Anisotropic Electron-Photon and Electron-Phonon Interactions in Black Phosphorus

DOE PAGES

Ling, Xi; Huang, Shengxi; Hasdeo, Eddwi; ...

2016-03-10

Orthorhombic black phosphorus (BP) and other layered materials, such as gallium telluride (GaTe) and tin selenide (SnSe), stand out among two-dimensional (2D) materials owing to their anisotropic in-plane structure. This anisotropy adds a new dimension to the properties of 2D materials and stimulates the development of angle-resolved photonics and electronics. However, understanding the effect of anisotropy has remained unsatisfactory to-date, as shown by a number of inconsistencies in the recent literatures. We use angle-resolved absorption and Raman spectroscopies to investigate the role of anisotropy on the electron-photon and electron-phonon interactions in BP. We highlight a non-trivial dependence between anisotropies andmore » flake thickness, photon and phonon energies. We show that once understood, the anisotropic optical absorption appears to be a reliable and simple way to identify the crystalline orientation of BP, which cannot be determined from Raman spectroscopy without the explicit consideration of excitation wavelength and flake thickness, as commonly used previously.« less

Energy spectrum of extragalactic gamma-ray sources

NASA Technical Reports Server (NTRS)

Protheroe, R. J.

1985-01-01

The result of Monte Carlo electron photon cascade calculations for propagation of gamma rays through regions of extragalactic space containing no magnetic field are given. These calculations then provide upper limits to the expected flux from extragalactic sources. Since gamma rays in the 10 to the 14th power eV to 10 to the 17th power eV energy range are of interest, interactions of electrons and photons with the 3 K microwave background radiation are considered. To obtain an upper limit to the expected gamma ray flux from sources, the intergalactic field is assumed to be so low that it can be ignored. Interactions with photons of the near-infrared background radiation are not considered here although these will have important implications for gamma rays below 10 to the 14th power eV if the near infrared background radiation is universal. Interaction lengths of electrons and photons in the microwave background radiation at a temperature of 2.96 K were calculated and are given.

Controlling Photons, Qubits and their Interactions in Superconducting Electronic Circuits

NASA Astrophysics Data System (ADS)

Wallraff, Andreas

2009-03-01

A combination of ideas from atomic physics, quantum optics and solid state physics allows us to investigate the fundamental interaction of matter and light on the level of single quanta in electronic circuits. In an approach known as circuit quantum electrodynamics, we coherently couple individual photons stored in a high quality microwave frequency resonator to a fully controllable superconducting two-level system (qubit) realized in a macroscopic electronic circuit [1]. In particular, we have recently observed the simultaneous interaction of one, two and three photons with a single qubit. In these experiments, we have probed the quantum nonlinearity of the qubit/light interaction governed by the Jaynes-Cummings hamiltonian, clearly demonstrating the quantization of the radiation field in the on-chip cavity. We have also performed quantum optics experiments with no photons at all. In this situation, i.e. in pure vacuum, we have resolved the renormalization of the qubit transition frequency - known as the Lamb shift - due to its non-resonant interaction with the cavity vacuum fluctuations [3].[4pt] [1] A. Wallraff et al., Nature (London) 431, 162 (2004)[0pt] [2] J. Fink et al., Nature (London) 454, 315 (2008)[0pt] [3] A. Fragner et al., Science 322, 1357 (2008)

On interaction of P-waves with one-dimensional photonic crystal consisting of weak conducting matter and transparent dielectric layers

NASA Astrophysics Data System (ADS)

Yushkanov, A. A.; Zverev, N. V.

2018-03-01

An influence of quantum and spatial dispersion properties of the non-degenerate electron plasma on the interaction of electromagnetic P-waves with one-dimensional photonic crystal consisting of conductor with low carrier electron density and transparent dielectric matter, is studied numerically. It is shown that at the frequencies of order of the plasma frequency and at small widths of the conducting and dielectric layers of the photonic crystal, optical coefficients in the quantum non-degenerate plasma approach differ from the coefficients in the classical electron gas approach. And also, at these frequencies one observes a temperature dependence of the optical coefficients.

Water and tissue equivalence properties of biological materials for photons, electrons, protons and alpha particles in the energy region 10 keV-1 GeV: a comparative study.

PubMed

Kurudirek, Murat

2016-09-01

To compare some biological materials in respect to the water and tissue equivalence properties for photon, electron, proton and alpha particle interactions as means of the effective atomic number (Zeff) and electron density (Ne). A Z-wise interpolation procedure has been adopted for calculation of Zeff using the mass attenuation coefficients for photons and the mass stopping powers for charged particles. At relatively low energies (100 keV-3 MeV), Zeff and Ne for photons and electrons were found to be constant while they vary much more for protons and alpha particles. In contrast, Zeff and Ne for protons and alpha particles were found to be constant after 3 MeV whereas for photons and electrons they were found to increase with the increasing energy. Also, muscle eq. liquid (with sucrose) have Zeff and Ne values close to the Muscle Skeletal (ICRP) and Muscle Striated (ICRU) within low relative differences below 9%. Muscle eq. liquid (without sucrose) have Zeff and Ne values close to the Muscle Skeletal (ICRP) and Muscle Striated (ICRU) with difference below 10%. The reported data should be useful in determining best water as well as tissue equivalent materials for photon, electron, proton and alpha particle interactions.

Gamma-ray generation in the interaction of two tightly focused laser pulses with a low-density target composed of electrons

NASA Astrophysics Data System (ADS)

Jirka, M.; Klimo, O.; Weber, S.; Bulanov, Sergei V.; Esirkepov, Timur Zh.; Korn, G.

