The stopping power and energy straggling of heavy ions in silicon nitride and polypropylene

International Nuclear Information System (INIS)

Mikšová, R.; Hnatowicz, V.; Macková, A.; Malinský, P.; Slepička, P.

2015-01-01

The stopping power and energy straggling of 12 C 3+ and 16 O 3+ ions with energies between 4.5 and 7.8 MeV in a 0.166-μm-thin silicon nitride and in 4-μm-thin polypropylene foils were measured by means of an indirect transmission method using a half-covered PIPS detector. Ions scattered from a thin gold layer under a scattering angle of 150° were used. The energy spectra of back-scattered and decelerated ions were registered and evaluated simultaneously. The measured stopping powers were compared with the theoretical predictions simulated by SRIM-2008 and MSTAR codes. SRIM prediction of energy stopping is reasonably close to the experimentally obtained values comparing to MSTAR values. Better agreement between experimental and predicted data was observed for C 3+ ion energy losses comparing to O 3+ ions. The experimental data from Paul’s database and our previous experimental data were also discussed. The obtained experimental energy-straggling data were compared to those calculated by using Bohr’s, Yang’s models etc. The predictions by Yang are in good agreement with our experiment within a frame of uncertainty of 25%

The stopping power and energy straggling of the energetic C and O ions in polyimide

Czech Academy of Sciences Publication Activity Database

Mikšová, Romana; Macková, Anna; Slepička, P.

2016-01-01

Roč. 371, MAR (2016), s. 81-85 ISSN 0168-583X. [22nd International conference on Ion Beam Analysis (IBA). Opatija, 14.06.2015-19.06.2015] R&D Projects: GA MŠk(CZ) LM2011019; GA ČR GA15-01602S Institutional support: RVO:61389005 Keywords : ion energy loss * ion energy straggling * ion irradiated polymers Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 1.109, year: 2016

Space distribution and energy straggling of charged particles via Fokker-Planck equation

International Nuclear Information System (INIS)

Manservisi, S.; Molinari, V.; Nespoli, A.

1996-01-01

The Fokker-Planck equation describing a beam of charged particles entering a homogeneous medium is solved here for a stationary case. Interactions are taken into account through Coulomb cross-section. Starting from the charged-particle distribution as a function of velocity and penetration depth, some important kinetic quantities are calculated, like mean velocity, range and the loss of energy per unit space. In such quantities the energy straggling is taken into account. This phenomenon is not considered in the continuous slowing-down approximation that is commonly used to obtain the range and the stopping power. Finally the well-know Bohr of Bethe formula is found as a first-order approximation of the Fokker-Planck equation

The effect of straggling on the slowing down of neutrons in radiation protection

International Nuclear Information System (INIS)

Mostacci, D.; Molinari, V.; Teodori, F.; Pesic, M.

1999-01-01

All those techniques developed to describe neutron transport that rely on the flux isotropy conditions prevailing within the reactor core can be of no help in the study of neutron beams. Two main problems must be solved in investigating beams: determining the relevant cross-sections and solving the transport equation. Often in addressing neutron radiation protection problems, the available cross-section data are extremely detailed whereas the transport equations used are rather unrefined, making wide use of the continuous slowing down approximation to calculate stopping powers (e.g., Bethe's expressions). In this paper a simple approach to calculating stopping power and range is presented, that takes into account the effect of neutron energy straggling. Comparison with MCNP results is also presented. (author)

Range-energy relation, range straggling and response function of CsI(Tl), BGO and GSO(Ce) scintillators for light ions

CERN Document Server

Avdeichikov, V; Jakobsson, B; Rodin, A M; Ter-Akopian, G M

2000-01-01

Range-energy relations and range straggling of sup 1 sup , sup 2 sup , sup 3 H and sup 4 sup , sup 6 He isotopes with the energy approx 50A MeV are measured for the CsI(Tl), BGO and GSO(Ce) scintillators with an accuracy better than 0.2% and 5%, respectively. The Si-Sci/PD telescope was exposed to secondary beams from the mass separator ACCULINNA. The experimental technique is based on the registration of the 'jump' in the amplitude of the photodiode signal for ions passing through the scintillation crystal. Light response of the scintillators for ions 1<=Z<=4 is measured in energy range (5-50)A MeV, the results are in good agreement with calculations based on Birks model. The energy loss straggling for particles with DELTA E/E=0.01-0.50 and mass up to A=10 in 286 mu m DELTA E silicon detector is studied and compared with theoretical prescriptions. The results allow a precise absolute calibration of the scintillation crystal and to optimize the particle identification by the DELTA E-E(Sci/PD) method.

Elastic energy loss and longitudinal straggling of a hard jet

International Nuclear Information System (INIS)

Majumder, A.

2009-01-01

The elastic energy loss encountered by jets produced in deep-inelastic scattering (DIS) off a large nucleus is studied in the collinear limit. In close analogy to the case of (nonradiative) transverse momentum broadening, which is dependent on the medium transport coefficient q, a class of medium enhanced higher twist operators which contribute to the nonradiative loss of the forward light-cone momentum of the jet (q - ) are identified and the leading correction in the limit of asymptotically high q - is isolated. Based on these operator products, a new transport coefficient e is motivated which quantifies the energy loss per unit length encountered by the hard jet. These operator products are then computed, explicitly, in the case of a similar hard jet traversing a deconfined quark-gluon plasma (QGP) in the hard-thermal-loop (HTL) approximation. This is followed by an evaluation of subleading contributions which are suppressed by the inverse light-cone momentum q - , which yields the longitudinal 'straggling', i.e., a slight change in light cone momentum due to the Brownian propagation through a medium with a fluctuating color field.

Stopping Power and Energy Straggling of Channeled He-Ions in GaN

International Nuclear Information System (INIS)

Turos, A.; Ratajczak, R.; Pagowska, K.; Nowicki, L.; Stonert, A.; Caban, P.

2011-01-01

GaN epitaxial layers are usually grown on sapphire substrates. To avoid disastrous effect of the large lattice mismatch a thin polycrystalline nucleation layer is grown at 500 o C followed by the deposition of thick GaN template at much higher temperature. Remnants of the nucleation layer were visualized by transmission electron microscopy as defect agglomeration at the GaN/sapphire interface and provide a very useful depth marker for the measurement of channeled ions stopping power. Random and aligned spectra of He ions incident at energies ranging from 1.7 to 3.7 MeV have been measured and evaluated using the Monte Carlo simulation code McChasy. Impact parameter dependent stopping power has been calculated for channeling direction and its parameters have been adjusted according to experimental data. For virgin, i.e. as grown, samples, the ratio of channeled to random stopping power is constant and amounts to 0.7 in the energy range studied. Defects produced by ion implantation largely influence the stopping power. For channeled ions the variety of possible trajectories leads to different energy loss at a given depth, thus resulting in much larger energy straggling than that for the random path. Beam energy distributions at different depths have been calculated using the McChasy code. They are significantly broader than those predicted by the Bohr formula for random direction. (author)

COREL, Ion Implantation in Solids, Range, Straggling Using Thomas-Fermi Cross-Sections. RASE4, Ion Implantation in Solids, Range, Straggling, Energy Deposition, Recoils. DAMG2, Ion Implantation in Solids, Energy Deposition Distribution with Recoils

International Nuclear Information System (INIS)

Brice, D. K.

1979-01-01

1 - Description of problem or function: COREL calculates the final average projected range, standard deviation in projected range, standard deviation in locations transverse to projected range, and average range along path for energetic atomic projectiles incident on amorphous targets or crystalline targets oriented such that the projectiles are not incident along low index crystallographic axes or planes. RASE4 calculates the instantaneous average projected range, standard deviation in projected range, standard deviation in locations transverse to projected range, and average range along path for energetic atomic projectiles incident on amorphous targets or crystalline targets oriented such that the projectiles are not incident along low index crystallographic axes or planes. RASE4 also calculates the instantaneous rate at which the projectile is depositing energy into atomic processes (damage) and into electronic processes (electronic excitation), the average range of target atom recoils projected onto the direction of motion of the projectiles, and the standard deviation in the recoil projected range. DAMG2 calculates the distribution in depth of the energy deposited into atomic processes (damage), electronic processes (electronic excitation), or other energy-dependent quality produced by energetic atomic projectiles incident on amorphous targets or crystalline targets oriented such that the projectiles are not incident along low index crystallographic axes or planes. 2 - Method of solution: COREL: The truncated differential equation which governs the several variables being sought is solved through second-order by trapezoidal integration. The energy-dependent coefficients in the equation are obtained by rectangular integration over the Thomas-Fermi elastic scattering cross section. RASE4: The truncated differential equation which governs the range and straggling variables is solved through second-order by trapezoidal integration. The energy

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

International Nuclear Information System (INIS)

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

1985-01-01

The stopping power and straggling for 5.5 MeV alpha particles in liquid and vapour phases of water, methanol, ethanol, propanol, h-hexane, n-octane and cyclohexane, and those for low energy protons in ethylene, styrene and propylene and their polymers, have been measured. Range-energy data have been fitted with inverse stopping power functions to give the cross sections. In each case, five parameters have been adjusted to obtain the best fit. The value of chi-squared per degree of freedom has been calculated, together with the parameters. The theoretical stopping cross section has been considered employing the Bethe-Bloch expression together with various corrections (shell correction using Walske and Bichsel procedure, Z 1 3 contribution according to Ashley and Bloch correction based on Lindhard formalism). The existence of a phase effect has been clearly demonstrated for the stopping of both alpha particles and protons. (author)

Multiple cell upset cross-section modeling: A possible interpretation for the role of the ion energy-loss straggling and Auger recombination

Energy Technology Data Exchange (ETDEWEB)

Zebrev, G.I., E-mail: gizebrev@mephi.ru; Zemtsov, K.S.

2016-08-11

We found that the energy deposition fluctuations in the sensitive volumes may cause the multiple cell upset (MCU) multiplicity scatter in the nanoscale (with feature sizes less than 100 nm) memories. A microdosimetric model of the MCU cross-section dependence on LET is proposed. It was shown that ideally a staircase-shaped cross-section vs LET curve spreads due to the energy-loss straggling impact into a quasi-linear dependence with a slope depending on the memory cell area, the cell critical energy and efficiency of charge collection. This paper also presents a new model of the Auger recombination as a limiting process of the electron–hole charge yield, especially at the high-LET ion impact. A modified form of the MCU cross-section vs LET data interpolation is proposed, discussed and validated.

Multiple cell upset cross-section modeling: A possible interpretation for the role of the ion energy-loss straggling and Auger recombination

International Nuclear Information System (INIS)

Zebrev, G.I.; Zemtsov, K.S.

2016-01-01

We found that the energy deposition fluctuations in the sensitive volumes may cause the multiple cell upset (MCU) multiplicity scatter in the nanoscale (with feature sizes less than 100 nm) memories. A microdosimetric model of the MCU cross-section dependence on LET is proposed. It was shown that ideally a staircase-shaped cross-section vs LET curve spreads due to the energy-loss straggling impact into a quasi-linear dependence with a slope depending on the memory cell area, the cell critical energy and efficiency of charge collection. This paper also presents a new model of the Auger recombination as a limiting process of the electron–hole charge yield, especially at the high-LET ion impact. A modified form of the MCU cross-section vs LET data interpolation is proposed, discussed and validated.

Mean free paths by inelastic interactions, stopping powers, and energy straggling for electrons of energies up to 20 keV in various solids

International Nuclear Information System (INIS)

Akkerman, A.F.; Chernov, G.Ya.

1978-01-01

For the elements C, Be, Mg, Al, Si, K, Ge, Sb, Bi calculations of the mean free paths and stopping powers of low energy electrons are performed. In the computational model Lindhard's formalism of the dielectric response function for pair and plasmon excitation and the classical cross-section for ionization processes are used. Anomalously high mean free paths and small stopping powers in potassium are found. This behaviour which is connected with low electron concentration in the valence band is expected to hold for all alkali metals. For energies above 10 keV the calculated dE/dx agree well with values calculated from the Bethe-Bloch formula. A Monte-Carlo method is used for the calculation of the energy loss distribution of electrons passing through thin targets. It is noted that Blunck-Leisegang's theory fails to render the energy straggling at electron energies below 10 keV. (author)

Energy-loss straggling study of proton and alpha-particle beams incident onto ZrO{sub 2} and Al{sub 2}O{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Behar, M.; Fadanelli, R.C. [Instituto de Fisica, Universidade Federal do Rio Grande do Sul, Porto Alegre, 91501-970 (Brazil); Abril, I. [Departamento de Fisica Aplicada, Universitat d' Alacant, 03080 Alacant (Spain); Garcia-Molina, R. [Departamento de Fisica, Centro de Investigacion en Optica y Nanofisica, Universidad de Murcia, 30100 Murcia (Spain); Nagamine, L.C.C. [Instituto de Fisica, Universidade de Sao Paulo, C.P.66318, 05315-970 Sao Paulo (Brazil)

2011-10-15

The energy-loss straggling of zirconia (ZrO{sub 2}) and alumina (Al{sub 2}O{sub 3}) has been experimentally determined for proton and alpha-particle beams mainly by means of the Rutherford backscattering technique and in some few cases using the transmission method. The incident energies of the projectiles covers a wide range, from 200 keV up to 2000 keV for H{sup +} and from 200 keV up to 4000 keV for He{sup +} in zirconia films. In the case of alumina films the studied energy range was 100 keV - 3000 keV for H{sup +} and 100 keV - 6000 keV for He{sup +}. Our experimental results compare very well with theoretical calculations based on the dielectric formalism and a suitable description of the electronic excitation spectrum of ZrO{sub 2} and Al{sub 2}O{sub 3} films through their energy-loss function. (authors)

Slowing down of 2–11 MeV {sup 12}C, {sup 16}O, {sup 28}Si and {sup 63}Cu heavy ions through Si{sub 3}N{sub 4} thin foil by using Time-of-Flight spectrometry

Energy Technology Data Exchange (ETDEWEB)

Guesmia, A., E-mail: guesmia@tlabs.ac.za [iThemba LABS, National Research Foundation, P.O. Box 722, Somerset West 7129 (South Africa); Departement de physique, Faculté des Sciences Université Saad Dahleb, B. P. 270, Route de Soumaa, Blida (Algeria); Departement de physique, Faculté des Sciences Université M’hamedBougara, Boumerdes (Algeria); Msimanga, M. [Physics Department, Tshwane University of Technology, P Bag X 680, Pretoria 0001 (South Africa); Pineda-Vargas, C.A. [iThemba LABS, National Research Foundation, P.O. Box 722, Somerset West 7129 (South Africa); Faculty of Health and Wellness Sciences, CPUT, P.O. Box 1906, Bellville 7535 (South Africa); Ammi, H.; Dib, A.; Ster, M. [Centre de Recherche Nucleaire d’Alger, 2 Bd. Frantz Fanon, B. P. 399, Alger-Gare, Algiers (Algeria)

2016-03-15

The stopping force and the energy-loss straggling of {sup 63}Cu, {sup 28}Si, {sup 16}O and {sup 12}C partially stripped heavy ions crossing silicon nitride foil has been determined over a continuous range of energies 2–11 MeV, by using a method based on the Heavy Ion-Elastic Recoil Detection Analysis (HI-ERDA) technique using a Time of Flight (ToF) spectrometer. The obtained energy loss straggling values corrected for non-statistical straggling and the thickness variation using the Besenbacher’s method have been analyzed and compared with the corresponding computed values. For computed electronic straggling we have used alternatively the widely used formulations such as, the universal Bohr straggling deduced from the Bohr stopping model, and the Lindhard–Scharff formula including the Bunching effect given by Hvelplund–Firsov formula according to the Besenbacher approach. The aim of such comparison is to check the reliability and accuracy of the existing energy loss straggling formulations, in the light of the present experimental results. The experimental results of energy loss straggling of all ions are found to be greater than those predicted by the Bohr stopping model or Lindhard–Scharff prediction model. The introduction of the bunching effect improves the comparison and gives an estimation of other effects such as charge exchange.

Range distribution of heavy ions in multi-elemental targets

International Nuclear Information System (INIS)

Wang Keming; Shandong Univ., Jinan; Liu Xiju; Wang Yihua; Liu Jitian; Shi Borong; Chen Huanchu

1989-01-01

Some results of range distribution on Hg + implanted NaSBN and CeSBN crystals are given. A computer program is written based on the angular diffusion model by Biersack to calculate the mean projected range and range straggling. For comparison, other published experimental data are also included. The comparison between experimental and theoretical values indicates that the measured projected ranges are in good agreement with those predicted by the Biersack model within experimental error, and a marked improvement in range stragglings is obtained after considering the second order energy loss. (author)

Transcript of the proceedings of the first Albuquerque informal range/energy workshop

International Nuclear Information System (INIS)

Brice, D.K.

1981-04-01

An informal workshop was held to discuss aspects of the calculation of range and energy deposition distributions which are of interest in ion implantation experiments. Topics covered include: problems encountered in using published range and energy deposition tabulations; some limitations in the solutions of range/energy transport equations; the effect of the scattering cross section on straggle; Monte Carlo calculations of ranges and straggling; damage studies in aluminum; simulation of heavy-ion irradiation of gold using MARLOWE; and MARLOWE calculations of range distribution parameters - dependence on input data and calculational model

A combined molecular dynamics and Monte Carlo simulation of the spatial distribution of energy deposition by proton beams in liquid water

Energy Technology Data Exchange (ETDEWEB)

Garcia-Molina, Rafael [Departamento de Fisica, Centro de Investigacion en Optica y Nanofisica (CIOyN), Universidad de Murcia, E-30100 Murcia (Spain); Abril, Isabel [Departament de Fisica Aplicada, Universitat d' Alacant, E-03080 Alacant (Spain); Heredia-Avalos, Santiago [Departament de Fisica, Enginyeria de Sistemes i Teoria del Senyal, Universitat d' Alacant, E-03080 Alacant (Spain); Kyriakou, Ioanna; Emfietzoglou, Dimitris, E-mail: rgm@um.es [Medical Physics Laboratory, University of Ioannina Medical School, GR-45110 Ioannina (Greece)

2011-10-07

We have evaluated the spatial distribution of energy deposition by proton beams in liquid water using the simulation code SEICS (Simulation of Energetic Ions and Clusters through Solids), which combines molecular dynamics and Monte Carlo techniques and includes the main interaction phenomena between the projectile and the target constituents: (i) the electronic stopping force due to energy loss to target electronic excitations, including fluctuations due to the energy-loss straggling, (ii) the elastic scattering with the target nuclei, with their corresponding energy loss and (iii) the dynamical changes in projectile charge state due to electronic capture and loss processes. An important feature of SEICS is the accurate account of the excitation spectrum of liquid water, based on a consistent solid-state description of its energy-loss-function over the whole energy and momentum space. We analyse how the above-mentioned interactions affect the depth distribution of the energy delivered in liquid water by proton beams with incident energies of the order of several MeV. Our simulations show that the position of the Bragg peak is determined mainly by the stopping power, whereas its width can be attributed to the energy-loss straggling. Multiple elastic scattering processes contribute slightly only at the distal part of the Bragg peak. The charge state of the projectiles only changes when approaching the end of their trajectories, i.e. near the Bragg peak. We have also simulated the proton-beam energy distribution at several depths in the liquid water target, and found that it is determined mainly by the fluctuation in the energy loss of the projectile, evaluated through the energy-loss straggling. We conclude that a proper description of the target excitation spectrum as well as the inclusion of the energy-loss straggling is essential in the calculation of the proton beam depth-dose distribution.

A combined molecular dynamics and Monte Carlo simulation of the spatial distribution of energy deposition by proton beams in liquid water

International Nuclear Information System (INIS)

Garcia-Molina, Rafael; Abril, Isabel; Heredia-Avalos, Santiago; Kyriakou, Ioanna; Emfietzoglou, Dimitris

2011-01-01

We have evaluated the spatial distribution of energy deposition by proton beams in liquid water using the simulation code SEICS (Simulation of Energetic Ions and Clusters through Solids), which combines molecular dynamics and Monte Carlo techniques and includes the main interaction phenomena between the projectile and the target constituents: (i) the electronic stopping force due to energy loss to target electronic excitations, including fluctuations due to the energy-loss straggling, (ii) the elastic scattering with the target nuclei, with their corresponding energy loss and (iii) the dynamical changes in projectile charge state due to electronic capture and loss processes. An important feature of SEICS is the accurate account of the excitation spectrum of liquid water, based on a consistent solid-state description of its energy-loss-function over the whole energy and momentum space. We analyse how the above-mentioned interactions affect the depth distribution of the energy delivered in liquid water by proton beams with incident energies of the order of several MeV. Our simulations show that the position of the Bragg peak is determined mainly by the stopping power, whereas its width can be attributed to the energy-loss straggling. Multiple elastic scattering processes contribute slightly only at the distal part of the Bragg peak. The charge state of the projectiles only changes when approaching the end of their trajectories, i.e. near the Bragg peak. We have also simulated the proton-beam energy distribution at several depths in the liquid water target, and found that it is determined mainly by the fluctuation in the energy loss of the projectile, evaluated through the energy-loss straggling. We conclude that a proper description of the target excitation spectrum as well as the inclusion of the energy-loss straggling is essential in the calculation of the proton beam depth-dose distribution.

Simplified models for the Monte Carlo simulation of energy distributions of keV electrons transmitted or back-scattered in various solids

International Nuclear Information System (INIS)

Liljequist, D.

1978-01-01

Simplified models, based on stopping power, transport mean free path and classical straggling, are shown to give results in rather good agreement with experiment and comparable with the results of more detailed, direct Monte Carlo procedure hitherto constructed. The small effects of features such as large-angle scattering and the interaction between straggling and scattering are studied. A description based on the near linearity of the transport mean free path is used to obtain empirical corrections in some cases of the total transmission and back-scattering simulation and empirical estimates of the (Bethe) range and the transport mean free path. The estimates of the range are consistent with a rough calculation of the effect of large binding energies. (author)

Gas bubble coalescence

International Nuclear Information System (INIS)

Ganeev, G.Z.; Turkebaev, T.Eh.; Kadyrov, Kh.G.

2001-01-01

Analysis of gaseous pores coalescence in area of the straggling of helium atoms is given. The considered coalescence is based on both the Brownian movement and the migration within the stress gradient. (author)

Experimental study of the slowing down of heavy ions at 20 to 100 MeV per nucleon in matter

International Nuclear Information System (INIS)

Herault, J.

1988-01-01

The measurements of typical parameters on heavy ions penetration through matter presented in this work have been performed at the GANIL accelerator facility, using the LISE magnetic spectrometer from 20 to 100 MeV per nucleon. Two magnetic optical configurations of the spectrometer LISE corresponding respectively to energy and angle analysis, have been used. In the first configuration, the analysis of the energy loss distribution, caused by the interaction of the heavy ions beam with the target material, permit to determine the stopping power and the energy straggling. The stopping power is defined experimentally by the ratio of the average energy loss in the target to the thickness of this one. This quantity has been measured for a set of heavy ions ( 17 O, 40 Ar, 86 Kr and 132 Xe) in gaseous media (H 2 , He, N 2 , Ne, Ar, Kr, Xe, CH 4 , C 4 H 10 , CO 2 and CF 4 ) and compared to semi-empirical tabulations. These determinations are compared to those obtained in solid media to study the evolution of the solid-gas difference. This effect vanishes progressively when the projectile tends to be totally stripped (the charge state becomes identical to the atomic number). The heavy ion energy distributions at the exit of degraders and particularly their full width at half maximum have been measured for various projectiles ( 16 O, 40 Ar, 84 Kr, 86 Kr, 100 Mo and 132 Xe) in solid (Be, C, Al, Si, Ti, Ni, Cu, Ag, Ta, Au and Mylar) and gaseous media (the same as for stopping power determinations). A significant contribution of charge exchange straggling to the energy loss straggling is observed for partially stripped ions. A second optical configuration of the beam line LISE has been used, to obtain an image of heavy ions beams passing through targets for various heavy ions ( 16 O, 17 O, 40 Ar, 86 Kr and 100 Mo) in gaseous and solid media. The scaling law for angular straggling is confirmed and extended over five orders of magnitude [fr

36Cl AMS measurement with 3 MV tandem accelerator

International Nuclear Information System (INIS)

Wang Huijuan; Guan Yongjing; Zhang Wei; Jiang Shan; He Ming

2012-01-01

Developing the 36 Cl and other medium heavy isotopes measurement at 3 MV AMS facilities is one of the vital trends in AMS measurement. To further increase suppression factor of 36 S, the energy loss straggling and angular straggling of 36 C1 and 36 S ions in various counter gases (Pl0, isobutane and propane) were investigated. Some water samples were measured with the energy of 32 MeV, the results are in good agreement with the result by ion energy of 72 MeV. The results indicate that the detection limit of 36 C1 with 3 MV AMS facility is approximately 36 Cl/Cl ≈ l0 -14 , and the uncertainty is 30% for the sample with isotopic ration 36 Cl/Cl ≈ lO -13 . (authors)

Calculation of projected ranges

International Nuclear Information System (INIS)

Biersack, J.P.

1980-09-01

The concept of multiple scattering is reconsidered for obtaining the directional spreading of ion motion as a function of energy loss. From this the mean projection of each pathlength element of the ion trajectory is derived which - upon summation or integration - leads to the desired mean projected range. In special cases, the calculation can be carried out analytically, otherwise a simple general algorithm is derived which is suitable even for the smallest programmable calculators. Necessary input for the present treatment consists only of generally accessable stopping power and straggling formulas. The procedure does not rely on scattering cross sections, e.g. power potential or f(t 1 sup(/) 2 ) approximations. The present approach lends itself easily to include electronic straggling or to treat composed target materials, or even to account for the so-called time integral. (orig.)

A Monte Carlo algorithm for the Vavilov distribution

International Nuclear Information System (INIS)

Yi, Chul-Young; Han, Hyon-Soo

1999-01-01

Using the convolution property of the inverse Laplace transform, an improved Monte Carlo algorithm for the Vavilov energy-loss straggling distribution of the charged particle is developed, which is relatively simple and gives enough accuracy to be used for most Monte Carlo applications

A computer code package for Monte Carlo photon-electron transport simulation Comparisons with experimental benchmarks

International Nuclear Information System (INIS)

Popescu, Lucretiu M.

2000-01-01

A computer code package (PTSIM) for particle transport Monte Carlo simulation was developed using object oriented techniques of design and programming. A flexible system for simulation of coupled photon, electron transport, facilitating development of efficient simulation applications, was obtained. For photons: Compton and photo-electric effects, pair production and Rayleigh interactions are simulated, while for electrons, a class II condensed history scheme was considered, in which catastrophic interactions (Moeller electron-electron interaction, bremsstrahlung, etc.) are treated in detail and all other interactions with reduced individual effect on electron history are grouped together using continuous slowing down approximation and energy straggling theories. Electron angular straggling is simulated using Moliere theory or a mixed model in which scatters at large angles are treated as distinct events. Comparisons with experimentally benchmarks for electron transmission and bremsstrahlung emissions energy and angular spectra, and for dose calculations are presented

TEM study of the ion beam induced damage during 14 kev P+ implantation in silicon

International Nuclear Information System (INIS)

Rubanov, S.; Tamanyan, G.; Hudson, F.; Jamieson, D.N.; McCallum, J.C.; Prawer, S.

2005-01-01

The proposed silicon-based quantum computer architecture comprises an array of phosphorus donor atoms (qubits) positioned with nanometre accuracy beneath the surface of a semiconductor host, using a single ion implantation technique. The average depth of the implanted ions (the projected range R p ), lateral range R p 1, and the distribution of ions about that depth can be approximated as two-dimensional Gaussian with standard deviation ΔR p and ΔR p 1 (lateral straggle). Using transmission electron microscopy (TEM) we studied ion beam induced damage after 14 keV P + implantation in Si. The TEM images allowed us to compare the depth of the amorphous cluster formation to R p , R p 1, ΔR p 1 calculated from SRIM and hence determine evidence for the limitation on the accuracy of the position of the implanted ions imposed by straggling. (author). 4 refs., 3 figs

Slowing down of relativistic heavy ions and new applications

International Nuclear Information System (INIS)

Geissel, H.; Scheidenberger, C.

1997-10-01

New precision experiments using powerful accelerator facilities and high-resolution spectrometers have contributed to a better understanding of the atomic and nuclear interactions of relativistic heavy ions with matter. Experimental results on stopping power and energy-loss straggling of bare heavy projectiles demonstrate large systematic deviations from theories based on first order perturbation. The energy-loss straggling is more than a factor of two enhanced for the heaviest projectiles compared to the relativistic Bohr formula. The interaction of cooled relativistic heavy ions with crystals opens up new fields for basic research and applications, i. e., for the first time resonant coherent excitations of both atomic and nuclear levels can be measured at the first harmonic. The spatial monoisotopic separation of exotic nuclei with in-flight separators and the tumor therapy with heavy ions are new applications based on a precise knowledge of slowing down. (orig.)

Transport mean free path related to trajectory patterns: Comparison of nonrelativistic and highly relativistic electron penetration through matter

International Nuclear Information System (INIS)

Liljequist, D.; Ismail, M.

1987-01-01

This analysis is based on the similarity between multiple scattering and slowing down (random walk) processes described by the same transport mean-free-path function λ/sub tr/(s) (s = path length). We discuss the connection between λ/sub tr/(s) and the characteristic appearance and scale of the trajectory pattern. Straggling is considered by means by stochastically discontinuous λ/sub tr/(s) functions. In the application to electron penetration, we show that while nonrelativistic electron penetration is modeled by λ/sub tr/ = (r-s)/α, where r is the range and α is a material-dependent dimensionless constant, highly relativistic electron penetration is modeled by λ/sub tr/proportionalexp(-s/Λ), where Λ is a length characteristic for the penetrated material. The respective trajectory patterns are distinctly different. The effect of straggling on the trajectory pattern in the highly relativistic case is demonstrated by means of a simple model of the stochastic λ/sub tr/(s) behavior

A Generalized Boltzmann Fokker-Planck Method for Coupled Charged Particle Transport

Energy Technology Data Exchange (ETDEWEB)

Prinja, Anil K

2012-01-09

The goal of this project was to develop and investigate the performance of reduced-physics formulations of high energy charged particle (electrons, protons and heavier ions) transport that are computationally more efficient than not only analog Monte Carlo methods but also the established condensed history Monte Carlo technique. Charged particles interact with matter by Coulomb collisions with target nuclei and electrons, by bremsstrahlung radiation loss and by nuclear reactions such as spallation and fission. Of these, inelastic electronic collisions and elastic nuclear collisions are the dominant cause of energy-loss straggling and angular deflection or range straggling of a primary particle. These collisions are characterized by extremely short mean free paths (sub-microns) and highly peaked, near-singular differential cross sections about forward directions and zero energy loss, with the situation for protons and heavier ions more extreme than for electrons. For this reason, analog or truephysics single-event Monte Carlo simulation, while possible in principle, is computationally prohibitive for routine calculation of charged particle interaction phenomena.

Evidence for age-related performance degradation of (241)Am foil sources commonly used in UK schools.

Science.gov (United States)

Whitcher, R; Page, R D; Cole, P R

2014-06-01

The characteristics of alpha radiation have for decades been demonstrated in UK schools using small sealed (241)Am sources. There is a small but steady number of schools who report a considerable reduction in the alpha count rate detected by an end-window GM detector compared with when the source was new. This cannot be explained by incorrect apparatus or set-up, foil surface contamination, or degradation of the GM detector. The University of Liverpool and CLEAPSS collaborated to research the cause of this performance degradation. The aim was to find what was causing the performance degradation and the ramifications for both the useful and safe service life of the sources. The research shows that these foil sources have greater energy straggling with a corresponding reduction in spectral peak energy. A likely cause for this increase in straggling is a significant diffusion of the metals over time. There was no evidence to suggest the foils have become unsafe, but precautionary checks should be made on old sources.

Energy-loss of He ions in carbon allotropes studied by elastic resonance in backscattering spectra

Energy Technology Data Exchange (ETDEWEB)

Tosaki, Mitsuo, E-mail: tosaki.mitsuo.3v@kyoto-u.ac.jp [Radioisotope Research Center, Kyoto University, Kyoto 606-8501 (Japan); Rauhala, Eero [Department of Physics, University of Helsinki (Finland)

2015-10-01

Backscattering spectra for {sup 4}He ions incident on carbon allotropes have been measured in the energy range from 4.30 to 4.95 MeV in steps of 50–100 keV at scattering angles of 106° and 170°. We used three carbon allotropes: graphite, diamond and amorphous carbon. For all these allotropes, we can observe the sharp ({sup 4}He, {sup 12}C) elastic nuclear resonance at the He ion energy of 4.265 MeV in the backscattering spectra. By varying the incident He energy, we have systematically analyzed the profiles of the resonance peaks to study the energy-loss processes: stopping cross-sections and energy-loss straggling around the interesting region of the stopping maximum at about 500 keV. We focus on the resonance profiles and investigate an allotropic effect concerning the energy-loss. Furthermore, an energy bunching effect on the straggling is presented and the mechanism is discussed.

