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1

Measurement of alpha particle energy using windowless electret ion chambers.  

PubMed

Electret ion chambers are inexpensive, lightweight, robust, commercially available, passive, charge-integrating devices for accurate measurement of different ionizing radiations. In an earlier work a chamber of dimensions larger than the range of alpha particles having aluminized Mylar windows of different thickness was used for measurement of alpha radiation. Correlation between electret mid-point voltage, alpha particle energy, and response was developed and it was shown that this chamber could be used for estimating the effective energy of an unknown alpha source. In the present study, the electret ion chamber is used in the windowless mode so that the alpha particles dissipate their entire energy inside the volume, and the alpha particle energy is determined from the first principles. This requires that alpha disintegration rate be accurately known or measured by an alternate method. The measured energies were within 1 to 4% of the true values for different sources (230Th, 237Np, 239Pu, 241Am, and 224Cm). This method finds application in quantitative determination of alpha energy absorbed in thin membrane and, hence, the absorbed dose. PMID:12240732

Dua, S K; Kotrappa, P; Srivastava, R; Ebadian, M A; Stieff, L R

2002-10-01

2

Enhanced production of low energy electrons by alpha particle impact  

PubMed Central

Radiation damage to living tissue stems not only from primary ionizing particles but to a substantial fraction from the dissociative attachment of secondary electrons with energies below the ionization threshold. We show that the emission yield of those low energy electrons increases dramatically in ion–atom collisions depending on whether or not the target atoms are isolated or embedded in an environment. Only when the atom that has been ionized and excited by the primary particle impact is in immediate proximity of another atom is a fragmentation route known as interatomic Coulombic decay (ICD) enabled. This leads to the emission of a low energy electron. Over the past decade ICD was explored in several experiments following photoionization. Most recent results show its observation even in water clusters. Here we show the quantitative role of ICD for the production of low energy electrons by ion impact, thus approaching a scenario closer to that of radiation damage by alpha particles: We choose ion energies on the maximum of the Bragg peak where energy is most efficiently deposited in tissue. We compare the electron production after colliding He+ ions on isolated Ne atoms and on Ne dimers (Ne2). In the latter case the Ne atom impacted is surrounded by a most simple environment already opening ICD as a deexcitation channel. As a consequence, we find a dramatically enhanced low energy electron yield. The results suggest that ICD may have a significant influence on cell survival after exposure to ionizing radiation.

Kim, Hong-Keun; Titze, Jasmin; Schoffler, Markus; Trinter, Florian; Waitz, Markus; Voigtsberger, Jorg; Sann, Hendrik; Meckel, Moritz; Stuck, Christian; Lenz, Ute; Odenweller, Matthias; Neumann, Nadine; Schossler, Sven; Ullmann-Pfleger, Klaus; Ulrich, Birte; Fraga, Rui Costa; Petridis, Nikos; Metz, Daniel; Jung, Annika; Grisenti, Robert; Czasch, Achim; Jagutzki, Ottmar; Schmidt, Lothar; Jahnke, Till; Schmidt-Bocking, Horst; Dorner, Reinhard

2011-01-01

3

Alpha particle nonionizing energy loss (NIEL) for device applications  

NASA Technical Reports Server (NTRS)

A method developed for the proton NIEL calculation previously is extended to incident alpha particles in this study: ZBL screened potential for Coulomb interactions and MCNPX 'thin target approximation' for nuclear interactions.

Jun, Insoo; Xapsos, Michael A.; Messenger, Scott R.; Burke, Edward A.; Walters, Robert J.; Summers, Geoff; Jordan, Thomas

2004-01-01

4

Alpha-particle diagnostics  

SciTech Connect

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.

Young, K.M.

1991-01-01

5

Utility of extracting {alpha}-particle energy by waves  

SciTech Connect

The utility of extracting {alpha}-particle power, and then diverting this power to fast fuel ions, is investigated. As power is diverted to fast ions and then to ions, a number of effects come into play, as the relative amounts of pressure taken up by electrons, fuel ions, and fast {alpha}-particles shift. In addition, if the {alpha}-particle power is diverted to fast fuel ions, there is an enhanced fusion reactivity because of the nonthermal component of the ion distribution. Some useful expressions for describing these effects are derived, and it is shown that fusion reactors with power density about twice what otherwise might be obtained can be contemplated, so long as a substantial amount of the {alpha}-particle power can be diverted. Interestingly, in this mode of operation, once the electron heat is sufficiently confined, further improvement in confinement is actually not desirable. A similar improvement in fusion power density can be obtained for advanced fuel mixtures such as D-He{sup 3}, where the power of both the energetic {alpha}-particles and the energetic protons might be diverted advantageously.

Fisch, N.J.; Herrmann, M.C.

1994-05-01

6

Alpha Particle Diagnostic  

SciTech Connect

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.

Fisher, Ray, K.

2009-05-13

7

Measurements of alpha particle energy using nuclear tracks in solids methodology.  

PubMed

In this paper we present a method for the measurement of alpha particle energy using polycarbonate materials as nuclear track detectors (NTDs). This method is based on the interaction of the radiation with the solid-state materials, using the relationship between the energy deposited in the material by the ionising particle and the track developed after an established chemical process. The determination of the geometrical parameters of the formed track, such as major axis, minor axis and overall track length, permit determination of the energy of the alpha particle. The track analysis is performed automatically using a digital image system, and the data are processed in a PC with commercial software. In this experiment 148Gd, 238U, 230Th, 239Pu and 244Cm alpha particle emitters were used. The values for alpha particle energy resolution, the linear response to energy, the confidence in the results and the automatisation of the procedure make this method a promising analysis system. PMID:12382812

Espinosa, G; Amero, C; Gammage, R B

2002-01-01

8

Nuclear reactions induced by high-energy alpha particles  

NASA Technical Reports Server (NTRS)

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.

Shen, B. S. P.

1974-01-01

9

Peroxidation of the dried thin film of lipid by high-energy alpha particles from a cyclotron  

SciTech Connect

High-energy ..cap alpha.. particles produced a dose-dependent linear increase in different lipid peroxidation products (e.g., malondialdehyde (MDA), conjugated dienes, and hydroperoxides) in the dried thin film state. An inverse dose-rate effect was observed when the dose rate was varied by changing either the ..cap alpha..-particle fluence rate or the ..cap alpha..-particle energy. The antioxidants ..cap alpha..-tocopherol and butylated hydroxytoluene (BHT) suppressed the ..cap alpha..-particle-induced lipid peroxidation in the dried thin film state, and in this respect ..cap alpha..-tocopherol was found superior to BHT. It was found that ..cap alpha..-tocopherol was equally efficient in inhibiting lipid peroxidations by ..cap alpha.. particles and ultraviolet light.

Agarwal, S.; Chatterjee, S.N.

1984-11-01

10

Imaging alpha particle detector  

DOEpatents

A method and apparatus for detecting and imaging alpha particles sources is described. A conducting coated high voltage electrode (1) and a tungsten wire grid (2) 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 (3) to be quantitatively or qualitatively analyzed. A thin polyester film window (4) 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.

Anderson, David F. (Los Alamos, NM)

1985-01-01

11

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

SciTech Connect

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.

Espinosa Garcia, Guillermo [ORNL; Golzarri y Moreno, Dr. Jose Ignacio [Instituto de Fisica, Mexico; Bogard, James S [ORNL

2008-01-01

12

Study of alpha-particle emission probabilities and energies in the decay of 240Pu.  

PubMed

In the frame of EUROMET Project No 325 "Analysis of Plutonium Alpha-Particle Spectra", the isotopic composition of a 238, 239, 240Pu mixture was measured by mass spectrometry and by high-resolution alpha-particle spectrometry. The latter revealed a discrepancy with published data of the alpha-particle emission probabilities (Palpha) and the energies (Ealpha) of the two major peaks of 240Pu. New values have been derived: Palpha1 = 0.7256 (6), Palpha2 = 0.2735 (7) and Ealpha1 = 5168.54 (14)keV, Ealpha2 = 5124.10 (15)keV, relative to reference peaks of 238Pu and 239Pu. PMID:14987635

Sibbens, G; Pommé, S

2004-01-01

13

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

NASA Astrophysics Data System (ADS)

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 ?m 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 ?m. 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 ?m scintillator plates.

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

2014-01-01

14

Acceleration of low-energy protons and alpha particles at interplanetary shock waves  

NASA Technical Reports Server (NTRS)

The low-energy protons and alpha particles in the energy range 30 keV/charge to 150 keV/charge associated with three different interplanetary shock waves in the immediate preshock and postshock region are studied using data obtained by the ISEE 3. The spatial distributions in the preshock and postshock medium are presented, and the dependence of the phase space density at different energies on the distance from the shock and on the form of the distribution function of both species immediately at the shock is examined. It is found that in the preshock region the particles are flowing in the solar wind frame of reference away from the shock and in the postshock medium the distribution is more or less isotropic in this frame of reference. The distribution function in the postshock region can be represented by a power law in energy which has the same spectral exponent for both protons and alpha particles. It is concluded that the first-order Fermi acceleration process can consistently explain the data, although the spectra of diffuse bow shock associated particles are different from the spectra of the interplanetary shock-associated particles in the immediate vicinity of the shock. In addition, the mean free path of the low energy ions in the preshock medium is found to be considerably smaller than the mean free path determined by the turbulence of the background interplanetary medium.

Scholer, M.; Hovestadt, D.; Ipavich, F. M.; Gloeckler, G.

1983-01-01

15

Energy loss of proton, alpha particle, and electron beams in hafnium dioxide films  

SciTech Connect

The electronic stopping power, S, of HfO{sub 2} films for proton and alpha particle beams has been measured and calculated. The experimental data have been obtained by the Rutherford backscattering technique and cover the range of 120-900 and 120-3000 keV for proton and alpha particle beams, respectively. Theoretical calculations of the energy loss for the same projectiles have been done by means of the dielectric formalism using the Mermin energy loss function--generalized oscillator strength (MELF-GOS) model for a proper description of the HfO{sub 2} target on the whole momentum-energy excitation spectrum. At low projectile energies, a nonlinear theory based on the extended Friedel sum rule has been employed. The calculations and experimental measurements show good agreement for protons and a quite good one for alpha particles. In particular, the experimental maximums of both stopping curves (around 120 and 800 keV, respectively) are well reproduced. On the basis of this good agreement, we have also calculated the inelastic mean-free path (IMFP) and the stopping power for electrons in HfO{sub 2} films. Our results predict a minimum value of the IMFP and a maximum value of the S for electrons with energies around 120 and 190 eV, respectively.

Behar, Moni; Fadanelli, Raul C.; Nagamine, Luiz C. C. M. [Instituto de Fisica, Universidade Federal do Rio Grande do Sul, Av. Bento Goncalves 9500, 91501-970 Porto Alegre, RS (Brazil); Abril, Isabel; Denton, Cristian D. [Departament de Fisica Aplicada, Universitat dAlacant, Apartat 99, E-03080 Alacant (Spain); Garcia-Molina, Rafael [Departamento de Fisica-CIOyN, Universidad de Murcia, Apartado 4021, E-30080 Murcia (Spain); Arista, Nestor R. [Division Colisiones Atomicas, Centro Atomico Bariloche, RA-8400 San Carlos de Bariloche (Argentina)

2009-12-15

16

Energy resolution of silicon surface-barrier detectors for alpha particles, oxygen ions, and fission fragments  

NASA Astrophysics Data System (ADS)

A group of 53 silicon surface-barrier detectors, 10 manufactured by ORTEC and 43 fabricated by the first author and his students, have been extensively tested for their energy resolutions with 244Cm alpha particles, oxygen ions of 25 and 50 MeV energy from the University of Pittsburgh Van de Graaff accelerator, and fission fragments from a 252Cf source. A total of 47 detectors were tested with alpha particles, 24 were tested with fission fragments, and 8 were tested with the oxygen ions. Six detectors were tested with all three sources. The resistivity of the silicon from which the detectors were made and the reverse bias at which they were operated were given special attention. Capacitance measurements were made on most of the detectors to get an independent measurement of the resistivity of the silicon starting material.

Klema, Ernest D.; Saladin, J. X.; Alessi, James G.; Schmitt, H. W.

1980-12-01

17

Energy and Mass Dependences of the Parameters of the Semimicroscopic Folding Model for Alpha Particles at Low and Intermediate Energies  

SciTech Connect

The energy and mass dependences of the parameters of the semimicroscopic alpha-particle potential are investigated for the first time in the region of low and intermediate energies. Within the semimicroscopic folding model, both elastic and inelastic differential and total cross sections for reactions on various nuclei are well described by using global parameters obtained in this study.

Kuterbekov, K.A.; Zholdybayev, T.K. [Institute of Nuclear Physics, National Nuclear Center of the Republic of Kazakhstan, Almaty, 480082 (Kazakhstan); Kukhtina, I.N.; Penionzhkevich, Yu.E. [Joint Institute for Nuclear Research, Dubna, Moscow oblast, 141980 (Russian Federation)

2005-06-01

18

Energy dependence of radiation damage in molybdenum irradiated by. cap alpha. particles  

SciTech Connect

Transmission electron microscopy and x-ray analysis are used to study the defect structure produced in polycrystalline molybdenum by irradiation with high-energy (10--50 MeV) ..cap alpha.. particles. The nature of the radiation-induced defect clusters is determined and it is shown that there is no change in the crystal lattice parameters when interstitial and vacancy clusters are present together with isolated voids.

Ibragimov, S.S.; Reutov, V.F.; Abdrashitov, I.Y.; Vagin, S.P.

1983-01-01

19

An Experiment to Measure Range, Range Straggling, Stopping Power, and Energy Straggling of Alpha Particles in Air  

ERIC Educational Resources Information Center

Experiments to measure range, range straggling, stopping power, and energy straggling of alpha particles are discussed in this article. Commercially available equipment with simple modifications is used for these measurements. (Author/GA)

Ouseph, P. J.; Mostovych, Andrew

1978-01-01

20

Redistribution of high energy alpha particles due to sawteeth with partial reconnection  

NASA Astrophysics Data System (ADS)

The redistribution of high energy alpha particles due to internal kink modes is studied in plasmas with ITER-like parameters. The exact particle trajectories in the total fields, equilibrium plus perturbation, are calculated. The equilibrium magnetic field is obtained by analytically solving the Grad-Shafranov equation and the perturbed electric and magnetic fields are reconstructed using ideal MHD and the experimental information about the displacement eigenfunction. The (1, 1), (2, 2) and (2, 1) modes are included and the effect of changing their amplitude and frequency is determined. The results show that if the conditions are similar to those reported in Igochine et al (2007 Nucl. Fusion 47 23), the peak density of counter-passing particles decreases between 25% and 40% (depending on the energy); the peak of the trapped particles density shifts outwards by approximately 10% of the minor radius and the total on axis density decreases by more than 25%. This redistribution occurs inside the q = 1 surface. The addition of a (2, 1) mode, which can produce the stochastization of the magnetic field, significantly increases particle redistribution and allows particles to spread beyond the q = 1 surface. Different groups of particles (co-passing, counter-passing, trapped) respond differently to the perturbations.

Farengo, R.; Ferrari, H. E.; García-Martínez, P. L.; Firpo, M.-C.; Ettoumi, W.; Lifschitz, A. F.

2013-04-01

21

Measurement of ion cascade energies through resolution degradation of alpha particle microcalorimeters  

SciTech Connect

Atomic cascades caused by ions impinging on bulk materials have remained of interest to the scientific community since their discovery by Goldstein in 1902. While considerable effort has been spent describing and, more recently, simulating these cascades, tools that can study individual events are lacking and several aspects of cascade behavior remain poorly known. These aspects include the material energies that determine cascade magnitude and the variation between cascades produced by monoenergetic ions. We have recently developed an alpha particle detector with a thermodynamic resolution near 100 eV full-width-at-half-maximum (FWHM) and an achieved resolution of 1.06 keV FWHM for 5.3 MeV particles. The detector relies on the absorption of particles by a bulk material and a thermal change in a superconducting thermometer. The achieved resolution of this detector provides the highest resolving power of any energy dispersive technique and a factor of 8 improvement over semiconductor detectors. The exquisite resolution can be directly applied to improved measurements of fundamental nuclear decays and nuclear forensics. In addition, we propose that the discrepancy between the thermodynamic and achieved resolution is due to fluctuations in lattice damage caused by ion-induced cascades in the absorber. Hence, this new detector is capable of measuring the kinetic energy converted to lattice damage in individual atomic cascades. This capability allows new measurements of cascade dynamics; for example, we find that the ubiquitous modeling program, SRIM, significantly underestimates the lattice damage caused in bulk tin by 5.3 MeV alpha particles.

Horansky, Robert D.; Stiehl, Gregory M.; Beall, James A.; Irwin, Kent D.; Ullom, Joel N. [National Institute of Standards and Technology, 325 Broadway MS 817.03, Boulder, Colorado (United States); Plionis, Alexander A.; Rabin, Michael W. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2010-02-15

22

Nuclear diagnostic for fast alpha particles  

DOEpatents

This invention relates generally to high energy confined plasmas and more particularly is directed to measuring the velocity distribution of confined energetic alpha particles resulting from deuterium-tritium fusion reactions in a confined energetic plasma.

Grisham, L.R.; Post, D.E. Jr.; Dawson, J.M.

1983-11-23

23

Long range alpha particle detector  

DOEpatents

An alpha particle detector capable of detecting alpha radiation from distant sources. In one embodiment, a high voltage is generated in a first electrically conductive mesh while a fan draws air containing air molecules ionized by alpha particles through an air passage and across a second electrically conductive mesh. The current in the second electrically conductive mesh can be detected and used for measurement or alarm. The detector can be used for area, personnel and equipment monitoring.

MacArthur, Duncan W. (Los Alamos, NM); Wolf, Michael A. (Los Alamos, NM); McAtee, James L. (Los Alamos, NM); Unruh, Wesley P. (Los Alamos, NM); Cucchiara, Alfred L. (Los Alamos, NM); Huchton, Roger L. (Los Alamos, NM)

1993-01-01

24

Long range alpha particle detector  

DOEpatents

An alpha particle detector capable of detecting alpha radiation from distant sources. In one embodiment, a high voltage is generated in a first electrically conductive mesh while a fan draws air containing air molecules ionized by alpha particles through an air passage and across a second electrically conductive mesh. The current in the second electrically conductive mesh can be detected and used for measurement or alarm. The detector can be used for area, personnel and equipment monitoring.

MacArthur, D.W.; Wolf, M.A.; McAtee, J.L.; Unruh, W.P.; Cucchiara, A.L.; Huchton, R.L.

1993-02-02

25

Improvements to alpha-particle spectrometry techniques.  

PubMed

Improvements to the conventional methods for alpha-particle spectrometry measurement and analysis have recently been implemented in our laboratory. They include the application of corrections for energy drift in long-duration measurements, the development and application of an efficient deconvolution method for complex alpha spectra using the new computer code ALFITeX, an alpha-gamma coincidence system using a dual-parameter multichannel analyzer, and the digitization of this coincidence system. PMID:24315085

Caro Marroyo, B; Martín Sánchez, A; Jurado Vargas, M

2014-05-01

26

Lower hybrid instability driven by mono-energy {alpha}-particles with finite pitch angle spread in a plasma  

SciTech Connect

A kinetic formalism of lower hybrid wave instability, driven by mono-energy {alpha}-particles with finite pitch angle spread, is developed. The instability arises through cyclotron resonance interaction with high cyclotron harmonics of {alpha}-particles. The {alpha}-particles produced in D-T fusion reactions have huge Larmor radii ({approx}10 cm) as compared to the wavelength of the lower hybrid wave, whereas their speed is an order of magnitude smaller than the speed of light in vacuum. As a result, large parallel phase velocity lower hybrid waves, suitable for current drive in tokamak, are driven unstable via coupling to high cyclotron harmonics. The growth rate decreases with increase in pitch angle spread of the beam. At typical electron density of {approx}10{sup 19} m{sup -3}, magnetic field {approx}4 Tesla and {alpha}-particle concentration {approx}0.1%, the large parallel phase velocity lower hybrid wave grows on the time scale of 20 ion cyclotron periods. The growth rate decreases with plasma density.

Kumar, Pawan; Singh, Vishwesh; Tripathi, V. K. [Department of Physics, IIT Delhi, New Delhi-110016 (India)

2013-02-15

27

Radioluminescence yield of alpha particles in air  

NASA Astrophysics Data System (ADS)

Alpha particles can be detected by measuring the radioluminescence light which they induce when absorbed in air. The light is emitted in the near ultraviolet region by nitrogen molecules excited by secondary electrons. The accurate knowledge of the radioluminescence yield is of utmost importance for novel radiation detection applications utilizing this secondary effect. Here, the radioluminescence yield of an alpha particle is investigated as a function of energy loss in air for the first time. Also, the total radioluminescence yield of the particle is measured with a carefully calibrated ^{239}Pu emitter used in the experiments. The obtained results consistently indicate that alpha particles generate 19±3 photons per one MeV of energy released in air at normal pressure (temperature 22°C, relative humidity 43%) and the dependence is found to be linear in the studied energy range from 0.3 MeV to 5.1 MeV. The determined radioluminescence yield is higher than previously reported for alpha particles and similar to the radioluminescence yield of electrons at comparable energies. This strengthens the evidence that the luminescence induced by charged particles is mostly proportional to the energy loss in the media and not very sensitive to the type of primary particle.

Sand, J.; Ihantola, S.; Peräjärvi, K.; Toivonen, H.; Toivonen, J.

2014-05-01

28

Alpha-particle spectrometer experiment  

NASA Technical Reports Server (NTRS)

Mapping the radon emanation of the moon was studied to find potential areas of high activity by detection of radon isotopes and their daughter products. It was felt that based on observation of regions overflown by Apollo spacecraft and within the field of view of the alpha-particle spectrometer, a radon map could be constructed, identifying and locating lunar areas of outgassing. The basic theory of radon migration from natural concentrations of uranium and thorium is discussed in terms of radon decay and the production of alpha particles. The preliminary analysis of the results indicates no significant alpha emission.

Gorenstein, P.; Bjorkholm, P.

1972-01-01

29

Elastic and inelastic scattering of alpha particles from 40,44Ca over a broad range of energies and angles  

Microsoft Academic Search

Angular distributions for alpha particle elastic scattering by 40,44Ca and excitation of the 3.73 MeV 3- collective state of 40Ca were measured for incident energies ranging from 40 to 62 MeV. An extensive optical model analysis of these elastic scattering cross sections and other available data, using squared Woods-Saxon form factors, results in potentials with fixed geometry for both real

Th. Delbar; Gh. Grégoire; G. Paic; R. Ceuleneer; F. Michel; R. Vanderpoorten; A. Budzanowski; H. Dabrowski; L. Freindl; K. Grotowski; S. Micek; R. Planeta; A. Strzalkowski; K. A. Eberhard

1978-01-01

30

Production cross sections of lithium and beryllium isotopes in 12C by high-energy protons and alpha particles  

Microsoft Academic Search

The formation cross sections of 6Li, 7Li and 7Be, 9Be, 10Be by high-energy protons and alpha-particles in a 12C target have been determined by a high sensitivity mass-spectrometric technique. A method for extracting lithium and beryllium from the irradiated graphite without interference by natural contamination has been developed. Cross sections have been measured for 150 MeV and 600 MeV protons

P. Fontes; C. Perron; J. Lestringuez; F. Yiou; R. Bernas

1971-01-01

31

Global alpha-particle optical potentials.  

National Technical Information Service (NTIS)

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. ...

N. Ferdous

1991-01-01

32

Alpha particle photoeffect  

SciTech Connect

Using sum rules we calculate four energy weighted moments for the /sup 4/He electric dipole photoeffect for a Volkov spin-independent potential with Serber exchange. Our results are sigma/sub -/1 = 2.83 mb; sigma/sub 0/ = 119 MeV mb, sigma/sub 1/ = 5430 MeV/sup 2/ mb, and sigma/sub 2/ = 2.76 x 10/sup 5/ MeV/sup 3/ mb. We use only the first term in the hyperspherical expansions of the potential and wave function. We invert either two, three, or four of these moments to determine the photoeffect cross section. Results with different numbers of moments agree with each other to about 15%. We find reasonable agreement with measurements of the total photoeffect cross section.

Elminyawi, I.; Levinger, J.S.

1983-07-01

33

Scattering of Alpha Particles by Oxygen. I. Bombarding Energy Range 5.8 to 10.0 MeV  

Microsoft Academic Search

Absolute differential cross sections for the elastic scattering of alpha particles by O16 have been measured as a function of bombarding energy in the range 5.8-10.0 MeV. Measurements were made at center-of-mass angles of 90.0°, 109.9°, 114.0°, 125.3°, 131.4°, 140.8°, 149.4°, 154.0°, 158.8°, and 163.8°. Detailed angular distributions have been measured at 6.97, 8.63, and 9.92 MeV (lab). Sixteen resonances

W. E. Hunt; M. K. Mehta; R. H. Davis

1967-01-01

34

Scattering of {alpha} Particles on {sup 11}B Nuclei at Energies 40 and 50 MeV  

SciTech Connect

The differential cross sections for elastic and inelastic scattering of {alpha} particles on {sup 11}B nuclei at energies of 40 and 50 MeV were measured in the entire angular range. The measured angular distributions were analyzed in terms of the optical model, the distorted-wave Born approximation, and the coupled-channel method. Optical model potentials and quadrupole ({beta}{sub 2}) and hexadecapole ({beta}{sub 4}) deformation parameters were found from this analysis. The rise in the cross sections at backward angles was shown to be associated with the transfer mechanism of the heavy {sup 7}Li cluster.

Burtebaev, N.; Baktybaev, M.K.; Duisebaev, B.A. [Institute of Nuclear Physics, National Nuclear Center, Almaty (Kazakhstan); Peterson, R.J. [University of Colorado (United States); Sakuta, S.B. [Russian Research Centre Kurchatov Institute, pl. Akademika Kurchatova 1, Moscow, 123182 (Russian Federation)

2005-08-01

35

Nuclear diagnostic for fast alpha particles  

DOEpatents

Measurement of the velocity distribution of confined energetic alpha particles resulting from deuterium-tritium fusion reactions in a magnetically contained plasma is provided. The fusion plasma is seeded with energetic boron neutrals for producing, by means of the reaction .sup.10 B (.alpha.,n) .sup.13 N reaction, radioactive nitrogen nuclei which are then collected by a probe. The radioactivity of the probe is then measured by conventional techniques in determining the energy distribution of the alpha particles in the plasma. In a preferred embodiment, diborane gas (B.sub.2 H.sub.6) is the source of the boron neutrals to produce .sup.13 N which decays almost exclusively by positron emission with a convenient half-life of 10 minutes.

Grisham, Larry R. (Lawrence Township, Mercer County, NJ); Post, Jr., Douglass E. (Belle Mead, NJ); Dawson, John M. (Pacific Palisades, CA)

1986-01-01

36

Alpha-particle-driven Alfven turbulence and its effect on alpha-particle transport  

SciTech Connect

Recent developments in computational and theoretical studies of alpha-particle-driven Alfven turbulence in both the long (k[perpendicular][rho][sub i] [much lt] 1) and the short (k[perpendicular][rho][sub i] [le] 1) wavelength regimes are reported. In the long wave-length regime, a hybrid particle-fluid model is solved numerically as well as analytically in a simple slab geometry. The dominant nonlinear interactions are found to be couplings between two Alfven waves to generate a zero-frequency electromagnetic convective cell and strong E x B convection of resonant alpha particles, which result in significant changes in plasma equilibria. The fluctuation energies first increase, then saturate and decay. The alpha-particle transport is convective and significant but does not necessarily lead to an appreciable alpha-particle loss. A mode-coupling theory is developed to explain the simulation results. In the short wavelength regime, a reduced turbulence model that describes the coupled nonlinear evolutions of fluctuation spectrum [vert bar][phi][vert bar][sub k][sup 2] and alpha-particle density profile n[sup [alpha

Gang, F.Y.; Sigmar, D.J. (Massachusetts Institute of Technology, Cambridge, MA (United States)); Leboeuf, J.N. (Oak Ridge National Lab., TN (United States)); Wising, F. (Chalmers Univ. of Technology, Gothenburg (Sweden))

1994-05-01

37

Characterization of alpha-particle tracks in cellulose nitrate LR-115 detectors at various incident energies and angles.  

PubMed

Cellulose nitrate LR-115 detectors were irradiated with alpha particles in the energy range from 1 to 5 MeV at incident angles from 20° to 90°, using an (241)Am source. After etching in a 2.5 N NaOH solution kept at 60 °C for various periods, the diameters of the major and minor axes of the track openings, track growing rate, track etch rate, etching ratio, and track length were found as a function of energies and incident angles. The measured track parameters were compared to calculated values, and the etching ratio was formulated as a Durrani-Green's function of the incident energy and angle. PMID:23727556

Mheemeed, A K; Hussein, A Kh; Kheder, R B

2013-09-01

38

Induction of single- and double-strand breaks in plasmid DNA by monoenergetic alpha-particles with energies below the Bragg-maximum.  

PubMed

The yield of single-strand breaks (ssb) and double-strand breaks (dsb) produced by alpha-particles at the end of their track in DNA-films was determined experimentally. Helium nuclei were accelerated to 600 keV in the 400 kV ion accelerator and scattered at a carbon target. The elastically scattered alpha-particles with energies of 344 keV and 485 keV were used to irradiate supercircular plasmid DNA in vacuo. For the dosimetry of the alpha-particles a surface barrier detector was used and the energy distribution of the alpha-particles determined. The energy loss of the particles in the DNA-layer was calculated. DNA samples were separated into the three conformational isomers using agarose gel electrophoresis. After fluorochromation the number of ssb and dsb per plasmid DNA molecule was established from the band intensities assuming the validity of Poisson statistics. Linear dose effect correlations were found for ssb and dsb per plasmid molecule. In the case of 344 keV-alpha-particles the yield of dsb was (8.6 +/- 0.9) x 10(-11) breaks/Gy x dalton. The ratio of ssb/dsb was 0.5 +/- 0.2. This is at least a factor of six larger than the ratio found in experiments with higher energy alpha-particles and from model calculations. Similar experiments with protons yielded a relative biological effectiveness (rbe) value of 2.8 for the induction of double-strand breaks by track end alpha-particles. PMID:9232893

Scholz, V; Weidner, J; Köhnlein, W; Frekers, D; Wörtche, H J

1997-01-01

39

Alpha particle diagnostics using impurity pellet injection  

NASA Astrophysics Data System (ADS)

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 F(sub o)(sup (infinity))(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 dn(sub He)2+/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 He-3 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.

Fisher, R. K.; McChesney, J. M.; Howald, A. W.; Parks, P. B.; Snipes, J. A.; Terry, J. L.; Marmar, E. S.; Zweben, S. J.; Medley, S.

1992-05-01

40

Measurement of the OXYGEN-17(PROTON, Alpha Particle) Nitrogen -14 Cross Section at Stellar Energies (proton Energies, Resonant Reaction)  

NASA Astrophysics Data System (ADS)

The isotopic abundance ratio 16O/17O has been shown to be a good probe of mass flow and mixing in stars. This ratio is sensitive to the depth of convective mixing which occurs on the giant branch and to the amount of nonconvective mixing occurring on the main sequence. The interpretation of recent observations of this ratio in red giants is limited by a large uncertainty in the value of the 17O(p, alpha)14N reaction rate. This reaction rate is dominated at stellar energies by a resonance at E_{rm x} = 5673 keV in the compound nucleus 18 F, whose strength was previously uncertain. We have carried out a measurement of the ^ {17}O(p,alpha)^{14 }N cross section at proton energies of 75 keV and 65 keV. Thick, high-purity rm Ta_2O _5 targets enriched to 77% ^ {17}O were used in conjunction with beam currents of 0.45 mA and large-solid-angle detectors. The background for the experiment was measured using targets of natural isotopic composition. The resonance peak was observed in the data collected at 75 keV, and we determined the proton width of the 5673 keV state to be 22 +/- 4 neV. This implies a rate for the 17O(p,alpha)^ {14}N reaction that is ten times greater than the typical rates used previously in stellar models.

Blackmon, Jeffery Curtis

41

Application of the Monte Carlo method to study the alpha particle energy spectra for radioactive aerosol sampled by an air filter.  

PubMed

An alpha spectrometer including a semi-conductor detector is commonly used for measurements of the emergent alpha particles from an air filter, on which was sampled a radioactive aerosol. The alpha spectrometry and the detection efficiency are necessary input information for real radioactivity measurements. The MCNPX code based on the Monte Carlo method has been applied to simulate the detection process in order to obtain spectrum peaks and determine the detection efficiency for modeled geometry. First simulations with MCNPX have been carried out in order to validate the alpha particle energy spectrometry of an electrodeposited solid source and an initial simulated filter model. Furthermore, to improve our first filter model, the real spatial distribution of radioactive aerosols across the filter thickness, found experimentally, is taken into account in a multi-layer filter model. Such an alpha particle distribution allows achieving an adequate simulation of the filter. Comparison between measured and simulated alpha spectra highlights the good agreement in spectral parameters and in detection efficiency even under different aerosol spatial distributions inside the volume of the filter. PMID:19590272

Geryes, T; Monsanglant-Louvet, C; Berger, L; Gehin, E

2009-08-01

42

A High-Throughput Screen for Alpha Particle Radiation Protectants  

PubMed Central

Abstract Alpha-particle-emitting elements are of increasing importance as environmental and occupational carcinogens, toxic components of radiation dispersal devices and accidents, and potent therapeutics in oncology. Alpha particle radiation differs from radiations of lower linear energy transfer in that it predominantly damages DNA via direct action. Because of this, radical scavengers effective for other radiations have had only limited effect in mitigating alpha particle toxicity. We describe here a simple assay and a pilot screen of 3,119 compounds in a high-throughput screen (HTS), using the alpha-particle-emitting isotope, 225Ac, for the discovery of compounds that might protect mammalian cells from alpha particles through novel mechanisms. The assay, which monitored the viability of a myeloid leukemic cell line upon alpha particle exposure, was robust and reproducible, yielding a Z' factor of 0.66 and a signal-to-noise ratio of nearly 10 to 1. Surprisingly, 1 compound emerged from this screen, epoxy-4,5-?-dihydroxysantonin (EDHS), that showed considerable protective activity. While the value of EDHS remains to be determined, its discovery is a proof of concept and validation of the utility of this HTS methodology. Further application of the described assay could yield compounds useful in minimizing the toxicity and carcinogenesis associated with alpha particle exposure.

Seideman, Jonathan H.; Shum, David; Djaballah, Hakim

2010-01-01

43

Control of alpha-particle transport by ion cyclotron resonance heating  

SciTech Connect

In this paper control of radial alpha-particle transport by using ion cyclotron range of frequency (ICRF) waves is investigated in a large-aspect-ratio tokamak geometry. Spatially inhomogeneous ICRF wave energy with properly selected frequencies and wave numbers can induce fast convective transports of alpha particles at the speed of order v{sub {alpha}} {approximately} (P{sub RF}/n{sub {alpha}}{epsilon}{sub 0}){rho}{sup p}, where R{sub RF} is the ICRF wave power density, n{sub {alpha}} is the alpha-particle density, {epsilon}{sub 0} is the alpha-particle birth energy, and {rho}{sub p} is the poloidal gyroradius of alpha particles at the birth energy. Application to International Thermonuclear Experimental Reactor (ITER) plasma is studied and possible antenna designs to control alpha-particle flux are discussed.

Chang, C.S.; Imre, K.; Weitzner, H.; Colestock, P. (Princeton Univ., NJ (United States). Plasma Physics Lab.)

1990-12-01

44

X-ray production cross-sections measurements for high-energy alpha particle beams: New dedicated set-up and first results with aluminum  

Microsoft Academic Search

The “IPNAS” laboratory, in collaboration with the “Centre Européen d’Archéométrie” is partly focused on material analysis by means of IBA techniques: PIXE, PIGE and RBS. A new transport beam line has been developed at our CGR-520MeV cyclotron to analyze Cultural Heritage objects using these techniques. This facility allows us to produce proton and alpha particle beams with energies up to

T. Dupuis; G. Chêne; F. Mathis; A. Marchal; H.-P. Garnir; D. Strivay

45

Alpha-particle sensitive test SRAMs  

NASA Technical Reports Server (NTRS)

A bench-level test is being developed to evaluate memory-cell upsets in a test SRAM designed with a cell offset voltage. This offset voltage controls the critical charge needed to upset the cell. The effect is demonstrated using a specially designed 2-micron n-well CMOS 4-kb test SRAM and a Po-208 5.1-MeV 0.61-LET alpha-particle source. This test SRAM has been made sensitive to alpha particles through the use of a cell offset voltage, and this has allowed a bench-level characterization in a laboratory setting. The experimental data are linked to a alpha-particle interaction physics and to SPICE circuit simulations through the alpha-particle collection depth. The collection depth is determined by two methods and found to be about 7 micron. In addition, alpha particles that struck outside the bloated drain were able to flip the SRAM cells. This lateral charge collection was observed to be more than 6 micron.

Buehler, M. G.; Blaes, B. R.

1990-01-01

46

Alternating current long range alpha particle detector  

DOEpatents

An alpha particle detector, utilizing alternating currents, which is capable of detecting alpha particles from distinct sources. The use of alternating currents allows use of simpler ac circuits which, in turn, are not susceptible to dc error components. It also allows the benefit of gas gain, if desired. In the invention, a voltage source creates an electric field between two conductive grids, and between the grids and a conductive enclosure. Air containing air ions created by collision with alpha particles is drawn into the enclosure and detected. In some embodiments, the air flow into the enclosure is interrupted, creating an alternating flow of ions. In another embodiment, a modulated voltage is applied to the grid, also modulating the detection of ions.

MacArthur, D.W.; McAtee, J.L.

1993-02-16

47

Nuclear reaction diagnostics of fast confined and escaping alpha particles  

SciTech Connect

The resonant nuclear reactions D(..cap alpha..,..gamma..) /sup 6/Li, /sup 6/Li(..cap alpha..,..gamma..) /sup 10/B, and /sup 7/Li(..cap alpha..,..gamma..) /sup 11/B are examined as diagnostics of the energy distribution of confined fast alpha particles in tokamak plasmas. Reaction rates for Q-italic = 1 D-T plasmas are estimated. The design of and preliminary results from the prototype fusion gamma ray detector on the tokamak fusion test reactor (TFTR) will be presented. The activation reactions /sup 10/B(..cap alpha..,n-italic) /sup 13/N, /sup 14/N(..cap alpha..,..gamma..) /sup 18/F, /sup 25/Mg(..cap alpha..,p-italic) /sup 28/Al, and /sup 27/Al(..cap alpha..,p-italic) /sup 30/P are similarly examined as diagnostics of fast escaping alpha particles. Count rate estimates for Q-italic = 1 D-T plasmas will be presented.

Cecil, F.E.; Medley, S.S.; Nieschmidt, E.B.; Zweben, S.J.

1986-08-01

48

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

SciTech Connect

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 {upsilon}{sub alpha} {approximately} (P{sub RF}/n{sub {alpha}}{epsilon}{sub 0}) {rho}{sub p}, where P{sub RF} is the ICRF-wave power density, n{sub {alpha}} is the alpha density, {epsilon}{sub 0} is the alpha birth energy, and {rho}{sub p} 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.

Chang, C.S.; Imre, K.; Weitzner, H. (New York Univ., NY (USA). Courant Inst. of Mathematical Sciences); Colestock, P. (Princeton Univ., NJ (USA). Plasma Physics Lab.)

1990-02-01

49

The biological effectiveness of radon-progeny alpha particles. II. Oncogenic transformation as a function of linear energy transfer  

SciTech Connect

Epidemiological studies have established an association between exposure to radon and carcinoma of the lung. However, based on data for either lung cancer in uranium miners exposed to radon or bronchial epithelial carcinomas in Japanese A-bomb survivors, it has not been possible to assign estimates of risk of lung cancer for the general population exposed to radon in their homes. Based on past success with the excellent quantitative properties of the C3H 10T1/2 in vitro oncogenic transformation assay system, the relative biological effectiveness (RBE) for radiation-induced transformation for charged particles of defined LET has been determined. As the LET of the radiation was increased, the rate of induction of oncogenic transformation increased and the RBE{sub m} approached 20. At higher LETs, RBE dropped precipitously. The rapid drop in effectiveness for {alpha} particles with LETs between 120 and 265 KeV/{mu}m implies a lower quality factor than the 20-25 currently considered appropriate when estimating lung cancer mortality. 29 refs., 3 figs., 21 tabs.

Miller, R.C.; Marino, S.A.; Brenner, D.J. [College of Physicians and Surgeons of Columbia Univ., New York, NY (United States)] [and others

1995-04-01

50

Alpha Particle Physics Experiments in the Tokamak Fusion Test Reactor  

SciTech Connect

Alpha particle physics experiments were done on the Tokamak Fusion Test Reactor (TFTR) during its deuterium-tritium (DT) run from 1993-1997. These experiments utilized several new alpha particle diagnostics and hundreds of DT discharges to characterize the alpha particle confinement and wave-particle interactions. In general, the results from the alpha particle diagnostics agreed with the classical single-particle confinement model in magnetohydrodynamic (MHD) quiescent discharges. Also, the observed alpha particle interactions with sawteeth, toroidal Alfvén eigenmodes (TAE), and ion cyclotron resonant frequency (ICRF) waves were roughly consistent with theoretical modeling. This paper reviews what was learned and identifies what remains to be understood.

Budny, R.V.; Darrow, D.S.; Medley, S.S.; Nazikian, R.; Zweben, S.J.; et al.

1998-12-14

51

Diamond detector for alpha-particle spectrometry.  

PubMed

An artificially grown high purity diamond was used as a detector for alpha-particle spectrometry. Diamond detectors can match the performance of silicon detectors employed in standard continuous air monitoring systems. Its radiation hardness and electronic properties make them ideal to work under extreme condition such as high temperature and ambient lights. A 50 ?m thickness single-crystal diamond detector has been compared with a 300 ?m passivated implanted planar silicon detector, under ambient conditions. PMID:24768983

Dueñas, J A; de la Torre Pérez, J; Martín Sánchez, A; Martel, I

2014-08-01

52

Alpha-particle-induced soft errors in dynamic memories  

Microsoft Academic Search

A new physical soft error mechanism in dynamic RAM's and CCD's is the upset of stored data by the passage of alpha particles through the memory array area. The alpha particles are emitted by the radioactive decay of uranium and thorium which are present in parts-per-million levels in packaging materials. When an alpha particle penetrates the die surface, it can

T. C. May; M. H. Woods

1979-01-01

53

High speed imaging system in continuum and H-alpha at the Hida observatory for the study of high energy particles in solar flares  

NASA Astrophysics Data System (ADS)

Non-thermal particles are the fundamental ingredient of solar flares that carry the bulk energy released from the coronal magnetic fields and cause subsequent heating of the solar atmosphere to produce the radiation of wide range of electro-magnetic waves. The observations of hard X-ray and radio emissions suggest a rapid change of population of high energy particles with a time scale of sub-second. Flare kernels observed in visible lights, ex., H-alpha and continuum, show drastic evolutions in space and time during the rising phase of solar flares, and thought to be representing the locations of the precipitation of high energy particles into the chromosphere. Therefore the observations of flare kernels with high spatial and temporal resolutions provide valuable diagnosis of the distribution of high energy particles together with the information of connectivity of coronal magnetic fields. We developed a new high speed imaging system on a 25cm diameter telescope of the Solar Magnetic Activity Research Telescope (SMART) at the Hida observatory of Kyoto University. Images in H-alpha (width~3A) and continuum (6547A, width~10A) are recorded simultaneously with two CCD cameras with a spatial sampling of 0.2 arcsec/pix, field coverage of 344 arcsec x 258 arcsec, and a frame rate of 30fr/sec. Observation is conducted continuously by focusing a targeted active region every day, while only data sets that capture flare events are permanently stored for further analysis. The spatial and temporal evolutions of flare kernels thus obtained are combined with photospheric vector magnetic field taken by the SMART, SOT/Hinode and HMI/SDO, radio data by NoRH, hard X-ray image by RHESSI, and X-ray / UV images by SXT/Hinode and AIA/SDO to identify the instantaneous locations of high energy particles injection in the corona. In this paper we will present an overview of the observing system and its initial results. This work was carried out by the joint research program of the Solar-Terrestorial Environment Laboratory, Nagoya University.

Ichimoto, K.; Kawate, T.; Yoshikazu, N.; Ishii, T.; Nagata, S.; Asai, A.; Masuda, S.; Kusano, K.; Yamamoto, T. T.; Minoshima, T.; Yokoyama, T.; Watanabe, K.

2011-12-01

54

Alpha particle collective Thomson scattering in TFTR  

SciTech Connect

A collective Thomson scattering diagnostic is being implemented on TFTR to measure alpha particle, energetic and thermal ion densities and velocity distributions. A 60 GHz, 0.1-1 kW gyrotron will be used as the transmitter source, and the scattering geometry will be perpendicular to the magnetic field in the extraordinary mode polarization. An enhanced scattered signal is anticipated from fluctuations in the lower hybrid frequency range with this scattering geometry. Millimeter wave collective Thomson scattering diagnostics have the advantage of larger scattering angles to decrease the amount of stray light, and long, high power, modulated pulses to obtain improved signal to noise through synchronous detection techniques.

Machuzak, J.S.; Woskov, P.P.; Rhee, D.Y.; Gilmore, J. [Massachusetts Inst. of Tech., Cambridge, MA (United States). Plasma Fusion Center; Bretz, N.L.; Park, H.K. [Princeton Univ., NJ (United States). Plasma Physics Lab.; Aamodt, R.E.; Cheung, P.Y.; Russell, D.A. [Lodestar Research Corp., Boulder, CO (United States); Bindslev, H. [JET Joint Undertaking, Abingdon (United Kingdom)

1993-11-01

55

Fission studies with 140 MeV {alpha} particles  

SciTech Connect

Binary fission induced by 140 MeV {alpha} particles has been measured for {sup nat}Ag, {sup 139}La, {sup 165}Ho, and {sup 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{sup 2}/A=24 is observed.

Buttkewitz, A.; Duhm, H. H.; Strauss, W. [I. Institut fuer Experimentalphysik, Universitaet Hamburg, Hamburg (Germany); Goldenbaum, F. [Institut fuer Kernphysik, Forschungszentrum Juelich, Juelich (Germany); Machner, H. [Institut fuer Kernphysik, Forschungszentrum Juelich, Juelich (Germany); Fachbereich Physik, Universitaet Duisburg-Essen, Duisburg (Germany)

2009-09-15

56

Bootstrap current induced by fusion born alpha particles  

SciTech Connect

The bootstrap current produced by fusion born alpha particles is obtained, retaining effects of slowing down drag, pitch angle scattering, and arbitrary aspect ratio. The result is presented both as a summation of a rapidly converging series and a simple Pade approximation good for arbitrary aspect ratio. Quantitative results are derived using the International Thermonuclear Experimental Reactor (ITER) (Plasma Phys. Controlled Nucl. Fusion Res. (International Atomic Energy Agency, Vienna, 1989), Vol. 3, p. 214) parameters.

Hsu, C.T.; Shaing, K.C.; Gormley, R.P.; Sigmar, D.J. (Massachusetts Institute of Technology, Plasma Fusion Center, 167 Albany Street, NW16-260, Cambridge, Massachusetts 02139 (United States))

1992-12-01

57

Explanation of the Anomalously Small Absorption of alpha Particles in exp 40 Ca Nuclei.  

National Technical Information Service (NTIS)

The reduced absorption at lower alpha particle energies (approximately 30 MeV) which is necessary to describe the anomalous large angle scattering of alpha particles from exp 40 Ca nuclei is explained by the angular momentum mismatch between the entrance ...

R. Planeta H. Dabrowski L. Freindl K. Grotowski

1979-01-01

58

A global 2.5-dimensional three fluid solar wind model with alpha particles  

Microsoft Academic Search

A global 2.5-dimensional three fluid solar wind model is presented. Two ion species, namely protons and alpha particles, are heated by an empirical energy flux while electrons are heated by the classical heat flux and Coulomb coupling with ions. It is found that for a reasonable relative speed between alpha particles and protons at 1 AU to be achieved, the

Bo Li; Xing Li; Nicolas Labrosse

2006-01-01

59

Analysis and experiment of an alpha particle emitter probe capable of direct air density measurements  

Microsoft Academic Search

A probe has been tested which can directly measure air densities. The probe uses an alpha-particle emitter (sealed Polonium 210), a surface barrier detector, filter amplifiers and sample\\/hold electronics for signal processing. The measurement of the residual energy of alpha particles directly relates to density of the medium they pass through, provided its composition is known. Optimum performance of such

R. A. Golobic; W. J. Honea

1978-01-01

60

Stopping power and energy loss straggling of thin Formvar foil for 0.3-2.7 MeV protons and alpha particles  

NASA Astrophysics Data System (ADS)

Stopping power and energy loss straggling data for protons (1H+) and alpha particles (4He+) crossing Formvar thin polymeric foils (thickness of ˜0.3 ?m) have been measured in the energy range (0.3-2.7) MeV by using the indirect transmission technique. The determined stopping power data were compared to SRIM-2010, PSTAR or ASTAR calculation codes and then analyzed in term of the modified Bethe-Bloch theory to extract the target mean excitation and ionization potential . A resulting value of ?(69.2±1.8) eV was deduced from proton stopping data. The measured straggling data were corrected from surface roughness effects due to target thickness inhomogeneity observed by the atomic force microscopy (AFM) technique. The obtained data were then compared to derived straggling values by Bohr's and Bethe-Livingston's classical theories or by Yang's empirical formula. A deviation of ˜40%-80% from the Bohr's straggling value has been observed for all reported energies, suggesting that the Bohr theory cannot be correctly applied to describe the electronic energy loss straggling process with the used low thickness of Formvar foil. The inner-shell contribution of target electrons to energy loss process is also advanced to explain the observed deviation from experiment in case of He+ ions. Finally, the reliability of Bragg's additivity rule was discussed in case of stopping power and straggling results.

Mammeri, S.; Ammi, H.; Dib, A.; Pineda-Vargas, C. A.; Ourabah, S.; Msimanga, M.; Chekirine, M.; Guesmia, A.

2012-12-01

61

Interaction of alpha particles with bronchial cells.  

