Generation device of a compact low-speed atomic source

Abstract

A generating device for a compact low-speed atomic source, comprising a vacuum chamber, an atomic furnace, a two-dimensional quadrupole magnetic field generating device, a cooling laser, and a pushing laser. The cooling laser and the two-dimensional quadrupole magnetic field generating device form a two-dimensional magneto-optical trap in the vacuum chamber. In the present invention, the atomic furnace generates a nearly collimated large-beam thermal atomic beam, and the thermal atoms generated by the atomic furnace are decelerated by the two-dimensional magneto-optical trap. The pushing laser pushes the low-speed atoms in the two-dimensional magneto-optical trap to the experimental area, ensuring a high vacuum degree in the experimental area on the premise of ensuring the beam current. The beam current of the atomic beam is switched on and off by switching the cooling laser and the pushing laser; by selecting appropriate frequencies of the cooling laser and the pushing laser, the isotopes of the decelerated atoms can be selected. The atomic furnace is located in the vacuum chamber as close as possible to the two-dimensional magneto-optical trap area, and the ejection direction of the atomic furnace forms a certain angle with the vacuum window of the two-dimensional magneto-optical trap, which can ensure that the un-decelerated atoms ejected from the atomic furnace do not adhere to the surface of the cavity mirror and contaminate the vacuum window. This device directly generates a large-beam low-speed atom from a thermal atomic beam by using a two-dimensional magneto-optical trap.

Description

Technical Field

[0001] The present invention relates to a low-speed atomic source generating device, in particular to a generating device for a compact low-speed atomic source. Background Art

[0002] Laser cooling technology can cool an atomic system to near absolute zero. Due to the characteristics of the cooled atoms such as low velocity and good coherence, it is essential for research in fields such as precision measurement and quantum simulation, and plays a crucial role in the research of new physics, new phenomena, and new technologies. In precision measurement, in order to minimize the dead time, the loading time of the three-dimensional magneto-optical trap needs to be as short as possible, which requires a low-speed and high-beam atomic source generating device. Traditional generation methods include Zeeman deceleration and two-dimensional magneto-optical traps. Since Zeeman deceleration requires a certain deceleration distance and cannot achieve a compact structure, while the two-dimensional magneto-optical trap has no such limitation. Summary of the Invention

[0003] The object of the present invention is to provide a device for generating a compact low-speed atomic source. The atomic furnace is placed in a vacuum chamber after adding a heat shield. The cooling laser and the two-dimensional quadrupole magnetic field generating device form a two-dimensional magneto-optical trap in the vacuum chamber. The atomic furnace is as close as possible to the center of the two-dimensional magneto-optical trap, so that the device can be small, compact and have low power consumption. The direction of the hot atoms ejected from the atomic furnace forms a certain angle with the directions of the cooling laser and the pushing laser respectively. On the one hand, it prevents the ejected hot atoms from contaminating the window of the vacuum chamber, and on the other hand, it prevents the hot atoms from directly spraying onto the experimental area and reducing the vacuum degree of the experimental area. The two-dimensional magneto-optical trap decelerates the hot atoms and quickly switches the low-speed atomic source by controlling the light intensity switches of the pushing laser and the cooling laser. By selecting an appropriate frequency of the cooling laser, the isotope of the decelerated atoms can be selected.

[0004] The technical solution of the present invention is as follows:

[0005] A generating device for a compact low-speed atomic source, characterized in that the device includes a vacuum chamber, an atomic furnace, a cooling laser, a two-dimensional quadrupole magnetic field generating device and a pushing laser. The cooling laser and the two-dimensional quadrupole magnetic field generating device form a two-dimensional magneto-optical trap in the vacuum chamber. The connection relationship of the above components is as follows:

