Ionization system for ionizing gases, associated spaceflight propulsion unit, method and use

Abstract

The invention relates to an ionization system (2) for ionizing gases, comprising an ionization chamber (4) and, connected to the ionization chamber (4), a feed line (8) for feeding neutral gas into the ionization chamber (4). According to the invention, a feed line (8) is assigned a predischarge stage (12) designed to pre-ionize the gas flowing through the feed line (8) and to generate free electrons, and the ionization chamber (4) is assigned a main discharge stage (14) designed to accelerate and impact-ionize the free electrons, in particular substantially over the entire volume (V) of the neutral gas, wherein the predischarge stage (12) and the main discharge stage (14) have a common coil assembly (15). The invention furthermore relates to an associated spaceflight propulsion unit (100) and to a spacecraft (300), to a use and to a method (200).

Description

[0001] Ionization system for ionizing gases, relevant space propulsion, method and use

[0002] The invention relates to an ionization system for ionizing gases, comprising an ionization chamber and a supply line connected to the ionization chamber for the supply of neutral gas to the ionization chamber. The invention further relates to a space propulsion system for propelling a spacecraft with such an ionization system, a spacecraft with such a space propulsion system, the use of such an ionization system, and a related method. Ionization systems of the type described above are known from the prior art and are used to ionize a neutral gas and generate a plasma. A plasma is understood to be an ionized gas consisting of a mixture of ions, electrons, and neutral particles. These particles are in constant interaction with each other and with photons, exhibiting various energy and excitation states.Ionization systems are used in measurement technology, for example in gas chromatographs. It is known to pre-ionize gas using a pre-discharge stage and then accelerate and impact-ionize this pre-ionized gas in an ionization chamber using a main discharge stage.

[0003] The application of such ionization systems is, however, narrowly limited to metrological applications. Furthermore, the complexity of such systems is as high as their energy consumption relative to the plasma generated. It is also known from the prior art to use ionization systems for propelling spacecraft, such as satellites. However, the ionization systems of the type described above, known from the field of metrology, are, due to their complexity and control requirements, not suitable or only partially suitable for ionizing gas intended for use as propulsion for such a spacecraft. Efficient plasma generation remains a technical challenge with existing designs.

[0004] Against this background, the invention was based on the objective of further developing an ionization system of the type described above in such a way as to eliminate the disadvantages found in the prior art as far as possible. In particular, an ionization system was to be provided which enables the ionization of a gas in a particularly compact, energy-efficient and holistic manner.

[0005] According to the invention, the problem in an ionization system of the type mentioned above is solved by associating a pre-discharge stage with the supply line, which is configured to pre-ionize the gas flowing through the supply line and to generate free electrons, and wherein a main discharge stage is associated with the ionization chamber, which is configured to accelerate and impact ionize the free electrons, in particular substantially over the entire volume of the neutral gas, wherein the pre-discharge stage and the main discharge stage have a common coil arrangement.

[0006] The invention is based on the understanding that the two-stage ionization system enables particularly efficient plasma ignition. After plasma ignition by the pre-discharge stage, the main discharge stage can sustain the plasma on its own. Furthermore, instead of using independent systems for generating the electric fields in the pre-discharge and main discharge stages, a common coil arrangement is proposed for generating the electric fields in both stages. This results in a particularly compact ionization system that is also significantly less complex than existing systems. The system can be easily scaled and thus used for a wide variety of aerospace applications.Furthermore, by providing a common coil arrangement for the pre-discharge stage and the main discharge stage, an improved efficiency is achieved compared to existing systems.

[0007] According to one embodiment, the main discharge stage comprises a secondary coil winding around the ionization chamber and a primary coil winding around the secondary coil, the secondary coil and the primary coil being part of the common coil arrangement. Preferably, at least two capacitive electrodes are associated with the lead wire, the capacitive electrodes being formed by the ends of the secondary coil or being conductively connected to the secondary coil. In other words, it is proposed that the secondary coil serves as the ionizing electrode for both the pre-stage and the main stage. The induced current generated in the secondary coil creates a vortex field inside the coil, which causes an inductively coupled gas discharge within the ionization chamber.

