WorldWideScience

Sample records for alpha particle model

  1. Model of cell response to {\\alpha}-particle radiation

    CERN Document Server

    Liu, Longjian

    2012-01-01

    Starting from a general equation for organism (or cell system) growth and attributing additional cell death rate (besides the natural rate) to therapy, we derive an equation for cell response to {\\alpha} radiation. Different from previous models that are based on statistical theory, the present model connects the consequence of radiation with the growth process of a biosystem and each variable or parameter has meaning regarding the cell evolving process. We apply this equation to model the dose response for {\\alpha}-particle radiation. It interprets the results of both high and low linear energy transfer (LET) radiations. When LET is high, the additional death rate is a constant, which implies that the localized cells are damaged immediately and the additional death rate is proportional to the number of cells present. While at low LET, the additional death rate includes a constant term and a linear term of radiation dose, implying that the damage to some cell nuclei has a time accumulating effect. This model ...

  2. Ionization cluster size distribution for alpha particles: Experiment, modelling

    International Nuclear Information System (INIS)

    The paper presents data for measured ionization cluster size distributions by alpha particles in tissue equivalent media and comparison with the simulated data for liquid water. The experiments were carried out with a beam of 4.6 MeV alpha particles performed in a setup called the JET Counter. The theoretically derived cluster size distributions for alphas particles were obtained using the K-means algorithm. The simulation was carried out by Monte Carlo track structure calculations using cross sections for liquid water. The first moments of cluster size distributions, derived from K-means algorithm as a function of diameter of cluster centroid, were compared with the corresponding moments derived from the experiments for nitrogen and propane targets. It was found that the ratio of the first moments for water to gas targets correlates well with the corresponding ratio of the mean free paths for primary ionization by alpha particles in the two media. It is shown that the cluster size distributions for alpha particles in water, obtained from K-means algorithm, are in agreement with the corresponding distributions measured experimentally in nitrogen or propane gas targets of nano-meter sizes. (authors)

  3. Gaseous swelling model in the alpha-particles straggling field

    International Nuclear Information System (INIS)

    In the work for the physical model the following key presuppositions were accepted: alpha particles Gauss distribution in the straggling field is expected; the helium embryo is the helium atom plus the two vacancies; gaseous pores coalescence is resulted their migration in the tension field and Brownian movement; the preservation of helium atoms in the coalescence process is expected; it consequence is swelling. At the initial stage the behavior of pores ensemble with taking into account of a point defects formation during irradiation process have been analyzed. It is expected, that development of this ensemble will be take place during the following annealing of the matrix. The main presuppositions on the this stage of calculation are as follows: there are the principal elements of the microstructure - are taking into account in the kinetic equations - implanted helium interstitials, vacancies, dislocation network, Frank loops, pores; it is excepted, that two interstitial helium atoms form the pore embryo; two interstitials Frank loops at distances between components equal to lattice constant; mechanisms of pores formation in the matrix and dislocation are expected different; the additional channel of pores growth is Frank loops dropping. The typical kinetic equation for interstitial from complete equation system is presented. The pores ensemble evolution for iron irradiated by helium ions with energy E=400 keV up to integral dose 101|7 ion/cm2 at 100 deg C temperature and following annealing at temperature 800 deg C is calculated. It is shown that pores distribution by sizes is shifting forward big sizes with increase of annealing time

  4. Nanodosimetry and nanodosimetric-based models of radiation action for radon alpha particles

    International Nuclear Information System (INIS)

    The objective of our research work is to provide -- with the aid of biophysical models of radiation action -- information on human risks following exposure to radon alpha particles. The approach proposed consists of (1) developing appropriate models (parametric and non-parametric) for alpha radiation induction of relevant end points (survival, cellular transformation), (2) providing an accurate physical characterization of the particle tracks in terms of nanodosimetric distributions, (3) supporting the models by detailed, molecular studies of the direct and indirect effects of alpha particles on DNA. Activities in the second year of this project are described

  5. Nanodosimetry and nanodosimetric-based models of radiation action for radon alpha particles

    Energy Technology Data Exchange (ETDEWEB)

    1992-01-01

    The objective of our research work is to provide -- with the aid of biophysical models of radiation action -- information on human risks following exposure to radon alpha particles. The approach proposed consists of (1) developing appropriate models (parametric and non-parametric) for alpha radiation induction of relevant end points (survival, cellular transformation), (2) providing an accurate physical characterization of the particle tracks in terms of nanodosimetric distributions, (3) supporting the models by detailed, molecular studies of the direct and indirect effects of alpha particles on DNA. Activities in the second year of this project are described.

  6. Fokker Planck kinetic modeling of suprathermal alpha-particles in a fusion plasma

    OpenAIRE

    Peigney, Benjamin-Edouard; Larroche, Olivier; Tikhonchuk, Vladimir

    2014-01-01

    We present an ion kinetic model describing the ignition and burn of the deuterium-tritium fuel of inertial fusion targets. The analysis of the underlying physical model enables us to develop efficient numerical methods to simulate the creation, transport and collisional relaxation of fusion reaction products (alpha-particles) at a kinetic level. A two-energy-scale approach leads to a self-consistent modeling of the coupling between suprathermal alpha-particles and the thermal bulk of the impl...

  7. Imaging alpha particle detector

    Science.gov (United States)

    Anderson, D.F.

    1980-10-29

    A method and apparatus for detecting and imaging alpha particles sources is described. A dielectric coated high voltage electrode and a tungsten wire grid constitute a diode configuration discharge generator for electrons dislodged from atoms or molecules located in between these electrodes when struck by alpha particles from a source to be quantitatively or qualitatively analyzed. A thin polyester film window allows the alpha particles to pass into the gas enclosure and the combination of the glass electrode, grid and window is light transparent such that the details of the source which is imaged with high resolution and sensitivity by the sparks produced can be observed visually as well. The source can be viewed directly, electronically counted or integrated over time using photographic methods. A significant increase in sensitivity over other alpha particle detectors is observed, and the device has very low sensitivity to gamma or beta emissions which might otherwise appear as noise on the alpha particle signal.

  8. Alpha-particle diagnostics

    Energy Technology Data Exchange (ETDEWEB)

    Young, K.M.

    1991-01-01

    This paper will focus on the state of development of diagnostics which are expected to provide the information needed for {alpha}- physics studies in the future. Conventional measurement of detailed temporal and spatial profiles of background plasma properties in DT will be essential for such aspects as determining heating effectiveness, shaping of the plasma profiles and effects of MHD, but will not be addressed here. This paper will address (1) the measurement of the neutron source, and hence {alpha}-particle birth profile, (2) measurement of the escaping {alpha}-particles and (3) measurement of the confined {alpha}-particles over their full energy range. There will also be a brief discussion of (4) the concerns about instabilities being generated by {alpha}-particles and the methods necessary for measuring these effects. 51 refs., 10 figs.

  9. The threshold states in the frame of the model of binding alpha particles

    International Nuclear Information System (INIS)

    A model of nuclear matter built from alpha-particles is proposed. In this model, nuclei possess the molecular structure. Analyzing the numbers of bonds, one gets the formula for the binding energy of a nucleus. The structure is determined by the minimum of the total potential energy, where interaction between alpha-particles is pairwise. The calculated binding energies show a good agreement with experiment. According to this model we can estimate the energy of Bose-Condensation for the 4N nuclei

  10. Alpha particles in fusion research

    International Nuclear Information System (INIS)

    This collection of 39 (mostly view graph) presentations addresses various aspects of alpha particle physics in thermonuclear fusion research, including energy balance and alpha particle losses, transport, the influence of alpha particles on plasma stability, helium ash, the transition to and sustainment of a burning fusion plasma, as well as alpha particle diagnostics. Refs, figs and tabs

  11. Alpha Particle Diagnostic

    Energy Technology Data Exchange (ETDEWEB)

    Fisher, Ray, K.

    2009-05-13

    The study of burning plasmas is the next frontier in fusion energy research, and will be a major objective of the U.S. fusion program through U.S. collaboration with our international partners on the ITER Project. For DT magnetic fusion to be useful for energy production, it is essential that the energetic alpha particles produced by the fusion reactions be confined long enough to deposit a significant fraction of their initial ~3.5 MeV energy in the plasma before they are lost. Development of diagnostics to study the behavior of energetic confined alpha particles is a very important if not essential part of burning plasma research. Despite the clear need for these measurements, development of diagnostics to study confined the fast confined alphas to date has proven extremely difficult, and the available techniques remain for the most part unproven and with significant uncertainties. Research under this grant had the goal of developing diagnostics of fast confined alphas, primarily based on measurements of the neutron and ion tails resulting from alpha particle knock-on collisions with the plasma deuterium and tritium fuel ions. One of the strengths of this approach is the ability to measure the alphas in the hot plasma core where the interesting ignition physics will occur.

  12. Fokker Planck kinetic modeling of suprathermal alpha-particles in a fusion plasma

    CERN Document Server

    Peigney, Benjamin-Edouard; Tikhonchuk, Vladimir

    2014-01-01

    We present an ion kinetic model describing the ignition and burn of the deuterium-tritium fuel of inertial fusion targets. The analysis of the underlying physical model enables us to develop efficient numerical methods to simulate the creation, transport and collisional relaxation of fusion reaction products (alpha-particles) at a kinetic level. A two-energy-scale approach leads to a self-consistent modeling of the coupling between suprathermal alpha-particles and the thermal bulk of the imploding plasma. This method provides an accurate numerical treatment of energy deposition and transport processes involving suprathermal particles. The numerical tools presented here are validated against known analytical results. This enables us to investigate the potential role of ion kinetic effects on the physics of ignition and thermonuclear burn in inertial confinement fusion schemes.

  13. Skeletal dosimetry models for alpha-particles for use in molecular radiotherapy

    Science.gov (United States)

    Watchman, Christopher J.

    Molecular radiotherapy is a cancer treatment methodology whereby a radionuclide is combined with a biologically active molecule to preferentially target cancer cells. Alpha-particle emitting radionuclides show significant potential for use in molecular radiotherapy due to the short range of the alpha-particles in tissue and their high rates of energy deposition. Current radiation dosimetry models used to assess alpha emitter dose in the skeleton were developed originally for occupational applications. In medical dosimetry, individual variability in uptake, translocation and other biological factors can result in poor correlation of clinical outcome with marrow dose estimates determined using existing skeletal models. Methods presented in this work were developed in response to the need for dosimetry models which account for these biological and patient-specific factors. Dosimetry models are presented for trabecular bone alpha particle dosimetry as well as a model for cortical bone dosimetry. These radiation transport models are the 3D chord-based infinite spongiosa transport model (3D-CBIST) and the chord-based infinite cortical transport model (CBICT), respectively. Absorbed fraction data for several skeletal tissues for several subjects are presented. Each modeling strategy accounts for biological parameters, such as bone marrow cellularity, not previously incorporated into alpha-particle skeletal dosimetry models used in radiation protection. Using these data a study investigating the variability in alpha-particle absorbed fractions in the human skeleton is also presented. Data is also offered relating skeletal tissue masses in individual bone sites for a range of ages. These data are necessary for dose calculations and have previously only been available as whole body tissue masses. A revised 3D-CBIST model is also presented which allows for changes in endosteum thickness to account for revised target cell location of tissues involved in the radiological

  14. Model of alpha particle diffusion in the outer limiter shadow of TFTR

    International Nuclear Information System (INIS)

    A new code, Monte Carlo Collisional Stochastic Orbit Retracing (MCCSOR), has been developed to model the alpha particle loss signal as measured by the outer midplane scintillator detector in TFTR. The shadowing effects due to the outer limiters and the detector itself have been included, along with a pitch angle scattering and stochastic ripple diffusion. Shadowing by the outer limiters has a strong effect on both the magnitude and pitch angle distribution of the calculated loss. There is at least qualitative agreement between the calculated results and the experimental data

  15. Mechanistic model of radon-induced lung cancer risk at low exposure levels based on cellular alpha particle hits

    Energy Technology Data Exchange (ETDEWEB)

    Werner, Hofmann; Hatim, Fakir [Salzburg Univ., Div. of Physics and Biophysics, Dept. of Material Science (Austria); Lucia-Adina, Truta-Popa [Babes-Bolyai Univ., Faculty of Physics (Romania)

    2006-07-01

    To explore the role of the multiplicity of cellular hits by radon progeny alpha particles for lung cancer incidence, the number of single and multiple alpha particle hits were computed for basal and secretory cells in the bronchial epithelium of human airway bifurcations employing Monte Carlo methods. Hot spots of alpha particle hits were observed at the branching points of bronchial airway bifurcations, suggesting that multiple alpha particle hits may occur primarily at carinal ridges. Random alpha particle intersections of bronchial cells during a given exposure period, selected from a Poisson distribution, were simulated by an initiation-promotion model, based on experimentally observed cellular transformation and survival functions. To consider potential bystander effects, which have been observed in cellular in vitro studies, alpha particle interactions were also simulated for larger sensitive target volumes in bronchial epithelium, consisting of a collection of cells. Lung cancer risk simulations indicated that cancer induction for continuous exposures is related to the cycle time of an irradiated cell, thus exhibiting a distinct dose-rate effect. While the dominant role of single hits leads to a linear dose-response relationship at low radon exposure levels, predicted lung cancer risk for a collection of interacting cells exhibits a linear-quadratic response, suggesting that bystander effects, if operating at all under in vivo irradiations, may be restricted to a small number of adjacent cells. (author)

  16. Mechanistic model of radon-induced lung cancer risk at low exposure levels based on cellular alpha particle hits

    International Nuclear Information System (INIS)

    To explore the role of the multiplicity of cellular hits by radon progeny alpha particles for lung cancer incidence, the number of single and multiple alpha particle hits were computed for basal and secretory cells in the bronchial epithelium of human airway bifurcations employing Monte Carlo methods. Hot spots of alpha particle hits were observed at the branching points of bronchial airway bifurcations, suggesting that multiple alpha particle hits may occur primarily at carinal ridges. Random alpha particle intersections of bronchial cells during a given exposure period, selected from a Poisson distribution, were simulated by an initiation-promotion model, based on experimentally observed cellular transformation and survival functions. To consider potential bystander effects, which have been observed in cellular in vitro studies, alpha particle interactions were also simulated for larger sensitive target volumes in bronchial epithelium, consisting of a collection of cells. Lung cancer risk simulations indicated that cancer induction for continuous exposures is related to the cycle time of an irradiated cell, thus exhibiting a distinct dose-rate effect. While the dominant role of single hits leads to a linear dose-response relationship at low radon exposure levels, predicted lung cancer risk for a collection of interacting cells exhibits a linear-quadratic response, suggesting that bystander effects, if operating at all under in vivo irradiations, may be restricted to a small number of adjacent cells. (author)

  17. The fine structure constant alpha: relevant for a model of a self-propelling photon and for particle masses

    Science.gov (United States)

    Greulich, Karl O.

    2015-09-01

    A model for a self propelling (i.e. massless) photon1 is based on oscillations of a pair of charges amounting to elementary charge divided by SQRT alpha, where alpha is the fine structure (Sommerfeld) constant. When one assumes a similar model for particles that do have rest mas (i.e. which are non- self propelling), alpha plays also a role in the rest masses of elementary particles. Indeed all fundamental elementary particle masses can be described by the alpha / beta rule2 --> m(particle) = alpha-n * betam* 27.2 eV /c2 where beta is the proton to electron mass ratio 183612 and n= 0….14, m= -1,0 or Thus, photons and particle masses are intimately related to the fine structure constant. If the latter would not have been strictly constant throughout all times, this would have had consequences for the nature of light and for all masses including those of elementary particles.

  18. Alpha Particle Emission in Fission

    International Nuclear Information System (INIS)

    Soon after it was discovered that alpha particles are occasionally emitted in fission, it was concluded, on the basis of the energy and angular distributions of these particles, that they are emitted from the space between the fragments at times close to that of the snapping of the neck that connects them. It is shown that, independent of any (still unknown) dynamic features of the alpha-particle ejection process, the energy required to emit alpha particles from between the fragments at the indicated time is barely available. Presumably the rareness of alpha particles in fission, and the apparent absence of still heavier ''third'' particles, is associated with the marginal energy supply at the time of actual fragment division. The fact that the total kinetic energy release in so-called ternary fission is roughly equal to that in normal binary fission instead of being about 20 MeV larger is shown to imply that the mean fragment separation at the division time is larger in ternary fission. This is interpreted to indicate that alpha particles are emitted with greatest probability n those fissions where ample energy happens to be provided through the stretching of an abnormally long neck between the fragments before they actually divide. It is suggested that the release of the alpha particles is a sudden rather than adiabatic process. (author)

  19. Alpha particle physics for ITER

    International Nuclear Information System (INIS)

    The paper is devoted to the analysis of a variety of physical processes which, in the ITER EDA configuration, determine the nature of alpha particle heating in the plasma interior and alpha particle losses to the first wall. The paper consists of results from the alpha particle toroidal field (TF) ripple loss calculations and an analysis of alpha particle collective effects including Alfven modes, sawtooth stabilization, etc. It is shown that the ripple loss in the present ITER configuration is only a few per cent, which cannot directly affect the achievement of ignition. In spite of the up-down asymmetry, the loss fraction does not strongly depend on the toroidal drift direction. However, the heat load is highly localized and can be as high as 1 MW/m2 on the top of the protective limiters. Preliminary calculations of toroidicity induced Alfven eigenmode (TAE) stability indicate that high n numbers may be unstable, but the computational tools, needed for reliable quantitative predictions, are still in a state of development. The likelihood of appreciable alpha particle loss will depend on whether TAE modes produce stochastic alpha particle diffusion or not. The effect of fast particles on the m = 1 mode is also discussed. (author). 15 refs, 2 figs, 1 tab

  20. Bernal liquid drop - alpha particle models of some heavy magic number nuclides

    International Nuclear Information System (INIS)

    Full text: Models of the bond structures of nickel 56, strontium 88, tin 120, cerium 140, lead 208 and uranium 240 nuclides based on Bernal's models of dense liquid drops, show good agreement between the binding energy data and shell structures when alpha particles are considered to be the densely packed hard spheres, of Bernal's models. These models, of the time-averaged structures of several closed shell nuclides have been developed as pedagogical aids for conceptualising some of the major aspects of nuclear matter and energy. These concepts include nuclear shape, size, charge density, quadrupole moment, viscosity, binding energy, coulomb repulsion, energy levels, magic numbers, shells and subshells; nucleon separation, bonding, pairing and clustering; nucleosynthesis, radioactivity and fission. The models discussed are based on those proposed by Bernal to account for the properties of normal liquids. Bernal's models have also been extended by others to explain the nature of metallic glasses considered as super cooled liquids. In Bernal's tetrahedral model of a normal liquid drop, a hard sphere representing an atom, ion, or molecule is added at whatever available position is closed to the centre of the existing cluster of spheres so that the densest possible configuration is created. Accordingly, two spheres form a dumbbell, three spheres form a triangle and four spheres form a tetrahedron and so on

  1. Alpha particle emitters in medicine

    International Nuclear Information System (INIS)

    Radiation-induced cancer of bone, liver and lung has been a prominent harmful side-effect of medical applications of alpha emitters. In recent years, however, the potential use of antibodies labeled with alpha emitting radionuclides against cancer has seemed promising because alpha particles are highly effective in cell killing. High dose rates at high LET, effectiveness under hypoxic conditions, and minimal expectancy of repair are additional advantages of alpha emitters over antibodies labeled with beta emitting radionuclides for cancer therapy. Cyclotron-produced astatine-211 (211At) and natural bismuth-212 (212Bi) have been proposed and are under extensive study in the United States and Europe. Radium-223 (223Ra) also has favorable properties as a potential alpha emitting label, including a short-lived daughter chain with four alpha emissions. The radiation dosimetry of internal alpha emitters is complex due to nonuniformly distributed sources, short particle tracks, and high relative specific ionization. The variations in dose at the cellular level may be extreme. Alpha-particle radiation dosimetry, therefore, must involve analysis of statistical energy deposition probabilities for cellular level targets. It must also account fully for nonuniform distributions of sources in tissues, source-target geometries, and particle-track physics. 18 refs., 4 figs

  2. A variational calculation of 12C in the alpha-particle model

    International Nuclear Information System (INIS)

    Some physical properties of three structureless alpha particles interacting through two-body potentials were discussed. Comparison between them and the corresponding experimental observations for the 12C nucleus is done. The wave function is expanded in terms of translationally invariant harmonic-oscillator states, the coefficients being variational parameters

  3. Nanodosimetry of radon alpha particles

    International Nuclear Information System (INIS)

    It is currently accepted that energy deposition at the nanometer level (rather than conventional microdosimetry) determines the biological effects of ionizing radiation. Many previously established experimental techniques (e.g., the Rossi proportional counter) or theoretical methods (e.g., simplified calculations using the continuous slowing-down approximation (CSDA)) are inapplicable to the study of nanodosimetry. The peculiarities of the geometry of exposure to radon progeny further complicate the problem. This is because the conditions under which several open-quotes classicalclose quotes models of radiation action are obtained (e.g., the alpha-beta formulation of the Theory of Dual Radiation Action, which is built on microdosimetry) are no longer valid. It thus becomes clear that not only new techniques but new concepts are required to describe the effects of radon alpha particles. In this paper we discuss a number of computational aspects specific to radon nanodosimetry. In particular, we describe the novel concept of open-quotes associated surfaceclose quotes (AS) which is necessary for efficiently converting Monte-Carlo-generated particle tracks to nanodosimetric spectra. The AS is the analog of Lea's associated volume, applied to radiation sources subject to the geometrical restrictions of internal exposure. We systematically analyze factors affecting the nanodosimetry of radon progeny, such as the distance between the radioactive source and the sensitive volume, the size of the sensitive volume, and CSDA versus full Monte-Carlo track generation

  4. Nanodosimetry of radon alpha particles

    Energy Technology Data Exchange (ETDEWEB)

    Zaider, M. [Columbia Univ. New York, NY (United States); Varma, M.N. [U.S. Department of Energy, Washington, DC (United States)

    1992-12-31

    It is currently accepted that energy deposition at the nanometer level (rather than conventional microdosimetry) determines the biological effects of ionizing radiation. Many previously established experimental techniques (e.g., the Rossi proportional counter) or theoretical methods (e.g., simplified calculations using the continuous slowing-down approximation (CSDA)) are inapplicable to the study of nanodosimetry. The peculiarities of the geometry of exposure to radon progeny further complicate the problem. This is because the conditions under which several {open_quotes}classical{close_quotes} models of radiation action are obtained (e.g., the alpha-beta formulation of the Theory of Dual Radiation Action, which is built on microdosimetry) are no longer valid. It thus becomes clear that not only new techniques but new concepts are required to describe the effects of radon alpha particles. In this paper we discuss a number of computational aspects specific to radon nanodosimetry. In particular, we describe the novel concept of {open_quotes}associated surface{close_quotes} (AS) which is necessary for efficiently converting Monte-Carlo-generated particle tracks to nanodosimetric spectra. The AS is the analog of Lea`s associated volume, applied to radiation sources subject to the geometrical restrictions of internal exposure. We systematically analyze factors affecting the nanodosimetry of radon progeny, such as the distance between the radioactive source and the sensitive volume, the size of the sensitive volume, and CSDA versus full Monte-Carlo track generation.

  5. Alpha-particle diagnostics

    International Nuclear Information System (INIS)

    This paper will focus on the state of development of diagnostics which are expected to provide the information needed for α- physics studies in the future. Conventional measurement of detailed temporal and spatial profiles of background plasma properties in DT will be essential for such aspects as determining heating effectiveness, shaping of the plasma profiles and effects of MHD, but will not be addressed here. This paper will address (1) the measurement of the neutron source, and hence α-particle birth profile, (2) measurement of the escaping α-particles and (3) measurement of the confined α-particles over their full energy range. There will also be a brief discussion of (4) the concerns about instabilities being generated by α-particles and the methods necessary for measuring these effects. 51 refs., 10 figs

  6. Nanodosimetry and nanodosimetric-based models of radiation action for radon alpha particles

    Energy Technology Data Exchange (ETDEWEB)

    Zaider, M.

    1992-01-01

    We report on a theory for describing the biological effects of ionizing radiation in particular radon [alpha] particles. Behind this approach is the recognition that biological effects such as chromosome aberrations, cellular transformation, cellular inactivation, etc, are the result of a hierarchic sequence of radiation effects. We indicate how to treat each of the individual processes in this sequence, and also how to relate one effect to the hierarchically superior one.

  7. Modelling TF ripple loss of alpha particles in TFTR DT experiments

    International Nuclear Information System (INIS)

    Modelling of TF ripple loss of alphas in DT experiments on TFTR now includes neoclassical calculations of first orbit loss, stochastic ripple diffusion, ripple trapping and collisional effects. A rapid way to simulate experiment has been developed which uses a simple stochastic domain model for TF ripple loss within the TRANSP analysis code, with the ripple diffusion threshold evaluated by comparison with more accurate but computationally expensive Hamiltonian coordinate guiding center code simulations. Typical TF collisional ripple loss predictions are 6-10% loss of alphas for TFTR D-T experiments at Ip = 1.0-2.0 MA and R = 2.52 m

  8. Alpha particle effects on MHD ballooning

    International Nuclear Information System (INIS)

    During the period, as the first step towards the goal of detail understanding of the effects of alpha particle on MHD Ballooning Modes, a new numerical approach to investigate the stability of low-frequency fluctuations in high temperature tokamaks was developed by solving the gyrokinetic equations for the ion and electron directly as an initial value problem. The advantage of this approach is the inclusion of many important kinetic features of the problem without approximations and computationally more economical than particle-pushing simulation. The ion-temperature-gradient-mode was investigated to benchmark this new simulation technique. Previous results in literature were recovered. Both the adiabatic electron model and the full drift-kinetic electron model are studied. Numerical result shows that the full drift-kinetic electron model is more unstable. The development of subcycling technique to handle the fast electron bounce time is particularly significant to apply this new approach to the alpha particle problem since alpha particle bounce frequency is also significantly higher than the mode frequency. This new numerical technique will be the basis of future study of the microstability in high temperature tokamaks with alpha particles (or any energetic species). 15 refs., 13 figs

  9. Nanodosimetry and nanodosimetric-based models of radiation action for radon alpha particles. Progress report, July 1, 1991--June 30, 1992

    Energy Technology Data Exchange (ETDEWEB)

    1992-04-01

    The objective of our research work is to provide -- with the aid of biophysical models of radiation action -- information on human risks following exposure to radon alpha particles. The approach proposed consists of (1) developing appropriate models (parametric and non-parametric) for alpha radiation induction of relevant end points (survival, cellular transformation), (2) providing an accurate physical characterization of the particle tracks in terms of nanodosimetric distributions, (3) supporting the models by detailed, molecular studies of the direct and indirect effects of alpha particles on DNA. Activities in the second year of this project are described.

  10. Alpha particles diffusion due to charge changes

    Energy Technology Data Exchange (ETDEWEB)

    Clauser, C. F., E-mail: cesar.clauser@ib.edu.ar; Farengo, R. [Centro Atómico Bariloche and Instituto Balseiro, Comisión Nacional de Energía Atómica and Universidad Nacional de Cuyo, Av. Bustillo 9500, 8400 Bariloche (Argentina)

    2015-12-15

    Alpha particles diffusion due to charge changes in a magnetized plasma is studied. Analytical calculations and numerical simulations are employed to show that this process can be very important in the pedestal-edge-SOL regions. This is the first study that presents clear evidence of the importance of atomic processes on the diffusion of alpha particles. A simple 1D model that includes inelastic collisions with plasma species, “cold” neutrals, and partially ionized species was employed. The code, which follows the exact particle orbits and includes the effect of inelastic collisions via a Monte Carlo type random process, runs on a graphic processor unit (GPU). The analytical and numerical results show excellent agreement when a uniform background (plasma and cold species) is assumed. The simulations also show that the gradients in the density of the plasma and cold species, which are large and opposite in the edge region, produce an inward flux of alpha particles. Calculations of the alpha particles flux reaching the walls or divertor plates should include these processes.

  11. Alpha particle problems in shielded support systems

    International Nuclear Information System (INIS)

    Alpha particle confinement is considered in the case of internal conductor systems with magnetically shielded supports. The treatment includes problems of energy transfer to the background plasma, the balance between radiation losses and alpha particle heating, mirror confinement in the main poloidal field, the cut-off and shielding conditions at the supports, ambipolar electric fields, wall interaction, and support location. With a proper and technically realizable choice of parameter values, it should become possible to achieve alpha particle heating as well as to manage the reactor technological problems due to alpha particle interaction with the supports. (Auth.)

  12. Monte Carlo particle-trajectory models for neutral cometary gases. I. Models and equations. II. The spatial morphology of the Lyman-alpha coma

    International Nuclear Information System (INIS)

    The mathematical derivations of various methods employed in the Monte Carlo particle-trajectory model (MCPTM) are presented, and the application of the MCPTM to the calculation of the photochemical heating of the inner coma through the partial thermalization of cometary hydrogen atoms produced by the photodissociation of water is discussed. This model is then used to explain the observed morphology of the spatially extended Ly-alpha comas of comets. The rocket and Skylab images of the Ly-alpha coma of Comet Kohoutek are examined. 90 references

  13. Alpha particle diagnostics using impurity pellet injection

    International Nuclear Information System (INIS)

    We have proposed using impurity injection to measure the energy distribution of the fast confined alpha particles in a reacting plasma. The ablation cloud surrounding the injected pellet is thick enough that an equilibrium fraction Fo∞(E) of the incident alphas should be neutralized as they pass through the cloud. By observing neutrals created in the large spatial region of the cloud which is expected to be dominated by the helium-like ionization state, e.g., Li+ ions, we can determine the incident alpha distribution dnHe2+/dE from the measured energy distribution of neutral helium atoms. Initial experiments were performed on TEXT in which we compared pellet penetration with our impurity pellet ablation model, and measured the spatial distribution of various ionization states in carbon pellet clouds. Experiments have recently begun on TFTR with the goal of measuring the alpha particle energy distribution during D-T operation in 1993--94. A series of preliminary experiments are planned to test the diagnostic concept. The first experiments will observe neutrals from beam-injected deuterium ions and the high energy 3He tail produced during ICH minority heating on TFTR interacting with the cloud. We will also monitor by line radiation the charge state distributions in lithium, boron, and carbon clouds

  14. Track structure based modelling of chromosome aberrations after photon and alpha-particle irradiation.

    Science.gov (United States)

    Friedland, Werner; Kundrát, Pavel

    2013-08-30

    A computational model of radiation-induced chromosome aberrations in human cells within the PARTRAC Monte Carlo simulation framework is presented. The model starts from radiation-induced DNA damage assessed by overlapping radiation track structures with multi-scale DNA and chromatin models, ranging from DNA double-helix in atomic resolution to chromatin fibre loops, heterochromatic and euchromatic regions, and chromosome territories. The repair of DNA double-strand breaks via non-homologous end-joining is followed. Initial spatial distribution and complexity, diffusive motion, enzymatic processing, synapsis and ligation of individual DNA ends from the breaks are simulated. To enable scoring of different chromosome aberration types resulting from improper joining of DNA fragments, the repair module has been complemented by tracking the chromosome origin of the ligated fragments and the positions of centromeres. The modelled motion of DNA ends has sub-diffusive characteristics and corresponds to measured chromatin mobility within time-scales of a few hours. The calculated formation of dicentrics after photon and α-particle irradiation in human fibroblasts is compared to experimental data (Cornforth et al., 2002, Radiat Res 158, 43). The predicted yields of dicentrics overestimate the measurements by factors of five for γ-rays and two for α-particle irradiation. Nevertheless, the observed relative dependence on radiation dose is correctly reproduced. Calculated yields and size distributions of other aberration types are discussed. The present work represents a first mechanistic approach to chromosome aberrations and their kinetics, combining full track structure simulations with detailed models of chromatin and accounting for the kinetics of DNA repair. PMID:23811166

  15. Prospects for alpha particle studies on TFTR

    International Nuclear Information System (INIS)

    TFTR is expected to produce approximately 5 MW of alpha heating during the D/T Q ≅ 1 phase of operation in 1990. At that point the collective confinement properties and the heating effects of alpha particles become accessible for study for the first time. This paper outlines the potential performance of TFTR with respect to alpha particle production, the diagnostics which will be available for alpha particle measurements, and the physics issues which can be studied both before and during D/T operation

  16. Alpha particle confinement in tandem mirrors

    International Nuclear Information System (INIS)

    Mechanisms leading to loss of alpha particles from non-axisymmetric tandem mirrors are considered. Stochastic diffusion due to bounce-drift resonances, which can cause rapid radial losses of high-energy alpha particles, can be suppressed by imposing a 20% rise in axisymmetric fields before the quadrupole transition sections. Alpha particles should then be well-confined until thermal energies when they enter the resonant plateau require. A fast code for computation of drift behavior in reactors is described. Sample calculations are presented for resonant particles in a proposed coil set for the Tandem Mirror Next Step

  17. High resolution alpha particle spectrometry through collimation

    International Nuclear Information System (INIS)

    Alpha particle spectrometry with collimation is a useful method for identifying nuclear materials among various nuclides. A mesh type collimator reduces the low energy tail and broadened energy distribution by cutting off particles with a low incidence angle. The relation between the resolution and the counting efficiency can be investigated by changing a ratio of the mesh hole diameter and the collimator thickness. Through collimation, a target particle can be distinguished by a PIPS® detector under a mixture of various nuclides. - Highlights: • Alpha particle spectrometry with collimation a useful method for identifying nuclear materials among various radionuclides. • A collimator cut off alpha particles with low angle emitted from a source. • We confirm that that a collimator improves the resolution of alpha spectra through both simulation and experiments

  18. The measurement and modeling of alpha-particle-induced charge collection in dynamic memories

    International Nuclear Information System (INIS)

    This thesis addresses the problem of α-particle-induced charge collection in high-density dynamic random access memories. A novel technique for the measurement of charge collection in high-density memory cells and bit lines due to α-particle strikes was developed. The technique involves D.C. tests on simple test structures with an α-particle source on the device package as a lid. The advantages of this new measurement technique are: the method allows for in-situ measurements of charge collection on both MOS capacitors and bit lines found in present-day memories; the on-chip measurement technique minimizes errors due to external probes loading the device under test; the measurements can be controlled by a personal computer, with the data being able to be reduced on the same machine. Results obtained using this new measurement technique show that the charge collection is found to depend upon test-structure size and the configuration of its neighbors. Results of two-dimensional simulations of charge flow along the surface of an MOS capacitor from current injection due to an α-particle strike indicate that a spatial potential variation of 0.5V may occur between the point of current injection and capacitor edge for a 1M dRAM capacitor

  19. Alpha emitters in Chernobyl hot particles

    International Nuclear Information System (INIS)

    The alpha radioactive component of hot particles from the Chernobyl fallout was analysed for cases studied previously by gamma spectroscopy. Correlations established from the absolute alpha activity determination and high resolution analysis provided information on actinides release during accident and on some aspects of the Chernobyl reactor fuel composition. Unexpected features revealed during the analysis of one specific particle are presented. 11 refs., 5 figs., 5 tabs. (author)

  20. Alpha emitters in Chernobyl hot particles

    Energy Technology Data Exchange (ETDEWEB)

    Broda, R.; Kubica, B.; Szeglowski, Z.; Zuber, K. (Institute of Nuclear Physics, Krakow (Poland))

    1989-01-01

    The alpha radioactive component of hot particles from the Chernobyl fallout was analyzed for cases studied previously by gamma spectroscopy. Correlations established from the absolute alpha activity determination and high resolution analysis provided information on the release of actinides during the accident and on some aspects of the Chernobyl reactor fuel composition. Unexpected features revealed during the analysis of one specific particle are presented. (orig.).

  1. Nanodosimetry and nanodosimetric-based models of radiation action for radon alpha particles. Final performance technical report

    International Nuclear Information System (INIS)

    The goal of this project was to develop theoretical/computational tools for evaluating the risks incurred by populations exposed to radon alpha particles. Topics of concern include the following: compound dual radiation action (general aspects); a mathematical formalism describing the yield of radiation induced single-and double-strand DNA breaks, and its dependence on radiation quality; a study of the excited states in cytosine and guanine stacks in the Hartree-Fock and exciton approximations; nanodosimetry of radon alpha particles; application of the HSEF to assessing radiation risks in the practice of radiation protection; carcinogenic risk coefficients at environmental levels of radon exposures: a microdosimetric approach; and hit-size effectiveness approach in radiation protection

  2. Nanodosimetry and nanodosimetric-based models of radiation action for radon alpha particles. Final performance technical report

    Energy Technology Data Exchange (ETDEWEB)

    Zaider, M.

    1997-12-31

    The goal of this project was to develop theoretical/computational tools for evaluating the risks incurred by populations exposed to radon alpha particles. Topics of concern include the following: compound dual radiation action (general aspects); a mathematical formalism describing the yield of radiation induced single-and double-strand DNA breaks, and its dependence on radiation quality; a study of the excited states in cytosine and guanine stacks in the Hartree-Fock and exciton approximations; nanodosimetry of radon alpha particles; application of the HSEF to assessing radiation risks in the practice of radiation protection; carcinogenic risk coefficients at environmental levels of radon exposures: a microdosimetric approach; and hit-size effectiveness approach in radiation protection.

  3. Nanodosimetry and nanodosimetric-based models of radiation action for radon alpha particles. Progress report, July 1990--June 1992

    Energy Technology Data Exchange (ETDEWEB)

    Zaider, M.

    1992-12-31

    We report on a theory for describing the biological effects of ionizing radiation in particular radon {alpha} particles. Behind this approach is the recognition that biological effects such as chromosome aberrations, cellular transformation, cellular inactivation, etc, are the result of a hierarchic sequence of radiation effects. We indicate how to treat each of the individual processes in this sequence, and also how to relate one effect to the hierarchically superior one.

  4. Alpha particles detection in nitrocellulose

    International Nuclear Information System (INIS)

    The method for the manufacturing of the detection films follows these steps: preparation of the mass which includes nitrocellulose in the form of cotton as raw material ethyl acetate, cellosolve acetate, isopropyl and butyl alcohols as solvents and dioctyl phtalate as plasticiser; dilution of the paste; pouring of the diluted mass; and drying of the detection films. The results obtained experimentally are: The determination of the development times of the different thicknesses of the manufactured films. Response linearity of the detectors, variation of the number of tracks according to the distance of the source to the detector. Sizes of the diameter of the tracks depending of the distance detector-alpha emmission source. As a conclusion we can say the the nitrocellulose detectors are specific for alpha radiation; the more effective thicknesses in uranium prospecting works were those of 60 microns, since for the laboratory works the thicknesses of 30 to 40 microns were the ideal; the development technique of the detection films is simple and cheap and can be realized even in another place than the laboratory; this way of the manufacturing of nitrocellulose detection film sensitive to alpha nuclear radiation is open to future research. (author)

  5. Analysis of radiation risk from alpha particle component of soalr particle events

    Science.gov (United States)

    Cucinotta, F. A.; Townsend, L. W.; Wilson, J. W.; Golightly, M. J.; Weyland, M.

    1994-01-01

    The Solar Particle Events (SPE) will contain a primary alpha particle component, representing a possible increase in the potential risk to astronauts during an SPE over the often studied proton component. We discuss the physical interactions of alpha particles important in describing the transport of these particles through spacecraft and body shielding. Models of light ion reactions are presented and their effects on energy and Linear Energy Transfer (LET) spectra in shielding are discussed. We present predictions of particle spectra, dose, and dose equivalent in organs of interest for SPE spectra typical of those occurring in recent solar cycles. The large events of solar cycle 19 are found to have substantial increase in biological risk from alpha particles, including a large increase in secondary neutron production from alpha particle breakup.

  6. Analysis of radiation risk from alpha particle component of solar particle events

    Science.gov (United States)

    Cucinotta, F. A.; Townsend, L. W.; Wilson, J. W.; Golightly, M. J.; Weyland, M.

    1994-01-01

    The solar particle events (SPE) will contain a primary alpha particle component, representing a possible increase in the potential risk to astronauts during an SPE over the often studied proton component. We discuss the physical interactions of alpha particles important in describing the transport of these particles through spacecraft and body shielding. Models of light ion reactions are presented and their effects on energy and linear energy transfer (LET) spectra in shielding discussed. We present predictions of particle spectra, dose, and dose equivalent in organs of interest for SPE spectra typical of those occurring in recent solar cycles. The large events of solar cycle 19 are found to have substantial increase in biological risk from alpha particles, including a large increase in secondary neutron production from alpha particle breakup.

  7. Alpha particles spectrometer with photodiode PIN

    International Nuclear Information System (INIS)

    The radiation propagates in form of electromagnetic waves or corpuscular radiation; if the radiation energy causes ionization in environment that crosses it is considered ionizing radiation. To detect radiation several detectors types are used, if the radiation are alpha particles are used detectors proportional type or trace elements. In this work the design results, construction and tests of an alpha particles spectrometer are presented, which was designed starting from a photodiode PIN type. The system design was simulated with a code for electronic circuits. With results of simulation phase was constructed the electronic phase that is coupled to a multichannel analyzer. The resulting electronic is evaluated analyzing the electronic circuit performance before an alphas triple source and alpha radiation that produce two smoke detectors of domestic use. On the tests phase we find that the system allows obtain, in a multichannel, the pulses height spectrum, with which we calibrate the system. (Author)

  8. Alpha particle spectroscopy by gridded ionization chamber

    International Nuclear Information System (INIS)

    A gridded ionization chamber has been constructed with the aim of determining its ultimate energy resolution in alpha spectroscopy, utilizing a cooled FET pre-amplifier of the type normally employed with semiconductor detectors. With suitable mechanical collimation of the alpha particles, their fine structure has been measured with an energy resolution of -11.5 keV (fwhm), achieved using an Ar + 0.75% C2H2 mixture as the filling gas. (orig.)

  9. An evaluation of alpha particle clustering in heavy nuclei

    International Nuclear Information System (INIS)

    In recent years, the pre-equilibrium models of nuclear reactions have been used to analyze many experiments involving the emission of alpha particles. The results of these analyses have been used as the basis for a calculation of the extent of alpha particle clustering in heavy nuclei. Calculations are presented of the rate of nucleon-nucleon and nucleon-alpha interactions in nuclear matter. Normalizing these to the preformation factors found in reaction studies, the number of alpha clusters in several complex nuclei has been obtained. It is suggested that the number of such performed alpha clusters in nuclei having A = 50, 90, 141, 202, and 232 are, respectively, 2.1, 3.6, 5.2, 6.9, and 7.8. (orig.) 891 FKS/orig. 892 MB

  10. Alpha particles energy straggling in noble gases

    International Nuclear Information System (INIS)

    The comparison of the calculated spectra by the Monte-Carlo simulation with the experimental alpha-particles spectra after their passage through noble gases target has good agreement for Ar, Kr, and Xe and significant deviation for He and Ne. These agreement or disagreement of the calculated and experimental spectra were ascribed to adequacy or inadequacy of the applied Bohr's charged particles energy loss formula for the specific medium. (author)

  11. Superparamagnetic relaxation in alpha-Fe particles

    DEFF Research Database (Denmark)

    Bødker, Franz; Mørup, Steen; Pedersen, Michael Stanley; Svedlindh, P.; Jonsson, G.T.; Garcia-Palacios, J.L.; Lazaro, F.J.

    1998-01-01

    The superparamagnetic relaxation time of carbon-supported alpha-Fe particles with an average size of 3.0 Mm has been studied over a large temperature range by the use of Mossbauer spectroscopy combined with AC and DC magnetization measurements. It is found that the relaxation time varies with...

  12. Turbulent transport of alpha particles in tokamak plasmas

    CERN Document Server

    Croitoru, A; Vlad, M; Spineanu, F

    2016-01-01

    We investigate the ExB diffusion of fusion born \\alpha particles in tokamak plasmas. We determine the transport regimes for a realistic model that has the characteristics of the ion temperature gradient (ITG) or of the trapped electron modes (TEM) driven turbulence. It includes a spectrum of potential fluctuations that is modeled using the results of the numerical simulations, the drift of the potential with the effective diamagnetic velocity and the parallel motion. Our semi-analytical statistical approach is based on the decorrelation trajectory method (DTM), which is adapted to the gyrokinetic approximation. We obtain the transport coefficients as a function of the parameters of the turbulence and of the energy of the \\alpha particle. According to our results, signficant turbulent transport of the \\alpha particles can appear only at energies of the order of 100KeV. We determine the corresponding conditions.

  13. A practical alpha particle irradiator for studying internal alpha particle exposure.

    Science.gov (United States)

    Lee, Ki-Man; Lee, Ui-Seob; Kim, Eun-Hee

    2016-09-01

    An alpha particle irradiator has been built in the Radiation Bioengineering Laboratory at Seoul National University (SNU) to investigate the cellular responses to alpha emissions from radon and the progeny. This irradiator is designed to have the energy of alpha particles entering target cells similar to that of alpha emissions from the radon progeny Po-218 and Po-214 residing in the human respiratory tract. For the SNU alpha particle irradiator, an irradiation system is equipped with cell dishes of 4µm thick Mylar bottom and a special setup of cells on slide for gamma-H2AX assay. Dose calibration for the alpha particle irradiator was performed by dual approaches, detection and computer simulation, in consideration of the source-to-target distance (STD) and the size of a cell dish. The uniformity of dose among cells in a dish is achieved by keeping the STD and the size of cell dish in certain ranges. The performance of the SNU alpha particle irradiator has been proven to be reliable through the gamma-H2AX assay with the human lung epithelial cells irradiated. PMID:27475622

  14. Measurements of DT alpha particle loss near the outer midplane of TFTR

    International Nuclear Information System (INIS)

    Measurements of DT alpha particle loss to the outer midplane region of TFTR have been made using a radially movable scintillator detector. The conclusion from this data is that mechanisms determining the DT alpha loss to the outer midplane are not substantially different from those for DD fusion products. Some of these results are compared with a simplified theoretical model for TF ripple-induced alpha loss, which is expected to be the dominant classical alpha loss mechanism near the outer midplane. An example of plasma-driven MHD-induced alpha particle loss is shown, but no signs of any ''collective'' alpha instability-induced alpha loss have yet been observed

  15. Intercomparison of alpha particle spectrometry software packages

    International Nuclear Information System (INIS)

    Software has reached an important level as the 'logical controller' at different levels, from a single instrument to an entire computer-controlled experiment. This is also the case for software packages in nuclear instruments and experiments. In particular, because of the range of applications of alpha-particle spectrometry, software packages in this field are often used. It is the aim of this intercomparison to test and describe the abilities of four such software packages. The main objectives of the intercomparison were the ability of the programs to determine the peak areas and the peak area uncertainties, and the statistical control and stability of reported results. In this report, the task, methods and results of the intercomparison are presented in order to asist the potential users of such software and to stimulate the development of even better alpha-particle spectrum analysis software

  16. Single particle level scheme for alpha decay

    International Nuclear Information System (INIS)

    The fine structure phenomenon in alpha decay was evidenced by Rosenblum. In this process the kinetic energy of the emitted particle has several determined values related to the structure of the parent and the daughter nucleus. The probability to find the daughter in a low lying state was considered strongly dependent on the spectroscopic factor defined as the square of overlap between the wave function of the parent in the ground state and the wave functions of the specific excited states of the daughter. This treatment provides a qualitative agreement with the experimental results if the variations of the penetrability between different excited states are neglected. Based on single particle structure during fission, a new formalism explained quantitatively the fine structure of the cluster decay. It was suggested that this formalism can be applied also to alpha decay. For this purpose, the first step is to construct the level scheme of this type of decay. Such a scheme, obtained with the super-asymmetric two-center potential, is plotted for the alpha decay of 223Ra. It is interesting to note that, diabatically, the level with spin 3/2 emerging from 1i11/2 (ground state of the parent) reaches an excited state of the daughter in agreement with the experiment. (author)

  17. Track-nanodosimetry of an alpha particle

    Energy Technology Data Exchange (ETDEWEB)

    De Nardo, L.; Tornielli, G. [Padova Univ., Padova (Italy); INFN, Padova (Italy); Cesari, V.; Colautti, P.; Conte, V. [INFN Laboratori Nazionali, Legnaro (Italy); Baek, W.Y.; Grosswendt, B. [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany); Alkaa, A.; Segur, P. [Centre de Physique des Plasmas et de leur Applications, Toulouse (France)

    2002-07-01

    Effects of radiation are primarily determined by what happens in individual small volumes representative of DNA segments. Such sites are so small that the interactions due to radiation are very few and it is necessary to consider the stochastic of the number and nature of primary interactions and of secondary processes in order to understand the subsequent biological effects. Track-nanodosimetry has the objective to investigate stochastic aspect of energy deposition in particle tracks, by measuring the ionisation distributions induced by a charged particle in nanometric volumes of tissue-equivalent matter, positioned at different distances from the track. This paper is concerned with measurements and Monte Carlo calculations of ionisation distributions produced in a site of about 20 nm by a {sup 244}Cm alpha particle.

  18. Track-nanodosimetry of an alpha particle

    International Nuclear Information System (INIS)

    Effects of radiation are primarily determined by what happens in individual small volumes representative of DNA segments. Such sites are so small that the interactions due to radiation are very few and it is necessary to consider the stochastic of the number and nature of primary interactions and of secondary processes in order to understand the subsequent biological effects. Track-nanodosimetry has the objective to investigate stochastic aspect of energy deposition in particle tracks, by measuring the ionisation distributions induced by a charged particle in nanometric volumes of tissue-equivalent matter, positioned at different distances from the track. This paper is concerned with measurements and Monte Carlo calculations of ionisation distributions produced in a site of about 20 nm by a 244Cm alpha particle

  19. The Fission of Thorium with Alpha Particles

    Energy Technology Data Exchange (ETDEWEB)

    Newton, Amos S.

    1948-04-15

    The fission distribution of fission of thorium with alpha particle of average energy 37.5 Mev has been measured by the chemical method. The distribution found shows that the characteristic dip in the fission yield mass spectrum has been raised to within a factor of two of the peaks compared to a factor of 600 in slow neutron fission of U{sup 235}. The raise in the deip has caused a corresponding lowering in fission yield of these elements at the peaks. The cross section for fission of thorium with 37.5 Mev alphas was found to be about 0.6 barn, and the threshold for fission was found to be 23 to 24 Mev.

  20. Track nanodosimetry of an alpha particle

    International Nuclear Information System (INIS)

    Experimental measurements and calculations are described of ionisation distributions in propane wall-less gas cavities of about 20 nm simulated size, performed at different distances from a 244Cm alpha particle track. Ionisation events are detected one by one by collecting electrons from the sensitive volume and by separating them with a drift column. Experimental results and Monte Carlo calculations indicate that, in the delta ray cloud, conditional probability curves, average cluster size and the ratio of second moment above first moment of the cluster distribution are invariant with track distance. (author)

  1. Track nanodosimetry of an alpha particle.

    Science.gov (United States)

    De Nardo, L; Colautti, P; Baek, W Y; Grosswendt, B; Alkaa, A; Ségur, P; Tornielli, G

    2002-01-01

    Experimental measurements and calculations are described of ionisation distributions in propane wall-less gas cavities of about 20 nm simulated size, performed at different distances from a 244Cm alpha particle track. Ionisation events are detected one by one by collecting electrons from the sensitive volume and by separating them with a drift column. Experimental results and Monte Carlo calculations indicate that, in the delta ray cloud, conditional probability curves, average cluster size and the ratio of second moment above first moment of the cluster distribution are invariant with track distance. PMID:12194323

  2. Track nanodosimetry of an alpha particle

    Energy Technology Data Exchange (ETDEWEB)

    De Nardo, L.; Colautti, P.; Baek, W.Y.; Grosswendt, B.; Alkaa, A.; Segur, P.; Tornielli, G

    2002-07-01

    Experimental measurements and calculations are described of ionisation distributions in propane wall-less gas cavities of about 20 nm simulated size, performed at different distances from a {sup 244}Cm alpha particle track. Ionisation events are detected one by one by collecting electrons from the sensitive volume and by separating them with a drift column. Experimental results and Monte Carlo calculations indicate that, in the delta ray cloud, conditional probability curves, average cluster size and the ratio of second moment above first moment of the cluster distribution are invariant with track distance. (author)

  3. Superparamagnetic relaxation in alpha-Fe particles

    DEFF Research Database (Denmark)

    Bødker, Franz; Mørup, Steen; Pedersen, Michael Stanley; Svedlindh, P.; Jonsson, G.T.; Garcia-Palacios, J.L.; Lazaro, F.J.

    1998-01-01

    The superparamagnetic relaxation time of carbon-supported alpha-Fe particles with an average size of 3.0 Mm has been studied over a large temperature range by the use of Mossbauer spectroscopy combined with AC and DC magnetization measurements. It is found that the relaxation time varies with...... temperature in accordance with Ni el's expression, tau = tau(0) exp (KV/kT) with tau(0) = (1.0 +/- 0.5) x 10(-10) s and K = (1.2 +/- 0.2) x 10(5) J m(-3). (C) 1998 Elsevier Science B.V. All rights reserved....

  4. Global alpha-particle optical potentials

    International Nuclear Information System (INIS)

    A search for a global optical potential for alpha-particles is described. It did not prove possible to find such a potential valid for a wide range of energies and nuclei, even treating the absorbing potential as an adjustable parameter for each nucleus. For practical purposes the best that can be done is to define an average potential, and such a potential is compared with a wide range of experimental data. Its energy variation is determined by fitting the total reaction cross-section. (author). 7 refs, 15 figs, 1 tab

  5. Investigation of advanced materials for fusion alpha particle diagnostics

    Energy Technology Data Exchange (ETDEWEB)

    Bonheure, G., E-mail: g.bonheure@fz-juelich.de [Laboratory for Plasma Physics, Association “Euratom-Belgian State”, Royal Military Academy, Avenue de la Renaissance, 30 Kunstherlevinglaan, B-1000 Brussels (Belgium); Van Wassenhove, G. [Laboratory for Plasma Physics, Association “Euratom-Belgian State”, Royal Military Academy, Avenue de la Renaissance, 30 Kunstherlevinglaan, B-1000 Brussels (Belgium); Hult, M.; González de Orduña, R. [Institute for Reference Materials and Measurements (IRMM), Retieseweg 111, B-2440 Geel (Belgium); Strivay, D. [Centre Européen d’Archéométrie, Institut de Physique Nucléaire, Atomique et de Spectroscopie, Université de Liège (Belgium); Vermaercke, P. [SCK-CEN, Boeretang, B-2400 Mol (Belgium); Delvigne, T. [DSI SPRL, 3 rue Mont d’Orcq, Froyennes B-7503 (Belgium); Chene, G.; Delhalle, R. [Centre Européen d’Archéométrie, Institut de Physique Nucléaire, Atomique et de Spectroscopie, Université de Liège (Belgium); Huber, A.; Schweer, B.; Esser, G.; Biel, W.; Neubauer, O. [Forschungszentrum Jülich GmbH, Institut für Plasmaphysik, EURATOM-Assoziation, Trilateral Euregio Cluster, D-52425 Jülich (Germany)

    2013-10-15

    Highlights: ► We examine the feasibility of alpha particle measurements in ITER. ► We test advanced material detectors borrowed from the GERDA neutrino experiment. ► We compare experimental results on TEXTOR tokamak with our detector response model. ► We investigate the detector response in ITER full power D–T plasmas. ► Advanced materials show good signal to noise ratio and alpha particle selectivity. -- Abstract: Fusion alpha particle diagnostics for ITER remain a challenging task. Standard escaping alpha particle detectors in present tokamaks are not applicable to ITER and techniques suitable for fusion reactor conditions need further research and development [1,2]. The activation technique is widely used for the characterization of high fluence rates inside neutron reactors. Tokamak applications of the neutron activation technique are already well developed [3] whereas measuring escaping ions using this technique is a novel fusion plasma diagnostic development. Despite low alpha particle fluence levels in present tokamaks, promising results using activation technique combined with ultra-low level gamma-ray spectrometry [4] were achieved before in JET [5,6]. In this research work, we use new advanced detector materials. The material properties beneficial for alpha induced activation are (i) moderate neutron cross-sections (ii) ultra-high purity which reduces neutron-induced background activation and (iii) isotopic tailoring which increases the activation yield of the measured activation product. Two samples were obtained from GERDA[7], an experiment aimed at measuring the neutrinoless double beta decay in {sup 76}Ge. These samples, made of highly pure (9 N) germanium highly enriched to 87% in isotope Ge-76, were irradiated in real D–D fusion plasma conditions inside the TEXTOR tokamak. Comparison of the calculated and the experimentally measured activity shows good agreement. Compared to previously investigated high temperature ceramic material [8

  6. The Emission of Long-Range Alpha Particles in Fission

    International Nuclear Information System (INIS)

    Fraenkel and Thompson (1964) have shown that the most probable direction of emission of the long-range alpha particles in the spontaneous fission of californium-252 varies with the ratio of the masses of the residual fission fragments. The angle of emission relative to the direction of motion of the lighter fragment increases significantly as the mass of the lighter fragment decreases. Assuming that the alpha particle is emitted at the scission point, these authors conclude that the scission point, in ternary fission, occurs progressively nearer to the lighter fragment as the fragment mass ratio is greater. They point out that this is one of the assumptions underlying the ''geometrical'' model of mass division of Whetstone (1959) and Vladimirski (1957), and is the feature of that model in terms of which the variation of the average number of neutrons with fragment mass in binary fission is successfully explained. They suggest that these various considerations together indicate that the configuration of the scissioning nucleus at (and before) scission in ternary fission closely resembles the corresponding configuration in binary fission. Adopting this last hypothesis in relation to the thermal-neutron-induced fission of uranium-235, the writer (1964) has shown that if the liberation cf the alpha particle occurs at or just after the moment of scission, so that it may be regarded as emitted from a newly formed, but still deformed, fragment then the probability of emission can be deduced from the experiments of Schmitt et al. (1962), if certain further assumptions are made. On the assumption that the alpha particle is derived from the heavy fragment exclusively, it appears that the prob-ability of release from that fragment correlates directly with the average number of secondary neutrons emitted in in binary fission, and also with the energy available for alpha-particle emission from the undeformed (ground state) fragment. There would be no correlation with the energy

  7. Folding model analysis of alpha radioactivity

    CERN Document Server

    Basu, D N

    2003-01-01

    Radioactive decay of nuclei via emission of $\\alpha$ particles has been studied theoretically in the framework of a superasymmetric fission model using the double folding (DF) procedure for obtaining the $\\alpha$-nucleus interaction potential. The DF nuclear potential has been obtained by folding in the density distribution functions of the $\\alpha$ nucleus and the daughter nucleus with a realistic effective interaction. The M3Y effective interaction has been used for calculating the nuclear interaction potential which has been supplemented by a zero-range pseudo-potential for exchange along with the density dependence. The nuclear microscopic $\\alpha$-nucleus potential thus obtained has been used along with the Coulomb interaction potential to calculate the action integral within the WKB approximation. This subsequently yields microscopic calculations for the half lives of $\\alpha$ decays of nuclei. The density dependence and the exchange effects have not been found to be very significant. These calculations...

