WO1992017755A1

WO1992017755A1 - Instrument for measuring the absolute temperature of solids, liq uids or gases

Info

Publication number: WO1992017755A1
Application number: PCT/DE1992/000258
Authority: WO
Inventors: Jochen Laakmann; Georg J. Schmitz; Klaus Hoffmann; Ulf Trociewitz
Original assignee: Access E.V.
Priority date: 1991-04-03
Filing date: 1992-03-28
Publication date: 1992-10-15
Also published as: DE4110714A1

Abstract

The instrument proposed includes a device with which the speed distribution of gas-phase particles of a material can be determined, the mass of the gas-phase particles also being determined either simultaneously or with a given time lag. Given the particle mass and speed distribution, the absolute temperature can then be calculated using Maxwell's speed-distribution curve.

Description

DEVICE FOR MEASURING THE ABSOLUTE TEMPERATURE OF SOLID, LIQUID, OR GASEOUS BODIES

description

The invention relates to a device according to the preamble of patent claim 1.

Numerous devices have been proposed for the measurement of temperatures, which are based in part on different principles. For example, there are several temperature measuring devices that take advantage of the physical properties of most substances to change their expansion with temperature. These devices include the gas pressure thermometer, the steam pressure thermometer, the liquid thermometer and the bimetal thermometer. Other temperature measuring devices are based on the physical effect that some substances generate electricity depending on the temperature, e.g. B. the thermocouples, or change their electrical resistance, for. B. the resistance thermometer. In another group of temperature measuring devices, the changes in physico-chemical states depending on the temperature play a role, e.g. B. with thermal chalks or liquid crystals.

All these temperature measuring devices have in common that they do not initially measure an absolute but a relative temperature. In order to make an absolute statement, a reference point and a scale, ie a subdivision, are also required. Such a reference point can be, for example, the ice or boiling point of the water. The international practical temperature scale (IPTS), the thermodynamic temperature scale and the radiation-theoretical temperature scale were proposed as scales. While the practical temperature scale with the help of a gas thermometer with an ideal gas as If tools can be realized, use is made of the radiation from a black body on the radiation-theoretical temperature scale. The thermodynamic temperature scale is characterized by the fact that it starts from the Camot cycle process of a heat machine, the efficiency of which is independent of the working medium, and is ultimately only a function of two temperatures. However, a direct determination of the absolute temperature of any substance is difficult to achieve using the known scale.

A method for determining the absolute temperature of a body to be measured, using a reference body whose thermal capacity is known when the heat transfer coefficient between the reference body and the body to be measured is known, has already been proposed (PCT / SE 87/00249 = WO 87/07372). The temperature difference between the body to be measured and the reference body is measured and the absolute temperature of the body to be measured is determined using a mathematical equation in which time plays a role. A disadvantage of this method is that a reference body with a known heat capacity is required.

Another determination of the absolute temperature would be possible in that an equation in which the absolute temperature appears with different and determinable quantities is resolved according to the absolute temperature. Such equations are found in kinetic gas theory. An ideal gas is characterized in that the particles are treated like point particles of classical mechanics without any interaction. The well-known Boyle-Mariott law p applies to this gas. V = po VQ = const at T = const (I)

d. H. the product pressure (p, pg) x volume (V, VQ) is constant at the same temperature for an ideal gas. If the pressure is kept constant and the temperature is changed, Gay-Lussac's law applies

V = ΪV ₀ p = const (II)

T ₀

ie the gas volume increases with increasing temperature. By further transforming these equations (see, for example, BG Wedler, Textbook of Physical Chemistry, 2nd ed., Weinheim 1985, p. 20, or Bergmann-Schäfer. Textbook of Experimental Physics Volume 1, 9th ed., 1974 , P. 585) gives the general gas equation p. V = n R. T (HI) where R is the general gas constant and n is the amount of substance.

While equations (I) and (II) only show the relationship between two state variables p. V or v. Show T, equation (III) shows the relationship between the three state variables p, V and T. From equation (III) the temperature could be determined by solving for T if p and V were known. However, p and V are not known for most substances whose temperature is to be determined. A measurement of the pressure would also involve a great deal of effort with many substances and would hardly be feasible, in particular with solids. The product n. R in the above equation in can be summarized as a constant k, which as Boltzmann's constant k = 1.38066. 10 ^-23 JK ^{"is 1} or 8.6178. ^{10" 5} eV. K ^{"1 is} known, in which K = Kelvin, eV = electron volt and J = Joule. Hence p. V = k. T (IV)

This equation still contains the variable p, which is difficult to determine, particularly at very low pressures, so that determination of the absolute temperature T using equation IV is hardly practical.

A further possibility for determining the absolute temperature would be to calculate the mean kinetic energy of a particle ensemble taking into account the uniform distribution law, according to which each degree of freedom that enters the energy of a system then contributes 1/2 kT on average,

Ekin. with = 3/2 k T = l / 2 v _with ² (V)

evaluate, d. H. to dissolve after T, whereby

results Here m is the mass of a particle of the particle ensemble and v _m j _{t is} the mean velocity. In order to be able to determine the absolute temperature from equation VI, m and v _mjt must therefore be known. If the substance to be measured is also known, m is also known and the problem is reduced to the determination of v _mj t. However, the average speed cannot be measured directly, since it is a statistical statement about the speeds of a large number of particles. Otherwise, the mass m is not known for many substances, in particular mixtures of substances.