Contribution of backscattered electrons to the total electron yield ...

Indian Academy of Sciences (India)

a better fit to the experiment compared to the power-law. Keywords ... is based on many different mechanisms, for example, ion-induced secondary elec- ... modified these theories using a Lindhard power potential formalism to describe SE ..... principle. The constant-loss indicates the importance of straggling of the primaries.

Fulltext PDF

Indian Academy of Sciences (India)

IAS Admin

LEAVED ALANGIUM) of Alangiaceae is a small deciduous tree, sometimes straggling and sometimes spinous. Leaves are alternate, variable, narrowly oblong or ovate-lanceolate. Flowers are in axillary fascicles. They are 1.5–2 cms long, white in color, attractive when in clusters and are sweet-scented. Fruits are ovoid or ...

Performance projections and design optimization of planar double gate SOI MOSFETs for logic technology applications

International Nuclear Information System (INIS)

Kranti, Abhinav; Hao Ying; Armstrong, G Alastair

2008-01-01

In this paper, by investigating the influence of source/drain extension region engineering (also known as gate–source/drain underlap) in nanoscale planar double gate (DG) SOI MOSFETs, we offer new insights into the design of future nanoscale gate-underlap DG devices to achieve ITRS projections for high performance (HP), low standby power (LSTP) and low operating power (LOP) logic technologies. The impact of high-κ gate dielectric, silicon film thickness, together with parameters associated with the lateral source/drain doping profile, is investigated in detail. The results show that spacer width along with lateral straggle can not only effectively control short-channel effects, thus presenting low off-current in a gate underlap device, but can also be optimized to achieve lower intrinsic delay and higher on–off current ratio (I on /I off ). Based on the investigation of on-current (I on ), off-current (I off ), I on /I off , intrinsic delay (τ), energy delay product and static power dissipation, we present design guidelines to select key device parameters to achieve ITRS projections. Using nominal gate lengths for different technologies, as recommended from ITRS specification, optimally designed gate-underlap DG MOSFETs with a spacer-to-straggle (s/σ) ratio of 2.3 for HP/LOP and 3.2 for LSTP logic technologies will meet ITRS projection. However, a relatively narrow range of lateral straggle lying between 7 to 8 nm is recommended. A sensitivity analysis of intrinsic delay, on-current and off-current to important parameters allows a comparative analysis of the various design options and shows that gate workfunction appears to be the most crucial parameter in the design of DG devices for all three technologies. The impact of back gate misalignment on I on , I off and τ is also investigated for optimized underlap devices

Minimization of the emittance growth of multi-charge particle beams in the charge stripping section of RAON

Energy Technology Data Exchange (ETDEWEB)

Hwang, Ji-Gwang [Department of Physics, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Kim, Eun-San, E-mail: eskim1@knu.ac.kr [Department of Physics, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Kim, Hye-Jin, E-mail: hjkim87@ibs.re.kr [Rare Isotope Science Project, Institute for Basic Science, Jeonmin-dong, Yuseong-gu, Daejeon (Korea, Republic of); Jeon, Dong-O [Rare Isotope Science Project, Institute for Basic Science, Jeonmin-dong, Yuseong-gu, Daejeon (Korea, Republic of)

2014-12-11

The charge stripping section of the Rare isotope Accelerator Of Newness (RAON), which is one of the critical components to achieve a high power of 400 kW with a short lianc, is a source of transverse emittance growth. The dominant effects are the angular straggling in the charge stripper required to increase the charge state of the beam and chromatic aberrations in the dispersive section required to separate the selected ion beam from the various ion beams produced in the stripper. Since the main source of transverse emittance growth in the stripper is the angular straggling, it can be compensated for by changing the angle of the phase ellipse. Therefore the emittance growth is minimized by optimizing the Twiss parameters at the stripper. The emittance growth in the charge selection section is also minimized by the correction of high-order aberrations using six sextupole magnets. In this paper, we present a method to minimize the transverse emittance growth in the stripper by changing the Twiss parameters and in the charge selection section by using sextupole magnets.

Monte carlo calculation of energy deposition and ionization yield for high energy protons

International Nuclear Information System (INIS)

Wilson, W.E.; McDonald, J.C.; Coyne, J.J.; Paretzke, H.G.

1985-01-01

Recent calculations of event size spectra for neutrons use a continuous slowing down approximation model for the energy losses experienced by secondary charged particles (protons and alphas) and thus do not allow for straggling effects. Discrepancies between the calculations and experimental measurements are thought to be, in part, due to the neglect of straggling. A tractable way of including stochastics in radiation transport calculations is via the Monte Carlo method and a number of efforts directed toward simulating positive ion track structure have been initiated employing this technique. Recent results obtained with our updated and extended MOCA code for charged particle track structure are presented here. Major emphasis has been on calculating energy deposition and ionization yield spectra for recoil proton crossers since they are the most prevalent event type at high energies (>99% at 14 MeV) for small volumes. Neutron event-size spectra can be obtained from them by numerical summing and folding techniques. Data for ionization yield spectra are presented for simulated recoil protons up to 20 MeV in sites of diameters 2-1000 nm

Stripping foils for the PSB H- injection system

CERN Document Server

Aiba, M; Goddard, B; Weterings, W

2009-01-01

Beam physics considerations for the stripping foil of the PSB H- injection system are described, including the arguments for the foil type, thickness, geometry and positioning. The foil performance considerations are described, including expected stripping efficiency, emittance growth, energy straggling, temperature and lifetime. The required movement ranges and tolerances are detailed, together with the assumptions used.

36Cl-AMS measurements with 3-MV tandem accelerator

International Nuclear Information System (INIS)

Wang Huijuan; Guan Yongjing; Zhang Wei; Jiang Shan; Ming He

2013-01-01

36 C- is one of the most interesting nuclides in accelerator mass spectrometry (AMS) measurements. The application of 36 Cl has been widely applied in various fields. All most all of 36 Cl AMS measurements at natural isotopic concentrations have yet been performed at tandem accelerator with 5 MV or higher terminal voltage. The measure improvement of 36 Cl and other medium heavy isotopes performed at 3 MV in AMS facilities is one of the hottest topics in AMS measurements. In order to increase the suppression factor of 36 S, the energy loss straggling and angular straggling of 36 Cl and 36 S ions in various counter gases (P10, isobutane and propane) were investigated. Some groundwater samples were measured with energy of 32 MeV, and the results were in good agreement with the result obtained with ion energy of 72 MeV. The results indicate that the approximate detection limit of 36 Cl in 3 MV AMS facility is 36 Cl/Cl=1 × 10 -14 , and the uncertainty is 30% when the sample with isotopic ration 36 Cl/Cl≈10 -13 . (authors)

Radiotherapy Proton Interactions in Matter

OpenAIRE

Gottschalk, Bernard

2018-01-01

A survey of physics useful to proton radiotherapy, centered on stopping, scattering and hard scatters: 1. Introduction 2. The fundamental formula dose = fluence x mass stopping power. Practical units, comments on effective stopping power. 3. Range: experimental definition, Beth-Bloch CSDA theory, range-energy tables and approximations, range straggling. 4. Multiple Coulomb Scattering: suggested reading, elements of Moliere theory, the Gaussian approximation, scattering power. 5. Hard scatters...

Stripping Foil Issues for H- Injection into the CERN PSB at 160 MeV

CERN Document Server

Goddard, B; Bracco, C; Carli, C; Meddahi, M; Weterings, W J M

2010-01-01

Beam physics considerations for the stripping foil of the 160 MeV PSB H- injection systems are described, including the arguments for the foil type, thickness, geometry and positioning. The foil performance considerations are described, including expected stripping efficiency, emittance growth, energy straggling, temperature and lifetime. The different beam loss mechanisms are quantified in the context of the aperture limits, operational considerations and collimation requirements.

ERYA (bulk)-finally available and ERYA profile-final adjustments

International Nuclear Information System (INIS)

Pedro de Jesus, A.

2014-01-01

Full text: It was announced and shown that the ERYA-bulk code for analysis of in-depth homogeneous samples is now available and may be downloaded from a web site, where a manual is available to explain how to use it. A tutorial on the code’s interface and capabilities was shown, namely the capability of calculating simultaneously the mass concentration of an arbitrary number of elements in a homogeneous sample (any thickness), with the additional capability of fitting the sample matrix composition. This may be done by using as an initial estimate either the results from another analytical technique such as PIXE (usually used as a complementary technique) or with prior knowledge of the main chemical composition. Regarding the development of a routine to perform depth profile measurements, the main aspects of what was already done were presented: 1. the routine was developed to be used interactively, as RUMP, or SigmaNRA, by comparing the calculated and experimental results for each concentration distribution given by the user; 2. the routine uses a division of the target into layers (as in the case of ERYA bulk) but within each layer the projectiles have an energy distribution and not a single energy value (as in the case of ERYA bulk); this implies that depth together with average energy must be calculated for every layer; 3. the energy distribution takes into account Beam Energy Resolution, Beam Energy Straggling and Doppler Broadening; 4. in order to implement energy straggling calculations, Landau, Vavilov and Gaussian distributions are used; 5. the resonant cross section function may be replaced by an ideal Breit-Wigner function; further efforts to implement the code to use resonance strengths are being developed; 6. the concentration may be given for any number of discrete layers or as a depth dependent continuous function. This profile routine is already working with a user-friendly interface, which was also presented. Further tests and improvements are

Penetration of charged particles through ordered isotropic matter

International Nuclear Information System (INIS)

Sigmund, P.

1977-01-01

A brief summary of some new results on fluctuation phenomena in particle penetration is presented. The results include collision statistics, positive and negative correlations and a framework for the treatment of cumulative effects in particle penetration. Incorporation of projectile and target states in the description and energy-loss straggling are discussed. Small-angle multiple scattering is considered and a comment made on ionic charge states. (B.R.H.)

Microdosimetry and its applications

International Nuclear Information System (INIS)

Sedlak, A.

1989-01-01

Basic microdosimetry principles and their theoretical and experimental aspects are explained and discussed. Part A gives a description of stochastic processes and presents the principles of microdosimetry, defines basic quantities and methods, such as linear energy transfer, the straggling theory, the theory of particle path structure, etc. Part B deals with practical applications of microdosimetry in radiobiology, radiotherapy, radiation protection, radiation chemistry, thermoluminescence and microelectronics. (J.J.). 57 figs

Energy loss and energy straggling of light ions in fullerite

Czech Academy of Sciences Publication Activity Database

Vacík, Jiří; Hnatowicz, Vladimír; Červená, Jarmila; Naramoto, H.; Yamamoto, S.; Fink, D.

2001-01-01

Roč. 9, č. 2 (2001), s. 197-209 ISSN 1064-122X R&D Projects: GA ČR GA202/96/0077; GA ČR GV202/97/K038; GA AV ČR KSK1010104 Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 0.800, year: 2001

Active Radiation Detectors for Use in Space Beyond Low Earth Orbit: Spatial and Energy Resolution Requirements and Methods for Heavy Ion Charge Classification

Science.gov (United States)

McBeth, Rafe A.

Space radiation exposure to astronauts will need to be carefully monitored on future missions beyond low earth orbit. NASA has proposed an updated radiation risk framework that takes into account a significant amount of radiobiological and heavy ion track structure information. These models require active radiation detection systems to measure the energy and ion charge Z. However, current radiation detection systems cannot meet these demands. The aim of this study was to investigate several topics that will help next generation detection systems meet the NASA objectives. Specifically, this work investigates the required spatial resolution to avoid coincident events in a detector, the effects of energy straggling and conversion of dose from silicon to water, and methods for ion identification (Z) using machine learning. The main results of this dissertation are as follows: 1. Spatial resolution on the order of 0.1 cm is required for active space radiation detectors to have high confidence in identifying individual particles, i.e., to eliminate coincident events. 2. Energy resolution of a detector system will be limited by energy straggling effects and the conversion of dose in silicon to dose in biological tissue (water). 3. Machine learning methods show strong promise for identification of ion charge (Z) with simple detector designs.

Interaction of heavy ions with matter. Progress report and summary report

International Nuclear Information System (INIS)

Boring, J.W.; Johnson, R.E.

1976-07-01

The processes that occur when a heavy atomic particle (ion, atom, etc.) interacts with matter, particularly the effects produced on biological systems, were investigated. Results of the investigations over a three year period are reviewed. Areas covered include: energy loss, straggling and stopping; projected ranges and first-order moments; damage cross section for inactivation of RNase; and spatial distribution of damage in RNase. History and objectives of the research program are included

Depth profiling of {sup 14} N and {sup 20} Ne implantation into iron and steel using(p, gamma) reactions. Vol. 2

Energy Technology Data Exchange (ETDEWEB)

Wriekat, A; Haj-Abdellah, M [Physics Department, University of Jordan, Amman (Jordan)

1996-03-01

Depth profiles of {sup 14} N and {sup 20} Ne ions at 800 KeV implanted into iron and by steel samples have been measured by means of the proton induced {gamma}- ray emission (Pige) technique. The range, R, and range straggling, {Delta}R for these profiles were obtained and compared with theoretical calculations. The experimental results did show that pure iron retains more N and Ne than steel. 2 figs., 1 tab.

Penetration of relativistic heavy ions through matter

International Nuclear Information System (INIS)

Scheidenberger, C.; Geissel, H.

1997-07-01

New heavy-ion accelerators covering the relativistic and ultra-relativistic energy regime allow to study atomic collisions with bare and few-electron projectiles. High-resolution magnetic spectrometers are used for precise stopping-power and energy-loss straggling measurements. Refined theories beyond the Born approximation have been developed and are confirmed by experiments. This paper summarizes the large progress in the understanding of relativistic heavy-ion penetration through matter, which has been achieved in the last few years. (orig.)

Slowing down and straggling of protons and heavy ions in matter

International Nuclear Information System (INIS)

Aernsbergen, L.M. van.

1986-01-01

The Doppler Shift Attenuation (DSA) method is widely used to measure lifetimes of nuclear states. However, many of the lifetimes resulting from DSA measurements display large variations which are caused by an insufficient knowledge of slowing down processes of nucleus recoils. The measurement of 'ranges' is an often used method to study these slowing down processes. In this kind of measurement the distributions of implanted ions are determined for example by the method of Rutherford backscattering or from the yield curve of a resonant nuclear reaction. In this thesis, research on energy-loss processes of protons and Si ions in aluminium is presented. The so-called Resonance Shift method has been improved for the measurements on the protons themselves. This method has only been used occasionally before. A new method has been developed, which is called the Transmission Doppler Shift Attenuation (TDSA) method, for the measurement on Si ions. (Auth.)

Analysis of a nuclear backscattering and reaction data by the method of convolution integrals

International Nuclear Information System (INIS)

Lewis, M.B.

1979-02-01

A quantitative description of nuclear backscattering and reaction processes is made. Various formulas pertinent to nuclear microanalysis are assembled in a manner useful for experimental application. Convolution integrals relating profiles of atoms in a metal substrate to the nuclear reaction spectra obtained in the laboratory are described and computed. Energy straggling and multiple scattering are explicitly included and shown to be important. Examples of the application of the method to simple backscattering, oxide films, and implanted gas are discussed. 7 figures, 1 table

High resistivity in InP by helium bombardment

International Nuclear Information System (INIS)

Focht, M.W.; Macrander, A.T.; Schwartz, B.; Feldman, L.C.

1984-01-01

Helium implants over a fluence range from 10 11 to 10 16 ions/cm 2 , reproducibly form high resistivity regions in both p- and n-type InP. Average resistivities of greater than 10 9 Ω cm for p-type InP and of 10 3 Ω cm for n-type InP are reported. Results are presented of a Monte Carlo simulation of helium bombardment into the compound target InP that yields the mean projected range and the range straggling

Proton therapy analysis using the Monte Carlo method

Energy Technology Data Exchange (ETDEWEB)

Noshad, Houshyar [Center for Theoretical Physics and Mathematics, AEOI, P.O. Box 14155-1339, Tehran (Iran, Islamic Republic of)]. E-mail: hnoshad@aeoi.org.ir; Givechi, Nasim [Islamic Azad University, Science and Research Branch, Tehran (Iran, Islamic Republic of)

2005-10-01

The range and straggling data obtained from the transport of ions in matter (TRIM) computer program were used to determine the trajectories of monoenergetic 60 MeV protons in muscle tissue by using the Monte Carlo technique. The appropriate profile for the shape of a proton pencil beam in proton therapy as well as the dose deposited in the tissue were computed. The good agreements between our results as compared with the corresponding experimental values are presented here to show the reliability of our Monte Carlo method.

A model and computer code for the Monte Carlo simulation of relativistic electron and positron penetration through matter

International Nuclear Information System (INIS)

Ismail, M.; Liljequist, D.

1986-10-01

In the present model, the treatment of elastic scattering is based on the similarity of multiple scattering processes with equal transport mean free path /LAMBDA/sub(tr). Elastic scattering events are separated by an artificially enlarged mean free path. In such events, scattering is optionally performed either by means of a single, energy-dependent scattering angle, or by means of a scattering angle distribution of the same form as the screened Rutherford cross section, but with an artificial screening factor. The physically correct /LAMBDA/sub(tr) value is obtained by appropriate choice of scattering angle or screening factor, respectively. We find good agreement with experimental transmission and with energy loss distributions. The Rutherford-like model gives good agreement with experimental angular distribution even for the penetration of very thin layers. Treatment of electron energy loss is based on the partial CSDA method: energy losses W WMINSE are treated as discrete electron-electron or positron-electron scattering events. Similarly, for bremsstrahlung photon energies W WMINR are treated at discrete events. The sensitivity of the model to the parameters WMINSE and WMINR is studied. WMINR can, in practise, be made negligibly small, and WMINSE can without any excessive computer time be made as small as to give results in good agreement with experiment and with computations based on Landau theory of straggling. Using this model, we study some of the characteristic features of relativistic electron transmission, energy loss distributions, straggling, angular distributions and trajectories. (authors)

Subnanosecond timing with ion-implanted detectors

International Nuclear Information System (INIS)

Rijken, H.A.; Klein, S.S.; Jacobs, W.; Teeuwen, L.J.H.G.W.; Voigt, M.J.A. de; Burger, P.

1992-01-01

The energy resolution of ion-implanted charged particle detectors may be improved by decreasing the thickness of the implanted detector window to minimize energy straggling. Because of the resistance of this layer, however, the timing depends on the position of entry. Two solutions to this conflict between energy resolution and time resolution are studied: evaporating a very thin aluminum layer on the detector window and fabricating a rectangular detector. Both solutions are shown to be successful with a total time resolution in the low subnanosecond region (<200 ps). (orig.)

Experimental studies of heavy-ion slowing down in matter

International Nuclear Information System (INIS)

Geissel, H.; Weick, H.; Scheidenberger, C.; Bimbot, R.; Gardes, D.

2002-08-01

Measurements of heavy-ion slowing down in matter differ in many aspects from experiments with light particles like protons and α-particles. An overview of the special experimental requirements, methods, data analysis and interpretation is presented for heavy-ion stopping powers, energy- and angular-straggling and ranges in the energy domain from keV/u up to GeV/u. Characteristic experimental results are presented and compared with theory and semiempirical predictions. New applications are outlined, which represent a challenge to continuously improve the knowledge of heavy-ion slowing down. (orig.)

Atomic and molecular data for radiotherapy and radiation research. Final report of a co-ordinated research programme

Energy Technology Data Exchange (ETDEWEB)

NONE

1995-05-01

The report includes 9 chapters and an appendix: Development of particle therapy in cancer management. Expectations and justification of the heavy-ion therapy programs; Ionization by fast charged particles; Electron collision cross sections; Low energy electron interaction with condensed matter; Photoabsorption, photoionization, and photodissociation cross sections; Collision processes between ions and excited neutrals and surrounding molecules; Stopping powers, ranges, and straggling; Yields of ionization and excitation in irradiated matter; Track structure quantities; ESTAR, PSTAR, and ASTAR: computer programs for calculating stopping powers and ranges for electrons, protons, and helium ions (appendix). A separate abstract was prepared for each chapter. Refs, figs and tabs.

An apparatus to measure stopping powers for low-energy antiprotons and protons

CERN Document Server

Andersen, H H; Ichioka, T; Knudsen, H; Møller, S P; Uggerhøj, U

2002-01-01

One of the experiments to be performed under the ASACUSA collaboration at the CERN Antiproton Decelerator is a measurement of the energy loss of low energy antiprotons in thin foils. An electrostatic spectrometer has been developed for this task. We describe the design and initial tests of the apparatus with protons. By changing a high-voltage applied on the target the energy of the projectile ions at impact on the target can easily be varied. In this way we have measured the stopping-power and the energy-loss straggling for protons over a wide energy range to below one keV.

Energy distribution measurements of 300 keV transmitted protons at the axial-to-planar channeling transition in silicon

International Nuclear Information System (INIS)

Bulgakov, Yu.V.; Lenkeit, K.; Stolle, R.

1983-01-01

The energy distribution of protons with initial energy of 300 keV which passed through a 0.76 μm thick Si monocrystal film was measured under the conditions of transition from the axial to planar (110) channeling. The experimental angular dependences of the transparency coefficient and of the first three moments of the energy distributions (energy loss, straggling, and skewness) for 300 keV protons are shown. The shape of curves are discussed explaining the resonance dechanneling effect and the non-monotonic behaviour of transparency in the case of the axial-to-planar channeling transition

Atomic and molecular data for radiotherapy and radiation research. Final report of a co-ordinated research programme

International Nuclear Information System (INIS)

1995-05-01

The report includes 9 chapters and an appendix: Development of particle therapy in cancer management. Expectations and justification of the heavy-ion therapy programs; Ionization by fast charged particles; Electron collision cross sections; Low energy electron interaction with condensed matter; Photoabsorption, photoionization, and photodissociation cross sections; Collision processes between ions and excited neutrals and surrounding molecules; Stopping powers, ranges, and straggling; Yields of ionization and excitation in irradiated matter; Track structure quantities; ESTAR, PSTAR, and ASTAR: computer programs for calculating stopping powers and ranges for electrons, protons, and helium ions (appendix). A separate abstract was prepared for each chapter. Refs, figs and tabs

Energy loss of charged particles to molecular gas targets

International Nuclear Information System (INIS)

Sigmund, P.

1976-01-01

The energy loss spectrum of fast charged particles penetrating a dilute molecular gas target has been analysed theoretically, with a homogeneous gas mixture in the state of complete dissociation as a reference standard. It is shown that the geometrical structure of molecules causes the energy-loss straggling and higher moments over the energy-loss spectrum to be greater than the corresponding quantities for a completely dissociated gas of equal composition. Such deviations from additivity are shown to be most pronounced at energies around the stopping-power maximum. There is found supporting evidence in the experimental literature. (Auth.)

The beam matching system between the preaccelerator and the main accelerator of the Van-de-Graaff cyclotron combination VICKSI

International Nuclear Information System (INIS)

Hinderer, G.

1975-01-01

The beam matching between the two accelerators of the heavy-ion accelerator combination VICKSI (Van de Graaff Isochron-Cyclotron Kombination fuer schwere Ionen) which is under construction at the Hahn-Meitner-Institut Berlin is investigated. The main elements are a combined gas- and carbon foil-stripper to increase the charge state of the ions and two clystron type high frequency bunchers for matching the longitudinal phase space. In order to minimize the enlargement of phase space due to energy- and angle straggling in the foil stripper a focus in all three dimensions is generated at this position. (orig./WL) [de

2-D analytical modeling of subthreshold current and subthreshold swing for ion-implanted strained-Si double-material double-gate (DMDG) MOSFETs

Science.gov (United States)

Goel, Ekta; Singh, Kunal; Singh, Balraj; Kumar, Sanjay; Jit, Satyabrata

2017-09-01

In this paper, the subthreshold behavior of ion-implanted strained-Si double-material double-gate (DMDG) MOSFETs has been analyzed by means of subthreshold current and subthreshold swing. The surface potential based formulation of subthreshold current and subthreshold swing is done by solving the 2-D Poisson's equations in the channel region using parabolic approximation method. The dependence of subthreshold characteristics on various device parameters such as gate length ratio, Ge mole fraction, peak doping concentration, projected range, straggle parameter etc. has been studied. The modeling results are found to be well matched with the simulation data obtained by a 2-D device simulator, ATLAS™, from SILVACO.

Statistical fluctuations in heavy-charged-particle tracks

International Nuclear Information System (INIS)

Hamm, R.N.; Turner, J.E.; Wright, H.A.

1985-01-01

We present the results of the following Monte Carlo track-segment calculations for protons with energies of 1, 2, 5, and 10 MeV in liquid water: (1) radial dose around a long segment of a proton track; (2) energy-loss straggling distributions for protons of different energies in 1 μm of water; (3) the distribution in the average absorbed dose around track segments of various lengths; (4) the relative standard deviations in these distributions as functions of the length of the track segments. Calculations such as those presented here are useful for studying track phenomena on a microdosimetric scale, where statistical fluctuations are substantial

Relation between the conditions of helium ion implantation and helium void equilibrium parameters

International Nuclear Information System (INIS)

Neklyudov, I.M.; Rybalko, V.F.; Ruzhitskij, V.V.; Tolstolutskaya, G.D.

1981-01-01

The conditions of helium thermodynamic equilibrium in a system of voids produced by helium ion bombardment of a metal sample are studied. As an initial equation for description of the equilibrium the Clapeyron equation was used. The equation is obtained relating basic parameters of helium voids (average diameter and density) to irradiation parameters (dose, ion energy (straggling)) and properties of the metal (surface tension coefficient, yield strength). Comparison of the calculations with experimental data on helium in nickel found in literature shows that the equation yields satisfactory resutls for the dose range 1.10 16 -1x10 17 cm -2 and temperatures T [ru

Ion implantation range and energy deposition codes COREL, RASE4, and DAMG2

International Nuclear Information System (INIS)

Brice, D.K.

1977-07-01

The FORTRAN codes COREL, RASE4 and DAMG2 can be used to calculate quantities associated with ion implantation range and energy deposition distributions within an amorphous target, or for ions incident far from low index directions and planes in crystalline targets. RASE4 calculates the projected range, R/sub p/, the root mean square spread in the projected range, ΔR/sub p/, and the root mean square spread of the distribution perpendicular to the projected range ΔR/sub perpendicular to/. These parameters are calculated as a function of incident ion energy, E, and the instantaneous energy of the ion, E'. They are sufficient to determine the three dimensional spatial distribution of the ions in the target in the Gaussian approximation when the depth distribution is independent of the lateral distribution. RASE4 can perform these calculations for targets having up to four different component atomic species. The code COREL is a short, economical version of RASE4 which calculates the range and straggling variables for E' = 0. Its primary use in the present package is to provide the average range and straggling variables for recoiling target atoms which are created by the incident ion. This information is used by RASE4 in calculating the redistribution of deposited energy by the target atom recoils. The code DAMG2 uses the output from RASE4 to calculate the depth distribution of energy deposition into either atomic processes or electronic processes. With other input DAMG2 can be used to calculate the depth distribution of any energy dependent interaction between the incident ions and target atoms. This report documents the basic theory behind COREL, RASE4 and DAMG2, including a description of codes, listings, and complete instructions for using the codes, and their limitations

Single ion implantation for single donor devices using Geiger mode detectors

International Nuclear Information System (INIS)

Bielejec, E; Seamons, J A; Carroll, M S

2010-01-01

Electronic devices that are designed to use the properties of single atoms such as donors or defects have become a reality with recent demonstrations of donor spectroscopy, single photon emission sources, and magnetic imaging using defect centers in diamond. Ion implantation, an industry standard for atom placement in materials, requires augmentation for single ion capability including a method for detecting a single ion arrival. Integrating single ion detection techniques with the single donor device construction region allows single ion arrival to be assured. Improving detector sensitivity is linked to improving control over the straggle of the ion as well as providing more flexibility in lay-out integration with the active region of the single donor device construction zone by allowing ion sensing at potentially greater distances. Using a remotely located passively gated single ion Geiger mode avalanche diode (SIGMA) detector we have demonstrated 100% detection efficiency at a distance of >75 μm from the center of the collecting junction. This detection efficiency is achieved with sensitivity to ∼600 or fewer electron-hole pairs produced by the implanted ion. Ion detectors with this sensitivity and integrated with a thin dielectric, for example a 5 nm gate oxide, using low energy Sb implantation would have an end of range straggle of -1 and 10 -4 for operation temperatures of ∼300 K and ∼77 K, respectively. Low temperature operation and reduced false, 'dark', counts are critical to achieving high confidence in single ion arrival. For the device performance in this work, the confidence is calculated as a probability of >98% for counting one and only one ion for a false count probability of 10 -4 at an average ion number per gated window of 0.015.

The momentum-loss achromat - a new method for the isotopical separation of relativistic heavy ions

International Nuclear Information System (INIS)

Schmidt, K.H.; Geissel, H.; Muenzenberg, G.; Dufour, J.P.; Hanelt, E.

1987-03-01

The application of the slowing-down process of relativistic heavy ions in a layer of matter in ion-optical devices is theoretically investigated. The modifications of the phase space of the ion beam due to the dissipative forces and the straggling phenomena are discussed. Methods are developed to study the properties of the momentum-loss achromat, an isotope separator consisting of an achromatic magnetic system with an energy degrader located in the intermediate dispersive focal plane. This device separates projectile fragments with respect to A and Z up to uranium over a wide energy range with an efficiency in the order of 50% and with separation times of several hundred nanoseconds. (orig.)

Algorithms for the rapid simulation of Rutherford backscattering spectra

Energy Technology Data Exchange (ETDEWEB)

Doolittle, L.R.

1985-06-01

A computer program which simulates Rutherford backscattering spectra is currently in use at Cornell University and other institutions. Straggling and detector resolution are among the effects included. Samples are considered to be made up of a finite number of layers, each with uniform composition. The emphasis in the mathematics is on accuracy beyond that of iterated surface approximation methods. Thicker layers can thus be analyzed without a net loss in accuracy. The mathematical description of the sample can then have fewer layers, and fewer calculations are required. This paper provides estimates of the number of arithmetic operations used by the program for any simulation to demonstrate the tradeoffs between accuracy, computation time, and algorithm sophistication.

Algorithms for the rapid simulation of Rutherford backscattering spectra

International Nuclear Information System (INIS)

Doolittle, L.R.

1985-01-01

A computer program which simulates Rutherford backscattering spectra is currently in use at Cornell University and other institutions. Straggling and detector resolution are among the effects included. Samples are considered to be made up of a finite number of layers, each with uniform composition. The emphasis in the mathematics is on accuracy beyond that of iterated surface approximation methods. Thicker layers can thus be analyzed without a net loss in accuracy. The mathematical description of the sample can then have fewer layers, and fewer calculations are required. This paper provides estimates of the number of arithmetic operations used by the program for any simulation to demonstrate the tradeoffs between accuracy, computation time, and algorithm sophistication. (orig.)

Cooling equilibrium and beam loss with internal targets in high energy storage rings

International Nuclear Information System (INIS)

Boine-Frankenheim, O.; Hasse, R.; Hinterberger, F.; Lehrach, A.; Zenkevich, P.

2006-01-01

The beam cooling equilibrium with internal target interaction is analyzed for parameters relevant to the proposed High Energy Storage Ring (HESR). For the proposed experiments with anti-protons high luminosities together with low momentum spreads are required. Rate equations are used to predict the rms equilibrium beam parameters. The cooling and IBS rate coefficients are obtained from simplified models. Energy loss straggling in the target and the associated beam loss are analyzed analytically assuming a thin target. A longitudinal kinetic simulation code is used to study the evolution of the momentum distribution in coasting and bunched beams. Analytic expressions for the target induced momentum tail are found in good agreement with the simulation results

An algorithm for computing screened Coulomb scattering in GEANT4

Energy Technology Data Exchange (ETDEWEB)

Mendenhall, Marcus H. [Vanderbilt University Free Electron Laser Center, P.O. Box 351816 Station B, Nashville, TN 37235-1816 (United States)]. E-mail: marcus.h.mendenhall@vanderbilt.edu; Weller, Robert A. [Department of Electrical Engineering and Computer Science, Vanderbilt University, P.O. Box 351821 Station B, Nashville, TN 37235-1821 (United States)]. E-mail: robert.a.weller@vanderbilt.edu

2005-01-01

An algorithm has been developed for the GEANT4 Monte-Carlo package for the efficient computation of screened Coulomb interatomic scattering. It explicitly integrates the classical equations of motion for scattering events, resulting in precise tracking of both the projectile and the recoil target nucleus. The algorithm permits the user to plug in an arbitrary screening function, such as Lens-Jensen screening, which is good for backscattering calculations, or Ziegler-Biersack-Littmark screening, which is good for nuclear straggling and implantation problems. This will allow many of the applications of the TRIM and SRIM codes to be extended into the much more general GEANT4 framework where nuclear and other effects can be included.

