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1

Fossil Alpha-Particle Recoil Tracks: A New Method of Age Determination  

Microsoft Academic Search

The discovery of a new type of fossil nuclear track in mica is reported. This track is produced by the recoil nucleus accompanying the alpha -particle decay of uranium and thorium impurities. The tracks are very short and can be seen with phase contrast microscopy. Measurement of fossil alpha -recoil track densities, coupled with determinations of the thorium and uranium

W. H. Huang; R. M. Walker

1967-01-01

2

In situ production of alpha particles and alpha recoil particles in quartz applied to ESR studies of oxygen vacancies  

Microsoft Academic Search

The intensity of an ESR signal associated with oxygen vacancies in quartz (E1? center and heat-treated E1? center) are correlated with the radiometric age of their host rocks. Two natural processes are responsible for the production of oxygen vacancies (1) lattice damage along alpha recoil and alpha particle tracks and (2) randomly distributed ionization damage from energetic electrons (beta particles)

S. Toyoda; W. J Rink; C Yonezawa; H Matsue; T Kagami

2001-01-01

3

Transport of Radioactive Material by Alpha Recoil  

SciTech Connect

The movement of high-specific-activity radioactive particles (i.e., alpha recoil) has been observed and studied since the early 1900s. These studies have been motivated by concerns about containment of radioactivity and the protection of human health. Additionally, studies have investigated the potential advantage of alpha recoil to effect separations of various isotopes. This report provides a review of the observations and results of a number of the studies.

Icenhour, A.S.

2005-05-19

4

Transport of Radioactive Material by Alpha Recoil  

Microsoft Academic Search

The movement of high-specific-activity radioactive particles (i.e., alpha recoil) has been observed and studied since the early 1900s. These studies have been motivated by concerns about containment of radioactivity and the protection of human health. Additionally, studies have investigated the potential advantage of alpha recoil to effect separations of various isotopes. This report provides a review of the observations and

A. S. Icenhour

2005-01-01

5

Alpha-Recoil Tracks in Mica: Registration Efficiency  

Microsoft Academic Search

Recoils from alpha-particle decay of naturally occurring radioactive nuclides have energies between 70 and 169 kiloelectron volts. It is shown that these alpha recoils register tracks in mica, observable as etch pits, with an efficiency of about 80 percent. When the recoil energy is degraded to 40 kiloelectron volts the efficiency drops to 50 percent. But, since the decay of

Seymour Katcoff

1969-01-01

6

Alpha-recoil track dating of Quaternary volcanics  

Microsoft Academic Search

Like fission-track dating, alpha-recoil track (ART) dating is based on the accumulation of nuclear particles that are released by natural radioactivity and produce etchable tracks in solids. ARTs are formed during the alpha-decay of uranium and thorium as well as of their daughter nuclei. When emitting an alpha-particle, the heavy remaining nucleus recoils 30–40 nm, leaving behind a trail of

K. Gögen; G. A. Wagner

2000-01-01

7

Monitoring of electron drift velocity in drift chambers with alpha-decay recoils  

Microsoft Academic Search

Electron drift velocity is measured by detecting alpha-decay recoils in a drift chamber in coincidence with alpha-particles registered with a Si detector. The precision of the measurements is demonstrated to be better than 0.1%.

A. A. Vorobyov; V. S. Guselnikov; A. Yu. Maiorov; O. E. Prokofiev; V. M. Zaitsev

1991-01-01

8

The etching of alpha-recoil tracks in phlogopite  

Microsoft Academic Search

This work uses three phlogopite samples to investigate the etching behavior of alpha-recoil tracks (?-recoil tracks), which is a key problem in dating procedures. At the initial stage of the etching process, the number of alpha-recoil tracks increased linearly with etching time, then the linearity was interrupted due to the overlapping of alpha-recoil tracks. The slope of the etching line

Wanming Yuan; Shaokai Gao; Jinquan Dong; Zenkuan Bao; Xiuming Jia

2008-01-01

9

Radioactive Waste Storage Materials: Their alpha Recoil Aging  

Microsoft Academic Search

Ion implantation experiments suggest that the accumulation of alpha -recoil damage in radioactive waste storage materials, which behave like solid-state track detectors, plays a drastic role in their long-term degradation. The understanding of alpha -recoil ``aging,'' overlooked in earlier studies, offers new guidelines for improving waste storage conditions.

J. C. Dran; M. Maurette; J. C. Petit

1980-01-01

10

Exerpts from the history of alpha recoils.  

PubMed

Any confined air volume holding radon ((222)Rn) gas bears a memory of past radon concentrations due to (210)Pb (T(1/2) = 22 y) and its progenies entrapped in all solid objects in the volume. The efforts of quantifying past radon exposures by means of the left-behind long-lived radon progenies started in 1987 with this author's unsuccessful trials of removing (214)Po from radon exposed glass objects. In this contribution the history and different techniques of assessing radon exposure to man in retrospect will be overviewed. The main focus will be on the implantation of alpha recoils into glass surfaces, but also potential traps in radon dwellings will be discussed. It is concluded that for a successful retrospective application, three crucial imperatives must be met, i.e. firstly, the object must persistently store a certain fraction of the created (210)Pb atoms, secondly, be resistant over decades towards disturbances from the outside and thirdly, all (210)Pb atoms analysed must originate from airborne radon only. For large-scale radon epidemiological studies, non-destructive and inexpensive measurement techniques are essential. Large-scale studies cannot be based on objects rarely found in dwellings or not available for measurements. PMID:21306801

Samuelsson, Christer

2011-02-08

11

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

12

Fossil Alpha-Recoil Analysis of Certain Variant Radioactive Halos  

Microsoft Academic Search

The distribution of alpha-radioactivity in the vicinity of uranium and of certain variant radioactive halos in biotite was investigated by the fossil alpha-recoil method. Within the limits of the method I could not confirm a previously proposed hydrothermal mechanism for the origin of certain variant halo types due to polonium isotopes.

Robert V. Gentry

1968-01-01

13

Implantation of Radioactive Atoms by alpha Recoil.  

National Technical Information Service (NTIS)

The penetration depths of exp 224 Ra recoils in a polycrystalline target (Au) were measured, for parallel and isotropic implantation beams. Also measured were the penetration depths of exp 212 Pb from a exp 224 Ra source. The peeling technique of Whitton ...

S. Abrashkin

1976-01-01

14

Annealing behavior of alpha recoil tracks in phlogopite  

Microsoft Academic Search

In this study we present and interpret a new experimental data set documenting thermal annealing of alpha recoil tracks (ARTs) in phlogopite. Through improvements in experimental technique, difficulties in obtaining useable data from material with an uneven distribution of U and Th were overcome. The resulting annealing pattern was well organized on an Arrhenius plot, allowing construction of a simple,

Wanming Yuan; Richard A. Ketcham; Shaokai Gao; Jinquan Dong; Zenkuan Bao; Jun Deng

2009-01-01

15

Isotopic Disequilibrium of Uranium: Alpha-Recoil Damage and Preferential Solution Effects  

Microsoft Academic Search

Preferential loss of uranium-234 relative to uranium-238 from rocks into solutions has long been attributed to recoiling alpha-emitting nuclei. Direct evidence has been obtained for two mechanisms, first, recoil ejection from grains, and now release by natural etching of alpha-recoil tracks. The observations have implications for radon emanation and for the storage of alpha-emitting radioactive waste.

Robert L. Fleischer

1980-01-01

16

Isotopic disequilibrium of uranium: alpha-recoil damage and preferential solution effects  

Microsoft Academic Search

Preferential loss of uranium-234 relative to uranium-238 from rocks into solutions has long been attributed to recoiling alpha-emitting nuclei. Direct evidence has been obtained for two mechanisms, first, recoil ejection from grains, and now release by natural etching of alpha-recoil tracks. The observations have implications for radon emanation and for the storage of alpha-emitting radioactive waste.

R. L. FLEISCHER

1980-01-01

17

Recoil proton, alpha particle, and heavy ion impacts on microdosimetry and RBE of fast neutrons: analysis of kerma spectra calculated by Monte Carlo simulation.  

PubMed

Fast neutrons (FN) have a higher radio-biological effectiveness (RBE) compared with photons, however the mechanism of this increase remains a controversial issue. RBE variations are seen among various FN facilities and at the same facility when different tissue depths or thicknesses of hardening filters are used. These variations lead to uncertainties in dose reporting as well as in the comparisons of clinical results. Besides radiobiology and microdosimetry, another powerful method for the characterization of FN beams is the calculation of total proton and heavy ion kerma spectra. FLUKA and MCNP Monte Carlo code were used to simulate these kerma spectra following a set of microdosimetry measurements performed at the National Accelerator Centre. The calculated spectra confirmed major classical statements: RBE increase is linked to both slow energy protons and alpha particles yielded by (n,alpha) reactions on carbon and oxygen nuclei. The slow energy protons are produced by neutrons having an energy between 10 keV and 10 MeV, while the alpha particles are produced by neutrons having an energy between 10 keV and 15 MeV. Looking at the heavy ion kerma from <15 MeV and the proton kerma from neutrons <10 MeV, it is possible to anticipate y* and RBE trends. PMID:11233567

Pignol, J P; Slabbert, J

2001-02-01

18

Separation of the alpha-emitting radioisotopes actinium-225 and bismuth-213 from thorium-229 using alpha recoil methods  

NASA Astrophysics Data System (ADS)

An innovative method has been demonstrated for separating alpha-emitting isotopes for medical radiotherapy applications. The method relies on recoil-ion separation rather than on conventional wet chemistry techniques to separate medical isotopes from their precursor sources. The isotopes 225Ac and 213Bi have been separated from electro-deposited sources of 229ThO2. Separations of 225Ac were carried out by placing nickel recoil collector foils in firm contact with the 229ThO2 sources. One-stage recoil-ion separations of 225Ac from 229Th have been performed as well as two-stage separations of 213Bi from previously recoil separated 225Ac. In addition, a direct recoil separation of 213Bi from 229Th has been demonstrated. The 213Bi from the one-stage direct separation has a high isotopic purity, but contains small amounts of long-lived 225Ac alpha activity. The two-stage separations of 213Bi produce high isotopic purity material (>99.9999%), but result in lower isotopic yields. Range-energy calculations have been carried out to determine the yields of recoil ions as a function of alpha-particle energy and ThO2 thickness. The results of the calculations have been benchmarked with recoil separation measurements carried out using ThO2 electro-deposits over a range of thickness. A computer code based on the generalized Bateman equations has been developed to allow calculations of the amounts of any isotope in the 229Th decay chain as a function of recoil separation exposure time and elapsed time after the separation. An excellent match has been obtained between the predictions of the Bateman calculations and the results of recoil separation measurements. The recoil separation method has proven to be a simple and effective way of separating medically useful isotopes such as 213Bi. In addition, the method has been shown to produce no chemical or radioactive wastes, in contrast to radiochemical separation methods, which generate mixed (chemical and radioactive) waste.

Ruddy, F. H.; Dulloo, A. R.; Seidel, J. G.; Petrovi?, B.

2004-01-01

19

Alpha-recoil track densities in mica and radiometric age determination  

Microsoft Academic Search

Recoiling daughters of ?-decaying U and Th impurities in mica and other minerals produce localised lattice damage: alpha-recoil tracks. The age of a sample can be calculated from the number of tracks per unit volume (NART). To this end, the mica is etched and the etch pits at the sites of recoil-tracks are counted under the optical microscope. Because the

K. Stübner; R. C. Jonckheere; L. Ratschbacher

2005-01-01

20

Mobilization of thorium, radium and radon radionuclides in ground water by successive alpha-recoils  

Microsoft Academic Search

Alpha-recoil is an important way for the mobilization of ?-decay daughters in ground water. The processes of decay and recoil from 238U to 222Rn and from 232Th to 220Rn are successive. The release rates of successive recoils in this study are quantitatively estimated under two extreme conditions: complete absorption; and no adsorption of recoil elements by the porous medium. The

Hongbing Sun; Thomas M. Semkow

1998-01-01

21

Alpha-recoil damage and solution effects in minerals: uranium isotopic disequilibrium and radon release  

Microsoft Academic Search

Preferential loss relative to 238 U of 234 U from rocks into solutions has long been attributed to recoiling alpha-emitting nuclei. Using fission-track activation direct evidence has been obtained for two mechanisms: 1. (1) recoil ejection from grains. 2. (2) release by natural etching of alpha-recoil tracks. Tests of the second mechanism have been done using 239 PuO 2 sources

Robert L. Fleischer

1982-01-01

22

Alpha-recoil damage: Relation to isotopic disequilibrium and leaching of radionuclides  

Microsoft Academic Search

The observation by Raabe et al. (1973) of large differences between the solubilities of isotopically different plutonium dioxides, has led to the recognition of preferential etching of recoil damage as a widespread phenomenon for alpha-active radionuclides. The associated preferential solubility of the products of alpha decay, along with direct recoil ejection, are the two specific microscopic mechanisms that are documented

R FLEISCHER

1988-01-01

23

Alpha-recoil damage: Relation to isotopic disequilibrium and leaching of radionuclides  

Microsoft Academic Search

The observation by et al. (1973) of large differences between the solubilities of isotopically different plutonium dioxides, has led to the recognition of preferential etching of recoil damage as a widespread phenomenon for alpha-active radionuclides. The associated preferential solubility of the products of alpha decay, along with direct recoil ejection, are the two specific microscopic mechanisms that are documented as

Robert L. Fleischer

1988-01-01

24

Determination of the Lifetime of the 40-kev Excited State of 81Tl208 Following Alpha Decay Using Recoil Shifts of the Conversion Electrons  

Microsoft Academic Search

The lifetime of the 40-kev excited state of 81Tl208 which is produced after alpha decay has been measured by using recoil shifts of the conversion electrons. By using an alpha-particle-conversion-electron coincidence arrangement, a beam of moving recoil nuclei in vacuum is effectively selected. The momenta of electrons emitted from such moving nuclei into the acceptance angle of a lens spectrometer

J. Burde; S. G. Cohen

1956-01-01

25

Digital characterization of recoil charged-particle tracks for neutron measurements  

SciTech Connect

We are developing a new optical ionization detector for imaging the track of a charged neutron-recoil particle in a gas. Electrons produced in the path of the recoil particle are excited by an external, high-voltage, RF, electric field of short duration. Their oscillatory motion causes ionization and excitation of nearby gas molecules, which then emit light in subsequent de-excitation. Two digital cameras image the optical radiation across two perpendicular planes and analyze it for the numbers of electrons in various volume elements along the track. These numbers constitute the digital characterization of the track. This information can then be used to infer the energy deposited in the track and the track LET in the gas. We have now observed alpha-particle tracks in a chamber utilizing these principles. The application of such a device for neutron dosimetry and neutron spectrometry will be described. 4 refs., 3 figs.

Turner, J.E.; Hunter, S.R.; Hamm, R.N.; Wright, H.A.; Hurst, G.S.; Gibson, W.A.

1988-01-01

26

Alpha-Recoil Thorium234: Dissolution into Water and the Uranium234\\/Uranium238 Disequilibrium in Nature  

Microsoft Academic Search

The rate of ejection of alpha-recoil thorium-234 into solution from the surface of zircon sand gives an alpha-recoil range of 550 angstroms. The alpha-recoil thorium-234 atoms ejected into the groundwater may supply excess uranium-234. In pelagic sediments, ejected alpha-recoil thorium-234 may contribute to the supply of mobile uranium-234 in the sedimentary column.

Kunihiko Kigoshi

1971-01-01

27

Imaging alpha particle detector  

DOEpatents

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

Anderson, D.F.

1980-10-29

28

alpha decay and recoil decay tagging studies of 183Tl  

Microsoft Academic Search

High-spin states in the nucleus 183Tl have been studied using the recoil decay tagging and recoil tagging techniques. The data have enabled new structures to be identified which are believed to be based on prolate f7\\/2 , h9\\/2 , and oblate h9\\/2 configurations. In addition, the prolate i3\\/2 structure has also been extended. The systematics of the newly identified structures

P. M. Raddon; D. G. Jenkins; C. D. O'Leary; A. J. Simons; R. Wadsworth; A. N. Andreyev; R. D. Page; M. P. Carpenter; F. G. Kondev; T. Enqvist; P. T. Greenlees; P. M. Jones; R. Julin; S. Juutinen; H. Kettunen; M. Leino; A.-P. Leppänen; P. Nieminen; J. Pakarinen; P. Rahkila; J. Uusitalo; D. T. Joss

2004-01-01

29

Etching behaviour of alpha-recoil tracks in natural dark mica studied via artificial ion tracks  

Microsoft Academic Search

Alpha-recoil tracks (ARTs) created by the alpha-decay of U, Th, and their daughter nuclei, are used by a new dating method to determine the formation age of dark mica bearing Quaternary and Neogene volcanic rocks and the cooling age of plutonic and metamorphic rocks [Chem. Geol. 166 (2000) 127, Science 155 (1967) 1103]. The age equation combines the volumetric density

M. Lang; U. A. Glasmacher; R. Neumann; G. A. Wagner

2003-01-01

30

A Monte-Carlo calculation of the size distribution of latent alpha-recoil tracks  

Microsoft Academic Search

This paper proposes a Monte-Carlo method for calculating the time-dependent size distribution of alpha-recoil tracks in minerals. The results show that, in the case of recoil tracks in phlogopite, produced by the uranium-series isotopes in the time interval between 0 and 1 Ma, the size distribution comprises two distinct track-populations. The first has a mean size of ?30 nm and

Raymond Jonckheere; Kür?ad Gögen

2001-01-01

31

Treatment of solid tumors by interstitial release of recoiling short-lived alpha emitters  

NASA Astrophysics Data System (ADS)

A new method utilizing alpha particles to treat solid tumors is presented. Tumors are treated with interstitial radioactive sources which continually release short-lived alpha emitting atoms from their surface. The atoms disperse inside the tumor, delivering a high dose through their alpha decays. We implement this scheme using thin wire sources impregnated with 224Ra, which release by recoil 220Rn, 216Po and 212Pb atoms. This work aims to demonstrate the feasibility of our method by measuring the activity patterns of the released radionuclides in experimental tumors. Sources carrying 224Ra activities in the range 10-130 kBq were used in experiments on murine squamous cell carcinoma tumors. These included gamma spectroscopy of the dissected tumors and major organs, Fuji-plate autoradiography of histological tumor sections and tissue damage detection by Hematoxylin-Eosin staining. The measurements focused on 212Pb and 212Bi. The 220Rn/216Po distribution was treated theoretically using a simple diffusion model. A simplified scheme was used to convert measured 212Pb activities to absorbed dose estimates. Both physical and histological measurements confirmed the formation of a 5-7 mm diameter necrotic region receiving a therapeutic alpha-particle dose around the source. The necrotic regions shape closely corresponded to the measured activity patterns. 212Pb was found to leave the tumor through the blood at a rate which decreased with tumor mass. Our results suggest that the proposed method, termed DART (diffusing alpha-emitters radiation therapy), may potentially be useful for the treatment of human patients.

Arazi, L.; Cooks, T.; Schmidt, M.; Keisari, Y.; Kelson, I.

2007-08-01

32

Treatment of solid tumors by interstitial release of recoiling short-lived alpha emitters.  

PubMed

A new method utilizing alpha particles to treat solid tumors is presented. Tumors are treated with interstitial radioactive sources which continually release short-lived alpha emitting atoms from their surface. The atoms disperse inside the tumor, delivering a high dose through their alpha decays. We implement this scheme using thin wire sources impregnated with (224)Ra, which release by recoil (220)Rn, (216)Po and (212)Pb atoms. This work aims to demonstrate the feasibility of our method by measuring the activity patterns of the released radionuclides in experimental tumors. Sources carrying (224)Ra activities in the range 10-130 kBq were used in experiments on murine squamous cell carcinoma tumors. These included gamma spectroscopy of the dissected tumors and major organs, Fuji-plate autoradiography of histological tumor sections and tissue damage detection by Hematoxylin-Eosin staining. The measurements focused on (212)Pb and (212)Bi. The (220)Rn/(216)Po distribution was treated theoretically using a simple diffusion model. A simplified scheme was used to convert measured (212)Pb activities to absorbed dose estimates. Both physical and histological measurements confirmed the formation of a 5-7 mm diameter necrotic region receiving a therapeutic alpha-particle dose around the source. The necrotic regions shape closely corresponded to the measured activity patterns. (212)Pb was found to leave the tumor through the blood at a rate which decreased with tumor mass. Our results suggest that the proposed method, termed DART (diffusing alpha-emitters radiation therapy), may potentially be useful for the treatment of human patients. PMID:17671351

Arazi, L; Cooks, T; Schmidt, M; Keisari, Y; Kelson, I

2007-08-01

33

Separation of the alpha-emitting radioisotopes actinium-225 and bismuth-213 from thorium-229 using alpha recoil methods  

Microsoft Academic Search

An innovative method has been demonstrated for separating alpha-emitting isotopes for medical radiotherapy applications. The method relies on recoil-ion separation rather than on conventional wet chemistry techniques to separate medical isotopes from their precursor sources. The isotopes 225Ac and 213Bi have been separated from electro-deposited sources of 229ThO2. Separations of 225Ac were carried out by placing nickel recoil collector foils

F. H. Ruddy; A. R. Dulloo; J. G. Seidel; B. Petrovic

2004-01-01

34

Range calculation of alpha-recoil atoms in some minerals using LSS-theory  

Microsoft Academic Search

Alpha-recoil ranges were calculated for fifteen interesting minerals, especially for naturally occurring alpha-emitters, on the basis of the simple LSS-theory. The ranges obtained from single decay process were represented as a comprehensive range expression in A units, as well as the physical ranges in g\\/cm2 units. Furthermore, the total mean ranges concerning overall alpha-decaying members within each natural decay series,

T. Hashimoto; Y. Aoyagi; H. Kudo; T. Sotobayashi

1985-01-01

35

Alpha-particle microdosimetry.  

PubMed

With the increasing availability of alpha emitters, targeted ?-particle therapy has emerged as a solution of choice to treat haematological cancers and micrometastatic and minimal residual diseases. Alpha-particles are highly cytotoxic because of their high linear energy transfer (LET) and have a short range of a few cell diameters in tissue, assuring good treatment specificity. These radiologic features make conventional dosimetry less relevant for that context. Stochastic variations in the energy deposited in cell nuclei are important because of the microscopic target size, low number of ?- particle traversals, and variation in LET along the ?-particle track. Microdosimetry provides a conceptual framework that aims at a systematic analysis of the stochastic distribution of energy deposits in irradiated matter. The different quantities of microdosimetry and the different methods of microdosimetric calculations were described in the early eighties. Since then, numerous models have been published through the years and applied to analyse experimental data or to model realistic therapeutic situations. Major results have been an accurate description of the high toxicity of ?-particles, and the description of the predominant effect of activity distribution at the cellular scale on toxicity or efficacy of potential targeted ?-particle therapies. This last factor represents a major limitation to the use of microdosimetry in vivo because determination of the source - target distribution is complicated. The future contributions of microdosimetry in targeted ?-particle therapy research will certainly depend on the ability to develop high-resolution detectors and on the implementation of pharmaco-kinetic models at the tumour microenvironment scale. PMID:22201713

Chouin, Nicolas; Bardies, Manuel

2011-07-01

36

Alpha-recoil atoms of plutonium in the environment  

Microsoft Academic Search

The -recoil effect of239Pu has been observed in environmental samples and theN\\u000a\\u000a5\\u000aP\\u000a\\/N5 ratio in these samples has been calculated. This ratio in atmospheric samples is in the range between 10–5 and 10–4 (atom\\/atom). For other contemporary terrestrial samples it is in the range between 10–7 and 10–6 (atom\\/atom), while that of uranium mineral is about 10–10 (atom\\/atom).

I. O. Essien

1994-01-01

37

Summary of Alpha Particle Transport  

SciTech Connect

This paper summarizes the talks on alpha particle transport which were presented at the 5th International Atomic Energy Agency's Technical Committee Meeting on "Alpha Particles in Fusion Research" held at the Joint European Torus, England in September 1997.

Medley, S.S.; White, R.B.; Zweben, S.J.

1998-08-19

38

Investigation of a gas-catcher\\/ion guide system using alpha-decay recoil products  

Microsoft Academic Search

219Rn recoils from the alpha decay of 223Ra have been used to study the efficiency and delay time distributions of a gas-catcher\\/ion guide system. Ions with charge states up to +4 were coming out of the gas cell. Combining efficiency and delay time measurements, ion survival times in plasma free conditions can be deduced.

K. Perajarvi; J. Huikari; S. Rinta-Antila; P. Dendooven

2002-01-01

39

Etching behaviour of alpha-recoil tracks in natural dark mica studied via artificial ion tracks  

Microsoft Academic Search

Alpha-recoil tracks (ARTs) created by the ?-decay of U, Th, and their daughter nuclei, are used by a new dating method to determine the formation age of dark mica bearing Quaternary and Neogene volcanic rocks and the cooling age of plutonic and metamorphic rocks [Chem. Geol. 166 (2000) 127, Science 155 (1967) 1103]. The age equation combines the volumetric density

M. Lang; U. A. Glasmacher; R. Neumann; G. A. Wagner

2003-01-01

40

Theory of alpha recoil effects on radon release and isotopic disequilibrium  

Microsoft Academic Search

Using the present understanding of the mechanisms of release from rocks and soils of recoiling products of alpha emission, physical predictions can be made of the fraction of these nuclei that are directly freed and the fraction that can subsequently be freed by the action of water. The fractions depend on the size and nature of the grains in which

Robert L. Fleischer

1983-01-01

41

Penetration of HEPA Filters by Alpha Recoil Aerosols.  

National Technical Information Service (NTIS)

Tests at Oak Ridge National Laboratory confirmed that alpha-emitting particulate matter does penetrate high-efficiency filter medium, identical to that used in HEPA filters, much more effectively than do non-radioactive or beta-gamma active aerosols. Filt...

W. J. McDowell F. G. Seeley M. T. Ryan

1976-01-01

42

The alpha-recoil effects of uranium in the Oklo reactor  

Microsoft Academic Search

A series of acid-leaching experiments have been carried out on a sample of uranium ore from reactor zone number 10 of the Oklo mines in Gabon. Anomalously high U-234\\/U-238 ratios were observed accompanied by modestly increased U-235\\/U-238 ratios in uranium fractions. These results, which can be interpreted as being due to the alpha-recoil effects of U-238 and Pu-239, provide a

Z. Z. Sheng; P. K. Kuroda

1984-01-01

43

Lunar Surface Outgassing and Alpha Particle Measurements  

NASA Astrophysics Data System (ADS)

The Lunar Prospector Alpha Particle Spectrometer (LP APS) searched for lunar surface gas release events and mapped their distribution by detecting alpha particles produced by the decay of gaseous radon-222 (5.5 MeV, 3.8 day half-life), solid polonium-218 (6.0 MeV, 3 minute half-life), and solid polonium-210 (5.3 MeV, 138 day half-life, but held up in production by the 21 year half-life of lead-210). These three nuclides are radioactive daughters from the decay of uranium-238. 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 randomwalk process. The half-life of radon-222 allows the gas to spread out by several 100 km before it decays (depositing approximately half of the polonium-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 lead-210 precursor to polonium-210 allows the mapping of gas vents which have been active over the last approximately 60 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.

Lawson, S. L.; Feldman, W. C.; Lawrence, D. J.; Moore, K. R.; Elphic, R. C.; Maurice, S.; Belian, R. D.; Binder, A. B.

2002-01-01

44

Characterization of the Response of CaWO4 on Recoiling Nuclei from Surface Alpha Decays  

NASA Astrophysics Data System (ADS)

A potentially harmful background for experiments attempting direct dark matter detection like the CRESST (= Cryogenic Rare Event Search with Superconducting Thermometers) experiment is caused by recoiling nuclei from 210Po alpha decays on surfaces close to the detector. In order to characterize this kind of background in CRESST, calibration measurements have been performed at the TU München. A for this purpose an optimized version of the CRESST detector has been developed consisting of a 38 g CaWO4 crystal and a separate cryogenic light detector, both equipped with Ir/Au transition edge sensors (TESs). The simultaneous measurement of the phonon signal and the scintillation light from the CaWO4 crystal allows to discriminate between electron and nuclear recoils using their different light outputs. The unexpected results of a first measurement with a 210Po source can be understood with the help of a Monte Carlo simulation performed for a similar system.

Westphal, W.; Ciemniak, C.; Coppi, C.; von Feilitzsch, F.; Gütlein, A.; Isaila, C.; Lanfranchi, J.-C.; Pfister, S.; Potzel, W.; Rau, W.; Roth, S.; Stark, M.

2008-05-01

45

A Monte-Carlo calculation of the size distribution of latent alpha-recoil tracks in phlogopite: Implications for the recoil-track dating method  

Microsoft Academic Search

We used a Monte-Carlo method to calculate the size distribution of alpha-recoil tracks in phlogopite. The calculations span the age range 0–1Ma and the range of Th\\/U-ratios encountered in phlogopites of different origin. The track-size distribution is bimodal, with a narrow maximum centred on ?30nm and a broader maximum centred on ?110nm. The bimodal distribution is a consequence of the

K. Stübner; R. C. Jonckheere

2006-01-01

46

Alpha-recoil damage in monazite: preferential dissolution of the radiogenic actinide isotopes  

Microsoft Academic Search

A preferential dissolution by a factor of 1.1 to about 10 of the radiogenic nuclides ²³⁴U, ²³°Th, and ²²⁸Th relative to their corresponding structurally incorporated isotopes ²³⁸U and ²³²Th has been observed upon leaching of natural monazite samples in a bicarbonate-carbonate solution. This isotopic fractionation may be attributed to radiation damage caused by alpha recoil atoms. The observations have implications

Y. Eyal; A. Kaufman

1982-01-01

47

Recoil corrections in the hydrogen isoelectronic sequence  

SciTech Connect

A version of the Bethe-Salpeter equation appropriate for calculating recoil corrections in highly charged hydrogenlike ions is presented. The nucleus is treated as a scalar particle of charge Z, and the electron treated relativistically. The known recoil corrections of order m{sup 2}/M(Z{alpha}){sup 4} are derived in both this formalism and in NRQED.

Adkins, G. S.; Sapirstein, J. [Department of Physics, Franklin and Marshall College, Lancaster, Pennsylvania 17604 (United States); Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556 (United States)

2006-03-15

48

An algorithm for unfolding neutron dose and dose equivalent from digitized recoil-particle tracks  

Microsoft Academic Search

Previous work conducted at the Oak Ridge National Laboratory (ORNL) has demonstrated the feasibility of a digital approach to neutron dosimetry. In contrast to current analog methods, the digital approach specifically refers to methods of collection and processing of ionization products created by recoil particles within detector volumes. A dosimeter utilizing the digital approach would consist of both a detector

Bolch

1986-01-01

49

Alpha particle confinement in tokamaks  

SciTech Connect

An assessment of diffusive tokamak transport mechanisms of concern for alpha particles indicates that the ''stochastic regime'' is the only one which appears to pose a real danger for adequate alpha confinement. This fact, in conjunction with the threshold character of that mechanism, allows one to decide whether an alpha born at a given location will be lost or confined, according to a very simple criterion. Implementing this criterion numerically results in a new code for the assessment of alpha confinement, which is orders of magnitude faster than earlier codes used for this purpose. 13 refs., 3 figs., 1 tab.

White, R.B.; Mynick, H.E.

1988-11-01

50

Charge distributions of alpha-recoil atoms from electrodeposited 210Po source  

Microsoft Academic Search

Charge distributions have been measured for 206Pb recoil atoms emerging from a 210Po source electrodeposited on platinum. It has been found that more than 50% of the recoils are neutrals when the average energy loss of the recoils is about 18 keV. The observed large fraction for the neutrals indicates that a strong neutralization of the recoil ions occurs with

Shin Ito; Nobuhiro Maeda

1987-01-01

51

Cosmogenic production rates and recoil loss effects in micrometeorites and interplanetary dust particles  

NASA Astrophysics Data System (ADS)

We present a purely physical model to determine cosmogenic production rates for noble gases and radionuclides in micrometeorites (MMs) and interplanetary dust particles (IDPs) by solar cosmic-rays (SCR) and galactic cosmic-rays (GCR) fully considering recoil loss effects. Our model is based on various nuclear model codes to calculate recoil cross sections, recoil ranges, and finally the percentages of the cosmogenic nuclides that are lost as a function of grain size, chemical composition of the grain, and the spectral distribution of the projectiles. The main advantage of our new model compared with earlier approaches is that we consider the entire SCR particle spectrum up to 240 MeV and not only single energy points. Recoil losses for GCR-produced nuclides are assumed to be equal to recoil losses for SCR-produced nuclides. Combining the model predictions with Poynting-Robertson orbital lifetimes, we calculate cosmic-ray exposure ages for recently studied MMs, cosmic spherules, and IDPs. The ages for MMs and the cosmic-spherule are in the range <2.2-233 Ma, which corresponds, according to the Poynting-Robertson drag, to orbital distances in the range 4.0-34 AU. For two IDPs, we determine exposure ages of longer than 900 Ma, which corresponds to orbital distances larger than 150 AU. The orbital distance in the range 4-6 AU for one MM and the cosmic spherule indicate an origin either in the asteroid belt or release from comets coming either from the Kuiper Belt or the Oort Cloud. Three of the studied MMs have orbital distances in the range 23-34 AU, clearly indicating a cometary origin, either from short-period comets from the Kuiper Belt or from the Oort Cloud. The two IDPs have orbital distances of more than 150 AU, indicating an origin from Oort Cloud comets.

Trappitsch, Reto; Leya, Ingo

2013-02-01

52

alpha-Actin: disposition, quantities, and estimated effects on lung recoil and compliance.  

PubMed

We have investigated the basis and implications of pneumoconstriction by measuring disposition and quantities of alpha-smooth muscle actin in rat and guinea pig lungs and modeling its effects on lung recoil and compliance. A robust marker of contractility, alpha-smooth muscle actin appears in smooth muscle or myofibroblast-like cells in pleura, airways, blood vessels, and alveolar ductal tissues. In each site, we measured its transected area by immunofluorescent staining and frequency-modulated scanning confocal microscopy. We incorporated these data in a model of the parenchyma consisting of an extensive elastic network with embedded contractile structures. We conclude that contraction at any one of these sites alone can decrease parenchymal compliance by 20-30% during tidal breathing. This is due mostly to the stiffness of activated contractile elements undergoing passive cycling; constant muscle tension would have little effect. The magnitude of the effect corresponds with known responses of the lung to hypocapnia, consistent with a homeostatic function in which gas exchange is defended by redistributing ventilation away from overventilated units. PMID:11408464

Oldmixon, E H; Carlsson, K; Kuhn, C; Butler, J P; Hoppin, F G

2001-07-01

53

The etching of natural alpha-recoil tracks in mica with an argon RF-plasma discharge and their imaging via atomic force microscopy  

Microsoft Academic Search

The conventional technique used to reveal the natural alpha-recoil tracks, as well as other nuclear tracks, in muscovite mica is to etch the mica sheets in a concentrated hydrofluoric (HF) acid solution. However, because of the fast etching along the basal plane of the mica when using HF acid, the recoil-disturbed regions are commonly enlarged laterally so that it is

Norman M. D. Brown; Zhi Hui Liu

1996-01-01

54

Alpha-recoil tracks in natural dark mica: Dating geological samples by optical and scanning force microscopy  

Microsoft Academic Search

Alpha-recoil tracks (ART) are lattice defects caused by the ?-decay of 238U, 235U, 232Th, and daughter products. Visualization of etched ARTs in dark mica by phase-contrast microscopy allows dating of Quaternary geological as well as archaeological materials. Visualization of etched ARTs by Nomarski-differential-interference-contrast microscopy (NDICM) and scanning force microscopy (SFM) enables the access to areal densities (?a) of ART etch

U. A. Glasmacher; M. Lang; S. Klemme; B. Moine; L. Barbero; R. Neumann; G. A. Wagner

2003-01-01

55

Secondary Fe-Mn-oxides in minerals heavily damaged by alpha-recoil: possible implications for palaeomagnetism  

Microsoft Academic Search

Sub-micron Fe,Mn-oxides in columbite-tantalite minerals are bound to metamict domains in the host. These nano-oxides are secondary minerals as the metamict zones formed through accumulation of damages from alpha-recoil, each of which in a small volume destroys the crystal lattice of the U and Th bearing columbite-tantalite host. Transmission electron microscope investigations demonstrate that the oxides fall in the compositional

Rolf L. Romer; Norbert Nowaczyk; Richard Wirth

2007-01-01

56

Alpha recoil phenomena used for radiolabelling of surface layers of solids  

Microsoft Academic Search

Various techniques are reviewed which can be used to introduce a radioactive label by recoil into the surface layers of solid specimens. These include 1) impregnation with a solution containing the parent natural radionuclide, 2) vacuum injection from a thin deposit of the parent nuclide and 3) electrostatic collection of the precursor nuclide followed by recoil injection from the specimen

C. Jech

1999-01-01

57

Uranium deposition and Th-234 alpha-recoil: An explanation for extreme U-234\\/U-238 fractionation within the trinity aquifer  

Microsoft Academic Search

234Th alpha-recoil appears to be a valid mechanism for explaining the generation of extreme 234U\\/238U disequilibria found in the waters of the Trinity aquifer. Present address: Groundwater Research Center, Hebrew University, Jerusalem, Israel.

