Gaseous X-ray polarimetry refers to a class of detectors used to measure the polarization of soft X-rays. The systematic effects of such detectors introduce residual modulation, which leads to systematic biases in the polarization detection results of the source. This paper discusses the systematic effects and their calibration and correction using a Gas Microchannel Plate-Pixel Detector (GMPD) prototype for the POLAR-2/Low-Energy X-ray Polarization Detector (LPD). Additionally, we propose an algorithm that combines parameterization with Monte Carlo simulation and Bayesian iteration to eliminate residual modulation. The residual modulation after data correction at different energy points was reduced to less than 1%, and a good linear relationship was observed between the degree of polarization and the modulation factor. The improvement in the degree of modulation after correction ranged from 2% to 15%, and the results exceeded those of the Imaging X-Ray Polarimetry Explorer (IXPE) above 5 keV.

We search for nuclear recoil signals of dark matter(DM)models with a light mediator using data taken from a p-type point-contact germanium detector of the CDEX-10 experiment at the China Jinping Underground Laboratory.The 90％confidence level upper limits on the DM-nucleon interaction cross section from 205.4 kg-day exposure data are derived,excluding the new parameter space in 2-3 GeV DM mass when the mediator mass is comparable to or lower than the typical momentum transfer.We further interpret our results to constrain a specific self-interacting DM model with a light mediator coupling to the photon through kinetic mixing and set experimental limits on the model parameter region favored by astrophysical observations.

The low-energy X-ray polarization detector (LPD) is a large-area and wide-field-of-view (FoV) X-ray polarimeter planned to be installed on the China Space Station. The LPD is designed to measure the polarization of gamma bursts and their early X-ray afterglows, facilitating studies of celestial bodies and radiation mechanisms at the centers of gamma bursts. The LPD consists of 15 detection units with identical structure and function. A detection unit prototype was developed, featuring six pixel detectors compactly placed on a bonding and front-end electronics (BFE) board with an effective detection area of 27.36 cm(2). Each pixel detector has 16 analog output channels, after which data are amplified, digitized, and transmitted via the board-to-board (BTB) connector to the data acquisition (DAQ) board for processing. The prototype also includes an internal high-voltage circuit with up to -4-kV voltages. The test results indicate that the detection unit prototype can simultaneously read data from 96 channels of pixel detectors with an equivalent charge noise of 49.49 e(-). It features comprehensive power management, offers configurable data compression, storage, and encoding, and meets all functional requirements of the detection unit.

With the daily acquisition of vast amounts of remote sensing images by satellites, effectively utilizing these images for Earth observation has become a significant research focus. Multispectral image scene classification plays a fundamental role in advancing the understanding of remote sensing imagery. Existing methods for multispectral image scene classification do not sufficiently explore the interrelationships between different bands, which limits the performance of models in this task. Unlike these, we propose a cross-band fusion method for multispectral scene classification. Specifically, we employ two appropriate visual backbones to extract band-level visual features from different bands, followed by a cross-band fusion module to fuse the features from various bands adaptively. This approach fully explores the complementary information between different bands, achieving enhanced accuracy in multispectral scene classification. Extensive experiments on a commonly used dataset BigEarthNet validate that our proposed cross-band fusion method outperforms state-of-the-art (SOTA) methods.

In order to ensure the quality and stability of power and remove the ice on the high voltage line, this study designed a patrol check and de-icing device that walks on the high voltage line. The device is a multi-functional device that integrates patrol check, de-icing, weather information collection, early warning and feedback. With STM32 microcontroller as the control core, the device can detect the data of some weather air near the high voltage line through a variety of different sensors, and can also distinguish some early trouble hidden dangers (such as broken stock, rust, deformation, etc.) of the high voltage line. This device adopts physical deicing method, deicing knife. This research adopts 3D printing method to make, through the ice cutting separation, to achieve the purpose of deicing. This device provides reference for the intellectualization of power system.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The soft X-ray polarimeter (SXP) is a detector with a wide energy range, large area, and large field of view. A SXP will be mounted on the Chinese Space Station and will mainly focus on detecting the polarization of transient soft X-ray (2–10 keV) sources, especially gamma-ray bursts (GRBs). In this work, a polarimeter detector unit is taken as an example, and Geant4 and Garfield++ software are used to simulate the detection efficiency and track production. An improved track reconstruction algorithm is proposed and used to reconstruct two-dimensional images of the tracks. In this method, the initial emission angle of photoelectrons is reconstructed from the initial part of the track by shortening or extending the initial part of the track until the remaining track is straight, and the number of pixels is within an adjustable threshold. The modulation factor of the photoelectronic tracks after reconstruction reaches approximately 57% in the photon energy range of 7–10 keV.