An algorithm for computing screened Coulomb scattering in GEANT4

International Nuclear Information System (INIS)

Mendenhall, Marcus H.; Weller, Robert A.

2005-01-01

An algorithm has been developed for the GEANT4 Monte-Carlo package for the efficient computation of screened Coulomb interatomic scattering. It explicitly integrates the classical equations of motion for scattering events, resulting in precise tracking of both the projectile and the recoil target nucleus. The algorithm permits the user to plug in an arbitrary screening function, such as Lens-Jensen screening, which is good for backscattering calculations, or Ziegler-Biersack-Littmark screening, which is good for nuclear straggling and implantation problems. This will allow many of the applications of the TRIM and SRIM codes to be extended into the much more general GEANT4 framework where nuclear and other effects can be included

Microanalysis of Fluorine Contamination and its Depth Distribution in Zircaloy by the Use of a Charged Particle Nuclear Reaction

Energy Technology Data Exchange (ETDEWEB)

Moeller, E; Starfelt, N

1966-07-15

Fluorine contamination on and below the surface of zircaloy has been studied by means of proton irradiation using a Van de Graaff accelerator and the detection of prompt gamma radiation from the {sup 19}F (p, {alpha}{gamma}) {sup 16}O reaction. Formulae for deriving depth distributions of impurities from the measured counting rates have been derived. The influence of energy straggling on the depth resolution has been studied. Both the total amount and the depth distribution have been measured in samples, which have undergone different treatments. Because of the high yield from the reaction used, a quantity of fluorine less than 0. 01 {mu}g/cm{sup 2} can be detected by this method.

Advances in Monte-Carlo code TRIPOLI-4®'s treatment of the electromagnetic cascade

Science.gov (United States)

Mancusi, Davide; Bonin, Alice; Hugot, François-Xavier; Malouch, Fadhel

2018-01-01

TRIPOLI-4® is a Monte-Carlo particle-transport code developed at CEA-Saclay (France) that is employed in the domains of nuclear-reactor physics, criticality-safety, shielding/radiation protection and nuclear instrumentation. The goal of this paper is to report on current developments, validation and verification made in TRIPOLI-4 in the electron/positron/photon sector. The new capabilities and improvements concern refinements to the electron transport algorithm, the introduction of a charge-deposition score, the new thick-target bremsstrahlung option, the upgrade of the bremsstrahlung model and the improvement of electron angular straggling at low energy. The importance of each of the developments above is illustrated by comparisons with calculations performed with other codes and with experimental data.

Advances in Monte-Carlo code TRIPOLI-4®’s treatment of the electromagnetic cascade

Directory of Open Access Journals (Sweden)

Mancusi Davide

2018-01-01

Full Text Available TRIPOLI-4® is a Monte-Carlo particle-transport code developed at CEA-Saclay (France that is employed in the domains of nuclear-reactor physics, criticality-safety, shielding/radiation protection and nuclear instrumentation. The goal of this paper is to report on current developments, validation and verification made in TRIPOLI-4 in the electron/positron/photon sector. The new capabilities and improvements concern refinements to the electron transport algorithm, the introduction of a charge-deposition score, the new thick-target bremsstrahlung option, the upgrade of the bremsstrahlung model and the improvement of electron angular straggling at low energy. The importance of each of the developments above is illustrated by comparisons with calculations performed with other codes and with experimental data.

Outbreak patterns of the novel avian influenza (H7N9)

Science.gov (United States)

Pan, Ya-Nan; Lou, Jing-Jing; Han, Xiao-Pu

2014-05-01

The attack of novel avian influenza (H7N9) in East China caused a serious health crisis and public panic. In this paper, we empirically analyze the onset patterns of human cases of the novel avian influenza and observe several spatial and temporal properties that are similar to other infectious diseases. More specifically, using the empirical analysis and modeling studies, we find that the spatio-temporal network that connects the cities with human cases along the order of outbreak timing emerges two-regime-power-law edge-length distribution, indicating the picture that several islands with higher and heterogeneous risk straggle in East China. The proposed method is applicable to the analysis of the spreading situation in the early stage of disease outbreak using quite limited dataset.

Dynamics of solid inner-shell electrons in collisions with bare and dressed swift ions

International Nuclear Information System (INIS)

Montanari, C.C.; Miraglia, J. E.; Arista, N.R.

2002-01-01

We analyze the dynamical interactions of swift heavy projectiles and solid inner-shell electrons. The dielectric formalism employed to deal with the free-electron gas is extended to account for the core electrons, by using the local plasma approximation. Results for stopping power, energy straggling, and inner-shell ionization in collisions of bare ions with metals are displayed, showing very good accord with the experimental data. Simultaneous excitations of projectile and target electrons are also analyzed. In the high-energy range we find a similar contribution of target core and valence electrons to the probability of projectile-electron loss. The problem of no excitation threshold within the local plasma approximation and the possibility of collective excitations of the shells are discussed

Proposal for a CINDA-type stopping data bibliography (CISDA)

International Nuclear Information System (INIS)

Ivascu, M.; Bucurescu, D.; Avrigeanu, V.

1980-11-01

The present status and requirements of stopping power data (SD) are reviewed, by considering the significant trends in applications of nuclear data. The need of centralized information on SD is emphasized. If the establishing of compiled and evaluated SD libraries format is possible only through an internationally co-ordinated action, to produce a computerized index to bibliographic references on SD is an easier task. One describes a plan of a CINDA-type SD bibliography (named CISDA - Computer Index of Stopping Data) containing experimental, theoretical and evaluated works for stopping powers, range, energy and range straggling of ions with atomic mass and charge both larger than or equal to 1. The index organization and detailed field descriptions of reference records are presented. (author)

Neutron interactions with biological tissue. Progress report, December 1, 1993--November 30, 1994

International Nuclear Information System (INIS)

1994-01-01

An attempt is made to obtain information about the physical stage of neutron interactions with tissue through secondary charged particles. The authors use theoretical calculations whose input includes neutron cross section data; range, stopping power, ion yield, and straggling information; and geometrical properties. Outputs are initial and slowing-down spectra of charged particles, kerma factors, average values of quality factors, microdosimetric spectra, and integral microdosimetric parameters such as bar y F , bar y D , y * . Since it has become apparent that nanometer site sizes are more relevant to radiobiological effects, the calculations of event size spectra and their parameters have been extended to these smaller diameters. This information is basic to radiological physics, radiation biology, radiation protection of workers, and standards for neutron dose measurement

Physical aspects of heavy charged particle beams for radiotherapy

International Nuclear Information System (INIS)

Kawashima, Katsuhiro

1989-01-01

Physical properties of heavy ion beams are discussed to improve the physical dose distributions in view of radiotherapy. Preservation of the structural and functional integrity of adjacent normal tissue is required to achieve great probability of tumor control. This will be accomplished with the reduction of irradiated volume of normal tissues and with greater relative biological effectiveness (RBE) on tumor cells than that on surrounding normal cells. This suggests the use of heavy ion beams as new source of radiation that increases the therapeutic ratio. The basis of the improvement in the physical dose distribution by use of heavy charged particles is due to the finite range of the beams and to the less multiple coulomb scattering of the particles having a heavier atomic mass than proton. The depth dose distributions and dose profiles of heavy particle beams are discussed in this article. The lateral sharpness of heavy charged particles is comparable to the penumbra of high energy photon and electron beams and is not of clinical concern due to less coulomb scattering of heavy ions to lateral direction in traversing a medium. The dose gradient at the end of range of primary beam is dependent upon the energy spread and range straggling of the particles. The magnitude of range straggling is nearly proportional to the range and inversely proportional to the inverse square root of the particle mass. Heavy ion beams also undergo nuclear interactions, in which the primary beam may produce lower atomic number particles. Therefore, the dose beyond the Bragg peak is due to those fragments. Fragmentation increases as a function of the atomic mass to the 2/3 power and with the energy of the particles. Thus, the production of fragments diminishes the depth dose advantages of heavy ions. The choice of ion for radiotherapy may depend on evaluation of important parameter for tumor control. (J.P.N.)

Innershell ionization by fast protons, alpha particles and carbon ions

International Nuclear Information System (INIS)

Dijk, J.H. van.

1984-01-01

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

Single-Ion Implantation for the Development of Si-Based MOSFET Devices with Quantum Functionalities

Directory of Open Access Journals (Sweden)

Jeffrey C. McCallum

2012-01-01

Full Text Available Interest in single-ion implantation is driven in part by research into development of solid-state devices that exhibit quantum behaviour in their electronic or optical characteristics. Here, we provide an overview of international research work on single ion implantation and single ion detection for development of electronic devices for quantum computing. The scope of international research into single ion implantation is presented in the context of our own research in the Centre for Quantum Computation and Communication Technology in Australia. Various single ion detection schemes are presented, and limitations on dopant placement accuracy due to ion straggling are discussed together with pathways for scale-up to multiple quantum devices on the one chip. Possible future directions for ion implantation in quantum computing and communications are also discussed.

Ion Implantation and Synthesis of Materials

CERN Document Server

Nastasi, Michael

2006-01-01

Ion implantation is one of the key processing steps in silicon integrated circuit technology. Some integrated circuits require up to 17 implantation steps and circuits are seldom processed with less than 10 implantation steps. Controlled doping at controlled depths is an essential feature of implantation. Ion beam processing can also be used to improve corrosion resistance, to harden surfaces, to reduce wear and, in general, to improve materials properties. This book presents the physics and materials science of ion implantation and ion beam modification of materials. It covers ion-solid interactions used to predict ion ranges, ion straggling and lattice disorder. Also treated are shallow-junction formation and slicing silicon with hydrogen ion beams. Topics important for materials modification, such as ion-beam mixing, stresses, and sputtering, are also described.

ATLAS beam properties: some implications for target making

International Nuclear Information System (INIS)

Pardo, R.

1984-01-01

The expansion of the tandem-linac booster into the Argonne Tandem-Linac Accelerator System, ATLAS, is approximately 40% complete. When completed, the facility will provide beams of heavy ions from lithium to tin with energies eventually, to 25 MeV/amu. The existing facility continues to provide beams for the experimental program in nuclear and atomic physics during the construction phase. The booster system is capable of accelerating ions as heavy as selenium to energies of 10 MeV/amu for the lighter ions. The good beam quality provided by the linac means that multiple scattering, energy straggling, and target inhomogeneities are major factors in the resolution attainable in experiments. The beam properties that can be expected from ATLAS will be discussed and the present state of high resolution experiments will be reported

Neutron interactions with biological tissue. Final report

International Nuclear Information System (INIS)

1998-01-01

This program was aimed at creating a quantitative physical description, at the micrometer and nanometer levels, of the physical interactions of neutrons with tissue through the ejected secondary charged particles. The authors used theoretical calculations whose input includes neutron cross section data; range, stopping power, ion yield, and straggling information; and geometrical properties. Outputs are initial and slowing-down spectra of charged particles, kerma factors, average values of quality factors, microdosimetric spectra, and integral microdosimetric parameters such as bar y F , bar y D , y * . Since it has become apparent that nanometer site sizes are also relevant to radiobiological effects, the calculations of event size spectra and their parameters were extended to these smaller diameters. This information is basic to radiological physics, radiation biology, radiation protection of workers, and standards for neutron dose measurement

Monte Carlo electron-transport calculations for clinical beams using energy grouping

Energy Technology Data Exchange (ETDEWEB)

Teng, S P; Anderson, D W; Lindstrom, D G

1986-01-01

A Monte Carlo program has been utilized to study the penetration of broad electron beams into a water phantom. The MORSE-E code, originally developed for neutron and photon transport, was chosen for adaptation to electrons because of its versatility. The electron energy degradation model employed logarithmic spacing of electron energy groups and included effects of elastic scattering, inelastic-moderate-energy-loss-processes and inelastic-large-energy-loss-processes (catastrophic). Energy straggling and angular deflections were modeled from group to group, using the Moeller cross section for energy loss, and Goudsmit-Saunderson theory to describe angular deflections. The resulting energy- and electron-deposition distributions in depth were obtained at 10 and 20 MeV and are compared with ETRAN results and broad beam experimental data from clinical accelerators.

Particle energy loss spectroscopy and SEM studies of topography development in thin aluminium films implanted with high doses of helium

International Nuclear Information System (INIS)

Barfoot, K.M.; Webb, R.P.; Donnelly, S.E.

1984-01-01

Development of topography in thin (55.5 μg cm -2 ) self-supporting aluminium films, caused by high fluence (approx. 10 17 ions cm -2 ) irradiation with 5 keV helium ions, has been observed. This has been achieved by measuring the topography-enhanced energy straggling of 0.40 MeV 4 He + ions transmitted through the foils and detected with an electrostatic analyser of resolution 0.2 keV. Features, about 0.7 μm in width, are observed with scanning electron microscopy. TRIM Monte Carlo calculations of the implantation processes are performed in order to follow the helium implantation and damage depth distributions. It is deduced that a form of thin film micro-wrinkling has occurred which is caused by the relief of stress brought about by the implantation of helium. (author)

Particle-solid interactions and 21st century materials science

International Nuclear Information System (INIS)

Feldman, L.C.; Lupke, G.; Tolk, N.H.; Lopez, R.; Haglund, R.F.; Haynes, T.E.; Boatner, L.A.

2003-01-01

The basic physics that governs the interaction of energetic ion beams with solids has its roots in the atomic and nuclear physics of the last century. The central formalism of Jens Lindhard, describing the 'particle-solid interaction', provides a valuable quantitative guide to statistically meaningful quantities such as energy loss, ranges, range straggling, channeling effects, sputtering coefficients, and damage intensity and profiles. Modern materials modification (nanoscience, solid state dynamics) requires atomic scale control of the particle-solid interaction. Two recent experimental examples are discussed: (1) the control of the size distribution of nanocrystals formed in implanted materials and (2) the investigation of the site-specific implantation of hydrogen into silicon. Both cases illustrate unique solid-state configurations, created by ion implantation, that address issues of current materials science interest

Exponential discontinuous numerical scheme for electron transport in the continuous slowing down approximation

International Nuclear Information System (INIS)

Prinja, A.K.

1997-01-01

A nonlinear discretization scheme in space and energy, based on the recently developed exponential discontinuous method, is applied to continuous slowing down dominated electron transport (i.e., in the absence of scattering.) Numerical results for dose and charge deposition are obtained and compared against results from the ONELD and ONEBFP codes, and against exact results from an adjoint Monte Carlo code. It is found that although the exponential discontinuous scheme yields strictly positive and monotonic solutions, the dose profile is considerably straggled when compared to results from the linear codes. On the other hand, the linear schemes produce negative results which, furthermore, do not damp effectively in some cases. A general conclusion is that while yielding strictly positive solutions, the exponential discontinuous method does not show the crude cell accuracy for charged particle transport as was apparent for neutral particle transport problems

Invited Article: Characterization of background sources in space-based time-of-flight mass spectrometers

International Nuclear Information System (INIS)

Gilbert, J. A.; Gershman, D. J.; Gloeckler, G.; Lundgren, R. A.; Zurbuchen, T. H.; Orlando, T. M.; McLain, J.; Steiger, R. von

2014-01-01

For instruments that use time-of-flight techniques to measure space plasma, there are common sources of background signals that evidence themselves in the data. The background from these sources may increase the complexity of data analysis and reduce the signal-to-noise response of the instrument, thereby diminishing the science value or usefulness of the data. This paper reviews several sources of background commonly found in time-of-flight mass spectrometers and illustrates their effect in actual data using examples from ACE-SWICS and MESSENGER-FIPS. Sources include penetrating particles and radiation, UV photons, energy straggling and angular scattering, electron stimulated desorption of ions, ion-induced electron emission, accidental coincidence events, and noise signatures from instrument electronics. Data signatures of these sources are shown, as well as mitigation strategies and design considerations for future instruments

U.S. Department Of Energy's nuclear engineering education research: highlights of recent and current research-II. 2. Advanced Finite Element Discretizations for High-Energy Ion Transport

International Nuclear Information System (INIS)

Gleicher, Frederick; Prinja, Anil K.

2001-01-01

An efficient multigroup model that accurately describes electronic energy loss straggling was recently presented for use in multigroup Monte Carlo and deterministic high-energy ion transport codes. The model preserves the mean energy loss per path length, using the continuous slowing down (CSD) approximation, and mean-squared energy loss per path length, using strictly down-scatter multigroup cross sections, and accurately captures the energy spectrum of an initially monoenergetic ion beam. However, the dominant CSD energy loss process coupled with the small (but non-negligible) straggling poses a significant challenge for deterministic numerical solution when incident beams are monoenergetic or have discontinuous energy spectra. Such spectra broaden very slowly with depth into the target material, and thus, the interior distributions display sharpness and discontinuities. Advanced space-energy discretization methods are consequently necessary to achieve numerical robustness. In this paper, we investigate finite element solutions to this problem using two general families of discontinuous trial functions, one linear and the other nonlinear. The two families have been numerically tested, and we show results for 1.7-GeV protons incident on a tungsten target. For benchmarking purposes, we have also performed Monte Carlo (MC) simulations. Figure 1 displays the spatially converged energy spectrum with 200 groups after the beam has penetrated two-thirds of the ion range (85 cm). We contrast results from linear (LD), bilinear (BLD), and quadratic (QD) discontinuous trail functions against those from exponential-linear (LE), exponential-bilinear (BLE), and exponential-quadratic (QE) discontinuous trail functions. It is clear that the linear and bilinear results from both families are grossly inaccurate, both showing unacceptably high numerical straggling when compared against the MC results. The nonlinear results are everywhere positive while the linear schemes display

Evaluation of the new electron-transport algorithm in MCNP6.1 for the simulation of dose point kernel in water

Science.gov (United States)

Antoni, Rodolphe; Bourgois, Laurent

2017-12-01

In this work, the calculation of specific dose distribution in water is evaluated in MCNP6.1 with the regular condensed history algorithm the "detailed electron energy-loss straggling logic" and the new electrons transport algorithm proposed the "single event algorithm". Dose Point Kernel (DPK) is calculated with monoenergetic electrons of 50, 100, 500, 1000 and 3000 keV for different scoring cells dimensions. A comparison between MCNP6 results and well-validated codes for electron-dosimetry, i.e., EGSnrc or Penelope, is performed. When the detailed electron energy-loss straggling logic is used with default setting (down to the cut-off energy 1 keV), we infer that the depth of the dose peak increases with decreasing thickness of the scoring cell, largely due to combined step-size and boundary crossing artifacts. This finding is less prominent for 500 keV, 1 MeV and 3 MeV dose profile. With an appropriate number of sub-steps (ESTEP value in MCNP6), the dose-peak shift is almost complete absent to 50 keV and 100 keV electrons. However, the dose-peak is more prominent compared to EGSnrc and the absorbed dose tends to be underestimated at greater depths, meaning that boundaries crossing artifact are still occurring while step-size artifacts are greatly reduced. When the single-event mode is used for the whole transport, we observe the good agreement of reference and calculated profile for 50 and 100 keV electrons. Remaining artifacts are fully vanished, showing a possible transport treatment for energies less than a hundred of keV and accordance with reference for whatever scoring cell dimension, even if the single event method initially intended to support electron transport at energies below 1 keV. Conversely, results for 500 keV, 1 MeV and 3 MeV undergo a dramatic discrepancy with reference curves. These poor results and so the current unreliability of the method is for a part due to inappropriate elastic cross section treatment from the ENDF/B-VI.8 library in those

The compact 14C AMS facility of Paleo Labo Co., Ltd., Japan

International Nuclear Information System (INIS)

Kobayashi, Koichi; Niu, Etsuko; Itoh, Shigeru; Yamagata, Hideki; Lomtatidze, Zaur; Jorjoliani, Ineza; Nakamura, Kentaro; Fujine, Hisashi

2007-01-01

A compact AMS system was installed by a private company in Japan for a 14 C dating business. Since this system was designed to be very compact with a low voltage accelerator, it has unique features compared to larger AMS systems. For example, the stripper gas pressure has to be maintained at a high level to dissociate molecular ions. However, it cannot be too high because ion transmission decreases at higher stripper gas pressures due to increased angular straggling of the ions scattered by the high density stripper gas. The optimum pressure of the stripper gas for the lowest background and the highest transmission was investigated. With all the features of the compact system, the produced measurements can be of quite high precision. In the ten months after the installation of the equipment in November 2004, we have measured more than 1400 dating samples

Subthreshold Current and Swing Modeling of Gate Underlap DG MOSFETs with a Source/Drain Lateral Gaussian Doping Profile

Science.gov (United States)

Singh, Kunal; Kumar, Sanjay; Goel, Ekta; Singh, Balraj; Kumar, Mirgender; Dubey, Sarvesh; Jit, Satyabrata

2017-01-01

This paper proposes a new model for the subthreshold current and swing of the short-channel symmetric underlap ultrathin double gate metal oxide field effect transistors with a source/drain lateral Gaussian doping profile. The channel potential model already reported earlier has been utilized to formulate the closed form expression for the subthreshold current and swing of the device. The effects of the lateral straggle and geometrical parameters such as the channel length, channel thickness, and oxide thickness on the off current and subthreshold slope have been demonstrated. The devices with source/drain lateral Gaussian doping profiles in the underlap structure are observed to be highly resistant to short channel effects while improving the current drive. The proposed model is validated by comparing the results with the numerical simulation data obtained by using the commercially available ATLAS™, a two-dimensional (2-D) device simulator from SILVACO.

Enhanced depth and mass resolution with HIRBS

International Nuclear Information System (INIS)

Yang, Q.; O'Connor, D.J.

1992-01-01

The extension of Rutherford backscattering spectrometry (RBS) to heavier mass projectiles (HIRBS) has been limited, as these projectiles cause much more radiation damage in the detectors and curtail their lifetime. Despite this limitation interest in the use of heavier projectiles continues as there are several significant benefits which can accrue from their use. To properly understand the interaction of heavy ions with solids a systematic study of the energy loss and straggling of MeV heavy ions has been conducted and an empirical expression for these terms has been obtained. This expression has allowed the development of a realistic computer simulation which accurately predicts the energy spectra for a wide range of energies, projectiles and targets. In parallel with that study, measurements of the depth resolution of Si/Ge multilayer films using 4-6 MeV C projectiles have been used to verify the simulation. (orig.)

From basic processes to sensors: particle-matter interactions

International Nuclear Information System (INIS)

Laforge, Bertrand; Bourgeois, Christian

2005-11-01

This academic course aims at presenting and explaining techniques of detection of radiations displaying an energy higher that some tens of keV, such as those met in nuclear physics or in particle physics. In a first part, the author first analyses the operation of a biological sensor (the eye), and then presents some generalities about matter: Rutherford experiment, the atom, molecules and solids. The second part deals with interactions between radiations and matter. The author there addresses interactions of heavy charged particles (ionization with high or low energy transfer), interactions of electrons (ionization, Bremsstrahlung), multiple scattering and straggling, the Cherenkov effect, transition radiation, the interaction of γ radiations in matter (Compton effect, photoelectric effect), the interaction of neutrons in matter. Appendices address γ spectrometry, the radiation of a charged particle moving in a dielectric medium, and issues related to statistical fluctuations (distribution functions, fluctuation propagation, energy resolution, noises)

Depth distribution analysis of Martensitic transformations in Xe implanted austenitic stainless steel

DEFF Research Database (Denmark)

Johnson, E.; Gerritsen, E.; Chechenin, N.G.

1989-01-01

In recent years the implantation of noble gases in metals has been found to induce some exciting phenomena such as formation of inclusions containing solid gas at extremely high pressures. In stainless steels these inclusions are the origin of a stress-induced martensitic fcc → bcc phase...... transformation in the implanted layer. In this work we present results from a depth distribution analysis of the martensitic phase change occurring in Xe implanted single crystals of austenitic stainless steel. Analysis was done by in situ RBS/channeling analysis, X-ray diffraction and cross-section transmission...... electron microscopy (XTEM) of the implanted surface. It is found that the martensitic transformation of the surface layer occurs for fluences above 1 × 1020 m−2. The thickness of the transformed layer increases with fluence to ≈ 150 nm at 1 × 10 21 m−2, which far exceeds the range plus straggling...

Theoretical study of magnetic pattern replication by He+ ion irradiation through stencil masks

International Nuclear Information System (INIS)

Devolder, T.; Chappert, C.; Bernas, H.

2002-01-01

We have developed an irradiation technique that allows us to tune the magnetic properties of Co/Pt multilayers without affecting their roughness. The planarity and the ability to independently control nanostructure size and coercivity make our technique very appealing for magnetic recording. We study the irradiation-induced 1:1 replication of features drilled in a stencil mask. Both the 'gap' G between the magnetic film and the mask, and the aspect ratio (AR) of the mask features are analyzed, in view of the ion straggling in the mask resulting in collateral damages. Optimal gap is such that D<< G<< D/tan(α) (typically 0.1<< G<<25 μm), where the D is the feature size. The replication quality is best for AR≥3. Since the allowed gap interval is wide, we anticipate that mask fast positioning will be possible for the applications to magnetic recording

SHIELD-HIT12A - a Monte Carlo particle transport program for ion therapy research

DEFF Research Database (Denmark)

Bassler, Niels; Hansen, David Christoffer; Lühr, Armin

2014-01-01

. We experienced that new users quickly learn to use SHIELD-HIT12A and setup new geometries. Contrary to previous versions of SHIELD-HIT, the 12A distribution comes along with easy-to-use example files and an English manual. A new implementation of Vavilov straggling resulted in a massive reduction......Abstract. Purpose: The Monte Carlo (MC) code SHIELD-HIT simulates the transport of ions through matter. Since SHIELD-HIT08 we added numerous features that improves speed, usability and underlying physics and thereby the user experience. The “-A” fork of SHIELD-HIT also aims to attach SHIELD....... It supports native formats compatible with the heavy ion treatment planning system TRiP. Stopping power files follow ICRU standard and are generated using the libdEdx library, which allows the user to choose from a multitude of stopping power tables. Results: SHIELD-HIT12A runs on Linux and Windows platforms...

CR-39 track detector for multi-MeV ion spectroscopy.

Science.gov (United States)

Jeong, T W; Singh, P K; Scullion, C; Ahmed, H; Hadjisolomou, P; Jeon, C; Yun, H; Kakolee, K F; Borghesi, M; Ter-Avetisyan, S

2017-05-19

We present the characteristics of track formation on the front and rear surfaces of CR-39 produced by laser-driven protons and carbon ions. A methodological approach, based on bulk etch length, is proposed to uniquely characterize the particle tracks in CR-39, enabling comparative description of the track characteristics in different experiments. The response of CR-39 to ions is studied based on the energy dependent growth rate of the track diameter to understand the intrinsic particle stopping process within the material. A large non-uniformity in the track diameter is observed for CR-39 with thickness matching with the stopping range of particles. Simulation and experimental results show the imprint of longitudinal range straggling for energetic protons. Moreover, by exploiting the energy dependence of the track diameter, the energy resolution (δE/E) of CR-39 for few MeV protons and Carbon ion is found to be about 3%.

Analytical modeling of subthreshold current and subthreshold swing of Gaussian-doped strained-Si-on-insulator MOSFETs

International Nuclear Information System (INIS)

Rawat, Gopal; Kumar, Sanjay; Goel, Ekta; Kumar, Mirgender; Jit, S.; Dubey, Sarvesh

2014-01-01

This paper presents the analytical modeling of subthreshold current and subthreshold swing of short-channel fully-depleted (FD) strained-Si-on-insulator (SSOI) MOSFETs having vertical Gaussian-like doping profile in the channel. The subthreshold current and subthreshold swing have been derived using the parabolic approximation method. In addition to the effect of strain on silicon layer, various other device parameters such as channel length (L), gate-oxide thickness (t ox ), strained-Si channel thickness (t s-Si ), peak doping concentration (N P ), project range (R p ) and straggle (σ p ) of the Gaussian profile have been considered while predicting the device characteristics. The present work may help to overcome the degradation in subthreshold characteristics with strain engineering. These subthreshold current and swing models provide valuable information for strained-Si MOSFET design. Accuracy of the proposed models is verified using the commercially available ATLAS™, a two-dimensional (2D) device simulator from SILVACO. (semiconductor devices)

Analytical threshold voltage modeling of ion-implanted strained-Si double-material double-gate (DMDG) MOSFETs

Science.gov (United States)

Goel, Ekta; Singh, Balraj; Kumar, Sanjay; Singh, Kunal; Jit, Satyabrata

2017-04-01

Two dimensional threshold voltage model of ion-implanted strained-Si double-material double-gate MOSFETs has been done based on the solution of two dimensional Poisson's equation in the channel region using the parabolic approximation method. Novelty of the proposed device structure lies in the amalgamation of the advantages of both the strained-Si channel and double-material double-gate structure with a vertical Gaussian-like doping profile. The effects of different device parameters (such as device channel length, gate length ratios, germanium mole fraction) and doping parameters (such as projected range, straggle parameter) on threshold voltage of the proposed structure have been investigated. It is observed that the subthreshold performance of the device can be improved by simply controlling the doping parameters while maintaining other device parameters constant. The modeling results show a good agreement with the numerical simulation data obtained by using ATLAS™, a 2D device simulator from SILVACO.

Highly-resolving Rutherford-scattering spectroscopy with heavy ions

International Nuclear Information System (INIS)

Klein, C.

2003-10-01

in the present thesis for the first time the Browne-Buechner spectrometer for the highly resolving ion-beam analysis in the ion beam center Rossendorf is completely presented. A main topic of this theis lied in the apparative construction and the taking-into-operation of the spectrometer and the scattering chamber including the facilities for the sample treatment and characterization. In the framework of this thesis for the chosen measurement arrangement the experimental conditions were elaborated, which allow the routine-like application of the spectrometer for analyses of thin-film systems. for C and Li ions as incident particles especially the straggling was more precisely determined in a large range of materials. By means of the spectrometer also the interaction of the ion with the solid respectively single atoms on its surface could be studied. For the first time the mean charge-state after the single collision on a gold atom was determined for differently heavy ions in a wide energy range

Extended wave-packet model to calculate energy-loss moments of protons in matter

Science.gov (United States)

Archubi, C. D.; Arista, N. R.

2017-12-01

In this work we introduce modifications to the wave-packet method proposed by Kaneko to calculate the energy-loss moments of a projectile traversing a target which is represented in terms of Gaussian functions for the momentum distributions of electrons in the atomic shells. These modifications are introduced using the Levine and Louie technique to take into account the energy gaps corresponding to the different atomic levels of the target. We use the extended wave-packet model to evaluate the stopping power, the energy straggling, the inverse mean free path, and the ionization cross sections for protons in several targets, obtaining good agreements for all these quantities on an extensive energy range that covers low-, intermediate-, and high-energy regions. The extended wave-packet model proposed here provides a method to calculate in a very straightforward way all the significant terms of the inelastic interaction of light ions with any element of the periodic table.

Determination of the initial energy in computerized tomography with proton beams

International Nuclear Information System (INIS)

Rocha, Rodrigo Luis da

2007-01-01

In earliest works devoted to proton computed tomography it was shown that the advantage of pCT image reconstruction appears when the energy is close to the Bragg peak region, since the proton passes the object. This effect provided by the Bragg peak makes the computerized tomography with protons possible. However, when decreasing the initial proton energy, with the increase of the irradiation dose, there are two effects that work simultaneously in opposite ways. First, the energy loss of a proton in an object becomes bigger at small initial energy. At the same time decreasing of the proton energy results in the increase of the energy straggling, requiring a larger number of protons. In this work the radiation dose dependence on the proton initial energy was studied using analytical formulas and computer simulations. The investigation determined that the radiation dose practically does not depend on the initial energy, except in the energy region very close to the minimum energy necessary to pass the object. (author)

Determination of the initial energy in computerized tomography with proton beams; Determinacao da energia inicial em tomografia computadorizada com feixe de protons

Energy Technology Data Exchange (ETDEWEB)

Rocha, Rodrigo Luis da

2007-07-01

In earliest works devoted to proton computed tomography it was shown that the advantage of pCT image reconstruction appears when the energy is close to the Bragg peak region, since the proton passes the object. This effect provided by the Bragg peak makes the computerized tomography with protons possible. However, when decreasing the initial proton energy, with the increase of the irradiation dose, there are two effects that work simultaneously in opposite ways. First, the energy loss of a proton in an object becomes bigger at small initial energy. At the same time decreasing of the proton energy results in the increase of the energy straggling, requiring a larger number of protons. In this work the radiation dose dependence on the proton initial energy was studied using analytical formulas and computer simulations. The investigation determined that the radiation dose practically does not depend on the initial energy, except in the energy region very close to the minimum energy necessary to pass the object. (author)

Role of the interaction processes in the depth-dose distribution of proton beams in liquid water

International Nuclear Information System (INIS)

Garcia-Molina, Rafael; Abril, Isabel; De Vera, Pablo; Kyriakou, Ioanna; Emfietzoglou, Dimitris

2012-01-01

We use a simulation code, based on Molecular Dynamics and Monte Carlo, to investigate the depth-dose profile and lateral radial spreading of swift proton beams in liquid water. The stochastic nature of the projectile-target interaction is accounted for in a detailed manner by including in a consistent way fluctuations in both the energy loss due to inelastic collisions and the angular deflection from multiple elastic scattering. Depth-variation of the projectile charge-state as it slows down into the target, due to electron capture and loss processes, is also considered. By selectively switching on/off these stochastic processes in the simulation, we evaluate the contribution of each one of them to the Bragg curve. Our simulations show that the inclusion of the energy-loss straggling sizeably affects the width of the Bragg peak, whose position is mainly determined by the stopping power. The lateral spread of the beam as a function of the depth in the target is also examined.

