<專題討論>2020/12/10(四)14:10綜合大樓2樓48218教室演講 : 林明緯 副教授(清華大學核子工程與科學研究所)

張貼者:2020年12月3日 下午7:49Dabby Lu

講題: Development of high-repetition-rate laser wakefield electron acceleration driven by few-TW or sub-TW laser pulses
摘要: Raising the repetition rate of ultrafast laser pulses that drive the laser wakefield acceleration (LWFA) can straightforwardly increase the average current of accelerated electrons and subsequently generate a high radiation flux desired in advanced X-ray radiography. Instead of using multi-TW laser pulses, the bottleneck of current ultrafast laser technology capable of producing pulses with an energy < 200 mJ at kHz-level frequencies motivates the development of LWFA methods that can be conducted with a moderate laser peak power approaching 1 TW. With the use of thin, high-density gas targets, principles of realizing the LWFA driven by pulses with a few-TW or even a sub-TW peak power will be introduced, including a comprehensive review to the recent simulations and experimental results in this field. Progress about the development of a diode-pumped, ytterbium-based ultrafast laser system expected to drive the sub-TW LWFA will be reported next. Moreover, results of LWFA experiments, when 800-nm pulses of a few-TW peak power are directed into sub-mm nitrogen gas jets and gas cells will be presented. This scheme exhibits a high potential for generating electrons with tens of MeV energies under a satisfactory reproducibility, which is the prerequisite for developing LWFA into a useful source in future radiation applications. 

<專題討論>2020/12/3(四)14:10綜合大樓2樓48218教室演講 : 簡瑞廷 經理(金屬工業研究發展中心升級處檢測組)

張貼者:2020年11月26日 下午10:44Dabby Lu

講題: 超精密製造與檢測技術應用
摘要: 本課程主要針對超精密加工製程如何從太空、軍事等研發,改為應用在球面/非球面、Fresnel透鏡、陣列透鏡、自由曲面…等產品開發。

<專題討論>2020/11/26(四)14:10綜合大樓2樓48218教室演講 : 鄭雲謙 副教授(交通大學機械工程學系)

張貼者:2020年11月19日 下午7:06Dabby Lu

講題: Atmospheric-pressure Plasma Effects on Cancer Cells and Impedance Matching Circuit to Improve Plasma Power Conversion Efficiency
摘要: We compared the effects of plasma-activated medium (PAM) with thermal therapy on lung cancer with malignant pleural effusion (MPE). The conventional MPE managements, such as local chemotherapy, regional hyperthermia with CDDP, and photodynamic therapy, have side effects on the patients so that we need a new therapy to avoid harmful side effects on cancer patients. Recent studies show that plasma effectively induce apoptosis in cancer cells with minor effects on normal cells because of reactive oxygen/nitrogen species (RONS). Additionally, PAM by atmospheric-pressure plasma jets (APPJ) also has the similar effect. The PAM effects on MPE have not been investigated yet so far. Thus, we applied PAM to lung cancer cells (CL1-5) and benign cells from lung cancer patients to see its lethal effect. This study find out that the PAM can selectively kill lung cancer cells and the benign cells remain its viability. Besides, the thermal therapy kills both cancer cell and benign cells. It indicates that PAM would be likely to enhance the effect of lung-cancer treatment as adjuvant therapy in the future.

We also constructed an impedance matching circuit for a partial-discharge calibrated (PDC) atmospheric-pressure plane-to-plane DBD equivalent circuit. The PDC plane-to-plane DBD equivalent circuit simulated the actual phase difference of plasma voltage and current. And we will design the tunable impedance matching circuit based on the structure of parallel impedance matching circuit. Previous studies proposed that an installation of impedance matching circuit between power supply and plasma can effectively increase the system power conversion efficiency. However, the adopted plasma equivalent circuit in the previous study may not consider the partial discharge phenomenon of DBD in atmospheric pressure and the phase difference between plasma voltage and current. Under atmospheric pressure, the charge does not distribute uniformly on the dielectric, so the discharge channels only generated on part of the dielectric area. Therefore, the impedance of plasma equivalent circuit may not correspond to the actual plasma impedance, and it result in an inaccurate impedance matching circuit design. In this study, we measured Q-V diagram to construct the PDC plasma equivalent circuit that can simulate the partial discharge phenomenon of atmospheric-pressure plasma, and the PDC plasma equivalent circuit is contributed to the corresponding impedance matching circuit design. For tunable impedance matching circuit design, we will design a system to control the variable capacitor for the tunable parallel matching circuit. As a result, the plasma discharging area ratio of 0.8275 was deduced from the slope of Q-V diagram and the PDC atmospheric-pressure plasma equivalent circuit was successfully established. Then we used Simulink software to calibrate the resistor of PDC plasma equivalent circuit for accurate phase shift. Through the phase difference calculation, the error of phase difference between simulation and measurement results was 1.01 degree. And a power supply equivalent circuit was also established by measuring the no-load voltage of power supply. The accurate PDC plasma equivalent circuit was then applied for more precise impedance matching circuit calculation under atmospheric pressure. Then we will check if the power conversion efficiency is enhanced with the installation of impedance matching circuit for PDC plasma equivalent circuit or not. Plasma impedance may be affected by different working gases, discharge gaps, dielectric materials, and operation voltage frequency. Therefore, the application of tunable impedance matching circuit will ensure the maximum power transmission under different plasma working conditions.