PubMed

The alpha-activity on the bronchial airways has been calculated for 222Rn daughter exposures producing observable excess bronchogenic lung cancer in underground miners. The activity distribution of aerosol particles with attached 222Rn daughters on the bronchial tree is truly diffuse because of the short half-life of the daughters and the large number of particles in the ambient aerosol. From the bronchial airway activity and the minor epidemiology, it can be shown that it requires, on average, 4 X 10(9) stem cells in bronchial epithelium to be hit in order to produce an observed lung cancer. For very high 222Rn daughter exposures of miners, multiply hit cells are highly probable; yet the lung cancer response is lower per unit exposure at high exposures than for mining exposures--near those sustained in the environment probably due to stem cell death. A knowledge of the number of multiply hit cells in miners permits some infererences to be made about the effectiveness of particulate versus diffusely distributed alpha emitters in the lung, namely, that particulates should not be significantly more effective in lung cancer induction than a diffuse distribution. PMID:2844698

Harley, N H

1988-10-01

62

Measurement of Alpha Particle Radioactivtiy in IC Device Packages  

Microsoft Academic Search

Alpha particle radioactivity in package materials has been shown to cause soft errors in semiconductor devices. The particles are emitted by uranium and thorium decay sequence radioactive isotopes present as trace impurities in the raw materials used to make the package component parts. Chemical and radiation analys s techniques were correlated to alpha particle fluxes, which range in value from

E. S. Meieran; P. R. Engel; T. C. May

1979-01-01

63

Turbulent transport of alpha particles in reactor plasmas  

SciTech Connect

A systematic study of the behavior of energetic ions in reactor plasmas is presented. Using self-consistent gyrokinetic simulations, in concert with an analytic asymptotic theory, it is found that alpha particles can interact significantly with core ion-temperature-gradient turbulence. Specifically, the per-particle flux of energetic alphas is comparable to the per-particle flux of thermal species (deuterium or helium ash). This finding opposes the conventional wisdom that energetic ions, because of their large gyroradii, do not interact with the turbulence. For the parameters studied, a turbulent modification of the alpha-particle density profile appears to be stronger than turbulent modification of the alpha-particle pressure profile. Crude estimates indicate that the alpha density modification, which is directly proportional to the core turbulence intensity, could be in the range of 15% at midradius in a reactor. The corresponding modification of the alpha-particle pressure profile is predicted to be smaller (in the 1% range)

Estrada-Mila, C.; Candy, J.; Waltz, R. E. [Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, California 92093 (United States); General Atomics, San Diego, California 92121 (United States)

2006-11-15

64

Destabilization of tokamak pressure-gradient driven instabilities by energetic alpha-particle populations  

SciTech Connect

This paper reports on alpha-particle populations that can significantly alter existing magnetohydrodynamic (MHD) instabilities in tokamaks through kinetic effects and coupling to otherwise stable shear Alfven waves. Resonances of the trapped alpha-particle precessional drift, with the usual ballooning mode diamagnetic frequency ({omega}{sub *i}/2) and the toroidicity-induced Alfven eigenmode (TAE), are considered. These are examined for noncircular tokamaks in the high-n ballooning limit using an isotopic alpha-particle slowing down distribution and retaining the full-energy and pitch-angle dispersion in the alpha-particle drift frequency. Applying this to the Compact Ignition Tokamak (CIT) and the International Thermonuclear Experimental Reactor (ITER) indicates that ballooning instabilities can persist at betas below the ideal MHD threshold. These are especially dominated by the destabilization of the TAE mode. In addition, a hybrid fluid-particle approach for simulating alpha-particle effects on pressure-gradient driven instabilities is described.

Spong, D.A.; Holmes, J.A.; LeBoeuf, J.N.; Christenson, D.J. (Oak Ridge National Lab., TN (United States))

1990-11-01

65

Alpha-Particle Gas-Pressure Sensor  

NASA Technical Reports Server (NTRS)

An approximate model was developed to establish design curves for the saturation region and a more complete model developed to characterize the current-voltage curves for an alpha-particle pressure sensor. A simple two-parameter current-voltage expression was developed to describe the dependence of the ion current on pressure. The parameters are the saturation-current pressure coefficient and mu/D, the ion mobility/diffusion coefficient. The sensor is useful in the pressure range between 0.1 and 1000 mb using a 1 - mu Ci(241) Am source. Experimental results, taken between 1 and up to 200 mb, show the sensor operates with an anode voltage of 5 V and a sensitivity of 20 fA/mb in nitrogen.

Buehler, M. C.; Bell, L. D.; Hecht, M. H.

1996-01-01

66

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

SciTech Connect

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 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.

Herrmann, Hans W.

1997-06-01

67

Use of /sup 3/He/sup + +/ ICRF minority heating to simulate alpha particle heating  

DOEpatents

It is an object of the present invention to provide a better understanding of alpha particle behavior in a magnetically confined, energetic plasma. Another object of the present invention is to provide an improved means and method for studying and measuring the energy distribution of heated alpha particles in a confined plasma. Yet another object of the present invention is to permit detailed analysis of energetic alpha particle behavior in a magnetically confined plasma for use in near term fusion reactor experiments. A still further object of the present invention is to simulate energetic alpha particle behavior in a deuterium-tritium plasma confined in a fusion reactor without producing the neutron activation associated with the thus produced alpha particles.

Post, D.E. Jr.; Hwang, D.Q.; Hovey, J.

1983-11-16

68

High-resolution alpha-particle spectrometry of the 230U decay series.  

PubMed

High-resolution alpha-particle spectrometry was performed on the (230)U decay series. A (230)U source was prepared on a stainless steel disc by electrodeposition in an ammonium nitrate solution. Spectrometry of the alpha-particle energy spectrum was performed with ion-implanted planar silicon detectors in vacuum. A set of alpha emission probabilities is presented for (230)U and (226)Th. The measured peak intensities were corrected mathematically for coincidental detection of alpha-particles and conversion electrons emitted in the same decay. A good agreement with literature data was observed. The uncertainty budget and the correlation matrix are presented. The validity of the alpha-particle energies was tested and could be confirmed for most peaks within a few keV, but discrepancies were found for the 2nd peak of (226)Th and the main peak of (218)Rn. PMID:22424835

Marouli, M; Pommé, S; Paepen, J; Van Ammel, R; Jobbágy, V; Dirican, A; Suliman, G; Stroh, H; Apostolidis, C; Abbas, K; Morgenstern, A

2012-09-01

69

Energetic alpha particle deposition in a magnetized plasma  

SciTech Connect

The problem of energetic alpha particle deposition in a dense, magnetized deuterium-tritium (DT) thermonuclear fuel has been studied numerically for the case of coulomb interactions in cylindrical geometry. This was done by following the particle trajectories initiated at various radii and in different directions through the plasma and its imposed field until they had either left the plasma or deposited all their energy. The resulting complex particle trajectories in the static magnetized fuel make a detailed treatment of the problem computationally intensive. Therefore, we have attempted to use detailed modeling to produce a data base for a neural nets algorithm for incorporation in an ignition critical profile code. While the accuracy of the neutral net in reproducing the detailed calculational results is not high, it is approximately 6000 times faster. 7 refs., 1 fig.

Smitherman, D.P.; Kirkpatrick, R.C.

1991-01-01

70

Energetic alpha particle deposition in a magnetized plasma  

NASA Astrophysics Data System (ADS)

The problem of energetic alpha particle deposition in a dense, magnetized deuterium-tritium (DT) thermonuclear fuel has been studied numerically for the case of coulomb interactions in cylindrical geometry. This was done by following the particle trajectories initiated at various radii and in different directions through the plasma and its imposed field until they had either left the plasma or deposited all their energy. The resulting complex particle trajectories in the static magnetized fuel make a detailed treatment of the problem computationally intensive. Therefore, we have attempted to use detailed modeling to produce a data base for a neural nets algorithm for incorporation in an ignition critical profile code. While the accuracy of the neutral net in reproducing the detailed calculated results is not high, it is approximately 6000 times faster.

Smitherman, D. P.; Kirkpatrick, R. C.

71

Isomeric yield ratios in proton-, 3-, and alpha-particle-induced reactions on 197Au  

Microsoft Academic Search

Excitation functions and mean projected recoil-ion ranges of the isomeric nuclei produced in proton-, 3-, and alpha-particle-induced reactions on 197Au were measured by an activation technique for bombarding energies Ep<~50 MeV, and E 3He, alpha<~40 MeV. Isomeric yield ratios (sigmam\\/sigmag) were determined as a function of the incident particle energy. The experimental excitation functions and isomeric yield ratios were compared

Y. Nagame; K. Sueki; S. Baba; H. Nakahara

1990-01-01

72

Excitation of high-n toroidicity-induced shear Alfven eigenmodes by energetic particles and fusion alpha particles in tokamaks  

SciTech Connect

The stability of high-n toroidicity-induced shear Alfven eigenmodes (TAE) in the presence of fusion alpha particles or energetic ions in tokamaks is investigated. The TAE modes are discrete in nature and thus can easily tap the free energy associated with energetic particle pressure gradient through wave particle resonant interaction. A quadratic form is derived for the high-n TAE modes using gyro-kinetic equation. The kinetic effects of energetic particles are calculated perturbatively using the ideal MHD solution as the lowest order eigenfunction. The finite Larmor radius (FLR) effects and the finite drift orbit width (FDW) effects are included for both circulating and trapped energetic particles. It is shown that, for circulating particles, FLR and FDW effects have two opposite influences on the stability of the high-n TAE modes. First, they have the usual stabilizing effects by reducing the wave particle interaction strength. Second, they also have destabilizing effects by allowing more particles to resonate with the TAE modes. It is found that the growth rate induced by the circulating alpha particles increase linearly with toroidal mode number n for small {kappa}{sub {theta}}{rho}{sub {alpha}}, and decreases as 1/n for {kappa}{sub {theta}}{rho}{sub {alpha}} {much_gt} 1. The maximum growth rate is obtained at {kappa}{sub {theta}}{rho}{sub {alpha}} on the order of unity and is nearly constant for the range of 0.7 < {upsilon}{sub {alpha}}/{upsilon}{sub A} < 2.5. On the other hand, the trapped particle response is dominated by the precessional drift resonance. The bounce resonant contribution is negligible. The growth rate peaks sharply at the value of {kappa}{sub {theta}}{rho}{sub {alpha}} such that the precessional drift resonance occurs for the most energetic trapped particles. The maximum growth rate due to the energetic trapped particles is comparable to that of circulating particles.

Fu, G.Y.; Cheng, C.Z.

1992-07-01

73

Excitation of high-n toroidicity-induced shear Alfven eigenmodes by energetic particles and fusion alpha particles in tokamaks  

SciTech Connect

The stability of high-n toroidicity-induced shear Alfven eigenmodes (TAE) in the presence of fusion alpha particles or energetic ions in tokamaks is investigated. The TAE modes are discrete in nature and thus can easily tap the free energy associated with energetic particle pressure gradient through wave particle resonant interaction. A quadratic form is derived for the high-n TAE modes using gyro-kinetic equation. The kinetic effects of energetic particles are calculated perturbatively using the ideal MHD solution as the lowest order eigenfunction. The finite Larmor radius (FLR) effects and the finite drift orbit width (FDW) effects are included for both circulating and trapped energetic particles. It is shown that, for circulating particles, FLR and FDW effects have two opposite influences on the stability of the high-n TAE modes. First, they have the usual stabilizing effects by reducing the wave particle interaction strength. Second, they also have destabilizing effects by allowing more particles to resonate with the TAE modes. It is found that the growth rate induced by the circulating alpha particles increase linearly with toroidal mode number n for small {kappa}{sub {theta}}{rho}{sub {alpha}}, and decreases as 1/n for {kappa}{sub {theta}}{rho}{sub {alpha}} {much gt} 1. The maximum growth rate is obtained at {kappa}{sub {theta}}{rho}{sub {alpha}} on the order of unity and is nearly constant for the range of 0.7 < {upsilon}{sub {alpha}}/{upsilon}{sub A} < 2.5. On the other hand, the trapped particle response is dominated by the precessional drift resonance. The bounce resonant contribution is negligible. The growth rate peaks sharply at the value of {kappa}{sub {theta}}{rho}{sub {alpha}} such that the precessional drift resonance occurs for the most energetic trapped particles. The maximum growth rate due to the energetic trapped particles is comparable to that of circulating particles.

Fu, G.Y.; Cheng, C.Z.

1992-07-01

74

Measurement of the internal magnetic field of plasmas using an alpha particle source  

NASA Astrophysics Data System (ADS)

The internal magnetic fields of plasmas can be measured under certain conditions from the integrated v×B deflection of MeV alpha particles emitted by a small radioactive source. The alpha source and large-area alpha particle detector would be located inside the vacuum vessel but outside the plasma. Alphas with a typical energy of 5.5 MeV (241Am) can reach the center of almost all laboratory plasmas and magnetic fusion devices, so this method can potentially determine the q(r) profile of tokamaks or spherical toris (STs). Orbit calculations, background evaluations, and conceptual designs for such ? v×B (or ``AVB'') detector are described.

Zweben, S. J.; Darrow, D. S.; Ross, P. W.; Lowrance, J. L.; Renda, G.

2004-10-01

75

PC-based analysis of alpha-particle spectra  

NASA Astrophysics Data System (ADS)

Recently developed personal-computer (PC) software performs analysis of alpha-particle spectra. The spectra are collected using a commercially available multichannel analyzer board in the PC, interfaced with up to eight alpha-particle detectors. The PC is an IBM PC-AT computer with a 20 Mbyte Bernoulli-Box removable cartridge disk, a math coprocessor and a printer. Once saved on disk, the spectra are analyzed using the software described here. The PC analysis software performs automatic peak-area determination with operator override. Sample analysis can use measured detector efficiencies or chemical yields obtained from a radionuclide spike or both. Background contribution corrections for all peaks are included. Upper limit values are calculated for nuclides specified by the operator and not found in the sample. Nuclide identification uses a master table of up to 64 nuclides with up to 8 alpha lines for each nuclide. Any one of 32 available subtables can be selected for use in an analysis. Analysis time is short and is limited by interaction with the operator, not by calculation time. Both detailed and summary versions of final results are printed for ease of data reporting. Utilities included with the software provide nuclide table editing, subset table editing, energy calibration, efficiency calibration and background analysis with background correction file update.

Chapman, Terry C.

1990-12-01

76

Complex-Energy Shell-Model Description of Alpha Decay  

SciTech Connect

In his pioneering work of alpha decay, Gamow assumed that the alpha particle formed inside the nucleus tunnels through the barrier of the alpha-daughter potential. The corresponding metastable state can be viewed as a complex-energy solution of the time-independent Schroedinger equation with the outgoing boundary condition. The formation of the alpha cluster, missing in the original Gamow formulation, can be described within the R-matrix theory in terms of the formation amplitude. In this work, the alpha decay process is described by computing the formation amplitude and barrier penetrability in a large complex-energy configuration space spanned by the complex-energy eigenstates of the finite Woods-Saxon (WS) potential. The proper normalization of the decay channel is essential as it strongly modifies the alpha-decay spectroscopic factor. The test calculations are carried out for the ^{212}Po alpha decay.

Id Betan, R. [Rosario Physics Institute, Rosario, Argentina] [Rosario Physics Institute, Rosario, Argentina; Nazarewicz, Witold [ORNL] [ORNL

2011-01-01

77

Nuclear {alpha}-particle condensates: Definitions, occurrence conditions, and consequences  

SciTech Connect

There has been a recent flurry of interest in the possibility of condensates of {alpha} particles in nuclei. In this Rapid Communication we discuss occurrence conditions for such states. Using the quantality condition of Mottelson we show that condensates are only marginally expected in {alpha}-particle states. We proceed to demonstrate that few-body nuclear condensates are ill defined and emphasize the conflict between {alpha}-localization and {alpha}-condensate formation. We also explore the connection between Ikeda diagrams, linear chains, and Tonks-Girardeau gases. Our findings show that no new information is contained in the approximations of nuclear states as {alpha}-cluster condensates. Furthermore, condensates of more than three {alpha} particles are very unlikely to exist due to couplings to other degrees of freedom.

Zinner, N. T.; Jensen, A. S. [Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C (Denmark)

2008-10-15

78

Thermoluminescence and Coloration of Lithium Fluoride Produced by Alpha Particles, Electrons, Gamma Rays, and Neutrons  

Microsoft Academic Search

The coloration and thermoluminescence produced in LiF by 2 Mev alpha particles, by 2 Mev electrons, by 1 Mev gamma rays from Co60, and by thermal neutrons are described. The energy initially required to produce an F center varies. It is about 700 ev for alpha, 140 ev for beta, 65 ev for gamma rays, and 65 ev for thermal

Frederick F. Morehead; Farrington Daniels

1957-01-01

79

Complex-energy shell model description of alpha decay  

NASA Astrophysics Data System (ADS)

In his pioneering work of alpha decay, Gamow assumed that the alpha particle formed inside the nucleus tunnels through the barrier of the alpha-daughter potential. The corresponding metastable state can be viewed as a complex-energy solution of the time-independent Schrödinger equation with the outgoing boundary condition. The formation of the alpha cluster, missing in the original Gamow formulation, can be described within the R-matrix theory in terms of the formation amplitude. In this work, the alpha decay process is described by computing the formation amplitude and barrier penetrability in a large complex-energy configuration space spanned by the complexenergy eigenstates of the finite Woods-Saxon (WS) potential. The proper normalization of the decay channel is essential as it strongly modifies the alpha-decay spectroscopic factor. The test calculations are carried out for the 212Po alpha decay.

Betan, R. Id; Nazarewicz, W.

2012-02-01

80

Effect of alpha particles on Toroidal Alfven Eigenmodes  

SciTech Connect

An overview is given of the analytic structure for the linear theory of the Toroidal Alfven Eigenmode (TAE), where multiple gap structures occur. A discussion is given of the alpha particle drive and the various dissipation mechanisms that can stabilize the system. A self-consistent calculation of the TAE mode, for a low-beta high-aspect-ratio plasma, indicates that though the alpha particle drive is comparable to the dissipation mechanisms, overall stability is still achieved for ignited ITER-like plasma. A brief discussion is given of the nonlinear theory for the TAE mode and how nonlinear alpha particle dynamics can be treated by mapping methods.

Berk, H.L.

1992-11-01

81

{alpha}-particle optical potentials for nuclear astrophysics (NA) and nuclear technology (NT)  

SciTech Connect

The high precision of recent measurements for low-energy {alpha}-particle elastic-scattering as well as induced-reaction data makes possible the understanding of actual limits and possible improvement of the global optical model potentials parameters. Involvement of recent optical potentials for reliable description of both the elastic scattering and emission of {alpha}-particles, of equal interest for nuclear astrophysics (NA) and nuclear technology (NT) for fusion devices, is discussed in the present work.

Avrigeanu, V.; Avrigeanu, M. [Horia Hulubei National Institute for Physics and Nuclear Engineering, POBox MG-6, 077125 Magurele, Ilfov (Romania)

2012-11-20

82

Determination of neutron-induced alpha-particle cross sections on carbon using the response of a liquid scintillation detector  

SciTech Connect

This paper presents the sums of the cross section {sup 12}C(n, {alpha}{sub 0}) {sup 9}Be and {sup 12}C(n, N{prime}3{alpha}) determined in the neutron energy range between 7.4 and 11 MeV. An NE-213 scintillation detector is simultaneously used as a carbon target, an alpha-particle detector, and a neutron fluence monitor. By comparing the measured and calculated response spectra, the neutron-induced alpha-particle events in the scintillation volume are separated and the cross sections {sigma}{sub n,{alpha}0} + {sigma}{sub n,n{prime}3{alpha}} are determined relative to the n-p scattering cross section. The pulse-height distribution due to alpha particles allows the angular distribution to be extracted on the basis of the reaction kinematics and an accurately determined light output function for alpha particles in the NE-213 detector.

Brede, H.J.; Dietze, G.; Klein, H.; Schoelermann, H. (Physikalisch-Technische Bundesanstalt, Bundesallee 100, D-3300 Braunschweig (DE))

1991-01-01

83

Kinetic Approach for Studying the Alpha Particle Transport in Plasma Liner Driven Magnetized Target Fusion  

NASA Astrophysics Data System (ADS)

A new promising concept for producing energy from thermonuclear fusion is magnetized target fusion (MTF). In MTF, an imploding material liner is used to compress magnetized plasma to fusion ignition and to inertially confine the resulting burning plasma to obtain the necessary energy gain. Plasma liners have the potential to be formed in a repeatable, standoff manner and allow for the possibility of secondary fusion burn in the liner, which allows for much higher fusion energy yields and relaxes the density and scale length requirements of the magnetized target. To date, no theoretical effort has adequately addressed the issue of thermal transport of high-energy alpha particles from the target to the liner. Although the liner/target system is highly collisional at ignition, the fast alpha particle mean free path is relatively large resulting in nonlocal deposition of the kinetic energy into the liner. Thus, a fluid approach may not be appropriate for assessing the possibility of secondary burn. A MATLAB computer code was developed that numerically modeled the alpha particles, electrons, and Deuterons using distribution functions. These distribution functions were separately evolved over time using the Boltzmann equation for the plasma transport and the nonlinear Fokker-Planck equation for the collisions between the alpha particles and the electrons and Deuterons. Preliminary results from this work shows that the alpha particles collide with the initially at rest Deuterons and transfer enough energy so that both species move outward away from the target. In addition, some of the Deuterons reach fusion burn energies.

Sommer, James

2003-10-01

84

Full orbit calculation for lost alpha particle measurement on ITER  

SciTech Connect

An orbit following calculation code with full gyromotion under the ITER magnetic field configuration has been developed to investigate escaping alpha particle orbits in ITER and to determine the geometrical arrangement for alpha particle detection. The code contained the full geometrical information of the first wall panels. It was carefully investigated whether an alpha particle escaping from the plasma through the last closed flux surface does not touch or intersect the first wall boundary before reaching the detection point. Candidates of blanket module modification have been studied to achieve effective measurement geometry for escaping alpha particle detection. The calculations showed that direct orbit loss and banana diffusion can be detected with a probe head recessed from the first wall surface.

Funaki, D.; Isobe, M.; Nishiura, M.; Sato, Y.; Okamoto, A.; Kobuchi, T.; Kitajima, S.; Sasao, M. [Department of Quantum Energy Science, Tohoku University, Sendai 980-8579 (Japan)

2008-10-15

85

Probing [alpha]-particle wave functions using ([ital [rvec d  

SciTech Connect

Wave functions of the [alpha] particle corresponding to different [ital S]- and [ital D]-state deuteron-deuteron overlaps, [l angle][ital dd][vert bar][alpha][r angle], were investigated using exact finite-range distorted-wave Born-approximation (DWBA) analyses of ([ital [rvec d

Crosson, E.R.; Lemieux, S.K.; Ludwig, E.J.; Thompson, W.J. (University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3255 (United States) Triangle Universities Nuclear Laboratory, Durham, North Carolina 27706 (United States)); Bisenberger, M.; Hertenberger, R.; Hofer, D.; Kader, H.; Schiemenz, P.; Graw, G. (Sektion Physik, Universitaet Muenchen, 8046 Garching (Germany)); Eiro, A.M.; Santos, F.D. (Departamento de Fisica, Universidade de Lisboa, 1700 Lisboa (Portugal))

1993-06-01

86

Alpha particle response characterization of CdZnTe  

SciTech Connect

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.

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

2001-06-28

87

Alpha particle effects on the internal kink modes  

SciTech Connect

The {alpha}-particle effects on the internal kink mode stability are studied. Finite Grad-Shafranov Shift, plasma {beta}, and plasma shape can significantly enhance the trapped particle drift reversal domain in pitch angle space and reduce average magnetic drift frequency. The drift reversal effect on the ideal kink mode is small, but the {beta}{sub {alpha}} threshold for the fishbone mode can be much lower than previously predicted. In addition, the ion diamagnetic drift has a stronger destabilizing effect.

Wu, Yanlin; Cheng, C.Z.

1994-08-01

88

Shielding of manned space vehicles against protons and alpha particles  

NASA Technical Reports Server (NTRS)

The available information on the shielding of manned space vehicles against protons and alpha particles is summarized. The emphasis is placed on shielding against Van Allen belt protons and against solar-flare protons and alpha particles, but information on shielding against galactic cosmic rays is also presented. The approximation methods for use by nonexperts in the space shielding field are those that are standard in the space shielding literature.

Alsmiller, R. G., Jr.; Santoro, R. T.; Barish, J.; Claiborne, H. C.

1972-01-01

89

Modification of alpha-particle emission spectrum in beam-injected deuterium-tritium plasmas  

SciTech Connect

The alpha ({alpha})-particle and neutron emission spectra in a deuterium-tritium plasma accompanied with neutral-beam-injection (NBI) heating are evaluated in a consistent way by solving the Boltzmann-Fokker-Planck equations for deuteron, triton, and {alpha}-particle simultaneously. It is shown that owing to the existence of non-Maxwellian tail component in fuel-ion distribution function due to NBI and/or nuclear elastic scattering, the generation rate of the energetic ({>=}4 MeV) {alpha}-particle increases significantly. When 20 MW intense deuterium beam with 1 MeV beam-injection energy is injected into an 800 m{sup 3} plasma (T{sub e}=10 keV, n{sub e}=6.2x10{sup 19} m{sup -3}), the enhancement of the fraction of the power carried by {alpha}-particles with energy above 4 (3.9) MeV to total {alpha}-particle power is almost twice (1.5 times) as much from the value for Gaussian distribution. A verification scenario for the modification of the emission spectrum by using the gamma ({gamma})-ray-generating {sup 9}Be({alpha},n{gamma}){sup 12}C reaction is also presented.

Matsuura, H.; Nakao, Y. [Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Motooka, Fukuoka 819-0395 (Japan)

2009-04-15

90

Oncogenic Transformation of Mammalian Cells by Ultrasoft X-Rays and Alpha Particles  

NASA Astrophysics Data System (ADS)

For a better understanding of oncogenic cell transformation by ionizing radiation, we conducted experiments with ultrasoft X rays and low energy alpha particles. Confluent C3HlOTl/2 cells were irradiated by Al-K (1.5 keV) X rays or alpha particles from plutonium through a thin mylar sheet, on which the cells attached and grew. Our results indicated that Al-K X rays were more effective in causing cell inactivation and oncogenic transformation than 60Co gamma rays but less effective than 1.0 and 3.7 MeV alpha particles. There was no significant difference between 1.0 and 3.7 MeV alpha particles in transforming cells although the latter were slightly more effective than the former in producing lethal effect. These results indicated that track structure is important in causing biological effects by ionizing radiation

Yang, T. C.; Craise, L. M.; Raju, M. R.

91

Monte Carlo Calculations of Suprathermal Alpha Particles Trajectories in the Rippled Field of TFTR  

Microsoft Academic Search

We study the transport of suprathermal alpha particles and their energy deposition into electrons, deuterons, tritons and carbon-12 impurity in the rippled field of TFTR. The Monte Carlo code (Punjabi A., Boozer A., Lam M., Kim M., and Burke K., J. Plasma Phys.), 44, 405 (1990) developed by Punjabi and Boozer for the transport of plasma particles due to MHD

Alkesh Punjabi; Maria Lam; Allen Boozer

1996-01-01

92

Variation of the track etch rates of alpha-particle trajectory in PADC  

Microsoft Academic Search

The formation of etched tracks in solid-state nuclear track detectors is usually described by assuming an unequivocal correlation of the etch-rate ratio with the energy loss of charged particles. For alpha particles, this assumption could be verified within the scatter of the experimental data. In this article, the dependence of the depth (x) on the track etch rate (VT) was

M. F. Zaki; Tarek M. Hegazy; U. Seddik; A. Ahmed Morsy

2005-01-01

93

Measurement of alphas from the structure of particle clusters produced in hadronic Z decays  

Microsoft Academic Search

Using 106 000 hadronic events obtained with the ALEPH detector at LEP at energies close to the Z resonance peak, the strong coupling constant alphas is measured by an analysis of energy-energy correlations (EEC) and the global event shape variables thrust, C-parameter and oblateness. It is shown that the theoretical uncertainties can be significantly reduced if the final state particles

D. Decamp; B. Deschizeaux; C. Goy; J.-P. Lees; M.-N. Minard; R. Alemany; J. M. Crespo; M. Delfino; E. Fernandez; V. Gaitan; Ll. Garrido; P. Mato; R. Miquel; Ll. M. Mir; S. Orteu; A. Pacheco; J. A. Perlas; E. Tubau; M. G. Catanesi; D. Creanza; M. de Palma; A. Farilla; G. Iaselli; G. Maggi; M. Maggi; S. Natali; S. Nuzzo; M. Quattromini; A. Ranieri; G. Raso; F. Romano; F. Ruggieri; G. Selvaggi; L. Silvestris; P. Tempesta; G. Zito; Y. Gao; H. Hu; D. Huang; X. Huang; J. Lin; J. Lou; C. Qiao; T. Ruan; T. Wang; Y. Xie; D. Xu; R. Xu; J. Zhang; W. Zhao; H. Albrecht; W. B. Atwood; F. Bird; E. Blucher; G. Bonvicini; F. Bossi; D. Brown; T. H. Burnett; H. Drevermann; F. Dydak; R. W. Forty; C. Grab; R. Hagelberg; S. Haywood; B. Jost; M. Kasemann; G. Kellner; J. Knobloch; A. Lacourt; I. Lehraus; T. Lohse; D. Lüke; A. Marchioro; M. Martinez; J. May; S. Menary; A. Minten; A. Miotto; J. Nash; P. Palazzi; F. Ranjard; G. Redlinger; A. Roth; J. Rothberg; H. Rotscheidt; W. von Rüden; R. St. Denis; D. Schlatter; M. Takashima; M. Talby; W. Tejessy; H. Wachsmuth; S. Wasserbaech; S. Wheeler; W. Wiedenmann; W. Witzeling; J. Wotschack; Z. Ajaltouni; M. Bardadin-Otwinowska; A. Falvard; R. El Fellous; P. Gay; J. Harvey; P. Henrard; J. Jousset; B. Michel; J.-C. Montret; D. Pallin; P. Perret; J. Proriol; F. Prulhière; G. Stimpfl; J. D. Hansen; J. R. Hansen; P. H. Hansen; R. Møllerud; E. R. Nielsen; B. S. Nilsson; I. Efthymiopoulos; E. Simopoulou; A. Vayaki; J. Badier; A. Blondel; G. Bonneaud; J. Bourotte; F. Braems; J. C. Brient; G. Fouque; A. Gamess; R. Guirlet; A. Rosowsky; A. Rougé; M. Rumpf; R. Tanaka; H. Videau; D. J. Candlin; E. Veitch; G. Parrini; M. Corden; C. Georgiopoulos; M. Ikeda; J. Lannutti; D. Levinthal; M. Mermikides; L. Sawyer; A. Antonelli; R. Baldini; G. Bencivenni; G. Bologna; P. Campana; G. Capon; V. Chiarella; B. D'Ettorre-Piazzoli; G. Felici; P. Laurelli; G. Mannocchi; F. Massimo-Brancaccio; F. Murtas; G. P. Murtas; G. Nicoletti; L. Passalacqua; M. Pepe-Altarelli; P. Picchi; P. Zografou; B. Altoon; O. Boyle; A. W. Halley; I. Ten Have; J. L. Hearns; J. G. Lynch; W. T. Morton; C. Raine; J. M. Scarr; K. Smith; A. S. Thompson; R. M. Turnbull; B. Brandl; O. Braun; R. Geiges; C. Geweniger; P. Hanke; V. Hepp; E. E. Kluge; Y. Maumary; A. Putzer; B. Rensch; A. Stahl; K. Tittel; M. Wunsch; A. T. Belk; R. Beuselinck; D. M. Binnie; W. Cameron; M. Cattaneo; P. J. Dornan; S. Dugeay; A. M. Greene; J. F. Hassard; N. M. Lieske; S. J. Patton; D. G. Payne; M. J. Phillips; J. K. Sedgbeer; G. Taylor; I. R. Tomalin; A. G. Wright; P. Girtler; D. Kuhn; G. Rudolph; C. K. Bowdery; T. J. Brodbeck; A. J. Finch; F. Foster; G. Hughes; N. R. Keemer; M. Nuttall; A. Patel; B. S. Rowlingson; T. Sloan; S. W. Snow; E. P. Whelan; T. Barczewski; L. A. T. Bauerdick; K. Kleinknecht; B. Renk; S. Roehn; H.-G. Sander; M. Schmelling; H. Schmidt; F. Steeg; J.-P. Albanese; J.-J. Aubert; C. Benchouk; V. Bernard; A. Bonissent; D. Courvoisier; F. Etienne; S. Papalexiou; P. Payre; B. Pietrzyk; Z. Qian; W. Blum; P. Cattaneo; G. Cowan; B. Dehning; H. Dietl; M. Fernandez-Bosman; T. Hansl-Kozanecka; A. Jahn; W. Kozanecki; E. Lange; G. Lütjens; G. Lutz; W. Männer; H.-G. Moser; Y. B. Pan; R. Richter; J. Schröder; A. S. Schwarz; R. Settles; U. Stierlin; J. Thomas; G. Wolf; V. Bertin; G. de Bouard; J. Boucrot; O. Callot; X. Chen; A. Cordier; M. Davier; G. Ganis; J.-F. Grivaz; Ph. Heusse; P. Janot; V. Journé; D. W. Kim; J. Lefrançois; A.-M. Lutz; J.-J. Veillet; I. Videau; Z. Zhang; F. Zomer; S. R. Amendolia; G. Bagliesi; G. Batignani; L. Bosisio; U. Bottigli; C. Bradaschia; M. Carpinelli; M. A. Ciocci; R. dell'Orso; I. Ferrante; F. Fidecaro; L. Foà; E. Focardi; F. Forti; A. Giassi; M. A. Giorgi; F. Ligabue; A. Lusiani; E. B. Mannelli; P. S. Marrocchesi; A. Messineo; L. Moneta; F. Palla; G. Sanguinetti; J. Steinberger; R. Tenchini; G. Tonelli; G. Triggiani; C. Vannini-Castaldi; A. Venturi; P. G. Verdini; J. Walsh; J. M. Carter; M. G. Green; P. V. March; T. Medcalf; I. S. Quazi; M. R. Saich; J. A. Strong; R. M. Thomas; L. R. West; T. Wildish; D. R. Botterill; R. W. Clifft; T. R. Edgecock; M. Edwards; S. M. Fisher; T. J. Jones; P. R. Norton; D. P. Salmon; J. C. Thompson; B. Bloch-Devaux; P. Colas; C. Klopfenstein; E. Lançon; E. Locci; S. Loucatos; E. Monnier; P. Perez; F. Perrier; J. Rander; J.-F. Renardy; A. Roussarie; J.-P. Schuller; J. Schwindling; J. G. Ashman; C. N. Booth; C. Buttar; R. Carney; S. Cartwright; F. Combley; M. Dinsdale; M. Dogru; F. Hatfield; J. Martin; D. Parker; P. Reeves; L. F. Thompson; S. Brandt; H. Burkhardt; C. Grupen; H. Meinhard; L. Mirabito; E. Neugebauer; U. Schäfer; H. Seywerd; G. Apollinari; G. Giannini; B. Gobbo; F. Liello; L. Rolandi; U. Stiegler; L. Bellantoni; J. F. Boudreau; D. Cinabro; J. S. Conway; D. F. Cowen; A. J. Deweerd; Z. Feng; D. P. S. Ferguson; J. Grahl; J. L. Harton; J. Hilgart

1991-01-01

94

Absorbed fractions for alpha-particles in tissues of cortical bone  

NASA Astrophysics Data System (ADS)

Bone-seeking alpha-particle emitting radionuclides are common health physics hazards. Additionally, they are under consideration as an option for therapeutic molecular radiotherapy applications. Current dose models do not account for energy or bone-site dependence as shown by alpha-particle absorbed fractions given in ICRP Publication 30. Energy-dependent, yet bone-site independent, alpha-particle absorbed fractions have been presented by the models of Stabin and Siegel (2003 Health Phys. 85 294-310). In this work, a chord-based computational model of alpha-particle transport in cortical bone has been developed that explicitly accounts for both the bone-site and particle-energy dependence of alpha-particle absorbed fractions in this region of the skeleton. The model accounts for energy deposition to three targets: cortical endosteum, haversian space tissues and cortical bone. Path length distributions for cortical bone given in Beddoe (1977 Phys. Med. Biol. 22 298-308) provided additional transport regions in the absorbed fraction calculation. Significant variations in absorbed fractions between different skeletal sites were observed. Differences were observed between this model and the absorbed fractions given in ICRP Publication 30, which varied by as much as a factor of 2.1 for a cortical bone surface source irradiating cortical endosteum.

Watchman, Christopher J.; Bolch, Wesley E.

2009-10-01

95

Alpha particle condensation in {sup 12}C and nuclear rainbow scattering  

SciTech Connect

It is shown that the large radius of the Hoyle state of {sup 12}C with a dilute density distribution in an {alpha} particle condensate can be clearly seen in the shift of the rainbow angle (therefore the Airy minimum) to a larger angle in {alpha}+{sup 12}C rainbow scattering at the high energy region and prerainbow oscillations in {sup 3}He+{sup 12}C scattering at the lower energy region.

Ohkubo, S. [Department of Applied Science and Environment, Kochi Women's University, Kochi 780-8515 (Japan); Hirabayashi, Y. [Information Initiative Center, Hokkaido University, Sapporo 060-0811 (Japan)

2008-05-12

96

Model for alpha particle induced nuclear reactions: 93Nb(alpha,xalphaypzn) from 40-140 MeV  

Microsoft Academic Search

A comprehensive model is introduced for alpha particle induced nuclear reactions. Five different mechanisms are examined and discussed. These include inelastic scattering of the incident alpha particle, nucleon pickup, binary fragmentation, dissolution of the alpha in the nuclear field, and preequilibrium processes initiated by alpha-nucleon collisions. A series of experiments was performed to measure the excitation functions of many nuclides

Ettore Gadioli; Enrica Gadioli-Erba; James J. Hogan; Barbara V. Jacak

1984-01-01

97

High energy particle astronomy.  

NASA Technical Reports Server (NTRS)

Discussion of techniques currently used in high energy particle astronomy for measuring charged and neutral cosmic rays and their isotope and momentum distribution. Derived from methods developed for accelerator experiments in particle physics, these techniques help perform important particle astronomy experiments pertaining to nuclear cosmic ray and gamma ray research, electron and position probes, and antimatter searches.

Buffington, A.; Muller, R. A.; Smith, L. H.; Smoot, G. F.

1972-01-01

98

Use of .sup.3 He.sup.30 + ICRF minority heating to simulate alpha particle heating  

DOEpatents

Neutron activation due to high levels of neutron production in a first heated deuterium-tritium plasma is substantially reduced by using Ion Cyclotron Resonance Frequency (ICRF) heating of energetic .sup.3 He.sup.++ ions in a second deuterium-.sup.3 He.sup.++ plasma which exhibit an energy distribution and density similar to that of alpha particles in fusion reactor experiments to simulate fusion alpha particle heating in the first plasma. The majority of the fast .sup.3 He.sup.++ ions and their slowing down spectrum can be studied using either a modulated hydrogen beam source for producing excited states of He.sup.+ in combination with spectrometers or double charge exchange with a high energy neutral lithium beam and charged particle detectors at the plasma edge. The maintenance problems thus associated with neutron activation are substantially reduced permitting energetic alpha particle behavior to be studied in near term large fusion experiments.

Post, Jr., Douglass E. (Belle Mead, NJ); Hwang, David Q. (Lawrencevill, NJ); Hovey, Jane (Plainsboro, NJ)

1986-04-22

99

Stopping power for alpha particles in organic liquids and vapours  

NASA Astrophysics Data System (ADS)

The stopping power for 5.5 MeV alpha particles has been studied in liquid and vapour phases of water, methanol, ethanol, propanol, pentane, hexane, cyclohexane, heptane and octane. Experimental values for stopping powers in the range 5.5 MeV to 0.5 MeV have been extracted by fitting the range-energy data with polynomial and inverse stopping power functions, and compared with existing results. The effect of phase of the absorber on the stopping power has been clearly demonstrated, the stopping power being higher in the vapour phase. Mean values of the excitation potential have been deduced from the experimental stopping powers after allowing for shell, Barkas and Bloch corrections, which are then compared with the recommended values of Berger and Seltzer.

Haque, A. K. M. M.; Nikjoo, H.

1991-01-01

100

Model for alpha particle induced nuclear reactions: ⁹³Nb(. cap alpha. ,x. cap alpha. ypzn) from 40--140 MeV  

Microsoft Academic Search

A comprehensive model is introduced for alpha particle induced nuclear reactions. Five different mechanisms are examined and discussed. These include inelastic scattering of the incident alpha particle, nucleon pickup, binary fragmentation, dissolution of the alpha in the nuclear field, and preequilibrium processes initiated by alpha-nucleon collisions. A series of experiments was performed to measure the excitation functions of many nuclides

E. Gadioli; E. Gadioli-Erba; J. J. Hogan; B. V. Jacak

1984-01-01

101

The energetic alpha particle transport method EATM  

SciTech Connect

The EATM method is an evolving attempt to find an efficient method of treating the transport of energetic charged particles in a dynamic magnetized (MHD) plasma for which the mean free path of the particles and the Larmor radius may be long compared to the gradient lengths in the plasma. The intent is to span the range of parameter space with the efficiency and accuracy thought necessary for experimental analysis and design of magnetized fusion targets.

Kirkpatrick, R.C.

1998-02-01

102

Breakup of {sup 12}C resonances into three alpha particles  

SciTech Connect

The reaction {sup 3}He+{sup 11}B->d+{sup 12}C* has been used to populate resonances in {sup 12}C up to an excitation energy of 15 MeV. The subsequent breakup to three alpha particles has been measured in complete kinematics. Dalitz plots are used to visualize and analyze the data. The Dalitz plot intensity distribution exhibits zero points characteristic of the total spin and parity of the 3alpha system allowing us to determine the spin and parity of a state in {sup 12}C at 13.35 MeV whose quantum numbers were hitherto not well established. The Dalitz plot intensity distributions of the 2{sup -} state at 11.83 MeV and the 1{sup +} state at 12.71 MeV are compared with the predictions of a recent three-body calculation as well as with simpler models. All are able to reproduce the gross structures seen in the Dalitz plot, but none give an accurate description of the detailed profile of the distributions.

Kirsebom, O. S.; Fynbo, H. O. U.; Hyldegaard, S.; Riisager, K. [Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); Alcorta, M.; Borge, M. J. G.; Cubero, M.; Dominguez-Reyes, R.; Madurga, M.; Perea, A.; Tengblad, O. [Instituto de Estructura de la Materia, CSIC, ES-28006 Madrid (Spain); Diget, C. A.; Fulton, B. R. [Department of Physics, University of York, York YO10 5DD (United Kingdom); Fraile, L. M. [PH Department, CERN, CH-1211 Geneva 23 (Switzerland); Jonson, B.; Nilsson, T.; Nyman, G. [Fundamental Physics, Chalmers University of Technology, SE-41296 Goeteborg (Sweden); Munoz Martin, A. [CMAM, Universidad Autonoma de Madrid, Cantoblanco, ES-28049 Madrid (Spain)

2010-06-15

103

Alpha-particle decays from excited states in 24Mg  

NASA Astrophysics Data System (ADS)

Using a cluster model based on the Woods-Saxon potential, alpha-particle decays from excited states in 24Mg have been systematically investigated. Calculations can in general reproduce experimental data, noticing the fact that the preformation factor P of alpha particle in alpha-decaying nuclei is of order from 100 to 10-2. This can be the evidence for the ?+20Ne structure in 24Mg. Meanwhile, the results also show the existence of other configurations, such as 16O+2 ?. Since the calculated decay widths are very sensitive to the angular momentum carried by the outgoing cluster ( ? particle), our results could serve as a guide to experimental spin assignments.

Wang, SiMin; Xu, Chen; Liotta, R. J.; Qi, Chong; Xu, FuRong; Jiang, DongXing

2011-08-01

104

Selective flow path alpha particle detector and method of use  

DOEpatents

A method and apparatus for monitoring alpha contamination are provided in which ions generated in the air surrounding the item, by the passage of alpha particles, are moved to a distant detector location. The parts of the item from which ions are withdrawn can be controlled by restricting the air flow over different portions of the apparatus. In this way, detection of internal and external surfaces separately, for instance, can be provided. The apparatus and method are particularly suited for use in undertaking alpha contamination measurements during the commissioning operations.

Orr, Christopher Henry (Sellafield, Seascale, Cumbria, GB); Luff, Craig Janson (Sellafield, Seascale, Cumbria, GB); Dockray, Thomas (Sellafield, Seascale, Cumbria, GB); Macarthur, Duncan Whittemore (P.O. Box 1663, Los Alamos, NM 87545)

2002-01-01

105

A survey of the physical processes which determine the response function of silicon detectors to alpha particles  

NASA Astrophysics Data System (ADS)

The spectra of monoenergetic alpha particles exhibit a well known asymmetric shape when measured with silicon detectors. The processes are described which determine the response of silicon detectors to alpha particles, particularly the energy dependence of the line shape. In this work particle implanted and passivated silicon (PIPS) detectors are assumed to have a thin dead layer at the front contact and an infinite sensitive volume. The incoming monoenergetic alpha particles lose energy in the dead layer where they develop a Gaussian energy distribution due to electronic energy-loss straggling. In the sensitive volume the alpha particles transfer most of their energy to electronic excitation and ionization ( Es,e) and the remaining fraction to the production of lattice vibrations and crystal damage. The statistical distribution of Es,e has been calculated by Monte Carlo simulation and shown to be asymmetric. The energy Es,e is subsequently used for the creation of electron-hole pairs, which are measured by an amplifier system with a Gaussian contribution to the energy resolution due to electronic noise. This model permits a quantitative calculation of the detector response function to alpha particles, and the result is in excellent agreement with measured spectra. On the basis of this model the energy dependence of the alpha particle line shape is also discussed.

Steinbauer, E.; Bortels, G.; Bauer, P.; Biersack, J. P.; Burger, P.; Ahmad, I.

1994-01-01

106

Experimental Studies of ZnS Alpha Particle Counters and Methods for Minimizing Detector Background  

Microsoft Academic Search

The zinc sulfide scintillation counter employed at IBM for low-level alpha flux monitoring of device and packaging materials is described. This counter provides almost 100% counting efficiency for alpha particles of 1.5MeV or greater energy emitted from the surface of planar samples up to 130 cm2 in area, and exhibits a sea level background count rate on the order of

B. J. Masters

1980-01-01

107

Effects of alpha-particles on survival and chromosomal aberrations in human mammary epithelial cells  

NASA Technical Reports Server (NTRS)

We have studied the radiation responses of a human mammary epithelial cell line, H184B5 F5-1 M/10. This cell line was derived from primary mammary cells after treatment with chemicals and heavy ions. The F5-1 M/10 cells are immortal, density-inhibited in growth, and non-tumorigenic in athymic nude mice and represent an in vitro model of the human epithelium for radiation studies. Because epithelial cells are the target of alpha-particles emitted from radon daughters, we concentrated our studies on the efficiency of alpha-particles. Confluent cultures of M/10 cells were exposed to accelerated alpha-particles [beam energy incident at the cell monolayer = 3.85 MeV, incident linear energy transfer (LET) in cell = 109 keV/microns] and, for comparison, to 80 kVp x-rays. The following endpoints were studied: (1) survival, (2) chromosome aberrations at the first postirradiation mitosis, and (3) chromosome alterations at later passages following irradiation. The survival curve was exponential for alpha-particles (D0 = 0.73 +/- 0.04 Gy), while a shoulder was observed for x-rays (alpha/beta = 2.9 Gy; D0 = 2.5 Gy, extrapolation number 1.6). The relative biological effectiveness (RBE) of high-LET alpha-particles for human epithelial cell killing was 3.3 at 37% survival. Dose-response curves for the induction of chromosome aberrations were linear for alpha-particles and linearquadratic for x-rays. The RBE for the induction of chromosome aberrations varied with the type of aberration scored and was high (about 5) for chromosome breaks and low (about 2) for chromosome exchanges.(ABSTRACT TRUNCATED AT 250 WORDS).

Durante, M.; Grossi, G. F.; Gialanella, G.; Pugliese, M.; Nappo, M.; Yang, T. C.

1995-01-01

108

MHD-Induced Alpha Particle Loss in TFTR  

SciTech Connect

MHD-induced increases in alpha particle loss to the wall were observed for both coherent modes and transient reconnection events using an array of scintillator detectors near the wall of Tokamak Fusion Test Reactor (TFTR). The magnitude of the coherent MHD-induced alpha loss as seen by these detectors was normally comparable to the MHD-quiescent first-orbit or toroidal-field ripple loss, but the magnitude of the alpha loss during reconnection events was up to 1000 times higher than this for a short time. Modeling suggest that the coherent MHD loss mechanism will be even less significant for future reactor-scale deuterium-tritium tokamaks due to the smaller ratio of the alpha gyroradius to minor radius.

Darrow, D.S.; Fredrickson, E.D.; Taylor, G.; White, R.B.; Zweben, S.J.; von Goeler, S.

1999-03-01

109

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

National Technical Information Service (NTIS)

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 ...

C. S. Chang K. Imre H. Weitzner P. Colestock

1990-01-01

110

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

NASA Astrophysics Data System (ADS)

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 90 degrees 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.

Richards, R. K.; Vandersluis, K. L.; Hutchinson, D. P.

1987-08-01

111

Variation of the track etch rates of alpha-particle trajectory in PADC  

Microsoft Academic Search

The formation of etched tracks in solid-state nuclear track detectors is usually described by assuming an unequivocal correlation of the etch-rate ratio with the energy loss of charged particles. For alpha particles, this assumption could be verified within the scatter of the experimental data. In this article, the dependence of the depth (x) on the track etch rate (V-T) was

M. F. Zaki; T. M. Hegazy; U. Seddik; A. A. Morsy

2005-01-01

112

Biological Effect of Lead-212 Localized in the Nucleus of Mammalian Cells: Role of Recoil Energy in the Radiotoxicity of Internal Alpha-Particle Emitters1  

PubMed Central

The radiochemical dipyrrolidinedithiocarbamato-212Pb(II) [212Pb(PDC)2] is synthesized and its effects on colony formation in cultured Chinese hamster V79 cells are investigated. The cellular uptake, biological retention, subcellular distribution and cytotoxicity of the radiocompound are determined. The 212Pb is taken up quickly by the cells, reaching saturation levels in 1.25 h. When the cells are washed, the intracellular activity is retained with a biological half-life of 11.6 h. Gamma-ray spectroscopy indicates that the 212Pb daughters (212Bi, 212Po and 208Tl) are in secular equilibrium within the cell. About 72% of the cellular activity localizes in the cell nucleus, of which 35% is bound specifically to nuclear DNA. The mean cellular uptake required to achieve 37% survival is 0.35 mBq of 212Pb per cell, which delivers a dose of 1.0 Gy to the cell nucleus when the recoil energy of 212Bi and 212Po decays is ignored and 1.7 Gy when recoil is included. The corresponding RBE values compared to acute external 137Cs ? rays at 37% survival are 4.0 and 2.3, respectively. The chemical Pb(PDC)2 is not chemotoxic at the concentrations used in this study. Because the ?-particle emitter 212Pb decays to the ?-particle-emitting daughters 212Bi and 212Po, these studies provide information on the biological effects of ?-particle decays that occur in the cell nucleus. Our earlier studies with cells of the same cell line using 210Po (emits 5.3 MeV ? particle) localized predominantly in the cytoplasm resulted in an RBE of 6. These earlier results for 210Po, along with the present results for 212Pb, suggest that the recoil energy associated with the 212Bi and 212Po daughter nuclei plays little or no role in imparting biological damage to critical targets in the cell nucleus.

