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Theoretical Interpretation of Pulsed Neutron Phenomena; Interpretation Theorique des Phenomenes dus aux Neutrons Pulses; Teoreticheskaya interpretatsiya yavlenij, svyazannykh s impul'snymi nejtronami; Interpretacion Teorica de los Fenomenos Debidos a Neutrones Pulsados

Conference:

Abstract

The author discusses the present understanding of transient effects in the variation of neutron distributions in space, time and energy. In the analysis, particular attention is given to the pulsed neutron experiment in non-multiplying media, and to its interpretation in terms of space-energy modes and (time) decay constants. Theoretical research in this field, much of which has come from the Brookhaven National Laboratory, has been built upon the exact solution of several special problems, and approximate, numerical solutions in more realistic situations. Recently, a unified point of view, based on the Van Hove-Glauber theory of the scattering of slow neutrons, has been proposed. It has been found that the long-time behaviour of the pair correlation function, which enables one to distinguish between different types of moderating materials, also controls the type of decay-constant spectrum that one finds. In his discussion the author emphasizes the case of infinite medium solutions that are proportional to exp(iB * r), in media having 1/v absorption. The analytical work is concerned with modal solutions, proportional to exp({lambda}t) as well, while the numerical work is directed at the full, ''life-history'' solution, as well as the modal solutions. The author also remarks on phenomena encountered when the  More>>
Authors:
Corngold, N. [1] 
  1. Brookhaven National Laboratory, Upton, NY (United States)
Publication Date:
Aug 15, 1965
Product Type:
Conference
Report Number:
IAEA-SM-62/79
Resource Relation:
Conference: Symposium on Pulsed Neutron Research, Karlsruhe (Germany), 10-14 May 1965; Other Information: 41 refs., 6 figs.; Related Information: In: Pulsed Neutron Research. Vol. I. Proceedings of the Symposium on Pulsed Neutron Research| 713 p.
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; 46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; ABSORPTION; CORRELATION FUNCTIONS; DIFFUSION; ENERGY DEPENDENCE; EXACT SOLUTIONS; GLAUBER THEORY; MODERATORS; NUMERICAL SOLUTION; PULSED NEUTRON TECHNIQUES; SCATTERING; SLOW NEUTRONS; SPATIAL DISTRIBUTION; TIME DEPENDENCE
OSTI ID:
22122974
Research Organizations:
International Atomic Energy Agency, Vienna (Austria)
Country of Origin:
IAEA
Language:
English
Other Identifying Numbers:
Other: ISSN 0074-1884; TRN: XA13M2575078776
Submitting Site:
INIS
Size:
page(s) 199-217
Announcement Date:
Aug 30, 2013

Conference:

