Development of miniaturized pick-up amplification circuit for plasma particle detectors on board satellites

Plasma particles and waves are important observation targets in space plasmas for understanding the mechanisms of energy and momentum transfer between waves and particles because space plasmas are essentially collisionless. Multi-point observations are crucial for understanding the spatial–temporal variations of space plasmas. To realize such observations by a large number of satellites, onboard instruments should be miniaturized to reduce their required resources. This paper proposes a small amplifier for plasma particle detectors onboard satellites. This charge-sensitive amplifier converts an electron cloud emitted from the detector, for example a microchannel plate, to a current pulse that can be handled by a time-of-flight measurement circuit to determine the particle velocity and thus mass. The amplifier is realized using application-specific integrated circuit technology to minimize size. Its dimensions are estimated to be $$2120, mathrm{ mu m }times 1680, mathrm{ mu m}$$, which are much smaller than those of a conventional amplifier. The response time of the proposed amplifier has a variation of less than $$1.2, mathrm{ ns}$$ over the range of expected input levels. The amplifier can handle up to $$2times {10}^{7}$$ signals per second and has a sensitivity of $$1.5, mathrm{ V}/mathrm{pC}$$ at $$20, mathrm{^circ{rm C} }$$

Small sensor probe for measuring plasma waves in space Space science

Background: Since conventional one-point observations of plasma phenomena in space cannot distinguish between time and spatial variations, the missions on the basis of multiple-point observations have become the trend. We propose a new system for multiple-point observation referred to as the monitor system for space electromagnetic environments (MSEE). Findings: The MSEE consists of small sensor probes that have a capability to measure electromagnetic waves and transfer received data to the central station through wireless communication. We developed the prototype model of the MSEE sensor probe. The sensor probe includes a plasma wave receiver, the microcontroller, the wireless communication module, and the battery in the 75-mm cubic housing. In addition, loop antennas, dipole antennas, and actuators that are used for expanding dipole antennas are attached on the housing. The whole mass of the sensor probe is 692 g, and the total power consumption is 462 mW. The sensor probe can work with both inner battery and external power supply. The maximum continuous operation time on battery power is more than 6 h. We verified the total performance for electric field measurements by inputting signal to preamplifier. In this test, we found that analog components had enough characteristics to measure electric fields, and the A/D conversion and the wireless transmission worked correctly. In the whole performance for electric fields, the sensor probe has equivalent noise level of - 135 dBV/m/√Hz. Conclusions: We succeed in developing the prototype model of the small sensor probe that had enough sensitivity for electric field to measure plasma waves and the ability to transfer observation data through wireless communication. The success in developing the small sensor probe for the measurement of plasma waves leads to the realization of the multiple-point observations using a lot of small probes scattered in space

プラズマ波動観測システムの小型化に関する研究

京都大学0048新制・課程博士博士(工学)甲第21769号工博第4586号新制||工||1715(附属図書館)京都大学大学院工学研究科電気工学専攻(主査)教授 小嶋 浩嗣, 准教授 海老原 祐輔, 准教授 三谷 友彦学位規則第4条第1項該当Doctor of Philosophy (Engineering)Kyoto UniversityDGA

One-chip analog circuits for a new type of plasma wave receiver on board space missions

Plasma waves are important observational targets for scientific missions investigating space plasma phenomena. Conventional fast Fourier transform (FFT)-based spectrum plasma wave receivers have the disadvantages of a large size and a narrow dynamic range. This paper proposes a new type of FFT-based spectrum plasma wave receiver that overcomes the disadvantages of conventional receivers. The receiver measures and calculates the whole spectrum by dividing the observation frequency range into three bands: Bands 1, 2, and 3, which span 1Hz to 1kHz, 1 to 10kHz, and 10 to 100kHz, respectively. To reduce the size of the receiver, its analog section was realized using application-specific integrated circuit (ASIC) technology, and an ASIC chip was successfully developed. The dimensions of the analog circuits were 4.21mm × 1.16mm. To confirm the performance of the ASIC, a test system for the receiver was developed using the ASIC, an analog-to-digital converter, and a personal computer. The frequency resolutions for bands 1, 2, and 3 were 3.2, 32, and 320Hz, respectively, and the average time resolution was 384ms. These frequency and time resolutions are superior to those of conventional FFT-based receivers

Development of a miniaturized spectrum-type plasma wave receiver comprising an application-specific integrated circuit analog front end and a field-programmable gate array