Joel Kronfeld

1974-01-01

58

Observation of the alpha particle "Knock-On" neutron emission from magnetically confined DT fusion plasmas  

PubMed

Suprathermal fuel ions from alpha-particle knock-on collisions in fusion DT plasmas are predicted to cause a weak feature in the neutron spectrum of d+t-->alpha+n. The knock-on feature has been searched for in the neutron emission of high ( >1 MW) fusion-power plasmas produced at JET and was found using a magnetic proton recoil type neutron spectrometer of high performance. Measurement and predictions agree both in absolute amplitude and in plasma-parameter dependence, supporting the interpretation and model. Moreover, the results provide input to projecting alpha-particle diagnostics for future self-heated fusion plasmas. PMID:10991523

Kallne; Ballabio; Frenje; Conroy; Ericsson; Tardocchi; Traneus; Gorini

2000-08-01

59

Alpha recoil phenomena used for radiolabelling of surface layers of solids  

Microsoft Academic Search

Various techniques are reviewed which can be used to introduce a radioactive label by recoil into the surface layers of solid\\u000a specimens. These include 1) impregnation with a solution containing the parent natural radionuclide, 2) vacuum injection from\\u000a a thin deposit of the parent nuclide and 3) electrostatic collection of the precursor nuclide followed by recoil injection\\u000a from the specimen

?. Jech

1999-01-01

60

Elastic recoil detection analysis using ion-induced electron emission for particle identification  

NASA Astrophysics Data System (ADS)

We propose a new method to identify particles in ERD analysis, using their electron emission yield from a thin carbon foil. Before the particles reach a silicon surface barrier detector (SB) they penetrate a set of thin foils (typically 6 foils) with a thickness of 3 ?g/cm2 each). The emission yield depends on the nuclear charge of the penetrating ion and it is roughly proportional to the energy loss in the foil. The emitted electrons are accelerated to a muchannel plate (MCP) by a voltage of 300 V. The electron signal from the MCP is proportional to the number of emitted electrons and it occurs in coincidence with the energy signal from the energy detector. For data acquisition we developed a dual parameter multichannel analyzer (M2D) as an add on board for an industry standard personal computer. The two-dimensional spectrum of coincidences and the one-dimensional spectra from both detectors are recorded simultaneously. The M2D has 256K channels which can be freely configured as a two-dimensional matrix. For example a resolution of 1024 × 256 channels is possible. For optimum suppression of random coincidences the coincidence time window can be set from 0.125 ?s up to 32 ?s. For this new setup the ability for particle identification is discussed for different projectiles (He, C, O, Cl) and targets. H recoil ions can be well separated from He projectiles so that for H analysis the H recoil spectrum and the He forward energy spectrum can be measured simultaneously. An example for depth-profiling of 100 keV H implantations in silicon is given.

Benka, O.; Brandstötter, A.; Steinbauer, E.

1994-03-01

61

Nuclear diagnostic for fast alpha particles  

SciTech Connect

We investigate the possibility of seeding a fusion plasma with nuclei which can undergo nuclear reactions with energetic alpha particles to produce product nuclei which are radioactive. If a fraction of these product nuclei can be collected and measured, one can obtain information about the presence of fast alpha particles. It appears that a feasible diagnostic could be based upon the /sup 10/B(..cap alpha..,n)/sup 13/N reaction.

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

1982-12-01

62

Alpha-recoil damage in titanite (CaTiSiO sub 5 ): Direct observation and annealing study using high resolution transmission electron microscopy  

Microsoft Academic Search

Tracks'' of alpha-recoil nuclei have been observed directly in titanite (CaTiSiOâ). Recoil tracks in titanite are 4 to 6 nm in diameter and consist of a central aperiodic zone surrounded by a narrow (0--2 nm) outer zone that is essentially crystalline, but which exhibits modulated image contrast due to interstitial defects. Previous work has suggested that titanite is 2 to

G. R. Lumpkin; R. K. Eby; R. C. Ewing

1991-01-01

63

Realistic Density Function of Alpha Particle  

NASA Astrophysics Data System (ADS)

In a framework of the ATMS method, one- and two-body density functions of the alpha particle are derived by using the Reid soft core V_{8} model potential. Deuteron-deuteron spectroscopic amplitudes describing the relative motion between the deuterons in the alpha particle for the (d, alpha) reaction are derived from the alpha and deuteron wave functions generated with the same potential. These functions are well represented as a sum of Gaussian functions. These Gaussian expansions have a real convenience of practical use, because their Fourier transforms can be obtained analytically.

Morita, H.; Akaishi, Y.; Endo, O.; Tanaka, H.

1987-11-01

64

Radioimmunotherapy with alpha-particle emitting radionuclides.  

PubMed

An important consideration in the development of effective strategies for radioimmunotherapy is the nature of the radiation emitted by the radionuclide. Radionuclides decaying by the emission of alpha-particles offer the possibility of matching the cell specific reactivity of monoclonal antibodies with radiation with a range of only a few cell diameters. Furthermore, alpha-particles have important biological advantages compared with external beam radiation and beta-particles including a higher biological effectiveness, which is nearly independent of oxygen concentration, dose rate and cell cycle position. In this review, the clinical settings most likely to benefit from alpha-particle radioimmunotherapy will be discussed. The current status of preclinical and clinical research with antibodies labeled with 3 promising alpha-particle emitting radionuclides - (213)Bi, (225)Ac, and (211)At - also will be summarized. PMID:15640792

Zalutsky, M R; Pozzi, O R

2004-12-01

65

Current status of alpha-particle spectrometry.  

PubMed

This paper describes the status of alpha-particle spectrometry. Some of the main contributions made to this field in the last years are reviewed. Topics covered include instrumentation, source characterization, numerical analysis, Monte Carlo simulations and applications. PMID:16554165

García-Toraño, Eduardo

2006-03-22

66

Concepts of nuclear {alpha}-particle condensation  

SciTech Connect

Certain aspects of the recently proposed antisymmetrized {alpha}-particle product state wave function, or THSR (Tohsaki-Horiuchi-Schuck-Roepke) {alpha}-cluster wave function, for the description of the ground state in {sup 8}Be, the Hoyle state in {sup 12}C, and analogous states in heavier nuclei are elaborated in detail. For instance, the influence of antisymmetrization in the Hoyle state on the bosonic character of the {alpha} particles is studied carefully. It is shown to be weak. Bosonic aspects in Hoyle and similar states in other self-conjugate nuclei are, therefore, predominant. Another issue is the de Broglie wavelength of {alpha} particles in the Hoyle state, which is shown to be much larger than the inter-{alpha} distance. It is pointed out that the bosonic features of low-density {alpha} gas states have measurable consequences, one of which, enhanced multi-{alpha} decay properties, has likely already been detected. Consistent with experiment, the width of the proposed analog to the Hoyle state in {sup 16}O at the excitation energy of E{sub x}=15.1 MeV is estimated to be very small (34 keV), lending credit to the existence of heavier Hoyle-like states. The intrinsic single-boson density matrix of a self-bound Bose system can, under physically desirable boundary conditions, be defined unambiguously. One eigenvalue then separates out, being close to the number of {alpha} particles in the system. Differences between Brink and THSR {alpha}-cluster wave functions are worked out. No cluster model of the Brink type can describe the Hoyle state with a single configuration. On the contrary, many superpositions of the Brink type are necessary, implying delocalization toward an {alpha}-product state. It is shown that single {alpha}-particle orbits in condensates of different nuclei are almost the same. It is thus argued that {alpha}-particle (quartet) antisymmetrized product states of the THSR type are a very promising novel and useful concept in nuclear physics.

Funaki, Y. [Institute of Physics, University of Tsukuba, Tsukuba 305-8571 (Japan); Horiuchi, H. [Research Center for Nuclear Physics, Osaka University, Osaka 567-0047 (Japan); International Institute for Advanced Studies, Kizugawa 619-0225 (Japan); Oertzen, W. von [Hahn-Meitner-Institut Berlin, Glienicker Strasse 100, D-14109 Berlin (Germany); Freie Universitaet Berlin, Fachbereich Physik, Arnimallee 14, D-14195 Berlin (Germany); Roepke, G. [Institut fuer Physik, Universitaet Rostock, D-18051 Rostock (Germany); Schuck, P. [Institut de Physique Nucleaire, F-91406 Orsay CEDEX (France); Universite Paris-Sud, F-91406 Orsay CEDEX (France); Laboratoire de Physique et Modelisation des Milieux Condenses, CNRS et Universite Joseph Fourier, 25 Avenue des Martyrs, BP 166, F-38042 Grenoble CEDEX 9 (France); Tohsaki, A. [Research Center for Nuclear Physics, Osaka University, Osaka 567-0047 (Japan); Yamada, T. [Laboratory of Physics, Kanto Gakuin University, Yokohama 236-8501 (Japan)

2009-12-15

67

Thermal recrystallization of alpha-recoil damaged minerals of the pyrochlore structure type.  

National Technical Information Service (NTIS)

Thermal recrystallization effects (heat of recrystallization and identification of phases formed), have been determined for naturally occurring members of the pyrochlore group which have received alpha doses of up to 4 X 10 to the 16th power alphas/mg. Th...

G. R. Lumpkin R. C. Ewing E. M. Foltyn

1985-01-01

68

Recoil-Implantation Of Multiple Radioisotopes Towards Wear Rate Measurements And Particle Tracing In Prosthetic Joints  

SciTech Connect

This study demonstrates a new method of radioisotope labeling of ultra-high molecular weight polyethylene inserts in prosthetic joints for wear studies. The radioisotopes {sup 97}Ru, {sup 100}Pd, {sup 100}Rh, and {sup 101m}Rh are produced in fusion evaporation reactions induced by {sup 12}C ions in a {sup 92}Zr target foil. The fusion products recoil-implant into ultra-high molecular weight polyethylene plugs, machined to fit into the surface of the inserts. During laboratory simulations of the joint motion, a wear rate of the labeled polyethylene may be measured and the pathways of wear debris particles can be traced by detecting characteristic gamma-rays. The concentration profiles of the radioisotopes extend effectively uniformly from the polyethylene surface to a depth of about 4 {mu}m. The multiplicity of labeling and the use of several gamma-ray lines aids with avoiding systematic measurement uncertainties. Two polyethylene plugs were labeled and one was fitted into the surface of the tibial insert of a knee prosthesis, which had been worn in. Actuation over close to 100,000 cycles with a 900 N axial load and a 24 deg. flexion angle removed (14{+-}1)% of the gamma-ray activity from the plug. Most of this activity dispersed into the serum lubricant identifying this as the important debris pathway. Less than 1% activity was transferred to the femoral component of the prosthesis and the measured activity on the tibial tray was insignificant. Assuming uniform wear across the superior surface of the insert, a wear rate of (12{+-}3) mm{sup 3}/Megacycle was determined. This is consistent with wear rate measurements under similar conditions using other techniques.

Warner, Jacob A.; Timmers, Heiko [School of Physical, Environmental and Mathematical Sciences, University of New South Wales at ADFA, Canberra, ACT 2600 (Australia); Smith, Paul N.; Scarvell, Jennifer M. [Trauma and Orthopaedic Research Unit, Canberra Hospital, PO BOX 11, Woden, ACT 2606 (Australia); Gladkis, Laura [School of Physical, Environmental and Mathematical Sciences, University of New South Wales at ADFA, Canberra, ACT 2600 (Australia); Trauma and Orthopaedic Research Unit, Canberra Hospital, PO BOX 11, Woden, ACT 2606 (Australia)

2011-06-01

69

Alpha particle analysis using PEARLS spectrometry  

Microsoft Academic Search

Alpha particle assay by conventional plate-counting methods is difficult because chemical separation, tracer techniques, and\\/or self-absorption losses in the final sample may cause either non-reproducible results or create unacceptable errors. PEARLS (Photon-Electron Rejecting Alpha Liquid Scintillation) Spectrometry is an attractive alternative since radionuclides may be extracted into a scintillator in which there would be no self-absorption or geometry problems and

J. W. McKlveen; G. W. Klingler; W. J. McDowell; G. N. Case

1984-01-01

70

The status of alpha-particle diagnostics  

SciTech Connect

There is a flurry of activity to complete alpha-particle diagnostics so that they can undergo some experimental testing in DT plasmas on JET or TFTR prior to implementation on ITER. Successful measurements of escaping charged fusion products have been made in DD plasmas, and the {alpha}-particle source can be well characterized by neutron profile measurement. These methods can be extrapolated to DT plasmas. Measurement of the confined {alpha}-particles requires a new technique. Collective Thomson scattering, methods involving charge-exchange interactions and nuclear reactions with impurities will be discussed. Some assessment is given of the capabilities of these techniques, bearing in mind the potential for their use in the physics phase of the ITER program.

Young, K.M.; Johnson, D.W.

1992-08-01

71

The status of alpha-particle diagnostics  

SciTech Connect

There is a flurry of activity to complete alpha-particle diagnostics so that they can undergo some experimental testing in DT plasmas on JET or TFTR prior to implementation on ITER. Successful measurements of escaping charged fusion products have been made in DD plasmas, and the {alpha}-particle source can be well characterized by neutron profile measurement. These methods can be extrapolated to DT plasmas. Measurement of the confined {alpha}-particles requires a new technique. Collective Thomson scattering, methods involving charge-exchange interactions and nuclear reactions with impurities will be discussed. Some assessment is given of the capabilities of these techniques, bearing in mind the potential for their use in the physics phase of the ITER program.

Young, K.M.; Johnson, D.W.

1992-01-01

72

Nuclear Alpha-Particle Condensates  

NASA Astrophysics Data System (ADS)

The ?-particle condensate in nuclei is a novel state described by a product state of ?'s, all with their c.o.m. in the lowest 0S orbit. We demonstrate that a typical ?-particle condensate is the Hoyle state (Ex=7.65 MeV,0^+_2 state in ^{12}C), which plays a crucial role for the synthesis of ^{12}C in the universe. The influence of antisymmentrization in the Hoyle state on the bosonic character of the ? particle is discussed in detail. It is shown to be weak. The bosonic aspects in the Hoyle state, therefore, are predominant. It is conjectured that ?-particle condensate states also exist in heavier n? nuclei, like ^{16}O,^{20}Ne, etc. For instance the 0^+_6 state of ^{16}O at Ex=15.1 MeV is identified from a theoretical analysis as being a strong candidate of a 4? condensate. The calculated small width (140 keV) of 0^+_6, consistent with data, lends credit to the existence of heavier Hoyle-analogue states. In non-self-conjugated nuclei such as ^{11} B and ^{13} C, we discuss candidates for the product states of clusters, composed of ?'s, triton's, and neutrons etc. The relationship of ?-particle condensation in finite nuclei to quartetting in symmetric nuclear matter is investigated with the help of an in-medium modified four-nucleon equation. A nonlinear order parameter equation for quartet condensation is derived and solved for ? particle condensation in infinite nuclear matter. The strong qualitative difference with the pairing case is pointed out.

Yamada, T.; Funaki, Y.; Horiuchi, H.; Röpke, G.; Schuck, P.; Tohsaki, A.

73

Effect of the recoil pressure induced by evaporation on motion of powder particles in the light field during laser cladding  

NASA Astrophysics Data System (ADS)

A model is proposed, which takes into account acceleration of powder particles by a force induced by recoil of material vapors from the irradiated region of the particle surface. Results of a numerical analysis of heat and mass transfer in the case of motion of individual stainless steel powder particles in a gas flow and in a light field of laser radiation under conditions of laser cladding are presented. Acceleration of particles is found to depend on their diameter, carrier gas velocity, powder material properties, laser radiation power, and degree of attenuation of the power density in the laser beam in the direction of its action on the substrate. The calculated results are compared with experimental data on light-propulsion acceleration of individual particles (of aluminum, aluminum oxide, and graphite) under the action of pulsed laser radiation.

Kovaleva, I. O.; Kovalev, O. B.

2012-01-01

74

Lunar Surface Outgassing and Alpha Particle Measurements  

Microsoft Academic Search

The Lunar Prospector Alpha Particle Spectrometer (LP APS) searched for lunar surface gas release events and mapped their distribution by detecting alpha particles produced by the decay of gaseous radon-222 (5.5 MeV, 3.8 day half-life), solid polonium-218 (6.0 MeV, 3 minute half-life), and solid polonium-210 (5.3 MeV, 138 day half-life, but held up in production by the 21 year half-life

S. L. Lawson; W. C. Feldman; David J. Lawrence; K. R. Moore; R. C. Elphic; S. Maurice; Richard D. Belian; Alan B. Binder

2002-01-01

75

Lunar surface outgassing and alpha particle measurements  

SciTech Connect

The Lunar Prospector Alpha Particle Spectrometer (LP APS) searched for lunar surface gas release events and mapped their distribution by detecting alpha particle?; produced by the decay of gaseous radon-222 (5.5 MeV, 3.8 day half-life), solid polonium-2 18 (6.0 MeV, 3 minute half-life), and solid polonium-210 (5.3 MeV, 138 day half-life, but held up in production by the 21 year half-life of lead-210). These three nuclides are radioactive daughters from the decay of uranium-238.

Lawson, S. L. (Stefanie L.); Feldman, W. C. (William C.); Lawrence, David J. (David Jeffery),; Moore, K. R. (Kurt R.); Elphic, R. C. (Richard C.); Maurice, S. (Sylvestre); Belian, Richard D.; Binder, Alan B.

2002-01-01

76

Realistic Momentum Distributions of the alpha Particle  

NASA Astrophysics Data System (ADS)

We present various types of momentum distributions of the alpha particle using ATMS wave function generated with the Reid soft core V_{8} model potential. Those are the momentum distributions of the single-nucleon, two-nucleon-cluster relative motion, two-nucleon-cluster center of mass, triton-proton relative motion and deuteron-deuteron relative motion. These momentum distributions are well represented as a sum of Gaussian functions. With these Gaussian expansions, the realistic momentum distributions of the alpha particle would become accessible to everyone.

Morita, H.; Akaishi, Y.; Tanaka, H.

1988-04-01

77

Thermal recrystallization of alpha-recoil damaged minerals of the pyrochlore structure type  

Microsoft Academic Search

Thermal recrystallization effects (heat of recrystallization and identification of phases formed), have been determined for naturally occurring members of the pyrochlore group which have received alpha doses of up to 4 X 10¹⁶ alphas\\/mg. The heats of recrystallization, E{sub t}, range from 125 to 210 J\\/g. Release of energy decreases as a function of crystallinity (estimated on the basis of

G. R. Lumpkin; R. C. Ewing; E. M. Foltyn

1985-01-01

78

Alpha-recoil damage in zirconolite (CaZrTiâOâ)  

Microsoft Academic Search

Radiation effects in a natural, metamict zirconolite from Sri Lanka that has received an alpha-decay dose greater than 10²⁶ alpha decays\\/m³ have been studied using x-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), electron paramagnetic resonance spectroscopy (EPR), extended x-ray absorption fine structure spectroscopy (EXAFS), and x-ray absorption near edge structure spectroscopy (XANES). The same techniques were applied to the

G. R. Lumpkin; R. C. Ewing; B. C. Chakoumakos; R. B. Greegor; F. W. Lytle; E. M. Foltyn; F. W. Jr. Clinard; L. A. Boatner; M. M. Abraham

1986-01-01

79

Alpha-Particle Decay Widths of Levels in (19)F.  

National Technical Information Service (NTIS)

Levels of /sup 19/F in the excitation region 4alpha)) reaction, using a recoil-coincidence technique to measure values of (Gamma)/sub (gamma)//(Gamma). The information obtained has been combined...

D. M. Pringle W. J. Vermeer

1989-01-01

80

Recoil Separators for Nuclear Astrophysics  

NASA Astrophysics Data System (ADS)

Hydrogen and helium capture reactions are important in many astrophysical environments. Measurements in inverse kinematics using recoil separators have demonstrated a particularly sensitive technique for studying low-yield capture reactions.(M. S. Smith, C. E. Rolfs, and C. A. Barnes, Nucl. Instrum. Meth. Phys. Res. A306) (1991) 233. This approach allows a low background rate to be achieved with a high detection efficiency (about 50%) for the particles of interest using a device with only modest acceptance. Recoil separators using a variety of ion-optic configurations have been installed at numerous accelerator facilities in the past decade and have been used to measure, for example, alpha capture reactions using stable beams(D. Rogalla et al.), Eur. Phys. J. 6 (1999) 471. and proton capture reactions using radioactive ion beams.(S. Bishop et al.), Phys. Rev. Lett. 90 (2003) 162501. Measurements in inverse kinematics are the only viable means for studying reactions on short-lived nuclei that are crucial for understanding stellar explosions, and a recoil separator optimized for the measurement of capture reactions with radioactive ion beams figures prominently into the design of the low energy experimental area at the Rare Isotope Accelerator (RIA). The operational requirements for such a device will be outlined, and recoil separator designs and characteristics will be presented.

Blackmon, J. C.

2004-10-01

81

Alpha-Particles within Nuclei  

NASA Astrophysics Data System (ADS)

We present a formalism describing the bound state of a large number of bosons and apply it to study nuclei consisting of A ? particles. The method has its roots in a few-body approach and is based on the expansion of the many-body Faddeev components in Potential Harmonics, and the subsequent reduction of the Faddeev equation into a two-variable, integro-differential equation. For A ? ? this equation is transformed into a new simpler integro-differential equation, which is easy to use in calculations for A up to as large as 1000. We use both integro-differential equations to investigate the behavior of nuclei subject to the assumption that they are composed of ? particles. Various ? ? forces were employed. For the Ali-Bodmer potential we found that the A = 5 system (i.e. 20Ne) is the most stable, while for the A = 10 system (i.e. 40Ca) the binding energy has a maximum. The formalism predicts ?-decay for larger nuclei, but the value of A where this begins to happen is strongly dependent on the ? ? potential.

Sofianos, S. A.; Lekala, M. L.; Adam, R. M.; Belyaev, V. B.

2013-03-01

82

Automatic spark counting of fast neutron induced recoil particle tracks in polymer foils  

Microsoft Academic Search

Preliminary results are given concerning the automatic spark counting of ; fast neutron-induced recoil nuclei tracks in thin polymer foils such as cellulose ; nitrate and polycarborate, based on extended etching of the foils to the point ; where electric breakdown begins to occur also in unexposed foils. The method ; shows promise in personnel dosimetry because it does not

K. Becker; M. Abd-el Razek

1974-01-01

83

The alpha-1 adrenergic blocking agent urapidil counteracts postrotational atherectomy "elastic recoil" where nitrates have failed.  

PubMed

Calcium antagonist pretreatment and intracoronary high doses of nitrates (9 mg of isosorbide dinitrate) do not counteract coronary vasoconstriction occurring after rotational atherectomy. In 30 patients undergoing Rotablator atherectomy, intracoronary injection of the alpha 1-sympathetic blocker urapidil abolished or prevented significant vasoconstriction occurring 15 minutes after the procedure despite repeated injections of nitrates. PMID:9114772

Gregorini, L; Marco, J; Bernies, M; Cassagneau, B; Pomidossi, G; Anguissola, G B; Fajadet, J

1997-04-15

84

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

85

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

86

Potential effects of alpha-recoil on uranium-series dating of calcrete  

USGS Publications Warehouse

Evaluation of paleosol ages in the vicinity of Yucca Mountain, Nevada, at the time the site of a proposed high-level nuclear waste repository, is important for fault-displacement hazard assessment. Uranium-series isotope data were obtained for surface and subsurface calcrete samples from trenches and boreholes in Midway Valley, Nevada, adjacent to Yucca Mountain. 230Th/U ages of 33 surface samples range from 1.3 to 423 thousand years (ka) and the back-calculated 234U/238U initial activity ratios (AR) are relatively constant with a mean value of 1.54 ± 0.15 (1?), which is consistent with the closed-system behavior. Subsurface calcrete samples are too old to be dated by the 230Th/U method. U-Pb data for post-pedogenic botryoidal opal from a subsurface calcrete sample show that these subsurface calcrete samples are older than ~ 1.65 million years (Ma), old enough to have attained secular equilibrium had their U-Th systems remained closed. However, subsurface calcrete samples show U-series disequilibrium indicating open-system behavior of 238U daughter isotopes, in contrast with the surface calcrete, where open-system behavior is not evident. Data for 21 subsurface calcrete samples yielded calculable 234U/238U model ages ranging from 130 to 1875 ka (assuming an initial AR of 1.54 ± 0.15, the mean value calculated for the surface calcrete samples). A simple model describing continuous ?-recoil loss predicts that the 234U/238U and 230Th/238U ARs reach steady-state values ~ 2 Ma after calcrete formation. Potential effects of open-system behavior on 230Th/U ages and initial 234U/238U ARs for younger surface calcrete were estimated using data for old subsurface calcrete samples with the 234U loss and assuming that the total time of water-rock interaction is the only difference between these soils. The difference between the conventional closed-system and open-system ages may exceed errors of the calculated conventional ages for samples older than ~ 250 ka, but is negligible for younger soils.

Neymark, L. A.

2011-01-01

87

Alpha particle analysis using PEARLS spectrometry  

SciTech Connect

Alpha particle assay by conventional plate-counting methods is difficult because chemical separation, tracer techniques, and/or self-absorption losses in the final sample may cause either non-reproducible results or create unacceptable errors. PEARLS (Photon-Electron Rejecting Alpha Liquid Scintillation) Spectrometry is an attractive alternative since radionuclides may be extracted into a scintillator in which there would be no self-absorption or geometry problems and in which up to 100% chemical recovery and counting efficiency is possible. Sample preparation may include extraction of the alpha emitter of interest by a specific organic-phase-soluble compound directly into the liquid scintillator. Detection electronics use energy and pulse-shape discrimination to provide discrete alpha spectra and virtual absence of beta and gamma backgrounds. Backgrounds on the order of 0.01 cpm are readily achievable. Accuracy and reproducibility are typically in the 100 +-1% range. Specific procedures have been developed for gross alpha, uranium, plutonium, thorium, and polonium assay. This paper will review liquid scintillation alpha counting methods and reference some of the specific applications. 8 refs., 1 fig.

McKlveen, J.W.; Klingler, G.W.; McDowell, W.J.; Case, G.N.

1984-01-01

88

Shielding of Manned Space Vehicles Against Protons and alpha Particles.  

National Technical Information Service (NTIS)

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 ...

R. G. Alsmiller R. T. Santoro J. Barish H. C. Claiborne

1972-01-01

89

Thermal recrystallization of alpha-recoil damaged minerals of the pyrochlore structure type  

SciTech Connect

Thermal recrystallization effects (heat of recrystallization and identification of phases formed), have been determined for naturally occurring members of the pyrochlore group which have received alpha doses of up to 4 X 10{sup 16} alphas/mg. The heats of recrystallization, E{sub t}, range from 125 to 210 J/g. Release of energy decreases as a function of crystallinity (estimated on the basis of the intensity of x-ray diffraction maxima), with the fully-metamict samples approaching 210 J/g. Lower measured values (40-125 J/g) are the result of alteration of the pyrochlores. Other metamict, complex oxides with stoichiometries of ABO{sub 4} and AB{sub 2}O{sub 6} have lower heats of recrystallization (40-85 J/g), and are easily distinguished from pyrochlore group minerals. Activation energies of recrystallization, E{sub a}, range between values of 0.29 to 0.97 eV, less than those measured for Pu-doped, synthetic zirconolites.

Lumpkin, G.R.; Ewing, R.C. [Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Geology; Foltyn, E.M. [Los Alamos National Lab., NM (United States)

1985-10-01

90

The Capture of Electrons by Swiftly Moving Alpha-Particles  

Microsoft Academic Search

Relative velocities of an alpha particle and an electron which are favorable for the capture of the electron.-A stream of electrons from a thermionic source is superposed on a beam of alpha-particles from polonium. To determine the number of captures, the alpha-particle beam is subjected to a magnetic field and the number of deflected alpha-particles counted by the scintillation method.

Bergen Davis; A. H. Barnes

1929-01-01

91

Design of lost alpha particle diagnostics for JET  

Microsoft Academic Search

In a future magnetic fusion reactor alpha particles will be utlilized for plasma heating. In order to achieve a high efficiency of this process, the aim has to be a good confinement of alpha particles. Therefore, direct measurement of alpha particle losses is of particular interest. Two diagnostics are being prepared for the JET Tokamak that are targeting on exactly

S. Baeumel; A. Werner; R. Semler; S. Mukherjee; D. S. Darrow; R. Ellis; F. E. Cecil; L. Pedrick; H. Altmann; V. Kiptily; J. Gafert

2005-01-01

92

Alpha-particle-induced cancer in humans.  

PubMed

Updated information is given on alpha-particle-induced cancer in persons internally exposed to 222Rn progeny, Thorotrast, long-lived 226Ra and 228Ra, and short-lived 224Ra. The lung cancer risk to persons breathing 222Rn progeny in the indoor air of offices, schools, and homes is of increasing concern. About half of the recent deaths among the German Thorotrast patients have been from liver cancer. Animal studies indicate that the liver cancer risk from Thorotrast is mainly from its radioactivity and that the risk coefficient for the Thorotrast patients can be used provisionally for other alpha emitters in the human liver. Six skeletal cancers have occurred in persons with average skeletal doses between 0.85 and 11.8 Gy from 226Ra and 228Ra. In the low-dose German 224Ra patients, two skeletal sarcomas have occurred at about 0.7 Gy compared to about six cases predicted by results from 224Ra patients at higher doses. The minimal appearance time for radiation-induced bone sarcomas in humans is about 4 y. Following brief irradiation, the vast majority of induced bone sarcomas are expressed by about 30 y. Recent evidence against the "practical threshold" hypothesis is given. With the downward revision of neutron doses to the atomic-bomb survivors, the follow-up of persons exposed to alpha particles may be the best opportunity to evaluate directly the effects of high LET radiation on humans. PMID:2844697

Mays, C W

1988-10-01

93

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

94

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

95

{alpha}-particle optical potential tests below the Coulomb barrier  

SciTech Connect

The results of two recent papers concerning ({alpha},{gamma}) and ({alpha},n) reaction cross sections close to the reaction thresholds are discussed with regard to predictions of a recent {alpha}-particle regional optical potential. It is found that the new measured cross sections are rather well described especially for the dominant reaction channels. Particular features of the {alpha}-particle optical potential at energies below the Coulomb barrier explain the failure of a former regional potential obtained by analysis of {alpha}-particle elastic scattering alone at higher energies. Additional limitations of statistical model calculations for minor reaction channels are also discussed.

Avrigeanu, M.; Avrigeanu, V. ['Horia Hulubei' National Institute for Physics and Nuclear Engineering, P. O. Box MG-6, Bucharest-Magurele (Romania)

2009-02-15

96

The Capture of Electrons by Alpha-Particles  

Microsoft Academic Search

A stream of electrons is superposed upon a beam of alpha-particles. The alpha-particles are then deflected by a magnetic field and counted by the scintillation method. Alpha-particles which have captured electrons will not be deflected to the point where observation is made, and consequently, the decrease in scintillations will indicate the number of captures which occur. Probability of capture as

Arthur H. Barnes

1930-01-01

97

Morphology and dynamics of craterlike structures created by recoiling elongated particles.  

PubMed

We study the morphology and dynamics of craterlike structures formed when free-falling, randomly oriented, elongated particles bounce off a flat surface in a single particle scattering mode. The origin of a sharply defined rim with its associated structure, the factors determining the rim diameter, and the scaling of the diameter with impact velocity are examined. The probability distribution of rebounding particle ranges is calculated for a particular example and shown to provide a precursor description of structure formation. PMID:22181139

Engelsberg, M; de Souza, R E; Campello, S L

2011-10-31

98

Alpha particle loss in the TFTR DT experiments  

SciTech Connect

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

Zweben, S.J.; Darrow, D.S.; Herrmann, H.W. [and others

1995-01-01

99

Alpha Particle Induced Reactions on Vanadium  

NASA Astrophysics Data System (ADS)

Alpha particle-induced reactions on the target element vanadium were investigated from threshold up to 55 MeV using the foil-stack activation technique and the Ge(Li) gamma ray spectroscopy method. Excitation functions for the formation of reaction residues 54Mn, 52Mn, 51Cr, 48V, 47Sc, 46Sc were investigated. The experimental cross-sections were compared with the predictions based on updated hybrid model (ALICE/90) using n0=4 (4p0h) and level density parameter a=A/9. A general agreement was found for all the reactions of (?, xn) type. However, the model failed badly in all cases of (?, z?xn) type of reactions.

Rao, A. V. Mohan; Chintalapudi, S. N.

100

Probing preformed {alpha} particles in the ground state of nuclei  

SciTech Connect

In this Rapid Communication, we report on {alpha}-particle emission through the nuclear breakup in the reaction {sup 40}Ca on a {sup 40}Ca target at 50 A MeV. It is observed that, similar to nucleons, {alpha} particles can be emitted to the continuum with very specific angular distribution during the reaction. The {alpha}-particle properties seem to be compatible with an {alpha} cluster in the daughter nucleus that is perturbed and is emitted by the short-range nuclear attraction of the collision partner. A time-dependent theory that describes the {alpha}-particle wave-function evolution is able to qualitatively reproduce the observed angular distribution. This mechanism offers new possibilities for studying {alpha}-particle properties in the nuclear medium.

Scarpaci, J. A.; Fallot, M.; Assie, M.; Lefevre, L.; Frascaria, N.; Beaumel, D.; Bhar, C.; Blumenfeld, Y.; Desesquelles, P.; Idbarkach, H.; Khan, E.; Plagnol, E.; Roynette, J. C.; Shrivastava, A.; Zerguerras, T. [Institut de Physique Nucleaire, Centre National de la Recherche Scientifique/Institut National de Physique Nucleaire et de Physique des Particules (CNRS/IN2P3), Universite Paris-Sud 11, F-91406 Orsay (France); Lacroix, D.; Chbihi, A.; Chomaz, Ph.; Frankland, J.; Laville, J. L. [Grand Accelerateur National d'Ions Lourds (GANIL), Commissariat a l'Energie Atomique et aux Energies Alternatives/Direction des Sciences de la Matiere (CEA/DSM)-CNRS/IN2P3, Bd Henri Becquerel, Boite Postale 55027, F-14076 Caen Cedex 5 (France)

2010-09-15

101

Analytic expressions for {alpha} particle preformation in heavy nuclei  

SciTech Connect

Experimental {alpha} decay energies and half-lives are investigated systematically to extract {alpha} particle preformation in heavy nuclei. Formulas for the preformation factors are proposed that can be used to guide microscopic studies on preformation factors and perform accurate calculations of the {alpha} decay half-lives. There is little evidence for the existence of an island of long stability of superheavy nuclei.

Zhang, H. F.; Wang, Y. J.; Dong, J. M. [School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000 (China); Royer, G. [Laboratoire Subatech, UMR IN2P3/CNRS Universite Ecole des Mines, Nantes 44 (France); Zuo, W.; Li, J. Q. [School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000 (China); Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)

2009-11-15

102

Faddeev Equations for Deuteron Break-Up on alpha Particles.  

National Technical Information Service (NTIS)

Faddeev equations for deuteron break-up on alpha particles are given. Total cross-sections for the reaction process d+ alpha implies n+p+ alpha are calculated by means of the Faddeev equations and separable potentials. Numerical solution of the resulting ...

A. Osman

1976-01-01

103

The measurement of alpha particle emissions from semiconductor memory materials  

Microsoft Academic Search

With the increasing concern for the affects of alpha particles on the reliability of semiconductor memories, an interest has arisen in characterizing semiconductor manufacturing materials for extremely low-level alpha-emitting contaminants. It is shown that four elements are of primary concern: uranium, thorium, radium, and polonium. Measurement of contamination levels are given relevance by first correlating them with alpha flux emission

D. P. Bouldin

1981-01-01

104

Inelastic Scattering of Alpha-Particles from Carbon  

Microsoft Academic Search

The inelastic scattering of alpha particles from C¹² was studied ; by observation of the alpha particles and of the gamma rays from the deexcitation ; of the first excited state, Gamma rays were detected with NaI(Tl) crystals. A ; yield curve from threshold to 17 Mev showed well isolated resonances-in the ; region below 11 Mev. Detailed angular distributions

Gary Earl Mitchell

1962-01-01

105

Coulomb Splitting of Relativistic C Ions into Three alpha -Particles.  

National Technical Information Service (NTIS)

Coulomb splitting of relativistic C ions to three alpha -particles has been considered. The basis of the mechanism is an assumption that the splitting takes place with preliminary excitation of carbon that is followed by its decay to three alpha -particle...

Kaptar L.P A. I. Titov

1978-01-01

106

The genotoxicity of alpha particles in human embryonic skin fibroblasts.  

PubMed

Cell inactivation and induced mutation frequencies at the hypoxanthine-guanine phosphoribosyl transferase (HGPRT) locus have been measured in cultured human fibroblasts (GM10) exposed to alpha particles from 238Pu (LET at the cell surface was 100 keV/microns) and 250 kVp X rays. The survival curves resulting from exposure to alpha particles are exponential. The mean lethal dose, D0, is approximately 1.3 Gy for X rays and 0.25 Gy for alpha particles. As a function of radiation dose, mutation induction at the HGPRT locus was linear for alpha particles whereas the X-ray-induced mutation data were better fitted by a quadratic function. When mutation frequencies were plotted against the log of survival, mutation frequency at a given survival level was greater in cells exposed to alpha particles than to X rays. PMID:6494443

Chen, D J; Strniste, G F; Tokita, N

1984-11-01

107

Genotoxicity of alpha particles in human embryonic skin fibroblasts  

SciTech Connect

Cell inactivation and induced mutation frequencies at the hypoxanthine-guanine phosphoribosyl transferase (HGPRT) locus have been measured in cultured human fibroblasts (GM10) exposed to ..cap alpha.. particles from /sup 238/ Pu and 250 kVp X rays. The survival curves resulting from exposure to ..cap alpha.. particles are exponential. The mean lethal dose, D/sub 0/, is approximately 1.3 Gy for X rays and 0.25 Gy for ..cap alpha.. particles. As a function of radiation dose, mutation induction at the HGPRT locus was linear for ..cap alpha.. particles whereas the X-ray-induced mutation data were better fitted by a quadratic function. When mutation frequencies were plotted against the log of survival, mutation frequency at a given survival level was greater in cells exposed to ..cap alpha.. particles than to X rays.

Chen, D.J.; Strniste, G.F.; Tokita, N.

