K. Narasimha Murty

Internal bremsstrahlung from32P and210Bi

SummaryThe continuous spectra of internal bremsstrahlung from the beta-decays of32P and210Bi are measured by using a single channel NaI(TI) scintillation spectrometer along with a standard geometrical arrangement. Sufficient care is taken to avoid spurious effects and corrections are made for several factors, such as background, energy resolution, backscattering, Compton and escape electrons, geometrical and gamma detection efficiency of the crystal and absorption of the radiation between source and detector. Also the total yields of intensity and of energy of internal bremsstrahlung from each of the isotopes32P and210Bi in the investigated energy regions are determined and compared with the corresponding theoretical values. The experimental results in the case of32P are compared in the energy region of 100 keV to 1200 keV with the allowed theory of Knipp and Uhlenbeck and of Bloch (KUB theory) and also with the Coulomb-corrected theory due to Lewis and Ford and it is found that in the energy region from 100 to 600 keV there is a small but definite experimental excess of 15% over the KUB theory while above 600 keV the experimental distribution coincides with the Lewis and Ford distribution. In the case of210Bi the experimental results are compared in the energy range from 90 keV to 550 keV with the KUB theory and also with the Coulomb-corrected theories of Lewis and Ford and of Nilsson. A fairly good agreement is obtained between the experimental distribution and the Nilsson theoretical distribution throughout the investigated energy region.RiassuntoCon uno spettrometro a scintillazione NaI(Tl) ad un canale e una disposizione geometrica normale si sono misurati gli spettri continui della bremsstrahlung interna dei decadimenti β del32P e del210Bi. Si è avuto cura di evitare effetti spuri e si sono effettuate le correzioni dipendenti da parecchi fattori come fondo, risoluzione dell’energia, riscattering, elettroni di Compton e sfuggiti, efficienza geometrica e di rivelazione dei gamma del cristallo e assorbimento della radiazione fra la sorgente ed il rivelatore. Si sono anche studiate le rese totali di intensità e di energia della bremsstrahlung interna di ciascuno degli isotopi32P e210Bi nell’intervallo di energie studiato e si confrontano con i valori teorici corrispondenti. Si confrontano i risultati del caso del32P nella regione di energie fra 100 keV e 1200 keV con la teoria (ammessa) di Knipp e Uhlenbeck e di Block (KUB theory) e anche con la teoria dovuta a Lewis e Ford che tiene conto degli effetti coulombiani e si trova che nell’intervallo di energie fra 100 e 600 keV c’è un piccolo ma definito eccesso sperimentale del 15% rispetto alla teoria KUB mentre sopra i 600 keV la distribuzione sperimentale coincide con la distribuzione di Lewis e Ford. Nel caso del210Bi si confrontano i risultati sperimentali nell’intervallo di energia tra 90 keV e 550 keV con la teoria KUB ed anche con le teorie corrette secondo Coulomb di Lewis e Ford e di Nilsson. Si ottiene un accordo abbastanza buno fra la distribuzione sperimentale e la distribuzione teorica di Nilsson in tutto l’intervallo di energie studiato.РеэюмеИэмеряется непрерывный спектр внутреннего тормоэного иэлучения от β-распада32Р и210Вi, посредством испольэования одноканального NаI(Т1) сцинтилляционного спектрометра со стандартным геометрическим устройством. Принимается достаточная осторожность, чтобы иэбежать ложных зффектов, и делаются поправки для некоторых факторов, таких, как фон, раэрещение по знергии, рассеяние наэад, комптоновское рассеяние и утечка злектронов, геометрическая зффективность и зффективность регистрации ψ-квантов кристаллом, а также поглошение радиации между источником и детектором. Также определяются полная интенсивность и полная знергия внутреннего тормоэного иэлучения от каждого иэотопа32Р и210Bi в иэучаемых знергетических областях и сравниваются с соответствуюшими теоретическими величинами. Экспериментальные реэультаты в случае32Р сравниваются в области знергий от 100 кзВ до 1200 кзВ с приэнанной теорией Книппа, Уленбзка и Блоха (КУБ-теория), а также с теорией Льюиса и Форда, включаюшей кулоновские поправки; и было обнаружено, что в области знергий от 100 до 600 кзВ имеется маленький, но конечный зкспериментальный иэлищек по сравнению с КУБ-теорией, тогда как при знергиях свыще 600 кзВ зкспериментальное распределение совпадает с распределением Льюиса-Форда. В случае210Bi зкспериментальные реэультаты сравниваются в области знергий от 90 кзВ до 550 кзВ с КУБ-теорией и с теорией Льюиса, форда и Нильсона, включаюшей кулоновские поправки. Внутри исследуемой области знергий получено довольно хорощее согласие между зкспериментальным распределением и теоретическим распределением Нильсона.

