DE2137520A1 - FLIGHT TIME MASS SPECTROMETER - Google Patents

Description

213752Q

July 26, 1971 8270-70 / Dr.ν.B / Ro.

Max Planck Society for the Advancement of Science e.V.

34 Göttingen , Bunsenstrasse 10

Time-of-flight mass spectrometer "

An overview of the known time-of-flight mass spectrometers can be found in the book by Erich W. Blauth "Dynamische Mass spectrometer "Verlag Friedrich Vieweg & Sohn, Braunschweig, 1965, pages 71 to 94. ...

Time of flight mass spectrometers have over other electronic mass spectrometers the often substantial advantage that Λ rait them · practically can all during an ionization process short duration resulting ions analyze electronically and immediately receive a complete mass spectrum. Compared to mass spectrographs with photographic registration, they have the advantage of a significantly higher absolute sensitivity. Time-of-flight mass spectrometers are therefore always superior to other _{types of mass spectrometer t} when it comes to fast analysis, high absolute sensitivity or the investigation of individual processes, since practically all other electronically recording mass spectrometers require a mass scan in which only ions of a specific specific one are used at a certain point in time Mass (mass / charge) can be detected and all other ions are lost. "

The resolving power of time-of-flight mass spectrometers can be improved by focusing measures. By "focusing" is meant for mass spectrometers, ion-optical measures by which the mass spectrum generated regardless of the initial power C "energy focus tion"), the initial pulse ( "pulse focusing"), the initial velocity ( "speed focusing"), the thermal essentially by the The initial energy of the ions is given, and should also be made from the direction of the ions emerging from the ion source ("directional focusing") or the location of the ion generation ("spatial focusing"). Speaking of "stigmatic focus"

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if a point of the ion source is mapped again to a point at the ion detection device, i.e. except for one radial focusing axial focusing is also carried out.

A time-of-flight Ilass spectrometer with spatial focusing and energy focusing is called "Bendix time-of-flight spectrometer" (Blauth, I.e. p. 65), and a circular period Time-of-flight spectrometer with speed and angle focusing is known under the name "Chronotron" (Blauth, I.e. p.71) become.

Finally, it is known that the time dispersion, which is due to the different initial kinetic energies of the ions, can be eliminated in a time-of-flight spectrometer by combining a field-free, straight flight path with a radial electrical deflection produced by a cylindrical capacitor, which is dimensioned in such a way that the time dispersion in the straight flight path and the electric field opposite each other are equal, i.e. a speed focusing does not occur (Int. J. Mass Spectron.Ion Phys., 6 (1971) 291-295.

The use of the known focusing time-of-flight Iiassenspektrometer mentioned in the penultimate paragraph is by one or restricted several of the following conditions:

a) The area, over which the initial energies of the ions extend, may only be a few tenths of an electron volt;

b) The amount of the most probable initial energy of the ions must also be only a few tenths of an electron volt;

c) The ion source with the acceleration system and the Ion detection devices must be in or immediately adjacent to the deflection field with which focusing is effected; arranged be;

d) The ion source must be operated with pulsed extraction fields.

These known focusing flying-side mass spectrometers can therefore usually not be used, if the ions, such as in the case of a micro-beam probe, generated by a particle beam or if pulsed extraction fields interfere, as is the case with

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liGi ^ ziäeiiz-Flugzeitraassenspektroraeter is a case, or if off any, ar. for practical reasons the ion source with the Acceleration system; and the ion detection system at some distance must be arranged by the focussing deflection field.

Bas with the last-mentioned time-of-flight mass spectrometer Speed focusing has the disadvantage that only in the deflection field there is also only radial directional focusing while the straight flight path is not in the directional focus is included. The transmission (light intensity) between the entry level (ion source) and exit level (ion detection device) is accordingly small and the sensitivity becomes therefore leave a lot to be desired.

Accordingly, it is an object of the present invention based on a time-of-flight POS spectrometer with speed focusing as well as over the entire flight path extending power focus and correspondingly high transmission and Specify the sensitivity at which the ions to be analyzed can have high initial velocities (i.e. initial energies or initial impulses) which vary over a wide range.

This object is given by that specified in claims 1 and 14 Invention solved.

