SU1305795A1 - Mass spectrometer - Google Patents

Abstract

The invention relates to the field of instrumentation and can be used for elemental analysis of solids. The goal is the twisting of the luminosity and acceleration of the registration process of the mass spectrometer (MSM). It is achieved by the fact that the MSM has a detector 5, a multislit diaphragm (MVD) 4, a scanning unit (B) and a B 6 registration, the slits (S) of the MVD 4 have the same dimensions, parallel to each other, and some of them are located on different distances one from the other so that the difference of the distances between u is not less than the width of u, and the number of u, per aperture of the detector is determined from the ratio (dN / dx) h, where h is the width u, and dN / dx is the maximum recorded number of ion beams Q per unit length along the focal plane S at the location of the detector a 5. The description of the invention describes the structural elements of the detector 5. 2 Cp. f-ly, 5 ill.

Description

The invention relates to the elemental analysis of solids, namely to static mass spectrometers with double focusing and can be used in mass spectrometry.

The aim of the invention is to increase the luminosity and speed up the registration process.

slots in a multislot diaphragm are located at different distances from each other, and in such a way that the difference in the distances between the slots is not less than the width of the slots themselves, i.e., for example, 30 μm, and the number of slots per detector aperture , should be no more than the reciprocal of the slit width and maximal cliHr, 1 shows the functional number of ion beams recorded.

scheme of the proposed mass spectrometer; Fig 2, embodiment of the diaphragm; FIG. 3 is a detector circuit; in fig. 4 and 5 signals, explaining the operation of the device.

The Mgcss spectrometer contains a pulsed laser and an ion source 1 consisting of a pulsed laser and an ion-optical unit, analyzer 2., state 15

with a unit length of the focal plane at the location of the detector. If, for example, the maximum detected beams of ions per unit length along the focal area of the detector are

lt 3 mm

then the number of slots

per detector aperture

from an electrostatic analyzer, it should be no more than 1 / 3-0.03 X11.

The magnetic analyzer connected to the sweep unit 3 is: a controlled digital current generator, a multislit diaphragm 4, which is a plate in which a series of parallel slots of equal width is created and installed in the focal plane of the analyzer 2 in front the aperture of the detector 5, which is a coordinate insensitive detector of positive ions, and the recording unit 6, consisting of an integrator, a microprocessor and a display,

Ion optic pulsed node. laser source of ions of 1 dispose in vacuum. Detector 5, a multislit diaphragm 4, and some components of analyzer 2 are also located in a vacuum, namely, an electrostatic analyzer and a gap of a magnetic analyzer. The registration block b is electrically connected to the detector 5, and the 3rd block by the analyzer 2. The direction of the possible movement of the ion beams relative to the fixed detectors. 5 and the multislit diaphragm 4 is indicated by an arrow, and the ion beams themselves are marked with arrows,

The width of the slits is equal to the minimum width (along the focal plane) of the ion beams and is for a double-focusing mass spectrometer and with a pulsed laser source of suits, for example, 30 microns. the slit is determined by the height of the output slit of the magnetic analyzer n, for example, 1 mm. At least part

slots in a multislot diaphragm are located at different distances from each other, and in such a way that the difference in the distances between the slots is not less than the width of the slots themselves, i.e., for example, 30 μm, and the number of slots per detector aperture , should be no more than the value inverse of the product of the gap width at the maximum

with units of length along the focal plane at the location of the detector. If, for example, the maximum detectable number of ion beams per unit length along the focal plane at the location of the detector is 3 mm.

, the number of slots per detector aperture should

The detector 5 (FIG. 3) contains a metal plate 7, a microchannel plate 8 and a collector 9 connected to the detector power supply 10, and the plane of the microchannel plate is non-parallel to the plane in which the detected ion beams move. The ion beam hits a metal plate 7 near its middle. In FIG. 3, ion beams are indicated by thin lines with arrows, and the secondary electrons created by them are indicated by thin dashed lines; the angle formed by the plane in which the ion beams move with the plane of the metal plate 7 is denoted by and with the plane of the micro-channel plate 8 - / 3.

