Papers by Lawrence Heilbronn
This report provides experimental data obtained using the Heavy Ion Medical Accelerator in Chiba ... more This report provides experimental data obtained using the Heavy Ion Medical Accelerator in Chiba (HIMAC) facility of the National Institute of Radiological Sciences (NIRS) in Japan. Previously, these data were only available from figures shown in [1-3]. The data from each paper are available starting on pages 3, 133, and 155, respectively. These data are also used in [4]. Listing 8: Double-differential Cross Section for 290 MeV/A C onto Cu (5 •) HIMAC_PRC_2001_DblDiff_290_MeVA_C_onto_Cu_05_deg.txt double-differential cross sections for 290 MeV/nucleon C + Cu 5 degree spectrum 1st column-energy (MeV) 2nd column-width of energy bin (MeV) 3rd column-double differential cross section (mb/sr/MeV) 4th column-uncertainty in cross section (mb/sr/MeV) Energy dE ddx d(ddx)
Physical Review Letters
Despite continued improvements in precision, an unexplained > 4 σ discrepancy persists between "b... more Despite continued improvements in precision, an unexplained > 4 σ discrepancy persists between "beam" and "bottle" measurements of the neutron lifetime. A new model proposed that conversions of neutrons into mirror neutrons can increase the apparent neutron lifetime by 1% via a small mass difference ∆m inside the 4.6 T magnetic field of the Beam Lifetime experiment. A search for neutron conversions in a 6.6 T magnetic field was performed at the Spallation Neutron Source. This explanation for the neutron lifetime discrepancy has been excluded for ∆m ≤ 400 neV.
Lawrence Berkeley National Laboratory, 2002
Neutron production cross sections have been measured from290 MeV/nucleon C and 600 MeV/nucleon Ne... more Neutron production cross sections have been measured from290 MeV/nucleon C and 600 MeV/nucleon Ne interacting in a slab ofsimulated Martian regolith/polyethylene composite, and from 400MeV/nucleon Ne interacting in a section of wall materials from theInternational Space Station. Neutron spectra were measured at 7 anglesbetween 5 degrees and 80 degrees, and for neutron energies 5 MeV andgreater. Spectra at forward angles are dominated by the breakup of theprojectile, whereas spectra at back angles show the typical exponentialfalloff with energy that is indicative of decay from the overlap regionand the target remnant. The measured total neutron production crosssections indicate that the regolith/polyethylene composite may be a moreeffective shielding material than the ISS wall materials, in terms of thenumber of neutrons produced.
Encyclopedia of Nuclear Energy, 2021
Applied Radiation and Isotopes, 2021
Monte Carlo transport codes PHITS and MCNP6 were used to calculate the production cross sections ... more Monte Carlo transport codes PHITS and MCNP6 were used to calculate the production cross sections of 225,227Ac, 227,229Th, 223,225Ra, and 229,230,231Pa via the bombardment of a232Th target with energetic protons, deuterons, and α-particles. The incident projectile energies ranged between 10 and 800 MeV/nucleon. When possible, the predicted production cross sections were compared with the available experimental data and other predictions. The degree of the codes' abilities to match the measured data provides a qualitative assessment of the codes' abilities to predict data from similar, but unmeasured, projectile/target systems. In addition, a comparison between calculated cross sections and data may provide insight into possible improvements in the physics models employed by those transport codes.
The Advanced Radiation Protection Thick Galactic Cosmic Ray (GCR) Shielding Project leverages exp... more The Advanced Radiation Protection Thick Galactic Cosmic Ray (GCR) Shielding Project leverages experimental and modeling approaches to validate a predicted minimum in the radiation exposure versus shielding depth curve. Preliminary results of space radiation models indicate that a minimum in the dose equivalent versus aluminum shielding thickness may exist in the 20-30 g/cm region. For greater shield thickness, dose equivalent increases due to secondary neutron and light particle production. This result goes against the long held belief in the space radiation shielding community that increasing shielding thickness will decrease risk to crew health. A comprehensive modeling effort was undertaken to verify the preliminary modeling results using multiple Monte Carlo and deterministic space radiation transport codes. These results verified the preliminary findings of a minimum and helped drive the design of the experimental component of the project. In first-of-theirkind experiments perf...
Bulletin of the American Physical Society, 2019
Frontiers in Physics, 2020
The helium (4He) component of the primary particles in the galactic cosmic ray spectrum makes sig... more The helium (4He) component of the primary particles in the galactic cosmic ray spectrum makes significant contributions to the total astronaut radiation exposure. 4He ions are also desirable for direct applications in ion therapy. They contribute smaller projectile fragmentation than carbon (12C) ions and smaller lateral beam spreading than protons. Space radiation protection and ion therapy applications need reliable nuclear reaction models and transport codes for energetic particles in matter. Neutrons and light ions (1H, 2H, 3H, 3He, and 4He) are the most important secondary particles produced in space radiation and ion therapy nuclear reactions; these particles penetrate deeply and make large contributions to dose equivalent. Since neutrons and light ions may scatter at large angles, double differential cross sections are required by transport codes that propagate radiation fields through radiation shielding and human tissue. This work will review the importance of 4He projectil...