[0008] The ends of the secondary coil are thus positioned as two electrodes in the area of ​​the lead wire and adjacent to the ionization chamber. The high voltage generated in the lead wire causes a local discharge there. Furthermore, the high-frequency alternating current induced in the secondary coil generates a high-frequency alternating field inside the coil. Since the secondary coil surrounds the ionization chamber, these alternating fields also exist inside the chamber. The plasma capacitively generated locally in the lead wire provides the basis for further ionization within the chamber. This further ionization is also known as volume ionization. One advantage of this arrangement is that it enables the ionization of neutral gases at higher pressures in the range of 0.1 to 5 bar.

[0009] In other words, the pre-discharge stage enables the generation of a local plasma through capacitive discharge, which in turn forms the basis for the inductive volume discharge and plasma formation in the ionization chamber. The neutral gas, partially ionized in the feed line, flows into the ionization chamber. Within the ionization chamber, the secondary coil induces closed-circuit alternating fields. These accelerate the partially ionized neutral gas, preferably ionizing the entire neutral gas via electron impact. This allows for particularly energy-efficient ionization of the neutral gas under higher pressure. According to one embodiment, the ionization chamber is made of a dielectric material, particularly quartz or ceramic, thus ensuring adequate electrical insulation.

[0010] According to one embodiment, the secondary coil and the primary coil are air-coupled and / or electromagnetically loosely coupled. In particular, the secondary coil and the primary coil do not have a common core.

[0011] According to one embodiment, the secondary coil and the primary coil are operated at a common resonant frequency. By operating the secondary coil and the primary coil at a common resonant frequency, electrical supply energy for plasma generation can be transferred in a particularly energy-efficient and loss-free manner.

[0012] According to one embodiment, the primary coil and the secondary coil generate a vortex field inside the ionization chamber. Preferably, the primary coil is operated with an alternating voltage of a frequency between 1 and 60 MHz. This frequency range has proven to be advantageous for the ionization of neutral gas.

[0013] According to one embodiment, the primary coil has a first number of turns and the secondary coil a second number of turns, with the ratio of the number of turns in the primary coil to the number of turns in the secondary coil being 1:10 or greater. This allows the generation of the correspondingly high-frequency alternating field inside the ionization chamber. In other words, the number of turns in the secondary coil is large compared to the primary coil, resulting in a high discharge voltage in the pre-discharge stage. The voltage applied between the coil ends of the secondary coil in the pre-discharge stage is used for the pre-ionization of the neutral gas, a process also known as high-voltage breakdown.

[0014] The electrodes are preferably isolated from the ionization chamber. According to one embodiment, the electrodes are designed as perforated electrodes. The isolation of the electrodes from the ionization chamber can be achieved, for example, by means of a holding structure in which the electrodes are accommodated, the holding structure being made of a non-conductive material. By isolating the electrodes from the ionization chamber, for example by means of a dielectric, electrode erosion during discharge is prevented. According to one embodiment, the primary coil and the secondary coil form a common transformer assembly. The transformer quality factor is preferably reduced when plasma is present in the ionization chamber. In other words, the presence of plasma in the ionization chamber reduces the transformer quality factor and thus the high voltage at the pre-discharge stage.The ionization system is thus adjusted so that after the formation of the plasma in the ionization chamber, no further breakdowns occur at the pre-discharge stage.

[0015] According to one embodiment, the transformer quality factor is increased when the plasma concentration in the ionization chamber decreases or the plasma in the ionization chamber is completely or partially extinguished. Thus, in the event of plasma extinction in the ionization chamber, the transformer quality factor increases. The voltage at the ends of the secondary coil, and therefore in the pre-discharge stage, also increases accordingly, so that the gas in the pre-discharge stage is pre-ionized, which then results in the main discharge stage being reignited. Thus, by adjusting the transformer quality factor, which depends on the presence of plasma, it can be ensured that the plasma always reignites after extinction. This achieves a continuous and robust plasma formation. According to one embodiment, the ionization system includes a pressure regulating device configured to supply the neutral gas to the feed line at a pressure of 0.1–5 bar.

