Physics Commons^™

Photoelectrochemical Properties Of Cdse:Sb Thin Film Based Solar Cells: Influence Of Electrode Thickness, Elahipasha U. Masumdar, L. P. Deshmukh

Turkish Journal of Physics

CdSe:Sb (0.1 mol%) thin films of varying thicknesses (423--1838 nm) have been deposited onto the glass and stainless steel substrates in an alkaline medium (pH = 10) using a solution growth technique. The photoelectrochemical activities of these films have been examined using CdSe:Sb (0.1 mol%)/0.25 M NaOH - 0.25M Na_2S- 0.25M S/graphite cell configuration. The films were characterized under illumination of 20 mW/cm^2} intensity to evaluate various cell parameters such as \eta, ff, R_s, R_{sh} etc. It is found that the efficiency \eta and fill factor ff increased from 0.24% to 0.45%, and 51% to 52.9%, respectively, with increase in …

Change Of Birefringence In Dye-Doped Nematic Liquid Crystals Under Laser Illumination, S. Eren San, Oğuz Köysal, Serhat Özder, F. Necati̇ Ecevi̇t

Turkish Journal of Physics

Birefringence property of E7 nematic liquid crystal is investigated via voltage dependent transmittance spectrums. Measurements are performed at wavelength 632.8 nm, which is the absorbance peak of our sample including anthraquinone derivative Disperse Blue 14. Results of dye-doped samples are compared with those undoped for dark and laser illuminated cases. It was observed that birefringence is dependent on laser illumination for dye-doped samples, up to a threshold voltage after which it is constant.

Electrical, Optical, Structural And Morphological Properties Of Nis Films, Ferhunde Atay, Sali̇h Köse, Vi̇ldan Bi̇lgi̇n, İdri̇s Akyüz

Turkish Journal of Physics

The electrical, optical, structural and morphological properties of NiS films are less studied than other materials such as CdS, CdTe, ZnS, ZnO, CdO etc. Our aim in this work is to deposit NiS films, examine some of their physical properties and investigate their suitability for photovoltaic devices. NiS films were deposited onto glass substrates at a substrate temperature of 300 \pm 5 °C using the ultrasonic spray pyrolysis (USP) technique. The variations of temperature-dependent conductivity under the conditions of light and dark were investigated and it was seen that illumination reduces conductivity. The activation energy for the doped region and …

Null Membranes In Dyonic Black Hole Background, Alexandr Lelyakov, Sergey Nikolaevich Roshchupkin

Turkish Journal of Physics

We consider null bosonic p-branes in curved spacetimes. The general solutions of the classical equations of motions and constraints for the null-membrane in four-dimensional dyonic black hole background are found.

Phase Measurements In Aharonov-Bohm Interferometers, Amnon Aharony, Ora Entin-Wohlman, Yoseph Imry

Turkish Journal of Physics

In this paper we address measurements of the resonant quantum transmission amplitude t_{QD} = -i t_{QD} e^{i\alpha_{QD}} through a quantum dot (QD), as function of the plunger gate voltage V. Mesoscopic solid state Aharonov-Bohm interferometers (ABI) have been used to measure the ``intrinsic" phase, \alpha_{QD}, when the QD is placed on one of the paths. In a ``closed" interferometer, connected to two terminals, the electron current is conserved, and Onsager's relations require that the conductance G through the ABI is an even function of the magnetic flux \Phi = \hbar c\phi/e threading the ABI ring. Therefore, if one fits G …

Dephasing Of Entangled Electron-Hole Pairs In A Degenerate Electron Gas, J. L. Van Velsen, M. Kindermann, C. W. J. Beenakker