1984-11-01

108

Recoil Based Fuel Breeding Fuel Structure  

SciTech Connect

Nuclear transmutation reactions are based on the absorption of a smaller particle as neutron, proton, deuteron, alpha, etc. The resulting compound nucleus gets out of its initial lattice mainly by taking the recoil, also with help from its sudden change in chemical properties. The recoil implantation is used in correlation with thin and ultra thin materials mainly for producing radiopharmaceuticals and ultra-thin layer radioactive tracers. In nuclear reactors, the use of nano-particulate pellets could facilitate the recoil implantation for breeding, transmutation and partitioning purposes. Using enriched {sup 238}U or {sup 232}Th leads to {sup 239}Pu and {sup 233}U production while using other actinides as {sup 240}Pu, {sup 241}Am etc. leads to actinide burning. When such a lattice is immersed into a radiation resistant fluid (water, methanol, etc.), the recoiled product is transferred into the flowing fluid and removed from the hot area using a concentrator/purifier, preventing the occurrence of secondary transmutation reactions. The simulation of nuclear collision and energy transfer shows that the impacted nucleus recoils in the interstitial space creating a defect or lives small lattices. The defect diffuses, and if no recombination occurs it stops at the lattices boundaries. The nano-grains are coated in thin layer to get a hydrophilic shell to be washed by the collection liquid the particle is immersed in. The efficiency of collection depends on particle magnitude and nuclear reaction channel parameters. For {sup 239}Pu the direct recoil extraction rate is about 70% for {sup 238}UO{sub 2} grains of 5 nm diameters and is brought up to 95% by diffusion due to {sup 239}Neptunium incompatibility with Uranium dioxide lattice. Particles of 5 nm are hard to produce so a structure using particles of 100 nm have been tested. The particles were obtained by plasma sputtering in oxygen atmosphere. A novel effect as nano-cluster radiation damage robustness and cluster amplified defects rejection will be discussed. The advantage of the method and device is its ability of producing small amount of isotopic materials easy to separate, using the nuclear reactors, with higher yield than the accelerator based methods and requiring less chemistry. (author)

Popa-Simil, Liviu [R and D, LAVM LLC., Los Alamos, NM, 87544 (United States)

2008-07-01

109

ITER alpha particle diagnostics using knock-on ion tails  

SciTech Connect

Alpha particles will play a critical role in the physics and successful operation of ITER. Achieving fusion ignition requires that the {alpha} particles created by deuterium-tritium (D-T) reactions deposit a large fraction of their energy in the reacting plasma before they are lost. Toroidal field ripple can localize any alpha particle losses and cause first wall damage. We have proposed a new method of measuring the fast confined {alpha}-particle distribution in a reacting plasma. The same elastic collisions that transfer the alpha energy to the D-T plasma ions and allow fusion ignition will also create a high energy tail on the deuterium and tritium ion energy distributions. Some of these energetic tail ions will undergo fusion reactions with the background plasma producing neutrons whose energy is increased significantly above 14 MeV due to the kinetic energy of the reacting ions. Measurement of this high energy tail on the D-T neutron distribution as a function of plasma minor radius would provide information on the alpha density profile with a time response equal to the ion slowing-down time. Although this technique may provide only limited information on the {alpha}-particle energy distribution, experimental studies of fast ions on existing tokamaks have shown that the observed slowing-down is essentially classical. Hence the {alpha}-energy distribution is expected to be classical except in situations where the {alpha}-confinement is poor. The confinement of {alpha}`s can be affected by ripple losses and a number of instabilities. Toroidal field ripple can cause both prompt orbit losses and stochastic ripple diffusion losses. Magnetohydrodynamic activity, including fishbone instabilities, toroidal Alfven eigenmodes, and sawtooth oscillations, may also affect alpha confinement. The diagnostic proposed here, by monitoring the confined alpha population, can provide valuable information on the confinement of fast alphas in a reacting plasma.

Fisher, R.K.; Parks, P.B.; McChesney, J.M. [and others

1995-09-01

110

Ionization of noble gas atoms by alpha particles and fission fragments from the decay of 252Cf1  

NASA Astrophysics Data System (ADS)

Charge state distributions of He, Ne, Ar, Kr, and Xe ions produced in single collisions with alpha particles and fission fragments from the decay of 252Cf have been measured using time of flight spectrometry. The measurements reveal that the maximum number of electrons removed in a fission fragment collision ranges from eight in the case of Ne to 20 in the case of Xe. Recoil-ion production cross sections have been determined for the resolvable ionic charge states and compared with the predictions of a model based upon the independent electron approximation.

Hill, B. M.; Watson, R. L.; Wohrer, K.; Bandong, B. B.; Sampoll, G.; Horvat, V.

1993-07-01

111

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

112

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

113

Measurement of alpha particles on PLT  

SciTech Connect

The radial emission profile of the d(/sup 3/He,p)..cap alpha.. fusion reaction was measured on PLT by pitch angle resolution of the escaping 3.7-MeV alphas. The d-/sup 3/He reactions were produced by /sup 3/He minority ICRF and the emission was strongly peaked at the ICRF resonance layer.

Murphy, T.J.; Strachan, J.D.

1984-12-01

114

Observational evidence of alpha-particle capture at Mars  

NASA Astrophysics Data System (ADS)

Solar wind alpha-particles are suggested to be the most important source of helium in the Martian atmosphere. Recent hybrid simulations show that as much as 30% of the alpha-particles passing through the planetary cross section can be lost from the solar wind due to charge-exchange processes associated with the Mars/solar wind interaction. We use ion data from the ASPERA-3 instrument on Mars Express to investigate the penetration of alpha-particles into the Martian atmosphere. We conclude that solar wind alpha-particles contribute to the helium observed in the atmosphere. In accordance with simulations we see an asymmetry in the capture efficiency related to the solar wind convection electric field.

Stenberg, G.; Nilsson, H.; Futaana, Y.; Barabash, S.; Fedorov, A.; Brain, D.

2011-05-01

115

Preliminary Results from the Lunar Prospector Alpha Particle Spectrometer  

NASA Astrophysics Data System (ADS)

Data measured using the Lunar Prospector Alpha Particle Spectrometer were surveyed to search for surface deposits of polonium-210. Preliminary results show that a marginal, yet statistically-significant signal was indeed detected on the lunar front side.

Lawson, S. L.; Feldman, W. C.; Moore, K. R.; Lawrence, D. J.; Maurice, S.; Belian, R. D.; Binder, A. B.

2001-03-01

116

The measurement of alpha particle emissions from semiconductor memory materials  

Microsoft Academic Search

With the increasing concern for the affects of alpha particles on the reliability of semiconductor memories, an interest has\\u000a arisen in characterizing semiconductor manufacturing materials for extremely low-level alpha-emitting contaminants. It is\\u000a shown that four elements are of primary concern: uranium, thorium, radium, and polonium. Measurement of contamination levels\\u000a are given relevance by first correlating them with alpha flux emission

D. P. Bouldin

1981-01-01

117

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

Microsoft Academic Search

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

E. R. Crosson; S. K. Lemieux; E. J. Ludwig; W. J. Thompson; M. Bisenberger; R. Hertenberger; D. Hofer; H. Kader; P. Schiemenz; G. Graw; A. M. Eiro; F. D. Santos

1993-01-01

118

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

119

Genotoxicity of alpha particles in human embryonic skin fibroblasts  

Microsoft Academic Search

Cell inactivation and induced mutation frequencies at the hypoxanthine-guanine phosphoribosyl transferase (HGPRT) locus have been measured in cultured human fibroblasts (GM10) exposed to ..cap alpha.. particles from ²³⁸ Pu and 250 kVp X rays. The survival curves resulting from exposure to ..cap alpha.. particles are exponential. The mean lethal dose, Dâ, is approximately 1.3 Gy for X rays and 0.25

D. J. Chen; G. F. Strniste; N. Tokita

1984-01-01

120

Plastic scintillator with phosphorescent dopants for alpha-particles registration  

Microsoft Academic Search

In the present work we try to study the difference between the conventional scintillator and the scintillator with Eu-organic complexes in response to alpha-particle of 239Pu source. It is shown that polystyrene-based scintillator film with 4 wt% of Eu-organic complex have 5650 photons\\/MeV light output for alpha-particle of 5.4 MeV energy. This is 7 times higher than light output of

A. F. Adadurov; P. N. Zhmurin; V. N. Lebedev; V. V. Kovalenko

2010-01-01

121

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

122

Actinium-225 in targeted alpha-particle therapeutic applications.  

PubMed

Alpha particle-emitting isotopes are being investigated in radioimmunotherapeutic applications because of their unparalleled cytotoxicity when targeted to cancer and their relative lack of toxicity towards untargeted normal tissue. Actinium- 225 has been developed into potent targeting drug constructs and is in clinical use against acute myelogenous leukemia. The key properties of the alpha particles generated by 225Ac are the following: i) limited range in tissue of a few cell diameters; ii) high linear energy transfer leading to dense radiation damage along each alpha track; iii) a 10 day halflife; and iv) four net alpha particles emitted per decay. Targeting 225Ac-drug constructs have potential in the treatment of cancer. PMID:22202153

Scheinberg, David A; McDevitt, Michael R

2011-10-01

123

Probing alpha-particle wave functions using (d-->,alpha) reactions  

Microsoft Academic Search

Wave functions of the alpha particle corresponding to different S- and D-state deuteron-deuteron overlaps, , were investigated using exact finite-range distorted-wave Born-approximation (DWBA) analyses of (d-->,alpha) reactions. Cross sections, vector, and tensor-analyzing powers were measured for (d-->,alpha) reactions populating the lowest Jpi=7+ state in 56Co at bombarding energies Ed of 16 and 22 MeV, the lowest 7+ state in 48Sc

E. R. Crosson; S. K. Lemieux; E. J. Ludwig; W. J. Thompson; M. Bisenberger; R. Hertenberger; D. Hofer; H. Kader; P. Schiemenz; G. Graw; A. M. Eiró; F. D. Santos

1993-01-01

124

Alpha particle destabilization of the toroidicity-induced Alfven eigenmodes.  

National Technical Information Service (NTIS)

The high frequency, low mode number toroidicity-induced Alfven eigenmodes (TAE) are shown to be driven unstable by the circulating and/or trapped (alpha)-particles through the wave-particle resonances. Satisfying the resonance condition requires that the ...

C. Z. Cheng

1990-01-01

125

The evaporation signal from [alpha] particles stopped in superfluid helium  

SciTech Connect

Alpha particles stopped in a 3 liter volume of liquid helium at 30 mK are observed by the calorimetric detection of helium atoms evaporated from the free surface of the liquid. Quantum evaporation of the helium is produced by the rotons that are created by the [alpha] particle. While the energy spectrum of the 5.5 MeV [alpha]'s from the [sup 241]Am source has a width of less than 0.5%, the energy distribution of the observed evaporation signals extends from the low energy threshold of several keV up to a maximum of several 100 keV, depending on geometrical factors and the collection area of the calorimeter. The origin of the observed distribution may result in part from the presence of the substrate and a dependence on the direction of the track of the [alpha] particle. A simple model of the generation of rotons by the [alpha] particle will be discussed.

Bandler, S.R.; Enss, C.; Goldhaber, G.; Lanou, R.E.; Maris, H.J.; More, T.; Porter, F.S.; Seidel, G.M. (Brown Univ., Providence, RI (United States))

1993-11-01

126

Ionization cluster size distribution for alpha particles: experiment, modelling.  

PubMed

The paper presents data for measured ionization cluster size distributions by alpha particles in tissue equivalent media and comparison with the simulated data for liquid water. The experiments were carried out with a beam of 4.6 MeV alpha particles performed in a setup called the JET Counter. The theoretically derived cluster size distributions for alphas particles were obtained using the K-means algorithm. The simulation was carried out by Monte Carlo track structure calculations using cross sections for liquid water. The first moments of cluster size distributions, derived from K-means algorithm as a function of diameter of cluster centroid, were compared with the corresponding moments derived from the experiments for nitrogen and propane targets. It was found that the ratio of the first moments for water to gas targets correlates well with the corresponding ratio of the mean free paths for primary ionization by alpha particles in the two media. It is shown that the cluster size distributions for alpha particles in water, obtained from K-means algorithm, are in agreement with the corresponding distributions measured experimentally in nitrogen or propane gas targets of nanometer sizes. PMID:17251255

Pszona, S; Bantsar, A; Nikjoo, H

2007-01-24

127

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

128

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

129

alpha-Particle stopping power for titanium and vanadium  

Microsoft Academic Search

A method for accurate measurement of the specific energy loss dE\\/dx of alpha-particles is described and results are given for titanium in the alpha-energy range 5.25-13 MeV and for vanadium in the range 5.25-12 MeV with uncertainties of about 3%. The results are in excellent agreement with the stopping power predictions of Ziegler and earlier precision measurements of the stopping

R. C. Haight; H. K. Vonach

1984-01-01

130

Morphology of cells malignantly transformed by alpha particle irradiation  

Microsoft Academic Search

The idea that one alpha particle (with LET approximately 100keV\\/micrometers) traversing a cell nucleus would kill a cell has been a concept which has been traditionally accepted by most radiation biologists. It was, therefore, difficult to see how alpha radiation could act directly on nuclear DNA to cause cancer. In experiments where mouse embryo cells (C3H 10T1\\/2) were irradiated with

E. L. Lloyd; C. B. Henning

1981-01-01

131

Radon monitor and control system based upon alpha particle detection  

SciTech Connect

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

Hurst, G.S.

1992-01-01

132

Solar wind alpha particle capture at Mars and Venus  

NASA Astrophysics Data System (ADS)

Helium is detected in the atmospheres of both Mars and Venus. It is believed that radioactive decay of uranium and thorium in the interior of the planets' is not sufficient to account for the abundance of helium observed. Alpha particles in the solar wind are suggested to be an additional source of helium, especially at Mars. Recent hybrid simulations show that as much as 30% of the alpha particles can be lost from the solar wind due to charge-exchange processes associated with the Mars/solar wind interaction. We use ion data from the ASPERA-3 and ASPERA-4 instruments on Mars and Venus Express to estimate how efficient solar wind alpha particles are captured in the atmospheres of the two planets.

Stenberg, Gabriella; Barabash, Stas; Nilsson, Hans; Fedorov, Andrei; Brain, Dave

2010-05-01

133

Scintillation of thin tetraphenyl butadiene films under alpha particle excitation  

Microsoft Academic Search

The alpha induced scintillation of the wavelength shifter\\u000a1,1,4,4-tetraphenyl-1,3-butadiene (TPB) was studied to improve the\\u000aunderstanding of possible surface alpha backgrounds in the DEAP dark matter\\u000asearch experiment. We found that vacuum deposited thin TPB films emit 882\\u000a+\\/-210 photons per MeV under alpha particle excitation. The scintillation pulse\\u000ashape consists of a double exponential decay with lifetimes of 11

Tina Pollmann; Mark Boulay; Marcin Ku?niak

2010-01-01

134

{alpha}-Particle Condensation in {sup 16}O  

SciTech Connect

In order to explore the 4{alpha}-particle condensate state in {sup 16}O, we solve a full four-body equation based on the 4{alpha} OCM (Orthogonality Condition Model) in a large 4{alpha} model space spanned by Gaussian basis functions. A full spectrum up to the 0{sub 6}{sup +} state is reproduced consistently with the lowest six 0{sup +} states of the experimental spectrum. It is suggested that the 0{sub 6}{sup +} state is the analog to the Hoyle state of {sup 12}C, to be identified with the well known 0{sub 6}{sup +} state at 15.1 MeV in {sup 16}O.

Schuck, P. [Institut de Physique Nucleaire, CNRS, UMR 8608, Orsay, F-91406, France Universite Paris-Sud, Orsay, F-91505 (France); Funaki, Y. [Institute of Physics, University of Tsukuba, Tsukuba 305-8571 (Japan); Yamada, T. [Laboratory of Physics, Kanto Gakuin University, Yokohama 236-8501 (Japan); Horiuchi, H.; Tohsaki, A. [Research Center for Nuclear Physics (RCNP), Osaka University, Osaka 567-0047 (Japan); Roepke, G. [Institut fuer Physik, Universitaet Rostock, D-18051 Rostock (Germany)

2009-08-26

135

Ion cyclotron emission spectroscopy as an. cap alpha. -particle monitor  

SciTech Connect

Since 1981, we have proposed and investigated spectral analysis of the harmonics of ion cyclotron emission (ICE) as a means of monitoring the energy content of ..cap alpha.. particles confined in a magnetic fusion device. A pair of crown probe antennas have been constructed for TFTR to collect ICE spectra and will be installed on that device in the near future. The design of this ICE spectroscopy system is described. Also, some calculations of ICE electromagnetic fluctuations in the ICRF, due to newborn ..cap alpha.. particles with a distribution function appropriate to typical fusion reactor parameters, are discussed. The calculated emission spectra are quite distinct from that of blackbody radiation.

Moses, K.G.; Sperling, J.L.; Dooling, J.C.; Chu, C.

1988-08-01

136

Solar wind alpha particle capture at Mars and Venus  

NASA Astrophysics Data System (ADS)

Helium is detected in the atmospheres of both Mars and Venus. It is believed that radioactive decay of uranium and thorium in the interior of the planets' is not sufficient to account for the abundance of helium observed. Alpha particles in the solar wind are suggested to be an additional source of helium, especially at Mars. Recent hybrid simulations show that as much as 30We use ion data from the ASPERA-3 and ASPERA-4 instruments on Mars and Venus Express to estimate how efficient solar wind alpha particles are captured in the atmospheres of the two planets.

Stenberg, Gabriella; Barabash, Stas; Nilsson, Hans; Fedorov, A.; Brain, David; André, Mats

137

Modeling of Alpha Particle Loss from a DT Spherical Tokamak  

NASA Astrophysics Data System (ADS)

A proposed follow-up to the present generation of spherical tokamak experiments (NSTX and MAST) would be a larger ST with parameters on the order of R=1.2 m, a=0.9 m, I_p=18 MA, B_T=1.7 T. Such an ST could be run with a DT fuel mixture and could have a breakeven parameter of 1 <= Q <= 40. For such a device to have high Q, it must confine the fusion-produced alpha particles until their energy has been transferred to cold incoming fuel. We are making an initial assessment of alpha particle confinement in a model DTST configuration by computing their prompt orbit loss fraction. The computation follows the orbits of a representative sample of alpha particles whose birth locations are distributed according to an expected fusion source profile. Orbits are tracked until they intersect the vessel wall or until a maximum orbit length (tilde 1 km, which is much less than the characteristic collisional slowing down distance in these plasmas) is reached. Because the gyroradii of 3.5 MeV alpha particles in such a device are a non-negligible fraction of the minor radius (r/a tilde 0.2), this model follows the full gyro-orbit of each particle. Progress in the modeling effort will be reported.

Wyatt, D.; Darrow, D.; Paoletti, F.

2000-10-01

138

Alpha-particle condensation in light hypernuclei  

NASA Astrophysics Data System (ADS)

Gas-like ?-cluster states are investigated in light ? hypernuclei. The ? condensate-type microscopic cluster model wave function is introduced to describe ? hypernuclei. In particular, the analogous state to the famous Hoyle state, the second 0+ state in 12C, is investigated in 13?C, with the use of the new type wave function. The Hoyle state is known to have a gas-like 3? cluster structure, where the 3? particles are condensed into an identical S orbit. The second 1/2+ state in 13?C is shown to have the 3?+? structure. A strong shrinkage effect by adding the ? particle is seen for the state, reducing the rms radius from 3.8 fm in the Hoyle state to 2.8 fm. In spite of the shrinkage effect, the ? condensate fraction of about 60% still survives, though it is reduced by about 20% from the Hoyle state.

Funaki, Yasuro; Yamada, Taiichi; Hiyama, Emiko; Ikeda, Kiyomi

2013-09-01

139

Particle Physics Aspects of Antihydrogen Studies with ALPHA at CERN  

Microsoft Academic Search

We discuss aspects of antihydrogen studies, that relate to particle physics ideas and techniques, within the context of the ALPHA experiment at CERN's Antiproton Decelerator facility. We review the fundamental physics motivations for antihydrogen studies, and their potential physics reach. We argue that initial spectroscopy measurements, once antihydrogen is trapped, could provide competitive tests of CPT, possibly probing physics at

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

2008-01-01

140

Particle Physics Aspects of Antihydrogen Studies with ALPHA at CERN  

Microsoft Academic Search

We discuss aspects of antihydrogen studies, that relate to particle physics ideas and techniques, within the context of the ALPHA experiment at CERN's Antiproton Decelerator facility. We review the fundamental physics motivations for antihydrogen studies, and their potential physics reach. We argue that initial spectroscopy measurements, once antihydrogen is trapped, could provide competitive tests of CPT, possibly probing physics at

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

2009-01-01

141

Fusion-Born Alpha Particle Ripple Loss Studies in ITER.  

National Technical Information Service (NTIS)

Fusion-born alpha particle losses are investigated for two ITER scenarios with and without test blanket modules (TBMs). When the TBMs were present it was found that the losses increased by a factor of two overall with a marked increase in its localization...

G. J. Kramer H. L. Berk R. Nazikian R. B. White

2008-01-01

142

Effect of alpha particles on bacteriophage T4Br(+)  

SciTech Connect

The effects of heavy particle radiation, which is believed to be responsible for the high relative biological effectiveness (RBE) of space hadrons, on bacteriophages are investigated. Dry film cultures of bacteriophage T4 were irradiated with 5.3 MeV Po-210 alpha particles to doses from 5 to 60 Gray, and compared with cultures irradiated by Co-60 gamma radiation. Examination of the exponential dose-response curves for bacteriophage survival indicates an RBE of 4.68 for the alpha particles. The r-mutation frequency per 10,000 surviving phages is found to peak at 7.1 at doses between 65 and 85 Gray for gamma radiation, however it declines steadily from a level of 10.2 per 10,000 survivors with increasing dose of alpha radiation. Comparison of the mutation frequencies at the same levels of lethality and the spectra of mutations produced by the two types of radiation indicates alpha and gamma radiation to differ as well in the mechanisms of mutation production. It is concluded that the observed high RBE of space hadrons cannot be explained by the presence of high-energy particles in the secondary radiation. 13 references.

Leonteva, G.A.; Akoev, I.G.; Grigorev, A.E.

1983-01-01

143

Stopping Power of Liquid Water for alpha-Particles  

Microsoft Academic Search

THE mean stopping power of liquid water averaged over the whole range has been determined for natural alpha-particles by Michl1 and by Philipp2. These authors find values for the molecular stopping power which are higher by about 20 and 14 per cent respectively than those predicted by the Bragg law and the accepted atomic stopping powers of hydrogen and oxygen.

R. K. Appleyard

1949-01-01

144

Alpha particle collimator for micron-sized beam  

Microsoft Academic Search

A collimated alpha source is constructed from a drawn glass microcapillary and a plated polonium wire source. The shape of the capillary is approximately Gaussian, allowing an analytical model for the collimated flux intensity. The very gradual taper results in a nearly monochromatic beam. Two models are presented characterizing the particle flux intensity and its profile on a surface below

F. J. Henley; W. G. Oldham

1982-01-01

145

Neutron production by alpha particles in thin uranium hexafluoride  

SciTech Connect

Alpha-particle-induced neutrons from UF/sub 6/ serve as an indicator of /sup 235/U enrichment and may be exploited for safeguards purposes. If the UF/sub 6/ density is low enough, neutron production is reduced as a result of alpha-particle escape before (..cap alpha..,n) reactions with /sup 19/F. Calculational methods and results are presented that enable prediction of neutron production in low-density (thin) UF/sub 6/ as encountered in the gas centrifugation method of uranium enrichment. Neutron production is shown to be strongly dependent on average UF/sub 6/ density and weakly dependent on rotational speed in an operating centrifuge.

Stewart, J.E.

1983-07-01

146

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

Microsoft Academic Search

Components of alpha-particle wave functions corresponding to d-d configurations are used to predict analyzing powers in the (d,alpha) reaction. Tensor analyzing powers, especially Axx, are shown to clearly distinguish between wave functions generated by different realistic nucleon-nucleon interactions. Data for the 58Ni(d,alpha)56Co reaction to the 7+ stretched-nucleon-orbital state at 2.283-MeV excitation in 56Co, measured with 22-MeV deuterons, are compared to

E. R. Crosson; R. K. Das; S. K. Lemieux; E. J. Ludwig; W. J. Thompson; M. Bisenberger; R. Hertenberger; D. Hofer; H. Kader; P. Schiemenz; G. Graw; A. M. Eiró; F. D. Santos

1992-01-01

147

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

NASA Astrophysics Data System (ADS)

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

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

2000-11-01

148

TF ripple loss of alpha particles in TFTR DT experiments  

SciTech Connect

Quantitative evaluation of TF ripple loss of DT alpha particles is a central issue for reactor design because of potentially severe first wall heat load problems. DT experiments on TFTR allow experimental measurements to be compared to modeling of the underlying alpha physics, with code validation an important goal. Modeling of TF ripple loss of alphas in TFTR now includes neoclassical calculations of alpha losses arising from first orbit loss, stochastic ripple diffusion, ripple trapping and collisional effects. Recent Hamiltonian coordinate guiding center code (ORBIT) simulations for TFTR have shown that collisions enhance the stochastic TF ripple losses at TFTR. A faster way to simulate experiment has been developed and is discussed here which uses a simple stochastic domain model for TF ripple loss within the TRANSP analysis code.

Redi, M.H.; Budny, R.V.; Darrow, D.S. [and others

1995-08-01

149

Michrochannel plate for position sensitive alpha particle detection  

SciTech Connect

This paper will describe the use of a microchannel plate (MCP) as the associated particle detector on a sealed tube neutron generator. The generator produces neutrons and associated alpha particles for use as a probe to locate and identify hidden explosives in associated particle imaging (API). The MCP measures the position in two dimensions and precise timing of the incident alpha particle, information which is then used to calculate the emission time and direction of the corresponding neutron. The MCP replaces the position-sensitive photomultipler tube (PSPMT) which, until recently, had been the only detector available for measuring position and timing for alpha particles in neutron generator applications. Where the PSPMT uses charge division for generating position information, a process that requires a first order correction to each pulse, the MCP uses delay-line timing, which requires no correction. The result is a device with an order of magnitude improvement in both position resolution and timing compared to the PSPMT. Hardware and software development and the measurements made to characterize the MCP for API applications are described.

Paul Hurley and James Tinsley

2007-08-31

150

Alpha-particle losses in compact torsatron reactors  

SciTech Connect

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

Painter, S.L.; Lyon, J.F.

1989-01-01

151

Historical trend in alpha-particle induced soft error rates of the AlphaTM microprocessor  

Microsoft Academic Search

In this work, we present ?-particle induced soft error rates (SER) for several generations of the Alpha microprocessor. In our analysis, we focus in particular on the historical trend of soft error rates for memory cells and random core logic. Our data demonstrate the impact of process, design and packaging material on the SER. The total chip-level SER trend has

N. Seifert; D. Moyer; N. Leland; R. Hokinson

2001-01-01

152

Additional alpha-particle optical potential tests below the Coulomb barrier  

Microsoft Academic Search

New results of (alpha,gamma) and (alpha,n) reaction cross section measurements close to the reaction thresholds support the setting up of recent parameters of the alpha-particle optical model potential (OMP) below the Coulomb barrier. Particular features of the alpha-particle optical potential at energies below the Coulomb barrier explain the failure of using the OMP parameters obtained by analysis of only alpha-particle

M. Avrigeanu; V. Avrigeanu

2010-01-01

153

Additional {alpha}-particle optical potential tests below the Coulomb barrier  

SciTech Connect

New results of ({alpha},{gamma}) and ({alpha},n) reaction cross section measurements close to the reaction thresholds support the setting up of recent parameters of the {alpha}-particle optical model potential (OMP) below the Coulomb barrier. Particular features of the {alpha}-particle optical potential at energies below the Coulomb barrier explain the failure of using the OMP parameters obtained by analysis of only {alpha}-particle elastic scattering at higher energies.

Avrigeanu, M.; Avrigeanu, V. ['Horia Hulubei' National Institute for Physics and Nuclear Engineering, P.O. Box MG-6, RO-077125 Bucharest-Magurele (Romania)

2010-03-15

154

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

155

Semiconducting detectors of alpha-particles fabricated by ion implantation  

Microsoft Academic Search

The low-energy ion implantation method of boron and phosphorus in p- and n-type silicon is used in conjunction with appropriate methods for mechanical and chemical surface treatments of the materials to fabricate semiconducting detectors for alpha-particle spectrometers. High-quality p-n junctions with low reverse currents were obtained. With a 30-sq-mm sensitive area, the detectors have a resolving power from 17 to

D. Sueva; B. Amov; A. Dzhakov; N. Chikov

1977-01-01

156

Stopping of Protons and alpha -Particles in Compounds. 1.  

National Technical Information Service (NTIS)

The stopping power and ranges of 0.1-100 MeV protons and alpha -particles were calculated in some compounds: air, water, CO, CO sub 2 , CaF sub 2 , LiF, (Csub(2)Fsub(4))sub(n), SiO sub 2 , Al sub 2 O sub 3 , NaCl, KCl, NaI, KI, CsI, C sub 6 H sub 5 CH, C ...

T. D. Chesnokova N. N . Pucherov A. E. Borzakovskij

1981-01-01

157

Stopping power for alpha particles in organic liquids and vapours  

Microsoft Academic Search

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.

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

1991-01-01

158

Effects of. alpha. -particle radiation on rat tracheal epithelial cells  

SciTech Connect

By a combination of methods, which included flow cytometry and magnetic cell sorting, we have demonstrated that the cells of the rat tracheal epithelium which have the greatest proliferative capacity in culture and in vivo are the basal cells. Because of these findings it seems reasonable to suppose that the basal cells are the most likely target for the action of {alpha}-particle radiation in pseudostratified respiratory epithelium. This hypothesis is further supported by the finding that the basal cells are the cells which appear to respond to the tumor promoter 12-O-tetradecanoylphorbol-13-acetate. The effects of {sup 210}Po {alpha}-particles on the survival and oncogenic transformation of rat tracheal epithelial cells in suspension were investigated. Since these effects were assayed in culture, the results pertain to the reaction of only the basal cells to irradiation. The results indicate that {alpha}-particles are extremely cytotoxic in that a track segment of 4 {mu}m, on average, is sufficient to cause the reproductive death of basal cells. This finding is supported by similar results obtained with two cell lines, Mv1Lu and CHO-K1 BH{sub 4}. Production of proliferating epithelial foci by {alpha}-particles was not distinguishable from control and sham treatments. These results are in direct conflict with many of the results that have been obtained with C3H 1OT1/2 cells in similar transformation assays. Some possible reasons for these disparities are discussed and supporting evidence is provided.

Ford, J.R. Jr.

1992-08-01

159

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

ERIC Educational Resources Information Center

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

Andrews, D. G. H.

2008-01-01

160

{alpha} particle preformation in heavy nuclei and penetration probability  

SciTech Connect

The {alpha} particle preformation in the even-even nuclei from {sup 108}Te to {sup 294}118 and the penetration probability have been studied. The isotopes from Pb to U have been firstly investigated since the experimental data allow us to extract the microscopic features for each element. The assault frequency has been estimated using classical methods and the penetration probability from tunneling through the Generalized Liquid Drop Model (GLDM) potential barrier. The preformation factor has been extracted from experimental {alpha} decay energies and half-lives. The shell closure effects play the key role in the {alpha} preformation. The more the nucleon number is close to the magic numbers, the more the formation of {alpha} cluster is difficult inside the mother nucleus. The penetration probabilities reflect that 126 is a neutron magic number. The penetration probability range is very large compared to that of the preformation factor. The penetration probability determines mainly the {alpha} decay half-life while the preformation factor allows us to obtain information on the nuclear structure. The study has been extended to the newly observed heaviest nuclei.

Zhang, H. F. [School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000 (China); Royer, G. [Laboratoire Subatech, UMR: IN2P3/CNRS-Universite-Ecole des Mines, F-44307 Nantes Cedex 03 (France)

2008-05-15

161

Recoil and Equilibrator Systems.  

National Technical Information Service (NTIS)

The pamphlet provides a general guide for the testing of recoil and equilibrator systems. Described are the arrival, prefiring, firing, post-firing and road tests to which the hydropneumatic and hydrospring recoil systems, and pneumatic, hydropneumatic an...

1966-01-01

162

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

163

An Investigation of Alpha-Particle Groups from Al27(d,alpha)Mg25  

Microsoft Academic Search

The alpha-particle groups produced by the bombardment of aluminum by 10.8-Mev deuterons have been measured using nuclear emulsion plates for detection. Seven new levels in Mg25 were found at 6.98, 7.85, 8.62, 9.06, 975, 10.78, and 11.89 Mev. The previously known level at 4.01 Mev has been resolved into two levels at 3.96 and 4.12 Mev.

E. C. Toops; M. B. Sampson; F. E. Steigert

1952-01-01

164

Alpha particle-driven toroidal rotation in burning plasmas  

NASA Astrophysics Data System (ADS)

The mechanism of a torque intrinsically produced by alpha particles and the subsequent possibility to create significant toroidal rotation and shear are numerically investigated. In steady-state DEMO plasmas, regardless of the magnetic configuration, the orbit-following Monte Carlo code OFMC predicts that co-directed collisional torque and a counter-directed \\vec{j}\\times\\vec{B} torque always emerge due to the gradient of the source profile of alpha particles and both of them virtually cancel each other out, as analytically predicted earlier. The magnitude of each torque is enhanced in the reversed shear configuration compared with the normal shear configuration, provided that the source gradient is finite and similar in both cases. The resultant rotation velocity estimated by the TASK/TX transport code is far below the threshold to stabilize resistive wall modes (RWMs) through intrinsic alpha-driven torque alone. It is estimated that a neutral beam injection at a moderate power level may be capable of producing toroidal rotation sufficient to stabilize RWMs.

Honda, M.; Takizuka, T.; Tobita, K.; Matsunaga, G.; Fukuyama, A.

2011-07-01

165

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

166

Emission of Long-Range Alpha Particles in the Spontaneous Fission of Cf252  

Microsoft Academic Search

An experimental investigation of alpha-particle emission in the spontaneous fission of Cf252 is described. The measured angular distribution and energy distribution of the alpha particles are presented, as well as the mass-ratio distribution of the fission fragments and the single-fragment energy distribution in fission accompanied by long-range alpha particles (LRA fission). Also shown is the angular distribution of the alpha

Z. Fraenkel

1967-01-01

167

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.

168

Isotopic uranium and plutonium analysis by alpha-particle spectrometry  

NASA Astrophysics Data System (ADS)

An isotopic uranium analysis of environmental and man-made samples was performed by alpha-particle spectrometry. A fitting technique using blocks of peaks in the spectra measured with silicon detectors was developed. Samples of natural uranium from conventional mines and from the Bangombé natural nuclear reactor were analysed. The isotope composition of depleted and enriched uranium samples was also determined. The technique was applied to determining the isotope composition of plutonium samples, identifying whether the samples were reactor-grade or weapons-grade plutonium. Spectra of soil samples from Palomares and others from an inter-laboratory comparison exercise were analysed, yielding very good results.

Rubio Montero, M. P.; Martín Sánchez, A.; Carrasco Lourtau, A. M.

2004-01-01

169

Alpha particle collimator for micron-sized beam  

SciTech Connect

A collimated alpha source is constructed from a drawn glass microcapillary and a plated polonium wire source. The shape of the capillary is approximately Gaussian, allowing an analytical model for the collimated flux intensity. The very gradual taper results in a nearly monochromatic beam. Two models are presented characterizing the particle flux intensity and its profile on a surface below the collimator tip. These models are experimentally verified using spectroscopy and isolated node mapping. Collimators having tip radii ranging from 5 to 25 ..mu.. have been successfully drawn and tested.

Henley, F.J.; Oldham, W.G.

1982-10-01

170

Probing Pre-Formed Alpha Particles in the Ground State of Nuclei  

NASA Astrophysics Data System (ADS)

In this proceeding we report on alpha particle emission through the nuclear break-up in the reaction 40Ca on a 40Ca target at 50A MeV. It is observed that alpha particles are emitted to the continuum with very specific angular distribution during the reaction. The alpha particle properties seem to be compatible with an alpha cluster in the daughter nucleus that is perturbed by the short range nuclear attraction of the collision partner and emitted as described by a time-dependent theory. This mechanism offers new possibilities to study alpha particle properties in the nuclear medium.

Scarpaci, J. A.; Fallot, M.; Lacroix, D.; Assié, M.; Lefebvre, L.; Frascaria, N.; Beaumel, D.; Bhar, C.; Blumenfeld, Y.; Chbihi, A.; Chomaz, Ph.; Désesquelle, P.; Frankland, J.; Idbarkach, H.; Khan, E.; Laville, J. L.; Plagnol, E.; Pollacco, E. C.; Roussel-Chomaz, P.; Roynette, J. C.; Shrivastava, A.; Zerguerras, T.

171

Direct high-resolution alpha spectrometry from nuclear fuel particles in an outdoor air sample.  

PubMed

The potential use of direct high-resolution alpha spectrometry to identify the presence of transactinium elements in air samples is illustrated in the case when alpha-particle-emitting radionuclides are incorporated in nuclear fuel particles. Alpha particle energy spectra are generated through Monte Carlo simulations assuming a nuclide composition similar to RBMK (Chernobyl) nuclear fuel. The major alpha-particle-emitting radionuclides, in terms of activity, are 242Cm, 239Pu and 240Pu. The characteristics of the alpha peaks are determined by fuel particle properties as well as the type of the air filter. It is shown that direct alpha spectrometry can be readily applied to membrane filter samples containing nuclear fuel particles when rapid nuclide identification is of relevance. However, the development of a novel spectrum analysis code is a prerequisite for unfolding complex alpha spectra. PMID:17951235

Pöllänen, R; Siiskonen, T

2007-10-19

172

Elastic recoil detection analysis for large recoil angles (LA-ERDA)  

NASA Astrophysics Data System (ADS)

In this paper, elastic recoil detection (ERD) measurements at recoil angle of 60° using ion-induced electron emission (IEE) for particle identification are presented. In our IEE system for particle identification, recoiled target atoms and scattered projectiles penetrate a set of thin carbon foils before their energy is analyzed in a solid state detector. Particle identification is based on the fact that the total number of electrons emitted from the foils depends on the particle nuclear charge. This method is characterized by its low minimum detectable energy, which stimulated us to study ERDA at 60°. Due to collision kinematics and due to the angular dependence of the scattering cross-sections, it is expected that the sensitivity can be significantly improved. In this work, the detection efficiency of the IEE particle identification system for H recoils at energies below 1 MeV was determined. LA-ERDA measurements were performed with 4He and 12C projectiles using two different types of samples with a well-known amount and depth distribution of H atoms near the surface. Sample 1 consisted of a 50 ?g/cm2 melamine layer evaporated on a flat Si substrate, sample 2 was a Si wafer with implanted H. Sensitivity and depth resolution were measured using LA-ERDA with a recoil angle of 60° and ERDA with recoil angles of 30° and 45°. The results for different recoil geometries and projectiles are discussed and compared with theoretical predictions.

