A dual-beam small-angle Zeeman decelerator

Abstract

The present application relates to the technical field of Zeeman decelerator, in particular to a kind of double-beam small-angle Zeeman decelerator, including sequentially connected and communicating atomic beam vacuum pipeline, vacuum deceleration area, cooling light vacuum pipeline, the atomic beam vacuum pipeline is provided with atomic reaction furnace, the rear end of the cooling light vacuum pipeline is equipped with vacuum optical window, the cooling light vacuum pipeline is two, and it is arranged in eight-character shape symmetry, the included angle of each cooling light vacuum pipeline axis and atomic beam vacuum pipeline axis is 3~30 °.Both can reduce the damage of vacuum optical window, and can meet the miniaturization application demand, compact and small, and the deceleration effect can also meet the experimental requirements.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of laser cooling technology, in particular to a small double-beam small-angle Zeeman decelerator capable of effectively protecting a vacuum optical window. BACKGROUND

[0002] The Zeeman decelerator is a key technology for obtaining cold atoms and is widely used for laser deceleration of high-temperature hot atoms (several hundred meters per second) to effectively reduce the speed of atoms to several meters per second. The Zeeman decelerator plays an indispensable key role in many experimental studies of quantum simplicities, especially in the quantum simplicity experiments of alkaline earth metal or rare earth metal atoms. At present, miniaturization and compactness are important directions for the further development of cold atom technology. Among them, a high-performance, compact, reliable, and durable, and simple water-cooled miniaturized general-purpose Zeeman decelerator is a key core for the development and application of cold atom technology in the next stage.

[0003] In terms of structure, the cooling beam (i.e. laser beam) in the Zeeman decelerator needs to be opposite to the direction of the hot atom beam, and the vacuum optical window is opposite to the atom beam. The cooling light enters the Zeeman decelerator through the vacuum optical window, and the vacuum deceleration area is covered on the rear end of the atom beam vacuum pipeline to cool the atom beam. In this direction, the energized coil provides a suitable gradient magnetic field to compensate for the Doppler shift caused by the change in atomic speed, so that the cooling light frequency always resonates with the atomic transition level, thereby producing a continuous laser deceleration effect, which greatly reduces the speed of high-temperature hot atoms in a short distance.

[0004] However, due to multiple physical factors, including length, the Zeeman decelerator is difficult to achieve deceleration of all hot atom beams, and can only produce deceleration effect on a small proportion of atom beams. During the deceleration process, although most of the hot atoms are lost, some high-temperature atoms that are not cooled by the two-dimensional vacuum deceleration area will reach the front vacuum optical window and interact with the vacuum optical window, which reduces the permeability of the vacuum optical window and damages the airtightness of the vacuum optical window, resulting in leakage of the vacuum and affecting the long-term stability of the system. In order to solve the above problems, the common method is to lengthen the distance between the atom deceleration outlet of the Zeeman decelerator and the vacuum optical window, and introduce a 45° metal mirror in the vacuum system to avoid the direct impact of hot atoms on the vacuum optical window. However, the above method greatly increases the length and complexity of the system, and on the other hand, the atoms can still interact with the metal mirror (evaporation or corrosion), affecting its optical performance. SUMMARY

[0005] The present application aims to provide a high-performance Zeeman decelerator that can reduce damage to the vacuum optical window and meet the application requirements of miniaturization.

[0006] To this end, the technical scheme adopted by the present application is as follows: a double-beam small-angle Zeeman decelerator, comprising an atomic beam vacuum pipeline, a vacuum deceleration area and cooling light vacuum pipelines which are connected in sequence and communicate with each other, wherein an atomic reaction furnace is arranged in the atomic beam vacuum pipeline, a vacuum optical window is mounted at the rear end of the cooling light vacuum pipeline, and the cooling light vacuum pipeline is in the shape of an eight-character and is symmetrically arranged, and the included angle between the axis of each cooling light vacuum pipeline and the axis of the atomic beam vacuum pipeline is 3-30°.

[0007] As a preferred embodiment of the above-mentioned scheme, a capillary array tube is coaxially mounted in the atomic beam vacuum pipeline, and a plurality of capillary pipelines arranged in an array and parallel to the axis of the atomic beam vacuum pipeline are formed in the capillary array tube, so that the atomic beam in the atomic beam vacuum pipeline enters the vacuum deceleration area after passing through the capillary array tube. The collimation of the atomic beam is enhanced by placing the capillary array tube in the atomic beam vacuum pipeline.

[0008] Further preferably, baffles are arranged on the side wall of the atomic beam vacuum pipeline and are arranged behind the capillary array tube. On the basis of the capillary array tube, the capillary array tube is used to collimate the angular distribution of the atomic beam once, and the baffles are used to collimate the angular distribution of the atomic beam twice. At the same time, the baffles can increase the collimation length and provide an atomic beam with higher collimation, thereby improving the Zeeman deceleration efficiency.

