A high-power proton–LaB\(_6\) glow-discharge system operated under low-pressure hydrogen atmosphere was investigated using continuous calorimetric measurements. Under specific operating conditions during prolonged discharge operation, periods of thermal output exceeding the measured electrical input were reproducibly observed. The experimental system was developed to study high-power proton–LaB\(_6\) glow-discharge phenomena under nonequilibrium plasma conditions, where LaB\(_6\) serves as both a boron-containing and thermionically stable cathode material. The calorimetric system was calibrated repeatedly using ISO/IEC 17025 standards, and both electrical input power and water-cooling thermal output were monitored continuously during operation. Under higher-power discharge conditions, integrated gain values exceeding unity were observed in several experimental runs. These phenomena were not observed across all discharge regimes and appeared more frequently near specific operating conditions where plasma instability also became more pronounced. Additional control experiments using tungsten cathodes under comparable calorimetric conditions did not reproduce the same elevated-gain phenomena. SEM-EDS analysis of used LaB\(_6\) cathodes further revealed oxidation, erosion, redeposition, and substantial local surface modification after prolonged plasma exposure. Thermochemical estimates based on cathode mass loss remained substantially below the observed excess-energy scale. At the present stage, the physical origin of the observed excess energy remains unresolved. The current work is therefore intended mainly as a report of calibrated experimental observations obtained in a proton–LaB\(_6\) glow-discharge system under specific nonequilibrium operating conditions.
