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A Brief Comment on Property of Electron Yield in Glow Discharge Cathode Material

2019-05-31 12:46:36 | 電離気体現象
A Brief Comment on Property of Electron Yield (Gamma Process) in Glow Discharge Cathode Materials by Ion Bombardment


The secondary electron emission by ion bombardment is usually measured under the condition of the monoenergetic ion beam irradiation to the materials. Here we try to discuss the property of electron yield in the cathode materials considering the characteristics of normal glow cathode fall.

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Influence of Initial Electrons on Formative Time Lag in Gaseous Breakdown .

2019-05-31 12:14:34 | 電離気体現象
Influence of Initial Electrons and Electron Multiplication on Formative Time Lag in Gaseous Breakdown


従来の線形破壊理論では、放電破壊の開始には無限の時間を必要とします.したがって放電形成時間の議論は出来ませんでした. 破壊が開始する臨界電子密度を定義できれば,初期電子が臨界電子密簡単な度まで増大する時間,すなわち放電形成時間を議論できます. 以下に報告を置きました.


The formative time lag in the gaseous breakdown strongly depends on the amount of initial electrons and the electronmultiplication in the electron avalanche. We discuss their influence on the formative time lag.

In the conventional linear breakdown theory, infinite time is required for starting breakdown. By defining the critical electron density required for starting breakdown, a finite time delay can be obtained. Therefor we can discuss the influence of the initial electrons and the electron multiplication on the time delay, that is the formative time lag.This is a summary of a part in the previous report titled "A Comment on Formative TimeLag of Gaseos Discharge”.


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Charge Transfer Process in Dielectric Barrier Discharge

2019-05-24 10:49:51 | 電離気体現象
Charge Transfer Process in Dielectric Barrier Discharge
-Essential Difference between DBD and Glow Discharge-


最近の傾向として,放電形態を見かけの状態から確たる検証をしないまま,プラズマとかグロ-放電とか表現してしまうことが多いように思われる.放電形態の厳密な定義にしたがうことが大切だろう.DBD (Dielectric Barrier Discharge)においてもある混同が見られる.そこでDBDとRF放電,グロ-放電との本質的な違いについて一考してみた.

Abstract
In the DBD (Dielectric Barrier Discharge), the surface of the dielectrics on the electrodes are charged up nearly applied voltage after a very short time from the beginning of the discharge and then the discharge is quenched, The electrons, which are charged up on the surface of dielectrics, play a role of the initial electrons in electron avalanche, when the gap is applied a high voltage of inverse polarity opposite to the preceding discharge, The discharge is never sustained in steady state. In order to continue the short pulse discharge, it is necessary to apply an AC voltage. While the discharge is happening, only the displacement current flows due to the charge transfer process.We discuss the charge transfer process in DBD and also clarify the essential difference between DBD and other discharges.
DBD is distinguished from the RF discharge by the operating frequency range. DBD in which the charge transfer by ion drift is to operate in much lower frequency than that of RF discharge.
The essential difference between DBD and glow discharge is the presence or absence of the effect of electron emission by ion bombardment on the negative electrode. In DBD the electron emission from the electrode is never required. Even if the DBD might look like an apparent glow discharge, it would not be referred to as a glow discharge.

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補遺
プラズマ よく間違える例 破壊前駆現象における発光気体. 代表例としてタウンゼント放電(正イオンの空間電荷層を速い電子が走っている放電形態でありプラズマ状態にはなっていない) 一般に高インピーダンス放電においてはプラスマは発生していない.


A Comment on Formative Time Lag of Gaseous Breadown

2019-05-24 10:18:42 | 電離気体現象
先に気体の絶縁破壊が開始される際の臨界電子密度について報告しました. 今回,初期電子がその臨界電子密度まで電離増殖する時間遅れ,すなわちFormative Time Lag についてのコメントを下記サイトに置きましたので,よろしかったらご覧下さい.ご批判頂けたら幸いです.

The breakdown starts at the time when the electron density near the anode increases up to the critical density by ionization growth in the electron avalanche.
We discuss the effect of initial electrons on the formative time lag.
http://www.ne.jp/asahi/iupl/sunsan-tuee/


pdf file

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Front-Sheath of Micro-Plasma Appeared at the Time of Just Starting Breakdown in Gases

2019-05-24 09:49:07 | 電離気体現象

以前,放電空間の電子密度が如何ほどになると破壊が開始されるのかを検討した結果をSTPIGのサイトに掲載しました(http://www.ne.jp/asahi/iupl/sunsan-tuee/ppt/Estimweb.pdf).その一部に正確さを欠く説明がありましたので,修正することにしました.
修正箇所は,マイクロプラズマの先端に形成されている空間電荷層の密度(平均イオン密度)の見積もりについてです.先の見積では,単純にポアッソンの式からイオンの平均密度を評価しました.これですとイオンの平均密度は電離エネルギーとマイクロプラズマの電子温度との比,eφi/Teに依存し一義的に決められません.
イオン密度はマイクロプラズマ側で臨界電子密度に等しく陰極側に指数関数的に減少することを考慮して評価すると,eφi/Teに関係なくイオンの平均密度を見積もれる上に,マイクロプラズマ中の電子温度の大凡を予測できます.
マイクロプラズマ前面のシース構造の新しい説明を下記サイトに置きました. ご覧下さい. コメント頂ければ幸いです.

