A metastable inert gas laser based on photoionization

Abstract

This invention relates to a metastable inert gas laser based on photoionization, comprising an inert gas metastable preparation chamber, a pump source, and a pre-ionization source. The inert gas metastable preparation chamber contains a radio frequency electrode and a ground electrode. Both the pump source and the pre-ionization source are located outside the inert gas metastable preparation chamber, with the emitted light from the pump source and the emitted light from the pre-ionization source perpendicular to each other within the inert gas metastable preparation chamber. A first reflecting mirror is positioned between the pump source and the inert gas metastable preparation chamber, and a second reflecting mirror is positioned on the side of the inert gas metastable preparation chamber away from the pump source. A lens is positioned between the pre-ionization source and the inert gas metastable preparation chamber. This invention combines an external electric field to accelerate electron collisions with inert gas atoms, further generating a high concentration of metastable inert gas atoms, thus avoiding the strong electromagnetic radiation problems associated with traditional discharge methods.

Description

Technical Field

[0001] This invention relates to the field of metastable inert gas laser technology, specifically a metastable inert gas laser based on photoionization. Background Technology

[0002] Optically pumped metastable rare gas lasers (OPRGLs) use metastable inert gas atoms as the gain medium. Similar to diode-pumped alkali lasers (DPALs), OPRGLs also belong to the three-level gas laser system. Through conventional discharge excitation, processes such as ionization, recombination, excited-state radiation, and relaxation are performed to excite the outermost electrons to form valence electrons, thus obtaining metastable atoms. The metastable Rg* state in the inert gas has a long lifetime, equivalent to the ground state nS of alkali metals. Then, by diode-pumping light, the metastable state is excited to a highly excited state, enabling the output of near-infrared laser light.

[0003] The differences between OPRGL and DPAL are: (1) the chemical properties of inert gas atoms are very stable, and (2) the buffer gas is helium, which does not require reliance on alkane gases. Therefore, OPRGL does not have many of the problems faced by DPAL, such as: alkali metal atoms reacting chemically with alkane gases, alkali metals being easily ionized, and alkane molecules decomposing and carbonizing to contaminate the window lens. Therefore, OPRGL has great potential to replace DPAL.

[0004] However, DPAL generates a sufficient concentration of alkali metal vapor through heating, while OPRGL, although not requiring heating, needs to generate a sufficient concentration of metastable atoms through discharge. In high-power operation, the electromagnetic interference (EMI) generated by this discharge is severe, originating from the high-voltage discharge process that initially breaks down atoms. This strong EMI significantly limits the application platforms of OPRGL. Furthermore, to greatly expand the application areas of lasers, they are currently being mounted on mobile platforms such as vehicles and aircraft. These mobile platforms have strict requirements regarding size and weight, especially airborne platforms. To shield against EMI generated by the discharge, electromagnetic shielding structures with metal structures are needed, increasing the size and weight of the laser system and limiting the integration of OPRGL with mobile platforms, thus impacting its future application areas. Therefore, it is essential to address the EMI problem from the perspective of the laser's operating mechanism to promote the development of OPRGL in the field of high-power lasers. Summary of the Invention

[0005] The purpose of this invention is to provide a metastable inert gas laser based on photoionization, which combines an external electric field to accelerate electrons to collide with inert gas atoms, thereby generating a high concentration of metastable inert gas atoms, thus avoiding the problem of strong electromagnetic radiation generated by traditional discharge methods.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A metastable inert gas laser based on photoionization includes an inert gas metastable preparation chamber, a pump source, and a pre-ionization source. The inert gas metastable preparation chamber contains an RF electrode and a ground electrode. Both the pump source and the pre-ionization source are located outside the inert gas metastable preparation chamber, with the emitted light from the pump source and the emitted light from the pre-ionization source perpendicular to each other within the inert gas metastable preparation chamber. A first reflecting mirror is positioned between the pump source and the inert gas metastable preparation chamber, and a second reflecting mirror is positioned on the side of the inert gas metastable preparation chamber furthest from the pump source. A lens is positioned between the pre-ionization source and the inert gas metastable preparation chamber.

[0008] The radio frequency electrode is connected to the radio frequency source, and a matching network is provided between the radio frequency electrode and the radio frequency source. The electric field direction between the radio frequency electrode and the ground electrode is changed periodically.