[0006] The described atomic furnace is fixed in the vacuum chamber through an electrode flange, near the two-dimensional magneto-optical trap region. The atomic furnace is placed inside a thermal shielding cylinder. By heating, atoms are ejected from the nozzle of the capillary tube of the atomic furnace to form a nearly collimated thermal atomic source. The emission direction of the thermal atoms is perpendicular to the z-direction and forms a certain angle with the x- and y-directions. The cooling lasers are located in the same x, y plane. The cooling lasers are two pairs of mutually perpendicular circularly polarized lasers, respectively along the x-direction and the y-direction. Their polarization directions are related to the magnetic field direction of the quadrupole trap: the light along the magnetic field direction is left-handed circularly polarized light, and the light against the magnetic field direction is right-handed circularly polarized light. The pushing laser is along the z-direction, pushing the thermal atoms in the two-dimensional magneto-optical trap to the experimental area. The two-dimensional magneto-optical trap decelerates the thermal atoms generated by the atomic furnace and traps them in two dimensions. The role of the two-dimensional quadrupole magnetic field generating device is to generate a two-dimensional magnetic field gradient, cooperate with the cooling lasers to decelerate the atoms and trap them in two dimensions. The magnetic field zero point is within the overlapping region of the cooling lasers. The nearly collimated thermal atomic beam generated by the atomic furnace passes through the magnetic field zero point. The pushing laser and the cooling lasers hit the atomic cloud cooled by the two-dimensional magneto-optical trap. The frequencies of the pushing laser and the cooling lasers are resonant or blue-detuned with the atoms, and their role is to push the decelerated atoms to the experimental area part.

[0007] The described two-dimensional quadrupole magnetic field generating device is generated by a coil group or a permanent magnet group.

[0008] The pushing laser forms a certain angle with the thermal atomic beam and the cooling light. By changing the temperature of the atomic furnace and the number, length, and inner diameter of the capillary tubes, the beam current and divergence angle of the thermal atomic source are adjusted. Generally, the divergence angle of the nearly collimated thermal atomic source is only a few tens of milliradians.

[0009] The effects of the present invention are as follows:

[0010] 1. Compact structure. In the present invention, the described atomic furnace is placed in the vacuum chamber of the two-dimensional magneto-optical trap, and its edge is only a few tens of millimeters away from the center of the two-dimensional magneto-optical trap. The structure is very compact, reducing the volume of the vacuum chamber.

[0011] 2. Generating low-speed atoms. The present invention uses the method of a two-dimensional magneto-optical trap to generate low-speed atoms. The nearly collimated thermal atomic source ejected from the atomic furnace has a divergence angle of only a few tens of milliradians. Therefore, basically all atoms can reach the cooling region of the two-dimensional magneto-optical trap, improving the atomic beam current. In addition, since the diameter of the thermal atomic beam in the two-dimensional magneto-optical trap region is only a few millimeters, the spot shape of the cooling laser can be adjusted to be elongated or elliptical in the atomic beam direction. In this way, at the same cooling laser power, the capture speed of the two-dimensional magneto-optical trap can be increased.

[0012] 3. Avoid contaminating the endoscope of the vacuum chamber and ensure the vacuum degree of the experimental area. In the present invention, the direction of the hot atoms ejected from the atomic furnace is almost orthogonal or at a certain angle to the direction of the low-speed atoms generated by the two-dimensional magneto-optical trap to the experimental area, so that the hot atoms will not reach the experimental area. On the one hand, it will not contaminate the window of the vacuum chamber, and on the other hand, it can ensure the vacuum degree of the experimental area.

[0013] 4. Low-speed atom switch. In the present invention, no mechanical switch is required. Only by switching the cooling laser and the pushing laser described above can the switch of the low-speed atoms to the experimental area be realized.

[0014] 5. Select low-speed atomic isotopes. The present invention can select low-speed atomic isotopes by selecting appropriate cooling laser frequencies and pushing laser frequencies and send them to the experimental area.

[0015] In summary, the structure of the present invention is simple and applicable to atoms that require heating by an atomic furnace with a low background vapor pressure, especially applicable to devices that need to reduce the volume such as portable or spaceborne devices. Description of the Drawings

[0016] Figure 1 Position diagram of the atomic furnace and the cooling laser.

