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Flute Characteristics of and Microwave Emission from a Plasma in a Mirror; Instabilite en Cannelures et Emission de Micro-Ondes par un Plasma dans une Machine a Miroirs; Zhelobkovye kharakteristiki i ehmissiya mikrovoln iz plazmy v zerkale; Caracteristicas del Estriado y Emision de Microondas por un Plasma en un Espejo

Abstract

A pulsed mirror has been constructed to study the stability of a plasma of modest energy. The 70 eV plasma is piped from a gun to the mirror by a linear octopole guide field. The mirror field is turned on in a plasma transit time. Plasma densities of 10{sup 13} electrons/cm{sup 3} are observed in the central plane of the mirror. Two distinct modes of operation are observed and depend only on conditions established in the guide field. In the first mode the plasma in the mirror appears flute stable, most of the plasma escapes axially, a slow anomalous radial diffusion is observed and microwave emission occurs at the electron cyclotron harmonics ranging from n = 1 to at least n = 19. The microwave emission is not compatible with the electron branch of the Harris instability. The stability of this mode is attributed to line tieing by cold plasma effusing from the guide field region. Densities above 10{sup 11} electrons/cm{sup 3} were observed for 200 {mu}sec in the region between the mirror and the guide field. With the addition of an axially symmetric cylinder in the guide field, this density is decreased. Measurements show plasma densities below 10{sup 11}  More>>
Authors:
Scott, F. R.; Jensen, T. H.; Wharton, C. B. [1] 
  1. General Atomic Division, General Dynamics Corporation, San Diego, CA (United States)
Publication Date:
Apr 15, 1966
Product Type:
Conference
Report Number:
IAEA-CN-21/84
Resource Relation:
Conference: Conference on Plasma Physics and Controlled Nuclear Fusion Research, Culham (United Kingdom), 6-10 Sep 1965; Other Information: 23 refs., 17 figs.; Related Information: In: Plasma Physics and Controlled Nuclear Fusion Research. Vol. II. Proceedings of a Conference on Plasma Physics and Controlled Physics Research Nuclear Fusion Research| 1017 p.
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; AXIAL SYMMETRY; COLD PLASMA; CYCLOTRON HARMONICS; DIFFUSION; ELECTRONS; FLUTE INSTABILITY; MICROWAVE RADIATION; PHASE VELOCITY; PLASMA DENSITY; PLASMA GUNS; PULSES; TRAPPING
OSTI ID:
22178054
Research Organizations:
International Atomic Energy Agency, Vienna (Austria)
Country of Origin:
IAEA
Language:
English
Other Identifying Numbers:
Other: ISSN 0074-1884; TRN: XA13M2274002498
Submitting Site:
INIS
Size:
page(s) 463-481
Announcement Date:
Jan 09, 2014

Citation Formats

Scott, F. R., Jensen, T. H., and Wharton, C. B. Flute Characteristics of and Microwave Emission from a Plasma in a Mirror; Instabilite en Cannelures et Emission de Micro-Ondes par un Plasma dans une Machine a Miroirs; Zhelobkovye kharakteristiki i ehmissiya mikrovoln iz plazmy v zerkale; Caracteristicas del Estriado y Emision de Microondas por un Plasma en un Espejo. IAEA: N. p., 1966. Web.
Scott, F. R., Jensen, T. H., & Wharton, C. B. Flute Characteristics of and Microwave Emission from a Plasma in a Mirror; Instabilite en Cannelures et Emission de Micro-Ondes par un Plasma dans une Machine a Miroirs; Zhelobkovye kharakteristiki i ehmissiya mikrovoln iz plazmy v zerkale; Caracteristicas del Estriado y Emision de Microondas por un Plasma en un Espejo. IAEA.
Scott, F. R., Jensen, T. H., and Wharton, C. B. 1966. "Flute Characteristics of and Microwave Emission from a Plasma in a Mirror; Instabilite en Cannelures et Emission de Micro-Ondes par un Plasma dans une Machine a Miroirs; Zhelobkovye kharakteristiki i ehmissiya mikrovoln iz plazmy v zerkale; Caracteristicas del Estriado y Emision de Microondas por un Plasma en un Espejo." IAEA.
