Fragmentation Cross Sections Research Articles

Validation of Light–Ion Quantum Molecular Dynamics (LIQMD) model for hadron therapy

Purpose:This study aims to validate the Light-Ion Quantum Molecular Dynamics (LIQMD) model, an advanced version of the QMD model for more accurate simulations in hadron therapy, incorporated into Geant4 (release 11.2). Methods:Two sets of experiments are employed. The first includes positron-emitter distributions along the beam path for 350 MeV/u 12C ions incident on a PMMA target, obtained from in–vivo Positron Emission Tomography (PET) experiments at QST (Chiba, Japan). The second comprises cross-sections for 95 MeV/u 12C ions incident on thin targets (H, C, O, Al, and Ti), obtained from experiments at GANIL (Caen, France). The LIQMD model’s performance is compared with the experimental data and the default QMD model results. Results:The LIQMD model can predict the profile shape of positron-emitting radionuclide yields with better accuracy than the default QMD model, although some discrepancies remains. The consistency observed in the production of positron-emitting radionuclides aligns with the thin target cross-section analysis. The LIQMD model significantly improves the differential and double-differential cross-sections of fragments produced in thin targets, especially in the forward direction. The overestimation of 10C production in the in–vivo PET benchmark is consistent with the 95 MeV/u 12C cross-section test. Overall, the LIQMD model demonstrates better agreement with experimental measurements for nearly all fragment species compared to the QMD model. Conclusions:The LIQMD model offers an improved description of the fragmentation process in hadron therapy. Future work should involve further validation against additional experimental measurements to confirm these findings.

Exploring the structural heterogeneity of IgG1s: A comprehensive analysis of glycosylated and deglycosylated forms using TIMS-TOF-MS technique

Denaturation of IgG is a complex and multistep process that involves various structural changes in the protein as it loses its native conformation. IgG denaturation is crucial in therapeutic antibody development, manufacturing, and storage. Glycosylated IgG is generally more resistant to denaturing conditions due to the stabilizing effect of its glycans. In contrast, deglycosylated IgG is more vulnerable to structural disruption. In this study, we examined the intact level and large fragments of IgG glycoforms. Our investigation focused on changes in structural heterogeneity through glycosylation under denaturing conditions. Collision cross-sections (CCS) of intact level and large fragments of IgG1 molecules have been determined using reversed phase-high performance liquid chromatography-electrospray ionization-trapped ion mobility-time-of-flight mass spectrometry (RP-HPLC-ESI-TIMS-TOF-MS) technique. At the intact level, deglycosylated bevacizumab (IgG1B) and trastuzumab (IgG1T) could be differentiated at specific charge states and CCS ranges. The deglycosylated IgG1B molecule showed a broader CCS range than the IgG1T molecule. This result demonstrated that the deglycosylated IgG1T was altered from deglycosylated IgG1B in the gas phase under denaturing conditions. The lowering in the collision cross-section distribution (CCSD) values indicates a decrease in the structural heterogeneity of the intact IgG after deglycosylation. The ion mobility-mass spectrometry (IM-MS) analyses performed in this study showed that the glycans on the Fc region of IgG1s can trigger structural changes in the molecule under denaturing conditions. Depending on whether they are glycosylated or deglycosylated, various conformations of IgG1 molecules could be distinguished in RP-HPLC-TIMS-TOF-MS analysis.

