Development of Laser-Ion Beam Photodissociation Methods
Energy Technology Data Exchange (ETDEWEB)
David H. Russell
2004-03-31
OAK-B135 Our BES funded research is aimed at determining structure(s) of model gas-phase ions and understanding how structure influences unimolecular reactivity. The model gas-phase ions include positional isomers of di- and tri-amino acids synthesized in my laboratory, i.e., RGG, GRG, and GGR, to peptides derived from proteolytic digestion of biologically relevant proteins. We are especially interested in understanding the role of intramolecular interactions in the stabilizing ion structure and how changing the charge-site affects structure. The location of charge of gas-phase ions can be manipulated by changing the position of the charge carrying amino acid (basic vs. acidic side chains) and by derivatization of the N- and/or C-terminus. For example, the proton of [M + H]+ ions is mobile and migrates over the entire molecule, whereas Li+, Na+, and to some extent K+ prefers to bind to the C-terminal or side-chain carboxylic acid groups, and Cu+ binds exclusively to the N-terminus and/or basic side-chains such as H, K, and R. The studies are carried out using tandem TOF mass spectrometry, viz. 193 nm (6.43 eV) photodissociation, low (Elab = 10-100 eV) and high kinetic energy (Elab = 1-10 keV) collision-induced dissociation (CID) and surface-induced dissociation (SID)(Elab = 20-70 eV). These techniques are used to probe the structure of model gas-phase ions, i.e., to determine the amino acid sequence of the peptide ions or metal ion (alkali metal and/or transition metal ions) binding site(s) or the site(s) of other charge-carrying functional groups, i.e., oxidized side-chains as well as phosphate or sulfate groups. We are especially interested in understanding how metal ion binding alters the secondary/tertiary (2o/3o) structure of the peptide, i.e., intra-molecular interactions. We have also combine these studies with solution-phase studies and ion mobility spectrometry (IMS), which can be used to study 2o/3o structure of low-internal energy (collisionally
Development of Laser-Ion Beam Photodissociation Methods
Energy Technology Data Exchange (ETDEWEB)
David H. Russell
2004-05-11
OAK-B135 Our BES funded research is aimed at determining structure(s) of model gas-phase ions and understanding how structure influences unimolecular reactivity. The model gas-phase ions include positional isomers of di- and tri-amino acids synthesized in my laboratory, i.e., RGG, GRG, and GGR, to peptides derived from proteolytic digestion of biologically relevant proteins. We are especially interested in understanding the role of intramolecular interactions in the stabilizing ion structure and how changing the charge-site affects structure. The location of charge of gas-phase ions can be manipulated by changing the position of the charge carrying amino acid (basic vs. acidic side chains) and by derivatization of the N- and/or C-terminus. For example, the proton of [M + H]+ ions is mobile and migrates over the entire molecule, whereas Li+, Na+, and to some extent K+ prefers to bind to the C-terminal or side-chain carboxylic acid groups, and Cu+ binds exclusively to the N-terminus and/or basic side-chains such as H, K, and R. The studies are carried out using tandem TOF mass spectrometry, viz. 193 nm (6.43 eV) photodissociation, low (Elab = 10-100 eV) and high kinetic energy (Elab = 1-10 keV) collision-induced dissociation (CID) and surface-induced dissociation (SID)(Elab = 20-70 eV). These techniques are used to probe the structure of model gas-phase ions, i.e., to determine the amino acid sequence of the peptide ions or metal ion (alkali metal and/or transition metal ions) binding site(s) or the site(s) of other charge-carrying functional groups, i.e., oxidized side-chains as well as phosphate or sulfate groups. We are especially interested in understanding how metal ion binding alters the secondary/tertiary (2o/3o) structure of the peptide, i.e., intra-molecular interactions. We have also combine these studies with solution-phase studies and ion mobility spectrometry (IMS)), which can be used to study 2o/3o structure of low-internal energy (collisionally
Photodissociation processes in molecular beams
International Nuclear Information System (INIS)
A description is presented of a study of the photodissociation dynamics of molecules in a molecular beam. Photo-fragmentation translational spectroscopy has been utilized to observe the photodissociation dynamics of ozone. Using a supersonic molecular beam and a 10 nanosecond pulsed laser at lambda = 266 nm, the velocities of the fragment products are measured by the method of time of flight. The resolution of the time of flight spectrum of ozone is sufficiently high that the electronic and vibrational states are clearly resolved and identified. Above the threshold (lambda 1D) has been estimated in the past to be unity for the process O3 (1A1) + hν)lambda 3(1B2) → O2(1Δ/sub g/) + O(1D). However a small production of O2 (3Σ/sub g/-) + O(3P) has been observed in this study. The O2(1Δ/sub g/) product yields four vibrational states (v = 0, 1, 2, 3) which yields a vibrational temperature of 27000K along with narrow energy distributions of rotational levels. These energy distributions are compared with photodissociation models along with the polarization dependence of the dissociative process which was also measured. 143 references
Energy Technology Data Exchange (ETDEWEB)
Russell, D.H.
1992-08-01
Research efforts were concentrated on developing the tandem magnetic sector (EB)/reflection-time-of-flight (TOF) instrument, preliminary experiments with tandem TOF/TOF instruments, developing method for performing photodissociation with pulsed lasers, experiments with laser ionization of aerosol particles, matrix-assisted laser desorption ionization (MALDI), and ion-molecule reaction chemistry of ground and excited state transition metal ions. This progress report is divided into: photodissociation, MALDI (including aerosols), and ion chemistry fundamentals.
Fast beam studies of free radical photodissociation
Energy Technology Data Exchange (ETDEWEB)
Neumark, D.M. [Lawrence Berkeley Laboratory, CA (United States)
1993-12-01
The authors have developed a novel technique for studying the photodissociation spectroscopy and dynamics of free radicals. In these experiments, radicals are generated by laser photodetachment of a fast (6-8 keV) mass-selected negative ion beam. The resulting radicals are photodissociated with a second laser, and the photofragments are collected and detected with high efficiency using a microchannel plate detector. The overall process is: ABC{sup -} {yields} ABC + e{sup -} {yields} A + BC, AB + C. Two types of fragment detection schemes are used. To map out the photodissociation cross-section of the radical, the photodissociation laser is scanned and the total photofragment yield is measured as a function of wavelength. In other experiments, the photodissociation frequency is fixed and the photofragment masses, kinetic energy release, and scattering angle is determined for each photodissociation event.
Fast beam studies of free radical photodissociation
Energy Technology Data Exchange (ETDEWEB)
Cyr, D R [Lawrence Berkeley Lab., CA (United States)
1993-11-01
The photodissociation of free radicals is studied in order to characterize the spectroscopy and dissociation dynamics of the dissociative electronic states in these species. To accomplish this, a novel method of radical production, based on the photodetachment of the corresponding negative ion, has been combined with a highly complementary form of photofragment translational spectroscopy. The optical spectroscopy of transitions to dissociative states is determined by monitoring the total photofragment yield as a function of dissociation photon energy. Branching ratios to various product channels, internal energy distributions of the fragments, bond dissociation energies, and the translational energy-dependent photofragment recoil angular distributions are then determined at selected excitation energies. A detailed picture of the dissociation dynamics can then be formulated, allowing insight concerning the interactions of potential energy surfaces involved in the dissociation. After an introduction to the concepts and techniques mentioned above, the experimental apparatus used in these experiments is described in detail. The basis and methods used in the treatment of data, especially in the dissociation dynamics experiments, are then put forward.
Fast beam studies of free radical photodissociation
International Nuclear Information System (INIS)
The photodissociation of free radicals is studied in order to characterize the spectroscopy and dissociation dynamics of the dissociative electronic states in these species. To accomplish this, a novel method of radical production, based on the photodetachment of the corresponding negative ion, has been combined with a highly complementary form of photofragment translational spectroscopy. The optical spectroscopy of transitions to dissociative states is determined by monitoring the total photofragment yield as a function of dissociation photon energy. Branching ratios to various product channels, internal energy distributions of the fragments, bond dissociation energies, and the translational energy-dependent photofragment recoil angular distributions are then determined at selected excitation energies. A detailed picture of the dissociation dynamics can then be formulated, allowing insight concerning the interactions of potential energy surfaces involved in the dissociation. After an introduction to the concepts and techniques mentioned above, the experimental apparatus used in these experiments is described in detail. The basis and methods used in the treatment of data, especially in the dissociation dynamics experiments, are then put forward
The investigation of photo-dissociation by time dependent quantum method
International Nuclear Information System (INIS)
The fragmentation of a bound molecule through absorption of one or more photons is called photo-dissociation. The electromagnetic energy of the light beam is converted into internal energy of the molecule and if the transferred energy exceeds the binding energy of the weakest bond, the molecule will irreversible break apart. Let us, as an example, consider the dissociation of a parent molecule AB into products A and B, where A and B represent either structureless atoms or molecules with internal degrees of freedom of their own. Formally we write a photo-dissociation process as, AB+Nphotonℎω→(AB)*→A(α)+B(β) Photo-dissociation can be roughly classified as either direct or indirect dissociation. In a direct process the parent molecule dissociates immediately after the photon has promoted it to the upper electronic state. No well or other dynamical constraint hinders the fragmentation and the 'lifetime' of the excited complex is very short, less than a vibrational period within the complex. In indirect photo-fragmentation, on the other hand, a potential well or some other dynamical force hinders direct fragmentation of the excited complex and the lifetime amounts to at least several internal vibrational periods. Photo-dissociation is one of the important topics of quantum chemistry. The basic principles of photo-dissociation and the time dependent quantum wave packet method, which is one of the methods developed to investigate dissociation have been applied to this study, which the dissociations of NH+ and HCl molecules.
Zare, P. N.; Herschbach, D. R.
1964-01-29
Conventional photochemical experiments give no information about the partitioning of energy between translational recoil and internal excitation of the fragment molecules formed in photodissociation of a polyatomic molecule. In a molecular beam experiment, it becomes possible to determine the energy partition from the form of the laboratory angular distribution of one of the photodissociation products. A general kinematic analysis is worked out in detail, and the uncertainty introduced by the finite angular resolution of the apparatus and the velocity spread in the parent beam is examined. The experimental requirements are evaluated for he photolysis of methyl iodide by the 2537 angstrom Hg line.
Photostop: Production of zero-velocity molecules by photodissociation in a molecular beam
Trottier, Alexandre; Wrede, Eckart
2011-01-01
We have demonstrated a new, accessible and economical technique, dubbed photostop, for producing high densities of trappable molecules. Direct measurements are presented of NO molecules produced with a narrow velocity distribution centered at zero in the laboratory frame. NO2, initially cooled in a pulsed molecular beam, is photodissociated such that the recoil velocity of the NO photofragments cancels out the velocity of the beam. NO(X^2Pi_3/2, v=0, J=1.5) molecules are observed up to 10 mircoseconds after the dissociation event in the probe volume at an estimated density of 1E7 cm-3 per quantum state and at a translational temperature of 1.6 K. Through the choice of suitable precursors, photostop has the potential to extend the list atoms and molecules that can be slowed or trapped. It should be possible to accumulate density in a trap through consecutive loading of multiple pulses.
Crider, Paul
2010-01-01
Fast beam photofragment translational spectroscopy has been used to elucidate the photodissociation dynamics of small radicals and closed-shell anions. Imaging of photofragments in time- and position-coincidence allows the determination of mass distributions, translational energy distributions [P(ET) distributions], and in the case of three-body fragmentation channels, ternary Dalitz plots depicting the momentum disposal among the fragments. These data yield information about the potential en...
Photodissociation of alkyl nitrites in a molecular beam. Primary and secondary reactions
International Nuclear Information System (INIS)
The translational energy distributions P(ET) for the 248-nm photodissociation products (NO + RO) of isopropyl nitrite and tert-butyl nitrite have been measured with a molecular beam time-of-flight (TOF) apparatus. Previous experiments with methyl nitrite and ethyl nitrite have been repeated with higher resolution. The average photofragment translational energies of these four alkyl nitrites are in good agreement with those predicted by an impulsive model that treats the NO as a rigid fragment and the alkoxy radical as a soft fragment. Hence, and in contrast to the vibrational predissociation on the S1 potential energy surface, S2 dissociation is direct and involves no significant vibrational-translational coupling between the reaction coordinate rO-N and the rNdouble-bondO coordinate. The width of the experimental P(ET) distributions decreases with increasing size of the alkoxy substituent. This result is discussed in terms of an anticorrelation between the internal energies of a fragment pair. Furthermore, the spontaneous secondary dissociation of isopropoxy and tert-butoxy photofragments was observed which yields CH3 radicals and acetaldehyde or acetone, respectively. The unimolecular decay of these alkoxy radicals confirms their relatively high internal energy as deduced from the primary P(ET) and it is shown that this decay occurs on a submicrosecond time scale
van Dishoeck, Ewine F.; Visser, Ruud
2011-01-01
Photodissociation is the dominant removal process of molecules in any region exposed to intense ultraviolet (UV) radiation. This includes diffuse and translucent interstellar clouds, dense photon-dominated regions, high velocity shocks, the surface layers of protoplanetary disks, and cometary and exoplanetary atmospheres. The rate of photodissociation depends on the cross sections for absorption into a range of excited electronic states, as well as on the intensity and shape of the radiation ...
Asimov, M. M.; Asimov, R. M.; Rubinov, A. N.
2010-08-01
We propose and examine an optical method for eliminating the toxic effect of carbon monoxide. The developed method is based on laser-induced photodissociation of carboxyhemoglobin in blood vessels and capillaries. By numerical simulation of the interaction of laser radiation with tissue, we calculate the spectra of the action of carboxyhemoglobin and oxyhemoglobin in cutaneous blood vessels. We show that, despite the sufficiently strong overlap of the action spectra of carboxyhemoglobin and oxyhemoglobin, the substantial difference in the quantum yield values makes it possible to develop an optical method for eliminating the toxic effect of carbon monoxide. We determine the criteria for the efficiency of laser-induced photodissociation of carboxyhemoglobin under direct action on lung alveoli through the skin tissue and intravenously.
Energy Technology Data Exchange (ETDEWEB)
Kim, B.
1990-10-01
This report discusses the following topics: molecular structure of NO{sub 3} radical studied by laser induced fluorescence; photodissociation and fluorescence spectroscopy of NO{sub 3} in molecular beam; vertical electronic spectrum of NO{sub 3}:{sup 2}A{prime}{sub 2}, {sup 2}E{double prime}({sup 2}A{sub 2}{sup 2}B{sub 1}), and {sup 2}E{prime} states; and Ab initio study of the vibrational spectra of NO{sub 3}.
Energy Technology Data Exchange (ETDEWEB)
Korol' kov, K.S.; Krylov, A.IU.; Nosach, O.IU.; Orlov, E.P. (Fizicheskii Institut, Moscow (USSR))
1990-07-01
A method is developed for determining the absolute gain of the nonstationary enthalpy stimulated scattering (NESS) of laser radiation by temperature waves by means of direct measurements of fundamental and impurity beam gains in the laser amplifier. The NESS gain is investigated as a function of the working gas mixture pressure in iodine photodissociation lasers. 11 refs.
Photodissociation of the CHFCl2 and CHCl3 molecules and the CHCl2 radical in a beam at 193 nm
Yang, Xuefeng; Felder, Peter; Huber, J. Robert
1994-11-01
The collision-free photodissociation of CHFCl2 and CHCl3 at 193 nm has been studied by photofragment translational spectroscopy. In both systems the primary dissociation proceeds exclusively via the rupture of a C-Cl bond. The broad and unstructured UV spectra of the parent molecules and the rather high kinetic energy release (approximately = 45% of the available energy) in conjunction with the narrow translational energy distributions of the fragments are consistent with the C-Cl bond fission being a direct dissociation process. The photofragment angular distributions are characterized by anisotropy parameters beta = 0.5 +/- 0.1 (CHFCl2) and beta = 0.0 +/- 0.1 (CHCl3). Therefore, the photolysis of CHFCl2 involves an electronic transition polarised parallel to the line connecting the two Cl atoms. In the case of CHCl3, the nearly isotropic fragment recoil is attributed to the excitation of overlapping transitions of A(sub 1) from A(sub 1) and E from A(sub 1) type, respectively, hence leading to an effective anisotropy parameter beta(sub eff) = a(beta) A(sub 1) +b(beta)(sub E) approximately = 0. The CHCl2 radical produced in the primary reaction CHCl3 + h(nu) yields CHCl2 + Cl can absorb a further photon and is then selectively dissociated by molecular elimination of HCl according to CHCl2 + h(nu) yields CCl + HCl.
Method of electron beam investigation
Directory of Open Access Journals (Sweden)
М. V. Derenovsky
1967-12-01
Full Text Available In this article the possibility of electron beam testing by a modified method of moving right edge is considered. The description of the working set made for the continuous indication of radial current density distribution on an oscilloscope is given. As an exemple the results of beam measurement under continuous operation are presented.
Photodissociation spectroscopy and dynamics of free radicals, clusters, and ions
Energy Technology Data Exchange (ETDEWEB)
Hyeon, Choi
1999-12-16
The photodissociation spectroscopy and dynamics of free radicals and ions is studied to characterize the dissociative electronic states in these species. To accomplish this, a special method of radical production, based on the photodetachment of the corresponding negative ion, has been combined with the technique of fast beam photofragment translational spectroscopy. The photofragment yield as a function of photon energy is obtained, mapping out the dissociative and predissociative electronic states. Branching ratios to various product channels, the translational energy distributions of the fragments, and bond dissociation energies are then determined at selected photon energies. The detailed picture of photodissociation dynamics is provided with the aid of ab initio calculations and a statistical model to interpret the observed data. Important reaction intermediates in combustion reactions have been studied: CCO, C{sub 2}H{sub 5}O, and linear C{sub n} (n = 4--6).
Half collisions by photodissociation
International Nuclear Information System (INIS)
The photodissociation of ICl, IBr and TlBr is studied. In the case of ICl and IBr, experiments are reported at various wavelengths between 480 and 530 nm. For TlBr, photodissociation for a range of wavelengths between 264 and 268 nm is reported. (Auth.)
Czech Academy of Sciences Publication Activity Database
Slavíček, Petr; Fárník, Michal
2011-01-01
Roč. 13, č. 26 (2011), s. 12123-12137. ISSN 1463-9076 R&D Projects: GA ČR GA203/09/0422; GA ČR GAP208/11/0161 Institutional research plan: CEZ:AV0Z40400503 Keywords : photochemistry * hydrogen bonded heterocycles * ab initio methods Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.573, year: 2011
Photodissociation of NaH using time-dependent Fourier grid method
Indian Academy of Sciences (India)
Anindita Bhattacharjee; Krishna Rai Dastidar
2002-03-01
We have solved the time dependent Schrödinger equation by using the Chebyshev polynomial scheme and Fourier grid Hamiltonian method to calculate the dissociation cross section of NaH molecule by 1-photon absorption from the 1+ state to the 1 state. We have found that the results differ signiﬁcantly from an earlier calculation [1] although we have used the same set of potential energy curves [2].
LASER-INDUCED PHOTODISSOCIATION
Rahman, N.
1985-01-01
The richness of the field of laser-induced photodissociation is pointed out. Some of the recent works in this area comprising theoretical, computational as well as experimental research are discussed.
Method for splitting low power laser beams
Energy Technology Data Exchange (ETDEWEB)
Pierscionek, B.K. (University of Melbourne, Optometry Department, Parkville, Victoria 3052, Australia (AU))
1990-04-01
A new method for producing parallel rays from a laser beam using a cylindrical lens and pinholes is presented. This method can produce a greater number of emergent rays than using a {ital beam} {ital splitter}.
Improved beam propagation method equations.
Nichelatti, E; Pozzi, G
1998-01-01
Improved beam propagation method (BPM) equations are derived for the general case of arbitrary refractive-index spatial distributions. It is shown that in the paraxial approximation the discrete equations admit an analytical solution for the propagation of a paraxial spherical wave, which converges to the analytical solution of the paraxial Helmholtz equation. The generalized Kirchhoff-Fresnel diffraction integral between the object and the image planes can be derived, with its coefficients expressed in terms of the standard ABCD matrix. This result allows the substitution, in the case of an unaberrated system, of the many numerical steps with a single analytical step. We compared the predictions of the standard and improved BPM equations by considering the cases of a Maxwell fish-eye and of a Luneburg lens. PMID:18268554
Photodissociation dynamics of O 3- at 523 nm
Garner, M. C.; Sherwood, C. R.; Hanold, K. A.; Continetti, R. E.
1996-01-01
The photodissociation dynamics of O 3- at 523 nm have been studied using fast-ion-beam translational energy spectroscopy. Translational energy and angular distributions of coincident O - + O 2 products from the process O 3- + hv → O - + O 2 were measured. O 3- was generated by electron-impact in a pulsed beam from two precursors — neat O 2 and a seeded beam of O 3. The observed photodissociation dynamics are very different in the two cases, indicating a great difference in internal excitation of ozonide in the two sources.
METHOD OF ELECTRON BEAM PROCESSING
DEFF Research Database (Denmark)
2003-01-01
As a rule, electron beam welding takes place in a vacuum. However, this means that the workpieces in question have to be placed in a vacuum chamber and have to be removed therefrom after welding. This is time−consuming and a serious limitation of a process the greatest advantage of which is the...... option of welding workpieces of large thicknesses. Therefore the idea is to guide the electron beam (2) to the workpiece via a hollow wire, said wire thereby acting as a prolongation of the vacuum chamber (4) down to workpiece. Thus, a workpiece need not be placed inside the vacuum chamber, thereby...... exploiting the potential of electron beam processing to a greater degree than previously possible, for example by means of electron beam welding...
Ion Beam Energy Calibration Method for Accelerator
International Nuclear Information System (INIS)
Ion beam energy calibration methods, i e : nuclear reaction method, magnetic field method and calorimeter method were elaborated and studied from its advantage and disadvantage in this paper. Ion beam energy calibration method for accelerator using the method of magnetic field on 3 MV Tandem Accelerator have been carried out at Tiara, JAERI, Japan. The result showed that the energy of ion beam current is 43.56 keV. The result of study conclude that nuclear reaction method generally used to calibrate ion beam energy at the accelerator of energy larger than 2 MeV, calorimetric method for the accelerator electron including linac, magnetic field method for all particle type of accelerator. (author)
Particle beam injector system and method
Guethlein, Gary
2013-06-18
Methods and devices enable coupling of a charged particle beam to a radio frequency quadrupole accelerator. Coupling of the charged particle beam is accomplished, at least in-part, by relying on of sensitivity of the input phase space acceptance of the radio frequency quadrupole to the angle of the input charged particle beam. A first electric field across a beam deflector deflects the particle beam at an angle that is beyond the acceptance angle of the radio frequency quadrupole. By momentarily reversing or reducing the established electric field, a narrow portion of the charged particle beam is deflected at an angle within the acceptance angle of the radio frequency quadrupole. In another configuration, beam is directed at an angle within the acceptance angle of the radio frequency quadrupole by the first electric field and is deflected beyond the acceptance angle of the radio frequency quadrupole due to the second electric field.
Ion beam sputter implantation method
International Nuclear Information System (INIS)
By means of ion beam atomizing or sputtering an integrally composed coating, the composition of which continuously changes from 100% of the substrate to 100% of the coating, can be surfaced on a substrate (e.g. molten quartz on plastic lenses). In order to do this in the facility there is directed a primary beam of accelerated noble gas ions on a target from the group of the following materials: SiO2, Al2O3, Corning Glass 7070, Corning Glass 7740 or borosilicate glass. The particles leaving the target are directed on the substrate by means of an acceleration potential of up to 10 KV. There may, however, be coated also metal layers (Ni, Co) on a mylar film resulting in a semireflecting metal film. (RW)
Photodissociation of neutron deficient nuclei
Energy Technology Data Exchange (ETDEWEB)
Sonnabend, K.; Babilon, M.; Hasper, J.; Mueller, S.; Zarza, M.; Zilges, A. [TU Darmstadt, Institut fuer Kernphysik, Darmstadt (Germany)
2006-03-15
The knowledge of the cross sections for photodissociation reactions like e.g. ({gamma}, n) of neutron deficient nuclei is of crucial interest for network calculations predicting the abundances of the so-called p nuclei. However, only single cross sections have been measured up to now, i.e., one has to rely nearly fully on theoretical predictions. While the cross sections of stable isotopes are accessible by experiments using real photons, the bulk of the involved reactions starts from unstable nuclei. Coulomb dissociation (CD) experiments in inverse kinematics might be a key to expand the experimental database for p-process network calculations. The approach to test the accuracy of the CD method is explained. (orig.)
Photodissociation of neutron deficient nuclei
Sonnabend, K.; Babilon, M.; Hasper, J.; Müller, S.; Zarza, M.; Zilges, A.
2006-03-01
The knowledge of the cross sections for photodissociation reactions like e.g. (γ, n) of neutron deficient nuclei is of crucial interest for network calculations predicting the abundances of the so-called p nuclei. However, only single cross sections have been measured up to now, i.e., one has to rely nearly fully on theoretical predictions. While the cross sections of stable isotopes are accessible by experiments using real photons, the bulk of the involved reactions starts from unstable nuclei. Coulomb dissociation (CD) experiments in inverse kinematics might be a key to expand the experimental database for p-process network calculations. The approach to test the accuracy of the CD method is explained.
Bond-selective photodissociation caused by vibrational excitation
International Nuclear Information System (INIS)
Ultraviolet photodissociations of partially deuterated water (HOD) and ammonia (NHD2/NH2D) molecules excited to the vibrationally excited states have been investigated by using a crossed laser and molecular beams method. Branching ratio between the H- and D-atom ejection channels has been determined by utilizing a (2+1) resonance enhanced multiphoton ionization scheme of H and D atoms. For 243 nm photolysis of HOD in the 5νOD state, the OD bond dissociation has been solely observed with the branching ratio ,,(D+OH)/ ,,(H+OD) >12, which has been determined by the detection limit for the H atom. For the photolysis of NHD2/NH2D in the vibrationally excited states, the branching ratio between the NH and ND dissociation channels has been largely altered by the vibrational state selection. (author)
Photodissociation dynamics and spectroscopy of free radical combustion intermediates
Energy Technology Data Exchange (ETDEWEB)
Osborn, D.L.
1996-12-01
The photodissociation spectroscopy and dynamics of free radicals is studied by the technique of fast beam photofragment translational spectroscopy. Photodetachment of internally cold, mass-selected negative ions produces a clean source of radicals, which are subsequently dissociated and detected. The photofragment yield as a function of photon energy is obtained, mapping out the dissociative and predissociative electronic states of the radical. In addition, the photodissociation dynamics, product branching ratios, and bond energies are probed at fixed photon energies by measuring the translational energy, P(E{sub T}), and angular distribution of the recoiling fragments using a time- and position-sensitive detector. Ab initio calculations are combined with dynamical and statistical models to interpret the observed data. The photodissociation of three prototypical hydrocarbon combustion intermediates forms the core of this work.
Effective beam method for element concentrations
International Nuclear Information System (INIS)
A method to evaluate chemical element concentrations in samples by generating an effective polychromatic beam using as initial input real monochromatic beam data is presented. There is a great diversity of research being conducted at synchrotron facilities around the world and a diverse set of beamlines to accommodate this research. Time is a precious commodity at synchrotron facilities; therefore, methods that can maximize the time spent collecting data are of value. At the same time the incident radiation spectrum, necessary for some research, may not be known on a given beamline. A preliminary presentation of a method applicable to X-ray fluorescence spectrocopic analyses that overcomes the lack of information about the incident beam spectrum that addresses both of these concerns is given here. The method is equally applicable for other X-ray sources so long as local conditions are considered. It relies on replacing the polychromatic spectrum in a standard fundamental parameters analysis with a set of effective monochromatic photon beams. A beam is associated with each element and can be described by an analytical function allowing extension to elements not included in the necessary calibration measurement(s)
Effective beam method for element concentrations
Energy Technology Data Exchange (ETDEWEB)
Tolhurst, Thomas; Barbi, Mauricio, E-mail: barbi@uregina.ca [University of Regina (Canada); Tokaryk, Tim [Royal Saskatchewan Museum (Canada)
2015-01-29
A method to evaluate chemical element concentrations in samples by generating an effective polychromatic beam using as initial input real monochromatic beam data is presented. There is a great diversity of research being conducted at synchrotron facilities around the world and a diverse set of beamlines to accommodate this research. Time is a precious commodity at synchrotron facilities; therefore, methods that can maximize the time spent collecting data are of value. At the same time the incident radiation spectrum, necessary for some research, may not be known on a given beamline. A preliminary presentation of a method applicable to X-ray fluorescence spectrocopic analyses that overcomes the lack of information about the incident beam spectrum that addresses both of these concerns is given here. The method is equally applicable for other X-ray sources so long as local conditions are considered. It relies on replacing the polychromatic spectrum in a standard fundamental parameters analysis with a set of effective monochromatic photon beams. A beam is associated with each element and can be described by an analytical function allowing extension to elements not included in the necessary calibration measurement(s)
Method for charged particle beam acceleration
International Nuclear Information System (INIS)
The method of charged particle beam acceleration based on its resonance interaction with electromagnetic field of travelling wave is suggested. The electron beam is injected into waveguide in which longitudinal magnetic field and electromagnetic wave are excited. With the purpose of reducing HF-power losses in the waveguide walls, the azimuthal particle motion is synchronized with azimuthal change of longitudinal component of electric field of the accelerating electromagnetic wave. The suggested method permits to increase the efficiency and shunting resistance of the accelerating waveguide by reducing its boundary surface
Photodissociation and photoionization of organosulfur radicals
International Nuclear Information System (INIS)
The dynamics of S(3P2,1,0, 1D2) production from the 193 nm photodissociation of CH3SCH3, H2S and CH3SH have been studied using 2 + 1 resonance-enhanced multiphoton ionization (REMPI) techniques. The 193 nm photodissociation cross sections for the formation of S from CH3S and HS initially prepared in the photodissociation of CH3SCH3 and H2S are estimated to be 1 x 10-18 and 1.1 x 10-18 cm2, respectively. The dominant product from CH3S is S(1D), while that from SH is S(3P). Possible potential energy surfaces involved in the 193 nm photodissociation of CH3S(X) and SH(X) have been also examined. Threshold photoelectron (PE) spectra for SH and CH3S formed in the ultraviolet photodissociation of H2S and CH3SH, respectively, have been measured using the nonresonant two-photon pulsed field ionization (N2P-PFI) technique. The rotationally resolved N2P-PFI-PE spectrum obtained for SH indicates that photoionization dynamics favors the rotational angular momentum change ΔN 2 product 3,2) and CH3S(X2E3/2) are determined to be 84,057.5 ± 3 cm-1 and 74,726 ± 8 cm-1 respectively. The spin-orbit splittings for SH(X2 product 3/2,1/2) and CH3S(X2E3/2,1/2) are found to be 377 ± 2 and 257 ± 5 cm-1, respectively, in agreement with previous measurements. The C-S stretching frequency for CH3S+(X3A2) is 733 ± 5 cm-1. This study illustrates that the PFI-PE detection method can be a sensitive probe for the nascent internal energy distribution of photoproducts
Institute of Scientific and Technical Information of China (English)
ZHANG Dong-Doug; NI Qiang; LUO Si-Zuo; ZHANG Jing; LIU Hang; XU Hai-Feng; JIN Ming-Xing; DING Da-Jun
2011-01-01
A femtosecond pump-probe method is employed to study the dissociation dynamics of sulfur dioxide.SO2 molecules are excited to the F state by absorbing two photons of 267nm femtosecond laser pulses, and ionized by 400nm laser pulses at different delay times between the two lasers. Transients of both parent ions(SO2+) and the fragment ions(SO+, S+ and O+) are observed. The S02+ transient can be well fitted to a biexponential decay comprising a fast and a slow component of 280fs and 2.97ps lifetimes, respectively. The SO+ transient consists of two growth components of 270 fs and 2.50 ps. The results clearly show that the F state of S02 dissociates along an S-0 bond. The transients of S+ and O+, however, have different behavior, which consist of a fast growth and a long decay component. A possible mechanism of the fragment formation is discussed to understand the dissociation dynamics of the F state of SO2.
Effective beam method for element concentrations.
Tolhurst, Thomas; Barbi, Mauricio; Tokaryk, Tim
2015-03-01
There is a great diversity of research being conducted at synchrotron facilities around the world and a diverse set of beamlines to accommodate this research. Time is a precious commodity at synchrotron facilities; therefore, methods that can maximize the time spent collecting data are of value. At the same time the incident radiation spectrum, necessary for some research, may not be known on a given beamline. A preliminary presentation of a method applicable to X-ray fluorescence spectrocopic analyses that overcomes the lack of information about the incident beam spectrum that addresses both of these concerns is given here. The method is equally applicable for other X-ray sources so long as local conditions are considered. It relies on replacing the polychromatic spectrum in a standard fundamental parameters analysis with a set of effective monochromatic photon beams. A beam is associated with each element and can be described by an analytical function allowing extension to elements not included in the necessary calibration measurement(s). PMID:25723941
Rovibrationally resolved photodissociation of SH+
McMillan, E. C.; Shen, G.; McCann, J. F.; McLaughlin, B. M.; Stancil, P. C.
2016-04-01
Photodissociation cross sections for the SH+ radical are computed from all rovibrational (RV) levels of the ground electronic state {{X}}{}3{{{Σ }}}- for wavelengths from threshold to 500 Å. The five electronic transitions, 2{}3{{{Σ }}}- ≤ftarrow {{X}}{}3{{{Σ }}}-,3{}3{{{Σ }}}- ≤ftarrow {{X}}{}3{{{Σ }}}-, A{}3{{\\Pi }} ≤ftarrow {{X}}{}3{{{Σ }}}-,2{}3{{\\Pi }} ≤ftarrow {{X}}{}3{{{Σ }}}-, and 3{}3{{\\Pi }} ≤ftarrow {{X}}{}3{{{Σ }}}-, are treated with a fully quantum–mechanical two-state model, i.e. nonadiabatic couplings between excited states were not included. The photodissociation calculations incorporate adiabatic potentials and transition dipole moment functions computed in the multireference configuration interaction approach along with the Davidson correction (MRCI+Q), but adjusted to match available experimental molecular data and asymptotic atomic limits. Local thermodynamic equilibrium (LTE) photodissociation cross sections were computed which assume a Boltzmann distribution of RV levels in the {{X}}{}3{{{Σ }}}- molecular state of the SH+ cation. The LTE cross sections are presented for temperatures in the range 1000–10 000 K. Applications of the current photodissociation cross sections to interstellar gas, photon-dominated regions, and stellar atmospheres are briefly discussed.
Surface chemistry in photodissociation regions
Esplugues, G. B.; Cazaux, S.; Meijerink, R.; Spaans, M.; Caselli, P.
2016-06-01
Context. The presence of dust can strongly affect the chemical composition of the interstellar medium. We model the chemistry in photodissociation regions (PDRs) using both gas-phase and dust-phase chemical reactions. Aims: Our aim is to determine the chemical compositions of the interstellar medium (gas/dust/ice) in regions with distinct (molecular) gas densities that are exposed to radiation fields with different intensities. Methods: We have significantly improved the Meijerink PDR code by including 3050 new gas-phase chemical reactions and also by implementing surface chemistry. In particular, we have included 117 chemical reactions occurring on grain surfaces covering different processes, such as adsorption, thermal desorption, chemical desorption, two-body reactions, photo processes, and cosmic-ray processes on dust grains. Results: We obtain abundances for different gas and solid species as a function of visual extinction, depending on the density and radiation field. We also analyse the rates of the formation of CO2 and H2O ices in different environments. In addition, we study how chemistry is affected by the presence/absence of ice mantles (bare dust or icy dust) and the impact of considering different desorption probabilities. Conclusions: The type of substrate (bare dust or icy dust) and the probability of desorption can significantly alter the chemistry occurring on grain surfaces, leading to differences of several orders of magnitude in the abundances of gas-phase species, such as CO, H2CO, and CH3OH. The type of substrate, together with the density and intensity of the radiation field, also determine the threshold extinction to form ices of CO2 and H2O. We also conclude that H2CO and CH3OH are mainly released into the gas phase of low, far-ultraviolet illuminated PDRs through chemical desorption upon two-body surface reactions, rather than through photodesorption.
Cluster beam sources. Part 1. Methods of cluster beams generation
Directory of Open Access Journals (Sweden)
A.Ju. Karpenko
2012-10-01
Full Text Available The short review on cluster beams generation is proposed. The basic types of cluster sources are considered and the processes leading to cluster formation are analyzed. The parameters, that affects the work of cluster sources are presented.
Cluster beam sources. Part 1. Methods of cluster beams generation
A.Ju. Karpenko; V.A. Baturin
2012-01-01
The short review on cluster beams generation is proposed. The basic types of cluster sources are considered and the processes leading to cluster formation are analyzed. The parameters, that affects the work of cluster sources are presented.
Production and Photodissociation of the Methyl Perthiyl Radical.
Cole-Filipiak, Neil C; Shapero, Mark; Haibach-Morris, Courtney; Neumark, Daniel M
2016-07-14
The photodissociation dynamics of the methyl perthiyl (CH3SS) radical are investigated via molecular beam photofragment translational spectroscopy, using "soft" electron ionization to detect the radicals and their photofragments. With this new capability, we have shown that CH3SS can be generated from flash pyrolysis of dimethyl trisulfide. Utilizing this source of radicals and the advantages afforded by soft electron ionization, we have reinvestigated the photodissociation dynamics of CH3SS at 248 nm, finding CH3S + S to be the dominant dissociation channel with CH3 + SS as a minor process. These results differ from previous work reported in our laboratory in which we found CH3 + SS and CH2S + SH as the main dissociation channels. The difference in results is discussed in light of our new capabilities for characterization of radical production. PMID:26859337
Optimal control methods for vertical and horizontal beam dynamics
International Nuclear Information System (INIS)
An application of the Macro Fiber Composite (MFC) actuators for damping of a composite beam is presented in this paper. The effectiveness of vibration reduction by a selected control method is tested for vertical and horizontal position of the beam. The original model has been studied numerically by using Galerkin's discretisation method. The numerical results for the vertical and horizontal beams are compared.
Initial alignment method for free space optics laser beam
Shimada, Yuta; Tashiro, Yuki; Izumi, Kiyotaka; Yoshida, Koichi; Tsujimura, Takeshi
2016-08-01
The authors have newly proposed and constructed an active free space optics transmission system. It is equipped with a motor driven laser emitting mechanism and positioning photodiodes, and it transmits a collimated thin laser beam and accurately steers the laser beam direction. It is necessary to introduce the laser beam within sensible range of the receiver in advance of laser beam tracking control. This paper studies an estimation method of laser reaching point for initial laser beam alignment. Distributed photodiodes detect laser luminescence at respective position, and the optical axis of laser beam is analytically presumed based on the Gaussian beam optics. Computer simulation evaluates the accuracy of the proposed estimation methods, and results disclose that the methods help us to guide the laser beam to a distant receiver.
Stability Analysis of Nonuniform Rectangular Beams Using Homotopy Perturbation Method
Directory of Open Access Journals (Sweden)
Seval Pinarbasi
2012-01-01
Full Text Available The design of slender beams, that is, beams with large laterally unsupported lengths, is commonly controlled by stability limit states. Beam buckling, also called “lateral torsional buckling,” is different from column buckling in that a beam not only displaces laterally but also twists about its axis during buckling. The coupling between twist and lateral displacement makes stability analysis of beams more complex than that of columns. For this reason, most of the analytical studies in the literature on beam stability are concentrated on simple cases: uniform beams with ideal boundary conditions and simple loadings. This paper shows that complex beam stability problems, such as lateral torsional buckling of rectangular beams with variable cross-sections, can successfully be solved using homotopy perturbation method (HPM.
Electron beam directed energy device and methods of using same
Retsky, Michael W.
2007-10-16
A method and apparatus is disclosed for an electron beam directed energy device. The device consists of an electron gun with one or more electron beams. The device includes one or more accelerating plates with holes aligned for beam passage. The plates may be flat or preferably shaped to direct each electron beam to exit the electron gun at a predetermined orientation. In one preferred application, the device is located in outer space with individual beams that are directed to focus at a distant target to be used to impact and destroy missiles. The aimings of the separate beams are designed to overcome Coulomb repulsion. A method is also presented for directing the beams to a target considering the variable terrestrial magnetic field. In another preferred application, the electron beam is directed into the ground to produce a subsurface x-ray source to locate and/or destroy buried or otherwise hidden objects including explosive devices.
Saturated photodissociation of CsI
International Nuclear Information System (INIS)
Every CsI molecule in a small volume was photodissociated with a laser pulse; a second pulsed laser detected each Cs atom through resonance ionization spectroscopy. Besides proving one-molecule detection, cross sections for photodissociation of CsI were obtained as a function of wavelength. (Auth.)
DEFF Research Database (Denmark)
Schmidt, J. A.; Olsen, J. M. H.
2014-01-01
examines the sensitivity of these quantities to changes in the employed electronic structure methodology. This study benchmarks the methodology employed in previous studies against highly correlated electronic structure methods (CC3 and MRAQCC) and provide evidence in support of the picture of the OCS...
Analytical And Numerical Methods In Beam Physics
Andrianov, S
2004-01-01
This report is devoted to discussion of numerical and symbolic computing ratio beam physics. We tray to draw attention on basic conceptual and computational problems first of all. It is known that the main problem in modern computational beam physics connected with high performance computing realization. The most of used approaches are not appropriate for computing using multiprocessing systems. Here we give some possible solutions, which based on symbolic presentation of necessary information and modern information technologies.
Photodissociation of interstellar N2
Li, Xiaohu; Visser, Ruud; Ubachs, Wim; Lewis, Brenton R; Gibson, Stephen T; van Dishoeck, Ewine F
2013-01-01
Molecular nitrogen is one of the key species in the chemistry of interstellar clouds and protoplanetary disks and the partitioning of nitrogen between N and N2 controls the formation of more complex prebiotic nitrogen-containing species. The aim of this work is to gain a better understanding of the interstellar N2 photodissociation processes based on recent detailed theoretical and experimental work and to provide accurate rates for use in chemical models. We simulated the full high-resolution line-by-line absorption + dissociation spectrum of N2 over the relevant 912-1000 \\AA\\ wavelength range, by using a quantum-mechanical model which solves the coupled-channels Schr\\"odinger equation. The simulated N2 spectra were compared with the absorption spectra of H2, H, CO, and dust to compute photodissociation rates in various radiation fields and shielding functions. The effects of the new rates in interstellar cloud models were illustrated for diffuse and translucent clouds, a dense photon dominated region and a ...
Photodissociation of sodium iodide and resonant ionization of sodium atom produced
Institute of Scientific and Technical Information of China (English)
HUO Bing-hai; Z.T.Salim; A.H.Bakery
2004-01-01
Resonant ionization spectroscopy (RIS) and resonant ionization mass spectroscopy (RIMS) are employed to detect the photodissociation product of sodium iodide molecules in a molecular beam in an intense laser field in the absence of the buffer gases. Time of flight mass spectra is recorded. In particular, the appearances of multiphoton ionization are discussed.
Photodissociation dynamics of the CNN free radical
International Nuclear Information System (INIS)
The spectroscopy and photodissociation dynamics of the A(tilde sign) 3Π and B(tilde sign) 3Σ- states of the CNN radical have been investigated by fast beam photofragment translational spectroscopy. Vibronic transitions located more than 1000 cm-1 above the A(tilde sign) 3Π(leftarrow)X(tilde sign) 3Σ- origin were found to predissociate. Photofragment yield spectra for the B(tilde sign) 3Σ-(leftarrow)X(tilde sign) 3Σ- band between 40 800 and 45 460 cm-1 display resolved vibrational progressions with peak spacing of ≅1000 cm-1 corresponding to symmetric stretch 10n and combination band 10n301 progressions. Ground state products C(3P)+N2 were found to be the major photodissociation channel for both the A(tilde sign) 3Π and B(tilde sign) 3Σ- states. The translational energy distributions for the A(tilde sign) 3Π state are bimodal with high and low translational energy components. The distributions for the B(tilde sign) 3Σ- state reveal partially resolved vibrational structure for the N2 photofragment and indicate extensive vibrational and rotational excitation of this fragment. These results suggest that bent geometries are involved in the dissociation mechanism and provide more accurate values: ΔfH0(CNN)=6.16±0.05 eV and ΔfH298(CNN)=6.15±0.05 eV. These values, coupled with recent D0(RH) and D298(RH) values from Clifford et al. [J. Phys. Chem. 102, 7100 (1998)], yield ΔfH0(HCNN)=5.02±0.18 eV, ΔfH298(HCNN)=4.98±0.18 eV, ΔfH0(H2CNN)=3.09±0.21 eV, and ΔfH0(H2CNN)=3.09±0.21 eV. (c) 2000 American Institute of Physics
Modified Wide-angle Beam Propagation Method Using Douglas Operators①
Institute of Scientific and Technical Information of China (English)
无
1997-01-01
A modified wide-angle beam propagation based on the Douglas operators is presented .The truncation error in the modified wide-angle beam propagation is reduced to o(△x)4in the transverse direction nearly without any increase of the computation time,whereas the error in the ordinary wide-angle beam propagation method is typically o(△x)2.With trivial programming changes,the accuracy is higher,especially in wide-angle propagation.
Synthetic methods for beam to beam power balancing capability of large laser facilities
International Nuclear Information System (INIS)
To account for output power balancing capability of large laser facilities, a synthetic method with beam to beam root-mean-square is presented. Firstly, a conversion process for the facilities from original data of beam powers to regular data is given. The regular data contribute to the normal distribution approximately, and then a corresponding simple method of root-mean-square for beam to beam power balancing capability is given.Secondly, based on theory of total control charts and cause-selecting control charts, control charts with root-mean-square are established which show short-term variety of power balancing capability of the facilities. Mean rate of failure occurrence is also defined and used to describe long-term trend of global balancing capabilities of the facilities. Finally, advantages of the intuitive and efficient diagnosis for synthetic methods are illustrated by analysis of experimental data. (authors)
Beam Conditioning for FELs: Consequences and Methods
Energy Technology Data Exchange (ETDEWEB)
Wolski, Andrzej; Penn, Gregory; Sessler, Andrew; Wurtele, Jonathan
2003-10-09
The consequences of beam conditioning in four example cases (VISA, a Soft X-Ray FEL, LCLS and a ''Greenfield'' FEL) are examined. It is shown that in emittance limited cases, proper conditioning reduces sensitivity to the transverse emittance, and allows stronger focusing in the undulator. Simulations show higher saturation power, with gain lengths reduced up to a factor of two. The beam dynamics in a general conditioning system are studied, with ''matching conditions'' derived for achieving conditioning without growth in effective emittance. Various conditioners are considered, and expressions derived for the amount of conditioning provided in each case when the matching conditions are satisfied. We discuss the prospects for conditioners based on laser and plasma systems.
Development of multi-bunch beam energy compensation method
International Nuclear Information System (INIS)
A method to compensate for beam loading effects in a multi-bunch beam is under development at Accelerator Test Facility (ATF) in KEK. In this paper we describe the rf high power test for ΔT energy compensation by using the SLED cavities. In this ΔT (early injection and amplitude modulation) energy compensation method, the input waveform into accelerating structure is changed by controlling the rf phase and combining the rf-power from two klystrons with a 3 dB hybrid combiner to compensate multi-bunch beam energy for various beam currents. In this test, an arbitrary waveform was generated by changing the rotating speed of the each klystron phase into the opposite direction and the beam test will be done soon. (author)
Analytical Evaluation of Beam Deformation Problem Using Approximate Methods
DEFF Research Database (Denmark)
Barari, Amin; Kimiaeifar, A.; Domairry, G.
2010-01-01
, and this process produces noise in the obtained answers. This paper deals with the solution of second order of differential equation governing beam deformation using four analytical approximate methods, namely the Perturbation, Homotopy Perturbation Method (HPM), Homotopy Analysis Method (HAM) and......The beam deformation equation has very wide applications in structural engineering. As a differential equation, it has its own problem concerning existence, uniqueness and methods of solutions. Often, original forms of governing differential equations used in engineering problems are simplified...... Variational Iteration Method (VIM). The comparisons of the results reveal that these methods are very effective, convenient and quite accurate for systems of non-linear differential equation....
Photodissociation and chemistry of N2 in the circumstellar envelope of carbon-rich AGB stars
Li, Xiaohu; Millar, Tom J.; Walsh, Catherine; Heays, Alan N.; van Dishoeck, Ewine F.
2014-08-01
Context. The envelopes of asymptotic giant branch (AGB) stars are irradiated externally by ultraviolet photons; hence, the chemistry is sensitive to the photodissociation of N2 and CO, which are major reservoirs of nitrogen and carbon, respectively. The photodissociation of N2 has recently been quantified by laboratory and theoretical studies. Improvements have also been made for CO photodissociation. Aims: For the first time, we use accurate N2 and CO photodissociation rates and shielding functions in a model of the circumstellar envelope of the carbon-rich AGB star, IRC +10216. Methods: We use a state-of-the-art chemical model of an AGB envelope, the latest CO and N2 photodissociation data, and a new method for implementing molecular shielding functions in full spherical geometry with isotropic incident radiation. We compare computed column densities and radial distributions of molecules with observations. Results: The transition of N2→ N (also, CO → C → C+) is shifted towards the outer envelope relative to previous models. This leads to different column densities and radial distributions of N-bearing species, especially those species whose formation/destruction processes largely depend on the availability of atomic or molecular nitrogen, for example, CnN (n = 1, 3, 5), CnN- (n = 1, 3, 5), HCnN (n = 1, 3, 5, 7, 9), H2CN and CH2CN. Conclusions: The chemistry of many species is directly or indirectly affected by the photodissociation of N2 and CO, especially in the outer shell of AGB stars where photodissociation is important. Thus, it is important to include N2 and CO shielding in astrochemical models of AGB envelopes and other irradiated environments. In general, while differences remain between our model of IRC +10216 and the observed molecular column densities, better agreement is found between the calculated and observed radii of peak abundance.
Accurate Method for Determining Adhesion of Cantilever Beams
Energy Technology Data Exchange (ETDEWEB)
Michalske, T.A.; de Boer, M.P.
1999-01-08
Using surface micromachined samples, we demonstrate the accurate measurement of cantilever beam adhesion by using test structures which are adhered over long attachment lengths. We show that this configuration has a deep energy well, such that a fracture equilibrium is easily reached. When compared to the commonly used method of determining the shortest attached beam, the present method is much less sensitive to variations in surface topography or to details of capillary drying.
New method of beam bunching in free-ion lasers
International Nuclear Information System (INIS)
An effective ion beam bunching method is suggested. This method is based on a selective interaction of line spectrum laser light (e.g. axial mode structure light) with non-fully stripped ion beam cooled in a storage rings, arranging the ion beam in layers in radial direction of an energy-longitudinal coordinate plane and following rotation of the beam at the right angle after switching on the RF cavity or undulator grouper/buncher. Laser cooling of the ion beam can be used at this position after switching off the resonator to decrease the energy spread caused by accelerating field of the resonator. A relativistic multilayer ion mirror will be produced this way. Both monochromatic laser beams and intermediate monochromaticity and bandwidth light sources of spontaneous incoherent radiation can be used for production of hard and high power electromagnetic radiation by reflection from this mirror. The reflectivity of the mirror is rather high because of the cross-section of the backward Rayleigh scattering of photon light by non-fully stripped relativistic ions (∼λ2) is much greater (∼ 10 divided-by 15 orders) then Thompson one (∼ re2). This position is valid even in the case of non-monochromatic laser light (Δω/ω ∼ 10-4). Ion cooling both in longitudinal plane and three-dimensional radiation ion cooling had been proposed based on this observation. The using of these cooling techniques will permit to store high current and low emittance relativistic ion beams in storage rings. The bunched ion beam can be used in ordinary Free-Ion Lasers as well. After bunching the ion beam can be extracted from the storage ring in this case. Storage rings with zero momentum compaction function will permit to keep bunching of the ion beam for a long time
New method of beam bunching in free-ion lasers
Energy Technology Data Exchange (ETDEWEB)
Bessonov, E.G. [Lebedev Physics Institute, Moscow (Russian Federation)
1995-12-31
An effective ion beam bunching method is suggested. This method is based on a selective interaction of line spectrum laser light (e.g. axial mode structure light) with non-fully stripped ion beam cooled in a storage rings, arranging the ion beam in layers in radial direction of an energy-longitudinal coordinate plane and following rotation of the beam at the right angle after switching on the RF cavity or undulator grouper/buncher. Laser cooling of the ion beam can be used at this position after switching off the resonator to decrease the energy spread caused by accelerating field of the resonator. A relativistic multilayer ion mirror will be produced this way. Both monochromatic laser beams and intermediate monochromaticity and bandwidth light sources of spontaneous incoherent radiation can be used for production of hard and high power electromagnetic radiation by reflection from this mirror. The reflectivity of the mirror is rather high because of the cross-section of the backward Rayleigh scattering of photon light by non-fully stripped relativistic ions ({approximately}{lambda}{sup 2}) is much greater ({approximately} 10{divided_by}15 orders) then Thompson one ({approximately} r{sub e}{sup 2}). This position is valid even in the case of non-monochromatic laser light ({Delta}{omega}/{omega} {approximately} 10{sup -4}). Ion cooling both in longitudinal plane and three-dimensional radiation ion cooling had been proposed based on this observation. The using of these cooling techniques will permit to store high current and low emittance relativistic ion beams in storage rings. The bunched ion beam can be used in ordinary Free-Ion Lasers as well. After bunching the ion beam can be extracted from the storage ring in this case. Storage rings with zero momentum compaction function will permit to keep bunching of the ion beam for a long time.
Surface chemistry in photodissociation regions
Esplugues, G B; Meijerink, R; Spaans, M; Caselli, P
2016-01-01
The presence of dust can strongly affect the chemical composition of the interstellar medium. We model the chemistry in photodissociation regions (PDRs) using both gas-phase and dust-phase chemical reactions. Our aim is to determine the chemical compositions of the interstellar medium (gas/dust/ice) in regions with distinct (molecular) gas densities that are exposed to radiation fields with different intensities. We have significantly improved the Meijerink PDR code by including 3050 new gas-phase chemical reactions and also by implementing surface chemistry. In particular, we have included 117 chemical reactions occurring on grain surfaces covering different processes, such as adsorption, thermal desorption, chemical desorption, two-body reactions, photo processes, and cosmic-ray processes on dust grains. We obtain abundances for different gas and solid species as a function of visual extinction, depending on the density and radiation field. We also analyse the rates of the formation of CO2 and H2O ices in d...
Photodissociation dynamics of trimethyltin iodide
International Nuclear Information System (INIS)
The photodissociation dynamics of (CH3)3SnI has been investigated in the semi-classical approximation and in the quasi-resonant approximation by URIMIR (Unimolecular Reactions Induced by Multiphoton or Infra-Red Radiation), as well as by direct numerical integration of the time dependent Schroedinger equation with a one-dimensional model describing the Sn-I bond elongation. Potential energy functions (PEF) and associated dipole moment functions (DMF) result from non-linear fits of the MS-CASPT2 (Multi-State Complete Active Space 2nd Order Perturbation Theory) potential energies and dipole transition moments including spin-orbit effects. Preliminary simulations of the excited states dynamics suggest that the ionic channel should be populated by irradiation at about 207 nm. The branching ratio for the formation of ionic products ((CH3)3Sn+ + I-) to that of radical products ((CH3)3Sn· + ·I) could be higher than 5:1 for pulse lengths on the order of 150-200 fs at 50 TW cm-2
Bertarelli, A; Carra, F; Cerutti, F; Dallocchio, A; Mariani, N; Timmins, M; Peroni, L; Scapin, M
2011-01-01
Beam Intercepting Devices are potentially exposed to severe accidental events triggered by direct impacts of energetic particle beams. State-of-the-art numerical methods are required to simulate the behaviour of affected components. A review of the different dynamic response regimes is presented, along with an indication of the most suited tools to treat each of them. The consequences on LHC tungsten collimators of a number of beam abort scenarios were extensively studied, resorting to a novel category of numerical explicit methods, named Hydrocodes. Full shower simulations were performed providing the energy deposition distribution. Structural dynamics and shock wave propagation analyses were carried out with varying beam parameters, identifying important thresholds for collimator operation, ranging from the onset of permanent damage up to catastrophic failure. Since the main limitation of these tools lies in the limited information available on constitutive material models under extreme conditions, a dedica...
Bertarelli, A; Carra, F; Cerutti, F; Dallocchio, A; Mariani, N; Timmins, M; Peroni, L; Scapin, M
2011-01-01
Beam Intercepting Devices are potentially exposed to severe accidental events triggered by direct impacts of energetic particle beams. State-of-the-art numerical methods are required to simulate the behaviour of affected components. A review of the different dynamic response regimes is presented, along with an indication of the most suited tools to treat each of them. The consequences on LHC tungsten collimators of a number of beam abort scenarios were extensively studied, resorting to a novel category of numerical explicit methods, named Hydrocodes. Full shower simulations were performed providing the energy deposition distribution. Structural dynamics and shock wave propagation analyses were carried out with varying beam parameters, identifying important thresholds for collimator operation, ranging from the onset of permanent damage up to catastrophic failure. Since the main limitation of these tools lies in the limited information available on constitutive material models under extreme conditions, a dedica...
Improved multistep method for wide-angle beam propagation
Yamauchi, Junji; Shibayama, Jun; Sekiguchi, Minoru; Nakano, Hisamatsu
1996-01-01
To improve a wide-angle beam propagation method using a finite-difference technique, the generalized Douglas scheme for variable coefficients is applied to a multistep method. A truncation error of O(Δx)4 is achieved in the transverse direction. The effectiveness of the present method is demonstrated in the analysis of a tilted step-index slab waveguide.
Effective beam method for element concentrations
Tolhurst, Thomas; Barbi, Mauricio; Tokaryk, Tim
2015-01-01
There is a great diversity of research being conducted at synchrotron facilities around the world and a diverse set of beamlines to accommodate this research. Time is a precious commodity at synchrotron facilities; therefore, methods that can maximize the time spent collecting data are of value. At the same time the incident radiation spectrum, necessary for some research, may not be known on a given beamline. A preliminary presentation of a method applicable to X-ray fluorescence spectrocopi...