El impacto del Tratado de Libre Comercio entre México, Estados Unidos y Canadá en el sector agropecuario de Coahuila

Directory of Open Access Journals (Sweden)

René Vidaurrázaga Obezo

1997-02-01

Full Text Available This paper analyzes the importance that has the agricultural sector in the Coahuila economy; the impact of the North America Free Trade Agreement (NAFTA in this sector as much as the perspectives with the NAFT Aoperation. The agrícultural sector of Coahuila is straggling in comparison with the other economic sectors of the state, and of agricultural activities of other regions of the country such as the Northwest and even more United States of America and Canada. In this conditions that you find the agricultural sector of Coahuila and if the same polices continued for the agrícultural, the competition process with the North AmericaFree Trade Agreement operation will not present in all their expansion at time expiration the agreement period to open the border totally. Of the joint branch that malees the agrícultural sector of Coahuila, few of them have the possibilities of competing in the internalional market.

Microstructural study of hydrogen-implanted beryllium

International Nuclear Information System (INIS)

Vagin, S.P.; Chakrov, P.V.; Utkelbayev, B.D.

1998-01-01

Hot pressed beryllium (TGP-56) was implanted by 650 keV H + ions to a dose of 6.7 x 10 16 cm -2 at a temperature below 50 C. TEM examinations were performed both at as-irradiated specimens and after post-irradiation annealings at 400-600 C for 15 min. After irradiation, a high density of ''black dot'' defects with a size of about 5 nm is observed in the straggling zone, some of which are resolved as small dislocation loops. During post-irradiation annealing, growth of dislocation loops and oriented gas-filled bubbles are observed in the damaged zone. The bubbles are strongly elongated along the left angle 0001 right angle direction, and their sidelong facts lie along {1-100} planes. These facets have a regular ''toothed'' surface with ''tooth'' facets on {1-100} planes. The size of the ''teeth'' increases with annealing temperature, as well as the total volume of bubbles, with their length growing faster than their width. (orig.)

Computer simulation program for medium-energy ion scattering and Rutherford backscattering spectrometry

Science.gov (United States)

Nishimura, Tomoaki

2016-03-01

A computer simulation program for ion scattering and its graphical user interface (MEISwin) has been developed. Using this program, researchers have analyzed medium-energy ion scattering and Rutherford backscattering spectrometry at Ritsumeikan University since 1998, and at Rutgers University since 2007. The main features of the program are as follows: (1) stopping power can be chosen from five datasets spanning several decades (from 1977 to 2011), (2) straggling can be chosen from two datasets, (3) spectral shape can be selected as Gaussian or exponentially modified Gaussian, (4) scattering cross sections can be selected as Coulomb or screened, (5) simulations adopt the resonant elastic scattering cross section of 16O(4He, 4He)16O, (6) pileup simulation for RBS spectra is supported, (7) natural and specific isotope abundances are supported, and (8) the charge fraction can be chosen from three patterns (fixed, energy-dependent, and ion fraction with charge-exchange parameters for medium-energy ion scattering). This study demonstrates and discusses the simulations and their results.

Energy and zenith angle dependence of atmospheric muons

CERN Document Server

Maeda, K

1973-01-01

The recently proposed new process for energetic-muon production in the atmosphere should be tested at Mt. Chacaltaya. Rigorous calculations of zenith-angle distribution of atmospheric muons have been made for the altitude of 5200 m above sea level with energy range from 100 GeV to 100 TeV and for zenith angles from 0 degrees to 92.3 degrees . Calculations are based on the extension of the Chapman function to the case of a non-isothermal atmosphere, taking into account (i) energy- dependent nuclear-interaction mean free path of cosmic-ray hadrons in air, (ii) different magnitudes of photonuclear cross-section in the energy-loss process of muons in the atmosphere, (iii) contributions of atmospheric muons arriving below the horizontal directions, and (iv) atmospheric structure and geomagnetic deflection. Results are compared with those corresponding to sea level. Range straggling, particularly its effect on horizontally incident muons, is investigated by Monte Carlo calculation, indicating that its effects and t...

Efficiency improvement in proton dose calculations with an equivalent restricted stopping power formalism

Science.gov (United States)

Maneval, Daniel; Bouchard, Hugo; Ozell, Benoît; Després, Philippe

2018-01-01

The equivalent restricted stopping power formalism is introduced for proton mean energy loss calculations under the continuous slowing down approximation. The objective is the acceleration of Monte Carlo dose calculations by allowing larger steps while preserving accuracy. The fractional energy loss per step length ɛ was obtained with a secant method and a Gauss-Kronrod quadrature estimation of the integral equation relating the mean energy loss to the step length. The midpoint rule of the Newton-Cotes formulae was then used to solve this equation, allowing the creation of a lookup table linking ɛ to the equivalent restricted stopping power L eq, used here as a key physical quantity. The mean energy loss for any step length was simply defined as the product of the step length with L eq. Proton inelastic collisions with electrons were added to GPUMCD, a GPU-based Monte Carlo dose calculation code. The proton continuous slowing-down was modelled with the L eq formalism. GPUMCD was compared to Geant4 in a validation study where ionization processes alone were activated and a voxelized geometry was used. The energy straggling was first switched off to validate the L eq formalism alone. Dose differences between Geant4 and GPUMCD were smaller than 0.31% for the L eq formalism. The mean error and the standard deviation were below 0.035% and 0.038% respectively. 99.4 to 100% of GPUMCD dose points were consistent with a 0.3% dose tolerance. GPUMCD 80% falloff positions (R80 ) matched Geant’s R80 within 1 μm. With the energy straggling, dose differences were below 2.7% in the Bragg peak falloff and smaller than 0.83% elsewhere. The R80 positions matched within 100 μm. The overall computation times to transport one million protons with GPUMCD were 31-173 ms. Under similar conditions, Geant4 computation times were 1.4-20 h. The L eq formalism led to an intrinsic efficiency gain factor ranging between 30-630, increasing with the prescribed accuracy of simulations. The

Monte Carlo modeling of neutron and gamma-ray imaging systems

International Nuclear Information System (INIS)

Hall, J.

1996-04-01

Detailed numerical prototypes are essential to design of efficient and cost-effective neutron and gamma-ray imaging systems. We have exploited the unique capabilities of an LLNL-developed radiation transport code (COG) to develop code modules capable of simulating the performance of neutron and gamma-ray imaging systems over a wide range of source energies. COG allows us to simulate complex, energy-, angle-, and time-dependent radiation sources, model 3-dimensional system geometries with ''real world'' complexity, specify detailed elemental and isotopic distributions and predict the responses of various types of imaging detectors with full Monte Carlo accuray. COG references detailed, evaluated nuclear interaction databases allowingusers to account for multiple scattering, energy straggling, and secondary particle production phenomena which may significantly effect the performance of an imaging system by may be difficult or even impossible to estimate using simple analytical models. This work presents examples illustrating the use of these routines in the analysis of industrial radiographic systems for thick target inspection, nonintrusive luggage and cargoscanning systems, and international treaty verification

Angular dispersion and energy loss of H+ and He+ in metals

International Nuclear Information System (INIS)

Cantero, Esteban

2006-01-01

In this master thesis the effects produced when a light ion beam traverses a thin metallic film were studied.In particular, the interactions of low energy (E ≤ 10 keV) light ions (H + ,H 2 + , D + , He + ) with monocrystalline and also polycrystalline gold samples were investigated.In first place, the dependence of the stopping power with projectiles' velocity was studied, analyzing the threshold effect in the excitation of the 5d electrons in the channelling regime for energies between 0,4 and 9 keV.Next, the angular dispersion of ions in polycrystalline and monocrystalline films was measured and analyzed.Comparisons for different energies and projectiles were done, studying molecular and isotopic effects.Using Lindhard's channeling theory, a scale law for the angular dispersion of angles greater than the critical angle was found.Additionally, the angular dependence of the energy loss and the energy loss straggling of protons transmitted through monocrystals were measured.To explain the angular variations of these magnitudes a theoretical model based on the electronic density fluctuations inside the channel was developed [es

Effects of cavitation on damage calculations in ion-irradiated P7 alloy

International Nuclear Information System (INIS)

Sindelar, R.L.; Farrens, S.N.; Kulcinski, G.L.

1985-01-01

The purpose of this study is to investigate the effect of voids on the depth-dependent damage energy in ion-irradiated metals. Corrections to the dose at the swelling peak will be used to obtain the swelling rate of ion-irradiated 316-type stainless steels. Samples of the P7 alloy were ion-irradiated to four fluence levels up to a peak dose level of 100 dpa at 650 0 C. The depth-dependent void parameters extracted in cross section were used to model the effect of voids on the depth-dependent damage produced during 14 MeV nickel ion irradiation. An increase in the range of damage produced from the original foil surface for the target containing voids was modeled as a first-order correction to the damage profile. A second-order effect, void straggling, was shown to cause a time-dependent decrease in the damage rate at the peak swelling depth. Corrections applied to the dose at the peak swelling depth yield swelling rates approaching 0.7%/dpa

Simulations of the azimuthal distribution of low-energy H atoms scattered off Ag(1 1 0) at grazing incidence: DFT many-body versus model pair potentials

CERN Document Server

Cafarelli, P; Benazeth, C; Nieuwjaer, N; Lorente, N

2003-01-01

We compare the azimuthal distribution of H atoms after scattering off Ag(1 1 0) obtained by molecular dynamics with different H-Ag(1 1 0) potential energy surfaces (PES) and experimental results. We use grazing incident H atoms and low energies (up to 4 keV). Density functional theory (DFT) calculations are performed for the static case of an H atom in front of an Ag(1 1 0) surface. The surface is represented by an 8-atom slab, and the H atoms form 1x1 and 2x2 supercells. The generalized gradient approximation is used. Classical trajectories are evaluated on the obtained PES, and the azimuthal distribution of the scattered atoms is calculated. Good agreement with experiment is obtained which gives us some confidence in the correct description of the system at low energies by the static DFT calculations. These results are also compared with pair-potential calculations. The accuracy of trajectories may be important for the correct evaluation of charge transfer, energy loss and straggling during ion-surface coll...

Photoproduction of long-lived holes and electronic processes in intrinsic electric fields seen through photoinduced absorption and dichroism in Ca sub 3 Ga sub 2 sub - sub x Mn sub x Ge sub 3 O sub 1 sub 2 garnets

CERN Document Server

Eremenko, V V; Kachur, I S; Piryatinskaya, V G; Ratner, A M; Kosmyna, M B; Nazarenko, B P; Puzikov, V M

2003-01-01

Long-lived photoinduced absorption and dichroism in the Ca sub 3 Ga sub 2 sub - sub x Mn sub x Ge sub 3 O sub 1 sub 2 garnets with x < 0.06 were examined versus temperature and pumping intensity. Unusual features of the kinetics of photoinduced phenomena are indicative of the underlying electronic processes. The comparison with the case of Ca sub 3 Mn sub 2 Ge sub 3 O sub 1 sub 2 , explored earlier by the authors, permits one to finally establish the main common mechanisms of photoinduced absorption and dichroism caused by random electric fields of photoproduced charges (hole polarons). The rate of their diffusion and relaxation through recombination is strongly influenced by the same fields, whose large statistical straggling is responsible for a broad continuous set of relaxation components (observed in the relaxation time range from 1 to about 1000 min). For Ca sub 3 Ga sub 2 sub - sub x Mn sub x Ge sub 3 O sub 1 sub 2 , the time and temperature dependences of photoinduced absorption and dichroism bear ...

The use of Monte-Carlo codes for treatment planning in external-beam radiotherapy

International Nuclear Information System (INIS)

Alan, E.; Nahum, PhD.

2003-01-01

Monte Carlo simulation of radiation transport is a very powerful technique. There are basically no exact solutions to the Boltzmann transport equation. Even, the 'straightforward' situation (in radiotherapy) of an electron beam depth-dose distribution in water proves to be too difficult for analytical methods without making gross approximations such as ignoring energy-loss straggling, large-angle single scattering and Bremsstrahlung production. monte Carlo is essential when radiation is transport from one medium into another. As the particle (be it a neutron, photon, electron, proton) crosses the boundary then a new set of interaction cross-sections is simply read in and the simulation continues as though the new medium were infinite until the next boundary is encountered. Radiotherapy involves directing a beam of megavoltage x rays or electrons (occasionally protons) at a very complex object, the human body. Monte Carlo simulation has proved in valuable at many stages of the process of accurately determining the distribution of absorbed dose in the patient. Some of these applications will be reviewed here. (Rogers and al 1990; Andreo 1991; Mackie 1990). (N.C.)

A fast and complete GEANT4 and ROOT Object-Oriented Toolkit: GROOT

Science.gov (United States)

Lattuada, D.; Balabanski, D. L.; Chesnevskaya, S.; Costa, M.; Crucillà, V.; Guardo, G. L.; La Cognata, M.; Matei, C.; Pizzone, R. G.; Romano, S.; Spitaleri, C.; Tumino, A.; Xu, Y.

2018-01-01

Present and future gamma-beam facilities represent a great opportunity to validate and evaluate the cross-sections of many photonuclear reactions at near-threshold energies. Monte Carlo (MC) simulations are very important to evaluate the reaction rates and to maximize the detection efficiency but, unfortunately, they can be very cputime-consuming and in some cases very hard to reproduce, especially when exploring near-threshold cross-section. We developed a software that makes use of the validated tracking GEANT4 libraries and the n-body event generator of ROOT in order to provide a fast, realiable and complete MC tool to be used for nuclear physics experiments. This tool is indeed intended to be used for photonuclear reactions at γ-beam facilities with ELISSA (ELI Silicon Strip Array), a new detector array under development at the Extreme Light Infrastructure - Nuclear Physics (ELI-NP). We discuss the results of MC simulations performed to evaluate the effects of the electromagnetic induced background, of the straggling due to the target thickness and of the resolution of the silicon detectors.

Beam Cooling with ionisation losses

CERN Document Server

Rubbia, Carlo; Kadi, Y; Vlachoudis, V

2006-01-01

A novel type of particle "cooling", called Ionization Cooling, is applicable to slow (v of the order of 0.1c) ions stored in a small ring. The many traversals through a thin foil enhance the nuclear reaction probability, in a steady configuration in which ionisation losses are recovered at each turn by a RF-cavity. For a uniform target "foil" the longitudinal momentum spread diverges exponentially since faster (slower) particles ionise less (more) than the average. In order to "cool" also longitudinally, a chromaticity has to be introduced with a wedge shaped "foil". Multiple scattering and straggling are then "cooled" in all three dimensions, with a method similar to the one of synchrotron cooling, but valid for low energy ions. Particles then stably circulate in the beam indefinitely, until they undergo for instance nuclear processes in the thin target foil. This new method is under consideration for the nuclear production of a few MeV/A ion beams. Simple reactions, for instance Li 7 + D Li 8 + p, are more ...

Coupled electron/photon transport in static external magnetic fields

International Nuclear Information System (INIS)

Halbleib, J.A. Sr.; Vandevender, W.H.

A model is presented which describes coupled electron/photon transport in the presence of static magnetic fields of arbitrary spatial dependence. The method combines state-of-the-art condensed-history electron collisional Monte Carlo and single-scattering photon Monte Carlo, including electron energy-loss straggling and the production and transport of all generations of secondaries, with numerical field integration via the best available variable-step-size Runge-Kutta-Fehlberg or variable-order/variable-step-size Adams PECE differential equation solvers. A three-dimensional cartesian system is employed in the description of particle trajectories. Although the present model is limited to multilayer material configurations, extension to more complex material geometries should not be difficult. Among the more important options are (1) a feature which permits the neglect of field effects in regions where transport is collision dominated and (2) a method for describing the transport in variable-density media where electron energies and material densities are sufficiently low that the density effect on electronic stopping powers may be neglected. (U.S.)

Investigation into the feasibility of a soft muon experiment

International Nuclear Information System (INIS)

Tincknell, M.L.

1990-06-01

Issues relevant in a soft ( -4 ). Absorber penetration is the only means available to identify high energy muons among a large number of hadrons. Three important sources of background are sail-through hadrons that fail to interact in the absorber, the decays of pions and kaons to muons in the absorber, and leakage of hadronic shower products through the absorber. An absorber thick enough to limit the ratio of combinatorical background pairs to pions to ο (10 -4 ) imposes a significant muon kinetic energy threshold due to muon range in the absorber. Absorbers with low atomic number Z are preferred to keep this threshold low, and to avoid loss of invariant mass resolution due to energy loss straggling and multiple coulomb scattering. Long-lived meson to muon decays can be directly suppressed only by picking an absorber with short interaction length, which implies a high density, high Z material. With sufficiently high statistics, a subtraction of the spectra of like-sign pairs from the spectrum of opposite-sign pairs should recover the direct muon pair spectrum. 9 refs., 9 figs., 2 tabs

Detailed analysis of the resonant backscattering spectrum for deeply penetrating protons in carbon

International Nuclear Information System (INIS)

Tosaki, Mitsuo; Ito, Shin; Maeda, Nobuhiro

2000-01-01

In order to study the spectral response in Rutherford backscattering spectroscopy (RBS) for deeply penetrating ions in matter, the resonant backscattering spectra for 5.05-, 5.5- and 6.0-MeV proton incidence on solid carbon material have been measured at a scattering angle of 179.2 deg. (in lab.). Prominent peaks resulting from the sharp 4.8-MeV resonance in 12 C(p,p) 12 C nuclear elastic scattering are observed, even for a penetration depth of 79 μm. Detailed numerical calculations based on an algorithm of straightforward step-by-step evaluation have been made to simulate the observed spectra. The algorithm enables one to rigorously treat both the effect of sharp resonance structure and that of energy-dependent energy loss. Calculations with the SIMNRA code are also made. Through comparison of these calculations with the measured results, some conclusions on the two effects above are presented. In addition, it is demonstrated that the peak profile due to a sharp resonance is very sensitive to the degree of energy straggling

Use of SRIM and Garfield with Geant4 for the characterization of a hybrid 10B/3He neutron detector

Science.gov (United States)

van der Ende, B. M.; Rand, E. T.; Erlandson, A.; Li, L.

2018-06-01

This paper describes a method for more complete neutron detector characterization using Geant4's Monte Carlo methods for characterizing overall detector response rate and Garfield interfaced with SRIM for the simulation of the detector's raw pulses, as applied to a hybrid 10B/3He detector. The Geant4 models characterizing the detector's interaction with a 252Cf point source and parallel beams of mono-energetic neutrons (assuming ISO 8529 reference energy values) compare and agree well with calibrated 252Cf measurements to within 6.4%. Validated Geant4 model outputs serve as input to Garfield+SRIM calculations to provide meaningful pulse height spectra. Modifications to Garfield for this work were necessary to account for simultaneous tracking of electrons resulting from proton and triton reaction products from a single 3He neutron capture event, and it was further necessary to interface Garfield with the energy loss, range, and straggling calculations provided by SRIM. Individual raw pulses generated by Garfield+SRIM are also observed to agree well with experimentally measured raw pulses from the detector.

Computer simulation program for medium-energy ion scattering and Rutherford backscattering spectrometry

Energy Technology Data Exchange (ETDEWEB)

Nishimura, Tomoaki, E-mail: t-nishi@hosei.ac.jp

2016-03-15

A computer simulation program for ion scattering and its graphical user interface (MEISwin) has been developed. Using this program, researchers have analyzed medium-energy ion scattering and Rutherford backscattering spectrometry at Ritsumeikan University since 1998, and at Rutgers University since 2007. The main features of the program are as follows: (1) stopping power can be chosen from five datasets spanning several decades (from 1977 to 2011), (2) straggling can be chosen from two datasets, (3) spectral shape can be selected as Gaussian or exponentially modified Gaussian, (4) scattering cross sections can be selected as Coulomb or screened, (5) simulations adopt the resonant elastic scattering cross section of {sup 16}O({sup 4}He, {sup 4}He){sup 16}O, (6) pileup simulation for RBS spectra is supported, (7) natural and specific isotope abundances are supported, and (8) the charge fraction can be chosen from three patterns (fixed, energy-dependent, and ion fraction with charge-exchange parameters for medium-energy ion scattering). This study demonstrates and discusses the simulations and their results.

Production of Long-Lived H2-, HD-, and D2- during Grazing Scattering Collisions of H2+, H3+, D2+, D3+ and D2H+ Ions with KBr, KCl, and LiF Surfaces

International Nuclear Information System (INIS)

Seely, D. G.; Meyer, F. W.; Zhang, H.; Havener, C. C.

2009-01-01

We have investigated atomic and molecular anion production from singly charged atomic and molecular hydrogen, deuterium, and mixed isotope beams during grazing interactions with large area KBr, KCl, and LiF single crystal targets in the incident energy range 4-22.5 keV. Electron capture and, in the case of incident molecular ions, dissociation occur during the grazing interactions without appreciable angular straggling or change in velocity. As a result, atomic and molecular cation and anion interaction products are strongly peaked in the specular reflection direction, and, in case of dissociation products, at the fractional kinetic energies determined by the product fragment mass to incident mass ratios. A large-acceptance electrostatic analysis and detection system is used to collect the charged scattering products with high efficiency. Of particular interest is the production of metastable molecular ions H 2 - , HD - , and D 2 - . By comparing molecular anion yields obtained from incident hydrogen, deuterium and mixed isotope molecular ions, effects arising from isobaric contamination are seen for some incident molecular species.

Hybrid Methods for Muon Accelerator Simulations with Ionization Cooling

Energy Technology Data Exchange (ETDEWEB)

Kunz, Josiah [Anderson U.; Snopok, Pavel [Fermilab; Berz, Martin [Michigan State U.; Makino, Kyoko [Michigan State U.

2018-03-28

Muon ionization cooling involves passing particles through solid or liquid absorbers. Careful simulations are required to design muon cooling channels. New features have been developed for inclusion in the transfer map code COSY Infinity to follow the distribution of charged particles through matter. To study the passage of muons through material, the transfer map approach alone is not sufficient. The interplay of beam optics and atomic processes must be studied by a hybrid transfer map--Monte-Carlo approach in which transfer map methods describe the deterministic behavior of the particles, and Monte-Carlo methods are used to provide corrections accounting for the stochastic nature of scattering and straggling of particles. The advantage of the new approach is that the vast majority of the dynamics are represented by fast application of the high-order transfer map of an entire element and accumulated stochastic effects. The gains in speed are expected to simplify the optimization of cooling channels which is usually computationally demanding. Progress on the development of the required algorithms and their application to modeling muon ionization cooling channels is reported.

Energy spread in ion beam analysis

International Nuclear Information System (INIS)

Szilagyi, E.

2000-01-01

In ion beam analysis (IBA) the depth profiles are extracted from the experimentally determined energy profiles. The spectra, however, are subject to finite energy resolution of both extrinsic and intrinsic origin. Calculation of those effects such as instrumental beam, geometry and detection-related energy and angular spreads as well as energy straggling, multiple scattering and Doppler effects in the sample itself is not trivial, especially since it involves treatment of non-independent random processes. A proper account for energy spread is vital in IBA not only for correct extraction of elemental and isotopic depth profiles from the measured spectra, but already prior to data acquisition, in optimising experimental conditions to reach the required depth resolution at a certain depth. After a short review of the literature on the different energy spread contributions experimental examples are given from resonance, RBS, elastic BS and ERDA practice in which an account for energy spread contributions is essential. Some further examples illustrate extraction of structural information (roughness, pore size, etc.) from elaborated depth resolution calculation for such layer structures

Energy spread in ion beam analysis

Energy Technology Data Exchange (ETDEWEB)

Szilagyi, E. E-mail: szilagyi@rmki.kkfki.hu

2000-03-01

In ion beam analysis (IBA) the depth profiles are extracted from the experimentally determined energy profiles. The spectra, however, are subject to finite energy resolution of both extrinsic and intrinsic origin. Calculation of those effects such as instrumental beam, geometry and detection-related energy and angular spreads as well as energy straggling, multiple scattering and Doppler effects in the sample itself is not trivial, especially since it involves treatment of non-independent random processes. A proper account for energy spread is vital in IBA not only for correct extraction of elemental and isotopic depth profiles from the measured spectra, but already prior to data acquisition, in optimising experimental conditions to reach the required depth resolution at a certain depth. After a short review of the literature on the different energy spread contributions experimental examples are given from resonance, RBS, elastic BS and ERDA practice in which an account for energy spread contributions is essential. Some further examples illustrate extraction of structural information (roughness, pore size, etc.) from elaborated depth resolution calculation for such layer structures.

Investigation into the feasibility of a soft muon experiment

International Nuclear Information System (INIS)

Tincknell, M.L.

1990-01-01

Issues relevant in a soft ( -4 ). Absorber penetration is the only means available to identify high energy muons among a large number of hadrons. Three important sources of background are sail-through hadrons that fail to interact in the absorber, the decays of pions and kaons to muons in the absorber, and leakage of hadronic shower products through the absorber. An absorber thick enough to limit the ratio of combinatorial background pairs to pions to Ο(10 -4 ) imposes a significant muon kinetic energy threshold due to muon range in the absorber. Absorbers with low atomic number Z are preferred to keep this threshold low, and to avoid loss of invariant mass resolution due to energy loss straggling and multiple coulomb scattering. Long-lived meson to muon decays can be directly suppressed only by picking an absorber with short interaction length, which implies a high density, high Z material. With sufficiently high statistics, a subtraction of the spectra of like-sign pairs from the spectrum of opposite-sign pairs should recover the direct muon pair spectrum

On the origin of apparent Z{sub 1}-oscillations in low-energy heavy-ion ranges

Energy Technology Data Exchange (ETDEWEB)

Wittmaack, Klaus, E-mail: wittmaack@helmholtz-muenchen.de

2016-12-01

It has been known for quite some time that projected ranges measured by Rutherford backscattering spectrometry for a variety of low-energy heavy ions (energy-to-mass ratio E/M{sub 1} less than ∼0.4 keV/u) exhibit significant or even pronounced deviations from the theoretically predicted smooth dependence on the projectile’s atomic number Z{sub 1}. Studied most thoroughly for silicon targets, the effect was attributed to ‘Z{sub 1} oscillations’ in nuclear stopping, in false analogy to the well established Z{sub 1} oscillations in electronic stopping of low-velocity light ions. In this study an attempt was made to get order into range data published by four different groups. To achieve the goal, the absolute values of the ranges from each group had to be (re-)adjusted by up to about ±10%. Adequate justification for this approach is provided. With the changes made, similarities and differences between the different sets of data became much more transparent than before. Very important is the finding that the distortions in heavy-ion ranges are not oscillatory in nature but mostly one-sided, reflecting element-specific transport of implanted atoms deeper into the solid. Exceptions are rare gas and alkali elements, known to exhibit bombardment induced transport towards the surface. Range distortions reported for Xe and Cs could be reproduced on the basis of the recently established rapid relocation model. The extent of transport into the bulk, observed with many other elements, notably noble metals and lanthanides, reflects their high mobility under ion bombardment. The complexity of the element specific transport phenomena became fully evident by also examining the limited number of data available for the apparent range straggling. Profile broadening was identified in several cases. One element (Eu) was found to exhibit profile narrowing. This observation suggests that implanted atoms may agglomerate at peak concentrations up to 2%, possibly a tool for

Clinical application of multislice CT enterography with hypertonic mannitol saline as oral contrast

International Nuclear Information System (INIS)

Yan Guixin; Wang Haitao; Chen Wenjing; Liu Wenya

2011-01-01

Objective: To assess the feasibility and value of multislice CT enterography (MSCTE) with large dose economy and convenience orally administered hypertonic mannitol salt water (2.5% mannitol and 1.5% NaCl salt water) as negative contrast in demonstrating normal and abnormal small bowel. Methods: 81 patients suffered from digestive disease and suspected of various kinds of small intestinal diseases were examined (male/female=47/34, 26-81 years old, average 57.8 years). About 1500 ml∼3000 ml hypertonic mannitol saline was oral administered within 90 minutes and 20 mg of raceanisodamine hydrochloride injection was injected intramuscularly. CT scanning was performed 20 minutes later. Imaging data were post processed with coronal, sagittal and oblique reconstruction, multiplanar reformation (MPR), maximum intensity projection (MIP), and volumer rendering technique (VRT). The filling degree of stomach, intestine and colon was classified as satisfactory, better and unsatisfactory. The length and superposition of small intestine was classified as dense-type, uniformity-type and straggling-type. The maximum outer diameters of duodenum, jejunum, and ileum were measured respectively in different segments. The degree of bowel wall enhancement in arterial phase and venous phase was classified as obvious enhancement (>90 HU), medium enhancement (60-90 HU) and mild enhancement (<60 HU). CT features of various kinds of small bowel diseases were analyzed. Results: The hypertonic mannitol saline was acceptable by patients, except 5 patients with diarrhea. The filling degree of stomach, intestine and and colon was classified as satisfactory in 46 cases, better in 23 cases and unsatisfactory in 12 cases. The maximum outer diameters of small bowel in different segments were 24 mm ± 4.5 mm at duodenum, 24 mm ±3.9 mm at jejunum and 23 mm ±3.3 mm at ileum respectively. The length and superposition of small intestine were classified as dense-type in 7 cases, uniformity-type in 58

The HARWELL version of the computer code E-DEP-1

International Nuclear Information System (INIS)

Matthews, M.D.

1983-03-01

This document describes the modified HARWELL version of the computer program EDEP-1 which has been in use on the IBM Central Computer for some years. The program can be used to calculate heavy ion ranges and/or profiles of energy deposited into nuclear processes for a wide variety of ion/target combinations. The initial setting up of this program on the IBM Central Computer has been described in an earlier report. A second report was later issued to bring the first report up to date following changes to this code required to suit the needs of workers at HARWELL. This later report described in particular the provision of new electronic stopping powers and an alternative method for calculating the energy straggle of beam ions with depth in a target. This new report describes further extensions to the electronic stopping powers available in the HARWELL version of this program and, for the first time, gives details of alternative nuclear stopping powers now available. This new document is intended as a reference manual for the use of the HARWELL version of EDEP-1. In this respect this document should be the final report on the status of this program. (author)

Study of the influence of color van der Waals forces and of non-Coulombian effects in 208pb+208pb scattering using a high-precision experiment

International Nuclear Information System (INIS)

Casandjian, Jean-Marc

1996-01-01

This work deals with the precise measurement of the absolute angular position of the elastic 208 pb+ 208 pb scattering cross section oscillations. The main objective is to verify if all of the elastic scattering ingredients are known even with an angular position precision of a few milli-degrees or if it is necessary to introduce new elements such as the color van der Waals force. This experiment was performed at Ganil. We obtained a precision of 0.004 deg. on the absolute cross section oscillation position and an angular shift of a few hundredths of degrees in relation to the expected position of a pure coulomb scattering. The attainment of this precision required particular precautions in the measurement of the absolute energy target position and scattering angle. First, the angular straggling on a thin target and the production of δ electrons during the scattering is studied. Next the origin of the angular shift is examined by the calculation of all the potentials that act during the scattering. The agreement between experimentation and theory allowed us to set a new limit on the color van der Waals interaction. (author) [fr

Comparison of various stopping gases for {sup 3}He-based position sensitive neutron detectors

Energy Technology Data Exchange (ETDEWEB)

Doumas, A. [United States Merchant Marine Academy, Steamboat Road, Kings Point, NY 11024 (United States); Smith, G.C., E-mail: gsmith@bnl.gov [Instrumentation Division, Brookhaven National Laboratory, Upton, NY 11973 (United States)

2012-05-21

A range of solid state, scintillator and gas based detectors are being developed for use at the next generation of high flux neutron facilities. Since gas detectors are expected to continue to play a key role in future specific thermal neutron experiments, a comparison of the performance characteristics of prospective stopping gases is beneficial. Gas detectors typically utilize the reaction {sup 3}He(n,p)t to detect thermal neutrons; the {sup 3}He gas is used in a mixture containing a particular stopping gas in order to maintain relatively short ranges for the proton and triton pair emitted from the n-{sup 3}He reaction. Common stopping gases include hydrocarbons (e.g. propane), carbon tetrafluoride, and noble gases such as argon and xenon. For this study, we utilized the Monte Carlo simulation code 'Stopping and Range of Ions in Matter' to analyze the expected behavior of argon, xenon, carbon dioxide, difluoroethane and octafluoropropane as stopping gases for thermal neutron detectors. We also compare these findings to our previously analyzed performance of propane, butane and carbon tetrafluoride. A discussion of these gases includes their behavior in terms of proton and triton range, ionization distribution and straggle.

