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Chakravarty, Ν.; Sarkar, Pradip; Ghosh, Sudip Kumar

doi:10.1103/physrevc.45.1171

Cited by 24 publications

(22 citation statements)

References 39 publications

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“…These include the non-standard positron emitters 57 Ni, 64 Cu, 86 Y, 89 Zr, 90 Nb, and the diagnostic agent 82m Rb.In addition to providing a potentially highly-valuable beam monitor, the Nb(p,x) reactions offer an opportunity to study the angular momentum deposition via pre-equilibrium reactions and the spin distribution in g 9/2 subshell nuclei via the observation of isomer-to-ground state ratios. Measurements of isomer-to-ground state ratios have been used for over 20 years to probe the spin distribution of excited nuclear states in the A ≈ 190 region [9,10]. These include the 52m Mn (t 1/2 = 21.1 ± 0.2 m; J π = 2 + ) to 52g Mn…”

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confidence: 99%

Excitation functions for (p,x) reactions of niobium in the energy range of Ep = 40–90 MeV

Voyles

Bernstein

Birnbaum

et al. 2018

Nuclear Instruments and Methods in Physics Research Section B:

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A stack of thin Nb foils was irradiated with the 100 MeV proton beam at Los Alamos National Laboratory's Isotope Production Facility, to investigate the 93 Nb(p,4n) 90 Mo nuclear reaction as a monitor for intermediate energy proton experiments and to benchmark state-of-the-art reaction model codes. A set of 38 measured cross sections for nat Nb(p,x) and nat Cu(p,x) reactions between 40-90 MeV, as well as 5 independent measurements of isomer branching ratios, are reported. These are useful in medical and basic science radionuclide productions at intermediate energies. The nat Cu(p,x) 56 Co, nat Cu(p,x) 62 Zn, and nat Cu(p,x) 65 Zn reactions were used to determine proton fluence, and all activities were quantified using HPGe spectrometry. Variance minimization techniques were employed to reduce systematic uncertainties in proton energy and fluence, improving the reliability of these measurements. The measured cross sections are shown to be in excellent agreement with literature values, and have been measured with improved precision compared with previous measurements. This work also reports the first measurement of the nat Nb(p,x) 82m Rb reaction, and of the independent cross sections for nat Cu(p,x) 52g Mn and nat Nb(p,x) 85g Y in the 40-90 MeV region. The effects of nat Si(p,x) 22,24 Na contamination, arising from silicone adhesive in the Kapton tape used to encapsulate the aluminum monitor foils, is also discussed as a cautionary note to future stacked-target cross section measurements. A priori predictions of the reaction modeling codes CoH, EMPIRE, and TALYS are compared with experimentally measured values and used to explore the differences between codes for the nat Nb(p,x) and nat Cu(p,x) reactions. 2 68 Ga, 82 Rb, and 123 I. These accelerators also produce non-medical radionuclides with commercial value, such as 22 Na, 73 As, 95m Tc, and 109 Cd [3,4]. Novel applications are being explored for several radionuclides whose production methodologies are not established, but their production requires accurate, high-fidelity cross section data. Candidate isotopes to meet these needs have been identified based on their chemical and radioactive decay properties [2,5,6], and a series of campaigns are underway to perform targeted, high-priority measurements of thin-target cross sections and thick-target integral yields. These studies will serve to facilitate the production of clinically relevant quantities of radioactivity.Accurate cross section measurements using activation methods benefit from well-characterized monitor reactions. Currently there is a paucity of such data at intermediate energies, and much of what exists have high uncertainties (>15%). Indeed, the development of new monitor reaction standards and the improved evaluation of existing standards is one of the areas of greatest cross-cutting need for nuclear data [6]. New reactions can expand the available range of options for the monitoring of charged particle beams. This work is an attempt to characterize a new monitor reaction for proton beams in exce...

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confidence: 99%

Excitation functions for (p,x) reactions of niobium in the energy range of Ep = 40–90 MeV

Voyles

Bernstein

Birnbaum

et al. 2018

Nuclear Instruments and Methods in Physics Research Section B:

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“…This saturation effect observed in the γ -ray multiplicity of 12 C + 158 Gd, relative to the same of 20 Ne + 150 Nd at the same CN excitation energy (and slightly different angular momenta), was said to be a clear signature of preequilibrium emissions of neutrons [110,[116][117][118]. The disagreement of theory and measurement for 4 He + 188 Os, 206 Pb may also be attributed to the emissions in the preequilibrium stage [110][111][112][113][114].…”

Section: Discussionmentioning

confidence: 95%

“…3-6 with the exception of 4 He + 188 Os, 206 Pb. The exception is possibly due to emission in the preequilibrium stage [110][111][112][113][114] which will be discussed shortly. It may also be mentioned here that a stronger dissipation in the saddle-to-scission region is expected to give a better fit to the experimental ν pre .…”

