Neutronic Design of an Accelerator Driven Sub-Critical Research Reactor

International Nuclear Information System (INIS)

Pesic, M.

2002-01-01

Conceptual design of an accelerator driven sub-critical research reactor (ADSRR), as a new project in the Vinca Institute of Nuclear Sciences, is suggested for support to the Ministry of science, technologies and development of Republic Serbia, Yugoslavia. This paper show initial results of neutronic analyses of the proposed ADSRR carried out by Monte Carlo based MCNP and SHIELD codes. According to the proposal, the ADSRR would be constructed, in a later phase, at high-energy channel H5B of the VINCY cyclotron of the TESLA Accelerator Installation, that is under completion in the Vinca Institute. The fuel elements of 80%-enriched uranium dioxide dispersed in aluminium matrix, available in the Vinca Institute, are proposed for the ADSRR core design. The HEU fuel elements are placed in aluminium tubes filled by the 'primary moderator' - light water. These 'fuel tubes' are placed in a square lattice within lead matrix in a stainless steel tank. The lead is used as a 'secondary moderator' in the core and as the axial and radial reflector. Such design of the ADSRR shows that this small low neutron flux system can be used as an experimental 'demonstration' ADS with some neutron characteristics similar to proposed well-known lead moderated and cooled power sub-critical ADS with intermediate or fast neutron spectrum. The proposed experimental ADSRR, beside usage as a valuable research machine in reactor and neutron physics, will contribute to following and developing new nuclear technologies in the country, useful for eventual nuclear power option and nuclear waste incineration in future. (author)

Journey from discovery of nuclear fission to accelerator-driven sub-critical reactor systems (ADS)

International Nuclear Information System (INIS)

Kapoor, S.S.

2005-01-01

The epoch making discovery of nuclear fission in 1939, which resulted purely from the curiosity driven basic research to understand the atomic and nuclear structure has changed the world forever with the onset of a new era in the history of human civilization. The basic nuclear physics research pursued after the discovery of fission has also been of much relevance in the harnessing of nuclear energy. In the recent years, there is considerable interest towards developing accelerator driven sub-critical reactor systems (ADS) for the incineration of the long-lived spent fuel radioactive waste and for the utilization of thorium fuel for nuclear power generation. In this talk, we discuss important milestones in the journey from discovery of nuclear fission to ADS. (author)

Conceptual design for accelerator-driven sodium-cooled sub-critical transmutation reactors using scale laws

Energy Technology Data Exchange (ETDEWEB)

Lee, Kwang Gu; Chang, Soon Heung [Korea Advanced Institute of Science and Technology, Taejon (Korea, Republic of)

1998-12-31

The feasibility study on conceptual design methodology for accelerator-driven sodium-cooled sub-critical transmutation reactors has been conducted to optimize the design parameters from the scale laws and validates the reactor performance with the integrated code system. A 1000 MWth sodium-cooled sub-critical transmutation reactor has been scaled and verified through the methodology in this paper, which is referred to Advanced Liquid Metal Reactor (ALMR). A Pb-Bi target material and a partitioned fuel are the liquid phases, and they are cooled by the circulation of secondary Pb-Bi coolant and by primary sodium coolant, respectively. Overall key design parameters are generated from the scale laws and they are improved and validated by the integrated code system. Integrated Code System (ICS) consists of LAHET, HMCNP, ORIGEN2, and COMMIX codes and some files. Through ICS the target region, the core region, and thermal-hydraulic related regions are analyzed once-through Results of conceptual design are attached in this paper. 5 refs., 4 figs., 1 tab. (Author)

Calculation and analysis of burnup and optimum core design in accelerator driven sub-critical system

International Nuclear Information System (INIS)

Wang Yuwei; Yang Yongwei; Cui Pengfei

2011-01-01

The premise of the accelerator driven sub-critical system (ADS) in the accident is still subcritical, the biggest k eff change with burn time is less than 1.5% and the cladding material, HT9 steel, can withstand the maximum radiation damage, core fuel area is divided into fuel transmutation area and fuel multiplication area, and fuel transmutation area maintains the same fuel composition in the whole process. Through the analysis of the composition of the fuel, shape of core layout and the power distribution, etc., supposed outer and inner Pu enrichment ratio range of 1.0-1.5, then the fuel components of fuel multiplication area was adjusted. Time evolution of k eff was calculated by COUPLED2 which coupled with MCNP and ORIGEN. At the same time the power peaking factors, minoractinides transmutation rate desired to maximization and burnup were considered. A sub-critical system fitting for engineering practice was established. (authors)

Assessments of the kinetic and dynamic transient behavior of sub-critical systems (ADS) in comparison to critical reactor systems

International Nuclear Information System (INIS)

Schikorr, W.M.

2001-01-01

The neutron kinetic and the reactor dynamic behavior of Accelerator Driven Systems (ADS) is significantly different from those of conventional power reactor systems currently in use for the production of power. It is the objective of this study to examine and to demonstrate the intrinsic differences of the kinetic and dynamic behavior of accelerator driven systems to typical plant transient initiators in comparison to the known, kinetic and dynamic behavior of critical thermal and fast reactor systems. It will be shown that in sub-critical assemblies, changes in reactivity or in the external neutron source strength lead to an asymptotic power level essentially described by the instantaneous power change (i.e. prompt jump). Shutdown of ADS operating at high levels of sub-criticality, (i.e. k eff ∼0.99), without the support of reactivity control systems (such as control or safety rods), may be problematic in case the ability of cooling of the core should be impaired (i.e. loss of coolant flow). In addition, the dynamic behavior of sub-critical systems to typical plant transients such as protected or unprotected loss of flow (LOF) or heat sink (LOH) transients are not necessarily substantially different from the plant dynamic behavior of critical systems if the reactivity feedback coefficients of the ADS design are unfavorable. As expected, the state of sub-criticality and the temperature feedback coefficients, such as Doppler and coolant temperature coefficient, play dominant roles in determining the course and direction of plant transients. Should the combination of these safety coefficients be very unfavorable, not much additional margin in safety may be gained by making a critical system only sub-critical (i.e. k eff ∼0.95). A careful optimization procedure between the selected operating level of sub-criticality, the safety reactivity coefficients and the possible need for additional reactivity control systems seems, therefore, advisable during the early

THz and Sub-THz Capabilities of a Table-Top Radiation Source Driven by an RF Thermionic Electron Gun

Energy Technology Data Exchange (ETDEWEB)

Smirnov, Alexei V.; Agustsson, R.; Boucher, S.; Campese, Tara; Chen, Y.C.; Hartzell, Josiah J.; Jocobson, B.T.; Murokh, A.; O' Shea, F.H.; Spranza, E.; Berg, W.; Borland, M.; Dooling, J. C.; Erwin, L.; Lindberg, R. R.; Pasky, S.J.; Sereno, N.; Sun, Y.; Zholents, A.

2017-06-01

Design features and experimental results are presented for a sub-mm wave source [1] based on APS RF thermionic electron gun. The setup includes compact alpha-magnet, quadrupoles, sub-mm-wave radiators, and THz optics. The sub-THz radiator is a planar, oversized structure with gratings. Source upgrade for generation frequencies above 1 THz is discussed. The THz radiator will use a short-period undulator having 1 T field amplitude, ~20 cm length, and integrated with a low-loss oversized waveguide. Both radiators are integrated with a miniature horn antenna and a small ~90°-degree in-vacuum bending magnet. The electron beamline is designed to operate different modes including conversion to a flat beam interacting efficiently with the radiator. The source can be used for cancer diagnostics, surface defectoscopy, and non-destructive testing. Sub-THz experiment demonstrated a good potential of a robust, table-top system for generation of a narrow bandwidth THz radiation. This setup can be considered as a prototype of a compact, laser-free, flexible source capable of generation of long trains of Sub-THz and THz pulses with repetition rates not available with laser-driven sources.

Laser-driven polarized sources of hydrogen and deuterium

International Nuclear Information System (INIS)

Young, L.; Holt, R.J.; Green, M.C.; Kowalczyk, R.S.

1988-01-01

A novel laser-driven polarized source of hydrogen and deuterium which operates on the principle of spin exchange optical pumping is described. The advantages of this method over conventional polarized sources for internal target experiments are presented. Technological difficulties which prevent ideal source operation are outlined along with proposed solutions. At present, the laser-driven polarized hydrogen source delivers 8 /times/ 10 16 atoms/s with a polarization (P/sub z/) of 24%. 9 refs., 2 figs

Research on neutron source multiplication method in nuclear critical safety

International Nuclear Information System (INIS)

Zhu Qingfu; Shi Yongqian; Hu Dingsheng

2005-01-01

The paper concerns in the neutron source multiplication method research in nuclear critical safety. Based on the neutron diffusion equation with external neutron source the effective sub-critical multiplication factor k s is deduced, and k s is different to the effective neutron multiplication factor k eff in the case of sub-critical system with external neutron source. The verification experiment on the sub-critical system indicates that the parameter measured with neutron source multiplication method is k s , and k s is related to the external neutron source position in sub-critical system and external neutron source spectrum. The relation between k s and k eff and the effect of them on nuclear critical safety is discussed. (author)

CM-244 as multiplier and breeder in a ThO/sub 2/ hybrid blanket driven by a (D,T) source

International Nuclear Information System (INIS)

Sahin, S.; Al-Kusayer, T.A.

1986-01-01

The safeguard aspects of Cm-244 - a nuclear waste product in LWRs - in a cylindrical hybrid blanket, driven by a (D,T) fusion neutron source have been analyzed. Cm-244 is investigated for two different applications: 1) as a neutron multiplier between the first wall and the fuel zone in a blanket with ThO/sub 2/; and 2) as a component of the mixed fuel, ThO/sub 2/-Cm/sup 244/O/sub 2/, used for power flattening in a hybrid blanket. The calculations show that a relatively small driven with 100 MW/sub th/ fusion power could produce about 5 kg/year Cm-245, enough to provide nuclear fuel for up to 50 explosives. The study suggests an extension of the safe-guarding regulations prior to the commercial introduction of fusion reactors in the energy market

Neutronic design and analysis on dual-cooled waste transmutation blanket for the fusion driven sub-critical system

International Nuclear Information System (INIS)

Zheng Shanliang; Wu Yican; Gao Chunjing; Xu Dezheng; Li Jingjing; Zhu Xiaoxiang

2004-01-01

Neutronics design and analysis of dual-cooled multi-functional waste transmutation blanket (DWTB) for the fusion driven sub-critical system (FDS) are performed to ensure the system be able to meet the requirements of fuel-sufficiency and more waste transmutation ratio with low initial loading fuel inventory, which is based on 1-D burn-up calculations with home-developed code Visual BUS and the multi-group (175 neutron groups-42 Gamma groups coupled) data library HENDL1.0/MG (Hybrid Evaluated Nuclear Data Library). (authors)

High pressure driven superconducting critical temperature tuning in Sb{sub 2}Se{sub 3} topological insulator

Energy Technology Data Exchange (ETDEWEB)

Anversa, Jonas [Departamento de Física, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS (Brazil); Escola de Engenharia Civil, Faculdade Meridional, 99070-220, Passo Fundo, RS (Brazil); Chakraborty, Sudip, E-mail: sudiphys@gmail.com [Condensed Matter Theory Group, Department of Physics and Astronomy, Box 516, Uppsala University, S-75120 Uppsala (Sweden); Piquini, Paulo [Departamento de Física, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS (Brazil); Ahuja, Rajeev [Condensed Matter Theory Group, Department of Physics and Astronomy, Box 516, Uppsala University, S-75120 Uppsala (Sweden); Applied Materials Physics, Department of Materials and Engineering, Royal Institute of Technology (KTH), S-100 44 Stockholm (Sweden)

2016-05-23

In this letter, we are reporting the change of superconducting critical temperature in Sb{sub 2}Se{sub 3} topological insulator under the influence of an external hydrostatic pressure based on first principles electronic structure calculations coupled with Migdal–Eliashberg model. Experimentally, it was shown previously that Sb{sub 2}Se{sub 3} was undergoing through a transition to a superconducting phase when subjected to a compressive pressure. Our results show that the critical temperature increases up to 6.15 K under the pressure unto 40 GPa and, subsequently, drops down until 70 GPa. Throughout this pressure range, the system is preserving the initial Pnma symmetry without any structural transformation. Our results suggest that the possible relevant mechanism behind the superconductivity in Sb{sub 2}Se{sub 3} is primarily the electron–phonon coupling.

Noise method for monitoring the sub-criticality in accelerator driven systems

International Nuclear Information System (INIS)

Rugama, Y.; Munoz-Cobo, J.L.; Valentine, T.E.; Mihalczo, J.T.; Perez, R.B.; Perez-Navarro, A.

2001-01-01

In this paper, an absolute measurements technique for the sub-criticality determination is presented. The development of ADS, requires of methods to monitor and control the sub-criticality of this kind of systems, without interfering it's normal operation mode. This method is based on the Stochastic Neutron and Photon Transport Theory developed by Munoz-Cobo et al., and which can be implemented in presently available neutron transport codes. As a by-product of the methodology a monitoring measurement technique has been developed and verified using two coupled Monte Carlo programs. The spallation collisions and the high-energy transport are simulated with LAHET. The neutrons transports with energies less than 20 MeV and the estimation of the count statistics for neutron and/or gamma ray counters in fissile systems, is simulated with MCNP-DSP. It is possible to get the kinetics parameters and the k eff value of the sub-critical system through the analysis of the counter detectors. (author)

YALINA facility a sub-critical Accelerator- Driven System (ADS) for nuclear energy research facility description and an overview of the research program (1997-2008).

Energy Technology Data Exchange (ETDEWEB)

Gohar, Y.; Smith, D. L.; Nuclear Engineering Division

2010-04-28

The YALINA facility is a zero-power, sub-critical assembly driven by a conventional neutron generator. It was conceived, constructed, and put into operation at the Radiation Physics and Chemistry Problems Institute of the National Academy of Sciences of Belarus located in Minsk-Sosny, Belarus. This facility was conceived for the purpose of investigating the static and dynamic neutronics properties of accelerator driven sub-critical systems, and to serve as a neutron source for investigating the properties of nuclear reactions, in particular transmutation reactions involving minor-actinide nuclei. This report provides a detailed description of this facility and documents the progress of research carried out there during a period of approximately a decade since the facility was conceived and built until the end of 2008. During its history of development and operation to date (1997-2008), the YALINA facility has hosted several foreign groups that worked with the resident staff as collaborators. The participation of Argonne National Laboratory in the YALINA research programs commenced in 2005. For obvious reasons, special emphasis is placed in this report on the work at YALINA facility that has involved Argonne's participation. Attention is given here to the experimental program at YALINA facility as well as to analytical investigations aimed at validating codes and computational procedures and at providing a better understanding of the physics and operational behavior of the YALINA facility in particular, and ADS systems in general, during the period 1997-2008.

Problems in the neutron dynamics of source-driven systems

International Nuclear Information System (INIS)

Ravetto, P.

2001-01-01

The present paper presents some neutronic features of source-driven neutron multiplying systems, with special regards to dynamics, discussing the validity and limitations of classical methods, developed for systems in the vicinity of criticality. Specific characteristics, such as source dominance and the role of delayed neutron emissions are illustrated. Some dynamic peculiarities of innovative concepts proposed for accelerator-driven systems, such as fluid-fuel, are also discussed. The second portion of the work formulates the quasi-static methods for source-driven systems, evidencing its novel features and presenting some numerical results. (author)

Consultancy on the potential of fusion/fission sub-critical neutron systems for energy production and transmutation. Working material

International Nuclear Information System (INIS)

2005-01-01

The Workshop on Sub-critical Neutron Production held at the University of Maryland and the Eisenhower Institute on 11-13 October 2004 brought together members of fusion, fission and accelerator technical communities to discuss issues of spent fuel, nonproliferation, reactor safety and the use of neutrons for sub-critical operation of nuclear reactors. The Workshop strongly recommended that the fusion community work closely with other technical communities to ensure that a wider range of technical solutions is available to solve the spent fuel problem and to utilize the current actinide inventories. Participants of the Workshop recommended that a follow-on Workshop, possibly under the aegis of the IAEA, should be held in the first half of the year 2005. The Consultancy Meeting is the response to this recommendation. The objectives of the Consultancy meeting were to hold discussions on the role of fusion/fission systems in sub-critical operations of nuclear reactors. The participants agreed that development of innovative (fourth generation) fission reactors, advanced fuel cycle options, and disposition of existing spent nuclear fuel inventories in various Member Sates can significantly benefit from including sub-critical systems, which are driven by external neutron sources. Spallation neutrons produced by accelerators have been accepted in the past as the means of driving sub-critical reactors. The accelerator community deserves credit in pioneering this novel approach to reactor design. Progress in the design and operation of fusion devices now offers additional innovative means, broadening the range of sub-critical operations of fission reactors. Participants felt that fusion should participate with accelerators in providing a range of technical options in reactor design. Participants discussed concrete steps to set up a small fusion/fission system to demonstrate actinide burning in the laboratory and what advice should be given to the Agency on its role in

Neutronics optimization of LiPb-He dual-cooled fuel breeding blanket for the fusion-driven sub-critical system

International Nuclear Information System (INIS)

Zheng Shanliang; Wu Yican

2002-01-01

The concept of the liquid Li 17 Pb 83 and Helium gas dual-cooled Fuel Breeding Blanket (FBB) for the Fusion-Driven sub-critical System (FDS) is presented and analyzed. Taking self-sustaining tritium (TBR > 1.05) and annual output of 100 kg or more fissile 239 Pu (FBR > 0.238) as objective parameters, and based on the three-dimensional Monte Carlo neutron-photon transport code MCNP/4A, a neutronics-optimized calculation of different cases was carried out and the concept is proved feasible. In addition, the total breeding ratio (Br = Tbr + Fbr) is listed corresponding to different cases

Insulating phase in Sr{sub 2}IrO{sub 4}: An investigation using critical analysis and magnetocaloric effect

Energy Technology Data Exchange (ETDEWEB)

Bhatti, Imtiaz Noor; Pramanik, A.K., E-mail: akpramanik@mail.jnu.ac.in

2017-01-15

The nature of insulating phase in 5d based Sr{sub 2}IrO{sub 4} is quite debated as the theoretical as well as experimental investigations have put forward evidences in favor of both magnetically driven Slater-type and interaction driven Mott-type insulator. To understand this insulating behavior, we have investigated the nature of magnetic state in Sr{sub 2}IrO{sub 4} through studying critical exponents, low temperature thermal demagnetization and magnetocaloric effect. The estimated critical exponents do not exactly match with any universality class, however, the values obey the scaling behavior. The exponent values suggest that spin interaction in present material is close to mean-field model. The analysis of low temperature thermal demagnetization data, however, shows dual presence of localized- and itinerant-type of magnetic interaction. Moreover, field dependent change in magnetic entropy indicates magnetic interaction is close to mean-field type. While this material shows an insulating behavior across the magnetic transition, yet a distinct change in slope in resistivity is observed around T{sub c}. We infer that though the insulating phase in Sr{sub 2}IrO{sub 4} is more close to be Slater-type but the simultaneous presence of both Slater- and Mott-type is the likely scenario for this material. - Highlights: • Critical analysis shows Sr{sub 2}IrO{sub 4} has ferromagnetic ordering temperature T{sub c}~225 K. • Obtained critical exponents imply spin interaction is close to mean-field model. • Analysis of magneto-entropy data also supports mean-field type interaction. • However, the presence of both itinerant and localized spin interaction is evident. • Sr{sub 2}IrO{sub 4} has simultaneous presence of both Slater- and Mott-type insulating phase.

Comparison of the transient behavior of lead-based advanced critical and sub-critical reactors

International Nuclear Information System (INIS)

Wang Gang; Gu Zhixing; Wang Zhen; Jin Ming; Bai Yunqing

2014-01-01

A lead-based reactor developed by FDS Team is proposed in 2011 and designed to be 10 MW. It is a pool type reactor and the primary coolant is driven by natural circulation. The reactor has two operation modes, which are a lead-based critical fast reactor mode and a lead-based sub-critical reactor mode. The conceptual designs of the two modes are both completed by 2013. In this paper, four transient accidents were simulated for both the critical and sub-critical reactors above by NTC-2D code, which is developed by FDS Team for advanced reactor safety analysis. The four accidents were protected and unprotected loss of heat sink accidents (PLOHS and ULOHS), protected and unprotected transient overpower accidents (PTOP and UTOP). The simulation results of the two reactors were compared and analyzed. The results showed that during PLOHS and PTOP accidents for both the two modes, all the key parameters (core power, fuel, cladding and coolant temperatures in the hottest channel) decreased to very small values after the reactor scrammed, which meant the reactors under the two modes were both safe. For ULOHS, the fuel, cladding and coolant temperatures of the sub-critical reactor increased bigger than those of the critical one. For UTOP, the parameters above of the critical fast reactor were much bigger than those of the sub-critical one. The analysis results showed different safety advantages of the lead-based critical fast and sub-critical reactors during different transient accidents. (author)

Validating criticality calculations for spent fuel with 252Cf-source-driven noise measurements

International Nuclear Information System (INIS)

Mihalczo, J.T.; Krass, A.W.; Valentine, T.E.

1992-01-01

The 252 Cf-Source-driven noise analysis method can be used for measuring the subcritical neutron multiplication factor k of arrays of spent light water reactor (LWR) fuel. This type of measurement provides a parameter that is directly related to the criticality state of arrays of LWR fuel. Measurements of this parameter can verify the criticality safety margins of spent LWR fuel configurations and thus could be a means of obtaining the information to justify burnup credit for spent LWR transportation/storage casks. The practicality of a measurement depends on the ability to install the hardware required to perform the measurement. Source chambers containing the 252 Cf at the required source intensity for this application have been constructed and have operated successfully for ∼10 years and can be fabricated to fit into control rod guide tubes of PWR fuel elements. Fission counters especially developed for spent-fuel measurements are available that would allow measurements of a special 3 x 3 spent fuel array and a typical burnup credit rail cask with spent fuel in unborated water. Adding a moderator around these fission counters would allow measurements with the typical burnup credit rail cask with borated water and the special 3 x 3 array with borated water. The recent work of Ficaro on modifying the KENO Va code to calculate by the Monte Carlo method the time sequences of pulses at two detectors near a fissile assembly from the fission chain multiplication process, initiated by a 252 Cf source in the assembly allows a direct computer calculation of the noise analysis data from this measurement method

Fusion-driven sub-critical dual-cooled waste transmutation blanket: design and analysis

International Nuclear Information System (INIS)

Wang Weihua; Wu Yican; Ke Yan; Kang Zhicheng; Wang Hongyan; Huang Qunying

2003-01-01

The Fusion-Driven Sub-critical System (FDS) is one of the Chinese programs to be further developed for fusion application. Its Dual-cooled Waste Transmutation Blanket (DWTB), as one the most important part of the FDS is cooled by helium and liquid metal, and have the features of safety, tritium self-sustaining, high efficiency and feasibility. Its conceptual design has been finished. This paper is mainly involved with the basic structure design and thermal-hydraulics analysis of DWTB. On the basis of a three-dimensional (3-D) model of radial-toroidal sections of the segment box, thermal temperature gradients and structure analysis made with a comprehensive finite element method (FEM) have been performed with the computer code ANSYS5.7 and computational fluid dynamic finite element codes. The analysis refers to the steady-state operating condition of an outboard blanket segment. Furthermore, the mechanical loads due to coolant pressure in normal operating conditions have been also taken into account. All the above loads have been combined as an input for a FEM stress analysis and the resulting stress distribution has been evaluated. Finally, the structure design and Pb-17Li flow velocity has been optimized according to the calculations and analysis

LESM: a laser-driven sub-MeV electron source delivering ultra-high dose rate on thin biological samples

Czech Academy of Sciences Publication Activity Database

Labate, L.; Andreassi, M.G.; Baffigi, F.; Bizzarri, B.M.; Borghini, A.; Bussolino, G.C.; Fulgentini, L.; Ghetti, F.; Giulietti, A.; Köster, P.; Lamia, D.; Levato, Tadzio; Oishi, Y.; Pulignani, S.; Russo, G.; Sgarbossa, A.; Gizzi, L.A.

2016-01-01

Roč. 49, č. 27 (2016), s. 1-9, č. článku 275401. ISSN 0022-3727 R&D Projects: GA MŠk EF15_008/0000162; GA MŠk LQ1606 Grant - others:ELI Beamlines(XE) CZ.02.1.01/0.0/0.0/15_008/0000162 Institutional support: RVO:68378271 Keywords : laser-driven electron accelerators * sub-MeV electron sources * ultrahigh dose rate * radiobiology * cell radiation damage Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics ) Impact factor: 2.588, year: 2016

Some problems of neutron source multiplication method for site measurement technology in nuclear critical safety

International Nuclear Information System (INIS)

Shi Yongqian; Zhu Qingfu; Hu Dingsheng; He Tao; Yao Shigui; Lin Shenghuo

2004-01-01

The paper gives experiment theory and experiment method of neutron source multiplication method for site measurement technology in the nuclear critical safety. The measured parameter by source multiplication method actually is a sub-critical with source neutron effective multiplication factor k s , but not the neutron effective multiplication factor k eff . The experiment research has been done on the uranium solution nuclear critical safety experiment assembly. The k s of different sub-criticality is measured by neutron source multiplication experiment method, and k eff of different sub-criticality, the reactivity coefficient of unit solution level, is first measured by period method, and then multiplied by difference of critical solution level and sub-critical solution level and obtained the reactivity of sub-critical solution level. The k eff finally can be extracted from reactivity formula. The effect on the nuclear critical safety and different between k eff and k s are discussed

Dynamical critical phenomena in driven-dissipative systems.

Science.gov (United States)

Sieberer, L M; Huber, S D; Altman, E; Diehl, S

2013-05-10

We explore the nature of the Bose condensation transition in driven open quantum systems, such as exciton-polariton condensates. Using a functional renormalization group approach formulated in the Keldysh framework, we characterize the dynamical critical behavior that governs decoherence and an effective thermalization of the low frequency dynamics. We identify a critical exponent special to the driven system, showing that it defines a new dynamical universality class. Hence critical points in driven systems lie beyond the standard classification of equilibrium dynamical phase transitions. We show how the new critical exponent can be probed in experiments with driven cold atomic systems and exciton-polariton condensates.

IAEA coordinated research project (CRP) on 'Analytical and experimental benchmark analyses of accelerator driven systems'

International Nuclear Information System (INIS)

Abanades, Alberto; Aliberti, Gerardo; Gohar, Yousry; Talamo, Alberto; Bornos, Victor; Kiyavitskaya, Anna; Carta, Mario; Janczyszyn, Jerzy; Maiorino, Jose; Pyeon, Cheolho; Stanculescu, Alexander; Titarenko, Yury; Westmeier, Wolfram

2008-01-01

In December 2005, the International Atomic Energy Agency (IAEA) has started a Coordinated Research Project (CRP) on 'Analytical and Experimental Benchmark Analyses of Accelerator Driven Systems'. The overall objective of the CRP, performed within the framework of the Technical Working Group on Fast Reactors (TWGFR) of IAEA's Nuclear Energy Department, is to increase the capability of interested Member States in developing and applying advanced reactor technologies in the area of long-lived radioactive waste utilization and transmutation. The specific objective of the CRP is to improve the present understanding of the coupling of an external neutron source (e.g. spallation source) with a multiplicative sub-critical core. The participants are performing computational and experimental benchmark analyses using integrated calculation schemes and simulation methods. The CRP aims at integrating some of the planned experimental demonstration projects of the coupling between a sub-critical core and an external neutron source (e.g. YALINA Booster in Belarus, and Kyoto University's Critical Assembly (KUCA)). The objective of these experimental programs is to validate computational methods, obtain high energy nuclear data, characterize the performance of sub-critical assemblies driven by external sources, and to develop and improve techniques for sub-criticality monitoring. The paper summarizes preliminary results obtained to-date for some of the CRP benchmarks. (authors)

A 3 A sink/source current fast transient response low-dropout G{sub m} driven linear regulator

Energy Technology Data Exchange (ETDEWEB)

Chu Xiuqin; Li Qingwei; Lai Xinquan; Yuan Bing [Institute of Electronic CAD, Xidian University, Xi' an 710071 (China); Li Yanming [School of Electronic and Control Engineering, Chang' an University, Xi' an 710064 (China); Zhao Yongrui, E-mail: liqw309@163.com, E-mail: xqchu@mail.xidian.edu.cn [Key Laboratory of High-Speed Circuit Design and EMC, Ministry of Education, Xidian University, Xi' an 710071 (China)

2011-06-15

A 3 A sink/source G{sub m}-driven CMOS low-dropout regulator (LDO), specially designed for low input voltage and low cost, is presented by utilizing the structure of a current mirror G{sub m} (transconductance) driving technique, which provides high stability as well as a fast load transient response. The proposed LDO was fabricated by a 0.5 {mu}m standard CMOS process, and the die size is as small as 1.0 mm{sup 2}. The proposed LDO dissipates 220 {mu}A of quiescent current in no-load conditions and is able to deliver up to 3 A of load current. The measured results show that the output voltage can be resumed within 2 {mu}s with a less than 1 mV overshoot and undershoot in the output current step from -1.8 to 1.8 A with a 0.1 {mu}s rising and falling time at three 10 {mu}F ceramic capacitors. (semiconductor integrated circuits)

Design of a molten heavy-metal coolant and target for fast-thermal accelerator driven sub-critical system (ADS)

International Nuclear Information System (INIS)

Satyamurthy, P.; Degwekar, S.B.; Nema, P.K.

2001-01-01

Accelerator Driven sub-critical Systems (ADS) have evoked considerable interest in recent years. The Energy Amplifier concept developed by C. Rubbia and others at CERN incorporates a buoyancy driven, lead-coolant primary system for extracting the heat generated in the fast reactor as well as that in neutron spallation target. In earlier publications, our BARC group has proposed a one-way coupled booster reactor system which could be operated at proton beam currents as low as 1-2 mA for a power output of 750 MW th . Here, the basic idea is to have a fast booster reactor zone of low power (- 100 MW th ) which is separated by a large gap from the main thermal reactor zone. In this arrangement, the spallation neutron source feeds neutrons to the fast reactor zone where neutrons are further multiplied. Further in this system, the neutrons from the booster region enter the main reactor but very few neutrons from main reactor return to booster, thus ensuring one-way coupling. In earlier work, several possible configurations of the booster and thermal regions were presented. In the present work, we describe an engineering design particularly with respect to thermal hydraulics of lead/lead-bismuth eutectic coolant also acting as spallation neutron source. This hybrid ADS reactor consists of fast and thermal reactor zones producing about 100 MW th and 650 MW th respectively. The scheme of the system is shown. The fast core consists of 48 hexagonal fuel bundles each containing 169 fuel pins of 8.2 mm diameter arranged in 11.4 mm triangular array pitch. The average thermal power per fuel pin is about 13.46 kw. However, due to neutron flux peaking effect, the maximum fuel pin power can be up to 2.5 times this average power. The thermal reactor consists of heavy water as moderator and coolant similar to a typical CANDU type Indian PHWR except for fuel composition. Though the gap between fast and thermal zones essentially provides one way coupling of neutron flux, a thermal

Proposed sub-criticality level for an 80 MWTHd-bismuth-cooled Ads

International Nuclear Information System (INIS)

Mansani, L.; Monti, R.; Neuhold, P.

2003-01-01

The degree of operational sub-criticality of an Accelerator-driven System (ADS) on the one hand directly affects key accelerator system parameters, such as the proton beam current required to sustain the selected rated power level and, on the other, the likelihood of approaching or attaining criticality under abnormal or accident conditions. Then, if in all such conditions the safety goal is pursued to design the sub-critical core so that it stays away from criticality with adequate margin, the required operational sub-criticality level must be determined by a properly balanced approach between excessively demanding accelerator system performances and risk of accidental criticality. The approach must necessarily include evaluation and appropriate combination of the relevant reactivity effects (e.g. from system cool-down, postulated accident scenarios, geometrical variations) and proper consideration of specific design features (such as, for instance, the absence of safety rods, intended as neutron absorbing devices having a role equivalent to the shutdown rods in critical reactors). The paper presents a possible approach to the determination of the operational sub-criticality level of an 80 MWth Lead-Bismuth-cooled pool type ADS, initially conceived and developed by a team of Italian Organisations led by Ansaldo, with funding from the Ministry of University and Scientific and Technological Research, and currently in the process of being assessed, versus a gas-cooled concept, in the frame of a contract with the Commission of the European Communities. After a brief description of the Lead-Bismuth-cooled ADS concept relevant features and of the key safety goals in terms of required sub-criticality margin, the evaluated reactivity effects are presented, a method to combine them is discussed and a proposed operational sub-criticality level is derived. (author)

A portable measurement system for subcriticality measurements by the CF-source-driven neutron noise analysis method

International Nuclear Information System (INIS)

Mihalczo, J.T.; Ragan, G.E.; Blakeman, E.D.

1988-01-01

A portable measurement system consisting of a personal computer used as a Fourier analyzer and three detection channels (with associated electronics that provide the signals to analog-to-digital (A/D) convertors) has been assembled to measure subcriticality by the /sup 252/Cf-source-driven neutron noise analysis method. The /sup 252/Cf-source-driven neutron noise analysis method for obtaining the subcritical neutron multiplication factor of a configuration of fissile material requires measurement of the frequency-dependent cross-power spectral density (CPSD), G/sub 23/(ω), between a pair of detectors (Nos. 2 and 3) located in or near the fissile material and CPSDs G/sub 12/(ω) and G/sub 13/(ω) between these same detectors and a source of neutrons emanating from an ionization chamber (No. 1) containing /sup 252/Cf, also positioned in or near the fissile material. The auto-power spectral density (APSD), G/sub 11/(ω), of the source is also required. A particular ratio of spectral densities, G/sub 12//sup */G/sub 13//G/sub 11/G/sub 23/ (/sup */ denotes complex conjugation), is then formed. This ratio is related to the subcritical neutron multiplication factor and is independent of detector efficiencies

Synchrotron-driven spallation sources

CERN Document Server

Bryant, P J

1996-01-01

The use of synchrotrons for pulsed neutron spallation sources is an example of scientific and technological spin-off from the accelerator development for particle physics. Accelerator-driven sources provide an alternative to the continuous-flux, nuclear reactors that currently furnish the majority of neutrons for research and development. Although the present demand for neutrons can be adequately met by the existing reactors, this situation is unlikely to continue due to the increasing severity of safety regulations and the declared policies of many countries to close down their reactors within the next decade or so. Since the demand for neutrons as a research tool is, in any case,expected to grow, there has been a corresponding interest in sources that are synchrotron-driven or linac-driven with a pulse compression ring and currently several design studies are being made. These accelerator-driven sources also have the advantage of a time structure with a high peak neutron flux. The basic requirement is for a...

Hybridized Kibble-Zurek scaling in the driven critical dynamics across an overlapping critical region

Science.gov (United States)

Zhai, Liang-Jun; Wang, Huai-Yu; Yin, Shuai

2018-04-01

The conventional Kibble-Zurek scaling describes the scaling behavior in the driven dynamics across a single critical region. In this paper, we study the driven dynamics across an overlapping critical region, in which a critical region (Region A) is overlaid by another critical region (Region B). We develop a hybridized Kibble-Zurek scaling (HKZS) to characterize the scaling behavior in the driven process. According to the HKZS, the driven dynamics in the overlapping region can be described by the critical theories for both Region A and Region B simultaneously. This results in a constraint on the scaling function in the overlapping critical region. We take the quantum Ising chain in an imaginary longitudinal field as an example. In this model, the critical region of the Yang-Lee edge singularity and the critical region of the ferromagnetic-paramagnetic phase transition overlap with each other. We numerically confirm the HKZS by simulating the driven dynamics in this overlapping critical region. The HKZSs in other models are also discussed.

Application of the modified neutron source multiplication method for a measurement of sub-criticality in AGN-201K reactor

International Nuclear Information System (INIS)

Myung-Hyun Kim

2010-01-01

Measurement of sub-criticality is a challenging and required task in nuclear industry both for nuclear criticality safety and physics test in nuclear power plant. A relatively new method named as Modified Neutron Source Multiplication Method (MNSM) was proposed in Japan. This method is an improvement of traditional Neutron Source Multiplication (NSM) Method, in which three correction factors are applied additionally. In this study, MNSM was tested in calculation of rod worth using an educational reactor in Kyung Hee University, AGN-201K. For this study, a revised nuclear data library and a neutron transport code system TRANSX-PARTISN were used for the calculation of correction factors for various control rod positions and source locations. Experiments were designed and performed to enhance errors in NSM from the location effects of source and detectors. MNSM can correct these effects but current results showed not much correction effects. (author)

IAEA coordinated research project (CRP) on 'Analytical and experimental benchmark analyses of accelerator driven systems'

Energy Technology Data Exchange (ETDEWEB)

Abanades, Alberto [Universidad Politecnica de Madrid (Spain); Aliberti, Gerardo; Gohar, Yousry; Talamo, Alberto [ANL, Argonne (United States); Bornos, Victor; Kiyavitskaya, Anna [Joint Institute of Power Eng. and Nucl. Research ' Sosny' , Minsk (Belarus); Carta, Mario [ENEA, Casaccia (Italy); Janczyszyn, Jerzy [AGH-University of Science and Technology, Krakow (Poland); Maiorino, Jose [IPEN, Sao Paulo (Brazil); Pyeon, Cheolho [Kyoto University (Japan); Stanculescu, Alexander [IAEA, Vienna (Austria); Titarenko, Yury [ITEP, Moscow (Russian Federation); Westmeier, Wolfram [Wolfram Westmeier GmbH, Ebsdorfergrund (Germany)

2008-07-01

In December 2005, the International Atomic Energy Agency (IAEA) has started a Coordinated Research Project (CRP) on 'Analytical and Experimental Benchmark Analyses of Accelerator Driven Systems'. The overall objective of the CRP, performed within the framework of the Technical Working Group on Fast Reactors (TWGFR) of IAEA's Nuclear Energy Department, is to increase the capability of interested Member States in developing and applying advanced reactor technologies in the area of long-lived radioactive waste utilization and transmutation. The specific objective of the CRP is to improve the present understanding of the coupling of an external neutron source (e.g. spallation source) with a multiplicative sub-critical core. The participants are performing computational and experimental benchmark analyses using integrated calculation schemes and simulation methods. The CRP aims at integrating some of the planned experimental demonstration projects of the coupling between a sub-critical core and an external neutron source (e.g. YALINA Booster in Belarus, and Kyoto University's Critical Assembly (KUCA)). The objective of these experimental programs is to validate computational methods, obtain high energy nuclear data, characterize the performance of sub-critical assemblies driven by external sources, and to develop and improve techniques for sub-criticality monitoring. The paper summarizes preliminary results obtained to-date for some of the CRP benchmarks. (authors)

Benchmarks of subcriticality in accelerator-driven system at Kyoto University Critical Assembly

Directory of Open Access Journals (Sweden)

Cheol Ho Pyeon

2017-09-01

Full Text Available Basic research on the accelerator-driven system is conducted by combining 235U-fueled and 232Th-loaded cores in the Kyoto University Critical Assembly with the pulsed neutron generator (14 MeV neutrons and the proton beam accelerator (100 MeV protons with a heavy metal target. The results of experimental subcriticality are presented with a wide range of subcriticality level between near critical and 10,000 pcm, as obtained by the pulsed neutron source method, the Feynman-α method, and the neutron source multiplication method.

The mechanical design and fabrication of 162.5 MHz buncher for China accelerator driven sub-critical system injector II

Energy Technology Data Exchange (ETDEWEB)

Niu, Hai Hua; Li, Youtang [Lanzhou University of Technology, Lanzhou (China); He, Yuan; Zhang, Bin; Huang, Shichun; Yuan, Chenzhang; Jia, Huan; Zhang, Shenghu [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou (China)

2017-08-15

A buncher is one of the main pieces of equipment in the medium energy beam transport line (MEBT) for China accelerator driven sub-critical system (C-ADS) Injector II. To focus the beam longitudinally and match the beam for the acceptance of the superconducting linac section, two room temperature quarter wave resonator (QWR) bunchers with frequency of 162.5 MHz have been designed as parts of the MEBT. According to the beam transmission matching of the MEBT and the geometric parameters requirements of bunchers, the unique mechanical structure and the main processing technology of buncher cavities and their couplers and tuners are described in this paper. The fabrication of bunchers and their parts have been completed and tested at high power, the test results agree well with the design requirements. These bunchers work well for about two years in Institute of Modern Physics, Chinese Academy of Sciences.

Evaluating laser-driven Bremsstrahlung radiation sources for imaging and analysis of nuclear waste packages.

Science.gov (United States)

Jones, Christopher P; Brenner, Ceri M; Stitt, Camilla A; Armstrong, Chris; Rusby, Dean R; Mirfayzi, Seyed R; Wilson, Lucy A; Alejo, Aarón; Ahmed, Hamad; Allott, Ric; Butler, Nicholas M H; Clarke, Robert J; Haddock, David; Hernandez-Gomez, Cristina; Higginson, Adam; Murphy, Christopher; Notley, Margaret; Paraskevoulakos, Charilaos; Jowsey, John; McKenna, Paul; Neely, David; Kar, Satya; Scott, Thomas B

2016-11-15

A small scale sample nuclear waste package, consisting of a 28mm diameter uranium penny encased in grout, was imaged by absorption contrast radiography using a single pulse exposure from an X-ray source driven by a high-power laser. The Vulcan laser was used to deliver a focused pulse of photons to a tantalum foil, in order to generate a bright burst of highly penetrating X-rays (with energy >500keV), with a source size of <0.5mm. BAS-TR and BAS-SR image plates were used for image capture, alongside a newly developed Thalium doped Caesium Iodide scintillator-based detector coupled to CCD chips. The uranium penny was clearly resolved to sub-mm accuracy over a 30cm(2) scan area from a single shot acquisition. In addition, neutron generation was demonstrated in situ with the X-ray beam, with a single shot, thus demonstrating the potential for multi-modal criticality testing of waste materials. This feasibility study successfully demonstrated non-destructive radiography of encapsulated, high density, nuclear material. With recent developments of high-power laser systems, to 10Hz operation, a laser-driven multi-modal beamline for waste monitoring applications is envisioned. Copyright © 2016. Published by Elsevier B.V.

A study of parameter setting and characterization of visible-light driven nitrogen-modified commercial TiO{sub 2} photocatalysts

Energy Technology Data Exchange (ETDEWEB)

Kuo, Yu-Lin, E-mail: ylkuo@mail.ntust.edu.tw [Department of Mechanical Engineering, National Taiwan University of Science and Technology, No. 43, Sec. 4, Keelung Rd., Taipei 106, Taiwan (China); Su, Te-Li [Department of Cosmetic Application and Management, St. Mary' s Medicine, Nursing and Management College, Yilan 266, Taiwan (China); Kung, Fu-Chen [Department of Health Developing and Health Marketing, Kainan University, Taoyuan County 338, Taiwan (China); Wu, Tsai-Jung [Department of Mechanical Engineering, National Taiwan University of Science and Technology, No. 43, Sec. 4, Keelung Rd., Taipei 106, Taiwan (China)

2011-06-15

Highlights: {yields} A cost-effective and highly-efficient visible-light driven nitrogen-modified TiO{sub 2} photocatalyst was prepared by a simple hydrolysis method. {yields} The obtained optimum conditions applied to Taguchi method for preparing visible-light driven photocatalyst were undergone by the process of stirring for 1 day using 4M ammonium as the nitrogen source, and then calcining at 400{sup Degree-Sign }C for 2 h. {yields} Several materials technologies of characterizing N-TiO2 photocatalyst have been used to realize the modification of TiO2 by ammonia water as the nitrogen source. - Abstract: An optimal condition applied to the Taguchi method with an L{sub 9} orthogonal array for preparing a visible-light driven nitrogen-modified TiO{sub 2} (N-TiO{sub 2}) photocatalyst by a simple hydrolysis method has been examined for material characteristics and a photodecolorization test of methyl blue (MB) under various visible light source (fluorescent and blue LED lamps) irradiations. Results of the material characterization showed that the absorption of prepared N-TiO{sub 2} powder exhibited a significant extension into visible light regimes with an optical bandgap (Eg) of around 2.96 eV, which subsequently improved the visible-light photocatalytic activity of N-TiO{sub 2} samples. The superior photocatalytic properties, the pseudo first-order reaction rate constants (k) and photodecolorization efficiency ({eta}%) of a N-TiO{sub 2} photocatalyst during the photodecolorization test of methyl blue (MB) under two different visible light irradiations were very evident compared to those for pure TiO{sub 2}. For photodecolorization of practical dyeing from the waste water from the dyeing and finishing industry, a higher photodecolorization efficiency of N-TiO{sub 2} powder toward Direct blue-86 (DB-86) (Direct Fast Turquoise Blue GL) dye was also achieved.

The physics of accelerator driven sub-critical reactors

Indian Academy of Sciences (India)

Accelerator driven systems (ADS) are attracting worldwide attention .... The region of interest (or the entire reactor core) is divided into a suitable number ..... have also presented the status of the theoretical and experimental activities being.

High Brightness, Laser-Driven X-ray Source for Nanoscale Metrology and Femtosecond Dynamics

Energy Technology Data Exchange (ETDEWEB)

Siders, C W; Crane, J K; Semenov, V; Betts, S; Kozioziemski, B; Wharton, K; Wilks, S; Barbee, T; Stuart, B; Kim, D E; An, J; Barty, C

2007-02-26

This project developed and demonstrated a new, bright, ultrafast x-ray source based upon laser-driven K-alpha generation, which can produce an x-ray flux 10 to 100 times greater than current microfocus x-ray tubes. The short-pulse (sub-picosecond) duration of this x-ray source also makes it ideal for observing time-resolved dynamics of atomic motion in solids and thin films.

Infield X-ray diffraction studies of field and temperature driven structural phase transition in Nd{sub 0.49}Sr{sub 0.51}MnO{sub 3+δ}

Energy Technology Data Exchange (ETDEWEB)

Shahee, Aga, E-mail: agashahee@gmail.com [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452001 (India); Department of Physics, IIT Bombay, Powai, Mumbai 400076 (India); Sharma, Shivani; Singh, K.; Lalla, N.P. [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452001 (India)

2017-07-15

Highlights: • Temperature and magnetic field driven coupled magneto-structural phase transition in Nd{sub 0.49}Sr{sub 0.51}MnO{sub 3+δ}. • Microscopic evidence of strong spin-charge-lattice coupling. • Iso-thermal magnetic field driven structure phase transition. • Field-driven structural phase transition origin of observed 1st order type CMR effect. - Abstract: Comprehensive X-ray diffraction (XRD) studies have been performed at different temperature (T) (4.2–300 K) and magnetic field (H) (0–8 T) to understand the evolution of crystal structure of Nd{sub 0.49}Sr{sub 0.51}MnO{sub 3+δ} (NSMO) under non ambient conditions. The T dependent XRD results show the abrupt change in the lattice parameters without any change in lattice symmetry at ∼200 K, which is associated with the first order structural phase transition from ferromagnetic to antiferromagnetic phase. This phase transition is strongly H dependent and shifted to lower temperature (∼150 K) on the application of 8 T field with phase coexistence (high temperature phase ∼18%), even down to 4.2 K. Isothermal XRD results at 150 K under different H clearly illustrate the H induced first order structural phase transition. The critical H at which this phase transformation starts is ∼1 T, with rapid growth above 4 T with hysteretic nature during increasing and decreasing H. These results are supported with the resistivity and magnetoresistance results and affirm the strong spin-lattice coupling in NSMO. Our detail studies reveal the structural correlations to the observed colossal magnetoresistance and magnetocaloric effect in this material.

Accelerator-driven sub-critical target concept for transmutation of nuclear wastes

International Nuclear Information System (INIS)

Van Tuyle, G.J.; Todosow, M.; Aronson, A.L.; Takahashi, H.; Geiger, M.J.

1991-01-01

A means of transmuting key long-lived nuclear wastes, primarily the minor actinides (Np, Am, Cm) and iodine, using a hybrid proton accelerator and sub-critical lattice, is proposed. By partitioning the components of the light water reactor (LWR) spent fuel and by transmuting key elements, such as the plutonium, the minor actinides, and a few of the long-lived fission products, some of the most significant challenges in building a waste repository can be substantially reduced. The proposed machine, based on the described PHOENIX Concept, would transmute the minor actinides and the iodine produced by 75 LWRs, and would generate usable electricity (beyond that required to run the large accelerator) of 850 MW e . 19 refs., 20 figs

Correlations between critical current density, j{sub c}, critical temperature, T{sub c}, and structural quality of Y{sub 1}B{sub 2}Cu{sub 3}O{sub 7-x} thin superconducting films

Energy Technology Data Exchange (ETDEWEB)

Chrzanowski, J.; Xing, W.B.; Atlan, D. [Simon Fraser Univ., British Columbia (Canada)] [and others

1994-12-31

Correlations between critical current density (j{sub c}) critical temperature (T{sub c}) and the density of edge dislocations and nonuniform strain have been observed in YBCO thin films deposited by pulsed laser ablation on (001) LaAlO{sub 3} single crystals. Distinct maxima in j{sub c} as a function of the linewidths of the (00{ell}) Bragg reflections and as a function of the mosaic spread have been found in the epitaxial films. These maxima in j{sub c} indicate that the magnetic flux lines, in films of structural quality approaching that of single crystals, are insufficiently pinned which results in a decreased critical current density. T{sub c} increased monotonically with improving crystalline quality and approached a value characteristic of a pure single crystal. A strong correlation between j{sub c} and the density of edge dislocations N{sub D} was found. At the maximum of the critical current density the density of edge dislocations was estimated to be N{sub D}{approximately}1-2 x 10{sup 9}/cm{sup 2}.

Evaluating laser-driven Bremsstrahlung radiation sources for imaging and analysis of nuclear waste packages

Energy Technology Data Exchange (ETDEWEB)

Jones, Christopher P., E-mail: cj0810@bristol.ac.uk [Interface Analysis Centre, HH Wills Physics Laboratory, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Brenner, Ceri M. [Central Laser Facility, STFC, Rutherford Appleton Laboratory, Didcot, Oxon OX11 0QX (United Kingdom); Stitt, Camilla A. [Interface Analysis Centre, HH Wills Physics Laboratory, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Armstrong, Chris; Rusby, Dean R. [Central Laser Facility, STFC, Rutherford Appleton Laboratory, Didcot, Oxon OX11 0QX (United Kingdom); Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Mirfayzi, Seyed R. [Centre for Plasma Physics, Queen' s University Belfast, Belfast BT7 1NN (United Kingdom); Wilson, Lucy A. [Central Laser Facility, STFC, Rutherford Appleton Laboratory, Didcot, Oxon OX11 0QX (United Kingdom); Alejo, Aarón; Ahmed, Hamad [Centre for Plasma Physics, Queen' s University Belfast, Belfast BT7 1NN (United Kingdom); Allott, Ric [Central Laser Facility, STFC, Rutherford Appleton Laboratory, Didcot, Oxon OX11 0QX (United Kingdom); Butler, Nicholas M.H. [Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Clarke, Robert J.; Haddock, David; Hernandez-Gomez, Cristina [Central Laser Facility, STFC, Rutherford Appleton Laboratory, Didcot, Oxon OX11 0QX (United Kingdom); Higginson, Adam [Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Murphy, Christopher [Department of Physics, University of York, York YO10 5DD (United Kingdom); Notley, Margaret [Central Laser Facility, STFC, Rutherford Appleton Laboratory, Didcot, Oxon OX11 0QX (United Kingdom); Paraskevoulakos, Charilaos [Interface Analysis Centre, HH Wills Physics Laboratory, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Jowsey, John [Ground Floor North B582, Sellafield Ltd, Seascale, Cumbria CA20 1PG (United Kingdom); and others

2016-11-15

Highlights: • X-ray generation was achieved via laser interaction with a tantalum thin foil target. • Picosecond X-ray pulse from a sub-mm spot generated high resolution images. • MeV X-ray emission is possible, permitting analysis of full scale waste containers. • In parallel neutron emission of 10{sup 7}–10{sup 9} neutrons per steradian per pulse was attained. • Development of a 10 Hz diode pumped laser system for waste monitoring is envisioned. - Abstract: A small scale sample nuclear waste package, consisting of a 28 mm diameter uranium penny encased in grout, was imaged by absorption contrast radiography using a single pulse exposure from an X-ray source driven by a high-power laser. The Vulcan laser was used to deliver a focused pulse of photons to a tantalum foil, in order to generate a bright burst of highly penetrating X-rays (with energy >500 keV), with a source size of <0.5 mm. BAS-TR and BAS-SR image plates were used for image capture, alongside a newly developed Thalium doped Caesium Iodide scintillator-based detector coupled to CCD chips. The uranium penny was clearly resolved to sub-mm accuracy over a 30 cm{sup 2} scan area from a single shot acquisition. In addition, neutron generation was demonstrated in situ with the X-ray beam, with a single shot, thus demonstrating the potential for multi-modal criticality testing of waste materials. This feasibility study successfully demonstrated non-destructive radiography of encapsulated, high density, nuclear material. With recent developments of high-power laser systems, to 10 Hz operation, a laser-driven multi-modal beamline for waste monitoring applications is envisioned.

Evaluating laser-driven Bremsstrahlung radiation sources for imaging and analysis of nuclear waste packages

International Nuclear Information System (INIS)

Jones, Christopher P.; Brenner, Ceri M.; Stitt, Camilla A.; Armstrong, Chris; Rusby, Dean R.; Mirfayzi, Seyed R.; Wilson, Lucy A.; Alejo, Aarón; Ahmed, Hamad; Allott, Ric; Butler, Nicholas M.H.; Clarke, Robert J.; Haddock, David; Hernandez-Gomez, Cristina; Higginson, Adam; Murphy, Christopher; Notley, Margaret; Paraskevoulakos, Charilaos; Jowsey, John

2016-01-01

Highlights: • X-ray generation was achieved via laser interaction with a tantalum thin foil target. • Picosecond X-ray pulse from a sub-mm spot generated high resolution images. • MeV X-ray emission is possible, permitting analysis of full scale waste containers. • In parallel neutron emission of 10"7–10"9 neutrons per steradian per pulse was attained. • Development of a 10 Hz diode pumped laser system for waste monitoring is envisioned. - Abstract: A small scale sample nuclear waste package, consisting of a 28 mm diameter uranium penny encased in grout, was imaged by absorption contrast radiography using a single pulse exposure from an X-ray source driven by a high-power laser. The Vulcan laser was used to deliver a focused pulse of photons to a tantalum foil, in order to generate a bright burst of highly penetrating X-rays (with energy >500 keV), with a source size of <0.5 mm. BAS-TR and BAS-SR image plates were used for image capture, alongside a newly developed Thalium doped Caesium Iodide scintillator-based detector coupled to CCD chips. The uranium penny was clearly resolved to sub-mm accuracy over a 30 cm"2 scan area from a single shot acquisition. In addition, neutron generation was demonstrated in situ with the X-ray beam, with a single shot, thus demonstrating the potential for multi-modal criticality testing of waste materials. This feasibility study successfully demonstrated non-destructive radiography of encapsulated, high density, nuclear material. With recent developments of high-power laser systems, to 10 Hz operation, a laser-driven multi-modal beamline for waste monitoring applications is envisioned.

A laser driven source of spin polarized atomic hydrogen and deuterium

International Nuclear Information System (INIS)

Poelker, M.; Coulter, K.P.; Holt, R.J.; Jones, C.E.; Kowalczyk, R.S.; Young, L.; Toporkov, D.

1993-01-01

Recent results from a laser-driven source of polarized hydrogen (H) and deuterium (D) are presented. The performance of the source is described as a function of atomic flow rate and magnetic field. The data suggest that because atomic densities in the source are high, the system can approach spin-temperature equilibrium although applied magnetic fields are much larger than the critical field of the atoms. The authors also observe that potassium contamination in the source emittance can be reduced to a negligible amount using a teflon-lined transport tube

The mechanical design and fabrication of 162.5 MHz buncher for China accelerator driven sub-critical system injector II

Directory of Open Access Journals (Sweden)

Haihua Niu

2017-08-01

Full Text Available A buncher is one of the main pieces of equipment in the medium energy beam transport line (MEBT for China accelerator driven sub-critical system (C-ADS Injector II. To focus the beam longitudinally and match the beam for the acceptance of the superconducting linac section, two room temperature quarter wave resonator (QWR bunchers with frequency of 162.5 MHz have been designed as parts of the MEBT. According to the beam transmission matching of the MEBT and the geometric parameters requirements of bunchers, the unique mechanical structure and the main processing technology of buncher cavities and their couplers and tuners are described in this paper. The fabrication of bunchers and their parts have been completed and tested at high power, the test results agree well with the design requirements. These bunchers work well for about two years in Institute of Modern Physics, Chinese Academy of Sciences.

Cylindrical IEC neutron source design for driven research reactor operation

International Nuclear Information System (INIS)

Miley, G.H.; Ulmen, B.; Amadio, G.; Leon, H.; Hora, H.

2009-01-01

A resurgence in nuclear power use is now underway worldwide. However, due many university research reactors shutdown, they must rely on using subcritical assemblies which employs a cylindrical Inertial Electrostatic Confinement (IEC) device to provide a fusion neutron source. The source is inserted in a fuel element position, with its power input controlled externally at a control panel. This feature opens the way to use of the critical assembly for a number of transient experiments such as sub-critical pulsing and neutron wave propagation. That in turn adds important new insights and excitement for the student teaching laboratory. (author)

Recent advances in laser-driven neutron sources

Science.gov (United States)

Alejo, A.; Ahmed, H.; Green, A.; Mirfayzi, S. R.; Borghesi, M.; Kar, S.

