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衝突輻射モデル（以下，CRモデル）に基づき，プラズマの電子温度・密度を非侵襲的に診断する方法は，原則として可能である．しかし，実際のプロセスプラズマにおいては，プロセスガス混入による励起状態への影響が懸念される．そこで本研究では，プロセスプラズマにしばしば用いられる低気圧Arプラズマについて，酸素分子混入を想定した損失項をArCRモデルに組み込むことで，励起状態数密度に生じる影響を理論計算により考察した．, Diagnostic techniques for measuring the state of the plasma are important for accurate control of the process plasma.According to previous studies, "a method of non-invasively diagnosing the temperature and density of electrons from the number density of excited states obtained by emission spectroscopy based on the collision emission (CR) model" is possible in principle.However, in actual process plasma, there is a concern that the mixing of process gas will affect the excited state. Therefore, in this study, we investigated the effect on the number density of excited states by incorporating a loss term assuming oxygen molecule contamination into the ArCR model of low-pressure Ar plasma, which is often used for process plasma.

非平衡プラズマ診断において，発光分光計測のため診断モデルは個別論的にならざるを得ない．計測対象とするパラメータ範囲を初期条件として与えれば，同範囲に対する最適な診断モデルを提示するアルゴリズムを考案した．診断モデルに内在する理論上の診断誤差を求めた．換算占有密度の未知パラメータ依存性に顕著な不単調性を呈した生成条件下において，診断誤差が大きくなった．, In non-equilibrium plasma diagnostics, it is difficult to obtain the general diagnostic model for optical emission spectroscopic measurement. In this work, an optimization algorithm was proposed for plasma diagnostic modeling under plasma conditions set according to the target of measurement. The theoretical diagnostic error was analyzed. It was found that the diagnostic error was increased under the condition where the reduced population density dependence of unknown parameters was shown to be non-monotonic.

第53回流体力学講演会/第39回航空宇宙数値シミュレーション技術シンポジウム (2021年6月30日-7月2日. 日本航空宇宙学会 : 宇宙航空研究開発機構(JAXA)オンライン会議), The 53rd Fluid Dynamics Conference / the 39th Aerospace Numerical Simulation Symposium (June 30 - July 2, 2021. The Japan Society for Aeronautical and Space Sciences : Japan Aerospace Exploration Agency (JAXA), Online meeting), The electron temperature and electron number density of argon plasma behind a shock wave are determined based on collisional and radiative (CR) model. Excited state population distribution of argon atoms is numerically deduced by solving rate equations with considering all elementary processes as functions of the electron temperature and electron number density. The theoretical spectra calculated using the excited state population distribution are fitted to experimental ones, giving the predicted electron temperature and electron number density of experimental spectra. The spectra are partly in good agreement with each other depending on the spectral lines. The spatial profile of the electron temperature and electron number density obtained by the CR model is compared to the calculated ones obtained by CFD simulation considering argon thermochemistry. Qualitative agreements are seen in their tendencies. There are, however discrepancies in their values which might be caused by precursor heating. None the less for the discrepancies, the present result has showed the applicability of this method to the diagnostics of argon plasma behind a shock wave., 形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA2130027024, レポート番号: JAXA-SP-21-008

衝突輻射モデルに基づき、電子温度・密度診断モデルを作成し、発光分光計測によりその診断モデルの有用性を検証した。対象としたのは低気圧マイクロ波放電Arプラズマである。電子温度は5p及び6p準位、電子密度は4s、4p及び5s準位を用いて診断モデルを作成した。また、モデル作成に際し、電子のエネルギー分布はMaxwell分布もしくはDruyvesteyn分布を仮定した。プローブ計測と診断結果を比較したところ、大略が一致する計測を行うことが出来た。, Diagnostic models of the electron temperature and density are developed for low-pressure microwave discharge Ar plasma based on the collisional radiative model, and the applicability of the diagnostic models is verified by optical emission spectroscopy. The diagnostic models of the electron temperature and density are described by Ar excited levels 5p, 6p and 4s, 4p, 5s, respectively. When developing the diagnostic models, the electron energy distribution function is assumed to be a Maxwell or a Druyvesteyn one. Comparison with the probe measurement reveals that the diagnostic results of the proposed method roughly agree with those of the probe measurement.

