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Measurements and Calculations of the Slowing-Down and Migration Time; Mesures et Calcul du Temps de Ralentissement et de Migration; Izmereniya i raschety vremeni zamedleniya i migratsii; Medicion y Calculo del Tiempo de Moderacion y de Migracion

Conference:

Abstract

The mean time and variance in time for neutrons from an impulse source to slow down and migrate to the energy, angle and position of observation are important quantities in many experiments. The mean time is a correction in time-of-flight measurements of neutron spectra in bulk media, and the variance limits the ultimate resolution of such experiments. These parameters are equally significant in detectors which depend on moderation, in time-of-flight experiments where low energy neutrons are provided by a moderator placed near the pulsed source, and in slowing-down-time spectrometry. Various analytical and numerical methods have been developed to calculate the space-energy-angle-time . dependence, or integrals thereof. It is shown that the time moments, Empty-Set {sup (n)} (r, {Omega}, v, t) = {integral}{sub 0}{sup {infinity}}t{sup n} Empty-Set (r, {Omega}, v, t)dt, can be calculated by repeated application of a steady state transport code. The source term for the calculation of the n{sup -tb} moment is equal to nv{sup -1} Empty-Set {sup (n-1)}. Results are presented for multiplying and non-multiplying mockups of the TRIGA reactor. Another powerful calculational method is the time-dependent Monte Carlo code. Results of a calculation of leakage flux from a thin lead slab are presented. Measurements have been  More>>
Authors:
Profio, A. E.; Koppel, J. U.; [1]  Adamantiades, A. [2] 
  1. General Atomic Division of General Dynamics Corporation, John Jay Hopkins Laboratory for Pure and Applied Science, San Diego, CA (United States)
  2. Massachusetts Institute of Technology, Cambridge, MA (United States)
Publication Date:
Aug 15, 1965
Product Type:
Conference
Report Number:
IAEA-SM-62/75
Resource Relation:
Conference: Symposium on Pulsed Neutron Research, Karlsruhe (Germany), 10-14 May 1965; Other Information: 22 refs., 2 tabs., 2 figs.; Related Information: In: Pulsed Neutron Research. Vol. I. Proceedings of the Symposium on Pulsed Neutron Research| 713 p.
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; 21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS; ENERGY DEPENDENCE; GAMMA DETECTION; INDIUM; LEAD; MODERATORS; MONTE CARLO METHOD; NEUTRON LEAKAGE; NEUTRON SPECTRA; NEUTRON TRANSPORT THEORY; PULSED NEUTRON TECHNIQUES; RESOLUTION; RESONANCE; SCINTILLATION COUNTERS; SLOWING-DOWN; SPECTROSCOPY; STEADY-STATE CONDITIONS; THERMAL NEUTRONS; TIME DEPENDENCE; TIME-OF-FLIGHT METHOD; TOLUENE; TRIGA TYPE REACTORS; WATER
OSTI ID:
22122971
Research Organizations:
International Atomic Energy Agency, Vienna (Austria)
Country of Origin:
IAEA
Language:
English
Other Identifying Numbers:
Other: ISSN 0074-1884; TRN: XA13M2569078773
Submitting Site:
INIS
Size:
page(s) 123-138
Announcement Date:
Aug 30, 2013

Conference:

Citation Formats

Profio, A. E., Koppel, J. U., and Adamantiades, A. Measurements and Calculations of the Slowing-Down and Migration Time; Mesures et Calcul du Temps de Ralentissement et de Migration; Izmereniya i raschety vremeni zamedleniya i migratsii; Medicion y Calculo del Tiempo de Moderacion y de Migracion. IAEA: N. p., 1965. Web.
Profio, A. E., Koppel, J. U., & Adamantiades, A. Measurements and Calculations of the Slowing-Down and Migration Time; Mesures et Calcul du Temps de Ralentissement et de Migration; Izmereniya i raschety vremeni zamedleniya i migratsii; Medicion y Calculo del Tiempo de Moderacion y de Migracion. IAEA.
Profio, A. E., Koppel, J. U., and Adamantiades, A. 1965. "Measurements and Calculations of the Slowing-Down and Migration Time; Mesures et Calcul du Temps de Ralentissement et de Migration; Izmereniya i raschety vremeni zamedleniya i migratsii; Medicion y Calculo del Tiempo de Moderacion y de Migracion." IAEA.
@misc{etde_22122971,
title = {Measurements and Calculations of the Slowing-Down and Migration Time; Mesures et Calcul du Temps de Ralentissement et de Migration; Izmereniya i raschety vremeni zamedleniya i migratsii; Medicion y Calculo del Tiempo de Moderacion y de Migracion}
author = {Profio, A. E., Koppel, J. U., and Adamantiades, A.}
abstractNote = {The mean time and variance in time for neutrons from an impulse source to slow down and migrate to the energy, angle and position of observation are important quantities in many experiments. The mean time is a correction in time-of-flight measurements of neutron spectra in bulk media, and the variance limits the ultimate resolution of such experiments. These parameters are equally significant in detectors which depend on moderation, in time-of-flight experiments where low energy neutrons are provided by a moderator placed near the pulsed source, and in slowing-down-time spectrometry. Various analytical and numerical methods have been developed to calculate the space-energy-angle-time . dependence, or integrals thereof. It is shown that the time moments, Empty-Set {sup (n)} (r, {Omega}, v, t) = {integral}{sub 0}{sup {infinity}}t{sup n} Empty-Set (r, {Omega}, v, t)dt, can be calculated by repeated application of a steady state transport code. The source term for the calculation of the n{sup -tb} moment is equal to nv{sup -1} Empty-Set {sup (n-1)}. Results are presented for multiplying and non-multiplying mockups of the TRIGA reactor. Another powerful calculational method is the time-dependent Monte Carlo code. Results of a calculation of leakage flux from a thin lead slab are presented. Measurements have been made of the slowing-down time to the cadmium edge and to the 1.46-eV resonance of indium in water and in toluene. Capture gamma rays are detected by a scintillation counter. The technique requires a fairly intense source and efficient detector because of the low duty cycle (short burst width for resolution of the slowing-down time, large interpulse period for thermal neutron die-away) and the small probability for capture. (author) [French] Dans le phenomene de ralentissement et de migration des neutrons puises, amenes a l'enetgie, a l'angle et S la position d'observation, le temps moyen et la variance en temps sont des grandeurs importantes pour beaucoup d'experiences. Le temps moyen est une correction pour les mesures par la methode du temps de vol des spectres de neutrons dans des milieux de grande diffusion, et la variance a pour effet d'imposer une limite a la resolution des experiences. La grandeur de ces parametres est egalement importante pour les detecteurs qui dependent du ralentissement, dans les experiences par | la methode du temps de vol des spectres de neutrons de faible energie sont fournis par un ralentisseur place pres de la source puisee, et en spectrometrie du temps de ralentissement. Diverses methodes analytiques et numeriques ont ete mises au point pour calculer la fonction espaceenergie- angle-temps ou des integrales de cette fonction. Les auteurs montrent que les moments Empty-Set {sup (n)} (r, {Omega}, v, t) = {integral}{sub 0}{sup {infinity}}t{sup n} Empty-Set (r, {Omega}, v, t)dt peuvent etre calcules par application repetee d'un code de transport pour un etat stationnaire. Le terme de la source pour le calcul du nieme moment est egal a nv{sup -1} Empty-Set {sup (n-1)}. Les auteurs presentent des resultats pour des modeles multiplicateurs et non multiplicateurs du reacteur Triga. Une autre methode de calcul tres utile est le code de Monte-Carlo variable dans le temps. Les auteurs presentent les resultats d'un calcul de flux de fuite a partir d'une mince plaque de plomb. Les auteurs ont mesure le temps de ralentissement jusqu 'au seuil cadmium et jusqu 'a la resonance 1,46 eV de l'indium dans l'eau et dans le toluene. Ils ont deceleles