A device for producing and detecting alkali metal Rydberg atoms

Abstract

The present invention discloses an alkali metal Rydberg atom generation and detection device, comprising a beam source chamber and an action chamber, the two of which are connected via a vacuum flange; the beam source chamber comprises a sputtering laser for producing an alkali metal ultrasonic atomic beam, an alkali metal solid target, a high-pressure gas nozzle, and a conical colander; the action chamber comprises an excitation light, a repulsive electric field plate, a deceleration electric field plate, a grid, and a detector, with through holes left between the repulsive electric field plate and the grid for the atomic beam to pass through. The present invention, by combining ultrasonic atomic beams, laser sputtering, and gradient electric field deceleration technology, can generate a cold, concentrated alkali metal Rydberg atom beam, and by applying a pulsed voltage, achieves intermittent detection, i.e., detection is performed only within the time range of the ion collision detector. This can effectively overcome the shortcomings of excessively high alkali metal gas temperature caused by atomic furnace heating and the noise impact caused by continuous pressurized detection.

Description

Technical Field

[0001] The present invention relates to the field of Rydberg atom dynamics in an external field, and in particular to an alkali metal Rydberg atom generation and detection device. Background Art

[0002] In the study of Rydberg atom dynamics in an external field, alkali metal Rydberg atoms are usually produced by heating in an atomic furnace. The specific method is to heat the atomic furnace in a vacuum environment to sublime the built-in solid alkali metal to generate hot atomic gas that diffuses throughout the vacuum cavity. Subsequently, it is excited to the Rydberg state under laser pumping to form Rydberg atoms. The detection of Rydberg atoms generally uses a microchannel plate to collect the impact signal of the Rydberg atoms ionized by the electric field, which is the so-called flight mass spectrometry. However, this traditional method of producing and detecting alkali metal Rydberg atoms has the following disadvantages:

[0003] First, the temperature of the alkali metal atomic gas heated during the atomic generation process is high, and the atomic translational velocity is very large, which will greatly reduce the resolution of Rydberg atom kinetic energy detection after ionization; second, during the atomic detection process, the continuous pressurization of the microchannel plate will record the messy background signal into the detection signal, which will seriously reduce the signal-to-noise ratio of the detection signal. Summary of the Invention

[0004] In view of the shortcomings of the above-mentioned traditional alkali metal Rydberg atom generation and detection methods, the purpose of the present invention is to provide an alkali metal Rydberg atom generation and detection device, which can generate a cold and concentrated alkali metal Rydberg atom beam by combining ultrasonic atomic beam, laser sputtering and gradient electric field deceleration technology, and realize intermittent detection by applying pulse voltage to the detector, that is, detection is only performed within the time range of the ion collision detector, which can effectively overcome the shortcomings of excessively high alkali metal gas temperature caused by atomic furnace heating and noise influence caused by continuous pressurized detection.

[0005] The present invention discloses an alkali metal Rydberg atom generation and detection device, which includes a beam source cavity and an action cavity;

[0006] The beam source cavity is used to prepare an alkali metal ultrasonic atomic beam, and comprises a gas nozzle, a sputtering laser, an alkali metal solid target and a conical colander;

[0007] The gas nozzle extends into the cavity through the gas inlet rod and is used to spray high-pressure carrier gas to generate an adiabatically expanding atomic gas cluster; the alkali metal solid target is located at a position directly opposite the atomic gas cluster; the sputtering laser sputters the alkali metal solid target to generate gaseous alkali metal atoms, which diffuse into the atomic gas cluster; the conical colander is fixed to the vacuum flange of the beam source cavity and is located at a position corresponding to the position where the alkali metal solid target generates gaseous alkali metal atoms and diffuses into the atomic gas cluster, and is used to pass through the ultrasonic atomic beam with a more concentrated velocity distribution at the center of the atomic gas cluster;

[0008] The action cavity includes a Rydberg excitation region, a free flight region and a detector, wherein the Rydberg excitation region includes a repulsive electric field plate, an excitation light and a deceleration electric field plate;