[0009] Further preferably, the atomic beam vacuum pipeline, the cooling light vacuum pipeline and the capillary array tube are all circular pipelines, the capillary pipelines on the capillary array tube are in the shape of a multi-circular ring array or a regular polygon ring array, and the regular polygon ring is at least a regular pentagon ring.

[0010] Further preferably, the baffles are in the shape of a circular ring and are welded and fixed to the inner wall of the atomic beam vacuum pipeline.

[0011] Further preferably, the atomic beam vacuum pipeline and the cooling light vacuum pipeline are integrally cast, and the vacuum deceleration area is arranged outside the rear end of the atomic beam vacuum pipeline.

[0012] Further preferably, the included angle between the axis of the cooling light vacuum pipeline and the axis of the atomic beam vacuum pipeline is 5-7°.

[0013] The present application has the following beneficial effects: by symmetrically arranging two cooling light vacuum pipelines in the shape of an eight-character, the direction of the cooling light of the Zeeman decelerator is changed so as to form a small angle with the direction of the atomic beam, the direct impact of the atomic beam which has not been decelerated by the vacuum deceleration area on the vacuum optical window can be greatly reduced, the damage of the atomic beam to the vacuum optical window can be significantly reduced, the service life of the Zeeman decelerator can be prolonged, the risk of vacuum leakage caused by the atomic beam with strong metal properties can be avoided, and the damage of the atomic beam to the vacuum optical window can be reduced.

[0014] The double-beam small-angle Zeeman decelerator can reduce damage of atomic beam to a vacuum optical window without increasing length of a cooling light vacuum pipeline, has a smaller volume than a conventional Zeeman decelerator, and can meet experimental requirements.

[0015] In addition, the double-beam small-angle Zeeman decelerator has a symmetric small-angle double-cooling light path structure, can reduce a requirement for single-path laser power, and can not require laser power output by all wavelengths of optical fibers to meet a power requirement of the Zeeman decelerator. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a principle schematic diagram of the double-beam small-angle Zeeman decelerator.

[0017] Figure 2 is a structure schematic diagram of the double-beam small-angle Zeeman decelerator.

[0018] Figure 3 is a structure schematic diagram of the capillary array tube.

[0019] Figure 4 is a proportion curve of the atomic beam that can reach the optical window under different angles of the Zeeman decelerator cooling light in the embodiment of the present application.

[0020] Figure 5 is a deceleration effect diagram of the Zeeman decelerator on the atomic beam in the embodiment of the present application.

[0021] In the drawings: 1, atomic beam vacuum pipeline; 2, capillary array tube; 3, vacuum deceleration region; 4, cooling light vacuum pipeline; 5, atomic reaction furnace; 6, vacuum optical window; and 7, baffle. DETAILED DESCRIPTION

[0022] The present application will be further described below in combination with the drawings, but the protection scope of the present application is not limited to the following description.

[0023] As shown in Figure 1 , Figure 3 , a double-beam small-angle Zeeman decelerator mainly comprises an atomic beam vacuum pipeline 1, a vacuum deceleration region 3, and a cooling light vacuum pipeline 4 connected in sequence and in communication. The atomic beam vacuum pipeline 1 is provided with an atomic reaction furnace 5 for generating a hot atomic beam. The vacuum deceleration region 3 is used for laser cooling of the atomic beam. The rear end of the cooling light vacuum pipeline 4 is provided with a vacuum optical window 6. The atomic beam vacuum pipeline 1 is used for passing the hot atomic beam. The cooling light beam (i.e. laser beam) enters the Zeeman decelerator through the vacuum optical window 6. The above belongs to the prior art, and will not be described here.

[0024] The difference lies in that: the two cooling light vacuum pipes 4 are arranged in a figure-of-eight shape and symmetrically, and the angle between the axis of each cooling light vacuum pipe 4 and the axis of the atomic beam vacuum pipe 1 is 3-30°, preferably 5-8°. With the axis of the atomic beam vacuum pipe 1 as the central axis, the two cooling light vacuum pipes 4 are arranged in a figure-of-eight shape and symmetrically.

[0025] The rear end of each cooling light vacuum pipe 4 is fixed with a light-transmitting glass as a vacuum optical window 6 through an M6 screw. Two beams of cooling light enter the cooling light vacuum pipe 4 through the vacuum optical window 6 and form a pair of beams with the atomic beam after being combined.

[0026] The capillary array pipe 2 is coaxially arranged in the atomic beam vacuum pipe 1. A plurality of capillary pipes arranged in an array and parallel to the axis of the atomic beam vacuum pipe 1 are arranged on the capillary array pipe 2, so that the atomic beam in the atomic beam vacuum pipe 1 enters the vacuum deceleration area 3 after passing through the capillary array pipe 2. The capillary pipes on the capillary array pipe 2 are completely symmetrically arranged with the axis of the atomic beam vacuum pipe 1 as the central axis.

[0027] Preferably, the side wall of the atomic beam vacuum pipe 1 is provided with a baffle 7, and the baffle 7 is arranged behind the capillary array pipe 2. The baffle 7 can be a circular ring, or two plates arranged oppositely up and down, and the baffle 7 is welded and fixed on the inner wall of the atomic beam vacuum pipe 1.