Azure, Michael T.; Archer, Ronald D.; Sastry, Kandula S. R.; Rao, Dandamudi V.; Howell, Roger W.

2012-01-01

113

Probing. alpha. -particle wave functions by ( d ,. alpha. ) tensor analyzing powers  

SciTech Connect

Components of {alpha}-particle wave functions corresponding to {ital d}-{ital d} configurations are used to predict analyzing powers in the ({ital d},{alpha}) reaction. Tensor analyzing powers, especially {ital A}{sub {ital x}{ital x}}, are shown to clearly distinguish between wave functions generated by different realistic nucleon-nucleon interactions. Data for the {sup 58}Ni({ital d},{alpha}){sup 56}Co reaction to the 7{sup +} stretched-nucleon-orbital state at 2.283-MeV excitation in {sup 56}Co, measured with 22-MeV deuterons, are compared to predictions from the Argonne and Urbana interactions. Similar comparisons are made to data for the lowest {ital J} {sup {pi}}=7{sup +} state in {sup 48}Sc populated by the {sup 50}Ti({ital d},{alpha}){sup 48}Sc reaction at 16 MeV.

Crosson, E.R.; Das, R.K.; Lemieux, S.K.; Ludwig, E.J.; Thompson, W.J. (University of North Carolina, Chapel Hill, North Carolina 27599-3255 (United States) Triangle Universities Nuclear Laboratory, Durham, North Carolina 27706 (United States)); Bisenberger, M.; Hertenberger, R.; Hofer, D.; Kader, H.; Schiemenz, P.; Graw, G. (Sektion Physik, Universitaet Muenchen, 8046 Garching (Germany)); Eiro, A.M.; Santos, F.D. (Centro de Fisica Nuclear da Universidade de Lisboa, 1699 Lisboa Codex (Portugal))

1992-02-01

114

Cryogenic Microcalorimeter System for Ultra-High Resolution Alpha-Particle Spectrometry  

NASA Astrophysics Data System (ADS)

Microcalorimeters have been shown to yield unsurpassed energy resolution for alpha spectrometry, up to 1.06 keV FWHM at 5.3 MeV. These detectors use a superconducting transition-edge sensor (TES) to measure the temperature change in an absorber from energy deposited by an interacting alpha particle. Our system has four independent detectors mounted inside a liquid nitrogen/liquid helium cryostat. An adiabatic demagnetization refrigerator (ADR) cools the detector stage to its operating temperature of 80 mK. Temperature regulation with ~15-?K peak-to-peak variation is achieved by PID control of the ADR. The detectors are voltage-biased, and the current signal is amplified by a commercial SQUID readout system and digitized for further analysis. This paper will discuss design and operation of our microcalorimeter alpha-particle spectrometer, and will show recent results.

Croce, M. P.; Bacrania, M. K.; Hoover, A. S.; Rabin, M. W.; Hoteling, N. J.; Lamont, S. P.; Plionis, A. A.; Dry, D. E.; Ullom, J. N.; Bennett, D. A.; Horansky, R. D.; Kotsubo, V.; Cantor, R.

2009-12-01

115

Multi-MeV Li/sup 0/ beam as a diagnostic for fast confined alpha particles  

SciTech Connect

We discuss a method of measuring the velocity distribution of confined energetic alpha particles resulting from deuterium-tritium fusion reactions in a magnetically contained plasma. We calculate the characteristics of the signals to be expected from injecting multi-MeV Li/sup 0/ into the plasma to undergo double charge-exchange reactions with the alpha particles. Neutralized alpha particles then escape from the plasma to be detected by a charge-exchange analyzer. We also examine the feasibility of producing a Li/sup 0/ beam of the required current and energy, and we discuss a conceptual design for an appropriate beam system.

Grisham, L.R.; Post, D.E.; Mikkelsen, D.R.

1982-04-01

116

Superconducting Transition-Edge Sensor Microcalorimeters for UltraHigh Resolution Alpha-Particle Spectrometry  

Microsoft Academic Search

Alpha-particle spectrometry is a powerful analytical tool for nuclear forensics and environmental monitoring. Super- conducting transition-edge sensor microcalorimeters have been shown to yield unsurpassed energy resolution for alpha spectrom- etry. With nearly an order of magnitude better energy resolution (1.06 keV FWHM at 5.3 MeV) than the current state-of-the-art silicon detectors (8-10 keV at 5.3 MeV), it is possible to

M. P. Croce; M. K. Bacrania; E. M. Bond; D. E. Dry; A. L. Klingensmith; W. A. Moody; S. P. LaMont; M. W. Rabin; J. H. Rim; J. A. Beall; D. A. Bennett; V. Kotsubo; R. D. Horansky; G. C. Hilton; D. Schmidt; J. N. Ullom; R. Cantor

2011-01-01

117

Recent outgassing from the lunar surface: The Lunar Prospector Alpha Particle Spectrometer  

NASA Astrophysics Data System (ADS)

The Lunar Prospector Alpha Particle Spectrometer (APS) was designed to detect characteristic-energy alpha particles from the decay of Rn-222, Po-218, and Po-210 and to therefore map sites of radon release on the lunar surface. These three nuclides are radioactive daughters from the decay of U-238 hence the background level of alpha particle activity is a function of the lunar crustal uranium distribution. Radon reaches the lunar surface either at areas of high soil porosity or where fissures release the trapped gases in which radon is entrained. Once released, the radon spreads out by ``bouncing'' across the surface on ballistic trajectories in a random-walk process. The half-life of Rn-222 allows the gas to spread out by several hundred kilometers before it decays (depositing approximately half of the Po-218 recoil nuclides on the lunar surface) and allows the APS to detect gas release events up to several days after they occur. The long residence time of the Pb-210 precursor to Po-210 allows the mapping of gas vents which have been active over the last approximately 60 years. The APS found only a faint indication of Po-218 alpha particles. However, the Rn-222 alpha particle map shows that radon gas was emanating from the vicinity of craters Aristarchus and Kepler at the time of Lunar Prospector. The Po-210 alpha particle distribution reveals a variability in time and space of lunar gas release events. Po-210 and Rn-222 detections are associated with both thorium enhancements and lunar pyroclastic deposits.

Lawson, Stefanie L.; Feldman, William C.; Lawrence, David J.; Moore, Kurt R.; Elphic, Richard C.; Belian, Richard D.; Maurice, Sylvestre

2005-09-01

118

Quality factors for alpha particles emitted in tissue  

NASA Technical Reports Server (NTRS)

A concept of a mean or dose averaged quality factor was defined in ICRP Publication 26 using relationships for quality factor as a function of LET. The concept of radiation weighting factors, wR, was introduced in ICRP Publication 60 in 1990. These are meant to be generalized factors that modify absorbed dose to reflect the risk of stochastic effects as a function of the quality of the radiation incident on the body or emitted by radioactivity within the body. The values of wr are equal to 20 for all alpha particles externally or internally emitted. This note compares the dose averaged quality factor for alpha particles originating in tissue using the old and revised recommendations for quality factor as a function of LET. The dose averaged quality factor never exceeds 20 using the old recommendations and is never less than 20 with the revised recommendations.

Borak, Thomas B.; Chatterjee, A. (Principal Investigator)

2002-01-01

119

Possibilities of alpha-particle diagnostics in future tokamaks using helium and lithium beam injection  

SciTech Connect

This paper considers the possibility of using active charge-exchange (CX) diagnostics based on helium and lithium beam injection to investigate the confined alpha-particle distribution function in future fusion experiments. The required helium beam densities are determined by mathematic modeling of the physical processes (double CX, attenuation of the doping beam, and CX flow, taking into account the step process). They are found to be {approximately}1 A for a 40-keV beam for thermalized (ash) alpha-particle diagnostics and 30 to 600 MA for a 0.35 to 0.65 MeV/amu HeH{sup +} ion source for hot alpha-particle diagnostics. A {sup 3}He beam with energy of 500 keV (He{sup +} ion source) and intensity of 0.1 to 3 A is proposed for measurement of the alpha-particle distribution function in the energy range of 0.2 to 2 MeV.

Gorelenkov, N.N.; Krasilnikov, A.V. (I.V. Kurchatov Inst. of Atomic Energy, Moscow (SU))

1991-03-01

120

Beams of protons and alpha particles greater than approximately 30 keV/charge from the earth's bow shock  

NASA Technical Reports Server (NTRS)

Two beamlike particle events (30 keV/charge to 160 keV/charge) upstream of the earth's bow shock have been investigated with the Max-Planck-Institut/University of Maryland ultralow energy and charge analyzer on ISEE 1. These beams consist of protons as well as of alpha particles, and the spectra are generally steep and are decreasing with increasing energy. During one event the spectra of both protons and alpha particles have a maximum at approximately 65 keV/charge. During these events, the interplanetary magnetic field through the satellite position was almost tangent to the bow shock, and application of the theory of acceleration predicts acceleration of a solar wind particle up to 60 keV/nucleon in a single reflection. The observation of reflected protons as well as alpha particles has implications for the physical reflection process usually not discussed in acceleration theories.

Scholer, M.; Ipavich, F. M.; Gloeckler, G.

1981-01-01

121

Alpha-particle Measurements Needed for Burning Plasma Experiments  

SciTech Connect

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.

Kenneth M. Young

2001-09-26

122

Ultrahigh-energy particles from cosmic strings  

SciTech Connect

The idea of production of ultrahigh-energy particles in the present universe due to annihilation or collapse of topological defects is discussed. Topological defects, formed in symmetry-breaking phase transitions in the early universe, can survive till today owing to their topological stability. However, under certain circumstances, topological defects may be physically destroyed. When topological defects are destroyed, the energy contained in the defects can be released in the form of massive gauge- and Higgs bosons of the underlying spontaneously broken gauge theory. Subsequent decay of these massive particles can give rise to energetic particles ranging up to an energy on the order of the mass of the original particles released from the defects. This may give us a natural'' mechanism of production of extremely energetic cosmic ray particles in the universe today, without the need for any acceleration mechanism. To illustrate this idea, I describe in detail the calculation of the expected ultrahigh-energy proton spectrum due to a specific process which involves collapse or multiple self-intersections of a class of closed cosmic string loops formed in a phase transition at a grand unification energy scale. I discuss the possibility that some of the highest-energy cosmic ray particles are of this origin. By comparing with the observational results on the ultrahigh-energy cosmic rays, we derive an upper limit to the average fraction of the total energy in all primary'' cosmic string loops that may be released in the form of particles due to collapse or multiple self-intersections of these loops. No nuclei such as {alpha}'s or Fe's are in the spectrum. 43 refs., 3 figs.

Bhattacharjee, P. (Chicago Univ., IL (USA). Astronomy and Astrophysics Center Fermi National Accelerator Lab., Batavia, IL (USA))

1991-02-01

123

Pre-Equilibrium Alpha-Particle Emission as a Probe to Explore Alpha Clustering in Nuclei  

NASA Astrophysics Data System (ADS)

Experimental data of the double-differential spectra of light particles emitted at pre-equilibrium stage of nuclear processes were obtained at Laboratori Nazionali di Legnaro for the heavy-ion reactions 130 and 250 MeV 16O + 116Sn. Light charged particles were measured in coincidence with evaporation residues in order to avoid unwanted competing mechanisms. The experimental data were collected in a wide angular range from 29 to 82 degrees in the laboratory system. Theoretical model was developed in order to describe simultaneously evaporative and pre-equilibrium emission of the light particles in heavy-ion reactions. Griffin exciton model was used for the description of the pre-equilibrium stage of the compound nucleus formation, while the equilibrium evaporation processes were analyzed in the framework of the statistical theory of heavy-ion reactions. Experimental data were compared with the results of the model calculations and new approach was suggested to take into account alpha cluster formation in the projectile nucleus by measuring and analyzing pre-equilibrium alpha-particle spectra.

Kravchuk, V. L.; Fotina, O. V.; Gramegna, F.; Bruno, M.; D'Agostino, M.; Sambi, S.; Barlini, S.; Casini, G.

124

Model for alpha particle induced nuclear reactions: /sup 93/Nb(. cap alpha. ,x. cap alpha. ypzn) from 40--140 MeV  

SciTech Connect

A comprehensive model is introduced for alpha particle induced nuclear reactions. Five different mechanisms are examined and discussed. These include inelastic scattering of the incident alpha particle, nucleon pickup, binary fragmentation, dissolution of the alpha in the nuclear field, and preequilibrium processes initiated by alpha-nucleon collisions. A series of experiments was performed to measure the excitation functions of many nuclides produced from the irradiation of /sup 93/Nb by 40--140 MeV alpha particles. Together with alpha particle and proton spectra measured by other authors, these data form the basis of a test of the model introduced. A detailed analysis of the comparison between the calculated and experimental results, with particular emphasis on the interpretation of breakup processes, leads to the conclusion that breakup to four nucleons is preferred to the more commonly assumed binary fragmentation in that a much broader range of experimental data may be reproduced.

Gadioli, E.; Gadioli-Erba, E.; Hogan, J.J.; Jacak, B.V.

1984-01-01

125

Angular Momentum Transport and Proton-Alpha-Particle Differential Streaming in the Solar Wind  

NASA Astrophysics Data System (ADS)

The interplay between the proton-alpha-particle differential flow speed, v?p, and angular momentum transport in the solar wind is explored by using a three-fluid model. The force introduced by the azimuthal components is found to play an important role in the force balance for ions in interplanetary space, bringing the radial flow speeds of protons and alpha particles closer to each other. For the fast solar wind, the model cannot account for the decrease of v?p observed by Helios between 0.3 and 1 AU. However, it can reproduce the v?p profile measured by Ulysses beyond 2 AU, if the right value for v?p is imposed at that distance. In the slow wind, the effect of solar rotation is more pronounced if one starts with the value measured by Helios at 0.3 AU: a relative change of 10%-16% is introduced in the radial speed of the alpha particles between 1 and 4 AU. The model calculations show that, although alpha particles consume only a small fraction of the energy and linear momentum fluxes of protons, they cannot be neglected when considering the proton angular momentum flux Lp. In most examples, it is found that Lp is determined by v?p for both the fast and the slow wind. In the slow solar wind, the proton and alpha particle angular momentum fluxes Lp and L? can be several times larger in magnitude than the flux carried by the magnetic stresses LM. While the sum LP=Lp+L? is smaller than LM, for the modeled fast and slow wind alike, this result is at variance with the Helios measurements.

Li, Bo; Habbal, Shadia Rifai; Li, Xing

2007-05-01

126

Thick Source Alpha Particle Spectroscopy: Possibilities And Prospects  

NASA Astrophysics Data System (ADS)

The new technique for the calculation of U and Th concentration which is based on the alpha particle spectrum taken from a thick sample by using a silicon detector is briefly described. Within the present study two major advantages of the technique will also be presented: the potentiality for detecting and providing an estimation of disequilibrium in the U and Th series -when present- for especially young sediments, and the potential use of the technique as a new method for isotopic dating of speleothems and other materials. Also the validity of the basic equation and the accuracy of this technique is tested.

Michael, C. T.; Zacharias, N.; Hein, A.

127

Protons and alpha particles in the solar wind  

NASA Astrophysics Data System (ADS)

We investigate energetic consequences of ion kinetic instabilitities in the solar wind connected with beam and core protons and alpha particles drifting with respect to each other. We compare theoretical predictions, simulations and observation results. For theoretical prediction we assume drifting bi-Maxwellian ion populations and we calculate theoretical quasilinear heating rates (Hellinger et al., 2013b). The nonlinear evolution of beam-core protons, and alpha particles in the expanding solar wind we investigate using hybrid expanding box system (Hellinger and Travnicek, 2013). The expansion leads to many different kinetic instabilities. In the simulation the beam protons and alpha particles are decelerated with respect to the core protons and all the populations are cooled in the parallel direction and heated in the perpendicular one in agreement with theoretical expectations. On the macroscopic level the kinetic instabilities cause large departures of the system evolution from the double adiabatic prediction and lead to a perpendicular heating and parallel cooling rates. The simulated heating rates are comparable to the heating rates estimated from the Helios observations (Hellinger et al., 2013a); furthermore, the differential velocity between core and beam protons observed by Ulysses exhibits apparent bounds which are compatible with the theoretical constaints imposed by the linear theory for the magnetosonic instability driven by beam-core differential velocity (Matteini et al., 2013). References Hellinger, P., P. M. Travnicek, S. Stverak, L. Matteini, and M. Velli (2013a), Proton thermal energetics in the solar wind: Helios reloaded, J. Geophys. Res., 118, 1351-1365, doi:10.1002/jgra.50107. Hellinger, P., T. Passot, P.-L. Sulem, and P. M. Travnicek (2013b), Quasi-linear heating and acceleration in bi-Maxwellian plasmas, Phys. Plasmas, 20, 122306. Hellinger, P., and P. M. Travnicek (2013), Protons and alpha particles in the expanding solar wind: Hybrid simulations, J. Geophys. Res., 118, 5421-5430, doi:10.1002/jgra.50540. Matteini, L., P. Hellinger, B. E. Goldstein, S. Landi, M. Velli, and M. Neugebauer (2013), Signatures of kinetic instabilities in the solar wind, J. Geophys. Res., 118, 2771-2782, doi:10.1002/jgra.50320.

Hellinger, Petr; Travnicek, Pavel M.; Passot, Thierry; Sulem, Pierre-Louis; Matteini, Lorenzo; Landi, Simone

2014-05-01

128

Scattering of 42-MeV alpha particles from Cu-65  

NASA Technical Reports Server (NTRS)

The extended particle-core coupling model was used to predict the properties of low-lying levels of Cu-65. A 42-MeV alpha particle cyclotron beam was used for the experiment. The experiment included magnetic analysis of the incident beam and particle detection by lithium-drifted silicon semiconductors. Angular distributions were measured for 10 to 50 degrees in the center of mass system. Data was reduced by fitting the peaks with a skewed Gaussian function using a least squares computer program with a linear background search. The energy calibration of each system was done by pulsar, and the excitation energies are accurate to + or - 25 keV. The simple weak coupling model cannot account for the experimentally observed quantities of the low-lying levels of Cu-65. The extended particle-core calculation showed that the coupling is not weak and that considerable configuration mixing of the low-lying states results.

Stewart, W. M.; Seth, K. K.

1972-01-01

129

Ionisation cross sections of Cd, Sn, Te, I and Ba for protons and alpha particles  

Microsoft Academic Search

K-shell X-ray production cross sections of 48Cd, 50Sn, 52Te, 53I and 56Ba have been measured for alpha particles with energies between 2.2 and 2.8 MeV. In addition, production cross sections for 52Te have been measured for protons between 1.6 and 3 MeV. The values have been compared with the earlier experiments and with the theoretical predictions given by four different

L. Avaldi; M. Milazzo; G. Trivia; I. V. Mitchell

1983-01-01

130

Alpha-particle emission from carbon bombarded with neutrons below 30 MeV  

SciTech Connect

Alpha-particle emission induced by neutron bombardment of carbon has been studied from threshold to over 30 MeV using the spallation neutron source at WNR/LAMPF. Targets include thin foils of CH{sub 2} and thicker foils of CH and polycrystalline graphite. Comparisons are made with evaluated data. Values for KERMA (kinetic energy released in materials) based on the results will be presented and compared with those obtained through other experimental approaches.

Haight, R.C.; Lee, T.M.; Sterbenz, S.M. [and others

1994-07-01

131

Charge-Collection Length Induced by Proton and Alpha Particle Injected Into Silicon Detectors Due to Funneling Effect  

Microsoft Academic Search

Measured deposited energies by 3 to 70 MeV protons and 9.5 to 24.5 MeV\\/nucleon alpha particles in partially depleted silicon detectors were 2 to 5 times larger than calculated deposited energies in an original depletion layer. All released charge carriers within a charge-collection length were collected. The charge-collection lengths are found to be independent of particle species, energies and stopping

Masashi Takada; Tomoya Nunomiya; Takeshi Ishikura; T. Nakamura

2009-01-01

132

A spin filter polarimeter and an {alpha}-particle D-state study  

SciTech Connect

A Spin Filter Polarimeter (SFP) which reveals populations of individual hyperfine states of nuclear spin-polarized H{sup {+-}} (or D{sup {+-}}) beams has been tested. the SFP is based on unique properties of a three-level interaction in the 2S{sub 1/2} and 2P{sub 1/2} states of the hydrogen (or deuterium) atoms, created when the polarized ion beams pick up electrons in cesium vapor. The SFP has potential for an absolute accuracy of better than 1.5%, thus it could be used for calibrating polarimeters absolutely for low energy experiments for which no nuclear polarization standard exists. Test results show that the SFP provides a quick and elegant measure of the relative hyperfine state populations in the beam. This {alpha}-particle study is a small part of a larger project studying the deuteron-deuteron configuration of the {alpha}-particle wave function. The differential cross section and tensor analyzing powers (TAP) were measured for the {sup 50}Ti({bar d},{alpha}){sup 48}Sc reaction to the J{sup {pi}} = 7{sup +} state in {sup 48}Sc at E{sub x} = 1.097 MeV and compared with exact finite-range distorted-wave Born approximation (DWBA) calculations. The DWBA calculations use realistic {alpha}-particle wave functions generated from variational Monte-Carlo calculations.

Lemieux, S.K.

1993-12-31

133

Preliminary results from the lunar prospector alpha particle spectrometer  

SciTech Connect

The Lunar Prospector Alpha Particle Spectrometer (LP APS) builds on Apollo heritage and maps the distribution of outgassing sites on the Moon. The APS searches for lunar surface gas release events and maps their distribution by detecting alpha particles produced by the decay of gaseous radon-222 (5.5 MeV, 3.8 day half-life) and solid polonium-210 (5.3 MeV, 138 day half-life, but remains on the surface with a 21 year half-life as lead-210), which are radioactive daughters from the decay of uranium-238. Radon is in such small quantities that it is not released directly from the lunar interior, rather it is entrained in a stream of gases and serves as a tracer for such gases. Once released, the radon spreads out by 'bouncing' across the surface on ballistic trajectories in a random-walk process. The 3.8 day half-life of radon-222 allows the gas to spread out by several 100 km before it decays and allows the APS to detect gas release events up to a few days after they occur. The long residence time (10s of years) of the lead-210 precursor to the polonium-210 allows the mapping of gas vents which have been active over the last approximately 50 years. Because radon and polonium are daughter products of the decay of uranium, the background level of alpha particle activity is a function of the lunar crustal uranium distribution. Using radioactive radon and polonium as tracers, the Apollo 15 and 16 Command Module orbital alpha particle experiments obtained evidence for the release of gases at several sites beneath the orbit tracks, especially over the Aristarchus Plateau and Mare Fecunditatis [1]. Aristarchus crater had previously been identified by ground-based observers as the site of transient optical events [2]. The Apollo 17 surface mass spectrometer showed that argon-40 is released from the lunar interior every few months, apparently in concert with some of the shallow moonquakes that are believed to be of tectonic origin [3]. The latter tectonic events could be associated with very young scarps identified in the lunar highlands [4] and are believed to indicate continued global contraction. Such quakes could open fissures leading to the release of gases that are trapped below the surface. The detection of radon-222 outgassing events at the margins of Fecunditatis basin was surprising because the observed surface distribution of uranium and thorium do not extend sufficiently eastward to cover Fecunditatis. If the Apollo detections prove sound, then those alpha particle emissions indicate substantial subsurface concentrations of uranium-238 within Fecunditatis. A primary goal of the APS was to map gas-release events, thus allowing both an appraisal of the current level of tectonic activity on the Moon and providing a probe of subsurface uranium concentrations.

Lawson, S. L. (Stefanie L.)

2001-01-01

134

Transport theory for energetic alpha particles and tolerable magnitude of error fields in tokamaks with broken symmetry  

NASA Astrophysics Data System (ADS)

A transport theory for energetic fusion born alpha particles in tokamaks with broken symmetry has been developed. The theory is a generalization of the theory for neoclassical toroidal plasma viscosity for thermal particles in tokamaks. It is shown that the radial energy transport rate can be comparable to the slowing down rate for energetic alpha particles when the ratio of the typical magnitude of the perturbed magnetic field strength to that of the equilibrium magnetic field strength is of the order of 10-4 or larger. This imposes a constraint on the magnitude of the error fields in thermonuclear fusion reactors. The implications on stellarators as potential fusion reactors are also discussed.

Shaing, K. C.; Hsu, C. T.

2014-03-01

135

Mutagenic effects of a single and an exact number of alpha particles in mammalian cells  

NASA Technical Reports Server (NTRS)

One of the main uncertainties in risk estimation for environmental radon exposure using lung cancer data from underground miners is the extrapolation from high- to low-dose exposure where multiple traversal is extremely rare. The biological effects of a single alpha particle are currently unknown. Using the recently available microbeam source at the Radiological Research Accelerator Facility at Columbia University, we examined the frequencies and molecular spectrum of S1- mutants induced in human-hamster hybrid (A(L)) cells by either a single or an exact number of alpha particles. Exponentially growing cells were stained briefly with a nontoxic concentration of Hoechst dye for image analysis, and the location of individual cells was computer-monitored. The nucleus of each cell was irradiated with either 1,2,4, or 8 alpha particles at a linear energy transfer of 90 keV/microm consistent with the energy spectrum of domestic radon exposure. Although single-particle traversal was only slightly cytotoxic to A(L) cells (survival fraction approximately 0.82), it was highly mutagenic, and the induced mutant fraction averaged 110 mutants per 10(5) survivors. In addition, both toxicity and mutant induction were dose-dependent. Multiplex PCR analysis of mutant DNA showed that the proportion of mutants with multilocus deletions increased with the number of particle traversals. These data provide direct evidence that a single a particle traversing a nucleus will have a high probability of resulting in a mutation and highlight the need for radiation protection at low doses.

Hei, T. K.; Wu, L. J.; Liu, S. X.; Vannais, D.; Waldren, C. A.; Randers-Pehrson, G.

1997-01-01

136

INSTABILITIES DRIVEN BY THE DRIFT AND TEMPERATURE ANISOTROPY OF ALPHA PARTICLES IN THE SOLAR WIND  

SciTech Connect

We investigate the conditions under which parallel-propagating Alfven/ion-cyclotron (A/IC) waves and fast-magnetosonic/whistler (FM/W) waves are driven unstable by the differential flow and temperature anisotropy of alpha particles in the solar wind. We focus on the limit in which w{sub Parallel-To {alpha}} {approx}> 0.25v{sub A}, where w{sub Parallel-To {alpha}} is the parallel alpha-particle thermal speed and v{sub A} is the Alfven speed. We derive analytic expressions for the instability thresholds of these waves, which show, e.g., how the minimum unstable alpha-particle beam speed depends upon w{sub Parallel-To {alpha}}/v{sub A}, the degree of alpha-particle temperature anisotropy, and the alpha-to-proton temperature ratio. We validate our analytical results using numerical solutions to the full hot-plasma dispersion relation. Consistent with previous work, we find that temperature anisotropy allows A/IC waves and FM/W waves to become unstable at significantly lower values of the alpha-particle beam speed U{sub {alpha}} than in the isotropic-temperature case. Likewise, differential flow lowers the minimum temperature anisotropy needed to excite A/IC or FM/W waves relative to the case in which U{sub {alpha}} = 0. We discuss the relevance of our results to alpha particles in the solar wind near 1 AU.

Verscharen, Daniel; Bourouaine, Sofiane [Space Science Center, University of New Hampshire, Durham, NH 03824 (United States); Chandran, Benjamin D. G., E-mail: daniel.verscharen@unh.edu, E-mail: s.bourouaine@unh.edu, E-mail: benjamin.chandran@unh.edu [Also at Department of Physics, University of New Hampshire, Durham, NH 03824 (United States)

2013-08-20

137

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

NASA Astrophysics Data System (ADS)

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 induction of bone cancer. In addition, new data are presented on the location of bone-marrow stem cells within the marrow cavities of trabecular bone of the pelvis. All results presented in this work may be applied to occupational exposures, but their greatest utility lies in dose assessments for alpha-emitters in molecular radiotherapy.

Watchman, Christopher J.

138

Determination of 239Pu/240Pu isotopic ratio by high-resolution alpha-particle spectrometry using the ADAM program.  

PubMed

A novel analysis program to unfold alpha-particle energy spectra was introduced, demonstrated and validated using radiochemically processed test sources, which contained different amounts of (239)Pu and (240)Pu. A high-resolution alpha spectrometer was used for data acquisition. The software known as ADAM unfolds the spectra using nuclide-specific decay data as a constraint. The peaks can have different shapes and the software can also cope with the coincidences between alpha particles and electrons/photons. In the present paper, the (239)Pu/(240)Pu activity ratios from alpha spectrometry agreed, within the stated uncertainties, with the reference values. Number of counts in the (239,240)Pu peak group must be larger than 100 to obtain reliable values when using semiconductor detector of energy resolution FWHM=10.6 keV. PMID:22227537

Pöllänen, R; Siiskonen, T; Ihantola, S; Toivonen, H; Pelikan, A; Inn, K; La Rosa, J; Bene, B J

2012-04-01

139

Study of the beta-delayed alpha-particle emission of 16N  

NASA Astrophysics Data System (ADS)

The beta-delayed alpha-particle emission of 16N has been studied, with 16N nuclei produced using 80 MeV/nucleon 18O beams on 9Be targets. The 16N secondary nuclei were mass analyzed and separated from the reaction products using the Michigan State University A1200 isotope separator. A detector array, including four thin surface barrier detectors, a p-i-n diode, a Ge gamma-ray detector, and a two-dimensional position sensitive parallel plate avalanche counter, was used for implantation and study of the separated nuclei. A beta-decay branching ratio of (1.3+/-0.3)×10-5 to the 1- state at 9.6 MeV and a centroid of 2.35+/-0.05 MeV for the beta-delayed alpha-particle emission were measured. These results are essential for the analysis of a high sensitivity measurement at Yale University of the low-energy beta-delayed alpha-particle emission of 16N, and for understanding the 12C(?,?)16O reaction in the helium burning process in massive stars.

Zhao, Z.; France, R. H., III; Lai, K. S.; Gai, M.; Wilds, E. L.; Kryger, R. A.; Winger, J. A.; Beard, K. B.

1993-07-01

140

A single particle energies  

SciTech Connect

We consider the binding energies of {Lambda} hypernuclei (HN), in particular the single-particle (s.p.) energy data, which have been obtained for a wide range of HN with mass numbers A {le} 89 and for orbital angular momenta {ell}{sub {Lambda}} {le} 4. We briefly review some of the relevant properties of A hypernuclei. These are nuclei {sub {Lambda}}{sup A}Z with baryon number A in which a single {Lambda} hyperon (baryon number = 1) is bound to an ordinary nucleus {sup A}Z consisting of A - 1 nucleons = Z protons + N neutrons. The {Lambda} hyperon is neutral, has spin 1/2, strangeness S = {minus}1, isospin I = O and a mass M{sub {Lambda}} = 1116 MeV/c{sup 2}. Although the {Lambda} interacts with a nucleon, its interaction is only about half as strong as that between two nucleons, and thus very roughly V{sub {Lambda}N} {approx} 0.5 V{sub NN}. As a result, the two-body {Lambda}N system is unbound, and the lightest bound HN is the three-body hypertriton {sub {Lambda}}{sup 3}H in which the {Lambda} is bound to a deuteron with the {Lambda}-d separation energy being only {approx} 0.1 MeV corresponding to an exponential tail of radius {approx} 15 fm! In strong interactions the strangeness S is of course conserved, and the {Lambda} is distinct from the nucleons. In a HN strangeness changes only in the weak decays of the {Lambda} which can decay either via ``free`` pionic decay {Lambda} {yields} N + {pi} or via induced decay {Lambda} + N {yields} N + N which is only possible in the presence of nucleons. Because of the small energy release the pionic decay is strongly suppressed in all but the lightest HN and the induced decay dominates. However, the weak decay lifetime {approx} 10{sup {minus}10}s is in fact close to the lifetime of a free {Lambda}. Since this is much longer than the strong interaction time {approx} 10{sup {minus}22}s we can ignore the weak interactions when considering the binding of HN, just as for ordinary nuclei.

Bodmer, A.R. [Illinois Univ., Chicago, IL (United States). Dept. of Physics]|[Argonne National Lab., IL (United States); Usmani, Q.N.; Sami, M. [Jamia Millia Islamia, New Delhi (India). Dept. of Physics

1993-09-01

141

Half-life estimation of the first excited state of {sup 229}Th by using {alpha}-particle spectrometry  

SciTech Connect

To search for a direct-decay signal from the isomer {sup 229}Th{sup m}, {alpha}-particle spectra of {sup 229}Th{sup m,g} produced from 93 mg of {sup 233}U have been measured by using a rapid and high-resolution {alpha}-particle spectrometry, which can distinguish {alpha} lines of {sup 229}Th{sup m} from those of its ground state. Although {alpha} events were not obtained in the expected energy region for {sup 229}Th{sup m} with the exception of those derived from {sup 229}Th{sup g}, we can estimate that the half-life of {sup 229}Th{sup m} is shorter than 2 h at 3{sigma} confidence level under the chemical condition of chloride or hydroxide.

Kikunaga, H. [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Nishina Center for Accelerator-Base Science, RIKEN, Wako, Saitama 351-0198 (Japan); Kasamatsu, Y. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Haba, H. [Nishina Center for Accelerator-Base Science, RIKEN, Wako, Saitama 351-0198 (Japan); Mitsugashira, T. [Institute for Material Research, Tohoku University, Sendai, Miyagi 980-8577 (Japan); Hara, M. [International Research Center for Nuclear Materials Science, Tohoku University, Oarai-machi, Ibaraki 311-1313 (Japan); Takamiya, K. [Research Reactor Institute, Kyoto University, Kumatori, Osaka 590-0494 (Japan); Ohtsuki, T. [Laboratory of Nuclear Science, Tohoku University, Sendai, Miyagi 982-0826 (Japan); Yokoyama, A.; Nakanishi, T. [Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa, Ishikawa 920-1192 (Japan); Shinohara, A. [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan)

2009-09-15

142

Search for {alpha}-states in {sup 13}C via elastic resonant scattering of {alpha} particles on {sup 9}Be  

SciTech Connect

We will discuss new experimental data concerning the elastic resonant scattering of {alpha}-particles on {sup 9}Be nuclei at bombarding energies from 3.5 MeV up to 9.9 MeV. Several excitation functions have been obtained at different polar angles, mainly in the backward hemisphere in the centre of mass frame. Excitation functions show various anomalies that can be linked to the presence of various excited states in the {sup 13}C compound nucleus. In the literature, some of these states have been proposed to belong to rotational bands built on deformed a-cluster excited state. Unfortunately, up to date the spin-parity assignment of many of these states is doubtful. The set of excitation functions we obtained from the present experiment can contribute to improve spectroscopy of highling excited states of {sup 13}C.

Lombardo, I.; Campajola, L.; Rosato, E.; Spadaccini, G.; Vigilante, M. [Dipartimento di Scienze Fisiche dell'Universita di Napoli Federico II INFN - Sezione di Napoli, Napoli (Italy)

2013-07-18

143

One-Step Acceleration of Deuterons and alpha -Particles at the JINR Synchrophasotron.  

National Technical Information Service (NTIS)

The problems are considered which are related to one-step acceleration mode of deuterons and alpha -particles at the JINR synchrophasotron. The one-step mode of acceleration of deuteron and alpha -particles has been realized by widening the driving oscill...

A. I. Mikhailov G. P. Puchkov K. V. Chekhlov

1976-01-01

144

Ion Densities and Particle Charges for Alpha Ionization in an Aerosol Atmosphere: Columnar Recombination Corrections  

Microsoft Academic Search

Ionization by alpha sources in an environment containing small aerosol particles is of interest in aerosol neutralizes, particle chargers and atmospheric electricity. It is known that the conventional ion-balance equation is inadequate in describing the bulk ion densities for alpha sources in view of the columnar recombination process. An earlier self-consistent formulation to include this effect is extended to the

Y. S. Mayya; W. Holländer

1995-01-01

145

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

NASA Astrophysics Data System (ADS)

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 ?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 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.

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

2007-08-01

146

The Rosetta Alpha Particle X-Ray Spectrometer (APXS)  

NASA Astrophysics Data System (ADS)

The Alpha Particle X-Ray Spectrometer (APXS) is a small instrument to determine the elemental composition of a given sample. For the ESA Rosetta mission, the periodical comet 67P/Churyumov-Gerasimenko was selected as the target comet, where the lander PHILAE (after landing) will carry out in-situ observations. One of the instruments onboard is the APXS to make measurements on the landing site. The APXS science goal is to provide basic compositional data of the comet surface. As comets consist of a mixture of ice and dust, the dust component can be characterized and compared with known meteoritic compositions. Various element ratios can be used to evaluate whether chemical fractionations occurred in cometary material by comparing them with known chondritic material. To enable observations of the local environment, APXS measurements of several spots on the surface and one spot as function of temperature can be made. Repetitive measurements as function of heliocentric distance can elucidate thermal processes at work. By measuring samples that were obtained by drilling subsurface material can be analyzed. The accumulated APXS data can be used to shed light on state, evolution, and origin of 67P/Churyumov- Gerasimenko.

Klingelhöfer, G.; Brückner, J.; D'Uston, C.; Gellert, R.; Rieder, R.

2007-02-01

147

Alpha particle detection with GaN Schottky diodes  

SciTech Connect

Ni/GaN Schottky diode radiation detectors were fabricated on 3-mum-thick unintentionally doped n-GaN films grown by molecular beam epitaxy (MBE) and metal organic chemical vapor deposition (MOCVD) and on 12-mum-thick undoped n-GaN layers prepared by epitaxial lateral overgrowth (ELOG). The reverse current of all detector structures was <10{sup -9} A for bias voltages necessary for detector operation, with the level of background donor doping of <10{sup 15} cm{sup -3}. With this doping level the space charge region of the Schottky diode could be extended to the entire thickness of the films. The charge collection efficiency of the detectors was close to 100% for MOCVD and ELOG detectors for alpha-particles with range comparable to the thickness of the layer. Electrical properties and deep trap spectra were also studied. The collection efficiency decreased when the concentra-tion of deep electron traps, particularly E{sub c}-0.6 eV traps, increased in MBE grown films.

Polyakov, A. Y.; Smirnov, N. B.; Govorkov, A. V.; Markov, A. V.; Kozhukhova, E. A.; Gazizov, I. M. [Institute of Rare Metals, B. Tolmachevsky 5, Moscow 119017 (Russian Federation); Kolin, N. G.; Merkurisov, D. I.; Boiko, V. M.; Korulin, A. V. [Obninsk Branch of Federal State Unitary Enterprise, Karpov Institute of Physical Chemistry, Kiev Avenue, Kaluga Region, Obninsk 249033 (Russian Federation); Zalyetin, V. M. [Institute of Physical-Technical Problems, Dubna (Russian Federation); Pearton, S. J. [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611 (United States); Lee, I.-H. [School of Advanced Materials Engineering and Research Center for Advanced Materials Development, Chonbuk National University, Chonju 561-756 (Korea, Republic of); Dabiran, A. M.; Chow, P. P. [SVT Associates, Inc., 7620 Executive Drive, Eden Prairie, Minnesota 55344 (United States)

2009-11-15

148

Results of the Alpha-Particle-X-Ray Spectrometer on Board of the Mars Exploration Rovers  

NASA Technical Reports Server (NTRS)

The Mars Exploration Rovers Spirit and Opportunity landed at Gusev crater and Meridiani Planum. The Alpha Particle X-ray Spectrometer (APXS) is part of the instrument suite on both rovers. It is equipped with six 244Cm sources which provide x-ray excitation with alpha-particles (PIXE) and x-ray radiation (XRF). This combination allows x-ray spectroscopy of elements from Na to Br in the energy range of 0.9 to 16 keV. X-ray detectors with a high energy resolution of 160 eV at Fe K allow us to separate even closely spaced energy peaks, such as Na, Mg, Al and Si. The APXS is attached to the rover s arm and provides in-situ measurements of the chemical composition of soils, surfaces of rocks and outcrops and their abraded surfaces. This abstract gives an overview of APXS results obtained during the first year of operation on both landing sites.

Geller, R.; Zipfel, J.; Brueckner, J.; Dreibus, G.; Lugmair, G.; Rieder, R.; Waenke, H.; Klingelhoefer, G.; Clark, B. C.; Ming, D. W.

2005-01-01

149

Microscopic study of 4{alpha}-particle condensation with inclusion of resonances  

SciTech Connect

The 4{alpha} condensate state for {sup 16}O is discussed with the Tohsaki-Horiuchi-Schuck-Roepke (THSR) wave function which has {alpha}-particle condensate character. With a treatment of resonances, it is found that the 4{alpha} THSR wave function yields a fourth 0{sup +} state in the continuum above the 4{alpha}-breakup threshold, in addition to the three 0{sup +} states obtained in a previous analysis. It is shown that this fourth 0{sup +} [(0{sub 4}{sup +}){sub THSR}] state has a structure analogous to that of the Hoyle state because it has a very dilute density and a large component of {alpha}+{sup 12}C(0{sub 2}{sup +}) configuration. Furthermore, single-{alpha} motions are extracted from the microscopic 16-nucleon wave function, and the condensate fraction and momentum distribution of {alpha} particles are quantitatively discussed. It is found that for the (0{sub 4}{sup +}){sub THSR} state a large {alpha}-particle occupation probability concentrates on a single-{alpha} 0S orbit and the {alpha}-particle momentum distribution has a {delta}-function-like peak at zero momentum, both indicating that the state has a strong 4{alpha} condensate character. It is argued that the (0{sub 4}{sup +}){sub THSR} state is the counterpart of the 0{sub 6}{sup +} state which was obtained as the 4{alpha} condensate state in the previous 4{alpha} orthogonality condition model calculation and therefore is likely to correspond to the 0{sub 6}{sup +} state observed at 15.1 MeV. The necessity of including {alpha}+{sup 12}C configurations in the THSR wave function is pointed out.

Funaki, Y. [Institute of Physics, University of Tsukuba, Tsukuba 305-8571 (Japan); Yamada, T. [Laboratory of Physics, Kanto Gakuin University, Yokohama 236-8501 (Japan); Tohsaki, A. [Research Center for Nuclear Physics (RCNP), Osaka University, Osaka 567-0047 (Japan); Horiuchi, H. [Research Center for Nuclear Physics (RCNP), Osaka University, Osaka 567-0047 (Japan); International Institute for Advanced Studies, Kizugawa 619-0225 (Japan); Roepke, G. [Institut fuer Physik, Universitaet Rostock, D-18051 Rostock (Germany); Schuck, P. [Institut de Physique Nucleaire, CNRS, UMR 8608, Orsay F-91406 (France); Universite Paris-Sud, Orsay F-91505 (France); Laboratoire de Physique et Modelisation des Milieux Condenses, CNRS et Universite Joseph Fourier, 25 Av. des Martyrs, BP 166, F-38042 Grenoble Cedex 9 (France)

2010-08-15

150

GR Schwarzschild Particle Energy Program  

NSDL National Science Digital Library

The GR Schwarzschild Particle Energy program simulates orbits of objects around a black hole using the Schwarzschild metric. It also displays a plot of the effective potential well in which the orbiting particle resides. The user can change the orbiterâs state by entering new energy and angular momentum values and dragging the marker to different positions. The default configuration is a circular orbit. GR Schwarzschild Particle Energy is part of a suite of Open Source Physics programs that model aspects of General Relativity. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the gr_schwarzschild_particle_energy.jar file will run the program if Java is installed. Other programs provide additional visualizations. They can be found by searching ComPADRE for Open Source Physics, OSP, or General Relativity.

Christian, Wolfgang; Belloni, Mario; Cox, Anne

2008-05-27

151

Biocompatibility enhancement of chemically etched CR39 SSNTDs through superficial pore formation by alpha-particle irradiation  

Microsoft Academic Search

Alpha-particle radiobiological experiments involve irradiating cells with alpha particles and require thin biocompatible materials as substrates for cell cultures, which can record alpha-particle transversals. CR-39 SSNTDs with a thickness of about 20?m are suitable substrates. In the present work, the biocompatibility enhancement of these thin CR-39 SSNTDs is studied through superficial pore formation by alpha-particle irradiation. HeLa cells were cultured

C. K. M. Ng; K. F. Chan; W. Y. Li; A. K. W. Tse; W. F. Fong; T. Cheung; K. N. Yu

2008-01-01

152

Test procedure for gross alpha-particle activity in drinking water: interlaboratory collaborative study  

SciTech Connect

Gross alpha-activity values were calculated with four different alpha-emitting radionuclide standard counting efficiencies to see which standard was best for gross alpha activity determinations. Thorium-230, a pure alpha emitter, appeared to be the best standard for gross alpha counting efficiency. A secondary purpose in the study was to see how well the Ra-226 concentration of a drinking-water sample could be estimated from an early gross alpha count subtracted from a late gross alpha count and calculated from the equation provided in the test procedure. The method for gross alpha-particle concentration measurement eliminates the dissolved solids interference problem (which is a significant problem for the EPA-approved method) and provides for greater sensitivity by allowing for the use of much larger samples in the analysis.

Whittaker, E.L.

1986-08-01

153

FISSION OF {sup 238}U INDUCED BY INELASTIC SCATTERING OF 120 MeV {alpha}-PARTICLES  

SciTech Connect

The fission decay of {sup 238}U has been measured as function of excitation energy in inelastic scattering of 120 MeV {alpha}-particles. Total kinetic energies and masses of fission fragments were measured by the double energy method. It is observed that the total kinetic energy E{sub K} decreases and that the valley in the mass distribution is reduced when the excitation energy of the system is increased. No indication of anomalous total kinetic energy release in the region of the giant quadrupole resonance has been found. A qualitative interpretation of the data is given on the basis of a static scission point model.

Back, B.B.; Shotter, A.C.; Symons, T.J.M.; Bice, A.; Gelbke, C.K.; Awes, T.C.; Scott, D.K.

1980-09-01

154

Alpha-particle effects on high-n instabilities in tokamaks  

SciTech Connect

Hot ..cap alpha..-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 ..cap alpha..-particles, the predominant interaction of the mode with the ..cap alpha..-particles is through resonances of various sorts. In turn, the modes can cause significant anomalous transport of the ..cap alpha..-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.

Rewoldt, G.

1988-06-01

155

Alpha particles in field-aligned beams upstream of the bow shock - Simulations  

NASA Technical Reports Server (NTRS)

The possibility that field-aligned ion beams (FABs) formed by direct reflection could contain alpha particles is studied using self-consistent hybrid simulations of an oblique collisionless, supercritical shock. It is found that alpha particles can backstream from a shock in which the angle between the shock normal and the upstream magnetic field is 45 degrees. The deficit of alpha particles in the FABs, expressed as a relative density ratio to H(+) normalized to the solar wind He(2+) to H(+) density ratio, varies between about 0.1 and less than 0.01 and depends on the upstream H(+) and He(2+) temperatures.

Burgess, D.

1989-01-01

156

The interaction of energetic alpha-particles with intense lower hybrid waves  

SciTech Connect

Lower hybrid waves are a demonstrated, continuous means of driving toroidal current in a tokamak. When these waves propagate in a tokamak fusion reactor, in which there are energetic {alpha}- particles, there are conditions under which the {alpha}-particles do not appreciably damp, and may even amplify, the wave, thereby enhancing the current-drive effect. Waves traveling in one poloidal direction, in addition to being directed in one toroidal direction, are shown to be the most efficient drivers of current in the presence of the energetic {alpha}-particles.

Fisch, N.J.; Rax, J.M.

1992-06-01

157

WIND measurements of proton and alpha particle flow and number density  

NASA Technical Reports Server (NTRS)

We propose to review measurements of the solar wind proton and alpha particle flow velocities and densities made since launch with the WIND SWE instrument. The SWE Faraday cup ion sensors are designed to be able to determine accurately flow vector directions, and thus can be used to detect proton-alpha particle differential flow. Instances of differential flow, and the solar wind features with which they are associated will be discussed. Additionally, the variability of the percentage of alpha particles as a fraction of the total solar wind ion density will be presented.

Steinberg, J. T.; Lazarus, A. J.; Ogilvie, J. T.; Lepping, R.; Byrnes, J.; Chornay, D.; Keller, J.; Torbert, R. B.; Bodet, D.; Needell, G. J.

1995-01-01

158

The continuum and the alpha-particle formation  

Microsoft Academic Search

The absolute alpha-decay width of 212Po is calculated within a harmonic oscillator representation. Clustering features induced by the nuclear interaction appear by considering a large configuration space. The role of the neutronproton interaction is analysed and a reasonable account of the experimental alpha-decay width is given.

Gordana Dodig-Crnkovic; F. A. Janouch; R. J. Liotta; Zhao Xiaolin

1988-01-01

159

[Production of 61Cu, 62Zn by alpha and 3He particle bombardment of natural nickel (author's transl)].  

PubMed

The optimum irradiation conditions were investigated for the production of 61Cu and 62Zn by alpha and 3He particle bombardment of natural nickel. Formation cross sections and thick-target yields were obtained for reaction products in the energy range of 10 to 40 MeV. For the production of 61Cu and 62Zn, the alpha particle bombardment was found superior to the 3He particle bombardment in so far as the yield was concerned. When the incident alpha energy of 21 MeV was chosen, after 2.4 hours of cooling, 2.1 mCi/muA.h of 61Cu could be produced with less than 1% of 60Cu contamination. For the production of 62Zn, when the incident alpha energy of 35 MeV and the target thickness of 57 mg /cm2 were chosen, 97.5 muCi/muA.h of 62Zn could be produced. Radiochemical purity of 62Zn was the highest at 12 hours after the end of bombardment. PMID:752170

Muramatsu, H; Shirai, E; Nakahara, H; Murakami, Y

1978-11-01

160

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

SciTech Connect

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{sup +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.