However, if it is known how the individual speeds of the particles of an ensemble are distributed, the average speed can be determined from this distribution. Such a distribution is given for a thin gas in thermal equilibrium by the Maxwell distribution of the amount of velocity (J. A. Campbell, Allgemeine Chemie, 2nd ed., 1985, p. 253).

In this equation: dN / N = fraction of the molecules with velocities between v and v + dv m = mass v = velocity

T = absolute temperature π. k = constants

The most likely because the maximum of the distribution curve forming speed (Greiner, Neise, Stöcker: Theoretical Physics, Volume 9, Thermodynamics and Statistical Mechanics, 1987, p. 179). is obtained by differentiating equation (VII) according to (V) and zeroing the first derivative:

If this most probable speed can be determined by measurement, the absolute temperature can be calculated from the formula

T = v _m , * - (x,

determine. The determination of the most probable speed by measurement technology is relatively simple if the speed distribution is recorded as such by measurement technology, ie. H. if this distribution z. B. can be represented as a curve on an oscilloscope.

The mean speed results (cf. Greiner, Neise, Stöcker, Theoretical Physics, Volume 9, Thermodynamics and Statistical Mechanics, 1987, p. 180)

^V with ^' = 1 - mm ** - ππ (XI)

while the mean quadratic speed increases (see Greiner, Neise, Stöcker, loc. cit., p. 180)

_ f3 3kkTT (xπ)

V mq " ^~ \ K mm results. The average kinetic energy of a molecule is, taking into account equation (XII)

It follows from the above that the absolute temperature can always be determined if either the maximum speed or the mean speed or the mean square speed and the mass are known. If the speed distribution function is known, these values can be taken from the curve.

The actual problem of determining the absolute temperature therefore consists in measuring both a type of speed (v- _j - ^, v _mjt or v _q ) or the speed distribution as well as the mass. The measurement of the speed distribution is of particular importance because it is still necessary if the masses of the substance to be measured are already known and therefore no longer have to be measured. If the masses are not known, mass spectrometers can be used to determine them.

Of the three types of speed, the most probable speed can be determined most easily and quickly from a measured speed distribution function. On the one hand, it is directly visible as the maximum of the distribution curve and, on the other hand, it can be determined mathematically by differentiation.

An arrangement for examining the speed distribution is already known, with which the number of molecules in each speed range can be "counted". Here, a gas flows from a container through collimator slots and, as a collimator bundle, strikes a first rotating disk which has a recess on its circumference (Alonso / Finn, Physik, 2nd edition, 1988, p. 259). A second rotating disk is rigidly coupled to this first rotating disk via an axis, which likewise has a recess on its circumference, but which is offset by an angle gegenüber with respect to the recess of the first disk if gas molecules with a certain one Temperature from the gas container and through the collimator slots on the disks, they only pass through both recesses of these disks if their speed v = sω Θ, where s = distance between the two disks from one another and ω the angular velocity of the disks. If either ω or Θ is changed, particles of different speeds are registered on a detector located in the extension line of the collimator slots. If different observations are made for different speeds, the speed distribution is obtained. By continuously changing ω with a constant distance between the disks, molecules hit the detector at different speeds, so that a curve for the speed distribution results. However, a mass determination is not carried out so that the absolute temperature cannot be determined either. In addition, no exact speed curves can be determined for substances with different atoms or molecules that relate to an atom type.

In another known molecular beam apparatus for examining the speed distribution of silver atoms, instead of two rotating disks, a rotating drum is provided which has an attachment surface for silver atoms on its inside (Frederick Reif; Berkeley Physics Course, Volume 5, Statistical Physics, 2nd edition. 1981, p. 149). Here silver is heated in a melting furnace until it is gaseous. It is then passed through collimator gaps through the opening of a rotating hollow cylinder onto said attachment surface. If the silver atoms are driven through the opening of the hollow cylinder, all that matters is their speed. what time it takes to reach the opposite side of the cylinder drum. They reach faster atoms earlier than slow ones. As the drum rotates, molecules will hit different places on the inside of the cylinder at different speeds and get stuck at these places. If the thickness of the deposited silver layer is measured later as a function of the distance on the inner surface of the drum, then this gives a measure of the speed distribution of the atoms. Even with this known apparatus, the masses are not determined, so that a temperature determination is only possible with prior precise knowledge of the sample used. In addition, no average or any other speed is determined from the speed distribution. In addition, with this method it is hardly possible to obtain a speed distribution curve from which specific speeds can be taken.

A further device for determining the speed distribution has been proposed by Miller and Kusch (Gerd Wedler. Textbook of Physical Chemistry, 2nd ed., 1985, p. 680). As with the devices described above, an atomic or molecular beam is first blanked out and then applied to a detector via a speed analyzer. The speed analyzer consists of a solid cylinder, in the surface of which closely milled helical grooves with a constant pitch are milled. At a certain rotation frequency, only atoms or molecules whose speed is in a narrowly limited range can pass the groove and hit the detector. The speed distribution can thus be measured by varying the rotational frequency. In this device too, however, there is no mass determination and therefore no temperature determination from the Maxwell's velocity distribution. In addition, it is not possible to determine the temperature precisely in the case of mixtures containing several types of atom.