Bogdanovi?, I.; Steinbauer, E.; Benka, O.

2000-09-01

173

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

174

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

175

Alpha particle loss in TFTR deuterium-tritium plasmas with reversed magnetic shear  

SciTech Connect

The confinement and loss of fusion alpha particles are examined for reversed magnetic shear plasmas in TFTR. Such plasmas, with high central q and non-monotonic q profiles can exhibit remarkably reduced energy and particle transport of the thermal ions. However, these same conditions are theoretically predicted to produce high levels of stochastic ripple loss of suprathermal particles, which may reduce the efficiency of plasma heating by the alpha particles and other heating schemes involving fast ions. This paper presents calculations of guiding-center code alpha particle orbit loss from deuterium-tritium (DT) simulations of TFTR deuterium-only experiments. They are compared to results of measurements made in DT reversed shear plasmas of both the confined alpha particle distribution and the alpha particles lost from the plasma. Large fast particle losses have also been found in reversed shear ITER simulations (up to 20%) and from measurements of triton burnup in reversed shear experiments on JT-60U (12%).

Redi, M.H.; Batha, S.H.; Budny, R.V. [and others

1997-06-01

176

Monte Carlo alpha deposition  

SciTech Connect

Prior work demonstrated the importance of nuclear scattering to fusion product energy deposition in hot plasmas. This suggests careful examination of nuclear physics details in burning plasma simulations. An existing Monte Carlo fast ion transport code is being expanded to be a test bed for this examination. An initial extension, the energy deposition of fast alpha particles in a hot deuterium plasma, is reported. The deposition times and deposition ranges are modified by allowing nuclear scattering. Up to 10% of the initial alpha particle energy is carried to greater ranges and times by the more mobile recoil deuterons. 4 refs., 5 figs., 2 tabs.

Talley, T.L.; Evans, F.

1988-01-01

177

Observations on the geometries of etched fission and alpha-recoil tracks with reference to models of track revelation in minerals  

Microsoft Academic Search

The kinetic and atomistic theories of crystal growth and dissolution are used to interpret the shapes and orientations of fission-track, recoil-track and dislocation etch pits in tri-octahedral phlogopite and di-octahedral muscovite. An atomistic approach combined with symmetry considerations lead to the identification of the periodic bond chains that determine the etch pit morphologies and relative etch rates at a chemical

R. Jonckheere; E. Enkelmann; K. Stübner

2005-01-01

178

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

Microsoft Academic Search

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

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

2005-01-01

179

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

Microsoft Academic Search

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

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

2005-01-01

180

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

Microsoft Academic Search

A method is formulated to describe the development of the alpha particles produced by fusion in a slender cylindrical plasma column that includes a fusion source and nonuniform thermalization. A numerical technique is presented which makes it possible to determine in a fully self-consistent manner the alpha-particle and background-plasma behavior in the case where the alpha particles transfer energy to

H. J. Willenberg

1979-01-01

181

The Li⁶(. cap alpha. ,2. cap alpha. )d reaction at 50 to 80 MeV  

Microsoft Academic Search

The Li⁶(..cap alpha..,2..cap alpha..)d reaction was studied at 50.4, 59.0, 60.5, 70.3 and 79.6 MeV bombarding energy. For each bombarding energy, several coincident energy spectra of the two emitted ..cap alpha..-particles were measured. The projected energy spectra were analyzed with the Plane Wave Impulse Approximation. From those points in the projected spectra which corresponded to zero deuteron recoil momentum, off-mass-shell

1970-01-01

182

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

183

Enhanced production of low energy electrons by alpha particle impact.  

PubMed

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 (Ne(2)). 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. PMID:21730184

Kim, Hong-Keun; Titze, Jasmin; Schöffler, Markus; Trinter, Florian; Waitz, Markus; Voigtsberger, Jörg; Sann, Hendrik; Meckel, Moritz; Stuck, Christian; Lenz, Ute; Odenweller, Matthias; Neumann, Nadine; Schössler, 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-Böcking, Horst; Dörner, Reinhard

2011-07-05

184

Enhancement of NEST capabilities for simulating low-energy recoils in liquid xenon  

NASA Astrophysics Data System (ADS)

The Noble Element Simulation Technique (NEST) is an extensive collection of models explaining both the scintillation light and ionization yields of noble elements as a function of particle type (nuclear recoils, electron recoils, alphas), electric field, and incident energy or energy loss (dE/dx). It is packaged as C++ code for Geant4 that implements said models, overriding the default model which does not account for certain complexities, such as the reduction in yields for nuclear recoils (NR) compared to electron recoils (ER). We present here improvements to the existing NEST models and updates to the code which make the package even more realistic and turn it into a more full-fledged Monte Carlo simulation. All available liquid xenon data on NR and ER to date have been taken into consideration in arriving at the current models. Furthermore, NEST addresses the question of the magnitude of the light and charge yields of nuclear recoils, including their electric field dependence, thereby helping to understand the capabilities of liquid xenon detectors for detection or exclusion of a low-mass dark matter WIMP.

Szydagis, M.; Fyhrie, A.; Thorngren, D.; Tripathi, M.

2013-10-01

185

A self-consistent theory of collective alpha particle losses induced by Alfvenic turbulence  

SciTech Connect

The nonlinear dynamics of kinetic Alfven waves, resonantly excited by energetic ions/alpha particles, is investigated. It is shown that {alpha}-particles govern both linear instability and nonlinear saturation dynamics, while the background MHD turbulence results only in a nonlinear real frequency shift. The most efficient saturation mechanism is found to be self-induced profile modification. Expressions for the fluctuation amplitudes and the {alpha}-particle radial flux are self-consistently derived. The work represents the first self-consistent, turbulent treatment of collective {alpha}-particle losses by Alfvenic fluctuations.

Biglari, H. [Princeton Univ., NJ (United States). Plasma Physics Lab.; Diamond, P.H. [California Univ., San Diego, La Jolla, CA (United States). Dept. of Physics

1992-01-01

186

Detection of lost alpha particle by concealed lost ion probe  

SciTech Connect

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

Okamoto, A.; Kitajima, S.; Sasao, M. [Department of Quantum Science and Energy Engineering, Tohoku University, Sendai 980-8579 (Japan); Isobe, M. [National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292 (Japan)

2010-10-15

187

Detection of lost alpha particle by concealed lost ion probe.  

PubMed

Full orbit-following calculation is performed for the final orbit of the lost alpha particles, showing some orbits escaping from the last closed flux surface could be detected by a concealed lost ion probe (CLIP) installed under the shadow of the original first wall surface. While both passing and trapped orbits hit the same wall panel, detecting a trapped orbit by the CLIP is easier than detecting passing orbits. Whether the final orbit is detected or not is determined by the position of the reflection point. The CLIP successfully detects the trapped orbits, which are reflected before they hit to a first wall. Then the pitch angles of the orbits at the CLIP are close to and smaller than 90°. Optimization of the position of the CLIP in terms of broader detection window is investigated. PMID:21033838

Okamoto, A; Isobe, M; Kitajima, S; Sasao, M

2010-10-01

188

Microscopic approach to the alpha-particle-nucleus optical potential  

NASA Astrophysics Data System (ADS)

A microscopic model for the alpha-particle-nucleus optical potential is presented and applied to ?-40Ca scattering. Starting with the M3Y force as the basic nucleon-nucleon interaction, the single-channel contribution to the optical potential is calculated by means of the fish-bone model which treats the antisymmetrization between the projectile and the target nucleus in an approximate way. The applicability of the fish-bone model to the ?-40Ca system is tested by comparison of resonating group calculations with fish-bone model calculations. The potential terms arising from the coupling of the elastic channel to other reaction channels have been calculated in the framework of the nuclear structure approach using random-phase approximation transition densities for intermediate excited states. The elastic scattering cross sections calculated from the microscopic potentials reproduce gross structures of the experimental data. However, the model cannot account for the whole absorption.

Leeb, H.; Osterfeld, F.

1985-09-01

189

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

190

A CMOS integrated pulse mode alpha-particle counter for application in radon monitoring  

SciTech Connect

A custom integrated circuit for detecting alpha particles for application in the monitoring of radon has been designed and tested. The design uses the reverse-biased well to a substrate capacitance of a p-n junction in a conventional CMOS process as a sense capacitor for incident alpha particles. A simple CMOS inverter is used as an analog amplifier to detect the small potential change induced by an alpha-particle strike on the sense capacitor. The design was implemented in a 1.2-{micro}m conventional CMOS process with a sense capacitor area of 110 {micro}m{sup 2}. Tests carried out under vacuum conditions using a calibrated {sup 241}Am alpha-particle source showed an output voltage swing of {ge}2.0 V for an alpha event. The detector is also shown to have good immunity to noise and high-quantum efficiency for alpha particles.

Ahmed, A.; Walkey, D.J.; Tarr, N.G. [Carleton Univ., Ottawa, Ontario (Canada). Dept. of Electronics

1997-06-01

191

Realizing the potential of the Actinium-225 radionuclide generator in targeted alpha-particle therapy applications  

PubMed Central

Alpha particle-emitting isotopes have been proposed as novel cytotoxic agents for augmenting targeted therapy. Properties of alpha particle radiation such as their limited range in tissue of a few cell diameters and their high linear energy transfer leading to dense radiation damage along each alpha track are promising in the treatment of cancer, especially when single cells or clusters of tumor cells are targeted. Actinium-225 (225Ac) is an alpha particle-emitting radionuclide that generates 4 net alpha particle isotopes in a short decay chain to stable 209Bi, and as such can be described as an alpha particle nanogenerator. This article reviews the literature pertaining to the research, development, and utilization of targeted 225Ac to potently and specifically affect cancer.

Miederer, Matthias; Scheinberg, David A.; McDevitt, Michael R.

2013-01-01

192

Realizing the potential of the Actinium-225 radionuclide generator in targeted alpha particle therapy applications.  

PubMed

Alpha particle-emitting isotopes have been proposed as novel cytotoxic agents for augmenting targeted therapy. Properties of alpha particle radiation such as their limited range in tissue of a few cell diameters and their high linear energy transfer leading to dense radiation damage along each alpha track are promising in the treatment of cancer, especially when single cells or clusters of tumor cells are targeted. Actinium-225 (225 Ac) is an alpha particle-emitting radionuclide that generates 4 net alpha particle isotopes in a short decay chain to stable 209 Bi, and as such can be described as an alpha particle nanogenerator. This article reviews the literature pertaining to the research, development, and utilization of targeted 225 Ac to potently and specifically affect cancer. PMID:18514364

Miederer, Matthias; Scheinberg, David A; McDevitt, Michael R

2008-04-23

193

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

SciTech Connect

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, H.W.

1997-09-01

194

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

195

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

196

PRODUCTION BY ALPHA PARTICLES OF FUNCTIONALLY STABLE BROKEN CHROMOSOME ENDS IN MAIZE  

Microsoft Academic Search

Maize pollen, carrying the linked dominant markers I Sh 13z Wx, was ; irradiated with alpha particles from an external plutonium source, and was used ; to pollinate plants carrying the corresponding recessives. The resulting marker ; losses and endosperm mosaics were analyzed to ascertain whether alpha particles ; are capable of breaking chromosomes so as to generate functionally stable

Faberge

1959-01-01

197

Detection of Radon Emanation from the Crater Aristarchus by the Apollo 15 Alpha Particle Spectrometer  

Microsoft Academic Search

The alpha particle spectrometer aboard the Apollo 15 command\\/service module was designed to detect alpha particles from radon decay and to locate regions with unusual activity on the moon. A significant increase in radon-222 activity was detected from a region containing the crater Aristarchus. The result is interpreted as probably indicating internal activity at the site. By analogy with terrestrial

Paul Gorenstein; Paul Bjorkholm

1973-01-01

198

{alpha}-particle production in {sup 6}He+{sup 120}Sn collisions  

SciTech Connect

The collision {sup 6}He+{sup 120}Sn has been investigated at four energies near the Coulomb barrier. A large yield of {alpha} particles has been detected, with energies around the energy of the scattered {sup 6}He beam. The energy and angular distributions of the {alpha} particles have been analyzed and compared with breakup and neutron transfer calculations.

Faria, P. N. de; Lichtenthaeler, R.; Pires, K. C. C.; Lepine-Szily, A.; Guimaraes, V.; Mendes, D. R. Jr.; Barioni, A.; Morcelle, V.; Morais, M. C. [Instituto de Fisica, Universidade de Sao Paulo, Caixa Postal 66318, 05314-970 Sao Paulo (Brazil); Moro, A. M. [Departamento de FAMN, Universidad de Sevilla, Apartado 1065, E-41080, Sevilla (Spain); Arazi, A. [Laboratorio Tandar, Departamento de Fisica, Comision Nacional de Energia Atomica, Avenida del Libertador 8250 (1429), Buenos Aires (Argentina)

2010-09-15

199

First Gamma-Ray Measurements of Fusion Alpha Particles in JET Trace Tritium Experiments  

Microsoft Academic Search

Gamma-ray spectra from nuclear reactions between fusion-born alpha (alpha) particles and Be impurities were measured for the first time in deuterium-tritium plasmas in the Joint European Torus. The time dependence of the measured spectra allowed the determination of the density evolution of fast alpha particles. Correlation between the decay time of the gamma-ray emission and the plasma parameters in different

V. G. Kiptily; Yu. F. Baranov; R. Barnsley; L. Bertalot; N. C. Hawkes; A. Murari; S. Popovichev; S. E. Sharapov; D. Stork; V. Yavorskij

2004-01-01

200

Experimental Study of the Cross Sections of {alpha}-Particle Induced Reactions on 209Bi  

SciTech Connect

Alpha particle induced reactions for generation of 211At used in therapeutic nuclear medicine and possible contaminants were investigated with the stacked foil activation technique on natural bismuth targets up to E{alpha}=39 MeV. Excitation functions for the reactions 209Bi({alpha},2n)211At, 209Bi({alpha},3n)210At, 209Bi({alpha},x) 210Po obtained from direct alpha emission measurements and gamma spectra from decay products are compared with earlier literature values. Thick target yields have been deduced from the experimental cross sections.

Hermanne, A. [Cyclotron Department, Vrije Universiteit Brussel, Laarbeeklaan 103, B1090 Brussels (Belgium); Tarkanyi, F.; Takacs, S.; Szucs, Z. [Atomki, Hungarian Academy of Sciences, Bem Ter, H4001 Debrecen (Hungary)

2005-05-24

201

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

SciTech Connect

It is very important to investigate the confinement of {alpha} 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 {alpha} 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 {alpha} particle diagnostic in LHD.

Ozaki, T.; Goncharov, P.; Sudo, S.; Tamura, N. [National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan); Veschev, E. [Graduate University for Advanced Studies, Hayama, Kanagawa, 240-0193 (Japan)

2008-03-12

202

The microdosimetry of lymphocytes irradiated by alpha-particles.  

PubMed

Although the concept of absorbed dose is commonly used in radiation biology as a parameter for comparing the toxic effect of different levels of radiation on a system, there are situations where the absorbed dose by itself is inadequate, and additional dose distribution information is required to explain the observed biological effects. A good example is the irradiation of cells by alpha-particles. This paper reports the use of internal microdosimetry techniques to reinvestigate the dosimetry to two very similar experiments with apparently contradictory dose-response results. Yields of dicentric chromosome aberrations induced in human blood lymphocytes following in vitro exposure to dissolved americium or plutonium at two separate laboratories produced linear dose-response functions, but the slopes of the best-fit straight lines differed by a factor of 12. Our microdosimetric analysis showed the results of one experiment to be inconsistent with a uniform distribution of activity. It also showed that the difference in slope could be attributed to differences in particulate size and spatial distribution as a result of dissimilarities in procedures used for preparing the actinide solutions. PMID:6978320

Fisher, D R; Harty, R

1982-03-01

203

Stopping power for alpha particles in hot dense Au plasmas  

NASA Astrophysics Data System (ADS)

Self-consistent calculations of the stopping power for alpha particles in hot dense Au plasmas are performed in a wide projectile energy range with a fixed density ?Au = 19.3 g cm?3 and the electron temperature range from 0.4 to 5 keV on the basis of the relativistic ion-sphere model. All the mechanisms, which have strong influences on stopping power, are discussed in detail. The distribution of the free electron velocity component is found to be much flatter than the Maxwellian distribution due to the strong electrostatic field within the ion sphere in the hot dense plasmas, which results in the suppression of the stopping mechanism by plasma polarization and close collision for a projectile energy below 1 MeV u?1. The influence of inelastic scattering is considerably weakened due to the strong neutralization from the impact excitation, ionization and their reverse processes almost in the entire energy range below 10 MeV u?1 although the contribution of each process is quite large. Nuclear stopping is found to increase with the temperature. Our calculations are compared with other models and some explanations are presented for the difference between our results and other models. The Bethe equation is found to overestimate the contribution of inelastic processes by at least 10%. Different mechanisms are found to play their role in different energy ranges and all the mechanisms should be considered in order to get reliable data of stopping power.

He, Bin; Wang, Jian-Guo

2013-09-01

204

Ionization Measurement of B10(n,alpha)Li7  

Microsoft Academic Search

A thin layer of boron on the wall of a cylindrical ionization chamber exposed to slow neutrons has been used to study the ionization produced by the recoiling particles of the transmutation B10(n,alpha)Li7. Polonium alpha-particles were used for calibration, and the ionization electron pulses were amplified and photographed on an oscilloscope screen. Calculated peak shapes taking into account wall effect

J. Rhodes; W. Franzen; W. E. Stephens

1952-01-01

205

Method for determining fast-alpha-particle confinement in tokamak plasmas using resonant nuclear reactors  

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 fast-alpha-particle confinement in tokamak plasmas. Gamma rays from these resonant reactions with energies from 2.1 MeV to 9.2 MeV may be used to infer the alpha-particle population between energies of 0.4 MeV and 2.6 MeV. The ratio of these alpha-burnup reactions to the reactions T(D,..gamma..)/sup 5/He and /sup 3/He(D,..gamma..)/sup 5/Li provides a technique for the measurement of alpha confinement.

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

1986-03-01

206

Alpha-particle Monte Carlo simulation for microdosimetric calculations using a commercial spreadsheet.  

PubMed

Alpha-particle emitters are currently being evaluated in the treatment of cancer. Because of the short range and high linear energy transfer (LET) of most therapeutic alpha-particle emitters, there are significant stochastic variations in the energy deposited within the cellular nucleus. Hence microdosimetric spectra are often necessary to interpret biological endpoints. However, alpha-particle microdosimetric codes are not readily available. In this paper, we describe how a commercial spreadsheet may be used to perform a Monte Carlo simulation of alpha-particle transport. Subsequently, this information is used to determine the distribution of path lengths, energy deposited, and specific energy for a single alpha-particle traversal through the cell nucleus. These data may then be used to determine microdosimetric parameters for multiple alpha-particle emissions. In our analysis, comparison of the first and second moments of the single-event spectra with previously published data show agreement on the order of a few per cent. These small discrepancies are due to differences in interpolation of stopping powers between the various algorithms. Thus, the spreadsheet Monte Carlo method represents a simple and efficient method to calculate single-event spectra for alpha-particle emitters. Copies of the spreadsheet are available from the corresponding author upon request. PMID:17374919

Roeske, John C; Hoggarth, Mark

2007-03-12

207

Alpha-particle Monte Carlo simulation for microdosimetric calculations using a commercial spreadsheet  

NASA Astrophysics Data System (ADS)

Alpha-particle emitters are currently being evaluated in the treatment of cancer. Because of the short range and high linear energy transfer (LET) of most therapeutic alpha-particle emitters, there are significant stochastic variations in the energy deposited within the cellular nucleus. Hence microdosimetric spectra are often necessary to interpret biological endpoints. However, alpha-particle microdosimetric codes are not readily available. In this paper, we describe how a commercial spreadsheet may be used to perform a Monte Carlo simulation of alpha-particle transport. Subsequently, this information is used to determine the distribution of path lengths, energy deposited, and specific energy for a single alpha-particle traversal through the cell nucleus. These data may then be used to determine microdosimetric parameters for multiple alpha-particle emissions. In our analysis, comparison of the first and second moments of the single-event spectra with previously published data show agreement on the order of a few per cent. These small discrepancies are due to differences in interpolation of stopping powers between the various algorithms. Thus, the spreadsheet Monte Carlo method represents a simple and efficient method to calculate single-event spectra for alpha-particle emitters. Copies of the spreadsheet are available from the corresponding author upon request.

Roeske, John C.; Hoggarth, Mark

2007-04-01

208

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

209

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

SciTech Connect

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

Not Available

1992-01-01

210

alpha-particle nuclear surface absorption below the Coulomb barrier in heavy nuclei  

SciTech Connect

An analysis of all available alpha-particle-induced reaction cross sections on nuclei within the mass number range 121<=A<=197, below the Coulomb barrier, is carried out. This analysis leads to an optical potential that describes the alpha-particle elastic scattering at low energies as well and both elastic-scattering and reaction data for 45<=A<=124. The energy dependence of the surface imaginary potential depth is proved to be essential for understanding alpha-particle interaction behavior below the Coulomb barrier.

Avrigeanu, M.; Avrigeanu, V. ['Horia Hulubei' National Institute for Physics and Nuclear Engineering, Post Office Box MG-6, R-077125 Bucharest-Magurele (Romania)

2010-07-15

211

MIRD Pamphlet No. 22 (Unabridged): Radiobiology and Dosimetry of alpha-Particle Emitters for Targeted Radionuclide Therapy  

SciTech Connect

The potential of alpha-particle emitters to treat cancer has been recognized since the early 1900s. Advances in the targeted delivery of radionuclides, in radionuclide conjugation chemistry, and in the increased availability of alpha-emitters appropriate for clinical use have recently led to patient trials of alpha-particle-emitter labeled radiopharmaceuticals. Although alpha-emitters have been studied for many decades, their current use in humans for targeted therapy is an important milestone. The objective of this work is to review those aspects of the field that are pertinent to targeted alpha-particle-emitter therapy and to provide guidance and recommendations for human alpha-particle-emitter dosimetry.

Sgouros, George; Roeske, John C.; McDevitt, Michael S.; Palm, Stig; Allen, Barry J.; Fisher, Darrell R.; Brill, Bertrand A.; Song, Hong; Howell, R. W.; Akabani, Gamal

2010-02-28

212

Neutron irradiation of bacteria in the presence and absence of secondary charged-particle equilibrium  

SciTech Connect

The survival rate of Shigella flexneri has been measured for irradiation with 7-MeV neutrons in the presence and absence of secondary charged-particle equilibrium. The data were analyzed to assess the separate response of the cells to the knock-on proton and ..cap alpha..-particle plus heavy-recoil components. A detailed consideration of the frequency of ..cap alpha..-particle and heavy-recoil traversals of the cell has been made to explain our results, and in addition we have applied this approach to analyze the earlier results obtained with mammalian cells. We conclude that of the secondary charged-particles produced by the Hammersmith neutron beam, the highest LET particles, the heavy-recoil nuclei, contribute a minor proportion of damage to bacteria but form a major contribution of damage in mammalian cells. The reduction in oxygen enhancement ratio (OER) with neutrons compared with low LET radiation for mammalian cells is due almost entirely to the influence of the heavy recoils and the contribution of the ..cap alpha..-particle and knock-on protons to the reduction of the OER is relatively minor. For Shigella flexneri the ..cap alpha.. particles and heavy recoils make approximately equal contributions to the reduction in OER.

Lunec, J.; Cramp, W.A.; Hornsey, S.

1980-09-01

213

Estimates of alpha particle heating in the solar wind inside 0.3 AU  

Microsoft Academic Search

Observations from the Helios plasma experiment (Rosenbauer et al., 1977) are used to determine the average temperature gradients of protons and alpha particles in the solar wind between 0.3 and 1 AU. It is found that He(2+) ions cool more slowly than adiabatically. The radial gradients of T(alpha) inside 0.3 AU are estimated. Evidence is found for continuous interplanetary alpha

K. M. Thieme; E. Marsch; H. Rosenbauer

1989-01-01

214

Ambiguities in the optical-model analysis of alpha-particle scattering  

Microsoft Academic Search

The phase-equivalent discrete ambiguities in the complex potential parameters which are obtained from optical-model analysis of alpha-particle elastic scattering differential cross sections are examined. A detailed analysis of the scattering of 10.8 MeV alpha particles by 24Mg is used to illustrate the discussion of these ambiguities. In principle, one technique for the reduction of the ambiguities is the coupled-equations analysis

W. J. Thompson; G. E. Crawford; R. H. Davis

1967-01-01

215

An alpha particle diagnostic based on measurements of lower hybrid wave fluctuations  

SciTech Connect

It is shown that the one-dimensional alpha particle velocity distribution function can be determined from the fluctuation- dissipation theorem based on measurements of lower hybrid wave fluctuations in an equilibrium plasma. This method uses collective Thomson scattering data with large signal-to-noise ratio, but it is applicable only when the alpha particles have an isotropic velocity distribution. 16 refs., 1 fig.

Wong, K.L.

1989-07-01

216

alpha-particle nuclear surface absorption below the Coulomb barrier in heavy nuclei  

Microsoft Academic Search

An analysis of all available alpha-particle-induced reaction cross sections on nuclei within the mass number range 121<=A<=197, below the Coulomb barrier, is carried out. This analysis leads to an optical potential that describes the alpha-particle elastic scattering at low energies as well and both elastic-scattering and reaction data for 45<=A<=124. The energy dependence of the surface imaginary potential depth is

M. Avrigeanu; V. Avrigeanu

2010-01-01

217

Physical aspects of precise spectrometry of alpha-particles with silicon pn-junction detectors  

Microsoft Academic Search

Investigations of energy and charge losses have been carried out for silicon planar alpha-particle detectors. The detectors were manufactured by an advanced technology, using ion implantation and various annealing temperatures. A detailed analysis of the recombination processes in alpha-particle tracks with a high electron-hole density and a measurement procedure for the main parameters of charge carrier loss have been developed.

E. Verbitskaya; V. Eremin; N. Strokan; J. Kemmer; B. Schmidt; J. von Borany

1994-01-01

218

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

Microsoft Academic Search

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 (Ï{sub *i}\\/2) and the toroidicity-induced Alfven eigenmode (TAE), are considered. These are examined for noncircular tokamaks in the high-n

D. A. Spong; J. A. Holmes; J. N. LeBoeuf; D. J. Christenson

1990-01-01

219

Detection of radon emanation from the crater aristarchus by the apollo 15 alpha particle spectrometer.  

PubMed

The alpha particle spectrometer aboard the Apollo 15 command/service module was designed to detect alpha particles from radon decay and to locate regions with unusual activity on the moon. A significant increase in radon-222 activity was detected from a region containing the crater Aristarchus. The result is interpreted as probably indicating internal activity at the site. By analogy with terrestrial processes, increased radon emanation may be associated with the emission of other volatiles. PMID:17806295

Gorenstein, P; Bjorkholm, P

1973-02-23

220

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

221

Limits on Alpha Particle Temperature Anisotropy and Differential Flow from Kinetic Instabilities: Solar Wind Observations  

NASA Astrophysics Data System (ADS)

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 ?/T p (T ??/T ?p ) when the alpha proton differential flow velocity is small, where T ? and T p (T ?? and T ?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.; Maruca, Bennett A.; Kasper, Justin C.

2013-11-01

222

Microstructure damage of thin aluminum films by irradiation with alpha particles and fission fragments  

SciTech Connect

The atomic force microscopy (AFM) has been used to study the microstructure damage of thin aluminum film surfaces induced by bombardment of alpha particles and fission fragments from {sup 252}Cf source. Different types of defects (dislocations lines, loops, voids, and blisters) and their complex morphologies appeared under both the beam of alpha particles and a mix of alpha particles and fission fragments. The first surface damage became clearly visible only after 250 hr irradiation of a mix of alpha particles and fission fragments (8.65 x 10{sup 8} ff/cm{sup 2} and 1.36 x 10{sup 10} {alpha}/cm{sup 2}). The number of voids and dislocation lines created on the aluminum surface were (3.8 {+-} 0.8) x 10{sup 7} cm{sup -2} and (2.1 {+-} 0.8) x 10{sup 6} cm{sup -2}, respectively. Single blisters were observed with the mean diameter of (933 {+-} 22) nm and the mean height of (102 {+-} 15) nm. The first ellipsoidal dislocation loops appeared at the fluence of (1.03 x 10{sup 9} ff/cm{sup 2} and 1.62 x 10{sup 10} {alpha}/cm{sup 2}). However, these ellipsoidal loops were not seen with low energetic alpha particles at the same fluence. Our results suggest that the fission fragments might maximize large voids and dislocations and increase the degradation in depth resolution. (authors)

Sadi, S. [Department of Nuclear Engineering and Radiation Health Physics, 100 Radiation Center, Oregon State University, Corvallis, OR 97331-5903 (United States); Paulenova, A. [Radiation Center, 100 Radiation Center, Oregon State University, Corvallis, OR 97331-5903 (United States); Loveland, W.D.; Watson, P.R. [Department of Chemistry, 100 Radiation Center, Oregon State University, Corvallis, OR 97331-5903 (United States)

2007-07-01

223

Differences Between Solar Wind Alpha Particle and Proton Temperatures at Times of Proton Temperature Depressions  

NASA Astrophysics Data System (ADS)

Using ACE SWEPAM measurements from February 5, 1998 through October 30, 2001 we have examined hourly averages of the solar wind alpha particle temperature TA and compared it to the proton temperature TP. The ratio TA/TP ranges from about 1 to 10, with the most probable value near 4, indicating that protons and alpha particles typically have the same thermal speed. We find that this ratio tends to vary with solar wind speed; ratios less than 4 are more common at lower speeds. In this study we investigate the character of the alpha particle temperature during intervals of depressed proton temperature. In general, the solar wind proton temperature increases with increasing flow speed. The temperature is considered depressed when it is much lower (by a factor of approximately 2) than the typical temperature observed at a given speed. For this work, we developed an expression for the expected proton temperature as a function of speed appropriate for the ACE level 2 data, and used this expression to identify intervals of unusually low proton temperature. When proton temperatures are lower than expected, we find that TA/TP tends toward values of 1. We conclude that proton temperature depressions usually have corresponding alpha particle temperature depressions, and the relative difference between typical and depressed temperatures is 4 times greater for alpha particles than for protons. We note that, similar to proton temperature depressions, alpha particle temperature depressions can serve as useful indicators of CME flows.

Steinberg, J. T.; Davenport, T. A.; Reisenfeld, D. B.; Skoug, R. M.

2002-12-01

224

Discrimination of recoil backgrounds in scintillating calorimeters  

NASA Astrophysics Data System (ADS)

The alpha decay of 210Po is a dangerous background to rare event searches. Here, we describe observations related to this alpha decay in the Cryogenic Rare Event Search with Superconducting Thermometers (CRESST). We find that lead nuclei show a scintillation light yield in our CaWO crystals of 0.0142±0.0013 relative to electrons of the same energy. We describe a way to discriminate this source of nuclear recoil background by means of a scintillating foil, and demonstrate its effectiveness. This leads to an observable difference in the pulse shape of the light detector, which can be used to tag these events. Differences in pulse shape of the phonon detector between lead and electron recoils are also extracted, opening the window to future additional background suppression techniques based on pulse shape discrimination in such experiments.

Lang, R. F.; Angloher, G.; Bauer, M.; Bavykina, I.; Bento, A.; Brown, A.; Bucci, C.; Ciemniak, C.; Coppi, C.; Deuter, G.; von Feilitzsch, F.; Hauff, D.; Henry, S.; Huff, P.; Imber, J.; Ingleby, S.; Isaila, C.; Jochum, J.; Kiefer, M.; Kimmerle, M.; Kraus, H.; Lanfranchi, J.-C.; Malek, M.; McGowan, R.; Mikhailik, V. B.; Pantic, E.; Petricca, F.; Pfister, S.; Potzel, W.; Pröbst, F.; Roth, S.; Rottler, K.; Sailer, C.; Schäffner, K.; Schmaler, J.; Scholl, S.; Seidel, W.; Stodolsky, L.; Tolhurst, A. J. B.; Usherov, I.; Westphal, W.

2010-02-01

225

Recoil Studies of Nuclear Reactions Induced by Heavy Ions  

Microsoft Academic Search

The mechanism of nuclear reactions induced by heavy ions was investigated by measuring the recoil ranges of Tb149, At211 and other alpha-emitting isotopes of At and neighboring elements and by determining the cross sections for the formation of Tb149 and At211. Recoil ranges were consistent with compound-nucleus formation at all energies studied for the following reactions: Pr141(C12, 4n)Tb149, Ce(N14, xn)Tb149,

John M. Alexander; Lester Winsberg

1961-01-01

226

Alpha particle destabilization of the toroidicity-induced Alfven eigenmodes  

Microsoft Academic Search

The high frequency, low mode number toroidicity-induced Alfven eigenmodes (TAE) are shown to be driven unstable by the circulating and\\/or trapped α-particles through the wave-particle resonances. Satisfying the resonance condition requires that the α-particle birth speed v{sub α} ⥠v{sub A}\\/2{vert bar}m-nq{vert bar}, where v{sub A} is the Alfven speed, m is the poloidal model number, and n is the

1990-01-01

227

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

Microsoft Academic Search

charged particle microbeam, we show here that irradiation of 20% of randomly selected AL 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

Hongning Zhou; Gerhard Randers-Pehrson; Charles A. Waldren; Diane Vannais; Eric J. Hall; Tom K. Hei

2000-01-01

228

Alfvénic instabilities driven by fusion generated alpha particles in ITER scenarios  

NASA Astrophysics Data System (ADS)

The stability of proposed ITER scenarios with respect to low-medium mode number Alfvénic instabilities driven by fusion-produced alpha particles is investigated by hybrid MHD-particle simulations. Three cases are considered: the monotonic safety factor scenario (SC2), the reversed-shear one (SC4) and a flat safety factor profile 'hybrid' scenario (SCH). All the three cases are found unstable, even though the mode growth rates are quite small. The investigation is extended to cases with larger drive, which could be realistically obtained because of a moderate increase in electron and bulk-ion temperatures as well as by inclusion of energetic particles produced by additional heating methods. It is shown that, in the SCH case, if the drive exceeds the reference value by a factor ~1.6, fast growing energetic-particle modes (EPMs) are driven unstable by the resonance with trapped alpha particles. The effects of nonlinear mode dynamics on the alpha-particle confinement at the reference drive are negligible for the SC2 and the SCH cases. For the SC4 scenario, some broadening of the alpha-particle pressure profile is observed, indicating inconsistency problems of the scenario itself. Simulations performed with increasing drive intensity show that a strong flattening of the alpha-particle pressure profile can occur in the inner plasma region for the SC2 case, while global confinement is not significantly affected. In the SC4 and SCH scenarios nonlinear effects are more pronounced in the outer portion of the discharge, where the modes are localized, with less impact on the on-axis pressure value with respect to the SC2 case. While for SCH such effects are observed only above the threshold for EPM destabilization, in the SC4 case significant alpha particle losses can occur even at moderately increased drive.

Vlad, G.; Briguglio, S.; Fogaccia, G.; Zonca, F.; Schneider, M.

2006-01-01

229

Direct decay of the GQR in 40Ca through alpha-particle emission  

NASA Astrophysics Data System (ADS)

Inelastic scattering of 40Ca on 40Ca at 50 MeV/A has been measured at the GANIL facility in coincidence with light charged particles. For the first time, the SPEG spectrometer was associated with 240 CsI(Tl) scintillators of the INDRA 4? array. The missing energy method, successfully used in previous experiments to study the nucleon decay of collective states is applied to the study of alpha-particle decay of the GQR. A significant direct decay branch by alpha-particles of the GQR in 40Ca is measured for the first time.

Fallot, M.; Scarpaci, J. A.; Frascaria, N.; Blumenfeld, Y.; Chbihi, A.; Chomaz, Ph.; Desesquelles, P.; Frankland, J.; Khan, E.; Laville, J. L.; Plagnol, E.; Pollacco, E. C.; Roussel-Chomaz, P.; Roynette, J. C.; Shrivastava, A.; Zerguerras, T.

2005-05-01

230

Bremsstrahlung in {alpha} Decay of {sup 210}Po: Do {alpha} Particles Emit Photons in Tunneling?  