Application of graphical design method to beam transport system
International Nuclear Information System (INIS)
A graphical design method in which a partical beam with initial divergence can realize waist to waist transport in both X and Y planed simultaneously by means of quadrupole doublet is presented. Graphical mathod and transport matrix as well as charts can be used so that a quick design can be carried out to save computer time considerably. A concrete example of the beam is given to demonstrate the practical application of the theory mentioned above
A standardized method for beam design in neutron capture therapy
International Nuclear Information System (INIS)
A desirable end point for a given beam design for Neutron Capture Therapy (NCT) should be quantitative description of tumour control probability and normal tissue damage. Achieving this goal will ultimately rely on data from NCT human clinical trials. Traditional descriptions of beam designs have used a variety of assessment methods to quantify proposed or installed beam designs. These methods include measurement and calculation of open-quotes free fieldclose quotes parameters, such as neutron and gamma flux intensities and energy spectra, and figures-of-merit in tissue equivalent phantoms. The authors propose here a standardized method for beam design in NCT. This method would allow all proposed and existing NCT beam facilities to be compared equally. The traditional approach to determining a quantitative description of tumour control probability and normal tissue damage in NCT research may be described by the following path: Beam design → dosimetry → macroscopic effects → microscopic effects. Methods exist that allow neutron and gamma fluxes and energy dependence to be calculated and measured to good accuracy. By using this information and intermediate dosimetric quantities such as kerma factors for neutrons and gammas, macroscopic effect (absorbed dose) in geometries of tissue or tissue-equivalent materials can be calculated. After this stage, for NCT the data begins to become more sparse and in some areas ambiguous. Uncertainties in the Relative Biological Effectiveness (RBE) of some NCT dose components means that beam designs based on assumptions considered valid a few years ago may have to be reassessed. A standard method is therefore useful for comparing different NCT facilities
Method for separating FEL output beams from long wavelength radiation
Energy Technology Data Exchange (ETDEWEB)
Neil, George; Shinn, Michelle D.; Gubeli, Joseph
2016-04-26
A method for improving the output beam quality of a free electron laser (FEL) by reducing the amount of emission at wavelengths longer than the electron pulse length and reducing the amount of edge radiation. A mirror constructed of thermally conductive material and having an aperture therein is placed at an oblique angle with respect to the beam downstream of the bending magnet but before any sensitive use of the FEL beam. The aperture in the mirror is sized to deflect emission longer than the wavelength of the FEL output while having a minor impact on the FEL output beam. A properly sized aperture will enable the FEL radiation, which is coherent and generally at a much shorter wavelength than the bending radiations, to pass through the aperture mirror. The much higher divergence bending radiations will subsequently strike the aperture mirror and be reflected safely out of the way.
Methods of steering and focusing ion and electron beams
International Nuclear Information System (INIS)
This patent describes a method for steering or focussing beams such as ion or electron beams with a magnetic field. The method consists of: generating a large electric current in a straight conducting wire; projecting charged particles in proximity with the conducting wire; deflecting the charged particles by generating in proximity with the wire a circular magnetic field; confining each of the charged particles to a path which extends in a direction substantially coplanar with the conducting wire wherein a deflecting force generated by the coaxial magnetic field is exerted on each particle in the plane defined by the conducting wire and the path of the particle
Institute of Scientific and Technical Information of China (English)
HUO Binghai; GAO Jie; CUI Shuanjin; H. H. Telle; Z. T. Salim
2000-01-01
It is reported on the recent research using resonant ionization spectroscopy (RIS) and resonant ionization mass spectroscopy (RIMS) to detect the photodissociation product of Rubidium iodide molecules in a molecular beam in an intense laser field. Time of flight mass spectra is recorded. In particular, the appearances of multiphoton ionization are discussed.
Isotope effects in photodissociation: Chemical reaction dynamics and implications for atmospheres
DEFF Research Database (Denmark)
Jørgensen, Solvejg; Grage, Mette Marie-Louise; Nyman, Gunnar;
2008-01-01
obtaining the absorption and/or photodissociation cross section is a threefold challenge: computing the electronic potential energy surfaces, interpolating the potentials, and finding the cross section either by time-dependent or time-independent methods. We review electronic structure methods us...
Shallow gas cloud illumination analysis by the focal beam method
Latiff, Abdul Halim Abdul
2016-02-01
This research will address the illumination issue of seismic data below a shallow gas cloud, also known as shallow gas accumulation. In general, poor and distorted seismic data underneath gas zones depend on four major factors; namely the velocity of the gas zones, the depth of the target reflector, the location of the source and the receiver during seismic acquisition, and the frequency of the seismic signals. These factors will be scrutinized in detail by using the focal beam method. The focal beam method incorporates the double focusing concept in order to obtain two important attributes for illumination analysis: (i) Resolution function beam, (ii) amplitude versus ray parameter (AVP) imprint, which is obtained by transforming the modelled data into the radon domain. Both illumination attributes are then applied to a gas-affected field in the Malaysia Basin. The results show well-defined illumination beneath the shallow anomalies and provide a better representation of the subsurface.
New Combined Electron-Beam Methods of Wastewater Purification
International Nuclear Information System (INIS)
The paper is a brief review of the results obtained with the participation of the authors from the study on combined electron-beam methods for purification of some wastewaters. The data on purification of wastewaters containing dyes or hydrogen peroxide and municipal wastewater in the aerosol flow are considered
Dynamic Response of Inextensible Beams by Improved Energy Balance Method
DEFF Research Database (Denmark)
Sfahani, M. G.; Barari, Amin; Omidvar, M.;
2011-01-01
An improved He's energy balance method (EBM) for solving non-linear oscillatory differential equation using a new trial function is presented. The problem considered represents the governing equations of the non-linear, large-amplitude free vibrations of a slender cantilever beam with a...
Mode selective photodissociation dynamics in V+(OCO)
International Nuclear Information System (INIS)
The electrostatic V+(OCO) complex has a vibrationally resolved photodissociation spectrum in the visible. Photodissociation produces V++CO2 (nonreactive pathway) and VO++CO (reactive pathway). Production of VO+ is energetically favored, but spin forbidden. One-photon dissociation studies confirm mode selectivity observed by Lessen et al. [J. Chem. Phys. 95, 1414 (1991)]: excitation of one quantum of rocking motion enhances VO+ production by >30%. Branching ratio measurements in one-photon dissociation are extended to higher energy. The effect of OCO antisymmetric stretch vibrations on reactivity is investigated using vibrationally mediated photodissociation, in which the OCO antisymmetric stretch is excited at 2390.9 cm-1. Vibrationally excited molecules are then dissociated in the visible. Seven vibronic bands are investigated, involving the antisymmetric stretch alone and in combination with the CO2 bend, the V+(OCO) stretch and rock. Exciting the antisymmetric stretch leads to a ∼15% increase in the reactive VO+ channel, compared to other states at similar energy. Combination bands involving the antisymmetric stretch all show slightly higher reactivity. Electronic structure calculations were performed to characterize the dissociation pathways and excited electronic states of V+(OCO). The geometries of reactants, products, and transition states and relative energies of quintet and triplet states were determined using hybrid density functional theory; energies were also calculated using the coupled cluster with single, double and perturbative triple excitations method. In addition, time-dependent density functional theory calculations were performed to predict the excited electronic states of quintet and triplet V+(OCO). Spin-orbit coupling of quintet states to triplet states was calculated and used to compute intersystem crossing rates, which reproduce many of the observed mode selective trends. The V+-OCO stretch and OCO antisymmetric stretch appear to enhance
A method for generating double-ring-shaped vector beams
Huan, Chen; Xiao-Hui, Ling; Zhi-Hong, Chen; Qian-Guang, Li; Hao, Lv; Hua-Qing, Yu; Xu-Nong, Yi
2016-07-01
We propose a method for generating double-ring-shaped vector beams. A step phase introduced by a spatial light modulator (SLM) first makes the incident laser beam have a nodal cycle. This phase is dynamic in nature because it depends on the optical length. Then a Pancharatnam–Berry phase (PBP) optical element is used to manipulate the local polarization of the optical field by modulating the geometric phase. The experimental results show that this scheme can effectively create double-ring-shaped vector beams. It provides much greater flexibility to manipulate the phase and polarization by simultaneously modulating the dynamic and the geometric phases. Project supported by the National Natural Science Foundation of China (Grant No. 11547017), the Hubei Engineering University Research Foundation, China (Grant No. z2014001), and the Natural Science Foundation of Hubei Province, China (Grant No. 2014CFB578).
Cardiac rate detection method based on the beam splitter prism
Yang, Lei; Liu, Xiaohua; Liu, Ming; Zhao, Yuejin; Dong, Liquan; Zhao, Ruirui; Jin, Xiaoli; Zhao, Jingsheng
2013-09-01
A new cardiac rate measurement method is proposed. Through the beam splitter prism, the common-path optical system of transmitting and receiving signals is achieved. By the focusing effect of the lens, the small amplitude motion artifact is inhibited and the signal-to-noise is improved. The cardiac rate is obtained based on the PhotoPlethysmoGraphy (PPG). We use LED as the light source and use photoelectric diode as the receiving tube. The LED and the photoelectric diode are on the different sides of the beam splitter prism and they form the optical system. The signal processing and display unit is composed by the signal processing circuit, data acquisition device and computer. The light emitted by the modulated LED is collimated by the lens and irradiates the measurement target through the beam splitter prism. The light reflected by the target is focused on the receiving tube through the beam splitter prism and another lens. The signal received by the photoelectric diode is processed by the analog circuit and obtained by the data acquisition device. Through the filtering and Fast Fourier Transform, the cardiac rate is achieved. We get the real time cardiac rate by the moving average method. We experiment with 30 volunteers, containing different genders and different ages. We compare the signals captured by this method to a conventional PPG signal captured concurrently from a finger. The results of the experiments are all relatively agreeable and the biggest deviation value is about 2bmp.
14th international symposium on molecular beams
Energy Technology Data Exchange (ETDEWEB)
1992-01-01
This report discusses research being conducted with molecular beams. The general topic areas are as follows: Clusters I; reaction dynamics; atomic and molecular spectroscopy; clusters II; new techniques; photodissociation dynamics; and surfaces.
14th international symposium on molecular beams
Energy Technology Data Exchange (ETDEWEB)
1992-09-01
This report discusses research being conducted with molecular beams. The general topic areas are as follows: Clusters I; reaction dynamics; atomic and molecular spectroscopy; clusters II; new techniques; photodissociation & dynamics; and surfaces.
14th international symposium on molecular beams
International Nuclear Information System (INIS)
This report discusses research being conducted with molecular beams. The general topic areas are as follows: Clusters I; reaction dynamics; atomic and molecular spectroscopy; clusters II; new techniques; photodissociation ampersand dynamics; and surfaces
Okada, Y.; Pilleri, P.; Berne, O.; Ossenkopf, V.; Fuente, A.; Goicoechea, J. R.; Joblin, C.; Kramer, C.; Roellig, M.; Teyssier, D.; van der Tak, F. F. S.
2013-01-01
Aims. We observationally investigate the relation between the photoelectric heating efficiency in photodissociation regions (PDRs) and the charge of polycyclic aromatic hydrocarbons (PAHs), which are considered to play a key role in photoelectric heating. Methods. Using PACS onboard Herschel, we obs
Photoisomerization and photodissociation dynamics of reactive free radicals
Energy Technology Data Exchange (ETDEWEB)
Bise, Ryan T.
2000-08-24
The photofragmentation pathways of chemically reactive free radicals have been examined using the technique of fast beam photofragment translational spectroscopy. Measurements of the photodissociation cross-sections, product branching ratios, product state energy distributions, and angular distributions provide insight into the excited state potential energy surfaces and nonadiabatic processes involved in the dissociation mechanisms. Photodissociation spectroscopy and dynamics of the predissociative {tilde A}{sup 2}A{sub 1} and {tilde B}{sup 2}A{sub 2} states of CH{sub 3}S have been investigated. At all photon energies, CH{sub 3} + S({sup 3}P{sub j}), was the main reaction channel. The translational energy distributions reveal resolved structure corresponding to vibrational excitation of the CH{sub 3} umbrella mode and the S({sup 3}P{sub j}) fine-structure distribution from which the nature of the coupled repulsive surfaces is inferred. Dissociation rates are deduced from the photofragment angular distributions, which depend intimately on the degree of vibrational excitation in the C-S stretch. Nitrogen combustion radicals, NCN, CNN and HNCN have also been studied. For all three radicals, the elimination of molecular nitrogen is the primary reaction channel. Excitation to linear excited triplet and singlet electronic states of the NCN radical generates resolved vibrational structure of the N{sub 2} photofragment. The relatively low fragment rotational excitation suggests dissociation via a symmetric C{sub 2V} transition state. Resolved vibrational structure of the N{sub 2} photofragment is also observed in the photodissociation of the HNCN radical. The fragment vibrational and rotational distributions broaden with increased excitation energy. Simple dissociation models suggest that the HNCN radical isomerizes to a cyclic intermediate (c-HCNN) which then dissociates via a tight cyclic transition state. In contrast to the radicals mentioned above, resolved
Material-point Method Analysis of Bending in Elastic Beams
DEFF Research Database (Denmark)
Andersen, Søren Mikkel; Andersen, Lars
The aim of this paper is to test different types of spatial interpolation for the materialpoint method. The interpolations include quadratic elements and cubic splines. A brief introduction to the material-point method is given. Simple liner-elastic problems are tested, including the classical...... cantilevered beam problem. As shown in the paper, the use of negative shape functions is not consistent with the material-point method in its current form, necessitating other types of interpolation such as cubic splines in order to obtain smoother representations of field quantities. It is shown that the...
Material-Point Method Analysis of Bending in Elastic Beams
DEFF Research Database (Denmark)
Andersen, Søren Mikkel; Andersen, Lars
2007-01-01
The aim of this paper is to test different types of spatial interpolation for the material-point method. The interpolations include quadratic elements and cubic splines. A brief introduction to the material-point method is given. Simple liner-elastic problems are tested, including the classical...... cantilevered beam problem. As shown in the paper, the use of negative shape functions is not consistent with the material-point method in its current form, necessitating other types of interpolation such as cubic splines in order to obtain smoother representations of field quantities. It is shown that the...
Photodissociation spectroscopy of the dysprosium monochloride molecular ion
International Nuclear Information System (INIS)
We have performed a combined experimental and theoretical study of the photodissociation cross section of the molecular ion DyCl+. The photodissociation cross section for the photon energy range 35 500 cm−1 to 47 500 cm−1 is measured using an integrated ion trap and time-of-flight mass spectrometer; we observe a broad, asymmetric profile that is peaked near 43 000 cm−1. The theoretical cross section is determined from electronic potentials and transition dipole moments calculated using the relativistic configuration-interaction valence-bond and coupled-cluster methods. The electronic structure of DyCl+ is extremely complex due to the presence of multiple open electronic shells, including the 4f10 configuration. The molecule has nine attractive potentials with ionically bonded electrons and 99 repulsive potentials dissociating to a ground state Dy+ ion and Cl atom. We explain the lack of symmetry in the cross section as due to multiple contributions from one-electron-dominated transitions between the vibrational ground state and several resolved repulsive excited states
Pulse compression method for amplified spontaneous emission smooth beams
International Nuclear Information System (INIS)
In order to increase the intensity on target and the coupling efficiency, based on optical gain switching theory the paper presents a method for shortening the amplified spontaneous emission (ASE) smooth pulses. The experiment has been per- formed on EMG-150, a discharge laser in the Department of Experimental Physics, University of Szeged. As a result, the pulse bandwidth is shortened to 7.5 ns from 14.5 ns. and the uniformity of the ASE beams is not affected. (authors)
Method and apparatus for laser-controlled proton beam radiology
Johnstone, Carol J.
1998-01-01
A proton beam radiology system provides cancer treatment and proton radiography. The system includes an accelerator for producing an H.sup.- beam and a laser source for generating a laser beam. A photodetachment module is located proximate the periphery of the accelerator. The photodetachment module combines the H.sup.- beam and laser beam to produce a neutral beam therefrom within a subsection of the H.sup.- beam. The photodetachment module emits the neutral beam along a trajectory defined by the laser beam. The photodetachment module includes a stripping foil which forms a proton beam from the neutral beam. The proton beam is delivered to a conveyance segment which transports the proton beam to a patient treatment station. The photodetachment module further includes a laser scanner which moves the laser beam along a path transverse to the cross-section of the H.sup.- beam in order to form the neutral beam in subsections of the H.sup.- beam. As the scanning laser moves across the H.sup.- beam, it similarly varies the trajectory of the proton beam emitted from the photodetachment module and in turn varies the target location of the proton beam upon the patient. Intensity modulation of the proton beam can also be achieved by controlling the output of the laser.
Photodissociation of the hydroxyl radical (OH) at 157 nm
Cody, R. J.; Moralejo, C.; Allen, J. E., Jr.
1991-01-01
The photodissociation of the OH radical was studied at 157 nm via the detection of the product H atoms with the resonance fluorescence technique. OH radicals were produced in a fast-flow cell from the reaction between H and NO2 and subsequently photodissociated by an excimer laser operating on the F2 emission. The quantum yield for photodissociation of OH was measured to be 1.10 + or - 0.28. The photodissociation cross section was calculated to be 6.6 x 10 to the -18th sq cm (+ or - 25 percent).
Energy Technology Data Exchange (ETDEWEB)
QIAN,S.TAKACS,P.
2003-08-03
A beam splitter to create two separated parallel beams is a critical unit of a pencil beam interferometer, for example the long trace profiler (LTP). The operating principle of the beam splitter can be based upon either amplitude-splitting (AS) or wavefront-splitting (WS). For precision measurements with the LTP, an equal optical path system with two parallel beams is desired. Frequency drift of the light source in a non-equal optical path system will cause the interference fringes to drift. An equal optical path prism beam splitter with an amplitude-splitting (AS-EBS) beam splitter and a phase shift beam splitter with a wavefront-splitting (WS-PSBS) are introduced. These beam splitters are well suited to the stability requirement for a pencil beam interferometer due to the characteristics of monolithic structure and equal optical path. Several techniques to produce WS-PSBS by hand are presented. In addition, the WS-PSBS using double thin plates, made from microscope cover plates, has great advantages of economy, convenience, availability and ease of adjustment over other beam splitting methods. Comparison of stability measurements made with the AS-EBS, WS-PSBS, and other beam splitters is presented.
Analysis of reinforced concrete beams by the equivalent section method
Schulz, Mauro
2014-01-01
This research investigates the analysis of reinforced concrete beams subjected to combined axial load, bending moment and shear force. Cross-sections of general shape are divided, along the height, into plane elements. The biaxial behavior is represented according to the smeared rotating crack approach. Using traditionally accepted hypotheses for beams, the shear flow is determined by applying the Jouravski formula to an "equivalent section", which takes into account the nonlinear material behavior. The "Equivalent Section Method", originally proposed by Diaz (1980) and Diaz and Schulz (1981), is improved and simplified. The formulation is implemented applying the bidimensional constitutive model A, proposed by Vecchio and Collins (1993). The tension-stiffening effect is considered as adopted by Polak and Vecchio (1993). Shear slip at crack surfaces, Poisson's ratio and other secondary effects are not considered. Validation is undertaken by comparison with experimental results obtained by other researchers. T...
Visser, R; Black, J H
2009-01-01
Aims. Photodissociation by UV light is an important destruction mechanism for CO in many astrophysical environments, ranging from interstellar clouds to protoplanetary disks. The aim of this work is to gain a better understanding of the depth dependence and isotope-selective nature of this process. Methods. We present a photodissociation model based on recent spectroscopic data from the literature, which allows us to compute depth-dependent and isotope-selective photodissociation rates at higher accuracy than in previous work. The model includes self-shielding, mutual shielding and shielding by atomic and molecular hydrogen, and it is the first such model to include the rare isotopologues C17O and 13C17O. We couple it to a simple chemical network to analyse CO abundances in diffuse and translucent clouds, photon-dominated regions, and circumstellar disks. Results. The photodissociation rate in the unattenuated interstellar radiation field is 2.6e-10 s^-1, 30% higher than currently adopted values. Increasing t...
CO emission from candidate photo-dissociation regions in M81
Knapen, J H; Heaton, H I; Kuno, N; Nakai, N
2006-01-01
Context At least a fraction of the atomic hydrogen in spiral galaxies is suspected to be the result of molecular hydrogen which has been dissociated by radiation from massive stars. Aims In this paper, we extend our earlier set of data from a small region of the Western spiral arm of M81 with CO observations in order to study the interplay between the radiation field and the molecular and atomic hydrogen. Methods We report CO(1-0) observations with the Nobeyama 45 m dish and the Owens Valley interferometer array of selected regions in the Western spiral arm of M81. Results From our Nobeyama data, we detect CO(1-0) emission at several locations, coinciding spatially with HI features near a far-UV source. The levels and widths of the detected CO profiles are consistent with the CO(1-0) emission that can be expected from several large photo-dissociation regions with typical sizes of some 50x150 pc located within our telescope beam. We do not detect emission at other pointings, even though several of those are ne...
An Improved Peak Sidelobe Reduction Method for Subarrayed Beam Scanning
Directory of Open Access Journals (Sweden)
Hang Hu
2015-01-01
Full Text Available This paper focused on PSL (peak sidelobe level reduction for subarrayed beam scanning in phased array radars. The desired GSP (Gaussian Subarray Patterns are achieved by creating a subarray weighting network. The GSP-based method could reduce PSL of array pattern; compared with the method based on the desired subarray pattern which is defined by ideal space-domain filter, the PSL reduction performance is improved remarkably. Further, based on the concept adopting superelement patterns to approximately express original subarray patterns, the simplified GSP-based method is proposed. So the dimension of each matrix required for creating the weighting network, which was originally the same as the element number, could be reduced to the same as the subarray number. Consequently, we achieve remarkable reduction of the computation burden; simultaneously, the PSL mitigation performance is degraded slightly. Simulation results demonstrate the validity of the introduced methods.
Design method for automotive high-beam LED optics
Byzov, Egor V.; Moiseev, Mikhail A.; Doskolovich, Leonid L.; Kazanskiy, Nikolay L.
2015-09-01
New analytical method for the calculation of the LED secondary optics for automotive high-beam lamps is presented. Automotive headlamps should illuminate the road and the curb at the distance of 100-150 meters and create a bright, flat, relatively powerful light beam. To generate intensity distribution of this kind we propose to use TIR optical element (collimator working on the total internal reflection principle) with array of microlenses (optical corrector) on the upper surface. TIR part of the optical element enables reflection of the side rays to the front direction and provides a collimated beam which incidents on the microrelief. Microrelief, in its turn, dissipates the light flux in horizontal direction to meet the requirements of the Regulations 112, 113 and to provide well-illuminated area across the road in the far field. As an example, we computed and simulated the optical element with the diameter of 33 millimeters and the height of 22 millimeters. Simulation data shows that three illuminating modules including Cree XP-G2 LED and lens allow generating an appropriate intensity distribution for the class D of UNECE Regulations.
Method and system for treating an interior surface of a workpiece using a charged particle beam
Swenson, David Richard
2007-05-23
A method and system of treating an interior surface on an internal cavity of a workpiece using a charged particle beam. A beam deflector surface of a beam deflector is placed within the internal cavity of the workpiece and is used to redirect the charged particle beam toward the interior surface to treat the interior surface.
Development of visual beam adjustment method for cyclotron
International Nuclear Information System (INIS)
We have developed a computer-based visual assistance system for JAERI AVF cyclotron operation. This system provides a CRT display about the cyclotron beam trajectories, feasible setting regions (FSRs), and search traces designed to improve beam parameter adjustment. As a result of the test in actual operation, it was realized that simulated beam trajectories and FSRs nearly agree with actual beam conditions. (author)
Lifa Air Secure Box method for chilled beam cleaning
Leppälä, Vesa-Jukka
2014-01-01
The objective of this Bachelor’s Thesis was to introduce a chilled beam cleaning method and to develop an improved version for the prototype introduced in 2011. This thesis was commissioned by Lifa Air Ltd. The company itself is specialized in improving Indoor Air Quality and offers a wide range of products meant for ventilation cleaning. The aim for the development work was to fill the requirements and needs set by the company based on the research done, and to construct a working and improv...
Simulation of intense beam bunching using 3D PIC method
International Nuclear Information System (INIS)
Most of the ion sources produce continuous beam of charged particles. In a cyclotron using such an external ion source, only a small fraction of the injected continuous beam is accepted in the central region for further acceleration. By transforming the continuous beam into a suitably bunched beam using a buncher prior to injection, the amount of accepted particles in the central region of cyclotron can be increased. To compress the continuous beam longitudinally one needs to impose a velocity modulation at the buncher gap which results in density modulation as the beam advances. In the case of low beam current the velocity modulation of the beam has very little effect on the transverse envelope of the beam. However, in the case of high intensity beams, the space-charge force introduces much collective behaviour and increase of current in the specified bunch width affects the transverse dynamics
Stability Analysis of Nonuniform Rectangular Beams Using Homotopy Perturbation Method
Seval Pinarbasi
2012-01-01
The design of slender beams, that is, beams with large laterally unsupported lengths, is commonly controlled by stability limit states. Beam buckling, also called “lateral torsional buckling,” is different from column buckling in that a beam not only displaces laterally but also twists about its axis during buckling. The coupling between twist and lateral displacement makes stability analysis of beams more complex than that of columns. For this reason, most of the analytical studies in the li...
International Nuclear Information System (INIS)
The University of Maryland Dynamical Systems and Accelerator Theory Group carries out research in two broad areas: the computation of charged particle beam transport using Lie algebraic methods and advanced methods for the computation of electromagnetic fields and beam-cavity interactions. Important improvements in the state of the art are believed to be possible in both of these areas. In addition, applications of these methods are made to problems of current interest in accelerator physics including the theoretical performance of present and proposed high energy machines. The Lie algebraic method of computing and analyzing beam transport handles both linear and nonlinear beam elements. Tests show this method to be superior to the earlier matrix or numerical integration methods. It has wide application to many areas including accelerator physics, intense particle beams, ion microprobes, high resolution electron microscopy, and light optics. With regard to the area of electromagnetic fields and beam cavity interactions, work is carried out on the theory of beam breakup in single pulses. Work is also done on the analysis of the high frequency behavior of longitudinal and transverse coupling impedances, including the examination of methods which may be used to measure these impedances. Finally, work is performed on the electromagnetic analysis of coupled cavities and on the coupling of cavities to waveguides
A hydrogen ion beam method of molecular density measurement inside a 4.2-K beam tube
International Nuclear Information System (INIS)
In our first experiments on synchrotron radiation-induced photodesorption in a 4.2-K beam tube, the moleculm density was measured by room temperature ion gauges and RGAs outside the beam tube. The molecular density inside the 4.2-K beam tube was therefore unknown, since the mean molecular speed of photodesorbed molecules had not been measured. To determine the density inside the 4.2-K beam tube we have developed a direct method of measurement utilizing the neutralization of H+ beams, which are proportional to gas density. The hydrogen ion beams (up to 20 keV, ∼1 μA) are extracted from an rf ion source and guided into the cold beam tube by a bending magnet. The H0 and H- produced in the beam tube are magnetically separated from H- and detected with secondary electron multipliers (SEMs). Small superconducting dipole magnets located near the center of the beam tube allow a ∼20-cm segment of the injected ion beam to be offset a few mm from the injection axis; detection of H0 and H- produced along this offset segment provides a localized density measurement. If necessary, detector background due to synchrotron radiation photons can be discriminated against by gating the detector on between the bursts of synchrotron radiation. The experimental setup and initial data will be presented
A hydrogen ion beam method of molecular density measurement inside a 4.2-K beam tube
Energy Technology Data Exchange (ETDEWEB)
Alinovsky, N.; Anashin, V.; Beschasny, P. [Budker Inst. of Nuclear Physics, Novosibirsk (Russian Federation)] [and others
1994-06-01
In our first experiments on synchrotron radiation-induced photodesorption in a 4.2-K beam tube, the moleculm density was measured by room temperature ion gauges and RGAs outside the beam tube. The molecular density inside the 4.2-K beam tube was therefore unknown, since the mean molecular speed of photodesorbed molecules had not been measured. To determine the density inside the 4.2-K beam tube we have developed a direct method of measurement utilizing the neutralization of H{sup +} beams, which are proportional to gas density. The hydrogen ion beams (up to 20 keV, {approximately}1 {mu}A) are extracted from an rf ion source and guided into the cold beam tube by a bending magnet. The H{sup 0} and H{sup {minus}} produced in the beam tube are magnetically separated from H{sup {minus}} and detected with secondary electron multipliers (SEMs). Small superconducting dipole magnets located near the center of the beam tube allow a {approximately}20-cm segment of the injected ion beam to be offset a few mm from the injection axis; detection of H{sup 0} and H{sup {minus}} produced along this offset segment provides a localized density measurement. If necessary, detector background due to synchrotron radiation photons can be discriminated against by gating the detector on between the bursts of synchrotron radiation. The experimental setup and initial data will be presented.
Multiphonon generation during photodissociation of slow Landau-Pekar polarons
International Nuclear Information System (INIS)
The spectra of the low-temperature photodissociation (photoionization) of Landau-Pekar polarons are calculated using the theory of quantum-coherent states and a new method of variation with respect to the parameters of phonon vacuum deformation. It is shown that the final polaron states upon photodissociation may have different numbers of phonons produced in a single dissociation event and different momenta of charge carriers. The spectrum of optical absorption related to the photodissociation of polarons exhibits a superposition of bands corresponding to various numbers of phonons formed as a result of dissociation of a single polaron. Due to a large width of the energy region corresponding to the final states of charge carriers, the halfwidth of each band is on the order of the energy of polaron coupling and is much greater than the phonon energy. For this reason, the individual phonon bands exhibit strong overlap. The very broad and, probably, structureless band formed as a result of the superposition of all these components begins at an energy equal to the sum of the polaron coupling energy (Ep) and the phonon energy. This band has a maximum at a frequency of about 5.6Ep/ℎ and a halfwidth on the order of 5.6Ep/ℎ at a unit effective mass (m* = me) of band electrons. For an effective charge carrier mass within m* = (1-3)me, the energy of the polaron band maximum can be estimated as 5Ep with an error of about 10%, and the halfwidth falls within 3.4Ep 1/2 p. The multiphonon character of this band is related to a decay of the phonon condensate after the escape of charge carrier from a polaron. Such polarons are likely to be observed in the spectra of complex metal oxides, including high-temperature superconductors. Examples of such polaron bands in the reported absorption and photoconductivity spectra of nonstoichiometric cuprates, manganites, nickelates, and titanates are presented. A theory of the formation of Landau-Pekar polarons with the participation of
New insights into the semiclassical Wigner treatment of photodissociation dynamics
Arbelo-González, W; García-Vela, A
2013-01-01
The \\emph{semiclassical Wigner treatment} of Brown and Heller [J. Chem. Phys. 75, 186 (1981)] is applied to triatomic direct photodissociations with the aim of accurately predicting final state distributions at relatively low computational cost, and having available a powerful interpretative tool. For the first time, the treatment is full-dimensional. The proposed formulation closely parallels the quantum description as far as possible. An approximate version is proposed, which is still accurate while numerically much more efficient. In addition to be weighted by usual vibrational Wigner distributions, final phase space states appear to be weighted by new \\emph{rotational Wigner distributions}. These densities have remarkable structures clearly showing that classical trajectories most contributing to rotational state $j$ are those reaching the products with a rotational angular momentum close to $[j(j+1)]^{1/2}$ (in $\\hbar$ unit). The previous methods involve running trajectories from the reagent molecule ont...
Underwater Environment SDAP Method Using Multi Single-Beam Sonars
Directory of Open Access Journals (Sweden)
Zheping Yan
2013-01-01
Full Text Available A new autopilot system for unmanned underwater vehicle (UUV using multi-single-beam sonars is proposed for environmental exploration. The proposed autopilot system is known as simultaneous detection and patrolling (SDAP, which addresses two fundamental challenges: autonomous guidance and control. Autonomous guidance, autonomous path planning, and target tracking are based on the desired reference path which is reconstructed from the sonar data collected from the environmental contour with the predefined safety distance. The reference path is first estimated by using a support vector clustering inertia method and then refined by Bézier curves in order to satisfy the inertia property of the UUV. Differential geometry feedback linearization method is used to guide the vehicle entering into the predefined path while finite predictive stable inversion control algorithm is employed for autonomous target approaching. The experimental results from sea trials have demonstrated that the proposed system can provide satisfactory performance implying its great potential for future underwater exploration tasks.
A new method for beam stacking in storage rings
Energy Technology Data Exchange (ETDEWEB)
Bhat, C.M.; /Fermilab
2008-06-01
Recently, I developed a new beam stacking scheme for synchrotron storage rings called 'longitudinal phase-space coating' (LPSC). This scheme has been convincingly validated by multi-particle beam dynamics simulations and has been demonstrated with beam experiments at the Fermilab Recycler. Here, I present the results from both simulations and experiments. The beam stacking scheme presented here is the first of its kind.
Development of visual beam adjustment method for cyclotron
International Nuclear Information System (INIS)
We have developed a computer-based visual assistance system for JAERI AVF-cyclotron operation. This system provides a CRT display about the cyclotron beam trajectories, feasible setting regions (FSR's), and search traces designed to enhance beam parameter adjustment. As a result of the test in actual operation, it was realized that simulated beam trajectories and FSR's were nearly agreeable with actual beam condition in the axial injection block and the extraction block. (author)
Ultraviolet photodissociation dynamics of the SH radical
International Nuclear Information System (INIS)
Ultraviolet (UV) photodissociation dynamics of jet-cooled SH radical (in X 2Π3/2, ν''=0-2) is studied in the photolysis wavelength region of 216-232 nm using high-n Rydberg atom time-of-flight technique. In this wavelength region, anisotropy β parameter of the H-atom product is ∼-1, and spin-orbit branching fractions of the S(3PJ) product are close to S(3P2):S(3P1):S(3P0)=0.51:0.36:0.13. The UV photolysis of SH is via a direct dissociation and is initiated on the repulsive 2Σ- potential-energy curve in the Franck-Condon region after the perpendicular transition 2Σ--X 2Π. The S(3PJ) product fine-structure state distribution approaches that in the sudden limit dissociation on the single repulsive 2Σ- state, but it is also affected by the nonadiabatic couplings among the repulsive 4Σ-, 2Σ-, and 4Π states, which redistribute the photodissociation flux from the initially excited 2Σ- state to the 4Σ- and 4Π states. The bond dissociation energy D0(S-H)=29 245±25 cm-1 is obtained
Robotics Methods for Beam Line Instrument Simulation and Control
International Nuclear Information System (INIS)
The majority of sample positioning systems in use at neutron and synchrotron beam line facilities around the world, may be accurately described as serial robot manipulators, i.e. they comprise a series of rotating or translating links connected together in a chain, with the tool or sample that is to be manipulated attached to one end. This characterization suggests that the methods of serial robot kinematic modeling might be usefully applied to the task of simulating and controlling beam line positioning systems. We describe how this approach is being developed within the planning, simulation and control software, SScanSS. The advantages of using the robotics approach are shown to include the ability to: (1) model any number of disparate positioning systems from within one software (and hence one user interface), with a minimum of instrument specific code, (2) accurately and speedily position and orientate samples of arbitrary complexity, and (3) provide options for automatically optimizing other important experimental parameters, such as the measurement count time. The possible extension of this technique to include parallel robotic systems, such as Stewart Platforms, is also discussed
A method of beam control for NFZ-10 industrial irradiation linac
International Nuclear Information System (INIS)
Traditionally negative feedback coming from output beam is used to stabilize output beam by regulating filament voltage of bombarding diode electron gun. The authors analysed the shortcomings of the method in detail and put forward a new method of regulating bombarding high voltage in NFZ-10 industrial irradiation linac. Output beam with high stability and high accuracy was obtained
Beam based gain calibration method for beam position monitor at J-PARC MR
International Nuclear Information System (INIS)
Stability of the closed orbit is one of very important points for stable operations to keep a small beam loss in MR. The relative gains of the output data may drift due to unpredictable imbalance among output signals from the pickup electrodes, because the output signals must travel through separate paths, such as cables, connectors, attenuators, switches, and then are measured by detectors. In KEKB, we found noticeable errors larger than 0.1mm in the almost all BPM readings. In KEKB, A non-linear chi-square method has received practical application to calibrate these errors come from the imbalance among 4 output voltage of a BPM. However, we were not able to apply a same method as KEKB to analyze a gain of BPMs in J-PARC. W noticed linear relations among 4 outputs voltage and analyzed the imbalance by the total least-squares method. This paper introduce the new method to estimate the related gains from four output data of a BPM head. (author)
Method and apparatus for efficient photodetachment and purification of negative ion beams
Beene, James R.; Liu, Yuan; Havener, Charles C.
2008-02-26
Methods and apparatus are described for efficient photodetachment and purification of negative ion beams. A method of purifying an ion beam includes: inputting the ion beam into a gas-filled multipole ion guide, the ion beam including a plurality of ions; increasing a laser-ion interaction time by collisional cooling the plurality of ions using the gas-filled multipole ion guide, the plurality of ions including at least one contaminant; and suppressing the at least one contaminant by selectively removing the at least one contaminant from the ion beam by electron photodetaching at least a portion of the at least one contaminant using a laser beam.
Theoretical study of ultraviolet induced photodissociation dynamics of sulfuric acid
International Nuclear Information System (INIS)
Highlights: • Photodissociation dynamics of H2SO4 at low-lying electronically excited states were investigated. • Photochemical processes were simulated by on-the-fly ab initio MD. • Sulfuric acid after the excitation to the S1 state dissociated to HSO4(12A″) + H(2S). • Sulfuric acid after the excitation to the S2 state dissociated to HSO4(22A″) + H(2S). • The energy region of the UV spectra where NMD fractionation may occur is predicted. - Abstract: Photodissociation dynamics of sulfuric acid after excitation to the first and second excited states (S1 and S2) were studied by an on-the-fly ab initio molecular dynamics simulations based on the Zhu–Nakamura version of the trajectory surface hopping (ZN-TSH). Forces acting on the nuclear motion were computed on-the-fly by CASSCF method with Dunning’s augmented cc-pVDZ basis set. It was newly found that the parent molecule dissociated into two reaction-channels (i) HSO4(12A″) + H(2S) by S1-excitation, and (ii) HSO4(22A″) + H(2S) by S2-excitation. The direct dissociation dynamics yield products different from the SO2 + 2OH fragments often presented in the literature. Both channels result in the same product and differs only in the electronic state of the HSO4 fragment. The trajectories running on S2 do not hop with S0 and a nonadiabatic transition happens at the S2–S1 conical intersection located at a longer OH bond-length than the S1–S0 intersection producing an electronic excited state (22A″) of HSO4 product
Dynamic Calculation Method of Beam System Under Low Velocity Impact
Institute of Scientific and Technical Information of China (English)
LI Wen-pei; WANG De-rong; SONG Chun-ming; WANG Ming-yang
2008-01-01
The beating beams and the supporting beams under low velocity impact may be in four different strain stages of deformation depending on the impact intensity and beam structure strength. Based on the different judging conditions of deformation stages, the corresponding calculation models are proposed, the calculation formulae for the determination of the impact force and the beam's lateral displacement are obtained. Calculation shows that the beam's total deflection is small when the flexibility of the supporting component is high and the effect of diminishing deflection disappears almost when the stiffness of the supporting component is high.
Supporting soil remediation at Fernald by electron beam methods
International Nuclear Information System (INIS)
Electron beam techniques have been used to characterize uranium-contaminated soils at the Fernald Site, Ohio. The major uranium phases have been identified by analytical electron microscopy (AEM) as uranyl phosphate (autunite), uranium oxide (uraninite), and uranium phosphite [U(PO3)4]. Luminescence and X-ray absorption spectroscopy incorrectly identified uranium oxide hydrate (schoepite) as the major phase in Fernald soils. The solubilities of schoepite and autunite are very different, so a solubility-dependent remediation method selected for schoepite will not be effective for removing autunite. AEM is the only technique capable of precisely identifying unknown submicron phases. The uranium phosphite has been found predominantly at the incinerator site at Fernald. This phase has not been removed successfully by any of the chemical remediation technologies. We suggest that an alternative physical extraction procedure be applied to remove this phase
Mathematical and Numerical Methods for Non-linear Beam Dynamics
Herr, W
2014-01-01
Non-linear effects in accelerator physics are important for both successful operation of accelerators and during the design stage. Since both of these aspects are closely related, they will be treated together in this overview. Some of the most important aspects are well described by methods established in other areas of physics and mathematics. The treatment will be focused on the problems in accelerators used for particle physics experiments. Although the main emphasis will be on accelerator physics issues, some of the aspects of more general interest will be discussed. In particular, we demonstrate that in recent years a framework has been built to handle the complex problems in a consistent form, technically superior and conceptually simpler than the traditional techniques. The need to understand the stability of particle beams has substantially contributed to the development of new techniques and is an important source of examples which can be verified experimentally. Unfortunately, the documentation of ...
Stability Analysis of Nonlinear Feedback Control Methods for Beam Halo-chaos
Institute of Scientific and Technical Information of China (English)
WANGZhong-sheng; FANGJin-qing; CHENGuan-rong
2003-01-01
Control of beam halo-chaos has been a more challenge subject in recent years, in which nonlinear feedback method for beam halo-chaos has been developed for control of beam halo-chaos in high-current proton linear accelerators. However, stability analysis of nonlinear feedback control methods for beam halo-chaos has still been an open and important topic in this field. In this letter.
Uniform irradiation system using beam scanning method for cyclotron
International Nuclear Information System (INIS)
JAERI AVF-cyclotron is equipped with an ion beam scanner for large area irradiation. The two-dimensional fluence distribution of ion beam obtained using cellulose triacetate film dosimeter was not uniform. This is resulted from the distortion of excitation current for electromagnet of the scanner. So, the beam scanning condition, i.e., the relation between the ion species, the beam profile and the scanning width, was extremely limited to make a good uniformity. We have developed a beam scanning simulator to get fluence distributions by calculation and then compared the simulated distributions with the measured ones. It was revealed that the both of them are in good agreement and the beam scanning condition to get good uniformity was led by using this simulator. On the basis of these results, the power supply of scanner was improved. A good uniformity of beam distribution was available. (author)
Methods for beam data acquisition offered by a mini-phantom
International Nuclear Information System (INIS)
Mini-phantoms are an important tool for measurement of basic head scatter parameters in high-energy photon beams, and recently they have also been used for beam quality specification. Therefore the feasibility and reliability of basic beam parameter acquisition using only a mini-phantom is checked in 6, 18 and 25 MV photon beams. These parameters include head scatter correction factors, phantom scatter correction factors, total scatter correction factors, wedge factors, off-axis ratios, as well as beam attenuation coefficients and beam hardening coefficients. In order to specify beam quality variations and beam quality modifications by a wedge, two different methods are compared: the first method uses a constant source to chamber distance of 1 m, the second method refers to narrow beam geometry. μ values derived with two different beam quality specification methods show a systematic deviation. However, relative variations of the attenuation coefficient within the beam and the associated beam quality modifications observed with the two methods show good agreement in open and wedged beams. Phantom scatter correction factors are calculated from measured head scatter correction factors and total scatter correction factors as well as from attenuation coefficients. Measured and calculated phantom scatter correction factors agree within 1% with the values given in literature. For 18 and 25 MV photon beam, wedge factors measured in water or in the mini-phantom agree within 0.5%, but maximum deviations of ∼1.5% are observed at 6 MV for the largest field sizes. It is demonstrated that the determination of several beam data related to full scatter conditions does not necessarily require the availability of a full scatter phantom. The mini-phantom is a reliable but very cheap and simple tool. It offers versatile possibilities to measure, check and verify basic beam parameters in high-energy photon beams. (author)
Etxaluze, M.; Cernicharo, J.; Goicoechea, J. R.; van Hoof, P. A. M.; Van de Steene, G. C.; Groenewegen, M. A. T.; Swinyard, B. M.; Barlow, M.J.; Matsuura, M.; Lim, T. L.; Pearson, C.; Polehampton, E. T.; Kerschbaum, F.; Lique, F.; Royer, P.
2014-01-01
Context. The Helix nebula (NGC 7293) is our closest planetary nebulae. Therefore, it is an ideal template for photochemical studies at small spatial scales in planetary nebulae. Aims. We aim to study the spatial distribution of the atomic and the molecular gas, and the structure of the photodissociation region along the western rims of the Helix nebula as seen in the submillimeter range with Herschel. Methods. We used five SPIRE FTS pointing observations to make atomic and molecular spectral ...
Fast beam cut-off method in RF-knockout extraction for spot-scanning
Furukawa, T
2002-01-01
An irradiation method with magnetic scanning has been developed in order to provide accurate irradiation even for an irregular target shape. The scanning method has strongly required a lower ripple of the beam spill and a faster response to beam-on/off in slow extraction from a synchrotron ring. At HIMAC, RF-knockout extraction has utilized a bunched beam to reduce the beam-spill ripple. Therefore, particles near the resonance can be spilled out from the separatrices by synchrotron oscillation as well as by a transverse RF field. From this point of view, a fast beam cut-off method has been proposed and verified by both simulations and experiments. The maximum delay from the beam cut-off signal to beam-off has been improved to around 60 mu s from 700 mu s by a usual method. Unwanted dose has been considerably reduced by around a factor of 10 compared with that by the usual method.
Arrayed waveguide grating using the finite difference beam propagation method
Toledo, M. C. F.; Alayo, M. I.
2013-03-01
The purpose of this work is to analyze by simulation the coupling effects occurring in Arrayed Waveguide Grating (AWG) using the finite difference beam propagation method (FD-BPM). Conventional FD-BPM techniques do not immediately lend themselves to the analysis of large structures such as AWG. Cooper et al.1 introduced a description of the coupling between the interface of arrayed waveguides and star couplers using the numerically-assisted coupled-mode theory. However, when the arrayed waveguides are spatially close, such that, there is strong coupling between them, and coupled-mode theory is not adequate. On the other hand, Payne2 developed an exact eigenvalue equation for the super modes of a straight arrayed waveguide which involve a computational overhead. In this work, an integration of both methods is accomplished in order to describe the behavior of the propagation of light in guided curves. This new method is expected to reduce the necessary effort for simulation while also enabling the simulation of large and curved arrayed waveguides using a fully vectorial finite difference technique.
International Nuclear Information System (INIS)
Description of an instrumental device allowing dielectronic recombination cross section measurement is presented. Recombination of C3+ for high quantum number is studied. This device, using the confluent beam method, entailed the development of an electron gun producing weakly divergent beam. A detector of highly excited ion allowing a quick and accurate measurement of ion beam energy is described in detail. Beam-residual gas interaction mechanisms are studied and instrumental incertitudes are calculated
International Nuclear Information System (INIS)
Based on the developed efficient numerical methods for calculating the propagation of light beams, the alternative methods for measuring the beam radius and propagation ratio proposed in the international standard ISO 11146 are analysed. The specific calculations of the alternative beam propagation ratios Mi2 performed for a number of test beams with a complicated spatial structure showed that the correlation coefficients ci used in the international standard do not establish the universal one-to-one relation between the alternative propagation ratios Mi2 and invariant propagation ratios Mσ2 found by the method of moments. (laser beams)
Isotope selective photodissociation of N2 by the interstellar radiation field and cosmic rays
Heays, Alan N.; Visser, Ruud; Gredel, Roland; Ubachs, Wim; Lewis, Brenton R.; Gibson, Stephen T.; van Dishoeck, Ewine F.
2014-02-01
Context. Photodissociation of 14N2 and 14N 15N occurs in interstellar clouds, circumstellar envelopes, protoplanetary discs, and other environments due to ultraviolet radiation originating from stellar sources and the presence of cosmic rays. This source of N atoms initiates the formation of more complex N-bearing species and may influence their isotopic composition. Aims: We study the photodissociation rates of 14N 15N by ultraviolet continuum radiation and both isotopologues in a field of cosmic ray induced photons. To determine the effect of these on the isotopic composition of more complex molecules. Methods: High-resolution theoretical photodissociation cross sections of N2 are used from an accurate and comprehensive quantum-mechanical model of the molecule based on laboratory experiments. A similarly high-resolution spectrum of H2 emission following interactions with cosmic rays has been constructed. The spectroscopic data are used to calculate photodissociation rates which are then input into isotopically differentiated chemical models, describing an interstellar cloud and a protoplanetary disc. Results: The photodissociation rate of 14N 15N in a Draine field assuming 30 K excitation is 1.73 × 10-10 s-1, within 4% of the rate for 14N2, and the rate due to cosmic ray induced photons assuming an H2 ionisation rate of ζ = 10-16 s-1 is about 10-15 s-1, with up to a factor of 10 difference between isotopologues. Shielding functions for 14N15N by 14N2, H2, and H are presented. Incorporating these into an interstellar cloud model, an enhancement of the atomic 15N/14N ratio over the elemental value is obtained due to the self-shielding of external radiation at an extinction of about 1.5 mag. This effect is larger where assumed grain growth has reduced the opacity of dust to ultraviolet radiation. The transfer of photolytic isotopic fractionation of N and N2 to other molecules is demonstrated to be significant in a protoplanetary disc model with grain growth, and
Method and apparatus for reducing coherence of high-power laser beams
Moncur, Norman K.; Mayer, Frederick J.
1978-01-01
Method and apparatus for reducing the coherence and for smoothing the power density profile of a collimated high-power laser beam in which the beam is focused at a point on the surface of a target fabricated of material having a low atomic number. The initial portion of the focused beam heats the material to form a hot reflective plasma at the material surface. The remaining, major portion of the focused beam is reflected by the plasma and recollected to form a collimated beam having reduced beam coherence.
Institute of Scientific and Technical Information of China (English)
苏为; 黄晓燕; 程恩; 袁飞; 孙海信
2011-01-01
A novel wideband beam-forming structure with constant beam width based on complex coefficients （FIR） digital filters used in underwater acoustic communication is proposed. First, the received signals are compensated with integer sampling period by using delay line. Then their complex envelopes are calculated by using frequency shift method. Finally, the envelopes are weighted by using complex coefficients FIR digital filters whose coefficients are optimized. Simulation re- sults show that, in the communication band, the maximum difference between the designed beam and desired beam is less than 0.3 dB when the ratio of communication band to carrier frequency is 0. 85.
Photodissociation of organic molecules in star-forming regions II: Acetic acid
Pilling, S; Boechat-Roberty, H M
2006-01-01
Fragments from organic molecule dissociation (such as reactive ions and radicals) can form interstellar complex molecules like amino acids. The goal of this work is to experimentally study photoionization and photodissociation processes of acetic acid (CH$_3$COOH), a glycine (NH$_2$CH$_2$COOH) precursor molecule, by soft X-ray photons. The measurements were taken at the Brazilian Synchrotron Light Laboratory (LNLS), employing soft X-ray photons from a toroidal grating monochromator (TGM) beamline (100 - 310 eV). Mass spectra were obtained using the photoelectron photoion coincidence (PEPICO) method. Kinetic energy distribution and abundances for each ionic fragment have been obtained from the analysis of the corresponding peak shapes in the mass spectra. Absolute photoionization and photodissociation cross sections were also determined. We have found, among the channels leading to ionization, that only 4-6% of CH$_3$COOH survive the strong ionization field. CH$_3$CO$^+$, COOH$^+$ and CH$_3^+$ ions are the mai...
Photodissociation of organic molecules in star-forming regions, III. Methanol
Pilling, S; Santos, A C F; Boechat-Roberty, H M
2006-01-01
The presence of methyl alcohol or methanol (CH$_3$OH) in several astrophysical environments has been characterized by its high abundance that depends on both the production rate and the destruction rate. In the present work, the photoionization and photodissociation processes of methanol have been experimentally studied, employing soft X-ray photons (100-310 eV) from a toroidal grating monochromator (TGM) beamline of the Brazilian Synchrotron Light Laboratory (LNLS). Mass spectra were obtained using the photoelectron photoion coincidence (PEPICO) method. Kinetic energy distribution and abundances for each ionic fragment have been obtained from the analysis of the corresponding peak shapes in the mass spectra. Absolute photoionization and photodissociation cross sections were also determined. We have found, among the channels leading to ionization, about 11-16% of CH$_3$OH survive the soft X-rays photons. This behavior, together with an efficient formation pathways, may be associated with the high column densi...
Photodissociation and excitation of interstellar molecules
International Nuclear Information System (INIS)
Apart from a rather long introduction containing some elementary astrophysics, quantum chemistry and spectroscopy and an incomplete, historical review of molecular observations, this thesis is divided into three sections. In part A, a rigorous quantum chemical and dynamical study is made of the photodissociation processes in the OH and HCl molecules. In part B, the cross sections obtained in part A are used in various astrophysical problems such as the study of the abundances of the OH and HCl molecules in interstellar clouds, the use of the OH abundance as a measure of the cosmic ray ionization rate, the lifetime of the OH radical in comets and the abundance of OH in the solar photosphere. Part C discusses the excitation of the C2 molecule under interstellar conditions, its use as a diagnostic probe of the temperature, density and strength of the radiation field in interstellar clouds. Quadrupole moments and oscillator strengths are analyzed. (Auth.)
Chou, J. S.; Sumida, D.; Stuke, M.; Wittig, C
1982-01-01
By using laser multiphoton ionization and a time-of-flight mass filter, we have detected nascent UF5 from the 266 nm laser photodissociation of UF6, following a single laser firing. The method can be used to monitor these species under conditions wherein isotopically selective excitation is responsible for the dissociation of UF6.
Study of biomaterials by ion-beam based methods
International Nuclear Information System (INIS)
primary beam and is activated following the nuclear reaction A(a,b)B. Some generated radioactive heavy ions B acquire sufficient kinetic energy to recoil out of the target and be implanted in the material. The nuclear reaction 56 Fe(p,n)56Co has been chosen to apply the UTLA (Ultra Thin Layer Activation) method because of its high cross section. Moreover, the half-life T= 77.1 days and the 846 keV gamma ray of the 56 Co radioelement is well suited for this study. The radioactive ions are implanted into the near surface (a few hundred nanometers). Wear/corrosion rate of the component by using tribological testers is observed via the variation of its activity caused by the loss of material. The layout of the experimental setup is presented as well as the angular distribution of the implanted recoil ions. In case of direct method the nuclear reaction occurs on the material surface. In order to obtain supplementary data concerning radiation influence on polyethylene samples doses up to 100 kGy were used. The advantages of this technique is the possibility to extend its applicability to any kind of solid material: plastics, ceramics, semiconductors , and metals. (authors)
The beam steering in beamlines and rings using the methods of sequential filtering
International Nuclear Information System (INIS)
The method of sequential filtering was used in the field of accelerator monitoring and control. The application of this method in wide field of accelerator identification and control is presented. The identification theory and sequential filtering survey, algorithms based on the methods of sequential filtering for the beam-kick errors and beam-focus errors estimation, for the trajectory and closed orbit correction in the beam-lines and rings are overviewed. (R.P.) 5 refs.; 3 figs
Suppression of beam halo-chaos using nonlinear feedback discrete control method
Fang Jin Qing; Chen Guan Rong; Luo Xiao Shu; Weng Jia Qiang
2002-01-01
Based on nonlinear feedback control method, wavelet-based feedback controller as a especial nonlinear feedback function is designed for controlling beam halo-chaos in high-current accelerators of driven clean nuclear power system. PIC simulations show that suppression of beam halo-chaos are realized effectively after discrete control of wavelet-based feed-back is applied to five kinds of the initial proton beam distributions, respectively. The beam halo strength factor is quickly reduced to zero, and other statistical physical quantities of beam halo-chaos are more than doubly reduced. These performed PIC simulation results demonstrate that the developed methods are very effective for control of beam halo-chaos. Potential application of the beam halo-chaos control methods is discussed finally
Kandel, Yudhishthir; Denbeaux, Gregory
2016-08-01
We develop a novel iterative method to accurately measure electron beam shape (current density distribution) and monotonic material response as a function of position. A common method is to scan an electron beam across a knife edge along many angles to give an approximate measure of the beam profile, however such scans are not easy to obtain in all systems. The present work uses only an electron beam and multiple exposed regions of a thin film of photoresist to measure the complete beam profile for any beam shape, where the material response is characterized externally. This simplifies the setup of new experimental tools. We solve for self-consistent photoresist thickness loss response to dose and the electron beam profile simultaneously by optimizing a novel functional iteratively. We also show the successful implementation of the method in a real world data set corrupted by noise and other experimental variabilities.
Radioactive ion beam production by the ISOL method for SPIRAL
International Nuclear Information System (INIS)
This work is directly related to the SPIRAL project (Systeme de Production d'Ions Radioactifs Acceleres en Lignes) of which the start up will begin in September 2001 at GANIL (Grand Accelerateur National d'Ions Lourds) in Caen. This thesis primarily concerns the development of radioactive ion production systems (target/ion source) by the thorough study of each production stage of the ISOL (Isotopic Separation On Line) method: target and/or projectile fragmentation production, diffusion out of target material, effusion into the ion source and finally the ionization of the radioactive atoms. A bibliographical research and thermal simulations allowed us to optimize materials and the shape of the production and diffusion targets. A first target was optimized and made reliable for the radioactive noble gases production (argon, neon...). A second target dedicated to the radioactive helium production was entirely designed and realised (from the specifications to the 'off line' and 'on line' tests). Finally, a third target source system was defined for singly-charged radioactive alkaline production. The intensities of secondary beams planned for SPIRAL are presented here. A detailed study of the diffusion effusion efficiency for these various targets showed that the use of a fine microstructure carbon (grain size of 1 μm) improved the diffusion and showed the importance of thickness of the lamella for the short lived isotope effusion. (author)
International Nuclear Information System (INIS)
The photodissociation of carbonyl sulfide (OCS) was investigated theoretically in a series of studies by Schmidt and co-workers. Initial studies [J. A. Schmidt, M. S. Johnson, G. C. McBane, and R. Schinke, J. Chem. Phys. 136, 131101 (2012); J. A. Schmidt, M. S. Johnson, G. C. McBane, and R. Schinke, J. Chem. Phys. 137, 054313 (2012)] found photodissociation in the first UV-band to occur mainly by excitation of the 21A′ (A) excited state. However, in a later study [G. C. McBane, J. A. Schmidt, M. S. Johnson, and R. Schinke, J. Chem. Phys. 138, 094314 (2013)] it was found that a significant fraction of photodissociation must occur by excitation of 11A″ (B) excited state to explain the product angular distribution. The branching between excitation of the A and B excited states is determined by the magnitude of the transition dipole moment vectors in the Franck-Condon region. This study examines the sensitivity of these quantities to changes in the employed electronic structure methodology. This study benchmarks the methodology employed in previous studies against highly correlated electronic structure methods (CC3 and MRAQCC) and provide evidence in support of the picture of the OCS photodissociation process presented in [G. C. McBane, J. A. Schmidt, M. S. Johnson, and R. Schinke, J. Chem. Phys. 138, 094314 (2013)] showing that excitation of A and B electronic states both contribute significantly to the first UV absorption band of OCS. In addition, this study presents evidence in support of the assertion that the A state potential energy surface employed in previous studies underestimates the energy at highly bent geometries (γ ∼ 70°) leading to overestimated rotational energy in the product CO
Heavy ion beams in extended materials - Computational methods and experiment
Wilson, J. W.; Schimmerling, W.; Wong, M.; Townsend, L. W.
