Relative Intensities Of Gamma Rays Research Articles

Gamma ray intensity standards for calibrating Ge(Li) detectors for the energy range 200–1700 keV

Gamma ray pulse height spectra for seven radioactive sources have been analyzed for the full energy peak areas. Using these areas in conjunction with the results of an extensive compilation of relative gamma ray intensities, a relatively simple efficiency function has been used to calibrate a coaxial Ge(Li) detector. The resulting relative intensities for each source have been used in investigating the consistency of the weighted averages of the compiled relative intensities. Possible systematic errors are discussed and recommendations are made with respect to the choice of gamma ray intensity standards.

Correlations between (n,γ) and (d,p) reactions on144Sm

The energies and relative intensities of the primary gamma rays from the 44Sm(n, gamma )145Sm reaction have been measured with a Ge(Li) pair-formation gamma -ray spectrometer from 3.0-7.2 MeV. The neutron separation energy of 145Sm was found to be 6757.1+or-0.3 keV. A comparison of the measured strengths of excitation of levels in 145Sm in the (n, gamma ) and (d,p) reactions reveals that they are strongly correlated. These results are discussed in terms of a number of simple neutron-capture reaction mechanisms.

Relative intensities of gamma-rays from 56Co standard source

The transition intensities of 56Co have been determined with the aid of the accurately known decay schemes of (p, γ) reaction resonances.

Use of a Gain Stabilized NaI(T1) Gamma Ray Detection System to Determine the Power Shape in Light Water Reactor Cores

A data acquisition system which consists of a NaI(T1) detector, associated electronics and a disc-based minicomputer has been used to obtain accurate relative gamma ray intensities over a large range of count rates (up to ~250 kHz) from light water reactor fuels. The system uses a green light-emitting diode optically coupled to the photomultiplier face to insure gain stabilization over a variation of count rates and environmental conditions, and to determine empirically the pileup and dead-time losses. The energy resolution of NaI(T1) is adequate for this application because only the well-isolated 1.6 MeV gamma from La-140 is used to relate fission product activity to power. Measurements have been performed on irradiated fuel during refueling outages at both boiling and pressurized water reactor (BWR and PWR) nuclear power plants.

226Ra as calibration standard for Ge(Li) spectrometers

The energies and relative intensities of gamma-rays from the decay of 226Ra and its short-lived daughters have been measured using various high-resolution Ge(Li) detectors. A technique based on a nonlinear least-squares method is proposed to fit the gamma-ray pulse height distribution. Results of the successive steps of the analysis performed by the computer code are displayed on a storage CRT. The peaks of interest and their vicinity are plotted along with the actual fitting function and can be checked visually. The typical uncertainties of the gamma-ray energies are about 15 eV, the relative intensities are given within an accuracy of 1.5%. The chain is recommended for use as a calibration standard for Ge(Li) spectrometers.

Relative efficiency calibration of Ge(Li) detector in low energy region

The relative gamma-ray intensities in the energy region between 122 and 411 keV in the decay of152Eu were measured by using a Ge(Li) detector. Its efficiency calibration was carried out with the radioactive sources of241Am,57Co,203Hg,137Cs,133Ba,75Se,169Yb and192Ir.

Influence of source-detector distance on relative intensity and angular correlation measurements with Ge(Li) spectrometers

Gamma-ray relative intensities determined with a Ge(Li) spectrometer can be incorrect unless the source-detector distance is several times the detector radius. This effect is a consequence of complete or partial energy loss in the detector by γ-rays in true coincidence. A computer program has been developed to calculate the integrated effects of all coincidence summing in a complex spectrum; it incorporates a general method for calculating full-energy and total detection efficiencies at any distance. The effects of positron decay can be accounted for. Calculations of the changes in measured relative intensities with distance are compared with data from 22Na, 207Bi and 214Bi. The influence of regions in a coaxial detector which show incomplete charge collection is considered; it is shown that their effect on angular distribution attenuation coefficients computed by standard methods becomes important at close distances for γ-rays with energy less than 300 keV.

Precise measurement of relative intensities of gamma-rays from 56Co

The relative intensities of gamma-rays from the decay of 77.3 d 56Co have been carefully determined using a high-resolution Ge(Li)NaI(Tl) Compton suppression spectrometer. Pure cascade sources were mainly employed for the efficiency calibration. The effect of Compton back-scattering was taken into consideration for the peak area determination. The results obtained were mostly in agreement with the data published so far except for a significant discrepancy in several gamma-ray components. The discrepancy is thought to be due to the Compton back-scattering effect neglected in the previous works.