Turkish Journal of Physics

A tunnel barrier in a degenerate electron gas was recently discovered as a source of entangled electron-hole pairs. Here, we investigate the loss of entanglement by dephasing. We calculate both the maximal violation E_{max} of the Bell inequality and the degree of entanglement (concurrence) C. If the initially maximally entangled electron-hole pair is in a Bell state, then the Bell inequality is violated for arbitrary strong dephasing. The same relation E_{max} = 2 \sqrt{1 + C^2} then holds as in the absence of dephasing. More generally, for a maximally entangled superposition of Bell states, the Bell inequality is satisfied for …

Decoherence In Ballistic Mesoscopic Interferometers, Georg Seelig, Sebastian Pilgram, Markus Büttiker

Turkish Journal of Physics

We provide a theoretical explanation for two recent experiments on decoherence of Aharonov-Bohm oscillations in two- and multi-terminal ballistic rings. We consider decoherence due to charge fluctuations and emphasize the role of charge exchange between the system and the reservoir or nearby gates. A time-dependent scattering matrix approach is shown to be a convenient tool for the discussion of decoherence in ballistic conductors.

Qce: A Simulator For Quantum Computer Hardware, Kristel Michielsen, Hans De Raedt

Turkish Journal of Physics

The Quantum Computer Emulator (QCE) described in this paper consists of a simulator of a generic, general purpose quantum computer and a graphical user interface. The latter is used to control the simulator, to define the hardware of the quantum computer and to debug and execute quantum algorithms. QCE runs in a Windows 98/NT/2000/ME/XP environment. It can be used to validate designs of physically realizable quantum processors and as an interactive educational tool to learn about quantum computers and quantum algorithms. A detailed exposition is given of the implementation of the CNOT and the Toffoli gate, the quantum Fourier transform, …

Adiabatic Quantum Pumping Of Coherent Electrons, Ora Entin-Wohlman, Amnon Aharony, Vyacheslavs Kashcheyevs

Turkish Journal of Physics

We review recent theoretical calculations of charge transfer through mesoscopic devices in response to slowly-oscillating, spatially-confined, potentials. The discussion is restricted to non-interacting electrons, and emphasizes the role of quantum interference and resonant transmission in producing almost integer values (in units of the electronic charge e) of the charge transmitted per cycle, Q. The expression for the pumped charge is derived from a systematic expansion of the system scattering states in terms of the temporal derivatives of the instantaneous solutions. This yields the effect of the modulating potential on the Landauer formula for the conductance in response to a constant …

Quantum Computing With Electrons On Liquid Helium, İsmai̇l Karakurt

Turkish Journal of Physics

A quantum computer based on electrons floating over liquid helium is described. Each qubit is made of combinations of ground and first excited states of an electron trapped over micro-electrodes just below the helium surface. We describe mechanisms for preparing the initial state of the qubit, operations with the qubits, and a proposed readout. This system is, in principle, capable of \sim 10^4 operations in a decoherence time, the time in which the wave function collapses.

Persistent Currents In Mesoscopic Loops And Networks, Igor O. Kulik

Turkish Journal of Physics

The paper describes persistent (also termed ``permanent", or ``non-decaying") currents in mesoscopic metallic and macromolecular rings, cylinders and networks. The current arises as a response of system to Aharonov-Bohm flux threading the conducting loop and does not require external voltage to support the current. Magnitude of the current is periodic function of magnetic flux with a period of normal-metal flux quantum \Phi_0 = hc/e. Spontaneous persistent currents arise in regular macromolecular structure without the Aharonov-Bohm flux provided the azimuthal periodicity of the ring is insured by strong coupling to periodic background (a ``substrate"), otherwise the system will undergo the Peierls …

Towards Quantum Communication With Electron Spins, D. S. Saraga, G. Burkard, J. C. Egues, H. A. Engel, P. Recher, Daniel Loss

Turkish Journal of Physics

We review our recent work towards quantum communication in a solid-state environment with qubits carried by electron spins. We propose three schemes to produce spin-entangled electrons, where the required separation of the partner electrons is achieved via Coulomb interaction. The non-product spin-states originate either from the Cooper pairs found in a superconductor, or in the ground state of a quantum dot with an even number of electrons. In a second stage, we show how spin-entanglement carried by a singlet can be detected in a beam-splitter geometry by an increased (bunching) or decreased (antibunching) noise signal. We also discuss how a …