In addition to devices for determining the speed distribution, devices for determining masses are also known (Wutz, Adam, Walcher: Theory and Practice of Vacuum Technology. 4th Edition, 1988, pp. 432 ff .; Edelmann: Vacuum Technology. 1985. Pp. 181 to 194) In addition to the magnetic field mass spectrometer, the cycloid mass Spectrometer, the time-of-flight or transit time mass spectrometer, the transit time resonance mass spectrometer, the Omegatron mass spectrometer and the monopole mass spectrometer, the quadrupole mass spectrometer is particularly suitable for the determination of masses. A quadrupole mass spectrometer or mass filter ideally consists of four hyperbolic cylindrical surfaces, which in practice, however, are mostly replaced by circular cylindrical tubes or rods. There is a direct voltage and an alternating voltage superimposed on each of these two rods (Wutz et al., P. 436, cf. also US Pat. No. 3,147,445). If a particle with a certain charge and a certain mass enters this four-pole field, which - coming from an ion source - has been accelerated by the voltage, this field leads to a complicated oscillation about an axis parallel to the tubes or rods. The amplitude of this oscillation and thus the distance of the particle path from this axis is either limited or it grows over all limits, so that the particles hit the rods acting as electrodes and separate from the ion bundle. Of the particles that run on stable orbits, all those pass through the "filter" when the amplitude is less than a certain value. There are thus stable ion trajectories in which the ions execute vibrations around the axis of symmetry of the four rods, the amplitude of which does not exceed a maximum value, and there are unstable ion trajectories in which the oscillation amplitude of the ions increases so that the ions on the Hit rods and be unloaded. In a given field configuration, only the specific mass m / Ne decides whether the ion trajectories are stable or unstable. At the exit of the channel, which is formed by the space between the four rods, there is generally a Faraday cup which is connected to an amplifier. Instead of a Faraday cup, a secondary electron multiplier is often used, in which the impinging ions trigger electrons from a converter electrode. The advantage of the multiplier is that smaller partial pressures can be measured and the measuring time can be shortened. By changing the voltage conditions at the electrode of the quadrupole mass spectrometer, a certain mass range can be traversed, ie a mass spectrum can be recorded.

A mass spectrometer is also known which has an ion chamber and a device for interrupted and successive acceleration or braking of ions (US Pat. No. 2,642,535). Since the acceleration of the ions depends on their masses, their masses can be determined in this way. A gas to be analyzed with regard to its composition enters an evacuated room, where it is ionized. Siert and accelerated by means of an electric field through an electrode in the direction of a target. A fixed, kinetic energy is supplied to the gas particles via the acceleration voltage. Due to the different mass numbers of the gas to be analyzed, the various types of atoms receive different final velocities at this fixed energy, so that the masses are determined by determining velocities. A necessary prerequisite for this is that the speed or energy distribution existing due to the temperature is negligible. It is therefore not possible to determine the absolute temperature via the speed distribution.

The object of the invention is therefore to create a device with which it is possible to determine the absolute temperature of a substance with the aid of the detection of properties of the particles emanating from this substance.

This object is achieved in accordance with the features of patent claim 1.

The advantage achieved by the invention is, in particular, that the absolute temperature can be deduced from the mere consideration of masses and the speeds of particle ensembles. In a special embodiment of the invention, the masses themselves are measured so that the temperature can also be determined for real, ie contaminated, samples. Since the temperature is determined from the speed distribution at a selected mass number, the temperature of a body of this mass number which is in a hotter environment can also be determined without contact. With the invention it is also possible to determine the temperature of solid bodies in a vacuum without contact if at least one of the elements from which this solid body has a sufficient vapor pressure, which is the case with most metals in wide temperature ranges. The temperatures of real gases, e.g. B. H2, N2, 02, also determine contactlessly at pressures of <10 ^"1 Pa, since the energy is distributed according to the equal distribution theorem with 1/2 k T each to each degree of freedom and thus the determination of the kinetic energy , ie the speed of a single spatial direction is sufficient for a temperature measurement. The non-contact measurement largely avoids that the temperature to be measured is influenced by the measuring probe. The temperature of solids, liquids and gases, the atoms of which, for example, in a quadrupole mass spectrometer (QMS) are absorbed, e.g. B. metal atoms is not affected.