[0028] In addition, the atomic beam vacuum pipe 1, the cooling light vacuum pipe 4 and the capillary array pipe 2 are all circular pipes, and the capillary pipes on the capillary array pipe 2 are arranged in a multi-circular ring array or a regular polygon ring array, and the regular polygon ring is at least a regular pentagon ring, and can also be a hexagon ring and a polygon ring with more sides.

[0029] The atomic beam vacuum pipe 1 and the cooling light vacuum pipe 4 are integrally cast, and the vacuum deceleration area 3 is covered outside the rear end of the atomic beam vacuum pipe 1.

[0030] The Zeeman decelerator can cool the hot atomic beam of rubidium, ytterbium and the like heated by the atomic reactor to form a low-speed high-flux atomic beam. The following describes the specific operation method by taking rubidium atoms as an example, using the double-beam small-angle Zeeman decelerator in the application:

[0031] Firstly, the capillary array pipe is modeled to obtain the angular distribution of the atomic beam after passing through the capillary array pipe. The length, diameter and atomic reactor heating temperature of the capillary pipe and other related parameters are optimized and calculated to obtain an atomic beam with good collimation, that is, narrow angular distribution.

[0032] Secondly, the atomic beam vacuum pipeline and the cooling light vacuum pipeline are analyzed, and the model is simplified to a solid angle model. By changing the related parameters such as the cooling light vacuum pipeline and the diameter, the proportion curve of the atomic beam current that can reach the optical window under the condition of the cooling light of the different angles of the Zeeman decelerator can be obtained, as shown in FIG. 2. The design parameters of the double-beam small-angle Zeeman decelerator suitable for rubidium atoms are determined by calculation in this embodiment: the length of the cooling light vacuum pipeline is 50 cm, the diameter is 20 mm, and the included angle between the cooling light vacuum pipeline and the atomic beam vacuum pipeline is 7°. Figure 4

[0033] Thirdly, the process of the deceleration experiment on the rubidium atoms under the condition of this embodiment and the magnetic field of the permanent magnet is simulated by establishing a Monte Carlo experiment model. In the above Monte Carlo experiment process, the position and magnetization intensity of the permanent magnet are adjusted to optimize the magnetic field distribution, so that more atoms are decelerated.

[0034] Fourthly, through simulation evaluation, the double-beam small-angle Zeeman decelerator in the embodiment of the present application can reduce the damage of about 4 times of the atomic beam current to the optical window, obtain about 200%-400% of the Zeeman deceleration efficiency, and meet the experimental requirements, as shown in FIG. 3. Figure 5

[0035] Although the embodiments of the present application have been shown and described, it can be understood by those skilled in the art that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirits of the present application, and the scope of the present application is defined by the appended claims and their equivalents.​​

Claims

1. A double-beam small-angle Zeeman decelerator, comprising an atomic beam vacuum pipe (1), a vacuum deceleration region (3), and a cooling light vacuum pipe (4) connected in sequence and in communication, an atomic reaction furnace (5) being arranged in the atomic beam vacuum pipe (1), and a vacuum optical window (6) being mounted at the rear end of the cooling light vacuum pipe (4), characterized in that: The cooling light vacuum pipe (4) is two in total and is arranged in a figure-eight shape, and the angle between the axis of each cooling light vacuum pipe (4) and the axis of the atomic beam vacuum pipe (1) is 5-7°. ​ 2. A dual-beam small-angle Zeeman decelerator according to claim 1, characterized in that: A capillary array pipe (2) is coaxially arranged in the atomic beam vacuum pipe (1), and a plurality of capillary pipes arranged in an array and parallel to the axis of the atomic beam vacuum pipe (1) are formed in the capillary array pipe (2), so that the atomic beam in the atomic beam vacuum pipe (1) passes through the capillary array pipe (2) and enters the vacuum deceleration area (3).

3. A dual-beam small-angle Zeeman decelerator according to claim 2, characterized in that: A baffle (7) is arranged on the side wall of the atomic beam vacuum pipe (1) and is arranged behind the capillary array pipe (2).

4. A dual-beam small-angle Zeeman decelerator according to claim 2 or 3, characterized in that: The atomic beam vacuum pipe (1), the cooling light vacuum pipe (4) and the capillary array pipe (2) are all circular pipes, the capillary pipes on the capillary array pipe (2) are arranged in a multi-circular ring array or a regular polygon ring array, and the regular polygon ring is at least a regular pentagon ring.

5. A dual-beam small-angle Zeeman decelerator according to claim 3, characterized in that: The baffle (7) is a circular ring and is welded and fixed to the inner wall of the atomic beam vacuum pipe (1).

6. A dual-beam small-angle Zeeman decelerator according to claim 1, characterized in that: The atomic beam vacuum pipe (1) and the cooling light vacuum pipe (4) are integrally cast, and the vacuum deceleration area (3) is arranged outside the rear end of the atomic beam vacuum pipe (1).

Images