Absolute efficiency calibration of coaxial Ge(Li) detectors for the energy range 160–1330 keV

A brief review of efficiency calibration techniques for Ge(Li) detectors is given, and the necessity for precise interpolation between absolute efficiencies measured at specific energies is discussed. Various analytical functions are fitted to experimental absolute efficiency data for a coaxial detector. The limits of validity of the most sucessful function are explored through measurement of relative gamma ray intensities for several widely used calibration sources.

Relative intensity and internal conversion coefficient measurements in the decays of 51Cr, 137Cs, 192Ir, and 207Bi

An “internal conversion coefficient spectrometer” utilizing Ge(Li) and Si(Li) detectors has been used to make precision measurements of relative gamma-ray intensities for transitions following the decay of 192Ir and 207Bi, relative internal conversion line intensities for some transitions from 192Ir, and conversion coefficients for some transitions from the decays of 51Cr, 137Cs, and 192Ir. Limits and values are given for E2 M1 mixing ratios and penetration effects for the 320.1-keV transition in 51V, the 484.5-keV transition in 192Os, and the 604.4-keV transition in 192Pt. The consequences of the results for nuclear structure are discussed.

Monte Carlo calculations of relative efficiencies of Ge(Li) detectors

Abstract By means of a Monte Carlo computer program the relative full energy peak efficiency and relative double escape peak efficiency for gamma rays of a cylindrical Ge(Li) detector with volume of 50 m 3 , a rectangular Ge(Li) detector with volume of 30 cm 3 and a trapezoidal Ge(Li) detector with volume of 50 cm 3 has been calculated. The gamma source was assumed to be a point placed 10 cm from the detector. The calculated efficiency curves for the cylindrical detector were compared with the curves experimentally obtained by other authors. The agreement was found to be within quoted errors. The calculated efficiency curves of all three detectors have been used to determine the gamma ray relative intensities in the decays of 22 Na, 60 Co, 56 Co and 226 Ra. It has been found that the relative intensity values of gamma rays for the above sources can be reproduced within 5%.

Experimental determination of penetration parameter forM1 conversion, and theE2 admixtures for 77 and 191 keV transitions in197Au

TheL-subshell conversion for 77 keV transition andK,L1,L2-shell conversion for 191 keV transition in197Au, as well asK-shell conversion transition of 158 keV in199Hg were measured by means of Π√2-iron free electron spectrometer. Relative gamma-ray intensities have been determined by Ge(Li) spectrometer. From these measurements the αK conversion coefficient value has been deduced for 191 keV transition as αK(191 keV)=0.86±0.03. This value shows that the spin of the level at 268 keV in197Au is 3/2+. For the penetration parameter (λ) and intensity ratio\(\left( {\delta ^2 = \frac{{\left\langle {E2} \right\rangle ^2 }}{{\left\langle {MI} \right\rangle ^2 }}} \right)\) the following values are obtained: $$\begin{gathered} \lambda = 3.4 \pm _{1.5}^{1.9} \delta ^2 = 0.11 \pm 0.03for 77 keV transition \hfill \\ \lambda = 3.2 \pm _{0.6}^{0.8} \delta ^2 = 0.17 \pm 0.04for 191 keV transition. \hfill \\ \end{gathered} $$

Gamma-ray transitions in 207Bi following the decay of 207Po

The decay of 5.7 h 207Po to levels in 207Bi has been studied using a Ge(Li) detector. Combining the relative gamma-ray intensities with previously established conversion electron intensities, K-conversion coefficients are determined. The multipolarities of 29 transitions are deduced from a comparison with theoretical conversion coefficients, thus establishing the following spins and parities for the excited levels: 669.5 keV ( 11 2 −), 742.6 keV 7 2 −, 892.3 keV ( 9 2 −), 992.3 keV 7 2 −, 1148.3 keV 5 2 −, (1360.4 keV 7 2 −), 1372.4 keV 5 2 −, 1680.0 keV 3 2 −, (1690.6 keV 5 2 −), 1762.7 keV 5 2 −, 1902.0 keV 1 2 +, 2060.0 keV 3 2 +, and 2405.2 keV 5 2 + . A comparison with a recent shell-model calculation shows good agreement for all negative parity levels.