[0017] Figure 2 It is a diagram showing the relationship between the cooling laser of the two-dimensional magneto-optical trap and the magnetic field. Detailed Embodiments

[0018] The present invention will be further described below in conjunction with the drawings, but the scope of transformation of the present invention should not be limited thereby.

[0019] First, please refer to Figure 1 , Figure 1 which is a schematic diagram of the generating device of the compact low-speed atomic source of the present invention. As can be seen from the figure, the generating device of the compact low-speed atomic source of the present invention is characterized in that the device includes a vacuum chamber, an atomic furnace, a cooling laser, a two-dimensional quadrupole magnetic field generating device and a pushing laser. The cooling laser and the two-dimensional quadrupole magnetic field generating device form a two-dimensional magneto-optical trap in the vacuum chamber. The connection relationship of the above devices is as follows:

[0020] The described atomic furnace is fixed in the vacuum chamber through an electrode flange, near the two-dimensional magneto-optical trap region. The atomic furnace is placed inside a thermal shield cylinder. By heating, atoms are ejected from the nozzle of the capillary of the atomic furnace to form a nearly collimated thermal atomic source. The emission direction of the thermal atoms is perpendicular to the z direction and at a certain angle with the x and y directions. The cooling lasers are located in the same x, y plane. The cooling lasers are two pairs of mutually perpendicular circularly polarized lasers, respectively along the x direction and the y direction, and the polarization direction thereof is related to the magnetic field direction of the quadrupole trap: the light along the magnetic field direction is left-handed circularly polarized light, and the light against the magnetic field direction is right-handed circularly polarized light; the pushing laser is along the z direction, and pushes the thermal atoms in the two-dimensional magneto-optical trap to the experimental area. The two-dimensional magneto-optical trap decelerates the thermal atoms generated by the atomic furnace.

[0021] The function of the described two-dimensional quadrupole magnetic field generating device is to generate a two-dimensional magnetic field gradient, cooperate with the cooling lasers to decelerate the atoms and trap them in two dimensions; the magnetic field zero point is within the overlapping region of the cooling lasers. The nearly collimated thermal atomic beam generated by the atomic furnace passes through the magnetic field zero point. The pushing laser and the cooling lasers act on the atomic cloud cooled by the two-dimensional magneto-optical trap. The frequencies of the pushing laser and the cooling lasers are resonant with the atoms or blue-detuned, and the function is to push the decelerated atoms to the experimental area part.

[0022] The described two-dimensional quadrupole magnetic field generating device is generated by a coil group or a permanent magnet group.

[0023] The pushing laser forms a certain angle with the thermal atomic beam and the cooling light. By changing the temperature of the atomic furnace and the number, length and inner diameter of the capillaries, the beam current and divergence angle of the thermal atomic source are adjusted. Generally, the divergence angle of the nearly collimated thermal atomic source is only dozens of milliradians.

[0024] The atomic furnace generates a nearly collimated thermal atomic source. High-purity atoms are placed in the atomic furnace, and the atomic furnace is electrically heated through the electrodes on the vacuum flange. The heated high-speed atoms are ejected after being collimated by the capillary at the furnace mouth. The emission direction of the thermal atoms is perpendicular to the z direction and at a certain angle with the x and y directions. By controlling the temperature of the atomic furnace and the number, length and inner diameter of the capillaries, the beam current and divergence angle of the thermal atoms can be controlled. One or more layers of thermal shields are added outside the atomic furnace to reduce the power consumption of the atomic furnace and at the same time reduce the blackbody radiation frequency shift of the atoms in the experimental area.

[0025] The cooling lasers are two pairs of mutually perpendicular circularly polarized lights respectively along the x direction and the y direction, and the polarization direction of the laser is related to the magnetic field direction of the quadrupole trap. Specifically, the light along the magnetic field direction is left-handed circularly polarized light, and the light against the magnetic field direction is right-handed circularly polarized light. The frequency of the cooling lasers is red-detuned from the atomic resonant transition.