  8. Unified model for alpha-decay and alpha-capture

    International Nuclear Information System (INIS)

    A unified model for alpha-decay and alpha-capture is discussed. Simultaneously the half-lives for alpha-transition between ground states as well as ground and excited states and alpha-capture cross-sections by spherical magic or near-magic nuclei are well described in the framework of this model. Using these data the alpha-nucleus potential is obtained. The simple empirical relations for handy evaluation of the half-lives for alpha-transition, which take into account both the angular momentum and parity of alpha-transition, are presented

  9. Alpha particle loss in the TFTR DT experiments

    International Nuclear Information System (INIS)

    Alpha particle loss was measured during the TFTR DT experiments using a scintillator detector located at the vessel bottom in the ion grad-B drift direction. The DT alpha particle loss to this detector was consistent with the calculated first-orbit loss over the whole range of plasma current I=0.6-2.7 MA. In particular, the alpha particle loss rate per DT neutron did not increase significantly with fusion power up to 10.7 MW, indicating the absence of any new ''collective'' alpha particle loss processes in these experiments

  10. Chromosomal aberrations induced by alpha particles

    International Nuclear Information System (INIS)

    The chromosomal aberrations produced by the ionizing radiation are commonly used when it is necessary to establish the exposure dose of an individual, it is a study that is used like complement of the traditional physical systems and its application is only in cases in that there is doubt about what indicates the conventional dosimetry. The biological dosimetry is based on the frequency of aberrations in the chromosomes of the lymphocytes of the individual in study and the dose is calculated taking like reference to the dose-response curves previously generated In vitro. A case of apparent over-exposure to alpha particles to which is practiced analysis of chromosomal aberrations to settle down if in fact there was exposure and as much as possible, to determine the presumed dose is presented. (Author)

  11. Lorentz alpha orbit calculation in search of position suitable for escaping alpha particle diagnostics in ITER

    International Nuclear Information System (INIS)

    The Lorentz orbit code is developed to understand escaping alpha particle orbits and to contribute to the design of an escaping alpha particle probe in ITER. The code follows the full gyromotion of an alpha particle in ITER equilibrium, considering the toroidal field magnetic field ripple produced by the finite number of toroidal field coils as well as full three-dimensional first wall panels placed at the outboard side of the torus. It is shown that alpha particles that exist in the peripheral region and have banana orbits intersect the first wall placed at the outboard side on the lower plane. (author)

  12. Cluster states and alpha particle condensation in 13C

    International Nuclear Information System (INIS)

    The structure of 13C is studied with the semi-microscopic cluster model, 3α+n orthogonality condition model (OCM). The energy spectra of four 1/2- states and three 1/2+ states up to Ex ~ 13 MeV are successfully reproduced, in particular, three monopole transition strengths are in fair agreement with the observed ones. We discuss the cluster states and alpha particle condensation in the 1/2± states appearing around the 12C+n, 9Be+α and 3α+n thresholds. (author)

  13. Synergy between chemotherapy and alpha particles: effects in cells directly hit and in bystander cells

    International Nuclear Information System (INIS)

    Full text: Radioimmunotherapy with alpha-emitting nuclides offers the potential for selective targeting of micrometastatic sites. The short range of alpha particles and limited penetration of the labeled antibody into the tumor make it difficult to deliver a lethal dose to all tumor cells. In an effort to improve the extent and uniformity of tumor cell kill, experiments are underway to evaluate the ability of chemotherapy agents to produce synergistic effects in cells directly hit by alpha particles and in bystander cells. An alpha particle cell irradiation system comprised of planar americium-241 alpha particle sources together with custom-made cell culture dishes with replaceable mylar bottoms has been constructed and characterized. By changing the alpha particle source, the dose rate to cells on the mylar membrane can be varied from 0.0013 Gy/min to 13 Gy/min. The residual range of the alpha particles after exiting the mylar membrane is approximately 30 ∝/m. Preliminary results with alpha particle exposure in the presence or absence of low concentrations of either taxol or oxaliplatin show evidence of synergistic effects. A series of plastic grids have been designed and constructed that can be interposed between the alpha particle source and the cells to partially block the alpha particles. The ratio of open area to shielded area is kept constant at 50% but the diameter and total number of circular openings in the grid is varied, thus changing the proportion of bystander cells present close to the edge between the open and shielded zones. This approach creates a two-dimensional model system for micrometastatic tumors of various sizes where the shielded areas represent the deeper portions of a tumor beyond the range of surface-bound alpha particles. Experiments are underway to determine whether there are synergistic effects between the chemotherapy agents and the bystander cells

  14. Alpha particle radiography of ants using a 244Cm alpha source

    International Nuclear Information System (INIS)

    Alpha particles emitted from a radioisotope 244Cm were used for the radiography of ants. Cellulose nitrate films, LR-115 from Kodak Pathe, were used as solid state nuclear track detectors to make the radiographs. Alpha particles of energies from 3.5 to 5.5 MeV were obtained by varying the air spacing between the 244Cm and the sample with stainless steel spacers of thickness from 2.4 to 0.5 cm to slow the 5.81 MeV alpha particles from the 244Cm by air. The resulting radiographs of the ants put on the LR-115 films and irradiated by alpha particles of different energies show that only the profiles of the ants were obtained when the ants were exposed to alpha particles of energies lower than 3.5 MeV, and almost all parts of the ant except a portion in the head were penetrated by alpha particles of energies higher than 5.0 MeV to register high density alpha tracks on the LR-115. The details of the internal organs of the ant can be shown clearly by radiography with alpha particles of energies between 4.0 and 5.0 MeV. (author)

  15. Cluster-shell competition in systems with a few alpha particles and valence neutrons

    International Nuclear Information System (INIS)

    We construct nuclear wave functions from alpha clusters and some additional valence nucleons, and allow the inter-cluster distance to change and one alpha to dissolve from the (0s)4 structure as a result of the nuclear interaction. The change of the inter-cluster distance and the dissolution of the alpha particle can be interpreted as resulting from the competition of the 'shell model' and 'cluster model'. We demonstrate this competition through a few parameters.

  16. Detection of alpha particles with undoped poly (ethylene naphthalate)

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, Hidehito, E-mail: hidehito@rri.kyoto-u.ac.jp [Kyoto University, 2, Asashiro-Nishi, Kumatori-cho, Sennan-gun, Osaka 590-0494 (Japan); National Institute of Radiological Sciences, 4-9-1, Anagawa, Inage-ku, Chiba 263-8555 (Japan); Shirakawa, Yoshiyuki; Kitamura, Hisashi [National Institute of Radiological Sciences, 4-9-1, Anagawa, Inage-ku, Chiba 263-8555 (Japan); Sato, Nobuhiro; Takahashi, Sentaro [Kyoto University, 2, Asashiro-Nishi, Kumatori-cho, Sennan-gun, Osaka 590-0494 (Japan)

    2014-03-01

    There has been recent interest in the use of undoped, aromatic-ring polymers as organic scintillation materials for radiation detectors. Here, we characterise the response of poly (ethylene naphthalate) (PEN) to alpha particles. The energy response to 5486 keV alpha particles emitted from {sup 241}Am was 554±45 keV electron equivalents (keVee), with an energy resolution of 11.2±0.1%. The energy response to 6118 keV alpha particles emitted from {sup 252}Cf was 618±45 keVee, with a resolution of 8.8±0.1%. It is also important to characterise the refractive index because it determines how efficiently light propagates in scintillation materials to the photodetector. By taking into account the PEN emission spectrum, it was revealed that its effective refractive index was 1.70. Overall, the results indicate that PEN has potential as a scintillation material for the detection of alpha particles. - Highlights: • PEN is characterised as a scintillation material for alpha particles. • The effective refractive index for PEN is 1.70 in its emission spectrum. • The response to 5486 (6118) keV alpha particles was 554±45 (618±45) keVee. • The energy resolution for 5486 (6118) keV alpha particles was 11.2±0.1 (8.8±0.1) %. • This work will stimulate future use of PEN for radiation detection.

  17. Investigation of fusion alpha particle ripple losses by means of a kinetic code - alpha particle ripple losses in ITER

    International Nuclear Information System (INIS)

    The discrete nature of a tokamak magnetic system as a consequence of N separate field coils leads to a deviation from axial symmetry and causes additional transport referred to as ripple transport. This loss mechanism whose effectiveness increases with the particle energy must be investigated carefully for fusion alpha particles. The first part of the paper treats the ripple problem by means of a kinetic equation based on a modified Fokker-Planck equation generalized for ripple transport in 1.5-dimensional geometry. For a NET-type tokamak, ripple fluxes have been calculated with the edge ripple δ as a parameter and have been compared to neoclassical and anomalous fluxes. It has been found that particle and power loss fractions are small if the ripple is less than 1%. This results has been confirmed in the second part of the paper that studies the alpha particle ripple losses in ITER by Monte Carlo numerical modelling. Calculations were performed for physics phase and technology phase operation, and it has been shown that the first wall heat deposition profile is very sensitive to the details of plasma equilibrium shape, first wall position and ripple profile. The peak heat load, being small for the reference configuration, may easily be increased up to small changes in the ripple profile and the plasma configuration. (author). 7 refs, 6 figs, 1 tab

  18. Scintillation of thin tetraphenyl butadiene films under alpha particle excitation

    CERN Document Server

    Pollmann, Tina; Kuźniak, Marcin

    2010-01-01

    The alpha induced scintillation of the wavelength shifter 1,1,4,4-tetraphenyl-1,3-butadiene (TPB) was studied to improve the understanding of possible surface alpha backgrounds in the DEAP dark matter search experiment. We found that vacuum deposited thin TPB films emit 882 +/-210 photons per MeV under alpha particle excitation. The scintillation pulse shape consists of a double exponential decay with lifetimes of 11 +/-5 ns and 275 +/-10ns.

  19. Detection of alpha particles using DNA/Al Schottky junctions

    Energy Technology Data Exchange (ETDEWEB)

    Al-Ta' ii, Hassan Maktuff Jaber, E-mail: hassankirkukly@gmail.com, E-mail: vengadeshp@um.edu.my [Low Dimensional Materials Research Centre (LDMRC), 50603 Kuala Lumpur (Malaysia); Department of Physics, Faculty of Science, University of Al-Muthana, Al-Muthana 66001 (Iraq); Periasamy, Vengadesh, E-mail: hassankirkukly@gmail.com, E-mail: vengadeshp@um.edu.my [Low Dimensional Materials Research Centre (LDMRC), 50603 Kuala Lumpur (Malaysia); Amin, Yusoff Mohd [Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia)

    2015-09-21

    Deoxyribonucleic acid or DNA can be utilized in an organic-metallic rectifying structure to detect radiation, especially alpha particles. This has become much more important in recent years due to crucial environmental detection needs in both peace and war. In this work, we fabricated an aluminum (Al)/DNA/Al structure and generated current–voltage characteristics upon exposure to alpha radiation. Two models were utilized to investigate these current profiles; the standard conventional thermionic emission model and Cheung and Cheung's method. Using these models, the barrier height, Richardson constant, ideality factor and series resistance of the metal-DNA-metal structure were analyzed in real time. The barrier height, Φ value calculated using the conventional method for non-radiated structure was 0.7149 eV, increasing to 0.7367 eV after 4 min of radiation. Barrier height values were observed to increase after 20, 30 and 40 min of radiation, except for 6, 8, and 10 min, which registered a decrease of about 0.67 eV. This was in comparison using Cheung and Cheung's method, which registered 0.6983 eV and 0.7528 eV for the non-radiated and 2 min of radiation, respectively. The barrier height values, meanwhile, were observed to decrease after 4 (0.61 eV) to 40 min (0.6945 eV). The study shows that conventional thermionic emission model could be practically utilized for estimating the diode parameters including the effect of series resistance. These changes in the electronic properties of the Al/DNA/Al junctions could therefore be utilized in the manufacture of sensitive alpha particle sensors.

  20. Detection of alpha particles using DNA/Al Schottky junctions

    International Nuclear Information System (INIS)

    Deoxyribonucleic acid or DNA can be utilized in an organic-metallic rectifying structure to detect radiation, especially alpha particles. This has become much more important in recent years due to crucial environmental detection needs in both peace and war. In this work, we fabricated an aluminum (Al)/DNA/Al structure and generated current–voltage characteristics upon exposure to alpha radiation. Two models were utilized to investigate these current profiles; the standard conventional thermionic emission model and Cheung and Cheung's method. Using these models, the barrier height, Richardson constant, ideality factor and series resistance of the metal-DNA-metal structure were analyzed in real time. The barrier height, Φ value calculated using the conventional method for non-radiated structure was 0.7149 eV, increasing to 0.7367 eV after 4 min of radiation. Barrier height values were observed to increase after 20, 30 and 40 min of radiation, except for 6, 8, and 10 min, which registered a decrease of about 0.67 eV. This was in comparison using Cheung and Cheung's method, which registered 0.6983 eV and 0.7528 eV for the non-radiated and 2 min of radiation, respectively. The barrier height values, meanwhile, were observed to decrease after 4 (0.61 eV) to 40 min (0.6945 eV). The study shows that conventional thermionic emission model could be practically utilized for estimating the diode parameters including the effect of series resistance. These changes in the electronic properties of the Al/DNA/Al junctions could therefore be utilized in the manufacture of sensitive alpha particle sensors

  1. Detection of alpha particles using DNA/Al Schottky junctions

    Science.gov (United States)

    Al-Ta'ii, Hassan Maktuff Jaber; Periasamy, Vengadesh; Amin, Yusoff Mohd

    2015-09-01

    Deoxyribonucleic acid or DNA can be utilized in an organic-metallic rectifying structure to detect radiation, especially alpha particles. This has become much more important in recent years due to crucial environmental detection needs in both peace and war. In this work, we fabricated an aluminum (Al)/DNA/Al structure and generated current-voltage characteristics upon exposure to alpha radiation. Two models were utilized to investigate these current profiles; the standard conventional thermionic emission model and Cheung and Cheung's method. Using these models, the barrier height, Richardson constant, ideality factor and series resistance of the metal-DNA-metal structure were analyzed in real time. The barrier height, Φ value calculated using the conventional method for non-radiated structure was 0.7149 eV, increasing to 0.7367 eV after 4 min of radiation. Barrier height values were observed to increase after 20, 30 and 40 min of radiation, except for 6, 8, and 10 min, which registered a decrease of about 0.67 eV. This was in comparison using Cheung and Cheung's method, which registered 0.6983 eV and 0.7528 eV for the non-radiated and 2 min of radiation, respectively. The barrier height values, meanwhile, were observed to decrease after 4 (0.61 eV) to 40 min (0.6945 eV). The study shows that conventional thermionic emission model could be practically utilized for estimating the diode parameters including the effect of series resistance. These changes in the electronic properties of the Al/DNA/Al junctions could therefore be utilized in the manufacture of sensitive alpha particle sensors.

  2. Transport theory for energetic alpha particles in finite aspect ratio tokamaks with broken symmetry

    Science.gov (United States)

    Shaing, K. C.; Schlutt, M.; Lai, A. L.

    2016-02-01

    Transport theory for the energetic alpha particles in finite aspect ratio tokamaks with broken symmetry is developed for the case where the slowing down collision operator dominates. The transport fluxes in the 1 /ν and superbanana plateau regimes are derived. Here, ν is the typical collision frequency. They can be used in modeling the energy loss of the alpha particles in thermonuclear fusion reactors. Numerical realizations of the superbanana orbits of alpha particles in tokamaks with broken symmetry are also presented. The existence of the superbananas corroborates the predictions of the theories presented here and elsewhere.

  3. The 1997 IAEA test spectra for alpha-particle spectrometry

    CERN Document Server

    Garcia-Torano, E; Woods, S; Blaauw, M; Fazinic, S

    1999-01-01

    In the framework of an IAEA intercomparison of software for alpha-particle spectrometry, a set of test spectra with reference files was produced for validation and comparison of alpha spectrum analysis programs. The considerations, the spectra and the methods employed to obtain them are presented.

  4. Analysis of uncertainties in alpha-particle optical-potential assessment below the Coulomb barrier

    CERN Document Server

    Avrigeanu, V

    2016-01-01

    Background: Recent high-precision measurements of alpha-induced reaction data below the Coulomb barrier have pointed out questions of the alpha-particle optical-model potential (OMP) which are yet open within various mass ranges. Purpose: The applicability of a previous optical potential and eventual uncertainties and/or systematic errors of the OMP assessment at low energies can be further considered on this basis. Method: Nuclear model parameters based on the analysis of recent independent data, particularly gamma-ray strength functions, have been involved within statistical model calculation of the (alpha,x) reaction cross sections. Results: The above-mentioned potential provides a consistent description of the recent alpha-induced reaction data with no empirical rescaling factors of the and/or nucleon widths. Conclusions: A suitable assessment of alpha-particle optical potential below the Coulomb barrier should involve the statistical-model parameters beyond this potential on the basis of a former analysi...

  5. Innershell ionization by fast protons, alpha particles and carbon ions

    International Nuclear Information System (INIS)

    The subject of this thesis is the study of inner-shell excitations of atoms induced by fast charged particle collisions. A new method is described for measuring the spectrum of delta-electrons emitted by 208Pb after excitation by 15 MeV protons or 50 MeV alpha particles. Experimental equipment is described. Results of both experiments are presented and compared with PWBA models and with calculations based on a semi-classical approximation. The small-impact-parameter ionization probabilities obtained are then compared with literature. Also small-impact-parameter measurements done with 100 MeV carbon ions are described. Besides K-shell measurements, the author also presents L-subshell ionization probability results for Pb. An appendix is added in which energy straggling problems in solid targets are treated. (Auth./G.J.P.)

  6. Luminescence imaging of water during alpha particle irradiation

    Science.gov (United States)

    Yamamoto, Seiichi; Komori, Masataka; Koyama, Shuji; Toshito, Toshiyuki

    2016-05-01

    The luminescence imaging of water using the alpha particle irradiation of several MeV energy range is thought to be impossible because this alpha particle energy is far below the Cerenkov-light threshold and the secondary electrons produced in this energy range do not emit Cerenkov-light. Contrary to this consensus, we found that the luminescence imaging of water was possible with 5.5 MeV alpha particle irradiation. We placed a 2 MBq of 241Am alpha source in water, and luminescence images of the source were conducted with a high-sensitivity, cooled charge-coupled device (CCD) camera. We also carried out such imaging of the alpha source in three different conditions to compare the photon productions with that of water, in air, with a plastic scintillator, and an acrylic plate. The luminescence imaging of water was observed from 10 to 20 s acquisition, and the intensity was linearly increased with time. The intensity of the luminescence with the alpha irradiation of water was 0.05% of that with the plastic scintillator, 4% with air, and 15% with the acrylic plate. The resolution of the luminescence image of water was better than 0.25 mm FWHM. Alpha particles of 5.5 MeV energy emit luminescence in water. Although the intensity of the luminescence was smaller than that in air, it was clearly observable. The luminescence of water with alpha particles would be a new method for alpha particle detection and distribution measurements in water.

  7. Strong absorption model analysis of alpha scattering

    International Nuclear Information System (INIS)

    Angular distribution of alpha-particles at several energies, Eα = 21 ∼ 85.6 MeV from a number of nuclei between 20Ni and 119Sn, extending to wide angular range up to ∼ 160 deg. C in some cases, have been analyzed in terms of three-parameter strong absorption model of Frahn and Venter. Interaction radius and surface diffuseness are obtained from the parameter values rendering the best fit to the elastic scattering data. The inelastic scattering of alpha-particles from a number of nuclei, leading to quadrupole and octupole excitations has also been studied giving the deformation parameters βL. (author). 14 refs, 7 figs, 3 tabs

  8. Particle Physics Aspects of Antihydrogen Studies with ALPHA at CERN

    CERN Document Server

    Fujiwara, M C; Bertsche, W; Bowe, P D; Bray, C C; Butler, E; Cesar, C L; Chapman, S; Charlton, M; Fajans, J; Funakoshi, R; Gill, D R; Hangst, J S; Hardy, W N; Hayano, R S; Hayden, M E; Humphries, A J; Hydomako, R; Jenkins, M J; Jørgensen, L V; Kurchaninov, L; Lai, W; Lambo, R; Madsen, N; Nolan, P; Olchanski, K; Olin, A; Povilus, A; Pusa, P; Robicheaux, F; Sarid, E; Seif El Nasr, S; Silveira, D M; Storey, J W; Thompson, R I; Van der Werf, D P; Wasilenko, L; Wurtele, J S; Yamazaki, Y

    2008-01-01

    We discuss aspects of antihydrogen studies, that relate to particle physics ideas and techniques, within the context of the ALPHA experiment at CERN's Antiproton Decelerator facility. We review the fundamental physics motivations for antihydrogen studies, and their potential physics reach. We argue that initial spectroscopy measurements, once antihydrogen is trapped, could provide competitive tests of CPT, possibly probing physics at the Planck Scale. We discuss some of the particle detection techniques used in ALPHA. Preliminary results from commissioning studies of a partial system of the ALPHA Si vertex detector are presented, the results of which highlight the power of annihilation vertex detection capability in antihydrogen studies.

  9. The alpha-particle structure of 44 Ti

    International Nuclear Information System (INIS)

    Some of the bound and unbound states of 44 Ti have a pronounced alpha-particle structure, and their energies and widths may be obtained from an alpha 40 Ca potential. The differential cross-sections for the elastic scattering of alpha particles by 40 a may also be described by such a potential, and some features indicate the presence of unbound states of 44 Ti. The attempts to unify these bound and scattering phenomena by the same potential are described, together with some new calculations using a cosh potential. (author)

  10. Experiments with nuclear track detectors for diagnostics of protons and alpha particles from fusion plasmas

    International Nuclear Information System (INIS)

    This report deals with the experimental development of a method of detecting charged particles from nuclear fusion plasmas by means of nuclear track detectors. The latter were bombarded with protons and alpha particles poduced with an accelerator from the fusion reactions D (3He, p) α and D (D, p) T. In the parameter range expected for the particles emitted from thermonuclearly burning plasma the detection probabilities of protons and alpha particles were determined as functions of the energy and angle of incidence, and also the crater radii and depths as functions of the particle species, particle energy and etching time. The following results were obtained: For alpha particles the detection probability in the entire energy range investigated and at angles of incidence between 00 and 700 to the foil normal is about 100%. The alpha particle energy can be approximately determined from the track depths. For protons, on the other hand, the detection probability already decreases monotonically at low energies as the energy increases, becoming zero at about Esub(p) = 7 MeV. Proton detection is only possible at angles of incidence between 00 and 300. The proton energy can be approximately determined from the track radii. The measured energy dependence of the track radii and depths of alpha particles and protons and their angular dependence can be explained with a simple model calculation in which it is assumed that the track etching rate decreases as the particle range in the material of the nuclear track foils increases. (orig.)

  11. Alpha-particle diagnostics with high energy neutral beams

    International Nuclear Information System (INIS)

    We have examined the feasibility of alpha-particle diagnostics using a high energy neutral beam on the R-tokamak, a planned device at IPP-Nagoya, Japan, for reacting plasma experiments. In this method, injected neutral particles neutralize alpha particles so as to escape from the magnetically confined plasma through double charge exchange processes, He++ + A0 -- → He0 + A++. Requirements for a probing beam are dis cussed from viewpoints of penetration of an injected beam in the plasma and a neutralization efficiency of alpha particles in a wide velocity range. Either a Li0 beam or a He0 beam in the ground state, produced from a negative ion beam is suitable. A method to neutralize a He- beam into the ground state through an auto-detachment process is proposed. (author)

  12. MODELING AEROSOL FORMATION FROM ALPHA-PINENE + NOX IN THE PRESENCE OF NATURAL SUNLIGHT USING GAS PHASE KINETICS AND GAS-PARTICLE PARTITIONING THEORY. (R826771)

    Science.gov (United States)

    A kinetic mechanism was used to link and model the gas-phase reactions and aerosol accumulation resulting from src="/ncer/pubs/images/alpha.gif">-pinene reactions in the presence of sunlight, ozone (O3), and oxides of nitrogen (NO

  13. Alpha particle destabilization of the TAE modes

    International Nuclear Information System (INIS)

    The high frequency, low mode number toroidicity-induced Alfven eigenmodes (TAE) are shown to be driven unstable by the circulating and/or trapped α-particles through the wave-particle resonances. For a poloidal harmonic to satisfy the resonance condition it requires that the α-particle birth speed vα ≥ vA/(2|m-nq|), where vA is the Alfven speed, m is the poloidal mode number, and n is the toroidal mode number. To destabilize the TAE modes, the inverse Landau damping associated with the α-particle pressure gradient free energy must overcome the velocity space Landau damping due to both the slowing-down α-particle and the core Maxwellian electron and ion distributions. Stability criteria in terms of the α-particle beta βα, α-particle pressure gradient parameter (ω*/ωA) (ω* is the α-particle diamagnetic drift frequency), and (vα/vA) parameters are presented for TFTR, CIT, and ITER tokamaks. The volume averaged α-particle beta threshold for TAE instability also depends sensitively on the core electron and ion temperature. Typically the volume averaged α-particle beta threshold is in the order of 10-4 if the continuum damping effect is absent. Typical growth rates of the n = 1 TAE mode can be in the order of 10-2ωA, where ωA = vA/qR. Stability of higher n TAE modes is also studied. Other types of global Alfven waves are stable due to sideband mode continuum damping resulting from toroidal coupling effects. If the Alfven continuum gap does not exist across the whole minor radius, continuum damping exists for some poloidal harmonics. The continuum damping effect is studied by employing both a resistive MHD stability code (NOVA-R) and an analytical matching method, and the results are presented. 1 ref

  14. Calculations of alpha particle loss for reversed magnetic shear in the Tokamak Fusion Test Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Redi, M.H.; White, R.B.; Batha, S.H.; Levinton, F.M.; McCune, D.C.

    1997-03-01

    Hamiltonian coordinate, guiding center code calculations of the toroidal field ripple loss of alpha particles from a reversed shear plasma predict both total alpha losses and ripple diffusion losses to be greater than those from a comparable non-reversed magnetic shear plasma in the Tokamak Fusion Test Reactor (TFTR) [Fusion Technol. 21, 1324 (1992)]. High central q is found to increase alpha ripple losses as well as first orbit losses of alphas in the reversed shear simulations. A simple ripple loss model, benchmarked against the guiding center code, is found to work satisfactorily in transport analysis modelling of reversed and monotonic shear scenarios. Alpha ripple transport on TFTR affects ions within r/a=0.5, not at the plasma edge. The entire plasma is above threshold for stochastic ripple loss of alpha particles at birth energy in the reversed shear case simulated, so that all trapped 3.5 MeV alphas are lost stochastically or through prompt losses. The 40% alpha particle loss predictions for TFTR suggest that reduction of toroidal field ripple will be a critical issue in the design of a reversed shear fusion reactor.

  15. Discrimination of nuclear recoils from alpha particles with superheated liquids

    Energy Technology Data Exchange (ETDEWEB)

    Aubin, F; Auger, M; Genest, M-H; Giroux, G; Gornea, R; Faust, R; Leroy, C; Lessard, L; Martin, J-P; Morlat, T; Piro, M-C; Starinski, N; Zacek, V [Departement de Physique, Universite de Montreal, Montreal, H3C 3J7 (Canada); Beltran, B; Krauss, C B [Department of Physics, University of Alberta, Edmonton, T6G 2G7 (Canada); Behnke, E; Levine, I; Shepherd, T [Department of Physics and Astronomy, Indiana University South Bend, South Bend, IN 46634 (United States); Nadeau, P; Wichoski, U [Department of Physics, Laurentian University, Sudbury, P3E 2C6 (Canada)], E-mail: zacekv@lps.umontreal.ca (and others)

    2008-10-15

    The PICASSO collaboration observed for the first time a significant difference between the acoustic signals induced by neutrons and alpha particles in a detector based on superheated liquids. This new discovery offers the possibility of improved background suppression and could be especially useful for dark matter experiments. This new effect may be attributed to the formation of multiple bubbles on alpha tracks, compared to single nucleations created by neutron-induced recoils.

  16. Nuclear track detector characterization for alpha-particle spectroscopy

    International Nuclear Information System (INIS)

    Solid State Nuclear Track Detectors (SSNTDs), CR-39™ type, are usually adopted in many applications in which it could be necessary to select tracks according to the incident alpha-particle energy; so several authors have argued that track parameters such as the major/minor axis being the most often reported, can be used to determine the alpha-particle’s energy. However, the use of these parameters only do an univocal result, for example the same axis length can be obtained for different combinations of incident angles and energies. We report on a track analysis performed by a semiautomatic system that classifies tracks according to two parameters, diameter length and mean grey level. This kind of analysis can give information about the track depth, that increases monotonically with the incident energy and angle of the alpha particle. Combining the information on the two parameters it is possible to determine univocally the incident alpha-particle energy values. In order to characterize CR-39 detectors according to the physical track parameters, detectors were irradiated, inside a vacuum chamber, by alpha particles at thirteen energy values, obtained by different mylar layers in front of a 241Am source. After the exposure the detectors were chemically etched to enlarge the tracks and then analyzed by means of a semiautomatic system, consisting on an optical microscope equipped with a CCD camera connected to a personal computer for image storage. A suitable routine analyzed the track parameters: diameter and mean grey level, allowing us to differentiate tracks according to the incident alpha-particle energy and then to individuate the discrimination factors for radon alpha tracks, when nuclear track detectors are applied in radon surveys. - Highlights: ► CR-39. ► Geometric and optical parameter. ► α spectrometry. ► Calibration

  17. Radon monitor and control system based upon alpha particle detection

    International Nuclear Information System (INIS)

    A system is designed for monitoring or controlling the level of radon in indoor air, based upon measuring alpha particles due to the decay of radon or its daughter atoms. In one embodiment, the alpha particle decay of radon itself is detected and analyzed to control a vent in the heating and air conditioning system to automatically keep the radon level below a preselected level. In another embodiment, the daughter atoms 218Po and 214Po are collected from the indoor air and their alpha particle decays are analyzed to provide a sensitive monitor of radon levels or to control vents in the HVAC system to reduce radon concentrations to permissible levels. In addition, the system provides information on the quality of the air filter and indicates when it needs servicing

  18. Alpha-particle radiobiological experiments using thin CR-39 detectors

    International Nuclear Information System (INIS)

    The present paper studied the feasibility of applying comet assay to evaluate the DNA damage in individual HeLa cervix cancer cells after alpha-particle irradiation. We prepared thin CR-39 detectors (<20 μm) as cell-culture substrates, with UV irradiation to shorten the track formation time. After irradiation of the HeLa cells by alpha particles, the tracks on the underside of the CR-39 detector were developed by chemical etching in (while floating on) a 14 N KOH solution at 37 deg. C. Comet assay was then applied. Diffusion of DNA out of the cells could be generally observed from the images of stained DNA. The alpha-particle tracks corresponding to the comets developed on the underside of the CR-39 detectors could also be observed by just changing the focal plane of the confocal microscope. (authors)

  19. Lambda alpha, Sigma alpha and Xi alpha potentials derived from the SU6 quark-model baryon-baryon interaction

    CERN Document Server

    Fujiwara, Y; Suzuki, Y

    2006-01-01

    We calculate Lambda alpha, Sigma alpha and Xi alpha potentials from the nuclear-matter G-matrices of the SU6 quark-model baryon-baryon interaction. The alpha-cluster wave function is assumed to be a simple harmonic-oscillator shell-model wave function. A new method is proposed to derive the direct and knock-on terms of the interaction Born kernel from the hyperon-nucleon G-matrices, with explicit treatments of the nonlocality and the center-of-mass motion between the hyperon and alpha. We find that the SU6 quark-model baryon-baryon interactions, FSS and fss2, yield a reasonable bound-state energy for 5 He Lambda, -3.18 -- -3.62 MeV, in spite of the fact that they give relatively large depths for the Lambda single-particle potentials, 46 -- 48 MeV, in symmetric nuclear matter. An equivalent local potential derived from the Wigner transform of the nonlocal Lambda alpha kernel shows a strong energy dependence for the incident Lambda-particle, indicating the importance of the strangeness-exchange process in the o...

  20. Nuclear structure and reaction mechanisms studied on alpha-particle transitions

    International Nuclear Information System (INIS)

    Since the observation of the natural alpha decay of atomic nuclei the alpha particle was and is considered as an important component of the nuclear matter. The modern studies of alpha-particle transfer reactions are devoted to the question on four-particle correlations (alpha-particle clusters) generally in nuclear matter or also on nuclear surfaces. Thereby one is today yet absolutely far away from a unified picture of the mechanism of the alpha transfer: It is shown that different reaction and nuclear models must be used with different success for the interpretation of the data. Theoretical and experimental determination of spectroscopic strength distribution were thereby developed mutually supportingly each other. On the experimental side the question of the reaction mechanism and the determination of its details is to be clarified. Here approaches were developed which lead to a unified description in the sd shell. Calculations in the formalism of the coupled channels with spectroscopic factors calculated in the framework of the shell model lead to convincing agreements between theoretical and experimental angular distributions regarding both their shape and their amplitude. Hereby it was shown that beside the determination of the potential parameters a two-stage reaction mechanism as in an alpha-particle transition after or before an inelastic excitation of the target or residual nucleus is of decicive importance. (HSI)

  1. Performance comparison of scintillators for alpha particle detectors

    Science.gov (United States)

    Morishita, Yuki; Yamamoto, Seiichi; Izaki, Kenji; Kaneko, Junichi H.; Toui, Kohei; Tsubota, Youichi; Higuchi, Mikio

    2014-11-01

    Scintillation detectors for alpha particles are often used in nuclear fuel facilities. Alpha particle detectors have also become important in the research field of radionuclide therapy using alpha emitters. ZnS(Ag) is the most often used scintillator for alpha particle detectors because its light output is high. However, the energy resolution of ZnS(Ag)-based scintillation detectors is poor because they are not transparent. A new ceramic sample, namely the cerium doped Gd2Si2O7 (GPS) scintillator, has been tested as alpha particle detector and its performances have been compared to that one of three different scintillating materials: ZnS(Ag), GAGG and a standard plastic scintillator. The different scintillating materials have been coupled to two different photodetectors, namely a photomultiplier tube (PMT) and a Silicon Photo-multiplier (Si-PM): the performances of each detection system have been compared. Promising results as far as the energy resolution performances (10% with PMT and 14% with Si-PM) have been obtained in the case of GPS and GAGG samples. Considering the quantum efficiencies of the photodetectors under test and their relation to the emission wavelength of the different scintillators, the best results were achieved coupling the GPS with the PMT and the GAGG with the Si-PM

  2. Development of low level alpha particle counting system

    International Nuclear Information System (INIS)

    Much attention has been paid to the trace analysis of uranium and thorium contained in the base material of LSI or VLSI, since the so-called ''soft-error'' of the memory device was known to be due to alpha particles emitted from these radioactive elements. We have developed an apparatus to meet the needs of estimating such a very small quantity of U and Th of the level of ppb, by directly counting alpha particles using a gas-flow type proportional counter. This method requires no sophisticated analytical skill, and the accuracy of the result is satisfactory. The instrumentation and some application of this apparatus are described. (author)

  3. Nuclear reaction diagnostics of fast confined and escaping alpha particles

    International Nuclear Information System (INIS)

    The resonant radiative capture nuclear reactions D(α,γ)6Li, 6Li(α,γ) 19B and 7Li(α,γ)11B are examined as diagnostics of the energy distribution of confined fast alpha particles in tokamak plasmas. Count rates for realistic Q=1 DT plasma conditions are presented and compared to expected backgrounds. The design of and preliminary results from the prototype fusion gamma ray detector on TFTR are presented. The activation reactions are similarly examined as diagnostics of escaping fast alpha particles. Where possible, count rate estimates for Q=1 DT plasmas and proposed ignition devices are presented

  4. Alpha-particle condensation in nuclei

    International Nuclear Information System (INIS)

    A round up of the present status of the conjecture that nα nuclei form an α-particle condensate in excited states close to the nα threshold is given. Experiments which could demonstrate the condensate character are proposed. Possible lines of further theoretical developments are discussed. (authors)

  5. Alpha-particle condensation in nuclei

    International Nuclear Information System (INIS)

    A round-up of the present status of the conjecture that nα nuclei form an α-particle condensate in excited states close to the nα threshold is given. Experiments which could demonstrate the condensate character are proposed. Possible lines of further theoretical developments are discussed. (author)

  6. Instrument for measuring total alpha particle energies of alpha emitters in ambient air

    Energy Technology Data Exchange (ETDEWEB)

    Kronenberg, S.; Brucker, G.J.; Cummings, B.; Bechtel, E.; Gentner, F.; Horne, S

    2000-11-11

    This paper describes the design, fabrication, testing and evaluation of a self-reading, carbon fiber, electrometer-type instrument. It is used for measuring the total energy of alpha particles emitted in air by progenies of {sup 222}Rn ({sup 218}Po, {sup 214}Pb, and {sup 214}Bi), and sometimes by other types of alpha emitters (e.g. {sup 212}Pb, {sup 238}U, and {sup 239}Pu). The purpose of these measurements is to assess the energy delivered by alpha emission from these sources to the lung tissue. A sample (charged progenies attached to aerosols) is collected on filter paper from a known volume of air and placed on the instrument. The discharge rate indicates the alpha energy in MeV l{sup -1} of air per min that is produced by the alpha emitters. The calibration procedure shows that the instrument has an energy sensitivity for alpha particles of 800.5 MeV/scale unit. The range of the readout scale is 30 units. Measurements of alpha contamination in air were made using this instrument in buildings, private homes and in a standard chamber. The value of the radon concentration in this chamber is traceable back to the US Environmental Protection Agency (EPA) and to the National Institute of Standards and Technology (NIST)

  7. Estimation of the {alpha} particles and neutron distribution generated during a fusion reaction; Evaluation de la distribution des particules {alpha} et des neutrons issus de la reaction de fusion

    Energy Technology Data Exchange (ETDEWEB)

    Dellacherie, S.

    1997-12-01

    The respective distributions (or density probabilities) of {alpha} particles and neutrons have been modeled using a Monte-Carlo method for the thermonuclear fusion reaction D + T {yields} {alpha} + n + 17.6 MeV. (N.T.).

  8. Alfven Eigenmode And Ion Bernstein Wave Studies For Controlling Fusion Alpha Particles

    CERN Document Server

    Franklin, F R

    1999-01-01

    In magnetic confinement fusion reactor plasmas, the charged fusion products (such as alpha particles in deuterium-tritium plasmas) will be the dominant power source, and by controlling these charged fusion products using wave-particle interactions the reactor performance could be optimized. This thesis studies two candidate waves: Mode- Converted Ion Bernstein Waves (MCIBWs) and Alfvé n Eigenmodes (AEs). Rates of MCIBW-driven losses of alpha-like fast deuterons, previously observed in the Tokamak Fusion Test Reactor (TFTR), are reproduced by a new model so that the wave-particle diffusion coefficient can be deduced. The MCIBW power in TFTR is found to be ∼ 1/3 that needed for collisionless alpha particle control...

  9. TCAD simulation for alpha-particle spectroscopy using SIC Schottky diode

    International Nuclear Information System (INIS)

    There is a growing requirement of alpha spectroscopy in the fields context of environmental radioactive contamination, nuclear waste management, site decommissioning and decontamination. Although silicon-based alpha-particle detection technology is mature, high leakage current, low displacement threshold and radiation hardness limits the operation of the detector in harsh environments. Silicon carbide (SiC) is considered to be excellent material for radiation detection application due to its high band gap, high displacement threshold and high thermal conductivity. In this report, an alpha-particle-induced electron-hole pair generation model for a reverse-biased n-type SiC Schottky diode has been proposed and verified using technology computer aided design (TCAD) simulations. First, the forward-biased I-V characteristics were studied to determine the diode ideality factor and compared with published experimental data. The ideality factor was found to be in the range of 1.4-1.7 for a corresponding temperature range of 300-500 K. Next, the energy-dependent, alpha-particle-induced EHP generation model parameters were optimised using transport of ions in matter (TRIM) simulation. Finally, the transient pulses generated due to alpha-particle bombardment were analysed for (1) different diode temperatures (300-500 K), (2) different incident alpha-particle energies (1-5 MeV), (3) different reverse bias voltages of the 4H-SiC-based Schottky diode (-50 to -250 V) and (4) different angles of incidence of the alpha particle (0 deg. -70 deg. ).The above model can be extended to other (wide band-gap semiconductor) device technologies useful for radiation-sensing application. (authors)

  10. 226Ra determination in phosphogypsum by alpha-particle spectrometry

    International Nuclear Information System (INIS)

    A radiochemical method for 226Ra determination by alpha-particle spectrometry in environmental samples has been developed in our laboratory. The method has been validated by measurements in samples with known concentrations of this radionuclide and it has been applied in studies related to 226Ra behaviour in phosphogypsum (the main by-product of producing phosphoric acid from phosphate rocks). (author)

  11. Discrimination of nuclear recoils from alpha particles with superheated liquids

    CERN Document Server

    Aubin, F; Behnke, E; Beltran, B; Clark, K; Dai, X; Davour, A; Genest, M-H; Giroux, G; Gornea, R; Faust, R; Krauss, C B; Leroy, C; Lessard, L; Levine, I; Levy, C; Martin, J -P; Noble, A J; Morlat, T; Nadeau, P; Piro, M -C; Pospísil, S; Shepherd, T; Sodomka, J; Starinski, N; Stekl, I; Storey, C; Wichoski, U; Zacek, V

    2008-01-01

    The PICASSO collaboration observed for the first time a significant difference between the acoustic signals induced by neutrons and alpha particles in a detector based on superheated liquids. This new effect offers the possibility of improved background suppression and could be especially useful for rare event searches such as dark matter experiments.

  12. Alpha-particle clustering in excited expanding self-conjugate nuclei

    CERN Document Server

    Borderie, B; Ademard, G; Rivet, M F; De Filippo, E; Geraci, E; Neindre, N Le; Cardella, G; Lanzalone, G; Lombardo, I; Lopez, O; Maiolino, C; Pagano, A; Pirrone, S; Politi, G; Rizzo, F; Russotto, P

    2016-01-01

    The fragmentation of quasi-projectiles from the nuclear reaction 40Ca + 12C at 25 MeV/nucleon was used to produce alpha-emission sources. From a careful selection of these sources provided by a complete detection and from comparisons with models of sequential and simultaneous decays, strong indications in favour of $\\alpha$-particle clustering in excited 16O, 20Ne and 24}Mg are reported.

  13. Effects of alpha particle transport driven by Alfvenic instabilities on proposed burning plasma scenarios on ITER

    International Nuclear Information System (INIS)

    The consistency of proposed burning plasma scenarios with Alfvenic instabilities driven by alpha particles is investigated. If the alpha particle pressure is above the threshold for resonant excitation of Energetic Particle driven Modes (EPMs), significant modification of the alpha particle pressure profile can take place. Model simulations are performed using the Hybrid MHD-Gyrokinetic Code (HMGC) retaining relevant thermal-plasma parameters, safety factor and alpha particle pressure profiles. ITER monotonic-q and reversed-shear scenarios are considered. A 'hybrid' ITER scenario is also studied and quantitatively compared with the previous ones. We find that, unlike the latter, the former equilibria are unstable. Nonlinear effects on the alpha-particle pressure profile result, however, to be negligible for the monotonic-q case. They can instead be relevant for the reversed-shear scenario. The assessment of such a conclusion requires further investigations concerning the possibility that the strong EPM instability is regulated, in realistic conditions, by nonlinear effects of weaker Alfven modes. (author)

  14. Pressure control and particle`s motion in ALPHA

    CERN Document Server

    Rudakov, Kirill

    2013-01-01

    The first project was a system to control the pressure of water and gas. The second project was the calculation of tracks of particles. The third project was to make an estimation of mutual inductance.

  15. Intrinsic efficiency of LR-115 in alpha particles detection: simulations and experiments

    International Nuclear Information System (INIS)

    A numerical simulation is developed to characterize the response of the cellulose nitrate detector ''LR-115 type II'' to alpha particles of different incidence angles and energies. It permits to know whether an alpha particle at a given energy and direction is able to produce a visible etched track or not. For this purpose, a Vt-variable track etch rate model is used. We have considered that the track etch rate is a function of the ionization rate and the defect created by delta rays along the alpha particle trajectory. Validation of the model is presented in the form of comparisons between theoretically computed values of the sensitive energy range and the track diameters and experimentally determined ones

  16. Alpha-particle losses in compact torsatron reactors

    International Nuclear Information System (INIS)

    Loss of alpha particles in compact torsatron reactors is studied. For 6, 9, and 12 field period reactors, the direct loss is a relatively weak function of radius and energy and varies from ≅33% for M = 6 to ≅18% for M = 12. Loss of alpha particles through scattering into the loss region is calculated using the Fokker-Plank equation for fast ions and found to contribute an additional alpha-particle energy loss of ≅15%. The consequences of these relatively large losses for torsatron reactor design are discussed. The relationship between the direct particle losses and the magnetic field structure is also studied. Orbit losses from a variety of stellarator configurations are calculated and a figure-of-merit that characterizes the orbit confinement of a magnetic configuration is deduced from these calculations. This figure-of-merit is used to show how the direct losses might be reduced at low aspect-ratio. Effects of finite beta on the direct particle losses are also addressed, and are shown to significantly increase the direct losses in some configurations. 15 refs., 8 figs

  17. Alpha particle emitters in cancer therapy: establishing the rationale and overcoming the difficulties

    International Nuclear Information System (INIS)

    Full text: Once a tumor has metastasized, the possibility of cure is significantly diminished, if not excluded. Since metastatic spread arises due to the release of single tumor cells or tumor cell clusters, treatment regimens following an overt metastasis must include agents that eradicate individual tumor cells and cell clusters or that prevent their dissemination. Alpha particles may be highly effective in eradicating rapidly accessible disease. The effectiveness of alpha particles arises because the amount of energy deposited per unit distance traveled (linear energy transfer or LET) is approximately 400 times greater than that of beta particles (80 keV/μm vs. 0.2 keV/μm). Each traversal of an alpha particle through a cell nucleus results in a very highly ionizing track. Cell survival studies have shown that alpha-particle killing is independent of oxygenation state or cell-cycle during irradiation and that as few as 1 to 6 tracks across the nucleus may result in cell death. Most studies with alpha-particle emitting radionuclides for therapy have examined either bismuth-212 or astatine-211. Both radionuclides are short-lived with 61 minute and 7.2 hour half-lives, respectively, yielding intermediates with 3-minute and 32 year half-lives, respectively. Both emit alpha particles whose range is 40 to 80 μm. Alpha-particle emitting radionuclides have been attached to antibodies against tumor cell associated antigen. Antibodies have been the most widely used vehicle for delivery of alpha particles due to their specificity. Bismuth-212 has demonstrated a significant curative potential with minimal toxicity. In an ascites tumor mouse model, specific targeting and 80% cure following injection of Bi-212-labeled antibody has been observed (Macklis RM et al, Science, 240:1024-1026, 1988). It is important to define the realm of applicability for alpha particle emitting radionuclides. The short half-life of most currently available radionuclides, limits their use to

  18. Effects of q(r) on the Alpha Particle Ripple Loss in TFTR

    Energy Technology Data Exchange (ETDEWEB)

    D.S. Darrow; M. Diesso; R.V. Budny; S. Batha; S.J. Zweben; et al.

    1997-09-01

    An experiment was done with TFTR DT plasmas to determine the effect of the q(r) profile on the alpha particle ripple loss to the outer midplane. The alpha particle loss measurements were made using a radially movable scintillator detector 20 degrees below the outer midplane. The experimental results were compared with TF ripple loss calculations done using a Monte Carlo guiding center orbit following code, ORBIT. Although some of the experimental results are consistent with the ORBIT code modeling, the variation of the alpha loss with the q(r) profiles is not well explained by this code. Quantitative interpretation of these measurements requires a careful analysis of the limiter shadowing effect, which strongly determines the diffusion of alphas into the detector aperture.

  19. Emission of alpha particles and other light nuclei as a fission process

    International Nuclear Information System (INIS)

    The fission theory was successfully applied to the emission of alpha particles and other light nuclei from a heavy nucleus. Good agreement (within +-0.8 orders of magnitude) of the theoretical life times with experimental ones over a range of 24 orders of magnitude, was obtained. Three macroscopic models have been extended for the nuclear systems with different charge densities. A phenomenological shell correction was introduced. WKB approximation was used. By taking into account the nuclear deformation, the life-time of the alpha decay from a shape isomeric state was predicted. A new semiempirical relationship for the alpha decay life-time was derived. (author)

  20. RPL in alpha particle irradiated Ag+-doped phosphate glass

    International Nuclear Information System (INIS)

    The objective of this study is to investigate the emission mechanism of radiophotoluminescence (RPL) in the Ag+-doped phosphate glass (glass dosimeter), which is now used as individual radiation dosimeter, because the emission mechanism of RPL in glass dosimeter has been not fully understood. We have investigated the assignments and characteristics of the X-ray induced color centers in the Ag+-doped phosphate glass up to now (Miyamoto et al., 2010). Optical properties such as optical absorption spectra related with alpha-particles and X-rays irradiation were measured for commercially available glass dosimeter. In this study optical properties such as optical absorption spectrum as a function of alpha-particles and X-rays irradiation were measured for commercially available glass dosimeter. Comparison of the RPL in Ag+-doped phosphate glass irradiated with alpha-particles and X-rays is discussed. - Highlights: • A Yellow and blue emission are included in the RPL of Ag+-doped phosphate glass. • The ratio of yellow and blue emission was different between alpha and X-ray irradiation. • RPL emission intensity increased in an atmosphere below room temperature

  1. Time-Varying alpha and Particle Physics

    CERN Document Server

    Banks, T; Douglas, M R

    2002-01-01

    We argue that models in which an observable variation of the fine structure constant is explained by motion of a cosmic scalar field, are not stable under renormalization, and require massive fine tuning that cannot be explained by any known mechanism.

  2. Phoswich Detector for Simultaneous Measuring Alpha/beta Particles

    International Nuclear Information System (INIS)

    The new type phoswich detector consisting of the ZnS(Ag) and plastic scintillator for alpha/beta-ray simultaneous counting was developed for monitoring radiological contamination inside pipes. The detection performance was estimated using the PSD (pulse shape discrimination) method as a function of distance between the scintillator and radioactive source. The attenuation of particles traveling through a thin film for preventing the detector from being contaminated was experimentally estimated. It is concluded from our investigation that the phoswich detector developed can provide a sufficient alpha/beta-ray discrimination. The application of a thin film for preventing the detector from being contaminated was proven to be feasible.

  3. Low energy alpha particle spectroscopy using CR-39 detector

    CERN Document Server

    Izerrouken, M; Ilic, R

    1999-01-01

    The possibility of using CR-39 to measure the depth profile of sup 1 sup 0 B in Si is analysed. The measuring technique exploits the sup 1 sup 0 B(n, alpha) sup 7 Li nuclear reaction. For this reason the track parameters (size, optical properties) of low energy alpha-particles (<1.47 MeV) were studied. The results showed that an energy resolution of about 100 keV could be obtained by an appropriate selection of etching conditions. The profile of sup 1 sup 0 B in Si at a depth as small as 1 mu m can be measured.

  4. Alpha particle density and energy distributions in tandem mirrors using Monte-Carlo techniques

    International Nuclear Information System (INIS)

    We have simulated the alpha thermalization process using a Monte-Carlo technique, in which the alpha guiding center is followed between simulated collisions and Spitzer's collision model is used for the alpha-plasma interaction. Monte-Carlo techniques are used to determine the alpha radial birth position, the alpha particle position at a collision, and the angle scatter and dispersion at a collision. The plasma is modeled as a hot reacting core, surrounded by a cold halo plasma (T approx.50 eV). Alpha orbits that intersect the halo lose 90% of their energy to the halo electrons because of the halo drag, which is ten times greater than the drag in the core. The uneven drag across the alpha orbit also produces an outward, radial, guiding center drift. This drag drift is dependent on the plasma density and temperature radial profiles. We have modeled these profiles and have specifically studied a single-scale-length model, in which the density scale length (r/sub pD/) equals the temperature scale length (r/sub pT/), and a two-scale-length model, in which r/sub pD//r/sub pT/ = 1.1

  5. Alpha particle effects on global MHD modes, and alpha particle transport in ignited tokamaks

    International Nuclear Information System (INIS)

    The high frequency, low mode number toroidicity-induced Alfven eigenmodes (TAE) are shown to be driven unstable primarily by the circulating α-particles through wave-particle resonances. To destabilize the TAE modes, the inverse Landau damping associated with the α-particle pressure gradient free energy must overcome the velocity space Landau damping due to both the α-particles and the core electrons and ions, as well as Alfven continuum damping. Stability criteria are presented for TFTR, CIT, and ITER tokamaks in terms of the α-particle beta βα, the α-particle pressure gradient parameter (ω*/ωA), where ω* is the α-particle diamagnetic drift frequency, and the α-particle velocity (vα/vA) parameter. Typically the volume averaged α-particle beta threshold is on the order of 10-4. Rough estimates of the TAE mode saturation level give δBr/B ∼ 10-3 for typical D-T tokamak operations. Significant α-particle losses are found when the amplitude of the global MHD modes is large, on the order of (δBr/B) ≥ 10-4. For (δBr/B) = 5 x 10-4, the α-particle loss time is appreciably shorter than the α-particle slowing-down time. 13 refs., 1 fig

  6. Alpha particle track coloration in CR-39: Improved observability

    CERN Document Server

    Oezguemues, A

    1999-01-01

    A comparative study of the observability of alpha particle tracks in CR-39 was performed with an optical microscope before and after coloration. The implantation of ink helped in observing the damage zones. At first glance through the microscope, the coloration makes the tracks stand out right away. This coloration is helpful, from the start, in the morphological study of the tracks (size, area, orientation, shape, perimeter). This operation is advantageous in distinguishing the alpha particle tracks from stains or scratches. Thus, the routine counting of the tracks is more easily performed. Consequently, this procedure allowed us: to decrease significantly the standard deviation of the approximate total of the parameters given from the image analysis system (Olympus CUE2); to envision the possibility of reasonably decreasing the etching time in order to limit the loss of information caused by the destruction of the CR-39 during chemical etching and to use a weaker enlarging lens in order to cover a larger fi...

  7. A fluid particle model

    OpenAIRE

    Español, Pep

    1997-01-01

    We present a mechanistic model for a Newtonian fluid called fluid particle dynamics. By analyzing the concept of ``fluid particle'' from the point of view of a Voronoi tessellation of a molecular fluid, we propose an heuristic derivation of a dissipative particle dynamics algorithm that incorporates shear forces between dissipative particles. The inclusion of these non-central shear forces requires the consideration of angular velocities of the dissipative particles in order to comply with th...

  8. The biokinetics of alpha-particle emitting radiopharmaceuticals

    International Nuclear Information System (INIS)

    The past two decades have seen wide interest in the application of alpha-particle emitting radionuclides for targeted endoradiotherapy and a large number of compounds labeled with 211At (T1/2 7.21 h), 212Bi (T1/2 1 h) or 213Bi (T1/2 0.78 h) have been studied. Knowledge of the biokinetic behaviour of such agents is important both for their optimal clinical exploitation and for general radiological protection purposes. Animal studies of the distribution and retention of 211At compounds, including ionic astatide, substituted aromatic compounds and labelled monoclonal antibodies, have provided new information on the biochemistry of astatine. With respect the thyroid gland the uptake of the astatide ion has been shown to be very much lower than that of the iodide ion. Less information is available for 212Bi-labelled radiopharmaceuticals. The available data for both 211At and 212Bi radiopharmaceuticals are reviewed. Cautious generic biokinetic models for inorganic and simple organic compounds of 211At and 212Bi; for [211At]-, and [212Bi]-biphosphonates and for [211At]-, and [212Bi]-monoclonal antibodies, are proposed for use in general radiological protection when compound-specific data are not available. (orig.)

  9. The biokinetics of alpha-particle emitting radiopharmaceuticals

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, D.M. [School of Chemistry, Cardiff Univ., Cardiff (United Kingdom); Duffield, J.R. [Faculty of Applied Sciences, Univ. of the West of England, Bristol (United Kingdom)

    2005-07-01

    The past two decades have seen wide interest in the application of alpha-particle emitting radionuclides for targeted endoradiotherapy and a large number of compounds labeled with {sup 211}At (T{sup 1}/{sub 2} 7.21 h), {sup 212}Bi (T{sup 1}/{sub 2} 1 h) or {sup 213}Bi (T{sup 1}/{sub 2} 0.78 h) have been studied. Knowledge of the biokinetic behaviour of such agents is important both for their optimal clinical exploitation and for general radiological protection purposes. Animal studies of the distribution and retention of {sup 211}At compounds, including ionic astatide, substituted aromatic compounds and labelled monoclonal antibodies, have provided new information on the biochemistry of astatine. With respect the thyroid gland the uptake of the astatide ion has been shown to be very much lower than that of the iodide ion. Less information is available for {sup 212}Bi-labelled radiopharmaceuticals. The available data for both {sup 211}At and {sup 212}Bi radiopharmaceuticals are reviewed. Cautious generic biokinetic models for inorganic and simple organic compounds of {sup 211}At and {sup 212}Bi; for [{sup 211}At]-, and [{sup 212}Bi]-biphosphonates and for [{sup 211}At]-, and [{sup 212}Bi]-monoclonal antibodies, are proposed for use in general radiological protection when compound-specific data are not available. (orig.)

  10. CIT alpha particle extraction and measurement: Low-Z ablation cloud profile simulation for alpha-particle diagnostics

    International Nuclear Information System (INIS)

    In order to determine the expected properties of the ablation cloud of low-Z pellets interacting with a thermonuclear plasma, which in turn is proposed as a charge-neutralization medium for confined alpha particles, a numerical program has been developed. The physical model for this program is based on Park's low-Z pellet-plasma interaction model for the interior of the cloud adjacent to the pellet's surface out to the sonic surface (roughly, a millimeter in separation), and then propagating outward from this region using the conservation laws of enthalpy, momentum, and mass, along with the assumption of charge-state equilibrium. The effects of local heating by the plasma electrons slowing down in the cloud, and ionization of the ablatant material are treated self-consistently in the model. In collaboration with Dr. Paul Parks of General Atomics Corporation, a joint ODU-GAC research plan for modeling low-Z pellet-plasma interactions has been devised, and considerable progress has been made in its implementation. Recently, using a constraint in the ablatant flow, so that it approximates its observed flow along the magnetic field, results from the program were obtained which could be compared with the results from the GAC experiments on TEXT. The predictions of the program are in poor agreement with the TEXT data as to the dimensions of the C+3 region of the cloud along the magnetic field. The failure of the model appears to be the breakdown of the assumption that charge-state equilibrium exists in the cloud. This problem is particularly severe for the TEXT parameters so modifications in the model to include non-equilibrium effects are being implemented

  11. A Novel Experiment to Investigate the Attenuation of Alpha Particles in Air

    Science.gov (United States)

    Andrews, D. G. H.

    2008-01-01

    A simple student experiment investigating dependence on air pressure of the attenuation of alpha particles in air is described. An equation giving the pressure needed to absorb all alpha particles of a given energy is derived from the Bethe-Bloch formula. Results are presented for the attenuation of alpha particles from americium 241 and radium…

  12. CIT alpha particle extraction and measurement: Low-Z ablation cloud profile simulation for alpha-particle diagnostics

    International Nuclear Information System (INIS)

    In order to determine the expected properties of the ablation cloud of low-Z pellets interacting with a thermonuclear plasma, which in turn is proposed as a charge-neutralization medium for confined alpha particles, a numerical program has been developed. The physical model for this program is based on Parks' low-Z pellet-plasma interaction model for the interior of the cloud adjacent to the pellet's surface out to the sonic surface (roughly, a millimeter in separation) and then propagating outward from this region using the conservation laws of enthalpy, momentum, and mass, along with the assumption of charge-state equilibrium. The effects of local heating by the plasma electrons slowing down in the cloud, and ionization of the ablatant material are treated self-consistently in the model. In collaboration with Dr. Paul Parks of General Atomics Corporation, a joint ODU-GAC research plan for modeling low-Z pellet-plasma interactions has been devised, and considerable progress has been made in its implementation. Recently, using a constraint in the ablatant flow, results from the program were obtained which could be compared with the results from the GAC experiments on TEXT. The predictions of the program are in pretty good agreement with the TEXT data as to the dimensions of the C+3 region of the cloud along the magnetic field. Also a small improvement has been made in the low-Z pellet plasma-penetration program, which brings the predictions of the model in closer agreement with the carbon pellet injection experiments on TFTR. 22 refs., 3 figs

  13. Monte Carlo nanodosimetry of alpha particle passages through the capillary endothelial nucleus application to systemic Targeted Alpha Therapy

    International Nuclear Information System (INIS)

    Full text: The biological effects of Targeted Alpha Therapy are strongly affected by the heterogeneous specific energy delivered to tumor cells. For systemic Targeted Alpha Therapy, all blood vessels inevitably received a background radiation from non-targeted decays with the blood circulation. The Geant4 Monte Carlo code was adapted to simulate the spatial non-uniform distribution of the alpha emitting radioisotope sources 213Bi, 212Bi and 211At. A cylindrical annulus was taken as a geometrical model to approximate the capillary. The endothelial cell nucleus was set to be an ellipsoid filled with liquid water to simulate nanometric target volumes at unit density. The Geant4 Low Energy physics model, based on the Livermore approach, was selected to model the particle interactions with the material in the experimental setup. The threshold of production of secondary particles was 7 eV. We validated the program with published results using spheroid cell geometry. The specific energy deposited in a capillary endothelial cell nucleus per radioactive decay and the capillary endothelial cell survival rates were calculated for the source constrained in the capillary lumen or the source binding to the surface antigen on the perivascular cancer cells. The measurement of nanodosimetric event size spectra based on simulated nanodosimetric data is presented. The value and limitations of this approach are discussed. (author)

  14. Gross {alpha}-particle activities in the ground waters in Western Anatolia

    Energy Technology Data Exchange (ETDEWEB)

    Akyil, S.; Erees, F.S.; Olmez, S. [Ege Universitesi, Izmir (Turkey)

    1996-07-01

    The purpose of this study is to present data on gross {alpha}-particle activity, pH and conductivity in the ground waters in Western Anatolia. The gross {alpha}-particle activities in 27 ground water samples were determined by radiochemical carrier-precipitation methods. The gross {alpha}-particle activities of water samples were measured by using a ZnS (Ag) detector system. Measureable {alpha}-particle activity is present in all ground water samples, with one ground water sample having a gross {alpha}-particle activity > 0.55 Bq/L. (Author).

  15. Alpha-particle Measurements Needed for Burning Plasma Experiments

    International Nuclear Information System (INIS)

    The next major step in magnetic fusion studies will be the construction of a burning plasma (BP) experiment where the goals will be to achieve and understand the plasma behavior with the internal heating provided by fusion-generated alpha particles. Two devices with these physics goals have been proposed: the International Thermonuclear Experimental Reactor (ITER) and the Fusion Ignition Research Experiment (FIRE). Extensive conceptual design work for the instrumentation to try to meet the physics demands has been done for these devices, especially ITER. This article provides a new look at the measurements specifically important for understanding the physics aspects of the alpha particles taking into account two significant events. The first is the completion of physics experiments on the Joint European Torus (JET) and the Tokamak Fusion Test Reactor (TFTR) with deuterium-tritium fueling with the first chances to study alpha physics and the second is the realization that relatively compact plasmas, making use of advanced tokamak plasma concepts, are the most probable route to burning plasmas and ultimately a fusion reactor

  16. Alpha-particle Measurements Needed for Burning Plasma Experiments

    Energy Technology Data Exchange (ETDEWEB)

    Kenneth M. Young

    2001-09-26

    The next major step in magnetic fusion studies will be the construction of a burning plasma (BP) experiment where the goals will be to achieve and understand the plasma behavior with the internal heating provided by fusion-generated alpha particles. Two devices with these physics goals have been proposed: the International Thermonuclear Experimental Reactor (ITER) and the Fusion Ignition Research Experiment (FIRE). Extensive conceptual design work for the instrumentation to try to meet the physics demands has been done for these devices, especially ITER. This article provides a new look at the measurements specifically important for understanding the physics aspects of the alpha particles taking into account two significant events. The first is the completion of physics experiments on the Joint European Torus (JET) and the Tokamak Fusion Test Reactor (TFTR) with deuterium-tritium fueling with the first chances to study alpha physics and the second is the realization that relatively compact plasmas, making use of advanced tokamak plasma concepts, are the most probable route to burning plasmas and ultimately a fusion reactor.