rayonsgamma de capture avec un compteura scintillation. La methode necessite l'utilisation d'une source assez intense et d'un detecteur efficace a cause de la brievete du cycle de fonctionnement (petite largeur de bouffee pour la resolution du temps de ralentissement, grand intervalle entre les bouffees pour l'evanouissement des neutrons thermiques) et de la faible probabilite de capture. (author) [Spanish] En muchos experimentos, reviste gran importancia el tiempo medio que transcurre hasta que la velocidad de los neutrones pulsados disminuya en la medida necesaria para que estos alcancen la energia, el angulo y la posicion de observacion apetecidas. El tiempo medio es una correccion de las mediciones de espectros neutronicos en la masa hechas segun el metodo del tiempo de vuelo, y la variacion impone limites al poder de resolucion efectivo de tales experimentos. Estos parametros son igualmente importantes en los detectores cuyo funcionamiento se base en la moderacion, en los experimentos con el metodo de tiempo de vuelo en los que un moderador situado cerca de la fuente de neutrones pulsados proporciona neutrones de baja energia, y en la espectrometria del tiempo de moderacion. Se han ideado diversos metodos analfticos y numericos para calcular la distribucion espacio-energia angulo-tiempo o sus integrales. Ha podido demostrarse que los momentos temporales Empty-Set {sup (n)} (r, {Omega}, v, t) = {integral}{sub 0}{sup {infinity}}t{sup n} Empty-Set (r, {Omega}, v, t)dt, pueden calcularse aplicando repetidamente una clave de transporte en regimen estacionario. El termino de la fuente para el calculo del momento 'n'es igual a nv{sup -1} Empty-Set {sup (n-1)}. Los autores presentan los resultados correspondientes a maquetas del reactor TRIGA en las que se emplean medios multiplicadores y no multiplicadores. Otro valioso metodo de calculo consiste en emplear una clave de Monte Cario en funcion del tiempo. Los autores exponen los resultados del calculo de un flujo que escapa de una delgada placa de plomo. Se han hecho mediciones del tiempo de moderacion hasta la energia de corte del Cd y hasta la resonancia de 1,46 eV del In en agua y en tolueno. Los rayos gamma de captura se detectaron con un contador de centelleo. Esta tecnica exige disponer de una fuente de suficiente intensidad y de un detector eficaz debido a la brevedad del ciclo de trabajo (escasa anchura de las rafagas para la resolucion del tiempo de moderacion y amplio intervalo entre los impulsos para observar la atenuacion neutronica de caracter termico) y a las escasas probabilidades de captura. (author) [Russian] Srednee vremja i izmenenie vo vremeni zhizni nejtronov, poluchaemyh ot impul'snogo istochnika, s cel'ju ih zamedlenija i migracii do velichiny energii, ugla i polozhenija, udobnogo dlja nabljudenija, javljajutsja sushhestvennymi kolichestvennymi velichinami vo mnogih jeksperimentah. Srednee vremja javljaetsja popravkoj v izmerenijah nejtronnyh spektrov po metodu vremeni proleta v bol'shih ob{sup e}mah materialov, a izmenenie ogranichivaet maksimal'nuju razreshajushhuju spo- sobnost' takih jeksperimentov. Jeti parametry odinakovo vazhny v detektorah, zavisjashhih ot zamedlenija, v jeksperimentah po vremeni proleta, gde nejtrony s maloj energiej postu- pajut iz zamedlitelja, nahodjashhegosja vblizi pul'sirujushhego istochnika, a takzhe spektrometrii vremeni zamedlenija. Razrabotany razlichnye analiticheskie i cifrovye sposoby dlja vychislenija zavisimosti prostranstvennogo-energeticheskogo-uglovogo i vremennogo raspredelenija ili integralov po nim. Pokazano, chto momenty vremeni Empty-Set {sup (n)} (r, {Omega}, v, t) = {integral}{sub 0}{sup {infinity}}t{sup n} Empty-Set (r, {Omega}, v, t)dt, mozhno vyschitat' putem povtornogo primenenija programmy rascheta dlja stacionarnogo so- stojanija perenosa. Uslovie istochnika dlja vychislenija momenta ''p'' ravno nv{sup -1} Empty-Set {sup (n-1)}. Pri- vodjatsja rezul'taty dlja razmnozhajushhih i nerazmnozhajushih modelej reaktora {sup T}riga{sup .} Dru- gim metodom energeticheskogo rascheta javljaetsja metod vremennoj zavisimosti Monte Karlo. Dajutsja takzhe rezul'taty vychislenija potoka utechki iz tonkoj svincovoj plastiny. Izmerenija provodili na zamedlenii po vremeni po otnosheniju kadmievoj grani i re- zonansa v 1,46 jev indija v vode i toluole. Zahvatnoe gamma-izluchenie detektiruetsja s po- moshh'ju scintilljacionnogo schetchika. Jetot metod trebuet iskljuchitel'no intensivnogo is- tochnika i jeffektivnogo detektora v svjazi s nizkoj polezno ispol'zuemoj dolej vremeni cikla (korotkaja prodolzhitel'nost' vspyshki dlja razreshajushhej sposobnosti zamedlenija bol'- shoj period promezhutochnogo pul'sa dlja zatuhanija teplovyh nejtronov) i nebol'shoj verojat- nosti dlja zahvata. (author)}
place = {IAEA}
year = {1965}
month = {Aug}
}