Intermediate Energy Protons Research Articles

Characteristics of radiation belt energetic protons and the movement of their core location in response to geomagnetic disturbances

The energetic protons trapped within the Earth's radiation belt play a crucial role in substantially impacting the behavior of the ring current, which in turn affects the dynamics of energetic particles. Here, we statistically analyze and discuss the global distributions and temporal evolutions of them at energies from 55 keV to 489 keV by using 7-year (2012–2019) observations by radiation belt storm probes ion composition experiment onboard Van Allen Probes. The observations show that low-energy protons (55–148 keV) are distributed at higher L shells (L > 4), which can deeply penetrate during intense storms. The high-energy protons (221–489 keV) are mainly located at L < 4.5 and are comparably stable. Moreover, the core location (i.e., Lc, the L shell with the peak flux) of them is typically energy-dependent and can be displaced due to geomagnetic storms. Detailed analysis reveals that the Lc for low-energy protons is primarily outside the plasmapause location (Lpp), which can rapidly radially move. However, the Lc for high-energy protons is essentially inside Lpp and is harder to move. The Lc for intermediate-energy protons exhibits fluctuations around Lpp, indicating a clear competition between source and loss processes. In addition, alternative mechanisms, such as wave–particle interactions, are primarily responsible for the gradual variation of them after storms. Our study provides the total configuration of the radiation belt energetic protons measured in the Van Allen Probe era, which would be useful for better understanding the variation of trapped particles in the inner magnetosphere.

Ground-based passive generation of Solar Particle Event spectra: Planning and manufacturing of a 3D-printed modulator

The generation of space radiation on Earth is essential to study and predict the effects of radiation on space travelers, electronics, or materials during future long-term space missions. Next to the heavy ions of the galactic cosmic rays, solar particle events play a major role concerning the radiation risk in space, which consist of intermediate-energy protons with broad spectra and energies up to a few hundred MeV. This work describes an approach for the ground-based generation of solar particle events. As a proof of principle, a passive beam modulator with a specific funnel-shaped periodic structure was designed and is used to convert a monoenergetic proton beam into a spectral proton energy distribution, mimicking a solar particle event from August 1972, which is known as one of the strongest recorded SPE events. The required proton beam of 220 MeV can be generated at many existing particle accelerators at research or particle therapy facilities. The planning, manufacturing and testing of the modulator is described step by step. Its correct manufacturing and the characteristics of the solar particle event simulator are tested experimentally and by means of Monte Carlo simulations. Future modulators will follow the same concept with minor adjustments such as a larger lateral extension. As of now, the presented beam modulator is available to the research community to conduct experiments at GSI for exposure under solar particle event conditions. In addition, researchers can use and apply the described concept to design and print their individualized modulator to reproduce any desired solar particle event spectrum or request the presented modulator geometry from the authors.

Single Ionization of Helium by Protons of Various Energies in the Parabolic Quasi-Sturmians Approach

The parabolic quasi-Sturmian approach, recently introduced for the calculation of ion–atom ionizing collisions, is adapted and applied here to the single ionization of helium induced by an intermediate-energy proton impact. Within the method, the ionization amplitude is represented as the sum of the products of the basis amplitudes associated with the asymptotic behavior of the continuum states of the two noninteracting hydrogenic subsystems (e−,He+) and (p+,He+). The p−e interaction is treated as a perturbation in the Lippmann–Schwinger-type (LS) equation for the three-body system (e−,He+,p+). This LS equation is solved numerically using separable expansions for the proton–electron potential. We examine the convergence behavior of the transition amplitude expansion as the number of terms in the representation of the p−e interaction is increased and find that, for some kinematic regimes, the convergence is poor. This difficulty, which is absent for a higher proton energy impact, is solved by varying the momentum of the auxiliary proton plane wave introduced into the basis function. Fully differential cross-sections are calculated and compared with experimental data for 75 keV protons and the results obtained with the 3C model.

Energy and angular distributions of electrons emitted in proton collisions with molecular hydrogen

The description of experimental data on energy and angular distributions of electrons produced in intermediate-energy proton collisions with ${\mathrm{H}}_{2}$ has remained an insurmountable problem for over five decades. A coupled-channel method is developed that provides an accurate solution to the problem. The doubly differential cross section as a function of the energy and angle of the ejected electron is calculated. Excellent agreement between the present results and the experimental data is found. This breakthrough in theoretical modeling of differential ionization in $p+{\mathrm{H}}_{2}$ collisions paves the way to accurate description of the recent kinematically complete experiments.