平成29年度衝撃波シンポジウム (2018年3月7日-9日. 東北大学片平さくらホール ）仙台市, 宮城県, (2018年3月7日-9日. 宇宙航空研究開発機構角田宇宙センター ）角田市, 宮城県, Symposium on Shock Waves in Japan, FY2017 (March 7-9, 2018. Sakura Hall), Sendai, Miyagi, (March 7-9, 2018. Kakuda Space Center, Japan Aerospace Exploration Agency (JAXA)(KSPC)), Kakuda, Miyagi, 資料番号: SA6000119104, レポート番号: 3B2-1

平成28年度衝撃波シンポジウム (2017年3月8日-10日. ヴェルクよこすか 横須賀市立勤労福祉会館）横須賀市, 神奈川県, Symposium on Shock Waves in Japan, FY2016 (March 8-10, 2017. Werk Yokosuka), Kanagawa, Japan, 資料番号: SA6000084062, レポート番号: 2A2-2

衝突輻射モデルに基づいた原子過程モデルを用いた，多数の発光線強度を入力とした，低気圧アルゴンプラズマに対する筆者らが提案する電子温度および電子密度診断法を検証した．マイクロ波放電プラズマを対象として，プローブ計測との対照実験を行った．マイクロ波電力および測定位置との依存性を測定した結果，特に電子密度についてはプローブ計測の傾向と一致することが確認でき，提案手法の妥当性が明らかとなった．, Line-pair method cannot be applied to wide-range electron temperature Te and density Ne diagnostics of plasmas in the state of non-equilibrium. Although the method using multi-emission lines is suitable, little has been reported for the low-pressure plasma measurement. We proposed the optical emission spectroscopic (OES) diagnostic method for the low-pressure argon plasma. In this presentation, the applicability for the microwave discharge argon plasma is reported. Based on the Ar collisional-radiative (CR) model, the dominant elementary possesses were extracted for the excitation kinetics for several excited states. And, the excitation-kinetic model for the OES diagnostics was established. As a result, the diagnostic model was obtained. In the model, input parameter is 15 optical emission lines (wavelength range: 340.7 – 912.5nm). Possible measurement range is 1.0 ≤ Te [eV] ≤ 3.8, and 1.0 × 109 ≤ Ne [cm-3] ≤ 5.0 × 1012. In order to examine the validity of the proposed method, microwave discharge argon plasma was diagnosed with (A) probe measurement: (A-1) under the assumption that the electron density distribution function (EEDF) is Maxwellian, (A-2) together with the measurement of the EEDF by the Druyvesteyn’s method, and equivalent Te measurement; and (B) OES measurement by the present proposed method at points (from the center of the waveguide) = 10, 14, and 18 cm, with the microwave power = 100, 300, and 500 W. Concerning Ne diagnosis, the trend of Ne determined with the scheme (B) was in good agreement with the scheme (A-1). Meanwhile, as for Te diagnosis, it was difficult to evaluate, because the result of the scheme (B) reached the limit value of root-finding range in the numerical procedure. However, at least, the result of (A-1) is considered to be reasonable. And by using input with arbitrary shaped EEDF is measured by the OES measurement, and the resultant improvement of the diagnostic result can be expected.

平成26年度衝撃波シンポジウム (2015年3月9日-11日. 群馬県伊香保温泉 ホテル天坊）渋川市, 群馬県, Symposium on Shock Waves in Japan, FY2014 (March 9-11, 2015. Hotel Tenbo), Shibukawa, Gunma, Japan, 資料番号: SA6000038051, レポート番号: 2A3-3

2006, 【要旨】

非接触をはじめとするダイバータプラズマの諸現象を理解するため，壁での粒子リサイクリング，荷電粒子，中性粒子を扱うコードの統合を進めている．水素分子には，電子状態のほか，回転および振動の内部自由度があり，分子活性化再結合をはじめとするプラズマ中の水素分子の各種の反応速度係数は，水素分子の始状態の振動・回転量子数により，数桁にわたって変化する．また，低温のプラズマでは，プラズマ中の電子やプロトン衝突による水素分子の振動・回転励起がプラズマのエネルギー損失チャンネルとして重要と考えられる．このため，水素分子の振動・回転状態を中性粒子やプラズマの輸送と組み合わせて解く統合モデルを開発した．

近年、トモグラフィを用いた診断が報告されつつある。しかし、原子分子過程を詳細に考慮した報告がなく、解析に起因する不確かさが著しいことが課題であった。本研究では、アルゴン誘導結合プラズマを対象にトモグラフィック発光分光計測を実施した。原子分子過程を詳細に記述できる原子分子過程モデルである、衝突輻射モデルに基づいて解析した。これにより、電子温度・電子密度の空間分布診断を定量的に実現した。, In recent years, tomography-based diagnostics have been reported. However, no reports have considered atomic-molecular processes in detail, and the significant uncertainty was caused by excitation-kinetic analysis. In this study, argon inductively coupled plasma by tomographic optical emission spectroscopic measurement. The excitation-kinetics analysis was based on the collisional radiation model, one of the atomic-molecular process models which can describe atomic-molecular processes in detail. A quantitative diagnosis of the spatial distribution of electron temperature and electron density has been produced.