2016-11-01

Due to the limited number and high cost of large-scale neutron facilities, there has been a growing interest in compact accelerator-driven sources. In this context, several potential schemes of laser-driven neutron sources are being intensively studied employing laser-accelerated electron and ion beams. In addition to the potential of delivering neutron beams with high brilliance, directionality and ultra-short burst duration, a laser-driven neutron source would offer further advantages in terms of cost-effectiveness, compactness and radiation confinement by closed-coupled experiments. Some of the recent advances in this field are discussed, showing improvements in the directionality and flux of the laser-driven neutron beams.

Critical currents of Y sub 1 Ba sub 2 Cu sub 3 O sub 7-. delta. ceramics

Energy Technology Data Exchange (ETDEWEB)

Vasiliev, B V; Obukhov, Yu V [Joint Inst. for Nuclear Research, Low Temperature Physics Dept., Moscow (USSR)

1991-12-01

The magnetization measurements on a ceramic YBaCuO sample were carried out. The M(H,T) dependence has demonstrated some peculiarities which we suppose to be connected with H{sub j1}, H{sub j2}, H{sub C1} fields. By analizing the magnetization in the field region between H{sub j1} and H{sub j2} within the frame of the critical state model one can found the dependence of the intergranular critical current density on field and temperature. (orig.).

252Cf-source-driven neutron noise analysis method

International Nuclear Information System (INIS)

Mihalczo, J.T.; King, W.T.; Blakeman, E.D.

1985-01-01

The 252 Cf-source-driven neutron noise analysis method has been tested in a a wide variety of experiments that have indicated the broad range of applicability of the method. The neutron multiplication factor, k/sub eff/ has been satisfactorily determined for a variety of materials including uranium metal, light water reactor fuel pins, fissile solutions, fuel plates in water, and interacting cylinders. For a uranyl nitrate solution tank which is typical of a fuel processing or reprocessing plant, the k/sub eff/ values were satisfactorily determined for values between 0.92 and 0.5 using a simple point kinetics interpretation of the experimental data. The short measurement times, in several cases as low as 1 min, have shown that the development of this method can lead to a practical subcriticality monitor for many in-plant applications. The further development of the method will require experiments and the development of theoretical methods to predict the experimental observables

252Cf-source-driven neutron noise analysis method

International Nuclear Information System (INIS)

Mihalczo, J.T.; King, W.T.; Blakeman, E.D.

1985-01-01

The 252 Cf-source-driven neutron noise analysis method has been tested in a wide variety of experiments that have indicated the broad range of applicability of the method. The neutron multiplication factor k/sub eff/ has been satisfactorily detemined for a variety of materials including uranium metal, light water reactor fuel pins, fissile solutions, fuel plates in water, and interacting cylinders. For a uranyl nitrate solution tank which is typical of a fuel processing or reprocessing plant, the k/sub eff/ values were satisfactorily determined for values between 0.92 and 0.5 using a simple point kinetics interpretation of the experimental data. The short measurement times, in several cases as low as 1 min, have shown that the development of this method can lead to a practical subcriticality monitor for many in-plant applications. The further development of the method will require experiments oriented toward particular applications including dynamic experiments and the development of theoretical methods to predict the experimental observables

Preparation of K-doped TiO{sub 2} nanostructures by wet corrosion and their sunlight-driven photocatalytic performance

Energy Technology Data Exchange (ETDEWEB)

Shin, Eunhye; Jin, Saera; Kim, Jiyoon; Chang, Sung-Jin [Department of Chemistry, Chung-Ang University, Seoul 06974 (Korea, Republic of); Jun, Byung-Hyuk [Neutron Science Division, Korea Atomic Energy Research Institute, Daejeon 34057 (Korea, Republic of); Park, Kwang-Won, E-mail: bryan.kwangwon.park@gmail.com [Department of Chemistry, Chung-Ang University, Seoul 06974 (Korea, Republic of); Hong, Jongin, E-mail: hongj@cau.ac.kr [Department of Chemistry, Chung-Ang University, Seoul 06974 (Korea, Republic of)

2016-08-30

Highlights: • Potassium-doped TiO{sub 2} nanowire networks were prepared by the corrosion reaction of Ti nanoparticles in an alkaline solution. • They were applied to sunlight-driven photocatalytic degradation of differently charged dye molecules. • The adsorption of the dye molecules on the photocatalyst surface is crucial for their sunlight-driven photodegradation. - Abstract: K-doped TiO{sub 2} nanowire networks were prepared by the corrosion reaction of Ti nanoparticles in an alkaline (potassium hydroxide: KOH) solution. The prepared nanostructures were characterized by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) analysis, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, X-ray diffraction (XRD) and photoluminescence (PL) spectra. Their sunlight-driven photocatalytic activity was also investigated with differently charged dye molecules, such as methylene blue, rhodamine B and methyl orange. The adsorption of the dye molecules on the photocatalyst surface would play a critical role in their selective photodegradation under sunlight illumination.

Sub-critical pulsed neutron experiments with uranyl nitrate solutions in spherical geometry

International Nuclear Information System (INIS)

Gurin, Victor N.; Ryazanov, Boris G.; Sviridov, Victor I.; Volnistov, Vladimir V.

2003-01-01

The pulse source method is used to study homogeneous solution assemblies. Three sets of sub-critical pulse experiments with spherical tanks filled with water solution of uranyl nitrate (90% enrichment) were carried out at the RF-GS facility, Obninsk, Russia. Seven spherical tanks with the volume within the range of 1.29 L to 19.8 L were used in the experiments. Three uranium concentrations were studied, i.e. 20.7, 29.6 and 37.5 g/L. The sub-critical experiments were analyzed with the MCNP 4A code based on the Monte-Carlo method, and with ENDF/B-V library. (author)

Accelerator-driven X-ray Sources

Energy Technology Data Exchange (ETDEWEB)

Nguyen, Dinh Cong [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2015-11-09

After an introduction which mentions x-ray tubes and storage rings and gives a brief review of special relativity, the subject is treated under the following topics and subtopics: synchrotron radiation (bending magnet radiation, wiggler radiation, undulator radiation, brightness and brilliance definition, synchrotron radiation facilities), x-ray free-electron lasers (linac-driven X-ray FEL, FEL interactions, self-amplified spontaneous emission (SASE), SASE self-seeding, fourth-generation light source facilities), and other X-ray sources (energy recovery linacs, Inverse Compton scattering, laser wakefield accelerator driven X-ray sources. In summary, accelerator-based light sources cover the entire electromagnetic spectrum. Synchrotron radiation (bending magnet, wiggler and undulator radiation) has unique properties that can be tailored to the users’ needs: bending magnet and wiggler radiation is broadband, undulator radiation has narrow spectral lines. X-ray FELs are the brightest coherent X-ray sources with high photon flux, femtosecond pulses, full transverse coherence, partial temporal coherence (SASE), and narrow spectral lines with seeding techniques. New developments in electron accelerators and radiation production can potentially lead to more compact sources of coherent X-rays.

Experimental study on neutronics in bombardment of thick targets by high energy proton beams for accelerator-driven sub-critical system

CERN Document Server

Guo Shi Lun; Shi Yong Qian; Shen Qing Biao; Wan Jun Sheng; Brandt, R; Vater, P; Kulakov, B A; Krivopustov, M I; Sosnin, A N

2002-01-01

The experimental study on neutronics in the target region of accelerator-driven sub-critical system is carried out by using the high energy accelerator in Joint Institute for Nuclear Research, Dubna, Russia. The experiments with targets U(Pb), Pb and Hg bombarded by 0.533, 1.0, 3.7 and 7.4 GeV proton beams show that the neutron yield ratio of U(Pb) to Hg and Pb to Hg targets is (2.10 +- 0.10) and (1.76 +- 0.33), respectively. Hg target is disadvantageous to U(Pb) and Pb targets to get more neutrons. Neutron yield drops along 20 cm thick targets as the thickness penetrated by protons increases. The lower the energy of protons, the steeper the neutron yield drops. In order to get more uniform field of neutrons in the targets, the energy of protons from accelerators should not be lower than 1 GeV. The spectra of secondary neutrons produced by different energies of protons are similar, but the proportion of neutrons with higher energy gradually increases as the proton energy increases

Quasi-monoenergetic ion beam acceleration by laser-driven shock and solitary waves in near-critical plasmas

Energy Technology Data Exchange (ETDEWEB)

Zhang, W. L.; Qiao, B., E-mail: bqiao@pku.edu.cn; Huang, T. W.; Shen, X. F.; You, W. Y. [Center for Applied Physics and Technology, HEDPS, and State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006 (China); Yan, X. Q. [Center for Applied Physics and Technology, HEDPS, and State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); Wu, S. Z. [Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China); Zhou, C. T.; He, X. T. [Center for Applied Physics and Technology, HEDPS, and State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China)

2016-07-15

Ion acceleration in near-critical plasmas driven by intense laser pulses is investigated theoretically and numerically. A theoretical model has been given for clarification of the ion acceleration dynamics in relation to different laser and target parameters. Two distinct regimes have been identified, where ions are accelerated by, respectively, the laser-induced shock wave in the weakly driven regime (comparatively low laser intensity) and the nonlinear solitary wave in the strongly driven regime (comparatively high laser intensity). Two-dimensional particle-in-cell simulations show that quasi-monoenergetic proton beams with a peak energy of 94.6 MeV and an energy spread 15.8% are obtained by intense laser pulses at intensity I{sub 0} = 3 × 10{sup 20 }W/cm{sup 2} and pulse duration τ = 0.5 ps in the strongly driven regime, which is more advantageous than that got in the weakly driven regime. In addition, 233 MeV proton beams with narrow spread can be produced by extending τ to 1.0 ps in the strongly driven regime.

Critical Source Area Delineation: The representation of hydrology in effective erosion modeling.

Science.gov (United States)

Fowler, A.; Boll, J.; Brooks, E. S.; Boylan, R. D.

2017-12-01

Despite decades of conservation and millions of conservation dollars, nonpoint source sediment loading associated with agricultural disturbance continues to be a significant problem in many parts of the world. Local and national conservation organizations are interested in targeting critical source areas for control strategy implementation. Currently, conservation practices are selected and located based on the Revised Universal Soil Loss Equation (RUSLE) hillslope erosion modeling, and the National Resource Conservation Service will soon be transiting to the Watershed Erosion Predict Project (WEPP) model for the same purpose. We present an assessment of critical source areas targeted with RUSLE, WEPP and a regionally validated hydrology model, the Soil Moisture Routing (SMR) model, to compare the location of critical areas for sediment loading and the effectiveness of control strategies. The three models are compared for the Palouse dryland cropping region of the inland northwest, with un-calibrated analyses of the Kamiache watershed using publicly available soils, land-use and long-term simulated climate data. Critical source areas were mapped and the side-by-side comparison exposes the differences in the location and timing of runoff and erosion predictions. RUSLE results appear most sensitive to slope driving processes associated with infiltration excess. SMR captured saturation excess driven runoff events located at the toe slope position, while WEPP was able to capture both infiltration excess and saturation excess processes depending on soil type and management. A methodology is presented for down-scaling basin level screening to the hillslope management scale for local control strategies. Information on the location of runoff and erosion, driven by the runoff mechanism, is critical for effective treatment and conservation.

Angular dependence of the upper critical field in Bi sub 2 Sr sub 2 CuO sub 6 sub + subdelta

CERN Document Server

Vedeneev, S I

2002-01-01

The angular dependence of the upper critical field has been investigated in a wide range of temperatures in very high-quality Bi sub 2 Sr sub 2 CuO sub 6 sub + subdelta single crystals with critical temperature approx = 9 K in magnetic fields up to 28 T. Although the typical value of the normal state resistivity ratio approx = 10 sup 4 , the anisotropy ratio of the upper critical fields is much smaller. A model is proposed based on a strong anisotropy and a small transparency between superconducting layers

Comparative analysis of performance and techno-economics for a H{sub 2}O-NH{sub 3}-H{sub 2} absorption refrigerator driven by different energy sources

Energy Technology Data Exchange (ETDEWEB)

Abdullah, Mohammad Omar; Hieng, Tang Chung [Department of Chemical Engineering and Energy Sustainability, 94300 Kota Samarahan, Sarawak, East Malaysia (Malaysia)

2010-05-15

The objectives of the present work are of two-folds. First, it evaluates the transient temperature performance of the H{sub 2}O-NH{sub 3}-H{sub 2} absorption cooling machine system's components under two types of energy sources, i.e. the conventional electric energy from grid (electric) and fuel energy from liquid petroleum gas (LPG). Results obtained have shown that performance of various components under different type of energy sources is almost coherent. For the evaporator, the system with electric supply has shorter starting time, around 6 min earlier than the system run with LPG. Meanwhile, the system powered by LPG produced a lower cooling temperature around -9 C, compared to the system run with electric which produced temperature at around -7 C. Economical study had been carried out subsequently, for three different energy sources, i.e. electric, LPG and solar energy (photovoltaic). From the techno-economical analyzes, it was found that the conventional electric from grid is still the best form of energy source for short-term application, as far as the present location and conditions are concerned. LPG is the next attractive energy source, especially at locations with constant LPG supply; the photovoltaic energy from solar is attractive for long term consideration since it has zero fuel cost and environmentally-friendly, but with the highest initial cost. (author)

Fast accelerator driven subcritical system for energy production: nuclear fuel evolution

International Nuclear Information System (INIS)

Barros, Graiciany de P.; Pereira, Claubia; Veloso, Maria A.F.; Costa, Antonella L.

2011-01-01

Accelerators Driven Systems (ADS) are an innovative type of nuclear system, which is useful for long-lived fission product transmutation and fuel regeneration. The ADS consist of a coupling of a sub-critical nuclear core reactor and a proton beam produced by a particle accelerator. These particles are injected into a target for the neutrons production by spallation reactions. The neutrons are then used to maintain the fission chain in the sub-critical core. The aim of this study is to investigate the nuclear fuel evolution of a lead cooled accelerator driven system used for energy production. The fuel studied is a mixture based upon "2"3"2Th and "2"3"3U. Since thorium is an abundant fertile material, there is hope for the thorium-cycle fuels for an accelerator driven sub-critical system. The target is a lead spallation target and the core is filled with a hexagonal lattice. High energy neutrons are used to reduce the negative reactivity caused by the presence of protoactinium, since this effect is most pronounced in the thermal range of the neutron spectrum. For that reason, such material is not added moderator to the system. In this work is used the Monte Carlo code MCNPX 2.6.0, that presents the the depletion/ burnup capability. The k_e_f_f evolution, the neutron energy spectrum in the core and the nuclear fuel evolution using ADS source (SDEF) and kcode-mode are evaluated during the burnup. (author)

Estimation of the sub-criticality of the sodium-cooled fast reactor Monju using the modified neutron source multiplication method

International Nuclear Information System (INIS)

Truchet, G.; Van Rooijen, W. F. G.; Shimazu, Y.; Yamaguchi, K.

2012-01-01

The Modified Neutron Source Method (MNSM) is applied to the Monju reactor. This static method to estimate sub-criticality has already given good results on commercial Pressurized Water Reactors. The MNSM consists both in the extraction of the fundamental mode seen by a detector to avoid the effect of higher modes near sources, and the correction of flux distortion effects due to control rod movement. Among Monju's particularities that have a big influence on MNSM factors are: the presence of two californium sources and the position of the detector which is located far from the core outside of the reactor vessel. The importance of spontaneous fission and (α, n) reactions which have increased during the shutdown period of 15 years will also be discussed. The relative position of detectors and sources deeply affect the correction factors in some regions. In order to evaluate the detector count rate, an analytical propagation has been conducted from the reactor vessel. For two subcritical states, an estimation of the reactivity has been made and compared to experimental data obtained in the restart experiments at Monju (2010). (authors)

Critical current anisotropy in Ag/(Pb,Bi){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10+x} multifilamentary tapes: influence of self-magnetic field

Energy Technology Data Exchange (ETDEWEB)

Majoros, M [IRC in Superconductivity, University of Cambridge, Cambridge (United Kingdom); Institute of Electrical Engineering, Slovak Academy of Sciences, Bratislava (Slovakia); Glowacki, B A [IRC in Superconductivity, University of Cambridge, Cambridge (United Kingdom); Department of Materials Science and Metallurgy, University of Cambridge, Cambridge (United Kingdom); Campbell, A M [IRC in Superconductivity, University of Cambridge, Cambridge (United Kingdom)

2001-06-01

Two factors affect critical current anisotropy in multifilamentary Ag/(Pb,Bi){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10+x} tapes - the intrinsic material anisotropy and the geometry. Experimental results on the magnetic field dependence and anisotropy of the critical current in a multifilamentary Ag/(Pb,Bi){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10+x} tape after correction for self-magnetic field effects were found to fit the anisotropic Kim relation. Based on this relation a finite-element-method numerical code for solving the nonlinear Poisson equation for vector magnetic potential was adopted. It allowed the experimental data to be reproduced by back calculation and made possible the study of the interplay of self and external magnetic fields in different cases with well defined physical parameters of the material. The model was used to analyse the distribution of the critical current in individual filaments as well as to evaluate the influence of their geometrical arrangements on the critical current of the tape. The self-field critical current of an individual filament 'extracted' from the tape was compared with the critical current of the overall tape. The effect of the self-magnetic field on critical current distribution obtained by the cutting method was determined. The critical currents of the tapes with different cross sections were calculated and compared with experiments and the influence of the self-field was analysed. The anisotropic properties of a low anisotropy architecture of a multifilamentary Ag/(Pb,Bi){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10+x} conductor were studied. The dependence of critical currents (normalized to self-field critical currents) on external magnetic field corrected for the self-field was found to follow nearly the same curves as those for tapes with different critical current densities (in the range 20-70 kA cm{sup -2} in a self-field), which makes the numerical model applicable to different tapes. (author)

Evaluation of the 252Cf-source-driven neutron noise analysis method for measuring the subcriticality of LWR fuel storage casks

International Nuclear Information System (INIS)

Mihalczo, J.T.

1987-01-01

The 252 Cf-source-driven neutron noise analysis method was evaluated to determine if it could be used to measure the subcriticality of storage casks of burnt LWR fuel submerged in fuel storage pools, fully loaded and as they are being loaded. The motivation for this evaluation was that measurements of k/sub eff/ would provide the parameter most directly related to the criticality safety of storage cask configurations of LWR fuel and could allow proper credit for fuel burnup without reliance on calculations. This in turn could lead to more cost-effective cask designs. Evaluation of the method for this application was based on (1) experiments already completed at a critical experiments facility using arrays of PWR fuel pins typical of the size of storage cask configurations, (2) the existence of neutron detectors that can function in shipping cask environments, and (3) the ability to construct ionization chambers containing 252 Cf of adequate intensity for these measurements. These three considerations are discussed

Bias in calculated keff from subcritical measurements by the 252Cf-source-driven noise analysis method

International Nuclear Information System (INIS)

Mihalczo, J.T.; Valentine, T.E.

1995-01-01

The development of MCNP-DSP, which allows direct calculation of the measured time and frequency analysis parameters from subcritical measurements using the 252 Cf-source-driven noise analysis method, permits the validation of calculational methods for criticality safety with in-plant subcritical measurements. In addition, a method of obtaining the bias in the calculations, which is essential to the criticality safety specialist, is illustrated using the results of measurements with 17.771-cm-diam, enriched (93.15), unreflected, and unmoderated uranium metal cylinders. For these uranium metal cylinders the bias obtained using MCNP-DSP and ENDF/B-V cross-section data increased with subcriticality. For a critical experiment [height (h) = 12.629 cm], it was -0.0061 ± 0.0003. For a 10.16-cm-high cylinder (k ∼ 0.93), it was 0.0060 ± 0.0016, and for a subcritical cylinder (h = 8.13 cm, k ∼ 0.85), the bias was -0.0137 ± 0.0037, more than a factor of 2 larger in magnitude. This method allows the nuclear criticality safety specialist to establish the bias in calculational methods for criticality safety from in-plant subcritical measurements by the 252 Cf-source-driven noise analysis method

Physics study of D-D/D-T neutron driven experimental subcritical assembly

International Nuclear Information System (INIS)

Sinha, Amar

2015-01-01

An experimental program to design and study external source driven subcritical assembly has been initiated at BARC. This program is aimed at understanding neutronic characteristics of accelerator driven system at low power level. In this series, a zero-power, sub-critical assembly driven by a D-D/D-T neutron generator has been developed. This system is modular in design and it is first in the series of subcritical assemblies being designed. The subcritical core consists of natural uranium fuel with high density polyethylene as moderator and beryllium oxide as reflector. The subcritical core is coupled to Purnima Neutron Generator. Preliminary experiments have been carried out for spatial flux measurement and reactivity estimation using pulsed neutron source (PNS) techniques. Further experiments are being planned to measure the reactivity and other kinetic parameters using noise methods. This facility would also be used for carrying out studies on effect of source importance and measurement of source multiplication factor k s and external neutron source efficiency φ* in great details. Some experiments with D-D and D-T neutrons have been presented. (author)

Analytical solution of point kinetic equations for sub-critical systems

International Nuclear Information System (INIS)

Henrice Junior, Edson; Goncalves, Alessandro C.

2013-01-01

This article presents an analytical solution for the set of point kinetic equations for sub-critical reactors. This solution stems from the ordinary, non-homogeneous differential equation that rules the neutron density and that presents the incomplete Gamma function in its functional form. The method used proved advantageous and allowed practical applications such as the linear insertion of reactivity, considering an external constant source or with both varying linearly. (author)

Evaluation of Importance of Source Neutrons in Accelerator-Driven System

International Nuclear Information System (INIS)

Kim, Yong Hee; Park, Won Seok

2002-01-01

An importance function of the external spallation neutrons in ADS (Accelerator-Driven System) is defined to characterize the source multiplication in subcritical blanket. For a model ADS problem, the source importance function is evaluated with the TRANSX/TWODANT code system. In order to assess the impact of the power distribution on the importance function, both homogeneous and heterogeneous cores are analyzed and corresponding source multiplications are compared. Also, based on the source importance function, an optimization of the shape of the proton current is performed from the source multiplication point of view. Additionally, the source importance function is compared with the conventional λ-mode adjoint flux, which is used as an importance function of fission neutrons in the critical reactors. Concerning an issue in the ADS design, i.e., difficulty in reducing the fission power unless the proton current is shut off, a study is performed to minimize the source importance, thereby minimizing the fission power, even when the k-eff value of the core is quite high. (authors)

Critical radius and critical number of gas atoms for cavities containing a Van der Waals gas

International Nuclear Information System (INIS)

Coghlan, W.A.; Mansur, L.K.

1983-01-01

The effect of gas on void nucleation and growth is particularly important for structural materials in fusion reactors because of the high production of helium by neutron-induced transmutation reactions. Gas reduces the critical radius for bias driven growth and there is a critical number of gas atoms, n/sub g/*, at which the critical radius is reduced essentially to zero. The significance of this is that the time interval to the accumulation of n/sub g/* gas atoms may determine the time to the onset of bias driven swelling where n/sub g/* is large. In previous papers these critical quantities were given for an ideal gas. Recently, we presented the results for a Van der Waals gas. Here the derivation of these relations is presented and further results of calculations are given. At low temperatures (high pressures) the results depart from those of the ideal gas, with the critical number affected more strongly than the critical radius. Comparisons are made with earlier calculations

Interferometrically enhanced sub-terahertz picosecond imaging utilizing a miniature collapsing-field-domain source

Science.gov (United States)

Vainshtein, Sergey N.; Duan, Guoyong; Mikhnev, Valeri A.; Zemlyakov, Valery E.; Egorkin, Vladimir I.; Kalyuzhnyy, Nikolay A.; Maleev, Nikolai A.; Näpänkangas, Juha; Sequeiros, Roberto Blanco; Kostamovaara, Juha T.

2018-05-01

Progress in terahertz spectroscopy and imaging is mostly associated with femtosecond laser-driven systems, while solid-state sources, mainly sub-millimetre integrated circuits, are still in an early development phase. As simple and cost-efficient an emitter as a Gunn oscillator could cause a breakthrough in the field, provided its frequency limitations could be overcome. Proposed here is an application of the recently discovered collapsing field domains effect that permits sub-THz oscillations in sub-micron semiconductor layers thanks to nanometer-scale powerfully ionizing domains arising due to negative differential mobility in extreme fields. This shifts the frequency limit by an order of magnitude relative to the conventional Gunn effect. Our first miniature picosecond pulsed sources cover the 100-200 GHz band and promise milliwatts up to ˜500 GHz. Thanks to the method of interferometrically enhanced time-domain imaging proposed here and the low single-shot jitter of ˜1 ps, our simple imaging system provides sufficient time-domain imaging contrast for fresh-tissue terahertz histology.

Accelerator Driven Sub-Critical System for the Radioactive Waste Transmutation

International Nuclear Information System (INIS)

Avramovic, I.; Pesic, M.

2008-01-01

Spent nuclear fuel discharged from nuclear power plants is the main problem during design of radioactive waste disposal. Most of the hazard stems from only a few chemical elements. The radiotoxicity of these elements can be efficiently reduced using partitioning and transmutation in fast reactors and accelerator driven subcritical systems. (author)

Superconducting critical state of Bi[sub 2]Sr[sub 2]CaCu[sub 2]O[sub 8]: two-dimensional effects at low temperatures

Energy Technology Data Exchange (ETDEWEB)

Rodriguez, E. (Comision Nacional de Energia Atomica, Centro Atomico Bariloche (Argentina)); Goffman, M.F. (Comision Nacional de Energia Atomica, Centro Atomico Bariloche (Argentina)); Arribere, A. (Comision Nacional de Energia Atomica, Centro Atomico Bariloche (Argentina)); Cruz, F. de la (Comision Nacional de Energia Atomica, Centro Atomico Bariloche (Argentina)); Schneemeyer, L.F. (AT and T Bell Labs., Murray Hill, NJ (United States))

1994-02-01

The critical current in the c direction of Bi[sub 2]Sr[sub 2]CaCu[sub 2]O[sub 8] is shown to increase with temperature in low temperature ZFC measurements. The results are consistent with a loss of the c direction long range phase correlation, induced by the temperature dependent critical current flowing in the ab planes. As a result of this and the loss of the long range correlation induced by thermal disorder, the low temperature electrical resistance of the ZFC critical state is finite at low temperatures, becomes zero and is finite again at higher temperature. (orig.)

252Cf-source-driven neutron noise measurements of subcriticality for a slab tank containing aqueous Pu-U nitrate

International Nuclear Information System (INIS)

Mihalczo, J.T.; Blakeman, E.D.; Ragan, G.E.; Kryter, R.C.; Robinson, R.C.; Seino, H.

1987-08-01

In order to study nuclear criticality safety related to the development of fast breeder technology, 252 Cf-source-driven neutron noise analysis measurements were performed with a Pu-U nitrate solution in a slab tank of various heights and thickness varying 11.43 cm to 19.05 cm. The results and conclusions of these experiments are (1) a capability to measure the subcriticality of a multiplying system of slab geometry to a k/sub eff/ as low as 0.7 was demonstrated, (2) calculated neutron multiplication factors agreed with those from the experiments within ∼0.02, and (3) the applicability of the method for plutonium solution systems was demonstrated. This paper describes measurements in which the height of the slab was varied for a fixed thickness and the thickness varied for a fixed height, which are the first applications of this measurement method to slab geometry

Optimization by simulation of the coupling between a sub-critical reactor and its spallation source. Towards a pilot reactor

International Nuclear Information System (INIS)

Kerdraon, D.

2001-10-01

Accelerator Driven Systems (ADS), based on a proton accelerator and a sub-critical core coupled with a spallation target, offer advantages in order to reduce the nuclear waste radiotoxicity before repository closure. Many studies carried out on the ADS should lead to the definition of an experimental plan which would federate the different works in progress. This thesis deals with the neutronic Monte Carlo simulations with the MCNPX code to optimize such a system in view of a pilot reactor building. First, we have recalled the main neutronic properties of an hybrid reactor. The concept of gas-cooled eXperimental Accelerator Driven System (XADS) chosen for our investigations comes from the preliminary studies done by the Framatome company. In order to transmute minor actinides, we have considered the time evolution of the main fuels which could be reasonably used for the demonstration phases. The neutronic parameters of the reactor, concerning minor actinide transmutation, are reported. Also, we have calculated the characteristic times and the transmutation rates in the case of 99 Tc and 129 I isotopes. We have identified some neutronic differences between an experimental and a power ADS according to the infinite multiplication coefficient, the shape factor and the level of flux to extend the demonstrator concept. We have proposed geometric solutions to keep the radial shape factor of a power ADS acceptable. In the last part, beyond the experimental XADS scope, we have examined the possible transition towards an uranium/thorium cycle based on Molten Salt Reactors using a power ADS in order to generate the required 233 U proportion. (author)

Source driven breeding thermal power reactors

International Nuclear Information System (INIS)

Greenspan, E.; Ben-Gurion Univ. of the Negev, Beersheba

1978-03-01

The feasibility of fusion devices operating in the semi-catalyzed deuterium (SCD) mode and of high energy proton accelerators to provide the neutron sources for driving subcritical breeding light water power reactors is assessed. The assessment is done by studying the energy balance of the resulting source driven light water reactors (SDLWR) and comparing it with the energy balance of the reference light water hybrid reactors (LWHR) driven by a D-T neutron source (DT-LWHR). The conditions the non-DT neutron sources should satisfy in order to make the SDLWR viable power reactors are identified. It is found that in order for a SCD-LWHR to have the same overall efficiency as a DT-LWHR, the fusion energy gain of the SCD device should be at least one half that the DT device. The efficienct of ADLWRs using uranium targets is comparable with that of DT-LWHRs having a fusion energy gain of unity. Advantages and disadvantages of the DT-LWHR, SCD-LWHR and ADLWR are discussed. (aurthor)

Optical properties and visible-light-driven photocatalytic activity of Bi{sub 8}V{sub 2}O{sub 17} nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Pu, Yinfu; Liu, Ting; Huang, Yanlin [Soochow University, College of Chemistry, Chemical Engineering and Materials Science (China); Chen, Cuili; Kim, Sun Il; Seo, Hyo Jin, E-mail: hjseo@pknu.ac.kr [Pukyong National University, Department of Physics and Interdisciplinary Program of Biomedical, Mechanical & Electrical Engineering (Korea, Republic of)

2015-05-15

Bi{sub 8}V{sub 2}O{sub 17} (4Bi{sub 2}O{sub 3}·V{sub 2}O{sub 5}) nanoparticles with the uniform size of about 50 nm were fabricated through the Pechini method. The crystal structure was investigated by X-ray powder diffraction and the structural refinement. The surface of the as-synthesized samples was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy, and X-ray photoelectron spectroscopy. The optical properties, band structure, and the degradation mechanisms were discussed. The experimental results demonstrate that Bi{sub 8}V{sub 2}O{sub 17} nanoparticles have an efficient visible-light absorption with band-gap energy of 1.85 eV and a direct allowed electronic transition. The photocatalytic activity was evaluated by the photodegradation of the methylene blue (MB) under visible-light irradiation (λ > 420 nm) as a function of time. These results indicate that Bi{sub 8}V{sub 2}O{sub 17} could be a potential photocatalyst driven by visible light. The effective photocatalytic activity was discussed on the base of the crystal structure characteristic.

Modelling of an experiment for the study of neutron spallation source at JINR

International Nuclear Information System (INIS)

Kumawat, Harphool; Goyal, Uttam; Kumar, V.; Barashenkov, V.S.

2002-01-01

Intense neutron spallation source (INSS) is a necessary requirement of accelerator driven sub-critical systems. INSS are proposed to be generated using the high current proton beams. Some studies are conducted for the neutron flux, transmutation rates and energy gains and a larger number of related experiments are being planned

Safety physics inter-comparison of advanced concepts of critical reactors and ADS

International Nuclear Information System (INIS)

Slessarev, I.

2001-01-01

Enhanced safety based on the principle of the natural ''self-defence'' is one of the most desirable features of innovative nuclear systems (critical or sub-critical) regarding both TRU transmutation and ''clean'' energy producer concepts. For the evaluation of the ''self-defence'' domain, the method of the asymptotic reactivity balance has been generalised. The promising option of Hybrids systems (that use a symbiosis of fission and spallation in sub-critical cores) which could benefit the advantages of both Accelerated Driven Systems of the traditional type and regular critical systems, has been advocated. General features of Hybrid dynamics have been presented and analysed. It was demonstrated that an external neutron source of Hybrids can expand the inherent safety potential significantly. This analysis has been applied to assess the safety physics potential of innovative concepts for prospective nuclear power both for energy producers and for transmutation. It has been found, that safety enhancement goal defines a choice of sub-criticality of Hybrids. As for energy producers with Th-fuel cycle, a significant sub-criticality level is required due to a necessity of an improvement of neutronics together with safety enhancement task. (author)

A visible-light-driven photocatalytic activity of vanadate garnet AgCa{sub 2}Ni{sub 2}V{sub 3}O{sub 12} nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Lu, Yuting; Chen, Luyang; Li, Yuze; Huang, Yanlin [Soochow University, College of Chemistry, Chemical Engineering and Materials Science (China); Cheng, Han; Seo, Hyo Jin, E-mail: hjseo@pknu.ac.kr [Pukyong National University, Department of Physics and Interdisciplinary Program of Biomedical, Mechanical and Electrical Engineering (Korea, Republic of)

2015-10-15

A visible-light-driven photocatalyst of nanosized vanadate garnet AgCa{sub 2}Ni{sub 2}V{sub 3}O{sub 12} was prepared by a modified Pechini method. The nanoparticles were characterized with the measurements such as X-ray powder diffraction (XRD) and structural refinements, scanning electron microscope (SEM), and UV–visible (UV–Vis) absorption spectrum. The sample has an efficient absorption in the UV–Vis light region with a narrow band-gap energy of 2.16 eV and an indirect allowed electronic transition. Besides, the photocatalysis of AgCa{sub 2}Ni{sub 2}V{sub 3}O{sub 12} nanoparticles was evaluated by photo-degradation of methylene blue under visible-light irradiation, which shows excellent photocatalytic activity. The effective photocatalytic activity was discussed on the base of the garnet crystal structure such as the activated optical centers of Ni–O octahedron and V–O tetrahedral, highly distorted Ag–O dodecahedra, and long V–V distance in the lattices.

Laser driven white light source for BRDF measurement

DEFF Research Database (Denmark)

Amdemeskel, Mekbib Wubishet; Thorseth, Anders; Dam-Hansen, Carsten

2017-01-01

In this paper, we will present a setup with laser driven light source (LDLS) for measuring a 2D bidirectional reflectance distribution function (BRDF). We have carried out measurements to acquire the BRDF of different samples based on our setup: which consists of a new laser driven broadband light...... source (UV-VIS-NIR), spectroradiometer and sample holder stepper motor in a dark UV-protected environment. Here, we introduced a special kind of light source which has a bright, stable, broad spectral range and well collimated light output to give a very good angular resolution. The experimental results...

LaCu<sub>6-xsub>Ag_{x>: A promising host of an elastic quantum critical point}

Energy Technology Data Exchange (ETDEWEB)

Poudel, Lekh [ORNL; Dela Cruz, Clarina R. [ORNL; Koehler, Michael R. [University of Tennessee, Knoxville (UTK); McGuire, Michael A. [ORNL; Keppens, Veerle [University of Tennessee, Knoxville (UTK); Mandrus, David [ORNL; Christianson, Andrew D. [ORNL

2018-05-01

Structural properties of LaCu<sub>6-xsub>Ag<sub>x> have been investigated using neutron and x-ray diffraction, and resonant ultrasound spectroscopy (RUS) measurements. Diffraction measurements indicate a continuous structural transition from orthorhombic (Pnma) to monoclinic (P2₁/C) structure. RUS measurements show softening of natural frequencies at the structural transition, consistent with the elastic nature of the structural ground state. The structural transition temperatures in LaCu<sub>6-xsub>Agx> decrease with Ag composition until the monoclinic phase is completely suppressed at x<sub>c>=0.225. All of the evidence is consistent with the presence of an elastic quantum critical point in LaCu_6-xsub>Agx>.

Estimated critical conditions for UO[sub 2]F[sub 2]--H[sub 2]O systems in fully water-reflected spherical geometry

Energy Technology Data Exchange (ETDEWEB)

Jordan, W.C.; Turner, J.C.

1992-12-01

The purpose of this report is to document reference calculations performed using the SCALE-4.0 code system to determine the critical parameters of UO[sub 2]F[sub 2]-H[sub 2]O spheres. The calculations are an extension of those documented in ORNL/CSD/TM-284. Specifically, the data for low-enriched UO[sub 2]F[sub 2]-H[sub 2]O spheres have been extended to highly enriched uranium. These calculations, together with those reported in ORNL/CSD/TM-284, provide a consistent set of critical parameters (k[sub [infinity

Microstructure and critical current of superconducting YBa/sub 2/Cu/sub 3/Osub(7-x)

Energy Technology Data Exchange (ETDEWEB)

Camps, R A; Evetts, J E; Glowacki, B A; Newcomb, S B; Somekh, R E; Stobbs, W M

1987-09-17

The authors present the main results of a detailed electron microscopical study of sintered YBa/sub 2/Cu/sub 3/0sub(7-x), and discuss their relevance to observed critical current and its modification by increased silicon impurity levels. In the light of these results, the prospects are assessed for controlling microstructure development so as to optimize the critical current for technological application.

On Mixed Data and Event Driven Design for Adaptive-Critic-Based Nonlinear $H_{\\infty}$ Control.

Science.gov (United States)

Wang, Ding; Mu, Chaoxu; Liu, Derong; Ma, Hongwen

2018-04-01

In this paper, based on the adaptive critic learning technique, the control for a class of unknown nonlinear dynamic systems is investigated by adopting a mixed data and event driven design approach. The nonlinear control problem is formulated as a two-player zero-sum differential game and the adaptive critic method is employed to cope with the data-based optimization. The novelty lies in that the data driven learning identifier is combined with the event driven design formulation, in order to develop the adaptive critic controller, thereby accomplishing the nonlinear control. The event driven optimal control law and the time driven worst case disturbance law are approximated by constructing and tuning a critic neural network. Applying the event driven feedback control, the closed-loop system is built with stability analysis. Simulation studies are conducted to verify the theoretical results and illustrate the control performance. It is significant to observe that the present research provides a new avenue of integrating data-based control and event-triggering mechanism into establishing advanced adaptive critic systems.

Development of reactivity feedback effect measurement techniques under sub-critical condition in fast reactors

International Nuclear Information System (INIS)

Kitano, A.; Nishi, H.; Suzuki, T.; Okajima, S.; Kanemoto, S.

2012-01-01

The first-of-a-kind reactor has been licensed by a safety examination of the plant design based on the measured data in precedent mock-up experiments. The validity of the safety design can be confirmed without a mock-up experiment, if the reactor feed-back characteristics can be measured before operation, with the constructed reactor itself. The 'Synthesis Method', a systematic and sophisticated method of sub-criticality measurement, is proposed in this work to ensure the safety margin before operation. The 'Synthesis Method' is based on the modified source multiplication method (MSM) combined with the noise analysis method to measure the reference sub-criticality level for MSM. A numerical simulation for the control-rod reactivity worth and the isothermal feed-back reactivity was conducted for typical fast reactors of 100 MWe-size, 300 MWe-size, 750 MWe-size, and 1500 MWe-size to investigate the applicability of Synthesis Method. The number of neutron detectors and their positions necessary for the measurement were investigated for both methods of MSM and the noise analysis by a series of parametric survey calculations. As a result, it was suggested that a neutron detector located above the core center and three or more neutron detectors located above the radial blanket region enable the measurement of sub-criticality within 10% uncertainty from -$0.5 to -$2 and within 15% uncertainty for the deeper sub-criticality. (authors)

Critical parameters and saturated density of trifluoroiodomethane (CF{sub 3}I)

Energy Technology Data Exchange (ETDEWEB)

Duan, Y.Y.; Shi, L.; Zhu, M.S.; Han, L.Z. [Tsinghua Univ., Beijing (China). Dept. of Thermal Engineering

1999-05-01

The vapor-liquid coexistence curve of trifluoroiodomethane (CF{sub 3}I) was measured by visual observation of the meniscus disappearance in an optical cell. Thirty-two saturated density data points were obtained along the vapor-liquid coexistence curve between 384.5 and 2024.9 kg/m{sup 3} in the temperature range from 301.02 K to the critical temperature. The experimental uncertainties in temperature and density were estimated to be within {+-}10 mK and {+-}0.5%, respectively. Measurements near the critical point were used to determine the critical temperature T{sub c} = 396.44 {+-} 0.01 K and the critical density {rho}{sub c} = 868 {+-} 3 kg/m{sup 3} for trifluoroiodomethane (CF{sub 3}I) on the basis of the meniscus disappearing level as well as the intensity of the critical opalescence. The critical pressure {rho}{sub c} = 3.953 {+-} 0.005 MPa was extrapolated from the existing vapor pressure equation proposed previously using the present {Tc} value. The critical exponent, {beta}, was also determined, and correlations of the saturated liquid and saturated vapor densities of CF{sub 3}I were developed.

Effect of pelletization pressure on structural properties and critical current hysteresis of ceramic superconducting Bi sub 1 sub . sub 7 Pb sub 0 sub . sub 3 Sr sub 2 Ca sub 2 Cu sub 3 O sub y

CERN Document Server

Tepe, M; Abukay, D

2003-01-01

The effect of pelletization pressures on structural properties and critical current hysteresis of Bi sub 1 sub . sub 7 Pb sub 0 sub . sub 3 Sr sub 2 Ca sub 2 Cu sub 3 O sub y samples was investigated. The samples used in this study were prepared by classical solid-state reaction at the pressures from 100 up to 500 MPa. The obtained samples were characterized by resistance vs. temperature, (R-T), critical current density vs. applied magnetic field, (J sub c -H), material density vs. pressure, (rho-P), XRD, SEM, and EDAX. The results of this study showed that the quality of electrical and structural properties of Bi-2223 bulk superconductors strongly depends on the pelletization pressure. Pressing of bulk samples at 400 MPa produces textured grain alignment and associates microstructural modifications in order to enhance flux pinning and thus increases current carrying capacities. (Abstract Copyright [2003], Wiley Periodicals, Inc.)

Estimated Critical Conditions for UO(Sub 2)F(Sub 2)-H(Sub 2)O Systems in Fully Water-Reflected Spherical Geometry

Energy Technology Data Exchange (ETDEWEB)

Jordan, W.C.

1992-01-01

The purpose of this report is to document reference calculations performed using the SCALE-4.0 code system to determine the critical parameters of UO{sub 2}F{sub 2}-H{sub 2}O spheres. The calculations are an extension of those documented in ORNL/CSD/TM-284. Specifically, the data for low-enriched UO{sub 2}F{sub 2}-H{sub 2}O spheres have been extended to highly enriched uranium. These calculations, together with those reported in ORNL/CSD/TM-284, provide a consistent set of critical parameters (k{sub {infinity}}, volume, mass, mass of water) for UO{sub 2}F{sub 2} and water over the full range of enrichment and moderation ratio.

Estimated critical conditions for UO{sub 2}F{sub 2}--H{sub 2}O systems in fully water-reflected spherical geometry

Energy Technology Data Exchange (ETDEWEB)

Jordan, W.C.; Turner, J.C.

1992-12-01

The purpose of this report is to document reference calculations performed using the SCALE-4.0 code system to determine the critical parameters of UO{sub 2}F{sub 2}-H{sub 2}O spheres. The calculations are an extension of those documented in ORNL/CSD/TM-284. Specifically, the data for low-enriched UO{sub 2}F{sub 2}-H{sub 2}O spheres have been extended to highly enriched uranium. These calculations, together with those reported in ORNL/CSD/TM-284, provide a consistent set of critical parameters (k{sub {infinity}}, volume, mass, mass of water) for UO{sub 2}F{sub 2} and water over the full range of enrichment and moderation ratio.

Recent developments in laser-driven polarized sources

International Nuclear Information System (INIS)

Young, L.; Coulter, K.P.; Holt, R.J.; Kinney, E.R.; Kowalczyk, R.S.; Potterveld, D.H.; Zghiche, A.

1990-01-01

Recent progress in the performance of laser-driven sources of polarized hydrogen and deuterium is described. The current status of the prototype source, I = 2.5 x 10 17 s -1 , polarization = 0.29 (including atomic fraction), is comparable to classical Stern-Gerlach sources. A scheme to improve source performance by approximately an order of magnitude, using a combination of optical-pumping spin-exchange and RF transitions, is outlined. 8 refs., 2 figs., 1 tab

Source driven breeding thermal power reactors

International Nuclear Information System (INIS)

Greenspan, E.; Schneider, A.; Misulovin, A.; Gilai, D.; Levin, P.; Ben-Gurion Univ. of the Negev, Beersheba

1978-03-01

Improvements in the performance of fission power reactors made possible by designing them subcritical driven by D-T neutron sources are investigated. Light-water thermal systems are found to be most promising, neutronically and energetically, for the source driven mode of operation. The range of performance characteristics expected from breeding Light Water Hybrid Reactors (LWHR) is defined. Several promising types of LWHR blankets are identified. Options opened for the nuclear energy strategy by four types of the LWHRs are examined, and the potential contribution of these LWHRs to the nuclear energy economy are discussed. The power systems based on these LWHRs are found to enable a high utilization of the energy content of the uranium resources in all forms available - including depleted uranium and spent fuel from LWRs, while being free from the need for uranium enrichment and plutonium separation capabilities. (author)

Achieving simultaneous CO{sub 2} and H{sub 2}S conversion via a coupled solar-driven electrochemical approach on non-precious-metal catalysts

Energy Technology Data Exchange (ETDEWEB)

Ma, Weiguang; Yu, Wei; Zong, Xu; Li, Can [State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian National Laboratory for Clean Energy, The Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Dalian (China); Wang, Hong; Wang, Xiaomei; Xu, Zhiqiang [State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian National Laboratory for Clean Energy, The Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Dalian (China); University of Chinese Academy of Sciences, Beijing (China)

2018-03-19

Carbon dioxide (CO{sub 2}) and hydrogen sulfide (H{sub 2}S) are generally concomitant with methane (CH{sub 4}) in natural gas and traditionally deemed useless or even harmful. Developing strategies that can simultaneously convert both CO{sub 2} and H{sub 2}S into value-added products is attractive; however it has not received enough attention. A solar-driven electrochemical process is demonstrated using graphene-encapsulated zinc oxide catalyst for CO{sub 2} reduction and graphene catalyst for H{sub 2}S oxidation mediated by EDTA-Fe{sup 2+}/EDTA-Fe{sup 3+} redox couples. The as-prepared solar-driven electrochemical system can realize the simultaneous conversion of CO{sub 2} and H{sub 2}S into carbon monoxide and elemental sulfur at near neutral conditions with high stability and selectivity. This conceptually provides an alternative avenue for the purification of natural gas with added economic and environmental benefits. (copyright 2018 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

K/sub infinity/-meter concept verified via subcritical-critical TRIGA experiments

International Nuclear Information System (INIS)

Ocampo Mansilla, H.

1983-01-01

This work presents a technique for building a device to measure the k/sub infinity/ of a spent nuclear fuel assembly discharged from the core of a nuclear power plant. The device, called a k/sub infinity/-meter, consists of a cross-shaped subcritical assembly, two artificial neutron sources, and two separate neutron counting systems. The central position of the subcritical assembly is used to measure k/sub infinity/ of the spent fuel assembly. The initial subcritical assembly is calibrated to determine its k/sub eff/ and verify the assigned k/sub infinity/ of a selected fuel assembly placed in the central position. Count rates are taken with the fuel assembly of known k/sub infinity/'s placed in the central position and then repeated with a fuel assembly of unknown k/sub infinity/ placed in the central position. The count rate ratio of the unknown fuel assembly to the known fuel assembly is used to determine the k/sub infinity/ of the unknown fuel assembly. The k/sub infinity/ of the unknown fuel assembly is represented as a polynomial function of the count rate ratios. The coefficients of the polynomial equation are determined using the neutronic codes LEOPARD and EXTERMINATOR-II. The analytical approach has been validated by performing several subcritical/critical experiments, using the Penn State Breazeale TRIGA Reactor (PSBR), and comparing the experimental results with the calculations

Experimental study of adsorption chiller driven by variable heat source

Energy Technology Data Exchange (ETDEWEB)

Wang, D.C.; Wang, Y.J.; Zhang, J.P.; Tian, X.L. [College of Electromechanical Engineering, Qingdao University, Qingdao 266071 (China); Wu, J.Y. [Institute of Refrigeration and Cryogenics, Shanghai Jiao Tong University, Shanghai 200030 (China)

2008-05-15

A silica gel-water adsorption chiller has been developed in recent years and has been applied in an air conditioning system driven by solar energy. The heat source used to drive the adsorption chiller is variable at any moment because the solar radiation intensity or the waste heat from engines varies frequently. An adsorption cooling system may be badly impacted by a variable heat source with temperature variations in a large range. In this work, a silica gel-water adsorption chiller driven by a variable heat source is experimentally studied. The influences of the variable heat source on the performance of the chiller are analyzed, especially for a continuous temperature increase process and a continuous temperature decrease process of the heat source. As an example, the dynamic characteristics of the heat source are also analyzed when solar energy is taken as the heat source of the adsorption chiller. According to the experimental results for the adsorption chiller and the characteristics of the heat source from solar energy, control strategies of the adsorption chiller driven by solar energy are proposed. (author)

Experimental study of adsorption chiller driven by variable heat source

International Nuclear Information System (INIS)

Wang, D.C.; Wang, Y.J.; Zhang, J.P.; Tian, X.L.; Wu, J.Y.

2008-01-01

A silica gel-water adsorption chiller has been developed in recent years and has been applied in an air conditioning system driven by solar energy. The heat source used to drive the adsorption chiller is variable at any moment because the solar radiation intensity or the waste heat from engines varies frequently. An adsorption cooling system may be badly impacted by a variable heat source with temperature variations in a large range. In this work, a silica gel-water adsorption chiller driven by a variable heat source is experimentally studied. The influences of the variable heat source on the performance of the chiller are analyzed, especially for a continuous temperature increase process and a continuous temperature decrease process of the heat source. As an example, the dynamic characteristics of the heat source are also analyzed when solar energy is taken as the heat source of the adsorption chiller. According to the experimental results for the adsorption chiller and the characteristics of the heat source from solar energy, control strategies of the adsorption chiller driven by solar energy are proposed

Neutron Imaging at Compact Accelerator-Driven Neutron Sources in Japan

Directory of Open Access Journals (Sweden)

Yoshiaki Kiyanagi

2018-03-01

Full Text Available Neutron imaging has been recognized to be very useful to investigate inside of materials and products that cannot be seen by X-ray. New imaging methods using the pulsed structure of neutron sources based on accelerators has been developed also at compact accelerator-driven neutron sources and opened new application fields in neutron imaging. The world’s first dedicated imaging instrument at pulsed neutron sources was constructed at J-PARC in Japan owing to the development of such new methods. Then, usefulness of the compact accelerator-driven neutron sources in neutron science was recognized and such facilities were newly constructed in Japan. Now, existing and new sources have been used for neutron imaging. Traditional imaging and newly developed pulsed neutron imaging such as Bragg edge transmission have been applied to various fields by using compact and large neutron facilities. Here, compact accelerator-driven neutron sources used for imaging in Japan are introduced and some of their activities are presented.

Critical parameters in the sputter-deposition of NdBa{sub 2}Cu{sub 3}O{sub 7-{delta}} thin films

Energy Technology Data Exchange (ETDEWEB)

Hakuraku, Y.; Yokoyama, N.; Doi, T.; Inoue, T. [Faculty of Engineering, Kagoshima University, Koorimoto, Kagoshima 890, (Japan); Mori, Z.; Koba, S. [Yatsushiro National College of Technology, Yatsushiro 866 (Japan)

1999-08-01

A superconducting thin film of NdBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (NBCO) was prepared on an MgO(100) substrate by dc magnetron sputtering. Superconducting properties as well as features such as resistivity at room temperature and surface morphology were improved by optimizing the composition of sputtering target and critical parameters such as substrate temperature and oxidation gas pressure. A highly c-axis oriented thin film with T{sub c} (zero resistance temperature) = 95.2 K was obtained reproducibly with NdBa{sub 2}Cu{sub 3.2}O{sub 7-{delta}} off-stoichiometric target sputtering. T{sub c} = 95.2 K was 8 K higher than that deposited by stoichiometric target sputtering. Critical current density was 1x10{sup 6} A cm{sup -2} at 77 K, and surface roughness was 35 nm. (author)

Critical current density of strained multilayer thin films of Nd sub 1. 83 Ce sub 0. 17 CuO sub x /YBa sub 2 Cu sub 3 O sub 7 minus. delta

Energy Technology Data Exchange (ETDEWEB)

Gross, R.; Gupta, A.; Olsson, E.; Segmueller, A.; Koren, G. (IBM T. J. Watson Research Center, P.O. Box 218, Yorktown Heights, New York 10598 (USA))

1990-07-09

The superconducting transport properties of strained multilayer thin films of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}/ Nd{sub 1.83}Ce{sub 0.17}CuO{sub {ital x}}, grown heteroepitaxially by laser ablation deposition, are reported. For individual layer thicknesses below a critical layer thickness of about 250 A, coherency strain removes the orthorhombic distortion in the YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} layers and makes them twin-free. Zero-field critical current densities as high as 1.1{times}10{sup 7} A/cm{sup 2} at 77 K have been measured for the YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} layers. Flux pinning energies at zero temperature and zero magnetic field in the range of 80--140 meV have been found.

Magnetic entropy change and critical exponents in double perovskite Y{sub 2}NiMnO{sub 6}

Energy Technology Data Exchange (ETDEWEB)

Sharma, G. [School of Physical Sciences, Jawaharlal Nehru University, New Delhi-110067 (India); Tripathi, T.S. [Inter-University Accelerator Centre, New Delhi-110067 (India); Saha, J. [School of Physical Sciences, Jawaharlal Nehru University, New Delhi-110067 (India); Patnaik, S., E-mail: spatnaik@mail.jnu.ac.in [School of Physical Sciences, Jawaharlal Nehru University, New Delhi-110067 (India)

2014-11-15

We report the magnetic entropy change (ΔS{sub M}) and the critical exponents in the double perovskite manganite Y{sub 2}NiMnO{sub 6} with a ferromagnetic to paramagnetic transition T{sub C}∼85K. For a magnetic field change ΔH=80kOe, a maximum magnetic entropy change ΔS{sub M}=−6.57J/kgK is recorded around T{sub C}. The critical exponents β=0.363±0.05 and γ=1.331±0.09 obtained from power law fitting to spontaneous magnetization M{sub S}(T) and the inverse initial susceptibility χ{sub 0}{sup −1}(T) satisfy well to values derived for a 3D-Heisenberg ferromagnet. The critical exponent δ=4.761±0.129 is determined from the isothermal magnetization at T{sub C}. The scaling exponents corresponding to second order phase transition are consistent with the exponents from Kouvel–Fisher analysis and satisfy Widom's scaling relation δ=1+(γ/β). Additionally, they also satisfy the single scaling equation M(H,ϵ)=ϵ{sup β}f±(H/ϵ{sup β+γ}) according to which the magnetization-field-temperature data around T{sub C} should collapse into two curves for temperatures below and above T{sub C}. - Highlights: • The magneto-caloric (MC) effect and the critical exponent analysis in Y{sub 2}NiMnO{sub 6} are studied. • Methods such as Kouvel–Fisher, Widom's and Mean-Field scaling are used. • The magnetic ground state in Y{sub 2}NiMnO{sub 6} is based on isotropic 3D Heisenberg model. • The large MC effect can be utilized towards magnetic refrigeration around 77 K. • The nearest neighbor interaction in Y{sub 2}NiMnO{sub 6} rules out ferroelectricity.

Safety physics inter-comparison of advanced concepts of critical reactors and ADS

Energy Technology Data Exchange (ETDEWEB)

Slessarev, I. [CEA Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. d' Etudes des Reacteurs

2001-07-01

Enhanced safety based on the principle of the natural ''self-defence'' is one of the most desirable features of innovative nuclear systems (critical or sub-critical) regarding both TRU transmutation and ''clean'' energy producer concepts. For the evaluation of the ''self-defence'' domain, the method of the asymptotic reactivity balance has been generalised. The promising option of Hybrids systems (that use a symbiosis of fission and spallation in sub-critical cores) which could benefit the advantages of both Accelerated Driven Systems of the traditional type and regular critical systems, has been advocated. General features of Hybrid dynamics have been presented and analysed. It was demonstrated that an external neutron source of Hybrids can expand the inherent safety potential significantly. This analysis has been applied to assess the safety physics potential of innovative concepts for prospective nuclear power both for energy producers and for transmutation. It has been found, that safety enhancement goal defines a choice of sub-criticality of Hybrids. As for energy producers with Th-fuel cycle, a significant sub-criticality level is required due to a necessity of an improvement of neutronics together with safety enhancement task. (author)

Critical and sub-critical experiments on U-BeO lattices

International Nuclear Information System (INIS)

Benoist, P.; Gourdon, Ch.; Martelly, J.; Sagot, M.; Wanner, G.