[0009] The repulsive electric field plate is located on the side adjacent to the working chamber and the beam source chamber, and is connected to a positive voltage to blow away the alkali metal ions carried in the atomic beam; the excitation light is emitted into the working chamber through the optical window to excite the alkali metal atoms to the high Rydberg state, thereby preparing alkali metal Rydberg atoms; the deceleration electric field plate is a pair of parallel electrode plates, which are used to generate a horizontal gradient electric field to decelerate and cool the Rydberg atoms; the free flight zone includes two grounded grids; the detector includes at least two circular microchannel plates with high pressure, and the microchannel plates are installed on the vacuum flange of the working chamber away from the beam source chamber. The external pressurizing equipment can apply high pressure through the electrodes to enable the microchannel plates to work normally.

[0010] Furthermore, the beam source chamber further includes a rotary motor; the alkali metal solid target is mounted on the rotary motor to improve the stability of the sputtering signal, and the rotary motor is controlled by an external controller.

[0011] Furthermore, the beam source cavity further comprises a square metal box, wherein openings are provided on the top of the square metal box, in the direction of incidence of the sputtering laser, and on one side adjacent to the conical colander, and the alkali metal solid target extends into the square metal box through the top opening;

[0012] The sputtering laser is injected into the interior of the square metal box through the opening, and generates gaseous metal atoms with the alkali metal solid target. The gaseous metal atoms are emitted through the opening on the side adjacent to the conical colander and diffuse into the atomic gas mass;

[0013] The square metal box is used to prevent the sputtering laser from reflecting and hitting the vacuum cavity to generate interference signals and to prevent the solid metal generated by sputtering from falling and adhering to the surface of the vacuum cavity.

[0014] Furthermore, the alkali metal Rydberg atom generation and detection device further includes a focusing lens;

[0015] The propagation direction of the sputtering laser is perpendicular to the direction of the atomic beam. After being focused by the focusing lens, the sputtering laser is transmitted through the optical window of the vacuum chamber into the cavity and hits the solid alkali metal target. Under the action of the laser, the solid alkali metal will quickly form a burn hole:

[0016]

[0017] Where ω0 is the beam waist radius, D is the hole size, E is the laser intensity, and E is the laser beam intensity. Th Threshold intensity.

[0018] Furthermore, the sputtering laser can change the light intensity and polarization state respectively by using a neutral density filter and a quarter wave plate, and the sputtering laser is circularly polarized to achieve uniformity in the diffusion direction of the sputtered atoms.

[0019] Furthermore, the deceleration electric field plate utilizes the large electric dipole moment of the Rydberg atoms to decelerate the Rydberg atoms through a horizontal gradient electric field. The force exerted on the atoms in the gradient electric field is:

[0020]

[0021] Among them, μ d is the electric dipole moment, which is proportional to the principal quantum number of the Rydberg state. is the electric field gradient.

[0022] Furthermore, the detector has three microchannel plates, each of which is pressed between stainless steel plates. Screws are passed through the four corners of the stainless steel plates, and the stainless steel plates are pressed and fixed to the screws with insulating materials such as polytetrafluoroethylene. The screws are fixed to the vacuum flange.

[0023] The pressurizing device applies high voltage to the microchannel plate through electrodes. The high voltage application method of the microchannel plate adopts a combination of bias voltage and pulse voltage to ionize alkali metal Rydberg atoms and accelerate the ionized ions to reach the energy threshold of the microchannel plate response.

[0024] Furthermore, the excitation light is a pulsed laser with a frequency of 10 Hz and a pulse width of 10 ns.

[0025] Furthermore, the carrier gas is helium, and the vacuum in the vacuum chamber is maintained at 10 -6 Pa level.

[0026] Furthermore, the conical colander is made of stainless steel, and the diameter of the central circular hole is 30-100um. Different hole diameters can produce atomic beams with different divergence angles.