Advantageous further developments of the invention are set out in the subclaims marked.

Because the speed focus. with the present Time-of-flight mass spectrometers are subject to much less stringent conditions is subject to than with the known time-of-flight mass spectrometers, there are many new areas of application, e.g. in connection with an ion microbeam probe, a field ion microscope etoinsonce or with a coincidence time-of-flight mass spectrometer.

In one embodiment of the invention, as a first approximation a fourfold focus is achieved, namely temporal speed focus (i.e. the temporal dispersion of ions of a given effective mass disappears), radial and axial V. 'angle focusing (i.e. stigmatic mapping of a point

' _n BADOWGINAL

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the object plane into a point in the image plane of the snectrometer), and spatial speed focusing (disappearance spatial dispersion).

In the following, exemplary embodiments of the invention are explained in more detail with reference to the drawing, which show:

1 is a schematic representation of a time-of-flight mass spectrometer according to a first embodiment of the invention, whose flight path contains an electrical deflection field;

FIGS. 2 and 3 each show a schematic representation of an exemplary embodiment a time-of-flight mass spectrometer according to the invention, whose flight path contains magnetic deflection fields and

4 shows a schematic representation of a further exemplary embodiment, in which a somewhat different approach has been taken than in the above exemplary embodiments.

The symbols and abbreviations used in the following are listed in a table at the end of the description.

GENERAL

A fundamental distinction is made between time-of-flight mass spectrometers between two different types:

A) Time-of-flight mass spectrometer with acceleration of the ions to the same impulse

In this type, they are in an ion formation or swelling volume The ions formed are accelerated in a pulsed electric field, which must be as homogeneous as possible can pass through different parts of the field during their acceleration.

B) Time-of-flight mass spectrometer with acceleration of the ions to the same energy

The acceleration field does not need to be homogeneous here, since all ions pass through the entire acceleration potential. There are various possibilities here to form a well-defined ion packet with the ion source. The easiest is that Use of a pulsed ionization process, i.e. the ions are generated e.g. by a pulsed electron beam (see e.g.

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Blauth, I.e. Section 5.222). The expansion of the "generated." The ion packet depends on the expansion of the ion formation volume calculated for the direction of acceleration and the duration of the ion formation pulse and the width of the range of initial energies.

With both types, the resolution is determined by the width of the range of the initial impulses or the initial energies limited if no measures for pulse or energy focusing are taken.

Are combined in addition to the momentum and energy focusing, under the generic term "velocity focussing" i can send a "angle focus to, as said, can be achieved. A further condition is / that by focusing effecting in the radial direction deflection no speed dependent spatial dispersion occur soil otherwise an extensive ion detection device (e.g. ion collector, influence collector, secondary electron multiplier) would be necessary they can be generated by means of a magnet with an air gap that is wedge-shaped in radial section, should be considered for the implementation of the present time-of-flight mass spectrometers, since other fields do not play an essential role in practice

if a stigmatic mapping is required. aside from that In the exemplary embodiments described first below, the additional condition that not be met only the ion source (or the thing plane) but also the ion detection device (or image plane) is arranged at a certain distance from the deflection field boundaries and that besides no additional lenses are required for the deflection fields.

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These prerequisites severely limit the number of geometries that are otherwise possible. It has been found that a running track i.e. the arrangement of the straight stretches and deflection fields, symmetrical with respect to the center (axially or mirror-symmetrically) Must be if there is no temporal and spatial dispersion due to the different initial speeds the ions of a given mass are allowed to enter and the entry area of the ions in a flight path delimiting the flight path on the side of the ion source into a flight path the exit plane delimiting the side of the ion detection direction is to be imaged at least radially.

If the ions in the ion source are accelerated to essentially the same energy, electrostatic focusing is required Use deflection fields to avoid spatial mass splitting.

Correspondingly, when the ions are accelerated to essentially the same momentum, one must work with magnetic deflection fields.

"Substantially the same" is used herein to mean that each ion the same amount of energy or pulse is supplied to the ion source for acceleration, so that the kinetic Energies or pulses of the ions entering the flight or drift path from the ion source only as a result of them differentiate between the initial speed present before the acceleration.