The AMS-02 Cosmic-Ray Deuteron Flux is Consistent with a Secondary Origin

The recent measurements of cosmic-ray (CR) deuteron fluxes by AMS-02 show that the rigidity dependence of deuterons is similar with that of protons but flatter than 3He, which has been attributed to the existence of primary deuterons with abundance much higher than that from the Big Bang nucleosynthesis. The requirement of highly deuteron-abundant sources imposes a serious challenge to modern astrophysics since there is no known process to produce a large amount of deuterons without violating other constraints. In this work we demonstrate that the fragmentation of heavy nuclei up to nickel plays a crucial role in shaping/enhancing the spectrum/flux of the CR deuterons. Based on the latest CR data, the predicted secondary fluxes of deuterons and 3He are found to be reasonably consistent with the AMS-02 measurements, and a primary deuteron component is not needed. The observed differences between the spectra of D and 3He, as well as those between the D/4He (D/p) and 3He/4He (3He/p) flux ratios, measured in the rigidity space, is probably due to the kinetic-energy-to-rigidity conversion and the solar modulation, given different charge-to-mass ratios of D and 3He. More precise measurements of the fragmentation cross sections of various nuclei to produce deuterons, tritons, and 3He in a wide energy range will be very helpful in further testing the secondary origin of cosmic-ray deuterons.

Targeted metabolomics assisted rapid screening and characterization of aristolochic acids and their DNA adducts in aristolochia plants by ultra-high performance liquid chromatography coupled with ion mobility quadrupole time-of-flight mass spectrometry

Aristolochic acids are one of the major compounds in aristolochia plants, which are nephrotoxic and carcinogenic. A method was established for the detection and identification of aristolochic acids and their DNA adducts in four different herbs using ultra-high performance liquid chromatography-ion mobility quadrupole time-of flight mass spectrometry. Solid phase extraction conditions were optimized to improve the sensitivity of the experiment by using 40 mg of C18 as adsorbent and 100 μL ethanol as elution solvent. At a collision energy of 10-40 eV, these compounds and cleavage patterns were precisely identified and analyzed by secondary fragmentation and collision cross section values. The obtained mass spectrometry data were then analyzed by targeted metabolomics, including principal component analysis, partial least squares-discriminant analysis and hierarchical clustering analysis, and importing the samples in the established model, the confidence values can reach 0.61 and 0.76. All in all, this method can provide a useful tool for the detection of aristolochic acids and deoxyribonucleic acid adducts. In conclusion, this method was successfully used for the detection and identification of aristolochic acids and their DNA adducts.

Triphenylamine Sensitized 8-Dimethylaminoquinoline: An Efficient Two-Photon Caging Group for Intracellular Delivery.

Triphenylamine-sensitized 8-dimethylaminoquinoline (TAQ) probes showed fair two-photon absorption and fragmentation cross sections in releasing kainate and GABA ligands. The water-soluble PEG and TEG-analogs allowed cell internalization and efficient light-gated liberation of the rhodamine reporter under UV and two-photon (NIR) irradiation conditions.

Predicting 28Si projectile fragmentation cross sections with Bayesian neural network method* *Supported by the National Nature Science Foundation of China (11075100, 11347198, 11565001), the Natural Science Foundation of Shanxi Province, China (2011011001-2), the Shanxi Provincial Foundation for Returned Overseas Chinese Scholars (2011-058), and the Postgraduate Science and Technology Innovation Project of Shanxi Normal University (2023XBY004)

This study utilizes the Bayesian neural network (BNN) method in machine learning to learn and predict the cross-sectional data of 28Si projectile fragmentation for different targets at different energies and to quantify the uncertainty. The detailed modeling process of the BNN is presented, and its prediction results are compared with those of the Cummings, Nilsen, EPAX2, EPAX3, and FRACS models and experimental measurement values. The results reveal that, compared with other models, the BNN method achieves the smallest root-mean-square error (RMSE) and the highest agreement with the experimental values. Only the BNN method and FRACS model show a significant odd-even staggering effect; however, the results of the BNN method are closer to the experimental values. Furthermore, the BNN method is the only model capable of reproducing data features with low cross-section values at Z = 9, and the average ratio of the predicted to experimental values of the BNN is close to 1.0. These results indicate that the BNN method can accurately reproduce and predict the fragment production cross sections of 28Si projectile fragmentation and demonstrate its ability to capture key data characteristics.