1958-01-01

Sub-critical experiments have allowed us to measure the material buckling of uranium natural oxide of beryllium lattices with a grid of 15 cm, and made up of uranium bars measuring 2.60 - 2.92 - 3.56 and 4.40 cm of diameter. A critical experiment has then been conducted with hollow 1.35 per cent enriched uranium bars. A study of U-BeO 18.03 cm grid lattices is at present being conducted. (author) [fr

Critical behavior of the ferromagnetic-paramagnetic phase transition in Fe{sub 90−x}Ni{sub x}Zr{sub 10} alloy ribbons

Energy Technology Data Exchange (ETDEWEB)

Thanh, Tran Dang, E-mail: thanhxraylab@yahoo.com [Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of); Institute of Materials Science, VAST, 18 Hoang Quoc Viet, Hanoi (Viet Nam); Huy Dan, Nguyen [Institute of Materials Science, VAST, 18 Hoang Quoc Viet, Hanoi (Viet Nam); Phan, The-Long; Yu, Seong-Cho, E-mail: scyu@chungbuk.ac.kr [Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of); Kumarakuru, Haridas; Olivier, Ezra J.; Neethling, Johannes H. [Centre for HRTEM, Department of Physics, Nelson Mandela Metropolitan University, Port Elizabeth 6031 (South Africa)

2014-01-14

This work presents a detailed study on the critical behavior of the ferromagnetic-paramagnetic (FM-PM) phase transition in Fe{sub 90−x}Ni{sub x}Zr{sub 10} (x = 0 and 5) alloy ribbons. Basing on field dependences of magnetization (M-H), M{sup 2} versus H/M plots prove the alloys exhibiting a second-order magnetic phase transition. To investigate the nature of the FM-PM phase transition at T{sub C} = 245 and 306 K for x = 0 and 5, respectively, we performed a critical-exponent study. The values of critical components β, γ, and δ determined by using the modified Arrott plots, Kouvel-Fisher (KF), and critical isotherm analyses agree with each other. For x = 0, the critical parameters β = 0.365 ± 0.013 and γ = 1.615 ± 0.033 are obtained by modified Arrott plots while β = 0.368 ± 0.008 and γ = 1.612 ± 0.016 are obtained by the KF method. These values are close to those expected for the 3D-Heisenberg model, revealing short-range FM interactions in Fe{sub 90}Zr{sub 10}. Meanwhile, for x = 5, the values of the critical parameters β = 0.423 ± 0.008 and γ = 1.325 ± 0.036 are obtained by modified Arrott plots, and β = 0.425 ± 0.006 and γ = 1.323 ± 0.012 are obtained by the KF method. The falling of the β value in between the values of the mean-field theory (β = 0.5) and the 3D-Heisenberg model (β = 0.365) indicates an existence of FM short-range order and magnetic inhomogeneity in Fe{sub 85}Ni{sub 5}Zr{sub 10}. With a partial replacement of Ni for Fe in Fe{sub 90−x}Ni{sub x}Zr{sub 10}, the value of the critical exponent β trends to shift towards that of the mean-field theory. Such the result proves the presence of Ni favors establishing FM long-range order. The nature of this phenomenon is carefully discussed.

Experimental subcritical facility driven by D-D/D-T neutron generator at BARC, India

Energy Technology Data Exchange (ETDEWEB)

Sinha, Amar, E-mail: image@barc.gov.in; Roy, Tushar; Kashyap, Yogesh; Ray, Nirmal; Shukla, Mayank; Patel, Tarun; Bajpai, Shefali; Sarkar, P.S.; Bishnoi, Saroj

2015-05-01

Highlights: •Experimental subcritical facility BRAHMMA coupled to D-D/D-T neutron generator. •Preliminary results of PNS experiments reported. •Feynman-alpha noise measurements explored with continuous source. -- Abstract: The paper presents design of an experimental subcritical assembly driven by D-D/D-T neutron and preliminary experimental measurements. The system has been developed for investigating the static and dynamic neutronic properties of accelerator driven sub-critical systems. This system is modular in design and it is first in the series of subcritical assemblies being designed. The subcritical core consists of natural uranium fuel with high density polyethylene as moderator and beryllium oxide as reflector. The fuel is embedded in high density polyethylene moderator matrix. Estimated k{sub eff} of the system is ∼0.89. One of the unique features of subcritical core is the use of Beryllium oxide (BeO) as reflector and HDPE as moderator making the assembly a compact modular system. The subcritical core is coupled to Purnima Neutron Generator which works in D-D and D-T mode with both DC and pulsed operation. It has facility for online source strength monitoring using neutron tagging and programmable source modulation. Preliminary experiments have been carried out for spatial flux measurement and reactivity estimation using pulsed neutron source (PNS) techniques with D-D neutrons. Further experiments are being planned to measure the reactivity and other kinetic parameters using noise methods. This facility would also be used for carrying out studies on effect of source importance and measurement of source multiplication factor k{sub s} and external neutron source efficiency φ{sup ∗} in great details. Experiments with D-T neutrons are also underway.

Effect of anisotropic strain on the quantum critical phase of Sr{sub 3}Ru{sub 2}O{sub 7}

Energy Technology Data Exchange (ETDEWEB)

Brodsky, Daniel; Barber, Mark; Mackenzie, Andrew [MPI-Chemische Physik fester Stoffe, Dresden (Germany); Scottish Universities Physics Alliance (SUPA), School of Physics and Astronomy, University of St Andrews, St Andrews (United Kingdom); Hicks, Clifford [MPI-Chemische Physik fester Stoffe, Dresden (Germany); Perry, Robin [SUPA, School of Physics, University of Edinburgh, Edinburgh (United Kingdom)

2015-07-01

We have developed a novel piezoelectric-based device for applying both compressive and tensile strains to single crystals. One particularly appealing target for such studies is Sr{sub 3}Ru{sub 2}O{sub 7}. Sr{sub 3}Ru{sub 2}O{sub 7} has a novel quantum critical phase around a metamagnetic transition at 8 T, which shows very strong transport anisotropy in the presence of weak symmetry-breaking fields. We discuss the response of this phase to applied anisotropic lattice strain.

Spin-driven pyroelectricity in Ni{sub 3}TeO{sub 6} without ferroelectric signatures of the transition at Neel temperature

Energy Technology Data Exchange (ETDEWEB)

Zhao, L.; Komarek, A.C. [Max-Planck-Institute for Chemical Physics of Solids, Dresden (Germany); Du, C.H. [Department of Physics, Tamkang University, Tamsui, Taiwan (China)

2017-07-15

Here we report on dielectric studies on Ni{sub 3}TeO{sub 6}. We confirm the spin-driven pyroelectric transition at the Neel temperature (T{sub N}) of ∝52.5 K. The measurement of single crystalline and polycrystalline samples excludes a ferroelectric nature of the transition at T{sub N} in this compound. The excellent pyroelectric properties without any intrinsic ferroelectric hysteresis make Ni{sub 3}TeO{sub 6} appropriate for applications in future devices. Pyroelectric measurements on our Ni{sub 3}TeO{sub 6} single crystals. The polarization that appears on cooling through T{sub N} can not be inverted by opposite poling fields (applied when cooling from above T{sub N} to base temperature). (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Synthesis and visible-light-driven photocatalytic activity of p–n heterojunction Ag{sub 2}O/NaTaO{sub 3} nanocubes

Energy Technology Data Exchange (ETDEWEB)

Yang, Songbo [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); Xu, Dongbo [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); School of Energy and Power Engineering, Jiangsu University, Zhenjiang 212013 (China); Chen, Biyi; Luo, Bifu [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); Yan, Xu [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); School of Energy and Power Engineering, Jiangsu University, Zhenjiang 212013 (China); Xiao, Lisong, E-mail: xiaolisong123@sina.com [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); Shi, Weidong, E-mail: swd1978@ujs.edu.cn [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China)

2016-10-15

Highlights: • We firstly report a facile way to prepare the visible-light-driven Ag{sub 2}O/NaTaO{sub 3}p–n heterojunction by chemical precipitation method. • The Ag{sub 2}O/NaTaO{sub 3} heterojunction shows the highest photocatalytic activity than the pure NaTaO{sub 3} and Ag{sub 2}O nanoparticles under visible light. • The enhancement of the heterojunction photocatalytic activity was discussed and the photocatalytic mechanism was tested in our paper. • In summary, we think that the Ag{sub 2}O/NaTaO{sub 3} heterojunction with the strong visible light absorption and efficient photocatalytic activity have been extended application in photocatalysis for organic dyes pollutants degradation and purification of water. - Abstract: The constructing of p–n heterojunction photocatalytic system has received much attention in environmental purification and hydrogen generation from water. In this study, an efficient visible-light-driven p–n heterojunction Ag{sub 2}O/NaTaO{sub 3} was successfully prepared by chemical precipitation method at room temperature. It showed an enhanced photocatalytic activity for the degradation of rhodamine B (RhB) under visible-light irradiation, much higher than those of either individual Ag{sub 2}O or NaTaO{sub 3}. The reactive species scavenger results indicated the superoxide anion radicals (·O{sup 2−}) played key roles in RhB decoloration. From the experimental results and the relative band gap position of these semiconductors, a detailed possible photocatalytic mechanism of the Ag{sub 2}O/NaTaO{sub 3} heterojunction under visible light was proposed. The enhancement of the photocatalytic activity was attributed to the interfacial electronic interaction between NaTaO{sub 3} and Ag{sub 2}O and the high migration efficiency of photogenerated carriers.

Critical Path Driven Cosynthesis for Heterogeneous Target Architectures

DEFF Research Database (Denmark)

Bjørn-Jørgensen, Peter; Madsen, Jan

1997-01-01

This paper presents a critical path driven algorithm to produce a static schedule of a single-rate system onto a heterogeneous target architecture. Our algorithm is a list based scheduling algorithm which concurrently assigns tasks to processors and allocates nets to interprocessor communication........ Experimental results show that our algorithm is able to find good results, as compared to other methods, in small amount of CPU time....

Analysis of fuel management in the KIPT neutron source facility

Energy Technology Data Exchange (ETDEWEB)

Zhong Zhaopeng, E-mail: zzhong@anl.gov [Nuclear Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Gohar, Yousry; Talamo, Alberto [Nuclear Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States)

2011-05-15

Research highlights: > Fuel management of KIPT ADS was analyzed. > Core arrangement was shuffled in stage wise. > New fuel assemblies was added into core periodically. > Beryllium reflector could also be utilized to increase the fuel life. - Abstract: Argonne National Laboratory (ANL) of USA and Kharkov Institute of Physics and Technology (KIPT) of Ukraine have been collaborating on the conceptual design development of an experimental neutron source facility consisting of an electron accelerator driven sub-critical assembly. The neutron source driving the sub-critical assembly is generated from the interaction of 100 KW electron beam with a natural uranium target. The sub-critical assembly surrounding the target is fueled with low enriched WWR-M2 type hexagonal fuel assemblies. The U-235 enrichment of the fuel material is <20%. The facility will be utilized for basic and applied research, producing medical isotopes, and training young specialists. With the 100 KW electron beam power, the total thermal power of the facility is {approx}360 kW including the fission power of {approx}260 kW. The burnup of the fissile materials and the buildup of fission products continuously reduce the system reactivity during the operation, decrease the neutron flux level, and consequently impact the facility performance. To preserve the neutron flux level during the operation, the fuel assemblies should be added and shuffled for compensating the lost reactivity caused by burnup. Beryllium reflector could also be utilized to increase the fuel life time in the sub-critical core. This paper studies the fuel cycles and shuffling schemes of the fuel assemblies of the sub-critical assembly to preserve the system reactivity and the neutron flux level during the operation.

Kinetic analysis of sub-prompt-critical reactor assemblies

International Nuclear Information System (INIS)

Das, S.

1992-01-01

Neutronic analysis of safety-related kinetics problems in experimental neutron multiplying assemblies has been carried out using a sub-prompt-critical reactor model. The model is based on the concept of a sub-prompt-critical nuclear reactor and the concept of instantaneous neutron multiplication in a reactor system. Computations of reactor power, period and reactivity using the model show excellent agreement with results obtained from exact kinetics method. Analytic expressions for the energy released in a controlled nuclear power excursion are derived. Application of the model to a Pulsed Fast Reactor gives its sensitivity between 4 and 5. (author). 6 refs., 4 figs., 1 tab

Microwave Ion Source and Beam Injection for an Accelerator-driven Neutron Source

International Nuclear Information System (INIS)

Vainionpaa, J.H.; Gough, R.; Hoff, M.; Kwan, J.W.; Ludewigt, B.A.; Regis, M.J.; Wallig, J.G.; Wells, R.

2007-01-01

An over-dense microwave driven ion source capable of producing deuterium (or hydrogen) beams at 100-200 mA/cm2 and with atomic fraction >90 percent was designed and tested with an electrostatic low energy beam transport section (LEBT). This ion source was incorporated into the design of an Accelerator Driven Neutron Source (ADNS). The other key components in the ADNS include a 6 MeV RFQ accelerator, a beam bending and scanning system, and a deuterium gas target. In this design a 40 mA D+ beam is produced from a 6 mm diameter aperture using a 60 kV extraction voltage. The LEBT section consists of 5 electrodes arranged to form 2 Einzel lenses that focus the beam into the RFQ entrance. To create the ECR condition, 2 induction coils are used to create ∼ 875 Gauss on axis inside the source chamber. To prevent HV breakdown in the LEBT a magnetic field clamp is necessary to minimize the field in this region. Matching of the microwave power from the waveguide to the plasma is done by an autotuner. We observed significant improvement of the beam quality after installing a boron nitride liner inside the ion source. The measured emittance data are compared with PBGUNS simulations

Microwave Ion Source and Beam Injection for an Accelerator-Driven Neutron Source

International Nuclear Information System (INIS)

Vainionpaa, J.H.; Gough, R.; Hoff, M.; Kwan, J.W.; Ludewigt, B.A.; Regis, M.J.; Wallig, J.G.; Wells, R.

2007-01-01

An over-dense microwave driven ion source capable of producing deuterium (or hydrogen) beams at 100-200 mA/cm 2 and with atomic fraction > 90% was designed and tested with an electrostatic low energy beam transport section (LEBT). This ion source was incorporated into the design of an Accelerator Driven Neutron Source (ADNS). The other key components in the ADNS include a 6 MeV RFQ accelerator, a beam bending and scanning system, and a deuterium gas target. In this design a 40 mA D + beam is produced from a 6 mm diameter aperture using a 60 kV extraction voltage. The LEBT section consists of 5 electrodes arranged to form 2 Einzel lenses that focus the beam into the RFQ entrance. To create the ECR condition, 2 induction coils are used to create ∼ 875 Gauss on axis inside the source chamber. To prevent HV breakdown in the LEBT a magnetic field clamp is necessary to minimize the field in this region. Matching of the microwave power from the waveguide to the plasma is done by an autotuner. They observed significant improvement of the beam quality after installing a boron nitride liner inside the ion source. The measured emittance data are compared with PBGUNS simulations

Unusually high critical current of P-doped BaFe{sub 2}As{sub 2} single crystalline thin film

Energy Technology Data Exchange (ETDEWEB)

Kurth, Fritz; Engelmann, Jan; Schultz, Ludwig [IMW, IFW Dresden, Dresden (Germany); TU Dresden, Dresden (Germany); Tarantini, Chiara; Jaroszynski, Jan [ASC, NHMFL, Florida (United States); Grinenko, Vadim; Reich, Elke; Huehne, Ruben [IMW, IFW Dresden, Dresden (Germany); Haenisch, Jens [IMW, IFW Dresden, Dresden (Germany); ITEP, KIT, Karlsruhe (Germany); Mori, Yasohiro; Sakagami, Akihiro; Kawaguchi, Takahiko; Ikuta, Hiroshi [Department of Crystalline Materials Science, Nagoya University, Nagoya (Japan); Holzapfel, Bernhard [ITEP, KIT, Karlsruhe (Germany); Iida, Kazumasa [IMW, IFW Dresden, Dresden (Germany); Department of Crystalline Materials Science, Nagoya University, Nagoya (Japan)

2015-07-01

Microstructurally clean, isovalently P-doped BaFe{sub 2}As{sub 2} single crystalline thin films have been prepared by molecular beam epitaxy. These films show a superconducting transition temperature (T{sub c}) of over 30 K and high transport self-field critical current densities (J{sub c}) of over 6 MA/cm{sup 2} at 4.2 K, which are among the highest for Fe based superconductors. In-field J{sub c} exceeds 0.1 MA/cm{sup 2} at μ{sub 0}H = 35 T for H parallel ab and μ{sub 0}H = 18 T for H parallel c, respectively, in spite of moderate upper critical fields compared to other FeSCs with similar T{sub c}. This unusually high J{sub c} makes P-doped Ba-122 very favorable for high-field magnet applications.

Uranium Enrichment Determination of the InSTEC Sub Critical Ensemble Fuel by Gamma Spectrometry

International Nuclear Information System (INIS)

Borrell Munnoz, Jose L.; LopezPino, Neivy; Diaz Rizo, Oscar; D'Alessandro Rodriguez, Katia; Padilla Cabal, Fatima; Arbelo Penna, Yunieski; Garcia Rios, Aczel R.; Quintas Munn, Ernesto L.; Casanova Diaz, Amaya O.

2009-01-01

Low background gamma spectrometry was applied to analyze the uranium enrichment of the nuclear fuel used in the InSTEC Sub Critical ensemble. The enrichment was calculated by two variants: an absolute method using the Monte Carlo method to simulated detector volumetric efficiency, and an iterative procedure without using standard sources. The results confirm that the nuclear fuel of the ensemble is natural uranium without any additional degree of enrichment. (author)

rf driven multicusp H- ion source

International Nuclear Information System (INIS)

Leung, K.N.; DeVries, G.J.; DiVergilio, W.F.; Hamm, R.W.; Hauck, C.A.; Kunkel, W.B.; McDonald, D.S.; Williams, M.D.

1991-01-01

An rf driven multicusp source capable of generating 1-ms H - beam pulses with a repetition rate as high as 150 Hz has been developed. This source can be operated with a filament or other types of starter. There is almost no lifetime limitation and a clean plasma can be maintained for a long period of operation. It is demonstrated that rf power as high as 25 kW could be coupled inductively to the plasma via a glass-coated copper-coil antenna. The extracted H - current density achieved is about 200 mA/cm 2

Linac-driven spallation-neutron source

International Nuclear Information System (INIS)

Jason, A.J.

1995-01-01

Strong interest has arisen in accelerator-driven spallation-neutron sources that surpass existing facilities (such as ISIS at Rutherford or LANSCE at Los Alamos) by more than an order of magnitude in beam power delivered to the spallation target. The approach chosen by Los Alamos (as well as the European Spallation Source) provides the full beam energy by acceleration in a linac as opposed to primary acceleration in a synchrotron or other circular device. Two modes of neutron production are visualized for the source. A short-pulse mode produces 1 MW of beam power (at 60 pps) in pulses, of length less than 1 ms, by compression of the linac macropulse through multi-turn injection in an accumulator ring. A long-pulse mode produces a similar beam power with 1-ms-long pulses directly applied to a target. This latter mode rivals the performance of existing reactor facilities to very low neutron energies. Combination with the short-pulse mode addresses virtually all applications

High critical currents in heavily doped (Gd,Y)Ba{sub 2}Cu{sub 3}O{sub x} superconductor tapes

Energy Technology Data Exchange (ETDEWEB)

Selvamanickam, V., E-mail: selva@uh.edu; Gharahcheshmeh, M. Heydari; Xu, A.; Galstyan, E.; Delgado, L. [Department of Mechanical Engineering and Texas Center for Superconductivity, University of Houston, 4800 Calhoun Rd., Houston, Texas 77204-4006 (United States); Cantoni, C. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37381 (United States)

2015-01-19

REBa{sub 2}Cu{sub 3}O{sub x} ((REBCO), RE = rare earth) superconductor tapes with moderate levels of dopants have been optimized for high critical current density in low magnetic fields at 77 K, but they do not exhibit exemplary performance in conditions of interest for practical applications, i.e., temperatures less than 50 K and fields of 2–30 T. Heavy doping of REBCO tapes has been avoided by researchers thus far due to deterioration in properties. Here, we report achievement of critical current densities (J{sub c}) above 20 MA/cm{sup 2} at 30 K, 3 T in heavily doped (25 mol. % Zr-added) (Gd,Y)Ba{sub 2}Cu{sub 3}O{sub x} superconductor tapes, which is more than three times higher than the J{sub c} typically obtained in moderately doped tapes. Pinning force levels above 1000 GN/m{sup 3} have also been attained at 20 K. A composition map of lift factor in J{sub c} (ratio of J{sub c} at 30 K, 3 T to the J{sub c} at 77 K, 0 T) has been developed which reveals the optimum film composition to obtain lift factors above six, which is thrice the typical value. A highly c-axis aligned BaZrO{sub 3} (BZO) nanocolumn defect density of nearly 7 × 10{sup 11 }cm{sup −2} as well as 2–3 nm sized particles rich in Cu and Zr have been found in the high J{sub c} films.

Critical parameters near the ferromagnetic-paramagnetic phase transition in La{sub 0.7}A{sub 0.3}(Mn{sub 1-x}b{sub x})O{sub 3} (A=Sr; B=Ti and Al; x=0.0 and 0.05) compounds

Energy Technology Data Exchange (ETDEWEB)

Khiem, N.V. [Hongduc University, 307 Lelai Street, Thanhhoa City (Viet Nam)], E-mail: nvkhiem2002@yahoo.com; Phong, P.T. [Institute of Materials Science, Vietnamese Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay District, Hanoi (Viet Nam); Bau, L.V. [Hongduc University, 307 Lelai Street, Thanhhoa City (Viet Nam); Nam, D.N.H.; Hong, L.V.; Phuc, N.X. [Institute of Materials Science, Vietnamese Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay District, Hanoi (Viet Nam)

2009-07-15

The critical parameters provide important information concerning the interaction mechanisms near the paramagnetic-to-ferromagnetic transition. In this paper, we present a thorough study for the critical behavior of La{sub 0.7}A{sub 0.3}(Mn{sub 1-x}B{sub x})O{sub 3} (A=Sr; B=Ti and Al; x=0.0 and 0.05) polycrystalline samples near ferromagnetic-paramagnetic phase transition temperature by analyzing isothermal magnetization data. We have analyzed our dc-magnetization data near the transition temperature with the help of the modified Arrot plot, Kouvel-Fisher method. We have determined the critical temperature T{sub C} and the critical parameters {beta}, {gamma} and {delta}. With the values of T{sub C}, {beta} and {gamma}, we plot Mx(1-T/T{sub C}){sup -{beta}} vs. Hx(1-T/T{sub C}){sup -{gamma}}. All the data collapse on one of the two curves. This suggests that the data below and above T{sub C} obey scaling, following a single equation of state. Critical parameters for x=0 and x{sub Ti}=0.05 samples are between those predicted for a 3D-Heisenberg model and mean-field theory and for x{sub Al}=0.05 samples the values obtained for the critical parameters are close to those predicted by the mean-field theory.

Characteristic signatures of quantum criticality driven by geometrical frustration.

Science.gov (United States)

Tokiwa, Yoshifumi; Stingl, Christian; Kim, Moo-Sung; Takabatake, Toshiro; Gegenwart, Philipp

2015-04-01

Geometrical frustration describes situations where interactions are incompatible with the lattice geometry and stabilizes exotic phases such as spin liquids. Whether geometrical frustration of magnetic interactions in metals can induce unconventional quantum critical points is an active area of research. We focus on the hexagonal heavy fermion metal CeRhSn, where the Kondo ions are located on distorted kagome planes stacked along the c axis. Low-temperature specific heat, thermal expansion, and magnetic Grüneisen parameter measurements prove a zero-field quantum critical point. The linear thermal expansion, which measures the initial uniaxial pressure derivative of the entropy, displays a striking anisotropy. Critical and noncritical behaviors along and perpendicular to the kagome planes, respectively, prove that quantum criticality is driven be geometrical frustration. We also discovered a spin flop-type metamagnetic crossover. This excludes an itinerant scenario and suggests that quantum criticality is related to local moments in a spin liquid-like state.

Perturbative Field-Theoretical Renormalization Group Approach to Driven-Dissipative Bose-Einstein Criticality

Directory of Open Access Journals (Sweden)

Uwe C. Täuber

2014-04-01

Full Text Available The universal critical behavior of the driven-dissipative nonequilibrium Bose-Einstein condensation transition is investigated employing the field-theoretical renormalization group method. Such criticality may be realized in broad ranges of driven open systems on the interface of quantum optics and many-body physics, from exciton-polariton condensates to cold atomic gases. The starting point is a noisy and dissipative Gross-Pitaevski equation corresponding to a complex-valued Landau-Ginzburg functional, which captures the near critical nonequilibrium dynamics, and generalizes model A for classical relaxational dynamics with nonconserved order parameter. We confirm and further develop the physical picture previously established by means of a functional renormalization group study of this system. Complementing this earlier numerical analysis, we analytically compute the static and dynamical critical exponents at the condensation transition to lowest nontrivial order in the dimensional ε expansion about the upper critical dimension d_{c}=4 and establish the emergence of a novel universal scaling exponent associated with the nonequilibrium drive. We also discuss the corresponding situation for a conserved order parameter field, i.e., (subdiffusive model B with complex coefficients.

Analysis of fuel management in the KIPT neutron source facility

International Nuclear Information System (INIS)

Zhong Zhaopeng; Gohar, Yousry; Talamo, Alberto

2011-01-01

Research highlights: → Fuel management of KIPT ADS was analyzed. → Core arrangement was shuffled in stage wise. → New fuel assemblies was added into core periodically. → Beryllium reflector could also be utilized to increase the fuel life. - Abstract: Argonne National Laboratory (ANL) of USA and Kharkov Institute of Physics and Technology (KIPT) of Ukraine have been collaborating on the conceptual design development of an experimental neutron source facility consisting of an electron accelerator driven sub-critical assembly. The neutron source driving the sub-critical assembly is generated from the interaction of 100 KW electron beam with a natural uranium target. The sub-critical assembly surrounding the target is fueled with low enriched WWR-M2 type hexagonal fuel assemblies. The U-235 enrichment of the fuel material is <20%. The facility will be utilized for basic and applied research, producing medical isotopes, and training young specialists. With the 100 KW electron beam power, the total thermal power of the facility is ∼360 kW including the fission power of ∼260 kW. The burnup of the fissile materials and the buildup of fission products continuously reduce the system reactivity during the operation, decrease the neutron flux level, and consequently impact the facility performance. To preserve the neutron flux level during the operation, the fuel assemblies should be added and shuffled for compensating the lost reactivity caused by burnup. Beryllium reflector could also be utilized to increase the fuel life time in the sub-critical core. This paper studies the fuel cycles and shuffling schemes of the fuel assemblies of the sub-critical assembly to preserve the system reactivity and the neutron flux level during the operation.

Compact sub-nanosecond pulse seed source with diode laser driven by a high-speed circuit

Science.gov (United States)

Wang, Xiaoqian; Wang, Bo; Wang, Junhua; Cheng, Wenyong

2018-06-01

A compact sub-nanosecond pulse seed source with 1550 nm diode laser (DL) was obtained by employing a high-speed circuit. The circuit mainly consisted of a short pulse generator and a short pulse driver. The short pulse generator, making up of a complex programmable logic device (CPLD), a level translator, two programmable delay chips and an AND gate chip, output a triggering signal to control metal-oxide-semiconductor field-effect transistor (MOSFET) switch of the short pulse driver. The MOSFET switch with fast rising time and falling time both shorter than 1 ns drove the DL to emit short optical pulses. Performances of the pulse seed source were tested. The results showed that continuously adjustable repetition frequency ranging from 500 kHz to 100 MHz and pulse duration in the range of 538 ps to 10 ns were obtained, respectively. 537 μW output was obtained at the highest repetition frequency of 100 MHz with the shortest pulse duration of 538 ps. These seed pulses were injected into an fiber amplifier, and no optical pulse distortions were found.

Fabrication of visible-light-driven Ag/TiO{sub 2} heterojunction composites induced by shock wave

Energy Technology Data Exchange (ETDEWEB)

Xu, Chunxiao [School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China); Chen, Pengwan, E-mail: pwchen@bit.edu.cn [School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China); State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing 100081 (China); Liu, Jianjun [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Yin, Hao [Institute of Systems Engineering, China Academy of Engineering Physics, Mianyang 612900, Sichuan Province (China); Gao, Xin; Mei, Xiaofeng [State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing 100081 (China)

2016-09-15

Using metatitanic acid (H{sub 2}TiO{sub 3}) and silver nitrate (AgNO{sub 3}) as titanium precursor and silver source respectively, a visible-light responsible Ag/TiO{sub 2} heterojunction photocatalyst is successfully prepared by shock wave with detonation-driven flyer impact. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–visible diffuse reflectance spectroscopy (UV–Vis DRS) and photoluminescence (PL) emission spectra are employed to characterize the phase structure, morphology, chemical composition and optical property of the recovered samples. The results indicate the metatitanic acid transforms to pure rutile TiO{sub 2} phase by shock wave which possess large surface area. Ag nanoparticles cover on the surface of TiO{sub 2} uniformly and a nanojunction structure is formed efficiently, which play important roles as an electron-conduction bridge and in the surface plasmon resonance effect. Ag modification feasibly improves the separation efficiency for photoinduced electron–hole pairs and enhances the visible-light response. Furthermore, due to the further enhanced separation for photogenerated charges resulting from close interfacial contact of the hetero structure, the obtained Ag/TiO{sub 2} photocatalyst exhibit remarkably improved photocatalytic activities (88% within 2 h) than that of P25 and shock induced pure TiO{sub 2} for the degradation of Rhodamine B under simulated sunlight irradiation. The experimental result shows the shock loading is an effective method to get Ag/TiO{sub 2} photocatalyst and offers new ideas to fabricate other heterojunction composite materials. - Highlights: • Shock wave was a new method of material modification. • The Ag/TiO{sub 2} hetero structure was formed efficiently by shock loading. • The visible-light responsible sample showed an enhanced photocatalytic activity. • This work gave new ideas to fabricate other heterojunction materials.

A High-Power Laser-Driven Source of Sub-nanosecond Soft X-Ray Pulses for Single-Shot Radiobiology Experiments

Czech Academy of Sciences Publication Activity Database

Davídková, Marie; Juha, Libor; Bittner, Michal; Koptyaev, Sergey; Hájková, Věra; Krása, Josef; Pfeifer, Miroslav; Štísová, Viktorie; Bartnik, A.; Fiedorowicz, H.; Mikolajczyk, J.; Ryc, L.; Pína, L.; Horváth, M.; Babánková, Dagmar; Cihelka, Jaroslav; Civiš, Svatopluk

2007-01-01

Roč. 168, č. 3 (2007), s. 382-387 ISSN 0033-7587 R&D Projects: GA ČR GA202/05/2316; GA MŠk(CZ) LC528; GA MŠk 1P04LA235; GA MŠk LC510 Institutional research plan: CEZ:AV0Z10480505; CEZ:AV0Z10100523; CEZ:AV0Z20430508; CEZ:AV0Z40400503 Keywords : soft X-rays * radiation damage to DNA * laser-driven source Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.599, year: 2007

Accelerator driven radiation clean nuclear power system conceptual research symposium

International Nuclear Information System (INIS)

Zhao Zhixiang

2000-06-01

The R and D of ADS (Accelerators Driven Subcritical System) in China introduced. 31 theses are presented. It includes the basic principle of ADS, accelerators, sub-critical reactors, neutron physics, nuclear data, partitioning and transmutation

Critical slowing down in driven-dissipative Bose-Hubbard lattices

Science.gov (United States)

Vicentini, Filippo; Minganti, Fabrizio; Rota, Riccardo; Orso, Giuliano; Ciuti, Cristiano

2018-01-01

We explore theoretically the dynamical properties of a first-order dissipative phase transition in coherently driven Bose-Hubbard systems, describing, e.g., lattices of coupled nonlinear optical cavities. Via stochastic trajectory calculations based on the truncated Wigner approximation, we investigate the dynamical behavior as a function of system size for one-dimensional (1D) and 2D square lattices in the regime where mean-field theory predicts nonlinear bistability. We show that a critical slowing down emerges for increasing number of sites in 2D square lattices, while it is absent in 1D arrays. We characterize the peculiar properties of the collective phases in the critical region.

A formulation for the critical temperature T/sub c/ of Ll2-type superconductors

International Nuclear Information System (INIS)

Wang Rong-Yao; Zhang Xiao

1985-01-01

From the examination of Ll 2 type superconductors, the superconducting critical temperature T/sub b/ of Ll 2 -type superconductors is obtained by: T/sub c/ = 15.9T/sub B/V(B)G/sub A//(√M/sub m/) V(Ll 2 )/sub m/ G/sub B/ where T/sub B/ is the superconducting critical temperature of pure B, V(B) the atomic volume in pure B, V(Ll 2 )/sub m/ the average atomic volume in the Ll 2 type compound, M/sub m/ the average atomic weight of the compound, and G/sub A/, G/sub B/ are the Gordy electronegative values. (author)

Effect of doping with magnetic 3D-elements on the thermal fluctuations and critical parameters of CaLaBaCu{sub 3-x}(Ni,Co){sub x}O{sub 7-{delta}} superconductors

Energy Technology Data Exchange (ETDEWEB)

Rojas Sarmiento, M.P.; Landinez Tellez, D.A. [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, AA 14490, Bogota DC (Colombia); Roa-Rojas, J. [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, AA 14490, Bogota DC (Colombia)], E-mail: jroar@unal.edu.co

2008-07-15

Systematic measurements on conductivity fluctuation in the CaLaBaCu{sub 3-x}(Ni,Co){sub x}O{sub 7-{delta}} system are reported. Samples with x=0, 0.03, 0.06, 0.09, 0.12, 0.15 and 0.18 were prepared by the standard solid-state reaction recipe. Results of resistivity measurements reveal a linear-like decreasing of the critical temperature T{sub c} with progressive substitution of magnetic elements Ni and Co into the Cu crystallographic sites. From the fluctuation analysis, above and close to T{sub c}, we found the occurrence of three- and two-dimensional Gaussian fluctuation regimes. Closer to T{sub c}, a genuinely critical regime is observed. On the Ginzburg-Landau formalism, from the reduced temperature of the three-dimensional Gaussian region and the mean field critical temperature, we have experimentally obtained the Ginzburg number for the CaLaBaCu{sub 3-x}(Ni,Co){sub x}O{sub 7-{delta}} material. Then, critical magnetic field, critical current density and the jump in the specific heat at the critical temperature are calculated. Critical parameters are strongly affected by the doping with magnetic ions.

Magnetocaloric effect and critical behavior in melt-extracted Gd{sub 60}Co{sub 15}Al{sub 25} microwires

Energy Technology Data Exchange (ETDEWEB)

Xing, Dawei; Jiang, Sida; Chen, Dongming; Liu, Yanfen; Sun, Jianfei [School of Materials Science and Engineering, Harbin Institute of Technology (China); Shen, Hongxian [School of Materials Science and Engineering, Harbin Institute of Technology (China); Institute of Materials and Department of Physics, University of South Florida, Tampa, FL (United States); Liu, Jingshun [School of Materials Science and Engineering, Inner Mongolia University of Technology, Hohhot (China); Phan, Manh-Huong [Institute of Materials and Department of Physics, University of South Florida, Tampa, FL (United States); Wang, Huan; Qin, Faxiang [Institute for Composites Science and Innovation (InCSI), College of Materials Science and Engineering, Zhejiang University, Hangzhou (China)

2015-09-15

High-quality Gd{sub 60}Co{sub 15}Al{sub 25} microwires with an average diameter of 40 μm were successfully fabricated by the melt-extraction method. The as-cast microwires undergo a second-order paramagnetic to ferromagnetic (PM-FM) transition at ∝100 K. Large values of the magnetic entropy change (-ΔS{sub M} ∝9.73 J kg{sup -1} K{sup -1}) and the refrigerant capacity (RC ∝732 J kg{sup -1}) are achieved for a field change of 5 T. A careful analysis of critical exponents near the PM-FM transition indicates the significant effects of structural disorder on the long-range ferromagnetic interaction and the magnetocaloric response of the microwires. The excellent magnetocaloric properties make the Gd{sub 60}Co{sub 15}Al{sub 25} microwires very promising for use in magnetic refrigerators operating in the liquid nitrogen temperature range. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Ternary g-C{sub 3}N{sub 4}/Fe{sub 3}O{sub 4}/Ag{sub 3}VO{sub 4} nanocomposites: Novel magnetically separable visible-light-driven photocatalysts for efficiently degradation of dye pollutants

Energy Technology Data Exchange (ETDEWEB)

Mousavi, Mitra; Habibi-Yangjeh, Aziz, E-mail: ahabibi@uma.ac.ir

2015-08-01

In this work, novel magnetically separable g-C{sub 3}N{sub 4}/Fe{sub 3}O{sub 4}/Ag{sub 3}VO{sub 4} nanocomposites were successfully prepared by anchoring Fe{sub 3}O{sub 4} and Ag{sub 3}VO{sub 4} on surface of the g-C{sub 3}N{sub 4} sheets. The prepared samples were fairly characterized using X-ray diffraction, energy dispersive analysis of X-rays, scanning electron microscopy, transmission electron microscopy, UV–vis diffuse reflectance spectroscopy, photoluminescence spectroscopy, thermogravimetric analysis, and vibrating sample magnetometry techniques. Compared with the g-C{sub 3}N{sub 4} and g-C{sub 3}N{sub 4}/Fe{sub 3}O{sub 4} samples, the g-C{sub 3}N{sub 4}/Fe{sub 3}O{sub 4}/Ag{sub 3}VO{sub 4} nanocomposites displayed higher photocatalytic activity for degradation of rhodamine B under visible-light irradiation. Photocatalytic activity of the nanocomposite with 60% of Ag{sub 3}VO{sub 4} was about 14, 8, and 3-fold higher than those of the g-C{sub 3}N{sub 4}, g-C{sub 3}N{sub 4}/Fe{sub 3}O{sub 4}, and Ag{sub 3}VO{sub 4} samples, respectively. Furthermore, influence of refluxing time, calcination temperature, and scavengers of the reactive species on the degradation activity was investigated in detail and the results were discussed. The enhanced photocatalytic activity of the nanocomposites was attributed to efficiently separation of the charge carriers and their increased visible-light harvesting ability. - Graphical abstract: Display Omitted - Highlights: • g-C{sub 3}N{sub 4}/Fe{sub 3}O{sub 4}/Ag{sub 3}VO{sub 4} was prepared as ternary novel visible-light-driven photocatalyst. • Among the prepared samples, g-C{sub 3}N{sub 4}/Fe{sub 3}O{sub 4}/Ag{sub 3}VO{sub 4} (60%) has the best activity. • The activity was related to efficiently generation and separation of charge carriers. • The photocatalyst was magnetically separated from the treated solution.

A novel visible light-driven Ag{sub 3}PO{sub 4}/SBA-15 nanocomposite: Preparation and application in the photo-degradation of pollutants

Energy Technology Data Exchange (ETDEWEB)

Chai, Yuanyuan; Wang, Li; Ren, Jia; Dai, Wei-Lin, E-mail: wldai@fudan.edu.cn

2015-01-01

Graphical abstract: - Highlights: • Highly efficient visible-light-driven Ag{sub 3}PO{sub 4}/SBA-15 nanocomposite. • Application in the photo-degradation of RhB. • Synthesis from a facile and simple colloidal method. • 20%-Ag{sub 3}PO{sub 4}/SBA-15 shows 8 times faster degradation rate than Ag{sub 3}PO{sub 4}. • Super stability and recycling ability. - Abstract: A novel visible light-driven environmental-benign Ag{sub 3}PO{sub 4}/SBA-15 nanocomposite photo-catalyst was synthesized for the photo-degradation of pollutants. The exploration on adsorption and photo-catalysis of dye or organic pollution for the nanocomposite was carried out. The adsorption capability for Ag{sub 3}PO{sub 4}/SBA-15 nanocomposite increases by 3 times compared with that of the Ag{sub 3}PO{sub 4} particles. The photo-catalytic activity of nanocomposite is higher than pristine Ag{sub 3}PO{sub 4} nanoparticle for the degradation of RhB or MO under visible light irradiation (λ > 420 nm). The effect of Ag{sub 3}PO{sub 4} loading on the catalytic performance was also studied. The results show that the optimum degradation is achieved over 20% Ag{sub 3}PO{sub 4}/SBA-15. Compared to pure Ag{sub 3}PO{sub 4} nanoparticle, the most efficient catalyst showed 8 times higher photo-catalytic activity for the degradation of RhB. The Ag{sub 3}PO{sub 4}/SBA-15 catalysts were systematically characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–Vis diffuse reflectance spectroscopy (DRS), and N{sub 2}-adsorption–desorption isotherms (BET). A possible mechanism scheme regarding photo-degradation enhancement induced by dye enrichments has been proposed on the Ag{sub 3}PO{sub 4}/SBA-15 nanocomposite. Additionally, the SBA-15 support can enhance the efficiency of separation of catalyst from the reaction mixture, implying that the Ag{sub 3}PO{sub 4} loading on the SBA-15 catalyst will not result in the extra environment and health

Recent advances in acceleration of source iterations for fixed-source slab-geometry S{sub N} calculations based on P{sub N} synthetic initial guess

Energy Technology Data Exchange (ETDEWEB)

Guida, Mateus Rodrigues; Alves Filho, Hermes; Barros, Ricardo C., E-mail: mguida@iprj.uerj.br, E-mail: halves@iprj.uerj.br, E-mail: rcbarros@pq.cnpq.br [Universidade do Estado do Rio de Janeiro (UERJ), Nova Friburgo, RJ (Brazil). Instituto Politecnico. Programa de Pos-Graduacao em Modelagem Computacional

2015-07-01

The scattering source iterative (SI) scheme is applied traditionally to converge fine-mesh numerical solutions to fixed-source discrete ordinates (S{sub N}) neutron transport problems with linearly anisotropic scattering. The SI scheme is very simple to implement under a computational viewpoint. However, the SI scheme may show very slow convergence rate, mainly for diffusive media (low absorption) with several mean free paths in extent. In this work we describe two acceleration techniques based on improved initial guesses for the SI scheme, wherein we initialize the scattering source distribution within the slab using the P{sub 1} and P{sub 3} approximations. In order to estimate these initial guesses, we use the coarse-mesh solution of the PN equations with special boundary conditions to account for the classical S{sub N} prescribed boundary conditions, including vacuum boundary conditions. To apply this coarse-mesh P{sub N} solution for the accelerated scheme, we first perform within-node spatial reconstruction, and then we determine the fine-mesh average scalar flux and total current for initializing the linearly anisotropic scattering source terms for the SI scheme. We consider a number of numerical experiments to illustrate the efficiency of the offered P{sub N} synthetic acceleration (P{sub N}SA) technique based on initial guess. (author)

Critical dynamics and domain motion from permittivity of the electronic ferroelectric (TMTTF){sub 2}AsF{sub 6}

Energy Technology Data Exchange (ETDEWEB)

Brazovskii, Serguei, E-mail: brazov@lptms.u-psud.fr [LPTMS, UMR8626, CNRS & University Paris-Sud, Bat. 100, Orsay F-91405 (France); International Institute of Physics, 59078-400 Natal, Rio Grande do Norte (Brazil); Monceau, Pierre [CNRS & University Grenoble Alpes, Institute NEEL, F-38042 Grenoble (France); Nad, Felix Ya.

2015-03-01

The quasi one-dimensional organic conductor (TMTTF){sub 2}AsF{sub 6} shows the charge ordering transition at T{sub CO}=101 K to a state of the ferroelectric Mott insulator which is still well conducting. We present and interpret the experimental data on the gigantic dielectric response in the vicinity of T{sub CO}, concentrating on the frequency dependence of the inverse 1/ε of the complex permittivity ε=ε′+iε′′. Surprisingly for a ferroelectric, we could closely approach the 2nd order phase transition and to deeply reach the critical dynamics of the polarization. We could analyze the critical slowing-down when approaching T{sub CO} from both sides and to extract the anomalous power law for the frequency dependence of the order parameter viscosity. Moreover, below T{sub CO} we could extract a sharp absorption feature coming from a motion of domain walls which shows up at a frequency well below the relaxation rate.

Improvement of critical current density in thallium-based (Tl,Bi)Sr{sub 1.6}Ba{sub 0.4}Ca{sub 2}Cu{sub 3}O{sub x} superconductors

Energy Technology Data Exchange (ETDEWEB)

Ren, Z.F.; Wang, C.A.; Wang, J.H. [State Univ. of New York at Buffalo, Amherst, NY (United States)] [and others

1994-12-31

Epitaxial (Tl,Bi)Sr{sub 1.6}Ba{sub 0.4}Ca{sub 2}Cu{sub 3}O{sub x} (Tl,Bi)-1223 thin films on (100) single crystal LaAlO{sub 3} substrates were synthesized by a two-step procedure. Phase development, microstructure, and relationships between film and substrate were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Resistance versus temperature, zero-field-cooled and field-cooled magnetization, and transport critical current density (J{sub c}) were measured. The zero-resistance temperature was 105-111 K. J{sub c} at 77 K and zero field was > 2 x 10{sup 6} A/cm{sup 2}. The films exhibited good flux pinning properties.

Sources of SO{sub 2}, SO{sub 4}{sup 2-}, NO{sub x} and NO{sub 3}{sup -} in the air of four Spanish remote stations

Energy Technology Data Exchange (ETDEWEB)

Rua, A.; Hernandez, E.; Parras, J. de las; Martin, I.; Gimeno, L. [Complutense University, Madrid (Spain). Dept. of Statistic and Operative Investigation II

1998-09-01

In this study we have analyzed the sources of SO{sub 2}, SO{sub 4}{sup 2-}, NO{sub x}, and NO{sub 3}{sup -} in the air of four remote Spanish stations belonging to the European Monitoring and Evaluation Programme (EMEP) network. Information about trajectories has been used together with the conditional probability functions (CPFs). The most remarkable result is that the Mediterranean area is the main source of these pollutants in the air of the Spanish EMEP stations. Northern Africa and Central Europe are also important sources while the Atlantic Ocean and British Islands are, in general terms, low sources of these pollutants. The role of the Iberian Peninsula as a source of these pollutants in one of the stations, Logrono, is analyzed with more details using smaller regions to define CPFs. 26 refs., 12 figs., 2 tabs.

Laser-driven soft-X-ray undulator source

International Nuclear Information System (INIS)

Fuchs, Matthias

2010-01-01

The experimental results described in this thesis demonstrate the successful synergy between the research fields described above: the development of an undulator source driven by laser-plasma accelerated electron beams. First efforts in this new field have led to the production of radiation in the visible to infrared part of the electromagnetic spectrum [Schlenvoigt et al., 2008]. In contrast to these early achievements, the experiment described here shows the successful production of laser-driven undulator radiation in the soft-X-ray range with a remarkable reproducibility. The source produced tunable, collimated beams with a wavelength of ∝17 nm from a compact setup. Undulator spectra were detected in ∝70% of consecutive driver-laser shots, which is a remarkable reproducibility for a first proof-of-concept demonstration using ultra-high intensity laser systems. This can be attributed to a stable electron acceleration scheme as well as to the first application of miniature magnetic quadrupole lenses with laseraccelerated beams. The lenses significantly reduce the electron beam divergence and its angular shot-to-shot fluctuations The setup of this experiment is the foundation of potential university-laboratory-sized, highly-brilliant hard X-ray sources. By increasing the electron energy to about 1 GeV, X-ray pulses with an expected duration of ∝10 fs and a photon energy of 1 keV could be produced in an almost identical arrangement. It can also be used as a testbed for the development of a free-electron laser of significantly smaller dimension than facilities based on conventional accelerators [Gruener et al., 2007]. Such compact sources have the potential for application in many fields of science. In addition, these developments could lead to ideal sources for ultrafast pump-probe experiments due to the perfect synchronization of the X-ray beam to the driver laser. (orig.)

Laser-driven soft-X-ray undulator source

Energy Technology Data Exchange (ETDEWEB)

Fuchs, Matthias

2010-08-04

The experimental results described in this thesis demonstrate the successful synergy between the research fields described above: the development of an undulator source driven by laser-plasma accelerated electron beams. First efforts in this new field have led to the production of radiation in the visible to infrared part of the electromagnetic spectrum [Schlenvoigt et al., 2008]. In contrast to these early achievements, the experiment described here shows the successful production of laser-driven undulator radiation in the soft-X-ray range with a remarkable reproducibility. The source produced tunable, collimated beams with a wavelength of {proportional_to}17 nm from a compact setup. Undulator spectra were detected in {proportional_to}70% of consecutive driver-laser shots, which is a remarkable reproducibility for a first proof-of-concept demonstration using ultra-high intensity laser systems. This can be attributed to a stable electron acceleration scheme as well as to the first application of miniature magnetic quadrupole lenses with laseraccelerated beams. The lenses significantly reduce the electron beam divergence and its angular shot-to-shot fluctuations The setup of this experiment is the foundation of potential university-laboratory-sized, highly-brilliant hard X-ray sources. By increasing the electron energy to about 1 GeV, X-ray pulses with an expected duration of {proportional_to}10 fs and a photon energy of 1 keV could be produced in an almost identical arrangement. It can also be used as a testbed for the development of a free-electron laser of significantly smaller dimension than facilities based on conventional accelerators [Gruener et al., 2007]. Such compact sources have the potential for application in many fields of science. In addition, these developments could lead to ideal sources for ultrafast pump-probe experiments due to the perfect synchronization of the X-ray beam to the driver laser. (orig.)

Monte Carlo study of the critical behavior and magnetic properties of La{sub 2/3}Ca{sub 1/3}MnO{sub 3} thin films

Energy Technology Data Exchange (ETDEWEB)

Restrepo-Parra, E., E-mail: erestrepopa@unal.edu.c [Departamento de Fisica y Quimica, Universidad Nacional de Colombia-Sede Manizales, A.A. 127 Manizales (Colombia); Bedoya-Hincapie, C.M.; Jurado, F.J.; Riano-Rojas, J.C. [Departamento de Fisica y Quimica, Universidad Nacional de Colombia-Sede Manizales, A.A. 127 Manizales (Colombia); Restrepo, J. [Grupo de Magnetismo y Simulacion G, Instituto de Fisica, Universidad de Antioquia, A.A. 1226 Medellin (Colombia)

2010-11-15

Critical exponents offer important information concerning the interaction mechanisms near the paramagnetic to ferromagnetic transition. In this work a Monte Carlo-Metropolis simulation of the critical behavior in La{sub 2/3}Ca{sub 1/3}MnO{sub 3} thin films is addressed. Canonical ensemble averages for magnetization per site, magnetic susceptibility and specific heat of stoichiometric manganite within a three-dimensional classical Heisenberg model with nearest magnetic neighbor interactions are computed. The La{sub 2/3}Ca{sub 1/3}MnO{sub 3} thin films were simulated addressing the thickness influence and thermal dependence. In the model, Mn magnetic ions are distributed on a simple cubic lattice according to the perovskite structure of this manganite. Ferromagnetic coupling for the bonds Mn{sup 3+}-Mn{sup 3+}(e{sub g}-e{sub g}'), Mn{sup 3+}-Mn{sup 4+}(e{sub g}-d{sup 3}) and Mn{sup 3+}-Mn{sup 4+}(e{sub g}'-d{sup 3}) were taken into account. On the basis of finite-size scaling theory, our best estimates of critical exponents, linked to the ferromagnetic to paramagnetic transition, for the correlation length, specific heat, magnetization and susceptibility are, respectively: v=0.56{+-}0.01, {alpha}=0.16{+-}0.03, {beta}=0.34{+-}0.04{gamma} and {gamma}=1.17{+-}0.05. These theoretical results are consistent with the Rushbrooke equalitiy {alpha}+2{beta}+{gamma}=2.

Higher Education Sub-Cultures and Open Source Adoption

Science.gov (United States)

van Rooij, Shahron Williams

2011-01-01

Successful adoption of new teaching and learning technologies in higher education requires the consensus of two sub-cultures, namely the technologist sub-culture and the academic sub-culture. This paper examines trends in adoption of open source software (OSS) for teaching and learning by comparing the results of a 2009 survey of 285 Chief…

Layer structured Na{sub 2}Ni(MoO{sub 4}){sub 2} particles as a visible-light-driven photocatalyst for degradation of methylene blue

Energy Technology Data Exchange (ETDEWEB)

Lu, Yuting; Chen, Luyang; Huang, Yanlin [College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123 (China); Chen, Cuili; Kim, Sun Il [Department of Physics and Interdisciplinary Program of Biomedical, Mechanical & Electrical Engineering, Pukyong National University, Busan 608-737 (Korea, Republic of); Seo, Hyo Jin, E-mail: hjseo@pknu.ac.kr [Department of Physics and Interdisciplinary Program of Biomedical, Mechanical & Electrical Engineering, Pukyong National University, Busan 608-737 (Korea, Republic of)

2015-03-15

Highlights: • Na{sub 2}Ni(MoO{sub 4}){sub 2} nanoparticles were developed by Pechini method. • The nanoparticles show high absorption in UV–vis wavelength region. • Na{sub 2}Ni(MoO{sub 4}){sub 2} has high activity in the MB dye degradation under visible light. • Hexagonal layers with heavily distorted NiO{sub 6} were superiority for photocatalysis. - Abstract: A new visible-light-driven photocatalyst of Na{sub 2}Ni(MoO{sub 4}){sub 2} particle was prepared by the modified Pechini method. The crystal structure was measured by X-ray diffraction (XRD) and the structural refinement. The sample was investigated by scanning electron microscope (SEM), transmission electron microscopy (TEM), and UV–vis absorption spectrum measurements. The average size of Na{sub 2}Ni(MoO{sub 4}){sub 2} particle is about 180 nm. Na{sub 2}Ni(MoO{sub 4}){sub 2} particle have an efficient optical absorption in the UV–visible light wavelength region with a direct allowed electronic transition of 2.06 eV. The effective photodegradation of methylene blue (MB) dye was demonstrated, which benefits from the special crystal structure of Na{sub 2}Ni(MoO{sub 4}){sub 2} particle. This crystal lattice has two infinite chains formed by (Ni,Na)O{sub 6} and MoO{sub 4} polyhedra standing in lines alone with the inner wall of the hexagonal tunnels. This results in the efficient optical absorption and provides more chances for electron–hole separations, which can further react with dye molecules to oxidize the dye pollutant into non-toxic products.

Critical end point of the first-order ferromagnetic transition in a Sm{sub 0.55}(Sr{sub 0.5}Ca{sub 0.5}){sub 0.45}MnO{sub 3} single crystal

Energy Technology Data Exchange (ETDEWEB)

Radheep, D. Mohan [Centre for High Pressure Research, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India); Sarkar, P. [Department of Physics, Serampore College, Serampore 712 201 (India); Arumugam, S. [Centre for High Pressure Research, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India); Suryanarayanan, R. [Laboratoire de Physico-Chimie de l' Etat Solide, ICMMO, CNRS, UMR8182, Universite Paris-Sud, 91405 Orsay (France); Mandal, P., E-mail: prabhat.mandal@saha.ac.in [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Calcutta 700 064 (India)

2014-09-01

We report on the magnetic field (H) and hydrostatic pressure (P) dependence of the order of the ferromagnetic (FM) to paramagnetic phase transition in a Sm{sub 0.55}(Sr{sub 0.5}Ca{sub 0.5}){sub 0.45}MnO{sub 3} single crystal. At ambient condition, the system exhibits a first-order FM transition at T{sub C}≈82K (in heating cycle) with strong thermal hysteresis (∼13 K). The application of external H and P increases T{sub C}, suppresses the hysteresis width, and thus weakens the first-order nature of the transition. Our analysis reveals that the hysteresis vanishes and the first-order FM transition becomes a crossover above a critical magnetic field H{sub cr}≈11.5T. The value of H{sub cr} is highest among the manganite family, although the first-order nature of the FM transition is believed to be strongest in Eu{sub 1−x}Sr{sub x}MnO{sub 3}(x≈0.45). - Highlights: • System shows a strong first-order ferromagnetic to paramagnetic phase transition. • Extremely sharp metal–insulator transition at around 82 K. • The value of critical magnetic field at which first-order transition becomes a crossover is highest among manganites. • The nature of transition is sensitive to external perturbations such as magnetic field and pressure.

Assessment of Laser-Driven Pulsed Neutron Sources for Poolside Neutron-based Advanced NDE – A Pathway to LANSCE-like Characterization at INL

Energy Technology Data Exchange (ETDEWEB)

Roth, Markus [Technische Univ. Darmstadt (Germany); Vogel, Sven C. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Bourke, Mark Andrew M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Fernandez, Juan Carlos [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Mocko, Michael Jeffrey [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Glenzer, Siegfried [Stanford Univ., CA (United States); Leemans, Wim [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Siders, Craig [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Haefner, Constantin [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

2017-04-19

A variety of opportunities for characterization of fresh nuclear fuels using thermal (~25meV) and epithermal (~10eV) neutrons have been documented at Los Alamos National Laboratory. They include spatially resolved non-destructive characterization of features, isotopic enrichment, chemical heterogeneity and stoichiometry. The LANSCE spallation neutron source is well suited in neutron fluence and temporal characteristics for studies of fuels. However, recent advances in high power short pulse lasers suggest that compact neutron sources might, over the next decade, become viable at a price point that would permit their consideration for poolside characterization on site at irradiation facilities. In a laser-driven neutron source the laser is used to accelerate deuterium ions into a beryllium target where neutrons are produced. At this time, the technology is new and their total neutron production is approximately four orders of magnitude less than a facility like LANSCE. However, recent measurements on a sub-optimized system demonstrated >10¹⁰ neutrons in sub-nanosecond pulses in predominantly forward direction. The compactness of the target system compared to a spallation target may allow exchanging the target during a measurement to e.g. characterize a highly radioactive sample with thermal, epithermal, and fast neutrons as well as hard X-rays, thus avoiding sample handling. At this time several groups are working on laser-driven neutron production and are advancing concepts for lasers, laser targets, and optimized neutron target/moderator systems. Advances in performance sufficient to enable poolside fuels characterization with LANSCE-like fluence on sample within a decade may be possible. This report describes the underlying physics and state-of-the-art of the laser-driven neutron production process from the perspective of the DOE/NE mission. It also discusses the development and understanding that will be necessary to provide customized capability for

Is alpha-V<sub>2sub>O>5sub> a cathode material for Mg insertion batteries?