[0027] The beneficial effects achieved by the present invention are:

[0028] This invention adds an alkali metal laser sputtering device to the ultrasonic atomic beam generation path. This allows the gaseous alkali metal atoms generated by the laser sputtering to be drawn into the atomic beam. Through further excitation and gradient electric field deceleration, cooler alkali metal Rydberg atoms are produced. Furthermore, by applying a pulsed voltage, the detector operates only within the timeframe of the measured particle's arrival at the detector, eliminating accumulated background noise. Compared to previous methods for generating and detecting alkali metal Rydberg atoms, this invention significantly improves Rydberg atom kinetic energy resolution and detection signal-to-noise ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 An alkali metal Rydberg atom generation and detection device is provided in an embodiment of the present invention.

[0030] In the figure: 1-beam source chamber; 2-action chamber; 11-gas nozzle; 12-alkali metal solid target; 13-square metal box; 14-conical colander; 15-rotating motor; 16-sputtering laser; 17-focusing lens; 18-intake rod; 19-vacuum bellows; 20-displacement platform; 21-repulsive electric field plate; 22-excitation light; 23-deceleration electric field plate; 24-first grid; 25-second grid; 26-detector. DETAILED DESCRIPTION

[0031] The present invention will be further described below with reference to specific embodiments, and the advantages and features of the present invention will become clearer as the description proceeds. However, these embodiments are merely exemplary and do not constitute any limitation to the scope of the present invention. It should be understood by those skilled in the art that the details and forms of the technical solutions of the present invention may be modified or replaced without departing from the spirit and scope of the present invention, and such modifications and replacements fall within the scope of protection of the present invention.

[0032] like Figure 1 As shown, this embodiment provides an alkali metal Rydberg atom generation and detection device, including a beam source cavity 1 and an action cavity 2.

[0033] The beam source chamber 1 includes a gas nozzle 11, a sputtering light 16, an alkali metal solid target 12, a square metal box 13, a rotary motor 15, and a conical colander 14. The gas nozzle 11 extends into the vacuum chamber through an air inlet rod 18. The air inlet rod 18 is made of stainless steel and has a diameter of 1 cm. The other side of the air inlet rod is fixed to a displacement platform 20. The displacement platform 20 is connected to the beam source chamber via a vacuum bellows 19. The connection method of the vacuum bellows 19 not only ensures the vacuum degree but also enables position adjustment. The up and down, front and back, and left and right positions of the gas nozzle 11 can therefore be freely adjusted through the displacement platform 20, with a maximum adjustment range of 5 cm. After the high-pressure carrier gas passes through the gas nozzle 11, it forms an adiabatically expanding atomic gas mass. During the expansion process, due to collisions between atoms, the atomic velocity distribution becomes more concentrated, and the temperature exhibited is also lower.

[0034] The alkali metal solid target 12 is a cylindrical solid material, located to the right of the gas nozzle 11 and directly behind the atomic beam, with a vertical distance of about 1 cm from the atomic beam. It is also fixed in the slot of the structural member, which is fixed to the vacuum flange through a connecting rod. The slot can rotate freely under the drive of the rotary motor 15. The rotary motor is controlled by a controller outside the beam source cavity, and the motor is interconnected with the controller through the vacuum electrode on the vacuum flange.

[0035] The sputtering laser 16 is generated by an external laser. The laser is preferably a continuous laser to avoid additional timing control of the sputtering laser 16 and simplify the experimental plan. The propagation direction of the sputtering laser 16 is perpendicular to the direction of the atomic beam. After being focused by a focusing lens 17 (focal length 15 cm), the sputtering laser 16 is transmitted through the optical window of the vacuum chamber into the cavity and hits the alkali metal solid target 12. Under the action of the laser, the solid alkali metal will quickly form a burn hole. The size of the burn hole is proportional to the laser intensity E, which is:

[0036]

[0037] Among them, ω0 is the beam waist radius, E Th Threshold intensity.

[0038] The hole formation process is accompanied by plasma sputtering. To prevent the solid metal produced by sputtering from contaminating the vacuum chamber, the present invention designs a square metal box 13 to prevent the solid metal produced by sputtering from falling and adhering to the surface of the vacuum chamber. The square metal box 13 has a circular hole on the top to allow the solid target to be placed inside, and a circular hole on the front surface to allow the sputtering laser 16 to be injected. The square metal box can not only limit the solid metal produced by sputtering from falling, but also prevent the sputtering laser 16 from reflecting and hitting the vacuum chamber to generate interference signals. The gaseous metal atoms produced by sputtering are emitted through the small hole in the front of the square metal box 13 and diffuse into the carrier gas atom gas cloud, where they are fully mixed and cooled by the carrier gas. The number of atoms produced by sputtering can be controlled by adjusting the laser intensity.