Exemplary embodiments of the invention are shown in the drawing and are described in more detail below. 1 shows a graph of the velocity distribution of atoms / molecules according to Maxwell;

2 shows a graph of the energy distribution of atom molecules;

3 shows a graph of the speed distribution, in which the most probable, the mean and the quadratic speed are indicated;

4 shows a mass spectrum of a gas mixture recorded with a Faraday measuring head;

5 shows a first arrangement for the measurement of the mass and the velocity of gaseous molecules, in which a quadrupole mass spectrograph is used together with an electrostatic deflection of charged particles;

FIG. 6 shows a schematic illustration of the course of particles in an arrangement according to FIG. 5, which are deflected by electric fields;

7 shows a second arrangement for measuring the mass and the velocity of a gaseous substance, in which the flight time of molecules is determined and a quadrupole mass spectrograph is used;

8 shows a third arrangement for the measurement of the mass and the velocity of gaseous molecules by means of combined electrical and magnetic deflection and using a Qiiadrupol mass spectrograph; 9 shows an arrangement for measuring the temperature of an object which is touched during measurement; and

10 shows a device for the simultaneous measurement of molecular mass and molecular velocity

1 shows the velocity distribution for nitrogen at 100 K (curve 101) and 300 K (curve 102). While the abscissa shows the speed of the nitrogen molecules in meters per second, the ordinate shows the number of molecules with the speed v, based on the total number of molecules. Characteristic of curves 101 and 102 is the fact that the maximum of the curve decreases with increasing temperature and at the same time changes towards higher speed. stores. Because of the factor v ² , the curve is not symmetrical with respect to the position of the maximum, ie the higher speeds are favored over the lower ones. It should be noted that the speed distribution at a given absolute temperature depends on the molecular mass.

In contrast, the distribution of the molecular energies, as shown in FIG. 2, is independent of the molecular mass. The abscissa of FIG. 2 shows the energy in electron volts, while the ordinate indicates the number of molecules with a certain energy. The curves 101, 102 of FIG. 1 result from the curves 103, 104 of FIG. 2 if the energy is substituted by the speed, that is to say E = 1/2 mv ² or dE = mvdv. The formula for energy distribution is then

Equation VII above, which fulfills curves 101, 102 in FIG. 1, describes the speed distribution of particles which have three degrees of freedom of translation. The velocity distribution according to equation VH therefore indicates the probability that v has any direction in space and v + dv.

FIG. 3 again shows a curve representation which essentially corresponds to the curve representation according to FIG. 1. Curve 110 shows the speed distribution of

Oxygen molecules at 73 K, while curve 111 represents the speed distribution of 10 "oxygen molecules at 273 K. With" v _maχ "the most likely speed is with the maximum distribution, with v the mean speed and with n ^v ) _r_it ^ ^em ittϊ ^ere square velocity is characterized be¬ of a molecule. the number of molecules within a specific speed range, for. example, between 300 and 600 m / s, is represented by the area within the corresponding Aus¬ section of the respective curve. Total the total number of molecules corresponds to 10 ^ under curve 110 or 111. This area is the same at every temperature, since the curves refer to the same number of particles.

4 shows the mass spectrum of a test gas which was recorded with a Faraday measuring head of a quadmole mass spectrometer. The operating mode was "constant sensitivity" and not - which would also have been possible - "constant line width". The masses of alloys or other compound substances can also be determined in a corresponding manner. The ordinate denotes the intensity of a received signal, which depends on the mass, while the abscissa indicates the mass. If one starts from a binary substance that contains two types of atoms, in FIG. 4 at least two amplitudes or " Peak "areas, the energies of these two types of atoms being distributed according to equation XIV. Although this energy distribution does not show an explicit dependence on mass, a direct experimental determination of this energy distribution cannot be carried out easily. One way out is by substituting the energy with the formula E = 1/2 mv ² , which leads to Equation VII, which defines the Maxwell distribution.

The now explicit mass dependence leads to the fact that two atom types, when they are at the same temperature, have the same energy distribution but a different velocity distribution with a binary substance. If no mass determination or selection is carried out, the measured speed distribution curve corresponds to the superposition of the speed distribution curves of the two atom types. It would not be possible to determine the absolute temperature.

5 shows the principle of an arrangement 1 with which the speed distribution and the masses of particles can be determined. This arrangement 1 has a vacuum chamber 2, in which there is a container 3 with a gaseous, liquid or solid substance 4. The vacuum of the chamber should be less than IQ ^" - ¹ - Pa, so that there is an average free path of the particles 1 = v / z = 1/4 2 π v of about 1 m. Such pressure ranges are, for example, during vacuum melting At these pressures, metal vapors form a monoatomic ideal gas. The substance 4 has a certain temperature and therefore emits particles with a certain speed distribution, which is indicated by an arrow 5. It is important here that according to the According to the invention, the absolute temperature of the substance 4 can also be determined if its temperature differs from the temperature of the environment, for example of the container 3. For example, the substance 4 can have a temperature of 1000 ° C. while the container 3 has a temperature of 1200 ° C. The only requirement for this is that the container 3 is made of a different material than the material 4, so that the mass can be used as a distinguishing criterion ann. The basic principle of arrangement 1 is that a particle ensemble of substance 4 is ionized and then separated into its velocities and masses. A particle bundle or ensemble of the particles escaping from the substance 4 is masked out by the diaphragm 6 and then moves along the straight line 7 in the direction of the speed v. The mostly electrically neutral particles of the particle bundle or ensemble are now ionized. For this purpose, an ionization device 33 is provided, which is represented by a glow emission wire 8 and two electrodes 9, 10. This ionization device 33 can be one that is provided in commercially available quadmolar mass spectrometers. It is even possible to remove the ionization device present in the arrangement 1 in the quadrupole mass spectrometer and to arrange it behind the diaphragm 6.