[0016] According to one embodiment, the ionization system has a magnetic array that surrounds and / or is located within the ionization chamber. The arrangement of the magnetic array is based on the understanding that the described ionization system primarily—but not exclusively—serves the ionization of neutral gases under high pressure. The plasma formed from the neutral gas increases in density analogously with the gas pressure. This, in turn, significantly increases turbulence within the plasma. Furthermore, the intensity of plasma-wall contacts also increases with increasing plasma density. This poses a challenge because the intensity of the potential corrosive effect of the plasma on the wall increases, and plasma-wall recombination, i.e., reverse processes of ionization, can lead to plasma extinction.The proposed magnetic arrangement can reduce or avoid these negative effects by subjecting the plasma to changes in direction, thereby avoiding wall contacts or mitigating their intensity.

[0017] Preferably, the magnetic arrangement comprises one or more magnets oriented such that the magnetic field lines of the magnets penetrate the ionization chamber parallel to a longitudinal axis of the ionization chamber. In this way, charged particles move unimpeded along the magnetic field lines and are deflected into circular paths perpendicular to the magnetic field lines. This results in unimpeded plasma movement towards the source outlet and suppressed movement transversely to it towards the bounding walls of the ionization vessel.

[0018] By aligning the charged plasma particles with the magnetic field lines, the entire plasma is aligned and turbulence is prevented. Suppressing the movement of charged plasma particles towards the wall of the ionization vessel prevents plasma contact with the wall and the resulting negative effects, such as corrosion and wall recombination. Preferably, the magnetic arrangement consists of two separate magnetic systems, one surrounding the ionization chamber and the other located inside the ionization chamber.

[0019] According to one embodiment, the magnet arrangement thus comprises an external magnet system that surrounds the ionization chamber in a ring-like fashion. According to one embodiment, the external magnet system can comprise a magnet with a closed surface or spaced-apart ring magnets. Magnets can generally be either electromagnets, preferably in the form of DC-carrying coils, or permanent magnets.

[0020] According to one embodiment, the magnet arrangement includes an internal magnet system located within the ionization chamber. This serves essentially two purposes. Firstly, the outer shape of the structure itself reduces the interior space of the ionization vessel for the plasma. In this embodiment, the ionization space is thus limited to a cylindrical region directly below the ionization coils. This increases efficiency. The high-frequency electric fields emanating from the ionization coils, which are used for ionization, have a limited penetration depth into conductive substances such as plasma. Therefore, the central cylindrical magnet system restricts the ionization space to a region where the external ionizing electromagnetic fields can penetrate the plasma.The field-free inner region of the ionization chamber is excluded from plasma from the outset.

[0021] Furthermore, the magnetic fields emanating from the inner magnet system fulfill the same function as already described with reference to the outer magnet system. The plasma can be stabilized by the inner magnet system to prevent turbulence. Additionally, the inner magnet system, located within the ionization chamber, is intended to prevent or reduce plasma-wall contact.

[0022] The inner magnet system is preferably arranged coaxially with the outer magnet system. Both magnet systems preferably extend along the longitudinal axis, in particular completely along the longitudinal extent of the ionization chamber. The length of the inner magnet system along the longitudinal axis preferably corresponds to the length of the outer magnet system along the longitudinal axis.

[0023] Both the inner and outer magnetic systems serve to increase the efficiency of the gas discharge itself. By magnetically deflecting the free electrons accelerated by the ionization field, their path in the plasma is artificially widened, which benefits the rate of impact ionization.

[0024] According to one embodiment, a magnetic nozzle is arranged adjacent to the primary coil at an output of the plasma source, which is formed, in particular, at least partially by the outer and inner magnetic systems. In this way, the outer and inner magnetic systems are extended, in a sense, towards an output of the plasma source beyond the ionization system. In this region, that is, at the output of the plasma source, the magnetic structure additionally serves for the directed extraction of plasma from the plasma source. The charged plasma particles, which in this region are no longer influenced by the ionizing electromagnetic high-frequency fields of the ionization system, align themselves in a spiral pattern around the magnetic field lines and thus flow directed out of the plasma source. The invention has been described above with reference to an ionization system.In another aspect, the invention relates to a space propulsion system for powering a spacecraft. The invention solves the problem described above with regard to the space propulsion system by providing it with an ionization system according to one of the preceding claims. The space propulsion system utilizes the same advantages and preferred embodiments as the ionization system according to the invention, and vice versa. Reference is made to the above statements, the content of which is incorporated herein by reference.