Citation Formats

Corngold, N. Theoretical Interpretation of Pulsed Neutron Phenomena; Interpretation Theorique des Phenomenes dus aux Neutrons Pulses; Teoreticheskaya interpretatsiya yavlenij, svyazannykh s impul'snymi nejtronami; Interpretacion Teorica de los Fenomenos Debidos a Neutrones Pulsados. IAEA: N. p., 1965. Web.
Corngold, N. Theoretical Interpretation of Pulsed Neutron Phenomena; Interpretation Theorique des Phenomenes dus aux Neutrons Pulses; Teoreticheskaya interpretatsiya yavlenij, svyazannykh s impul'snymi nejtronami; Interpretacion Teorica de los Fenomenos Debidos a Neutrones Pulsados. IAEA.
Corngold, N. 1965. "Theoretical Interpretation of Pulsed Neutron Phenomena; Interpretation Theorique des Phenomenes dus aux Neutrons Pulses; Teoreticheskaya interpretatsiya yavlenij, svyazannykh s impul'snymi nejtronami; Interpretacion Teorica de los Fenomenos Debidos a Neutrones Pulsados." IAEA.
@misc{etde_22122974,
title = {Theoretical Interpretation of Pulsed Neutron Phenomena; Interpretation Theorique des Phenomenes dus aux Neutrons Pulses; Teoreticheskaya interpretatsiya yavlenij, svyazannykh s impul'snymi nejtronami; Interpretacion Teorica de los Fenomenos Debidos a Neutrones Pulsados}
author = {Corngold, N.}
abstractNote = {The author discusses the present understanding of transient effects in the variation of neutron distributions in space, time and energy. In the analysis, particular attention is given to the pulsed neutron experiment in non-multiplying media, and to its interpretation in terms of space-energy modes and (time) decay constants. Theoretical research in this field, much of which has come from the Brookhaven National Laboratory, has been built upon the exact solution of several special problems, and approximate, numerical solutions in more realistic situations. Recently, a unified point of view, based on the Van Hove-Glauber theory of the scattering of slow neutrons, has been proposed. It has been found that the long-time behaviour of the pair correlation function, which enables one to distinguish between different types of moderating materials, also controls the type of decay-constant spectrum that one finds. In his discussion the author emphasizes the case of infinite medium solutions that are proportional to exp(iB * r), in media having 1/v absorption. The analytical work is concerned with modal solutions, proportional to exp({lambda}t) as well, while the numerical work is directed at the full, ''life-history'' solution, as well as the modal solutions. The author also remarks on phenomena encountered when the absorption is not 1/v and when the moderator sample is so small that the long-time solutions are no longer separable in space and energy. Finally, the paper discusses the bearing of these recent developments upon the interpretation of pulsed experiments. Particular reference is made to the measurement of diffusion and diffusion cooling coefficients, and to the nature of the approach to the asymptotic distribution. (author) [French] L'auteur examine la conception actuelle des effets transitoires dans la variation des distributions des neutrons dans l'espace, dans le temps et selon l'energie. Dans son etude, il accorde une attention particuliere aux experiences, au moyen des neutrons puises, portant sur des milieux non multiplicateurs, ainsi qu'a leur interpretation en fonction des modes espace-energie et des constantes de decroissance (en temps). Les etudes theoriques dans ce domaine, dont la plupart one ete executees au Laboratoire national de Brookhaven, sont fondees sur la solution exacte de plusieurs problemes particuliers et sur des solutions numeriques approximatives de problemes serrant la realite de plus pres. A une data recente, on a propose une interpretation unjforme fondee sur la theorie de la diffusion des neutrons lents etablie par Van Hove et Glauber. On a constate que le comportement a long terme de la fonction de correlation de paire, qui permet de distinguer entre les differents types de ralentisseurs, determine egalement le genre du spectre des constantes de decroissance que l'on obtient. Au cours de son examen critique, l'auteur met en evidence le cas des solutions relatives a un milieu infini, qui sont proportionnelles a exp(iB * r) dans les milieux a absorption 1/v. Le calcul analytique porte sur des solutions modales, egalement proportionnelles a exp({lambda}t), alors que le calcul numerique vise a obtenir la solution complete pour toute la duree depuis l'origine, ainsi que les solutions