The neutral particles from the container 3 are ionized by means of an impact by the electrons of the ionization device 33, whereby it should be noted that the velocity component of the ionized particles in the direction of the line 7 is not changed by incident electrons, because the velocity vector of these impacting electrons decreases ¬ runs right to line 7. The at least theoretically given probability that a horizontally moving electron is hit frontally by a particle coming out of the container 3, so that the speed of this particle changes in the direction of the line 7, is negligible.

The ionization source 33 preferably has a constant electron emission, so that the particle ensemble from the vessel 3 is ionized as evenly as possible over time. The ionized particle beam now passes through an aperture 11, which suppresses the scattering that occurs and thus prevents unwanted vapor deposition of parts of the arrangement 1.

The ion beam emerging from the ionizing device 33 is deflected slightly out of the axis 7 by the impact or impact ionization and by the voltage applied to the electrodes 9, 10. This deflection is reversed by a downstream compensation capacitor on its plate 12, 58 there is a DC voltage, the amount of which is correlated with the voltage applied to the electrodes 9, 10. However, the polarities of the two voltages are opposite. After the ionized particle beam has returned to the original direction of velocity, it passes through two deflection plates 13, 14 which, viewed in the plane of the drawing, cross each other opposite. In comparison to the plates 9, 10 and the plates 12, 58 of the capacitor, the deflection plates 13, 14 are offset by 90 degrees. This arrangement is recommended because in this way it is possible to work with those components of the momentum of a particle that were not influenced by the impact ionization in the ion generating device. The voltage at the deflection plates 13, 14 is fed from a function generator 15. It increases z. B. linear or is a sawtooth voltage.

It is of particular importance for the invention that by applying a voltage to the plates 13, 14 a part of the ionized particles, which are deflected more strongly than the faster ones due to their lower speed, is masked out. These slow particles then run against a downstream diaphragm 16 and no longer reach a quadmolar mass spectrometer 17, with which the masses of the particles can be determined. This means that from a certain limit speed only the fastest to fastest particles from a particle ensemble are detected by the quadrupole mass spectrometer 17. Takes the voltage on the plates 13, 14 z. B. linearly to, more and more charged particles are faded out over time, until at the end no more particles reach the mass spectrometer. Since the charged particles represent a current, there is a current course, such as that shown in FIG. B. can be displayed on an oscillograph 19: at low voltage values, the current is high and then decreases non-linearly with increasing voltage on the plates 13, 14.

The number of particles reaching the quadmolar mass spectrometer 17 can be very small, so that it is advisable to provide a secondary electron multiplier 18 as a reinforcing element for the detection of these particles between the quadrupole mass spectrometer 17 and the oscillograph 19.

In the case of a substance which is composed of different types of atoms, slow and heavy as well as fast and light particles hit the mass spectrometer 17 at the same time with a thermal energy distribution. To measure the speed of only one type of particle, e.g. B. only a heavy or only a light type of tissue, in the mass spectrometer 17 the corresponding particle type is filtered. The mass spectrometer 17 is thus used as a mass filter in order to record the time course of the intensity of this one type of particle at a predetermined voltage on the mass spectrometer. The ions are through one at the entrance Extraction voltage present in the mass spectrometer 17 is sucked into the mass spectrometer 17, there - if it is a quadmolar mass spectrometer - pass through the rod system and generate the signal of a single mass number, which is preselected by the voltage on the spectrometer. This signal goes to the detection in the Se_aιnd-Lrelek multiplier 18.

Ions that pass through the quadrature mass spectrometer 17 are thus sucked into the spectrometer 17 through an extraction field at the entrance of the spectrometer 17 and detected there according to their mass.

The I / U curve represented by the oscillograph 19 indirectly shows the velocity distribution of the charged particles. In order to be able to directly represent the speed distribution, the I / U curve is differentiated according to U. This can be done with a lock-in amplifier 20. The result of the differentiation is Maxwell's speed distribution, as represented by an oscilloscope or an oscillograph 21.

If the curve representing the speed distribution is calibrated, the speed distribution can be read directly from it. However, it should be emphasized that the proportionality factors which connect the curve in the oscillograph 21 and the actual speed curve to one another are unimportant for the temperature determination, since the absolute temperature can already be determined solely on the basis of the position of the distribution maximum.

It is possible. determine the values v _mjt , v _m q and v _maχ (cf. equations IX, X, XI) from the curve and, if the mass of the particles is characteristic, calculate the absolute temperature using a computer 22.

Since the masses of the particles are determined in a conventional manner with the quad polar mass spectrometer 17, the calculation of the absolute temperature can be carried out.

FIG. 6 shows the left side of the arrangement according to FIG. 5 again in principle and in perspective. The particles 54 emerging from the container 3 pass through an opening 55 in the diaphragm 6 into the area of an ionization device 33, which here is caused by the Plates 9, 10 is symbolized. In the ionization device 33 ionizes the initially neutral particles, which usually consist of several atom types or isotopes of the same material, into positively charged ions. Because of the bombardment with electrons, some of the particles are deflected somewhat from their original path. These positively charged ions 56 then reach the aperture 11, where some of them reach the horizontal deflection 12, 58 through an opening 57 in this aperture 11. There they are deflected towards the negatively charged plate 58. The heavy particles in the particle ensemble 59 are deflected less strongly than the light particles that are in the same ensemble. The deflection of the particle ensemble 59 in the horizontal deflection 12, 58 is as great as the deflection of the particle ensemble in the ionization device 9, 10, so that the original deflection error is compensated for.