1987-01-01
The transport of heavy ion beams in extended materials is a problem of interest in accelerator and space shielding, radiation therapy, and astrophysical and radiobiological studies. The beam particles change their energy and direction of motion through atomic/molecular collisions and undergo occasional radical transformation in nuclear collision. In health physics applications, a heavy ion beam of initially well defined radiation quality is transformed into a complex mixture of diverse quality components after passing through a modest amount of material. This transformation of radiation quality must be understood to adequately explain the biological response of tissue to heavy ion radiation. A theoretical/experimental program to define an ion beam and its products in extended matter is described.
Electrostatic dispersion lenses and ion beam dispersion methods
Dahl, David A [Idaho Falls, ID; Appelhans, Anthony D [Idaho Falls, ID
2010-12-28
An EDL includes a case surface and at least one electrode surface. The EDL is configured to receive through the EDL a plurality of ion beams, to generate an electrostatic field between the one electrode surface and either the case surface or another electrode surface, and to increase the separation between the beams using the field. Other than an optional mid-plane intended to contain trajectories of the beams, the electrode surface or surfaces do not exhibit a plane of symmetry through which any beam received through the EDL must pass. In addition or in the alternative, the one electrode surface and either the case surface or the other electrode surface have geometries configured to shape the field to exhibit a less abrupt entrance and/or exit field transition in comparison to another electrostatic field shaped by two nested, one-quarter section, right cylindrical electrode surfaces with a constant gap width.
ANALYSIS OF REINFORCED CONCRETE BEAMS BY THE EQUIVALENT SECTION METHOD
Schulz, Mauro; Santisi D'Avila, Maria Paola
2011-01-01
This research investigates the analysis of reinforced concrete beams subjected to combined axial load, bending moment and shear force. Cross-sections of general shape are divided, along the height, into plane elements. The biaxial behavior is represented according to the smeared rotating crack approach. Using traditionally accepted hypotheses for beams, the shear flow is determined by applying the Jouravski formula to an "equivalent section", which takes into account the nonlinear material be...
CRIS: A new method in isomeric beam production
Directory of Open Access Journals (Sweden)
Lynch K.M.
2013-12-01
Full Text Available The Collinear Resonance Ionization Spectroscopy (CRIS experiment at ISOLDE, CERN, uses laser radiation to stepwise excite and ionize an atomic beam for the purpose of ultra-sensitive detection of rare isotopes, and hyperfine-structure measurements. The technique also offers the ability to purify an ion beam that is heavily contaminated with radioactive isobars, including the ground state of an isotope from its isomer, allowing decay spectroscopy on nuclear isomeric states to be performed. The isomeric ion beam is selected by resonantly exciting one of its hyperfine structure levels, and subsequently ionizing it. This selectively ionized beam is deflected to a decay spectroscopy station (DSS. This consists of a rotating wheel implantation system for alpha- and beta-decay spectroscopy, and up to three germanium detectors around the implantation site for gamma-ray detection. Resonance ionization spectroscopy and the new technique of laser assisted nuclear decay spectroscopy have recently been performed at the CRIS beam line on the neutron-deficient francium isotopes. Here an overview of the two techniques will be presented, alongside a description of the CRIS beam line and DSS.
CRIS: A new method in isomeric beam production
International Nuclear Information System (INIS)
The Collinear Resonance Ionization Spectroscopy (CRIS) experiment at ISOLDE, CERN, uses laser radiation to stepwise excite and ionize an atomic beam for the purpose of ultra-sensitive detection of rare isotopes, and hyperfine-structure measurements. The technique also offers the ability to purify an ion beam that is heavily contaminated with radioactive isobars, including the ground state of an isotope from its isomer, allowing decay spectroscopy on nuclear isomeric states to be performed. The isomeric ion beam is selected by resonantly exciting one of its hyperfine structure levels, and subsequently ionizing it. This selectively ionized beam is deflected to a decay spectroscopy station (DSS). This consists of a rotating wheel implantation system for alpha- and beta-decay spectroscopy, and up to three germanium detectors around the implantation site for gamma-ray detection. Resonance ionization spectroscopy and the new technique of laser assisted nuclear decay spectroscopy have recently been performed at the CRIS beam line on the neutron-deficient francium isotopes. Here an overview of the two techniques will be presented, alongside a description of the CRIS beam line and DSS. (authors)
Preparation of Permalloy nanostructures using focused ion beam methods
International Nuclear Information System (INIS)
Focused ion beam (FIB) milling is a powerful and versatile tool for the maskless fabrication of structures and devices at micro- and nanometer scales. The approach is based on the milling and deposition capabilities of a focused ion beam, where the latter is achieved by ion-beam-assisted decomposition of a metalorganic gas precursor of the specific material that has to be deposited. The combination of FIB and scanning electron microscopy in the same unit (so-called dual-beam unit) further expands the capabilities of the approach by the possibility of performing electron-beam-assisted deposition and inspection. Permalloy nanowires with electrical contacts patterned by FIB-Pt deposition were prepared in the dual-beam unit. Various types of notches to pin magnetic domain walls were additionally fabricated by means of FIB. The fabrication parameters for a structural modification of the Permalloy structures without too strongly affecting the material properties were determined previously. Magnetic force microscopy was employed for an observation of the resulting magnetic domain structures.
LHCb: A novel method for an absolute luminosity measurement at LHCb using beam-gas imaging
Barschel, C
2013-01-01
A novel technique to measure the absolute luminosity at the Large Hadron Collider (LHC) using beam-gas interactions has been successfully used in the LHCb experiment. A gas injection device (SMOG) has been installed in the LHCb experiment to increase the pressure around the interaction point during dedicated fills. The Beam Gas Imaging method (BGI) has now the potential to surpass the accuracy of the commonly used van der Meer scan method (VDM). This poster presents the principles of the Beam Gas Imaging method used to measure the beam overlap integral. Furthermore the gas injection increased the accuracy measurement of the so-called ghost charges and also intensities per bunch.
Analytical examination of a spiral beam scanning method for uniform irradiation
Energy Technology Data Exchange (ETDEWEB)
Fukuda, Mitsuhiro; Okumura, Susumu; Arakawa, Kazuo [Japan Atomic Energy Research Inst., Takasaki, Gunma (Japan). Takasaki Radiation Chemistry Research Establishment
1997-03-01
A new circular beam scanning method for uniform irradiation of high-energy, intense ion beams over a large area has been developed. A sweeping speed and a trajectory density in a radial direction are kept constant to obtain uniform fluence distribution. A radial position of a beam spot on a target and an angular frequency of the circular motion are expressed by an irrational function of time. The beam is swept continuously, and a beam trajectory becomes spiral. More than 90 % uniformity of the fluence distribution can been achieved over a large area. (author)
Investigation of the transverse beam dynamics in the thermal wave model with a functional method
Jang, Ji-Ho; Cho, Yong-sub; Kwon, Hyeok-jung
2006-01-01
We investigated the transverse beam dynamics in a thermal wave model by using a functional method. It can describe the beam optical elements separately with a kernel for a component. The method can be applied to general quadrupole magnets beyond a thin lens approximation as well as drift spaces. We found that the model can successfully describe the PARMILA simulation result through an FODO lattice structure for the Gaussian input beam without space charge effects.
Free Vibration Analysis of Laminated Composite Beams Using Differential Quadrature Method
Institute of Scientific and Technical Information of China (English)
冯丽娟; 钟宏志; 郝照平; 吴德隆
2002-01-01
A higher-order theory for laminated composite beams is used to study the free vibration of laminated composite beams, and the differential quadrature method is employed to obtain the numerical solution of the governing differential equations. Free vibration analysis of beams with rectangular cross-section for various combinations of end conditions is studied. The results show that the differential quadrature method is reliable and accurate compared with other available results.
GÖKDAĞ, Hakan
2013-01-01
In this work a crack identification method for beam type structures under moving vehicle is proposed. The basic of the method is to formulate damage detection as an inverse problem, and solve for damage locations and extents. To this end, an objective function is defined based on the difference of damaged beam dynamic response and the response calculated by the mathematical model of the beam. The optimization problem is solved through a popular evolutionary algorithm, i.e. the particle swarm ...
Method for traveling-wave deceleration of buffer-gas beams of CH
Fabrikant, M. I.; Li, Tian; Fitch, N J; N. Farrow; Weinstein, Jonathan D.; Lewandowski, H. J.
2013-01-01
Cryogenic buffer-gas beams are a promising method for producing bright sources of cold molecular radicals for cold collision and chemical reaction experiments. In order to use these beams in studies of reactions with controlled collision energies, or in trapping experiments, one needs a method of controlling the forward velocity of the beam. A Stark decelerator can be an effective tool for controlling the mean speed of molecules produced by supersonic jets, but efficient deceleration of buffe...
On the absorbed dose determination method in high energy electrons beams
International Nuclear Information System (INIS)
The absorbed dose determination method in water for electron beams with energies in the range from 1 MeV to 50 MeV is presented herein. The dosimetry equipment for measurements is composed of an UNIDOS.PTW electrometer and different ionization chambers calibrated in air kerma in a Co60 beam. Starting from the code of practice for high energy electron beams, this paper describes the method adopted by the secondary standard dosimetry laboratory (SSDL) in NILPRP - Bucharest
International Nuclear Information System (INIS)
We report the application of molecular tagging velocimetry (MTV) toward two-component velocimetry as demonstrated in an underexpanded free jet flowfield. Two variants of the MTV technique are presented: 1) electronic excitation of seeded nitric oxide (NO) with gated fluorescence imaging (fluorescence lifetime) and 2) photodissociation of seeded NO2 followed by NO fluorescence imaging (NO2 photodissociation). The seeded NO fluorescence lifetime technique is advantageous in low-quenching, high-velocity flowfields, while the photodissociation technique is useful in high-quenching environments, and either high- or low-velocity flowfields due to long lifetime of the NO photoproduct. Both techniques are viable for single-shot measurements, with determined root mean squared results for streamwise and radial velocities of ∼5%. This study represents the first known application of MTV utilizing either the fluorescence lifetime or the photodissociation technique toward two-component velocity mapping in a gaseous flowfield. Methods for increasing the spatial resolution to be comparable to particle-based tracking techniques are discussed.
Orientation dependence in the reaction of Xe* with photodissociation polarized IBr
International Nuclear Information System (INIS)
The reaction of metastable Xe* with IBr to produce XeI* and XeBr* excimers was studied in crossed molecular beams. The IBr beam was rotationally polarized by using laser photodissociation to selectively remove most of the M state distribution. The reaction cross section was found to be largest when the Xe* approaches parallel to the plane of rotation of the IBr, and smallest when the Xe* approaches perpendicular to the plane of rotation. Reaction models for excimer formation are discussed, and it is concluded that the observed steric effect results from the anisotropy of the ionic Xe+/IBr-(2Pi) potential surface, involving the first excited state of IBr-, which is the intermediate state in the formation of XeI*
Comparison of methods of producing very highly stripped uranium beams
International Nuclear Information System (INIS)
A comparison is made between the production of high intensity beams of helium-like uranium ions, U90+, by conventional and exotic ion sources, and by the foil stripping of highly accelerated ions output from the Bevalac. The parameter requirements are specified and compared to the parameters achievable by present day ion source technology. The EBIS (Electron Beam Ion Source) comes closest to satisfying the necessary parameters, and this possibility is considered in some detail. We conclude that existing and near-future ion source technology does not provide a means of production of high intensity U90+ beams. Foil stripping of lower charge state species that have been accelerated through the Bevalac provides a convenient approach
An interpretation and guide to single-pass beam shaping methods using SLMs and DMDs
Stilgoe, Alexander B.; Kashchuk, Anatolii V.; Preece, Daryl; Rubinsztein-Dunlop, Halina
2016-06-01
Exquisite manipulations of light can be performed with devices such as spatial light modulators (SLMs) and digital micromirror devices (DMDs). These devices can be used to simulate transverse paraxial beam wavefunction eigenstates such as the Hermite–Laguerre–Gaussian mode families. We investigate several beam shaping methods in terms of the wavefunctions of scattered light. Our analysis of the efficiency, behaviour and limitations of beam shaping methods is applied to both theory and experiment. The deviation from the ideal output from a valid beam shaping method is shown to be due to experimental factors which are not necessarily being accounted for. Incident beam mode shape, aberration, and the amplitude/phase transfer functions of the DMD and SLM impact the distribution of scattered light and hence the effectiveness and efficiency of a beam shaping method. Correcting for these particular details of the optical system accounts for all differences in efficiency and mode fidelity between experiment and theory. We explicitly show the impact of experimental parameter variations so that these problems may be diagnosed and corrected in an experimental beam shaping apparatus. We show that several beam shaping methods can be used for the production of beam modes in a single pass and the choice is based on the particular experimental conditions.
Theoretical study of ultraviolet induced photodissociation dynamics of sulfuric acid
Energy Technology Data Exchange (ETDEWEB)
Murakami, Tatsuhiro; Ohta, Ayumi; Suzuki, Tomoya; Ikeda, Kumiko [Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioi-Cho, Chiyoda-ku, Tokyo 102-8554 (Japan); Danielache, Sebastian O. [Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioi-Cho, Chiyoda-ku, Tokyo 102-8554 (Japan); Earth-Life Science Institute (ELSI), Tokyo Institute of Technology (Japan); Department of Environmental Science and Techonology, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Yoohama 226-8502 (Japan); Nanbu, Shinkoh, E-mail: shinkoh.nanbu@sophia.ac.jp [Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioi-Cho, Chiyoda-ku, Tokyo 102-8554 (Japan)
2015-05-01
Highlights: • Photodissociation dynamics of H{sub 2}SO{sub 4} at low-lying electronically excited states were investigated. • Photochemical processes were simulated by on-the-fly ab initio MD. • Sulfuric acid after the excitation to the S{sub 1} state dissociated to HSO{sub 4}(1{sup 2}A″) + H({sup 2}S). • Sulfuric acid after the excitation to the S{sub 2} state dissociated to HSO{sub 4}(2{sup 2}A″) + H({sup 2}S). • The energy region of the UV spectra where NMD fractionation may occur is predicted. - Abstract: Photodissociation dynamics of sulfuric acid after excitation to the first and second excited states (S{sub 1} and S{sub 2}) were studied by an on-the-fly ab initio molecular dynamics simulations based on the Zhu–Nakamura version of the trajectory surface hopping (ZN-TSH). Forces acting on the nuclear motion were computed on-the-fly by CASSCF method with Dunning’s augmented cc-pVDZ basis set. It was newly found that the parent molecule dissociated into two reaction-channels (i) HSO{sub 4}(1{sup 2}A″) + H({sup 2}S) by S{sub 1}-excitation, and (ii) HSO{sub 4}(2{sup 2}A″) + H({sup 2}S) by S{sub 2}-excitation. The direct dissociation dynamics yield products different from the SO{sub 2} + 2OH fragments often presented in the literature. Both channels result in the same product and differs only in the electronic state of the HSO{sub 4} fragment{sub .} The trajectories running on S{sub 2} do not hop with S{sub 0} and a nonadiabatic transition happens at the S{sub 2}–S{sub 1} conical intersection located at a longer OH bond-length than the S{sub 1}–S{sub 0} intersection producing an electronic excited state (2{sup 2}A″) of HSO{sub 4} product.
Photodissociation of Cerium Oxide Nanocluster Cations.
Akin, S T; Ard, S G; Dye, B E; Schaefer, H F; Duncan, M A
2016-04-21
Cerium oxide cluster cations, CexOy(+), are produced via laser vaporization in a pulsed nozzle source and detected with time-of-flight mass spectrometry. The mass spectrum displays a strongly preferred oxide stoichiometry for each cluster with a specific number of metal atoms x, with x ≤ y. Specifically, the most prominent clusters correspond to the formula CeO(CeO2)n(+). The cluster cations are mass selected and photodissociated with a Nd:YAG laser at either 532 or 355 nm. The prominent clusters dissociate to produce smaller species also having a similar CeO(CeO2)n(+) formula, always with apparent leaving groups of (CeO2). The production of CeO(CeO2)n(+) from the dissociation of many cluster sizes establishes the relative stability of these clusters. Furthermore, the consistent loss of neutral CeO2 shows that the smallest neutral clusters adopt the same oxidation state (IV) as the most common form of bulk cerium oxide. Clusters with higher oxygen content than the CeO(CeO2)n(+) masses are present with much lower abundance. These species dissociate by the loss of O2, leaving surviving clusters with the CeO(CeO2)n(+) formula. Density functional theory calculations on these clusters suggest structures composed of stable CeO(CeO2)n(+) cores with excess oxygen bound to the surface as a superoxide unit (O2(-)). PMID:27035210
Magnetic Field Strengths in Photodissociation Regions
Balser, Dana S; Jeyakumar, S; Bania, T M; Montet, Benjamin T; Shitanishi, J A
2015-01-01
We measure carbon radio recombination line (RRL) emission at 5.3 GHz toward four HII regions with the Green Bank Telescope (GBT) to determine the magnetic field strength in the photodissociation region (PDR) that surrounds the ionized gas. Roshi (2007) suggests that the non-thermal line widths of carbon RRLs from PDRs are predominantly due to magneto-hydrodynamic (MHD) waves, thus allowing the magnetic field strength to be derived. We model the PDR with a simple geometry and perform the non-LTE radiative transfer of the carbon RRL emission to solve for the PDR physical properties. Using the PDR mass density from these models and the carbon RRL non-thermal line width we estimate total magnetic field strengths of B ~ 100-300 micro Gauss in W3 and NGC6334A. Our results for W49 and NGC6334D are less well constrained with total magnetic field strengths between B ~ 200-1000 micro Gauss. HI and OH Zeeman measurements of the line-of-sight magnetic field strength (B_los), taken from the literature, are between a facto...
A Photodissociation Region study of NGC 4038
Bisbas, T G; Viti, S; Barlow, M J; Yates, J; Vasta, M
2014-01-01
We present a model of the photodissociation regions of NGC 4038, which is part of the Antennae galaxies. We have considered one-dimensional slabs of uniform density all having a maximum $A_V=10\\,{\\rm mag}$, interacting with plane-parallel radiation. The density range in our simulations spans four orders of magnitude ($100\\le n\\le 10^6\\,{\\rm cm}^{-3}$) and the UV field strength spans more than three orders of magnitude ($10\\le\\chi\\le10^{4.5}$ multiples of the ${\\rm Draine}$ field), from which we generated a grid of about 1400 simulations. We compare our results with Herschel SPIRE-FTS, CSO and ISO-LWS observations of eight CO transition lines ($J=1-0$ to $8-7$) and the [CI] 609\\mu m and [OI] 146\\mu m fine structure lines. We find that the molecular and atomic emission lines trace different gas components of NGC 4038, thus single emission models are insufficient to reproduce the observed values. In general, low-$J$ CO transition lines correspond to either low density regions interacting with low UV field streng...
Photoevaporation of Clumps in Photodissociation Regions
Gorti, U; Gorti, Uma; Hollenbach, David
2002-01-01
We present the results of an investigation of the effects of Far Ultraviolet (FUV) radiation from hot early type OB stars on clumps in star-forming molecular clouds. Clumps in Photodissociation regions (PDRs) undergo external heating which, if rapid, creates strong photoevaporative mass flows off the clump surfaces, and drives shocks into the clumps, compressing them to high densities. The clumps lose mass on relatively short timescales. The evolution of an individual clump is found to be sensitive to its initial colunm density, the temperature of the heated surface and the ratio of the ``turn-on time'' $t_{FUV}$ of the heating flux on a clump to its initial sound crossing-time $t_{c}$. In this paper, we use spherical 1-D numerical hydrodynamic models as well as approximate analytical models to study the evolution of turbulence-generated and pressure-confined clumps in PDRs. Turbulent clumps evolve so that their column densities are equal to a critical value determined by the local FUV field, and typically ha...
Ultraviolet photodissociation dynamics of the phenyl radical
International Nuclear Information System (INIS)
Ultraviolet (UV) photodissociation dynamics of jet-cooled phenyl radicals (C6H5 and C6D5) are studied in the photolysis wavelength region of 215-268 nm using high-n Rydberg atom time-of-flight and resonance enhanced multiphoton ionization techniques. The phenyl radicals are produced from 193-nm photolysis of chlorobenzene and bromobenzene precursors. The H-atom photofragment yield spectra have a broad peak centered around 235 nm and are in good agreement with the UV absorption spectra of phenyl. The H + C6H4 product translational energy distributions, P(ET)'s, peak near ∼7 kcal/mol, and the fraction of average translational energy in the total excess energy, T>, is in the range of 0.20-0.35 from 215 to 268 nm. The H-atom product angular distribution is isotropic. The dissociation rates are in the range of 107-108 s-1 with internal energy from 30 to 46 kcal/mol above the threshold of the lowest energy channel H +o-C6H4 (ortho-benzyne), comparable with the rates from the Rice-Ramsperger-Kassel-Marcus theory. The results from the fully deuterated phenyl radical are identical. The dissociation mechanism is consistent with production of H +o-C6H4, as the main channel from unimolecular decomposition of the ground electronic state phenyl radical following internal conversion of the electronically excited state.
International Nuclear Information System (INIS)
Purpose/Objective: Many clinical situations indicate that an electron beam with a modified dose profile, i.e., tilted, concave or other shape is useful for the treatment with a curved, oblique or other non-flat skin surface. The well known difficulty in electron beam dose profile modification is the energy degradation while using absorbers with different thickness, such as wedge shape filter, similar to photon wedges. In this presentation, we describe the principle and applications of an iso-energetic electron beam intensity modulation method, a general technique which can be used to modified the intensity of a static electron field with virtually no alteration of the original beam energy. Materials and Methods: Due to the Coulomb multiple-scattering effect in air medium, Gaussian spread in air of the electron beam broadens with increasing distance from the source. Two narrow parallel electron beams with limited separation will join together as one composite distribution at certain distance from the source. Based on this physical principle, the intensity distribution of a broad electron beam can be modulated into different shapes by dividing the broad beam into a plurality of narrow slit electron beams with different spatial separation. With an adequate distance, these narrow electron beams merge to form a profile with desired shape and smoothness. Since an intensity modulated electron beam results from the plurality of narrow electron beams which have the same energy characteristics, the modulated beam will have the same energy as the original open beam. The applications of this new technique include the constructions of iso-energetic electron beam 'wedge' filters, concave filters (for dome shape skin surface such as skull), flattening filters for total skin treatment at an extended SSD, linac internal electron beam scattering/flattening filter, and other general electron beam compensating filters for irregular skin surface. Results: Several iso-energetic electron
Radiogram enhancement and linearization using the beam hardening correction method
Czech Academy of Sciences Publication Activity Database
Vavřík, Daniel; Jakůbek, J.
2009-01-01
Roč. 607, - (2009), s. 212-214. ISSN 0168-9002. [International Workshop on Radiation Imaging Detectors. Helsinky, 29.06.2008-03.07.2008] Institutional research plan: CEZ:AV0Z20710524 Keywords : beam hardening correction * flat-field correction * digital radiography Subject RIV: JB - Sensors, Measurment, Regulation Impact factor: 1.317, year: 2009
A new method for RF power generation for two-beam linear colliders
International Nuclear Information System (INIS)
In this paper we discuss a new approach to two-beam acceleration. The energy for RF production is initially stored in a long-pulse electron beam which is efficiently accelerated to about 1.2 GeV by a fully loaded, conventional, low frequency (∼1 GHz) linac. The beam pulse length is twice the length of the high-gradient linac. Segments of this long pulse beam are compressed using combiner rings to create a sequence of higher peak power drive beams with gaps in between. This train of drive beams is distributed from the end of the linac against the main beam direction down a common transport line so that each drive beam can power a section of the main linac. After a 180-degree turn, each high-current, low-energy drive beam is decelerated in low-impedance decelerator structures, and the resulting power is used to accelerate the low-current, high-energy beam in the main linac. The method discussed here seems relatively inexpensive, is very flexible and can be used to accelerate beams for linear colliders over the entire frequency and energy range
Shishlo, A.; Aleksandrov, A.
2013-06-01
A new method of measuring of the rms longitudinal Twiss parameters of a beam in linear accelerators is presented. It is based on using sum signals from beam position monitors sensitive to the longitudinal charge distribution in the bunch. The applicability of the method is demonstrated on the superconducting section of the Oak Ridge Spallation Neutron Source linear accelerator. The results are compared to a direct measurement of the bunch longitudinal profiles using an interceptive bunch shape monitor in the linac warm section of the same accelerator. Limitations of the method are discussed. The method is fast and simple, and can be used to obtain the initial parameters for the longitudinal matching in linear accelerators where interceptive diagnostics are not desirable.
Matrix method and program design of intense beam transport in quadrupole magnet
International Nuclear Information System (INIS)
It is very difficult to calculate the nonlinear transport of a intense beam,because the particle trajectories depend on the electric potentials excited by the particle beams, and the electric potentials of the beams depend on the particle trajectories and the particle distributions in the phase spaces. So, it is necessary to solve the problem by iterations to get self-consistent solutions. We use transport matrix method to analyze the transportation in quadrupole magnet of non-intense pulsed beam and intense pulsed beam respectively, and write a computer code for the pulsed beam transporting in quadrupole magnet. The self-consistent solution can obtained by using iteration calculation method. During the calculation, the result can be shown by the prompt graph. (authors)
A new method of rapid power measurement for MW-scale high-current particle beams
Energy Technology Data Exchange (ETDEWEB)
Xu, Yongjian, E-mail: yjxu@ipp.ac.cn; Hu, Chundong; Xie, Yuanlai; Liu, Zhimin; Xie, Yahong; Liu, Sheng; Liang, Lizheng; Jiang, Caichao; Sheng, Peng; Yu, Ling
2015-09-21
MW-scale high current particle beams are widely applied for plasma heating in the magnetic confinement fusion devices, in which beam power is an important indicator for efficient heating. Generally, power measurement of MW-scale high current particle beam adopts water flow calorimetry (WFC). Limited by the principles of WFC, the beam power given by WFC is an averaged value. In this article a new method of beam power for MW-scale high-current particle beams is introduced: (1) the temperature data of thermocouples embedded in the beam stopping elements were obtained using high data acquire system, (2) the surface heat flux of the beam stopping elements are calculated using heat transfer, (3) the relationships between positions and heat flux were acquired using numerical simulation, (4) the real-time power deposited on the beam stopping elements can be calculated using surface integral. The principle of measurement was described in detail and applied to the EAST neutral beam injector for demonstration. The result is compared with that measured by WFC. Comparison of the results shows good accuracy and applicability of this measuring method.
A new method of rapid power measurement for MW-scale high-current particle beams
Xu, Yongjian; Hu, Chundong; Xie, Yuanlai; Liu, Zhimin; Xie, Yahong; Liu, Sheng; Liang, Lizheng; Jiang, Caichao; Sheng, Peng; Yu, Ling
2015-09-01
MW-scale high current particle beams are widely applied for plasma heating in the magnetic confinement fusion devices, in which beam power is an important indicator for efficient heating. Generally, power measurement of MW-scale high current particle beam adopts water flow calorimetry (WFC). Limited by the principles of WFC, the beam power given by WFC is an averaged value. In this article a new method of beam power for MW-scale high-current particle beams is introduced: (1) the temperature data of thermocouples embedded in the beam stopping elements were obtained using high data acquire system, (2) the surface heat flux of the beam stopping elements are calculated using heat transfer, (3) the relationships between positions and heat flux were acquired using numerical simulation, (4) the real-time power deposited on the beam stopping elements can be calculated using surface integral. The principle of measurement was described in detail and applied to the EAST neutral beam injector for demonstration. The result is compared with that measured by WFC. Comparison of the results shows good accuracy and applicability of this measuring method.
A calculation method of cracking moment for the high strength concrete beams under pure torsion
Indian Academy of Sciences (India)
Metin Husem; Ertekin Oztekin; Selim Pul
2011-02-01
In this study, a method is given to calculate cracking moments of high strength reinforced concrete beams under the effect of pure torsion. To determine the method, both elastic and plastic theories were used. In this method, dimensions of beam cross-section were considered besides stirrup and longitudinal reinforcements. Two plain high strength concrete (without reinforcement) and eight high strength reinforced concrete beams which have two different cross-sections (150 × 250 mm and 150 × 300 mm) were produced to examine the validity of the proposed method. The predictions of the proposed approach for the calculation of the cracking moment of beams under pure torsion were compared with the experimental and the analytical results of previous studies. From these comparisons it is concluded that the predictions of the proposed equations for the cracking moment of plain and reinforced high strength concrete beams under pure torsion are closer to the experimental data compared to the analytical results of previous theories.
Comparative study of beam losses and heat loads reduction methods in MITICA beam source
Energy Technology Data Exchange (ETDEWEB)
Sartori, E., E-mail: emanuele.sartori@igi.cnr.it; Agostinetti, P.; Dal Bello, S.; Marcuzzi, D.; Serianni, G.; Veltri, P. [Consorzio RFX, Euratom-ENEA association, C.so Stati Uniti 4, 35127 Padova (Italy); Sonato, P. [Consorzio RFX, Euratom-ENEA association, C.so Stati Uniti 4, 35127 Padova (Italy); Dipartimento di Ingegneria Elettrica, Padova University, Via Gradenigo 6/a, 35131 Padova (Italy)
2014-02-15
In negative ion electrostatic accelerators a considerable fraction of extracted ions is lost by collision processes causing efficiency loss and heat deposition over the components. Stripping is proportional to the local density of gas, which is steadily injected in the plasma source; its pumping from the extraction and acceleration stages is a key functionality for the prototype of the ITER Neutral Beam Injector, and it can be simulated with the 3D code AVOCADO. Different geometric solutions were tested aiming at the reduction of the gas density. The parameter space considered is limited by constraints given by optics, aiming, voltage holding, beam uniformity, and mechanical feasibility. The guidelines of the optimization process are presented together with the proposed solutions and the results of numerical simulations.
International Nuclear Information System (INIS)
The vibrational to translational (V→T) energy transfer in collisions between large highly vibrationally excited polyatomics and rare gases was investigated by time-of-flight techniques. Two different methods, UV excitation followed by intemal conversion and infrared multiphoton excitation (IRMPE), were used to form vibrationally excited molecular beams of hexafluorobenzene and sulfur hexafluoride, respectively. The product translational energy was found to be independent of the vibrational excitation. These results indicate that the probability distribution function for V→T energy transfer is peaked at zero. The collisional relaxation of large polyatomic molecules with rare gases most likely occurs through a rotationally mediated process. Photodissociation of nitrobenzene in a molecular beam was studied at 266 nm. Two primary dissociation channels were identified including simple bond rupture to produce nitrogen dioxide and phenyl radical and isomerization to form nitric oxide and phenoxy radical. The time-of-flight spectra indicate that simple bond rupture and isomerization occurs via two different mechanisms. Secondary dissociation of the phenoxy radicals to carbon monoxide and cyclopentadienyl radicals was observed as well as secondary photodissociation of phenyl radical to give H atom and benzyne. A supersonic methyl radical beam source is developed. The beam source configuration and conditions were optimized for CH3 production from the thermal decomposition of azomethane. Elastic scattering of methyl radical and neon was used to differentiate between the methyl radicals and the residual azomethane in the molecular beam
Photodissociation spectroscopy of the dysprosium monochloride molecular ion
Dunning, Alexander; Showalter, Steven J; Puri, Prateek; Kotochigova, Svetlana; Hudson, Eric R
2015-01-01
We have performed a combined experimental and theoretical study of the photodissociation cross section of the molecular ion DyCl$^+$. The cross section for the photon energy range 35,500 cm$^{-1}$ to 47,500 cm$^{-1}$ is measured using an integrated ion trap and time-of-flight mass spectrometer, and we observe a broad, asymmetric profile that is peaked near 43,000 cm$^{-1}$. The theoretical cross section is determined from electronic potentials and transition dipole moments calculated using the relativistic configuration-interaction valence-bond and coupled-cluster methods. The electronic structure of DyCl$^+$ is unprecedentedly complex due to the presence of multiple open electronic shells, including 4f$^{10}$ orbitals. The molecule has nine attractive potentials with ionically-bonded electrons and 99 repulsive potentials dissociating to a ground state Dy$^+$ ion and Cl atom. We explain the lack of symmetry in the cross section as due to multiple contributions from one-electron-dominated transitions between t...
Ion Micro Beam, promising methods for interdisciplinary research
Cutroneo, M.; Havranek, V.; Torrisi, L.; Svecova, B.
2016-05-01
An increasing attractiveness of top-down nanotechnology using nuclear microprobe techniques have been gathered to the micro and nano patterning process for polymers. This paper presents the research activity on innovative promising techniques able to produce three- dimensional (3D) micro-structures in polymeric resists as well as to obtain images of fabricated nanostructures at Tandetron Laboratory (LT) of the Nuclear Physics Institute in Rez (Czech Republic). The Proton Beam Writing (PBW) technique was used to irradiate PMMA resist with energy of MeVs protons. The fabricated patterns were developed in chemical bath using different etching rates. An overview of micro-scale structures have been fabricated selecting the beam, the energy, the fluence and the exposition time. The produced structures were investigated by different analysis techniques among which Scanning Transmission Ion Microscopy (STIM). The characterizations of the fabricated microtunnels are presented and discussed.
Creation of biomaterials using the dual beam IBAD methods
International Nuclear Information System (INIS)
The Dual Beam Ion Assisted Deposition technique (IBAD) application for creation of the hard, biocompatible coating layers has been presented and discussed. As substrate the stainless steel, Ti, special titanium alloys, the Al2O3 or other solid materials can be used. Presently, the biocompatible coating layers such as DLC (Diamond Like Coating), β-SiC, TiC, hydroxyapatite and thin coating layer based on Ca, P, O, H have been prepared and investigated
Apparatus and methods for continuous beam fourier transform mass spectrometry
McLuckey, Scott A.; Goeringer, Douglas E.
2002-01-01
A continuous beam Fourier transform mass spectrometer in which a sample of ions to be analyzed is trapped in a trapping field, and the ions in the range of the mass-to-charge ratios to be analyzed are excited at their characteristic frequencies of motion by a continuous excitation signal. The excited ions in resonant motions generate real or image currents continuously which can be detected and processed to provide a mass spectrum.
Beam-cooling methods in the NICA project
Kostromin, S. A.; Meshkov, I. N.; Sidorin, A. O.; Smirnov, A. V.; Trubnikov, G. V.; Shurkhno, N.
2012-07-01
The Nuclotron-based Ion Collider Facility (NICA) is a new accelerator complex under construction at the Joint Institute for Nuclear Research (JINR) for experiments with colliding beams of heavy ions up to gold at energies as high as 4.5 × 4.5 GeV/u aimed at studying hot and dense strongly interacting nuclear matter and searching for possible indications of the mixed phase state and critical points of phase transitions. This facility comprises an ion source of the electron-string type, a 3-MeV/u linear accelerator, a 600-MeV/u superconducting booster synchrotron (Booster), a Nuclotron (upgraded superconducting synchrotron with a maximum energy of 4.5 GeV/u for ions with the charge-to-mass ratio Z/ A = 1/3), and a collider consisting of two vertically separated superconducting rings with an average luminosity of 1027 cm-2 s-1 in an energy range over 3.0 GeV/u. Beam cooling is supposed to be used in two NICA elements, the Booster, and the collider rings. The Booster is intended for the storage of 197Au31+ ions to an intensity of about 4 × 109 particles; their acceleration to the energy 600 MeV/u, which is sufficient for the complete stripping of nuclei (an increase in the injection energy and the charge state of ions makes the requirements for vacuum conditions in the Nuclotron less stringent); and the formation of the necessary beam emittance using the electron cooling system. Two independent beam-cooling systems, a stochastic one and an electron one, are supposed to be used in the collider. The parameters of the cooling systems, the optimum mode of operation for the collider, and the arrangement and design of the elements of the systems are discussed.
Institute of Scientific and Technical Information of China (English)
Changguo Wang; Huifeng Tan; Xingwen Du
2009-01-01
This paper extends Le van's work to the case of nonlinear problem and the complicated configuration. The wrinkling stress distribution and the pressure effects are also included in our analysis. Pseudo-beam method is presented based on the inflatable beam theory to model the inflatable structures as a set of inflatable beam elements with a pre-stressed state. In this method, the discretized nonlinear equations are given based upon the virtual work principle with a 3-node Timoshenko's beam model. Finite element simulation is performed by using a 3-node BEAM189 element incorporating ANSYS nonlinear program. The pressure effect is equivalent included in our method by modifying beam element cross-section parameters related to pressure. A benchmark example, the bending case of an inflatable cantilever beam, is performed to verify the accuracy of our pro-posed method. The comparisons reveal that the numerical results obtained with our method are close to open published analytical and membrane finite element results. The method is then used to evaluate the whole buckling and the load-carrying characteristics of an inflatable support frame subjected to a compression force. The wrinkling stress and region characteristics are also shown in the end. This method gives better convergence characteristics, and requires much less computation time. It is very effective to deal with the whole load-carrying ability analytical problems for large scale inflatable structures with complex configuration.
Method of temperature rising velocity and threshold control of electron beam brazing
Institute of Scientific and Technical Information of China (English)
Xuedong Wang; Shun Yao
2005-01-01
In order to accommodate electron beam to the brazing of the joints with various curve shapes and the brazing of thermo sensitive materials, the method of electron beam scanning and brazing temperature control was developed, in which electron beam was controlled to scan according to predefined scanning track, and the actual temperature rising velocity of the brazed seam was limited in an allowed scope by detecting the brazed seam temperature, calculating the temperature rising velocity and adjusting the beam current during the brazing process; in addition, through the setting of the highest allowed temperature, the actual temperature of the brazed seam could be controlled not exceeding the threshold set value, and these two methods could be employed alone or jointly. It is shown that high precision temperature control in electron beam brazing could be realized and the productivity be increased by the proposed method.
C{sub 60} in photodissociation regions
Energy Technology Data Exchange (ETDEWEB)
Castellanos, Pablo; Tielens, Alexander G.G.M. [Leiden Observatory, P.O. Box 9513, 2300 RA Leiden (Netherlands); Berné, Olivier [Université de Toulouse, UPS-OMP, IRAP, F-31400 Toulouse (France); Sheffer, Yaron; Wolfire, Mark G., E-mail: pablo@strw.leidenuniv.nl [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States)
2014-10-10
Recent studies have confirmed the presence of buckminsterfullerene (C{sub 60}) in different interstellar and circumstellar environments. However, several aspects regarding C{sub 60} in space are not yet well understood, such as the formation and excitation processes, and the connection between C{sub 60} and other carbonaceous compounds in the interstellar medium, in particular polycyclic aromatic hydrocarbons (PAHs). In this paper, we study several photodissociation regions (PDRs) where C{sub 60} and PAHs are detected and the local physical conditions are reasonably well constrained to provide observational insights into these questions. C{sub 60} is found to emit in PDRs where the dust is cool (T{sub d} = 20-40 K) and even in PDRs with cool stars. These results exclude the possibility for C{sub 60} to be locked in grains at thermal equilibrium in these environments. We observe that PAH and C{sub 60} emission are spatially uncorrelated and that C{sub 60} is present in PDRs where the physical conditions (in terms of radiation field and hydrogen density) allow for full dehydrogenation of PAHs, with the exception of Ced 201. We also find trends indicative of an increase in C{sub 60} abundance within individual PDRs, but these trends are not universal. These results support models where the dehydrogenation of carbonaceous species is the first step toward C{sub 60} formation. However, this is not the only parameter involved and C{sub 60} formation is likely affected by shocks and PDR age.
Ultraviolet photodissociation dynamics of the cyclohexyl radical
Lucas, Michael; Liu, Yanlin; Zhang, Jingsong
2015-03-01
Cycloalkanes are important components in conventional fuels and oil shale derived fuels and the combustion of cyclohexane fuels leads to the production of benzene, a pollutant precursor. One of the pathways from cyclohexane to benzene is through sequential hydrogen loss, including the cyclohexyl radical as an intermediate. The ultraviolet (UV) photodissociation dynamics of the cyclohexyl (c-C6H11) radical was studied for the first time using the high- n Rydberg atom time-of-flight (HRTOF) technique in the range of 232-262 nm. The translational energy distributions of the H-atom loss product channel, P (ET) 's, show a large translational energy release and a large fraction of average translational energy in the total excess energy, , from 232-262 nm. The H-atom product angular distribution is anisotropic with a positive β parameter. The most likely H-atom loss pathway is an axial H ejection from the β-carbon in cyclohexyl to form cyclohexene + H, which along with the positive β parameter, indicates that the transition dipole moment, μ, is perpendicular to the ring. The P (ET) and anisotropy of the H-atom loss product channel are significantly larger than those expected for a statistical unimolecular dissociation of a hot radical, indicating a non-statistical dissociation mechanism. The dissociation mechanism is consistent with direct dissociation on a repulsive excited state surface or on the repulsive part of the ground state surface to produce cyclohexene + H, possibly mediated by a conical intersection. Cyclohexyl is the largest radical so far showing a direct dissociation mechanism.
The application of Monte Carlo method to electron and photon beams transport
International Nuclear Information System (INIS)
The application of a Monte Carlo method to study a transport in matter of electron and photon beams is presented, especially for electrons with energies up to 18 MeV. The SHOWME Monte Carlo code, a modified version of GEANT3 code, was used on the CONVEX C3210 computer at Swierk. It was assumed that an electron beam is mono directional and monoenergetic. Arbitrary user-defined, complex geometries made of any element or material can be used in calculation. All principal phenomena occurring when electron beam penetrates the matter are taken into account. The use of calculation for a therapeutic electron beam collimation is presented. (author). 20 refs, 29 figs
Vieira, Tárcio A.; Zamboni-Rached, Michel; Gesualdi, Marcos R. R.
2014-03-01
In this paper we experimentally implement the spatial shape modeling of nondiffracting optical beams via computer generated holograms reconstructed optically by spatial light modulators. The results reported here are an experimental confirmation of the so-called Frozen Wave method, developed a few years ago. Optical beams of this type have potential applications in optical tweezers, medicine, atom guiding, remote sensing, etc.
A simple method for boosting the beam quality of commercial DPL
Institute of Scientific and Technical Information of China (English)
张光寅; 焦志勇; 颜彩繁; 丁欣; 张潮波; 张晓华; 顾学文; 宋峰
2003-01-01
A simple method for boosting the beam quality of a commercial laser diode pumped laser (DPL) is put forward.By keeping one of the mirrors unchanged and the moving the other mirror a proper distance away from the laser rod,high beam quality laser output is realized.
Fano interference and cross-section fluctuations in molecular photodissociation
International Nuclear Information System (INIS)
We derive an expression for the total photodissociation cross section of a molecule incorporating both direct and indirect processes that proceed through excited resonances, and show that it exhibits generalized Beutler-Fano line shapes. Assuming that the closed system can be modeled by random-matrix theory, we derive the statistical properties of the photodissociation cross section and find that they are significantly affected by the direct processes. In the limit of isolated resonances, we find that direct processes suppress the correlation hole of the cross-section autocorrelation function and lead to a maximum in the cross-section distribution
The photodissociation and reaction dynamics of vibrationally excited molecules
Energy Technology Data Exchange (ETDEWEB)
Crim, F.F. [Univ. of Wisconsin, Madison (United States)
1993-12-01
This research determines the nature of highly vibrationally excited molecules, their unimolecular reactions, and their photodissociation dynamics. The goal is to characterize vibrationally excited molecules and to exploit that understanding to discover and control their chemical pathways. Most recently the author has used a combination of vibrational overtone excitation and laser induced fluorescence both to characterize vibrationally excited molecules and to study their photodissociation dynamics. The author has also begun laser induced grating spectroscopy experiments designed to obtain the electronic absorption spectra of highly vibrationally excited molecules.
Photodissociation spectroscopy of the dysprosium monochloride molecular ion
Dunning, Alexander; Petrov, Alexander; Schowalter, Steven J.; Puri, Prateek; Kotochigova, Svetlana; Hudson, Eric R.
2015-01-01
We have performed a combined experimental and theoretical study of the photodissociation cross section of the molecular ion DyCl$^+$. The photodissociation cross section for the photon energy range 35,500 cm$^{-1}$ to 47,500 cm$^{-1}$ is measured using an integrated ion trap and time-of-flight mass spectrometer; we observe a broad, asymmetric profile that is peaked near 43,000 cm$^{-1}$. The theoretical cross section is determined from electronic potentials and transition dipole moments calcu...
SYSTEMATIC ERROR REDUCTION: NON-TILTED REFERENCE BEAM METHOD FOR LONG TRACE PROFILER.
Energy Technology Data Exchange (ETDEWEB)
QIAN,S.; QIAN, K.; HONG, Y.; SENG, L.; HO, T.; TAKACS, P.
2007-08-25
Systematic error in the Long Trace Profiler (LTP) has become the major error source as measurement accuracy enters the nanoradian and nanometer regime. Great efforts have been made to reduce the systematic error at a number of synchrotron radiation laboratories around the world. Generally, the LTP reference beam has to be tilted away from the optical axis in order to avoid fringe overlap between the sample and reference beams. However, a tilted reference beam will result in considerable systematic error due to optical system imperfections, which is difficult to correct. Six methods of implementing a non-tilted reference beam in the LTP are introduced: (1) application of an external precision angle device to measure and remove slide pitch error without a reference beam, (2) independent slide pitch test by use of not tilted reference beam, (3) non-tilted reference test combined with tilted sample, (4) penta-prism scanning mode without a reference beam correction, (5) non-tilted reference using a second optical head, and (6) alternate switching of data acquisition between the sample and reference beams. With a non-tilted reference method, the measurement accuracy can be improved significantly. Some measurement results are presented. Systematic error in the sample beam arm is not addressed in this paper and should be treated separately.
Stability Analysis of Some Nonlinear Feedback Control Methods for Beam Halo-Chaos Suppression
Institute of Scientific and Technical Information of China (English)
FANG Jin-Qing; WANG Zhong-Sheng; CHEN Guan-Rong
2004-01-01
Control of beam halo-chaos has been a very challenging subject for research in recent years, in which some nonlinear feedback methods have been developed for suppression of beam halo-chaos in high-current proton linear accelerators. However, stability analysis of such successful nonlinear feedback control methods has not yet been rigorously carried out, which remains an important open topic in the field. In this letter, we present a rigorous mathematical analysis of several nonlinear feedback control methods that are applied to control beam halo-chaos with great success on simulations.
Stability Analysis of Some Nonlinear Feedback Control Methods for Beam Halo-ChaosSuppression
Institute of Scientific and Technical Information of China (English)
FANGJin-Qing; WANGZhong-Sheng; CHENGuan-Rong
2004-01-01
Control of beam halo-chaos has been a very challenging subject for research in recent years, in which some nonlinear feedback methods have been developed for suppression of beam halo-chaos in high-current proton linear accelerators. However, stability analysis of such successful nonlinear feedback control methods has not yet been rigorously carried out, which remains an important open topic in the field. In this letter, we present a rigorous mathematical analysis of several nonlinear feedback control methods that are applied to control beam halo-chaos with great success on simulations.
You, Oubo; Bai, Benfeng; Wu, Xiaoyu; Zhu, Zhendong; Wang, Qixia
2015-12-01
The efficient steering of surface plasmon polariton (SPP) fields is a vital issue in various plasmonic applications, such as plasmonic circuitry. We present a straightforward and efficient method for generating unidirectionally propagating SPP beams with arbitrary amplitude and phase profiles by manipulating Δ-shaped nanoantennas. As an example, a second-order Hermite-Gauss SPP beam is generated with this method. The near-field distribution of the generated SPP beam is experimentally characterized to validate the effectiveness of the method. PMID:26625032
A new method for improving beam quality of LINAC
International Nuclear Information System (INIS)
The principle of the self-adaptive feed-forward (SAFF) control to improve the beam quality of linac is introduced. the analytical procedure for calculating the control signals, the structure of a practical control system, and applications of SAFF in klystron, RF gun, and linac are presented, especially the application in the thermionic gun whose response is non-linear, time-variant and of large time-delay. The described control system is operational and some primary experimental results have been obtained, including the control of amplitude and phase fluctuations of the klystron output, the microwave field in the gun cavity and linac
International Nuclear Information System (INIS)
The University of Maryland Dynamical Systems and Accelerator Theory Group has been carrying out long-term research work in the general area of Dynamical Systems with a particular emphasis on applications to Accelerator Physics. This work is broadly divided into two tasks: Charged Particle Beam Transport and the Computation of Electromagnetic Fields and Beam-Cavity Interactions. Each of these tasks is described briefly. Work is devoted both to the development of new methods and the application of these methods to problems of current interest in accelerator physics including the theoretical performance of present and proposed high energy machines. In addition to its research effort, the Dynamical Systems and Accelerator Theory Group is actively engaged in the education of students and postdoctoral research associates
Accurate finite difference beam propagation method for complex integrated optical structures
DEFF Research Database (Denmark)
Rasmussen, Thomas; Povlsen, Jørn Hedegaard; Bjarklev, Anders Overgaard
1993-01-01
A simple and effective finite-difference beam propagation method in a z-varying nonuniform mesh is developed. The accuracy and computation time for this method are compared with a standard finite-difference method for both the 3-D and 2-D versions......A simple and effective finite-difference beam propagation method in a z-varying nonuniform mesh is developed. The accuracy and computation time for this method are compared with a standard finite-difference method for both the 3-D and 2-D versions...
Three-beam interferogram analysis method for surface flatness testing of glass plates and wedges
Sunderland, Zofia; Patorski, Krzysztof
2015-09-01
When testing transparent plates with high quality flat surfaces and a small angle between them the three-beam interference phenomenon is observed. Since the reference beam and the object beams reflected from both the front and back surface of a sample are detected, the recorded intensity distribution may be regarded as a sum of three fringe patterns. Images of that type cannot be succesfully analyzed with standard interferogram analysis methods. They contain, however, useful information on the tested plate surface flatness and its optical thickness variations. Several methods were elaborated to decode the plate parameters. Our technique represents a competitive solution which allows for retrieval of phase components of the three-beam interferogram. It requires recording two images: a three-beam interferogram and the two-beam one with the reference beam blocked. Mutually subtracting these images leads to the intensity distribution which, under some assumptions, provides access to the two component fringe sets which encode surfaces flatness. At various stages of processing we take advantage of nonlinear operations as well as single-frame interferogram analysis methods. Two-dimensional continuous wavelet transform (2D CWT) is used to separate a particular fringe family from the overall interferogram intensity distribution as well as to estimate the phase distribution from a pattern. We distinguish two processing paths depending on the relative density of fringe sets which is connected with geometry of a sample and optical setup. The proposed method is tested on simulated data.
Dynamic modeling and analysis of the PZT-bonded composite Timoshenko beams: Spectral element method
Lee, Usik; Kim, Daehwan; Park, Ilwook
2013-03-01
The health of thin laminated composite beams is often monitored using the ultrasonic guided waves excited by wafer-type piezoelectric transducers (PZTs). Thus, for the smart composite beams which consist of a laminated composite base beam and PZT layers, it is very important to develop a very reliable mathematical model and to use a very accurate computational method to predict accurate dynamic characteristics at very high ultrasonic frequency. In this paper, the axial-bending-shear-lateral contraction coupled differential equations of motion are derived first by the Hamilton's principle with Lagrange multipliers. The smart composite beam is represented by a Timoshenko beam model by adopting the first-order shear deformation theory (FSDT) for the laminated composite base beam. The axial deformation of smart composite beam is improved by taking into account the effects of lateral contraction by adopting the concept of Mindlin-Herrmann rod theory. The spectral element model is then formulated by the variation approach from coupled differential equations of motion transformed into the frequency domain via the discrete Fourier transform. The high accuracy of the present spectral element model is verified by comparing with other solution methods: the finite element model developed in this paper and the commercial FEA package ANSYS. Finally the dynamics and wave characteristics of some example smart composite beams are investigated through the numerical studies.
A finite element beam propagation method for simulation of liquid crystal devices
Vanbrabant, P. J. M.; Beeckman, J.; Neyts, K.; James, R.; Fernandez, F. A.
2009-01-01
An efficient full-vectorial finite element beam propagation method is presented that uses higher order vector elements to calculate the wide angle propagation of an optical field through inhomogeneous, anisotropic optical materials such as liquid crystals. The full dielectric permittivity tensor is considered in solving Maxwell's equations. The wide applicability of the method is illustrated with different examples: the propagation of a laser beam in a uniaxial medium, the tunability of a dir...
Chou, Chia-Chun
2014-03-14
The complex quantum Hamilton-Jacobi equation-Bohmian trajectories (CQHJE-BT) method is introduced as a synthetic trajectory method for integrating the complex quantum Hamilton-Jacobi equation for the complex action function by propagating an ensemble of real-valued correlated Bohmian trajectories. Substituting the wave function expressed in exponential form in terms of the complex action into the time-dependent Schrödinger equation yields the complex quantum Hamilton-Jacobi equation. We transform this equation into the arbitrary Lagrangian-Eulerian version with the grid velocity matching the flow velocity of the probability fluid. The resulting equation describing the rate of change in the complex action transported along Bohmian trajectories is simultaneously integrated with the guidance equation for Bohmian trajectories, and the time-dependent wave function is readily synthesized. The spatial derivatives of the complex action required for the integration scheme are obtained by solving one moving least squares matrix equation. In addition, the method is applied to the photodissociation of NOCl. The photodissociation dynamics of NOCl can be accurately described by propagating a small ensemble of trajectories. This study demonstrates that the CQHJE-BT method combines the considerable advantages of both the real and the complex quantum trajectory methods previously developed for wave packet dynamics. PMID:24628169
Energy Technology Data Exchange (ETDEWEB)
Chou, Chia-Chun, E-mail: ccchou@mx.nthu.edu.tw [Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan (China)
2014-03-14
The complex quantum Hamilton-Jacobi equation-Bohmian trajectories (CQHJE-BT) method is introduced as a synthetic trajectory method for integrating the complex quantum Hamilton-Jacobi equation for the complex action function by propagating an ensemble of real-valued correlated Bohmian trajectories. Substituting the wave function expressed in exponential form in terms of the complex action into the time-dependent Schrödinger equation yields the complex quantum Hamilton-Jacobi equation. We transform this equation into the arbitrary Lagrangian-Eulerian version with the grid velocity matching the flow velocity of the probability fluid. The resulting equation describing the rate of change in the complex action transported along Bohmian trajectories is simultaneously integrated with the guidance equation for Bohmian trajectories, and the time-dependent wave function is readily synthesized. The spatial derivatives of the complex action required for the integration scheme are obtained by solving one moving least squares matrix equation. In addition, the method is applied to the photodissociation of NOCl. The photodissociation dynamics of NOCl can be accurately described by propagating a small ensemble of trajectories. This study demonstrates that the CQHJE-BT method combines the considerable advantages of both the real and the complex quantum trajectory methods previously developed for wave packet dynamics.
Pickup and Photodissociation of Hydrogen Halides in Floppy Neon Clusters
Czech Academy of Sciences Publication Activity Database
Slavíček, Petr; Jungwirth, Pavel; Lewerenz, M.; Nahler, N. H.; Fárnik, M.; Buck, U.
2003-01-01
Roč. 107, - (2003), s. 7743-7754. ISSN 1089-5639 R&D Projects: GA MŠk LN00A032 Institutional research plan: CEZ:AV0Z4040901 Keywords : photodissociation * neon clusters Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.792, year: 2003
Giant enhancement of photodissociation of polar dimers in electric fields
González-Férez, R.; Schmelcher, P.
2011-01-01
We explore the photodissociation of polar dimers in static electric fields in the cold regime using the example of the LiCs molecule. A giant enhancement of the differential cross section is found for laboratory electric field strengths, and analyzed with varying rovibrational bound states, continuum energies as well as field strengths.
Combining UV photodissociation with electron transfer for peptide structure analysis
Czech Academy of Sciences Publication Activity Database
Shaffer, C. J.; Marek, Aleš; Pepin, R.; Slováková, K.; Tureček, F.
2015-01-01
Roč. 50, č. 3 (2015), s. 470-475. ISSN 1076-5174 Institutional support: RVO:61388963 Keywords : electron transfer dissociation * laser photodissociation * peptide ions * cation radical * chromophores * isomer distinction Subject RIV: CE - Biochemistry Impact factor: 2.379, year: 2014
Classical trajectory study of the photodissociation spectrum of H+3
International Nuclear Information System (INIS)
The photodissociation spectrum of H+3 is studied using classical mechanical methods. Tunneling rates and product translational energies are computed for a large range of total angular momentum and energy. We predict that the experimentally measured spectrum of Carrington and Kennedy is dominated by low total angular momentum and low energy (relative to dissociation). There is an almost one to one correspondence between the measured product translational energy and the total angular momentum. The classical dipole spectrum of chaotic trajectories is found to be relatively structureless, changes slowly with total J, and does not show any correspondence or indication of the experimentally measured regular structure found in the coarse grained spectrum. We conclude that the regularity found in the coarse grained spectrum should be associated with a stable manifold of trajectories. We find that the horseshoe periodic orbit previously found to be stable at J = 0 exists also for nonzero J and is stable with respect to small perturbations in 3D. The rotational constant of the rotating horseshoe is 30 cm-1 in interesting agreement with the experiment. The properties of the rotating horseshoe are studied in detail, a novel adiabatic switching method is used to study the stability of the orbit. A quantum formalism of Taylor and Zakrzewski that shows how periodic orbits may cause structure in quantal spectra is used to indicate why the features of the rotating horseshoe orbit may appear in the coarse grained spectrum. The experimental coarse grained features are interpreted as an R branch of the ν3 mode of the rotating horseshoe
Material-Point Method Analysis of Bending in Elastic Beams
DEFF Research Database (Denmark)
Andersen, Søren Mikkel; Andersen, Lars
2007-01-01
The aim of this paper is to rest different kinds of spatial interpolation for the material-point method.......The aim of this paper is to rest different kinds of spatial interpolation for the material-point method....
