Intermediate Energy Protons Research Articles

Target Mass Dependency of Light Mass Fragment Energy Spectra for Intermediate Energy Proton Induced Reactions

Double differential fragment production cross sections were measured for intermediate energy protons using a specially designed Bragg Curve Counter. Target mass dependency of Lithium and Beryllium energy spectra were obtained by fitting of the equation describing a Maxwellian distribution with a Coulomb barrier effect. Two parameters of the equation, s and T, which corresponds to absolute normalization and temperature of the Maxwellian respectively, show clear dependency on target mass.

Dynamic transmission of intermediate energy proton through polycarbonate nanocapillary

Dynamic transmission of 10~120keV proton through polycarbonate nanocapillary were observed. 10keV proton is guided along the capillary and the charge purity is about 80%. But protons with energies near 100keV show remarkable differences. The charge purity of them is also high, but the transmitted particles move along the direction of incident beam, while not along the capillary axis.

Long-term residual radioactivity in an intermediate-energy proton linac

A new 160MeV H− linear accelerator (LINAC4) is being installed at CERN to replace the present 50MeV LINAC2 as proton injector of the PS Booster (PSB). During operation, the accelerator components will be activated by the beam itself and by the secondary radiation field. Detailed Monte Carlo simulations, for various beam energies and several decay times, were performed to predict the residual radioactivity in the main accelerator components and to estimate the residual dose rate inside the tunnel. The results of this study will facilitate future dismantling, handling and storage of the activated parts and consequently minimize the radiation dose to involved workers. The component activation was also compared with the exemption limits given in the current Swiss legislation and to the CERN design values, in order to make predictions for the future storage and disposal of radioactive waste. The airborne radioactivity induced by particles escaping the beam dump and the activation of the beam dump cooling water circuit were also quantified. The aim of this paper is to provide data of sufficiently general interest to be used for similar studies at other intermediate-energy proton accelerator facilities.

Photon and proton induced fission on heavy nuclei at intermediate energies

We present an analysis of fission induced by intermediate energy protons or photons on actinides. The 660 MeV proton induced reactions are on 241 Am, 238 U, and 237 Np targets and the Bremmstrahlung-photons with end-point energies at 50 MeV and 3500 MeV are on 232 Th and 238 U targets. The study was performed by means of the Monte Carlo simulation code CRISP. A multimodal fission extension was added to the code within an approach which accounts for the contribution of symmetric and asymmetric fission. This procedure allowed the investigation of fission cross sections, fissility, num- ber of evaporated nucleons and fission-fragment charge distributions. The comparison with experimental data show a good agreement between calculations and experiments.

Superasymmetric fission of heavy nuclei induced by intermediate-energy protons

In this work we present the results for the investigation of intermediate-mass fragment (IMF) production with the proton-induced reaction at 660 MeV on 238U and 237Np target. The data were obtained with the LNR Phasotron U-400M Cyclotron at Joint Institute for Nuclear Research (JINR), Dubna, Russia. A total of 93 isotopes, in the mass range of 30 < A < 200, were unambiguously identified with high precision. The fragment production cross sections were obtained by means of the induced-activation method in an off-line analysis. Mass-yield distributions were derived from the data and compared with the results of the simulation code CRISP for multimodal fission. A discussion of the super-asymmetric fragment production mechanism is also given.

Excitation of high-spin nuclear isomeric states by intermediate energy protons at the Moscow Meson Factory of the Russian Academy of Sciences’ Institute for Nuclear Research

Isomeric ratios of reaction products obtained by irradiating 197Au, 181Ta, and 93Nb targets by protons with energies of 143–325 MeV are measured via activation. The results do not agree with measurements of stopped ions [1], even though the theoretical model in [2] predicted the same mechanism for the formation of high-spin isomers in these reactions. The obtained isomeric ratios in reactions with protons of intermediate energy are 10–100 times lower than the theoretical values; consequently, the excitation mechanisms of high-spin isomers in reactions with protons and stopped ions are different.