Mass spectrometer works as follows.

After turning on the mass spectrometer, the unit 3 is set to the initial current of the magnetic analyzer and the scanning speed 45 of the NIN ion beams, and to the unit 6, the frequency of the measurement cycle of the integral of the detector signal 5.

The mass spectrum is recorded as follows.

Jq. As a result of the operation of the pulsed laser ion source 1 and the analyzer 2, pulsing ion beams appear from the output slit of the magnetic analyzer, focused on the shallow plane, where a multi-purpose diaphragm is installed 4. A part of the ion beams that hit some of the slit multi-slit diaphragm 1 4 is in the aperture detector 5, with ions.

having a few tens of kilo-electronvolts of energy, they fall onto a metal plate 7 and knock out secondary electrons from it, which are accelerated by an electric field applied to the gap by a metal plate 7 - a microcavity plate 8,

In order to reduce high flux densities of secondary electrons pinching microchannels in the microchannel plate 8, the metal plate 7 is located almost parallel to the plane in which the ion beams move, for example, at an angle d from 30 ° to 5 ° or less, and The microchannel plate 8 deviates from parallelism by an angle of / 3 5 - 30 ° and more. At the same time, the ion flux touches the metal plate 7 at a great length exceeding the height of the exit slit of the magnetic analyzer as many times as the cotangent of the angle is greater than one. Due to the non-parallelism of the microchannel plate 8 and the specified plane, non-parallelism of the magnetic induction vector of the scattered (parasitic) magnetic field, the magnetic analyzer that inevitably exists near the gap of the magnetic analyzer, and the intensity vector of the electric field created between the metal plate 7 and the microchannel plate 8, the secondary electrons spin around the lines magnetic induction and cover a large area of a microchannel plate 8, for example 50 mm, instead of the initial section of the ion beam s in the focal plane, equal, for example, 0.03 mm. As a result, the microchannel plate 8 is capable of efficiently, without saturation, detecting pulsed beams of high current density ions generated by a pulsed laser ion source 1 of ions. Once in the channels of the microchannel plate 8, the secondary electrons multiply and, on leaving the microchannel plate 8, reach the collector 9, where they create a recording signal that goes to the integrator input.

Unit 3 performs a uniform change in the current feeding the magnet of the magnet analyzer, as a result of which the magnetic induction in the gap of the magnet analyzer changes uniformly, for example, increases, and the ion beams are shifted along the focal plane of the magnetic analyzer.

The integrator of the recording unit 6, for a time equal to the measurement cycle, integrates the signal over time, and after this time, transfers the integral value to the microprocessor memory, nulls and starts the integration again. Since the duration of the measurement cycle is chosen less than the time required for the ion beam to move along the focal plane by a distance equal to the width of the slit in the multislit diaphragm 4, the time dependence of the integrator signal always has increments and decreasing areas and allows you to confidently determine the time of maximum occurrence during the passage ion beam through the slit.

Integration of the detector signal over a period of time that is substantially longer during the pulse period of a pulsed laser ion source is necessary because the pulsed laser ion source, like other pulsed ion sources, does not provide a high signal stability from pulse to pulse. The integration of the signal thus improves the relative accuracy of the recording.

A typical sweep of the signal generated by the integrator as a result of the movement of ion beams is shown in FIG. 4. The T axis represents the time of ion beam transport, while the Y axis shows the integrator signal. In order to simplify, the step waveform is depicted by smooth curves.

The microprocessor input signal is processed by the microprocessor in real time: a maximum is allocated, the time of its occurrence and the sum of the integrator's signals (the area under the envelope) are determined. The last two numbers are sent to the memory.

The algorithm for analyzing the pre-processed numbers is comparing the difference in the moments of onset of the maxima with the difference in the distances between the gaps in the multislit diaphragm divided by the scanning speed. Information about the time of passage of the slots is entered into the microprocessor initially. The criteria for identifying the initial position of the ion beam are the following features: the registration of the passage of the ion beam through two or three slits, the absence of an ion beam maximum signal in two or three intervals in the coordinate sequence of the maxima recorded in the memory, and the relative constant of the sum of the integrator signals .

