Charge-changing Cross Sections Research Articles

Projectile fragmentation of 471 A MeV 56Fe in polyethylene, carbon and aluminum targets

The total charge changing and partial projectile fragment production cross sections of 471 A MeV 56 Fe on C, Al and CH 2 targets are investigated using CR-39 plastic nuclear track detector. It is found that the total charge changing cross sections are consistent with the prediction from Bradt–Peters semi-empirical formula. The partial cross sections for projectile fragment production agree with the results from other experiments and show a significant enhancement for the fragments with even-Z. Finally, the partial cross sections of fragments with charge 5 ≤ Z ≤ 9 are firstly investigated in present paper. ► Total charge changing cross sections are consistent with theoretical predictions. ► The partial cross sections show an enhancement for the fragments with even-Z. ► The partial cross sections of fragments with charge 5 ≤ Z ≤ 9 are firstly investigated.

Evaluation of nuclear reaction cross-sections and fragment yields in carbon beams using the SHIELD-HIT Monte Carlo code. Comparison with experiments

In light ion therapy, the knowledge of the spectra of both primary and secondary particles in the target volume is needed in order to accurately describe the treatment. The transport of ions in matter is complex and comprises both atomic and nuclear processes involving primary and secondary ions produced in the cascade of events. One of the critical issues in the simulation of ion transport is the modeling of inelastic nuclear reaction processes, in which projectile nuclei interact with target nuclei and give rise to nuclear fragments. In the Monte Carlo code SHIELD-HIT, inelastic nuclear reactions are described by the Many Stage Dynamical Model (MSDM), which includes models for the different stages of the interaction process. In this work, the capability of SHIELD-HIT to simulate the nuclear fragmentation of carbon ions in tissue-like materials was studied. The value of the parameter κ, which determines the so-called freeze-out volume in the Fermi break-up stage of the nuclear interaction process, was adjusted in order to achieve better agreement with experimental data. In this paper, results are shown both with the default value κ = 1 and the modified value κ = 10 which resulted in the best overall agreement. Comparisons with published experimental data were made in terms of total and partial charge-changing cross-sections generated by the MSDM, as well as integral and differential fragment yields simulated by SHIELD-HIT in intermediate and thick water targets irradiated with a beam of 400 MeV u−1 12C ions. Better agreement with the experimental data was in general obtained with the modified parameter value (κ = 10), both on the level of partial charge-changing cross-sections and fragment yields.

Optimizing SHIELD-HIT for carbon ion treatment

The SHIELD-HIT Monte Carlo transport code has been widely used in particle therapy, but has previously shown some discrepancies, when compared with experimental data. In this work, the inelastic nuclear cross sections of SHIELD-HIT are calibrated to experimental data for carbon ions. In addition, the models for nuclear fragmentation were adjusted to experiments, for the partial charge-changing cross section of carbon ions in water. Comparison with fragmentation yield experiments for carbon and neon primaries were made for validation. For carbon primaries, excellent agreement between simulation and experiment was observed, with only minor discrepancies. For neon primaries, the agreement was also good, but larger discrepancies were observed, which require further investigation. In conclusion, the current version SHIELD-HIT10A is well suited for simulating problems arising in particle therapy for clinical ion beams.

Projectile fragmentation of 388 A MeV 20Ne in polyethylene, carbon and aluminum targets

The total charge-changing cross sections and the partial cross sections for the production of projectile fragment are measured in the interactions of 388A MeV 20Ne with aluminum, carbon and polyethylene targets sandwiched with CR-39 plastic nuclear track detectors. The measured total charge-changing cross sections are compared with the prediction using Bradt–Peters semi-empirical formula, and NUCFRG2 and PHITS models. It is shown that the measured experimental results are in good agreement with theoretical model predictions. The partial cross sections for projectile fragment production are consistent with other experimental results at same and nearly the same energies except for fragment with charge Z=5. The partial cross sections of fragment with charge Z=5 from C and Al targets are smaller than other experimental results, and the result from H target is greater than that of other experiments, which can be explained by the limitation of detection efficiency of CR-39. Finally, it is clearly seen that the partial cross sections for projectile fragment production show obvious odd–even effects.

