Practical Implementation of Light Ion Beam Treatments
No abstract prepared.
62 RADIOLOGY AND NUCLEAR MEDICINE↗
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WE-H-BRA-09: Application of a Modified Microdosimetric-Kinetic Model to Analyze Relative Biological Effectiveness of Ions Relevant to Light Ion Therapy Using the Particle Heavy Ion Transport System
Purpose: To evaluate the dose and biological effectiveness of various ions that could potentially be used for actively scanned particle therapy. Methods: The PHITS Monte Carlo code paired with a microscopic analytical function was used to determine probability distribution functions of the lineal energy in 0.3µm diameter spheres throughout a water phantom. Twenty million primary particles for 1H beams and ten million particles for 4He, 7Li, 10B, 12C, 14N, 16O, and 20Ne were simulated for 0.6cm diameter pencil beams. Beam energies corresponding to Bragg peak depths of 50, 100, 150, 200, 250, and 300mm were used and evaluated transversely every millimeter and radially in annuli with outer radius of 1.0, 2.0, 3.0, 3.2, 3.4, 3.6, 4.0, 5.0, 10.0, 15.0, 20.0 and 25.0mm. The acquired probability distributions were reduced to dose-mean lineal energies and applied to the modified microdosimetric kinetic model for five different cell types to calculate relative biological effectiveness (RBE) compared to 60Co beams at the 10% survival threshold. The product of the calculated RBEs and the simulated physical dose was taken to create biological dose and comparisons were then made between the various ions. Results: Transversely, the 10B beam was seen to minimize relative biological dose in both the constant and accelerated dose change regions, proximal to the Bragg Peak, for all beams traveling greater than 50mm. For the 50mm beam, 7Li was seen to provide the most optimal biological dose profile. Radially small fluctuations (<4.2%) were seen in RBE while physical dose was greater than 1% for all beams. Conclusion: Even with the growing usage of 12C, it may not be the most optimal ion in all clinical situations. Boron was calculated to have slightly enhanced RBE characteristics, leading to lower relative biological doses.
60 APPLIED LIFE SCIENCES↗
Improved charge breeding efficiency of light ions with an electron cyclotron resonance ion source
The Californium Rare Isotope Breeder Upgrade is a new radioactive beam facility for the Argonne Tandem Linac Accelerator System (ATLAS). The facility utilizes a {sup 252}Cf fission source coupled with an electron cyclotron resonance ion source to provide radioactive beam species for the ATLAS experimental program. The californium fission fragment distribution provides nuclei in the mid-mass range which are difficult to extract from production targets using the isotope separation on line technique and are not well populated by low-energy fission of uranium. To date the charge breeding program has focused on optimizing these mid-mass beams, achieving high charge breeding efficiencies of both gaseous and solid species including 14.7% for the radioactive species {sup 143}Ba{sup 27+}. In an effort to better understand the charge breeding mechanism, we have recently focused on the low-mass species sodium and potassium which up to present have been difficult to charge breed efficiently. Unprecedented charge breeding efficiencies of 10.1% for {sup 23}Na{sup 7+} and 17.9% for {sup 39}K{sup 10+} were obtained injecting stable Na{sup +} and K{sup +} beams from a surface ionization source.
