CN106068453B

CN106068453B - Magnetic method for determining the concentration of a vapor and device for carrying out the method

Info

Publication number: CN106068453B
Application number: CN201580012732.5A
Authority: CN
Inventors: M.朗
Original assignee: Aixtron SE
Current assignee: Aixtron SE
Priority date: 2014-02-17
Filing date: 2015-02-03
Publication date: 2019-12-31
Anticipated expiration: 2035-02-03
Also published as: KR20160120299A; CN106068453A; TW201534916A; DE102014101971A1; WO2015121105A1; TWI655430B

Abstract

The invention relates to a device and a method for determining the concentration of a vapor in a measurement chamber, in particular for determining or regulating the flow rate of the vapor transported by a carrier gas through the measurement chamber (3), by using the paramagnetic or diamagnetic properties of the vapor, wherein the measurement chamber (3) is arranged in a coil that can be energized by an alternating current, and an evaluation circuit provides a measurement value of the magnetic susceptibility that depends on the magnetism of the gas. The coil is a primary coil (1) of a transformer and a measuring chamber (3) is also arranged in a secondary coil (2) of the transformer. The evaluation circuit measures the alternating voltage transmitted to the secondary coil (2) and forms a measurement value from the transmission properties of the transformer, which are influenced by the magnetic susceptibility of the gas. The invention also relates to a device for evaporating liquid or solid raw materials having a heatable evaporator, and to a method for producing a vapor of solid or liquid raw materials conveyed in a carrier gas.

Description

Magnetic method for determining the concentration of a vapor and device for carrying out the method

The invention relates to a device for determining the concentration of a vapor in a measurement chamber, in particular for determining or regulating the flow rate of a vapor transported by a carrier gas through the measurement chamber (by using the paramagnetic or diamagnetic properties of the vapor), wherein the measurement chamber is arranged in a coil arrangement having at least one coil that can be energized by an alternating current, and an evaluation circuit provides a measurement value of the magnetic susceptibility that depends on the magnetic properties of the gas.

The invention also relates to a method for determining the concentration of a vapor in a measurement chamber, in particular for determining or regulating the flow rate of a vapor transported by a carrier gas through the measurement chamber (by using the paramagnetic or diamagnetic properties of the vapor), wherein the measurement chamber is arranged in a coil arrangement having at least one coil that can be energized by an alternating current, and an evaluation circuit provides a measurement value of the magnetic susceptibility that depends on the magnetic properties of the gas.

Devices and methods of the aforementioned form are known from US3076929 or DE 3544966. The measuring cell is located in a coil arrangement, which constitutes the primary and secondary coil of the transformer. The primary coil is energized with an alternating current. The measured value can be obtained from the voltage induced in the secondary coil.

DE102011051931a1 discloses a device for depositing OLEDs on a substrate by means of the OVPD method. The substrate is located on a cooled receptacle, on which the vaporous starting material introduced into the process chamber condenses. The delivery of the vapor takes place by means of a carrier gas, which is fed into an inlet device having a shower-head-like outlet nozzle, through which the carrier gas vapor mixture enters the process chamber. The inlet means, like the entire upstream supply line, is heated to a temperature above the condensation temperature of the vapor but below the decomposition temperature of the vapor. The vapor generation is carried out by means of an evaporator, which evaporates the solid and liquid starting materials. The starting material is introduced as an aerosol into a carrier gas stream. The aerosol is introduced into the evaporation body, where heat is introduced for the vapour, so that it transforms the state of matter into the gaseous state. Two sensors are used here. The mass of the carrier gas fed into the evaporator can be determined by means of a first sensor which is part of the mass flow regulator. A sensor signal is generated by means of a second sensor arranged downstream of the evaporator, which sensor signal is dependent on the concentration of the vapor transported in the carrier gas.

DE102010014883a1, US2012/203529a1, US2011/304322a1, US7,752,886B2, US7,102,346B2, US6,389,880B1, WO92/07256a1, US5,369,980A, US4,988,946A, US4,875,357A, US4,808,921A, US4,563,894A, US4,432,226A disclose devices by means of which the concentration of a gas in a measurement chamber is determined by using the magnetic properties of the gas. The temperature dependence of the magnetic susceptibility of the gas is used in particular.