[0025] The space propulsion system is particularly suitable as an orbital propulsion system for satellites in Earth orbit, for example for communication satellites, for so-called in-space Transportation Vehicles (ISTV) or as the main propulsion system for interplanetary exploration probes.

[0026] Since the ionization system and the corresponding propulsion system are specifically designed to generate high thrusts through the ionization of gases under higher pressure and the resulting extraction of larger quantities of particles per unit of time, satellites and orbital platforms with higher mass and / or the requirement of high acceleration are the preferred application. This means that such a propulsion system can be used for medium- to heavy-weight satellites and also for satellites where prolonged exposure to critical regions of space, such as the Van Allen belts, would endanger the payload.

[0027] In another aspect, the invention relates to a spacecraft with a space propulsion system. The invention solves the problem described above with regard to the spacecraft by providing it with a space propulsion system according to the exemplary embodiment described above. The spacecraft is preferably a satellite for Earth orbit, in particular a communications satellite, an in-space transportation vehicle (ISTV), or an interplanetary exploration probe. The spacecraft also benefits from the same advantages and preferred embodiments as the ionization system and the space propulsion system according to the invention, and vice versa. In this respect, reference is made to the above explanations, and their content is incorporated herein.

[0028] In a further aspect, the invention relates to the use of an ionization system according to one of the preceding embodiments for propelling a spacecraft. The ionization system is particularly suitable as an orbital propulsion system for satellites in Earth orbit, for example for communication satellites, for so-called in-space transportation vehicles (ISTVs), or also as the main propulsion system for interplanetary exploration probes.

[0029] The application also takes advantage of the same benefits and preferred embodiments as the ionization system, the space propulsion system, and the spacecraft according to the invention, and vice versa. Reference is made to the above explanations in this regard, and their content is incorporated herein.

[0030] In another aspect, the invention relates to a method for ionizing a gas by means of an ionization system which is designed from two discharge stages, in particular an ionization system according to one of the above embodiments.

[0031] The invention solves the problem described above with regard to the method by comprising the following steps: spatially limited pre-ionization of the neutral gas by means of a pre-discharge stage, acceleration and impact ionization of the pre-ionized gas by means of a main discharge stage, essentially over the entire volume of the neutral gas, wherein the pre-discharge stage and the main discharge stage have a common coil arrangement.

[0032] This method also utilizes the same advantages and preferred embodiments as the ionization system according to the invention, the space propulsion system, the spacecraft, and their respective uses, and vice versa. In this regard, reference is made to the above explanations, and their content is incorporated herein.

[0033] The invention is described in more detail below with reference to a preferred embodiment and the accompanying figures. These figures show:

[0034] Fig. 1 shows an embodiment of an ionization system according to the invention in a sectional view;

[0035] Fig. 2 shows a detailed view of a pre-discharge stage in a sectional view;

[0036] Fig. 3 shows a schematic representation of an ionization system according to the invention; Fig. 4 shows a schematic representation of a common coil arrangement of the ionization system according to the invention;

[0037] Fig. 5a shows a further embodiment of an ionization system according to the invention in a perspective view;

[0038] Fig. 5b shows the embodiment of the ionization system according to the invention as shown in Fig. 5a in a sectional view;

[0039] Fig. 6 shows an embodiment of a spacecraft according to the invention with a space propulsion system which has an ionization system according to the invention;

[0040] Fig. 7 shows an embodiment of a method according to the invention, represented as a block diagram.

[0041] Fig. 1 shows an ionization system 2 for ionizing gases. The ionization system 2 has an ionization chamber 4 and a feed line 8 connected to the ionization chamber 4. The feed line 8 serves to supply neutral gas to the ionization chamber 4. A pre-discharge stage 12 is associated with the feed line 8. The pre-discharge stage 12 is configured to pre-ionize the gas flowing through the feed line 8 and to generate free electrons, so that plasma is formed in the region of the pre-discharge stage 12.