Part of the relationships that exist in the present time-of-flight mass spectrometer must be fulfilled, are formulaically the same for the cases of acceleration to the same impulses or energies, only that the field inhomogeneity parameters h and k are defined differently for the respective magnetic or electrical deflection fields are.

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The following applies to the magnetic field;

h = / l-n; k = / n ~, (la; Ib)

Here η is the usual inhomogeneity factor, which is the ratio contains the pole shoe slope to the radius of the deflection path. In particular, the width b of the air gap between the pole pieces is independent of the deflection angle ψ and because of the rotational symmetry it is with η in a first approximation by the relation

b = b _o (1 + nu) (Ic)

connected. Mean

b the width of the air gap at the location of the main beam path, and

u = (r - r) / r the normalized radial distance from the main beam path .

The following applies to the electrostatic toroidal field;

h = v ^ c; k = / c (2; 2b)

where c = r / R is the so-called aspect ratio.

If the entry plane (in which there is usually a circular or slit-shaped diaphragm which separates the ion source from the path and limits the entry area of the ions) without velocity-dependent local dispersion ("achromatic") into the exit plane (in which usually a slit or circular Diaphragm that separates the flight path from the ion detection device) and, as the simplest case, it is assumed that the plane of symmetry or the radial intermediate image lie within a single deflection field, then for the distance g between the entry plane and the entry-side field boundary as well as the Distance g ^s between the field boundary on the exit side and the exit plane, the following relationship must be met:

209886/0487

where ψ is the sector angle of the field and thus the deflection angle is.

In the case of stigmatic imaging with an axial intermediate image at the location of the radial intermediate image, in addition to condition (3), the the following condition must be met:

g _a = g _a «g _r = * i = ^ f tg (i8o ° - ψ-) (4)

It can be seen that conditions (3) and (4) only for k = h, i.e. for η = 1/2 (magnetic field) or c = 1 (electric field) can be fulfilled.

Should, however, be the "axial" beam path in the case of stigmatic imaging (i.e. the beam path seen in a tangential plane passing through the radial intermediate image) must run parallel the following relationship apply:

In this case η and c still depend on ψ.

The equations (3), (4) and (5) apply, as said, for the simplest case that the plane of symmetry or the radial Intermediate image lie within the deflection field (see e.g. Fig. 1). However, it is easily possible to split the deflection field into two symmetrical halves that the plane of symmetry in one field-free space between the two field areas. It is also possible to have several such systems in a row switch (see Fig. 2), so that the exit level of the preceding system coincides with the entry level of the following system. In addition, symmetrical arrangements with alternating fields and / or additional electrostatic resp. magnetic lenses possible, but also with angled beam

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occurs in the deflection fields can be worked. Since there is nothing fundamentally new, we will not go into this further will.

Time-of-flight hatred spectrometer with acceleration of the ions to the same energies:

Example 1; This embodiment of the invention, which will be explained with reference to FIG. 1, operates with an ion source 10 of known type in which the ions are accelerated to essentially the same energy. Since the ion Thus, besides the like from their lying in an energy ΔΕ initial energy, all have the same energy, an electric deflection field must for focusing are used to a spatial separation of the ions m because of their effective mass to avoid that with the desired splitting would interfere due to the mass-dependent flight time. In the case of an electrostatic deflection field, the conditions are somewhat different from the magnetic field in that an ion of higher energy not only runs on a further path, but is also somewhat slowed down by the higher potential prevailing on this path. The deflection field is generated by a so-called toroidal capacitor 12. The temporally separated packets of ions of the same mass, but of different mass from packet to packet, are detected by an ion detection device 14.

In a toroidal field with the mean orbit radius r and The time of flight t of an ion becomes the deflection or sector angle ψ with the specific mass m (m = · ion mass / ion charge) and of energy E ^ - (I + ß)

"Aim Γ ,, η I / I 1 \ ι SillllllUll.li I i. . /,.ν. / ι. «.Ii β y \

"e ο E, ₀

b 2 ν η η 'η ~ ~ ο

In order for the flight time to be independent of the entry angle ο, equation (5) must also be fulfilled.

