Measurement Of Isomeric Yield Ratios Research Articles

Measurement of isomeric yield ratios of 119m,gTe in the 60 and 70 MeV bremsstrahlung induced reaction of natTe

The isomeric yield ratio i.e. the yield ratio of high to low spin state (IR=Yh/Yl) of 119m,gTe in the natTe(γ,xn) reaction at the bremsstrahlung end-point energies (Ee) of 60-, and 70-MeV were measured for the first time by using an off-line gamma-ray spectrometric technique. The bremsstrahlung energies were generated by impinging pulsed electron energies of 60-, and 70-MeV on a thin W-target at the Pohang Accelerator Laboratory. The present data at 60 and 70-MeV and similar literature data at other energies shows that the IR values of 119m,gTe increases sharply from 10 MeV to 18 MeV, which indicates the role of excitation energy. Thereafter it increases marginally due the opening of other reaction channels, which indicates the partition of excitation energy in different reaction channels.

Applying machine learning methods for the analysis of two-dimensional mass spectra

In a measurement of isomeric yield-ratios in fission, the Phase-Imaging Ion-Cyclotron-Resonance technique, which projects the radial motions of ions in the Penning trap (JYFLTRAP) onto a position-sensitive micro-channel plate detector, has been applied. To obtain the yield ratio, that is the relative population of two states of an isomer pair, a novel analysis procedure has been developed to determine the number of detected ions in each state, as well as corrections for the detector efficiency and decay losses. In order to determine the population of the states in cases where their mass difference is too small to reach full separation, a Bayesian Gaussian Mixture model was implemented. The position-dependent efficiency of the micro-channel plate detector was calibrated by mapping it with ^{133}Cs^+ ions, and a Gaussian Process was trained with the position data to construct an efficiency function that could be used to correct the recorded distributions. The obtained numbers of counts of excited and ground-state ions were used to derive the isomeric yield ratio, taking into account decay losses as well as feeding from precursors.

Measurement of isomeric yield ratios of 86m,gY and 87m,gY in the quasi-monoenergetic neutron induced reactions of 89Y

The isomeric yield ratios (IR) of 86m,gY and 87m,gY were measured in the 23 to 37 MeV quasi-monoenergetic neutron induced reaction of 89Y by using an off-line γ-ray spectrometric technique. The IR values in the 89Y(n,xn) reactions were also calculated using the TALYS 1.8 code and found to be in good agreement for 87m,gY but slightly less for 86m,gY. The IR values of 86m,gY and 87m,gY from the present work in the 89Y(n,xn) reactions were compared with the literature data in the 89Y(γ,xn), 89Y(p,x) and 89Y(α,x) reactions. It was found that the IR values of 86m,gY and 87m,gY in all these reactions increase with excitation energy. At the same excitation energy, the IR values are higher in the alpha induced reaction than in the proton, neutron and photon induced reactions due to higher input angular momentum in the former than in the later. These two observations indicate the role of entrance parameters. However, it is surprising to see that at the same excitation energy, the IR values of 86m,gY and 87m,gY in the 89Y(n,xn) reaction are nearly constant and significantly higher than in the 89Y(γ,xn) reaction.

Measurement of fission yields and isomeric yield ratios at IGISOL

Data on fission yields and isomeric yield ratios (IYR) are tools to study the fission process, in particular the generation of angular momentum. We use the IGISOL facility with the Penning trap JYFLTRAP in Jyväskylä, Finland, for such measurements on 232Th and natU targets. Previously published fission yield data from IGISOL concern the 232Th(p,f) and 238U(p,f) reactions at 25 and 50 MeV. Recently, a neutron source, using the Be(p,n) reaction, has been developed, installed and tested. We summarize the results for (p,f) focusing on the first measurement of IYR by direct ion counting. We also present first results for IYR and relative yields for Sn and Sb isotopes in the 128-133 mass range from natU(n,f) based on γ-spectrometry. We find a staggering behaviour in the cumulative yields for Sn and a shift in the independent fission yields for Sb as compared to current evaluations. Plans for the future experimental program on fission yields and IYR measurements are discussed.

Measurement of isomeric yield ratios for the heavy cerium isotopes in the (γ,n) reactions

Measurement of isomeric yield ratios for the heavy cerium isotopes in the (γ,n) reactions

Measurement of isomeric yield ratios of 99m,g;101m,g;102m,gRh in the natPd(γ,pxn) reactions with the bremsstrahlung end-point energies of 50–70 MeV

The isomeric yield ratios of 99m,gRh, 101m,ggRh, and 102m,gRh isomeric pairs produced from the natPd(γ,pxn) reactions were measured with the bremsstrahlung end-point energies of 50-, 55-, 60-, 65-, and 70-MeV at the 100MeV electron linac of the Pohang Accelerator Laboratory, Korea. The measurements were carried out with the activation method in combination with off-line γ-ray spectrometry. In order to improve the accuracy of the activity measurements, the separation of the overlapping γ-rays and the necessary corrections for the counting losses were made. The new experimental results are compared with the theoretical values of the TALYS-1.6 code.