Plasma waves are an important target for satellite-based in situ observation to understand electromagnetic phenomena in space. Recent scientific satellites have carried fast Fourier transform (FFT)-based spectrum receivers; however, such receivers have a disadvantage because they use wideband analog parts. The new receiver overcomes the disadvantage by adding bandlimiting in the first stage of the analog part, and it covers the entire observation frequency range of each band by switching its cutoff frequency. In order to miniaturize circuit size, the new receiver comprises application-specific integrated circuits (ASICs) and a field-programmable gate array (FPGA). The ASIC chip includes the analog part of the receiver and the analog-to-digital converter, and the FPGA includes an FFT module and the controller of the receiver. The proposed spectrum receiver was successfully implemented with a size of 55 mm  ×  80 mm  ×  35 mm and a total power consumption of 948.3 mW. The time resolution of the receiver was 112 ms, and the frequency resolutions for frequency bands from 10 Hz to 1 kHz, from 1 kHz to 10 kHz, and from 10 kHz to 100 kHz were 13 Hz, 130 Hz, and 1.3 kHz, respectively. Overall, the developed receiver showed sufficient performance for plasma wave observation

Development of an ASIC preamplifier for electromagnetic sensor probes for monitoring space electromagnetic environments

[Background]Multipoint observations of plasma waves are essential for separating spatial and temporal variations of a plasma turbulence. Miniaturization and high environmental (temperature and radiation) robustness are key requirements for scientific instrument design toward a sensor network consisting of palm-sized probes. With increasing these demands, a preamplifier for the 3-axis loop antenna of an electromagnetic sensor probe has been developed by using application-specific integrated circuit (ASIC) technology with a 0.25-μm complementary metal-oxide-semiconductor process. [Findings]In the present study, a new temperature compensation method is proposed by using the open-loop gain of the ASIC preamplifier with a bandgap reference (BGR) circuit. Usually, the gain is characterized by the closed-loop gain, which is governed by the accuracy of the polysilicon resistances in a chip. The open-loop gain is characterized by the effective transconductance of the ASIC preamplifier, which often has a negative temperature dependence. The temperature dependence of the gain can be dramatically improved by using the temperature-compensated BGR circuit to cancel out the negative dependence of the transconductance. The temperature dependence of the gain was about −0.01−0.01 dB/∘∘C in the frequency range within the closed-loop bandwidth. On the other hand, the temperature dependence of the gain at 60 kHz operating with the open-loop gain was improved from −39×10[−3]−39×10−3 to −2.6×10[−3]−2.6×10[−3] dB/℃ by using the temperature-compensated BGR circuit. Moreover, the radiation robustness for the total ionizing dose (TID) level is evaluated by irradiation with gamma rays from cobalt-60. The ASIC preamplifier is not sensitive to TID effects when a thin gate oxide is used. The ASIC preamplifier showed a high radiation tolerance to at least a total ionizing dose level of 400 krad(Si). Finally, the effectiveness of the ASIC preamplifier is evaluated on the basis of a virtual sounding rocket experiment using theoretical calculations of LF standard electromagnetic waves. [Conclusions]Fundamental issues (miniaturization, low-noise performance, and high environmental robustness) are solved by the presented ASIC preamplifier. The success in developing the high robustness ASIC preamplifier leads to a future mission using a lot of palm-sized probes in space

Changes in the Bacterial Community of Soybean Rhizospheres during Growth in the Field

<div><p>Highly diverse communities of bacteria inhabiting soybean rhizospheres play pivotal roles in plant growth and crop production; however, little is known about the changes that occur in these communities during growth. We used both culture-dependent physiological profiling and culture independent DNA-based approaches to characterize the bacterial communities of the soybean rhizosphere during growth in the field. The physiological properties of the bacterial communities were analyzed by a community-level substrate utilization assay with BioLog Eco plates, and the composition of the communities was assessed by gene pyrosequencing. Higher metabolic capabilities were found in rhizosphere soil than in bulk soil during all stages of the BioLog assay. Pyrosequencing analysis revealed that differences between the bacterial communities of rhizosphere and bulk soils at the phylum level; i.e., Proteobacteria were increased, while Acidobacteria and Firmicutes were decreased in rhizosphere soil during growth. Analysis of operational taxonomic units showed that the bacterial communities of the rhizosphere changed significantly during growth, with a higher abundance of potential plant growth promoting rhizobacteria, including <i>Bacillus</i>, <i>Bradyrhizobium,</i> and <i>Rhizobium</i>, in a stage-specific manner. These findings demonstrated that rhizosphere bacterial communities were changed during soybean growth in the field.</p></div