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Cold traps are locations on the Moon that are shielded from sunlight where volatiles such as water could accumulate and persist against sublimation for geologic timescales. We model how long it takes accumulating craters to produce and then obliterate sub‐kilometer scale cold traps. Sub‐meter cold traps are extremely ephemeral, evolving in and out of existence over less than a few thousand years; however, larger 100 m to 1 km‐scale cold traps may persevere for geologic timescales and preserve a record of the volatile history of the Moon. Plain Language Summary Volatiles like water may exist in the shadows at the bottom of craters near the poles of the Moon; however, the Moon is subjected to intense bombardment by high‐velocity meteorites, and the subsequent bombardment by the rocks meteorite impacts kick up. Crater‐forming bombardment controls both the production and destruction of craters where volatiles may be safe. Using knowledge of the intensity of bombardment, we model how long volatile‐harboring cold traps last on the Moon and find that small cold traps (<10 m) are extremely ephemeral, while large cold traps (>100 m) could last for geologic time. Key Points Lunar micro cold traps are extremely ephemeral (<1 m scale last only thousands of years) Volatiles discovered within micro cold traps will have been transported there recently Large cold traps are exponentially more durable than small cold traps and may harbor ancient volatiles

We present simulations of space weathering effects on ice deposits in regions of permanent shadow on the Moon. These Monte Carlo simulations follow the effects of space weathering processes on the distribution of the volatiles over time. The model output constrains the coherence of volatile deposits with depth, lateral separation, and time. The results suggest that ice sheets become broken and buried with time. As impacts begin to puncture an initially coherent surficial ice sheet, small areas with a deficit of ice compared to surrounding areas are formed first. As time progresses, holes become prevalent and the anomalous regions are local enhancements of ice concentration in a volume. The 3‐D distribution is also heterogeneous because the ice is buried to varying depths in different locations. Analysis of the coherence of ice on 10 cm scales predicts that putative ice sheets in anomalous radar craters are <100 Myr old. Surface frost becomes homogenized within 20 Myr. The simulations show the data from the LCROSS impact and surrounding region are consistent with the ice deposit in Cabeus being >1000 Myr old. For future in situ analysis of cold trap volatiles, a horizontal range of 10 m is sufficient to acquire surface‐based measurements of heterogeneously distributed ice. These results also support previous analyses that Mercury's cold traps are young. Key Points Ice detectable by radar disappears in < 100 Myr Widespread surface frost represents continual processes A lateral range of 10 m is sufficient to acquire measurements of heterogeneity

The present study explores the status of nuclear energy developments for generation of electric power. Notably, India's pivotal role in advancing nuclear technology is highlighted, particularly with the development of a cutting-edge nuclear Fast Breeder Reactor (FBR) technology-based power plant. India has been developing the latest nuclear Fast Breeder Reactor (FBR) technology-based power plant having power generation capacity 10 times higher than the existing nuclear power plants. The review incorporates the most important component of the FBR system i.e. cold trap. Model Sodium Cold Trap (MSCT) is used by India to demonstrate the regeneration of secondary sodium cold trap.The development, advancements and challenges towards the Model Sodium Cold Trap (MSCT) are discussed in detail. It is possible to increase the maximum in-situ regeneration of MSCT up to 82%. This paper also reviews status of energy production using renewable and non-renewable energy sources. Finally, the scope in the advancements of nuclear reactor technology and related future opportunities has also been included.