Charge measurement with nuclear emulsions spectrometers for hadron therapy fragmentation cross section measurements with the FOOT experiment

Experimental data concerning projectile and target fragmentation is limited, increasing the uncertainty on the dose in the entrance channel in particle therapy treatments. The FOOT experiment measures nuclear fragmentation cross sections with two complementary detectors. The performance of the FOOT nuclear emulsion detectors in identifying the charge of nuclear fragments has recently been studied using 16O beams at 200 and 400MeV/n, directed at carbon and polyethylene targets. This work extends the previous analysis, comparing experimental data and FLUKA Monte Carlo predictions, focusing on the angular distribution and relative abundances of fragments with Z≤5 originating from the interactions of a 400MeV/n oxygen beam with a carbon target.

Inelastic Scattering of Dark Matter with Heavy Cosmic Rays

We investigate the impact of inelastic collisions between dark matter (DM) and heavy cosmic ray (CR) nuclei on CR propagation. We approximate the fragmentation cross-sections for DM-CR collisions using collider-measured proton-nuclei scattering cross-sections, allowing us to assess how these collisions affect the spectra of CR boron and carbon. We derive new CR spectra from DM-CR collisions by incorporating their cross-sections into the source terms and solving the diffusion equation for the complete network of reactions involved in generating secondary species. In a specific example with a coupling strength of b χ = 0.1 and a DM mass of m χ = 0.1 GeV, considering a simplified scenario where DM interacts exclusively with oxygen, a notable modification in the boron-to-carbon spectrum due to the DM-CR interaction is observed. Particularly, the peak within the spectrum, spanning from 0.1 to 10 GeV, experiences an enhancement of approximately 1.5 times. However, in a more realistic scenario where DM particles interact with all CRs, this peak can be amplified to twice its original value. Utilizing the latest data from AMS-02 and DAMPE on the boron-to-carbon ratio, we estimate a 95% upper limit for the effective inelastic cross-section of DM-proton as a function of DM mass. Our findings reveal that at m χ ≃ 2 MeV, the effective inelastic cross-section between DM and protons must be less than O(10−32)cm2 .

Antiproton bounds on dark matter annihilation from a combined analysis using the DRAGON2 code

Early studies of the AMS-02 antiproton ratio identified a possible excess over the expected astrophysical background that could be fit by the annihilation of a weakly interacting massive particle (WIMP). However, recent efforts have shown that uncertainties in cosmic-ray propagation, the antiproton production cross-section, and correlated systematic uncertainties in the AMS-02 data, may combine to decrease or eliminate the significance of this feature. We produce an advanced analysis using the DRAGON2 code which, for the first time, simultaneously fits the antiproton ratio along with multiple secondary cosmic-ray flux measurements to constrain astrophysical and nuclear uncertainties. Compared to previous work, our analysis benefits from a combination of: (1) recently released AMS-02 antiproton data, (2) updated nuclear fragmentation cross-section fits, (3) a rigorous Bayesian parameter space scan that constrains cosmic-ray propagation parameters.We find no statistically significant preference for a dark matter signal and set strong constraints on WIMP annihilation to bb̅, ruling out annihilation at the thermal cross-section for dark matter masses below ∼ 200 GeV. We do find a positive residual that is consistent with previous work, and can be explained by a ∼ 70 GeV WIMP annihilating below the thermal cross-section. However, our default analysis finds this excess to have a local significance of only 2.8σ, which is decreased to 1.8σ when the look-elsewhere effect is taken into account.