Energy Technology Data Exchange (ETDEWEB)

Sa, Niya; Wang, Hao; Proffit, Danielle L.; Lipson, Albert L.; Key, Baris; Liu, Miao; Feng, Zhenxing; Fister, Timothy T.; Ren, Yang; Sun, Cheng-Jun; Vaughey, John T.; Fenter, Paul A.; Persson, Kristin A.; Burrell, Anthony K.

2016-08-01

When designing a high energy density battery, one of the critical features is a high voltage, high capacity cathode material. In the development of Mg batteries, oxide cathodes that can reversibly intercalate Mg, while at the same time being compatible with an electrolyte that can deposit Mg reversibly are rare. Herein, we report the compatibility of Mg anodes with a-V<sub>2sub>O>5sub> by employing magnesium bis(trifluoromethane sulfonyl)imide in diglyme electrolytes at very low water levels. Electrolytes that contain a high water level do not reversibly deposit Mg, but interestingly these electrolytes appear to enable much higher capacities for an a-V<sub>2sub>O>5sub> cathode. Solid state NMR indicates that the major source of the higher capacity in high water content electrolytes originates from reversible proton insertion. In contrast, we found that lowering the water level of the magnesium bis(trifluoromethane sulfonyl)imide in diglyme electrolyte is critical to achieve reversible Mg deposition and direct evidence for reversible Mg intercalation is shown. Findings we report here elucidate the role of proton intercalation in water-containing electrolytes and clarify numerous conflicting reports of Mg insertion into a-V<sub>2sub>O>5sub>.

Structural and electric properties of AgGaTe{sub 2} layers prepared using mixed source of Ag{sub 2}Te and Ga{sub 2}Te{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Uruno, Aya [Department of Electrical Engineering and Bioscience, Waseda University, Tokyo (Japan); Kobayashi, Masakazu [Department of Electrical Engineering and Bioscience, Waseda University, Tokyo (Japan); Kagami Memorial Research Institute for Materials Science and Technology, Waseda University, Tokyo (Japan)

2017-01-15

AgGaTe{sub 2} layers were prepared on Si substrates by a closed space sublimation method using a mixed powder source of Ag{sub 2}Te and Ga{sub 2}Te{sub 3}. Ag{sub 2}Te buffer layer deposition was introduced to eliminate melt-back etching. The effect of the molar ratio of Ag{sub 2}Te and Ga{sub 2}Te{sub 3} in the mixed source on the crystallinity of the AgGaTe{sub 2} layer was investigated. The composition and the phase of the layer was found to change depending on the molar ratio in the deposits, which could be controlled by the source molar ratio along with the Ag{sub 2}Te buffer layer thickness. It was confirmed that (112) oriented uniform AgGaTe{sub 2} layer with an abrupt interface between AgGaTe{sub 2} and Si was formed after those parameters were tuned. The obtained layer exhibited the acceptor concentration of around 2.5 x 10{sup 16} cm{sup -3}. A solar cell was fabricated using the p-AgGaTe{sub 2}/n-Si heterojunction, and exhibited a conversion efficiency of 1.15%. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Avalanches and Criticality in Driven Magnetic Skyrmions

Science.gov (United States)

Díaz, S. A.; Reichhardt, C.; Arovas, D. P.; Saxena, A.; Reichhardt, C. J. O.

2018-03-01

We show using numerical simulations that slowly driven Skyrmions interacting with random pinning move via correlated jumps or avalanches. The avalanches exhibit power-law distributions in their duration and size, and the average avalanche shape for different avalanche durations can be scaled to a universal function, in agreement with theoretical predictions for systems in a nonequilibrium critical state. A distinctive feature of Skyrmions is the influence of the nondissipative Magnus term. When we increase the ratio of the Magnus term to the damping term, a change in the universality class of the behavior occurs, the average avalanche shape becomes increasingly asymmetric, and individual avalanches exhibit motion in the direction perpendicular to their own density gradient.

A facile approach to pure-phase Bi{sub 2}Fe{sub 4}O{sub 9} nanoparticles sensitive to visible light

Energy Technology Data Exchange (ETDEWEB)

Wang, X., E-mail: xiongwang@njust.edu.cn [School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Department of Chemistry, Faculty of Science, National University of Singapore, 3 Science Drive 3, 117543 (Singapore); Zhang, M.; Tian, P. [School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Chin, W.S. [Department of Chemistry, Faculty of Science, National University of Singapore, 3 Science Drive 3, 117543 (Singapore); Zhang, C.M. [School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China)

2014-12-01

Graphical abstract: - Highlights: • Pure-phase Bi{sub 2}Fe{sub 4}O{sub 9} nanoparticles were prepared by a facile and environmentally benign sol–gel method. • The multiband characteristic of the nanoparticles greatly expands the visible light absorption. • The visible-light-driven photocatalytic activity of the obtained nanoparticles was improved by 30-fold as compared to the bulk. - Abstract: Pure-phase Bi{sub 2}Fe{sub 4}O{sub 9} nanoparticles with mullite-type structure were successfully fabricated through a facile and environmentally benign sol–gel process. According to the UV–Vis diffuse reflection spectrum, the multiband structure and the band edge position of the nanoparticles were confirmed, indicating the prominent absorption in the expanded visible-light region. As compared to the bulk, the visible-light-driven photocatalytic activity of the obtained nanoparticles was improved by 30-fold. The much improved photocatalytic efficiency of the sample mainly owed to the small crystal size and the multiband characteristic as well as the adding of H{sub 2}O{sub 2} as electron scavenger and a source of hydroxide free radicals instead of Fenton-like reaction, leading to a low recombination of the photogenerated e{sup −}/h{sup +} pairs.

Monte Carlo simulation of a TRIGA source driven core configuration: Preliminary results

International Nuclear Information System (INIS)

Burgio, N.; Ciavola, C.; Santagata, A.

2002-01-01

The different core configurations with a k eff ranging from 0.93 to 0.98, and their response when driven by a pulsed neutron source were simulated with MCNP4C3 (Los Alamos - Monte Carlo N Particles). Simulation results could be considered both as preliminary check for nuclear data and a conceptual design for 'source jerk' experiments on the frame of TRIGA Accelerator Driven Experiment (TRADE) on the reactor facility of Casaccia research center. (author)

Characterization of neutron leakage probability, k /SUB eff/ , and critical core surface mass density of small reactor assemblies through the Trombay criticality formula

International Nuclear Information System (INIS)

Kumar, A.; Rao, K.S.; Srinivasan, M.

1983-01-01

The Trombay criticality formula (TCF) has been derived by incorporating a number of well-known concepts of criticality physics to enable prediction of changes in critical size or k /SUB eff/ following alterations in geometrical and physical parameters of uniformly reflected small reactor assemblies characterized by large neutron leakage from the core. The variant parameters considered are size, shape, density and diluent concentration of the core, and density and thickness of the reflector. The effect of these changes (except core size) manifests, through sigma /SUB c/ the critical surface mass density of the ''corresponding critical core,'' that sigma, the massto-surface-area ratio of the core,'' is essentially a measure of the product /rho/ extended to nonspherical systems and plays a dominant role in the TCF. The functional dependence of k /SUB eff/ on sigma/sigma /SUB c/ , the system size relative to critical, is expressed in the TCF through two alternative representations, namely the modified Wigner rational form and, an exponential form, which is given

SIMULTANEOUS OBSERVATIONS OF SiO AND H{sub 2}O MASERS TOWARD KNOWN STELLAR H{sub 2}O MASER SOURCES

Energy Technology Data Exchange (ETDEWEB)

Kim, Jaeheon [Yonsei University Observatory, Seongsan-ro 262, Seodaemun, Seoul 120-749 (Korea, Republic of); Cho, Se-Hyung [Korean VLBI Network Yonsei Radio Astronomy Observatory, Yonsei University, Seongsan-ro 262, Seodaemun, Seoul 120-749 (Korea, Republic of); Kim, Sang Joon, E-mail: jhkim@kasi.re.kr, E-mail: cho@kasi.re.kr, E-mail: sjkim1@khu.ac.kr [Department of Astronomy and Space Science, Kyung Hee University, Seocheon-Dong, Giheung-Gu, Yongin, Gyeonggi-Do 446-701 (Korea, Republic of)

2013-01-01

We present the results of simultaneous observations of SiO v = 1, 2, {sup 29}SiO v = 0, J = 1-0, and H{sub 2}O 6{sub 16}-5{sub 23} maser lines toward 152 known stellar H{sub 2}O maser sources using the Yonsei 21 m radio telescope of the Korean VLBI Network from 2009 June to 2011 January. Both SiO and H{sub 2}O masers were detected from 62 sources with a detection rate of 40.8%. The SiO-only maser emission without H{sub 2}O maser detection was detected from 27 sources, while the H{sub 2}O-only maser without SiO maser detection was detected from 22 sources. Therefore, the overall SiO maser emission was detected from 89 sources, resulting in a detection rate of 58.6%. We have identified 70 new detections of the SiO maser emission. For both H{sub 2}O and SiO maser detected sources, the peak and integrated antenna temperatures of SiO masers are stronger than those of H{sub 2}O masers in both Mira variables and OH/IR stars and the relative intensity ratios of H{sub 2}O to SiO masers in OH/IR stars are larger than those in Mira variables. In addition, distributions of 152 observed sources were investigated in the IRAS two-color diagram.

A nuclear criticality safety assessment of the loss of moderation control in 2 1/2 and 10-ton cylinders containing enriched UF{sub 6}

Energy Technology Data Exchange (ETDEWEB)

Newvahner, R.L. [Martin Marietta Energy Systems, Inc., Piketon, OH (United States); Pryor, W.A. [PAI Corp., Oak Ridge, TN (United States)

1991-12-31

Moderation control for maintaining nuclear criticality safety in 2 {1/2}-ton, 10-ton, and 14-ton cylinders containing enriched uranium hexafluoride (UF{sub 6}) has been used safely within the nuclear industry for over thirty years, and is dependent on cylinder integrity and containment. This assessment evaluates the loss of moderation control by the breaching of containment and entry of water into the cylinders. The first objective of this study was to estimate the required amounts of water entering these large UF{sub 6} cylinders to react with, and to moderate the uranium compounds sufficiently to cause criticality. Hypothetical accident situations were modeled as a uranyl fluoride (UO{sub 2}F{sub 2}) slab above a UF{sub 6} hemicylinder, and a UO{sub 2}F{sub 2} sphere centered within a UF{sub 6} hemicylinder. These situations were investigated by computational analyses utilizing the KENO V.a Monte Carlo Computer Code. The results were used to estimate both the masses of water required for criticality, and the limiting masses of water that could be considered safe. The second objective of the assessment was to calculate the time available for emergency control actions before a criticality would occur, i.e., a {open_quotes}safetime{close_quotes}, for various sources of water and different size openings in a breached cylinder. In the situations considered, except the case for a fire hose, the safetime appears adequate for emergency control actions. The assessment shows that current practices for handling moderation controlled cylinders of low enriched UF{sub 6}, along with the continuation of established personnel training programs, ensure nuclear criticality safety for routine and emergency operations.

Kinetic parameters for source driven systems

International Nuclear Information System (INIS)

Dulla, S.; Ravetto, P.; Carta, M.; D'Angelo, A.

2006-01-01

The definition of the characteristic kinetic parameters of a subcritical source-driven system constitutes an interesting problem in reactor physics with important consequences for practical applications. Consistent and physically meaningful values of the parameters allow to obtain accurate results from kinetic simulation tools and to correctly interpret kinetic experiments. For subcritical systems a preliminary problem arises for the adoption of a suitable weighting function to be used in the projection procedure to derive a point model. The present work illustrates a consistent factorization-projection procedure which leads to the definition of the kinetic parameters in a straightforward manner. The reactivity term is introduced coherently with the generalized perturbation theory applied to the source multiplication factor ks, which is thus given a physical role in the kinetic model. The effective prompt lifetime is introduced on the assumption that a neutron generation can be initiated by both the fission process and the source emission. Results are presented for simplified configurations to fully comprehend the physical features and for a more complicated highly decoupled system treated in transport theory. (authors)

Instability and transport driven by an electron temperature gradient close to critical

International Nuclear Information System (INIS)

Dong, J.Q.; Jian, G.D.; Wang, A.K.; Sanuki, H.; Itoh, K.

2003-01-01

Electron temperature gradient (ETG) driven instability in toroidal plasmas is studied with gyrokinetic theory. The full electron kinetics is considered. The upgraded numerical scheme for solving the integral eigenvalue equations allows the study of both growing and damping modes, and thus direct calculation of critical gradient. Algebraic formulas for the critical gradient with respect to ratio of electron temperature over ion temperature and to toroidicity are given. An estimation for turbulence induced transport is presented. (author)

Recovery Act: Innovative CO<sub>2sub> Sequestration from Flue Gas Using Industrial Sources and Innovative Concept for Beneficial CO<sub>2sub> Use

Energy Technology Data Exchange (ETDEWEB)

Dando, Neal [Alcoa Inc., Pittsburgh, PA (United States); Gershenzon, Mike [Alcoa Inc., Pittsburgh, PA (United States); Ghosh, Rajat [Alcoa Inc., Pittsburgh, PA (United States)

2012-07-31

The overall goal of this DOE Phase 2 project was to further develop and conduct pilot-scale and field testing of a biomimetic in-duct scrubbing system for the capture of gaseous CO<sub>2sub> coupled with sequestration of captured carbon by carbonation of alkaline industrial wastes. The Phase 2 project, reported on here, combined efforts in enzyme development, scrubber optimization, and sequestrant evaluations to perform an economic feasibility study of technology deployment. The optimization of carbonic anhydrase (CA) enzyme reactivity and stability are critical steps in deployment of this technology. A variety of CA enzyme variants were evaluated for reactivity and stability in both bench scale and in laboratory pilot scale testing to determine current limits in enzyme performance. Optimization of scrubber design allowed for improved process economics while maintaining desired capture efficiencies. A range of configurations, materials, and operating conditions were examined at the Alcoa Technical Center on a pilot scale scrubber. This work indicated that a cross current flow utilizing a specialized gas-liquid contactor offered the lowest system operating energy. Various industrial waste materials were evaluated as sources of alkalinity for the scrubber feed solution and as sources of calcium for precipitation of carbonate. Solids were mixed with a simulated sodium bicarbonate scrubber blowdown to comparatively examine reactivity. Supernatant solutions and post-test solids were analyzed to quantify and model the sequestration reactions. The best performing solids were found to sequester between 2.3 and 2.9 moles of CO<sub>2sub> per kg of dry solid in 1-4 hours of reaction time. These best performing solids were cement kiln dust, circulating dry scrubber ash, and spray dryer absorber ash. A techno-economic analysis was performed to evaluate the commercial viability of the proposed carbon capture and sequestration process in full-scale at an aluminum smelter and

Fundamental-mode sources in approach to critical experiments

International Nuclear Information System (INIS)

Goda, J.; Busch, R.

2000-01-01

An equivalent fundamental-mode source is an imaginary source that is distributed identically in space, energy, and angle to the fundamental-mode fission source. Therefore, it produces the same neutron multiplication as the fundamental-mode fission source. Even if two source distributions produce the same number of spontaneous fission neutrons, they will not necessarily contribute equally toward the multiplication of a given system. A method of comparing the relative importance of source distributions is needed. A factor, denoted as g* and defined as the ratio of the fixed-source multiplication to the fundamental-mode multiplication, is used to convert a given source strength to its equivalent fundamental-mode source strength. This factor is of interest to criticality safety as it relates to the 1/M method of approach to critical. Ideally, a plot of 1/M versus κ eff is linear. However, since 1/M = (1 minus κ eff )/g*, the plot will be linear only if g* is constant with κ eff . When g* increases with κ eff , the 1/M plot is said to be conservative because the critical mass is underestimated. However, it is possible for g* to decrease with κ eff yielding a nonconservative 1/M plot. A better understanding of g* would help predict whether a given approach to critical will be conservative or nonconservative. The equivalent fundamental-mode source strength g*S can be predicted by experiment. The experimental method was tested on the XIX-1 core on the Fast Critical Assembly at the Japan Atomic Energy Research Institute. The results showed a 30% difference between measured and calculated values. However, the XIX-1 reactor had significant intermediate-energy neutrons. The presence of intermediate-energy neutrons may have made the cross-section set used for predicted values less than ideal for the system

Implementation of 252Cf-source-driven power spectrum density measurement system

International Nuclear Information System (INIS)

Ren Yong; Wei Biao; Feng Peng; Li Jiansheng; Ye Cenming

2012-01-01

The principle of 252 Cf-source-driven power spectrum density measurement method is introduced. A measurement system and platform is realized accordingly, which is a combination of hardware and software, for measuring nuclear parameters. The detection method of neutron pulses based on an ultra-high-speed data acquisition card (three channels, 1 GHz sampling rate, 1 ns synchronization) is described, and the data processing process and the power spectrum density algorithm on PC are designed. This 252 Cf-source-driven power spectrum density measurement system can effectively obtain the nuclear tag parameters of nuclear random processes, such as correlation function and power spectrum density. (authors)

Experimental research on novel adsorption chiller driven by low grade heat source

International Nuclear Information System (INIS)

Wang, D.C.; Shi, Z.X.; Yang, Q.R.; Tian, X.L.; Zhang, J.C.; Wu, J.Y.

2007-01-01

A novel silica gel-water adsorption chiller is developed. This chiller consists of three vacuum chambers: two adsorption/desorption (or evaporation/condensation) vacuum chambers and one heat pipe working vacuum chamber. In this chiller, only one vacuum valve is installed between the two adsorption/desorption vacuum chambers to improve its performance when it is driven by a low temperature heat source. The operational reliability of the chiller is highly improved because of fewer moving parts. In this work, the performance of the chiller is experimentally tested under a low grade heat source, such as 55-67 o C. The test results show that the performance of this chiller is satisfying when it is driven by a low grade heat source, such as 65 o C, and the cooling capacity (or refrigeration capacity) will reach about 5 kW when the hot water temperature is 65 o C, the cooling water temperature is 30.5 o C and the chilled water inlet temperature is 15.1 o C. The test results confirm that this kind of adsorption chiller can be effectively driven by a low grade heat source

The participation of IPEN in the IAEA coordinated research projects on accelerators driven systems (ADS)

Energy Technology Data Exchange (ETDEWEB)

Maiorino, J.R.; Santos, A.; Carluccio, T.; Rossi, P.C.R.; Antunes, A.; Oliveira, F. de; Lee, S.M. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)]. E-mail: maiorino@ipen.br

2007-07-01

This paper describes the participation of the IPEN in the International Atomic Energy Agency (IAEA) Coordinated Research Projects(CRP) on Analytical and Experimental Benchmark Analysis on ADS and Low Enriched Uranium Fuel Utilization in ADS. The first CRP has as specific objective to improve the present understanding of the coupling of an external neutron source [e.g. a spallation source in the case of the accelerator driven system (ADS)] with a multiplicative sub-critical core, and the second CRP, or collaborative work, the utilization of LEU in existing or planned ADS facilities. IPEN participate in both CRP through a research contract (13388), and although there are several benchmarks defined in both CRP, presently IPEN is participating in the activities related with reactor physics benchmark of the Yalina Booster facility in Belarus, in the analytical and numerical benchmarking of methods and codes for ADS kinetics, and in the ADS target calculations. Besides, since there are plans to introduce a compact neutron generator in a sub critical core of the IPEN-MB-01 facility, a benchmark of a simulation of such project has been proposed in the LEU-ADS CRP. The paper will review the CRPs with details on the activities in which IPEN is participating. (author)

The participation of IPEN in the IAEA coordinated research projects on accelerators driven systems (ADS)

International Nuclear Information System (INIS)

Maiorino, J.R.; Santos, A.; Carluccio, T.; Rossi, P.C.R.; Antunes, A.; Oliveira, F. de; Lee, S.M.

2007-01-01

This paper describes the participation of the IPEN in the International Atomic Energy Agency (IAEA) Coordinated Research Projects(CRP) on Analytical and Experimental Benchmark Analysis on ADS and Low Enriched Uranium Fuel Utilization in ADS. The first CRP has as specific objective to improve the present understanding of the coupling of an external neutron source [e.g. a spallation source in the case of the accelerator driven system (ADS)] with a multiplicative sub-critical core, and the second CRP, or collaborative work, the utilization of LEU in existing or planned ADS facilities. IPEN participate in both CRP through a research contract (13388), and although there are several benchmarks defined in both CRP, presently IPEN is participating in the activities related with reactor physics benchmark of the Yalina Booster facility in Belarus, in the analytical and numerical benchmarking of methods and codes for ADS kinetics, and in the ADS target calculations. Besides, since there are plans to introduce a compact neutron generator in a sub critical core of the IPEN-MB-01 facility, a benchmark of a simulation of such project has been proposed in the LEU-ADS CRP. The paper will review the CRPs with details on the activities in which IPEN is participating. (author)

Laser-driven polarized H/D sources and targets

International Nuclear Information System (INIS)

Clasie, B.; Crawford, C.; Dutta, D.; Gao, H.; Seely, J.; Xu, W.

2005-01-01

Traditionally, Atomic Beam Sources are used to produce targets of nuclear polarized hydrogen (H) or deuterium (D) for experiments using storage rings. Laser-Driven Sources (LDSs) offer a factor of 20-30 gain in the target thickness (however, with lower polarization) and may produce a higher overall figure of merit. The LDS is based on the technique of spin-exchange optical pumping where alkali vapor is polarized by absorbing circularly polarized laser photons. The H or D atoms are nuclear-polarized through spin-exchange collisions with the polarized alkali vapor and through subsequent hyperfine interactions during frequent H-H or D-D collisions

Experimental and Numerical Analysis of S-CO{sub 2} Critical Flow for SFR Recovery System Design

Energy Technology Data Exchange (ETDEWEB)

Kim, Min Seok; Jung, Hwa-Young; Ahn, Yoonhan; Lee, Jekyoung; Lee, Jeong Ik [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

2016-05-15

This paper presents both numerical and experimental studies of the critical flow of S-CO{sub 2} while special attention is given to the turbo-machinery seal design. A computational critical flow model is described first. The experiments were conducted to validate the critical flow model. Various conditions have been tested to study the flow characteristic and provide validation data for the model. The comparison of numerical and experimental results of S-CO{sub 2} critical flow will be presented. In order to eliminate SWR, a concept of coupling the Supercritical CO{sub 2} (S-CO{sub 2}) cycle with SFR has been proposed. It is known that for a closed system controlling the inventory is important for stable operation and achieving high efficiency. Since the S-CO{sub 2} power cycle is a highly pressurized system, certain amount of leakage flow is inevitable in the rotating turbo-machinery via seals. To simulate the CO{sub 2} leak flow in a turbo-machinery with higher accuracy in the future, the real gas effect and friction factor will be considered for the CO{sub 2} critical flow model. Moreover, experimentally obtained temperature data were somewhat different from the numerically obtained temperature due to the insufficient insulation and large thermal inertia of the CO{sub 2} critical flow facility. Insulation in connecting pipes and the low-pressure tank will be added and additional tests will be conducted.

Etching of LiNbO/sub 3/ by laser-driven fusion of salts

International Nuclear Information System (INIS)

Ashby, C.I.H.; Brannon, P.J.

1987-01-01

Lithium niobate exhibits low reactivity with most chemical etchants. Consequently, etching a LiNbO/sub 3/ surface to produce optical structures such as ridge waveguides or grooves for fiber coupling normally requires relatively slow processes such as ion milling. The authors have developed a laser-driven chemical etching process for etching highly unreactive ionic solids based on the fusion of salts in the molten phase and show that the etch rate can be more than 100 times faster than ion milling rates. This process involves spatially localized melting of LiNbO/sub 3/ by high-power density laser pulses with photon energies in excess of the band gap of LiNbO/sub 3/. While molten, LiNbO/sub 3/ undergoes reaction with a surface coating of KF to form niobium oxyfluoride anions by fusion of the salts. The resulting solid is highly water soluble. The insolubility of LiNbO/sub 3/ permits subsequent removal of only the irradiated area by rinsing in water. Surface morphology is determined by laser power density. The process exhibits a wavelength dependence

LaNiO{sub 3} buffer layers for high critical current density YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} and Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8{minus}{delta}} films

Energy Technology Data Exchange (ETDEWEB)

Carlson, C.M.; Parilla, P.A.; Siegal, M.P.; Ginley, D.S.; Wang, Y.; Blaugher, R.D.; Price, J.C.; Overmyer, D.L.; Venturini, E.L.

1999-10-01

We demonstrate high critical current density superconducting films of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} (YBCO) and Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8{minus}{delta}} (Tl-2212) using LaNiO{sub 3} (LNO) buffer layers. YBCO films grown on an LNO buffer layer have only a slightly lower J{sub c} (5 K, H=0) than films grown directly on a bare LaAlO{sub 3} substrate. YBCO films grown on LNO buffer layers exhibit minor microstructural disorder and enhanced flux pinning. LNO-buffered Tl-2212 samples show large reductions in J{sub c} at all temperatures and fields compared to those grown on bare LaAlO{sub 3}, correlating to both {ital a}-axis grain and nonsuperconducting phase formation. LNO could be a promising buffer layer for both YBCO and Tl-based superconducting films in coated conductor applications. {copyright} {ital 1999 American Institute of Physics.}

Effect of uniaxial strain on the quantum critical phase of Sr{sub 3}Ru{sub 2}O{sub 7}

Energy Technology Data Exchange (ETDEWEB)

Barber, Mark E.; Brodsky, Daniel O.; Mackenzie, Andrew P. [Scottish Universities Physics Alliance (SUPA), School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS (United Kingdom); Max Planck Institute for Chemical Physics of Solids, Noethnitzer Strasse 40, Dresden 01187 (Germany); Hicks, Clifford W. [Max Planck Institute for Chemical Physics of Solids, Noethnitzer Strasse 40, Dresden 01187 (Germany); Perry, Robin [School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3FD (United Kingdom)

2016-07-01

Sr{sub 3}Ru{sub 2}O{sub 7} has a metamagnetic quantum critical endpoint, which in highly pure samples is masked by a novel phase. This phase is isotropic in the absence of symmetry-breaking fields, but weak in-plane magnetic fields are well-known to induce strong resistive anisotropy, leading to speculation that the phase intrinsically breaks the tetragonal symmetry of the lattice. We have used uniaxial strain to break the symmetry of the lattice and have found a dramatic response: compression by 0.1%, for example, induces a resistive anisotropy of ∝ 2.5. I will discuss these results in the context of the underlying symmetry of the anomalous phase.

Transmutation of uranium and thorium in the particle field of the Quinta sub-critical assembly

Science.gov (United States)

Hashemi-Nezhad, S. R.; Asquith, N. L.; Voronko, V. A.; Sotnikov, V. V.; Zhadan, Alina; Zhuk, I. V.; Potapenko, A.; Husak, Krystsina; Chilap, V.; Adam, J.; Baldin, A.; Berlev, A.; Furman, W.; Kadykov, M.; Khushvaktov, J.; Kudashkin, I.; Mar'in, I.; Paraipan, M.; Pronskih, V.; Solnyshkin, A.; Tyutyunnikov, S.

2018-03-01

The fission rates of natural uranium and thorium were measured in the particle field of Quinta, a 512 kg natural uranium target-blanket sub-critical assembly. The Quinta assembly was irradiated with deuterons of energy 4 GeV from the Nuclotron accelerator of the Joint Institute for Nuclear Research (JINR), Dubna, Russia. Fission rates of uranium and thorium were measured using Gamma spectroscopy and fission track techniques. The production rate of 239Np was also measured. The obtained experimental results were compared with Monte Carlo predictions using the MCNPX 2.7 code employing the physics and fission-evaporation models of INCL4-ABLA, CEM03.03 and LAQGSM03.03. Some of the neutronic characteristics of the Quinta are compared with the "Energy plus Transmutation (EpT)" subcritical assembly, which is composed of a lead target and natU blanket. This comparison clearly demonstrates the importance of target material, neutron moderator and reflector types on the performance of a spallation neutron driven subcritical system. As the dimensions of the Quinta are very close to those of an optimal multi-rod-uranium target, the experimental and Monte Carlo calculation results presented in this paper provide insights on the particle field within a uranium target as well as in Accelerator Driven Systems in general.

Fabrication and high visible-light-driven photocurrent response of g-C{sub 3}N{sub 4} film: The role of thiourea

Energy Technology Data Exchange (ETDEWEB)

Ye, Lijuan; Chen, Shijian, E-mail: sjchen@cqu.edu.cn

2016-12-15

Highlights: • Thiourea promotes the growth and crystalline of the g-C{sub 3}N{sub 4} films on ITO. • Thiourea introduces S dopants into the g-C{sub 3}N{sub 4} films. • The obtained S-doped g-C{sub 3}N{sub 4} thin films show high VLD photocurrent response. • Three heterojunction structure types based on the g-C{sub 3}N{sub 4} films are proposed. - Abstract: We report on a convenient CVD fabrication of the uniform, compact and reproducible g-C{sub 3}N{sub 4} solid films on indium-tin oxide substrates. It is found that mixing quantitative thiourea into melamine as co-precursor prompts the deposition of greenish-yellow, transparent and smooth g-C{sub 3}N{sub 4} thin films. The thiourea apparently affects the crystalline, the surface morphologies and the energy band structures of g-C{sub 3}N{sub 4} films by modulating the polymerization process of the precursors, and simultaneously introduces S dopants into the g-C{sub 3}N{sub 4} films. Due to these roles of thiourea, the obtained S-doped g-C{sub 3}N{sub 4} films as a photoelectrode show a high and stable visible-light-driven photocurrent response. To further improve the photocurrent, the construction of three heterojunction structure types based on g-C{sub 3}N{sub 4} films is proposed and the corresponding charge transfer mechanisms are well discussed. The successful fabrication of high quality g-C{sub 3}N{sub 4} films in this work provides a footstone to construct the heterojunction film structures based on the carbon nitrides for the photoelectrochemical overall water splitting.

Open-source, community-driven microfluidics with Metafluidics.

Science.gov (United States)

Kong, David S; Thorsen, Todd A; Babb, Jonathan; Wick, Scott T; Gam, Jeremy J; Weiss, Ron; Carr, Peter A

2017-06-07

Microfluidic devices have the potential to automate and miniaturize biological experiments, but open-source sharing of device designs has lagged behind sharing of other resources such as software. Synthetic biologists have used microfluidics for DNA assembly, cell-free expression, and cell culture, but a combination of expense, device complexity, and reliance on custom set-ups hampers their widespread adoption. We present Metafluidics, an open-source, community-driven repository that hosts digital design files, assembly specifications, and open-source software to enable users to build, configure, and operate a microfluidic device. We use Metafluidics to share designs and fabrication instructions for both a microfluidic ring-mixer device and a 32-channel tabletop microfluidic controller. This device and controller are applied to build genetic circuits using standard DNA assembly methods including ligation, Gateway, Gibson, and Golden Gate. Metafluidics is intended to enable a broad community of engineers, DIY enthusiasts, and other nontraditional participants with limited fabrication skills to contribute to microfluidic research.

Time-Dependent S{sub N} Calculations Describing Pulsed Source Experiments at the FRO Reactor

Energy Technology Data Exchange (ETDEWEB)

Bergstrom, A.; Kockum, J.; Soderberg, S. [Research Institute of National Defence, Stockholm (Sweden)

1968-04-15

In view of the difficulties in describing pulsed source experiments quantitatively in assemblies consisting of a fast core and a light reflector, a time-dependent S{sub N} code has been applied to this type of assembly. The code, written for the IBM 7090 computer, divides time into short intervals and computes the flux in spherical geometry for each interval using the Carlson S{sub N} scheme. The source term is obtained by extrapolation from two earlier time-intervals. Several problems in connection with the discretization of the time, space and energy dimensions are discussed. For the sub-critical assembly studied the treatment of the lower energy-groups is decisive for the numerical stability. A 22-group cross-section set with a low energy cut-off at 0.04 eV obtained with the SPENG programme has been used. The time intervals are varied continuously and are set proportional to the inverse of the maximum logarithmic time-derivative of the space and energy-dependent flux with the further restriction that they are not allowed to increase above a predetermined value. In a typical case, the intervals vary between 10{sup -9} and 10{sup -8} sec. The memory of the computer is fully exploited when 22 energy groups and 46 radial points are used. The computing time for each time-interval is about 6 sec. The code has been applied to a 3.5% sub-critical assembly consisting of a 20% enriched, spherical uranium metal core with a thick copper reflector and the calculations have been compared to experiments with good agreement. The calculations show that spectral equilibrium below 10 keV is not reached until times long compared to the usual measuring times and that the exponential decay finally reached is entirely determined by reflector properties at almost thermal energies. It is also shown that the simple one- and two-region models are inadequate in this case and that no time-independent prompt neutron life-time can be obtained from the measurements. (author)

Photocatalytic applications of Cr{sub 2}S{sub 3} synthesized from single and multi-source precursors

Energy Technology Data Exchange (ETDEWEB)

Hussain, Wajid [Department of Chemistry, Quaid-i-Azam University, 45320, Islamabad (Pakistan); Badshah, Amin, E-mail: aminbadshah@qau.edu.pk [Department of Chemistry, Quaid-i-Azam University, 45320, Islamabad (Pakistan); Hussain, Raja Azadar; Imtiaz-ud-Din [Department of Chemistry, Quaid-i-Azam University, 45320, Islamabad (Pakistan); Aleem, Muhammad Adeel [The Pakistan Institute of Engineering and Applied Sciences (PIEAS) (Pakistan); Bahadur, Ali [Department of Chemistry, Quaid-i-Azam University, 45320, Islamabad (Pakistan); Iqbal, Shahid [School of Chemistry and Chemical Engineering, University of Chinese Academy of Sciences, Beijing, 100049 (China); Farooq, Muhammad Umar; Ali, Hassan [Department of Chemistry, Quaid-i-Azam University, 45320, Islamabad (Pakistan)

2017-06-15

Most of the material research work is pertinent to the synthesis of transition-metal sulfides nanoparticles but here the studies are limited to the synthesis of chromium sulfide. However, the preparation method, presented in this work, may be extended to other metal chalcogenides nanoparticles for various potential applications. The ligand (precursor), 1-(2-chloro-4-nitrophenyl)-3,3-chlorobenzoyl and Cr{sub 2}S{sub 3} have been synthesized initially from single source precursor and then from multi source precursors. The target was to alter the morphologies of nanomaterial while altering the synthetic route and that was successfully achieved. Chromium sulfide nano-rods were synthesized using single source precursors while nanoparticles were fabricated using multi source precursors. Characterization were carried out through {sup 1}H and {sup 13}C NMR, scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction microscopy (PXRD), energy dispersive X-ray spectroscopy (EDX), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM). Our objective is to change the morphologies by changing the synthetic route so that is why further applications were done only for multi-source product, denying single source product. The metal sulfides nanoparticles exhibit higher activity than their bulk material for the photocatalytic degradation of organic dyes under visible-light irradiation. So, photocatalytic activity was successfully achieved under direct sunlight against five different cationic and anionic organic dyes including malachite green (MG), methylene blue (MB), rhodamine B (RhB), methyl violet (MV) and methyl orange (MO). These organic dyes MV, MG, MB, and RB were almost diminished or decolorized by Cr{sub 2}S{sub 3} within 110, 90, 100, and 130, minutes, respectively expect MO. - Highlights: • Synthesis of Cr{sub 2}S{sub 3} from single and multisource precursors is

Numerical Analysis of S-CO{sub 2} Test Loop Transient Conditions near the Critical Point of CO{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Bae, Seong Jun; Oh, Bongseong; Ahn, Yoonhan; Baik, Seongjoon; Lee, Jekyoung; Lee, Jeong Ik [KAIST, Daejeon (Korea, Republic of)

2016-05-15

It was identified that controlling CO{sub 2} compressor operation near the critical point is one of the most important issues to operate a S-CO{sub 2} Brayton cycle with a high efficiency. Despite the growing interest in the S-CO{sub 2} Brayton cycle, a few previous research on the transient analysis of the S-CO{sub 2} system has been conducted previously. Moreover, previous studies have some limitation in the modelled test facility, and the experiment was not performed to observe specific scenario. The KAIST research team has conducted S-CO{sub 2} system transient experiments with the CO{sub 2} compressing test facility called SCO{sub 2}PE (Supercritical CO{sub 2} Pressurizing Experiment) at KAIST In this study, authors use the transient analysis code GAMMA (Gas Multidimensional Multicomponent mixture Analysis) code for analyzing the experiment. Two transient scenarios were selected in this study; over cooling and under cooling situations. The selected transient situation is of particular interest since the compressor inlet conditions start to drift away from the critical point of CO{sub 2}. The results represent that the GAMMA code can simulate the S-CO{sub 2} test facility, SCO{sub 2}PE. However, as shown in the cooling water flow rate increasing scenario, the GAMMA code shows calculation error when the phase change occurs. Furthermore, although the results of the cooling water flow rate decrease case shows reasonable agreement with the experimental data, there are still some unexplained differences between the experimental data and the GAMMA code prediction.

A Critical Review of the Impacts of Leaking CO<sub>2sub> Gas and Brine on Groundwater Quality

Energy Technology Data Exchange (ETDEWEB)

Qafoku, Nikolla [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Zheng, Liange [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Bacon, Diana H. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lawter, Amanda R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Brown, Christopher F. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

2015-09-30

Geological carbon sequestration (GCS) is a global carbon emission reduction strategy involving the capture of CO<sub>2sub> emitted from fossil fuel burning power plants, as well as the subsequent injection of the captured CO<sub>2sub> gas into deep saline aquifers or depleted oil and gas reservoirs. A critical question that arises from the proposed GCS is the potential impacts of CO<sub>2sub> injection on the quality of drinking-water systems overlying CO<sub>2sub> sequestration storage sites. Although storage reservoirs are evaluated and selected based on their ability to safely and securely store emplaced fluids, leakage of CO<sub>2sub> from storage reservoirs is a primary risk factor and potential barrier to the widespread acceptance of geologic CO<sub>2sub> sequestration (OR Harvey et al. 2013; Y-S Jun et al. 2013; DOE 2007). Therefore, a systematic understanding of how CO<sub>2sub> leakage would affect the geochemistry of potable aquifers, and subsequently control or affect elemental and contaminant release via sequential and/or simultaneous abiotic and biotic processes and reactions is vital.

Effects of Li source and calcination temperature on the electrochemical properties of LiNi{sub 0.5}Co{sub 0.2}Mn{sub 0.3}O{sub 2} lithium-ion cathode materials

Energy Technology Data Exchange (ETDEWEB)

Kong, Ji-Zhou [State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, No. 29 Yudao Street, Nanjing 210016 (China); Zhou, Fei, E-mail: fzhou@nuaa.edu.cn [State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, No. 29 Yudao Street, Nanjing 210016 (China); Wang, Chuan-Bao; Yang, Xiao-Yan [State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, No. 29 Yudao Street, Nanjing 210016 (China); Zhai, Hai-Fa; Li, Hui [Materials Science and Engineering Department, National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Li, Jun-Xiu; Tang, Zhou; Zhang, Shi-Qin [Jiangsu Cobalt Nickel Metal Co., Ltd. (KLK), Taixing 225404 (China)

2013-03-25

Highlights: ► Instead of ammonia, oxalic acid was used as chelating agent to prepare the hydroxide precursor. ► Effects of Li source and calcination temperature on physical and electrochemical properties were investigated. ► LiCO{sub 3} was considered as a more suitable Li source, compared with LiNO{sub 3}. ► The optimal calcination temperature was considered to be 850 °C. ► This sample exhibited excellent discharge capacity, cycle stability and rate capability. -- Abstract: Spherical Ni{sub 0.5}Co{sub 0.2}Mn{sub 0.3}(OH){sub 2} precursor was prepared via co-precipitation method using oxalic acid as chelating agent. And layered structure Li(Ni{sub 0.5}Co{sub 0.2}Mn{sub 0.3})O{sub 2} cathode materials were synthesized by calcining the mixture of different lithium salts and hydroxide precursor (Ni{sub 0.5}Co{sub 0.2}Mn{sub 0.3})(OH){sub 2} at the temperatures ranged from 800 to 900 °C. The effects of the Li source and calcination temperature on physical and electrochemical properties of the electrode samples were deeply investigated. And Li{sub 2}CO{sub 3} is considered to be the suitable Li source for the synthesis of Li[Ni{sub 0.5}Co{sub 0.2}Mn{sub 0.3}]O{sub 2}. The results also show the sample calcined at 850 °C gives the highest integrated intensity ratio I{sub (003)}/I{sub (104)}, indicating that this sample has the lowest amount of cation mixing. At the same time, this sample shows excellent electrochemical properties, such as the largest initial discharge capacity of 176 mAh g{sup −1} at 0.1 C, best cycle stability of about 100% at 0.2 C and highest rate capability.

Spray drying of spherical Li{sub 4}Ti{sub 5}O{sub 12}/C powders using polyvinyl pyrrolidone as binder and carbon source

Energy Technology Data Exchange (ETDEWEB)

Liu, Wei [Research Center for New Energy Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); University of Chinese Academy of Sciences, Beijing 110049 (China); Shanghai Nanotechnology Promotion Center, Shanghai 200237 (China); Wang, Qian; Cao, Chunhui [Research Center for New Energy Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); University of Chinese Academy of Sciences, Beijing 110049 (China); Han, Xuewu [Research Center for New Energy Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Zhang, Jian, E-mail: zjskycn@163.com [Research Center for New Energy Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Xie, Xiaohua, E-mail: xiaohuaxie@126.com [Research Center for New Energy Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Xia, Baojia [Research Center for New Energy Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); University of Chinese Academy of Sciences, Beijing 110049 (China)

2015-02-05

Highlights: • The spherical Li{sub 4}Ti{sub 5}O{sub 12}/C granules were prepared by spray drying. • Polyvinyl pyrrolidone (PVP) was used as binder and carbon source. • Tap density and spherical structure increase with the increase of PVP content. • Li{sub 4}Ti{sub 5}O{sub 12}/C granules exhibits better rate capability and excellent cyclability. - Abstract: Polyvinyl pyrrolidone (PVP) was used as binder and carbon source to synthesize stable and spherical Li{sub 4}Ti{sub 5}O{sub 12}/C granules by spray drying. The effects of PVP content and atmospheres on the properties of Li{sub 4}Ti{sub 5}O{sub 12} were investigated. The obtained samples were characterized by X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and electrochemical tests, respectively. The results indicate that the average particle size, tap density and degree of spherical structure increase accordingly to the increase of PVP content. However, the large secondary particle would deteriorate the rate capacity at high current density. The carbon coating could significantly improve the rate capacity, which is attributed to the smaller primary particle and higher electrical conductivity.

A hybrid source-driven method to compute fast neutron fluence in reactor pressure vessel - 017

International Nuclear Information System (INIS)

Ren-Tai, Chiang

2010-01-01

A hybrid source-driven method is developed to compute fast neutron fluence with neutron energy greater than 1 MeV in nuclear reactor pressure vessel (RPV). The method determines neutron flux by solving a steady-state neutron transport equation with hybrid neutron sources composed of peripheral fixed fission neutron sources and interior chain-reacted fission neutron sources. The relative rod-by-rod power distribution of the peripheral assemblies in a nuclear reactor obtained from reactor core depletion calculations and subsequent rod-by-rod power reconstruction is employed as the relative rod-by-rod fixed fission neutron source distribution. All fissionable nuclides other than U-238 (such as U-234, U-235, U-236, Pu-239 etc) are replaced with U-238 to avoid counting the fission contribution twice and to preserve fast neutron attenuation for heavy nuclides in the peripheral assemblies. An example is provided to show the feasibility of the method. Since the interior fuels only have a marginal impact on RPV fluence results due to rapid attenuation of interior fast fission neutrons, a generic set or one of several generic sets of interior fuels can be used as the driver and only the neutron sources in the peripheral assemblies will be changed in subsequent hybrid source-driven fluence calculations. Consequently, this hybrid source-driven method can simplify and reduce cost for fast neutron fluence computations. This newly developed hybrid source-driven method should be a useful and simplified tool for computing fast neutron fluence at selected locations of interest in RPV of contemporary nuclear power reactors. (authors)

Benchmarking shielding simulations for an accelerator-driven spallation neutron source

Directory of Open Access Journals (Sweden)

Nataliia Cherkashyna

2015-08-01

Full Text Available The shielding at an accelerator-driven spallation neutron facility plays a critical role in the performance of the neutron scattering instruments, the overall safety, and the total cost of the facility. Accurate simulation of shielding components is thus key for the design of upcoming facilities, such as the European Spallation Source (ESS, currently in construction in Lund, Sweden. In this paper, we present a comparative study between the measured and the simulated neutron background at the Swiss Spallation Neutron Source (SINQ, at the Paul Scherrer Institute (PSI, Villigen, Switzerland. The measurements were carried out at several positions along the SINQ monolith wall with the neutron dosimeter WENDI-2, which has a well-characterized response up to 5 GeV. The simulations were performed using the Monte-Carlo radiation transport code geant4, and include a complete transport from the proton beam to the measurement locations in a single calculation. An agreement between measurements and simulations is about a factor of 2 for the points where the measured radiation dose is above the background level, which is a satisfactory result for such simulations spanning many energy regimes, different physics processes and transport through several meters of shielding materials. The neutrons contributing to the radiation field emanating from the monolith were confirmed to originate from neutrons with energies above 1 MeV in the target region. The current work validates geant4 as being well suited for deep-shielding calculations at accelerator-based spallation sources. We also extrapolate what the simulated flux levels might imply for short (several tens of meters instruments at ESS.

Effects of carbon source and carbon content on electrochemical performances of Li{sub 4}Ti{sub 5}O{sub 12}/C prepared by one-step solid-state reaction

Energy Technology Data Exchange (ETDEWEB)

Hu Xuebu [College of Chemistry and Materials Science, Sichuan Normal University, Chengdu, Sichuan 610066 (China); Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu, Sichuan 610041 (China); Lin Ziji [China National Quality Supervision and Inspection Center for Alcoholic Beverage Products and Processed Food, Luzhou, Sichuan 646100 (China); Yang Kerun [Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu, Sichuan 610041 (China); Hua, Yongjian [China Aviation Lithium Battery Co. Ltd., Luoyang, Henan 471009 (China); Deng Zhenghua, E-mail: zhdeng@cioc.ac.cn [Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu, Sichuan 610041 (China)

2011-05-30

Highlights: > A simple route to prepare the Li{sub 4}Ti{sub 5}O{sub 12}/C by one-step solid-state reaction. > Carbon source and carbon content are two important factors on the electrochemical performances of Li{sub 4}Ti{sub 5}O{sub 12}/C. > As-prepared Li{sub 4}Ti{sub 5}O{sub 12}/C under optimized conditions shows excellent electrochemical performances. - Abstract: Li{sub 4}Ti{sub 5}O{sub 12}/C composites were synthesized by one-step solid-state reaction method using four commonly used organic compounds or organic polymers as carbon source, i.e., polyacrylate acid (PAA), citric acid (CA), maleic acid (MA) and polyvinyl alcohol (PVA). The physical characteristics of Li{sub 4}Ti{sub 5}O{sub 12}/C composites were investigated by X-ray diffraction, electron microscopy, Raman spectroscopy, particle size distribution and thermogravimetry-derivative thermogravimetry techniques. Their electrochemical properties were characterized by cyclic voltammograms, electrochemical impedance spectra, constant current charge-discharge and rate charge-discharge. These analyses indicated that the carbon source and carbon content have a great effect on the physical and electrochemical performances of Li{sub 4}Ti{sub 5}O{sub 12}/C composites. An ideal carbon source and appropriate carbon content effectively improved the electrical contact between the Li{sub 4}Ti{sub 5}O{sub 12} particles, which enhanced the discharge capacity and rate capability of Li{sub 4}Ti{sub 5}O{sub 12}/C composites. PAA was the best carbon source for the synthesis of Li{sub 4}Ti{sub 5}O{sub 12}/C composites. When the carbon content was 3.49 wt.% (LiOH.H{sub 2}O/PAA molar ratio of 1), as-prepared Li{sub 4}Ti{sub 5}O{sub 12}/C showed the maximum discharge capacity. At 0.2 C, initial capacity of the optimized sample was 168.6 mAh g{sup -1} with capacity loss of 2.8% after 50 cycles. At 8 and 10 C, it showed discharge capacities of 143.5 and 132.7 mAh g{sup -1}, with capacity loss of 8.7 and 9.9% after 50 cycles

Direction-division multiplexed holographic free-electron-driven light sources

Science.gov (United States)

Clarke, Brendan P.; MacDonald, Kevin F.; Zheludev, Nikolay I.

2018-01-01

We report on a free-electron-driven light source with a controllable direction of emission. The source comprises a microscopic array of plasmonic surface-relief holographic domains, each tailored to direct electron-induced light emission at a selected wavelength into a collimated beam in a prescribed direction. The direction-division multiplexed source is tested by driving it with the 30 kV electron beam of a scanning electron microscope: light emission, at a wavelength of 800 nm in the present case, is switched among different output angles by micron-scale repositioning of the electron injection point among domains. Such sources, with directional switching/tuning possible at picosecond timescales, may be applied to field-emission and surface-conduction electron-emission display technologies, optical multiplexing, and charged-particle-beam position metrology.

Study of the kinetics parameters for subcritical media driven by source

International Nuclear Information System (INIS)

Lee, S.M.; Maiorino, J.R.

2009-01-01

This paper presents a theoretical study of reactor kinetics focusing on the methodology of calculation and the experimental measurements of the so-called kinetic parameters. A comparison between the methodology based on the Dulla's formalism and the classical method is made. The objective is to exhibit the dependence of the parameters on sub criticality level and perturbation. Two different slab type systems were considered: thermal one and fast one, both with homogeneous media. One group diffusion model was used for the fast reactor, and for the thermal system, two group diffusion model, considering, in both case only one precursor's family. For reason of simplicity, several additional assumptions were made for calculation of two group method: no up-scattering, fission reaction occurring only in thermal group, etc. The solutions for subcritical systems were obtained using the expansion method, and for critical systems, the methods presented in classical textbooks of reactor physics were applied. The numerical results presented their dependence on sub criticality level and perturbation. (author)

Evaluation of Model Driven Development of Safety Critical Software in the Nuclear Power Plant I and C system

International Nuclear Information System (INIS)

Jung, Jae Cheon; Chang, Hoon Seon; Chang, Young Woo; Kim, Jae Hack; Sohn, Se Do

2005-01-01

The major issues of the safety critical software are formalism and V and V. Implementing these two characteristics in the safety critical software will greatly enhance the quality of software product. The structure based development requires lots of output documents from the requirements phase to the testing phase. The requirements analysis phase is open omitted. According to the Standish group report in 2001, 49% of software project is cancelled before completion or never implemented. In addition, 23% is completed and become operational, but over-budget, over the time estimation, and with fewer features and functions than initially specified. They identified ten success factors. Among them, firm basic requirements and formal methods are technically achievable factors while the remaining eight are management related. Misunderstanding of requirements due to lack of communication between the design engineer and verification engineer causes unexpected result such as functionality error of system. Safety critical software shall comply with such characteristics as; modularity, simplicity, minimizing the sub-routine, and excluding the interrupt routine. In addition, the crosslink fault and erroneous function shall be eliminated. The easiness of repairing work after the installation shall be achieved as well. In consideration of the above issues, we evaluate the model driven development (MDD) methods for nuclear I and C systems software. For qualitative analysis, the unified modeling language (UML), functional block language (FBL) and the safety critical application environment (SCADE) are tested for the above characteristics

Critical condition for current-driven instability excited in turbulent heating of TRIAM-1 tokamak plasma

Energy Technology Data Exchange (ETDEWEB)

Nakamura, Y; Watanabe, T; Nagao, A; Nakamura, K; Kikuchi, M; Aoki, T; Hiraki, N; Itoh, S [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics; Mitarai, O

1982-02-01

Critical condition for current-driven instability excited in turbulently heated TRIAM-1 tokamak plasma is investigated experimentally. Resistive hump in loop voltage, plasma density fluctuation and rapid increase of electron temperature in a skin layer are simultaneously observed at the time when the electron drift velocity amounts to the critical drift velocity for low-frequency ion acoustic instability.

Measurements of the critical parameters for {l_brace}xNH{sub 3} + (1 - x)H{sub 2}O{r_brace} with x = (0.9098, 0.7757, 0.6808)

Energy Technology Data Exchange (ETDEWEB)

Sakabe, A.; Arai, D. [Centre for Multiscale Mechanics and Mechanical Systems, Keio University, Yokohama 223-8522 (Japan); Miyamoto, H. [Department of Mechanical Systems Engineering, Toyama Prefectural University, Imizu 939-0398 (Japan)], E-mail: miyamoto@pu-toyama.ac.jp; Uematsu, M. [Centre for Multiscale Mechanics and Mechanical Systems, Keio University, Yokohama 223-8522 (Japan)

2008-10-15

Measurements of the critical parameters for {l_brace}xNH{sub 3} + (1 - x)H{sub 2}O{r_brace} with x = (0.9098, 0.7757, 0.6808) were carried out by using a metal-bellows variable volumometer with an optical cell. The expanded uncertainties (k = 2) in temperature, pressure, density, and composition measurements have been estimated to be less than 3.2 mK, 3.2 kPa, 0.3 kg . m{sup -3}, and 8.8 . 10{sup -4}, respectively. In each mole fraction, the critical temperature T{sub c} was first determined on the basis of the intensity of the critical opalescence. The critical pressure p{sub c} and critical density {rho}{sub c} were then determined as the point at which the meniscus disappears on the isotherm at T = T{sub c}. The expanded uncertainties (k = 2) in the present critical parameters have also been estimated. Comparisons of the present values with the literature data as well as the calculated values afforded using the equation of state are also presented.

Laser-driven source of spin-polarized atomic hydrogen and deuterium

International Nuclear Information System (INIS)

Poelker, M.

1995-01-01

A laser-driven source of spin-polarized hydrogen (H) and deuterium (D) that relies on the technique of optical pumping spin exchange has been constructed. In this source, H or D atoms and potassium atoms flow continuously through a drifilm-coated spin-exchange cell where potassium atoms are optically pumped with circularly-polarized laser light in a high magnetic field. The H or D atoms become polarized through spin-exchange collisions with polarized potassium atoms. High electron polarization (∼80%) has been measured for H and D atoms at flow rates ∼2x10 17 atoms/s. Lower polarization values are measured for flow rates exceeding 1x10 18 atoms/s. In this paper, we describe the performance of the laser-driven source as a function of H and D atomic flow rate, magnetic field strength, alkali density and pump-laser power. Polarization measurements as a function of flow rate and magnetic field suggest that, despite a high magnetic field, atoms within the optical-pumping spin-exchange apparatus evolve to spin-temperature equilibrium which results in direct polarization of the H and D nuclei. (orig.)

The effect of heterogeneity on the character of density-driven natural convection of CO{sub 2} overlying a brine layer

Energy Technology Data Exchange (ETDEWEB)

Farajzadeh, R. [Shell International Exploration and Production, Houston, TX (United States); Ranganathan, P.; Zitha, P.L.J.; Bruining, J. [Delft Univ. of Technology, Delft (Netherlands)

2010-07-01

This paper investigated the effect of heterogeneity on the character of natural-convection flow of carbon dioxide (CO{sub 2}) in aquifers and on the dissolution rate of CO{sub 2} in brine, contributing to a better understanding of the effect of heterogeneity on CO{sub 2} mass transfer in aquifers, which is necessary for efficient storage of CO{sub 2} in aquifers. The aquifer permeability, which is in practice heterogeneous, largely governs the efficiency of mixing in density-driven natural convection. The aquifer's degree of permeability variance and the correlation length informs the character of flow-driven mixing processes. Numerical simulation was used to identify different flow regimes of a density-driven natural flow regime. Heterogeneous fields were generated using a spectral method that allows the use of power-law variograms. From the simulations it was observed that the rate of mass transfer of carbon dioxide (CO{sub 2}) into water is higher for heterogeneous media. The formulation of the physical model and related equations and the method for generating the permeability fields were described. The simulation results indicated that gravity-induced fingering is the dominant pattern in low heterogeneity, but fingering will not occur in realistic porous media. The results also showed that the permeability field structure dominates at moderate heterogeneity, and that the flow is dispersive at high heterogeneity when the correlation length of the field is small. Heterogeneous media facilitate a larger rate of CO{sub 2} dissolution than homogenous media, which means that the former can store larger volumes of CO{sub 2}. 49 refs., 3 tabs., 13 figs.

A 1D ion species model for an RF driven negative ion source

Science.gov (United States)

Turner, I.; Holmes, A. J. T.

2017-08-01

A one-dimensional model for an RF driven negative ion source has been developed based on an inductive discharge. The RF source differs from traditional filament and arc ion sources because there are no primary electrons present, and is simply composed of an antenna region (driver) and a main plasma discharge region. However the model does still make use of the classical plasma transport equations for particle energy and flow, which have previously worked well for modelling DC driven sources. The model has been developed primarily to model the Small Negative Ion Facility (SNIF) ion source at CCFE, but may be easily adapted to model other RF sources. Currently the model considers the hydrogen ion species, and provides a detailed description of the plasma parameters along the source axis, i.e. plasma temperature, density and potential, as well as current densities and species fluxes. The inputs to the model are currently the RF power, the magnetic filter field and the source gas pressure. Results from the model are presented and where possible compared to existing experimental data from SNIF, with varying RF power, source pressure.