Controllable, coherent many-body systems can provide insights into the fundamental properties of quantum matter, enable the realization of new quantum phases and could ultimately lead to computational systems that outperform existing computers based on classical approaches. Here we demonstrate a method for creating controlled many-body quantum matter that combines deterministically prepared, reconfigurable arrays of individually trapped cold atoms with strong, coherent interactions enabled by excitation to Rydberg states. We realize a programmable Ising-type quantum spin model with tunable interactions and system sizes of up to 51 qubits. Within this model, we observe phase transitions into spatially ordered states that break various discrete symmetries, verify the high-fidelity preparation of these states and investigate the dynamics across the phase transition in large arrays of atoms. In particular, we observe robust many-body dynamics corresponding to persistent oscillations of the order after a rapid quantum quench that results from a sudden transition across the phase boundary. Our method provides a way of exploring many-body phenomena on a programmable quantum simulator and could enable realizations of new quantum algorithms. Programmable quantum simulations of many-body systems are demonstrated using a reconfigurable array of 51 individually trapped cold atoms with strong, coherent interactions controlled via excitation to Rydberg states. Many bodies on a quantum simulator Richard Feynman proposed the quantum computer in 1982 as a technique for simulating states of matter and the various complex interactions that occur within these systems. In the past few years, quantum simulators have become a reality, with several different qubit approaches. For example, small numbers of individually controlled qubits have already been used to simulate molecules and quantum magnets. However, it has remained a challenge to perform tasks that are beyond the capabilities of classical computers. In this issue, two papers demonstrate quantum simulators with an unprecedentedly high number of controlled qubits. Mikhail Lukin and colleagues used 51 cold Rydberg atoms and Christopher Monroe and colleagues used 53 trapped ions to study phase transitions in Ising-type quantum magnets. Both groups observed novel many-body interactions that are computationally intractable with classical computers.

Cold atoms are important for precision atomic applications including timekeeping and sensing. The 3D magneto-optical trap (3D-MOT), used to produce cold atoms, will benefit from photonic integration to improve reliability and reduce size, weight, and cost. These traps require the delivery of multiple, large area, collimated laser beams to an atomic vacuum cell. Yet, to date, beam delivery using an integrated waveguide approach has remained elusive. Here we report the demonstration of a 87 Rb 3D-MOT using a fiber-coupled photonic integrated circuit to deliver all beams to cool and trap > 1 ×10 6 atoms to near 200 μK. The silicon nitride photonic circuit transforms fiber-coupled 780 nm cooling and repump light via waveguides to three mm-width non-diverging free-space cooling and repump beams directly to the rubidium cell. This planar, CMOS foundry-compatible integrated beam delivery is compatible with other components, such as lasers and modulators, promising system-on-chip solutions for cold atom applications. Ultracold atoms are generated in the lab using optical trapping and cooling. Here the authors implement a fiber-coupled photonic integrated circuit for a beam delivery to a three-dimensional magneto-optical trap where greater than 1 million rubidium atoms are cooled near 200 μK.

The paper presents the results of studying the peculiarities of heat and mass exchange in cold traps for the sodium purification of impurities in fast reactor circuits both in dedicated test areas simulating various trap components (isothermal sump, nonisothermal sump, filters, final cooling area) and in trap prototype models. As a result, a scientific rationale has been formed for developing traps of a unique design for various reactors. The impurity capacity of the traps is three to four times as high as that of the best foreign counterparts. Tests have shown these to be highly efficient in purifying sodium of oxygen and hydrogen and much less efficient in sodium purification of corrosion products and carbon. Taking into account the leakage of radioactive sodium during operation of the BN-600 reactor primary circuit traps, a decision was made to install the purification system in the reactor tank to improve the safety of the large fast reactor. It was resolved to exclude the accumulation of hydrogen in the primary circuit traps in nominal conditions. Two trap designs, with argon and sodium cooling, are discussed. It has been shown that operation of the reactor purification system with argon cooling will require 20 trap replacements during the reactor operating life and seven replacements if the deposition of hydrogen into the primary circuit cold traps is excluded. The sodium-cooled version of the trap built in the reactor tank has the same overall dimensions as the argon-cooled trap. The cooling sodium circulates in two trains: outside the jacketed working space body (up to 30% of the flow rate) and in the coil inside of the working space (up to 70% of the flow rate). Updates have been proposed to the trap design based on the calculations using the codes simulating the in-trap processes of heat and mass exchange.

Ultracold molecules are ideal platforms for many important applications, ranging from quantum simulation1–5 and quantum information processing 6,7 to precision tests of fundamental physics2,8–11. Producing trapped, dense samples of ultracold molecules is a challenging task. One promising approach is direct laser cooling, which can be applied to several classes of molecules not easily assembled from ultracold atoms12,13. Here, we report the production of trapped samples of laser-cooled CaF molecules with densities of 8 × 107 cm−3 and at phase-space densities of 2 × 10−9, 35 times higher than for sub-Doppler-cooled samples in free space14. These advances are made possible by efficient laser cooling of optically trapped molecules to well below the Doppler limit, a key step towards many future applications. These range from ultracold chemistry to quantum simulation, where conservative trapping of cold and dense samples is desirable. In addition, the ability to cool optically trapped molecules opens up new paths towards quantum degeneracy.