Dosimetry and microdosimetry of 10–220 MeV proton beams with CR-39 and their verifications by calculation of reaction cross sections using ALICE, TALYS and GEANT4 codes

Abstract High- and intermediate-energy protons are not able to directly form a track in a CR-39 etch detector (TED). Such detectors, however, can be used for the detection and dosimetry of the beams of these particles through the registration of secondary charged particles with sufficiently high values of linear energy transfer (LET). High-energy protons (72–220 MeV) and Intermediate-energy protons (10–30 MeV) with low LET values ranging from 1.1 down to 0.4 keV/μm and 5.87 down to 2.40 keV/μm, respectively are considered in this study. It seems to be sufficient to create secondary particles, although the LET values are low. This phenomenon can modify the characteristics of the energy transfer process due to these particles, which should be taken into account when such particles are used for radiobiology studies or for radiotherapy. The importance of these secondary particles was investigated experimentally by means of an LET spectrometer based on a chemically etched track detector in which the tracks of the primary protons are not revealed. Experiments were performed with proton beams available at the Nuclear Research Center for Agriculture and Medicine (NRCAM) in Karaj, Iran and at the National Cancer Center (NCC) in Seoul, Korea with protons of primary energies of about 10–30 MeV and 72–220 MeV respectively. The contribution of the secondary particle dose increases as the proton energy decreases. The origin of the secondary particles in interactions with protons having high and intermediate energies due to various nuclear reactions was calculated by the both ALICE and TALYS computer codes. The secondary microdosimetry doses were also calculated by GEANT4 code. There is large discrepancy between experimental and calculated results in low proton energies. It has been verified that there is a good correlation between the experimentally obtained results and the reaction cross sections predicted by ALICE and TALYS codes.

Interaction of intermediate-energy protons with 20Ne and 24Mg nuclei within the multiple-scattering model

Observables of the elastic and inelastic scattering of 800- and 250-MeV protons on 20Ne and 24Mg nuclei were calculated on the basis of the theory of multiple diffractive scattering and the dispersive α-cluster model. The 20Ne and 24Mg nuclei were assumed to consist of a core (16O nucleus) and additional alpha-particle clusters, which could be situated with the highest probability both in the vicinity of the center of mass of the core and outside the core. The multiparticle densities of these nuclei and single-particle nucleon-distribution densities as obtained from the dispersive α-cluster model were used in the calculations. The differential cross sections and polarizations for elastic and inelastic p 20Ne and p 24Mg scattering at the energy of 800 MeV are in better agreement with experimental data than the analogous calculations at the energy of 250 MeV. The spin-rotation functions calculated in the singleparticle approximation for elastic p 20Ne and p 24Mg scattering at these two energy values differ qualitatively from their counterparts calculated on the basis of the dispersive α-cluster model.

A new experimental approach to investigate intermediate-energy proton elastic scattering and breakup reactions on exotic nuclei in inverse kinematics

We report on a new experimental setup for the investigation of proton induced reactions on exotic nuclei in inverse kinematics. It was installed and successfully used in the scattering study of intermediate-energy protons ( ∼ 700 MeV / u ) on neutron-rich nuclei 6,8He produced with the FRagment Separator (FRS) at the GSI facility, Darmstadt. A new pure liquid-hydrogen target was successfully adapted allowing to obtain low-background data as compared to commonly used (CH 2) n targets. Absolute differential cross-sections for elastic (p, 6,8He) scattering were obtained at angles corresponding to 0.05 ⩽ | t | ⩽ 0.125 (GeV/ c) 2 of the four-momentum transfer squared (− t) leading to the first diffraction minimum and spanning more than two orders of magnitude. They complement an earlier measurement at smaller angles 0.0025 ⩽ | t | ⩽ 0.05 (GeV/ c) 2 performed at the same energy with an active target. Both data sets agree well in the overlap region t ≈ 0.05 (GeV/ c) 2 and enable a refined and comparative study of the radial distribution of the nuclear matter density.

Comparison of the FLUKA, MCNPX, and PHITS Codes in Yield Calculation of Secondary Particles Produced by Intermediate Energy Proton Beam

The accurate estimation of secondary particle production from thick targets by intermediate energy proton or heavy ion is very important factor to determine source term in radiation shielding design. Three well-proved Monte Carlo codes of the FLUKA, MCNPX, and PHITS were reviewed and benchmarking calculations for proton-induced neutrons and photons have been carried out. Neutron yields from Be, C, Al, and Fe target for 113 and 256 MeV protons were calculated and compared with Meier's experimental data. From those comparisons, the property of above Monte Carlo codes could be observed for application of shielding design. The proton energies of 100, 150, 200 and 230 MeV were reviewed for thick Al, Fe, Cu, and Pb targets to develop the source term. Dependence properties of neutron and photon production yields were found for target materials and target thickness. In this paper, a part of comparison results are presented and the discrepancies and agreements between each code are discussed for various target materials and proton energies.