Enhancement of critical current density of in situ processed MgB sub 2 tapes by WB addition

CERN Document Server

Fujii, H; Kumakura, H

2003-01-01

The effect of tungsten boride (WB) addition on the microstructure and superconducting properties of Fe-sheathed MgB sub 2 tapes has been investigated. The microstructure was not influenced appreciably by the addition, whereas the superconducting properties changed. Even by a 5 mol% addition, the critical temperature (T sub c) decreased by about 0.5 K. However, the field dependence of the inductive critical current density (J sub c sub i) became smaller with the increase in the amount of addition, suggesting that pinning centres effective in a high-field region were possibly introduced. The transport critical current density (J sub c sub t) at 4.2 K increased about twice by the 5 mol% addition and reached 15 and 5 kA cm sup - sup 2 at 8 and 10 T, respectively.

Phase-Separated, Epitaxial, Nanostructured LaMnO<sub>3sub>+MgO Composite Cap Layer Films for Propagation of Pinning Defects in YBa<sub>2sub>Cu>3sub>O>7-xsub> Coated Conductors

Energy Technology Data Exchange (ETDEWEB)

Wee, Sung Hun [ORNL; Shin, Junsoo [ORNL; Cantoni, Claudia [ORNL; Meyer III, Harry M [ORNL; Cook, Sylvester W [ORNL; Zuev, Yuri L [ORNL; Specht, Eliot D [ORNL; Xiong, Xuming [ORNL; Paranthaman, Mariappan Parans [ORNL; Selvamanickam, V. [SuperPower Incorporated, Schenectady, New York; Goyal, Amit [ORNL

2009-01-01

Nanostructural modulation in the cap layer used in coated conductors can be a potential source for nucleating microstructural defects into the superconducting layer for improving the flux-pinning. We report on the successful fabrication of phase separated, epitaxial, nanostructured films comprised of LaMnO{sub 3} (LMO) and MgO via pulsed laser deposition (PLD) on biaxially-textured MgO metallic templates with a LMO buffer layer. Scanning Auger compositional mapping and transmission electron microscopy cross sectional images confirm the nanoscale, spatial modulation corresponding to the nanostructured phase separation in the film. YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} films (0.8 {micro}m thick) grown using PLD on such phase separated, nanostructured cap layers show reduced field dependence of the critical current density with an ? value of -0.38 (in J{sub c}-H{sup -{alpha}}).

Design-theoretical study of cascade CO2 sub-critical mechanical compression/butane ejector cooling cycle

KAUST Repository

Petrenko, V.O.

2011-11-01

In this paper an innovative micro-trigeneration system composed of a cogeneration system and a cascade refrigeration cycle is proposed. The cogeneration system is a combined heat and power system for electricity generation and heat production. The cascade refrigeration cycle is the combination of a CO2 mechanical compression refrigerating machine (MCRM), powered by generated electricity, and an ejector cooling machine (ECM), driven by waste heat and using refrigerant R600. Effect of the cycle operating conditions on ejector and ejector cycle performances is studied. Optimal geometry of the ejector and performance characteristics of ECM are determined at wide range of the operating conditions. The paper also describes a theoretical analysis of the CO2 sub-critical cycle and shows the effect of the MCRM evaporating temperature on the cascade system performance. The obtained data provide necessary information to design a small-scale cascade system with cooling capacity of 10 kW for application in micro-trigeneration systems. © 2010 Elsevier Ltd and IIR. All rights reserved.

Conductivity fluctuation and superconducting parameters of the YBa{sub 2}Cu{sub 3-} {sub x} (PO{sub 4}) {sub x} O{sub 7-} {sub {delta}} material

Energy Technology Data Exchange (ETDEWEB)

Rojas Sarmiento, M.P. [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, AA 14490, Bogota DC (Colombia); Uribe Laverde, M.A. [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, AA 14490, Bogota DC (Colombia); Vera Lopez, E. [Grupo de Superficies, Electroquimica y Corrosion, UPTC, Tunja (Colombia); Landinez Tellez, D.A. [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, AA 14490, Bogota DC (Colombia); Roa-Rojas, J. [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, AA 14490, Bogota DC (Colombia)]. E-mail: jroar@unal.edu.co

2007-09-01

Synthesis of the YBa{sub 2}Cu{sub 3-} {sub x} (PO{sub 4}) {sub x} O{sub 7-} {sub {delta}} superconducting material by the standard solid-state reaction is reported. DC resistivity measurements reveal the improvement of the critical temperature (T {sub C}) when substitution of phosphate in the Cu sites is performed. A bulk T {sub C}=97 K was determined by the criterion of the maximum in the temperature derivative of electrical resistivity. Structure characterization by means the X-ray diffraction technique shows the crystalline appropriated distribution of PO{sub 4} into the CuO{sub 2} superconducting planes. In order to examine the effect of phosphates on the pairing mechanism close to T {sub C}, conductivity fluctuation analysis was performed by the method of logarithmic temperature derivative of the conductivity excess. We found the occurrence of Gaussian-like fluctuations. The correlations of the critical exponents with the dimensionality of the fluctuation system for each Gaussian regime were performed by using the Aslamazov-Larkin theory. The Ginzburg number for this superconducting material is predicted and the critical magnetic fields, critical current density and the jump in the specific heat at the critical temperature are theoretically determined.

Nuclear Material Detection by One-Short-Pulse-Laser-Driven Neutron Source

International Nuclear Information System (INIS)

Favalli, Andrea; Aymond, F.; Bridgewater, Jon S.; Croft, Stephen; Deppert, O.; Devlin, Matthew James; Falk, Katerina; Fernandez, Juan Carlos; Gautier, Donald Cort; Gonzales, Manuel A.; Goodsell, Alison Victoria; Guler, Nevzat; Hamilton, Christopher Eric; Hegelich, Bjorn Manuel; Henzlova, Daniela; Ianakiev, Kiril Dimitrov; Iliev, Metodi; Johnson, Randall Philip; Jung, Daniel; Kleinschmidt, Annika; Koehler, Katrina Elizabeth; Pomerantz, Ishay; Roth, Markus; Santi, Peter Angelo; Shimada, Tsutomu; Swinhoe, Martyn Thomas; Taddeucci, Terry Nicholas; Wurden, Glen Anthony; Palaniyappan, Sasikumar; McCary, E.

2015-01-01

Covered in the PowerPoint presentation are the following areas: Motivation and requirements for active interrogation of nuclear material; laser-driven neutron source; neutron diagnostics; active interrogation of nuclear material; and, conclusions, remarks, and future works.

Hydrothermal synthesis of CdS/Bi{sub 2}MoO{sub 6} heterojunction photocatalysts with excellent visible-light-driven photocatalytic performance

Energy Technology Data Exchange (ETDEWEB)

Feng, Yi; Yan, Xu; Liu, Chunbo; Hong, Yuanzhi; Zhu, Lin; Zhou, Mingjun; Shi, Weidong, E-mail: swd1978@ujs.edu.cn

2015-10-30

Graphical abstract: - Highlights: • The novel CdS/Bi{sub 2}MoO{sub 6} heterojunction were synthesized for the first time via a two-step hydrothermal process. • The CdS/Bi{sub 2}MoO{sub 6} heterojunction exhibited an excellent visible-light-driven photocatalytic activity for RhB degradation. • The photocatalytic activity of this heterojunction also evaluated by TC, MB degradation. • The mechanism of this photocatalysis system was firstly proposed. - Abstract: A novel CdS/Bi{sub 2}MoO{sub 6} heterojunction photocatalysts were successfully prepared via two-step hydrothermal methods. The prepared samples were characterized by various physicochemical techniques, such as XRD, SEM, TEM, HRTEM, XPS, UV–vis and PL. The obtained samples exhibited highly photocatalytic activity toward the degradation of the different kinds of organic dyes and tetracycline in aqueous solution under visible light irradiation (λ > 420 nm). The optimum photocatalytic efficiency of CdS-2 sample for the degradation rhodamine B (RhB) was about 25.3 and 3.7 times higher than that of individual CdS and Bi{sub 2}MoO{sub 6}, respectively. In addition, the possible photocatalytic mechanism was analyzed by different active species trapping experiments. The results indicated that the h{sup +} and ·O{sub 2}{sup −} were the main active species for the photocatalytic degradation of RhB. Moreover, the prepared sample shows good stability and recyclability properties which are beneficial for its practical application.

Na{sub 2}V{sub 3}O{sub 7}: An unusual low-dimensional quantum magnet

Energy Technology Data Exchange (ETDEWEB)

Gavilano, J.L. [Laboratorium fuer Festkoerperphysik, ETHZ, CH-8093 Zurich (Switzerland)]. E-mail: gavilano@phys.ethz.ch; Felder, E. [Laboratorium fuer Festkoerperphysik, ETHZ, CH-8093 Zurich (Switzerland); Rau, D. [Laboratorium fuer Festkoerperphysik, ETHZ, CH-8093 Zurich (Switzerland); Ott, H.R. [Laboratorium fuer Festkoerperphysik, ETHZ, CH-8093 Zurich (Switzerland); Millet, P. [Centre d' Elaboration des Materiaux et d' Etudes Structurales, 29, rue J. Marvig, 31055 Toulouse Cedex (France); Mila, F. [Institute of Theoretical Physics, EPFL, CH - 1015 Lausanne (Switzerland); Cichorek, T. [Max-Planck-Institut fuer Chemische Physik fester Stoffe, 01187 Dresden (Germany); Mota, A.C. [Max-Planck-Institut fuer Chemische Physik fester Stoffe, 01187 Dresden (Germany)

2006-05-01

Results of present and previous measurements of the {sup 23}Na NMR response, dc- and ac-magnetic susceptibilities and the specific heat of Na{sub 2}V{sub 3}O{sub 7} at low temperatures suggest that this material is close to a quantum critical point (QCP) at {mu}{sub 0}H=0T. The experimental data can be explained by assuming that below 100K the localized V magnetic moments (S=12) form a collection of dimers, with a broad distribution of singlet-triplet gaps. Most of the dimers adopt a singlet ground state with gaps between 0 and 350K. A small fraction of them forms triplet ground states with gaps between 0 and 15K. The degeneracy of the triplet ground states is lifted by a phase transition at an unusually low temperature of 0.086K. Modest magnetic fields effectively quench this low-temperature state and the system is driven away from the QCP as the applied fields are enhanced to above 1T.

Open Source Software: critical review of scientific literature and other sources

OpenAIRE

Querol del Amo, Marc

2007-01-01

This thesis presents the results of a survey of Open Source Licensing literature. It aims to assist the reader in choosing the best license for his/her business. For this reason, the content of this thesis can be divided into: (i) an open source licensing overview, (ii) the explication of the main features of the most popular open source licenses, (iii) the consequences of using one or another and (iv) the critical or controversial issues related to Open Source Licensing. Furthermore, at the ...

Magneto-acoustic study near the quantum critical point of the frustrated quantum antiferromagnet Cs{sub 2}CuCl{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Cong, P. T., E-mail: t.pham@hzdr.de [Dresden High Magnetic Field Laboratory, Helmholtz-Zentrum Dresden-Rossendorf, D-01314 Dresden (Germany); Physics Institute, Goethe University Frankfurt, D-60438 Frankfurt am Main (Germany); Postulka, L.; Wolf, B.; Ritter, F.; Assmus, W.; Krellner, C.; Lang, M., E-mail: michael.lang@physik.uni-frankfurt.de [Physics Institute, Goethe University Frankfurt, D-60438 Frankfurt am Main (Germany); Well, N. van [Physics Institute, Goethe University Frankfurt, D-60438 Frankfurt am Main (Germany); Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, CH-5232 Villigen (Switzerland)

2016-10-14

Magneto-acoustic investigations of the frustrated triangular-lattice antiferromagnet Cs{sub 2}CuCl{sub 4} were performed for the longitudinal modes c{sub 11} and c{sub 33} in magnetic fields along the a-axis. The temperature dependence of the sound velocity at zero field shows a mild softening at low temperature and displays a small kink-like anomaly at T{sub N}. Isothermal measurements at T < T{sub N} of the sound attenuation α reveal two closely spaced features of different characters on approaching the material's quantum-critical point (QCP) at B{sub s} ≈ 8.5 T for B || a. The peak at slightly lower fields remains sharp down to the lowest temperature and can be attributed to the ordering temperature T{sub N}(B). The second anomaly, which is rounded and which becomes reduced in size upon cooling, is assigned to the material's spin-liquid properties preceding the long-range antiferromagnetic ordering with decreasing temperature. These two features merge upon cooling suggesting a coincidence at the QCP. The elastic constant at lowest temperatures of our experiment at 32 mK can be well described by a Landau free energy model with a very small magnetoelastic coupling constant G/k{sub B} ≈ 2.8 K. The applicability of this classical model indicates the existence of a small gap in the magnetic excitation spectrum which drives the system away from quantum criticality.

Solar Dynamo Driven by Periodic Flow Oscillation

Science.gov (United States)

Mayr, Hans G.; Hartle, Richard E.; Einaudi, Franco (Technical Monitor)

2001-01-01

We have proposed that the periodicity of the solar magnetic cycle is determined by wave mean flow interactions analogous to those driving the Quasi Biennial Oscillation in the Earth's atmosphere. Upward propagating gravity waves would produce oscillating flows near the top of the radiation zone that in turn would drive a kinematic dynamo to generate the 22-year solar magnetic cycle. The dynamo we propose is built on a given time independent magnetic field B, which allows us to estimate the time dependent, oscillating components of the magnetic field, (Delta)B. The toroidal magnetic field (Delta)B(sub phi) is directly driven by zonal flow and is relatively large in the source region, (Delta)(sub phi)/B(sub Theta) much greater than 1. Consistent with observations, this field peaks at low latitudes and has opposite polarities in both hemispheres. The oscillating poloidal magnetic field component, (Delta)B(sub Theta), is driven by the meridional circulation, which is difficult to assess without a numerical model that properly accounts for the solar atmosphere dynamics. Scale-analysis suggests that (Delta)B(sub Theta) is small compared to B(sub Theta) in the dynamo region. Relative to B(sub Theta), however, the oscillating magnetic field perturbations are expected to be transported more rapidly upwards in the convection zone to the solar surface. As a result, (Delta)B(sub Theta) (and (Delta)B(sub phi)) should grow relative to B(sub Theta), so that the magnetic fields reverse at the surface as observed. Since the meridional and zonai flow oscillations are out of phase, the poloidal magnetic field peaks during times when the toroidal field reverses direction, which is observed. With the proposed wave driven flow oscillation, the magnitude of the oscillating poloidal magnetic field increases with the mean rotation rate of the fluid. This is consistent with the Bode-Blackett empirical scaling law, which reveals that in massive astrophysical bodies the magnetic moment tends

Tuning of a non-Fermi-liquid state in CeNiGa{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Hauser, R.; Bauer, E.; Kottar, A.; Hilscher, G. [T.U. Wien (Austria). Inst. fuer Experimentalphys.; Galli, M. [Inst. Naz. di Fisica della Materia and Dipt. di Fisica A. Volta, Univ. di Pavia (Italy); Kaczorowski, D. [Inst. of Low Temperature and Structure Research, Polish Acadamy of Sciences, Wroclaw (Poland)

1998-01-01

The antiferromagnetic order in the Kondo lattice CeNiGa{sub 2} is found to vanish at a critical pressure P{sub cr}{approx}4 kbar. For pressures ranging from 4 to 9 kbar a non-Fermi-liquid state where {rho}-{rho}{sub 0}{proportional_to}T{sup 3/2} is observed. By further increasing pressure or external magnetic field this compound is driven towards Fermi-liquid behavior. (orig.) 12 refs.

Influence of two-stage annealing treatment on critical current of bronze-processed multifilamentary Nb/sub 3/Sn superconducting materials

International Nuclear Information System (INIS)

Ochiai, S.; Osamura, K.; Ryoji, M.

1987-01-01

The influence of changes of volume fraction of Nb/sub 3/Sn, grain size and upper critical magnetic field due to two-stage annealing treatment (low temperature annealing to form fine grains + high temperature annealing to raise upper critical magnetic field) on overall critical current and critical current density were studied at magnetic field of 3-15 T. When annealing temperature was low (773-923 K) and the volume fraction of Nb/sub 3/Sn was low in first stage annealing, second stage annealing could raise the overall critical current over the range of the applied magnetic field due to increase in upper critical magnetic field H/sub c2/ and volume fraction of Nb/sub 3/Sn accompanying with reduction in Sn concentration in the bronze matrix, which played a role to reduce residual strain in Nb/sub 3/Sn, leading to high H/sub c2/ although the loss in pinning force arose from the coarsening of the grains. When the annealing temperature was high (973 K) and the Nb/sub 3/Sn was formed until the Sn was consumed in the first stage, second stage annealing could not raise the critical current due to increase in grain size and no effective increase in H/sub c2/. The critical current density at low magnetic fields below several Teslas was reduced by the second stage annealing due to increase in grain size but that at high fields was raised due to increase in high H/sub c2/. The reverse two-stage annealing treatment (high temperature annealing in the first stage+low temperature annealing in the second stage) reduced the H/sub c2/ slightly with increasing second stage annealing temperature and time. The critical current density at low magnetic fields was determined mainly by the grain size and that at high fields was determined by the combination of the upper critical field and grain size

Nb/sub 3/Sn critical-current measurements using tubular fiberglass-epoxy mandrels

International Nuclear Information System (INIS)

Goodrich, L.F.; Bray, S.L.; Stauffer, T.C.

1989-01-01

A systematic study of the effect of sample mounting techniques on the superconducting critical-current measurement was made in conjunction with the VAMAS (Versailles Agreement on Advanced Materials and Standards) interlaboratory comparison (round robin) measurements. A seemingly small change in mandrel geometry can result in a 40% change in the measured critical current of a Nb/sub 3/Sn sample at 12 T. This is a result of a change in the conductor pre-strain at 4 K caused by variation in thermal contraction between thick- and thin-walled fiberglass-epoxy composite (G-10) tubes. An approximate measure of the variations in thermal contraction (from room to liquid nitrogen temperature) indicate a 0.2% greater contraction for the thick-walled tube. This difference, combined with strain sensitivity measurements, is consistent with the observed decrease in critical current. Previous publications on thermal contraction of G-10 have addressed the plate geometry, but not the tube geometry. The contraction of a G-10 plate is highly anisotropic. The radial contraction of a tube is different than the contraction of a plate, however, because the circumferential fiberglass is put into hoop compression by the epoxy, and the resulting contraction is a competition between the two structural components. This appears to be the source of the variation in thermal contraction with tube wall thickness

Advanced electrical current measurements of microdischarges: evidence of sub-critical pulses and ion currents in barrier discharge in air

Science.gov (United States)

Synek, Petr; Zemánek, Miroslav; Kudrle, Vít; Hoder, Tomáš

2018-04-01

Electrical current measurements in corona or barrier microdischarges are a challenge as they require both high temporal resolution and a large dynamic range of the current probe used. In this article, we apply a simple self-assembled current probe and compare it to commercial ones. An analysis in the time and frequency domain is carried out. Moreover, an improved methodology is presented, enabling both temporal resolution in sub-nanosecond times and current sensitivity in the order of tens of micro-amperes. Combining this methodology with a high-tech oscilloscope and self-developed software, a unique statistical analysis of currents in volume barrier discharge driven in atmospheric-pressure air is made for over 80 consecutive periods of a 15 kHz applied voltage. We reveal the presence of repetitive sub-critical current pulses and conclude that these can be identified with the discharging of surface charge microdomains. Moreover, extremely low, long-lasting microsecond currents were detected which are caused by ion flow, and are analysed in detail. The statistical behaviour presented gives deeper insight into the discharge physics of these usually undetectable current signals.

EVIDENCE FOR H{sub 2} FORMATION DRIVEN DUST GRAIN ALIGNMENT IN IC 63

Energy Technology Data Exchange (ETDEWEB)

Andersson, B-G; De Buizer, J.; Charcos-Llorens, M. [SOFIA Science Center, USRA, NASA Ames Research Center, M.S. N211-3 Moffett Field, CA 94035 (United States); Piirola, V. [Finnish Centre for Astronomy with ESO, University of Turku, Väisäläntie 20, FI-21500 Piikkiö (Finland); Clemens, D. P. [Institute for Astrophysical Research, Boston University, Boston, MA 02215 (United States); Uomoto, A. [Observatories of the Carnegie Institution, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Geballe, T. R. [Gemini Observatory, Northern Operations Center, 670 N. A' ohoku Place, Hilo, HI 96720 (United States); Lazarian, A.; Hoang, T. [Department of Astronomy, University of Wisconsin, 475 North Charter Street, Madison, WI 53706 (United States); Vornanen, T., E-mail: bg@sofia.usra.edu [Tuorla Observatory, University of Turku, Väisäläntie 20, FI-21500 Piikkiö (Finland)

2013-10-01

In the interstellar medium (ISM), molecular hydrogen is expected to form almost exclusively on the surfaces of dust grains. Due to that molecule's large formation energy (–4.5 eV), several dynamical effects are likely associated with the process, including the alignment of asymmetric dust grains with the ambient magnetic field. Such aligned dust grains are, in turn, believed to cause the broadband optical/infrared polarization observed in the ISM. Here, we present the first observational evidence for grain alignment driven by H{sub 2} formation, by showing that the polarization of the light from stars behind the reflection nebula IC 63 appears to correlate with the intensity of H{sub 2} fluorescence. While our results strongly suggest a role for 'Purcell rockets' in grain alignment, additional observations are needed to conclusively confirm their role. By showing a direct connection between H{sub 2} formation and a probe of the dust characteristics, these results also provide one of the first direct confirmations of the grain-surface formation of H{sub 2}. We compare our observations to ab initio modeling based on Radiative Torque Alignment (RAT) theory.

Production of H- ions by an RF driven multicusp source

International Nuclear Information System (INIS)

Leung, K.N.; Bachman, D.A.; McDonald, D.S.

1992-01-01

An RF driven H - source has been developed at LBL for use in the Superconducting Super Collider (SSC). To date, an H - current of ∼40 mA can be obtained from a 5.6-cm-diameter aperture with the source operated at a pressure of about 12 mTorr and 50 kW of RF power. Attempts have been made to enhance the H - beam current by introducing a small quantity of cesium vapor into the source chamber. It is found that the H - output current can be increased by a factor larger than three if some cesium is applied in the collar around the exit aperture

Critical Behavior of Thermal Expansion and Magnetostriction in the Vicinity of the First order transition at the Curie Point of Gd<sub>5sub>(Si_xGe>1-xsub>)>4sub>

Energy Technology Data Exchange (ETDEWEB)

Han, Mangui [Iowa State Univ., Ames, IA (United States)

2004-01-01

Thermal expansion (TE) and magnetostriction (MS) measurements have been conducted for Gd<sub>5sub>(Si_xGe>1-xsub>)>4sub> with a series of x values to study its critical behavior in the vicinity of transition temperatures. It was found that the Curie temperature of Gd<sub>5sub>(Si_xGe>1-xsub>)>4sub> for x 0 ~ 0.5 is dependent on magnetic field, direction of change of temperature (Tc on cooling was lower than Tc on heating), purity of Gd starting material, compositions, material preparation methods, and also can be triggered by the external magnetic field with a different dT/dB rate for different x values. For Gd<sub>5sub>(Si>1.95sub>Ge>2.05sub>), Gd<sub>5sub>(Si>2sub>Ge>2sub>), Gd<sub>5sub>(Si>2.09sub>Ge>1.91sub>), it was also found that the transition is a first order magneto-structural transition, which means the magnetic transition and crystalline structure transition occur simultaneously, and completely reversible. Temperature hysteresis and phase coexistence have been found to confirm that it is a first order transformation. While for Gd<sub>5sub>(Si>0.15sub>Ge>3.85sub>), it is partially reversible at some temperature range between the antiferromagnetic and the ferromagnetic state. For Gd<sub>5sub>(Si>2.3sub>Ge>1.7sub>) and Gd<sub>5sub>(Si>3sub>Ge>1sub>), it was a second order transformation between the paramagnetic and ferromagnetic state, because no ΔT have been found. Giant magnetostriction was only found on Gd<sub>5sub>(Si>1.95sub>Ge>2.05sub>), Gd<sub>5sub>(Si>2sub>Ge>2sub>), Gd<sub>5sub>(Si>2.09sub>Ge>1.91sub>) in their vicinity of first order transformation. MFM images have also been taken on polycrystal sample Gd<sub>5sub>(Si>2.09sub>Ge>1.91sub>) to investigate the transformation process. The results also indicates that the Curie temperature was lower and the thermally

Development of an asymmetric multiple-position neutron source (AMPNS) method to monitor the criticality of a degraded reactor core

International Nuclear Information System (INIS)

Kim, S.S.; Levine, S.H.

1985-01-01

An analytical/experimental method has been developed to monitor the subcritical reactivity and unfold the k/sub infinity/ distribution of a degraded reactor core. The method uses several fixed neutron detectors and a Cf-252 neutron source placed sequentially in multiple positions in the core. Therefore, it is called the Asymmetric Multiple Position Neutron Source (AMPNS) method. The AMPNS method employs nucleonic codes to analyze the neutron multiplication of a Cf-252 neutron source. An optimization program, GPM, is utilized to unfold the k/sub infinity/ distribution of the degraded core, in which the desired performance measure minimizes the error between the calculated and the measured count rates of the degraded reactor core. The analytical/experimental approach is validated by performing experiments using the Penn State Breazeale TRIGA Reactor (PSBR). A significant result of this study is that it provides a method to monitor the criticality of a damaged core during the recovery period

Effect on C-axis transport properties of a critical state in Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}

Energy Technology Data Exchange (ETDEWEB)

Cho, J.H.; Maley, M.P.; Bulaevskii, L.N.

1995-12-31

At low temperatures, the c-axis transport properties of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} single crystals depend strongly on the magnetic field history for fields applied along the c-axis, indicating the effect of a critical state in the ab direction. In this study, the authors report zero field cooled (ZFC), field cooled warming (FCW), and field cooled cooling (FCC) c-axis transport properties. In addition, they also report magnetic relaxation measurements on the same samples to identify the c-axis dissipation mechanism. They observe a relaxation of the c-axis resistivity that follows the relaxation of the flux profile across the ab plane. By identifying the irreversible temperature vs. magnetic field for H // c, they construct a phase diagram of vortex states. Finally, they will discuss the implication of the phase diagram and the features related to the transport properties of the Josephson-coupled system and the role of pancake vortices in highly two-dimensional superconductors.

Recent development on RF-driven multicusp H- ion sources

International Nuclear Information System (INIS)

Leung, K.N.; De Vries, G.J.; Kunkel, W.B.; Perkins, L.T.; Pickard, D.S.; Saadatmand, K.; Wengrow, A.B.; Williams, M.D.

1996-06-01

The radio-frequency (rf) driven multicusp source was originally developed for use in the Superconducting Super Collider injector. The source routinely provided 35 keV, 30 mA of beam at 0.1% duty factor. By using a new cesium dispensing system, beam current in excess of 100 mA and e/H - ∼1 have been observed. For pulse mode operation, the rf discharge can be started by means of a xenon flash lamp. Extracted electrons in the beam can be efficiently removed by employing a permanent magnet insert structure. Chopping of the H - beam can be accomplished by applying a pulsed positive voltage on the plasma electrode

Calculation of neutron interior source distribution within subcritical fission-chain reacting systems for a prescribed power density generation

Energy Technology Data Exchange (ETDEWEB)

Moraes, Leonardo R.C.; Alves Filho, Hermes; Barros, Ricardo C., E-mail: lrcmoraes@iprj.uerj.br, E-mail: halves@iprj.uerj.br, E-mail: ricardob@iprj.uerj.br [Universidade do Estado do Rio de Janeiro (UERJ), Nova Friburgo, RJ (Brazil). Programa de Pós-Graduação em Modelagem Computacional

2017-07-01

Accelerator Driven Systems (ADS) are sub-critical systems stabilized by stationary external sources of neutrons. A system is subcritical when the removal by absorption and leakage exceeds the production by fission and tends to shut down. On the other hand, any subcritical system can be stabilized by including time-independent external sources of neutrons. The goal of this work is to determine the intensity of uniform and isotropic sources of neutrons that must be added inside all fuel regions of a subcritical system so that it becomes stabilized, generating a prescribed distribution of electric power. A computer program has been developed in Java language to estimate the intensity of stationary sources of neutrons that must be included in the fuel regions to drive the subcritical system with a fixed power distribution prescribed by the user. The mathematical model used to achieve this goal was the energy multigroup, slab-geometry neutron transport equation in the discrete ordinates (S{sub N}) formulation and the response matrix method was applied to solve the forward and the adjoint S{sub N} problems. Numerical results are given to verify the present. (author)

Enhancement of localization phenomena driven by covalency in the SrBiMn{sub 1.75}Ti{sub 0.25}O{sub 6} manganite

Energy Technology Data Exchange (ETDEWEB)

Asensio de Lucas, E.; Alvarez-Serrano, I. [Depto. Quimica Inorganica I, Facultad Ciencias Quimicas, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Cuello, G.J. [Institut Laue-Langevin, 6 rue Jules Horowitz, F-38042 Grenoble (France); Garcia-Hernandez, M. [Instituto de Ciencia de Materiales de Madrid, CSIC, E-28049 Cantoblanco, Madrid (Spain); Lopez, M.L., E-mail: marisal@quim.ucm.es [Depto. Quimica Inorganica I, Facultad Ciencias Quimicas, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Pico, C.; Veiga, M.L. [Depto. Quimica Inorganica I, Facultad Ciencias Quimicas, Universidad Complutense de Madrid, E-28040 Madrid (Spain)

2012-05-05

Graphical abstract: Enhancement of localization phenomena driven by covalency in the BiSrMn{sub 1.75}Ti{sub 0.25}O{sub 6} manganite. The CO/OO phenomena and magnetic clusters (Mn{sub 4}) stabilization at temperatures up to 520 K in BiSrMn{sub 1.75}Ti{sub 0.25}O{sub 6} are connected to a structural transition. The observed enhancement of electronic localization is interpreted considering covalent effects of Ti{sup 4+} and Bi{sup 3+} cations as the main driving force. Highlights: Black-Right-Pointing-Pointer The structural, electronic and magnetic behaviour of the new SrBiMn{sub 1.75}Ti{sub 0.25}O{sub 6} manganite is reported. Black-Right-Pointing-Pointer A structural transition above 520 K takes place, coinciding with relevant changes in the transport properties. Black-Right-Pointing-Pointer The electronic behavior is interpreted in terms of a remarkably high orbital and charge ordering temperature and cluster models. Black-Right-Pointing-Pointer The observed features are explained considering a scenario in which bonds covalence is enhanced by the Bi{sup 3+} and Ti{sup 4+} cations. - Abstract: Manganites are materials that show remarkable phenomena related to charge orbital ordering (CO/OO) and it is extremely important to understand the fundamental nature of this behaviour. This paper reports on the structural, electronic and magnetic behaviour of the new SrBiMn{sub 1.75}Ti{sub 0.25}O{sub 6} manganite and the dependence of these properties with temperature. A detailed structural analysis has been carried out by electron, X-ray, neutron diffraction between 4 and 700 K. The electron diffraction patterns obtained at room temperature (RT) evidence that the average structure (a{approx}b{approx}{radical}(2)a{sub p} and c {approx} 2a{sub p}) presents a modulation that doubles the a and c lattice parameters. A very high charge ordering (CO) transition temperature of 510 K, similar to that found for the non-doped material, SrBiMn{sub 2}O{sub 6}, is observed. Above this

Dense plasma focus x-ray source for sub-micron lithography

International Nuclear Information System (INIS)

Prasad, R.R.; Krishnan, M.; Mangano, J.; Greene, P.; Qi, Niansheng

1993-01-01

A discharge driven, dense plasma focus in neon is under development at SRL for use as a point x-ray source for sub-micron lithography. This source is presently capable of delivering ∼ 13j/pulse of neon K-shell x-rays (8--14 angstrom) into 4π steradians with 2 kj of electrical energy stored in the capacitor bank charged to 9 kV at a pulse repetition rate of 2 Hz. The discharge is produced by a ≤4 kj, ≤12 kV, capacitor bank circuit, which has a fixed inductance of 12 nH and drives ≤450 kA currents into the DPF load, with ∼1.1 μs rise-times. X-rays are produced when a dense pinch of neon is formed along the axis of the DPF electrodes. A new rail-gap switched capacitor bank and DPF have been built, designed for continuous operation at 2 Hz and burst mode operation at 20 Hz. This paper will present measurements of the x-ray output at a repetition rate of 2 Hz using the new capacitor bank. It will also describe measurements of the spot size (0.3--0.8 mm) and the spectrum (8--14 angstrom) of the DPF source. The dependence of these parameters on the DPF head geometry, bank energy and operating pressure will be discussed. The x-ray output has been measured using filtered pin diodes, x-ray diodes, and absolutely calibrated x-ray crystal spectra. Results from the source operating at 2 Hz will be presented. A novel concept of a windowless beamline has also been developed. The results of preliminary experiments to test the concept will be discussed. At a pulse repetition rate of 20 Hz, this source should produce 200--400 W of x-ray power in the 8-14 angstrom wavelength band, with an input power of 40--60 kW

Sub-Critical Nuclear Reactor Based on FFAG-Accelerator

Energy Technology Data Exchange (ETDEWEB)

Lee, Hee Seok; Kang, Hung Sik; Lee, Tae Yeon [Pohang Accelerator Laboratory, Pohang (Korea, Republic of)

2011-10-15

After the East-Japan earthquake and the subsequent nuclear disaster, the anti-nuclear mood has been wide spread. It is very unfortunate both for nuclear science community and for the future of mankind, which is threatened by two serious challenges, the global warming caused by the greenhouse effect and the shortage of energy cause by the petroleum exhaustion. While the nuclear energy seemed to be the only solution to these problems, it is clear that it has its own problems, one of which broke out so strikingly in Japan. There are also other problems such as the radiotoxic nuclear wastes that survive up to even tens of thousands years and the limited reserves of Uranium. To solve these problems of nuclear fission energy, accelerator-based sub-critical nuclear reactor was once proposed. (Its details will be explained below.) First of all, it is safe in a disaster such as an earthquake, because the deriving accelerator stops immediately by the earthquake. It also minimizes the nuclear waste problem by reducing the amount of the toxic waste and shortening their half lifetime to only a few hundred years. Finally, it solves the Uranium reserve problem because it can use Thorium as its fuel. The Thorium reserve is much larger than that of Uranium. Although the idea of the accelerator-driven nuclear reactor was proposed long time ago, it has not been utilized yet first by technical difficulty and economical reasons. The accelerator-based system needs 1 GeV, 10 MW power proton accelerator. A conventional linear accelerator would need several hundred m length, which is highly costly particularly in Korea because of the high land cost. However, recent technologies make it possible to realize that scale accelerator by a reasonable size. That is the fixed-field alternating gradient (FFAG) accelerator that is described in this article

Sub-Critical Nuclear Reactor Based on FFAG-Accelerator

International Nuclear Information System (INIS)

Lee, Hee Seok; Kang, Hung Sik; Lee, Tae Yeon

2011-01-01

After the East-Japan earthquake and the subsequent nuclear disaster, the anti-nuclear mood has been wide spread. It is very unfortunate both for nuclear science community and for the future of mankind, which is threatened by two serious challenges, the global warming caused by the greenhouse effect and the shortage of energy cause by the petroleum exhaustion. While the nuclear energy seemed to be the only solution to these problems, it is clear that it has its own problems, one of which broke out so strikingly in Japan. There are also other problems such as the radiotoxic nuclear wastes that survive up to even tens of thousands years and the limited reserves of Uranium. To solve these problems of nuclear fission energy, accelerator-based sub-critical nuclear reactor was once proposed. (Its details will be explained below.) First of all, it is safe in a disaster such as an earthquake, because the deriving accelerator stops immediately by the earthquake. It also minimizes the nuclear waste problem by reducing the amount of the toxic waste and shortening their half lifetime to only a few hundred years. Finally, it solves the Uranium reserve problem because it can use Thorium as its fuel. The Thorium reserve is much larger than that of Uranium. Although the idea of the accelerator-driven nuclear reactor was proposed long time ago, it has not been utilized yet first by technical difficulty and economical reasons. The accelerator-based system needs 1 GeV, 10 MW power proton accelerator. A conventional linear accelerator would need several hundred m length, which is highly costly particularly in Korea because of the high land cost. However, recent technologies make it possible to realize that scale accelerator by a reasonable size. That is the fixed-field alternating gradient (FFAG) accelerator that is described in this article

A laser-driven source of polarized hydrogen and deuterium

International Nuclear Information System (INIS)

Young, L.; Holt, R.J.; Gilman, R.A.; Kowalczyk, R.; Coulter, K.

1989-01-01

A novel laser-driven polarized source of hydrogen and deuterium which operates on the principle of spin-exchange optical pumping is being developed. This source is designed to operate as an internal target in an electron storage ring for fundamental studies of spin-dependent structure of nuclei. It has the potential to exceed the flux from existing conventional sources (3 times 10 16/ s) by an order of magnitude. Currently, the source delivers hydrogen at a flux of 8 times 10 16 atoms/s with an atomic polarization of 24% and deuterium at 6 times 10 16 atoms/s with a polarization of 29%. Technical obstacles which have been overcome, with varying degrees of success are complete Doppler-coverage in the optical-pumping stage without the use of a buffer gas, wall-induced depolarization and radiation-trapping. Future improvements should allow achievement of the design goals of 4 times 10 17 atoms/s with a polarization of 50%. 8 refs., 2 figs

Influence of the constant load sintering on the improvement of the transport critical current in Ag-(Bi,Pb)[sub 2]Sr[sub 2]Ca[sub 2]Cu[sub 3]O[sub x] tape form conductor

Energy Technology Data Exchange (ETDEWEB)

Jackiewicz, J [IRC in Superconductivity, Univ. of Cambridge (United Kingdom); Glowacki, B A [IRC in Superconductivity, Univ. of Cambridge (United Kingdom) Dept. of Materials Science and Metallurgy, Univ. of Cambridge (United Kingdom)

1993-05-10

The effects of the short time, low value constant load pressing process of cold rolled silver clad wires conducted at temperatures close to the partial melting point of the ceramic core, from 800 C to 866 C on the microstructure and critical current anisotropy have been studied in detail. The strong influence of the constant load sintering at up to 2 MPa for 1 hour on the improvement of the alignment of the ceramic core in the tape form conductors was confirmred by microstructure investigations and also by the I[sub c] versus [mu][sub 0]H measurements. The magnetic field dependence of the transport critical current, for [mu][sub 0]H parallel to the surface of the tape and also for [mu][sub 0]H perpendicular to the surface of the tape, is very significantly reduced in the tapes sintered under constant load. The analysis of the mechanical creep of silver and ceramic core versus temperature allowed us to optimise the densification conditions of the investigated single core Ag-''2223'' tape form conductor for the load used. (orig.)

Laser-ablation-based ion source characterization and manipulation for laser-driven ion acceleration

Science.gov (United States)

Sommer, P.; Metzkes-Ng, J.; Brack, F.-E.; Cowan, T. E.; Kraft, S. D.; Obst, L.; Rehwald, M.; Schlenvoigt, H.-P.; Schramm, U.; Zeil, K.

2018-05-01

For laser-driven ion acceleration from thin foils (∼10 μm–100 nm) in the target normal sheath acceleration regime, the hydro-carbon contaminant layer at the target surface generally serves as the ion source and hence determines the accelerated ion species, i.e. mainly protons, carbon and oxygen ions. The specific characteristics of the source layer—thickness and relevant lateral extent—as well as its manipulation have both been investigated since the first experiments on laser-driven ion acceleration using a variety of techniques from direct source imaging to knife-edge or mesh imaging. In this publication, we present an experimental study in which laser ablation in two fluence regimes (low: F ∼ 0.6 J cm‑2, high: F ∼ 4 J cm‑2) was applied to characterize and manipulate the hydro-carbon source layer. The high-fluence ablation in combination with a timed laser pulse for particle acceleration allowed for an estimation of the relevant source layer thickness for proton acceleration. Moreover, from these data and independently from the low-fluence regime, the lateral extent of the ion source layer became accessible.

Record critical current densities in IG processed bulk YBa{sub 2}Cu{sub 3}O{sub y} fabricated using ball-milled Y{sub 2}Ba{sub 1}Cu{sub 1}O{sub 5} phase

Energy Technology Data Exchange (ETDEWEB)

Muralidhar, Miryala; Kenta, Nakazato; Murakami, Masato [Department of Materials Science and Engineering, Superconducting Materials Laboratory, Shibaura Institute of Technology, Tokyo (Japan); Zeng, XianLin; Koblischka, Michael R. [Institute of Experimental Physics, Saarland University, Saarbruecken (Germany); Diko, Pavel [Institute of Experimental Physics, Material Physics Laboratory, Slovak Academy of Sciences, Kosice (Slovakia)

2016-02-15

The infiltration-growth (IG) technique enables the uniform and controllable Y{sub 2}BaCuO{sub 5} (Y211) secondary phase particles formation within the YBa{sub 2}Cu{sub 3}O{sub y} (Y123) matrix. Recent results clarified that the flux pinning performance of the Y123 material was dramatically improved by optimizing the processing conditions during the IG process. In this paper, we adapted the IG technique and produced several samples with addition of nanometer-sized Y211 secondary phase particles, which were produced by a ball milling technique. We found that the performance of the IG processed Y123 material dramatically improved in the low field region for a ball milling time of 12 h as compared to the samples without a ball milling step. Magnetization measurements showed a sharp superconducting transition with an onset T{sub c} at around 92 K. The critical current density (J{sub c}) at 77 K and zero field was determined to be 224 022 Acm{sup -2}, which is higher than the not ball-milled sample. Furthermore, microstructural observations exhibited a uniform microstructure with homogenous distribution of nanosized Y-211 inclusions within the Y-123 matrix. The improved performance of the Y-123 material can be understood in terms of fine distribution of the secondary phases. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Comparison of a Shastry-Sutherland lattice stability in Ce{sub 2}Pd{sub 2}Sn as a function of field and doping

Energy Technology Data Exchange (ETDEWEB)

Sereni, Julian G, E-mail: jsereni@cab.cnea.gov.ar [Low Temperature Div., CAB-CNEA and CONICET, 8400 S.C. de Bariloche (Argentina)

2011-01-01

A comparative study of the stability of a Shastry-Sutherland lattice (SSL) in Ce{sub 2}Pd{sub 2}Sn under different physical conditions is presented. Applied magnetic field suppresses the SSL of stoichiometric Ce{sub 2}Pd{sub 2}Sn in a magnetic critical point at T{sub cr}(B) = 4.2K and B{sub cr} = 0.13 T, whereas 25% of Ni does it at T{sub cr}(Ni) = 3.4 K. Electronic concentration variation, driven by the increase of Pd (holes) concentration in Ce{sub 2}Pd{sub 2+y}In{sub 1-y}, decreases the magnetic transition down to T{sub M} = 2.8 K in the limit of the alloy solubility, i.e. y = 0.4. The existence of a M(B) plateau in SSL predicted by theory and the crossing of those isotherms, previously observed in the model compound SrCu{sub 2}(BO{sub 3}){sub 2} are analyzed.

Characteristics of membrane fouling in submerged membrane bioreactor under sub-critical flux operation.

Science.gov (United States)

Su, Y C; Huang, C P; Pan, Jill R; Lee, H C

2008-01-01

Recently, the membrane bioreactor (MBR) process has become one of the novel technologies to enhance the performance of biological treatment of wastewater. Membrane bioreactor process uses the membrane unit to replace a sediment tank, and this can greatly enhance treatment performance. However, membrane fouling in MBR restricts its widespread application because it leads to permeate flux decline, making more frequent membrane cleaning and replacement necessary, which then increases operating and maintenance costs. This study investigated the sludge characteristics in membrane fouling under sub-critical flux operation and also assessed the effect of shear stress on membrane fouling. Membrane fouling was slow under sub-critical flux operation. However, as filamentous microbes became dominant in the reactor, membrane fouling increased dramatically due to the increased viscosity and polysaccharides. A close link was found between membrane fouling and the amount of polysaccharides in soluble EPS. The predominant resistance was the cake resistance which could be minimized by increasing the shear stress. However, the resistance of colloids and solutes was not apparently reduced by increasing shear stress. Therefore, smaller particles such as macromolecules (e.g. polysaccharides) may play an important role in membrane fouling under sub-critical flux operation.

Sources of CO{sub 2} efflux from soil and review of partitioning methods

Energy Technology Data Exchange (ETDEWEB)

Kuzyakov, Y. [University of Hohenheim, Stuttgart (Germany). Institute of Soil Science and Land Evaluation

2006-03-15

Five main biogenic sources of CO{sub 2} efflux from soils have been distinguished and described according to their turnover rates and the mean residence time of carbon. They are root respiration, rhizomicrobial respiration, decomposition of plant residues, the priming effect induced by root exudation or by addition of plant residues, and basal respiration by microbial decomposition of soil organic matter (SOM). These sources can be grouped in several combinations to summarize CO{sub 2} efflux from the soil including: root-derived CO{sub 2}, plant-derived CO{sub 2}, SOM-derived CO{sub 2}, rhizosphere respiration, heterotrophic microbial respiration (respiration by heterotrophs), and respiration by autotrophs. These distinctions are important because without separation of SOM-derived CO{sub 2} from plant-derived CO{sub 2}, measurements of total soil respiration have very limited value for evaluation of the soil as a source or sink of atmospheric CO{sub 2} and for interpreting the sources of CO{sub 2} and the fate of carbon within soils and ecosystems. Additionally, the processes linked to the five sources of CO{sub 2} efflux from soil have various responses to environmental variables and consequently to global warming. This review describes the basic principles and assumptions of the following methods which allow SOM-derived and root-derived CO{sub 2} efflux to be separated under laboratory and field conditions: root exclusion techniques, shading and clipping, tree girdling, regression, component integration, excised roots and in situ root respiration; continuous and pulse labeling, {sup 13}C natural abundance and FACE, and radiocarbon dating and bomb-{sup 14}C. A short sections cover the separation of the respiration of autotrophs and that of heterotrophs, i.e. the separation of actual root respiration from microbial respiration, as well as methods allowing the amount of CO{sub 2} evolved by decomposition of plant residues and by priming effects to be estimated. All

Possible influence of the ferromagnetic/antiferromagnetic interface on the effective critical behavior of bilayers based on La{sub 1−x}Sr{sub x}MnO{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Álvarez Miño, Lucero, E-mail: lalvarezm@unal.edu.co [Universidad Nacional de Colombia, Sede Manizales, Cra. 27 #64-60, Manizales (Colombia); Grupo de Superconductividad y Nuevos Materiales, Universidad Nacional de Colombia, Sede Bogotá, Avenida Carrera 30 #45, Bogotá (Colombia); Mulcué-Nieto, Luis Fernando, E-mail: lfmulcuen@unal.edu.co [Laboratorio de Magnetismo y Materiales Avanzados, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Colombia, Sede Manizales, Cra. 27 #64-60, Manizales (Colombia)

2015-03-01

In this work, the effective critical exponent of the spontaneous magnetization, β, and the transition temperature, T{sub C}, were calculated from magnetization measurements of three bilayers based on La{sub 1−x}Sr{sub x}MnO{sub 3} (LSMO). The bilayers structure is a ferromagnetic (FM) LSMO film grown on top of an antiferromagnetic (AF) LSMO film. The value of the antiferromagnetic film thickness was kept the same for the three samples, while the ferromagnetic film had different thickness for each bilayer. Applying a method of calculation based on a linear superposition of the magnetization close to the critical temperature, a β value corresponding to the 3D Ising model was found for the bilayer with the thinnest ferromagnetic film. This result, and the other obtained values are explained taking into account the possible influence of the FM/AF interface on the magnetic and crystal orderings. - Highlights: • The critical exponent β of three LSMO bilayers was determined. • Two bilayers with the thinner FM layer have very similar transition temperature. • Two bilayers with the thinner FM layer have very similar width values. • We have found values of β of the 3D Ising model. • Interface also seems to be responsible for some structural disorder.

Quasi-monoenergetic ion beam acceleration by laser-driven shock and solitary waves in near-critical plasmas

International Nuclear Information System (INIS)

Zhang, W. L.; Qiao, B.; Huang, T. W.; Shen, X. F.; You, W. Y.; Yan, X. Q.; Wu, S. Z.; Zhou, C. T.; He, X. T.

2016-01-01

Ion acceleration in near-critical plasmas driven by intense laser pulses is investigated theoretically and numerically. A theoretical model has been given for clarification of the ion acceleration dynamics in relation to different laser and target parameters. Two distinct regimes have been identified, where ions are accelerated by, respectively, the laser-induced shock wave in the weakly driven regime (comparatively low laser intensity) and the nonlinear solitary wave in the strongly driven regime (comparatively high laser intensity). Two-dimensional particle-in-cell simulations show that quasi-monoenergetic proton beams with a peak energy of 94.6 MeV and an energy spread 15.8% are obtained by intense laser pulses at intensity I_0 = 3 × 10"2"0" W/cm"2 and pulse duration τ = 0.5 ps in the strongly driven regime, which is more advantageous than that got in the weakly driven regime. In addition, 233 MeV proton beams with narrow spread can be produced by extending τ to 1.0 ps in the strongly driven regime.

Elemental characterization and source apportionment of PM{sub 10} and PM{sub 2.5} in the western coastal area of central Taiwan

Energy Technology Data Exchange (ETDEWEB)

Hsu, Chin-Yu; Chiang, Hung-Che [National Environmental Health Research Center, National Health Research Institutes, 35 Keyan Road, Zhunan Town, Miaoli 35053, Taiwan (China); Lin, Sheng-Lun [Super Micro Mass Research and Technology Center, Cheng Shiu University, No. 840, Chengcing Rd., Kaohsiung 83347, Taiwan (China); Chen, Mu-Jean; Lin, Tzu-Yu [National Environmental Health Research Center, National Health Research Institutes, 35 Keyan Road, Zhunan Town, Miaoli 35053, Taiwan (China); Chen, Yu-Cheng, E-mail: yucheng@nhri.org.tw [National Environmental Health Research Center, National Health Research Institutes, 35 Keyan Road, Zhunan Town, Miaoli 35053, Taiwan (China); Department of Occupational Safety and Health, China Medical University, 91 Hsueh-Shih Road, Taichung 40402, Taiwan (China)

2016-01-15

ABSTRACT: This study investigated seasonal variations in PM{sub 10} and PM{sub 2.5} mass and associated trace metal concentrations in a residential area in proximity to the crude oil refinery plants and industrial parks of central Taiwan. Particle measurements were conducted during winter, spring and summer in 2013 and 2014. Twenty-six trace metals in PM{sub 10} and PM{sub 2.5} were analyzed using ICP-MS. Multiple approaches of the backward trajectory model, enrichment factor (EF), Lanthanum enrichment and positive matrix fraction (PMF) were used to identify potential sources of particulate metals. Mean concentrations of PM{sub 10} in winter, spring and summer were 76.4 ± 22.6, 33.2 ± 9.9 and 37.4 ± 17.0 μg m{sup −3}, respectively, while mean levels of PM{sub 2.5} in winter, spring and summer were 47.8 ± 20.0, 23.9 ± 11.2 and 16.3 ± 8.2 μg m{sup −3}, respectively. The concentrations of carcinogenic metals (Ni, As and adjusted Cr(VI)) in PM{sub 10} and PM{sub 2.5} exceeded the guideline limits published by WHO. The result of EF analysis confirmed that Mo, Sb, Cd, Zn, Mg, Cr, As, Pb, Cu, Ni and V were attributable to anthropogenic emission. PMF analysis demonstrated that trace metals in PM{sub 10} and PM{sub 2.5} were from the similar sources, such as coal combustion, oil combustion and traffic-related emission, except for soil dust and crustal element emissions only observed in PM{sub 10} and secondary aluminum smelter only observed in PM{sub 2.5}. Considering health-related particulate metals, the traffic-related emission and coal combustion for PM{sub 10} and PM{sub 2.5}, respectively, are important to control for reducing potential carcinogenic risk. The results could aid efforts to clarify the impact of source-specific origins on human health. - Highlights: • Multiple approaches to identify sources of PM{sub 10} and PM{sub 2.5} metals were used. • Four similar sources contributed to metals in PM{sub 10} and PM{sub 2.5} in the study area. • Six

Influence of source batch S{sub K} dispersion on dosimetry for prostate cancer treatment with permanent implants

Energy Technology Data Exchange (ETDEWEB)

Nuñez-Cumplido, E., E-mail: ejnc-mccg@hotmail.com; Hernandez-Armas, J. [Medical Physics Department, University Hospital of the Canary Island, La Cuesta – Ofra, 38003 La Laguna (Spain); Perez-Calatayud, J. [Radiotherapy Department, La Fe University Hospital, Bulevar Sur, 46026 Valencia (Spain); Casares-Magaz, O. [Medical Physics Department, University Hospital of the Canary Island, La Cuesta – Ofra, 38003 La Laguna, Spain and Medical Physics Department, Aarhus University Hospital, Nørrebrogade 44, 8000 Aarhus (Denmark)

2015-08-15

Purpose: In clinical practice, specific air kerma strength (S{sub K}) value is used in treatment planning system (TPS) permanent brachytherapy implant calculations with {sup 125}I and {sup 103}Pd sources; in fact, commercial TPS provide only one S{sub K} input value for all implanted sources and the certified shipment average is typically used. However, the value for S{sub K} is dispersed: this dispersion is not only due to the manufacturing process and variation between different source batches but also due to the classification of sources into different classes according to their S{sub K} values. The purpose of this work is to examine the impact of S{sub K} dispersion on typical implant parameters that are used to evaluate the dose volume histogram (DVH) for both planning target volume (PTV) and organs at risk (OARs). Methods: The authors have developed a new algorithm to compute dose distributions with different S{sub K} values for each source. Three different prostate volumes (20, 30, and 40 cm{sup 3}) were considered and two typical commercial sources of different radionuclides were used. Using a conventional TPS, clinically accepted calculations were made for {sup 125}I sources; for the palladium, typical implants were simulated. To assess the many different possible S{sub K} values for each source belonging to a class, the authors assigned an S{sub K} value to each source in a randomized process 1000 times for each source and volume. All the dose distributions generated for each set of simulations were assessed through the DVH distributions comparing with dose distributions obtained using a uniform S{sub K} value for all the implanted sources. The authors analyzed several dose coverage (V{sub 100} and D{sub 90}) and overdosage parameters for prostate and PTV and also the limiting and overdosage parameters for OARs, urethra and rectum. Results: The parameters analyzed followed a Gaussian distribution for the entire set of computed dosimetries. PTV and

Theory of the current-driven ion cyclotron instability in the bottomside ionosphere

International Nuclear Information System (INIS)

Satyanarayana, P.; Chaturvedi, P.K.; Keskinen, M.J.; Huba, J.D.; Ossakow, S.L.

1985-01-01

A theory of the current-driven electrostatic ion cyclotron (EIC) instability in the collisional bottomside ionosphere is presented. It is found that electron collisions are destabilizing and are crucial for the excitation of the EIC instability in the collisional bottomside ionosphere. Furthermore, the growth rates of the ion cyclotron instability in the bottomside ionosphere maximize for k/sub perpendicular/ rho/sub i/> or =1, where 2π/k/sub perpendicular/ is the mode scale size perpendicular to the magnetic field and rho/sub i/ the ion gyroradius. Realistic plasma density and temperature profiles typical of the high-latitude ionosphere are used to compute the altitude dependence of the linear growth rate of the maximally growing modes and critical drift velocity of the EIC instability. The maximally growing modes correspond to observed tens of meter size irregularities, and the threshold drift velocity required for the excitation of EIC instability is lower for heavier ions (NO + , O + ) than that for the lighter ions (H + ). Dupree's resonance-broadening theory is used to estimate nonlinear saturated amplitudes for the ion cyclotron instability in the high-latitude ionosphere. Comparison with experimental observations is also made. It is conjectured that the EIC instability in the bottomside ionosphere could be a source of transversely accelerated heavier ions and energetic heavy-ion conic distributions at higher altitudes

Structural, magnetic, magnetocaloric effect and critical behavior of La{sub 0.7}Sr{sub 0.3−x}□{sub x}MnO{sub 3}(0 ≤ x ≤ 0.05)

Energy Technology Data Exchange (ETDEWEB)

Makni-Chakroun, J., E-mail: makni.jihed@yahoo.fr [LT2S Lab, Digital Research Centre of Sfax, Sfax Technopark, BP 275, 3021 Sakiet-Ezzit (Tunisia); Sfifir, I.; Cheikhrouhou-Koubaa, W.; Koubaa, M. [LT2S Lab, Digital Research Centre of Sfax, Sfax Technopark, BP 275, 3021 Sakiet-Ezzit (Tunisia); Cheikhrouhou, A. [Material Physics Laboratory, Faculty of Sciences of Sfax, B.P. 1171, Sfax University, 3000 Sfax (Tunisia)

2017-06-15

Highlights: • The samples crystallize in the rhombohedral structure with R-3C space group. • Curie temperature T{sub C} decreases with lacuna. • (1/χ) versus temperature indicates Griffiths phase occurrence. • Result show that the paramagnetic-ferromagnetic transition is of second order. • Widom scaling relation confirms the critical exponent value. - Abstract: In this paper, we present the effect of Strontium vacancies on the structure and magnetic properties of La{sub 0.7}Sr{sub 0.3−x}□{sub x}MnO{sub 3} nano-sized compounds (x = 0; 0.01; 0.03 and 0.05), synthesized using the sol-gel method. X-ray diffraction revealed that these manganites crystallized in the rhombohedral structure with space group R3-C. From magnetization measurements as function of temperature and magnetic applied field, we have noticed a large magnetic entropy change (∆S{sub M}) around Curie temperature. ∆S{sub M} is found to decrease with the deficiency content (2.30 J/kg·K for x = 0–1.33 J/kg·K for x = 0.05 under magnetic field change µ{sub 0}∆H = 5 T). This behavior is accompanied by a slight reduction of the Curie temperature (T{sub C} = 338 and 328 K for x = 0 and 0.05, respectively). These results show that our materials are potential candidates for magnetic refrigerants working in above room temperature. The refined values of the critical exponents β, γ and δ obtained from the modified Arrott plots and Kouvel-Fisher method indicated that the behavior of the parent sample and the samples with 1and 3% of strontium-deficient are characterized by long-range mean-field behavior (with β = 0.50; γ = 1). However, for 5% lacuna, the magnetic behavior is close to the theoretical 3D-Heisemberg prediction with short-range exchange coupling.