  17. Simulations of alpha particle ripple loss from the International Thermonuclear Experimental Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Redi, M.H.; Budny, R.V.; McCune, D.C.; Miller, C.O.; White, R.B.

    1996-05-01

    Calculations of collisional stochastic ripple loss of alpha particles from the new 20 toroidal field (TF) coil International Thermonuclear Experimental Reactor (ITER) predict small alpha ripple losses, less than 0.4%, close to the loss calculated for the full current operation of the earlier 24 TF coil design. An analytic fit is obtained to the ITER ripple data field demonstrating the nonlinear height dependence of the ripple minimum for D shaped ripple contours. In contrast to alpha loss simulations for the Tokamak Fusion Test Reactor (TFTR), a simple Goldston, White, Boozer stochastic loss criterion ripple loss model is found to require an increased renormalization of the stochastic threshold {delta}{sub s}/{delta}{sub GWB} {ge} 1. Effects of collisions, sawtooth broadening and reversal of the grad B drift direction are included in the particle following simulations.

  18. Simulations of alpha particle ripple loss from the International Thermonuclear Experimental Reactor

    International Nuclear Information System (INIS)

    Calculations of collisional stochastic ripple loss of alpha particles from the new 20 toroidal field (TF) coil International Thermonuclear Experimental Reactor (ITER) predict small alpha ripple losses, less than 0.4%, close to the loss calculated for the full current operation of the earlier 24 TF coil design. An analytic fit is obtained to the ITER ripple data field demonstrating the nonlinear height dependence of the ripple minimum for D shaped ripple contours. In contrast to alpha loss simulations for the Tokamak Fusion Test Reactor (TFTR), a simple Goldston, White, Boozer stochastic loss criterion ripple loss model is found to require an increased renormalization of the stochastic threshold δs/δGWB ≥ 1. Effects of collisions, sawtooth broadening and reversal of the grad B drift direction are included in the particle following simulations

  19. A dynamical $\\alpha$-cluster model of $^{16}$O

    CERN Document Server

    Halcrow, C J; Manton, N S

    2016-01-01

    We calculate the low-lying spectrum of the $^{16}$O nucleus using an $\\alpha$-cluster model which includes the important tetrahedral and square configurations. Our approach is motivated by the dynamics of $\\alpha$-particle scattering in the Skyrme model. We are able to replicate the large energy splitting that is observed between states of identical spin but opposite parities, as well as introduce states that were previously not found in other cluster models, such as a $0^-$ state. We also provide a novel interpretation of the first excited state of $^{16}$O and make predictions for the energies of $6^-$ states that have yet to be observed experimentally.

  20. GaN-based PIN alpha particle detectors

    Energy Technology Data Exchange (ETDEWEB)

    Wang Guo [Peking University, Shenzhen Graduate School, Guangdong Shenzhen 518055 (China); Peking University, Beijing, 100871 (China); Fu Kai; Yao Changsheng [Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Science, Jiangsu Suzhou 215123 (China); Su Dan; Zhang Guoguang [China Institute of Atomic Energy, Beijing 102413 (China); Wang Jinyan [Peking University, Beijing, 100871 (China); Lu Min, E-mail: mlu2006@sinano.ac.cn [Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Science, Jiangsu Suzhou 215123 (China)

    2012-01-21

    GaN-based PIN alpha particle detectors are studied in this article. The electrical properties of detectors have been investigated, such as current-voltage (I-V) and capacitance-voltage (C-V). The reverse current of all detectors is in nA range applied at 30 V, which is suitable for detector operation. The charge collection efficiency (CCE) is measured to be approximately 80% but the energy resolution is calculated to be about 40% mostly because the intrinsic layer is not sufficiently thick enough.

  1. GaN-based PIN alpha particle detectors

    International Nuclear Information System (INIS)

    GaN-based PIN alpha particle detectors are studied in this article. The electrical properties of detectors have been investigated, such as current-voltage (I-V) and capacitance-voltage (C-V). The reverse current of all detectors is in nA range applied at 30 V, which is suitable for detector operation. The charge collection efficiency (CCE) is measured to be approximately 80% but the energy resolution is calculated to be about 40% mostly because the intrinsic layer is not sufficiently thick enough.

  2. Alpha particle response characterization of CdZnTe

    Energy Technology Data Exchange (ETDEWEB)

    Amman, Mark; Lee, Julie S.; Luke, Paul N.

    2001-06-28

    The coplanar-grid as well as other electron-only detection techniques are effective in overcoming some of the material problems of CdZnTe and, consequently, have led to efficient gamma-ray detectors with good energy resolution while operating at room temperature. The performance of these detectors is limited by the degree of uniformity in both electron generation and transport. Despite recent progress in the growth of CdZnTe material, small variations in these properties remain a barrier to the widespread success of such detectors. Alpha-particle response characterization of CdZnTe crystals fabricated into simple planar detectors is an effective tool to accurately study electron generation and transport. We have used a finely collimated alpha source to produce two-dimensional maps of detector response. A clear correlation has been observed between the distribution of precipitates near the entrance contact on some crystals and their alpha-response maps. Further studies are ongoing to determine the mechanism for the observed response variations and the reason for the correlation. This paper presents the results of these studies and their relationship to coplanar-grid gamma-ray detector performance.

  3. Alpha particle response characterization of CdZnTe

    International Nuclear Information System (INIS)

    The coplanar-grid as well as other electron-only detection techniques are effective in overcoming some of the material problems of CdZnTe and, consequently, have led to efficient gamma-ray detectors with good energy resolution while operating at room temperature. The performance of these detectors is limited by the degree of uniformity in both electron generation and transport. Despite recent progress in the growth of CdZnTe material, small variations in these properties remain a barrier to the widespread success of such detectors. Alpha-particle response characterization of CdZnTe crystals fabricated into simple planar detectors is an effective tool to accurately study electron generation and transport. We have used a finely collimated alpha source to produce two-dimensional maps of detector response. A clear correlation has been observed between the distribution of precipitates near the entrance contact on some crystals and their alpha-response maps. Further studies are ongoing to determine the mechanism for the observed response variations and the reason for the correlation. This paper presents the results of these studies and their relationship to coplanar-grid gamma-ray detector performance

  4. Stability of the Global Alfven Eigenmode in the presence of fusion alpha particles in an ignited tokamak plasma

    International Nuclear Information System (INIS)

    The stability of the Global Alfven Eigenmodes is investigated in the presence of super-Alfvenic energetic particles, such as the fusion-product alpha particles in an ignited deuterium-tritium tokamak plasma. Alpha particles tend to destabilize these modes when ω*α > ωA, where ωA is the shear-Alfven modal frequency and ω*α is the alpha particle diamagnetic drift frequency. This destabilization due to alpha particles is found to be significantly enhanced when the alpha particles are modeled with a slowing-down distribution function rather than with a Maxwellian. However, previously neglected electron damping due to the magnetic curvature drift is found to be comparable in magnitude to the destabilizing alpha particle term. Furthermore, the effects of toroidicity are also found to be stabilizing, since the intrinsic toroidicity induces poloidal mode coupling, which enhances the parallel electron damping from the sideband shear-Alfven Landau resonance. In particular, for the parameters of the proposed Compact Ignition Tokamak, the Global Alfven Eigenmodes are found to be completely stabilized by either the electron damping that enters through the magnetic curvature drift or the damping introduced by finite toroidicity. 29 refs., 8 figs., 1 tab

  5. Alpha particle track coloration in CR-39: Improved observability

    International Nuclear Information System (INIS)

    A comparative study of the observability of alpha particle tracks in CR-39 was performed with an optical microscope before and after coloration. The implantation of ink helped in observing the damage zones. At first glance through the microscope, the coloration makes the tracks stand out right away. This coloration is helpful, from the start, in the morphological study of the tracks (size, area, orientation, shape, perimeter). This operation is advantageous in distinguishing the alpha particle tracks from stains or scratches. Thus, the routine counting of the tracks is more easily performed. Consequently, this procedure allowed us: to decrease significantly the standard deviation of the approximate total of the parameters given from the image analysis system (Olympus CUE2); to envision the possibility of reasonably decreasing the etching time in order to limit the loss of information caused by the destruction of the CR-39 during chemical etching and to use a weaker enlarging lens in order to cover a larger field of observation for the counting operations

  6. DEM Particle Fracture Model

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Boning [Univ. of Colorado, Boulder, CO (United States); Herbold, Eric B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Homel, Michael A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Regueiro, Richard A. [Univ. of Colorado, Boulder, CO (United States)

    2015-12-01

    An adaptive particle fracture model in poly-ellipsoidal Discrete Element Method is developed. The poly-ellipsoidal particle will break into several sub-poly-ellipsoids by Hoek-Brown fracture criterion based on continuum stress and the maximum tensile stress in contacts. Also Weibull theory is introduced to consider the statistics and size effects on particle strength. Finally, high strain-rate split Hopkinson pressure bar experiment of silica sand is simulated using this newly developed model. Comparisons with experiments show that our particle fracture model can capture the mechanical behavior of this experiment very well, both in stress-strain response and particle size redistribution. The effects of density and packings o the samples are also studied in numerical examples.

  7. Comparative analysis of inelastic interactions of protons, deuterons, and. cap alpha. particles with nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Barashenkov, V.S.; Zheregi, F.G.; Musul' manbekov, Z.Z.; Plyushchev, V.A.; Solov' eva, Z.I.

    1981-04-01

    Inelastic interactions of protons, deuterons, and ..cap alpha.. particles with emulsion nuclei at 3.6 Gev/nucleon are analyzed within the framework of the cascade-evaporation model. The model accounts well, within the limits of experimental error, for all the principal characteristics measured in experiment; in particular, it explains why the energy of the g protons emitted into the rear hemisphere is independent of the emission angle of these protons, of the mass of the primary particle, and of the degree of spallation of the target nucleus. Some discrepancy with experiment manifests itself only in the details.

  8. A Feasibility Study of a Portable Alpha Particle Spectrometer

    International Nuclear Information System (INIS)

    Alpha spectroscopy is widely used for detecting undeclared nuclear facilities, activities, and materials. Due to the heavy equipment required to carry out this technique, its applications is limited. With the goal of quickly and efficiently responding to undeclared nuclear facilities, activities, and materials, the present authors have designed and built a portable α-particle spectrometer. This study was conducted in order to develop a new portable α-particle spectrometer with the purpose of detecting undeclared nuclear facilities, activities, and materials on site quickly and efficiently. All heavy and large components, which are typically required for a laboratory such as a αparticle spectrometry system, were minimized and placed in a small container with a weight of 14 kg and a size of 30 cm x 30 cm x 30 cm. In the feasibility study, the calculated enrichment values of 235U obtained from the portable α-particle spectrometer were 1.868 % and 3.083 %, similar to the results from a commercial spectrometry system used in laboratories, 2.049 % and 3.253 %. These differences were possibly caused by different channel setups for each system

  9. Bremsstrahlung during $\\alpha$-decay: quantum multipolar model

    CERN Document Server

    Maydanyuk, Sergei P

    2008-01-01

    In this paper the improved multipolar model of bremsstrahlung accompanied the $\\alpha$-decay is presented. The angular formalism of calculations of the matrix elements, being enough complicated component of the model, is stated in details. A new definition of the angular (differential) probability of the photon emission in the $\\alpha$-decay is proposed where direction of motion of the $\\alpha$-particle outside (with its tunneling inside barrier) is defined on the basis of angular distribution of its spacial wave function. In such approach, the model gives values of the angular probability of the photons emission in absolute scale, without its normalization on experimental data. Effectiveness of the proposed definition and accuracy of the spectra calculations of the bremsstrahlung spectra are analyzed in their comparison with experimental data for the $^{210}{\\rm Po}$, $^{214}{\\rm Po}$, $^{226}{\\rm Ra}$ and $^{244}{\\rm Cm}$ nuclei, and for some other nuclei predictions are performed (in absolute scale). With ...

  10. Alpha Decay in the Complex Energy Shell Model

    CERN Document Server

    Betan, R Id

    2012-01-01

    Alpha emission from a nucleus is a fundamental decay process in which the alpha particle formed inside the nucleus tunnels out through the potential barrier. We describe alpha decay of $^{212}$Po and $^{104}$Te by means of the configuration interaction approach. To compute the preformation factor and penetrability, we use the complex-energy shell model with a separable T=1 interaction. The single-particle space is expanded in a Woods-Saxon basis that consists of bound and unbound resonant states. Special attention is paid to the treatment of the norm kernel appearing in the definition of the formation amplitude that guarantees the normalization of the channel function. Without explicitly considering the alpha-cluster component in the wave function of the parent nucleus, we reproduce the experimental alpha-decay width of $^{212}$Po and predict an upper limit of T_{1/2}=5.5x10^{-7} sec for the half-life of $^{104}$Te. The complex-energy shell model in a large valence configuration space is capable of providing ...

  11. Alpha particle losses from Tokamak Fusion Test Reactor deuterium-tritium plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Darrow, D.S.; Zweben, S.J. [Princeton Univ., NJ (United States). Plasma Physics Lab.; Batha, S. [Fusion Physics and Technology, Torrance, CA (United States)

    1996-01-01

    Because alpha particle losses can have a significant influence on tokamak reactor viability, the loss of deuterium-tritium alpha particles from the Tokamak Fusion Test Reactor (TFTR) has been measured under a wide range of conditions. In TFTR, first orbit loss and stochastic toroidal field ripple diffusion are always present. Other losses can arise due to magnetohydrodynamic instabilities or due to waves in the ion cyclotron range of frequencies. No alpha particle losses have yet been seen due to collective instabilities driven by alphas. Ion Bernstein waves can drive large losses of fast ions from TFTR, and details of those losses support one element of the alpha energy channeling scenario.

  12. Alpha particle losses from Tokamak Fusion Test Reactor deuterium-tritium plasmas

    International Nuclear Information System (INIS)

    Because alpha particle losses can have a significant influence on tokamak reactor viability, the loss of deuterium-tritium alpha particles from the Tokamak Fusion Test Reactor (TFTR) has been measured under a wide range of conditions. In TFTR, first orbit loss and stochastic toroidal field ripple diffusion are always present. Other losses can arise due to magnetohydrodynamic instabilities or due to waves in the ion cyclotron range of frequencies. No alpha particle losses have yet been seen due to collective instabilities driven by alphas. Ion Bernstein waves can drive large losses of fast ions from TFTR, and details of those losses support one element of the alpha energy channeling scenario

  13. Study on cytotoxicities induced by alpha particle irradiation combined with NNK treatment

    International Nuclear Information System (INIS)

    Objective: To investigate cytotoxicities of alpha-particle irradiation combined with NNK treatment. Methods: Exponentially growing immortalized human bronchial epithelial cells were divided into normal control group (NC), alpha particle irradiation group (α), NNK administration group (NNK), NNK administration (100 μg/ml) followed by alpha particle irradiation group (NNK + α), and alphaparticle irradiation followed by NNK administration (100 μg/ml) group (α + NNK). Cell survival fractions were measured by cloning rate of low-density plating cell. Ethidium bromide and 2', 7'-dichlorofluorescein, fluorescent products of the membrane-permeable dyes hydroethine and 2', 7'-dichloroflurescindiacetate were used to monitor the inarticulate reactive oxygen species (ROS) . Damage to membrane permeability was evaluated through testing LDH activity in medium. Results: In the groups exposed to both alpha particles and NNK, the survival rates were significantly lower than that of the groups administrated with the same dose of alpha particles or NNK alone. The levels of intracellular ROS and the activity of LDH in medium were significantly higher than that of the groups administrated with the same dose of alpha particles or NNK alone. Subtracted the NNK effect, the survival rates of the groups received both alpha particle irradiation and NNK treatment were significantly lower than that of alpha particle irradiated only group. However, the intracellular ROS level and the activity of LDH in medium were significantly higher than that of alpha-particle irradiated only group. In addition, the survival rates of the cells in groups exposed to alpha particle irradiation followed by NNK administration were significantly lower than that of cells treated with NNK administration followed by alpha particle irradiation. Conclusions: Alpha particle irradiation and NNK administration had synergisticity in cytotoxicity, and furthermore different schedules of the administration resulted in

  14. Influence of Magnolol on the bystander effect induced by alpha-particle irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Wong, T.P.W.; Law, Y.L. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong (Hong Kong); Tse, A.K.W.; Fong, W.F. [Research and Development Division, School of Chinese Medicine, Hong Kong Baptist University, Baptist University Road, Kowloon Tong (Hong Kong); Yu, K.N. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong (Hong Kong)], E-mail: peter.yu@cityu.edu.hk

    2010-04-15

    In this work, the influence of Magnolol on the bystander effect in alpha-particle irradiated Chinese hamster ovary (CHO) cells was examined. The bystander effect was studied through medium transfer experiments. Cytokinesis-block micronucleus (CBMN) assay was performed to quantify the chromosome damage induced by alpha-particle irradiation. Our results showed that the alpha-particle induced micronuclei (MN) frequencies were suppressed with the presence of Magnolol.

  15. A novel experiment to investigate the attenuation of alpha particles in air

    International Nuclear Information System (INIS)

    A simple student experiment investigating dependence on air pressure of the attenuation of alpha particles in air is described. An equation giving the pressure needed to absorb all alpha particles of a given energy is derived from the Bethe-Bloch formula. Results are presented for the attenuation of alpha particles from americium 241 and radium 226. The experimental results are in close agreement with the theoretical predictions

  16. New alpha particle counter based on micro-pixel avalanche photodiode

    International Nuclear Information System (INIS)

    Full text : The main goal of this work is study of possibility to detect alpha particles with micro-pixel avalanche photodiode which has very thin active volume. The obtained results show that alpha detectors based on the micro-pixel avalanche photodiodes can be used as alpha particle counter in many experiments : public security, radioactive contamination monitoring in various environments and detection of charged particles from nuclear reactions

  17. Alpha particles (citations from the International Aerospace Abstracts data base). Report for 1974-July 1979

    International Nuclear Information System (INIS)

    This bibliography of citations to the international literature covers various aspects of alpha particles as applied to controlled fusion devices, solar activity, and geomagnetically trapped particles. Included are articles concerning Tokamak devices, plasma heating and control, plasma-particle interactions, solar particles, solar wind, solar flares, energy spectra, and magnetohydrodynamic stability. Articles concerning effects of alpha particles on different kinds of devices are also included

  18. Reviews Book: Marie Curie and Her Daughters Resource: Cumulus Equipment: Alpha Particle Scattering Apparatus Equipment: 3D Magnetic Tube Equipment: National Grid Transmission Model Book: Einstein's Physics Equipment: Barton's Pendulums Equipment: Weather Station Web Watch

    Science.gov (United States)

    2013-09-01

    WE RECOMMEND Marie Curie and Her Daughters An insightful study of a resilient and ingenious family and their achievements Cumulus Simple to install and operate and with obvious teaching applications, this weather station 'donationware' is as easy to recommend as it is to use Alpha Particle Scattering Apparatus Good design and construction make for good results National Grid Transmission Model Despite its expense, this resource offers excellent value Einstein's Physics A vivid, accurate, compelling and rigorous treatment, but requiring an investment of time and thought WORTH A LOOK 3D Magnetic Tube Magnetic fields in three dimensions at a low cost Barton's Pendulums A neat, well-made and handy variant, but not a replacement for the more traditional version Weather Station Though not as robust or substantial as hoped for, this can be put to good use with the right software WEB WATCH An online experiment and worksheet are useful for teaching motor efficiency, a glance at CERN, and NASA's interesting information on the alpha-magnetic spectrometer and climate change

  19. Control of alpha particle transport by spatially inhomogeneous ion cyclotron resonance heating

    International Nuclear Information System (INIS)

    Control of the radial alpha particle transport by using Ion Cyclotron Range of Frequency waves is investigated in a large-aspect-ratio tokamak geometry. It is shown that spatially inhomogeneous ICRF-wave energy with properly selected frequencies and wave numbers can induce fast convective transport of alpha particles at the speed of order υalpha ∼ (PRF/nαε0) ρp, where PRF is the ICRF-wave power density, nα is the alpha density, ε0 is the alpha birth energy, and ρp is the poloidal gyroradius of alpha particles at the birth energy. Application to ITER plasmas is studied and possible antenna designs to control alpha particle flux are discussed. 8 refs., 3 figs

  20. Alfven Eigenmode And Ion Bernstein Wave Studies For Controlling Fusion Alpha Particles

    CERN Document Server

    Heeter, R F

    1999-01-01

    In magnetic confinement fusion reactor plasmas, the charged fusion products (such as alpha particles in deuterium-tritium plasmas) will be the dominant power source, and by controlling these charged fusion products using wave-particle interactions the reactor performance could be optimized. This thesis studies two candidate waves: Mode-Converted Ion Bernstein Waves (MCIBWs) and Alfvén Eigenmodes (AEs). Rates of MCIBW-driven losses of alpha-like fast deuterons, previously observed in the Tokamak Fusion Test Reactor (TFTR), are reproduced by a new model so that the wave-particle diffusion coefficient can be deduced. The MCIBW power in TFTR is found to be ∼ 1/3 that needed for collisionless alpha particle control. A reasonable reactor power scaling is derived. To study AEs, existing magnetic fluctuation probes at the Joint European Torus (JET) have been absolutely calibrated from 30–500 kHz for the first time, allowing fluctuation measurements with &vbm0;dBpol&vbm0;/B0&am...

  1. New concept for a wall detector for alpha particles

    International Nuclear Information System (INIS)

    A new concept for a wall-mounted detector is described here that would measure D-T alpha flux and corresponding pitch angle distribution in tokamaks (or related toroidal devices). The sensing element is a conical Micro Channel Ring (MCR) coated with 1 to 2μ of ZnS scintillator (or possibly ZnO). The collimation of the α particles is provided by two circumferential slots at the wall surface. The alpha scintillation events on the MCR are transferred through the ring channels and coupled fiber optics bundle to an external processor. From the magnetic field vector at a given point on the device wall, a certain relation can be set up between the α-induced scintillation position on the MCR and its original pitch angle (i.e., the angle between the α emission from the fusion reaction and the magnetic field vector) which is equal to the local pitch angle since the wall α flux is dominated by prompt losses

  2. Detection of lost alpha particle by concealed lost ion probe

    International Nuclear Information System (INIS)

    Full orbit-following calculation is performed for the final orbit of the lost alpha particles, showing some orbits escaping from the last closed flux surface could be detected by a concealed lost ion probe (CLIP) installed under the shadow of the original first wall surface. While both passing and trapped orbits hit the same wall panel, detecting a trapped orbit by the CLIP is easier than detecting passing orbits. Whether the final orbit is detected or not is determined by the position of the reflection point. The CLIP successfully detects the trapped orbits, which are reflected before they hit to a first wall. Then the pitch angles of the orbits at the CLIP are close to and smaller than 90 deg. Optimization of the position of the CLIP in terms of broader detection window is investigated.

  3. Anomalous loss of DT alpha particles in the Tokamak Fusion Test Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Herrmann, H.W.

    1997-09-01

    An escaping alpha collector probe has been developed for TFTR`s DT phase. Energy distributions of escaping alphas have been determined by measuring the range of {alpha}-particles implanted into nickel foils located within the alpha collector. Results at 1.0 MA of plasma current are in good agreement with predictions for first orbit alpha loss. Results at 1.8 MA, however, show a significant anomalous loss of partially thermalized alphas (in addition to the expected first orbit loss), which is not observed with the lost alpha scintillator detectors in DT plasmas, but does resemble the anomalous delayed loss seen in DD plasmas. None of the candidate explanations proposed thus far are fully consistent with the anomalous loss observations. An experiment designed to study the effect of plasma major radius shifts on {alpha}-particle loss has led to a better understanding of {alpha}-particle dynamics in tokamaks. Intuitively, one might suppose that confined marginally passing {alpha}-particles forced to move toward higher magnetic field during an inward major radius shift (i.e., compression) would mirror and become trapped particles, leading to increased alpha loss. Such an effect was looked for during the shift experiment, however, no significant changes in alpha loss to the 90{degree} lost alpha scintillator detector were observed during the shifts. It is calculated that the energy gained by an {alpha}-particle during the inward shift is sufficient to explain this result. However, an unexpected loss of partially thermalized {alpha}-particles near the passing/trapped boundary was observed to occur between inward and outward shifts at an intermediate value of plasma current (1.4 MA). This anomalous loss feature is not yet understood.

  4. Alpha particle destabilization of the toroidicity-induced Alfven eigenmodes

    International Nuclear Information System (INIS)

    The high frequency, low mode number toroidicity-induced Alfven eigenmodes (TAE) are shown to be driven unstable by the circulating and/or trapped α-particles through the wave-particle resonances. Satisfying the resonance condition requires that the α-particle birth speed vα ≥ vA/2|m-nq|, where vA is the Alfven speed, m is the poloidal model number, and n is the toroidal mode number. To destabilize the TAE modes, the inverse Landau damping associated with the α-particle pressure gradient free energy must overcome the velocity space Landau damping due to both the α-particles and the core electrons and ions. The growth rate was studied analytically with a perturbative formula derived from the quadratic dispersion relation, and numerically with the aid of the NOVA-K code. Stability criteria in terms of the α-particle beta βα, α-particle pressure gradient parameter (ω*/ωA) (ω* is the α-particle diamagnetic drift frequency), and (vα/vA) parameters will be presented for TFTR, CIT, and ITER tokamaks. The volume averaged α-particle beta threshold for TAE instability also depends sensitively on the core electron and ion temperature. Typically the volume averaged α-particle beta threshold is in the order of 10-4. Typical growth rates of the n=1 TAE mode can be in the order of 10-2ωA, where ωA=vA/qR. Other types of global Alfven waves are stable in D-T tokamaks due to toroidal coupling effects

  5. Chromosomal aberrations induced by alpha particles; Aberraciones cromosomicas inducidas por particulas {alpha}

    Energy Technology Data Exchange (ETDEWEB)

    Guerrero C, C.; Brena V, M. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico)]. e-mail: cgc@nuclear.inin.mx

    2005-07-01

    The chromosomal aberrations produced by the ionizing radiation are commonly used when it is necessary to establish the exposure dose of an individual, it is a study that is used like complement of the traditional physical systems and its application is only in cases in that there is doubt about what indicates the conventional dosimetry. The biological dosimetry is based on the frequency of aberrations in the chromosomes of the lymphocytes of the individual in study and the dose is calculated taking like reference to the dose-response curves previously generated In vitro. A case of apparent over-exposure to alpha particles to which is practiced analysis of chromosomal aberrations to settle down if in fact there was exposure and as much as possible, to determine the presumed dose is presented. (Author)

  6. Anomalous Loss of DT Alpha Particles in the Tokamak Fusion Test Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Herrmann, Hans W.

    1997-06-01

    Princeton's Tokamak Fusion Test Reactor (TFTR) is the first experimental fusion device to routinely use tritium to study the deuterium-tritium (DT) fusion reaction,allowing the first systematic study of DT alpha particles in tokamak plasmas. A crucial aspect of alpha-particle physics is the fraction of alphas that escape from the plasma, particularly since these energetic particles can do severe damage to the first wall of a reactor. An escaping alpha collector probe has been developed for TFTR's DT phase. Energy distributions of escaping alphas have been determined by measuring the range of alpha-particles implanted into nickel foils located within the alpha collector. Results at 1.0 MA of plasma current are in good agreement with predictions for first orbit alpha loss. Results at 1.8 MA, however, show a significant anomalous loss of partially thermalized alphas (in addition to the expected first orbit loss), which is not observed with the lost alpha scintillator detectors in DT plasmas, but does resemble the anomalous "delayed" loss seen in DD plasmas. None of the candidate explanations proposed thus far are fully consistent with the anomalous loss observations. An experiment designed to study the effect of plasma major radius shifts on alpha-particle loss has led to a better understanding of alpha-particle dynamics in tokamaks. Intuitively, one might suppose that confined marginally passing alpha-particles forced to move toward higher magnetic field during an inward major radius shift (i.e. compression) would mirror and become trapped particles, leading to increased alpha loss. Such an effect was looked for during the shift experiment, however, no significant changes in alpha loss to the 90 degree lost alpha scintillator detector were observed during the shifts. It is calculated that the energy gained by an alpha-particle during the inward shift is sufficient to explain this result. However, an unexpected loss of partially thermalized alpha-particles

  7. Alpha spectrometry for particle size determination of mineral sands dust samples

    International Nuclear Information System (INIS)

    A method is proposed for assessing the size distribution of the radioactive particles directly from the alpha spectrum of a dust sample. The residual range distribution of alpha particles emerging from a sphere containing a monoenergetic alpha emitter is simply a quadratic function of the diameter of the sphere. The residual range distribution from a typical dust particle closely approximates that of a sphere of the same mass. For mixtures of various size particles of similar density the (multiparticle) residual range distribution can thus readily be calculated for each of the alpha emitters contained in the particles. Measurement of the composite residual range distribution can be made in a vacuum alpha spectrometer provided the dust sample has no more than a monolayer of particles. The measured energy distribution is particularly sensitive to upper particle size distributions in the diameter region of 4μm to 20μm of 5 mg/cm3 density particles, i.e. 2 to 10 mg/ch2. For dust particles containing212Po or known ratios of alpha emitters a measured alpha spectrum can be unraveled to the underlying particle size distribution. Uncertainty in the size distribution has been listed as deserving research priority in the overall radiation protection program of the mineral sands industry. The proposed method had the potential of reducing this uncertainty, thus permitting more effective radiation protection control. 2 refs., 1 tabs., 1 figs

  8. Bond scission cross sections for alpha-particles in cellulose nitrate (LR115)

    CERN Document Server

    Barillon, R; Chambaudet, A; Katz, R; Stoquert, J P; Pape, A

    1999-01-01

    Chemical damage created by alpha-particles in cellulose nitrate (LR115) have been studied by infrared spectroscopy. This technique enables identifying the sensitive bonds and giving an order of magnitude of their scission cross sections for given alpha-particle energies. The high cross sections observed suggest a new description of the track etch velocity in this material.

  9. Computation and measurement of differential ranges of low-energy alpha particles in matter

    International Nuclear Information System (INIS)

    The stopping power formula of Bethe is discussed and is used to compute differential ranges of low-energy alpha particles in air, argon, aluminium and copper. A single radioactive source containing three active elements is used in experiments to measure the differential ranges in these materials. Finally a range-energy relationship for the alpha particles in air is deduced. (author)

  10. Simulation of Alpha Particles in Rotating Plasma Interacting with a Stationary Ripple

    Energy Technology Data Exchange (ETDEWEB)

    Abraham J. Fetterman and Nathaniel J. Fisch

    2011-01-11

    Superthermal ExB rotation can provide magnetohydrodynamic (MHD) stability and enhanced confinement to axisymmetric mirrors. However, the rotation speed has been limited by phenomena at end electrodes. A new prediction is that rotation might instead be produced using a magnetic ripple and alpha particle kinetic energy, in an extension of the alpha channeling concept. The interaction of alpha particles with the ripple results in visually interesting and practically useful orbits.

  11. Simulation of Alpha Particles in Rotating Plasma Interacting with a Stationary Ripple

    International Nuclear Information System (INIS)

    Superthermal ExB rotation can provide magnetohydrodynamic (MHD) stability and enhanced confinement to axisymmetric mirrors. However, the rotation speed has been limited by phenomena at end electrodes. A new prediction is that rotation might instead be produced using a magnetic ripple and alpha particle kinetic energy, in an extension of the alpha channeling concept. The interaction of alpha particles with the ripple results in visually interesting and practically useful orbits.

  12. Folding model study of the elastic $\\alpha + \\alpha$ scattering at low energies

    CERN Document Server

    Tan, Ngo Hai; Khoa, Dao T

    2014-01-01

    The folding model analysis of the elastic $\\alpha + \\alpha$ scattering at the incident energies below the reaction threshold of 34.7 MeV (in the lab system) has been done using the well-tested density dependent versions of the M3Y interaction and realistic choices for the $^4$He density. Because the absorption is negligible at the energies below the reaction threshold, we were able to probe the $\\alpha + \\alpha$ optical potential at low energies quite unambiguously and found that the $\\alpha + \\alpha$ overlap density used to construct the density dependence of the M3Y interaction is strongly distorted by the Pauli blocking. This result gives possible explanation of a long-standing inconsistency of the double-folding model in its study of the elastic $\\alpha + \\alpha$ and $\\alpha$-nucleus scattering at low energies using the same realistic density dependent M3Y interaction.

  13. Study of compound nucleus formation via bremsstrahlung emission in proton $\\alpha$-particle scattering

    CERN Document Server

    Maydanyuk, Sergei P

    2016-01-01

    In this paper a role of many-nucleon dynamics in formation of the compound $^{5}{\\rm Li}$ nucleus in the scattering of protons off $\\alpha$-particles at the proton incident energies up to 20 MeV is investigated. We propose a bremsstrahlung model allowing to extract information about probabilities of formation of such nucleus on the basis of analysis of experimental cross-sections of the bremsstrahlung photons. In order to realize this approach, the model includes elements of microscopic theory and also probabilities of formation of the short-lived compound nucleus. Results of calculations of the bremsstrahlung spectra are in good agreement with the experimental cross-sections.

  14. Stochastic loss of alpha particles in a Helias reactor

    International Nuclear Information System (INIS)

    It is shown that collisionless orbit transformation of the locally trapped particles to the locally passing ones and vice versa in the Wendelstein-line optimized stellarators results in stochastic diffusion of energetic ions. This diffusion can lead to the loss of an essential fraction of energetic ion population from the region where the characteristic diffusion time is small compared to the slowing down time. The loss region and the magnitude of the loss can be minimized by shaping the plasma temperature and density profiles so that they satisfy certain requirements. The predictions of the developed theory are in agreement with the results of numerical modelling of confinement of α-particles in a Helias reactor, which was carried out in this work with the use of the orbit following code. The considered diffusion seems to represent the dominant mechanism of classical losses of α-particles in a Helias reactor. (author)

  15. Determination of the range of alpha particles in SSNTD by optical density method

    CERN Document Server

    El-Hofy, M; Arafa, W

    1999-01-01

    A technique based on the optical density (D) measurement of the etched track is useful for charged particles spectroscopy using SSNTD. It was shown that the stopping power of alpha particles in CR-39 is proportional to D. We measured the optical density and derived an expression to estimate the range of alpha particles in CR-39 detector as a function of the bulk etching rate and etching time. The relation between the etching time, track parameters (depth, radius) and D for different alpha particles energy and etching conditions were studied. A relation describing D as a function of track size is proposed.

  16. A cluster expansion for bound three-alpha particles as a three-body problem

    International Nuclear Information System (INIS)

    A three-body model is proposed to study the nuclear bound states. The nucleus is described as a bound state of three clusters. A cluster expansion is introduced for the three cluster bound state problem. The present integral equations are treated by simple approximate solutions, which lead to effective potentials by using the present cluster expansion. The 12C nucleus is described as a three-alpha particle bound state. The binding energy of 12C is calculated numerically using the present cluster expansion as bound three-alpha clusters. The present three-body cluster expansion calculations are very near to the exact three-body calculations using separable potentials. The present theoretical calculations are in good agreement with the experimental measurements. (author)

  17. Coulomb excitation effects on alpha-particle optical potential below the Coulomb barrier

    CERN Document Server

    Avrigeanu, V; Mănăilescu, C

    2016-01-01

    A competition of the low-energy Coulomb excitation (CE) with the compound nucleus (CN) formation in alpha-induced reactions below the Coulomb barrier has recently been assumed in order to make possible the description of the latter as well as the alpha-particle emission by the same optical model (OM) potential. On the contrary, we show in the present work that the corresponding partial waves and integration radii provide evidence for the distinct account of the CE cross section and OM total-reaction cross section $\\sigma_R$. Thus the largest contribution to CE cross section comes by far from partial waves larger than the ones contributing to the $\\sigma_R$ values.

  18. The Use Of Optical Properties Of Cr-39 In Alpha Particle Equivalent Dose Measurements

    International Nuclear Information System (INIS)

    In this work, optical properties of alpha irradiated Cr-39 were measured as a function of optical photon wavelength from 200-1100 nm. Optical energy gap and optical absorption at finite wavelength was also calculated and correlated to alpha fluence and dose equivalent. Alpha doses were calculated from the corresponding irradiation fluence and specific energy loss using TRIM computer program. It was found that, the optical absorption of unattached Cr-39 was varied with alpha fluence and corresponding equivalent doses. Also the optical energy gab was varied with fluence and dose equivalent of alpha particles. This work introduces a reasonably simple method for the Rn dose equivalent calculation by Cr-39 track

  19. Alpha Ni optical model potentials

    Science.gov (United States)

    Billah, M. M.; Abdullah, M. N. A.; Das, S. K.; Uddin, M. A.; Basak, A. K.; Reichstein, I.; Sen Gupta, H. M.; Malik, F. B.

    2005-11-01

    The present work reports the analyses of the experimental differential cross-sections of α elastic scattering on 58,60,62,64Ni, over a wide range of incident energies, in terms of four types of optical potentials, namely shallow (molecular), deep non-monotonic, squared Woods-Saxon and semi-microscopic folding. All the four potentials produce a reasonable description of the experimental data. The potential parameters, calculated from the energy density functional theory using a realistic two-nucleon interaction, resemble closely the molecular potential parameters, which produce the best description of the experimental data for the four isotopes. The volume integrals and the energy variation of the parameters indicate the effect of the shell-model structure on the potentials. The folding potentials, without any need for renormalization, are found to describe reasonably well the elastic scattering cross-section data for the four isotopes within the energy range considered. In conformity with the previous observation on Ca isotopes, the number of nucleons, 4A=49, existing in α-like clusters in the target nucleus, is the same for the four isotopes, considered herein.

  20. Proton and alpha-particle capture reactions at sub-Coulomb energies relevant to the p process

    Energy Technology Data Exchange (ETDEWEB)

    Harissopulos, S [Tandem Accelerator Facility, Institute of Nuclear Physics, NCSR ' Demokritos' , 153.10 Aghia Paraskevi, Athens (Greece); Lagoyannis, A [Tandem Accelerator Facility, Institute of Nuclear Physics, NCSR ' Demokritos' , 153.10 Aghia Paraskevi, Athens (Greece); Spyrou, A [Tandem Accelerator Facility, Institute of Nuclear Physics, NCSR ' Demokritos' , 153.10 Aghia Paraskevi, Athens (Greece); Zarkadas, Ch [Tandem Accelerator Facility, Institute of Nuclear Physics, NCSR ' Demokritos' , 153.10 Aghia Paraskevi, Athens (Greece); Galanopoulos, S [Tandem Accelerator Facility, Institute of Nuclear Physics, NCSR ' Demokritos' , 153.10 Aghia Paraskevi, Athens (Greece); Perdikakis, G [Tandem Accelerator Facility, Institute of Nuclear Physics, NCSR ' Demokritos' , 153.10 Aghia Paraskevi, Athens (Greece); Becker, H-W [Dynamitron-Tandem-Laboratorium, Ruhr Universitaet Bochum, 44801 Bochum (Germany); Rolfs, C [Institut fuer Physik mit Ionenstrahlen, EP-II, Ruhr-Universitaet BochumI, 44801 Bochum (Germany); Strieder, F [Institut fuer Physik mit Ionenstrahlen, EP-II, Ruhr-Universitaet BochumI, 44801 Bochum (Germany); Kunz, R [Institut fuer Strahlenphysik, Universitaet Stuttgart, 70569 Stuttgart (Germany); Fey, M [Institut fuer Strahlenphysik, Universitaet Stuttgart, 70569 Stuttgart (Germany); Hammer, J W [Institut fuer Strahlenphysik, Universitaet Stuttgart, 70569 Stuttgart (Germany); Dewald, A [Institut fuer Kernphysik, Universitaet zu Koeln, 50937 Cologne (Germany); Zell, K-O [Institut fuer Kernphysik, Universitaet zu Koeln, 50937 Cologne (Germany); Brentano, P von [Institut fuer Kernphysik, Universitaet zu Koeln, 50937 Cologne (Germany); Julin, R [Department of Physics, University of Jyvaeskylae, 40014 Jyvaeskylae (Finland); Demetriou, P [Institut d' Astronomie et d' Astrophysique, Universite Libre de Bruxelles, CP226, 1050 Brussels (Belgium)

    2005-10-01

    Several cross-section measurements of proton as well as {alpha}-particle capture reactions in the Se-Sb region have been carried out at sub-Coulomb energies with the aim to obtain global input parameters for Hauser-Feshbach (HF) calculations. Some of the results are compared with HF calculations using various optical model potentials and nuclear level densities.

  1. AVERAGE REACTION CROSS-SECTIONS FOR 74-MEV TO 112-MEV ALPHA-PARTICLES ON I-127 AND CS-133

    NARCIS (Netherlands)

    WARNER, RE; WILSCHUT, HW; RULLA, WF; FELDER, GN

    1991-01-01

    The average reaction cross section for 74- to 112-MeV alpha particles on I-127 and Cs-133 was measured by a new method using a magnetic spectrograph and a CsI scintillation detector. The result, sigma-R = 2220+/-50 mb, is in good agreement with optical model calculations and finite-range microscopic

  2. Hauser-Feshbach cross-section calculations for elastic and inelastic scattering of alpha particles-program CORA

    International Nuclear Information System (INIS)

    The program CORA was prepared on the basis of Hauser and Feshbach compound reaction formalism. It allows the differential cross-section distributions for the elastic and inelastic scattering of alpha particles (via compound nucleus state) to be calculated. The transmission coefficients are calculated on the basis of a four parameter optical model. The search procedure is also included. (author)

  3. The Effects of Alpha Particle Confinement on Burning Plasma Tokamak Performance

    Science.gov (United States)

    Gormley, Robert P.

    In this thesis, three effects of alpha particle plasma interactions on the global performance of a fusion reactor are studied, namely, (i) the energy coupling efficiency of the fast alpha particles with the bulk plasma, (ii) the relationship between imperfect alpha energy coupling to the bulk plasma and the resultant alpha particle/helium ash fuel dilution; and (iii) the neoclassical bootstrap current induced by fusion born alpha particles calculated self-consistently with the plasma equilibrium. First, the ion drift kinetic equation for the high energy alpha particles is reduced from the exact five dimensional form to a two dimensional form in radius r and energy E (plus time t). The resulting slowing-down diffusion equation is solved by a multiple energy group method. A theoretically based anomalous diffusion coefficient D_sp{alpha}{an} is then introduced from a self-consistent alpha particle Alfven wave turbulence solution (by F. Gang), in which D_sp{alpha}{an } itself depends on the gradient in alpha density. The temporal and spatial behavior of eta_ alpha is analyzed for an ITER-CDA physics phase fusion reactor. We find that eta_ alpha can be as low as 0.95 depending on the plasma operating temperature. Next, the relationship between the alpha-particle power coupling efficiency and the actual alpha-particle power that is coupled with the bulk plasma is investigated, this time taking into account the concomitant helium ash accumulation. It is found that the coupled power varies less than linearly with eta_alpha and is, in fact, significantly depressed for eta_alpha near unity. Combining these effects with a thermal power balance shows that the high temperature "thermally stable" side of the ignition boundary is pushed toward lower temperatures if either D_alpha increases (which results in a lower eta_alpha) or the helium-ash confinement time lengthens. This is a consequence of strengthened fuel dilution and imperfect alpha power coupling. Implications on the

  4. Theoretical and empirical status of the two-deuteron-alpha-particle vertex

    International Nuclear Information System (INIS)

    The two-deuteron-alpha-particle overlap, including its D-wave component, is evaluated in the case of realistic two- and four-body wavefunctions. The deduced theoretical value is compared with improved empirical estimates based upon DWBA analyses of (d,α) reactions in the sd shell and which incorporate the best available shell-model information for the nuclear states involved. The theoretical and empirical values of this analysis are in agreement. The result differs substantially from other recent empirical estimates obtained from (d,α) reactions upon heavier target nuclei and from simple theoretical estimates which make use of a point-deuteron approximation. (author)

  5. The simulation of the response of superheated emulsion to alpha particles

    International Nuclear Information System (INIS)

    The response of superheated emulsion of liquid perfluorobutane (C4F10; b.p.:  −1.7o C) to alpha particle has been studied by performing the simulation using GEANT3.21 toolkit. The simulations have been performed to generate two different experimental situations. In one case, the alpha contamination is present only in polymer and in another case, the alpha contamination is present both in polymer and active liquid. The value of the nucleation parameter, k, for bubble nucleation induced by alpha particle in superheated emulsion detector is determined by comparing the simulated normalized count rates with the available experimental results. The results show that the nucleation parameter for alpha particle in C4F10 liquid is about 0.19. The energy and position of alpha particle are not able to change the response of the alpha particle in C4F10 liquid. The recoiling nuclei associated with the alpha decay chain are responsible for making the detector sensitive at lower threshold temperatures

  6. The simulation of the response of superheated emulsion to alpha particles

    Science.gov (United States)

    Seth, Susnata; Das, Mala

    2016-04-01

    The response of superheated emulsion of liquid perfluorobutane (C4F10; b.p.: ‑1.7o C) to alpha particle has been studied by performing the simulation using GEANT3.21 toolkit. The simulations have been performed to generate two different experimental situations. In one case, the alpha contamination is present only in polymer and in another case, the alpha contamination is present both in polymer and active liquid. The value of the nucleation parameter, k, for bubble nucleation induced by alpha particle in superheated emulsion detector is determined by comparing the simulated normalized count rates with the available experimental results. The results show that the nucleation parameter for alpha particle in C4F10 liquid is about 0.19. The energy and position of alpha particle are not able to change the response of the alpha particle in C4F10 liquid. The recoiling nuclei associated with the alpha decay chain are responsible for making the detector sensitive at lower threshold temperatures.

  7. Anomalous loss of DT alpha particles in the Tokamak Fusion Test Reactor

    International Nuclear Information System (INIS)

    An escaping alpha collector probe has been developed for TFTR's DT phase. Energy distributions of escaping alphas have been determined by measuring the range of α-particles implanted into nickel foils located within the alpha collector. Results at 1.0 MA of plasma current are in good agreement with predictions for first orbit alpha loss. Results at 1.8 MA, however, show a significant anomalous loss of partially thermalized alphas (in addition to the expected first orbit loss), which is not observed with the lost alpha scintillator detectors in DT plasmas, but does resemble the anomalous delayed loss seen in DD plasmas. None of the candidate explanations proposed thus far are fully consistent with the anomalous loss observations. An experiment designed to study the effect of plasma major radius shifts on α-particle loss has led to a better understanding of α-particle dynamics in tokamaks. Intuitively, one might suppose that confined marginally passing α-particles forced to move toward higher magnetic field during an inward major radius shift (i.e., compression) would mirror and become trapped particles, leading to increased alpha loss. Such an effect was looked for during the shift experiment, however, no significant changes in alpha loss to the 90 degree lost alpha scintillator detector were observed during the shifts. It is calculated that the energy gained by an α-particle during the inward shift is sufficient to explain this result. However, an unexpected loss of partially thermalized α-particles near the passing/trapped boundary was observed to occur between inward and outward shifts at an intermediate value of plasma current (1.4 MA). This anomalous loss feature is not yet understood

  8. Cross sections of nuclear reactions induced by protons, deuterons, and alpha particles. Pt.6. Phosphorus

    International Nuclear Information System (INIS)

    Cross sections are reviewed for nuclear reactions induced by protons, deuterons, and alpha particles on phosphorus targets. When necessary, published experimental data are corrected, and, when possible, excitation functions are proposed

  9. Interaction of neutrons with alpha particles: A tribute to Heinz Barschall

    OpenAIRE

    Hoop, B. de

    2015-01-01

    As a tribute to our teacher and mentor on the occasion of his centennial celebration, we provide a brief historical overview and a summary of sustained interest in the topic of interaction of neutrons with alpha particles.

  10. Measurement of $\\alpha$-particle quenching in LAB based scintillator in independent small-scale experiments

    CERN Document Server

    von Krosigk, B; Hans, S; Junghans, A R; Kögler, T; Kraus, C; Kuckert, L; Liu, X; Nolte, R; O'Keeffe, H M; Tseung, H S Wan Chan; Wilson, J R; Wright, A; Yeh, M; Zuber, K

    2015-01-01

    The $\\alpha$-particle light response of liquid scintillators based on linear alkylbenzene (LAB) has been measured with three different experimental approaches. In the first approach, $\\alpha$-particles were produced in the scintillator via $^{12}$C($n$,$\\alpha$)$^9$Be reactions. In the second approach, the scintillator was loaded with 2% of $^{\\mathrm{nat}}$Sm providing an $\\alpha$-emitter, $^{147}$Sm, as an internal source. In the third approach, a scintillator flask was deployed into the water-filled SNO+ detector and the radioactive contaminants $^{222}$Rn, $^{218}$Po and $^{214}$Po provided the $\\alpha$-particle signal. The behavior of the observed $\\alpha$-particle light outputs are in agreement with each case successfully described by Birks' law. The resulting Birks parameter $kB$ ranges from $(0.0071\\pm0.0003)$ cm/MeV to $(0.0076\\pm0.0003)$ cm/MeV. In the first approach, the $\\alpha$-particle light response was measured simultaneously with the light response of recoil protons produced via neutron-proto...

  11. Feasibility of ion temperature measurement with a gyrotron scattering alpha particle diagnostic

    International Nuclear Information System (INIS)

    Collective Thomson scattering can be used to diagnose localized ion temperature as well as alpha particle velocity distribution and density in a D-T burning tokamak. With one diagnostic beam a simultaneous, but independent, measure of the bulk ion temperature and alpha particle parameters can be made. Use of a long pulse, millimeter-wave gyrotron offers a significant margin in signal to noise ratio capability (√Δftau > 1000) not previously possible with lasers. 9 refs., 2 figs

  12. Modification of thermal, optical and structural properties of bayfol nuclear track detector by alpha particles irradiation

    International Nuclear Information System (INIS)

    The effect of alpha particle dose on the thermal, optical and structural properties of Bayfol solid state nuclear track detector (SSNTD) was investigated. Non-isothermal studies were carried out using thermal gravimetric analysis (TGA) and differential thermal gravimetric (DTG) to obtain the activation energy of decomposition for Bayfol detector. Thermal gravimetric analysis (TGA) indicates that the Bayfol samples decompose in one main break down stage. Samples from 250 cm thickness sheets were exposed to alpha particles in the dose range 3.5-67.03 Gy. The variation of transition temperatures with the alpha particle dose has been determined using differential thermal analysis (DTA). The results indicate that the irradiation with alpha particles in the dose range 26.81-67.03 Gy decreases the melting temperature of the Bayfol samples and this is most suitable for applications requiring the molding of this polymer at lower temperatures. Also, the alpha particle dose gives advantage for increasing the correlation between melting temperatures and the amount of crystalline regions that is related to both cross-linking and degradation phenomena. In addition, optical and structural property studies using refractive index, IR spectroscopy, and x-ray diffraction measurements were performed on non irradiated and irradiated Bayfol samples. The results indicate that the anisotropic character, absorbance and the degree of ordering of the Bayfol polymer are dependent on the alpha particle dose

  13. Development of the MICROMEGAS Detector for Measuring the Energy Spectrum of Alpha Particles by using a 241-Am Source

    CERN Document Server

    Kim, Do Yoon; Shin, Jae Won; Park, Tae-Sun; Hong, Seung-Woo; Andriamonje, Samuel; Kadi, Yacine; Tenreiro, Claudio

    2016-01-01

    We have developed MICROMEGAS (MICRO MEsh GASeous) detectors for detecting {\\alpha} particles emitted from an 241-Am standard source. The voltage applied to the ionization region of the detector is optimized for stable operation at room temperature and atmospheric pressure. The energy of {\\alpha} particles from the 241-Am source can be varied by changing the flight path of the {\\alpha} particle from the 241 Am source. The channel numbers of the experimentally-measured pulse peak positions for different energies of the {\\alpha} particles are associated with the energies deposited by the alpha particles in the ionization region of the detector as calculated by using GEANT4 simulations; thus, the energy calibration of the MICROMEGAS detector for {\\alpha} particles is done. For the energy calibration, the thickness of the ionization region is adjusted so that {\\alpha} particles may completely stop in the ionization region and their kinetic energies are fully deposited in the region. The efficiency of our MICROMEGA...

  14. Stochastic model error in the LANS-alpha and NS-alpha deconvolution models of turbulence

    CERN Document Server

    Olson, Eric

    2015-01-01

    This paper reports on a computational study of the model error in the LANS-alpha and NS-alpha deconvolution models of homogeneous isotropic turbulence. The focus is on how well the model error may be characterized by a stochastic force. Computations are also performed for a new turbulence model obtained as a rescaled limit of the deconvolution model. The technique used is to plug a solution obtained from direct numerical simulation of the incompressible Navier--Stokes equations into the competing turbulence models and to then compute the time evolution of the resulting residual. All computations have been done in two dimensions rather than three for convenience and efficiency. When the effective averaging length scale in any of the models is $\\alpha_0=0.01$ the time evolution of the root-mean-squared residual error grows as $\\sqrt t$. This growth rate is consistent with the hypothesis that the model error may be characterized by a stochastic force. When $\\alpha_0=0.20$ the residual error grows linearly. Linea...

  15. Coincidence techniques (time correlation) alpha-gamma particles associated experiments on PGFNAA

    International Nuclear Information System (INIS)

    PGFNAA (Prompt Gamma Fast Neutron Alpha Associated) techniques offers capabilities far beyond those of the conventional inspection system to detect hazardous materials such as explosives or drugs. This technique uses the time coincidence between alpha and gamma particles to reduce the background produced by fast neutron interactions not only with the objects but also with the surrounding material. This paper reports the experimental setup that have been conducted to capture coincident events between alpha and gamma particles. Although not perfect, but the reduction of the background almost 100 % had been obtained on the outside area of the spectrum energy interest for water and graphite samples. (author)

  16. Characterization of a alpha particle detector CR-39 exposed to a source of radium

    International Nuclear Information System (INIS)

    In this project, the main goal is the characterization of a alpha particle detector CR-39 exposed to a source of radio. Three detectors were exposed to a source of radium and then chemically treated for different periods. This way, we could analyze these samples and collect the information needed to verify that at least one of the chemical attack, there has been a separation of the energies alpha particles incident with distinct peaks, thus characterizing the CR-39 as alpha spectrometer in the range 2.5 to 6.3 MeV . (author)

  17. Downstream energetic proton and alpha particles during quasi-parallel interplanetary shock events

    Science.gov (United States)

    Tan, L. C.; Mason, G. M.; Gloeckler, G.; Ipavich, F. M.

    1988-01-01

    This paper considers the energetic particle populations in the downstream region of three quasi-parallel interplanetary shock events, which was explored using the ISEE 3 Ultra Low Energy Charge Analyzer sensor, which unambiguously identifies protons and alpha particles using the electrostatic deflection versus residual energy technique. The downstream particles were found to exhibit anisotropies due largely to convection in the solar wind. The spectral indices of the proton and the alpha-particle distribution functions were found to be remarkably constant during the downstream period, being generally insensitive to changes in particle flux levels, magnetic field direction, and solar wind densities. In two of the three events, the proton and the alpha spectra were the same throughout the entire downstream period, supporting the prediction of diffusive shock acceleration theory.

  18. Modeling of non-stationary autoregressive alpha-stable processe

    Data.gov (United States)

    National Aeronautics and Space Administration — In the literature, impulsive signals are mostly modeled by symmetric alpha-stable processes. To represent their temporal dependencies, usually autoregressive models...

  19. ICRF enhancement of fusion reactivity in the presence of alpha particles

    International Nuclear Information System (INIS)

    Absorption of ICRF (ion cyclotron range of frequency) waves by alpha particles and fusion reactivity enhancement due to the ICRF induced ion tail are investigated. The rate of linear absorption by alpha particles increases with the cyclotron harmonic number, and decreases with the ratio of the electron plasma frequency to the electron cyclotron frequency. The deformation of the distribution due to ICRF waves is also examined by using a solution to a Fokker-Planck equation combined with a quasi-linear RF (radiofrequency) diffusion term. It is found that second harmonic ICRF heating is comparatively applicable to the enhancement of the fusion power density even in the presence of alpha particles, while the efficiency of the enhancement is deteriorated markedly by wave deposition to alphas for higher harmonic ICRF heating in the high magnetic field. (author)

  20. Feasibility of alpha particle measurement by CO2 laser Thomson scattering

    International Nuclear Information System (INIS)

    The feasibility of CO2 laser Thomson scattering from a multi-component burning plasma has been evaluated for the measurement of the velocity distribution of D-T produced alpha particles. The density and velocity distribution of the alpha particles from their initial energy of 3.5 MeV down to near-thermal energies may be measured by small angle (0) Thomson scattering. A computer simulation of the experiment indicates that a 100 MW pulsed laser combined with a bank of heterodyne receivers will be able to measure a scattered signal from the alpha particles with a post-detection signal-to-noise ratio of 75 for an assumed alpha density of 7.5 x 1011 cm-3

  1. Project and construction of a spectrometer for alpha particles using surface barrier detectors

    International Nuclear Information System (INIS)

    The project, construction, tests and some applications of a system for alpha and beta spectrometry, using surface barrier detector are described. The device includes a solid state detector ORTEC-Series F coupled to a system for amplifying the charges produced by passage of an ionizing particle through the detector. The amplifying system is composed by a charge sensitive pre-amplifier, which employs an operational amplifier CA 3140, and a low noise linear amplifier, which is based on the operational amplifiers CA 3140 and LM 301. The pre-amplifier stage input impedance is on the order of TΩ and produces output pulses which heights are proportional to total charge produced by passage of particle through the detector sensitive volume. The main advantage to use charge sensitive system lies in obtention of independent pulse heights of the distributed capacity of connecting cable between the detector and the pre-amplifier. The total system amplification ca reach a maximum of 50.000 in the linear region. Pulses are analysed in a multichannel system ORTEC, model 6240. The amplifier system is easily constructed and low cost using components available in the national market, and it can be employed with ionization chambers, proportional counters, scitillation counters and semiconductor detectors. The results of spectrometer application for alpha spectrometry of AM241 source were compared to systems made with imported stages. (Author)

  2. Investigating SOA from alpha-pinene ozonolysis with the GECKO modeling tool.

    Science.gov (United States)

    Lee-Taylor, J. M.; Madronich, S.; Aumont, B.; Lawler, M. J.; Smith, J. N.; Camredon, M.

    2014-12-01

    Atmospheric oxidation of terpenes leads to a rich variety of functionalized organic molecules of vapor pressures low enough to permit their condensation on particles. GECKO-A is an explicit chemical model useful for investigating fine details of tropospheric oxidation chemistry. The TDCIMS measurement technique allows the identification of specific molecular formulae in aerosol particles. We have incorporated recent advances in alpha-pinene chemistry into the model and apply it to study alpha-pinene ozonolysis and its subsequent condensable products. We assess the degree to which particle size affects modeled aerosol chemical composition and structure from alpha-pinene ozonolysis and compare the statistical composition of the modeled aerosol to that observed by TDCIMS in chamber studies.

  3. Physical consequences of the alpha/beta rule which accurately calculates particle masses

    International Nuclear Information System (INIS)

    Using the fine structure constant α (=1/137.036), the proton vs. electron mass ratio β (= 1836.2) and the integers m and n, the α/β rule: mparticle = α-n x β m x 27.2 eV/c2 allows almost exact calculation of particle masses. (K.O.Greulich, DPG Spring meeting 2014, Mainz, T99.4) With n=2, m=0 the electron mass becomes 510.79 keV/c2 (experimental 511 keV/c2) With n=2, m=1 the proton mass is 937.9 MeV/c2 (literature 938.3 MeV/c2). For n=3 and m=1 a particle with 128.6 GeV/c2 close to the reported Higgs mass, is expected. For n=14 and m=-1 the Planck mass results. The calculated masses for gauge bosons and for quarks have similar accuracy. All masses fit into the same scheme (the alpha/beta rule), indicating that non of these particle masses play an extraordinary role. Particularly, the Higgs Boson, often termed the *God particle* plays in this sense no extraordinary role. In addition, particle masses are intimately correlated with the fine structure constant α. If particle masses have been constant over all times, α must have been constant over these times. In addition, the ionization energy of the hydrogen atom (13.6 eV) needs to have been constant if particle masses have been unchanged or vice versa. In conclusion, the α/β rule needs to be taken into account when cosmological models are developed.

  4. Alpha spectrometric characterization of process-related particle size distributions from active particle sampling at the Los Alamos National Laboratory uranium foundry

    International Nuclear Information System (INIS)

    Uranium particles within the respirable size range pose a significant hazard to the health and safety of workers. Significant differences in the deposition and incorporation patterns of aerosols within the respirable range can be identified and integrated into sophisticated health physics models. Data characterizing the uranium particle size distribution resulting from specific foundry-related processes are needed. Using personal air sampling cascade impactors, particles collected from several foundry processes were sorted by activity median aerodynamic diameter onto various Marple substrates. After an initial gravimetric assessment of each impactor stage, the substrates were analyzed by alpha spectrometry to determine the uranium content of each stage. Alpha spectrometry provides rapid non-distructive isotopic data that can distinguish process uranium from natural sources and the degree of uranium contribution to the total accumulated particle load. In addition, the particle size bins utilized by the impactors provide adequate resolution to determine if a process particle size distribution is: lognormal, bimodal, or trimodal. Data on process uranium particle size values and distributions facilitate the development of more sophisticated and accurate models for internal dosimetry, resulting in an improved understanding of foundry worker health and safety.