[0039] In this embodiment, the neutral density filter and the quarter wave plate can be used to change the light intensity and polarization state of the sputtering laser 16 respectively. The polarization of the sputtering laser 16 is preferably set to circular polarization to achieve uniformity in the diffusion direction of the sputtered atoms.

[0040] A conical colander 14 is fixed to a vacuum flange connected to the working chamber 2 and is used to extract an atomic beam with a more concentrated velocity distribution at the center. Conical colander 14 is made of stainless steel and has a central aperture diameter of 30-100 μm. Different aperture diameters can produce atomic beams with different divergence angles. In this embodiment, the aperture diameter is 50 μm.

[0041] In this embodiment, helium gas with more stable chemical properties is preferably used as the carrier gas. The high ionization potential of helium gas ensures that it will not be affected by the sputtering laser 16 and the excitation light 22. The high-pressure helium carrier gas (about three atmospheres) is sprayed into the vacuum chamber through the gas nozzle 11 to form an adiabatic expansion atomic gas group. The vacuum in the vacuum chamber is maintained at 10 -6 At the same time, under the irradiation of the sputtering laser 16, the continuously rotating alkali metal solid target 12 produces stable gas-phase alkali metal atoms and diffuses them. Some of these alkali metal atoms collide with the expanding helium gas cloud. During the continuous collision process, the speed of the alkali metal atoms gradually aligns with the helium gas cloud, eventually forming a mixed gas cloud of alkali metal atoms and helium. The conical colander 14 further extracts the gas cloud to form a mixed atomic beam with a more concentrated velocity distribution. The velocity distribution and atom number of the atomic beam can be optimized by adjusting the left and right positions of the gas impact nozzle.

[0042] The beam source chamber 1 and the processing chamber 2 are connected via a vacuum flange, which features a 1cm diameter circular hole for the atomic beam. The atomic beam entering the processing chamber first passes through a repulsive electric field plate 21, a rectangular copper structure with a 2mm diameter circular hole in the center. Copper wire is welded to the plate and connected to an electrode on the vacuum flange. External equipment applies a positive voltage to the plate through the vacuum electrode on the flange. This positive voltage effectively removes alkali metal ions generated by laser sputtering from the atomic beam, thereby purifying the alkali metal atomic sample.

[0043] The Rydberg states of alkali metal atoms are prepared through single-photon excitation. The excitation light 22 is a pulsed laser with a frequency of 10 Hz and a pulse width of 10 ns. Different laser wavelengths correspond to different Rydberg states, and the efficiency of Rydberg state excitation is closely related to the intensity of the excitation light 22. In this embodiment, neutral density filters of different specifications are added to the propagation path of the excitation light 22 to adjust the intensity of the excitation light 22. The laser wavelength is tuned by scanning a frequency-doubling crystal. The output of the laser pulse is triggered by an external signal generated by a signal generator.

[0044] Typically, the temperature of an atomic beam in the direction of propagation is higher than that in the vertical direction. To further reduce the temperature of the atomic beam, it is necessary to decelerate the speed in the horizontal direction of propagation. The present invention utilizes the large electric dipole moment of Rydberg atoms and decelerates the Rydberg atoms through a horizontal gradient electric field. The force on the atoms in the gradient electric field is:

[0045]

[0046] Among them, μ d is the electric dipole moment, which is proportional to the principal quantum number of the Rydberg state. The horizontal gradient electric field is generated by a pair of horizontally placed electric field plates consisting of a deceleration electric field plate 23. The plates are rectangular copper structures. The gradient of the horizontal electric field can be adjusted by the spacing between the plates.