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2018
Aiming to provide critical information in the fields of heavy ion therapy, radiation shielding in... more Aiming to provide critical information in the fields of heavy ion therapy, radiation shielding in space, and facility design for heavy-ion research accelerators, the physics models in three Monte Carlo simulation codes-PHITS, FLUKA, and MCNP6, were systematically benchmarked with comparisons to fifteen sets of experimental data for neutron production cross sections, which include various combinations of 12 C, 20 Ne, 40 Ar, 84 Kr and 132 Xe projectiles and nat Li, nat C, nat Al, nat Cu, and nat Pb target nuclides at incident energies between 135 MeV/nucleon and 600 MeV/nucleon. For neutron energies above 60% of the specific projectile energy per nucleon, the LAQGMS03.03 in MCNP6, the JQMD/JQMD-2.0 in PHITS, and the RQMD-2.4 in FLUKA all show a better agreement with data in heavyprojectile systems than with light-projectile systems, suggesting that the collective properties of projectile nuclei and nucleon interactions in the nucleus should be considered for light projectiles. For intermediate-energy neutrons whose energies are below the 60% projectile energy per nucleon and above 20 MeV, FLUKA is likely to overestimate the secondary neutron production, while MCNP6 tends towards underestimation. PHITS with JQMD shows a mild tendency for underestimation, but the JQMD-2.0 model with a modified physics description for central collisions generally improves the agreement between data and calculations. For low-energy neutrons (below 20 MeV), which are dominated by the evaporation mechanism, PHITS (which uses GEM linked with JQMD and JQMD-2.0) and FLUKA both tend to overestimate the production cross section, whereas MCNP6 tends to underestimate more systems than to overestimate. For total neutron production cross sections, the trends of the benchmark results over the entire energy range are similar to the trends seen in the dominate energy region. Also, the comparison of GEM coupled with either JQMD or JQMD-2.0 in the PHITS code indicates that the model used to describe the first stage of a nucleus-nucleus collision also affects the low-energy neutron production. Thus, in this case, a proper combination of two physics models is desired to reproduce the measured results. In addition, code users should be aware that certain models consistently produce secondary neutrons within a constant fraction of another model in certain energy regions, which might be correlated to different physics treatments in different models.
RADIOISOTOPES, 2019
The measurements of secondary neutron production cross sections from heavy-ion interactions play ... more The measurements of secondary neutron production cross sections from heavy-ion interactions play a key role in the development of transport model calculations that are used in a wide variety of applications. We briefly describe and highlight experiments conducted at HIMAC since the late 1990 s that measured secondary neutron cross sections over a wide variety of beam species, beam energies, and heavy target materials.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2019
RADIOISOTOPES, 2019
Measurements of nuclear fragmentation cross sections and of particle production in thick targets ... more Measurements of nuclear fragmentation cross sections and of particle production in thick targets are needed for the development of space radiation shielding. Cross sections are used as source terms for models of fragmentation and transport, and thick target measurements for model validation and to evaluate candidate shielding materials and concepts. Here we briefly review how HIMAC ion beams have been used to simulate elements of the space radiation field for cross section and thick target measurements.
AIP Conference Proceedings, 2002
Heavy ions with energies of hundreds to thousands of MeV/nucleon are present in the Galactic Cosm... more Heavy ions with energies of hundreds to thousands of MeV/nucleon are present in the Galactic Cosmic Rays and will be a source of risk to astronaut health when long-duration crewed missions are undertaken. Nuclear interactions of these GCR ions in shielding materials must be accurately modeled by transport codes in order to estimate the dose and dose equivalent at points inside a spacecraft. Uncertainties in the nuclear fragmentation cross sections are propagated into these estimates, and the overall uncertainties increase as shielding depth increases. A program of fragmentation cross section measurements has therefore been undertaken to reduce these uncertainties, using GCR-like ion species and energies in particle accelerators in the United States, at the Brookhaven National Laboratory's Alternating Gradient Synchrotron (AGS) and in Japan at the National Institute of Radiological Science's Heavy Ion Medical Accelerator in Chiba (HIMAC). An extensive set of data has been obtained with beams ranging from helium to iron and including most of the species that are prominent in the GCR.
SAE Technical Paper Series, 2003
EPJ Web of Conferences, 2017
The aim of this research is to produce double differential thick target yields, angular distribut... more 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 acceleratorbased 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.
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Papers by Lawrence Heilbronn