Nuclear matter distributions in the neutron-rich carbon isotopes 14−17C from intermediate-energy proton elastic scattering in inverse kinematics

The absolute differential cross sections for small-angle proton elastic scattering off the nuclei 12,14−17C have been measured in inverse kinematics at energies near 700 MeV/u at GSI Darmstadt. The hydrogen-filled ionization chamber IKAR served simultaneously as a gas target and a detector for the recoil protons. The projectile scattering angles were measured with multi-wire tracking detectors. The radial nuclear matter density distributions and the root-mean-square nuclear matter radii were deduced from the measured cross sections using the Glauber multiple-scattering theory. A possible neutron halo structure in 15C, 16C and 17C is discussed. The obtained data show evidence for a halo structure in the 15C nucleus.

An accelerator facility for intermediate energy proton irradiation and testing of nuclear materials

The bulk irradiation of materials with 10–30 MeV protons promises to advance the study of radiation damage for fission and fusion power plants. Intermediate energy proton beams can now be dedicated to materials irradiation within university-scale laboratories. This paper describes the first such facility, with an Ionetix ION-12SC cyclotron producing 12 MeV proton beams. Samples are mm-scale tensile specimens with thicknesses up to 300 μm, mounted to a cooled beam target with control over temperature. A specialized tensile tester for radioactive specimens at high temperature (500+ °C) and/or vacuum represents the conditions in fission and fusion systems, while a digital image correlation system remotely measures strain. Overall, the facility provides university-scale irradiation and testing capability with intermediate energy protons to complement traditional in-core fission reactor and micro-scale ion irradiation. This facility demonstrates that bulk proton irradiation is a scalable and effective approach for nuclear materials research, down-selection, and qualification.

Intermediate energy proton irradiation: Rapid, high-fidelity materials testing for fusion and fission energy systems

Fusion and advanced fission power plants require advanced nuclear materials to function under new, extreme environments. Understanding the evolution of mechanical and functional properties during radiation damage is essential to the design and commercial deployment of these systems. The shortcomings of existing methods could be addressed by a new technique - intermediate energy proton irradiation (IEPI) - using beams of 10–30 MeV protons to rapidly and uniformly damage bulk material specimens before direct testing of engineering properties. IEPI is shown to achieve high fidelity to fusion and fission environments in both primary damage production and transmutation, often superior to nuclear reactor or typical (low-range) ion irradiation. Modeling demonstrates that high dose rates (0.1–1 DPA/per day) can be achieved in bulk material specimens (100–300 μm) with low temperature gradients and induced radioactivity. The capabilities of IEPI are demonstrated through a 12 MeV proton irradiation and tensile test of 250 μm thick tensile specimens of a nickel alloy (Alloy 718), reproducing neutron-induced data. These results demonstrate that IEPI enables high throughput assessment of materials under reactor-relevant conditions, positioning IEPI to accelerate the pace of engineering-scale radiation damage testing and allow for quicker and more effective design of nuclear energy systems.

Taper angle dependence of the dynamical transmission of several-hundred-keV protons through PC conical capillary

The dynamical transmission of intermediate-energy protons through a polycarbonate (PC) conical capillary with taper angle from 0.48° to 2° are simulated. The results show that for small taper angle of 0.48°, the transmission of 100 keV protons is dominated by the deposited-charge-assisted specular reflection. This reflection effect decreases with the increase of the taper angle. When the taper angle is increased to 2°, the transmission of the protons is mainly influenced by small angle scattering, which is consistent with the experimental data. The asymptotic transmission rate decreases with the increase of the capillary taper angle. These results suggest that the deposited-charge-assisted specular reflection is significant in focusing several-hundred-keV protons.

Ionization and fragmentation of fluorene in collisions with 50-300 keV proton

SynopsisIn this report, we present the study of ionization and fragmentation of fluorene (C13H10) molecule upon intermediate energy proton impact. We have measured the TOF spectra of fluorene molecule to identify various fragmentation channels. We have also measured the projectile energy dependence of single and double ionization of fluorene molecule.

Projectile Coherence Effects in Simple Atomic Systems

Recent studies of projectile coherence effects in ion-atom collisions are presented. For intermediate-energy proton collisions an extensive literature provides strong support for the importance of such effects. In this regime coherence effects are now used as a tool to study the few-body dynamics very sensitively. In contrast, for high-energy ion impact the literature is much sparser and here an important role of coherence effects cannot be regarded as being established. In this context, a recent claim that in COLTRIMS experiments the coherence properties are determined only by the target beam is rebutted.