We present weakly interacting massive particles (WIMPs) search results performed using two approaches of effective field theory from the China Dark Matter Experiment (CDEX), based on the data from both CDEX-1B and CDEX-10 stages. In the nonrelativistic effective field theory approach, both time-integrated and annual modulation analyses were used to set new limits for the coupling of WIMP-nucleon effective operators at 90% confidence level (C.L.) and improve over the current bounds in the low mχregion. In the chiral effective field theory approach, data from CDEX-10 were used to set an upper limit on WIMP-pion coupling at 90% C.L. We for the first time extended the limit to the mχ < 6 GeV/c2 region.

Accelerator-driven subcritical system (ADS) is a new generation nuclear reactor with various highly coupled physical fields. A typical system is a liquid metal, lead-bismuth eutectic cooled subcritical reactor core coupled to a neutron spallation target. Therefore, ADS simulations require multi-physics coupling among the proton, neutronics, and thermal hydraulics. In this work, GEANT4, RMC, and FLUENT were used to simulate the multiphysics processes in MYRRHA. The GEANT4/RMC was used for the spallation process and the proton-neutron transport calculations, with the power distributions verified against the MCNP6 code with an average difference of about 1.85%. A hybrid RMC/FLUENT coupling scheme was used for the neutronics thermal-hydraulics calculations. The subcritical reactor was simplified using the porous media method for the FLUENT simulations to obtain the coolant temperature and density fields. A temperature-dependent thermal conductivity model used to calculate the temperature filed in typical fuel pellets gave consistent results with the FLUENT predictions within an absolute error of 3 K. The neutronics and thermal-hydraulics coupling took the temperature and the lead-bismuth eutectic density feedback into consideration. Simulations show that thermal-hydraulics feedback has a fairly small effect on the power distribution in the ADS reactor. In this case, the radial power difference between the coupling and coupling-free is within 5%. In addition, the mechanisms of neutronics/thermalhydraulics are compared for lead-bismuth eutectic cooled reactors and water-cooled reactors. The feedback is much more significant in water-cooled reactors than in the Pb-Bi cooled reactor since the water moderation, and the water density is more sensitive to the temperature.

A new method for directional fast neutron detection is proposed based on a neutron time projection chamber (TPC) and position-sensitive plastic scintillation detectors. The detection system can efficiently locate the approximate location of a hot spot with 4π field-of-view using only the neutron TPC. Then, the system generates a high-resolution image of the hot spot using selected coincidence events in the TPC and the scintillation detectors. A prototype was built and tested using a 252Cf source. An efficiency of 7.1×10−3 was achieved for fast searching. The angular resolution was 7.8°(full width at half maximum, FWHM) for high-resolution imaging using the simple back projection method.

A neutron time projection chamber can locate the approximate direction of a neutron hot spot with high efficiency and a 4 pi field of view. The angular resolution can be significantly improved by adding several plastic scintillation detectors and using coincidence events. The specific performances of such a coincidence imaging system are studied based on theoretical calculations and experimental results. The calculated value of the angular resolution is approximately 2 degrees for the current system, which agrees well with the experimental results and sets an upper limit for the angular resolution of traditional back projection based online reconstruction methods. Although the statistical iterative method can breakthrough this limit and further improve the angular resolution, the time consumption is usually a problem. The coincidence imaging system can be further optimized for future applications based on the theoretical model.

