potential of the aperture diaphragm or tube of the ion mirror is changed for a short time so that the ions can pass for injection or ejection. The time-of-flight mass spectrometer according to any one of items 4 to 4. 6. The time-of-flight mass spectrometer according to any one of claims 1 to 4, wherein the deflection angle of the ion mirror can be changed for a short time for injection or ejection.