Search results for: V.R. Vanin

Items from 1 to 17 out of 17 results

article

Ag K-shell ionization by electron impact: New cross-section measurements between 50 and 100keV and review of previous experimental data

V.R. Vanin, M.V. Manso Guevara, N.L. Maidana, M.N. Martins, more

Radiation Physics and Chemistry > 2016 > 119 > Complete > 14-23

We report the measurement of Ag K-shell ionization cross-section by electron impact in the range 50–100keV and review the experimental data found in the literature. The sample consisted in a thin film of Ag evaporated on a thin C backing. The x-ray spectra generated by electron bombardment in the São Paulo Microtron were observed with a planar HPGe detector. The ratios between characteristic and bremsstrahlung...

article

Triple- and quadruple-escape peaks in HPGe detectors: Experimental observation and Monte Carlo simulation

N.L. Maidana, L. Brualla, V.R. Vanin, J.R.B. Oliveira, more

Nuclear Inst. and Methods in Physics Research, A > 2010 > 615 > 3 > 285-294

The triple- and quadruple-escape peaks of 6.128MeV photons from the F(p,αγ)19O16 nuclear reaction were observed in an HPGe detector. The experimental peak areas, measured in spectra projected with a restriction function that allows quantitative comparison of data from different multiplicities, are in reasonably good agreement with those predicted by Monte Carlo simulations done with the general-purpose...

article

Decay chain differential equations: Solution through matrix algebra

M. Amaku, P.R. Pascholati, V.R. Vanin

Computer Physics Communications > 2010 > 181 > 1 > 21-23

A matricial method to solve the decay chain differential equations system is presented. The quantity of each nuclide in the chain at a time t may be evaluated by analytical expressions obtained in a simple way using recurrence relations. This method may be applied to problems of radioactive buildup and decay and can be easily implemented computationally.

article

Statistical analysis of the Doppler broadening coincidence spectrum of electron–positron annihilation radiation in silicon

E. do Nascimento, O. Helene, V.R. Vanin, M.T.F. da Cruz, more

Nuclear Inst. and Methods in Physics Research, A > 2009 > 609 > 2-3 > 244-249

We report a statistical analysis of Doppler broadening coincidence data of electron–positron annihilation radiation in silicon using a ²² Na source. The Doppler broadening coincidence spectrum was fit using a model function that included positron annihilation at rest with 1s, 2s, 2p, and valence band electrons. In-flight positron annihilation was also fit. The response functions of the detectors...

article

Absolute determination of soluble potassium in tea infusion by gamma-ray spectroscopy

N.L. Maidana, V.R. Vanin, C.L. Horii, F.A. Ferreira, more

Food Chemistry > 2009 > 116 > 2 > 555-560

Potassium content in tea brew was determined by gamma-ray spectroscopy, using the 1461keV gamma-ray from ⁴⁰ K, the naturally occurring radioactive isotope of potassium. We measured radiation with a shielded HPGe detector from individual test samples of tea leaves, before and after infusion preparation, and from commercial instant tea powder. The correction factor for the gamma-ray self-absorption...

article

Nuclear Data Sheets for A = 191

V.R. Vanin, N.L. Maidana, R.M. Castro, E. Achterberg, more

Nuclear Data Sheets > 2007 > 108 > 11 > 2393-2588

The present revision of the nuclear structure properties for the nuclides belonging to the A = 191 mass chain contains many improvements, corrections and additions to the material presented in previous evaluations (1995Br38, Nucl. Data Sheets 74, 611 (1995)). Besides updating many values, and including supplementary data for already known levels, transitions and level schemes, the most noteworthy...

article

Variances, covariances and artifacts in image deconvolution

O. Helene, V.R. Vanin, Z.O. Guimarães-Filho, C. Takiya

Nuclear Inst. and Methods in Physics Research, A > 2007 > 580 > 3 > 1466-1473

In this paper we investigate the role of estimator variance and covariance in signal and image deconvolution, where artificial structures and large fluctuations are frequently observed. The deconvolution procedure adopted in this paper is based on the Least Squares Method and the regularization, on a minimum variance property. The whole covariance matrices were taken into account in every step of...

article

Search for the triple-escape peak in HPGe detectors

N.L. Maidana, D.B. Tridapalli, M.A. Rizzutto, P.R. Pascholati, more

Nuclear Inst. and Methods in Physics Research, A > 2007 > 580 > 1 > 106-109

Triple-escape peaks can be generated when either the electron or the positron created by the pair-formation interaction inside the active volume generates a Bremsstrahlung γ-ray with enough energy to produce another pair; however, they were never observed. MCNP5 and MCNPX simulations differ greatly in the triple-escape peak intensity for photon energies around 6MeV but agree for 14MeV incoming photons...

article

Statistical analysis of the Doppler broadening coincidence spectrum of the electron–positron annihilation radiation in aluminum