  5. Selective alpha-particle mediated depletion of tumor vasculature with vascular normalization.

    Directory of Open Access Journals (Sweden)

    Jaspreet Singh Jaggi

    Full Text Available BACKGROUND: Abnormal regulation of angiogenesis in tumors results in the formation of vessels that are necessary for tumor growth, but compromised in structure and function. Abnormal tumor vasculature impairs oxygen and drug delivery and results in radiotherapy and chemotherapy resistance, respectively. Alpha particles are extraordinarily potent, short-ranged radiations with geometry uniquely suitable for selectively killing neovasculature. METHODOLOGY AND PRINCIPAL FINDINGS: Actinium-225 ((225Ac-E4G10, an alpha-emitting antibody construct reactive with the unengaged form of vascular endothelial cadherin, is capable of potent, selective killing of tumor neovascular endothelium and late endothelial progenitors in bone-marrow and blood. No specific normal-tissue uptake of E4G10 was seen by imaging or post-mortem biodistribution studies in mice. In a mouse-model of prostatic carcinoma, (225Ac-E4G10 treatment resulted in inhibition of tumor growth, lower serum prostate specific antigen level and markedly prolonged survival, which was further enhanced by subsequent administration of paclitaxel. Immunohistochemistry revealed lower vessel density and enhanced tumor cell apoptosis in (225Ac-E4G10 treated tumors. Additionally, the residual tumor vasculature appeared normalized as evident by enhanced pericyte coverage following (225Ac-E4G10 therapy. However, no toxicity was observed in vascularized normal organs following (225Ac-E4G10 therapy. CONCLUSIONS: The data suggest that alpha-particle immunotherapy to neovasculature, alone or in combination with sequential chemotherapy, is an effective approach to cancer therapy.

  6. Cell survival following alpha particle irradiation: critical sites and implications for carcinogenesis

    International Nuclear Information System (INIS)

    In experiments in which mammalian cells were irradiated with 5.6 MeV alpha particles from a Tandem Van de Graaff machine we have confirmed the finding of others that the mean lethal dose (D0) is about 100 rad, but by measurements of the area of the cell nuclei as irradiated we found that this mean lethal dose corresponds not to 1, as expected, but to about 27 alpha particles per cell nucleus. (The exact number appears to change slightly with cell passage number.) This allows for the possibility that the direct action of alpha particles on the nucleus may be the important event in carcinogenesis, a theory which was previously difficult to accept if a single particle hitting the nucleus anywhere was considered to be lethal. Evidence is presented to implicate the nucleolus as a possible critical site for the inhibition of reproductive integrity of the cell

  7. The role of alpha particles in the dynamics of ring-stabilized devices

    International Nuclear Information System (INIS)

    The use of relativistic electron rings to stabilize plasmas against the interchange modes has been utilized in such devices as the Elmo Bumpy Torus (EBT) and the plugs of a Tandem Mirror device (STM). In the EBT case enhanced stability is reflected in higher betas (ratio of plasma to magnetic field pressures), while in the Tandem Mirror case symmetry in the plug magnetic geometry results in reduced particle diffusion across the magnetic field in the central cell. Regardless of the application, the question arises as to what effect would alpha particles generated by the Deuterium-Tritium (DT) reactions have on the stability of such ring-stabilized devices. In this paper the macroscopic stability of such systems is reexamined in order to assess the effect of alphas on the background interchange mode, the interacting interchange mode, and the high frequency compressional Alfven and coupled modes. A fluid description is used for the background plasma while a kinetic treatment is utilized for the hot electron species and alpha particles. It is shown that the alphas tend to mildly destabilize the interacting interchange while stabilizing the background interchange due to their sizeable Larmor radii. The destabilization is most pronounced at high alpha energies i.e., at birth, and near complete recovery of stability is achieved as these particles approach thermalization with the background ions. It is also shown that the alphas completely stabilize the high frequency modes. (orig.)

  8. Effect of alpha particles on the stability of Elmo Bumpy Torus (EBT) reactor. Final report

    International Nuclear Information System (INIS)

    The macroscopic stability of an ignited EBT reactor is investigated by studying the effects of the alpha particles generated by the Deuterium-Tritium (D-T) fusion reaction on the background interchange mode, the interacting interchange mode, and the high-frequency compressional Alfven and coupled modes. A fluid description is used for the background plasma while a kinetic treatment is utilized for the hot electron species and the alpha particles. It is shown that the alphas tend to mildly destabilize the interacting interchange while stabilizing the background interchange due to their sizable Larmor radii. The destabilization is most pronounced when the beta of the alpha particles in highest, i.e., at birth, and recovery of stabilization takes place as these particles slow down toward thermalization. It is also shown that the alphas completely stabilize the high frequency modes so that it can safely be concluded that fusion alphas present no detrimental effects on the stability of an EBT reactor that possesses an appropriate hot electron ring for macroscopic stability

  9. Nucleon-alpha particle interactions from inversion of scattering phase shifts

    International Nuclear Information System (INIS)

    Scattering amplitudes have been extracted from (elastic scattering) neutron-alpha (n-α) differential cross sections below threshold using the constraint that the scattering function is unitary. Real phase shifts have been obtained therefrom. A modification to the Newton iteration method has been used to solve the nonlinear equation that specifies the phase of the scattering amplitude in terms of the complete (0 to 180 deg) cross section since the condition for a unique and convergent solution by an exact iterated fixed point method, the 'Martin' condition, is not satisfied. The results compare well with those found using standard optical model search procedures. Those optical model phase shifts, from both n - α and p - α (proton-alpha) calculations in which spin-orbit effects were included, were used in the second phase of this study, namely to determine the scattering potentials by inversion of that phase shift data. A modified Newton-Sabatier scheme to solve the inverse scattering problem has been used to obtain inversion potentials (both central and spin-orbit) for nucleon energies in the range 1 to 24 MeV. The inversion interactions differ noticeably from the Woods-Saxon forms used to give the input phase shifts. Not only do those inversion potentials when used in Schroedinger equations reproduce the starting phase shifts but they are also very smooth, decay rapidly, and are as feasible as the optical model potentials of others to be the local form for interactions deduced by folding realistic two-nucleon g matrices with the density matrix elements of the alpha particle. 23 refs., 8 tabs., 9 figs

  10. Formulation of alpha-particle condensation in the macroscopic limit

    International Nuclear Information System (INIS)

    Following closely BCS theory for pairs, an eventually viable theory for α-particle condensation (quartetting) is sketched. In the final formula the quartet wave function is replaced by a Slater determinant projected on good total momentum. The only variational field is then the single particle 0S wave function. This should reduce the numerical complexity to solve the quartet equations considerably. (author)

  11. Questions of the optical potential for alpha-particles at low energies

    International Nuclear Information System (INIS)

    Among the high-priority elements for the accelerator driven systems (ADS) and fusion-reactor projects are also Zr, Mo and Li, so that the corresponding nuclear data for nucleon-, deuteron-, and α-particle interactions are of actual interest for neutron production, activation, heating, shielding requirements, and material damage estimation as well as radioactive waste transmutation projects. By using advanced nuclear models that account for details of nuclear structure and the quantum nature of the nuclear scattering, significant gains in accuracy can be achieved below 150 MeV, where intranuclear cascade calculations become less accurate. It is why this work reports on the progress of the analysis of optical potentials for nucleons, deuterons and α-particles on isotopes of these elements, and corresponding reaction cross sections calculations. The elastic-scattering angular distributions measured at deuteron energies between 3 and 50 MeV on the target nucleus 6Li, and between 1 and 14.7 MeV for the target nucleus 7Li have been thus analyzed by using the computer codes SCAT2 for pure elastic scattering processes and FRESCO for the coupled reaction channels for taking into account the effects of the elastic and inelastic alpha transfer in the d+6Li interaction. The good overall agreement obtained with the experimental data for both 6,7Li target nuclei from 1 to 50 MeV has finally proved suitable optical model potentials (OMPs). Within the double folding formalism of the alpha-nucleus optical potential, used previously for a semi-microscopic analysis of the alpha-particle elastic scattering on A∼100 nuclei at energies below 32 MeV, effects due to changes of the nuclear density at a finite temperature are considered. Parameterizations of the double-folding (DF) real potential as well as of a regional phenomenological potential have been used in the study of the (n,α) reaction cross sections for the target nuclei 92,95,98,100Mo. Taking the microscopic DF potentials

  12. Alpha-particle emission probabilities in the decay of {sup 240}Pu

    Energy Technology Data Exchange (ETDEWEB)

    Sibbens, G., E-mail: goedele.sibbens@ec.europa.e [European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, Retieseweg 111, B-2440 Geel (Belgium); Pomme, S.; Altzitzoglou, T. [European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, Retieseweg 111, B-2440 Geel (Belgium); Garcia-Torano, E. [Laboratorio de Metrologia de Radiaciones Ionizantes, CIEMAT, Avda. Complutense 22, 28040 Madrid (Spain); Janssen, H.; Dersch, R.; Ott, O. [Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig (Germany); Martin Sanchez, A. [Departamento de Fisica, Universidad de Extremadura, Badajoz, E-06071 (Spain); Rubio Montero, M.P. [Departamento de Fisica Aplicada, Universidad de Extremadura, Merida, Badajoz, E-06800 (Spain); Loidl, M. [Laboratoire National Henri Becquerel, LNE/CEA-LIST, 91191 Gif-sur-Yvette (France); Coron, N.; Marcillac, P. de [Institut d' Astrophysique Spatiale, CNRS, 91405 Orsay Campus (France); Semkow, T.M. [Wadsworth Center, New York State Department of Health, Albany, NY 12201 (United States)

    2010-07-15

    Sources of enriched {sup 240}Pu were prepared by vacuum evaporation on quartz substrates. High-resolution alpha-particle spectrometry of {sup 240}Pu was performed with high statistical accuracy using silicon detectors and with low statistical accuracy using a bolometer. The alpha-particle emission probabilities of six transitions were derived from the spectra and compared with literature values. Additionally, some alpha-particle emission probabilities were derived from {gamma}-ray intensity measurements with a high-purity germanium detector. The alpha-particle emission probabilities of the three main transitions at 5168.1, 5123.6 and 5021.2 keV were derived from seven aggregate spectra analysed with five different fit functions and the results were compatible with evaluated data. Two additional weak peaks at 4863.5 and 4492.0 keV were fitted separately, using the exponential of a polynomial function to represent the underlying tailing of the larger peaks. The peak at 4655 keV could not be detected by alpha-particle spectrometry, while {gamma}-ray spectrometry confirms that its intensity is much lower than expected from literature.

  13. Review of alpha-particle spectrometric measurements of actinides

    International Nuclear Information System (INIS)

    At present the silicon surface-barrier detector is the most used α-particle detector mainly due to its high energy resolution, excellent stability, low background and low cost. In this presentation various parameters of importance for α-particle spectrometry are discussed, i.e. energy resolution and interval selection, energy calibration, background and peak tailing. Examples of α-particle spectra recorded from various actinides (Th, U, Np, Pu, Am, and Cm) separated from environmental samples are shown, and the choice of yield determinants is discussed for each case. (author)

  14. Alpha particles spectrometer with photodiode PIN; Espectrometro de particulas alfa con fotodiodo PIN

    Energy Technology Data Exchange (ETDEWEB)

    Chacon R, A.; Hernandez V, R.; Hernandez D, V. M.; Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidades Academicas de Estudios Nucleares e Ingenieria Electrica, Calle Cipres No. 10, Fracc. La Penuela, 09869 Zacatecas (Mexico); Ramirez G, J. [Instituto Nacional de Estadistica Geografia e Informatica, Direccion General de Innovacion y Tecnologia de Informacion, Av. Heroes de Nacozari Sur 2301, Fracc. Jardines del Parque, 20276 Aguascalientes (Mexico)], e-mail: achruiz@hotmail.com

    2009-10-15

    The radiation propagates in form of electromagnetic waves or corpuscular radiation; if the radiation energy causes ionization in environment that crosses it is considered ionizing radiation. To detect radiation several detectors types are used, if the radiation are alpha particles are used detectors proportional type or trace elements. In this work the design results, construction and tests of an alpha particles spectrometer are presented, which was designed starting from a photodiode PIN type. The system design was simulated with a code for electronic circuits. With results of simulation phase was constructed the electronic phase that is coupled to a multichannel analyzer. The resulting electronic is evaluated analyzing the electronic circuit performance before an alphas triple source and alpha radiation that produce two smoke detectors of domestic use. On the tests phase we find that the system allows obtain, in a multichannel, the pulses height spectrum, with which we calibrate the system. (Author)

  15. Energetic/alpha particle effects on MHD modes and transport

    International Nuclear Information System (INIS)

    A nonvariational kinetic-MHD stability code (NOVA-K) has been employed to study TAE stability in TFRR D-T and DIII-D experiments and to achieve understanding of TAE instability drive and damping mechanism. Reasonably good agreement between theory and experiment has been obtained. In these experiments the dominant damping mechanism is due to both the thermal ion Landau damping and/or the beam ion Landau damping. Based on ITER EDA parameters, the TAE modes are expected to be unstable in normal ITER operations. Energetic particle transport has been studied using a test particle code (ORBIT). Energetic particle loss scales linearly with the TAE mode amplitude and can be large for TFRR and DIII-D for δBr/B > 10-4 due to large banana orbit. From quasi-linear (ORBIT) and nonlinear kinetic-MHD (MH3D-K) simulations the saturation of TAE modes is due to nonlinear wave particle trapping and energetic particle profile modification in both radial and energy space. Finally, a convective bucket transport mechanism by MHD waves with time-dependent frequency is presented. Based on the energy-selective characteristics of the bucket transport mechanism, undesirable particles such as helium ash can be removed from the plasma core efficiently

  16. The 1997 IAEA intercomparison of commercially available PC-based software for alpha-particle spectrometry

    CERN Document Server

    Blaauw, M; Woods, S; Fazinic, S

    1999-01-01

    Four commercially available, PC-based analysis programs for alpha-particle spectrometry were compared using the 1997 IAEA test spectra, i.e. AlphaVision 1.20 (EG and G Ortec, USA), Alps 4.21 (Westmeier GmbH, Germany), Winner Alpha 4.0f5 (Eurisys Mesures, France) and Genie-2000 (Canberra Industries Inc., USA). A systematic statistical study of the analysis results was performed based on z-scores. The results indicate that the four programs leave room for substantial improvement.

  17. Non-adiabatic dynamics in 10Be with the microscopic alpha+alpha+n+n model

    CERN Document Server

    Ito, M

    2006-01-01

    The alpha+6He low-energy reactions and the structural changes of 10Be in the microscopic alpha+alpha+n+n model are studied by the generalized two-center cluster model with the Kohn-Hulthen-Kato variation method. It is found that, in the inelastic scattering to the alpha+6He(2+) channel, characteristic enhancements are expected as the results of the parity-dependent non-adiabatic dynamics. In the positive parity state, the enhancement originates from the no-adiabatic eigenstate generated by the radial excitation of the relative motion between two alpha-cores. On the other hand, the enhancement in the negative parity state is induced by the Landau-Zener level-crossing. These non-adiabatic processes are discussed in connection to the formation of the inversion doublet in the compound system of 10Be.

  18. Ionization and scintillation response of high-pressure xenon gas to alpha particles

    CERN Document Server

    Álvarez, V; Cárcel, S; Cebrián, S; Cervera, A; Conde, C A N; Dafni, T; Díaz, J; Egorov, M; Esteve, R; Evtoukhovitch, P; Fernandes, L M P; Ferrario, P; Ferreira, A L; Freitas, E D C; Gehman, V M; Gil, A; Goldschmidt, A; Gómez, H; Gómez-Cadenas, J J; González-Díaz, D; Gutiérrez, R M; Hauptman, J; Morata, J A Hernando; Herrera, D C; Irastorza, I G; Jinete, M A; Labarga, L; Laing, A; Liubarsky, I; Lopes, J A M; Lorca, D; Losada, M; Luzón, G; Marí, A; Martín-Albo, J; Miller, T; Moiseenko, A; Monrabal, F; Monteiro, C M B; Mora, F J; Moutinho, L M; Vidal, J Muñoz; da Luz, H Natal; Navarro, G; Nebot, M; Nygren, D; Oliveira, C A B; Palma, R; Pérez, J; Aparicio, J L Pérez; Renner, J; Ripoll, L; Rodríguez, A; Rodríguez, J; Santos, F P; Santos, J M F dos; Segui, L; Serra, L; Shuman, D; Simón, A; Sofka, C; Sorel, M; Toledo, J F; Tomás, A; Torrent, J; Tsamalaidze, Z; Vázquez, D; Veloso, J F C A; Webb, R; White, J T; Yahlali, N

    2012-01-01

    High-pressure xenon gas is an attractive detection medium for a variety of applications in fundamental and applied physics. In this paper we study the transport properties of ionization electrons, and the mechanism of electron-ion recombination, in xenon gas at 10 bar pressure. For this purpose, we use a source of alpha particles in the NEXT-DEMO time projection chamber, the large scale prototype of the NEXT-100 neutrinoless double beta decay experiment, in three different drift electric field configurations. Our electron drift velocity and longitudinal diffusion results are similar to expectations based on available electron scattering cross sections on pure xenon, favoring low-diffusion models. In addition, two types of measurements addressing the connection between the ionization and scintillation yields were performed. On the one hand we observe, for the first time in xenon gas, large event-by-event correlated fluctuations between the ionization and scintillation signals, similarly to what has already bee...

  19. Feasibility of alpha particle measurement in a magnetically confined plasma by CO2 laser Thomson scattering

    International Nuclear Information System (INIS)

    Fusion-product alpha particles will dominate the behavior of the next generation of ignited D-T fusion reactors. Advanced diagnostics will be required to characterize the energy deposition of these fast alpha particles in the magnetically confined plasma. For small-angle coherent Thomson scattering of a CO2 laser beam from such a plasma, a resonance in the scattered power occurs near 900 with respect to the magnetic field direction. This spatial concentration permits a simplified detection of the scattered laser power from the plasma using a heterodyne system. The signal produced by the presence of fusion-product alpha particles in an ignited plasma is calculated to be well above the noise level, which results from statistical variations of the background signal produced by scattering from free electrons. 7 refs

  20. An application of 222Rn alpha particle's tracks to uranium exploration

    International Nuclear Information System (INIS)

    The uranium exploration method is based on the register of 222Rn alpha particles; 222Rn gas is generated in the chain 238U desintegration. The detection of alpha particles was performed with cellulose nitrate films (NTC), located in a grid at the region in study. The alpha particles produce latent tracks in the NTC films; these tracks may be enlarged by chemical etching and are observed with an ordinary optic microscope, ninety seven NTC films were used, these were distributed in an area of approximately seventeen square kilometers, located in the municipalities of Granados and Huasabas in Sonora Mexico, the detectors remain in the ground for a thirty days mean period. The results obtained show an area with high 222Rn concentration, this can be related with an underground uranium ore deposit. The more important conclusion is that the results obtained in this work can be used as preliminary results for other prospection methods in this particular area. (author)

  1. Ripple Loss of Alpha Particles in a Low-Aspect-Ratio Tokamak Reactor

    International Nuclear Information System (INIS)

    Studies on the loss of alpha particles enhanced by toroidal field (TF) ripple in a low-aspect-ratio tokamak reactor (VECTOR) have been made by using an orbit-following Monte-Carlo code. In actual TF coil systems, the ripple loss of alpha particles is strongly reduced as the aspect ratio becomes low (the power loss ∝ A8.8 for A≥2.5) and the reduction of the number of TF coils results in a large amount of ripple loss even in a low-aspect-ratio tokamak. To reduce the number of TF coils from 12 to 6, about 40% of coil size enlargement is necessary in VECTOR. Ferrite plates are very effective to reduce ripple losses of alpha particles. By using ferrite plates, the coil size enlargement for N=6 can be relaxed to 15% and the number of coils can be reduced from 12 to 8 without enlargement of coil size in VECTOR. (author)

  2. High resolution alpha particle detectors based on 4H-SiC epitaxial layer

    International Nuclear Information System (INIS)

    We fabricated and characterized 4H-SiC Schottky diodes as a spectrometric detector of alpha particles. A thin blocking contact of Ni/Au (15 nm) was used to minimize the influence on alpha particles energy. Current-voltage characteristics of the detector were measured and a low current density below 0.3 nAcm−2 was observed at room temperature. 239Pu241Am244Cm was used as a source of alpha particles within the energy range between 5.1 MeV and 5.8 MeV for detector testing. The charge collection efficiency close to 100 % at reverse bias exceeding 50 V was determined. The best spectrometric performance shows a pulse height spectrum at a reverse bias of 200 V giving an energy resolution of 0.25 % in the full width and half maximum for 5.486 MeV of 241Am

  3. Alpha particle induced DNA damage and repair in normal cultured thyrocytes of different proliferation status

    DEFF Research Database (Denmark)

    Lyckesvärd, Madeleine Nordén; Delle, Ulla; Kahu, Helena;

    2014-01-01

    Childhood exposure to ionizing radiation increases the risk of developing thyroid cancer later in life and this is suggested to be due to higher proliferation of the young thyroid. The interest of using high-LET alpha particles from Astatine-211 ((211)At), concentrated in the thyroid by the same...... levels of γH2AX decreased during the first 24h in both cycling and stationary cultures and complete repair was seen in all cultures but cycling cells exposed to (211)At. Compared to stationary cells alpha particles were more harmful for cycling cultures, an effect also seen at the pChk2 levels...... cultures at a modest level of damage, clearly demonstrating that cell cycle status influences the relative effectiveness of alpha particles....

  4. Alpha-particle confinement control of the geodesic winding of LHD-type fusion reactors

    International Nuclear Information System (INIS)

    It is calculated that the geodesic winding D-shaped helical magnetic field configuration can actively control the confinement and exhaust of alpha particles. A trapped particle orbit diagram (TPOD), which shows the presence of re-entering particles and specifies the loss-cone depth, is obtained from the deeply trapped particle orbits in a helical mirror magnetic field. The loss-cone depth becomes shallow when the magnetic axis is shifted to the inner side. On the other hand, the loss-cone depth can reach to the magnetic axis when the magnetic axis is shifted fairly to the outer side. Active control of the confinement and exhaust of 3.52 MeV alpha particles by controlling the magnetic axis position is also confirmed by collisionless orbit calculations. (author)

  5. Modelling high redshift Lyman-alpha Emitters

    CERN Document Server

    Garel, Thibault; Guiderdoni, Bruno; Schaerer, Daniel; Verhamme, Anne; Hayes, Matthew

    2012-01-01

    We present a new model for high redshift Lyman-Alpha Emitters (LAEs) in the cosmological context which takes into account the resonant scattering of Ly-a photons through expanding gas. The GALICS semi-analytic model provides us with the physical properties of a large sample of high redshift galaxies. We implement a gas outflow model for each galaxy based on simple scaling arguments. The coupling with a library of numerical experiments of Ly-a transfer through expanding or static dusty shells of gas allows us to derive the Ly-a escape fractions and profiles. The predicted distribution of Ly-a photons escape fraction shows that galaxies with a low star formation rate have a f_esc of the order of unity, suggesting that, for those objects, Ly-a may be used to trace the star formation rate assuming a given conversion law. In galaxies forming stars intensely, the escape fraction spans the whole range from 0 to 1. The model is able to get a good match to the UV and Ly-a luminosity function (LF) data at 3 < z <...

  6. Preliminary Study of Natural Alpha Particle Track Areal Distribution Behind Eyeglasses Obstacles

    International Nuclear Information System (INIS)

    Plastic nuclear track detectors are widely used to register tracks of alpha particles emitted from radon gas nuclei and radioactive daughter nuclei. Eye glasses, finger rings, necklaces and many other accessories intimately accompany most people. The eyeglasses may modify the surface distribution of alpha particle pass spots just behind them. There may be some effects due to the earth's magnetic field on the motion of the charged alpha particle emitters (radon ions). In metallic frames of the eyeglasses, the earth's magnetic field and charged radio-ions enforce free electrons to move setting electric current, which reduces the magnetic field at the frame. Being weak at the frame and stronger on both sides away, the magnetic field lines may form a magnetic trap of some charged radio-ions in the air. The polymer Solid State Nuclear Track Detector (SSNTD) CR-39 which is a polyalyl diglycol carbonate is used to register alpha particles behind the eyeglasses obstacles. Remarkable decrease in alpha track density was noticed in CR-39 registration due both to glass and magnetic screening. The obtained results call for more studies on all metallic tools used or possessed in mines and non-ventilated underground cavities.

  7. Applying alpha particle background ionization device in the development of pulsed nitrogen laser technology

    International Nuclear Information System (INIS)

    An investigation on the application of alpha particles in the induction of a bias ionized background plasma before, during and after the discharge of the N2 TE UV laser (337.1 nm), built in the LEL-IF/UFF is presented. The alpha particles are provided by Americium (241-Am) stripes placed inside the discharge channel of the laser device. The stimulated radiation output characteristics, in terms of gas pressure, charging voltage and pulse width, of a N2 TE UV laser (337.1 nm) circuit are presented. The increased laser yield is interpreted qualitatively through plasma impedance in the discharge circuit. (author)

  8. Applying alpha particle background ionization device in the development of pulsed nitrogen laser technology

    Energy Technology Data Exchange (ETDEWEB)

    Fellows, C.E.; Rodegheri, C.C.; Tauber, U. [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Inst. de Fisica. Lab. de Espectroscopia e Laser (LEL); Guterres, R.F. [Comissao Nacional de Energia Nuclear (CNEN), Rio de Janeiro, RJ (Brazil). Coordenacao de Instalacoes Radiativas]. E-mail: rgutterr@cnen.gov.br

    2005-11-15

    An investigation on the application of alpha particles in the induction of a bias ionized background plasma before, during and after the discharge of the N2 TE UV laser (337.1 nm), built in the LEL-IF/UFF is presented. The alpha particles are provided by Americium (241-Am) stripes placed inside the discharge channel of the laser device. The stimulated radiation output characteristics, in terms of gas pressure, charging voltage and pulse width, of a N2 TE UV laser (337.1 nm) circuit are presented. The increased laser yield is interpreted qualitatively through plasma impedance in the discharge circuit. (author)

  9. Preparation and preclinical evaluation of {sup 211}At-labelled compounds for {alpha}-particle radiotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Larsen, R.H.

    1994-12-31

    The interest for {alpha}-particle emitters in internal radiotherapy is increasing due to improved conjugation chemistry. Experimental work has concentrated on {sup 211}At and {sup 212}Bi since these to nuclides have radiochemical and physical properties suitable for medical application. In this report it is demonstrated that biologically active {sup 211}At-labelled compounds can be prepared within a relatively short time allowing utilization of this 7.2 h {alpha}-particle. It is further shown that {sup 211}At-TP-3 treatment of human osteosarcoma in vitro gives promising therapeutic ratios. 76 refs., 5 figs., 3 tabs.

  10. CMB and reheating constraints to \\alpha-attractor inflationary models

    CERN Document Server

    Eshaghi, Mehdi; Riazi, Nematollah; Kiasatpour, Ahmad

    2016-01-01

    After Planck 2013, a broad class of inflationary models called \\alpha-attractors was developed which has universal observational predictions. For small values of the parameter \\alpha, the models have good consistency with the recent CMB data. In this work, we first calculate analytically (and verify numerically) the predictions of these models for spectral index, n_s and tensor-to-scalar ratio, r and then using BICEP2/Keck 2015 data we impose constraints on \\alpha-attractors. Then, we study the reheating in \\alpha-attractors. The reheating temperature, T_{re} and the number of e-folds during reheating, N_{re} are calculated as functions of n_s. Using these results, we determine the range of free parameter \\alpha for two clasees of \\alpha-attractors which satisfy the constraints of recent CMB data.

  11. Natural protection from zoonosis by alpha-gal epitopes on virus particles in xenotransmission.

    Science.gov (United States)

    Kim, Na Young; Jung, Woon-Won; Oh, Yu-Kyung; Chun, Taehoon; Park, Hong-Yang; Lee, Hoon-Taek; Han, In-Kwon; Yang, Jai Myung; Kim, Young Bong

    2007-03-01

    Clinical transplantation has become one of the preferred treatments for end-stage organ failure, and one of the novel approaches being pursued to overcome the limited supply of human organs involves the use of organs from other species. The pig appears to be a near ideal animal due to proximity to humans, domestication, and ability to procreate. The presence of Gal-alpha1,3-Gal residues on the surfaces of pig cells is a major immunological obstacle to xenotransplantation. Alpha1,3galactosyltransferase (alpha1,3GT) catalyzes the synthesis of Gal alpha 1-3Gal beta 1-4GlcNAc-R (alpha-gal epitope) on the glycoproteins and glycolipids of non-primate mammals, but this does not occur in humans. Moreover, the alpha-gal epitope causes hyperacute rejection of pig organs in humans, and thus, the elimination of this antigen from pig tissues is highly desirable. Recently, concerns have been raised that the risk of virus transmission from such pigs may be increased due to the absence of alpha-gal on their viral particles. In this study, transgenic cells expressing alpha1,3GT were selected using 1.25 mg/ml neomycin. The development of HeLa cells expressing alpha1,3GT now allows accurate studies to be conducted on the function of the alpha-gal epitope in xenotransmission. The expressions of alpha-gal epitopes on HeLa/alpha-gal cells were demonstrated by flow cytometry and confocal microscopy using cells stained with IB4-fluorescein isothiocyanate lectin. Vaccinia viruses propagated in HeLa/alpha-gal cells also expressed alpha-gal on their viral envelopes and were more sensitive to inactivation by human sera than vaccinia virus propagated in HeLa cells. Moreover, neutralization of vaccinia virus was inhibited in human serum by 10 mm ethylene glycol bis(beta-aminoethylether)tetraacetic acid (EDTA) treatment. Our data indicated that alpha-gal epitopes are one of the major barriers to zoonosis via xenotransmission. PMID:17381684

  12. Correlations of $\\alpha$-particles in splitting of $^{12}$C nuclei by neutrons of energy of 14.1 MeV

    CERN Document Server

    Kattabekov, R R; Artemenkov, D A; Bradnova, V; Zarubin, P I; Zarubina, I G; Majling, L; Rusakova, V V; Sadovsky, A B

    2014-01-01

    Correlations of $\\alpha$-particles are studied on statistics of 400 events of splitting $^{12}$C $\\rightarrow$ 3$\\alpha$ in nuclear track emulsion exposed to $14.1 MeV$ neutrons. The ranges and emission angles of the $\\alpha$-particles are measured. Distributions over energy of $\\alpha$-particle pairs and triples are obtained.

  13. Nuclear reactions induced by high-energy alpha particles

    Science.gov (United States)

    Shen, B. S. P.

    1974-01-01

    Experimental and theoretical studies of nuclear reactions induced by high energy protons and heavier ions are included. Fundamental data needed in the shielding, dosimetry, and radiobiology of high energy particles produced by accelerators were generated, along with data on cosmic ray interaction with matter. The mechanism of high energy nucleon-nucleus reactions is also examined, especially for light target nuclei of mass number comparable to that of biological tissue.

  14. Alpha-particle momentum distributions from 12C decaying resonances

    International Nuclear Information System (INIS)

    The computed α particle momentum distributions from the decay of low-lying 12C resonances are shown. The wave function of the decaying fragments is computed by means of the complex scaled hyperspherical adiabatic expansion method. The large-distance part of the wave functions is crucial and has to be accurately calculated. We discuss energy distributions, angular distributions and Dalitz plots for the 4+, 1+ and 4- states of 12C. (author)

  15. Alpha Particles Induce Apoptosis through the Sphingomyelin Pathway

    OpenAIRE

    Seideman, Jonathan H.; Stancevic, Branka; Rotolo, Jimmy A.; McDevitt, Michael R.; Howell, Roger W.; Kolesnick, Richard N; Scheinberg, David A.

    2011-01-01

    The sphingomyelin pathway involves the enzymatic cleavage of sphingomyelin to produce ceramide, a second messenger that serves as a key mediator in the rapid apoptotic response to various cell stressors. Low-linear energy transfer (LET) γ radiation can initiate this pathway, independent of DNA damage, via the cell membrane. Whether short-ranged, high-LET a particles, which are of interest as potent environmental carcinogens, radiotherapies and potential components of dirty bombs, can act thro...

  16. Classical Models of Subatomic Particles

    OpenAIRE

    Mann, R. B.; Morris, M. S.

    1993-01-01

    We look at the program of modelling a subatomic particle---one having mass, charge, and angular momentum---as an interior solution joined to a classical general-relativistic Kerr-Newman exterior spacetime. We find that the assumption of stationarity upon which the validity of the Kerr-Newman exterior solution depends is in fact violated quantum mechanically for all known subatomic particles. We conclude that the appropriate stationary spacetime matched to any known subatomic particle is flat ...

  17. Classical models of subatomic particles

    International Nuclear Information System (INIS)

    We look at the program of modelling a subatomic particle - one having mass, charge, and angular momentum - as an interior solution joined to a classical general-relativistic Kerr-Newman exterior spacetime. We find that the assumption of stationarity upon which the validity of the Kerr-Newman exterior solution depends is in fact violated quantum mechanically for all known subatomic particles. We conclude that the appropriate stationary spacetime matched to any known subatomic particle is flat space. (orig.)

  18. Scanning of irradiated silicon detectors using $\\alpha$ particles and low energy protons

    CERN Document Server

    Casse, G L; Glaser, M; Kohout, Z; Konícek, J; Lemeilleur, F; Leroy, C; Linhart, V; Mares, J J; Pospísil, S; Roy, P; Sopko, B; Sinor, M; Svejda, J; Vorobel, V; Wilhelm, I

    1999-01-01

    In a spectroscopic study of non-irradiated and proton-irradiated silicon diodes, the detectors were illuminated from the front side and from the rear side by various alpha particle sources (mainly ThC') and by monoenergetic protons with energies from 1.0 to 2.5~MeV. Their response characteristics have been studied as a function of the incoming particle energy and the applied bias voltage. The charge collection efficiency was determined as a function of fluence

  19. Alpha-particle emission from contaminants in counter materials

    International Nuclear Information System (INIS)

    Energy spectra of surface activities from thorium and uranium contaminants have been investigated for typical counter materials. Soft-tempered stainless steel with a rate of 1.2±0.1 α-particles emitted per 100 cm2 in one hour was found better than other stainless steel and far better than brass and aluminum. Energy spectra provide information about the contaminating activity and about its depth profile. Thorium, uranium and 210Pb contamination was also observed for thin sources of other materials including isotopically enriched materials. (orig.)

  20. Preequilibrium decay in alpha particle induced reactions in terbium

    International Nuclear Information System (INIS)

    The excitation functions of 159 Tb(α,n), (α,3 n), (α,4 n), (α,α3 n) reactions were measured using stacked foil activation technique and HPGe gamma ray spectroscopy method up to 50 MeV. The experimental results were compared with the theoretical predictions considering equilibrium as well as preequilibrium contributions using code ALICE/90. It was found that the initial exciton configuration n0 = 4(4p0h) that is pure particle state, appears to give good fit to the experimental data. (Authors)

  1. Production of $\\alpha$-particle condensate states in heavy-ion collisions

    CERN Document Server

    Raduta, Ad R; Geraci, E; Neindre, N Le; Napolitani, P; Rivet, M F; Alba, R; Amorini, F; Cardella, G; Chatterjee, M; De Filippo, E; Guinet, D; Lautesse, P; La Guidara, E; Lanzalone, G; Lanzano, G; Lombardo, I; Lopez, O; Maiolino, C; Pagano, A; Pirrone, S; Politi, G; Porto, F; Rizzo, F; Russotto, P; Wieleczko, J P

    2010-01-01

    The fragmentation of quasi-projectiles from the nuclear reaction $^{40}Ca$ + $^{12}C$ at 25 MeV/nucleon was used to produce excited states candidates to $\\alpha$-particle condensation. The experiment was performed at LNS-Catania using the CHIMERA multidetector. Accepting the emission simultaneity and equality among the $\\alpha$-particle kinetic energies as experimental criteria for deciding in favor of the condensate nature of an excited state, we analyze the $0_2^+$ and $2_2^+$ states of $^{12}$C and the $0_6^+$ state of $^{16}$O. A sub-class of events corresponding to the direct 3-$\\alpha$ decay of the Hoyle state is isolated.

  2. Collisionless Evolution of Isotropic Alpha-Particle Distribution in a Tokamak

    International Nuclear Information System (INIS)

    Full text: The density of the noninductive current generated due to collisionless motion of alpha-particles in the tokamak magnetic field is calculated. The analysis is based on fully three-dimensional calculations of charged particle trajectories without simplifying assumptions typical for drift and neoclassical approaches. The current is calculated over the entire cross section of the plasma column, including the magnetic axis. It is shown that the current density is not a function of a magnetic surface and is strongly polarized over the poloidal angle. The current density distribution in the tokamak poloidal cross section is obtained, and the current density as a function of the safety factor profile, the tokamak aspect ratio, and the ratio of the particle Larmor radius on the axis to the tokamak minor radius is determined. It is shown that, when the source of alpha-particles is spatially nonuniform, the current density in the center of the tokamak is nonzero due to asymmetry of the phase-space boundary between trapped and passing particles. The current density scaling in the tokamak center differs from the known approximations for the bootstrap current and is sensitive to the spatial distribution of alpha-particles. (author)

  3. Interaction of alpha particles at the cellular level - Implications for the radiation weighting factor

    International Nuclear Information System (INIS)

    Since low dose effects of alpha particles are produced by cellular hits in a relatively small fraction of exposed cells, the present study focuses on alpha particle interactions in bronchial epithelial cells following exposure to inhaled radon progeny. A computer code was developed for the calculation of microdosimetric spectra, dose and hit probabilities for alpha particles emitted from uniform and non-uniform source distributions in cylindrical and Y-shaped bronchial airway geometries. Activity accumulations at the dividing spur of bronchial airway bifurcations produce hot spots of cellular hits, indicating that a small fraction of cells located at such sites may receive substantially higher doses. While presently available data on in vitro transformation frequencies suggest that the relative biological effectiveness for alpha particles ranges from about 3 to 10, the effect of inhomogeneous activity distributions of radon progeny may slightly increase the radiation weighting factor relative to a uniform distribution. Thus a radiation weighting factor of about 10 may be more realistic than the current value of 20, at least for lung cancer risk following inhalation of short-lived radon progeny. (authors)

  4. alpha-particle radioactivity from LR 115 by two methods of analysis

    CERN Document Server

    Azkour, K; Adloff, J C; Pape, A

    1999-01-01

    LR115 track detectors were exposed to samples of Moroccan phosphate and phosphogypsum to measure their alpha-particle radioactivity. Then two formalisms were used for the dosimetry: simulation by a Monte Carlo method and determination of concentrations from a numerically integrated track registration equation. The results were compared with those deduced gamma-ray spectrometry.

  5. Alpha and beta particle induced scintillations in liquid and solid neon

    CERN Document Server

    Michniak, R A; McKinsey, D N; Doyle, J M

    2002-01-01

    Scintillations induced by alpha and beta particles in liquid and solid neon are studied and their light yield measured. Charged particle scintillation in neon is primarily in the extreme ultraviolet (EUV). We detect this EUV light by converting it to blue using a wavelength shifting fluor and detecting the blue light with a photomultiplier tube. It is observed that liquid neon is a somewhat less-efficient scintillator than liquid helium for both alpha and beta radiation while the light yield in solid neon is greater than in liquid helium. Based on our measurements of the relative light yields of liquid and solid neon to liquid helium whose absolute light yield has previously been determined, we find that an alpha source in liquid neon produces up to 5900 photons per MeV while a beta source produces up to 7400 photons per MeV. In solid neon, we find that an alpha particle produces up to 9300 photons per MeV while a beta particle produces up to 17,000 photons per MeV. We observe a significant dependence of the ...

  6. Alpha particle effects as a test domain for PAP, a Plasma Apprentice Program

    International Nuclear Information System (INIS)

    A new type of computational tool under development, employing techniques of symbolic computation and artificial intelligence to automate as far as possible the research activities of a human plasma theorist, is described. Its present and potential uses are illustrated using the area of the theory of alpha particle effects in fusion plasmas as a sample domain. (orig.)

  7. RADON AND PROGENY ALPHA-PARTICLE ENERGY ANALYSIS USING NUCLEAR TRACK METHODOLOGY

    International Nuclear Information System (INIS)

    A preliminary procedure for alpha energy analysis of radon and progeny using Nuclear Track Methodology (NTM) is described in this paper. The method is based on the relationship between alpha-particle energies deposited in polycarbonate material (CR-39) and the track size developed after a well-established chemical etching process. Track geometry, defined by parameters such as major or minor diameters, track area and overall track length, is shown to correlate with alpha-particle energy over the range 6.00 MeV (218Po) to 7.69 MeV (214Po). Track features are measured and the data analyzed automatically using a digital imaging system and commercial PC software. Examination of particle track diameters in CR-39 exposed to environmental radon reveals a multi-modal distribution. Locations of the maxima in this distribution are highly correlated with alpha particle energies of radon daughters, and the distributions are sufficiently resolved to identify the radioisotopes. This method can be useful for estimating the radiation dose from indoor exposure to radon and its progeny.

  8. Cross section balance in the 14N+159Tb reaction and the origin of fast alpha particles

    International Nuclear Information System (INIS)

    Exclusive cross sections have been obtained from particle-K X-ray coincidence data measured at 236 MeV for ejectiles ranging from 4He to 15N. Production cross sections for primary fragments and alpha particle multiplicities associated with different channels have been deduced. The major fraction of the alpha particles appears to originate from inelastic (damped) processes in which only light particles with Z<=2 are emitted. (orig.)

  9. Investigations of electrical properties of structures Al-DNA-ITO-Al exposed to alpha particles

    International Nuclear Information System (INIS)

    The detection of alpha particles and other radiation sources has been an important field of research since the inception of radioactive materials in medical technology approximately a century ago. While different types of radiation sensors exist, in recent history, in light of a few catastrophic nuclear meltdowns, the development of sensors with rapid and effective detection properties have become crucial. To probe the feasibility of incorporating such features into the detector architecture, a simple sensor based on mushroom Deoxyribonucleic acid or DNA (Aluminium (Al)/DNA/Indium Tin Oxide (ITO)) was built, and the possibility of employing DNA electronics for the potential detection of alpha particles was investigated. Current–voltage (I–V) profiles were obtained following radiation using alpha particles at different dosages and exposure periods at room temperature. Properties such as series resistance, RS and other properties (barrier height, ideality factor and hypersensitivity) were calculated and analyzed using Conventional, Cheung and Cheung and Norde methods. RS values of the non-radiated samples calculated using the first method was about 8.6 MΩ. Using Conventional and Norde methods, samples irradiated for 4 min demonstrated the highest RS values of 5.79 and 1.81 MΩ, respectively. The results obtained were used to demonstrate the possibility of applying the sensitivity of DNA sensors to the measurement of alpha radiation. - Highlights: • Freshly prepared DNA solution was deposited as thin films by using the self-assembly method. • Series resistances, barrier heights and ideality factors were determined from I–V measurements. • A novel DNA hypersensitivity phenomenon was observed at low alpha radiation. • DNA based diodes can be employed as sensitive alpha particle sensors

  10. Lung cancer risk from exposure to alpha particles and inhalation of other pollutants in rats

    Energy Technology Data Exchange (ETDEWEB)

    Burns, F.J.

    1990-01-01

    The goal of these experiments is to establish a quantitative correlation between early DNA damage and cancer incidence in a way that would be helpful for assessing the carcinogenic risk of radon alone or in combination with specific indoor pollutants. Rat tracheal epithelium has been exposed in vivo to {sup 210}Po alpha particles in the presence and absence of NO{sub 2} or cigarette smoke. The major accomplishments so far are: the design and implementation of a tracheal implant to simulate radon alpha particle exposure, the measurement of DNA breaks in a small 7.0 mm segment of the trachea exposed to external x-irradiation, the measurement of the rate of repair of the x-ray induced tracheal DNA strand breaks, the measurement of DNA strand breaks following inhalation of cigarette smoke or NO{sub 2}, the measurement of tracheal DNA stand breaks following exposure to high doses {sup 210}Po alpha particle radiation, the assessment of the amount of mucous in the goblet cells and in the underlying mucous glands. So far we have been unable to detect DNA strand breaks in the tracheal epithelium as a result of exposure to NO{sub 2} cigarette smoke or {sup 210}Po alpha particles. We have developed a simple artificial' trachea consisting of rat tracheal epithelial cells growing on a basement membrane coated millipore filter. Experiments are proposed to utilize these artificial tracheas to eliminate the potential interference of increased mucous secretion and/or inflammation that can significantly affect the radiation dose from the alpha particles. 61 refs., 17 figs.

  11. Alfvenic behavior of alpha particle driven ion cyclotron emission in TFTR

    International Nuclear Information System (INIS)

    Ion cyclotron emission (ICE) has been observed during D-T discharges in the Tokamak Fusion Test Reactor (TFTR), using rf probes located near the top and bottom of the vacuum vessel. Harmonics of the alpha cyclotron frequency (Ωα) evaluated at the outer midplane plasma edge are observed at the onset of the beam injection phase of TFTR supershots, and persist for approximately 100-250 ms. These results are in contrast with observations of ICE in JET, in which harmonics of Ωα evolve with the alpha population in the plasma edge. Such differences are believed to be due to the fact that newly-born fusion alpha particles are super-Alfvenic near the edge of JET plasmas, while they are sub-Alfvenic near the edge of TFTR supershot plasmas. In TFTR discharges with edge densities such that newly-born alpha particles are super-Alfvenic, alpha cyclotron harmonics are observed to persist. These results are in qualitative agreement with numerical calculations of growth rates due to the magnetoacoustic cyclotron instability

  12. Modeling of alpha mass-efficiency curve

    International Nuclear Information System (INIS)

    We present a model for efficiency of a detector counting gross α radioactivity from both thin and thick samples, corresponding to low and high sample masses in the counting planchette. The model includes self-absorption of α particles in the sample, energy loss in the absorber, range straggling, as well as detector edge effects. The surface roughness of the sample is treated in terms of fractal geometry. The model reveals a linear dependence of the detector efficiency on the sample mass, for low masses, as well as a power-law dependence for high masses. It is, therefore, named the linear-power-law (LPL) model. In addition, we consider an empirical power-law (EPL) curve, and an exponential (EXP) curve. A comparison is made of the LPL, EPL, and EXP fits to the experimental α mass-efficiency data from gas-proportional detectors for selected radionuclides: 238U, 230Th, 239Pu, 241Am, and 244Cm. Based on this comparison, we recommend working equations for fitting mass-efficiency data. Measurement of α radioactivity from a thick sample can determine the fractal dimension of its surface

  13. A Further Measurement of the beta-Delayed alpha-Particle Emission of 16N

    CERN Document Server

    III, R H F; McDonald, J E; Wilds, E L

    2007-01-01

    We measured the beta-delayed alpha-particle emission spectrum of 16N with a sensitivity for beta-decay branching ratios of the order of 10-10. The 16N nuclei were produced using the d(15N,16N)p reaction with 70 MeV 15N beams and a deuterium gas target 7.5 cm long at a pressure of 1250 torr. The 16N nuclei were collected (over 10 s) using a thin aluminum foil with an areal density of 180 mu g/cm2 tilted at 7 Deg with respect to the beam. The activity was transferred to the counting area by means of a stepping motor in less than 3 s with the counting carried out over 8 s. The beta-delayed alpha-particles were measured using a time of flight method to achieve a sufficiently low background. Standard calibration sources (148Gd, 241Am, 208,209Po, and 227Ac) as well as alpha-particles and 7Li from the 10B(n,alpha)7Li reaction were used for an accurate energy calibration. The energy resolution of the catcher foil (180-220 keV) was calculated and the time of flight resolution (3-10 nsec) was measured using the beta-de...

  14. Electronic Properties of DNA-Based Schottky Barrier Diodes in Response to Alpha Particles

    Directory of Open Access Journals (Sweden)

    Hassan Maktuff Jaber Al-Ta'ii

    2015-05-01

    Full Text Available Detection of nuclear radiation such as alpha particles has become an important field of research in recent history due to nuclear threats and accidents. In this context; deoxyribonucleic acid (DNA acting as an organic semiconducting material could be utilized in a metal/semiconductor Schottky junction for detecting alpha particles. In this work we demonstrate for the first time the effect of alpha irradiation on an Al/DNA/p-Si/Al Schottky diode by investigating its current-voltage characteristics. The diodes were exposed for different periods (0–20 min of irradiation. Various diode parameters such as ideality factor, barrier height, series resistance, Richardson constant and saturation current were then determined using conventional, Cheung and Cheung’s and Norde methods. Generally, ideality factor or n values were observed to be greater than unity, which indicates the influence of some other current transport mechanism besides thermionic processes. Results indicated ideality factor variation between 9.97 and 9.57 for irradiation times between the ranges 0 to 20 min. Increase in the series resistance with increase in irradiation time was also observed when calculated using conventional and Cheung and Cheung’s methods. These responses demonstrate that changes in the electrical characteristics of the metal-semiconductor-metal diode could be further utilized as sensing elements to detect alpha particles.

  15. Track Reconstruction and Performance of DRIFT Directional Dark Matter Detectors using Alpha Particles

    CERN Document Server

    Burgos, S; Ghag, C; Gold, M; Kudryavtsev, V A; Lawson, T B; Loomba, D; Majewski, P; McMillan, J E; Muna, D; Murphy, A StJ; Nicklin, G G; Paling, S M; Petkov, A; Plank, S J S; Robinson, M; Sanghi, N; Smith, N J T; Snowden-Ifft, D P; Spooner, N J C; Sumner, T J; Turk, J; Tziaferi, T

    2007-01-01

    First results are presented from an analysis of data from the DRIFT-IIa and DRIFT-IIb directional dark matter detectors at Boulby Mine in which alpha particle tracks were reconstructed and used to characterise detector performance--an important step towards optimising directional technology. The drift velocity in DRIFT-IIa was [59.3 +/- 0.2 (stat) +/- 7.5 (sys)] m/s based on an analysis of naturally-occurring alpha-emitting background. The drift velocity in DRIFT-IIb was [57 +/- 1 (stat) +/- 3 (sys)] m/s determined by the analysis of alpha particle tracks from a Po-210 source. 3D range reconstruction and energy spectra were used to identify alpha particles from the decay of Rn-222, Po-218, Rn-220 and Po-216. This study found that (22 +/- 2)% of Po-218 progeny (from Rn-222 decay) are produced with no net charge in 40 Torr CS2. For Po-216 progeny (from Rn-220 decay) the uncharged fraction is (100 +0 -35)%.

  16. Registration of alpha particles in Makrofol-E nuclear track detectors

    Science.gov (United States)

    Rammah, Y. S.; Abdalla, Ayman M.; Ashraf, O.; Ashry, A. H.

    2016-06-01

    Fast detection of alpha particles in the range from 1 to 5 MeV in Makrofol-E polycarbonate nuclear track detectors (PCTDs) using a new chemical etchant was investigated. 252Cf and 241Am-thin open sources were used for irradiating Makrofol-E detectors with fission fragments and alpha particles in air at normal pressure and temperature (NPT). A chain of experimental work has been carried out using new etchants to register alpha particle in short time in Makrofol-E polycarbonate detectors. The etching efficiency were exhibited a clear dependence on the amount of methanol in the etching solution and etching time. The optimized chemical condition obtained at this stage of development for 200 μm Makrofol-E detectors are (8 ml of 10 N NaOH + 2 ml CH3OH) etching solutions at 60 °C for 3 h. In this study; it is possible to observe energy detection windows for Makrofol-E detectors according to applied etching duration. Makrofol-E introduced the characteristic Bragg peak, which indicates the advantages of this detector as alpha spectrometer. Consequently, the suggested new etchant can be developed for heavy ions detection and monitoring radon levels and its daughters.

  17. A new alpha particle diagnostic using knock-on ion tails

    International Nuclear Information System (INIS)

    We propose a new method of measuring the fast confined ct-particle distribution in a reacting plasma. The presence of ct-particles in a D-T plasma will create a high energy tail on the deuterium and tritium ion energy distributions. A 3.5 MeV alpha can transfer 3.4 MeV to a tritium ion in a single elastic scattering interaction. Calculations of the size of these knock-on tails in tokamaks such as TFTR, JET, and ITER show that it may be possible to measure these tails and provide information on the fast confined alphas. The knock-on tail ions will produce D-T neutrons with energies up to 20.7 MeV, so that D-T neutron spectroscopy can be used to monitor the alpha population. Neutron spectroscopy looks especially attractive for ITER. A collimated array of threshold neutron activation detectors could be used to deduce the confined alpha density profile. Tests of this diagnostic can also be done on TFTR and JET. Existing high energy neutral particle analyzers may allow observation of the ion tails directly via passive and/or active charge exchange

  18. Influences of target geometry on the microdosimetry of alpha particles in water

    International Nuclear Information System (INIS)

    Application of microdosimetric concepts to radiation exposure situations requires knowledge of the single-event density function, f1 (z) , where z denotes specific energy imparted to target matter. Multiple-event density functions are calculated by taking convolutions of f1(z) with itself with the overall specific energy density function is then found by employing a compound Poisson process involving single and multiple-event spectra. The fl(z), depends strongly on the geometric details of a the source, target, and all intermediate matter. While most past applications of microdosimetry have been represented targets as spheres, may be better modeled as prolate or oblate spheroids. Using a ray-tracing technique coupled with a continuous-slowing-down approximation, methods are developed and presented for calculating single-event density functions for spheroidal targets irradiated by alpha-emitting point sources. Computational methods are incorporated into a fortran computer code entitled SEROID (single-event density functions for spheroids), which is listed in this paper. This was used to generate several single-event density functions, along with related means and standard deviations in specific energy, for spheroidal targets irradiated by alpha particles. Targets of varying shapes and orientations are examined. Results for non-spherical targets are compared to spherical targets of equal volume in order to assess influences which target geometry has on single-event quantities. From these comparisons it is found that both target shape and orientation are important in adequately characterizing the quantities examined in this study; over-simplifying the target geometry can lead to substantial error

  19. Standard model without Higgs particles

    International Nuclear Information System (INIS)

    A modification of the standard model of electroweak interactions with the nonlocal Higgs sector is proposed. Proper form of nonlocality makes Higgs particles unobservable after the electroweak symmetry breaking. They appear only as a virtual state because their propagator is an entire function. We discuss some specific consequences of this approach comparing it with the conventional standard model. 12 refs

  20. Standard model without Higgs particles

    International Nuclear Information System (INIS)

    A modification of the standard model of electroweak interactions with the nonlocal Higgs sector is proposed. Proper form of nonlocality makes Higgs particles unobservable after the electroweak symmetry breaking. They appear only as a virtual state because their propagator is an entire function. We discuss some specific consequences of this approach comparing it with the conventional standard model. (author). 12 refs

  1. Alpha particle induced DNA damage and repair in normal cultured thyrocytes of different proliferation status

    Energy Technology Data Exchange (ETDEWEB)

    Lyckesvärd, Madeleine Nordén, E-mail: madeleine.lyckesvard@oncology.gu.se [Department of Oncology, Sahlgrenska Academy, University of Gothenburg (Sweden); Delle, Ulla; Kahu, Helena [Department of Oncology, Sahlgrenska Academy, University of Gothenburg (Sweden); Lindegren, Sture [Department of Radiation Physics, Sahlgrenska Academy, University of Gothenburg (Sweden); Jensen, Holger [The PET and Cyclotron Unit Copenhagen University Hospital, Rigshospitalet (Denmark); Bäck, Tom [Department of Radiation Physics, Sahlgrenska Academy, University of Gothenburg (Sweden); Swanpalmer, John [Department of Medical Physics and Biomedical Engineering, Sahlgrenska University Hospital, Gothenburg (Sweden); Elmroth, Kecke [Department of Oncology, Sahlgrenska Academy, University of Gothenburg (Sweden)

    2014-07-15

    Highlights: • We study DNA damage response to low-LET photons and high-LET alpha particles. • Cycling primary thyrocytes are more sensitive to radiation than stationary cells. • Influence of radiation quality varies due to cell cycle status of normal cells. • High-LET radiation gives rise to a sustained DNA damage response. - Abstract: Childhood exposure to ionizing radiation increases the risk of developing thyroid cancer later in life and this is suggested to be due to higher proliferation of the young thyroid. The interest of using high-LET alpha particles from Astatine-211 ({sup 211}At), concentrated in the thyroid by the same mechanism as {sup 131}I [1], in cancer treatment has increased during recent years because of its high efficiency in inducing biological damage and beneficial dose distribution when compared to low-LET radiation. Most knowledge of the DNA damage response in thyroid is from studies using low-LET irradiation and much less is known of high-LET irradiation. In this paper we investigated the DNA damage response and biological consequences to photons from Cobolt-60 ({sup 60}Co) and alpha particles from {sup 211}At in normal primary thyrocytes of different cell cycle status. For both radiation qualities the intensity levels of γH2AX decreased during the first 24 h in both cycling and stationary cultures and complete repair was seen in all cultures but cycling cells exposed to {sup 211}At. Compared to stationary cells alpha particles were more harmful for cycling cultures, an effect also seen at the pChk2 levels. Increasing ratios of micronuclei per cell nuclei were seen up to 1 Gy {sup 211}At. We found that primary thyrocytes were much more sensitive to alpha particle exposure compared with low-LET photons. Calculations of the relative biological effectiveness yielded higher RBE for cycling cells compared with stationary cultures at a modest level of damage, clearly demonstrating that cell cycle status influences the relative

  2. Photoluminescence detection of alpha particle using DAM-ADC nuclear detector

    Science.gov (United States)

    Abdalla, Ayman M.; Harraz, Farid A.; Ali, Atif M.; Al-Sayari, S. A.; Al-Hajry, A.

    2016-09-01

    The photoluminescence (PL) and UV-vis spectral analysis of DAM-ADC (diallyl maleate: DAM, polyallyl diglycol carbonate: ADC) nuclear detector are demonstrated for the first time. The DAM-ADC surfaces were exposed to thin 241Am disk source that emits alpha particles with activity 333 kBq. It is found that the track density of the irradiated samples remarkably influences the PL characteristics of the DAM-ADC detector. The spectral peak heights and the integrated intensities under the peaks exhibit linear correlations with correlation coefficient R2=0.9636 and 0.9806, respectively for different alpha particle fluences ranging from 8.16-40.82×107 particles/cm2. Additionally, a correlation coefficient R2=0.9734 was achieved for the UV-vis spectral analysis. The linear fitting functions, along with the corresponding fitting parameters were evaluated in each case. Both the PL and the UV-vis data of the irradiated DAM-ADC samples showed considerable spectral differences, and hence they would be used to offer sensitive approaches for alpha particle detection.

  3. Effect of Alpha-Particle Irradiation on Brain Glycogen in the Rat

    Science.gov (United States)

    Wolfe, L. S.; Klatzo, Igor; Miquel, Jaime; Tobias, Cornelius; Haymaker, Webb

    1962-01-01

    The studies of Klatzo, Miquel, Tobias and Haymaker (1961) have shown that one of the earliest and most sensitive indications of the effects of alpha-particle irradiation on rat bran is the appearance of glycogen granules mainly in the neuroglia of the exposed area of the brain. Periodic acid-Schiff (PAS) positive, alpha-amylase soluble granules were demonstrated within 12 hr after irradiation, preceding by approximately 36 hr the first microscopically detectable vascular permeability disturbances, as shown by the fluorescein labeled serum protein technique. These studies suggested that the injurious effects of alpha-particle energy were on cellular elements primarily, according to the physical properties and distribution of the radiation in the tissue, and that the vascular permeability disturbances played a secondary role in pathogenesis. The purpose of this study was to correlate the histochemical observations on glycogen with a quantitative assessment of the glycogen in the irradiated brain tissue. It is felt that such a study may contribute to the understanding of radiation injury at the molecular level. A practical aspect of this problem is that the information on biological radiation effects due to accelerated particles from the cyclotron source, is employed in this study, is applicable to radiation from cosmic particles both in free space and entrapped in the Van Allen belts.

  4. Factors affecting the energy resolution in alpha particle spectrometry with silicon diodes

    International Nuclear Information System (INIS)

    In this work are presented the studies about the response of a multi-structure guard rings silicon diode for detection and spectrometry of alpha particles. This ion-implanted diode (Al/p+/n/n+/Al) was processed out of 300 μm thick, n type substrate with a resistivity of 3 kΩ·cm and an active area of 4 mm2. In order to use this diode as a detector, the bias voltage was applied on the n+ side, the first guard ring was grounded and the electrical signals were readout from the p+ side. These signals were directly sent to a tailor made preamplifier, based on the hybrid circuit A250 (Amptek), followed by a conventional nuclear electronic. The results obtained with this system for the direct detection of alpha particles from 241Am showed an excellent response stability with a high detection efficiency (≅ 100 %). The performance of this diode for alpha particle spectrometry was studied and it was prioritized the influence of the polarization voltage, the electronic noise, the temperature and the source-diode distance on the energy resolution. The results showed that the major contribution for the deterioration of this parameter is due to the diode dead layer thickness (1 μm). However, even at room temperature, the energy resolution (FWHM = 18.8 keV) measured for the 5485.6 MeV alpha particles (241Am) is comparable to those obtained with ordinary silicon barrier detectors frequently used for these particles spectrometry. (author)

  5. Large angle scattering of {alpha}-particles from {sup 32}S

    Energy Technology Data Exchange (ETDEWEB)

    Coban, A.; Abdelmonem, M.S.; Khiari, F.Z.; Naqvi, A.A.; Aksoy, A

    1999-01-04

    The elastic scattering of {alpha}-particles from {sup 32}S was studied in the incident energy range between 4 and 8.9 MeV. In order to ascertain whether quasi-molecular states exist, as predicted in the {alpha}-{sup 32}S system, excitation functions were measured, and angular distribution measurements were carried out using targets with different thicknesses in the angular range from {theta}{sub lab} = 30 deg. to 175 deg. at each extreme in the excitation functions. The analysis of the angular distribution data at back angles was performed using the Regge-pole method. A resonance with J=3 was observed at 7.7 MeV in the {alpha}-{sup 32}S system. Evidence was also found for both a broad resonance which can be characterized by an angular momentum J=1, and for a narrow J=2 resonance.