Thus, when analyzing the sweep (Fig. 4) of the signal of ion beams that passed through a multislit diaphragm as a result of sorting the difference between the moments of occurrence of maxima t-- tj (i, j are integers), starting from the highest values of the maxima and ending at the lowest, for example, , the coincidence of the difference between the moments t - t, t, - tg, tg- t, t - t maxima 1,3,6,7 and 8 and the distance between the second (by counting the gaps - from left to right), third, recorded in the microprocessor memory, the fourth, fifth and sixth slit in the multislit diaphragm, divided by the speed

Similarly

t, - ts of ion beam scans of the difference in moments of t t correspond to the distances between the fourth, fifth and sixth slit in the multislit diaphragm divided by the ion beam scanning rate.

In those cases, when one maximum of a given ion beam was observed (the ion beam was located near the edge

multi-slit diaphragm), microprocess., force, because the registration of beams

The sorrow also analyzes those scanner regions of the integrator signal where there is no signal. In the presence of this information, the microprocessor reconstructs the location of the ion beams with respect to the multislot diaphragm 4 at the time of the start of scanning. The reconstructed signal corresponding to the signal of the integrator (FIG. 4) is shown in FIG. 5. The X-axis shows the relative distances of the ion beams and the slots of the multislit diaphragm. Points 1 (X 0) and 6 indicate the position of the first and sixth slits relative to the ion beams at the time of the start of scanning. On the Y axis, the calculated intensities of the registered ion beams are reproduced as signals of standard Gaussian shape, with

ions are produced simultaneously by several crevices. To ensure the specified static accuracy of the registration result of each ion beam with

Taking into account the instability of a pulsed laser ion source, each ion beam must be registered with a certain minimum number of laser pulses. As each

45 an ion beam passes several times through the slits of the multislit diaphragm, and the scanning speed can be increased as many times as the number of identified passages provided.

50 ion beam through the slit multi-gap diaphragm. When moving beams of ions to a distance much larger than the detector's detector, almost every ion beam will cross all the gaps

the integral of the calculated intensity of each slit diaphragm. In this case, the previous Ion beam is equal to the corresponding mass spectrometer, which provides an arithmetic average that saves time compared to the integrator components, the mass spectrometer equipped with a single-aperture averager, in

The static reliability of the result is improved.

The reconstructed signal is displayed on the screen.

Thus, the multislot diaphragm 4 performs the function of encoding the intensity and coordinates distributed along the focal plane of the ion beams, and the microprocessor decoding these quantities. The prerequisites for such a procedure are the relatively rare arrangement of ion beams along the focal plane (despite the large

the total number of ion beams) and the substantial simplicity of the mass spectrum obtained using a pulsed laser ion source — the highest ion charge does not exceed three.

In order to carry out the encoding and decoding process, it is necessary to ensure the relative motion of the detector 5 with the diaphragm 4 and the ion beams, this does not matter which of them is resting with respect to the mass spectrometer. However, the quiescent detector 5 and the diaphragm 4 are preferred for constructive reasons.

The proposed mass spectrometer, which contains a detector with a multi-gap diaphragm, has an increased number of light ions produced simultaneously by several peaks. To ensure a given static accuracy of the result of the registration of each ion beam with

Taking into account the instability of a pulsed laser ion source, each ion beam must be registered with a certain minimum number of laser pulses. As each

the ion beam passes several times through the slits of the multi-gap diaphragm, then the scanning speed can be increased as many times as the passages provided

ion beam through the slit multi-gap diaphragm. When the ion beams are moved to a distance much larger than the detector aperture, practically each ion beam will cross all the gaps many times, like the gaps in the multi-slit diaphragm.

