J. Rama Rao

Neutron activation cross-sections in rare earths and heavier nuclei

SummaryRadiative neutron capture cross-sections for the isotopes138Ba,140Ce,142Ce,146Nd,148Nd,160Gd,165Ho,180Hf,181Ta,190Os,197Au and202Hg have been measured at the neutron energy (23±5) keV by means of the activation method and 4π-geometry gamma-counting technique. In 9 cases for each of which there is a single previous report of the cross-section, the present work serves as a check on the previous value. In the remaining cases the present study helps to resolve the existing discrepancies in the reported values. The present results are generally supported by the recent semi-empirical estimates of the cross-section by Musgrove.RiassuntoSi sono misurate le sezioni d’urto di cattura di neutroni radiativi per gli isotopi138Ba,140Ce,142Ce,146Nd,148Nd,160Gd,165Ho,180Hf,181Ta,190Os,197Au e202Hg ad un’energia dei neutroni di (35 ± 5) keV per mezzo del metodo dell’attivazione e di una tecnica di conteggio dei gamma con una geometria 4π. In nove casi per ciascuno dei quali vi è una sola indicazione precedente sulla sezione d’urto, l’articolo presente serve come controllo del valore precedente. Nei rimanenti casi il presente studio aiuta a risolvere le discrepanze esistenti fra i valori riportati. I risultati attuali sono in generale confortati dalle recenti stime semiempiriche delle sezioni d’urto fatte da Musgrove.РеэюмеБыли иэмерены поперечные сечения радиационного эахвата нейтронов для иэотопов138Ва,140Се,142Се,146Nd,148Nd,160Gd,165Но,180Hf,181Та,190Оs,197Аu и202Нg при знергии нейтронов (23 ± 5) кзВ, испольэуя метод активации и технику счета гамма-квантов с геометрией Ал. В девяти случаях, для каждого иэ которых сушествуют ранее опубликованные поперечные сечения, настояшая работа служит проверкой сушествуюших реэультатов. В оставщихся случаях предлагаемое исследование помогает раэрещить сушествуюшие раэличия в опубликованных эначениях. Полученные реэультаты подтверждают недавние полу-змпирические оценки поперечного сечения Мусгрова.

Some neutron activation cross sections in the heavy mass region at 14 MeV

Abstract Neutron activation cross sections were measured for the reactions, 158 Gd( n , α ) 155 Sm, 176 Yb( n , 2 n ) 175 Yb, 174 Hf( n , 2 n ) 173 Hf, 181 Ta( n , α ) 178 m Lu and 208 Pb( n , p ) 208 Tl, at 14.2 ± 0.2 MeV, using the mixed-powder technique and high-resolution Ge(Li) detection. The measured ( n , 2 n ) cross sections were compared with the predictions based on statistical and preequilibrium theories. The ( n , α ) and ( n , p ) cross sections were compared with the recent empirical estimates.

Total photon cross-sections in the energy region (5÷1100) keV

SummaryTotal photon cross-sections are measured by using the transmission method in a good geometry set-up in elements 6≤Z≤92 at twenty-one energies in the region (5÷1100) keV by means of proportional counters and a Ge(Li) detector system. The measured cross-sections are compared with the theoretical predictions of Scofield and Storm and Israel. The values in general agree within 1%.RiassuntoSi misurano le sezioni d’urto totali usando il metodo di transmissione con un buon ordinamento di geometria in elementi 6≤Z≤92 a ventuno energie nella regione (5÷1100) keV per mezzo di contatori proporzionali e un sistema di rivelatori a Ge(Li). Si confrontano le sezioni d’urto misurate con le predizioni teoriche di Scofield, Storm e Israel. I valori generalmente sono in accordo entro l’1%.РезюмеИзмеряются полные поперечные сечения рассеяния фотонов с помощью метода прохождения в установке с хорошей геометрией для элементов 6≤Z≤92 при двадцати одном значении энергии в области (5÷1100) КэВ, используя пропорциональные счетчики и детекторную систему Ge(Li). Измеренные поперечные сечения сравниваются с теоретическими предсказаниями Шофилда, Сторма и Израэла. Получается согласие в пределах 1%.

Neutron capture cross sections at 25 keV

The radiative capture cross sections for eight even-even nuclei in the mass region 80<A<160 have been investigated using the activation method and gamma counting technique. The cross sections for the three isotopes 84Kr, 110Cd and 146Nd are reported for the first time and in the rest of the cases a comparison is made with previously reported values. The case of 115In(n, gamma )116In is reinvestigated as there is a discrepancy between the values reported using beta and gamma counting methods. The present results are in better agreement with gamma counting values.