SciTech Connect

Emission probability of bremsstrahlung in the {alpha} decay of {sup 210}Po was measured in {alpha} -{gamma} coincidence measurements with Si and Ge detectors. It was found that the bremsstrahlung yields are much smaller than those predicted by a Coulomb acceleration model, in which {gamma} rays are emitted during acceleration outside the barrier. This suggests that the radiation amplitude in the barrier cannot be neglected, and the discussion based on a quasiclassical approach is given. {copyright} {ital 1997} {ital The American Physical Society}

Kasagi, J.; Yamazaki, H.; Kasajima, N.; Ohtsuki, T.; Yuki, H. [Laboratory of Nuclear Science, Tohoku University, Mikamine, Taihaku, Sendai 982 (Japan)

1997-07-01

231

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

Microsoft Academic Search

Event-integrated fluxes of protons and alpha particles in solar-flare-associated particle events during solar cycle 21 (1976--1986) are determined from data obtained by detectors on board the IMP-7 and IMP-8 satellites. Sixty-three solar particle events with proton fluence (E>10 MeV)>10⁷ cm⁻² were identified from October 1972 to March 1987. The average omnidirectional flux of protons with kinetic energy>10 MeV for cycle

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

1988-01-01

232

Alpha particle destabilization of the toroidicity-induced Alfvén eigenmodes  

Microsoft Academic Search

The high-frequency, low mode number toroidicity-induced Alfven eigenmodes (TAE) (Phys. Fluids {bold 29}, 3695 (1986)) are shown to be driven unstable by the circulating and\\/or trapped α particles through the wave--particle resonances. Satisfying the resonance condition requires that the α-particle birth speed {ital v}{sub α}â¥{ital v}{sub A}\\/2{vert bar}{ital m}-{ital nq}{vert bar}, where {ital v}{sub A} is the Alfven speed, {ital

C. Z. Cheng

1991-01-01

233

Alpha Particles Play a Relatively Minor Role in Magnetized Target Fusion Systems  

SciTech Connect

Two problems related to alpha particle physics in magnetized target fusion (MTF) systems are briefly discussed. First, we evaluate the pressure and density of alpha particles under the assumption that they are perfectly confined and have a classical slowing-down distribution. It turns out that because of a comparatively low plasma temperature in MTF systems, the relative pressure and density of alpha particles are more than an order of magnitude less than in fusion reactors based on ITER-type tokamaks. Therefore, one may expect that even in the extreme case of a perfect confinement of alpha particles, their presence will have a much weaker (than in the case of tokamaks) effect on plasma stability and transport. Second, we discuss the kinetics of plasma burn under the opposite extreme assumption that all the alpha particles are instantaneously lost, without leaving any energy in a plasma. It turns out that even in this case, the plasma energy yield in batch-burn systems is only weakly affected by burnout effects.

Ryutov, D.D. [Lawrence Livermore National Laboratory (United States)

2002-03-15

234

Destabilization of planar lipid bilayers by. cap alpha. particles from polonium-210  

SciTech Connect

A system for measuring the interacton between ..cap alpha.. particles from /sup 210/Polonium and planar lipid bilayers is described. Membrane capacitance and conductance were simultaneously measured with a voltage clamp. A micrometer advance mechanism was used to control the position of a /sup 210/Polonium source with respect to a bowed-out bilayer. Conductance records showed an abrupt failure of the bilayer when the source was approximately 30 microns or less from the bilayer. Comparisons of conductance noise characteristics just prior to membrane breakage and noise characteristics with a source - bilayer separation of 50 microns or greater showed no difference. The range of the ..cap alpha.. particles inferred from observations of membrane failure is consistent with the expected maximum range of approximately 35 microns for ..cap alpha.. particles from the particular gold-covered source in water. The breakage mechanism is not directly peroxide-mediated as experiments with added peroxide alone did not show significant alterations. The breakdown of lipid bilayers by ..cap alpha.. particles may be analogous to the observations in a set of experiments which showed ..cap alpha.. particle destabilization of surfactant films in air. Evidence supports the hypothesis that free radicals generated in the bilayer, as opposed to aqueous solution free radicals, are the most important agent for bilayer destabilization.

Nelson, G.A.

1984-01-01

235

Discovery of the alpha decay of 109I  

Microsoft Academic Search

Alpha emission is a rich source for nuclear-structure information [1]. The alpha-particle energies Ealpha, corrected for the recoil effect, yield the difference between the ground-state masses of parent and daughter nuclides (Qalpha). Far from stability the determination of Qalpha often represents the only way to determine the masses of ground and isomeric states. The evolution of Qalpha values along an

C. Mazzocchi; R. Grzywacz; C. R. Bingham; D. Simpson; C. J. Gross; K. P. Rykaczewski; J. C. Batchelder; S. N. Liddick; R. D. Page; A. Korgul; W. Krolas; S. Ilyushkin; J. A. Winger; J. H. Hamilton; J. K. Hwang; K. Li

2006-01-01

236

Energetic/alpha particle effects on MHD modes and transport  

SciTech Connect

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

Cheng, C.Z.; Budny, R. [Princeton Univ., NJ (United States). Plasma Physics Lab.; Chen, L. [Univ. of California, Irvine, CA (United States). Dept. of Physics

1995-01-01

237

Alpha particles induce apoptosis through the sphingomyelin pathway.  

PubMed

The sphingomyelin pathway involves the enzymatic cleavage of sphingomyelin to produce ceramide, a second messenger that serves as a key mediator in the rapid apoptotic response to various cell stressors. Low-linear energy transfer (LET) ? radiation can initiate this pathway, independent of DNA damage, via the cell membrane. Whether short-ranged, high-LET ? particles, which are of interest as potent environmental carcinogens, radiotherapies and potential components of dirty bombs, can act through this mechanism to signal apoptosis is unknown. Here we show that irradiation of Jurkat cells with ? particles emitted by the ²²?Ac-DOTA-anti-CD3 IgG antibody construct results in dose-dependent apoptosis. This apoptosis was significantly reduced by pretreating cells with cholesterol-depleting nystatin, a reagent known to inhibit ceramide signaling by interfering with membrane raft coalescence and ceramide-rich platform generation. The effects of nystatin on ?-particle-induced apoptosis were related to disruption of the ceramide pathway and not to microdosimetry alterations, because similar results were obtained after external irradiation of the cells with a broad beam of collimated ? particles using a planar ²?¹Am source. External irradiation allowed for more precise control of the dosimetry and geometry of the irradiation, independent of antibody binding or cell internalization kinetics. Mechanistically consistent with these findings, Jurkat cells rapidly increased membrane concentrations of ceramide after external irradiation with an average of five ?-particle traversals per cell. These data indicate that ? particles can activate the sphingomyelin pathway to induce apoptosis. PMID:21631289

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

2011-06-01

238

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

SciTech Connect

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

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

1997-09-01

239

Confinement of fusion alpha-particles in JET hollow current equilibrium  

Microsoft Academic Search

The effect of a toroidal current hole on the first orbit (FO) loss and on the collisional loss of alpha particles in JET is investigated. Numerical results of predictive three-dimensional Fokker-Planck modelling of the distribution function of D-T fusion alphas in hollow current JET discharges are presented. If the current hole region is kept reasonably small, it induces only a

V. Yavorskij; V. Goloborod'ko; K. Schoepf; S. E. Sharapov; C. D. Challis; S. Reznik; D. Stork

2003-01-01

240

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

241

Effect of alpha-particle irradiation on the electrical properties of n-type Ge  

NASA Astrophysics Data System (ADS)

Deep-level transient spectroscopy was used to investigate the effect of alpha particle irradiation on the electrical properties of n-type Ge. The samples were irradiated with alpha particles at room temperature using an americium-241 (Am-241) radionuclide source. The main defects introduced were found to be electron traps with energy levels at EC-0.38, EC-0.21, EC-0.20, EC-0.15, and EC-0.10 eV, respectively. The main defects in alpha particle irradiation are similar to those introduced by MeV electron irradiation, where the main defect is the E-center. A quadratic increase in concentration as a function of dose is observed.

Roro, K. T.; Janse van Rensburg, P. J.; Auret, F. D.; Coelho, S.

2009-12-01

242

Relativistic reduced-mass and recoil corrections to vacuum polarization in muonic hydrogen, muonic deuterium, and muonic helium ions  

SciTech Connect

The reduced-mass dependence of relativistic and radiative effects in simple muonic bound systems is investigated. The spin-dependent nuclear recoil correction of order (Z{alpha}){sup 4} {mu}{sup 3}/m{sub N}{sup 2} is evaluated for muonic hydrogen and deuterium and muonic helium ions ({mu} is the reduced mass and m{sub N} is the nuclear mass). Relativistic corrections to vacuum polarization of order {alpha}(Z{alpha}){sup 4}{mu} are calculated, with a full account of the reduced-mass dependence. The results shift theoretical predictions. The radiative-recoil correction to vacuum polarization of order {alpha}(Z{alpha}){sup 5} ln{sup 2}(Z{alpha}){mu}{sup 2}/m{sub N} is obtained in leading logarithmic approximation. The results emphasize the need for a unified treatment of relativistic corrections to vacuum polarization in muonic hydrogen, muonic deuterium, and muonic helium ions, where the mass ratio of the orbiting particle to the nuclear mass is larger than the fine-structure constant.

Jentschura, U. D. [Department of Physics, Missouri University of Science and Technology, Rolla, Missouri 65409 (United States)

2011-07-15

243

Enhanced retention of the alpha-particle-emitting daughters of Actinium-225 by liposome carriers.  

PubMed

Targeted alpha-particle emitters hold great promise as therapeutics for micrometastatic disease. Because of their high energy deposition and short range, tumor targeted alpha-particles can result in high cancer-cell killing with minimal normal-tissue irradiation. Actinium-225 is a potential generator for alpha-particle therapy: it decays with a 10-day half-life and generates three alpha-particle-emitting daughters. Retention of (225)Ac daughters at the target increases efficacy; escape and distribution throughout the body increases toxicity. During circulation, molecular carriers conjugated to (225)Ac cannot retain any of the daughters. We previously proposed liposomal encapsulation of (225)Ac to retain the daughters, whose retention was shown to be liposome-size dependent. However, daughter retention was lower than expected: 22% of theoretical maximum decreasing to 14%, partially due to the binding of (225)Ac to the phospholipid membrane. In this study, Multivesicular liposomes (MUVELs) composed of different phospholipids were developed to increase daughter retention. MUVELs are large liposomes with entrapped smaller lipid-vesicles containing (225)Ac. PEGylated MUVELs stably retained over time 98% of encapsulated (225)Ac. Retention of (213)Bi, the last daughter, was 31% of the theoretical maximum retention of (213)Bi for the liposome sizes studied. MUVELs were conjugated to an anti-HER2/neu antibody (immunolabeled MUVELs) and were evaluated in vitro with SKOV3-NMP2 ovarian cancer cells, exhibiting significant cellular internalization (83%). This work demonstrates that immunolabeled MUVELs might be able to deliver higher fractions of generated alpha-particles per targeted (225)Ac compared to the relative fractions of alpha-particles delivered by (225)Ac-labeled molecular carriers. PMID:17935286

Sofou, Stavroula; Kappel, Barry J; Jaggi, Jaspreet S; McDevitt, Michael R; Scheinberg, David A; Sgouros, George

2007-10-13

244

Cavity cooling below the recoil limit.  

PubMed

Conventional laser cooling relies on repeated electronic excitations by near-resonant light, which constrains its area of application to a selected number of atomic species prepared at moderate particle densities. Optical cavities with sufficiently large Purcell factors allow for laser cooling schemes, avoiding these limitations. Here, we report on an atom-cavity system, combining a Purcell factor above 40 with a cavity bandwidth below the recoil frequency associated with the kinetic energy transfer in a single photon scattering event. This lets us access a yet-unexplored regime of atom-cavity interactions, in which the atomic motion can be manipulated by targeted dissipation with sub-recoil resolution. We demonstrate cavity-induced heating of a Bose-Einstein condensate and subsequent cooling at particle densities and temperatures incompatible with conventional laser cooling. PMID:22767925

Wolke, Matthias; Klinner, Julian; Keßler, Hans; Hemmerich, Andreas

2012-07-01

245

Scintillation of liquid helium for low-energy nuclear recoils  

NASA Astrophysics Data System (ADS)

The scintillation properties of liquid helium upon the recoil of a low-energy helium atom are discussed in the context of the possible use of this medium as a detector of dark matter. It is found that the prompt scintillation yield in the range of recoil energies from a few keV to 100 keV is somewhat higher than that obtained by a linear extrapolation from the measured yield for a 5-MeV ? particle. A comparison is made of both the scintillation yield and the charge separation by an electric field for nuclear recoils and for electrons stopped in helium.

Ito, T. M.; Seidel, G. M.

2013-08-01

246

Theory of energetic/alpha particle effects on magnetohydrodynamic modes in tokamaks  

SciTech Connect

The presence of energetic particles is shown to qualitatively modify the stability properties of ideal as well as resistive magnetohydrodynamic (MHD) modes in tokamaks. Specifically, we demonstrate that, consistent with highpower ICRF heating experiments in JET, high energy trapped particles can effectively stabilize the sawtooth mode, providing a possible route to stable high current tokamak operation. An alternative stabilization scheme employing barely circulating energetic particles is also proposed. Finally, we present analytical and numerical studies on the excitations of high-n MHD modes via transit resonances with circulating alpha particles. 14 refs., 3 figs.

Chen, L.; White, R.B.; Rewoldt, G.; Colestock, P.; Rutherford, P.H.; Chen, Y.P.; Ke, F.J.; Tsai, S.T.; Bussac, M.N.

1989-01-01

247

Directional recoil rates for WIMP direct detection  

SciTech Connect

New techniques for the laboratory direct detection of dark matter weakly interacting massive particles (WIMPs) are sensitive to the recoil direction of the struck nuclei. We compute and compare the directional recoil rates dR/dcos{theta} (where {theta} is the angle measured from a reference direction in the sky) for several WIMP velocity distributions including the standard dark halo and anisotropic models such as Sikivie's late-infall halo model and logarithmic-ellipsoidal models. Since some detectors may be unable to distinguish the beginning of the recoil track from its end (lack of head-tail discrimination), we introduce a folded directional recoil rate dR/d|cos{theta}|, where |cos{theta}| does not distinguish the head from the tail of the track. We compute the CS{sub 2} and CF{sub 4} exposures required to distinguish a signal from an isotropic background noise, and find that dR/d|cos{theta}| is effective for the standard dark halo and some but not all anisotropic models.

Alenazi, Moqbil S.; Gondolo, Paolo [Department of Physics, University of Utah, 115 S 1400 E Rm 201, Salt Lake City, Utah 84112-0830 (United States)

2008-02-15

248

Range of Medium and High Energy Protons and Alpha Particles in NaI Scintillator  

NASA Astrophysics Data System (ADS)

We have calculated the range of protons and alpha particles in NaI scintillator which is a commonly used substance in scintillation detector manufacturing. The electronic stopping power of protons and alpha particles in NaI is calculated first by using the theoretical formulation of Montenegro et al. The range calculation has been performed by applying a technique that we developed in the earlier works. The results are compared with Monte Carlo simulation program SRIM2003 and PRAL. It is found that the obtained results are in satisfactory agreement with the literature.

Kabadayi, Oe.

2006-06-01

249

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

250

Excited analog state of 12?C and the alpha-particle model  

NASA Astrophysics Data System (ADS)

The idea that 12?C* is a strangeness analog state is examined using the alpha particle model. Volkov, Gillet, and Brink-Boeker potentials are used for the nucleon-nucleon and lambda-nucleon interactions, to calculate the binding energies of 12C and 12?C*. 12C is described by an equilateral triangle. When an allowance is made for the exchange character of the potentials used, the required potential strengths seem to be consistent with those obtained from low energy and light hypernuclear data, thus supporting the idea of a strangeness analog state. NUCLEAR STRUCTURE 12?C*, binding energy calculated assuming strangeness analog state in alpha particle model.

Mukherjee, Swapna; Panchapakesan, N.

1982-10-01

251

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

SciTech Connect

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 stability of internal kink modes, high-number ballooning modes, and toroidicity-induced shear Alfven eigen-modes is investigated in the presence of fusion alpha particles. These modes can be either stable or unstable depending on the selected operational regime at ignition.

Carrera, R.; Montalvo, E. (Texas Univ., Austin, TX (United States)); Fu, G.Y. (CRPP, Lausanne (CH)); Miley, G.H. (Illinois Univ., Urbana, IL (United States)); Hively, L.M. (Oak Ridge National Lab., TN (United States)); Rosenbluth, M.N. (California Univ., San Diego, CA (United States)); Tamor, S. (La Jolla Inst., Arlington, VA (United States))

1990-12-01

252

Constraints from Instabilities on Alpha-Particle Temperature Anisotropy in the Solar Wind  

NASA Astrophysics Data System (ADS)

Various dynamic processes in the expanding solar wind produce a range of non-thermal ion and electron properties, which include different velocities, different temperatures, and non-unity temperature anisotropies for each particle species. If these deviations become too severe, a kinetic microinstability can arise, in which exponentially-growing wave modes scatter the particles. In this way, instabilities help to limit the departures of plasma from thermal equilibrium. The work presented here specifically relates to instabilities driven by ion temperature anisotropy: the cyclotron, mirror, and parallel and oblique firehose instabilities. Previous studies have provided strong evidence that instabilities limit proton temperature anisotropy and that the two-dimensional (i.e., mirror and oblique firehose) instabilities are significantly more active in this regard than the one-dimensional (i.e., cyclotron and parallel firehose) instabilities. However, this work considers instabilities driven by alpha-particle temperature anisotropy, which have received far less attention in the literature. Linear Vlasov analysis was used to derive the expected threshold conditions for these alpha-particle instabilities. When data from the Wind spacecraft's Faraday cups was compared to these threshold conditions, it was found to be consistent with instabilities (particularly the mirror and oblique firehose) constraining alpha-particle temperature anisotropy in the solar wind. While this result may seem counterintuitive because of the low alpha-particle relative abundance, the theoretical analysis indicates that the low collision rates in the solar wind often allow protons and alpha-particles to resonate separately and with different wave modes. These results provide new insight into how instabilities redistribute energy in the plasma and have important implication for the interpretation of the observations of minor-ions in the solar wind and corona.

Maruca, B. A.; Kasper, J. C.; Gary, S. P.

2011-12-01

253

Gene expression profile of human lymphocytes exposed to (211)At alpha particles.  

PubMed

In this study, the Whole Human Genome 44K DNA microarray assay was used for the first time to obtain gene expression profiles in human peripheral blood lymphocytes 2 h after exposure (in suspension) to 6.78 MeV mean energy alpha particles from extracellular (211)At. Lymphocytes were exposed to fluences of 0.3-9.6 x 10(6) alpha particles/cm(2) [corresponding to mean absorbed alpha-particle doses (D(alpha)) of 0.05-1.60 Gy] over 30 min. Significantly modulated expression was identified in 338 early-response genes. Up-regulated expression was evident in 183 early-response genes, while the remaining 155 were down-regulated. Over half of the up-regulated genes and 40% of the down-regulated genes had a known biological process related primarily to cell growth and maintenance and cell communication. Genes associated with cell death were found only in the up-regulated genes and those with development only in the down-regulated genes. Eight selected early-response genes that displayed a sustained up- or down-regulation (CD36, HSPA2, MS4A6A, NFIL3, IL1F9, IRX5, RASL11B and SULT1B1) were further validated in alpha-particle-irradiated lymphocytes of two human individuals using the TaqMan(R) RT-qPCR technique. The results confirmed the observed microarray gene expression patterns. The expression modulation profiles of IL1F9, IRX5, RASL11B and SULT1B1 genes demonstrated similar trends in the two individuals studied. However, no significant linear correlation between increasing relative gene expression and the alpha-particle dose was evident. The results suggest the possibility that a panel of genes that react to alpha-particle radiation does exist and that they merit further study in a greater number of individuals to determine their possible value regarding alpha-particle biodosimetry. PMID:20681779

Turtoi, A; Brown, I; Schläger, M; Schneeweiss, F H A

2010-08-01

254

Alpha-particle capture reactions in inverse kinematics relevant to p-process nucleosynthesis  

NASA Astrophysics Data System (ADS)

The first feasibility study of an ?-particle capture reaction in inverse kinematics at energies relevant to the p process was performed at the Wien Filter of the LISE spectrometer at GANIL. Hereby, the 4He(78Kr,?)82Sr reaction was investigated using as target an 4He-implanted thin Al foil. The analysis of the data has shown that the determination of (?,?) reaction cross sections at rather low energies around 2 MeV/u in inverse kinematics is indeed feasible regarding the high rejection rate of the primary beam, which in the present work was better than a factor of 109. However, the expected position of the recoils of interest was completely masked by particles of currently unknown origin that could hardly be attributed to scattering of the primary beam. The most probable explanation for the origin of these ``pollutants'' could be microscopic dust particles of 10 ?m diameter and less, that are extremely difficult to avoid in standard experimental conditions. Hence, the use of a gas-jet target instead of a solid one is compulsory.

Uji?, P.; Lagoyannis, A.; Mertzimekis, T. J.; de Oliveira Santos, F.; Harissopulos, S.; Demetriou, P.; Perrot, L.; Stodel, Ch.; Saint-Laurent, M.-G.; Kamalou, O.; Lefebvre-Schuhl, A.; Spyrou, A.; Amthor, M. A.; Grevy, S.; Caceres, L.; Koivisto, H.; Laitinen, M.; Uusitalo, J.; Julin, R.

2011-10-01

255

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

NASA Astrophysics Data System (ADS)

Exclusive cross sections have been obtained from particle-K X-ray coincidence data measured at 236 MeV for ejectiles ranging from 4He to 15N. Production cross sections for primary fragments and alpha particle multiplicities associated with different channels have been deduced. The major fraction of the alpha particles appears to originate from inelastic (damped) processes in which only light particles with Z <= 2 are emitted. Institute for Nuclear Research, 05-400 Swierk, Poland.

Siemssen, R. H.; Balster, G. J.; Wilschut, H. W.; Bond, P. D.; Crouzen, P. C. N.; Goldhoorn, P. B.; Shukui, Han; Sujkowski, Z.

1985-10-01

256

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

Microsoft Academic Search

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

R. H. Siemssen; G. J. Balster; H. W. Wilschut; P. D. Bond; P. C. N. Crouzen; P. B. Goldhoorn; Han Shukui; Z. Sujkowski

1985-01-01

257

Distributions of Alpha Particles Escaping to the Wall because of Sawtooth Oscillations in TFTR  

SciTech Connect

It has been observed experimentally in deuterium-tritium shots of the Tokamak Fusion Test Reactor (TFTR) that crashes of sawtooth oscillations may result in very inhomogeneous flux of alpha particles to the wall. Namely, measurements with four detectors installed at the wall at 20°, 45°, 60°, and 90° below the midplane of the torus have shown that the alpha flux to the wall is strongly peaked at the 20° and 90° detectors and on the noise level at the 45° detector. To explain this phenomenon, both theoretical analysis and numerical simulation have been carried out. It is concluded that the "crash-induced prompt loss," i.e., the orbital loss of marginally trapped particles arising because of the crash-induced orbit transformation of circulating particles, is responsible for the flux to the 90° and 60° detectors, whereas the crash-induced stochastic diffusion of moderately trapped particles explains the large signal at the 20° detector. The calculated poloidal distributions of the integral alpha flux are in reasonable agreement with experimental data. In addition to the integral flux, the flux of particles with given energy was calculated. The energy spectrum of the escaping particles has also been calculated, which can be used for diagnostics of the crash type.

Kolesnichenko, Ya.I.; Lutsenko, V.V.; White, R.B.; Yakovenko, Yu.V., Zweben, S.J.

1998-11-01

258

The feasibility of 225Ac as a source of alpha-particles in radioimmunotherapy.  

PubMed

This paper proposes the utilization of 225Ac for the alpha-radioimmunotherapy of cancer. The isotope decays with a radioactive half-life of 10 days into a cascade of short-lived alpha- and beta-emitting isotopes. In addition, when indicated by the pharmacokinetic requirements of particular clinical applications, 213Bi, with a radioactive half-life of 47 min, can be chosen as an alternative source of alpha-particles in radioimmunotherapy. This isotope is the last alpha emitter in the 225Ac decay-cascade and can be extracted from a 225Ac source at the bedside of the patient. 225Ac can quasi ad infinitum be obtained from one of its precursors, 229Th, which can be made available by various means. The indications for the use of alpha-particles as an alternative to more traditional classes of radiation are derived from the particle-kinetic characteristics and the radioactive half-life of their source isotope, as well as from the properties of the target-selective carrier moiety for the source isotope. It may be expected that useful applications, complementary to and/or in conjunction with other means of therapy will be identified. PMID:8429990

Geerlings, M W; Kaspersen, F M; Apostolidis, C; van der Hout, R

1993-02-01

259

Thermal relative efficiency factor for recoiling 206Pb nuclei in a sapphire bolometer  

NASA Astrophysics Data System (ADS)

Scintillating bolometers are very suitable detectors for dark matter searches. They offer a wide absorber choice allowing to tune up different masses and couplings of WIMPs, background rejection capability and high efficiency in the conversion into heat of nuclear recoil energy releases. In a previous work we have shown that undoped sapphire can be an excellent dark matter detector since, due to its high light yield at very low temperature, very low particle discrimination energy thresholds are achievable. In this Letter, we report the results of an experiment devoted to the estimate of its thermal relative efficiency factor (REF) for nuclear recoil versus gamma events which is a relevant parameter in WIMP search experiments. Taking advantage of the discrimination capability of scintillating bolometers, we have registered the energy spectrum of 206Pb recoiling nuclei from a 210Po alpha-source. Ensuing from the analysis we obtain an REF=1.044±0.008stat-0.008+0.056 close to but slightly greater than unity.

Coron, N.; García, E.; Gironnet, J.; Leblanc, J.; de Marcillac, P.; Martínez, M.; Ortigoza, Y.; Pobes, C.; Puimedón, J.; Redon, T.; Sarsa, M. L.; Torres, L.; Villar, J. A.

2008-01-01

260

Analysis of Collective Thomson Scattering for alpha Particles Diagnostics on Tokamaks.  

National Technical Information Service (NTIS)

An analysis is carried out of the alpha particles feature of the scattering dynamic form factor in a tokamak configuration. It is shown that the magnetic field in general causes two main effects: (1) a frequency roll-off affects the form factor for small ...

F. P. Orsitto P. Buratti

1989-01-01

261

Diffusive Model for alpha -Particle Energy Transport in a Laser Plasma.  

National Technical Information Service (NTIS)

The ignition of a laser-fusion pellet is essential due to the energy that the alpha -particles yielded by the D-T reactions in a small inner hot spot transfer to the outer cold and dense plasma. It is shown that if the plasma temperature is less than or e...

S. Atzeni A. Caruso

1980-01-01

262

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

NASA Astrophysics Data System (ADS)

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.

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

2002-03-01

263

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

264

Alpha-particle induced charge transfer between closely spaced trench capacitor memory cells  

Microsoft Academic Search

A detailed analysis of various mechanisms involved in alpha-particle induced charge transfer between two trench type dRAM cells is reported and an analytical model has been developed to represent the transfered charge. The results compare very favorably with detailed simulation results.

J. H. Chern; P. Yang; P. Pattnaik; J. A. Seitchik; K. C.-K. Weng

1985-01-01

265

Quasi-linear absorption of LH waves by fusion generated alpha particles.  

National Technical Information Service (NTIS)

Lower hybrid waves are foreseen to be used in a steady state reactor to produce current and control the current profile and the stability of internal modes. In the ignited phase, however, the presence of energetic alpha-particles may prevent wave-electron...

E. Barbato F. Santini

1989-01-01

266

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

267

Synthetic doublets from 234U alpha-particle spectra for assessing accuracy in peak fitting  

NASA Astrophysics Data System (ADS)

A series of well-characterized doublets has been constructed from 234U alpha-particle spectra to compare fitted peak-area ratios and positions with the known values. Results obtained using fitting models at CBNM and CIEMAT are discussed.

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

1990-01-01

268

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

269

Alfve´n waves, alpha particles, and pickup ions in the solar wind  

Microsoft Academic Search

Past studies of the properties of Alfv6n waves in the solar wind have indicated that: 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 the alpha particle transverse velocities are less (often close to zero)

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

1996-01-01

270

Binding Energies of the Alpha Particle and the A=3 Isobars from a Theoretical Geometric Model  

Microsoft Academic Search

We assume a triple geometric structure for the electromagnetic nuclear interaction. This nuclear electromagnetism is used to calculate the binding energies of the alpha particle and the A=3 isobar nuclides. The approximation for the resultant wave equation which lead to the deuteron binding energy from the modified Mathieu equation for the radial eigenvalue equation also establishes proton-electron-proton magnetic bonds in

Gustavo R. Gonzalez-Martin

2008-01-01

271

Experimental setup for studying the effects of alpha particles on zebrafish embryos  

NASA Astrophysics Data System (ADS)

In the present work, we have studied the feasibility to use an experimental setup based on polyallyldiglycol-carbonate (PADC) films to study effects of alpha particles on dechorionated zebrafish embryos. Thin PADC films with a thickness of 16 ?m were prepared from commercially available CR-39 films by chemical etching and used as support substrates for holding zebrafish embryos for alpha-particle irradiation. These films recorded alpha-particle hit positions, quantified the number and energy of alpha particles actually incident on the embryo cells, and thus enabled the calculation of the dose absorbed by the embryo cells. Irradiation was made at 4 h post fertilization (hpf) with absorbed doses up to 2.3 mGy. Images of the embryos at 48 hpf were examined for identification of morphologic abnormalities. The preliminary results showed that absorbed doses corresponding to the abnormally developed embryos ranged from 0.41 to 2.3 mGy, which was equivalent to 0.21 1.2 mGy in human.

Yum, E. H. W.; Ng, C. K. M.; Lin, A. C. C.; Cheng, S. H.; Yu, K. N.

2007-11-01

272

Prediction of lung cancer risk for radon exposures based on cellular alpha particle hits.  

PubMed

To explore the role of the multiplicity of cellular hits by radon progeny alpha particles for lung cancer incidence, the number of single and multiple alpha particle hits were computed for basal and secretory cells in the bronchial epithelium of human airway bifurcations. Hot spots of alpha particle hits were observed at the branching points of bronchial airway bifurcations. The effect of single and multiple alpha particle intersections of bronchial cells during a given exposure period, selected from a Poisson distribution, on lung cancer risk were simulated by a transformation frequency--tissue response model, based on experimentally observed cellular transformation and survival functions. Calculations of lung cancer risk at low radon exposure levels suggest that single hits produce a linear-dose response relationship, while the superposition of single and increasing multiple hits at higher exposure levels may also be approximated by a quasi-linear dose-effect curve. The simulations predict a carcinogenic enhancement effect for radon progeny accumulations at bifurcation branching sites, which may increase current risk estimates. PMID:21471125

Truta-Popa, L-A; Hofmann, W; Cosma, C

2011-04-06

273

NOVEL METHOD FOR BEAM DYNAMICS STUDY USING AN ALPHA PARTICLE SOURCE  

Microsoft Academic Search

A new method for beam dynamic study has been devel- oped by using alpha particles emitted from a commercially available radioactive source. The precision of the method is estimated in consideration of an event rate in a reason- able measuring time and statistical accuracy. The method could be applied not only for a circular accelerator but also for a unit

A. Sato; M. Aoki; Y. Arimoto; T. Itahashi; Y. Kuno; T. Oki; M. Yoshida

274

RANGE-ENERGY RELATIONS FOR PROTONS AND ALPHA-PARTICLES IN VARIOUS EXPLOSIVES  

Microsoft Academic Search

Differential energy loss and range data were calculated for low and ; medium-energy protons and alpha particles in various explosives. The ; explosives include cyclonite; cyclotetramethylene tetranitramine; 2,4,6-; trinitrotoluene; pentaerythritol tetranitrate; 2,4,6-trinitrophenyl methyl ; nitramine; lead styphnate; mercury fulminate; and lead azide. (C.H.);

JOSEPH CERNY; MAURICE S. KIRSHENBAUM; ROGER C. NICHOLS

1963-01-01

275

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

276

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

277

Variational calculations with correlated basis functions: Three-nucleon and three-alpha-particle systems  

NASA Astrophysics Data System (ADS)

A new variational method is applied to the solution of the Schroedinger equation for interacting few-body systems. The results for three nucleons interacting via the spin-dependent Malfliet-Tjon potential and three alpha particles interacting via the Ali-Bodmer potential are presented and compared with Faddeev and ATMS results, respectively.

Atti, C. Ciofi; Simula, S.

1985-09-01

278

Cancer incidence and lifespan vs. alpha-particle dose in beagles  

SciTech Connect

Young adult beagles were injected with graded activities of /sup 239/Pu, /sup 241/Am, /sup 228/Th, /sup 228/Ra or /sup 226/Ra and observed throughout their lifespans. The vast majority of the dose was from alpha particles. The lifetime incidence of bone sarcoma increased with average skeletal dose, more or less linearly up to high incidence for /sup 239/Pu, /sup 241/Am, /sup 228/Th and /sup 226/Ra, but sigmoid fashion for /sup 228/Ra. Based on average skeletal dose, the toxicity of the emitters relative to /sup 226/Ra = 1.0 was /sup 239/Pu = 16.6 +/- 4.5, /sup 241/Am = 5.4 +/- 1.6, /sup 228/Th = 8.5 +/- 2.3 and /sup 228/Ra = 2.0 +/- 0.5. At the lowest doses, the average lifespans were 97% +/- 3% of that in the controls. If beneficial effects occurred, they may have been overwhelmed by the destructiveness of the densely ionizing alpha particles. A cell nucleus 5 micron in diameter receives a mean dose of about 1 Gy (100 rad) when traversed by a single alpha particle. We found no evidence that alpha-particle doses suppressed cancer or lengthened lifespan in beagles.

Mays, C.W.; Lloyd, R.D.; Taylor, G.N.; Wrenn, M.E.

1987-05-01

279

Electron transport uniformity characterization of CdZnTe using alpha particles  

SciTech Connect

Novel electrode configurations, such as coplanar grids, have been successful in mitigating the effects of poor hole transport in CdZnTe gamma-ray detectors. However, poor material uniformity remains a major problem preventing the widespread application of such detectors in gamma-ray spectroscopy. Uniform electron transport is critical for achieving good gamma-ray detection performance in the coplanar-grid configuration. The authors have investigated the use of alpha-particle response as a quick and simple electron transport uniformity screening technique for material selection, and as a method to study other spectral broadening mechanisms in coplanar-grid detectors. The method consists of uniformly illuminating, with an alpha-particle source, the cathode side of the CdZnTe crystal in either a planar or a coplanar-grid detector configuration. In the planar geometry, the variation in the measured pulse heights is dictated in large part by the uniformity of the electron transport. An alpha-particle spectrum that has a single sharp peak with little background indicates uniform electron transport and, consequently, that the CdZnTe crystal should result in a coplanar-grid detector with good gamma-ray detection performance. In the coplanar geometry, the measured pulse-height variation provides information on additional sources of spectral broadening. In this paper the authors present the results of their study to measure the correlation between these simple alpha-particle measurements and the coplanar-grid gamma-ray detector response.

Amman, M.; Lee, J.S.; Luke, P.N.

1998-04-01

280

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

SciTech Connect

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

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

1996-05-01

281

Candidate reactions for mercury detection induced by neutron and alpha particles  

NASA Astrophysics Data System (ADS)

This paper summarizes modeling of mercury to activated states with alpha particles, neutrons, or deuterons, and the spectral emission from the activated products. Activation can occur with a neutron source such as 242Cf, 241Am-Be, a neutron generator, or a particle accelerator, and the activation products are measured if sufficient signal is provided. Identification and measurement of mercury by prompt gamma emission, generated by bombardment with neutrons are reported. Activation product reactions of (?, xn) (d, xn) (n, ?) and (n, p) are screened as candidate reactions. In addition to prompt gamma emission, products and cross-sections of delayed activation involving alphas, deuterons and neutrons are also reported. Initial calculations indicate the potential use of either alpha, or 14 MeV neutron activation to assess part per billion concentrations of mercury in the gaseous phase. Ultimately, data from sample analysis of ambient-condition flue gas will be used to assess mercury detection sensitivity and specificity under typical operating conditions.

Toth, James J.; Wittman, Richard; Schenter, Robert E.; Cooper, John A.

2007-03-01

282

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

283

Time-of-flight scattering and recoiling spectrometry  

SciTech Connect

Ion scattering and recoiling spectrometry consists of directing a collimated beam of monoenergetic ions towards a surface and measuring the flux of scattered and recoiled particles from this surface. When the neutral plus ion flux is velocity selected by measuring the flight times from the sample to the detector, the technique is called time-of-flight scattering and recoiling spectrometry (TOF-SARS). TOF-SARS is capable of (1) surface elemental analysis by applying classical mechanics to the velocities of the particles, (2) surface structural analysis by monitoring the angular anisotropies in the particle flux, and (3) ion-surface electron exchange probabilities by analysis of the ion/neutral fractions in the particle flux. Examples of these three areas are presented herein.

Rabalais, J.W. (Department of Chemistry, University of Houston, Houston, Texas 77204-5641 (US))

1991-05-01

284

Enhancing the sensitivity of recoil-beta tagging  

NASA Astrophysics Data System (ADS)

Tagging with ?-particles at the focal plane of a recoil separator has been shown to be an effective technique for the study of exotic proton-rich nuclei. This article describes three new pieces of apparatus used to greatly improve the sensitivity of the recoil-beta tagging technique. These include a highly-pixelated double-sided silicon strip detector, a plastic phoswich detector for discriminating high-energy ?-particles, and a charged-particle veto box. The performance of these new detectors is described and characterised, and the resulting improvements are discussed.

Henderson, J.; Ruotsalainen, P.; Jenkins, D. G.; Scholey, C.; Auranen, K.; Davies, P. J.; Grahn, T.; Greenlees, P. T.; Henry, T. W.; Herzá?, A.; Jakobsson, U.; Joshi, P.; Julin, R.; Juutinen, S.; Konki, J.; Leino, M.; Lotay, G.; Nichols, A. J.; Obertelli, A.; Pakarinen, J.; Partanen, J.; Peura, P.; Rahkila, P.; Sandzelius, M.; Sarén, J.; Sorri, J.; Stolze, S.; Uusitalo, J.; Wadsworth, R.

2013-04-01

285

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

SciTech Connect

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

Kerns, J.A.

1986-05-01

286

Many-particle decays of {alpha}-chain structures in {sup 24}Mg  

SciTech Connect

We have searched for evidence of exotic cluster configurations in {sup 24}Mg resembling a linear chain of {alpha} particles in various many-particle final states of the {sup 12}C+{sup 12}C system, including {sup 1}C(O{sub 2}{sup +})+{sup 12}C(O{sub 2}{sup +}) and {sup 8}Be+{sup 16}O*(4a). Such configurations are predicted to occur by a number of different theoretical models of the structure of {sup 24}Mg. An array of highly segmented Double-Sided Silicon Strip Detectors permits detailed, high resolution reconstruction of these many-charged-particle final states.