Signal decoding is performed reliably, in real time and with a small amount of microprocessor memory, if the slots in the multislit diaphragm 4 are of the same size and at least some of them are located at different distances from each other and in such a way that the distance difference is between the gaps not less than the width of the gaps themselves, and the number of gaps n per aperture of the detector is determined from the ratio n 1 / (dN /

Aperture in the multislit diaphragm. In this case, the likelihood of the ion beam falling into the gap between the extreme gaps in the multislit diaphragm decreases, which means that the likelihood of the beam crossing two and even three slits increases, which makes decoding its coordinates more reliable.

Claims (3)

1. A mass spectrometer containing successively located pulsed ion source, magnetic analysis- / dx) h, where h is the slit width, dN / dx - J5 mash connected to the scanner, the maximum recorded number of the detector with the box in front of it ions per unit length along the aperture, which differs from the crown plane at the location of the detector. The meaning of the restriction on the greatest number of slots n is By the fact that, in order to increase the luminosity and speed up the registration process, the diaphragm is made multi-slotted, with the slits being parallel and of equal size and at least some of them are located at different distances from one another, the difference When (dN / dx) h we happen that, in order to increase the luminosity and speed up the registration process, the diaphragm is made multi-gap, while the slits are parallel and of equal size and at least some of them are located at different distances x one from the other, the difference at location The simultaneous passage of ion beams through two (and more) slots in a multislit diaphragm becomes so frequent that the allocation of the maximum 25 distances between the slots is no less than the width of the signal and the sum of the signal components of the slots themselves, and the number of slots n, the integrator is not occurring on the detector aperture, it is possible. It meets the condition n if 1 / (dN / dx) h, Thus, the number of slits is n, with - where h is the width of the slit, m; dN / dx - maximally per detector aperture, a long-30 maximum recorded number of beams can be optimal: at small n, ions per unit length along the focal — for example, at n 2, the detector has a low aperture and possible coincidence between the slots distance between ion beams, reducing decoding reliability. The optimum corresponds to approximately n 0.5 / (dN / dx) h. The reliability of signal decoding (i.e., the number of decoded I-40 beams to the total number of ion beams that fell on the detector aperture with respect to displacement) can be increased by the fact that the distance between the two leftmost and the two right ends is The second multiplier multipliers are the smallest among the bright electrons based on microcavity values of the distances between the inter-channel plate and the collector. detector plane. 2. A mass spectrometer according to claim 1, wherein the distance between the two leftmost and the two rightmost slits is the smallest among other distances between the slits in the multi-gap diaphragm 3. The mass spectrometer according to claim 1, wherein the detector is made in the form of a metal plate located at an acute angle to the path of movement of the ions. 795g Aperture in the multislit diaphragm. In this case, the likelihood of the ion beam falling into the gap between the extreme gaps in the multislit diaphragm decreases, which means that the likelihood of the beam crossing two and even three slits increases, which makes decoding its coordinates more reliable. fO Claims of invention 1. A mass spectrometer containing successively located pulsed ion source, a magnetic analyzer connected to the scanner, a detector with a diaphragm in front of it, differing the fact that, in order to increase the luminosity and speed up the registration process, the diaphragm is made multi-slit, the slots are parallel and of equal size and at least some of them are located at different distances from one another; the distances between the gaps are not less than the width of the gaps themselves, and the number of gaps n per aperture of the detector corresponds to the condition n if 1 / (dN / dx) h, at location  where h is the slot width, m; dN / dx is the maximum recorded number of ion beams per unit length along the focal length 40 45 behind which is located the multiplier of secondary electrons on the basis of a microchannel plate and a collector. detector plane. 2. A mass spectrometer according to claim 1, wherein the distance between the two leftmost and the two rightmost slits is the smallest among other distances between the slits in the multi-gap diaphragm 3. The mass spectrometer according to claim 1, wherein the detector is made in the form of a metal plate located at an acute angle to the path of movement of the ions. FIG. 2 FIG. H / I  I V | V1 tz t3 it t sis Figm Editor O. Yurkovetska Compiled by N. Katinova Tehred L. Serdyukova Proofreader M. Demchik Order 1461/52 Circulation 699 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., d. A / 5 Production and printing company, Uzhgorod, Projecto st., 4 ii is FIG. five