Polyethylene Target Research Articles

Development of an MeV proton generator using a 3He ion source at the Research Center for Nuclear Physics.

For simple applications, such as the calibration of a charged particle detector, a multi-MeV proton generator may be preferable to cyclotrons or electrostatic accelerators such as Van de Graaff generator. Thus, a proton generating system, consisting of an 18 GHz superconducting (SC)-ECR ion source and a deuterated polyethylene target, was developed at the Research Center for Nuclear Physics at Osaka University. A 3He2+ beam of 400 eμA was generated by the SC-ECR ion source with the acceleration voltage of 20 kV in an experiment that utilized the fusion reaction 3He + deuteron (D) → proton(P) + 4He. Protons with energies of the order of several MeV were successfully generated at 3.67 Hz at the atmosphere side of the target in the experimental setup, using a novel target base with a thin aluminum window.

Studying time-like electromagnetic baryonic transitions with HADES in pion induced reactions

A dedicated programme aiming at studying electromagnetic baryonic transitions in the time-like region has started at GSI using the pion beam and the High Acceptance Di-Electron Spectrometer (HADES) set-up. A pioneering experiment has been carried out in the second resonance region, at a center-of-mass energy of 1.49 GeV, using carbon and polyethylene targets, allowing for an analysis of the inclusivee+e-production and of the exclusive quasi-freeπ-p→ne+e-reaction, in complement to hadronic channels. Predictions for the Dalitz decay of N(1520) and N(1535) based on real photon couplings strongly underestimate thee+e-yield at invariant masses larger than 300 MeV/c2, which signals effects of time-like baryon transition form factors, in qualitative agreement with the Vector Dominance Models (VDM). A quantitative description of the observede+e-yield is achieved by taking into account the contribution from off-shellρs. The latter was provided by the preliminary results of a Bonn-Gatchina Partial Wave Analysis of the two-pion production channels, which were measured simultaneously in our experiment. A good agreement is also obtained using a covariant model for the time-like electromagnetic form factors for the N-N(1520) transition. The angular distributions for thee+e-production contain additional selective information on the spin structure of the different transitions. The measurements with the pion beam will be extended in future in the third resonance region. Hyperon Dalitz decay studies in proton induced reactions are also foreseen.

The production of deuterated polyethylene targets

In this contribution, we describe the method used to produce deuterated polyethylene (C2D4) targets. The modification of method based on polyethylene dissolution in hot xylene resulted with stable thin C2D4 targets.

Partial Wave Analysis of HADES Data for Two-Pion Production in Pion-Nucleon Reactions

Pion beams are important tools to study features of baryonic resonances and their decay channels because resonances are produced in s-channel at fixed mass equal to √s. In 2014 the HADES collaboration has performed systematic measurements in the second resonance region scanning around the mass of the N*(1520). Pion beams at four momenta (0.654, 0.686, 0.738 and 0.787 GeV/c) impinging on polyethylene and carbon targets have been used. With the use of the multichannel Partial Wave Analysis (PWA) the role of the N*(1520) resonance in conjunction with the intermediate ρ-meson production has been studied. Preliminary results at 0.654 GeV/c on exclusive production of two pions (ηπ+π- and pπ-π0) in the final state are presented.

Simulation Study of the Effect of Projectile Length-Diameter Ratio on Anti-Penetration Performance of Composite Armor

We studied the failure modes of 55 g cylindrical projectile penetrating ceramic/titanium alloy/gap/polyethylene/gap/921A steel composite armor structure by numerical simulation, obtained the influence of projectile length-diameter ratio on the anti-penetration performance of structure by analysis. The results showed that, ceramic breaks in-plane and forms ceramic cone, titanium alloy target shows shear failure and bending deformation, 921A steel target shows adiabatic shear failure mode when it is penetrated, bulging when it is not penetrated, the front polyethylene target shows compressive shear deformation, the rear polyethylene target shows bending deformation, and fiber tensile failure is the main failure mode, the impact fiber layer has obvious delamination and degumming phenomenon. Under the same mass condition, the larger the length-diameter ratio of the projectile, the smaller the size of the breach and the greater the penetration depth. With the further increase of the length-diameter ratio, the impact of the projectile on the penetration effect is weakened.

Projectile fragment emission in the fragmentation of $$^{\bf 56}\mathbf{Fe}$$ on Al, C, and $$\mathbf{CH}_{\mathbf{2}}$$ targets

The emission angle distribution of projectile fragments (PFs) and the temperature of PF emission sources for fragmentation of $$^{56}\hbox {Fe}$$ on polyethylene, carbon, and aluminum targets at the highest energy of 497 A MeV are investigated on the basis of corrected data, using a CR-39 plastic nuclear track detector. It is found that the average emission angle of PFs increases with the decrease in PF charge for the same target, and no obvious dependence of angular distribution on the mass of the target nucleus is found for the same PF. The cumulative squared transverse momentum distribution of PFs can be well represented by a single Rayleigh distribution. The temperature of PF emission sources is extracted from the distribution, and it is about 1.0–8.0 MeV and does not depend on the mass of the target for PFs with charges of $$9\le {Z}\le 25$$.