Wuosmaa, A.H.

1993-12-31

287

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

288

Kerma-factor determination by charged-particle spectroscopy  

SciTech Connect

Neutron kerma factors can determined by measuring the cross sections, angular distributions and charged-particle emission spectra from (n,z) reactions where z stands for the light charged particles, namely protons, deuterons, tritons, {sup 3}He, or {alpha}-particles, and combining these data with information on the heavy nuclear recoils. This approach is compared with other approaches of determining kerma factors. Data are given near 14 MeV for materials from carbon to niobium.

Haight, R.C.

1994-07-01

289

Production of actinium-225 for alpha particle mediated radioimmunotherapy.  

PubMed

The initial clinical trials for treatment of acute myeloid leukemia have demonstrated the effectiveness of the alpha emitter (213)Bi in killing cancer cells. Bismuth-213 is obtained from a radionuclide generator system from decay of 10-days (225)Ac parent. Recent pre-clinical studies have also shown the potential application of both (213)Bi, and the (225)Ac parent radionuclide in a variety of cancer systems and targeted radiotherapy. This paper describes our five years of experience in production of (225)Ac in partial support of the on-going clinical trials. A four-step chemical process, consisting of both anion and cation exchange chromatography, is utilized for routine separation of carrier-free (225)Ac from a mixture of (228)Th, (229)Th and (232)Th. The separation of Ra and Ac from Th is achieved using the marcoporous anion exchange resin MP1 in 8M HNO(3) media. Two sequential MP1/NO(3) columns provide a separation factor of approximately 10(6) for Ra and Ac from Th. The separation of Ac from Ra is accomplished on a low cross-linking cation exchange resin AG50-X4 using 1.2M HNO(3) as eluant. Two sequential AG50/NO(3) columns provide a separation factor of approximately 10(2) for Ac from Ra. A 60-day processing schedule has been adopted in order to reduce the processing cost and to provide the highest levels of (225)Ac possible. Over an 8-week campaign, a total of approximately 100 mCi of (225)Ac (approximately 80% of the theoretical yield) is shipped in 5-6 batches, with the first batch typically consisting of approximately 50 mCi. After the initial separation and purification of Ac, the Ra pool is re-processed on a bi-weekly schedule or as needed to provide smaller batches of (225)Ac. The averaged radioisotopic purity of the (225)Ac was 99.6 +/- 0.7% with a (225)Ra content of < or =0.6%, and an average (229)Th content of (4(-4)(+5)) x 10(-5)%. PMID:15763472

Boll, Rose A; Malkemus, Dairin; Mirzadeh, Saed

2005-01-28

290

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 [Phys. Plasmas {bold 5}, 1577 (1998)] 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 calculations show that monotonic shear alpha particles are virtually unaffected by toroidal field ripple. The calculations show that in reversed shear the confinement domain is not empty for trapped alphas at birth and allow an estimate of the actual alpha particle densities measured with the pellet charge exchange diagnostic. {copyright} {ital 1999 American Institute of Physics.}

Redi, M.H.; Batha, S.H.; Budny, R.V.; Darrow, D.S.; Levinton, F.M.; McCune, D.C.; Medley, S.S.; Petrov, M.P.; von Goeler, S.; White, R.B.; Zarnstorff, M.C.; Zweben, S.J. [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States); TFTR Team

1999-07-01

291

Confined alpha particle diagnostic system using an energetic He{sup 0} beam for ITER  

SciTech Connect

The beam neutralization system for measurement of the spatial and velocity distributions of alpha particles of ITER plasmas was studied. As forward angle detection against the beam injection direction is required for effective neutralization, arrangement of the measurement system using possible ports in ITER configuration is proposed. The count rate of neutralized alpha particles produced by the double charge exchange interaction with energetic He{sup 0} beam particles injected is estimated. The ratios of signal to neutron-induced noise are evaluated. When a He{sup 0} beam produced by autodetachment from a 1-1.5 MeV He{sup -} beam of 10 mA is injected, the signal to noise ratio becomes greater than 1 at {rho}<0.4, even without beam modulation. Usage of a lock-in technique at the frequency of radio-frequency quadrapole accelerator will make measurement at the outer region possible.

Sasao, M.; Shinto, K.; Isobe, M.; Nishiura, M.; Kaneko, O.; Wada, M.; Walker, C. I.; Kitajima, S.; Okamoto, A.; Sugawara, H.; Takeuchi, S.; Tanaka, N.; Aoyama, H.; Kisaki, M. [Tohoku University, Aoba, Sendai 980-8579 (Japan); National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan); Doshisha University, Kyotanabe, Kyoto 610-0321 (Japan); ITER Joint Work Site, Cadarache, 13108 Saint-Paul-lez-Durance cedex (France); Tohoku University, Aoba, Sendai 980-8579 (Japan)

2006-10-15

292

Further measurement of the {beta}-delayed {alpha}-particle emission of {sup 16}N  

SciTech Connect

We measured the {beta}-delayed {alpha}-particle emission spectrum of {sup 16}N with a sensitivity for {beta}-decay branching ratios of the order of 10{sup -10}. The {sup 16}N nuclei were produced using the d({sup 15}N,{sup 16}N)p reaction with 70 MeV {sup 15}N beams and a deuterium gas target 7.5 cm long at a pressure of 1250 torr. The {sup 16}N nuclei were collected (over 10 s) using a thin aluminum foil with an areal density of 180 {mu}g/cm{sup 2} tilted at 7 deg. with respect to the beam. The activity was transferred to the counting area by means of a stepping motor in less than 3 s with the counting carried out over 8 s. The {beta}-delayed {alpha}-particles were measured using a time-of-flight method to achieve a sufficiently low background. Standard calibration sources ({sup 148}Gd, {sup 241}Am, {sup 208,209}Po, and {sup 227}Ac) as well as {alpha} particles and {sup 7}Li from the {sup 10}B(n,{alpha}){sup 7}Li reaction were used for an accurate energy calibration. The energy resolution of the catcher foil (180-220 keV) was calculated and the time-of-flight resolution (3-10 nsec) was measured using the {beta}-delayed {alpha}-particle emission from {sup 8}Li that was produced using the d({sup 7}Li,{sup 8}Li)p reaction with the same setup. The line shape was corrected to account for the variation in the energy and time resolution and a high statistics spectrum of the {beta}-delayed {alpha}-particle emission of {sup 16}N is reported. However, our data (as well as earlier Mainz data and unpublished Seattle data) do not agree with an earlier measurement of the {beta}-delayed {alpha}-particle emission of {sup 16}N taken at TRIUMF after averaging over the energy resolution of our collection system. This disagreement, among other issues, prohibits accurate inclusion of the f-wave component in the R-matrix analysis.

France III, R. H.; Wilds, E. L.; McDonald, J. E.; Gai, M. [Department of Chemistry and Physics, Campus Box 82, Georgia College and State University, Milledgeville, Georgia 31061 (United States); Division of Radiation Safety, Connecticut-DEP, 79 Elm Street, Hartford, Connecticut 06106 (United States); Department of Physics, University of Hartford, West Hartford, Connecticut 06117-1599 (United States); Laboratory for Nuclear Sciences at Avery Point, University of Connecticut, Groton, Connecticut 06340-6097 (United States) and Department of Physics, WNSL-102, P.O. Box 208124, Yale University, 272 Whitney Avenue, New Haven, Connecticut 06520-8124 (United States)

2007-06-15

293

Recoil-reducing shooting rest  

US Patent & Trademark Office Database

A shooting rest supports a firearm and reduces recoil energy of the firearm. The shooting rest has a rear support and a front support for supporting the firearm and a frame connecting the rear support and the front support. The frame supports at least one weight to reduce the amount of recoil energy felt by a shooter.

Cauley; Dennis (Boonville, MO); Morrow; Tim (Jefferson City, MO)

2011-09-06

294

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

295

Exerpts from the history of alpha recoils  

Microsoft Academic Search

Any confined air volume holding radon (222Rn) gas bears a memory of past radon concentrations due to 210Pb (T1\\/2 = 22 y) and its progenies entrapped in all solid objects in the volume. The efforts of quantifying past radon exposures by means of the left-behind long-lived radon progenies started in 1987 with this author’s unsuccessful trials of removing 214Po from radon exposed glass

Christer Samuelsson

2011-01-01

296

Alfven eigenmode and ion Bernstein wave studies for controlling fusion alpha particles  

NASA Astrophysics Data System (ADS)

In magnetic confinement fusion reactor plasmas, the charged fusion products (such as alpha particles in deuterium-tritium plasmas) will be the dominant power source, and by controlling these charged fusion products using wave-particle interactions the reactor performance could be optimized. This thesis studies two candidate waves: Mode-Converted Ion Bernstein Waves (MCIBWs) and Alfvén Eigenmodes (AEs). Rates of MCIBW-driven losses of alpha-like fast deuterons, previously observed in the Tokamak Fusion Test Reactor (TFTR), are reproduced by a new model so that the wave-particle diffusion coefficient can be deduced. The MCIBW power in TFTR is found to be ~ 1/3 that needed for collisionless alpha particle control. A reasonable reactor power scaling is derived. To study AEs, existing magnetic fluctuation probes at the Joint European Torus (JET) have been absolutely calibrated from 30-500 kHz for the first time, allowing fluctuation measurements with |dBpol|/B0>10- 8 and toroidal mode numbers |n|<32 using an 8-channel, 4-second, 1-MHz digitizer. Data analysis and database tools have been developed and applied to 4280 JET discharges using hydrogen, deuterium, tritium and helium-3. Three classes of AEs (driven by fast ions from various ion cyclotron range-of-frequency heating (ICRH) schemes) are identified. New AE phenomena are observed. AEs are less stable in ``Optimised Shear'' plasmas. AE ``pitchfork splitting'' (amplitude modulation) has been discovered. In other discharges, chaotic AE amplitude evolution and two types of explosive behavior have been discovered and found to be consistent with theoretical expectations. The strongest AEs appear to redistribute fast ions. No evidence for alpha-particle driven AEs has been found. ICRH beatwaves are studied as a potential AE driver. The beatwave spectrum has been discovered to include multiple beat-frequency harmonies plus sums and differences of beat frequencies. AE excitation with beatwaves remains an area for future work. Data obtained incidentally regarding other plasma instabilities, including some of possible use for alpha particle control, are included for completeness. Finally, an integrated alpha particle control experiment is suggested, including a candidate scenario for JET.

Heeter, Robert Franklin

1999-12-01

297

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

298

Evidence for alpha-particle chain configurations in {sup 24}Mg  

SciTech Connect

Many theoretical models have been employed to described the structure of the nucleus {sup 24}Mg. Among these are the Cranked Shell model (CSM), the Cranked Cluster Model (CCM), and calculations have also been performed using the Hartree-Fock formalism. One very striking prediction of these calculations is that in this nucleus there exist very unusual configurations, with structures reminiscent of linear chains of alpha particles. In the CSM, for instance, such a configuration is identified with a pronounced minimum in the potential energy energy at very large prolate deformation. In the CCM, several very different alpha-particle duster configurations are identified, many having rather large deformations. These cluster configurations can be associated with the different potential-energy minima obtained in the CSM results. In the case of the CCM, a 6{alpha} chain-like configuration is predicted to occur at excitation energies between 40 and 50 MeV, with predicted rotational spacing given by {Dirac_h}{sup 2}/2I=22 keV. At this excitation energy, such a chain configuration would lie well above the threshold for the decay of {sup 24}Mg into 6 alpha particles, and its identification poses a difficult experimental challenge. This report discusses this challenge.

Wuosmaa, A.H.; Back, B.B.; Betts, R.R.; Ferre, M.; Gehring, J.; Glagola, P.G.; Happ, Th.; Henderson, D.J.; Wilt, P. [Argonne National Lab., IL (United States); Bearden, I.G. [Purdue Univ., Lafayette, IN (United States). Dept. of Physics

1992-09-01

299

Evidence for alpha-particle chain configurations in sup 24 Mg  

SciTech Connect

Many theoretical models have been employed to described the structure of the nucleus {sup 24}Mg. Among these are the Cranked Shell model (CSM), the Cranked Cluster Model (CCM), and calculations have also been performed using the Hartree-Fock formalism. One very striking prediction of these calculations is that in this nucleus there exist very unusual configurations, with structures reminiscent of linear chains of alpha particles. In the CSM, for instance, such a configuration is identified with a pronounced minimum in the potential energy energy at very large prolate deformation. In the CCM, several very different alpha-particle duster configurations are identified, many having rather large deformations. These cluster configurations can be associated with the different potential-energy minima obtained in the CSM results. In the case of the CCM, a 6{alpha} chain-like configuration is predicted to occur at excitation energies between 40 and 50 MeV, with predicted rotational spacing given by {Dirac h}{sup 2}/2I=22 keV. At this excitation energy, such a chain configuration would lie well above the threshold for the decay of {sup 24}Mg into 6 alpha particles, and its identification poses a difficult experimental challenge. This report discusses this challenge.

Wuosmaa, A.H.; Back, B.B.; Betts, R.R.; Ferre, M.; Gehring, J.; Glagola, P.G.; Happ, Th.; Henderson, D.J.; Wilt, P. (Argonne National Lab., IL (United States)); Bearden, I.G. (Purdue Univ., Lafayette, IN (United States). Dept. of Physics)

1992-01-01

300

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

301

Alpha-Particle Angular Distributions of At and Rn Isotopes and Their Relation to Nuclear Structure  

SciTech Connect

We report on an extensive on-line nuclear orientation study of the angular distribution of {alpha} particles emitted in the favored decay of neutron deficient At and Rn nuclei near the {ital N}=126 shell closure. Surprisingly large anisotropies were observed, showing pronounced changes from one isotope to another. Comparing these data with several theoretical models shows that anisotropic {alpha} emission in favored decays from near-spherical nuclei can well be explained within the shell model, implying that it is mainly determined by the structure of the decaying nucleus. {copyright} {ital 1996 The American Physical Society.}

NICOLE Collaboration and ISOLDE Collaboration

1996-12-01

302

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.

303

Density-induced suppression of the {alpha}-particle condensate in nuclear matter and the structure of {alpha}-cluster states in nuclei  

SciTech Connect

At low densities, with decreasing temperatures, in symmetric nuclear matter {alpha} particles are formed, which eventually give raise to a quantum condensate with four-nucleon {alpha}-like correlations (quartetting). Starting with a model of {alpha} matter, where undistorted {alpha} particles interact via an effective interaction such as the Ali-Bodmer potential, the suppression of the condensate fraction at zero temperature with increasing density is considered. Using a Jastrow-Feenberg approach, it is found that the condensate fraction vanishes near saturation density. Additionally, the modification of the internal state of the {alpha} particle due to medium effects will further reduce the condensate. In finite systems, an enhancement of the S-state wave function of the center-of-mass orbital of {alpha}-particle motion is considered as the correspondence to the condensate. Wave functions have been constructed for self-conjugate 4n nuclei that describe the condensate state but are fully antisymmetrized on the nucleonic level. These condensate-like cluster wave functions have been successfully applied to describe properties of low-density states near the n{alpha} threshold. Comparison with orthogonality condition model calculations in {sup 12}C and {sup 16}O shows strong enhancement of the occupation of the S-state center-of-mass orbital of the {alpha} particles. This enhancement is decreasing if the baryon density increases, similar to the density-induced suppression of the condensate fraction in {alpha} matter. The ground states of {sup 12}C and {sup 16}O show no enhancement at all, thus a quartetting condensate cannot be formed at saturation densities.

Funaki, Y. [Nishina Center for Accelerator-Based Science, The Institute of Physical and Chemical Research (RIKEN), Wako, Saitama 351-0198 (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, F-91406 Orsay Cedex (France); Universite Paris-Sud, F-91406 Orsay-Cedex (France); Tohsaki, A. [Research Center for Nuclear Physics (RCNP), Osaka University, Osaka 567-0047 (Japan); Yamada, T. [Laboratory of Physics, Kanto Gakuin University, Yokohama 236-8501 (Japan)

2008-06-15

304

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

305

Exchange of Alpha Particle in the {sup 16}O+{sup 12}C Elastic Scattering  

SciTech Connect

We have analyzed twenty elastic scattering angular distributions of the {sup 16}O+{sup 12}C system, measured at Sao Paulo Pelletron Laboratory and also data from the literature. The energies cover the region around and above Coulomb barrier, ranging from 8.54 up to 75.43 MeV in the center of mass reference frame. In the {sup 16}O+{sup 12}C scattering, two different processes can occur which result in same exit channel, the elastic scattering and the exchange of an alpha particle between projectile and target. We have used the Optical Model formalism for the elastic scattering and the DWBA to describe the alpha transfer reaction contribution. Thus, by analyzing the {sup 16}O+C elastic scattering at backward angles we have obtained the {sup 16}O{sub gs} alpha spectroscopic factor.

Morais, M. C.; Filho, R. Lichtenthaeler [Departamento de Fisica Nuclear, Universidade de Sao Paulo, C.P. 66318, Sao Paulo (Brazil)

2009-06-03

306

Cryogenic microcalorimeter system for ultra-high resolution alpha-particle spectrometry  

SciTech Connect

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 {approx}15 uK 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 spectrometer, and will show recent results.

Rabin, Michael W [Los Alamos National Laboratory; Hoover, Andrew S [Los Alamos National Laboratory; Bacrania, Mnesh K [Los Alamos National Laboratory; Croce, Mark P [Los Alamos National Laboratory; Hoteling, N J [Los Alamos National Laboratory; Lamont, S P [Los Alamos National Laboratory; Plionis, A A [Los Alamos National Laboratory; Dry, D E [Los Alamos National Laboratory; Ullom, J N [NIST; Bennett, D A [NIST; Horansky, R [NIST; Kotsubo, V [NIST; Cantor, R [STAR CRYOELECTRONICS

2009-01-01

307

Targeted alpha-particle radiotherapy with 211At-labeled monoclonal antibodies.  

PubMed

An attractive feature of targeted radionuclide therapy is the ability to select radionuclides and targeting vehicles with characteristics that are best suited for a particular clinical application. One combination that has been receiving increasing attention is the use of monoclonal antibodies (mAbs) specifically reactive to receptors and antigens that are expressed in tumor cells to selectively deliver the alpha-particle-emitting radiohalogen astatine-211 (211At) to malignant cell populations. Promising results have been obtained in preclinical models with multiple 211At-labeled mAbs; however, translation of the concept to the clinic has been slow. Impediments to this process include limited radionuclide availability, the need for suitable radiochemistry methods operant at high activity levels and lack of data concerning the toxicity of alpha-particle emitters in humans. Nonetheless, two clinical trials have been initiated to date with 211At-labeled mAbs, and others are planned for the near future. PMID:17921029

Zalutsky, Michael R; Reardon, David A; Pozzi, Oscar R; Vaidyanathan, Ganesan; Bigner, Darell D

2007-05-11

308

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

2009-04-27

309

Sequential determination of 210Po and uranium radioisotopes in drinking water by alpha-particle spectrometry.  

PubMed

Procedures for the sequential determination of low level (210)Po and uranium radioisotopes in drinking water by alpha-particle spectrometry are presented. After addition of (208)Po and (232)U tracers, the radionuclides were preconcentrated from water samples by co-precipitation on Fe(OH)(3) or MnO(2) at pH 9 using ammonia solution. The (210)Po source was prepared by spontaneous deposition onto a copper disc either before or after uranium separation. The uranium source for alpha-particle counting was prepared by micro co-precipitation with CeF(3). The procedures were tested on mineral water and the results obtained are compared. PMID:19231220

Benedik, L; Vasile, M; Spasova, Y; Wätjen, U

2009-01-24

310

Results from the Lunar Prospector Alpha Particle Spectrometer: Detection of Radon-222 Over Craters Aristarchus and Kepler  

NASA Astrophysics Data System (ADS)

The Lunar Prospector Alpha Particle Spectrometer (LP APS) searched for lunar surface gas release events and mapped their distribution by detecting alpha particles produced by the decay of gaseous radon-222 (5.5 MeV, 3.8 day half-life), solid polonium-218 (6.0 MeV, 3 minute half-life), and solid polonium-210 (5.3 MeV, 138 day half-life, but held up in production by the 21 year half-life of lead-210). These three nuclides are radioactive daughters from the decay of uranium-238. Radon reaches the lunar surface either at areas of high soil porosity or where fissures release the trapped gases in which radon is entrained. We have examined APS data within +/- 45 degrees of the equator acquired during periods of low interplanetary alpha particle flux. The spectra were summed over all LP mapping cycles when the instrument was turned on (approximately 229 days over 16 months). To yield lunar alpha particle maps, we summed over a 0.2 MeV energy range centered on each of the three alpha particle energies noted above. The LP APS found only a faint indication of alpha particles resulting from the decay of polonium-218 and only a marginal detection of alpha particles from polonium-210. However, our radon-222 alpha particle map indicates that radon gas is presently emanating from the vicinity of craters Aristarchus and Kepler. The LP gamma-ray spectrometer, which effectively has significantly higher spatial resolution than the APS, identified thorium enrichments at these two craters. Thorium and uranium are both incompatible elements whose lunar surface abundances are highly correlated; thus, it is likely that the radon-222 alpha particles measured using the LP APS originate from Kepler and Aristarchus. Our detection of radon over Aristarchus is consistent with the results of the Apollo 15 APS.

Lawson, S. L.; Feldman, W. C.; Lawrence, D. J.; Moore, K. R.; Belian, R. D.; Maurice, S.; Binder, A. B.

2001-11-01

311

LETTER: Ripple induced stochastic loss of alpha particles in a tokamak  

NASA Astrophysics Data System (ADS)

The Fokker-Planck equation is solved for alpha particles in a tokamak, including both pitch angle scattering and slowing down. Losses of the toroidally trapped particles due to stochastic diffusion related to magnetic ripple are accounted for by assuming that all the stochastic orbits leave the device immediately. This assumption permits the problem to be solved by the introduction of a loss cone corresponding to the stochastic region of the velocity space. The eigenvalue problem is solved numerically, to show that the additional stochastic loss of energy due to scattering into the loss cone substitutes about 30% of the birth energy for typical fusion parameters

Yanashima, K.; Yamasaki, D.; Watabe, S.; Hara, K.; Yoshino, J.; Kukimoto, H.

312

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

313

Effects of [alpha]-particle radiation on rat tracheal epithelial cells  

SciTech Connect

By a combination of methods, which included flow cytometry and magnetic cell sorting, the author has demonstrated that the cells of the rat tracheal epithelium which have the greatest proliferative capacity in culture and in vivo are the basal cells. Because of these findings it seems reasonable to suppose that the basal cells are the most likely target for the action of [alpha]-particle radiation in pseudostratified respiratory epithelium. This hypothesis is further supported by the finding that the basal cells are the cells which appear to respond to the tumor promoter 12-O-tetra-decanoylphorbol-13-acetate. The effects of [sup 210]Po [alpha]-particles on the survival and oncogenic transformation of rat tracheal epithelial cells in suspension were investigated. Since these effects were assayed in culture, the results pertain to the reaction of only the basal cells to irradiation. The results indicate that [alpha]-particles are extremely cytotoxic in that a track segment of 4 [mu]m, on average, is sufficient to cause the reproductive death of basal cells. This finding is supported by similar results obtained with two cell lines, Mv1Lu and CHO-K1 BH[sub 4]. Production of proliferating epithelial foci by [alpha]-particles was not distinguishable from control and sham treatments. These results are in direct conflict with many of the results that have been obtained with C3H 10T1/2 cells in similar transformation assays. Some possible reasons for these disparities are discussed and supporting evidence is provided.

Ford, J.R. Jr.

1992-01-01

314

Effects of {alpha}-particle radiation on rat tracheal epithelial cells  

SciTech Connect

By a combination of methods, which included flow cytometry and magnetic cell sorting, we have demonstrated that the cells of the rat tracheal epithelium which have the greatest proliferative capacity in culture and in vivo are the basal cells. Because of these findings it seems reasonable to suppose that the basal cells are the most likely target for the action of {alpha}-particle radiation in pseudostratified respiratory epithelium. This hypothesis is further supported by the finding that the basal cells are the cells which appear to respond to the tumor promoter 12-O-tetradecanoylphorbol-13-acetate. The effects of {sup 210}Po {alpha}-particles on the survival and oncogenic transformation of rat tracheal epithelial cells in suspension were investigated. Since these effects were assayed in culture, the results pertain to the reaction of only the basal cells to irradiation. The results indicate that {alpha}-particles are extremely cytotoxic in that a track segment of 4 {mu}m, on average, is sufficient to cause the reproductive death of basal cells. This finding is supported by similar results obtained with two cell lines, Mv1Lu and CHO-K1 BH{sub 4}. Production of proliferating epithelial foci by {alpha}-particles was not distinguishable from control and sham treatments. These results are in direct conflict with many of the results that have been obtained with C3H 1OT1/2 cells in similar transformation assays. Some possible reasons for these disparities are discussed and supporting evidence is provided.

Ford, J.R. Jr.

1992-08-01

315

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

316

Critical temperature for {alpha}-particle condensation in asymmetric nuclear matter  

SciTech Connect

The critical temperature for {alpha}-particle condensation in nuclear matter with Fermi surface imbalance between protons and neutrons is determined. The in-medium four-body Schroedinger equation, generalizing the Thouless criterion of the BCS transition, is applied using a Hartree-Fock wave function for the quartet projected onto zero total momentum in matter with different chemical potentials for protons and neutrons.

Sogo, Takaaki; Roepke, Gerd; Schuck, Peter [Institut fuer Physik, Universitaet Rostock, D-18051 Rostock (Germany); Institut de Physique Nucleaire, CNRS, UMR 8608, Orsay F-91406, France, Universite Paris-Sud, Orsay F-91505, France, and Laboratoire de Physique et Modelisation des Milieux Condenses, CNRS and Universite Joseph Fourier, 25 Avenue des Martyrs, Boite Postale 166, F-38042 Grenoble Cedex 9 (France)

2010-09-15

317

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

Microsoft Academic Search

Neoclassical transport of minority suprathermal alpha particles is investigated. This paper departs from previous investigations in that (a) the banana-width ordering parameter ρ{sub θ}\\/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

G. T. Sager; G. H. Miley; K. H. Burrell

1990-01-01

318

Data needs for the track structure of alpha particles and electrons in water  

SciTech Connect

We have made calculations of the ionization spectra for alpha particle and electron tracks in water. We have also computed the number of ions created per micrometre of track length, the energy distribution of the secondaries, and the energy expended per ion pair created. Our aim is less toward theoretical derivations than to obtain a numerically accurate description of the track structure at all energies in a form suitable for biomedical applications. 13 references.

Pagnamenta, A.

1983-01-01

319

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

320

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

Microsoft Academic Search

The time dependence and the intensity of the primary scintillation light in liquid xenon excited by 241Am alpha particles and 207Bi internal conversion electrons were measured at different electric field strengths. High-purity liquid xenon was used to fill a parallel-plate ionization chamber equipped with a CaF2 window coupled to a UV (ultraviolet) sensitive photomultiplier tube. The effect of the specific

Elena Aprile; Reshmi Mukherjee; Masayo Suzuki

1990-01-01

321

Low-Temperature Electron and Alpha-Particle Irradiation of Titanium  

Microsoft Academic Search

The recovery of point defects produced by 1.2-MeV electron and 40-MeV alpha-particle irradiation has been studied from 50 to 270°K. The recovery spectrum qualitatively resembles that of copper, although shifted to higher temperature. The influence of varying irradiation dose, preirradiation at elevated temperatures, predeformation and dilute alloying were also studied. The recovery below 150°K is dominated by the annihilation of

Walter Bauer; K. Herschbach; J. J. Jackson

1969-01-01

322

Binding Energies of the Alpha Particle and the A=3 Isobars from a Theoretical Geometric Model  

Microsoft Academic Search

We assume a triple geometric structure for the electromagnetic nuclear\\u000ainteraction. This nuclear electromagnetism is used to calculate the binding\\u000aenergies of the alpha particle and the A=3 isobar nuclides. The approximation\\u000afor the resultant wave equation which lead to the deuteron binding energy from\\u000athe modified Mathieu equation for the radial eigenvalue equation also\\u000aestablishes proton-electron-proton magnetic bonds in

Gustavo R. Gonzalez-Martin

2008-01-01

323

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

324

Development of ZnO:Ga as an Ultra-Fast Alpha Particle Detector  

Microsoft Academic Search

We report on ZnO:Ga to produce a high luminosity, ultra fast alpha detector as a system component that provides associated particle imaging (API) capability to neutron generators. ZnO:Ga has been shown to be well suited as the scintillator screen of the detector. Fast luminescence is observed but its intensity and decay time is strongly dependent on the method used for

E. D. Bourret-Courchesne; S. E. Derenzo; M. J. Weber

2006-01-01

325

Emission of Neutrons from Argon, Chlorine, Aluminum and Some Heavier Elements Under Alpha-Particle Bombardment  

Microsoft Academic Search

The emission of neutrons from chlorine, argon, scandium, titanium, manganese and iron under alpha-particle bombardment was established. The yield from argon is considerable and enabled a measurement of the energy of the neutrons to be made: the majority are associated with a group of energy change -5.6+\\/-1.0 Mev, but two groups must be present. The excitation curve for these neutrons

Ernest Pollard; Howard L. Schultz; Gordon Brubaker

1938-01-01

326

Accuracy testing using thick source alpha-particle spectroscopy for the U and Th series estimations.  

PubMed

The new technique for the calculation of U and Th based on the alpha particle spectrum taken from a thick sample by using a silicon detector (PIPS) is tested and some technical problems are encountered and also some notifications for better accuracy are addressed. This technique which is mainly developed to be used for dose rate determination in TL, OSL and ESR dating applications, gives also the possibility for detecting and estimating possible disequilibrium in U and Th series. PMID:19900816

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

2009-10-24

327

Fabrication of micropillar substrates using replicas of alpha-particle irradiated and chemically etched PADC films.  

PubMed

We proposed a simple method to fabricate micropillar substrates. Polyallyldiglycol carbonate (PADC) films were irradiated by alpha particles and then chemically etched to form a cast with micron-scale spherical pores. A polydimethylsiloxane (PDMS) replica of this PADC film gave a micropillar substrate with micron-scale spherical pillars. HeLa cells cultured on such a micropillar substrate had significantly larger percentage of cells entering S-phase, attached cell numbers and cell spreading areas. PMID:22130471

Ng, C K M; Chong, E Y W; Roy, V A L; Cheung, K M C; Yeung, K W K; Yu, K N

2011-11-18

328

The Ionization and Stopping Power of Various Gases for Alpha Particles from Polonium. II  

Microsoft Academic Search

The ionizations of nitric oxide, nitrous oxide, and air were found to be strictly proportional along the range, while methyl iodide shows definite systematic deviations. A method of determining differential stopping powers for alpha-particles has been applied to a number of gases. The results show that such unstable molecules as NO and H3C-N=NCH3 give strictly additive stopping powers. The stopping

G. E. Gibson; H. Eyring

1927-01-01

329

Recoil corrections in highly charged ions  

SciTech Connect

A recently introduced Bethe-Salpeter formalism is applied to the calculation of recoil corrections to the energy levels of all n=1, 2, and 3 states of hydrogenic ions. Finite basis set techniques are shown to allow the accurate evaluation of expressions that sum all orders of Z{alpha}, which are rederived in the formalism using combinatoric techniques. A comparison of the all-order results with one-loop calculations and known terms of the perturbation expansion in Z{alpha} is made. Good agreement of the results of the present work with previous calculations is shown, and a discussion of issues that will have to be treated for the many-electron case, where highly accurate experiments have been carried out, is given.

Adkins, G. S.; Morrison, S.; Sapirstein, J. [Department of Physics, Franklin and Marshall College, Lancaster, Pennsylvania 17604 (United States); Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556 (United States)

2007-10-15

330

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

331

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

SciTech Connect

Nonlinear electrostatic instabilities have been shown to occur frequently and under very different conditions in plasma with two ion beams such as the fast solar wind. These instabilities can be triggered when the phase velocity of electrostatic ion-acoustic waves propagating forward and backward relative to the interplanetary magnetic field overlaps 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 percent of the local Alfven velocity--can trigger a very rich variety of nonlinear electrostatic acousticlike instabilities. Their growth rates can be rather large and they persist for larger negative alpha particles drift velocities and temperatures.

Gomberoff, L. [Departamento de Fisica, Facultad de Ciencias, Universidad de Chile, Santiago (Chile); Gomberoff, K. [Department of Physics, Technion, Haifa 32000 (Israel); Deutsch, A. [Rafael, P.O. Box 2250, Haifa 31021 (Israel)

2010-06-15

332

A bipolar mechanism for alpha-particle-induced soft errors in GaAs integrated circuits  

NASA Astrophysics Data System (ADS)

The alpha-particle-induced collected charge in undoped LEC semi-insulating GaAs is measured in n+-i-n+ and n+-p-n+ isolation structures and is compared with the results of an analytical model based on a bipolar mechnism. In n+-i-n+ isolation structures, a collected-storage multiplication phenomenon induced by alpha-particle incidence is observed. The measured collected charge is about three times the alpha-particle-generated charge. This phenomenon can be attributed to charge transfer between two adjacent n+ regions. The dominant charge-collection process continues for 2.4 ns in n+-i-n+ isolation structures, but in n+-p-n+ isolation structures, it stops within 0.8 ns. The measured collected charge decreases as the isolation gap and background acceptor concentration increase. These experimental results can be explained semiquantitatively by the analytical model. This suggests that the primary mechanism of soft errors in GaAs ICs is a bipolar mechanism.

Umemoto, Yasunari; Matsunaga, Nobutoshi; Mitsusada, Kazumichi

1989-05-01

333

Ultra-high Resolution Alpha Particle Spectrometry with Transition-Edge Sensor Microcalorimeters  

NASA Astrophysics Data System (ADS)

Alpha particle spectrometry is a powerful analytical tool for nuclear forensics and environmental monitoring. Microcalorimeter detectors have been shown to yield nearly an order of magnitude better energy resolution (1.06 keV FWHM at 5.3 MeV) than current state-of-the-art silicon detectors (8-10 keV FWHM at 5.3 MeV). This superior resolution allows isotopic analysis with a single non-consumptive measurement of samples that contain multiple radioisotopes with overlapping alpha energies. Measurement of such a sample with a silicon detector would require expensive and time-consuming radiochemical separations. We are developing two alpha spectrometer systems with superconducting transition-edge sensor microcalorimeters. The first system has eight independent detector channels that measure eight different alpha sources, and is optimized for detector development experiments. The second system incorporates a prototype cryogenic load lock that allows for rapid exchange of alpha samples. This paper will present results from these two systems.

Croce, M.; Bacrania, M.; Bond, E.; Dry, D.; Moody, W. A.; Rabin, M.; Bennett, D.; Hilton, G.; Horansky, R.; Kotsubo, V.; Schmidt, D.; Ullom, J.; Vale, L.; Cantor, R.

2012-06-01

334

Further insight into gravitational recoil  

SciTech Connect

We test the accuracy of our recently proposed empirical formula to model the recoil velocity imparted to the merger remnant of spinning, unequal-mass black-hole binaries. We study three families of black-hole binary configurations, all with mass ratio q=3/8 (to nearly maximize the unequal-mass contribution to the kick) and spins aligned (or counter-aligned) with the orbital angular momentum, two with spin configurations chosen to minimize the spin-induced tangential and radial accelerations of the trajectories, respectively, and a third family where the trajectories are significantly altered by spin-orbit coupling. We find good agreement between the measured and predicted recoil velocities for the first two families, and reasonable agreement for the third. We also reexamine our original generic binary configuration that led to the discovery of extremely large spin-driven recoil velocities and inspired our empirical formula, and find rough agreement between the predicted and measured recoil speeds.

Lousto, Carlos O.; Zlochower, Yosef [Center for Computational Relativity and Gravitation, School of Mathematical Sciences, Rochester Institute of Technology, 78 Lomb Memorial Drive, Rochester, New York 14623 (United States)

2008-02-15

335

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

336

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

337

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

338

Preparation and combustion properties of {alpha}-Fe{sub 2}O{sub 3} coated Zr particles  

SciTech Connect

Zirconium particles with irregular morphology and broad size distribution were uniformly coated by spherical {alpha}-Fe{sub 2}O{sub 3} crystal grain via a facile route without polymer or surfactant as directing agents. The synthesized {alpha}-Fe{sub 2}O{sub 3}/Zr composite particles were characterized by X-ray diffraction, scanning electron microscopy, energy dispersion X-ray, UV-vis spectroscopy and Raman spectroscopy. The synthesis mechanism could be explained by cooperated heterogeneous nucleation and solid state transformation reaction. The combustion properties of {alpha}-Fe{sub 2}O{sub 3}/Zr composite particles were investigated. Compared with Zr particles, the combustion lasting time decreased from 16 s of Zr particles to 0.13 s of {alpha}-Fe{sub 2}O{sub 3}/Zr composite particles, and the top point of temperature reached in combustion increased from 2004 deg. C of Zr particles to 2378 deg. C of {alpha}-Fe{sub 2}O{sub 3}/Zr particles.

Lv Baoliang [State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001 (China); Graduate University of the Chinese Academy of Sciences, Beijing 100039 (China); Xu Yao [State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001 (China)], E-mail: xuyao@sxicc.ac.cn; Hou Bo; Wu Dong; Sun Yuhan [State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001 (China)

2008-10-02

339

Phase relations and probabilities of alpha-particle formation in the surface region of even-even nuclei  

Microsoft Academic Search

The concept of the probability of formation Wc of alpha particles in the surface region of nuclei is used in a classification of alpha transitions of even-even deformed nuclei (226 <= A <= 254) to the first four levels of the ground-state rotational band of the daughter nuclei with allowance for coupling of the decay channels. The calculated values of

S. G. Kadmenskii; S. D. Kurgalin

1980-01-01

340

[Modification of the damaging effect of alpha-particles on Escherichia coli K-12 by low-intensity laser irradiation].  