Precision measurements of gamma-ray intensities and energies in the decay of 152g, 154Eu, 56Co, 110mAg and 125Sb

With the aid of a computarized program the relative intensities of the prominent transitions present in the decay of 152g, 154Eu, 56Co, 110mAg and 125Sb have been calculated with very high precision. The energy values of the same transitions in the 152g, 154Eu, 110mAg and 125Sb decays were also determined, very precisely, so that each of these sources, could be employed both for energy calibration measurements, and for linearity calibration of multichannel analysers. The measurements were performed with two Ge(Li) coaxial detectors with active volume of 5.3 cm 3 and 30 cm 3, respectively. It is shown that with the aid of these radioactive sources, one can construct a very precise efficiency curve for any other Ge(Li) detector from 100 keV to 3500 keV and reproduce to within 2%–3% the well measured gamma ray relative intensities in sources as 22Na, 207Bi, 88Y, 133Ba and ThC″. For these latter measurements a third Ge(Li) coaxial detector, with active volume of 32 cm 3, was employed.

Calculated relative efficiency for coaxial and planar Ge(Li) detectors

With the aid of a Monte Carlo computer program, the relative efficiency to monoenergetic γ-rays of coaxial and planar Ge(Li) detectors has been calculated. Considering a point source, placed on the extended axis of the detector, at a fixed distance, radiations of different energies are generated within the solid angle subtended by the crystal. The gamma-rays impinging on the detector are followed until a fraction whatsoever of their energy escapes from the active region of the crystal. If the γ-ray releases all its energy in the active region, a photopeak is counted and then its efficiency is calculated. At the end of the program the efficiency for the double-escape peak is also obtained. Following this procedure the photopeak efficiency was calculated for three Ge(Li) detectors, having volumes of: 2.0 cm 3 (planar), 5.3 cm 3 and 30 cm 3 (coaxial) from ≈ 100 keV up to 4000 keV. By means of these calculated efficiency curves, the well measured gamma-ray relative intensities in sources as 22Na, 88Y, 207Bi, 133Ba and ThC″ could be reproduced to within 1%–3%.

The decay of 97Ru

The decay of 97Ru to the levels in 97Tc has been studied with the use of semiconductor detectors, a NaI(Tl) crystal and coincidence equipment. Gamma-ray energies and relative gamma-ray intensities were determined as well as conversion coefficients for some transitions. Excited states were found at 215, 324, 784 and 976 keV. The level structure has been compared to current theoretical calculations.

Energies and intensities of 125Sb gamma rays

Energies and relative intensities of 125Sb gamma rays are reported.

Gamma rays following the decay of 75Se

The gamma-ray spectrum of 75Se has been studied using lithium-drifted detectors. Seven new transitions have been observed for the first time. The energies in keV and the relative intensities (indicated in parentheses) of the new gamma rays observed are 335.14(0.18), 415.10 (2.76 × 10 −2), 485.58(3.68 × 10 −3), 528.55(1.46 × 10 −2), 535.79(9.34 × 10 −3), 543.03(1.40 × 10 −2) and 556.55(3.04 × 10 −3). The energies and relative intensities of the other gamma rays in the decay are also measured.

Nuclear structure in 133,135Xe and 133,135Cs

The relative gamma-ray intensities of transitions depopulating the 133,135Xe ground and isomeric states as well as the 133Ba ground state have been measured using a semiconductor detector. The half-lives of these xenon states have been measured and are found to differ slightly from the reported values. The K internal conversion coefficient of the 133Xe isomeric transition was determined to have the value α K = 7.68±0.25. The 130Te(α, n) 133,133mXe cross sections were measured in a stacked-foil experiment. More than nine new transitions have been observed from unreported levels in 135Cs. New levels are proposed at 408.2, 981.7 and 1062.6 keV. The above results are discussed in terms of the level schemes.

The 63Cu(p, p′γ) 63Cu and 65Cu(p, p′γ) 65Cu reactions at 6.5 MeV

The gamma-ray de-excitation of the first five excited states of 63Cu and 65Cu was studied by means of the 63, 65Cu(p, p′γ) 63, 65Cu reactions. Thin-film targets of copper enriched in 63Cu and 65Cu, respectively, were bombarded with a 6.5 MeV proton beam from the MIT-ONR Van de Graaff generator. A gamma spectrum for each level was obtained in coincidence with protons of the right energy, as determined by a high-intensity magnetic spectrometer designed in this laboratory. Measured relative intensities of the de-excitation gamma rays were not corrected for angular correlation effects. The experimental results provide evidence for spin and parity assignments of 5 2 − to the 1412 keV fourth excited level of 63Cu and to the 1623 keV fourth excited level of 65Cu. A striking over-all similarity in the decay schemesof the two nuclei is observed.