43 PARTICLE ACCELERATORS↗
Ab initio calculations of light-ion fusion reactions
The exact treatment of nuclei starting from the constituent nucleons and the fundamental interactions among them has been a long-standing goal in nuclear physics. Above all nuclear scattering and reactions, which require the solution of the many-body quantum-mechanical problem in the continuum, represent an extraordinary theoretical as well as computational challenge for ab initio approaches. The ab initio No-Core Shell Model/Resonating-Group Method (NCSM/RGM) complements a microscopic cluster technique with the use of realistic interactions, and a microscopic and consistent description of the nucleon clusters. This approach is capable of describing simultaneously both bound and scattering states in light nuclei. Recent applications to light nuclei scattering and fusion reactions relevant to energy production in stars and Earth based fusion facilities, such as the deuterium-{sup 3}He fusion, are presented. Progress toward the inclusion of the three nucleon force into the formalism is outlined.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Ab Initio Calculations Of Light-Ion Reactions
The exact treatment of nuclei starting from the constituent nucleons and the fundamental interactions among them has been a long-standing goal in nuclear physics. In addition to the complex nature of nuclear forces, one faces the quantum-mechanical many-nucleon problem governed by an interplay between bound and continuum states. In recent years, significant progress has been made in ab initio nuclear structure and reaction calculations based on input from QCD employing Hamiltonians constructed within chiral effective field theory. In this contribution, we present one of such promising techniques capable of describing simultaneously both bound and scattering states in light nuclei. By combining the resonating-group method (RGM) with the ab initio no-core shell model (NCSM), we complement a microscopic cluster approach with the use of realistic interactions and a microscopic and consistent description of the clusters. We discuss applications to light nuclei scattering, radiative capture and fusion reactions.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Light ion concentrations in Jupiter's inner magnetosphere
The light ion distribution in the inner Jovian magnetosphere is investigated using whistler dispersion measurements from the Voyager 1 plasma wave instrument and heavy ion plasma concentrations from the plasma instrument. Two models are developed for the light ion concentration over 14 L shells between L = 5.2 and 6.2, one giving a constant concentration along the field line and the other corresponding to an exponential density distribution. Due to heavy ion concentrations near the equator that are typically an order of magnitude larger than the light ion concentration, results obtained are mainly relevant to the light ion concentration outside of the torus. Light ion concentration near the equator ranges from about 1-10% of the heavy ion concentration, while outside the torus the light ions are the dominant species.
Tokar, R. L.↗
An interpretation of OGO light ion abundance measurements.
Light ion abundance measurements of OGO satellites and field aligned diffusive equilibrium theory with temperature and concentration latitudinal variations
Colin, L.↗
Dynamics of midlatitude light ion trough and plasmatails
Light ion trough measurements near midnight made by the RF ion mass spectrometer on OGO-4 operating in the high resolution mode in Feb. 1968 reveal the existence of irregular structure on the low latitude side of the midlatitude trough. Using two different relations between the equatorial convection electric field, assumed spatially invariant and directed from dawn to dusk, and Kp (one based on plasmapause measurements, the other on polar cap E field measurements) a model development was made of the outer plasmasphere. The model calculations produced multiple plasmatail extensions of the plasmasphere which compare favorably with the observed irregularities. Due to magnetic local time differences between the Northern and Southern Hemisphere along OGO's orbit, the time dependent irregularity structure observed is not symmetrical about the equator. The model development produces an outer plasmasphere boundary location which varies similarly to the observed minimum density point of the light ion trough. However the measurements are not extensive enough to yield conclusive proof that one of the electric field models is better than the other.
Chen, A. J.↗
Transport of Light Ions in Matter
A recent set of light ion experiments are analyzed using the Green's function method of solving the Boltzmann equation for ions of high charge and energy (the GRNTRN transport code) and the NUCFRG2 fragmentation database generator code. Although the NUCFRG2 code reasonably represents the fragmentation of heavy ions, the effects of light ion fragmentation requires a more detailed nuclear model including shell structure and short range correlations appearing as tightly bound clusters in the light ion nucleus. The most recent NTJCFRG2 code is augmented with a quasielastic alpha knockout model and semiempirical adjustments (up to 30 percent in charge removal) in the fragmentation process allowing reasonable agreement with the experiments to be obtained. A final resolution of the appropriate cross sections must await the full development of a coupled channel reaction model in which shell structure and clustering can be accurately evaluated.