Cold atom traps are at the heart of many quantum applications in science and technology. The preparation and control of atomic clouds involves complex optimization processes, that could be supported and accelerated by machine learning. In this work, we introduce reinforcement learning to cold atom experiments and demonstrate a flexible and adaptive approach to control a magneto-optical trap. Instead of following a set of predetermined rules to accomplish a specific task, the objectives are defined by a reward function. This approach not only optimizes the cooling of atoms just as an experimentalist would do, but also enables new operational modes such as the preparation of pre-defined numbers of atoms in a cloud. The machine control is trained to be robust against external perturbations and able to react to situations not seen during the training. Finally, we show that the time consuming training can be performed in-silico using a generic simulation and demonstrate successful transfer to the real world experiment. The preparation and control of atomic clouds which are commonly used in scientific and technological applications is a complex process. Here, authors demonstrate reinforcement learning as a flexible and adaptive approach to control of a cold atoms trap, opening an avenue to robust experiments and applications.

Water ice may be allowed to accumulate in permanently shaded regions on airless bodies in the inner solar system such as Mercury, the Moon, and Ceres [Watson K, et al. (1961) J Geophys Res 66:3033–3045]. Unlike Mercury and Ceres, direct evidence for water ice exposed at the lunar surface has remained elusive. We utilize indirect lighting in regions of permanent shadow to report the detection of diagnostic near-infrared absorption features of water ice in reflectance spectra acquired by the Moon Mineralogy Mapper [M (3)] instrument. Several thousand M (3) pixels (∼280 × 280 m) with signatures of water ice at the optical surface (depth of less than a few millimeters) are identified within 20° latitude of both poles, including locations where independent measurements have suggested that water ice may be present. Most ice locations detected in M (3) data also exhibit lunar orbiter laser altimeter reflectance values and Lyman Alpha Mapping Project instrument UV ratio values consistent with the presence of water ice and also exhibit annual maximum temperatures below 110 K. However, only ∼3.5% of cold traps exhibit ice exposures. Spectral modeling shows that some ice-bearing pixels may contain ∼30 wt % ice that is intimately mixed with dry regolith. The patchy distribution and low abundance of lunar surface-exposed water ice might be associated with the true polar wander and impact gardening. The observation of spectral features of H₂O confirms that water ice is trapped and accumulates in permanently shadowed regions of the Moon, and in some locations, it is exposed at the modern optical surface.

We analyze the quantum phases, correlation functions and edge modes for a class of spin-1/2 and fermionic models related to the one-dimensional Ising chain in the presence of a transverse field. These models are the Ising chain with anti-ferromagnetic long-range interactions that decay with distance r as , as well as a related class of fermionic Hamiltonians that generalize the Kitaev chain, where both the hopping and pairing terms are long-range and their relative strength can be varied. For these models, we provide the phase diagram for all exponents , based on an analysis of the entanglement entropy, the decay of correlation functions, and the edge modes in the case of open chains. We demonstrate that violations of the area law can occur for , while connected correlation functions can decay with a hybrid exponential and power-law behavior, with a power that is -dependent. Interestingly, for the fermionic models we provide an exact analytical derivation for the decay of the correlation functions at every . Along the critical lines, for all models breaking of conformal symmetry is argued at low enough . For the fermionic models we show that the edge modes, massless for , can acquire a mass for . The mass of these modes can be tuned by varying the relative strength of the kinetic and pairing terms in the Hamiltonian. Interestingly, for the Ising chain a similar edge localization appears for the first and second excited states on the paramagnetic side of the phase diagram, where edge modes are not expected. We argue that, at least for the fermionic chains, these massive states correspond to the appearance of new phases, notably approached via quantum phase transitions without mass gap closure. Finally, we discuss the possibility to detect some of these effects in experiments with cold trapped ions.