2019年度衝撃波シンポジウム (2020年3月4日-6日. 神戸大学 海事科学研究科（深江キャンパス)）神戸市, 兵庫県, Symposium on Shock Waves in Japan, FY2019 (March 3-4, 2020. Kobe University), Kobe, Hyogo Japan, 2019年度衝撃波シンポジウムは、新型コロナウイルスの感染拡大防止のため開催中止, 資料番号: SA6000148091, レポート番号: 3B1-2

エッチング装置で生成したアルゴン低気圧誘導結合プラズマの電子温度Te，電子密度Neおよび電子エネルギー分布関数(EEDF)を，発光分光計測により診断した．診断誤差を低減するため，励起準位数密度分布に対するTe，Ne, EEDFの依存性を分析し，この結果に基づいて診断に用いる励起準位を選定した．上準位4p[1/2]1，4p’[3/2]1，4p[1/2]0，4p’[1/2]0の発光線に基づいて算出した励起準位数密度分布を，衝突輻射モデルから求めた理論値とフィッテングして診断を行った．, Electron temperature Te, density Ne, and energy distribution function (EEDF) of the argon low pressure inductively coupled plasma generated by an etching unit were diagnosed by optical emission spectroscopic measurement. In order to reduce diagnostic errors, the dependence of reduced population density distribution on Te, Ne, and EEDF was surveyed. The excitation levels which used for diagnosis were selected based on the survey result. The diagnosis was based on fitting reduced population densities with calculated value by collisional-radiative model and experimental value by OES measurement of emission lines which upper levels were 4p[1/2]1, 4p’[3/2]1, 4p[1/2]0, and 4p’[1/2]0.

The non-equilibrium atmospheric-pressure plasma is applied for various industries. However, the measurement method of the plasma is not fully established yet. This time, we measure electron temperature of non-equilibrium atmospheric-pressure Ar plasma by using two methods. One is by line spectrum measurement together with interpretation based on collisional radiative model, and the other is by continuum spectrum interpreted as electron-atom Bremsstrahlung. After all, the experimental results by the three methods are consistent.

"The collisional-radiative (CR) model is introduced as an improvement to the corona model. Its formulation indicates that the population of every excited level is divided into two independent components, i.e., the ionizing and recombining plasma components. For the pulsed discharge with helium gas in a Pyrex tube which exhibits intense line radiations twice, the first and second peaks are found to correspond to the ionizing and recombining plasmas, respectively, from the different population distributions over the n3D levels. The spectrum taken in the stationary phase of the main discharge in the Large Helical Device (LHD) with helium gas suggests an ionizing plasma, and for the other two spectra taken in the plasma terminating phase, the first and the second spectra indicate the recombiningplasmas of ionized and neutral helium, respectively. In all these analyses, the electron temperature and density are the variable parameters and are determined as a result of fitting of calculation to the experimental data. The spectrum observed in the helium glow discharge cannot be reproduced by CR model calculations even if the quasi-steady-state approximation for metastable states of neutral helium is removed. The opacity effect may be the origin of this difficulty."

連続スペクトルにより、大気圧非平衡アルゴンプラズマの電子温度・密度の計測可能性を研究した。放電空間を限定できる放電装置を用い、絶対校正済の測定系で発光分光計測を実施した. このスペクトルを理論曲線でフィッティングする。Druyvesteyn 電子エネルギー分布関数を仮定すると適切な値が導出された。衝突輻射モデルによる励起状態密度と線スペクトル強度とのクロスチェックにより、妥当性を確認した。, The feasibility of spectroscopic measurement of electron temperature and density of atmospheric-pressure non-equilibrium argon plasma was investigated, applying optical emission spectroscopic measurement of a continuum spectrum due to electron-atom bremsstrahlung. Emission spectroscopy was performed with an absolutely calibrated measurement system using a discharge device that can limit the discharge space to one point. The obtained spectrum is fitted with a theoretical curve. Assuming the Druyvesteyn electron energy distribution function, appropriate electron temperature and density were derived. The validity was confirmed by the cross-check between the line spectral intensity and the excited state density calculated with the Ar collisional radiative model with atomic collisional processes.