@misc{etde_22178054,
title = {Flute Characteristics of and Microwave Emission from a Plasma in a Mirror; Instabilite en Cannelures et Emission de Micro-Ondes par un Plasma dans une Machine a Miroirs; Zhelobkovye kharakteristiki i ehmissiya mikrovoln iz plazmy v zerkale; Caracteristicas del Estriado y Emision de Microondas por un Plasma en un Espejo}
author = {Scott, F. R., Jensen, T. H., and Wharton, C. B.}
abstractNote = {A pulsed mirror has been constructed to study the stability of a plasma of modest energy. The 70 eV plasma is piped from a gun to the mirror by a linear octopole guide field. The mirror field is turned on in a plasma transit time. Plasma densities of 10{sup 13} electrons/cm{sup 3} are observed in the central plane of the mirror. Two distinct modes of operation are observed and depend only on conditions established in the guide field. In the first mode the plasma in the mirror appears flute stable, most of the plasma escapes axially, a slow anomalous radial diffusion is observed and microwave emission occurs at the electron cyclotron harmonics ranging from n = 1 to at least n = 19. The microwave emission is not compatible with the electron branch of the Harris instability. The stability of this mode is attributed to line tieing by cold plasma effusing from the guide field region. Densities above 10{sup 11} electrons/cm{sup 3} were observed for 200 {mu}sec in the region between the mirror and the guide field. With the addition of an axially symmetric cylinder in the guide field, this density is decreased. Measurements show plasma densities below 10{sup 11} cm{sup -3} after 40 {mu}sec in this region. The resulting plasma trapped in the mirror exhibits flute instabilities, radial plasma loss, intense erratic microwave emission and rapid density decay. The m = 1 flute is identified and its phase is followed through 4{pi}. The phase velocity is in the direction of the electron B drift. The sign of this phase velocity may be explained by the theory of Krall if the electron energy exceeds the ion energy sufficiently. The addition of conducting plates in the downstream mirror region tempered the violence of the flute instability. This tempering depends only on the surface resistance of these plates. This effect was examined by measuring the frequency spectrum of signals from coated scintillator probes placed near the vacuum envelope. (author) [French] Les auteurs ont construit une machine a miroirs puisee pour etudier la stabilite d'un plasma d'energie relativement faible. Le plasma de 70 eV, forme dans un canon, est canalise ven le miroir par un champ de guidage octopolaire lineaire. La duree du champ du miroir est egale au temps de transit du plasma. Les auteurs ont mesure des densites d'electrons de 10{sup 13} cm{sup -3} dans le plan central du miroir. Ils ont observe deux modes distincts de fonctionnement qui ne dependent que des conditions regnant dans le champ de guidage. Dans le premier mode, le plasma dans le miroir ne semble pas presenter d'instabilite en cannelures, la plus grande partie du plasma d'echappe le long de l'axe', on observe une diffusion radiale anormale lente, il se produit une emission de micro-ondes dont les frequences sont des harmoniques de la frequence cyclotronique des electrons dans l'intervalle entre n = 1 et n = 19 au moins. L'emission de micro-ondes n'est pas compatible avec la branche electronique de l'instabilite de Harris. Les auteurs attribuent la stabilite de ce mode a la fixation des lignes de force par le plasma froid diffusant de la region du champ de guidage. Ils ont observe des densites d'electrons superieurs a 10{sup 11} cm{sup 3} pendant 200 {mu}s dans la region situee entre le miroir et le champ de guidage. La presence d'un cylindre de symetrie axiale dans le champ de guidage a pour effet de diminuer cette densite. Des mesures faites dans cette region fournissent des densites inferieures a 10u cm{sup 3}apres 40 {mu}s. Le plasma qui en resulte, piege dans le miroir, presente des instabilites en cannelures, des pertes de plasma radiales, une emission de micro-ondes irreguliere intense, ainsi qu'une decroissance de densite rapide. Les auteurs ont identifie la cannelure m = 1, dont ils ont suivi la phase dans l'angle 4{pi}. La vitesse de phase possede la meme direction que la derive electronique sous l'influence de B. Le signe de cette vitesse de phase peut s'expliquer par la theorie de Krall, si l'energie des electrons est suffisamment superieure a celle des ions. L'addition de plaques conductrices dans la region aval du miroir a pour effet d'attenuer la violence de l'instabilite en cannelures. Cette attenuation ne depend que de la resistance surfacique de ces plaques. Les auteurs ont etudie cet effet en mesurant le spectre de frequence des signaux