Elastic scattering of 145 keV gamma rays

The differential elastic scattering cross sections of 145 keV gamma rays in Pb, Ta, Sn and Zr have been measured at angles ranging from 45 degrees and 115 degrees using a high-resolution lithium-drifted germanium detector. The experimental cross sections are compared with the available theoretical data. The present experimental results are in agreement with the theoretical results of Johnston et al. (1976) calculated using S-matrix theory of quantum electrodynamics. For medium- and low-Z elements the present experimental values are in agreement with the theoretical values compiled by Hubbell et al. (1975). At 45 degrees the experimental results for all elements are in agreement with the values calculated using Moileres expression. The experimental results are in good agreement with the theoretical values of Smend et al. (1973) at all angles in high- and low-Z elements.

Internal Bremsstrahlung from Pr-143

The internal bremsstrahlung (IB) spectrum of143Pr is measured in the energy region from 40 to 830 keV by using a multichannel NaI(Tl) scintillation spectrometer and a standard geometrical set up and corrections are applied for various factors. The measured intensity of IB in the investigated energy region is compared with the corresponding theoretical values of Ford and Martin (direct and detour). The present experimental values of IB are coinciding with the direct theory from 40 to 130 keV while from 130 to 500 keV, they are agreeing fairly well with the detour theory. Above 500 keV, the results are deviating positively even from the detour theory.

External bremsstrahlung spectral shape dependence on target thickness

Spectral shapes of bremsstrahlung were measured when32P and45Ca beta rays were absorbed in several elements Al, Cu, Sn and Pb of different thicknesses. While in aluminium, the experimental values and Bethe-Heitler theory agree for all thicknesses, in the case of the other elements an increase in the experimental value is observed which increases with Z of the target material and thickness of the target.

Inner Bremsstrahlung Following the 169Er Beta Decay

The spectral distribution of the Internal Bremsstrahlung from the forbidden beta decay of 169 Er was measured from 50 to 290 keV with a NaI(Tl) scintillation spectrometer with a standard geometrical arrangement. The experimental results agree fairly well in the middle photon energy region i.e., from 70 to 210 keV with the KUB theory and at high as well as at low photon energies, the Nilsson theory is found to explain the observed excess over KUB theory.

Internal bremsstrahlung spectral shapes of 45Ca and 3aS

The internal bremsstrahlung spectra emitted in the beta decays of 45Ca and 35S were measured using a multichannel NaI(Tl) scintillation spectrometer with a standard geometrical arrangement. After making all the necessary corrections, the experimental results were compared with theory.

Growth of external bremsstrahlung generated in various elements by beta radiation

The external bremsstrahlung (EB) produced in different thicknesses of various elements-aluminium, copper, silver, tin and lead-covering an atomic number range from 13 to 82 due to the absorption of the continuous beta rays from 32P, 91Y, 204Tl, 185W and 169Er is measured integrally as a function of the target thickness with a NaI(Tl) scintillation spectrometer.