Contribution to the study of radioactive ion beam production by the ISOL method
International Nuclear Information System (INIS)
This thesis is related to the R and D program for the production of radioactive ion beams by the ISOL method at GANIL in Caen. This work concerns several different techniques based on the ISOL method. The first one is the production of radioactive ion beams with a SPIRAL target-source system (target + ECR source). The production rates of radioactive neon beams were determined on the SIRa test bench and previsions for SPIRAL were established. The feasibility of the production of radioactive condensable element beams with such target-source system, using a transport under a volatile molecular form between the target and the source, was experimentally proven by the production of radioactive oxygen beams via the CO molecule. The second technique is the production of radioactive alkaline beams with the target-source system MONOLITHE (target + hot cavity source). The production efficiencies of lithium and sodium radioactive beams were determined. A new methodology, the 'global method', has been developed as part of this thesis, for deducing diffusion, effusion and ionisation properties of these two elements with this ensemble. It is shown that the evolution of diffusion properties between different alkali elements is similar to noble gases. The third one is the IGISOL technique (target + ion guide). The MI-GI-CHEMIN code was created for simulating the movement of ions in an ion guide filled with helium and a given concentration of impurities, including electric and magnetic fields. A first IGISOL prototype is in realisation at GANIL. (author)
Computing the laser beam path in optical cavities: a geometric Newton's method based approach
Cuccato, Davide; Ortolan, Antonello; Beghi, Alessandro
2015-01-01
In the last decade, increasing attention has been drawn to high precision optical experiments, which push resolution and accuracy of the measured quantities beyond their current limits. This challenge requires to place optical elements (e.g. mirrors, lenses, etc.) and to steer light beams with sub-nanometer precision. Existing methods for beam direction computing in resonators, e.g. iterative ray tracing or generalized ray transfer matrices, are either computationally expensive or rely on overparametrized models of optical elements. By exploiting Fermat's principle, we develop a novel method to compute the steady-state beam configurations in resonant optical cavities formed by spherical mirrors, as a function of mirror positions and curvature radii. The proposed procedure is based on the geometric Newton method on matrix manifold, a tool with second order convergence rate that relies on a second order model of the cavity optical length. As we avoid coordinates to parametrize the beam position on mirror surfac...
Matsumoto, Tetsuro; Harano, Hideki; Masuda, Akihiko; Nishiyama, Jun; Matsue, Hideaki; Uritani, Akira; Nunomiya, Tomoya
2013-08-01
A new thermal neutron calibration method to experimentally determine the energy response function of a neutron detector using a pulse parallel beam and the time-of-flight (TOF) technique is developed. The calibration method was experimentally demonstrated for a (3)He proportional counter and an electric personal dosemeter using a pulsed thermal neutron beam from the research reactor JRR-3M. The responses of the detectors were successfully obtained as a function of neutron energy. However, detailed information on the detector structure is required to obtain the spatial response distribution for the detector. The authors further propose an improved calibration method obtaining the spatial response distribution using a pulsed narrow beam, the TOF technique and a beam scanning technique. PMID:23509397
International Nuclear Information System (INIS)
The graft polymerization method is one of the most effective techniques to produce a new polymer with unique function. To produce the polymer, we conducted experiments on radiation graft polymerization using ion beams of several hundred keV energy. A high density polyethylene (PE) film was irradiated with H+ beams, then, graft polymerization with monomer solution such as acrylic acid or acrylonitrile was conducted. Radicals generated by the interaction between the beam ions and the PE molecules become the starting point of the graft polymerization. Since the range in PE depends on ion energy, the density distribution of the graft chain can be controlled by the ion energy. Using a mask which restricts the ion beam incidence, PE sheets containing graft chains only in the unmasked area were obtained. Multiple ion beam graft polymerization can produce a polymer which has some functional bases at specified position. We have demonstrated the production of a polymer film with a three-dimensional structure.
System and method for deflecting and focusing a broad ion beam
International Nuclear Information System (INIS)
A method and system for deflecting a broad ion plasma beam which includes an ion source for forming an ion plasma, an extraction means for extracting a broad ion plasma beam from the ion plasma, and deflection means including a non-grounded surface located in the path of the ion plasam beam and at an angle to the path for deflecting the ion plasma beam to a target material. A grounded, screen grid is located in front of the deflecting means in the path of the ion plasma. The screen grid has openings which permit passage of the ions in the ion plasma, but block passage of the electrons. The plasma beam is deflected by the deflection means and the grounded, screen grid onto the target material for sputter cleaning, deposition and ion milling applications
Madsen, James A.; Ko, Byoung Joon; Xu, Hua; Iwashkiw, Jeremy A; Robotham, Scott A.; Shaw, Jared B.; Feldman, Mario F.; Brodbelt, Jennifer S.
2013-01-01
O -glycopeptides are often acidic owing to the frequent occurrence of acidic saccharides in the glycan, rendering traditional proteomic workflows that rely on positive mode tandem mass spectrometry (MS/MS) less effective. In this report, we demonstrate the utility of negative mode ultraviolet photodissociation (UVPD) MS for the characterization of acidic O-linked glycopeptide anions. This method was evaluated for a series of singly- and multiply-deprotonated glycopeptides from the model glyco...
Energy Technology Data Exchange (ETDEWEB)
Korolkov, K.S.; Nosach, O.Iu.; Orlov, E.P.
1985-01-01
It is found that in a flashlamp-pumped iodine laser the experimentally measured trough depths in the inhomogeneity-wave profiles in various media coincide with the ratios of theoretically calculated nonstationary gains under stimulated enthalpy scattering. Based on this knowledge a method of determining the relative stability of the active media of iodine photodissociation lasers with respect to the development of stimulated enthalpy scattering is presented. 6 references.
International Nuclear Information System (INIS)
Buckling analysis of nanobeams is investigated using nonlocal continuum beam models of the different classical beam theories namely as Euler-Bernoulli beam theory (EBT), Timoshenko beam theory (TBT), and Levinson beam theory (LBT). To this end, Eringen's equations of nonlocal elasticity are incorporated into the classical beam theories for buckling of nanobeams with rectangular cross-section. In contrast to the classical theories, the nonlocal elastic beam models developed here have the capability to predict critical buckling loads that allowing for the inclusion of size effects. The values of critical buckling loads corresponding to four commonly used boundary conditions are obtained using state-space method. The results are presented for different geometric parameters, boundary conditions, and values of nonlocal parameter to show the effects of each of them in detail. Then the results are fitted with those of molecular dynamics simulations through a nonlinear least square fitting procedure to find the appropriate values of nonlocal parameter for the buckling analysis of nanobeams relevant to each type of nonlocal beam model and boundary conditions analysis
Two methods of beam position signal processing for closed orbit measurement
International Nuclear Information System (INIS)
This paper describes two methods of processing lineraly detected signals of the beam position from pickup electrodes. The first method is based on the tracking self-balanced analog-digital bridge and the second one is based on the tracking ADC with varying reference. The operating features of the units realizing these methods are presented
Homotopy perturbation method for free vibration analysis of beams on elastic foundation
International Nuclear Information System (INIS)
In this study, the homotopy perturbation method (HPM) is applied for free vibration analysis of beam on elastic foundation. This numerical method is applied on a previously available case study. Analytical solutions and frequency factors are evaluated for different ratios of axial load N acting on the beam to Euler buckling load, Nr. The application of HPM for the particular problem in this study gives results which are in excellent agreement with both analytical solutions and the variational iteration method (VIM) solutions for the case considered in this study and the differential transform method (DTM) results available in the literature.
The ultraviolet photodissociation dynamics of the hydrogen halides
International Nuclear Information System (INIS)
The first electronic absorption bands of hydrogen halide (HX) molecules - HI, HBr, HCl and DCl - have been studied using two experimental, laser-based techniques. Each band of HX consists of absorption of ultraviolet (UV) radiation and leads to fragmentation into two sets of products: H(2S) + X(2Pj); j=3/2, 1/2. Numerous measurements that cover most of the UV absorption bands (λ∼200-300 nm) of HI and HBr were made using H Rydberg atom photofragment translational spectroscopy (HRPTS). The results comprise two important properties: the branching between the accessible product channels and the spatial distributions of the recoil velocities of the photofragments. These extensive observations afford a detailed interpretation of the featureless absorption bands in terms of the relative influences of transitions and dissociations involving multiple electronic states: 3Π(1), 3Π(0+), 1Π(1) and 3Σ+(1). The photolysis of HCl between 201 and 210 nm was also studied by HRPTS to provide a number of direct determinations of the relative product yield for comparison with the best available theoretical predictions based on ab initio electronic structure calculations and a time-independent treatment of the photodissociation dynamics. The good agreement between the calculations and observations provided encouraging support for the theoretical description. The second experimental method combined resonance enhanced multiphoton ionization (REMPI) and a time-of-flight mass spectrometer (TOF MS) to quantify the relative production of die spin-orbit components of the halogen photoproducts from HI, DCl and vibrationally-excited HCl. Relating the observed REMPI yields for each quantum state to the nascent populations required a scaling factor to account for the different ionization probabilities. This was derived for the ground state of the chlorine atom by comparing the Cl(2Pj) REMPI signal recorded following photolysis of HCl at λ=205.5 nm with a direct determination obtained by
Evaporation model for beam based additive manufacturing using free surface lattice Boltzmann methods
International Nuclear Information System (INIS)
Evaporation plays an important role in many technical applications including beam-based additive manufacturing processes, such as selective electron beam or selective laser melting (SEBM/SLM). In this paper, we describe an evaporation model which we employ within the framework of a two-dimensional free surface lattice Boltzmann method. With this method, we solve the hydrodynamics as well as thermodynamics of the molten material taking into account the mass and energy losses due to evaporation and the recoil pressure acting on the melt pool. Validation of the numerical model is performed by measuring maximum melt depths and evaporative losses in samples of pure titanium and Ti–6Al–4V molten by an electron beam. Finally, the model is applied to create processing maps for an SEBM process. The results predict that the penetration depth of the electron beam, which is a function of the acceleration voltage, has a significant influence on evaporation effects. (paper)
New Spectral Method for Halo Particle Definition in Intense Mis-matched Beams
International Nuclear Information System (INIS)
An advanced spectral analysis of a mis-matched charged particle beam propagating through a periodic focusing transport lattice is utilized in particle-in-cell (PIC) simulations. It is found that the betatron frequency distribution function of a mismatched space-charge-dominated beam has a bump-on-tail structure attributed to the beam halo particles. Based on this observation, a new spectral method for halo particle definition is proposed that provides the opportunity to carry out a quantitative analysis of halo particle production by a beam mismatch. In addition, it is shown that the spectral analysis of the mismatch relaxation process provides important insights into the emittance growth attributed to the halo formation and the core relaxation processes. Finally, the spectral method is applied to the problem of space-charge transport limits.
ANALYSIS OF COMPOSITE LAMINATE BEAMS USING COUPLING CROSS-SECTION FINITE ELEMENT METHOD
Institute of Scientific and Technical Information of China (English)
JIANG Wen-guang; John L. Henshall
2006-01-01
Beams and plates manufactured from laminates of composite materials have distinct advantages in a significant number of applications. However, the anisotropy arising from these materials adds a significant degree of complexity, and thus time, to the stress and deformation analyses of such components, even using numerical approaches such as finite elements. The analysis of composite laminate beams subjected to uniform extension, bending, and/or twisting loads was performed by a novel implementation of the usual finite element method. Due to the symmetric features of the deformations,only a thin slice of the beam to be analysed needs to be modelled. Conventional threedimensional ,solid finite elements were used for the structural discretization. The accurate deformation relationships were formulated and implemented through the coupling of nodal translational degrees of freedom in the numerical analysis. A sample solution for a rectangular composite laminate beam is presented to show the validity and accuracy of the proposed method.
Evaporation model for beam based additive manufacturing using free surface lattice Boltzmann methods
Klassen, Alexander; Scharowsky, Thorsten; Körner, Carolin
2014-07-01
Evaporation plays an important role in many technical applications including beam-based additive manufacturing processes, such as selective electron beam or selective laser melting (SEBM/SLM). In this paper, we describe an evaporation model which we employ within the framework of a two-dimensional free surface lattice Boltzmann method. With this method, we solve the hydrodynamics as well as thermodynamics of the molten material taking into account the mass and energy losses due to evaporation and the recoil pressure acting on the melt pool. Validation of the numerical model is performed by measuring maximum melt depths and evaporative losses in samples of pure titanium and Ti-6Al-4V molten by an electron beam. Finally, the model is applied to create processing maps for an SEBM process. The results predict that the penetration depth of the electron beam, which is a function of the acceleration voltage, has a significant influence on evaporation effects.
Asimov, Mustafo M.; Asimov, Rustam M.; Gisbrecht, Alexander
2005-04-01
A new approach to carbon monoxide poisoning treatment based on laser-induced photodissociation of the carboxyhemoglobin is proposed. Using the simple model of laser tissue interaction the action spectra of laser radiation on carboxyhemoglobin of cutaneous blood vessels has been calculated. The results of the calculatoins indicate that there is a relatively narrow spectral range in the visible region where one could effectively irradiate carboxyhemoglobin through the tissue not in a deep distances. In the case of deeper penetration, the action spectra of laser radiation shifts toward the longer wavelength region. Despite the similarity of the carboxyhemoglobin and oxyhemoglobin action spectra, the significant difference in quantum yields of photodissociation makes possible to develop an effective method of carbon monoxide poisoning treatment.
Oblique Du-Fort Frankel Beam Propagation Method
Directory of Open Access Journals (Sweden)
Ken Chan
2011-01-01
Full Text Available The oblique BPM based on the Du-Fort Frankel method is presented. The paper demonstrates the accuracy and the computational improvements of the scheme compared to the oblique BPM based on Crank-Nicholson (CN scheme.
Intense Electron Beams Formation and Analysis Methods in Static Electromagnetic Fields (Review
Directory of Open Access Journals (Sweden)
G.S. Vorobyov
2011-01-01
Full Text Available In this review basic principles of electron beams formation in static electric and magnetic fields are reported. Traditional and new perspective designs of electron-optical systems and magnetic systems are also considered. Questions of charged-particle beam focusing and transport on the level of modern technologies are being analyzed and their theoretic and experimental parameter research methods are examined as well.
The principles of a new method of determining ion beam profile density distribution
International Nuclear Information System (INIS)
The theoretical basis of a technique to determine the spatial density flux distribution in non-uniform ion beams is described. The technique relies on the mapping of the flux distribution into fluence collected distributions when the flux is translated at variable prescribed velocity relative to a series of ion collectors. The method determines the spatial moments of the flux distribution and does not require collector dimensions to be small with respect to the ion beam profile dimensions. (author)
Baloïtcha, Ezinvi; Balint-Kurti, Gabriel G.
2005-07-01
Ab initio potential energy and transition dipole moment surfaces are presented for the five lowest singlet even symmetry electronic states of ozone. The surfaces are calculated using the complete active space self consistent field method followed by contracted multireference configuration interaction (MRCI) calculations. A slightly reduced augmented correlation consistent valence triple-zeta orbital basis set is used. The ground and excited state energies of the molecule have been computed at 9282 separate nuclear geometries. Cuts through the potential energy surfaces, which pass through the geometry of the minimum of the ground electronic state, show several closely avoided crossings. Close examination, and higher level calculations, very strongly suggests that some of these seemingly avoided crossings are in fact associated with non-symmetry related conical intersections. Diabatic potential energy and transition dipole moment surfaces are created from the computed ab initio adiabatic MRCI energies and transition dipole moments. The transition dipole moment connecting the ground electronic state to the diabatic B˜ state surface is by far the strongest. Vibrational-rotational wavefunctions and energies are computed using the ground electronic state. The energy level separations compare well with experimentally determined values. The ground vibrational state wavefunction is then used, together with the diabatic B˜←X transition dipole moment surface, to form an initial wavepacket. The analysis of the time-dependent quantum dynamics of this wavepacket provides the total and partial photodissociation cross sections for the system. Both the total absorption cross section and the predicted product quantum state distributions compare well with experimental observations. A discussion is also given as to how the observed alternation in product diatom rotational state populations might be explained.
International Nuclear Information System (INIS)
In this work, the recently introduced quantum trajectory mean-field (QTMF) approach is implemented and employed to explore photodissociation dynamics of diazirinone (N2CO), which are based on the high-level ab initio calculation. For comparison, the photodissociation process has been simulated as well with the fewest-switches surface hopping (FSSH) and the ab initio multiple spawning (AIMS) methods. Overall, the dynamical behavior predicted by the three methods is consistent. The N2CO photodissociation at λ > 335 nm is an ultrafast process and the two C—N bonds are broken in a stepwise way, giving birth to CO and N2 as the final products in the ground state. Meanwhile, some noticeable differences were found in the QTMF, FSSH, and AIMS simulated time constants for fission of the C—N bonds, excited-state lifetime, and nonadiabatic transition ratios in different intersection regions. These have been discussed in detail. The present study provides a clear evidence that direct ab initio QTMF approach is one of the reliable tools for simulating nonadiabatic dynamics processes
International Nuclear Information System (INIS)
An important element of radiation treatment planning for cancer therapy is the selection of beam angles (out of all possible coplanar and non-coplanar angles in relation to the patient) in order to maximize the delivery of radiation to the tumor site and minimize radiation damage to nearby organs-at-risk. This category of combinatorial optimization problem is particularly difficult because direct evaluation of the quality of treatment corresponding to any proposed selection of beams requires the solution of a large-scale dose optimization problem involving many thousands of variables that represent doses delivered to volume elements (voxels) in the patient. However, if the quality of angle sets can be accurately estimated without expensive computation, a large number of angle sets can be considered, increasing the likelihood of identifying a very high quality set. Using a computationally efficient surrogate beam set evaluation procedure based on single-beam data extracted from plans employing equally-spaced beams (eplans), we have developed a global search metaheuristic process based on the nested partitions framework for this combinatorial optimization problem. The surrogate scoring mechanism allows us to assess thousands of beam set samples within a clinically acceptable time frame. Tests on difficult clinical cases demonstrate that the beam sets obtained via our method are of superior quality. (paper)
Adaptive synthesis method for broadband array with frequency invariant beam pattern
Institute of Scientific and Technical Information of China (English)
ZHUWeijie; SUNJincai; ZENGXiangyang
2003-01-01
Based on adaptive technique, a design method for broadband array with frequency invariant beam pattern is presented. For a given beam pattern, the all design process can be completed automatically by computer without deriving expression of weight vector. The design process is divided into three steps: (1) Evaluate the weight vector in reference frequency by numerical method. (2) Obtain the weight vectors in other frequency by adaptive technique.(3) For the design target of frequency response given by weight vector at different frequency point, design FIR filter. The proposed method can be applied to arbitrary array and have no restriction on element patterns.
Sohda, Yasunari; Ohta, Hiroya; Saitou, Norio
2002-02-01
A method for evaluating aberration in the crossover image in a cell projection lithography system has been developed. In an electron-beam lithography system of projection-type such as a cell projection lithography system, the aberration in the crossover image causes the electron beam to pass off-axis in the electron optics. Optical simulation has quantitatively shown that the aberration in the crossover image causes an electron-beam blur and a positioning error on a writing sample. The evaluating method consists of four square apertures and a mark-detection function in a cell projection system. By measuring each position of the images of the four square apertures on the writing sample at difference focuses, the aberration can be calculated. The field curvature and the astigmatism in a cell projection system were evaluated by using this method. The field curvature agrees with the simulation. In addition, the measurement of the effect of beam alignment is also demonstrated. It is thus concluded that the method can effectively evaluate the aberration in the crossover image. This method is also useful for other projection-type lithographies of charged particles—like ion and electron beams.
Slemp, Wesley C. H.; Kapania, Rakesh K.; Tessler, Alexander
2010-01-01
Computation of interlaminar stresses from the higher-order shear and normal deformable beam theory and the refined zigzag theory was performed using the Sinc method based on Interpolation of Highest Derivative. The Sinc method based on Interpolation of Highest Derivative was proposed as an efficient method for determining through-the-thickness variations of interlaminar stresses from one- and two-dimensional analysis by integration of the equilibrium equations of three-dimensional elasticity. However, the use of traditional equivalent single layer theories often results in inaccuracies near the boundaries and when the lamina have extremely large differences in material properties. Interlaminar stresses in symmetric cross-ply laminated beams were obtained by solving the higher-order shear and normal deformable beam theory and the refined zigzag theory with the Sinc method based on Interpolation of Highest Derivative. Interlaminar stresses and bending stresses from the present approach were compared with a detailed finite element solution obtained by ABAQUS/Standard. The results illustrate the ease with which the Sinc method based on Interpolation of Highest Derivative can be used to obtain the through-the-thickness distributions of interlaminar stresses from the beam theories. Moreover, the results indicate that the refined zigzag theory is a substantial improvement over the Timoshenko beam theory due to the piecewise continuous displacement field which more accurately represents interlaminar discontinuities in the strain field. The higher-order shear and normal deformable beam theory more accurately captures the interlaminar stresses at the ends of the beam because it allows transverse normal strain. However, the continuous nature of the displacement field requires a large number of monomial terms before the interlaminar stresses are computed as accurately as the refined zigzag theory.
International Nuclear Information System (INIS)
Purpose: The purpose of this article is to explore the use of the accelerated exhaustive search strategy for developing and validating methods for optimizing beam orientations for intensity-modulated radiation therapy (IMRT). Combining beam-angle optimization (BAO) with intensity distribution optimization is expected to improve the quality of IMRT treatment plans. However, BAO is one of the most difficult problems to solve adequately because of the huge hyperspace of possible beam configurations (e.g., selecting 7 of 36 uniformly spaced coplanar beams would require the intercomparison of 8,347,680 IMRT plans). Methods and materials: An 'influence vector' (IV) approximation technique for high-speed estimation of IMRT dose distributions was used in combination with a fast gradient search algorithm (Newton's method) for IMRT optimization. In the IV approximation, it is assumed that the change in intensity of a ray (or bixel) proportionately changes dose along the ray. Evidence is presented that the IV approximation is valid for BAO. The scatter contribution at points away from the ray is accounted for fully in IMRT optimization after the optimum beam orientation has been determined. IVs for all candidate beam angles are generated before the start of optimization. For all subsets of beams selected from a given pool of beams (e.g., 5 of 24 uniformly spaced beams), the distribution of planning scores for the best and the worst plans, optimum angle distributions, dose distributions, and dose-volume histograms (DVH) were analyzed for one prostate and two lung cancer cases. The results of the exhaustive search technique were used to develop a 'multiresolution' search strategy. In this approach, a smaller number of beams (e.g., three) is first used to explore the hyperspace of solutions to determine the most preferred and the least preferred directions. The results of such exploration are then used as a starting point for determining an optimum configuration comprising a
Concept Modelling of Vehicle Joints and Beam-Like Structures through Dynamic FE-Based Methods
Directory of Open Access Journals (Sweden)
G. De Gaetano
2014-01-01
Full Text Available This paper presents dynamic methodologies able to obtain concept models of automotive beams and joints, which compare favourably with the existing literature methods, in terms of accuracy, easiness of implementation, and computational loads. For the concept beams, the proposed method is based on a dynamic finite element (FE approach, which estimates the stiffness characteristics of equivalent 1D beam elements using the natural frequencies, computed by a modal analysis of the detailed 3D FE model of the structure. Concept beams are then connected to each other by a concept joint, which is obtained through a dynamic reduction technique that makes use of its vibration normal modes. The joint reduction is improved through the application of a new interface beam-to-joint element, able to interpolate accurately the nodal displacements of the outer contour of the section, to obtain displacements and rotations of the central connection node. The proposed approach is validated through an application case that is typical in vehicle body engineering: the analysis of a structure formed by three spot-welded thin-walled beams, connected by a joint.
Reconstruction of Sound Source Pressures in an Enclosure Using the Phased Beam Tracing Method
DEFF Research Database (Denmark)
Jeong, Cheol-Ho; Ih, Jeong-Guon
2009-01-01
Source identification in an enclosure is not an easy task due to complicated wave interference and wall reflections, in particular, at mid-high frequencies. In this study, a phased beam tracing method was applied to the reconstruction of source pressures inside an enclosure at medium frequencies...... all the pressure histories at the field points, source-observer relations can be constructed in a matrix-vector form for each frequency. By multiplying the measured field data with the pseudo-inverse of the calculated transfer function, one obtains the distribution of source pressure. An omni....... First, surfaces of an extended source are divided into reasonably small segments. From each source segment, one beam is projected into the field and all emitted beams are traced. Radiated beams from the source reach array sensors after traveling various paths including the wall reflections. Collecting...
Method of Light Beam Orbital Angular Momentum Evaluation by Means of Space-Angle Intensity Moments
Directory of Open Access Journals (Sweden)
A.Ya. Bekshaev
2002-12-01
Full Text Available Value of the orbital angular momentum (OAM of an optical beam can be determined through the structure of matrix of its space-angle intensity moments. Considering the properties of these moments and their transformations, a conclusion has been made that any light beam with the OAM experiences a characteristic transverse shift during its interaction with a plane refracting boundary or a diffraction grating. On this base, a method for the immediate measurement of the beam OAM is proposed. The simple experimental arrangement for such a measurement includes a self-collimating diffraction grating, a position-sensitive quadrant photodetector and a device for the beam rotation around its longitudinal axis.
Damage identification in beam type structures based on statistical moment using a two step method
Wang, Dansheng; Xiang, Wei; Zhu, Hongping
2014-02-01
This paper defines a novel damage index-strain statistical moment, and formulates the fourth strain statistical moment (FSSM) of beam-type structures under white noise excitation. Based on this newly defined strain statistical moment index and the least square optimization algorithm, a two-step damage identification method is proposed. This two-step method is operated like this: first use the difference curves of FSSMs before and after damage to locate damage elements; then for those identified damage elements, employ the model updating method based on the least square algorithm to assess their damage severity. Numerical studies on a simply supported beam and a two-span continuous beam are performed and the study results show that the newly defined index is effective to locate damages, even when the noise intensity is as high as 15 percent. Integrating with the least square-based model updating technique, the damage severities of beam-type structures can also be determined quantitatively. In this way, the proposed two-step method is verified and found to be capable of identifying damage positions and severities of beam-type structures and insensitive to measurement noise.
Analysis of transverse shear strains in pre-twisted thick beams using variational asymptotic method
Energy Technology Data Exchange (ETDEWEB)
Ameen, Maqsood M.; Harursampath, Dineshkumar, E-mail: m.ameen@tue.nl, E-mail: dinesh@aero.iisc.ernet.in [Department of Aerospace Engineering, Indian Institute of Science, Bangalore-560012 (India)
2015-03-10
The cross-sectional stiffness matrix is derived for a pre-twisted, moderately thick beam made of transversely isotropic materials and having rectangular cross sections. An asymptotically-exact methodology is used to model the anisotropic beam from 3-D elasticity, without any further assumptions. The beam is allowed to have large displacements and rotations, but small strain is assumed. The strain energy is computed making use of the beam constitutive law and kinematical relations derived with the inclusion of geometrical nonlinearities and an initial twist. The energy functional is minimized making use of the Variational Asymptotic Method (VAM), thereby reducing the cross section to a point on the beam reference line with appropriate properties, forming a 1-D constitutive law. VAM is a mathematical technique employed in the current problem to rigorously split the 3-D analysis of beams into two: a 2-D analysis over the beam cross-sectional domain, which provides a compact semi-analytical form of the properties of the cross sections, and a nonlinear 1-D analysis of the beam ref-erence curve. In this method, as applied herein, the cross-sectional analysis is performed asymptotically by taking advantage of a material small parameter and two geometric small parameters. 3-D strain components are derived using kinematics and arranged in orders of the small parameters. Closed-form expressions are derived for the 3-D non-linear warping and stress fields. Warping functions are obtained by the minimization of strain energy subject to certain set of constraints that render the 1-D strain measures well-defined. The zeroth-order 3-D warping field thus yielded is then used to integrate the 3-D strain energy density over the cross section, resulting in the 1-D strain energy density, which in turn helps identify the corresponding cross-sectional stiffness matrix. The model is capable of predicting interlaminar and transverse shear stresses accurately up to first order.
Analysis of transverse shear strains in pre-twisted thick beams using variational asymptotic method
International Nuclear Information System (INIS)
The cross-sectional stiffness matrix is derived for a pre-twisted, moderately thick beam made of transversely isotropic materials and having rectangular cross sections. An asymptotically-exact methodology is used to model the anisotropic beam from 3-D elasticity, without any further assumptions. The beam is allowed to have large displacements and rotations, but small strain is assumed. The strain energy is computed making use of the beam constitutive law and kinematical relations derived with the inclusion of geometrical nonlinearities and an initial twist. The energy functional is minimized making use of the Variational Asymptotic Method (VAM), thereby reducing the cross section to a point on the beam reference line with appropriate properties, forming a 1-D constitutive law. VAM is a mathematical technique employed in the current problem to rigorously split the 3-D analysis of beams into two: a 2-D analysis over the beam cross-sectional domain, which provides a compact semi-analytical form of the properties of the cross sections, and a nonlinear 1-D analysis of the beam ref-erence curve. In this method, as applied herein, the cross-sectional analysis is performed asymptotically by taking advantage of a material small parameter and two geometric small parameters. 3-D strain components are derived using kinematics and arranged in orders of the small parameters. Closed-form expressions are derived for the 3-D non-linear warping and stress fields. Warping functions are obtained by the minimization of strain energy subject to certain set of constraints that render the 1-D strain measures well-defined. The zeroth-order 3-D warping field thus yielded is then used to integrate the 3-D strain energy density over the cross section, resulting in the 1-D strain energy density, which in turn helps identify the corresponding cross-sectional stiffness matrix. The model is capable of predicting interlaminar and transverse shear stresses accurately up to first order
Photodissociation spectroscopy of the Mg+-acetic acid complex
International Nuclear Information System (INIS)
We have studied the structure and photodissociation of Mg+-acetic acid clusters. Ab initio calculations suggest four relatively strongly bound ground state isomers for the [MgC2H4O2]+ complex. These isomers include the cis and trans forms of the Mg+-acetic acid association complex with Mg+ bonded to the carbonyl O atom of acetic acid, the Mg+-acetic acid association complex with Mg+ bonded to the hydroxyl O atom of acetic acid, or to a Mg+-ethenediol association complex. Photodissociation through the Mg+-based 3p+, MgOH+, Mg(H2O)+, CH3CO+, and MgCH3+. At low energies the dominant reactive quenching pathway is through dehydration to Mg(H2O)+, but additional reaction channels involving C-H and C-C bond activation are also open at higher energies
Indian Academy of Sciences (India)
Almuth Laeuter; Hans-Robert Volpp; Jai P Mittal; Rajesh K Vatsa
2007-07-01
The collision-free, room temperature gas-phase photodissociation dynamics of CH3CFCl2 (HCFC-141b) was studied using Lyman- laser radiation (121.6 nm) by the laser photolysis/laserinduced fluorescence `pump/probe’ technique. Lyman- radiation was used both to photodissociate the parent molecule and to detect the nascent H atom products via (22P → 12S) laser-induced fluorescence. Absolute H atom quantum yield, H = (0.39 ± 0.09) was determined by calibration method in which CH4 photolysis at 121.6 nm was used as a reference source of well-defined H atom concentrations. The line shapes of the measured H atom Doppler profiles indicate a Gaussian velocity distribution suggesting the presence of indirect H atom formation pathways in the Lyman- photodissociation of CH3CFCl2. The average kinetic energy of H atoms calculated from Doppler profiles was found to be T(lab) = (50 ± 3) kJ/mol. The nearly statistical translational energy together with the observed Maxwell-Boltzmann velocity distribution indicates that for CH3CFCl2 the H atom forming dissociation process comes closer to the statistical limit.
Ioan, M.-R.
2016-08-01
In ionizing radiation related experiments, precisely knowing of the involved parameters it is a very important task. Some of these experiments are involving the use of electromagnetic ionizing radiation such are gamma rays and X rays, others make use of energetic charged or not charged small dimensions particles such are protons, electrons, neutrons and even, in other cases, larger accelerated particles such are helium or deuterium nuclei are used. In all these cases the beam used to hit an exposed target must be previously collimated and precisely characterized. In this paper, a novel method to determine the distribution of the collimated beam involving Matlab coding is proposed. The method was implemented by using of some Pyrex glass test samples placed in the beam where its distribution and dimension must be determined, followed by taking high quality pictures of them and then by digital processing the resulted images. By this method, information regarding the doses absorbed in the exposed samples volume are obtained too.
Simplified vibration analysis method of shells of revolution using beam model
International Nuclear Information System (INIS)
A simplified vibration analysis method for the shells of revolution using the beam model is now under consideration. In the beam model, the relations between the shear forces and horizontal deformations are used for the calculations of the shear area and the relations between the overturning moments and rotation angles are for those of the inertia moment. The calculations of the vibration characteristics of the cylindrical shell, spherical shell and the cylindrical shell with the spherical cap were conducted to verify the accuracy of the beam model. The natural frequencies and the vibration modes of the proposed method are in good agreement with that of the FEM analysis using the axisymmetrical shell model. The proposed method is easily applicable to the vibration analysis of actual shell structures. (author)
Rovibrational analysis of the XUV photodissociation of HeH{sup +} ions
Energy Technology Data Exchange (ETDEWEB)
Loreau, J. [Institute for Theoretical Atomic, Molecular and Optical Physics, Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138 (United States); Lecointre, J.; Urbain, X. [Institute of Condensed Matter and Nanosciences, Universite Catholique de Louvain, B-1348 Louvain-la-Neuve (Belgium); Vaeck, N. [Laboratoire de Chimie Quantique et Photophysique, Universite Libre de Bruxelles, CP160/09, B-1050 Bruxelles (Belgium)
2011-11-15
We investigate the dynamics of the photodissociation of the helium hydride ion HeH{sup +} by XUV radiation with the aim to establish a detailed comparison with a recent experimental work carried out at the FLASH free electron laser using both vibrationally hot and cold ions. We determine the corresponding rovibrational distributions using a dissociative charge transfer setup and the same source conditions as in the FLASH experiment. Using a nonadiabatic time-dependent wave-packet method, we calculate the partial photodissociation cross sections for the n=1-3 coupled electronic states of HeH{sup +}. We find good agreement with the experiment for the cross section into the He + H{sup +} dissociative channel. On the other hand, we show that the experimental observation of the importance of the electronic states with n>3 cannot be well explained theoretically, especially for cold (v=0) ions. We find a good agreement with the experiment on the relative contribution of the {Sigma} and {Pi} states to the cross section for the He{sup +} + H channel, but only a qualitative one for the He + H{sup +} channel. We discuss the factors that could explain the remaining discrepancies between theory and experiment.
Controlling the branching ratio of photodissociation using aligned molecules
DEFF Research Database (Denmark)
Larsen, J.J.; Wendt-Larsen, I.; Stapelfeldt, H.
1999-01-01
Using a sample of iodine molecules, aligned by a strong, linearly polarized laser pulse, we control the branching ratio of the I+I and I+I* photodissociation channels by a factor of 26. The control relies on selective photoexcitation of two potential curves that each correlate adiabatically with...... one of the product channels. The selectivity is achieved by irradiating the aligned molecules with light polarized parallel or perpendicular to the polarization axis of the alignment laser....
On the photodissociation of uranium hexafluoride in the B band
Menghini, M.; Morales, P.; Dore, P.; Schisano, M. I.
1986-06-01
The rate of photodissociation of uranium hexafluoride is measured for the first time as a function of wavelength in the B band. The experimental technique used tests the collision-free behavior and, with the addition of a buffer gas, the collisional effects on molecular relaxation. In both cases, the dissociation yield is strongly nonuniform. A qualitative interpretation of these results is attempted. Their relevance to the subject of laser isotopic separation and more generally of selective photochemistry is outlined.
Photodissociation of the HeH+ molecular ion
International Nuclear Information System (INIS)
The photodissociation cross section of the molecular ion HeH+ was calculated within the Born-Oppenheimer approximation for a parallel, a perpendicular, and an isotropic orientation of the molecular axis with respect to the field, considering also different initial vibrational and rotational states. The results were compared to recent data from a free-electron laser experiment performed at the FLASH facility. Within the experimental uncertainties theoretical and experimental results are compatible with each other.
Physical conditions in photodissociation regions: Application to galactic nuclei
Wolfire, M. G.; Tielens, A. G. G. M.; Hollenbach, David J.
1990-01-01
Infrared and sub-millimeter observations are used in a simple procedure to determine average physical properties of the neutral interstellar medium in Galactic photodissociation regions as well as in ensembles of clouds which exist in the nuclei of luminous infrared galaxies. The relevant observations include the Infrared Astronomy Satellite (IRAS) infrared continuum measurements, infrared spectroscopy of the fine-structure lines of SiII 35 microns, OI 63 microns, and CII 158 microns, and the 2.6 mm CO (J=1-0) rotational transition. The diagnostic capabilities of the OI 145 microns line is also addressed. Researchers attribute these emission lines as well as the continuum to the atomic/molecular photodissociation region on the surfaces of molecular clouds which are illuminated by strong ultraviolet fields. They use the theoretical photodissociation region models of Tielens and Hollenbach (1985, Ap. J., 291, 722) to construct simple diagrams which utilize line ratios and line to continuum ratios to determine the average gas density n, the average incident far-ultraviolet flux G sub o, and the temperature of the atomic gas T.
Photodissociation of ultracold diatomic strontium molecules with quantum state control
McDonald, M.; McGuyer, B. H.; Apfelbeck, F.; Lee, C.-H.; Majewska, I.; Moszynski, R.; Zelevinsky, T.
2016-07-01
Chemical reactions at ultracold temperatures are expected to be dominated by quantum mechanical effects. Although progress towards ultracold chemistry has been made through atomic photoassociation, Feshbach resonances and bimolecular collisions, these approaches have been limited by imperfect quantum state selectivity. In particular, attaining complete control of the ground or excited continuum quantum states has remained a challenge. Here we achieve this control using photodissociation, an approach that encodes a wealth of information in the angular distribution of outgoing fragments. By photodissociating ultracold 88Sr2 molecules with full control of the low-energy continuum, we access the quantum regime of ultracold chemistry, observing resonant and nonresonant barrier tunnelling, matter–wave interference of reaction products and forbidden reaction pathways. Our results illustrate the failure of the traditional quasiclassical model of photodissociation and instead are accurately described by a quantum mechanical model. The experimental ability to produce well-defined quantum continuum states at low energies will enable high-precision studies of long-range molecular potentials for which accurate quantum chemistry models are unavailable, and may serve as a source of entangled states and coherent matter waves for a wide range of experiments in quantum optics.
Photodissociation of ultracold diatomic strontium molecules with quantum state control.
McDonald, M; McGuyer, B H; Apfelbeck, F; Lee, C-H; Majewska, I; Moszynski, R; Zelevinsky, T
2016-07-01
Chemical reactions at ultracold temperatures are expected to be dominated by quantum mechanical effects. Although progress towards ultracold chemistry has been made through atomic photoassociation, Feshbach resonances and bimolecular collisions, these approaches have been limited by imperfect quantum state selectivity. In particular, attaining complete control of the ground or excited continuum quantum states has remained a challenge. Here we achieve this control using photodissociation, an approach that encodes a wealth of information in the angular distribution of outgoing fragments. By photodissociating ultracold (88)Sr2 molecules with full control of the low-energy continuum, we access the quantum regime of ultracold chemistry, observing resonant and nonresonant barrier tunnelling, matter-wave interference of reaction products and forbidden reaction pathways. Our results illustrate the failure of the traditional quasiclassical model of photodissociation and instead are accurately described by a quantum mechanical model. The experimental ability to produce well-defined quantum continuum states at low energies will enable high-precision studies of long-range molecular potentials for which accurate quantum chemistry models are unavailable, and may serve as a source of entangled states and coherent matter waves for a wide range of experiments in quantum optics. PMID:27383945
Halim, Mohammad A.; Girod, Marion; MacAleese, Luke; Lemoine, Jérôme; Antoine, Rodolphe; Dugourd, Philippe
2016-06-01
Herein we report the successful implementation of the consecutive and simultaneous photodissociation with high (213 nm) and low (10.6 μm) energy photons (HiLoPD, high-low photodissociation) on ubiquitin in a quadrupole-Orbitrap mass spectrometer. Absorption of high-energy UV photon is dispersed over the whole protein and stimulates extensive C-Cα backbone fragmentation, whereas low-energy IR photon gradually increases the internal energy and thus preferentially dissociates the most labile amide (C-N) bonds. We noticed that simultaneous irradiation of UV and IR lasers on intact ubiquitin in a single MS/MS experiment provides a rich and well-balanced fragmentation array of a/x, b/y, and z ions. Moreover, secondary fragmentation from a/x and z ions leads to the formation of satellite side-chain ions (d, v, and w) and can help to distinguish isomeric residues in a protein. Implementation of high-low photodissociation in a high-resolution mass spectrometer may offer considerable benefits to promote a comprehensive portrait of protein characterization.
System and method for sonic wave measurements using an acoustic beam source
Vu, Cung Khac; Sinha, Dipen N.; Pantea, Cristian
2015-08-11
A method and system for investigating structure near a borehole are described herein. The method includes generating an acoustic beam by an acoustic source; directing at one or more azimuthal angles the acoustic beam towards a selected location in a vicinity of a borehole; receiving at one or more receivers an acoustic signal, the acoustic signal originating from a reflection or a refraction of the acoustic wave by a material at the selected location; and analyzing the received acoustic signal to characterize features of the material around the borehole.
A Simple and Accurate Method for Calculating the Gaussian Beam Expansion Coefficients
Institute of Scientific and Technical Information of China (English)
LIU Wei; YANG Jun
2010-01-01
@@ The calculation of the diffraction field radiated from the ultrasonic transducer can be simplified by using the Gaussian beam expansion technique.The key problem of this technique is how to determine the coefficients of Gaussian functions.We present a simple and accurate optimization method to calculate the Gaussian beam expansion Coefficients.Half of the coefficients are obtained by solving linear equations.The other half are derived from the Fourier series expansion.Wave field simulation results demonstrate the validity of the new method.
Energy Technology Data Exchange (ETDEWEB)
Hannon, Fay
2016-08-02
A method for maximizing the brightness of the bunches in a particle injector by converting a highly space-charged beam to a relativistic and emittance-dominated beam. The method includes 1) determining the bunch charge and the initial kinetic energy of the highly space-charge dominated input beam; 2) applying the bunch charge and initial kinetic energy properties of the highly space-charge dominated input beam to determine the number of accelerator cavities required to accelerate the bunches to relativistic speed; 3) providing the required number of accelerator cavities; and 4) setting the gradient of the radio frequency (RF) cavities; and 5) operating the phase of the accelerator cavities between -90 and zero degrees of the sinusoid of phase to simultaneously accelerate and bunch the charged particles to maximize brightness, and until the beam is relativistic and emittance-dominated.
Directory of Open Access Journals (Sweden)
Jinhua Xie
2012-01-01
Full Text Available Based on the transmission and equilibrium relationship of vibration energy in beam-like structures, the Galerkin weighted residual method was applied to equation discretization. An equivalent transformation of feedback element was suggested to develop the Energy Finite Element model of a composite piezoelectric cantilever beam driven by harmonic excitation on lateral direction, with both systems with and without time delay being studied and the power input estimation of harmonic excitation was discussed for the resolution of Energy Finite Element function. Then the energy density solutions of the piezoelectric coupling beam through Energy Finite Element Method (EFEM and classical wave theory were compared to verify the EFEM model, which presented a good accordance. Further investigation was undertaken about the influence of control parameters including the feedback gain and arrangement of piezoelectric patches on characteristics of system energy density distribution.
Mixed-DT neutral-beam injection: An alternative heating method for tokamaks
International Nuclear Information System (INIS)
In this paper, the authors propose an alternative method for the heating, and perhaps also refueling, of tokamak fusion devices. The alternative method replaces the deuterium neutral-beam injectors (NBIs) such as those now used, for example, on the Tokamak Fusion Test Reactor (TFTR) device. Instead they make use of a mixed (deuterium-tritium) NBI (MNBI) and thereby vastly reduce the cost and complexity of the fuel-recovery cycle. Another like consequence is the reduction of the total amount of tritium in the on-site inventory. The authors suspect that the alternative plant design would have a positive effect on safety, although they have not done an accident analysis based on the mixed-beam injectors. They have, however, studied the requirements of the new fuel cycle and have looked at the question of optimizing some of the parameters associated with a mixed-beam injector. 3 refs
Modeling liquid-crystal devices with the three-dimensional full-vector beam propagation method
Wang, Qian; Farrell, Gerald; Semenova, Yuliya
2006-08-01
Simulation of light propagation within nematic liquid-crystal (LC) devices is considered, of which the director is aligned normal to the z axis. A three-dimensional full-vector finite-difference beam propagation method for an anisotropic medium is presented and an alternating direction implicit scheme is adopted. Simulations of light propagation in a bulk polarization converter, a waveguide with a LC covering layer, and an integrated polarization splitter and optical switch are presented. Comparison with an existing simulation method is carried out for beam behavior within the bulk polarization converter. The effect of strong surface anchoring of a LC cell on the beam behaviors within the integrated switch is also demonstrated.
A Method to Improve Electron Density Measurement of Cone-Beam CT Using Dual Energy Technique
Kuo Men; Jian-Rong Dai; Ming-Hui Li; Xin-Yuan Chen; Ke Zhang; Yuan Tian; Peng Huang; Ying-Jie Xu
2015-01-01
Purpose. To develop a dual energy imaging method to improve the accuracy of electron density measurement with a cone-beam CT (CBCT) device. Materials and Methods. The imaging system is the XVI CBCT system on Elekta Synergy linac. Projection data were acquired with the high and low energy X-ray, respectively, to set up a basis material decomposition model. Virtual phantom simulation and phantoms experiments were carried out for quantitative evaluation of the method. Phantoms were also scanned ...
A generalized reverse projection method for fan beam geometry under partially coherent illumination
Wu, Z.; Wang, Z. L.; Gao, K.; Zhang, K.; Ge, X.; Wang, D. J.; Wang, S. H.; Chen, J.; Pan, Z. Y.; Zhu, P. P.; Wu, Z. Y.
2014-02-01
In this paper, a generalized reverse projection (RP) method for grating-based fan beam phase contrast imaging is presented. Compared to the original RP method, rays rather than projection images are taken into account during the information extraction process. We also discuss the influence of partial coherence on the extracted information. Theoretical derivations and numerical simulations are performed to confirm the validity of the method.
Treatment of liquid separated from sludge by the method using electron beam and ozone in combination
International Nuclear Information System (INIS)
Since the liquid separated from sludge in the dehydration or concentration process of sewer sludge contains considerable amount of organic compositions that are hard to be decomposed by microorganisms, it has become difficult to be treated by conventional activated sludge process. In the case of discharging the separated liquid into closed water areas, the higher quality treatment is required. The method of using electron beam irradiation and ozone oxidation in combination for cleaning the liquid separated from sludge was examined, therefore, the results are reported. The water quality of the sample from the sludge treatment plant in A City is shown. The method of bio-pretreatment, the treatment method by using electron beam and ozone in combination, and the method of analyzing the water quality are described. The effect of the treatment by activated sludge process, as the effect of the treatment by the combined use of electron beam and ozone, the change of COD and TOC, the change of chromaticity, the change of gel chromatogram, and the reaction mechanism are reported. In this paper, only the basic concept on the model plant for applying the method of the combined use of electron beam and ozone to the treatment of the liquid separated from sludge is discussed. (K.I.)
Riccati discrete time transfer matrix method for elastic beam undergoing large overall motion
International Nuclear Information System (INIS)
An efficient method for dynamics simulation for elastic beam with large overall spatial motion and nonlinear deformation, namely, the Riccati discrete time transfer matrix method (Riccati-DT-TMM), is proposed in this investigation. With finite segments, continuous deformation field of a beam can be decomposed into many rigid bodies connected by rotational springs. Discrete time transfer matrices of rigid bodies and rotational springs are used to analyze the dynamic characteristic of the beam, and the Riccati transform is used to improve the numerical stability of discrete time transfer matrix method of multibody system dynamics. A predictor-corrector method is used to improve the numerical accuracy of the Riccati-DT-TMM. Using the Riccati-DT-TMM in dynamics analysis, the global dynamics equations of the system are not needed and the computation time required increases linearly with the system's number of degrees of freedom. Three numerical examples are given to validate the method for the dynamic simulation of a geometric nonlinear beam undergoing large overall motion
Iterative method for determination of the laser beam profile and τV-T
Directory of Open Access Journals (Sweden)
Rabasović Mihailo D.
2008-01-01
Full Text Available Measuring the vibrational-to-translational relaxation time τV-T in gases is one of the first applications of the photoacoustic effect. The spatial profile of the laser beam is crucial in these measurements because the multiphoton excitation is investigated. The multiphoton absorption is a non-linear process. Because of this, the top hat profile is preferable. It allows one to deal with nonlinearity in a simple manner. In order to reveal the real laser beam profile, we have slightly changed the theoretical profiles in such a manner that the best matching is obtained between theoretical and experimental photoacoustic signals. Still, there was a question: Is it possible to deduce the laser beam profile directly from the photoacoustic signal, thus avoiding manual changing of the laser beam profile? According to this paper, it is possible. The appropriate method has been found in another photoacoustics application: photoacoustic tomography. Thus, the method for the simultaneous determination of the spatial profile of the laser beam and vibrational-to-translational relaxation time is presented in this paper. It employs pulsed photoacoustics and an algorithm developed for photoacoustic tomography.
International Nuclear Information System (INIS)
Spectral and amplitude-time characteristics of optical emission of a relativistic electron beam in air is stidied by the photoelectron method. Application of the optical method for absolute measurements of characteristics of the dose field of an impulse relativistic electron beam is considered. The distribution of the energy absorbed along the 1 MeV electron beam axis is experimentally investigated. The absolute method of impulse dosimetry of heightened accuracy is substantiated on the basis of the results obtained
The equivalence problem for the Euler-Bernoulli beam equation via Cartan's method
International Nuclear Information System (INIS)
We completely solve the local point equivalence problem for the Euler-Bernoulli beam equation using Cartan's method of equivalence. We obtain five equivalence classes. For each equivalence class, we establish the necessary and sufficient conditions for similarity, and derive a basis of differential invariants as well as operators of invariant differentiation
A steering magnet optimized by random search method for high current beam transport line
International Nuclear Information System (INIS)
We present an improved design of the steering magnet which produces almost uniform magnetic field in the region through which beam passes. Optimization of the parameters of the steering magnet is done by random search method. It is shown that use of a suitable shim reduces the field deviation by a great extent. (author)
Highly Accurate Beam Torsion Solutions Using the p-Version Finite Element Method
Smith, James P.
1996-01-01
A new treatment of the classical beam torsion boundary value problem is applied. Using the p-version finite element method with shape functions based on Legendre polynomials, torsion solutions for generic cross-sections comprised of isotropic materials are developed. Element shape functions for quadrilateral and triangular elements are discussed, and numerical examples are provided.
Damping of rotating beams with particle dampers: Discrete element method analysis
Els, D. N. J.
2013-06-01
The performance of particle dampers (PDs) under centrifugal loads was investigated. A test bench consisting of a rotating cantilever beam with a particle damper at the tip was developed (D. N. J. Els, AIAA Journal 49, 2228-2238 (2011)). Equal mass containers with different depths, filled with a range of uniform-sized steel ball bearings, were used as particle dampers. The experiments were duplicated numerically with a discrete element method (DEM) model, calibrated against the experimental data. The DEM model of the rotating beam with a PD at the tip captured the performance of the PD very well over a wide range of tests with different configurations and rotation velocities.
Fractal Two-Level Finite Element Method For Free Vibration of Cracked Beams
Directory of Open Access Journals (Sweden)
A.Y.T. Leung
1998-01-01
Full Text Available The fractal two-level finite element method is extended to the free vibration behavior of cracked beams for various end boundary conditions. A cracked beam is separated into its singular and regular regions. Within the singular region, infinite number of finite elements are virturally generated by fractal geometry to model the singular behavior of the crack tip. The corresponding numerous degrees of freedom are reduced to a small set of generalized displacements by fractal transformation technique. The solution time and computer storage can be remarkably reduced without sacrifying accuracy. The resonant frequencies and mode shapes computed compared well with the results from a commercial program.
Future carbon beams at SPIRAL1 facility: Which method is the most efficient?
International Nuclear Information System (INIS)
Compared to in-flight facilities, Isotope Separator On-Line ones can in principle produce significantly higher radioactive ion beam intensities. On the other hand, they have to cope with delays for the release and ionization which make the production of short-lived isotopes ion beams of reactive and refractory elements particularly difficult. Many efforts are focused on extending the capabilities of ISOL facilities to those challenging beams. In this context, the development of carbon beams is triggering interest [H. Frånberg, M. Ammann, H. W. Gäggeler, and U. Köster, Rev. Sci. Instrum. 77, 03A708 (2006); M. Kronberger, A. Gottberg, T. M. Mendonca, J. P. Ramos, C. Seiffert, P. Suominen, and T. Stora, in Proceedings of the EMIS 2012 [Nucl. Instrum. Methods Phys. Res. B Production of molecular sideband radioisotope beams at CERN-ISOLDE using a Helicon-type plasma ion source (to be published)]: despite its refractory nature, radioactive carbon beams can be produced from molecules (CO or CO2), which can subsequently be broken up and multi-ionized to the required charge state in charge breeders or ECR sources. This contribution will present results of experiments conducted at LPSC with the Phoenix charge breeder and at GANIL with the Nanogan ECR ion source for the ionization of carbon beams in the frame of the ENSAR and EMILIE projects. Carbon is to date the lightest condensable element charge bred with an ECR ion source. Charge breeding efficiencies will be compared with those obtained using Nanogan ECRIS and charge breeding times will be presented as well
Method of beam steering with FWM in ICF. Compensation and generation of a PC beam for a foam target
International Nuclear Information System (INIS)
In beam steering with a phase conjugate (PC) mirror in inertial fusion energy (ICF), the path of the PC beam has to be compensated since the target moves several hundred micrometers during beam propagation. In this paper we show that compensation can be achieved by adjusting the angle between two pump beams in four-wave mixing (FWM) used as a PC mirror. The compensation angle depends on the target position along the optical axis, focal point of the final optics, and angle adjusted with FWM. For the parameter values of GEKKO XII and an accuracy of laser irradiation of ±10 µm, the compensation angle is 4.5 mrad and the margin of error for target injection is ±0.3 mm. We also show that a PC beam can be generated from the beam scattered by a foam target rotating at ∼ 43 m/s is confirmed. (author)
The FLUKA code for application of Monte Carlo methods to promote high precision ion beam therapy
Parodi, K; Cerutti, F; Ferrari, A; Mairani, A; Paganetti, H; Sommerer, F
2010-01-01
Monte Carlo (MC) methods are increasingly being utilized to support several aspects of commissioning and clinical operation of ion beam therapy facilities. In this contribution two emerging areas of MC applications are outlined. The value of MC modeling to promote accurate treatment planning is addressed via examples of application of the FLUKA code to proton and carbon ion therapy at the Heidelberg Ion Beam Therapy Center in Heidelberg, Germany, and at the Proton Therapy Center of Massachusetts General Hospital (MGH) Boston, USA. These include generation of basic data for input into the treatment planning system (TPS) and validation of the TPS analytical pencil-beam dose computations. Moreover, we review the implementation of PET/CT (Positron-Emission-Tomography / Computed- Tomography) imaging for in-vivo verification of proton therapy at MGH. Here, MC is used to calculate irradiation-induced positron-emitter production in tissue for comparison with the +-activity measurement in order to infer indirect infor...
Single-slice rebinning method for helical cone-beam CT.
Noo, F; Defrise, M; Clackdoyle, R
1999-02-01
In this paper, we present reconstruction results from helical cone-beam CT data, obtained using a simple and fast algorithm, which we call the CB-SSRB algorithm. This algorithm combines the single-slice rebinning method of PET imaging with the weighting schemes of spiral CT algorithms. The reconstruction is approximate but can be performed using 2D multislice fan-beam filtered backprojection. The quality of the results is surprisingly good, and far exceeds what one might expect, even when the pitch of the helix is large. In particular, with this algorithm comparable quality is obtained using helical cone-beam data with a normalized pitch of 10 to that obtained using standard spiral CT reconstruction with a normalized pitch of 2. PMID:10070801
Single-slice rebinning method for helical cone-beam CT
International Nuclear Information System (INIS)
In this paper, we present reconstruction results from helical cone-beam CT data, obtained using a simple and fast algorithm, which we call the CB-SSRB algorithm. This algorithm combines the single-slice rebinning method of PET imaging with the weighting schemes of spiral CT algorithms. The reconstruction is approximate but can be performed using 2D multislice fan-beam filtered backprojection. The quality of the results is surprisingly good, and far exceeds what one might expect, even when the pitch of the helix is large. In particular, with this algorithm comparable quality is obtained using helical cone-beam data with a normalized pitch of 10 to that obtained using standard spiral CT reconstruction with a normalized pitch of 2. (author)
High precision beam momentum determination in a synchrotron using a spin resonance method
Goslawski, P; Gebel, R; Hartmann, M; Kacharava, A; Lehrach, A; Lorentz, B; Maier, R; Mielke, M; Papenbrock, M; Prasuhn, D; Stassen, R; Stein, H J; Stockhorst, H; Ströher, H; Wilkin, C
2009-01-01
In order to measure the mass of the eta meson with high accuracy using the d+p -> 3He+eta reaction, the momentum of the circulating deuteron beam in the Cooler Synchrotron COSY of the Forschungszentrum Juelich has to be determined with unprecedented precision. This has been achieved by studying the spin dynamics of the polarized deuteron beam. By depolarizing the beam through the use of an artificially induced spin resonance, it was possible to evaluate its momentum p with a precision of dp/p < 10-4 for a momentum of roughly 3 GeV/c. Different possible sources of error in the application of the spin resonance method are discussed in detail and its possible use during a standard experiment is considered.