en provenance de sondes a sintillateur enrobe placees au voisinage de l'enceinte a vide. (author) [Spanish] Los autores construyeron un espejo pulsado para estudiar la estabilidad de un plasma de modesta energfa. El plasma de 70 eV se inyecta mediante un cation en el espejo, con ayuda de un campo de gufa octopolar de tipo lineal. El campo especular se aplica durante un lapso igual al tiempo de transito del plasma. En el plano central del espejo se alcanzan densidades de plasma iguales a 10{sup 13} electrones/cm{sup 3}. Se observan dos modos definidos de operacion, dependientes exclusivamente de las condiciones establecidas en el campo de gufa. Segun el primer modo, en el espejo el plasma no sufre estriado alguno, la mayor parte del mismo escapa en direccion axial, se observa una lenta, y anomala difusion radial y se emiten microondas en los ar- . monicos ciclotronicos de los electrones, desde n = 1 hasta por lo menos n = 19. La emision de microondas no es compatible con la rama electronica de la inestabilidad de Harris. La estabilidad de este modo se atribuye a la union lineal por el plasma frio que sale por efusion de la zona del campo de gufa. En la zona comprendida entre el espejo y el campo de gufa, se observaron densidades superiores a 10{sup 11} electrones/cm{sup 3} durante 200 {mu}s. Esta densidad disminuye al agregar al campo de gufa un cilindro de simetria axial. Al cabo de 40 us, las mediciones ponen de manifiesto en esta zona densidades de plasma inferiores 10{sup 11} electrones/cm{sup 3}. El plasma resultante, atrapado en el espejo presenta inestabilidades en forma de estrias, perdidas radiales, intensa e irregular emision de microondas y rapida disminucion de la densidad. Se identifica en la memoria la estrfa de m = 1 y se sigue su fase hasta abarcar 4{pi}. La velocidad de fase coincide con la direccion de la deriva B de los electrones. El signo de esta velocidad de fase puede explicarse mediante la teorfa de Krall si la energfa de los electrones es mucho mayor que la energfa de los iones. El agregado de placas conductoras despues del espejo, atempero la violencia de la inestabilidad en forma de.estrias. Esta atenuacion solo depende de la resistencia superficial de dichas placas. El efecto se estudio midiendo el espectro de frecuencias de las sefiales provenientes de sondas de centelleo provistas de revestimiento y colocadas en la proximidad del recipiente de vacfo. (author) [Russian] Postroen impul'snyj probkotron dlja issledovanija ustojchivosti plazmy s umerennoj jenergiej. Plazma s jenergiej 70 jev inzhektiruetsja iz plazmennoj pushki v probkotron s pomoshh'ju linejnogo vos'mipoljusnogo napravljajushhego polja. Probochnoe pole sozdaetsja v moment prohozhdenija plazmy. V central'noj ploskosti probkotrona nabljudajutsja plotnosti plazmy 10{sup 13} jelektronov cm{sup -3}. Nabljudajutsja dva razlichnyh rezhima raboty, kotorye zavisjat tol'ko ot uslovij, sozdannyh v napravljajushhem pole. Pri pervom rezhime raboty plazma v probko- trone, po-vidimomu, javljaetsja ustojchivoj k zhelobkam, bol'shaja chast' plazmy uhodit vdol' osi, nabljudaetsja medlennaja anomal'naja radial'naja diffuzija i voznikaet mikrovolnovoe izluchenie na jelektronno-ciklotronnyh garmonikah v diapazone ot p = 1 i po krajnej mere do p = 19. Mikrovolnovoe izluchenie ne soglasuetsja s jelektronnoj vetv'ju neustojchivosti Garrisa. Schitaetsja, chto ustojchivost' jetogo tipa vyzvana provodimost'ju za schet holodnoj plazmy, istekajushhej iz oblasti napravljajushhego polja. Nabljudajutsja plotnosti svyshe 10{sup 11} jelektronov cm{sup -3} v techenie 200 mksek v oblasti mezhdu probkoj i napravljajushhim polem. Pri pomeshhenii aksial'no simmetrichnogo cilindra v napravljajushhee pole jeta plotnost' umen'shaetsja. Izmerenija pokazyvajut nalichie plazmy s plotnost'ju nizhe 10{sup 11} jelektronov cm{sup -3} posle 40 mksek v jetoj oblasti. V zahvachennoj takim obrazom v probkotrone plazme, voznikaet zhelobkovaja neustojchivost', pojavljajutsja radial'nye poteri, intensivnoe mikrovolnovoe izluchenie i bystryj spad plotnosti. Obnaruzhivajutsja zhelobkovye kolebanija cm = 1, i ih faza proslezhivaetsja cherez 4{pi}. Napravlenie fazovoj skorosti sovpadaet s napravleniem drejfa jelektronov. Znak jetoj fazovoj skorosti mozhno ob{sup j}asnit' na osnove teorii Kralla, esli jenergija jelektronov sushhestvenno prevyshaet jenergiju ionov. Pomeshhenie provodjashhih plastin v oblast' probki umen'shilo zhelobkovuju neustojchivost'. Jeto umen'shenie zavisit tol'ko ot poverhnostnogo soprotivlenija jetih plastin. Jetot jeffekt issledovalsja pri pomoshhi izmerenija chastotnogo spektra signalov, postupajushhih iz jekranirovannyh scintilljaciej- nyh detektorov, nahodjashhihsja vblizi vakuumnogo sosuda. (author)}
place = {IAEA}
year = {1966}
month = {Apr}
}