The object of the invention is to improve such a method or such a device in such a way that the measurement method is possible at gas temperatures in the range between 200 and 450 ℃ and at pressures in the range from 0.1 to 10 mbar.

With the device according to the invention and the method according to the invention, it is possible in particular to determine the partial pressure of the vapor in the carrier gas-vapor mixture.

Said technical problem is solved by the invention as specified in claims 1 and 2.

First, it is basically provided that a magnetic core, which is open and magnetically permeable, is provided in the coil arrangement, which is preferably formed by the primary and secondary coils of the transformer, in order to form an air gap. The measuring chamber is preferably arranged within the primary and secondary winding of the transformer. The evaluation circuit is designed in such a way that it can tap the alternating voltage transmitted to the secondary coil. If the concentration of the gas in the measurement chamber changes, it produces an effect on the transmission performance of the transformer. Changes in the concentration of the gas lead in particular to changes in the quality (Q-factor) or coupling (k-factor). The inductivity is changed by a change in the concentration of the gas in the measurement chamber.

The invention further relates to a device as described in the aforementioned DE102011051931a1, and to a method as described in said document. What is important for the process effect is a flow rate of the vapor which is as precise and constant in time as possible in the process chamber, wherein the flow rate depends on the one hand on the varying vapor occurrence rate due to tolerances and on the other hand on the carrier gas flow. In the prior art, sensor signals are generated by means of sensors arranged in the carrier gas-vapor mixture, which are influenced both by the carrier gas and by the vapor. It is desirable, however, to use a sensor in which the sensor signal is not influenced by the carrier gas.

The device according to the invention or the method according to the invention uses a first sensor which is arranged upstream of the inlet of the evaporator. A calibrated inlet flow of carrier gas flows through the inlet. In a heated evaporator, solid or liquid starting materials are converted into the gaseous state by heating. The incoming fluid (which flows through the evaporator) together with the vapor produced by the evaporation of the raw material exits the evaporator through the outlet as an outgoing fluid.

The first sensor, which is arranged upstream of the inlet in the flow direction, is designed to determine a first value which is associated with the mass flow of the incoming fluid. A second sensor downstream of the outlet in the flow direction is used to determine a second value that is dependent on the partial pressure of the vapor. A value corresponding to the mass flow rate of the vapor carried by the outgoing fluid is provided by a relationship of the two values with the aid of a computing device. According to the invention, the second sensor provides a sensor signal that depends on the magnetic susceptibility of the gas. The second sensor is therefore insensitive to the carrier gas, which has a negligible susceptibility compared to the vapour. For example, the magnetic susceptibility of the vapor is at least several times greater than the magnetic susceptibility of the carrier gas. The carrier gas may be nitrogen. The measuring chamber is preferably arranged in the coil arrangement of the transformer, the transmission properties of which change when the vapour concentration changes.

