High-energy Nuclear Particles Research Articles

Optically based dosimetry of high-energy radiation using the undoped lithium tetraborate crystals: Nonlinear features

The lithium tetraborate (LTB) optical characteristics studies, particularly the luminescence and phosphorescence after irradiation on the M − 30 microtron to create radiation defects, are presented. The investigation was conducted in a wide range of intensities of accelerated electrons, their energies within 7–15 MeV, and absorbed radiation doses.The threshold character and nonlinear influence of the radiation defects on the optical dosimetric characteristics of LTB were established when their concentration became comparable to that of intrinsic or structural defects. Undoped optical crystals LTB are a convenient target for this type of research. It is shown that the combination of optical data from the study of thermally stimulated luminescence and phosphorescence allows one to control the irradiation conditions: flux density and absorbed dose.The obtained results are important for radiation technologies that use high doses of radiation, and can also be taken into account when planning of dosimetric procedures in medicine using high-energy nuclear particles.

Effect of Irradiation on the Tensile Properties of Nano-sized Ti-Al Alloy Single Crystals: A Study Using Molecular Dynamics Simulations

The present work reports molecular dynamics (MD) simulation based study on the irradiation phenomena and its effect on the tensile properties of nanosized single crystals of Ti-Al alloy nanoparticles of varying compositions using Embedded Atom Method (EAM) potential. It is observed that after the alloy nano-crystals are hit by some high energy nuclear particles some atoms within the crystal are knocked out from their regular positions and subsequently give rise to displacement cascade which grows, propagate and after some instance achieves an equilibrium size. In the present study, the vacancy concentration of the irradiated crystal, which can be taken as a parameter for assessing the damage has been estimated for the crystals with varying size and initial temperature. Moreover, the damaging effect of the crystals has been assessed in terms of the temperature rise. It has been observed that the damaging effect of the crystals markedly increases with increase in the velocity of the primary knock-on atoms (PKA). The effect of radiation damage of Ti-Al alloy nanoparticles with varying compositions on their mechanical properties has been investigated by means of a subsequent tensile modelling of the irradiated particles. It was seen that the strength and ductility of the irradiated particle has decreased significantly as compared to the non-irradiated particle of same size and alloy composition. This kind of study can be extended with an objective to design and develop a new type of radiation resistant materials for the application in nuclear reactors.

Charged particle energy spectra from laser-induced processes: Nuclear fusion in ultra-dense deuterium D(0)

Clear high-energy particle signatures of laser-induced nuclear fusion are now observed by energy spectroscopy with standard scintillation detectors. The particles observed are ejected from ultra-dense deuterium D(0) on the laser target. A colored glass-filter is used to distinguish between particles that create multiple photons in the plastic scintillator (electrons and ions) and those that interact only in the glass filter or in the photomultiplier (mesons and muons). Ions are observed with energy in the MeV range as in previous time-of-flight experiments. They lose kinetic energy in a gas at a pressure up to 20 mbar as expected. Electron energy distributions with exponential shape corresponding to a temperature up to 600 MK indicate ignition of fusion. Intense emission of penetrating high-energy nuclear particles is detected at a high signal level as also reported previously (in this journal) for spontaneous processes. Both line-spectra and broad energy distributions are observed for these particles. The broad distributions give linear Kurie plots and are thus due to beta decay as concluded previously.

Excess noise and deep levels in GaAs detectors of nuclear particles and ionizing radiation

Experimental results on various electric noises in the Al/GaAs structures with Schottky barriers and the AlGaAs/i-GaAs heterostructures that are employed in GaAs detectors of high-energy nuclear particles and ionizing radiation are reviewed. Methods for the study of the parameters of deep levels (DLs) are described. The systematization of DLs that are formed in GaAs barrier structures and heterostructures in the presence of various impurities and defects of crystal lattice is performed. The results on the effect of DLs on the 1/f noise of the detectors and the data on radiation stability under the action of high-energy electrons and γ radiation are presented. Practical recommendations on the type and production technology of a detector with the minimum level of the 1/f noise are proposed. The method for the measurement of the 1/f noise of the detectors based on the Al/i-GaAs barrier structures is recommended for evaluation of the radiation stability and the breakdown voltage of high-voltage detectors.

Biological characterization of low-energy ions with high-energy deposition on human cells.

During space travel, astronauts are exposed to cosmic radiation that is comprised of high-energy nuclear particles. Cancer patients are also exposed to high-energy nuclear particles when treated with proton and carbon beams. Nuclear interactions from high-energy particles traversing shielding materials and tissue produce low-energy (<10 MeV/n) secondary particles of high-LET that contribute significantly to overall radiation exposures. Track structure theories suggest that high charge and energy (HZE) particles and low-energy secondary ions of similar LET will have distinct biological effects for cellular and tissue damage endpoints. We investigated the biological effects of low-energy ions of high LET utilizing the Tandem Van de Graaff accelerator at the Brookhaven National Laboratory (BNL), and compared these to experiments with HZE particles, that mimic the space environment produced at NASA Space Radiation Laboratory (NSRL) at BNL. Immunostaining for DNA damage response proteins was carried out after irradiation with 5.6 MeV/n boron (LET 205 keV/μm), 5.3 MeV/n silicon (LET 1241 keV/μm), 600 MeV/n Fe (LET 180 keV/μm) and 77 MeV/n oxygen (LET 58 keV/μm) particles. Low-energy ions caused more persistent DNA damage response (DDR) protein foci in irradiated human fibroblasts and esophageal epithelial cells compared to HZE particles. More detailed studies comparing boron ions to Fe particles, showed that boron-ion radiation resulted in a stronger G2 delay compared to Fe-particle exposure, and boron ions also showed an early recruitment of Rad51 at double-strand break (DSB) sites, which suggests a preference of homologous recombination for DSB repair in low-energy albeit high-LET particles. Our experiments suggest that the very high-energy radiation deposition by low-energy ions, representative of galactic cosmic radiation and solar particle event secondary radiation, generates massive but localized DNA damage leading to delayed DSB repair, and distinct cellular responses from HZE particles. Thus, low-energy heavy ions provide a valuable probe for studies of homologous recombination repair in radiation responses.