Study on advanced cancer treatment method using quantum beam fusion technology
International Nuclear Information System (INIS)
This study on advanced cancer treatment method using quantum beam fusion technology aims at the realization of the fusion therapy device between boron neutron capture therapy device and THz wave hyperthermia device. To achieve this purpose, it is necessary to develop an intra-body transmission technology of THz beams. From the transmission experiment of 0.2 THz wave using sapphire microfiber, it has been found that the transmission of THz microbeam into the intra-body cancer affected part is possible. As the technologies to commercially realize the intra-body transmission of THz beams, this paper describes the coupler for transmission, flexible corrugated horn, and the micro-fabrication techniques of microfibers. In addition, the authors conducted the development of an optical fiber type rotary encoder for the long-distance transmission of THz waves, and confirmed that the effects of vibration did not exist through the evaluation of vibration durability. (A.O.)
International Nuclear Information System (INIS)
The mathematics model of particle transportation was built, based on the sample of the impaction trace of the narrow beam γ photon in the medium according to the principle of interaction between γ photon and the material, and a computer procedure was organized to simulate the process of transportation for the γ photon in the medium and record the emission probability of γ photon and its corresponding thickness of medium with LabWindows/CVI, which was used to calculate narrow beam γ ray mass attenuation coefficients of absorbing medium. The results show that it is feasible for Monte Carlo method to calculate narrow beam γ ray mass attenuation coefficients of absorbing medium. (authors)
Measurement and evaluation methods for beam characterization of commercial excimer lasers
Albrecht, Hans Stephen; Rebhan, Ulrich; Mann, Klaus R.; Ohlenbusch, J.
1996-11-01
This paper describes the specific requirements for measurement of excimer laser beam profiles for standardized characterization 'of commercial excimer lasers. A corresponding measurement system is presented which allows a simultaneous characterization of energy density distribution in the near field as well as in the focal plane of a lens (far field). Specially adapted UV-cameras make possible sings pulse diagnostic. Beam widths are calculated from the digitized camera data by different methods corresponding to the proposals of ISO 11146 (second moment, moving knife edge, and moving slit) and the results are compared. In particular, the influence of background signals as well as the typical shape of energy density distribution in the near field to the determined beam widths are analyzed.
A Numerical Method of the Euler-Bernoulli Beam with Optimal Local Kelvin-Voigt Damping
Directory of Open Access Journals (Sweden)
Xin Yu
2014-01-01
Full Text Available This paper deals with the numerical approximation problem of the optimal control problem governed by the Euler-Bernoulli beam equation with local Kelvin-Voigt damping, which is a nonlinear coefficient control problem with control constraints. The goal of this problem is to design a control input numerically, which is the damping and distributes locally on a subinterval of the region occupied by the beam, such that the total energy of the beam and the control on a given time period is minimal. We firstly use the finite element method (FEM to obtain a finite-dimensional model based on the original PDE system. Then, using the control parameterization method, we approximate the finite-dimensional problem by a standard optimal parameter selection problem, which is a suboptimal problem and can be solved numerically by nonlinear mathematical programming algorithm. At last, some simulation studies will be presented by the proposed numerical approximation method in this paper, where the damping controls act on different locations of the Euler-Bernoulli beam.
Beam propagation method using a [(p- 1)/ p] Padé approximant of the propagator.
Lu, Ya Yan; Ho, Pui Lin
2002-05-01
A new beam propagation method (BPM) is developed based on a direct approximation to the propagator by its [(p-1)/p] Padé approximant. The approximant is simple to construct and has the desired damping effect for the evanescent modes. The method is applied to a tapered waveguide for TM-polarized waves, based on the energy-conserving improvement of the one-way Helmholtz equation. Numerical results are compared with those obtained with other variants of the BPM. PMID:18007898
Implicit Yee-Mesh-Based Finite-Difference Full-Vectorial Beam-Propagation Method
Yamauchi, Junji; Mugita, Takanori; Nakano, Hisamatsu
2005-01-01
A novel Yee-mesh-based finite-difference fullvectorialbeam-propagation method is proposed with the aid of animplicit scheme. The efficient algorithm is developed by splittingthe propagation axis into two steps. The eigenmode analysisof a rib waveguide is performed using the imaginary-distanceprocedure. The results show that the present method offers reductionin computational time and memory, while maintainingthe same accuracy as the conventional explicit Yee-mesh-basedimaginary-distance beam-...
Zeeman effects in the hyperfine structure of atomic iodine photodissociation laser emission.
Hwang, W. C.; Kasper, J. V. V.
1972-01-01
Observation of hyperfine structure in laser emission from CF3I and C2F5I photodissociation lasers. Constant magnetic fields affect the time behavior of the emission by changing the relative gains of the hyperfine transitions. Time-varying fields usually present in photodissociation lasers further complicate the emission.
Single photon excimer laser photodissociation of highly vibrationally excited polyatomic molecules
International Nuclear Information System (INIS)
The ir + uv photodissociation of SF6 has been performed using CO2 and ArF lasers. The two-color photolysis significantly enhances the photodissociation process over ArF irradiation alone and is found to preserve the initial isotopic specificity of the ir excitation process
Method for measuring the speed distribution of blown sand using laser beam
International Nuclear Information System (INIS)
A new method for measuring the speed distribution of blown sand grains using He-Ne laser beam has been developed. This method enables us to measure the rate of sand movement as well as the number of blown sand at the some region in the wind tunnel and field. The apparatus is composed of a He-Ne laser (l mW)., a photodetection system with a slit (width: 0.3-3.0 mm), a five channel pulse width analyzer and a multi-purpose counter. When a sand grain passes across the laser beam, a shadow is thrown upon the light sensitive area of photodetector. The change in photocurrent after amplification and pulse shaping, is fed to the pulse width analyzer. The pulse width has information on both the speed and size of blown sand. Using nearly uniform size of sand grains, the speed distribution of blown sand can be measured. This method has many merits for studying the physical phenomena of blown sand in the field. First, the laser beam does not disturb the stream line of wind, but this condition is not satisfied in the case of using the sand trap. Second, in case of use of sand trap, the base of this must be buried in the sand surface and this handling affect the physical properties of sand surface. Third, this method is strong differential method in time and space, whereas the sand trap is .strong in integral method and easy handling
Low temperature Ti-Si-C thin film deposition by ion beam assisted methods
Twardowska, Agnieszka; Rajchel, Boguslaw; Jaworska, Lucyna
2010-11-01
Thin, multiphase Ti-Si-C coatings were formed by IBSD or by IBAD methods on AISI 316L steel substrates in room temperature, using single Ti3SiC2 target. In those methods the TiXSiCY coatings were formed from the flux of energetic atoms and ions obtained by ion sputtering of the Ti3SiC2 compound sample. As sputtering beam the beam of Ar+ ions at energy of 15keV was applied. In the IBAD method the dynamically formed coatings were additionally bombarded by beam of Ar+ ions at energy of 15keV. The ion beams parameters were obtained by using Monte Carlo computer simulations. The morphology (SEM, TEM), chemical (EDS/EDX) and phase composition (XRD) examinations of formed coatings were provided as well as confocal Raman microspectroscopy. Analyzed coatings were relatively thin (150nm-1μm), flat and dense. XRD analysis indicated in amorphous TiSi, the traces of Ti5Si3 and other phases from Ti-Si-C system (TiSi, TiSi2,Ti3SiC2). For chemical bonds investigation, the laser beam with length of 532nm was used. Those analyses were performed in the low (LR) or in high (HR) resolution modes in room temperature and in 4000C. In the HR mode the spectral resolution was close to 2 cm-1. In Raman spectra peaks at: 152cm-1, 216cm-1, 278cm-1, 311 cm-1, 608cm-1, 691cm-1 were recorded. Nanoindentation tests were done on coated and uncoated substrates with diamond, Berkovich-type indenter. Vickers hardness HIT and reduced elastic modulus EIT were calculated using Olivier& Pharr method. HIT for coated substrates was in the range 2.7 to 5.3 GPa, EIT was 160 GPa.
Low temperature Ti-Si-C thin film deposition by ion beam assisted methods
International Nuclear Information System (INIS)
Thin, multiphase Ti-Si-C coatings were formed by IBSD or by IBAD methods on AISI 316L steel substrates in room temperature, using single Ti3SiC2 target. In those methods the TiXSiCY coatings were formed from the flux of energetic atoms and ions obtained by ion sputtering of the Ti3SiC2 compound sample. As sputtering beam the beam of Ar+ ions at energy of 15keV was applied. In the IBAD method the dynamically formed coatings were additionally bombarded by beam of Ar+ ions at energy of 15keV. The ion beams parameters were obtained by using Monte Carlo computer simulations. The morphology (SEM, TEM), chemical (EDS/EDX) and phase composition (XRD) examinations of formed coatings were provided as well as confocal Raman microspectroscopy. Analyzed coatings were relatively thin (150nm-1μm), flat and dense. XRD analysis indicated in amorphous TiSi, the traces of Ti5Si3 and other phases from Ti-Si-C system (TiSi, TiSi2,Ti3SiC2). For chemical bonds investigation, the laser beam with length of 532nm was used. Those analyses were performed in the low (LR) or in high (HR) resolution modes in room temperature and in 400deg. C. In the HR mode the spectral resolution was close to 2 cm-1. In Raman spectra peaks at: 152cm-1, 216cm-1, 278cm-1, 311 cm-1, 608cm-1, 691cm-1 were recorded. Nanoindentation tests were done on coated and uncoated substrates with diamond, Berkovich-type indenter. Vickers hardness HIT and reduced elastic modulus EIT were calculated using Olivier and Pharr method. HIT for coated substrates was in the range 2.7 to 5.3 GPa, EIT was 160 GPa.
Booth, Ryan S; Lam, Chow-Shing; Brynteson, Matthew D; Wang, Lei; Butler, Laurie J
2013-10-01
These experiments photolytically generate two key intermediates in the decomposition mechanisms of energetic materials with nitro substituents, 2-nitropropene, and 2-nitro-2-propyl radicals. These intermediates are produced at high internal energies and access a number of competing unimolecular dissociation channels investigated herein. We use a combination of crossed laser-molecular beam scattering and velocity map imaging to study the photodissociation of 2-bromo-2-nitropropane at 193 nm and the subsequent unimolecular dissociation of the intermediates above. Our results demonstrate that 2-bromo-2-nitropropane has four primary photodissociation pathways: C-Br bond fission yielding the 2-nitro-2-propyl radical, HBr elimination yielding 2-nitropropene, C-N bond fission yielding the 2-bromo-2-propyl radical, and HONO elimination yielding 2-bromopropene. The photofragments are formed with significant internal energy and undergo many secondary dissociation events, including the exothermic dissociation of 2-nitro-2-propyl radicals to NO + acetone. Calculations at the G4//B3LYP/6-311++g(3df,2p) level show that the presence of a radical at a nitroalkyl center changes the mechanism for and substantially lowers the barrier to NO loss. This mechanism involves an intermediate with a three-center ring rather than the intermediate formed during the traditional nitro-nitrite isomerization. The observed dissociation pathways of the 2-nitro-2-propyl radical and 2-nitropropene help elucidate the decomposition mechanism of larger energetic materials with geminal dinitro groups. PMID:23496411
Beam-Based Error Identification and Correction Methods for Particle Accelerators
AUTHOR|(SzGeCERN)692826; Tomas, Rogelio; Nilsson, Thomas
2014-06-10
Modern particle accelerators have tight tolerances on the acceptable deviation from their desired machine parameters. The control of the parameters is of crucial importance for safe machine operation and performance. This thesis focuses on beam-based methods and algorithms to identify and correct errors in particle accelerators. The optics measurements and corrections of the Large Hadron Collider (LHC), which resulted in an unprecedented low β-beat for a hadron collider is described. The transverse coupling is another parameter which is of importance to control. Improvement in the reconstruction of the coupling from turn-by-turn data has resulted in a significant decrease of the measurement uncertainty. An automatic coupling correction method, which is based on the injected beam oscillations, has been successfully used in normal operation of the LHC. Furthermore, a new method to measure and correct chromatic coupling that was applied to the LHC, is described. It resulted in a decrease of the chromatic coupli...
International Nuclear Information System (INIS)
Correlative microscopy allows imaging of the same feature over multiple length scales, combining light microscopy with high resolution information provided by electron microscopy. We demonstrate two procedures for coordinate transformation based correlative microscopy of vitrified biological samples applicable to different imaging modes. The first procedure aims at navigating cryo-electron tomography to cellular regions identified by fluorescent labels. The second procedure, allowing navigation of focused ion beam milling to fluorescently labeled molecules, is based on the introduction of an intermediate scanning electron microscopy imaging step to overcome the large difference between cryo-light microscopy and focused ion beam imaging modes. These methods make it possible to image fluorescently labeled macromolecular complexes in their natural environments by cryo-electron tomography, while minimizing exposure to the electron beam during the search for features of interest. - Highlights: • Correlative light microscopy and focused ion beam milling of vitrified samples. • Coordinate transformation based cryo-correlative method. • Improved correlative light microscopy and cryo-electron tomography
Energy Technology Data Exchange (ETDEWEB)
Fukuda, Yoshiyuki; Schrod, Nikolas; Schaffer, Miroslava; Feng, Li Rebekah; Baumeister, Wolfgang; Lucic, Vladan, E-mail: vladan@biochem.mpg.de
2014-08-01
Correlative microscopy allows imaging of the same feature over multiple length scales, combining light microscopy with high resolution information provided by electron microscopy. We demonstrate two procedures for coordinate transformation based correlative microscopy of vitrified biological samples applicable to different imaging modes. The first procedure aims at navigating cryo-electron tomography to cellular regions identified by fluorescent labels. The second procedure, allowing navigation of focused ion beam milling to fluorescently labeled molecules, is based on the introduction of an intermediate scanning electron microscopy imaging step to overcome the large difference between cryo-light microscopy and focused ion beam imaging modes. These methods make it possible to image fluorescently labeled macromolecular complexes in their natural environments by cryo-electron tomography, while minimizing exposure to the electron beam during the search for features of interest. - Highlights: • Correlative light microscopy and focused ion beam milling of vitrified samples. • Coordinate transformation based cryo-correlative method. • Improved correlative light microscopy and cryo-electron tomography.
Terzić, Balša; Bassi, Gabriele
2011-07-01
In this paper we discuss representations of charge particle densities in particle-in-cell simulations, analyze the sources and profiles of the intrinsic numerical noise, and present efficient methods for their removal. We devise two alternative estimation methods for charged particle distribution which represent significant improvement over the Monte Carlo cosine expansion used in the 2D code of Bassi et al. [G. Bassi, J. A. Ellison, K. Heinemann, and R. Warnock, Phys. Rev. ST Accel. Beams 12, 080704 (2009); PRABFM1098-440210.1103/PhysRevSTAB.12.080704G. Bassi and B. Terzić, in Proceedings of the 23rd Particle Accelerator Conference, Vancouver, Canada, 2009 (IEEE, Piscataway, NJ, 2009), TH5PFP043], designed to simulate coherent synchrotron radiation (CSR) in charged particle beams. The improvement is achieved by employing an alternative beam density estimation to the Monte Carlo cosine expansion. The representation is first binned onto a finite grid, after which two grid-based methods are employed to approximate particle distributions: (i) truncated fast cosine transform; and (ii) thresholded wavelet transform (TWT). We demonstrate that these alternative methods represent a staggering upgrade over the original Monte Carlo cosine expansion in terms of efficiency, while the TWT approximation also provides an appreciable improvement in accuracy. The improvement in accuracy comes from a judicious removal of the numerical noise enabled by the wavelet formulation. The TWT method is then integrated into the CSR code [G. Bassi, J. A. Ellison, K. Heinemann, and R. Warnock, Phys. Rev. ST Accel. Beams 12, 080704 (2009)PRABFM1098-440210.1103/PhysRevSTAB.12.080704], and benchmarked against the original version. We show that the new density estimation method provides a superior performance in terms of efficiency and spatial resolution, thus enabling high-fidelity simulations of CSR effects, including microbunching instability.
International Nuclear Information System (INIS)
In this paper we discuss representations of charge particle densities in particle-in-cell simulations, analyze the sources and profiles of the intrinsic numerical noise, and present efficient methods for their removal. We devise two alternative estimation methods for charged particle distribution which represent significant improvement over the Monte Carlo cosine expansion used in the 2D code of Bassi et al. (G. Bassi, J.A. Ellison, K. Heinemann and R. Warnock Phys. Rev. ST Accel. Beams 12 080704 (2009)G. Bassi and B. Terzic, in Proceedings of the 23rd Particle Accelerator Conference, Vancouver, Canada, 2009 (IEEE, Piscataway, NJ, 2009), TH5PFP043), designed to simulate coherent synchrotron radiation (CSR) in charged particle beams. The improvement is achieved by employing an alternative beam density estimation to the Monte Carlo cosine expansion. The representation is first binned onto a finite grid, after which two grid-based methods are employed to approximate particle distributions: (i) truncated fast cosine transform; and (ii) thresholded wavelet transform (TWT). We demonstrate that these alternative methods represent a staggering upgrade over the original Monte Carlo cosine expansion in terms of efficiency, while the TWT approximation also provides an appreciable improvement in accuracy. The improvement in accuracy comes from a judicious removal of the numerical noise enabled by the wavelet formulation. The TWT method is then integrated into the CSR code (G. Bassi, J.A. Ellison, K. Heinemann and R. Warnock Phys. Rev. ST Accel. Beams 12 080704 (2009)), and benchmarked against the original version. We show that the new density estimation method provides a superior performance in terms of efficiency and spatial resolution, thus enabling high-fidelity simulations of CSR effects, including microbunching instability.
International Nuclear Information System (INIS)
Purpose: To determine the effectiveness of noncoplanar beam configurations and the benefit of plans using fewer but optimally placed beams designed by a parallelized multiple-resolution beam angle optimization (PMBAO) approach. Methods and Materials: The PMBAO approach uses a combination of coplanar and noncoplanar beam configurations for intensity-modulated radiation therapy (IMRT) treatment planning of paranasal sinus cancers. A smaller number of beams (e.g. 3) are first used to explore the solution space to determine the best and worst beam directions. The results of this exploration are then used as a starting point for determining an optimum beam orientation configuration with more beams (e.g. 5). This process is parallelized using a message passing interface, which greatly reduces the overall computation time for routine clinical practice. To test this approach, treatment for 10 patients with paranasal sinus cancer was planned using a total of 5 beams from a pool of 46 possible beam angles. The PMBAO treatment plans were also compared with IMRT plans designed using 9 equally spaced coplanar beams, which is the standard approach in our clinic. Plans with these two different beam configurations were compared with respect to dose conformity, dose heterogeneity, dose-volume histograms, and doses to organs at risk (i.e., eyes, optic nerve, optic chiasm, and brain). Results: The noncoplanar beam configuration was superior in most paranasal sinus carcinoma cases. The target dose homogeneity was better using a PMBAO 5-beam configuration. However, the dose conformity using PMBAO was not improved and was case dependent. Compared with the 9-beam configuration, the PMBAO configuration significantly reduced the mean dose to the eyes and optic nerves and the maximum dose to the contralateral optical path (e.g. the contralateral eye and optic nerve). The maximum dose to the ipsilateral eye and optic nerve was also lower using the PMBAO configuration than using the 9-beam
Infrared Photodissociation Spectroscopy of Metal Oxide Carbonyl Cations.
Brathwaite, Antonio D.; Duncan, Michael A.
2013-06-01
Mass selected metal oxide-carbonyl cations of the form MO_{m}(CO)_{n}^{+} are studied via infrared laser photodissociation spectroscopy, in the 600-2300cm^{1} region. Insight into the structure and bonding of these complexes is obtained from the number of infrared active bands, their relative intensities and their frequency positions. Density functional theory calculations are carried out in support of the experimental data. Insight into the bonding of CO ligands to metal oxides is obtained and the effect of oxidation on the carbonyl stretching frequency is revealed.
Photodissociation of N2O: excitation of 1A" states.
Schinke, Reinhard; Schmidt, Johan A
2012-11-26
We investigate the contributions of the lowest two (1)A" states in the UV photodissociation of N(2)O employing three-dimensional potential energy surfaces and transition dipole moment functions. Because the transition dipole moments are much smaller than for the 2 (1)A' state, we conclude that excitation of the (1)A" states has a marginal effect. The dense vibrational spectrum of the quasi-bound 2(1)A" state possibly explains some of the tiny, noise-like structures of the measured absorption spectrum. PMID:22536943
Vacuum ultraviolet photoionization and photodissociation of polyatomic molecules and radicals
Energy Technology Data Exchange (ETDEWEB)
Ng, C.Y. [Iowa State Univ., Ames (United States)
1993-12-01
In the past decade, tremendous progress has been made in understanding the photodissociation (PD) dynamics of triatomic molecules. However, the PD study of radicals, especially polyatomic radicals, has remained essentially an unexplored research area. Detailed state-to-state PD cross sections for radicals in the UV and VUV provide challenges not only for dynamical calculations, but also for ab initio quantum chemical studies. The authors have developed a laser based pump-probe apparatus for the measurement of absolute PD cross sections for CH{sub 3}S and HS is summarized.
Photodissociation of the HeH+ molecular ion
International Nuclear Information System (INIS)
The photodissociation cross section of the molecular ion HeH+ was calculated within the Born-Oppenheimer approximation for a parallel, a perpendicular and an isotropic orientation of the molecular axis with respect to the field, considering also different initial vibrational and rotational states. The results were compared to recent data from a free-electron laser experiment performed at the FLASH facility by Pedersen et al(2007 Phys. Rev. Lett. 98 223202). Within the experimental uncertainties theoretical and experimental results are compatible with each other.
DEFF Research Database (Denmark)
Jeong, Cheol-Ho; Ih, Jeong-Guon
2012-01-01
The accuracy of a phased beam tracing method in predicting transfer functions is investigated with a special focus on the positions of the source and receiver. Simulated transfer functions for various source-receiver pairs using the phased beam tracing method were compared with analytical Green’s...
Selective Beam Shielding Method of Gamma-Knife Unit Using Various Plugging Patterns
International Nuclear Information System (INIS)
The B-type gamma knife unit was installed at Kyung-Hee University Hospital in March 1992. The selective beam plugging method can be used to reduce the low percentage isodose profiles of normal sensitive organ and to codify the isodose cuties of treatment volume for better shaping of the target volume. For representing the changes of the law percentage isodose profiles, the variations of dose distribution for several cases were discussed in this paper. The film dosimetry was performed for the evaluation of calculated isodose profiles predicted by KULA dose planning system. The results were verified by RFA-3 automatic densitometry. The clinical application of selective beam shielding method was performed in 17 patients in 100 patients who have undergone gamma knife radiosurgery for a year. The calculated and the measured isodose profiles for the high percentage regions were well consistent with each other. When the target of pituitary tumor is macro-size, the selective beam shielding method is the most applicable method. When the target size, however, is small, the correct selection of the proper helmet size is very important. All patients were exposed almost about 3-12 Gy for brain stem, and 3-11.2 Gy for optic apparatus. It is recommended that the same or other plugging patterns with multiple isocenters should be used for protection of the radiosensitive normal structures with precise treatment of CNS lesions
International Nuclear Information System (INIS)
A novel method to produce spin-aligned rare-isotope (RI) beam has been developed, that is the two-step projectile fragmentation method with a technique of dispersion matching. The present method was verified in an experiment at the RIKEN RIBF, where an RI beam of 32Al with spin alignment of 8(1) % was successfully produced from a primary beam of 48Ca, with 33Al as an intermediate nucleus. Figure of merit of the present method was found to be improved by a factor larger than 50 compared with a conventional method employing single-step projectile fragmentation.
Energy Technology Data Exchange (ETDEWEB)
Ichikawa, Y., E-mail: yuichikawa@phys.titech.ac.jp [Tokyo Institute of Technology, Department of Physics (Japan); Ueno, H. [RIKEN Nishina Center (Japan); Ishii, Y. [Tokyo Institute of Technology, Department of Physics (Japan); Furukawa, T. [Tokyo Metropolitan University, Department of Physics (Japan); Yoshimi, A. [Okayama University, Research Core for Extreme Quantum World (Japan); Kameda, D.; Watanabe, H.; Aoi, N. [RIKEN Nishina Center (Japan); Asahi, K. [Tokyo Institute of Technology, Department of Physics (Japan); Balabanski, D. L. [Bulgarian Academy of Sciences, Institute for Nuclear Research and Nuclear Energy (Bulgaria); Chevrier, R.; Daugas, J. M. [CEA, DAM, DIF (France); Fukuda, N. [RIKEN Nishina Center (Japan); Georgiev, G. [CSNSM, IN2P3-CNRS, Universite Paris-sud (France); Hayashi, H.; Iijima, H. [Tokyo Institute of Technology, Department of Physics (Japan); Inabe, N. [RIKEN Nishina Center (Japan); Inoue, T. [Tokyo Institute of Technology, Department of Physics (Japan); Ishihara, M.; Kubo, T. [RIKEN Nishina Center (Japan); and others
2013-05-15
A novel method to produce spin-aligned rare-isotope (RI) beam has been developed, that is the two-step projectile fragmentation method with a technique of dispersion matching. The present method was verified in an experiment at the RIKEN RIBF, where an RI beam of {sup 32}Al with spin alignment of 8(1) % was successfully produced from a primary beam of {sup 48}Ca, with {sup 33}Al as an intermediate nucleus. Figure of merit of the present method was found to be improved by a factor larger than 50 compared with a conventional method employing single-step projectile fragmentation.
Adrich, Przemysław
2016-05-01
In Part I of this work a new method for designing dual foil electron beam forming systems was introduced. In this method, an optimal configuration of the dual foil system is found by means of a systematic, automatized scan of system performance in function of its parameters. At each point of the scan, Monte Carlo method is used to calculate the off-axis dose profile in water taking into account detailed and complete geometry of the system. The new method, while being computationally intensive, minimizes the involvement of the designer. In this Part II paper, feasibility of practical implementation of the new method is demonstrated. For this, a prototype software tools were developed and applied to solve a real life design problem. It is demonstrated that system optimization can be completed within few hours time using rather moderate computing resources. It is also demonstrated that, perhaps for the first time, the designer can gain deep insight into system behavior, such that the construction can be simultaneously optimized in respect to a number of functional characteristics besides the flatness of the off-axis dose profile. In the presented example, the system is optimized in respect to both, flatness of the off-axis dose profile and the beam transmission. A number of practical issues related to application of the new method as well as its possible extensions are discussed.
A Numerical Method for Cavity Identification in Beams on an Elastic Foundation
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
An analytical solution for the natural frequencies of a beam containing a cavity on an elastic foundation is presented. Based on the analytical solution, a numerical method for identifying cavities in the foundation is developed. The position and size of the cavities are identified by minimizing an objective function, which is formulated according to the difference between the computed and measured natural frequencies of the system. The conjugate gradient algorithm is adopted for minimizing the objective function. Some numerical examples are presented to demonstrate the applicability of the presented cavity determination method. The results show that the presented method can be used to identify the cavity position and size conveniently and efficiently.
Preparation of PbSe nanoparticles by electron beam irradiation method
Indian Academy of Sciences (India)
Zhen Li; Chao Wu; Yanyan Liu; Tiebing Liu; Zheng Jiao; Minghong Wu
2008-11-01
A novel method has been developed by electron beam irradiation to prepare PbSe nanoparticles. 2 MeV 10mA GJ-2-II electronic accelerator was used as radiation source. Nanocrystalline PbSe was prepared rapidly at room temperature under atmospheric pressure without any kind of toxic reagents. The structure and morphology of prepared PbSe nanoparticles were analysed by X-ray diffraction, transmission electron microscope and atomic force microscope. The results indicated that the obtained materials were cubic nanocrystalline PbSe with an average grain size of 30 nm. The optical properties of prepared PbSe nanocrystalline were characterized by using photoluminescence spectroscopy. The possible mechanism of the PbSe grain growth by electron beam irradiation method is proposed.
DEFF Research Database (Denmark)
Jeong, Cheol-Ho; Ih, Jeong-Guon; Rindel, Jens Holger
The phased beam tracing method (PBTM) is a technique which can calculate the pressure impulse response instead of energy impulse response, by taking the phase information into account. Inclusion of the phase information can extend the application of beam tracing technique to the mid frequency range...... in spite of the fact that the usual assumptions of geometric acoustics still hold. In the calculation of pressure impulse response, it is essential to have the reflection characteristics of the surfaces in the enclosed space. There is a method to obtain the reflection coefficient of the surface using...... the measured surface impedance. However, it is not always possible to get the measured impedance data of the surface, so that a practical way of getting reflection characteristics is needed. Generally, in the architectural acoustics field, the absorption coefficients have been employed in the...
Generation of Shaped beam Radiation patterns from a Line source using Iterative sampling method
Directory of Open Access Journals (Sweden)
G.R.L.V.N.Srinivasa Raju
2013-08-01
Full Text Available For the generation of cosecant and trapezoidal radiation patterns an iterative sampling method is introduced by Stutzman. In this paper, an original radiation pattern which is some approximation to the desired radiation pattern is generated by a standard synthesis method and a series of correction patterns are applied to it by addinga correction pattern. This process is continued until the desired performance is achieved. In the present work, ramp, sector, cosecant, trapezoidal and stair stepped radiation patterns are generated using iterative procedure. The current distribution is found after corrections are applied. Studies are made with good number of examples, which showed that patterns with low side lobe level or low main beam ripple or sharp cut off from the main beam can be obtained. An iterative procedure is simple and converges rapidly.
In situ baking method for degassing of a kicker magnet in accelerator beam line
Energy Technology Data Exchange (ETDEWEB)
Kamiya, Junichiro, E-mail: kamiya.junichiro@jaea.go.jp; Ogiwara, Norio; Yanagibashi, Toru; Kinsho, Michikazu [Japan Atomic Energy Agency, J-PARC Center, Ooaza Shirakata 2-4, Tokai, Naka, Ibaraki 319-1195 (Japan); Yasuda, Yuichi [SAKAGUCHI E.H VOC CORP., Sakura Dai-san Kogyodanchi 1-8-6, Osaku, Sakura, Chiba 285-0802 (Japan)
2016-03-15
In this study, the authors propose a new in situ degassing method by which only kicker magnets in the accelerator beam line are baked out without raising the temperature of the vacuum chamber to prevent unwanted thermal expansion of the chamber. By simply installing the heater and thermal radiation shield plates between the kicker magnet and the chamber wall, most of the heat flux from the heater directs toward the kicker magnet. The result of the verification test showed that each part of the kicker magnet was heated to above the target temperature with a small rise in the vacuum chamber temperature. A graphite heater was selected in this application to bake-out the kicker magnet in the beam line to ensure reliability and easy maintainability of the heater. The vacuum characteristics of graphite were suitable for heater operation in the beam line. A preliminary heat-up test conducted in the accelerator beam line also showed that each part of the kicker magnet was successfully heated and that thermal expansion of the chamber was negligibly small.
International Nuclear Information System (INIS)
The scanning irradiation of the pencil beam is superior in comparison to the conventional extended-field irradiation in dose concentration. The carbon pencil beam spreads its profile in matter. The factors that cause the profile change are the nuclear fragmentation reactions and the multiple Coulomb scatterings. The fragmentation reaction is a type of nuclear reactions, where the high-energy incident particles interact with target nuclei and fragment the incident particles themselves or the target nucleus. In order to improve the accuracy of the treatment planning for the carbon beam, it is necessary to evaluate quantitatively the effect of the nuclear fragmentation reactions. The objective of this study is to establish the evaluation method for the carbon pencil beam profile in matter by selectively acquiring the nuclear fragmentation reactions and the multiple Coulomb scattering. This experiment was proposed to carry out in three years. Events with the nuclear fragmentation reactions and the multiple Coulomb scatterings were separately identified by a dedicated detector devised by our group. Profiles of these events were successfully measured. (author)
Deflection of a monochromatic THz beam by acousto-optic methods
International Nuclear Information System (INIS)
The possibility of controlled deflection of an electromagnetic THz beam of a free-electron laser by acousto-optic (AO) methods has been demonstrated for the first time. The material of the AO deflector was chosen to be single-crystal germanium, which has a fairly large refractive index (n = 4.0) and a relatively low absorption coefficient for electromagnetic waves. The absorption coefficient α in germanium is 0.75 ± 0.02 cm-1 at a wavelength λ = 140 μm. The diffracted beam intensity is shown to be maximum at an effective AO interaction length l = 1/α. A diffraction efficiency of 0.05% at a travelling acoustic wave power of 1.0 W is experimentally obtained. It is established that a change in the ultrasonic frequency from 25 to 39 MHz leads to variation in the external Bragg angle in the range from 19.5° to 27.5°. At a fixed Bragg angle θB = 22.4° the frequency band of diffraction is 4.2 ± 0.1 MHz and the angular range of laser beam scanning reaches 2.5° ± 0.5°. The results obtained indicate that AO interaction can be used for controlled deflection of electromagnetic THz beams. (terahertz radiation)
A design method for two-layer beams consisting of normal and fibered high strength concrete
International Nuclear Information System (INIS)
Two-layer fibered concrete beams can be analyzed using conventional methods for composite elements. The compressed zone of such beam section is made of high strength concrete (HSC), and the tensile one of normal strength concrete (NSC). The problems related to such type of beams are revealed and studied. An appropriate depth of each layer is prescribed. Compatibility conditions between HSC and NSC layers are found. It is based on the shear deformations equality on the layers border in a section with maximal depth of the compression zone. For the first time a rigorous definition of HSC is given using a comparative analysis of deformability and strength characteristics of different concrete classes. According to this definition, HSC has no download branch in the stress-strain diagram, the stress-strain function has minimum exponent, the ductility parameter is minimal and the concrete tensile strength remains constant with an increase in concrete compression strength. The application fields of two-layer concrete beams based on different static schemes and load conditions make known. It is known that the main disadvantage of HSCs is their low ductility. In order to overcome this problem, fibers are added to the HSC layer. Influence of different fiber volume ratios on structural ductility is discussed. An upper limit of the required fibers volume ratio is found based on compatibility equation of transverse tensile concrete deformations and deformations of fibers
Electron beam irradiation as a method to modify the wheat starch characteristics
International Nuclear Information System (INIS)
Full text: Starch is a renewable bioresource with wide range of potential applications. At present time, considerable efforts are made worldwide with respect to research and mainly to development of processes for treating and modifying of different starches in order to extend their industrial applicability. Our previous work proved the potential of the electron beam irradiation to modify the functional properties of maize starch. The aim of this work is to investigate the possibility to use the electron beam irradiation to change some characteristics of wheat starch. The physicochemical and structural characteristics of the irradiated wheat starch are analyzed in comparison to the native wheat starch ones. The electron beam irradiation lead to the reduction of the paste pH, clarity and apparent viscosity as the absorbed dose increase, while the thermal stability is not affected. Also, changes at the structure level in the irradiated starch can be observed. Electron beam irradiation may be an alternative method to modify some of the wheat starch properties
Deflection of a monochromatic THz beam by acousto-optic methods
Energy Technology Data Exchange (ETDEWEB)
Voloshinov, V B; Nikitin, P A [Department of Physics, M.V. Lomonosov Moscow State University (Russian Federation); Gerasimov, V V; Choporova, Yu Yu [G.I. Budker Institute of Nuclear Physics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk (Russian Federation); Knyazev, B A [Novosibirsk National Research State University, Novosibirsk (Russian Federation)
2013-12-31
The possibility of controlled deflection of an electromagnetic THz beam of a free-electron laser by acousto-optic (AO) methods has been demonstrated for the first time. The material of the AO deflector was chosen to be single-crystal germanium, which has a fairly large refractive index (n = 4.0) and a relatively low absorption coefficient for electromagnetic waves. The absorption coefficient α in germanium is 0.75 ± 0.02 cm{sup -1} at a wavelength λ = 140 μm. The diffracted beam intensity is shown to be maximum at an effective AO interaction length l = 1/α. A diffraction efficiency of 0.05% at a travelling acoustic wave power of 1.0 W is experimentally obtained. It is established that a change in the ultrasonic frequency from 25 to 39 MHz leads to variation in the external Bragg angle in the range from 19.5° to 27.5°. At a fixed Bragg angle θ{sub B} = 22.4° the frequency band of diffraction is 4.2 ± 0.1 MHz and the angular range of laser beam scanning reaches 2.5° ± 0.5°. The results obtained indicate that AO interaction can be used for controlled deflection of electromagnetic THz beams. (terahertz radiation)
PReBeaM FOR PLANCK: A POLARIZED REGULARIZED BEAM DECONVOLUTION MAP-MAKING METHOD
International Nuclear Information System (INIS)
We describe a maximum-likelihood regularized beam deconvolution map-making algorithm for data from high-resolution, polarization-sensitive instruments, such as the Planck data set. The resulting algorithm, which we call PReBeaM, is pixel-free and solves for the map directly in spherical harmonic space, avoiding pixelization artifacts. While Fourier methods like ours are expected to work best when applied to smooth, large-scale asymmetric beam systematics (such as far-side lobe effects), we show that our m-truncated spherical harmonic representation of the beam results in negligible reconstruction error-even for m as small as 4 for a polarized elliptically asymmetric beam. We describe a hybrid OpenMP/MPI parallelization scheme which allows us to store and manipulate the time-ordered data from satellite instruments with a typical full-sky scanning strategy. Finally, we apply our technique to noisy data and show that it succeeds in removing visible power spectrum artifacts without generating excess noise on small scales.
Research of photon beam dose deposition kernel based on Monte Carlo method
International Nuclear Information System (INIS)
Using Monte Carlo program BEAMnrc to simulate Siemens accelerator 6 MV photon beam, using BEAMdp program to analyse the energy spectrum distribution and mean energy from phase space data of different field sizes, then building beam source, energy spectrum and mono-energy source, to use DOSXYZnrc program to calculate the dose deposition kernels at dmax in standard water phantom with different beam sources and make comparison with different dose deposition kernels. The results show that the dose difference using energy spectrum source is small, the maximum percentage dose discrepancy is 1.47%, but it is large using mono-energy source, which is 6.28%. The maximum dose difference for the kernels derived from energy spectrum source and mono-energy source of the same field is larger than 9%, up to 13.2%. Thus, dose deposition has dependence on photon energy, it can lead to larger errors only using mono-energy source because of the beam spectrum distribution of accelerator. A good method to calculate dose more accurately is to use deposition kernel of energy spectrum source. (authors)
International Nuclear Information System (INIS)
Shape sensing, i.e., reconstruction of the displacement field of a structure from surface-measured strains, has relevant implications for the monitoring, control and actuation of smart structures. The inverse finite element method (iFEM) is a shape-sensing methodology shown to be fast, accurate and robust. This paper aims to demonstrate that the recently presented iFEM for beam and frame structures is reliable when experimentally measured strains are used as input data. The theoretical framework of the methodology is first reviewed. Timoshenko beam theory is adopted, including stretching, bending, transverse shear and torsion deformation modes. The variational statement and its discretization with C0-continuous inverse elements are briefly recalled. The three-dimensional displacement field of the beam structure is reconstructed under the condition that least-squares compatibility is guaranteed between the measured strains and those interpolated within the inverse elements. The experimental setup is then described. A thin-walled cantilevered beam is subjected to different static and dynamic loads. Measured surface strains are used as input data for shape sensing at first with a single inverse element. For the same test cases, convergence is also investigated using an increasing number of inverse elements. The iFEM-recovered deflections and twist rotations are then compared with those measured experimentally. The accuracy, convergence and robustness of the iFEM with respect to unavoidable measurement errors, due to strain sensor locations, measurement systems and geometry imperfections, are demonstrated for both static and dynamic loadings. (paper)
Impact resonance method for damage detection in RC beams strengthened with composites
Gheorghiu, Catalin; Rhazi, Jamal E.; Labossiere, Pierre
2005-05-01
There are numerous successful applications of fibre-reinforced composites for strengthening the civil engineering infrastructure. Most of these repairs are being continuously or intermittently monitored for assessing their effectiveness and safety. The impact resonance method (IRM), a non-destructive technique, utilized in civil engineering exclusively for determining the dynamic concrete properties, could be a valuable and viable damage detection tool for structural elements. The IRM gives useful information about the dynamic characteristics of rectangular and circular concrete members such as beams and columns. In this experimental program, a 1.2-m-long reinforced concrete beam strengthened with a carbon fibre-reinforced polymer (CFRP) plate has been employed. The CFRP-strengthened beam has been loaded in fatigue for two million cycles at 3 Hz. The load amplitude was from 15 to 35% of the anticipated yielding load of the beam. Throughout fatigue testing the cycling was stopped for IRM measurements to be taken. The obtained data provided information about changes in modal properties such as natural frequencies of vibration. These results have shown the successful use of the IRM for detecting fatigue damage in concrete members strengthened with composites.
Directory of Open Access Journals (Sweden)
E.V.V.Ramanamurthy
2011-07-01
Full Text Available The objective of this paper is to develop a damage detection method in a composite cantilever beam with an edge crack has been studied using finite element method. A number of analytical, numerical andexperimental techniques are available for the study of damage identification in beams. Studies were carried out for three different types of analysis on a composite cantilever beam with an edge crack as damage. The material used in this analysis is glass-epoxy composite material. The finite element formulation was carried out in the analysis section of the package, known as ANSYS. The types of vibration analysis studied on a composite beam are Modal, Harmonic andTransient analysis. The crack is modeled such that the cantilever beam is replaced with two intact beams with the crack as additional boundary condition. Damage algorithms are used to identify and locate the damage. Damage index method is also used to find the severity of the damage. The results obtained from modal analysis were compared with the transient analysis results.The vibration-based damage detection methods are based on the fact that changes of physical properties (stiffness, mass and damping due to damage will manifest themselves as changes in the structural modal parameters (natural frequencies, mode shapes and modal damping. The task is then to monitor the selected indicators derived from modal parameters to distinguish between undamaged and damaged states. However, the quantitative changes of global modal parameters are not sufficiently sensitive to a local damage. The proposed approach, on the other hand, interprets the dynamic changes caused by damage in a different way. Although the basis for vibration-based damage detection appears intuitive, the implementation in real structures may encounter many significant challenges. The most fundamental issue is the fact that damage typically is a local phenomenon and may not dramatically influence the global dynamic response of a
Complexity Theory of Beam Halo-Chaos and Its Control Methods With Prospective Applications
Institute of Scientific and Technical Information of China (English)
2002-01-01
This article offers an overview and comprehensive survey of the complexity theory of beamhalo-chaos and its control methods with prospective applications. In recent years, there has been growinginterest in proton beams of high power linear accelerator due to its attractive features in possiblebreakthrough applications, such as production of nuclear materials (e.g., tritium, transforming 232Th to233U), transmutation of radioactive wastes, productions of radioactive isotopes for medical use, heavy ion
A method for the dimensioning of a cantileva-beam submitted to aleatory effects
International Nuclear Information System (INIS)
The laboratory study of behavior of materials, related to fatigue, is generally done by applying constant amplitude sine wave excitation. The data can be used for the stochastic approach of the problem. One of the methods is called RCA, which incorporates the Linear Rule or Miner's Cumulative Damage Rule. A summary of the theory and a computer program for the calculations are here presented. A cantilever beam is studied as a numerical example and the results are discussed. (Author)
Modeling Liquid-Crystal Devices with the Three-Dimensional Full-Vector Beam Propagation Method
Wang, Qian; Farrell, Gerald; Semenova, Yuliya
2006-01-01
Simulation of light propagation within nematic liquid-crystal (LC) devices is considered, of which the director is aligned normal to the z axis. A three-dimensional full-vector finite-difference beam propagation method for an anisotropic medium is presented and an alternating direction implicit scheme is adopted. Simulations of light propagation in a bulk polarization converter, a waveguide with a LC covering layer, and an integrated polarization splitter and optical switch are presented. Com...
Robust methods for automatic image-to-world registration in cone-beam CT interventional guidance
Dang, H; Otake, Y.; Schafer, S.; Stayman, J. W.; Kleinszig, G.; Siewerdsen, J. H.
2012-01-01
Purpose: Real-time surgical navigation relies on accurate image-to-world registration to align the coordinate systems of the image and patient. Conventional manual registration can present a workflow bottleneck and is prone to manual error and intraoperator variability. This work reports alternative means of automatic image-to-world registration, each method involving an automatic registration marker (ARM) used in conjunction with C-arm cone-beam CT (CBCT). The first involves a Known-Model re...
Photodissociation dynamics of CH3C(O)SH in argon matrix: A QM/MM nonadiabatic dynamics simulation
International Nuclear Information System (INIS)
In this work, we have first employed the combined quantum mechanics/molecular mechanics (QM/MM) method to study the photodissociation mechanism of thioacetic acid CH3C(O)SH in the S1, T1, and S0 states in argon matrix. CH3C(O)SH is treated quantum mechanically using the complete active space self-consistent field and complete active space second-order perturbation theory methods; argon matrix is described classically using Lennard-Jones potentials. We find that the C-S bond fission is predominant due to its small barriers of ca. 3.0 and 1.0 kcal/mol in the S1 and T1 states. It completely suppresses the nearby C—C bond fission. After the bond fission, the S1 radical pair of CH3CO and SH can decay to the S0 and T1 states via internal conversion and intersystem crossing, respectively. In the S0 state, the radical pair can either recombine to form CH3C(O)SH or proceed to form molecular products of CH2CO and H2S. We have further employed our recently developed QM/MM generalized trajectory-based surface-hopping method to simulate the photodissociation dynamics of CH3C(O)SH. In 1 ps dynamics simulation, 56% trajectories stay at the Franck-Condon region; the S1 C—S bond fission takes place in the remaining 44% trajectories. Among all nonadiabatic transitions, the S1 → S0 internal conversion is major (55%) but the S1 → T1 intersystem crossing is still comparable and cannot be ignored, which accounts for 28%. Finally, we have found a radical channel generating the molecular products of CH2CO and H2S, which is complementary to the concerted molecular channel. The present work sets the stage for simulating photodissociation dynamics of similar thio-carbonyl systems in matrix
A modified time-of-flight method for precise determination of high speed ratios in molecular beams
International Nuclear Information System (INIS)
Time-of-flight (TOF) is a standard experimental technique for determining, among others, the speed ratio S (velocity spread) of a molecular beam. The speed ratio is a measure for the monochromaticity of the beam and an accurate determination of S is crucial for various applications, for example, for characterising chromatic aberrations in focussing experiments related to helium microscopy or for precise measurements of surface phonons and surface structures in molecular beam scattering experiments. For both of these applications, it is desirable to have as high a speed ratio as possible. Molecular beam TOF measurements are typically performed by chopping the beam using a rotating chopper with one or more slit openings. The TOF spectra are evaluated using a standard deconvolution method. However, for higher speed ratios, this method is very sensitive to errors related to the determination of the slit width and the beam diameter. The exact sensitivity depends on the beam diameter, the number of slits, the chopper radius, and the chopper rotation frequency. We present a modified method suitable for the evaluation of TOF measurements of high speed ratio beams. The modified method is based on a systematic variation of the chopper convolution parameters so that a set of independent measurements that can be fitted with an appropriate function are obtained. We show that with this modified method, it is possible to reduce the error by typically one order of magnitude compared to the standard method
A modified time-of-flight method for precise determination of high speed ratios in molecular beams
Energy Technology Data Exchange (ETDEWEB)
Salvador Palau, A.; Eder, S. D., E-mail: sabrina.eder@uib.no; Kaltenbacher, T.; Samelin, B.; Holst, B. [Department of Physics and Technology, University of Bergen, Allégaten 55, 5007 Bergen (Norway); Bracco, G. [Department of Physics and Technology, University of Bergen, Allégaten 55, 5007 Bergen (Norway); CNR-IMEM, Department of Physics, University of Genova, V. Dodecaneso 33, 16146 Genova (Italy)
2016-02-15
Time-of-flight (TOF) is a standard experimental technique for determining, among others, the speed ratio S (velocity spread) of a molecular beam. The speed ratio is a measure for the monochromaticity of the beam and an accurate determination of S is crucial for various applications, for example, for characterising chromatic aberrations in focussing experiments related to helium microscopy or for precise measurements of surface phonons and surface structures in molecular beam scattering experiments. For both of these applications, it is desirable to have as high a speed ratio as possible. Molecular beam TOF measurements are typically performed by chopping the beam using a rotating chopper with one or more slit openings. The TOF spectra are evaluated using a standard deconvolution method. However, for higher speed ratios, this method is very sensitive to errors related to the determination of the slit width and the beam diameter. The exact sensitivity depends on the beam diameter, the number of slits, the chopper radius, and the chopper rotation frequency. We present a modified method suitable for the evaluation of TOF measurements of high speed ratio beams. The modified method is based on a systematic variation of the chopper convolution parameters so that a set of independent measurements that can be fitted with an appropriate function are obtained. We show that with this modified method, it is possible to reduce the error by typically one order of magnitude compared to the standard method.
Photodissociation and photoisomerization dynamics of CH2=CHCHO in solution
International Nuclear Information System (INIS)
By means of time-resolved Fourier transform infrared absorption spectroscopy, we have investigated the 193 nm photodissociation and photoisomerization dynamics of the prototype molecule of α,β-enones, acrolein (CH2=CHCHO) in CH3CN solution. The primary photolysis channels and absolute branching ratios are determined. The most probable reaction mechanisms are clarified by control experiments monitoring the product yields varied with the triplet quencher addition. The predominant channel is the 1,3-H migration yielding the rearrangement product CH3CH=C=O with a branching ratio of 0.78 and the less important channel is the α cleavage of C-H bond yielding radical fragments CH2=CHCO+H with a branching ratio of only 0.12. The 1,3-H migration is strongly suggested to correlate with the triplet 3(ππ*) state rather than the ground S0 state and the α cleavage of C-H bond is more likely to proceed in the singlet S11(nπ*) state. From the solution experiments we have not only acquired clues clarifying the previous controversial mechanisms, but also explored different photochemistry in solution. Compared to the gas phase photolysis which is dominated by photodissociation channels, the most important channel in solution is the photoisomerization of 1,3-H migration. The reason leading to the different photochemistry in solution is further ascribed to the solvent cage effect.
Analytic H i-to-H2 Photodissociation Transition Profiles
Bialy, Shmuel; Sternberg, Amiel
2016-05-01
We present a simple analytic procedure for generating atomic (H i) to molecular ({{{H}}}2) density profiles for optically thick hydrogen gas clouds illuminated by far-ultraviolet radiation fields. Our procedure is based on the analytic theory for the structure of one-dimensional H i/{{{H}}}2 photon-dominated regions, presented by Sternberg et al. Depth-dependent atomic and molecular density fractions may be computed for arbitrary gas density, far-ultraviolet field intensity, and the metallicity-dependent H2 formation rate coefficient, and dust absorption cross section in the Lyman-Werner photodissociation band. We use our procedure to generate a set of {{H}} {{I}}{-}{to}{-}{{{H}}}2 transition profiles for a wide range of conditions, from the weak- to strong-field limits, and from super-solar down to low metallicities. We show that if presented as functions of dust optical depth, the {{H}} {{I}} and {{{H}}}2 density profiles depend primarily on the Sternberg “α G parameter” (dimensionless) that determines the dust optical depth associated with the total photodissociated {{H}} {{I}} column. We derive a universal analytic formula for the {{H}} {{I}}{-}{to}{-}{{{H}}}2 transition points as a function of just α G. Our formula will be useful for interpreting emission-line observations of H i/{{{H}}}2 interfaces, for estimating star formation thresholds, and for sub-grid components in hydrodynamics simulations.
Photodissociation and Density Functional Calculations of Small+ Clusters
Institute of Scientific and Technical Information of China (English)
Ren-zhong Li; Hong-guang Xu; Guo-jin Cao; Yu-chao Zhao; Wei-iun Zheng
2011-01-01
Oxygen-poor vanadium oxide clusters,V2O,n+ (n=1,2),V3On+ (n=1,2,3),and V4O3+,were produced by laser vaporization and were mass-selected and photodissociated with 532 and 266 nm photons.The geometric structures and possible dissociation channels of these clusters were determined based on the comparison of density functional calculations and photodissociation experiments.The experiments show that the dissociation of V2O+,V2O2+,and V3O3+ mainly occurs by loss of VO,while the dissociation of V3O+ and V4O3+ mainly occurs by loss of V atom.For the dissociation of V3O2+,the VO loss channel is slightly dominant compared to the V loss channel.The combination of experimental results and theoretical calculations suggests that the V loss channels of V3O+ and V4O3+ are single photon processes at both 532 and 266 nm.The VO loss channels of V2O2+ and V3O3+ are multiple-photon processes at both 532 and 266 nm.
Photodissociation dynamics of OCS near 214 nm using ion imaging
Wei, Wei; Wallace, Colin J.; McBane, George C.; North, Simon W.
2016-07-01
The OCS photodissociation dynamics of the dominant S(1D2) channel near 214 nm have been studied using velocity map ion imaging. We report a CO vibrational branching ratio of 0.79:0.21 for v = 0:v = 1, indicating substantially higher vibrational excitation than that observed at slightly longer wavelengths. The CO rotational distribution is bimodal for both v = 0 and v = 1, although the bimodality is less pronounced than at longer wavelengths. Vector correlations, including rotational alignment, indicate that absorption to both the 21A' (A) and 11A″ (B) states is important in the lower-j part of the rotational distribution, while only 21A' state absorption contributes to the upper part; this conclusion is consistent with work at longer wavelengths. Classical trajectory calculations including surface hopping reproduce the measured CO rotational distributions and their dependence on wavelength well, though they underestimate the v = 1 population. The calculations indicate that the higher-j peak in the rotational distribution arises from molecules that begin on the 21A' state but make nonadiabatic transitions to the 11A' (X) state during the dissociation, while the lower-j peak arises from direct photodissociation on either the 21A' or the 11A″ states, as found in previous work.
SU-E-J-126: An Online Replanning Method for FFF Beams Without Couch Shift
Energy Technology Data Exchange (ETDEWEB)
Ahunbay, E; Ates, O; Li, X [Medical College of Wisconsin, Milwaukee, WI (United States)
2015-06-15
Purpose: In a situation that couch shift for patient positioning is not preferred or prohibited (e.g., MR-Linac), segment aperture morphing (SAM) can address target dislocation and deformation. For IMRT/VMAT with flattening filter free (FFF) beams, however, SAM method would lead to an adverse translational dose effect due to the beam unflattening. Here we propose a new 2-step process to address both the translational effect of FFF beams and the target deformation. Methods: The replanning method consists of an offline and an online steps. The offline step is to create a series of pre-shifted plans (PSP) obtained by a so called “warm start” optimization (starting optimization from the original plan, rather from scratch) at a series of isocenter shifts with fixed distance (e.g. 2 cm, at x,y,z = 2,0,0 ; 2,2,0 ; 0,2,0; …;− 2,0,0). The PSPs all have the same number of segments with very similar shapes, since the warm-start optimization only adjusts the MLC positions instead of regenerating them. In the online step, a new plan is obtained by linearly interpolating the MLC positions and the monitor units of the closest PSPs for the shift determined from the image of the day. This two-step process is completely automated, and instantaneously fast (no optimization or dose calculation needed). The previously-developed SAM algorithm is then applied for daily deformation. We tested the method on sample prostate and pancreas cases. Results: The two-step interpolation method can account for the adverse dose effects from FFF beams, while SAM corrects for the target deformation. The whole process takes the same time as the previously reported SAM process (5–10 min). Conclusion: The new two-step method plus SAM can address both the translation effects of FFF beams and target deformation, and can be executed in full automation requiring no additional time from the SAM process. This research was supported by Elekta inc. (Crawley, UK)
SU-E-J-126: An Online Replanning Method for FFF Beams Without Couch Shift
International Nuclear Information System (INIS)
Purpose: In a situation that couch shift for patient positioning is not preferred or prohibited (e.g., MR-Linac), segment aperture morphing (SAM) can address target dislocation and deformation. For IMRT/VMAT with flattening filter free (FFF) beams, however, SAM method would lead to an adverse translational dose effect due to the beam unflattening. Here we propose a new 2-step process to address both the translational effect of FFF beams and the target deformation. Methods: The replanning method consists of an offline and an online steps. The offline step is to create a series of pre-shifted plans (PSP) obtained by a so called “warm start” optimization (starting optimization from the original plan, rather from scratch) at a series of isocenter shifts with fixed distance (e.g. 2 cm, at x,y,z = 2,0,0 ; 2,2,0 ; 0,2,0; …;− 2,0,0). The PSPs all have the same number of segments with very similar shapes, since the warm-start optimization only adjusts the MLC positions instead of regenerating them. In the online step, a new plan is obtained by linearly interpolating the MLC positions and the monitor units of the closest PSPs for the shift determined from the image of the day. This two-step process is completely automated, and instantaneously fast (no optimization or dose calculation needed). The previously-developed SAM algorithm is then applied for daily deformation. We tested the method on sample prostate and pancreas cases. Results: The two-step interpolation method can account for the adverse dose effects from FFF beams, while SAM corrects for the target deformation. The whole process takes the same time as the previously reported SAM process (5–10 min). Conclusion: The new two-step method plus SAM can address both the translation effects of FFF beams and target deformation, and can be executed in full automation requiring no additional time from the SAM process. This research was supported by Elekta inc. (Crawley, UK)
A new and simple calibration-independent method for measuring the beam energy of a cyclotron
Energy Technology Data Exchange (ETDEWEB)
Gagnon, Katherine, E-mail: kgagnon1@ualberta.c [Cross Cancer Institute, Edmonton PET Centre, University of Alberta, Edmonton, AB, T6G 1Z2 (Canada); Jensen, Mikael; Thisgaard, Helge [Hevesy Laboratory, Risoe-DTU, Technical University of Denmark, Frederiksborgvej 399, DK-4000 Roskilde (Denmark); Publicover, Julia; Lapi, Suzanne [TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3 (Canada); McQuarrie, Steve A. [Cross Cancer Institute, Edmonton PET Centre, University of Alberta, Edmonton, AB, T6G 1Z2 (Canada); Ruth, Thomas J. [TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3 (Canada)
2011-01-15
This work recommends a new and simple-to-perform method for measuring the beam energy of an accelerator. The proposed method requires the irradiation of two monitor foils interspaced by an energy degrader. The primary advantage of the proposed method, which makes this method unique from previous energy evaluation strategies that employ the use of monitor foils, is that this method is independent of the detector efficiency calibration. This method was evaluated by performing proton activation of {sup nat}Cu foils using both a cyclotron and a tandem Van de Graaff accelerator. The monitor foil activities were read using a dose calibrator set to an arbitrary calibration setting. Excellent agreement was noted between the nominal and measured proton energies.