E. do Nascimento, O. Helene, V.R. Vanin, M.T.F. da Cruz

Nuclear Inst. and Methods in Physics Research, B > 2006 > 247 > 1 > 38-41

We report a new, simplified and more efficient modeling on the statistical analysis of Doppler broadening coincidence data of the electron–positron annihilation radiation in aluminum, when compared with previous works. The Doppler broadening coincidence spectrum was fitted using a model function. The model function included positron annihilation at rest with the conduction band, 2p, 2s and 1s electrons...

article

Nuclear Data Sheets for A = 193

E. Achterberg, O.A. Capurro, G.V. Marti, V.R. Vanin, more

Nuclear Data Sheets > 2006 > 107 > 1 > 1-224

The present revision of the properties for the nuclides belonging to the A = 193 mass chain contains many improvements, corrections and additions to the material presented in previous evaluations (1998Ar07, Nucl. Data Sheets 83, 921 (1998); 1990Sh30, Nucl, Data Sheets 61, 519 (1990)). Among these are measurement results for quadrupole moments, angular distribution coefficients, half-lives and g-factors,...

article

Doppler broadening of positron annihilation radiation: fitting the coincidence spectrum

E. do Nascimento, O. Helene, C. Takiya, V.R. Vanin

Nuclear Inst. and Methods in Physics Research, A > 2005 > 538 > 1-3 > 723-730

The profile of the annihilation radiation in aluminum using positrons from a 22Na source was observed in a two-HPGe-detectors arrangement. The coincidence photon energy spectrum was fitted using a model function, accounting for both Doppler broadening and detector system response. Intensities of the thermalized positron annihilation with band, 2p, 2s, and 1s electrons, and in-flight positron annihilation...

article

Combination of nonlinear function and mixing method for fitting HPGe efficiency curve in the 59-2754kev energy range

M.S. Dias, V. Cardoso, V.R. Vanin, M.F. Koskinas

Applied Radiation and Isotopes > 2004 > 60 > 5 > 683-687

A nonlinear function in combination with the method of mixing activity-calibrated and uncalibrated gamma-ray sources is applied for fitting the experimental peak efficiency of HPGe spectrometers in the 59-2754keV energy range. In addition, a step function was developed for fitting the gamma-ray background under the peak. Calibrated ² ⁴ ¹ Am, ¹ ³ ³ Ba, ¹ ³ ...

article

Minimum variance regularization in linear inverse problems

C. Takiya, O. Helene, E. do Nascimento, V.R. Vanin

Nuclear Inst. and Methods in Physics Research, A > 2004 > 523 > 1-2 > 186-192

In this paper we propose a minimum variance regularization procedure for the solution of ill-posed linear inverse problems. The method was applied to the deconvolution of Doppler broadening positron-electron annihilation radiation in aluminum. The characteristics of the procedure were tested through simulation.

article

Analysis of discrepant data using a bootstrap procedure

O. Helene, V.R. Vanin

Nuclear Inst. and Methods in Physics Research, A > 2002 > 481 > 1-3 > 626-631

We present in this paper a statistical procedure to deduce a best value and its standard deviation for a discrepant set of data. This method, rather than using the conventional average, uses a Bootstrap Method to estimate these quantities. The usual weighted average may be used to combine this estimate with additional data, thus avoiding a more complex calculation required by other methods, which...

article

Transfer coefficient measurements of uranium to the organs of Wistar rats, as a function of the uranium content in the food

J.D.T. Arruda-Neto, V.P. Likhachev, G.P. Nogueira, G.W. Araujo, more

Applied Radiation and Isotopes > 2001 > 54 > 6 > 947-956

Groups of animals (Wistar rats) were fed with rations doped with uranyl nitrate at concentrations ranging from 0.5 to 100ppm. The uranium content in the ashes of the organs was measured by the neutron-fission track counting technique. The most striking result is that the transfer coefficients, as a function of the uranium concentration, exhibit a concave shape with a minimum around 20ppm-U for all...

article

Covariances between gamma-ray energies

O. Helene, Z.O. Guimarães-Filho, V.R. Vanin, T.M. Pauliquevis, more

Nuclear Inst. and Methods in Physics Research, A > 2001 > 460 > 2-3 > 289-296

Covariances between experimental data are as significant as variances both in the evaluation of uncertainties and to perform statistical tests. If standard data are used in calibrations, covariances must be taken into account. Covariances are also necessary in order to update values every time when new data are obtained. In this paper we determined covariances between the most important gamma-ray...

article

An experimental method for a precise determination of gamma-ray energies with semiconductor detectors

V.R. Vanin, G. Kenchian, M. Moralles, O. Helene, more

Nuclear Inst. and Methods in Physics Research, A > 1997 > 391 > 2 > 338-344

This paper presents a method for determining gamma-ray energies with a precision similar to that of the primary standards. The method consists of both an experimental procedure which employs Ge detectors, and the statistical treatment of data. An actual example with ¹ ⁵ ⁹ Gd β ^- decay illustrates its use.

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