[0042] The ionization chamber 4 is associated with a main discharge stage 14. The main discharge stage 14 is configured to accelerate and impact ionize the pre-ionized free electrons, thus generating further plasma in the ionization chamber 4. Essentially, the acceleration of the free electrons and the impact ionization in the ionization chamber 4 occur over the entire volume V of the neutral gas. The pre-discharge stage 12 and the main discharge stage 14 share a common coil arrangement 15. In the pre-discharge stage 12, the neutral gas is thus pre-ionized to a limited extent, producing free electrodes.

[0043] The main discharge stage 14 has a secondary coil 18 that winds around the ionization chamber 4. A primary coil 20 is wound around the secondary coil 18. The secondary coil 18 and the primary coil 20 are part of the common coil assembly 15. Preferably, the common coil assembly 15 consists of the secondary coil 18 and the primary coil 20. The secondary coil 18 and the primary coil 20 are air-coupled.

[0044] The ionization chamber 4 is formed by an ionization chamber housing 7. This housing is closed on one side opposite the gas supply line 8 by a base plate 32. An insulating cylinder 6, which contains or is formed from a dielectric material, for example quartz, is also arranged between the secondary stage 18 and the primary coil 20. In the embodiment shown in Fig. 1, the gas supply line 8 is formed by a supply pipe 10. The base plate 32 has recesses 34, which serve, for example, for connecting a scroll pump.

[0045] The secondary coil 18 and the primary coil 20 are operated at a common resonant frequency. This allows for particularly energy-efficient and low-loss transfer of electrical supply energy to plasma generation. For this purpose, the primary coil 20 and the secondary coil 18 generate a vortex field inside the ionization chamber 4. The primary coil 20 is operated with an alternating voltage at a frequency between 1 and 60 MHz. The primary coil 20 and the secondary coil 18 form a common transformer assembly 30. The transformer assembly 30 has a variable transformer quality factor, such that the transformer quality factor is reduced when plasma is present in the ionization chamber 4, and the transformer quality factor is increased when the plasma concentration in the ionization chamber 4 decreases or the plasma in the ionization chamber 4 is completely or partially extinguished.

[0046] Fig. 2 shows a detailed representation of a pre-discharge stage 12. Such a pre-discharge stage 12 can also be arranged, for example, in the embodiment shown in Fig. 1, but is not shown in Fig. 1 for clarity. The pre-discharge stage 12 has a supply line 8 for the supply of neutral gas to the ionization chamber housing 7. The gas supply line 8 is designed as a supply pipe 10. By way of example, a pressure regulating device 38 is arranged in Fig. 2, which is fluidly connected to the gas supply line 8 and is configured here to supply the neutral gas to the supply line 8 at a pressure of 0.1–5 bar. Two capacitive electrodes 22, 24 are associated with the supply line 8. The capacitive electrodes 22, 24 are formed by the ends 28 of the secondary coil 18. The electrodes 22, 24 are arranged in an electrode holding device 26.The electrode holding device 26 serves as a dielectric, separating the electrodes 22, 24 from the ionization chamber 4. This prevents erosion of the electrodes 22, 24 during discharge. Fig. 3 schematically shows an ionization system 2 with its essential electromagnetic components for generating the vortex field, which is the cause of the inductively coupled gas discharge within the ionization chamber 4. The ionization system 2 shown in Fig. 3 includes the ionization chamber 4 and the supply line 8 connected to the ionization chamber 4, which is designed to supply neutral gas into the ionization chamber 4. The pre-discharge stage 12 is associated with the supply line 8. The pre-discharge stage 12 is designed to pre-ionize the gas flowing through the supply line 8 and to generate free electrons. In this way, plasma is formed in the region of the pre-discharge stage 12. The main discharge stage 14 is assigned to the ionization chamber 4.This acts on the pre-ionized gas supplied from the pre-discharge stage 12 and causes further impact ionization of the free electrons, resulting in further ionization and thus plasma formation in the ionization chamber 4. Fig. 3 illustrates the common coil arrangement 15 of the pre-discharge stage 12 and the main discharge stage 14 particularly clearly. The ionization chamber 4 is wound by a secondary coil 18, which in turn is connected to a primary coil 20 air-coupled to the secondary coil 18. The ends of the secondary coil 18 are connected to the electrodes 22, 24 of the pre-discharge stage 12. The voltage applied between the coil ends 28 of the secondary coil 18 is thus used for the pre-ionization of the neutral gas in the pre-discharge stage 12, similar to a high-voltage breakdown. Here, the secondary coil 18 is, in a sense, the ionizing electrode for both the pre-discharge stage 12 and the main discharge stage 14.The ionization chamber 4 has an ionization chamber housing 7 as already described. The gas supply line 8 is designed as a supply pipe 10.