  6. Geometrical parameters of tracks registered by collimated alpha particles on CR-39 detector

    International Nuclear Information System (INIS)

    The latent tracks formed on CR-39 solid state track detector on exposure of alpha radiations emanating from a collimated 241Am source were developed by a chemical etching method. Alpha track images were captured by an optical microscope and were processed by using Image Pro-Plus (6.0) software. GEANT4 simulations were carried out to obtain the angular and energy distribution profiles of the alpha particles. Apart from fluence, geometric parameters like aspect ratio (the ratio of the major to minor axis) and the depth profiles of etched tracks were measured experimentally and correlated with simulated angular and energy profile of incident radiations. Reasonable agreement was observed in the fluence and depth profile information obtained from experiments and simulations

  7. Alpha Particle Induced X-ray Emission in the Classroom

    International Nuclear Information System (INIS)

    We report on an experimental demonstration in an introductory modern physics course to elucidate the X-ray line spectra, and how they arise from transitions of electrons to inner shells. We seek to determine the effect of limited use of an interactive component as a supplement to a traditional lecture, and how it would improve the student achievement. In this preliminary study the students were exposed to traditional lectures on X-ray production and Bohr's model, they then were given a homework on the abc of X-ray spectra, after which they were given a pre-test on the materials, followed by an in-class demonstration, and a final post-exam. The gain, as measured from pre- to post-exams appears to remark the differences in how students approached the subject before and after the use of the demonstration. This initial study shows the validity of in-class demonstrations as teaching tools and opens a wide new area of research in modern physics teaching

  8. Simulation study for high resolution alpha particle spectrometry with mesh type collimator

    International Nuclear Information System (INIS)

    An alpha particle spectrometry with a mesh type collimator plays a crucial role in identifying specific radionuclide in a radioactive source collected from the atmosphere or environment. The energy resolution is degraded without collimation because particles with a high angle have a longer path to travel in the air. Therefore, collision with the background increases. The collimator can cut out particles which traveling at a high angle. As a result, an energy distribution with high resolution can be obtained. Therefore, the mesh type collimator is simulated for high resolution alpha particle spectrometry. In conclusion, the collimator can improve resolution. With collimator, the collimator is a role of cutting out particles with a high angle, so, low energy tail and broadened energy distribution can be reduced. The mesh diameter is found out as an important factor to control resolution and counting efficiency. Therefore, a target particle, for example, 235U, can be distinguished by a detector with a collimator under a mixture of various nuclides, for example: 232U, 238U, and 232Th

  9. Alpha decay by cubic plus Yukawa plus exponential model

    International Nuclear Information System (INIS)

    The half life of alpha decay in some nuclei by using cubic plus Yukawa plus exponential model (CYCM) of Shanmugam and Kamalaharan is calculated in this project and compared with the available experimental values

  10. Alpha-cluster model of nuclear structure

    International Nuclear Information System (INIS)

    Full text: The approach based on the α-cluster model proposes some formulas to calculate the binding energies and the charge radii of the nuclei of the β-stability valley and around it [1]. The formulas have been derived on the basis of the idea of isospin independence of inter-nucleon interactions. The approach implies that the nucleus is a dense package of alpha-clusters. The inter-cluster distances are determined by the charge radii of the clusters, so the radius of the nucleus R is defined by their number. Some amount of excess neutrons fill in the gap between the matter bodies of the -clusters of the core [2]. Then the radius Rm of a β - stable isotope can be estimated by the volume occupied by the matter of the core and the volume of the charge of a few peripheral clusters. It has been shown that the condition Rm = R determines the amount of excess neutrons. The energy of these excess neutrons is described by a smooth function on the number of the neutron pairs. The formula to calculate the binding energy proper for the nucleus with five α-clusters turned out to be good for the other nuclei up to the most heavy ones. The formula to calculate the nuclear binding energy is evidently different from the well known Weizsacker formula. These two approaches give different estimations of the total Coulomb energy and the energy due to all inter-nucleon interactions, but the values of the total binding energies of these approaches are close. To calculate the charge radii both the approaches propose successful but different formulas, one is R ∼A1/3 and the other R∼Z1/3. A few useful phenomenological formulas have been found in the approach. These are the formulas to calculate the root mean square charge radius, the Coulomb radius and the radius of the last proton's position in dependence on the number of α-clusters. Besides, the empirical values of the Coulomb energy and the surface tension energy with a good accuracy have been obtained for the nuclei with N

  11. Survival of human osteosarcoma cells and normal human fibroblasts following alpha particle irradiation

    International Nuclear Information System (INIS)

    Cell survival of human osteosarcoma cells in culture following alpha particle irradiation is reported here for the first time. The osteosarcoma cell line (TE-85) is found to be less sensitive to inactivation by 5.6 MeV alpha particles (LET 86 keV/μm) than normal diploid human fibroblasts (NFS). Values for the mean lethal doses were estimated to be 103 rads for the TE-85 cells compared with 68 rads for the NFS cultures irradiated under identical conditions. It is postulated that the aneuploidy of the tumor cells with increased DNA chromosomal material may confer a selective advantage for the survival of tumor cells relative to normal cells with diploid chromosomes

  12. Collisional stochastic ripple diffusion of alpha particles and beam ions on TFTR

    Energy Technology Data Exchange (ETDEWEB)

    Redi, M.H.; Zarnstorff, M.C,; White, R.B.; Budny, R.V.; Schivell, J.F.; Scott, S.D.; Zweben, S.J.

    1994-09-01

    Predictions for ripple loss of fast ions from TFTR are investigated with a guiding center including both collisional and ripple effects. Discrepancies between measurements and calculations of plasma beta at low current and large major radius are resolved when both effects are included for neutral beam ions. A synergistic enhancement of fast ion diffusion is found for toroidal field ripple with collisions. S = 5.4 for neutral beam ions and S = 1.4--2.4 for alpha particles. A 20--30% reduction in alpha particle heating is predicted for R = 2.6 m DT plasmas on TFTR due to first orbit and collisional stochastic ripple diffusion, although these losses will be reduced if q{sub a} and R are smaller, as for most planned DT experiments.

  13. Collisional stochastic ripple diffusion of alpha particles and beam ions on TFTR

    International Nuclear Information System (INIS)

    Predictions for ripple loss of fast ions from TFTR are investigated with a guiding center including both collisional and ripple effects. Discrepancies between measurements and calculations of plasma beta at low current and large major radius are resolved when both effects are included for neutral beam ions. A synergistic enhancement of fast ion diffusion is found for toroidal field ripple with collisions. S = 5.4 for neutral beam ions and S = 1.4--2.4 for alpha particles. A 20--30% reduction in alpha particle heating is predicted for R = 2.6 m DT plasmas on TFTR due to first orbit and collisional stochastic ripple diffusion, although these losses will be reduced if qa and R are smaller, as for most planned DT experiments

  14. Turbulent transport of MeV range cyclotron heated minorities as compared to alpha particles

    CERN Document Server

    Pusztai, István; Kazakov, Yevgen O; Fülöp, Tünde

    2016-01-01

    We study the turbulent transport of an ion cyclotron resonance heated (ICRH), MeV range minority ion species in tokamak plasmas. Such highly energetic minorities, which can be produced in the three ion minority heating scheme [Ye. O. Kazakov et al. (2015) Nucl. Fusion 55, 032001], have been proposed to be used to experimentally study the confinement properties of fast ions without the generation of fusion alphas. We compare the turbulent transport properties of ICRH ions with that of fusion born alpha particles. Our results indicate that care must be taken when conclusions are drawn from experimental results: While the effect of turbulence on these particles is similar in terms of transport coefficients, differences in their distribution functions - ultimately their generation processes - make the resulting turbulent fluxes different.

  15. Biological dosimeter for UV-radiation and alpha particles, based on DNA damages

    International Nuclear Information System (INIS)

    A bioluminescence method for determination of biologically relevant (DNA damaging) doses of UV-radiation and alpha particles is developed. The method is based on bacterial luminescence as a bio-marker regulated by the SOS system. Cultures of E. coli cells transformed with the plasmid pPSL1 which carries the lux gene under control of the col promotor, an SOS-controlling gene, is used. The lux gene encode the enzyme luciferase which takes part in the reaction, resulting in the emission of a visible light at 490 nm. The light output is measured by photomultiplier and one channel analyzer. SOS-response kinetic curves of bacteria, UV-irradiated and treated with alpha particles, are obtained. An assessment of the risk from solar UV-radiation is made. The method has the sensitivity required to be used as biological UV-dosimeter (author)

  16. GAMCAT - a personal computer database on alpha particles and gamma rays from radioactive decay

    International Nuclear Information System (INIS)

    The GAMCAT database is a compilation of data describing the alpha particles and gamma rays that occur in the radioactive decay of all known nuclides, adapted for IBM Personal Computers and compatible systems. These compiled data have been previously published, and are now available as a compact database. Entries can be retrieved by defining the properties of the parent nuclei as well as alpha-particle and gamma-ray energies or any combination of these parameters. The system provides fast access to the data and has been completely written in C to run on an AT-compatible computer, with a hard disk and 640K of memory under DOS 2.11 or higher. GAMCAT is available from the Fachinformationszentrum Karlsruhe. (orig.)

  17. IAEA consultants' meeting on He-beam data base for alpha particle diagnostics of fusion plasmas

    International Nuclear Information System (INIS)

    The present Report contains the Summary of the IAEA Consultants' Meeting on ''He-Beam Data Base for Alpha Particle Diagnostics of Fusion Plasmas'' which was organized by the Atomic and Molecular Data Unit and held on June 3-5, 1991 at the IAEA Headquarters in Vienna, Austria. The Meeting Proceedings are briefly described and the reports of the Working Groups on the electron- and ion-impact processes are reproduced. A survey on the atomic data needs and required cross section accuracies for helium beam stopping calculations and alpha particle diagnostics of JET- and ITER-like plasmas is included. The conclusions and recommendations of the Meeting regarding the status of present data base (availability and quality) and the needs for its improvement are also given in this Summary Report. (author). Refs, figs and tabs

  18. Technique for measuring the losses of alpha particles to the wall in TFTR

    International Nuclear Information System (INIS)

    It is proposed to measure the losses of alpha particles to the wall in the Tokamak Fusion Test Reactor (TFTR) or any large deuterium-tritium (D-T) burning tokamak by a nuclear technique. For this purpose, a chamber containing a suitable fluid would be mounted near the wall of the tokamak. Alpha particles would enter the chamber through a thin window and cause nuclear reactions in the fluid. The material would then be transported through a tube to a remote, low-background location for measurement of the activity. The most favorable reaction suggested here is 10B(α,n)13N, although 14N(α,γ)18F and others may be possible. The system, the sensitivity, the probe design, and the sources of error are described

  19. Development of scintillator plates with high energy resolution for alpha particles made of GPS scintillator grains

    Science.gov (United States)

    Shimaoka, Takehiro; Kaneko, Junichi H.; Izaki, Kenji; Tsubota, Youichi; Higuchi, Mikio; Nishiyama, Shusuke

    2014-01-01

    A scintillator plate with high energy resolution was developed to produce an alpha particle monitor used in nuclear fuel reprocessing plants and mixed plutonium-uranium oxide (MOX) fuel plants. Grains of a Gd2Si2O7 (GPS) scintillator of several 10 to 550 μm were fixed on a glass substrate and were then mechanically polished. By increasing the size of scintillator grains and removing fine powders, the collected light yield and energy resolution for alpha particles were drastically improved. Energy resolution of 9.3% was achieved using average grain size of 91 μm. Furthermore, the ratios between counts in a peak and total counts were improved by more than 60% by the further increase of grain size and adoption of mechanically polished surfaces on both sides. Beta and gamma ray influences were suppressed sufficiently by the thin 100 μm scintillator plates.

  20. Conceptual design of confined alpha particle diagnostic system for ITER using an energetic He0 beam

    International Nuclear Information System (INIS)

    A conceptual design of an active-neutral-beam-probe-diagnostic-system for alpha particles produced by D-T nuclear reaction in a plasma confined by a magnetic fusion reactor has been examined. An energetic He0 beam plays an important role in the system. To detect a signal of neutralized alpha particles from the fusion plasma with enough S/N ratios, a high brightness He0 beam produced by spontaneous electron detachment from He- ions is required. A prototype of a He+ ion source has been designed and assembled to test the performance in producing a source beam for high intensity He- beam through a double-charge-exchange process in alkali metal vapor. (author)

  1. In-situ cross calibration method for alpha particle loss diagnostics at JET

    Czech Academy of Sciences Publication Activity Database

    Bonheure, G.; Perez Von Thun, Ch.; Reich, M.; Jachmich, S.; Murari, A.; Mlynář, Jan; Hult, M.; Arnold, D.; Dombrowski, T.; Laubenstein, M.; Wieslander, E.; Vidmar, T.; Vermaercke, P.; Cecil, F.E.; Cecconelo, M.; Craciunescu, T.; Darrow, D.; Lerche, E.; Tardocchi, M.; Van Eester, D.; Salmi, A.; Garcia-Munoz, M.; Yavorskij, V.; Popovichev, S.; Koslowski, H.R.; JET EFDA, Contributors.; Pinches, S.D.

    Vol. 33E. Sofia : European Physical Society, 2009 - (Mateev, M.; Benova, E.), P-2.145 ISBN 2-914771-61-4. - (Europhysics conference abstracts). [European Physical Society Conference on Plasma Physics /36th./. Sofia (BG), 29.06.2009-03.07.2009] Institutional research plan: CEZ:AV0Z20430508 Keywords : Tokamak * transport * tritium * in-situ * alpha particles Subject RIV: BL - Plasma and Gas Discharge Physics http://epsppd.epfl.ch/Sofia/pdf/P2_145.pdf

  2. Fission studies with 140 MeV $\\bm{\\alpha}$-Particles

    OpenAIRE

    Buttkewitz, A.; Duhm, H. H.; F. Goldenbaum(Forschungszentrum Jülich, Institut für Kernphysik, Jülich Germany); Machner, W.; Strauß, W.

    2009-01-01

    Binary fission induced by 140 MeV $\\alpha$-particles has been measured for $^{\\rm nat}$Ag, $^{139}$La, $^{165}$Ho and $^{197}$Au targets. The measured quantities are the total kinetic energies, fragment masses, and fission cross sections. The results are compared with other data and systematics. A minimum of the fission probability in the vicinity $Z^2/A=24$ is observed.

  3. Alpha particles energy estimation from track diameter development in a CR-39 detector.

    Science.gov (United States)

    Azooz, Aassim A; Al-Jubbori, Mushtaq A

    2016-09-01

    The slight nonlinearity in temporal development of tracks diameter in CR-39 nuclear track detectors is examined with the aim of attempting to find if such nonlinearity can be directly related to the charged particle energy. Narrowly spaced etching time-diameter experimental data for alpha particles at five energy values and for one additional energy value etched at five different temperatures are obtained. Initial results show good indication that measuring such time-diameter relationship can form a useful energy estimation tool. Good consistency with other independent published results is obtained. PMID:27341133

  4. Wurtzite Gallium Nitride as a scintillator detector for alpha particles (a Geant4 simulation)

    International Nuclear Information System (INIS)

    Gallium Nitride has become a very popular material in electronics and optoelectronics. Because of its interesting properties, it is suitable for a large range of applications. This material also shows very good scintillation properties that make it a possible candidate for use as a charged particles scintillator detector. In this work, we simulated the scintillation and optical properties of the gallium nitride in the presence of alpha particles using Geant4. The results show that gallium nitride can be an appropriate choice for this purpose

  5. Characterization of actinide targets by low solid-angle alpha particle counting

    CERN Document Server

    Denecke, B; Pauwels, J; Robouch, P; Gilliam, D M; Hodge, P; Hutchinson, J M R; Nico, J S

    1999-01-01

    Actinide samples were characterized in an interlaboratory comparison between IRMM and NIST, including alpha-particle counting at defined low solid angle and counting in a 2 pi proportional gas counter. For this comparison, nine sup 2 sup 3 sup 3 UF sub 4 samples with high uniformity in the layer thickness were prepared at IRMM by deposition under vacuum. Polished silicon wafers were used as source substrates, and these were rotated during the deposition using a planetary rotation system. The estimated uncertainties for the defined low solid-angle methods were about 0.1% at both NIST and IRMM. The agreement of reported alpha-particle emission rates in the energy range 2.5-5.09 MeV was better than or equal to 0.02% for the defined solid-angle methods. When comparing total alpha-particle emission rates over the larger energy range 0-9 MeV (which includes all emissions from the daughter nuclides and the impurities), the agreement of the defined solid-angle methods was better than or equal to 0.05%. The 2 pi propo...

  6. Radon and progeny alpha-particle energy analysis using nuclear track methodology

    International Nuclear Information System (INIS)

    A preliminary procedure for alpha-energy analysis of radon and its progeny using nuclear track methodology (NTM) is described in this paper. The method is based on the relationship between alpha-particle energies deposited in polycarbonate material (CR-39) and the track size developed after a well-established chemical etching process. Track geometry, defined by parameters such as major or minor diameters, track area and overall track length, is shown to correlate with alpha-particle energy over the range 6.00 MeV (218Po) to 7.69 MeV (214Po). Track features are measured and the data analyzed automatically using a digital imaging system and commercial PC software. Examination of particle track diameters in CR-39 exposed to environmental radon reveals a multi-modal distribution. Locations of the maxima in this distribution are highly correlated with alphaparticle energies of radon daughters, and the distributions are sufficiently resolved to identify the radioisotopes. This method can be useful for estimating the radiation dose from indoor exposure to radon and its progeny. (author)

  7. A multichannel model for clusters of an $\\alpha$ and select $N=Z$ nuclei

    OpenAIRE

    Amos, K.; Canton, L.; Fraser, P. R.; Karataglidis, S.; Svenne, J. P.; van der Knijff, D.

    2014-01-01

    A multi-channel algebraic scattering (MCAS) method has been used to solve coupled sets of Lippmann-Schwinger equations for $\\alpha$+nucleus systems to find spectra of the compound systems. Low energy spectra for ${}^{12}$C, ${}^{16}$O, and ${}^{20}$Ne are found with the systems considered as the coupling of an $\\alpha$ particle with low-excitation states of the core nuclei, ${}^8$Be, ${}^{12}$C, and ${}^{16}$O, respectively. Collective models have been used to define the matrices of interacti...

  8. Backangle anomaly in scattering of {alpha} -particles from {sup 28} Si at low energies[25.55.Ci; 25.70.Ef; Nuclear reactions 28 Si( {alpha},{alpha})28 Si; E{alpha}=3.0 -7.8 MeV; Measured {sigma}(E{alpha},{theta}); {theta}lab=30 deg. -175 deg.; Deduced Regge-pole parameters; Natural target

    Energy Technology Data Exchange (ETDEWEB)

    Coban, A.; Khiari, F.Z.; Abdelmonem, M.S.; Aksoy, A.; Naqvi, A.A

    2000-09-25

    In order to resolve the differences in the literature on the existence of quasi-molecular states in the {alpha} -{sup 28} Si system, excitation functions were measured for the scattering of {alpha} -particles from {sup 28} Si in the incident energy range E{sub lab}=3 -7.8 MeV. An angular distribution measurement was carried out in the angular range {theta}{sub lab}=30 deg. -174.5 deg. for every potential resonance observed in the excitation functions. Data was analysed using a Regge-pole formalism by coherently adding specific resonances to an underlying diffraction term calculated by a strong absorption model. Furthermore, the usual compound elastic contribution was incoherently added to the direct interaction part of the cross section. The 6.8 MeV resonance was confirmed with J=3 and some evidence was observed for a J=1 resonance around 6.0 MeV.

  9. Particles in thickening: mathematical model

    International Nuclear Information System (INIS)

    A mathematical model to describe the changes in the particle size distribution immediately below the solid/liquid interface in gravity thickening was formulated and tested against experimental results. The distribution is predicted to change by coagulation and differential sedimentation. Modifications to the collision efficiency functions for Brownian motion, fluid shear, and differential sedimentation were necessary to account for the high concentrations in thickening. The model correctly predicted the observed trends for both the coagulation and differential sedimentation aspects of the experimental results for changes with time, solids concentration, particle stability, and the subsidence velocity of the interface. The model is limited by the fact that the subsidence velocity cannot be predicted and by the simplified approach to the hydrodynamics of differential sedimentation which is incorporated. The substantial agreement between the model and experimental results indicates that the conceptual approach of the model is well-founded. The lack of agreement in some cases also has led to further insight into the mechanisms of particle transport in a concentrated heterodisperse suspension

  10. Particle-in-cell simulations of the magnetoacoustic cyclotron instability of fusion-born alpha-particles in tokamak plasmas

    Science.gov (United States)

    Cook, J. W. S.; Dendy, R. O.; Chapman, S. C.

    2013-06-01

    Ion cyclotron emission (ICE) is the only collective radiative instability, driven by confined fusion-born alpha-particles, observed from deuterium-tritium (DT) plasmas in both JET and TFTR. Using first principles particle-in-cell simulations of the magnetoacoustic cyclotron instability (MCI), we elucidate some of the fully kinetic nonlinear processes that may underlie observations of ICE from fusion products in these large tokamaks. We find that the MCI is intrinsically self-limiting on very fast timescales, which may help explain the observed correlation between linear theory and observed ICE intensity. The simulations elaborate the nature of the excited electric and magnetic fluctuations, from first principles, confirming the dominant role of fast Alfvénic and electrostatic components which is assumed ab initio in analytical treatments.

  11. Self-consistent analysis of alpha-particle heating of a fast-solenoid plasma

    International Nuclear Information System (INIS)

    A numerical technique has been developed to analyse the dynamics of a linear, magnetically confined plasma column and its associated fusion-produced alpha-particles in a self consistent manner. The thermonuclear background plasma is considered as a radially non-uniform, axially symmetric magnetofluid in pressure equilibrium with the surrounding axial magnetic field. A multi-group technique is utilized to examine the alphas as a collection of particles distributed among a continuous spectrum of confined orbits. The technique is shown to be an effective one for observing the interaction between super-thermal particles with large orbit sizes and a stable plasma of comparable size. The use of a distribution function in an adiabatic-invariant representation results in an enormous increase in the time scale which can be treated. This enables analysis of the entire duty cycle of a laser solenoid plasma in reasonable computation times. An analysis of a fast solenoid plasma is described, where the initial plasma radius and temperature are varied parametrically. A plasma column of radius 7mm, temperature 6keV, and β=0.95 will reach an ion temperature of 10keV, corresponding to a fusion energy gain of 8, after 3ms. A range of maximum gain occurs for initial temperatures of 5 to 7keV, with larger radius plasmas more favoured by the cooler limits. The effect of increasing the alpha-particle-electron energy transfer rate by a moderate amount to account for anomalous effects is to increase the plasma temperature at longer times, as long as this energy transfer is well-coupled to the electron-ion energy transfer. Increasing the rate at which plasma transport processes occur (''anomalous transport'') always results in lower fusion yield, because of rapid plasma diffusion. (author)

  12. Disturbance from Am-241 Photons of the Cellular Dose by Am-241 Alpha Emissions: Am-241 as an alternative source of alpha particles to radon daughters

    International Nuclear Information System (INIS)

    The Radiation Bioengineering Laboratory (RadBio Lab) at Seoul National University (SNU) has built an Am-241 alpha particle irradiator for study of cellular responses to radiation from radon daughters. The radon daughters of concern that cause internal exposure from inhalation of radon-contaminated air are Po-218, Po-214 and Po-210. In their alpha decay schemes, the yields of photon emissions are negligible. Unfortunately, Am-241, the source of alpha irradiator in RadBio Lab, emits photons at every alpha decay while transforming to Np-237 of long half-life. Employing Am-241 as the source simulating radon daughters, therefore, requires that photon emissions from Am-241 be specified in term of dose contribution. In this study, Monte Carlo calculations have been made to characterize dose contributions of Am-241 photon emissions. This study confirms that disturbance from Am-241 photon emissions of the cellular dose by Am-241 alpha emissions is negligible. Dose contamination fraction from photon emissions was 8.02 .. 10-6 at 25 mm SSD at maximum. Also, note that LET in tissue-equivalent medium varies within about 20% for alpha particles at energies over 5 MeV

  13. Disturbance from Am-241 Photons of the Cellular Dose by Am-241 Alpha Emissions: Am-241 as an alternative source of alpha particles to radon daughters

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ki-Man; Kim, Eun-Hee [Seoul National University, Seoul (Korea, Republic of)

    2015-05-15

    The Radiation Bioengineering Laboratory (RadBio Lab) at Seoul National University (SNU) has built an Am-241 alpha particle irradiator for study of cellular responses to radiation from radon daughters. The radon daughters of concern that cause internal exposure from inhalation of radon-contaminated air are Po-218, Po-214 and Po-210. In their alpha decay schemes, the yields of photon emissions are negligible. Unfortunately, Am-241, the source of alpha irradiator in RadBio Lab, emits photons at every alpha decay while transforming to Np-237 of long half-life. Employing Am-241 as the source simulating radon daughters, therefore, requires that photon emissions from Am-241 be specified in term of dose contribution. In this study, Monte Carlo calculations have been made to characterize dose contributions of Am-241 photon emissions. This study confirms that disturbance from Am-241 photon emissions of the cellular dose by Am-241 alpha emissions is negligible. Dose contamination fraction from photon emissions was 8.02 .. 10{sup -6} at 25 mm SSD at maximum. Also, note that LET in tissue-equivalent medium varies within about 20% for alpha particles at energies over 5 MeV.

  14. Immuno-vectorization of radioelements emitters of alpha particles: a new therapy in cancerology

    International Nuclear Information System (INIS)

    The radio-immunotherapy is an anti cancerous therapy which consists in vectorising with immuno-specific agents very radio toxic radioelements on tumors or in their environment to destroy them. The first part of this report presents the different characteristics of antibodies as well as their means of production under monoclonal shapes specifically steered against a tumoral antigen of interest. The second part of this report replaces the importance of the immunological vectors in the context of the nuclear medicine. It is notably described that the different methods which allow to radio-label the vector, as well as the different ways of optimization which were envisaged to improve the targeting of radioelements on a tumor. These different developments allow to define the potential place of the alpha radio-immunotherapy in treatments and so re-place the interest of the experimental part. If the radio-immunotherapy, using beta emitters isotopes as the 131iodine or the90yttrium, is today current in anti cancerous therapy, it finds limits because of the disintegration characteristics of the isotopes it uses. Indeed, compared with alpha particles, the beta particles deposit less energy by unit of length in the crossed material.The experimental part of this report aims at studying the feasibility of the coupling between an immunological vector and an alpha emitter isotope.The different tests led on the bismuth 213, the bismuth 212, the lead 212 and the astatine 211 demonstrated that the fixation of these radionuclides was possible. This research theme is strengthened by the construction in Nantes of a cyclotron with high energy ( A.R.R.O.N.A.X.) and the optimization of the obtained promising results should allow a therapeutic use in oncology of the alpha radio-immunotherapy. (N.C.)

  15. Charge-exchange limits on low-energy alpha-particle fluxes in solar flares

    CERN Document Server

    Hudson, Hugh; MacKinnon, Alec; Woods, Tom

    2014-01-01

    This paper reports on a search for flare emission via charge-exchange radiation in the wings of the Lyman-alpha line of He ii at 304 A, as originally suggested for hydrogen by Orrall and Zirker. Via this mechanism a primary alpha particle that penetrates into the neutral chromosphere can pick up an atomic electron and emit in the He ii bound-bound spectrum before it stops. The Extreme-ultraviolet Variability Experiment (EVE) on board the Solar Dynamics Observatory (SDO) gives us our first chance to search for this effect systematically. The Orrall-Zirker mechanism has great importance for flare physics because of the essential roles that particle acceleration plays; this mechanism is one of the few proposed that would allow remote sensing of primary accelerated particles below a few MeV/nucleon. We study ten events in total, including the gamma-ray events SOL2010-06-12 (M2.0) and SOL2011-02-24 (M3.5) (the latter a limb flare), seven X-class flares, and one prominent M-class event that produced solar energetic...

  16. A model for the generic alpha relaxation in viscous liquids

    DEFF Research Database (Denmark)

    Dyre, Jeppe

    2005-01-01

    Dielectric measurements on molecular liquids just above the glass transition indicate that alpha relaxation is characterized by a generic high-frequency loss varying as one over square root of frequency, whereas deviations from this come from one or more low-lying beta processes [Olsen et al., Phys....... Rev. Lett., 86 (2001) 1271]. Assuming that long-wavelength fluctuations dominate the dynamics, a model for the dielectric alpha relaxation based on the simplest coupling between the density and dipole density fields is proposed here. The model, which is solved in second-order perturbation theory in...

  17. Cranial nerve damage in patients after alpha (heavy)-particle radiation to the pituitary

    International Nuclear Information System (INIS)

    The records of 161 patients were reviewed to determine if radiation damage had occurred following cranial irradiation. All of these patients had received alpha-particle radiation to their pituitary glands during the period when this form of therapy was given for diabetic retinopathy. Extraocular muscle palsy developed in 11 of these patients, iridoplegia in six, and fifth nerve damage in six. All of the palsies developed within a short period following their irradiation, and a definite dose relationship was present. The dose rate was approximately 100 rads/min for all cases. Fractionation varied but it is known for all cases

  18. Cranial nerve damage in patients after alpha (heavy)-particle radiation to the pituitary

    International Nuclear Information System (INIS)

    The records of 161 patients were reviewed to determine if radiation damage had occurred following cranial irradiation. All of these patients had received alpha-particle radiation to their pituitary glands for diabetic retinopathy. Extraocular muscle palsy developed in 11 of these patients, iridoplegia in six, and fifth nerve damage in six. All of the palsies developed within a short period following their irradiation, and a definite dose relationship was present. The estimated doses to the third, fourth, fifth, and sixth cranial nerves was calculated at a saggital plane 13 to 15 mm from the pituitary by using computer-drawn dosimetry charts for the respective aperture size

  19. Selection of filter media used for monitoring airborne alpha-emitting particles in a radiological emergency

    International Nuclear Information System (INIS)

    We have developed on air monitor for alpha-emitting particles released to the atmosphere at an accident of nuclear reprocessing plant. Selection of a suitable filter for the monitor is considerably important in order to achieve the high-sensitive measurement of radioactive concentration. We have examined surface collection efficiencies and pressure drops for the various filters that are commercially available in Japan. It was found that the PTFE membrane filter with backing had superior performance to the others, that is, a high surface collection efficiency and low pressure drop. (author)

  20. Mapping alpha-Particle X-Ray Fluorescence Spectrometer (Map-X)

    Science.gov (United States)

    Blake, D. F.; Sarrazin, P.; Bristow, T.

    2014-01-01

    Many planetary surface processes (like physical and chemical weathering, water activity, diagenesis, low-temperature or impact metamorphism, and biogenic activity) leave traces of their actions as features in the size range 10s to 100s of micron. The Mapping alpha-particle X-ray Spectrometer ("Map-X") is intended to provide chemical imaging at 2 orders of magnitude higher spatial resolution than previously flown instruments, yielding elemental chemistry at or below the scale length where many relict physical, chemical, and biological features can be imaged and interpreted in ancient rocks.

  1. Influence of catechins on bystander responses in CHO cells induced by alpha-particle irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Law, Y.L.; Wong, T.P.W. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong (Hong Kong); Yu, K.N. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong (Hong Kong)], E-mail: peter.yu@cityu.edu.hk

    2010-04-15

    In this work, we studied alpha-particle induced and medium-mediated bystander effects in Chinese hamster ovary (CHO) cells through micronucleus (MN) assay. We showed that signal transduction from irradiated cells to bystander cells occur within a short time after irradiation. We then studied the effects of ROS (reactive oxygen species)-scavenging catechins in the medium before irradiation. We observed decreases in the percentage of bystander cells with MN formation and thus proved the protection effect of catechins on bystander cells from radiation.

  2. Chemistry of Rocks and Soils in Gusev Crater from the Alpha Particle X-ray Spectrometer

    Science.gov (United States)

    Gellert, R.; Rieder, R.; Anderson, R. C.; Brueckner, J.; Clark, B. C.; Dreibus, G.; Economou, T.; Klingelhoefer, G.; Lugmair, G. W.; Ming, D. W.

    2005-01-01

    The alpha particle x-ray spectrometer on the Spirit rover determined major and minor elements of soils and rocks in Gusev crater in order to unravel the crustal evolution of planet Mars. The composition of soils is similar to those at previous landing sites, as a result of global mixing and distribution by dust storms. Rocks (fresh surfaces exposed by the rock abrasion tool) resemble volcanic rocks of primitive basaltic composition with low intrinsic potassium contents. High abundance of bromine (up to 170 parts per million) in rocks may indicate the alteration of surfaces formed during a past period of aqueous activity in Gusev crater.

  3. Deuteron-and alpha particle-induced K-shell ionisation of W and Au atoms

    International Nuclear Information System (INIS)

    Deuteron - and alpha particle - induced K-shell ionisation cross sections for W and Au were obtained from thick-target measurements for low impact velocities. They were compared to proton-induced cross sections in the same range of velocities. Equal-velocity cross sections ratios are a very stringent test to the corrections incorporated to the PWBA calculations. The σd/σp data presented in this paper sheds some light on the Coulomb-deflection corrections discussed in the literature. The consequences of the inelastic character of the ionisation process are thoroughly examined. (Author)

  4. Sensitivity of alpha-particle-driven Alfven eigenmodes to q-profile variation in ITER scenarios

    CERN Document Server

    Rodrigues, P; Fazendeiro, L; Ferreira, J; Coelho, R; Nabais, F; Borba, D; Polevoi, N F Loureiro A R; Pinches, S D; Sharapov, S E

    2016-01-01

    An hybrid ideal-MHD/drift-kinetic approach to assess the stability of alpha-particle-driven Alfven eigenmodes in burning plasmas is used to show that certain foreseen ITER scenarios, namely the $I_\\mathrm{p} = 15$ MA baseline scenario with very low and broad core magnetic shear, are sensitive to small changes in the background magnetic equilibrium. Slight perturbations (of the order of 1%) in the total plasma current are seen to cause large variations in the growth rate, toroidal mode number, and radial location of the most unstable eigenmodes found. The observed sensitivity is shown to proceed from the very low magnetic shear values attained throughout the plasma core.

  5. Investigation of the performance of alpha particle counting and alpha-gamma discrimination by pulse shape with micro-pixel avalanche photodiode

    International Nuclear Information System (INIS)

    Being capable measuring small lights gives possibility to use micro-pixel avalanche photodiodes with scintillators. It is shown two prototypes to use micro-pixel avalanche photodiodes with and without scintillators as alpha and gamma counters in this paper. First prototype is to use two micro-pixel avalanche photodiodes. One for detecting alpha particles and closer to it, the second one with a thin plastic scintillator for detecting gamma rays. Second prototype is called two-layers configuration in which it is used only one micro-pixel avalanche photodiode, but two scntillators with different decay times. One can distinquish alpha particle and gamma ray events by using pulse shape discrimination techniques in the two-layer configuration. In this work an alpha particle and gamma ray counting performance of micro-pixel avalanche photodiodes without scintillators and its combination of plastic and BGO+ plastic scintillators was investigated. Obtained results showed the detection performance of the micro-pixel avalanche photodiodes in combination with plastic scintillator was about the same as conventional semiconductor detectors

  6. Etching characteristic studies for the detection of alpha particles in DAM–ADC nuclear track detector

    International Nuclear Information System (INIS)

    This study reports the characteristic studies for the detection of alpha particles in DAM–ADC nuclear track detector. Several important parameters that control the track formation such as, the bulk etch rate (VB), track etching rate (VT), dependence of VB and VT on etching concentration and temperature have been extensively studied. The activation energy (Eb) of the bulk etching rate for the DAM–ADC sheets has been calculated, the dependence of etching efficiency and sensitivity upon etchant concentrations and temperature has been investigated, registration efficiency of DAM–ADC detector etched at the optimum etching condition has been examined. The detailed studied results presented in this study provide various useful information about the mechanism of track formation in polymers. - Highlights: • Detection of alpha particles in DAM–ADC nuclear track detector. • The activation energy of the bulk etching rate for the DAM–ADC sheets. • The dependence of etching efficiency upon etchant concentrations • Registration efficiency of DAM–ADC detector

  7. An improved electrostatic integrating radon monitor with the CR-39 as alpha-particle detector

    International Nuclear Information System (INIS)

    In this study, based on the electrostatic integrating radon monitor (EIRM) developed by Iida et al., a new type of EIRM with the allyl glycol carbonate (CR-39) as alpha-particle detector was developed for outdoor radon measurements. Besides using the CR-39 to replace the cellulose nitrate film as alpha-particle detector, the electrode and the setting place of the CR-39 were also optimally designed based on the simulation results of the electric field and the detection efficiency. The calibration factor of the new EIRM was estimated to be 0.136±0.002 tracks cm-2 (Bq m-3 h)-1, with the lower detection limit of 0.6 Bq m-3 for a 2-month exposure. Furthermore, both the battery and the dry agent were also replaced to protect the environment. The results of intercomparison and field experiments showed that the performances of the new EIRM were much better than the original one. It suggests that the new type of ERIM is more suitable for large-scale and long-term outdoor radon surveys. (authors)

  8. Revisiting alpha decay-based near-light-speed particle propulsion.

    Science.gov (United States)

    Zhang, Wenwu; Liu, Zhen; Yang, Yang; Du, Shiyu

    2016-08-01

    Interplanet and interstellar travels require long-term propulsion of spacecrafts, whereas the conventional schemes of propulsion are limited by the velocity of the ejected mass. In this study, alpha particles released by nuclear decay are considered as a potential solution for long-time acceleration. The principle of near-light-speed particle propulsion (NcPP) was elucidated and the stopping and range of ions in matter (SRIM) was used to predict theoretical accelerations. The results show that NcPP by means of alpha decay is feasible for long-term spacecraft propulsion and posture adjustment in space. A practical NcPP sail can achieve a speed >150km/s and reach the brink of the solar system faster than a mass equivalent solar sail. Finally, to significantly improve the NcPP sail, the hypothesis of stimulated acceleration of nuclear decay (SAND) was proposed, which may shorten the travel time to Mars to within 20 days. PMID:27161512

  9. Development of scintillator plates with high energy resolution for alpha particles made of GPS scintillator grains

    International Nuclear Information System (INIS)

    A scintillator plate with high energy resolution was developed to produce an alpha particle monitor used in nuclear fuel reprocessing plants and mixed plutonium-uranium oxide (MOX) fuel plants. Grains of a Gd2Si2O7 (GPS) scintillator of several 10 to 550 μm were fixed on a glass substrate and were then mechanically polished. By increasing the size of scintillator grains and removing fine powders, the collected light yield and energy resolution for alpha particles were drastically improved. Energy resolution of 9.3% was achieved using average grain size of 91 μm. Furthermore, the ratios between counts in a peak and total counts were improved by more than 60% by the further increase of grain size and adoption of mechanically polished surfaces on both sides. Beta and gamma ray influences were suppressed sufficiently by the thin 100 μm scintillator plates. -- Highlights: • A scintillator plate was fabricated using Gd2Si2O7 grains of several 10 to 550 μm. • Scintillator grains were fixed on a glass substrate and were mechanically polished. • Energy resolution of 9.3% was achieved using average grains size of 91 μm. • This technique has no limitation in area size. • Radiation background was eliminated by thin thickness of scintillator, i.e. 100 μm

  10. Activation cross sections of longer-lived radionuclides produced in germanium by alpha particle irradiation

    Science.gov (United States)

    Takács, S.; Takács, M. P.; Ditrói, F.; Aikawa, M.; Haba, H.; Komori, Y.

    2016-09-01

    The cross sections of alpha particles induced nuclear reactions on natural germanium were investigated by using the standard stacked foil target technique, the activation method and high resolution gamma spectrometry. Targets with thickness of about 1 μm were prepared from natural Ge by vacuum evaporation onto 25 μm thick polyimide (Kapton) backing foils. Stacks were composed of Kapton-Ge-Ge-Kapton sandwich target foils and additional titanium monitor foils with nominal thickness of 11 μm to monitor the beam parameters using the natTi(α,x)51Cr reaction. The irradiations were done with Eα = 20.7 and Eα = 51.25 MeV, Iα = 50 nA alpha particle beams for about 1 h. Direct or cumulative activation cross sections were determined for production of the 72,73,75Se, 71,72,74,76,78As, and 69Ge radionuclides. The obtained experimental cross sections were compared to the results of theoretical calculations taken from the TENDL data library based on the TALYS computer code. A comparison was made with available experimental data measured earlier. Thick target yields were deduced from the experimental cross sections and compared with the data published before.

  11. Targeted Cytoplasmic Irradiation with Alpha Particles Induces Mutations in Mammalian Cells

    Science.gov (United States)

    Wu, Li-Jun; Randers-Pehrson, Gerhard; Xu, An; Waldren, Charles A.; Geard, Charles R.; Yu, Zengliang; Hei, Tom K.

    1999-04-01

    Ever since x-rays were shown to induce mutation in Drosophila more than 70 years ago, prevailing dogma considered the genotoxic effects of ionizing radiation, such as mutations and carcinogenesis, as being due mostly to direct damage to the nucleus. Although there was indication that alpha particle traversal through cellular cytoplasm was innocuous, the full impact remained unknown. The availability of the microbeam at the Radiological Research Accelerator Facility of Columbia University made it possible to target and irradiate the cytoplasm of individual cells in a highly localized spatial region. By using dual fluorochrome dyes (Hoechst and Nile Red) to locate nucleus and cellular cytoplasm, respectively, thereby avoiding inadvertent traversal of nuclei, we show here that cytoplasmic irradiation is mutagenic at the CD59 (S1) locus of human-hamster hybrid (AL) cells, while inflicting minimal cytotoxicity. The principal class of mutations induced are similar to those of spontaneous origin and are entirely different from those of nuclear irradiation. Furthermore, experiments with radical scavenger and inhibitor of intracellular glutathione indicated that the mutagenicity of cytoplasmic irradiation depends on generation of reactive oxygen species. These findings suggest that cytoplasm is an important target for genotoxic effects of ionizing radiation, particularly radon, the second leading cause of lung cancer in the United States. In addition, cytoplasmic traversal by alpha particles may be more dangerous than nuclear traversal, because the mutagenicity is accomplished by little or no killing of the target cells.

  12. A new method for alpha-particle detection in a classroom experiment

    International Nuclear Information System (INIS)

    Complete text of publication follows. The World Year of Physics (WYP 2005) was a worldwide celebration of Physics and its importance in our everyday lives. In harmony with its aims, that is to raise the worldwide awareness of Physics and Physical Science, we introduced a novel lab work involving a new imaging and data evaluation method for alpha-particle detection, which can be easily implemented in a classroom environment. The target group of the experiments is mainly secondary school students (age between 16-18 years). Our aim is to motivate students to develop a better understanding of Physics, allowing them to experience for themselves something of its fascination. In order to increase their attractiveness, the experiments include using a CMOS video image sensor with a video output. The covering glass window of the sensor must be carefully removed in order to make it sensitive for alpha rays. The sensor is connected to a computer where the images are recorded as a short video clip. The recorded video is played back by frames. The resulted frames are then merged together into one image. On this image the student can count the number of spots, where each spot corresponds to a hit of an alpha particle. The experiment can also be visible on a TV screen even by a whole class, however the authors suggest implementing the following experiments as a practical work individually or in small groups. As students are familiar with modern information technology, we think that they will be highly motivated to make these experiments on their own. Acknowledgements. The development of the above experimental setup was funded by ATOMKI and it was presented to the interactive science centre 'Magic corner', Debrecen, Hungary at Christmas, 2005. (author)

  13. Alpha particle interactions with nuclei at 12 A GeV/c

    International Nuclear Information System (INIS)

    Pseudo-rapidity density distributions of shower particles from 12 A GeV/c α-emulsion interactions are presented. As compaerd to extrapolations from p-nucleus data, the central α+(Ag,Br) interactions exhibit an excess of particles in the mid pseudo-rapidity region. The correlation between and -1 are understood within a wounded nucleon model. (Author)

  14. Hazardous gas production by alpha particles in solid organic transuranic waste matrices. 1998 annual progress report

    International Nuclear Information System (INIS)

    'This project uses fundamental radiation chemical techniques to elucidate the basic processes occurring in the heavy-ion radiolysis of solid hydrocarbon matrices such as polymers and organic resins that are associated with many of the transuranic waste deposits or the transportation of these radionuclides. The environmental management of mixed waste containing transuranic radionuclides is difficult because these nuclides are alpha particle emitters and the energy deposited by the alpha particles causes chemical transformations in the matrices accompanying the waste. Most radiolysis programs focus on conventional radiation such as gamma rays, but the chemical changes induced by alpha particles and other heavy ions are typically very different and product yields can vary by more than an order of magnitude. The objective of this research is to measure the production of gases, especially molecular hydrogen, produced in the proton, helium ion, and carbon ion radiolysis of selected solid organic matrices in order to obtain fundamental mechanistic information on the radiolytic decomposition of these materials. This knowledge can also be used to directly give reasonable estimates of explosive or flammability hazards in the storage or transport of transuranic wastes in order to enhance the safety of DOE sites. This report summarizes the work after eight months of a three-year project on determining the production of hazardous gases in transuranic waste. The first stage of the project was to design and build an assembly to irradiate solid organic matrices using accelerated ion beams. It is necessary to measure absolute radiolytic yields, and simulate some of the conditions found in the field. A window assembly was constructed allowing the beam to pass consecutively through a collimator, a vacuum exit window and into the solid sample. The beam is stopped in the sample and the entire end of the assembly is a Faraday cup. Integration of the collected current, in conjunction

  15. Direct photon pair production at the LHC to order alpha_s in TeV scale gravity models

    CERN Document Server

    Kumar, M C; Ravindran, V; Tripathi, Anurag

    2009-01-01

    The first results on next-to-leading order QCD corrections to production of direct photon pairs in hadronic collisions in the large extra dimension models- ADD and RS are presented. Various kinematical distributions are obtained to order alpha_s in QCD by taking into account all the parton level subprocesses. Our Monte Carlo based code incorporates all the experimental cuts suitable for physics studies at the LHC. We estimate the impact of the QCD corrections on various observables and find that they are significant. We also show the reduction in factorisation scale uncertainity when order alpha_s effects are included.

  16. Studying effects of Magnolol on alpha-particle induced bystander effects using PADC-film based dishes

    Energy Technology Data Exchange (ETDEWEB)

    Wong, T.P.W. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong (Hong Kong); Tse, A.K.W.; Fong, W.F. [Research and Development Division, School of Chinese Medicine, Hong Kong Baptist University, Baptist University Road, Kowloon Tong (Hong Kong); Yu, K.N., E-mail: peter.yu@cityu.edu.h [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong (Hong Kong)

    2009-10-15

    Radiation-induced bystander effect refers to the biological response found in cells (called bystander cells) which are not irradiated directly by ionizing radiation but are next to cells irradiated directly by ionizing radiation. In the present paper, the effects of Magnolol, an extract from the bark of Magnolia officinalis which is used as a traditional Chinese medicine, were studied on alpha-particle induced bystander effects. In our experiments, Chinese hamster ovary (CHO) cells were cultured in PADC-film based dishes and were irradiated with low fluences of alpha particles passing through the PADC films. The precise number of cells traversed or missed by alpha particles could be determined by studying the alpha-particle tracks developed on the PADC films upon subsequent chemical etching. TdT-mediated dUTP Nick-End Labeling (TUNEL) assay was employed to analyze the biological response of bystander cells in terms of DNA strand breaks. With the pretreatment of Magnolol, the DNA strand breaks in bystander cells were reduced, which showed that the alpha-particle induced bystander effects were suppressed with the presence of Magnolol. Since Magnolol is an antioxidant which can scavenge reactive oxygen species (ROS), our results give support to that ROS play a role in the bystander signal transmission in our experiments.

  17. Feasibility study on the use of polyallyldiglycol-carbonate cell dishes in TUNEL assay for alpha particle radiobiological experiments

    Science.gov (United States)

    Chan, K. F.; Yum, E. H. W.; Wan, C. K.; Fong, W. F.; Yu, K. N.

    2007-08-01

    In the present work, we have studied the feasibility of a method based on polyallyldiglycol-carbonate (PADC) films to investigate the effects of alpha particles on HeLa cervix cancer cells. Thin PADC films with thickness of about 20 μm were prepared from commercially available CR-39 films by chemical etching to fabricate custom-made petri dishes for cell culture, which could accurately record alpha particle hit positions. A special method involving "base tracks" for aligning the images of cell nuclei and alpha particle hits has been proposed, so that alpha particle transversals of cell nuclei can be visually counted. Radiobiological experiments were carried out to induce DNA damages, with the TdT-mediated d UTP Nick- End Labeling (TUNEL) fluorescence method employed to detect DNA strand breaks. The staining results were investigated by flow cytometer. The preliminary results showed that more strand breaks occurred in cells hit by alpha particles with lower energies. Moreover, large TUNEL positive signals were obtained even with small percentages of cells irradiated and TUNEL signals were also obtained from non-targeted cells. These provided evidence for the bystander effect.

  18. Feasibility study on the use of polyallyldiglycol-carbonate cell dishes in TUNEL assay for alpha particle radiobiological experiments

    Energy Technology Data Exchange (ETDEWEB)

    Chan, K.F. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong (China); Yum, E.H.W. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong (China); Wan, C.K. [Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong (China); Fong, W.F. [Research and Development Division, School of Chinese Medicine, Hong Kong Baptist University, Baptist University Road, Kowloon Tong, Hong Kong (China); Yu, K.N. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong (China)]. E-mail: peter.yu@cityu.edu.hk

    2007-08-15

    In the present work, we have studied the feasibility of a method based on polyallyldiglycol-carbonate (PADC) films to investigate the effects of alpha particles on HeLa cervix cancer cells. Thin PADC films with thickness of about 20 {mu}m were prepared from commercially available CR-39 films by chemical etching to fabricate custom-made petri dishes for cell culture, which could accurately record alpha particle hit positions. A special method involving 'base tracks' for aligning the images of cell nuclei and alpha particle hits has been proposed, so that alpha particle transversals of cell nuclei can be visually counted. Radiobiological experiments were carried out to induce DNA damages, with the TdT-mediated dUTP Nick-End Labeling (TUNEL) fluorescence method employed to detect DNA strand breaks. The staining results were investigated by flow cytometer. The preliminary results showed that more strand breaks occurred in cells hit by alpha particles with lower energies. Moreover, large TUNEL positive signals were obtained even with small percentages of cells irradiated and TUNEL signals were also obtained from non-targeted cells. These provided evidence for the bystander effect.

  19. Implementation of the LANS-alpha turbulence model in a primitive equation ocean model

    CERN Document Server

    Hecht, M W; Petersen, M R; Wingate, B A; Hecht, Matthew W.; Holm, Darryl D.; Petersen, Mark R.; Wingate, Beth A.

    2007-01-01

    This paper presents the first numerical implementation and tests of the Lagrangian-averaged Navier-Stokes-alpha (LANS-alpha) turbulence model in a primitive equation ocean model. The ocean model in which we work is the Los Alamos Parallel Ocean Program (POP); we refer to POP and our implementation of LANS-alpha as POP-alpha. Two versions of POP-alpha are presented: the full POP-alpha algorithm is derived from the LANS-alpha primitive equations, but requires a nested iteration that makes it too slow for practical simulations; a reduced POP-alpha algorithm is proposed, which lacks the nested iteration and is two to three times faster than the full algorithm. The reduced algorithm does not follow from a formal derivation of the LANS-alpha model equations. Despite this, simulations of the reduced algorithm are nearly identical to the full algorithm, as judged by globally averaged temperature and kinetic energy, and snapshots of temperature and velocity fields. Both POP-alpha algorithms can run stably with longer ...

  20. Ab initio alpha-alpha scattering.

    Science.gov (United States)

    Elhatisari, Serdar; Lee, Dean; Rupak, Gautam; Epelbaum, Evgeny; Krebs, Hermann; Lähde, Timo A; Luu, Thomas; Meißner, Ulf-G

    2015-12-01

    Processes such as the scattering of alpha particles ((4)He), the triple-alpha reaction, and alpha capture play a major role in stellar nucleosynthesis. In particular, alpha capture on carbon determines the ratio of carbon to oxygen during helium burning, and affects subsequent carbon, neon, oxygen, and silicon burning stages. It also substantially affects models of thermonuclear type Ia supernovae, owing to carbon detonation in accreting carbon-oxygen white-dwarf stars. In these reactions, the accurate calculation of the elastic scattering of alpha particles and alpha-like nuclei--nuclei with even and equal numbers of protons and neutrons--is important for understanding background and resonant scattering contributions. First-principles calculations of processes involving alpha particles and alpha-like nuclei have so far been impractical, owing to the exponential growth of the number of computational operations with the number of particles. Here we describe an ab initio calculation of alpha-alpha scattering that uses lattice Monte Carlo simulations. We use lattice effective field theory to describe the low-energy interactions of protons and neutrons, and apply a technique called the 'adiabatic projection method' to reduce the eight-body system to a two-cluster system. We take advantage of the computational efficiency and the more favourable scaling with system size of auxiliary-field Monte Carlo simulations to compute an ab initio effective Hamiltonian for the two clusters. We find promising agreement between lattice results and experimental phase shifts for s-wave and d-wave scattering. The approximately quadratic scaling of computational operations with particle number suggests that it should be possible to compute alpha scattering and capture on carbon and oxygen in the near future. The methods described here can be applied to ultracold atomic few-body systems as well as to hadronic systems using lattice quantum chromodynamics to describe the interactions of

  1. Ab initio alpha-alpha scattering

    Science.gov (United States)

    Elhatisari, Serdar; Lee, Dean; Rupak, Gautam; Epelbaum, Evgeny; Krebs, Hermann; Lähde, Timo A.; Luu, Thomas; Meißner, Ulf-G.

    2015-12-01

    Processes such as the scattering of alpha particles (4He), the triple-alpha reaction, and alpha capture play a major role in stellar nucleosynthesis. In particular, alpha capture on carbon determines the ratio of carbon to oxygen during helium burning, and affects subsequent carbon, neon, oxygen, and silicon burning stages. It also substantially affects models of thermonuclear type Ia supernovae, owing to carbon detonation in accreting carbon-oxygen white-dwarf stars. In these reactions, the accurate calculation of the elastic scattering of alpha particles and alpha-like nuclei—nuclei with even and equal numbers of protons and neutrons—is important for understanding background and resonant scattering contributions. First-principles calculations of processes involving alpha particles and alpha-like nuclei have so far been impractical, owing to the exponential growth of the number of computational operations with the number of particles. Here we describe an ab initio calculation of alpha-alpha scattering that uses lattice Monte Carlo simulations. We use lattice effective field theory to describe the low-energy interactions of protons and neutrons, and apply a technique called the ‘adiabatic projection method’ to reduce the eight-body system to a two-cluster system. We take advantage of the computational efficiency and the more favourable scaling with system size of auxiliary-field Monte Carlo simulations to compute an ab initio effective Hamiltonian for the two clusters. We find promising agreement between lattice results and experimental phase shifts for s-wave and d-wave scattering. The approximately quadratic scaling of computational operations with particle number suggests that it should be possible to compute alpha scattering and capture on carbon and oxygen in the near future. The methods described here can be applied to ultracold atomic few-body systems as well as to hadronic systems using lattice quantum chromodynamics to describe the interactions of

  2. Broadband distortion modeling in Lyman-$\\alpha$ forest BAO fitting

    CERN Document Server

    Blomqvist, Michael; Bautista, Julian E; Ariño, Andreu; Busca, Nicolás G; Miralda-Escudé, Jordi; Slosar, Anže; Font-Ribera, Andreu; Margala, Daniel; Schneider, Donald P; Vazquez, Jose A

    2015-01-01

    In recent years, the Lyman-$\\alpha$ absorption observed in the spectra of high-redshift quasars has been used as a tracer of large-scale structure by means of the three-dimensional Lyman-$\\alpha$ forest auto-correlation function at redshift $z\\simeq 2.3$, but the need to fit the quasar continuum in every absorption spectrum introduces a broadband distortion that is difficult to correct and causes a systematic error for measuring any broadband properties. We describe a $k$-space model for this broadband distortion based on a multiplicative correction to the power spectrum of the transmitted flux fraction that suppresses power on scales corresponding to the typical length of a Lyman-$\\alpha$ forest spectrum. Implementing the distortion model in fits for the baryon acoustic oscillation (BAO) peak position in the Lyman-$\\alpha$ forest auto-correlation, we find that the fitting method recovers the input values of the linear bias parameter $b_{F}$ and the redshift-space distortion parameter $\\beta_{F}$ for mock dat...

  3. Alpha-Ni optical model potentials

    International Nuclear Information System (INIS)

    The present work reports the analyses of the experimental differential cross-sections of α elastic scattering on 58,60,62,64Ni, over a wide range of incident energies, in terms of four types of optical potentials, namely shallow (molecular), deep non-monotonic, squared Woods-Saxon and semi-microscopic folding. All the four potentials produce a reasonable description of the experimental data. The potential parameters, calculated from the energy density functional theory using a realistic two-nucleon interaction, resemble closely the molecular potential parameters, which produce the best description of the experimental data for the four isotopes. The volume integrals and the energy variation of the parameters indicate the effect of the shell-model structure on the potentials. The folding potentials, without any need for renormalization, are found to describe reasonably well the elastic scattering cross-section data for the four isotopes within the energy range considered. In conformity with the previous observation on Ca isotopes, the number of nucleons, 4Aα=49, existing in α-like clusters in the target nucleus, is the same for the four isotopes, considered herein

  4. Alpha Particle Emitter Radiolabeled Antibody for Metastatic Cancer: What Can We Learn from Heavy Ion Beam Radiobiology?

    Directory of Open Access Journals (Sweden)

    Hong Song

    2012-06-01

    Full Text Available Alpha-particle emitter labeled monoclonal antibodies are being actively developed for treatment of metastatic cancer due to the high linear energy transfer (LET and the resulting greater biological efficacy of alpha-emitters. Our knowledge of high LET particle radiobiology derives primarily from accelerated heavy ion beam studies. In heavy ion beam therapy of loco-regional tumors, the modulation of steep transition to very high LET peak as the particle approaches the end of its track (known as the Bragg peak enables greater delivery of biologically potent radiation to the deep seated tumors while sparing normal tissues surrounding the tumor with the relatively low LET track segment part of the heavy ion beam. Moreover, fractionation of the heavy ion beam can further enhance the peak-to-plateau relative biological effectiveness (RBE ratio. In contrast, internally delivered alpha particle radiopharmaceutical therapy lack the control of Bragg peak energy deposition and the dose rate is determined by the administered activity, alpha-emitter half-life and biological kinetics of the radiopharmaceutical. The therapeutic ratio of tumor to normal tissue is mainly achieved by tumor specific targeting of the carrier antibody. In this brief overview, we review the radiobiology of high LET radiations learned from ion beam studies and identify the features that are also applicable for the development of alpha-emitter labeled antibodies. The molecular mechanisms underlying DNA double strand break repair response to high LET radiation are also discussed.

  5. Bayesian analysis of nanodosimetric ionisation distributions due to alpha particles and protons.

    Science.gov (United States)

    De Nardo, L; Ferretti, A; Colautti, P; Grosswendt, B

    2011-02-01

    Track-nanodosimetry has the objective to investigate the stochastic aspect of ionisation events in particle tracks, by evaluating the probability distribution of the number of ionisations produced in a nanometric target volume positioned at distance d from a particle track. Such kind of measurements makes use of electron (or ion) gas detectors with detecting efficiencies non-uniformly distributed inside the target volume. This fact makes the reconstruction of true ionisation distributions, which correspond to an ideal efficiency of 100%, non-trivial. Bayesian unfolding has been applied to ionisation distributions produced by 5.4 MeV alpha particles and 20 MeV protons in cylindrical volumes of propane of 20 nm equivalent size, positioned at different impact parameters with respect to the primary beam. It will be shown that a Bayesian analysis performed by subdividing the target volume in sub-regions of different detection efficiencies is able to provide a good reconstruction of the true nanodosimetric ionisation distributions. PMID:21112893

  6. Partition of cross sections in asymmetric nucleus-nucleus reactions and the origin of fast alpha particles

    International Nuclear Information System (INIS)

    To investigate the mechanism of asymmetric nucleus-nucleus reactions from the Coulomb barrier to intermediate energies the 14N + 159Tb reaction was studied at five bombarding energies between 8 and 23 MeV/u via particle-particle correlations (at selected energies) and particle KX-ray coincidences to identify the specific reaction channels. With the KX-ray method partial cross sections for projectile-like fragments (PLF) as a function of the atomic number (Z/sub res/) of the residual nucleus can be determined. The charge balance yields the ''missing charge'' dZ = Z/sub proj/ + Z/sub targ/ - Z/sub PLF/ - Z/sub TLF/ that indicates whether, in addition to the PLF, other charged particles are emitted. A large fraction of the inclusive cross sections is found to originate from such channels with two or more fragments in the exit channel, and this fraction increases as the PLF is further removed in mass from the incident projectile, and with increasing bombarding energy. From the particle-particle correlation studies it is found that sequential decays of PLF's are dominant. ''Non-sequential'' processes, if present, are associated with inelastic reactions involving excitations of both projectile and target. The bulk of the large alpha-particle cross section at small angles is found to be associated with channels in which, in addition to the alpha particle, only nucleons and other alpha particles are emitted. From γ-ray multiplicity measurements and from the broad distribution of the strength with Z/sub res/ it is concluded that these alpha particles originate from inelastic (damped) processes. 27 refs., 10 figs

  7. Modelling the Evolution of Ly$\\alpha$ Blobs and Ly$\\alpha$ Emitters

    CERN Document Server

    Smailagić, Marijana; Martinovic, Nemanja

    2016-01-01

    In this work we model the observed evolution in comoving number density of Lyman-alpha blobs (LABs) as a function of redshift, and try to find which mechanism of emission is dominant in LAB. Our model calculates LAB emission both from cooling radiation from the intergalactic gas accreting onto galaxies and from star formation (SF). We have used dark matter (DM) cosmological simulation to which we applied empirical recipes for Ly$\\alpha$ emission produced by cooling radiation and SF in every halo. In difference to the previous work, the simulated volume in the DM simulation is large enough to produce an average LABs number density. At a range of redshifts $z\\sim 1-7$ we compare our results with the observed luminosity functions of LABs and LAEs. Our cooling radiation luminosities appeared to be too small to explain LAB luminosities at all redshifts. In contrast, for SF we obtained a good agreement with observed LFs at all redshifts studied. We also discuss uncertainties which could influence the obtained resul...