A preferred development of the invention has the following features: the magnetically conductive core is located within a coil assembly formed by a primary coil and a secondary coil. The core, which is in particular made of metal, in particular ferromagnetic metal, is preferably of two parts. An air gap remains between the two parts of the core. The primary coil and the secondary coil have a coaxial arrangement. The magnetic core extends along the axis of the coil arrangement. The core extends radially only over the central region of the measuring chamber, so that a radially spaced free space remains around the core up to the coil. The coil arrangement is formed by two coils wound on a cylindrical coil core. The core extends from both end sides up to the substantially axial coil center. Where the two parts of the core are spaced from each other. The end of the wick means thereat constitutes a tip. The two tips are opposed to each other with an air gap therebetween. The air gaps are sensitive to the concentration of paramagnetic or diamagnetic gases. The measurement chamber is disposed inside the housing. The housing encloses the coil arrangement. The housing has an end plate provided with a gas through hole. The core member may protrude into the measurement chamber in suspension from the end plate. The measuring chamber forms a flow channel which allows the carrier gas-vapor mixture to flow axially through the measuring chamber along the coil. The carrier gas may be nitrogen or another gas whose magnetic susceptibility is very small and which has in particular only diamagnetic properties. The vapor carried by the carrier gas has a relatively high magnetic susceptibility. It is preferably an aromatic hydrocarbon. The aromatic hydrocarbon as the OLED Precursor (prefrosor) is evaporated in a vaporizer. This is carried out at temperatures up to 450 ℃. The vapor is transported into the measurement chamber by a carrier gas. The carrier gas is provided by a mass flow regulator. The mass flow regulator provides a constant mass flow and is connected to a control circuit. The steam generator is also connected to the control circuit. The mass flow of the carrier gas and the mass flow of the vapour are thus adjustable. The measurement chamber has an analysis circuit that provides a measurement of the vapor concentration within the measurement chamber. Since the flow velocity of the carrier gas is known, the measured value corresponds to the flow rate of the vapor. The net-vapor flow rate to the coating apparatus can be adjusted to a constant value by changes in the vapor generation rate or carrier gas mass flow. The primary coil and/or the secondary coil are preferably connected to a capacitor as a resonant circuit. The primary coil is energized with an alternating current, the frequency of which may be the resonant frequency of the tank circuit. When the vapor concentration in the measurement chamber changes, the inductivity changes and the oscillation circuit is therefore detuned. The frequency of the excited alternating current may however also be slightly shifted with respect to the resonance frequency, so that the resonance frequency of the oscillating circuit approaches the excitation frequency when the vapor concentration in the measurement chamber changes. When the measurement chamber is empty (vacuum condition), the excitation frequency may be the resonance frequency of the capacitor-coil arrangement. Alternatively, however, the excitation frequency can also be the resonance frequency when the maximum permissible partial pressure of the paramagnetic gas is set in the measuring chamber. The amplitude of the voltage tapped at the secondary coil is therefore an indicator for measuring the vapor concentration of the vapor in the chamber. The coil arrangement of the transformer is referred to as a two-wire winding. A wire pair of two wires is wound around the cylindrical coil body. Which may be a single layer or a multilayer winding. A heating device is provided, by means of which the measuring chamber or the coil arrangement and the sensor, in particular with a housing, are heated to a temperature above the condensation temperature of the vapor. Furthermore, a temperature sensor is provided, by means of which the temperature of the vapor inside or outside the measurement chamber is measured.

Embodiments of the present invention are described below with reference to the accompanying drawings. In the drawings:

figure 1 shows a longitudinal sectioned perspective view of a sensor element according to the invention,

figure 2 shows a perspective view of the sensor housing,

figure 3 shows a longitudinal section through the sensor,

figure 4 shows a part of the circuit for exciting the primary coil and for tapping the sensor signal,

FIG. 5 schematically shows the voltage E associated with the resonant frequency₂Sensor signal of

Fig. 6 schematically shows the configuration of a vapor supply apparatus for an OLED coating apparatus.

Fig. 6 schematically shows an OLED coating apparatus. The carrier gas 15 is fed into the mass flow regulator 14. The mass flow regulator 14 obtains a mass flow regulation value from the control circuit 20. In accordance with the specified value, the mass flow regulator 14 provides a constant mass flow of the carrier gas, in particular nitrogen. The carrier gas is fed into the vapor generator 16 through a fluid channel 18.

Steam is generated in the steam generator 16 by heating a liquid or solid. The solids or liquids are fed from the storage vessel 17 into the steam generator 16. A sensor element 13 is arranged in a fluid channel 21, which fluid channel 21 connects the vapor generator 16 to a coating device 22. The sensor element 13 is able to determine the concentration of the vapor in the carrier gas-vapor mixture flowing through the fluid channel 21. The measured value is input to the control circuit 20. The vapor flow rate through the flow channel 21 into the coating apparatus 22 can be maintained at a constant value by variation of the vapor generation rate or carrier gas flow in the vapor generator 16.

In order to avoid condensation of the vapour, the fluid channel 21 and the sensor element 13 are kept at a temperature above the condensation temperature of the vapour.