Systematic Relativistic Analyses of Intermediate Energy Proton Scatterings from Axially-Symmetric Deformed Nuclei

Systematic Relativistic Analyses of Intermediate Energy Proton Scatterings from Axially-Symmetric Deformed Nuclei

THE INTERMEDIATE ENERGY ELASTIC SCATTERING OF PROTONS BY α-CLUSTER 20Ne AND 24Mg NUCLEI

The multiple diffraction scattering theory and the α-cluster model with dispersion have been applied for calculations of the observables for the elastic scattering of intermediate energy protons by 20 Ne and 24 Mg nuclei. The target nuclei are considered as composed of the core (16 O nucleus) and additional α-clusters (one α-cluster for 20 Ne nucleus and a dumb-bell α-cluster configuration for 24 Mg nucleus). Taking into account the α-cluster configuration of the core, it was supposed that the additional α-cluster or center of mass of the dumb-bell are arranged with the most probability inside or outside of the core. The calculated observables for the elastic p–20 Ne and p–24 Mg scattering are in agreement with the existing experimental data. The influence of the deformed core contribution on the behavior of the calculated observables also is tested.

Intermediate-energy proton- 20Ne elastic scattering in the $ \alpha$ + 16O model of 20Ne

The ground state of 20Ne is described as the clustering structure of $ \alpha$ + 16 O . The cluster wave function with an analytical and simple form is presented. Based on this model, the intermediate-energy proton- 20Ne elastic scattering is calculated and compared with the experimental data.

Intermediate energy proton knockout to the “island of inversion” isotopeMg31

The ``island of the inversion'' isotope $^{31}\mathrm{Mg}$ was investigated using an intermediate energy proton knockout reaction from $^{32}\mathrm{Al}$ at 90 MeV/nucleon at the National Superconducting Cyclotron Laboratory. A negligible cross section to the ground state supports an intruder-dominant configuration in $^{31}\mathrm{Mg}$. The partial cross sections to excited final states preferentially populate configurations in the $^{31}\mathrm{Mg}$ residues which have no neutron excitations across the $N=20$ shell closure. There is strong evidence that the reaction populates the $3/{2}^{+}$ and $5/{2}^{+}$ states which correspond with the neutron-hole states predicted by the shell model with the model space truncated above the $\mathit{sd}$-shell.

The Edinburgh Ge6 Array; an array of stacked HpGe detectors for observing medium energy pions and protons in tagged photon experiments

The Edinburgh Ge6 Array is an array of 5 stacked HpGe detectors that were designed to detect intermediate energy pions and protons with energy resolutions comparable to magnetic spectrometers but with considerably larger solid angles and energy range acceptances. The array was designed primarily to be used in conjunction with tagged photon spectrometers to study photonuclear reactions. In this article we present results from a test measurement carried out using a secondary beam of π + -particles at the Paul Scherrer Institute, Villigen, Switzerland and describe a pilot study of the 6 Li ( γ , π + ) 6 He reaction carried out using tagged photons at the Institut für Kernphysik, Mainz, Germany.

New cross section measurements for production of the positron emitters 75Br and 76Br via intermediate energy proton induced reactions

The radionuclides 75 Br and 76 Br are of considerable interest for application in Positron Emission Tomography (PET). For their production so far mostly low-energy or low-yield production processes have been employed. In this work the production of both isotopes was investigated using intermediate energy proton induced reactions and enriched target materials. Cross section data of the 77,78,80 Se(p, xn) 75 Br processes were measured up to 66 MeV and those of the 77,78,80 Se(p, xn ) 76 Br processes up to 85 MeV. The measured excitation functions were compared with calculated results of the nuclear model code ALICE-IPPE. From the experimental excitation curves, thick target yields were calculated. They are fairly high over the investigated intermediate energy ranges. The production possibilities of 75 Br and 76 Br via various routes and the radionuclidic impurities associated with them are discussed.