A study on cosmogenic activation in germanium was carried out to evaluate the cosmogenic background level of natural and 70 Ge depleted germanium detectors. The production rates of long-lived radionuclides were calculated with Geant4 and CRY.Results were validated by comparing the simulated and experimental spectra of CDEX-1B detector. Based on the validated codes, the cosmogenic background level was predicted for further tonne-scale CDEX experiment. The suppression of cosmogenic background level could be achieved by underground germanium crystal growth and high-purity germanium detector fabrication to reach the sensitivity requirement for direct detection of dark matter. With the low cosmogenic background, new physics channels,such as solar neutrino research and neutrinoless double-beta decay experiments, were opened and the corresponding simulations and evaluations were carried out.

The CDEX-10 experiment searches for light weakly interacting massive particles, a form of dark matter, at the China Jinping Underground Laboratory, where approximately 10 kg of germanium detectors are arranged in an array and immersed in liquid nitrogen. Herein, we report on the experimental apparatus, detector characterization, and spectrum analysis of one prototype detector. Owing to the higher rise-time resolution of the CDEX-10 prototype detector as compared with CDEX-1B, we identified the origin of an observed category of extremely fast events. For data analysis of the CDEX-10 prototype detector, we introduced and applied an improved bulk/surface event discrimination method. The results of the new method were compared to those of the CDEX-1B spectrum. Both sets of results showed good consistency in the 0–12 keVee energy range, except for the 8.0 keV K-shell X-ray peak from the external copper.

To better understand the energy response of the Antineutrino Detector (AD), the Daya Bay Reactor Neutrino Experiment installed a full Flash ADC readout system on one AD that allowed for simultaneous data taking with the current readout system. This paper presents the design, data acquisition, and simulation of the Flash ADC system, and focuses on the PMT waveform reconstruction algorithms. For liquid scintillator calorimetry, the most critical requirement to waveform reconstruction is linearity. Several common reconstruction methods were tested but the linearity performance was not satisfactory. A new method based on the deconvolution technique was developed with 1% residual non-linearity, which fulfills the requirement. The performance was validated with both data and Monte Carlo (MC) simulations, and 1% consistency between them has been achieved.

The60Co-γ ray total ionizing dose radiation responses of 55-nm silicon-oxide-nitride-oxide-silicon (SONOS) memory cells in pulse mode (programmed/erased with pulse voltage) and dc mode (programmed/erased with direct voltage sweeping) are investigated. The threshold voltage and off-state current of memory cells before and after radiation are measured. The experimental results show that the memory cells in pulse mode have a better radiation-hard capability. The normalized memory window still remains at 60% for cells in dc mode and 76% for cells in pulse mode after 300 krad(Si) radiation. The charge loss process physical mechanisms of programmed SONOS devices during radiation are analyzed.

We report results of a search for light weakly interacting massive particle (WIMP) dark matter from the CDEX-1 experiment at the China Jinping Underground Laboratory (CJPL). Constraints on WIMP-nucleon spin-independent (SI) and spin-dependent (SD) couplings are derived with a physics threshold of 160 eVee, from an exposure of 737.1 kg-days. The SI and SD limits extend the lower reach of light WIMPs to 2 GeV and improve over our earlier bounds at WIMP mass less than 6 GeV.

We report the first results on 76Ge neutrinoless double beta decay from stage one of the China dark-matter experiment (CDEX). A p-type point-contact high-purity germanium detector with a mass of 994 g has been installed to detect neutrinoless double beta decay events, as well as to directly detect dark matter particles. An exposure of 304 kg d has been analyzed over a wide spectral band from 500 keV to 3 MeV. The average event rate obtained was about 0.012 counts per keV per kg per day over the 2.039 MeV energy range. The half-life of 76Ge neutrinoless double beta decay derived based on this result is T 1/2 0ν >6.4×1022 yr (90% C.L.). An upper limit on the effective Majorana-neutrino mass of 5.0 eV has been achieved.

The China Jinping Underground Laboratory, inaugurated in 2010, is an underground research facility with the deepest rock overburden and largest space by volume in the world. The first-generation science programs include dark matter searches conducted by the CDEX and PandaX experiments. These activities are complemented by measurements of ambient radioactivity and the installation of low-background counting systems. Phase II of the facility is being constructed, and its potential research projects are being formulated. In this review, we discuss the history, key features, results, and status of this facility and its experimental programs, as well as their future evolution and plans.