Comparison of the Radiation Shielding Properties of Wall Materials for the Manned Spacecraft for Future China Space Exploration Missions

The radiation environment in space poses significant challenges to human health, and it is a major concern in long duration, manned space missions. Outside Earth’s protective magnetosphere, astronauts are exposed to higher levels of galactic cosmic rays (GCRs), whose physical characteristics are distinct from those of terrestrial sources of radiation, such as X-rays and gamma-rays. GCRs include high-energy heavy ions, many of which have ranges that exceed the depth of shielding and can be launched in realistic scenarios. Protecting the astronauts from these particles has been a key issue in manned space missions. Therefore, a need exists for reliable simulations of these harmful effects for risk assessment and shielding optimization in manned space missions. The aim of this work was to investigate shielding materials that can be used in deep space and planetary exploration. In this work, we used the Geant4 radiation transport code, originally developed by the International Geant4 Collaboration, and we compared the radiation shielding effectivenesses of polyethylene, aluminum, water, and carbon fiber targets hit by 1GeV/nucleon 56Fe (considered as a representative of high-energy GCR). In addition, the total absorbed doses at the water phantom behind these targets were calculated using the Geant4 simulation code. The calculated results were analyzed, compared, and discussed. The results show that polyethylene is the best space radiation shielding material for a given areal density, followed by water, carbon fiber, and then aluminum.

Suggestion of coherent radio reflections from an electron-beam induced particle cascade

Testbeam experiment 576 (T576) at the SLAC National Accelerator Laboratory sought to make the first measurement of coherent radio reflections from the ionization produced in the wake of a high-energy particle shower. The >10 GeV electron beam at SLAC End Station A was directed into a large high-density polyethylene target to produce a shower analogous to that produced by an EeV neutrino interaction in ice. Continuous wave (CW) radio was transmitted into the target, and receiving antennas monitored for reflection of the transmitted signal from the ionization left in the wake of the shower. We detail the experiment and report on preliminary hints of a signal consistent with a radio reflection at a significance of 2.36$\sigma$. We recommend another test-beam measurement in order to verify the signal.

The acceleration of laser plasma in a strong non-stationary magnetic field

Based on experimental and computer simulation the acceleration of deuterons from laser plasma in a strong non-stationary magnetic field was studied. The possibility of reaching an energy of ∼100 keV, corresponding to the effective course of the nuclear reactions D (d, n) 3He and T (d, n) 4He, was demonstrated. YAG: Nd3+ laser (W ≤ 0.85 J, τ ≈ 10 ns) was used in the experiment with focusing laser radiation on a deuterated polyethylene target. The high voltage pulse generator with a conical spiral coil was used to generate a high-speed magnetic field (2·107 T/s). A mathematical model of the process is proposed. According to this model, the acceleration of a laser plasma is analyzed by means of a computer. The algorithm is based on a numerical solution of the system of Newton-Lorentz equations.

The total charge-changing cross sections and the partial cross sections of 56Fe fragmentation on Al, C and CH2 targets

The total charge-changing cross sections and the partial cross sections of 56Fe fragmentation on polyethylene, carbon and aluminum targets at the highest energy of 496 A MeV are investigated using CR-39 plastic nuclear track detector. The total charge-changing cross-section for hydrogen target is calculated based on the results of polyethylene and carbon targets. It is found that the total charge-changing cross sections for fragmentation of 56Fe on hydrogen, carbon and aluminum targets are independent on the beam energy in our studied energies, and are consistent with the predictions of Bradt–Peter semi-empirical formula, Nilsen parameterized formula, NUCFRG2 and QMSFRG theoretical simulation codes. The partial cross sections for projectile fragment production are independent on beam energy in our studied energies for each targets and do not show a significant even-odd effect.

Qualitative measurement of spatial shielding isotopics via Compton imaging neutron-induced gamma rays using 3-D CdZnTe detectors

Abstract Characterization of shielding around special nuclear materials (SNMs) in unknown objects is important for homeland security, international safeguards and potential nuclear disarmament verification. Shielding modulates source photons and neutrons, complicating radiation-based SNM characterization, and indicates object purpose and guides response. Previous gamma-ray-based shielding detection algorithms only estimate effective shielding atomic number and areal thickness, complicating the characterization of compound shields comprised of multiple elements. Neutron-induced gamma rays, from inelastic scatter or capture, provide a complementary, isotope-specific shielding signal which can be localized using Compton imaging. Qualitative, angularly-resolved isotopic distributions in a compound shield were measured using polyethylene and polyvinyl chloride targets, excited via a single PuBe neutron source, and a 3-D, position-sensitive CdZnTe imaging spectrometer. Hydrogen capture gamma rays, which predominately originate from the polyethylene target, were well separated in angular space from chlorine capture gamma rays, originating in the polyvinyl chloride target, using Compton imaging. The described qualitative probe of spatial shielding isotopics can be immediately applied on any commercial gamma-ray imaging spectrometer without modification.