  8. Nuclear transparency in {alpha}-particle scattering beyond the eikonal approach

    Energy Technology Data Exchange (ETDEWEB)

    Eliseev, S.M. [Bogoliubov Laboraroty of Theoretical Physics, Joint Institute for Nuclear Research, Dubna (Russian Federation); Hanna, K.M. [Matematics and Theoretical Physics Departement, AtomyEnergy Authority, Cairo (Egypt)

    1999-08-01

    An independent, complementary, and unbiased study to calculate the transparency functions beyond the eikonal approach by adding the higher-order (up to the third-order term) non eikonal (Ne) corrections, in five different effective optical potentials all of them reproduce well the elastic scattering of intermediate energy {alpha}-particles ({epsilon}{sub {alpha}} 140-288 MeV) from the two neighborly nuclei {sup 48}Ti and {sup 58}Ni. The effects of switching (off/on) the Coulomb potential on the results are studied. The individual and the combined effects of the Ne corrections and Coulomb potential are explored in the transparency function for a wide range of the impact parameter 'b' from the nuclear surface towards the nuclear interior. No violation is detected in the flux conservation for the considered projectile incident energy and the impact parameter ranges. It is found that, in some cases, it is not necessarily true, as usually believed, that the Coulomb potential decreases the absorption (less transparency) in the central region of the nucleus, the phenomenon which can be explained by a modification of the balance between the nominal real and imaginary parts of some optical potential in the rather complicate transparency function.

  9. Properties of an $\\alpha$ particle in a Bohrium $270$ Nucleus under the Generalized Symmetric Woods-Saxon Potential

    CERN Document Server

    Lütfüoğlu, B C

    2016-01-01

    The energy eigenvalues and the wave functions of an $\\alpha$ particle in a Bohrium $270$ nucleus were calculated by solving Schr\\"odinger equation for Generalized Symmetric Woods-Saxon potential. Using the energy spectrum by excluding and including the quasi-bound eigenvalues, entropy, internal energy, Helmholtz energy, and specific heat, as functions of reduced temperature were calculated. Stability and emission characteristics are interpreted in terms of the wave and thermodynamic functions. The kinetic energy of a decayed $\\alpha$ particle was calculated using the quasi-bound states, which is found close to the experimental value.

  10. Collisional stochastic ripple diffusion of alpha particles and beam ions on TFTR

    International Nuclear Information System (INIS)

    Predictions for ripple loss of fast ions from TFTR are investigated with a guiding center code including both collisional and ripple effects. A synergistic enhancement of fast ion diffusion is found for toroidal field ripple with collisions. The total loss is calculated to be roughly twice the sum of ripple and collisional losses calculated separately. Discrepancies between measurements and calculations of plasma beta at low current and large major radius are resolved when both effects are included for neutral beam ions. A 20--30% reduction in alpha particle heating is predicted for qa = 6--14, R = 2.6 m DT plasmas on TFTR due to first orbit and collisional stochastic ripple diffusion

  11. A route for polonium 210 production from alpha-particle irradiated bismuth-209 target

    International Nuclear Information System (INIS)

    A method is proposed for production of polonium-210 via the 209Bi(α,3n)210 At nuclear reaction. Bombardment of a bismuth-209 target was performed with a 37 MeV alpha-particle beam that leads to the production of astatine-210 (T1/2 = 8.1 h), which decays to polonium-210. It is purified from the bismuth target matrix by employing liquid-liquid extraction using tributyl phosphate (TBP) in para-xylene from 7 M hydrochloric acid. Back extraction of polonium-210 was performed by 9 M nitric acid. This method allows to purify a tracer amount of Po-210 (2.6 x 10-13 mol) from macroscopic amount of Bi (2.8 x 10-2 mol).

  12. Assessment of gamma, beta and alpha-particle-emitting nuclides in marine samples

    International Nuclear Information System (INIS)

    Depending on the physical properties of radionuclides different systems must be used for their measurement. Most convenient is if gamma spectrometry can be used by germanium, Silicon or Scintillation detectors (eg. NaI). If, however, the main emission consists of beta or alpha particles or low-energy photons as is the case for radionuclides decaying by electron capture, radiochemical separation and specific source preparations must be undertaken. In such cases also the radiochemical yield must be determined. The radiochemical part mainly follows the lines presented by prof. T. Jaakkola, Department of Radiochemistry, Helsinki, Finland, at a course in radioecology in Lurid, 1991. For very long-lived radionuclides other methods such as mass spectrometry are superior although often associated with sophisticated expensive instrumentation. (author)

  13. Gas production due to alpha particle degradation of polyethylene and polyvinylchloride

    International Nuclear Information System (INIS)

    Alpha particle degradation experiments were performed on polyethylene (PE) and polyvinylchloride (PVC) plastic samples typical of Westinghouse Savannah River Company (WSRC) transuranic (TRU) waste. This was done to evaluate the effects of sealing TRU waste during shipment. Experiments were conducted at three temperatures using low dose rates. Predominant products from both plastics were hydrogen, carbon dioxide, and various organic species, with the addition of hydrochloric acid from PVC. In all experiments, the total pressure decreased. Irradiation at 30 and 60 C and at various dose rates caused small changes for both plastics, but at 100 C coupled thermal-radiolytic effects included discoloration of the material as well as large differences in the gas phase composition

  14. Is the first excited state of the $\\alpha$-particle a breathing mode?

    CERN Document Server

    Bacca, Sonia; Leidemann, Winfried; Orlandini, Giuseppina

    2014-01-01

    The isoscalar monopole excitation of 4He is studied within a few-body ab initio approach. We consider the transition density to the low-lying and narrow 0+ resonance, as well as various sum rules and the strength energy distribution itself at different momentum transfers q. Realistic nuclear forces of chiral and phenomenological nature are employed. Various indications for a collective breathing mode are found: i) the specific shape of the transition density, ii) the high degree of exhaustion of the non-energy-weighted sum rule at low q and iii) the complete dominance of the resonance peak in the excitation spectrum. For the incompressibility K of the alpha-particle values between 20 and 30 MeV are found.

  15. Specific features of reactor or cyclotron {alpha}-particles irradiated beryllium microstructure

    Energy Technology Data Exchange (ETDEWEB)

    Khomutov, A.M. [A.A.Bochvar All-Russia Research Inst. of Inorganic Materials (VNIINM), Moscow (Russian Federation); Gromov, B.F.; Karabanov, V.N. [and others

    1998-01-01

    Studies were carried out into microstructure changes accompanying helium swelling of Be reactor neutron irradiated at 450degC or {alpha}-particles implanted in cyclotron to reach the same volume accumulation of He (6-8 ncm{sup 3} He/cm{sup 3} Be). The microstructures of reactor irradiated and implanted samples were compared after vacuum anneal at 600-800degC up to 50h. The irradiated samples revealed the etchability along the grain boundaries in zones formed by adequately large equilibrium helium pores. The width of the zones increased with the annealing time and after 50h reached 30{mu}. Depleted areas 2-3{mu} dia were observed in some regions of near grain boundary zones. The roles of grain boundaries and manufacturing pores as vacancies` sources and helium sinks are considered. (author)

  16. CO2 laser collective Thomson scattering for alpha-particle diagnostics

    International Nuclear Information System (INIS)

    In JT-60U (JAEA Tokamak 60 - Upgrade), a collective Thomson scattering (CTS) technique based on a CO2 laser is being developed in order to establish a diagnostic method of confined alpha-particles in burning plasmas. In order to the demonstrate feasibility of the CTS system, a new laser systems is being developed, with which improved signal-to-Noise (S/N) ratio of a detection signal and temporal resolution will be obtained. The laser has cavity length of ∼4 m and has high repetition rate (10 Hz). To improve the spectral purity of the laser, cavity length will be feedback-controlled and a spectral filter will be installed in the output of the laser. Numerical calculation shows that ion temperature will be evaluated from the scattered spectrum with the new CO2 laser. (author)

  17. Traversal of cells by radiation and absorbed fraction estimates for electrons and alpha particles

    International Nuclear Information System (INIS)

    Consideration of the pathlength which radiation traverses in a cell is central to algorithms for estimating energy deposition on a cellular level. Distinct pathlength distributions occur for radionuclides: (1) uniformly distributed in space about the cell (referred to as μ-randomness); (2) uniformly distributed on the surface of the cell (S-randomness); and (3) uniformly distributed within the cell volume (I-randomness). For a spherical cell of diameter d, the mean pathlengths are 2/3d, and 3/4d, respectively, for these distributions. Algorithms for simulating the path of radiation through a cell are presented and the absorbed fraction in the cell and its nucleus are tabulated for low energy electrons and alpha particles emitted on the surface of spherical cells. The algorithms and absorbed fraction data should be of interest to those concerned with the dosimetry of radionuclide-labeled monoclonal antibodies. 8 references, 3 figures, 2 tables

  18. Long-Range Alpha Particle Emission in the Fission of U235 by 3-MeV Neutrons

    International Nuclear Information System (INIS)

    The energy and angular distribution of long-range alpha particles emitted in the fission of U235 induced by 3-MeV neutrons have been measured. The alpha panicles were detected by solid-state detector and the fission fragments were detected by a gas scintillation counter. The neutrons were produced by the T (p, n) He3 reaction using a 5.5- MeV Van de Graaff accelerator. About 3000 fission events accompanied by the emission of a high-energy alpha panicle were recorded. The most probable energy of the alpha particles is between 15-16 MeV. and the energy distribution has a full width at half maximum of about D MeV, which is the same as observed in tliermal- neutron fission. The angular distribution of the long-range alpha panicles with respect to the incident neutron direction was found to be forward-peaked, in agreement with previous work on alpha emission in 14-MeV neutron-induced fission of LP. At angles of 0° and 90° with respect to the incident neutron direction the alpha panicles were detected with an angular spread of about ± 25°. The anisotropy [Nα(0°)/ Nα(90°)] was found to be 1.320 ± 0.12. This value is in agreement with the anisotropy calculated on the basis of statistical evaporation of panicles. The results of the present investigation are consistent with the hypothesis that the emission of long-range alpha panicles in fission is an evaporation process. The implications of the results of this work and of other recent investigations on long-range alpha emission are discussed. (author)

  19. Lyman alpha solar spectral irradiance line profile observations and models

    Science.gov (United States)

    Snow, Martin; Machol, Janet; Quemerais, Eric; Curdt, Werner; Kretschmar, Matthieu; Haberreiter, Margit

    2016-04-01

    Solar lyman alpha solar spectral irradiance measurements are available on a daily basis, but only the 1-nm integrated flux is typically published. The International Space Science Institute (ISSI) in Bern, Switzerland has sponsored a team to make higher spectral resolution data available to the community. Using a combination of SORCE/SOLSTICE and SOHO/SUMER observations plus empirical and semi-empirical modeling, we will produce a dataset of the line profile. Our poster will describe progress towards this goal.

  20. New features of nuclear excitation by {alpha} particles scattering; Nouveaux aspects de l'excitation nucleaire par diffusion de particules {alpha}

    Energy Technology Data Exchange (ETDEWEB)

    Saudinos, J. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1962-07-01

    Inelastic scattering of medium energy a particles by nuclei is known to excite preferentially levels of collective character. We have studied the scattering of isotopically enriched targets of Ca, Fe, Ni, Cu, Zn. In part I, we discuss the theoretical features of the interaction. In part II, we describe the experimental procedure. Results are presented and analysed in part III. {alpha} particles scattering by Ca{sup 40} is showed to excite preferentially odd parity levels. In odd nuclei we have observed multiplets due to the coupling of the odd nucleon with the even-even core vibrations. For even-even nuclei, a few levels are excited with lower cross-sections between the well-known first 2{sup +} and 3{sup -} states. Some could be members of the two phonon quadrupole excitation and involve a double nuclear excitation process. (author) [French] On sait que la diffusion inelastique des particules alpha de moyenne energie excite preferentiellement des niveaux de caractere collectif. Nous avons etudie la diffusion des particules alpha de 44 MeV du cyclotron de Saclay par des isotopes separes de Ca, Fe, Ni, Cu, Zn. Dans la premiere partie nous exposons les theories de cette interaction. Dans la seconde nous decrivons le systeme experimental. Les resultats sont donnes dans la troisieme partie. Nous montrons que les niveaux excites preferentiellement pour {sup 40}Ca par diffusion ({alpha},{alpha}') sont de parite negative. Dans les noyaux pair-impair nous avons observe des multiplets dus au couplage du nucleon celibataire avec les vibrations du coeur pair-pair. Pour les noyaux pair-pair nous avons pu etudier entre le premier niveau 2{sup +} et le niveau 3{sup -} deja bien connus certains etats plus faiblement excites. Il semble qu'ils sont dus a une excitation quadrupolaire a deux phonons et impliquent un processus de double excitation nucleaire. (auteur)

  1. Particle dispersion modeling in FFB/pipes

    Energy Technology Data Exchange (ETDEWEB)

    Wu, B.X.; Chang, S.L.; Lottes, S.; Petrick, M. [Academia Sinica, Beijing (China). Multiphase Reaction Lab.

    1995-12-31

    In this paper a new idea on the active behaviour of particles in its dispersion process in fast fluidized beds (FFB)/pipes is presented. Following a review of some preparatory modelling efforts, a new particle dispersion model and, associated with it, a system of particle transport equations suitable for FFB/pipes application are described. The preliminary numerical results verify that the new model is reasonable. 16 refs., 4 figs., 1 tab.

  2. ON THE RELATIVE SPEED AND TEMPERATURE RATIO OF SOLAR WIND ALPHA PARTICLES AND PROTONS: COLLISIONS VERSUS WAVE EFFECTS

    International Nuclear Information System (INIS)

    We study the relative flow speed and the temperature ratio of alpha particles and protons and their connections to the helium ion abundance, the collisional age, and the power of transverse fluctuations within the inertial range. It is found that the alpha-to-proton temperature ratio, Tα/Tp , anti-correlates with the helium ion abundance. Despite a relatively high collisional age and small wave power, the ratio Tα/Tp can reach comparatively high values (even above 2) whenever the helium ion abundance is below about 0.02. In contrast, the differential speed of alpha particles with respect to protons is correlated with the total wave power and anti-correlated with the collisional age. Ultimately, the individual heating of each ion species is positively correlated with the total wave power. Our findings suggest that a high-friction collision could be efficient in reducing the differential speed between alpha particles and protons, but appears not to be sufficient to equalize the alpha and proton temperatures, i.e., to make Tα ≅ Tp . This is a hint that the local wave heating process is acting on a timescale shorter than the collision time.

  3. Angular and velocity distributions of secondary particles emitted in interaction of 3. 6-GeV/nucleon. cap alpha. particles and lead nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Antonenko, V.G.; Vinogradov, A.A.; Galitskii, V.M.; Grigor' yan, Y.I.; Ippolitov, M.S.; Karadzhev, K.V.; Kuz' min, E.A.; Man' ko, V.I.; Ogloblin, A.A.; Paramonov, V.V.; Tsvetkov, A.A.

    1980-04-01

    The technique is described and results presented of measurements of the velocity and angular distributions of pions, protons, and deuterons, and tritons emitted in bombardment of lead nuclei by ..cap alpha.. particles with energy 3.6 GeV/nucleon.

  4. Astrophysics and particle physics in space with the Alpha Magnetic Spectrometer

    CERN Document Server

    Lamanna, G

    2003-01-01

    The Alpha Magnetic Spectrometer is a high energy particle physics experiment in space scheduled to be installed on the International Space Station (ISS) by 2006 for a three-year mission. After a precursor flight of a prototype detector on board of the NASA Space Shuttle in June 1998, the construction of the detector in its final configuration is started and it will be completed by 2004. The purpose of this experiment is to provide a high statistics measurement of charged particles and nuclei in rigidity range 0.5 GV to few TV and to explore the high-energy (>1 GeV) gamma-ray sky. In this paper we describe the detector layout and present an overview of the main scientific goals both in the domain of astrophysics: cosmic- ray origin, age and propagation and the exploration of the most energetic gamma-ray sources; and in the domain of astroparticle: the antimatter and the dark matter searches. (53 refs).

  5. Modeling the Lyman-alpha Forest in Collisionless Simulations

    CERN Document Server

    Sorini, Daniele; Lukić, Zarija; Hennawi, Joseph F

    2016-01-01

    Cosmological hydrodynamic simulations can accurately predict the properties of the intergalactic medium (IGM), but only under the condition of retaining high spatial resolution necessary to resolve density fluctuations in the IGM. This resolution constraint prohibits simulating large volumes, such as those probed by BOSS and future surveys, like DESI and 4MOST. To overcome this limitation, we present Iteratively Matched Statistics (IMS), a novel method to accurately model the Lyman-alpha forest with collisionless N-body simulations, where the relevant density fluctuations are unresolved. We use a small-box, high-resolution hydrodynamic simulation to obtain the probability distribution function (PDF) and the power spectrum of the real-space Lyman-alpha forest flux. These two statistics are iteratively mapped onto a pseudo-flux field of an N-body simulation, which we construct from the matter density. We demonstrate that our method can perfectly reproduce line-of-sight observables, such as the PDF and power spe...

  6. Design of a preamplifier for an alpha particles spectrometer; Diseno de un preamplificador para un espectrometro de particulas alfa

    Energy Technology Data Exchange (ETDEWEB)

    Murillo O, R.; Hernandez D, V. M.; Chacon R, A.; Vega C, H. R., E-mail: fermineutron@yahoo.co [Universidad Autonoma de Zacatecas, Unidades Academicas de Estudios Nucleares e Ingenieria Electrica, Calle Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico)

    2010-09-15

    To detect radiation diverse detector types are used, when these are alpha particles proportional type detectors are used, semiconductor, of scintillation or traces. In this work the design results, the construction and the first tests of a spectrometer (preamplifier) are presented for alpha particles that was designed starting from a Pin type photodiode. The system was designed and simulated with a program for electronic circuits. With the results of the simulation phase was constructed the electronics that is coupled to a spectroscopic amplifier and a multichannel analyzer. The total of the system is evaluated analyzing its performance before a triple source of alphas and that they are produced by two smoke detectors of domestic use. Of the tests phase we find that the system allows to obtain in a multichannel, the pulses height spectrum, with which we calibrate the system. (Author)

  7. Moisture content of seeds affects relative biological effectiveness of alpha particles but not protons in thermal neutron exposure

    International Nuclear Information System (INIS)

    The influences of moisture content of barley (Hordeum vulgare L.) seeds which were presoaked for 13 h and re-dried before irradiation on boron addition effect (BAE) and relative biological effectiveness (RBE) of alpha particles and protons were evaluated. Seeds of normal (10.21% in embryo), low (2.55%) and high (28.0%) moisture content showed different regression of BAE values on the absorbed amount of sup(10)B. The regression coefficient was highest for normal moisture content, followed by low moisture content, and the lowest for high moisture content. RBE of alpha particles also significantly differed between the moisture contents. Seeds of normal, low and high moisture contents showed 46.4, 37.4 and 17.0 of RBE value, respectively. Contrarily, RBE values of protons did not significantly vary with moisture content. It was found that the ratio of RBE of alpha particles between different moisture contents could be expressed by the product of the three ratios, i.e. ratio of sensitivity to gamma-rays, ratio of BAE, and ratio of moisture content. It was concluded that adjustment of moisture of the seeds to normal content (about 10%) is important to get a high value of both BAE and RBE of alpha particles

  8. Structural and optical investigation on alpha particle irradiated CR-39 surface coated by MEH-PPV conducting polymer

    International Nuclear Information System (INIS)

    Highlights: • The CR-39 polymeric surface was exposed to alpha particles. • Dip coating of CR-39 surface was done using MEH-PPV conducting polymer. • FTIR is insensitive approach to detect the induced modifications in the irradiated surfaces. • Photoluminescence and UV–Vis responses exhibited remarkable spectral differences. • Both techniques could be used to provide sensitive methods for alpha particle detection. - Abstract: Photoluminescence and UV–Vis spectral evaluation of a poly allyl diglycol carbonate (CR-39) detector coated by poly(2-methoxy-5-(2-ethyl-hexyloxy)-1,4-phenylene-vinylene) (MEH-PPV) conducting polymer are demonstrated. The CR-39 surfaces were exposed to thin 241Am disk source that emits alpha particles with activity 333 kBq. Surface modification of the detector by MEH-PPV was acquired by a simple dip coating process. Our findings revealed that the spectroscopic analysis using FTIR is insensitive approach to detect the induced modifications in the irradiated samples. Additionally, the track density of the irradiated samples affects significantly the photoluminescence and UV–Vis responses of the CR-39 samples. The spectral peak heights and the integrated intensities under the peaks exhibit linear correlations (correlation coefficient R2 = 0.9904 to 0.9968) with the fluence of alpha particles. The linear fitting functions together with the corresponding fitting parameters were evaluated. Both techniques exhibited remarkable spectral differences for the irradiated samples, and hence they could be employed to provide sensitive methods for alpha particle detection. Results of sample fabrication and modification, along with structural and optical evaluation are addressed and thoroughly discussed

  9. Low doses of alpha particles do not induce sister chromatid exchanges in bystander Chinese hamster cells defective in homologous recombination

    Energy Technology Data Exchange (ETDEWEB)

    Nagasawa, H; Wilson, P F; Chen, D J; Thompson, L H; Bedford, J S; Little, J B

    2007-10-26

    We reported previously that the homologous recombinational repair (HRR)-deficient Chinese hamster mutant cell line irs3 (deficient in the Rad51 paralog Rad51C) showed only a 50% spontaneous frequency of sister chromatid exchange (SCE) as compared to parental wild-type V79 cells. Furthermore, when irradiated with very low doses of alpha particles, SCEs were not induced in irs3 cells, as compared to a prominent bystander effect observed in V79 cells (Nagasawa et al., Radiat. Res. 164, 141-147, 2005). In the present study, we examined additional Chinese hamster cell lines deficient in the Rad51 paralogs Rad51C, Rad51D, Xrcc2, and Xrcc3 as well as another essential HRR protein, Brca2. Spontaneous SCE frequencies in non-irradiated wild-type cell lines CHO, AA8 and V79 were 0.33 SCE/chromosome, whereas two Rad51C-deficient cell lines showed only 0.16 SCE/chromosome. Spontaneous SCE frequencies in cell lines defective in Rad51D, Xrcc2, Xrcc3, and Brca2 ranged from 0.23-0.33 SCE/chromosome, 0-30% lower than wild-type cells. SCEs were induced significantly 20-50% above spontaneous levels in wild-type cells exposed to a mean dose of 1.3 mGy of alpha particles (<1% of nuclei traversed by an alpha particle). However, induction of SCEs above spontaneous levels was minimal or absent after {alpha}-particle irradiation in all of the HRR-deficient cell lines. These data suggest that Brca2 and the Rad51 paralogs contribute to DNA damage repair processes induced in bystander cells (presumably oxidative damage repair in S-phase cells) following irradiation with very low doses of alpha particles.

  10. Direct photon pair production at the LHC to order alpha_s in TeV scale gravity models

    OpenAIRE

    Kumar, M. C.; Mathews, Prakash; Ravindran, V.; Tripathi, Anurag

    2009-01-01

    The first results on next-to-leading order QCD corrections to production of direct photon pairs in hadronic collisions in the large extra dimension models- ADD and RS are presented. Various kinematical distributions are obtained to order alpha_s in QCD by taking into account all the parton level subprocesses. Our Monte Carlo based code incorporates all the experimental cuts suitable for physics studies at the LHC. We estimate the impact of the QCD corrections on various observables and find t...

  11. Discrete Element Modeling of Triboelectrically Charged Particles

    Science.gov (United States)

    Hogue, Michael D.; Calle, Carlos I.; Weitzman, Peter S.; Curry, David R.

    2008-01-01

    Tribocharging of particles is common in many processes including fine powder handling and mixing, printer toner transport and dust extraction. In a lunar environment with its high vacuum and lack of water, electrostatic forces are an important factor to consider when designing and operating equipment. Dust mitigation and management is critical to safe and predictable performance of people and equipment. The extreme nature of lunar conditions makes it difficult and costly to carry out experiments on earth which are necessary to better understand how particles gather and transfer charge between each other and with equipment surfaces. DEM (Discrete Element Modeling) provides an excellent virtual laboratory for studying tribocharging of particles as well as for design of devices for dust mitigation and for other purposes related to handling and processing of lunar regolith. Theoretical and experimental work has been performed pursuant to incorporating screened Coulombic electrostatic forces into EDEM, a commercial DEM software package. The DEM software is used to model the trajectories of large numbers of particles for industrial particulate handling and processing applications and can be coupled with other solvers and numerical models to calculate particle interaction with surrounding media and force fields. While simple Coulombic force between two particles is well understood, its operation in an ensemble of particles is more complex. When the tribocharging of particles and surfaces due to frictional contact is also considered, it is necessary to consider longer range of interaction of particles in response to electrostatic charging. The standard DEM algorithm accounts for particle mechanical properties and inertia as a function of particle shape and mass. If fluid drag is neglected, then particle dynamics are governed by contact between particles, between particles and equipment surfaces and gravity forces. Consideration of particle charge and any tribocharging and

  12. Exploring the Standard Model of Particles

    Science.gov (United States)

    Johansson, K. E.; Watkins, P. M.

    2013-01-01

    With the recent discovery of a new particle at the CERN Large Hadron Collider (LHC) the Higgs boson could be about to be discovered. This paper provides a brief summary of the standard model of particle physics and the importance of the Higgs boson and field in that model for non-specialists. The role of Feynman diagrams in making predictions for…

  13. New Electroweak Model Without a Higgs Particle

    Institute of Scientific and Technical Information of China (English)

    WUNing

    2002-01-01

    A new unified electroweak model is proposed in this paper,In this unified electroweak model,Higgs echanism is not used.So no Higgs particle exists in the model.In order to keep the masses of intermediate gauge bosons non-zero,two sets of gauge fields will be introduced.In order to introduce symmetry breaking and to help to introduce the masses of all fileds.a vacuum potential is needed.Except for those terms concerning Higgs particle,the fundamental dynamical properties of this model are similar to those of the standard model.And in a proper limit,this model with approximately return to the standard model.The purpose of this paper is not to say that the Higgs particle does not exist in Nature,it is only to prove that,without a Higgs particle,we can also set up a unified electroweak model which is consistent with present experiments.

  14. Stability and {alpha}-particle confinement in the Sphellamak reactor concept

    Energy Technology Data Exchange (ETDEWEB)

    Cooper, W. Anthony; Fischer, Olivier [Ecole Polytechnique Federale de Lausanne, Centre de Recherches en Physique des Plasmas (CRPP), CH-1015 Lausanne (Switzerland)

    2000-10-01

    The Sphellamak is a coreless hybrid system with Tokamak, Stellarator and Spheromak features.The absence of a central conductor permits the realisation of a compact toroidal system, as internal shielding becomes un- necessary. With a peaked toroidal current profile, a sequence of reactor-sized Sphellamak equilibria is computed numerically in which the current in the helical coils I{sub hc} is varied while the toroidal plasma current I{sub p} = -30 MA and the volume average {beta} = 7.3% remain fixed. Ideal global external kink modes are weakly unstable but indicate stability for I{sub hc} > 138 MA. The local ideal magnetohydrodynamic stability criteria are satisfied in the range 42 MA < I{sub hc} < 122 MA. The peaked toroidal current generates local maximal of the modulus of the magnetic field strength in the central region of the plasma, which has very favourable implications for energetic and thermal particle confinement. This is confirmed through the computation of a very small {alpha}-particle guiding centre orbit loss fraction. (author) [French] Le Sphellamak est un systeme hybride sans noyau central compose par des elements de Tokamak, de Stellerateur et de Spheromak. L'absence de colonne centrale permet la realisation d 'un systeme toroidal compact puisque le manteau de protection interne ne devient plus necessaire. Avec un profil de courant pique, une sequence d 'equilibres Sphellamak de dimension reacteur est calculee numeriquement en variant le courant des bobines helicoidales I{sub hc} tout en fixant le courant toroidal du plasma I{sub p} = -30 MA ainsi que la moyenne volumique {beta} = 7.3%. Les modes globaux externes du type kink sont faiblement instables mais suffisent a garantir la stabilite pour I{sub hc} > 138 MA. Les criteres de stabilite magnetohydrodynamique ideale locale sont realises pour des courants de 42 MA < I{sub hc} < 122 MA. Le courant toroidal pique pro- duit localement des valeurs maximales pour le module du champs

  15. Computation of Cosmic Ray Ionization and Dose at Mars: a Comparison of HZETRN and Planetocosmics for Proton and Alpha Particles

    Science.gov (United States)

    Gronoff, Guillaume; Norman, Ryan B.; Mertens, Christopher J.

    2014-01-01

    The ability to evaluate the cosmic ray environment at Mars is of interest for future manned exploration. To support exploration, tools must be developed to accurately access the radiation environment in both free space and on planetary surfaces. The primary tool NASA uses to quantify radiation exposure behind shielding materials is the space radiation transport code, HZETRN. In order to build confidence in HZETRN, code benchmarking against Monte Carlo radiation transport codes is often used. This work compares the dose calculations at Mars by HZETRN and the Geant4 application Planetocosmics. The dose at ground and the energy deposited in the atmosphere by galactic cosmic ray protons and alpha particles has been calculated for the Curiosity landing conditions. In addition, this work has considered Solar Energetic Particle events, allowing for the comparison of varying input radiation environments. The results for protons and alpha particles show very good agreement between HZETRN and Planetocosmics.

  16. Modeling and simulation of bubbles and particles

    Science.gov (United States)

    Dorgan, Andrew James

    The interaction of particles, drops, and bubbles with a fluid (gas or liquid) is important in a number of engineering problems. The present works seeks to extend the understanding of these interactions through numerical simulation. To model many of these relevant flows, it is often important to consider finite Reynolds number effects on drag, lift, torque and history force. Thus, the present work develops an equation of motion for spherical particles with a no-slip surface based on theoretical analysis, experimental data and surface-resolved simulations which is appropriate for dispersed multiphase flows. The equation of motion is then extended to account for finite particle size. This extension is critical for particles which will have a size significantly larger than the grid cell size, particularly important for bubbles and low-density particles. The extension to finite particle size is accomplished through spatial-averaging (both volume-based and surface-based) of the continuous flow properties. This averaging is consistent with the Faxen limit for solid spheres at small Reynolds numbers and added mass and fluid stress forces at inviscid limits. Further work is needed for more quantitative assessment of the truncation terms in complex flows. The new equation of motion is then used to assess the relative importance of each force in the context of two low-density particles (an air bubble and a sand particle) in a boundary layer of water. This relative importance is measured by considering effects on particle concentration, visualization of particle-fluid interactions, diffusion rates, and Lagrangian statistics collected along the particle trajectory. Strong added mass and stress gradient effects are observed for the bubble but these were found to have little effect on a sand particle of equal diameter. Lift was shown to be important for both conditions provided the terminal velocity was aligned with the flow direction. The influence of lift was found to be

  17. Optical potentials and isoscalar transition rates from 104 MeV alpha-particle scattering by the N=28 isotopes 48Ca, 50Ti and 52Cr

    International Nuclear Information System (INIS)

    Precisely measured differential cross sections for elastic and inelastic scattering from 104 MeV alpha-particles by 48Ca, 50Ti and 52Cr are reported. The analyses aim primarily at the determination of strength, radial shapes and deformation of the scattering potentials, looking for isotonic differences of N = 28 isotones. The mean square radii of the (real) potentials are discussed in terms of mean square radius differences of the matter distributions. The isoscalar transition rates derived by coupled channel analyses of the measured cross sections are compared with electromagnetic rates. In addition to the analyses on the basis of a slightly generalized extended optical model a semi-microscopic deformed folding model has been applied, using a density-dependent effective alpha-bound nucleon interaction. Though an excellent description of the data over the full angular range is obtained the resulting values of the deformation parameters appear to be not consistent with results from various different methods. (orig.)

  18. Alpha-Calcitonin Gene-Related Peptide Can Reverse The Catabolic Influence Of UHMWPE Particles On RANKL Expression In Primary Human Osteoblasts

    Directory of Open Access Journals (Sweden)

    Max D. Kauther, Jie Xu, Christian Wedemeyer

    2010-01-01

    Full Text Available Background and purpose: A linkage between the neurotransmitter alpha-calcitonin gene-related peptide (alpha-CGRP and particle-induced osteolysis has been shown previously. The suggested osteoprotective influence of alpha-CGRP on the catabolic effects of ultra-high molecular weight polyethylene (UHMWPE particles is analyzed in this study in primary human osteoblasts. Methods: Primary human osteoblasts were stimulated by UHMWPE particles (cell/particle ratios 1:100 and 1:500 and different doses of alpha-CGRP (10-7 M, 10-9 M, 10-11 M. Receptor activator of nuclear factor-κB ligand (RANKL and osteoprotegerin (OPG mRNA expression and protein levels were measured by RT-PCR and Western blot. Results: Particle stimulation leads to a significant dose-dependent increase of RANKL mRNA in both cell-particle ratios and a significant down-regulation of OPG mRNA in cell-particle concentrations of 1:500. A significant depression of alkaline phosphatase was found due to particle stimulation. Alpha-CGRP in all tested concentrations showed a significant depressive effect on the expression of RANKL mRNA in primary human osteoblasts under particle stimulation. Comparable reactions of RANKL protein levels due to particles and alpha-CGRP were found by Western blot analysis. In cell-particle ratios of 1:100 after 24 hours the osteoprotective influence of alpha-CGRP reversed the catabolic effects of particles on the RANKL expression. Interpretation: The in-vivo use of alpha-CGRP, which leads to down-regulated RANKL in-vitro, might inhibit the catabolic effect of particles in conditions of particle induced osteolysis.

  19. Present status of alpha-particle condensate states in self-conjugate 4n nuclei

    International Nuclear Information System (INIS)

    Low density states near the 3α and 4α breakup threshold in 12C and 16O, respectively, are discussed in terms of the α-particle condensation. Calculations are performed in OCM (Orthogonality Condition Model) and THSR (Tohsaki-Horiuchi-Schuck-Roepke) approaches. The 02+ state in 12C and the 06+ state in 16C are shown to have dilute density structures and give strong enhancement of the occupation of the S-state c.o.m. orbital of the α-particles. The 06+ state in 16C has a large component of α + 12C(02+) configuration, which is another reliable evidence of the state to be of 4α condensate nature. The possibility of the existence of α-particle condensed states in heavier nα nuclei is also discussed. (author)

  20. Development of thin foil Faraday collector as a lost alpha particle diagnostic for high yield D-T tokamak fusion plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Van Belle, P.; Jarvis, O.N.; Sadler, G.J. [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking; Cecil, F.E. [Colorado School of Mines, Golden, CO (United States)

    1994-07-01

    Alpha particle confinement is necessary for ignition of a D-T tokamak fusion plasma and for first wall protection. Due to high radiation backgrounds and temperatures, scintillators and semiconductor detectors may not be used to study alpha particles which are lost to the first wall during the D-T programs on JET and ITER. An alternative method of charged particle spectrometry capable of operation in these harsh environments, is proposed: it consists of thin foils of electrically isolated conductors with the flux of alpha particles determined by the positive current flowing from the foils. 2 refs., 3 figs.

  1. The Alpha Particle X-Ray Spectrometer (APXS): Results from Gusev Crater and Calibration Report

    Science.gov (United States)

    Gellert, R.; Rieder, R.; Brueckner, J.; Clark, B.; Dreibus, G.; Klingelhoefer, G.; Lugmair, G.; Ming, D.; Waenke, H.; Yen, A.; Zipfel, J.; Squyres, S.

    2006-01-01

    The chemical composition of rocks and soils on Mars analyzed during the Mars Exploration Rover Spirit Mission was determined by X-ray analyses with the Alpha Particle X-Ray Spectrometer (APXS). Details of the data analysis method and the instrument calibration are presented. Measurements performed on Mars to address geometry effects and background contributions are shown. Cross calibration measurements among several instrument sensors and sources are discussed. An unintentional swap of the two flight instruments is evaluated. New concentration data acquired during the first 470 sols of rover Spirit in Gusev Crater are presented. There are two geological regions, the Gusev plains and the Columbia Hills. The plains contain soils that are very similar to previous landing sites on Mars. A meteoritic component in the soil is identified. Rocks in the plains revealed thin weathering rinds. The underlying abraded rock was classified as primitive basalt. One of these rocks contained significant Br that is probably associated with vein-filling material of different composition. One of the trenches showed large subsurface enrichments of Mg, S, and Br. Disturbed soils and rocks in the Columbia Hills revealed different elemental compositions. These rocks are significantly weathered and enriched in mobile elements, such as P, S, Cl, or Br. Even abraded rock surfaces have high Br concentrations. Thus, in contrast to the rocks and soils in the Gusev Plains, the Columbia Hills material shows more significant evidence of ancient aqueous alteration.

  2. The blistering of 316L stainless steel irradiated with energetic alpha particles at 500 degrees C

    International Nuclear Information System (INIS)

    The physical process of blistering is investigated in the 316L stainless steel in both the solid solution and 20% cold-worked states. The material was irradiated with 1.8 MeV alpha particles to various fluences at 500deg C. There is a threshold fluence for blistering in the range of (0.869-1.346)x 1018 α/cm2. The microstructure, determined by TEM observation in the cross-section of irradiated samples, shows that the bubbles are accumulated at the surface layer. There is a bubble size and density distribution along the direction of depth. The bubble size and swelling increase progressively from the edge of the specimen to the damage peak region (DPR), then decrease. After 3 μm there are no bubbles. Due to bubble formation the thermal conductivity of the surface layer becomes lower and the temperature increases due to the irradiation energy deposited. Beyond the threshold fluence, the temperature of the surface layer is high, bubble coalescence at DPR becomes more serious and the bubble pressure becomes high enough that blistering occurs. (orig.)

  3. Metallothionein bioconjugates as delivery vehicles for bismuth-212 alpha particle therapy

    International Nuclear Information System (INIS)

    Metallothioneins (MTHs) are small cysteine-rich polypeptides that binds cationic metals at physiologic pH ranges through noncovalent -SH ligand interactions. Some leucine-rich renal MTHs have a particular avidity for bismuth. The authors have examined the ability of MTHs to selectively incorporate Bi-212, a short-lived high-energy alpha particle emitter currently under exploration as a potential therapeutic radiolabel for use in molecularly targeted cancer therapy. They find that under physiologic conditions, MTH will selectively incorporate Bi-212 after incubation with an equilibrium mixture of its upstream and downstream parents. The MTH moieties may be linked to tumor-binding macromolecules such as antibodies via thiolation reactions using SPDP, and the resultant Bismuth-avid molecules may be used either as primary delivery vehicles for the Bi-212 or as part of a 2-step release-and-catch isotope localization system in which the MTH-antibody conjugate is pre-localized at the tumor site and the radiometal is then administered and chelated in situ. They present the chemistry, dosimetry and potential clinical applications of this system

  4. Modeling particle deposition on HVAC heat exchangers

    International Nuclear Information System (INIS)

    Fouling of fin-and-tube heat exchangers by particle deposition leads to diminished effectiveness in supplying ventilation and air conditioning. This paper explores mechanisms that cause particle deposition on heat exchanger surfaces. We present a model that accounts for impaction, diffusion, gravitational settling, and turbulence. Simulation results suggest that some submicron particles deposit in the heat exchanger core, but do not cause significant performance impacts. Particles between 1 and 10(micro)m deposit with probabilities ranging from 1-20% with fin edge impaction representing the dominant mechanism. Particles larger than 10(micro)m deposit by impaction on refrigerant tubes, gravitational settling on fin corrugations, and mechanisms associated with turbulent airflow. The model results agree reasonably well with experimental data, but the deposition of larger particles at high velocities is underpredicted. Geometric factors, such as discontinuities in the fins, are hypothesized to be responsible for the discrepancy

  5. Modeling of magnetic particle suspensions for simulations

    CERN Document Server

    Satoh, Akira

    2016-01-01

    The main objective of the book is to highlight the modeling of magnetic particles with different shapes and magnetic properties, to provide graduate students and young researchers information on the theoretical aspects and actual techniques for the treatment of magnetic particles in particle-based simulations. In simulation, we focus on the Monte Carlo, molecular dynamics, Brownian dynamics, lattice Boltzmann and stochastic rotation dynamics (multi-particle collision dynamics) methods. The latter two simulation methods can simulate both the particle motion and the ambient flow field simultaneously. In general, specialized knowledge can only be obtained in an effective manner under the supervision of an expert. The present book is written to play such a role for readers who wish to develop the skill of modeling magnetic particles and develop a computer simulation program using their own ability. This book is therefore a self-learning book for graduate students and young researchers. Armed with this knowledge,...

  6. Model stars for the modelling of galaxies: $\\alpha$-enhancement in stellar populations models

    CERN Document Server

    Coelho, P

    2008-01-01

    Stellar population (SP) models are an essential tool to understand the observations of galaxies and clusters. One of the main ingredients of a SP model is a library of stellar spectra, and both empirical and theoretical libraries can been used for this purpose. Here I will start by giving a short overview of the pros and cons of using theoretical libraries, i.e. model stars, to produce our galaxy models. Then I will address the question on how theoretical libraries can be used to model stellar populations, in particular to explore the effect of $\\alpha$-enhancement on spectral observables.

  7. A Bayesian approach to the modelling of alpha Cen A

    CERN Document Server

    Bazot, M; Christensen-Dalsgaard, J

    2012-01-01

    Determining the physical characteristics of a star is an inverse problem consisting in estimating the parameters of models for the stellar structure and evolution, knowing certain observable quantities. We use a Bayesian approach to solve this problem for alpha Cen A, which allows us to incorporate prior information on the parameters to be estimated, in order to better constrain the problem. Our strategy is based on the use of a Markov Chain Monte Carlo (MCMC) algorithm to estimate the posterior probability densities of the stellar parameters: mass, age, initial chemical composition,... We use the stellar evolutionary code ASTEC to model the star. To constrain this model both seismic and non-seismic observations were considered. Several different strategies were tested to fit these values, either using two or five free parameters in ASTEC. We are thus able to show evidence that MCMC methods become efficient with respect to more classical grid-based strategies when the number of parameters increases. The resul...

  8. Particle hopping models and traffic flow theory

    OpenAIRE

    Nagel, Kai

    1995-01-01

    This paper shows how particle hopping models fit into the context of traffic flow theory. Connections between fluid-dynamical traffic flow models, which derive from the Navier-Stokes-equations, and particle hopping models are shown. In some cases, these connections are exact and have long been established, but have never been viewed in the context of traffic theory. In other cases, critical behavior of traffic jam clusters can be compared to instabilities in the partial differential equations...

  9. Amelioration of psoriasis by anti-TNF-alpha RNAi in the xenograft transplantation model

    DEFF Research Database (Denmark)

    Jakobsen, Maria; Stenderup, Karin; Rosada, Cecilia; Moldt, Brian; Kamp, Søren; Dam, Tomas N; Jensen, Thomas G; Mikkelsen, Jacob Giehm

    2009-01-01

    Tumor necrosis factor-alpha (TNF-alpha) is upregulated in psoriatic skin and represents a prominent target in psoriasis treatment. The level of TNF-alpha-encoding mRNA, however, is not increased in psoriatic skin, and it remains unclear whether intervention strategies based on RNA interference...... skin in the psoriasis xenograft transplantation model by the use of lentiviral vectors. TNF-alpha shRNA treatment leads to amelioration of the psoriasis phentotype in the model, as documented by reduced epidermal thickness, normalization of the skin morphology, and reduced levels of TNF-alpha mRNA as...... detected in skin biopsies 3 weeks after a single vector injection of lentiviral vectors encoding TNF-alpha shRNA. Our data show efficient lentiviral gene delivery to psoriatic skin and therapeutic applicability of anti-TNF-alpha shRNAs in human skin. These findings validate TNF-alpha mRNA as a target...

  10. Observations and Modeling of Geospace Energetic Particles

    Science.gov (United States)

    Li, Xinlin

    2016-07-01

    Comprehensive measurements of energetic particles and electric and magnetic fields from state-of-art instruments onboard Van Allen Probes, in a geo-transfer-like orbit, revealed new features of the energetic particles and the fields in the inner magnetosphere and impose new challenges to any quantitative modeling of the physical processes responsible for these observations. Concurrent measurements of energetic particles by satellites in highly inclined low Earth orbits and plasma and fields by satellites in farther distances in the magnetospheres and in the up stream solar wind are the critically needed information for quantitative modeling and for leading to eventual accurate forecast of the variations of the energetic particles in the magnetosphere. In this presentation, emphasis will be on the most recent advance in our understanding of the energetic particles in the magnetosphere and the missing links for significantly advance in our modeling and forecasting capabilities.

  11. Polarizable water model for Dissipative Particle Dynamics

    Science.gov (United States)

    Pivkin, Igor; Peter, Emanuel

    2015-11-01

    Dissipative Particle Dynamics (DPD) is an efficient particle-based method for modeling mesoscopic behavior of fluid systems. DPD forces conserve the momentum resulting in a correct description of hydrodynamic interactions. Polarizability has been introduced into some coarse-grained particle-based simulation methods; however it has not been done with DPD before. We developed a new polarizable coarse-grained water model for DPD, which employs long-range electrostatics and Drude oscillators. In this talk, we will present the model and its applications in simulations of membrane systems, where polarization effects play an essential role.

  12. Study of the stopping power and straggling for alpha particles and protons in organic solids, liquids and gases

    International Nuclear Information System (INIS)

    The stopping power and straggling for 5.5 MeV alpha particles in liquid and vapour phases of water, methanol, ethanol, propanol, h-hexane, n-octane and cyclohexane, and those for low energy protons in ethylene, styrene and propylene and their polymers, have been measured. Range-energy data have been fitted with inverse stopping power functions to give the cross sections. In each case, five parameters have been adjusted to obtain the best fit. The value of chi-squared per degree of freedom has been calculated, together with the parameters. The theoretical stopping cross section has been considered employing the Bethe-Bloch expression together with various corrections (shell correction using Walske and Bichsel procedure, Z13 contribution according to Ashley and Bloch correction based on Lindhard formalism). The existence of a phase effect has been clearly demonstrated for the stopping of both alpha particles and protons. (author)

  13. Differential gene expression in human fibroblasts after alpha-particle emitter (211)At compared with (60)Co irradiation

    DEFF Research Database (Denmark)

    Danielsson, Anna; Claesson, Kristina; Parris, Toshima Z; Helou, Khalil; Nemes, Szilárd; Elmroth, Kecke; Elgqvist, Jörgen; Jensen, Holger; Hultborn, Ragnar

    2013-01-01

    Purpose: The aim of this study was to identify gene expression profiles distinguishing alpha-particle (211)At and (60)Co irradiation. Materials and methods: Gene expression microarray profiling was performed using total RNA from confluent human fibroblasts 5 hours after exposure to (211)At labeled...... trastuzumab monoclonal antibody (0.25, 0.5, and 1 Gy) and (60)Co (1, 2, and 3 Gy). Results: We report gene expression profiles that distinguish the effect different radiation qualities and absorbed doses have on cellular functions in human fibroblasts. In addition, we identified commonly expressed transcripts...... transcription, cell cycle regulation, and cell cycle arrest, whereas mitosis, spindle assembly checkpoint, and apoptotic chromosome condensation were uniquely enriched for alpha particle irradiation. Conclusions: LET-dependent transcriptional modulations were observed in human fibroblasts 5 hours after...

  14. Energetic resolution study on pure and CsBr doped CsI under gamma excitations and alpha particles

    International Nuclear Information System (INIS)

    Pure and doped CsI crystals were grown using the Bridgman technique. Bromine was the doping element which was studied in the range of 1.5x10-1 M to 10-2 M. The distribution of the doping element at crystalline volume was determined by neutron activation. Concerning gamma radiation response it was carried out measurements to evaluate the developed scintillators in the energy range of 350 keV to 1330 keV. For alpha particles measurements an 241Am source was used with 5.54 MeV energy. The resolution of 3.7% was obtained for the CsI:Br 10-2 M crystal, when excited with alpha particles from an 241Am source. For CsI:Br 10-1 M crystal 9.1% resolution was obtained when excited with gamma radiation from 22Na source, with 1275 keV energy. (author)

  15. Study of influence of catechins on bystander responses in alpha-particle radiobiological experiments using thin PADC films

    Energy Technology Data Exchange (ETDEWEB)

    Law, Y.L. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong (Hong Kong); Yu, K.N., E-mail: peter.yu@cityu.edu.h [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong (Hong Kong)

    2009-10-15

    In this study, Chinese hamster ovary (CHO) cells were cultured in custom-made petri dishes with thin PADC films as substrates. Alpha particles with energies of 5 MeV were then irradiated from the bottom of PADC films. The DNA strand breaks in the bystander cells induced by irradiation were quantified with the use of terminal dUTP transferase-mediated nick end-labeling (TUNEL) assay. To study the influence of catechins on the bystander responses, catechins were added into the medium before alpha-particle irradiation of the cells. Fewer DNA strand breaks in the bystander cells were observed. As catechins are ROS (reactive oxygen species)-scavengers, the studied bystander cells might have been protected from radiation through scavenging of ROS by catechins.

  16. Comparative cytotoxicity, mutagenicity, and transforming potency of X-rays, alpha particles and MNNG for rat tracheal epithelial cells

    International Nuclear Information System (INIS)

    To characterize the potential roles of high- and low-LET radiation in respiratory carcino-genesis, the biological effects of X rays and alpha particles on rat tracheal epithelial (RTE) cells were determined and compared to the effects of the direct-acting carcinogen, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Each agent caused logarithmic, dose-dependent killing of RTE cells, although the curve for X rays had a significant shoulder. At equitoxic doses, all three agents induced similar frequencies of preneoplastic transformation. Similarly, each agent was capable of inducing a similar level of mutations in RTE cell lines. These data suggest that both high- and low-LET radiation can induce changes involved in early stages of carcinogenesis. In addition, it suggests that inactivation of critical genes, caused by alpha particle-induced deletions, may play a role in the preneoplastic transformation of RTE cells. (author)

  17. Increase in the area of etched alpha-particle tracks in CR-39 plastic with increasing storage time under nitrogen

    CERN Document Server

    Bhakta, J R; Miles, J C H

    1999-01-01

    The area of etched tracks in CR-39 (polyallyl diglycol carbonate, PADC) exposed to alpha-particles from an americium-241 source has been investigated as a function of post-exposure storage time in a dry nitrogen atmosphere. Data were collected over 2.5 years and the results show that the nominal maximum area of the track area distribution increases with increasing storage time.

  18. Formation of blisters in tantalum by 30 MeV alpha particle bombardment

    International Nuclear Information System (INIS)

    The phenomenon of radiation blistering by helium ion bombardment has been the subject of extensive studies in recent years because of its technological importance in thermonuclear fusion devices and reactors. However, the mechanism of radiation blistering is still not well understood. There are two different models of blister formation: the gas-pressure model and the lateral stress model. The former model is, however, supported by many experimental observations, the prominent one is that of Evans and Eyre who observed blisters appearing on the front and rear surfaces of a thin wedge-shaped molybdenum foil irradiated by helium ions. Their experiment also indicates that the thickness of the irradiated specimen could be important in affecting the characteristics of blisters. With this in view, we have studied the development of blisters in thin foils of tantalum by 30 MeV α-particle bombardment. (orig.)

  19. Scintillation response of CsI: Tl crystal under neutron, gamma, alpha particles and beta excitations

    International Nuclear Information System (INIS)

    Among the converters of X and gamma radiation in light photons, known as scintillators, the one which is the most efficient emits photons with a wavelength near 400 nm. Particularly, among them, the cesium iodine doped with thallium (CsI:Tl) crystal is that which matches better between the light emission spectrum (peak at 540 nm) and the quantum sensitivity curve of the photodiodes and CCD (Charge Coupled Device). This explains the renewed interest in using this crystal as scintillator. Although the CsI:Tl crystal is commercially available, its local development would give the possibility to obtain it in different geometric configurations and coupling. Moreover, there is a special interest in studying new conditions that will alter the properties of this crystal in order to achieve a optimal level of its functional characteristics. Having an efficient national scintillator with low cost is a strategic opportunity to study the response of a detector applied to different types of radiation. The crystal of cesium iodide activated with thallium (CsI:Tl) has a high gamma detection efficiency per unit volume. In this paper, the CsI:Tl crystal, grown by the vertical Bridgman technique in evacuated silica ampoules and with the purpose of use as radiation detectors, is described. To evaluate the scintillator, measures of the thallium distribution in the crystal volume were taken, with overall efficiency score. The scintillator response was studied through gamma radiation from sources of 137Cs, 60Co, 22Na, 54Mn, 131I and 99mTc; the beta radiation from source of 90Sr/90Y, alpha particles from 241Am source and the scintillator response to neutrons from Am/Be source. The energetic resolution for 137Cs gamma rays (662 keV) was 10%. The results showed the validity of using the CsI:Tl crystal developed in our laboratory, in many applications in the area of radiation detectors. (author)

  20. Production of helium and helium-hydrogen positive ion beams for the alpha particle measurement

    International Nuclear Information System (INIS)

    In order to produce diagnostic helium neutral beam for alpha particle measurement in nuclear fusion plant of deuterium-tritium reation, helium ion (He+) or helium-hydrogen ion (HeH+) beams of ∼20 keV have been considered as a primary beam. For He+ beam, it is important to produce focused high-current-density ion beam in order to pass through small apertures of alkali gas cell with an enough signal level. For HeH+ beam, conditions producing HeH+ has not been investigated in detail as yet. In order to extract these beams, focused high-current-density neutral beam system is applied. For He+ beam extraction of ∼22 kV, it is confirmed that current density of ∼86 mA/cm2 is achieved, whose value is close to necessary value in ITER. For HeH+ beam extraction in the case of ∼300 V acceleration, the production rate of HeH+ component increases with the increase of helium gas pressure ratio to hydrogen gas pressure when its value is > ∼75%. In the case of 25 kV acceleration, if 15% of total current (which includes H+, H2+, H3+, He+ and HeH+ components) is HeH+ component, current density of HeH+ is estimated as ∼13 mA/cm2, whose value is larger than necessary value in ITER. From melted traces of the target plate, it is estimated that the divergence angle is about ±0.8deg. (author)

  1. Effect of Alpha-Particle Energies on CR-39 Line-Shape Parameters using Positron Annihilation Technique

    Directory of Open Access Journals (Sweden)

    Lotfy Y. A.

    2006-07-01

    Full Text Available Polyally diglycol carbonate "CR-39" is widely used as etched track type particle detector. Doppler broadening positron annihilation (DBPAT provides direct information about core and valance electrons in (CR-39 due to radiation effects. It provides a non-destructive and non-interfering probe having a detecting efficiency. This paper reports the effect of irradiation alpha-particle intensity emitted from 241-Am (5.486 MeV source on the line shape S- and W-parameters for CR-39 samples. Modification of the CR-39 samples due to irradiation were studied using X-ray diffraction (XRD and scanning electron microscopy (SEM techniques.

  2. Dependence of alpha particle track diameter on the free volume holes size using positron annihilation lifetime technique

    Energy Technology Data Exchange (ETDEWEB)

    El-Gamal, S. [Physics Department, Faculty of Education, Ain Shams University, Roxy, 11711 Cairo (Egypt); Abdalla, Ayman M., E-mail: aymanabdalla62@hotmail.com [Physics Department, Faculty of Arts and Sciences, Najran University, Najran (Saudi Arabia); Centre for Advanced Materials and Nano-Engineering, Najran University, Najran 11001 (Saudi Arabia); Abdel-Hady, E.E. [Physics Department, Faculty of Science, Minia University, BO 61519, Minia (Egypt)

    2015-09-15

    The alpha particle track diameter dependence of the free volume holes size (V{sub f}) in DAM–ADC and CR-39 nuclear track detectors was investigated using positron annihilation lifetime technique. The effect of temperature on the alpha particle track diameter and free volume were also investigated in the T-range (RT-130 °C). The obtained results revealed that the values of ortho-positronium lifetime τ{sub 3} and V{sub f} increases while I{sub 3} slightly increases as T increases for the two detectors. The values of τ{sub 3}, V{sub f} and I{sub 3} are higher in CR-39 than DAM–ADC. The interpretation of obtained results is based on the fact that increasing T leads to significant enhancement of thermal expansion of the polymer matrix and consequently V{sub f} increases. The track diameter increases as T increases. This can be explained by the fact that the increase in T increases the crystal size and V{sub f} in the polymer. A relationship between V{sub f} and the alpha particle track diameter was obtained. Moreover results of detector irradiation, along with free volume evaluation are addressed and thoroughly discussed.

  3. Dependence of alpha particle track diameter on the free volume holes size using positron annihilation lifetime technique

    International Nuclear Information System (INIS)

    The alpha particle track diameter dependence of the free volume holes size (Vf) in DAM–ADC and CR-39 nuclear track detectors was investigated using positron annihilation lifetime technique. The effect of temperature on the alpha particle track diameter and free volume were also investigated in the T-range (RT-130 °C). The obtained results revealed that the values of ortho-positronium lifetime τ3 and Vf increases while I3 slightly increases as T increases for the two detectors. The values of τ3, Vf and I3 are higher in CR-39 than DAM–ADC. The interpretation of obtained results is based on the fact that increasing T leads to significant enhancement of thermal expansion of the polymer matrix and consequently Vf increases. The track diameter increases as T increases. This can be explained by the fact that the increase in T increases the crystal size and Vf in the polymer. A relationship between Vf and the alpha particle track diameter was obtained. Moreover results of detector irradiation, along with free volume evaluation are addressed and thoroughly discussed

  4. Calibration of a Thomson parabola ion spectrometer and Fujifilm imaging plate detectors for protons, deuterons, and alpha particles

    International Nuclear Information System (INIS)

    A Thomson parabola ion spectrometer has been designed for use at the Multiterawatt (MTW) laser facility at the Laboratory for Laser Energetics (LLE) at University of Rochester. This device uses parallel electric and magnetic fields to deflect particles of a given mass-to-charge ratio onto parabolic curves on the detector plane. Once calibrated, the position of the ions on the detector plane can be used to determine the particle energy. The position dispersion of both the electric and magnetic fields of the Thomson parabola was measured using monoenergetic proton and alpha particle beams from the SUNY Geneseo 1.7 MV tandem Pelletron accelerator. The sensitivity of Fujifilm BAS-TR imaging plates, used as a detector in the Thomson parabola, was also measured as a function of the incident particle energy over the range from 0.6 MeV to 3.4 MeV for protons and deuterons and from 0.9 MeV to 5.4 MeV for alpha particles. The device was used to measure the energy spectrum of laser-produced protons at MTW.

  5. Calibration of a Thomson parabola ion spectrometer and Fujifilm imaging plate detectors for protons, deuterons, and alpha particles

    Science.gov (United States)

    Freeman, C. G.; Fiksel, G.; Stoeckl, C.; Sinenian, N.; Canfield, M. J.; Graeper, G. B.; Lombardo, A. T.; Stillman, C. R.; Padalino, S. J.; Mileham, C.; Sangster, T. C.; Frenje, J. A.

    2011-07-01

    A Thomson parabola ion spectrometer has been designed for use at the Multiterawatt (MTW) laser facility at the Laboratory for Laser Energetics (LLE) at the University of Rochester. This device uses parallel electric and magnetic fields to deflect particles of a given mass-to-charge ratio onto parabolic curves on the detector plane. Once calibrated, the position of the ions on the detector plane can be used to determine the particle energy. The position dispersion of both the electric and magnetic fields of the Thomson parabola was measured using monoenergetic proton and alpha particle beams from the SUNY Geneseo 1.7 MV tandem Pelletron accelerator. The sensitivity of Fujifilm BAS-TR imaging plates, used as a detector in the Thomson parabola, was also measured as a function of the incident particle energy over the range from 0.6 MeV to 3.4 MeV for protons and deuterons and from 0.9 MeV to 5.4 MeV for alpha particles. The device was used to measure the energy spectrum of laser-produced protons at MTW.