[0047] Fig. 4 details the configurations of the secondary coil 18 and the primary coil 20. Fig. 4 clearly shows that the secondary coil 18 and the primary coil 20 do not share a common core. Furthermore, the primary coil 20 has a first number of turns N1, and the secondary coil 18 has a second number of turns N2. The ratio of the number of turns N1 of the primary coil 20 to the number of turns N2 of the secondary coil 18 is 1:10 or greater. This ensures that the high discharge voltages required for the pre-discharge stage 12 are achieved. The ratio of the number of turns N1 to N2 determines the amplification factor of the voltage applied to the primary coil 20 relative to the voltage drop across the secondary coil 18. The primary coil 20 and the secondary coil 18 thus form, in effect, a common transformer assembly 30, which, as described, exhibits a variable transformer quality factor.This achieves a particularly energy-efficient ionization of the neutral gas. The pre-discharge stage 12 is responsible for at least partially ionizing the neutral gas, thus creating the initial conditions for an inductive volume discharge of the neutral gas in the main discharge stage 14. The two-stage design of the ionization system 2 facilitates particularly efficient plasma ignition. After plasma ignition, the main discharge stage 14 can sustain the plasma on its own. The plasma in the ionization chamber 4 reduces the quality factor of the transformer arrangement 30, thereby lowering the high voltage at the pre-discharge stage 12. The ionization system 2 is thus adjusted so that, after the formation of the volume plasma in the ionization chamber 4, no further breakdowns occur at the pre-discharge stage 12.However, when the plasma in the ionization chamber 4 is extinguished, the quality factor of the transformer assembly 30 increases, and consequently, the voltage at the ends 28 of the secondary coil 18 also increases. This pre-ionizes the neutral gas in the area of ​​the gas supply line 8 by the pre-discharge stage 12, thus causing the main discharge stage to reignite. In this way, the presence of plasma in the area of ​​the ionization chamber 4 of the main discharge stage 14 is the decisive criterion for controlling the transformer assembly 30, ensuring that the plasma reignites after extinguishing, thereby achieving a continuous and robust plasma formation.

[0048] Figures 5a and 5b show an alternative embodiment of an ionization system 2 according to the invention in a perspective view (Fig. 5a) and a sectional view (Fig. 5b), respectively. In relation to the embodiment described in Figures 1-4, the ionization system 2 has an ionization chamber 4. This chamber is surrounded by an ionization chamber housing 7. Coaxially, an insulating cylinder 6 is provided, which is surrounded by a primary coil 20. The primary coil 20 is part of a main discharge stage 14, which has been described in detail previously. The ionization system 2 of Figures 5a and 5b is characterized by a magnet arrangement 40. The magnet arrangement 40 surrounds the ionization chamber 4 and is arranged within the ionization chamber 4.The magnet arrangement 40 comprises several magnets 46, 50 for this purpose, which are aligned such that the magnetic field lines of the magnets 46, 50 penetrate the ionization chamber 4 parallel to a longitudinal axis L of the ionization chamber 4. The magnet arrangement 40 has an outer magnet system 42, which surrounds the ionization chamber 4 in a ring-like fashion. The outer magnet system 42 has several spaced-apart ring magnets 44. These are held by a holding device 46. The holding device 46 is connected to a flange 58a, 58b on its upper and lower sides and to a base plate 60 on its lower side, as shown in Fig. 5b. The ring magnets 44 are designed as permanent magnets 46 in this case, but can also be designed as electromagnets.