Studying Time-Like Electromagnetic Baryon Transitions with HADES in $$\pi \hbox {N}$$ π N Reactions

A dedicated program to study electromagnetic baryonic transitions in the time-like region has started using the pion beam and the High Acceptance Di-Electron Spectrometer set-up at GSI. Combined measurements of hadronic and dielectron final states have been performed for the first time in \(\pi \)-N reactions, using polyethylene and carbon targets. Differential cross sections of the exclusive channels with two pions in the final state (\(\pi ^-\pi ^+ n\), \(\pi ^0\pi ^- p\)) were obtained in the second resonance region with an unprecedented statistics. These new data were included in the partial wave analysis of the Bonn–Gatchina group together with the world data from pion and photon beam facilities. The obtained solution provides the excitation function of the two-pion production in photo- and pion- induced reactions around the pole of the D\(_{13}\) resonance N(1520) and of its decomposition into the different resonant, non-resonant and \(\rho \) contributions. Moreover, the exclusive \(ne^+e^-\) production gives insight into time-like electromagnetic structure of baryons using both \(e^+e^-\) invariant masses and angular distributions as most sensitive observables for model comparison. In addition, the extraction of the \(\rho \) contribution in the two-pion production channels can be used to investigate the validity of the Vector Dominance Model for electromagnetic baryon transitions. The prospects for future experiments in the third resonance region is also discussed.

∆E/∆E Measurements of Energetic Ions Using CVD Diamond Detectors

Experimental and computational results of a ΔE/ΔE diamond detection system are presented. The ΔE/ΔE detection system was evaluated using energetic proton and iron beams striking thick polyethylene targets at the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory (BNL). The measured data for diamond sensor A show good agreement with the Geant4 simulation. In addition, simulations have demonstrated the ability to identify hydrogen isotopes using a diamond detection system.

Comparison of electromagnetic and nuclear dissociation of Ne17

The Borromean drip-line nucleus Ne17 has been suggested to possess a two-proton halo structure in its ground state. In the astrophysical rp-process, where the two-proton capture reaction O15(2p,γ)Ne17 plays an important role, the calculated reaction rate differs by several orders of magnitude between different theoretical approaches. To add to the understanding of the Ne17 structure we have studied nuclear and electromagnetic dissociation. A 500 MeV/u Ne17 beam was directed toward lead, carbon, and polyethylene targets. Oxygen isotopes in the final state were measured in coincidence with one or two protons. Different reaction branches in the dissociation of Ne17 were disentangled. The relative populations of s and d states in F16 were determined for light and heavy targets. The differential cross section for electromagnetic dissociation (EMD) shows a continuous internal energy spectrum in the three-body system O15+2p. The Ne17 EMD data were compared to current theoretical models. None of them, however, yields satisfactory agreement with the experimental data presented here. These new data may facilitate future development of adequate models for description of the fragmentation process.

The 12C(n, 2n)11C cross section from threshold to 26.5 MeV.

The 12C(n, 2n)11C cross section was measured from just below threshold to 26.5 MeV using the Pelletron accelerator at Ohio University. Monoenergetic neutrons, produced via the 3H(d,n)4He reaction, were allowed to strike targets of polyethylene and graphite. Activation of both targets was measured by counting positron annihilations resulting from the β+ decay of 11C. Annihilation gamma rays were detected, both in coincidence and singly, using back-to-back NaI detectors. The incident neutron flux was determined indirectly via 1H(n,p) protons elastically scattered from the polyethylene target. Previous measurements fall into upper and lower bands; the results of the present measurement are consistent with the upper band.

Improved technique for preparation of deuterated-polyethylene targets

Abstract An improved method for preparation of self-supporting deuterated polyethylene targets using solvent casting technique is described. The improved method provides recommendations for solvent heating, solvent casting of the thin film, and subsequent heating treatment which is shown to greatly enhance the overall target strength and durability as needed for accelerator experiments. A detailed characterization using both optical and electron microscopy, differential scanning calorimetry, and Fourier transform infrared spectroscopy demonstrates the improvements using the post-casting heating treatment. The effects of heavy ion-induced target degradation and recommendations for use under these conditions is also discussed.