Nuclear-matter distribution in the proton-rich nuclei 7Be and 8B from intermediate energy proton elastic scattering in inverse kinematics

Absolute differential cross sections for elastic p7Be and p8B small-angle scattering were measured in inverse kinematics at an energy of 0.7 GeV/u at GSI Darmstadt. The hydrogen-filled ionization chamber IKAR was used as an active target to detect the recoil protons. The projectile tracking and isotope identification were performed with multi-wire proportional chambers and scintillation detectors. The measured cross sections were analysed using the Glauber multiple-scattering theory. The root-mean-square (rms) nuclear matter radii Rm=2.42(4) fm for 7Be and Rm=2.58(6) fm for 8B were obtained. The radial density distribution deduced for 8B exhibits a proton halo structure with the rms halo radius Rh=4.24(25) fm. A comparison of the deduced experimental radii is displayed with existing experimental and theoretical data.

Dirac phenomenological analyses for the proton scatterings from nickel isotopes

Relativistic Dirac coupled channel analyses are performed phenomenologically using an optical potential model for the intermediate energy proton inelastic scatterings from nickel isotopes, 58Ni and 60Ni. The first-order rotational collective model is used for the transition optical potentials to describe the low-lying excited collective states of the ground state rotational band. The complicated Dirac coupled channel equations are solved phenomenologically by varying the optical potential and the deformation parameters to reproduce the experimental data, using a computer program that uses a sequential iteration method. The channel-coupling effects of the multistep transition process for the excited states of the ground state rotational band are found to be strong and lead the calculation results to better agreement with the experimental data when the channel coupling between the excited states is added in the calculation. The Dirac equations are reduced to the second-order differential equations to obtain the Schrödinger equivalent effective central and spin–orbit optical potentials, and the obtained effective potentials are analyzed.

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

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 $^{\text{nat}}$Nb(p,x) and $^{\text{nat}}$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 $^{\text{nat}}$Cu(p,x)$^{56}$Co, $^{\text{nat}}$Cu(p,x)$^{62}$Zn, and $^{\text{nat}}$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 $^{\text{nat}}$Nb(p,x)$^{82\text{m}}$Rb reaction, and of the independent cross sections for $^{\text{nat}}$Cu(p,x)$^{52\text{g}}$Mn and $^{\text{nat}}$Nb(p,x)$^{85\text{g}}$Y in the 40-90 MeV region. The effects of $^{\text{nat}}$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. \emph{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 $^{\text{nat}}$Nb(p,x) and $^{\text{nat}}$Cu(p,x) reactions.

Halo structure of 8B determined from intermediate energy proton elastic scattering in inverse kinematics

The absolute differential cross section for small-angle proton elastic scattering on the proton-rich 8B nucleus has been measured in inverse kinematics for the first time. The experiment was performed using a secondary radioactive beam with an energy of 0.7 GeV/u at GSI, Darmstadt. The active target, namely hydrogen-filled time projection ionization chamber IKAR, was used to measure the energy, angle and vertex point of the recoil protons. The scattering angle of the projectiles was simultaneously determined by the tracking detectors. The measured differential cross section is analyzed on the basis of the Glauber multiple scattering theory using phenomenological nuclear-density distributions with two free parameters. The radial density distribution deduced for 8B exhibits a halo structure with the root-mean-square (rms) matter radius Rm=2.58(6) fm and the rms halo radius Rh=4.24(25) fm. The results on 8B are compared to those on the mirror nucleus 8Li investigated earlier by the same method. A comparison is also made with previous experimental results and theoretical predictions for both nuclei.

Density reconstruction based on energy loss in proton radiography

A method of using energy loss to reconstruct the density is presented with protons at intermediate and high energy for proton radiography, and the equation and condition of density reconstruction are given based on the Bethe-Bolch formula. For the intermediate and high energy proton radiography, the stopping power of material is changed slowly within a certain energy range, and the stopping power can be approximated as a constant, then the multi-material object can be reconstructed by using the energy loss information. In this work, the protons at 1.6 GeV which can be obtained by China Spallation Neutron Source are used in the radiography, and the energy loss information is used in the reconstruction, and the Geant 4 is applied to Monte Carlo simulation. From the theoretical calculation and the Geant4 simulation, it can be seen that when the protons energy ranges from 1.45 GeV to 1.6 GeV the stopping power of material can be approximately constant, and the relative change of material stopping power is less than 1%, thus the stopping power of material is only dependent on the incident proton energy, and the density of the multimaterial object can be reconstructed by the energy loss information. The proton scanning imaging system which can avoid blurring image caused by multiple coulomb scattering at the receiving plane is used in the proton radiography to obtain the energy loss information. In the imaging system, two energy detectors are employed to record the incident energy and exit energy of protons, the object is scanned by the protons with a certain step length, and the object is rotated 180 or 360. The energy loss distribution of the object can be obtained by the scanning imaging system, and the density of the object can be reconstructed by solving corresponding equations. The Geant 4 is used to simulate the proton scanning imaging system. In the simulation, the object is the scaling french test object (FTO) that the areal density is 113 g/cm2, the protons are monoenergetic at 1.6 GeV, the scanning interval is 0.5 mm, and the rotation angle is 0.9. The results of the density reconstruction of the scaling FTO are in good agreement with the true values.