[0047] The free flight zone in the working chamber is composed of a first grid 24 and a second grid 25. The grids are rectangular mesh structures woven from copper wire, with a spacing of 15 cm between the two grids. Copper wire is welded to the grids and connected to the electrodes of the vacuum flange. Grounding the vacuum electrodes grounds the grids, which creates a free flight zone free of electric field distribution. This free flight zone is essential for time-resolved detection of Rydberg atom kinetic energy. The grid arrangement ensures electric field shielding while maximizing the flow of the Rydberg atom beam, especially when the Rydberg atoms are deflected. Furthermore, the electric field shielding effect can be further improved by adding a shielding tube. A thin copper shielding tube encasing the entire free flight zone can more thoroughly shield against external electromagnetic interference.

[0048] A circular microchannel plate detector 26 is located on the far right side of the working chamber. The microchannel plate has an 80mm diameter and is preferably three in number to achieve optimal amplification of the collision signal. The normal operating pressure differential of the microchannel plate is at least 2000V. In this embodiment, the microchannel plate is pressed between stainless steel plates. Screws extend through the four corners of the stainless steel plates and are secured to the screws with an insulating material such as polytetrafluoroethylene. The screws are fixed to the screws in the screw holes of the rightmost vacuum flange. The electrodes of the microchannel are extended through the flange. A pressure device applies high voltage to the microchannel plate through the electrodes. This high voltage not only ionizes the alkali metal Rydberg atoms but also accelerates the ionized ions to the energy threshold of the microchannel plate's response. To more clearly illustrate the detection method, the fastening components are not shown in the accompanying drawings.

[0049] like Figure 1 As shown, the present invention employs a unique detection voltage application method, which combines a high bias voltage with a pulse voltage. The high bias voltage is provided by a DC high-voltage power supply, and the pulse voltage is provided by a pulse voltage source, which is activated by an external trigger signal. The high bias voltage is set below the normal operating voltage of the microchannel plate. The microchannel plate can only respond to ion collision signals and perform detection when both the high bias voltage and the pulse voltage are applied simultaneously.

[0050] In actual operation, the pulse voltage and the trigger signal of the excitation light 22 maintain the same frequency and are set with a certain delay. The delay of the two trigger signals can be set by a pulse delay generator, so that the detector can only start detection when the Rydberg atom flies to the microchannel plate. This not only avoids the use loss caused by continuous operation of the detector, but more importantly, reduces the accumulated background noise and improves the signal-to-noise ratio of the detection.

[0051] Although the preferred embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the above-mentioned specific embodiments. The above-mentioned specific embodiments are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms of specific changes without departing from the scope of protection of the invention and the claims. These all fall within the scope of protection of the present invention.

Claims

1. An alkali metal Rydberg atom generation and detection device, characterized in that: The alkali metal Rydberg atom generation and detection device comprises a beam source cavity (1) and an action cavity (2); The beam source cavity (1) is used to prepare an alkali metal ultrasonic atomic beam, and comprises a gas nozzle (11), a sputtering laser (16), an alkali metal solid target (12), and a conical colander (14); The gas nozzle (11) extends into the cavity through the gas inlet rod (18) and is used to spray high-pressure carrier gas to generate an adiabatically expanded atomic gas cluster; the alkali metal solid target (12) is located at a position directly opposite the atomic gas cluster; the sputtering laser (16) sputters the alkali metal solid target (12) to generate gaseous alkali metal atoms and diffuse into the atomic gas cluster; the conical colander is fixed on the vacuum flange of the beam source cavity (1) and is located at a corresponding position where the alkali metal solid target (12) generates gaseous alkali metal atoms and diffuses into the atomic gas cluster, and is used to pass through an ultrasonic atomic beam with a more concentrated velocity distribution at the center of the atomic gas cluster; The action chamber (2) includes a Rydberg excitation region, a free flight region, and a detector (26); the Rydberg excitation region includes a repulsive electric field plate (21), an excitation light (22), and a deceleration electric field plate (23); The repulsive electric field plate (21) is located on a side of the action chamber (2) adjacent to the beam source chamber (1), and the repulsive electric field plate (21) is connected to a positive voltage for blowing out the alkali metal ions carried in the atomic beam; the excitation light (22) is incident into the action chamber (2) through the optical window, for exciting the alkali metal atoms to a high Rydberg state, thereby preparing alkali metal Rydberg atoms; the deceleration electric field plate (23) is a pair of parallel electrode plates, for generating a horizontal gradient electric field to decelerate and cool the Rydberg atoms; the free flight zone includes two grounding grids; the detector (26) includes at least two circular microchannel plates with high voltage applied, and the microchannel plates are mounted on a vacuum flange on the action chamber (2) away from the beam source chamber (1), and an external pressurizing device can apply high voltage through the electrodes to enable the microchannel plates to work normally; The deceleration electric field plate (23) utilizes the large electric dipole moment characteristic of the Rydberg atoms to decelerate the Rydberg atoms through a horizontal gradient electric field. The force exerted on the atoms in the gradient electric field is: ； in, is the electric dipole moment, which is proportional to the principal quantum number of the Rydberg state. is the electric field gradient; The pressurizing device applies high voltage to the microchannel plate through electrodes. The high voltage application method of the microchannel plate adopts a combination of bias voltage and pulse voltage to ionize alkali metal Rydberg atoms and accelerate the ionized ions to reach the energy threshold of the microchannel plate response.

