We develop novel GaN-based high temperature and radiation-hard electronics to realize data acquisition electronics and transmitters suitable for operations in harsh planetary environments. In this paper, we discuss our research on AlGaN/GaN metal-oxide-semiconductor (MOS) transistors that are targeted for 500 ºC operation and >2 Mrad radiation hardness. For the target device performance, we develop Schottky-free AlGaN/GaN MOS transistors, where a gate electrode is processed in a MOS layout using an Al 2 O 3 gate dielectric layer. The AlGaN/GaN MOS transistors fabricated with the wide-bandgap gate oxide layer enable Schottky-free gate electrodes, resulting in a much reduced gate leakage current and an improved sub-threshold current than the current AlGaN/GaN field effect transistors. In this study, characterization of our AlGaN/GaN MOS transistors is carried out over the temperature range of 25°C to 500°C. The I ds -V gs and I ds -V ds curves measured as a function of temperature show an excellent pinch-off behavior up to 450°C. Off-state degradation is not observed up to 400 °C, but it becomes measurable at 450 °C. The off-state current is increased at 500 °C due to the gate leakage current, and the AlGaN/GaN MOS HEMT does not get pinched-off completely. Radiation hardness testing of the AlGaN/GaN MOS transistors is performed using a 50 MeV 60 Co gamma source to explore effects of TID (total ion dose). Excellent I ds -V gs and I ds -V ds characteristics are measured even after exposures to a TID of 2Mrad. A slight decrease of saturation current (ΔI dss~3 mA/mm) is observed due to the 2Mrad irradiation.

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In experiments conducted at Sandia National Laboratories' RITS-6 accelerator, the self-magnetic-pinch diode exhibits significant shot-to-shot variability. Specifically, for identical hardware operated at the same voltage, some shots exhibit a catastrophic drop in diode impedance. A study is underway to identify sources of shot-to-shot variations which correlate with diode impedance collapse. The scope of this report is limited to data collected at 4.5-MV peak voltage and sources of variability which occur away from the diode, such as sheath electron emission and trajectories, variations in pulsed power, load and transmission line alignment, and different field shapers. We find no changes in the transmission line hardware, alignment, or hardware preparation methods which correlate with impedance collapse. However, in classifying good versus poor shots, we find that there is not a continuous spectrum of diode impedance behavior but that the good and poor shots can be grouped into two distinct impedance profiles. In poor shots, the sheath current in the load region falls from 16%-30% of the total current to less than 10%. This result will form the basis of a follow-up study focusing on the variability resulting from diode physics.

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Malignant hyperthermia (MH) is a rare neuromuscular hereditary disorder, triggered in susceptible individuals by exposure to inhalational agents or succinylcholine and manifested as a hypermetabolic state. We report the case of a 22 years old male patient anesthetized with Desflurane in whom MH was suspected because of unexplained increased levels of End-Tidal carbon dioxide. Dantrolene was administered with good response. Respiratory acidosis and hyperkalemia were also detected but could be easily controlled. The postoperative period was uneventful with the exception of a superficial venous thrombosis at the dantrolene's injection site. The patient was discharged eight days after the episode without sequela. Successful management of a malignant hyperthemia episode must include: early suspicion, asking for help and early treatment with dantrolene. ResumenLa Hipertermia Maligna es un trastorno neuromuscular hereditario infrecuente, manifestado por un estado hipermetabólico desencadenado en individuos susceptibles por la exposición a anestésicos halogenados o Succinilcolina. Se reporta el caso de un hombre de 22 años anestesiado con Desflurano, en quien el diagnóstico de Hipertermia Maligna se sospechó por la presencia de elevación inexplicada del CO 2 espirado, que respondió a la suspensión del Desflurano y administración de Dantroleno. Se observó además hiperkalemia y acidosis respiratoria, que fueron fácilmente compensadas. La evolución postoperatoria fue satisfactoria, a excepción de una trombosis venosa superficial en el sitio de inyección del Dantroleno. El paciente fue dado de alta al 8 avo día postoperatorio, sin secuelas. Las claves del manejo exitoso de un episodio de hipertermia maligna están en: Sospecha precoz, solicitar ayuda e inició rápido del tratamiento con Dantroleno.