Spallation and fission products in the (p+ 179Hf) and (p+ natHf) reactions

Production of Hf and Lu high-spin isomers has been experimentally studied in spallation reactions induced by intermediate energy protons. Targets of enriched 179Hf (91%) and natHf were bombarded with protons of energy in the range from 90 to 650 MeV provided by the internal beam of the Dubna Phasotron synchrocyclotron. The activation yields of the reaction products were measured by using the γ-ray spectroscopy and radiochemistry methods. The production cross-sections obtained for the 179m2Hf, 178m2Hf and 177mLu isomers are similar to the previously measured values from the spallation of Ta, Re and W targets. Therefore, the reactions involving emission of only a few nucleons, like (p,p′), (p,p′n) and (p,2pn), can transfer high enough angular momentum to the final residual nuclei with reasonable large cross-sections. A significant gain in the isomeric yields was obtained when enriched 179Hf targets were used. The mass distribution of the residual nuclei was measured over a wide range of masses and the fission-to-spallation ratio could be deduced as a function of the projectile energy. Features of the reaction mechanism are briefly discussed.

THE DYNAMICAL ISOSPIN EFFECT ON PROTON-INDUCED REACTIONS ON Sn ISOTOPES

In this talk we present a model, Improved Quantum Molecular Dynamics (ImQMD05) model incorporated with a Statistical Decay Model (SDM), to describe intermediate energy proton induced spallation reactions. A good agreement with experimental data of double differential cross sections of emitted neutrons is obtained. We further apply this model to study the isospin effect in proton induced spallation reactions on a series Sn isotope targets. We find that the systematic behavior of the reaction cross sections for Sn isotope targets deviates from the empirical expression obtained by fitting the experimental data for proton induced spallation reactions on target nuclei along β-stability line. The extent of the deviation depends on the density dependence of the symmetry energy strongly. We also find an obvious shift of the elastic scattering angular distribution of emitted protons when the symmetry energy is taken into account for neutron-rich Sn isotope targets and the angle shifted strongly depends on the stiffness of the symmetry energy. The attractive effect of the symmetry potential of target on incident proton directly influences the motion of the incident proton leading to strong isospin effect on the reaction dynamics and thus on these reaction observables. We conclude that the measurement of reaction cross sections and the elastic scattering angular distributions in proton induced spallation reactions on Sn isotopes can provide clear constraint for the density dependence of symmetry energy.

Relativistic Analysis of Intermediate Energy Proton Inelastic Scatterings from Heavy Deformed Nuclei

A relativistic coupled channel analysis based on the Dirac equation is performed for inelastic scattering of an intermediate energy proton from a heavy, deformed nucleus by using an optical potential model. In order to describe the low-lying excited states of the deformed nucleus, we used a rotational collective model to get the transition optical potentials. The Dirac coupled-channel equations are solved numerically to calculate the di erential cross sections by using the sequential iteration method. Employing Dirac phenomenology, we vary the optical potential parameters and deformation parameters to reproduce the experimental observables. The theoretical results are observed to agree reasonably well with the inelastic scattering experimental data of 800 MeV p+176Yb, and the importance of the multistep process for inelastic scatterings at a deformed nucleus is con rmed. The e ective Schr odinger-equivalent central and spin-orbit potentials are calculated by reducing the Dirac equation to a Schr odinger-like second-order di erential equation and by comparison them with those of a Schr odinger calculation in which the spin-orbit potential is not included, showing the relatively large strength of a real central potential. Surface-peaked phenomena are not observed for e ective central potentials when the heavy, deformed nucleus of 176Yb is considered.

Total cross sections for fission of heavy nuclei by intermediate-energy protons

The results of measuring total cross sections for proton-induced fission of natPb, 209Bi, 232Th, 233U, 235U, 238U, 237Np, and 239Pu nuclei at proton energies from 200 to 1000 MeV are reported. The measurements were carried out in steps of ≈100 MeV. Complementary fission fragments were detected in coincidence by two parallel-plate avalanche gas counters placed in the beam line on both sides of the thin target close to it. Energy and isotope dependences of the fission cross sections are analyzed.