Heavy Particle Tracks Research Articles

Irradiation of Neurons with High-Energy Charged Particles: An In Silico Modeling Approach.

In this work, a stochastic computational model of microscopic energy deposition events is used to study for the first time damage to irradiated neuronal cells of the mouse hippocampus. An extensive library of radiation tracks for different particle types is created to score energy deposition in small voxels and volume segments describing a neuron’s morphology that later are sampled for given particle fluence or dose. Methods included the construction of in silico mouse hippocampal granule cells from neuromorpho.org with spine and filopodia segments stochastically distributed along the dendritic branches. The model is tested with high-energy 56Fe, 12C, and 1H particles and electrons. Results indicate that the tree-like structure of the neuronal morphology and the microscopic dose deposition of distinct particles may lead to different outcomes when cellular injury is assessed, leading to differences in structural damage for the same absorbed dose. The significance of the microscopic dose in neuron components is to introduce specific local and global modes of cellular injury that likely contribute to spine, filopodia, and dendrite pruning, impacting cognition and possibly the collapse of the neuron. Results show that the heterogeneity of heavy particle tracks at low doses, compared to the more uniform dose distribution of electrons, juxtaposed with neuron morphology make it necessary to model the spatial dose painting for specific neuronal components. Going forward, this work can directly support the development of biophysical models of the modifications of spine and dendritic morphology observed after low dose charged particle irradiation by providing accurate descriptions of the underlying physical insults to complex neuron structures at the nano-meter scale.

A theoretical model for the microdosimetry of discontinuous distributions of heavy particle tracks.

A novel approach to solving microdosimetry problems using conditional probabilities and geometric concepts has been developed. This approach is valid for cases where a convex site is immersed in uniform or discontinuous distributions of heavy charged particle tracks and assumes no restrictions in site geometry or the kind of randomness. These conditions are relevant to the study of microdosimetry in applications such as neutron capture therapy (NCT), irradiation experiments using heavy ion particle beams, environmental radon, or occupational exposure to radioactive materials. Expressions applicable to the case of surface-distributed sources of tracks are presented that may represent situations such as NCT, where boron compounds are bound to the membranes of cellular nuclei. Microdosimetric spectra, specific energy averages, and mean number of 10B capture reactions for cell inactivation are calculated, showing their dependence on 10B localisation.

Contribution of excited states in the heavy ion radiolysis of cyclooctane

The yields of the major end products produced in cyclooctane have been used to probe the effects of the track structure on radiation chemical processes induced by γ-rays, 1–15 MeV protons (LET 50–10 eV/nm), 5–20 MeV helium ions (LET 150–70 eV/nm), 7–29 MeV carbon ions (LET 800–660 eV/nm) and 10 MeV oxygen ions (LET 1150 eV/nm). There is a gradual decrease in the yields of cyclooctene, bicyclooctyl, and bicyclo[3.3.0]octane (pentalane) with increasing LET and there appears to be a considerable change in the yields of individual primary decomposition channels with varying LET. Shifting from γ-radiolysis to proton radiolysis results in an increase in product formation through the triplet state with a concomitant decrease in the singlet excited state, probably due to the enhanced probability of cross combination reactions of electrons and cations in the high density region of heavy particle tracks. It appears that the yield of both the triplet and singlet excited states of cyclooctane slowly decrease with increasing LET.

The rate of the electron-ion heat transfer in swift heavy particle tracks in metals

A model of the heat transfer from the excited electron gas to the ionic framework in tracks formed by swift heavy particles in metals is discussed. The model allows to predict the rate of the electron-to-ion heat transfer in tracks in the broad range of electron temperatures, both above and below the Fermi energy.

Particle track detection and relaxation transitions in polymer

The sensitivity of polymeric track detectors is influenced by the registration temperature, i.e. the temperature of the polymer at the moment of the particle impact. Here, temperature effects on registration were considered in terms of molecular mobility and relaxation transitions. An attempt was made to find a correlation between the formation of heavy particle tracks in polypropylene (PP) and known transitions in this polymer. The track etch rate was measured as function of temperature in the range between 77 and 373 K. The obtained results were compared with radiothermoluminescence curves and thermally stimulated currents used for detecting charges in molecular mobility. It was found that the increase of the track etch rate with decreasing registration temperature seems to correlate with γ and glass transitions. The decrease of the track etch rate at the irradiation temperatures below 130 K can be assigned to the situation when oxidation is prohibited but some structure reparation reactions still take place. The heating of irradiated PP samples at the temperatures above ca. 340 K leads to a dramatic increase of damage in heavy ion tracks which can be associated with another transition occurring in semicrystalline polyolefins.