Optimization of an RF driven H- ion source

International Nuclear Information System (INIS)

Leung, K.N.; DiVergilio, W.F.; Hauck, C.A.; Kunkel, W.B.; McDonald, D.S.

1991-04-01

A radio-frequency driven multicusp source has recently been developed to generate volume-produced H - ion beams with extracted current density higher than 200 mA/cm 2 . We have improved the output power of the rf generator and the insulation coating of the antenna coil. We have also optimized the antenna positions and geometry and the filter magnetic field for high power pulsed operation. A total H - current of 30 mA can be obtained with a 5.4-mm-diam extraction aperture and with an rf input power of 50 kW. 4 refs., 5 figs

Photoacoustic imaging driven by an interstitial irradiation source

Directory of Open Access Journals (Sweden)

Trevor Mitcham

2015-06-01

Full Text Available Photoacoustic (PA imaging has shown tremendous promise in providing valuable diagnostic and therapy-monitoring information in select clinical procedures. Many of these pursued applications, however, have been relatively superficial due to difficulties with delivering light deep into tissue. To address this limitation, this work investigates generating a PA image using an interstitial irradiation source with a clinical ultrasound (US system, which was shown to yield improved PA signal quality at distances beyond 13 mm and to provide improved spectral fidelity. Additionally, interstitially driven multi-wavelength PA imaging was able to provide accurate spectra of gold nanoshells and deoxyhemoglobin in excised prostate and liver tissue, respectively, and allowed for clear visualization of a wire at 7 cm in excised liver. This work demonstrates the potential of using a local irradiation source to extend the depth capabilities of future PA imaging techniques for minimally invasive interventional radiology procedures.

Research opportunities with compact accelerator-driven neutron sources

Energy Technology Data Exchange (ETDEWEB)

Anderson, I.S. [Oak Ridge National Laboratory, Oak Ridge, TN (United States); Andreani, C., E-mail: carla.andreani@uniroma2.it [Università degli Studi di Roma “Tor Vergata”, Physics Department and NAST Centre, Via della Ricerca Scientifica 1, 00133 Roma (Italy); CNR-IPCF Sezione di Messina, Messina (Italy); Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi, Roma (Italy); Carpenter, J.M. [Argonne National Laboratory, Argonne, IL (United States); Festa, G., E-mail: giulia.festa@uniroma2.it [Università degli Studi di Roma “Tor Vergata”, Physics Department and NAST Centre, Via della Ricerca Scientifica 1, 00133 Roma (Italy); Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi, Roma (Italy); Gorini, G. [Università degli Studi di Milano—Bicocca, Milano (Italy); Loong, C.-K. [Università degli Studi di Roma “Tor Vergata”, Centro NAST, Via della Ricerca Scientifica 1, 00133 Roma (Italy); Senesi, R. [Università degli Studi di Roma “Tor Vergata”, Physics Department and NAST Centre, Via della Ricerca Scientifica 1, 00133 Roma (Italy); CNR-IPCF Sezione di Messina, Messina (Italy); Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi, Roma (Italy)

2016-10-13

Since the discovery of the neutron in 1932 neutron beams have been used in a very broad range of applications, As an aging fleet of nuclear reactor sources is retired the use of compact accelerator-driven neutron sources (CANS) is becoming more prevalent. CANS are playing a significant and expanding role in research and development in science and engineering, as well as in education and training. In the realm of multidisciplinary applications, CANS offer opportunities over a wide range of technical utilization, from interrogation of civil structures to medical therapy to cultural heritage study. This paper aims to provide the first comprehensive overview of the history, current status of operation, and ongoing development of CANS worldwide. The basic physics and engineering regarding neutron production by accelerators, target–moderator systems, and beam line instrumentation are introduced, followed by an extensive discussion of various evolving applications currently exploited at CANS.

Research opportunities with compact accelerator-driven neutron sources

International Nuclear Information System (INIS)

Anderson, I.S.; Andreani, C.; Carpenter, J.M.; Festa, G.; Gorini, G.; Loong, C.-K.; Senesi, R.

2016-01-01

Since the discovery of the neutron in 1932 neutron beams have been used in a very broad range of applications, As an aging fleet of nuclear reactor sources is retired the use of compact accelerator-driven neutron sources (CANS) is becoming more prevalent. CANS are playing a significant and expanding role in research and development in science and engineering, as well as in education and training. In the realm of multidisciplinary applications, CANS offer opportunities over a wide range of technical utilization, from interrogation of civil structures to medical therapy to cultural heritage study. This paper aims to provide the first comprehensive overview of the history, current status of operation, and ongoing development of CANS worldwide. The basic physics and engineering regarding neutron production by accelerators, target–moderator systems, and beam line instrumentation are introduced, followed by an extensive discussion of various evolving applications currently exploited at CANS.

Research opportunities with compact accelerator-driven neutron sources

Science.gov (United States)

Anderson, I. S.; Andreani, C.; Carpenter, J. M.; Festa, G.; Gorini, G.; Loong, C.-K.; Senesi, R.

2016-10-01

Since the discovery of the neutron in 1932 neutron beams have been used in a very broad range of applications, As an aging fleet of nuclear reactor sources is retired the use of compact accelerator-driven neutron sources (CANS) is becoming more prevalent. CANS are playing a significant and expanding role in research and development in science and engineering, as well as in education and training. In the realm of multidisciplinary applications, CANS offer opportunities over a wide range of technical utilization, from interrogation of civil structures to medical therapy to cultural heritage study. This paper aims to provide the first comprehensive overview of the history, current status of operation, and ongoing development of CANS worldwide. The basic physics and engineering regarding neutron production by accelerators, target-moderator systems, and beam line instrumentation are introduced, followed by an extensive discussion of various evolving applications currently exploited at CANS.

Optimization by simulation of the coupling between a sub-critical reactor and its spallation source. Towards a pilot reactor; Optimisation par simulation du couplage entre un reacteur sous-critique et sa source de spallation. Application a un demonstrateur

Energy Technology Data Exchange (ETDEWEB)

Kerdraon, D

2001-10-01

Accelerator Driven Systems (ADS), based on a proton accelerator and a sub-critical core coupled with a spallation target, offer advantages in order to reduce the nuclear waste radiotoxicity before repository closure. Many studies carried out on the ADS should lead to the definition of an experimental plan which would federate the different works in progress. This thesis deals with the neutronic Monte Carlo simulations with the MCNPX code to optimize such a system in view of a pilot reactor building. First, we have recalled the main neutronic properties of an hybrid reactor. The concept of gas-cooled eXperimental Accelerator Driven System (XADS) chosen for our investigations comes from the preliminary studies done by the Framatome company. In order to transmute minor actinides, we have considered the time evolution of the main fuels which could be reasonably used for the demonstration phases. The neutronic parameters of the reactor, concerning minor actinide transmutation, are reported. Also, we have calculated the characteristic times and the transmutation rates in the case of {sup 99}Tc and {sup 129}I isotopes. We have identified some neutronic differences between an experimental and a power ADS according to the infinite multiplication coefficient, the shape factor and the level of flux to extend the demonstrator concept. We have proposed geometric solutions to keep the radial shape factor of a power ADS acceptable. In the last part, beyond the experimental XADS scope, we have examined the possible transition towards an uranium/thorium cycle based on Molten Salt Reactors using a power ADS in order to generate the required {sup 233}U proportion. (author)

Neutron source multiplication method

International Nuclear Information System (INIS)

Clayton, E.D.

1985-01-01

Extensive use has been made of neutron source multiplication in thousands of measurements of critical masses and configurations and in subcritical neutron-multiplication measurements in situ that provide data for criticality prevention and control in nuclear materials operations. There is continuing interest in developing reliable methods for monitoring the reactivity, or k/sub eff/, of plant operations, but the required measurements are difficult to carry out and interpret on the far subcritical configurations usually encountered. The relationship between neutron multiplication and reactivity is briefly discussed and data presented to illustrate problems associated with the absolute measurement of neutron multiplication and reactivity in subcritical systems. A number of curves of inverse multiplication have been selected from a variety of experiments showing variations observed in multiplication during the course of critical and subcritical experiments where different methods of reactivity addition were used, with different neutron source detector position locations. Concern is raised regarding the meaning and interpretation of k/sub eff/ as might be measured in a far subcritical system because of the modal effects and spectrum differences that exist between the subcritical and critical systems. Because of this, the calculation of k/sub eff/ identical with unity for the critical assembly, although necessary, may not be sufficient to assure safety margins in calculations pertaining to far subcritical systems. Further study is needed on the interpretation and meaning of k/sub eff/ in the far subcritical system

A compact rf driven H- ion source for linac injection

International Nuclear Information System (INIS)

Rymer, J.P.; Engeman, G.A.; Hamm, R.W.; Potter, J.M.

1991-01-01

A compact rf driven H - ion source has been developed for use as an injector for the AccSys radio frequency quadrupole (RFQ) linacs. A multicusp magnetic bucket geometry developed at Lawrence Berkeley Laboratory confines the plasma created by an antenna driven by 35 kW (peak) of pulsed rf power at 1.8 MHz. A three electrode system is used to extract and accelerate the H - beam, which is then focused into the RFQ by an einzel lens. Permanent magnets in the extraction region sweep electrons onto the second electrode at energies up to half of the full acceleration voltage. A fast pulsed valve allows the hydrogen gas supply to be pulsed, thus minimizing the average gas flow rate into the system. The design features and performance data from the prototype are discussed

Thermal properties and Ising critical behavior in EuFe{sub 2}As{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Oleaga, A., E-mail: alberto.oleaga@ehu.es [Departamento de Física Aplicada I, Escuela Técnica Superior de Ingeniería, Universidad del País Vasco UPV/EHU, Alameda Urquijo s/n, 48013 Bilbao (Spain); Salazar, A. [Departamento de Física Aplicada I, Escuela Técnica Superior de Ingeniería, Universidad del País Vasco UPV/EHU, Alameda Urquijo s/n, 48013 Bilbao (Spain); Thamizhavel, A.; Dhar, S.K. [Department of Condensed Matter Physics and Material Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005 (India)

2014-12-25

Highlights: • A high resolution ac photopyroelectric calorimeter is used. • Thermal diffusivity and specific heat are measured at the phase transitions. • Latent heat is exchanged at the Fe{sup 2+} spin-ordering transition. • Eu{sup 2+} spin-ordering transition belongs to the 3D-Ising universality class. - Abstract: Specific heat and thermal diffusivity have been studied by means of a high resolution ac photopyroelectric calorimeter in the vicinity of phase transitions in EuFe{sub 2}As{sub 2}: the first one corresponding to the ordering of the Fe{sup 2+} spins concomitant to a structural transition at 188.1 K and the second one to the antiferromagnetic ordering of the Eu{sup 2+} spins at 18.4 K. The weak first order character of the first transition has been confirmed while the critical behavior of the second transition at lower temperature has been established to correspond to the 3D-Ising universality class (α{sub exp} = 0.11 ± 0.03). This is in agreement with the proposed uniaxial arrangement of the Eu{sup 2+} spins lying along the long orthorhombic axis a as reported in literature.

Sequential coating upconversion NaYF{sub 4}:Yb,Tm nanocrystals with SiO{sub 2} and ZnO layers for NIR-driven photocatalytic and antibacterial applications

Energy Technology Data Exchange (ETDEWEB)

Tou, Meijie; Luo, Zhenguo; Bai, Song; Liu, Fangying; Chai, Qunxia; Li, Sheng; Li, Zhengquan, E-mail: zqli@zjnu.edu.cn

2017-01-01

ZnO is one of the most promising materials for both photocatalytic and antibacterial applications, but its wide bandgap requires the excitation of UV light which limits their applications under visible and NIR bands. Herein, we demonstrate a facile approach to synthesize core-shell-shell hybrid nanoparticles consisting of hexagonal NaYF{sub 4}:Yb,Tm, amorphous SiO{sub 2} and wurtzite ZnO. The upconversion nanocrystals are used as the core seeds and sequentially coated with an insulting shell and a semiconductor layer. Such hybrid nanoparticles can efficiently utilize the NIR light through the upconverting process, and display notable photocatalytic performance and antibacterial activity under NIR irradiation. The developed NaYF{sub 4}:Yb,Tm@SiO{sub 2}@ZnO nanoparticles are characterized with TEM, XRD, EDS, XPS and PL spectra, and their working mechanism is also elucidated. - Highlights: • Core-shell NaYF{sub 4}:Yb,Tm@SiO{sub 2}@TiO{sub 2} NPs were synthesized via a sequential coating method. • Hybrid NaYF{sub 4}:Yb,Tm@SiO{sub 2}@TiO{sub 2} NPs show NIR-light enhanced photocatalytic activity. • NIR-driven antibacterial performance has been realized with NaYF{sub 4}:Yb,Tm@SiO{sub 2}@TiO{sub 2} NPs. • Working mechanism of the hybrid photocatalysts as antibacterial agents was proposed.

Coral reefs - sources or sinks of atmospheric CO[sub 2

Energy Technology Data Exchange (ETDEWEB)

Ware, J R; Smith, S V; Reakakudla, M L [Hawaii University, Honolulu, HI (USA). Dept. of Oceanography

1992-09-01

Because the precipitation of calcium carbonate results in the sequestering of carbon, it frequently has been thought that coral reefs function as sinks of global atmospheric CO[sub 2]. However, the precipitation of calcium carbonate is accompanied by a shift of pH that results in the release of CO[sub 2]. This release of CO[sub 2] is less in buffered sea water than fresh water systems; nevertheless, coral reefs are sources, not sinks, of atmospheric carbon. Using estimated rates of coral reef carbonate production, we compute that coral reefs release 0.02 to 0.08 Gt C as CO[sub 2] annually. This is approximately 0.4% to 1.4% of the current anthropogenic CO[sub 2] production due to fossil fuel combustion.

CLUMPED LIGHT WATER MODERATED UO$sub 2$ SUPERHEAT CRITICALS. PART II. ANALYSIS

Energy Technology Data Exchange (ETDEWEB)

Petersen, G. T.

1963-11-15

Critical and subcritical reactivity measurements on an EVESR-type core, using EVESR UO/sub 2/ superheat fuel elements, are analyzed in order to obtain a physics design model for use in the EVESR. (T.F.H.)

Performance of a C{sub 60}{sup +} ion source on a dynamic SIMS instrument

Energy Technology Data Exchange (ETDEWEB)

Fahey, Albert J. [Surface and Microanalysis Science Division, National Institute of Standards and Technology, 100 Bureau Dr. Stop 8371, Gaithersburg, MD 20899-8371 (United States)]. E-mail: albert.fahey@nist.gov; Gillen, Greg [Surface and Microanalysis Science Division, National Institute of Standards and Technology, 100 Bureau Dr. Stop 8371, Gaithersburg, MD 20899-8371 (United States); Chi, Peter [Surface and Microanalysis Science Division, National Institute of Standards and Technology, 100 Bureau Dr. Stop 8371, Gaithersburg, MD 20899-8371 (United States); Mahoney, Christine M. [Surface and Microanalysis Science Division, National Institute of Standards and Technology, 100 Bureau Dr. Stop 8371, Gaithersburg, MD 20899-8371 (United States)

2006-07-30

An IonOptika C{sub 60}{sup +} ion source has been fitted onto a CAMECA{sup 1} ims-4f. Stable ion beams of C{sub 60}{sup +} and C{sub 60}{sup 2+} have been obtained with typical currents approaching 20nA under conditions that allow for several days of source operation. The beam has been able to be focussed into a spot size of {approx}3{mu}m with an anode voltage of 10keV and scanning ion images have been acquired. We have performed analyses to characterize the performance of C{sub 60}{sup +} and C{sub 60}{sup 2+}. Depth profiles of a Cr-Ni multi-layer and polymer films with C{sub 60}{sup +} have produced excellent results. We have discovered that, under bombardment energies of <12keV on Si, C{sub 60}{sup +} will sputter material from the sample but will also produce deposition at a rate that exceeds the sputter rate. The performance of the source and our experiences with its operation will be discussed and some characteristic analysis data will be shown.

Applicability of light sources and the inner filter effect in UV/acetylacetone and UV/H{sub 2}O{sub 2} processes

Energy Technology Data Exchange (ETDEWEB)

Wu, Bingdang; Yang, Minghui [State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, 210023 (China); Yin, Ran [Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong); Zhang, Shujuan, E-mail: sjzhang@nju.edu.cn [State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, 210023 (China)

2017-08-05

Highlights: • Acetylacetone (AA) could directly use solar irradiation to decolorize dyes. • AA had a wider applicability than H{sub 2}O{sub 2} to a variety of light sources. • The photonic efficiency in the UV/AA process was target-dependent. • An accurate calculation approach for the inner filter effect was developed. - Abstract: Light source is a crucial factor in the application of a photochemical process, which determines the energy efficiency. The performances of acetylacetone (AA) in conversion of aqueous contaminants under irradiation with a low-pressure mercury lamp, a medium-pressure mercury lamp, a xenon lamp, and natural sunlight were investigated and compared with those of H{sub 2}O{sub 2} as reference. In all cases, AA was superior to H{sub 2}O{sub 2} in the degradation of Acid Orange 7. Using combinations of the different light sources with various cut-off and band-pass filters, the spectra responses of the absorbed photons in the UV/AA and UV/H{sub 2}O{sub 2} processes were determined for two colored and two colorless compounds. The photonic efficiency (φ) of the two photochemical processes was found to be target-dependent. A calculation approach for the inner filter effect was developed by taking the obtained φ into account, which provides a more accurate indication of the reaction mechanisms.

Determination of Key Risk Supervision Areas around River-Type Water Sources Affected by Multiple Risk Sources: A Case Study of Water Sources along the Yangtze’s Nanjing Section

Directory of Open Access Journals (Sweden)

Qi Zhou

2017-02-01

Full Text Available To provide a reference for risk management of water sources, this study screens the key risk supervision areas around river-type water sources (hereinafter referred to as the water sources threatened by multiple fixed risk sources (the risk sources, and establishes a comprehensive methodological system. Specifically, it comprises: (1 method of partitioning risk source concentrated sub-regions for screening water source perimeter key risk supervision areas; (2 approach of determining sub-regional risk indexes (SrRI, which characterizes the scale of sub-regional risks considering factors like risk distribution intensity within sub-regions, risk indexes of risk sources (RIRS, characterizing the risk scale of risk sources and the number of risk sources; and (3 method of calculating sub-region’s risk threats to the water sources (SrTWS which considers the positional relationship between water sources and sub-regions as well as SrRI, and the criteria for determining key supervision sub-regions. Favorable effects are achieved by applying this methodological system in determining water source perimeter sub-regions distributed along the Yangtze’s Nanjing section. Results revealed that for water sources, the key sub-regions needing supervision were SD16, SD06, SD21, SD26, SD15, SD03, SD02, SD32, SD10, SD11, SD14, SD05, SD27, etc., in the order of criticality. The sub-region with the greatest risk threats on the water sources was SD16, which was located in the middle reaches of Yangtze River. In general, sub-regions along the upper Yangtze reaches had greater threats to water sources than the lower reach sub-regions other than SD26 and SD21. Upstream water sources were less subject to the threats of sub-regions than the downstream sources other than NJ09B and NJ03.

Sub-megahertz linewidth single photon source

Directory of Open Access Journals (Sweden)

Markus Rambach

2016-12-01

Full Text Available We report 100% duty cycle generation of sub-MHz single photon pairs at the rubidium D1 line using cavity-enhanced spontaneous parametric downconversion. The temporal intensity cross correlation function exhibits a bandwidth of 666±16 kHz for the single photons, an order of magnitude below the natural linewidth of the target transition. A half-wave plate inside our cavity helps to achieve triple resonance between pump, signal, and idler photon, reducing the bandwidth and simplifying the locking scheme. Additionally, stabilisation of the cavity to the pump frequency enables the 100% duty cycle. The quantum nature of the source is confirmed by the idler-triggered second-order autocorrelation function at τ=0 to be gs,s(2(0= 0.016±0.002 for a heralding rate of 5 kHz. The generated photons are well-suited for storage in quantum memory schemes with sub-natural linewidths, such as gradient echo memories.

The influence of different diffusion pattern to the sub- and super-critical fluid flow in brown coal

Science.gov (United States)

Peng, Peihuo

2018-03-01

Sub- and super-critical CO2 flowing in nanoscale pores are recently becoming of great interest due to that it is closely related to many engineering applications, such as geological burial and sequestration of carbon dioxide, Enhanced Coal Bed Methane recovery ( ECBM), super-critical CO2 fracturing and so on. Gas flow in nanopores cannot be described simply by the Darcy equation. Different diffusion pattern such as Fick diffusion, Knudsen diffusion, transitional diffusion and slip flow at the solid matrix separate the seepage behaviour from Darcy-type flow. According to the principle of different diffusion pattern, the flow of sub- and super-critical CO2 in brown coal was simulated by numerical method, and the results were compared with the experimental results to explore the contribution of different diffusion pattern and swelling effect in sub- and super-critical CO2 flow in nanoscale pores.

Daylight-driven photocatalytic degradation of ionic dyes with negatively surface-charged In{sub 2}S{sub 3} nanoflowers: dye charge-dependent roles of reactive species

Energy Technology Data Exchange (ETDEWEB)

Ge, Suxiang [Xuchang University, Key Laboratory of Micro-Nano Materials for Energy Storage and Conversion of Henan Province, Institute of Surface Micro and Nano Materials, and School of Chemistry and Chemical Engineering (China); Cai, Lejuan, E-mail: 494169965@qq.com [Central China Normal University, Key Laboratory of Pesticide and Chemical Biology of Ministry of Education, College of Chemistry (China); Li, Dapeng, E-mail: lidapengabc@126.com; Fa, Wenjun; Zhang, Yange; Zheng, Zhi [Xuchang University, Key Laboratory of Micro-Nano Materials for Energy Storage and Conversion of Henan Province, Institute of Surface Micro and Nano Materials, and School of Chemistry and Chemical Engineering (China)

2015-12-15

Even though dye degradation is a successful application of semiconductor photocatalysis, the roles of reactive species in dye degradation have not received adequate attention. In this study, we systematically investigated the degradation of two cationic dyes (rhodamine B and methylene blue) and two anionic dyes (methyl orange and orange G) over negatively surface-charged In{sub 2}S{sub 3} nanoflowers synthesized at 80 °C under indoor daylight lamp irradiation. It is notable to find In{sub 2}S{sub 3} nanoflowers were more stable in anionic dyes degradation compared to that in cationic dyes removal. The active species trapping experiments indicated photogenerated electrons were mainly responsible for cationic dyes degradation, but holes were more important in anionic dyes degradation. A surface-charge-dependent role of reactive species in ionic dye degradation was proposed for revealing such interesting phenomenon. This study would provide a new insight for preparing highly efficient daylight-driven photocatalyst for ionic dyes degradation.

RF plasma deposition of thin Si{sub x}Ge{sub y}C{sub z}:H films using a combination of organometallic source materials

Energy Technology Data Exchange (ETDEWEB)

Rapiejko, C. [Institute for Materials Science and Engineering, Technical University of LodzLz Stefanowskiego 1, 90-924 Lodz (Poland); Gazicki-Lipman, M. [Institute for Materials Science and Engineering, Technical University of LodzLz Stefanowskiego 1, 90-924 Lodz (Poland)]. E-mail: gazickim@p.lodz.pl; Klimek, L. [Institute for Materials Science and Engineering, Technical University of LodzLz Stefanowskiego 1, 90-924 Lodz (Poland); Szymanowski, H. [Institute for Materials Science and Engineering, Technical University of LodzLz Stefanowskiego 1, 90-924 Lodz (Poland); Strojek, M. [Institute for Materials Science and Engineering, Technical University of LodzLz Stefanowskiego 1, 90-924 Lodz (Poland)

2004-12-22

Elements of the IV group of periodic table have been strongly present in the fast development of PECVD techniques for the last two decades at least. As a result, deposition technologies of such materials as a-Si:H, a-C:H, m{mu}-C:H or DLC have been successfully established. What has followed is an ever growing interest in binary systems of the A{sub x}(IV)B{sub y}(IV):H kind. One possible way to deposit such systems is to use organosilicon compounds (to deposit Si{sub x}C{sub y}:H films) or organogermanium compounds (to deposit Ge{sub x}C{sub y}:H films), as source substances. The present paper reports on a RF plasma deposition of a Si{sub x}Ge{sub y}C{sub z}:H ternary system, using a combination of organosilicon and organogermanium compounds. Thin Si/Ge/C films have been fabricated in a small volume (ca. 2 dm{sup 3}) parallel plate RF plasma reactor using, as a source material, a combination of tetramethylsilane (TMS) and tetramethylgermanium (TMG) vapours carried by argon. SEM investigations reveal a continuous compact character of the coatings and their uniform thickness. The elemental composition of the films has been studied using EDX analysis. The results of the analysis show that the elemental composition of the films can be controlled by both the TMG/TMS ratio of the initial mixture and the RF power input. Ellipsometric measurements show good homogeneity of these materials. Chemical bonding in the films has been studied using the FTIR technique. Bandgap calculations have been carried out using ellipsometric data and by applying both the Tauc law and the Moss approach.

Shielded radiography with a laser-driven MeV-energy X-ray source

Energy Technology Data Exchange (ETDEWEB)

Chen, Shouyuan; Golovin, Grigory [Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE 68588 (United States); Miller, Cameron [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI 48109 (United States); Haden, Daniel; Banerjee, Sudeep; Zhang, Ping; Liu, Cheng; Zhang, Jun; Zhao, Baozhen [Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE 68588 (United States); Clarke, Shaun; Pozzi, Sara [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI 48109 (United States); Umstadter, Donald, E-mail: donald.umstadter@unl.edu [Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE 68588 (United States)

2016-01-01

We report the results of experimental and numerical-simulation studies of shielded radiography using narrowband MeV-energy X-rays from a compact all-laser-driven inverse-Compton-scattering X-ray light source. This recently developed X-ray light source is based on a laser-wakefield accelerator with ultra-high-field gradient (GeV/cm). We demonstrate experimentally high-quality radiographic imaging (image contrast of 0.4 and signal-to-noise ratio of 2:1) of a target composed of 8-mm thick depleted uranium shielded by 80-mm thick steel, using a 6-MeV X-ray beam with a spread of 45% (FWHM) and 10{sup 7} photons in a single shot. The corresponding dose of the X-ray pulse measured in front of the target is ∼100 nGy/pulse. Simulations performed using the Monte-Carlo code MCNPX accurately reproduce the experimental results. These simulations also demonstrate that the narrow bandwidth of the Compton X-ray source operating at 6 and 9 MeV leads to a reduction of deposited dose as compared to broadband bremsstrahlung sources with the same end-point energy. The X-ray beam’s inherently low-divergence angle (∼mrad) is advantageous and effective for interrogation at standoff distance. These results demonstrate significant benefits of all-laser driven Compton X-rays for shielded radiography.

Criticality safety assessment of FBTR fuel sub-assemblies using WIMS cross section set

International Nuclear Information System (INIS)

Gupta, H.C.; Chakraborty, B.

2002-01-01

Full text: FBTR's irradiated fuel sub-assemblies (FSAs) are sent to RML at Indira Gandhi Centre for Atomic Research for post irradiation examination. The FSAs are cut open and the fuel pins are separated for examination in the hot cells. It was required to evaluate the criticality safety in handling the FSAs in the hot cells. Criticality safety studies for handling two as well as three irradiated FSAs in the hot cells under dry conditions were carried out by the Safety Group at IGCAR, Kalpakkam. Monte Carlo code KENO (Version Va) which uses 16-group Hansen-Roach cross-section set was used for the calculations. Subsequently, during the safety review of the proposition by the Safety Review Committee (SARCOP) of AERB, it was stipulated to carry out the criticality safety studies under flooded condition also. We carried out the criticality safety studies for these fuel sub assemblies in different configurations under dry (buried in concrete) as well as wet condition (flooded with light water) using Monte Carlo codes MONALI (developed at BARC) and KENO4 using WlMS-69 group cross section set. Results of our analyses under various conditions are presented in this paper

A fuzzy multi-criteria decision-making model for CCHP systems driven by different energy sources

International Nuclear Information System (INIS)

Jing Youyin; Bai He; Wang Jiangjiang

2012-01-01

Because of its energy-saving and pollutant emission reduction potentials, combined cooling, heating and power (CCHP) system has been widely used in different kinds of buildings to solve building-related energetic problems and environmental issues. As various kinds of clean energy and renewable energy have been focused and applied to CCHP systems, it is urgent to find a practical decision making methodology for CCHP systems driven by different energy sources. In this paper, an evaluation model which integrates fuzzy theory with multi-criteria decision making process is proposed to assess the comprehensive benefits of CCHP systems from technology, economic, society and environment criterions. Grey relation analysis and combination weighting method are also employed to compare the integrated performances of CCHP systems driven by natural gas, fuel cell, biomass energy and combined gas-steam cycle respectively with a separation production system. Finally, a baseline residential building in Beijing, China is selected as a case to obtain the optimal CCHP system alternative. The results indicate that gas–steam combined cycle CCHP system is the optimum scheme among the five options. - Graphical abstract: A fuzzy multi-criteria decision-making model combined with combination weighting method and grey system theory is presented in this paper, which can be used to evaluate CCHP systems driven by different energy sources from technology, economic, environment and society criteria. Highlights: ► The integrated benefits of CCHP systems driven by different energy sources are evaluated. ► A fuzzy multi-criteria model combined with combination weighting method is proposed. ► Environment evaluation criteria play an important role in the decision-making process. ► CCHP system driven by gas–steam combined cycle is the optimal alternative.

Microstructural and crystallographic imperfections of MgB{sub 2} superconducting wire and their correlation with the critical current density

Energy Technology Data Exchange (ETDEWEB)

Shahabuddin, Mohammed; Alzayed, Nasser S. [Department of Physics and Astronomy, College of Science, P. O. Box 2455, King Saud University, Riyadh 11451 (Saudi Arabia); Oh, Sangjun [Materials Research Team, National Fusion Research Institute, Yueeong, Daejeon 305-333 (Korea, Republic of); Choi, Seyong [Busan Center, Korea Basic Science Institute, Geumjeong, Busan 609-735 (Korea, Republic of); Maeda, Minoru [Department of Physics, College of Science and Technology, Nihon University, 1-8 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8308 (Japan); Hata, Satoshi; Shimada, Yusuke [Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580 (Japan); Hossain, Md Shahriar Al [Institute for Superconducting and Electronic Materials, University of Wollongong, North Wollongong, New South Wales 2500 (Australia); Kim, Jung Ho, E-mail: jhk@uow.edu.au [Department of Physics and Astronomy, College of Science, P. O. Box 2455, King Saud University, Riyadh 11451 (Saudi Arabia); Institute for Superconducting and Electronic Materials, University of Wollongong, North Wollongong, New South Wales 2500 (Australia)

2014-01-15

A comprehensive study of the effects of structural imperfections in MgB{sub 2} superconducting wire has been conducted. As the sintering temperature becomes lower, the structural imperfections of the MgB{sub 2} material are increased, as reflected by detailed X-ray refinement and the normal state resistivity. The crystalline imperfections, caused by lattice disorder, directly affect the impurity scattering between the π and σ bands of MgB{sub 2}, resulting in a larger upper critical field. In addition, low sintering temperature keeps the grain size small, which leads to a strong enhancement of pinning, and thereby, enhanced critical current density. Owing to both the impurity scattering and the grain boundary pinning, the critical current density, irreversibility field, and upper critical field are enhanced. Residual voids or porosities obviously remain in the MgB{sub 2}, however, even at low sintering temperature, and thus block current transport paths.

New applications of laser-driven neutron sources in the car industry

International Nuclear Information System (INIS)

Kakeno, Mitsutaka

2015-01-01

New applications of LDNS (Laser-Driven Neutron Sources) are described. One of them is ib-DATA (in-beam Double Activation Tracer Analysis) with which we can measure mean drift velocity and mass flow rate in a variety of fluid. In ib-DATA, LDNS with very light and compact beam-head will be constructed to shoot pulsed neutrons into the fluid in pinpoint. (author)

Analysis of Fuel Cell Driven Ground Source Heat Pump Systems in Community Buildings

Directory of Open Access Journals (Sweden)

Jong-Keun Shin

2013-05-01

Full Text Available In the present study, a fuel cell driven ground source heat pump (GSHP system is applied in a community building and heat pump system performance is analyzed by computational methods. Conduction heat transfer between the brine pipe and ground is analyzed by TEACH code in order to predict the performance of the heat pump system. The predicted coefficient of performance (COP of the heat pump system and the energy cost were compared with the variation of the location of the objective building, the water saturation rate of the soil, and the driven powers of the heat pump system. Compared to the late-night electricity driven system, a significant reduction of energy cost can be accomplished by employing the fuel cell driven heat pump system. This is due to the low cost of electricity production of the fuel cell system and to the application of the recovered waste heat generated during the electricity production process to the heating of the community building.

Experimental Verification of Isotropic Radiation from a Coherent Dipole Source via Electric-Field-Driven LC Resonator Metamaterials

Science.gov (United States)

Tichit, Paul-Henri; Burokur, Shah Nawaz; Qiu, Cheng-Wei; de Lustrac, André

2013-09-01

It has long been conjectured that isotropic radiation by a simple coherent source is impossible due to changes in polarization. Though hypothetical, the isotropic source is usually taken as the reference for determining a radiator’s gain and directivity. Here, we demonstrate both theoretically and experimentally that an isotropic radiator can be made of a simple and finite source surrounded by electric-field-driven LC resonator metamaterials designed by space manipulation. As a proof-of-concept demonstration, we show the first isotropic source with omnidirectional radiation from a dipole source (applicable to all distributed sources), which can open up several possibilities in axion electrodynamics, optical illusion, novel transformation-optic devices, wireless communication, and antenna engineering. Owing to the electric- field-driven LC resonator realization scheme, this principle can be readily applied to higher frequency regimes where magnetism is usually not present.

Studies on a laser driven photoemissive high-brightness electron source and novel photocathodes

International Nuclear Information System (INIS)

Geng Rongli; Song Jinhu; Yu Jin

1997-01-01

A laser driven photoemissive high-brightness electron source at Beijing University is reported. Through a DC accelerating gap of 100 kV voltage, the device is capable of delivering high-brightness electron beam of 35-100 ps pulse duration when irradiated with a mode-locked YAG laser. The geometry of the gun is optimized with the aid of simulation codes EGUN and POISSON. The results of experimental studies on ion implanted photocathode and cesium telluride photocathode are given. The proposed laser driven superconducting RF gun is also discussed

Recovery of Organic and Amino Acids from Sludge and Fish Waste in Sub Critical Water Conditions

Directory of Open Access Journals (Sweden)

Muhammad Faisal

2011-12-01

Full Text Available The possibility of organic and amino acid production from the treatment of sludge and fish waste using water at sub critical conditions was investigated. The results indicated that at sub-critical conditions, where the ion product of water went through a maximum, the formation of organic acids was favorable. The presence of oxidant favored formation of acetic and formic acid. Other organic acids of significant amount were propionic, succinic and lactic acids. Depending on the type of wastes, formation of other organic acids was also possible. Knowing the organic acids obtained by hydrolysis and oxidation in sub-critical water of various wastes are useful in designing of applicable waste treatment process, complete degradation of organic wastes into volatile carbon and water, and also on the viewpoint of resource recovery. The production of lactic acid was discussed as well. The results indicated that temperature of 573 K, with the absence of oxidant, yield of lactic acid from fish waste was higher than sewage sludge. The maximum yield of total amino acids (137 mg/g-dry fish from waste fish entrails was obtained at subcritical condition (T = 523 K, P = 4 MPa at reaction time of 60 min by using the batch reactor. The amino acids obtained in this study were mainly alanine and glycine. Keywords:  organic acids, amino acids, sub-critical water, hydrothermal, resources recovery

Gate-controlled metal-insulator transition in the LaAlO{sub 3}/SrTiO{sub 3} system with sub-critical LaAlO{sub 3} thickness

Energy Technology Data Exchange (ETDEWEB)

Lee, Joon Sung; Lee, Seung Ran; Chang, Jung-Won; Noh, Hyunho; Baasandorj, Lkhagvasuren; Shim, Seung-Bo; Kim, Jinhee [Korea Research Institute of Standards and Science, Daejeon 305-600 (Korea, Republic of); Seung, Sang Keun; Shin, Hyun Sup; Song, Jonghyun [Department of Physics, Chungnam National University, Daejeon 305-764 (Korea, Republic of)

2012-12-15

We studied the electrical conduction in the LaAlO{sub 3}/SrTiO{sub 3} (LAO/STO) interface electron system with a sub-critical LAO layer thickness of {proportional_to}3.5 unit cells (uc). It was found that the true dividing point between metallic and insulating behaviour without gating lies near the LAO thickness of 3.5 uc. Our marginally metallic 3.5 uc sample showed a sharp transition to insulating state at temperatures which strongly depended on the applied negative back-gate voltage. The superior gate-controllability of the sample was attributed to its sheet carrier density which was an order of magnitude lower than those of conducting LAO/STO samples with 4 uc or more of LAO layers. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Power generation from low-temperature heat source

Energy Technology Data Exchange (ETDEWEB)

Lakew, Amlaku Abie

2012-07-01

transcritical power cycle is operating at lower pump efficiency, the effect of a decrease in pump efficiency is equivalent to a decrease in turbine efficiency. The thermodynamic analysis is coupled with a 1D mean line turbine design. Both axial and radial turbines are considered. The Ainely and Mathieson loss model is used in the 1D axial turbine designs. It is observed that the blade height is generally small; the reason being high operating pressure and low flow rate. A novel approach to enhance the performance of low-temperature CO{sub 2} transcritical power cycles is investigated. From the thermodynamic analysis, it is observed that the pump work is significant and reduction of pump work will be translated to a gain in net power output. The mechanical driven pump is suggested to be replaced by a thermally driven pump. The working principle of thermally driven pump is by exploiting the phenomena in which the pressure of a closed vessel filled full with saturated liquid will rise when heated. A cascade of vessels is used to make the pressurizing process continuous. The time taken to pressurize is an important parameter for the performance of thermally driven pump. Pressurizing time depends on isochoric specific heat capacity of the working fluid, heat transfer coefficient, inlet conditions of heat source, tube diameter, and initial mass of the working fluid. When the pressurizing time is longer, more vessels are required to make the process continuous. It is shown that it possible to increase power output using a thermal driven pump, but additional equipments are required. An example of a possible application is a low-temperature CO{sub 2} power cycle integrated with a post-combustion carbon dioxide capture plant. The heat rejected by low temperature streams in the capture plant is used as a heat sources for power generation. It is found that utilization of heat of the capture plant improves the performance of the overall process. It shows that low-temperature transcritical

A new hybrid two-zone/crucible furnace process for the growth of epitaxial Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8} superconducting films

Energy Technology Data Exchange (ETDEWEB)

Siegal, M.P.; Overmyer, D.L.; Venturini, E.L.; Dominguez, F.; Padilla, R.R. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1421 (United States)

1998-12-01

Epitaxial Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8} (Tl-2212) films {approximately}5500 {Angstrom} thick are grown on LaAlO{sub 3}(100) substrates using a new hybrid two-zone/crucible furnace process enabling precise control of thallination. This method combines the best features of both conventional crucible and two-zone processing for the first time: superb film properties and reduced handling of hazardous Tl-oxide powders. Single-phase, highly {ital c}-axis oriented Tl-2212 films are grown with smooth morphology, Meissner transition {approximately}103 K, and critical current density {approximately}1.1{times}10{sup 7}A/cm{sup 2} at 5 K for twenty consecutive runs without having to change or add to the Tl-oxide source. {copyright} {ital 1998 Materials Research Society.}

Design and analysis of nuclear battery driven by the external neutron source

International Nuclear Information System (INIS)

Wang, Sanbing; He, Chaohui

2014-01-01

Highlights: • A new type of space nuclear power called NBDEx is investigated. • NBDEx with 252 Cf has better performance than RTG with similar structure. • Its thermal power gets great improvement with increment of fuel enrichment. • The service life of NBDEx is about 2.96 year. • The launch abortion accident analysis fully demonstrates the advantage of NBDEx. - Abstract: Based on the theory of ADS (Accelerator Driven Subcritical reactor), a new type of nuclear battery was investigated, which was composed of a subcritical fission module and an isotope neutron source, called NBDEx (Nuclear Battery Driven by External neutron source). According to the structure of GPHS-RTG (General Purpose Heat Source Radioisotope Thermoelectric Generator), the fuel cell model and fuel assembly model of NBDEx were set up, and then their performances were analyzed with MCNP code. From these results, it was found that the power and power density of NBDEx were almost six times higher than the RTG’s. For fully demonstrating the advantage of NBDEx, the analysis of its impact factors was performed with MCNP code, and its lifetime was also calculated using the Origen code. These results verified that NBDEx was more suitable for the space missions than RTG

Source contributions to PM{sub 2.5} and PM{sub 10} at an urban background and a street location

Energy Technology Data Exchange (ETDEWEB)

Keuken, M.; Voogt, M.; Moerman, M. [TNO, Utrecht (Netherlands); Blom, M.; Weijers, E.P. [Energy research Centre of the Netherlands ECN, Petten (Netherlands); Roeckmann, T.; Dusek, U. [Institute for Marine and Atmospheric Research IMAU, Utrecht (Netherlands)

2013-06-15

The contribution of regional, urban and traffic sources to PM{sub 2.5} and PM{sub 10} in an urban area was investigated in this study. The chemical composition of PM{sub 2.5} and PM{sub 10} was measured over a year at a street location and up- and down-wind of the city of Rotterdam, Netherlands. The {sup 14}C content in EC and OC concentrations was also determined, to distinguish the contribution from 'modern' carbon (e.g., biogenic emissions, biomass burning and wildfires) and fossil fuel combustion. It was concluded that the urban background of PM{sub 2.5} and PM{sub 10} is dominated by the regional background, and that primary and secondary PM emission by urban sources contribute less than 15%. The {sup 14}C analysis revealed that 70% of OC originates from modern carbon and 30% from fossil fuel combustion. The corresponding percentages for EC are, respectively 17% and 83%. It is concluded that in particular the urban population living in street canyons with intense road traffic has potential health risks. This is due to exposure to elevated concentrations of a factor two for EC from exhaust emissions in PM{sub 2.5} and a factor 2-3 for heavy metals from brake and tyre wear, and re-suspended road dust in PM{sub 10}. It follows that local air quality management may focus on local measures to street canyons with intense road traffic.

Anisotropy of critical current density in the superconducting Nb/sub 3/Sn tape wires

Energy Technology Data Exchange (ETDEWEB)

Glowacki, B A [Technical Univ., Wroclaw (Poland). Inst. of Fundamental Electrotechnics and Electrotechnology

1985-04-01

In this letter the results are presented of an investigation of Isub(c parallel) and Isub(c perpendicular) in Nb/sub 3/Sn layers obtained in the process diffusion of tin atoms from liquid bronze solution Cu-80% Sn to the Nb-1.5% Zr substrate. Measurements of critical current density in Nb/sub 3/Sn layers were carried out in a perpendicular magnetic field of the induction value 4.25 T for different sample surface orientations in relation to the magnetic field strength vector defined by the value of angle. The critical current density was measured at a temperature of 4.2 K. Phase identification and investigation of the microstructure of superconducting Nb-Sn layers were performed on the Moessbauer spectrometer and scanning electron microscope, respectively. Classification measurements of grains in Nb-Sn layers were carried out with TV automatic image analyser. The texture and lattice parameter in Nb/sub 3/Sn layers were investigated by means of an X-ray diffractometer. The surface zone of Nb/sub 3/Sn layer was removed with the use of an argon ion gun. Results are presented and discussed.

Critical thickness of high structural quality SrTiO{sub 3} films grown on orthorhombic (101) DyScO{sub 3}.

Energy Technology Data Exchange (ETDEWEB)

Biegalski, M. D.; Trolier-McKinstry, S.; Nelson, C. T.; Schlom, D. G.; Fong, D. D.; Eastman, J. A.; Fuoss, P. H.; Streiffer, S. K.; Heeg, T.; Schubert, J.; Tian, W.; Pan, X. Q.; Hawley, M. E.; Bernhagen, M.; Reiche, P.; Uecker, R.; Pennsylvania State Univ.; Forschungszentrum Julich; Univ. Michigan; LANL; Max-Born-Strabe

2008-12-01

Strained epitaxial SrTiO{sub 3} films were grown on orthorhombic (101) DyScO{sub 3} substrates by reactive molecular-beam epitaxy. The epitaxy of this substrate/film combination is cube on cube with a pseudocubic out-of-plane (001) orientation. The strain state and structural perfection of films with thicknesses ranging from 50 to 1000 {angstrom} were examined using x-ray scattering. The critical thickness at which misfit dislocations was introduced was between 350 and 500 {angstrom}. These films have the narrowest rocking curves (full width at half maximum) ever reported for any heteroepitaxial oxide film (0.0018{sup o}). Only a modest amount of relaxation is seen in films exceeding the critical thicknesses even after postdeposition annealing at 700 C in 1 atm of oxygen. The dependence of strain relaxation on crystallographic direction is attributed to the anisotropy of the substrate. These SrTiO{sub 3} films show structural quality more typical of semiconductors such as GaAs and silicon than perovskite materials; their structural relaxation behavior also shows similarity to that of compound semiconductor films.

Study on the method of determining the sub-criticality of a reactor via the measurement of core neutron flux spatial distribution

International Nuclear Information System (INIS)

Ma Aifeng; Jiang Xiaofeng; Zhang Shaohong

2007-01-01

A new methodology based on rigorous reactor physics theory astead of the point reactor assumption was proposed to determine or monitor the sub-criticality ora reactor, especially the sub-critical reactor of ADS, via the measurement of in-core flux spatial distribution. Preliminary numerical studies on the 1st ADS sub-critical experimental facilities-Venus No.1 in China have demonstrated the feasibility of this new method. Related discussions pointed out the potential applications of the method. (authors)

Experimental investigation on flow patterns of RP-3 kerosene under sub-critical and supercritical pressures

Science.gov (United States)

Wang, Ning; Zhou, Jin; Pan, Yu; Wang, Hui

2014-02-01

Active cooling with endothermic hydrocarbon fuel is proved to be one of the most promising approaches to solve the thermal problem for hypersonic aircraft such as scramjet. The flow patterns of two-phase flow inside the cooling channels have a great influence on the heat transfer characteristics. In this study, phase transition processes of RP-3 kerosene flowing inside a square quartz-glass tube were experimentally investigated. Three distinct phase transition phenomena (liquid-gas two phase flow under sub-critical pressures, critical opalescence under critical pressure, and corrugation under supercritical pressures) were identified. The conventional flow patterns of liquid-gas two phase flow, namely bubble flow, slug flow, churn flow and annular flow are observed under sub-critical pressures. Dense bubble flow and dispersed flow are recognized when pressure is increased towards the critical pressure whilst slug flow, churn flow and annular flow disappear. Under critical pressure, the opalescence phenomenon is observed. Under supercritical pressures, no conventional phase transition characteristics, such as bubbles are observed. But some kind of corrugation appears when RP-3 transfers from liquid to supercritical. The refraction index variation caused by sharp density gradient near the critical temperature is thought to be responsible for this corrugation.

Indoor NO{sub 2} levels in homes with different sources of air pollution - traffic, gas-use, smoking

Energy Technology Data Exchange (ETDEWEB)

Rudnai, P.; Farkas, I.; Bacskai, J.; Sarkany, E. [Bela Johan National Inst. of Hygiene, Budapest (Hungary); Somogyi, J. [Public Health Inst. of County Gyor-Moson-Sopron, Gyor (Hungary)

1993-12-31

Outdoor and indoor levels of NO{sub 2} in and around the homes of 300 children living in different parts of two Hungarian towns, Gyor and Sopron, were measured. Possible sources of NO{sub 2} pollution were assessed by questionnaires. NO{sub 2} levels in homes without any further known sources (like gas use for cooking and/or heating and smoking) varied according to the outdoor levels mainly depending on traffic density. Gas heaters had the strongest influence on the indoor NO{sub 2} levels measured in the children`s bedrooms while gas use for cooking and smoking proved to be the second and third most important source of indoor NO{sub 2} pollution. Different outdoor and indoor NO{sub 2} sources should be taken into account when planning the heating and ventilation systems of new buildings. (author)

Ternary g-C{sub 3}N{sub 4}/ZnO/AgCl nanocomposites: Synergistic collaboration on visible-light-driven activity in photodegradation of an organic pollutant

Energy Technology Data Exchange (ETDEWEB)

Akhundi, Anise; Habibi-Yangjeh, Aziz, E-mail: ahabibi@uma.ac.ir

2015-12-15

Graphical abstract: - Highlights: • Novel ternary g-C{sub 3}N{sub 4}/ZnO/AgCl nanocomposites were prepared using a facile method. • g-C{sub 3}N{sub 4}/ZnO/AgCl (40%) has superior activity in degradation of RhB under visible-light. • The activity is 7.5 and 6-fold higher than g-C{sub 3}N{sub 4}/ZnO and g-C{sub 3}N{sub 4}/AgCl, respectively. • There are synergistic collaboration between ZnO and AgCl in enhancing the activity. - Abstract: The present work demonstrates the preparation of ternary g-C{sub 3}N{sub 4}/ZnO/AgCl nanocomposites, as novel visible-light-driven photocatalysts, using a facile large-scale methodology. The microstructure, morphology, purity, thermal, and spectroscopic properties of the prepared samples were studied using XRD, TEM, EDX, TG, UV–vis DRS, FT-IR, and PL techniques. Compared with the g-C{sub 3}N{sub 4}/ZnO and g-C{sub 3}N{sub 4}/AgCl nanocomposites, the g-C{sub 3}N{sub 4}/ZnO/AgCl nanocomposites displayed higher photocatalytic activity for degradation of rhodamine B under visible-light irradiation. Photocatalytic activity of the g-C{sub 3}N{sub 4}/ZnO/AgCl (40%) nanocomposite is about 9.5, 7.5, and 6-fold higher than those of the g-C{sub 3}N{sub 4}, g-C{sub 3}N{sub 4}/ZnO, and g-C{sub 3}N{sub 4}/AgCl samples, respectively. The enhanced photocatalytic activity of the nanocomposites was mainly attributed to efficiently separation of the charge carriers by synergistic collaboration of ZnO and AgCl in removing photogenerated electrons from g-C{sub 3}N{sub 4}. Furthermore, the results showed that the photocatalytic activity of the nanocomposite considerably depends on the preparation time, calcination temperature, and scavengers of the reactive species. Finally, the nanocomposite was found to be a reusable photocatalyst.

A comparison of lightning and aircraft sources of NO{sub x} in the upper troposphere

Energy Technology Data Exchange (ETDEWEB)

Penner, J E; Walton, J J [Michigan Univ., Ann Arbor, MI (United States). Dept. of Atmospheric, Oceanic and Space Physics; Bergmann, D J; Kinnison, D; Rotman, D [Lawrence Livermore National Lab., CA (United States). Atmospheric Science Div.; Price, C [Tel Aviv Univ. (Israel). Dept. of Geophysics and Planetary Sciences; Prather, M J [California Univ., Irvine, CA (United States). Dept. of Earth System Science; Pickering, K E [Maryland Univ., College Park, MD (United States). Dept. of Meteorology; Baughcum, S L [Boeing Commerial Airplane Group, Seatlle, WA (United States)

1998-12-31

Uncertainties in the assessment of the contribution of aircraft to upper tropospheric NO{sub x} arise from uncertainties in model treatment of transport, uncertainties in source strengths, and uncertainties in chemical rates and reactions determining the partitioning between NO{sub x} and NO{sub y}. Two different chemical transport models are used to examine the range of uncertainty in the contribution of aircraft to upper tropospheric NO{sub x} from model representations of transport. Uncertainties caused by uncertainties in the rate of production of NO{sub x} from lightning and uncertainties from the range of background concentrations of HNO{sub 3} are also examined. Uncertainties in the treatment of vertical transport and uncertainties in the source strength from lightning contribute to a large range in model results for background NO{sub x}. (author) 18 refs.

A comparison of lightning and aircraft sources of NO{sub x} in the upper troposphere

Energy Technology Data Exchange (ETDEWEB)

Penner, J.E.; Walton, J.J. [Michigan Univ., Ann Arbor, MI (United States). Dept. of Atmospheric, Oceanic and Space Physics; Bergmann, D.J.; Kinnison, D.; Rotman, D. [Lawrence Livermore National Lab., CA (United States). Atmospheric Science Div.; Price, C. [Tel Aviv Univ. (Israel). Dept. of Geophysics and Planetary Sciences; Prather, M.J. [California Univ., Irvine, CA (United States). Dept. of Earth System Science; Pickering, K.E. [Maryland Univ., College Park, MD (United States). Dept. of Meteorology; Baughcum, S.L. [Boeing Commerial Airplane Group, Seatlle, WA (United States)

1997-12-31

Uncertainties in the assessment of the contribution of aircraft to upper tropospheric NO{sub x} arise from uncertainties in model treatment of transport, uncertainties in source strengths, and uncertainties in chemical rates and reactions determining the partitioning between NO{sub x} and NO{sub y}. Two different chemical transport models are used to examine the range of uncertainty in the contribution of aircraft to upper tropospheric NO{sub x} from model representations of transport. Uncertainties caused by uncertainties in the rate of production of NO{sub x} from lightning and uncertainties from the range of background concentrations of HNO{sub 3} are also examined. Uncertainties in the treatment of vertical transport and uncertainties in the source strength from lightning contribute to a large range in model results for background NO{sub x}. (author) 18 refs.

Design status and future research programme for a sub-critical assembly driven by a proton accelerator with proton energy 660 MeV for experiments on long-lived fission products and minor actinides transmutation (Sad)

International Nuclear Information System (INIS)

Gustov, S.A.; Mirokhin, I.V.; Morozov, N.A.; Onischenko, L.M.; Savchenko, O.V.; Sissakian, A.N.; Shvetsov, V.N.; Tretyakov, I.T.; Lopatkin, A.V.; Vorontsov, M.T.

2003-01-01

Report presents project for the construction of a low power integral system on the basis of the proton accelerator of energy 660 MeV and sub-critical MOX blanket with uranium-plutonium fuel. Installation includes sub-critical core with a nominal thermal power of 15-20 kW. Multiplication coefficient k eff = 0,95 and the accelerator beam power of 0.75-1 kW. The experimental programme for SAD will be focused on solving different aspects of reactor physics, reaction rates measurements and benchmarking. The first conceptual design of the SAD experiment is completed in the form of the ISTC Project Proposal 2267. Realisation of the SAD facility may be expected in about 3-4 years. (author)

Determination of the criticality parameters in heterogeneous Slab by the LTS{sub N} method

Energy Technology Data Exchange (ETDEWEB)

Borges, Volnei [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Dept. de Engenharia Nuclear; Derivi, Alexandre Guimaraes [Universidade Regional Integrada (URI), Erechim, RS (Brazil)

2001-07-01

The goal of this work consists in the use of the LTS{sub N} method in criticality problems. This method consists basically in the application of the Laplace Transform to a system of ordinary differential equations generated by the SN approach, resulting in a system of symbolic algebraic equations dependent on the complex parameters. After solving the algebraic system by means of the Schurr and diagonalization methods, the angular fluxes are obtained performing the inverse Laplace transform, which is carried out using the Heaviside formula. This methodology is used in determination of K{sub eff}, critical thickness and the atomic density for a heterogeneous planar slab. This procedure leads the solution of eigenvalue problem to the solution of a transcendental equation. Numerical results are reported. (author)

Flux-driven simulations of turbulence collapse

Energy Technology Data Exchange (ETDEWEB)

Park, G. Y.; Kim, S. S.; Jhang, Hogun; Rhee, T. [National Fusion Research Institute, Daejeon 305-333 (Korea, Republic of); Diamond, P. H. [National Fusion Research Institute, Daejeon 305-333 (Korea, Republic of); CASS and Department of Physics, University of California, San Diego, La Jolla, California 92093-0429 (United States); Xu, X. Q. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)

2015-03-15

Using three-dimensional nonlinear simulations of tokamak turbulence, we show that an edge transport barrier (ETB) forms naturally once input power exceeds a threshold value. Profiles, turbulence-driven flows, and neoclassical coefficients are evolved self-consistently. A slow power ramp-up simulation shows that ETB transition is triggered by the turbulence-driven flows via an intermediate phase which involves coherent oscillation of turbulence intensity and E×B flow shear. A novel observation of the evolution is that the turbulence collapses and the ETB transition begins when R{sub T} > 1 at t = t{sub R} (R{sub T}: normalized Reynolds power), while the conventional transition criterion (ω{sub E×B}>γ{sub lin} where ω{sub E×B} denotes mean flow shear) is satisfied only after t = t{sub C} ( >t{sub R}), when the mean flow shear grows due to positive feedback.