The particle ensemble 71, which is now in its old path again, is now deflected upward by the vertical deflection 13, 14, where the negative electrode 14 is located. The partial beam 78 emerging from the vertical deflection 13, 14 passes through an opening 79 in the diaphragm and arrives at the quadmole mass spectrometer 17, which has at its entrance a negative grid electrode, not shown, which, as far as it is positively charged, has the particles of the particle ensemble 80 are drawn into the spectrometer 17. Neutral and negative particles 81 fly over the spectrometer 17. The beam 78 consisting of positively charged particles is directed once more and once less with the linearly changing voltage on the plates 13, 14. From a certain voltage, therefore, only the fast particles will pass through the opening 79, while the slow particles will hit the aperture 16. If the voltage on the plates increases linearly from zero to a certain value, then first all particles get to the mass spectrometer 17, then only the fast ones, so that a U / J ratio results, as shown in the block of FIG 19 is shown. Since the particle beam 80 can still consist of different atom types with different masses, not only the slow particles are deflected more strongly by the voltage on the plates 13, 14, but also the lighter ones. The distribution of the particle velocities in the beam 80 is therefore a velocity distribution composed of several individual velocity distributions - corresponding to the different mass numbers - which has approximately the curve shape of two or more overlapping Maxwell's velocity distribution curves. This speed distribution can be represented indirectly by a J / U ratio, where U is the voltage on the plates 13. 14 and J is the current formed by the particles of beam 80.

From the multi-atom ensemble with the composite velocity distribution, only those atoms with the same and predetermined mass number are filtered out by the mass spectrometer 17. They appear as a beam 82 at the output of the mass spectrometer 17. This beam 82 is fed to a Se-ainda ^ electron multiplier 18, which has several dynodes 83 to 91, to which an electrode 19 is connected, which is connected to ground 93 via a resistor 92 . The signal 94 supplied by the secondary electron multiplier can be processed further by a circuit arrangement not shown in FIG. 6. This signal 94 is a current signal which represents the quantity of particles in the beam 82, this current signal depending on the voltage at the plates 13, 14. By differentiating this current 94 according to the time-varying voltage U on the plates 13, 14, the speed distribution of the atom type selected by the mass spectrometer 17 results.

Knowing this speed distribution and the number of masses, it is now easy to determine the absolute temperature. One possible method of determining the absolute temperature from the known speed distribution and mass consists in adapting the measured speed distribution curve to the theoretical Maxwell's distribution curve by changing parameters (so-called "least squares fit" method). ). In another method, certain speeds are read from the measured distribution curve or calculated, e.g. B. the most likely speed or another of the speeds shown in FIG. 3.

7 shows a further arrangement 98 with which it is possible. to determine the temperature of substances. This arrangement 98 corresponds in many points to the arrangement 1 according to FIG. 5, which is why the corresponding devices have been provided with the same reference numbers. In contrast to arrangement 1, arrangement 98 of FIG. 7 attempts to measure the flight time of charged particles between two defined points. These two points are formed by the electrodes 9, 10 of the ionizing device 33 on the one hand and the center of the quadripolar mass spectrometer 17 on the other hand. The distance between the electrodes 9, 10 and the mass spectrometer 17 is, for example, L = 150 mm. After the particles of the z. B. gaseous substance 4, the temperature of which is to be measured, have left the container 3, they reach the ionizing device 33, which is provided with a control grid 24 and is pulsing. A negative square-wave signal applied to the control grid now permits the ionization of the neutral particle beam for a very short period of time, based on the flight time of the particles from the ionization device 33 to the mass spectrometer 17. The ion packets produced in this way consist of ions of different speeds which reach the mass spectrometer 17 at different times with different intensities. The pulse determines the start and end of the ionization of the particles to be measured. The ionizing electron pulse thus generates an ion packet that moves within a beam of neutral particles. Ions, which have different speeds at the location of the ionizing device 8, 9, 10, arrive at the mass spectrometer 17 at different times after passing through the distance L with a characteristic intensity distribution. A time-of-flight spectrum m thus arises in this way, which can be traced back to a Maxwell distribution function given a known drift distance L.

The time of flight spectrum determined in this way can be displayed on an oscillograph 25, which in turn is connected to a computer 26. The curve J - N (t) visible on the oscillograph 25 has in principle the same shape as the curve dJ / dN - N (v) on the oscillograph 21 in FIG. 5. The relationship between the flight time and the current er¬ is given by the fact that the ion packet contains an electrical charge which "discharges" in time, because in succession first the fast ions, then the medium and slow ions form the current. This can be clearly seen from the representation of the oscillograph 25, where the current is initially relatively small - when the fast ions arrive at the mass spectrometer 17 - and then increases when the large mass of the medium-speed ions arrives. The current characteristic then flattens out again when the slow ions arrive, until it ends completely because the last ions of the ion packet have arrived. The mass selection in arrangement 98 of FIG. 7 is the same as in arrangement 1 according to FIG. 5.