Heavy particle tracks in polymers and polymeric track membranes

The review describes the evolution and present state of the use of accelerated heavy ion beams for investigation of track radiation effects and track membrane production at FLNR JINR. The research and development activity on track membranes (TMs) included studies of track formation process, latent track structure, environmental effects, sensitization of tracks, track etching, methods of membrane testing, designing and constructing facilities for membrane production. Some results on the physics and chemistry of ion tracks in polymers are described with the emphasis on the experiments performed during the last few years.

Single track effects, biostack and risk assessment

The scientific career of Prof. Bücker has spanned a very exciting period in the fledgling science of Space Radiation Biology. The capability for placing biological objects in space was developed, and the methods for properly packaging, retrieving and analyzing them were worked out. Meaningful results on the effects of radiation were obtained for the first time. In fact, many of the successful techniques and methodologies for handling biological samples were developed in Prof. Bücker's laboratories, as attested by the extensive Biostack program. He was the first to suggest and successfully carry out experiments in space directly aimed at measuring effects of single tracks of high-energy heavy galactic cosmic rays by specifically identifying whether or not the object had been hit by a heavy particle track. Because the “hit” frequencies of heavy galactic cosmic rays to cell nuclei in the bodies of space travelers will be low, it is expected that any effects to humans on the cellular level will be dominated by single-track cell traversals. This includes the most important generally recognized late effect of space radiation exposure: radiation-induced cancer. This paper addresses the single-track nature of the space radiation environment, and points out the importance of single “hits” in the evaluation of radiation risk for long-term missions occurring outside the earth's magnetic field. A short review is made of biological objects found to show increased effects when “hit” by a single heavy charged-particle in space. A brief discussion is given of the most provocative results from the bacterial spore Bacillus subtilis: experimental evidence that tracks can affect biological systems at much larger distances from the trajectory than previously suspected, and that the resultant inactivation cross section in space calculated for this system is very large. When taken at face value, the implication of these results, when compared to those from experiments performed at ground-based accelerators with beams at low energies in the same LET range, is that high-energy particles can exert their influence a surprising distance from their trajectory and the inactivation cross sections are some 20 times larger than expected. Clearly, beams from high-energy heavy-ion accelerators should be used to confirm these results. For those end points that can also be caused by low-LET beams such as high-energy protons, it is important to measure their action cross sections as well. The ratio of the cross sections for a high-LET beam to that of a low-LET beam is an interesting experimental ratio and, we suggest, of more intrinsic interest than the RBE (Relative Biological Effectiveness). It is a measure of the “biological” importance of one particle type relative to another particle type. This ratio will be introduced and given the name RPPE (Relative Per Particle Effectiveness). Values of RPPE have appeared in the literature and will be discussed. A rather well-known value of this quantity (13,520) has been suggested for the RPPE of high-energy iron ions to high-energy protons. This value was suggested by Letaw et al. Nature 330, 709–710 (1987)]; we will call it the Letaw limit. It will be discussed in terms of the importance of the heavy-ion component vs light-ion component of the galactic cosmic rays. It is also pointed out, however, that there may be unique effects from single tracks of heavy ions that do not occur from light-ion tracks. For such effects, the concepts of both RBE and RPPE lose their meaning.

Specifics of the formation of radiation defects in tracks of heavy particles in alkali-halide crystals

In this work the authors make a comparative analysis of the laws that govern the formation of stable hole defects in KBr crystals under irradiation with high-energy proton beams in comparison with the effects that are attained under low-intensity x-ray and intense pulsed electron excitation.

Production of perhydroxyl (HO2) within the track core in the heavy particle radiolysis of water

The radiolysis of the ferrous sulfate-cupric sulfate system with /sup 12/C ions has been examined to provide a measure of HO/sub 2/ production within heavy particle tracks. The HO/sub 2/ yield decreases rapidly with increased /sup 12/C ion energy and at a given LET is considerably less than found for /sup 4/He ions. It is concluded that HO/sub 2/ production primarily reflects the local density of energy deposition within the track core and not the partition of energy between the core and delta rays. Substantial revision of currently existing models is required to take into account the increase in core size with increased particle Z. 19 references, 1 figure.