In the vapor generator 16, aromatic hydrocarbons, in particular precursors for the coating process of the OLEDs, are vaporized. This vapor is supplied to the coating device 22 via the fluid channel 21. Where the substrate is placed on a cooled substrate holder and the precursor is condensed into an OLED layer on the substrate surface.

The sensor element 13 is shown in fig. 1 to 3. Having a primary coil 1 and a secondary coil 2. The two coils 1, 2 form a transformer. They are supported by a cylindrical coil support 8. The two coils 1, 2 are formed by pairs of wires extending parallel to each other. The wire pairs constitute a single layer winding around the coil support 8. The windings of the primary coil 1 and of the secondary coil 2 alternate with one another in the axial extension direction of the coil arrangements 1, 2. The coil devices 1, 2 are arranged in a housing. The housing is formed by a cylindrical casing 9 which surrounds the coil arrangements 1, 2 at a radial distance from one another. The two end faces of the housing are formed by end plates 7 which have openings 10 so that gas can flow through the measuring chambers 3 arranged in the coil arrangements 1, 2.

The connecting lines 11, 12 of the primary coil 1 and the secondary coil 2 pass out of the housing wall 9.

The coil arrangements 1, 2 are essentially air coil arrangements in which nail-like pins (which consist of ferromagnetic material) each project from two end plates 7 into the measuring chamber 3. Said pins constitute the parts 4 of the coil core. The core part 4 projects into the measuring chamber 3 in an overhanging manner. The ends of the core member 4, which respectively constitute the tips 5, are spaced apart from each other to constitute air gaps 6. The air gap 6 is located approximately at the axial center of the coil arrangement 1, 2.

The self-inductance of the transformer depends not only on the magnetic susceptibility of the core but also on the magnetic susceptibility of the gas flowing through the measuring chamber 3. The inductivity of the two coils also depends on the susceptibility of the gas in the measuring chamber. The magnetic properties of the gas inside the measuring chamber 3 however also influence the quality (Q factor) or the coupling (k factor) of the transformer.

Figure 4 shows a preferred circuit. Resistance R₁And R₂The unavoidable coil resistance of the primary coil 1 or the secondary coil 2 is characterized. Resistance R₁、R₂However, additional ohmic resistors can also be provided, which are each connected in the resonant circuit.

The first oscillating circuit is composed of a primary coil 1 and a capacitor C₁And (4) forming. The second oscillation circuit is composed of the secondary coil 2 and the capacitor C₂And (4) forming. The resonant frequencies of the two tanks may be the same. Thus forming a resonance curve with a unique tip as shown in fig. 5. Two oscillating circuits 1, C₁Or 2, C₂May however also differ slightly from each other. Thus forming a resonance curve having a double tip (refer to fig. 5).

The primary coil 1 being supplied with an alternating voltage E₁Or alternating current I₁A current flow, which is located in the resonance frequency of the resonant circuit of the primary coil 1 or the secondary coil 2. If a gas with paramagnetic properties passes throughA measuring chamber 3, two oscillators 1, C₁Or 2, C₂Becoming detuned. Secondary voltage E₂Where the amplitude of the signal changes. From the height of the amplitude, a value for the concentration or partial pressure of the vapor located in the measuring chamber 3 can be obtained.

Since oxygen has a relatively high paramagnetic susceptibility compared to nitrogen, not only the aromatic hydrocarbon concentration can be determined by means of the sensor element 13. It is also possible that a gas containing oxygen can be detected by means of the sensor element. The sensor element 13 is therefore also suitable as a leak detector.

The magnetic susceptibility within the air gap 6 may be two orders of magnitude less than the magnetic susceptibility in the axially adjacent region in which the ferromagnetic core 4 is located. The coil arrangement is also highly sensitive with respect to changes in the magnetic susceptibility in the air gap 6. The primary coil 1 is excited by means of an alternating voltage which deviates only slightly from the resonant frequency of the two resonant circuits, i.e. when no vapor is present in the measuring chamber 3.

The above-described embodiments serve to illustrate the inventive content contained in the present application, which improves the prior art independently of one another at least by the following combinations of features:

a device is characterized by a magnetically conductive core 4 which is arranged in a coil arrangement formed by a secondary coil 2 and a primary coil 1 and is interrupted in order to form an air gap (6).