The Potential for Electrofuels Production in Sweden Utilizing Fossil and Biogenic CO{sub 2} Point Sources

Energy Technology Data Exchange (ETDEWEB)

Hansson, Julia, E-mail: julia.hansson@ivl.se [Climate and Sustainable Cities, IVL Swedish Environmental Research Institute, Stockholm (Sweden); Division of Physical Resource Theory, Department of Energy and Environment, Chalmers University of Technology, Göteborg (Sweden); Hackl, Roman [Climate and Sustainable Cities, IVL Swedish Environmental Research Institute, Stockholm (Sweden); Taljegard, Maria [Division of Energy Technology, Department of Energy and Environment, Chalmers University of Technology, Göteborg (Sweden); Brynolf, Selma; Grahn, Maria [Division of Physical Resource Theory, Department of Energy and Environment, Chalmers University of Technology, Göteborg (Sweden)

2017-03-13

This paper maps, categorizes, and quantifies all major point sources of carbon dioxide (CO{sub 2}) emissions from industrial and combustion processes in Sweden. The paper also estimates the Swedish technical potential for electrofuels (power-to-gas/fuels) based on carbon capture and utilization. With our bottom-up approach using European databases, we find that Sweden emits approximately 50 million metric tons of CO{sub 2} per year from different types of point sources, with 65% (or about 32 million tons) from biogenic sources. The major sources are the pulp and paper industry (46%), heat and power production (23%), and waste treatment and incineration (8%). Most of the CO{sub 2} is emitted at low concentrations (<15%) from sources in the southern part of Sweden where power demand generally exceeds in-region supply. The potentially recoverable emissions from all the included point sources amount to 45 million tons. If all the recoverable CO{sub 2} were used to produce electrofuels, the yield would correspond to 2–3 times the current Swedish demand for transportation fuels. The electricity required would correspond to about 3 times the current Swedish electricity supply. The current relatively few emission sources with high concentrations of CO{sub 2} (>90%, biofuel operations) would yield electrofuels corresponding to approximately 2% of the current demand for transportation fuels (corresponding to 1.5–2 TWh/year). In a 2030 scenario with large-scale biofuels operations based on lignocellulosic feedstocks, the potential for electrofuels production from high-concentration sources increases to 8–11 TWh/year. Finally, renewable electricity and production costs, rather than CO{sub 2} supply, limit the potential for production of electrofuels in Sweden.

A Microwave Driven Ion Source for Continuous-Flow AMS (Abstract)

International Nuclear Information System (INIS)

Wills, J.; Schneider, R.J.; Reden, K.F. von; Hayes, J.M.; Roberts, M.L.; Benthien, A.

2005-01-01

A microwave-driven, gas-fed ion source originally developed as a high-current positive ion injector for a Tandem accelerator at Chalk River has been the subject of a three-year development program at the Woods Hole Oceanographic Institution NOSAMS facility. Off-line tests have demonstrated positive carbon currents of 1 mA and negative carbon currents of 80 μA from CO2 gas feed. This source and a magnesium charge-exchange canal were coupled to the recombinator of the NOSAMS Tandetron for on-line tests, with the source fed with reference gasses and a combustion device.The promising results obtained have prompted the redesign of the microwave source for use as an on-line, continuous-flow injector for a new AMS facility under construction at NOSAMS. The new design is optimized for best transmission of the extracted positive-ion beam through the charge-exchange canal and for reliable operation at 40 kV extraction voltage. Other goals of the re-design include improved lifetime of the microwave window and the elimination of dead volumes in the plasma generator that increase sample hold-up time.This talk will include a summary of results obtained to date at NOSAMS with the Chalk River source and a detailed description of the new design

Critical behavior of order-parameter fluctuations in liquid 4He near T/sub lambda/

International Nuclear Information System (INIS)

Lambert, B.; Perzynski, R.; Salin, D.

1979-01-01

We hve measured the critical attenuation of first sound in liquid 4 He from 550 to 1700 MHz. We can describe the attenuation due to the fluctuations of the order parameter up to 1.7 GHz, using experimental data at lower frequencies from various authors. Above T/sub lambda/, the fluctuations are the only phenomena and are analyzed with a scaling function of ωtau 2 with a characteristic time tau 2 = 2 x 10 -12 x t/sup -1.062/ sec, t = vertical-bar (T-T/sub lambda/)/T/sub lambda/vertical-bar. Below T/sub lambda/, several phenomena are present. In the range of 1 GHz, the main contribution is due to the fluctuations. We demonstrate experimentally that the fluctuation attenuation is not symmetric about T/sub lambda/. We fit our data with a scaling function of ωtau 2

Reusable sunlight activated photocatalyst Ag{sub 3}PO{sub 4} and its significant antibacterial activity

Energy Technology Data Exchange (ETDEWEB)

Thiyagarajan, Shankar; Singh, Sarika; Bahadur, D., E-mail: dhirenb@iitb.ac.in

2016-04-15

A simple and surfactant free soft chemical approach is adopted for the successful synthesis of Ag{sub 3}PO{sub 4} nanoparticles (NPs) at room temperature. The obtained Ag{sub 3}PO{sub 4} NPs are nearly spherical in shape with a size of 250 ± 50 nm. These NPs are highly efficient for the degradation of three organic dyes (methylene blue, rhodamine B and methyl orange) under four different types of light sources. In this case, the superior photocatalytic activity is mainly driven by singlet oxygen radicals and it is confirmed through the electron spin resonance (ESR) spin trapping technique, using several quenchers/sources. Notably, these NPs have the ability to absorb large portion of solar spectrum and therefore it displays higher efficiency under sunlight as compared to UV-C light and a 60 W household compact fluorescence lamp (CFL). Furthermore, these NPs exhibit excellent colloidal stability and recycling capability for the degradation of dyes. In addition, it possesses significant antibacterial activity with complete inhibition of bacterial pathogen, Escherichia coli at a very low concentration (0.01 mg/mL) after a mere 15 min of incubation time. The inhibition of bacterial growth is also suggested from the generation of intracellular reactive oxygen species (ROS) in E. coli by fluorescence microscopy. Thus, these NPs may provide a potential outcome for the environmental remediation. - Graphical abstract: Schematic representation of the mechanism involved in photodegradation of organic dyes and inhibition of bacterial growth using Ag{sub 3}PO{sub 4} nanoparticles. - Highlights: • Excellent catalytic activity for dyes degradation under different light sources. • Mechanism involving catalyst mediated ROS generation in photocatalysis suggested. • Good recycling capability of Ag{sub 3}PO{sub 4} even after the fifth cycles. • Extraordinary antibacterial activity of Ag{sub 3}PO{sub 4} after a very short incubation time. • Detection of intracellular

Transfer functions of double- and multiple-cavity Fabry-Perot filters driven by Lorentzian sources.

Science.gov (United States)

Marti, J; Capmany, J

1996-12-20

We derive expressions for the transfer functions of double- and multiple-cavity Fabry-Perot filters driven by laser sources with Lorentzian spectrum. These are of interest because of their applications in sensing and channel filtering in optical frequency-division multiplexing networks.

Recovery of Palm Oil and Valuable Material from Oil Palm Empty Fruit Bunch by Sub-critical Water.

Science.gov (United States)

Ahmad Kurnin, Nor Azrin; Shah Ismail, Mohd Halim; Yoshida, Hiroyuki; Izhar, Shamsul

2016-01-01

Oil palm empty fruit bunch (EFB) is one of the solid wastes produced in huge volume by palm oil mill. Whilst it still contains valuable oil, approximately 22.6 million tons is generated annually and treated as solid waste. In this work, sub-critical water (sub-cw) was used to extract oil, sugar and tar from spikelet of EFB. The spikelet was treated with sub-cw between 180-280°C and a reaction time of 2 and 5 minutes. The highest yield of oil was 0.075 g-oil/g-dry EFB, obtained at 240°C and reaction time of 5 minutes. Astonishingly, oil that was extracted through this method was 84.5% of that obtained through Soxhlet method using hexane. Yield of oil extracted was strongly affected by the reaction temperature and time. Higher reaction temperature induces the dielectric constant of water towards the non-polar properties of solvent; thus increases the oil extraction capability. Meanwhile, the highest yield of sugar was 0.20 g-sugar/g-dry EFB obtained at 220°C. At this temperature, the ion product of water is high enough to enable maximum sub-critical water hydrolysis reaction. This study showed that oil and other valuable material can be recovered using water at sub-critical condition, and most attractive without the use of harmful organic solvent.

Parachors in terms of critical temperature, critical pressure and acentric factor

Energy Technology Data Exchange (ETDEWEB)

Broseta, D.; Ragil, K.

1995-12-31

The method of parachors is widely used in conventional thermodynamic codes and reservoir simulators to calculate oil/gas interfacial tensions of complex hydrocarbon mixtures. In the low-to-moderate interfacial tension regime, a value p{approx}11/3 has previously been shown to be the {open_quotes}best{close_quotes} parachor exponent. This exponent is a critical exponent and its value is consistent with the values of critical exponents characterizing the liquid/vapor critical behavior. Therefore parachors may be viewed as critical amplitudes. By using critical scaling theory, parachors are related to other critical amplitudes and critical parameters that describe the bulk thermodynamic behavior of fluids. A simple expression relating the parachor of a pure compound to its critical temperature T{sub c}, critical pressure P{sub c}, and acentric factor {omega} is proposed: P= (0.85-0.19{omega})T{sub c}{sup 12/11}/P{sub c}{sup 9/11} where the parachor P is in units of (dyn/cm){sup 3/11}cm{sup 3}/mol, T{sub c} in K and P{sub c} in MPa. This equation matches (within experimental error) the known parachor values of normal fluids (e.g. alkanes, aromatics, CO{sub 2}, N{sub 2}, H{sub 2}S, etc...).

Effect of hydrostatic pressure on magnetic and magnetocaloric properties in La{sub 0.35}Pr{sub 0.35}Ca{sub 0.3}MnO{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Thiyagarajan, R. [Centre for High Pressure Research, School of Physics, Bharathidasan University, Tiruchirapalli 620024, Tamil Nadu (India); Esakki Muthu, S. [Centre for High Pressure Research, School of Physics, Bharathidasan University, Tiruchirapalli 620024, Tamil Nadu (India); Univ. Grenoble Alpes and CEA, INAC-SPSMS, F-38000 Grenoble (France); Manikandan, K. [Centre for High Pressure Research, School of Physics, Bharathidasan University, Tiruchirapalli 620024, Tamil Nadu (India); Arumugam, S., E-mail: sarumugam1963@yahoo.com [Centre for High Pressure Research, School of Physics, Bharathidasan University, Tiruchirapalli 620024, Tamil Nadu (India)

2016-01-15

Magnetization of polycrystalline La{sub 0.35}Pr{sub 0.35}Ca{sub 0.3}MnO{sub 3} sample has been measured as a function of temperature (T) and magnetic field (H) under various external hydrostatic pressures (P) up to ~1 GPa. At ambient P, the sample exhibits paramagnetic (PM)–ferromagnetic (FM) transition (T{sub C}) at 167 K and 173 K in cooling and warming cycles respectively under the magnetic field (µ{sub 0}.H) of 0.1 T. It also shows a hysteresis during both temperature- and field- dependence of magnetization measurements at ambient P, suggests the presence of a first-order transition. Moreover, the field dependence of magnetization shows S type field-induced metamagnetic transition (FIMMT) over a temperature range below T{sub C} in the FM state. The application of P in M(T) increases T{sub C} at a rate [dT{sub C}/dP] of 13.9 K/GPa, but the thermally-driven first-order transition is not affected by P. However, the applied P suppresses FIMMT and reduces field-driven first-order transition in the magnetization isotherms [M(H)]below T{sub C}. H increases both magnetic entropy change (∆S{sub m}) and Relative Cooling Power (RCP), whereas the P slightly increases ∆S{sub m}{sup max} and no appreciable change in RCP. These results suggest that H and P can be used as a tool to enhance magnetocaloric values in the phase separated manganites. - Highlights: • At ambient P, La{sub 0.35}Pr{sub 0.35}Ca{sub 0.3}MnO{sub 3} sample shows first-order PM–FM transition. • P increases the T{sub C} at a rate of 13.9 K/GPa, thermal hysteresis is not affected. • P diminishes the field-driven first-order PM–FM transition, suppresses FIMMMT. • H increases ∆S{sub m} and RCP. P slightly increases ∆S{sub m}{sup max}, but no change in RCP by P.

Prompt nuclear analytical techniques for material research in accelerator driven transmutation technologies: Prospects and quantitative analyses

International Nuclear Information System (INIS)

Vacik, J.; Hnatowicz, V.; Cervena, J.; Perina, V.; Mach, R.

1998-01-01

Accelerator driven transmutation technology (ADTT) is a promising way toward liquidation of spent nuclear fuel, nuclear wastes and weapon grade Pu. The ADTT facility comprises a high current (proton) accelerator supplying a sub-critical reactor assembly with spallation neutrons. The reactor part is supposed to be cooled by molten fluorides or metals which serve, at the same time, as a carrier of nuclear fuel. Assumed high working temperature (400-600 C) and high radiation load in the subcritical reactor and spallation neutron source put forward the problem of optimal choice of ADTT construction materials, especially from the point of their radiation and corrosion resistance when in contact with liquid working media. The use of prompt nuclear analytical techniques in ADTT related material research is considered and examples of preliminary analytical results obtained using neutron depth profiling method are shown for illustration. (orig.)

Controllable synthesis of p-type Cu{sub 2}S nanowires for self-driven NIR photodetector application

Energy Technology Data Exchange (ETDEWEB)

Wu, Chun-Yan, E-mail: cywu@hfut.edu.cn; Pan, Zhi-Qiang; Liu, Zhu; Wang, You-Yi [Hefei University of Technology, School of Electronic Science and Applied Physics (China); Liang, Feng-Xia [Hefei University of Technology, School of Materials Science and Engineering and Anhui Provincial Key Laboratory of Advanced Functional Materials and Devices (China); Yu, Yong-Qiang; Wang, Li; Luo, Lin-Bao, E-mail: luolb@hfut.edu.cn [Hefei University of Technology, School of Electronic Science and Applied Physics (China)

2017-02-15

Face-centered cubic Cu{sub 2}S nanowires with length of up to 50 μm and diameters in the range of 100–500 nm are synthesized on Si substrates through the chemical vapor deposition method using a mixed gas of Ar and H{sub 2} as the carrier gas under a chamber pressure of about 700 Torr. It was found that the growth of quasi 1D nanostructure followed a typical vapor-liquid-solid (VLS) mechanism in which the element Cu was reduced by H{sub 2} as the catalyst. The as-synthesized Cu{sub 2}S nanowires exhibited typical p-type semiconducting characteristics with a conductivity of about 600 S cm{sup −1} and a hole mobility (μ{sub h}) of about 72 cm{sup 2} V{sup −1} s{sup −1}. Further study reveals that p-Cu{sub 2}S nanowires/n-Si heterojunction exhibits distinct rectifying characteristics with a turn-on voltage of ~0.6 V and a rectification ratio of ~300 at ±1 V in the dark and a pronounced photovoltaic behavior with an open circuit voltage (V{sub oc}) of 0.09 V and a short circuit current (I{sub sc}) of 65 nA when illuminated by the NIR light (790 nm, 0.35 mW cm{sup −1}), giving rise to a responsivity (R) about 0.8 mA W{sup −1} and specific detectivity (D*) 6.7 × 10{sup 10} cm Hz{sup 1/2} W{sup −1} at zero bias, which suggests the potential of as-synthesized Cu{sub 2}S nanowires applied in the field of self-driven NIR photodetector.

Atrial fibrillation driven by micro-anatomic intramural re-entry revealed by simultaneous sub-epicardial and sub-endocardial optical mapping in explanted human hearts.

Science.gov (United States)

Hansen, Brian J; Zhao, Jichao; Csepe, Thomas A; Moore, Brandon T; Li, Ning; Jayne, Laura A; Kalyanasundaram, Anuradha; Lim, Praise; Bratasz, Anna; Powell, Kimerly A; Simonetti, Orlando P; Higgins, Robert S D; Kilic, Ahmet; Mohler, Peter J; Janssen, Paul M L; Weiss, Raul; Hummel, John D; Fedorov, Vadim V

2015-09-14

The complex architecture of the human atria may create physical substrates for sustained re-entry to drive atrial fibrillation (AF). The existence of sustained, anatomically defined AF drivers in humans has been challenged partly due to the lack of simultaneous endocardial-epicardial (Endo-Epi) mapping coupled with high-resolution 3D structural imaging. Coronary-perfused human right atria from explanted diseased hearts (n = 8, 43-72 years old) were optically mapped simultaneously by three high-resolution CMOS cameras (two aligned Endo-Epi views (330 µm2 resolution) and one panoramic view). 3D gadolinium-enhanced magnetic resonance imaging (GE-MRI, 80 µm3 resolution) revealed the atrial wall structure varied in thickness (1.0 ± 0.7-6.8 ± 2.4 mm), transmural fiber angle differences, and interstitial fibrosis causing transmural activation delay from 23 ± 11 to 43 ± 22 ms at increased pacing rates. Sustained AF (>90 min) was induced by burst pacing during pinacidil (30-100 µM) perfusion. Dual-sided sub-Endo-sub-Epi optical mapping revealed that AF was driven by spatially and temporally stable intramural re-entry with 107 ± 50 ms cycle length and transmural activation delay of 67 ± 31 ms. Intramural re-entrant drivers were captured primarily by sub-Endo mapping, while sub-Epi mapping visualized re-entry or 'breakthrough' patterns. Re-entrant drivers were anchored on 3D micro-anatomic tracks (15.4 ± 2.2 × 6.0 ± 2.3 mm2, 2.9 ± 0.9 mm depth) formed by atrial musculature characterized by increased transmural fiber angle differences and interstitial fibrosis. Targeted radiofrequency ablation of the tracks verified these re-entries as drivers of AF. Integrated 3D structural-functional mapping of diseased human right atria ex vivo revealed that the complex atrial microstructure caused significant differences between Endo vs. Epi activation during pacing and sustained AF driven by intramural re-entry anchored to fibrosis-insulated atrial bundles. Published on

Study of critical beta non-circular tokamak equilibria sustained in steady state by beam driven currents

International Nuclear Information System (INIS)

Okano, K.; Ogawa, Y.; Naitou, H.

1988-07-01

A new MHD-equilibrium/current-drive analysis code was developed to analyse the high beta tokamak equilibria consistent with the beam driven current profiles. In this new code, the critical beta equilibrium, which is stable against the ballooning mode, the kink mode and the Mercier mode, is determined first using MHD equilibrium and stability analysis codes (EQLAUS/ERATO). Then, the current drive parameters and the plasma parameters, required to sustain this critical beta equilibrium, are determined by iterative calculations. The beam driven current profiles are evaluated by the Fokker-Planck calculations on individual flux surfaces, where the toroidal effects on the beam ion and plasma electron trajectories are considered. The pressure calculation takes into account the beam ion and fast alpha components. A peculiarity of our new method is that the obtained solution is not only consistent with the MHD equilibrium but also consistent with the critical beta limit conditions, in the current profile and the pressure profile. Using this new method, β ∼ 21 % bean and β ∼ 6 % D-type critical beta equilibria were scanned for various parameters; the major radius, magnetic field, temperature, injection energy, etc. It was found that the achievable Q value for the bean type was always about 30 % larger than for the D-type cases, where Q = fusion power/beam power. With strong beanness, Q ∼ 6 for DEMO type tokamaks (∼500 MWth) and Q ∼ 20 for power reactor size (4.5 GWth) are achievable. On the other hand, the Q value would not exceed sixteen for the D-type machines. (author)

Synthesis and characterization of highly efficient and stable Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt ternary hybrid structure

Energy Technology Data Exchange (ETDEWEB)

Deng, Jiatao; Liu, Lin; Niu, Tongjun; Sun, Xiaosong, E-mail: sunxs@scu.edu.cn

2017-05-01

Highlights: • Visible-light-driven Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt photocatalysts were prepared. • Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt showed highly efficient and stable photocatalystic activity. • The photocatalytic mechanism of Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt composite was given. - Abstract: Ag{sub 3}PO{sub 4} is an excellent photocatalyst with high efficiency and quantum yield, but suffers from the fast recombination of photogenerated electron-hole pairs and photo-corrosion. Hereby, the highly efficient and stable visible-light-driven Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt photocatalyst were prepared via a three-step wet chemical approach. The as-prepared Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt composite was characterized by X-ray diffraction, US-vis diffuse reflectance spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, photoluminescence spectra and transient photocurrent as well. Comparing with single Pr{sub 6}O{sub 11} or Ag{sub 3}PO{sub 4}, the prepared Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt composite exhibited much higher photocatalytic activity and stability for the degradation of Rhodamine B under visible light irradiation (>420 nm). The enhanced photocatalytic performance of Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt composite has been attributed to the efficient separation of photo-generated electron-hole pairs through a scheme system composed of Pr{sub 6}O{sub 11,} Ag{sub 3}PO{sub 4} and Pt.

Supercurrents in HgBa{sub 2}CaCu{sub 2}O{sub 6+{delta}} and TlBa{sub 2}CaCu{sub 2}O{sub 7} epitaxial thin films

Energy Technology Data Exchange (ETDEWEB)

Gapud, A.A.; Wu, J.Z.; Fang, L.; Yan, S.L.; Xie, Y.Y. [Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045-2151 (United States); Siegal, M.P.; Overmyer, D.L. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

1999-06-01

The availability of high-quality epitaxial thin films of HgBa{sub 2}CaCu{sub 2}O{sub 6+{delta}} (Hg-1212) and TlBa{sub 2}CaCu{sub 2}O{sub 7} (Tl-1212) with high critical current densities (J{sub c}) has made it possible to examine and compare the J{sub c} of these species. Results reveal that the J{sub c} of 1212 species have very similar temperature behavior at low fields, strongly suggesting that the 30 K shift in critical temperature (T{sub c}) induced by the exchange of Hg and Tl in the 1212 structure is due largely to a change in charge carrier density and/or electronic band structure. {copyright} {ital 1999 American Institute of Physics.}

T-S criticality of black holes with power Maxwell invariant source

Science.gov (United States)

Lin, Ze-Tao; Li, Gu-Qiang; Long, Kun; He, Fang; Mo, Jie-Xiong

2017-09-01

In this paper, we show that black holes with PMI source exhibit the T-S criticality and derive the relevant critical physical quantities analytically. The values of critical quantities for the case s≠1 vary from those for the case s=1, showing the effect of PMI field on the critical phenomena of black holes. When qPMI field does not affect the Maxwell equal area law.

CLUMPED LIGHT WATER MODERATED UO$sub 2$ SUPERHEAT CRITICALS. PART I. EXPERIMENTS

Energy Technology Data Exchange (ETDEWEB)

Warzek, F. G.; Johnston, H. F.

1963-11-15

The following critical and subcritical measurements were made in the EVESR core: reactivity with no control rods; full core reactivity with control rods; and power distribution in the full core with control rods. The fuel was UO/ sub 2/, and the elements were of the superheating type. The reactor was light- water-cooled and -moderated. (T.F.H.)

Theory of ion-temperature-gradient-driven turbulence in tokamaks

International Nuclear Information System (INIS)

Lee, G.S.; Diamond, P.H.

1986-01-01

An analytic theory of ion-temperature-gradient-driven turbulence in tokamaks is presented. Energy-conserving, renormalized spectrum equations are derived and solved in order to obtain the spectra of stationary ion-temperature-gradient-driven turbulence. Corrections to mixing-length estimates are calculated explicitly. The resulting anomalous ion thermal diffusivity chi/sub i/ = 0.4[(π/2)ln(1 + eta/sub i/)] 2 [(1 + eta/sub i/)/tau] 2 rho/sub s/ 2 c/sub s//L/sub s/ is derived and is found to be consistent with experimentally-deduced thermal diffusivities. The associated electron thermal diffusivity and particle and heat-pinch velocities are also calculated. The effect of impurity gradients on saturated ion-temperature-gradient-driven turbulence is discussed and a related explanation of density profile steepening during Z-mode operation is proposed. 35 refs., 4 figs

Table-top laser-driven ultrashort electron and X-ray source: the CIBER-X source project

Science.gov (United States)

Girardeau-Montaut, Jean-Pierre; Kiraly, Bélà; Girardeau-Montaut, Claire; Leboutet, Hubert

2000-09-01

We report on the development of a new laser-driven table-top ultrashort electron and X-ray source, also called the CIBER-X source . X-ray pulses are produced by a three-step process which consists of the photoelectron emission from a thin metallic photocathode illuminated by 16 ps duration laser pulses at 213 nm. The e-gun is a standard Pierce diode electrode type, in which electrons are accelerated by a cw electric field of ˜11 MV/m up to a hole made in the anode. The photoinjector produces a train of 70-80 keV electron pulses of ˜0.5 nC and 20 A peak current at a repetition rate of 10 Hz. The electrons are then transported outside the diode along a path of 20 cm length, and are focused onto a target of thullium by magnetic fields produced by two electromagnetic coils. X-rays are then produced by the impact of electrons on the target. Simulations of geometrical, electromagnetic fields and energetic characteristics of the complete source were performed previously with the assistance of the code PIXEL1 also developed at the laboratory. Finally, experimental electron and X-ray performances of the CIBER-X source as well as its application to very low dose imagery are presented and discussed. source Compacte d' Impulsions Brèves d' Electrons et de Rayons X

Comparison of GaP and PH{sub 3} as dopant sources for STM-based device fabrication

Energy Technology Data Exchange (ETDEWEB)

Goh, Kuan Eng Johnson [Australian Research Council Centre of Excellence for Quantum Computer Technology, University of New South Wales, Sydney, New South Wales 2052 (Australia); Oberbeck, L [Australian Research Council Centre of Excellence for Quantum Computer Technology, University of New South Wales, Sydney, New South Wales 2052 (Australia); Butcher, M J [School of Physics, University of New South Wales, Sydney, New South Wales 2052 (Australia); Curson, N J [Australian Research Council Centre of Excellence for Quantum Computer Technology, University of New South Wales, Sydney, New South Wales 2052 (Australia); Ruess, F J [Australian Research Council Centre of Excellence for Quantum Computer Technology, University of New South Wales, Sydney, New South Wales 2052 (Australia); Simmons, M Y [Australian Research Council Centre of Excellence for Quantum Computer Technology, University of New South Wales, Sydney, New South Wales 2052 (Australia)

2007-02-14

We present a comparative study of the use of a GaP solid source as an alternative to gaseous PH{sub 3} for controlled phosphorus {delta}-doping of lithographic patterns on H:Si(001) fabricated by scanning tunnelling microscopy (STM). Whilst our electrical studies show that P {delta}-doping of Si with the GaP solid source and gaseous PH{sub 3} result in essentially the same electrical characteristics, our STM studies reveal that P{sub 2} molecules from the GaP source exhibit a lower selectivity between bare Si(001) and H:Si(001) compared to PH{sub 3} molecules. We discuss the significance of our findings in the context of fabricating nanoscale P dopant devices in Si using STM-based lithography.

Building and managing strategic alliances in technology-driven start-ups: a critical review of literature

OpenAIRE

Comi, Alice; Eppler, Martin J.

2009-01-01

In this article, we critically review the current literature on alliance formation and management with a particular emphasis on small businesses, and on managerial implications for start-up enterprises. In the beginning of the article, we discuss the advantages and the challenges of inter-organizational collaboration, by taking the perspective of technology-driven start-ups operating in highly competitive environments. We then review the managerial advice suggested by the current liter...

Characterization of Si sub 1 sub - sub x Ge sub x thin films prepared by sputtering

CERN Document Server

Noguchi, T

2000-01-01

By bombarding solid targets, we deposited Si sub 1 sub - sub x Ge sub x thin films by sputtering without using inflammable CVD (chemical vapor deposition) gases. After the B sup + -implanted Si sub 1 sub - sub x Ge sub x films were thermally annealed, they were characterized. As the content of Ge increased, the refractive index increased and the band edge narrowed. The higher the annealing temperature, the lower the resistivity. For Si sub 1 sub - sub x Ge sub x films with a high Ge content (X approx 0.5), the flat-band voltage of the gate deduced from C-V curve was adjusted to the middle point between p sup + and n sup + polySi gates. Boron-doped SiGe films are promising gate materials for MOS (metal oxide semiconductor) and SOI (silicon on insulator) transistors driven at low driving voltage.

Two-dimensional TiO{sub 2}-based nanosheets co-modified by surface-enriched carbon dots and Gd{sub 2}O{sub 3} nanoparticles for efficient visible-light-driven photocatalysis

Energy Technology Data Exchange (ETDEWEB)

Lu, Dingze, E-mail: 1005116870@qq.com [Department of Physics and Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Wuhan University, Wuhan 430072 (China); Fang, Pengfei, E-mail: fangpf@whu.edu.cn [Department of Physics and Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Wuhan University, Wuhan 430072 (China); Ding, Junqian, E-mail: 630736958@qq.com [Department of Physics and Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Wuhan University, Wuhan 430072 (China); Yang, Minchen, E-mail: 1023635028@qq.com [Department of Physics and Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Wuhan University, Wuhan 430072 (China); Cao, Yufei, E-mail: 344541464@qq.com [Department of Physics and Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Wuhan University, Wuhan 430072 (China); Zhou, Yawei, E-mail: 769107311@qq.com [Department of Physics and Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Wuhan University, Wuhan 430072 (China); Peng, Kui, E-mail: 758007737@qq.com [Department of Physics and Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Wuhan University, Wuhan 430072 (China); Kondamareddy, Kiran Kumar, E-mail: kokila_kkk@yahoo.co.in [Department of Physics and Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Wuhan University, Wuhan 430072 (China); Liu, Min, E-mail: liumhb@126.com [State Grid Zhejiang Electric Power Research Institute, Hangzhou, Zhejiang 310007 (China)

2017-02-28

Highlights: • Gd-C-TNSs with high stability and recycle usability were prepared by two-pot method. • Gd{sub 2}O{sub 3} loading results in the structure changes of TNSs and increase of the Ti{sup 3+} ions. • Modified CDs leads to obvious increase of optical absorption ability and red shift. • Appropriate amount of Gd{sub 2}O{sub 3} nanoparticles and CDs improve the separation of charges. • Gd-C-TNSs exhibit excellent synergistic photocatalytic activity for Cr(VI) and RhB. - Abstract: Two-dimensional TiO{sub 2}-based nanosheets (TNSs) co-modified by surface-enriched carbon dots (CDs) and Gd{sub 2}O{sub 3} nanoparticles: (Gd-C-TNSs), capable of exhibiting visible-light-driven photo catalysis were synthesized using a two-pot hydrothermal route. The samples had a sheet-like structure, thickness of approximately 3.6 nm, large specific surface area of 240–350 cm{sup 2}/g. The CDs (2–3 nm) and Gd{sub 2}O{sub 3} nanoparticles (1–2 nm) were highly dispersed over the surface of the nanosheets. The co-modification by Gd{sub 2}O{sub 3} nanoparticles and CDs influenced the crystallinity, crystal structure, and surface area of the TNSs, and improved the visible-light absorption. Surface photocurrent and fluorescence spectral studies revealed that the photo-generated charge carrier separation efficiency could be improved by an appropriate amount of modification. A very high efficiency was obtained using 0.5 at% Gd/Ti and 3.0 g/L of CDs. The visible-light-induced photocatalytic activity is enhanced under the isolated Cr(VI) system, isolated Rhodamin B (RhB) system, and the synergism between RhB degradation and Cr(VI) reduction for the Gd-C-TNSs photocatalysts. Initially, the photocatalytic activity gradually increased with an increase in the amount of CDs, and then decreased after attaining a maximum, in the case where 0.5 at% Gd/Ti and 3.0 g/L of CDs were used. The enhancement in the photocatalytic activity was attributed to the synergetic effect of the Gd{sub 2}O{sub

Spin dynamics in the high-field phase of quantum-critical S =1/2 TlCuCl sub 3

CERN Document Server

Rueegg, C; Furrer, A; Krämer, K; Güdel, H U; Vorderwisch, P; Mutka, H

2002-01-01

An external magnetic field suppresses the spin-energy gap in singlet ground state S=1/2 TlCuCl sub 3. The system becomes quantum-critical at H sub c approx 5.7 T, where the energy of the lowest Zeeman-split triplet excitation crosses the nonmagnetic ground state. Antiferromagnetic ordering is reported above H sub c , which underlines the three-dimensional nature of the observed quantum phase transition. The intrinsic parameters of S=1/2 TlCuCl sub 3 allow us to access the critical region microscopically by neutron scattering. A substantial study of the spin dynamics in the high-field phase of TlCuCl sub 3 at T=1.5 K up to H=12 T was performed for the first time. The results possibly indicate two dynamical regimes, which can be understood within characteristically renormalized triplet modes and a low-lying dynamics of potentially collective origin. (orig.)

Critical behavior of Y-doped Nd{sub 0.7}Sr{sub 0.3}MnO{sub 3} manganites exhibiting the tricritical point and large magnetocaloric effect

Energy Technology Data Exchange (ETDEWEB)

Phan, The-Long; Ho, T.A. [Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of); Thang, P.D. [Faculty of Engineering Physics and Nanotechnology, VNU-University of Engineering and Technology, Xuan Thuy, Cau Giay, Hanoi (Viet Nam); Tran, Q.T. [Center for Science and Technology Communication, Ministry of Science and Technology, 113 Tran Duy Hung, Hanoi (Viet Nam); Thanh, T.D.; Phuc, N.X. [Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi (Viet Nam); Phan, M.H. [Department of Physics, University of South Florida, Tampa, FL 33620 (United States); Huy, B.T. [Department of Chemistry, Changwon National University, Changwon 641-773 (Korea, Republic of); Yu, S.C., E-mail: scyu@chungbuk.ac.kr [Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of)

2014-12-05

Highlights: • Tricritical point in Y-doped Nd{sub 0.7}Sr{sub 0.3}MnO{sub 3} manganites. • A large magnetic-entropy change. • Magnetic inhomogeneity and phase separation. - Abstract: We have determined the values of critical exponents of two polycrystalline samples (Nd{sub 1−x}Y{sub x}){sub 0.7}Sr{sub 0.3}MnO{sub 3} (x = 0 and 0.07) from the magnetization data versus temperature and magnetic field, M(H, T), to learn about their magnetic and magnetocaloric (MC) properties. The results reveal the samples exhibiting the crossover of first-order and second-order phase transitions, where the exponent values β = 0.271 and γ = 0.922 for x = 0, and β = 0.234–0.236 and γ = 1.044–1.063 for x = 0.07 determined by using modified Arrott plots and static-scaling hypothesis are close to those expected for the tricritical mean-field theory (β = 0.25 and γ = 1.0). Particularly, the T{sub C} of x = 0 and 0.07 can be any value in the temperature ranges of 240–255 K and 170–278 K, respectively, depending on the magnitude of applied magnetic field and determination techniques. Around the T{sub C}, studying the MC effect of the samples has revealed a large magnetic-entropy change (ΔS{sub m}) up to ∼8 J/kg K for the applied field interval ΔH = 50 kOe, corresponding to refrigerant capacity values of 200–245 J/kg. These phenomena are related to the crossover nature and the persisting of FM/anti-FM interactions even above the T{sub C}, as further confirmed by electron-spin-resonance data, Curie–Weiss law-based analyses, and an exponential parameter characteristic of magnetic order n = dLn|ΔS{sub m}|/dLnH.

Status of the RF-driven H− ion source for J-PARC linac

International Nuclear Information System (INIS)

Oguri, H.; Ohkoshi, K.; Ikegami, K.; Takagi, A.; Asano, H.; Ueno, A.; Shibata, T.

2016-01-01

For the upgrade of the Japan Proton Accelerator Research Complex linac beam current, a cesiated RF-driven negative hydrogen ion source was installed during the 2014 summer shutdown period, with subsequent operations commencing on September 29, 2014. The ion source has been successfully operating with a beam current and duty factor of 33 mA and 1.25% (500 μs and 25 Hz), respectively. The result of recent beam operation has demonstrated that the ion source is capable of continuous operation for approximately 1100 h. The spark rate at the beam extractor was observed to be at a frequency of less than once a day, which is an acceptable level for user operation. Although an antenna failure occurred during operation on October 26, 2014, no subsequent serious issues have occurred since then

Characterization of a high repetition-rate laser-driven short-pulsed neutron source

Science.gov (United States)

Hah, J.; Nees, J. A.; Hammig, M. D.; Krushelnick, K.; Thomas, A. G. R.

2018-05-01

We demonstrate a repetitive, high flux, short-pulsed laser-driven neutron source using a heavy-water jet target. We measure neutron generation at 1/2 kHz repetition rate using several-mJ pulse energies, yielding a time-averaged neutron flux of 2 × 105 neutrons s‑1 (into 4π steradians). Deuteron spectra are also measured in order to understand source characteristics. Analyses of time-of-flight neutron spectra indicate that two separate populations of neutrons, ‘prompt’ and ‘delayed’, are generated at different locations. Gamma-ray emission from neutron capture 1H(n,γ) is also measured to confirm the neutron flux.

Observation of the strain-driven charge-ordered state in La sub 0 sub . sub 7 sub C a sub 0 sub . sub 3 MnO sub 3 sub - sub d elta thin film with oxygen deficiency

CERN Document Server

Prokhorov, V G; Kaminsky, G G; Svetchnikov, V L; Zandbergen, H W; Lee, Y P; Park, J S; Kim, K W

2003-01-01

The magnetic and transport properties of La sub 0 sub . sub 7 Ca sub 0 sub . sub 3 MnO sub 3 sub - sub d elta films with an oxygen deficiency (delta approx 0.1) and a La sub 0 sub . sub 9 Ca sub 0 sub . sub 1 MnO sub 3 film with the stoichiometric oxygen content are investigated in a wide temperature range. It is shown that the charge-ordered insulating (COI) state is observed for a La sub 0 sub . sub 7 Ca sub 0 sub . sub 3 MnO sub 2 sub . sub 9 film with thickness d <= 30 nm, which manifests mainly a cubic crystal structure with an anomalously small lattice parameter for this composition. An increase in the film thickness (d approx 60 nm) leads to a structural transition from the lattice-strained cubic to the relaxed rhombohedral phase, is accompanied by a shift of the Curie point (T sub C) to lower temperature and a frustration of the COI state. The magnetic and transport properties of the La sub 0 sub . sub 7 Ca sub 0 sub . sub 3 MnO sub 2 sub . sub 9 film with d approx 60 nm are similar to those exhibi...

A vibrating membrane bioreactor operated at supra- and sub-critical flux: Influence of extracellular polymeric substances from yeast cells

DEFF Research Database (Denmark)

Beier, Søren Prip; Jonsson, Gunnar Eigil

2007-01-01

A vibrating membrane bioreactor, in which the fouling problems are reduced by vibrating a hollow fiber membrane module, has been tested in constant flux microfiltration above (supra-critical) and below (sub-critical) an experimentally determined critical flux. Suspensions of bakers yeast cells were...... chosen as filtration medium (dry weight 4 g/l). The influence of extracellular polymeric substances (EPS) from the yeast cells is evaluated by UV absorbance measurements of the bulk supernatant during filtration. The critical flux seems to be an interval or a relative value rather than an absolute value....... Filtration just below the critical flux (sub-critical) seems to be a good compromise between acceptable flux level and acceptable increase of fouling resistance and trans-membrane pressure (TMP) in a given time period. EPS from the yeast cells causes the membrane module to foul and part of the fouling...

Lightwave-driven quasiparticle collisions on a sub-cycle timescale

Science.gov (United States)

Langer, F.; Hohenleutner, M.; Schmid, C.; Poellmann, C.; Nagler, P.; Korn, T.; Schüller, C.; Sherwin, M. S.; Huttner, U.; Steiner, J. T.; Koch, S. W.; Kira, M.; Huber, R.

2016-01-01

Ever since Ernest Rutherford first scattered α-particles from gold foils1, collision experiments have revealed unique insights into atoms, nuclei, and elementary particles2. In solids, many-body correlations also lead to characteristic resonances3, called quasiparticles, such as excitons, dropletons4, polarons, or Cooper pairs. Their structure and dynamics define spectacular macroscopic phenomena, ranging from Mott insulating states via spontaneous spin and charge order to high-temperature superconductivity5. Fundamental research would immensely benefit from quasiparticle colliders, but the notoriously short lifetimes of quasiparticles6 have challenged practical solutions. Here we exploit lightwave-driven charge transport7–24, the backbone of attosecond science9–13, to explore ultrafast quasiparticle collisions directly in the time domain: A femtosecond optical pulse creates excitonic electron–hole pairs in the layered dichalcogenide tungsten diselenide while a strong terahertz field accelerates and collides the electrons with the holes. The underlying wave packet dynamics, including collision, pair annihilation, quantum interference and dephasing, are detected as light emission in high-order spectral sidebands17–19 of the optical excitation. A full quantum theory explains our observations microscopically. This approach opens the door to collision experiments with a broad variety of complex quasiparticles and suggests a promising new way of sub-femtosecond pulse generation. PMID:27172045

Development and assessment of a sub-channel code applicable for trans-critical transient of SCWR

International Nuclear Information System (INIS)

Liu, X.J.; Yang, T.; Cheng, X.

2013-01-01

Highlights: • A new sub-channel code COBRA-SC for SCWR is developed. • Pseudo two-phase method is employed to realize trans-critical transient calculation. • Good suitability of COBRA-SC is demonstrated by preliminary assessment. • The calculation results of COBRA-SC agree well with ATHLET code. -- Abstract: In the last few years, extensive R and D activities have been launched covering various aspects of supercritical water-cooled reactor (SCWR), especially the thermal-hydraulic analysis. Sub-channel code plays an indispensable role to predict the detail thermal-hydraulic behavior of the SCWR fuel assembly. This paper develops a new version of sub-channel code COBRA-SC based on the previous COBRA-IV code. The supercritical water property and heat transfer/pressure drop correlations under supercritical pressure are implemented to this code. Moreover, in order to simulate the trans-critical transient (the pressure undergo a decrease from the supercritical pressure to the subcritical pressure), pseudo two-phase method is employed in COBRA-SC code. This work is completed by introduction of a virtual two-phase region near the pseudo-critical line. A smooth transition of void fraction can be realized. In addition, several heat transfer correlations right underneath the critical point are introduced into this code to capture the heat transfer behavior during the trans-critical transient. Some experimental data from simple geometry, e.g. the single tube, small rod bundle, is used to validate and evaluate this new developed COBRA-SC code. The predicted results show a good agreement with the experimental data, demonstrating good feasibility of this code for SCWR condition. A code to code comparison between COBRA-SC and ATHLET for a blowdown transient of a small fuel assembly is also presented and discussed in this paper

Numerical simulation of lambda phi sup(4) sub(4)

International Nuclear Information System (INIS)

Amaral, M.G. do; Carvalho, C.A.A. de; Shellard, R.C.

1984-01-01

The behaviour of a lattice theory where spontaneous symmetry breaking occurs is studied. The effective potential is calculated and discussed and the phase diagram of an Euclidean lambda phi 4 4 theory using Monte Carlo methods on a hypercubic lattice with 4 4 sites and periodic boundary conditions is obtained. The vacuum expectation value sub(j) is examined in the presence of an external source j(x), keeping the parameter β=1/lambda fixed. The limit of sub(j) as j→O is called phi sub(c). It is found that for values of β larger than β critical, phi sub(c) not = 0, while for values of β smaller than β critical phi sub(c) = 0. It is observed that the lambda phi 4 4 field theory exhibits two phases, a disordered phase in which the vacuum expectation value of the field vanishes, and an ordered phase characterized by spontaneous magnetization. The value of β critical is estimated through the behaviour of the specific heat and susceptibility as function of β. (Author) [pt

Comparison study of hybrid VS critical systems in point kinetics

International Nuclear Information System (INIS)

Ritter, G.; Tommasi, J.; Slessarev, L.; Salvatores, M.; Mouney, H.; Vergnes, J.

1999-01-01

An essential motivation for hybrid systems is a potentially high level of intrinsic safety against reactivity accidents. In this respect, it is necessary to assess the behaviour of an Accelerator Driven System during a TOP, LOF or TOC accident. A comparison between a critical and sub-critical reactor shows a larger sensitivity for the critical system. The ADS has an unquestionable advantage in case of TOP but a less favourable behaviour as for LOFWS type of accidents. However in the ADS cases, the beam could be easily shut off during the transient. Therefore, a part of the R and D effort should be focused on the monitoring and control of power. (author)

Fluctuation dynamics near the quantum critical point in the S=1/2 Ising chain CoNb{sub 2}O{sub 6}

Energy Technology Data Exchange (ETDEWEB)

Harms, Steffen; Engelmayer, Johannes; Lorenz, Thomas; Hemberger, Joachim [II. Physikalisches Institut, Koeln Univ. (Germany)

2016-07-01

CoNb{sub 2}O{sub 6} is a model system for quantum phase transitions in magnetic field. Its structure consists of layers of CoO{sub 6} octahedrons separated by non-magnetic NbO{sub 6} layers. The edge-sharing oxygen octahedrons link the Co{sup 2+} spins via Co-O-Co superexchange and form 1D ferromagnetic zigzag chains along the orthorhombic c axis. Crystal field effects lead to an easy-axis anisotropy of the Co{sup 2+} moments in the ac plane and to an effective spin-1/2 chain system. The 1D spin system can be described by the Ising model. At T=0 K a transverse magnetic field can induce a quantum phase transition from a long range ferromagnetic state into a quantum paramagnetic state. Employing measurements of the complex AC-susceptibility in the frequency range 10 MHz < ν < 5 GHz for temperatures down to 50 mK we investigate the slowing down of the magnetic fluctuation dynamics in the vicinity of the critical field at μ{sub 0}H=5.25 T.

Information theory explanation of the fluctuation theorem, maximum entropy production and self-organized criticality in non-equilibrium stationary states

CERN Document Server

Dewar, R

2003-01-01

Jaynes' information theory formalism of statistical mechanics is applied to the stationary states of open, non-equilibrium systems. First, it is shown that the probability distribution p subGAMMA of the underlying microscopic phase space trajectories GAMMA over a time interval of length tau satisfies p subGAMMA propor to exp(tau sigma subGAMMA/2k sub B) where sigma subGAMMA is the time-averaged rate of entropy production of GAMMA. Three consequences of this result are then derived: (1) the fluctuation theorem, which describes the exponentially declining probability of deviations from the second law of thermodynamics as tau -> infinity; (2) the selection principle of maximum entropy production for non-equilibrium stationary states, empirical support for which has been found in studies of phenomena as diverse as the Earth's climate and crystal growth morphology; and (3) the emergence of self-organized criticality for flux-driven systems in the slowly-driven limit. The explanation of these results on general inf...

Electron heating caused by parametrically driven turbulence near the critical density

International Nuclear Information System (INIS)

Mizuno, K.; DeGroot, J.S.; Estabrook, K.G.

1986-01-01

Microwave-driven experiments and particle simulation calculations are presented that model s-polarized laser light incident on a pellet. In the microwave experiments, the incident microwaves are observed to decay into ion and electron waves near the critical density if the microwave power is above a well-defined threshold. Significant absorption, thermal electron heating, and hot electron generation are observed for microwave powers above a few times threshold. Strong absorption, strong profile modification, strongly heated hot electrons with a Maxwellian distribution, a hot-electron temperature that increases slowly with power, and a hot-electron density that is almost constant, are all observed in both the microwave experiments and simulation calculations for high powers. In addition, the thermal electrons are strongly heated for high powers in the microwave experiments

A multi-fluid PSO-based algorithm for the search of the best performance of sub-critical Organic Rankine Cycles

International Nuclear Information System (INIS)

Cavazzini, G.; Bari, S.; Pavesi, G.; Ardizzon, G.

2017-01-01

The present paper focuses on the thermodynamic optimization of a sub-critical ORC for heat source temperatures in the range between 80 and 150 °C. The most significant novelty of the optimization procedure is that the optimization algorithm was modified for this particular application in order to allow the swarm particles to dynamically choose the working fluid among a list of 37 candidates during their heuristic movement, by continuously and dynamically modifying the search domain of each particle iteration-by-iteration due to the different vapour saturation lines of the chosen working fluid. The significant amount of data obtained by the optimization procedure highlighted the dependency of the system efficiency on two main parameters: the Jakob number related to the optimized cycle (Ja_o_p_t) and the ratio between the critical temperature of the working fluid and the inlet heat source temperature. At closer inspection, a third new parameter Ω was identified, resulting from the combination of the previous two, whose minimization is correlated to the maximization of system efficiency. A procedure for the preliminary estimation of the optimal cycle allowing to estimate with good accuracy the Jakob number Ja_o_p_t and the corresponding value of Ω was also developed. - Highlights: • An PSO algorithm allowing for the dynamic choice of the working fluid is presented. • Thermodynamic optimizations for several heat source temperatures were carried out. • An effective parameter for choosing the best performing working fluids is presented.

Ability to burn plutonium and minor actinides. Interest of accelerator driven system compared to critical reactor

International Nuclear Information System (INIS)

Vergnes, J.; Mouney, H.

1998-01-01

In the frame of the French Act of December 1991, EDF is presently assessing the interest of Acceleration Driven System (ADS) for the Transmutation of the Plutonium and Minor Actinides (MA) produced by its park of nuclear reactors. The studies presented here assess the efficiency of ADS and critical reactors to incinerate Pu and MA (Minor Actinides) and the potential interest of ADS for that purpose. (author)

Synthesis, surface and optical properties of Ag{sub 2}CaV{sub 4}O{sub 12} nanoparticles for dye removal under visible irradiation

Energy Technology Data Exchange (ETDEWEB)

Lu, Yuting [State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123 (China); Wan, Yingpeng [Department of Physics and Interdisciplinary Program of Biomedical, Mechanical & Electrical Engineering, Pukyong National University, Busan 608-737 (Korea, Republic of); Bi, Shala; Weng, Honggen [State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123 (China); Huang, Yanlin, E-mail: huang@suda.edu.cn [State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123 (China); Qin, Lin [Department of Physics and Interdisciplinary Program of Biomedical, Mechanical & Electrical Engineering, Pukyong National University, Busan 608-737 (Korea, Republic of); Seo, Hyo Jin, E-mail: hjseo@pknu.ac.kr [Department of Physics and Interdisciplinary Program of Biomedical, Mechanical & Electrical Engineering, Pukyong National University, Busan 608-737 (Korea, Republic of)

2016-09-01

Ag-containing compounds are regarded as potential candidates for the efficient photocatalyst driven by visible-light. In this work, nano-sized Ag{sub 2}CaV{sub 4}O{sub 12} was prepared via a modified Pechini synthesis. The detailed structural refinement of X-ray diffraction (XRD) pattern indicates that the Ag{sub 2}CaV{sub 4}O{sub 12} crystallizes in tetragonal system with the space group of P4/nbm (125), Z = 2. The surface property of this vanadate was measured by the scanning electron microscope (SEM), energy dispersive spectra (EDS), transmission electron microscopy (TEM), and nitrogen adsorption-desorption isotherm. The sample has an efficient optical absorption in the wavelength from UV to visible region characterized by its narrow band-gap energy of 2.231 eV with an indirect allowed property. The valence band maximum is composed of multiple states of Ag-d and O-p resulting in a narrow band. The excellent photocatalytic activity of Ag{sub 2}CaV{sub 4}O{sub 12} nanoparticles was tested by the photodegradation of rhodamine B (RhB), methylene blue (MB) and phenol solutions excited by visible-light. The photocatalytic mechanism was suggested according to experimental results and the band energy positions. - Highlights: • A new visible-light-driven photocatalyst of Ag{sub 2}CaV{sub 4}O{sub 12} was developed. • It has a narrow band gap of 2.231 eV with an indirect allowed characteristic. • Ag{sub 2}CaV{sub 4}O{sub 12} shows high activity in the MB degradation under visible light. • The photocatalytic ability is mainly driven by the ·OH radicals.

Improved solar-driven photocatalytic performance of Ag{sub 2}CO{sub 3}/(BiO){sub 2}CO{sub 3} prepared in-situ

Energy Technology Data Exchange (ETDEWEB)

Zhong, Junbo, E-mail: junbozhong@163.com [Key Laboratory of Green Catalysis of Higher Education Institutes of Sichuan, College of Chemistry and Pharmaceutical Engineering, Sichuan University of Science and Engineering, Zigong 643000 (China); Li, Jianzhang, E-mail: lschmanuscript@163.com [Key Laboratory of Green Catalysis of Higher Education Institutes of Sichuan, College of Chemistry and Pharmaceutical Engineering, Sichuan University of Science and Engineering, Zigong 643000 (China); Huang, Shengtian; Cheng, Chaozhu; Yuan, Wei [Key Laboratory of Green Catalysis of Higher Education Institutes of Sichuan, College of Chemistry and Pharmaceutical Engineering, Sichuan University of Science and Engineering, Zigong 643000 (China); Li, Minjiao [Key Laboratory of Green Catalysis of Higher Education Institutes of Sichuan, College of Chemistry and Pharmaceutical Engineering, Sichuan University of Science and Engineering, Zigong 643000 (China); Sichuan Provincial Academician (Expert) Workstation, Sichuan University of Science and Engineering, Zigong 643000 (China); Ding, Jie [Key Laboratory of Green Catalysis of Higher Education Institutes of Sichuan, College of Chemistry and Pharmaceutical Engineering, Sichuan University of Science and Engineering, Zigong 643000 (China)

2016-05-15

Highlights: • Ag{sub 2}CO{sub 3}/(BiO){sub 2}CO{sub 3} photocatalysts were prepared in-situ. • The photo-induced charge separation rate has been greatly increased. • The photocatalytic activity has been greatly promoted. - Abstract: Ag{sub 2}CO{sub 3}/(BiO){sub 2}CO{sub 3} composites have been fabricated in-situ via a facile parallel flaw co-precipitation method. The specific surface area, structure, morphology, and the separation rate of photo-induced charge pairs of the photocatalysts were characterized by Brunauer–Emmett–Teller (BET) method, X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy(DRS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and surface photovoltage (SPV) spectroscopy, respectively. XRD patterns and DRS demonstrated that Ag{sub 2}CO{sub 3} has no effect on the crystal phase and bandgap of (BiO){sub 2}CO{sub 3}. The existence of Ag{sub 2}CO{sub 3} in the composites enhances the separation rate of photo-induced charge pairs of the photocatalysts. The photocatalytic performance of Ag{sub 2}CO{sub 3}/(BiO){sub 2}CO{sub 3} was evaluated by the decolorization of methyl orange (MO) aqueous solution under simulated solar irradiation. It was found that the simulated solar-induced photocatalytic activity of Ag{sub 2}CO{sub 3}/(BiO){sub 2}CO{sub 3} copmposites was significantly improved, which was mainly attributed to the enhanced surface area and the separation rate of photo-induced charge pairs.

Intermittency and transition to chaos in the cubical lid-driven cavity flow

Energy Technology Data Exchange (ETDEWEB)

Loiseau, J-Ch [Department of Mechanics, Royal Institute of Technology (KTH), SE-100 44 Stockholm (Sweden); Robinet, J-Ch [Laboratoire DynFluid, Arts et Métiers ParisTech, F-75013 Paris (France); Leriche, E, E-mail: loiseau@mech.kth.se [Laboratoire de Mécanique de Lille, Université Lille 1, F-59655 Villeneuve d’Ascq (France)

2016-12-15

Transition from steady state to intermittent chaos in the cubical lid-driven cavity flow is investigated numerically. Fully three-dimensional stability analyses have revealed that the flow experiences an Andronov–Poincaré–Hopf bifurcation at a critical Reynolds number Re {sub c} = 1914. As for the 2D-periodic lid-driven cavity flows, the unstable mode originates from a centrifugal instability of the primary vortex core. A Reynolds–Orr analysis reveals that the unstable perturbation relies on a combination of the lift-up and anti lift-up mechanisms to extract its energy from the base flow. Once linearly unstable, direct numerical simulations show that the flow is driven toward a primary limit cycle before eventually exhibiting intermittent chaotic dynamics. Though only one eigenpair of the linearized Navier–Stokes operator is unstable, the dynamics during the intermittencies are surprisingly well characterized by one of the stable eigenpairs. (paper)

Laser-driven electron beam and radiation sources for basic, medical and industrial sciences

Science.gov (United States)

NAKAJIMA, Kazuhisa

2015-01-01

To date active research on laser-driven plasma-based accelerators have achieved great progress on production of high-energy, high-quality electron and photon beams in a compact scale. Such laser plasma accelerators have been envisaged bringing a wide range of applications in basic, medical and industrial sciences. Here inheriting the groundbreaker’s review article on “Laser Acceleration and its future” [Toshiki Tajima, (2010)],1) we would like to review recent progress of producing such electron beams due to relativistic laser-plasma interactions followed by laser wakefield acceleration and lead to the scaling formulas that are useful to design laser plasma accelerators with controllability of beam energy and charge. Lastly specific examples of such laser-driven electron/photon beam sources are illustrated. PMID:26062737

Table-top laser-driven ultrashort electron and X-ray source: the CIBER-X source project

Energy Technology Data Exchange (ETDEWEB)

Girardeau-Montaut, J.-P. E-mail: jean-pierre.girardeau@univ-lyonl.fr; Kiraly, Bela; Girardeau-Montaut, Claire; Leboutet, Hubert

2000-09-21

We report on the development of a new laser-driven table-top ultrashort electron and X-ray source, also called the CIBER-X source . X-ray pulses are produced by a three-step process which consists of the photoelectron emission from a thin metallic photocathode illuminated by 16 ps duration laser pulses at 213 nm. The e-gun is a standard Pierce diode electrode type, in which electrons are accelerated by a cw electric field of {approx}11 MV/m up to a hole made in the anode. The photoinjector produces a train of 70-80 keV electron pulses of {approx}0.5 nC and 20 A peak current at a repetition rate of 10 Hz. The electrons are then transported outside the diode along a path of 20 cm length, and are focused onto a target of thulium by magnetic fields produced by two electromagnetic coils. X-rays are then produced by the impact of electrons on the target. Simulations of geometrical, electromagnetic fields and energetic characteristics of the complete source were performed previously with the assistance of the code PIXEL1 also developed at the laboratory. Finally, experimental electron and X-ray performances of the CIBER-X source as well as its application to very low dose imagery are presented and discussed.