Structure of 3P size resonance in neutron strength functions

Abstract Neutron capture cross sections of 21 nuclei have been determined using the activation technique and an antimony-beryllium photoneutron source. The nuclei have been selected in the mass range 60 A A

Neutron strength functions of nuclei in the deformed region

P-wave neutron strength functions of 21 nuclei, in the rare-earth and deformed region 138 <A < 202, have been extracted from the average capture cross sections measured using SbBe photoneutrons and activation technique. S-wave neutron contribution is computed using the s-wave resonance parameters available in literature and subtracted out from the measured total capture cross section to yield the p-wave neutron capture contribution from which the p-wave neutron strength functions are extracted. Present results are found to be in general agreement with the values reported in literature. The experimental p-wave neutron strength functions are also compared with the theoretical predictions based on the different versions of the optical model potential, and qualitative agreement is observed with the deformed optical model theory of Buck and Perey. Strong evidence for shell structure effects is also noticed.

Capture Cross Sections of Intermediate Neutrons

Radiative neutron capture cross sections for the isotopes /sup 59/Co, / sup 68/Zn/, /sup 86/Sr, /sup 87/Rb,/sup 976/Ryu, /sup 98/Mo, /sup 100/Mo, /sup 102/Ru, /sup 104/Ru, / sup 113/In, /sup 115/In, /sup 122/Sn and /sup 133/Cs were remeasured at the neutron energy 24 plus or minus 5 keV in view of the wide discrepancies in their values as reported in literature. The activation method and 4 pi geometry absolute gamma counting technique were used to obtain the cross sections. By making a critical comparison of the present results with the earlier experimental values on the one hand and with semi-theoretical estimates on the other, an attempt is made to resolve the discrepancies. (auth)

Activation Cross-Sections for 14.2 MeV Neutrons on Molybdenum

Using the activation method, the cross-section for the following reactions on molybdenum were measured employing the mixed powder technique and Ge(Li) gamma-ray spectroscopy: 94Mo(n, 2n)93mMo, 3.5 ± 0.5 mbarn; 92Mo(n, 2n)91mMo, 19 ± 3 mbarn; 92Mo(n, 2n)91m+gMo, 226 ± 11 mbarn; 100Mo(n, p)100m2Nb, 9 ± 1 mbarn; 98Mo(n, p)98Nb, 10 ± 1 mbarn; 97Mo(n, p)97mNb, 5 ± 1 mbarn; 96Mo(n, p)96Nb, 12 ± 2 mbarn; 92Mo(n, α)89mZr, 2.1 ± 0.5 mbarn; and 92Mo(n, α)89m+gZr; 24 ± 6 mbarn; the neutron energy was 14.2 ± 0.2 MeV. The experimental cross-sections were compared with the predictions of evaporation model and of different versions of pre-equilibrium model. The master equation approach appears to give satisfactory results.

Neutron activation cross sections in some barium isotopes at 14.2 MeV

Activation cross sections were measured for the reactions 136Ba(n,2n)135mBa, 138Ba(n,p)138Cs and 138Ba(n, alpha )135m,gXe at an incident neutron energy of 14.2+or-0.2 MeV using the mixed powder technique. A high-resolution Ge(Li) detector was used to measure the induced gamma-ray activities. The cross sections were compared with both experimental and theoretical values reported in the literature.

Ge(Li) measurement of some neutron activation cross-sections at (14.2±0.2) MeV

SummaryPrecision measurements of activation cross-sections were made for the reactions138Ba(n, 2n)137Bam,167Er(n, p)167Ho and181Ta(n, 2n)180Tam at an incident-neutron energy of (14.2±0.2) MeV. The mixed-powder technique and high-resolution Ge(Li) detector coupled to a ND 512 channel analyser system were employed. The cross-section values were compared with the values reported in the literature.RiassuntoSono state fatte precise misurazioni delle sezioni d’urto d’attivazione per le reazioni138Ba(n, 2n)137Bam,167Er(n, p)167Ho e181Ta(n, 2n)180Tam a un’energia del neutrone incidente di (14.2±0.2) MeV. Sono state impiegate la tecnica della miscela di polveri e un rivelatore a Ge(Li) ad alta risoluzione accoppiato a un sistema analizzatore ND a 512 canali. Si confrontano i valori delle sezioni d’urto con quelli riportati nella letteratura.РезюмеПроводятся точные измерения поперечных сечений активации для реакций138Ba(n, 2n)137Ba,167Er(n, p)167Ho и181Ta(n, 2n)180Tam при энергии падающего нейтрона (14.2±0.2) МэВ. Используется Ge(Li) детектор с высоким разрешением, связанный с ND 512 канальным анализатором. Полученные поперечные сечения сравниваются с результатамич имеющимися в литературе.