Nuclear Fragmentation Cross-Section Measurements with the FOOT Experiment

Nuclear Fragmentation Cross-Section Measurements with the FOOT Experiment

Monte Carlo simulation of spallation fragments cross-sections and yield for proton beam interaction with 222Rn

Accurate determination of cross-sections for residual radionuclide products (spallation fragments) resulting from proton spallation reactions is imperative for the detection of primary and secondary particles etc. Experimental measurement of these cross-sections faces challenges due to the complexities associated with target preparation and detection of spallation fragments. Monte Carlo simulations have emerged as a potent tool for estimation of spallation fragments yield. This research, with introducing an innovative formulation method based on spallation yield, focuses on calculating the cross-section for the detection of primary and secondary particles in particle interaction with matter. Investigations indicate that the introduced method achieves remarkable agreement, ranging from 85.4% to 95.15%, with experimental outcomes at MeV energies. Consequently, this method can confidently be utilized for calculating the spallation cross-section fragments. In a case study, the spallation fragment cross-section was calculated for proton beam interaction with 222Rn in the range of 10 MeV to 60 MeV for the application of 222Rn detection. Among the 28 common spallation products of radon with the proton interaction in the energy range of 10 MeV to 60 MeV, elements 106Mo, 109Tc, 118Cd, 112Ru, 110Pd, and 114Rh exhibit dominant spallation cross-sections, emphasizing their exceptional significance.

Threshold collision induced dissociation of protonated water clusters.

We report threshold collision induced dissociation experiments on protonated water clusters thermalized at low temperature for sizes n = 19-23. Fragmentation cross sections are recorded as a function of the collision energy and analyzed with a statistical model. This model allows us to account for dissociation cascades and provides values for the dissociation energies of each cluster. These values, averaging around 0.47eV, are in good agreement with theoretical predictions at various levels of theory. Furthermore, the dissociation energies show a trend for the n = 21 magic and n = 22 anti-magic numbers relative to their neighbours, which is also in agreement with theory. These results provide further evidence to resolve the disagreement between previously published experimental values. A careful quantitative treatment of cascade dissociation in this model introduces interdependence between the dissociation energies of neighboring sizes, which reduces the number of free fitting parameters and improves both reliability and uncertainties on absolute dissociation energies deduced from experiments.

Soft X-Ray-induced Dimerization of Methane

Carbon 1s excitation of methane, CH4, has been studied in the gas phase using the ion trap integrated with the photon–ion instrument at PETRA III/DESY and soft X-rays from the beamline P04. The created photoions are stored within the ion trap so that in further steps the photoions can undergo reactions with neutral methane molecules. The ionic photoproducts as well as reaction products created thereby are mass-over-charge analyzed by an ion time-of-flight spectrometer. Besides the photoions, product ions with up to three carbon atoms are found. In contrast to experiments using vacuum ultraviolet radiation, especially highly reactive product ions with a small number of hydrogen atoms such as and are found, which are important precursors for larger hydrocarbons such as C6H6. Possible production routes of the product ions are analyzed on the basis of a model that considers the probabilities for photofragmentation and the first subsequent chemical reaction step. The model indicates that the high degree of fragmentation by photons with energies around 280 eV is favoring these products. The results of the measurements show that the products like and can be generated by a single collision of the ionization product with neutral methane. The results suggest that soft X-rays might be important for chemical reactions in planetary atmospheres, which has usually not been taken into account. However, due to the high degree of fragmentation and large cross sections involved, they can have a large influence even when the corresponding photon flux is rather small.

Analyses of queen Hetepheres’ bracelets from her celebrated tomb in Giza reveals new information on silver, metallurgy and trade in Old Kingdom Egypt, c. 2600 BC

Egypt has no domestic silver ore sources and silver is rarely found in the Egyptian archaeological record until the Middle Bronze Age. Bracelets found in the tomb of queen Hetepheres I, mother of pyramid builder king Khufu (date of reign c. 2589–2566 BC), form the largest and most famous collection of silver artefacts from early Egypt, but they have not been analysed for decades. We analysed samples from the collection in the Museum of Fine Arts, Boston using bulk XRF, micro-XRF, SEM-EDS, X-ray diffractometry and MC-ICP-MS to obtain elemental and mineralogical compositions and lead isotope ratios, to understand the nature and metallurgical treatment of the metal and identify the possible ore source. We found that the pieces consist of silver with trace copper, gold, lead and other elements. The minerals are silver, silver chloride and a possible trace of copper chloride. Surprisingly, the lead isotope ratios are consistent with ores from the Cyclades (Aegean islands, Greece), and to a lesser extent from Lavrion (Attica, Greece), and not partitioned from gold or electrum as previously surmised. Sources in Anatolia (Western Asia) can be excluded with a high degree of confidence. Imaging of a cross-section of a bracelet fragment reveals that the metal was repeatedly annealed and cold-hammered during creation of the artefacts. The results provide new information about silver ore sources, commodity exchange networks and metallurgy in Egypt during the Early Bronze Age.