A method is characterized in that a magnetically conductive core 4, which is interrupted in order to form an air gap (6), is arranged in a coil arrangement formed by a secondary coil 2 and a primary coil 1.

An arrangement or a method is characterized in that the coil is a primary coil 1 of a transformer, a measuring chamber 3 is also arranged in a secondary coil 2 of the transformer, and an evaluation circuit 20 taps an alternating voltage transmitted to the secondary coil 2 and forms a measurement value from the transmission properties of the transformer influenced by the magnetic susceptibility of the gas.

An arrangement or method is characterised by a fluid passage extending coaxially with the axis of the coil arrangement 1, 2, in which a magnetically conductive core 4 is provided.

An arrangement or method is characterized in that an air gap 6 is arranged at the axial centre of the coil arrangement 1, 2.

A device or method characterised in that a core formed of two parts 4 is surrounded by radial free space.

A device or method characterised in that the elements 4 of the wick have mutually directed tips 5.

A device or method is characterized in that two parts 4 of the core each project into the measuring chamber 3 in an overhanging manner from an end plate 7 of a housing 7, 9 surrounding the measuring chamber 3, in particular having gas passage openings 10.

An arrangement or method characterised by a primary winding 1 and/or a secondary winding 2 and a capacitor C₁、C₂The resonant circuit is formed, wherein it is provided in particular that the frequency of the alternating current fed into the primary coil 1 in the empty measuring chamber 3 or in the measuring chamber 3 filled with the maximum partial pressure of the paramagnetic gas is the resonant frequency of the resonant circuit or differs slightly from the resonant frequency.

An arrangement or a method is characterized in that the primary coil 1 and the secondary coil 2 are formed by bifilar windings, which in particular have a cylindrical shape.

An arrangement or method is characterized by a heating device 10, by means of which heating device 10 the coil arrangement 1, 2 is heated to a temperature above the condensation temperature of the vapour and/or a temperature sensor 23 for determining the temperature of the vapour.

A device, characterized in that the second sensor is a sensor element 13 influenced by the magnetic susceptibility of the vapor, in particular according to one of the preceding claims.

A method is characterized in that a second sensor 13 provides a sensor signal which is influenced by the magnetic susceptibility of the magnetic properties of the vapor, wherein the magnetic susceptibility of the magnetic properties of the vapor is significantly greater in value than the magnetic susceptibility of the magnetic properties of the carrier gas, in particular at least 10 times greater than the magnetic susceptibility of the magnetic properties of the carrier gas.

A method, characterized in that nitrogen is used as carrier gas and the vapor is a precursor of the OLED.

All the disclosed features are essential features of the invention as such, but may also be combined with each other. While the accompanying/subordinate priority documents (copies of the prior application) are fully contained in the disclosure of the present invention, the features of these materials may be included for this purpose in the claims of this application. The dependent claims form inventive improvements to the prior art with their features, and are especially applicable in divisional applications based on these claims.

List of reference numerals

1 primary coil

2 secondary coil

3 measuring chamber

4 coil core

5 point of the design

6 air gap

7 end plate

8 coil support

9 casing wall

10 gas through hole

11 connecting wire

12 connecting wire

13 sensor element

14 mass flow regulator

15 carrier gas

16 steam generator

17 storage container

18 fluid channel

19 heating device

20 control circuit

21 fluid channel

22 coating apparatus

23 temperature sensor

C₁Capacitor with a capacitor element

C₂Capacitor with a capacitor element

E₁Resistance voltage

E₂Second order voltage

I₁Alternating current

R₁Resistance (RC)

R₂Resistance (RC)

