New calculations of cyclotron production cross sections of some positron emitting radioisotopes in proton induced reactions

In this study, new calculations on the excitation functions of ¹³C(p,n)¹³N, ¹⁴N(p,a)¹¹C, ¹⁵N(p,n)¹⁵O, ¹⁶O(p,a)¹³N, ¹⁸O(p,n)¹⁸F, ⁶²Ni(p,n)⁶²Cu, ⁶⁸Zn(p,n)⁶⁸Ga and ⁷²Ge(p,n)⁷² As reactions have been carried out in the 5–40 MeV incident proton energy range. In these calculations, the pre-equilibrium and equilibrium effects have been investigated. The pre-equilibrium calculations involve hybrid model, geometry dependent hybrid model, the cascade exciton model and full exciton model. Equilibrium effects were calculated according to Weisskopf-Ewing model. The calculated results have been compared with experimental data taken from literature.      

Preequilibrium proton and α emission from neutron induced reactions in CsI

Angle integrated energy spectra of protons (plus deuterons) andα particles have been obtained from neutron bombardment of a CsI crystal serving both as detector and target. Measurements were performed for neutron energies between 14 and 32 MeV. An explanation of proton andα yields cannot be given by statistical evaporation, but requires the assumption of a preequilibrium mechanism dominating for projectile energies in excess of 20 MeV. For these neutron energies the hard components of the proton andα particle spectra can be described quantitatively with the hybrid and the quasi free scattering preequilibrium model, respectively.     

Direct versus thermal particle emission in high-energy heavy-ion collisions: Light fragment emission and the ratio of neutron to proton inclusive cross sections

An additive two-component model (direct plus thermal) is used together with an empirical power law for composite particle production to calculate inclusive cross sections for light fragment emission. The ratio of neutron to proton inclusive production is also studied. We compare our results with recent experimental data.     

Theoretical analysis of double-differential neutron emission cross sections for n+56Fe reactions at incident energies of 7-13 MeV

The double-differential neutron emission cross sections for n+56Fe reactions at incident energies of 7-13 MeV at different angles are calculated by the UNF(abbreviation for unified,2009 Version)code,which is based on the unified Hauser-Feshbach and exciton model.The results indicate that the higher the incident energies,the better the results,although there are some discrepancies between the calculated results and the measured data for natural iron.These discrepancies are analyzed in detail in this paper.In addition,the calculated results are also compared with the evaluated results of ENDF/B VII.O and JEFF-3.1.1 near the angle of 90°at incident energies of 8.17 and 11.5 MeV,respectively.     

Theoretical analysis of double-differential neutron emission cross sections for n+~(56)Fe reactions at incident energies of 7-13 MeV

The double-differential neutron emission cross sections for n+⁵⁶Fe reactions at incident energies of 7-13 MeV at different angles are calculated by the UNF (abbreviation for unified, 2009 Version) code, which is based on the unified Hauser-Feshbach and exciton model. The results indicate that the higher the incident energies, the better the results, although there are some discrepancies between the calculated results and the measured data for natural iron. These discrepancies are analyzed in detail in this paper. In addition, the calculated results are also compared with the evaluated results of ENDFB Ⅶ.0 and JEFF-3.1.1 near the angle of 90° at incident energies of 8.17 and 11.5 MeV, respectively.     

New semi‐empirical formulas for calculation of K‐shell ionization cross sections of elements from beryllium to uranium by proton impact

Experimental ionization cross sections for K‐shell by protons in target atoms from beryllium to uranium available in the literature from 1953 to 1999 (nearly 5400 values) are collected to deduce the semi‐empirical K‐shell ionization cross sections by fitting the experimental data normalized to their corresponding theoretical values based on the ECPSSR model which accounts for Coulomb deflection, Energy loss of the projectile, Perturbed Stationary State and Relativistic effects, as a function of the reduced velocity parameter. Our results are compared with the experimental data and with the ECPSSR values and reference ionization cross sections obtained by Paul and Sacher [H. Paul and J. Sacher, At. Data. Nucl. Data. Tables 1989 , 42, 105]. Copyright © 2010 John Wiley & Sons, Ltd.     

Measurement of differential cross sections of neutron-induced deuteron production reactions on carbon from 25 to 52 MeV

The angle-differential cross sections of neutron-induced deuteron production from carbon were measured at six neutron energies from 25 to 52 MeV relative to those of n-p elastic scattering at the China Spallation Neutron Source(CSNS) Back-n white neutron source.By employing the ΔE-E telescopes of the Light-charged Particle Detector Array(LPD A) system at 15.1° to 55.0° in the laboratory system,ratios of the angle-differential cross sections of the ~(12)C(n,xd) reactions to those of the n-p scattering were measured,and then,the angle-differential cross sections of the ~(12)C(n,xd) reactions were obtained using the angle-differential cross sections of the n-p elastic scattering from the JENDL-4.0/HE-2015 library as the standard.The obtained results are compared with data from previous measurements,all of which are based on mono-energic neutrons,the evaluated data from the JENDL-4.0/HE-2015 library and the ENDF-B/Ⅷ.0 library,and those from theoretical calculations based on INCA code and Talys-1.9 code.Being the first white-neutron-source-based systematic measurement of the angle-differential cross sections of neutron-induced deuteron production reactions on carbon in several tens of MeV,the present work can provide a reference to the data library considering the lack of experimental data.     

Experimental study for the production cross sections of positron emitters induced from 12C and 16O nuclei by low-energy proton beams

In proton therapy, positron emitters are induced from ¹²C and ¹⁶O nuclei by protons on the beam path in the patient. Many studies for monitoring positron emitters with beam-induced PET technique have been performed by various groups to verify the proton beam range and the dose in the patient for quality assurance (QA). The QA methods proposed by some groups require accurate production cross sections of the positron emitters produced by protons, especially in the low-energy region. The aim of this study was to develop a method for measuring the production cross sections of positron emitters using standard equipment for proton therapy, and to measure the cross sections of positron emitters produced by low-energy protons and verify them in comparison with data of previous experiments. An 80-MeV proton beam was produced by a synchrotron, and the energy was degraded by polyethylene blocks to obtain various beam energies. The number of protons was estimated from the charge induced in a parallel-plate ionization chamber by protons. Low-energy protons of 14–70 MeV were used to bombard ¹²C-rich and ¹⁶O-rich target materials: namely, polyethylene and gelatinous water. The time-activity curve was then measured by a high-sensitivity PET scanner to extract the number of positron emitters produced in the target. The production cross sections for four reaction channels: ¹⁶O(p, pn)¹⁵O, ¹⁶O(p, 3p3n)¹¹C, ¹⁶O(p, 2p2n)¹³N, and ¹²C(p, pn)¹¹C were then measured. The cross sections for the ¹⁶O(p, pn)¹⁵O reaction channel were consistent with data of previous experiments within the uncertainties, while those of ¹²C(p, pn)¹¹C were generally lower than data of previous experiments. These results suggested that further measurements of the production cross sections will be necessary.