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The time-of-flight dispersion At in the deflection field is obtained then

Λ4- - Q Ri ¹ _ ¹ Xj ₁ _ sin (hip) _(Ί .

The time-of-flight dispersion At in a straight path of the Length g is:

^J b

Around the entire energy-dependent time-of-flight dispersion to disappear To bring about, the energy-dependent time-of-flight dispersion At in the deflection field must be opposite to the energy-dependent time-of-flight dispersion At be in the straight running route. This leads to the focus condition

1 , . sin (ln | /)

h ^{2 4 Ψ} h ³

For a system working with radial imaging, which is between If the entry and exit level should not have an energy-dependent time-of-flight dispersion, condition (3) must apply:

r tg (l80 ° - ψ -) = 2r f <± * - J) ψ - ^ iMi], ₍₁₀ )

A radial intermediate image appears in the middle of the deflection field 20, through which the plane of symmetry 21 of the system also goes

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Example 2: This example corresponds to example 1 with the exception that the entry area of the ions into the path is not only imaged radially but also axially, that is, stigmatically, in the exit plane. In this example, an axial intermediate image also occurs at the location of the radial intermediate image.

With stigmatic focusing with an axial intermediate image is

c = h = k = 1 (11)

and one obtains the condition:

| = 2 Ξΐη (ψ) - Ι ψ (12)

The values are obtained by solving this equation graphically

g = g ¹ = 5.9 r
^ r ^y r '

ψ = 199.2

ο
°

Example 3: This example corresponds to example 2 with the exception that no axial intermediate image occurs at the location of the radial intermediate image, but rather the beam path runs parallel there, viewed in the radial I direction.

For stigmatic focusing without an axial intermediate image, taking equation (5) into account, the following are obtained Condition equations:

= g _r =

Ζψα .. 2r _o (1. Ι _{) φ} .Slnüüij ₍₁₄₎

h ² h

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_ TO _

The solution can again be done graphically, and one obtains:

g _r = g; = 2.35 r _Q
ψ = 163.2 °
c = r _Q / R = 0.26.

A time-of-flight mass spectrometer with these parameters is characterized by a small footprint, since the straight flight paths and the deflection angle are relatively small. The mass spectrometer can be used as a "quadruple focusing" mass spectrometer because the mass spectrum is independent of the initial velocity or initial energy of the ions (before the acceleration) and the entry plane 16 is stigmatic with regard to flight time and imaging location, that is, both radially and also axially focusing, is imaged in the exit plane 18.

At the location of the radial intermediate image 2O (FIG. 1) one has the largest spatial energy dispersion and you can limit the detected energy range there by a diaphragm 22 ("energy diaphragm"). In the case of the geometry discussed last, the magnification V of the intermediate image is approximately equal to 0.33 and the energy dispersion D at the location of the intermediate image is 0.76.

An ion that deflects the electrical field outside the central orbit enters or leaves, is accelerated or decelerated at the field boundaries 24 and 26, respectively. A calculation of these effects showed that with the required symmetrical beam path there is primarily no disturbance of the time-of-flight compensation. The stray field at the limits of the toroidal condenser only leads to a slight correction of the length g of the effective straight running route.

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Time-of-flight mass spectrometer with acceleration of the ions to equal pulses;

Equations (la), (Ib) and 0b) apply here in conjunction with equation (3). If a stigmatic mapping is desired equation (4) or (5) must also be satisfied.

As a focusing condition, the for the case of acceleration to the same energy, n valid equation (9) the following focusing condition;

_ ^r o ί., ϊ .. sin (hif))} ,,, -, "

² ^ r ⁼ IT [ ^{ψ (} ^ 2 ° ^X) - · J ⁽¹⁵⁾

Example 4; For a time-of-flight mass spectrometer with a single sector-shaped magnetic field, stigmatic image and axial intermediate image at the location of the radial intermediate image at half the deflection angle, the following equation

J? / ö / ö

~ Ψ - sin -if ψ = - tg 1 | ψ (16)

be fulfilled. This equation can be derived from equations (3) and (4) and (15) if one also takes into account

that η = 1/2 and h = k = / 2 must be. "

The solution of equation (16) _T, which can be determined graphically, for example, is:

ψ = 314 °

The time-of-flight mass spectrometer according to Example 4 can be implemented with the following numerical values, for example:

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Mean orbit radius r = 10 cm

Length χ of the flight path = 129 cm

Acceleration field strength F = 1000 V / cm

mm * 7

Pulse duration t. = 10 see

Length of the acceleration path for the ions £ 4.2 cm

Magnetic induction B on site _

of the mean orbit radius r 10 Gauss

Example 5: This example corresponds essentially to example 4 with the exception that no axial intermediate image occurs at the location of the radial intermediate image, but the beam trajectories there, seen perpendicular to the axis of the sector-shaped magnetic deflection field, run parallel. Here then, in addition to equation (15), equation (5) instead of equation (4) must be taken into account and the following equation is obtained

^ ^ A ^ f (17)

The solution to this equation, which can be obtained graphically, for example, is:

ψ = 290 °

g _r - g £ = 1.23 r _o

η = 0.177

Examples 4 and 5 can be practically realized easily and each have their own Vorzüae * When flying time mass spec L- Tromen ter of Example 4 enters stigma table? \ '? Rule image on which enables precise boundary of the detected Geschwlndigkeitsbereiches the ions. The resolution is high, the deflection radius small, but the flight distance is relatively long.

209886/0487 ^{ßAD 0WGiNAL}

The time-of-flight mass spectrometer according to Example 5 is distinguished by a shorter flight path and thus shorter distances between the ion source or ion detection device on the one hand and deflection field limits on the other hand, so that with a given The size of the magnet generating the deflection field achieves a more compact structure and greater transmission (higher light intensity) can be used as in the example "4.

Examples 4 and 5 are of course not, contain the only possibilities of realization of time of flight mass spectrometer according to the invention with magnetic deflection fields but represent only the simplest embodiments. It is% obviously readily possible to provide other embodiments, the plurality of magnetic Sektorfeider between which there are straight sections of the flight path. In all cases, however, the geometry must be in relation to a plane or an axis (corresponding to a twofold axis in crystallography and there must be at least one intermediate image in a radial plane.

The rectilinear parts of the flight path can also contain ion-optical lenses to allow a little more freedom of movement to enable in the construction.

Two particularly interesting exemplary embodiments are intended below can be specified. ™

Example 6; The time-of-flight mass spectrometer shown in FIG. 2 consists of two identical parts, each of which can correspond to a mass spectrometer according to Example 4 or 5. However, these two parts are arranged in such a way that the deflection of the ions in the two parts takes place in opposite angular directions.

The first part lies between an exit slit 31 of an ion source, not shown, which is the entrance slit of the time-of-flight mass spectrometer forms, and a gap 33 which is the exit gap of the first part and at the same time the entry

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represents the gap of the second part. The second part lies between the gap 33 and a gap 34, the one through the entrance gap ion detection device, not shown, is formed. The first part contains a magnetic sector field 37, the second part a magnetic sector field 39. Located in the sector field 37 At the location of the radial intermediate image there is a loin 46 which contains the detected pulse area (and thus the area of the initial velocities of ions).

Example 7; The time-of-flight mass spectrometer shown schematically in FIG. 3 is a further development of the time-of-flight mass spectrometer according to example 4. It contains two magnetic sector fields 38, 40, each having a sector angle of 270 °, for example. The distance g or g ¹ between an exit slit 30 of an ion source (not shown) or an entry slit 32 of an ion detection device (not shown) on the one hand and the adjacent boundaries 34 and 36 of the first and second deflection fields 38 and 40, respectively

9 _r = g; = - ctn (ηψ) (18)

^rr h

The length g of the straight flight path between the exit side Boundary 42 of the deflection field 38 and the entry-side field boundary 44 of the deflection field 40 is

_ _ 2r cos (hifr-l) _MQ .

^g h sin (hifi) ⁽ ^ '

The radial focus condition is

f ctn (Ιιψ) = i L (I. - 1) - sin (Ml 1 ₍₂₀₎ h ^ψ 2 {\ 2 3 h 5ΐη (1ιψ) J

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In the deflection field 38, a diaphragm 46 (pulse diaphragm) is arranged at the location of the radial intermediate image, which is a delimitation of the transmitted pulse range and thus the initial speed range which enables ions.