Wilson, J. W.↗
Data-driven method to estimate contamination from light ion beam transmutation at colliders
Collisions of relativistic light ions, such as oxygen, neon, and magnesium, have been proposed as a way to examine the system-size dependence of dynamics typically associated with the quark-gluon plasma produced in collisions of heavier ions such as xenon, gold, or lead. Recent efforts at both the Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) have produced large datasets of proton-oxygen, oxygen-oxygen, and neon-neon collisions, catalyzing intense interest in experimental backgrounds associated with light-ion collisions. In particular, electromagnetic dissociation of light ions while they are circulating in a collider can result in beam contamination that is difficult to simulate precisely. Here we propose a data-driven method for evaluating the potential impact of beam contaminants on physics analyses. The method exploits the time dependence and smaller size of contaminant ion species to define control regions that can be used to quantify potential contamination effects. A simple model is used to illustrate the method and to study its robustness. Furthermore, this method can inform studies of recent LHC and RHIC data and could also be useful for future light-ion programs at the LHC and beyond.
Beam loss↗
Dynamics of Mid-latitude light ion trough and plasma tails
Light ion trough measurements near midnight made by the Bennett RF ion mass spectrometer on Ogo 4 operating in the high-resolution mode reveal the existence of irregular structure on the low-latitude side of the mid-latitude trough. By using two different relations between the equatorial convection electric field, assumed to be spatially invariant and directed from dawn to dusk, and Kp, a model development was made of the outer plasmasphere. The model calculations produced multiple plasma tails that compare favorably with the observed thermal proton irregularities. The model development produces an outer plasmasphere boundary location that varies similarly to the observed minimum density point of the light ion trough. However, the measurements are not extensive enough to yield conclusive proof that one of the electric field models is better than the other.
Chen, A. J.↗
Light Ion Double-Differential Cross Sections for Space Radiation
Neutrons and light ions have been shown to make large contributions to space radiation dose equivalent for realistic shielding scenarios. However, there are considerable uncertainties in the calculation of light ion production. Efficient and accurate calculation of light ion double-differential cross sections are required for input into space radiation transport codes. A thermal proton cross section model is developed which includes proton production from the 3 sources of projectile, central fireball, and target. It is shown that this 3-source model is able to explain the low-momentum, small-angle shoulder seen in proton spectra. Using the coalescence model, the thermal proton model is used to calculate light ion double-differential cross sections for use in space radiation transport codes. The 3-source model is also seen to be essential to explain the light ion shoulders, which are even more pronounced than the proton shoulders. Extensive comparisons between models and experimental measurements are shown and necessary future work is discussed.
Norbury, John W.↗
A data-driven method to estimate contamination from light ion beam transmutation at colliders
Collisions of relativistic light ions such as oxygen, neon, and magnesium, have been proposed as a way to examine the system-size dependence of dynamics typically associated with the quark-gluon plasma produced in collisions of heavier ions such as xenon, gold, or lead. Recent efforts at both the Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) have produced large datasets of proton-oxygen, oxygen-oxygen, and neon-neon collisions, catalyzing intense interest in experimental backgrounds associated with light ion collisions. In particular, electromagnetic dissociation of light ions while they are circulating in a collider can result in beam contamination that is difficult to simulate precisely. Here we propose a data-driven method for evaluating the potential impact of beam contaminants on physics analyses. The method exploits the time-dependence and smaller size of contaminant ion species to define control regions that can be used to quantify potential contamination effects. A simple mode
Accelerator Physics (physics.acc-ph)↗
Light ion components of the galactic cosmic rays: Nuclear interactions and transport theory
Light nuclei are present in the primary galactic cosmic rays (GCR) and are produced in thick targets due to projectile or target fragmentation from both nucleon and heavy induced reactions. In the primary GCR, He-4 is the most abundant nucleus after H-1. However, there are also a substantial fluxes of H-2 and He-3. In this paper we describe theoretical models based on quantum multiple scattering theory for the description of light ion nuclear interactions. The energy dependence of the light ion fragmentation cross section is considered with comparisons of inclusive yields and secondary momentum distributions to experiments described. We also analyze the importance of a fast component of lights ions from proton and neutron induced target fragementation. These theoretical models have been incorporated into the cosmic ray transport code HZETRN and will be used to analyze the role of shielding materials in modulating the production and the energy spectrum of light ions.