The fragmentation of 20Ne at 400 A MeV

The total charge-changing cross sections and partial cross sections for the production of projectile fragments are measured in the interactions of 400 A MeV 20Ne with aluminum, carbon and polyethylene targets sandwiched with CR-39 plastic nuclear track detectors. The measured total charge-changing cross sections are compared with the predictions using the Bradt-Peters semi-empirical formula, and the NUCFRAG2 and PHITS models. It is shown that the measured experimental results are in good agreement with the theoretical model prediction and other experimental results, and it can be clearly seen that the partial cross sections for fragment production show obvious odd-even effects.

Improvement of charge resolution for trans-iron nuclei (<i>Z</i> ≥ 30) in CR-39 plastic nuclear track detectors using trajectory tracing technique

Charge identification of trans-iron nuclei (nuclear charge: Z = 30) using CR-39 plastic nuclear track detector (PNTD) is essential as a part of an effort to our future mea- surements of the projectile charge changing cross sections for galactic cosmic ray nuclei, but extremely hard. There- fore, an improvement method of the charge resolution (Z ) for 350 MeV/n Ge in CR-39 PNTD using the trajectory trac- ing technique with averaging the signals of nuclear tracks for each ion was studied. Eight sheets of CR-39 PNTDs were aligned and exposed to Ge beam behind a graphite target to produce projectile fragments. Average of the nuclear track data was taken over 16 detector surfaces for each ion, then the Z of Ge was successfully improved from 0.31 charge unit on single surface to 0.15 charge unit in rms, which is good enough for making the precise cross section measure- ments and no other experiments using CR-39 PNTDs or the other passive detectors have achieved such a good Z for the trans-iron nuclei with Z/ < 50 ( : relativistic velocity). This method will be very important for our future cross sec- tion measurements toward the study of galactic cosmic ray origin.

Response of CR39 track etch detector to 10 A GeV Fe 26+ ion beam and total charge changing cross section measurement

Total charge changing cross-section of 10 A GeV Fe 26+ ion beam on polyethylene and CR39 targets was measured. Charge of the fragments of projectiles was detected using CR39 nuclear track detectors by a new technique of one-side etching using an automated optical microscope with an image analysing software. The calculated value of total charge changing cross-section is σ tot = (2694 ± 142)mb and is in good agreement with the experimental values by other methods within error. The restricted energy loss ( REL) at energy 10 A GeV for all the fragments was theoretically calculated by using Bethe–Bloch equation and then obtained a calibration curve of reduced etch-rate ratio ( p) versus REL showing the response of CR39 track detectors to 10 A GeV Fe 26+ beam. The curve was fitted by a polynomial showing the relation between p and REL.

Scaling of Charge-Changing Interaction Cross Sections and Point-Proton Radii of Neutron-Rich Carbon Isotopes

Charge-changing cross sections σ(cc) of stable and unstable nuclei ((9-11)Be, (14-16)C, and (16-18)O) on a carbon target were investigated at 300 MeV/nucleon. A phenomenological analysis based on the Glauber theory indicates an approximate, but universal, scaling of σ(cc) over a wide range of A/Z. This allows the determination of the density distributions of protons tightly bound in the nuclei. An application to (16)C, which is considered to be an anomalously deformed nucleus, indicates a systematic evolution of proton root-mean-square radii and has revealed for the first time a neutron skin effect in carbon isotopes. Being complementary to isotope-shift and electron-scattering experiments, the present method can open up a new approach to explore the structure of exotic nuclei.

Nuclear reactions of 19,20C on a liquid hydrogen target measured with the superconducting TOF spectrometer