Second-order generalized perturbation theory for source-driven systems

International Nuclear Information System (INIS)

Greenspan, E.; Gilai, D.; Oblow, E.M.

1978-01-01

A second-order generalized perturbation theory (GPT) for the effect of multiple system variations on a general flux functional in source-driven systems is derived. The derivation is based on a functional Taylor series in which second-order derivatives are retained. The resulting formulation accounts for the nonlinear effect of a given variation accurate to third order in the flux and adjoint perturbations. It also accounts for the effect of interaction between any number of variations. The new formulation is compared with exact perturbation theory as well as with perturbation theory for altered systems. The usefulnes of the second-order GPT formulation is illustrated by applying it to optimization problems. Its applicability to areas of cross-section sensitivity analysis and system design and evaluation is also discussed

Analytical results on the periodically driven damped pendulum. Application to sliding charge-density waves and Josephson junctions

International Nuclear Information System (INIS)

Azbel, M.Y.; Bak, P.

1984-01-01

The differential equation epsilonphi-dieresis+phi-dot-(1/2)α sin(2phi) = I+summation/sub n/ = -infinity/sup infinity/A/sub n/delta(t-t/sub n/) describing the periodically driven damped pendulum is analyzed in the strong damping limit epsilon<<1, using first-order perturbation theory. The equation may represent the motion of a sliding charge-density wave (CDW) in ac plus dc electric fields, and the resistively shunted Josephson junction driven by dc and microwave currents. When the torque I exceeds a critical value the pendulum rotates with a frequency ω. For infinite damping, or zero mass (epsilon = 0), the equation can be transformed to the Schroedinger equation of the Kronig-Penney model. When A/sub n/ is random the pendulum exhibits chaotic motion. In the regular case A/sub n/ = A the frequency ω is a smooth function of the parameters, so there are no phase-locked subharmonic plateaus in the ω(I) curve, or the I-V characteristics for the CDW or Josephson-junction systems. For small nonzero epsilon the return map expressing the phase phi(t/sub n/+1) as a function of the phase phi(t/sub n/) is a one-dimensional circle map. Applying known analytical results for the circle map one finds narrow subharmonic plateaus at all rational frequencies, in agreement with experiments on CDW systems

Second order magnetic phase transition and scaling analysis in iron doped manganite La{sub 0.7}Ca{sub 0.3}Mn{sub 1−x}Fe{sub x}O{sub 3} compounds

Energy Technology Data Exchange (ETDEWEB)

Ginting, Dianta [Department of Applied Physics and Institute of Natural Sciences, Kyung Hee University, Yong-in 446-701 (Korea, Republic of); Nanto, Dwi [Physics Education, Syarif Hidayatullah State Islamic University, Jakarta 15412 (Indonesia); Denny, Yus Rama [Department of Electrical Engineering, University of Sultan Ageng Tirtayasa, Banten 42435 (Indonesia); Tarigan, Kontan [Department of Mechanical Engineering, Mercu Buana University, Jakarta-Barat, Jakarta 11650 (Indonesia); Hadi, Syamsul [Department of Mechanical Engineering, State Polytechnic of Malang, East Java 65100 (Indonesia); Ihsan, Mohammad [PSTBM-BATAN, Kawasan Puspiptek Serpong, Tangerang Selatan, Banten 15314 (Indonesia); Institute of Electronic Materials, University of Wollongong, Wollongong NSW 2522 (Australia); Rhyee, Jong-Soo, E-mail: jsrhyee@khu.ac.kr [Department of Applied Physics and Institute of Natural Sciences, Kyung Hee University, Yong-in 446-701 (Korea, Republic of)

2015-12-01

We investigated magnetic properties of La{sub 0.7}Ca{sub 0.3}Mn{sub 1−x}Fe{sub x}O{sub 3} (x=0.09 and 0.11) compounds in terms of isothermal magnetization analysis and scaling behavior with various critical exponents. From the Landau theory of magnetic phase transition, we found that the paramagnetic to ferromagnetic phase transition in La{sub 0.7}Ca{sub 0.3}Mn{sub 1−x}Fe{sub x}O{sub 3} (x=0.09 and 0.11) compounds is the type of second order magnetic transition (SOMT), which contrary to the first order magnetic transition (FOMT) for low Fe-doped compounds (x<0.09) in previous reports. When we investigate the critical behavior of the compounds near T=T{sub c} by the modified Arrott plot, Kouvel–Fisher plots, and critical isothermal analysis, the estimated critical exponents β, γ, and δ are in between the theoretically predicted values for three-dimensional Heisenberg and mean-field interaction models. It is noteworthy that the scaling relations are obeyed in terms of renormalization magnetization m=ε{sup −β}M(H,ε) and renormalized field h=|ε|{sup β+γ}H. Temperature-dependent effective exponents β{sub eff} and γ{sub eff} correspond to the ones of disordered ferromagnets. It is shown that the magnetic state of the compounds is not fully described by the conventional localized-spin interaction model because the ferromagnetic interaction has itinerant character by increasing Fe-doping concentration. - Highlights: • The ferromagnetic phase transition is of second order in La{sub 0.7}Ca{sub 0.3}Mn{sub 1−x}Fe{sub x}O{sub 3}. • The critical exponents are in between the 3D Heisenberg and mean-field models. • The ferromagnetic interaction becomes more itinerant by Fe-doping.

New shielding material development for compact accelerator-driven neutron source

Directory of Open Access Journals (Sweden)

Guang Hu

2017-04-01

Full Text Available The Compact Accelerator-driven Neutron Source (CANS, especially the transportable neutron source is longing for high effectiveness shielding material. For this reason, new shielding material is researched in this investigation. The component of shielding material is designed and many samples are manufactured. Then the attenuation detection experiments were carried out. In the detections, the dead time of the detector appeases when the proton beam is too strong. To grasp the linear range and nonlinear range of the detector, two currents of proton are employed in Pb attenuation detections. The transmission ratio of new shielding material, polyethylene (PE, PE + Pb, BPE + Pb is detected under suitable current of proton. Since the results of experimental neutrons and γ-rays appear as together, the MCNP and PHITS simulations are applied to assisting the analysis. The new shielding material could reduce of the weight and volume compared with BPE + Pb and PE + Pb.

Photoelectrochemical behavior of Al{sub x}In{sub 1−x}N thin films grown by plasma-assisted dual source reactive evaporation

Energy Technology Data Exchange (ETDEWEB)

Alizadeh, M., E-mail: alizadeh_kozerash@yahoo.com; Ganesh, V.; Pandikumar, A.; Goh, B.T.; Azianty, S.; Huang, N.M.; Rahman, S.A., E-mail: saadah@um.edu.my

2016-06-15

In this work the dependence of photoelectrochemical (PEC) behavior of Al{sub x}In{sub 1−x}N (0.48 ≤x ≤ 0.66) thin films grown by plasma-assisted dual source reactive evaporation, on the plasma dynamics and the alloys properties was studied. The influence of nitrogen flow rate on the compositional, morphological, structural and optical properties of the as-prepared films were investigated using X-ray photoelectron spectroscopy (XPS), Field emission scanning electron microscopy (FESEM), micro Raman spectroscopy and UV–vis spectroscopy. The PEC study of the as-grown Al{sub x}In{sub 1−x}N thin films targeted for water splitting application were performed in the presence of simulated solar irradiation of AM 1.5G (100 mW/cm{sup 2}). The PEC results revealed that the photocurrent for the Al{sub x}In{sub 1−x}N thin film grown at nitrogen flow rate of 80 sccm is ∼10-fold higher than the dark current. From the Mott–Schottky (MS) plots it was deduced that by increasing N{sub 2} flow rate up to 80 sccm, the flat band potential shifts toward more negative values. The good photoelectrochemical behavior of Al{sub x}In{sub 1−x}N thin films showed that this material could be a potential candidate for PEC water splitting. - Highlights: • Al{sub x}In{sub 1−x}N films were grown by Plasma-aided dual source reactive evaporation. • Effect of nitrogen flow rate on the films properties was investigated. • The band gap of the films decreased from 2.33 to 1.92 eV. • A good photoelectrochemical behavior of the Al{sub x}In{sub 1−x}N thin films was shown. • The photocurrent for the Al{sub 0.55}In{sub 0.45}N films is ∼10-fold higher than dark current.

Enhanced, robust light-driven H<sub>2sub> generation by gallium-doped titania nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Luo, Si [Chemistry Department, Brookhaven National Laboratory; Upton; USA; Department of Chemistry, Stony Brook University, Stony Brook; USA; Nguyen-Phan, Thuy-Duong [Chemistry Department, Brookhaven National Laboratory; Upton; USA; Vovchok, Dimitriy [Chemistry Department, Brookhaven National Laboratory; Upton; USA; Department of Chemistry, Stony Brook University, Stony Brook; USA; Waluyo, Iradwikanari [Photon Sciences Division, National Synchrotron Light Source II, Brookhaven National Laboratory; Upton; USA; Palomino, Robert M. [Chemistry Department, Brookhaven National Laboratory; Upton; USA; Gamalski, Andrew D. [Center for Functional Nanomaterials, Brookhaven National Laboratory; Upton; USA; Barrio, Laura [CSIC – Instituto de Catalisis y Petroleoquimica Cantoblanco; E-28049 Madrid; Spain; Xu, Wenqian [X-ray Science Division, Advanced Photon Source, Argonne National Laboratory; Argonne; USA; Polyansky, Dmitry E. [Chemistry Department, Brookhaven National Laboratory; Upton; USA; Rodriguez, José A. [Chemistry Department, Brookhaven National Laboratory; Upton; USA; Department of Chemistry, Stony Brook University, Stony Brook; USA; Senanayake, Sanjaya D. [Chemistry Department, Brookhaven National Laboratory; Upton; USA

2017-12-14

Successful introduction of gallium ions into TiO<sub>2sub>nanoparticles significantly promotes the H<sub>2sub>evolution activity and stability, increasing the opportunities for designing promising photocatalysts for green fuel production.

Clinical review: optimizing enteral nutrition for critically ill patients - a simple data-driven formula

Science.gov (United States)

2011-01-01

In modern critical care, the paradigm of 'therapeutic nutrition' is replacing traditional 'supportive nutrition'. Standard enteral formulas meet basic macro- and micronutrient needs; therapeutic enteral formulas meet these basic needs and also contain specific pharmaconutrients that may attenuate hyperinflammatory responses, enhance the immune responses to infection, or improve gastrointestinal tolerance. Choosing the right enteral feeding formula may positively affect a patient's outcome; targeted use of therapeutic formulas can reduce the incidence of infectious complications, shorten lengths of stay in the ICU and in the hospital, and lower risk for mortality. In this paper, we review principles of how to feed (enteral, parenteral, or both) and when to feed (early versus delayed start) patients who are critically ill. We discuss what to feed these patients in the context of specific pharmaconutrients in specialized feeding formulations, that is, arginine, glutamine, antioxidants, certain ω-3 and ω-6 fatty acids, hydrolyzed proteins, and medium-chain triglycerides. We summarize current expert guidelines for nutrition in patients with critical illness, and we present specific clinical evidence on the use of enteral formulas supplemented with anti-inflammatory or immune-modulating nutrients, and gastrointestinal tolerance-promoting nutritional formulas. Finally, we introduce an algorithm to help bedside clinicians make data-driven feeding decisions for patients with critical illness. PMID:22136305

Alcohol solvents evaporation-induced self-assembly synthesis of mesoporous TiO{sub 2−x−y}C{sub x}N{sub y} nanoparticles toward visible-light driven photocatalytic activity

Energy Technology Data Exchange (ETDEWEB)

Liu, Shou-Heng, E-mail: shliu@kuas.edu.tw; Syu, Han-Ren; Wu, Chung-Yi [National Kaohsiung University of Applied Sciences, Department of Chemical and Materials Engineering (China)

2014-12-15

A one-step solvent evaporation-induced self-assembly (SEISA) process was demonstrated to prepare carbon and nitrogen co-doping mesoporous TiO{sub 2} nanoparticles (MesoTiO{sub 2−x−y}C{sub x}N{sub y}-S) using an ionic liquid as carbon and nitrogen sources as well as mesoporous template. After the evaporation of different solvents (methanol, ethanol, and isopropanol) and subsequent calcinations at 773 K, the obtained MesoTiO{sub 2−x−y}C{sub x}N{sub y}-S samples were systematically characterized by a variety of spectroscopic and analytical techniques, including small- and large-angle X-ray diffraction (XRD), Raman, transmission electron microscopy (TEM), N{sub 2} adsorption–desorption isotherms, Fourier transform infrared (FTIR), and X-ray photoelectron (XPS) spectroscopies. The results indicate that the solvents play an essential role on the chemical microstructure, doping elemental states, and photocatalytic performance of catalysts. The MesoTiO{sub 2−x−y}C{sub x}N{sub y}-I samples have the lowest band gap of ca. 2.75 eV and strongest absorbance of visible light in the range of 400–600 nm. Among the MesoTiO{sub 2−x−y}C{sub x}N{sub y}-S photocatalysts, the MesoTiO{sub 2−x−y}C{sub x}N{sub y}-M catalysts show superior photocatalytic activity of hydrogen generation in methanol aqueous solution under visible light irradiation as compared to MesoTiO{sub 2−x−y}C{sub x}N{sub y}-E, MesoTiO{sub 2−x−y}C{sub x}N{sub y}-I, and commercial Degussa TiO{sub 2}. This result could be attributed to the moderate C,N co-doping amounts on their developed mesoporous texture (pore size = 8.0 nm) and high surface area (107 m{sup 2} g{sup −1}) of TiO{sub 2} (crystallite size = 9.9 nm) in the MesoTiO{sub 2−x−y}C{sub x}N{sub y}-M catalysts.

An Analysis of Source Tilting and Sub-cell Opacity Sampling for IMC

Energy Technology Data Exchange (ETDEWEB)

Wollaeger, Ryan T. [Los Alamos National Laboratory; Urbatsch, Todd J. [Los Alamos National Laboratory; Wollaber, Allan B. [Los Alamos National Laboratory; Densmore, Jeffery D. [Los Alamos National Laboratory

2012-08-02

Implicit Monte Carlo (IMC) is a stochastic method for solving the radiative transfer equations for multiphysics application with the material in local thermodynamic equilibrium. The IMC method employs a fictitious scattering term that is computed from an implicit discretization of the material temperature equation. Unfortunately, the original histogram representation of the temperature and opacity with respect to the spatial domain leads to nonphysically fast propagation of radiation waves through optically thick material. In the past, heuristic source tilting schemes have been used to mitigate the numerical teleportation error of the radiation particles in IMC that cause this overly rapid radiation wave propagation. While improving the material temperature profile throughout the time duration, these tilting schemes alone do not generally alleviate the teleportation error to suitable levels. Another means of potentially reducing teleportation error in IMC is implementing continuous sub-cell opacities based on sub-cell temperature profiles. We present here an analysis of source tilting and continuous sub-cell opacity sampling applied to various discretizations of the temperature equation. Through this analysis, we demonstrate that applying both heuristics does not necessarily yield more accurate results if the discretization of the material equation is inconsistent with the Monte Carlo sub-cell transport.

Characteristics and major sources of carbonaceous aerosols in PM{sub 2.5} from Sanya, China

Energy Technology Data Exchange (ETDEWEB)

Wang, Jingzhi [Key Lab of Aerosol Chemistry & Physics, Institute of Earth Environment, Chinese Academy of Sciences, Xi' an (China); State Key Lab of Loess and Quaternary Geology (SKLLQG), Institute of Earth Environment, Chinese Academy of Sciences, Xi' an (China); Ho, Steven Sai Hang [Key Lab of Aerosol Chemistry & Physics, Institute of Earth Environment, Chinese Academy of Sciences, Xi' an (China); Division of Atmospheric Sciences, Desert Research Institute, Reno, NV (United States); Cao, Junji, E-mail: cao@loess.llqg.ac.cn [Key Lab of Aerosol Chemistry & Physics, Institute of Earth Environment, Chinese Academy of Sciences, Xi' an (China); State Key Lab of Loess and Quaternary Geology (SKLLQG), Institute of Earth Environment, Chinese Academy of Sciences, Xi' an (China); Institute of Global Environmental Change, Xi' an Jiaotong University, Xi' an (China); Huang, Rujin [Key Lab of Aerosol Chemistry & Physics, Institute of Earth Environment, Chinese Academy of Sciences, Xi' an (China); State Key Lab of Loess and Quaternary Geology (SKLLQG), Institute of Earth Environment, Chinese Academy of Sciences, Xi' an (China); Laboratory of Atmospheric Chemistry, Paul Scherrer Institute (PSI), 5232 Villigen (Switzerland); Zhou, Jiamao [Key Lab of Aerosol Chemistry & Physics, Institute of Earth Environment, Chinese Academy of Sciences, Xi' an (China); State Key Lab of Loess and Quaternary Geology (SKLLQG), Institute of Earth Environment, Chinese Academy of Sciences, Xi' an (China); Zhao, Youzhi [College of Science and Technology, Qiongzhou University, Sanya (China); Xu, Hongmei [Department of Environmntal Science and Engineering, Xi' an Jiaotong University, Xi' an (China); Liu, Suixin; Wang, Gehui [Key Lab of Aerosol Chemistry & Physics, Institute of Earth Environment, Chinese Academy of Sciences, Xi' an (China); State Key Lab of Loess and Quaternary Geology (SKLLQG), Institute of Earth Environment, Chinese Academy of Sciences, Xi' an (China); and others

2015-10-15

PM{sub 2.5} samples were collected in Sanya, China in summer and winter in 2012/2013. Organic carbon (OC), elemental carbon (EC), and non-polar organic compounds including n-alkanes (n-C{sub 14}-n-C{sub 40}) and polycyclic aromatic hydrocarbons (PAHs) were quantified. The concentrations of these carbonaceous matters were generally higher in winter than summer. The estimated secondary organic carbon (OC{sub sec}) accounted for 38% and 54% of the total organic carbon (TOC) in winter and summer, respectively. The higher value of OC{sub sec} in addition to the presences of photochemically-produced PAHs in summer supports that photochemical conversions of organics are much active at the higher air temperatures and with stronger intense solar radiation. Carbon preference index (CPI) and percent contribution of wax n-alkanes suggest that anthropogenic sources were more dominant than derivation from terrestrial plants in Sanya. Diagnostic ratios of atmospheric PAHs further indicate that there was a wide mix of pollution sources in winter while fossil fuel combustion was the most dominant in summer. Positive Matrix Factorization (PMF) analysis with 18 PAHs in the winter samples found that motor vehicle emissions and biomass burning were the two main pollution sources, contributing 37.5% and 24.6% of the total quantified PAHs, respectively. - Highlights: • The first comprehensive study to investigate carbonaceous PM{sub 2.5} in Sanya, China • Higher carbonaceous levels in winter while more SOC formation in summer • Anthropogenic emission is the dominant sources of n-alkanes • Vehicle emission and biomass burning contributed ≥60% of the total PAHs in winter • The result supports better air quality in Sanya than most megacities in China.

Curvature-driven instabilities in the Elmo Bumpy Torus (EBT)

International Nuclear Information System (INIS)

Abe, H.; Spong, D.A.; Antonsen, T.M. Jr.; Tsang, K.T.; Nguyen, K.T.

1982-01-01

Curvature-driven instabilities are analyzed for an EBT configuration which consists of plasma interacting with a hot electron ring whose drift frequencies are larger than the growth rates predicted from conventional magnetohydrodynamic (MHD) theory. Stability criteria are obtained for five possible modes: the conventional hot electron interchange, a high-frequency hot electron interchange (at frequencies greater than the ion-cyclotron frequency), a compressional instability, a background plasma interchange, and an interacting pressure-driven interchange. A wide parameter regime for stable operation is found, which, however, severely deteriorates for a band of intermediate mode numbers. Finite Larmor radius effects can eliminate this deterioration; moreover, all short-wavelength curvature-driven modes are stabilized if the hot electron Larmor radius rho/sub h/ satisfies (kappa/sub perpendicular/rho/sub h/) 2 > 2Δ/[Rβ/sub h/(1 + P'/sub parallel//P'/sub perpendicular/)], where kappa/sub perpendicular/ is the transverse wavenumber, Δ is the ring half-width, R is the mid-plane radius of curvature, β/sub h/ is the hot electron beta value, and P' is the pressure gradient. Resonant wave-particle instabilities predicted by a new low frequency variational principle show that a variety of remnant instabilities may still persist

Electrically-driven GHz range ultrafast graphene light emitter (Conference Presentation)

Science.gov (United States)

Kim, Youngduck; Gao, Yuanda; Shiue, Ren-Jye; Wang, Lei; Aslan, Ozgur Burak; Kim, Hyungsik; Nemilentsau, Andrei M.; Low, Tony; Taniguchi, Takashi; Watanabe, Kenji; Bae, Myung-Ho; Heinz, Tony F.; Englund, Dirk R.; Hone, James

2017-02-01

Ultrafast electrically driven light emitter is a critical component in the development of the high bandwidth free-space and on-chip optical communications. Traditional semiconductor based light sources for integration to photonic platform have therefore been heavily studied over the past decades. However, there are still challenges such as absence of monolithic on-chip light sources with high bandwidth density, large-scale integration, low-cost, small foot print, and complementary metal-oxide-semiconductor (CMOS) technology compatibility. Here, we demonstrate the first electrically driven ultrafast graphene light emitter that operate up to 10 GHz bandwidth and broadband range (400 1600 nm), which are possible due to the strong coupling of charge carriers in graphene and surface optical phonons in hBN allow the ultrafast energy and heat transfer. In addition, incorporation of atomically thin hexagonal boron nitride (hBN) encapsulation layers enable the stable and practical high performance even under the ambient condition. Therefore, electrically driven ultrafast graphene light emitters paves the way towards the realization of ultrahigh bandwidth density photonic integrated circuits and efficient optical communications networks.

Synthesis, optical properties and photodegradation for methylene blue of Ni-vanadate K{sub 2}Ni(VO{sub 3}){sub 4} nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Lu, Yuting; Pu, Yinfu; Huang, Yanlin, E-mail: huang@suda.edu.cn; Wang, Jing; Lu, Juan, E-mail: lujuan@suda.edu.cn, E-mail: juanlu@suda.edu.cn [Soochow University, College of Chemistry, Chemical Engineering and Materials Science (China)

2015-11-15

A Ni{sup 2+}-containing vanadate, K{sub 2}Ni(VO{sub 3}){sub 4} was developed as a new visible-light-driven photocatalyst. The nanoparticles were prepared by the modified Pechini method. The sample was characterized by the measurements such as X-ray powder diffraction, scanning electron microscope, and UV–Vis absorption spectrum. The photocatalytic activity of K{sub 2}Ni(VO{sub 3}){sub 4} nanoparticles was evaluated by the photodegradation of methylene blue under visible-light irradiation in air. K{sub 2}Ni(VO{sub 3}){sub 4} shows a photocatalytic activity due to the efficient absorption in the UV–Visible-light wavelength region with a narrowed band-gap energy of 2.08 eV and an indirectly allowed electronic transition. These results indicate that this vanadate garnet could be a potential photocatalyst driven by visible light. The effective photocatalytic activity was discussed on the basis of the special structural characteristic such as heavily distorted NiO{sub 6}, rich, activated optical centers with tunnel structure for high photocatalytic capacity, and discussed on the basis of the photoluminescence and the decay lifetime.

Reliable method for fission source convergence of Monte Carlo criticality calculation with Wielandt's method

International Nuclear Information System (INIS)

Yamamoto, Toshihiro; Miyoshi, Yoshinori

2004-01-01

A new algorithm of Monte Carlo criticality calculations for implementing Wielandt's method, which is one of acceleration techniques for deterministic source iteration methods, is developed, and the algorithm can be successfully implemented into MCNP code. In this algorithm, part of fission neutrons emitted during random walk processes are tracked within the current cycle, and thus a fission source distribution used in the next cycle spread more widely. Applying this method intensifies a neutron interaction effect even in a loosely-coupled array where conventional Monte Carlo criticality methods have difficulties, and a converged fission source distribution can be obtained with fewer cycles. Computing time spent for one cycle, however, increases because of tracking fission neutrons within the current cycle, which eventually results in an increase of total computing time up to convergence. In addition, statistical fluctuations of a fission source distribution in a cycle are worsened by applying Wielandt's method to Monte Carlo criticality calculations. However, since a fission source convergence is attained with fewer source iterations, a reliable determination of convergence can easily be made even in a system with a slow convergence. This acceleration method is expected to contribute to prevention of incorrect Monte Carlo criticality calculations. (author)

Critical thickness for strain relaxation of Ge{sub 1−x}Sn{sub x} (x ≤ 0.17) grown by molecular beam epitaxy on Ge(001)

Energy Technology Data Exchange (ETDEWEB)

Wang, Wei; Zhou, Qian; Dong, Yuan; Yeo, Yee-Chia, E-mail: yeo@ieee.org [Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576 (Singapore); Tok, Eng Soon [Department of Physics, National University of Singapore, Singapore 117551 (Singapore)

2015-06-08

We investigated the critical thickness (h{sub c}) for plastic relaxation of Ge{sub 1−x}Sn{sub x} grown by molecular beam epitaxy. Ge{sub 1−x}Sn{sub x} films with various Sn mole fraction x (x ≤ 0.17) and different thicknesses were grown on Ge(001). The strain relaxation of Ge{sub 1−x}Sn{sub x} films and the h{sub c} were investigated by high-resolution x-ray diffraction and reciprocal space mapping. It demonstrates that the measured h{sub c} values of Ge{sub 1−x}Sn{sub x} layers are as much as an order of magnitude larger than that predicted by the Matthews and Blakeslee (M-B) model. The People and Bean (P-B) model was also used to predict the h{sub c} values in Ge{sub 1−x}Sn{sub x}/Ge system. The measured h{sub c} values for various Sn content follow the trend, but slightly larger than that predicted by the P-B model.

Mini-D{sub 2} a source for ultracold neutrons at FRM-II

Energy Technology Data Exchange (ETDEWEB)

Altarev, I.; Hartmann, F.J.; Paul, S.; Schott, W.; Trinks, U.; Gobrecht, K.; Gutsmiedl, E. [Technische Universitaet Muenchen, Garching (Germany); Scheuer, A. [TUEV Rheinland, Koeln (Germany)

2001-03-01

The new Munich high-flux reactor FRM-II offers the possibility to install a unique source for ultracold neutrons (UCN), the Mini-D{sub 2} UCN source, with a small volume of solid deuterium at a temperature of 5 K as converter, exposed to the cold neutron flux. This new source, being dedicated for storage experiments, is designed to be much superior to any existing UCN facility. In the pulsed operation mode the Mini-D{sub 2} source is expected to provide UCN densities up to 10{sup 4} n/cm{sup 3}. This density is orders of magnitude larger than that from the best existing source at Institut Laue Langevin (ILL) in Grenoble ({approx}50 n/cm{sup 3} at the exit of the neutron turbine). The large gain factor will enable new precision measurements of elementary properties of the free neutron, especially the electric dipole moment, the lifetime, and the angular correlation coefficients of the decay. These quantities are of fundamental interest in particle physics. Operated in the continuous mode, the UCN source will provide an UCN flux density of up to 5{center_dot}10{sup 5} n/cm{sup 2}s at the exit, to be compared with {approx}3{center_dot}10{sup 4} n/cm{sup 2}s at ILL. This improved UCN-flux offers new possibilities for traditional studies with UCN. (author)

Properties of the (Sm sub 0 sub . sub 3 sub 3 Eu sub 0 sub . sub 3 sub 3 Gd sub 0 sub . sub 3 sub 3)Ba sub 2 Cu sub 3 O sub y superconductor prepared by different processes in air

CERN Document Server

Giovannelli, F; Monot-Laffez, I

2003-01-01

Bars and pellets of the (Sm sub 0 sub . sub 3 sub 3 Eu sub 0 sub . sub 3 sub 3 Gd sub 0 sub . sub 3 sub 3)Ba sub 2 Cu sub 3 O sub x superconductor were processed in air, using the floating zone method and the top-seeded melt-textured growth method, respectively. The samples were prepared using different experimental conditions, i.e. maximal processing temperature, translation rate or cooling rate. Their physical properties and their microstructure were studied. All the samples exhibit a satisfying superconducting transition whereas the critical current density greatly depends on the processing parameters. The sample prepared by the floating zone method at 1070 deg C with a translation rate of 2 mm h sup - sup 1 exhibits a very high J sub c value of 70000 A cm sup - sup 2 in the self-field and more than 30000 A cm sup - sup 2 at 1.7 T. The pellet processed at 1080 deg C with a cooling rate of 2 deg C h sup - sup 1 has a high J sub c reaching about 56000 A cm sup - sup 2 in the self-field and more than 32000 A ...

DESIGN OF LABORATORY EXPERIMENTS TO STUDY PHOTOIONIZATION FRONTS DRIVEN BY THERMAL SOURCES

Energy Technology Data Exchange (ETDEWEB)

Drake, R. P.; Keiter, P. A.; Davis, J. S.; Patterson, C. R [Climate and Space Science, University of Michigan, Ann Arbor, MI 48109 (United States); Hazak, G. [Physics Department, Nuclear Research Center-Negev (Israel); Frank, A.; Blackman, E. G. [Physics and Astronomy, University of Rochester, Rochester, NY 14611 (United States); Busquet, Michel, E-mail: rpdrake@umich.edu [ARTEP Incorporated, Ellicot City, MD 21042 (United States)

2016-12-20

This paper analyzes the requirements of a photoionization-front experiment that could be driven in the laboratory, using thermal sources to produce the necessary flux of ionizing photons. It reports several associated conclusions. Such experiments will need to employ the largest available facilities, capable of delivering many kJ to MJ of energy to an X-ray source. They will use this source to irradiate a volume of neutral gas, likely of N, on a scale of a few mm to a few cm, increasing with source energy. For a gas pressure of several to ten atmospheres at room temperature, and a source temperature near 100 eV, one will be able to drive a photoionization front through a system of tens to hundreds of photon mean free paths. The front should make the familiar transition from the so-called R-Type to D-Type as the radiation flux diminishes with distance. The N is likely to reach the He-like state. Preheating from the energetic photons appears unlikely to become large enough to alter the essential dynamics of the front beyond some layer near the surface. For well-chosen experimental conditions, competing energy transport mechanisms are small.

DESIGN OF LABORATORY EXPERIMENTS TO STUDY PHOTOIONIZATION FRONTS DRIVEN BY THERMAL SOURCES

International Nuclear Information System (INIS)

Drake, R. P.; Keiter, P. A.; Davis, J. S.; Patterson, C. R; Hazak, G.; Frank, A.; Blackman, E. G.; Busquet, Michel

2016-01-01

This paper analyzes the requirements of a photoionization-front experiment that could be driven in the laboratory, using thermal sources to produce the necessary flux of ionizing photons. It reports several associated conclusions. Such experiments will need to employ the largest available facilities, capable of delivering many kJ to MJ of energy to an X-ray source. They will use this source to irradiate a volume of neutral gas, likely of N, on a scale of a few mm to a few cm, increasing with source energy. For a gas pressure of several to ten atmospheres at room temperature, and a source temperature near 100 eV, one will be able to drive a photoionization front through a system of tens to hundreds of photon mean free paths. The front should make the familiar transition from the so-called R-Type to D-Type as the radiation flux diminishes with distance. The N is likely to reach the He-like state. Preheating from the energetic photons appears unlikely to become large enough to alter the essential dynamics of the front beyond some layer near the surface. For well-chosen experimental conditions, competing energy transport mechanisms are small.

High order statistical signatures from source-driven measurements of subcritical fissile systems

International Nuclear Information System (INIS)

Mattingly, J.K.

1998-01-01

This research focuses on the development and application of high order statistical analyses applied to measurements performed with subcritical fissile systems driven by an introduced neutron source. The signatures presented are derived from counting statistics of the introduced source and radiation detectors that observe the response of the fissile system. It is demonstrated that successively higher order counting statistics possess progressively higher sensitivity to reactivity. Consequently, these signatures are more sensitive to changes in the composition, fissile mass, and configuration of the fissile assembly. Furthermore, it is shown that these techniques are capable of distinguishing the response of the fissile system to the introduced source from its response to any internal or inherent sources. This ability combined with the enhanced sensitivity of higher order signatures indicates that these techniques will be of significant utility in a variety of applications. Potential applications include enhanced radiation signature identification of weapons components for nuclear disarmament and safeguards applications and augmented nondestructive analysis of spent nuclear fuel. In general, these techniques expand present capabilities in the analysis of subcritical measurements

The magnetic properties of oxide spinel Li{sub 0.5}Fe{sub 2.5-2x}Al{sub x}Cr{sub x}O{sub 4} solid solutions

Energy Technology Data Exchange (ETDEWEB)

Masrour, R., E-mail: rachidmasrour@hotmail.com [Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, Sidi bouzid, Safi (Morocco); LMPHE, Faculte des Sciences, Universite Mohamed V, Rabat (Morocco); Hamedoun, M. [Institute for Nanomaterials and Nanotechnologies, MaScIR, Rabat (Morocco); Academie Hassan II des Sciences et Techniques, Rabat (Morocco); Benyoussef, A. [LMPHE, Faculte des Sciences, Universite Mohamed V, Rabat (Morocco); Institute for Nanomaterials and Nanotechnologies, MaScIR, Rabat (Morocco); Academie Hassan II des Sciences et Techniques, Rabat (Morocco)

2012-04-01

The exchange interactions (J{sub BB} and J{sub AB} are the intra and the inter-sublattice exchange interactions between neighbouring spins, respectively) are obtained by using the general expressions of canting angle and critical temperature obtained by mean field theory of Li{sub 0.5}Fe{sub 2.5-2x}Al{sub x}Cr{sub x}O{sub 4}. The expression of magnetic energy of Li{sub 0.5}Fe{sub 2.5-2x}Al{sub x}Cr{sub x}O{sub 4} is obtained for different spin configurations and dilution x. The saturation magnetisation of Li{sub 0.5}Fe{sub 2.5-2x}Al{sub x}Cr{sub x}O{sub 4} is obtained with different values of dilution x. The magnetic phase diagram of Li{sub 0.5}Fe{sub 2.5-2x}Al{sub x}Cr{sub x}O{sub 4} materials is obtained by high temperature series expansions (HTSEs). The critical exponent associated with the magnetic susceptibility of Li{sub 0.5}Fe{sub 2.5-2x}Al{sub x}Cr{sub x}O{sub 4} is deduced.

Ferro and antiferro orbital ordering in Fe{sub 0.5}Mn{sub 0.5}V{sub 2}O{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Dey, Dibyendu, E-mail: dibyendu@phy.iitkgp.ernet.in; Taraphder, A. [Department of Physics, Indian Institute of Technology, Kharagpur 721302 (India); Maitra, T. [Department of Physics, Indian Institute of Technology, Roorkee 247667 (India)

2016-05-23

Using density functional theory calculations, we have investigated the orbital ordering in Fe{sub 0.5}Mn{sub 0.5}V{sub 2}O{sub 4} where Fe and V sites are orbitally active. Our first principles study within GGA+U and GGA+U+SO shows ferro-orbital ordering of d{sub x2−y2} orbital at all Fe sites, whereas A-type antiferro-orbital ordering at V sites where one 3d electron occupies d{sub xy} orbital at every V site and another electron occupies either 1/√2 (d{sub xz} + d{sub yz}) or 1/√2 (d{sub xz} - d{sub yz}) orbital alternatively along c axis. Insulating nature and the orbital ordering of this compound are found to be correlation driven while the effect of spin-orbit interaction on orbital ordering is not significant.

Sub-channel analysis of LBE-cooled fuel assemblies of accelerator driven systems

International Nuclear Information System (INIS)

Cheng, X.; Hwang, D.H.

2005-01-01

In the frame of the European PDS-XADS project, two concepts of the sub-critical reactor core cooled by liquid lead-bismuth eutectic (LBE) were proposed. In this paper, the local thermal-hydraulic behavior of both LBE-cooled fuel assemblies was analyzed. For this purpose, the sub-channel analysis code MATRA was selected, and modification was made for its applications to XADS conditions. Compared to the small core concept, the large core concept has a much lower temperatures of coolant, cladding and fuel pins. This enables a short-term realization of the core design using available technologies. The high power density of the small core results in high local temperatures of coolant, cladding and fuel. Both coolant velocity and cladding temperature are such that special attention has to be paid to avoid corrosion and erosion damage of cladding materials. A parametric study shows that under the parameters considered, mixing coefficient has the biggest effect on the coolant temperature distribution, whereas the cladding temperature is strongly affected by the selection of heat transfer correlations. (author)

Application of stable isotopes (δ{sup 34}S-SO{sub 4}, δ{sup 18}O-SO{sub 4,} δ{sup 15}N-NO{sub 3}, δ{sup 18}O-NO{sub 3}) to determine natural background and contamination sources in the Guadalhorce River Basin (southern Spain)

Energy Technology Data Exchange (ETDEWEB)

Urresti-Estala, Begoña, E-mail: b.urresti@uma.es [Universidad de Málaga, Facultad de Ciencias, Grupo de Geodinámica Externa, Campus de Teatinos s/n, 29071 Málaga (Spain); Vadillo-Pérez, Iñaki; Jiménez-Gavilán, Pablo [Universidad de Málaga, Facultad de Ciencias, Grupo de Geodinámica Externa, Campus de Teatinos s/n, 29071 Málaga (Spain); Soler, Albert [Grup de Mineralogia Aplicada i Medi Ambient, Fac. Geologia, Universitat de Barcelona, Barcelona (Spain); Sánchez-García, Damián; Carrasco-Cantos, Francisco [Universidad de Málaga, Facultad de Ciencias, Grupo de Geodinámica Externa, Campus de Teatinos s/n, 29071 Málaga (Spain)

2015-02-15

The integrated use of isotopes (δ{sup 34}S-SO{sub 4}, δ{sup 18}O-SO{sub 4,} δ{sup 15}N-NO{sub 3}, δ{sup 18}O-NO{sub 3}), taking into account existing hydrogeological knowledge of the study area (mainly hydrochemical), was applied in the Guadalhorce River Basin (southern Spain) to characterise SO{sub 4}{sup 2−} and NO{sub 3}{sup −} sources, and to quantify natural background levels (NBLs) in groundwater bodies. According to Water Framework Directive 2000/60/EC and, more recently, Groundwater Directive 2006/118/EC, it is important to determine NBLs, as their correct assessment is the first, essential step to characterising groundwater bodies, establishing threshold values, assessing chemical status and identifying trends in pollutant concentrations. In many cases, NBLs are high for some parameters and types of groundwater, making it difficult to distinguish clearly between factors of natural or human origin. The main advantages of using stable isotopes in a complex area like the Guadalhorce River Basin that exhibits widely varying hydrogeological and hydrochemical conditions and longstanding anthropogenic influences (mainly agriculture, but also many others) is accurate determination of pollution sources and precise quantification of NBLs. Since chemical analyses only provides the concentration of pollutants in water and not the source, three isotopic sampling campaigns for sulphates (δ{sup 34}S-SO{sub 4}, δ{sup 18}O-SO{sub 4}) were carried out, in 2006, 2007 and 2012, and another one was conducted for nitrates (δ{sup 15}N-NO{sub 3}, δ{sup 18}O-NO{sub 3}), in 2009, in groundwater bodies in order to trace the origins of each pollutant. The present study identified different pollution sources of dissolved NO{sub 3}{sup −} in groundwater using an isotopic composition and quantified the percentage of natural (lithology, chemical and biological processes) and anthropogenic (fertilisers, manure and sewage) SO{sub 4}{sup 2−} and matched a concentration

Minor actinide transmutation in accelerator driven systems

Energy Technology Data Exchange (ETDEWEB)

Friess, Friederike [IANUS, TU Darmstadt (Germany)

2015-07-01

Transmutation of radioactive waste, the legacy of nuclear energy use, gains rising interest. This includes the development of facilities able to transmute minor actinides (MA) into stable or short-lived isotopes before final disposal. The most common proposal is to use a double-strata approach with accelerator-driven-systems (ADS) for the efficient transmutation of MA and power reactors to dispose plutonium. An ADS consists of a sub-critical core that reaches criticality with neutrons supplied by a spallation target. An MCNP model of the ADS system Multi Purpose Research Reactor for Hightech Applications will be presented. Depletion calculations have been performed for both standard MOX fuel and transmutation fuel with an increased content of minor actinides. The resulting transmutation rates for MAs are compared to published values. Special attention is given to selected fission products such as Tc-99 and I-129, which impact the radiation from the spent fuel significantly.

Conductivity fluctuation in the high temperature superconductor with planar weight disparity Y{sub 0.5}Sm{sub 0.5}Ba{sub 2}Cu{sub 3}O{sub 7-{delta}}

Energy Technology Data Exchange (ETDEWEB)

Barrera, E.W.; Rojas Sarmiento, M.P.; Rincon, L.F.; Landinez Tellez, D.A.; Roa-Rojas, J. [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, A.A. 14490, Bogota DC (Colombia)

2007-07-01

The synthesis of the Y{sub 0.5}Sm{sub 0.5}Ba{sub 2}Cu{sub 3}O{sub 7-{delta}} superconducting material by the standard solid state reaction is reported. DC resistivity measurements reveal the improvement of the critical temperature (T{sub c}) when substitution of exact 50-50 mix of Yttrium and Samarium is performed. A bulk T{sub c} = 101 K was determined by the criterion of the maximum in the temperature derivative of electrical resistivity. Structure characterization by means the x-ray diffraction technique shows the crystalline appropriated distribution of Yttrium and Samarium to create substantial planar weight disparity (PWD) in alternating layers. This PWD increases T{sub c} in copper-oxide superconductors. In order to examine the effect of PWD on the pairing mechanism close to T{sub c}, conductivity fluctuation analysis was performed by the method of logarithmic temperature derivative of the conductivity excess. We found the occurrence of Gaussian and genuinely critical fluctuations. Our results are in agreement with reports on YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}, but an enhancement of the Gaussian fluctuation regimes was experimentally detected as a result of the PWD. The correlations of the critical exponents with the dimensionality of the fluctuation system for each Gaussian regime were performed by using the Aslamazov-Larkin theory. The genuinely critical exponent is interpreted by the 3D-XY model as corresponding with the dynamical universality class of the E-model. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Studies on the Extraction Region of the Type VI RF Driven H- Ion Source

Science.gov (United States)

McNeely, P.; Bandyopadhyay, M.; Franzen, P.; Heinemann, B.; Hu, C.; Kraus, W.; Riedl, R.; Speth, E.; Wilhelm, R.

2002-11-01

IPP Garching has spent several years developing a RF driven H- ion source intended to be an alternative to the current ITER (International Thermonuclear Experimental Reactor) reference design ion source. A RF driven source offers a number of advantages to ITER in terms of reduced costs and maintenance requirements. Although the RF driven ion source has shown itself to be competitive with a standard arc filament ion source for positive ions many questions still remain on the physics behind the production of the H- ion beam extracted from the source. With the improvements that have been implemented to the BATMAN (Bavarian Test Machine for Negative Ions) facility over the last two years it is now possible to study both the extracted ion beam and the plasma in the vicinity of the extraction grid in greater detail. This paper will show the effect of changing the extraction and acceleration voltage on both the current and shape of the beam as measured on the calorimeter some 1.5 m downstream from the source. The extraction voltage required to operate in the plasma limit is 3 kV. The perveance optimum for the extraction system was determined to be 2.2 x 10-6 A/V3/2 and occurs at 2.7 kV extraction voltage. The horizontal and vertical beam half widths vary as a function of the extracted ion current and the horizontal half width is generally smaller than the vertical. The effect of reducing the co-extracted electron current via plasma grid biasing on the H- current extractable and the beam profile from the source is shown. It is possible in the case of a silver contaminated plasma to reduce the co-extracted electron current to 20% of the initial value by applying a bias of 12 V. In the case where argon is present in the plasma, biasing is observed to have minimal effect on the beam half width but in a pure hydrogen plasma the beam half width increases as the bias voltage increases. New Langmuir probe studies that have been carried out parallel to the plasma grid (in the

The use of sub-critical water hydrolysis for the recovery of peptides and free amino acids from food processing wastes. Review of sources and main parameters.

Science.gov (United States)

Marcet, Ismael; Álvarez, Carlos; Paredes, Benjamín; Díaz, Mario

2016-03-01

Food industry processing wastes are produced in enormous amounts every year, such wastes are usually disposed with the corresponding economical cost it implies, in the best scenario they can be used for pet food or composting. However new promising technologies and tools have been developed in the last years aimed at recovering valuable compounds from this type of materials. In particular, sub-critical water hydrolysis (SWH) has been revealed as an interesting way for recovering high added-value molecules, and its applications have been broadly referred in the bibliography. Special interest has been focused on recovering protein hydrolysates in form of peptides or amino acids, from both animal and vegetable wastes, by means of SWH. These recovered biomolecules have a capital importance in fields such as biotechnology research, nutraceuticals, and above all in food industry, where such products can be applied with very different objectives. Present work reviews the current state of art of using sub-critical water hydrolysis for protein recovering from food industry wastes. Key parameters as reaction time, temperature, amino acid degradation and kinetic constants have been discussed. Besides, the characteristics of the raw material and the type of products that can be obtained depending on the substrate have been reviewed. Finally, the application of these hydrolysates based on their functional properties and antioxidant activity is described. Copyright © 2016 Elsevier Ltd. All rights reserved.

Laser driven source of spin polarized atomic deuterium and hydrogen

International Nuclear Information System (INIS)

Poelker, M.; Coulter, K.P.; Holt, R.J.

1993-01-01

Optical pumping of potassium atoms in the presence of a high magnetic field followed by spin exchange collisions with deuterium (hydrogen) is shown to yield a high flux of spin polarized atomic deuterium (hydrogen). The performance of the laser driven source has been characterized as a function of deuterium (hydrogen) flow rate, potassium density, pump laser power, and magnetic field. Under appropriate conditions, the authors have observed deuterium atomic polarization as high as 75% at a flow rate 4.2x10 17 atoms/second. Preliminary results suggest that high nuclear polarizations are obtained in the absence of weak field rf transitions as a result of a spin temperature distribution that evolves through frequent H-H (D-D) collisions

Characterisation and quantification of the sources of PM{sub 10} during air pollution episodes in the UK

Energy Technology Data Exchange (ETDEWEB)

Muir, David [Environmental Quality Unit, Department of Planning, Transport and Sustainable Development, Bristol City Council, The CREATE Centre, Smeaton Road, Bristol BS1 6XN (United Kingdom); Longhurst, J.W.S.; Tubb, A. [Faculty of Applied Sciences, University of the West of England, Frenchay Campus, Coldharbour Lane, Bristol BS16 1QY (United Kingdom)

2006-04-01

Data for concentrations of PM{sub 10} and gaseous pollutants from sites in the UK Automatic Urban and Rural Network have been examined during periods of elevated concentrations of PM{sub 10}. The ratios of concentrations of PM{sub 10} to those of the other pollutants were used to determine the most probable source of the additional particles. The hypothesis is that because the concentrations of PM{sub 10} were divided by those of the other pollutants, the ratio should decrease when PM{sub 10} and the other pollutants have a common source. Conversely, the ratio should increase when the sources are different. During episodes where road traffic was the most probable source of the additional particles, the ratios of concentrations of PM{sub 10} to carbon monoxide and oxides of nitrogen did decrease, but the comparable ratios for sulphur dioxide and ozone increased. In contrast, during episodes known to have been caused by construction activity, all these ratios increased. This is taken to show that the basic hypothesis is valid. For prolonged episodes, it was possible to use data averaged over the total duration of the episode for the purposes of source identification. For sporadic construction, or other short-duration episodes, it was necessary to use time series data. The data have also been used to calculate the differences between hourly average concentrations of pollutants measured during episodes and long-term hourly average concentrations. These have been used to model the additional PM{sub 10} during air pollution episodes associated with construction activities and road traffic emissions. This confirms the lack of relationship between PM{sub 10} and other pollutants during construction works. During episodes arising from road traffic emissions, there was good agreement between measured and modelled additional concentrations of PM{sub 10} when an appropriate factor, F, related to the contribution of road traffic emissions to PM{sub 10} at different site types

Synthesis, structural characterization and fluctuation conductivity of HoBa{sub 2}Cu{sub 3}O{sub 7-{delta}-}SrTiO{sub 3} composites

Energy Technology Data Exchange (ETDEWEB)

Uribe Laverde, M.A., E-mail: mauribel@bt.unal.edu.c [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, Bogota (Colombia); Landinez Tellez, D.A.; Roa-Rojas, J. [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, Bogota (Colombia)

2010-12-15

Single-phase polycrystalline samples of HoBa{sub 2}Cu{sub 3}O{sub 7-{delta}} superconductor and SrTiO{sub 3} isolator were produced by means of the solid state reaction technique. After structural characterization of both materials, superconductor-isolator composites were produced with nominal isolator volume percentages between 0% and 10%. Resistivity measurements for the composites and the HoBa{sub 2}Cu{sub 3}O{sub 7-{delta}} sample with different currents evidenced a superconducting transition with critical temperature T{sub C} = 92 K, with wider transitions with increasing either isolator content or measurement current. Fluctuation conductivity analyses were carried out to obtain the exponents characterizing the conductivity divergence. Above T{sub C}, apart from the typical Gaussian and critical fluctuations an atypical regime with critical exponent about 0.14 is observed as a precursor of the transition. Below T{sub C}, it is observed that the coherence transition characteristic exponent increases rapidly with increasing isolator percentage in the composites and does not show important changes when modifying the current in the pure superconductor sample.

Structural and intrinsic Josephson properties of Bi{sub 2}Sr{sub 2}Ca{sub 1−y}Y{sub y}Cu{sub 2}O{sub 8+δ} single crystal

Energy Technology Data Exchange (ETDEWEB)

Yamaki, K., E-mail: kyamaki@cc.utsunomiya-u.ac.jp; Murata, K.; Irie, A.

2016-10-15

Highlights: • Single crystals of yttrium-doped BSCCO (BSCYCO) were grown by a self-flux method. • T{sub c} and c-axis lattice constant of BSCYCO were controlled by the substitution of Y. • A multibranch structure was observed up to y = 0.10 (Bi{sub 2}Sr{sub 2}Ca{sub 1−y}Y{sub y}Cu{sub 2}O{sub 8+δ}). • The BSCYCO mesa has higher maximum voltage compared with nondoped BSCCO. - Abstract: In this study, Bi{sub 2}Sr{sub 2}Ca{sub 1−y}Y{sub y}Cu{sub 2}O{sub 8+δ} (BSCYCO) single crystals with yttrium doping content of y = 0–0.30 were synthesized by a self-flux method. The critical temperature and c-axis lattice constant of BSCYCO were controlled by the substitution of yttrium at the calcium site. A 290 × 90 × 0.4 µm{sup 3} mesa structure was fabricated using photolithography and argon-ion milling. A multibranch structure in current–voltage characteristics was successfully observed for mesas of BSCYCO (y = 0–0.10). The critical current of intrinsic Josephson junctions (IJJs) in BSCYCO mesas was systematically investigated.

Sensitivity analysis of source driven subcritical systems by the HGPT methodology

International Nuclear Information System (INIS)

Gandini, A.

1997-01-01

The heuristically based generalized perturbation theory (HGPT) methodology has been extensively used in the last decades for analysis studies in the nuclear reactor field. Its use leads to fundamental reciprocity relationships from which perturbation, or sensitivity expressions can be derived, to first and higher order, in terms of simple integration operation of quantities calculated at unperturbed system conditions. Its application to subcritical, source-driven systems, now considered with increasing interest in many laboratories for their potential use as nuclear waste burners and/or safer energy producers, is here commented, with particular emphasis to problems implying an intensive system control variable. (author)

Critical parameters for ammonia

Energy Technology Data Exchange (ETDEWEB)

Sato, M. [Center for Mechanical Engineering and Applied Mechanics, Keio University, Hiyoshi 3-14-1, Kohoku-ku, Yokohama 223-8522 (Japan); Masui, G. [Center for Mechanical Engineering and Applied Mechanics, Keio University, Hiyoshi 3-14-1, Kohoku-ku, Yokohama 223-8522 (Japan); Uematsu, M. [Center for Mechanical Engineering and Applied Mechanics, Keio University, Hiyoshi 3-14-1, Kohoku-ku, Yokohama 223-8522 (Japan)]. E-mail: uematsu@mech.keio.ac.jp

2005-09-15

(p, {rho}, T) measurements and visual observations of the meniscus for ammonia were carried out carefully in the critical region over the range of temperatures: -1 K (T - T {sub c}) 0.04 K, and of densities: -19 kg . m{sup -3} ({rho} - {rho} {sub c}) 19 kg . m{sup -3} by a metal-bellows volumometer with an optical cell. Vapor pressures were also measured at T = (310, 350, and 400) K. The critical parameters of T {sub c} and {rho} {sub c} were determined based on the results of observation of the critical opalescence. The critical pressure p {sub c} was determined from the present measurements at T {sub c} on the vapor pressure curve. Comparisons of the critical parameters with values given in the literature are presented.

Neutrino oscillations in magnetically driven supernova explosions

Energy Technology Data Exchange (ETDEWEB)

Kawagoe, Shio; Kotake, Kei [Division of Theoretical Astronomy, National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, Tokyo, 181-8588 (Japan); Takiwaki, Tomoya, E-mail: shio.k@nao.ac.jp, E-mail: takiwaki.tomoya@nao.ac.jp, E-mail: kkotake@th.nao.ac.jp [Center for Computational Astrophysics, National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, Tokyo, 181-8588 (Japan)

2009-09-01

We investigate neutrino oscillations from core-collapse supernovae that produce magnetohydrodynamic (MHD) explosions. By calculating numerically the flavor conversion of neutrinos in the highly non-spherical envelope, we study how the explosion anisotropy has impacts on the emergent neutrino spectra through the Mikheyev-Smirnov-Wolfenstein effect. In the case of the inverted mass hierarchy with a relatively large θ{sub 13} (sin{sup 2} 2θ{sub 13} ∼> 10{sup −3}), we show that survival probabilities of ν-bar {sub e} and ν{sub e} seen from the rotational axis of the MHD supernovae (i.e., polar direction), can be significantly different from those along the equatorial direction. The event numbers of ν-bar {sub e} observed from the polar direction are predicted to show steepest decrease, reflecting the passage of the magneto-driven shock to the so-called high-resonance regions. Furthermore we point out that such a shock effect, depending on the original neutrino spectra, appears also for the low-resonance regions, which could lead to a noticeable decrease in the ν{sub e} signals. This reflects a unique nature of the magnetic explosion featuring a very early shock-arrival to the resonance regions, which is in sharp contrast to the neutrino-driven delayed supernova models. Our results suggest that the two features in the ν-bar {sub e} and ν{sub e} signals, if visible to the Super-Kamiokande for a Galactic supernova, could mark an observational signature of the magnetically driven explosions, presumably linked to the formation of magnetars and/or long-duration gamma-ray bursts.

An empirical assessment of near-source strong ground motion for a 6.6 m{sub b} (7.5 M{sub S}) earthquake in the Eastern United States

Energy Technology Data Exchange (ETDEWEB)

Campbell, Kenneth W

1984-06-01

To help assess the impact of the current U.S. Geological Survey position on the seismic safety of nuclear power plants in the Eastern United States (EUS), several techniques for estimating near-source strong ground motion for a Charleston size earthquake were evaluated. The techniques for estimating the near-source strong ground motion for a 6.6 m{sub b} (7.5 M{sub S}) in the Eastern United States which were assessed are methods based on site specific analyses, semi-theoretical scaling techniques, and intensity-based estimates. The first involves the statistical analysis of ground motion records from earthquakes and recording stations having the same general characteristics (earthquakes with magnitudes of 7.5 M{sub S} or larger, epicentral distances of 25 km or less, and sites of either soil or rock). Some recommendations for source and characterization scaling of the bias resulting primarily from an inadequate sample of near-source recordings from earthquakes of large magnitude are discussed. The second technique evaluated requires that semi-theoretical estimates of peak ground motion parameters for a 6.6 m{sub b} (7.5 M{sub S}) earthquake be obtained from scaling relations. Each relation uses a theoretical expression between peak acceleration magnitude and distance together with available strong motion data (majority coming from California) to develop a scaling relation appropriate for the Eastern United States. None of the existing ground motion models for the EUS include the potential effects of source or site characteristics. Adjustments to account for fault mechanisms, site topography, site geology, and the size and embedment of buildings are discussed. The final approach used relations between strong ground motion parameters and Modified Mercalli Intensity in conjunction with two methods to estimate peak parameters for a 6.6 m{sub s} (7.5 M{sub S}) earthquake. As with other techniques, adjustment of peak acceleration estimates are discussed. Each method

Thermoelectric power measurements in Fe doped La sub 0 sub . sub 6 sub 5 Ca sub 0 sub . sub 3 sub 5 MnO sub 3

CERN Document Server

Aslam, A; Zubair, M; Akhtar, M J; Nadeem, M

2002-01-01

We report measurements of the thermoelectric power (TEP) on the La sub 0 sub . sub 6 sub 5 Ca sub 0 sub . sub 3 sub 5 Mn sub 1 sub - sub x Fe sub x O sub 3 system for 0.00 <= x <= 0.07. The ferromagnetic and metallic transition temperatures are lowered and the TEP shows an increasingly positive trend with the addition of Fe. We also observe a clear magnetic contribution that manifests itself as a peak in the TEP close to the critical temperature. The activation energies determined from the TEP are seen to be insensitive to the Fe content. The data are interpreted firstly as showing a decrease in the density of active holes, i.e. holes that can participate in the hopping process, with increasing Fe content. Secondly the data suggest the role of magnetic scattering due to the clusters formed by the antiferromagnetically coupled Fe. Abrupt changes in the variation of the TEP are observed at the concentration region x approx 0.04 consistent with the hole density variation and with previously reported transp...