First Principles Modeling Of Nanostructures, Serdar Öğüt

Turkish Journal of Physics

Among the various theoretical tools for investigating microscopic material properties, ab initio (first principles) methods based on density functional theory and pseudopotentials have had a very good track record over the last two decades in terms of accuracy, reliability, and efficiency. The application of these methods to nanostructures to investigate their structural, electronic, and optical properties has, however, not been quite straightforward due to the large computational demand and new physics inherent in the nanometer and sub-nanometer size region. One particularly useful extension to overcome the computational demand imposed by localized nanostructures has been the introduction of methods based on …

Quantum State Generation And Entanglement Manipulation Using Linear Optics, Şahi̇n Kaya Özdemi̇r, Takashi Yamamoto, Masato Koashi, Nobuyuki Imoto

Turkish Journal of Physics

Quantum information processing (QIP) requires unitary operations, measurements and synthesis, manipulation and characterization of arbitrary quantum states. Linear optics provides efficient tools for these purposes. In this review paper, we introduce the elements of linear optics toolbox, and briefly discuss some experimental and theoretical investigations using this toolbox. Our main focus will be the qubit state generation and entanglement extraction using linear optics toolbox.

Orbital Entanglement And Violation Of Bell Inequalities In The Presence Of Dephasing, P. Samuelsson, Eugene Sukhorukov, Markus Büttiker

Turkish Journal of Physics

We discuss orbital entanglement in mesoscopic conductors, focusing on the effect of dephasing. The entanglement is detected via violation of a Bell Inequality formulated in terms of zero-frequency current correlations. Following closely the recent work by Samuelsson, Sukhorukov and Büttiker [1], we investigate how the dephasing affects the possibility to violate the Bell Inequality and how system parameters can be adjusted for optimal violation.

Mesoscopic D-Wave Qubits: Can High-T_C Cuprates Play A Role In Quantum Computing?, Alexandre M. Zagoskin

Turkish Journal of Physics

Due to nontrivial orbital pairing symmetry, surfaces and interfaces of high-T_c superconductors support states which violate time-reversal (T-) symmetry. Such naturally degenerate states, useful as working states of a qubit, are standard for atomic or molecular-size qubit prototypes (e.g. based on nuclear spins), but exceptional for mesoscopic qubits. (In particular, they hold promise of a better scalability.) In these lectures I review the physics of T-breaking on surfaces and interfaces of high-T_c superconductors; then describe existing proposals for high-T_c based qubits and the current state of experiments; finally, I discuss the decoherence sources in the system, open questions, and future …

Growth Mechanism And Some Properties Of Cd_{1-X}Mn_X Se Semimagnetic Semiconductor Thin Films, V. S. Karande, S. H. Mane, Vithal Bhivaba Pujari, L. P. Deshmukh

Turkish Journal of Physics

(Cd, Mn) Se dilute semiconductor or semimagnetic semiconductors have recently became the focus of intense research due to their interesting combination of magnetic and semiconducting properties, and are employed in a variety of devices including solar cells, gas sensors etc. A series of thin films of this material, Cd_{1 - x}Mn_xSe (0 \le x \le 0.5), were therefore synthesized onto precleaned amorphous glass substrates using a solution growth technique. The sources of cadmium (Cd^{2+}) and manganese (Mn^{2+}) were aqueous solutions of cadmium sulphate and manganese sulphate, and selenium (Se^{2-}) was extracted from a reflux of sodium selenosulphite. The different deposition …

Assessment Of The Acoustic Properties Of Common Tissue-Mimicking Test Phantoms, Jacinta Browne, K. Ramnarine, A. Watson, P. Hoskins