Reaction cross sections with various kinds of breakup channels for neutron-rich carbon isotopes 18–20C and for 9Be impinging on a liquid hydrogen target were investigated at 40 MeV/nucleon. The nuclides of interest were produced via projectile fragmentation from a 63 MeV/nucleon 40Ar beam and were separated in flight at the RIKEN projectile fragment separator (RIPS). The combination of the large-acceptance superconducting TOF spectrometer, TOMBEE (TOF Mass analyzer for exotic BEam Experiment), with a liquid hydrogen target, CRYPTA (CRYogenic ProTon and Alpha target system), enables simultaneous measurements of several reaction channels: the reaction cross sections (σR), individual elemental fragmentation cross sections (σΔZ), charge-changing cross sections (σcc), neutron-removal cross sections (σ−xn), and charge-pickup cross sections (σΔZ+1) for 19,20C; σΔZ, σ−xn, and σΔZ+1 for 18C; and σR for 9Be. The present σR of 9Be on proton, σR=397±23 mb, measured in the inverse kinematics, was consistent with the previous measurements using proton beams at different laboratories. The σR of 19C and 20C on proton were determined to be σR=754±22 mb and σR=791±34 mb, respectively. Taking into account the beam energy and target dependence of σR, the present σR are found to be considerably enhanced compared with those measured at around 1 GeV/nucleon. The σΔZ+1 appears to increase with the mass number of the projectiles, and it significantly contributes to σR in the present energy range. The finite-range optical-limit and few-body Glauber model analyses were performed for σR to study the nuclear matter density distributions and to derive the relative strength of the s-wave components of the valence neutrons in 19C and 20C. A neutron halo structure of 19C is confirmed with an s-wave dominance of the valence neutron when the effect of the charge-pickup reaction is taken into account. The large σ−n of 19C and σ−2n of 20C also support the decoupled structures of 18C +n and 18C+2n, respectively. The σcc of 19C and 20C agree with each other within their experimental uncertainties, which might indicate a similar proton density distribution in 19C and 20C. The σΔZ decreases monotonically without the even–odd effect as the number of removed protons increases.

Fragmentation ofN14,O16,Ne20, andMg24nuclei at 290 to 1000 MeV/nucleon

We report fragmentation cross sections measured at 0 deg for beams of 14-N, 16-O, 20-Ne, and 24-Mg ions, at energies ranging from 290 MeV/nucleon to 1000 MeV/nucleon. Beams were incident on targets of C, CH2, Al, Cu, Sn, and Pb, with the C and CH2 target data used to obtain hydrogen-target cross sections. Using methods established in earlier work, cross sections obtained with both large-acceptance and small-acceptance detectors are extracted from the data and when necessary corrected for acceptance effects. The large-acceptance data yield cross sections for fragments with charges approximately half of the beam charge and above, with minimal corrections. Cross sections for lighter fragments are obtained from small-acceptance spectra, with more significant, model-dependent corrections that account for the fragment angular distributions. Results for both charge-changing and fragment production cross sections are compared to the predictions of the Los Alamos version of the Quark Gluon String Model (LAQGSM) as well as the NUCFRG2 and PHITS models. For all beams and targets, cross sections for fragments as light as He are compared to the models. Estimates of multiplicity-weighted helium production cross sections are obtained from the data and compared to PHITS and LAQGSM predictions. Summary statistics show that the level of agreement between data and predictions is slightly better for PHITS than for either NUCFRG2 or LAQGSM.

Charge resolution of CR-39 plastic nuclear track detectors for intermediate energy heavy ions

The charge resolution ( δZ) for heavy ions (nuclear charge: Z < 40) of 0.1–1 GeV/n energy in CR-39 plastic nuclear track detector (PNTD) and its dependence on etching time, and on projectile Z and energy were investigated and optimized as part of an effort to make precise measurements of projectile charge-changing cross sections. Two types of CR-39 PNTD, HARZLAS TD-1 and BARYOTRAK, were exposed to heavy ion beams with seven values of Z behind thick targets to produce projectile fragments. Following chemical etching (7 N NaOH at 70 °C) for varying etch times, δZ of the projectiles was determined for each detector type. A strong dependence of δZ on the amount of bulk etch ( B) was seen. It was also observed that δZ can be remarkably improved with longer etching time as a function of B −1/2, in accordance with the trend seen in other types of track detector such as glass nuclear track detector. However, for B ⩾ 60 μm (30 h etching), saturation occurs and there is no further improvement in δZ. Analysis of the correlations between projectile Z, energy, detector response, and fluctuation of the response make it possible to develop a model to predict the δZ for projectiles of given Z and energy. The predicted and measured values of δZ show good agreement within 10%. We conclude that 4 ⩽ Z ⩽ 30 at intermediate energy can be identified with good δZ in these detectors. The predictive model will be used in designing future cross section measurement experiments.