ウエハ表面クリーニング用途に使用される大気圧アルゴンプラズマジェットの電子温度及び電子密度を診断した．上準位4p’[3/2]1，4p’[1/2]1，4p[1/2]0，4p’[1/2]0の発光線に基づいて算出した励起準位数密度分布を，衝突輻射モデルから求めた理論値とフィッテングして診断を行った．放電管の下流になるにつれて，電子温度，電子密度ともに低下した．, Electron temperature and density of the atmospheric pressure argon plasma jet for surface cleaning of wafers were diagnosed based on optical emission spectroscopic measurement. The diagnose was based on fitting with the excitation-level number density distribution of the theoretical value based on the collisional-radiative model and the experimental value based on the optical emission lines which upper levels are 4p’[3/2]1, 4p’[1/2]1, 4p[1/2]0, and 4p’[1/2]0 . The electron temperature and density were decreased in the downstream of discharge tube.

In the tandem mirror GAMMA 10/PDX, molecular activated recombination (MAR) leading to plasma de- tachment has been observed by additional hydrogen gas injection to the divertor simulation plasma (i.e. end loss plasma) which is exposed to the V-shaped target in the divertor simulation experimental mod- ule (D-module). The temperature near the corner of the V-shaped target decreased from ∼23 eV to ∼2 eV as the neutral pressure in the D-module increased. A clear density rollover was observed at ∼2 Pa. A po- sition of the density maximum moves to upstream of the plasma with increase in the neutral pressure and the density near the corner of the target decreases to detach the plasma from the target. After the occurrence of the density rollover, the Balmer βintensity decreases as with the density but the Balmer αintensity continues to increase, indicating the dissociative attachment process in MAR is more dominant than the ion conversion process although the rate coefficient of the former process is lower than that of the latter one, which is calculated by using a collisional radiative model. This would be caused by the MAR process related to triatomic hydrogen molecules which significantly contributed to the detachment process.

大気圧下でも適用可能な非平衡プラズマの電子温度・密度計測法には，簡便・安価な実用法として期待される発光分光計測法がある．本稿では，その中でも重要と考えられる2 つの方法，衝突輻射（CR）モデルに基づいた線スペクトル強度測定法，および電子-中性粒子制動放射による連続スペクトル測定法につい て，その原理と実測例を紹介する．特に前者については，モデル計算の結果を実際の分光測定結果に実用レベルで適用するための手法として，「主要素過程抽出法」，「2 線対法」，そして「励起温度換算法」の3 手法を紹介する．最後に，連続スペクトル計測による実測例を紹介し，この方法ならば原理的には電子エネルギー分布関数（EEDF）をも求められることに触れ，今後の研究展望を述べる．, We describe the principles and applications of two essential methods for measurement of electron temperature and the density of non-equilibrium plasmas including atmospheric-pressure discharge, based on optical emission spectroscopic (OES) measurement, i.e., line intensity measurement assisted with a collisional radiative model, and continuum spectrum measurement as electron-neutral bremsstrahlung. For the former scheme, we introduce three practical procedures to interpret the OES results based on the excitation kinetic model, which are the “selection of the dominant elementary processes”, the “measurement of two pairs of line intensities”, and the “conversion of the excitation temperature to the electron temperature”. In the last part, examples are shown for the demonstration of the continuum measurement, which has the potential to deduce the electron energy distribution function, followed by its future prospects.

Experimental results on micro-hollow cathode discharge are presented. First, breakdown voltages in air glow discharge and current-voltage characteristics are examined with a hollow cathode, 0.8mm in diameter and 3mm depth separated by ceramic insulator of 1mm thickness. Then electron temperatures and rotational temperatures in negative glow plasma in hollow cathode are measured by optical emission spectroscopy, intensity ratio of hydrogen line-spectra and spectral intensity distribution of nitrogen first negative band respectively. Electron temperatures measured decreased from 2eV to 0.5eV, increasing discharge current from 10mA to 120mA at about a few kilo-Pa. And gas temperature, corresponding to rotational temperature increased from 0.03eV to 0.14eV with the same increase of current. But with collisional-radiative model, calculated electron temperatures, from 5eV to 1eV for the same current decrease, are higher than experimentally obtained result. This difference means that negative glow plasma does not attain in thermo-dynamical equilibrium.