  6. Scalar particles in superstring models

    International Nuclear Information System (INIS)

    The role played by scalar fields in superstring models is reviewed, with an emphasis on recent developments. The case of the dilaton and moduli fields is discussed in connection with the issues of spacetime duality and supersymmetry breaking. Constraints on the Higgs sector are reviewed in the different classes of models

  7. Effects of spins and resonance parities of 12C on the mechanism of emission of three alpha particles in the 11B (p, 3 α) reaction

    International Nuclear Information System (INIS)

    This research thesis reports the study of the mechanism of emission of alpha particles in the 11B (p, 3 α) reaction with respect to the effects of spins and parities of the various resonances met between 150 keV and 4 MeV. From an experimental point of view, the reaction has been studied by two methods: the detection of alpha particles by a semiconductor-based counter located at a given angle with respect to the beam direction and study of continuous spectra of alpha particles with respect to projectile energies, and recording, for a given resonance, of alpha-alpha coincidences by using the multi-parametric technique with two semiconductor-based sensors with a varying relative angular position. After a discussion of the main characteristics of resonance and of the mechanism of emission of alpha particles, the author first reports the theoretical study of a reaction producing three particles in the final state, and then reports the theoretical calculation of direct alpha spectrum shapes in the case of the 11B (p, 3 α) reaction (statistic hypothesis, hypothesis of interaction with two particles in the final state). The next part reports the experimental study of the 11B (p, 3 α) reaction

  8. The atmosphere of comet 67P/Churyumov-Gerasimenko diagnosed by charge-exchanged solar wind alpha particles

    Science.gov (United States)

    Simon Wedlund, C.; Kallio, E.; Alho, M.; Nilsson, H.; Stenberg Wieser, G.; Gunell, H.; Behar, E.; Pusa, J.; Gronoff, G.

    2016-03-01

    Context. The ESA/Rosetta mission has been orbiting comet 67P/Churyumov-Gerasimenko since August 2014, measuring its dayside plasma environment. The ion spectrometer onboard Rosetta has detected two ion populations, one energetic with a solar wind origin (H+, He2+, He+), the other at lower energies with a cometary origin (water group ions such as H2O+). He+ ions arise mainly from charge-exchange between solar wind alpha particles and cometary neutrals such as H2O. Aims: The He+ and He2+ ion fluxes measured by the Rosetta Plasma Consortium Ion Composition Analyser (RPC-ICA) give insight into the composition of the dayside neutral coma, into the importance of charge-exchange processes between the solar wind and cometary neutrals, and into the way these evolve when the comet draws closer to the Sun. Methods: We combine observations by the ion spectrometer RPC-ICA onboard Rosetta with calculations from an analytical model based on a collisionless neutral Haser atmosphere and nearly undisturbed solar wind conditions. Results: Equivalent neutral outgassing rates Q can be derived using the observed RPC-ICA He+/He2+ particle flux ratios as input into the analytical model in inverse mode. A revised dependence of Q on heliocentric distance Rh in AU is found to be Rh-7.06 between 1.8 and 3.3 AU, suggesting that the activity in 2015 differed from that of the 2008 perihelion passage. Conversely, using an outgassing rate determined from optical remote sensing measurements from Earth, the forward analytical model results are in relatively good agreement with the measured RPC-ICA flux ratios. Modelled ratios in a 2D spherically-symmetric plane are also presented, showing that charge exchange is most efficient with solar wind protons. Detailed cometocentric profiles of these ratios are also presented. Conclusions: In conclusion, we show that, with the help of a simple analytical model of charge-exchange processes, a mass-capable ion spectrometer such as RPC-ICA can be used as a

  9. Modeling proton and alpha elastic scattering in liquid water in Geant4-DNA

    Energy Technology Data Exchange (ETDEWEB)

    Tran, H.N., E-mail: tranngochoang@tdt.edu.vn [Division of Nuclear Physics, Ton Duc Thang University, Tan Phong Ward, District 7, Ho Chi Minh City (Viet Nam); Faculty of Applied Sciences, Ton Duc Thang University, Tan Phong Ward, District 7, Ho Chi Minh City (Viet Nam); El Bitar, Z. [Institut Pluridisciplinaire Hubert Curien/IN2P3/CNRS, Strasbourg (France); Champion, C. [Univ. Bordeaux, CENBG, UMR 5797, F-33170 Gradignan (France); CNRS, IN2P3, CENBG, UMR 5797, F-33170 Gradignan (France); Karamitros, M. [Univ. Bordeaux, CENBG, UMR 5797, F-33170 Gradignan (France); CNRS, IN2P3, CENBG, UMR 5797, F-33170 Gradignan (France); CNRS, INCIA, UMR 5287, F-33400 Talence (France); Bernal, M.A. [Instituto de FísicaGleb Wataghin, Universida de Estadual de Campinas, SP (Brazil); Francis, Z. [Université Saint Joseph, Faculty of Science, Department of Physics, Beirut (Lebanon); The Open University, Faculty of Science, Department of Physical Sciences, Walton Hall, MK7 6AA Milton Keynes (United Kingdom); Ivantchenko, V. [Ecoanalytica, 119899 Moscow (Russian Federation); Lee, S.B.; Shin, J.I. [Proton Therapy Center, National Cancer Center, 323 Ilsan-ro, Ilsandong-gu, Goyang-si, Gyeonggi-do 410-769 (Korea, Republic of); Incerti, S. [Univ. Bordeaux, CENBG, UMR 5797, F-33170 Gradignan (France); CNRS, IN2P3, CENBG, UMR 5797, F-33170 Gradignan (France)

    2015-01-15

    Elastic scattering of protons and alpha (α) particles by water molecules cannot be neglected at low incident energies. However, this physical process is currently not available in the “Geant4-DNA” extension of the Geant4 Monte Carlo simulation toolkit. In this work, we report on theoretical differential and integral cross sections of the elastic scattering process for 100 eV–1 MeV incident protons and for 100 eV–10 MeV incident α particles in liquid water. The calculations are performed within the classical framework described by Everhart et al., Ziegler et al. and by the ICRU 49 Report. Then, we propose an implementation of the corresponding classes into the Geant4-DNA toolkit for modeling the elastic scattering of protons and α particles. Stopping powers as well as ranges are also reported. Then, it clearly appears that the account of the elastic scattering process in the slowing-down of the charged particle improves the agreement with the existing data in particular with the ICRU recommendations.

  10. Alpha-1 Antitrypsin Investigations Using Animal Models of Emphysema.

    Science.gov (United States)

    Ni, Kevin; Serban, Karina A; Batra, Chanan; Petrache, Irina

    2016-08-01

    Animal models of disease help accelerate the translation of basic science discoveries to the bedside, because they permit experimental interrogation of mechanisms at relatively high throughput, while accounting for the complexity of an intact organism. From the groundbreaking observation of emphysema-like alveolar destruction after direct instillation of elastase in the lungs to the more clinically relevant model of airspace enlargement induced by chronic exposure to cigarette smoke, animal models have advanced our understanding of alpha-1 antitrypsin (AAT) function. Experimental in vivo models that, at least in part, replicate clinical human phenotypes facilitate the translation of mechanistic findings into individuals with chronic obstructive pulmonary disease and with AAT deficiency. In addition, unexpected findings of alveolar enlargement in various transgenic mice have led to novel hypotheses of emphysema development. Previous challenges in manipulating the AAT genes in mice can now be overcome with new transgenic approaches that will likely advance our understanding of functions of this essential, lung-protective serine protease inhibitor (serpin). PMID:27564666

  11. Polarizable protein model for Dissipative Particle Dynamics

    Science.gov (United States)

    Peter, Emanuel; Lykov, Kirill; Pivkin, Igor

    2015-11-01

    In this talk, we present a novel polarizable protein model for the Dissipative Particle Dynamics (DPD) simulation technique, a coarse-grained particle-based method widely used in modeling of fluid systems at the mesoscale. We employ long-range electrostatics and Drude oscillators in combination with a newly developed polarizable water model. The protein in our model is resembled by a polarizable backbone and a simplified representation of the sidechains. We define the model parameters using the experimental structures of 2 proteins: TrpZip2 and TrpCage. We validate the model on folding of five other proteins and demonstrate that it successfully predicts folding of these proteins into their native conformations. As a perspective of this model, we will give a short outlook on simulations of protein aggregation in the bulk and near a model membrane, a relevant process in several Amyloid diseases, e.g. Alzheimer's and Diabetes II.

  12. Binary Particle Model of Weak Interactions

    CERN Document Server

    Ndili, F N

    2011-01-01

    We introduce the new concept of binary particle as the basic matter unit that participates in weak interactions and not any one fermion singly. We state the quantum numbers of this binary particle, and show the concept leads us to a natural explanation of the standard model puzzle of the origin of flavor mixing and the CKM matrix. Certain other puzzles of the standard model such as the absence of flavor changing neutral currents (FCNC), are also explained naturally by the binary particle model. These puzzles are currently thought to be esoteric properties of electro weak interactions that have origins in physics beyond the standard model at some ultra high energy scales. We show that this is not necessarily the case.

  13. Studies of SSNTDs made from LR-115 in view of their applicability in radiobiological experiments with alpha particles

    Energy Technology Data Exchange (ETDEWEB)

    Doerschel, B. E-mail: doerschel@physik.tu-dresden.de; Hermsdorf, D.; Pieck, S.; Starke, S.; Thiele, H.; Weickert, F

    2003-06-01

    Radiobiological studies on cell monolayers irradiated by charged particles need to determine the number and position of particle traversals. Solid state nuclear track detectors used as basic substrate for the cell layers are in principle suitable for this purpose. The detector foils must be as thin as possible but still guaranteeing mechanical stability. Two types of LR-115, red coloured and colourless, were tested in the present work. The studies aimed at optimisation of the etching conditions and determination of the registration efficiency for alpha particles in a wide range of energies and angles of incidence. Specific requirements have to be fulfilled for application of the detector foils under the environmental conditions of radiobiological experiments. Most important are biocompatibility between detector and cells and registration properties insensible against special treatments, as UV sterilisation and cell plating prior to irradiation as well as cell incubation after the irradiation. The experimental studies performed with alpha particles showed that environmental conditions of radiobiological experiments do not change the registration properties of LR-115 detectors significantly.

  14. Nuclear densities of 1fsub(7/2) nuclei from elastic alpha-particle scattering

    International Nuclear Information System (INIS)

    The elastic scattering of 104 MeV α particles by sup(40,42,43,44,48)Ca, 50Ti, 51V, 52Cr has been analyzed by phenomenological and semimicroscopic optical potentials in order to get information on isotopic and isotonic differences of the α particle optical potentials and of nuclear matter densities. The phenomenological optical potentials based on a Fourier-Bessel description of the real part reveal different behaviour in size and shape for the isotonic chain as compared to the isotopic chain. Odd-even effects are also indicated to be different for isotones and isotopes. The semi-microscopic analyses use a single-folding model with a density-dependent effective αN-interaction including a realistic local density approximation. The calculated potentials are fully consistent with the phenomenological ones. Isopotic and isotonic differences of the nuclear matter densities obtained from the folding model in general show a similar behavior as the optical potential differences. The results on matter densities are compared to other investigations. (orig.)

  15. Alpha particle energy response of 1-mm-thick polycarbonate track detectors by 50 Hz-HV electrochemical etching method

    International Nuclear Information System (INIS)

    The electrochemical etching (ECE) method enlarges charged particle tracks to enhance its applications in particular in health physics and radiation dosimetry. The ECE method is usually based on using a high frequency-high voltage (HF-HV) generator with 250-μm-thick polycarbonate track detectors (PCTDs). The authors' recent studies on nitrogen and helium ions and alpha tracks in 1-mm-thick large-size PCTDs under a 50 Hz-HV ECE process provided promising results. In this study, alpha track efficiency and mean track diameter versus energy responses and registration energy range as well as alpha and background track shapes under three sets of 50 Hz-4, 5 and 6 kV applied field conditions have been studied and are reported. The efficiency versus alpha energy has a Bragg-type response from ∼15 keV to ∼4.5 MeV for the field conditions applied with an efficiency value of 40-50 % at the Bragg peak. The results are presented and discussed. (authors)

  16. Effect of UV radiation on the bulk etching rate activation energy and response of Cr-39 to alpha particles

    International Nuclear Information System (INIS)

    A set of CR-39 plastic sheets is exposed to UV radiation from mercury lamp for different periods of time. Then irradiated by alpha particles from 241Am point source at different energies. The Bulk etching rate activation energy is calculated for non-exposed and exposed sheets for time periods of 1.5 and 3 hr. It is found that their energy values are 0.76, 0.75 and 0.72 eV respectively. The track diameter (d) is calculated for different exposure times, it is found that d increased gradually as the exposure time increases before saturation. Further, two samples are irradiated by alpha particles but one is pre-exposed to UV for a time period of 3 h before being exposed to alpha, then the response function (V) is calculated for both. The values of V decreased for pre-exposed sample. The present data are the first measurements of the recent nuclear track laboratory at the experimental nuclear physics department, NRC, AEA

  17. Humidity influenced capacitance and resistance of an Al/DNA/Al Schottky diode irradiated by alpha particles

    Science.gov (United States)

    Al-Ta’Ii, Hassan Maktuff Jaber; Amin, Yusoff Mohd; Periasamy, Vengadesh

    2016-05-01

    Deoxyribonucleic acid or DNA based sensors, especially as humidity and alpha particle sensors have become quite popular in recent times due to flexible and highly optimizable nature of this fundamental biomaterial. Application of DNA electronics allow for more sensitive, accurate and effective sensors to be developed and fabricated. In this work, we examined the effect of different humidity conditions on the capacitive and resistive response of Aluminum (Al)/DNA/Al Schottky barrier structure when bombarded by time-dependent dosages of alpha particles. Based on current-voltage profiles, which demonstrated rectifying behaviours, Schottky diode parameters such as ideality factor, barrier height and series resistance was calculated. Results observed generally pointed towards a decrease in the resistance value from the pristine to the radiated structures. It was also demonstrated that under the effect of humidity, the capacitance of the DNA thin film increased from 0.05894 to 92.736 nF, with rising relative humidity level. We also observed the occurrence of the hypersensitivity phenomena after alpha irradiation between 2 to 4 min by observing a drop in the series resistance, crucial in the study of DNA damage and repair mechanisms. These observations may also suggest the exciting possibility of utilizing Al/DNA/Al Schottky diodes as potentially sensitive humidity sensors.

  18. The emission probabilities of long range alpha particles from even-even 244-252Cm isotopes

    CERN Document Server

    Santhosh, K P; Priyanka, B

    2014-01-01

    The alpha accompanied cold ternary fission of even-even 244Cm, 246Cm, 248Cm, 250Cm and 252Cm isotopes have been studied by taking the interacting barrier as the sum of Coulomb and proximity potential with the fragments in equatorial configuration. The favorable fragment combinations are obtained from the cold reaction valley plot and by calculating the relative yield for the charge minimized fragments. In the alpha accompanied ternary fission of 244Cm isotope, the highest yield is found for the fragment combination 110Ru+4He+130Sn, which possess near doubly magic nuclei 130Sn. For the ternary fission of 246Cm, 248Cm, 250Cm and 252Cm isotopes with 4He as light charged particle, the highest yield is obtained for the fragment combination with doubly magic nuclei 132Sn as the heavier fragment. The emission probabilities and kinetic energies of long range alpha particle have been computed for the 242,244,246,248Cm isotopes and are found to be in good agreement with the experimental data. The relative yields for th...

  19. An octahedral deformation with six alpha particles at the Z = 12 system, Mg nuclides: Third nucleons, Alpharons

    CERN Document Server

    Moon, Chang-Bum

    2016-01-01

    We suggest that the emergence of a large deformation in the magnesium, Mg, nuclides, especially at the Z = 12, N = 12, should be associated with an octahedral deformed shape. Within the framework of molecular geometrical symmetry, we find a possibility that the Z = 12, N = 12 system would form an octahedral structure consisting of six points of alpha(4He) particles, yielding the ground collectivity. With this point of view, we draw the following serial molecular structures; the Z = 10, N = 10, 20Ne, corresponds to a hexahedral, the Z = 8, N = 8, 16O, does to a tetrahedral, and the Z = 6, N = 6, 12C, does to a trigonal symmetry. Moreover, the Z = 2, N = 2, 4He(alpha), fits into a tetrahedral symmetry with four points of nucleons; two protons and two neutrons. The enhanced deformation at Z = 12 with N > 20 would be explained by a deformed shape related to an Ethene(Ethylene)-like skeleton with six alpha particles. The deformation at Z = 10, with N = 10 and 12, can be interpreted as being attributed to a hexahed...

  20. Cognitive improvement by activation of alpha7 nicotinic acetylcholine receptors: from animal models to human pathophysiology

    DEFF Research Database (Denmark)

    Thomsen, Morten S; Hansen, Henrik H; Timmerman, Daniel B;

    2010-01-01

    -enhancing effects seen in animal models are not mimicked in healthy humans and schizophrenic patients, where attentional improvement predominates. This discrepancy may result from inherent differences in testing methods or from species differences in the level of expression of alpha(7) nAChRs in limbic brain...... alpha(7) nAChR agonists improves learning, memory, and attentional function in variety of animal models, and pro-cognitive effects of alpha(7) nAChR agonists have recently been demonstrated in patients with schizophrenia or Alzheimer's disease. The alpha(7) nAChR desensitizes rapidly in vitro, and this...... has been a major concern in the development of alpha(7) nAChR agonists as putative drugs. Our review of the existing literature shows that development of tolerance to the behavioral effects of alpha(7) nAChR agonists does not occur in animal models or humans. However, the long-term memory...

  1. Cognitive improvement by activation of alpha7 nicotinic acetylcholine receptors: from animal models to human pathophysiology

    DEFF Research Database (Denmark)

    Thomsen, Morten S; Hansen, Henrik H; Timmerman, Daniel B;

    2010-01-01

    has been a major concern in the development of alpha(7) nAChR agonists as putative drugs. Our review of the existing literature shows that development of tolerance to the behavioral effects of alpha(7) nAChR agonists does not occur in animal models or humans. However, the long-term memory...... alpha(7) nAChR agonists improves learning, memory, and attentional function in variety of animal models, and pro-cognitive effects of alpha(7) nAChR agonists have recently been demonstrated in patients with schizophrenia or Alzheimer's disease. The alpha(7) nAChR desensitizes rapidly in vitro, and this......-enhancing effects seen in animal models are not mimicked in healthy humans and schizophrenic patients, where attentional improvement predominates. This discrepancy may result from inherent differences in testing methods or from species differences in the level of expression of alpha(7) nAChRs in limbic brain...

  2. Computer Models Simulate Fine Particle Dispersion

    Science.gov (United States)

    2010-01-01

    Through a NASA Seed Fund partnership with DEM Solutions Inc., of Lebanon, New Hampshire, scientists at Kennedy Space Center refined existing software to study the electrostatic phenomena of granular and bulk materials as they apply to planetary surfaces. The software, EDEM, allows users to import particles and obtain accurate representations of their shapes for modeling purposes, such as simulating bulk solids behavior, and was enhanced to be able to more accurately model fine, abrasive, cohesive particles. These new EDEM capabilities can be applied in many industries unrelated to space exploration and have been adopted by several prominent U.S. companies, including John Deere, Pfizer, and Procter & Gamble.

  3. Particle production beyond the thermal model

    Science.gov (United States)

    Wolschin, Georg

    2016-07-01

    The sources of particle production in relativistic heavy-ion collisions are investigated from RHIC to LHC energies. Whereas charged-hadron production in the fragmentation sources follows a ln(sNN/s0) law, particle production in the mid-rapidity low-x gluon-gluon source exhibits a much stronger dependence ∝ ln3(sNN/s0), and becomes dominant between RHIC and LHC energies. The equilibration of the three sources is investigated in a relativistic diffusion model (RDM). It agrees with the thermal model only for t → ∞.

  4. Particle production beyond the thermal model

    Directory of Open Access Journals (Sweden)

    Wolschin Georg

    2016-01-01

    Full Text Available The sources of particle production in relativistic heavy-ion collisions are investigated from RHIC to LHC energies. Whereas charged-hadron production in the fragmentation sources follows a ln(sNN/s0 law, particle production in the mid-rapidity low-x gluon-gluon source exhibits a much stronger dependence ∝ ln3(sNN/s0, and becomes dominant between RHIC and LHC energies. The equilibration of the three sources is investigated in a relativistic diffusion model (RDM. It agrees with the thermal model only for t → ∞.

  5. The implications of particle energy and acidic media on gross alpha and gross beta determination using liquid scintillation

    Energy Technology Data Exchange (ETDEWEB)

    Zapata-Garcia, D. [Laboratori de Radiologia Ambiental (LRA), Departament de Quimica Analitica, Universitat de Barcelona, Marti i Franques, 1-11 Planta 3, E-08028 Barcelona (Spain); Llaurado, M., E-mail: montse.llaurado@ub.edu [Laboratori de Radiologia Ambiental (LRA), Departament de Quimica Analitica, Universitat de Barcelona, Marti i Franques, 1-11 Planta 3, E-08028 Barcelona (Spain); Rauret, G. [Laboratori de Radiologia Ambiental (LRA), Departament de Quimica Analitica, Universitat de Barcelona, Marti i Franques, 1-11 Planta 3, E-08028 Barcelona (Spain)

    2012-04-15

    The interaction of humans with radioactivity present in the environment from natural and artificial sources necessitates an evaluation of its risk on human health. Gross alpha and gross beta activities can provide a rapid evaluation of the radioactive content of a sample and can be simultaneously determined by using liquid scintillation counters. However, calibration of the liquid scintillation counter is required and is affected by many factors, such as particle energy and the acidity of the media. This study investigates what effect the particle energy used for calibration has on misclassification and how to account for this misclassification in routine measurements. The variability in measurement produced by the final pH, as well as any acids used in sample treatment, was also studied. These results showed that the most commonly used acid for these types of analyses, HNO{sub 3}, produced a high amount of misclassifications at very low pH. The results improved when HCl was used to adjust the sample to low pH. - Highlights: Black-Right-Pointing-Pointer We study the effect of alpha and beta energies on PSA optimisation. Black-Right-Pointing-Pointer The optimum PSA shifts to higher values as the alpha energy increases. Beta energies do not affect it. Black-Right-Pointing-Pointer We study the effect of pH on the simultaneous determination of gross alpha/beta activities. Black-Right-Pointing-Pointer HNO{sub 3} produces a high amount of misclassification at very low pH. Black-Right-Pointing-Pointer The results improve when HCl is used to adjust the sample to low pH.

  6. Bismuth-212-labeled anti-Tac monoclonal antibody: alpha-particle-emitting radionuclides as modalities for radioimmunotherapy

    International Nuclear Information System (INIS)

    Anti-Tac, a monoclonal antibody directed to the human interleukin 2 (IL-2) receptor, has been successfully conjugated to the alpha-particle-emitting radionuclide bismuth-212 by use of a bifunctional ligand, the isobutylcarboxycarbonic anhydride of diethylenetriaminepentaacetic acid. The physical properties of 212Bi are appropriate for radioimmunotherapy in that it has a short half-life, deposits its high energy over a short distance, and can be obtained in large quantities from a radium generator. Antibody specific activities of 1-40 microCi/microgram (1 Ci = 37 GBq) were achieved. Specificity of the 212Bi-labeled anti-Tac was demonstrated for the IL-2 receptor-positive adult T-cell leukemia line HUT-102B2 by protein synthesis inhibition and clonogenic assays. Activity levels of 0.5 microCi or the equivalent of 12 rad/ml of alpha radiation targeted by anti-Tac eliminated greater than 98% the proliferative capabilities of HUT-102B2 cells with more modest effects on IL-2 receptor-negative cell lines. Specific cytotoxicity was blocked by excess unlabeled anti-Tac but not by human IgG. In addition, an irrelevant control monoclonal antibody of the same isotype labeled with 212Bi was unable to target alpha radiation to cell lines. Therefore, 212Bi-labeled anti-Tac is a potentially effective and specific immunocytotoxic reagent for the elimination of IL-2 receptor-positive cells. These experiments thus provide the scientific basis for use of alpha-particle-emitting radionuclides in immunotherapy

  7. Lagrangian Trajectory Modeling of Lunar Dust Particles

    Science.gov (United States)

    Lane, John E.; Metzger, Philip T.; Immer, Christopher D.

    2008-01-01

    Apollo landing videos shot from inside the right LEM window, provide a quantitative measure of the characteristics and dynamics of the ejecta spray of lunar regolith particles beneath the Lander during the final 10 [m] or so of descent. Photogrammetry analysis gives an estimate of the thickness of the dust layer and angle of trajectory. In addition, Apollo landing video analysis divulges valuable information on the regolith ejecta interactions with lunar surface topography. For example, dense dust streaks are seen to originate at the outer rims of craters within a critical radius of the Lander during descent. The primary intent of this work was to develop a mathematical model and software implementation for the trajectory simulation of lunar dust particles acted on by gas jets originating from the nozzle of a lunar Lander, where the particle sizes typically range from 10 micron to 500 micron. The high temperature, supersonic jet of gas that is exhausted from a rocket engine can propel dust, soil, gravel, as well as small rocks to high velocities. The lunar vacuum allows ejected particles to travel great distances unimpeded, and in the case of smaller particles, escape velocities may be reached. The particle size distributions and kinetic energies of ejected particles can lead to damage to the landing spacecraft or to other hardware that has previously been deployed in the vicinity. Thus the primary motivation behind this work is to seek a better understanding for the purpose of modeling and predicting the behavior of regolith dust particle trajectories during powered rocket descent and ascent.

  8. Readout cross-talk for alpha-particle measurements in a pixelated sensor system

    International Nuclear Information System (INIS)

    Simulations in Medici are performed to quantify crosstalk and charge sharing in a hybrid pixelated silicon detector. Crosstalk and charge sharing degrades the spatial and spectral resolution of single photon processing X-ray imaging systems. For typical medical X-ray imaging applications, the process is dominated by charge sharing between the pixels in the sensor. For heavier particles each impact generates a large amount of charge and the simulation seems to over predict the charge collection efficiency. This indicates that some type of non modelled degradation of the charge transport efficiency exists, like the plasma effect where the plasma might shield the generated charges from the electric field and hence distorts the charge transport process. Based on the simulations it can be reasoned that saturation of the amplifiers in the Timepix system might generate crosstalk that increases the charge spread measured from ion impact on the sensor

  9. Readout cross-talk for alpha-particle measurements in a pixelated sensor system

    Science.gov (United States)

    Norlin, B.; Reza, S.; Krapohl, D.; Fröjdh, E.; Thungström, G.

    2015-05-01

    Simulations in Medici are performed to quantify crosstalk and charge sharing in a hybrid pixelated silicon detector. Crosstalk and charge sharing degrades the spatial and spectral resolution of single photon processing X-ray imaging systems. For typical medical X-ray imaging applications, the process is dominated by charge sharing between the pixels in the sensor. For heavier particles each impact generates a large amount of charge and the simulation seems to over predict the charge collection efficiency. This indicates that some type of non modelled degradation of the charge transport efficiency exists, like the plasma effect where the plasma might shield the generated charges from the electric field and hence distorts the charge transport process. Based on the simulations it can be reasoned that saturation of the amplifiers in the Timepix system might generate crosstalk that increases the charge spread measured from ion impact on the sensor.

  10. Final Report (1994 to 1996) Diagnostic of the Spatial and Velocity Distribution of Alpha Particles in Tokamak Fusion Reactor using Beat-wave Generated Lower Hybrid Wave

    International Nuclear Information System (INIS)

    The alpha particles in a fusion reactor play a key role in the sustaining the fusion reaction. It is the heating provided by the alpha particles that help a fusion reactor operating in the ignition regime. It is, therefore, essential to understand the behavior of the alpha population both in real space and velocity space in order to design the optimal confinement device for fusion application. Moreover, the alphas represent a strong source of free energy that may generate plasma instabilities. Theoretical studies has identified the Toroidal Alfven Eigenmode (TAE) as an instability that can be excited by the alpha population in a toroidal device. Since the alpha has an energy of 3.5 MeV, a good confinement device will retain it in the interior of the plasma. Therefore, alpha measurement system need to probe the interior of a high density plasma. Due to the conducting nature of a plasma, wave with frequencies below the plasma frequency can not penetrate into the interior of the plasma where the alphas reside. This project uses a wave that can interact with the perpendicular motion of the alphas to probe its characteristics. However, this wave (the lower hybrid wave) is below the plasma frequency and can not be directly launched from the plasma edge. This project was designed to non-linearly excite the lower hybrid in the interior of a magnetized plasma and measure its interaction with a fast ion population

  11. The $\\alpha-\\alpha$ fishbone potential revisited

    CERN Document Server

    Day, J P; Elhanafy, M; Smith, E; Woodhouse, R; Papp, Z

    2011-01-01

    The fishbone potential of composite particles simulates the Pauli effect by nonlocal terms. We determine the $\\alpha-\\alpha$ fishbone potential by simultaneously fitting to two-$\\alpha$ resonance energies, experimental phase shifts and three-$\\alpha$ binding energies. We found that essentially a simple gaussian can provide a good description of two-$\\alpha$ and three-$\\alpha$ experimental data without invoking three-body potentials.

  12. Cloth Modeling Based on Particle System

    Institute of Scientific and Technical Information of China (English)

    钟跃崎; 王善元

    2001-01-01

    A physical-based particle system is employed for cloth modeling supported by two basic algorithms, between which one is the construction of the internal and external forces acting on the particle system in terms of KES-F bending and shearing tests, and the other is the collision algorithm of which the collision detection is carried by means of bi-section of time step and the collision response is handled according to the empirical law for frictionless collision With these algorithms. the geometric state of parcles can be expressed as ordinary differential equationswhich is numerically solved by fourth order Runge- Kutta integration. Different draping figures of cotton fabric and wool fabric prove that such a particle system is suitable for 3D cloth modeling and simulation.

  13. Effects of complex symmetry-breakings on alpha particle power loads on first wall structures and equilibrium in ITER

    International Nuclear Information System (INIS)

    Within the ITPA Topical Group on Energetic Particles, we have investigated the impact that various mechanisms breaking the tokamak axisymmetry can have on the fusion alpha particle confinement in ITER as well as on the wall power loads due to these alphas. In addition to the well-known TF ripple, the 3D effect due to ferromagnetic materials (in ferritic inserts and test blanket modules) and ELM mitigation coils are included in these mechanisms. ITER scenario 4 was chosen since, due to its lower plasma current, it is more vulnerable for various off-normal features. First, the validity of using a 2D equilibrium was investigated: a 3D equilibrium was reconstructed using the VMEC code, and it was verified that no 3D equilibrium reconstruction is needed but it is sufficient to add the vacuum field perturbations onto an axisymmetric equilibrium. Then the alpha particle confinement was studied using three independent codes, ASCOT, DELTA5D and F3D OFMC, all of which assume MHD quiescent background plasma and no anomalous diffusion. All the codes gave a loss power fraction of about 0.2%. The distribution of the peak power load was found to depend on the first wall shape. We also made the first attempt to accommodate the effect of fast-ion-related MHD on the wall loads in ITER using the HMGC and ASCOT codes. The power flux to the wall was found to increase due to the redistribution of fast ions by the MHD activity. Furthermore, the effect of the ELM mitigation field on the fast-ion confinement was addressed by simulating NBI ions with the F3D OFMC code. The loss power fraction of NBI ions was found to increase from 0.3% without the ELM mitigation field to 4-5% with the ELM mitigation field.

  14. Effects of Complex Symmetry-Breakings on Alpha Particle Power Loads on First Wall Structures and Equilibrium in ITER

    Energy Technology Data Exchange (ETDEWEB)

    Shinohara, K. [Japan Atomic Energy Agency (JAEA), Naka; Kurki-Suonio, T. [Aalto University, Finland; Spong, Donald A [ORNL; Asunta, O. [Aalto University, Finland; Tani, K. [Japan Atomic Energy Agency (JAEA), Naka; Strumberger, E. [Max Planck Institute for Plasma Physics, Garching, Germany; Briguglio, S. [EURATOM / ENEA, Italy; Koskela, T. [Aalto University, Finland; Vlad, G. [EURATOM / ENEA, Italy; Günter, S. [Max-Planck Institute, Garching, Germany; Kramer, G. [Princeton Plasma Physics Laboratory (PPPL); Putvinski, S. [ITER Organization, Cadarache, France; Hamamatsu, K. [Japan Atomic Energy Agency (JAEA), Naka

    2011-01-01

    Within the ITPA Topical Group on Energetic Particles, we have investigated the impact that various mechanisms breaking the tokamak axisymmetry can have on the fusion alpha particle confinement in ITER as well as on the wall power loads due to these alphas. In addition to the well-known TF ripple, the 3D effect due to ferromagnetic materials (in ferritic inserts and test blanket modules) and ELM mitigation coils are included in these mechanisms. ITER scenario 4 was chosen since, due to its lower plasma current, it is more vulnerable for various off-normal features. First, the validity of using a 2D equilibrium was investigated: a 3D equilibrium was reconstructed using the VMEC code, and it was verified that no 3D equilibrium reconstruction is needed but it is sufficient to add the vacuum field perturbations onto an axisymmetric equilibrium. Then the alpha particle confinement was studied using three independent codes, ASCOT, DELTA5D and F3D OFMC, all of which assume MHD quiescent background plasma and no anomalous diffusion. All the codes gave a loss power fraction of about 0.2%. The distribution of the peak power load was found to depend on the first wall shape. We also made the first attempt to accommodate the effect of fast-ion-related MHD on the wall loads in ITER using the HMGC and ASCOT codes. The power flux to the wall was found to increase due to the redistribution of fast ions by the MHD activity. Furthermore, the effect of the ELM mitigation field on the fast-ion confinement was addressed by simulating NBI ions with the F3D OFMC code. The loss power fraction of NBI ions was found to increase from 0.3% without the ELM mitigation field to 4-5% with the ELM mitigation field.

  15. Response of Ni/4H-SiC Schottky barrier diodes to alpha-particle irradiation at different fluences

    Science.gov (United States)

    Omotoso, E.; Meyer, W. E.; Auret, F. D.; Diale, M.; Ngoepe, P. N. M.

    2016-01-01

    Irradiation experiments have been carried out on 1.9×1016 cm-3 nitrogen-doped 4H-SiC at room temperature using 5.4 MeV alpha-particle irradiation over a fluence ranges from 2.6×1010 to 9.2×1011 cm-2. Current-voltage (I-V), capacitance-voltage (C-V) and deep level transient spectroscopy (DLTS) measurements have been carried out to study the change in characteristics of the devices and free carrier removal rate due to alpha-particle irradiation, respectively. As radiation fluence increases, the ideality factors increased from 1.20 to 1.85 but the Schottky barrier height (SBHI-V) decreased from 1.47 to 1.34 eV. Free carrier concentration, Nd decreased with increasing fluence from 1.7×1016 to 1.1×1016 cm-2 at approximately 0.70 μm depth. The reduction in Nd shows that defects were induced during the irradiation and have effect on compensating the free carrier. The free carrier removal rate was estimated to be 6480±70 cm-1. Alpha-particle irradiation introduced two electron traps (E0.39 and E0.62), with activation energies of 0.39±0.03 eV and 0.62±0.08 eV, respectively. The E0.39 as attribute related to silicon or carbon vacancy, while the E0.62 has the attribute of Z1/Z2.

  16. I. Excluded Volume Effects in Ising Cluster Distributions and Nuclear Multifragmentation II. Multiple-Chance Effects in Alpha-Particle Evaporation

    Energy Technology Data Exchange (ETDEWEB)

    Breus, Dimitry E.

    2005-05-16

    In Part 1, geometric clusters of the Ising model are studied as possible model clusters for nuclear multifragmentation. These clusters may not be considered as non-interacting (ideal gas) due to excluded volume effect which predominantly is the artifact of the cluster's finite size. Interaction significantly complicates the use of clusters in the analysis of thermodynamic systems. Stillinger's theory is used as a basis for the analysis, which within the RFL (Reiss, Frisch, Lebowitz) fluid-of-spheres approximation produces a prediction for cluster concentrations well obeyed by geometric clusters of the Ising model. If thermodynamic condition of phase coexistence is met, these concentrations can be incorporated into a differential equation procedure of moderate complexity to elucidate the liquid-vapor phase diagram of the system with cluster interaction included. The drawback of increased complexity is outweighted by the reward of greater accuracy of the phase diagram, as it is demonstrated by the Ising model. A novel nuclear-cluster analysis procedure is developed by modifying Fisher's model to contain cluster interaction and employing the differential equation procedure to obtain thermodynamic variables. With this procedure applied to geometric clusters, the guidelines are developed to look for excluded volume effect in nuclear multifragmentation. In part 2, an explanation is offered for the recently observed oscillations in the energy spectra of {alpha}-particles emitted from hot compound nuclei. Contrary to what was previously expected, the oscillations are assumed to be caused by the multiple-chance nature of {alpha}-evaporation. In a semi-empirical fashion this assumption is successfully confirmed by a technique of two-spectra decomposition which treats experimental {alpha}-spectra has having contributions from at least two independent emitters. Building upon the success of the multiple-chance explanation of the oscillations, Moretto

  17. Modelling of aircrew radiation exposure during solar particle events

    Science.gov (United States)

    Al Anid, Hani Khaled

    In 1990, the International Commission on Radiological Protection recognized the occupational exposure of aircrew to cosmic radiation. In Canada, a Commercial and Business Aviation Advisory Circular was issued by Transport Canada suggesting that action should be taken to manage such exposure. In anticipation of possible regulations on exposure of Canadian-based aircrew in the near future, an extensive study was carried out at the Royal Military College of Canada to measure the radiation exposure during commercial flights. The radiation exposure to aircrew is a result of a complex mixed-radiation field resulting from Galactic Cosmic Rays (GCRs) and Solar Energetic Particles (SEPs). Supernova explosions and active galactic nuclei are responsible for GCRs which consist of 90% protons, 9% alpha particles, and 1% heavy nuclei. While they have a fairly constant fluence rate, their interaction with the magnetic field of the Earth varies throughout the solar cycles, which has a period of approximately 11 years. SEPs are highly sporadic events that are associated with solar flares and coronal mass ejections. This type of exposure may be of concern to certain aircrew members, such as pregnant flight crew, for which the annual effective dose is limited to 1 mSv over the remainder of the pregnancy. The composition of SEPs is very similar to GCRs, in that they consist of mostly protons, some alpha particles and a few heavy nuclei, but with a softer energy spectrum. An additional factor when analysing SEPs is the effect of flare anisotropy. This refers to the way charged particles are transported through the Earth's magnetosphere in an anisotropic fashion. Solar flares that are fairly isotropic produce a uniform radiation exposure for areas that have similar geomagnetic shielding, while highly anisotropic events produce variable exposures at different locations on the Earth. Studies of neutron monitor count rates from detectors sharing similar geomagnetic shielding properties

  18. Comparative study of alpha + nucleus elastic scattering using different models

    International Nuclear Information System (INIS)

    The alpha (α) elastic scattering from different targets potential over the energy range 10–240 MeV has been analyzed in the framework of the single-folding (SF) optical model. Four targets are considered, namely, 24Mg, 28Si, 32S and 40Ca. The SF calculations for the real central part of the nuclear optical potential are performed by folding an effective α–α interaction with the α-cluster distribution density in the target nucleus. The imaginary part of the optical potential is expressed in the phenomenological Woods–Saxon (WS) form. The calculated angular distributions of the elastic scattering differential cross-section using the derived semimicroscopic potentials successfully reproduce 36 sets of data all over the measured angular ranges. The obtained results confirm the validity of the α-cluster structure of the considered nuclei. For the sake of comparison, the same sets of data are reanalyzed using microscopic double-folded optical potentials based upon the density-dependent Jeukenne–Lejeune–Mahaux (JLM) effective nucleon–nucleon interaction. (author)

  19. Detection of Alpha Particles and Low Energy Gamma Rays by Thermo-Bonded Micromegas in Xenon Gas

    CERN Document Server

    Wei, Yuehuan; Zhang, Zhiyong; Lin, Qing; Wang, Xiaolian; Ni, Kaixuan; Zhao, Tianchi

    2013-01-01

    Micromegas is a type of micro-pattern gaseous detector currently under R&D for applications in rare event search experiments. Here we report the performance of a Micromegas structure constructed with a micromesh thermo-bonded to a readout plane, motivated by its potential application in two-phase xenon detectors for dark matter and neutrinoless double beta decay experiments. The study is carried out in pure xenon at room temperature. Measurements with alpha particles from the Americium-241 source showed that gas gains larger than 200 can be obtained at xenon pressure up to 3 atm. Gamma rays down to 8 keV were observed with such a device.

  20. Diffraction scattering of alpha particles on C, Al, Cu and Pb at 17.9 GeV/c

    International Nuclear Information System (INIS)

    New data on the diffraction scattering of relativistic alpha particles on C, Al, Cu and Pb targets at incident momentum of 17.9 GeV/c are presented. Differential cross sections at four-momentum transfers squared |t| ranging from 0.038 (GeV/c)2 up to 0.55 (GeV/c)2 have been measured with an accuracy of 3% of the absolute normalization. These data are compared with the predictions of the Glauber-Sitenko multiple scattering theory. (author)

  1. Attempt of analysis of the elastic scattering of 44 MeV alpha particles using a phase shift parameterization

    International Nuclear Information System (INIS)

    In order to ease the resolution of the problem of interaction of an alpha particle with a nucleus, and determine simpler hypotheses which enable the analysis of experimental results, this research thesis reports the use of a parameterization of phase shifts to reduce ambiguities and the number of parameters. After general remarks, a description of the Hamiltonian and a formulation of phase shifts, the author presents experimental data and the analytical method. Analysis is then performed for two-, three-, four- or five-parameter formulations. Efficient cross sections are then studied

  2. Activation cross sections of $\\alpha$-particle induced nuclear reactions on hafnium and deuteron induced nuclear reaction on tantalum: production of $^{178}$W/$^{178m}$Ta generator

    CERN Document Server

    Tárk'anyi, F; Ditrói, F; Hermanne, A; Ignatyuk, A V; Uddin, M S

    2014-01-01

    In the frame of a systematic study of charged particle production routes of medically relevant radionuclei, the excitation function for indirect production of $^{178m}$Ta through $^{nat}$Hf($\\alpha$,xn)$^{178}$W-$^{178m}$Ta nuclear reaction was measured for the first time up to 40 MeV. In parallel, the side reactions $^{nat}$Hf($\\alpha$,x)$^{179,177,176,175}$W, $^{183,182,178g,177,176,175}$Ta, $^{179m,177m,175}$Hf were also assessed. Stacked foil irradiation technique and $\\gamma$-ray spectrometry were used. New experimental cross section data for the $^{nat}$Ta(d,xn)$^{178}$W reaction are also reported up to 40 MeV. The measured excitation functions are compared with the results of the ALICE-IPPE, and EMPIRE nuclear reaction model codes and with the TALYS 1.4 based data in the TENDL-2013 library. The thick target yields were deduced and compared with yields of other charged particle ((p,4n), (d,5n) and ($^3$He,x)) production routes for $^{178}$W.

  3. Particle in the Brusselator Model with Flow

    DEFF Research Database (Denmark)

    Kuptsov, P.V.; Kuznetsov, S.P.; Mosekilde, Erik

    2002-01-01

    We consider the interaction of a small moving particle with a stationary space-periodic pattern in a chemical reaction-diffusion system with a flow. The pattern is produced by a one-dimensional Brusselator model that is perturbed by a constant displacement from the equilibrium state at the inlet....

  4. On Uncertainty Quantification in Particle Accelerators Modelling

    CERN Document Server

    Adelmann, Andreas

    2015-01-01

    Using a cyclotron based model problem, we demonstrate for the first time the applicability and usefulness of a uncertainty quantification (UQ) approach in order to construct surrogate models for quantities such as emittance, energy spread but also the halo parameter, and construct a global sensitivity analysis together with error propagation and $L_{2}$ error analysis. The model problem is selected in a way that it represents a template for general high intensity particle accelerator modelling tasks. The presented physics problem has to be seen as hypothetical, with the aim to demonstrate the usefulness and applicability of the presented UQ approach and not solving a particulate problem. The proposed UQ approach is based on sparse polynomial chaos expansions and relies on a small number of high fidelity particle accelerator simulations. Within this UQ framework, the identification of most important uncertainty sources is achieved by performing a global sensitivity analysis via computing the so-called Sobols' ...

  5. Remote Sensing of Alpha and Beta Sources - Modeling Summary

    International Nuclear Information System (INIS)

    Evaluating the potential for optical detection of the products of interactions of energetic electrons or other particles with the background atmosphere depends on predictions of change in atmospheric concentrations of species which would generate detectable spectral signals within the range of observation. The solar blind region of the spectrum, in the ultra violet, would be the logical band for outdoor detection (see Figure 1). The chemistry relevant to these processes is composed of ion-molecule reactions involving the initially created N2+ and O2+ ions, and their subsequent interactions with ambient trace atmospheric constituents. Effective modeling of the atmospheric chemical system acted upon by energetic particles requires knowledge of the dominant mechanism that exchange charge and associate it with atmospheric constituents, kinetic parameters of the individual processes (see e.g. Brasseur and Solomon, 1995), and a solver for the coupled differential equations that is accurate for the very stiff set of time constants involved. The LLNL box model, VOLVO, simulates the diel cycle of trace constituent photochemistry for any point on the globe over the wide range of time scales present using a stiff Gear-type ODE solver, i.e. LSODE. It has been applied to problems such as tropospheric and stratospheric nitrogen oxides, stratospheric ozone production and loss, and tropospheric hydrocarbon oxidation. For this study we have included the appropriate ion flux

  6. Alpha-particle emitting 213Bi-anti-EGFR immunoconjugates eradicate tumor cells independent of oxygenation.

    Directory of Open Access Journals (Sweden)

    Christian Wulbrand

    Full Text Available Hypoxia is a central problem in tumor treatment because hypoxic cells are less sensitive to chemo- and radiotherapy than normoxic cells. Radioresistance of hypoxic tumor cells is due to reduced sensitivity towards low Linear Energy Transfer (LET radiation. High LET α-emitters are thought to eradicate tumor cells independent of cellular oxygenation. Therefore, the aim of this study was to demonstrate that cell-bound α-particle emitting (213Bi immunoconjugates kill hypoxic and normoxic CAL33 tumor cells with identical efficiency. For that purpose CAL33 cells were incubated with (213Bi-anti-EGFR-MAb or irradiated with photons with a nominal energy of 6 MeV both under hypoxic and normoxic conditions. Oxygenation of cells was checked via the hypoxia-associated marker HIF-1α. Survival of cells was analysed using the clonogenic assay. Cell viability was monitored with the WST colorimetric assay. Results were evaluated statistically using a t-test and a Generalized Linear Mixed Model (GLMM. Survival and viability of CAL33 cells decreased both after incubation with increasing (213Bi-anti-EGFR-MAb activity concentrations (9.25 kBq/ml-1.48 MBq/ml and irradiation with increasing doses of photons (0.5-12 Gy. Following photon irradiation survival and viability of normoxic cells were significantly lower than those of hypoxic cells at all doses analysed. In contrast, cell death induced by (213Bi-anti-EGFR-MAb turned out to be independent of cellular oxygenation. These results demonstrate that α-particle emitting (213Bi-immunoconjugates eradicate hypoxic tumor cells as effective as normoxic cells. Therefore, (213Bi-radioimmunotherapy seems to be an appropriate strategy for treatment of hypoxic tumors.

  7. Very High Efficiency, Miniaturized, Long-Lived Alpha Particle Power Source Using Diamond Devices for Extreme Space Environments

    Science.gov (United States)

    Kolawa, Elizabeth A. (Inventor); Patel, Jagdishbhai U. (Inventor); Fleurial, Jean-Pierre (Inventor)

    2004-01-01

    A power source that converts a-particle energy into electricity by coulomb collision in doped diamond films is described. Alpha particle decay from curium-244 creates electron-hole pairs by free- ing electrons and holes inside the crystal lattice in N- and P-doped diamond films. Ohmic contacts provide electrical connection to an electronic device. Due to the built-in electric field at the rectifying junction across the hT- and P-doped diamond films, the free electrons are constrained to traveling in generally one direction. This one direction then supplies electrons in a manner similar to that of a battery. The radioactive curium layer may be disposed on diamond films for even distribution of a-particle radiation. The resulting power source may be mounted on a diamond substrate that serves to insulate structures below the diamond substrate from a-particle emission. Additional insulation or isolation may be provided in order to prevent damage from a-particle collision. N-doped silicon may be used instead of N-doped diamond.

  8. A Comparitive Assessement of Cytokine Expression in Human-Derived Cell Lines Exposed to Alpha Particles and X-Rays

    Directory of Open Access Journals (Sweden)

    Vinita Chauhan

    2012-01-01

    Full Text Available Alpha- (α- particle radiation exposure has been linked to the development of lung cancer and has been identified as a radiation type likely to be employed in radiological dispersal devices. Currently, there exists a knowledge gap concerning cytokine modulations associated with exposure to α-particles. Bio-plex technology was employed to investigate changes in proinflammatory cytokines in two human-derived cell lines. Cells were irradiated at a dose of 1.5 Gy to either α-particles or X-rays at equivalent dose rates. The two cell lines exhibited a unique pattern of cytokine expression and the response varied with radiation type. Of the 27 cytokines assessed, only vascular endothelin growth factor (VEGF was observed to be modulated in both cell lines solely after α-particle exposure, and the expression of VEGF was shown to be dose responsive. These results suggest that certain proinflammatory cytokines may be involved in the biological effects related to α- particle exposure and the responses are cell type and radiation type specific.

  9. Impact modeling with Smooth Particle Hydrodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Stellingwerf, R.F.; Wingate, C.A.

    1993-07-01

    Smooth Particle Hydrodynamics (SPH) can be used to model hypervelocity impact phenomena via the addition of a strength of materials treatment. SPH is the only technique that can model such problems efficiently due to the combination of 3-dimensional geometry, large translations of material, large deformations, and large void fractions for most problems of interest. This makes SPH an ideal candidate for modeling of asteroid impact, spacecraft shield modeling, and planetary accretion. In this paper we describe the derivation of the strength equations in SPH, show several basic code tests, and present several impact test cases with experimental comparisons.

  10. Particle in the Brusselator Model with Flow

    DEFF Research Database (Denmark)

    Kuptsov, P.V.; Kuznetsov, S.P.; Mosekilde, Erik

    . By partially blocking the flow, the particle gives rise to a local increment of the flow rate. For certain parameter values a response with intermittent Hopf and Turing type structures is observed. In other regimes a wave of substitution of missing peaks runs across the pattern.......We consider the interaction of a small moving particle with a stationary space-periodic pattern in a chemical reaction-diffusion system with a flow. The pattern is produced by a one-dimensional Brusselator model that is perturbed by a constant displacement from the equilibrium state at the inlet...

  11. Particle filters for random set models

    CERN Document Server

    Ristic, Branko

    2013-01-01

    Particle Filters for Random Set Models” presents coverage of state estimation of stochastic dynamic systems from noisy measurements, specifically sequential Bayesian estimation and nonlinear or stochastic filtering. The class of solutions presented in this book is based  on the Monte Carlo statistical method. The resulting  algorithms, known as particle filters, in the last decade have become one of the essential tools for stochastic filtering, with applications ranging from  navigation and autonomous vehicles to bio-informatics and finance. While particle filters have been around for more than a decade, the recent theoretical developments of sequential Bayesian estimation in the framework of random set theory have provided new opportunities which are not widely known and are covered in this book. These recent developments have dramatically widened the scope of applications, from single to multiple appearing/disappearing objects, from precise to imprecise measurements and measurement models. This book...

  12. Beyond the standard model of particle physics.

    Science.gov (United States)

    Virdee, T S

    2016-08-28

    The Large Hadron Collider (LHC) at CERN and its experiments were conceived to tackle open questions in particle physics. The mechanism of the generation of mass of fundamental particles has been elucidated with the discovery of the Higgs boson. It is clear that the standard model is not the final theory. The open questions still awaiting clues or answers, from the LHC and other experiments, include: What is the composition of dark matter and of dark energy? Why is there more matter than anti-matter? Are there more space dimensions than the familiar three? What is the path to the unification of all the fundamental forces? This talk will discuss the status of, and prospects for, the search for new particles, symmetries and forces in order to address the open questions.This article is part of the themed issue 'Unifying physics and technology in light of Maxwell's equations'. PMID:27458261

  13. Investigation of double strand breaks induced by alpha particle irradiation using C.N.B.G. microbeam in human keratinocytes

    International Nuclear Information System (INIS)

    To understand the mechanisms of interaction of ionizing radiation with living tissues exposed to low and protracted doses remains a major issue for risk evaluation. The response cannot be found in epidemiological studies because the only available data concern accidental exposures to high doses of radiation. The natural exposure represents the main source of exposure in the daily life, just before the medical sources (radiology, radiotherapy). In addition, this kind of exposure is very difficult to reproduce in vitro by irradiating cell lines. The method per preference is based on random irradiation of cell populations. The mean number of particles having traversed cells is then calculated on the basis of Poisson statistics. In addition to inevitable multiple impacts, the numerous potential intracellular targets (nuclei, cytoplasm), the indirect effects induced by the impact of particles on neighbouring cells or simply the extracellular targets, constitute phenomena that make more complex the interpretation of experimental data. A charged particle microbeam was developed at C.E.N.B.G. to perform the targeted irradiation of individual cells with a targeting precision of a few microns. It is possible to deliver a counted number of alpha particles down to the ultimate dose of one alpha per cell, to target predetermined cells and then to observe the response of the neighbouring cells. This facility has been validated during this work on human keratinocyte cells expressing a recombinant nuclear fluorescent protein (histone H2B-GFP). The combination of ion micro-beams with confocal microscopy and numeric quantitative analysis allowed the measurement of DNA double strand breaks via the phosphorylation of the histone H2A.X in individual cells. The mechanisms of DNA reparation and apoptosis induction were also in the scope of those studies. The experimental results obtained during this thesis validate the methodology we have developed by demonstrating the targeting

  14. Comprehensive evaluation of the linear stability of Alfv\\'en eigenmodes driven by alpha particles in an ITER baseline scenario

    CERN Document Server

    Figueiredo, A C A; Borba, D; Coelho, R; Fazendeiro, L; Ferreira, J; Loureiro, N F; Nabais, F; Pinches, S D; Polevoi, A R; Sharapov, S E

    2016-01-01

    The linear stability of Alfv\\'en eigenmodes in the presence of fusion-born alpha particles is thoroughly assessed for two variants of an ITER baseline scenario, which differ significantly in their core and pedestal temperatures. A systematic approach is used that considers all possible eigenmodes for a given magnetic equilibrium and determines their growth rates due to alpha-particle drive and Landau damping on fuel ions, helium ashes and electrons. This extensive stability study is efficiently conducted through the use of a specialized workflow that profits from the performance of the hybrid MHD drift-kinetic code $\\mbox{CASTOR-K}$ (Borba D. and Kerner W. 1999 J. Comput. Phys. ${\\bf 153}$ 101; Nabais F. ${\\it et\\,al}$ 2015 Plasma Sci. Technol. ${\\bf 17}$ 89), which can rapidly evaluate the linear growth rate of an eigenmode. It is found that the fastest growing instabilities in the aforementioned ITER scenario are core-localized, low-shear toroidal Alfv\\'en eigenmodes. The largest growth-rates occur in the s...

  15. Nitric oxide mediated DNA double strand breaks induced in proliferating bystander cells after {alpha}-particle irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Han Wei [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong (Hong Kong); Chen Shaopeng [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong (Hong Kong); Key Laboratory of Ion Beam Bioengineering, Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Yu, K.N., E-mail: peter.yu@cityu.edu.hk [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong (Hong Kong); Wu Lijun [Key Laboratory of Ion Beam Bioengineering, Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China)

    2010-02-03

    Low-dose {alpha}-particle exposures comprise 55% of the environmental dose to the human population and have been shown to induce bystander responses. Previous studies showed that bystander effect could induce stimulated cell growth or genotoxicity, such as excessive DNA double strand breaks (DSBs), micronuclei (MN), mutation and decreased cell viability, in the bystander cell population. In the present study, the stimulated cell growth, detected with flow cytometry (FCM), and the increased MN and DSB, detected with p53 binding protein 1 (53BP1) immunofluorescence, were observed simultaneously in the bystander cell population, which were co-cultured with cells irradiated by low-dose {alpha}-particles (1-10 cGy) in a mixed system. Further studies indicated that nitric oxide (NO) and transforming growth factor {beta}1 (TGF-{beta}1) played very important roles in mediating cell proliferation and inducing MN and DSB in the bystander population through treatments with NO scavenger and TGF-{beta}1 antibody. Low-concentrations of NO, generated by spermidine, were proved to induce cell proliferation, DSB and MN simultaneously. The proliferation or shortened cell cycle in bystander cells gave them insufficient time to repair DSBs. The increased cell division might increase the probability of carcinogenesis in bystander cells since cell proliferation increased the probability of mutation from the mis-repaired or un-repaired DSBs.

  16. The induction of bystander mutagenic effects in vivo by alpha-particle irradiation in whole Arabidopsis thaliana plants.

    Science.gov (United States)

    Li, Fanghua; Liu, Ping; Wang, Ting; Bian, Po; Wu, Yuejin; Wu, Lijun; Yu, Zengliang

    2010-08-01

    Our previous studies demonstrated distant/abscopal bystander effects in A. thaliana seeds and embryos; the postembryonic development of bystander tissues, such as root hair differentiation, primary root elongation, lateral root initiation and survival, were inhibited significantly by localized irradiation with microbeam protons and low-energy ions. In the present study, we further investigated radiation-induced bystander mutagenic effects in vivo in A. thaliana plants using homologous recombination (HR) and the expression level of the HR-related AtRAD54 gene as mutagenic end points. We found that alpha-particle irradiation of distal primary roots of young seedlings resulted in a significant increase in the frequency of HR in the aerial plants; the increased induction of HR occurred in every true leaf over the course of rosette development. Moreover, we also found that localized alpha-particle irradiation of roots induced a short-term up-regulated expression of the HR-related AtRAD54 gene in the nonirradiated aerial plants. These results suggested the existence of bystander mutagenic effects in vivo in plants. Treatment with the ROS scavenger DMSO dramatically reduced the effects of localized root irradiation on the induction of HR and expression of the AtRAD54 gene in bystander tissues, suggesting that ROS play a critical role in mediating the bystander mutagenic effects in plants. PMID:20681789

  17. The alpha-particle irradiator set up at the ISS for radiobiological studies on targeted and non-targeted effects

    International Nuclear Information System (INIS)

    In this paper we describe the alpha-particle irradiator that has been set up at the Istituto Superiore di Sanita (ISS) for controlled exposure of cultured mammalian cells. It can be equipped with two different sources, namely 2'4'4'Cm and 2'4'1'Am, allowing irradiation at different dose-rates (typically 1-100 mGy/min). The irradiator has dimensions small enough to be inserted into a standard cell culture incubator to perform irradiation of cultured cells in physiological conditions. The dose uniformity is such that the variations in the irradiation area are less than ± 12% of the average dose value on different irradiation areas up to ∼ 25 cm'2. Moreover, in the framework of the FP6 Euratom Integrated Project Non-targeted effects of ionizing radiation (NOTE), Petri dishes were realized for housing permeable membrane insert(s) to be used in co-culture experiments. Aluminium shields were also realized for half shield irradiation experiments. The alpha-particle irradiator of the ISS has been successfully used for studying DNA damage, namely double strand breaks (DSB, as measured by the γ-H2AX assay), in directly hit and in bystander primary human fibroblasts

  18. Alpha-particle effects on high-n instabilities in tokamaks

    International Nuclear Information System (INIS)

    Hot α-particles and thermalized helium ash particles in tokamaks can have significant effects on high toroidal mode number instabilities such as the trapped-electron drift mode and the kinetically calculated magnetohydrodynamic ballooning mode. In particular, the effects can be stabilizing, destabilizing, or negligible, depending on the parameters involved. In high-temperature tokamaks capable of producing significant numbers of hot α-particles, the predominant interaction of the mode with the α-particles is through resonances of various sorts. In turn, the modes can cause significant anomalous transport of the α-particles and the helium ash. Here, results of comprehensive linear eigenfrequency-eigenfunction calculations are presented for relevant realistic cases to show these effects. 24 refs., 12 figs., 6 tabs

  19. Generalized Chaplygin gas with $alpha = 0$ and the $Lambda CDM$ cosmological model

    CERN Document Server

    Fabris, J C

    2004-01-01

    The generalized Chaplygin gas model is characterized by the equation of state $p = - frac{A}{rho^alpha}$. It is generally stated that the case $alpha = 0$ is equivalent to a model with cosmological constant and dust ($Lambda CDM$). In this work we show that, if this is true for the background equations, this is not true for the perturbation equations. Hence, the mass spectrum predicted for both models may differ.

  20. Cyclic deformation behavior of an {alpha}/{beta} titanium alloy. 2: Internal stresses and micromechanic modelling

    Energy Technology Data Exchange (ETDEWEB)

    Feaugas, X.; Clavel, M. [Univ. de Technologie de Compiegne (France); Pilvin, P. [Univ. Paris VI, Evry (France)]|[Ecole des Mines de Paris, Evry (France). Centre des Materiaux

    1997-07-01

    A micromechanic model was used to study the influence of the different microstructure heterogeneity levels of an {alpha}/{beta} titanium alloy during monotonic and cyclic loadings. In the micromechanic model two levels of heterogeneity were considered: the cell and the two phases ({alpha} and {beta}). The cell is defined as an {alpha} (h.c.p.) crystal surrounded by {beta}-phase (b.c.c.). A modified Kroener`s rule is used to describe the stress localization. This rule takes into account the elasto-plastic accommodation between cells and between phases. The main results are the following: the rate of reduction of the {alpha}/{beta} incompatibilities is greater than that associated with inter-cells and the cyclic softening depends not only on the reduction of the transgranular incompatibilities ({alpha}-phase), but also on inter-cell internal stress redistribution.