Measurement of the fragmentation of Carbon nuclei used in hadron-therapy

The increasing use of Carbon nuclei in cancer therapy centres is motivated by their potential advantages as a very precise high LET radiation. The knowledge of the fragmentation of Carbon nuclei when they interact with the human body is important to evaluate the spatial profile of their energy deposition in the tissues, hence the damage to the tissues neighbouring the tumour. We report here a study of the fragmentation with the nuclear emulsion experimental technique. We have designed, built and exposed to a Carbon nuclei beam a chamber made of Lexan plates alternated with nuclear emulsion films. Lexan plates acted as passive material simulating human body tissues while nuclear emulsion films were used as both tracking devices with micrometric accuracy and ionisation detectors. Such a detector allowed the detection of Carbon interactions produced along their path, the identification of the fragments produced and the measurement of their scattering angle. We have measured the Carbon ion survival probability and studied their interactions. We report on the secondary particle multiplicity and the electrical charge distribution. We give results of the scattering angle of final state fragments as well as the range for H and He. Finally we give the total and partial charge-changing cross-sections for Δ z = 1 , 2 , 3 , 4 which are compared with previous results when available. The present work aims at providing data required as input to Monte Carlo simulations of Carbon ion interactions in the human body and ultimately of their therapeutic effectiveness.

Lead Projectile Fragmentation on Aluminum Target: Improved Experimental Results

We investigate 158A GeV 207Pb projectile fragmentation on Al target using CR-39 nuclear track detectors. A stack containing target-detectors assembly was irradiated at SPS-CERN. After chemical etching, detectors were scanned using an optical microscope to collect the data in the form of etched cone heights. From the cone height measurements, total and partial charge changing cross sections of 207Pb projectiles on aluminum target are determined. The results are compared with both relevant published measurements available in the literature and model predictions. Odd-even effect in the formation of the fragments of 158A GeV 207Pb pro-jectiles is observed in a consistent and a clear manner over the observed range of fragments (Z=63-81). This is achieved by using optimized etching and track measurement conditions.

CHARGE AND MASS CHANGING CROSS-SECTIONS OF 158A GeV Pb PROJECTILES ON Al, Cu, Bi, AND Pb TARGETS: FRAGMENTATION PROCESSES

We report here on total and partial charge changing cross-sections of 158A GeV lead projectiles on Al , Cu , Pb and Bi stationary targets using CR-39 detectors. Present results are compared with relevant published results. Deep discussion of nuclear fragmentation processes is provided. Stacks of CR-39 Track Detectors with above-mentioned targets were exposed to 158 A GeV 207 Pb projectiles at the CERN-SPS beam facility at normal incidence with a fluence of about 1500 ions/cm 2. Lengths of etched cones on one face of the CR-39 detectors before and after the target were measured for each stack. These measurements were used for determination of total and partial charge changing cross-sections of 158 A GeV Pb 82+ projectiles on these targets in the charge region 63 &lt; Z &lt; 82. The charge resolution (σZ) achieved in the present experiment is ~0.18e. Mass changing cross-sections are derived from the measured charge changing cross-sections using hyper-geometric relationship. A new method is proposed for separate measurements of electromagnetic and nuclear parts of fragmentation cross-sections using ion channeling and blocking conditions of projectiles in crystalline targets.

Benchmarking nuclear models of FLUKA and GEANT4 for carbon ion therapy

As carbon ions, at therapeutic energies, penetrate tissue, they undergo inelastic nuclear reactions and give rise to significant yields of secondary fragment fluences. Therefore, an accurate prediction of these fluences resulting from the primary carbon interactions is necessary in the patient's body in order to precisely simulate the spatial dose distribution and the resulting biological effect. In this paper, the performance of nuclear fragmentation models of the Monte Carlo transport codes, FLUKA and GEANT4, in tissue-like media and for an energy regime relevant for therapeutic carbon ions is investigated. The ability of these Monte Carlo codes to reproduce experimental data of charge-changing cross sections and integral and differential yields of secondary charged fragments is evaluated. For the fragment yields, the main focus is on the consideration of experimental approximations and uncertainties such as the energy measurement by time-of-flight. For GEANT4, the hadronic models G4BinaryLightIonReaction and G4QMD are benchmarked together with some recently enhanced de-excitation models. For non-differential quantities, discrepancies of some tens of percent are found for both codes. For differential quantities, even larger deviations are found. Implications of these findings for the therapeutic use of carbon ions are discussed.