Comparison of various stopping gases for 3He-based position sensitive neutron detectors

International Nuclear Information System (INIS)

Doumas, A.; Smith, G.C.

2012-01-01

A range of solid state, scintillator and gas based detectors are being developed for use at the next generation of high flux neutron facilities. Since gas detectors are expected to continue to play a key role in future specific thermal neutron experiments, a comparison of the performance characteristics of prospective stopping gases is beneficial. Gas detectors typically utilize the reaction 3 He(n,p)t to detect thermal neutrons; the 3 He gas is used in a mixture containing a particular stopping gas in order to maintain relatively short ranges for the proton and triton pair emitted from the n- 3 He reaction. Common stopping gases include hydrocarbons (e.g. propane), carbon tetrafluoride, and noble gases such as argon and xenon. For this study, we utilized the Monte Carlo simulation code “Stopping and Range of Ions in Matter” to analyze the expected behavior of argon, xenon, carbon dioxide, difluoroethane and octafluoropropane as stopping gases for thermal neutron detectors. We also compare these findings to our previously analyzed performance of propane, butane and carbon tetrafluoride. A discussion of these gases includes their behavior in terms of proton and triton range, ionization distribution and straggle.

Comparison of various stopping gases for 3He-based position sensitive neutron detectors

Science.gov (United States)

Doumas, A.; Smith, G. C.

2012-05-01

A range of solid state, scintillator and gas based detectors are being developed for use at the next generation of high flux neutron facilities. Since gas detectors are expected to continue to play a key role in future specific thermal neutron experiments, a comparison of the performance characteristics of prospective stopping gases is beneficial. Gas detectors typically utilize the reaction 3He(n,p)t to detect thermal neutrons; the 3He gas is used in a mixture containing a particular stopping gas in order to maintain relatively short ranges for the proton and triton pair emitted from the n-3He reaction. Common stopping gases include hydrocarbons (e.g. propane), carbon tetrafluoride, and noble gases such as argon and xenon. For this study, we utilized the Monte Carlo simulation code "Stopping and Range of Ions in Matter" to analyze the expected behavior of argon, xenon, carbon dioxide, difluoroethane and octafluoropropane as stopping gases for thermal neutron detectors. We also compare these findings to our previously analyzed performance of propane, butane and carbon tetrafluoride. A discussion of these gases includes their behavior in terms of proton and triton range, ionization distribution and straggle.

Calculations on displacement damage and its related parameters for heavy ion bombardment in reactor materials

International Nuclear Information System (INIS)

Sone, Kazuho; Shiraishi, Kensuke

1975-04-01

The depth distribution of displacement damage expressed in displacements per atom (DPA) in reactor materials such as Mo, Nb, V, Fe and Ni bombarded by energetic nitrogen, argon and self ions with incident energy below 2 MeV was calculated following the theory developed by Lindhard and co-workers for the partition of energy as an energetic ion slowing down. In this calculation, energy loss due to electron excitation was taken into account for the atomic collision cascade after the primary knock-on process. Some parameters indispensable for the calculation such as energy loss rate, damage efficiency, projected range and its straggling were tabulated as a function of incident ion energy of 20 keV to 2 MeV. The damage and parameters were also calculated for 2 MeV nickel ions bombarding Fe targets. In this case, the DPA value is of 40--75% overestimated in a calculation disregarding electronic energy loss for primary knock-on atoms. The formula proposed in this report is significant for calculations on displacement damage produced by heavy ion bombardment as a simulation of high fluence fast neutron damage. (auth.)

Heavy-ion radiography

International Nuclear Information System (INIS)

Fabrikant, J.I.; Tobias, C.A.; Holley, W.R.; Benton, E.V.; Woodruff, K.H.; MacFarland, E.W.

1983-01-01

High energy, heavy-ion beams offer superior discrimination of tissue electron densities at very low radiation doses. This characteristic has potential for diagnostic medical imaging of neoplasms arising in the soft tissues and organs because it can detect smaller inhomogeneities than x rays. Heavy-ion imaging may also increase the accuracy of cancer radiotherapy planning involving use of accelerated charged particles. In the current physics research program of passive heavy-ion imaging, critical modulation transfer function tests are being carried out in heavy-ion projection radiography and heavy-ion computerized tomography. The research goal is to improve the heavy-ion imaging method until it reaches the limits of its theoretical resolution defined by range straggling, multiple scattering, and other factors involved in the beam quality characteristics. Clinical uses of the imaging method include the application of heavy-ion computerized tomography to heavy-ion radiotherapy planning, to the study of brain tumors and other structures of the head, and to low-dose heavy-ion projection mammography, particularly for women with dense breasts where other methods of diagnosis fail. The ions used are primarily 300 to 570 MeV/amu carbon and neon ions accelerated at the Lawrence Berkeley Laboratory Bevalac

Modeling of alpha mass-efficiency curve

International Nuclear Information System (INIS)

Semkow, T.M.; Jeter, H.W.; Parsa, B.; Parekh, P.P.; Haines, D.K.; Bari, A.

2005-01-01

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

Beam emittance of the Stony Brook Tandem-LINAC booster

International Nuclear Information System (INIS)

Scholldorf, A.H.

1984-01-01

This dissertation is primarily a study of the longitudinal and transverse beam emittance of the Stony Brook Heavy Ion Tandem LINAC Accelerator Facility, with a secondary emphasis on the beam dynamical design of two key elements of the system: a low energy double-drift buncher, and an achromatic double-90 0 LINAC injection system. A transverse emittance measuring system consisting of two translation stages controlled by stepper motors is described. Each stage carried a pair of beam defining slits mounted so that both horizontal and vertical emittances could be measured with only linear motion of the stage assembly. Beam currents were measured directly by a low-noise, high-sensitivity electrometer circuit integrated with the second slit-stage assembly. A mini-computer controlled the motors and acquired and displayed the data. Transverse emittance areas of beams of 12 C, 16 O, 32 S, and 58 Ni were measured at ion source extraction potential, after ion source acceleration, after tandem acceleration, and after LINAC acceleration. The results were analyzed in terms of source sputter-cone geometry, angle straggling in gas and foil strippers, and a variety of other factors

Calculations on displacement damage and its related parameters for heavy ion bombardment in reactor materials

Energy Technology Data Exchange (ETDEWEB)

Sone, K; Shiraishi, K

1975-04-01

The depth distribution of displacement damage expressed in displacements per atom (DPA) in reactor materials such as Mo, Nb, V, Fe and Ni bombarded by energetic nitrogen, argon and self ions with incident energy below 2 MeV was calculated following the theory developed by Lindhard and co-workers for the partition of energy as an energetic ion slowing down. In this calculation, energy loss due to electron excitation was taken into account for the atomic collision cascade after the primary knock-on process. Some parameters indispensable for the calculation such as energy loss rate, damage efficiency, projected range and its straggling were tabulated as a function of incident ion energy of 20 keV to 2 MeV. The damage and parameters were also calculated for 2 MeV nickel ions bombarding Fe targets. In this case, the DPA value is of 40--75% overestimated in a calculation disregarding electronic energy loss for primary knock-on atoms. The formula proposed in this report is significant for calculations on displacement damage produced by heavy ion bombardment as a simulation of high fluence fast neutron damage.

States of 15C via the (18O,16O) reaction

CERN Document Server

Cappuzzello, F; Cunsolo, A; Foti, A; Orrigo, S E A; Rodrigues, M R D; Borello-Lewin, T; Carbone, D; Schillaci, C

2010-01-01

A study of the 15C states was pursued in 2008 at the Catania INFN-LNS laboratory by the 13C(18O,16O)15C reaction at 84 MeV incident energy. The 16O ejectiles were detected at forward angles by the MAGNEX magnetic spectrometer. Thanks to an innovative technique the ejectiles were identified without the need of time of flight measurements. Exploiting the large momentum acceptance (25%) and solid angle (50 msr) of the spectrometer, the 15C energy spectra were obtained with a quite relevant yield up to about 20 MeV excitation energy. The application of the powerful technique of the trajectory reconstruction did allow to get an energy resolution of about 250 keV FWHM, limited mainly by straggling effects. The spectra show several known low lying states up to about 7 MeV excitation energy as well as two unknown resonant structures at about 11.4 and 13.5 MeV. The strong excitation of these latter together with the measured width of about 2 MeV FWHM could indicate the presence of collective modes of excitation connec...

Measurement of the 234U(n, f ) cross-section with quasi-monoenergetic beams in the keV and MeV range using a Micromegas detector assembly

Science.gov (United States)

Stamatopoulos, A.; Kanellakopoulos, A.; Kalamara, A.; Diakaki, M.; Tsinganis, A.; Kokkoris, M.; Michalopoulou, V.; Axiotis, M.; Lagoyiannis, A.; Vlastou, R.

2018-01-01

The 234U neutron-induced fission cross-section has been measured at incident neutron energies of 452, 550, 651 keV and 7.5, 8.7, 10 MeV using the 7Li ( p, n) and the 2H( d, n) reactions, respectively, relative to the 235U( n, f ) and 238U( n, f ) reference reactions. The measurement was performed at the neutron beam facility of the National Center for Scientific Research "Demokritos", using a set-up based on Micromegas detectors. The active mass of the actinide samples and the corresponding impurities were determined via α-spectroscopy using a surface barrier silicon detector. The neutron spectra intercepted by the actinide samples have been thoroughly studied by coupling the NeuSDesc and MCNP5 codes, taking into account the energy and angular straggling of the primary ion beams in the neutron source targets in addition to contributions from competing reactions ( e.g. deuteron break-up) and neutron scattering in the surrounding materials. Auxiliary Monte Carlo simulations were performed making combined use of the FLUKA and GEF codes, focusing particularly on the determination of the fission fragment detection efficiency. The developed methodology and the final results are presented.

Simulation studies of gas and plasma-based charge strippers

Energy Technology Data Exchange (ETDEWEB)

Haas, Oliver Sebastian [Institut fuer Theorie Elektromagnetischer Felder, Technische Univ. Darmstadt (Germany); Boine-Frankenheim, Oliver [Institut fuer Theorie Elektromagnetischer Felder, Technische Univ. Darmstadt (Germany); GSI Helmholtz Centre for Heavy Ion Research, Darmstadt (Germany)

2016-07-01

Charge stripping of heavy ion beams at high intensities is a major challenge in current and future facilities with high intensity heavy ion beams. Conventional stripping techniques are limited in their applicability, e.g. solid carbon foils suffer from short lifetimes at high intensities and gas strippers usually achieve only low charge states. One possible alternative is the use of a plasma as a stripping medium. The presented work focuses on theoretical studies of the interaction of an heavy ion beam with a plasma and accompanying effects in possible charge strippers. The main interest in the presented studies is the final charge state distribution of the ion beam. Different models for solving the corresponding rate equations were developed, taking into account ionization, recombination, energy loss and straggling processes. Sophisticated models, e.g. for ionization cross sections, as well as limits and applicability of simplified models are discussed. Quantitative results are presented in form an overview of the charge state distributions of different - conventional and novel - charge stripping media. Furthermore comparisons are done with charge state distributions of available experimental data. Typical practically relevant target conditions are discussed as well as deterioration of beam quality.

Evaluation of ion chamber dependent correction factors for ionisation chamber dosimetry in proton beams using a Monte Carlo method

Energy Technology Data Exchange (ETDEWEB)

Palmans, H [Ghent Univ. (Belgium). Dept. of Biomedical Physics; Verhaegen, F

1995-12-01

In the last decade, several clinical proton beam therapy facilities have been developed. To satisfy the demand for uniformity in clinical (routine) proton beam dosimetry two dosimetry protocols (ECHED and AAPM) have been published. Both protocols neglect the influence of ion chamber dependent parameters on dose determination in proton beams because of the scatter properties of these beams, although the problem has not been studied thoroughly yet. A comparison between water calorimetry and ionisation chamber dosimetry showed a discrepancy of 2.6% between the former method and ionometry following the ECHED protocol. Possibly, a small part of this difference can be attributed to chamber dependent correction factors. Indications for this possibility are found in ionometry measurements. To allow the simulation of complex geometries with different media necessary for the study of those corrections, an existing proton Monte Carlo code (PTRAN, Berger) has been modified. The original code, that applies Mollire`s multiple scattering theory and Vavilov`s energy straggling theory, calculates depth dose profiles, energy distributions and radial distributions for pencil beams in water. Comparisons with measurements and calculations reported in the literature are done to test the program`s accuracy. Preliminary results of the influence of chamber design and chamber materials on dose to water determination are presented.

Depth distribution analysis of martensitic transformations in Xe implanted austenitic stainless steel

International Nuclear Information System (INIS)

Johnson, E.; Johansen, A.; Sarholt-Kristensen, L.; Chechenin, N.G.; Grabaek, L.; Bohr, J.

1988-01-01

In this work we present results from a depth distribution analysis of the martensitic phase change occurring in Xe implanted single crystals of austenitic stainless steel. Analysis was done by 'in situ' RBS/channeling analysis, X-ray diffraction and cross-section transmission electron microscopy (XTEM) of the implanted surface. It is found that the martensitic transformation of the surface layer occurs for fluences above 1x10 20 m -2 . The thickness of the transformed layer increases with fluence to ≅ 150 nm at 1x10 21 m -2 , which far exceeds the range plus straggling of the implanted Xe as calculated by the TRIM computer simulation code. Simulations using the MARLOWE code indicate that the thickness of the transformed layer coincides with the range of the small fraction of ions channeled under random implantation conditions. Using cross sectional TEM on the Xe implanted crystals, the depth distribution of gas inclusions and defects can be directly observed. Using X-ray diffraction on implanted single crystals, the solid epitaxial nature of the Xe inclusions, induced prior to the martensitic transformation, was established. The lattice constant obtained from the broad diffraction peak indicates that the pressure in the inclusions is ≅ 5 GPa. (orig./BHO)

Nuclear stopping in transmission experiments

International Nuclear Information System (INIS)

Glazov, Lev G.; Sigmund, Peter

2003-01-01

Energy-loss spectra, mean and peak energy loss, and straggling due to elastic nuclear scattering have been studied theoretically as a function of target thickness and deflection angle of an initially monochromatic and well-collimated ion beam. The goal of this work has been to provide a generally valid scheme for nuclear-stopping corrections, allowing to determine electronic-stopping forces from energy-loss spectra measured in transmission geometry. Calculations have been based on the generalized Bothe-Landau theory of energy loss and multiple scattering. Our peak energy losses at zero emergence angle show close (∼10%) agreement with predictions of Fastrup et al. on the basis of the Bohr-Williams theory. However, predicted mean and peak energy losses are found to more sensitively depend on the underlying interatomic potential than unrestricted, i.e. angle-integrated mean or peak energy losses. Both elastic energy loss and multiple scattering are known to obey scaling laws involving only two combinations of the pertinent variables and atomic parameters. The dependence on deflection angle and foil thickness of mean and peak energy loss obeys a simple combination of these scaling laws. Comments are made on potential errors due to uncertainties in the nuclear-stopping correction applied in the literature with specific reference to central papers in low-velocity stopping

Evaluation of ion chamber dependent correction factors for ionisation chamber dosimetry in proton beams using a Monte Carlo method

International Nuclear Information System (INIS)

Palmans, H.; Verhaegen, F.

1995-01-01

In the last decade, several clinical proton beam therapy facilities have been developed. To satisfy the demand for uniformity in clinical (routine) proton beam dosimetry two dosimetry protocols (ECHED and AAPM) have been published. Both protocols neglect the influence of ion chamber dependent parameters on dose determination in proton beams because of the scatter properties of these beams, although the problem has not been studied thoroughly yet. A comparison between water calorimetry and ionisation chamber dosimetry showed a discrepancy of 2.6% between the former method and ionometry following the ECHED protocol. Possibly, a small part of this difference can be attributed to chamber dependent correction factors. Indications for this possibility are found in ionometry measurements. To allow the simulation of complex geometries with different media necessary for the study of those corrections, an existing proton Monte Carlo code (PTRAN, Berger) has been modified. The original code, that applies Mollire's multiple scattering theory and Vavilov's energy straggling theory, calculates depth dose profiles, energy distributions and radial distributions for pencil beams in water. Comparisons with measurements and calculations reported in the literature are done to test the program's accuracy. Preliminary results of the influence of chamber design and chamber materials on dose to water determination are presented

Half-life and mass measurement of the short-lived {sup 215}Po isotope (1.78 ms) at the FRS ion catcher

Energy Technology Data Exchange (ETDEWEB)

Rink, Ann-Kathrin; Bergmann, Julian; Ebert, Jens; Hornung, Christine; Miskun, Ivan; Reiter, Moritz P. [Justus-Liebig Universitaet Giessen (Germany); Ayet San Andres, Samuel; Dickel, Timo; Plass, Wolfgang R.; Scheidenberger, Christoph [Justus-Liebig Universitaet Giessen (Germany); GSI, Darmstadt (Germany); Geissel, Hans; Purushothaman, Sivaji [GSI, Darmstadt (Germany)

2016-07-01

At the Low-Energy Branch (LEB) of the Super-FRS at FAIR, precision experiments with exotic nuclei will be performed using ion traps and lasers. The nuclei will be produced at relativistic energies, slowed down, thermalised in a cryogenic stopping cell (CSC) and made available to various experiments. The thermalisation is a challenging task because of the large energy straggling of the nuclei after production, which requires a stopping cell with large areal densities. Also, the process needs to be performed on a millisecond time scale in order to give access to short-lived nuclides. This method has already been successfully applied at the FRS Ion Catcher at GSI using a prototype CSC. Recently the potential of the method has been demonstrated by the mass and half-life measurement of the {sup 215}Po nuclide with a half-life of 1.78 ms only. The multiple-reflection time-of-flight mass spectrometer at the FRS Ion Catcher has been used to determine the mass to a sub-ppm accuracy and to provide a mass-selected beam for alpha spectroscopy. Furthermore, experiments have been performed with the prototype CSC in order to test novel concepts to be used with the final version of the CSC for the LEB.

Implementation of pencil kernel and depth penetration algorithms for treatment planning of proton beams

International Nuclear Information System (INIS)

Russell, K.R.; Saxner, M.; Ahnesjoe, A.; Montelius, A.; Grusell, E.; Dahlgren, C.V.

2000-01-01

The implementation of two algorithms for calculating dose distributions for radiation therapy treatment planning of intermediate energy proton beams is described. A pencil kernel algorithm and a depth penetration algorithm have been incorporated into a commercial three-dimensional treatment planning system (Helax-TMS, Helax AB, Sweden) to allow conformal planning techniques using irregularly shaped fields, proton range modulation, range modification and dose calculation for non-coplanar beams. The pencil kernel algorithm is developed from the Fermi-Eyges formalism and Moliere multiple-scattering theory with range straggling corrections applied. The depth penetration algorithm is based on the energy loss in the continuous slowing down approximation with simple correction factors applied to the beam penumbra region and has been implemented for fast, interactive treatment planning. Modelling of the effects of air gaps and range modifying device thickness and position are implicit to both algorithms. Measured and calculated dose values are compared for a therapeutic proton beam in both homogeneous and heterogeneous phantoms of varying complexity. Both algorithms model the beam penumbra as a function of depth in a homogeneous phantom with acceptable accuracy. Results show that the pencil kernel algorithm is required for modelling the dose perturbation effects from scattering in heterogeneous media. (author)

Materials research with ion beams

International Nuclear Information System (INIS)

Meyer, J.D.

1988-01-01

This report gives a series of helpful programs which are used in materials research with ion beams. In this context algorithms which can substitute table books are dealt with. This is true for the programs DEDX and PRAL; they are used in order to determine the energy loss of ions in solid bodies, their working range and straggling. Furthermore, simulator routines and analyzers are described. The program TRIM simulates the physical phenomena which occur with the penetration of high-energy ions into solid bodies. In this context electronic excitations, phonons and lattice distortions which are caused by the ions are dealt with. For the experimental ion implantation it is interesting to know the final distribution of the simulated ions in the solid body. The program RBS simulates the Rutherford spectrum of ions which are scattered from a solid body which may consist of up to nine elements and up to one hundred layers. The unknown composition of a solid body can be determined in direct comparison with the experimental spectrum. The program NRA determines concentration and penetrative distribution of an impurity by means of the experimental nuclear reaction spectrum of this impurity. All programs are written in FORTRAN 77. (orig./MM) [de

Aggravation of serum Hepatocyte Growth Factor levels during hepato carcinogenesis in Rats

International Nuclear Information System (INIS)

Abdelgawad, M.R.; Ghareeb, N.A.

2010-01-01

Hepatocyte growth factor (HGF) has an essential role during liver development and it plays an important role in the regeneration and repair of injured tissues and acting as a mitogen, motogen and morphogens for a variety of epithelial cells. The role of HGF in carcinogenesis is in straggle and so, the present study aimed to through light through the level of HGF during different steps of carcinogenesis. Forty male rats were given diethylnitrosamine (DEN) in drinking water (100 mg/l) for up to 16 weeks. Eight rats were sacrificed at 8, 12 and 16 weeks. Besides, 8 hepatoma bearing rats were exposed to a single dose gamma irradiation (3 Gy) were sacrificed after 2 weeks from exposure (2 rats died, 36 hrs post irradiation) and 8 hepatoma bearing rats were sacrificed after 4 weeks from receiving a combined antioxidant (N-acetylcysteine and Lmethionine). Serum HGF was assayed by enzyme linked immunosorbent assay (ELISA). Serum HGF level in DEN treated rats and in exposed hepatoma bearing rats was significantly higher than in control rats whereas, serum HGF level after treatment with N acetylcysteine and L-methionine for 4 weeks was significantly decreased than DEN treated rats and concluded that serum HGF may play a role during promotion and progression of hepatocellular carcinoma (HCC) and during treatment

Measurement of the {sup 234}U(n, f) cross-section with quasi-monoenergetic beams in the keV and MeV range using a Micromegas detector assembly

Energy Technology Data Exchange (ETDEWEB)

Stamatopoulos, A.; Kanellakopoulos, A.; Kalamara, A.; Kokkoris, M.; Michalopoulou, V.; Vlastou, R. [National Technical University of Athens, Department of Physics, Athens (Greece); Diakaki, M. [National Technical University of Athens, Department of Physics, Athens (Greece); European Organisation for Nuclear Research (CERN), Geneva (Switzerland); Tsinganis, A. [European Organisation for Nuclear Research (CERN), Geneva (Switzerland); Axiotis, M.; Lagoyiannis, A. [Tandem Accelerator Laboratory, Institute of Nuclear and Particle Physics, N.C.S.R. Demokritos, Athens (Greece)

2018-01-15

The {sup 234}U neutron-induced fission cross-section has been measured at incident neutron energies of 452, 550, 651 keV and 7.5, 8.7, 10 MeV using the {sup 7}Li (p, n) and the {sup 2}H(d, n) reactions, respectively, relative to the {sup 235}U(n, f) and {sup 238}U(n, f) reference reactions. The measurement was performed at the neutron beam facility of the National Center for Scientific Research ''Demokritos'', using a set-up based on Micromegas detectors. The active mass of the actinide samples and the corresponding impurities were determined via α-spectroscopy using a surface barrier silicon detector. The neutron spectra intercepted by the actinide samples have been thoroughly studied by coupling the NeuSDesc and MCNP5 codes, taking into account the energy and angular straggling of the primary ion beams in the neutron source targets in addition to contributions from competing reactions (e.g. deuteron break-up) and neutron scattering in the surrounding materials. Auxiliary Monte Carlo simulations were performed making combined use of the FLUKA and GEF codes, focusing particularly on the determination of the fission fragment detection efficiency. The developed methodology and the final results are presented. (orig.)

Accurate transport simulation of electron tracks in the energy range 1 keV-4 MeV

International Nuclear Information System (INIS)

Cobut, V.; Cirioni, L.; Patau, J.P.

2004-01-01

Multipurpose electron transport simulation codes are widely used in the fields of radiation protection and dosimetry. Broadly based on multiple scattering theories and continuous energy loss stopping powers with some mechanism taking straggling into account, they give reliable answers to many problems. However they may be unsuitable in some specific situations. In fact, many of them are not able to accurately describe particle transport through very thin slabs and/or in high atomic number materials, or also when knowledge of high-resolution depth dose distributions is required. To circumvent these deficiencies, we developed a Monte Carlo code simulating each interaction along electron tracks. Gas phase elastic cross sections are corrected to take into account solid state effects. Inelastic interactions are described within the framework of the Martinez et al. [J. Appl. Phys. 67 (1990) 2955] theory intended to deal with energy deposition in both condensed insulators and conductors. The model described in this paper is validated for some materials as aluminium and silicon, encountered in spectrometric and dosimetric devices. Comparisons with experimental, theoretical and other simulation results are made for angular distributions and energy spectra of transmitted electrons through slabs of different thicknesses and for depth energy distributions in semi-infinite media. These comparisons are quite satisfactory

La sociedad de la información en la modernización de la gestión estratégica: Integración de sistemas de información distribuidos y la inteligencia organizacional

Directory of Open Access Journals (Sweden)

Germán Eduardo Vargas Guerrero

2006-05-01

Full Text Available La situación de las organizaciones en Colombia evidencia que prioritariamente no hace falta (des información ni (des conocimiento en (tre los actores, de quienes se asume su idónea intencionalidad y preparación. Estas condiciones precisan que, por defecto, se requieren instrumentos para compartir y utilizar información pertinente, por las personas adecuadas en momentos oportunos, que permitan construir estrategias más conscientes y efectivas. En este orden de ideas, el propósito del siguiente documento es identificar metodológicamente un acercamiento que potencia la simbiosis entre tecnología intelectual - cultura estratégica - toma de decisiones. / The straggled, reactive and inertial, orientation of Colombian entrepreneurship has been justified, inconsistently, by the hardness of resources management, a concept that intensifies their deficient technological capabilities, because this situation is more than trouble of means: rather strategic purposes. In fact, a classical effect of no conscientious recognition of this limitation, explain why so many organizations connect your successful with your "intelligence", but failure with exogenous factors impact. The purpose of the following document is the methodological identification of both analysis and organizational intervention points, to develop the symbiosis between intelligence technologies, strategic culture and decision processes.

Study on influences of experimental factors on energy and absolute activity measurements of alpha-emitters

International Nuclear Information System (INIS)

Terini, R.A.

1991-01-01

This work presents firstly a review of the fundamental results and conclusions obtained through alpha-spectrometry and alpha-counting, and the influence of energy straggling, energy loss, self-absorption and backscattering, on the determination of the energy and the absolute activity of alpha samples. Is is shown that the techniques of source fabrication and the methods of measurements play a capital influence on the obtained results. Moreover, measurements made by us, with a silicon surface barrier detector, show that the peak-asymmetry and peak-shift of an alpha-spectrum increases with the angle of emission, and that the magnitude of this effect depends on the thickness and homogeneity of the sample, as well as on the geometry of the measuring system. Through an analysis of the angular distribution of the emitted particles, the degree of isotropy of some thin Am sup(241) sources was measured and the influence of source backing and the geometry was analysed. We can conclude that, in general, there is a larger precision in measurements made under very small solid angles around the normal to the sample, and we enphasize the necessary cares required on the production of the source and on the set up of the measuring system. (author)

STIM with energy loss contrast: An imaging modality unique to MeV ions

International Nuclear Information System (INIS)

Lefevre, H.W.; Schofield, R.M.S.; Bench, G.S.; Legge, G.J.F.

1991-01-01

Scanning transmission ion microscopy (STIM) through measurement of energy loss of individual ions is a quantitative imaging technique with several unique capabilities. The uniqueness derives conjointly from the large penetration with small scattering of MeV ions in low-Z specimens, from the simple relationship between energy loss and projected or areal density, and from the almost 100% efficiency with which one obtains pixel data from individual ions. Since contrast is in energy loss and not in numbers of events, the statistics of energy loss straggling affects the image but the statistics of counting does not. Small scattering makes it possible to observe details within transparent specimens. High efficiency makes it possible to collect large data sets for computed tomography, stereo, or high-definition imaging with a small radiation dose. High efficiency allows one to minimize aberrations by use of small apertures, to achieve good precision in the determination of areal density, or even to image live biological specimens in air since only one or a few ions per pixel are required. This paper includes a bibliography on STIM with MeV ions, it discusses the accuracy that one can achieve in the areal density coloring of a pixel with data from one or a few ions, and it supplements that review with recent examples from the Melbourne and the Eugene microprobes. (orig.)

Depth profiling of tritium by neutron time-of-flight

International Nuclear Information System (INIS)

Davis, J.C.; Anderson, J.D.; Lefevre, H.W.

1976-01-01

A method to measure the depth profile of tritium implanted or absorbed in materials was developed. The sample to be analyzed is bombarded with a pulsed proton beam and the energy of neutrons produced by the T(p,n) reaction is measured by the time-of-flight technique. From the neutron energy the depth in the target of the T atoms may be inferred. A sensitivity of 0.1 at. percent T or greater is possible. The technique is non-destructive and may be used with thick or radioactive host materials. Samples up to 20 μm in thickness may be profiled with resolution limited by straggling of the proton beam for depths greater than 1 μm. Deuterium depth profiling has been demonstrated using the D(d,n) reaction. The technique has been used to observe the behavior of an implantation spike of T produced by a 400 keV T + beam stopping at a depth of 3 μm in 11 μm thick layers of Ti and TiH. The presence of H in the Ti lattice is observed to inhibit the diffusion of T through the lattice. Effects of the total hydrogen concentration (H + T) being forced above stochiometry at the implantation site are suggested by the shapes of the implantation spikes

Secondary electrons detectors for beam tracking: micromegas and wire chamber

International Nuclear Information System (INIS)

Pancin, J; Chaminade, T; Drouart, A; Kebbiri, M; Riallot, M; Fernandez, B; Naqvi, F

2009-01-01

SPIRAL2 or FAIR will be able to deliver beams of radioactive isotopes of low energy (less than 10 MeV/n). The emittance of these new beams will impose the use of beam tracking detectors to reconstruct the exact impact position of the nuclei on the experimental target. However, due to their thickness, the classical detectors will generate a lot of energy and angular straggling. A possible alternative is the SED principle (Secondary Electron Detector). It consists of an emissive foil placed in beam and a detector for the secondary electrons ejected by the passing of the nuclei through the foil. An R and D program has been initiated at CEA Saclay to study the possibility to use low pressure gaseous detectors as SED for beam tracking. Some SED have been already used on the VAMOS spectrometer at GANIL since 2004. We have constructed new detectors on this model to measure their performances in time and spatial resolution, and counting rate. Other detector types are also under study. For the first time, a test with different micromegas detectors at 4 Torr has been realized. A comparison on the time resolution has been performed between wire chamber and micromegas at very low pressure. The use of micromegas could be promising to improve the counting rate capability and the robustness of beam tracking detectors.

Arquitectura del cambio organizacional: liderazgo, gestión del conocimiento e innovación tecnológica

Directory of Open Access Journals (Sweden)

Germán Eduardo Vargas

2008-11-01

Full Text Available La actividad de las firmas, como unidad socioeconómica, en el marco evolucionista está orientada integralmente por procesos de identidad, cohesión y mecanismos de adaptación y evolución. En este orden, el presente documento ilustra cómo la orientación e integración estratégica basada en el conocimiento para la innovación se constituye como un imperativo de desarrollo que, a partir de un pequeño apalancamiento, permite distinguir entre dos trayectorias de evolución: firmas económicas tradicionales (inerciales, pues introducen mejoras incrementales esporádicas y modernas (dinámicas y radicalmente innovadoras. A partir de este hecho, se obtienen reveladoras conclusiones y desafíos para intervenir y adecuar el comportamiento de las empresas. / Enterprises activities -straggled on reactionary and inertial orientation- have been inconsistently justified with the low availability of internal and leveraged resources and their deficient technological capacity. For this reason an orientation within an evolutionary framework defined by company identity and its cohesion illustrates how strategic orientation based on knowledge and innovation have become an imperative for organizational development, distinguishing between two evolutionary company forms: traditional economic (inertial, as they introduce sporadic incremental improvements and modern companies (dynamic and radical innovators.