<專題討論>2020/11/19(四)14:10綜合大樓2樓48218教室演講 : 楊湘怡 助理教授(清華大學天文研究所)

張貼者:2020年11月12日 下午7:01Dabby Lu

講題: 黑洞噴流反饋效應中的電漿物理
摘要: 現今宇宙論中,星系的形成和演化與中心的超大質量黑洞有密不可分的關係。其中黑洞的噴射流跨越的尺度極大、能量極高,足以影響黑洞所處的星系及星系團的演化,這樣的黑洞噴射流所產生的能量反饋效應,甚至能夠將星系團的氣體加熱。以往這方面的數值模擬通常拘限於純流體計算,但近年來的研究發現許多電漿物理的現象對結果有重要的影響。本次演講我將會介紹黑洞噴射流在星系與星系團中的反饋效應,與其中電漿物理所扮演的角色。

<專題討論>2020/11/5(四)14:10綜合大樓2樓48218教室演講 : 潘國全 助理教授(清華大學天文研究所)

張貼者:2020年11月1日 下午6:29Dabby Lu

講題: Hearing the sound of gravitational waves from Core-Collapse Supernovae
摘要: Core-Collapse supernovae are among the most energetic explosions in the universe and are birthplaces of neutron stars and stellar-mass black holes. Detection of gravitational waves from a nearby core-collapse supernova could be the next milestone of gravitational-wave astronomy and multimessenger astrophysics. In this presentation, I will discuss the numerical challenges in modeling for these systems that involved detailed both micro- and macro-physics and present a few recent full 3D simulations with neutrino transport. In particular, I will focus on the effects of the nuclear equation of state, rotation, and magnetic fields on the explosion engines and unique gravitational wave features that might be detected with the current gravitational wave detectors, e.g., Advanced LIGO and Virgo. 

<專題討論>2020/10/29(四)14:10綜合大樓2樓48218教室演講 : 呂育廷 組長(金屬工業研究發展中心 精微處)

張貼者:2020年10月25日 下午7:44Dabby Lu

講題: 精微製造技術與應用簡介
摘要: 全球可攜式微型產品的需求大增,帶動精微零組件技術能量的急速攀升,精微製造是因應輕薄短小產品發展而衍生的製造生態體系,當中涉及了製程技術、設備、模具到周邊系統等需求;其技術涵蓋面包括切削加工、研磨加工及非傳統加工等。94年金屬中心在技術處的經費支援下,建立「精微模具及成形共用實驗室」;以建立精微零組件的設計與生產解決能力為宗旨,並肩負建構新興產業群聚與研發的協力與通路體系的任務。因精微製造的複雜難度,非比尋常,故精微零組件設計與材料選用,除了考量精細化外,還要顧及機械性能與環境耐用性,因此衍生各層面的製造與生產困難度,期望透過此次專題研討向各位同學分享相關技術與應用。

<專題討論>2020/10/22(四)14:10綜合大樓2樓48218教室演講 : 張木彬 特聘教授(中央大學環境工程研究所)

張貼者:2020年10月20日 下午7:47Dabby Lu

講題: 電漿在環境工程之應用
摘要: 電漿(plasma)在環境工程有諸多應用,如殺菌、水質淨化、室內空氣品質管理、空氣污染防制、溫室氣體轉化及臭氧生成等。臭氧(O3)具強氧化能力,廣泛應用於消毒、殺菌、廢水處理及空氣污染物去除等,臭氧生成技術已臻成熟,然現今市售臭氧機操作成本偏高。本團隊發展觸媒結合電漿系統進行臭氧合成研究,結果顯示電漿觸媒系統不論於臭氧濃度或能量效率之表現均優於單獨DBD反應器,證實觸媒及電漿間存在加乘作用。空氣污染物控制方面,懸浮微粒如PM2.5為最受關注的污染物之一,靜電集塵器(Electrostatic precipitator)為高效除塵設備,其以施加高壓電於放電電極產生電暈放電,為電漿的應用之一,重要之操作參數包括操作電壓、比收集板面積、電阻係數等。氮氧化物對人類健康及環境之影響深遠,包括致生酸雨、光化學煙霧、危害人體呼吸系統等。工業上多以SCR技術將煙道氣中的NOx還原成氮氣和水,而氮氧化物儲存還原法(NOx storage and reduction, NSR)可應用於柴油引擎之NOx排放控制。本團隊研發低溫、低成本、高效率之NSR觸媒並結合非熱電漿技術針對柴油引擎排氣之NOx去除進行研究,結果顯示此系統於不添加還原劑的操作條件下即可達良好的去除效率。