Gerdin, G.; Vahala, L.; El Cashlan, A.G.

1990-01-01

161

Deletion-pattern analysis of alpha-particle and X-ray induced mutations at the HPRT locus of V79 Chinese hamster cells.  

PubMed

To investigate the mutagenic mechanisms of low-energy alpha particles V79 Chinese hamster cells were irradiated with 241Am-alpha particles (mean LET of 112 keV/micron). Parallel experiments were performed using 300 kV X-rays. Cell inactivation and mutation induction cross sections were measured. At approximately 20%--survival level, DNA deletions were analysed at the HPRT locus by multiplex-PCR-analysis of all nine exons of 47 alpha-irradiated and 36 background mutants. 92 HPRT- mutants isolated after 300 kV-X-irradiation were analysed similarly for comparison, along with 15 corresponding background mutants. The resulting mutant deletion-pattern distributions were corrected for background mutations. alpha Particles induced a larger fraction of deletions than X-rays. Furthermore, non-contiguous partial deletions were present among the alpha-induced mutants, a type not found after X-irradiation. PMID:9852989

Schmidt, P; Kiefer, J

1998-11-01

162

Some Calculations for exp 12 C in the alpha Particle Model.  

National Technical Information Service (NTIS)

The exp 12 C nucleus as three finite structurelesse alpha particles interacting through phenomenological potentials due to Ali and Bodmer is represented. These potentials are angular-momentum dependent and reproduce the experimental phase shifts delta sub...

V. C. Aguilera-Navarro O. Portilho

1976-01-01

163

CONCERNING THE MULTIPLE-WIRE SPARK COUNTER FOR ALPHA-PARTICLE DETECTION  

Microsoft Academic Search

A guard-wire type of multiple-wire spark counter for alpha-particle ; detection is designed and its operating characteristics studied. It appears that ; its counting properties approach those of the multiple wire-cavity spark counter. ; (auth);

G. Singh; N. K. Saha

1963-01-01

164

LIMITS ON ALPHA PARTICLE TEMPERATURE ANISOTROPY AND DIFFERENTIAL FLOW FROM KINETIC INSTABILITIES: SOLAR WIND OBSERVATIONS  

SciTech Connect

Previous studies have shown that the observed temperature anisotropies of protons and alpha particles in the solar wind are constrained by theoretical thresholds for pressure and anisotropy driven instabilities such as the Alfvén/ion-cyclotron (A/IC) and fast-magnetosonic/whistler (FM/W) instabilities. In this Letter, we use a long period of in situ measurements provided by the Wind spacecraft's Faraday cups to investigate the combined constraint on the alpha proton differential flow velocity and the alpha particle temperature anisotropy due to A/IC and FM/W instabilities. We show that the majority of the data are constrained to lie within the region of parameter space in which A/IC and FM/W waves are either stable or have extremely low growth rates. In the minority of observed cases in which the growth rate of the A/IC (FM/W) instability is comparatively large, we find relatively higher values of T {sub ?}/T {sub p} (T {sub ??}/T {sub ?p}) when the alpha proton differential flow velocity is small, where T {sub ?} and T {sub p} (T {sub ??} and T {sub ?p}) are the perpendicular (parallel) temperatures of alpha particles and protons. We conjecture that this observed feature might arise from preferential alpha particle heating which can drive the alpha particles beyond the instability thresholds.

Bourouaine, Sofiane; Verscharen, Daniel; Chandran, Benjamin D. G. [Space Science Center, University of New Hampshire, Durham, NH 03824 (United States)] [Space Science Center, University of New Hampshire, Durham, NH 03824 (United States); Maruca, Bennett A. [Space Science Laboratory, University of California, Berkeley, CA 94720 (United States)] [Space Science Laboratory, University of California, Berkeley, CA 94720 (United States); Kasper, Justin C., E-mail: s.bourouaine@unh.edu [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)

2013-11-01

165

Relative Yields of Ions Produced by alpha-Particles in Air and Water Vapour  

Microsoft Academic Search

IN continuation1 of the examination of the radiological properties of water, the yield of ion-pairs in water vapour under the action of alpha-particles has been compared with the yield in air. A sector-shaped parallel-plate ionization chamber containing either water vapour at 95° C. or air has been exposed to a semi-collimated beam of 5.0-MeV. alpha-particles derived from a polonium source.

R. K. Appleyard

1949-01-01

166

Cytotoxicity of alpha-particle-emitting astatine-211-labelled antibody in tumour spheroids: no effect of hyperthermia.  

PubMed Central

The high linear energy transfer, alpha-particle-emitting radionuclide astatine-211 (211At) is of interest for certain therapeutic applications; however, because of the 55- to 70-microm path length of its alpha-particles, achieving homogeneous tracer distribution is critical. Hyperthermia may enhance the therapeutic efficacy of alpha-particle endoradiotherapy if it can improve tracer distribution. In this study, we have investigated whether hyperthermia increased the cytotoxicity of an 211At-labelled monoclonal antibody (MAb) in tumour spheroids with a radius (approximately 100 microm) greater than the range of 211At alpha-particles. Hyperthermia for 1 h at 42 degrees C was used because this treatment itself resulted in no regrowth delay. Radiolabelled chimeric MAb 81C6 reactive with the extracellular matrix antigen tenascin was added to spheroids grown from the D-247 MG human glioma cell line at activity concentrations ranging from 0.125 to 250 kBq ml(-1). A significant regrowth delay was observed at 125 and 250 kBq ml(-1) in both hyperthermia-treated and untreated spheroids. For groups receiving hyperthermia, no increase in cytotoxicity was seen compared with normothermic controls at any activity concentration. These results and those from autoradiographs indicate that hyperthermia at 42 degrees C for 1 h had no significant effect on the uptake or distribution of this antitenascin MAb in D-247 MG spheroids. Images Figure 4 Figure 5

Hauck, M. L.; Larsen, R. H.; Welsh, P. C.; Zalutsky, M. R.

1998-01-01

167

On resonant excitations of high-n magnetohydrodynamic modes by energetic/alpha particles in tokamaks  

SciTech Connect

Analytical theories for the excitations in tokamaks of magnetohydrodynamic (MHD) modes with large toroidal mode numbers (n>>1) are presented. Specifically, only instability mechanisms due to resonances with energetic ions/alpha particles are considered. It is noted that, while trapped energetic particles contribute to the ideal region, circulating energetic particles contribute mainly to the singular layer dynamics. A unified dispersion relation manifesting both fishbone-like modes and beam transit-resonance modes is then driven. Finally, we also analyze the stability property of toroidicity-induced shear Alfven waves excited via transit resonances with alpha particles in ignited tokamaks. 11 refs.

Chen, Liu

1989-03-01

168

Protons and alpha particles in the expanding solar wind: Hybrid simulations  

NASA Astrophysics Data System (ADS)

We present results of a two-dimensional hybrid expanding box simulation of a plasma system with three ion populations, beam and core protons, and alpha particles (and fluid electrons), drifting with respect to each other. The expansion with a strictly radial magnetic field leads to a decrease of the ion perpendicular to parallel temperature ratios as well as to an increase of the ratio between the ion relative velocities and the local Alfven velocity creating a free energy for many different instabilities. The system is most of the time marginally stable with respect to kinetic instabilities mainly due to the ion relative velocities; these instabilities determine the system evolution counteracting some effects of the expansion. Nonlinear evolution of these instabilities leads to large modifications of the ion velocity distribution functions. The beam protons and alpha particles are decelerated with respect to the core protons and all the populations are cooled in the parallel direction and heated in the perpendicular one. On the macroscopic level the kinetic instabilities cause large departures of the system evolution from the double adiabatic prediction and lead to to perpendicular heating and parallel cooling rates which are comparable to the heating rates estimated from the Helios observations.

Travnicek, P. M.; Hellinger, P.

2013-12-01

169

Protons and alpha particles in the expanding solar wind: Hybrid simulations  

NASA Astrophysics Data System (ADS)

We present results of a two?dimensional hybrid expanding box simulation of a plasma system with three ion populations, beam and core protons, and alpha particles (and fluid electrons), drifting with respect to each other. The expansion with a strictly radial magnetic field leads to a decrease of the ion perpendicular to parallel temperature ratios as well as to an increase of the ratio between the ion relative velocities and the local Alfvén velocity creating a free energy for many different instabilities. The system is most of the time marginally stable with respect to kinetic instabilities mainly due to the ion relative velocities; these instabilities determine the system evolution counteracting some effects of the expansion. Nonlinear evolution of these instabilities leads to large modifications of the ion velocity distribution functions. The beam protons and alpha particles are decelerated with respect to the core protons and all the populations are cooled in the parallel direction and heated in the perpendicular one. On the macroscopic level, the kinetic instabilities cause large departures of the system evolution from the double adiabatic prediction and lead to perpendicular heating and parallel cooling rates which are comparable to the heating rates estimated from the Helios observations.

Hellinger, Petr; Trávní?ek, Pavel M.

2013-09-01

170

Investigation of the reactions {alpha}p {yields} tpp and {alpha}p {yields} {tau}pn induced by 2.7-GeV/c {alpha} particles  

SciTech Connect

The underlying mechanisms of the reactions {alpha}p {yields} tpp and {alpha}p {yields} {tau}pn are studied. Data from the ITEP two-meter bubble chamber filled with liquid hydrogen and irradiated by a 2.7-GeV/c separated {alpha}-particle beam are analyzed. The total cross sections for the two reactions are estimated at 20.7 {plus_minus} 0.4 and 34.4 {plus_minus} 0.4 mb, respectively. The phase-space domains in which quasifree scattering and final-state interactions play leading roles are isolated. The angular, momentum, and invariant-mass distributions of secondary particles are a obtained over the entire allowed kinematic range. In the region of quasifree scattering, the data are compared with the pole-model predictions. 25 refs., 8 figs.

Blinov, A.V.; Grechko, V.E.; Zombkovsky, S.M. [Institute of Theoretical and Experimental Physics, Moscow (Russian Federation)] [and others

1995-10-01

171

Bose-Einstein condensation of {alpha} particles and Airy structure in nuclear rainbow scattering  

SciTech Connect

It is shown that the dilute density distribution of {alpha} particles in nuclei can be observed in the Airy structure in nuclear rainbow scattering. We have analyzed {alpha}+{sup 12}C rainbow scattering to the 0{sub 2}{sup +} (7.65 MeV) state of {sup 12}C in a coupled-channel method with the precise wave functions for {sup 12}C. It is found that the enhanced Airy oscillations in the experimental angular distributions for the 0{sub 2}{sup +} state is caused by the dilute density distribution of this state in agreement for the idea of Bose-Einstein condensation of the three alpha particles.

Ohkubo, S. [Department of Applied Science and Environment, Kochi Women's University, Kochi 780-8515 (Japan); Hirabayashi, Y. [Information Initiative Center, Hokkaido University, Sapporo 060-0810 (Japan)

2004-10-01

172

DYNAMICS OF A SPHERICAL ACCRETION SHOCK WITH NEUTRINO HEATING AND ALPHA-PARTICLE RECOMBINATION  

SciTech Connect

We investigate the effects of neutrino heating and alpha-particle recombination on the hydrodynamics of core-collapse supernovae. Our focus is on the nonlinear dynamics of the shock wave that forms in the collapse and the assembly of positive energy material below it. To this end, we perform time-dependent hydrodynamic simulations with FLASH2.5 in spherical and axial symmetry. These generalize our previous calculations by allowing for bulk neutrino heating and for nuclear statistical equilibrium between n, p, and alpha. The heating rate is freely tunable, as is the starting radius of the shock relative to the recombination radius of alpha-particles. An explosion in spherical symmetry involves the excitation of an overstable mode, which may be viewed as the l = 0 version of the 'Standing Accretion Shock Instability'. In two-dimensional simulations, nonspherical deformations of the shock are driven by plumes of material with positive Bernoulli parameter, which are concentrated well outside the zone of strong neutrino heating. The nonspherical modes of the shock reach a large amplitude only when the heating rate is also high enough to excite convection below the shock. The critical heating rate that causes an explosion depends sensitively on the initial position of the shock relative to the recombination radius. Weaker heating is required to drive an explosion in two dimensions than in one, but the difference also depends on the size of the shock. Forcing the infalling heavy nuclei to break up into n and p below the shock only causes a slight increase in the critical heating rate, except when the shock starts out at a large radius. This shows that heating by neutrinos (or some other mechanism) must play a significant role in pushing the shock far enough out that recombination heating takes over.

Fernandez, Rodrigo [Department of Astronomy and Astrophysics, University of Toronto, Toronto, Ontario M5S 3H4 (Canada); Thompson, Christopher [CITA, 60 St. George Street, Toronto, Ontario M5S 3H8 (Canada)

2009-10-01

173

The measurement of 240Pu/ 239Pu and 238Pu/ 239Pu isotopic ratios by alpha-particle spectrometry  

NASA Astrophysics Data System (ADS)

The measurement of the alpha-activity ratio of {238Pu }/{( 239Pu + 240Pu) } is a routine practice in the determination of the isotopic composition of plutonium. However, measurement of the atomic ratio of 240Pu/ 239Pu by alpha-particle spectrometry is hampered due to insufficient energy resolution for the set of closely spaced peaks of these two isotopes. Passivated and implanted, planar silicon (PIPS) detectors have recently become available with an energy resolution of 10 keV or better, which significantly improves the deconvolution of spectra from plutonium samples. A set of alpha sources was prepared on porcelain disks by ignition, and the spectra were accumulated at a gain of approximately 1 keV per channel. The GRPANL computer program as developed by Lawrence Livermore National Laboratory was used to analyze the spectra. The isotopic ratios were measured in parallel by mass spectrometry. It was found that the agreement on the ratios of 240Pu/ 239Pu and 238Pu/ 239Pu between mass spectrometry and measurements by PIPS detectors was within ±2%. Half-life values were obtained from the literature (M. Lammer and O. Schwerer, Handbook of Nuclear Data for Safeguards, Rep. INDC(NDS)-248, IAEA, Vienna, 1991; ref. [5]). Other factors were also studied to improve the accuracy of the data. The alpha-particle emission probabilities of highly enriched 239Pu and 240Pu have been measured. The alpha-particle energies obtained in the fitting were in agreement with those in ref. [5]. The fitted energy values were used throughout this work.

Raab, W.; Parus, J. L.

1994-01-01

174

High energy proton and alpha radiation effects on GaAs\\/AlGaAs quantum well infrared photodetectors  

Microsoft Academic Search

Gallium arsenide quantum well infrared photodetectors (QWIPs) are ideally suited for infrared imagery due to their detection capability over a wide infrared wavelength region and the feasibility of fabrication of monolithic two-dimensional arrays of such detectors. This paper reports on the effects of high energy proton and alpha particle radiations on the performance of these devices. The particle energies ranged

S. M. Khanna; H. C. Liu; P. H. Wilson; L. Li; M. Buchanan

1996-01-01

175

Optical Model Potential Parameters for p, d, {sup 3}He and Alpha-Particle Scattering on Lithium Nuclei  

SciTech Connect

Analysis of the p, d, {sup 3}He and {alpha}-particles elastic scattering on the {sup 6}Li and {sup 7}Li nuclei has been done in the framework of the optical model at the beam energies up to 72 MeV. It was shown that the account of the cluster exchange mechanism together with the potential scattering allow reproducing the experimental cross-sections in the whole angular range.

Burtebayev, N.; Nassurlla, Marzhan; Nassurlla, Maulen; Kerimkulov, Zh. K. [Institute of Nuclear Physics, Almaty (Kazakhstan); Sakuta, S. B. [Russian Research Center 'Kurchatov Institute', Moscow (Russian Federation)

2008-11-11

176

Bismuth212-labeled anti-Tac monoclonal antibody: alpha-particle-emitting radionuclides as modalities for radioimmunotherapy  

Microsoft Academic Search

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

R. W. Kozak; R. W. Atcher; O. A. Gansow; A. M. Friedman; J. J. Hines; T. A. Waldmann

1986-01-01

177

Intense alpha-particle emitting crystallites in uranium mill wastes  

USGS Publications Warehouse

Nuclear emulsion microscopy has demonstrated the presence of small, intense ??-particle emitting crystallites in laboratory-produced tailings derived from the sulfuric acid milling of uranium ores. The ??-particle activity is associated with the isotope pair 210Pb 210Po, and the host mineral appears to be PbSO4 occurring as inclusions in gypsum laths. These particles represent potential inhalation hazards at uranium mill tailings disposal areas. ?? 1994.

Landa, E. R.; Stieff, L. R.; Germani, M. S.; Tanner, A. B.; Evans, J. R.

1994-01-01

178

Alpha particle source for radiolysis of gaseous systems  

Microsoft Academic Search

A mechanically stable AmâOâ alpha source for use in gas ; radiolysis was made by depositing americium nitrate, from a suspension, on both ; sides of a platinum disk and calcining at 500 to 550 deg C. In all, 50 layers ; were deposited on each side of the disk, giving a thickness of 0.3 mg\\/cm² ; ond a total

K. Ezerska; M. Fopys

1973-01-01

179

The continuum and the alpha-particle formation  

Microsoft Academic Search

The absolute ?-decay width of 212Po is calculated within a harmonic oscillator representation. Clustering features induced by the nuclear interaction appear by considering a large configuration space. The role of the neutronproton interaction is analysed and a reasonable account of the experimental alpha-decay width is given.

Gordana Dodig-Crnkovic; F A Janouch; R J Liotta; Zhao Xiaolin

1988-01-01

180

Alpha CAM filter particle collection pattern study results.  

National Technical Information Service (NTIS)

During a January 1991 Westinghouse Internal Audit of the WIPP Radiological Air Monitoring Program, an auditor observed that on an Eberline Alpha-6A CAM filter, some particulate was deposited outside the 25 mm diameter area that the filter is planned to us...

S. G. Clayton K. B. Steinbruegge T. D. Merkling

1992-01-01

181

Reexamination of the {alpha}-{alpha}''fishbone'' potential  

SciTech Connect

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.

Day, J. P.; McEwen, J. E.; Elhanafy, M.; Smith, E.; Woodhouse, R.; Papp, Z. [Department of Physics and Astronomy, California State University Long Beach, Long Beach, California (United States)

2011-09-15

182

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  

SciTech Connect

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.

Hwang, D.Q.; Horton, R.D.; Evans, R.W.

1999-06-03

183

An alpha particle measurement system using an energetic neutral helium beam in ITER (invited).  

PubMed

An energetic helium neutral beam is involved in the beam neutralization measurement system of alpha particles confined in a DT fusion plasma. A full size strong-focusing He(+) ion source (2 A, the beam radius of 11.3 mm, the beam energy less than 20 keV). Present strong-focusing He(+) ion source shows an emittance diagram separated for each beamlet of multiple apertures without phase space mixing, despite the space charge of a beamlet is asymmetric and the beam flow is non-laminar. The emittance of beamlets in the peripheral region was larger than that of center. The heat load to the plasma electrode was studied to estimate the duty factor for the ITER application. PMID:22380323

Sasao, M; Kisaki, M; Kobuchi, T; Tsumori, K; Tanaka, N; Terai, K; Okamoto, A; Kitajima, S; Kaneko, O; Shinto, K; Wada, M

2012-02-01

184

Charge exchange recombination spectroscopy for {alpha} particles colliding with hydrogen atoms  

SciTech Connect

The intensities of charge exchange recombination spectroscopy (CXRS) of {alpha} particles colliding with the hydrogen atoms in the neutral beam injection (NBI) are calculated by solving the rate equations including electron collision processes in the quasi-static state approximation. The effects of electron collision processes on the CXRS signals for He{sup +}(n=4{yields}3) at {lambda}=468.6nm in various plasma conditions are discussed, and it is found that these effects can increase the CXRS signals by 50% for electron density n{sub e}{>=}10{sup 15}cm{sup -3}. However, their importance decreases with the increasing of NBI energy. For the short pulse of NBI, the influences of electron collision processes can be neglected for n{sub e}{<=}10{sup 14}cm{sup -3}. Furthermore, the spectra of He{sup +}(n{yields}n') are present for the plasma conditions of HT-7 tokamak.

Liu, X. J.; Xiao, B. J. [Institute of Plasma Physics, Chinese Academy of Sciences, PO Box 1126, Hefei 230031 (China); Liu, L. [Institute of Applied Physics and Computational Mathematics, PO Box 8009, Beijing 100088 (China); College of Material Sciences and Optoelectronic Technology, Graduate University of the Chinese Academy of Sciences, PO Box 4588, Beijing 100049 (China); Wang, J. G. [Institute of Applied Physics and Computational Mathematics, PO Box 8009, Beijing 100088 (China); Qu, Y. Z. [College of Material Sciences and Optoelectronic Technology, Graduate University of the Chinese Academy of Sciences, PO Box 4588, Beijing 100049 (China)

2011-10-15

185

Experimental investigations of electron capture from atomic hydrogen and deuterium by alpha particles  

SciTech Connect

We report progress made during the period 15 September 1991--14 September 1992 on the project Experimental Investigations of Electron Capture from Atomic Hydrogen and Deuterium by Alpha Particles''. In the past year we have developed reliable, narrow energy spread, high-current sources of He[sup ++] based on direct-current magentron and electron-cyclotron resonance discharges. These sources have been proven on our test bench accelerator which has been upgraded to also allow us to test atomic hydrogen effusive targets. We have thus made substantial progress toward our goal of studying single electron capture from atomic hydrogen by doubly-ionized helium. A research plan for the upcoming year is also presented.

Gay, T.J.; Park, J.T.

1992-01-01

186

Alpha-particles as probes of nuclear shape and structure effects in proton evaporation spectra  

SciTech Connect

The emission barriers and subbarrier anisotropies in the alpha-particle decay with respect to the spin direction on Sn and rare earth compound nuclei are examined in the light of recent calculations incorporating deformation effects in the decay process. For the Sn systems the spectral shapes and anisotropies can be examined without involving deformation. For the rare earth systems deformation which increases with spin is necessary to explain the data. Energy spectra and angular correlations of evaporated protons from the {sup 52}Cr ({sup 34}S, 2p2n){sup 82}Sr reaction were measured in coincidence with discrete transitions. Large shifts in proton spectra were observed when high spin states in different rotational bands are populated. These effects cannot be explained by statistical model calculations that do not include explicitly nuclear structure effects in the deexcitation process. They are interpreted as due to near-yrast stretched proton emission, which preferentially populates the yrast band by subbarrier protons.

Sarantites, D.G.; Nicolis, N.G.; Abenante, V.; Majka, Z.; Semkow, T.M. (Washington Univ., St. Louis, MO (USA)); Baktash, C.; Beene, J.R.; Garcia-Bermudez, G.; Halbert, M.L.; Hensley, D.C.; Johnson, N.R.; Lee, I.Y.; McGowan, F.K.; Riley, M.A.; Virtanen, A. (Oak Ridge National Lab., TN (USA)); Griffin, H.C. (Michigan Univ., Ann Arbor, MI (USA))

1990-01-01

187

An alpha particle measurement system using an energetic neutral helium beam in ITER (invited)  

SciTech Connect

An energetic helium neutral beam is involved in the beam neutralization measurement system of alpha particles confined in a DT fusion plasma. A full size strong-focusing He{sup +} ion source (2 A, the beam radius of 11.3 mm, the beam energy less than 20 keV). Present strong-focusing He{sup +} ion source shows an emittance diagram separated for each beamlet of multiple apertures without phase space mixing, despite the space charge of a beamlet is asymmetric and the beam flow is non-laminar. The emittance of beamlets in the peripheral region was larger than that of center. The heat load to the plasma electrode was studied to estimate the duty factor for the ITER application.

Sasao, M.; Tanaka, N.; Terai, K.; Kaneko, O. [Graduate school of Engineering, Tohoku University, Sendai 980-8579 (Japan); Kisaki, M.; Kobuchi, T.; Tsumori, K.; Okamoto, A.; Kitajima, S. [National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan); Shinto, K. [IFMIF R and D Center, Japan Atomic Energy Agency, Rokkasho, Aomori 039-3212 (Japan); Wada, M. [Graduate School of Engineering, Doshisha University, Kyotanabe, Kyoto 610-0321 (Japan)

2012-02-15

188

Solar flare protons and alpha particles during the last three solar cycles  

NASA Technical Reports Server (NTRS)

This paper presents solar-flare-associated proton and alpha-particle fluxes determined for major events from October 1972 through March 1987 (the period that represents the last part of solar cycle 20 and the whole of solar cycle 21), using data obtained by detectors on board the IMP-7 and IMP-8 satellites, along with earlier obtained data for cycle 20. It was found that the average omnidirectional flux of protons with kinetic energy above 10 MeV for cycle 21 (64/sq cm per sec) is lower than the corresponding number for cycle 20 (92/sq cm per sec) and for the cycle 19 (378/sq cm per sec). No definitive correlation was found to exist between cycle-averaged solar flare proton fluxes and peak sunspot numbers.

Goswami, J. N.; Mcguire, R. E.; Reedy, R. C.; Lal, D.; Jha, R.

1988-01-01

189

Etching characteristic studies for the detection of alpha particles in DAM-ADC nuclear track detector  

NASA Astrophysics Data System (ADS)

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.

El-Samman, H.; Ashry, A. H.; Arafa, W.; Abou-leila, M.; Abdalla, A. M.; Tsuruta, T.

2014-09-01

190

Simple experimental method for alpha particle range determination in lead iodide films  

SciTech Connect

An experimental method for determining the range of alpha particles in films based on I-V{sub s} analysis has been suggested. The range of 5.5 MeV alpha particles in PbI{sub 2} films determined by this technique is 30{+-}5 {mu}m, and this value is in agreement with the value calculated by SRIM (the stopping and range of ions in matter), r=24 {mu}m in PbI{sub 2}. More than 100 I-V{sub s} of PbI{sub 2} films with different thicknesses and quality have been analyzed, and the influence of alpha particle radiation on PbI{sub 2} I-V{sub s} curves has been studied. Developed analytical methods (dependence of current density on electric field and conception of surface defects) were used, and the method limitations are discussed. It was shown that I-V{sub s} demonstrate the tendency to obey Ohm's law under alpha radiation. On the other hand, dark conductivity of the lead iodide films shows a typical impure character that can lead to an overestimation of the alpha particles' range in PbI{sub 2} films. After films were exposed to alpha radiation, the dark resistivity and I-V shape of some films improved. Also, a weak decrease of the charge carrier concentration, due to a decrease of the ''surface defect'' concentration (''surface refining''), was registered after successive measurements of I-V{sub s}.

Dmitriev, Yuri; Bennett, Paul R.; Cirignano, Leonard J.; Klugerman, Mikhail; Shah, Kanai S. [Radiation Monitoring Devices, Inc., Watertown, Massachusetts 02472 (United States)

2007-05-15

191

Simple experimental method for alpha particle range determination in lead iodide films.  

PubMed

An experimental method for determining the range of alpha particles in films based on I-V(s) analysis has been suggested. The range of 5.5 MeV alpha particles in PbI(2) films determined by this technique is 30+/-5 microm, and this value is in agreement with the value calculated by SRIM (the stopping and range of ions in matter), r=24 microm in PbI(2). More than 100 I-V(s) of PbI(2) films with different thicknesses and quality have been analyzed, and the influence of alpha particle radiation on PbI(2) I-V(s) curves has been studied. Developed analytical methods (dependence of current density on electric field and conception of surface defects) were used, and the method limitations are discussed. It was shown that I-V(s) demonstrate the tendency to obey Ohm's law under alpha radiation. On the other hand, dark conductivity of the lead iodide films shows a typical impure character that can lead to an overestimation of the alpha particles' range in PbI(2) films. After films were exposed to alpha radiation, the dark resistivity and I-V shape of some films improved. Also, a weak decrease of the charge carrier concentration, due to a decrease of the "surface defect" concentration ("surface refining"), was registered after successive measurements of I-V(s). PMID:17552841

Dmitriev, Yuri; Bennett, Paul R; Cirignano, Leonard J; Klugerman, Mikhail; Shah, Kanai S

2007-05-01

192

Mechanics and multiple-particle tracking microheterogeneity of alpha-actinin-cross-linked actin filament networks.  

PubMed Central

Cell morphology is controlled by the actin cytoskeleton organization and mechanical properties, which are regulated by the available contents in actin and actin regulatory proteins. Using rheometry and the recently developed multiple-particle tracking method, we compare the mechanical properties and microheterogeneity of actin filament networks containing the F-actin cross-linking protein alpha-actinin. The elasticity of F-actin/alpha-actinin networks increases with actin concentration more rapidly for a fixed molar ratio of actin to alpha-actinin than in the absence of alpha-actinin, for networks of fixed alpha-actinin concentration and of fixed actin concentration, but more slowly than theoretically predicted for a homogeneous cross-linked semiflexible polymer network. These rheological measurements are complemented by multiple-particle tracking of fluorescent microspheres imbedded in the networks. The distribution of the mean squared displacements of these microspheres becomes progressively more asymmetric and wider for increasing concentration in alpha-actinin and, to a lesser extent, for increasing actin concentration, which suggests that F-actin networks become progressively heterogeneous for increasing protein content. This may explain the slower-than-predicted rise in elasticity of F-actin/alpha-actinin networks. Together these in vitro results suggest that actin and alpha-actinin provides the cell with an unsuspected range of regulatory pathways to modulate its cytoskeleton's micromechanics and local organization in vivo.

Tseng, Y; Wirtz, D

2001-01-01

193

Alpha-particle emission probabilities in the decay of 240Pu.  

PubMed

Sources of enriched (240)Pu were prepared by vacuum evaporation on quartz substrates. High-resolution alpha-particle spectrometry of (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. PMID:20106670

Sibbens, G; Pommé, S; Altzitzoglou, T; García-Toraño, E; Janssen, H; Dersch, R; Ott, O; Sánchez, A Martín; Montero, M P Rubio; Loidl, M; Coron, N; de Marcillac, P; Semkow, T M

2010-01-01

194

Evaluation of ZnO(Ga)Coatings as Alpha Particle Transducers Within a Neutron Generator  

SciTech Connect

We report investigations and preliminary results from efforts to develop a recoil alpha particle detector for use in a portable neutron generator. The associated particle sealed tube neutron generator (APSTNG) will be used as an interrogation source for the Nuclear Materials Identification System (NMIS). With the emission of 14.1 MeV neutrons produced by the D-T reaction, associated 3.5 MeV alpha particles are emitted. These neutrons and alphas may then be correlated in time and direction, thus effectively ''tagging'' the neutrons of interest for subsequent use as an active nuclear materials interrogation source. The alpha particle detector uses a ZnO(Ga) scintillator coating applied to a fiber optic face plate. Gallium-doped zinc oxide is a fast (1.5 ns decay time), inorganic scintillator with a high melting point (1975C) and an absolute light yield of 1.5% of NaI(Tl). The scintillator is coated with a thin layer of nickel in order to screen out light produced in the tube and scattered deuterons and tritons. This coating also serves to prevent the buildup of charge on the detector surface. Results to date indicate promise as an effective alpha particle detector for the APSTNG for future use in the NMIS.

Mihalczo, J. T.; Neal, J. S.; Cooper, J. C.; Koltick, D. S.

2002-05-02

195

Monte Carlo study of alpha (?) particles transport in nanoscale gallium arsenide semiconductor materials  

NASA Astrophysics Data System (ADS)

Space and ground level electronic equipment with semiconductor devices are always subjected to the deleterious effects by radiation. The study of ion-solid interaction can show the radiation effects of scattering and stopping of high speed atomic particles when passing through matter. This study had been of theoretical interest and of practical important in these recent years, driven by the need to control material properties at nanoscale. This paper is attempted to present the calculations of final 3D distribution of the ions and all kinetic phenomena associated with the ion's energy loss: target damage, sputtering, ionization, and phonon production of alpha (?) particle in Gallium Arsenide(GaAs) material. This calculation is being simulated using the Monte Carlo simulation, SRIM (Stopping and Range of Ions in Matter). The comparison of radiation tolerance between the conventional scale and nanoscale GaAs layer will be discussed as well. From the findings, it is observed that most of the damage formed in the GaAs layer induced by the production of lattice defects in the form of vacancies, defect clusters and dislocations. However, when the GaAs layer is scaled down (nanoscaling), it is found that the GaAs layer can withstand higher radiation energy, in term of displacement damage.

Amir, Haider F. Abdul; Chee, Fuei Pien

2012-09-01

196

Onboard detection of intrinsic Ly. alpha. radiation from a neutral particle beam  

SciTech Connect

We consider photometers onboard a hydrogen neutral particle beam (NPB) space platform which monitor the instrinsic radiation from excited atoms in the NPB in flight. The radiation of choice is the Lyman {alpha} (Ly{alpha}) line 1216 A, emitted when the beam's {approx equal} 7% fraction of H (2S) atoms is motionally quenched in the earth's magnetic field. At nominal 20-MeV NPB energy, the Ly{alpha} radiation persists at 1% of its initial intensity out to 100 m along the beam, and is red-shifted to 1494 A when viewed form behind the exciting NPB pulse. A photosensitive detector with a {approximately} 5{degree} field of view, placed adjacent to the NPB exit port and viewing the NPB pulse along its limb, shows marked changes in detected Ly{alpha} intensity when the NPB axis shifts direction. If the NPB pulse is nominally 50 MA times 100 {mu}s, and if the detector is a 1-cm{sup 2} array of 25 {mu}m times 25 {mu}m photosensitive pixels located in the focal plane of an 8-cm diam. f/1 LiF lens, then pixels at the brightest part of the beam image are illuminated by up to 2300 Ly{alpha} photons per NPB pulse. The pixel quantum efficiency, optics transmission losses, and a geometric correction for viewing angle reduce the maximum count rate to {approximately} 200 photoelectrons per pixel per pulse under realistic operating conditions, and at a limb-viewing angle (i.e., angle between beam and detector axes) of {approx equal} 6 mrad. At smaller viewing angles the pixels count rate declines rapidly, but rapidly, but becomes sensitive to small angular shifts in the NPB axis direction. In the limit of shot-noise on the pixel count, and at optimum viewing angle ({approx equal} 0.54 mrad), we find that a single pixel can sense beam-axis shifts of {approx equal} {plus minus}50 {mu}rad. 8 refs., 7 figs., 2 tabs.

Robiscoe, R.T. (Montana State Univ., Bozeman, MT (USA). Dept. of Physics); Cobb, D.D.; Maier, W.B. II (Los Alamos National Lab., NM (USA))

1990-05-01

197

Analysis of alpha3 GlyR single particle tracking in the cell membrane.  

PubMed

Single particle tracking (SPT) of transmembrane receptors in the plasma membrane often reveals heterogeneous diffusion. A thorough interpretation of the displacements requires an extensive analysis suited for discrimination of different motion types present in the data. Here the diffusion pattern of the homomeric alpha3-containing glycine receptor (GlyR) is analyzed in the membrane of HEK 293 cells. More specifically, the influence of the alpha3 RNA splice variants alpha3K and alpha3L on lateral membrane diffusion of the receptor is revealed in detail. Using a combination of ensemble and local SPT analysis, free and anomalous diffusion parameters are determined. The GlyR alpha3 free diffusion coefficient is found to be 0.13 +/- 0.01 microm2/s and both receptor variants display confined motion. The confinement probability level and residence time are significantly elevated for the alpha3L variant compared to the alpha3K variant. Furthermore, for the alpha3L GlyR, the presence of directed motion was also established, with a velocity matching that of saltatory vesicular transport. These findings reveal that alpha3 GlyRs are prone to different types of anomalous diffusion and reinforce the role of RNA splicing in determining lateral membrane trafficking. PMID:24316136

Notelaers, Kristof; Rocha, Susana; Paesen, Rik; Smisdom, Nick; De Clercq, Ben; Meier, Jochen C; Rigo, Jean-Michel; Hofkens, Johan; Ameloot, Marcel

2014-03-01

198

Ultra-low background alpha particle counter using pulse shape analysis  

Microsoft Academic Search

The need to measure alpha particle emissivities at levels below 0.005 ?\\/cm2-hr is becoming increasingly important in fundamental physics experiments (e.g. neutrino and rare decay measurements), environmental monitoring, nuclear activities monitoring and semiconductor packaging materials. Present counters can barely reach this level, being limited both by cosmic ray events and by their own alpha emissions. Here we report a detector

W. K. Warburton; Brendan Dwyer-McNally; Michael Momayezi; John E. Wahl

2004-01-01

199

Mode coupling effects on alpha-particle-driven long wavelength Alfven wave instability  

SciTech Connect

It is demonstrated both analytically and numerically that mode couplings play an important role in the nonlinear evolution of alpha-particle-driven [ital long] [ital wavelength] Alfven wave instabilities. The mode coupling process is characterized by a beat between two linearly unstable Alfven waves having opposite frequencies, which generates a linearly stable, static (zero frequency) mode. The backreaction of the static mode tends to stabilize the Alfven instabilities by eliminating the phase shift between the alpha pressure and the Alfven fluctuations.

Gang, F.Y. (Plasma Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)); Leboeuf, J. (Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830 (United States))

1993-08-01

200

Charged-particle mutagenesis 2. Mutagenic effects of high energy charged particles in normal human fibroblasts  

NASA Technical Reports Server (NTRS)

The biological effects of high Linear Energy Transfer (LET) charged particles are a subject of great concern with regard to the prediction of radiation risk in space. In this report, mutagenic effects of high LET charged particles are quantitatively measured using primary cultures of human skin fibroblasts, and the spectrum of induced mutations are analyzed. The LET of the charged particles ranged from 25 KeV/micrometer to 975 KeV/micrometer with particle energy (on the cells) between 94-603 MeV/u. The X-chromosome linked hypoxanthine guanine phosphoribosyl transferase (hprt) locus was used as the target gene. Exposure to these high LET charged particles resulted in exponential survival curves; whereas, mutation induction was fitted by a linear model. The Relative Biological Effect (RBE) for cell-killing ranged from 3.73 to 1.25, while that for mutant induction ranged from 5.74 to 0.48. Maximum RBE values were obtained at the LET of 150 keV/micrometer. The inactivation cross-section (alpha i) and the action cross-section for mutant induction (alpha m) ranged from 2.2 to 92.0 sq micrometer and 0.09 to 5.56 x 10(exp -3) sq micrometer respectively. The maximum values were obtained by Fe-56 with an LET of 200 keV/micrometer. The mutagenicity (alpha m/alpha i) ranged from 2.05 to 7.99 x 10(exp -5) with the maximum value at 150 keV/micrometer. Furthermore, molecular analysis of mutants induced by charged particles indicates that higher LET beams are more likely to cause larger deletions in the hprt locus.

Chen, D. J.; Tsuboi, K.; Nguyen, T.; Yang, T. C.

1994-01-01

201

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

NASA Astrophysics Data System (ADS)

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&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.

Blaauw, M.; García-Toraño, E.; Woods, S.; Fazinic, S.

1999-06-01

202

Alfvenic behavior of alpha particle driven ion cyclotron emission in TFTR  

SciTech Connect

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 ({Omega}{sub {alpha}}) 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 {Omega}{sub {alpha}} 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.

Cauffman, S.; Majeski, R. [Princeton Plasma Physics Lab., NJ (United States); McClements, K.G. [UKAEA Government Division, Oxfordshire (United Kingdom). Euratom/UKAEA Fusion Association] [and others

1995-07-01

203

Emission rates of alpha particles from supports with different surface conditions in direct deposition sources.  

PubMed

Direct deposition is the only method that can be utilised for the standardisation of radioactive solutions because there is no deposition loss on a support. The present study investigated how much the roughness of the support influences the emission rate of alpha particles for direct deposition sources from the practical viewpoint of use of the method. A number of samples were prepared by evaporating a 0.1-ml aliquot of a dilute nitric acid aqueous solution that contained (241)Am on stainless steel supports with four different surface conditions; untreated supports were either polished (using metal abrasives available commercially) or not polished, and buffed supports (grid size of #400) were either polished or not polished. Alpha spectrometry of the samples revealed that the detection efficiency was significantly different between the non-polished and polished supports; the former was lower by 3 % than the latter for both the untreated and buffed supports. Microscopic observations clarified that the counting loss was attributed to irregular flaws or polishing lines on the non-polished supports, most of which were found to be in the order of submicron in depth and were diminished on the polished supports. One may usually assume that a direct deposition source offers no counting loss if its entire energy spectrum is seen above a low-energy discrimination limit of the spectrometer. However, this should be experimentally confirmed using a solution with known activity. It was difficult to identify the counting loss for the buffed supports without polishing because their energy spectra showed little degradation. PMID:21097486

Kurihara, Osamu; Saito, Fumihiro; Koarashi, Jun; Kim, Eunjoo; Shiraishi, Kunio; Yamada, Yuji; Akashi, Makoto

2011-04-01

204

Exploitation of the charge sharing effect in Timepix device to achieve sub-pixel resolution in imaging applications with alpha particles.  

NASA Astrophysics Data System (ADS)

The Timepix device is a pixelated silicon detector. Because of its structure, an incoming particle can deposit its energy in several adjacent pixels as a result of the charge sharing effect. The distribution of energy in the pixels activated by a heavy charged particle can be exploited to determine the entering point of the particle with a precision better than the pixel dimensions. This is experimentally illustrated by images of different samples obtained with alpha particles. This work was carried out within the CERN Medipix Collaboration.

Teyssier, C.; Guérin, P. Allard; Bergeron, G.; Dallaire, F.; Leroy, C.; Pospisil, S.; Trudeau, Y. B.

2012-08-01

205

Modeling of alpha-particle-induced soft error rate in DRAM  

SciTech Connect

Alpha-particle-induced soft error in 256M DRAM was numerically investigated. A unified model for alpha-particle-induced charge collection and a soft-error-rate simulator (SERS) was developed. The author investigated the soft error rate of 256M DRAM and identified the bit-bar mode as one of dominant modes for soft error. In addition, for the first time, it was found that trench-oxide depth has a significant influence on soft error rate, and it should be determined by the tradeoff between soft error rate and cell-to-cell isolation characteristics.

Shin, H. [Ewha Womans Univ., Seoul (Korea, Republic of). Dept. of Electronic Engineering

1999-09-01

206

Charged-particle mutagenesis II. Mutagenic effects of high energy charged particles in normal human fibroblasts  

NASA Technical Reports Server (NTRS)

The biological effects of high LET charged particles are a subject of great concern with regard to the prediction of radiation risk in space. In this report, mutagenic effects of high LET charged particles are quantitatively measured using primary cultures of human skin fibroblasts, and the spectrum of induced mutations are analyzed. The LET of the charged particles ranged from 25 KeV/micrometer to 975 KeV/micrometer with particle energy (on the cells) between 94-603 MeV/u. The X-chromosome linked hypoxanthine guanine phosphoribosyl transferase (hprt) locus was used as the target gene. Exposure to these high LET charged particles resulted in exponential survival curves; whereas, mutation induction was fitted by a linear model. The Relative Biological Effect (RBE) for cell-killing ranged from 3.73 to 1.25, while that for mutant induction ranged from 5.74 to 0.48. Maximum RBE values were obtained at the LET of 150 keV/micrometer. The inactivation cross-section (alpha i) and the action cross-section for mutant induction (alpha m) ranged from 2.2 to 92.0 micrometer2 and 0.09 to 5.56 x 10(-3) micrometer2, respectively. The maximum values were obtained by 56Fe with an LET of 200 keV/micrometer. The mutagenicity (alpha m/alpha i) ranged from 2.05 to 7.99 x 10(-5) with the maximum value at 150 keV/micrometer. Furthermore, molecular analysis of mutants induced by charged particles indicates that higher LET beams are more likely to cause larger deletions in the hprt locus.

Chen, D. J.; Tsuboi, K.; Nguyen, T.; Yang, T. C.

1994-01-01

207

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

PubMed

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

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

208

Alpha-particle dose to the liver and spleen tissues of Japanese Thorotrast patients.  

PubMed

We set out to establish an appropriate and convenient method for calculating alpha-particle absorbed doses to the liver and spleen of Thorotrast patients and to estimate a representative dose rate to the liver for the whole population of surviving and deceased Thorotrast patients in Japan. First, we determined steady-state activity ratios of 232Th progeny from 13 autopsy cases and found them to be identical to those reported in German subjects. Second, we estimated the alpha dose rates in 206 subjects at autopsy from radioactivity measurements and terminal weights of the organs. Combining these results with measurements of exhaled 220Rn in survivors, we considered the representative dose rates at injection to be 0.22 Gy y-1. Additionally, our data suggest that deposition in the spleen has previously been overestimated. This is an error with some bearing on the evaluation of leukemia risks from alpha-particle irradiation. PMID:8225986

Ishikawa, Y; Kato, Y; Mori, T; Machinami, R; Kitagawa, T

1993-11-01

209

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

PubMed

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. PMID:15623884

Hofmann, W; Fakir, H; Aubineau-Laniece, I; Pihet, P

2004-01-01

210

Alpha Particle Pressure Gauge for High Altitude Constant Level Balloon Flights  

Microsoft Academic Search

This paper describes an alpha particle pressure gauge designed for use on very high altitude constant level balloon flights. The instrument gives continuous readings from sea level to pressures less than 1 millibar with an accuracy in the 1–10 millibar range of a few tenths of a millibar. The instrument utilizes a sensitive electrometer measuring the ionization current due to

R. L. Howard; S. W. Nelson; J. R. Winckler

1968-01-01

211

Alternate method for treating Alfven waves driven unstable by {alpha} particles  

SciTech Connect

For treating Alfven waves driven unstable by {alpha} particles, an alternative to the Oak Ridge National Laboratory gyro-Landau fluid approach is suggested. Its primary advantage is that this method can simultaneously treat fluid nonlinearities and kinetic quasilinear effects. It is argued that more perturbative approaches could overestimate the kinetic quasilinear effects. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

Hedrick, C.L.; Leboeuf, J.; Prochaska, M.D.; Spong, D.A.; Carreras, B.A. [Oak Ridge National Laboratory, P.O. Box 2009, Oak Ridge, Tennessee 37831-8071 (United States)] [Oak Ridge National Laboratory, P.O. Box 2009, Oak Ridge, Tennessee 37831-8071 (United States)

1995-12-01

212

Alpha Particle X-Ray Spectrometer (APXS): Results from Gusev crater and calibration report  

Microsoft Academic Search

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

R. Gellert; R. Rieder; J. Brückner; B. C. Clark; G. Dreibus; G. Klingelhöfer; G. Lugmair; D. W. Ming; H. Wänke; A. Yen; J. Zipfel; S. W. Squyres

2006-01-01

213

The new Athena alpha particle X-ray spectrometer for the Mars Exploration Rovers  

Microsoft Academic Search

The new alpha particle X-ray spectrometer (APXS) is part of the Athena payload of the two Mars Exploration Rovers (MER). The APXS sensor head is attached to the turret of the instrument deployment device (IDD) of the rover. The APXS is a very light-weight instrument for determining the major and minor elemental composition of Martian soils, rocks, and other geological

R. Rieder; R. Gellert; J. Brückner; G. Klingelhöfer; G. Dreibus; A. Yen; S. W. Squyres

2003-01-01

214

Can Bose condensation of alpha particles be observed in heavy ion collisions?  

NASA Technical Reports Server (NTRS)

Using a fully self-consistent quantum statistical model, we demonstrate the possibility of Bose condensation of alpha particles with a concomitant phase transition in heavy ion collisions. Suggestions for the experimental observation of the signature of the onset of this phenomenon are made.

Tripathi, Ram K.; Townsend, Lawrence W.

1993-01-01

215

Boron compounds as a dominant source of alpha particles in semiconductor devices  

Microsoft Academic Search

The interaction of cosmic ray neutrons and boron is demonstrated as the dominant source of alpha particles and other radiations in electronic devices utilizing borophosphosilicate glass (BPSG). A simple process modification is proposed to significantly reduce this intense source of ionizing radiation without compromising the reflow and passivation properties of BPSG.

Robert Baumann; Tim Hossain; Shinya Murata; Hideki Kitagawa

1995-01-01

216

Nuclear Densities of 1FSUB(7/2) Nuclei from Elastic alpha-Particle Scattering.  

National Technical Information Service (NTIS)

The elastic scattering of 104 MeV alpha particles by sup(40,42,43,44,48)Ca, exp 50 Ti, exp 51 V, exp 52 Cr has been analyzed by phenomenological and semimicroscopic optical potentials in order to get information on isotopic and isotonic differences of the...

E. Friedman H. J. Gils H. Rebel

1983-01-01

217

Nucleon-Alpha Particle Disequilibrium and Short-Lived r-Process Radioactivities  

NASA Technical Reports Server (NTRS)

r-Process yields can be extremely sensitive to expansion parameters when a persistent disequilibrium between free nucleons and alpha particles is present. This may provide a natural scenario for understanding the variation of heavy and light r-process isotopes in different r-process events. Additional information is contained in the original extended abstract.

Meyer, B. S.; Clayton, D. D.; Chellapilla, S.; The, L.-S.

2002-01-01

218

Effects of fusion-product alpha particles on plasma stability in the fusion ignition experiment IGNITEX  

Microsoft Academic Search

Summary form only given. The effects of alpha particles on the stability of MHD modes in IGNITEX plasmas are investigated analytically and numerically. The sawtooth and fishbone oscillations, which may occur in the central part of the plasma column, are associated with the n =1, m=1 internal kink modes and are considered to be a potential threat to the attainment

Z. Guo; R. Carrera; G. Y. Fu; G. Miley; E. Montalvo; M. N. Rosenbluth; J. W. Van Dam

1990-01-01

219

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

SciTech Connect

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.

Burns, F.J.

1990-01-01

220

Stripping of two protons and one alpha particle transfer reactions for (sup 16) O + (sup A) Sm and their influence on the fusion cross section.  

National Technical Information Service (NTIS)

Transfer cross section angular distribution data for the stripping of two protons and one alpha particle are studied for the (sup 16) O + (sup A) Sm systems (A=144, 148, 150, 152 and 154), at near barrier energies. A semiclassical formalism is used to der...

A. M. M. Maciel P. R. Gomes

1995-01-01

221

High-Energy Laser-Particle Interaction.  

National Technical Information Service (NTIS)

This project investigates the spectral signatures associated with high-energy laser-particle interactions. Our main research objective is to improve predictive modeling of laser interaction with atmospheric particles by systematically studying the emissio...