Low- Z shore of the “island of inversion” and the reduced neutron magicity toward O28

The two odd-even fluorine isotopes $^{27,29}\mathrm{F}$ were studied via in-beam $\ensuremath{\gamma}$-ray spectroscopy at the RIKEN Radioactive Isotope Beam Factory. A secondary beam of $^{30}\mathrm{Ne}$ was used to induce one-proton and one-proton--two-neutron removal reactions on carbon and polyethylene targets at midtarget energies of 228 MeV/$u$. Excited states were observed at 915(12) keV for $^{27}\mathrm{F}$ and at 1080(18) keV for $^{29}\mathrm{F}$. Both were assigned a $1/{2}_{1}^{+}$ spin and parity. The low transition energy for $^{29}\mathrm{F}$ largely disagrees with shell model predictions restricted to the $sd$ model space. Calculations using effective interactions that include the neutron $pf$ shell indicate that the $N=20$ gap is quenched for $^{29}\mathrm{F}$, thus extending the ``island of inversion'' to isotopes with proton number $Z=9$. Variations of the $N=20$ gap further reveal a strong correlation to the $1/{2}_{1}^{+}$ level energy in $^{29}\mathrm{F}$ and suggest a persistent reduced neutron gap for $^{28}\mathrm{O}$.

Secondary light-ion transport from intermediate-energy hadron experiments

The aim of this research is to produce double differential thick target yields, angular distributions and integrated yields for the inclusive production of neutrons, protons, deuterons, tritons, 3 He, and 4 He from intermediate heavy-ion interactions on thick targets of aluminium, polyethylene and other targets of interest to the radiation shielding program as specified by the National Aeronautics and Space Administration (NASA). In tandem with the experimental research, transport model calculations of these thick target yields were also performed. The first such experimental run was conducted in May 2015, with the expectation of improved experimental results at a following March 2016 run at the NASA Space Radiation Laboratory (NSRL) on the campus of Brookhaven National Laboratory (BNL). The May 2015 commissioning run served to test the electronics of the experimental setup, as well as the various detectors and other equipment under the conditions in which the following measurements will be run. The series of future accelerator-based experiments will rely on the inclusion of two separate upstream and downstream targets. Analysis of the data from both sets of detectors – liquid scintillator and sodium iodide – using both pulse height and time-of-flight methods will allow NASA to perform uncertainty quantification and sensitivity analysis on their transport codes and future shielding studies.

Production of an 15O beam using a stable oxygen ion beam for in-beam PET imaging

In advanced ion therapy, the 15O ion beam is a promising candidate to treat hypoxic tumors and simultaneously monitor the delivered dose to a patient using PET imaging. This study aimed at production of an 15O beam by projectile fragmentation of a stable 16O beam in an optimal material, followed by in-beam PET imaging using a prototype OpenPET system, which was developed in the authors’ group. The study was carried out in three steps: selection of the optimal target based on the highest production rate of 15O fragments; experimental production of the beam using the optimal target in the Heavy Ion Medical Accelerator Chiba (HIMAC) secondary beam course; and realization of in-beam PET imaging for the produced beam. The optimal target evaluations were done using the Monte Carlo simulation code PHITS. The fluence and mean energy of the secondary particles were simulated and the optimal target was selected based on the production rate of 15O fragments. The highest production rate of 15O was observed for a liquid hydrogen target, 3.27% for a 53cm thick target from the 16O beam of 430MeV/u. Since liquid hydrogen is not practically applicable in the HIMAC secondary beam course a hydrogen-rich polyethylene material, which was the second optimal target from the simulation results, was selected as the experimental target. Three polyethylene targets with thicknesses of 5, 11 or 14cm were used to produce the 15O beam without any degrader in the beam course. The highest production rate was measured as around 0.87% for the 11cm thick polyethylene target from the 16O beam of 430MeV/u when the angular acceptance and momentum acceptance were set at ±13 mrad and ±2.5%, respectively. The purity of the produced beam for the three targets were around 75%, insufficient for clinical application, but it was increased to 97% by inserting a wedge shape aluminum degrader with a thickness of 1.76cm into the beam course and that is sufficiently high. In-beam PET imaging was also performed for all produced beams using the OpenPET system. The purity improvement of the produced 15O beams was confirmed from the PET images.

Acceleration of deuterons from laser plasma in direct pulsed electron fluxes for generation of neutrons

We report the results of experiments in which laser plasma deuterons are accelerated toward beryllium and deuterated polyethylene targets in a drift tube by means of a direct pulsed flux of electrons accelerated to maximum energy of 250 keV. Neutrons produced as a result of the interaction of deuterons with the targets are detected. The yield of neutrons in some of the experimental series reaches 106 n/pulse. Using a pulsed magnetic field synchronized with the generation of laser plasma is proposed for increasing the neutron yield as a result of electron flux compression. This magnetic field in the drift region of electrons is created by a spiral coil of conical shape.