Post-acceleration of protons in helical coil targets driven by intense, ultrashort laser pulses can enhance ion energy by utilizing the transient current from the targets’ self-discharge. The acceleration length of protons can exceed a few millimeters, and the acceleration gradient is of the order of GeV/m. How to ensure the synchronization between the accelerating electric field and the protons is a crucial problem for efficient post-acceleration. In this paper, we study how the electric field mismatch induced by current dispersion affects the synchronous acceleration of protons. We propose a scheme using a two-stage helical coil to control the current dispersion. With optimized parameters, the energy gain of protons is increased by four times. Proton energy is expected to reach 45 MeV using a hundreds-of-terawatts laser, or more than 100 MeV using a petawatt laser, by controlling the current dispersion.

Carbon nanotube foams (CNFs) have been successfully used as near-critical-density targets in the laser-driven acceleration of high-energy ions and electrons. Here we report the recent advances in the fabrication technique of such targets. With the further developed floating catalyst chemical vapor deposition (FCCVD) method, large-area ($>25\kern0.5em {\mathrm{cm}}^2$) and highly uniform CNFs are successfully deposited on nanometer-thin metal or plastic foils as double-layer targets. The density and thickness of the CNF can be controlled in the range of $1{-}13\kern0.5em \mathrm{mg}/{\mathrm{cm}}^3$ and $10{-}200\kern0.5em \mu \mathrm{m}$, respectively, by varying the synthesis parameters. The dependence of the target properties on the synthesis parameters and the details of the target characterization methods are presented for the first time.

Single-shot laser-induced damage threshold (LIDT) measurements of multi-type free-standing ultrathin foils were performed in a vacuum environment for 800 nm laser pulses with durations τ ranging from 50 fs to 200 ps. The results show that the laser damage threshold fluences (DTFs) of the ultrathin foils are significantly lower than those of corresponding bulk materials. Wide band gap dielectric targets such as SiN and formvar have larger DTFs than semiconductive and conductive targets by 1–3 orders of magnitude depending on the pulse duration. The damage mechanisms for different types of targets are studied. Based on the measurement, the constrain of the LIDTs on the laser contrast is discussed.

The Micro-Nano satellite TianTuo-3 (TT-3) developed by the National University of Defense Technology (NUDT) was successfully launched on 20 September 2015. The space-based Automatic Identification System (AIS) on board TT-3 works well and stably receives AIS signals from global vessels. In this work, we perform statistical analysis on the detection probability of the vessels in the concerned areas by using the TT-3 AIS data. The results suggest that the detection probability of vessels decreases as the distribution density increases, especially in the offshore areas of dense traffic and the TT3-AIS vessel detection probability in the oceans can be higher than 40%, indicating that the TT-3 AIS has achieved a high probability of coverage of vessels for a single receiving antenna. The analysis results will present helpful references both in evaluating the potential application of satellite-based AIS and for designing the next generation space-based AIS which might greatly improve the detection probability of ocean-going vessels.

The Automatic Identification System (AIS) receiver on board the main satellite of the TianTuo-3 constellation, LvLiang-1, is a new generation of AIS receiver. Having partly solved the signal conflict problems and with larger coverage over the ground, the AIS receiver on board TianTuo-3 greatly improves the signal detection ability. The data received by the AIS receiver during the TianTuo-3 debugging stage is employed for detailed analysis in this paper. Results include: TianTuo-3 implements four-frequency detection at the same time, and a time-flag is inserted into the received AIS data, a small portion of Class A vessels (at least 1480) have been equipped with AIS sending the long range AIS broadcast message with two new frequency channels and the hourly averaged count of the message received by TianTuo-3’s AIS is between 1500 ~ 2500. This AIS receiver is capable of real-time tracking a single vessel. In conclusion, the TianTuo-3 space-based AIS receiver is capable of continuously receiving AIS messages sent by global maritime vessels.

Kesterite Cu2ZnSnS4 (CZTS) and Cu2ZnSnSe4 (CZTSe) compounds are candidate low-cost absorber materials for thin-film solar cells, and a light-to-electricity efficiency as high as ~10% has been achieved in the solar cell based on their alloys, Cu2ZnSn(S,Se)4 (CZTSSe). In this paper, we discuss the crystal and electronic structure of CZTSSe alloys with different composition, showing that the mixed-anion alloys keep the kesterite cation ordering, and are highly miscible with a small band gap bowing parameter. The phase stability of CZTS and CZTSe relative to secondary compounds such as ZnS and Cu2SnS3 has also been studied, showing that chemical potential control is important for growing high-quality crystals, and the coexistence of these secondary compounds is difficult to be excluded using X-ray diffraction technique. Both CZTS and CZTSe are self-doped to p-type by their intrinsic defects, and the acceptor level of the dominant CuZn antisite is deeper than Cu vacancy. Relatively speaking, CZTSe has shallower acceptor level and easier n-type doping than CZTS, which gives an explanation to the high efficiency of CZTSSe based solar cells.

A study of the influence of mesoporous SiO2 on the dehydrogenation of NaAlH4 and TiF3-doped NaAlH4 revealed that the amount of hydrogen evolved is 3.8 wt% for the pristine NaAlH4 and around 4.2 wt% for the TiF3-doped NaAlH4, but increases to 4.9–5.0 wt% once the samples are doped with mesoporous SiO2 in the temperature range of 100–350 °C. A favorable synergistic effect on the NaAlH4 dehydrogenation is achieved as mesoporous SiO2 is added as a codopant along with TiF3, which is associated with the nanosized pores and high specific surface area of mesoporous SiO2. The catalytic mechanism of mesoporous SiO2 is more physical than chemical relative to the catalytic mechanism of TiF3.