D. W. Pack

1991-01-01

222

The biological effects of Auger electrons compared to alpha-particles and Li ions.  

PubMed

The present study reports the results of V-79 Chinese hamster cell survival studies in which Auger electron emission was stimulated in gadolinium (Gd) after thermal neutron capture. When a porphyrin that had previously been labeled with boron (10BOPP) was also labeled with Gd (Gd-10BOPP), the cells were incubated with Gd-10BOPP to assess the compound's ability to physiologically transport the Gd into the cell, and localize the Gd atoms in or near the cell's critical target, presumably the DNA. It was anticipated that Auger electron emission, stimulated during the 157Gd (n, gamma)158Gd interaction, would impart additional high LET damage to that observed from the alpha-particle and Li ion during the 10B(n, alpha) 7Li reaction. Following irradiation with thermal neutrons from the Brookhaven Medical Research Reactor, the effectiveness of the Auger electrons was determined by comparing the response of cells incubated with 10BOPP, where damage was imparted by the boron neutron capture (BNC) products, to that from Gd-10BOPP, with equal concentration of 10B in both solutions. An Auger effectiveness factor of approximately 2 was found for the Gd-10BOPP cells. The Auger effectiveness observed with Gd strongly suggested that the 10BOPP molecule physiologically transported the Gd3+ ion intracellularly where it probably bound to DNA. Others have reported that Gd3+ does, in fact, complex with DNA. While depositing less energy per interaction than the high LET BNC reaction by-products, Auger electron ionization was more effective. PMID:9004772

Laster, B H; Shani, G; Kahl, S B; Warkentien, L

1996-01-01

223

Chemically Enhanced Alpha-Energy Spectroscopy in Liquids  

SciTech Connect

We have demonstrated the direct isotopic assay of alpha-emitters in liquids using passivated implanted planar silicon (PIPS) diodes coupled with selective chemical preconcentration. Direct alpha energy spectroscopy has been enabled by placing a chemically selective polymer film or sorbent layer that concentrate ions of interest into a thin layer upon the diode surface. With thin film-coated we were able to obtain in situ alpha spectra with energy resolution comparable to that of conventional alpha spectroscopy. Moreover, by utilizing sorbent coatings with high affinity for the actinides of interest, we have been able to selectively concentrate actinides of interest upon the diode surface resulting in a substantial increase in sensitivity relative to a direct measurement.

Addleman, Raymond S.; O'Hara, Matthew J.; Grate, Jay W.; Egorov, Oleg B.

2005-01-01

224

Neoclassical Simulations of Fusion Alpha Particles in Pellet Charge Exchange Experiments on the Tokamak Fusion Test Reactor  

SciTech Connect

Neoclassical simulations of alpha particle density profiles in high fusion power plasmas on the Tokamak Fusion Test Reactor (TFTR) [Phys. Plasmas 5 (1998) 1577] are found to be in good agreement with measurements of the alpha distribution function made with a sensitive active neutral particle diagnostic. The calculations are carried out in Hamiltonian magnetic coordinates with a fast, particle-following Monte Carlo code which includes the neoclassical transport processes, a recent first-principles model for stochastic ripple loss and collisional effects. New global loss and confinement domain calculations allow an estimate of the actual alpha particle densities measured with the pellet charge exchange diagnostic.

Batha, S.H.; Budny, R.V.; Darrow, D.S.; Levinton, F.M.; Redi, M.H.; et al

1999-02-01

225

Relative biological effectiveness of alpha-particle emitters in vivo at low doses  

SciTech Connect

The therapeutic potential of radionuclides that emit [alpha] particles, as well as their associated health hazards, have attracted considerable attention. The [sup 224]Ra daughters [sup 212]Pb and [sup 212]Bi, by virtue of their radiation properties which involve emission of [alpha] and [beta] particles in their decay to stable [sup 208]Pb, have been proposed as candidates for radioimmunotherapy. Using mouse testes as the experimental model and testicular spermhead survival as the biological end point, the present work examines the radiotoxicity of [sup 212]Pb and its daughters. When [sup 212]Pb, in equilibrium with its daughters [sup 212]Bi, [sup 212]Po and [sup 208]Tl, was administered directly into the testis, the dose required to achieve 37% survival (D[sub 37]) was 0.143 [+-] 0.014 Gy and the corresponding RBE of the mixed radiation field was 4.7 when compared to the D[sub 37] for acute external 120 kVp X rays. This datum, in conjunction with our earlier results for [sup 210]Po, was used to obtain an RBE-LET relationship for [alpha] particles emitted by tissue-incorporated radionuclides: RBE[sub [alpha

Howell, R.W.; Azure, M.T.; Narra, V.R.; Rao, D.V. (Univ. of Medicine and Dentistry of New Jersey, Newark, NJ (United States))

1994-03-01

226

Alpha particle induced gamma yields in uranium hexafluoride  

NASA Astrophysics Data System (ADS)

Fluorine has a relatively large (?,n) production cross-section in the MeV range, the energy range of interest for special nuclear materials. In the uranium fuel cycle enriched UF6 in particular is a reasonably prolific source of (?,n) neutrons because along with 235U, 234U becomes enriched and it has a relatively short half-life. This enables the mass content of storage cylinders containing UF6 to be verified by neutron counting methods. In association with such measurements high resolution gamma-ray spectrometry (HRGS) measurements using a high-purity Ge detector are often undertaken to determine the 235U enrichment based off the intensity of the direct 186 keV line. The specific (?,n) neutron production, neutrons per second per gram of U, is sensitive to the relative isotopic composition, particularly the 234U concentration, and the traditional gross neutron counting approach is needed to quantitatively interpret the data. In addition to F(?,n) neutrons, ?-induced reaction ?-rays are generated, notably at 110, 197, 582, 891, 1236 and 1275 keV. If one could observe 19F(?,x?) gamma-lines in the HRGS spectra the thought was that perhaps the ?-activity could be estimated directly, and in turn the 234U abundance obtained. For example, by utilizing the ratio of the detected 197-186 keV full energy peaks. However, until now there has been no readily available estimate of the expected strength of the reaction gamma-rays nor any serious consideration as to whether they might be diagnostic or not. In this work we compute the thick target yields of the chief reaction gamma-rays in UF6 using published thin target data. Comparisons are made to the neutron production rates to obtain ?/n estimates, and also to the 235U decay line at 186 keV which we take as a fiducial line. It is shown that the reaction gamma-rays are produced but are far too weak for practical safeguards purposes. Now that the underlying numerical data is readily available however, it can be used to support neutron and gamma production calculations in other fluorine compounds, for example impure plutonium reference materials where fluorine may be present only at the parts per million by weight level yet still present a serious nuisance addition to the neutron production rate.

Croft, Stephen; Swinhoe, Martyn T.; Miller, Karen A.

2013-01-01

227

Neutron production in the lunar subsurface from alpha particles in galactic cosmic rays  

NASA Astrophysics Data System (ADS)

The neutron production from alpha particles in galactic cosmic rays (GCR) in the lunar subsurface has not been estimated with reliable precision despite its importance for lunar nuclear spectroscopy and space dosimetry. Here, we report our estimation of neutron production from GCR nuclei (protons and alpha particles) with the Particle and Heavy Ion Transport code System (PHITS), which includes several heavy ion interaction models. PHITS simulations of the equilibrium neutron density profiles in the lunar subsurface are compared with experimental data obtained in the Apollo 17 Lunar Neutron Probe Experiment. Our calculations successfully reproduced the data within an experimental error of 15%. Our estimation of neutron production from GCR nuclei, estimated by scaling that from protons by a factor of 1.27, is in good agreement within an error of 1% with the calculations using two different alpha particle interaction models in PHITS during a period of average activity of the solar cycle. However, we show that the factor depends on the incident GCR spectrum model used in the simulation. Therefore, we conclude that the use of heavy ion interaction models is important for estimating neutron production in the lunar subsurface.

Ota, S.; Kobayashi, S.; Sihver, L.; Yamashita, N.; Hasebe, N.

2011-01-01

228

Reduced proton and alpha particle precipitations at Mars during solar wind pressure pulses: Mars Express results  

NASA Astrophysics Data System (ADS)

We performed a statistical study of downward moving protons and alpha particles of ~keV energy (assumed to be of solar wind origin) inside the Martian induced magnetosphere from July 2006 to July 2010. Ion and electron data are from the Analyzer of Space Plasma and Energetic Atoms (ASPERA-3) package on board Mars Express. We investigated the solar wind ion entry into the ionosphere, excluding intervals of low-altitude magnetosheath encounters. The study compares periods of quiet solar wind conditions and periods of solar wind pressure pulses, including interplanetary coronal mass ejections and corotating interaction regions. The solar wind ion precipitation appears localized and/or intermittent, consistent with previous measurements. Precipitation events are less frequent, and the precipitating fluxes do not increase during pressure pulse encounters. During pressure pulses, the occurrence frequency of observed proton precipitation events is reduced by a factor of ~3, and for He2+ events the occurrence frequency is reduced by a factor of ~2. One explanation is that during pressure pulse periods, the mass loading of the solar wind plasma increases due to a deeper penetration of the interplanetary magnetic flux tubes into the ionosphere. The associated decrease of the solar wind speed thus increases the pileup of the interplanetary magnetic field on the dayside of the planet. The magnetic barrier becomes thicker in terms of solar wind ion gyroradii, causing the observed reduction of H+/He2+ precipitations.

DiéVal, C.; Stenberg, G.; Nilsson, H.; Edberg, N. J. T.; Barabash, S.

2013-06-01

229

Alpha-Energy-Deposition-Profiling of Radioisotope p-i-n Diodes for Power Generation  

NASA Astrophysics Data System (ADS)

The high energy density and long half-life of certain alpha-emitting radioisotopes enables viable and long-lived power supplies to be fabricated on the micro-scale. A design incorporating an InGaP p-i-n photovoltaic (PV) device that directly converts the kinetic energy of the alpha-particles into electricity represents both a scalable and efficient microsystem design. To better understand the relationship between the alpha-energy-deposition-profile (ADEP) and the maximum power conversion efficiency for this device structure, we have performed two systematic studies. In these studies, I-V characteristics for the InGaP PV device under alpha-flux are measured as a function of alpha source distance, and as function of aluminum film thickness (10 nm to 10 ?m) which is deposited onto the surface of the PV device. Both techniques will alter the ADEP in relation to the active region of the PV device. These experimental results are compared to a theoretical model which utilizes Monte Carlo simulations and numerical calculations to determine the ADEP for the same device configuration. The understanding gained from this analysis has direct implications towards the fabrication of radioisotope microbatteries with structural characteristics that enable optimal power conversion efficiencies to be achieved.

Cress, Cory; Raffaelle, Ryne

2006-03-01

230

Large-angle {alpha}-particle scattering on {sup 12}C and search for signatures of {alpha}-particle Bose condensation  

SciTech Connect

Evidence of the 3{alpha}-particle condensate character of the Hoyle state (the 0{sub 2}{sup +} state at 7.65 MeV in {sup 12}C) implies not only an enhanced radius of {sup 12}C in this state, which was established by many theoretical calculations and confirmed by the recent diffraction model analysis, but also zero relative angular momenta between clusters. We performed coupled-channels model calculations of the angular distributions of {alpha}+{sup 12}C elastic and inelastic (to the 4.44-MeV 2{sup +}, 7.65-MeV 0{sub 2}{sup +}, and 9.65-MeV 3{sub 1}{sup -} states) scattering at 110 MeV and found the ratio of the empirical spectroscopic factors S(L). As the differential cross sections of these reactions are characterized by pronounced enhancement and strong oscillations at large angles, we assumed a potential scattering in the forward hemisphere and the direct transfer of a {sup 8}Be cluster at {theta}{sub c.m.}>90 deg. and took into account the direct transfer of {sup 8}Be in the ground state and in the first excited 2{sup +} and 4{sup +} states. We found that the cluster configuration with L=0 dominates in the 0{sub 2}{sup +} state, being more than three times larger than that in the ground state. This result provides additional evidence of the condensed structure of the Hoyle state in {sup 12}C with a dominance of zero relative angular momentum. The negative-parity 3{sub 1}{sup -} excited state in {sup 12}C observed above the 3{alpha} threshold is also considered to have the 3{alpha}-cluster structure. The present calculations described well the structure of the large-angle cross section on this state. We found a positive interference for all allowed {alpha}+{sup 8}Be configurations with a dominance of the p-orbital (69%){alpha}+{sup 8}Be motion and confirmed the exotic, but hardly a condensed, structure of this state.

Belyaeva, T. L. [Universidad Autonoma del Estado de Mexico, C.P. 50000, Toluca (Mexico); Danilov, A. N.; Demyanova, A. S.; Ogloblin, A. A. [RRC Kurchatov Institute, Moscow RU-123182 (Russian Federation); Goncharov, S. A. [Skobeltsyn Institute of Nuclear Physics, Vorob'evy Gory, Moscow (Russian Federation); Perez-Torres, R. [Universidad Tecnologico del Valle de Toluca (Mexico)

2010-11-15

231

Radiation Damage in Indium-Antimonide by Alpha Particles.  

NASA Astrophysics Data System (ADS)

The development and annealing of radiation damage in InSb, caused by helium ions, were examined using mainly Rutherford backscattering analysis with channeling. Transmission electron microscopy and secondary ion mass spectroscopy were also done on some samples after implantation. Damage caused by the analysing beam in InSb--about an order of magnitude more than in GaAs--complicates ion beam analysis. InSb was implanted with 50 keV He^ {+} up to a dose of 10^ {17} ions/cm^2, at temperatures from 77 K to 525 K and rates varying from 2,2 times 10^{13 } to 2,6 times 10 ^{14} ions.cm^{ -2}.s^{-1}. Three different temperature regimes in the development of radiation damage in InSb, can be distinguished after implantation of helium ions: (i) Complete amorphization after high dose, low temperature implantations. (ii) The development of extensive defect complexes, mainly dislocation loops, at intermediate temperatures. (iii) The absence of defect complexes at higher implantation temperatures and low dose rates. No bubbles or large voids--often found after heavier ion implantations--could be observed near the surface. The presence of helium in InSb--in contrast to GaP and metals --does not seem to be an important factor in the development of damage structures. Amorphous InSb started to anneal from the inside of the material, beyond the damage range. The thickness of the regrown crystalline layer increased, while the amount of dechanneling in the layer decreased, at higher temperatures. Only incomplete annealing of the crystal, implanted near room temperature, could be accomplished by isochronous heating up to the melting temperature. Roughly equivalent annealing is found after the crystal is subjected to a pulsed electron beam with a relatively low energy density (~ 0,08 J/cm^2). The results can be explained by considering the density of vacancies after the initial recombination of close Frenkel pairs. While the development of dislocation loops is prevented at low dose rates above 0,6 times T_{rm melt }, the high point defect densities reached at 77 K due to the immobility of point defects, can render the crystal completely amorphous.

van Tonder, Barend Johannes Ernst

232

Cytotoxic reaction and TNF-alpha response of macrophages to polyurethane particles.  

PubMed

Their unique mechanical and biological properties make polyurethanes (PUs) ideal materials for many implantable devices. However, uncertain long-term biostability in the human physiological environment limits their extensive clinical applications. Chronic inflammatory response associated with macrophage activation has been suggested as a prime factor; although the mechanism of macrophage activation in response to biomaterial surfaces and debris is still unknown. The overall objective of this work was to study the response of macrophages to PU materials in vitro by measuring cell viability and activity. The studies were carried out using phagocytozable-size PU particles from three types of commercially-available PUs: Pellethane 2363 80ABA (PL); Tecothane TT2065 (TC65); and Tecothane TT2085 (TC85). These polymers posess the same generic composition but differ in the length of hard and soft segments, as revealed by the FTIR and NMR studies. The results showed that PU particles affected both viability and activity of J774 macrophages. The percentage of mortality ranged from 1 to 15% with 10-100 microg ml(-1) of particles after 24 and 48 h incubation. These three types of particles induced different mortality on the macrophages. Specifically, the mortality with PL particles was 1-4% (p > 0.05), while the mortality with TC85 particles was 2-10% (p < 0.05) and 4-15% with TC65 (p < 0.05). Conversely, these particles also affected cell proliferation. Cell numbers increased by 132 and 167% after 24 and 48 h incubation, respectively, without particles, whereas the cell numbers increased only 46 and 78% with TC65, 66 and 105% with TC85, and 67 and 110% with PL in the presence of 100 microg ml(-1) of particles for the respective incubation times. PU particles also increased TNF-alpha release from macrophage. After having been incubated for 24 h with 100 microg ml(-1) particles of TC65, TC85, and PL, macrophages release TNF-alpha 7.4, 5.2, and 4.1 times more than the control. In conclusion, PU particles had cytotoxic effects on J774 macrophage at high concentrations. The order of macrophage response for three types of particles was TC65 > TC85 > PL. PU particles' effect on macrophage viability and activity depends on the concentration of particles and their chemical composition, especially on the ratio of hard to soft segments. PMID:12102593

Ma, Nan; Petit, Alain; Yahia, L'Hocine; Huk, Olga L; Tabrizian, Maryam

2002-01-01

233

Preferential heating and acceleration of alpha particles by Alfvén-cyclotron waves.  

PubMed

Preferential heating and acceleration of heavy ions in the solar wind and corona represent a long-standing theoretical problem in space physics, and are distinct experimental signatures of kinetic processes occurring in collisionless plasmas. We show that fast and slow ion-acoustic waves (IAW) and transverse waves, driven by Alfvén-cyclotron wave parametric instabilities can selectively destroy the coherent fluid motion of different ion species and, in this way lead to their differential heating and acceleration. Trapping of the more abundant protons by the fast IAW generates a proton beam with drift speed of about the Alfvén speed. Because of their larger mass, alpha particles do not become significantly trapped and start, by conservation of total ion momentum, drifting relative to the receding bulk protons. Thus the resulting core protons and the alpha particles are differentially heated via pitch-angle scattering. PMID:19518788

Araneda, J A; Maneva, Y; Marsch, E

2009-05-01

234

Status of the JET Faraday cup lost alpha particle diagnostic KA-2  

NASA Astrophysics Data System (ADS)

We review the operational status and present a few recent results from the JET lost alpha particle diagnostic KA2. We summarize the results of our study of the correlation between KA2 signals and JET magnetic fields and the correlation between KA2 signals and the scintillator-based lost alpha probe KA3. In addition we quantify the relative insensitivity of the diagnostic to intense neutron and gamma ray background radiation fields and our observations of the electro-mechanical noise in the diagnostics signals. We present recent observations carried out during the 2011 JET campaign following the installation of the beryllium ITER-like wall. These observations include lost energetic deuterons during both ion-cyclotron and neutral beam heated plasmas; in particular we have measured relatively intense fluxes of energetic particles during sawtooth plasmas.

Cecil, F. E.; Kiptily, V.; Darrow, D. S.; Murari, A.; Contributors, JET-EFDA

2012-09-01

235

THE ANGULAR DISTRIBUTION OF ALPHA PARTICLES EMITTED BY ORIENTED Np²³⁷ NUCLEI (thesis)  

Microsoft Academic Search

Neptunium-237 nuclei were aligned when a monocrystalline sample of ; neptunyl rubidium nitrate was cooled to 0.2 to 4.2 deg K. The rotatable sample ; was placed in a capsule filled with He³ gas for heat transfer. Also in tbe ; capsule were a germanium surface-barrier alpha-particle counter, a thermometer, ; and rotation indicators. The capsule was in thermal contact

S. H. Hanauer; J. W. T. Dabbs; L. D. Roberts; G. W. Parker

1960-01-01

236

Absolute number of scintillation photons in liquid xenon by alpha-particles  

SciTech Connect

This paper reports on the absolute scintillation yield obtained to be 3.26 [times] 10[sup 5] for alpha-particles of 5.303 MeV in liquid xenon. This result followed from fitting the absolute photo-electron yields measured with a VUV sensitive photomultiplier, which was used as a photo-diode, to the results of Monte-Carlo simulation.

Miyajima, M.; Sasaki, S.; Tawara, H. (National Lab. for High Energy Physics, Tsukuba, Ibaraki (Japan)); Shibamura, E. (Saitama College of Health, Kamiokubo 519, Urawa, Saitama 338 (Japan))

1992-08-01

237

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

SciTech Connect

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.

Zaider, M.

1992-01-01

238

Fusion alpha-particle losses in a high-beta rippled tokamak  

SciTech Connect

In tokamak plasmas, the confinement of energetic ions depends on the magnetic field structure. If the plasma pressure is finite, the equilibrium current (i.e., the Pfirsch-Schlüter current and diamagnetic current) flows in the plasma to maintain the magnetohydrodynamic (MHD) equilibrium. These plasma currents generate poloidal and toroidal magnetic field and alter the field structure. Moreover, if we consider the non-axisymmetry of magnetic field structures such as toroidal field (TF) ripples, the non-axisymmetric component of the equilibrium current can alter TF ripples themselves. When the plasma beta becomes high, the changes in the field structure due to the equilibrium current might affect the confinement of energetic ions significantly. We intend to clarify how these currents alter the field structure and affect the confinement of alpha particles in high-beta plasma. The MHD equilibrium is calculated using VMEC and the orbits of fusion alpha particles are followed by using the fully three-dimensional magnetic field orbit-following Monte Carlo code. In relatively low-beta plasma (e.g., the volume-averaged beta value ?2%), the changes in the magnetic field component due to the plasma current negligibly affect the confinement of alpha particles except for the Shafranov shift effect. However, for ?3%, the diamagnetic effect reduces the magnetic field strength and significantly increases alpha-particle losses. In these high-beta cases, the non-axisymmetric field component generated by the equilibrium current also increases these losses, but not as effectively as compared to the diamagnetic effect.

Bunno, M.; Nakamura, Y. [Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan)] [Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Suzuki, Y. [National Institute for Fusion Science, Toki 509-5292 (Japan)] [National Institute for Fusion Science, Toki 509-5292 (Japan); Shinohara, K.; Matsunaga, G. [Japan Atomic Energy Agency, Naka, Ibaraki 311-0193 (Japan)] [Japan Atomic Energy Agency, Naka, Ibaraki 311-0193 (Japan); Tani, K. [Nippon Advanced Technology, Naka, Ibaraki 311-0102 (Japan)] [Nippon Advanced Technology, Naka, Ibaraki 311-0102 (Japan)

2013-08-15

239

Preliminary analysis of alpha-particle effects in the fusion ignition experiment ignitex  

Microsoft Academic Search

In this paper a simple fusion experiment for the production and control do deuterium-tritium-ignited plasmas for scientific study is considered. The basic elements of fusion product alpha-particle containment is rather high even with the assumption of significant levels of toroidal asymmetries. Production of thermally stable plasmas is possible because of the low-beta thermal damping provided by electron cyclotron emission. The

R. Carrera; E. Montalvo; G. Y. Fu; G. H. Miley; L. M. Hively; M. N. Rosenbluth; S. Tamor

1990-01-01

240

Polycrystalline BN and LiF Based Semiconductor Alpha Particle and Neutron Detectors  

Microsoft Academic Search

Composite, polycrystalline, semiconductor, hexagonal BN alone or mixed with B4C or BMg2 and cubic LiF were embedded in an insulating matrix which acts as a binder and tested as alpha particle and neutron detectors. The boron containing semiconductors have the natural abundance of 10B which is ~20%. In the case of LiF is the natural content of 6Li only 7.4%.

M. Schieber; M. Roth; A. Zuck; O. Khakhan; J. Uher; V. Linhart; S. Pospisil; M. Fiederle

2006-01-01

241

Bismuth-212-labeled anti-Tac monoclonal antibody: alpha-particle-emitting radionuclides as modalities for radioimmunotherapy  

SciTech Connect

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.

Kozak, R.W.; Atcher, R.W.; Gansow, O.A.; Friedman, A.M.; Hines, J.J.; Waldmann, T.A.

1986-01-01

242

Energy and particle confinement in ITER (International Thermonuclear Experimental Reactor)  

SciTech Connect

ITER will require a level of energy ({tau}{sub E}) and particle ({tau}{sub p}) confinement sufficient for reaching ignition and extended burn of DT plasmas, with steady-state, high-Q (Q = P{sub fusion}/P{sub aux} = 5P{sub {alpha}}/P{sub aux}) operation as an ultimate goal. This translates into a required confinement capability of T{sub i}(0)n{sub DT}(0){tau}{sub E} {approximately}4--8 {times} 10{sup 21} keV{center dot}s/m{sup 3} for Q {approximately}5--{infinity} (where T{sub i}(0) is the central ion temperature, n{sub DT}(0) is the central DT fuel ion density, {tau}{sub E} is the global energy confinement time). In addition, {tau}{sub p} {sup He}/{tau}{sub E} < 10 is required to ensure that the thermal {alpha}-particle (He) accumulation (n{sub He}/n{sub e}) is less than 10% (where {tau}{sub p}{sup He} is the global thermal alpha particle containment time). Furthermore, the tritium fuel burnup fraction under nominal burn conditions must be greater than 1.5%. While the ITER Tn{tau}{sub E} requirement is about ten times the highest value achieved in JET (3), the extrapolation in plasma physics parameters is less. If {beta} (ratio of plasma kinetic pressure to magnetic pressure), {nu}* (collisionality), and {rho}/a (ratio of the ion gyroradius to the plasma minor radius) are taken as the relevant dimensionless parameters to characterize the plasma, the extrapolation from present JET performance to ITER is a factor {le}2. The ITER concept is based on the expectation that H-mode confinement can be achieved for long pulse. This paper covers the energy and particle confinement issues for ITER. 15 refs.

Uckan, N.A. (Oak Ridge National Lab., TN (USA)); Yushmanov, P.N.; Mukhovatov, V.S.; Parail, V.V.; Putvinskii, S. (Gosudarstvennyj Komitet po Ispol'zovaniyu Atomnoj Ehnergii SSSR, Moscow (USSR). Inst. Atomnoj Ehnergii); Takizuka, T.; Tsunematsu, T.; Yoshino, R. (Japan Atomic Energy Research Inst., Tokyo (Japan)); Borrass, K.; Engelmann, F.; Kardaun, O.; Lackner, K. (Max-Planck-Institut fuer Plasmaphysik,

1990-01-01

243

Use of 4.7 MeV alpha particles in elemental analysis and fusion reactor materials studies  

NASA Astrophysics Data System (ADS)

The possibilities for using 4.7 MeV alpha particles produced at the U-120 CIP Cyclotron for charged particle induced X- and gamma-ray emission applications (PIXE and PIGE, respectively) and for fast neutron radiation damage simulation are presented. The combined analysis using PIGE and PIXE methods either separately or simultaneously is an excellent means of determining the relative abundances of lighter elements with gamma-ray spectra and of heavier elements ( Z ? 16) with X-ray spectra. Some aspects of surface deformation effects by neutrons were simulated by means of medium-energy helium ions. An investigation of three types of commercial stainless steel (Romanian W 4016, Soviet 12KH18N10T and Japanese W 4541) was started using 3.0 [1], 4.7 and 6.8 MeV helium ions. The main post-irradiation effects observed are discussed.

Constantinescu, B.; Dima, S.; Florescu, V.; Ivanov, E. A.; Plo?tinaru, D.; Sârbu, C.

1986-07-01

244

The local skin dose conversion coefficients of electrons, protons and alpha particles calculated using the Geant4 code.  

PubMed

The skin tissue-equivalent slab reported in the International Commission on Radiological Protection (ICRP) Publication 116 to calculate the localised skin dose conversion coefficients (LSDCCs) was adopted into the Monte Carlo transport code Geant4. The Geant4 code was then utilised for computation of LSDCCs due to a circular parallel beam of monoenergetic electrons, protons and alpha particles <10 MeV. The computed LSDCCs for both electrons and alpha particles are found to be in good agreement with the results using the MCNPX code of ICRP 116 data. The present work thus validates the LSDCC values for both electrons and alpha particles using the Geant4 code. PMID:23610196

Zhang, Bintuan; Dang, Bingrong; Wang, Zhuanzi; Wei, Wei; Li, Wenjian

2013-10-01

245

First evidence of collective alpha particle effect on TAE modes in the TFTR D-T experiment  

SciTech Connect

The alpha particle effect on the excitation of toroidal Alfven eigenmodes (TAE) was investigated in deuterium-tritium (d-t) plasmas in the Tokamak Fusion Test Reactor (TFTR). RF power was used to position the plasma near the instability threshold, and the alpha particle effect was inferred from the reduction of RF power threshold for TAE instability in d-t plasmas. Initial calculations indicate that the alpha particles contribute 10--30% of the total drive in a d-t plasma with 3 MW of peak fusion power.

Wong, K.L.; Schmidt, G.; Batha, S.H. [and others

1995-08-01

246

alpha-Particle and gamma-ray spectrometry of a plutonium solution for impurity determination.  

PubMed

A highly enriched (240)Pu solution was measured by alpha-particle and gamma-ray spectrometry to determine other radionuclides present in the material as impurities. Low activities of (238)Pu, (241)Am, (243)Cm and (244)Cm were determined by measuring thin sources, made from the original solution, in a high-resolution alpha-particle spectrometer. The sources were prepared by evaporating the plutonium solution on quartz plates in a vacuum chamber. From the ingrowth of (241)Am in the original solution, the amount of (241)Pu could be calculated. After radiochemical separation of (241)Am, the plutonium was measured by high-efficiency alpha-particle spectrometry to determine the amount of (238)Pu. The enriched (240)Pu material was also measured by high-resolution gamma-ray spectrometry, using two different HPGe detectors to determine the impurities of (239)Pu and (241)Am. The preparation of the sources and the measurement methods are described and discussed. The measured impurities, given in % of the (240)Pu activity, are compared with the values on the certificate. PMID:18356064

Sibbens, G; Altzitzoglou, T; Benedik, L; Pommé, S; Van Ammel, R

2008-01-01

247

Electrostatic ion-acoustic-like instabilities in the solar wind with a backstreaming alpha particle beam  

NASA Astrophysics Data System (ADS)

Nonlinear electrostatic instabilities have been shown to occur frequently and under very different conditions in a plasma with two ion beams such as the fast solar wind. These instabilities can be triggered when the phase velocity of electrostatic ion-acoustic propagating forward and backward relative to the interplanetary magnetic field overlap, due to the presence of a finite amplitude of circularly polarized wave. The instabilities can be triggered by waves supported by the same ion-component, or by waves supported by different ion-components. By assuming a beam of alpha particles moving backward relative to the external magnetic field, as observed in some events in the fast solar wind, it is shown that a very small negative drift velocity of the alpha particle beam relative to the core plasma - a few per cent of the local Alfvén velocity - can trigger a very rich variety of nonlinear electrostatic acoustic-like instabilities. Their growth rates can be rather large and they persist for a wide range of ion temperatures, provided that the alpha particle backstreaming beams, have much larger drift velocities.

Gomberoff, L.; Gomberoff, K.; Deutsch, A.

2009-12-01

248

Phagocytosis of titanium particles and necrosis in TNF-alpha-resistant mouse sarcoma L929 cells.  

PubMed

In the oral cavity, titanium is an excellent biocompatible material. However, it is reported that high ratios of intracellular titanium particles can cause cell apoptosis or necrosis by as-yet unknown mechanisms. The purpose of this study was to investigate the response of tumor necrosis factor alpha (TNF-alpha)-resistant L929 fibroblasts to titanium particles. Cells were cultured in Eagle's medium supplemented with fetal bovine serum and L-glutamine. Titanium particle sizes were less than 9 micro. Cytotoxicity was assayed by a cell counting kit, trypan blue dye exclusion test and lactate dehydrogenase (LDH) leakage. The production of reactive oxygen species (ROS) was detected by a confocal laser scanning microscope (CLSM) using dichlorofluorescein diacetate as a fluorescent probe. Morphology was viewed by a CLSM and with an X-ray microanalyser (XMA). When titanium particles were added to cells, the viability decreased to around 50% at a particle concentration of 2.0%. The number of dead cells and LDH activity in the culture media increased significantly between 1 and 2 days. However, formation of active oxygen species did not occur, since no dichlorofluorescein fluorescence was observed. A scanning electron photomicrograph (SEM) revealed a large number of particles covering or adhering to cellular components in lysed cells compared with flattened control cells attached to the substrate. The XMA showed that the titanium accumulation was coincident with the deformed cell shape. The CLSM also confirmed that particles were within the cells. From these results it was concluded that titanium particles ingested in large quantities into the cell induced necrosis by a pathway other than by producing ROS. PMID:12537961

Osano, E; Kishi, J; Takahashi, Y

2003-02-01

249

1-15 MeV proton and alpha particle radiation effects on GaAs quantum well light emitting diodes [and QWIPs  

Microsoft Academic Search

Permanent radiation damage was investigated in GaAs quantum well light emitting diodes (QW LEDs) due to protons and alpha particles in the 1-15 MeV energy range. At room temperature, these devices under forward bias emit infrared radiation at 980 mm. Current-voltage (I-V) and light emission characteristics of these devices were studied as a function of fluence and energy of protons

S. M. Khanna; D. Estan; H. C. Liu; M. Gao; M. Buchanan; A. J. SpringThorpe

2000-01-01

250

Effects of heavy particles at low energies  

Microsoft Academic Search

The low-energy effects of heavy particles are discussed in the context of the quantum field theories with local gauge invariance and in general. The evaluation of the one-loop heavy particle contribution to a low-energy relation valid in the SU(5)grand unified theory is presented. The calculation shows that heavy particles decouple (i.e. have negligible effect) in agreement with the decoupling theorem

A. Sokorac

1980-01-01

251

Very High Efficiency, Miniaturized, Long-Lived Alpha Particle Power Source Using Diamond Devices for Extreme Space Environments  

NASA Technical Reports Server (NTRS)

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.

Kolawa, Elizabeth A. (Inventor); Patel, Jagdishbhai U. (Inventor); Fleurial, Jean-Pierre (Inventor)

2004-01-01

252

High-energy K{alpha} radiography using high-intensity, short-pulse lasers  

SciTech Connect

The characteristics of 22-40 keV K{alpha} x-ray sources are measured. These high-energy sources are produced by 100 TW and petawatt high-intensity lasers and will be used to develop and implement workable radiography solutions to probe high-Z and dense materials for the high-energy density experiments. The measurements show that the K{alpha} source size from a simple foil target is larger than 60 {mu}m, too large for most radiography applications. The total K{alpha} yield is independent of target thicknesses, verifying that refluxing plays a major role in photon generation. Smaller radiating volumes emit brighter K{alpha} radiation. One-dimensional radiography experiments using small-edge-on foils resolved 10 {mu}m features with high contrast. Experiments were performed to test a variety of small volume two-dimensional point sources such as cones, wires, and embedded wires, measured photon yields, and compared the measurements with predictions from hybrid-particle-in-cell simulations. In addition to high-energy, high-resolution backlighters, future experiments will also need imaging detectors and diagnostic tools that are workable in the high-energy range. An initial look at some of these detector issues is also presented.

Park, H.-S.; Chung, H.-K.; Izumi, N.; Key, M.H.; King, J.A.; Koch, J.A.; Landen, O.L.; Patel, P.K.; Price, D.F.; Remington, B.A.; Robey, H.F.; Snavely, R.A.; Tabak, M.; Town, R.P.J.; Wickersham, J.E. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Chambers, D.M.; Eagleton, R.; Goldsack, T. [Atomic Weapons Establishment, Aldermaston, Reading, RG7 4PR (United Kingdom); Clarke, R.J.; Heathcote, R. [Rutherford Appleton Laboratory, Chilton, Didcot, OX11 0QX (United Kingdom)] (and others)

2006-05-15

253

The CARBON-12(ALPHA, GAMMA)OXYGEN-16 Reaction at Low Energies  

NASA Astrophysics Data System (ADS)

Angular distributions for the 12C(alpha,gamma)^ {16}O reaction at each of 8 center-of -mass energies from 2.0 to 3.1 MeV were measured. A pulsed alpha-particle beam of several and thin enriched 12C foil targets were used. Gamma rays were detected in singles mode using an advanced NaI spectrometer with active cosmic ray discrimination, neutron rejection through shielding and electronic discrimination, and high gamma-ray detection efficiency. The availability of complete angular distribution measurements allows a model-independent analysis of the cross section in terms of electric dipole and quadrupole amplitudes, and their relative phase, at each energy. These separated multipole amplitudes have been used in a K-matrix analysis to extrapolate the E2 cross section to stellar energies.

Trice, James Hampton

254

Alpha-particle autoradiography in CR-39: The determination of the microdistribution of activity and trace element analysis  

NASA Astrophysics Data System (ADS)

New and elaborate techniques for alpha-particle autoradiography of thick specimens based on the plastic nuclear track detector CR-39 have been developed. These permit a full analysis of both trace element and microdistribution of alpha-active nuclides present. The important features of the techniques are: (1) reliable low level counting down to 10 -15Ci g -1, (2) high resolution alpha-particle spectroscopy in CR-39, (3) determination of the absolute abundance of alpha active nuclides present in the specimen, (4) determination of the distribution of emission with height up to 30 microns above the surface of the autoradiograph, (5) the local determination of the radon diffusion coefficient in the specimen which is needed to calculate the activity levels of 222Rn and daughter nuclei, (6) the analysis of small and large clusters of alpha-particle activity recorded on the autoradiograph. These techniques are briefly discussed.

Peter Fews, A.; Henshaw, Denis L.

255

Channel coupling and exchange of an alpha-particle cluster in deuteron scattering on {sup 6}Li nuclei  

SciTech Connect

Existing experimental data on elastic and inelastic deuteron scattering on {sup 6}Li nuclei in the energy range from 8 to 50 MeV were analyzed within the approach of coupled reaction channels. The coupling of elastic scattering and inelastic scattering accompanied by the transition to the 3{sup +} state at E{sub x} 2.186 MeV and the mechanism involving the exchange of an alpha-particle cluster were taken into account in respective calculations. The phenomenological potentials obtained from the present analysis describe well experimental angular distributions at all energies and in full angular ranges. The depths of the real and imaginary parts of the potentials in question depend smoothly on energy at fixed values of the remaining parameters. The energy dependence of relevant volume integrals agrees well with similar data for the p + {sup 6}Li, {alpha} + {sup 6}Li, and {sup 12}C + {sup 12}C systems and with the predictions of a microscopic theory.

Sakuta, S. B., E-mail: sakuta@dni.polyn.kiae.su [Russian Research Centre Kurchatov Institute (Russian Federation); Burtebaev, N. [National Nuclear Center of the Republic Kazakhstan, Institute of Nuclear Physics (Kazakhstan); Artemov, S. V.; Yarmukhamedov, R. [National Nuclear Center of the Republic Uzbekistan, Institute of Nuclear Physics (Uzbekistan)

2012-07-15

256

PGC-1{alpha}: a key regulator of energy metabolism  

NSDL National Science Digital Library

Peroxisome proliferator-activated receptor-{gamma} coactivator (PGC)-1{alpha} is a member of a family of transcription coactivators that plays a central role in the regulation of cellular energy metabolism. This makes it an inviting target for pharmacological intervention in the treatment of obesity and Type 2 diabetes.

Huiyun Liang (University of Texas Health Science Center Department of Cellular and Structural Biology, Barshop Institute for Longevity and Aging Studies); Walter F. Ward (University of Texas Health Science Center Barshop Institute for Longevity and Aging Studies)

2006-12-01

257

Gamma-H2AX foci in cells exposed to a mixed beam of X-rays and alpha particles  

PubMed Central

Background Little is known about the cellular effects of exposure to mixed beams of high and low linear energy transfer radiation. So far, the effects of combined exposures have mainly been assessed with clonogenic survival or cytogenetic methods, and the results are contradictory. The gamma-H2AX assay has up to now not been applied in this context, and it is a promising tool for investigating the early cellular response to mixed beam irradiation. Purpose To determine the dose response and repair kinetics of gamma-H2AX ionizing radiation-induced foci in VH10 human fibroblasts exposed to mixed beams of 241Am alpha particles and X-rays. Results VH10 human fibroblasts were irradiated with each radiation type individually or both in combination at 37°C. Foci were scored for repair kinetics 0.5, 1, 3 and 24 h after irradiation (one dose per irradiation type), and for dose response at the 1 h time point. The dose response effect of mixed beam was additive, and the relative biological effectiveness for alpha particles (as compared to X-rays) was of 0.76 ± 0.52 for the total number of foci, and 2.54 ± 1.11 for large foci. The repair kinetics for total number of foci in cells exposed to mixed beam irradiation was intermediate to that of cells exposed to alpha particles and X-rays. However, for mixed beam-irradiated cells the frequency and area of large foci were initially lower than predicted and increased during the first 3 hours of repair (while the predicted number and area did not). Conclusions The repair kinetics of large foci after mixed beam exposure was significantly different from predicted based on the effect of the single dose components. The formation of large foci was delayed and they did not reach their maximum area until 1 h after irradiation. We hypothesize that the presence of low X-ray-induced damage engages the DNA repair machinery leading to a delayed DNA damage response to the more complex DNA damage induced by alpha particles.

2012-01-01

258

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

National Technical Information Service (NTIS)

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 inac...

M. Zaider

1992-01-01

259

Analysis of neutron emission spectra for 30 50 MeV alpha-particle induced reactions in thick targets  

Microsoft Academic Search

Comparisons of calculated neutron yield distributions from alpha-particle induced reactions on thick targets are made with measured data to analyze the initial reaction process in the framework of the exciton (hybrid) model code ALICE91 (M. Blann, Lawrence Livermore National Laboratory Report UCID 19614, 1982). We have considered two reaction mechanisms: dissolution of the alpha in the nuclear field, and preequilibrium

D. Dhar; S. N. Roy; Maitreyee Nandy; P. K. Sarkar

2003-01-01

260

Microdosimetry of alpha particles for simple and 3D voxelised geometries using MCNPX and Geant4 Monte Carlo codes.  

PubMed

Microdosimetry using Monte Carlo simulation is a suitable technique to describe the stochastic nature of energy deposition by alpha particle at cellular level. Because of its short range, the energy imparted by this particle to the targets is highly non-uniform. Thus, to achieve accurate dosimetric results, the modelling of the geometry should be as realistic as possible. The objectives of the present study were to validate the use of the MCNPX and Geant4 Monte Carlo codes for microdosimetric studies using simple and three-dimensional voxelised geometry and to study their limit of validity in this last case. To that aim, the specific energy (z) deposited in the cell nucleus, the single-hit density of specific energy f(1)(z) and the mean-specific energy were calculated. Results show a good agreement when compared with the literature using simple geometry. The maximum percentage difference found is <6 %. For voxelised phantom, the study of the voxel size highlighted that the shape of the curve f(1)(z) obtained with MCNPX for <1 µm voxel size presents a significant difference with the shape of non-voxelised geometry. When using Geant4, little differences are observed whatever the voxel size is. Below 1 µm, the use of Geant4 is required. However, the calculation time is 10 times higher with Geant4 than MCNPX code in the same conditions. PMID:21993801

Elbast, M; Saudo, A; Franck, D; Petitot, F; Desbrée, A

2012-07-01

261

ENERGY IDSTRIBUTION FO $alpha$RECOIL NUCLEI IN FORMVAR  

Microsoft Academic Search

BS>The energy distribution curve of the recoil nuclei from Po²¹² ; alpha decay (energy of origin 169 kev) after their passage through formvar films ; between 1.4 and 7.0 mu g\\/cm² thick was ascertained with the help of an ; electronic transmission time measurement. The spectra showed for the thin films ; a strongly asymmetric form, wiuch could be explained

Zahn

1963-01-01

262

Dependence of scintillation characteristics in the CsI(Tl) crystal on Tl* concentrations under electron and alpha particles excitations  

Microsoft Academic Search

This paper reports the emission spectra, pulse heights and decay curves of CsI(Tl) crystals with a Tl* concentration ranging from 10-6 mol to 10-2 mol, under electron and alpha particle excitations. Larger pulse heights from the crystals with Tl+concentration of more than 10-3 mol were observed for a higher ionization density of alpha particle excitation, compared with those of electron

M. M. Hamadaa; F. E. Costa; M. C. C. Pereira; S. Kubota

2000-01-01

263

Dependence of scintillation characteristics in the CsI(Tl) crystal on Tl+ concentrations under electron and alpha particles excitations  

Microsoft Academic Search

This paper reports the emission spectra, pulse heights, and decay curves of CsI(TI) crystals with a Tl+ concentration ranging from 10-6 to 10-2 mol under electron and alpha particle excitations. Larger pulse heights from the crystals with Tl+ concentration of more than 10-3 mol were observed for a higher ionization density of alpha particle excitation compared with those of electron

Margarida M. Hamada; Fabio E. Costa; Maria C. C. Pereira; Shinzou Kubota

2001-01-01

264

Deep level defects and carrier removal due to proton and alpha particle irradiation of InP  

Microsoft Academic Search

Deep level transient spectroscopy and capacitance voltage measurements of the defect introduction rates and carrier removal rates for 2 MeV proton and 2 MeV alpha particle irradiations in p-type InP have been performed. The carrier removal rate for 2 MeV protons was 6500 cm?1 and for 2 MeV alpha particles was 73 400 cm?1, or 12 times higher. The defect

George C. Rybicki; Christian A. Zorman

1994-01-01

265

Influence of cell position relative to planar alpha-particle sources on survival and preneoplastic transformation of primary rat tracheal epithelial cells  

SciTech Connect

Rat tracheal epithelial cells exposed directly on planar {sup 210}Po sources exhibited exponential cell killing; however, no significant increase in induction of preneoplastic transformation was observed over a range of {alpha}-particle fluences (0.017-0.050 {mu}m{sup {minus}2}). In contrast, up to 10-fold increases in frequencies of preneoplastic transformants, above control levels, were observed after exposure of rat tracheal epithelial cells to similar {alpha}-particle fluences on {sup 238}Pu and {sup 241}Am sources. Two alternative hypotheses are evaluated as an explanation for this apparent difference in the biological effect of {alpha} particles emitted from different sources: (a) possible interactions between effects produced by {alpha} particles and by low-energy photons, which occur with {sup 238}Pu and {sup 241}Am but not with {sup 210}Po; and (b) the influence of spatial relationships between exposed cells and the surface of the planar source. The data suggest that the cell-to-source spatial relationships affect both survival and transformation markedly. 29 refs., 4 figs., 6 tabs.

Terzaghi-Howe, M.; Turner, J.E. [Oak Ridge National Laboratory, TN (United States); Ford, J.R. [Medical Research Council, Oxon (United Kingdom)

1996-04-01

266

Induction of a bystander mutagenic effect of alpha particles in mammalian cells  

NASA Technical Reports Server (NTRS)

Ever since the discovery of X-rays was made by Rontgen more than a hundred years ago, it has always been accepted that the deleterious effects of ionizing radiation such as mutation and carcinogenesis are attributable mainly to direct damage to DNA. Although evidence based on microdosimetric estimation in support of a bystander effect appears to be consistent, direct proof of such extranuclear/extracellular effects are limited. Using a precision charged particle microbeam, we show here that irradiation of 20% of randomly selected A(L) cells with 20 alpha particles each results in a mutant fraction that is 3-fold higher than expected, assuming no bystander modulation effect. Furthermore, analysis by multiplex PCR shows that the types of mutants induced are significantly different from those of spontaneous origin. Pretreatment of cells with the radical scavenger DMSO had no effect on the mutagenic incidence. In contrast, cells pretreated with a 40 microM dose of lindane, which inhibits cell-cell communication, significantly decreased the mutant yield. The doses of DMSO and lindane used in these experiments are nontoxic and nonmutagenic. We further examined the mutagenic yield when 5-10% of randomly selected cells were irradiated with 20 alpha particles each. Results showed, likewise, a higher mutant yield than expected assuming no bystander effects. Our studies provide clear evidence that irradiated cells can induce a bystander mutagenic response in neighboring cells not directly traversed by alpha particles and that cell-cell communication process play a critical role in mediating the bystander phenomenon.

Zhou, H.; Randers-Pehrson, G.; Waldren, C. A.; Vannais, D.; Hall, E. J.; Hei, T. K.; Chatterjee, A. (Principal Investigator)

2000-01-01

267

Malignant transformation of human bronchial epithelial cells by radon-simulated alpha-particles.  

PubMed

Epidemiological studies have shown that inhalation of radon is associated with an increased risk for bronchogenic carcinoma in uranium miners. These alpha-emitting radon daughters also represent the largest component of background radiation to the general public. In the present study, the oncogenic transforming effects of single versus multiple doses of radon-simulated alpha-particles were examined using human papillomavirus-immortalized human bronchial epithelial cells. Endpoints such as growth kinetics, resistance to serum and 12-O-tetradecanoylphorbol-13-acetate-induced terminal differentiation, anchorage-independent growth and tumorigenicity in nude mice were used to assess the various stages of transformation in the bronchial epithelial cells. We show here, for the first time, that immortalized human cells in culture can be malignantly transformed by a single 30 cGy dose of alpha-particles. Transformed cells produced progressively growing subcutaneous tumors upon inoculation into athymic nude mice. Immunofluorescent staining of keratin and isozyme analysis of the cell lines subsequently generated from these tumors indicated that the cells were of human epithelial origin. Analysis of genomic DNA from the tumorigenic cell lines using PCR amplification and restriction enzyme analysis demonstrated no point mutation at either codon 12/13 or 61 in any of the ras oncogenes examined (K-, N- and H-ras). This system provides an opportunity to study the cellular and molecular changes at the various stages in radiation carcinogenesis involving human cells. PMID:8118924

Hei, T K; Piao, C Q; Willey, J C; Thomas, S; Hall, E J

1994-03-01

268

Cytogenetic and molecular genetic analysis of tumorigenic human bronchial epithelial cells induced by radon alpha particles.  