Track effects in radiation chemistry: core processes in heavy-particle tracks as manifest by the hydrogen yield in benzene radiolysis

The energy dependences of the yields of H/sub 2/ produced in the radiolysis of liquid benzene by /sup 9/Be, /sup 11/B, and /sup 12/C ions have been examined over the particle energy range of 8-32 MeV. With increasing energy the differential yields rapidly decrease from maximum values of 0.52, 0.60, and 0.70 molecules/100 eV found at low energies. Extrapolation of the observed dependences indicates that the yields will approach that observed for fast electrons (G(H/sub 2/) = 0.038) in the region of 50-100 MeV even though the LET of the particle at these energies is still considerably greater than a few eV/Angstrom. The total amount of hydrogen produced by these particles in excess of that expected for fast electrons is estimated as 86,000, 141,000, and 190,000 molecules/particle, respectively, with most of this excess being produced at LETs well above 10 eV/Angstrom. The results presented here, together with previous data on /sup 1/H, /sup 2/D, /sup 4/He, and /sup 7/Li, give a comprehensive picture of the dependence of more processes in heavy-particle tracks on particle charge and energy. At a given LET the differential yields decrease by 20-40% for each unit increase in charge on the irradiating particle. This decrease cannotmore » be explained by delta-ray effects but rather reflects the increased diameter of the track core produced by the core highly charged ions. The local density of energy deposition and not the LET per se controls the H/sub 2/ yield. The authors conclude that the H/sub 2/ is produced almost entirely from high-order processes that occur within the track core as the result of events in very close proximity and at very early times. 7 figures, 2 tables.« less

Radiation chemistry of heavy-particle tracks. 1. General considerations

The radiation chemistry of heavy-particle tracks in dilute aqueous solution is considered in a unified manner. Emphasis is on the physical and chemical phenomena which are involved rather than on the construction of models to be used in actual calculations although the latter problem is discussed. A differential segment of a heavy-particle track is composed of two parts which we call core and penumbra; elementary considerations show that all properties of such a differential track can be uniquely specified in terms of a two-parameter system, and we choose energy per nucleon (E) and atomic numbers (Z) as independent parameters. The nature of heavy-particle-track processes varies with the magnitude of the energy deposit (LET), and we discuss three categories of track problems, for low-, intermediate-, and high-LET cases, respectively. Scavenger reactions normally terminate radical recombination in a track, and for heavy-particle tracks we find a criterion involving the scavenger concentration for a convenient separation of core and penumbra into essentially noninteracting parts which can be treated independently. Problems of the core expansion in the three regions are considered, and it is found that a versatile model can be constructed on concepts previously introduced by Ganguly and Magee. A model for themore » penumbra, based on the authors' electron-track theory, is presented and discussed.« less

Radiation chemistry of heavy-particle tracks. 2. Fricke dosimeter system

LBL-10283 Preprint Submitted to the Journal of Physical Chemistry RADIATION CHEMISTRY OF HEAVY PARTICLE TRACKS. II. THE FRICKE DOSIMETER SYSTEM Aloke Chatterjee and John L. Magee March 1980 TWO-WEEK LOAN COPY This is a Library Circulating Copy which may be borrowed for two weeks. For a personal retention copy, call . Info. Division, Ext. 6782. Prepared for the U.S. Department of Energy under Contract W-7405-ENG-48

Anisotropy of track registration in natural feldspar crystals

Abstract Terrestrial feldspars (orthoclase, anorthite, bytownite, labradorite, oligoclase, and albite) have been irradiated with 252Cf-fission products as well as Kr and Xe ions of different energies in order to study track length and track diameter as a function of crystal orientation. Both track length and track diameter of heavy particle tracks in orthoclase depend on the angle of incidence as well as on the angle of azimuth with respect to a fixed direction in the crystal surface plane. As to the plagioclase feldspars, only the track diameters appear to vary with crystal orientation. The different bulk and track etch rates for the main cleavage planes {001} and {010} are given. Within the plagioclase group the track registration properties were found to vary distinctly with the Ca content. Possible explanations for this observation are discussed.

Microdosimetric structure of heavy ion tracks in tissue.

