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Direct measurement of the half-life of Rb{sup 87}; Mesure directe de la periode du rubidium-87; Pryamoe izmerenie poluraspada rubidiya-87; Medicion directa del periodo del {sup 87}Rb

Conference:

Abstract

The half-life of Rb{sup 87} has been measured directly by determining the specific activity by a counting method. The half-lives previously obtained lie in the range 4 - 6 x 10{sup 10} years, a value of 5 x 10{sup 10} years being taken usually. Direct counting is rather difficult because of the presence of a large number of very-low-energy electrons in the Rb{sup 87} spectrum. However, it is clearly very desirable to obtain a precise value by the counting method and this the authors have tried to do. In these measurements special attention must be paid to the reduction of thickness of source and of source backing. To increase the accuracy of the measurements, the following methods were used. The source thickness was reduced by use of (i) a 4-{pi} proportional counter of large source area (up to 100 cm{sup 2}), (ii) anti-coincidence operation to reduce background, and (iii) enriched Rb{sup 87} which permits a four-fold reduction in source thickness for a given activity. By these methods, sources down to 5 {mu}g/cm{sup 2} have been measured. Also the relationship between half-life and source thickness was examined so that correction could be made for the very small absorption which remained. The  More>>
Authors:
McNair, A; Wilson, H W [1] 
  1. United Kingdom Atomic Energy Authority, Aldermaston, Berks. (United Kingdom)
Publication Date:
Jan 15, 1962
Product Type:
Conference
Resource Relation:
Conference: Conference on the Use of Radioisotopes in the Physical Sciences and Industry, Copenhagen (Denmark), 6-17 Sep 1960; Other Information: 4 figs, 4 refs; Related Information: In: Radioisotopes in the Physical Sciences and Industry. Proceedings of the Conference on the Use of Radioisotopes in the Physical Sciences and Industry. V. 1| 556 p.
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; ABSORPTION; ACCURACY; COUNTING RATES; HALF-LIFE; PROPORTIONAL COUNTERS; RUBIDIUM 87; SPECTRA; THICKNESS
OSTI ID:
22025612
Research Organizations:
International Atomic Energy Agency, Vienna (Austria); United Nations Educational, Scientific and Cultural Organization, Paris (France)
Country of Origin:
IAEA
Language:
English
Other Identifying Numbers:
Other: ISSN 0074-1884; TRN: XA12N1591112905
Submitting Site:
INIS
Size:
page(s) 37-44
Announcement Date:
Jan 16, 2013

Conference:

Citation Formats

McNair, A, and Wilson, H W. Direct measurement of the half-life of Rb{sup 87}; Mesure directe de la periode du rubidium-87; Pryamoe izmerenie poluraspada rubidiya-87; Medicion directa del periodo del {sup 87}Rb. IAEA: N. p., 1962. Web.
McNair, A, & Wilson, H W. Direct measurement of the half-life of Rb{sup 87}; Mesure directe de la periode du rubidium-87; Pryamoe izmerenie poluraspada rubidiya-87; Medicion directa del periodo del {sup 87}Rb. IAEA.
McNair, A, and Wilson, H W. 1962. "Direct measurement of the half-life of Rb{sup 87}; Mesure directe de la periode du rubidium-87; Pryamoe izmerenie poluraspada rubidiya-87; Medicion directa del periodo del {sup 87}Rb." IAEA.
@misc{etde_22025612,
title = {Direct measurement of the half-life of Rb{sup 87}; Mesure directe de la periode du rubidium-87; Pryamoe izmerenie poluraspada rubidiya-87; Medicion directa del periodo del {sup 87}Rb}
author = {McNair, A, and Wilson, H W}
abstractNote = {The half-life of Rb{sup 87} has been measured directly by determining the specific activity by a counting method. The half-lives previously obtained lie in the range 4 - 6 x 10{sup 10} years, a value of 5 x 10{sup 10} years being taken usually. Direct counting is rather difficult because of the presence of a large number of very-low-energy electrons in the Rb{sup 87} spectrum. However, it is clearly very desirable to obtain a precise value by the counting method and this the authors have tried to do. In these measurements special attention must be paid to the reduction of thickness of source and of source backing. To increase the accuracy of the measurements, the following methods were used. The source thickness was reduced by use of (i) a 4-{pi} proportional counter of large source area (up to 100 cm{sup 2}), (ii) anti-coincidence operation to reduce background, and (iii) enriched Rb{sup 87} which permits a four-fold reduction in source thickness for a given activity. By these methods, sources down to 5 {mu}g/cm{sup 2} have been measured. Also the relationship between half-life and source thickness was examined so that correction could be made for the very small absorption which remained. The effect of source backing thickness is not so great and can be calculated from (i) the difference in count-rates on either side of the thin supports used and (ii) a study of dependence of half-life on source support thickness. These experiments give a value of about 5.25 x 10{sup 10} years for the half-life. (author) [French] On a mesure la periode du Tubidium-87 directement, en determinant l'activite specifique par comptage. Les periodes obtenues anterieurement se situent entre 4 et 6 {center_dot} 10{sup 10} ans; la valeur habituellement adoptee est de 5 {center_dot} 10{sup 10} ans. Le comptage direct est d'un emploi assez difficile par suite de la presence d'un grand nombre d'electrons de tres faible energie dans le spectre du rubidium-87. Il n'en serait pas moins tres utile d'obtenir une valeur precise par comptage direct, et c'est ce que les auteurs se sont efforces de faire. En procedant a ces mesures, il faut veiller particulierement a reduire l'epaisseur de la source et celle du support de la source. Les auteurs ont procede comme suit pour augmenter l'exactitude des mesures. Us ont reduit l'epaisseur de la source : a) en utilisant un compteur proportionnel 4 {pi} a grande surface utile (jusqu'a 100 cm{sup 2}); b) en effectuant un montage en anticoincidence pour reduire le bruit de fond; c) en employant du rubidium-87 enrichi, qui permet de ramener au quart l'epaisseur de la source pour line radioactivite donnee. Ils ont ainsi pu mesurer des sources ramenees a 5 {mu}g/cm. Ils ont en. outre etudie le rapport entre la periode et l'epaisseur de la source, afin de pouvoir effectuer les ajustements necessaires pour' tenir compte de la tres faible absorption restante. L'epaisseur du support de la source n'a pas d'effet aussi notable; celui-ci peut etre calcule d'apres : a) la difference entre les taux de comptage obtenus de part et d'autre des minces supports utilises; b) les resultats d4me etude sur les liens entre la periode et l'epaisseur du support de la source. Ces experiences donnent une valeur de 5,25 {center_dot} 10{sup 10} ans environ comme periode du rubidium-87. (author) [Spanish] El periodo de semidesintegracion del {sup 87}Rb se ha medido directamente determinando la actividad especifica del nuclido con ayuda de un metodo de recuento. Los periodos de semidesintegracion obtenidos previamente oscilaban entre 4 x 10{sup 10} y 6 x 10{sup 10} anos, adoptandose por regla general 5 x 10{sup 10} anos como valor medio. El recuento directo ofrece dificultades debidas a la presencia de un gran numero de electrones de muy baja energia en el espectro del {sup 87}Rb. No obstante, los autores han procurado obtener un valor preciso siguiendo dicho metodo, por la gran utilidad que ello representa. Al efectuar estas mediciones, debe prestarse especial atencion a una reduccion del espesor de la fuente y de su soporte. Los autores han recurrido a diversos procedimientos para aumentar la precision de las mediciones. El espesor de la fuente se redujo empleando: i) un contador proporcional 4 {pi} de gran superficie util (hasta 100 cm{sup 2}), ii) un circuito de anticoincidencias para disminuir la intensidad de la radiacion de fondo, y iii) {sup 87}Rb enriquecido, lo que permite reducir a la cuarta parte el espesor de la fuente para una actividad dada. De esta forma, se han podido medir fuentes hasta de 5 {mu}g/cm{sup 2}. Tambien examinaron la relacion entre el periodo de semidesintegracion y el espesor de la fuente, a fin de poder introducir una correccion para tener en cuenta la debil absorcion remanente. El efecto del espesor del soporte de la fuente no estan considerable y puede calcularse partiendo: i) de la diferencia entre la velocidad de recuento en ambos lados de los delgados soportes utilizados, y ii) de un estudio de la relacion existente entre el periodo de semidesintegracion y el espesor del soporte de la fuente. Estos experimentos dan un valor aproximado de 5,25 x 10{sup 12} anos para el periodo de semidesintegracion del {sup 87}Rb. (author) [Russian] Period poluraspada Rb''8''7 izmeryalsya neposredstvenno putem opredeleniya spetsificheskoj aktivnosti metodom scheta. Poluchennye ranee periody poluraspada nakhodyatsya v predelakh 4 - 6 kh 10''1''0 let s velichinoj, kotoraya beretsya obychno v 5 kh 10''1''0 let. Metod pryamogo scheta yavlyaetsya dovol'no slozhnym iz-za nalichiya bol'shogo chisla ehlektronov ochen' maloj ehnergii v spektre rubidiya-87. Odnako ves'ma aktual'nym yavlyaetsya poluchenie tochnoj velichiny metodom scheta, t.e. to, chto avtory pytalis' prodelat'. V ehtikh izmereniyakh sleduet udelit' osoboe vnimanie umen'sheniyu tolshchiny istochnika i ego podkladki. Dlya uvelicheniya tochnosti izmerenij byli ispol'zovany sleduyushchie metody. Tolshchina istochnika umen'shalas' putem ispol'zovaniya: i) 4-{pi} proportsional'nogo schetchika dlya istochnika s bol'shoj poverkhnost'yu ploshchadi ({pi}o 100 cm{sup 2}), ii) operatsii antisovpadeniya dlya umen'sheniya fona i iii) obogashchennogo rubidiya-87, kotoryj umen'shaet tolshchinu istochnika dlya dannoj aktivnosti. EHtimi metodami izmeryalis' istochniki do 5 mikrogramm/cm{sup 2}. Issledovalas' takzhe svyaz' mezhdu periodom poluraspada i tolshchinoj istochnika s tem, chtoby mozhno bylo vnesti popravku dlya ochen' neznachitel'nogo ostavshegosya pogloshcheniya. EHffekt podkladki tolshchiny istochnika ne tak uzh bol'shoj i mozhet byt' vychislen iz: i) raznosti v skorostyakh scheta na lyuboj storone ispol'zuemykh tonkikh opor i ii) issledovaniya zavisimosti perioda poluraspada ot tolshchiny opor istochnika. EHti ehksperimenty dayut velichinu okolo 5,25 x 10{sup 10} let dlya perioda poluraspada. (author)}
place = {IAEA}
year = {1962}
month = {Jan}
}