PubMed

To establish a cell culture model for lung carcinogenesis, independent populations of the human papillomavirus 18-immortalized human bronchial epithelial cell line BEP2D were treated with high linear energy transfer radon-simulated alpha-particles, expanded and xenotransplanted into Nu/Nu mice. Six independent cell lines were established from tumors that developed from three separate radiation treatments as follows: treatment (Tx) 1 (30 cGy--two doses), H2BT, Tx 2 (30 cGy--single dose), R30T1L, R30T2 and R30T3L, Tx 3 (30 cGy--single dose), H1ATN and H1ATBA1. Cytogenetic analysis revealed common changes in all tumor lines: loss of the Y chromosome (ch), one of three copies of ch8, one of three copies of ch14, and one of two copies of ch4p16-pter and ch11p15-pter. Analysis of polymerase chain reaction-amplified short tandem repeats of informative loci confirmed the loss of chY in all lines and loss of heterozygosity (LOH) at eight loci spanning the length of ch8 in all lines from Tx's 1 and 2. Our data support previous studies indicating the presence of tumor suppressor genes on ch8. LOH also was confirmed on ch14 at locus D14S306 in all cell lines from Tx 2 and in one of two lines from Tx 3. This region, 14q12-q13, may contain changes in one of the five known somatostatin receptor genes (SSTR1). No LOH was detected at any of the informative loci tested for on ch4 or ch11. PMID:9214610

Weaver, D A; Hei, T K; Hukku, B; McRaven, J A; Willey, J C

1997-06-01

269

Role of channel coupling and deuteron-exchange mechanisms in anomalous alpha-particle scattering on {sup 6}Li  

SciTech Connect

A unified description of existing experimental data on alpha-particle scattering by {sup 6}Li over the broad energy range from 18 to 166 MeV was obtained with allowance for channel-coupling effects and mechanisms involving the exchange of a deuteron cluster. Angular distributions were analyzed on the basis of the optical model and the coupled reaction channels method. It was shown that the inclusion of channel coupling and the contributions from one- and two-step exchangemechanismsmakes it possible to describe special features of the behavior of differential cross sections for both elastic and inelastic scattering in a full energy range. Optimum values found for the parameters of optical potentials agree with the parameters of the global potential proposed previously for nuclei in the mass region A > 12.

Sakuta, S. B., E-mail: sakuta@dni.polyn.kiae.s [Russian Research Centre Kurchatov Institute (Russian Federation); Artemov, S.V. [Uzbek Academy of Sciences, Institute of Nuclear Physics (Uzbekistan); Burtebaev, N.; Kerimkulov, Zh. [National Nuclear Center of the Republic of Kazakhstan, Institute of Nuclear Physics (Kazakhstan); Novatsky, B. G.; Stepanov, D.N. [Russian Research Centre Kurchatov Institute (Russian Federation); Yarmukhamedov, R. [Uzbek Academy of Sciences, Institute of Nuclear Physics (Uzbekistan)

2009-12-15

270

Secondary electron yields from the bombardment of Al 2O 3 by protons, deuterons, alpha-particles and positively charged hydrogen molecules at energies in the range of 10 to 80 MeV  

Microsoft Academic Search

Measurements of the electron coefficients of Al2O3 surfaces bombarded by protons, deuterons, alphas and single ionized hydrogen molecules are presented. The 76?-cyclotron of the Crocker Nuclear Laboratory of the University of California was used to accelerate those ions in the range of 10 to 80 MeV. The data has been compared to theoretical predictions and to previous experimental work. For

C. M. Castaneda; L. McGarry; C. Cahill; T. Essert

1997-01-01

271

High resolution alpha particle detection using 4H-SiC epitaxial layers: Fabrication, characterization, and noise analysis  

NASA Astrophysics Data System (ADS)

In this article we report the fabrication and characterization of large area, room-temperature operable and very high resolution Schottky barrier detectors for alpha particles using 20 ?m thick n-type 4H-SiC epitaxial layers. Schottky barriers were fabricated by depositing circular nickel contacts of ~11 mm2 area on the 4H-SiC epitaxial layers. Room temperature current-voltage measurements revealed very high Schottky barrier height of 1.6 eV and extremely low leakage current of 3.5 pA at an operating reverse bias of -90 V. We also report an energy resolution of 0.29%, which is the best resolution obtained so far for uncollimated 5.48 MeV alpha particles in 4H-SiC epitaxial detectors with such a large area. Very low micropipe density (<1 cm-2) and low effective doping concentration (2.4×1014 cm-3) in the epilayer helped to achieve a high resolution even with the large detector area and a broad source. A diffusion length of ~18.6 ?m for holes has been determined in these detectors following a calculation based on a drift-diffusion model. A noise analysis in terms of equivalent noise charge revealed that the white series noise due to the detector capacitance has substantial effect on their spectroscopic performance.

Chaudhuri, Sandeep K.; Zavalla, Kelvin J.; Mandal, Krishna C.

2013-11-01

272

High energy-resolution electron energy-loss spectroscopy study of the electronic structures of Li- and Mg-doped alpha-rhombohedral boron.  

PubMed

Electron-doped alpha-rhombohedral boron (alpha-r-B) crystals were synthesized by Li- and Mg-dopings. The doped alpha-r-B particles showed a shiny metallic colour, though non-doped alpha-r-B crystals showed a dark red colour (red boron). The electronic structures of doped alpha-r-B single crystals were examined by a high energy-resolution electron energy-loss spectroscopy microscope. Boron 1s electron-excitation spectra, which show the density of states of the conduction bands, of Li-doped alpha-r-B showed a chemical shift toward a smaller binding-energy side, indicating a charge transfer from the doped atoms to alpha-r-B. These spectra also showed a sharp intensity increase at the onset with a width of an energy resolution of the experiment. The sharp intensity increase may be assigned to a Fermi edge produced by the electron doping. The spectra of Mg-doped alpha-r-B showed a chemical shift indicating an electron doping, but did not show the presence of a Fermi edge. PMID:15582971

Terauchi, Masami; Oguri, Atsushi; Kimura, Kaoru; Fujiwara, Akihiko

2004-01-01

273

Low energy charged particles at Saturn  

SciTech Connect

The Low Energy Charged Particle (LECP) experiment measures charged particles with energies greater than about 20 kiloelectron volts and can provide information about the chemical composition of the particles. In addition, the instrument scans through a full 360 deg and is thus the only detector on board Voyager capable of determining actual flow anisotropies of charged particles. An overview of representative particle data from the Saturn encounter is shown in a graph. The LECP instrumentation was able to measure perturbations in the corotational flow of plasma caused by the relative motion of Titan. The composition of the Saturnian magnetosphere is particularly interesting. At energies sampled by the LECP detectors, nearly all the ions are protons. The proton to helium ratio can be as large as 5000:1 and is larger than that seen in any other magnetosphere. The large ratio suggests that plasma within Saturn's magnetosphere does not originate within Saturn's magnetosphere.

Carbary, J.F.; Krimigis, S.M.

1981-04-01

274

Orbit-averaged drift kinetic equation for the study of alpha-particle transport in tokamaks  

SciTech Connect

Neoclassical transport of minority suprathermal alpha particles is investigated. This paper departs from previous investigations in that (a) the banana-width ordering parameter {rho}{sub {theta}}/L is not formally restricted to be a small parameter and (b) a linearized collision operator that retains the effects of pitch-angle scattering, electron and ion drag, and speed diffusion is used. A step model approximation for the large-aspect-ratio, circular-cross-section tokamak magnetic field is adopted to simplify the orbit-averaging procedure. Assuming that the suprathermal alphas are in the banana regime, an asymptotic expansion in {tau}{sub B}/{tau}{sub S} {much lt} l is carried out.

Sager, G.T.; Miley, G.H. (Illinois Univ., Urbana, IL (United States). Fusion Studies Lab.); Burrell, K.H. (General Atomics Co., San Diego, CA (United States))

1990-11-01

275

Étude de la réaction (alpha, 2alpha) sur 12C par particules alpha de 100 MeV  

Microsoft Academic Search

The reaction 12C(alpha, 2alpha)8Be is observed by using 90 MeV alpha particles in ionographic matter. The excitation energy spectrum of the residual nucleus 8Be clearly shows the 0+, 2+, 4+ states. The spectrum calculated with the cluster-model wave function for 12C is compared with the observed data. The energy spectrum of the energetic outgoing alpha-particle is calculated and compared with

C. Jacquot; Y. Sakamoto; M. Jung; C. Baixeras-Aiguabella; L. Girardin; H. Braun

1970-01-01

276

An analysis of 25Al energy levels observed in the 28Si(p,alpha)25Al reaction  

SciTech Connect

The level structure of {sup 25}Al has been studied at the ORNL Holifield Radioactive Ion Beam Facility (HRIBF) by measuring the angular and energy distributions of alpha particles from the {sup 28}Si(p,{alpha}){sup 25}Al reaction. Proton beams ({approx}10 nA) at laboratory energies of 40- and 42-MeV were generated by the 25 MV tandem accelerator and bombarded a natural silicon target (50 {micro}g/cm{sup 2}). Alpha particles were detected and identified in the Silicon Detector Array (SIDAR) in the 'telescope' configuration [1]. Eighteen levels have been observed and spins for several have been constrained through a distorted-wave Born approximation (DWBA) analysis of the angular distributions.

Pittman, S. T. [University of Tennessee, Knoxville (UTK); Bardayan, Daniel W [ORNL; Blackmon, Jeff C [ORNL; Kozub, R. L. [Tennessee Technological University; Smith, Michael Scott [ORNL

2009-01-01

277

Helium measurements simulating alpha-particle diagnostics by the pellet charge exchange in Large Helical Device  

NASA Astrophysics Data System (ADS)

It is very important to investigate the confinement of ? particle, which is produced by the nuclear reaction in ITER or fusion reactor. The pellet charge exchange measurement (PCX) is one of the most powerful methods because it can directly provide the profile of ? particle energy spectra in plasma. In Large Helical Device (LHD), it is possible to confine the high energetic particle (helium) accelerated by using the ion cyclotron resonance heating (ICH). Therefore it is possible to perform the simulation experiment of ? particle diagnostic in LHD.

Ozaki, T.; Goncharov, P.; Veschev, E.; Sudo, S.; Tamura, N.

2008-03-01

278

Differential Velocity between Solar Wind Protons and Alpha Particles in Pressure Balance Structures  

NASA Technical Reports Server (NTRS)

Pressure balance structures (PBSs) are a common high-plasma beta feature in high-latitude, high-speed solar wind. They have been proposed as remnants of coronal plumes. If true, they should reflect the observation that plumes are rooted in unipolar magnetic flux concentrations in the photosphere and are heated as oppositely directed flux is advected into and reconnects with the flux concentration. A minimum variance analysis (MVA) of magnetic discontinuities in PBSs showed there is a larger proportion of tangential discontinuities than in the surrounding high-speed wind, supporting the hypothesis that plasmoids or extended current sheets are formed during reconnection at the base of plumes. To further evaluate the character of magnetic field discontinuities in PBSs, differential streaming between alpha particles and protons is analyzed here for the same sample of PBSs used in the MVA. Alpha particles in high-speed wind generally have a higher radial flow speed than protons. However, if the magnetic field is folded back on itself, as in a large-amplitude Alfven wave, alpha particles will locally have a radial flow speed less than protons. This characteristic is used here to distinguish between folded back magnetic fields (which would contain rotational discontinuities) and tangential discontinuities using Ulysses high-latitude, high-speed solar wind data. The analysis indicates that almost all reversals in the radial magnetic field in PBSs are folded back field lines. This is found to also be true outside PBSs, supporting existing results for typical high-speed, high-latitude wind. There remains a small number of cases that appear not to be folds in the magnetic field and which may be flux tubes with both ends rooted in the Sun. The distinct difference in MVA results inside and outside PBSs remains unexplained.

Yamauchi, Yohei; Suess, Steven T.; Steinberg, John T.; Sakurai, Takashi

2004-01-01

279

Differential Velocity Between Solar Wind Protons and Alpha Particles in Pressure Balance Structures  

NASA Technical Reports Server (NTRS)

Pressure balance structures (PBSs) are a common high plasma beta feature in high latitude, high speed solar wind. They have been proposed as remnants of coronal plumes. If true, they should reflect the observation that plumes are rooted in unipolar magnetic flux concentrations in the photosphere and are heated as oppositely directed flux is advected into and reconnects with the flux concentration. A minimum variance analysis (MVA) of magnetic discontinuities in PBSs showed there is a larger proportion of tangential discontinuities than in the surrounding high speed wind, supporting the hypothesis that plasmoids or extended current sheets are formed during reconnection at the base of plumes. To further evaluate the character of magnetic field discontinuities in PBSs, differential streaming between alpha particles and protons is analyzed here for the same sample of PBSs used in the MVA. Alpha particles in high speed wind generally have a higher radial flow speed than protons. However, if the magnetic field is folded back on itself, as in a large amplitude Alfven wave, alpha particles will locally have a radial flow speed less than protons. This characteristic is used here to distinguish between folded back magnetic fields (which would contain rotational discontinuities) and tangential discontinuities using Ulysses high latitude, high speed solar wind data. The analysis indicates that almost all reversals in the radial magnetic field in PBSs are folded back field lines. This is found to also be true outside PBSs, supporting existing results for typical high speed, high latitude wind. There remains a small number of cases that appear not to be folds in the magnetic field and which may be flux tubes with both ends rooted in the Sun. The distinct difference in MVA results inside and outside PBSs remains unexplained.

Yamauchi, Y.; Suess, S. T.; Steinberg, J. T.; Sakurai, T.

2003-01-01

280

High-energy laser-particle interaction  

Microsoft Academic Search

This project investigates the spectral signatures associated with high-energy laser-particle interactions. Our main research objective is to improve predictive modeling of laser interaction with atmospheric particles by systematically studying the emissions from atmospheric aerosols interacting with high-energy lasers as a function of laser wavelength and intensity. Development of the theoretical formalism to interpret the results is an important part of

D. W. Pack

1991-01-01

281

The comparative effects of gamma radiation and in situ alpha particles on five strong-base anion exchange resins  

SciTech Connect

The effects of external gamma radiation and in situ alpha particles were measured on a recently available, macroporous, strong-base polyvinylpyridine resin and on four strong-base polystyrene anion exchange resins. Each resin was irradiated in 7 M nitric acid to 1--10 megaGray of gamma radiation from external {sup 60}Co, or to 5--14 megaGray of alpha particles from sorbed {sup 238}Pu. Each irradiated resin was measured for changes in dry weight, wet volume, weak-base and strong-base chloride exchange capacities, and exchange capacities for Pu(4) from nitric acid. Alpha-induced resin damage was significantly less than that caused by an equivalent dose of gamma radiation. The polyvinylpyridine resin offers the greatest resistance to damage from gamma radiation and from alpha particles. 5 refs., 1 figs. 5 tabs.

Marsh, S.F.

1991-01-01

282

Test Procedure for Gross Alpha Particle Activity in Drinking Water: Interlaboratory Collaborative Study.  

National Technical Information Service (NTIS)

Gross alpha activity values were calculated with four different alpha emitting radionuclide standard counting efficiencies to see which standard was best for gross alpha activity determinations. Thorium-230, a pure alpha emitter, appeared to be the best s...

E. L. Whittaker

1986-01-01

283

The instrumental blank of the Mars Science Laboratory alpha particle X-ray spectrometer  

NASA Astrophysics Data System (ADS)

The alpha particle X-ray spectrometers on the Mars exploration rovers Spirit and Opportunity accomplished extensive elemental analysis of the Martian surface through a combination of XRF and PIXE. An advanced APXS is now part of the Mars Science Laboratory's Curiosity rover. APXS spectra contain contributions which enhance elemental peak areas but which do not arise from these elements within the sample under study, thereby introducing error into derived concentrations. A detailed examination of these effects in the MSL APXS enables us to test two schemes for making the necessary corrections.

Campbell, J. L.

2012-10-01

284

Alpha particles are extremely damaging to developing hemopoiesis compared to gamma irradiation  

SciTech Connect

Estimates of risk of stochastic effects from contamination with [alpha]-particle-emitting radionuclides are based on equivalent doses which take into account the RBE of the high-LET radiation. It is assumed that the RBEs for deterministic effects are considerably less than those for stochastic effects. However, the offspring of mice injected with 30 Bq g[sup [minus]1] [sup 239]Pu at 13 days gestation develop a persistent deficit in hemopoietic stem cells which is primarily the result of damage to their regulatory microenvironment. Their spatial distribution in the marrow is also perturbed, and recent observations on those mice suggested a considerably higher factor than 20. To define a more realistic RBE for hemopoiesis, the effects of external [gamma] irradiation during the fetal development period have been compared directly with those of [sup 239]Pu incorporated via placental transfer on the development of hemopoietic tissue. Pregnant mice were irradiated with [sup 60]Co [gamma] rays (a) continuously from day 13 of gestation to birth at 0.15 or 0.6 Gy/day; (b) six repeated acute doses (0.6 Gy/min) at 0.1 or 0.3 Gy from day 13 of gestation; (c) one acute dose of 0.6 or 1.8 Gy on day 15 of gestation. The spatial distribution of hemopoietic stem cells in 8-week-old offspring was then determined and compared to that resulting from [alpha]-particle irradiation. In each case, the higher dose was required to match the results for [alpha] particles, suggesting an RBE for developing hemopoiesis of 250-360 compared to a continuous [gamma]-ray dose and a rather lower value of 130-180 compared to a single acute dose of [gamma] rays. This contrasts greatly to values for direct irradiation of the stem cells but argues that the effective RBE, measured for long-term effects in vivo, is the more realistic. It is concluded that an all-embracing factor can be grossly misleading and can greatly underestimate the risks of exposure to [alpha] particles. 21 refs., 3 figs., 1 tab.

Tie-Nan Jiang (Institute of Radiation Medicine, Tianjin (China)); Lord, B.I.; Hendry, J.H. (Paterson Institute for Cancer Research, Manchester (United Kingdom))

1994-03-01

285

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

SciTech Connect

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.

Wang, S. [Princeton Plasma Physics Lab., NJ (United States)]|[Academia Sinica, Hefei, Anhui (China). Inst. of Plasma Physics; Zweben, S.J. [Princeton Univ., NJ (United States). Plasma Physics Lab.

1996-05-01

286

NBS (National Bureau of Standards) large-area alpha-particle counting systems  

SciTech Connect

Two alpha-particle counting systems for the measurement of large-area sources were developed at the National Bureau of Standards. The systems and their characteristics are described. One system uses an internal-source proportional counter and the other measures sources external to the counting volume through a thin aluminized mylar window. The internal system is used to measure sources in the lower-activity ranges. These calibrated sources are then used to establish the efficiency of the external counter used to measure the higher-activity sources.

Hutchinson, J.M.R.; Bright, S.J.

1987-01-01

287

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

NASA Astrophysics Data System (ADS)

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.

Gellert, R.; Rieder, R.; Anderson, R. C.; Brückner, J.; Clark, B. C.; Dreibus, G.; Economou, T.; Klingelhöfer, G.; Lugmair, G. W.; Ming, D. W.; Squyres, S. W.; d'Uston, C.; Wänke, H.; Yen, A.; Zipfel, J.

2004-08-01

288

Alpha-particle emission probabilities in the decay of 239Pu  

NASA Astrophysics Data System (ADS)

The alpha-particle emission probabilities ( P?) of 239Pu have been measured using material of highest enrichment and radiochemical purity, thin sources produced by vacuum sublimation, and high-resolution ? spectroscopy with ion-implanted Si detectors (PIPS). The results for the major emissions are P?0.07 = 0.7077±0.0014, P?13 = 0.1711 ± 0.0014 and P?51 = 0.1194±0.0007, which for the P?0.07 is about 3.6% lower than the recent evaluated value in the literature.

García-Toraño, E.; Aceña, M. L.; Bortels, G.; Mouchel, D.

1993-10-01

289

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

NASA Technical Reports Server (NTRS)

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.

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

290

Current-drive by lower hybrid waves in the presence of energetic alpha-particles  

SciTech Connect

Many experiments have now proved the effectiveness of lower hybrid waves for driving toroidal current in tokamaks. The use of these waves, however, to provide all the current in a reactor is thought to be uncertain because the waves may not penetrate the center of the more energetic reactor plasma, and, if they did, the wave power may be absorbed by alpha particles rather than by electrons. This paper explores the conditions under which lower-hybrid waves might actually drive all the current. 26 refs.

Fisch, N.J.; Rax, J.M.

1991-10-01

291

Spectroscopic studies on alpha particle-irradiated PADC (CR-39 detector)  

NASA Astrophysics Data System (ADS)

Spectroscopic studies on a Poly Allyl Diglycol Carbonate (PADC or CR-39) detector irradiated with 5 MeV ?-particles were carried out. The CR-39 samples were exposed to perpendicular incidence of ?-particles with different fluence ranging from 0.85 × 109 to 6.79 × 109 particles/cm2. The induced modifications in the CR-39 detectors were investigated using UV-Vis, FTIR, and photoluminescence (PL) spectroscopy. The results reveal that UV-Visible and FTIR spectroscopic techniques are insensitive to detect the induced modifications in the irradiated CR-39 detector within the selected range of fluence. Photoluminescence (PL) spectra, on the other hand, showed a reasonable difference between the detected spectra of the irradiated samples. The integrated intensity (N) under the PL emission band and peak’s heights (P) exhibits a linear correlation with the alpha particles fluence. The fitting linear formula and the relevant parameters for both relations (N and P vs. fluence) were determined. The comparison study between the three spectroscopic techniques indicated that PL spectroscopy provides a sensitive method for ?-particles dosimetric applications using a CR-39 detector.

El Ghazaly, M.; Hassan, H. E.

292

A study of the scintillation light induced in liquid xenon by electrons and alpha particles  

SciTech Connect

The authors have measured the time dependence and the intensity of the primary scintillation light in liquid xenon excited by {sup 241}Am alpha particles and {sup 207}Bi internal conversion electrons, at different electric field strengths. High purity liquid xenon was used to fill a parallel plate ionization chamber equipped with a CaF{sub 2} window coupled to a UV sensitive photomultiplier tube. The effect of the specific ionization density on the scintillation light as well as the time correlation between the light signal and the charge signal is reported. The authors demonstrate that the fast scintillation signal produced in liquid xenon by an ionizing particle provides an ideal trigger in a detector aiming at a complete three-dimensional even reconstruction with an excellent background rejection capability.

Aprile, E.; Mukherjee, R.; Suzuki, M. (Columbia Univ., New York, NY (USA). Dept. of Physics)

1990-04-01

293

The severity of alpha-particle-induced DNA damage is revealed by exposure to cell-free extracts  

SciTech Connect

The rejoining of single-strand breaks induced by {alpha}-particle and {gamma} irradiation in plasmid DNA under two scavenging conditions has been compared. At the two scavenger conditions has been compared. At the two scavenger capacities used of 1.5 {times} 10{sup 7} and 3 {times} 10{sup 8}s{sup {minus}1} using Tris-HCl as the scavenger, the ratio of single- to double-strand breaks for {alpha} particles is fivefold less than the corresponding ratios for {gamma} irradiation. The repair of such radiation-induced single-strand breaks has been examined using a cell-free system derived from human whole-cell extracts. We show that the rejoining of single-strand breaks for both {alpha}-particle- and {gamma}-irradiated plasmid is dependent upon the scavenging capacity and that the efficiency of rejoining of {alpha}-particle-induced single-strand breaks is significantly less than that observed for {gamma}-ray-induced breaks. In addition, for DNA that had been irradiated under conditions that mimic the cellular environment with respect to the radical scavenging capacity, 50 of {alpha}-particle-induced single-strand breaks are converted to double-strand breaks, in contrast with only {approximately}12% conversion of {gamma}-ray-induced single-strand breaks, indicating that the initial damage caused by {alpha} particles is more severe. These studies provide experimental evidence for increased clustering of damage which may have important implications for the induction of cancer by low-level {alpha}-particle sources such as domestic radon. 37 refs., 5 figs., 1 tab.

Hodgkins, P.S.; O`Neill, P.; Stevens, D.; Fairman, M.P. [Medical Research Council, Oxfordshire (United Kingdom)

1996-12-01

294

Single particle characterization of iron-induced pore-forming alpha-synuclein oligomers.  

PubMed

Aggregation of alpha-synuclein is a key event in several neurodegenerative diseases, including Parkinson disease. Recent findings suggest that oligomers represent the principal toxic aggregate species. Using confocal single-molecule fluorescence techniques, such as scanning for intensely fluorescent targets (SIFT) and atomic force microscopy, we monitored alpha-synuclein oligomer formation at the single particle level. Organic solvents were used to trigger aggregation, which resulted in small oligomers ("intermediate I"). Under these conditions, Fe(3+) at low micromolar concentrations dramatically increased aggregation and induced formation of larger oligomers ("intermediate II"). Both oligomer species were on-pathway to amyloid fibrils and could seed amyloid formation. Notably, only Fe(3+)-induced oligomers were SDS-resistant and could form ion-permeable pores in a planar lipid bilayer, which were inhibited by the oligomer-specific A11 antibody. Moreover, baicalein and N'-benzylidene-benzohydrazide derivatives inhibited oligomer formation. Baicalein also inhibited alpha-synuclein-dependent toxicity in neuronal cells. Our results may provide a potential disease mechanism regarding the role of ferric iron and of toxic oligomer species in Parkinson diseases. Moreover, scanning for intensely fluorescent targets allows high throughput screening for aggregation inhibitors and may provide new approaches for drug development and therapy. PMID:18258594

Kostka, Marcus; Högen, Tobias; Danzer, Karin M; Levin, Johannes; Habeck, Matthias; Wirth, Andreas; Wagner, Richard; Glabe, Charles G; Finger, Sabine; Heinzelmann, Udo; Garidel, Patrick; Duan, Wenzhen; Ross, Christopher A; Kretzschmar, Hans; Giese, Armin

2008-04-18

295

Alfven waves, alpha particles, and pickup ions in the solar wind  

NASA Technical Reports Server (NTRS)

Past studies of the properties of Alfven waves in the solar wind have indicated that (1) the amplitude of the velocity fluctuations is almost always smaller than expected on the basis of the amplitude of the field fluctuations, even when the anisotropy of the plasma is taken into account, and (2) the alpha particles do not participate in the wave motions because they 'surf' on the waves carried by the proton fluid. Ulysses data are used to demonstrate that (1) the discrepancy between the velocity and field fluctuations is greater at high heliographic latitudes than in the ecliptic plane, and (2) the alphas do participate in the waves, being either in phase or out of phase with the proton motions depending on whether the differential flow speed between the alphas and protons is greater than or less than the 'observed' wave speed, B(sub o)(delta v squared / delta B squared)exp 1/2, as determined from the ratio of the amplitudes of the velocity and magnetic fluctuations. It is proposed that the modification of Alfven wave propagation speed is due to pressure anisotropies resulting from asymmetric distributions of interstellar pickup ions. If the proposed explanation is correct, it indicates that scattering of pickup ions onto a (bi)spherical shell may not be as complete as generally supposed.

Goldstein, B. E.; Neugebauer, M.; Smith, E. J.

1995-01-01

296

Targeted Cytoplasmic Irradiation with Alpha Particles Induces Mutations in Mammalian Cells  

NASA Astrophysics Data System (ADS)

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.

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

1999-04-01

297

Calibration of the Mars Science Laboratory Alpha Particle X-Ray Spectrometer  

NASA Astrophysics Data System (ADS)

We have used a suite of over 60 geochemical reference standards for the calibration of the Mars Science Laboratory (MSL) Alpha Particle X-ray Spectrometer (APXS). For the elements P, S, Cl and Br we have supplemented this suite by adding various amounts of relevant chemical compounds to a powdered basalt standard. Special attention has been paid to include phyllosilicates, sulphates and a broad selection of igneous basalts as these are predicted key deposits at the MSL landing site, Gale Crater. The calibration is performed from first principles using x-ray excitation cross sections for the alpha particle and x-ray radiation source and an assumed homogeneous sample matrix. Remaining deviations indicate significant influences of mineral phases especially for light elements in basalts, ultra-mafic rocks and trachytes. Supporting x-ray diffraction work has helped to derive empirical, iterative corrections for distinct rock types, based on the first APXS analysis, assuming a homogeneous sample. These corrections have the potential to significantly improve the accuracy of APXS analyses, especially when other MSL instrument results, such as x-ray diffraction data from ChemMin, are included in the overall analysis process.

Perrett, G. M.; Campbell, J. L.; Gellert, R.; King, P. L.; Maxwell, J. A.; Andrushenko, S. M.

2011-12-01

298

Observation of lunar radon emanation with the Apollo 15 alpha particle spectrometer.  

NASA Technical Reports Server (NTRS)

The alpha particle spectrometer, a component of the orbital Sim Bay group of 'geochemistry' experiments on Apollo 15, was designed to detect alpha particles emitted during the decay of isotopes of radon gas and her daughter products. The purpose was to measure the gross activity of radon on the lunar surface and to find possible regions of increased local activity. Results are presented from a partial analysis of Apollo 15 data. For the moon as a whole, Rn220 was not observed and the upper limit on its decay rate above the lunar surface is 0.00038 disintegrations/sq cm-sec. Rn222 was marginally observed. Possible variations of radon activity on the lunar surface are being investigated. Po210 (a daughter product of Rn222) has been detected in a broad region from west of Mare Crisium to the Van de Graaff-Orlov region. The observed count rate is (4.6 plus or minus 1.4) x 0.001 disintegrations/sq cm-sec. The observed level of Po210 activity is in excess of the amount that would be in equilibrium with Rn222 by about an order of magnitude. This implies that larger levels of radon emanation have occurred on the moon within a time scale of 10 to 100 years.

Gorenstein, P.; Bjorkholm, P.

1972-01-01

299

Use of infinitely thick source alpha particle pulse height distributions in the determination of individual specific alpha activities  

NASA Astrophysics Data System (ADS)

A method is presented in which material containing a complex mixture of alpha emitting radionuclides might be analyzed with minimal sample preparation and the individual specific activities of each alpha emitting species found. A theoretical relationship describing the pulse height distribution of an infinitely thick source of alpha activity is developed. This relationship is then fit to uranium and thorium oxide pulse height distribution data obtained with a PIPS detector/MCA counting system, confirming the validity of the theoretical pulse height distribution. The method does not require complex and time consuming sample preparation common to conventional alpha spectroscopy. Results obtained from fits to the pulse height distributions are in agreement with the specific alpha activities of the oxides.

Phoenix, Kevin A.

1997-10-01

300

Helium energy levels including m{alpha}{sup 6} corrections  

SciTech Connect

The m{alpha}{sup 6} correction to energy is expressed in terms of an effective Hamiltonian H{sup (6)} for an arbitrary state of helium. Numerical calculations are performed for n=2 levels, and the previous result for the 2 {sup 3}P centroid is corrected. While the resulting theoretical predictions for the ionization energy are in moderate agreement with experimental values for 2 {sup 3}S{sub 1}, 2 {sup 3}P, and 2 {sup 1}S{sub 0} states, they are in significant disagreement for the singlet state 2{sup 1}P{sub 1}.

Pachucki, Krzysztof [Institute of Theoretical Physics, Warsaw University, Hoza 69, 00-681 Warsaw (Poland)

2006-12-15

301

Alpha voltaic batteries and methods thereof  

NASA Technical Reports Server (NTRS)

An alpha voltaic battery includes at least one layer of a semiconductor material comprising at least one p/n junction, at least one absorption and conversion layer on the at least one layer of semiconductor layer, and at least one alpha particle emitter. The absorption and conversion layer prevents at least a portion of alpha particles from the alpha particle emitter from damaging the p/n junction in the layer of semiconductor material. The absorption and conversion layer also converts at least a portion of energy from the alpha particles into electron-hole pairs for collection by the one p/n junction in the layer of semiconductor material.

Raffaelle, Ryne P. (Inventor); Jenkins, Phillip (Inventor); Wilt, David (Inventor); Scheiman, David (Inventor); Chubb, Donald (Inventor); Castro, Stephanie (Inventor)

2011-01-01

302

Decay of the 112Sn compound nucleus: Excitation functions of evaporation residues, energy spectra, and angular distributions of evaporated protons and alphas  

NASA Astrophysics Data System (ADS)

Evaporation residue excitation functions of the reaction 19F + 93Nb --> 112Sn*, in the bombarding energy range between 54 and 95 MeV, have been measured using the recoil catcher technique. Energy spectra, angular distributions, and correlations between angular anisotropy and ejectile energy of evaporated protons and alpha particles have been measured for the above system at 73 and 95 MeV bombarding energies. The experimental data are compared with the predictions of the statistical model code PACE2 making use of two different level density formalisms. The level density parameters derived from the proton and alpha spectra are presented. The angular-anisotropy ejectile-energy correlations of the alpha particles show a peak in the variation of the anisotropy with the ejectile energy in the subevaporation barrier range. The sensitivity of the angular-anisotropy ejectile-energy correlations to the statistical model parameters is discussed.

John, Bency; Kataria, S. K.; Tomar, B. S.; Goswami, A.; Gubbi, G. K.; Manohar, S. B.

1997-11-01

303

Measurement of alphas from energy-energy correlations at the Z0 resonance  

Microsoft Academic Search

We determine the strong coupling alphas from a comprehensive study of energy-energy correlations (EEC's) and their asymmetry (AEEC's) in hadronic decays of Z0 bosons collected by the SLD experiment at SLAC. The data are compared with all four available predictions of QCD calculated up to O(alpha2s) in perturbation theory, and also with a resummed calculation matched to all four of

K. Abe; I. Abt; W. W. Ash; D. Aston; N. Bacchetta; K. G. Baird; C. Baltay; H. R. Band; M. B. Barakat; G. Baranko; O. Bardon; T. Barklow; A. O. Bazarko; R. Ben-David; A. C. Benvenuti; T. Bienz; G. M. Bilei; D. Bisello; G. Blaylock; J. R. Bogart; T. Bolton; G. R. Bower; J. E. Brau; M. Breidenbach; W. M. Bugg; D. Burke; T. H. Burnett; P. N. Burrows; W. Busza; A. Calcaterra; D. O. Caldwell; D. Calloway; B. Camanzi; M. Carpinelli; R. Cassell; R. Castaldi; A. Castro; M. Cavalli-Sforza; E. Church; H. O. Cohn; J. A. Coller; V. Cook; R. Cotton; R. F. Cowan; D. G. Coyne; A. D'oliveira; C. J. Damerell; S. Dasu; R. de Sangro; P. de Simone; R. dell'orso; Y. C. Du; R. Dubois; B. I. Eisenstein; R. Elia; C. Fan; M. J. Fero; R. Frey; K. Furuno; T. Gillman; G. Gladding; S. Gonzalez; G. D. Hallewell; E. L. Hart; Y. Hasegawa; S. Hedges; S. S. Hertzbach; M. D. Hildreth; J. Huber; M. E. Huffer; E. W. Hughes; H. Hwang; Y. Iwasaki; P. Jacques; J. Jaros; A. S. Johnson; J. R. Johnson; R. A. Johnson; T. Junk; R. Kajikawa; M. Kalelkar; I. Karliner; H. Kawahara; H. W. Kendall; M. E. King; R. King; R. R. Kofler; N. M. Krishna; R. S. Kroeger; Y. Kwon; J. F. Labs; M. Langston; A. Lath; J. A. Lauber; D. W. Leith; X. Liu; M. Loreti; A. Lu; H. L. Lynch; J. Ma; G. Mancinelli; S. Manly; G. Mantovani; T. W. Markiewicz; T. Maruyama; H. Masuda; E. Mazzucato; A. K. McKemey; B. T. Meadows; R. Messner; P. M. Mockett; K. C. Moffeit; B. Mours; G. Müller; D. Muller; T. Nagamine; U. Nauenberg; H. Neal; M. Nussbaum; L. S. Osborne; R. S. Panvini; T. J. Pavel; I. Peruzzi; L. Pescara; M. Piccolo; L. Piemontese; E. Pieroni; K. T. Pitts; R. J. Plano; R. Prepost; C. Y. Prescott; G. D. Punkar; J. Quigley; B. N. Ratcliff; T. W. Reeves; P. E. Rensing; L. S. Rochester; J. E. Rothberg; P. C. Rowson; J. J. Russell; O. H. Saxton; T. Schalk; R. H. Schindler; U. Schneekloth; B. A. Schumm; A. Seiden; S. Sen; M. H. Shaevitz; J. T. Shank; G. Shapiro; D. J. Sherden; C. Simopoulos; S. R. Smith; J. A. Snyder; P. Stamer; H. Steiner; R. Steiner; M. G. Strauss; D. Su; F. Suekane; A. Sugiyama; S. Suzuki; M. Swartz; A. Szumilo; T. Takahashi; F. E. Taylor; E. Torrence; J. D. Turk; T. Usher; J. Va'vra; C. Vannini; E. Vella; J. P. Venuti; P. G. Verdini; S. R. Wagner; A. P. Waite; S. J. Watts; A. W. Weidemann; J. S. Whitaker; S. L. White; F. J. Wickens; D. A. Williams; S. H. Williams; S. Willocq; R. J. Wilson; W. J. Wisniewski; M. Woods; G. B. Word; J. Wyss; R. K. Yamamoto; J. M. Yamartino; S. J. Yellin; C. C. Young; H. Yuta; G. Zapalac; R. W. Zdarko; C. Zeitlin; J. Zhou

1994-01-01

304

Some Properties of Supported Small alpha-Fe2O3 Particles Determined with the Mössbauer Effect  

Microsoft Academic Search

Mössbauer spectra of Fe57 in alpha-Fe2O3 have been measured as a function of particle size and temperature. Bulk alpha-Fe2O3 shows a change in the sign of the quadrupole interaction in going through the Morin transition temperature, 263°K. Analyses of the spectra show that the magnetization vector is in the c plane above the transition temperature and parallel to the c

Walter Kündig; Hans Bömmel; G. Constabaris; R. H. Lindquist

1966-01-01

305

Gene expression responses in human lung fibroblasts exposed to alpha particle radiation.  

PubMed

This study examined alpha (?-) particle radiation effects on global changes in gene expression for the purposes of identifying potential signaling pathways that may be involved in Radon ((222)Rn) gas exposure and lung carcinogenesis. Human lung fibroblast cells were exposed to ?-particle radiation at a dose range of 0-1.5Gy. Twenty-four hours post-exposure, transcript modulations were monitored using microarray technology. A total of 208 genes were shown to be dose-responsive (FDR adjusted p<0.05, Fold change>|2|) of which 32% were upregulated and 68% downregulated. Fourteen of the high expressing genes (>|4| fold) were further validated using alternate technology and among these genes, GDF15 and FGF2 were assessed at the protein level. GDF15, a known marker of lung injury, had expression levels 3-fold higher in exposed cell culture media, 24h post-irradiation as detected by ELISA. Further, pathway analysis of the dose-responsive transcripts showed them to be involved in biological processes related to cell cycle control/mitosis, chromosome instability and cell differentiation. This panel of genes with particular focus on GDF15 may merit further analysis to determine their specific role in mechanisms leading to ?-particle induced lung carcinogenesis. PMID:24945610

Chauhan, Vinita; Howland, Matthew

2014-10-01

306

Detection of alpha radiation in a beta radiation field  

DOEpatents

An apparatus and method for detecting alpha particles in the presence of high activities of beta particles utilizing an alpha spectrometer. The apparatus of the present invention utilizes a magnetic field applied around the sample in an alpha spectrometer to deflect the beta particles from the sample prior to reaching the detector, thus permitting detection of low concentrations of alpha particles. In the method of the invention, the strength of magnetic field required to adequately deflect the beta particles and permit alpha particle detection is given by an algorithm that controls the field strength as a function of sample beta energy and the distance of the sample to the detector.

Mohagheghi, Amir H. (Albuquerque, NM); Reese, Robert P. (Edgewood, NM)

2001-01-01

307

149Sm(n,alpha)146Nd cross sections in the MeV energy region  

SciTech Connect

We have measured the {sup 149}Sm(n,{alpha}){sup 146}Nd cross section at 4.5, 5.0, 5.5, 6.0, and 6.5 MeV. Measurements were performed at the 4.5 MV Van de Graaff accelerator of Peking University with monoenergetic neutrons produced via the {sup 2}H(d,n){sup 3}He reaction using a deuterium gas target. Alpha particles were detected with a double-section gridded ionization chamber having two back-to-back {sup 149}Sm{sub 2}O{sub 3} samples attached to the common cathode. Absolute neutron flux was measured using a small {sup 238}U fission chamber and monitored by a BF{sub 3} long counter. These are the first reported cross sections for this reaction at these energies, except at 6.0 eV, where our new data are in good agreement with our earlier result. The present results help to much better constrain the {sup 149}Sm(n,{alpha}){sup 146}Nd cross section in a region where its energy dependence is changing fairly rapidly and there are large differences between evaluated nuclear data libraries.

Zhang, Guohui [Peking University; Gledenov, Yu. M. [Joint Institute for Nuclear Research, Dubna, Russia; Khuukhenkhuu, G [National University of Mongolia; Sedysheva, M. V. [Joint Institute for Nuclear Research, Dubna, Russia; Szalanski, P. [University of Lodz; Koehler, Paul Edward [ORNL; Voronov, Yu. N. [Joint Institute for Nuclear Research, Dubna, Russia; Liu, Jiaming [Peking University; Liu, Xiang [Peking University; Han, Jinhua [Peking University; Chen, Jinxiang [Peking University

2011-01-01

308

Effect of crystal thickness and geometry on the alpha-particle resolution of CsI (Tl)  

USGS Publications Warehouse

The resolution of CsI(Tl) for Po210 alpha particles has been measured as a function of crystal thickness. The best resolution of a 12;-in. diam cylindrical crystal was obtained for a thickness of 0.38 mm, and the effect of thickness on the resolution is discussed. Based on the proposed model, a conical crystal was designed, which yielded a line width of 1.8% for Po 210 alpha particles with a selected photomultiplier tube. ?? 1960 The American Institute of Physics.

Martinez, P.; Senftle, F. E.

1960-01-01

309

Channeling of Fusion Alpha-Particle Power Using Minority Ion Catalysis  

NASA Astrophysics Data System (ADS)

Maintaining fuel ions hotter than electrons would greatly facilitate controlled nuclear fusion. The parameter range for achieving this temperature disparity is shown here to be enhanced by catalyzing the ?-channeling effect (wave-induced simultaneous expulsion and cooling of ? particles) through minority-ion heating. Specifically, a wave can extract energy from hot ? particles and transfer it to colder minority ions, which act as a catalyst, eventually forwarding the energy to still colder fuel ions through collisions. In comparison with the traditional ?-channeling mechanism, the requirements are thereby relaxed on the waves that accomplish the ? channeling, which no longer have to interact simultaneously with ? particles and fuel ions. Numerical simulations illustrate how the new scheme may increase, for example, the effective fusion reactivity of mirror-confined plasmas.

Zhmoginov, A. I.; Fisch, N. J.

2011-10-01

310

Positron study of alpha particles effect on oxide-dispersion-strengthened steels  

NASA Astrophysics Data System (ADS)

Microstructure of oxide-dispersion-strengthened steels with different chromium content - MA 956 (20% Cr), ODM 751 (16% Cr) and MA 957 (14% Cr) were studied by positron annihilation lifetime spectroscopy. Samples were measured before and after helium ion implantation (He2+); therefore microstructure changes and radiation resistance to alpha particles of these steels were observed. Defect accumulation due to the radiation treatment was proven in all investigated materials. After ion implantation, mean lifetimes increased of about ~ 10 ps, which indicates significant change in microstructure. According to calculations of a defect volume from defect concentration and pre-dominant size of defects, ODM 751 is the most resistant steel in comparison to other investigated materials.

Veternikova, J.; Slugen, V.; Stancek, S.; Degmova, J.; Sabelova, V.; Sojak, S.; Petriska, M.; Hinca, R.

2013-06-01

311

Gas production due to alpha particle degradation of polyethylene and polyvinylchloride  

SciTech Connect

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.

Reed, D.T.; Hoh, J.; Emery, J.; Okajima, S.; Krause, T.

1998-07-01

312

Beat wave launch of lower-hybrid wave for alpha particle diagnostic  

SciTech Connect

By use of nonlinear mixing of oppositely-directed pump waves of frequency {ital f}{sub 0}{plus_minus}{delta}{ital f}{gt}{ital f}{sub {ital pe}},{ital f}{sub {ital ce}}, a beat wave of frequency {ital f}{sub 12}=2{delta}{ital f} and velocity {ital v}{sub 12}={ital c}{delta}{ital f}/{ital f}{sub 0} may be launched deeply into the interior of a confined plasma. For launch perpendicular to magnetic field at a beat frequency in the lower-hybrid range, {ital f}{sub {ital ci}}{lt}{ital f}{sub 12}{lt}{ital f}{sub {ital ce}}, wave damping is proportional to the local derivative of the fast ion distribution function, {partial_derivative}{ital f}{sub {alpha}}/{ital dv}{parallel}{sub {ital v}}{sub 12}, thus providing (in combination with a wave-scattering diagnostic) a potential means for direct, noninvasive measurement of the local alpha-particle distribution. Present experiments on the Davis Divertor Torus (DDT) are aimed at developing quantitative agreement between computed and actual Langmuir probe measurements of spatial and temporal beat-wave distributions in a three-dimensional plasma volume. {copyright} {ital 1996 American Institute of Physics.}

Horton, R.D.; Evans, R.W.; Hwang, D.Q.; McLean, H.S. [UC Davis/LLNL Livermore, California 94551 (United States); Rogers, J.H. [Princeton Plasma Physics Laboratory, Princeton, New Jersey (United States)

1996-02-01

313

Mitigation of radiation nephropathy after internal {alpha}-particle irradiation of kidneys  

SciTech Connect

Purpose: Internal irradiation of kidneys as a consequence of radioimmunotherapy, radiation accidents, or nuclear terrorism can result in radiation nephropathy. We attempted to modify pharmacologically, the functional and morphologic changes in mouse kidneys after injection with the actinium ({sup 225}Ac) nanogenerator, an in vivo generator of {alpha}- and {beta}-particle emitting elements. Methods and Materials: The animals were injected with 0.35 {mu}Ci of the {sup 225}Ac nanogenerator, which delivers a dose of 27.6 Gy to the kidneys. Then, they were randomized to receive captopril (angiotensin-converting enzyme inhibitor), L-158,809 (angiotensin II receptor-1 blocker), spironolactone (aldosterone receptor antagonist), or a placebo. Results: Forty weeks after the {sup 225}Ac injection, the placebo-control mice showed a significant increase in blood urea nitrogen (BUN) (87.6 {+-} 6.9 mg/dL), dilated Bowman spaces, and tubulolysis with basement membrane thickening. Captopril treatment accentuated the functional (BUN 119.0 {+-} 4.0 mg/dL; p <0.01 vs. placebo controls) and histopathologic damage. In contrast, L-158,809 offered moderate protection (BUN 66.6 {+-} 3.9 mg/dL; p = 0.02 vs. placebo controls). Spironolactone treatment, however, significantly prevented the development of histopathologic and functional changes (BUN 31.2 {+-} 2.5 mg/dL; p <0.001 vs. placebo controls). Conclusions: Low-dose spironolactone and, to a lesser extent, angiotensin receptor-1 blockade can offer renal protection in a mouse model of internal {alpha}-particle irradiation.

Jaggi, Jaspreet Singh [Molecular Pharmacology and Chemistry Program, Memorial Sloan-Kettering Cancer Center, New York, NY (United States); Seshan, Surya V. [Department of Pathology, Cornell University Weill Medical College, New York, NY (United States); McDevitt, Michael R. [Molecular Pharmacology and Chemistry Program, Memorial Sloan-Kettering Cancer Center, New York, NY (United States); Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, NY (United States); Sgouros, George [Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD (United States); Hyjek, Elizabeth [Department of Pathology, Cornell University Weill Medical College, New York, NY (United States); Scheinberg, David A. [Molecular Pharmacology and Chemistry Program, Memorial Sloan-Kettering Cancer Center, New York, NY (United States) and Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, NY (United States)]. E-mail: d-scheinberg@ski.mskcc.org

2006-04-01

314

Correlation between {alpha}-Decay Energies of Superheavy Nuclei Involving the Effects of Symmetry Energy  

SciTech Connect

A formula for the relationship between the {alpha}-decay energies (Q values) of superheavy nuclei (SHN) is presented, which is composed of the effects of Coulomb energy and symmetry energy. It can be employed not only to validate the experimental observations and measurements to a large extent, but also to predict the Q values of heaviest SHN with a high accuracy generally which will be very useful for future experiments. Furthermore, the shell closures in superheavy region and the effect of the symmetry energy on the stability of SHN against {alpha} decay are discussed with the help of this formula.

Dong Jianmin [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Graduate University of Chinese Academy of Sciences, Beijing 100049 (China); School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000 (China); Institute for Theoretical Physics, Justus-Liebig-University, D-35392 Giessen (Germany); Zuo Wei [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000 (China); Scheid, Werner [Institute for Theoretical Physics, Justus-Liebig-University, D-35392 Giessen (Germany)

2011-07-01

315

Biodegradation process of alpha-TCP particles and new bone formation in a rabbit cranial defect model.  

PubMed

The purpose of the present study was to observe the biodegradation process of pure alpha-tricalcium phosphate (alpha-TCP) particles and to determine the efficacy of alpha-TCP as a space maintainer in a bone defect. We used 14 rabbits and prepared two cranial bone defects in each rabbit. One defect was left empty as a control, whereas the other was filled with alpha-TCP particles about 300 mum in diameter. Animals were sacrificed at 1 week, 4 weeks, and 8 weeks. The cranial bone was then embedded either in paraffin wax for the preparation of decalcified specimens, or in polyester resin for the preparation of nondecalcified specimens. All specimens were evaluated histologically and histomorphometrically. As a consequence of the degradation of alpha-TCP, a "reticulate structure" appeared in the particles at 1 week and new bone was observed in this structure at 8 weeks. The amount of new bone between the control and experimental groups was not significantly different at any of the time points. However, in the experimental group, new bone at the surface of alpha-TCP was evident even in the center of the defect whereas fibrous connective tissue was dominant in the control group. These results indicate that alpha-TCP is a degradable osteoconductive material that is able to act as a space maintainer for bone regeneration when applied to a bone defect. While there was no significant difference in total bone formation between the experimental and negative control groups, the space-maintaining and osteoconductive properties of the particles may result in more complete bone formation in longer-term studies. PMID:16680680

Kihara, Hidemichi; Shiota, Makoto; Yamashita, Yasuo; Kasugai, Shohei

2006-11-01

316

High-energy laser-particle interaction  

NASA Astrophysics Data System (ADS)

This project investigates the spectral signatures associated with high-energy laser-particle interactions. Our main research objective is to improve predictive modeling of laser interaction with atmospheric particles by systematically studying the emissions from atmospheric aerosols interacting with high-energy lasers as a function of laser wavelength and intensity. Development of the theoretical formalism to interpret the results is an important part of this effort. The samples that are being analyzed mimic atmospheric particles: droplets of water and water soluble salts, ammonium and calcium sulfates, and microsamples of sand and carbon. This year, our theoretical work emphasized the optics of cloud-sized water droplets, and experiments were conducted to detail the power dependence of the two strongest nonlinear signals: stimulated Raman scattering (SRS) and breakdown-induced plasma emission.

Pack, D. W.