Measurement of isomeric yield ratios of 197m,gPt and 190m2,g+m1Ir from the 198Pt(γ,n) and natPt(γ,xn1p) reactions induced by 55-, 60-, and 65-MeV bremsstrahlung

We have measured the isomeric yield ratios of 197m,gPt from the 198Pt(γ,n) reaction and 190m2,g+m1Ir from the natPt(γ,xn1p) reaction, induced with the bremsstrahlung end-point energies of 55-, 60-, and 65-MeV. The measurements were carried out by the activation method in combination with the direct γ-spectrometry. The experiments were performed at the 100MeV electron linac of the Pohang Accelerator Laboratory (PAL). The obtained results at 55-, 60- and 65-MeV for the 197m,gPt from the 198Pt(γ,n) reaction are 0.166±0.012, 0.174±0.011, and 0.175±0.011, whereas for the 190m2,g+m1Ir from the natPt(γ,xn1p) reaction are 0.072±0.006, 0.084±0.006 and 0.087±0.006, respectively. The present results are measured for the first time over the investigated energy range. The present data are compared with the similar literature data at lower energy to examine the role of excitation energy.

Measurement of isomeric yield ratios of 86m,gY, 87m,gY, and 89m,gZr in the photonuclear reactions of 89Y and natZr at the end-point bremsstrahlung energies of 45 and 55 MeV

The isomeric yield ratios of 86m,gY, 87m,gY, and 89m,gZr produced in the reactions of 89Y and natZr with end-point bremsstrahlung energies of 45 and 55MeV have been determined by activation and off-line γ-ray spectrometric technique using the 100MeV electron linac at Pohang Accelerator Laboratory (PAL), Korea. The present data along with literature data show that the isomeric yield ratios of 86m,gY and 87m,gY in the 89Y(γ,xn) and natZr(γ,x) reactions and those of 89m,gZr in the natZr(γ,x) reaction increase with the end-point bremsstrahlung energy, which indicates the effect of excitation energy. However, the increase trend of the isomeric yield ratios of 87m,gY in the 89Y(γ,xn) reaction and 89m,gZr in the natZr(γ,x) reaction are very fast from the threshold value to 30MeV due to the giant dipole resonance effect. After certain point of excitation energy, the isomeric yield ratios increase slowly with the end-point bremsstrahlung energy due to the partition of energy in different reaction channels. It was also observed that in both the reactions, the isomeric yield ratios of 87m,gY are always higher than those of 86m,gY. This is because of more number of particle emission and thus the disposition of more excitation energy needed for the formation of 86m,gY compared to 87m,gY.

Accurate Fission Data for Nuclear Safety

The Accurate fission data for nuclear safety (AlFONS) project aims at high precision measurements of fission yields, using the renewed IGISOL mass separator facility in combination with a new high current light ion cyclotron at the University of Jyväskylä. The 30 MeV proton beam will be used to create fast and thermal neutron spectra for the study of neutron induced fission yields. Thanks to a series of mass separating elements, culminating with the JYFLTRAP Penning trap, it is possible to achieve a mass resolving power in the order of a few hundred thousands. In this paper we present the experimental setup and the design of a neutron converter target for IGISOL. The goal is to have a flexible design. For studies of exotic nuclei far from stability a high neutron flux (1012 neutrons/s) at energies 1 – 30 MeV is desired while for reactor applications neutron spectra that resembles those of thermal and fast nuclear reactors are preferred. It is also desirable to be able to produce (semi-)monoenergetic neutrons for benchmarking and to study the energy dependence of fission yields. The scientific program is extensive and is planed to start in 2013 with a measurement of isomeric yield ratios of proton induced fission in uranium. This will be followed by studies of independent yields of thermal and fast neutron induced fission of various actinides.

Measurement of isomeric yield ratios of the 104m,g,106m,gAg in the 45- and 55-MeV bremsstrahlung induced reactions of natural silver

The isomeric yield ratios for the natAg(γ,xn)104m,g,106m,gAg reactions with the end-point bremsstrahlung energies of 45- and 55-MeV have been determined by the off-line γ-ray spectrometric technique using 100 MeV electron linac at Pohang accelerator laboratory, Korea. The present data were compared with literature data in comparable compound nucleus from the natAg(γ,xn), natPd(p,xn), and 103Rh(α,xn) reactions to examine the effects of an excitation energy and an input angular momentum. It is observed that the isomeric yield ratios of 104,106Ag in natAg(γ,xn), natPd(p,xn) and 103Rh(α,xn) reactions increase with the end-point bremsstrahlung energy, proton and alpha energy, which indicate the role of excitation energy. It is also found that for the similar compound nucleus at same excitation energy, the isomeric yield ratio of 104m,gAg is higher in the natPd(p,xn) and 103Rh(α,xn) reactions than those in natAg(γ,xn) reaction, which indicate the effect of an input angular momentum.