Cucinotta, F. A.↗
Light Ion Double-Differential Cross Section Parameterization and Results from the SHIELD Transport Code
Light ions and neutrons have been shown to make large contributions to space radiation dose equivalent for realistic shielding scenarios. Efficient and accurate calculations of light ion double-differential cross sections are required for input into space radiation transport codes. A thermal proton cross section model is developed which includes proton production from the three sources of projectile, central fireball, and target. It is shown that this three-source model is able to explain the low momentum shoulder seen in proton spectra. Using the coalescence model, the thermal proton model is used to calculate light ion double-differential cross sections employed in space radiation transport codes. The three-source model is also seen to be essential to explain the light ion shoulders, which are even more pronounced than the proton shoulders. Comparisons are also made to the cross section models used in the SHIELD transport code.
Space radiation↗
Experimental investigation of beam-ion losses induced by magnetic perturbations using the light ion beam probe technique in the ASDEX Upgrade tokamak
The impact of externally applied magnetic perturbations (MPs) on fast-ion losses has been investigated by means of the light ion beam probe (LIBP) technique in the ASDEX Upgrade tokamak. The LIBP technique allows to experimentally infer the fast-ion orbit displacement induced by MPs via first-orbit losses using scintillator based fast-ion loss detector (FILD) measurements. The fast-ion orbit displacement against different applied MP spectra has been studied. These shots were conducted in ELM mitigated H-mode plasmas. A rigid rotation of the MP coils was applied with a frequency of 1 Hz, with an n = 2 configuration and changing the differential phase between the upper and lower set of coils (ΔΦ ul ) on a shot-to-shot basis. Beam sources Q7 (tangential) and Q8 (radial) were used to probe different fast-ion orbits with FILD1. The measured fast-ion orbit displacement ranges from 3 to 20 mm approximately, and no qualitative difference is observed between ions from beam sources Q7 and Q8. The minimum is found for a ΔΦ ul ~ 50°, which is shifted with respect to the minimum of the plasma boundary displacement, found at ΔΦ ul ~ 0°. A first attempt to validate the orbit following code ASCOT—including the plasma response calculated with the MARS-F code—against these experimental measurements is performed. Finally, while the dependence of the first-orbit fast-ion displacement with ΔΦ ul does not match the experimental measurements, these simulations do capture other features such as the order of magnitude of the orbit displacement and the importance of the toroidal spectrum of the applied perturbation.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
The light ion trough.
A distinct feature of the ion composition results from the OGO-2, 4 and 6 satellites is the light ion trough, wherein the mid-latitude concentrations of H+ and He+ decrease sharply with latitude. In contrast to the 'main trough' in electron density observed primarily as a nightside phenomenon, the light ion trough persists during both day and night. For daytime winter hemisphere conditions and for all seasons during night, the mid-latitude light ion concentration decrease is a pronounced feature. In the dayside summer and equinox hemispheres, the rate of light ion decrease with latitude is comparatively gradual, and the trough boundary is less well defined, particularly for quiet magnetic conditions. In response to magnetic storms, the light ion trough minimum moves equatorward, and deepens, consistent with earlier evidence of the contraction of the plasmasphere in response to storm time enhancements in magnetospheric plasma convection.
Taylor, H. A., Jr.↗
Design of a compact electron cyclotron resonance ion source for medium charge state light ions
At the Australian Nuclear Science and Technology Organization we are developing a new isotope ratio mass spectrometer based on the measurement of multiple charge state ions. We have carried out a review of our existing ECR ion source and identified a number of design flaws. For the new instrument, we are producing a new ECR source and have refined the design, in particular by using 3D simulations to improve the magnetic confinement field and by a combination of simulations and experiments to improve the design of the microwave coupling.
43 PARTICLE ACCELERATORS↗