[0009] The electrode plate of the radio frequency electrode is arranged parallel to the electrode plate of the ground electrode. The inert gas metastable preparation chamber is provided with a side window on the side near the pre-ionization light source. The laser output from the pre-ionization light source is focused by a lens to form a focal line, and the focal line is located between the radio frequency electrode and the ground electrode. The plane of the focal line is parallel to the electrode plates of the radio frequency electrode and the ground electrode, and the focal line is located on the side near the electrode plate of the radio frequency electrode.

[0010] The inert gas metastable preparation chamber includes an outer wall of the preparation chamber, with a first end face window at one end and a second end face window at the other end.

[0011] Both the first end face window and the second end face window are coated with a band anti-reflective coating.

[0012] The surface of the first reflector is coated with a band antireflection film and a band high reflection film, and the surface of the second reflector is coated with a band antireflection film and a band reflection film.

[0013] Both the first and second reflecting mirrors are concave reflecting mirrors, and the lens is a cylindrical convex lens.

[0014] The inert gas metastable state preparation chamber is equipped with an inert gas and a buffer gas for preparing metastable states.

[0015] The advantages and positive effects of this invention are as follows:

[0016] 1. This invention utilizes laser-induced photoionization of inert gas to generate high-density electrons while avoiding the strong electromagnetic radiation problem caused by traditional discharge ionization.

[0017] 2. After photoionization, the present invention accelerates electrons to collide with inert gas atoms through an external radio frequency electric field, thereby obtaining a uniformly distributed, high-concentration metastable inert gas atom.

[0018] 3. This invention effectively reduces the size and weight of the laser, which helps to expand the application areas of this type of laser. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of the present invention.

[0020] Figure 2 for Figure 1 A schematic diagram of the inert gas metastable preparation chamber structure.

[0021] Wherein, 1 is the pump light source, 2 is the first reflector, 3 is the inert gas metastable preparation chamber, 301 is the first end face window, 302 is the outer wall of the preparation chamber, 303 is the radio frequency electrode, 304 is the ground electrode, 305 is the second end face window, 4 is the pre-ionization light source, 5 is the lens, 6 is the matching network, 7 is the second reflector, and 8 is the radio frequency source. Detailed Implementation

[0022] The invention will now be described in further detail with reference to the accompanying drawings.

[0023] like Figures 1-2 As shown, the present invention includes an inert gas metastable preparation chamber 3, a pump light source 1, and a pre-ionization light source 4, wherein, as Figure 2 As shown, the inert gas metastable preparation chamber 3 is equipped with a radio frequency electrode 303 and a grounding electrode 304, such as... Figure 1 As shown, both the pump light source 1 and the pre-ionization light source 4 are located outside the inert gas metastable preparation chamber 3, and the light emitted from the pump light source 1 and the light emitted from the pre-ionization light source 4 are perpendicular to each other in the inert gas metastable preparation chamber 3. A first reflector 2 is provided between the pump light source 1 and the inert gas metastable preparation chamber 3, and a second reflector 7 is provided on the side of the inert gas metastable preparation chamber 3 away from the pump light source 1. A lens 5 is provided between the pre-ionization light source 4 and the inert gas metastable preparation chamber 3. The first reflector 2 and the second reflector 7 can be concave reflectors, and the lens 5 can be a cylindrical convex lens.

[0024] like Figure 2 As shown, the inert gas metastable state preparation chamber 3 includes an outer wall 302, one end of which is provided with a first end face window 301, and the other end with a second end face window 305, as shown. Figure 1As shown, the light emitted from the pump source 1 enters the inert gas metastable preparation chamber 3 through the first end window 301 and exits through the second end window 305. The first end window 301 and the second end window 305 must be able to satisfy the transmission requirements of the laser output from the pump source and the transmission requirements of the laser generated by the metastable inert gas laser system. Both the first end window 301 and the second end window 305 are coated with a band-specific anti-reflective coating, which is a well-known technique in the art.

[0025] like Figure 1 As shown, the first reflector 2 serves as a high-reflectivity cavity mirror, with its surface coated with a band-specific anti-reflection coating and a band-specific high-reflectivity coating. This surface coating achieves high transmittance for the pump laser band and high reflectivity for the metastable laser band. The second reflector 7 serves as an output coupling cavity mirror, with its surface coated with a band-specific anti-reflection coating and a band-specific reflectivity coating. This surface coating achieves high transmittance for the pump laser band and partial transmittance for the metastable laser band. The surface coating of the reflectors is a technique known in the art.