An axial intermediate image occurs at location 48, that is, at half of the straight flight path between the two deflection fields on.

Examples 6 and 7 have the additional advantage that the finite width of the entrance slit 31 and 32, respectively, is primarily Approximation has no influence on the resolving power.

The designs described for electrostatic deflection fields * Examples can of course be implemented in a corresponding manner with magnetic fields and vice versa, such as due to the explanations in the section "GENERAL" is readily available.

When applying Example 7 to the case of acceleration of ions at the same energies then the following equation applies instead of equation (20):

I etn (ht) - 2 (, (I ₂ - I) - BiBjMI] ₍₂₁₎

The Aμfqabe, a time-of-flight mass spectrometer with speed focusing It is also possible to create in which a directional focus is also ensured over the entire system solve in at least one other way than described above became. To explain this other approach, reference should again be made to the known time-of-flight mass spectro mentioned last meter can be referred to as speed focus.

The well-known time-of-flight mass spectrometer has a single one straight flight path and a single one that only focuses radially

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electrostatic deflection field created by a cylindrical capacitor

is produced. The focusing conditions in the deflection field

running part of the beam path can be written as follows:

_, _4 "r. , Ι JU _ sin (hfl) _{1 fO9} .

g -fr _o Ιψ (~ 2 - j) —1 "3} (22)

This equation corresponds to equation (9) given above.

Furthermore applies

^g r ^{= g} r ⁼ TT ^{tg (l80} ° " Ψ ^{) =} ° ⁽²³⁾

The above-mentioned exemplary _{embodiments of the invention, which operate iPit electrostatic in} A. Menkfeidern and in which only radial focusing occurs, differ from the known time-of-flight mass spectrometer in that α (and g ¹ ) are not equal to zero.

Another solution to the problem posed at the beginning, namely a directional focusing over the whole system including To achieve the straight parts of the flight path, there is in case B the acceleration of the ions to the same energies now in the fact that, as in the known case, equations (22) and (23) are fulfilled and that in addition the equation

^ ctg {Ά = O (24)

or the equation

^ - tg (180 ° - | i) = O (25)

is applicable. In addition, the straight part of the flight route must be at least

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an ion optical lens, ZiB. a single lens, contain the the entry slit of the mass spectrometer stigmatically into the The entry plane of the electrostatic deflection field that in the present case consists of an inhomogeneous toroidal field.

An embodiment in which the equations (22), (23) and (24) apply, is shown schematically in FIG.

A single straight part of the flight path, the length of which is denoted by g, adjoins the entry aperture 30. In the straight part J-litte is a single lens 50, the stigmatic mapping in an intermediate diaphragm 52, the entrance aperture 30, which separates the straight part of the running distance etc. of the deflection field generated by a Toroidkondensator 12 '. The beam path in the toroidal capacitor 12 'is symmetrical; an energy diaphragm 22 is arranged in the plane of symmetry, as in the example according to FIG. 1.

The exit aperture 32 of the mass spectrometer is located directly at the boundary of the electrical deflection or sector field. In front of the inlet aperture 30 or behind the outlet aperture 32 are an ion source 10 or an ion detection device (not shown here).

Of course, the straight part of the running route could also be divided into two parts, one of which is different between the entrance aperture 30 and the toroidal capacitor 12 'f and the other is located between the latter and an outlet diaphragm which is then arranged at a distance from the condenser. Of course both straight parts should then each contain an imaging lens.

At deir. practical embodiment according to Fig. 4 were: ψ = 284.5 °

c = 0.4

g = 1.5 r _o ψ.

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The solution approach described last can in principle also be applied to the case where the ions are accelerated to the same impulses. However, the implementation possibilities are problematic in that the sector angle ψ of the required in this case Magnetic field is greater than 360 °. A plane beam path is then not possible.

Finally it should be noted that the flight route in the the compensation of the velocity dispersion (i.e. the velocity focusing) occurs, not exactly equal to the distance 'between the object point and the image point, i.e. the line in the one Imaging (directional focusing) must take place. For example, you can still advance a certain distance for directional focusing the inlet orifice or behind the outlet orifice. The beam cross-section is then, for example, at the location of the ion detection device slightly larger than in the image plane, but this usually does not matter in practice. The same also applies for the ion source.