Alpha-spectrometry and fractal analysis of surface micro-images for characterisation of porous materials used in manufacture of targets for laser plasma experiments

Energy Technology Data Exchange (ETDEWEB)

Aushev, A A; Barinov, S P; Vasin, M G; Drozdov, Yu M; Ignat' ev, Yu V; Izgorodin, V M; Kovshov, D K; Lakhtikov, A E; Lukovkina, D D; Markelov, V V; Morovov, A P; Shishlov, V V [Russian Federal Nuclear Center ' All-Russian Research Institute of Experimental Physics' , Sarov, Nizhnii Novgorod region (Russian Federation)

2015-06-30

We present the results of employing the alpha-spectrometry method to determine the characteristics of porous materials used in targets for laser plasma experiments. It is shown that the energy spectrum of alpha-particles, after their passage through porous samples, allows one to determine the distribution of their path length in the foam skeleton. We describe the procedure of deriving such a distribution, excluding both the distribution broadening due to statistical nature of the alpha-particle interaction with an atomic structure (straggling) and hardware effects. The fractal analysis of micro-images is applied to the same porous surface samples that have been studied by alpha-spectrometry. The fractal dimension and size distribution of the number of the foam skeleton grains are obtained. Using the data obtained, a distribution of the total foam skeleton thickness along a chosen direction is constructed. It roughly coincides with the path length distribution of alpha-particles within a range of larger path lengths. It is concluded that the combined use of the alpha-spectrometry method and fractal analysis of images will make it possible to determine the size distribution of foam skeleton grains (or pores). The results can be used as initial data in theoretical studies on propagation of the laser and X-ray radiation in specific porous samples. (laser plasma)

Influence of surface topography on RBS measurements: case studies of (Cu/Fe/Pd) multilayers and FePdCu alloys nanopatterned by self-assembly

Science.gov (United States)

Krupinski, M.; Perzanowski, M.; Zabila, Y.; Zarzycki, A.; Marszałek, M.

2017-03-01

In this paper the influence of surface topography on Rutherford backscattering spectrometry (RBS) is discussed. (Cu/Fe/Pd) multilayers with total thickness of about 10 nm were deposited by physical vapor deposition on self-organized array of SiO2 nanoparticles with the size of 50 nm and 100 nm. As a reference, the multilayered systems were also prepared on flat substrates under the same conditions. After the deposition, morphology of the systems was studied by scanning electron microscopy (SEM), while chemical analysis was performed using Rutherford backscattering spectrometry. It was found that the RBS spectra and determined compositions for flat and patterned multilayers differ. The difference is discussed by taking into account the effect of additional inelastic scattering and energy straggling occurring due to developed topography of patterned systems. Then, the multilayers were annealed in 600 °C in order to obtain FePdCu alloy. The phenomenon of solid-state dewetting resulted in the formation of isolated alloy islands on the top of SiO2 nanoparticles. The SEM and RBS analysis were repeated showing correlation between the size distribution of obtained alloy islands and broadening of peaks appearing in RBS spectra. Invited talk at 8th International Workshop on Advanced Materials Science and Nanotechnology (IWAMSN2016), 8-12 November 2016, Ha Long City, Vietnam.

Angular scattering of 1–50 keV ions through graphene and thin carbon foils: Potential applications for space plasma instrumentation

International Nuclear Information System (INIS)

Ebert, Robert W.; Allegrini, Frédéric; Fuselier, Stephen A.; Nicolaou, Georgios; Bedworth, Peter; Sinton, Steve; Trattner, Karlheinz J.

2014-01-01

We present experimental results for the angular scattering of ∼1–50 keV H, He, C, O, N, Ne, and Ar ions transiting through graphene foils and compare them with scattering through nominal ∼0.5 μg cm −2 carbon foils. Thin carbon foils play a critical role in time-of-flight ion mass spectrometers and energetic neutral atom sensors in space. These instruments take advantage of the charge exchange and secondary electron emission produced as ions or neutral atoms transit these foils. This interaction also produces angular scattering and energy straggling for the incident ion or neutral atom that acts to decrease the performance of a given instrument. Our results show that the angular scattering of ions through graphene is less pronounced than through the state-of-the-art 0.5 μg cm −2 carbon foils used in space-based particle detectors. At energies less than 50 keV, the scattering angle half width at half maximum, ψ 1/2 , for ∼3–5 atoms thick graphene is up to a factor of 3.5 smaller than for 0.5 μg cm −2 (∼20 atoms thick) carbon foils. Thus, graphene foils have the potential to improve the performance of space-based plasma instruments for energies below ∼50 keV

Radiation damage in urania crystals implanted with low-energy ions

Energy Technology Data Exchange (ETDEWEB)

Nguyen, Tien Hien, E-mail: tien-hien.nguyen@u-psud.fr [Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM – UMR 8609), CNRS-IN2P3-Université Paris-Sud, Bâtiments 104-108, 91405 Orsay Campus (France); Garrido, Frédérico; Debelle, Aurélien; Mylonas, Stamatis [Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM – UMR 8609), CNRS-IN2P3-Université Paris-Sud, Bâtiments 104-108, 91405 Orsay Campus (France); Nowicki, Lech [The Andrzej Soltan Institute for Nuclear Studies, Hoza 69, 00-681 Warsaw (Poland); Thomé, Lionel; Bourçois, Jérôme; Moeyaert, Jérémy [Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM – UMR 8609), CNRS-IN2P3-Université Paris-Sud, Bâtiments 104-108, 91405 Orsay Campus (France)

2014-05-01

Implantations with low-energy ions (470-keV Xe and 500-keV La with corresponding ion range Rp ∼ 85 nm and range straggling ΔRp ∼ 40 nm) have been performed to investigate both radiation and chemical effects due to the incorporation of different species in UO{sub 2} (urania) crystals. The presence of defects was monitored in situ after each implantation fluence step by the RBS/C technique. Channelling data were analysed afterwards by Monte-Carlo simulations with a model of defects involving (i) randomly displaced atoms (RDA) and (ii) distorted rows, i.e. bent channels (BC). While increasing the ion fluence, the accumulation of RDA leads to a steep increase of the defect fraction in the range from 4 to 7 dpa regardless of the nature of bombarding ions followed by a saturation plateau over a large dpa range. A clear difference of 6% in the yield of saturation plateaus between irradiation with Xe and La ions was observed. Conversely, the evolutions of the fraction of BC showed a similar regular increase with increasing ion fluence for both ions. Moreover, this increase is shifted to a larger fluence in comparison to the sharp increase step of RDA. This phenomenon indicates a continuous structural modification of UO{sub 2} crystals under irradiation unseen by the measurement of RDA.

Fractal theory of radon emanation from solids

International Nuclear Information System (INIS)

Semkow, T.M.

1991-01-01

The author developed a fractal theory of Rn emanation from solids, based on α recoil from the α decay of Ra. Range straggling of the recoiling Rn atoms in the solid state is included and the fractal geometry is used to describe the roughness of the emanating surface. A fractal dimension D of the surface and the median projected range become important parameters in calculating the radon emanating power E R from solids. A relation between E R and the specific surface area measured by the gas adsorption is derived for the first time, assuming a uniform distribution of the precursor Ra throughout the samples. It is suggested that the E R measurements can be used to determine D of the surfaces on the scale from tens to hundreds of nm. One obtains, for instance, D = 2.17 ± 0.06 for Lipari volcanic glass and D = 2.83 ± 0.03 for pitchblende. In addition, the author suggests a new process of penetrating recoil and modify the role of indirect recoil. The penetrating recoil may be important for rough surfaces, in which case Rn loses its kinetic energy by penetrating a large number of small surface irregularities. The indirect recoil may be important at the very last stage of energy-loss process, for kinetic energies below ∼ 5 keV

Thin-target excitation functions: a powerful tool for optimizing yield, radionuclidic purity and specific activity of cyclotron produced radionuclides

International Nuclear Information System (INIS)

Bonardi, M.L.

2002-01-01

In accelerator production of radionuclides, thin-target yield, y(E), is defined as a function of the projectile energy E, at the End Of an Instantaneous Bombardment (EOIB), as the slope at the origin of the growing curve of the activity per unit beam current (A/I) of a specific radionuclide vs. irradiation time, for a target in which the energy loss is negligible with respect to the projectile energy itself. In practice, y(E) is defined as the second derivative of A/I with respect to particle energy and irradiation time, calculated when the irradiation time tends to zero (EOIB). The thin-target yields of different radionuclides, produced by direct and side reactions, are numerically fitted, taking into account the overall statistical errors as weights. The 'effective' cross-section σ ± (E) as a function of projectile energy is proportional to thin-target yield, but the physical meaning of this parameter is poor, being only a raw summation of the several cross sections of the reaction channels concerned, weighted on target isotopic composition. Conversely, Thick-Target Yield, Y(E,ΔE), is defined as a two parameter function of the incident particle energy E(MeV) onto the target and the energy loss ΔE (MeV), in the target itself, obtained by integration of thin-target excitation function, y(E). This approach holds in the strict approximation of a monochromatic beam of energy E, not affected by either intrinsic energy spread or straggling. The energy straggling is computed by Monte Carlo computer codes, like TRIM 2001. In case of total particle energy absorption in the target, for a nuclear reaction of energy threshold E th , the function Y(E,ΔE) reaches a value Y(E,E- E th ), for ΔE=E- E th , that represents mathematically the envelope of the Y(E,ΔE) family of curves. This envelope is a monotonically increasing curve, never reaching either a maximum or a saturation value, even if its slope becomes negligible for high particle energies and energy losses. Some

Studies of neutron measurement methods for fusion plasma diagnostics

International Nuclear Information System (INIS)

Beimer, K.H.

1986-03-01

This thesis comprises several studies mainly devoted to neutron measurement systems for plasma diagnostics at JET (Joint European Torus). An in situ calibration of the U-235 fission chamber detectors located at JET is presented. These detectors are used for measuring the neutron yield from the thermonuclear reactions in the plasma. The energy spectrum of the neutrons from the reactions D(d,n) 3 He has been studied by means of a 3 He spectrometer. Especially, it was found that by measuring the width of the full energy peak in the response spectrum of the 3 He-spectrometer, the deuterium distribution in the deuterium targets used can be estimated. In order to measure different neutron energies it is necessary to obtain a detailed knowledge of the response of the spectrometer. Therefore, the response function to monoenergetic neutrons in the energy range 130-3030 keV was experimentally determined. Some work has been related to a design study of a 14 MeV spectrometer for neutron diagnostics. It is a combined proton-recoil and time-of-flight spectrometer for high resolution measurements. The main parts of it are the collimator, the scattering foil, and the detectors for the recoil protons and the scattered neutrons. The influence of proton straggling in the foil on the resolution and efficiency of the spectrometer has been studied. Furthermore, a three dimensional Monte Carlo code has been written and used for the design of the collimator. (author)

Transport Measurements on Si Nanostructures with Counted Sb Donors

Science.gov (United States)

Singh, Meenakshi; Bielejec, Edward; Garratt, Elias; Ten Eyck, Gregory; Bishop, Nathaniel; Wendt, Joel; Luhman, Dwight; Carroll, Malcolm; Lilly, Michael

2014-03-01

Donor based spin qubits are a promising platform for quantum computing. Single qubits using timed implant of donors have been demonstrated.1 Extending this to multiple qubits requires precise control over the placement and number of donors. Such control can be achieved by using a combination of low-energy heavy-ion implants (to reduce depth straggle), electron-beam lithography (to define position), focused ion beam (to localize implants to one lithographic site) and counting the number of implants with a single ion detector.2 We report transport measurements on MOS quantum dots implanted with 5, 10 and 20 Sb donors using the approach described above. A donor charge transition is identified by a charge offset in the transport characteristics. Correlation between the number of donors and the charge offsets is studied. These results are necessary first steps towards fabricating donor nanostructures for two qubit interactions. This work was performed, in part, at the Center for Integrated Nanotechnologies, a U.S. DOE Office of Basic Energy Sciences user facility. The work was supported by Sandia National Laboratories Directed Research and Development Program. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a Lockheed-Martin Company, for the U. S. Department of Energy under Contract No. DE-AC04-94AL85000. 1J. J. Pla et al., Nature 496, 334 (2013) 2J. A. Seamons et al., APL 93, 043124 (2008).

Microbulk MicrOMEGAs for the search of 0νββ of 136Xe in the PandaX-III experiment

International Nuclear Information System (INIS)

Galan, J.

2016-01-01

The search for the neutrinoless double beta decay (0νββ) is one of the most important quests nowadays in neutrino physics. Among the different techniques used, high pressure xenon (HPXe) gas time projection chambers (TPC) stand out because they allow to image the topology of the 0νββ event (one straggling track ending in two blobs), and use it to discriminate signal from background events. Recent results with microbulk Micromegas in Xe + trimethylamine (TMA) mixtures show high promise in terms of gain, stability of operation, and energy resolution at high pressures (up to 10 bar). The addition of TMA at levels of 1% reduces electron diffusion in up to a factor of 10 with respect pure Xe, improving the quality of the topological pattern, and therefore the discrimination capability. Moreover microbulk Micromegas have very low levels of intrinsic radioactivity. All these results show that a Micromegas-read High Pressure Xenon TPC (HPXe-TPC) can be a competitive technique in the search for 0νββ. The recently proposed PandaX-III experiment, based on these results, aims at building a large TPC of 200 kg of enriched Xe, to be located at Jinping Underground laboratory in China. In this document the main features of the experiment will be presented, with an emphasis on the design and tests of the microbulk readout, as well as the status of the project and first results of the prototyping phase.

The center for production of single-photon emitters at the electrostatic-deflector line of the Tandem accelerator of LABEC (Florence)

Science.gov (United States)

Lagomarsino, Stefano; Sciortino, Silvio; Gelli, Nicla; Flatae, Assegid M.; Gorelli, Federico; Santoro, Mario; Chiari, Massimo; Czelusniac, Caroline; Massi, Mirko; Taccetti, Francesco; Agio, Mario; Giuntini, Lorenzo

2018-05-01

The line for the pulsed beam of the 3 MeV Tandetron accelerator at LABEC (Florence) has been upgraded for ion implantation experiments aiming at the fabrication of single-photon emitters in a solid-state matrix. A system based on Al attenuators has been calibrated in order to extend the energy range of the implanted ions from MeV down to the tens of keV. A new motorized XY stage has been installed in the implantation chamber for achieving ultra-fine control on the position of each implanted ion, allowing to reach the scale imposed by lateral straggling. A set-up for the activation of the implanted ions has been developed, based on an annealing furnace operating under controlled high-vacuum conditions. The first experiments have been performed with silicon ions implanted in diamond and the luminescent signal of the silicon-vacancy (SiV) center, peaked at 738 nm, has been observed for a wide range of implantation fluences (108 ÷ 1015 cm-2) and implantation depths (from a few nm to 2.4 μm). Studies on the efficiency of the annealing process have been performed and the activation yield has been measured to range from 1% to 3%. The implantation and annealing facility has thus been tuned for the production of SiV centers in diamond, but is in principle suitable for other ion species and solid-state matrices.

Effects of organic and biological fertilizers on fruit yield and essential oil of sweet fennel (Foeniculum vulgare var. dulce)

Energy Technology Data Exchange (ETDEWEB)

Moradi, R.; Rezvani Moghaddam, P.; Nasiri Mahallati, M.; Nezhadali, A.

2011-07-01

In order to evaluate the effects of different organic and biological fertilizers on quantity and quality of fennel essential oil, an experiment was conducted in a completely randomized block design with three replications. The experimental treatments included two organic (compost and vermicompost) and two biological (Pseudomonas putida and Azotobacter chroococcum) fertilizers, their all twin combinations (Ps. putida + A. chroococcum, Ps. putida + compost, Ps. putida + vermicompost, A. chroococcum + compost, A. chroococcum + vermicompost and compost + vermicompost) and control (non fertilized). There were significant differences between treatments in terms of seed essential oil percentage, essential oil yield; anethole, fenchone, limonene and straggle content in seed essential oil. Results showed that the highest and the lowest percentages of essential oil were obtained in control (2.9%) and A. chroococcum + vermicompost (2.2%) treatments, respectively. The highest essential oil yield (29.9 L ha{sup -}1) and anethole content of essential oil (69.7%) and the lowest contents of fenchone (6.14%), limonene (4.84%) and estragole (2.78%) in essential oil were obtained in compost + vermicompost treatment. It seems that compost + vermicompost treatment compared to other treatments supplied the highest equilibrium of nutrients and water in the root zone of sweet fennel which is led to increasing the anethole content, there upon, decreasing other compounds. Essential oil yield and percentage of anethole content in essential oil were significantly higher in all organic and biological treatments compared with control. (Author) 43 refs.

Fast Monte Carlo for ion beam analysis simulations

International Nuclear Information System (INIS)

Schiettekatte, Francois

2008-01-01

A Monte Carlo program for the simulation of ion beam analysis data is presented. It combines mainly four features: (i) ion slowdown is computed separately from the main scattering/recoil event, which is directed towards the detector. (ii) A virtual detector, that is, a detector larger than the actual one can be used, followed by trajectory correction. (iii) For each collision during ion slowdown, scattering angle components are extracted form tables. (iv) Tables of scattering angle components, stopping power and energy straggling are indexed using the binary representation of floating point numbers, which allows logarithmic distribution of these tables without the computation of logarithms to access them. Tables are sufficiently fine-grained that interpolation is not necessary. Ion slowdown computation thus avoids trigonometric, inverse and transcendental function calls and, as much as possible, divisions. All these improvements make possible the computation of 10 7 collisions/s on current PCs. Results for transmitted ions of several masses in various substrates are well comparable to those obtained using SRIM-2006 in terms of both angular and energy distributions, as long as a sufficiently large number of collisions is considered for each ion. Examples of simulated spectrum show good agreement with experimental data, although a large detector rather than the virtual detector has to be used to properly simulate background signals that are due to plural collisions. The program, written in standard C, is open-source and distributed under the terms of the GNU General Public License

Status of electron transport in MCNP trademark

International Nuclear Information System (INIS)

Hughes, H.G.

1997-01-01

The latest version of MCNP, the Los Alamos Monte Carlo transport code, has now been officially released. MCNP4B has been sent to the Radiation Safety Information Computational Center (RSICC), in Oak Ridge, Tennessee, which is responsible for the further distribution of the code within the US. International distribution of MCNP is done by the Nuclear Energy Agency (ECD/NEA), in Paris, France. Readers with access to the World-Wide-Web should consult the MCNP distribution site http://www-xdiv.lanl.gov/XTM/mcnp/about.html for specific information about contacting RSICC and OECD/NEA. A variety of new features are available in MCNP4B. Among these are differential operator perturbations, cross-section plotting capabilities, enhanced diagnostics for transport in repeated structures and lattices, improved efficiency in distributed-memory multiprocessing, corrected particle lifetime and lifespan estimators, and expanded software quality assurance procedures and testing, including testing of the multigroup Boltzmann-Fokker-Planck capability. New and improved cross section sets in the form of ENDF/B-VI evaluations have also been recently released and can be used in MCNP4B. Perhaps most significant for the interests of this special session, the electron transport algorithm has been improved, especially in the collisional energy-loss straggling and the angular-deflection treatments. In this paper, the author concentrates on a fairly complete documentation of the current status of the electron transport methods in MCNP

Study of new germanium bolometers with interleaved concentric electrodes for non-baryonic cold dark matter direct detection in the Edelweiss-II experiment

International Nuclear Information System (INIS)

Domange, J.

2011-09-01

EDELWEISS is a direct non-baryonic cold dark matter detection experiment in the form of weakly interacting massive particles (also known as WIMPs), which currently constitute the most popular candidates to account for the missing mass in the Universe. To this purpose, EDELWEISS uses germanium bolometers at cryogenic temperature (20 mK approximately) in the Underground Laboratory of Modane (LSM) at the French-Italian border. Since 2008, a new type of detector is operated, equipped with concentric electrodes to optimize the rejection of surface events (coplanar-grid detectors). This thesis work is divided into several research orientations. First, we carried out measurements concerning charge collection in the crystals. The velocity laws of the carriers (electrons and holes) have been determined in germanium at 20 mK in the orientation, and a complete study of charge sharing has been done, including an evaluation of the transport anisotropy and of the straggling of the carriers. These results lead to a better understanding of the inner properties of the EDELWEISS detectors. Then, studies relating to the improvement of the performances were carried out. In particular, we have optimized the space-charge cancellation procedure in the crystals and improved the passive rejection of surface events (β). The fiducial volume of the detectors has been evaluated using two X-ray lines from cosmically activated radionuclides: 68 Ge and 65 Zn. Finally, an exhaustive study of the low energy spectra has been carried out, which makes it possible to develop a systematic analysis method for the search of low-mass WIMPs in EDELWEISS. (author)

Development of radiation detection and measurement system - Development of microcalorimeter for the radioactivity measurement

Energy Technology Data Exchange (ETDEWEB)

Jun, Jae Shik; Jung, H. J.; Chai, H. S.; Han, W. S. [Chungnam National University, Taejon (Korea)

2000-03-01

A unique multi-purpose radiation transport code has been developed and expected to be used in various fields of radiation physics and engineering. The present model is a hybrid in which the restricted energy-loss straggling is applied as in the Class I algorithm and the correlation in the secondary electron production is maintained explicitly. Output electromotive forces from the several types of the heat flux sensors have been measured as a function of the temperature differences between both end-plates of the sensors. Based on the analysis of the measurements, we could select the most appropriate type for our purpose, the sensitivity of which is greater than 45 mV/K. Heat source has also been fabricated with manganin wires and the uncertainty has been estimated to be less than 0.1%. The calorimetric core has been installed in the temporary thermal jacket surrounded by thick styrofoam and the signal from the core has been measured with power varying in the range {mu}W {approx} mW. The reproducibility has been found to be better than 0.5% for power greater than 60 {mu}W/s. In addition, it is confirmed that the heat generated by Co-60 and Ir-192 sources frequently used in industries, medicine and biology with very high level of the activity could be measured with the reproducibility better than that above mentioned. On the whole, the performance characteristics of the calorimetric core could be comparable to those commercially available. 139 refs., 40 figs., 7 tabs. (Author)

Quantitative analysis of light elements in thick samples by PIGE

International Nuclear Information System (INIS)

Mateus, R.; Jesus, A.P.; Ribeiro, J.P.

2004-01-01

PIGE analysis of thick and intermediate samples is usually performed with the help of standards, but this method gives only good results when the standard is very similar to the sample to be analysed. In this work, we present an alternative method for PIGE analysis of light elements in thick samples. This method is based on a code that integrates the nuclear reaction excitation function along the depth of the sample. For the integration procedure the sample is divided in sublayers, defined by the energy steps that were used to measure accurately the excitation function. This function is used as input. Within each sublayer the stopping power cross-sections may be assumed as constant. With these two conditions the calculus of the contribution of each sublayer for the total yield becomes an easy task. This work presents results for the analysis of lithium, boron, fluorine and sodium in thick samples. For this purpose, excitation functions of the reactions 7 Li(p,p ' γ) 7 Li, 19 F(p,p ' γ) 19 F, 10 B(p,αγ) 7 Be and 23 Na(p,p ' γ) 23 Na were employed. Calculated γ-ray yields were compared, at several proton energy values, with experimental yields for thick samples made of inorganic compounds of the referred elements. The agreement is better than 7.5%. Taking into consideration the experimental uncertainty of the measured yields and the errors related to the stopping power values used, this agreement shows that effects as the beam energy straggling, ignored in the calculation, seem to play a minor role

Aligned ion implantation using scanning probes

International Nuclear Information System (INIS)

Persaud, A.

2006-01-01

A new technique for precision ion implantation has been developed. A scanning probe has been equipped with a small aperture and incorporated into an ion beamline, so that ions can be implanted through the aperture into a sample. By using a scanning probe the target can be imaged in a non-destructive way prior to implantation and the probe together with the aperture can be placed at the desired location with nanometer precision. In this work first results of a scanning probe integrated into an ion beamline are presented. A placement resolution of about 120 nm is reported. The final placement accuracy is determined by the size of the aperture hole and by the straggle of the implanted ion inside the target material. The limits of this technology are expected to be set by the latter, which is of the order of 10 nm for low energy ions. This research has been carried out in the context of a larger program concerned with the development of quantum computer test structures. For that the placement accuracy needs to be increased and a detector for single ion detection has to be integrated into the setup. Both issues are discussed in this thesis. To achieve single ion detection highly charged ions are used for the implantation, as in addition to their kinetic energy they also deposit their potential energy in the target material, therefore making detection easier. A special ion source for producing these highly charged ions was used and their creation and interactions with solids of are discussed in detail. (orig.)

Aligned ion implementation using scanning probes

Energy Technology Data Exchange (ETDEWEB)

Persaud, A

2006-12-12

A new technique for precision ion implantation has been developed. A scanning probe has been equipped with a small aperture and incorporated into an ion beamline, so that ions can be implanted through the aperture into a sample. By using a scanning probe the target can be imaged in a non-destructive way prior to implantation and the probe together with the aperture can be placed at the desired location with nanometer precision. In this work first results of a scanning probe integrated into an ion beamline are presented. A placement resolution of about 120 nm is reported. The final placement accuracy is determined by the size of the aperture hole and by the straggle of the implanted ion inside the target material. The limits of this technology are expected to be set by the latter, which is of the order of 10 nm for low energy ions. This research has been carried out in the context of a larger program concerned with the development of quantum computer test structures. For that the placement accuracy needs to be increased and a detector for single ion detection has to be integrated into the setup. Both issues are discussed in this thesis. To achieve single ion detection highly charged ions are used for the implantation, as in addition to their kinetic energy they also deposit their potential energy in the target material, therefore making detection easier. A special ion source for producing these highly charged ions was used and their creation and interactions with solids of are discussed in detail. (orig.)

The Plasma Proton Environment within Saturn's inner magnetosphere as Observed by the Cassini Plasma Spectrometer (CAPS) during Saturn Orbit Insertion

Science.gov (United States)

Sittler, E. C., Jr.; Elrod, M. K.; Johnson, R. E.; Cooper, J. F.; Tseng, W. L.; Smith, H. T.; Chornay, D. J.; Shappirio, M.; Simpson, D. G.

2017-12-01

In analyzing the Cassini data between Saturn's A-ring outer edge and Mimas' L shell numerous inconsistencies have been reported in estimates of total ionic charge and electron density. The primary focus of our work is to understand these inconsistencies. We present our recent discovery of plasma protons during Saturn Orbit Insertion (SOI) outbound pass of the magnetospheric region between the F and G rings. We also searched for H2+ ions but no such events were found. The discovery of protons was made possible by a recent analysis of the CAPS Ion Mass Spectrometer's (IMS's) time-of-flight (TOF) composition data in a mode of reduced post-acceleration voltage at 6 kV instead of the usual 14.6 kV. All previous work for this region had not considered the TOF data. The new proton analysis was enabled by minimum scattering of 6 kV protons in the instrument's ultrathin carbon foils (CF), in comparison to larger scattering for the heavier ions such as for O+ and O2+. We use a SIMION model of the CAPS IMS including the effects of energy straggling and scattering by the instrument's CFs in an attempt to understand the TOF composition data for the heavier ions. This analysis within the uncertainties of the instrument allows us to estimate the relative abundances of the heavier ions and thus run our 2D velocity ion moments code to get ion densities, temperatures and velocities during the SOI outbound pass through the F-ring and G-ring gap. Comparisons with other data sets will be made.

The VERDI fission fragment spectrometer

Directory of Open Access Journals (Sweden)

Frégeau M.O.

2013-12-01

Full Text Available The VERDI time-of-flight spectrometer is dedicated to measurements of fission product yields and of prompt neutron emission data. Pre-neutron fission-fragment masses will be determined by the double time-of-flight (TOF technique. For this purpose an excellent time resolution is required. The time of flight of the fragments will be measured by electrostatic mirrors located near the target and the time signal coming from silicon detectors located at 50 cm on both sides of the target. This configuration, where the stop detector will provide us simultaneously with the kinetic energy of the fragment and timing information, significantly limits energy straggling in comparison to legacy experimental setup where a thin foil was usually used as a stop detector. In order to improve timing resolution, neutron transmutation doped silicon will be used. The high resistivity homogeneity of this material should significantly improve resolution in comparison to standard silicon detectors. Post-neutron fission fragment masses are obtained form the time-of-flight and the energy signal in the silicon detector. As an intermediary step a diamond detector will also be used as start detector located very close to the target. Previous tests have shown that poly-crystalline chemical vapour deposition (pCVD diamonds provides a coincidence time resolution of 150 ps not allowing complete separation between very low-energy fission fragments, alpha particles and noise. New results from using artificial single-crystal diamonds (sCVD show similar time resolution as from pCVD diamonds but also sufficiently good energy resolution.

Heavy-ion accelerator mass spectrometry with a 'small' accelerator

International Nuclear Information System (INIS)

Steier, P.; Golser, R.; Priller, A.; Vockenhuber, C.; Irlweck, K.; Kutschera, W.; Lichtenstein, V.

2001-01-01

Full text: VERA, the Vienna environmental research accelerator, is based on a 3-MV pelletron tandem accelerator and is designed to allow the transport of ions of all elements, from the lightest to the heaviest. The VERA heavy ion program tries to establish measurement methods which work for the long-lived radionuclides where suppression of isobars is not required. Among these are 129 I, 210 Pb, 236 U and all heavier ions where no stable isobars exist. To suppress neighboring masses, the resolution of VERA was increased, both by improving the ion optics of existing elements and by installing a new electrostatic separator after the analyzing magnet. Interfering ions which pass all beam filters are identified with a high-resolution time-of-flight system, using a 0.5 μg/cm 2 DLC (diamond-like carbon) foil in the start detector, which substantially reduces beam straggling. Compared to heavy ion AMS at large tandem accelerators (TV ≥ 8 MV) and for cases where stable isobar interference is absent, it is possible to offset the disadvantage of lower ion energy. Moreover, the more compact facilities like VERA achieve higher stability and reliability and provide advanced computer control. This promises even higher precision and sensitivity for a larger number of samples, which is a prerequisite for research on natural-occurring heavy radioisotopes at environmental levels. First results on the measurement of 210 Pb (half-life 22 a) and 236 U (23 Ma) encourages us to push towards even heavier radionuclides (e.g. 224 Pu, 81 Ma). (author)

SU-E-T-561: Development of Depth Dose Measurement Technique Using the Multilayer Ionization Chamber for Spot Scanning Method

International Nuclear Information System (INIS)

Takayanagi, T; Fujitaka, S; Umezawa, M; Ito, Y; Nakashima, C; Matsuda, K

2014-01-01

Purpose: To develop a measurement technique which suppresses the difference between profiles obtained with a multilayer ionization chamber (MLIC) and with a water phantom. Methods: The developed technique multiplies the raw MLIC data by a correction factor that depends on the initial beam range and water equivalent depth. The correction factor is derived based on a Bragg curve calculation formula considering range straggling and fluence loss caused by nuclear reactions. Furthermore, the correction factor is adjusted based on several integrated depth doses measured with a water phantom and the MLIC. The measured depth dose profiles along the central axis of the proton field with a nominal field size of 10 by 10 cm were compared between the MLIC using the new technique and the water phantom. The spread out Bragg peak was 20 cm for fields with a range of 30.6 cm and 6.9 cm. Raw MLIC data were obtained with each energy layer, and integrated after multiplying by the correction factor. The measurements were performed by a spot scanning nozzle at Nagoya Proton Therapy Center, Japan. Results: The profile measured with the MLIC using the new technique is consistent with that of the water phantom. Moreover, 97% of the points passed the 1% dose /1mm distance agreement criterion of the gamma index. Conclusion: We have demonstrated that the new technique suppresses the difference between profiles obtained with the MLIC and with the water phantom. It was concluded that this technique is useful for depth dose measurement in proton spot scanning method

Neutron-induced fission cross-section measurement of 234U with quasi-monoenergetic beams in the keV and MeV range using micromegas detectors

Science.gov (United States)

Tsinganis, A.; Kokkoris, M.; Vlastou, R.; Kalamara, A.; Stamatopoulos, A.; Kanellakopoulos, A.; Lagoyannis, A.; Axiotis, M.