[0026] The described two-dimensional quadrupole magnetic field generating device can be produced by a coil set or a permanent magnet set, and its magnetic field direction is coordinated with the polarization of the cooling laser. The magnetic field gradients in the x and y directions are generally from several G / cm to dozens of G / cm, and its magnetic field zero point is within the overlapping region of the cooling laser. The nearly collimated thermal atomic beam generated by the described atomic furnace passes through the magnetic field zero point.

[0027] The overlapping region of the described cooling laser is the cooling region of the two-dimensional magneto-optical trap. By selecting different spot sizes and detunings of the cooling laser and the magnetic field gradient of the magnetic field, different maximum capture velocities of the two-dimensional magneto-optical trap can be selected. In addition, since the atomic furnace has good collimation and is very close to the two-dimensional magneto-optical trap, it can be considered that the atoms ejected from the atomic furnace all reach the deceleration region of the two-dimensional magneto-optical trap, and the atoms with velocities less than the maximum capture velocity of the two-dimensional magneto-optical trap can be cooled by the two-dimensional magneto-optical trap and trapped at the magnetic field zero point.

[0028] The described push laser is along the z direction and hits the atomic cloud cooled by the two-dimensional magneto-optical trap. Its frequency is resonant or blue-detuned with the atoms, and its function is to push the atoms decelerated by the two-dimensional magneto-optical trap to the experimental area part and enhance the decelerated atomic beam current in the experimental area.

[0029] Experiments show that the structure of the present invention is simple and applicable to atoms that require heating by an atomic furnace with a low background vapor pressure, and is particularly applicable to devices such as portable or spaceborne devices that require volume reduction.

Claims

1. A generating device for a compact low-speed atomic source, characterized in that The device includes a vacuum chamber, an atomic furnace, cooling lasers, a two-dimensional quadrupole magnetic field generating device, and a push laser. The cooling lasers and the two-dimensional quadrupole magnetic field generating device form a two-dimensional magneto-optical trap in the vacuum chamber; The atomic furnace is fixed in the vacuum chamber through an electrode flange, near the two-dimensional magneto-optical trap region. The atomic furnace is placed in a thermal shielding cylinder. By heating, atoms are ejected from the nozzle of the capillary of the atomic furnace to form a nearly collimated hot atomic source. The emission direction of the hot atoms is perpendicular to the z direction and forms a certain angle with the x and y directions. The cooling lasers are located in the same x, y plane. The cooling lasers are two pairs of mutually perpendicular circularly polarized lasers, respectively along the x direction and the y direction. Their polarization directions are related to the direction of the two-dimensional quadrupole magnetic field: the light along the magnetic field direction is left-handed circularly polarized light, and the light against the magnetic field direction is right-handed circularly polarized light. The push laser is along the z direction, pushing the hot atoms in the two-dimensional magneto-optical trap to the experimental area. The two-dimensional magneto-optical trap decelerates the hot atoms generated by the atomic furnace and traps them in two dimensions. The function of the two-dimensional quadrupole magnetic field generating device is to generate a two-dimensional magnetic field gradient, cooperate with the cooling lasers to decelerate the atoms and trap them in two dimensions. The magnetic field zero point is within the overlapping region of the cooling lasers. The nearly collimated hot atomic beam generated by the atomic furnace passes through the magnetic field zero point. The push laser and the cooling lasers hit the atomic cloud cooled by the two-dimensional magneto-optical trap. The frequencies of the push laser and the cooling lasers are resonant or blue-detuned with the atoms, and their function is to push the decelerated atoms to the experimental area part.

2. The generating device of the compact low-speed atomic source according to claim 1, characterized in that The two-dimensional quadrupole magnetic field generating device is generated by a coil group or a permanent magnet group.

3. The generating device of the compact low-speed atomic source according to claim 1 or 2, characterized in that The push laser forms a certain angle with the hot atomic beam and the cooling lasers. By changing the temperature of the atomic furnace and the number, length, and inner diameter of the capillaries, the beam current and divergence angle of the hot atomic source are adjusted. The divergence angle of the nearly collimated hot atomic source is several tens of milliradians.

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