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ATTACHMENT

Explanation of the symbols used .

B Magnetic induction at the location of the main beam path (Hittelbahn)

b Air gap width at the location of the main beam path

c Aspect ratio of a toroidal capacitor

e charge of the electron

E, ion energy through acceleration

g Total length of the straight parts of the flight route i

g _a (g ^J ) Distance between the ion source or the object point or the entry aperture (ion detection device, image point or exit aperture) and the entry side (exit side) of the deflection field for axial imaging

g (g ') distance between the ion source or the object point or the entry slit (ion detection device or the image point or exit slit) and entry side (exit side) of the Deflection field for the radial image

h Inhomogeneity parameter (see equations Ib and 2a)

k inhomogeneity parameter (see equations Ib and 2b)

m Effective ion mass

(Ion mass / ion charge)

η Inhomogeneity factor of a magnetic ™

Deflection field

R bead radius of a toroidal capacitor r radius of the orbit of a given ion

r Radius of the main beam path or the central path of the ions in the deflection field

t time

t time of flight of an ion between ion source _c and ion detection device

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t. Duration of the acceleration pulse U, acceleration voltage

u Normalized, radial distance from the central track

V Magnification between the entrance plane and the intermediate image

ν Speed of an ion as a result of its acceleration through a given one pulse

χ Total length of the flight path between the ion source and ion detection device

α angle of entry of the ions into the deflection field ß AE / E _b

ΔΕ. Initial energy range of ions

At time-of-flight dispersion in the electrical deflection field

At time-of-flight dispersion of the ions in the straight ^g parts of the flight path

ψ Sector or deflection angle

209886/0487

Claims (16)