2017-09-01

Accurate data on neutron-induced fission cross-sections of actinides are essential for the design of advanced nuclear reactors based either on fast neutron spectra or alternative fuel cycles, as well as for the reduction of safety margins of existing and future conventional facilities. The fission cross-section of 234U was measured at incident neutron energies of 560 and 660 keV and 7.5 MeV with a setup based on `microbulk' Micromegas detectors and the same samples previously used for the measurement performed at the CERN n_TOF facility (Karadimos et al., 2014). The 235U fission cross-section was used as reference. The (quasi-)monoenergetic neutron beams were produced via the 7Li(p,n) and the 2H(d,n) reactions at the neutron beam facility of the Institute of Nuclear and Particle Physics at the `Demokritos' National Centre for Scientific Research. A detailed study of the neutron spectra produced in the targets and intercepted by the samples was performed coupling the NeuSDesc and MCNPX codes, taking into account the energy spread, energy loss and angular straggling of the beam ions in the target assemblies, as well as contributions from competing reactions and neutron scattering in the experimental setup. Auxiliary Monte-Carlo simulations were performed with the FLUKA code to study the behaviour of the detectors, focusing particularly on the reproduction of the pulse height spectra of α-particles and fission fragments (using distributions produced with the GEF code) for the evaluation of the detector efficiency. An overview of the developed methodology and preliminary results are presented.

P- and N-type implantation doping of GaN with Ca and O

International Nuclear Information System (INIS)

Zolper, J.C.; Wilson, R.G.; Pearton, S.J.

1996-01-01

III-N photonic devices have made great advances in recent years following the demonstration of doping of GaN p-type with Mg and n-type with Si. However, the deep ionization energy level of Mg in GaN (∼ 160 meV) limits the ionized of acceptors at room temperature to less than 1.0% of the substitutional Mg. With this in mind, the authors used ion implantation to characterize the ionization level of Ca in GaN since Ca had been suggested by Strite to be a shallow acceptor in GaN. Ca-implanted GaN converted from n-to-p type after a 1,100 C activation anneal. Variable temperature Hall measurements give an ionization level at 169 meV. Although this level is equivalent to that of Mg, Ca-implantation may have advantages (shallower projected range and less straggle for a given energy) than Mg for electronic devices. In particular, the authors report the first GaN device using ion implantation doping. This is a GaN junction field effect transistor (JFET) which employed Ca-implantation. A 1.7 microm JFET had a transconductance of 7 mS/mm, a saturation current at 0 V gate bias of 33 mA/mm, a f t of 2.7 GHz, and a f max of 9.4 GHz. O-implantation was also studied and shown to create a shallow donor level (∼ 25 meV) that is similar to Si. SIMS profiles of as-implanted and annealed samples showed no measurable redistribution of either Ca or O in GaN at 1,125 C

"O exército dos mortos": sentido do sacrifício e da transcendentalidade na militância revolucionária, caso do exército de libertação nacional (ELN da Colômbia

Directory of Open Access Journals (Sweden)

Andrea Lissett Pérez

2012-08-01

Full Text Available Neste artigo discuto a força do religioso na constituição identitária da guerrilha revolucionária da Colômbia, o Exército de Libertação Nacional (ELN, surgida em 1964 e ainda vigente como projeto de luta armada. Embora o ELN se defina como uma organização ateia, seguidora dos princípios do marxismo-leninismo, a morte em combate do sacerdote Camilo Torres ativou um dos princípios germinais da tradição cristã no interior do grupo: o sacrifício de Jesus pela humanidade, mensagem traduzida para a linguagem da luta social e convertida em premissa de luta. Essa visão sacrificial perpassará os distintos contextos, práticas, formas expressivas e discursos do mundo dos elenos. Constitui-se num elemento estruturante e significante da identidade do grupo.In this article I discuss the strength of the religious in the identifiable constitution of the Colombian revolutionary guerrilla (ELN national liberation army, arisen in 1964 and yet in force as an army struggle project. Although the ELN defines itself as an atheist organization that follow the Marxism-Leninism principles, the dead in combat of the priest Camilo Torres activated one of the germinal principles of the Christian traditions to the inner of the group: Jesus sacrifice by humanity, it is a message translated to the social fight and converted in straggle premise. This sacrifying vision will pass by the distinct contexts, practices, ways of expression and lectures from the elenos world that bind itself into a significant and structural element of the identity of the group.

GEANT 4.8.2, 9.2 and 9.4 simulations versus experimental proton energy loss in thick absorbers

Energy Technology Data Exchange (ETDEWEB)

Evseev, Ivan; Schelin, Hugo R.; Ahmann, Francielle; Milhoretto, Edney; Paschuk, Sergei A., E-mail: evseev@utfpr.edu.b, E-mail: schelin@utfpr.edu.b, E-mail: sergei@utfpr.edu.b [Universidade Tecnologica Federal do Parana (UTFPR), Curitiba, PR (Brazil); Yevseyeva, Olga; Assis, Joaquim T. de; Ievsieieva, Ievgeniia, E-mail: yevseveva@iprj.uerj.b, E-mail: joaquim@iprj.uerj.b [Instituto Politecnico do Rio de Janeiro (IPRJ/UERJ), Nova Friburgo, RJ (Brazil). Dept. de Modelagem Computacional; Hormaza, Joel M., E-mail: jmesa@ibb.unesp.b [Universidade Estadual Paulista (IBB/UNESP), Botucatu, SP (Brazil). Inst. de Biociencias; Diaz, Katherin S. [Centro de Aplicaciones Tecnologicas y Desarrollo Nuclear, Havana (Cuba); Lopes, Ricardo T. [Coordenacao dos Programas de Pos-Graduacao de Engenharia (LIN/COPPE/UFRJ), RJ (Brazil). Lab. de Instrumentacao Nuclear

2011-07-01

Monte Carlo simulations are a powerful tool to estimate the proton energy loss and straggling in medical applications. The physics of proton interaction with matter for thick absorbers (like a human body) has a well-established theory for the so-called Bethe-Bloch domain, and the basic principles of Monte Carlo simulation for such processes are well known since the middle of the past century. However, in spite of GEANT4 has been validated against proton stopping powers from the NIST PSTAR, the evolution of the code leads to some result instability within the various code releases. In this work, we present the recent results for the comparison of our GEANT4 simulations against experimental proton energy loss for some thick absorbers. All the simulations were performed using the GEANT4 Hadrontherapy Advanced Example. The GEANT4 versions 4.8.2, 4.9.2, and 4.9.4 were tested with different simulation parameters, such as varied cut values. In addition to the Standard model, some other models for the electromagnetic processes from the GEANT4 Low Energy Extension Pack were tested as well. Experimental data were taken from for polyethylene, and from for aluminum and gold absorbers. The theoretical predictions for the spectra were calculated using the self-consistent Gaussian solution of the Boltzmann kinetic equation in the Fokker-Plank form. In order to compare the GEANT4 simulations with other popular codes, the same spectra were simulated by TRIM/SRIM2011 and MCNPX2.4.0. The simultaneous comparison of the results obtained for different materials at various initial proton energies were done using the reduced calibration curve approach. (author)

Spectroscopy of very heavy nuclei with a view to study super-heavy nuclei

International Nuclear Information System (INIS)

Khalfallah, F.

2007-08-01

Within the recent years, the spectroscopic study of single particle orbitals of very heavy elements (VHE) has become possible with the development of increasingly efficient experimental setups. This allows us, through nuclear deformation, to access with these deformed nuclei to orbitals situated around the Fermi level in the spherical superheavy elements (SHE) and learn more about the nuclear structure of these nuclei. The aim of this work is the spectroscopic studies of heavy and very heavy elements. Because of the experimental difficulties associated with the fusion reactions in the VHE region, a detailed optimization studies is essential. Simulation of energy loss and angular straggling of these nuclei due to the interaction in the target and to neutron's evaporation was carried out and allowed us to optimize the angular acceptance of the separators according to the target thickness. An extensive survey and exploration in the VHE region was also conducted on the basis of cross section's systematics in the literature and simulations carried out using the statistical code Hivap. In this framework, the possible extension of the range of validity of a set of Hivap parameters was investigated. This work has enabled us to prepare a list of experiments of interest for the production of very heavy nuclei. In this thesis, our work was concentrated on the spectroscopy of the nuclei No 256 et Rf 256 for which two experimental proposals were accepted. The octupole deformations predicted in the actinides region is studied in another part of this thesis, a part witch is dedicated to the gamma spectroscopy of Pa 223 . The data from a new experiment carried out using the Jurogam-Ritu-Great setup are analysed and compared to previous results. They confirm the octupole deformed shape in this nucleus. (author)

Spectroscopy of very heavy nuclei with a view to study super-heavy nuclei; Spectroscopie de noyaux tres lourds en vue de l'etude des noyaux super-lourds

Energy Technology Data Exchange (ETDEWEB)

Khalfallah, F

2007-08-15

Within the recent years, the spectroscopic study of single particle orbitals of very heavy elements (VHE) has become possible with the development of increasingly efficient experimental setups. This allows us, through nuclear deformation, to access with these deformed nuclei to orbitals situated around the Fermi level in the spherical superheavy elements (SHE) and learn more about the nuclear structure of these nuclei. The aim of this work is the spectroscopic studies of heavy and very heavy elements. Because of the experimental difficulties associated with the fusion reactions in the VHE region, a detailed optimization studies is essential. Simulation of energy loss and angular straggling of these nuclei due to the interaction in the target and to neutron's evaporation was carried out and allowed us to optimize the angular acceptance of the separators according to the target thickness. An extensive survey and exploration in the VHE region was also conducted on the basis of cross section's systematics in the literature and simulations carried out using the statistical code Hivap. In this framework, the possible extension of the range of validity of a set of Hivap parameters was investigated. This work has enabled us to prepare a list of experiments of interest for the production of very heavy nuclei. In this thesis, our work was concentrated on the spectroscopy of the nuclei No{sup 256} et Rf{sup 256} for which two experimental proposals were accepted. The octupole deformations predicted in the actinides region is studied in another part of this thesis, a part witch is dedicated to the gamma spectroscopy of Pa{sup 223}. The data from a new experiment carried out using the Jurogam-Ritu-Great setup are analysed and compared to previous results. They confirm the octupole deformed shape in this nucleus. (author)

Depth of origin and angular spectrum of sputtered atoms

International Nuclear Information System (INIS)

Vicanek, M.; Jimenez Rodriguez, J.J.; Sigmund, P.

1989-01-01

A theoretical analysis is presented of the depth of origin of atoms sputtered from a random target. The physical model aims at high energy sputtering under linear cascade conditions and assumes a dilute source of recoil atoms. The initial distribution of the recoils is assumed isotropic, and their energy distribution is E -2 like without an upper or lower cutoff. The scattering medium is either infinite or bounded by a plane surface. Atoms scatter according to the m=0 power cross section. Electronic stopping is ignored. The sputtered flux, differential in depth of origin, ejection energy and ejection angle has been evaluated by Monte Carlo simulation and by five distinct methods of solution of the linear Boltzmann equation reaching from continuous slowing down neglecting angular scattering to the P 3 approximation and a Gram-Charlier expansion going over spatial moments. The continuous slowing down approximation used in previous work leads to results that are identical to those found from a scheme that only ignores angular scattering but allows for energy loss straggling. Moreover, these predictions match more closely with the Monte Carlo results than any of the approximate analytical schemes that take account of angular scattering. The results confirm the common assertion that the depth of origin of sputtered atoms is determined mainly by the stopping of low energy recoil atoms. The effect of angular scattering turns out to be astonishingly small. The distributions in depth of origin, energy, and angle do not depend significantly on whether the scattering medium is a halfspace or an infinite medium with a reference plane. The angular spectrum comes out only very slightly over cosine from the model as it stands, in agreement with previous experience, but comments are made on essential features that are not incorporated in the physical model but might influence the angular spectrum. (orig./WL)

Allelic interaction of F1 pollen sterility loci and abnormal chromosome behaviour caused pollen sterility in intersubspecific autotetraploid rice hybrids.

Science.gov (United States)

He, J H; Shahid, M Q; Li, Y J; Guo, H B; Cheng, X A; Liu, X D; Lu, Y G

2011-08-01

The intersubspecific hybrids of autotetraploid rice has many features that increase rice yield, but lower seed set is a major hindrance in its utilization. Pollen sterility is one of the most important factors which cause intersubspecific hybrid sterility. The hybrids with greater variation in seed set were used to study how the F(1) pollen sterile loci (S-a, S-b, and S-c) interact with each other and how abnormal chromosome behaviour and allelic interaction of F(1) sterility loci affect pollen fertility and seed set of intersubspecific autotetraploid rice hybrids. The results showed that interaction between pollen sterility loci have significant effects on the pollen fertility of autotetraploid hybrids, and pollen fertility further decreased with an increase in the allelic interaction of F(1) pollen sterility loci. Abnormal ultra-structure and microtubule distribution patterns during pollen mother cell (PMC) meiosis were found in the hybrids with low pollen fertility in interphase and leptotene, suggesting that the effect-time of pollen sterility loci interaction was very early. There were highly significant differences in the number of quadrivalents and bivalents, and in chromosome configuration among all the hybrids, and quadrivalents decreased with an increase in the seed set of autotetraploid hybrids. Many different kinds of chromosomal abnormalities, such as chromosome straggling, chromosome lagging, asynchrony of chromosome disjunction, and tri-fission were found during the various developmental stages of PMC meiosis. All these abnormalities were significantly higher in sterile hybrids than in fertile hybrids, suggesting that pollen sterility gene interactions tend to increase the chromosomal abnormalities which cause the partial abortion of male gametes and leads to the decline in the seed set of the autotetraploid rice hybrids. © 2011 The Author(s).

Relativistic theory of stopping for heavy ions

International Nuclear Information System (INIS)

Lindhard, J.; So/rensen, A.H.

1996-01-01

We calculate the electronic stopping power and the corresponding straggling for ions of arbitrary charge number, penetrating matter at any relativistic energy. The stopping powers are calculated by a simple method. Its starting point is the deviation of the precise theory from first-order quantum perturbation. We show that this deviation can be expressed in terms of the transport cross section, σ tr , for scattering of a free electron by the ion. In the nonrelativistic case the deviation is precisely the Bloch correction to Bethe close-quote s formula; we look into the nonrelativistic case in order to clarify both some features of our method and a seeming paradox in Rutherford scattering. The corresponding relativistic correction is obtained from σ tr for scattering of a Dirac electron in the ion potential. Here, the major practical advantage of the method shows up; we need not find the scattering distribution, but merely a single quantity, σ tr , determined by differences of successive phase shifts. For a point nucleus our results improve and extend those of Ahlen. Our final results, however, are based on atomic nuclei with standard radii. Thereby, the stopping is changed substantially already for moderate values of γ=(1-v 2 /c 2 ) -1/2 . An asymptotic saturation in stopping is obtained. Because of finite nuclear size, recoil corrections remain negligible at all energies. The average square fluctuation in energy loss is calculated as a simple fluctuation cross section for a free electron. The fluctuation in the relativistic case is generally larger than that of the perturbation formula, by a factor of ∼2 endash 3 for heavy ions. But the finite nuclear radius leads to a strong reduction at high energies and the elimination of the factor γ 2 belonging to point nuclei. copyright 1996 The American Physical Society

Non-Liouvillean ion injection via resonantly enhanced two-photon ionization

Directory of Open Access Journals (Sweden)

B. A. Knyazev

2004-03-01

Full Text Available The charge-exchange method is now one of the main techniques for ion injection into accelerators and storage rings. The disadvantages of conventional methods, based on the atom or ion stripping in a material target, are emittance growth, energy straggling, and production of ions in many charge states. Recently suggested stripping methods based on direct photoionization require employment of hard-UV lasers, which still do not exist and must obviously be very bulky and expensive. An alternative method, suggested for injection of proton beams, employs excitation of the atom to 3p intermediate state with subsequent Lorentz ionization in a magnetic field gradient. This technique applies rigid requirements to laser characteristic and is not free of growing of the beam divergence. In this paper a variant of the stripping technique based on the resonantly enhanced two-photon ionization (RETPI is considered. The technique allows ionization of singly charged ions of the elements from helium to bismuth. A variant of the technique can be used for proton injection. RETPI can be applied for both ion injection and stacking, as well as for diagnostics of ion beam characteristics on the orbit. Stripping efficiency can be about 100% for the singly charged ions having the singlet ground state and decreases for the other ions. Special methods for “cleaning” unwanted atomic states in such ions, that can provide high stripping efficiency, are discussed. Excimer lasers with very moderate parameters can be employed for implementation of this technique for almost all elements. Numerical examples show that for most of the singly charged ions and for hydrogen atom necessary laser-beam energy density is merely 0.5–8  J/cm^{2} for a 1 m interaction region, and is 10 times higher for several light ions.

Power output and efficiency of beta-emitting microspheres

International Nuclear Information System (INIS)

Cheneler, David; Ward, Michael

2015-01-01

Current standard methods to calculate the dose of radiation emitted during medical applications by beta-minus emitting microspheres rely on an over-simplistic formalism. This formalism is a function of the average activity of the radioisotope used and the physiological dimensions of the patient only. It neglects the variation in energy of the emitted beta particle due to self-attenuation, or self-absorption, effects related to the finite size of the sphere. Here it is assumed the sphere is comprised of a pure radioisotope with beta particles being emitted isotropically throughout the material. The full initial possible kinetic energy distribution of a beta particle is taken into account as well as the energy losses due to scattering by other atoms in the microsphere and bremsstrahlung radiation. By combining Longmire’s theory of the mean forward range of charged particles and the Rayleigh distribution to take into account the statistical nature of scattering and energy straggling, the linear attenuation, or self-absorption, coefficient for beta-emitting radioisotopes has been deduced. By analogy with gamma radiation transport in spheres, this result was used to calculate the rate of energy emitted by a beta-emitting microsphere and its efficiency. Comparisons to standard point dose kernel formulations generated using Monte Carlo data show the efficacy of the proposed method. Yttrium-90 is used as a specific example throughout, as a medically significant radioisotope, frequently used in radiation therapy for treating cancer. - Highlights: • Range-energy relationship for the beta particles in yttrium-90 is calculated. • Formalism for the semi-analytical calculation of self-absorption coefficients. • Energy-dependent self-absorption coefficient calculated for yttrium-90. • Flux rate of beta particles from a self-attenuating radioactive sphere is shown. • The efficiency of beta particle emitting radioactive microspheres is calculated

Construction and operation of an universal stopping equipment for the fragment separator of the GSI Darmstadt

International Nuclear Information System (INIS)

Weckenmann, J.; Hanelt, E.; Schmidt, K.H.

1990-07-01

The fragment separator is a magnetic spectrometer, in which an especially-shaped layer of matter is applied as ion-optical element. The energy loss occurring there is accompanied by a series of unwanted effects like nuclear reaction, elecromagnetic dissociation, energy and angle straggling. These effects reduce on the one hand the total resolution of the separator and on the other hand the number of the fragments, which reach the exit of the separator. In the present study it was stated that the influence of these effects exhibits in most of the cases only a weak dependence on the material of the stopper. The ideal stopper material has a mass number, which corresponds nearly to the mass number of the selected fragment. If only one single stopper material will be applied, a material with low mass number seems to be the best compromise. Therefore for the universal stopper equipment of the fragment separator aluminium was selected. A further object of this study was the profile of the stopper. In a symmetrically constructed magnet spectrometer as the fragment separator the highest resolution is then reached, when the required particles are stopped in the whole width of their momentum distribution by a constant factor. This requirement leads to a curved profile of the stopper. It was stated that the profile can be approached by a linear wedge shape without a disadvantageous change of the resolution of the separator. The technical realization of the universal stopping equipment for the fragment separator consists mainly of very accurately manufactured, shiftable, and rotatable wedge-shaped layers. By means of a step-motor guiding the profiles required for the isotope separation can thus be obtained in a wide range. (orig.) [de

SU-E-T-499: Initial Developments of An OpenCL-Based Cross-Platform Monte Carlo Dose Engine for Carbon Ion Therapy

Energy Technology Data Exchange (ETDEWEB)

Qin, N; Tian, Z; Pompos, A; Jiang, S; Jia, X [UT Southwestern Medical Center, Dallas, TX (United States); Pinto, M; Dedes, G; Parodi, K [Ludwig-Maximilians-Univ. Munchen, Garching B. Munich (Germany)

2015-06-15

Purpose Dose calculation is of critical importance for carbon ion therapy. Monte Carlo (MC) simulation is considered to be the most accurate method for calculation of absorbed dose and of all the more fundamental physical quantities related to biological effects. The long computation time, however, limits its routine clinical applications. We have recently started developing a fast MC package, gCMC for carbon therapy on a parallel processing platform, e.g. GPU, aiming at achieving sufficient efficiency to enable MC in clinically important tasks. This abstract reports our progress. Methods gCMC was developed in OpenCL environment. Our initial developments focused on water material. gCMC supported carbon ion transport in the energy range of 1–450 MeV/u. A Class II condensed history algorithm was implemented for charged particle transport simulations with stopping power computed via Bethe-Bloch equation. Energy straggling and multiple scattering were modeled. Total cross section of nuclear interaction was extracted from Geant4. At present, nuclear interaction events were sampled but transports of secondary particles were not included. Results We tested cases with a homogeneous water phantom and a pencil carbon ion beam with energy of 200–400 MeV/u. When only electro-magnetic channel was included, dose/fluence difference between gCMC and Geant4 results averaged within 10% isodose line was <0.5% of the maximum dose/fluence. After enabling nuclear interactions without transporting secondary particles, dose and fluence agreed with the corresponding results computed by Geant4 with <1% difference. Due to the support for multiple platforms of OpenCL, gCMC was executable on NVidia and AMD GPUs, and Intel CPUs. It took ∼50 sec to transport 107 200MeV/u source carbon ions on an NVidia Titan GPU card. Conclusion Preliminary studies have demonstrated the accuracy and efficiency of gCMC. With further developments in near future, gCMC will potentially achieve clinically

SU-E-T-499: Initial Developments of An OpenCL-Based Cross-Platform Monte Carlo Dose Engine for Carbon Ion Therapy

International Nuclear Information System (INIS)

Qin, N; Tian, Z; Pompos, A; Jiang, S; Jia, X; Pinto, M; Dedes, G; Parodi, K

2015-01-01

Purpose Dose calculation is of critical importance for carbon ion therapy. Monte Carlo (MC) simulation is considered to be the most accurate method for calculation of absorbed dose and of all the more fundamental physical quantities related to biological effects. The long computation time, however, limits its routine clinical applications. We have recently started developing a fast MC package, gCMC for carbon therapy on a parallel processing platform, e.g. GPU, aiming at achieving sufficient efficiency to enable MC in clinically important tasks. This abstract reports our progress. Methods gCMC was developed in OpenCL environment. Our initial developments focused on water material. gCMC supported carbon ion transport in the energy range of 1–450 MeV/u. A Class II condensed history algorithm was implemented for charged particle transport simulations with stopping power computed via Bethe-Bloch equation. Energy straggling and multiple scattering were modeled. Total cross section of nuclear interaction was extracted from Geant4. At present, nuclear interaction events were sampled but transports of secondary particles were not included. Results We tested cases with a homogeneous water phantom and a pencil carbon ion beam with energy of 200–400 MeV/u. When only electro-magnetic channel was included, dose/fluence difference between gCMC and Geant4 results averaged within 10% isodose line was <0.5% of the maximum dose/fluence. After enabling nuclear interactions without transporting secondary particles, dose and fluence agreed with the corresponding results computed by Geant4 with <1% difference. Due to the support for multiple platforms of OpenCL, gCMC was executable on NVidia and AMD GPUs, and Intel CPUs. It took ∼50 sec to transport 107 200MeV/u source carbon ions on an NVidia Titan GPU card. Conclusion Preliminary studies have demonstrated the accuracy and efficiency of gCMC. With further developments in near future, gCMC will potentially achieve clinically

Heavy ion medical accelerator, HIMAC

International Nuclear Information System (INIS)

Yamada, Satoru

1993-01-01

The heavy ion beam is undoutedly suitable for the cancer treatment. The supriority of the heavy ions over the conventional radiations including protons and neutrons comes mainly from physical characteristics of a heavy particle with multiple charges. A straggling angle due to a multiple Coulomb scattering process in a human body is small for heavy ions, and the small scattering angle results in a good dose localization in a transverse direction. An ionization ratio of the heavy ion beam makes a very sharp peak at the ends of their range. The height of the peak is higher for the heavier ions and shows excellent biomedical effects around Ne ions. In order to apply heavy ion beams to cancer treatment, Heavy Ion Medical Accelerator in Chiba (HIMAC) has been constructed at National Institute of Radiological Sciences. The accelerator complex consists of two ion sources, two successive linac tanks, a pair of synchrotron rings, a beam transport system and an irradiation system. An operation frequency is 100 MHz for two linacs, and the ion energy is 6.0 MeV/u at the output end of the linac. The other four experimental rooms are prepared for basic experiments. The synchrotron accelerates ions up to 800 MeV/u for a charge to mass ratio of 1/2. The long beam transport line provides two vertical beams in addition with two horizontal beams for the treatment. The three treatment rooms are prepared one of which is equipped with both horizontal and vertical beam lines. The whole facility will be open for all scientists who have interests in the heavy ion science as well as the biophysics. The conceptual design study of HIMAC started in 1984, and the construction of the accelerator complex was begun in March 1988. The beam acceleration tests of the injector system was successfully completed in March of this year, and tests of the whole system will be finished throughout this fyscal year. (author)

Characterization of solar cell materials by Proton Back Scattering Spectroscopy

International Nuclear Information System (INIS)

Joynal Abedin, M.; Fazlul Hoque, A.K.M.; Firoz Hasan, S.M.

2001-01-01

The need for accurate chemical characterization of samples specially related to electronic and solar cell materials has assumed increasing importance in recent years. The importance of the study of the surfaces of materials of different origin also increased in recent years to a great extent. This need has created a worldwide spurt to develop rapid, accurate and sensitive tools for the characterization of materials. In recent years the proton backscattering spectrometry (PBS) method has been recognized as one of the useful analytical tool in several applications of material analysis and technology. The lack of information of the relevant scattering cross sections as a function of proton energy and the problems arising in conventional data analysis have so far rendered proton backscattering analysis of multielemental samples difficult at low energies. On the other hand advances in the computer evaluation of experimental data have, however, made it possible to utilize low-MeV protons as a sensitive probe for light elements in the μm range. The benefits of the method in comparison to alpha particle backscattering include the relatively higher non-Rutherford scattering cross sections of the light elements and to the lower proton stopping in the target material. These lead to higher sensitivity in detecting and profiling light elements in heavy targets and to significantly larger accessible depths and smaller straggling than with alpha particles. Research works on the development of methodologies of Proton Backscattering Spectrometry (PBS) for the analysis of thin films and surfaces has been in progress in the 3 MeV Van de Graaff Accelerator facilities of Atomic Energy Centre, Dhaka for some years. The PBS system comprises a target chamber with appropriate sample holders and a Surface Barrier Detector (SBD) with the associated electronics for data acquisition and reduction. For the evaluation of the PBS data RBS Universal Master Package, RUMP has been installed in the

Hydrogen Contamination of Niobium Surfaces

International Nuclear Information System (INIS)

Viet Nguyen-Tuong; Lawrence Doolittle

1993-01-01

The presence of hydrogen is blamed for dramatic reductions in cavity Q's. Hydrogen concentration is difficult to measure, so there is a great deal of Fear, Uncertainty, and Doubt (FUD) associated with the problem. This paper presents measurements of hydrogen concentration depth profiles, commenting on the pitfalls of the methods used and exploring how material handling can change the amount of hydrogen in pieces of niobium. Hydrogen analysis was performed by a forward scattering experiment with Helium used as the primary beam. This technique is variously known as FRES (Forward Recoil Elastic Scattering), FRS, HFS (Hydrogen Forward Scattering), and HRA (Hydrogen Recoil Analysis). Some measurements were also made using SIMS (Secondary Ion Mass Spectrometry). Both HFS and SIMS are capable of measuring a depth profile of Hydrogen. The primary difficulty in interpreting the results from these techniques is the presence of a surface peak which is due (at least in part) to contamination with either water or hydrocarbons. With HFS, the depth resolution is about 30 nm, and the maximum depth profiled is about 300 nm. (This 10-1 ratio is unusually low for ion beam techniques, and is a consequence of the compromises that must be made in the geometry of the experiment, surface roughness, and energy straggling in the absorber foil that must be used to filter out the forward scattered helium.) All the observed HFS spectra include a surface peak which includes both surface contamination and any real hydrogen uptake by the niobium surface. Some contamination occurs during the analysis. The vacuum in the analysis chamber is typically a few times 10(sup -6) torr, and some of the contamination is in the form of hydrocarbons from the pumping system. Hydrocarbons normally form a very thin (less than a monolayer) film which is in equilibrium between arrival rate and the evaporation rate. In the presence of the incoming ion beam, however, these hydrocarbons crack on the surface into non

AMS of 36Cl with the VERA 3 MV tandem accelerator

International Nuclear Information System (INIS)

Martschini, Martin; Andersson, Pontus; Forstner, Oliver; Golser, Robin; Hanstorp, Dag; Lindahl, Anton O.; Kutschera, Walter; Pavetich, Stefan; Priller, Alfred; Rohlén, Johan; Steier, Peter; Suter, Martin; Wallner, Anton

2013-01-01

Recent progress with compact ionization chambers has opened new possibilities for isobar suppression in accelerator mass spectrometry (AMS). Separation of 36 Cl (t 1/2 = 0.30 Ma) at natural isotopic levels from its stable isobar 36 S became feasible at particle energies of 24 MeV, which are also accessible for medium-sized tandem accelerators with 3 MV terminal voltage like VERA (Vienna Environmental Research Accelerator). Investigations with an ionization chamber revealed how physics favors isobar separation even at energies below the maximum of the Bragg curve. The strong energy focusing effect at high energy losses reduces energy straggling significantly and isobar separation steadily increases up to almost full energy loss. With an optimized detection setup, sulfur suppression factors of 2 × 10 4 have been achieved. Refraining from the additional use of degrader foils has the benefit of high transmission to the detector (∼16%), but requires a low sulfur output from the ion source. Therefore several backing materials have been screened for sulfur content. The dependence of the sulfur output on the AgCl sample size has been investigated as well. Precision and accuracy have been thoroughly assessed over the last two years. Since drifts in the spectra are efficiently corrected by monitoring the position of the 36 S peak, the reproducibility for high ratio samples ( 36 Cl/Cl > 10 −12 ) is better than 2%. Our blank value of 36 Cl/Cl ≈ (5 ± 5) × 10 −16 is competitive to other labs. 36 Cl has become a routine AMS-isotope at VERA. Recently we also explored novel techniques for additional sulfur suppression already in the ion source. While results with a small gas reaction cell in front of the sputter target were discouraging, a decrease in the sulfur/chlorine ratio by one order of magnitude was achieved by directing 300 mW continuous wave laser beam at 445 nm towards the cathode in the ion source.

Interaction of radiation with matter

International Nuclear Information System (INIS)

1978-05-01

During 1978, these conclusions were reached and are reported: Innershell Coulomb ionization cross sections show significant relativistic effects even for the lighter atoms, because ionization occurs near the nucleus in our range of low particle energies. Atomic excitation and ionization in deep atom--atom collisions can be described in terms of a model with random walk in energy space to the continuum. This model may be best suited for the analysis of heavy ion--atom encounters. Energy straggling of charged particles in matter are affected by inhomogeneities in and surface conditions of the medium. Using molecular ions as incident projectiles it is concluded that moving protons do not have bound states in solids. Projectiles in close proximity to each other exhibit larger energy losses than isolated projectiles indicating interactions of the electron density fluctuations established behind moving projectiles in solids. Heterogeneous oxidation of SO 2 by holes has been found at an organic (PAH) aqueous interface. The process has a reasonably high quantum efficiency (approx. >0.1) for anthracene. Various experiments are being carried out to determine whether SO 3 /sup =/ or HSO 3 - is involved. Photoemission from PAH organic aerosols has been investigated. The rate of emission from tetracene is found to go as the maximum electron kinetic energy cubed. It is found that the particle may be used as an electron spectrometer for determining the electron kinetic energy distribution. A new way of characterizing small aerosols by mass has been found. The method utilizes the detection of a single electron imbalance in a Millikan chamber. Aerosol masses as small as 1 pgm can be measured to better than 1%. The potent carcinogen benzo (a) pyrene (BP) when metabolized in vivo is found to have a physical structure in which the BP7,8-dihydrodial 9,10-oxide adduct (BPDE) is bound on the outside of the helix. Models and measurements support this conclusion

SU-C-BRC-06: OpenCL-Based Cross-Platform Monte Carlo Simulation Package for Carbon Ion Therapy

Energy Technology Data Exchange (ETDEWEB)

Qin, N; Tian, Z; Pompos, A; Jiang, S; Jia, X [UT Southwestern Medical Ctr, Dallas, TX (United States); Pinto, M; Dedes, G; Parodi, K [Ludwig-Maximilians-Universitaet Muenchen, Garching / Munich (Germany)

2016-06-15

Purpose: Monte Carlo (MC) simulation is considered to be the most accurate method for calculation of absorbed dose and fundamental physical quantities related to biological effects in carbon ion therapy. Its long computation time impedes clinical and research applications. We have developed an MC package, goCMC, on parallel processing platforms, aiming at achieving accurate and efficient simulations for carbon therapy. Methods: goCMC was developed under OpenCL framework. It supported transport simulation in voxelized geometry with kinetic energy up to 450 MeV/u. Class II condensed history algorithm was employed for charged particle transport with stopping power computed via Bethe-Bloch equation. Secondary electrons were not transported with their energy locally deposited. Energy straggling and multiple scattering were modeled. Production of secondary charged particles from nuclear interactions was implemented based on cross section and yield data from Geant4. They were transported via the condensed history scheme. goCMC supported scoring various quantities of interest e.g. physical dose, particle fluence, spectrum, linear energy transfer, and positron emitting nuclei. Results: goCMC has been benchmarked against Geant4 with different phantoms and beam energies. For 100 MeV/u, 250 MeV/u and 400 MeV/u beams impinging to a water phantom, range difference was 0.03 mm, 0.20 mm and 0.53 mm, and mean dose difference was 0.47%, 0.72% and 0.79%, respectively. goCMC can run on various computing devices. Depending on the beam energy and voxel size, it took 20∼100 seconds to simulate 10{sup 7} carbons on an AMD Radeon GPU card. The corresponding CPU time for Geant4 with the same setup was 60∼100 hours. Conclusion: We have developed an OpenCL-based cross-platform carbon MC simulation package, goCMC. Its accuracy, efficiency and portability make goCMC attractive for research and clinical applications in carbon therapy.