  1. 3D Effect of Ferromagnetic Materials on Alpha Particle Power Loads on First Wall Structures and Equilibrium on ITER

    International Nuclear Information System (INIS)

    Full text: The finite number and limited toroidal extent of the TF coils cause a periodic variation of the toroidal field called the magnetic ripple. This ripple can provide a significant channel for fast particle leakage, leading to very localized fast particle loads on the walls. Ferromagnetic inserts will be embedded in the double wall structure of the vacuum vessel in order to reduce the ripple. In ITER the toroidal field deviations are locally further enhanced by the presence of discrete ferromagnetic structures, e.g. TBM. Thus, there are complex symmetry-breaking effects. It is not yet fully understood how superimposing the periodic ripple and a local perturbation affect the fast ion confinement and concerns have been voiced that the combined effect might lead to significant channelling of the alpha power. In this work, the wall power loads due to fusion-born alpha particles were restudied for a variety of cases addressing issues such as different wall configurations, proper inclusion of the TBM effect on the magnetic background, and the possible corrections to 3D equilibrium introduced by the ferromagnetic materials using the 3D equilibrium code, VMEC, since 3D corrections to the equilibrium might enhance the alpha particle loss. To properly include the TBM effect on the magnetic background, the FEMAG code was used, and the effect was calculated on the total field including the poloidal field by the plasma current as well as the vacuum field. In the VMEC analysis, it was found that the difference between a full 3D equilibrium reconstruction and 'an axisymmetric equilibrium + vacuum fields' was small. Thus, it was concluded that no 3D equilibrium reconstruction was needed and that it was sufficient to add the vacuum field perturbations onto an axisymmetric equilibrium. Under the new boundary condition, the wall load calculation was carried out by using ASCOT, DELTA5D, and F3D OFMC code. Including the plasma current contribution in the magnetic field

  2. Online maintaining appearance model using particle filter

    Science.gov (United States)

    Chen, Siying; Lan, Tian; Wang, Jianyu; Ni, Guoqiang

    2008-03-01

    Tracking by foreground matching heavily depends on the appearance model to establish object correspondences among frames and essentially, the appearance model should encode both the difference part between the object and background to guarantee the robustness and the stable part to ensure tracking consistency. This paper provides a solution for online maintaining appearance models by adjusting features in the model. Object appearance is co-modeled by a subset of Haar features selected from the over-complete feature dictionary which encodes the discriminative part of object appearance and the color histogram which describes the stable appearance. During the particle filtering process, feature values both from background patches and object observations are sampled efficiently by the aid of "foreground" and "background" particles respectively. Based on these sampled values, top-ranked discriminative features are added and invalid features are removed out to ensure the object being distinguishable from current background according to the evolving appearance model. The tracker based on this online appearance model maintaining technique has been tested on people and car tracking tasks and promising experimental results are obtained.

  3. Modeling Deep Burn TRISO particle nuclear fuel

    Science.gov (United States)

    Besmann, T. M.; Stoller, R. E.; Samolyuk, G.; Schuck, P. C.; Golubov, S. I.; Rudin, S. P.; Wills, J. M.; Coe, J. D.; Wirth, B. D.; Kim, S.; Morgan, D. D.; Szlufarska, I.

    2012-11-01

    Under the DOE Deep Burn program TRISO fuel is being investigated as a fuel form for consuming plutonium and minor actinides, and for greater efficiency in uranium utilization. The result will thus be to drive TRISO particulate fuel to very high burn-ups. In the current effort the various phenomena in the TRISO particle are being modeled using a variety of techniques. The chemical behavior is being treated utilizing thermochemical analysis to identify phase formation/transformation and chemical activities in the particle, including kernel migration. Density functional theory is being used to understand fission product diffusion within the plutonia oxide kernel, the fission product's attack on the SiC coating layer, as well as fission product diffusion through an alternative coating layer, ZrC. Finally, a multiscale approach is being used to understand thermal transport, including the effect of radiation damage induced defects, in a model SiC material.

  4. Efficient particle continuation model predictive control

    OpenAIRE

    Knyazev, Andrew; Malyshev, Alexander,

    2015-01-01

    Continuation model predictive control (MPC), introduced by T. Ohtsuka in 2004, uses Krylov-Newton approaches to solve MPC optimization and is suitable for nonlinear and minimum time problems. We suggest particle continuation MPC in the case, where the system dynamics or constraints can discretely change on-line. We propose an algorithm for on-line controller implementation of continuation MPC for ensembles of predictions corresponding to various anticipated changes and demonstrate its numeric...

  5. Moderate Deviations for Mean Field Particle Models

    CERN Document Server

    Del Moral, Pierre; Wu, Liming

    2012-01-01

    This article is concerned with moderate deviation principles of a general class of mean eld type interacting particle models. We discuss functional moderate deviations of the occupation measures for both the strong -topology on the space of fi nite and bounded measures as well as for the corresponding stochastic processes on some class of functions equipped with the uniform topology. Our approach is based on an original semigroup analysis combined with stochastic perturbation techniques and projective limit large deviation methods.

  6. Simulated ablation of carbon wall by alpha particles for a laser fusion reactor

    International Nuclear Information System (INIS)

    Thermal reactions of materials heated by charged particles may lead to serious damage in a laser fusion reactor. When charged particles irradiate and heat the wall material with high intensity like at above 109 W/cm2, the material can be ablated. Once the wall is ablated, expanding gas or plasma can disturb the propagation of laser light irradiating the fuel target if it stagnates long enough for next laser shot. In order to understand the ablation dynamics in detail, we have performed 1-D hydro simulation to evaluate this ablation. As a new feature, we introduce the calculation of energy deposition by charged particles focusing on the interaction between ablated material and charged particles

  7. On the decay of compound nuclei following alpha-particle and 12C induced reactions

    International Nuclear Information System (INIS)

    Multiple coincidence rates have been measured using a detector system consisting of a Ge(Li) spectrometer and eight NaI(Tl) or eight liquid scintillators. Reactions induced by α-particles with energies of 51-55 MeV and 118 MeV 12C ions are studied. The data are analysed to give the first and second central moments of the distribution of the number of γ-rays feeding individual levels in the final nuclei. When these numbers are compared to spin distributions calculated with the statistical model code GROGI the relative importance of dipole and quadrupole deexcitation modes can be ascertained. In particular, in the 122Te(α,4n)122Xe reaction the γ-decay prior to the entry into the ground band is well described as a statistical process proceeding to 50% by dipole and 50% by quadrupole radiation. In the 166Er(α,4n)166Yb and 192Os(α,4n)192Pt reactions the relative amount of quadrupole radiation is larger and it seems that the dipole and quadrupole decay takes place via separate cascades. In the 164Dy(12C,7-8n) reactions the average multiplicity is independent of spin, suggesting that the nucleus forgets the spin of the entry state before the process enters into the ground band. In the 176Yb(12C,8n)180Os reaction, finally, the nucleus difinitely retains memory of the entry state during the decay. In this last case the multiplicity measurement is combined with a γ-ray singles measurement to give an average excitation energy prior to the α-decay and the average moment of inertia characterising the decay of the high-spin states. (orig.)

  8. Energy resolution for alpha particles in liquid argon doped with allene

    International Nuclear Information System (INIS)

    The charge response of liquid argon doped with small quantities of allene (C3H4) to α-particles has been studied. The addition of allene increased the amount of collected charge through photoionization and greatly improved the energy resolution of the incident α-particles. The noise subtracted resolution was 1.4% FWHM at the best with 4 ppm allene doped liquid argon. (orig.)

  9. Evolutionary stellar population synthesis with MILES - II. Scaled-solar and \\alpha-enhanced models

    CERN Document Server

    Vazdekis, A; Cassisi, S; Ricciardelli, E; Falcón-Barroso, J; Sánchez-Blázquez, P; La Barbera, F; Beasley, M A; Pietrinferni, A

    2015-01-01

    We present models that predict spectra of old- and intermediate-aged stellar populations at 2.51\\AA\\ (FWHM) with varying [\\alpha/Fe] abundance. The models are based on the MILES library and on corrections from theoretical stellar spectra. The models employ recent [Mg/Fe] determinations for the MILES stars and BaSTI scaled-solar and \\alpha-enhanced isochrones. We compute models for a suite of IMF shapes and slopes, covering a wide age/metallicity range. Using BaSTI, we also compute "base models" matching The Galactic abundance pattern. We confirm that the \\alpha-enhanced models show a flux excess with respect to the scaled-solar models blue-ward $\\sim$4500\\AA, which increases with age and metallicity. We also confirm that both [MgFe] and [MgFe]' indices are [\\alpha/Fe]-insensitive. We show that the sensitivity of the higher order Balmer lines to [\\alpha/Fe] resides in their pseudo-continua, with narrower index definitions yielding lower sensitivity. We confirm that the \\alpha-enhanced models yield bluer (redde...

  10. Cross-sections for Balmer-alpha excitation in heavy-particle collisions

    International Nuclear Information System (INIS)

    Doppler shifted and unshifted Balmer-alpha radiation has been observed in the absolute sense for energetic H+, H2+ and H3+ ions incident on molecular hydrogen by the method of decay inside the target within the energy range of 20 keV to 150 keV. Most of the measurements were based on single-collision conditions, but a simple thick-target experiment has been tried for the case of dissociative excitation of the target molecules by H atoms

  11. Magnetic dynamics of small alpha-Fe2O3 and NiO particles

    DEFF Research Database (Denmark)

    Lefmann, K.; Bødker, Franz; Hansen, Mikkel Fougt; Vazquez, H.; Christensen, N.B.; Clausen, K.N.; Mørup, Steen

    We have studied the magnetic dynamics in nanocrystalline samples of alpha-Fe2O3 (hematite) and NiO by inelastic neutron scattering. By measuring around the structural and the antiferromagnetic reflections, we have probed uniform and staggered magnetic oscillations, respectively. In the hematite...... sign of superparamagnetic relaxation. Studies of the antiferromagnetic signal from NiO also show evidence of collective magnetic excitations, but with a higher energy of the precession state than for hematite. The inelastic signal at the structural reflection of NiO presents evidence for uniform...

  12. Experimental validation of an analytical method to obtain the response function of an alpha particle spectrometer

    International Nuclear Information System (INIS)

    In a previous paper, one of the authors suggested an analytical method for calculation of the response function of an alpha spectrometer for the case of large solid angles. This paper describes the experimental verification of the method. Spectra of a well-known natural uranium sample were measured with a 450 mm2 Si detector and compared to the theoretical predictions. The measurements were carried out with two different geometrical configurations. In both cases a good agreement was observed between experimental and theoretical results

  13. Charge State Model of Solar Energetic Particles

    Science.gov (United States)

    Del Peral, L.; Pérez-Peraza, J. A.; Rodríguez Frías, M. D.

    2013-05-01

    Charge states of heavy ions in Solar Energetic Particle (SEP) events observed at the Earth's neighborhood with experiments on board satellites give us information about physical properties of plasma where acceleration occurs. SEP detection is performed near the Earth, therefore not only physical condition of the plasma source of accelerated particles have to be taken into account. We have developed a charge state model in order to explain the evolution of particle charge states under solar acceleration. Charge-interchange processes between the accelerated ions and the plasma matter in the acceleration region are considered on basis of electron loss and capture cross sections at high energies. We have applied the model to observational data from satellites measuring charge states of SEPs. In contrast with other models that use ionization and recombination cross-sections that require application of thermal equilibrium, our model assumes that the acceleration is so fast that thermal equilibrium can not be applied to the change interchange processes. Therefore we employ in our model high energy cross-sections for electron capture and loss, since the population which is being accelerated acquires a non-thermal spectrum. We have developed temperature dependent cross-sections. Acceleration begins from a thermal distribution. As soon as the particles increase their energy by the acceleration process, they acquire an energy spectrum which differs from the Maxwellian thermal one while interacting with the background thermal matter. Figure 1 presents the results of our model that fit experimental charge states of Fe ions from two impulsive SEP events detected by the SEPICA satellite in July 1999. We obtain good fitting for source temperature of 1.8 \\cdot 106 K and density of 5\\cdot108 cm-3 and acceleration efficiency of 1.8\\cdot 10-2 s-1 for the July 20th 1999 event and 3.3\\cdot 10-2 s-1 for the July 3rd 1999. Good concordance between experimental data and our model have

  14. Modeling positronium beyond the single particle approximation

    Science.gov (United States)

    Zubiaga, A.; Ervasti, M. M.; Makkonen, I.; Harju, A.; Tuomisto, F.; Puska, M. J.

    2016-03-01

    Understanding the properties of the positronium atom in matter is of interest for the interpretation of positron annihilation experiments. This technique has a unique capability for the investigation of nanometer sized voids and pores in soft molecular materials (polymers, liquids or biostructures) and porous materials. However, detailed interpretations of the experimental data rely on modeling of the annihilation properties of positronium in the host material. New applications of the technique are being developed but the computational models still are based on single particle approaches and there is no way to address the influence of the electronic properties of the host material. In this work we discuss new directions of research.

  15. Empirical particle transport model for tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Petravic, M.; Kuo-Petravic, G.

    1986-08-01

    A simple empirical particle transport model has been constructed with the purpose of gaining insight into the L- to H-mode transition in tokamaks. The aim was to construct the simplest possible model which would reproduce the measured density profiles in the L-regime, and also produce a qualitatively correct transition to the H-regime without having to assume a completely different transport mode for the bulk of the plasma. Rather than using completely ad hoc constructions for the particle diffusion coefficient, we assume D = 1/5 chi/sub total/, where chi/sub total/ approx. = chi/sub e/ is the thermal diffusivity, and then use the kappa/sub e/ = n/sub e/chi/sub e/ values derived from experiments. The observed temperature profiles are then automatically reproduced, but nontrivially, the correct density profiles are also obtained, for realistic fueling rates and profiles. Our conclusion is that it is sufficient to reduce the transport coefficients within a few centimeters of the surface to produce the H-mode behavior. An additional simple assumption, concerning the particle mean-free path, leads to a convective transport term which reverses sign a few centimeters inside the surface, as required by the H-mode density profiles.

  16. Evaluation through comet assay of DNA damage induced in human lymphocytes by alpha particles. Comparison with protons and Co-60 gamma rays

    International Nuclear Information System (INIS)

    Several techniques with different sensitivity to single-strand breaks and/or double strand breaks were applied to detect DNA breaks generated by high LET particles. Tests that assess DNA damage in single cells might be the appropriate tool to estimate damage induced by particles, facilitating the assessment of heterogeneity of damage in a cell population. The microgel electrophoresis (comet) assay is a sensitive method for measuring DNA damage in single cells. The objective of this work was to evaluate the proficiency of comet assay to assess the effect of high LET radiation on peripheral blood lymphocytes, compared to protons and Co-60 gamma rays. Materials and methods: Irradiations of blood samples were performed at TANDAR laboratory (Argentina). Thin samples of human peripheral blood were irradiated with different doses (0-2.5 Gy) of 20.2 MeV helium-4 particles in the track segment mode, at nearly constant LET. Data obtained were compared with the effect induced by a MeV protons and Co-60 gamma rays. Alkaline comet assay was applied. Comets were quantified by the Olive tail moment. Distribution of the helium-4 particle and protons were evaluated considering Poisson distribution in lymphocyte nuclei. The mean dose per nucleus per particle result 0.053 Gy for protons and 0.178 Gy for helium-4 particles. When cells are exposed to a dose of 0.1 Gy, the hit probability model predicts that 43% of the nuclei should have experienced and alpha traversal while with protons, 85% of the nuclei should be hit. The experimental results show a biphasic response for helium-4 particles (0.1 Gy), indicating the existence of two subpopulations: unhit and hit. Distributions of tail moment as a function of fluence and experimental dose for comets induced by helium-4 particles, protons and Co-60 gamma rays were analyzed. With helium-4 irradiations, lymphocyte nuclei show an Olive tail moment distribution flattened to higher tail moments a dose increase. However, for irradiations with

  17. Discrete mathematical physics and particle modeling

    International Nuclear Information System (INIS)

    The theory and application of the arithmetic approach to the foundations of both Newtonian and special relativistic mechanics are explored. Using only arithmetic, a reformulation of the Newtonian approach is given for: gravity; particle modeling of solids, liquids, and gases; conservative modeling of laminar and turbulent fluid flow, heat conduction, and elastic vibration; and nonconservative modeling of heat convection, shock-wave generation, the liquid drop problem, porous flow, the interface motion of a melting solid, soap films, string vibrations, and solitons. An arithmetic reformulation of special relativistic mechanics is given for theory in one space dimension, relativistic harmonic oscillation, and theory in three space dimensions. A speculative quantum mechanical model of vibrations in the water molecule is also discussed. 82 references

  18. A Deformable Model for Bringing Particles in Focus

    DEFF Research Database (Denmark)

    Dahl, Anders Lindbjerg; Jørgensen, Thomas Martini; Larsen, Rasmus

    We provide a deformable model for particle analysis. We in- vestigate particle images from a backlit microscope system where parti- cles suer from out-of-focus blur. The blur is a result of particles being in front or behind the focus plane, and the out-of-focus gives a bias towards overestimating...... the particle size. This can be handled by only including the particles in focus, but most of the depicted particles will be left out of the analysis, which weakens the statistical estimate of the monitored process. We propose a new method for particle analysis. The model in- corporates particle shape...

  19. General transformation of alpha cluster model wave function to jj-coupling shell model in various 4N nuclei

    OpenAIRE

    Itagaki, N.; Matsuno, H.; Suhara, T.

    2015-01-01

    The antisymmetrized quasi-cluster model (AQCM) is a method to describe a transition from the alpha-cluster wave function to the jj-coupling shell model wave function. In this model, the cluster-shell transition is characterized by only two parameters; R representing the distance between alpha clusters and Lambda describing the breaking of alpha clusters, and the contribution of the spin-orbit interaction, very important in the jj-coupling shell model, can be taken into account starting with t...

  20. Evidence of DNA double strand breaks formation in Escherichia coli bacteria exposed to alpha particles of different LET assessed by the SOS response

    International Nuclear Information System (INIS)

    Ionizing radiation produces a plethora of lesion upon DNA which sometimes is generated among a relatively small region due to clustered energy deposition events, the so called locally multiply damaged sites that could change to DSB. Such clustered damages are more likely to occur in high LET radiation exposures. The effect of alpha particles of different LET was evaluated on the bacterium Escherichia coli either by survival properties or the SOS response activity. Alpha radiation and LET distribution was controlled by means of Nuclear Track Detectors. The results suggest that alpha particles produce two types of lesion: lethal lesions and SOS inducing-mutagenic, a proportion that varies depending on the LET values. The SOS response as a sensitive parameter to assess RBE is mentioned. - Highlights: ► High LET radiation produce locally multiple damaged sites upon DNA. ► Bacteria were exposed to alpha particles of different LET. ► Results suggest that alpha particles produce lethal and SOS inducing/mutagenic. ► The proportion of such lesions varies depending on the LET values.

  1. Influence of second phase particles on the deformation of. alpha. -Fe at cryogenic temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Yue, S.; Bratina, W.J. (Univ. of Toronto (Canada))

    The deformation of fine grained polygonal ferrite (HSLA) steels was shown to be sensitive to variations in second phase particle characteristics. In particular a steel which contained a dispersion of fine niobium carbonitrides exhibited virtually no elongation to fracture at 77K, whereas a steel containing both fine niobium carbonitrides and coarser Fe{sub 3}C type particles exhibited considerable Luders strain and strain to fracture at 77K. It was observed that for the first steel, necking coincided with the nucleation of a Luders band whereas in the second steel, the nucleated Luders band propagated along the entire gauge length even at 77K. Luders band propagation and the delay of the onset of necking are connected by work hardening which, in turn, is governed by microstructural parameters such as grain size and second phase particles and it is these that result in this contrasting deformation behavior at 77K.

  2. Particle Tracking and Deposition from CFD Simulations using a Viscoelastic Particle Model

    OpenAIRE

    Losurdo, M.

    2009-01-01

    In the present dissertation the mathematical modelling of particle deposition is studied and the solution algorithms for particle tracking, deposition and deposit growth are developed. Particle deposition is modelled according to mechanical impact and contact mechanics taking into account the dependency on time, temperature and particle-deposit composition explicitly. Indeed, such a model lies in the field of the rheology of visco-elastic solids which the author of this dissertation refers to...

  3. Constituent-Quark Model and New Particles

    CERN Document Server

    Akers, D

    2003-01-01

    An elementary constituent-quark (CQ) model by Mac Gregor is reviewed with currently published data from light meson spectroscopy. It was previously shown in the CQ model that there existed several mass quanta m = 70 MeV, B = 140 MeV and X = 420 MeV, which were responsible for the quantization of meson yrast levels. The existence of a 70-MeV quantum was postulated by Mac Gregor and was shown to fit the Nambu empirical mass formula mn = (n/2)137me, n a positive integer. It is shown in this paper that recent data of new light mesons fit into the CQ model. With the introduction of the Russell-Saunders coupling scheme into the CQ model, several new meson particles are predicted to exist. The existence of the f0(560) meson is predicted and is shown to fit current experimental data from the Particle Data Group listing. The existence of meson partners or groupings is shown.

  4. Measurements of nuclear $\\gamma$-ray line emission in interactions of protons and $\\alpha$ particles with N, O, Ne and Si

    OpenAIRE

    Benhabiles-Mezhoud, H.; Kiener, J.; Thibaud, J. -P.; Tatischeff, V.; Deloncle, I.; Coc, A.; Duprat, J.; Hamadache, C.; Lefebvre-Schuhl, A.; Dalouzy, J. -C.; de Grancey, F.; Oliveira, F.; Dayras, F.; De Séréville, N.; Pellegriti, M. -G.

    2010-01-01

    $\\gamma$-ray production cross sections have been measured in proton irradiations of N, Ne and Si and $\\alpha$-particle irradiations of N and Ne. In the same experiment we extracted also line shapes for strong $\\gamma$-ray lines of $^{16}$O produced in proton and $\\alpha$-particle irradiations of O. For the measurements gas targets were used for N, O and Ne and a thick foil was used for Si. All targets were of natural isotopic composition. Beams in the energy range up to 26 MeV for protons and...

  5. Radiation damage effects from alpha particle and influence of thermal annealing to defects at room temperature in silicon multiplication avalanche photo diode (MAPD)

    International Nuclear Information System (INIS)

    The increasing interest of new generation accelerators demand to produce detectors based on semiconductors which have radiation hardness. The getting progress in detectors based on semiconductor do not allow to say that the problem was solved. Thus producing radiation hardness detectors became problem for today. In the last several years the advanced progress in area MAPD allows to use this type diode in high energy physics as multiplier tube and detectors so investigation of radiation hardness of MAPD is very important. Influence of high energy protons, neutron and positron to MAPD were investigated. Influence of alpha particle is not investigated yet so this paper dedicated to investigate influence of alpha particle to MAPD.

  6. Results of solid state nuclear track detector technique application in radon detection, by alpha particles tracks, for uranium prospecting in Caetite (BA-Brazil)

    International Nuclear Information System (INIS)

    The solid state nuclear track detector technique has been used in radon detection, by alpha particles tracks for uranium prospecting on the ground in Caetite city (Bahia-Brazil). The sensitive film to alpha particles used were CA 8015 exposed during 15 days and the results of three anomalies of this region are showed in a form of maps, made with the density of tracks obtained, and were compared with scintillation counter measurements. The technique showed to be simple and an effective auxiliary for the prospection of uranium ore bodies. The initial uranium exploration costs can be reduced by using this technique. (author)

  7. Alpha particle slowing-down characteristics and the effect on MHD instability excitation at high-density operation points in FFHRs

    International Nuclear Information System (INIS)

    Alpha-particle slowing-down behaviors at low-temperature, high-density operation points in force-free helical reactors (FFHRs) are examined on the basis of a Fokker-Planck (FP) simulation that simultaneously consider the balance among generation, slowing down, and loss from the plasma in parallel with the density dependence of the Alfvén speed. An accurate treatment of the boundary velocity region between thermal and non-thermal components is shown to be important in evaluating the alpha particle population that can induce instability. In a typical high-density, low-temperature operation point in an FFHR, this population is reduced. (author)

  8. Study by {alpha}-particle scattering, of the collective states of closed shell nuclei with 28 neutrons, 28 and 50 protons; Etude des etats a caractere collectif des noyaux au voisinage des couches fermees par diffusion inelastique des particules {alpha}

    Energy Technology Data Exchange (ETDEWEB)

    Bruge, G. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1967-01-01

    This report gives the results from a systematic study by 44 MeV {alpha} particle scattering on the collective states of closed shell nuclei with 28 neutrons, 28 and 50 protons especially in the energy region corresponding to the two phonon vibrational triplet. The nuclei studied are: {sup 46}Ti, {sup 48}Ti, {sup 50}Ti, {sup 52}Cr, {sup 54}Fe, {sup 56}Fe, {sup 58}Fe, {sup 58}Ni, {sup 60}Ni, {sup 62}Ni, {sup 64}Ni, {sup 112}Sn, {sup 114}Sn, {sup 116}Sn, {sup 118}Sn, {sup 120}Sn, {sup 122}Sn and {sup 124}Sn. The theoretical analysis has been made with the Austern and Blair model using a phase shift analysis of the elastic scattering. Deformation lengths {delta}{sub I} = {beta}{sub I}R and transition probabilities obtained are compared with several experimental and theoretical data. (author) [French] Ce rapport donne les resultats d'une etude systematique par diffusion de particules {alpha} de 44 MeV des etats collectifs des noyaux au voisinage des couches fermees a 28 neutrons et 28 et 50 protons, specialement dans la region correspondant au triplet vibrationnel a deux phonons. Les noyaux etudies sont: {sup 46}Ti, {sup 48}Ti, {sup 50}Ti, {sup 52}Cr, {sup 54}Fe, {sup 56}Fe, {sup 58}Fe, {sup 58}Ni, {sup 60}Ni, {sup 62}Ni, {sup 64}Ni, {sup 112}Sn, {sup 114}Sn, {sup 116}Sn, {sup 118}Sn, {sup 120}Sn, {sup 122}Sn et {sup 124}Sn. L'analyse theorique a ete faite a l'aide du modele de Austern et Blair utilisant une analyse en dephasages de la diffusion elastique. Les longueurs de deformation {delta}I = {beta}{sub I}R obtenues pour chaque niveau sont comparees a plusieurs donnees experimentales et theoriques. (auteur)

  9. Alpha particle effects in burning tokamak plasmas: overview and specific examples

    International Nuclear Information System (INIS)

    Using the total power balance of an ignited tokamak plasma as a guideline, a range of alpha driven effects is surveyed regarding their impact on achieving and maintaining fusion burn. Specific examples of MHD and kinetic modes and multi species transport dynamics are discussed, including the possible interaction of these categories of effects. This power balance approach rather than a straightforward enumeration of possible effects serves to reveal their non-linear dependence and the ensuing fragility of our understanding of the approach to and maintenance of ignition. Specific examples are given of the interaction between α-power driven sawtoothing and ideal MHD stability, and direct α-effects on MHD modes including kinetic corrections. Anomalous ion heat transport and central impurity peaking mechanisms and anomalous and collisional α-transport including the ambipolar electric field are discussed

  10. Use of the Kalman filter in signal processing to reduce beam requirements for alpha-particle diagnostics

    International Nuclear Information System (INIS)

    Several techniques proposed for diagnosing the velocity distribution of fast alpha-particles in a burning plasma require the injection of a beam of fast neutral atoms as probes. The author discusses how improving signal detection techniques is a high leverage factor in reducing the cost of the diagnostic beam. Optimal estimation theory provides a computational algorithm, the Kalman filter, that can optimally estimate the amplitude of a signal with arbitrary (but known) time dependence in the presence of noise. In one example presented, based on a square-wave signal and assumed noise levels, the Kalman filter achieves an enhancement of signal detection efficiency of about a factor of 10 (as compared with the straightforward observation of the signal superimposed on noise) with an observation time of 100 signal periods

  11. Hit rates and radiation doses to nuclei of bone lining cells from alpha-particle-emitting radionuclides

    Science.gov (United States)

    Polig, E.; Jee, W. S.; Kruglikov, I. L.

    1992-01-01

    Factors relating the local concentration of a bone-seeking alpha-particle emitter to the mean hit rate have been determined for nuclei of bone lining cells using a Monte Carlo procedure. Cell nuclei were approximated by oblate spheroids with dimensions and location taken from a previous histomorphometric study. The Monte Carlo simulation is applicable for planar and diffuse labels at plane or cylindrical bone surfaces. Additionally, the mean nuclear dose per hit, the dose mean per hit, the mean track segment length and its second moment, the percentage of stoppers, and the frequency distribution of the dose have been determined. Some basic features of the hit statistics for bone lining cells have been outlined, and the consequences of existing standards of radiation protection with regard to the hit frequency to cell nuclei are discussed.

  12. Alpha-particle spectrometry of large-area samples using an open-flow pulse ionisation chamber

    International Nuclear Information System (INIS)

    Ionization chambers are established and well known detectors of ionizing radiation. Current-mode chambers are in frequent use in such fields as dosimetry, environmental surveillance and radiation protection, while pulse-mode, Frisch-grid, chambers used to be used for spectrometry and have largely been replaced by scintillation and semiconducting-diode detectors. Dealing specifically with low-level alpha-particle spectrometry, the surface-barrier or ion-implanted semiconducting detectors are the standard choice, but in some applications where radiochemical treatment and production of small electroplated samples are impossible or inconvenient, pulse-ionization chambers are still in use. For breath and air-radon samples scintillation cells dominate, but pulse ionization chambers are utilized as high-standard laboratory instruments. For continuous measurements of radon concentration in air, a multiwire-electrode ionization chamber has been described. A commercial radon-in-air system, based on a pulse ionization chamber is described. (author)

  13. Development of diamond thin film-based alpha particle detectors for online assay of plutonium content in corrosive liquid medium

    International Nuclear Information System (INIS)

    In the present work, diamond thin films were prepared using microwave plasma chemical vapor deposition (MPCVD) method and characterized using XRD, OES, SEM, Raman spectroscopy and I-V techniques. These films were subjected to annealing and chemical cleaning for further improving the film quality. Surface metallization was obtained by gold deposition using PVD. These films were configured in semiconductor-insulator-metal heterostructure and mounted in SS shells. Gold coated growth surface (detector's active area) was sealed by chemical resistant sealing. Suitable bias was applied between the front and back electrical contacts to enable charge collection generated upon alpha particle interaction with diamond. The photograph of developed detector in the lab is shown

  14. Poloidal drift enhancement for improved collisionless alpha particle confinement in stellarator configurations in the quasi-isodynamic category

    International Nuclear Information System (INIS)

    Poloidal closure of contours of the second adiabatic invariant has been reported to be an essential issue in the realization of good collisionless alpha particle confinement in stellarator configurations in the quasi-isodynamic category. This common feature is examined from a different aspect, that of the poloidal drift enhancement. This is realized by radial variation of the uniform magnetic field component with a diamagnetic effect for finite beta equilibria in the W7-X stellarator, which gives poloidal drift enhancement everywhere on a flux surface. On the other hand, the additional helicity introduced to the vacuum field in the quasi-isodynamic configuration can also enhance poloidal drift. The different methods for poloidal drift enhancement are clarified systematically on the basis of the magnetic field spectrum and the magnetic topography. (author)

  15. Development of a strongly focusing high-intensity He(+) ion source for a confined alpha particle measurement at ITER.

    Science.gov (United States)

    Kisaki, M; Shinto, K; Kobuchi, T; Okamoto, A; Kitajima, S; Sasao, M; Tsumori, K; Nishiura, M; Kaneko, O; Matsuda, Y; Wada, M; Sakakita, H; Kiyama, S; Hirano, Y

    2008-02-01

    A strongly focusing high-intensity He(+) ion source has been designed and constructed as a beam source for a high-energy He(0) beam probe system for diagnosis of fusion produced alpha particles in the thermonuclear fusion plasmas. The He(+) beam was extracted from the ion source at an acceleration voltage of 18-35 kV. Temperature distributions of the beam target were observed with an IR camera. The 1/e-holding beam profile half-width was about 15 mm at optimum perveance (Perv) of 0.03 (I(beam)=2.4 A). A beam current about 3 A was achieved at an acceleration voltage of 26.7 kV with an arc power of 10 kW (Perv=0.023). PMID:18315239

  16. Optimizing the Delivery of Short-Lived Alpha Particle-Emitting Isotopes to Solid Tumors

    International Nuclear Information System (INIS)

    The underlying hypothesis of this project was that optimal alpha emitter-based radioimmunotherapy (RAIT) could be achieved by pairing the physical half-life of the radioisotope to the biological half-life of the targeting vehicle. The project had two specific aims. The first aim was to create and optimize the therapeutic efficacy of 211At-SAPS-C6.5 diabody conjugates. The second aim was to develop bispecific-targeting strategies that increase the specificity and efficacy of alpha-emitter-based RAIT. In the performance of the first aim, we created 211At-SAPS-C6.5 diabody conjugates that specifically targeted the HER2 tumor associated antigen. In evaluating these immunoconjugates we determined that they were capable of efficient tumor targeting and therapeutic efficacy of established human tumor xenografts growing in immunodeficient mice. We also determined that therapeutic doses were associated with late renal toxicity, likely due to the role of the kidneys in the systemic elimination o f these agents. We are currently performing more studies focused on better understanding the observed toxicity. In the second aim, we successfully generated bispecific single-chain Fv (bs-scFv) molecules that co-targeted HER2 and HER3 or HER2 and HER4. The in vitro kinetics and in vivo tumor-targeting properties of these molecules were evaluated. These studies revealed that the bs-scFv molecules selectively localized in vitro on tumor cells that expressed both antigens and were capable of effective tumor localization in in vivo studies

  17. Optimizing the Delivery of Short-Lived Alpha Particle-Emitting Isotopes to Solid Tumors

    Energy Technology Data Exchange (ETDEWEB)

    Adams, Gregory P.

    2004-11-24

    The underlying hypothesis of this project was that optimal alpha emitter-based radioimmunotherapy (RAIT) could be achieved by pairing the physical half-life of the radioisotope to the biological half-life of the targeting vehicle. The project had two specific aims. The first aim was to create and optimize the therapeutic efficacy of 211At-SAPS-C6.5 diabody conjugates. The second aim was to develop bispecific-targeting strategies that increase the specificity and efficacy of alpha-emitter-based RAIT. In the performance of the first aim, we created 211At-SAPS-C6.5 diabody conjugates that specifically targeted the HER2 tumor associated antigen. In evaluating these immunoconjugates we determined that they were capable of efficient tumor targeting and therapeutic efficacy of established human tumor xenografts growing in immunodeficient mice. We also determined that therapeutic doses were associated with late renal toxicity, likely due to the role of the kidneys in the systemic elimination o f these agents. We are currently performing more studies focused on better understanding the observed toxicity. In the second aim, we successfully generated bispecific single-chain Fv (bs-scFv) molecules that co-targeted HER2 and HER3 or HER2 and HER4. The in vitro kinetics and in vivo tumor-targeting properties of these molecules were evaluated. These studies revealed that the bs-scFv molecules selectively localized in vitro on tumor cells that expressed both antigens and were capable of effective tumor localization in in vivo studies.

  18. Alpha particle angular distribution of oriented 189,191,193Bi

    International Nuclear Information System (INIS)

    Angular distribution data for α particles emitted in the enhanced decay of on-line oriented neutron deficient isotopes 189,191,193Bi near mid-shell (N=104) are presented. They give additional support for the recent finding that anisotropic α emission in enhanced decays from near-spherical nuclei is mainly determined by nuclear structure effects. (authors)

  19. Low-level measurement of alpha-particle emitting nuclei in ceramics and lead

    International Nuclear Information System (INIS)

    Nearly all natural materials contain trace quantities of uranium (U) and thorium (Th) and their daughter nuclides, many of which emit α-particles in their decay. Lead, at the end of the U-decay chain, typically contains some radioactive 210Pb which is chemically inseparable from the other Pb isotopes. α-particle emission from these decays can affect sensitive electronic components, such as memory chips or processors. Measurement of α-particle emitters can be accomplished by direct detection of the α-particles (which typically provides no positive identification of the emitting isotope because of energy loss in the sample) or by low-background γ-ray spectroscopy (which does provide positive identification via characteristic γ-rays). The latter is by far the best method for screening kg-sized samples of materials like ceramics, aluminum, iron, or copper. The difference between α counting and γ-ray spectroscopy is less for measuring 210Pb in Pb since the 46.5 keV characteristic γ-rays directly following the 210Pb decay are strongly absorbed and both methods are limited to thin layers. This paper discusses these two cases and concludes that a large n-type germanium γ-ray spectrometer is probably the best overall system for both measurements. (author)

  20. Study of pure and Pb{sup 2+} ions doped CsI crystals under alpha particles excitations

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, Maria da Conceicao Costa; Madi Filho, Tufic; Hamada, Margarida Mizue, E-mail: macoper@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2011-07-01

    Scintillation crystals have been used in various fields, such as high energy physics, nuclear instrumentation, radiation measurements, medical imaging, nuclear tomography, astrophysics and other fields of science and engineering. For these applications, the development of good performance scintillation crystals is required. Scintillation crystals based on cesium iodide (CsI) matrix are matters with relatively low hygroscope, easy handling and low cost, characteristics that favor their use as radiation detectors. In this work, pure CsI crystal and lead doped CsI crystals were grown using the Bridgman vertical technique. The concentration of the lead doping element (Pb) was studied in the range of 10{sup -2} M to 5x10{sup -4} M. The distribution of the doping element in the crystalline volume was determined by flame atomic absorption. The CsI:Pb crystal with nominal concentration of 10{sup -3} M was cut into 14 slices of 6 mm. The results show a higher concentration at the top of the crystal with a decrease in the initial phase of growth. The dopant concentration of Pb showed good uniformity from the slice 2 to the slice 12: the region is, therefore, suitable for use as radiation detector. The luminescence emission of these crystals were measured. A predominant luminescence band near 450 nm and a single broad band around 320 nm were found with the addition of the Pb{sup 2+} ions. Analyses were carried out to evaluate the developed scintillators, concerning alpha particles. The resolution of 5.6% was obtained for the CsI:Pb 5x10{sup -4} M crystal, when excited with alpha particles from a {sup 241}Am source, with energy of 5.54 MeV. (author)

  1. NOGAPS-ALPHA model simulations of stratospheric ozone during the SOLVE2 campaign

    Directory of Open Access Journals (Sweden)

    J. P. McCormack

    2004-01-01

    Full Text Available This paper presents three-dimensional prognostic O3 simulations with parameterized gas-phase photochemistry from the new NOGAPS-ALPHA middle atmosphere forecast model. We compare 5-day NOGAPS-ALPHA hindcasts of stratospheric O3 with satellite and DC-8 aircraft measurements for two cases during the SOLVE II campaign: (1 the cold, isolated vortex during 11-16 January 2003; and (2 the rapidly developing stratospheric warming of 17-22 January 2003. In the first case we test three different photochemistry parameterizations. NOGAPS-ALPHA O3 simulations using the NRL-CHEM2D parameterization give the best agreement with SAGE III and POAM III profile measurements. 5-day NOGAPS-ALPHA hindcasts of polar O3 initialized with the NASA GEOS4 analyses produce better agreement with observations than do the operational ECMWF O3 forecasts of case 1. For case 2, both NOGAPS-ALPHA and ECMWF 114-h forecasts of the split vortex structure in lower stratospheric O3 on 21 January 2003 show comparable skill. Updated ECMWF O3 forecasts of this event at hour 42 display marked improvement from the 114-h forecast; corresponding updated 42-hour NOGAPS-ALPHA prognostic O3 fields initialized with the GEOS4 analyses do not improve significantly. When NOGAPS-ALPHA prognostic O3 is initialized with the higher resolution ECMWF O3 analyses, the NOGAPS-ALPHA 42-hour lower stratospheric O3 fields closely match the operational 42-hour ECMWF O3 forecast of the 21 January event. We find that stratospheric O3 forecasts at high latitudes in winter can depend on both model initial conditions and the treatment of photochemistry over periods of 1-5 days. Overall, these results show that the new O3 initialization, photochemistry parameterization, and spectral transport in the NOGAPS-ALPHA NWP model can provide reliable short-range stratospheric O3 forecasts during Arctic winter.

  2. Particle Tracking and Deposition from CFD Simulations using a Viscoelastic Particle Model

    NARCIS (Netherlands)

    Losurdo, M.

    2009-01-01

    In the present dissertation the mathematical modelling of particle deposition is studied and the solution algorithms for particle tracking, deposition and deposit growth are developed. Particle deposition is modelled according to mechanical impact and contact mechanics taking into account the depend

  3. Is the Double Giant Dipole Resonance Process Responsible for Alpha Emission in Ternary Fission?

    Institute of Scientific and Technical Information of China (English)

    HAN Hong-Yin(韩洪银); WAND Yi-Hua(王屹华); G.Mouze

    2001-01-01

    The Monte Carlo program built on the double giant dipole resonance model proposed by Mouze et al. [Nuovo Cimento A 110(1997)1097] was employed to calculate the energy spectrum of alpha particles emitted in the spontaneous ternary fission of 252Cf. It has been found that in the case of the zero orbital angular momentum of alpha particles in the alpha decay of the fragments, the measured alpha spectrum can be reproduced approximately by the model without any adjustable parameter.

  4. In vitro measurements of the release of 232U and its daughters from UO2 particles by dissolution, alpha-recoil and inert gas diffusion

    International Nuclear Information System (INIS)

    Three mechanisms that are potentially important in the release of 232U and its decay products from UO2 particles in the lungs were studied in vitro. Particles of UO2 uniformly labeled with 1% 232U were aerosolized and separated by aerodynamic size in a Lovelace Aerosol Particle Separator. Monodisperse size fractions ranging from 0.7 to 2.5 μm activity median aerodynamic diameter were used to study release of radionuclides by particle dissolution, recoil of atoms after alpha-decay and diffusion of the inert gas, 220Rn

  5. Are Pressure-Confined Clouds in Galactic Halos Possible for a Model of Lyman Alpha Clouds?

    Science.gov (United States)

    Miyahata, K.; Ikeuchi, S.

    Lanzetta et al (1995) found that most luminous galaxies at low redshifts produce Ly alpha absorptions at the mean impact parameter ~160h-1 kpc. Motivated by this observation, we propose the two-component protogalaxy model as a model for the Ly alpha cloud besed upon the previous work (MI 1995). In our model, the Ly alpha clouds are supposed to be stable cold clouds confined by the pressure of ambient hot gas in galactic halo. We determine the properties of these cold clouds and hot gas on the basis of theoretical and observational constraints. Especially, we take into account the stability of cold cloud in the galactic halo in addition to the general stability conditions in a two-component medium, and compare the derived quantities of Ly alpha cloud both cases in galactic halo and in intergalactic medium. We conclude that the condition that cloud is stable against both evaporation and tidal destruction by a hot galactic halo is very severe. As a result, at z ~0.5, it is concluded that a pressure-confined, stable spherical Ly alpha cloud of typical column density NHI = 1014 cm-2 cannot survive in the galactic halo, although much higher column density clouds of NHI = 1017 cm-2 can do there. We discuss how our result constraints an alternative model for a Ly alpha cloud which associates with galaxy observed by Lanzetta et.al.

  6. Stochastic particle based models for suspended particle movement in surface flows

    Institute of Scientific and Technical Information of China (English)

    Christina W.TSAI; Chuanjian MAN; Jungsun OH

    2014-01-01

    Modeling of suspended sediment particle movement in surface water can be achieved by stochastic particle tracking model approaches. In this paper, different mathematical forms of particle tracking models are introduced to describe particle movement under various flow conditions, i.e., the stochastic diffusion process, stochastic jump process, and stochastic jump diffusion process. While the stochastic diffusion process can be used to represent the stochastic movement of suspended particles in turbulent flows, the stochastic jump and the stochastic jump diffusion processes can be used to describe suspended particle movement in the occurrences of a sequence of extreme flows. An extreme flow herein is defined as a hydrologic flow event or a hydrodynamic flow phenomenon with a low probability of occurrence and a high impact on its ambient flow environment. In this paper, the suspended sediment particle is assumed to immediately follow the extreme flows in the jump process (i.e. the time lag between the flow particle and the sediment particle in extreme flows is considered negligible). In the proposed particle tracking models, a random term mainly caused by fluid eddy motions is modeled as a Wiener process, while the random occurrences of a sequence of extreme flows can be modeled as a Poisson process. The frequency of occurrence of the extreme flows in the proposed particle tracking model can be explicitly accounted for by the Poisson process when evaluating particle movement. The ensemble mean and variance of particle trajectory can be obtained from the proposed stochastic models via simulations. The ensemble mean and variance of particle velocity are verified with available data. Applicability of the proposed stochastic particle tracking models for sediment transport modeling is also discussed.

  7. Effect of Particle Shape on Mechanical Behaviors of Rocks: A Numerical Study Using Clumped Particle Model

    OpenAIRE

    Guan Rong; Guang Liu; Di Hou; Chuang-bing Zhou

    2013-01-01

    Since rocks are aggregates of mineral particles, the effect of mineral microstructure on macroscopic mechanical behaviors of rocks is inneglectable. Rock samples of four different particle shapes are established in this study based on clumped particle model, and a sphericity index is used to quantify particle shape. Model parameters for simulation in PFC are obtained by triaxial compression test of quartz sandstone, and simulation of triaxial compression test is then conducted on four rock sa...

  8. Modelling Ser129 phosphorylation inhibits membrane binding of pore-forming alpha-synuclein oligomers.

    Directory of Open Access Journals (Sweden)

    Georg Sebastian Nübling

    Full Text Available BACKGROUND: In several neurodegenerative diseases, hyperphosphorylation at position Ser129 is found in fibrillar deposits of alpha-synuclein (asyn, implying a pathophysiological role of asyn phosphorylation in neurodegeneration. However, recent animal models applying asyn phosphorylation mimics demonstrated a protective effect of phosphorylation. Since metal-ion induced asyn oligomers were identified as a potential neurotoxic aggregate species with membrane pore-forming abilities, the current study was undertaken to determine effects of asyn phosphorylation on oligomer membrane binding. METHODS: We investigated the influence of S129 phosphorylation on interactions of metal-ion induced asyn oligomers with small unilamellar lipid vesicles (SUV composed of POPC and DPPC applying the phosphorylation mimic asyn129E. Confocal single-particle fluorescence techniques were used to monitor membrane binding at the single-particle level. RESULTS: Binding of asyn129E monomers to gel-state membranes (DPPC-SUV is slightly reduced compared to wild-type asyn, while no interactions with membranes in the liquid-crystalline state (POPC-SUV are seen for both asyn and asyn129E. Conversely, metal-ion induced oligomer formation is markedly increased in asyn129E. Surprisingly, membrane binding to POPC-SUV is nearly absent in Fe(3+ induced asyn129E oligomers and markedly reduced in Al(3+ induced oligomers. CONCLUSION: The protective effect of pseudophosphorylation seen in animal models may be due to impeded oligomer membrane binding. Phosphorylation at Ser129 may thus have a protective effect against neurotoxic asyn oligomers by preventing oligomer membrane binding and disruption of the cellular electrophysiological equilibrium. Importantly, these findings put a new complexion on experimental pharmaceutical interventions against POLO-2 kinase.

  9. Energy resolution of alpha particles in a Micromegas detector at high pressure

    International Nuclear Information System (INIS)

    The latest Micromesh Gas amplification Structures (Micromegas) are achieving outstanding energy resolution for low energy photons, with values as low as 11% FWHM for the 5.9 keV line of 55Fe in Argon/Isobutane mixtures at atmospheric pressure. At higher energies (MeV scale), these measurements are more complicated due to the difficulty in confining the events in the chamber, although there is no fundamental reason why resolutions of 1% FWHM or below could not be reached. There is much motivation to demonstrate experimentally this fact in Xe mixtures due to the possible application of Micromegas readouts to the Double Beta Decay (DBD) search of 136Xe, or in other experiments needing calorimetry and topology in the same detector. We report on systematic measurements of energy resolution with state-of-the-art Micromegas using a 5.5 MeV alpha source in high pressure Ar/Isobutane mixtures. Values as low as 1.6% FWHM have been obtained. Same measurements in Xe, of which a preliminary result is also shown here, are under progress.

  10. Brassinolide activities 2alpha, 3alpha - diols versus 3alpha, 4alpha - diols in the bean second internode bioassay: explanation by molecular modeling methods

    Czech Academy of Sciences Publication Activity Database

    Šíša, Miroslav; Vilaplana-Polo, M.; Ballesteros, C. B.; Kohout, Ladislav

    Brno : Mendelova zemědělská a lesnická univerzita v Brně, 2007. s. 7. ISBN 978-80-7375-090-9. [Funkční genomika a proteomika ve šlechtění rostlin. 24.09.2007-25.09.2007, Křtiny] Institutional research plan: CEZ:AV0Z40550506 Keywords : brassinolid * plant stress * molecular modeling Subject RIV: CC - Organic Chemistry

  11. The role of alpha-rhythm states in perceptual learning: insights from experiments and computational models

    Directory of Open Access Journals (Sweden)

    Rodrigo Sigala

    2014-04-01

    Full Text Available During the past two decades growing evidence indicates that brain oscillations in the alpha band (~10 Hz not only reflect an ‘idle’ state of cortical activity, but also take a more active role in the generation of complex cognitive functions. A recent study shows that more than 60% of the observed inter-subject variability in perceptual learning can be ascribed to ongoing alpha activity. This evidence indicates a significant role of alpha oscillations for perceptual learning and hence motivates to explore the potential underlying mechanisms. Hence, it is the purpose of this review to highlight existent evidence that ascribes intrinsic alpha oscillations a role in shaping our ability to learn. In the review, we disentangle the alpha rhythm into different neural signatures that control information processing within individual functional building blocks of perceptual learning. We further highlight computational studies that shed light on potential mechanisms regarding how alpha oscillations may modulate information transfer and connectivity changes relevant for learning. To enable testing of those model based hypotheses, we emphasize the need for multidisciplinary approaches combining assessment of behavior and multi-scale neuronal activity, active modulation of ongoing brain states and computational modeling to reveal the mathematical principles of the complex neuronal interactions. In particular we highlight the relevance of multi-scale modeling frameworks such as the one currently being developed by “The Virtual Brain” project.

  12. Some characteristics of the CR-39 solid state nuclear - Track Detector for register of protons and low energy alpha particles

    International Nuclear Information System (INIS)

    Experimental results related to registration properties of the CR-39 Solid State Nuclear Track Detector for charged particles are presented and discussed. The existence of an inverse proportion between the induction time and the temperature as well as normal concentration of solutions, is showed by the study of CR-39 chemical etching characteristics in NaOH and KOH solutions, comprising varied concentration and temperature. The bulk-etch rate and activation energy of the process were obtained. The critical energy and critical energy-loss rate of CR-39 track-detectors for registration of protons were experimentally determined. Samples were exposed to 24 Mev proton beams in the IEN/CNEN Cyclotron (CV-28), using scattering chamber with a tantalum thin target and aluminium absorbers in contact with the samples, in order to provide the required fluctuation in the scattered beam energy. From the mean track-diameter plotted against incident proton energy the critical energy was obtained. From the calculated energy-loss rate vs. energy curve, the critical energy loss rate were evaluated. The CR-39 response for low energy alpha particles (E = 7h) under the conditions of 6.25 N NaOH at 700C. It is shown that successive chemical etchings do not produce the same track geometry as obtained by means of a continous revelation with the same total etching time. (Author)

  13. RADIOACTIVE POSITRON EMITTER PRODUCTION BY ENERGETIC ALPHA PARTICLES IN SOLAR FLARES

    International Nuclear Information System (INIS)

    Measurements of the 0.511 MeV positron-annihilation line from solar flares are used to explore the flare process in general and ion acceleration in particular. In flares, positrons are produced primarily by the decay of radioactive positron-emitting isotopes resulting from nuclear interactions of flare-accelerated ions with ambient solar material. Kozlovsky et al. provided ion-energy-dependent production cross sections for 67 positron emitters evaluated from their threshold energies (some <1 MeV nucleon–1) to a GeV nucleon–1, incorporating them into a computer code for calculating positron-emitter production. Adequate cross-section measurements were available for proton reactions, but not for α-particle reactions where only crude estimates were possible. Here we re-evaluate the α-particle cross sections using new measurements and nuclear reaction codes. In typical large gamma-ray line flares, proton reactions dominate positron production, but α-particle reactions will dominate for steeper accelerated-ion spectra because of their relatively low threshold energies. With the accelerated-3He reactions added previously, the code is now reliable for calculating positron production from any distribution of accelerated-ion energies, not just those of typical flares. We have made the code available in the online version of the Journal. We investigate which reactions, projectiles, and ion energies contribute to positron production. We calculate ratios of the annihilation-line fluence to fluences of other gamma-ray lines. Such ratios can be used in interpreting flare data and in determining which nuclear radiation is most sensitive for revealing acceleration of low-energy ions at the Sun

  14. RADIOACTIVE POSITRON EMITTER PRODUCTION BY ENERGETIC ALPHA PARTICLES IN SOLAR FLARES

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, R. J. [Code 7650, Naval Research Laboratory, Washington, DC 20375 (United States); Kozlovsky, B. [Tel Aviv University, Tel Aviv (Israel); Share, G. H., E-mail: murphy@ssd5.nrl.navy.mil, E-mail: benz@wise.tau.ac.il, E-mail: share@astro.umd.edu [University of Maryland, College Park, MD 20742 (United States)

    2015-01-01

    Measurements of the 0.511 MeV positron-annihilation line from solar flares are used to explore the flare process in general and ion acceleration in particular. In flares, positrons are produced primarily by the decay of radioactive positron-emitting isotopes resulting from nuclear interactions of flare-accelerated ions with ambient solar material. Kozlovsky et al. provided ion-energy-dependent production cross sections for 67 positron emitters evaluated from their threshold energies (some <1 MeV nucleon{sup –1}) to a GeV nucleon{sup –1}, incorporating them into a computer code for calculating positron-emitter production. Adequate cross-section measurements were available for proton reactions, but not for α-particle reactions where only crude estimates were possible. Here we re-evaluate the α-particle cross sections using new measurements and nuclear reaction codes. In typical large gamma-ray line flares, proton reactions dominate positron production, but α-particle reactions will dominate for steeper accelerated-ion spectra because of their relatively low threshold energies. With the accelerated-{sup 3}He reactions added previously, the code is now reliable for calculating positron production from any distribution of accelerated-ion energies, not just those of typical flares. We have made the code available in the online version of the Journal. We investigate which reactions, projectiles, and ion energies contribute to positron production. We calculate ratios of the annihilation-line fluence to fluences of other gamma-ray lines. Such ratios can be used in interpreting flare data and in determining which nuclear radiation is most sensitive for revealing acceleration of low-energy ions at the Sun.

  15. Quantum design using a multiple internal reflections method in a study of fusion processes in the capture of alpha-particles by nuclei

    CERN Document Server

    Maydanyuk, Sergei P; Belchikov, Sergei V

    2015-01-01

    A high precision method to determine fusion in the capture of $\\alpha$-particles by nuclei is presented. For $\\alpha$-capture by $^{40}{\\rm Ca}$ and $^{44}{\\rm Ca}$, such an approach gives (1) the parameters of the $\\alpha$--nucleus potential and (2) fusion probabilities. This method found new parametrization and fusion probabilities and decreased the error by $41.72$ times for $\\alpha + ^{40}{\\rm Ca}$ and $34.06$ times for $\\alpha + ^{44}{\\rm Ca}$ in a description of experimental data in comparison with existing results. We show that the sharp angular momentum cutoff proposed by Glas and Mosel is a rough approximation, Wong's formula and the Hill-Wheeler approach determine the penetrability of the barrier without a correct consideration of the barrier shape, and the WKB approach gives reduced fusion probabilities. Based on our fusion probability formula, we explain the difference between experimental cross-sections for $\\alpha + ^{40}{\\rm Ca}$ and $\\alpha + ^{44}{\\rm Ca}$, which is connected with the theory ...

  16. A numerical study of the alpha model for two-dimensional magnetohydrodynamic turbulent flows

    CERN Document Server

    Mininni, P D; Pouquet, A G

    2004-01-01

    We explore some consequences of the ``alpha model,'' also called the ``Lagrangian-averaged'' model, for two-dimensional incompressible magnetohydrodynamic (MHD) turbulence. This model is an extension of the smoothing procedure in fluid dynamics which filters velocity fields locally while leaving their associated vorticities unsmoothed, and has proved useful for high Reynolds number turbulence computations. We consider several known effects (selective decay, dynamic alignment, inverse cascades, and the probability distribution functions of fluctuating turbulent quantities) in magnetofluid turbulence and compare the results of numerical solutions of the primitive MHD equations with their alpha-model counterparts' performance for the same flows, in regimes where available resolution is adequate to explore both. The hope is to justify the use of the alpha model in regimes that lie outside currently available resolution, as will be the case in particular in three-dimensional geometry or for magnetic Prandtl number...

  17. Murine model of otitis media with effusion: immunohistochemical demonstration of IL-1 alpha antigen expression.

    Science.gov (United States)

    Johnson, M D; Contrino, A; Contrino, J; Maxwell, K; Leonard, G; Kreutzer, D

    1994-09-01

    Recent studies have suggested that cytokines likely play a central role in the formation and maintenance of otitis media with effusion (OME). Currently, there is no immunologically defined animal model for the study of cytokines as they contribute to the formation of OME. In the present study, a murine model of OME, using eustachian tube blockage via an external surgical approach, was developed. The murine model temporal bone histology appears to mimic the histology found in chronic otitis media with effusion in humans. Additionally, using this murine model, interleukin-1 alpha (IL-1 alpha) expression was detected in the middle ear using standard immunohistochemical techniques. IL-1 alpha seemed localized to the epithelial lining of the middle ear as well as 5% to 10% of inflammatory cells. This model should provide the necessary tool to further study the immunologic aspects of OME. PMID:8072363

  18. Ly$\\alpha$ Spectra from Multiphase Outflows, and their Connection to Shell Models

    CERN Document Server

    Gronke, Max

    2016-01-01

    We perform Lyman-$\\alpha$ (Ly$\\alpha$) Monte-Carlo radiative transfer calculations on a suite of $2500$ models of multiphase, outflowing media, which are characterized by $14$ parameters. We focus on the Ly$\\alpha$ spectra emerging from these media, and investigate which properties are dominant in shaping the emerging Ly$\\alpha$ profile. Multiphase models give rise to a wide variety of emerging spectra, including single, double and triple peaked spectra. We find that the dominant parameters in shaping the spectra include (i) the cloud covering factor, $f_c$, in agreement with earlier studies, and (ii) the temperature and number density of residual HI in the hot ionized medium. We attempt to reproduce spectra emerging from multiphase models with `shell models' which are commonly used to fit observed Ly$\\alpha$ spectra, and investigate the connection between shell-model parameters and the physical parameters of the clumpy media. In shell models, the neutral hydrogen content of the shell is one of the key parame...

  19. Modeling of a-particle redistribution by sawteeth in TFTR using FPPT code

    International Nuclear Information System (INIS)

    Results from recent DT experiments on TFTR to measure the radial density profiles of fast confined well trapped α-particles using the Pellet Charge eXchange (PCX) diagnostic [PETROV M. P., et. al. Nucl. Fusion, 35 (1995) 1437] indicate that sawtooth oscillations produce a significant broadening of the trapped alpha radial density profiles. ' Conventional models consistent with measured sawtooth effects on passing particles do not provide satisfactory simulations of the trapped particle mixing measured by PCX diagnostic. We propose a different mechanism for fast particle mixing during the sawtooth crash to explain the trapped α-particle density profile broadening after the crash. The model is based on the fast particle orbit averaged toroidal drift in a perturbed helical electric field with an adjustable absolute value. Such a drift of the fast particles results in a change of their energy and a redistribution in phase space. The energy redistribution is shown to obey the diffusion equation, while the redistribution in toroidal momentum P var-phi (or in minor radius) is assumed stochastic with large diffusion coefficient and was taken flat. The distribution function in a pre- sawtooth plasma and its evolution in a post-sawtooth crash plasma is simulated using the Fokker-Planck Post-TRANSP (FPPT) processor code. It is shown that FPPT calculated α-particle distributions are consistent with TRANSP Monte-Carlo calculations. Comparison of FPPT results with Pellet Char eXchange (PCX) measurements shows good agreement for 9 both sawtooth free and sawtoothing plasmas

  20. Tissue dose conversion factors for protons and alpha particles in case of different detector materials

    International Nuclear Information System (INIS)

    Accurate dose measurement as well as the measurement of the linear energy transfer (LET) data will become increasingly important in forthcoming years during the operation of the International Space Station. Since the space radiation mainly consists of heavy charged particles (protons and heavier particles), the equivalent dose significantly differs from the absorbed dose. While the recently used measuring equipment is not fully suitable to measure both quantities simultaneously, a new combined device is under development. The efficiency of the TL dosemeter is a function of the LET, therefore the value of the absorbed dose should be corrected. LET spectra or mean LET value should be used for the determination of the radiation weighting factor (wR) and for the evaluation of the equivalent dose as well. Since the radiation weighting factor defined as a function of LETwater, LETSi or LETTL should be converted to LETwater for this purpose. Correction needed for the calculation of the dose in tissue and for the comparison of the different measurements as well. Recently an average value has been used for the correction of the LET between different materials, despite the fact that the value of the correction factor depends on the energy of the concerning radiation. The discrepancy of the mean values with and without considering the energy spectrum could be more than 5%. (authors)