Cross-sectional microstructural analysis to evaluate the crack growth pattern of weathered marine plastics

Fragmentation of degraded plastics and release of smaller secondary microplastics is usually attributed to the growth of environmental stress cracks. Analysis of crack patterns derived from chemical degradation can be useful not only for assessing the cause of plastic fracture and evaluating the useful lifetime of a product, but it can also potentially provide valuable information on the generation of microplastics. However, the literature with respect to microplastics generation is generally limited to surface observations of polypropylene and polyethylene. Here, we used ion-beam milling to prepare cross-sections of fragments of 15 plastic products made from five commodity plastics (polypropylene, polyethylene, polystyrene, polyvinyl chloride, and polyethylene terephthalate) that were collected at two beaches in Japan, and then we examined the microstructures of those cross-sections by means of scanning electron microscopy and energy dispersive X-ray spectroscopy. Crack growth in the depth direction was examined to provide insights into microplastic generation behavior. In all of the polypropylene samples, and some of the low-density polyethylene and polystyrene samples, cracks with a depth exceeding 100 μm from the sample surface were observed. Considering that crack growth causes fracture of degraded plastic and microplastic release, these observations suggest the release of sharp-edged microplastics from the crack fracture surface. In contrast, in the high-density polyethylene and polyvinyl chloride samples, crack growth was limited to within 20 μm of the sample surface, suggesting the release of irregularly shaped microplastics and additive particles. The present results suggest that the degradation behavior of plastic products in the depth direction is dependent on the type of plastic.

Fragmentation of the 4He2 dimer with the emission of three or four electrons by fast highly charged projectiles

We investigate the fragmentation of the helium dimer, 4He2, into He2+ + He+ and He2+ + He2+ ions in collisions with fast highly charged projectiles. We discuss the main physical mechanisms driving these processes. We explore the energy and angular distributions of the ionic fragments produced during collisions of the dimer with 1 GeV/u U92+ and 11.37 MeV/u S14+ projectiles and also present the total fragmentation cross-sections. According to our results, the fragmentation in these collisions is fully dominated by the direct removal of three or four electrons from the dimer by the projectile in a single collision. Our results also suggest that the total fragmentation cross-sections depend on the binding energy IHe2 of the dimer, being roughly proportional to IHe2.

New measurement of the elemental fragmentation cross sections of 218 MeV/nucleon Si28 on a carbon target

Elemental fragmentation cross sections (EFCSs) of stable and unstable nuclides have been investigated with various projectile-target combinations at a wide range of incident energies. These data are critical to constrain and develop the theoretical reaction models and to study the propagation of galactic cosmic rays (GCR). In this work, we present a new EFCS measurement for $^{28}$Si on carbon at 218~MeV/nucleon performed at the Heavy Ion Research Facility (HIRFL-CSR) complex in Lanzhou. The impact of the target thickness has been well corrected to derive an accurate EFCS. Our present results with charge changes $\Delta Z$ = 1-6 are compared to the previous measurements and to the predictions from the models modified EPAX2, EPAX3, FRACS, ABRABLA07, NUCFRG2, and IQMD coupled with GEMINI (IQMD+GEMINI). All the models fail to describe the odd-even staggering strength in the elemental distribution, with the exception of the IQMD+GEMINI model, which can reproduce the EFCSs with an accuracy of better than 3.5\% for $\Delta Z\leq5$. The IQMD+GEMINI analysis shows that the odd-even staggering in EFCSs occurs in the sequential statistical decay stage rather than in the initial dynamical collision stage. This offers a reasonable approach to understand the underlying mechanism of fragmentation reactions.