Energy dissipation in tracks of high energy heavy ions in tissue shows a lateral spread of several to many microns depending on the energy of the primary particle. Complete dosimetric characterization, therefore, requires in addition to the Linear Energy Transfer (LET) information on the radial energy distribution. The theory of track structure distinguishes two regions: core and penumbra. The core is a narrow central zone with a radius in tissue far below 1 micron where energy deposition occurs mainly in processes of excitation and electron plasma oscillation. According to the Equipartition Principle, half of the total energy dissipation accrues in this manner. The penumbra is a peripheral zone enveloping the core where energy deposition occurs mainly in ionization events by energetic secondary electrons released by the primary particle in the center of the core traveling at rather high speed thus spreading laterally. The extension of the penumbra depends in a complex manner on the maximum transferable energy to electrons which in turn depends on the speed of the primary particle. Local energy density in the penumbra decreases with the square of increasing radius. It therefore amounts only to a very small fraction of the core density already a few microns away from the center. In general terms, track structure can be described as exhibiting a core of enormous energy density with lateral dimensions remaining entirely on the submicroscopic level surrounded by a penumbra where energy density drops precipitously to very small levels. The relationships are illustrated with micrographs of different sections of a heavy particle track in nuclear emulsion and their counterpart graphical plots.

Étude des traces de particules induites par les interactions de protons de 3 GeV dans différents minéraux

We present here an optical microscope study of heavy particle tracks induced by 3 GeV proton interactions in samples of mica, tektite, and olivine. The results are used to specify the conditions under which it should be possible to observe cosmic ray interactions in natural samples of these minerals. A new method of estimating cosmic ray exposure ages of tektites is also proposed.

LXXI. The abundance of lithium, beryllium, and boron in the primary cosmic radiation

Summary In a previous paper, a method of determining the charge, of heavy nuclei in the cosmic radiation was described which depended on measuring the δ-ray density along a track in a photographic emulsion and the multiple scattering of the particle. The results suggested the presence of a large proportion of the light elements lithium, beryllium and boron in the radiation, a result in contradiction with that of other workers. The first part of the present paper describes a re-examination of the original method and evidence for its reliability. It is shown that an alternative method, based on observations of grain-density in the tracks of heavy particles recorded in less sensitive emulsions, gives results in agreement with those obtained by the δ-ray method. In the second part, the results of a more extended series of measurements by the, δ-ray method are described. The results indicate that at geo-magnetic latitude 55° N., the flux of lithium, beryllium and boron nuclei in the cosmic radiation is equal t...

Grain Density in Photographic Tracks of Heavy Particles

The relation between grain density in photographic tracks and particle energy has been derived theoretically assuming that the probability that a grain be developed is given by $P=c[1\ensuremath{-}\mathrm{exp}[\ensuremath{-}b{(\frac{\mathrm{dE}}{\mathrm{dR}})}^{\frac{1}{2}}]$. Using a single pair of parameters $b$ and $c$ we can represent with this equation all experimental curves so far published for alpha-particles, tritons, protons, $\ensuremath{\pi}$ and $\ensuremath{\mu}$ mesons (University of Bristol). The agreement between experiments and theory is very satisfactory.

Measurements of range and angle of projection for the protons produced in the photo-disintegration of deuterium

The disintegration of a nucleus by the action of γ -rays—the nuclear photo-effect—was first observed by Chadwick and Goldhaber (1934) in the case of deuterium. The products of the disintegration are of course a proton and a neutron. In the first experiments only the protons liberated in the transformation were detected. This was done by means of an ionization chamber and “proportional” valve amplifier, and in this way a rough esti­mate was obtained of the mean kinetic energy with which the protons were ejected. Later the same authors (1935) supplemented the earlier evidence by detecting the neutrons liberated in the disintegration. For this purpose a boron-lined ionization chamber embedded in paraffin wax was used. They were further able to show that, per unit solid angle, the number of neutrons emitted in the direction of the γ -ray quanta was roughly about half the number emitted at right angles to that direction. The present paper describes an attempt to obtain more detailed information concerning the angular distribution of the disintegration particles and their binding energy in the deuterium nucleus. As was pointed out in each of the earlier discussions, such information can be obtained easily only by use of the expansion chamber. With the expansion chamber it is merely necessary to employ a deuterium-rich gas as filling and to be able to take satisfactory photographs of heavy particle tracks in the presence of the relatively intense background of cloud arising from the general γ -ray ionization in the chamber. These two conditions were successfully realized in the early summer of 1935, and a large number of photographs was taken with various arrangements. This work was carried out in the Cavendish Laboratory. Before all the photographs had been measured a preliminary report was made to the Norwich meeting of the British Association in September 1935. About the same time all three authors left Cambridge, and the task of completing the measurements and writing the final account of the research was considerably delayed in consequence. Two of us (J. C. and N. F.), however, made an entirely new set of measurements on all the photographs in March and April 1936. The results of these observations, carried out in the Physics Laboratory of the University of Liverpool, showed good agreement with the earlier incomplete data, and the final range and angular distributions have been based upon them exclusively.