8 shows an arrangement which essentially corresponds to the arrangement according to FIG. 5. In contrast to the arrangement according to FIG. 5, however, the arrangement according to FIG. 8 also has an additional magnetic field B which is perpendicular to the electric field E of the deflection plates 13, 14. Such a combination of a variable electrostatic and magnetic field serves as Speed filter. The ions passing through the fixed B field experience, depending on the size of their velocity a more or less strong distraction due to the Lorentz force.

With the help of the adjustable E-field between the deflection plates 13, 14 it is possible to undo the deflection by the magnetic field for certain speeds. Only those fields for which this is the case pass through the aperture 16. All other charged particles hit the aperture 16.

A variation of the E-field in a certain area corresponds to a scanning of ion velocities in the velocity interval of interest. There is therefore a speed distribution function at the output of the mass spectrometer 17, the intensity of which depends on the size of the time interval in which the E field is traversed.

As in the arrangement according to FIG. 5, the signals are further processed by means of a secondary electron multiplier 18, an oscillograph 29 and a computer 22.

FIG. 9 shows a further arrangement which largely corresponds to the arrangement according to FIG. 7, for which reason blocks 25 and 26 have been omitted. In contrast to this, however, it is not designed for a measurement without famous. Rather, it has a tube 30 which is connected to the vacuum chamber 2 and is brought into contact with one end with the substance 40 to be measured. At one end of the tube there is a reference substance 31 which is in thermal contact with the sample 40 via the tube 30. Particles of the comparison substance 31 brought to the temperature of the sample 40 enter the vacuum chamber 2 through a small aperture 41 and the temperature of the comparison substance is determined.

In another variant of the invention, not shown here, the container with the substance to be measured in terms of temperature is located outside the vacuum chamber, only a small connecting path from the substance to the vacuum chamber having to be present.

FIG. 10 once again shows in detail the most important elements of FIGS. 5, 7 to 9. For the sake of clarity, however, the EB field combination according to FIG. 7 is not shown. The sample 4 in the container 3 is shown on the right side of a cylindrical housing 35 in which various devices are located. The housing 35 itself and all elements in it and the container 3 are under vacuum. A turbopump is indicated at 60 on the left-hand side.

An ionization device 52 with a control grid 53 is fastened to a support frame 38, 39 with two holding devices 50, 51. To the left of this ionization device 52 there are deflection plates 61, 62, which are fastened to the support frame 38, 39 with holding elements 45, 46. This deflector plate 61, 62 is followed by a diaphragm 42, which is also connected to the support frame 38, 39 via a holding element 63. The baffle plates 61, 62 perform the same task as the compensation capacitor 12 according to the embodiments of FIGS. 5, 7 to 9. With 64, 65 ceramic plates are designated which isolate the baffle plates 61, 62 from the frame 38, 39.

A further deflection unit is shown to the left of the diaphragm 42, the deflection plates of which are rotated by 90 degrees with respect to the deflection plates 61, 62. Because of this rotation, only one of the two deflection plates can be seen in FIG. 10, namely the deflection plate 66. These deflection plates, which correspond to the plates 13, 14 in FIG. 5, are connected via ceramic elements 47, 48 and holding elements 67, 68 connected to the support frame 38, 39.

A downstream diaphragm 43, which is connected to the support frame 38, 39 via holding elements 69, 70, corresponds functionally to the diaphragm 16 in FIG. 5. On this diaphragm 43, a device for generating an EB field combination can be provided, but here is not shown. 49 denotes a mass spectrometer on which there is an extraction grid 71 with which ions are sucked into the mass spectrometer 49.

The flange 37, 73 to the turbopump 60, in front of which there is a plate 44, forms the end of the housing 35, which is connected to this flange 37, 73 via a shoulder 76 and a connecting element 74. A corresponding connection exists on the right-hand side of the housing 35, where the flange 36 is connected to the housing 35 via a part 75 and an extension 77. A support ring 40a is connected upstream of the part 75.

For the determination of the absolute temperature according to the invention, it is in itself irrelevant whether first the speed distribution and then the mass or first the mass and then the speed distribution or whether mass and speed distribution are determined simultaneously. It is only important that a certain mass of a certain agreed speed distribution is assigned.

With the invention it is easily possible to check the absolute temperatures determined by a first measurement by a second measurement. For this purpose, for example, the absolute temperature is first determined via a first mass which is located in the substance to be measured. The same determination is then carried out using a second mass. If the two measurement results match, this is an indication that the measurement carried out is correct.

Claims

1. Device for measuring temperatures of gaseous, liquid or solid substances, characterized by the combination of the following features: a) a vacuum chamber (2); b) a substance (4, 40, 30) whose temperature is to be measured; c) a device for measuring the speed distribution of particles of the substance to be measured (4, 40, 30); d) a device which determines the absolute temperature of the substance (4) taking into account the determined speed distribution and the mass of the particles.