Claims

1. A device for determining the concentration of a vapor in a measurement chamber (3) and for determining or regulating the flow rate of the vapor transported through the measurement chamber (3) by a carrier gas by using the paramagnetic or diamagnetic properties of the vapor, wherein the measurement chamber (3) is arranged in a coil arrangement with at least one primary coil (1) which can be energized by an alternating current, a secondary coil (2) and a magnetically conductive core (4) which is open to form an air gap (6), and an analysis circuit (20) provides a measurement of the magnetic susceptibility which depends on the magnetism of the gas, characterized in that the device for determining the concentration of the vapor in the measurement chamber (3) and for determining or regulating the flow rate of the vapor transported through the measurement chamber (3) by the carrier gas by using the paramagnetic or diamagnetic properties of the vapor comprises a housing which is equipped at its end plates with gas through-holes (10), the coil arrangement being located inside the housing, the gas passage holes (10) define a fluid passage for gas to flow into the housing, the axis of the coil arrangement being parallel to the gas flow, the coil arrangement being a hollow coil arrangement which leaves a radial gap with the magnetically conductive core (4).

2. Device for determining the concentration of a vapor in a measurement chamber (3) and for determining or regulating the flow rate of the vapor transported by a carrier gas through the measurement chamber (3) by using the paramagnetic or diamagnetic properties of the vapor according to claim 1, characterized in that the primary coil is the primary coil (1) of a transformer and the measurement chamber (3) is also arranged in the secondary coil (2) of the transformer, and in that the evaluation circuit taps off the alternating voltage transmitted to the secondary coil (2) and the transmission properties of the transformer influenced by the magnetic susceptibility of the gas constitute the measured values.

3. Device for determining the concentration of a vapour in a measurement chamber (3) and for determining or regulating the flow rate of the vapour conveyed by a carrier gas through the measurement chamber (3) by using the paramagnetic or diamagnetic properties of the vapour according to claim 1, characterized by a flow channel extending coaxially to the axis of the coil arrangement, in which flow channel a magnetically conductive core (4) is arranged.

4. Device for determining the concentration of a vapour in a measurement chamber (3) and for determining or regulating the flow rate of the vapour transported by a carrier gas through the measurement chamber (3) by using the paramagnetic or diamagnetic properties of the vapour according to claim 1, characterized in that the air gap (6) is arranged at the axial center of the coil arrangement.

5. Device for determining the concentration of a vapour in a measurement chamber (3) and for determining or regulating the flow rate of the vapour transported through the measurement chamber (3) by a carrier gas, by using the paramagnetic or diamagnetic properties of the vapour, according to claim 1, characterized in that the core consisting of two parts is surrounded by a radial free space.

6. Device for determining the concentration of a vapour in a measurement chamber (3) and for determining or regulating the flow rate of the vapour transported through the measurement chamber (3) by a carrier gas, by using the paramagnetic or diamagnetic properties of the vapour, according to claim 5, characterized in that the parts of the wick have mutually directed tips (5).

7. The device for determining the concentration of a vapor in a measurement chamber (3) and for determining or regulating the flow rate of the vapor transported by a carrier gas through the measurement chamber (3) by using the paramagnetic or diamagnetic properties of the vapor according to claim 6, characterized in that the two parts of the core each project into the measurement chamber (3) in suspension from an end plate (7) with gas through-holes (10) of a housing (7, 9) surrounding the measurement chamber (3).

8. Device for determining the concentration of a vapour in a measurement chamber (3) and for determining or regulating the flow rate of the vapour transported by a carrier gas through the measurement chamber (3) by using the paramagnetic or diamagnetic properties of the vapour according to claim 1, characterized in that the primary coil (1) and/or the secondary coil (2) and the capacitor (C)₁、C₂) Forming an oscillation circuit.

9. The device for determining the concentration of a vapor in a measurement chamber (3) and for determining or regulating the flow rate of the vapor transported by a carrier gas through the measurement chamber (3) by using the paramagnetic or diamagnetic properties of the vapor according to claim 8, characterized in that the frequency of the alternating current fed into the primary coil (1) in an empty measurement chamber (3) or in a measurement chamber (3) filled with the maximum partial pressure of the paramagnetic gas is the resonance frequency of the oscillatory circuit or is slightly different from said resonance frequency.

10. The device for determining the concentration of a vapor in a measurement chamber (3) and for determining or regulating the flow rate of the vapor transported by a carrier gas through the measurement chamber (3) by using the paramagnetic or diamagnetic properties of the vapor according to claim 1, characterized in that the primary coil (1) and the secondary coil (2) are formed by bifilar windings, which have a cylindrical shape.