1991-12-01

317

Energy losses of channeled particles at high energies  

Microsoft Academic Search

The ratio of the energy loss of channeled particles to the enrgy loss in the amorphous medium has been calculated including relativistic corrections. In the limit of high velocities, the ratio has been shown not to tend to unity.

M. A. Kumakhov; R. Wedell; F. F. Komarov

1975-01-01

318

Use of 4.7 MeV alpha particles in elemental analysis and fusion reactor materials studies  

Microsoft Academic Search

The possibilities for using 4.7 MeV alpha particles produced at the U-120 CIP Cyclotron for charged particle induced X- and gamma-ray emission applications (PIXE and PIGE, respectively) and for fast neutron radiation damage simulation are presented. The combined analysis using PIGE and PIXE methods either separately or simultaneously is an excellent means of determining the relative abundances of lighter elements

B. Constantinescu; S. Dima; V. Florescu; E. A. Ivanov; D. Plostinaru; C. Sârbu

1986-01-01

319

Calculation of extracted ion beam particle distribution including within-extractor collisions from H-alpha Doppler shift measurements.  

PubMed

Prototype long pulse ion sources are being developed and tested toward the goal of a deuterium beam extraction of 120 keV/65 A. The latest prototype source consists of a magnetic bucket plasma generator and a four-grid copper accelerator system with multicircular apertures of 568 holes. To measure the angular divergence and the ion species of the ion beam, an optical multichannel analyzer (OMA) system for a Doppler-shifted H-alpha lights was set up at the end of a gas-cell neutralizer. But the OMA data are very difficult to analyze due to a large background level on the top of the three energy peaks (coming from H(+), H(2) (+), and H(3) (+)). These background spectra in the OMA signals seem to result from partially accelerated ion beams in the accelerator. Extracted ions could undergo a premature charge exchange as the accelerator column tends to have a high hydrogen partial pressure from the unused gas from the plasma generator, resulting in a continuous background of partially accelerated beam particles at the accelerator exit. This effect is calculated by accounting for all the possible atomic collision processes and numerically summing up three ion species across the accelerator column. The collection of all the atomic reaction cross sections and the numerical summing up will be presented. The result considerably depends on the background pressure and the ion beam species ratio (H(+), H(2) (+), and H(3) (+)). This effect constitutes more than 20% of the whole particle distribution. And the energy distribution of those suffering from collisions is broad and shows a broad maximum in the vicinity of the half and the third energy region. PMID:18315152

Kim, Tae-Seong; Kim, Jinchoon; In, Sang Ryul; Jeong, Seung Ho

2008-02-01

320

Self-consistent calculations of alpha-decay energies  

SciTech Connect

On the basis of the self-consistent theory of finite Fermi systems, the energies of alphadecay chains were calculated for several new superheavy nuclei discovered recently in experiments of the Dubna-Livermore Collaboration headed by Yu.Ts. Oganessian. The approach in question is implemented on the basis of the generalized method of the density functional proposed by Fayans and his coauthors. The version used here relies on the functional DF3-a proposed recently for describing a wide array of nuclear data, including data on superheavy nuclei. A detailed comparison of the results obtained on this basis with the predictions of different approaches, including the self-consistent Skyrme-Hartree-Fock method, the micro-macro method in the version developed by Sobiczewski and his coauthors, and the phenomenological method of Liran and his coauthors, is performed. The resulting alpha-decay energies are used to calculate respective lifetimes with the aid of the phenomenological Parkhomenko-Sobiczewski formula.

Tolokonnikov, S. V.; Lutostansky, Yu. S.; Saperstein, E. E., E-mail: saper@mbslab.kiae.ru [National Research Center Kurchatov Institute (Russian Federation)

2013-06-15

321

Alpha-quartz-induced chemokine expression by rat lung epithelial cells: effects of in vivo and in vitro particle exposure.  

PubMed Central

Chemokines are chemotactic cytokines that can play a key role in leukocyte recruitment to sites of tissue injury or infection. Previous studies have demonstrated that exposure to alpha-quartz as well as other noxious particles increases chemokine gene expression in rat lung, although the cells responsible for chemokine expression and the mechanisms underlying this response have remained unclear. The present studies demonstrate that exposure of rats to alpha-quartz induced expression of mRNA for the chemokine macrophage-inflammatory protein (MIP)-2 in epithelial cells lining the terminal bronchioles and alveolar ducts as well as macrophages and alveolar type II cells in the more distal lung. Treatment of rats with an anti-MIP-2 antiserum before alpha-quartz exposure markedly attenuated neutrophilic infiltration of the lungs demonstrating an important role for MIP-2 in alpha-quartz-induced pulmonary inflammation. In vitro exposure of primary cultures of rat alveolar type II cells or the rat alveolar type II cell line RLE-6TN to tumor necrosis factor-alpha, endotoxin, or alpha-quartz increased mRNA for MIP-2 as well as the structurally and functionally similar chemokine cytokine-induced neutrophil chemoattractant but not the chemokine MIP-1 alpha. The alpha-quartz-induced increase in epithelial MIP-2 mRNA resulted, at least in part, from increased gene transcription and was associated with the release of active MIP-2 protein. Induction of RLE-6TN MIP-2 and cytokine-induced neutrophil chemoattractant mRNA expression was not unique to alpha-quartz, being also increased by crocidolite asbestus fibers but not by titanium dioxide or MMVF-10 glass fibers. These findings indicate that epithelial cells contribute to chemokine expression in rat lung after exposure to alpha-quartz and potentially other noxious particles and suggest that alpha-quartz-activated MIP-2 expression in vivo results, at least in part, from a direct action of the particles on the lung epithelium. Images Figure 1 Figure 3 Figure 5 Figure 6 Figure 7 Figure 8

Driscoll, K. E.; Howard, B. W.; Carter, J. M.; Asquith, T.; Johnston, C.; Detilleux, P.; Kunkel, S. L.; Isfort, R. J.

1996-01-01

322

Determination of alphas from energy-energy correlations measured on the Z0 resonance  

Microsoft Academic Search

We present a study of energy-energy correlations based on 83 000 hadronic Z0 decays. From this data we determine the strong coupling constant alphas to second order QCD: alphas(91.2 GeV)=0.121+\\/-0.004(exp.)+\\/-0.002(hadr.)-0.006+0.009(scale)+\\/-0.006(theor.) from the energy-energy correlation and alphas(91.2 GeV)=0.115+\\/-0.004(exp.)-0.004+0.007(hadr.)-0.000+0.002(scale)-0.005+0.003 (theor.) from its asymmetry using a renormalization scale mu1=0.1 s. The first error (exp.) is the systematic experimental uncertainly, the statistical error is

B. Adeva; O. Adriani; M. Aguilar-Benitez; H. Akbari; J. Alcaraz; A. Aloisio; G. Alverson; M. G. Alviggi; Q. An; H. Anderhub; A. L. Anderson; V. P. Andreev; T. Angelov; L. Antonov; D. Antreasyan; P. Arce; A. Arefiev; T. Azemoon; T. Aziz; P. V. K. S. Baba; P. Bagnaia; J. A. Bakken; L. Baksay; R. C. Ball; S. Banerjee; J. Bao; L. Barone; A. Bay; U. Becker; J. Behrens; S. Beingessner; Gy. L. Bencze; J. Berdugo; P. Berges; B. Bertucci; B. L. Betev; A. Biland; R. Bizzarri; J. J. Blaising; P. Blömeke; B. Blumenfeld; G. J. Bobbink; M. Bocciolini; W. Böhlen; A. Böhn; T. Böhringer; B. Borgia; D. Bourilkov; M. Bourquin; D. Boutigny; B. Bouwens; J. G. Branson; I. C. Brock; F. Bruyant; C. Buisson; A. Bujak; J. D. Burger; J. P. Burq; J. Busenitz; X. D. Cai; C. Camps; M. Capell; F. Carbonara; F. Carminati; A. M. Cartacci; M. Cerrada; F. Cesaroni; Y. H. Chang; U. K. Chaturvedi; M. Chemarin; A. Chen; C. Chen; G. M. Chen; H. F. Chen; H. S. Chen; M. Chen; M. L. Chen; G. Chiefari; C. Y. Chien; F. Chollet; C. Civinini; I. Clare; R. Clare; H. O. Cohn; G. Coignet; N. Colino; V. Commichau; G. Conforto; A. Contin; F. Crijns; X. Y. Cui; T. S. Dai; R. D'Alessandro; R. de Asmundis; A. Degré; K. Deiters; E. Dénes; P. Denes; F. Denotaristefani; M. Dhina; M. Diemoz; F. Diez-Hedo; H. R. Dimitrov; C. Dionisi; F. Dittus; R. Dolin; E. Drago; T. Driever; D. Duchesneau; P. Duinker; I. Duran; H. El Mamouni; A. Engler; F. J. Eppling; F. C. Erné; P. Extermann; R. Fabbretti; G. Faber; M. Fabre; S. Falciano; Q. Fan; S. J. Fan; O. Fackler; J. Fay; J. Fehlmann; H. Fenker; T. Ferguson; G. Fernandez; F. Ferroni; H. Fesefeldt; J. Field; F. Filthaut; G. Finocchiaro; P. H. Fisher; G. Forconi; T. Foreman; K. Freudenreich; W. Friebel; M. Fukushima; M. Gailloud; Yu. Galaktionov; E. Gallo; S. N. Ganguli; P. Garcia-Abia; S. S. Gau; S. Gentile; M. Glaubman; S. Goldfarb; Z. F. Gong; E. Gonzalez; A. Gordeev; P. Göttlicher; D. Goujon; G. Gratta; C. Grinnell; M. Gruenewald; M. Guanziroli; A. Gurtu; H. R. Gustafson; L. J. Gutay; H. Haan; S. Hancke; K. Hangarter; M. Harris; A. Hasan; D. Hauschildt; C. F. He; T. Hebbeker; M. Hebert; G. Herten; U. Herten; A. Hervé; K. Hilgers; H. Hofer; H. Hoorani; L. S. Hsu; G. Hu; B. Ille; M. M. Ilyas; V. Innocente; E. Isiksal; E. Jagel; B. N. Jin; L. W. Jones; R. A. Khan; Yu. Kamyshkov; Y. Karyotakis; M. Kaur; S. Khokhar; V. Khoze; M. N. Kienzle-Focacci; W. Kinnison; D. Kirkby; W. Kittel; A. Klimentov; A. C. König; O. Kornadt; V. Koutsenko; R. W. Kraemer; T. Kramer; V. R. Krastev; W. Krenz; J. Krizmanic; A. Kuhn; K. S. Kumar; V. Kumar; A. Kunin; A. van Laak; V. Lalieu; G. Landi; K. Lanius; D. Lanske; S. Lanzano; P. Lebrun; P. Lecomte; P. Lecoq; P. Le Coultre; D. Lee; I. Leedom; J. M. Le Goff; L. Leistam; R. Leiste; M. Lenti; J. Lettry; P. M. Levchenko; X. Leytens; C. Li; H. T. Li; J. F. Li; L. Li; P. J. Li; Q. Li; X. G. Li; J. Y. Liao; Z. Y. Lin; F. L. Linde; D. Linnhofer; R. Liu; Y. Liu; W. Lohmann; S. Lökös; E. Longo; Y. S. Lu; J. M. Lubbers; K. Lübelsmeyer; C. Luci; D. Luckey; L. Ludovici; X. Lue; L. Luminari; W. G. Ma; M. MacDermott; R. Magahiz; M. Maire; P. K. Malhotra; R. Malik; A. Malinin; C. Maña; D. N. Mao; Y. F. Mao; M. Maolinbay; P. Marchesini; A. Marchionni; J. P. Martin; L. Martinez; F. Marzano; G. G. G. Massaro; T. Matsuda; K. Mazumdar; P. McBride; T. McMahon; D. McNally; Th. Meinholz; M. Merk; L. Merola; M. Meschini; W. J. Metzger; Y. Mi; M. Micke; U. Micke; G. B. Mills; Y. Mir; G. Mirabelli; J. Mnich; M. Möller; B. Monteleoni; G. Morand; R. Morand; S. Morganti; R. Mount; E. Nagy; M. Napolitano; H. Newman; M. A. Niaz; L. Niessen; D. Pandoulas; F. Plasil; G. Passaleva; G. Paternoster; S. Patricelli; Y. J. Pei; D. Perret-Gallix; J. Perrier; A. Pevsner; M. Pieri; P. A. Piroué; V. Plyaskin; M. Pohl; V. Pojidaev; N. Produit; J. M. Qian; K. N. Qureshi; R. Raghavan; G. Rahal-Callot; P. Razis; K. Read; D. Ren; Z. Ren; S. Reucroft; S. Riemann; O. Rind; C. Rippich; H. A. Rizvi; B. P. Roe; M. Röhner; S. Röhner; U. Roeser; Th. Rombach; L. Romero; J. Rose; S. Rosier-Lees; R. Rosmalen; Ph. Rosselet; J. A. Rubio; W. Ruckstuhl; H. Rykaczewski; M. Sachwitz; J. Salicio; G. Sanders; G. Sartorelli; G. Sauvage; A. Savin; V. Schegelsky; D. Schmitz; P. Schmitz; M. Schneegans; M. Schöntag; H. Schopper; D. J. Schotanus; H. J. Schreiber; R. Schulte; S. Schulte; K. Schultze; J. Schütte; J. Schwenke; G. Schwering; C. Sciacca; I. Scott; R. Sehgal; P. G. Seiler; J. C. Sens; I. Sheer; V. Shevchenko; S. Shevchenko; X. R. Shi; K. Shmakov; V. Shoutko; E. Shumilov; N. Smirnov; A. Sopczak; C. Spartiotis; T. Spickermann; B. Spiess; P. Spillantini; R. Starosta; M. Steuer; D. P. Stickland; W. Stoeffl; B. Stöhr; H. Stone; K. Strauch; B. C. Stringfellow; K. Sudhakar; G. Sultanov; R. L. Sumner; L. Z. Sun; H. Suter; R. B. Sutton; J. D. Swain; A. A. Syed; X. W. Tang; E. Tarkovsky; L. Taylor; E. Thomas; C. Timmermans

1991-01-01

323

Comparison of the total neutral energy spectra of. cap alpha cap alpha. , dd and pp interactions at the ISR  

SciTech Connect

The total neutral energy spectra, E/sub TOT//sub /sup 0// = ..sigma../sub 1/epsilon/sub i//sup 0/, have been measured in the central region of ..cap alpha cap alpha.., dd and pp interactions at ..sqrt../sup s/NN = 31 GeV with an electromagnetic calorimeter covering 2..pi.. in azimuth. The data were collected in the light-ion run at the CERN ISR during August 1983. The cross section ratio of the ..cap alpha cap alpha.. to the pp interactions increases rapidly wth E/sub TOT//sup 0/ from 7 to 10/sup 5/ in the range 1.5

Not Available

1984-11-15

324

Evidence for Direct Durable Capture of 1- to 8-Mev Solar Alpha Particles onto Geomagnetically Trapped Orbits.  

National Technical Information Service (NTIS)

By using satellite observations from Injun 5, an examination of the temporal variations of the intensity of geomagnetically trapped alpha particles has been made for the 8-month period September 1968 to April 1969. The most prominent change was a stepwise...

J. A. Van Allen B. A. Randall

1970-01-01

325

Determination of Geometry and Absorption Effects and Their Impact on the Accuracy of Alpha Particle Soft Error Rate Extrapolations  

Microsoft Academic Search

The results of a physical experiment and extensive simulation runs are presented for the first time demonstrating the significant effects of geometry and air absorption on accelerated alpha particle soft error rate tests. These results show that geometry and absorption must be properly accounted for even when the source is in close proximity to the device to avoid substantial underestimation

Robert C. Baumann; Daniele Radaelli

2007-01-01

326

Origin of High Energy Solar Energetic Particles  

NASA Astrophysics Data System (ADS)

Some of the major challenges in understanding solar energetic particles (SEPs) include 1) identifying the origin and the governing acceleration process for the highest energy SEPs that occasionally result in ground level enhancements (GLEs), and 2) relating GLEs to their lower energy counterparts both in terms of the composition and the overall morphology of the energy spectra. To address these questions, we utilize measurements from the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA), a Russian-Italian mission. PAMELA not only spans the energy range between the ground-based neutron monitor data and the in-situ observations of SEPs, but also directly measures the composition for the highest energy SEP events. We employ several techniques to identify the origin of SEPs, including particle onset times, composition, and spectral variations. In addition, we compare the SEP population derived from PAMELA at 1 AU with population of precipitating ions at the Sun, responsible for the high-energy gamma-ray emission. We will discuss results of a study of a handful of SEP events during cycle 24 that were observed by PAMELA, using a variety of techniques to identify the origins of the highest energy SEPs.

Thakur, N.; de Nolfo, G. A.; Boezio, M.; Bravar, U.; Carbone, R.; Christian, E. R.; Martucci, M.; Mergè, M.; Mocchiutti, E.; Munini, R.; Ricci, M.; Ryan, J. M.; Stochaj, S.; Stockton, J.

2013-12-01

327

The effects of radon daughter alpha-particle irradiation in K1 and xrs-5 CHO cell lines.  

PubMed

We investigated the radiobiological effects of the radon daughter bismuth-212 (212Bi) in Chinese hamster ovary (CHO) K1 cells and in xrs-5 cells, which are X-ray sensitive and deficient in the ability to rejoin DNA double-strand breaks. The cells were exposed to 250 kVp X-rays or to 212Bi chelated to diethylene triamine pentaacetic acid (DTPA); chelation of 212Bi to DTPA prevented its attachment to or entry into the cells. Cytotoxic, clastogenic, and mutagenic responses of the cells were measured and RBEs (D10, 2 chromatid aberrations/cell and 10 induced 6-thioguanine-resistant mutants) were calculated to be 3.8, 3.5, and 3.9, respectively for K1, and 1.4, 0.8, and 5.1, respectively, for xrs-5. With the exception of the RBE of less than 1 for alpha-induced aberrations in xrs-5, the results are consistent with the following conclusions: (1) alpha-particles are in general more effective cytotoxic, clastogenic and mutagenic agents than X-rays; (2) the primary lethal and clastogenic lesion induced by both X-rays and alpha-particles is probably a DNA double-strand break; (3) DNA double-strand breaks induced by alpha-radiation are less well repaired than those induced by X-rays, although a portion of alpha-induced damage is repairable; and (4) deficiencies in rejoining DNA double-strand breaks affect the clastogenic and cytotoxic effects of X-rays and alpha-radiation, not their mutagenic effects. The RBE of 0.8 for aberration induction in xrs-5 cells could reflect a deficiency in the ability of these cells to convert alpha-induced damage to chromosome aberrations. Alternatively, the RBE of less than 1 might reflect an unusual sensitivity of xrs-5 cells to alpha-induced G2 delays. PMID:2030713

Shadley, J D; Whitlock, J L; Rotmensch, J; Atcher, R W; Tang, J; Schwartz, J L

1991-05-01

328

Relative Biological Effectiveness of Alpha-Particle Emitters In Vivo at Low Doses  

PubMed Central

The therapeutic potential of radionuclides that emit ? particles, as well as their associated health hazards, have attracted considerable attention. The 224Ra daughters 212Pb and 212Bi, by virtue of their radiation properties which involve emission of ? and ? particles in their decay to stable 208Pb, have been proposed as candidates for radioimmunotherapy. Using mouse testes as the experimental model and testicular spermhead survival as the biological end point, the present work examines the radiotoxicity of 212Pb and its daughters. When 212Pb, in equilibrium with its daughters 212Bi, 212Po and 208Tl, was administered directly into the testis, the dose required to achieve 37% survival (D37) was 0.143 ± 0.014 Gy and the corresponding RBE of the mixed radiation field was 4.7 when compared to the D37 for acute external 120 kVp X rays. This datum, in conjunction with our earlier results for 210Po, was used to obtain an RBE–LET relationship for ? particles emitted by tissue-incorporated radionuclides: RBE? = 4.8 ? 6.1 × 10?2 LET + 1.0 × 10?3 LET2. Similarly, the dependence of RBE on ?-particle energy E? was given by RBE?=22E??0.73. These relationships, based on in vivo experimental data, may be valuable in predicting biological effects of ?-particle emitters.

Howell, Roger W.; Azure, Michael T.; Narra, Venkat R.; Rao, Dandamudi V.

2012-01-01

329

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

NASA Astrophysics Data System (ADS)

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.

Plionis, A. A.; Peterson, D. S.; Tandon, L.; LaMont, S. P.

2010-03-01

330

Investigation of Chemical-Vapour-Deposition Diamond Alpha-Particle Detectors  

NASA Astrophysics Data System (ADS)

Diamond films with [100] texture were prepared by a hot-filament chemical vapour deposition technique to fabricate particle detectors. The response of detectors to 5.5 MeV 241Am particles is studied. The photocurrent increases linearly and then levels off with voltage, and 7 nA is obtained at bias voltage of 100 V. The time-dependent photocurrent initially increases rapidly and then tends to reach saturation. Furthermore, a little increase of the dark-current after irradiation can be accounted for by the release of the charges captured by the trapping centres at low energy levels during irradiation. An obvious peak of the pulse height distribution can be observed, associated with the energy of 5.5 MeV.

Gu, Bei-Bei; Wang, Lin-Jun; Zhang, Ming-Long; Xia, Yi-Ben

2004-10-01

331

On alpha heating in toroidal devices  

Microsoft Academic Search

Studies of the alpha particle losses and heating profiles for an alpha-heated TFTR-sized tokamak and a small field-reversed mirror reactor (FRM) are presented. The slowing-down and drift of high-energy alpha particles, including detailed orbital effects, is approximated for tokamak geometry using the SYMALF multi-energy-angle code. Results of the calculation for a beam-driven TFTR-type plasma indicate that, except for the center

G. H. Miley

1979-01-01

332

Minimum ionizing and alpha particles detectors based on epitaxial semiconductor silicon carbide  

Microsoft Academic Search

The relatively high value of the energy required to produce an electron-hole pair in silicon carbide, SiC, by a minimum ionizing particle (MIP) against the value for Si, imposes severe constrains in the crystallographic quality, the thickness and the doping concentration of the SiC epitaxial layer used as the detection medium. In this work, a 40 ?m thick 4 H-SiC

F. Nava; P. Vanni; M. Bruzzi; S. Lagomarsino; S. Sciortino; G. Wagner; C. Lanzieri

2004-01-01

333

Scenarios for the nonlinear evolution of alpha particle induced Alfven wave instability  

SciTech Connect

Various nonlinear scenarios are given for the evolution of energetic particles that are slowing down in a background plasma and simultaneously causing instability of the background plasma waves. If the background damping is sufficiently weak, a steady-state wave is established as described by Berk and Breizman. For larger background damping rate pulsations develop. Saturation occurs when the wave amplitude rises to where the wave trapping frequency equals the growth rate. The wave then damps due to the small background dissipation present and a relatively long quiet interval exists between bursts while the free energy of the distribution is refilled by classical transport. In this scenario the anomalous energy loss of energetic particles due to diffusion is small compared to the classical collisional energy exchange with the background plasma. However, if at the trapping frequency, the wave amplitude is large enough to cause orbit stochasticity, a phase space explosion'' occurs where the wave amplitudes rise to higher levels which leads to rapid loss of energetic particles.

Berk, H.L.; Breizman, B.N.; Ye, Huanchun.

1992-03-01

334

Scenarios for the nonlinear evolution of alpha particle induced Alfven wave instability  

SciTech Connect

Various nonlinear scenarios are given for the evolution of energetic particles that are slowing down in a background plasma and simultaneously causing instability of the background plasma waves. If the background damping is sufficiently weak, a steady-state wave is established as described by Berk and Breizman. For larger background damping rate pulsations develop. Saturation occurs when the wave amplitude rises to where the wave trapping frequency equals the growth rate. The wave then damps due to the small background dissipation present and a relatively long quiet interval exists between bursts while the free energy of the distribution is refilled by classical transport. In this scenario the anomalous energy loss of energetic particles due to diffusion is small compared to the classical collisional energy exchange with the background plasma. However, if at the trapping frequency, the wave amplitude is large enough to cause orbit stochasticity, a phase space ``explosion`` occurs where the wave amplitudes rise to higher levels which leads to rapid loss of energetic particles.

Berk, H.L.; Breizman, B.N.; Ye, Huanchun

1992-03-01

335

Interaction of the human cytomegalovirus particle with the host cell induces hypoxia-inducible factor 1 alpha  

SciTech Connect

The cellular protein hypoxia-inducible factor 1 alpha (HIF-1{alpha}) was induced after infection of human fibroblasts with human cytomegalovirus (HCMV). HCMV irradiated with ultraviolet light (uv-HCMV) also elicited the effect, demonstrating that the response was provoked by interaction of the infecting virion with the cell and that viral gene expression was not required. Although induction of HIF-1{alpha} was initiated by an early event, accumulation of the protein was not detected until 9 hours post infection, with levels increasing thereafter. Infection with uv-HCMV resulted in increased abundance of HIF-1{alpha}-specific RNA, indicating stimulation of transcription. In addition, greater phosphorylation of the protein kinase Akt was observed, and the activity of this enzyme was required for induction of HIF-1{alpha} to occur. HIF-1{alpha} controls the expression of many cellular gene products; therefore the findings reveal new ways in which interaction of the HCMV particle with the host cell may cause significant alterations to cellular physiology.

McFarlane, Steven; Nicholl, Mary Jane; Sutherland, Jane S.; Preston, Chris M., E-mail: Christopher.preston@glasgow.ac.u

2011-05-25

336

Particle size and interfacial effects on heat transfer characteristics of water and {alpha}-SiC nanofluids.  

SciTech Connect

The effect of average particle sizes on basic macroscopic properties and heat transfer performance of {alpha}-SiC/water nanofluids was investigated. The average particle sizes, calculated from the specific surface area of nanoparticles, were varied from 16 to 90 nm. Nanofluids with larger particles of the same material and volume concentration provide higher thermal conductivity and lower viscosity increases than those with smaller particles because of the smaller solid/liquid interfacial area of larger particles. It was also demonstrated that the viscosity of water-based nanofluids can be significantly decreased by pH of the suspension independently from the thermal conductivity. Heat transfer coefficients were measured and compared to the performance of base fluids as well as to nanofluids reported in the literature. Criteria for evaluation of the heat transfer performance of nanofluids are discussed and optimum directions in nanofluid development are suggested.

Timofeeva, E.; Smith, D. S.; Yu, W.; France, D. M.; Singh, D.; Routbort, J. L. (Energy Systems); ( NE); (Univ. of Illinois)

2010-01-01

337

Primary scintillation characteristics of Ar+CF4 gas mixtures excited by proton and alpha particles  

NASA Astrophysics Data System (ADS)

In this paper, we report how the concentration of carbon-tetrafluoride (CF4) affects the primary scintillation from Ar+CF4 gas mixtures excited by proton and alpha particles. The single photon counting method was used to measure the time spectra of the primary scintillation from Ar, CF4 and their mixtures at atmospheric pressure. Pure Ar exhibits a fast decay time constant, which is approximately 6 ns, and a slow decay time tail. Initially, increases in the concentration of CF4 increase the decay time of the Ar+CF4 gas mixture. However, when the concentration of CF4 exceeds a certain threshold, the decay time decreases to that of pure CF4, approximately 8-9 ns. We also report the photon emission spectra of Ar+CF4 mixtures excited by protons. The emission spectrum of the primary scintillation from Ar is improved by CF4 in both the ultraviolet region and the visible to near-infrared region.

Liu, Jinliang; Ouyang, Xiaoping; Chen, Liang; Zhang, Xianpeng; Liu, Jun; Zhang, Zhongbing; Ruan, Jinlu

2012-12-01

338

Calibration of the Mars Science Laboratory Alpha Particle X-ray Spectrometer  

NASA Astrophysics Data System (ADS)

The alpha-particle X-ray spectrometer (APXS) for the Mars Science Laboratory (MSL) mission was calibrated for routine analysis of: Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, Cr, Mn, Fe, Ni, Zn, Br, Rb, Sr, and Y. The following elements were also calibrated, but may be too low to be measured (10s-100s ppm) for their usual abundance on Mars: V, Cu, Ga, As, Se and W. An extensive suite of geological reference materials, supplemented by pure chemical elements and compounds was used. Special attention was paid to include phyllosilicates, sulfates and a broad selection of basalts as these are predicted minerals and rocks at the Gale Crater landing site. The calibration approach is from first principles, using fundamental physics parameters and an assumed homogeneous sample matrix to calculate expected elemental signals for a given instrument setup and sample composition. Resulting concentrations for most elements accord with expected values. Deviations in elements of lower atomic number (Na, Mg, Al) indicate significant influences of mineral phases, especially in basalts, ultramafic rocks and trachytes. The systematics of these deviations help us to derive empirical, iterative corrections for different rock groups, based on a preliminary APXS analysis which assumes a homogeneous sample. These corrections have the potential to significantly improve the accuracy of APXS analyses, especially when other MSL instrument results, such as the X-ray diffraction data from CheMin, are included in the overall analysis process.

Campbell, John L.; Perrett, Glynis M.; Gellert, Ralf; Andrushenko, Stefan M.; Boyd, Nicholas I.; Maxwell, John A.; King, Penelope L.; Schofield, Céleste D. M.

2012-09-01

339

Alpha Particle X-Ray Spectrometer (APXS): Results from Gusev crater and calibration report  

NASA Astrophysics Data System (ADS)

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.

Gellert, R.; Rieder, R.; Brückner, J.; Clark, B. C.; Dreibus, G.; Klingelhöfer, G.; Lugmair, G.; Ming, D. W.; Wänke, H.; Yen, A.; Zipfel, J.; Squyres, S. W.

2006-01-01

340

Gamma-Ray, Neutron, and Alpha-Particle Spectrometers for the Lunar Prospector mission  

NASA Astrophysics Data System (ADS)

Gamma-Ray, Neutron, and Alpha-Particle Spectrometers (GRS, NS, and APS, respectively) were included in the payload complement of Lunar Prospector (LP). Specific objectives of the GRS were to map abundances of Fe, Ti, Th, K, Si, O, Mg, Al, and Ca to depths of 20 cm. Those of the NS were to search for water ice to depths of 100 cm near the lunar poles and to map regolith maturity. Objectives of the APS were to search for, map, and provide a measure of the time history of gaseous release events at the lunar surface. The purpose of this paper is to document the mechanical, analog electronic, digital electronic, and microprocessor designs of the suite of spectrometers, present a representative sample of the calibrated response functions of all sensors, and document the operation of all three LP spectrometers in sufficient detail as to enable the full knowledgeable use of all data products that were archived in the Planetary Data System for future use by the planetary-science community.

Feldman, W. C.; Ahola, K.; Barraclough, B. L.; Belian, R. D.; Black, R. K.; Elphic, R. C.; Everett, D. T.; Fuller, K. R.; Kroesche, J.; Lawrence, D. J.; Lawson, S. L.; Longmire, J. L.; Maurice, S.; Miller, M. C.; Prettyman, T. H.; Storms, S. A.; Thornton, G. W.

2004-07-01

341

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

NASA Technical Reports Server (NTRS)

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.

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

342

Biophysical analysis of the dose-dependent overdispersion and the restricted linear energy transfer dependence expressed in dicentric chromosome data from alpha-irradiated human lymphocytes.  

PubMed

Experimental data for the induction of dicentric chromosomes in phytohemagglutinin (PHA)-stimulated human T lymphocytes by 241Am alpha-particles obtained by Schmid et al. have been analyzed in the light of biophysical theory. As usual in experiments with alpha-particles, the relative variance of the intercellular distribution of the number of aberrations per cell exceeds unity, and the multiplicity of the aberrations per particle traversal through the cell is understood as the basic effect causing this overdispersion. However, the clearly expressed dose dependence of the relative variance differs from the dose-independent relative variance predicted by the multiplicity effect alone. Since such dose dependence is often observed in experiments with alpha-particles, protons, and high-energy neutrons, the interpretation of the overdispersion needs to be supplemented. In a new, more general statistical model, the distribution function of the number of aberrations is interpreted as resulting from the convolution of a Poisson distribution for the spontaneous aberrations with the overdispersed distributions for the aberrations caused by intratrack or intertrack lesion interaction, and the fluctuation of the cross-sectional area of the cellular chromatin must also be considered. Using a suitable mathematical formulation of the resulting dose-dependent over-dispersion, the mean number lambda 1 of the aberrations produced by a single particle traversal through the cell nucleus and the mean number lambda 2 of the aberrations per pairwise approach between two alpha-particle tracks could be estimated. Coefficient alpha of the dose-proportional yield component, when compared between 241Am alpha-particle irradiation and 137Cs gamma-ray exposure, is found to increase approximately in proportion to dose-mean restricted linear energy transfer, which indicates an underlying pairwise molecular lesion interaction on the nanometer scale. PMID:9271796

Greinert, R; Harder, D

1997-06-01

343

Nanocrystalline particle coatings on alpha-alumina powders by a carbonate precipitation and thermal-assisted combustion route.  

PubMed

We have suggested ultrafine particle coating processes for preparing nanocrystalline particle coated alpha-alumina powders by a carbonate precipitation and thermal-assisted combustion route, which is environmentally friendly. The nanometric ammonium aluminum carbonate hydroxide (AACH) as a precursor for coating of alumina was produced from precipitation reaction of ammonium aluminum sulfate and ammonium hydrogen carbonate. The synthetic crystalline size and morphology were greatly dependent on pH and temperature. By adding ammonium aluminum sulfate solution dispersed the alpha-alumina core particle in the ammonium hydrogen carbonate aqueous solution, nanometric AACH with a size of 5 nm was tightly bonded and uniformly coated on the core powder due to formation of surface complexes by the adsorption of carbonates, hydroxyl and ammonia groups on the surface of aluminum oxide. The synthetic precursor rapidly converted to amorphous- and y-alumina phase without significant change in the morphological features through decomposition of surface complexes and thermal-assisted phase transformation. As a result, the nanocrystalline polymorphic particle coated alpha-alumina core powders with highly uniform distribution were prepared from the route of carbonate precipitation and thermal-assisted combustion. PMID:18047085

Kim, Sang Woo; Jung, Young Mi

2007-11-01

344

Mutations in the tumor suppressor gene p53 in human liver cancer induced by alpha-particles.  

PubMed

The p53 tumor suppressor gene is mutated in varying fractions of almost all tumor types studied. The rate of mutations and the mutational spectrum in some tumors are specific for environmental mutagens assumed to be involved in the carcinogenic process. Thus, hepatocellular carcinomas supposedly induced by aflatoxin exposure often contain a specific point mutation in codon 249, and in lung cancers of miners with heavy radon exposure, another specific point mutation in codon 249 suggestive of an alpha-particle-specific mutation has been shown. The interpretation of studies linking the mutational spectrum with specific environmental exposures is complicated by the multifactorial or unknown genesis of most tumors. However, people given injections of the X-ray contrast medium Thorotrast (Th) in the past have experienced an enormous risk of liver tumors, and virtually all of these are supposedly induced by alpha-particles from the decay of 232Th. The examination of these tumors may provide evidence as to whether specific p53 point mutations are relevant in alpha-particle carcinogenesis. Therefore, we collected paraffin-embedded, formalin-fixed archival tissues from 18 hepatocellular carcinomas, 9 cholangiocarcinomas, and 9 hepatic angiosarcomas from Thorotrast-exposed patients. The tissues were analyzed for p53 protein expression by immunohistochemical staining by using the mAb DO-7 and for mutations of exons 5-8 by PCR and constant denaturant gel electrophoresis. G --> T transversions of the third base of codon 249 of the p53 gene were specifically screened for by restriction enzymes. No high score for p53 protein expression (i.e., positive staining of >20% of examined cells) was observed; lower scores were seen in 5 of 18 (28%) hepatocellular carcinomas, 1 of 9 (11%) cholangiocarcinomas, and 0 of 8 (0%) hepatic angiosarcomas. Only one p53 mutation, a heterozygous T --> G transversion of the first base codon 176, occurred in a hepatocellular carcinoma. The rate of p53 point mutations in alpha-particle-induced liver tumors seems to be lower than in European hepatocellular carcinomas in general. The study does not exclude the possibility that alpha-particle carcinogenesis may involve inactivation of p53 by gross deletions of the gene, but it speaks against the proposed specificity of point mutations of codon 249 in cancer supposedly induced by alpha-particles from radon progeny. PMID:8672994

Andersson, M; Jönsson, M; Nielsen, L L; Vyberg, M; Visfeldt, J; Storm, H H; Wallin, H

1995-01-01

345

Method and apparatus for generating low energy nuclear particles  

DOEpatents

A particle accelerator generates an input particle beam having an initial energy level above a threshold for generating secondary nuclear particles. A thin target is rotated in the path of the input beam for undergoing nuclear reactions to generate the secondary particles and correspondingly decrease energy of the input beam to about the threshold. The target produces low energy secondary particles and is effectively cooled by radiation and conduction. A neutron scatterer and a neutron filter are also used for preferentially degrading the secondary particles into a lower energy range if desired. 18 figs.

Powell, J.R.; Reich, M.; Ludewig, H.; Todosow, M.

1999-02-09

346

Method and apparatus for generating low energy nuclear particles  

DOEpatents

A particle accelerator (12) generates an input particle beam having an initial energy level above a threshold for generating secondary nuclear particles. A thin target (14) is rotated in the path of the input beam for undergoing nuclear reactions to generate the secondary particles and correspondingly decrease energy of the input beam to about the threshold. The target (14) produces low energy secondary particles and is effectively cooled by radiation and conduction. A neutron scatterer (44) and a neutron filter (42) are also used for preferentially degrading the secondary particles into a lower energy range if desired.

Powell, James R. (Shoreham, NY); Reich, Morris (Flushing, NY); Ludewig, Hans (Brookhaven, NY); Todosow, Michael (Miller Place, NY)

1999-02-09

347

Summary of the IEA Workshop on Alpha Physics and Tritium Issues in Large Tokamaks  

SciTech Connect

A brief summary is presented of the talks given during this meeting, which was held at PPPL and sponsored by the IEA (International Energy Agency) as part of the Large Tokamak collaboration. These talks are summarized into four sessions: tritium issues in large tokamaks, alpha particle simulation experiments, alpha particle theory, and alpha particle diagnostics.

Cheng, C.Z.; Stratton, B.; Zweben, S.J. [Princeton Univ., NJ (United States). Plasma Physics Lab.; Pitcher, C.S. [Toronto Univ., Downsview, ON (Canada)

1993-11-01

348

Refueling pellets as a source of charge exchange neutrals for alpha particle measurements  

Microsoft Academic Search

Alpha interactions with neutrals in the ablation cloud of a refueling pellet are considered as a fast alpha diagnostic through charge-capture radiation (ACCR) by the alphas or their complete neutralization and escape. Calculations of pellet penetration into a reactor plasma indicate that regions of r\\/a>0.61 could be reached by refueling pellets with initial radii of 4 mm, hence this would

G. Gerdin

1987-01-01

349

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

SciTech Connect

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.

Zaider, M.

1997-12-31

350

Effects of corotating interaction regions on Ulysses high energy particles  

SciTech Connect

We investigate the intensity variation of low energy ({approx}6-23 MeV/N) heliospheric ions and of galactic protons (250-2200 MeV) observed by the Kiel Electron Telescope onboard the Ulysses spacecraft associated with Corotating Interaction Regions (CIR) from mid-1992 to end of June 1995. This period covers Ulysses' transit to high southern latitudes, the south polar pass, return to the solar equator and ascent to the north pole up to 70 deg. We find that the flux of high energy protons exhibits a periodicity of about 26 days with a relative intensity variation of 10%. At latitudes below {approx}50 deg. the recurrent variations of galactic protons are in coincidence with the passage of CIRs and enhancements of low energies protons and alpha particles which are accelerated at the shocks of the CIRs. The modulation of galactic protons is observed up to high southern latitudes, where the signatures of a CIR are no longer visible in plasma or magnetic field data. The periodicity does not depend on latitude and its phase apparently remains constant during Ulysses' pass over the south pole as well as through the solar equator.

Droege, W.; Kunow, H.; Heber, B.; Mueller-Mellin, R.; Sierks, H.; Wibberenz, G.; Raviart, A.; Ducros, R.; Ferrando, P.; Rastoin, C.; Paizis, C.; Gosling, J. T. [Institut fuer Kernphysik, Universitaet Kiel, 24118 Kiel (Germany); CEA, DSM/DAPNIA/Service d'Astrophysique, C.E. Saclay, 91191 Gif-sur-Yvette (France); Instituto Fisica Cosmica CNR, Universita di Milano, 20133 Milano (Italy); Los Alamos National Laboratory, Los Alamos New Mexico 87545 (United States)

1996-07-20

351

Refueling pellets as a source of charge exchange neutrals for alpha particle measurements  

SciTech Connect

Alpha interactions with neutrals in the ablation cloud of a refueling pellet are considered as a fast alpha diagnostic through charge-capture radiation (ACCR) by the alphas or their complete neutralization and escape. Calculations of pellet penetration into a reactor plasma indicate that regions of r/a>0.61 could be reached by refueling pellets with initial radii of 4 mm, hence this would be an outer core diagnostic. A spherically symmetric neutral-gas shielding model (SSMNGSM) in which ionization is treated self-consistently and governed by local thermodynamic equilibrium is used in these calculations. Collisional processes are found to govern the alpha--cloud interactions and local equilibrium calculations were performed in which the charge exchange and ionization cross sections are used to obtain the state fractions of the alphas in the cloud. At 1640 A the ratio of ACCR to cloud bremsstrahlung is found to be 10/sup -5/ whereas at 304 A this ratio ranges from 3 x 10/sup -3/ to 0.5 for the cases considered; no neutralized alphas escape the cloud. Magnetic field effects are considered and they appear to reduce the bremsstrahlung from the cloud by a factor of 300 at 304 A in regions perpendicular to the magnetic field from the pellet's surface; escape of neutralized alphas may be possible in these directions. Alpha refueling pellet interactions are potentially useful as outer core fast alpha diagnostics and this could be tested in near term experiments.

Gerdin, G.

1987-12-01

352

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

SciTech Connect

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.

Zaider, M.

1992-12-31

353

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

Microsoft Academic Search

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

Hatsumi Nagasawa; Paul F. Wilson; David J. Chen; Larry H. Thompson; Joel S. Bedford; John B. Little

2008-01-01

354

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

Microsoft Academic Search

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

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

2007-01-01

355

The Role of Heat Flux in Governing the Thermal Behavior of Alpha Particles in the Fast Solar Wind  

Microsoft Academic Search

We present a 16-moment, three-fluid description of the solar wind consisting of electrons, protons, and alpha particles. We assume gyrotropic flow (transport across the magnetic field is neglected) which reduces the 16-moment set of transport equations to a six-moment set yielding the density, velocity, temperatures parallel and perpendicular to the magnetic field, and parallel heat conductive fluxes from the parallel

L. A. Allen; X. Li

2005-01-01

356

Optical Model Parameters for the Ar-36+{alpha} and Ca-40+{alpha} Systems  

SciTech Connect

For 36Ar+{alpha} and 40Ca+{alpha} systems there are presented the parameters of Woods-Saxon potential with volume absorption in the {alpha}-particle energy range lower and higher than the Coulomb barrier. They were obtained as a result of existing optical potentials modification.

Generalov, L.; Zvenigorodskii, A. [Russian Federal Nuclear Center-VNIIEF, Sarov (Russian Federation)

2005-05-24

357

Confined energy distribution for charged particle beams  

DOEpatents

A charged particle beam is formed to a relatively larger area beam which is well-contained and has a beam area which relatively uniformly deposits energy over a beam target. Linear optics receive an accelerator beam and output a first beam with a first waist defined by a relatively small size in a first dimension normal to a second dimension. Nonlinear optics, such as an octupole magnet, are located about the first waist and output a second beam having a phase-space distribution which folds the beam edges along the second dimension toward the beam core to develop a well-contained beam and a relatively uniform particle intensity across the beam core. The beam may then be expanded along the second dimension to form the uniform ribbon beam at a selected distance from the nonlinear optics. Alternately, the beam may be passed through a second set of nonlinear optics to fold the beam edges in the first dimension. The beam may then be uniformly expanded along the first and second dimensions to form a well-contained, two-dimensional beam for illuminating a two-dimensional target with a relatively uniform energy deposition.

Jason, Andrew J. (Los Alamos, NM); Blind, Barbara (Los Alamos, NM)

1990-01-01

358

Beams of Protons and Alpha Particles ? 30 keV\\/Charge From the Earth’s Bow Shock  

Microsoft Academic Search

surements were obtained with the ultralow energy and charge analyzer (ULECA) of the Max-Planck-Institut\\/University of Maryland sensor system on Isee 1. The ULECA sensor utilizes a multislit collimator, an electrostatic deflection system, and an array of solid state detectors to determine an incident particle's energy per charge and total energy. Energy discriminators for each detector allow the reliable separation of

M. Scholer; F. M. Ipavich; G. Gloeckler

1981-01-01

359

A thin film device as a low energy, high flux charged particle spectrometer  

SciTech Connect

We are continuing our investigation of the use of stacks of electrically isolated thin metal foils as spectrometers for lost ions from tokamak fusion plasmas. Devices of this type in which the foil thicknesses were a few micrometers were installed on the Joint European Torus during the recent first deuterium--tritium experiment in an effort to observe lost energetic alpha particles. While there was no convincing evidence of lost alpha particles in this experiment, we did observe significant fluxes of low energy (<500 keV) charged particles. In an effort to provide an instrument for the investigation of this phenomenon and of escaping relatively low energy (<100 keV) ions from other fusion plasma devices, we have developed alternative devices with very thin (few hundred nanometers) alternating layers of conductor and insulator. Four such devices have been fabricated and tested for protons with energies between 20 and 160 keV and demonstrated good energy resolution (typically about 10%) for proton bombarding energies between about 40 and 120 keV. One of the devices, consisting of deposited layers of Al, Ti, and SiO{sub 2} was operated up to a current density of about 100 m/cm2 at an energy of 100 keV, corresponding to a power volume density of 100 kW/cm3.

Cecil, F. E.; Roy, Brian; Sutton, Christian; Wasinger, Nicole

2001-01-01

360

{alpha}-decay energy formula for superheavy nuclei based on the liquid-drop model  

SciTech Connect

A formula of {alpha}-decay energy for superheavy nuclei based on the method of macroscopic model plus shell corrections is proposed. The macroscopic part of this formula is derived from the Bethe-Weizsaecker binding energy formula, and the shell corrections at N=152 and N=162 are expressed by the Mexican hat wavelet functions. The parameters of this formula are obtained through fitting to 170 {alpha}-decay energies for nuclei ranging from Z=90 to Z=118 with N{>=}140. Numerical results show that 170 existing {alpha}-decay energies can be reproduced very well; the average and standard deviations between theoretical results and experimental data are 0.177 and 0.226 MeV, respectively. The {alpha}-decay energies of newly synthesized nuclei {sup 293,294}117 and their {alpha}-decay products are also reproduced very well. In addition, the {alpha}-decay energies for nuclei with Z=110-120 are predicted and compared with the results calculated by the macroscopic-microscopic model. Great differences are found for nuclei with Z{>=}116 and N{>=}176 due to the shell effects near the hypothetical doubly magic nucleus {sup 298}114{sub 184} in the macroscopic-microscopic model. Therefore, by comparing experimental {alpha}-decay energies measured in the future with the ones predicted by these two methods, one can obtain useful information about the next proton and neutron magic numbers.

Dong Tiekuang [Department of Physics, Nanjing University, Nanjing 210008 (China); Faculty of Information Technology, Macau University of Science and Technology, Macau 999078 (China); Ren Zhongzhou [Department of Physics, Nanjing University, Nanjing 210008 (China); Center of Theoretical Nuclear Physics, National Laboratory of Heavy-Ion Accelerator, Lanzhou 730000 (China)

2010-09-15

361

Enhancement of solar wind low-energy energetic particles as precursor of geomagnetic disturbance in operational geomagnetic forecast  

Microsoft Academic Search

A study of the relationship between solar wind low-energy energetic particles using data from the Electron, Proton, and Alpha Monitor (EPAM) onboard the Advanced Compositional Explorer spacecraft (ACE) and geomagnetic activity using data from Canadian magnetic observatories in Canada's polar cap, auroral zone, and subauroral zone was carried out for a period spanning 1997-2005. Full halo coronal mass ejections (CMEs)

H.-L. Lam

2009-01-01

362

Gamma-diagnostics of alpha-particles in 4He and D-T plasmas  

NASA Astrophysics Data System (ADS)

This article reports on ?-ray diagnosis of ICRF-accelerated 4He ions and fusion ? particles used in the JET tokamak. This diagnostic based on the analysis of ? rays emitted in nuclear reaction 9Be(?,n?)12C. The results of the first observation of the 4.44-MeV ?-radiation due to the reaction 9Be(?,n?)12C in JET deuterium-tritium experiment (DTE1) are presented. Gamma-ray spectra have been recorded with collimated spectrometer, and the ?-ray emission radial profiles measured with the JET neutron/gamma profile monitor. Doppler broadening effects which could be used for the ICRF-accelerated 4He-ion diagnosis with high energy resolution ?-ray detectors are discussed. Capabilities of the ?-ray measurements in next step D-T devices are discussed.

Kiptily, V. G.; Popovichev, S.; Sharapov, S. E.; Bertalot, L.; Cecil, F. E.; Conroy, S.; Mantsinen, M. J.

2003-03-01

363

Alpha-Particle Emitting 213Bi-Anti-EGFR Immunoconjugates Eradicate Tumor Cells Independent of Oxygenation  

PubMed Central

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 ?-emitters are thought to eradicate tumor cells independent of cellular oxygenation. Therefore, the aim of this study was to demonstrate that cell-bound ?-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-1?. 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 ?-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.

Gaertner, Florian C.; Bruchertseifer, Frank; Morgenstern, Alfred; Essler, Markus; Senekowitsch-Schmidtke, Reingard

2013-01-01

364

Alpha-particle emitting 213Bi-anti-EGFR immunoconjugates eradicate tumor cells independent of oxygenation.  