[0026] like Figure 1 As shown, the radio frequency electrode 303 is connected to the radio frequency source 8 via a circuit, and a matching network 6 is provided between the radio frequency electrode 303 and the radio frequency source 8. The low-voltage radio frequency electric field generated by the radio frequency source 8 periodically changes the direction of the electric field between the radio frequency electrode 303 and the ground electrode 304, thereby accelerating the reciprocating motion of electrons between the radio frequency electrode 303 and the ground electrode 304. The radio frequency source 8 and the matching network 6 are both technologies known in the art and are commercially available products. The radio frequency source 8 outputs a sinusoidal low-voltage radio frequency electric field with a repetition frequency on the order of MHz, thereby achieving periodic changes in the direction of the electric field.

[0027] like Figure 2 As shown, the electrode plate of the radio frequency electrode 303 is arranged parallel to the electrode plate of the ground electrode 304.

[0028] The inert gas metastable state preparation chamber 3 has a side window near the pre-ionization light source 4. The chamber contains an inert gas and a buffer gas for preparing metastable states. After the laser output from the pre-ionization light source 4 passes through lens 5 (a cylindrical convex lens), the laser spot is compressed and focused longitudinally, while the spot diameter remains unchanged laterally. Therefore, the laser output from the pre-ionization light source 4, after being focused by lens 5, generates a focal line laterally, located between the radio frequency electrode 303 and the ground electrode 304. The plane of the focal line is parallel to the electrode plates of both the radio frequency electrode 303 and the ground electrode 304, and the focal line is closer to the electrode plate of the radio frequency electrode 303. After being linearly focused by lens 5, the laser output from the pre-ionization light source 4 acts on the inert gas near the radio frequency electrode 303. A small number of inert gas atoms absorb multiple photons and undergo multiphoton ionization, generating initial electrons. Subsequently, these electrons absorb photon energy to generate kinetic energy and continue to collide with inert gas atoms, resulting in avalanche ionization and the generation of a high-density electrons.

[0029] The working principle of this invention is as follows:

[0030] The inert gas metastable preparation chamber 3 contains an inert gas and a buffer gas for preparing metastable atoms. When preparing metastable atoms, the laser output from the pre-ionization light source 4 passes through the lens 5 (cylindrical convex lens) and generates a focused line, which acts on the inert gas near the radio frequency electrode 303. A small number of inert gas atoms absorb multiple photons and undergo multiphoton ionization, generating initial electrons. Subsequently, the electrons absorb photon energy to generate kinetic energy and continue to collide with inert gas atoms, causing avalanche ionization and generating high-density electrons with a certain distribution range. The low-voltage radio frequency electric field generated by the radio frequency source 8 periodically changes the direction of the electric field between the radio frequency electrode 303 and the ground electrode 304, thereby accelerating the reciprocating motion of electrons between the radio frequency electrode 303 and the ground electrode 304, realizing sufficient collisions between electrons and inert gas atoms, and generating metastable inert gas atoms with uniform distribution and sufficient concentration.

[0031] During the optical pumping stage, the laser output from the pump source 1 enters the inert gas metastable preparation chamber 3 through the first end face window 301 and exits through the second end face window 305. The laser output from the pump source 1 excites the metastable atoms in the inert gas metastable preparation chamber 3, and the emitted photons oscillate and amplify in the resonant cavity composed of the first reflector 2 and the second reflector 7. The laser directly generated is output from the second reflector 7.

[0032] The following are some application examples to further illustrate the working principle of the present invention. The laser wavelength output by the pump light source 1 will resonate and excite the metastable inert gas atoms located at the ns[3 / 2]2 energy level (Racah notation, corresponding Paschen notation is 1s5) to the np[5 / 2]3 energy level (Racah notation, corresponding Paschen notation is 2p9). For convenience, the Paschen notation will be used as the main term in the present invention.

[0033] Application Example 1:

[0034] In this application example, the inert gas metastable preparation chamber 3 is filled with neon gas to prepare metastable neon atoms. The neon gas filling pressure at room temperature is 65 torr (8.7 × 10⁻⁶). 3 It is also filled with helium as a buffer gas, and the helium filling pressure at room temperature is 695 torr (9.3 × 10⁻⁶ Pa). 4 Pa).