A new and simple calibration-independent method for measuring the beam energy of a cyclotron.
Gagnon, Katherine; Jensen, Mikael; Thisgaard, Helge; Publicover, Julia; Lapi, Suzanne; McQuarrie, Steve A; Ruth, Thomas J
2011-01-01
This work recommends a new and simple-to-perform method for measuring the beam energy of an accelerator. The proposed method requires the irradiation of two monitor foils interspaced by an energy degrader. The primary advantage of the proposed method, which makes this method unique from previous energy evaluation strategies that employ the use of monitor foils, is that this method is independent of the detector efficiency calibration. This method was evaluated by performing proton activation of (nat)Cu foils using both a cyclotron and a tandem Van de Graaff accelerator. The monitor foil activities were read using a dose calibrator set to an arbitrary calibration setting. Excellent agreement was noted between the nominal and measured proton energies. PMID:20926304
Impact of beam smoothing method on direct drive target performance for the NIF
International Nuclear Information System (INIS)
The impact of smoothing method on the performance of a direct drive target is modeled and examined in terms of its l-mode spectrum. In particular, two classes of smoothing methods are compared, smoothing by spectral dispersion (SSD) and the induced spatial incoherence (ISI) method. It is found that SSD using sinusoidal phase modulation (FM) results in poor smoothing at low l-modes and therefore inferior target performance at both peak velocity and ignition. Modeling of the hydrodynamic nonlinearity shows that saturation tends to reduce the difference between target performance for the smoothing methods considered. However, using SSD with more generalized phase modulation results in a smoothed spatial spectrum, and therefore target performance, which is identical to that obtained with the ISI or similar method where random phase plates are present in both methods and identical beam divergence is assumed
A new source number estimation method based on the beam eigenvalue
Institute of Scientific and Technical Information of China (English)
JIANG Lei; CAI Ping; YANG Juan; WANG Yi-ling; XU Dan
2007-01-01
Most source number estimation methods based on the eigenvalues are decomposed by covariance matrix in MUSIC algorithm. To develop the source number estimation method which has lower signal to noise ratio and is suitable to both correlated and uncorrelated impinging signals, a new source number estimation method called beam eigenvalue method (BEM) is proposed in this paper.Through analyzing the space power spectrum and the correlation of the line array, the covariance matrix is constructed in a new way, which is decided by the line array shape when the signal frequency is given.Both of the theory analysis and the simulation results show that the BEM method can estimate the source number for correlated signals and can be more effective at lower signal to noise ratios than the normal source number estimation methods.
International Nuclear Information System (INIS)
In this paper we discuss representations of charge particle densities in particle-in-cell (PIC) simulations, analyze the sources and profiles of the intrinsic numerical noise, and present efficient methods for their removal. We devise two alternative estimation methods for charged particle distribution which represent significant improvement over the Monte Carlo cosine expansion used in the 2d code of Bassi, designed to simulate coherent synchrotron radiation (CSR) in charged particle beams. The improvement is achieved by employing an alternative beam density estimation to the Monte Carlo cosine expansion. The representation is first binned onto a finite grid, after which two grid-based methods are employed to approximate particle distributions: (i) truncated fast cosine transform (TFCT); and (ii) thresholded wavelet transform (TWT). We demonstrate that these alternative methods represent a staggering upgrade over the original Monte Carlo cosine expansion in terms of efficiency, while the TWT approximation also provides an appreciable improvement in accuracy. The improvement in accuracy comes from a judicious removal of the numerical noise enabled by the wavelet formulation. The TWT method is then integrated into Bassi's CSR code, and benchmarked against the original version. We show that the new density estimation method provides a superior performance in terms of efficiency and spatial resolution, thus enabling high-fidelity simulations of CSR effects, including microbunching instability.
Energy Technology Data Exchange (ETDEWEB)
Balsa Terzic, Gabriele Bassi
2011-07-01
In this paper we discuss representations of charge particle densities in particle-in-cell (PIC) simulations, analyze the sources and profiles of the intrinsic numerical noise, and present efficient methods for their removal. We devise two alternative estimation methods for charged particle distribution which represent significant improvement over the Monte Carlo cosine expansion used in the 2d code of Bassi, designed to simulate coherent synchrotron radiation (CSR) in charged particle beams. The improvement is achieved by employing an alternative beam density estimation to the Monte Carlo cosine expansion. The representation is first binned onto a finite grid, after which two grid-based methods are employed to approximate particle distributions: (i) truncated fast cosine transform (TFCT); and (ii) thresholded wavelet transform (TWT). We demonstrate that these alternative methods represent a staggering upgrade over the original Monte Carlo cosine expansion in terms of efficiency, while the TWT approximation also provides an appreciable improvement in accuracy. The improvement in accuracy comes from a judicious removal of the numerical noise enabled by the wavelet formulation. The TWT method is then integrated into Bassi's CSR code, and benchmarked against the original version. We show that the new density estimation method provides a superior performance in terms of efficiency and spatial resolution, thus enabling high-fidelity simulations of CSR effects, including microbunching instability.
Indian Academy of Sciences (India)
Ming-Hsiang Shih; Wen-Pei Sung
2013-08-01
The Digital Image Correlation (DIC) method is a fast-growing emerging technology that provides a low-cost method for measuring the strain of an object. In this study, the feasibility of using this method to observe cracks developed in reinforced concrete beams will be explored so that a practical application can be proposed. The DIC method has been applied for analysing the ﬁeld of surface displacement and strain; it is not applicable for measuring non-continuous ﬁeld of displacement. However, if a singular point (i.e., crack points) can be considered as the area of concentrated strain by imitating the treatment of micro-cracks using the ﬁnite element method, the region of concentrated strain ﬁeld based on analyses of digital images can be applied for determining the locations of cracks. Laboratory results show that cracks developed in reinforced cement beams can be observed with a good precision using the von Mises strain ﬁeld, and that smaller grids lead to clearer crack images. In addition to identifying visible cracks, the DIC image analysis will enable researchers to identify minute cracks that are not visible to naked eyes. Additionally, the DIC method has more accuracy and precision than visual observation for analysing crack loadings so that earlier warnings can be realized before cracks develop in the specimen.
A new method of measurement of trace elements by using particle beams
International Nuclear Information System (INIS)
A new method of measurement of light elements by using the particle beam from an accelerator was developed. This paper reports on the results of analyses of N-15 and O-18. The tandem accelerator of University of Tokyo was used to accelerate proton beam. The energy of protons was determined from the excitation curves of elastic scattering by N-15, O-18 and O-16. The scattering by O-16 was background count. Therefore, The measurement was made at the energy of small background and large true counting. Biological samples were examined. The linearity of counts with the concentration of N-15 and O-18 was confirmed. The cells which contain glycine (O-18, 71.8 percent) and methionine (N-15, 95 percent) were analyzed. The peaks of N-15 and O-18 were well separated from teh peaks by N-14 and O-16. The natural amounts of N-15 in adenine and O-18 in glucose were also measured. The resonance reaction method of measurement by using particle beam was developed. (Kato, T.)
DEFF Research Database (Denmark)
Kimiaeifar, Amin; Lund, Erik; Thomsen, Ole Thybo; Barari, Amin
2010-01-01
In this work, an analytical method, which is referred to as Parameter-expansion Method is used to obtain the exact solution for the problem of nonlinear vibrations of an inextensible beam. It is shown that one term in the series expansion is sufficient to obtain a highly accurate solution, which is...... valid for the whole domain of the problem. A comparison of the obtained the numerical solution demonstrates that PEM is effective and convenient for solving such problems. After validation of the obtained results, the system response and stability are also discussed....
Characterization of X-ray beams by attenuation method for personnel dosemeters calibration
International Nuclear Information System (INIS)
It has been used the attenuation method to characterize the X rays beams used for calibration of personal dosemeters at Calibration and Dosimetry Laboratory of Peruvian Institute of Nuclear Energy (IPEN). Voltages applied to the X ray tube and the additional filters have been made according to publication ANSI No.13. Half value layer, the homogeneity coefficient and mean energy were determined from attenuation data. Average relative differences of 3, 40 and 4 % respectively were found with respect to values published in ANSI No.13. Also spectral distributions and their resolutions were determined. Relative differences of 16 and 9% respectively were found in comparison with values calculated by the Montecarlo's Method. (author)
Atmospheric processes on ice nanoparticles in molecular beams
Czech Academy of Sciences Publication Activity Database
Fárník, Michal; Poterya, Viktoriya
2014-01-01
Roč. 2, č. 2014 (2014), s. 4. ISSN 2296-2646 R&D Projects: GA ČR GA203/09/0422; GA ČR GAP208/11/0161 Institutional support: RVO:61388955 Keywords : molecular beams * photodissociation * water clusters Subject RIV: BL - Plasma and Gas Discharge Physics
Calculational methods for estimating skin dose from electrons in Co-60 gamma-ray beams
International Nuclear Information System (INIS)
Several methods have been employed to calculate the relative contribution to skin dose due to scattered electrons in Co-60 γ-ray beams. Either the Klein--Nishina differential scattering probability is employed to determine the number and initial energy of electrons scattered into the direction of a detector, or a Gaussian approximation is used to specify the surface distribution of initial pencil electron beams created by parallel or diverging photon fields. Results of these calculations are compared with experimental data. In addition, that fraction of relative surface dose resulting from photon interactions in air alone is estimated and compared with data extrapolated from measurements at large source--surface distance (SSD). The contribution to surface dose from electrons generated in air is 50% or more of the total skin dose for SSDs greater than 80 cm
Beam injection and accumulation method in storage rings for heavy ion fusion
International Nuclear Information System (INIS)
A combination of multiturn injection and rf stacking is proposed as an efficient beam injection method in storage rings for heavy ion fusion. Five turn injection in each transverse phase space and four rf stackings give a total of 100 stacking turns. This represents a compromise between the tolerable emittances and momentum spread in the ring. Space charge limitations and coherent beam instabilities are investigated. The most severe limit is found to be the transverse coherent instability, but this can be controlled by the use of sextupole and octupole magnetic fields. Assuming a charge exchange cross section of 1 x 10-15 cm2, the e-folding life time is estimated at 180 ms, while the stacking time is 40 ms
A precise method for analyzing Bessel-like beams generated by broadband waves
Cheng, Zhiming; Wu, Fengtie; Fan, Dandan; Fang, Xiang
2013-11-01
The current study proposes spectrum analysis, which is a novel analytical method proposed for the first time, for analyzing Bessel-like beams generated by broadband wave. The main idea is to decompose the consecutive spectrum into an incoherent superposition of a series of different wavelengths. Integrating spheres play a significant role in spectrum analysis and a series of wavelengths matched with relative intensity can be read according to the spectrum measured by an integral ball. Moreover, the Sellmeier dispersion equation, which indicates that the refractive index can be matched with wavelength, is also employed. Combining with the Fresnel diffraction integral formula, the distribution of fields behind an axicon is obtained. Two broadband sources, including a light-emitting diode (LED) with a narrow band and a halogen lamp with a broad band, are used to generate a Bessel-like beam. The experimental results fit well with the theoretical analysis.
Formation of Hard Surfacing Layers of WC-Co with Electron Beam Cladding Method
Abe, Nobuyuki; Morimoto, Junji
Hard surfacing layers of WC-Co/Ni-base self-fluxing alloy were successfully formed on a steel substrate using an electron beam cladding method. The WC particles were densely and homogenously dispersed within the Ni-base self-fluxing alloy without porosity. The effect of the electron beam conditions on layer formation was investigated, and the cladding layer properties were examined by hardness tests, abrasive wear tests and immersion corrosion tests. It was found that the cladding layers showed higher hardness and abrasion resistance with increasing WC-Co mixing ratio, however, corrosion resistance decreased with WC-Co mixing ratio. A coating layer having high abrasive and corrosion resistance simultaneously was achieved by multiple cladding of high WC-Co mixing ratio layers after low WC-Co mixing ratio layers.
Effect of Scanning Beam Profile to Fabricate Fused Fiber Tapers by CO_2 Laser Irradiation Method
Institute of Scientific and Technical Information of China (English)
Bayle; Fabien; Luo; Aiping; Marin; Emmanuel; Meunier; Jean-Pierre
2003-01-01
Beam uniformity is a crucial building block of CO2 experiments aimed at fusing and stretching optical fibers in a lossless manner. When the irradiation beam is expanded through a galvanometer mirror, ways to achieve beam uniformity are investigated.
Effect of Scanning Beam Profile to Fabricate Fused Fiber Tapers by CO2 Laser Irradiation Method
Institute of Scientific and Technical Information of China (English)
Bayle Fabien; Luo Aiping; Marin Emmanuel; Meunier Jean-Pierre
2003-01-01
Beam uniformity is a crucial building block of CO2 experiments aimed at fusing and stretching optical fibers in a lossless manner. When the irradiation beam is expanded through a galvanometer mirror, ways to achieve beam uniformity are investigated.
Low temperature Ti-Si-C thin film deposition by ion beam assisted methods
Energy Technology Data Exchange (ETDEWEB)
Twardowska, Agnieszka; Rajchel, Boguslaw; Jaworska, Lucyna, E-mail: atwardow@up.krakow.pl
2010-11-15
Thin, multiphase Ti-Si-C coatings were formed by IBSD or by IBAD methods on AISI 316L steel substrates in room temperature, using single Ti{sub 3}SiC{sub 2} target. In those methods the Ti{sub X}SiC{sub Y} coatings were formed from the flux of energetic atoms and ions obtained by ion sputtering of the Ti{sub 3}SiC{sub 2} compound sample. As sputtering beam the beam of Ar{sup +} ions at energy of 15keV was applied. In the IBAD method the dynamically formed coatings were additionally bombarded by beam of Ar{sup +} ions at energy of 15keV. The ion beams parameters were obtained by using Monte Carlo computer simulations. The morphology (SEM, TEM), chemical (EDS/EDX) and phase composition (XRD) examinations of formed coatings were provided as well as confocal Raman microspectroscopy. Analyzed coatings were relatively thin (150nm-1{mu}m), flat and dense. XRD analysis indicated in amorphous TiSi, the traces of Ti{sub 5}Si{sub 3} and other phases from Ti-Si-C system (TiSi, TiSi{sub 2},Ti{sub 3}SiC{sub 2}). For chemical bonds investigation, the laser beam with length of 532nm was used. Those analyses were performed in the low (LR) or in high (HR) resolution modes in room temperature and in 400deg. C. In the HR mode the spectral resolution was close to 2 cm{sup -1}. In Raman spectra peaks at: 152cm{sup -1}, 216cm{sup -1}, 278cm{sup -1}, 311 cm{sup -1}, 608cm{sup -1}, 691cm{sup -1} were recorded. Nanoindentation tests were done on coated and uncoated substrates with diamond, Berkovich-type indenter. Vickers hardness H{sub IT} and reduced elastic modulus E{sub IT} were calculated using Olivier and Pharr method. H{sub IT} for coated substrates was in the range 2.7 to 5.3 GPa, E{sub IT} was 160 GPa.
International Nuclear Information System (INIS)
Currently an ion optical solution for beam tracking of moving targets with scanned ion beams is being investigated at GSI for the treatment of moving tumours, such as lung cancer. Beam tracking compensates target motion by adapting the lateral beam position as well as the beam range according to the motion parameters. Tracking of the lateral position is achieved via scanning magnets. For range adaptation the proposed ion optical solution uses an energy degrader with variable thickness inserted into the therapy beam line downstream of the synchrotron. By deflecting the particle beam via dipole magnets to different positions on the degrader, the range of the Bragg peak can be adjusted in real-time. Hence density changes due to organ motion can be compensated for each target spot during beam scanning. In order to reach a beam quality suitable for therapy with this method, systematic studies on the ion optical parameters have to be carried out. Different degrader designs (ramp or discrete step shaped), different materials (e.g. PMMA, graphite), as well as optimised degrader positions have been examined. The results of simulated beam profiles are presented.
An optimization-based method for geometrical calibration in cone-beam CT without dedicated phantoms
Panetta, D.; Belcari, N.; DelGuerra, A.; Moehrs, S.
2008-07-01
In this paper we present a new method for the determination of geometrical misalignments in cone-beam CT scanners, from the analysis of the projection data of a generic object. No a priori knowledge of the object shape and positioning is required. We show that a cost function, which depends on the misalignment parameters, can be defined using the projection data and that such a cost function has a local minimum in correspondence to the actual parameters of the system. Hence, the calibration of the scanner can be carried out by minimizing the cost function using standard optimization techniques. The method is developed for a particular class of 3D object functions, for which the redundancy of the fan beam sinogram in the transaxial midplane can be extended to cone-beam projection data, even at wide cone angles. The method has an approximated validity for objects which do not belong to that class; in that case, a suitable subset of the projection data can be selected in order to compute the cost function. We show by numerical simulations that our method is capable to determine with high accuracy the most critical misalignment parameters of the scanner, i.e., the transversal shift and the skew of the detector. Additionally, the detector slant can be determined. Other parameters such as the detector tilt, the longitudinal shift and the error in the source-detector distance cannot be determined with our method, as the proposed cost function has a very weak dependence on them. However, due to the negligible influence of these latter parameters in the reconstructed image quality, they can be kept fixed at estimated values in both calibration and reconstruction processes without compromising the final result. A trade-off between computational cost and calibration accuracy must be considered when choosing the data subset used for the computation of the cost function. Results on real data of a mouse femur as obtained with a small animal micro-CT are shown as well, proving
A Method to Improve Electron Density Measurement of Cone-Beam CT Using Dual Energy Technique
Directory of Open Access Journals (Sweden)
Kuo Men
2015-01-01
Full Text Available Purpose. To develop a dual energy imaging method to improve the accuracy of electron density measurement with a cone-beam CT (CBCT device. Materials and Methods. The imaging system is the XVI CBCT system on Elekta Synergy linac. Projection data were acquired with the high and low energy X-ray, respectively, to set up a basis material decomposition model. Virtual phantom simulation and phantoms experiments were carried out for quantitative evaluation of the method. Phantoms were also scanned twice with the high and low energy X-ray, respectively. The data were decomposed into projections of the two basis material coefficients according to the model set up earlier. The two sets of decomposed projections were used to reconstruct CBCT images of the basis material coefficients. Then, the images of electron densities were calculated with these CBCT images. Results. The difference between the calculated and theoretical values was within 2% and the correlation coefficient of them was about 1.0. The dual energy imaging method obtained more accurate electron density values and reduced the beam hardening artifacts obviously. Conclusion. A novel dual energy CBCT imaging method to calculate the electron densities was developed. It can acquire more accurate values and provide a platform potentially for dose calculation.
Rangel, Frits A.; Maal, Thomas J. J.; Ewald M Bronkhorst; K Hero Breuning; Schols, Jan G. J. H.; Bergé, Stefaan J.; Anne Marie Kuijpers-Jagtman
2013-01-01
Several methods have been proposed to integrate digital models into Cone Beam Computed Tomography scans. Since all these methods have some drawbacks such as radiation exposure, soft tissue deformation and time-consuming digital handling processes, we propose a new method to integrate digital dental casts into Cone Beam Computed Tomography scans. Plaster casts of 10 patients were randomly selected and 5 titanium markers were glued to the upper and lower plaster cast. The plaster models were sc...
Characterization of non-Gaussian mid-infrared free-electron laser beams by the knife-edge method
Qin, Yu; Nakajima, Takashi; Zen, Heishun; Wang, Xiaolong; Kii, Toshiteru; Ohgaki, Hideaki
2014-01-01
We report the characterization of mid-infrared free-electron laser (FEL) beams at the wavelength of 11 μm by the knife-edge method. From the knife-edge data we find that the FEL beam has a non-Gaussian shape. To represent the non-Gaussian beam shape we employ two methods: fitting the knife-edge data to some analytical functions with a few free parameters and numerical smoothing of the knife-edge data. Both methods work equally well. Using those data we can reconstruct the two-dimensional (2D)...
Rocha, Humberto; Dias, Joana M.; Ferreira, Brígida C.; Lopes, Maria C.
2013-05-01
Generally, the inverse planning of radiation therapy consists mainly of the fluence optimization. The beam angle optimization (BAO) in intensity-modulated radiation therapy (IMRT) consists of selecting appropriate radiation incidence directions and may influence the quality of the IMRT plans, both to enhance better organ sparing and to improve tumor coverage. However, in clinical practice, most of the time, beam directions continue to be manually selected by the treatment planner without objective and rigorous criteria. The goal of this paper is to introduce a novel approach that uses beam’s-eye-view dose ray tracing metrics within a pattern search method framework in the optimization of the highly non-convex BAO problem. Pattern search methods are derivative-free optimization methods that require a few function evaluations to progress and converge and have the ability to better avoid local entrapment. The pattern search method framework is composed of a search step and a poll step at each iteration. The poll step performs a local search in a mesh neighborhood and ensures the convergence to a local minimizer or stationary point. The search step provides the flexibility for a global search since it allows searches away from the neighborhood of the current iterate. Beam’s-eye-view dose metrics assign a score to each radiation beam direction and can be used within the pattern search framework furnishing a priori knowledge of the problem so that directions with larger dosimetric scores are tested first. A set of clinical cases of head-and-neck tumors treated at the Portuguese Institute of Oncology of Coimbra is used to discuss the potential of this approach in the optimization of the BAO problem.
International Nuclear Information System (INIS)
Generally, the inverse planning of radiation therapy consists mainly of the fluence optimization. The beam angle optimization (BAO) in intensity-modulated radiation therapy (IMRT) consists of selecting appropriate radiation incidence directions and may influence the quality of the IMRT plans, both to enhance better organ sparing and to improve tumor coverage. However, in clinical practice, most of the time, beam directions continue to be manually selected by the treatment planner without objective and rigorous criteria. The goal of this paper is to introduce a novel approach that uses beam’s-eye-view dose ray tracing metrics within a pattern search method framework in the optimization of the highly non-convex BAO problem. Pattern search methods are derivative-free optimization methods that require a few function evaluations to progress and converge and have the ability to better avoid local entrapment. The pattern search method framework is composed of a search step and a poll step at each iteration. The poll step performs a local search in a mesh neighborhood and ensures the convergence to a local minimizer or stationary point. The search step provides the flexibility for a global search since it allows searches away from the neighborhood of the current iterate. Beam’s-eye-view dose metrics assign a score to each radiation beam direction and can be used within the pattern search framework furnishing a priori knowledge of the problem so that directions with larger dosimetric scores are tested first. A set of clinical cases of head-and-neck tumors treated at the Portuguese Institute of Oncology of Coimbra is used to discuss the potential of this approach in the optimization of the BAO problem. (paper)
International Nuclear Information System (INIS)
Physical detection methods, photostimulated luminescence (PSL), thermoluminescence (TL) and electron spin resonance (ESR) were applied to detect electron beam-irradiated agricultural products, such as red pepper, black pepper, raisin, walnut, beef seasoning and pistachio. The absorbed irradiation doses for representative samples were controlled at 0, 1, 3, 5 and 10 kGy. PSL values for non-irradiated samples were 1) except beef seasoning, whereas those of irradiated samples were more than 5,000 photon counts, upper threshold (T2) in black pepper, raisin, and beef seasoning and intermediates values of T1-T2 in red pepper, walnut, and pistachio. Minerals separated from the samples for TL measurement showed that non-irradiated samples except pistachio (TL ratio, 0.12) were characterized by no glow curves situated at temperature range of 50 ∼ 400 .deg. C with TL ratio (0.01 ∼ 0.08), while irradiated samples except pistachio at only 1 kGy (TL ratio, 0.08) indicated glow curve at about 150 ∼ 250 .deg. C with TL ratio (0.28 ∼ 3.10). ESR measurements of irradiated samples any specific signals to irradiation. The samples of both red pepper ad pistachio were produced specific signals derived from cellulose radicals as well as single line signals for black pepper and walnut, and multiple signals derived from crystalline sugar radicals for raisin and beef seasoning. In conclusion, The ESR methods can apply for detection of pistachio exposed to electron beam but PSL and TL are not suitable methods. Furthermore, TL and ESR suggested that both techniques were more useful detection method than PSL to confirm whether red pepper, walnut and beef seasoning samples have been exposed to electron beam
Shokrieh, M. M.; Zeinedini, A.
2014-06-01
In this research, a novel data reduction method for calculation of the strain energy release rate ( SERR) of asymmetric double cantilever beams ( ADCB) is presented. For this purpose the elastic beam theory ( EBT) is modified and the new method is called as the modified elastic beam theory ( MEBT). Also, the ADCB specimens are modeled using ABAQUS/Standard software. Then, the initiation of delamination of ADCB specimens is modeled using the virtual crack closure technique ( VCCT). Furthermore, magnitudes of the SERR for different samples are also calculated by an available data reduction method, called modified beam theory ( MBT). Using the hand lay-up method, different laminated composite samples are manufactured by E-glass/epoxy unidirectional plies. In order to measure the SERR, all samples are tested using an experimental setup. The results determined by the new data reduction method ( MEBT) show good agreements with the results of the VCCT and the MBT.
Doughnut magnesium fluoride nanoparticles prepared by an electron-beam irradiation method
Energy Technology Data Exchange (ETDEWEB)
Nandiyanto, Asep Bayu Dani; Ogi, Takashi; Okuyama, Kikuo, E-mail: okuyama@hiroshima-u.ac.jp [Hiroshima University, Department of Chemical Engineering, Graduate School of Engineering (Japan)
2012-10-15
Doughnut magnesium fluoride particles with controllable size (from 6 to 50 nm) and shape (sphere and cube) were successfully prepared using an electron-beam irradiation method. While common reports typically produced doughnut particles in the micrometer range, the present method succeeded in preparing this type of particles with sizes of nanometers. Different from other methods that pointed out the importance of the additional additive and specific process to support the formation of doughnut structure, we preferred exploiting the electron-beam irradiation method that was simpler and free of additive. Transformation of the particle from its original morphology (dense structure) into doughnut shape were also investigated, along with the analysis of irradiation time and elemental composition. Outer sizes and shapes of the final particles were identical to those of the initial particles (before irradiation process), giving a potential way for controlling the size and the shape of the doughnut particles by adjusting the size and the shape of the initial magnesium fluoride particles only.
Institute of Scientific and Technical Information of China (English)
Xiao-Ting Rui; Edwin Kreuzer; Bao Rong; Bin He
2012-01-01
In this paper,by defining new state vectors and developing new transfer matrices of various elements moving in space,the discrete time transfer matrix method of multi-rigid-flexible-body system is expanded to study the dynamics of muhibody system with flexible beams moving in space.Formulations and numerical example of a rigidflexible-body three pendulums system moving in space are given to validate the method. Using the new method to study the dynamics of multi-rigid-flexible-body system mov ing in space,the global dynamics equations of system are not needed,the orders of involved matrices of the system are very low and the computational speed is high,irrespective of the size of the system.The new method is simple,straightforward,practical,and provides a powerful tool for multi-rigid-flexible-body system dynamics.
Robust scatter correction method for cone-beam CT using an interlacing-slit plate
Huang, Kuidong; Zhang, Dinghua; Zhang, Hua; Shi, Wenlong
2015-01-01
Cone-beam computed tomography (CBCT) has been widely used in medical imaging and industrial nondestructive testing, but the presence of scattered radiation will cause significant reduction of image quality. In this article, a robust scatter correction method for CBCT using an interlacing-slit plate (ISP) is carried out for convenient practice. Firstly, a Gaussian filtering method is proposed to compensate the missing data of the inner scatter image, and simultaneously avoid too-large values of calculated inner scatter and smooth the inner scatter field. Secondly, an interlacing-slit scan without detector gain correction is carried out to enhance the practicality and convenience of the scatter correction method. Finally, a denoising step for scatter-corrected projection images is added in the process flow to control the noise amplification. The experimental results show that the improved method can not only make the scatter correction more robust and convenient, but also achieve a good quality of scatter-corre...
A method for the production of an intense negative 14C beam
International Nuclear Information System (INIS)
For the purpose of studying low cross section nuclear reactions the method for the production of negative ion 14C beams with a current of some μA order by means of a cylindrical source with Fe3, 14C target sputtering is developed. The source target is fabricated in the following way: 100 mg of 14C black is mixed with a binder diluted by alcohol and acetone. The mixing is continued until the solvents do not evaporate and the mixture does not take the appearance of a slightly moistsand, small portions of the mixture are pressed in a substrate deepening the target is warmed up in the air during 1h at the temperature of 200 deg C, after cooling the target is thoroughly cleaned up by alcohol from surface impurities. The source configuration admits the passage of a part of cesium beam produced at the Van-de-Graaff accelerator near the target which later is reflected back and focused on the graphite surface. At 0.5 mA cesium current the 14C negative ions beam approximately 2 μA is produced. After 500 hrs of operation the source of surface contamination behined the target by 14C particles has not been found
A post-reconstruction method to correct cupping artifacts in cone beam breast computed tomography
International Nuclear Information System (INIS)
In cone beam breast computed tomography (CT), scattered radiation leads to nonuniform biasing of CT numbers known as a cupping artifact. Besides being visual distractions, cupping artifacts appear as background nonuniformities, which impair efficient gray scale windowing and pose a problem in threshold based volume visualization/segmentation. To overcome this problem, we have developed a background nonuniformity correction method specifically designed for cone beam breast CT. With this technique, the cupping artifact is modeled as an additive background signal profile in the reconstructed breast images. Due to the largely circularly symmetric shape of a typical breast, the additive background signal profile was also assumed to be circularly symmetric. The radial variation of the background signals was estimated by measuring the spatial variation of adipose tissue signals in front view breast images. To extract adipose tissue signals in an automated manner, a signal sampling scheme in polar coordinates and a background trend fitting algorithm were implemented. The background fits compared with targeted adipose tissue signal value (constant throughout the breast volume) to get an additive correction value for each tissue voxel. To test the accuracy, we applied the technique to cone beam CT images of mastectomy specimens. After correction, the images demonstrated significantly improved signal uniformity in both front and side view slices. The reduction of both intraslice and interslice variations in adipose tissue CT numbers supported our observations
Adrich, Przemysław
2016-05-01
In Part I of this work existing methods and problems in dual foil electron beam forming system design are presented. On this basis, a new method of designing these systems is introduced. The motivation behind this work is to eliminate the shortcomings of the existing design methods and improve overall efficiency of the dual foil design process. The existing methods are based on approximate analytical models applied in an unrealistically simplified geometry. Designing a dual foil system with these methods is a rather labor intensive task as corrections to account for the effects not included in the analytical models have to be calculated separately and accounted for in an iterative procedure. To eliminate these drawbacks, the new design method is based entirely on Monte Carlo modeling in a realistic geometry and using physics models that include all relevant processes. In our approach, an optimal configuration of the dual foil system is found by means of a systematic, automatized scan of the system performance in function of parameters of the foils. The new method, while being computationally intensive, minimizes the involvement of the designer and considerably shortens the overall design time. The results are of high quality as all the relevant physics and geometry details are naturally accounted for. To demonstrate the feasibility of practical implementation of the new method, specialized software tools were developed and applied to solve a real life design problem, as described in Part II of this work.
Nelli, Flavio Enrico
2016-03-01
A very simple method to measure the effect of the backscatter from secondary collimators into the beam monitor chambers in linear accelerators equipped with multi-leaf collimators (MLC) is presented here. The backscatter to the monitor chambers from the upper jaws of the secondary collimator was measured on three beam-matched linacs by means of three methods: this new methodology, the ecliptic method, and assessing the variation of the beam-on time per monitor unit with dose rate feedback disabled. This new methodology was used to assess the backscatter characteristics of asymmetric over-traveling jaws. Excellent agreement between the backscatter values measured using the new methodology introduced here and the ones obtained using the other two methods was established. The experimental values reported here differ by less than 1% from published data. The sensitivity of this novel technique allowed differences in backscatter due to the same opening of the jaws, when placed at different positions on the beam path, to be resolved. The introduction of the ecliptic method has made the determination of the backscatter to the monitor chambers an easy procedure. The method presented here for machines equipped with MLCs makes the determination of backscatter to the beam monitor chambers even easier, and suitable to characterize linacs equipped with over-traveling asymmetric secondary collimators. This experimental procedure could be simply implemented to fully characterize the backscatter output factor constituent when detailed dosimetric modeling of the machine's head is required. The methodology proved to be uncomplicated, accurate and suitable for clinical or experimental environments. PMID:26671445
A method for elemental analysis of bones by recoiling atoms in heavy ion beams
International Nuclear Information System (INIS)
This contribution is the first attempt to analyse the elemental composition of bones by the recoil atoms in heavy ion beams. The aim of this study was to observe differences in light elements depth gradients, concentrations and ratios (P/Ca, Mg/Ca, N/Ca, Li/Ca) of different human femoral bone compartment: cortical bone (C sample) and trabecular (T sample) bone. The differences could be linked to the function of these areas. An interesting feature concerning lithium has to be pointed out. Lithium continues to be a substance of interest as a potential therapeutic agent in a number of blood disorders as well as a very effective experimental agent to understand the basic biochemical and pharmacological properties that regulate cellular proliferation and differentiation. The first method of analysing and profiling of light elements by recoil atoms in heavy ion beams by using an ionization ΔE, E ionization chamber, was described in a previous paper. In this paper a 32 S beam accelerated at the Van de Graaff Tandem Accelerator was used. Further developing of this method has been presented. It was shown that the monitoring problem can be solved by using beams of ion substantially heavier than the sample to be analysed. For the analysis of bones an 127 I beam has been used. The ΔE,E ionization chamber has been built according to a recent patent. By introducing a getter in the compartment 7 of the chamber one could work in conditions of high purity of the gas inside the chamber. The entrance window of the chamber was made of mylar 2 μm thick. Very good stability of the chamber has been obtained over long runs, ∼ 5 hours, in conditions of closed circuit of the gas. Results are presented. In conclusion: 1) A large difference between the normal sample N and the osteoporotic samples T and C for the Mg/Ca ratio has been found; 2) A very high concentration of Li was observed in the T sample. (authors)
Photodissociation of methyl formate: Conical intersections, roaming and triple fragmentation
Energy Technology Data Exchange (ETDEWEB)
Lin, King-Chuen; Tsai, Po-Yu [Department of Chemistry, National Taiwan University, Taipei 106, Taiwan (China); Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan (China); Chao, Meng-Hsuan [Department of Chemistry, National Taiwan University, Taipei 106, Taiwan (China); Kasai, Toshio [Department of Chemistry, National Taiwan University, Taipei 106, Taiwan (China); Graduate School of Science, Department of Chemistry, Osaka University, Toyonaka, 560-0043 Osaka (Japan); Lombardi, Andrea [Dipartimento di Chimica, Università di Perugia, 06123 Perugia (Italy); Palazzetti, Federico [Scuola Normale Superiore, 56126 Pisa (Italy); Aquilanti, Vincenzo [Dipartimento di Chimica, Università di Perugia, 06123 Perugia (Italy); Consiglio Nazionale delle Ricerche, Istituto di Struttura della Materia, 00016 Roma (Italy)
2015-12-31
The photodissociation channels of methyl formate have been extensively investigated by two different advanced experimental techniques, ion imaging and Fourier-Transform-Infrared emission spectroscopy, combined with quantum chemical calculations and molecular dynamics simulations. Our aim is to characterize the role of alternative routes to the conventional transition-state mediated pathway: the roaming and the triple fragmentation processes. The photolysis experiments, carried out at a range of laser wavelengths in the vicinity of the triple fragmentation threshold, beside the simulation of large bunches of classical trajectories with different initial conditions, have shown that both mechanisms share a common path that involves a conical intersection during the relaxation process from the electronic excited state S{sub 1} to the ground state S{sub 0}.
Photodissociation of methyl formate: Conical intersections, roaming and triple fragmentation
Lin, King-Chuen; Tsai, Po-Yu; Chao, Meng-Hsuan; Kasai, Toshio; Lombardi, Andrea; Palazzetti, Federico; Aquilanti, Vincenzo
2015-12-01
The photodissociation channels of methyl formate have been extensively investigated by two different advanced experimental techniques, ion imaging and Fourier-Transform-Infrared emission spectroscopy, combined with quantum chemical calculations and molecular dynamics simulations. Our aim is to characterize the role of alternative routes to the conventional transition-state mediated pathway: the roaming and the triple fragmentation processes. The photolysis experiments, carried out at a range of laser wavelengths in the vicinity of the triple fragmentation threshold, beside the simulation of large bunches of classical trajectories with different initial conditions, have shown that both mechanisms share a common path that involves a conical intersection during the relaxation process from the electronic excited state S1 to the ground state S0.
Chemical "Double Slits": dynamical interference of photodissociation pathways in water
Dixon; Hwang; Yang; Harich; Lin; Yang
1999-08-20
Photodissociation of water at a wavelength of 121.6 nanometers has been investigated by using the H-atom Rydberg tagging technique. A striking even-odd intensity oscillation was observed in the OH(X) product rotational distribution. Model calculations attribute this oscillation to an unusual dynamical interference brought about by two dissociation pathways that pass through dissimilar conical intersections of potential energy surfaces, but result in the same products. The interference pattern and the OH product rotational distribution are sensitive to the positions and energies of the conical intersections, one with the atoms collinear as H-OH and the other as H-HO. An accurate simulation of the observations would provide a detailed test of global H(2)O potential energy surfaces for the three (&Xtilde;/A/&Btilde;) contributing states. The interference observed from the two conical intersection pathways provides a chemical analog of Young's well-known double-slit experiment. PMID:10455048
Drescher, L.; Galbraith, M. C. E.; Reitsma, G.; Dura, J.; Zhavoronkov, N.; Patchkovskii, S.; Vrakking, M. J. J.; Mikosch, J.
2016-07-01
Time-resolved extreme ultraviolet (XUV) transient absorption spectroscopy of iodomethane and iodobenzene photodissociation at the iodine pre-N4,5 edge is presented, using femtosecond UV pump pulses and XUV probe pulses from high harmonic generation. For both molecules the molecular core-to-valence absorption lines fade immediately, within the pump-probe time-resolution. Absorption lines converging to the atomic iodine product emerge promptly in CH3I but are time-delayed in C6H5I. We attribute this delay to the initial π → σ* excitation in iodobenzene, which is distant from the iodine reporter atom. We measure a continuous shift in energy of the emerging atomic absorption lines in CH3I, attributed to relaxation of the excited valence shell. An independent particle model is used to rationalize the observed experimental findings.
Lone-pair interactions and photodissociation of compressed nitrogen trifluoride
International Nuclear Information System (INIS)
High-pressure behavior of nitrogen trifluoride (NF3) was investigated by Raman and IR spectroscopy at pressures up to 55 GPa and room temperature, as well as by periodic calculations up to 100 GPa. Experimentally, we find three solid-solid phase transitions at 9, 18, and 39.5 GPa. Vibrational spectroscopy indicates that in all observed phases NF3 remains in the molecular form, in contrast to the behavior of compressed ammonia. This finding is confirmed by density functional theory calculations, which also indicate that the phase transitions of compressed NF3 are governed by the interplay between lone‑pair interactions and efficient molecule packing. Although nitrogen trifluoride is molecular in the whole pressure range studied, we show that it can be photodissociated by mid-IR laser radiation. This finding paves the way for the use of NF3 as an oxidizing and fluorinating agent in high-pressure reactions
Photodissociation pathways and lifetimes of protonated peptides and their dimers
DEFF Research Database (Denmark)
Gopalan, Aravind; Klærke, Benedikte; Rajput, Jyoti;
2012-01-01
Photodissociation lifetimes and fragment channels of gas-phase, protonated YAn (n = 1,2) peptides and their dimers were measured with 266 nm photons. The protonated monomers were found to have a fast dissociation channel with an exponential lifetime of ∼200 ns while the protonated dimers show an...... channel in the dimer was found to result in cleavage of the H-bonds after energy transfer through these H-bonds. In general, the dissociation of these protonated peptides is non-prompt and the decay time was found to increase with the size of the peptides. Quantum RRKM calculations of the microcanonical...... equipartition theorem. It demonstrates encouraging results in predicting fragmentation lifetimes of protonated peptides. Finally, we present the first experimental evidence for a photo-induced conversion of tyrosine-containing peptides into monocyclic aromatic hydrocarbon along with a formamide molecule both...
Multiple product pathways in photodissociation of nitromethane at 213 nm
Energy Technology Data Exchange (ETDEWEB)
Sumida, Masataka; Kohge, Yasunori; Yamasaki, Katsuyoshi; Kohguchi, Hiroshi, E-mail: kohguchi@hiroshima-u.ac.jp [Department of Chemistry, Graduate School of Science, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima, Hiroshima 739-8526 (Japan)
2016-02-14
In this paper, we present a photodissociation dynamics study of nitromethane at 213 nm in the π → π{sup *} transition. Resonantly enhanced multiphoton ionization spectroscopy and ion-imaging were applied to measure the internal state distributions and state-resolved scattering distributions of the CH{sub 3}, NO(X {sup 2}Π, A {sup 2}Σ{sup +}), and O({sup 3}P{sub J}) photofragments. The rotationally state-resolved scattering distribution of the CH{sub 3} fragment showed two velocity components, of which the slower one decreased the relative intensity as the rotational and vibrational excitations. The translational energy distribution of the faster CH{sub 3} fragment indicated the production of the NO{sub 2} counter-product in the electronic excited state, wherein 1 {sup 2}B{sub 2} was the most probable. The NO(v = 0) fragment exhibited a bimodal translational energy distribution, whereas the NO(v = 1 and 2) fragment exhibited a single translational energy component with a relatively larger internal energy. The translational energy of a portion of the O({sup 3}P{sub J}) photofragment was found to be higher than the one-photon dissociation threshold, indicating the two-photon process involved. The NO(A {sup 2}Σ{sup +}) fragment, which was detected by ionization spectroscopy via the Rydberg ←A {sup 2}Σ{sup +} transition, also required two-photon energy. These experimental data corroborate the existence of competing photodissociation product pathways, CH{sub 3} + NO{sub 2},CH{sub 3} + NO + O,CH{sub 3}O + NO, and CH{sub 3}NO + O, following the π → π{sup *} transition. The origins of the observed photofragments are discussed in this report along with recent theoretical studies and previous dynamics experiments performed at 193 nm.
Multiple product pathways in photodissociation of nitromethane at 213 nm.
Sumida, Masataka; Kohge, Yasunori; Yamasaki, Katsuyoshi; Kohguchi, Hiroshi
2016-02-14
In this paper, we present a photodissociation dynamics study of nitromethane at 213 nm in the π → π(*) transition. Resonantly enhanced multiphoton ionization spectroscopy and ion-imaging were applied to measure the internal state distributions and state-resolved scattering distributions of the CH3, NO(X (2)Π, A (2)Σ(+)), and O((3)PJ) photofragments. The rotationally state-resolved scattering distribution of the CH3 fragment showed two velocity components, of which the slower one decreased the relative intensity as the rotational and vibrational excitations. The translational energy distribution of the faster CH3 fragment indicated the production of the NO2 counter-product in the electronic excited state, wherein 1 (2)B2 was the most probable. The NO(v = 0) fragment exhibited a bimodal translational energy distribution, whereas the NO(v = 1 and 2) fragment exhibited a single translational energy component with a relatively larger internal energy. The translational energy of a portion of the O((3)PJ) photofragment was found to be higher than the one-photon dissociation threshold, indicating the two-photon process involved. The NO(A (2)Σ(+)) fragment, which was detected by ionization spectroscopy via the Rydberg ← A (2)Σ(+) transition, also required two-photon energy. These experimental data corroborate the existence of competing photodissociation product pathways, CH3 + NO2,CH3 + NO + O,CH3O + NO, and CH3NO + O, following the π → π(*) transition. The origins of the observed photofragments are discussed in this report along with recent theoretical studies and previous dynamics experiments performed at 193 nm. PMID:26874485
Multiple product pathways in photodissociation of nitromethane at 213 nm
Sumida, Masataka; Kohge, Yasunori; Yamasaki, Katsuyoshi; Kohguchi, Hiroshi
2016-02-01
In this paper, we present a photodissociation dynamics study of nitromethane at 213 nm in the π → π* transition. Resonantly enhanced multiphoton ionization spectroscopy and ion-imaging were applied to measure the internal state distributions and state-resolved scattering distributions of the CH3, NO(X 2Π, A 2Σ+), and O(3PJ) photofragments. The rotationally state-resolved scattering distribution of the CH3 fragment showed two velocity components, of which the slower one decreased the relative intensity as the rotational and vibrational excitations. The translational energy distribution of the faster CH3 fragment indicated the production of the NO2 counter-product in the electronic excited state, wherein 1 2B2 was the most probable. The NO(v = 0) fragment exhibited a bimodal translational energy distribution, whereas the NO(v = 1 and 2) fragment exhibited a single translational energy component with a relatively larger internal energy. The translational energy of a portion of the O(3PJ) photofragment was found to be higher than the one-photon dissociation threshold, indicating the two-photon process involved. The NO(A 2Σ+) fragment, which was detected by ionization spectroscopy via the Rydberg ←A 2Σ+ transition, also required two-photon energy. These experimental data corroborate the existence of competing photodissociation product pathways, CH3 + NO2,CH3 + NO + O,CH3O + NO, and CH3NO + O, following the π → π* transition. The origins of the observed photofragments are discussed in this report along with recent theoretical studies and previous dynamics experiments performed at 193 nm.
Multiple product pathways in photodissociation of nitromethane at 213 nm
International Nuclear Information System (INIS)
In this paper, we present a photodissociation dynamics study of nitromethane at 213 nm in the π → π* transition. Resonantly enhanced multiphoton ionization spectroscopy and ion-imaging were applied to measure the internal state distributions and state-resolved scattering distributions of the CH3, NO(X 2Π, A 2Σ+), and O(3PJ) photofragments. The rotationally state-resolved scattering distribution of the CH3 fragment showed two velocity components, of which the slower one decreased the relative intensity as the rotational and vibrational excitations. The translational energy distribution of the faster CH3 fragment indicated the production of the NO2 counter-product in the electronic excited state, wherein 1 2B2 was the most probable. The NO(v = 0) fragment exhibited a bimodal translational energy distribution, whereas the NO(v = 1 and 2) fragment exhibited a single translational energy component with a relatively larger internal energy. The translational energy of a portion of the O(3PJ) photofragment was found to be higher than the one-photon dissociation threshold, indicating the two-photon process involved. The NO(A 2Σ+) fragment, which was detected by ionization spectroscopy via the Rydberg ←A 2Σ+ transition, also required two-photon energy. These experimental data corroborate the existence of competing photodissociation product pathways, CH3 + NO2,CH3 + NO + O,CH3O + NO, and CH3NO + O, following the π → π* transition. The origins of the observed photofragments are discussed in this report along with recent theoretical studies and previous dynamics experiments performed at 193 nm
Photodissociation in Quantum Chaotic Systems: Random Matrix Theory of Cross-Section Fluctuations
Fyodorov, Yan V.; Alhassid, Yoram
1998-01-01
Using the random matrix description of open quantum chaotic systems we calculate in closed form the universal autocorrelation function and the probability distribution of the total photodissociation cross section in the regime of quantum chaos.
Photodissociation of HBr/LiF(001): A quantum mechanical model
Seideman, Tamar
1993-01-01
The photodissociation dynamics of HBr adsorbed on a LiF(001) surface is studied using time-independent quantum mechanics. The photodissociation lineshape and the Br(P(sub 1/2)-2)/Br(P(sub 3/2)-2) yield ratio are computed and compared with the corresponding quantities for gas phase photodissociation. The angular distribution of the hydrogen photofragments following excitation of adsorbed HBr is computed and found to agree qualitatively with experimental data. The effect of polarization of the photon is illustrated and discussed. The field polarization is found to affect significantly the magnitude of the photodissociation signal but not the angular dependence of the photofragment distribution, in agreement with experiment and in accord with expectations for a strongly aligned adsorbed phase.
Photodissociation of HBr/LiF(001) - A quantum mechanical model
Seideman, Tamar
1993-01-01
The photodissociation dynamics of HBr adsorbed on an LiF(001) surface is studied using time-independent quantum mechanics. The photodissociation line shape and the Br(2P(1/2))/Br(2P(3/2)) yield ratio are computed and compared with the corresponding quantities for gas phase photodissociation. The angular distribution of the hydrogen photofragments following excitation of adsorbed HBr is computed and found to agree qualitatively with experimental data. The effect of polarization of the photon is illustrated and discussed. We find the field polarization to affect significantly the magnitude of the photodissociation signal but not the angular dependence of the photofragment distribution, in agreement with experiment and in accord with expectations for a strongly aligned adsorbed phase.
Directory of Open Access Journals (Sweden)
P. A. Loiko
2015-04-01
Full Text Available The experimental setup for thermooptic coefficients dn/dT measurements by a laser beam deviation method for the medium with linear thermal gradient was developed. By means of this approach, the dispersion of the dn/dT values in the optically biaxial potassium gadolinium tungstate crystal KGd(WO42 was investigated in the 0,4–1,06 μm spectral range for light polarized along the principal directions in the crystal.
A simple method for creating a robust optical vortex beam with a single cylinder lens
Nam, Hannarae Annie; Cohen, Martin G.; Noé, John W.
2011-06-01
We describe a simple method for creating Laguerre-Gauss (LG) optical vortex beams from Hermite-Gauss (HG) modes with a single cylinder lens. The diverging vortex created by the cylinder lens has the correct intensity distribution in the far-field but its residual longitudinal astigmatism causes the vortex to revert to the original HG mode when it is brought to a focus. We show that an appropriate small tilt of the focusing lens can prevent this effect by introducing a compensating astigmatism. The corrected vortex is a good approximation to an exact LG mode and should be useful for a variety of demonstrations and experiments.
A simple method for creating a robust optical vortex beam with a single cylinder lens
International Nuclear Information System (INIS)
We describe a simple method for creating Laguerre–Gauss (LG) optical vortex beams from Hermite–Gauss (HG) modes with a single cylinder lens. The diverging vortex created by the cylinder lens has the correct intensity distribution in the far-field but its residual longitudinal astigmatism causes the vortex to revert to the original HG mode when it is brought to a focus. We show that an appropriate small tilt of the focusing lens can prevent this effect by introducing a compensating astigmatism. The corrected vortex is a good approximation to an exact LG mode and should be useful for a variety of demonstrations and experiments
A method of beam combination of high-power incoherent fiber laser
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
Diffraction efficiency of grating plays an important role in output power of incoherent fiber laser beam combination.Through theoretic analysis and numerical simulations it has been proved that the diffraction efficiency would increase with the decrease of grating frequency and wavelength bandwidth. On the condition that the width of a fiber array is fixed at W=10 cm, an optimum grating frequency were numerically simulated as f=230 mm-1. Also an unequal interval method was proposed to improve the system efficiency of diffraction into 0.4293, which is higher than 0.3824 under the equal interval condition.
Buss, R. J.; Baseman, R. J.; Guozhong, H.; Lee, Y. T.
1982-04-01
From a series of studies of the reaction of oxygen atoms with unsaturated hydrocarbons using the crossed molecular beam method, the dominant reaction mechanisms were found to be the simple substitution reactions with oxygen atoms replacing H, Cl, Br atom or alkyl groups. Complication due to secondary reaction was avoided by carrying out experiments under single collisions and observing primary products directly. Primary products were identified by measuring the angular and velocity distributions of products at all the mass numbers which could be detected by the mass spectrometer, and from comparison of these distributions, applying the requirement of energy and momentum conservation.
Douglas, David R.; Tennant, Christopher D.
2012-07-10
A method of avoiding CSR induced beam quality defects in free electron laser operation by a) controlling the rate of compression and b) using a novel means of integrating the compression with the remainder of the transport system: both are accomplished by means of dispersion modulation. A large dispersion is created in the penultimate dipole magnet of the compression region leading to rapid compression; this large dispersion is demagnified and dispersion suppression performed in a final small dipole. As a result, the bunch is short for only a small angular extent of the transport, and the resulting CSR excitation is small.
Characterization of non-Gaussian mid-infrared free-electron laser beams by the knife-edge method
Qin, Yu; Nakajima, Takashi; Zen, Heishun; Wang, Xiaolong; Kii, Toshiteru; Ohgaki, Hideaki
2014-09-01
We report the characterization of mid-infrared free-electron laser (FEL) beams at the wavelength of 11 μm by the knife-edge method. From the knife-edge data we find that the FEL beam has a non-Gaussian shape. To represent the non-Gaussian beam shape we employ two methods: fitting the knife-edge data to some analytical functions with a few free parameters and numerical smoothing of the knife-edge data. Both methods work equally well. Using those data we can reconstruct the two-dimensional (2D) beam profiles at different positions around the focus by assuming that the 2D intensity distribution function is separable in x (horizontal) and y (vertical) directions. Using the 2D beam profiles at different positions around the focus, we find that the beam propagation factor (M2 factor) is ∼1.1 in both x and y directions. As a cross-check, we also carry out the burn pattern experiment to find that the behavior of the focused FEL beam along the propagation is consistent with the results obtained by the knife-edge method.
A fast high-order method to calculate wakefield forces in an electron beam
Energy Technology Data Exchange (ETDEWEB)
Qiang, Ji; Mitchell, Chad; Ryne, Robert D.
2012-03-22
In this paper we report on a high-order fast method to numerically calculate wakefield forces in an electron beam given a wake function model. This method is based on a Newton-Cotes quadrature rule for integral approximation and an FFT method for discrete summation that results in an O(Nlog(N)) computational cost, where N is the number of grid points. Using the Simpson quadrature rule with an accuracy of O(h4), where h is the grid size, we present numerical calculation of the wakefields from a resonator wake function model and from a one-dimensional coherent synchrotron radiation (CSR) wake model. Besides the fast speed and high numerical accuracy, the calculation using the direct line density instead of the first derivative of the line density avoids numerical filtering of the electron density function for computing the CSR wakefield force. I. INTRODUCTION
A fast high-order method to calculate wakefields in an electron beam
Qiang, Ji; Mitchell, Chad; Ryne, Robert D.
2012-08-01
In this paper, we report on a high-order fast method to numerically calculate wakefields in an electron beam given a wake function model. This method is based on a Newton-Cotes quadrature rule for integral approximation and an FFT method for discrete summation that results in an O(N log(N)) computational cost, where N is the number of grid points. Using the Simpson quadrature rule with an accuracy of O(h4), where h is the grid size, we present numerical calculation of the wakefields from a resonator wake function model and from a one-dimensional coherent synchrotron radiation (CSR) wake model. Besides the fast speed and high numerical accuracy, the calculation using the direct line density instead of the first derivative of the line density avoids numerical filtering of the electron density function for computing the CSR wakefield.
A fast high-order method to calculate wakefields in an electron beam
International Nuclear Information System (INIS)
In this paper, we report on a high-order fast method to numerically calculate wakefields in an electron beam given a wake function model. This method is based on a Newton–Cotes quadrature rule for integral approximation and an FFT method for discrete summation that results in an O(Nlog(N)) computational cost, where N is the number of grid points. Using the Simpson quadrature rule with an accuracy of O(h4), where h is the grid size, we present numerical calculation of the wakefields from a resonator wake function model and from a one-dimensional coherent synchrotron radiation (CSR) wake model. Besides the fast speed and high numerical accuracy, the calculation using the direct line density instead of the first derivative of the line density avoids numerical filtering of the electron density function for computing the CSR wakefield.
A fast high-order method to calculate wakefield forces in an electron beam
Qiang, Ji; Ryne, Robert D
2012-01-01
In this paper we report on a high-order fast method to numerically calculate wakefield forces in an electron beam given a wake function model. This method is based on a Newton-Cotes quadrature rule for integral approximation and an FFT method for discrete summation that results in an $O(Nlog(N))$ computational cost, where $N$ is the number of grid points. Using the Simpson quadrature rule with an accuracy of $O(h^4)$, where $h$ is the grid size, we present numerical calculation of the wakefields from a resonator wake function model and from a one-dimensional coherent synchrotron radiation (CSR) wake model. Besides the fast speed and high numerical accuracy, the calculation using the direct line density instead of the first derivative of the line density avoids numerical filtering of the electron density function for computing the CSR wakefield force.
Chui, Siu Lit; Lu, Ya Yan
2004-03-01
Wide-angle full-vector beam propagation methods (BPMs) for three-dimensional wave-guiding structures can be derived on the basis of rational approximants of a square root operator or its exponential (i.e., the one-way propagator). While the less accurate BPM based on the slowly varying envelope approximation can be efficiently solved by the alternating direction implicit (ADI) method, the wide-angle variants involve linear systems that are more difficult to handle. We present an efficient solver for these linear systems that is based on a Krylov subspace method with an ADI preconditioner. The resulting wide-angle full-vector BPM is used to simulate the propagation of wave fields in a Y branch and a taper. PMID:15005407
Energy Technology Data Exchange (ETDEWEB)
Xie, Binbin; Liu, Lihong; Cui, Ganglong; Fang, Wei-Hai, E-mail: fangwh@bnu.edu.cn [Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875 (China); Cao, Jun [Guizhou Provincial Key Laboratory of Computational Nano-material Science, Guizhou Normal College, Guiyang 550018 (China); Feng, Wei; Li, Xin-qi [Department of Physics, Beijing Normal University, Beijing 100875 (China)
2015-11-21
In this work, the recently introduced quantum trajectory mean-field (QTMF) approach is implemented and employed to explore photodissociation dynamics of diazirinone (N{sub 2}CO), which are based on the high-level ab initio calculation. For comparison, the photodissociation process has been simulated as well with the fewest-switches surface hopping (FSSH) and the ab initio multiple spawning (AIMS) methods. Overall, the dynamical behavior predicted by the three methods is consistent. The N{sub 2}CO photodissociation at λ > 335 nm is an ultrafast process and the two C—N bonds are broken in a stepwise way, giving birth to CO and N{sub 2} as the final products in the ground state. Meanwhile, some noticeable differences were found in the QTMF, FSSH, and AIMS simulated time constants for fission of the C—N bonds, excited-state lifetime, and nonadiabatic transition ratios in different intersection regions. These have been discussed in detail. The present study provides a clear evidence that direct ab initio QTMF approach is one of the reliable tools for simulating nonadiabatic dynamics processes.