Internal bremsstrahlung from89Sr and90Sr

SummaryThe internal bremsstrahlung (IB) spectra emitted in the beta-decays of89Sr and90Sr were measured with a HPGe detector and a multichannel analyser along with a standard geometrical set-up. Sufficient care has been taken to avoid spurious effects. After making all the necessary corrections, the experimental results were compared with the corresponding theoretical distributions due to Knipp and Uhlenbeck and Bloch (KUB), Lewis and Ford, Nilsson, and also due to Ford and Martin (detour theory). The total IB yields of intensity and energy from each of the isotopes in the investigated energy regions are also determined and compared with the corresponding theoretical values. The present results of IB from89Sr are satisfactorily accounted for by the KUB theory. In the case of90Sr the experimental results of IB coincide with the Coulomb-corrected theoretical distribution due to Nilsson in the energy range from 60 keV to 110 keV and beyond 110 keV, they are found to be in excess over Nilsson’s theory as well as the detour theory due to Ford and Martin up to the maximum photon energy studied, namely 350 keV.RiassuntoGli spettri di bremsstrahlung interno (IB) emessi durante i decadimenti beta di89Sr e90Sr sono stati misurati con un rivelatore HPGe e con analizzatore multicanale insieme ad un apparato geometrico standard. Ci si è assicurati di evitare effetti spuri. Dopo aver fatto tutte le necessarie correzioni, i valori sperimentali sono stati confrontati con le corrispondenti distribuzioni teoriche di Knipp, Hulenbeck e Bloch (KUB), Lewis e Ford, Nilsson, e anche di Ford e Martin (teoria del detour). I prodotti totali di IB dell’intensità e dell’energia di ognuno degli isotopi nelle zone di energia studiate sono stati inoltre determinati e confrontati con i corrispondenti valori teorici. I risultati attuali di IB provenienti dallo89Sr sono spiegati in maniera soddisfacente dalla teoria KUB. Nel caso dello90Sr i risultati sperimentali dell’IB coincidono con la distribuzione teorica corretta secondo Coulomb di Nilsson nell’intervallo di energia (60÷110) keV e oltre i 110 keV, essi si trovano in eccesso sia rispetto alla teoria del detour di Ford e Martin, fino a raggiungere la massima energia fotonica studiata, 350 keV.РеэюмеИэмеряются спектры внутреннего тормоэного иэлучения, испускаемого при бета-распаде89Sr и90Sr, с помошью детектора и многоканального аналиэатора вместе со стандартной геометрической установкой. Особое внимание уделяется, чтобы иэбежать ложных зффектов. Учитывая все необходимые поправки, зкспериментальные реэультаты сравниваются с соответствуюшими теоретическими распределениями, полученными Книппом, Уленбеком и Блоком, Левисом, Фордом и Нильсоном, а также Фордом и Мартиным. Определяются полные выходы внутреннего тормоэного иэлучения для каждого иэотопа и сравниваются с соответствуюшими теоретическими величинами. Полученные реэультаты для внутреннего тормоэного иэлучения иэ89Sr удовлетворительно общясняются теорией Книппа, Уленбека и Блока. В случае90Sr зкспериментальные реэультаты для внутреннего тормоэного иэлучения совпадают с теоретическим распределением Нильсона в области знергий от 60 кзВ до 110 кзВ, однако эа пределами 110 кзВ зкспериментальные реэультаты окаэываются больще предскаэаний теории Нильсона и теории Форда и Мартина вплоть до максимальной исследованной знергии фотонов, а именно 350 кзВ.

Hydrodynamic control of microphytoplankton bloom in a coastal sea

The influence of hydrodynamics on phytoplankton bloom occurrence/formation has not been adequately reported. Here, we document diurnal observations in the tropical Bay of Bengal’s mid-western shelf region which reveal microphytoplankton cell density maxima in association with neap tide many times more than what could be accounted for by solar insolation and nutrient levels. When in summer, phytoplankton cells were abundant and the cell density of Guinardia delicatula reached critical value by tide caused zonation, aggregation happened to an intense bloom. Mucilaginous exudates from the alga due to heat and silicate stress likely promoted and stable water column and weak winds left undisturbed, the transient bloom. The phytoplankton aggregates have implication as food resource in the benthic region implying higher fishery potential, in carbon dioxide sequestration (carbon burial) and in efforts towards improving remote sensing algorithms for chlorophyll in the coastal region.