PubMed

A study was made of the combined effect of laser (helium-neon laser, lambda = 633 nm) and alpha-radiation on survival of Escherichia coli K-12 cells of different genotypes. Pre- and post-irradiation exposures to laser-radiation diminished the damaging effect of alpha-particles. In the latter case, modification of survival was more pronounced. PMID:3526394

Voskanian, K Sh; Simonian, N V; Avakian, Ts M; Arutiunian, A G

341

A new mechanism for DNA alterations induced by alpha particles such as those emitted by radon and radon progeny.  

PubMed Central

The mechanism(s) by which alpha (alpha) particles like those emitted from inhaled radon and radon progeny cause their carcinogenic effects in the lung remains unclear. Although direct nuclear traversals by alpha-particles may be involved in mediating these outcomes, increasing evidence indicates that a particles can cause alterations in DNA in the absence of direct hits to cell nuclei. Using the occurrence of excessive sister chromatid exchanges (SCE) as an index of DNA damage in human lung fibroblasts, we investigated the hypothesis that alpha-particles may induce DNA damage through the generation of extracellular factors. We have found that a relatively low dose of alpha-particles can result in the generation of extracellular factors, which, upon transfer to unexposed normal human cells, can cause excessive SCE to an extent equivalent to that observed when the cells are directly irradiated with the same irradiation dose. A short-lived, SCE-inducing factor(s) is generated in alpha-irradiated culture medium containing serum in the absence of cells. A more persistent SCE-inducing factor(s), which can survive freeze-thaw and is heat labile is produced by fibroblasts after exposure to the alpha-particles. These results indicate that the initiating target for alpha-particle-induced genetic changes can be larger than a cell's nucleus or even a whole cell. How transmissible factors like those observed here in vitro may extend to the in vivo condition in the context of a-particle-induced carcinogenesis in the respiratory tract remains to be determined.

Lehnert, B E; Goodwin, E H

1997-01-01

342

Variation of luminescence decay in BaF2 crystal excited by electrons, alpha particles and fission fragments  

Microsoft Academic Search

The time dependence of the luminescence from BaF2 crystal excited by electrons, alpha particles and fission fragments has been studied for wavelengths of 180-400 nm by a single-photon counting technique. A (220 +\\/- 10) nm component with a lifetime of 0.88 ns is observed for electron and fission fragment excitation. No 220 nm component is observed for alpha particle excitation.

S. Kubota; M. Suzuki; F. Shiraishi; Y. Takami

1986-01-01

343

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

344

Selective Alpha-Particle Mediated Depletion of Tumor Vasculature with Vascular Normalization  

PubMed Central

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

Seshan, Surya V.; Kappel, Barry J.; Chattopadhyay, Debjit; May, Chad; McDevitt, Michael R.; Nolan, Daniel; Mittal, Vivek; Benezra, Robert; Scheinberg, David A.

2007-01-01

345

The limitations of associated alpha particle technique for contraband container inspections  

NASA Astrophysics Data System (ADS)

Inspection of a shipping container for the presence of the threat materials has been investigated in the laboratory by using a 14 MeV neutron beam, a BaF2 gamma detector and the associated alpha particle technique. The associated alpha particle technique is proposed as a part of a two sensor system for contraband container inspections. This method is effective in the reduction of background radiation with the possibility of collimating electronically the neutron beam. The intrinsic time resolution has been experimentally estimated to be 1.3 ns (FWHM), which allows inspection of a minimum voxel having 7 cm depth along the neutron flight path. The neutron beam intensity plays a crucial role as a limiting factor for the acquisition time reduction. Single counting rates of the gamma and alpha detector were investigated as a function of the neutron intensity, distance between the gamma detector and the neutron source and the type of shielding. The time and the energy spectra for different neutron intensities were evaluated.

Sudac, Davorin; Blagus, Sasa; Valkovic, Vladivoj

2007-10-01

346

Experimental detection of alpha-particles from the radioactive decay of natural bismuth.  

PubMed

The only naturally occurring isotope of bismuth, 209Bi, is commonly regarded as the heaviest stable isotope. But like most other heavy nuclei abundant in nature and characterized by an exceptionally long lifetime, it is metastable with respect to alpha-decay. However, the decay usually evades observation because the nuclear structure of 209Bi gives rise to an extremely low decay probability and, moreover, generates low-energy alpha-particles difficult to detect. Indeed, dedicated experiments attempting to record the alpha-decay of 209Bi in nuclear emulsions failed. However, scintillating bolometers operated at temperatures below 100 mK offer improved detection efficiency and sensitivity, whereas a broad palette of targets could be available. Here we report the successful use of this method for the unambiguous detection of 209Bi alpha-decay in bismuth germanate detectors cooled to 20 mK. We measure an energy release of 3,137 +/- 1 (statistical) +/- 2 (systematic) keV and a half-life of (1.9 +/- 0.2) x 10(19) yr, which are in agreement with expected values. PMID:12712201

de Marcillac, Pierre; Coron, Noël; Dambier, Gérard; Leblanc, Jacques; Moalic, Jean-Pierre

2003-04-24

347

Electron-hole pair generation in SiC high-temperature alpha particle detectors  

NASA Astrophysics Data System (ADS)

We demonstrate alpha-particle detection in an n-type 4H-SiC Schottky diode detector up to a temperature of 500 °C using an Am-241 disc source. The measured spectra were used to calculate the electron-hole pair creation energy in 4H-SiC and its non-bandgap contribution, which are both found to decrease with increasing temperature. The full width at half maximum (FWHM) of the measured alpha-energy peaks was found to increase exponentially with temperature due to an exponential increase of leakage current. For our measurement system, above 300 °C, where the leakage current was 10-6 A, this increase exceeded the FWHM at room temperature.

Garcia, Timothy R.; Kumar, Ashutosh; Reinke, Benjamin; Blue, Thomas E.; Windl, Wolfgang

2013-10-01

348

Measurement of high momentum transfer reactions by recoil detection  

Microsoft Academic Search

A method is described for studying reactions at medium energies by measuring the magnetic rigidity, time of flight, and energy loss of the resulting recoil products. The method works best for reactions with two-body final states where one of the outgoing particles is relatively light. A magnetic spectrometer with a special focal plane detector has been used. The detector consists

J. Homolka; W. Schott; W. Wagner; W. Wilhelm; R. D. Bent; M. Fatyga; R. E. Pollock; M. Saber; R. E. Segel; P. Kienle; K. E. Rehm

1987-01-01

349

WITCH:a recoil spectrometer for $\\\\beta$-decay  

Microsoft Academic Search

An experimental set-up is described for the precise measurement of the recoil energy spectrum of the daughter ions from nuclear beta decay. The experiment is called WITCH, short for Weak Interaction Trap for CHarged particles, and is set up at the ISOLDE facility at CERN. The principle of the experiment and its realization are explained as well as the main

M Beck; B J Delauré; V V Golovko; V Yu Kolzlov; I S Kraev; A Lindroth; T Phalet; P Schuurmans; N Severijns; B Vereecke; S Versyck; D Beck; W Quint; F Ames; G Bollen

2002-01-01

350

Energy distribution of ternary {alpha} particles in spontaneous fission of {sup 252}Cf  

SciTech Connect

The energy distribution of the ternary {alpha} particles in spontaneous fission of {sup 252}Cf was measured. For the first time an energy threshold as low as 1 MeV was reached. The experiment used an array of unshielded silicon detectors measuring energy and time-of-flight (TOF) of ternary particles in coincidence with fission fragments. The TOF resolution of the system was sufficient for clear separation of {sup 6}He and tritons from {sup 4}He. The statistics were adequate to extract the {sup 6}He/{sup 4}He yield ratio. For both {sup 4}He and {sup 6}He, an excess in the yield (as compared to a Gaussian shape) was observed at energies below 9 MeV. The measured ternary {alpha} spectrum was corrected for the distortion induced by the detection geometry covering equatorial particle emission only. The emission angle was found to affect mainly the width of the energy distribution by up to 1 MeV.

Mutterer, M.; Kalben, J. von [Institute of Nuclear Physics, University of Technology, Darmstadt (Germany); Kopatch, Yu. N. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Yamaledtinov, S. R.; Lyapin, V. G.; Sillanpaeae, M.; Trzaska, W. H. [Department of Physics, University of Jyvaeskylae, Jyvaeskylae (Finland); Khlebnikov, S. V.; Tyurin, G. P. [V. G. Khlopin Radium Institute, St. Petersburg (Russian Federation)

2008-12-15

351

Cytogenetic effects of extremely low doses of plutonium-238 alpha-particle irradiation in CHO K-1 cells.  

PubMed

CHO K-1 cells were irradiated during the G1 phase with 0.5-6 rad of alpha particles. There was no appreciable cell killing in this low dose range. Significantly increased frequencies of sister-chromatid exchanges were induced by doses as low as 0.5 rad of alpha-particle irradiation, whereas increased numbers of chromosomal aberrations were observed following exposure to 2 rad. These results suggest that very low doses of alpha radiation may lead to radiation-induced genetic alterations. PMID:2366817

Nagasawa, H; Little, J B; Inkret, W C; Carpenter, S; Thompson, K; Raju, M R; Chen, D J; Strniste, G F

1990-07-01

352

An alpha-particle irradiator for radiobiological research and its implementation for bystander effect studies.  

PubMed

An experimental system based on an improved version of an existing alpha-particle irradiator has been developed for radiobiological studies, in particular those investigating bystander effects. It consists of a 20-mm-diameter stainless steel chamber that can be equipped alternatively with 244Cm or 241Am sources of different activities. Mylar-based petri dishes 56 mm in diameter were specially designed to house adaptors for permeable membrane inserts that reproduce the geometry of commercial cell culture insert companion plates. Characterization of the radiation field at the cell level was performed by experimental measurements and calculations. The average incident LET was about 122 keV/microm for 244Cm and about 125 keV/microm for 241Am. Dose rates at the chosen source-sample distance were 2.8 and 88.6 mGy/min, respectively. These low dose rates are suitable for our planned experiments on low-dose effects. For both sources, the uniformity of the alpha-particle dose was better than +/-7%, and the photon dose calculated at the cell entrance was negligible compared to the alpha-particle dose. The irradiator is small enough to be inserted into a cell incubator for irradiation under physiological conditions or into a refrigerator to prevent metabolic processes during irradiation. Benchmark experiments using the 241Am source to examine DNA double-strand breaks in directly hit and bystander primary human fibroblasts have shown that the irradiator can be used successfully for bystander effect studies. PMID:19883232

Esposito, Giuseppe; Antonelli, Francesca; Belli, Mauro; Campa, Alessandro; Simone, Giustina; Sorrentino, Eugenio; Tabocchini, Maria Antonella

2009-11-01

353

Excited analog state of /sub. lambda. //sup 12/C and the alpha-particle model  

SciTech Connect

The idea that /sub ..lambda..//sup 12/C* is a strangeness analog state is examined using the alpha particle model. Volkov, Gillet, and Brink-Boeker potentials are used for the nucleon-nucleon and lambda-nucleon interactions, to calculate the binding energies of /sup 12/C and /sub ..lambda..//sup 12/C*. /sup 12/C is described by an equilateral triangle. When an allowance is made for the exchange character of the potentials used, the required potential strengths seem to be consistent with those obtained from low energy and light hypernuclear data, thus supporting the idea of a strangeness analog state.

Mukherjee, S.; Panchapakesan, N.

1982-10-01

354

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

355

Chemistry of rocks and soils in Gusev Crater from the alpha particle x-ray spectrometer.  

PubMed

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. PMID:15297665

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

356

Chemistry of rocks and soils at Meridiani Planum from the Alpha Particle X-ray Spectrometer.  

PubMed

The Alpha Particle X-ray Spectrometer on the Opportunity rover determined major and minor elements of soils and rocks in Meridiani Planum. Chemical compositions differentiate between basaltic rocks, evaporite-rich rocks, basaltic soils, and hematite-rich soils. Although soils are compositionally similar to those at previous landing sites, differences in iron and some minor element concentrations signify the addition of local components. Rocky outcrops are rich in sulfur and variably enriched in bromine relative to chlorine. The interaction with water in the past is indicated by the chemical features in rocks and soils at this site. PMID:15576611

Rieder, R; Gellert, 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

2004-12-01

357

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

358

Optical potentials for alpha particles on Ca isotopes at 1.37 GeV  

Microsoft Academic Search

A phenomenological optical-model analysis is performed for the elastic scattering of alpha particles on 40.42,44,48Ca at 1.37 GeV. Two geometries are considered for optical potentials, i.e., the traditional Woods-Saxon form and the double-Woods-Saxon form which can represent a change of the potential shape from the Woods-Saxon one. Among them, the best-fit potential has a ``Mexican-hat'' shape which is characterized by

M. Nakano; H. Matsuura; T. Maki; M. Matoba; H. Ohgaki

1989-01-01

359

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

360

Elevated sodium chloride concentrations enhance the bystander effects induced by low dose alpha-particle irradiation.  

PubMed

Previous studies have shown that high NaCl can be genotoxic, either alone or combined with irradiation. However, little is known about the relationship between environmental NaCl at elevated conditions and radiation-induced bystander effects (RIBE). RIBE, which has been considered as non-targeted bystander responses, has been demonstrated to occur widely in various cell lines. In the present study, RIBE under the elevated NaCl culture condition was assessed in AG 1522 cells by both the induction of gamma-H2AX, a reliable marker of DNA double-strand break (DSB) for the early process (<1h post irradiation), and the generation of micronuclei (MN), a sensitive marker for relative long process of RIBE. Our results showed that in the absence of irradiation, NaCl at elevated concentration such as 8.0, 9.0 and 10.0g/L did not significantly increase the frequency of gamma-H2AX foci-positive cells and the number of foci per positive cell comparing with that NaCl at a normal concentration (6.8g/L). However, with 0.2cGy alpha-particle irradiation, the induced fraction of gamma-H2AX foci-positive cells and the number of induced gamma-H2AX foci per positive cell were significantly increased in both irradiated and adjacent non-irradiated regions. Similarly, the induction of MN by 0.2cGy alpha-particle irradiation also increased with the elevated NaCl concentrations. With N(G)-methyl-l-arginine, an inhibitor of nitric oxide synthase, the induced fraction of foci-positive cells was effectively inhibited both in 0.2cGy alpha-particle irradiated and adjacent non-irradiated regions under either normal or elevated NaCl conditions. These results suggested that the cultures with elevated NaCl medium magnified the damage effects induced by the low dose alpha-particle irradiation and nitric oxide generated by irradiation was also very important in this process. PMID:17560616

Han, Wei; Zhu, Lingyan; Jiang, Erkang; Wang, Jun; Chen, Shaopeng; Bao, Linzhi; Zhao, Ye; Xu, An; Yu, Zengliang; Wu, Lijun

2007-05-05

361

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

362

Development of a He{sup 0} Source for Confined Alpha Particle Measurement  

SciTech Connect

A probing He{sup 0} beam for confined alpha particle measurement using a double charge exchange process is now under development. A proof of principle experiment for ground-state He{sup 0} beam production will be performed on a test stand. Several methods are developed to measure the metastable fraction of a He{sup 0} beam. A full-size strong-focusing He{sup +} source has been constructed and sufficient beam current was achieved with a beam size tolerable to be used on ITER.

Tanaka, N.; Kisaki, M.; Iwazaki, K.; Kikuchi, M.; Okamoto, A.; Kobuchi, T.; Shinto, K.; Kitajima, S.; Sasao, M. [Tohoku University, Sendai 980-8579 (Japan); Tsumori, K.; Kaneko, O. [National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan); Wada, M. [Doshisha University, Kyotanabe, Kyoto 610-0321 (Japan)

2008-03-12

363

Chemistry of Rocks and Soils at Meridiani Planum from the Alpha Particle X-ray Spectrometer  

NASA Astrophysics Data System (ADS)

The Alpha Particle X-ray Spectrometer on the Opportunity rover determined major and minor elements of soils and rocks in Meridiani Planum. Chemical compositions differentiate between basaltic rocks, evaporite-rich rocks, basaltic soils, and hematite-rich soils. Although soils are compositionally similar to those at previous landing sites, differences in iron and some minor element concentrations signify the addition of local components. Rocky outcrops are rich in sulfur and variably enriched in bromine relative to chlorine. The interaction with water in the past is indicated by the chemical features in rocks and soils at this site.

Rieder, R.; Gellert, 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.

2004-12-01

364

THE ROLE OF ALPHA PARTICLES IN THE EVOLUTION OF THE SOLAR-WIND TURBULENCE TOWARD SHORT SPATIAL SCALES  

SciTech Connect

We present a numerical study of the kinetic dynamics of protons and alpha particles during the evolution of the solar-wind turbulent cascade, in which the energy injected in large-scale slab-type Alfvenic fluctuations is transferred toward short spatial scale lengths, across the proton skin depth. We make use of a hybrid Vlasov-Maxwell code that integrates numerically the Vlasov equation for both the ion species, while the electrons are considered as a fluid. The system evolution is investigated in terms of different values of the electron to proton and alpha particle to proton temperature ratios. The numerical results show that the previously studied kinetic dynamics of protons is not strongly affected by the presence of alpha particles, at least when they are present in low concentration. Our simulations not only provide a physical explanation for the generation of beams of accelerated particles along the direction of the ambient magnetic field for both protons and alpha particles, but also show that this mechanism is more efficient for protons than for alpha particles, in agreement with recent solar-wind data analyses.

Perrone, D.; Valentini, F.; Veltri, P. [Dipartimento di Fisica and CNISM, Universita della Calabria, I-87030 Rende (Italy)

2011-11-01

365

Relative biological effectiveness of the alpha-particle emitter (211)At for double-strand break induction in human fibroblasts.  

PubMed

The purpose of this study was to quantify and to determine the distribution of DNA double-strand breaks (DSBs) in human cells irradiated in vitro and to evaluate the relative biological effectiveness (RBE) of the alpha-particle emitter (211)At for DSB induction. The influence of the irradiation temperature on the induction of DSBs was also investigated. Human fibroblasts were irradiated as intact cells with alpha particles from (211)At, (60)Co gamma rays and X rays. The numbers and distributions of DSBs were determined by pulsed-field gel electrophoresis with fragment analysis for separation of DNA fragments in sizes 10 kbp-5.7 Mbp. A non-random distribution was found for DSB induction after irradiation with alpha particles from (211)At, while irradiation with low-LET radiation led to more random distributions. The RBEs for DSB induction were 2.1 and 3.1 for (60)Co gamma rays and X rays as the reference radiation, respectively. In the experiments studying temperature effects, nuclear monolayers were irradiated with (211)At alpha particles or (60)Co gamma rays at 2 degrees C or 37 degrees C and intact cells were irradiated with (211)At alpha particles at the same temperatures. The dose-modifying factor (DMF(temp)) for irradiation of nuclear monolayers at 37 degrees C compared with 2 degrees C was 1.7 for (211)At alpha particles and 1.6 for (60)Co gamma rays. No temperature effect was observed for intact cells irradiated with (211)At. In conclusion, irradiation with alpha particles from (211)At induced two to three times more DSB than gamma rays and X rays. PMID:17316073

Claesson, Anna Kristina; Stenerlöw, Bo; Jacobsson, Lars; Elmroth, Kecke

2007-03-01

366

A Model of Nuclear Recoil Scintillation Efficiency in Noble Liquids  

NASA Astrophysics Data System (ADS)

Scintillation efficiency of low-energy nuclear recoils in noble liquids plays a crucial role in interpreting results from some direct searches for Weakly Interacting Massive Particle (WIMP) dark matter. However, the cause of a reduced scintillation efficiency relative to electronic recoils in noble liquids remains unclear at the moment. We attribute such a reduction of scintillation efficiency to two major mechanisms: 1) energy loss and 2) scintillation quenching. The former is commonly described by Lindhard's theory and the latter by Birk's saturation law. We propose to combine these two to explain the observed reduction of scintillation yield for nuclear recoils in noble liquids. Birk's constants kB for argon, neon and xenon determined from existing data are used to predict noble liquid scintillator's response to low-energy nuclear recoils and low-energy electrons. We find that energy loss due to nuclear stopping power that contributes little to ionization and excitation is the dominant reduction mechanism in scintillation efficiency for nuclear recoils, but that significant additional quenching results from the nonlinear response of scintillation to the ionization density.

Mei, Dongming; Yin, Zhongbao; Stonehill, Laura; Hime, Andrew

2008-10-01

367

A model of nuclear recoil scintillation efficiency in noble liquids  

NASA Astrophysics Data System (ADS)

Scintillation efficiency of low-energy nuclear recoils in noble liquids plays a crucial role in interpreting results from some direct searches for weakly interacting massive particle (WIMP) dark matter. However, the cause of a reduced scintillation efficiency relative to electronic recoils in noble liquids remains unclear at the moment. We attribute such a reduction of scintillation efficiency to two major mechanisms: (1) energy loss and (2) scintillation quenching. The former is commonly described by Lindhard's theory and the latter by Birk's saturation law. We propose to combine these two to explain the observed reduction of scintillation yield for nuclear recoils in noble liquids. Birk's constants kB for argon, neon and xenon determined from experimental data are used to predict noble liquid scintillator's response to low-energy nuclear recoils and low-energy electrons. We find that energy loss due to nuclear stopping power that contributes little to ionization and excitation is the dominant reduction mechanism in scintillation efficiency for nuclear recoils, but that significant additional quenching results from the nonlinear response of scintillation to the ionization density.

Mei, D.-M.; Yin, Z.-B.; Stonehill, L. C.; Hime, A.

2008-08-01

368

Median recoil direction as a WIMP directional detection signal  

SciTech Connect

Direct detection experiments have reached the sensitivity to detect dark matter weakly interacting massive particles (WIMPs). Demonstrating that a putative signal is due to WIMPs, and not backgrounds, is a major challenge, however. The direction dependence of the WIMP scattering rate provides a potential WIMP 'smoking gun'. If the WIMP distribution is predominantly smooth, the Galactic recoil distribution is peaked in the direction opposite to the direction of Solar motion. Previous studies have found that, for an ideal detector, of order 10 WIMP events would be sufficient to reject isotropy, and rule out an isotropic background. We examine how the median recoil direction could be used to confirm the WIMP origin of an anisotropic recoil signal. Specifically, we determine the number of events required to confirm the direction of solar motion as the median inverse recoil direction at 95% confidence. We find that for zero background 31 events are required, a factor of {approx}2 more than are required to simply reject isotropy. We also investigate the effect of a nonzero isotropic background. As the background rate is increased the number of events required increases, initially fairly gradually and then more rapidly, once the signal becomes subdominant. We also discuss the effect of features in the speed distribution at large speeds, as found in recent high resolution simulations, on the median recoil direction.

Green, Anne M. [School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom); Morgan, Ben [Department of Physics, University of Warwick, Coventry, CV4 7AL (United Kingdom)

2010-03-15

369

Nuclear astrophysics at the DRAGON recoil separator  

NASA Astrophysics Data System (ADS)

The DRAGON recoil separator facility at TRIUMF measures radiative alpha and proton capture reactions of astrophysical importance in inverse kinematics. This is done using radioactive and stable ion beams produced and accelerated using the ISAC (Isotope Separator and ACcelerator) facility in conjunction with a windowless gas target. Over the last few years, the DRAGON collaboration has embarked on a programme to measure a variety of reactions considered vital to the understanding of various astrophysical scenarios. An overview of DRAGON's separation, beam suppression, and detection capabilities will be given. In addition, examples of recent reaction cross section measurements will be discussed, such as the ^16O(?,?)^20Ne reaction, which plays an important part in the He-burning in massive stars.

Hager, Ulrike

2011-10-01

370

Semileptonic b decay at intermediate recoil  

SciTech Connect

We compute the O({alpha}{sub s}{sup 2}) corrections to the differential rate of the semileptonic decay b{yields}cl{nu}{sub l} at the 'intermediate recoil' point, where the c-quark mass and the invariant mass of the leptons are equal. The calculation is based on an expansion around two opposite limits of the quark masses m{sub b,c}: m{sub c}{approx_equal}m{sub b} and m{sub c}<

Dowling, Matthew; Pak, Alexey; Czarnecki, Andrzej [Department of Physics, University of Alberta, Edmonton, Alberta, T6G 2G7 (Canada)

2008-10-01

371

Review of Mathematics, Numerical Factors, and Corrections for Dark Matter Experiments Based on Elastic Nuclear Recoil.  

National Technical Information Service (NTIS)

We present a systematic derivation and discussion of the practical formulae needed to design and interpret direct searches for nuclear recoil events caused by hypothetical weakly interacting dark matter particles. Modifications to the differential energy ...

J. D. Lewin P. F. Smith

1996-01-01

372

p53 gene mutation analysis in tumors of patients exposed to alpha-particles.  

PubMed

The p53 gene was examined for point mutations in archived, alpha-radiation-associated lung and liver cancers. Lung tumors of 50 uranium miners in Germany were screened by restriction fragment length analysis for the putative hotspot mutation at codon 249 (Arg-->Met) previously detected in a significant fraction of miners from the Colorado Plateau, USA. This mutation has been proposed as a marker of radon exposure. None of the tumors we examined harbored the hotspot mutation. Five of the 50 tumors, however, did indeed harbor exon 7 mutations, as determined by subsequent mutation analysis of exon 7. These mutations were dispersed among various codons and may be attributable to heavy tobacco smoking in this cohort. In support of this interpretation, we found no mutations in exons 5-8 of the p53 gene in 13 iatrogenic liver cancers induced by injection of Thorotrast, an alpha-emitting radiocontrast agent. We propose that if the p53 tumor suppressor gene is a target for the carcinogenic action of alpha-particle radiation, loss of suppressor function may occur preferentially by mechanisms such as intrachromosomal deletions, rather than by base substitution mutations. PMID:9067550

Hollstein, M; Bartsch, H; Wesch, H; Kure, E H; Mustonen, R; Mühlbauer, K R; Spiethoff, A; Wegener, K; Wiethege, T; Müller, K M

1997-03-01

373

Effects of alpha particle radiation on gene expression in human pulmonary epithelial cells.  

PubMed

The general public receives approximately half of its exposure to natural radiation through alpha (?)-particles from radon ((222)Rn) gas and its decay progeny. Epidemiological studies have found a positive correlation between exposure to (222)Rn and lung carcinogenesis. An understanding of the transcriptional responses involved in these effects remains limited. In this study, genomic technology was employed to mine for subtle changes in gene expression that may be representative of an altered physiological state. Human lung epithelial cells were exposed to 0, 0.03, 0.3 and 0.9Gy of ?-particle radiation. Microarray analysis was employed to determine transcript expression levels 4h and 24h after exposure. A total of 590 genes were shown to be differentially expressed in the ?-particle radiated samples (false discovery rate (FDR)?0.05). Sub-set of these transcripts were time-responsive, dose-responsive and both time- and dose-responsive. Pathway analysis showed functions related to cell cycle arrest, and DNA replication, recombination and repair (FDR?0.05). The canonical pathways associated with these genes were in relation to pyrimidine metabolism, G2/M damage checkpoint regulation and p53 signaling (FDR?0.05). Overall, this gene expression profile suggests that ?-particle radiation inhibits DNA synthesis and subsequent mitosis, and causes cell cycle arrest. PMID:22608759

Chauhan, Vinita; Howland, Matthew; Mendenhall, Amy; O'Hara, Shifawn; Stocki, Trevor J; McNamee, James P; Wilkins, Ruth C

2012-05-17

374

Biological effects of alpha particle radiation exposure on human monocytic cells.  

PubMed

Radon ((222)Rn) gas produces decay progeny that emits high energy alpha (?)-particles. Epidemiological studies have shown that exposure to (222)Rn is linked with elevated risk of developing lung cancer, however clear mechanisms leading to such effects have not been delineated. Cytokines play a critical role in inflammation and their dysregulated production often contributes to disease pathogenesis. In this study, Bio-plex multiplex technology was employed to investigate modulations of 27 pro-inflammatory cytokines following exposure of human monocytic cells to 1.5 Gy of ?-particle radiation. Concurrently, DNA damage was assessed by examining the formation of phosphorylated H2A histone family X (?-H2AX) sites. Of the 27 cytokines assessed, 4 cytokines were shown to be statistically downregulated by ?2 fold relative to the untreated controls and included the interleukin (IL) family of proteins (IL-2, IL-15 and IL-17) and macrophage inflammatory protein 1 beta (MIP-1b). Interferon-inducible protein-12 (IP-12), vascular endothelial growth factor and regulated on activation normal T cell expressed and secreted (RANTES) were shown to be high expressors and upregulated. Cells irradiated with ?-particles ranging from 0.27 to 2.14 Gy showed statistically significant, dose-dependant increases in ?-H2AX formation. These data suggest that ?-particle radiation causes dysregulation in the production of a number of pro-inflammatory cytokines and results in significant DNA damage. PMID:22153871

Chauhan, Vinita; Howland, Matthew; Kutzner, Barbara; McNamee, James P; Bellier, Pascale V; Wilkins, Ruth C

2011-12-06

375

Differential Effects of Alpha-Particle Radiation and X-Irradiation on Genes Associated with Apoptosis  

PubMed Central

This study examined differential effects of alpha-(?-) particle radiation and X-rays on apoptosis and associated changes in gene expression. Human monocytic cells were exposed to ?-particle radiation and X-rays from 0 to 1.5?Gy. Four days postexposure, cell death was measured by flow cytometry and 84 genes related to apoptosis were analyzed using real-time PCR. On average, 33% of the cells were apoptotic at 1.5?Gy of ?-particle radiation. Transcript profiling showed statistical expression of 15 genes at all three doses tested. Cells exposed to X-rays were <5% apoptotic at ~1.5?Gy and induced less than a 2-fold expression in 6 apoptotic genes at the higher doses of radiation. Among these 6 genes, Fas and TNF-? were common to the ?-irradiated cells. This data suggests that ?-particle radiation initiates cell death by TNF-? and Fas activation and through intermediate signalling mediators that are distinct from X-irradiated cells.

Chauhan, Vinita; Howland, Matthew; Chen, Jeremy; Kutzner, Barbara; Wilkins, Ruth C.

2011-01-01

376

Partition of thorium between organs of monkeys injected with thorotrast: implications for alpha-particle dosimetry.  

PubMed

Risk estimates for alpha-particle-induced malignancies have been based mainly on studies of Thorotrast patients, but certain aspects of its deposition in the body have been at issue: the partition between the liver, spleen and red bone marrow, and the deposition at lower concentrations in other organs, such as muscle and fat, which may contribute to the risk. To supplement the existing data for humans, thorium concentrations were measured in the organs of two female monkeys 3-4 years after injection with Thorotrast. Relative deposits (liver:spleen:red bone marrow) were 54:6:41 and 75:4:21, in better agreement with the most recent observations in Thorotrast patients than with previous reports. Whereas the human testis had ranked among intermediate-level organs such as the adrenal glands and pancreas, the ovary of the monkey was among the organs with the lowest concentrations. The data suggest that risk factors for induction of malignancies by alpha-particle irradiation should be re-examined. PMID:9728666

Ishikawa, Y; Humphreys, J A; Wesch, H; Priest, N D

1998-09-01

377

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

378

Possible observation of light neutron nuclei in the alpha-particle-induced fission of 238U  

NASA Astrophysics Data System (ADS)

Searches for nuclear-stable multineutrons among products originating from the fission of 238U nuclei that is induced by 62-MeV alpha particles were performed by the activation method. The reaction involving the transfer of four neutrons and occurring on the isotope 88Sr, 88Sr( x n, ( x - 4) n)92Sr?92Y, was used to identify nuclear-stable multineutrons. A line at the energy of E = 1384 keV was found in the measured gamma-ray spectra of irradiated samples. This line, together with the measured time dependence of the decrease in its activity, is indicative of the formation of the beta-active nucleus 92Sr. This result was reproduced in repeated measurements. It suggests the possible existence of nuclear-stable multineutrons ( x n) for x ? 6. The differential cross section for the x n yield at an angle of 30° in the alpha-particle-induced fission of 238U was about 6 × 10-2 mb/sr.

Novatsky, B. G.; Nikolsky, E. Yu.; Sakuta, S. B.; Stepanov, D. N.

2012-11-01

379

Monte-Carlo dosimetry on a realistic cell monolayer geometry exposed to alpha particles.  

PubMed

The energy and specific energy absorbed in the main cell compartments (nucleus and cytoplasm) in typical radiobiology experiments are usually estimated by calculations as they are not accessible for a direct measurement. In most of the work, the cell geometry is modelled using the combination of simple mathematical volumes. We propose a method based on high resolution confocal imaging and ion beam analysis (IBA) in order to import realistic cell nuclei geometries in Monte-Carlo simulations and thus take into account the variety of different geometries encountered in a typical cell population. Seventy-six cell nuclei have been imaged using confocal microscopy and their chemical composition has been measured using IBA. A cellular phantom was created from these data using the ImageJ image analysis software and imported in the Geant4 Monte-Carlo simulation toolkit. Total energy and specific energy distributions in the 76 cell nuclei have been calculated for two types of irradiation protocols: a 3 MeV alpha particle microbeam used for targeted irradiation and a ²³?Pu alpha source used for large angle random irradiation. Qualitative images of the energy deposited along the particle tracks have been produced and show good agreement with images of DNA double strand break signalling proteins obtained experimentally. The methodology presented in this paper provides microdosimetric quantities calculated from realistic cellular volumes. It is based on open-source oriented software that is publicly available. PMID:22456322

Barberet, Ph; Vianna, F; Karamitros, M; Brun, T; Gordillo, N; Moretto, Ph; Incerti, S; Seznec, H

2012-03-29

380

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

381

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

382

Targeted cytoplasmic irradiation with alpha particles induces mutations in mammalian cells  

PubMed Central

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.

1999-01-01

383

Systematics of pre- and near-scission {alpha}-particle multiplicities in heavy-ion-induced fusion-fission reactions  

SciTech Connect

The {alpha}-particle energy spectra have been measured in coincidence with fission fragments over a wide range of relative angles with respect to fragment emission direction in the {sup 11}B (62 MeV) + {sup 232}Th reaction. The {alpha}-particle multiplicity spectra have been fitted with moving source model to extract the precision ({alpha}{sub pre}) and near-scission ({alpha}{sub nse}) components. The present results, along with available data from the literature over a wide range of Z{sup 2}/A and the excitation energy of a compound system, have been analyzed to develop certain global features of the pre- and near-scission emission characteristics. It is seen that {alpha}{sub pre} values when normalized to E{sub CN}{sup 2.3} (E{sub CN} is the compound nucleus excitation energy) show a systematic linearly increasing trend with the {alpha}-particle emission Q value (Q{sub {alpha}}). The fraction of near-scission multiplicity is observed to be nearly the same at around 10% of the total precision multiplicity for all the systems.

Gupta, Y. K.; Biswas, D. C.; Choudhury, R. K.; Saxena, A.; Nayak, B. K.; John, Bency; Ramachandran, K.; Thomas, R. G.; Danu, L. S.; Joshi, B. N.; Mahata, K.; Pandit, S. K.; Chatterjee, A. [Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)

2011-09-15

384

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 dUTP Nick-End Labeling (TUNEL) fluorescence method employed to detect DNA strand breaks. The staining results were investigated by flow cytometer. The preliminary results showed that more strand breaks occurred in cells hit by alpha particles with lower energies. Moreover, large TUNEL positive signals were obtained even with small percentages of cells irradiated and TUNEL signals were also obtained from non-targeted cells. These provided evidence for the bystander effect.

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

2007-08-01

385

Mass and energy dispersive recoil spectrometry of GaAs structures.  

National Technical Information Service (NTIS)

Mass and energy dispersive Recoil Spectrometry (RS) using heavy ions at energies of about 0.2(Alpha)-0.8(Alpha) MeV has attracted much interest recently due to its potential for separately and unambiguously generating information on isotopic depth distrib...

M. Hult

1994-01-01

386

The compound factor of the 10B(n,alpha)7Li reaction from borocaptate sodium and the relative biological effectiveness of recoil protons for induction of brain damage in boron neutron capture therapy.  

PubMed

To make clinical trials of boron neutron capture therapy safe for patients, it is necessary to know the relative biological effectiveness (RBE) of the radiation components and the compound factor of the boron carrier to be used. Here a method is derived to determine the RBE of recoil protons and the compound factor of compounds from in vivo experiments with different concentrations of boron. The method uses a simultaneous fit of both these parameters to all experimental data. This method is applied to the studies of tolerance of healthy tissue in dogs at the High Flux Reactor in Petten, The Netherlands. The RBE for the recoil protons generated by the neutrons present in the epithermal neutron beam [together with the RBE of the protons from the 14N(n,p)14C reaction] for induction of severe neurological symptoms was found to be 3.93+/-0.43 (95% confidence limits 3.06-4.79), and 2.33+/-0.14 (2.04-2.61) for induction of changes detectable by magnetic resonance imaging. The compound factor for Na2B12H11SH in brain tissue, using severe neurological symptoms as end point, was determined to be 0.37+/-0.06 (95% confidence limits 0.24-0.50). For changes detectable by magnetic resonance imaging, the value was found to be 0.65+/-0.04 (0.58-0.73). PMID:9525503

Gabel, D; Philipp, K H; Wheeler, F J; Huiskamp, R

1998-04-01

387

Radiative-recoil corrections to hyperfine splitting: Polarization insertions in the muon factor  

SciTech Connect

We consider three-loop radiative-recoil corrections to hyperfine splitting in muonium due to insertions of a one-loop polarization operator in the muon factor. The contribution produced by electron polarization insertions is enhanced by the large logarithm of the electron-muon mass ratio. We obtained all single-logarithmic and nonlogarithmic radiative-recoil corrections of order {alpha}{sup 3}(m/M)E{sub F} generated by the diagrams with electron and muon polarization insertions.

Eides, Michael I.; Shelyuto, Valery A. [Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506 (United States); D. I. Mendeleev Institute of Metrology, St. Petersburg 190005 (Russian Federation)

2009-09-01

388

Quantum recoil and Bohm diffusion  

SciTech Connect

It is argued that the inclusion of the Bohm potential in quantum fluid equations is equivalent to inclusion of a nonrelativistic form of the quantum recoil in plasma kinetic theory. The Bohm term is incorrect when applied to waves with phase speed greater than the speed of light.