<專題討論>2020/10/15(四)14:10綜合大樓2樓48218教室演講 : 張博宇 助理教授(成功大學電漿所)

張貼者:2020年10月11日 下午8:40Dabby Lu

講題: Development of EUV light source and studies of high-energy-density plasma (HEDP) on a 1-kJ pulsed-power system
摘要: A pulsed-power system was built for studying various topics related to high-energy-density plasma, a regime with pressure higher than 1 MBar in general, and for generating extreme ultraviolet (EUV) light for EUV lithography. Astrophysics and space sciences can be studied experimentally using the pulsed-power system due to the magnetohydrodynamic scaling. Extreme ultraviolet light can also be generated in the HEDP regime via discharge produced plasma (DPP). The pulsed-power system we built stores 1 kJ of energy using high voltage capacitors charged to 20 kV. When it is discharged, a peak current of 110±20 kA with a rise time of 1.51±0.06 μs, i.e., a power of ~700 MW, is provided. It is the pulsed current that will be used to drive different loads for different experiments. To diagnose plasma in different experiments, a suite of ultrafast x-ray imaging systems such as time-integrated pinhole camera with an exposure time of 1 μs, a streak camera with a temporal resolution of 15 ps, and a framing camera with a potential temporal resolution of 10 ns are being built. Interferometry, collective thomson scattering for measuring plasma densities and temperatures will be implemented using a q-switch laser with the single longitudinal mode. The laser pulse will be compressed using stimulated brillouin scattering (SBS) in water so that a temporal resolution of sub-ns can be achieved. In experiments, a theta pinch will be used to compress an argon plasma plume. Temperature about 30 eV at the peak compression can be achieved so that EUV light can be radiated. On the other hand, supersonic plasma jets are generated via imploding conical-wire arrays made of tungsten wires driven by the pulsed-power system. The supersonic plasma jets will be used to simulate solar winds in the laboratory based on the hydrodynamic similarity between the solar system and the laboratory. Time-integrated images of plasma jets in visible light will be shown. This work was supported by the Ministry of Science and Technology (MOST), under Award Number 105-2112-M-006-014-MY3 and 109-2112-M-006-011.

<專題討論>2020/10/8(四)14:10綜合大樓2樓48218教室演講 : 江旭禎 特聘教授(中山大學化學系)

張貼者:2020年10月4日 下午7:51Dabby Lu

講題: 感應耦合電漿質譜儀(ICP-MS)及其在食品中元素型態分析之應用
摘要: 感應耦合電漿質譜儀(Inductively Coupled Plasma Mass Spectrometry,ICP-MS)於元素分析上之應用越來越廣泛,由於其具有許多優點,例如:對多數元素有較低的偵測極限、質譜圖較吸收或發射光譜簡單許多、可直接對同位素進行定性與定量分析、可以預測的光譜干擾等,感應耦合電漿質譜儀已經成為微量無機元素分析領域中重要的技術之一。在這報告我將先簡單的介紹ICP-MS儀器及其工作原理。

<專題討論>2020/9/24(四)14:10綜合大樓2樓48218教室演講 : 陳科榮 博士(中央研究院天文所)

張貼者:2020年9月17日 上午12:57Dabby Lu

講題: Cosmic Dawn : Physics of the First Stars, Supernovae, and Galaxies
摘要: One of the paramount problems in modern cosmology is to elucidate how the first generation of luminous objects, stars, supernovae, accreting black holes, and galaxies, shaped the early universe at the end of the cosmic dark ages. According to the modern theory of cosmological structure formation, the hierarchical assembly of dark matter halos provided the gravitational potential wells that allowed gas to form stars and galaxies inside them. Modern large telescopes have pushed the detection of galaxies up to a redshift of z ~ 10. However, models of the first luminous objects still require considerable effort to reach the level of sophistication necessary for meaningful predictions, Due to the complexity of involved physical phenomena, this physical understanding may only come by the proper use of numerical simulations. Therefore, I have used state-of-the-art simulations on some of largest supercomputers to study these objects. In my talk, I will discuss the possible physics behind the formation of these first luminous objects by presenting the results from our simulations.
I will also give possible observational signatures of the cosmic dawn that will be the prime targets for the future telescopes such as the James Webb Space Telescope (JWST).

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