Production of Ca61, Sc63, Ti65, V68,69, Cr71, Fe77 , and Co79 in projectile fragmentation with radioactive ion beams at 1A GeV

Projectile fragmentation provides an method to produce the unknown neutron-rich isotopes. In this work, the isospin-dependent Boltzmann-Langevin equation is employed to investigate the influence of projectiles on the fragments production. The cross sections of fragments with proton number $Z=20$--27 are calculated under the reaction systems $^{81,84,86}\mathrm{Ga}+^{9}\mathrm{Be}$. The obtained results suggest that the radioactive projectile $^{86}\mathrm{Ga}$ is favorable to the yields of neutron-rich nuclei. The newly produced isotopes $^{61}\mathrm{Ca}, ^{63}\mathrm{Sc}, ^{65}\mathrm{Ti}, ^{68,69}\mathrm{V}, ^{71}\mathrm{Cr}, ^{77}\mathrm{Fe}$, and $^{79}\mathrm{Co}$, whose cross sections are characterized by the order of 1 to 100 $\ensuremath{\mu}\mathrm{b}$, can be observed in the reaction $^{86}\mathrm{Ga}+^{9}\mathrm{Be}$ at $1A$ GeV. This means the production cross sections of neutron-rich nuclei are very highly sensitive to the neutron-proton excess of projectile.

Atomistic modeling of thermal effects in focused electron beam-induced deposition of Me$$_2$$Au(tfac)

The role of thermal effects in the focused electron beam induced deposition (FEBID) process of Me$_2$Au(tfac) is studied by means of irradiation-driven molecular dynamics simulations. The FEBID of Me$_2$Au(tfac), a commonly used precursor molecule for the fabrication of gold nanostructures, is simulated at different temperatures in the range of $300-450$ K. The deposit's structure, morphology, growth rate, and elemental composition at different temperatures are analyzed. The fragmentation cross section for Me$_2$Au(tfac) is evaluated on the basis of the cross sections for structurally similar molecules. Different fragmentation channels involving the dissociative ionization (DI) and dissociative electron attachment (DEA) mechanisms are considered. The conducted simulations of FEBID confirm experimental observations that deposits consist of small gold clusters embedded into a carbon-rich organic matrix. The simulation results indicate that accounting for both DEA- and DI-induced fragmentation of all the covalent bonds in Me$_2$Au(tfac) and increasing the amount of energy transferred to the system upon fragmentation increase the concentration of gold in the deposit. The simulations predict an increase in Au:C ratio in the deposit from 0.18 to 0.25 upon the temperature increase from 300 K to 450 K, being within the range of experimentally reported values.

Nuclear fragmentation cross section measurements with the FOOT experiment

Different fields can profit by nuclear fragmentation cross section measurements: among them hadrontherapy and space radioprotection are of particular interest. Hadrontherapy employs high-energy beams of charged particles (protons and heavier ions) to treat deep-seated tumours. In these treatments nuclear interactions have to be considered: beam particles can fragment in the human body releasing a non-zero dose beyond the tumour while fragments of human body nuclei can modify the dose released in healthy tissues. On the radioprotection side, the interest in long-term manned space missions beyond Low Earth Orbit is growing in these years but it has to cope with significant health concerns from radiation in space, necessitating an accurate cross section data description. The FOOT (FragmentatiOn Of Target) experiment was proposed to cover these gaps in data. It was designed to detect, track and identify nuclear fragments and aims to measure double differential cross sections both in angle and kinetic energy which is the most complete information to address existing questions. The FOOT experimental setups, the experimental program and a first cross section analysis of 400 MeV/u 16O beam on Carbon target data acquired in July 2021 at GSI (Darmstadt, Germany) will be presented.