Internal bremsstrahlung from 89 Sr and 90 Sr

SummaryThe internal bremsstrahlung (IB) spectra emitted in the beta-decays of89Sr and90Sr were measured with a HPGe detector and a multichannel analyser along with a standard geometrical set-up. Sufficient care has been taken to avoid spurious effects. After making all the necessary corrections, the experimental results were compared with the corresponding theoretical distributions due to Knipp and Uhlenbeck and Bloch (KUB), Lewis and Ford, Nilsson, and also due to Ford and Martin (detour theory). The total IB yields of intensity and energy from each of the isotopes in the investigated energy regions are also determined and compared with the corresponding theoretical values. The present results of IB from89Sr are satisfactorily accounted for by the KUB theory. In the case of90Sr the experimental results of IB coincide with the Coulomb-corrected theoretical distribution due to Nilsson in the energy range from 60 keV to 110 keV and beyond 110 keV, they are found to be in excess over Nilsson’s theory as well as the detour theory due to Ford and Martin up to the maximum photon energy studied, namely 350 keV.RiassuntoGli spettri di bremsstrahlung interno (IB) emessi durante i decadimenti beta di89Sr e90Sr sono stati misurati con un rivelatore HPGe e con analizzatore multicanale insieme ad un apparato geometrico standard. Ci si è assicurati di evitare effetti spuri. Dopo aver fatto tutte le necessarie correzioni, i valori sperimentali sono stati confrontati con le corrispondenti distribuzioni teoriche di Knipp, Hulenbeck e Bloch (KUB), Lewis e Ford, Nilsson, e anche di Ford e Martin (teoria del detour). I prodotti totali di IB dell’intensità e dell’energia di ognuno degli isotopi nelle zone di energia studiate sono stati inoltre determinati e confrontati con i corrispondenti valori teorici. I risultati attuali di IB provenienti dallo89Sr sono spiegati in maniera soddisfacente dalla teoria KUB. Nel caso dello90Sr i risultati sperimentali dell’IB coincidono con la distribuzione teorica corretta secondo Coulomb di Nilsson nell’intervallo di energia (60÷110) keV e oltre i 110 keV, essi si trovano in eccesso sia rispetto alla teoria del detour di Ford e Martin, fino a raggiungere la massima energia fotonica studiata, 350 keV.РеэюмеИэмеряются спектры внутреннего тормоэного иэлучения, испускаемого при бета-распаде89Sr и90Sr, с помошью детектора и многоканального аналиэатора вместе со стандартной геометрической установкой. Особое внимание уделяется, чтобы иэбежать ложных зффектов. Учитывая все необходимые поправки, зкспериментальные реэультаты сравниваются с соответствуюшими теоретическими распределениями, полученными Книппом, Уленбеком и Блоком, Левисом, Фордом и Нильсоном, а также Фордом и Мартиным. Определяются полные выходы внутреннего тормоэного иэлучения для каждого иэотопа и сравниваются с соответствуюшими теоретическими величинами. Полученные реэультаты для внутреннего тормоэного иэлучения иэ89Sr удовлетворительно общясняются теорией Книппа, Уленбека и Блока. В случае90Sr зкспериментальные реэультаты для внутреннего тормоэного иэлучения совпадают с теоретическим распределением Нильсона в области знергий от 60 кзВ до 110 кзВ, однако эа пределами 110 кзВ зкспериментальные реэультаты окаэываются больще предскаэаний теории Нильсона и теории Форда и Мартина вплоть до максимальной исследованной знергии фотонов, а именно 350 кзВ.