- 23 - 213752Q Claims Time-of-flight mass spectrometer with a pulsed ion source that emits a packet of accelerated ions in a flight path, in which the ion packet separates into sub-packets of ions with the same effective mass, but from sub-packet to sub-packet of different effective mass and which begins at an entry plane, at an exit plane ends as well as at least an intermediate image plane, a straight part and a deflection field contains, which is traversed by the ions in a substantially circular arc-shaped paths and which is dimensioned in respect of the straight 'g portion so that the same by different initial velocities of ions effective mass caused transit time dispersion is opposite to that in the straight part, and with an ion detection device arranged at the end of the flight path, characterized in that the flight path is symmetrical with respect to the center between the entry plane (16) and the exit plane (18) and at least two are straight e contains parts (g ', g') which each adjoin a deflection field boundary (24, 26), and in that the deflection field boundaries at which the straight parts end are adjoined in each case by deflection field regions which are dimensioned so that ions that coming from an ion entry area in the entry plane radially outside (resp. inside) a central path (r) enter one of the deflection fields and run to the next intermediate image (20) radially outside (or inside) the central path from which? other deflection area radially inside (or outside) the central path and converge at least in the radial direction to an image of the ion entry area located in the exit plane. 209886/0487 213752Q 2.) time-of-flight mass spectrometer according to claim 1, characterized in that a first straight part (g) of the running track adjoin the entry level (16) and a second straight part (σ ') adjoin the exit level (18). 3.) time-of-flight mass spectrometer according to claim 1, characterized in that the two deflection field areas adjoin one another with the ends facing away from the straight parts and are formed by a single deflection field in which An axial intermediate image and the plane of symmetry are centered find and that equation • g _r = g ^ = f ° tg (18O ° -ψ.) 4.) Time-of-flight mass spectrometer according to claim 1, 2 or 3, characterized in that in addition the equation. g _r = gi = ^ tg (i8o ° - | t) is satisfied. 5.) time-of-flight mass spectrometer according to claim 1, 2 or 3, characterized in that in addition the equation ι ^r ° *. fior ^ o hi |>. ^r o, kij> ^ r = 9 _r "" IT ^{tg (18} ° 2 ^{) =} k "- ^ct * 2 is satisfied. 6.) Time-of-flight mass spectrometer according to claim 3 with an ion source, which supplies ions with essentially the same energies, characterized in that the deflection field an electric toroidal field with the mean orbit radius r and the sector angle ψ and that the equation 209888/0 487 is satisfied. 7.) time-of-flight mass spectrometer according to claim 6, characterized in that c = h = k = 1 g _r = g «= 5.9 r _o ψ = 199.2 ° ä 8.) time-of-flight-ülas senspek trome ter according to claim 6, characterized marked that. g _r = g ^ = 2.35 r _o ψ = 163.2 ° c = 0.234 9.) Time-of-flight mass spectrometer according to claim 3 with an ion source, which delivers ions with substantially equal pulses, characterized in that the deflection field " is a magnetic sector field with the mean orbit radius r and the sector angle ψ and that the equation _2g = fo L ₍ i _ _1} _ B ^rn ih ² h ³ 10.) time-of-flight mass spectrometer according to claim 3 and 9, characterized in that the deflection field 209886 / 0A87 213752Q areas are formed by a magnetic field with the inhomogeneity factor η = 0.5 and the deflection angle ψ = 314 °, and that the distance of the entry plane or exit plane from the limits of the magnetic field is 3.7 times the mean orbit radius r is the ion in the magnetic field. 11.) time-of-flight mass spectrometer according to claim 9, characterized characterized in that the sector-shaped deflection field regions be formed by a magnetic field with the inhomogeneity factor 0.5 and the deflection angle 290 °, and that the distance (g or g ^.) the entry or exit plane of the Mass spectrometer from the corresponding limits of the magnetic field is equal to 1.23 times the mean orbit radius r of the ions in the magnetic field. 12.) time-of-flight mass spectrometer according to claim 10 or 11, characterized in that there are two series-connected arrangements according to one of these claims contains (Fig. 2). 13.) time-of-flight mass spectrometer according to claim 2, characterized in that it is in the specified order between an entry gap (30) and an exit gap (32) contains: a first straight flight path of the Length g = g '= r- ° - ctn (hij;), a first sector-shaped deflection field with the sector angle ψ ', in which there is a diaphragm (46) at the location of a radial intermediate image that is formed, a straight line Flight route with length 9 _ 2r cos (hy-l)
h sin (hift) a second sector-shaped deflection field with the sector angle ψ and a third straight flight path of length g _r , the following equation for the case of the acceleration of the ions to equal pulses 209886/0487 213752Q - 27 - and the equation for the case of the acceleration of the ions to the same energies -ο L ti- - h - sin (frfr) I h ^ ⁴ h ^J is satisfied. ^ 14.) Time-of-flight mass spectrometer with a pulsed ion source, which emits a packet of accelerated ions with essentially the same energies into a flight path in which the ion packet is located separates into partial packets of ions each with the same effective mass, but from partial packet to partial packet different effective mass, and which starts at an entry level, at an exit level ends and contains at least one intermediate image plane, a straight part and an electrostatic deflection field, which is traversed by the ions on essentially circular arc-shaped paths and which is so dimensioned in relation to the straight part is that the different initial speeds ^ of the ions of the same effective mass caused transit time dispersion is opposite to that in the straight part, where the equations ^ - tg (18C - τρ) = 0 are fulfilled, and with a beir. Arranged at the end of the flight route th ion detection device, characterized that in addition the equation 9886/0487 ρ- ctg (y ^) = O
or the Gleichuna fSL tg (180 ° - Ά = O are fulfilled and that each straight part of the flight path adjoining a boundary of the deflection field (12 ') is an ion-optical Lens (50) contains, which causes a stigma table image between the planes delimiting the straight flight path in question. 15.) Time-of-flight Ilassenspektroneter according to claim 14, wherein ¹ the flight path contains a single straight part and a single electrostatic deflection field, characterized in that a toroidal capacitor (12 ') with the aspect ratio 0.4 and the sector angle 284 to generate the deflection field , 5 ° is provided and that the length of the straight part of the running distance is 1.5 r ψ. 16.) time-of-flight? 4as senspektrome ter according to claim 15, characterized marked that the straight part of the flight route a single lens (50), which is preferably arranged in the middle of the flight path, contains. 209886/0487 Lee r s e i 1 * - e