[0035] In the preparation stage of metastable neon atoms, the 532nm laser output from the pre-ionization light source 4 is linearly focused by the lens 5 and acts on the neon-helium inert gas mixture near the radio frequency electrode 303 through the side window of the outer wall 302 of the preparation room. A small number of neon and helium atoms absorb multiple photons and undergo multiphoton ionization, generating initial electrons. Subsequently, the electrons absorb photon energy to generate kinetic energy and continue to collide with neon and helium atoms, resulting in avalanche ionization. Thus, high-density electrons with a certain distribution range are obtained through laser-induced photoionization. The radio frequency source 8 is connected to the radio frequency electrode 303 through the matching network 6. The low-voltage radio frequency electric field generated by the radio frequency source 8 periodically changes the direction of the electric field between the radio frequency electrode 303 and the ground electrode 304, accelerating the electrons to reciprocate between the radio frequency electrode 303 and the ground electrode 304, realizing sufficient collisions between electrons and neon atoms, and generating 1s5 metastable neon atoms with uniform distribution and sufficient concentration.

[0036] During the optical pumping stage, the laser output from pump source 1 enters the inert gas metastable state preparation chamber 3 through the first end-face window 301 and exits through the second end-face window 305. The outer surfaces of the first end-face window 301 and the second end-face window 305 are coated with antireflective films in the 635-645nm and 700-705nm bands, respectively. The surface of the first reflector 2 is coated with an antireflective film in the 635-645nm band and a high-reflection film in the 700-705nm band. The surface of the second reflector 7 is coated with an antireflective film in the 635-645nm band and a partial reflection film in the 700-705nm band. The 640.2nm laser output from pump source 1 excites the 1s5 metastable neon atoms in the inert gas metastable state preparation chamber 3 to the 2p9 energy level. Under the collision of helium atoms, the neon atoms in the 2p9 energy level rapidly relax to the 2p9 level. 10 Energy level, at 2p 10A population inversion occurs between the 1s5 energy level and the radiated photons oscillate and amplify within a resonant cavity formed by the first reflector 2 and the second reflector 7. The directly generated 703.2nm laser is output from the second reflector 7.

[0037] Application Example 2:

[0038] In this application example, the inert gas metastable preparation chamber 3 is filled with argon gas to prepare metastable argon atoms. The argon gas filling pressure at room temperature is 40 torr (5.3 × 10⁻⁶). 3 It is also filled with helium as a buffer gas, and the helium filling pressure at room temperature is 600 torr (8.0 × 10⁻⁶ Pa). 4 Pa).

[0039] In the preparation stage of metastable argon atoms, the 532nm laser output from the pre-ionization light source 4 is linearly focused by the lens 5 and acts on the argon-helium inert gas mixture near the radio frequency electrode 303 through the side window of the outer wall 302 of the preparation room. A small number of argon and helium atoms absorb multiple photons and undergo multiphoton ionization, generating initial electrons. Subsequently, the electrons absorb photon energy to generate kinetic energy and continue to collide with argon and helium atoms, resulting in avalanche ionization. Thus, high-density electrons with a certain distribution range are obtained through laser-induced photoionization. The radio frequency source 8 is connected to the radio frequency electrode 303 through the matching network 6. The low-voltage radio frequency electric field generated by the radio frequency source 8 periodically changes the direction of the electric field between the radio frequency electrode 303 and the ground electrode 304, accelerating the electrons to reciprocate between the radio frequency electrode 303 and the ground electrode 304, realizing sufficient collisions between electrons and argon atoms, and generating 1s5 metastable argon atoms with uniform distribution and sufficient concentration.