We revised a part of the previous report entitled “An Estimation of Critical Electron Density at Just Starting Breakdown in Gases”(http://www.ne.jp/asahi/iupl/sunsan-tuee/ppt/Estimweb.pdf).
"Front-Sheath of Micro-Plasma Appeared at the Time of Just Starting Breakdown in Gases" was put on the STPIG site.
http://www.ne.jp/asahi/iupl/sunsan-tuee/


pdf file

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Polyatron (Inverse Dekatron)

2019-05-19 20:12:55 | 電離気体現象

Polyatron, これは小生が50余年まえ大学院学生時代に開発に携わった多陽極計数放電管につけた名称です.
先日,たまたま”Polyarton"でGoogle検索したところいくつかのサイトがヒットし,その一つがPolyatronの写真を探しておりました.ともすれば忘れ去られてしまう過去の技術資料の収集をされていることに敬意を表して,手元にある資料を探しだして提供いたしました.その写真を掲載しましたのでご覧下さい.


After J.Brit.IRE.Vol26,383(1963)



Advanced Model
J.IEE.Japan.86,72(1966/7,Translated Juornal)


検索の結果,ほかにも興味あるサイトがありました. ロシアでPolyatron A201が市販されていたこと,現在もPloyatron A201でNixie管を駆動して楽しんでいるグループがあることを知りました.
放電管は半導体デバイスの発達によって駆逐されてしまいましが,電子管には半導体デバイスと異なり不思議と心を温かく和ませるところがありますね.たしか柴田翔の「されどわれらが日々」にも真空管の不思議な魅力について語ったところがあったかと思います.

http://www.decadecounter.com/vta/articleview.php?item=877
http://www.youtube.com/watch?v=At6Iq_reUSQ
http://www.youtube.com/watch?v=Ica8ETl4Adg

2013/08/21 追記
この記事を公開して数日して,計数管の歴史を研究している英国の研究者から連絡ありました. 何度かのメールのやり取りをしましたが,かなり本格的に昔の技術を調べているのに感心しました.


Generation of Homogeneous Discharge Plasmas at Atmospheric Pressure

2019-05-19 15:38:23 | 電離気体現象
Generation of Homogeneous Discharge Plasmas at Atmospheric Pressure

Required condition for generating homogeneous atmospheric plasmas in Dielectric Barrier Discharge is determined by the uniform distribution of electrons, which are charged up on the surface of dielectrics during the preceding discharge and play a role of the initial electrons as the seeds of following electron avalanche. We developed a new Barrier Discharge System Using Dielectrics with Uniformly-Distributed Metal Pieces Inside, which makes it possible to control the distribution of electrons charged up on the surface of dielectrics. The new DBD device was evolutionarily designed after the Capacity-Coupled Multi-Discharge, CCMD.

more The Paper of Technical Meeting on Plasma Science and Technology IEE Japan, PST-13-011,

Slide

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Propagation Speed of Streamer in Diode Discharge

2019-05-19 15:18:59 | 電離気体現象

Propagation Speed of Streamer in Diode Discharge


When the breakdown is just starting in gaseous diodes, the front of plasma column generated near tha anode is quickly moving toward the cathode. We discuss the moving velocity of the plasma front (that is propagation speed of streamer). This text is partially revised following document “ An Estimation of Critical Electron Density at Just Starting Breakdown in Gases”

pdf file

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Models of Cathode Sheath in Low-Pressure Glow

2019-05-19 14:29:51 | 電離気体現象


Models of Cathode Sheath in Low-Pressure Glow


Abstract: A brief review of cathode sheath models and some defects of them are described. The conventional theories of the cathode sheath in the glow mode are based on collisional sheath in which the electron multiplication is essential process and hence they contain some principal problems to be solved, when we will derive theself-consistent solution. We propose a new concept for comprehensive treatment of the cathode sheath in the cold- and hot- cathode discharges. The new concept is based on the collisionless sheath model and plasma balance equations. In addition, tow-component velocity distribution of ions is introduced for the explanation of linearly varying field in the normal glow mode. The new concept makes it possible to clarify the structure of cathode sheath in both the cold- and the hot- cathode discharges.

Reported on the Topical Lectures of XXX|V ICPIG, Nagoya Japan

従来の冷陰極シース理論の見直し.冷,熱両陰極シースに対応可能なモデルを提案.

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