A Cylindrical Triode Ultrahigh Vacuum Ionization Gauge with a Carbon Nanotube Cathode

In this study, a cylindrical triode ultrahigh vacuum ionization gauge with a screen-printed carbon nanotube (CNT) electron source was developed, and its metrological performance in different gases was systematically investigated using an ultrahigh vacuum system. The resulting ionization gauge with a CNT cathode responded linearly to nitrogen, argon, and air pressures in the range from ~4.0 ± 1.0 × 10−7 to 6 × 10−4 Pa, which is the first reported CNT emitter-based ionization gauge whose lower limit of pressure measurement is lower than its hot cathode counterpart. In addition, the sensitivities of this novel gauge were ~0.05 Pa−1 for nitrogen, ~0.06 Pa−1 for argon, and ~0.04 Pa−1 for air, respectively. The trend of sensitivity with anode voltage, obtained by the experimental method, was roughly consistent with that gained through theoretical simulation. The advantages of the present sensor (including low power consumption for electron emissions, invisible to infrared light radiation and thermal radiation, high stability, etc.) mean that it has potential applications in space exploration.

Field Emission Air-Channel Devices as a Voltage Adder

Field emission air-channel (FEAC) devices can work under atmospheric pressure with a low operation voltage when the electron channel is far less than the mean free path (MFP) in the air, thereby making them a practical component in circuits. Forward and reverse electron emissions of the current FEAC devices demonstrated symmetric Fowler–Nordheim (F–N) plots owing to the symmetric cathode and anode electrodes. This research aimed to demonstrate the arithmetic application of the FEAC devices, their substrate effect, and reliability. A voltage adder was composed of two FEAC devices whose two inputs were connected to two separate function generators, and one output was wire-connected to an oscilloscope. The devices were on a thin dielectric film and low-resistivity silicon substrate to evaluate the parasitic components and substrate effect, resulting in frequency-dependent impedance. The results show that the FEAC devices possessed arithmetic function, but the output voltage decreased. The FEAC devices were still capable of serving as a voltage adder after the reliability test, but electric current leakage increased. Finite element analysis indicated that the highest electrical fields and electron trajectories occur at the apices where the electrons travel with the shortest route less than the MFP in the air, thereby meeting the FEAC devices’ design. The modeling also showed that a sharp apex would generate a high electric field at the tip-gap-tip, enhancing the tunneling current.

Connecting Jupiter's Auroral Pulsations with In-situ Measurements by Juno

<p><strong>In 1979, the Voyager spacecraft arrived at Jupiter. Amongst their rich array of discoveries, they identified bright bursts of radio emission at kHz frequencies</strong><sup>1</sup><strong>, often called quasi-periodic (QP) bursts, and discovered Jupiter’s ultraviolet (UV) aurora</strong><sup>2</sup><strong> - the most powerful aurora in the Solar System</strong><sup>3</sup><strong>. The same year that the Voyager spacecraft explored the Jovian system, the Einstein X-ray Observatory took the first X-ray images of Jupiter</strong><sup>4</sup><strong> and discovered that planets can also produce bright and dynamic X-ray aurora</strong><sup>5,6</sup><strong>. Over the subsequent decades, these distinct multi-waveband emissions have all been observed to pulse with quasi-periodic regularity</strong><sup>7–10</sup><strong>. Here, we combine simultaneous observations by the Juno spacecraft with the X-ray and UV observatories: XMM-Newton, Chandra and the Hubble Space Telescope. These observations show that the radio, UV and X-ray pulses are all synchronised, beating in time together. Further, they reveal that the X-ray and radio pulses share an identical 42.5 minute periodicity with simultaneously measured compression-mode Ultra Low Frequency (ULF) waves in Jupiter’s outer magnetosphere</strong><sup>11</sup><strong>. ULF waves are known to modulate wave-particle interactions that can cause electron and ion precipitation, providing a physically consistent explanation for the observed simultaneous ion and electron emissions.  The unification of Jupiter’s X-ray, UV and radio pulsations and their connection to ULF waves provides fundamental and potentially universal insights into the redistribution of energy in magnetised space environments.</strong></p>