Melrose, D. B.; Mushtaq, A. [School of Physics, University of Sydney, Sydney, New South Wales 2006 (Australia)

2009-09-15

389

Rubber band recoil in fluids  

Microsoft Academic Search

The recoil of a stretched rubber band is a familiar phenomenon which does not last for more than a millisecond. When an initially stretched rubber band is released at one end, a front leaving behind it stress-free elastic material propagates towards the clamped end. Its rebound results in a compression front propagating backwards, which triggers an elastic instability referred to

Romain Vermorel

2005-01-01

390

Confined alpha particle diagnostics for ITER based on measurements of gamma rays emitted from D({alpha},{gamma}){sup 6}Li reaction  

SciTech Connect

For the diagnosis of confined alpha particles in D-T plasma, we propose the observation of 2.186 MeV gamma ray produced by D({alpha},{gamma}){sup 6}Li reaction. However, there are few nuclear data of the D({alpha},{gamma}){sup 6}Li reaction rate. Therefore, we carried out the experimental verification of the gamma ray diagnostics technique by using an accelerator. Helium ions in the energy range of 2-4 MeV were bombarded into a thick deuterated polyethylene, where the gamma ray spectrum was measured with a Ge detector. Photopeak of the 2.186 MeV gamma ray was clearly observed. From our experiment, the emission rate of the 2.186 MeV gamma ray from the D({alpha},{gamma}){sup 6}Li reaction is estimated to be 10{sup 12}-10{sup 13} s{sup -1} in the ITER typical plasma condition. So we obtained a good prospect of the gamma ray measurement as the confined alpha particle diagnostics by using a high efficiency detector.

Ochiai, K.; Kubota, N.; Taniike, A.; Kitamura, A.; Nishitani, T. [Directorates of Fusion Energy Research, Japan Atomic Energy Agency, 2-4 Shirakata-Shirane-Tokai, Ibaraki 319-1195 (Japan); Department of Environmental Energy Science, Faculty of Maritime Sciences, Kobe University, 5-1-1 Fukaeminami-machi, Higashinada-ku, Kobe 658-0022 (Japan); Directorates of Fusion Energy Research, Japan Atomic Energy Agency, 2-4 Shirakata-Shirane-Tokai, Ibaraki 319-1195 (Japan)

2006-10-15

391

Synchrotron-radiation experiments with recoil ions  

SciTech Connect

Studies of atoms, ions and molecules with synchrotron radiation have generally focused on measurements of properties of the electrons ejected during, or after, the photoionization process. Much can also be learned, however, about the atomic or molecular relaxation process by studies of the residual ions or molecular fragments following inner-shell photoionization. Measurements are reported of mean kinetic energies of highly charged argon, krypton, and xenon recoil ions produced by vacancy cascades following inner-shell photoionization using white and monochromatic synchrotron x radiation. Energies are much lower than for the same charge-state ions produced by charged-particle impact. The results may be applicable to design of future angle-resolved ion-atom collision experiments. Photoion charge distributions are presented and compared with other measurements and calculations. Related experiments with synchrotron-radiation produced recoil ion, including photoionization of stored ions and measurement of shakeoff in near-threshold excitation, are briefly discussed. 24 refs., 6 figs., 1 tab.

Levin, J.C.

1989-01-01

392

Study of excitation functions of alpha-particle induced nuclear reactions on holmium for 167Tm production.  

PubMed

(167)Tm is a candidate radioisotope for both nuclear medicine diagnostics and therapy due to its emitted Auger-electrons, low energy X- and gamma-rays. In the frame of a systematic study of excitation functions for production of medically relevant radioisotopes by charged particle induced reactions on rare earths, the (165)Ho(alpha,2n)(167)Tm reaction and the (165)Ho(alpha,n)(168)Tm, (165)Ho(alpha,3n)(166)Tm, (165)Ho(alpha,4n)(165)Tm side reactions were measured up to 40 MeV by the stacked foil irradiation technique and gamma-ray spectroscopy. The measured results were compared to the ALICE-IPPE and EMPIRE-II theoretical curves. Thick target yields, impurity levels and specific activities were deduced and compared with the same parameters for other charged particle production routes of (167)Tm. PMID:20022515

Tárkányi, F; Hermanne, A; Király, B; Takács, S; Ignatyuk, A V

2009-12-01

393

First detection and energy measurement of recoil ions following beta decay in a Penning trap with the WITCH experiment  

NASA Astrophysics Data System (ADS)

The WITCH experiment (Weak Interaction Trap for CHarged particles) will search for exotic interactions by investigating the ? - ? angular correlation via the measurement of the recoil energy spectrum after ? -decay. As a first step the recoil ions from the ?-_{} -decay of 124In stored in a Penning trap have been detected. The evidence for the detection of recoil ions is shown and the properties of the ion cloud that forms the radioactive source for the experiment in the Penning trap are presented.

Beck, M.; Coeck, S.; Kozlov, V. Yu.; Breitenfeldt, M.; Delahaye, P.; Friedag, P.; Glück, F.; Herbane, M.; Herlert, A.; Kraev, I. S.; Mader, J.; Tandecki, M.; Van Gorp, S.; Wauters, F.; Weinheimer, Ch.; Wenander, F.; Severijns, N.

2011-03-01

394

Transcriptional and secretomic profiling of epidermal cells exposed to alpha particle radiation.  

PubMed

Alpha (?)-particle emitters are probable isotopes to be used in a terrorist attack. The development of biological assessment tools to identify those who have handled these difficult to detect materials would be an asset to our current forensic capacity. In this study, for the purposes of biomarker discovery, human keratinocytes were exposed to ?-particle and X-radiation (0.98 Gy/h at 0, 0.5, 1.0, 1.5 Gy) and assessed for differential gene and protein expression using microarray and Bio-Plex technology, respectively. Secretomic analysis of supernatants showed expression of two pro-inflammatory cytokines (IL-13 and PDGF-bb) to be exclusively affected in ?-particle exposed cells. The highest dose of ?-particle radiation modulated a total of 67 transcripts (fold change>|1.5|, (False discovery rate) FDR<0.05) in exposed cells. Several genes which responded with high expression levels (>2 fold) included KIF20A, NEFM, C7orf10, HIST1H2BD, BMP6, and HIST1H2AC. Among the high expressing genes, five (CCNB2, BUB1, NEK2, CDC20, AURKA) were also differentially expressed at the medium (1.0 Gy) dose however, these genes were unmodulated following exposure to X-irradiation. Networks of these genes clustered around tumor protein-53 and transforming growth factor-beta signaling. This study has identified some potential gene /protein responses and networks that may be validated further to confirm their specificity and potential to be signature biomarkers of ?-particle exposure. PMID:23002402

Chauhan, Vinita; Howland, Matthew; Greene, Hillary Boulay; Wilkins, Ruth C

2012-09-07

395

Transcriptional and Secretomic Profiling of Epidermal Cells Exposed to Alpha Particle Radiation  

PubMed Central

Alpha (?)-particle emitters are probable isotopes to be used in a terrorist attack. The development of biological assessment tools to identify those who have handled these difficult to detect materials would be an asset to our current forensic capacity. In this study, for the purposes of biomarker discovery, human keratinocytes were exposed to ?-particle and X-radiation (0.98 Gy/h at 0, 0.5, 1.0, 1.5 Gy) and assessed for differential gene and protein expression using microarray and Bio-Plex technology, respectively. Secretomic analysis of supernatants showed expression of two pro-inflammatory cytokines (IL-13 and PDGF-bb) to be exclusively affected in ?-particle exposed cells. The highest dose of ?-particle radiation modulated a total of 67 transcripts (fold change>|1.5|, (False discovery rate) FDR<0.05) in exposed cells. Several genes which responded with high expression levels (>2 fold) included KIF20A, NEFM, C7orf10, HIST1H2BD, BMP6, and HIST1H2AC. Among the high expressing genes, five (CCNB2, BUB1, NEK2, CDC20, AURKA) were also differentially expressed at the medium (1.0 Gy) dose however, these genes were unmodulated following exposure to X-irradiation. Networks of these genes clustered around tumor protein-53 and transforming growth factor-beta signaling. This study has identified some potential gene /protein responses and networks that may be validated further to confirm their specificity and potential to be signature biomarkers of ?-particle exposure.

Chauhan, Vinita; Howland, Matthew; Greene, Hillary Boulay; Wilkins, Ruth C

2012-01-01

396

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

SciTech Connect

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

Siemssen, R.H.

1985-01-01

397

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

Microsoft Academic Search

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

W. Raab; J. L. Parus

1994-01-01

398

Design, spectrum measurements and simulations for a 238Pu alpha-particle irradiator for bystander effect and genomic instability experiments.  

PubMed

Design, spectrum measurements and simulations for an alpha-particle irradiator for bystander effect and genomic instability experiments are presented. Measured alpha-particle energy spectra were used to confirm the characteristics of the source of the irradiator specified by the manufacturer of the source. The spectra were measured in vacuum with a high-resolution spectrometer and simulated with an AASI Monte Carlo code. As a next step, we simulated alpha-particle energy spectra at the target plane of the irradiator for three different source-to-target distances. In these simulations, helium was used as the medium between the source and the exit window of the irradiator; its pressure and temperature corresponded to those of the ambient air. Mean energies and full-widths at half-maximum (FWHM) were calculated for the three different helium gas tracks. PMID:16618543

Hakanen, Arvi; Siiskonen, Teemu; Pöllänen, Roy; Kosunen, Antti; Turunen, Asko; Belyakov, Oleg

2006-04-18

399

A 244Cm irradiator for protracted exposure of cultured Mammalian cells with alpha particles.  

PubMed

A 244Cm alpha-particle irradiator was designed and constructed for radiobiological studies where protracted exposure at a low dose rate of cultured mammalian cells is required. It allows irradiation of a cell monolayer attached to the Mylar bottom of a specially designed Petri dish of 56 mm diameter (approximately 25 cm(2) area). The irradiator is based on a 20-mm-diameter stainless steel chamber containing a 148 kBq 244Cm source. The chamber, flushed with helium gas at a pressure kept slightly above the external pressure, is inserted into a cell incubator where temperature and CO2 concentration are controlled. Spectrometric and dosimetric characterization of the irradiator was carried out by means of an ion-implanted-silicon charged-particle detector, CR39 detectors, and Monte Carlo simulations with the TRIM code. Average LET of particles incident on the cells at the center of the Petri dish was evaluated to be 120 keV microm(-1) at 59 mm from the source, and the average dose rate was 5.69 x 10 Gy s(-1), with +12% and -8% variations at the center and the edge, respectively. The irradiator has been successfully tested and used for several experiments involving 16-d exposure of human fibroblasts monolayers. PMID:16340609

Esposito, G; Belli, M; Simone, G; Sorrentino, E; Tabocchini, M A

2006-01-01

400

Complementary optical-potential analysis of {alpha}-particle elastic scattering and induced reactions at low energies  

SciTech Connect

A previously derived semi-microscopic analysis based on the Double Folding Model, for {alpha}-particle elastic scattering on A{approx}100 nuclei at energies below 32 MeV, is extended to medium mass A{approx}50-120 nuclei and energies from {approx}13 to 50 MeV. The energy-dependent phenomenological imaginary part for this semi-microscopic optical model potential was obtained including the dispersive correction to the microscopic real potential, and used within a concurrent phenomenological analysis of the same data basis. A regional parameter set for low-energy {alpha}-particles entirely based on elastic scattering data analysis was also obtained for nuclei within the above mentioned mass and energy ranges. Then, an ultimate assessment of ({alpha},{gamma}), ({alpha},n), and ({alpha},p) reaction cross sections considered target nuclei from {sup 45}Sc to {sup 118}Sn and incident energies below {approx}12 MeV. The former diffuseness of the real part of optical potential as well as the surface imaginary potential depth have been found to be responsible for the actual difficulties in the description of these data, and modified in order to obtain an optical potential which describes equally well both the low-energy elastic scattering and induced reaction data for {alpha}-particles.

Avrigeanu, M. ['Horia Hulubei' National Institute for Physics and Nuclear Engineering, P.O. Box MG-6, 76900 Bucharest (Romania)], E-mail: mavrig@ifin.nipne.ro; Obreja, A.C.; Roman, F.L.; Avrigeanu, V. ['Horia Hulubei' National Institute for Physics and Nuclear Engineering, P.O. Box MG-6, 76900 Bucharest (Romania); Oertzen, W. von [Freie Universitaet Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin (Germany); Hahn-Meitner-Institut, Glienicker Strasse 100, 14109 Berlin (Germany)

2009-07-15

401

Cancer Stem Cell Targeting Using the Alpha-Particle Emitter, 213Bi: Mathematical Modeling and Feasibility Analysis  

PubMed Central

There is increasing recognition that treatment failure in cancer may be associated with the failure to sterilize a small subpopulation of tumor cells that have been characterized as tumor stem cells. Defined as cells that are able to self-renew and also to replenish a phenotypically diverse tumor-cell population, such cells are also considered resistant to chemotherapy. These characteristics are optimal for targeting by using alpha-particle-emitting radionuclides. Because of their high-energy deposition density per track, alpha-particles are capable of targeting single cells or small clusters of cells with minimal normal organ toxicity. The DNA damage induced by alpha-particles is largely irreparable and, therefore, alpha-particle-induced damage is minimally susceptible to resistance mechanisms. In this work, theoretical modeling was performed to examine the potential of alpha-emitter targeting of such small clusters of cancer stem cells. Critical parameters influencing efficacy and toxicity were identified and their relationship elucidated. The results identify specific activity, antigen site density, and number of target cells as critical parameters for effective cell killing and demonstrate substantial efficacy gains by targeting a smaller number of stem cells, as opposed to the entire tumor-cell population.

Sgouros, George; Song, Hong

2010-01-01

402

Fission time scale from prescission neutron, proton, and {alpha} particle multiplicities in {sup 28}Si+{sup 175}Lu  

SciTech Connect

Prescission neutron, proton, and {alpha}-particle multiplicities for the reaction {sup 28}Si+{sup 175}Lu at 159 MeV were measured simultaneously. The multiplicity data were analyzed using deformation dependent particle transmission coefficients, binding energies, and level densities to extract fission time scales and the mean deformation of the saddle-to-scission emitter. The neutron and charged particle data could be explained consistently, a better fit being obtained by considering the emission of neutrons to be favored toward larger deformation as compared to charged particles. The total fission time scale is deduced as 36-41x10{sup -21}s.

Ramachandran, K.; Chatterjee, A.; Navin, A.; Mahata, K.; Shrivastava, A.; Tripathi, V.; Kailas, S.; Saxena, A.; Thomas, R.G.; Kumar, Suresh; Sahu, P.K. [Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Nanal, V.; Pillay, R.G. [Department of Nuclear and Atomic Physics, T.I.F.R, Colaba, Mumbai 400 005 (India)

2006-06-15

403

Results from the Lunar Prospector Alpha Particle Spectrometer: Detection of Radon222 Over Craters Aristarchus and Kepler  

Microsoft Academic Search

The Lunar Prospector Alpha Particle Spectrometer (LP APS) searched for lunar surface gas release events and mapped their distribution by detecting alpha particles produced by the decay of gaseous radon-222 (5.5 MeV, 3.8 day half-life), solid polonium-218 (6.0 MeV, 3 minute half-life), and solid polonium-210 (5.3 MeV, 138 day half-life, but held up in production by the 21 year half-life

S. L. Lawson; W. C. Feldman; D. J. Lawrence; K. R. Moore; R. D. Belian; S. Maurice; A. B. Binder

2001-01-01

404

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

405

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

406

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

407

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

408

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

NASA Astrophysics Data System (ADS)

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.

1988-07-01

409

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

410

Propagation distance of the alpha-particle-induced bystander effect: the role of nuclear traversal and gap junction communication.  

PubMed

When cell populations are exposed to low-dose alpha-particle radiation, a significant fraction of the cells will not be traversed by a radiation track. However, stressful effects occur in both irradiated and bystander cells in the population. Characterizing these effects, and investigating their underlying mechanism(s), is critical to understanding human health risks associated with exposure to alpha particles. To this end, confluent normal human fibroblast cultures were grown on polyethylene terephthalate foil grafted to an ultrathin solid-state nuclear track detector and exposed under non-perturbing conditions to low-fluence alpha particles from a broadbeam irradiator. Irradiated and affected bystander cells were localized with micrometer precision. The stress-responsive protein p21(Waf1) (also known as CDKN1A) was induced in bystander cells within a 100-microm radius from an irradiated cell. The mean propagation distance ranged from 20 to 40 microm around the intranuclear alpha-particle impact point, which corresponds to a set of approximately 30 cells. Nuclear traversal, induced DNA damage, and gap junction communication were critical contributors to propagation of this stressful effect. The strategy described here may be ideal to investigate the size of radiation-affected target and the relative contribution of different cellular organelles to bystander effects induced by energetic particles, which is relevant to radioprotection and cancer radiotherapy. PMID:19580486

Gaillard, Sylvain; Pusset, David; de Toledo, Sonia M; Fromm, Michel; Azzam, Edouard I

2009-05-01

411

Renal tubulointerstitial changes after internal irradiation with alpha-particle-emitting actinium daughters.  

PubMed

The effect of external gamma irradiation on the kidneys is well described. However, the mechanisms of radiation nephropathy as a consequence of targeted radionuclide therapies are poorly understood. The functional and morphologic changes were studied chronologically (from 10 to 40 wk) in mouse kidneys after injection with an actinium-225 (225Ac) nanogenerator, a molecular-sized, antibody-targeted, in vivo generator of alpha-particle-emitting elements. Renal irradiation from free, radioactive daughters of 225Ac led to time-dependent reduction in renal function manifesting as increase in blood urea nitrogen. The histopathologic changes corresponded with the decline in renal function. Glomerular, tubular, and endothelial cell nuclear pleomorphism and focal tubular cell injury, lysis, and karyorrhexis were observed as early as 10 wk. Progressive thinning of the cortex as a result of widespread tubulolysis, collapsed tubules, glomerular crowding, decrease in glomerular cellularity, interstitial inflammation, and an elevated juxtaglomerular cell count were noted at 20 to 30 wk after treatment. By 35 to 40 wk, regeneration of simplified tubules with tubular atrophy and loss with focal, mild interstitial fibrosis had occurred. A lower juxtaglomerular cell count with focal cytoplasmic vacuolization, suggesting increased degranulation, was also observed in this period. A focal increase in tubular and interstitial cell TGF-beta1 expression starting at 20 wk, peaking at 25 wk, and later declining in intensity with mild increase in the extracellular matrix deposition was noticed. These findings suggest that internally delivered alpha-particle irradiation-induced loss of tubular epithelial cells triggers a chain of adaptive changes that result in progressive renal parenchymal damage accompanied by a loss of renal function. These findings are dissimilar to those seen after gamma or beta irradiation of kidneys. PMID:15987754

Jaggi, Jaspreet Singh; Seshan, Surya V; McDevitt, Michael R; LaPerle, Krista; Sgouros, George; Scheinberg, David A

2005-06-29

412

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

413

Alignment of atomic inner-shells following alpha-decay-induced ionization  

NASA Astrophysics Data System (ADS)

Nuclear alpha decay may induce the emission of electrons originally bound to the nucleus. If the ejected electron initially resides in a state with the total angular momentum j > 1/2, the residual ion may be aligned. In this theoretical analysis, we pay particular attention to the alignment following LIII shell ionization. Focus has also been given to the effects of shake-off, recoil and nuclear potential screening. To illustrate these effects, we have performed calculations on neutral atoms of 210Po and 228Th nuclei, subject to their respective alpha decay, over a range of commonly encountered alpha particle kinetic energies (epsilon? ~ O(10?MeV)).

McConnell, S. R.; Artemyev, A. N.; Surzhykov, A.

2011-07-01

414

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

415

On the Relative Speed and Temperature Ratio of Solar Wind Alpha Particles and Protons: Collisions Versus Wave Effects  

NASA Astrophysics Data System (ADS)

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

Bourouaine, Sofiane; Marsch, Eckart; Neubauer, Fritz M.

2011-02-01

416

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

SciTech Connect

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 nondestructive 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, Alexander A [Los Alamos National Laboratory; Peterson, Dominic S [Los Alamos National Laboratory; Tandon, Lav [Los Alamos National Laboratory; Lamont, Stephen P [Los Alamos National Laboratory

2009-01-01

417

Alpha-particle analysis of a triple isotope 239 Pu – 241 Am – 244 Cm source by nuclear track methodology  

Microsoft Academic Search

This work presents a new approach using nuclear track in solids methodology (NTSM) for the energy analysis of alpha-particles. This method is based on the quantitative relationship between the energy deposited in the polycarbonate by the geometrical parameters of the developed track after the chemical etching. We used separated calibrated sources of 239Pu and 241Am, and a mixed source with

G. Espinosa; R. J. Silva

2001-01-01

418

Velocity dependence of double inner-shell ionization in vanadium by proton and alpha-particle impact  

Microsoft Academic Search

Ratios of double (KL) to single (K) ionization cross sections for proton and alpha-particle impact on vanadium are measured with velocities V = 0.53 to 1.7 (in units relative to the L-shell electron velocity) and are found to be reproduced by the recipe of McGuire and Richard.

N. Cue; V. Dutkiewicz; P. Sen; H. Bakhru

1973-01-01

419

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

420

Distributions of cell populations within. cap alpha. -particle range of plutonium deposits in the rat and beagle testis  

SciTech Connect

Plutonium is not uniformly distributed in testicular tissues; thus some cell populations may receive larger or smaller radiation exposures than would be expected if the nuclide were uniformly distributed. The distributions of cell populations within ..cap alpha..-particle range of Pu deposits in rat and beagle testes were determined. The data were collected from autoradiographs of testicular tissues containing /sup 241/Pu. A cell distribution factor (CDF) was determined for each cell population and is defined as the average number of each cell type within ..cap alpha..-particle range of each observed Pu deposit relative to the number of each cell type that would be expected within ..cap alpha..-particle range of each Pu deposit, if the deposits were distributed uniformly. In addition, the percentage of the spermatogonial stem cell population within ..cap alpha..-particle range of Pu deposits was determined. The largest CDFs seen in both species were in the interstitial tissues, particulary for Leydig cells. Because the organization of testicular tissues in the beagle is quite different from rodents but more similar to human, the results from this study suggest that extrapolations from rodents to humans may tend to overestimate the potential for radiation exposure to spermatogonial stem cells as well as the fraction of the spermatogonial stem cell population at risk to exposure from internally deposited /sup 239/Pu.

Miller, S.C.; Rowland, H.G.; Bowman, B.M.

1985-01-01

421

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

422

A note on the nucleosynthesis of light elements by proton and alpha-particle fluxes in cosmic gases  

Microsoft Academic Search

Calculations were performed on the L-elements abundances, produced by proton and alpha-particle fluxes, on cosmic gases containing helium, carbon, oxygen, nitrogen, and neon (M-elements). Results showed that if strong enough fluxes are available, the abundances of the L-elements produced are near those of the target nuclei. The research is of astrophysical interest.

R. Canal

1974-01-01

423

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

424

Rayleigh scattering from a trapped bose condensate and the corresponding recoil atom velocity distribution  

SciTech Connect

An approach has been developed that allows the Rayleigh scattering cross section to be calculated with allowance for the quantum character of motion of the center of mass of the trapped scattering particles. The shape of the line of light scattering from a Bose condensate in a parabolic trap has been studied. A shift of the scattering line center is equal to the recoil shift, while the line width depends on the chemical potential of the Bose gas and on the relaxation time of the velocity of the above-condensate recoil particles. A velocity distribution function in the beam of recoil atoms formed in the course of induced Rayleigh scattering is determined. It is shown that, under the typical experimental conditions, the characteristic width {delta}v/v of the recoil velocity distribution in this beam is on the order of 10{sup -3} at a velocity v on the order of several centimeters per second.

Alekseev, V. A. [Russian Academy of Sciences, Lebedev Institute of Physics (Russian Federation)], E-mail: valeks@sci.lebedev.ru

2007-03-15

425

Influence of variability of 214Pb recoil factor on lung dose.  

PubMed

Different parameters enter models of the human respiratory tract. The unattached fraction of the radon progeny was identified as the most important parameter, with the strongest influence on lung dose. The unattached fraction depends on the indoor aerosol concentration and other environmental conditions. The recoil factor, p, which influences the unattached fraction of 214Pb and 214Bi, defined as the average detachment probability from the aerosol after an alpha decay of 218Po, has almost always been taken as a constant. Here the recoil factor was recalculated under different assumptions and found to be in the range between 0.1 and 0.8. A smaller recoil factor means lower unattached fractions of 214Pb and 214Bi. The influence of the recoil factor on lung dose was also estimated. The lung dose is smaller by about 10% if p = 0.1 is assumed in calculating the unattached fraction instead of p = 0.8. PMID:15254323

Nikezic, D; Stevanovic, N

2004-01-01

426

First observation of alpha particle loss induced by kinetic ballooning modes in TFTR deuterium-tritium experiments  

SciTech Connect

A correlation between the measured alpha particle loss and high frequency ({approximately}100{endash}200 kHz) magnetohydrodynamic (MHD) modes has been observed in some high {beta} (= plasma pressure/magnetic pressure) DT plasmas in TFTR. These modes are localized around the peak plasma pressure gradient and have ballooning characteristics. Particle simulation shows that the loss is due to wave-particle resonances. Linear instability analysis indicates that the plasma is unstable to the kinetic MHD ballooning modes driven by strong local pressure gradients. {copyright} {ital 1996 The American Physical Society.}

Chang, Z.; Budny, R.V.; Chen, L.; Darrow, D.; Fredrickson, E.D.; Janos, A.; Mansfield, D.; Mazzucato, E.; McGuire, K.M.; Nazikian, R.; Rewoldt, G.; Strachan, J.D.; Tang, W.M.; Taylor, G.; White, R.B.; Zweben, S. [Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States)]|[Department of Physics, University of California, Irvine, California 92717-4575 (United States); TFTR group

1996-02-01

427

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

SciTech Connect

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

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

2007-10-26

428

EFFECT OF DIFFERENTIAL FLOW OF ALPHA PARTICLES ON PROTON PRESSURE ANISOTROPY INSTABILITIES IN THE SOLAR WIND  

SciTech Connect

In the solar wind, when the effects of proton-proton Coulomb collisions are negligible, alpha particles usually flow faster than the protons in such a way that the differential alpha-proton flow velocity V{sub d} = V{sub {alpha}} - V{sub p} is on the order of the Alfven speed, is directed away from the Sun, and is nearly aligned with the local mean magnetic field. When this differential flow is taken into account, solutions of the hot plasma dispersion relation show that for the parallel propagating electromagnetic ion cyclotron (EMIC) instability driven by the proton temperature anisotropy T{sub perpendicularp} > T{sub ||p}, the maximum growth rate occurs in the + V{sub d} direction and for the parallel firehose instability driven by the opposite proton temperature anisotropy T{sub ||p} > T{sub perpendicularp}, the maximum growth rate occurs in the - V{sub d} direction. Thus, the EMIC instability preferentially generates left circularly polarized Alfven-ion-cyclotron waves propagating away from the Sun and the parallel firehose instability preferentially generates right circularly polarized magnetosonic-whistler waves propagating toward the Sun with the maximum growth rates occurring for frequencies on the order of the proton cyclotron frequency and wavenumbers on the order of the proton inertial length. Because of the Doppler shift caused by the motion of the solar wind, both types of waves are left circularly polarized in the spacecraft frame for observations taken when the local mean magnetic field is collinear with the solar wind flow velocity. Theoretical investigation of these instabilities also shows that regions of parameter space exist where the unstable waves are generated propagating unidirectionally such as, for the EMIC instability for example, when the temperature anisotropy is small |(T{sub perpendicular{sub p}}/T{sub ||{sub p}}) - 1| < 1. Taken together, the above properties can explain the origin of parallel propagating electromagnetic waves recently observed near the proton inertial length in high-speed solar wind. The observed waves are most likely produced in situ by these instabilities. A remarkable property of the proposed mechanism that may be of practical importance is that the magnetic helicity of the unstable waves has the same sign no matter whether the proton temperature anisotropy (T{sub p{sub perpendicular}}/T{sub p{sub ||}}) - 1 is positive or negative.

Podesta, John J.; Gary, S. Peter, E-mail: jpodesta@solar.stanford.edu [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

2011-11-20

429

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

430

Microscopic description of excitation of nuclear isoscalar giant resonances by inelastic scattering of 240 MeV {alpha} particles  

SciTech Connect

A microscopic description of the excitation of isoscalar giant monopole resonance (ISGMR) and quadrupole resonance (ISGQR) in {sup 28}Si, {sup 40}Ca, {sup 58}Ni, and {sup 116}Sn by 240 MeV bombarding energy {alpha} particles is provided based on self-consistent Hartree-Fock- (HF-) random-phase-approximation (RPA) approach and the distorted-wave Born approximation (DWBA). The folding model is used to obtain optical potentials from the HF ground-state density and a density dependent Gaussian nucleon-{alpha} interaction (V{sub {alpha}}{sub n}). The parameters of V{sub {alpha}}{sub n} are determined by fitting experimentally measured angular distributions for the case of elastic scattering. Angular distributions of inelastically scattered {alpha} particles for ISGMR and ISGQR excitations of the target nucleus are obtained using the folding model DWBA and both microscopic (RPA) and hydrodynamical (collective model) transition densities (found from HF ground state densities). A possible overestimation of the energy weighted sum rules and shifts of centroid energies due to the collective-model-based DWBA reaction description is reported. (c) 2000 The American Physical Society.

Kolomiets, A. [Cyclotron Institute, Texas A and M University, College Station, Texas 77843 (United States); Pochivalov, O. [Cyclotron Institute, Texas A and M University, College Station, Texas 77843 (United States); Shlomo, S. [Cyclotron Institute, Texas A and M University, College Station, Texas 77843 (United States)

2000-03-01

431

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

432

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

433

Prompt detection of alpha particles from 210Po: another clue to the origin of rock varnish?  

PubMed

Alpha particles have been measured coming from the surfaces of rocks covered with dark red-brown rock varnish, as well as rocks that appear to have little, if any, varnish. A pronounced peak at 5.3 MeV indicates the presence of 210Po, a short-lived natural-radioactive element. Surface activities for 33 samples range from 0.008 Bq/cm2 to 0.065 Bq/cm2. It is estimated that this nuclide is concentrated 10(11) times in these paper-thin coatings above its concentration in ground-level air. Gamma rays from the decay of 137Cs, a product of testing nuclear weapons some 50 years ago, were also detected. Analysis of samples of varnish stripped from the rock revealed traces of 239,240Pu and 238Pu. The presence of all of these isotopes strongly supports the theory that varnish films derive their building blocks from the atmosphere and, with time, all rocks in arid environments will become coated. PMID:15511566

Hodge, Vernon F; Farmer, Dennis E; Diaz, Tammy; Orndorff, Richard L

2005-01-01

434

Thorium and actinium polyphosphonate compounds as bone-seeking alpha particle-emitting agents.  

PubMed

The present study explores the use of alpha-particle-emitting, bone-seeking agents as candidates for targeted radiotherapy. Actinium and thorium 1,4,7,10 tetraazacyclododecane N,N',N'',N''' 1,4,7,10-tetra(methylene) phosphonic acid (DOTMP) and thorium-diethylene triamine N,N',N'' penta(methylene) phosphonic acid (DTMP) were prepared and their biodistribution evaluated in conventional Balb/C mice at four hours after injection. All three bone-seeking agents showed a high uptake in bone and a low uptake in soft tissues. Among the soft tissue organs, only kidney had a relatively high uptake. The femur/kidney ratios for 227Th-DTMP, 228-Ac-DOTMP and 227Th-DOTMP were 14.2, 7.6 and 6.0, respectively. A higher liver uptake of 228Ac-DOTMP was seen than for 227Th-DTMP and 227Th-DOTMP. This suggests that some demetallation of the 228Ac-DOTMP complex had occurred. The results indicate that 225Ac-DOTMP, 227Th-DOTMP and 227Th-DTMP have promising properties as potential therapeutic bone-seeking agents. PMID:15015582

Henriksen, Gjermund; Bruland, Oyvind S; Larsen, Roy H

435

Log Normal Distribution of Cellular Uptake of Radioactivity: Statistical Analysis of Alpha Particle Track Autoradiography  

PubMed Central

Recently, the distribution of radioactivity among a population of cells labeled with 210Po was shown to be well described by a log normal distribution function (J Nucl Med 47, 6 (2006) 1049-1058) with the aid of an autoradiographic approach. To ascertain the influence of Poisson statistics on the interpretation of the autoradiographic data, the present work reports on a detailed statistical analyses of these data. Methods The measured distributions of alpha particle tracks per cell were subjected to statistical tests with Poisson (P), log normal (LN), and Poisson – log normal (P – LN) models. Results The LN distribution function best describes the distribution of radioactivity among cell populations exposed to 0.52 and 3.8 kBq/mL 210Po-citrate. When cells were exposed to 67 kBq/mL, the P – LN distribution function gave a better fit, however, the underlying activity distribution remained log normal. Conclusions The present analysis generally provides further support for the use of LN distributions to describe the cellular uptake of radioactivity. Care should be exercised when analyzing autoradiographic data on activity distributions to ensure that Poisson processes do not distort the underlying LN distribution.

Neti, Prasad V.S.V.; Howell, Roger W.

2008-01-01

436

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

437

''Magic'' Energies for Detecting Light Elements with Resonant Alpha Particle Backscattering  

SciTech Connect

Resonant backscattering is widely used to improve the detection limit of the light elements such as B, C, N and O. One disadvantage, however, is that several incident energies are normally needed if the sample contains a number of the light elements. There are ''magic'' energies at which several light elements can be detected simultaneously with suitable sensitivities. When these energies are used along with the elastic recoil detection of hydrogen, multiple elements can be detected without changing the beam energy, and the analysis time is greatly reduced. These reactions along with examples will be discussed.

Wetteland, C.J.; Maggiore, C.J.; Tesmer, J.R.; He, X-M.; Lee, D-H.

1998-11-04

438

Alpha-Particle Decay Measurements for Very Long - Quasi-Stable Isotopes of Neodymium, Platinum, Samarium and Uranium.  

NASA Astrophysics Data System (ADS)

Half lives and alpha-particle energies of very long-lived (10('9) - 10('16) years) quasi-stable nuclei with A > 140 have been measured using a cylindrical gas -flow proportional counter. The source materials were deposited on the inner surface of the cathode cylinder over an area of about 1700 cm('2). Low-level counting techniques were developed with emphasis on the reduction of background from external and internal sources. External background can be reduced by shielding and rise-time discrimination. Internal background from (alpha)-contaminants in the counter materials and the source materials was a major source of background and was studied in detail. Stainless steel was found to be superior to brass and aluminum. Ultrapure source materials had to be superior to brass and aluminum. Ultrapure source materials had to be used. Half lives and energies were measured for ('144)Nd, ('147)Sm, ('190)Pt, ('234)U, ('235)U, ('238)U, and lower limit was obtained for ('148)Sm. Reduced alpha widths which describe the preformation of (alpha)-clusters in the nuclear surface were obtained for the entire region N > 82 to Z (LESSTHEQ) 84 from all available data. Systematic trends which reflect upon the nuclear structure of these nuclei make it possible to predict new short-lived proton-rich alpha emitters as well as additional very long-lived quasi-stable alpha emitters.

Al-Bataina, Barakat Atwan Mofaddi

439

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

440

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

441

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

PubMed

We reported previously that the homologous recombinational repair (HRR)-deficient Chinese hamster mutant cell line irs3 (deficient in the Rad51 paralog Rad51C) showed only a 50% spontaneous frequency of sister chromatid exchange (SCE) as compared to parental wild-type V79 cells. Furthermore, when irradiated with very low doses of alpha particles, SCEs were not induced in irs3 cells, as compared to a prominent bystander effect observed in V79 cells [H. Nagasawa, Y. Peng, P.F. Wilson, Y.C. Lio, D.J. Chen, J.S. Bedford, J.B. Little, Role of homologous recombination in the alpha-particle-induced bystander effect for sister chromatid exchanges and chromosomal aberrations, Radiat. Res. 164 (2005) 141-147]. In the present study, we examined additional Chinese hamster cell lines deficient in the Rad51 paralogs Rad51C, Rad51D, Xrcc2, and Xrcc3 as well as another essential HRR protein, Brca2. Spontaneous SCE frequencies in non-irradiated wild-type cell lines CHO, AA8 and V79 were 0.33SCE/chromosome, whereas two Rad51C-deficient cell lines showed only 0.16SCE/chromosome. Spontaneous SCE frequencies in cell lines defective in Rad51D, Xrcc2, Xrcc3, and Brca2 ranged from 0.23 to 0.33SCE/chromosome, 0-30% lower than wild-type cells. SCEs were induced significantly 20-50% above spontaneous levels in wild-type cells exposed to a mean dose of 1.3mGy of alpha particles (<1% of nuclei traversed by an alpha particle). However, induction of SCEs above spontaneous levels was minimal or absent after alpha-particle irradiation in all of the HRR-deficient cell lines. These data suggest that Brca2 and the Rad51 paralogs contribute to DNA damage repair processes induced in bystander cells (presumably oxidative damage repair in S-phase cells) following irradiation with very low doses of alpha particles. PMID:18182331

Nagasawa, Hatsumi; Wilson, Paul F; Chen, David J; Thompson, Larry H; Bedford, Joel S; Little, John B

2008-01-07

442

A multi-port low-fluence alpha-particle irradiator: fabrication, testing and benchmark radiobiological studies.  

PubMed

A new multi-port irradiator, designed to facilitate the study of the effects of low fluences of alpha particles on monolayer cultures, has been developed. The irradiator consists of four individual planar (241)Am alpha-particle sources that are housed inside a helium-filled Lucite chamber. Three of the radioactive sources consist of 20 MBq of (241)A