International Nuclear Information System (INIS)
The photodissociation and laser assisted dissociation of the carbon monoxide dication X3Π CO2+ into the 3Σ− states are investigated. Ab initio electronic structure calculations of the adiabatic potential energy curves, radial nonadiabatic couplings, and dipole moments for the X 3Π state are performed for 13 excited 3Σ− states of CO2+. The photodissociation cross section, calculated by time-dependent methods, shows that the C+ + O+ channels dominate the process in the studied energy range. The carbon monoxide dication CO2+ is an interesting candidate for control because it can be produced in a single, long lived, v = 0 vibrational state due to the instability of all the other excited vibrational states of the ground 3Π electronic state. In a spectral range of about 25 eV, perpendicular transition dipoles couple this 3Π state to a manifold of 3Σ− excited states leading to numerous C+ + O+ channels and a single C2+ + O channel. This unique channel is used as target for control calculations using local control theory. We illustrate the efficiency of this method in order to find a tailored electric field driving the photodissociation in a manifold of strongly interacting electronic states. The selected local pulses are then concatenated in a sequence inspired by the “laser distillation” strategy. Finally, the local pulse is compared with optimal control theory
Energy Technology Data Exchange (ETDEWEB)
Petropaviovskikh, I.
1995-07-01
The chemistry of the atmosphere is strongly influenced by solar radiation, In addition to the obvious heating effect, solar radiation at visible and ultra-violet (UV) wavelengths drives atmospheric chemistry by photodissociating relatively stable molecules into usually highly reactive fragments. Photodissociation coefficients (J-values) describe quantitatively the frequency of atmospheric photolysis reactions, and therefore it is important to calculate them accurately. The author has examined a number of outstanding problems in the calculation of J-values.
DEFF Research Database (Denmark)
Farrokhzad, F.; Mowlaee, P.; Barari, Amin;
2011-01-01
The beam deformation equation has very wide applications in structural engineering. As a differential equation, it has its own problem concerning existence, uniqueness and methods of solutions. Often, original forms of governing differential equations used in engineering problems are simplified, ...... Asymptotic Method (OHAM). The comparisons of the results reveal that these methods are very effective, convenient and quite accurate to systems of non-linear differential equation.......The beam deformation equation has very wide applications in structural engineering. As a differential equation, it has its own problem concerning existence, uniqueness and methods of solutions. Often, original forms of governing differential equations used in engineering problems are simplified......, and this process produces noise in the obtained answers. This paper deals with solution of second order of differential equation governing beam deformation using four analytical approximate methods, namely the Homotopy Perturbation Method (HPM), Variational Iteration Method (VIM) and Optimal Homotopy...
Picosecond Laser Chemistry in Supersonic Jet Beams
Zewail, Ahmed H.
1983-01-01
In this review we describe the development and the applications of the picosecond-jet technique, which utilizes a picosecond laser and a supersonically-cold jet beam of large molecules. The applications include studies of coherence (quantum beats), photodissociation, isomerization, and partial solvation. The results emphasize the role of intramolecular energy redistribution, and provide evidence for intramolecular threshold effect for rates vs. excess molecular energy. Simple theory for this ...
Photodissociation of CS and SiO+ from Excited Rovibrational Levels
Pattillo, Ryan; Stancil, Phillip C.; McLaughlin, Brendan; McCann, Jim; Forrey, Robert C.; Babb, James
2016-06-01
Photodissociation due to ultraviolet (UV) photons is a dominant molecular destruction process in a variety of UV-irradiated interstellar (IS) environments. While most astrochemical models adopt photodissociation rates computed from cross sections out of the molecule's ground rovibrational level (v=0,J=0), they also assume a standard local IS radiation field and opacity due to standard IS dust. However, none of these conditions are satisfied in a host of environments including photodissociation regions, protoplanetary disks, and outflows from AGB stars. To allow for the calculation of reliable photodissociation rates, we compute cross sections from all bound v,J levels of the ground electronic state for two example molecules, CS and SiO+. The cross sections are computed for a large number of excited electronic states using a two-state fully quantum perturbation approach. New ab initio potential energies and transition dipole moment functions, used in the photodissociation calculations, were obtained at the MRCI+Q level of theory using the quantum chemistry package MOLPRO. Applications of the v,J-state-resolved cross sections will be presented as well as LTE photodissociation cross sections which assume a Boltzmann distribution of initial v,J levels.This work is supported at UGA by NASA grant NNX15AI61G.
A method for varying the diameter of a charged particle beam
International Nuclear Information System (INIS)
This invention concerns the monitoring of the diameter of charged particle beams, particularly ion or electron beams utilised for ionic or electron beam writing (manufacture of integrated circuits). The process includes the focusing of the beam through a lens, then passing the focused beam through an envelope of conducting material, this envelope being spaced out from the beam and coaxial to it. A selected continuous potential is applied to the envelope. The beam diameter is then checked by modifying the potential applied to the envelope. In order to increase the diameter of the beam, the potential is altered so as to move it away from the potential of the earth. Conversely, to reduce the beam diameter the potential is altered by bringing it closer to the potential of the earth
The nuclear interaction analysis methods for diagnostics of high power ion beam technologies
International Nuclear Information System (INIS)
The complex of Nuclear Interaction Analysis Methods including charged particle activation analysis (CPAA and HIAA), spectrometry of ion induced gamma-emission (PIGE and HIIGE) , characteristic X-ray emission (PIXE), and Rutherford Backscattering Spectrometry (RBS), have been used for diagnostics of the High Power Ion Beam (HPIB) assisted technologies. Accelerated ion beams from the EG-2.5 electrostatic generator and U-120 cyclotron were used for implementation of the techniques. The complex allows a lot of problems of elemental and isotopic analysis to be addressed. First, it is the determination of micro- and macrocomponents of modified materials; second, determination of surface density of thin films, multilayers and coatings, total surface gaseous contamination and amounts of the elements implanted in specimens; third, measurement of concentration depth profiles of the elements. Experiments have shown that the preferable application of nuclear analysis methods allows us to avoid the considerable errors arising when the concentration depth profiles of elements are measured by SIMS or AES in studies of mass transfer processes induced by HPIBs. (author). 1 tab., 2 figs., 3 refs
Direct fourier methods in 3D-reconstruction from cone-beam data
International Nuclear Information System (INIS)
The problem of 3D-reconstruction is encountered in both medical and industrial applications of X-ray tomography. A method able to utilize a complete set of projections complying with Tuys condition was proposed by Grangeat. His method is mathematically exact and consists of two distinct phases. In phase 1 cone-beam projection data are used to produce the derivative of the radon transform. In phase 2, after interpolation, the radon transform data are used to reconstruct the three-dimensional object function. To a large extent our method is an extension of the Grangeat method. Our aim is to reduce the computational complexity, i.e. to produce a faster method. The most taxing procedure during phase 1 is computation of line-integrals in the detector plane. By applying the direct Fourier method in reverse for this computation, we reduce the complexity of phase 1 from O(N4) to O(N3logN). Phase 2 can be performed either as a straight 3D-reconstruction or as a sequence of two 2D-reconstructions in vertical and horizontal planes, respectively. Direct Fourier methods can be applied for the 2D- and for the 3D-reconstruction, which reduces the complexity of phase 2 from O(N4) to O(N3logN) as well. In both cases, linogram techniques are applied. For 3D-reconstruction the inversion formula contains the second derivative filter instead of the well-known ramp-filter employed in the 2D-case. The derivative filter is more well-behaved than the 2D ramp-filter. This implies that less zeropadding is necessary which brings about a further reduction of the computational efforts. The method has been verified by experiments on simulated data. The image quality is satisfactory and independent of cone-beam angles. For a 5123 volume we estimate that our method is ten times faster than Grangeats method
International Nuclear Information System (INIS)
Nonthermal plasma (NTP)-based treatments of volatile organic compounds (VOCs) have potential for effective environmental remediation. Theory and experiment that consider the basic science pertaining to discharge events have helped improve NTP remediation outcomes. If direct information on early post-discharge chemical intermediates were also available, it would likely lead to additional improvement in NTP remediation outcomes. To this point, however, experiments yielding direct information on post-NTP VOC intermediates have been limited. An approach using supersonic expansion molecular beam methods offers general promise for detection of post-discharge VOC intermediates. To illustrate the potential utility of these methods, we present mass spectra showing the growth of early products formed when pulsed corona discharges were carried out on toluene in He and then in He with added O2. Good general detection of neutral post-discharge species was obtained using 800 nm 150 fs photoionization pulses.
Energy Technology Data Exchange (ETDEWEB)
Tan Yongjun, E-mail: yj.tan@curtin.edu.a [Western Australian Corrosion Research Group, Department of Chemistry, Curtin University, GPO Box U1987, Perth (Australia); Fwu, Young; Bhardwaj, Kriti [Western Australian Corrosion Research Group, Department of Chemistry, Curtin University, GPO Box U1987, Perth (Australia)
2011-04-15
Research highlights: A new experiment method for evaluating under-deposit corrosion and its inhibitors. Under-deposit corrosion did not occur in a CO{sub 2} saturated pure brine solution. Inhibitor imidazoline addition and O{sub 2} contamination initiated under-deposit corrosion. Inhibitor imidazoline reduced general corrosion but enhanced localised corrosion. - Abstract: A new experimental method has been applied to evaluate under-deposit corrosion and its inhibition by means of an electrochemically integrated multi-electrode array, namely the wire beam electrode (WBE). Maps showing galvanic current and corrosion potential distributions were measured from a WBE surface that was partially covered by sand. Under-deposit corrosion did not occur during the exposure of the WBE to carbon dioxide saturated brine under ambient temperature. The introduction of corrosion inhibitor imidazoline and oxygen into the brine was found to significantly affect the patterns and rates of corrosion, leading to the initiation of under-deposit corrosion over the WBE.
Ion beam analysis of zeolites type Li-ABW synthesized by hydrothermal method
Energy Technology Data Exchange (ETDEWEB)
Andrade, E.; De Lucio, O. G.; Solis, C.; Zavala, E. P.; Cruz, J. [UNAM, Instituto de Fisica, Circuito Exterior, Ciudad Universitaria, 04510 Mexico D. F. (Mexico); Alfaro, S.; Rodriguez, C.; Valenzuela, M. A. [IPN, Escuela Superior de Ingenieria Quimica e Industrias Extractivas, Laboratorio de Catalisis y Materiales, Zacantenco, 07738 Mexico D. F. (Mexico); Rocha, M. F. [IPN, Escuela Superior de Ingenieria Mecanica y Electrica, Av. Instituto Politecnico Nacional s/n, Col. Lindavista, 07738 Mexico D. F. (Mexico); Murillo, G.; Policroniades, R. [ININ, Carretera Mexico-Toluca s/n, Ocoyoacac 52750, Estado de Mexico (Mexico)
2010-02-15
This work reports a method to synthesize and characterize Li-ABW zeolites by a hydrothermal method. These materials are good candidates for CO{sub 2} capture because of the high reactivity between the Li{sup +} with CO{sub 2} to form Li{sub 2}CO{sub 3}. We performed and elemental profile concentration using ion beam analysis. The elastic backscattered proton energy spectra from the Al, Si, O and Li nuclei, in combination with the {alpha} particles from the {sup 7}Li ({rho}, {alpha}){sup 4}He nuclear reaction energy spectra, were employed for this task. X-ray diffraction was also applied to determine the crystalline structure. (Author)
X-ray beams characterization by the attenuation method for the personal dosemeters calibration
International Nuclear Information System (INIS)
The choice of the attenuation method to characterize the x-ray beams used in the calibration of personal dosemeters at the Calibration and Dosimetry Laboratory of the Peruvian Institute of Nuclear Energy (IPEN). Voltages applied to the X-ray tube and the addition of filters have been made according to the publication ANSI No. 13. Half value layer, homogeneity coefficient and mean energy were determined from attenuation data. Average relative differences of 3, 40 and 4% respectively were found with respect to values published in ANSI No. 13. Also spectral distributions and their resolutions were determined. relative differences of 6 and 19% respectively were found in comparison with values calculated by the Monte Carlo Method
Charge evolution of swift-heavy-ion beams explored by matrix method
Energy Technology Data Exchange (ETDEWEB)
Osmani, O. [Department of Physics, University of Duisburg-Essen, D-47048 Duisburg (Germany); Department of Physics, University of Kaiserslautern and Research Center OPTIMAS, D-67653 Kaiserslautern (Germany); Sigmund, P. [Department of Physics and Chemistry, University of Southern Denmark, DK-5230 Odense M (Denmark)
2011-05-01
The approach to charge equilibrium of a beam of swift ions can be expressed by a matrix with rows and columns expressing the initial and instantaneous charge state, respectively. We have explored the capability of this matrix formalism in comparison with the standard method, i.e., numerical solution of linear rate equations as implemented in the ETACHA code. The matrix method is computationally more efficient, and the acceptable numerical error can be pre-defined. The agreement with predictions based on ETACHA is generally good. Significant discrepancies are primarily due to differences in the applied cross sections for electron capture and loss. Comparisons have been made also with experimental results for sulphur in carbon.
Energy Technology Data Exchange (ETDEWEB)
He Luning; Sulkes, Mark, E-mail: cm06acf@tulane.edu [Chemistry Department, Tulane University, New Orleans, LA 70118 (United States)
2011-07-13
Nonthermal plasma (NTP)-based treatments of volatile organic compounds (VOCs) have potential for effective environmental remediation. Theory and experiment that consider the basic science pertaining to discharge events have helped improve NTP remediation outcomes. If direct information on early post-discharge chemical intermediates were also available, it would likely lead to additional improvement in NTP remediation outcomes. To this point, however, experiments yielding direct information on post-NTP VOC intermediates have been limited. An approach using supersonic expansion molecular beam methods offers general promise for detection of post-discharge VOC intermediates. To illustrate the potential utility of these methods, we present mass spectra showing the growth of early products formed when pulsed corona discharges were carried out on toluene in He and then in He with added O{sub 2}. Good general detection of neutral post-discharge species was obtained using 800 nm 150 fs photoionization pulses.
Radiation safety assessment of cobalt 60 external beam radiotherapy using the risk-matrix method
International Nuclear Information System (INIS)
External beam radiotherapy is the only practice in which humans are placed directly in a radiation beam with the intention to deliver a very high dose. This is why safety in radiotherapy is very critical, and is a matter of interest to both radiotherapy departments and regulatory bodies. Accidental exposures have occurred throughout the world, thus showing the need for systematic safety assessments, capable to identify preventive measures and to minimize consequences of accidental exposure. Risk-matrix is a systematic approach which combines the relevant event features to assess the overall risk of each particular event. Once an event sequence is identified, questions such as how frequent the event, how severe the potential consequences and how reliable the existing safety measures are answered in a risk-matrix table. The ultimate goal is to achieve that the overall risk for events with severe consequences should always be low o very low. In the present study, the risk-matrix method has been applied to an hypothetical radiotherapy department, which could be equivalent to an upper level hospital of the Ibero American region, in terms of safety checks and preventive measures. The application of the method has identified 76 event sequences and revealed that the hypothetical radiotherapy department is sufficiently protected (low risk) against them, including 23 event sequences with severe consequences. The method has revealed that the risk of these sequences could grow to high level if certain specific preventive measures were degraded with time. This study has identified these preventive measures, thus facilitating a rational allocation of resources in regular controls to detect any loss of reliability. The method has proven to have an important practical value and is affordable at hospital level. The elaborated risk-matrix can be easily adapted to local circumstances, in terms of existing controls and safety measures. This approach can help hospitals to identify
Cost-reduction method for delamination monitoring using electrical resistance changes of CFRP beam
Todoroki, A.; Ueda, M.
2004-02-01
Delamination is a significant defect of laminated composites. The present study employs an electrical resistance change method in an attempt to identify internal delaminations experimentally. The method adopts reinforcing carbon fibers as sensors. In our previous paper, an actual delamination crack in a Carbon Fiber Reinforced Plastics (CFRP) laminate was experimentally identified with artificial neural networks (ANN) or response surfaces created from a large number of experiments. The experimental results were used for learning of the ANN or regression of the response surfaces. For the actual application of the method, it is indispensable to reduce the number of experiments to suppress the total experimental cost. In the present study, therefore, FEM analyses are employed to make sets of data for learning of the ANN. First, electrical conductivity of the CFRP laminate is identified by means of the least estimation error method. After that, the results of FEM analyses are used for learning of the ANN. The method is applied to actual delamination monitoring of CFRP beams. As a result, the method successfully monitored the delamination location and size only with ten experiments.
Creation of the SiCx layers as interface of hard wear protective coatings by dual beam IBAD method
International Nuclear Information System (INIS)
The paper presents the current status of research connected with forming one- and multi-layer, anti wear, microcrystalline and amorphous coatings, one-element (e.g. Diamond Like carbon coatings) (DLC) and multi-element (e. g. SiC) at the application of dual beam IBAD (Ion Beam Assisted Deposition) method. This method features high technological flexibility, consisting in the possibility of composing layers with desired properties with the coating's good adhesion to the substrate. In the research on the formed coatings, the method of detecting backscattered charged particles (RBS - Rutherford Backscattering Spectroscopy) and for specifying tribological features set of mechanical methods were used. (author)
DEFF Research Database (Denmark)
Jeong, Cheol-Ho; Rindel, Jens Holger
2006-01-01
the phased method is advantageous compared to the conventional ray/beam tracing method: accurate prediction of early part of impulse response, better agreement with measured data, lower and extendable frequency range. This means that the technique can be employed in calculating the sound quality......High frequency acoustic analysis of an enclosure has been dealt with by geometrical acoustic techniques and low frequency response can be estimated by modal methods; however, mid frequency range has been a grey zone. The phased beam tracing method (PBTM) is one of the mid-frequency techniques...
Institute of Scientific and Technical Information of China (English)
ZANG Wei-Ping; CHENG Hua; TIAN Jian-Guo
2009-01-01
A novel three-dimensional wide-angle beam propagation method based on the split-step fast Fourier transform is developed. The formulation is based on the three-dimensional Helmholtz wave equation. Each propagation step is performed by utilizing both the FFT and split-step scheme. The solution of Helmholtz wave equation does not make the slowly varying envelope and one-way propagation approximations. To validate the efficiency and accuracy, numerical results for a propagation beam in a tilted step-index optical waveguide are compared with other beam propagation algorithms.
DEFF Research Database (Denmark)
Blasques, José Pedro Albergaria Amaral; Bitsche, Robert
2015-01-01
Crack Closure Technique is used for computation of strain energy release rates. The devised framework was employed for analysis of cracks in beams with different cross section geometries. The results show that the accuracy of the proposed method is comparable to that of conventional three......This paper proposes a novel, efficient, and accurate framework for fracture analysis of beam structures with longitudinal cracks. The three-dimensional local stress field is determined using a high-fidelity beam model incorporating a finite element based cross section analysis tool. The Virtual......-dimensional solid finite element models while using only a fraction of the computation time....
Dilmanian, F. Avraham; McDonald, III, John W.
2007-12-04
A method of assisting recovery of an injury site of brain or spinal cord injury includes providing a therapeutic dose of X-ray radiation to the injury site through an array of parallel microplanar beams. The dose at least temporarily removes regeneration inhibitors from the irradiated regions. Substantially unirradiated cells surviving between the microplanar beams migrate to the in-beam irradiated portion and assist in recovery. The dose may be administered in dose fractions over several sessions, separated in time, using angle-variable intersecting microbeam arrays (AVIMA). Additional doses may be administered by varying the orientation of the microplanar beams. The method may be enhanced by injecting stem cells into the injury site.
Koutchouk, Jean-Pierre; Ptitsyn, V I
2001-01-01
The multipolar content of the dipoles and quadrupoles is known to limit the stability of the beam dynamics in super-conducting machines like RHIC and even more in LHC. The low-beta quadrupoles are thus equipped with correcting coils up to the dodecapole order. The correction is planned to rely on magnetic measurements. We show that a relatively simple method allows an accurate measurement of the multipolar field aberrations using the beam. The principle is to displace the beam in the non-linear fields by local closed orbit bumps and to measure the variation of sensitive beam observable. The resolution and robustness of the method are found appropriate. Experimentation at RHIC showed clearly the presence of normal and skew sextupolar field components in addition to a skew quadrupolar component in the interaction regions. Higher-order components up to decapole order appear as well.
International Nuclear Information System (INIS)
The University of Maryland Dynamical Systems and Accelerator Theory Group has been carrying out long-term research work in the general area of Dynamical Systems with a particular emphasis on applications to Accelerator Physics. This work is broadly divided into two tasks: the computation of charged particle beam transport and the computation of electromagnetic fields and beam-cavity interactions. Each of these tasks is described briefly. Work is devoted both to the development of new methods and the application of these methods to problems of current interest in accelerator physics including the theoretical performance of present and proposed high energy machines. In addition to its research effort, the Dynamical Systems and Accelerator Theory Group is actively engaged in the education of students and postdoctoral research associates. Substantial progress in research has been made during the past year. These achievements are summarized in the following report
Estimation of keV submicron ion beam width using a knife-edge method
Ishii, Yasuyuki; Isoya, Akira; Kojima, Takuji; Arakawa, Kazuo
2003-11-01
A beam width measurement system has been developed for keV submicron ion beams of 0.1 μm or less in width assuming a round shape beam. The system enables to measure beam current change as a function of knife-edge position by cutting a beam focusing point (beam spot) with the sharp edge within a spatial resolution of 0.02 μm. The width of 30 keV order submicron H + ion beam was estimated by fitting current change curves based on three different ion density models: uniform, flat-top and Gaussian. Among these models, the flat-top model provide the most reasonable beam width of 0.56 μm interpreting contribution of halo around the beam spot to beam width estimation. The beam width measurement system with the high spatial resolution and the data analysis based on the flat-top ion density model should contribute to accelerate developments of submicron ion beam production technologies.
Estimation of keV submicron ion beam width using a knife-edge method
International Nuclear Information System (INIS)
A beam width measurement system has been developed for keV submicron ion beams of 0.1 μm or less in width assuming a round shape beam. The system enables to measure beam current change as a function of knife-edge position by cutting a beam focusing point (beam spot) with the sharp edge within a spatial resolution of 0.02 μm. The width of 30 keV order submicron H+ ion beam was estimated by fitting current change curves based on three different ion density models: uniform, flat-top and Gaussian. Among these models, the flat-top model provide the most reasonable beam width of 0.56 μm interpreting contribution of halo around the beam spot to beam width estimation. The beam width measurement system with the high spatial resolution and the data analysis based on the flat-top ion density model should contribute to accelerate developments of submicron ion beam production technologies
Low temperature VLS growth of ITO nanowires by electron beam evaporation method
International Nuclear Information System (INIS)
Indium tin oxide (ITO) nanowires were grown at a lower substrate temperature of 400 °C via Au-catalyzed vapor–liquid–solid (VLS) growth mechanism by electron beam evaporation method. The grown nanowires had length and diameter of 0.8–1.2 μm and 20–50 nm, respectively for growth duration of 20 min. Transmission electron microscope studies confirm the single crystalline nature of the nanowires, and energy dispersive spectroscopy studies on the individual nanowires also confirm that nanowire growth proceeds via Au-catalyzed VLS growth mechanism. Transition in the growth mechanism from Au-catalyzed VLS growth to self-catalyzed VLS growth was observed as the growth temperature changed from 400 to 200 °C. Self-catalytic VLS growth as well as Au catalyzed VLS growth was observed in a growth temperature window of 350–250 °C. This transition in the growth mechanism is mainly due to differences in the growth kinetics of Au-VLS and self-catalyzed VLS mechanism. These results indicate a good understanding of ITO nanowires growth by e-beam evaporation method. Diameters of the nanowires were tuned in a broad range of 20–90 nm by changing the Au catalyst layer thickness. This catalyst-assisted and low temperature growth method can be implemented for precise diameter controlled synthesis of ITO nanowires with mono dispersed gold catalyst particles instead of Au catalyst film to tune the optical properties of the nanowires. (paper)
High fluence irradiation effect on the ion beam graft polymerization method
International Nuclear Information System (INIS)
Radiation graft polymerization method has been applied to make many industrial product. Ion beam graft polymerization method has been developed by Betz and many researchers, and we have also developed the method with proton whose energy is below a few MeV. Using the method, the substrate, e.g. polyethylene film, is graft-polymerized and has the graft chains near the surface. To conduct the method for some times, the structure of graft chains near the surface can be formed. When we want to produce the graft chains inside of the substrate, the graft chains near the surface are unnecessary. One of our objectives is to produce a functional polymer with a structure in the film. When the sample is irradiated in sufficiently high fluence, the sample can’t be graft-polymerized in the next irradiation. Comparing the density of radicals and the number of double bond with the degree of grafting, the reason why formation of a part not grafted in high fluence irradiation was discussed. Because the number of the double bond and the allyl radicals in PE are increased for high fluence irradiation, the number of the alkyl radical as a grafting point is decreased. Moreover, the alkyl radical is not produced in following irradiation since existence of double bond and peroxy radical
Method for extremal control of the beam parameters in charged particle accelerators
International Nuclear Information System (INIS)
The method of extremal control of charged particle beam parameters is suggested for the solution of the timization problem ophe IHEP boster operation mode. Motion along the estimation of drift direction with simultaneous adaptation to the value of drift rate is organized in the suggested method of extremal control. It is assumed that trajectory of the drift extremum can be approximated by the piecewise-linear function. Estimation of the drift direction is exercised on the base of fixation of two consequent positions of the extremum in the control space. The identification of the drift-direction are introduced in the algorithm of tracing the extrenum drift. Investigation of the method on the test two-dimensional square surface has shown that the method provides drift tracing within the rate of 0.01 a deg - 2 a deg where a deg - the initial working step of the stochastic approximation method. The average deviation does not exceed 0.7 a deg, and the accuracy of adaptation to the value of drift rate 10-3 K
International Nuclear Information System (INIS)
In the present paper we report a theoretical study on mechanistic photodissociation of acetaldehyde (CH3CHO). Stationary structures for H2 and CO eliminations in the ground state (S0) have been optimized with density functional theory method, which is followed by the intrinsic reaction coordinate and ab initio molecular dynamics calculations to confirm the elimination mechanism. Equilibrium geometries, transition states, and intersection structures for the C-C and C-H dissociations in excited states were determined by the complete-active-space self-consistent field (CASSCF) method. Based on the CASSCF optimized structures, the potential energy profiles for the dissociations were refined by performing the single-point calculations using the multireference configuration interaction method. Upon the low-energy irradiation of CH3CHO (265 nm1 C-C bond fission following intersystem crossing from the S1 state is the predominant channel and the minor channel, the ground-state elimination to CH4+CO after internal conversion (IC) from S1 to S0, could not be excluded. With the photon energy increasing, another pathway of IC, achieved via an S1/S0 intersection point resulting from the S1 C-C bond fission, becomes accessible and increases the yield of CH4+CO.
Photodissociation dynamics of IBr-(CO2)n, n<15
International Nuclear Information System (INIS)
We report the ionic photoproducts produced following photoexcitation of mass selected IBr-(CO2)n, n=0-14, cluster ions at 790 and 355 nm. These wavelengths provide single state excitation to two dissociative states, corresponding to the A'2Π1/2 and B 2 2Σ1/2+ states of the IBr- chromophore. Excitation of these states in IBr- leads to production of I-+Br and Br-+I*, respectively. Potential energy curves for the six lowest electronic states of IBr- are calculated, together with structures for IBr-(CO2)n, n=1-14. Translational energy release measurements on photodissociated IBr- determine the I-Br- bond strength to be 1.10±0.04 eV; related measurements characterize the A'2Π1/2(leftarrow)X 2Σ1/2+ absorption band. Photodissociation product distributions are measured as a function of cluster size following excitation to the A'2Π1/2 and B 2 2Σ1/2+ states. The solvent is shown to drive processes such as spin-orbit relaxation, charge transfer, recombination, and vibrational relaxation on the ground electronic state. Following excitation to the A'2Π1/2 electronic state, IBr-(CO2)n exhibits size-dependent cage fractions remarkably similar to those observed for I2-(CO2)n. In contrast, excitation to the B 2 2Σ1/2+ state shows extensive trapping in excited states that dominates the recombination behavior for all cluster sizes we investigated. Finally, a pump-probe experiment on IBr-(CO2)8 determines the time required for recombination on the ground state following excitation to the A' state. While the photofragmentation experiments establish 100% recombination in the ground electronic state for this and larger IBr- cluster ions, the time required for recombination is found to be ∼5 ns, some three orders of magnitude longer than observed for the analogous I2- cluster ion. Comparisons are made with similar experiments carried out on I2-(CO2)n and ICl-(CO2)n cluster ions
DNA comet assay as a rapid detection method of irradiated bovine meat by electron beam
International Nuclear Information System (INIS)
Full text: Introduction: The presence in food of pathogenic microorganisms, such as Salmonella species, Escherichia coli 0157:H7, Listeria Monocytogenes or Yersinia enterolitica, is a problem of growing concern to public health authorities all over the world. Thus, irradiation of certain prepackaged meat products such as ground beef, minced meat, and hamburgers may help in controlling meatborne pathogens and parasites. Pathogenic microorganisms and parasites in meat products, which are commonly consumed raw, are of particular importance, Up to now, only electron-beam accelerators and gamma-ray cells have been used for commercial applications. At the international conference on 'The Acceptance, Control of, and Trade in Irradiated Food', it was recommended that governments should encourage research into detection methods (Anon, 1989), Already five international standards are available to food control agencies. A number of physical, chemical, and biological techniques of detection of irradiated foods have been discussed in the literature. A rapid and inexpensive screening test employing DNA Comet Assay to identify radiation treatment of food has been described by Cerda et al. (1997). This method is restricted to foods that have not been subjected to heat or other treatments, which also induce DNA fragmentation. Advantages are its simplicity, low cost and speed of measurement. This method was proposed to the European Committee for Standardization (CEN) as a screening protocol (presumptive) and not as a proof (definitive). The DNA comet assay have been yielded good results with chicken, pork, fish meat, exotic meat, hamburgers, fruits and cereals. In this work we studied a DNA fragmentation of bovine meat irradiated by electron beam. Experimental: Bovine meat was purchased in local shops in Sao Paulo. Irradiation was performed with electron beam of accelerator facility of Radiation Dynamics Inc., USA (E=1,5 MeV, l=25 mA). The irradiation doses were 3,5; 4,5, 5,5, and 7
Computational methods for the identification of spatially varying stiffness and damping in beams
Banks, H. T.; Rosen, I. G.
1986-01-01
A numerical approximation scheme for the estimation of functional parameters in Euler-Bernoulli models for the transverse vibration of flexible beams with tip bodies is developed. The method permits the identification of spatially varying flexural stiffness and Voigt-Kelvin viscoelastic damping coefficients which appear in the hybrid system of ordinary and partial differential equations and boundary conditions describing the dynamics of such structures. An inverse problem is formulated as a least squares fit to data subject to constraints in the form of a vector system of abstract first order evolution equations. Spline-based finite element approximations are used to finite dimensionalize the problem. Theoretical convergence results are given and numerical studies carried out on both conventional (serial) and vector computers are discussed.
Laser systems configured to output a spectrally-consolidated laser beam and related methods
Koplow, Jeffrey P.
2012-01-10
A laser apparatus includes a plurality of pumps each of which is configured to emit a corresponding pump laser beam having a unique peak wavelength. The laser apparatus includes a spectral beam combiner configured to combine the corresponding pump laser beams into a substantially spatially-coherent pump laser beam having a pump spectrum that includes the unique peak wavelengths, and first and second selectively reflective elements spaced from each other to define a lasing cavity including a lasing medium therein. The lasing medium generates a plurality of gain spectra responsive to absorbing the pump laser beam. Each gain spectrum corresponds to a respective one of the unique peak wavelengths of the substantially spatially-coherent pump laser beam and partially overlaps with all other ones of the gain spectra. The reflective elements are configured to promote emission of a laser beam from the lasing medium with a peak wavelength common to each gain spectrum.
A Vibration Reliability Analysis Method for the Uncertain Space Beam Structure
Directory of Open Access Journals (Sweden)
Yanyu Mo
2016-01-01
Full Text Available Considering that uncertainty is inherent and unavoidable in engineering practice and the available information about the uncertain parameters is always not sufficient, the paper tries to carry out the nonprobabilistic vibration reliability analysis so as to avoid resonance on uncertain structure with bounded parameters. The input uncertain-but-bounded parameters are treated as interval variables, and an interval model is adopted to describe bounded uncertainties. Then a theory of nonprobabilistic reliability is introduced, in which the dimensionless nonprobabilistic reliability index and system reliability index are defined. In order to investigate the resonance failure with reliability method, the resonance failure domains are stated according to the relationships between the natural frequencies and the excitation frequencies. Then the uncertain structure is modeled as a series system and a system reliability index is proposed to evaluate the safety of the structure. The paper also takes a frequency analysis on the uncertain space beam structure to get the resonance failure modes. A frequency analysis method based on the monotonicity discriminant of the frequency sensitivity is presented. Then an optimization algorithm is introduced to verify the validity of the former frequency analysis method. Two examples are provided to illustrate the effectiveness and feasibility of the presented method.
Robust scatter correction method for cone-beam CT using an interlacing-slit plate
Huang, Kui-Dong; Xu, Zhe; Zhang, Ding-Hua; Zhang, Hua; Shi, Wen-Long
2016-06-01
Cone-beam computed tomography (CBCT) has been widely used in medical imaging and industrial nondestructive testing, but the presence of scattered radiation will cause significant reduction of image quality. In this article, a robust scatter correction method for CBCT using an interlacing-slit plate (ISP) is carried out for convenient practice. Firstly, a Gaussian filtering method is proposed to compensate the missing data of the inner scatter image, and simultaneously avoid too-large values of calculated inner scatter and smooth the inner scatter field. Secondly, an interlacing-slit scan without detector gain correction is carried out to enhance the practicality and convenience of the scatter correction method. Finally, a denoising step for scatter-corrected projection images is added in the process flow to control the noise amplification The experimental results show that the improved method can not only make the scatter correction more robust and convenient, but also achieve a good quality of scatter-corrected slice images. Supported by National Science and Technology Major Project of the Ministry of Industry and Information Technology of China (2012ZX04007021), Aeronautical Science Fund of China (2014ZE53059), and Fundamental Research Funds for Central Universities of China (3102014KYJD022)
International Nuclear Information System (INIS)
Recent absorbed-dose-based protocols allow for two methods of calibrating electron beams using plane-parallel chambers, one using the ND,wCo for a plane-parallel chamber, and the other relying on cross-calibration of the plane-parallel chamber in a high-energy electron beam against a cylindrical chamber which has an ND,wCo factor. The second method is recommended as it avoids problems associated with the Pwall correction factors at 60Co for plane-parallel chambers which are used in the determination of the beam quality conversion factors. In this article we investigate the consistency of these two methods for the PTW Roos, Scanditronics NACP02, and PTW Markus chambers. We processed our data using both the AAPM TG-51 and the IAEA TRS-398 protocols. Wall correction factors in 60Co beams and absorbed-dose beam quality conversion factors for 20 MeV electrons were derived for these chambers by cross-calibration against a cylindrical ionization chamber. Systematic differences of up to 1.6% were found between our values of Pwall and those from the Monte Carlo calculations underlying AAPM TG-51, and up to 0.6% when comparing with the IAEA TRS-398 protocol. The differences in Pwall translate directly into differences in the beam quality conversion factors in the respective protocols. The relatively large spread in the experimental data of Pwall, and consequently the absorbed-dose beam quality conversion factor, confirms the importance of the cross-calibration technique when using plane-parallel chambers for calibrating clinical electron beams. We confirmed that for well-guarded plane-parallel chambers, the fluence perturbation correction factor at dmax is not significantly different from the value at dref. For the PTW Markus chamber the variation in the latter factor is consistent with published fits relating it to average energy at depth
Analytic HI-to-H2 Photodissociation Transition Profiles
Bialy, Shmuel
2016-01-01
We present a simple analytic procedure for generating atomic-to-molecular (HI-to-H$_2$) density profiles for optically thick clouds illuminated by far-ultraviolet radiation. Our procedure is based on the analytic theory for the structure of 1D HI/H$_2$ photon-dominated regions, presented by Sternberg et al. (2014). Depth-dependent HI and H$_2$ density fractions may be computed for arbitrary gas density, far-ultraviolet field intensity, and the metallicity dependent H$_2$ formation rate coefficient, and dust absorption cross section. We use our procedure to generate a set of HI-to-H$_2$ transition profiles for a wide range of conditions, from the weak- to strong-field limits, and from super-solar down to low metallicities. We show that if presented as functions of dust optical depth the HI and H$_2$ density profiles depend primarily on the Sternberg "$\\alpha G$ parameter" (dimensionless) that determines the dust optical depth associated with the total photodissociated HI column. We derive a universal analytic ...
Model of comet comae. II. Effects of solar photodissociative ionization
International Nuclear Information System (INIS)
Improvements to our computer model of coma plotochemistry are described. These include an expansion of the chemical reactions network and new rate constants that have been measured only recently. Photolytic reactions of additional molecules are incorporated, and photolytic branching ratios are treated in far greater detail than in our previous work. A total of 25 photodissociative ionization (PDI) reactions are now considered (as compared to only 3 PDI reactions previously). Solar PDI of the mother molecule CO2 is shown to compete effectively with photoionization of CO in the production of observed CO+. The CO+ density peak predicted by our improved model, for COP2 or CO mother molecules, is deep in the inner coma, in better agreement with observation than our old CO2 model. However, neither CO2 nor CO mother molecule calculations reproduce the CO+/H2O+ ratio observed in comet Kohoutek. PDI products of CO2, CO, CH4, and NH3 mother molecules fuel a complex chemistry scheme, producing inner coma abundances of CN, C2, and C3 much greater than previously calculated
Roaming-mediated isomerization in the photodissociation of nitrobenzene
Hause, Michael L.; Herath, Nuradhika; Zhu, Rongshun; Lin, M. C.; Suits, Arthur G.
2011-12-01
Roaming reactions comprise a new class of reaction in which a molecule undergoes frustrated dissociation to radicals, followed by an intramolecular abstraction reaction. Nitro compounds have long been known to dissociate to give NO as a major product. However, rates based upon isomerization via calculated tight transition states are implausibly slow, so the key dissociation pathway for this important class of molecules remains obscure. Here, we present an imaging study of the photodissociation of nitrobenzene with state-specific detection of the resulting NO products. We observe a bimodal translational energy distribution in which the slow products are formed with low NO rotational excitation, and the fast component is associated with high rotational excitation. High-level ab initio calculations identified a ‘roaming-type’ saddle point on the ground state. Branching ratio calculations then show that thermal dissociation of nitrobenzene is dominated by ‘roaming-mediated isomerization’ to phenyl nitrite, which subsequently decomposes to give C6H5O + NO.
Evolution of PAHs in photodissociation regions: Hydrogenation and charge states
Montillaud, J; Toublanc, D
2013-01-01
Various studies have emphasized variations of the charge state and composition of the interstellar polycyclic aromatic hydrocarbon (PAH) population in photodissociation regions (PDRs). We aim to model the spatial evolution of the charge and hydrogenation states of PAHs in PDRs. We focus on the specific case of the north-west (NW) PDR of NGC 7023 and also discuss the case of the diffuse interstellar medium (ISM). The physical conditions in NGC 7023 NW are modelled using a state-of-the-art PDR code. We then use a new PAH chemical evolution model that includes recent experimental data on PAHs and describes multiphoton events. We consider a family of compact PAHs bearing up to 96 carbon atoms. The calculated ionization ratio is in good agreement with observations in NGC 7023 NW. Within the PDR, PAHs evolve into three major populations: medium-sized PAHs (5090) can be superhydrogenated, and smaller species (Nc<50) are fully dehydrogenated. In the cavity, where the fullerene C60 was recently detected, all the st...
Photodissociation Spectroscopy of Ruthenium Polypyridyl Complexes in Vacuo
Xu, Shuang; Smith, James; Weber, J. Mathias
Photoelectrochemical water oxidation is a direct way to produce solar fuels from renewable sources. Since this reaction has a high reaction barrier, a cost-effective catalyst is necessary. Ruthenium polypyridyl complexes are promising catalysts for water oxidation. However, the mechanism of catalytic action is not well understood. One major difficulty of a mechanistic understanding is the complexity of reactive solutions under turnover conditions. To circumvent this problem, we applied electronic photodissociation spectroscopy in the UV and visible spectral range to a series of mass selected ruthenium polypyridyl complex ions in vacuo. The ions in this work are of the form [RuII-L]2+, where RuII represents ruthenium(II)-bipyridine-terpyridine, a prototype catalyst belonging to the ruthenium-polypyridyl family. By varying the ligand L, we were able to study the ligand influence on the photophysical properties of the complex. The cases where L = (H2O)1 , 2 , 3 are of particular interest because they are directly related to an intermediate in the catalytic cycle for water oxidation. Our experiment in vacuo is an essential complement to experiments in solution and provides unique information for understanding the photophysics and photochemistry of these complexes on a molecular level.
Selective control of HOD photodissociation using CW lasers
Indian Academy of Sciences (India)
Manabendra Sarma; S Adhikari; Manoj K Mishra
2007-09-01
Selective control of HOD photodissociation (H-O + D ← HOD → H + O-D) has been theoretically investigated using CW lasers with appropriate carrier frequency and |0, 0〉, |0, 1〉 and |0, 2〉 with zero quantum of excitation in the O-H bond and zero, one and two quanta of excitation in the O-D bond as the initial states. Results indicate that the O-H bond in HOD can be selectively dissociated with a maximum flux of 87% in the H + O-D channel from the ground vibrational state |0, 0〉. For the O-D bond dissociation, it requires two quanta of excitation (|0, 2〉) in the O-D mode to obtain 83% flux in the H-O + D channel. Use of a two colour laser set-up in conjunction with the field optimized initial state (FOIST) scheme to obtain an optimal linear combination of |0, 0〉 and |0, 1〉 vibrational states as the initial state provides an additional 7% improvement to flux in the H-O + D channel as compared to that from the pure |0, 1〉 state.
Indian Academy of Sciences (India)
Ş Şentürk; F Demiray; O Özsoy
2007-09-01
Energy resolution of the time-of-ﬂight mass spectrometer was considered. The estimations indicate that the time-lag energy focusing method provides better resolution for the parallel case while the turnaround time is more convenient for the perpendicular position. Hence the applicability of the methods used for the energy resolution depends on beam source arrangement.
International Nuclear Information System (INIS)
To reduce the cross-talk between nanoscale devices, low-k materials such as methyl silsesquioxane (MSQ), which is damaged easily during plasma etching, are introduced as an intermetallic dielectric material in addition to the use of copper as the conducting material for the reduction of parasitic resistance and capacitance. In this study, beam techniques such as neutral/ion beams were used in the etching of MSQ and the effect of these beam techniques on the reduction of the degradation of the MSQ were investigated. When MSQ was etched using the same CF4 etch gas at the similar etch rate as that used for conventional MSQ etching using inductively coupled plasmas (ICPs), the neutral/ion beam etching showed lower F contents and lower penetration depth of F, indicating decreased degradation by fluorination of MSQ during etching using the beam techniques. Especially, the neutral beam etching technique showed the lowest F contamination and the lower penetration depth of F among the etch methods. When the dielectric constant was measured after the etching of the same depth, the MSQ etched with the neutral beam showed the lowest change of the dielectric constant, while that etched using the ICP showed the highest change of dielectric constant. The lower degradation, that is, the lower chemical modification of MSQ material with the beam technique is believed to be related to the decreased concentration of radical species in the processing chamber reacting with the MSQ surface, while the lowest degradation using the neutral beam is believed to be due to the lower reaction rate of the reactive neutral compared to reactive ions
Energy Technology Data Exchange (ETDEWEB)
Kang, Seung Hyun [Department of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Gyeonggi-Do 440-746 (Korea, Republic of); Kim, Jong Kyu [Department of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Gyeonggi-Do 440-746, South Korea and Memory Division Semiconductor Business, Samsung Electronics, San No. 16 Banwol-Ri, Taean-Eup, Hwasung-City, Gyeonggi-Do 449-711 (Korea, Republic of); Lee, Sung Ho [Memory Division Semiconductor Business, Samsung Electronics, San No. 16 Banwol-Ri, Taean-Eup, Hwasung-City, Gyeonggi-Do 449-711 (Korea, Republic of); Kim, Jin Woo [School of Information and Communication Engineering, Sungkyunkwan University, Suwon, Gyeonggi-Do 440-746 (Korea, Republic of); Yeom, Geun Young, E-mail: gyyeom@skku.edu [Department of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Gyeonggi-Do 440-746, South Korea and SKKU Advanced Institute of Nano Technology (SAINT), Sungkyunkwan University, Suwon, Gyeonggi-Do 440-746 (Korea, Republic of)
2015-03-15
To reduce the cross-talk between nanoscale devices, low-k materials such as methyl silsesquioxane (MSQ), which is damaged easily during plasma etching, are introduced as an intermetallic dielectric material in addition to the use of copper as the conducting material for the reduction of parasitic resistance and capacitance. In this study, beam techniques such as neutral/ion beams were used in the etching of MSQ and the effect of these beam techniques on the reduction of the degradation of the MSQ were investigated. When MSQ was etched using the same CF{sub 4} etch gas at the similar etch rate as that used for conventional MSQ etching using inductively coupled plasmas (ICPs), the neutral/ion beam etching showed lower F contents and lower penetration depth of F, indicating decreased degradation by fluorination of MSQ during etching using the beam techniques. Especially, the neutral beam etching technique showed the lowest F contamination and the lower penetration depth of F among the etch methods. When the dielectric constant was measured after the etching of the same depth, the MSQ etched with the neutral beam showed the lowest change of the dielectric constant, while that etched using the ICP showed the highest change of dielectric constant. The lower degradation, that is, the lower chemical modification of MSQ material with the beam technique is believed to be related to the decreased concentration of radical species in the processing chamber reacting with the MSQ surface, while the lowest degradation using the neutral beam is believed to be due to the lower reaction rate of the reactive neutral compared to reactive ions.
Sátor, Ladislav; Sládek, Vladimír; Sládek, Ján
2014-03-01
A numerical analysis based on the meshless local Petrov- Galerkin (MLPG) method is proposed for a functionally graded material FGM (FGMfunctionally graded material) beam. The planar bending of the beam is considered with a transversal gradation of Young's modulus and a variable depth of the beam. The collocation formulation is constructed from the equilibrium equations for the mechanical fields. Dirac's delta function is employed as a test function in the derivation of a strong formulation. The Moving Least Squares (MLS) approximation technique is applied for an approximation of the spatial variations of all the physical quantities. An investigation of the accuracy, the convergence of the accuracy, the computational efficiency and the effect of the level of the gradation of Young's modulus on the behaviour of coupled mechanical fields is presented in various boundary value problems for a rectangular beam with a functionally graded Young's modulus.
International Nuclear Information System (INIS)
In this paper a new method of determining the energy spread of a relativistic electron beam from a laser-driven plasma wakefield accelerator by measuring radiation from an undulator is presented. This could be used to determine the beam characteristics of multi-GeV accelerators where conventional spectrometers are very large and cumbersome. Simultaneous measurement of the energy spectra of electrons from the wakefield accelerator in the 55-70 MeV range and the radiation spectra in the wavelength range of 700-900 nm of synchrotron radiation emitted from a 50 period undulator confirm a narrow energy spread for electrons accelerated over the dephasing distance where beam loading leads to energy compression. Measured energy spreads of less than 1% indicates the potential of using a wakefield accelerator as a driver of future compact and brilliant ultrashort pulse synchrotron sources and free-electron lasers that require high peak brightness beams.
Directory of Open Access Journals (Sweden)
A.V. Lysenko
2015-12-01
Full Text Available We demonstrate the technique use of the modernized method of averaged characteristics in the cubic-nonlinear theory of plasma-beam superheterodyne free electron lasers (SFEL of the H-ubitron type with helical electron beams. We obtain the truncated differential equations set for wave amplitudes that take into account plural parametric interactions of harmonics of space charge wave (SCW using this technique. The saturation levels have been found. We show that the multiharmonic interactions of SCW harmonics result in decreases of the signal saturation two or more times. It was demonstrated that plasma-beam SFEL of the H-ubitron type with helical electron beams can be used as powerful sources of coherent electromagnetic radiation in the millimeter wavelength range.
Optimisation of numerical methods for plasma physics. Application to charged particle beams
International Nuclear Information System (INIS)
This thesis presents different numerical methods in order to simulate plasmas or charged particles beams with reduced cost. Movement of charged particles in an electromagnetic field is given by the Vlasov equation. This equation is coupled to the Maxwell equations for the electromagnetic field, or to the Poisson equation in a more simple case. Several models exist for solving this system. In kinetic models, particles are represented by a distribution function f(x,v,t) verifying the Vlasov equation. In the general 3-dimensional case, 7 variables appear in the system and computations become heavy. Fluid models consider macroscopic quantities linked to f, such as density, mean velocity and temperature. These quantities only depend on position x and time t. The cost, but also the precision, are reduced. In the first part of this thesis, a multi-fluid method is used for solving the 1-dimensional Vlasov-Poisson system. It is based on the 'a priori' knowledge of the shape of f. Two possibilities are studied: a sum of Dirac masses and the multi-water-bag model. This kind of methods is rather adapted to systems staying close to the equilibrium. The second part presents the decomposition of f between an equilibrium part and a perturbation. The equilibrium part is solved by a fluid method whereas we use a kinetic method for the perturbation. We construct an asymptotic preserving scheme for the Vlasov-Poisson-BGK system using such a decomposition. The third part deals with the Particle-In-Cell (PIC) method in 2D axisymmetric geometry. A work based on iso-geometric analysis is presented, and then a PIC - Discontinuous Galerkin program computed on graphic card (GPU). This architecture reduces significantly calculation time. (author)
International Nuclear Information System (INIS)
Purpose: In-vivo dosimetry and beam range verification in proton therapy could play significant role in proton treatment validation and improvements. In-vivo beam range verification, in particular, could enable new treatment techniques one of which could be the use of anterior fields for prostate treatment instead of opposed lateral fields as in current practice. This paper reports validation study of an in-vivo range verification method which can reduce the range uncertainty to submillimeter levels and potentially allow for in-vivo dosimetry. Methods: An anthropomorphic pelvic phantom is used to validate the clinical potential of the time-resolved dose method for range verification in the case of prostrate treatment using range modulated anterior proton beams. The method uses a 3 × 4 matrix of 1 mm diodes mounted in water balloon which are read by an ADC system at 100 kHz. The method is first validated against beam range measurements by dose extinction measurements. The validation is first completed in water phantom and then in pelvic phantom for both open field and treatment field configurations. Later, the beam range results are compared with the water equivalent path length (WEPL) values computed from the treatment planning system XIO. Results: Beam range measurements from both time-resolved dose method and the dose extinction method agree with submillimeter precision in water phantom. For the pelvic phantom, when discarding two of the diodes that show sign of significant range mixing, the two methods agree with ±1 mm. Only a dose of 7 mGy is sufficient to achieve this result. The comparison to the computed WEPL by the treatment planning system (XIO) shows that XIO underestimates the protons beam range. Quantifying the exact XIO range underestimation depends on the strategy used to evaluate the WEPL results. To our best evaluation, XIO underestimates the treatment beam range between a minimum of 1.7% and maximum of 4.1%. Conclusions: Time-resolved dose
Automatic calibration method of voxel size for cone-beam 3D-CT scanning system
International Nuclear Information System (INIS)
For a cone-beam three-dimensional computed tomography (3D-CT) scanning system, voxel size is an important indicator to guarantee the accuracy of data analysis and feature measurement based on 3D-CT images. Meanwhile, the voxel size changes with the movement of the rotary stage along X-ray direction. In order to realize the automatic calibration of the voxel size, a new and easily-implemented method is proposed. According to this method, several projections of a spherical phantom are captured at different imaging positions and the corresponding voxel size values are calculated by non-linear least-square fitting. Through these interpolation values, a linear equation is obtained that reflects the relationship between the voxel size and the rotary stage translation distance from its nominal zero position. Finally, the linear equation is imported into the calibration module of the 3D-CT scanning system. When the rotary stage is moving along X-ray direction, the accurate value of the voxel size is dynamically exported. The experimental results prove that this method meets the requirements of the actual CT scanning system, and has virtues of easy implementation and high accuracy. (authors)
Scatter correction method for cone-beam CT based on interlacing-slit scan
International Nuclear Information System (INIS)
Cone-beam computed tomography (CBCT) has the notable features of high efficiency and high precision, and is widely used in areas such as medical imaging and industrial non-destructive testing. However, the presence of the ray scatter reduces the quality of CT images. By referencing the slit collimation approach, a scatter correction method for CBCT based on the interlacing-slit scan is proposed. Firstly, according to the characteristics of CBCT imaging, a scatter suppression plate with interlacing slits is designed and fabricated. Then the imaging of the scatter suppression plate is analyzed, and a scatter correction calculation method for CBCT based on the image fusion is proposed, which can splice out a complete set of scatter suppression projection images according to the interlacing-slit projection images of the left and the right imaging regions in the scatter suppression plate, and simultaneously complete the scatter correction within the flat panel detector (FPD). Finally, the overall process of scatter suppression and correction is provided. The experimental results show that this method can significantly improve the clarity of the slice images and achieve a good scatter correction. (interdisciplinary physics and related areas of science and technology)
Scatter correction method for cone-beam CT based on interlacing-slit scan
Huang, Kui-Dong; Zhang, Hua; Shi, Yi-Kai; Zhang, Liang; Xu, Zhe
2014-09-01
Cone-beam computed tomography (CBCT) has the notable features of high efficiency and high precision, and is widely used in areas such as medical imaging and industrial non-destructive testing. However, the presence of the ray scatter reduces the quality of CT images. By referencing the slit collimation approach, a scatter correction method for CBCT based on the interlacing-slit scan is proposed. Firstly, according to the characteristics of CBCT imaging, a scatter suppression plate with interlacing slits is designed and fabricated. Then the imaging of the scatter suppression plate is analyzed, and a scatter correction calculation method for CBCT based on the image fusion is proposed, which can splice out a complete set of scatter suppression projection images according to the interlacing-slit projection images of the left and the right imaging regions in the scatter suppression plate, and simultaneously complete the scatter correction within the flat panel detector (FPD). Finally, the overall process of scatter suppression and correction is provided. The experimental results show that this method can significantly improve the clarity of the slice images and achieve a good scatter correction.
Analytical method of capsizing probability in the time domain for ships in the random beam seas
Institute of Scientific and Technical Information of China (English)
LIU Liqin; TANG Yougang; LI Hongxia
2007-01-01
The methods for constructing safe basins of ships and predicting their survival probability in random waves were studied.The nonlinear differential equation of the rolling motion of ships in random beam seas was established considering nonlinear damping,nonlinear restoring moment,and random waves.The random rolling differential equation was solved in the time domain by applying the harmonic acceleration method and by synthetically considering the instantaneous state of ships and the narrowband wave energy spectrum.The numerical simulation of random capsizing course was brought forward,the safe basins were constructed for safe navigation,and the survival probabilities of ships were calculated.As an example,the safe basins on the rolling initial value plane were constructed for a 30.27-meter-long fishing vessel according to different initial conditions and random wave parameters.The survival probabilities of the fishing vessel under different significant wave heights were predicted.Thus,the survival probabilities of ships in random seas can be predicted quantitatively by the proposed method.
Optics analysis of Final Focus Test Beam with the help of methods based on Lie algebra
International Nuclear Information System (INIS)
The Final Focus Test Beam being built at SLAC is a test bed for future linear collider final focus systems. The parameters and the optics of the FFTB are presented in chapter one. The mathematical tools for this thesis which are based on Lie algebras are then reviewed in chapter two. One relies particularly on the Lie transformations together with the similarity transformation and the Campbell-Baler-Haussdorff theorem for the manipulation of Hamiltonians. Chapter three presents the application of these methods to magnetic optics in accelerators; the separation of linear and non-linear effects and the building of the total Hamiltonian of the line from the thin-lens formulation. Chapter four analytically establishes a catalog of aberrations, up to order five in the Hamiltonians, at the FFTB. The emphasis is put on the methods of analysis. It is shown that the system has a significant fifth-order aberration and that no higher-order aberration appears. Finally chapter six presents some stability tolerances - alignment strength and multipole content - for the FFTB. In the conclusion the present situation of these methods, as well as possible computer codes using them, are reviewed
A cone beam computed tomography inspection method for fuel rod cladding tubes
Fu, Jian; Tan, Renbo; Wang, Qianli; Deng, Jingshan; Liu, Ming
2012-10-01
Fuel rods in nuclear power plants consist of UO2 pellets enclosed in Zirconium alloy (Zircaloy) cladding tube, which is composed of a body and a plug. The body is manufactured separately from the plug and, before its use, the plug is welded with the body. It is vitally important for the welding zone to remain free from defects after the fuel pellets are loaded into the cladding tube to prevent the radioactive fission products from leaking. X-ray computed tomography (CT) is in principle a feasible inspection method for the welding zone, but it faces several challenges due to the high attenuation of Zircaloy. In this paper, a cone beam CT method is proposed to address these issues and perform the welding flaw inspection. A Zircaloy compensator is adopted to narrow the signal range, a structure-based background removal technique to reveal the defects, a linear extension technique to determine the reference X-ray intensity signal and FDK algorithm to reconstruct the slice images. A prototype system, based on X-ray tube source and flat panel detector, has been developed and the experiments in this system have demonstrated that the welding void and the incomplete joint penetrations could be detected by this method. This approach may find applications in the quality control of nuclear fuel rods.