[0049] The magnet arrangement 40 has an inner magnet system 48, which is arranged within the ionization chamber 4 and is also formed from a plurality of magnets 50 arranged side by side. Adjacent to the primary coil 20, a magnetic nozzle 54 is provided at an outlet of the plasma source 52. The magnetic nozzle 54 is formed here by individual magnets 46, 50 of the outer magnet system 42 and the inner magnet system 48.

[0050] Fig. 6 schematically shows a spacecraft 300. The spacecraft 300 could, for example, be a satellite. The spacecraft 300 has a space propulsion system 100. The space propulsion system 100 has an ionization system 2 according to one of the preceding Figures 1-5b.

[0051] Fig. 7 shows an exemplary method 200 for ionizing a gas using an ionization system 2. The method 200 comprises the following steps: spatially limited pre-ionization 202 of the neutral gas using a pre-discharge stage 12, acceleration and impact ionization 204 of the pre-ionized gas using a main discharge stage 14, substantially over the entire volume of the neutral gas, wherein the pre-discharge stage 12 and the main discharge stage 14 have a common coil arrangement 15.

[0052] List of reference signs

[0053] 2 ionization system

[0054] 4 Ionization chamber

[0055] 6 insulating cylinders

[0056] 7 Ionization chamber housings

[0057] 8 Gas supply line

[0058] 10 supply pipe

[0059] 12 Pre-discharge stage

[0060] 14 Main discharge stage

[0061] 15 common coil arrangement

[0062] 16 Dielectric

[0063] 18 Secondary coil

[0064] 20 Primary coil

[0065] 22 first capacitive electrode

[0066] 24 second capacitive electrode

[0067] 26 insulating electrode holding device

[0068] 28 ends of the secondary coil

[0069] 30 Transformer arrangement

[0070] 32 Base plate

[0071] 34 cutouts in the base plate

[0072] 38 Pressure regulating device

[0073] 40 Magnet arrangement

[0074] 42 external magnetic system

[0075] 44 ring magnets of the outer magnet system

[0076] 46 permanent magnets of the outer magnet system

[0077] 48 internal magnetic system

[0078] 50 permanent magnets of the inner magnet system

[0079] 52 Plasma source output

[0080] 54 Magnetic nozzle

[0081] 56 Holding device

[0082] 58a, b flange

[0083] 60 Base plate

[0084] 100 space propulsion

[0085] 200 methods for ionizing a gas using a plasma source

[0086] 202 Pre-ionization of neural gas

[0087] 204 Acceleration and impact ionization of the pre-ionized gas 300 Spacecraft

[0088] L Longitudinal axis

[0089] N1 Number of turns of the primary coil

[0090] N2 Number of turns of the secondary coil V Total volume of the neutral gas

Claims

Claims 1. Ionization system (2) for ionizing gases, comprising an ionization chamber (4) and a feed line (8) connected to the ionization chamber (4) for supplying neutral gas into the ionization chamber (4), wherein a pre-discharge stage (12) is associated with the feed line (8), which is configured to pre-ionize the gas flowing through the feed line (8) and to generate free electrons, and wherein a main discharge stage (14) is associated with the ionization chamber (4), which is configured to accelerate and impact ionize the free electrons, in particular substantially over the entire volume (V) of the neutral gas, wherein the pre-discharge stage (12) and the main discharge stage (14) have a common coil arrangement (15).

2. Ionization system (2) according to claim 1, wherein the main discharge stage (14) comprises a secondary coil (18) winding around the ionization chamber (4) and a primary coil (20) winding around the secondary coil (18), and wherein the secondary coil (18) and the primary coil (20) are part of the common coil arrangement (15).

3. Ionization system (2) according to one of the preceding claims, wherein at least two capacitive electrodes (22, 24) are associated with the supply line (8), and wherein the capacitive electrodes (22, 24) are formed by ends (28) of the secondary coil (18) or the capacitive electrodes (22, 24) are conductively connected to the secondary coil (18).

4. Ionization system (2) according to one of the preceding claims, wherein the ionization chamber (4) is formed from a dielectric (16), in particular from quartz or ceramic.

5. Ionization system (2) according to one of claims 2 to 4, wherein the secondary coil (18) and the primary coil (20) are air-coupled and / or electromagnetically loosely coupled.