Articles

Ultrasound (US) test phantoms incorporating tissue-mimicking materials (TMMs) play an important role in the quality control (QC) and performance testing of US equipment. Three commercially available TMMs (ZerdineTM from CIRS Inc.; condensed-milk-based gel from Gammex RMI; urethane-rubber-based from ATS Labs) and a noncommercial agar-based TMM, were investigated. Acoustic properties were measured over the frequency range 2.25 to 15 MHz at a range of ambient temperatures (10 to 35°C). The acoustic velocity of the TMMs remained relatively constant with increasing frequency. Only the agar-based TMM had a linear increase of attenuation with frequency, with the other materials exhibiting nonlinear responses to …

Radiation Transport Modeling Using Parallel Computational Techniques, William Culbreth

Reactor Campaign (TRP)

The Advanced Fuel Cycle Initiative (AFCI) program will rely on the use of accurate calculations and simulations of criticality and shielding for the separation process of the longlived isotopes that present a significant safety hazard in commercial spent fuel. To help design and verify the safety of the separation process, the neutronics code MCNPX will be used to model the distribution of neutron flux within the fuel blanket and to determine the neutron multiplication, k_eff. However, the cross section libraries and computational methods used by MCNPX at these neutron energies still have some uncertainty and will require validation. …

Radiation Transport Modeling Using Parallel Computational Techniques, William Culbreth, Denis Beller

Reactor Campaign (TRP)

The second year of this project involved modeling several aspects of the LANCSE beam experiments:

• Modeling targets of varying diameter in air, in a vacuum, and in the presence of humid air;
• Modeling various proton beam profiles;
• Modeling the effects of off-axis proton beam impingement on the target;
• Modeling the asymmetry introduced by the steel table below the target;
• Modeling the effect of varying ratios of Pb to Bi and the effect of impurities; and
• Modeling the system, including other structures within the test room.

With the experience gained through modeling these systems, the UNLV researchers plan, with the assistance …

Monte Carlo Verification And Modeling Of Lead-Bismuth Spallation Targets, Daniel R. Lowe

Reactor Campaign (TRP)

No abstract provided.

University Of Nevada, Las Vegas Transmutation Research Program Annual Report 2002, Anthony Hechanova, Elizabeth Johnson, Gary Cerefice

Transmutation Research Program Reports (TRP)

The UNLV Transmutation Research Program consists of four components: Program Support, Research Infrastructure Augmentation, International Collaboration, and Student Research.

In the first year of the program, the student research component was supported by the infrastructure augmentation and the program support components. In the second year of the program, the fourth leg of the support system, international collaborations, was added to the research support system.

Corrosion Of Steel By Lead Bismuth Eutectic, John Farley, Allen L. Johnson, Dale L. Perry

Transmutation Sciences Materials (TRP)

Materials for transmuter systems must be able to tolerate high neutron fluxes, great temperatures, and chemical corrosion. For lead bismuth eutectic (LBE) systems, there is an additional challenge in that the corrosive behaviors of materials in LBE are not well understood. Most of the available information on LBE systems has come from the Russians, who have over 80 reactor-years experience with LBE coolant in their Alpha-class submarine reactors. The Russians found that the presence of small amounts of oxygen (on the order of parts per million) in the LBE significantly reduced corrosion. However, a fundamental understanding and verification of its …

Surface Studies Of Corrosion Of Stainless Steel By Lead Bismuth Eutectic, Daniel Koury, Brian D. Hosterman, John Farley, Dale L. Perry, D. Parsons, J. Manzerova, Allen L. Johnson

Transmutation Sciences Materials (TRP)

Why is Lead Bismuth Eutectic Important?

