學術演講


<專題討論>2017/12/14(四)14:10綜合大樓2樓48218教室演講「Implementation of a 10 kJ pulsed-power generator」( 張博宇 助理教授 / 成大電漿所 )

張貼者:2017年12月10日 下午6:16Dabby Lu

A 10 kJ pulsed-power generator as a platform is being built to study plasma jets in space, nuclear fusion, specifically on inertial-confinement fusion (ICF), and to generate neutrons, soft-x rays, and extreme ultraviolet (EUV). The system will be built using an architecture called parallel plate capacitor bank (PPCB). In PPCB, all capacitors are connected in parallel and the current from all capacitors are delivered to the load through a parallel plate transmission line due to its low inductance and simple system configuration. Twenty 1 µF capacitors which can be charged up to 40 kV are used.  The total discharge energy can be up to 16 kJ and the expected output current will be more than 100 kA with a rise time of 1 µs, i.e., an output power of 10 GW.

Any loads will be heated and ionized by the high current. The generated plasma can potentially be used for following purposes: (1) generating plasma jets to study interactions between plasma flows and unmagnetized/magnetized obstacles analogous to the interactions between solar winds and planetary magnetic fields or unmagnetized planets; (2) generating soft x-ray/EUV using gas- puff z pinches for bio-medical research or EUV lithography; (3) generating soft x-ray lasers using capillary discharge; and (4) studying the pinch in a dense plasma focus device as a high efficient neutron source for Neutron capture therapy of cancer. The pulsed-power generator is being built by students in the lab from scratch and is expected to be finished by next Summer. The preliminary design and some testing results of each hand-made component will be given.

<專題討論>2017/12/7(四)14:10綜合大樓2樓48218教室演講「Status and vision of the KSTAR program to resolve critical issues of the steady-state high beta operation in ITER and K-DEMO operation」( Dr. Yeong-Kook Oh / KSTAR research center, National Fusion Research Institute (NFRI), Daejeon, Korea )

張貼者:2017年12月4日 下午7:36Dabby Lu

Developing energy resources that are environmentally friendly and free from high-level radioactive waste is especially important for next generation, particularly in Korea where underground resources are lacking. Fusion energy development is of great significance pursuing one of the alternatives that is less dependent on fossil resources.

 

The fusion energy development in Korea is based on the Fusion Energy Development Promotion Law, and the KSTAR project plays a very important role in resolving the critical issues required for future fusion reactor development and in raising the human resources capable of the research. The KSTAR project has several unique features (extremely low error field, versatile in-vessel control coils, 2D advanced imaging diagnostics, and high efficient long pulse capable heating system) to achieve a high performance steady-state operation research vision. The KSTAR

 

The KSTAR project started in 1995, achieving the first plasma in 2008, and has shown a lot of remarkable results for 10 years’ operation. In particular, KSTAR achieved the long pulse (over 70s) H-mode discharge with confinement equivalent to ITER (betaN ~ 1.8) and suppressed Edge Localized Mode (ELM) crash robustly up to 34 s using n=1 Resonance magnetic Perturbation (RMP). In addition, progress in fundamental physics interpretation on the turbulence and instability due to advanced diagnostics system and modeling studies.

 

In order to explore the plasma confinement and instability at higher confinement (betaN > 3.0), heating systems are under upgrade (NBI heating 5.5.MW à 12 MW, ECCD system 1 MW à 6 MW), and Divertor and current driving system will be upgraded also around in 2021 to develop a steady-state scenario for K-DEMO.

We acknowledge the contribution and collaboration to KSTAR from national and international collaborators. This work is supported by Ministry of Science and ICT (MSIC) of Korea under KSTAR project.

<演講公告>2017/12/4(一)11:00綜合大樓2樓48218教室演講「Two types of asymmetries of field –aligned currents distribution in polar ionosphere and of magnetosphere –ionosphere feedbacks during the substorm expansion phase」( Prof. Vladimir Mishin / Institute of Solar-Terrestrial Physics, Irkutsk, Russia )

張貼者:2017年11月27日 下午5:53Dabby Lu

We use original magnetogram inversion technique created by Vilen Mishin, A.

