Abstract The China Seismo-Electromagnetic Satellite (CSES) project is aimed at developing a satellite constellation dedicated to the measurement of electric and magnetic fields, plasma currents and particle fluxes in the terrestrial magnetosphere. The first satellite in the series, CSES-01, was launched in 2018 and is still operational. The second satellite, CSES-02, was successfully launched into orbit on 14 June 2025. Within this framework, the Italian Limadou collaboration developed the High-Energy Particle Detector (HEPD) for both missions. This article focuses on the technological development and qualification of the HEPD-02 apparatus, operating on board CSES-02. HEPD-02 is composed of various scintillator detectors and a pixel direction detector, aimed at measuring the energy spectra of charged particles, either incoming or trapped in the terrestrial magnetosphere. It is optimized for the identification of individual electrons with kinetic energies in the range between 3 and 100 MeV, and of protons between 30 and 200 MeV. This paper illustrates instrument and electronics design, outlining the main technological challenges and adopted solutions to ensure the desired operation and performance in the space environment for the expected lifetime of at least 6 years. It also describes the test campaign which was carried out to demonstrate the fulfilment of mechanical, thermal and electromagnetic requirements.
Abstract The performance of a millimeter-wave radiometer is strongly influenced by the characteristics of its radio-frequency (RF) front-end, making comprehensive experimental characterization essential prior to system deployment. This work presents the characterization methodology and performance evaluation of a commercially available D-band heterodyne receiver front-end operating over the 130–170 GHz frequency range. The study investigates the performance of the principal passive and active microwave components, including IMPATT local oscillators, balanced mixers, high-pass filters, cavity band-pass filters, isolators, directional couplers, and the calibration noise source, followed by evaluation of the integrated receiver front-end and its interface with an 8-channel intermediate-frequency (IF) receiver covering 1–20 GHz. The 130 GHz and 150 GHz IMPATT oscillators were characterized in terms of output power, phase noise, frequency stability, and short-term frequency drift. The balanced mixers exhibited an average conversion loss of approximately 9 dB while providing down-conversion from the 130–170 GHz RF band to a 1–20 GHz IF. Passive microwave components were evaluated through measurements of insertion loss, isolation, coupling characteristics, and transmission response, while a calibrated noise source with manufacturer-specified excess noise ratio (ENR) values was used as part of the receiver characterisation procedure.The complete receiver chain was subsequently validated through RF-to-IF measurements using an 8-channel IF receiver. The experimental results establish the performance of the individual receiver components as well as the integrated front-end architecture, demonstrating its suitability for high-sensitivity millimeter-wave radiometry and electron cyclotron emission diagnostic applications. The characterization methodology presented in this work also provides a practical framework for the evaluation and integration of D-band heterodyne receiver systems.
Abstract The ATLAS detector at CERN and its supporting infrastructure form a highly complex system. It covers numerous interdependent sub-systems and requires collaboration across a team of multi-disciplinary experts. The ATLAS Technical Coordination Expert System provides an interactive description of the technical infrastructure and enhances its understanding. It features tools to assess the impact of interventions and document expert knowledge. However, the detector's complexity is inevitably reflected in the expert system, making the web-based information retrieval more complex and affecting the user experience. The submission proposes a natural language-based user interface for the Expert System. A large language model is used to interpret user queries and return the responses as human-friendly texts. This paper discusses the key aspects of the system's architecture and model selection, the process for building a domain-specific knowledge base, and evaluates the performance of an initial pilot. The pilot is based on the expected use cases and interactions defined by a range of Expert System users. The pilot interface is evaluated based on the factual correctness, task success and execution time. The results are promising, with a median factual correctness of 100% (percentile 5th=92%) and a median execution time of 7 s. Ultimately, this approach seeks to improve the user experience and increase its usage and impact within the ATLAS collaboration.
Abstract We report results from a 13-liter purified liquid argon test stand at Wellesley College in Massachusetts, U.S.A.. The system includes a single-pass liquid-phase purification column that can achieve sub-part-per-billion impurity levels. The liquid argon purity is measured with a double-gridded purity monitor to assess the electron lifetime. Measurements demonstrate an O 2 -equivalent impurity concentration of 0.21 ± 0.05 ppb (stable over a 20-hour duration), corresponding to an electron lifetime of 1.6 ms at a drift field of 500 V/cm. This test stand supports ongoing detector R&D on charge and light readout for liquid argon time projection chambers, such as Q-Pix and other cold electronics systems.