Measurement of isomeric yield ratios for the natHo(γ,xn)164m,g;162m,gHo reactions in the bremsstrahlung energy region from 45 to 65 MeV

We have measured the isomeric yield ratios for the 164m,gHo and the 162m,gHo isomeric pairs formed via photonuclear reactions 165Ho(γ,n)164m,gHo and 165Ho(γ,3n)162m,gHo in the bremsstrahlung energy region from 45 to 65 MeV in steps of ∆E = 5 MeV by the activation method. The induced γ-activities of the irradiated holmium foils were measured by a coaxial high-purity germanium detector coupled to a PC-based multichannel analyzer. In order to improve the accuracy of the experimental results the necessary corrections were made. The experimental results at bremsstrahlung energies of 45, 50, 55, 60, and 65 MeV are 0.408 ± 0.027, 0.413 ± 0.027, 0.427 ± 0.029, 0.452 ± 0.032, and 0.448 ± 0.031 for the 164m,gHo isomeric pair, and 0.587 ± 0.041, 0.624 ± 0.044, 0.652 ± 0.045, 0.637 ± 0.045, and 0.668 ± 0.046 for the 162m,gHo isomeric pair, respectively. The present results are the first measurements at bremsstrahlung energies just above the giant dipole resonance region. The obtained results confirm the dependence of isomeric ratios on the incident photon energy as observed in some earlier experiments.

Measurement of isomeric yield ratios for the 44m,gSc isomeric pairs produced from 45Sc and natTi targets at 50-, 60-, and 70-MeV bremsstrahlung

We measured the isomeric yield ratios for the 44m,gSc isomeric pairs produced from different reaction channels 45Sc(γ,n)44m,gSc and natTi(γ,xnp)44m,gSc by using the activation method and γ-ray spectroscopic methods at 50-, 60-, and 70-MeV bremsstrahlung energies. The high-purity natural Sc and Ti foils in disc shape were irradiated with uncollimated bremsstrahlung beams generated from an electron linear accelerator at Pohang Accelerator Laboratory. The induced activities in the irradiated foils were measured by the high-resolution γ-ray spectrometric system which consists of a high-purity Germanium detector and a multichannel analyzer. In order to improve the accuracy of the experimental results the necessary corrections were made in the γ-ray activity measurements and data analysis. The measured isomeric yield ratios for the 45Sc(γ,n)44m,gSc reaction are 0.20 ± 0.02, 0.21 ± 0.02, and 0.21 ± 0.02 and those for the natTi(γ,xnp)44m,gSc reaction are 0.063 ± 0.012, 0.079 ± 0.014, and 0.124 ± 0.022 at 50-, 60-, and 70-MeV bremsstrahlung energies, respectively. The obtained results are compared with the corresponding values found in the literature. We observed that the isomeric yield ratios for the 45Sc(γ,n)44m,gSc reaction increase rapidly with the increasing bremsstrahlung energies from the reaction threshold up to giant resonance region, and then those are almost constant in the energy range from about 30 to 2.5 GeV. The isomeric yield ratios for the natTi(γ,xnp)44m,gSc reaction increase with increasing bremsstrahlung energies in a wide range of bremsstrahlung energies from 50 to 2.5 GeV.

Measurement of isomeric yield ratios in natIn and natSn with 50, 60, and 70 MeV bremsstrahlung photons

The isomeric yield ratios of 110m,gIn, 111m,gIn, 112m,gIn, and 117m,gIn were measured in photonuclear reactions for the end point energies of bremsstrahlung about 50, 60, and 70 MeV. The isomeric yield ratios were determined from the induced activities in the irradiated samples using a high-purity germanium detector equipped with a multichannel analyzer. The results are the first measurements in this energy region. Experimental values of the isomeric yield ratios are compared with the corresponding values found in the literature.

Measurement of isomeric yield ratios for 90Zr(γ, n) 89m,gZr, natZr(γ, xn1p) 86m,gY, and 89Y(γ, xn) 87m,g,86m,gY reactions with 50-, 60-, and 70-MeV bremsstrahlung

We measured the isomeric yield ratios in the photonuclear reactions of natZr(γ, n) 89m,gZr, natZr(γ, xn1p) 86m,gY, and 89Y(γ, xn) 87m,g,86m,gY by the activation method. The high-purity natural Zr and Y metallic foils in disc shape were irradiated with uncollimated bremsstrahlung beams of 50-, 60-, and 70-MeV generated from an electron linear accelerator at Pohang Accelerator Laboratory. The induced activities in the irradiated foils were measured by the high-resolution γ-ray spectrometric system consisting of a high-purity germanium detector and a multichannel analyzer. The obtained isomeric yield ratios in the formation of 89m,gZr, 87m,gY, and 86m,gY are compared with the corresponding values found in the literature. The measured isomeric yield ratios at the bremsstrahlung energies of 50-, 60-, and 70-MeV are the first measurement except 87Y at 50-MeV bremsstrahlung.

Measurement of Isomeric Yield Ratios in Nuclear Reactions

Measurement of Isomeric Yield Ratios in Nuclear Reactions