11. Device for determining the concentration of a vapour in a measurement chamber (3) and for determining or regulating the flow rate of the vapour conveyed through the measurement chamber (3) by a carrier gas by using the paramagnetic or diamagnetic properties of the vapour according to claim 1, characterized by a heating device (19), by means of which heating device (19) the coil arrangement can be heated to a temperature above the condensation temperature of the vapour.

12. The device for determining the concentration of a vapor in a measurement chamber (3) and for determining or regulating the flow rate of the vapor transported by a carrier gas through the measurement chamber (3) by using the paramagnetic or diamagnetic properties of the vapor according to the preceding claim 11, characterized by a sensor (23) for determining the temperature of the vapor.

13. A method for determining the concentration of a vapour in a measurement chamber by using the paramagnetic or diamagnetic properties of the vapour and for determining or adjusting the flow rate of the vapour conveyed by a carrier gas through the measurement chamber (3), wherein the measuring chamber (3) is arranged in a coil arrangement having a primary coil (1) which is energized by an alternating current, a secondary coil (2) and a magnetically conductive core (4) which is interrupted in order to form an air gap (6), and the analysis circuit (20) provides a measure of the magnetic susceptibility dependent on the magnetism of the gas, characterized in that the coil arrangement is arranged in a housing having an end face with a gas passage opening (10), wherein the gas through-hole (10) defines a fluid passage through which a gas flow flows, the axis of the coil device is parallel to the air flow, the coil device is a hollow coil device, and a radial gap is reserved between the coil device and the magnetic conductive core (4).

14. A device for evaporating a liquid or solid starting material having a heatable evaporator (16), wherein an inlet fluid of a carrier gas enters the evaporator via an inlet, flows through the evaporator (16) and exits the evaporator (16) as an outlet fluid via an outlet together with the vapor produced by evaporation of the starting material, having a first sensor (14) arranged in the flow direction upstream of the inlet, which is designed to determine a first value which is correlated with the mass flow of the inlet fluid, having a second sensor (13) arranged in the flow direction downstream of the outlet, which is used to determine a second value which is dependent on the partial pressure of the vapor, having a computing device which, by correlation of the two values, provides a value which corresponds to the mass flow of the vapor conveyed in the outlet fluid, characterized in that the second sensor is a sensor element which can be influenced by the magnetic susceptibility of the vapour, wherein the sensor element is designed as a device according to one of claims 1 to 12 for determining the concentration of the vapour in the measurement chamber (3) and for determining or regulating the flow rate of the vapour conveyed by the carrier gas through the measurement chamber (3) by using the paramagnetic or diamagnetic properties of the vapour.

15. A method for generating a vapor of a solid or liquid starting material conveyed in a carrier gas, comprising the steps of:

heating an evaporator (16) having an inlet and an outlet;

inputting an inlet fluid with a carrier gas into a vaporizer (16) through an inlet;

evaporating solid or liquid raw materials in an evaporator (16);

passing the so generated vapour through an outlet as an effluent stream together with a carrier gas;

determining a first value associated with a mass flow of carrier gas into the fluid by means of a first sensor (14);

determining a second value influenced by the partial pressure of the vapour in the outgoing fluid by means of a second sensor (13);

calculating a value corresponding to the mass flow of the vapour conveyed in the outgoing fluid by correlation of the two values determined by means of the two sensors (13,14), characterized in that the second sensor (13) is designed to provide a sensor signal influenced by the magnetic susceptibility of the vapour by the magnetic nature of the carrier gas, which is significantly greater in value than the magnetic susceptibility of the carrier gas, at least by a factor of 10 greater than the magnetic susceptibility of the carrier gas, by using the paramagnetic or diamagnetic properties of the vapour to determine the concentration of the vapour in the measurement chamber (3) and for determining or adjusting the flow rate of the vapour transported by the carrier gas through the measurement chamber (3), as claimed in any one of claims 1 to 12.

16. The method of claim 15, wherein nitrogen is used as a carrier gas and the vapor is a precursor to the OLED.