Taking into Account the Centre-of-Mass Correlations in the Cross Sections for Elastic Scattering of Intermediate Energy Protons on the Exotic Nuclei 6He and 8He

We calculate the differential cross sections for proton elastic scattering on the exotic halo nuclei $^6$He and $^8$He at energies around $\sim$0.7 GeV at the momentum transfers squared up to 0.30 (GeV/$c$)$^2$ and investigate the influence of the nucleon centre-of-mass correlations on the calculated cross sections. In particular, we show that the approximate account of the centre-of-mass correlations used previously considerably overestimates the cross sections at high values of the momentum transfer.

Investigation of selenium compounds as targets for 76,77Br production using protons of energies up to 34 MeV

Abstract Selenium compounds of Zn, Sn and Cu were prepared using a conventional sintering method and the phase composition of each compound was investigated using X-ray diffraction. The compounds prepared were tested under variable irradiation and separation conditions for 76,77Br production. The activity of 77Br was measured as a function of proton beam current within the range 2–15 μA and the thermal stability of the irradiated compound was investigated. The results showed that the compounds ZnSe and Cu2Se are thermally more stable in comparison to the SnSe. The effects of several factors, such as temperature, gas flow rate and separation time, were studied to obtain the maximum separation yield of radiobromine by the dry distillation method. The data showed that the compound Cu2Se is the most suitable target for proton irradiation to produce 76,77Br at energies up to 20 MeV. A simplified method was used to prepare also CuSe, which was tested in irradiations with intermediate energy protons of beam currents up to 10 μA. The data of a typical production run using 17 MeV protons and the Cu2Se target are reported.

Electron scattering and reactions from exotic nuclei

The SCRIT and FAIR/ELISe experiments are the first to attempt to measure directly electron scattering form factors from nuclei far from stability. This will give direct information for the (one-body) charge densities of those systems, about which there is little information available. The SCRIT experiment will be taking data for medium-mass exotic nuclei, while the electron-ion collider at ELISe, when constructed, will be able to measure form factors for a wide range of exotic nuclei, as available from the radioactive ion beams produced by the FAIR experiment. Other facilities are now being proposed, which will also consider electron scattering from exotic nuclei at higher energies, to study short-range correlations in exclusive reactions. This review will consider all available information concerning the current status (largely theoretical) of electron scattering from exotic nuclei and, where possible, complement such information with equivalent information concerning the neutron densities of those exotic systems, as obtained from intermediate energy proton scattering. The issue of long- and short-range correlations will be discussed, and whether extending such studies to the exotic sector will elicit new information.

Probing the neutron-skin thickness by photon production from reactions induced by intermediate-energy protons

Photon from neutron-proton bremsstrahlung in p+Pb reactions is examined as a potential probe of the neutron-skin thickness in different centralities and at different proton incident energies. It is shown that the best choice of reaction environment is about 140MeV for the incident proton and the 95\%-100\% centrality for the reaction system since the incident proton mainly interacts with neutrons inside the skin of the target and thus leads to different photon production to maximal extent. Moreover, considering two main uncertainties from both photon production probability and nucleon-nucleon cross section in the reaction, I propose to use the ratio of photon production from two reactions to measure the neutron-skin thickness because of its cancellation effects on these uncertainties simultaneously, but the preserved about 13\%-15\% sensitivities on the varied neutron-skin thickness from 0.1 to 0.3fm within the current experimental uncertainty range of the neutron-skin size in $^{208}$Pb.

Evaluation of A-dependence of cross-sections for light charged particle production in proton induced reactions at intermediate energies

Abstract Proton-, deuteron-, triton-, 3He, and α-particle production cross-sections were evaluated for proton induced reactions for 278 stable target nuclei with an atomic number from 3 to 83 for a number of incident proton energies from 62 to 1200 MeV using available experimental data and results of model calculations. Data obtained can be used for the evaluation of gas production cross-sections and gas production rates in reactions induced by intermediate energy protons. An example of the use of the data is given for 9Be(p,x) reactions.