PubMed

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 ?-emitters are thought to eradicate tumor cells independent of cellular oxygenation. Therefore, the aim of this study was to demonstrate that cell-bound ?-particle emitting (213)Bi immunoconjugates kill hypoxic and normoxic CAL33 tumor cells with identical efficiency. For that purpose CAL33 cells were incubated with (213)Bi-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-1?. 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 (213)Bi-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 (213)Bi-anti-EGFR-MAb turned out to be independent of cellular oxygenation. These results demonstrate that ?-particle emitting (213)Bi-immunoconjugates eradicate hypoxic tumor cells as effective as normoxic cells. Therefore, (213)Bi-radioimmunotherapy seems to be an appropriate strategy for treatment of hypoxic tumors. PMID:23724085

Wulbrand, Christian; Seidl, Christof; Gaertner, Florian C; Bruchertseifer, Frank; Morgenstern, Alfred; Essler, Markus; Senekowitsch-Schmidtke, Reingard

2013-01-01

365

Alpha-induced reaction studies using low-energy RI beams at CRIB  

SciTech Connect

CRIB (CNS Radioactive Ion Beam separator) is a low-energy RI beam separator at the Center for Nuclear Study (CNS) of the University of Tokyo. Studies on proton and alpha resonance scatterings, ({alpha}, p) reactions, and other types of measurements ({beta}-decay lifetimes etc.) have been performed using RI beams at CRIB, motivated by interests on astrophysical reactions and exotic nuclear structure. Among the studies at CRIB, the measurement of {sup 7}Li+{alpha}/{sup 7}Be+{alpha} resonant scatterings are presented.

Yamaguchi, H.; Kahl, D.; Hu, J.; Kubono, S.; Hayakawa, S.; Hashimoto, T. [Center for Nuclear Study (CNS), University of Tokyo, RIKEN campus, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Istituto Nazionale Fisica Nucleare - Laboratori Nazionali del Sud (INFN-LNS), via S.Sofia 62, 95125 Catania (Italy); Research Center for Nuclear Physics (RCNP), Osaka University, 10-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan)

2012-11-12

366

Energy-loss rate of a fast particle in graphene  

SciTech Connect

The energy-loss rate of a fast particle in graphene is studied. The energy-loss rate always increases with increasing incident particle energy, which is quite unusual when compared to electron gas in normal metal. Graphene exhibits a ''discriminating'' behavior where there exists a low energy cut-off below which the scattering process is strictly forbidden, leading to lossless traverse of an external particle in graphene. This low energy cutoff is of the order of nearest neighbor hopping bandwidth. Our results suggest that backscattering is also absent in the external particle scattering of graphene.

Ang, Yee Sin; Zhang, C. [School of Engineering Physics, University of Wollongong, 2522 NSW (Australia); Kee, Chun Yun [Department of Mathematics, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260 (Singapore)

2011-08-01

367

Monte Carlo charged-particle tracking and energy deposition on a Lagrangian mesh  

NASA Astrophysics Data System (ADS)

A Monte Carlo algorithm for alpha particle tracking and energy deposition on a RZ cylindrical computational mesh in a Lagrangian hydrodynamics code used for inertial confinement fusion (ICF) simulations is presented. The straight line approximation is used to follow propagation of “Monte Carlo particles” which represent collections of alpha particles generated from thermonuclear deuterium-tritium (DT) reactions. Energy deposition in the plasma is modeled by the continuous slowing down approximation. The scheme addresses various aspects arising in the coupling of Monte Carlo tracking with Lagrangian hydrodynamics; such as non-orthogonal severely distorted mesh cells, particle relocation on the moving mesh and particle relocation after rezoning. A comparison with the flux-limited multi-group diffusion transport method is presented for a polar direct drive target design for the National Ignition Facility. Simulations show the Monte Carlo transport method predicts about 30picosecond earlier ignition than predicted by the diffusion method, and generates higher hot spot temperature. Nearly linear speed-up is achieved for multi-processor parallel simulations.

Yuan, J.; Moses, G. A.; McKenty, P. W.

2005-10-01

368

The Role of Heat Flux in Governing the Thermal Behavior of Alpha Particles in the Fast Solar Wind  

NASA Astrophysics Data System (ADS)

We present a 16-moment, three-fluid description of the solar wind consisting of electrons, protons, and alpha particles. We assume gyrotropic flow (transport across the magnetic field is neglected) which reduces the 16-moment set of transport equations to a six-moment set yielding the density, velocity, temperatures parallel and perpendicular to the magnetic field, and parallel heat conductive fluxes from the parallel and perpendicular directions for each particles species. The model incorporates the effects of Coulomb collisions. It allows for non-radial divergence of the magnetic field and heating and momentum addition to the particles. We investigate the influence of the heat conductive flux in shaping the temperature anisotropy.

Allen, L. A.; Li, X.

2005-12-01

369

The biological effectiveness of radon-progeny alpha particles. III. Quality factors  

SciTech Connect

Domestic radon risk estimates are typically based either on data for uranium miners or on data derived from A-bomb survivors; comparison of domestic radon risk estimates derived from these two disparate sources represents an important test of their reliability. There is currently a significant discrepancy of about a factor of three between domestic radon risk estimates generated with these two independent methods. To base such risk estimates on the data for A-bomb survivors, who were exposed mainly to low-LET radiation, requires a quality factor for {alpha} particles from radon progeny; the final risk estimate is then directly proportional to this quality factor. We have used the most extensive quantitative in vitro data set currently available at high LET for an oncogenic end point, to make the best estimate we can that could be used as a basis for a quality factor. Our best estimates of values appropriate for the quality factor for radon progeny are significantly lower than those currently used (20-25) in estimating lung cancer mortality due to radon. Specifically, our best estimate for home dwellers is around 10. In addition, because of the different geometry in the bronchial epithelia of nonsmokers compared to smokers, our best estimate of an appropriate quality factor for home dwellers is about 18% greater than that for miners; thus our best estimate of the {open_quotes}effective K factor{close_quotes} to convert to effective dose/WLM in miners would be increased by this factor. Based on a quality factor of {approximately}10, the dosimetrically based estimate of radon-induced mortality would be {approximately}35,000 per year in the U.S. rather than the value of {approximately}70,000 obtained using a quality factor of 20. The value of 35,000, while larger than the values based on data for miners ({approximately}20,000), is much smaller than previous estimates of {approximately}70,000 based on dosimetric methods. 54 refs., 7 figs.

Brenner, D.J.; Miller, R.C.; Huang, Y. [Columbia Univ., New York, NY (United States)] [and others

1995-04-01

370

The biological effectiveness of radon-progeny alpha particles. III. Quality factors.  

PubMed

Domestic radon risk estimates are typically based either on data for uranium miners or on data derived from A-bomb survivors; comparison of domestic radon risk estimates derived from these two disparate sources represents an important test of their reliability. There is currently a significant discrepancy of about a factor of three between domestic radon risk estimates generated with these two independent methods. To base such risk estimates on the data for A-bomb survivors, who were exposed mainly to low-LET radiation, requires a quality factor for alpha particles from random progeny; the final risk estimate is then directly proportional to this quality factor. We have used the most extensive quantitative in vitro data set currently available at high LET for an oncogenic end point, to make the best estimate we can that could be used as a basis for a quality factor. Our best estimates of values appropriate for the quality factor for radom progeny are significantly lower than those currently used (20-25) in estimating lung cancer mortality due to randon. Specifically, our best estimate for home dwellers is around 10. In addition, because of the different geometry in the bronchial epithelia of nonsmokers compared to smokers, our best estimate of an appropriate quality factor for home dwellers is about 18% greater than that for miners; thus our best estimate of the "effective K factor" to convert to effective dose/WLM in home dwellers from effective dose/WLM in miners would be increased by this factor. Based on a quality factor of approximately 10, the dosimetrically based estimate of radon-induced mortality would be approximately 35,000 per year in the U.S. rather than the value of approximately 70,000 obtained using a quality factor of 20. The value of 35,000, while larger than the values based on data for miners (approximately 20,000), is much smaller than previous estimates of approximately 70,000 based on dosimetric methods; thus risk estimates based on the two approaches, dosimetric and epidemiological, may be partially reconciled. Finally, a quality factor of 10 would reduce the proportion of the collective effective dose caused by radon progeny from the currently accepted value of 55% down to about 38%. PMID:7899560

Brenner, D J; Miller, R C; Huang, Y; Hall, E J

1995-04-01

371

An improved measuremebts of alphaS (MZ0) using energy correlations with the OPAL detector at LEP  

Microsoft Academic Search

We report on an improved measurement of the value of the strong coupling constant sigmas at the Z0 peak, using the asymmetry of the energy-energy correlation function. The analysis, based on second-order perturbation theory and a data sample of about 145000 multihadronic Z0 decays, yields alphas(Mz0 = 0.118+\\/-0.001(stat.)+\\/-0.003(exp.syst.)-0.004+0.0009 (theor. syst.), where the theoretical systematic error accounts for uncertainties due to

P. D. Acton; G. Alexander; J. Allison; P. P. Allport; K. J. Anderson; S. Arcelli; P. Ashton; A. Astbury; D. Axen; G. Azuelos; G. A. Bahan; J. T. M. Baines; A. H. Ball; J. Banks; G. J. Barker; R. J. Barlow; J. R. Batley; G. Beaudoin; A. Beck; J. Becker; T. Behnke; K. W. Bell; G. Bella; P. Berlich; S. Bethke; O. Biebel; U. Binder; I. J. Bloodworth; P. Bock; B. Boden; H. M. Bosch; S. Bougerolle; B. B. Brabson; H. Breuker; R. M. Brown; R. Brun; A. Buijs; H. J. Burckhart; P. Capiluppi; R. K. Carnegie; A. A. Carter; J. R. Carter; C. Y. Chang; D. G. Charlton; P. E. L. Clarke; I. Cohen; W. J. Collins; J. E. Conboy; M. Cooper; M. Couch; M. Coupland; M. Cuffiani; S. Dado; G. M. Dallavalle; S. de Jong; P. Debu; L. A. del Pozo; M. M. Dennino; A. Dieckmann; M. Dittmar; M. S. Dixit; E. Duchovni; G. Duckeck; I. P. Duerdoth; D. J. P. Dumas; G. Eckerlin; P. A. Elcombe; P. G. Estabrooks; E. Etzion; F. Fabbri; M. Fincke-Keeler; H. M. Fischer; D. G. Fong; C. Fukunaga; A. Gaidot; O. Ganel; J. W. Gary; J. Gascon; R. F. McGowan; N. I. Geddes; C. Geich-Gimbel; S. W. Gensler; F. X. Gentit; G. Giacomelli; V. Gibson; W. R. Gibson; J. D. Gillies; J. Goldberg; M. J. Goodrick; W. Gorn; C. Grandi; F. C. Grant; J. Hagemann; G. G. Hanson; M. Hansroul; C. K. Hargrove; P. F. Harrison; J. Hart; P. M. Hattersley; M. Hauschild; C. M. Hawkes; E. Heflin; R. J. Hemingway; R. D. Heuer; J. C. Hill; S. J. Hillier; D. A. Hinshaw; C. Ho; J. D. Hobbs; P. R. Hobson; D. Hochman; B. Holl; R. J. Homer; A. K. Honma; S. R. Hou; C. P. Howarth; R. E. Hughes-Jones; R. Humbert; P. Igo-Kemenes; H. Ihssen; D. C. Imrie; A. C. Janissen; A. Jawahery; P. W. Jeffreys; H. Jeremie; M. Jimack; M. Jobes; R. W. L. Jones; P. Jovanovic; D. Karlen; K. Kawagoe; T. Kawamoto; R. K. Keeler; R. G. Kellogg; B. W. Kennedy; C. Kleinwort; D. E. Klem; T. Kobayashi; T. P. Kokott; S. Komamiya; L. Köpke; J. F. Kral; R. Kowalewski; H. Kreutzmann; J. von Krogh; J. Kroll; M. Kuwano; P. Kyberd; G. D. Lafferty; F. Lamarche; W. J. Larson; J. G. Layter; P. Le Du; P. Leblanc; A. M. Lee; M. H. Lehto; D. Lellouch; P. Lennert; C. Leroy; J. Letts; S. Levegrün; L. Levinson; S. L. Lloyd; F. K. Loebinger; J. M. Lorah; B. Lorazo; M. J. Losty; X. C. Lou; J. Ludwig; M. Mannelli; S. Marcellini; G. Maringer; A. J. Martin; J. P. Martin; T. Mashimo; P. Mättig; U. Maur; J. McKenna; T. J. McMahon; J. R. McNutt; F. Meijers; D. Menszner; F. S. Merritt; H. Mes; A. Michelini; R. P. Middleton; G. Mikenberg; J. Mildenberger; D. J. Miller; R. Mir; W. Mohr; C. Moisan; A. Montanari; T. Mori; M. W. Moss; T. Mouthuy; B. Nellen; H. H. Nguyen; M. Nozaki; S. W. O'Neale; B. P. O'Neill; F. G. Oakham; F. Odorici; M. Ogg; H. O. Ogren; H. Oh; C. J. Oram; M. J. Oreglia; S. Orito; J. P. Pansart; B. Panzer-Steindel; P. Paschievici; G. N. Patrick; S. J. Pawley; P. Pfister; J. E. Pilcher; J. L. Pinfold; D. Pitman; D. E. Plane; P. Poffenberger; B. Poli; A. Pouladdej; E. Prebys; T. W. Pritchard; H. Przysiezniak; G. Quast; M. W. Redmond; D. L. Rees; K. Riles; S. A. Robins; D. Robinson; A. Rollnik; J. M. Roney; E. Ros; S. Rossberg; A. M. Rossi; M. Rosvick; P. Routenburg; K. Runge; O. Runolfsson; D. R. Rust; S. Sanghera; M. Sasaki; A. D. Schaile; O. Schaile; W. Schappert; P. Scharff-Hansen; P. Schenk; H. von der Schmitt; S. Schreiber; J. Schweining; W. G. Scott; M. Settles; B. C. Shen; P. Sherwood; R. Shypit; A. Simon; P. Singh; G. P. Siroli; A. Skuja; A. M. Smith; T. J. Smith; G. A. Snow; R. Sobie; R. W. Springer; M. Sproston; K. Stephens; H. E. Stier; R. Ströhmer; D. Strom; H. Takeda; T. Takeshita; P. Taras; S. Tarem; P. Teixeira-Dias; N. J. Thackray; G. Transtromer; T. Tsukamoto; M. F. Turner; G. Tysarczyk-Niemeyer; D. van den Plas; R. van Kooten; G. J. Vandalen; G. Vasseur; C. J. Virtue; A. Wagner; C. Wahl; J. P. Walker; C. P. Ward; D. R. Ward; P. M. Watkins; A. T. Watson; N. K. Watson; M. Weber; P. Weber; S. Weisz; P. S. Wells; N. Wermes; M. Weymann; M. A. Whalley; G. W. Wilson; J. A. Wilson; I. Wingerter; V.-H. Winterer; N. C. Wood; S. Wotton; T. R. Wyatt; R. Yaari; Y. Yang; G. Yekutieli; M. Yurko; I. Zacharov; W. Zeuner; G. T. Zorn

1992-01-01

372

The Apollo Alpha Spectrometer.  

NASA Technical Reports Server (NTRS)

Located in the Science Instrument Module of Apollo 15 and 16, the Alpha Particle Spectrometer was designed to detect and measure the energy of alpha particles emitted by the radon isotopes and their daughter products. The spectrometer sensor consisted of an array of totally depleted silicon surface barrier detectors. Biased amplifier and linear gate techniques were utilized to reduce resolution degradation, thereby permitting the use of a single 512 channel PHA. Sensor identification and in-flight radioactive calibration were incorporated to enhance data reduction.

Jagoda, N.; Kubierschky, K.; Frank, R.; Carroll, J.

1973-01-01

373

Low energy particle composition. [cosmic rays produced in solar system  

NASA Technical Reports Server (NTRS)

A review is given of current knowledge of low-energy cosmic ray particles produced in the solar system. It is argued that the notion that the sun alone can accelerate particles in the solar system must be abandoned in light of evidence that Jupiter and earth may be sources of observed low-energy particles. Measurements of the composition and energy spectra of low-energy particles during quiet times are examined, emphasizing the abundance of protons and helium and of anomalous N, O, and Ne. The abundance of heavy particles (B, C, N, O, Ne, Ca and Fe) of unknown origin in the earth magnetosphere is examined. Reported observations of Jovian electrons are discussed and solar particle events with anomalous compositions (He-3 rich events and Fe rich events) are treated in detail. Nuclear abundances of solar particles, emphasizing their temporal and spatial variations are considered together with the nature of nuclear reaction products in solar flares.

Gloeckler, G.

1975-01-01

374

Analysis of secondary electron emission spectra of equal-LET protons and alpha particles for purposes of radiation quality and spaceflight hazard assessment.  

PubMed

Amongst the great variety of heavy particles present in the galactic and solar cosmic ray spectra, hydrogen and helium nuclei are significantly more abundant than all other heavier ions and, as such, represent a major radiation hazard to humans in space. Experimental data have suggested that differences in relative biological effectiveness (RBE) exist between the two species at the same value of linear energy transfer (LET). This has consequences for heavily ionising radiation protection procedures, which currently still assume a simple dependence of radiation quality on LET. By analysing the secondary electron (delta-ray) emission spectra of protons and alpha particles, in terms of the spatial characteristics of energy deposition in cellular targets and the likelihood of complex lesion formation, a numerical quantity representing biological effectiveness is generated. When expressed relative to a reference radiation, this quantity is found to differ for protons and a particles of the same LET, demonstrating not only the ion-specific nature of RBE but also the inadequacy of specifying radiation quality as a function of LET only. Such a method for numerically assessing radiation quality may have implications for procedures for heavy ion protection in space at low doses and for understanding the initial mechanisms of radiation action. PMID:15934210

Craven, P A; Rycroft, M J

2005-01-01

375

Fabrication of high resolution n-type 4H-SiC epitaxial layer alpha particle detectors, defect characterization and electronic noise analysis  

NASA Astrophysics Data System (ADS)

In the present work high-resolution alpha particle detectors have been fabricated on high quality 20 ?m thick n-type 4H-SiC epitaxial layers. Schottky barrier detectors have been fabricated by depositing 10 nm thick nickel contacts on the Si face of the epilayers. The detectors were characterized using current-voltage (I-V), capacitance-voltage (CV), alpha spectroscopic measurements, and deep level transient spectroscopy (DLTS). I-V measurements revealed a barrier height of ~1.6 eV, diode ideality factor of 1.09, and leakage current of the order of 14 pA at an operating bias of 110 V. C-V measurements revealed low effective doping concentrations of 3.1 × 1014 cm-3 in the epilayers. A micropipe density lower than 1 cm-2 was evaluated in the epilayers. Pulse-height spectroscopy exhibited energy resolution as high as 0.37 % for 5.48 MeV alpha particles with a detector active area of 11 mm2. A diffusion length of ~13.2 ?m for holes has been determined in these detectors following a calculation based on a drift-diffusion model. Detailed electronic noise analysis in terms of equivalent noise charge (ENC) was carried out to study the effect of various noise components that contribute to the total electronic noise in the detection system. The noise analysis revealed that the white series noise due to the detector capacitance has substantial effect on the detector's overall performance. DLTS measurements have revealed the presence of at least four majority (electron) carrier trap levels that can act as recombination/generation or trapping centers.

Zavalla, Kelvin J.; Chaudhuri, Sandeep K.; Mandal, Krishna C.

2013-09-01

376

Effects of Complex Symmetry-Breakings on Alpha Particle Power Loads on First Wall Structures and Equilibrium in ITER  

SciTech Connect

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.

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

377

Development of a He- and He0 beam source for alpha particle measurement in a burning plasma  

NASA Astrophysics Data System (ADS)

Proof of principle experiments of neutral helium beam production for alpha particle diagnostics was carried out on a test stand. Negative helium ions were produced in the Li charge exchange cell, in which stable and long time operation was possible. He- beam was accelerated to 157 keV. Finally, He0 beam was successfully produced after the flight in the drift-tube through the auto-electron-detachment process from He- to He0. A neutral beam detector using a pyroelectric device was also developed to measure He0 beam intensity. The metastable component in the neutral helium beam was found to be less than 2%.

Tanaka, N.; Sasao, M.; Terai, K.; Okamoto, A.; Kitajima, S.; Yamaoka, H.; Wada, M.

2012-02-01

378

A New Interpretation of Alpha-particle-driven Instabilities in Deuterium-Tritium Experiments on the Tokamak Fusion Test Reactor  

SciTech Connect

The original description of alpha-particle-driven instabilities in the Tokamak Fusion Test Reactor (TFTR) in terms of Toroidal Alfvin Eigenmodes (TAEs) remained inconsistent with three fundamental characteristics of the observations: (i) the variation of the mode frequency with toroidal mode number, (ii) the chirping of the mode frequency for a given toroidal mode number, and (iii) the anti-ballooning density perturbation of the modes. It is now shown that these characteristics can be explained by observing that cylindrical-like modes can exist in the weak magnetic shear region of the plasma that then make a transition to TAEs as the central safety factor decreases in time.

R. Nazikian; G.J. Kramer; C.Z. Cheng; N.N. Gorelenkov; H.L. Berk; S.E. Sharapov

2003-03-26

379

Standardisation of low-activity actinide solutions by alpha-particle counting at a defined solid angle.  

PubMed

In the frame of an IAEA co-ordinated research project 232U, 236Pu and 229Th tracers were standardised by alpha-particle counting at a defined solid angle. The aim of this project was to assign property values that are traceable to the International System of Units (SI). This article depicts the standardisation of the tracers, elaborating on problems related to low activity and interference from daughter nuclides. The activity concentrations of 232U, 236Pu and 229Th were found to be, respectively (734+/-4), (142.0+/-0.9) and (528.2+/-2.6) Bq g(-1), at reference date (1 January 2003). PMID:15177379

Sibbens, G; Pommé, S; Altzitzoglou, T

2004-01-01

380

Contribution from the inner shell of water vapour to dose profiles under proton and alpha particle irradiation  

NASA Astrophysics Data System (ADS)

Doubly differential cross sections for electron emission calculated using the CDW - EIS model and a simple approximation for the electron transport in the target are used to obtain dose profiles around the ion path for proton and alpha particles in water vapour. The contribution from each initial molecular orbital is determined. At large distances from the track, discrepancies are found with other models and with the well known dependence.

Olivera, G. H.; Fainstein, P. D.; Rivarola, R. D.

1996-09-01

381

1.5D Quasilinear Model for Alpha Particle-TAE Interaction in ARIES ACT-I  

SciTech Connect

We study the TAE interaction with alpha particle fusion products in ARIES ACT-I using the 1.5D quasilinear model. 1.5D uses linear analytic expressions for growth and damping rates of TAE modes evaluated using TRANSP pro les to calculates the relaxation of pressure pro les. NOVA- K simulations are conducted to validate the analytic dependancies of the rates, and to normalize their absolute value. The low dimensionality of the model permits calculating loss diagrams in large parameter spaces.

K. Ghantous, N.N. Gorelenkov, C. Kessel, F. Poli

2013-01-30

382

Turbulent Heating of Plasmas by High Energy Particle Beams.  

National Technical Information Service (NTIS)

During the performance period on this contract, 30 June 1976, substantial progress has been made in our research on the interactions of high energy beams of charged particles. The mechanisms and efficiency of energy transfer have been investigated from re...

W. E. Drummond J. R. Thompson G. I. Bourianoff D. E. Hasti M. L. Sloan

1976-01-01

383

Isomeric yield ratios and excitation functions in alpha-induced reactions on 107,109Ag  

Microsoft Academic Search

Isomeric yield ratios for the reactions 107Ag(alpha,3n)108In, 107Ag(alpha,alpha3n)104Ag, 109Ag(alpha,2n)111In, and 109Ag(alpha,3n)110In are determined in the energy range of 20-63 MeV alpha particles. Excitation functions for the above reactions as well as for the 107Ag(alpha,2n)109In, 107Ag(alpha,alpha2n)105Ag, 109Ag(alpha,4n)109In, 109Ag(alpha,5n)108In, and 109Ag(alpha,alpha4n)105Ag reactions are also presented. Experimental excitation functions are compared with statistical model calculations taking into account precompound particle emission. Isomeric yield

R. Guin; S. K. Saha; Satya Prakash; M. Uhl

1992-01-01

384

Comparison of alpha-particle and neutron-induced combinational and sequential logic error rates at the 32nm technology node  

Microsoft Academic Search

We report on particle induced upset rates of combinational and sequential logic. A novel test chip has been designed in a 32 nm process to study the effects of single event transients (SET) and to verify the accuracy of our simulation models. The test chip has been tested under neutron and alpha particle radiation. Our measured data verify simulation-based projections

B. Gill; N. Seifert; V. Zia

2009-01-01

385

Bystander effect for chromosomal aberrations induced in wild-type and repair deficient CHO cells by low fluences of alpha particles  

Microsoft Academic Search

We have previously shown that when confluent cultures of mammalian cells are exposed to very low fluences of alpha particles, fluences whereby as few as 1% of the cell nuclei are traversed by a single particle, genetic effects including specific gene mutations and sister chromatid exchanges (SCE) are induced in neighboring, non-irradiated “bystander” cells. The present investigation was designed to

Hatsumi Nagasawa; John B. Little

2002-01-01

386

Enhancement of particle-wave energy exchange by resonance sweeping  

SciTech Connect

When the resonance condition of the particle-wave interaction is varied adiabatically, the particles trapped in a wave are found to form phase space holes or clumps that enhance the particle-wave energy exchange. This mechanism can cause increased saturation levels of instabilities and even allow the free energy associated with instability to be tapped in a system in which background dissipation suppresses linear instability.

Berk, H.L.; Breizman, B.N.

1996-01-01

387

Enhancement of particle-wave energy exchange by resonance sweeping  

SciTech Connect

It is shown that as the resonance condition of the particle-wave interaction is varied adiabatically, that the particles trapped in the wave will form phase space holes or clumps that can enhance the particle-wave energy exchange. This mechanism can cause much larger saturation levels of instabilities, and even allow the free energy associated with instability, to be tapped in a system that is linearly stable due to background dissipation.

Berk, H.L.; Breizman, B.N.

1995-10-01

388

High Energy Charged Particles in Space at One Astronomical Unit  

NASA Technical Reports Server (NTRS)

Single event effects and many other spacecraft anomalies are caused by positively charged high energy particles impinging on the vehicle and its component parts. Reviewed here are the current knowledge of the interplanetary particle environment in the energy ranges that are most important for these effects. State-of-the-art engineering models are briefly described along with comments on the future work required.

Feynman, J.; Gabriel, S. B.

1995-01-01

389

Experimental investigations of electron capture from atomic hydrogen and deuterium by alpha particles. Annual progress report, 15 September 1991--14 September 1992  

SciTech Connect

We report progress made during the period 15 September 1991--14 September 1992 on the project ``Experimental Investigations of Electron Capture from Atomic Hydrogen and Deuterium by Alpha Particles``. In the past year we have developed reliable, narrow energy spread, high-current sources of He{sup ++} based on direct-current magentron and electron-cyclotron resonance discharges. These sources have been proven on our test bench accelerator which has been upgraded to also allow us to test atomic hydrogen effusive targets. We have thus made substantial progress toward our goal of studying single electron capture from atomic hydrogen by doubly-ionized helium. A research plan for the upcoming year is also presented.

Gay, T.J.; Park, J.T.

1992-11-01

390

Fabrication of substrates with curvature for cell cultivation by alpha-particle irradiation and chemical etching of PADC films  

NASA Astrophysics Data System (ADS)

In the present paper, we developed a microfabrication technology to generate cell-culture substrates with identical chemistry and well-defined curvature. Micrometer-sized pits with curved surfaces were created on a two-dimensional surface of a polymer known as polyallyldiglycol carbonate (PADC). A PADC film was first irradiated by alpha particles and then chemically etched under specific conditions to generate pits with well-defined curvature at the incident positions of the alpha particles. The surface with these pits was employed as a model system for studying the effects of substrate curvature on cell behavior. As an application, the present work studied mechanosensing of substrate curvature by epithelial cells (HeLa cells) through regulation of microtubule (MT) dynamics. We used end-binding protein 3-green fluorescent protein (EB3-GFP) as a marker of MT growth to show that epithelial cells having migrated into the pits with curved surfaces had significantly smaller MT growth speeds than those having stayed on flat surfaces without the pits.

Ng, C. K. M.; Tjhin, V. T.; Lin, A. C. C.; Cheng, J. P.; Cheng, S. H.; Yu, K. N.

2012-05-01

391

A neutral-beam diagnostic for fast confined alpha particles in a burning plasma: Application on CIT (Compact Ignition Tokamak)  

SciTech Connect

Diagnostic methods for fast confined alpha particles are essential for a burning-plasma experiment. We review one- and two-electron-capture methods using energetic neutral beams, and provide quantitative estimates of signal level for a two-electron-capture method applicable to CIT. The best probe is a ground-state helium-atom beam because of its relatively good penetration into a CIT plasma and the large cross section for two-electron capture; it can be produced in useful quantities from HeH/sup +/. We calculate a signal level of the order of 10/sup 7/ counts/s for 100 mA of accelerated HeH/sup +/, which is sufficient to allow time-resolved measurements of the alpha-particle velocity distribution. Limited position information could be obtained for appropriate access port geometry. This diagnostic is feasible, and we recommend further research and development leading to implementation on CIT. 39 refs., 16 figs., 5 tabs.

Schlachter, A.S.; Stearns, J.W.; Cooper, W.S.

1987-10-01

392

Preliminary calculations of expected signal levels of a thin Faraday foil lost alpha particle diagnostic for International Thermonuclear Experimental Reactor  

SciTech Connect

Thin Faraday collectors are being considered as a diagnostic of lost alpha particles on International Thermonuclear Experimental Reactor (ITER). In an effort to evaluate the viability of this diagnostic, we are undertaking a series of calculations of the signal levels (A/cm{sup 2}) for such devices. Preliminary results assuming a model high yield ITER plasma have been obtained for locations near the outer wall assuming a toroidally symmetric vacuum vessel. We find signal levels to be a strong function of foil location and orientation. Specifically the signal level will be optimized at a vertical location 0.5 m above the machine midplane and with the normal to the foil directed in the lower, radially outward, toroidally counterclockwise octant. A foil thus oriented at a radial distance of 15 cm from the vessel wall at a height of 0.583 m above the machine midplane will have an efficiency of 3.5x10{sup -8}/cm{sup 2} for alpha particles which undergo classic loss during the first ten revolutions around the torus during this model plasma. For the assumed D-T fusion power of this model plasma of 410 MW, this calculated efficiency will correspond to a measured current in the Faraday foil of 1.7 {mu}A/cm{sup 2}. Future, more realistic calculations must incorporate the effects of an asymmetrical vessel and of toroidal field ripple.

Cecil, F.E.; Darrow, D.S.; Budny, R.V. [Department of Physics, Colorado School of Mines, Golden, Colorado (United States); Princeton Plasma Physics Laboratory, Princeton, New Jersey (United States)

2004-10-01

393

Gene amplification and microsatellite instability induced in tumorigenic human bronchial epithelial cells by alpha particles and heavy ions  

NASA Technical Reports Server (NTRS)

Gene amplification and microsatellite alteration are useful markers of genomic instability in tumor and transformed cell lines. It has been suggested that genomic instability contributes to the progression of tumorigenesis by accumulating genetic changes. In this study, amplification of the carbamyl-P-synthetase, aspartate transcarbamylase, dihydro-orotase (CAD) gene in transformed and tumorigenic human bronchial epithelial (BEP2D) cells induced by either alpha particles or (56)Fe ions was assessed by measuring resistance to N-(phosphonacetyl)-l-aspartate (PALA). In addition, alterations of microsatellite loci located on chromosomes 3p and 18q were analyzed in a series of primary and secondary tumor cell lines generated in nude mice. The frequency of PALA-resistant colonies was 1-3 x 10(-3) in tumor cell lines, 5-8 x 10(-5) in transformed cells prior to inoculation into nude mice, and less than 10(-7) in control BEP2D cells. Microsatellite alterations were detected in all 11 tumor cell lines examined at the following loci: D18S34, D18S363, D18S877, D3S1038 and D3S1607. No significant difference in either PALA resistance or microsatellite instability was found in tumor cell lines that were induced by alpha particles compared to those induced by (56)Fe ions.

Piao, C. Q.; Hei, T. K.; Hall, E. J. (Principal Investigator)

2001-01-01

394

Quantitative determination of superficial alpha activity by means of plastic track detectors  

Microsoft Academic Search

The influences of alpha particles' energy and angle of incidence on the readout obtained from cellulose nitrate plastic track detectors, exposed to materials emitting alpha particles, have been studied as a function of etching time. Simple detection equipment has been developed to allow precision measurement of superficial alpha activity. The technique has been applied to determine the air concentration of

Alfredo Cecchi; Cesare Gori; Giovanna Zatelli

1986-01-01

395

Evaluation of internal alpha-particle radiation exposure and subsequent fertility among a cohort of women formerly employed in the radium dial industry.  

PubMed

This study examined the effect of internal exposure to alpha-particle radiation on subsequent fertility among women employed in the radium dial industry prior to 1930, when appreciable amounts of radium were often ingested through the practice of pointing the paint brush with the lips. The analysis was limited to women for whom a radium body burden measurement had been obtained and who were married prior to age 45 (n = 603). Internal radiation dose to the ovary was calculated based on initial intakes of radium-226 and radium-228, average ovarian mass, number and energy of alpha particles emitted, fraction of energy absorbed within the ovary, effective retention integrals and estimated photon irradiation. Time between marriage and pregnancy, number of pregnancies and number of live births served as surrogates for fertility. Radiation appeared to have no effect on fertility at estimated cumulative ovarian dose equivalents below 5 Sv; above this dose, however, statistically significant declines in both number of pregnancies and live births were observed. These trends persisted after multivariable adjustment for potential confounding variables and after exclusion of subjects contributing a potential classification or selection bias to the study. Additionally, the high-dose group experienced fewer live births than would have been expected based on population rates. There were no differences in time to first pregnancy between high- and low-dose groups. These results are consistent with earlier studies of gamma-ray exposures and suggest that exposure to high doses of radiation from internally deposited radium reduces fertility rather than inducing sterility. PMID:9008216

Schieve, L A; Davis, F; Roeske, J; Handler, A; Freels, S; Stinchcomb, T; Keane, A

1997-02-01

396

Evaluation of internal alpha-particle radiation exposure and subsequent fertility among a cohort of women formerly employed in the radium dial industry  

SciTech Connect

This study examined the effect of internal exposure to {alpha}-particle radiation on subsequent fertility among women employed in radium dial industry prior to 1930, when appreciable amounts of radium were often ingested through the practice of pointing the paint brush with the lips. The analysis was limited to women for whom a radium body burden measurement had been obtained and who were married prior to age 45 (n = 603). Internal radiation dose to the ovary was calculated based on initial intakes of radium-226 and radium-228, average ovarian mass, number and energy of {alpha} particles emitted, fraction of energy absorbed within the ovary, effective retention integrals and estimated photon irradiation. Time between marriage and pregnancy, number of pregnancies and number of live births served as surrogates for fertility. Radiation appeared to have no effect on fertility at estimated cumulative ovarian dose equivalents below 5 Sv; above this dose, however, statistically significant declines in both number of pregnancies and live births were observed. These trends persisted after multivariable adjustment for potential confounding variables and after exclusion of subjects contributing a potential classification or selection bias to the study. Additionally, the high-dose group experienced fewer live births than would have been expected based on population rates. There were no differences in time to first pregnancy between high- and low-dose groups. These results are consistent with earlier studies of {gamma}-ray exposures and suggest that exposure to high doses of radiation from internally deposited radium reduces fertility rather than inducing sterility. 42 refs., 5 tabs.

Schieve, L.A.; Davis, F.; Freels, S. [Univ. of Illinois, Chicago, IL (United States)] [and others

1997-02-01

397

Alpha track analysis and fission track analysis for localizing actinide-bearing micro-particles in the Yenisey River bottom sediments  

Microsoft Academic Search

Distribution of actinides in bottom sediment and flood land soil cores collected from the Yenisey River near the Krasnoyarsk Mining and Chemical Combine (MCC) were analyzed. Actinide-bearing micro-particles were localized using alpha track analysis (ATA) and fission track analysis (FTA). Different types of radioactive micro-particles were found by analysis of the ratios of fission tracks to ?-tracks from single particles.

I. E. Vlasova; St. N. Kalmykov; Yu. V. Konevnik; S. G. Simakin; I. S. Simakin; A. Yu. Anokhin; Yu. A. Sapozhnikov

2008-01-01

398

Screening materials with the XIA UltraLo alpha particle counter at Southern Methodist University  

SciTech Connect

Southern Methodist University houses one of five existing commercially available UltraLo 1800 production model alpha counters made by XIA LLC. The instrument has an electron drift chamber with a 707 cm{sup 2} or 1800 cm{sup 2} counting region which is determined by selecting the inner electrode size. The SMU team operating this device is part of the SuperCDMS screening working group, and uses the alpha counter to study the background rates from the decay of radon in materials used to construct the SuperCDMS experiment. We have studied four acrylic samples obtained from the MiniCLEAN direct dark matter search with the XIA instrument demonstrating its utility in low background experiments by investigating the plate-out of {sup 210}Pb and comparing the effectiveness of cleaning procedures in removing {sup 222}Rn progenies from the samples.

Nakib, M. Z.; Cooley, J.; Kara, B.; Qiu, H.; Scorza, S. [Department of Physics, Southern Methodist University, Dallas, TX (United States)] [Department of Physics, Southern Methodist University, Dallas, TX (United States); Guiseppe, V. E. [Department of Physics, University of South Dakota, Vermillion, SD (United States)] [Department of Physics, University of South Dakota, Vermillion, SD (United States); Rielage, K. [Los Alamos National Laboratory, Los Alamos, NM (United States)] [Los Alamos National Laboratory, Los Alamos, NM (United States); Schnee, R. W. [Department of Physics, Syracuse University, Syracuse, NY (United States)] [Department of Physics, Syracuse University, Syracuse, NY (United States)

2013-08-08

399

Localized cyclotron mode driven by fast alpha particles under a nonuniform magnetic field  

SciTech Connect

Resonance requires precise synchronization. Surprisingly, relativistic cyclotron instability can survive under a magnetic field with its nonuniformity larger than the requirement of synchronism. Localized eigenmode observed in a hybrid simulation is found to be consistent with that predicted by an analytical theory including both profile and eigenvalue. Half of the spatial area of the wave profile is located where the frequency mismatch is negative as against to the positive requirement generally believed. The consequence on the alpha dynamics is also demonstrated.

Chen, K. R.; Tsai, T. H.; Chen, L. [Physics Department, Institute of Electro-Optical Science and Engineering, and Plasma and Space Science Center, National Cheng Kung University, Tainan 701, Taiwan (China); Physics Department and Plasma and Space Science Center, National Cheng Kung University, Tainan 701, Taiwan (China); Department of Physics and Astronomy, University of California, Irvine, California 92697 (United States)

2010-02-15

400

Localized cyclotron mode driven by fast alpha particles under a nonuniform magnetic field.  

PubMed

Resonance requires precise synchronization. Surprisingly, relativistic cyclotron instability can survive under a magnetic field with its nonuniformity larger than the requirement of synchronism. Localized eigenmode observed in a hybrid simulation is found to be consistent with that predicted by an analytical theory including both profile and eigenvalue. Half of the spatial area of the wave profile is located where the frequency mismatch is negative as against to the positive requirement generally believed. The consequence on the alpha dynamics is also demonstrated. PMID:20365662

Chen, K R; Tsai, T H; Chen, L

2010-02-01

401

Design considerations for thin film coated semiconductor thermal neutron detectors—I: basics regarding alpha particle emitting neutron reactive films  

Microsoft Academic Search

Semiconductor-based thermal neutron detectors provide a compact technology for neutron detection and imaging. Such devices can be produced by externally coating semiconductor-charged-particle detectors with neutron reactive films that convert free neutrons into charged-particle reaction products. Commonly used films for such devices utilize the 10B(n,?)7Li reaction or the 6Li(n,?)3H reaction, which are attractive due to the relatively high energies imparted to

D. S. McGregor; M. D. Hammig; Y.-H. Yang; H. K. Gersch; R. T. Klann

2003-01-01

402

Introduction: The High-energy Corona – Waves, Eruptions, Particles  

Microsoft Academic Search

Flares and coronal mass ejections (CME) are the most violent manifestations of solar activity. They are the consequence of the explosive conversion of energy stored in coronal magnetic fields into plasma heating, the kinetic energy of supra-thermal to high energy particles and the mechanical energy of magnetic structures that are propelled through the corona and into interplanetary space. The corona

Karl-Ludwig Klein; Alexander MacKinnon

2007-01-01

403

Electron optics of spheroid charged particle energy analyzers  

Microsoft Academic Search

A new class of charged particle energy analyzers, spheroid energy analyzers (SEA) that are characterized with very high energy resolution and transmission, is presented. A prototype analyzer was built that has achieved a relative energy resolution of 0.05% at a transmission of 21% out of a 2? steradian. A very high order of focusing of these analyzers is presented via

D. Cubric; N. Kholine; I. Konishi

2011-01-01

404

Neutron angular and energy distributions from 710MeV alphas stopping in water, carbon, steel, and lead, and 640MeV alphas stopping in lead  

Microsoft Academic Search

We measured neutron angular and energy distributions from 710-MeV alphas stopping in targets of water, carbon, steel, and lead for neutron energies from 3 MeV to above 300 MeV. We also measured neutron spectra from 640-MeV alphas stopping in lead. These spectra are similar to the 710-MeV spectra but are reduced in magnitude by about 20 percent. The angular distributions

R. A. Cecil; B. D. Anderson; A. R. Baldwin; R. Madey; A. Galonsky; P. Miller; L. Young; F. M. Waterman

1980-01-01

405

Outgassing from alpha particle irradiation of lithium hydride and lithium hydroxide  

Microsoft Academic Search

We have experimentally studied the effects of ?-particle radiation on isotopically enriched lithium hydride (6LiH) and its corrosion product lithium hydroxide (6LiOH) to determine, in particular, the type and amount of gases evolved during irradiation. SRIM Monte Carlo simulations suggest that irradiating these materials with 2.2-MeV ?-particles will ionize atoms and form hydrogen vacancies in the target material, and that

Carol Haertling; Igor Usov; Yongqiang Wang

2011-01-01

406

Accounting for long alpha-particle stopping distances in (U-Th-Sm)/He geochronology: Refinement of the baseline case  

NASA Astrophysics Data System (ADS)

This contribution proposes a number of methodological refinements for accounting for ejection of energetic particles, most particularly in the case of long alpha-particle stopping distance effects in (U-Th-Sm)/He thermochronometry. Recent stopping-distance estimates for minerals commonly used for thermochronometry are up to 1.5 ?m shorter than previously thought, which directly affects the magnitude of the ejection correction parameter FT. The revision in stopping distances necessitates re-fitting the empirical polynomials that have been used to calculate FT corrections for various crystal forms. Reformulation and re-parameterization of these polynomials enables them to account for present and any future change in stopping distances without needing to be recalibrated. The library of shapes described with these polynomials to accommodate habits is expanded for all crystal systems and also ellipsoids, thus covering all minerals currently used and under development for (U-Th-Sm)/He thermochronometry. In addition, the inaccuracy caused by characterizing a set of alpha particles from a decay chain with a single mean stopping distance is examined, and a simple method for compensation is recommended. A new method of using FT parameters to calculate corrected ages by applying them to parents instead of daughters or age is presented, which maximizes accuracy for old specimens such as meteorites. Altogether, the refinements proposed will affect (U-Th-Sm)/He ages by ˜1-5%, depending on size and age. Finally, the concept of an FT-equivalent sphere is introduced as a sphere with the same effective FT value as a given mineral grain. Testing indicates that the FT-equivalent sphere is of comparable or superior accuracy to a sphere of the same surface to volume ratio for diffusion modeling. This finding greatly facilitates utilization of (U-Th-Sm)/He data from standard data tables for forward and inverse modeling.

Ketcham, Richard A.; Gautheron, Cécile; Tassan-Got, Laurent

2011-12-01

407

A particle energy determination with an imaging plate  

Microsoft Academic Search

It is shown that the stimulation spectra of Eu2+ luminescence in BaFBr:Eu2+ based imaging plates are strongly dependent on the energies of the incident charged particles and the ratios of the luminescences stimulated by two different light wave lengths, e.g. of 600 and 500 nm, indicate simply the energies. This additional feature enables us to determine the incident particle energies

Masahiro Takebe; Ken Abe; Manabu Souda; Yoshiyuki Satoh; Yasuhiro Kondo

1995-01-01

408

The Radiation Chemistsry of Aqueous Solutions. III. The Isotope Effect for Polonium alpha-Particles and Tritium beta-Particles  

Microsoft Academic Search

Investigations similar to those described in parts I and II for ordinary water have been made on D_2O. For tritium beta-particles the derived yields are GD = 3\\\\cdot34±0\\\\cdot03, GOD = 2\\\\cdot26±0\\\\cdot1, GD_2O_2 = 0\\\\cdot81_5± 0\\\\cdot02, GD_2 = 0.27_5±0.08_5 and G-D_2O = 3\\\\cdot89±0\\\\cdot14. Observed yields G(Ce3+)T1^+ = 7\\\\cdot50±0.5, G(Fe3+)-O_2 = 7\\\\cdot15±0\\\\cdot15, G(D_2)0\\\\cdot1N = 0\\\\cdot61±0\\\\cdot02 and G(D_2O_2)O_2_i = 1\\\\cdot02±0\\\\cdot1 are close to

E. Collinson; F. S. Dainton; J. Kroh

1962-01-01

409

I. Excluded Volume Effects in Ising Cluster Distributions and Nuclear Multifragmentation II. Multiple-Chance Effects in Alpha-Particle Evaporation  

SciTech Connect

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's single-chance evaporation theory is augmented to include multiple-chance emission and tested on experimental data to yield positive results.

Breus, Dimitry E.

2005-05-16

410

Isomeric yield ratios in proton-, sup 3 He, and. alpha. -particle-induced reactions on sup 197 Au  

Microsoft Academic Search

Excitation functions and mean projected recoil-ion ranges of the isomeric nuclei produced in proton-, ³He-, and α-particle-induced reactions on ¹⁹⁷Au were measured by an activation technique for bombarding energies {ital E}{sub {ital p}}{approx lt}50 MeV, and {ital E} {sub ³He,α}{approx lt}40 MeV. Isomeric yield ratios (Ï{sub {ital m}}\\/Ï{sub {ital g}}) were determined as a function of the incident particle energy.

Y. Nagame; K. Sueki; S. Baba; H. Nakahara

1990-01-01

411

Experimental validation of an analytical method to obtain the response function of an alpha particle spectrometer  

PubMed

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. PMID:10724372

Romanikhin; Garcia-Torano Martinez E

2000-03-01

412

Single particle tracking of alpha7 nicotinic AChR in hippocampal neurons reveals regulated confinement at glutamatergic and GABAergic perisynaptic sites.  

PubMed

Alpha7 neuronal nicotinic acetylcholine receptors (alpha7-nAChR) form Ca(2+)-permeable homopentameric channels modulating cortical network activity and cognitive processing. They are located pre- and postsynaptically and are highly abundant in hippocampal GABAergic interneurons. It is unclear how alpha7-nAChRs are positioned in specific membrane microdomains, particularly in cultured neurons which are devoid of cholinergic synapses. To address this issue, we monitored by single particle tracking the lateral mobility of individual alpha7-nAChRs labeled with alpha-bungarotoxin linked to quantum dots in live rat cultured hippocampal interneurons. Quantitative analysis revealed different modes of lateral diffusion of alpha7-nAChR dependent on their subcellular localization. Confined receptors were found in the immediate vicinity of glutamatergic and GABAergic postsynaptic densities, as well as in extrasynaptic clusters of alpha-bungarotoxin labeling on dendrites. alpha7-nAChRs avoided entering postsynaptic densities, but exhibited reduced mobility and long dwell times at perisynaptic locations, indicative of regulated confinement. Their diffusion coefficient was lower, on average, at glutamatergic than at GABAergic perisynaptic sites, suggesting differential, synapse-specific tethering mechanisms. Disruption of the cytoskeleton affected alpha7-nAChR mobility and cell surface expression, but not their ability to form clusters. Finally, using tetrodotoxin to silence network activity, as well as exposure to a selective alpha7-nAChR agonist or antagonist, we observed that alpha7-nAChRs cell surface dynamics is modulated by chronic changes in neuronal activity. Altogether, given their high Ca(2+)-permeability, our results suggest a possible role of alpha7-nAChR on interneurons for activating Ca(2+)-dependent signaling in the vicinity of GABAergic and glutamatergic synapses. PMID:20634896

Bürli, Thomas; Baer, Kristin; Ewers, Helge; Sidler, Corinne; Fuhrer, Christian; Fritschy, Jean-Marc

2010-01-01

413

The problem of low energy particle measurements in the magnetosphere  

NASA Technical Reports Server (NTRS)

The accurate measurement of low energy (less than 100 eV) particle properties in the magnetosphere has been difficult, partly because of the low density of such particles, but more particularly because of spacecraft interference effects. Some early examples of how these phenomena have affected particle measurements on an OGO spacecraft are presented. Data obtained with the UCSD particle detectors on ATS-6 are then presented showing how some of these difficulties have been partially overcome. Future measurements of low energy particles in the magnetosphere can be improved by: (1) improving the low energy resolution of detectors; (2) building electrostatically clean spacecraft; (3) controlling spacecraft potential; and (4) using auxiliary measurements, particularly wave data.

Whipple, E. C., Jr.

1978-01-01

414

Constraints on Dirac-Born-Infeld type dark energy models from varying alpha  

SciTech Connect

We study the variation of the effective fine-structure constant alpha for Dirac-Born-Infeld (DBI) type dark energy models. The DBI action based on string theory naturally gives rise to a coupling between gauge fields and a scalar field responsible for accelerated expansion of the universe. This leads to the change of alpha due to a dynamical evolution of the scalar field, which can be compatible with the recently observed cosmological data around the redshift z-tilde < or approx. 3. We place constraints on several different DBI models including exponential, inverse power-law and rolling massive scalar potentials. We find that these models can satisfy the varying alpha constraint provided that mass scales of the potentials are fine-tuned. When we adopt the mass scales which are motivated by string theory, both exponential and inverse power-law potentials give unacceptably large change of alpha, thus ruled out from observations. On the other hand the rolling massive scalar potential is compatible with the observationally allowed variation of alpha. Therefore the information of varying alpha provides a powerful way to distinguish between a number of string-inspired DBI dark energy models.

Garousi, Mohammad R. [Department of Physics, Ferdowsi University, P.O.Box 1436, Mashhad, Iran (Iran, Islamic Republic of); Institute for Studies in Theoretical Physics and Mathematics IPMP.O.Box 19395-5531, Tehran, Iran (Iran, Islamic Republic of); Sami, M. [IUCAA, Post Bag 4, Ganeshkh