RF and Microwave Ion Sources Study at Institute of Modern Physics

Intense ion beam production is of high importance for various versatile applications from accelerator injectors to secondary ion mass spectrometry (SIMS). For these purposes, different types of ion beams are needed and, accordingly, the optimum plasma to produce the desired ion beams. RF-type plasma features a simple structure, high plasma density and low plasma temperature, which is essential for negative ion beam production. A very compact RF-type ion source using a planar coil antenna has been developed at IMP for negative molecular oxygen ion beam production. In terms of high-intensity positive ion beam production, 2.45 GHz microwave power-excited plasma has been widely used. At IMP, we developed a 2.45 GHz plasma source with both ridged waveguide and coaxial antenna coupling schemes, tested successfully with intense beam production. Thanks to the plasma built with an external planar coil antenna, high O2− production efficiency has been achieved, i.e., up to 43%. With 2.45 GHz microwave plasma, the ridged waveguide can support a higher power coupling of high efficiency that leads to the production of intense hydrogen beams up to 90 emA, whereas the coaxial antenna is less efficient in power coupling to plasma but can lead to attractive ion source compactness, with a reasonable beam extraction of several emA.

A Complete Flow of Miniaturizing Coil Antennas Based on Matching Circuit

This paper proposes and verifies a complete design flow of miniaturizing a coil antenna and widening its impedance bandwidth for near-field application, such as NFC, RFID and WPT. The proposed scheme based on mature electronic element matching technology is interpreted in detail by two equivalent circuit models in theory. For convenience, only the series equivalent circuit and its matching circuit are respectively established in the circuit simulator ADS and ANSYS HFSS to assess the scheme proposed from two aspects. The parallel equivalent circuit can be optimized by a similar approach. Then, a WPT system is established in HFSS to further verify the feasibility of miniaturization. Finally, the dimension of the coil antenna can be reduced by about 70%, and its impedance bandwidth can be increased by approximately 40% after two electronic modules are integrated.

Development of Ingestible Thermometer with Built-in Coil Antenna Charged by Gastric Acid Battery and Demonstration of Long-Time in vivo Telemetry

<p><i>Objective:</i> A safe and affordable ingestible thermometer measuring core body temperature has the potential to become a future healthcare device for versatile applications in daily life. In this study, we developed an ingestible thermometer charged by a gastric acid battery. <i>Methods: </i>The device can operate in bowels by using the charged energy in multilayer ceramic capacitors as a storage capacitor. Adopting this strategy for energy storage solves the issues related to a conventional button battery: risk of injury to the digestive tract, bad disposability, and degradation. Additionally, to make it easy to assemble a coil antenna and electrical circuits in the device automatically, we developed a fabrication process based on a vertical stacking process of printed circuit boards with coil patterns. The dimensions of the prototyped device were smaller than those of existing ingestible thermometers. <i>Results: </i>In an experiment involving a dog, we successfully recorded the temperature in the digestive tract for 24 h in cycles of approximately 10 or 20 min, using a rectal thermometer and an existing ingestible thermometer as references. The temperature variations in time among our device, rectal thermometer, and existing ingestible thermometer were almost parallel. <i>Conclusion:</i> The recording ability of the core body temperature using our device has the potential to measure basal body temperature during sleep, the circadian rhythm, and fever type easily and robustly in daily life. <i>Significance: </i>Our ingestible thermometer is a step toward the development of sensors that can be swallowed for preventive medicine and health promotion. </p>

Development of Ingestible Thermometer with Built-in Coil Antenna Charged by Gastric Acid Battery and Demonstration of Long-Time in vivo Telemetry

<p><i>Objective:</i> A safe and affordable ingestible thermometer measuring core body temperature has the potential to become a future healthcare device for versatile applications in daily life. In this study, we developed an ingestible thermometer charged by a gastric acid battery. <i>Methods: </i>The device can operate in bowels by using the charged energy in multilayer ceramic capacitors as a storage capacitor. Adopting this strategy for energy storage solves the issues related to a conventional button battery: risk of injury to the digestive tract, bad disposability, and degradation. Additionally, to make it easy to assemble a coil antenna and electrical circuits in the device automatically, we developed a fabrication process based on a vertical stacking process of printed circuit boards with coil patterns. The dimensions of the prototyped device were smaller than those of existing ingestible thermometers. <i>Results: </i>In an experiment involving a dog, we successfully recorded the temperature in the digestive tract for 24 h in cycles of approximately 10 or 20 min, using a rectal thermometer and an existing ingestible thermometer as references. The temperature variations in time among our device, rectal thermometer, and existing ingestible thermometer were almost parallel. <i>Conclusion:</i> The recording ability of the core body temperature using our device has the potential to measure basal body temperature during sleep, the circadian rhythm, and fever type easily and robustly in daily life. <i>Significance: </i>Our ingestible thermometer is a step toward the development of sensors that can be swallowed for preventive medicine and health promotion. </p>

Organ-specific, multimodal, wireless optoelectronics for high-throughput phenotyping of peripheral neural pathways

The vagus nerve supports diverse autonomic functions and behaviors important for health and survival. To understand how specific components of the vagus contribute to behaviors and long-term physiological effects, it is critical to modulate their activity with anatomical specificity in awake, freely behaving conditions using reliable methods. Here, we introduce an organ-specific scalable, multimodal, wireless optoelectronic device for precise and chronic optogenetic manipulations in vivo. When combined with an advanced, coil-antenna system and a multiplexing strategy for powering 8 individual homecages using a single RF transmitter, the proposed wireless telemetry enables low cost, high-throughput, and precise functional mapping of peripheral neural circuits, including long-term behavioral and physiological measurements. Deployment of these technologies reveals an unexpected role for stomach, non-stretch vagal sensory fibers in suppressing appetite and demonstrates the durability of the miniature wireless device inside harsh gastric conditions.