[0040] During the optical pumping stage, the laser output from pump source 1 enters the inert gas metastable state preparation chamber 3 through the first end-face window 301 and exits through the second end-face window 305. The outer surfaces of the first end-face window 301 and the second end-face window 305 are coated with antireflective films in the 810–815 nm and 910–915 nm bands, respectively. The surface of the first reflector 2 is coated with an antireflective film in the 810–815 nm band and a high-reflection film in the 910–915 nm band. The surface of the second reflector 7 is coated with an antireflective film in the 810–815 nm band and a partial-reflective film in the 910–915 nm band. The 811.5 nm laser output from pump source 1 excites the 1s5 metastable argon atoms in the inert gas metastable state preparation chamber 3 to the 2p9 energy level. Under the collision of helium atoms, the argon atoms in the 2p9 energy level rapidly relax to the 2p9 level. 10 Energy level, at 2p 10 A population inversion occurs between the 1s5 energy level and the radiated photons oscillate and amplify within a resonant cavity formed by the first reflector 2 and the second reflector 7. The directly generated 912.3nm laser is output from the second reflector 7.

[0041] Application Example 3:

[0042] In this application example, the inert gas metastable preparation chamber 3 is filled with krypton gas for preparing metastable krypton atoms. The krypton gas filling pressure at room temperature is 15 torr (2.0 × 10⁻⁶). 3 It is also filled with helium as a buffer gas, and the helium filling pressure at room temperature is 560 torr (7.5 × 10⁻⁶ Pa). 4 Pa).

[0043] In the preparation stage of metastable krypton atoms, the 532nm laser output from the pre-ionization light source 4 is linearly focused by the lens 5 and acts on the krypton-helium inert gas mixture near the radio frequency electrode 303 through the side window of the outer wall 302 of the preparation room. A small number of krypton and helium atoms absorb multiple photons and undergo multiphoton ionization, generating initial electrons. Subsequently, the electrons absorb photon energy to generate kinetic energy and continue to collide with krypton and helium atoms, resulting in avalanche ionization. Thus, high-density electrons with a certain distribution range are obtained through laser-induced photoionization. The radio frequency source 8 is connected to the radio frequency electrode 303 through the matching network 6. The low-voltage radio frequency electric field generated by the radio frequency source 8 periodically changes the direction of the electric field between the radio frequency electrode 303 and the ground electrode 304, accelerating the electrons to reciprocate between the radio frequency electrode 303 and the ground electrode 304, realizing sufficient collisions between electrons and krypton atoms, and generating 1s5 metastable krypton atoms with uniform distribution and sufficient concentration.

[0044] During the optical pumping stage, the laser output from pump source 1 enters the inert gas metastable state preparation chamber 3 through the first end-face window 301 and exits through the second end-face window 305. The outer surfaces of the first end-face window 301 and the second end-face window 305 are coated with antireflective films in the 810–815 nm and 890–895 nm bands, respectively. The surface of the first reflector 2 is coated with an antireflective film in the 810–815 nm band and a high-reflection film in the 890–895 nm band. The surface of the second reflector 7 is coated with an antireflective film in the 810–815 nm band and a partial-reflective film in the 890–895 nm band. The 813.3 nm laser output from pump source 1 excites the 1s5 metastable krypton atoms in the inert gas metastable state preparation chamber 3 to the 2p9 energy level. Under the collision of helium atoms, the krypton atoms in the 2p9 energy level rapidly relax to the 2p9 level. 10 Energy level, at 2p 10 A population inversion occurs between the 1s5 energy level and the radiated photons oscillate and amplify within a resonant cavity formed by the first reflector 2 and the second reflector 7. The directly generated 892.9nm laser is output from the second reflector 7.

[0045] Application Example 4:

[0046] In this application example, the inert gas metastable preparation chamber 3 is filled with xenon gas for preparing metastable xenon atoms. The xenon gas filling pressure at room temperature is 10 torr (1.3 × 10⁻⁶). 3 It is also filled with helium as a buffer gas, and the helium filling pressure at room temperature is 550 torr (7.3 × 10⁻⁶ Pa). 4 Pa).

[0047] In the metastable xenon atom preparation stage, the 532nm laser output from the pre-ionization light source 4 is linearly focused by the lens 5 and acts on the xenon-helium inert gas mixture near the radio frequency electrode 303 through the side window of the outer wall 302 of the preparation room. A small number of xenon and helium atoms absorb multiple photons and undergo multiphoton ionization, generating initial electrons. Subsequently, the electrons absorb photon energy to generate kinetic energy and continue to collide with xenon and helium atoms, resulting in avalanche ionization. Thus, high-density electrons with a certain distribution range are obtained through laser-induced photoionization. The radio frequency source 8 is connected to the radio frequency electrode 303 through the matching network 6. The low-voltage radio frequency electric field generated by the radio frequency source 8 periodically changes the direction of the electric field between the radio frequency electrode 303 and the ground electrode 304, accelerating the electrons to reciprocate between the radio frequency electrode 303 and the ground electrode 304, achieving sufficient collisions between electrons and xenon atoms, and producing 1s5 metastable xenon atoms with uniform distribution and sufficient concentration.