6. Ionization system (2) according to one of claims 2 to 5, wherein the secondary coil (18) and the primary coil (20) are operated with a common resonant frequency.

7. Ionization system (2) according to one of claims 2 to 6, wherein the primary coil (20) and the secondary coil (18) generate a vortex field inside the ionization chamber (4).

8. Ionization system (2) according to one of claims 2 to 7, wherein the primary coil (20) is operated with alternating voltage of a frequency between 1 and 60 MHz.

9. Ionization system (2) according to any one of claims 2 to 8, wherein the primary coil (20) has a first number of turns (N1) and the secondary coil (18) has a second number of turns (N2), wherein the ratio of the number of turns (N1) of the primary coil (20) to the number of turns (N2) of the secondary coil (18) is 1 :10 or greater.

10. Ionization system (2) according to one of claims 3 to 9, wherein the electrodes (22, 24) are isolated from the ionization chamber (4), in particular wherein the electrodes (22, 24) are designed as flat electrodes.

11. Ionization system (2) according to one of claims 2 to 10, wherein the primary coil (20) and the secondary coil (18) form a common transformer arrangement (30).

12. Ionization system (2) according to claim 11, wherein the transformer arrangement (30) has a variable transformer quality.

13. Ionization system (2) according to claim 12, wherein the transformer quality is reduced when plasma is present in the ionization chamber (4), and / or the transformer quality is increased when the plasma content in the ionization chamber (4) decreases or the plasma in the ionization chamber (4) is completely or partially extinguished.

14. Ionization system (2) according to one of the preceding claims, comprising a pressure regulating device (38) which is configured to supply the neutral gas to the supply line (8) at a pressure of 0.1 bar to 5 bar.

15. Ionization system (2) according to one of the preceding claims, comprising a magnet arrangement (40) which surrounds the ionization chamber (4) and / or is arranged in the ionization chamber (4).

16. Ionization system (2) according to claim 15, wherein the magnet arrangement (40) comprises one or more magnets (46, 50) which are aligned such that the magnetic field lines of the magnets (46, 50) penetrate the ionization chamber (4) parallel to a longitudinal axis (L) of the ionization chamber (4).

17. Ionization system (2) according to claim 15 or 16, wherein the magnet arrangement (40) has an external magnet system (42) which surrounds the ionization chamber (4) on the outside in a ring shape.

18. Ionization system (2) according to claim 17, wherein the outer magnet system (42) comprises a magnet with a closed lateral surface or ring magnets (44) spaced apart from each other along the longitudinal axis (L).

19. Ionization system (2) according to claim 18, wherein the at least one magnet (44) is designed as a permanent magnet (46) or as an electromagnet.

20. Ionization system (2) according to one of claims 15 to 19, wherein the magnet arrangement (40) has an internal magnet system (48) which is arranged within the ionization chamber (4).

21. Ionization system (2) according to one of claims 15 to 20, wherein a magnetic nozzle (54) is arranged adjacent to the primary coil (20) at an output of the plasma source (52), which in particular is formed at least partially by the outer magnetic system (42) and the inner magnetic system (48).

22. Space propulsion system (100) for propelling a spacecraft (300), comprising an ionization system (2) according to one of the preceding claims.

23. Spacecraft (300) with a space propulsion system (100), wherein the space propulsion system (100) is configured according to claim 22.

24. Use of an ionization system (2) according to one of the preceding claims for propelling a spacecraft (300), in particular a satellite in Earth orbit, an In-Space Transportation Vehicle (ISTV) or as the main propulsion system for interplanetary exploration probes.

25. Method (200) for ionizing a gas by means of an ionization system (2) which is formed from two discharge stages (12, 14), in particular an ionization system (2) according to one of the preceding claims, wherein the method (200) comprises the steps: - Spatially limited pre-ionization (202) of the neural gas by means of a Pre-discharge stage (12), - Acceleration and impact ionization (204) of the pre-ionized gas by means of a main discharge stage (14), substantially over the entire volume of the neutral gas, wherein the pre-discharge stage (12) and the main discharge stage (14) have a common coil arrangement (15).

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