2. The alkali metal Rydberg atom generation and detection device according to claim 1, characterized in that: The beam source chamber (1) further comprises a rotary motor (15); the alkali metal solid target (12) is mounted on the rotary motor (15) to improve the stability of the sputtering signal, and the rotary motor (15) is controlled by an external controller.

3. The alkali metal Rydberg atom generation and detection device according to claim 1, characterized in that: The beam source cavity (1) further comprises a square metal box (13), wherein openings are provided on the top of the square metal box (13), in the incident direction of the sputtering laser (16), and on the side adjacent to the conical colander (14), and the alkali metal solid target (12) extends into the square metal box (13) through the top opening; The sputtering laser (16) is injected into the interior of the square metal box through the opening, and generates gaseous metal atoms with the alkali metal solid target (12). The gaseous metal atoms are emitted through the opening on the side adjacent to the conical colander (14) and diffuse into the atomic gas mass; The square metal box (13) is used to prevent the sputtering laser (16) from reflecting and hitting the vacuum cavity to generate interference signals, and to prevent solid metal generated by sputtering from falling and adhering to the surface of the vacuum cavity.

4. The alkali metal Rydberg atom generation and detection device according to claim 1, characterized in that: The alkali metal Rydberg atom generation and detection device further includes a focusing lens (17); The propagation direction of the sputtering laser (16) is perpendicular to the direction of the atomic beam. After being focused by the focusing lens (17), the sputtering laser (16) is transmitted into the cavity through the optical window of the vacuum cavity and hits the alkali metal solid target (12). Under the action of the laser, the solid alkali metal will quickly form a burn hole: ； in, is the beam waist radius, is the burnt hole size, is the laser intensity, Threshold intensity.

5. The alkali metal Rydberg atom generation and detection device according to claim 1, characterized in that: The sputtering laser (16) can respectively change the light intensity and polarization state by using a neutral density filter and a quarter wave plate, and the sputtering laser (16) is circularly polarized to achieve uniformity in the diffusion direction of sputtered atoms.

6. The alkali metal Rydberg atom generation and detection device according to claim 1, characterized in that: The detector (26) has three microchannel plates, each of which is pressed between stainless steel plates. Screws are passed through the four corners of the stainless steel plates. The stainless steel plates are pressed and fixed on the screws with insulating materials such as polytetrafluoroethylene, and the screws are fixed on the vacuum flange.

7. The alkali metal Rydberg atom generation and detection device according to claim 1, characterized in that: The excitation light (22) is a pulsed laser with a frequency of 10 Hz and a pulse width of 10 ns.

8. The alkali metal Rydberg atom generation and detection device according to claim 1, characterized in that: The carrier gas is helium, and the vacuum in the vacuum chamber is maintained at 10 -6 Pa level.

9. The alkali metal Rydberg atom generation and detection device according to claim 1, characterized in that: The conical colander (14) is made of stainless steel, and the diameter of the central circular hole is 30-100 μm. Different hole diameters are used to generate atomic beams with different divergence angles.

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