[0048] During the optical pumping stage, the laser output from pump source 1 enters the inert gas metastable state preparation chamber 3 through the first end-face window 301 and exits through the second end-face window 305. The outer surfaces of the first end-face window 301 and the second end-face window 305 are coated with antireflective films in the 880–885 nm and 978–983 nm bands, respectively. The surface of the first reflector 2 is coated with an antireflective film in the 880–885 nm band and a high-reflection film in the 978–983 nm band. The surface of the second reflector 7 is coated with an antireflective film in the 880–885 nm band and a partial-reflective film in the 978–983 nm band. The 881.9 nm laser output from pump source 1 excites the 1s5 metastable xenon atoms in the inert gas metastable state preparation chamber 3 to the 2p9 energy level. Under the collision of helium atoms, the xenon atoms in the 2p9 energy level rapidly relax to the 2p9 level. 10 Energy level, at 2p 10 A population inversion occurs between the 1s5 energy level and the radiated photons oscillate and amplify within a resonant cavity formed by the first reflector 2 and the second reflector 7. The directly generated 980.0nm laser is output from the second reflector 7.

Claims

1. A metastable inert gas laser based on photoionization, characterized in that: The system includes an inert gas metastable preparation chamber (3), a pump light source (1), and a pre-ionization light source (4). The inert gas metastable preparation chamber (3) is equipped with a radio frequency electrode (303) and a ground electrode (304). The pump light source (1) and the pre-ionization light source (4) are both located outside the inert gas metastable preparation chamber (3). The light emitted from the pump light source (1) and the light emitted from the pre-ionization light source (4) are perpendicular to each other in the inert gas metastable preparation chamber (3). A first reflector (2) is provided between the pump light source (1) and the inert gas metastable preparation chamber (3). A second reflector (7) is provided on the side of the inert gas metastable preparation chamber (3) away from the pump light source (1). A lens (5) is provided between the pre-ionization light source (4) and the inert gas metastable preparation chamber (3). The electrode plate of the radio frequency electrode (303) is arranged parallel to the electrode plate of the ground electrode (304). The inert gas metastable preparation chamber (3) is provided with a side window on the side near the pre-ionization light source (4). The laser output by the pre-ionization light source (4) is focused by the lens (5) to form a focal line, and the focal line is located between the radio frequency electrode (303) and the ground electrode (304). The plane where the focal line is located is parallel to the electrode plate of the radio frequency electrode (303) and the electrode plate of the ground electrode (304), and the focal line is located on the side near the electrode plate of the radio frequency electrode (303).

2. The metastable inert gas laser based on photoionization according to claim 1, characterized in that: The radio frequency electrode (303) is connected to the radio frequency source (8), and a matching network (6) is provided between the radio frequency electrode (303) and the radio frequency source (8). The electric field direction between the radio frequency electrode (303) and the ground electrode (304) is changed periodically.

3. The metastable inert gas laser based on photoionization according to claim 1, characterized in that: The inert gas metastable state preparation chamber (3) includes an outer wall (302) of the preparation chamber, one end of which is provided with a first end face window (301) and the other end is provided with a second end face window (305).

4. The metastable inert gas laser based on photoionization according to claim 3, characterized in that: Both the first end face window (301) and the second end face window (305) are coated with a band anti-reflective film.

5. The metastable inert gas laser based on photoionization according to claim 1, characterized in that: The surface of the first reflector (2) is coated with a band antireflection film and a band high reflection film, and the surface of the second reflector (7) is coated with a band antireflection film and a band reflection film.

6. The metastable inert gas laser based on photoionization according to claim 1, characterized in that: The first reflector (2) and the second reflector (7) are both concave reflectors, and the lens (5) is a cylindrical convex lens.

7. The metastable inert gas laser based on photoionization according to claim 1, characterized in that: The inert gas metastable preparation chamber (3) is filled with inert gas and buffer gas for preparing metastable states.

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