2. Device for measuring temperatures of gaseous, liquid or solid substances, characterized by the combination of the following features: a) a vacuum chamber (2); b) a substance (4, 40, 30) whose temperature is to be measured; c) a mass filter (17), which filters particles that emanate from the substance (4, 40, 30) according to their mass in such a way that only one type of particle appears at the outlet of the mass filter (17); . d) a device which determines the speed distribution of the particles passing through the mass filter (17); e) a device (22) which, taking into account the speed distribution and the mass of the particles determined by the mass filter (17), determines the absolute temperature of the particles.

3. Device according to Anspmch 1 or Anspmch 2, characterized in that the total pressure of the vacuum chamber (2) is less than 10 ^" Pa.

4. Apparatus according to Anspmch 1. characterized in that the mass of the substance to be measured (4, 40, 30) is taken into account as a known quantity by the device (22) for determining the absolute temperature.

5. Anspmch 1 or Anspmch 2, characterized in that the mass of the substance to be measured (4) measured by a mass measuring device (17) and the device (22) is supplied.

6. The device according to claim 1 or Anspmch 2, characterized in that the absolute temperature over the most likely speed (v _maχ ) is calculated from the determined speed distribution.

7. The device according to claim 1 or claim 2, characterized in that the absolute temperature over the average speed (v) is calculated from the determined speed distribution.

8. The device according to claim 1 or Anspmch 2, characterized in that the absolute temperature over the mean square speed (/ v ² ) is calculated from the determined speed distribution.

9. The device according to claim 1 or claim 2, characterized in that the determination of the absolute temperature is carried out by adapting the measured speed distribution to the theoretical Maxwell 'see speed distribution curve

10. Apparatus according to claim 1 or claim 2, characterized by a) an ionization device (33) which temporarily or continuously ionizes at least some of the particles of the substance (4); b) a deflection unit (13, 14, 15) which deflects the ionized particles depending on their speed and c) a device (17, 18) which registers the impact of particles depending on their mass.

11. The device according to Anspmch 10. characterized in that the deflection unit (27) has a magnetic field.

12. The device according to Anspmch 10, characterized in that an aperture (6) is arranged between the substance (4) and the ionization chamber (33).

13. The apparatus according to Anspmch 10, characterized in that the ionization device (33) generates charged particles, preferably electrons, which are accelerated perpendicular to the direction of travel of the particles of the substance (4). 14. The apparatus according to Anspmch 10, characterized in that between the ionization device (33) and the deflection unit (13,

14) a further deflection unit (12) is provided which compensates for the influence of the ionization on the transverse component of the speeds of the particles of the substance (4) by the ionization device (33).

15. Device according to Anspmch 10, marked by a) a device (18) which converts the incident and mass-selected particles into an electric current; b) a device (19) which represents this current as a function of the deflecting size of the deflecting unit (13, 14, 15); c) a device (20) which differentiates the current according to the deflecting variable and thereby determines the speed increase curve; d) a device (22) which calculates the absolute temperature of the substance (4) from the determined speed distribution curve.

16. The device according to Anspmch 10, characterized in that the deflection unit (13, 14, 15), which deflects the particles as a function of their speed, has two electrodes (13, 14) which with an at least occasionally linearly increasing voltage (U (t)) can be supplied.

17. The apparatus according to claim 10 and Anspmch 16, characterized in that in addition to the deflection unit (13, 14, 15) which generates an electrical field, a deflection unit (27) is provided which generates a static magnetic field, that is superimposed on the electric field.

18. The apparatus according to Anspmch 1 or claim 2, characterized in that the substance to be measured (4) is in a container (3), the container (3) being arranged in a vacuum chamber (2).

19. The device according to Anspmch 1 or Anspmch 2, characterized in that the substance to be measured (4) is located in a container which is arranged outside the vacuum chamber (2), with a passage for gaseous particles of the substance (4) from the container to the vacuum chamber is provided.

20. The apparatus according to claim 1 or claim 2, characterized in that the substance to be measured (6) is outside the vacuum chamber and with a tube (30) has thermal contact (31) via an aperture (32) with the vacuum chamber (2) communicates.

21. The apparatus according to claim 1, characterized by a) an ionization device (8, 9, 10, 24) which, within a short period of time relative to the flight time of a particle, from the substance (4) to the device for detecting the speed distribution Part of a beam of particles ionized; b) a device (17, 28, 25) distant from the ionization device (8, 9, 10, 24) by a distance L, which device receives an ensemble of ionized particles and the number of impinging particles per mass selected Unit of time determined; c) a device (26) which calculates the absolute temperature from the arrival time distribution of the particle ensemble determined in this way, which corresponds to the velocity distribution of the impacting particles.

21. The device according to Anspmch 2, characterized in that the mass filter (17) is a quadmolar mass spectrometer.

22. Device according to Anspmch 21, characterized in that the egg device for detecting the speed distribution contains a mechanical chopper instead of an ionization device.

23. The device according to Anspmch 22, characterized in that the determination of the speed distribution is carried out by measuring the flight time of the particles whose

Starting time is specified via a mechanical chopper.

24. The device according to Anspmch 1 or Anspmch 2, characterized in that the speed distribution is determined for a first mass of the substance (4) and for a second mass of the substance (4) and that the two masses or speed distribution absolute absolute temperatures.