This work presents a numerical model for quench simulation in the non-planar superconducting magnets of the GIGA stellarator reactor (Gauss Fusion), which stores energies on the order of 100 GJ. The study focuses on the development and application of a predictive multi-physics model for an innovative active protection concept that eliminates external dump resistors by using the structural steel plates of the winding pack as distributed resistive elements for energy dissipation. The approach is based on an integrated simulation model coupling the THEA code, specialized in one-dimensional thermo-electro-hydraulic modelling of superconducting cables, with a dedicated electrical circuit model. The THEA component resolves the transient behavior of the conductor in both LTS (Nb₃Sn) and HTS (REBCO) configurations, including quench initiation and propagation, helium coolant dynamics, and current redistribution. The circuit model represents the current paths through the structural steel plates, which run parallel to the conductor but are connected in series with it, and evaluates their electro-thermal response. The model simulates quench initiation mechanisms through localized thermal disturbances and critical current degradation and implements different quench detection logic based on voltage and temperature thresholds. Following quench detection, the coupled model captures the transient transfer of current from the superconductor to the resistive steel plates and the associated Joule dissipation of magnetic energy. Owing to the one-dimensional description of the conductor and the lumped description of the plates, a complete quench transient of 200 s is simulated in a few minutes on a laptop-class computer, and the same framework handles LTS and HTS conductors, different quench initiation mechanisms and both voltage- and temperature-based detection. A systematic parametric study is performed using the model to assess sensitivity to geometric, thermal, and electrical design parameters, conductor characteristics, and quench detection strategies. The simulation results demonstrate the capability of the model to predict the thermal, hydraulic and electric transient response of the coil, a useful aid to achieve successful mitigation of hot-spot temperature and terminal voltage, and a quantitative guidance for the design of the magnet and associated systems.
Recent trends in satellite miniaturization and mission advancement have increased the demand for the simultaneous detection of mid-wave infrared and long-wave infrared bands. This dual-band infrared detection requires a dual-cryocooler configuration to cool the MWIR and LWIR detectors independently. The dual cryocooler can operate in either single- or dual-compressor operating modes according to the mission requirements, and micro-vibration isolation for each operating mode is required. To satisfy this requirement, we developed a passive vibration isolator for a dual-cryocooler assembly to attenuate micro-vibrations in both operating modes. The micro-vibration isolation performance was predicted based on the basic characteristics of the vibration isolator, and the dynamic behavior of the dual-cryocooler assembly with the vibration isolator was analyzed using finite-element modal analysis. Results of a micro-vibration measurement test demonstrated that the proposed vibration isolator effectively attenuated micro-vibrations better than the rigid condition in both single- and dual-compressor operating modes. In addition, the structural integrity of the proposed vibration isolator was verified through launch-environment tests.
Amid the global shift toward carbon neutrality, liquid hydrogen (LH2) is gaining recognition as a promising clean energy carrier for maritime transport. Independent Type-C tanks require cryogenic insulation materials with low thermal conductivity, stable thermal deformation behavior, and sufficient compressive integrity under 20 K cold-boundary conditions. However, quantitative data on low-density glass bubble-reinforced polyurethane foam (GB-PUF) under such conditions remain limited. In this study, neat polyurethane foam (neat PUF) and GB-PUF (36–38 kg/m3) were fabricated using 0.25 wt% glass bubbles. The microstructure was characterized by scanning electron microscopy. The apparent thermal conductivity, coefficient of thermal expansion (CTE), compressive yield strength, and compressive Young's modulus were experimentally evaluated. Thermal conductivity was measured under room-temperature atmospheric conditions and under a vacuum pressure of 1 mTorr with a cold-side temperature of 20 K. The coefficient of thermal expansion was measured over 113–293 K, and compression tests were conducted at 293, 173, 77, and 20 K. Under the 20 K vacuum condition, GB-PUF exhibited an apparent thermal conductivity 75.8% lower than that of neat PUF. The average CTE of GB-PUF was 13.1% lower than that of neat PUF over 113–293 K. The compressive yield strength of GB-PUF reached its maximum at 77 K, where it was 49.4% higher than that of neat PUF. On further cooling to 20 K, however, the compressive yield strength of GB-PUF decreased by 28.5% to 0.231 MPa, whereas that of neat PUF remained essentially unchanged. This reduction is consistent with cooling-induced interfacial damage associated with the CTE mismatch between the glass bubbles and the polyurethane matrix, although partial GB fracture cannot be excluded. These results provide quantitative reference data for the design of cryogenic insulation systems for LH2 carrier Type-C tanks.
Excessive heat degrades laser device performance, necessitating liquid nitrogen (LN₂) cooling. This paper numerically investigates flow boiling heat transfer of LN₂ in a typical Manifold microchannel (MMC) unit for laser cooling. The numerical model is validated against HFE-7100 and LN₂ flow boiling data. Key parameters—phase distribution, wall temperature, heat transfer coefficient (HTC), pressure drop, and entropy generation—are analyzed under varying heat fluxes and LN₂ flow rates. Inside the MMC channel, temperature uniformity is poor with coexisting boiling and subcooled regions. In contrast, the heated surface shows excellent temperature uniformity, and its mean temperature rises parabolically with heat flux. Response surface methodology (RSM) fits temperature with a maximum error of 1.13%. The overall HTC first increases then decreases with heat flux, marking transitions from single-phase flow to nucleate boiling and then to film boiling. At a mass flux of 130.32 kg/(m2s), the HTC at 50 W/cm2 is only 59.7% of that at 10 W/cm2. RSM fitting for HTC yields a maximum error of 6.72%. Average pressure drop remains below 2 kPa. Thermal conduction entropy generation dominates (>50%), while friction contributes the least (<10%). Convective entropy generation increases with higher heat flux or lower mass flux. For the studied MMC, an optimal matching between heat flux and LN₂ mass flux exists: for a given heat flux, a specific mass flux minimizes entropy generation, and this optimal mass flux increases with heat flux.
A highly aligned cryogenic mechanical testing system was developed for reliable material characterization over a wide temperature range from 10 K to room temperature. The system integrated an in-house helium liquefaction, purification, and recovery loop to achieve closed-loop operation with reduced helium consumption. A combined cooling strategy, coupling liquid nitrogen precooling with liquid helium spray cooling, was implemented to improve cooling efficiency and realize continuous temperature tunability. Precise temperature control was achieved by regulating the liquid helium flow rate and applying auxiliary heating. The alignment performance of the loading frame was verified according to ASTM E1012–19, with a maximum measured percentage bending value of 4.8%, satisfying the Class 5 requirement. The system cooled from room temperature to 10 K within 93 mins, while temperature fluctuations remained within ±0.4 K at both 20 K and 77 K. Reproducible thermal responses were observed over repeated cooling cycles, demonstrating stable operation and repeatability over multiple cooling cycles. Furthermore, the functionality of the testing platform was validated by conducting tensile tests on 30,408 stainless steel and compact-tension fracture toughness tests on 316LN stainless steel at 20 K. The proposed design provides an effective solution for high-accuracy mechanical testing under cryogenic conditions.