A cone beam computed tomography inspection method for fuel rod cladding tubes
International Nuclear Information System (INIS)
Fuel rods in nuclear power plants consist of UO2 pellets enclosed in Zirconium alloy (Zircaloy) cladding tube, which is composed of a body and a plug. The body is manufactured separately from the plug and, before its use, the plug is welded with the body. It is vitally important for the welding zone to remain free from defects after the fuel pellets are loaded into the cladding tube to prevent the radioactive fission products from leaking. X-ray computed tomography (CT) is in principle a feasible inspection method for the welding zone, but it faces several challenges due to the high attenuation of Zircaloy. In this paper, a cone beam CT method is proposed to address these issues and perform the welding flaw inspection. A Zircaloy compensator is adopted to narrow the signal range, a structure-based background removal technique to reveal the defects, a linear extension technique to determine the reference X-ray intensity signal and FDK algorithm to reconstruct the slice images. A prototype system, based on X-ray tube source and flat panel detector, has been developed and the experiments in this system have demonstrated that the welding void and the incomplete joint penetrations could be detected by this method. This approach may find applications in the quality control of nuclear fuel rods.
Energy Technology Data Exchange (ETDEWEB)
Zittel, P.F.
1991-12-23
Computer model calculations are presented for enrichments of carbon, oxygen, and sulfur isotopes by two-step, IR/UV, laser photodissociation of OCS in rare gas liquid solutions. The model calculations are based on previously measured fundamental physical properties, including spectroscopic parameters of the IR absorption bands of OCS in cryogenic solution, UV photodissociation cross sections for specific vibrational levels of OCS, and rates for vibrational relaxation of OCS by cryogenic solvents. Results are presented for both pulsed and continuous wave laser sources. Photodissociation through both the 2{nu}{sub 2} and {nu}{sub 1} intermediate vibrational levels of OCS is investigated. The laser characteristics required to obtain optimum enrichments are determined by modeling the dependence of enrichment on laser wavelength and intensity, as well as pulse width and timing for pulsed sources. Optimum carbon and oxygen isotope enrichment factors of 9--14 are found for two-step photodissociation through the OCS(2{nu}{sub 2}) vibrational level, using pulsed CO{sub 2} and KrF excimer laser sources. Optimum sulfur isotope enrichment factors of 5--6 are found for photodissociation through the OCS({nu}{sub 1}) level, using a pulsed 12 {mu}m laser and a KrF excimer laser. The enrichments found for continuous wave laser sources are smaller than those for pulsed sources. 19 figs., 4 tabs.
A new method for x-ray scatter correction: first assessment on a cone-beam CT experimental setup
Energy Technology Data Exchange (ETDEWEB)
Rinkel, J [CEA-LETI MINATEC, Division of Micro Technologies for Biology and Healthcare, 38054 Grenoble Cedex 09 (France); Gerfault, L [CEA-LETI MINATEC, Division of Micro Technologies for Biology and Healthcare, 38054 Grenoble Cedex 09 (France); Esteve, F [INSERM U647-RSRM, ESRF, BP200, 38043 Grenoble Cedex 09 (France); Dinten, J-M [CEA-LETI MINATEC, Division of Micro Technologies for Biology and Healthcare, 38054 Grenoble Cedex 09 (France)
2007-08-07
Cone-beam computed tomography (CBCT) enables three-dimensional imaging with isotropic resolution and a shorter acquisition time compared to a helical CT scanner. Because a larger object volume is exposed for each projection, scatter levels are much higher than in collimated fan-beam systems, resulting in cupping artifacts, streaks and quantification inaccuracies. In this paper, a general method to correct for scatter in CBCT, without supplementary on-line acquisition, is presented. This method is based on scatter calibration through off-line acquisition combined with on-line analytical transformation based on physical equations, to adapt calibration to the object observed. The method was tested on a PMMA phantom and on an anthropomorphic thorax phantom. The results were validated by comparison to simulation for the PMMA phantom and by comparison to scans obtained on a commercial multi-slice CT scanner for the thorax phantom. Finally, the improvements achieved with the new method were compared to those obtained using a standard beam-stop method. The new method provided results that closely agreed with the simulation and with the conventional CT scanner, eliminating cupping artifacts and significantly improving quantification. Compared to the beam-stop method, lower x-ray doses and shorter acquisition times were needed, both divided by a factor of 9 for the same scatter estimation accuracy.
Method of forming a coating layer using low energy electron beams
International Nuclear Information System (INIS)
A prepolymer monosyrup is prepared by dissolving a mixture of an acrylic prepolymer and an unsaturated polyester prepolymer in a vinyl monomer. The method allows the mixture of prepolymers to be hardened with low energy electron beams, as they are polymerized. The thus hardened coating layer improves the performance and production of the precoated plates and reduces production costs. The prepolymer monosyrup is so prepared that (A)/(B) or (A)/(C) is 1/9 to 9/1 in weight ratio and the unsaturated polyester is less than 50%, wherein (A), (B), (C) and (II) are shown below. The mixture (A) is prepared by mixing (I) and (II), in which (I), the acrylic prepolymer, is a prepolymer with molecular weights in the 1,000 to 3,000,000 range, consisting of 50 to 99.5% of alkyl acrylate esters or their monomer, and 0.5 to 50% of a copolymerizable vinyl monomer; and (II), the unsaturated polyester prepolymer, is a polymer with molecular weights in the 500 to 50,000 range, including saturated polybasic acids and higher alcohols, wherein the unsaturated polybasic acids are 9 to 95 moles of the total acids. The mixture (B) consists of 5 to 99% to alkyl acrylate ester and/or methacrylate ester or their monomers, and 1 to 95% of other copolymerizable vinyl monomers. The monomer mixture (C) consists of 5 to 99.5% of (B), and 0.5 to 95% of a monomer with two or more vinyl radicals in its molecule. The electron beams to be employed are in the range 50 to 500 keV, with 0.1 to 30 Mrad at a dose rate of 0.1 to 20 Mrad/sec. (Iwakiri, K.)
Free vibration of a three-layered sandwich beam using the dynamic stiffness method and experiment
Banerjee, J. R.; Cheung, C. W.; Morishima, R; Perera, M; Njuguna, James A. K.
2007-01-01
In this paper, an accurate dynamic stiffness model for a three-layered sandwich beam of unequal thicknesses is developed and subsequently used to investigate its free vibration characteristics. Each layer of the beam is idealised by the Timoshenko beam theory and the combined system is reduced to a tenth-order system using symbolic computation. An exact dynamic stiffness matrix is then developed by relating amplitudes of harmonically varying loads to those of the responses. ...
Energy Technology Data Exchange (ETDEWEB)
Poulsen, Per Rugaard; Fledelius, Walther; Keall, Paul J.; Weiss, Elisabeth; Lu Jun; Brackbill, Emily; Hugo, Geoffrey D. [Department of Oncology, Aarhus University Hospital, Nr Brogade 44, 8000 Aarhus C (Denmark); Department of Radiation Oncology, Stanford University, Stanford, California 94305 (United States) and Sydney Medical School-Central, University of Sydney, NSW 2006 (Australia); Virginia Commonwealth University, Richmond, Virginia 23284 (United States)
2011-04-15
Purpose: Implanted markers are commonly used in radiotherapy for x-ray based target localization. The projected marker position in a series of cone-beam CT (CBCT) projections can be used to estimate the three dimensional (3D) target trajectory during the CBCT acquisition. This has important applications in tumor motion management such as motion inclusive, gating, and tumor tracking strategies. However, for irregularly shaped markers, reliable segmentation is challenged by large variations in the marker shape with projection angle. The purpose of this study was to develop a semiautomated method for robust and reliable segmentation of arbitrarily shaped radiopaque markers in CBCT projections. Methods: The segmentation method involved the following three steps: (1) Threshold based segmentation of the marker in three to six selected projections with large angular separation, good marker contrast, and uniform background; (2) construction of a 3D marker model by coalignment and backprojection of the threshold-based segmentations; and (3) construction of marker templates at all imaging angles by projection of the 3D model and use of these templates for template-based segmentation. The versatility of the segmentation method was demonstrated by segmentation of the following structures in the projections from two clinical CBCT scans: (1) Three linear fiducial markers (Visicoil) implanted in or near a lung tumor and (2) an artificial cardiac valve in a lung cancer patient. Results: Automatic marker segmentation was obtained in more than 99.9% of the cases. The segmentation failed in a few cases where the marker was either close to a structure of similar appearance or hidden behind a dense structure (data cable). Conclusions: A robust template-based method for segmentation of arbitrarily shaped radiopaque markers in CBCT projections was developed.
International Nuclear Information System (INIS)
Purpose: Implanted markers are commonly used in radiotherapy for x-ray based target localization. The projected marker position in a series of cone-beam CT (CBCT) projections can be used to estimate the three dimensional (3D) target trajectory during the CBCT acquisition. This has important applications in tumor motion management such as motion inclusive, gating, and tumor tracking strategies. However, for irregularly shaped markers, reliable segmentation is challenged by large variations in the marker shape with projection angle. The purpose of this study was to develop a semiautomated method for robust and reliable segmentation of arbitrarily shaped radiopaque markers in CBCT projections. Methods: The segmentation method involved the following three steps: (1) Threshold based segmentation of the marker in three to six selected projections with large angular separation, good marker contrast, and uniform background; (2) construction of a 3D marker model by coalignment and backprojection of the threshold-based segmentations; and (3) construction of marker templates at all imaging angles by projection of the 3D model and use of these templates for template-based segmentation. The versatility of the segmentation method was demonstrated by segmentation of the following structures in the projections from two clinical CBCT scans: (1) Three linear fiducial markers (Visicoil) implanted in or near a lung tumor and (2) an artificial cardiac valve in a lung cancer patient. Results: Automatic marker segmentation was obtained in more than 99.9% of the cases. The segmentation failed in a few cases where the marker was either close to a structure of similar appearance or hidden behind a dense structure (data cable). Conclusions: A robust template-based method for segmentation of arbitrarily shaped radiopaque markers in CBCT projections was developed.
International Nuclear Information System (INIS)
Applicability of the gold foil activation method for precise measurements of density of a neutron beam extracted from the reactor core is investigated experimentally. Comparison of density ratios of cold and hot beams is carried out to determine the error of measurements conducted with the use of gold foils and the detector with 6LiF target. Based on the analysis of the data obtained it is concluded that the total error of measurements using the activation method, comprising errors of determining cross section of gold activation Δσ=+-0.3% and absolute value of foil activity (also +- 0.3%) makes up +-0.7%
Fort, Kyle L; Dyachenko, Andrey; Potel, Clement M; Corradini, Eleonora; Marino, Fabio; Barendregt, Arjan; Makarov, Alexander A; Scheltema, Richard A; Heck, Albert J R
2016-02-16
Proteomics applications performed on the popular benchtop Q Exactive Orbitrap mass spectrometer have so far relied exclusively on higher collision-energy dissociation (HCD) fragmentation for peptide sequencing. While this fragmentation technique is applicable to a wide range of biological questions, it also has limitations, and all questions cannot be addressed equally well. Here, we demonstrate that the fragmentation capabilities of the Q Exactive mass spectrometer can be extended with ultraviolet photodissociation (UVPD) fragmentation, complete with synchronization triggering to make it compatible with liquid chromatography (LC)/tandem mass spectrometry (MS/MS) workflows. We show that UVPD not only is directly compatible with LC/MS workflows but also, when combined with these workflows, can result in higher database scores and increased identification rates for complex samples as compared to HCD methods. UVPD as a fragmentation technique offers prompt, high-energy fragmentation, which can potentially lead to improved analyses of labile post-translational modifications. Techniques like HCD result in substantial amounts of modification losses, competing with fragmentation pathways that provide information-rich ion fragments. We investigate here the utility of UVPD for identification of phosphorylated peptides and find that UVPD fragmentation reduces the extent of labile modification loss by up to ∼60%. Collectively, when integrated into a complete workflow on the Q Exactive Orbitrap, UVPD provides distinct advantages to the analysis of post-translational modifications and is a powerful and complementary addition to the proteomic toolbox. PMID:26760441
Robinson, Michelle R; Taliaferro, Juliana M; Dalby, Kevin N; Brodbelt, Jennifer S
2016-08-01
Advances in liquid chromatography tandem mass spectrometry (LC-MS/MS) have permitted phosphoproteomic analysis on a grand scale, but ongoing challenges specifically associated with confident phosphate localization continue to motivate the development of new fragmentation techniques. In the present study, ultraviolet photodissociation (UVPD) at 193 nm is evaluated for the characterization of phosphopeptides in both positive and negative ion modes. Compared to the more standard higher energy collisional dissociation (HCD), UVPD provided more extensive fragmentation with improved phosphate retention on product ions. Negative mode UVPD showed particular merit for detecting and sequencing highly acidic phosphopeptides from alpha and beta casein, but was not as robust for larger scale analysis because of lower ionization efficiencies in the negative mode. HeLa and HCC70 cell lysates were analyzed by both UVPD and HCD. While HCD identified more phosphopeptides and proteins compared to UVPD, the unique matches from UVPD analysis could be combined with the HCD data set to improve the overall depth of coverage compared to either method alone. PMID:27425180
Gray, Carl E., Jr.
1988-01-01
Using the Newtonian method, the equations of motion are developed for the coupled bending-torsion steady-state response of beams rotating at constant angular velocity in a fixed plane. The resulting equations are valid to first order strain-displacement relationships for a long beam with all other nonlinear terms retained. In addition, the equations are valid for beams with the mass centroidal axis offset (eccentric) from the elastic axis, nonuniform mass and section properties, and variable twist. The solution of these coupled, nonlinear, nonhomogeneous, differential equations is obtained by modifying a Hunter linear second-order transfer-matrix solution procedure to solve the nonlinear differential equations and programming the solution for a desk-top personal computer. The modified transfer-matrix method was verified by comparing the solution for a rotating beam with a geometric, nonlinear, finite-element computer code solution; and for a simple rotating beam problem, the modified method demonstrated a significant advantage over the finite-element solution in accuracy, ease of solution, and actual computer processing time required to effect a solution.
International Nuclear Information System (INIS)
Different methods have been proposed to calculate the vertical position of the photon beam centroid from the four blade currents of staggered pair X-ray beam position monitors (XBPMs) at bending magnet beamlines since they emerged about 15 years ago. The original difference-over-sum method introduced by Peatman and Holldack is still widely used, even though it has been proven to be rather inaccurate at large beam displacements. By systematically generating bumps in the electron orbit of the ANKA storage ring and comparing synchronized data from electron BPMs and XBPM blade currents, we have been able to show that the log-ratio method by S. F. Lin, B.G. Sun et al. is superior (meaning the characteristic being closer to linear) to the ratio method, which in turn is superior to the difference over sum method. These findings are supported by simulations of the XBPM response to changes of the beam centroid. The heuristic basis for each of the methods is investigated. The implications on using XBPM readings for orbit correction are discussed
Automatic inspection of electron beam weld for stainless steel using phased array method
International Nuclear Information System (INIS)
The CEA laboratory of Non destructive testing of Valduc implements various techniques of controls (radiography, sealing by tracer gas helium, ultrasounds...) to check the quality of the welding and health matter of materials. To have a perfect command of the manufacture of the welding and to detect any anomaly during the manufacturing process (lacks of penetration, defects of joining, porosities...), it developed in partnership with company METALSCAN an ultrasonic technique of imagery phased array designed to the complete and automatic control of homogeneous stainless steel welding carried out by electron beam. To achieve this goal, an acoustic study by simulation with software CIVA was undertaken in order to determine the optimal characteristics of the phased array probes (their number and their site). Finally, the developed method allows, on the one hand, to locate lacks of fusion of welding equivalents to flat holes with bottom 0,5 mms in diameter, and on the other hand, to detect lacks of penetration of 0,1 mm. In order to ensure a perfect reproducibility of controls, a mechanical system ensuring the setting in rotation of the part, allows to inspect the whole of the welding. The results are then analyzed automatically using application software ensuring the traceability of controls. The method was first of all validated using parts spread out, then it was brought into service after confrontation of the results obtained on real defects with other techniques (metallographic radiography and characterizations). (authors)
Energy Technology Data Exchange (ETDEWEB)
Noo, F.; Clackdoyle, R.; Mennessier, C.; White, Timothy Andrew; Roney, Timothy Joseph
2000-11-01
This paper is about calibration of cone-beam (CB) scanners for both x-ray computed tomography and single-photon emission computed tomography. Scanner calibration refers here to the estimation of a set of parameters which fully describe the geometry of data acquisition. Such parameters are needed for the tomographic reconstruction step. The discussion is limited to the usual case where the cone vertex and planar detector move along a circular path relative to the object. It is also assumed that the detector does not have spatial distortions. We propose a new method which requires a small set of measurements of a simple calibration object consisting of two spherical objects, that can be considered as `point' objects. This object traces two ellipses on the detector and from the parametric description of these ellipses, the calibration geometry can be determined analytically using explicit formulae. The method is robust and easy to implement. However, it is not fully general as it is assumed that the detector is parallel to the rotation axis of the scanner. Implementation details are given for an experimental x-ray CB scanner.
International Nuclear Information System (INIS)
This paper is about calibration of cone-beam (CB) scanners for both x-ray computed tomography and single-photon emission computed tomography. Scanner calibration refers here to the estimation of a set of parameters which fully describe the geometry of data acquisition. Such parameters are needed for the tomographic reconstruction step. The discussion is limited to the usual case where the cone vertex and planar detector move along a circular path relative to the object. It is also assumed that the detector does not have spatial distortions. We propose a new method which requires a small set of measurements of a simple calibration object consisting of two spherical objects, that can be considered as 'point' objects. This object traces two ellipses on the detector and from the parametric description of these ellipses, the calibration geometry can be determined analytically using explicit formulae. The method is robust and easy to implement. However, it is not fully general as it is assumed that the detector is parallel to the rotation axis of the scanner. Implementation details are given for an experimental x-ray CB scanner. (author)
Energy Technology Data Exchange (ETDEWEB)
Noo, Frederic [Institut d' Electricite Montefiore, Universite de Liege (Belgium); Department of Radiology, University of Utah (United States). E-mail: noo at montefiore.ulg.ac.be; Clackdoyle, Rolf [Department of Radiology, University of Utah (United States); Mennessier, Catherine [Universite J. Fourier, Grenoble (France); White, Timothy A.; Roney, Timothy J. [Idaho National Engineering and Environmental Laboratory (United States)
2000-11-01
This paper is about calibration of cone-beam (CB) scanners for both x-ray computed tomography and single-photon emission computed tomography. Scanner calibration refers here to the estimation of a set of parameters which fully describe the geometry of data acquisition. Such parameters are needed for the tomographic reconstruction step. The discussion is limited to the usual case where the cone vertex and planar detector move along a circular path relative to the object. It is also assumed that the detector does not have spatial distortions. We propose a new method which requires a small set of measurements of a simple calibration object consisting of two spherical objects, that can be considered as 'point' objects. This object traces two ellipses on the detector and from the parametric description of these ellipses, the calibration geometry can be determined analytically using explicit formulae. The method is robust and easy to implement. However, it is not fully general as it is assumed that the detector is parallel to the rotation axis of the scanner. Implementation details are given for an experimental x-ray CB scanner. (author)
Noo, F; Clackdoyle, R; Mennessier, C; White, T A; Roney, T J
2000-11-01
This paper is about calibration of cone-beam (CB) scanners for both x-ray computed tomography and single-photon emission computed tomography. Scanner calibration refers here to the estimation of a set of parameters which fully describe the geometry of data acquisition. Such parameters are needed for the tomographic reconstruction step. The discussion is limited to the usual case where the cone vertex and planar detector move along a circular path relative to the object. It is also assumed that the detector does not have spatial distortions. We propose a new method which requires a small set of measurements of a simple calibration object consisting of two spherical objects, that can be considered as 'point' objects. This object traces two ellipses on the detector and from the parametric description of these ellipses, the calibration geometry can be determined analytically using explicit formulae. The method is robust and easy to implement. However, it is not fully general as it is assumed that the detector is parallel to the rotation axis of the scanner. Implementation details are given for an experimental x-ray CB scanner. PMID:11098919
Automatic Calibration Method of Voxel Size for Cone-beam 3D-CT Scanning System
Yang, Min; Liu, Yipeng; Men, Fanyong; Li, Xingdong; Liu, Wenli; Wei, Dongbo
2013-01-01
For cone-beam three-dimensional computed tomography (3D-CT) scanning system, voxel size is an important indicator to guarantee the accuracy of data analysis and feature measurement based on 3D-CT images. Meanwhile, the voxel size changes with the movement of the rotary table along X-ray direction. In order to realize the automatic calibration of the voxel size, a new easily-implemented method is proposed. According to this method, several projections of a spherical phantom are captured at different imaging positions and the corresponding voxel size values are calculated by non-linear least square fitting. Through these interpolation values, a linear equation is obtained, which reflects the relationship between the rotary table displacement distance from its nominal zero position and the voxel size. Finally, the linear equation is imported into the calibration module of the 3D-CT scanning system, and when the rotary table is moving along X-ray direction, the accurate value of the voxel size is dynamically expo...
Facile time-of-flight methods for characterizing pulsed superfluid helium droplet beams
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He, Yunteng; Zhang, Jie; Li, Yang; Freund, William M.; Kong, Wei, E-mail: wei.kong@oregonstate.edu [Department of Chemistry, Oregon State University, Corvallis, Oregon 97331 (United States)
2015-08-15
We present two facile time-of-flight (TOF) methods of detecting superfluid helium droplets and droplets with neutral dopants. Without an electron gun and with only a heated filament and pulsed electrodes, the electron impact ionization TOF mass spectrometer can resolve ionized helium clusters such as He{sub 2}{sup +} and He{sub 4}{sup +}, which are signatures of superfluid helium droplets. Without ionizing any helium atoms, multiphoton non-resonant laser ionization of CCl{sub 4} doped in superfluid helium droplets at 266 nm generates complex cluster ions of dopant fragments with helium atoms, including (He){sub n}C{sup +}, (He){sub n}Cl{sup +}, and (He){sub n}CCl{sup +}. Using both methods, we have characterized our cryogenic pulsed valve—the Even-Lavie valve. We have observed a primary pulse with larger helium droplets traveling at a slower speed and a rebound pulse with smaller droplets at a faster speed. In addition, the pickup efficiency of dopant is higher for the primary pulse when the nozzle temperature is higher than 13 K, and the total time duration of the doped droplet pulse is only on the order of 20 μs. These results stress the importance of fast and easy characterization of the droplet beam for sensitive measurements such as electron diffraction of doped droplets.
Facile time-of-flight methods for characterizing pulsed superfluid helium droplet beams.
He, Yunteng; Zhang, Jie; Li, Yang; Freund, William M; Kong, Wei
2015-08-01
We present two facile time-of-flight (TOF) methods of detecting superfluid helium droplets and droplets with neutral dopants. Without an electron gun and with only a heated filament and pulsed electrodes, the electron impact ionization TOF mass spectrometer can resolve ionized helium clusters such as He2(+) and He4(+), which are signatures of superfluid helium droplets. Without ionizing any helium atoms, multiphoton non-resonant laser ionization of CCl4 doped in superfluid helium droplets at 266 nm generates complex cluster ions of dopant fragments with helium atoms, including (He)(n)C(+), (He)(n)Cl(+), and (He)(n)CCl(+). Using both methods, we have characterized our cryogenic pulsed valve—the Even-Lavie valve. We have observed a primary pulse with larger helium droplets traveling at a slower speed and a rebound pulse with smaller droplets at a faster speed. In addition, the pickup efficiency of dopant is higher for the primary pulse when the nozzle temperature is higher than 13 K, and the total time duration of the doped droplet pulse is only on the order of 20 μs. These results stress the importance of fast and easy characterization of the droplet beam for sensitive measurements such as electron diffraction of doped droplets. PMID:26329210
Energy Technology Data Exchange (ETDEWEB)
Witham, L.C.G.; Jamieson, D.N.; Bardos, R.A. [Melbourne Univ., Parkville, VIC (Australia). School of Physics, Microanalytical Research Centre
1998-06-01
Ion Beam Induced Charge (IBIC) is a valuable method for the mapping of charge carrier transport and recombination in silicon solar cells. However performing IBIC analysis of polycrystalline silicon solar cells is problematic in a manner unlike previous uses of IBIC on silicon-based electronic devices. Typical solar cells have a surface area of several square centimeters and a p-n junction thickness of only few microns. This means the cell has a large junction capacitance in the many nanoFarads range which leads to a large amount of noise on the preamplifier inputs which typically swamps the transient IBIC signal. The normal method of improving the signal-to-noise (S/N) ratio by biasing the junction is impractical for these cells as the low-quality silicon used leads to a large leakage current across the device. We present several experimental techniques which improve the S/N ratio which when used together should make IBIC analysis of many low crystalline quality devices a viable and reliable procedure. (authors). Extended abstract. 4 refs., 2 figs.
Facile time-of-flight methods for characterizing pulsed superfluid helium droplet beams
International Nuclear Information System (INIS)
We present two facile time-of-flight (TOF) methods of detecting superfluid helium droplets and droplets with neutral dopants. Without an electron gun and with only a heated filament and pulsed electrodes, the electron impact ionization TOF mass spectrometer can resolve ionized helium clusters such as He2+ and He4+, which are signatures of superfluid helium droplets. Without ionizing any helium atoms, multiphoton non-resonant laser ionization of CCl4 doped in superfluid helium droplets at 266 nm generates complex cluster ions of dopant fragments with helium atoms, including (He)nC+, (He)nCl+, and (He)nCCl+. Using both methods, we have characterized our cryogenic pulsed valve—the Even-Lavie valve. We have observed a primary pulse with larger helium droplets traveling at a slower speed and a rebound pulse with smaller droplets at a faster speed. In addition, the pickup efficiency of dopant is higher for the primary pulse when the nozzle temperature is higher than 13 K, and the total time duration of the doped droplet pulse is only on the order of 20 μs. These results stress the importance of fast and easy characterization of the droplet beam for sensitive measurements such as electron diffraction of doped droplets
International Nuclear Information System (INIS)
Ion Beam Induced Charge (IBIC) is a valuable method for the mapping of charge carrier transport and recombination in silicon solar cells. However performing IBIC analysis of polycrystalline silicon solar cells is problematic in a manner unlike previous uses of IBIC on silicon-based electronic devices. Typical solar cells have a surface area of several square centimeters and a p-n junction thickness of only few microns. This means the cell has a large junction capacitance in the many nanoFarads range which leads to a large amount of noise on the preamplifier inputs which typically swamps the transient IBIC signal. The normal method of improving the signal-to-noise (S/N) ratio by biasing the junction is impractical for these cells as the low-quality silicon used leads to a large leakage current across the device. We present several experimental techniques which improve the S/N ratio which when used together should make IBIC analysis of many low crystalline quality devices a viable and reliable procedure. (authors)
Institute of Scientific and Technical Information of China (English)
Qing Chun; Koenraad Van Balen; Yidan Han
2016-01-01
In order to study the calculation methods of shear behavior of reinforced concrete beams of Chinese modern reinforced concrete buildings, this paper carried out tests on the concrete compressive strength of 12 Chinese modern concrete buildings, the mechanical properties of 66 rebars from different Chinese modern concrete buildings, and the concrete cover thickness of 9 Chinese modern concrete buildings, and the actual material properties and structural configurations have been obtained. Then, the comparison on calculation methods include the Chinese original calculation method, the Chinese present calculation method, the American present calculation method and the European present calculation method is studied with case analysis method. The results show that the Chinese original calculation method of shear behavior of reinforced concrete beams is based on the allowable stress calculation method, and the design safety factors are 3. 55-4. 00. The standard value of the compressive strength of concrete cubes is 8. 48 MPa, the standard value of the concrete tensile strength is 1.20 MPa, the standard value of the yield strength of rectangular rebars is 229. 56 MPa, and the standard value of the yield strength of round rebars is 276. 82 MPa. The average value of the concrete cover thickness of beams and columns is 35.96 mm. In term of calculation area of hoop rebars of reinforced concrete beams, without considering earthquake loads, the Chinese original structural calculation method is safer than the Chinese present structural calculation method, but is more unsafe than the American present structural calculation method and the European present structural calculation method. The results can provide the support for structural safety assessments and repair designs of Chinese modern reinforced concrete buildings.
Energy Technology Data Exchange (ETDEWEB)
Lillhoek, J E [Swedish Radiation Protection Authority, Stockholm (Sweden); Grindborg, J-E [Swedish Radiation Protection Authority, Stockholm (Sweden); Lindborg, L [Department of Medical Radiation Physics, Karolinska Institutet and Stockholm University (Sweden); Gudowska, I [Department of Medical Radiation Physics, Karolinska Institutet and Stockholm University (Sweden); Carlsson, G Alm [Department of Radiation Physics, Faculty of Health Sciences, Linkoeping University (Sweden); Soederberg, J [Department of Radiation Physics, Faculty of Health Sciences, Linkoeping University (Sweden); Kopec, M [Department of Theoretical and Computational Physics, AGH University of Science and Technology, Krakow (Poland); Medin, J [Department of Radiation Oncology, Copenhagen University Hospital (Denmark)
2007-08-21
Nanodosimetric single-event distributions or their mean values may contribute to a better understanding of how radiation induced biological damages are produced. They may also provide means for radiation quality characterization in therapy beams. Experimental nanodosimetry is however technically challenging and Monte Carlo simulations are valuable as a complementary tool for such investigations. The dose-mean lineal energy was determined in a therapeutic p(65)+Be neutron beam and in a {sup 60}Co {gamma} beam using low-pressure gas detectors and the variance-covariance method. The neutron beam was simulated using the condensed history Monte Carlo codes MCNPX and SHIELD-HIT. The dose-mean lineal energy was calculated using the simulated dose and fluence spectra together with published data from track-structure simulations. A comparison between simulated and measured results revealed some systematic differences and different dependencies on the simulated object size. The results show that both experimental and theoretical approaches are needed for an accurate dosimetry in the nanometer region. In line with previously reported results, the dose-mean lineal energy determined at 10 nm was shown to be related to clinical RBE values in the neutron beam and in a simulated 175 MeV proton beam as well.
International Nuclear Information System (INIS)
Nanodosimetric single-event distributions or their mean values may contribute to a better understanding of how radiation induced biological damages are produced. They may also provide means for radiation quality characterization in therapy beams. Experimental nanodosimetry is however technically challenging and Monte Carlo simulations are valuable as a complementary tool for such investigations. The dose-mean lineal energy was determined in a therapeutic p(65)+Be neutron beam and in a 60Co γ beam using low-pressure gas detectors and the variance-covariance method. The neutron beam was simulated using the condensed history Monte Carlo codes MCNPX and SHIELD-HIT. The dose-mean lineal energy was calculated using the simulated dose and fluence spectra together with published data from track-structure simulations. A comparison between simulated and measured results revealed some systematic differences and different dependencies on the simulated object size. The results show that both experimental and theoretical approaches are needed for an accurate dosimetry in the nanometer region. In line with previously reported results, the dose-mean lineal energy determined at 10 nm was shown to be related to clinical RBE values in the neutron beam and in a simulated 175 MeV proton beam as well
Lillhök, J. E.; Grindborg, J.-E.; Lindborg, L.; Gudowska, I.; Alm Carlsson, G.; Söderberg, J.; Kopeć, M.; Medin, J.
2007-08-01
Nanodosimetric single-event distributions or their mean values may contribute to a better understanding of how radiation induced biological damages are produced. They may also provide means for radiation quality characterization in therapy beams. Experimental nanodosimetry is however technically challenging and Monte Carlo simulations are valuable as a complementary tool for such investigations. The dose-mean lineal energy was determined in a therapeutic p(65)+Be neutron beam and in a 60Co γ beam using low-pressure gas detectors and the variance-covariance method. The neutron beam was simulated using the condensed history Monte Carlo codes MCNPX and SHIELD-HIT. The dose-mean lineal energy was calculated using the simulated dose and fluence spectra together with published data from track-structure simulations. A comparison between simulated and measured results revealed some systematic differences and different dependencies on the simulated object size. The results show that both experimental and theoretical approaches are needed for an accurate dosimetry in the nanometer region. In line with previously reported results, the dose-mean lineal energy determined at 10 nm was shown to be related to clinical RBE values in the neutron beam and in a simulated 175 MeV proton beam as well.
Photodissociation of a diatomic molecule in the quantum regime reveals ultracold chemistry
McDonald, M; Apfelbeck, F; Lee, C -H; Majewska, I; Moszynski, R; Zelevinsky, T
2015-01-01
Chemical reactions at temperatures near absolute zero require a full quantum description of the reaction pathways and enable enhanced control of the products via quantum state selection. Ultracold molecule experiments have provided initial insight into the quantum nature of basic chemical processes involving diatomic molecules, for example from studies of bimolecular reactions, but complete control over the reactants and products has remained elusive. The "half-collision" process of photodissociation is an indispensable tool in molecular physics and offers significantly more control than the reverse process of photoassociation. Here we reach a fully quantum regime with photodissociation of ultracold $^{88}$Sr$_2$ molecules where the initial bound state of the molecule and the target continuum state of the fragments are strictly controlled. Detection of the photodissociation products via optical absorption imaging reveals the hallmarks of ultracold chemistry: resonant and nonresonant barrier tunneling, importa...
Investigation on the Photodissociation of Oxygen from Oxymyoglobin by Fluorescence Spectroscopy
Institute of Scientific and Technical Information of China (English)
ZHOU Hua-wei; CAO Hong-yu; TANG Qian; MA Jun-yan; ZHANG Ying-ying; ZHENG Xue-fang
2011-01-01
Photodissociation of oxygen from oxymyoglobin(oxyMb)was investigated by means of fluorescence spectroscopy.One of the most important findings of the photodissociation of oxyMb was the discovery of two processes which were affected by excitation intensity,temperature,solvent viscosity,and excitation wavelength.Process Ⅰ(PⅠ)corresponded to oxygen escaping from the binding site at ferrous heme iron atom within the porphyrin ring into the heme pocket,whereas process Ⅱ(PⅡ)was ascribed to oxygen escaping from the heme pocket into the solvent.To elucidate this interesting phenomenon,we proposed a model that oxygen encountered two barriers on its way from the binding site at the ferrous heme iron to the solvent.Reversibility and wavelength sensitivity of the photodissociation were also observed.
Photodissociation of trapped Rb$^+_2$ : Implications for hybrid molecular ion-atom trapping
Jyothi, S; Dutta, Sourav; Allouche, A R; Vexiau, Romain; Dulieu, Olivier; Rangwala, S A
2016-01-01
We observe direct photodissociation of trapped $^{85}$Rb$_2^+$ molecular ions in the presence of cooling light for the $^{85}$Rb magneto optical trap (MOT). Vibrationally excited Rb$_{2}^{+}$ ions are created by photoionization of Rb$_{2}$ molecules formed photoassociatively in the rubidium (Rb) MOT and are trapped in a modified spherical Paul trap co-centric with the MOT. The decay rate of the trapped Rb$_{2}^{+}$ ion signal in the presence of the MOT cooling light is measured and agreement with our calculated rates for molecular ion photodissociation is established. The photodissociation mechanism due to the MOT light is expected to be active and therefore universal for all homonuclear diatomic alkali metal molecular ions.
Isotope selective photodissociation of N2 by the interstellar radiation field and cosmic rays
Heays, Alan N; Gredel, Roland; Ubachs, Wim; Lewis, Brenton R; Gibson, Stephen T; van Dishoeck, Ewine F
2014-01-01
Photodissociation of 14N2 and 14N15N occurs in interstellar clouds, circumstellar envelopes, protoplanetary discs, and other environments due to UV radiation from stellar sources and the presence of cosmic rays. This source of N atoms initiates the formation of complex N-bearing species and influences their isotopic composition. To study the photodissociation rates of 14N15N by UV continuum radiation and both isotopologues in a field of cosmic ray induced photons. To determine the effect of these on the isotopic composition of more complex molecules. High-resolution photodissociation cross sections of N2 are used from an accurate and comprehensive quantum- mechanical model of the molecule based on laboratory experiments. A similarly high-resolution spectrum of H2 emission following interactions with cosmic rays has been constructed. The spectroscopic data are used to calculate dissociation rates which are input into isotopically differentiated chemical models, describing an interstellar cloud and a protoplane...
A Method to Produce Intense Positron Beams via Electro Pair Production on Electrons
Schoch, Berthold
2016-01-01
Intense positron beams can be prepared via electro production with the reaction $e^{-} + e^{-} \\rightarrow e^{-}+e^{+}+e^{-}+e^{-}$ due to the availability of high current electron beams. Head on collisions inside of a magnetic field of a solenoid are used to produce unpolarized/polarized positrons via $e^{-}-e^{+}$ - pair production. A flux of unpolarized positrons, $N_{positron}=6.55 \\cdot 10^{11} s^{-1}$, has been obtained as a result of calculations for a special case of parameters with beam currents for both electron beams of $I_{e}$=10 mA and beam momenta of $p_{beam 1}$=0.63 MeV/c and $p_{beam 2}$=10.0 MeV/c. Intensities are an order of magnitude smaller in the case of polarized positrons due to a reduced current of one of the electron beams. Suitable cuts on momenta of the positrons allow to achieve a polarization transfer from electrons to positrons of $\\geq $ 85\\% reducing, however, the intensity to 27\\%
Quantification of dental prostheses on cone-beam CT images by the Taguchi method.
Kuo, Rong-Fu; Fang, Kwang-Ming; Ty, Wong; Hu, Chia Yu
2016-01-01
The gray values accuracy of dental cone-beam computed tomography (CBCT) is affected by dental metal prostheses. The distortion of dental CBCT gray values could lead to inaccuracies of orthodontic and implant treatment. The aim of this study was to quantify the effect of scanning parameters and dental metal prostheses on the accuracy of dental cone-beam computed tomography (CBCT) gray values using the Taguchi method. Eight dental model casts of an upper jaw including prostheses, and a ninth prosthesis-free dental model cast, were scanned by two dental CBCT devices. The mean gray value of the selected circular regions of interest (ROIs) were measured using dental CBCT images of eight dental model casts and were compared with those measured from CBCT images of the prosthesis-free dental model cast. For each image set, four consecutive slices of gingiva were selected. The seven factors (CBCTs, occlusal plane canting, implant connection, prosthesis position, coping material, coping thickness, and types of dental restoration) were used to evaluate scanning parameter and dental prostheses effects. Statistical methods of signal to noise ratio (S/N) and analysis of variance (ANOVA) with 95% confidence were applied to quantify the effects of scanning parameters and dental prostheses on dental CBCT gray values accuracy. For ROIs surrounding dental prostheses, the accuracy of CBCT gray values were affected primarily by implant connection (42%), followed by type of restoration (29%), prostheses position (19%), coping material (4%), and coping thickness (4%). For a single crown prosthesis (without support of implants) placed in dental model casts, gray value differences for ROIs 1-9 were below 12% and gray value differences for ROIs 13-18 away from pros-theses were below 10%. We found the gray value differences set to be between 7% and 8% for regions next to a single implant-supported titanium prosthesis, and between 46% and 59% for regions between double implant
A new measurement method of electrode gains for orthogonal symmetric type beam position monitor
Zou, J Y; Yang, Y L; Sun, B G; Zhou, Z R; Luo, Q; Lu, P; Xu, H L
2014-01-01
The new beam position monitor (BPM) system of the injector at the upgrade project of Hefei Light Source (HLS II) has 19 stripline beam position monitors. Most consist of four orthogonal symmetric stripline electrodes. The differences in electronic gain and mismachining tolerance can cause the change of the beam response of the BPM electrodes. This variation will couple the two measured horizontal positions in order to bring the measuring error. To alleviate this effect, a new technique to measure the relative response of the four electrodes has been developed. It is irrelevant to the beam charge and the related coefficient can be theoretical calculated. The effect of electrodes coupling on this technique is analyzed. The calibration data is used to fit the gain for all 19 injector beam position monitors. The results show the standard deviation of the distribution of measured gains is about 5%.
Physical principles of the surface plasma method for producing beams of negative ions
International Nuclear Information System (INIS)
The processes which are important for the production of intense beams of negative ions from surface plasma sources (SPS) are examined. The formation of negative ions when atomic particles interact with a surface is analyzed on the basis of both experimental results obtained when a surface was bombarded with beams and recently developed theoretical considerations of reflection, scattering, and electron exchange. The characteristic features of these processes in SPS, when a surface is bombarded with intense fluxes of plasma particles, are revealed in special experiments. The characteristics of generation and acceleration of the bombarding particles in a gas discharge SPS plasma, the characteristics of transportation of negative ions through the plasma toward the beam forming system, the role of cesium in SPS, and the characteristics of formation of the intense negative ion beams as well as the removal of parasite electrons from the beam
International Nuclear Information System (INIS)
We propose a new method for selecting importance factors (for regions of interest like organs at risk) used to plan conformal radiotherapy. Importance factors, also known as weighting factors or penalty factors, are essential in determining the relative importance of multiple objectives or the penalty ratios of constraints incorporated into cost functions, especially in dealing with dose optimization in radiotherapy treatment planning. Researchers usually choose importance factors on the basis of a trial-and-error process to reach a balance between all the objectives. In this study, we used a genetic algorithm and adopted a real-number encoding method to represent both beam weights and importance factors in each chromosome. The algorithm starts by optimizing the beam weights for a fixed number of iterations then modifying the importance factors for another fixed number of iterations. During the first phase, the genetic operators, such as crossover and mutation, are carried out only on beam weights, and importance factors for each chromosome are not changed or 'frozen'. In the second phase, the situation is reversed: the beam weights are 'frozen' and the importance factors are changed after crossover and mutation. Through alternation of these two phases, both beam weights and importance factors are adjusted according to a fitness function that describes the conformity of dose distribution in planning target volume and dose-tolerance constraints in organs at risk. Those chromosomes with better fitness are passed into the next generation, showing that they have a better combination of beam weights and importance factors. Although the ranges of the importance factors should be set in advance by using this algorithm, it is much more convenient than selecting specific numbers for importance factors. Three clinical examples are presented and compared with manual plans to verify this method. Three-dimensional standard displays and dose-volume histograms are shown to
Robust methods for automatic image-to-world registration in cone-beam CT interventional guidance
International Nuclear Information System (INIS)
Purpose: Real-time surgical navigation relies on accurate image-to-world registration to align the coordinate systems of the image and patient. Conventional manual registration can present a workflow bottleneck and is prone to manual error and intraoperator variability. This work reports alternative means of automatic image-to-world registration, each method involving an automatic registration marker (ARM) used in conjunction with C-arm cone-beam CT (CBCT). The first involves a Known-Model registration method in which the ARM is a predefined tool, and the second is a Free-Form method in which the ARM is freely configurable. Methods: Studies were performed using a prototype C-arm for CBCT and a surgical tracking system. A simple ARM was designed with markers comprising a tungsten sphere within infrared reflectors to permit detection of markers in both x-ray projections and by an infrared tracker. The Known-Model method exercised a predefined specification of the ARM in combination with 3D-2D registration to estimate the transformation that yields the optimal match between forward projection of the ARM and the measured projection images. The Free-Form method localizes markers individually in projection data by a robust Hough transform approach extended from previous work, backprojected to 3D image coordinates based on C-arm geometric calibration. Image-domain point sets were transformed to world coordinates by rigid-body point-based registration. The robustness and registration accuracy of each method was tested in comparison to manual registration across a range of body sites (head, thorax, and abdomen) of interest in CBCT-guided surgery, including cases with interventional tools in the radiographic scene. Results: The automatic methods exhibited similar target registration error (TRE) and were comparable or superior to manual registration for placement of the ARM within ∼200 mm of C-arm isocenter. Marker localization in projection data was robust across all
International Nuclear Information System (INIS)
Photoelectron-current measurement by low-frequency electromodulation probe (PMMP) is proposed as a sensitive method to determine the rate Gr of neutral free radical production by the photodeionization of negative ion beams (PDINIB). The PMMP method was employed to evaluate the production rate in a trial surface-processing apparatus developed in the author's laboratory utilizing a steady-flux refined beam of neutral free radicals produced by the PDINIB procedure. A 63Cu- negative ion beam of kinetic energy Ei varied up to 15 keV was irradiated with a 514.5 nm visible light beam from a 25 W cw Ar+ ion laser. The detection limit of the production rate by the measurement setup was 6x109/s under the conditions that Ei=15 keV, the negative ion beam current Ii=4 μA, and the laser power P=6 W. Based on the results of these basic experiments, furthermore, the photodeionization efficiency defined by eGr/Ii where e is the elementary electric charge was estimated to be 27±6% under the conditions that Ei=15 keV, Ii=40 μA, and P=18 W
International Nuclear Information System (INIS)
A relatively new technique for achieving the right dose to the right tissue, is intensity modulated radiation therapy (IMRT). In this technique, a megavoltage x-ray beam is rotated around a patient, and the intensity and shape of the beam is modulated as a function of source position and patient anatomy. The relationship between beam-let intensity and patient dose can be expressed under a matrix form where the matrix Dij represents the dose delivered to voxel i by beam-let j per unit fluence. The Dij influence matrix is the key element that enables this approach. In this regard, sensitivity theory lends itself in a natural way to the process of computing beam weights for treatment planning. The solution of the adjoint form of the Boltzmann equation is an adjoint function that describes the importance of particles throughout the system in contributing to the detector response. In this case, adjoint methods can provide the sensitivity of the dose at a single point in the patient with respect to all points in the source field. The purpose of this study is to investigate the feasibility of using the adjoint method and Monte Carlo transport for radiation therapy treatment planning
On the origin of the asymmetric shape of the HCl photodissociation cross section
DEFF Research Database (Denmark)
Schmidt, Johan Albrecht; Johnson, Matthew Stanley; Grage, Mette Marie-Louise;
2009-01-01
A first principles treatment of the photodissociation of HCl and DCl from 50000 cm1 to 75000 cm1 is presented. The treatment is the first to correctly reproduce the asymmetric absorption profile observed for HCl. The theoretical model for the HCl and DCl photodissociation presented in this study ...... considers a dissociation process that occurs on a repulsive electronic state (A1P) coupled to a bound electronic state (C1P). The asymmetry in the HCl cross section arises because of the radial coupling introduced by the rotation-free nuclear kinetic energy operator....
Roaming is the dominant mechanism for molecular products in acetaldehyde photodissociation
Heazlewood, Brianna R.; Jordan, Meredith J. T.; Kable, Scott H.; Selby, Talitha M.; Osborn, David L.; Shepler, Benjamin C.; Braams, Bastiaan J.; Joel M. Bowman
2008-01-01
Reaction pathways that bypass the conventional saddle-point transition state (TS) are of considerable interest and importance. An example of such a pathway, termed “roaming,” has been described in the photodissociation of H2CO. In a combined experimental and theoretical study, we show that roaming pathways are important in the 308-nm photodissociation of CH3CHO to CH4 + CO. The CH4 product is found to have extreme vibrational excitation, with the vibrational distribution peaked at ≈95% of the...
Charge-transfer photodissociation of adsorbed molecules via electron image states
Jensen, E T
2007-01-01
The 248nm and 193nm photodissociation of submonolayer quantities of CH$_3$Br and CH$_3$I adsorbed on thin layers of n-hexane indicate that the dissociation is caused by dissociative electron attachment from sub-vacuum level photoelectrons created in the copper substrate. The characteristics of this photodissociation-- translation energy distributions and coverage dependences show that the dissociation is mediated by an image potential state which temporarily traps the photoelectrons near the n-hexane--vacuum interface, and then the charge transfers from this image state to the affinity level of a co-adsorbed halomethane which then dissociates.
International Nuclear Information System (INIS)
This study introduced a quantitative method that can be used to measure the concentration of analytes directly from a single-beam spectrum of open-path Fourier Transform Infrared Spectroscopy (OP-FTIR). The peak shapes of the analytes in a single-beam spectrum were gradually canceled (i.e., “titrated”) by dividing an aliquot of a standard transmittance spectrum with a known concentration, and the sum of the squared differential synthetic spectrum was calculated as an indicator for the end point of this titration. The quantity of a standard transmittance spectrum that is needed to reach the end point can be used to calculate the concentrations of the analytes. A NIST traceable gas standard containing six known compounds was used to compare the quantitative accuracy of both this titration method and that of a classic least square (CLS) using a closed-cell FTIR spectrum. The continuous FTIR analysis of industrial exhausting stack showed that concentration trends were consistent between the CLS and titration methods. The titration method allowed the quantification to be performed without the need of a clean single-beam background spectrum, which was beneficial for the field measurement of OP-FTIR. Persistent constituents of the atmosphere, such as NH3, CH4 and CO, were successfully quantified using the single-beam titration method with OP-FTIR data that is normally inaccurate when using the CLS method due to the lack of a suitable background spectrum. Also, the synthetic spectrum at the titration end point contained virtually no peaks of analytes, but it did contain the remaining information needed to provide an alternative means of obtaining an ideal single-beam background for OP-FTIR. - Highlights: • Establish single beam titration quantification method for OP-FTIR. • Define the indicator for the end-point of spectrum titration. • An ideal background spectrum can be obtained using single beam titration. • Compare the quantification between titration and
Herr, W; Pieloni, T.
2016-01-01
One of the most severe limitations in high-intensity particle colliders is the beam-beam interaction, i.e. the perturbation of the beams as they cross the opposing beams. This introduction to beam-beam effects concentrates on a description of the phenomena that are present in modern colliding beam facilities.
Herr, W
2014-01-01
One of the most severe limitations in high-intensity particle colliders is the beam-beam interaction, i.e. the perturbation of the beams as they cross the opposing beams. This introduction to beam-beam effects concentrates on a description of the phenomena that are present in modern colliding beam facilities.
Sung, Lung-Yu; Lu, Chia-Jung
2014-09-01
This study introduced a quantitative method that can be used to measure the concentration of analytes directly from a single-beam spectrum of open-path Fourier Transform Infrared Spectroscopy (OP-FTIR). The peak shapes of the analytes in a single-beam spectrum were gradually canceled (i.e., "titrated") by dividing an aliquot of a standard transmittance spectrum with a known concentration, and the sum of the squared differential synthetic spectrum was calculated as an indicator for the end point of this titration. The quantity of a standard transmittance spectrum that is needed to reach the end point can be used to calculate the concentrations of the analytes. A NIST traceable gas standard containing six known compounds was used to compare the quantitative accuracy of both this titration method and that of a classic least square (CLS) using a closed-cell FTIR spectrum. The continuous FTIR analysis of industrial exhausting stack showed that concentration trends were consistent between the CLS and titration methods. The titration method allowed the quantification to be performed without the need of a clean single-beam background spectrum, which was beneficial for the field measurement of OP-FTIR. Persistent constituents of the atmosphere, such as NH3, CH4 and CO, were successfully quantified using the single-beam titration method with OP-FTIR data that is normally inaccurate when using the CLS method due to the lack of a suitable background spectrum. Also, the synthetic spectrum at the titration end point contained virtually no peaks of analytes, but it did contain the remaining information needed to provide an alternative means of obtaining an ideal single-beam background for OP-FTIR.
Energy Technology Data Exchange (ETDEWEB)
Ali, Fazlat; Gunji, Michiharu; Yang, Sung-Chae; Suzuki, Tsuneo; Suematsu, Hisayuki; Jiang, Weihua; Yatsui, Kiyoshi [Nagaoka Univ. of Technology, Extreme Energy-Density Research Inst., Nagaoka, Niigata (Japan)
2002-06-01
The deposition of polycrystalline silicon thin films has been tried by a pulsed ion-beam evaporation method, where high crystallinity and deposition rate have been achieved without heating the substrate. The crystallinity and the deposition rate were improved by applying bias voltage to the substrate, where instantaneous substrate heating might have occurred by ion-bombardment. (author)
International Nuclear Information System (INIS)
The deposition of polycrystalline silicon thin films has been tried by a pulsed ion-beam evaporation method, where high crystallinity and deposition rate have been achieved without heating the substrate. The crystallinity and the deposition rate were improved by applying bias voltage to the substrate, where instantaneous substrate heating might have occurred by ion-bombardment. (author)
Determination of wafer center position during the transfer process by using the beam-breaking method
International Nuclear Information System (INIS)
A wafer on a robot blade may slip due to inertia sliding during the acceleration or deceleration process. This study presents the implementation and experimental verification of a novel real-time wafer positioning system to be used during the transfer process. A system-integration computer program involving a human–machine interface (HMI) was also developed, exhibiting the following functions: (a) moving direction judgment; (b) notch-passing judgment; (c) indicating the sensor by which the notch passes; and (d) computing the wafer center in real time. The position of the wafer center is calculated based on the time-sequence of the beam-breaking signals from two optical sensors, and the geometric relations among the sensing points of the robot blade and wafer. When using eight-inch wafers, the experimental results indicated the capabilities of the proposed positioning system under various conditions, including distinct parameters regarding the moving direction, wafer displacement and notch-passing sensors. The accuracy and precision (repeatability) of the measurement in various conditions were calculated and discussed. Furthermore, the experimental results demonstrate that, after combining the novel wafer positioning system and HMI program, the proposed method can be used to compute the position of the wafer center in real time in various conditions. (paper)
DEVICE FOR MEASURING OF THERMAL LENS PARAMETERS IN LASER ACTIVE ELEMENTS WITH A PROBE BEAM METHOD
Directory of Open Access Journals (Sweden)
A. N. Zakharova
2015-01-01
Full Text Available We have developed a device for measuring of parameters of thermal lens (TL in laser active elements under longitudinal diode pumping. The measurements are based on the probe beam method. This device allows one to determine sign and optical power of the lens in the principal meridional planes, its sensitivity factor with respect to the absorbed pump power and astigmatism degree, fractional heat loading which make it possible to estimate integral impact of the photoelastic effect to the formation of TL in the laser element. The measurements are performed in a linearly polarized light at the wavelength of 532 nm. Pumping of the laser element is performed at 960 nm that makes it possible to study laser materials doped with Yb3+ and (Er3+, Yb3+ ions. The precision of measurements: for sensitivity factor of TL – 0,1 m-1/W, for astigmatism degree – 0,2 m-1/W, for fractional heat loading – 5 %, for the impact of the photoelastic effect – 0,5 × 10-6 K-1. This device is used for characterization of thermal lens in the laser active element from an yttrium vanadate crystal, Er3+,Yb3+:YVO .
International Nuclear Information System (INIS)
The works were carried out in the framework of the research program PARRNe (production of radioactive neutron-rich nuclei). This program aims to determine optimal conditions to produce intense beams of neutron-rich isotopes. This thesis treats multiple technical aspects related to the production of separate radioactive isotopes in line (ISOL). It deals mainly with the development of the target-source unit which is the key element for projects such as SPIRAL-2 or EURISOL.The first part presents the various methods using fission as production mode and compares them: fission induced by thermal neutrons, induced by fast neutrons and photofission. The experiment carried out at CERN validated the interest of the photofission as a promising production mode of radioactive ions. That is why the institute of nuclear physics of Orsay decided to build a linear electron accelerator at the Tandem d'Orsay (ALTO).The second part of this thesis deals with the development of uranium targets. The X-rays diffraction and Scanning Electron Microscopy have been used as analysis techniques. They allowed to determine the chemical and structural characteristics of uranium carbide targets as function of various heating temperatures. After the production, the process of ionization has been studied. Two types of ion source have been worked out: the first one is a surface ion source and the second one is a source based on resonant ionization by laser. These two types of sources will be used for the ALTO project. (author)
Velocity analysis of shock-heated molecular beams by a time-of-flight method
International Nuclear Information System (INIS)
Measurements of the mean velocities u sub(infinity) and the velocity distributions of the molecular beams from a shock-heated source have been carried out by a conventional time-of-flight method, and their translational temperatures T sub(parallel)sup(infinity) parallel to the flow direction have been determined. The speed ratios, S sub(parallel)sup(infinity) = (mu sub(infinity)/2kT sub(parallel)sup(infinity))sup(1/2), of 6 - 20 have been obtained in the source temperature range of T0 = 1,400 - 10,800 K and its pressure range of P0 = 1.3 - 6.8 atm for argon. They have been less than the theoretical terminal speed ratios for a free jet. In the present apparatus with a convergentdivergent conical nozzle, the boundary layer from the nozzle wall limits the expansion and results in a decrease of the speed ratio. Although the flow is strongly affected by the background gas in the far downstream from the nozzle exit, higher speed ratios have been obtained. (author)
Studies on tin oxide films prepared by electron beam evaporation and spray pyrolysis methods
Indian Academy of Sciences (India)
K S Shamala; L C S Murthy; K Narasimha Rao
2004-06-01
Transparent conducting tin oxide thin films have been prepared by electron beam evaporation and spray pyrolysis methods. Structural, optical and electrical properties were studied under different preparation conditions like substrate temperature, solution flow rate and rate of deposition. Resistivity of undoped evaporated films varied from 2.65 × 10-2 -cm to 3.57 × 10-3 -cm in the temperature range 150–200°C. For undoped spray pyrolyzed films, the resistivity was observed to be in the range 1.2 × 10-1 to 1.69 × 10-2 -cm in the temperature range 250–370°C. Hall effect measurements indicated that the mobility as well as carrier concentration of evaporated films were greater than that of spray deposited films. The lowest resistivity for antimony doped tin oxide film was found to be 7.74 × 10-4 -cm, which was deposited at 350°C with 0.26 g of SbCl3 and 4 g of SnCl4 (SbCl3/SnCl4 = 0.065). Evaporated films were found to be amorphous in the temperature range up to 200°C, whereas spray pyrolyzed films prepared at substrate temperature of 300–370°C were polycrystalline. The morphology of tin oxide films was studied using SEM.
Disinfection of sewage sludge by gamma radiation, electron beams and alternative methods
International Nuclear Information System (INIS)
Sewage sludges generally contain high concentrations of pathogens, even after digestion or other conventional treatments for stabilization. Disinfection can be effected by irradiation (e.g. gamma or electron beam), by heat treatment (pasteurization or thermophilic stabilization), and by changing the pH (lime treatment). Irradiation is a simple and reliable process for disinfection with special advantages and favorable side-effects. Irradiation can be combined with oxygenation, heat or other treatments, with favorable synergistic effects. The total costs for the irradiation treatment of sewage sludges are comparable to those of alternative disinfection methods. Most of the worldwide practical experience has been obtained at the sewage-sludge irradiation plant in Geiselbullach (10 km west of Munich, Germany), which was continuously in operation from 1973 to 1993. A multidisciplinary research programme was conducted during the first 8 years. In subsequent years, the plant was operated commercially for sewage-sludge disinfection, without public funds. Other demonstration or research plants for sewage-sludge irradiation have been reported in the USA, India, Russia, Japan, Austria, Germany and Hungary. (author)