The space cold atom interferometer for testing the equivalence principle in the China Space Station.

The precision of the weak equivalence principle (WEP) test using atom interferometers (AIs) is expected to be extremely high in microgravity environment. The microgravity scientific laboratory cabinet (MSLC) in the China Space Station (CSS) can provide a higher-level microgravity than the CSS itself, which provides a good experimental environment for scientific experiments that require high microgravity. We designed and realized a payload of a dual-species cold rubidium atom interferometer. The payload is highly integrated and has a size of [Formula: see text]. It will be installed in the MSLC to carry out high-precision WEP test experiment. In this article, we introduce the constraints and guidelines of the payload design, the compositions and functions of the scientific payload, the expected test precision in space, and some results of the ground test experiments.

The space cold atom interferometer for testing the equivalence principle in the China Space Station.

The precision of the weak equivalence principle (WEP) test using atom interferometers (AIs) is expected to be extremely high in microgravity environment. The microgravity scientific laboratory cabinet (MSLC) in the China Space Station (CSS) can provide a higher-level microgravity than the CSS itself, which provides a good experimental environment for scientific experiments that require high microgravity. We designed and realized a payload of a dual-species cold rubidium atom interferometer. The payload is highly integrated and has a size of 460 mm × 330 mm × 260 mm. It will be installed in the MSLC to carry out high-precision WEP test experiment. In this article, we introduce the constraints and guidelines of the payload design, the compositions and functions of the scientific payload, the expected test precision in space, and some results of the ground test experiments.

Modular-assembled laser system for a long-baseline atom interferometer.

The Zhaoshan long-baseline Atom Interferometer Gravitation Antenna (ZAIGA) is a new, to the best of our knowledge, type of large-scale atom interferometer facility under construction for the study of gravitation and related problems. To meet the different requirements of the laser system for the atom interferometer using various atoms (including 85Rb, 87Rb, 87Sr, and 88Sr), we design and implement a modular assembled laser system. By dividing the laser system into different basic units according to their functions and modularizing each unit, the laser system is made highly scalable while being compact and stable. Its intensity stability is better than 0.1% in 102s and 0.5% in 104s. We test the performance of the laser system with two experimental systems, i.e., an 85Rb-87Rb dual-species ultracold atom source and an 85Rb atom interferometer. The 85Rb-87Rb dual-species magneto-optical trap and the 85Rb atom interference fringes are realized by using this laser system, indicating that its technical performance can meet the major experimental requirements.

An actively compensated 8 nT-level magnetic shielding system for 10-m atom interferometer.

We design and develop a high-performance magnetic shielding system for a long baseline fountain-type atom interferometer. The shielding system is achieved by a combination of passive shielding using permalloy and active compensation with coils. An 11.4 m-long three-layer cylindrical shield is completed by the process of welding, local annealing, and entire annealing. The active compensations compress the residual magnetic field to 8.0 nT max-to-min and the corresponding gradient below 30 nT/m over 10 m along the axial direction in which external compensation, internal compensation, and constant magnetic field (C-field) compensation reduce the inhomogeneities to 25.0, 12.6, and 1.7 nT (standard deviation) sequentially. We estimate that this system could reduce the systematic error of the quadratic Zeeman shift to the 10-13 level for the weak equivalence principle test with a simultaneous 85Rb-87Rb dual-species atom interferometer.

All acousto-optic modulator laser system for a 12 m fountain-type dual-species atom interferometer.

We design and implement a laser system for 85Rb and 87Rb dual-species atom interferometers based on acousto-optic frequency shift and tapered amplifier laser technologies. We use eight-pass acousto-optic modulators to generate repumping lasers for 85Rb and 87Rb atoms. The maximum frequency shift of the laser is 2.8 GHz, and the diffraction efficiency is higher than 20%. We use high-frequency acousto-optic modulators to generate the Raman lasers. This laser system uses only two seed lasers to provide the various frequencies required by 85Rb and 87Rb dual-species atom interferometers, which greatly improves laser usage. The laser system is applied in the equivalence principle test experiment using an 85Rb and 87Rb dual-species atom interferometer. The signal of atoms launched to 12 meters is successfully observed, and the resolution of gravity differential measurement is improved from 8×10-9 g to 1×10-10g.

Limited carbon source retards inorganic arsenic release during roxarsone degradation in Shewanella oneidensis microbial fuel cells.

Directly relevant to the toxicity, mobility, and fate of arsenic, the biotransformation of inorganic and organic arsenicals has been extensively concerned, including roxarsone, a widely applied organoarsenical feed additive in poultry industry. Yet, little is known about the transformation details of roxarsone in microbial fuel cells (MFC). In this study, a two-chambered Shewanella oneidensis MR-1 microbial fuel cell was employed to investigate the transformation processes of roxarsone at various carbon source levels. Results show that limited carbon source remarkably inhibited inorganic arsenic release along roxarsone transformation, whereas numerous arsenical species were detected to be released into systems with sufficient carbon source supply, including trivalent and pentavalent inorganic arsenics, monomethylarsonous acid (MMA), and 4-hydroxy-3-aminobenzene arsonic acid (HAPA). Shewanella oneidensis MR-1 was able to cleave the C-As bond of trivalent HAPA yielding inorganic arsenics and MMA, even in the absence of the arsI gene encoding ArsI C-As lyase. We proposed a two-step nitro- and pentavalent-arsenate group reduction pathway for the roxarsone bioelectrochemical transformation. In addition, results indicated that the attached cells onto the electrode surface played a key function in the two-step reduction of roxarsone to trivalent HAPA, whereas planktonic cells were most likely responsible for the C-As bond breakage and the following dearylation. With these qualitative and quantitative estimations, it provides new insights into the mechanistic understanding of the roxarsone biotransformation process in microbial fuel cells, which is important for the biogeochemical cycling of arsenic.

Observation and deperturbation of near-dissociation ro-vibrational structure of the Cs2 state 0u(+) (A(1)Σu(+)∼b(3)Π0+u) at the asymptote 6S1/2 + 6P1/2.

New ro-vibrational structures of cold Cs2 in the 0u(+) state near the asymptote 6S1/2 + 6P1/2 are resolved. The variation of the rotational constants shows that the related energy spectra are strongly perturbed. An analysis of new data along with the empirical and theoretical information available from other sources is performed. For this purpose the model of spin-orbit coupling of the Hund's case (a) states A(1)Σu(+)∼b(3)Πu proposed by Bai et al. [Phys. Rev. A 83, 032514 (2011)] is extrapolated to the dissociation limit, and the parameters of the extrapolation are fitted from the near-dissociation experimental data.