modales. Le memoire traite aussi de phenomenes qui se produisent lorsque l'absorption n'est pas 1/v et que l'echantillon de ralentisseur est si petit que les solutions a long terme ne peuvent plus Etre separees selon l'espace et l'energie. Enfin, l'auteur examine l'influence de ces faits nouveaux sur l'interpretation des experiences au moyen de neutrons puises - il mentionne notamment la mesure des coefficients de diffusion et de refroidissement par diffusion - ainsi que sur la nature de la methode a employer pour etudier la distribution asymptotique. (author) [Spanish] El autor discute los conocimientos y las teorias modernas sobre los efectos transitorios en las variaciones de la distribucion de los neutrones en el espacio, en el tiempo y en la energia. El analisis se refiere principalmente a los experimentos con neutrones pulsados en medios no multiplicadores y a su interpretacion segun los modos espacioenergia y segun las constantes de decrecimiento (de tiempo). Una gran parte de las investigaciones teoricas en este campo se han realizado en el Brookhaven National Laboratory; se ha tratado de encontrar la solucion exacta de varios problemas especiales y soluciones aproximadas, numericas, para situaciones mas reales. Recientemente se ha propuesto un punto de vista unificado que se basa en la teorfa de Van Hove-Glauber sobre la dispersion de neutrones lentos. Se ha encontrado que el comportamiento a largo plazo de la funcion de correlacion de pares, que permite distinguir entre diferentes tipos de moderadores, controla tambien el tipo de espectro de constante de decrecimiento que se encuentra. En su discusion, el autor destaca el caso de las soluciones relativas a un medio infinito que son proporcionales a exp(iB * r) en medios cuya absorcion obedece a la ley 1/v. Los estudios analiticos se ocupan de las soluciones modales, tambien proporcionales a exp({lambda}t), mientras que los estudios numericos se refieren tanto a la solucion completa, la solucion 'historial', como a las soluciones modales. Tambien habla de fenomenos que se observan cuando la absorcion no obedece a la ley 1/v y cuando la muestra de moderador es tan pequena que las soluciones a largo plazo no se pueden separar ya en el espacio ni en la energia. Por ultimo se discuten las consecuencias de estos ultimos desarrollos para la interpretacion de los experimentos con neutrones pulsados. En particular se trata de la medicion de la difusion y de los coeficientes de enfriamiento por difusion, y de la naturaleza de la aproximacion a la distribucion asintotica. (author) [Russian] Rassmatrivaetsja sovremennoe tolkovanie perehodnyh jeffektov v izmenenii prostranstvennyh, vremennyh i energeticheskih raspredelenij nejtronov. Osoboe vnimanie obrashhaetsja na jeksperiment s impul'snymi nejtronami v nerazmnozhajushhih sredah i na ego interpretaciju s tochki zrenija prostranstvenno-energeticheskih raspredelenij i postojannyh spada (vo vremeni). Teoreticheskie issledovanija v jetoj oblasti, bol'shuju chast' kotoryh provodit Bruk- hejvenskaja nacional'naja la''rratorija, osnovany na tochnom reshenii neskol'kih special'nyh problem, a takzhe na priblizhennyh chislennyh reshenijah v bolee real'nyh situacijah. Ne- davno predlozhena edinaja tochka zrenija, osnovannaja na teorii Van Hov-Glaubera o rassejanii medlennyh nejtronov. Vyjasneno, chto vremennaja zavisimost' parno-korreljacionnoj funk- cii, kotoraja pozvoljaet provodit' raznicu mezhdu razlichnymi zamedliteljami, takzhe regu- liruet obnaruzhivaemyj spektr postojannoj spada. V rabote podcherkivaetsja sluchaj reshenija dlja beskonechnoj sredy, hotorye proporcional'ny jeksponente (iB * r), v sredah s pogloshheniem, podchinennym zakonu 1/v. Analiticheskaja rabota svjazana s naibolee verojatnymi reshenijami, proporcional'nymi takzhe jeksponente ({lambda}t), a chislennyj raschet napravlen na reshenie, uchi- tyvajushhee polnuju ''istoriju processa'', a takzhe na modal'nye reshenija. Zatragivajutsja takzhe javlenija, s kotorymi stalkivalis', kogda pogloshhenie ne podchinjaetsja zakonu 1/v i kogda ob- razec zamedlitelja nastol'ko mal, chto vremennye reshenija ne razdeljajutsja bol'she v pro- stranstvenno energeticheskom otnoshenii. Nakonec, obsuzhdaetsja znachenie jetih rezul'tatov dlja interpretacii impul'snyh jeks- perimentov. V chastnosti, avtory imejut v vidu izmerenie diffuzii, kojefficienty dif- fuzionnogo ohlazhdenija, a takzhe, v zavisimosti ot haraktera podhoda, asimptoticheskoe ras- predelenie . (author)}
place = {IAEA}
year = {1965}
month = {Aug}
}