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Chinese Optics Letters

Momentum filtering scheme of cooling atomic clouds for the Chinese Space Station

Hui Li, Biao Wu, Jiachen Yu, Xiaolong Yuan, Xiaoji Zhou, Bin Wang, Weibiao Chen, Wei Xiong, Xuzong Chen

Published Jan 1, 2023• 4 citations
Publisher

Abstract

To obtain cold atom samples with temperatures lower than 100 pK in the cold atom physics rack experiment of the Chinese Space Station, we propose to use the momentum filtering method for deep cooling of atoms.This paper introduces the experimental results of the momentum filtering method verified by our ground testing system.In the experiment, we designed a specific experimental sequence of standing-wave light pulses to control the temperature, atomic number, and size of the atomic cloud.The results show that the momentum filter can effectively and conveniently reduce the temperature of the atomic cloud and the energy of Bose-Einstein condensation, and can be flexibly combined with other cooling methods to enhance the cooling effect.This work provides a method for the atomic cooling scheme of the ultra-cold atomic system on the ground and on the space station, and shows a way of deep cooling atoms.

DOI
10.3788/col202321.080201

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To obtain cold atom samples with temperatures lower than 100 pK in the cold atom physics rack experiment of the Chinese Space Station, we propose to use the momentum filtering method for deep cooling of atoms.This paper introduces the experimental results of the momentum filtering method verified by our ground testing system.In the experiment, we designed a specific experimental sequence of standing-wave light pulses to control the temperature, atomic number, and size of the atomic cloud.The results show that the momentum filter can effectively and conveniently reduce the temperature of the atomic cloud and the energy of Bose-Einstein condensation, and can be flexibly combined with other cooling methods to enhance the cooling effect.This work provides a method for the atomic cooling scheme of the ultra-cold atomic system on the ground and on the space station, and shows a way of deep cooling atoms.
The Cold Atom Physics Rack (CAPR) of Chinese space station will be launched at the end of 2022. The important goal of CAPR is to achieve BEC at 100 pk. In order to obtain ultracold atoms in microgravity of space station, we propose a two-stage cooling scheme using all-optical trap with different waist beams. The cold atom cloud obtained by this scheme is composed of condensate and thermal atoms around condensate. The design of our two-stage cooling scheme will effectively reduce the temperature of the thermal atom cloud and the effective temperature generated by the interaction energy of the condensate. The atomic temperature of 5 nk is obtained from the ground test experiment, and the corresponding temperature under the microgravity condition of the space station is theoretically predicted to be less than 100 pk. Taking the advantages of ultracold temperature and long-time detection, many scientific experiments will be arranged. In this paper, the ground test experiments based on ground principle prototype and pre-prototype for CAPR are also introduced.
The China Space Station (CSS) provides an ideal experimental platform for researching and applying ultracold atoms in microgravity. On 31 October 2022, the Cold Atom Physics Research Rack (CAPR) was launched to the CSS together with the Mengtian lab module, designed by the Shanghai Institute of Optics and Fine Mechanics of the Chinese Academy of Sciences (SIOM) and Peking University. The main goal of the CAPR is to build an ultracold atomic physics experiment platform using 87Rb Bose Einstein Condensate (BEC) in the CSS. In microgravity, ultracold atoms can be cooled to picokelvin (pK) via Two-Stage Crossed Beams Cooling (TSCBC), which is three orders of magnitude lower than on earth and can inspire the novel physical phenomena. The preparation of the BEC and the deep cooling are introduced in this paper, as well as a series of advancements in ultracold atoms in microgravity. The CAPR is an experimental platform that relies on evaporative cooling in a crossed optical dipole trap. Furthermore, the CAPR’s design scheme and ground verification experiment are also introduced. So far, the CAPR has continued to conduct research on ultracold atoms in microgravity, with more than two years of uninterrupted operation in orbit. Up to now, preliminary experimental results have been achieved, realizing the primary purpose of the CAPR.
In microgravity, atoms can be prepared to a lower temperature and manipulated with a longer time. The Cold Atom Physics Research Rack (CAPR) in Chinese Space Station, which aims to prepare quantum degenerate gas for deep cooling and quantum simulation in microgravity, has been designed, realized, and validated. We built an integrated CAPR, consisting of a physical system, an all-fiber 780nm laser system and a low phase noise 1064nm fiber laser system, and an electrical driving and controlling system. With the CAPR, a87Rb quantum degenerate gas with 1.2ⅹ105atoms and a temperature below 30nK was achieved on ground. In this article, we also show the robustness of the rack, based on the experimental results before and after the simulation of the vibration and impact during the launch.
Abstract In order to infer the expected temperature of the two-stage cooling experiment onboard the Chinese space station (CSS) through ground experiments, we apply the direct simulation Monte Carlo algorithm to construct a simulation model suitable for both the standard gravity and the microgravity conditions. The simulations are verified by the ground experimental results, from which we can deduce that the on-orbit experiments can reach the order of as low as 100 pK. This algorithm calculates the corresponding relationship between the temperature in the ground experiments and that in the microgravity conditions, keeping the other experimental parameters unchanged, which provides an important basis of design for the on-orbit atomic cooling experiment onboard the CSS which is due to be launched at the end of 2022.
In this paper, we report the design, implementation and experimental results of a portable, compact cold Cs atom physics package for atom interferometer experiments. With the physics package, we trapped and deep-cooled Cs atoms to ultracold temperatures of <; 5 μK. The deep-cooling method used in this work is relatively simple and effective, with which we obtained controlled temperature adjustment between 5 and 80 μK. The portability of the physics package makes it suitable for implementing atom interferometry with various interrogation configurations and relative orientations. The system is also good for studies of compact cold atom frequency standards. With the Raman laser and light pulse manipulation system we developed in this work, this portable cold Cs atom physics package is being used for atom interferometer experiments in our laboratory.
Abstract Ultracold quantum gases are ideal sources for high-precision space-borne sensing as proposed for Earth observation, relativistic geodesy and tests of fundamental physical laws as well as for studying new phenomena in many-body physics during extended free fall. Here we report on experiments with the Cold Atom Lab aboard the International Space Station, where we have achieved exquisite control over the quantum state of single 87Rb Bose-Einstein condensates paving the way for future high-precision measurements. In particular, we have applied fast transport protocols to shuttle the atomic cloud over a millimeter distance with sub-micrometer accuracy and subsequently drastically reduced the total expansion energy to below 100 pK with matter-wave lensing techniques.