Size characterisation of noble-metal nano-crystals formed in sapphire by ion irradiation and subsequent thermal annealing

Energy Technology Data Exchange (ETDEWEB)

Mota-Santiago, Pablo-Ernesto [Instituto de Fisica, Universidad Nacional Autonoma de Mexico A.P. 20-364 01000 Mexico D.F. (Mexico); Crespo-Sosa, Alejandro, E-mail: crespo@fisica.unam.mx [Instituto de Fisica, Universidad Nacional Autonoma de Mexico A.P. 20-364 01000 Mexico D.F. (Mexico); Jimenez-Hernandez, Jose-Luis; Silva-Pereyra, Hector-Gabriel; Reyes-Esqueda, Jorge-Alejandro; Oliver, Alicia [Instituto de Fisica, Universidad Nacional Autonoma de Mexico A.P. 20-364 01000 Mexico D.F. (Mexico)

2012-10-15

Highlights: Black-Right-Pointing-Pointer Systematic study on the formation of Ag and Au nano-particles in Al{sub 2}O{sub 3}. Black-Right-Pointing-Pointer Annealing in a reducing atmosphere, below the metal melting point is more suitable. Black-Right-Pointing-Pointer Au nano-particles grow up to 15 nm and Ag nano-particles up to 45 nm in radius. Black-Right-Pointing-Pointer Ostwald ripening is the mechanism responsible for the formation of large nanoparticles. Black-Right-Pointing-Pointer Optical properties of metallic nano-particles in Al{sub 2}O{sub 3} can be related to their size. - Abstract: Metallic nano-particles embedded in transparent dielectrics are very important for new technological applications because of their unique optical properties. These properties depend strongly on the size and shape of the nano-particles. In order to achieve the synthesis of metallic nano-particles it has been used the technique of ion implantation. This is a very common technique because it allows the control of the depth and concentration of the metallic ions inside the sample, limited mostly by straggling, without introducing other contaminant agents. The purpose of this work was to measure the size of the nano-particles grown under different conditions in Sapphire and its size evolution during the growth process. To achieve this goal, {alpha}-Al{sub 2}O{sub 3} single crystals were implanted with Ag or Au ions at room temperature with different fluences (from 2 Multiplication-Sign 10{sup 16} ions/cm{sup 2} to 8 Multiplication-Sign 10{sup 16} ions/cm{sup 2}). Afterwards, the samples were annealed at different temperatures (from 600 Degree-Sign C to 1100 Degree-Sign C) in oxidising, reducing, Ar or N{sub 2} atmospheres. We measured the ion depth profile by Rutherford Backscattering Spectroscopy (RBS) and the nano-crystals size distribution by using two methods, the surface plasmon resonance in the optical extinction spectrum and the Transmission Electron Microscopy (TEM).

MO-A-BRD-10: A Fast and Accurate GPU-Based Proton Transport Monte Carlo Simulation for Validating Proton Therapy Treatment Plans

Energy Technology Data Exchange (ETDEWEB)

Wan Chan Tseung, H; Ma, J; Beltran, C [Mayo Clinic, Rochester, MN (United States)

2014-06-15

Purpose: To build a GPU-based Monte Carlo (MC) simulation of proton transport with detailed modeling of elastic and non-elastic (NE) protonnucleus interactions, for use in a very fast and cost-effective proton therapy treatment plan verification system. Methods: Using the CUDA framework, we implemented kernels for the following tasks: (1) Simulation of beam spots from our possible scanning nozzle configurations, (2) Proton propagation through CT geometry, taking into account nuclear elastic and multiple scattering, as well as energy straggling, (3) Bertini-style modeling of the intranuclear cascade stage of NE interactions, and (4) Simulation of nuclear evaporation. To validate our MC, we performed: (1) Secondary particle yield calculations in NE collisions with therapeutically-relevant nuclei, (2) Pencil-beam dose calculations in homogeneous phantoms, (3) A large number of treatment plan dose recalculations, and compared with Geant4.9.6p2/TOPAS. A workflow was devised for calculating plans from a commercially available treatment planning system, with scripts for reading DICOM files and generating inputs for our MC. Results: Yields, energy and angular distributions of secondaries from NE collisions on various nuclei are in good agreement with the Geant4.9.6p2 Bertini and Binary cascade models. The 3D-gamma pass rate at 2%–2mm for 70–230 MeV pencil-beam dose distributions in water, soft tissue, bone and Ti phantoms is 100%. The pass rate at 2%–2mm for treatment plan calculations is typically above 98%. The net computational time on a NVIDIA GTX680 card, including all CPU-GPU data transfers, is around 20s for 1×10{sup 7} proton histories. Conclusion: Our GPU-based proton transport MC is the first of its kind to include a detailed nuclear model to handle NE interactions on any nucleus. Dosimetric calculations demonstrate very good agreement with Geant4.9.6p2/TOPAS. Our MC is being integrated into a framework to perform fast routine clinical QA of pencil

Analysis of ion implanted doped insulators by nuclear reactions

International Nuclear Information System (INIS)

Gheith, B.M.

1992-01-01

Nuclear resonance reaction an6520750JOalysis (NRA), using a proton beam at 1350 KeV, and the complementary rutherford backscattering, using a 1.8 MeV helium beam, techniques were utilized to investigate the level of impurities and the influencs of structural defects created by an 40 Ar + beam irradation induced in single crysttalline pure, and 10 and 20 mole % Eu doped, CaF 2 targets. The energetic proton, helium and argon beams were all supplied from the Uniersity of Jordan Van De Graaff accelerator, JOVAC. The depth distribuation of intrinsic defecta altered by the radiation damage was determined, using the resonance(p,α reaction at 1350 KeV resulting, from the halogen with proton beams of incident energies above resonance. Results are compared with transport of ions in matter calculations (TRIM), using the computer code 'TRIM-89'. Results indicate that the influence of doping alters tje crystal structure by pbserving a Ca-surfaace rich layer. The Ca enrichment is explained based on the defect model of trivalent Eu occupying the divalent substitutional places of the Ca atoms. The extra positive charge is linked to a negative one available on the the neighbouring F in order to preserve charge neutrality. The Ar irradiation results on the other hand revealed that the low level Eu doping stabilizes hte crystal better than the higher doping level. Chanages in the Eu signal from uniformly even distribution to an enhancement below the surface art a depth that is correlated with the mean and straggling values of the Ar impurrity distribution, is observed. This is consistant with the calculated Ar impurity distributions in which the 250 KeV Ar irradiation results in narrow distributions gradient of defects, possibly by a radiation enhanced diffusion mechanism. Preferential sputtering of the halogen, being the lightest element in the matrix, was alos noted. Surface topographic changes due to formation of large complexes and cracks are found to distort a large volume of

New MCNPX developments

Energy Technology Data Exchange (ETDEWEB)

Hendricks, J. S. (John S.); McKinney, G. W. (Gregg W.); Waters, L. S. (Laurie S.); Hughes, H. G. (Henry Grady); Snow, E. C. (Edward Clark)

2002-01-01

The Los Alamos National Laboratory Monte Carlo N-Particle extended (MCNPX) radiation transport code has been upgraded significantly to Version MCNPX2.4.0. It is now based on the latest MCNP4C3 and MCNPX2.3.0 releases to the Radiation Safety Information Computational Center (RSICC). In addition to all of the advances from earlier versions of MCNP and MCNPX, important new capabilities have been developed. The Monte Carlo method was developed at Los Alamos National Laboratory during the Manhattan Project in the early 1940s. MCNP and MCNPX are heirs to those early efforts. Over 400 person-years have been invested in the research, development, programming, documentation, and databases for these codes. MCNP is a general-purpose neutron (0-MeV to 20-MeV), photon (1-keV to 1-GeV), and electron (1-keV to 1-GeV) transport code for calculating *MCNPX, MCNP, LAHET, and LCS are trademarks of the Regents of the University of California, Los Alamos National Laboratory. the time-dependent, continuous-energy transport of these particles in three-dimensional geometries. MCNP is perhaps the most widely used and well-known physics simulation code in the world today. MCNPX extends MCNP to track nearly all particles at all energies. MCNPX combined MCNP and the LAHET Code System (LCS). LCS is based on the Oak Ridge High Energy Transport Code. LCS uses models for particles in physics regimes where there are no tabulated data, including the Bertini and ISABEL models. MCNPX has additional models to LCS, such as the CEM model. MCNPX2.3.0 was released to RSICC in December 2001 and is based on MCNP4B. The principal features of MCNPX2.3.0 are (1) Physics for 34 particle types; (2) High-energy physics above the giga-electron volt range; (3) Neutron, proton, and photonuclear 150-MeV libraries: (4) Photonuclear physics; (5) Mesh tallies; (6) Radiography tallies; (7) Secondary particle production biasing; (8) VAVILOV energy straggling for charged particles; and (9) Automatic configuration for

SANDYL, 3-D Time-Dependent and Space-Dependent Gamma Electron Cascade Transport by Monte-Carlo

International Nuclear Information System (INIS)

Haggmark, L.G.

1980-01-01

1 - Description of problem or function: SANDYL performs three- dimensional, time and space dependent Monte Carlo transport calculations for photon-electron cascades in complex systems. 2 - Method of solution: The problem geometry is divided into zones of homogeneous atomic composition bounded by sections of planes and quadrics. The material of each zone is a specified element or combination of elements. For a photon history, the trajectory is generated by following the photon from scattering to scattering using the various probability distributions to find distances between collisions, types of collisions, types of secondaries, and their energies and scattering angles. The photon interactions are photoelectric absorption (atomic ionization), coherent scattering, incoherent scattering, and pair production. The secondary photons which are followed include Bremsstrahlung, fluorescence photons, and positron-electron annihilation radiation. The condensed-history Monte Carlo method is used for the electron transport. In a history, the spatial steps taken by an electron are pre-computed and may include the effects of a number of collisions. The corresponding scattering angle and energy loss in the step are found from the multiple scattering distributions of these quantities. Atomic ionization and secondary particles are generated with the step according to the probabilities for their occurrence. Electron energy loss is through inelastic electron-electron collisions, Bremsstrahlung generation, and polarization of the medium (density effect). Included in the loss is the fluctuation due to the variation in the number of energy-loss collisions in a given Monte Carlo step (straggling). Scattering angular distributions are determined from elastic nuclear-collision cross sections corrected for electron-electron interactions. The secondary electrons which are followed included knock-on, pair, Auger (through atomic ionizations), Compton, and photoelectric electrons. 3

Experimental study on the aging process of the LR 115 cellulose nitrate radon detector

International Nuclear Information System (INIS)

Siems, M.; Freyer, K.; Treutler, H.-C.; Joensson, G.; Enge, W.

2001-01-01

An experimental determination of the aging process of cellulose nitrate detector material was based on the examination of special properties of the LR 115 solid state nuclear track detectors (SSNTDs) of various ages up to 18 years. The examined relevant parameters are the bulk etching rate v b and the track etching rate v t . These parameters are responsible for the appearance, the size and the registration efficiency of tracks of α-particles from radon gas in the detector. To find a correlation between these material parameters and the detector sensitivity an experimental calibration of indoor room and outdoor soil detector devices based on LR 115 took place at the Umweltforschungszentrum Leipzig-Halle (Germany). To avoid routine calibration work in external radon exposure facilities a correction of the age dependent calibration factors with the material parameters measured in one's own laboratory was targeted. In this study a general age dependence, however, was not found. The following statements for practical applications can be made. (i) the bulk etching rate v b for detectors of the same batch has a depth dependence and this dependence is constant over 2 years (LR 115 September 1994). (ii) detectors of different batches older than 5 years and stored at room temperature show an odd v b behaviour when v b is used for describing track shapes. (iii) the calibration factor of detectors of different batches that were stored at about +4 deg. C is constant over 5 years (LR 115 September 1994 and February 1999, Table 2). The conclusion is that LR 115 detectors not older than 5 years and stored in a refrigerator at about +4 deg. C should be preferred for radon measurements. Furthermore these detectors should be recalibrated every year and the microscope work of this calibrations should be performed by the same person who performs the measurements. In addition, a phenomenon related to fundamental track formation mechanisms was found, that the time straggling of the

Gaseous time projection chambers for rare event detection: results from the T-REX project. I. Double beta decay

Energy Technology Data Exchange (ETDEWEB)

Irastorza, I.G.; Aznar, F.; Castel, J., E-mail: igor.irastorza@cern.ch, E-mail: faznar@unizar.es, E-mail: jfcastel@unizar.es [Grupo de Física Nuclear y Astropartículas, Departamento de Física Teórica, Universidad de Zaragoza, C/ P. Cerbuna 12, Zaragoza, 50009 (Spain); and others

2016-01-01

As part of the T-REX project, a number of R and D and prototyping activities have been carried out during the last years to explore the applicability of gaseous Time Projection Chambers (TPCs) with Micromesh Gas Structures (Micromegas) in rare event searches like double beta decay, axion research and low-mass WIMP searches. In both this and its companion paper, we compile the main results of the project and give an outlook of application prospects for this detection technique. While in the companion paper we focus on axions and WIMPs, in this paper we focus on the results regarding the measurement of the double beta decay (DBD) of {sup 136}Xe in a high pressure Xe (HPXe) TPC. Micromegas of the microbulk type have been extensively studied in high pressure Xe and Xe mixtures. Particularly relevant are the results obtained in Xe + trimethylamine (TMA) mixtures, showing very promising results in terms of gain, stability of operation, and energy resolution at high pressures up to 10 bar. The addition of TMA at levels of ∼ 1% reduces electron diffusion by up to a factor of 10 with respect to pure Xe, improving the quality of the topological pattern, with a positive impact on the discrimination capability. Operation with a medium size prototype of 30 cm diameter and 38 cm of drift (holding about 1 kg of Xe at 10 bar in the fiducial volume, enough to contain high energy electron tracks in the detector volume) has allowed to test the detection concept in realistic experimental conditions. Microbulk Micromegas are able to image the DBD ionization signature with high quality while, at the same time, measuring its energy deposition with a resolution of at least a ∼ 3% FWHM @ Q{sub ββ}. This value was experimentally demonstrated for high-energy extended tracks at 10 bar, and is probably improvable down to the ∼ 1% FWHM levels as extrapolated from low energy events. In addition, first results on the topological signature information (one straggling track ending in two

A Fano cavity test for Monte Carlo proton transport algorithms

International Nuclear Information System (INIS)

Sterpin, Edmond; Sorriaux, Jefferson; Souris, Kevin; Vynckier, Stefaan; Bouchard, Hugo

2014-01-01

Purpose: In the scope of reference dosimetry of radiotherapy beams, Monte Carlo (MC) simulations are widely used to compute ionization chamber dose response accurately. Uncertainties related to the transport algorithm can be verified performing self-consistency tests, i.e., the so-called “Fano cavity test.” The Fano cavity test is based on the Fano theorem, which states that under charged particle equilibrium conditions, the charged particle fluence is independent of the mass density of the media as long as the cross-sections are uniform. Such tests have not been performed yet for MC codes simulating proton transport. The objectives of this study are to design a new Fano cavity test for proton MC and to implement the methodology in two MC codes: Geant4 and PENELOPE extended to protons (PENH). Methods: The new Fano test is designed to evaluate the accuracy of proton transport. Virtual particles with an energy ofE 0 and a mass macroscopic cross section of (Σ)/(ρ) are transported, having the ability to generate protons with kinetic energy E 0 and to be restored after each interaction, thus providing proton equilibrium. To perform the test, the authors use a simplified simulation model and rigorously demonstrate that the computed cavity dose per incident fluence must equal (ΣE 0 )/(ρ) , as expected in classic Fano tests. The implementation of the test is performed in Geant4 and PENH. The geometry used for testing is a 10 × 10 cm 2 parallel virtual field and a cavity (2 × 2 × 0.2 cm 3 size) in a water phantom with dimensions large enough to ensure proton equilibrium. Results: For conservative user-defined simulation parameters (leading to small step sizes), both Geant4 and PENH pass the Fano cavity test within 0.1%. However, differences of 0.6% and 0.7% were observed for PENH and Geant4, respectively, using larger step sizes. For PENH, the difference is attributed to the random-hinge method that introduces an artificial energy straggling if step size is not

Sparse-view proton computed tomography using modulated proton beams

Energy Technology Data Exchange (ETDEWEB)

Lee, Jiseoc; Kim, Changhwan; Cho, Seungryong, E-mail: scho@kaist.ac.kr [Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejon 305-701 (Korea, Republic of); Min, Byungjun [Department of Radiation Oncology, Kangbuk Samsung Hospital, 110–746 (Korea, Republic of); Kwak, Jungwon [Department of Radiation Oncology, Asan Medical Center, 138–736 (Korea, Republic of); Park, Seyjoon; Lee, Se Byeong [Proton Therapy Center, National Cancer Center, 410–769 (Korea, Republic of); Park, Sungyong [Proton Therapy Center, McLaren Cancer Institute, Flint, Michigan 48532 (United States)

2015-02-15

Purpose: Proton imaging that uses a modulated proton beam and an intensity detector allows a relatively fast image acquisition compared to the imaging approach based on a trajectory tracking detector. In addition, it requires a relatively simple implementation in a conventional proton therapy equipment. The model of geometric straight ray assumed in conventional computed tomography (CT) image reconstruction is however challenged by multiple-Coulomb scattering and energy straggling in the proton imaging. Radiation dose to the patient is another important issue that has to be taken care of for practical applications. In this work, the authors have investigated iterative image reconstructions after a deconvolution of the sparsely view-sampled data to address these issues in proton CT. Methods: Proton projection images were acquired using the modulated proton beams and the EBT2 film as an intensity detector. Four electron-density cylinders representing normal soft tissues and bone were used as imaged object and scanned at 40 views that are equally separated over 360°. Digitized film images were converted to water-equivalent thickness by use of an empirically derived conversion curve. For improving the image quality, a deconvolution-based image deblurring with an empirically acquired point spread function was employed. They have implemented iterative image reconstruction algorithms such as adaptive steepest descent-projection onto convex sets (ASD-POCS), superiorization method–projection onto convex sets (SM-POCS), superiorization method–expectation maximization (SM-EM), and expectation maximization-total variation minimization (EM-TV). Performance of the four image reconstruction algorithms was analyzed and compared quantitatively via contrast-to-noise ratio (CNR) and root-mean-square-error (RMSE). Results: Objects of higher electron density have been reconstructed more accurately than those of lower density objects. The bone, for example, has been reconstructed

International Atomic Energy Agency intercomparison of ion beam analysis software

Energy Technology Data Exchange (ETDEWEB)

Barradas, N.P. [Instituto Tecnologico e Nuclear, Estrada Nacional No. 10, Apartado 21, 2686-953 Sacavem (Portugal); Centro de Fisica Nuclear da Universidade de Lisboa, Avenida do Professor Gama Pinto 2, 1649-003 Lisboa (Portugal)], E-mail: nunoni@itn.pt; Arstila, K. [K.U. Leuven, Instituut voor Kern-en Stralingsfysica, Celestijnenlaan 200D, B-3001 Leuven (Belgium); Battistig, G. [MFA Research Institute for Technical Physics and Materials Science, P.O. Box 49, H-1525 Budapest (Hungary); Bianconi, M. [CNR-IMM-Sezione di Bologna, Via P. Gobetti, 101, I-40129 Bologna (Italy); Dytlewski, N. [International Atomic Energy Agency, Wagramer Strasse 5, P.O. Box 100, A-1400 Vienna (Austria); Jeynes, C. [Surrey Ion Beam Centre, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom); Kotai, E. [KFKI Research Institute for Particle and Nuclear Physics, P.O. Box 49, H-1525 Budapest (Hungary); Lulli, G. [CNR-IMM-Sezione di Bologna, Via P. Gobetti, 101, I-40129 Bologna (Italy); Mayer, M. [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, Boltzmannstrasse 2, D-85748 Garching (Germany); Rauhala, E. [Accelerator Laboratory, Department of Physics, University of Helsinki, P.O. Box 43, FIN-00014 Helsinki (Finland); Szilagyi, E. [KFKI Research Institute for Particle and Nuclear Physics, P.O. Box 49, H-1525 Budapest (Hungary); Thompson, M. [Department of MS and E/Bard Hall 328, Cornell University, Ithaca, NY 14853 (United States)

2007-09-15

Ion beam analysis (IBA) includes a group of techniques for the determination of elemental concentration depth profiles of thin film materials. Often the final results rely on simulations, fits and calculations, made by dedicated codes written for specific techniques. Here we evaluate numerical codes dedicated to the analysis of Rutherford backscattering spectrometry, non-Rutherford elastic backscattering spectrometry, elastic recoil detection analysis and non-resonant nuclear reaction analysis data. Several software packages have been presented and made available to the community. New codes regularly appear, and old codes continue to be used and occasionally updated and expanded. However, those codes have to date not been validated, or even compared to each other. Consequently, IBA practitioners use codes whose validity, correctness and accuracy have never been validated beyond the authors' efforts. In this work, we present the results of an IBA software intercomparison exercise, where seven different packages participated. These were DEPTH, GISA, DataFurnace (NDF), RBX, RUMP, SIMNRA (all analytical codes) and MCERD (a Monte Carlo code). In a first step, a series of simulations were defined, testing different capabilities of the codes, for fixed conditions. In a second step, a set of real experimental data were analysed. The main conclusion is that the codes perform well within the limits of their design, and that the largest differences in the results obtained are due to differences in the fundamental databases used (stopping power and scattering cross section). In particular, spectra can be calculated including Rutherford cross sections with screening, energy resolution convolutions including energy straggling, and pileup effects, with agreement between the codes available at the 0.1% level. This same agreement is also available for the non-RBS techniques. This agreement is not limited to calculation of spectra from particular structures with predetermined

Development of grazing incidence devices for space-borne time of flight mass spectrometry

Science.gov (United States)

Cadu, A.; Devoto, P.; Louarn, P.; Sauvaud, J.-A.

2012-04-01

Time of flight mass spectrometer is widely used to study space plasmas in planetary and solar missions. This space-borne instrument selects ions in function of their energy through an electrostatic analyzer. Particles are then post-accelerated to energies in the range of 20 keV to cross a carbon foil. At the foil exit, electrons are emitted and separated from ion beam in the time of flight section. A first detector (a Micro-Channel Plate or MCP) emits a start signal at electron arrival and a second one emits a stop signal at incident ion end of path. The time difference gives the speed of the particle and its mass can be calculated, knowing its initial energy. However, current instruments suffer from strong limitations. The post acceleration needs very high voltage power supplies which are heavy, have a high power consumption and imply technical constraints for the development. A typical instrument weighs from 5 to 6 kg, includes a 20 kV power supply, consumes a least 5 W and encounters corona effect and electrical breakdown problems. Moreover, despite the particle high energy range, scattering and straggling phenomena in the carbon foil significantly reduce the instrument overall resolution. Some methods, such as electrostatic focus lenses or reflectrons, really improve mass separation but global system efficiency remains very low because of the charge state dependence of such devices. The main purpose of our work is to replace carbon foil by grazing incidence MCP's - also known as MPO's, for Micro Pore Optics - for electron emission. Thus, incident particles would back-scatter onto the channel inner surface with an angle of a few degrees. With this solution, we can decrease dispersion sources and lower the power supplies to post accelerate ions. The result would be a lighter and simpler instrument with a substantial resolution improvement. We have first simulated MPO's behavior with TRIM and MARLOWE Monte-Carlo codes. Energy scattering and output angle computed

40. anniversary of cyclotron of Institute of Nuclear Physics, Tashkent

International Nuclear Information System (INIS)

Umerov, R.A.; Uzakov, J.M.; Gulamov, I.R.

2004-01-01

Full text: The Cyclotron U-150-II of Institute of Nuclear Physics was projected in middle of the last century for nuclear-physical researches in a scientific research institute of electro physical equipment in Leningrad. The Cyclotron can accelerate positive ions with beam energy of the protons 18 MeV, deuterons 20 MeV, alpha particles 40 MeV. Intensity of a beam a little some microampere. The building of a Cyclotron represents an impressive three-floor construction in volume of 2000 m 3 . The capital equipment, the high-frequency generator, sources of power supplies, vacuum pumps and other technological units are placed on the first and socle floors of a building. The second and third floors served for accommodation of scientific laboratories. A building of a Cyclotron has three experimental halls, where it was possible to carry out physical researches. They have divided from each other, and the main thing from the accelerator, concrete walls with the purpose of reduction of the big radiating background at the working accelerator, preventing realization of experiments. It provided also biological protection of the on duty personnel. The first some years of operation of the Cyclotron have revealed a line of lacks of this machine. For example, for change of energy of a beam of a Cyclotron it took 2-3 weeks. Also, for transition of acceleration of one particles to others it take same time. Time parameters of a beam were unstable. In 1968 reconstruction of the Cyclotron has been started that has allowed to bring in basic changes to parameters U-150-II. The time took on change of an operating mode of a Cyclotron was sharply reduced, and it was possible to reduce it till 10-20 hours, to improve the energy and time resolution of a beam many times over, to reduce angular straggling of particles in a beam. And, all this enormous amount of works was spent by forces of institute. In 70 th years the big development was received with works on radiating stability of materials

Effect of Ion Flux (Dose Rate) in Source-Drain Extension Ion Implantation for 10-nm Node FinFET and Beyond on 300/450mm Platforms

Science.gov (United States)

Shen, Ming-Yi

The improvement of wafer equipment productivity has been a continuous effort of the semiconductor industry. Higher productivity implies lower product price, which economically drives more demand from the market. This is desired by the semiconductor manufacturing industry. By raising the ion beam current of the ion implanter for 300/450mm platforms, it is possible to increase the throughput of the ion implanter. The resulting dose rate can be comparable to the performance of conventional ion implanters or higher, depending on beam current and beam size. Thus, effects caused by higher dose rate must be investigated further. One of the major applications of ion implantation (I/I) is source-drain extension (SDE) I/I for the silicon FinFET device. This study investigated the dose rate effects on the material properties and device performance of the 10-nm node silicon FinFET. In order to gain better understanding of the dose rate effects, the dose rate study is based on Synopsys Technology CAD (TCAD) process and device simulations that are calibrated and validated using available structural silicon fin samples. We have successfully shown that the kinetic monte carlo (KMC) I/I simulation can precisely model both the silicon amorphization and the arsenic distribution in the fin by comparing the KMC simulation results with TEM images. The results of the KMC I/I simulation show that at high dose rate more activated arsenic dopants were in the source-drain extension (SDE) region. This finding matches with the increased silicon amorphization caused by the high dose-rate I/I, given that the arsenic atoms could be more easily activated by the solid phase epitaxial regrowth process. This increased silicon amorphization led to not only higher arsenic activation near the spacer edge, but also less arsenic atoms straggling into the channel. Hence, it is possible to improve the throughput of the ion implanter when the dopants are implanted at high dose rate if the same doping level

Patriarch Ephrem: A late medieval saintly cult

Directory of Open Access Journals (Sweden)

Popović Danica

2006-01-01

extremely complex, even dramatic, political and social circumstances created by the conflict between the patriarchates of Serbia and Constantinople, on the one hand, and rivalries between local lords, on the other. There is a difference of interpretation as to his role as the holder of patriarchal office. The latest findings appear to suggest that Ephrem, as an exponent of Mount Athos, loyal to the Patriarchate of Constantinople and close to Vuk Brankovic, was unacceptable to the Lazarević dynasty who emerged victorious in the power straggles in Serbia. Their victory was crowned with the creation of the cult of the holy prince Lazar, a Kosovo martyr. Although a supporter of the defeated side, patriarch Ephrem, as an unquestionable spiritual authority and very deserving personage, was included among the saints shortly after his death. His cult, however, had never been made complete. He was given a Life and service, but the attempted elevation of his body, i.e. creation of the cult of his relics, was thwarted. The reasons, political in nature, were given in the form of a coded hagiographical message in his Life composed by bishop Mark, an active protagonist in all the events. .

Fast neutron forward distributions from C, Be and U thick targets bombarded by deuterons

International Nuclear Information System (INIS)

Menard, S.; Clapier, F.; Pauwels, N.; Proust, J.; Donzaud, C.; Guillemaud-Mueller, D.; Lhenry, I.; Mueller, A.C.; Scarpaci, J.A.; Sorlin, O.; Mirea, M.

1999-01-01

In principle, to produce neutron rich radioactive beams with sufficient intensities, a source of isotopes far from the valley of β--stability can be obtained through the fission of 238 U induced by fast neutrons. A very promising way to assess the feasibility of these very intense neutron beams is to break an intense 2 H beam in a dedicated converter. The main objective of SPIRAL and PARRNe R - D projects is the investigation of the optimum parameters for a neutron rich isotope source in accordance with the scheme presented above. In such conditions, the charge particle energy loss can prevent the destruction of the fission target. In the frame of these project, a special attention is dedicated to the energetic and angular distributions of the neutrons emerging from a set of converters at a series of 2 H incident energies. Deuteron beams at energies less than 30 MeV are particularly interesting because it is expected that, after the decay in the 238 U target, the neutron rich radioactive fission products are cold enough, thus avoiding the evaporation of a too large number of neutrons. For such purposes, one needs experimental angular distributions at given energies for different types of converters and to elaborate a theoretical tool in order to estimate accurately the characteristics of the secondary neutron beam. In this paper, the experimental results were obtained with 17, 20 and 28 MeV deuteron energies on Be, C and U converters using the time of flight method. These data are compared to results given by a model valid at higher energy in order to obtain pertinent simulations in a large range of incident energies. Many theoretical tools were developed to characterize the properties of the neutron beams emerging from thick targets. In this contribution the Serber's model, considered with its improvements which account for the Coulomb deflection and the mean straggling of the beam in the material, is compared to experimental data in order to verify the validity

ETRAN, Electron Transport and Gamma Transport with Secondary Radiation in Slab by Monte-Carlo

International Nuclear Information System (INIS)

1992-01-01

photon will be produced in a single short step. Allowance is made for such a contingency by sampling the frequency of Bremsstrahlung production events from a Poisson distribution. The energy of the secondary Bremsstrahlung photons is subtracted from the energy of the electrons producing them. Thus photon emission contributes to the energy-loss straggling of the electrons. The photons are started out at a random position in the short step in a direction relative to that of the primary electron specified by the sampled intrinsic Bremsstrahlung emission angle. For problems in which the production of the thick-target Bremsstrahlung is of prime interest, there is an option to increase the rate of occurrence of Bremsstrahlung events artificially by a specified factor. The production of secondary characteristic x-rays in each short step is sampled with the use of the k-ionization cross sections of Arthurs and Moiseiwitsch and Kolbenstvedt. The programme is arranged so as to treat simultaneously many slab targets with different thicknesses. Boundary crossings (transmission and reflection) usually occur in the middle of a short step. The energy with which the electron crosses the border is determined by subtracting from the energy at the beginning of the step an energy loss sampled from the Landau- Blunck-Leisegang distribution for the fraction of the step taken to the boundary. The direction at the time of crossing is determined by changing the direction of motion at the beginning of the short step involved, using a deflection sampled from an exponential approximation to the Goudsmit-Saunderson distribution for the fraction of the short step to the boundary. The target is subdivided into many thin sub-layers of equal thickness, and the energy deposited in each sublayer is recorded for each sampled track