Fragmentation of 370MeV/n 20Ne and 470MeV/n 24Mg in light targets

Total charge-changing cross sections and cross sections for the production of projectile-like fragments were determined for fragmentation reactions induced by 370 MeV/n Ne-20 ions in water and lucite, and 490 MeV/n Mg-24 ions in polyethylene, carbon and aluminum targets sandwiched with CR-39 plastic nuclear track detectors. An automated microscope system and a track-to-track matching algorithm were used to count and recognize the primary and secondary particles. The measured cross sections were then compared with published cross sections and predictions of different models. Two models and the three-dimensional Monte Carlo Particle Heavy Ion Transport Code System (PHITS) were used to calculate total charge-changing cross sections. Both models agreed within a few percent for the system Mg-24 + CH2, however a deviation up to 20% was observed for the systems Ne-20 + H2O and C5H8O2, when using one of the models. For all the studied systems, PHITS systematically underestimated the total charge-changing cross section. It was also found that the partial fragmentation cross sections for Mg-24 + CH2 measured in present and earlier works deviated up to 20% for Z = 6-11. Measured cross sections for the production of fragments (Z = 4-9) for Ne-20 + H2O and C5H8O2 were compared with predictions of three different semi-empirical models and JQMD which is used in the PHITS code. The calculated cross sections differed from the measured data by 10-90% depending on which fragment and charge was studied, and which model was used. (C) 2010 Elsevier Ltd. All rights reserved.

Energy-dependent charge-changing cross sections and proton distribution ofSi28

The charge-changing cross sections (${\ensuremath{\sigma}}_{\mathrm{cc}}$) of $^{28}\mathrm{Si}$ on a carbon target were measured with high precision at intermediate energies from 100 to 600 MeV/nucleon. The measured ${\ensuremath{\sigma}}_{\mathrm{cc}}$ decreases rapidly from low energies up to 200 MeV/nucleon, whereas at higher energies it appears almost constant. The energy dependence of ${\ensuremath{\sigma}}_{\mathrm{cc}}$ is compared with a Glauber-type model calculation where only the proton distribution of $^{28}\mathrm{Si}$ is taken into account. A phenomenological correction factor deduced from the present data satisfactorily reproduces the experimental ${\ensuremath{\sigma}}_{\mathrm{cc}}$ for other stable nuclei, whose charge distributions were determined by electron scattering and muon capture experiments.

Nuclear fragmentation database for GCR transport code development

A critical need for NASA is the ability to accurately model the transport of heavy ions in the Galactic Cosmic Rays (GCR) through matter, including spacecraft walls, equipment racks, etc. Nuclear interactions are of great importance in the GCR transport problem, as they can cause fragmentation of the incoming ion into lighter ions. Since the radiation dose delivered by a particle is proportional to the square of (charge/velocity), fragmentation reduces the dose delivered by incident ions. The other mechanism by which dose can be reduced is ionization energy loss, which can lead to some particles stopping in the shielding. This is the conventional notion of shielding, but it is not applicable to human spaceflight since the particles in the GCR tend to be too energetic to be stopped in the relatively thin shielding that is possible within payload mass constraints. Our group has measured a large number of fragmentation cross sections, intended to be used as input to, or for validation of, NASA’s radiation transport models. A database containing over 200 charge-changing cross sections and over 2000 fragment production cross sections has been compiled. In this report, we examine in detail the contrast between fragment measurements at large acceptance and small acceptance. We use output from the PHITS Monte Carlo code to test our assumptions using as an example 40Ar data (and simulated data) at a beam energy of 650 MeV/nucleon. We also present preliminary analysis in which isotopic resolution was attained for beryllium fragments produced by beams of 10B and 11B. Future work on the experimental data set will focus on extracting and interpreting production cross sections for light fragments.

Experimental electron loss and capture cross sections in ion–atom collisions

This work presents a compilation of experimental data for electron capture and loss cross sections obtained at the Scobeltsyn Institute of Nuclear Physics for neutral atoms and negative and positive ions with nuclear charge Z = 2–36 in collisions with atomic and molecular gases. The charge-changing cross sections are summarized in tables with the reference list attached.

Database on charge – changing cross sections in ion – atom collisions

The database on charge changing cross sections in ion-atom collisions is presented. The capture and loss of one or more electron cross sections are summarized in tables and figures as a function of incident ion energy. The experimental, theoretical and recommended data are compiled.