Bazarzhapov and G. Shpynev in Irkutsk more than 40 years ago. This method  uses data of world net of ground-based magnetometers. It was also then developed in parallel in Russia in IZMIRAN (Feldshtein, Levitin, Belov, Papitashvili) and abroad by Kamide et all. Recently, this method is already very few people engaged in, all use the expensive data of multi-satellite projects such as AMPERE. However, our inexpensive method allows, with a 1 min resolution, to build maps of the distribution of field-aligned currents (FACs) and fields and to reveal fine structures in their zones–mesoscale cells, which is inaccessible for other methods. The report deals with two types of FAC distribution in the mesoscale cells of night auroral ionosphere. Also, two types of feedback in the magnetosphere-ionosphere system are investigated: of the intensity of field-aligned currents (FACs) with the ionosphere conductivity (type 1), and with the electric field (type 2). Explosive development of FACs during the substorm expansion phase in the nighttime mesoscale cells of the three Iijima and Potemra (I-P) regions connected by meridional currents, is described.

<專題討論>2017/11/30(四)14:10綜合大樓2樓48218教室演講「BCS-type second-order phase transition of classical Langmuir wave system」( 河森榮一郎 教授 / 成大電漿所 )

張貼者:2017年11月23日 下午6:53Dabby Lu

The BCS-type second-order phase transition of a classical Langmuir wave system is identified theoretically and numerically. The transition takes place between two states: Langmuir wave turbulence (LWT) and Langmuir wave supercontinuum (LWSC), the latter of which exhibits broad power spectra with significant spatiotemporal coherence when a certain number of plasmons (plasma wave quanta) are excited in the system. In the LWT-LWSC transition, the modulational instability and resulting creation of plasmon pairs are the classical counterparts of the Cooper instability and creation of Cooper pairs in superconducting states. The Bose–Einstein condensation of Cooper pairs in superconducting states is replaced by the Kuramoto oscillator-entrainment of plasmon pairs in a LWSC. The order parameter of the LWSC state, which is defined as the mean field of the plasmon pairs, takes on a significant value, which clearly indicates that a macroscopic number of plasmon pairs occupy a single momentum state with an identical phase in the LWSC. The emergence of spatiotemporal coherence and the decrease in the phase randomization are considered as development of long-range order and spontaneous symmetry breaking, respectively, indicating that the LWT-LWSC transition is a second order phase transition phenomenon. By this transition, U(1) symmetry of LWT is broken. The LWSC is, in terms of plasma physics, a so-called Bernstein–Greene–Kruskal mode characterized by its undamped nature.

<專題討論>2017/11/23(四)14:10綜合大樓2樓48218教室演講「Micro Power System and its Application / 微動力系統與其應用」( 李約亨 助理教授 / 成大航太系 )

張貼者:2017年11月16日 下午10:28Dabby Lu

The application of micro power system is prevailing. This talk would introduce the concept, design and demonstration of micro-thermophotovoltaic (micro-TPV) power system. However, the overall efficiency of micro-TPV is strongly associated with radiant efficiency and quantum efficiency. How to improve the overall efficiency of micro-TPV power system during the miniaturization process is a quintessential question to researchers. The talk would point out the inherent deficiency of a small combustion system, and propose some promising strategies to overcome these defaults. Ultimately, the combination of TPV power system and Stirling Engine fueling with (bio-) syngas is demonstrated and discussed.

<專題討論>2017/11/16(四)14:10綜合大樓2樓48218教室演講「We live in a world of mathematical models」( 許瑞麟 教授 / 成大數學系 )

張貼者:2017年11月9日 下午10:45Dabby Lu

We are so used to many daily lives that we mistakenly think they are natural. They are not. For example, the calendar is not nature. It is just a model for us to explain the nature. In the calendar (model), we use the term "year" to call, roughly, a full round of a revolution of the earth around the sun; and then divide a year into seasons and months; and into the dates and the time. The calendar is certainly not the nature itself though. Models are subject to change whenever they become inaccurate or whenever we change the way we understand the world. As such, some radical mathematicians claim that " Every model is wrong."  In this talk, I will first give some general senses about the mathematical models for the hope that we can properly use models, rather than believe in models. Then, we will see as many concrete examples as possible, subject to the time limitation, that the models help/abuse us.