Section: Discussionmentioning

confidence: 99%

Detailed statistical model analysis of observables from fusion-fission reactions

2019

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Background:Despite remarkable success of the statistical model (SM) in describing decay of excited compound nuclei (CN), reproduction of the observables from heavy ion-induced fusion-fission reactions is often quite challenging. Ambiguities in choosing the input parameters, lack of clarity about inclusion of various physical effects in the model, and contradictory requirements of input parameters while describing different observables from similar reactions are among the major difficulties of modeling decay of fissile CN. Purpose: This work attempts to overcome the existing inconsistencies by inclusion of important physical effects in the model and through a systematic analysis of a large set of data over a wide range of CN mass (A CN ). Method: The model includes the shell effect in the level density (LD) parameter, shell correction in the fission barrier (B f ), the effect of the orientation degree of freedom of the CN spin (K or ), collective enhancement of level density (CELD), and dissipation in fission. Input parameters are not tuned to reproduce observables from specific reaction(s) and the reduced dissipation coefficient (β) is treated as the only adjustable parameter. Calculated evaporation residue (ER) cross sections (σ ER ), fission cross sections (σ fiss ), and particle, i.e., neutron, proton, and α particle, multiplicities are compared with data covering A CN = 156-248. Results: The model produces reasonable fits to ER and fission excitation functions for all the reactions considered in this work. Pre-scission neutron multiplicities (ν pre ) are underestimated by the calculation beyond A CN ∼ 200. An increasingly higher value of β, in the range of 2-4 × 10 21 s −1 , is required to reproduce the data with increasing A CN . Proton and α-particle multiplicities, measured in coincidence with both ERs and fission fragments, are in qualitative agreement with model predictions. Conclusions:The present work mitigates the existing inconsistencies in modeling statistical decay of the fissile CN to a large extent. Contradictory requirements of fission enhancement-obtained by scaling down the fission barrier to reproduce σ ER or σ fiss and fission suppression realized by introducing dissipation in the fission channel to reproduce ν pre , for similar reactions-have now become redundant. There are scopes for further refinement of the model, as is evident from the mismatch between measured and calculated particle multiplicities in a few cases.

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“…The corresponding IR [ Fig. 2 (a)] is slightly different from the IR for the same isotope obtained via the fusion reaction in the bombardment of gold by α-particles [13]. In [8], excitation functions were measured for the formation of 198 Tl in the ground and isomeric states via fusion reaction 197 Au( 6 He, 5n) 198 Tl.…”

Section: Formation Of Isomers Of Nuclei Near Shells Z = 82 and N = 126mentioning

confidence: 95%

Population of Isomeric States in Fusion and Transfer Reactions with Beams of Radioactive and Weakly Bound Nuclei

Penionzhkevich¹,

Скобелев²,

Науменко³

et al. 2019

Acta Phys. Pol. B

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The influence of the mechanisms of nuclear reactions on the population of isomeric states 44m Sc (6 +), 196m Au (12 −), 198m Au (12 −), 195m Hg (13/2 +), 197m Hg (13/2 +), 198m Tl (7 +), 196m Tl (7 +) obtained in reactions induced by beams of weakly bound and radioactive nuclei 3 He, 6 Li, 6 He are studied. In direct reactions involving cluster transfer, the isomeric ratio is lower than in reactions, where fusion with evaporation of nucleons occurs. In the case of charge exchange reactions with beams of weakly bound nuclei, the isomeric ratios change only slightly. If the reaction Q-value is positive, neutron transfer is observed with high probability in interactions of all weakly bound nuclei with both light and heavy stable target nuclei. Cross sections and their isomeric ratios differ for nucleon stripping and pickup channels owing to the difference in population of excited single-particle and collective states.

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Pre-equilibrium emission effects in the measured isomeric yield ratios in alpha-induced reactions onAu197

Cited by 24 publications

References 39 publications

Excitation functions for (p,x) reactions of niobium in the energy range of Ep = 40–90 MeV

Excitation functions for (p,x) reactions of niobium in the energy range of Ep = 40–90 MeV

Detailed statistical model analysis of observables from fusion-fission reactions

Population of Isomeric States in Fusion and Transfer Reactions with Beams of Radioactive and Weakly Bound Nuclei

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Pre-equilibrium emission effects in the measured isomeric yield ratios in alpha-induced reactions onAu197

Cited by 24 publications

References 39 publications

Excitation functions for (p,x) reactions of niobium in the energy range of Ep = 40–90 MeV

Excitation functions for (p,x) reactions of niobium in the energy range of Ep = 40–90 MeV

Detailed statistical model analysis of observables from fusion-fission reactions

Population of Isomeric States in Fusion and Transfer Reactions with Beams of Radioactive and Weakly Bound Nuclei

Contact Info

Product

Resources

About

Excitation functions for (p,x) reactions of niobium in the energy range of Ep = 40–90 MeV

Excitation functions for (p,x) reactions of niobium in the energy range of Ep = 40–90 MeV