Marietta Blau: Pioneer of Photographic Nuclear Emulsions and Particle Physics

During the 1920s and 1930s, Viennese physicist Marietta Blau (1894–1970) pioneered the use of photographic methods for imaging high-energy nuclear particles and events. In 1937 she and Hertha Wambacher discovered “disintegration stars” – the tracks of massive nuclear disintegrations – in emulsions exposed to cosmic radiation. This discovery launched the field of particle physics, but Blau’s contributions were underrecognized and she herself was nearly forgotten. I trace Blau’s career at the Institut fur Radiumforschung in Vienna and the causes of this “forgetting,” including her forced emigration from Austria in 1938, the behavior of her colleagues in Vienna during and after the National Socialist period, and the flawed Nobel decision process that excluded her from a Nobel Prize.

Experimental investigation of the effect of high-energy protons on charge-coupled devices

The effect of 1000-MeV protons on CCD matrix based image sensors, which are widely used in various equipment on-board space vehicles, have been studied in order to determine how the local structural damage of crystalline lattice caused by high-energy nuclear particles influences the parameters of CCD matrices. The dependence of the dark current of CCD matrices on the proton irradiation has been studied in a range of fluences up to 2 × 1011 cm−2.

Martensitic Transformations in Neutron Irradiated and Helium Implanted Stainless Steels

Abstract Results of experiments aimed at revealing the phase-structure stability as well as mechanisms of the mechanical property changes formation in austenitic chrome-nickel and manganese steels irradiated with high-energy nuclear particles and subjected to elevated temperatures are presented and discussed. Influence of the phase-structure transformations on radiation hardening and embrittlement of steels used in nuclear power industry is analyzed. Change in the experimentally determined “true” values of critical strains and peculiarities of the α'-phase initiation in deformed steels Cr18Ni9Ti, 12Cr18Ni10Ti as a function of temperature and deformation rate, type and fluence of the bombarding particles are discussed. Influence of irradiation on the martensitic structure morphology, critical γ→α' transformation parameters, and thermal effects accompanying the nondiffusion phase transformation is analyzed. The revealed effects are discussed in terms of the internal strength field changes due to thermal and radiation effects.

Study of extensive air showers at Mount Norikura. III. Core structure and high-energy events

An area of 3 × 4 m2 is covered by 48 plastic scintillators above and below a water tank 2 m in depth. From maps of the charged-particle density and the energy-flow density in the core region, properties of EAS cores and of the high-energy nucleon component have been studied. About 25% of observed cores show the complicated structure of a "multiple core". These can be understood as due to effects of high-energy nuclear particles having large transverse momenta of several GeV/c to a few tens of GeV/c. The frequency of occurrence of such events increases with the size of EAS only slowly, but it decreases rapidly with increasing distance between the main cores and subcores. There is no clear distinction in the average lateral density distribution of charged particles between these multiple-core EAS and ordinary EAS at points distant from the cores.Comparing the particle density in both layers of detectors (top and bottom), the activity of cores has been studied. This fluctuates more than would be expected from the lateral structure of the showers.

Three-dimensional simulation of air showers. Core structures

Three-dimensional Monte Carlo simulations of extensive air showers were made with a model of nuclear interaction based essentially on the two-fireball model. Monte Carlo simulations were tried with primary protons of energy 106 and 2.5 × 105 GeV. Various quantities related to electrons, nuclear-active particles, and muons were obtained which enable us to get detailed information on the development of individual showers.Among various features so far simulated, those of core structures, in particular, are presented in great detail and discussed in connection with shower development. Within the framework of the fireball model the following main features were noted for the formation of multiple electron cores. The fraction of multicored events is strongly dependent on the primary energy, and decreases considerably with increasing height. These events were all initiated at high altitudes and none of them had high-density peaks with a separation of a few or more meters. High-energy nuclear particles play an important role in producing multicored events, but none of the peaks in multi-cored events were produced by a single γ ray.These features, in comparison with the experimental results, require the introduction of a large mean transverse momentum for nucleons, particularly at high energies [Formula: see text]. It seems likely that it increases with energy.

The measurement of the momenta of high energy charged particles in a diffusion cloud chamber

The problems associated with the measurement of the momenta of high energy nuclear particles in a diffusion cloud chamber are described. An optical system has been developed for which the apparent curvatures in the object due to distortion have an average value of 0.005 m-1 over the field of view. Spurious track curvatures due to convective gas motions within the cloud chamber are of similar magnitude, when a flash delay time adequate to allow the photography of the tracks of minimally ionizing particles in hydrogen is used. These figures result in a nominal accuracy of about 2% in the momentum of a 1000 MeV proton (momentum 1.7 × 109 eV/c) in a magnetic field of 1.3 × 104 G for tracks 20 cm long. The corresponding maximum detectable momentum is 8.5 × 1010 eV/c.

Collisions of High Energy Nuclear Particles with Nuclei

The experimental results for n-p and p-p scattering at high energies are described, and a review of the present status of theoretical interpretation is given. For the scattering of 90-Mev neutrons by protons the angular distribution indicates that only even states of angular momentum are strongly effective. Evidence of the operation of exchange forces is mentioned. In the scattering of 32-Mev protons by protons the angular distribution is appropriate to s-state interaction alone. The 340-Mev p-p results indicate the existence of noncentral (tensor) forces in states of odd orbital angular momentum.