<專題討論>2017/11/9(四)14:10綜合大樓2樓48218教室演講「Simulation of runaway electrons with MHD modes」( Dr. Masatoshi Yagi / National Institute for Quantum and Radiological Science and Technology, (QST), Japan )

張貼者:2017年11月2日 上午2:45Dabby Lu

Dynamics of runaway electrons in the presence of macroscopic MHD instabilities is studied. Generation of massive runaway beam currents has become a crucial issue for the development of reliable disruption mitigation schemes in ITER. A difficulty arises in a large gap of the avalanche growth gain between present tokamaks and ITER, which prevents us from a straightforward extrapolation of the experimental data towards disruptions with 10MA-order plasma currents. Therefore – in addition to experimental demonstration of runaway mitigation – the development of numerical simulations increases its importance. To clarify possible effects of MHD modes on runaway electron generation, we have applied a nonlinear reduced fluid model [1] for long- term simulations of runaway generation scenario in a post-disruption plasma. In a plasma unstable to resistive kink modes, the coupling between MHD modes, runaway electrons, and electric fields becomes important. It is shown that seed electrons can be enhanced with inductive electric fields and the final runaway beam profile develops to be consistent with the resistive MHD stability [2]. For exploring the possibility of runaway suppression, magnetic and orbit stochasticity is suggested to cause radially global transport of runaway electrons [3].

 

[1] A. Matsuyama, N. Aiba, M. Yagi, submitted.

[2] A. Matsuyama, N. Aiba, M. Yagi, 26th IAEA Fusion Energy Conference, 17-22 October 2016, Kyoto, Japan, TH/P1-34.

[3] A. Matsuyama, M. Yagi, Y. Kagei, and N. Nakajima, Nucl. Fusion 54, 123007 (2014).

<專題討論>2017/11/2(四)14:10綜合大樓2樓48218教室演講「邁向公職之路-評估與選擇」( 汪德彥 / 交通部民用航空局 飛航服務總臺 北部飛航服務園區 臺北航空通信中心)

張貼者:2017年10月29日 下午7:03Dabby Lu

介紹公職領域。

當對個人職涯產生茫然或是生活與工作無法取得平衡,公職就是可以考慮的一個選擇。但是準備公職是一個對自己個性的磨練與考驗,如何能在短時間考上公職,減輕自己的負擔是另一個需要考慮的重點。所以當下定決心考試後,如何擬定策略,達成目標,才是需要時間思考的。

<專題討論>2017/10/26(四)14:10綜合大樓2樓48218教室演講「什麼是太空天氣? What is Space Weather ?」( 江致宇 博士候選人 / 成大電漿所 )

張貼者:2017年10月22日 下午7:20Dabby Lu   [ 已更新 2017年10月22日 下午7:23 ]

近年來,隨著太空科技的日新月異,人類對太空探索和研究已從過去為了解決單一議題,擴大成為整體性太空環境的監測和討論,尤其是會影響人類生活的地球磁層到電離層區域。而想了解太空天氣,學習"電漿"絕對是入門的基本條件,因為從地球大氣層以上,幾乎都是電漿的天下,所有影響太空天氣的活動,也都必須從電漿物理出發。所以這次的演講課題,將跟大家說明太空天氣的源頭在哪裡? 在磁層中有哪些的動力學驅動機制? 以及最後在電離層當中所呈現的結果是什麼? 歡迎大家一起來學習與討論。

<專題討論>2017/10/19(四)14:10綜合大樓2樓48218教室演講「In-situ plasma measurements in the Earth’s ionosphere」( 方惠寬 博士 / 成大電漿所 )

張貼者:2017年10月12日 下午7:00Dabby Lu   [ 已更新 2017年10月12日 下午7:06 ]

Measurements of plasma are fundamental for space physics, especially for space weather. Recently, giant progress of the CubeSat technologies greatly lowers the barrier to insert a satellite into a lower earth orbit for space exploration. Satellite constellation missions consisting of tens of CubeSats is planned and launched. These missions provide multi-point measurements and make it possible to separate spatial and temporal effects regarding couplings between ionosphere, atmosphere and even lithosphere. And the altitude of these missions are rarely explored by conventional satellites because of large air drag and short mission lifetime. In addition to Cubesat missions, simultaneous multi-instrument measurements onboard sounding rockets aiming for the plasma characteristic investigations in the ionosphere D layers, which is the least-explored region in the ionosphere, is planned. In this presentation, the plasma diagnostic techniques onboard CubeSats and sounding rockets will be introduced. The design concepts of the solar EUV probe onboard the Phoenix CubeSat in QB50 mission and the “Mesosphere and Ionosphere Plasma Exploration complex (MIPEX)” instrument onboard the NCKU sounding rocket, which is planned to be launched in 2020, will be shown. These experiments can provide unique high-quality data of the plasma environment to explore the ion distribution and the electrodynamic processes in the Ionosphere D, E layers.


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