• Changing national security stances have led to reexamination of nuclear waste reprocessing

• Dangerous actinides can be separated and

• Transmuted into safer products, creating a waste form dangerous for only hundreds of years, in addition to the production (up to 1/3 of the original fission energy) of useful energy

• Non-moderating coolants or spallation targets for production of fast neutrons is required for transmutation

• Russian experience with LBE coolants in their nuclear submarine fleet makes LBE an attractive possible transmutation coolant technology

• Corrosion of steel by LBE is an important …

Neutron Multiplicity Measurements Of Target/Blanket Materials, Carter D. Hull, Denis Beller

Transmutation Sciences Physics (TRP)

To optimize the performance of accelerator driven transmutation systems (ADS), engineers will need to design the system to operate with a neutron multiplication factor just below that of a critical, or self-sustaining, system. This design criteria requires particle transport codes that instill the highest level of confidence with minimal uncertainty, because the larger the uncertainties in the codes, the larger the safety margin required in the design and the lower the efficiency of the ADS transmuter. For current design efforts, the MCNPX code is used to determine neutron production and transport for spallation neutron systems.

While providing a very useful …

Development Of Dose Coefficients For Radionuclides Produced In Spallation Targets, Phillip W. Patton, Mark Rudin

Transmutation Sciences Physics (TRP)

Dose coefficients permit simple determination of radiation dose associated with various exposure scenarios, and ultimately permit radiation safety personnel to assess the health risks to workers in a nuclear facility. Specifically, radiation safety personnel use dose coefficients to determine the radiation dose incurred to a tissue or organ system from a given exposure. These parameters are often expressed in terms of Annual Limits on Intake (ALIs) and Derived Air Concentrations (DACs).

Results from this study will be used to produce ALIs and DACs for these rare radionuclides created by spallation target systems that are not included in Federal Guidance Report …

Development Of Dose Coefficients For Radionulides Produced In Spallation Neutron Sources: Annual Report, Phillip W. Patton, Mark Rudin

Transmutation Sciences Physics (TRP)

The University of Nevada, Las Vegas (UNLV) Transmutation Research Program has been tasked to support U.S. Department of Energy (DOE) efforts to assess the health risks associated with the operation of each of their accelerator-driven nuclear facilities for both NEPA and PSAR development. Quantifying the radiological risks to workers will have to be addressed during the design and siting of each of these facilities. U.S. Environmental Protection Agency (EPA) Federal Guidance Report No. 11 “Limiting Values of Intake and Air Concentration and Dose Conversion Factors for Inhalation, Submersion, and Ingestion”, developed two derived guides, Annual Limit on Intake (ALI) and …

Nuclear Criticality, Shielding, And Thermal Analyses Of Separations Processes For The Transmutation Fuel Cycle, William Culbreth, Denis Beller

Separations Campaign (TRP)

The first step in any transmutation strategy is the separation of radionuclides in used nuclear fuel. The current separation strategy supporting the Advanced Fuel Cycle Initiative (AFCI) program is based on the use of a solvent extraction separation process to separate the actinides, fission products, and uranium from used commercial nuclear fuel, and on the use of pyrochemical separation technologies to process used transmuter fuels. To separate the fission products and transuranic elements from the uranium in used fuel, the national program is developing a new solvent extraction process, the Uranium Extraction Plus, or UREX+, process, based on the traditional …

Design And Analysis Of A Process For Melt Casting Metallic Fuel Pins Incorporating Volatile Actinides, Yitung Chen, Darrell Pepper, Randy Clarksean

Fuels Campaign (TRP)

The goal of this project is to investigate the casting processes for metallic fuels to help design a process that minimizes the loss of the volatile actinide elements from the fuel.

The research effort centers on the development of advanced numerical models to assess conditions that significantly impact the transport of volatile actinides during the melt casting process and represents a joint effort between researchers at the University of Nevada, Las Vegas (UNLV) and Argonne National Laboratory (ANL).

Comment On ‘‘Why Is The Dna Denaturation Transition First Order?’’, Andreas Hanke, Ralf Metzler

Physics & Astronomy Faculty Publications

A Comment on the Letter by . The authors of the Letter offer a Reply.