2015-05-01

With the continuing development of laser systems, new important and so-far unexplored fields of research related to interaction of ultra-intense laser beams with matter are opening. At intensities of the order of 1022 W=cm2, electrons may be accelerated in the electromagnetic field of the laser wave and achieve such a high energy that they can enter the regime affected by the radiation reaction. Due to the non-linear Thomson and Compton scattering the accelerated electrons emit photons. The interaction of emitted photons with the laser field may result in effective generation of electron-positron pairs by means of the Breit-Wheeler process. In this work we study the influence of laser pulse polarization on gamma-ray generation during interaction of two colliding and tightly focused laser pulses with a low density target composed of electrons. This paper focuses on evolution of electron trajectories and key parameters χe (probability of photon emission) and χγ(probability of pair generation) in the laser field. These interactions are studied using 2D PIC simulations. It is shown that in the case of circularly polarized and tightly focused laser beams, electrons are not following circular trajectories at the magnetic node of the standing wave established in the focus, which leads to lowering the radiation emission efficiency.

Unraveling the role of secondary electrons upon their interaction with photoresist during EUV exposure

NASA Astrophysics Data System (ADS)

Pollentier, Ivan; Vesters, Yannick; Jiang, Jing; Vanelderen, Pieter; de Simone, Danilo

2017-10-01

The interaction of 91.6eV EUV photons with photoresist is very different to that of optical lithography at DUV wavelength. The latter is understood quite well and it is known that photons interact with the resist in a molecular way through the photoacid generator (PAG) of the chemically amplified resist (CAR). In EUV however, the high energy photons interact with the matter on atomic scale, resulting in the generation of secondary electrons. It is believed that these secondary electrons in their turn are responsible in chemical modification and lead to switching reactions that enable resist local dissolution. However, details of the interaction are still unclear, e.g. which reaction an electron with a given energy can initiate. In this work we have introduced a method to measure the chemical interaction of the secondary electrons with the EUV resist. The method is based on electron gun exposures of low energy electrons (range 1eV to 80eV) in the photoresist. The chemical interaction is then measured by Residual Gas Analysis (RGA), which can analyze out of the outgassing which and how much reaction products are generated. In this way a `chemical yield' can be quantified as function of electron energy. This method has been successfully applied to understand the interaction of secondary electrons on the traditional CAR materials. The understanding was facilitated by testing different compositions of an advanced EUV CAR, where resp. polymer only, polymer+PAG, and polymer+PAG+quencher are tested with the electron gun. It was found that low energy electrons down to 3-4eV can activate PAG dissociation, which can lead to polymer deprotection. However it was observed too that energy electrons of 12eV and higher can do direct deprotection even in absence of the PAG. In addition, testing suggests that electrons can generate also other chemical changes on the polymer chain that could lead to cross-linking.

Measurement of GEP/GMP to Q2 = 5.6 GEV2 via Recoil Polarization at Jefferson Lab

NASA Astrophysics Data System (ADS)

Gayou, Olivier

2001-10-01

The measurement of the elastic form factors is a key ingredient to any complete understanding of the internal structure of the nucleons, and ultimately of the strong force. Precise data are essential to impose stringent tests on any QCD-based theory. The electromagnetic interaction provides a unique tool to investigate these form factors. In elastic electron scattering off a proton, the electron interacts with the nucleon exchanging a virtual photon. The electron-photon interaction is fully understood from QED, hence making the hadron vertex the only unknown of the reaction...

Relativistic spin-orbit interactions of photons and electrons

NASA Astrophysics Data System (ADS)

Smirnova, D. A.; Travin, V. M.; Bliokh, K. Y.; Nori, F.

2018-04-01

Laboratory optics, typically dealing with monochromatic light beams in a single reference frame, exhibits numerous spin-orbit interaction phenomena due to the coupling between the spin and orbital degrees of freedom of light. Similar phenomena appear for electrons and other spinning particles. Here we examine transformations of paraxial photon and relativistic-electron states carrying the spin and orbital angular momenta (AM) under the Lorentz boosts between different reference frames. We show that transverse boosts inevitably produce a rather nontrivial conversion from spin to orbital AM. The converted part is then separated between the intrinsic (vortex) and extrinsic (transverse shift or Hall effect) contributions. Although the spin, intrinsic-orbital, and extrinsic-orbital parts all point in different directions, such complex behavior is necessary for the proper Lorentz transformation of the total AM of the particle. Relativistic spin-orbit interactions can be important in scattering processes involving photons, electrons, and other relativistic spinning particles, as well as when studying light emitted by fast-moving bodies.

Optical radiation from the interaction of energetic atoms, ions, electrons, and photons with surfaces

NASA Technical Reports Server (NTRS)

Tolk, N. H.; Albridge, R. G.; Haglund, R. F., Jr.; Mendenhall, M. H.

1985-01-01

Heavy particle, electron, and UV photon bombardment of solid surfaces has been recently observed to result in the emission of infrared, visible, and ultraviolet radiation. This effect occurs over a wide range of incident projectile energies. Line radiation arising from transitions between discrete atomic or molecular levels may be attributed to the decay of excited particles which have been sputtered or electronically/chemically desorbed from the surface. Broadband continuum radiation, which is also observed, is believed to arise either from fluorescence of the near surface bulk or from the radiative decay of desorbed excited clusters. Spacecraft, in the ambient near Earth environment, are subject to such bombardment. The dynamics of energetic particle and photon beam interactions with surfaces which lead to surface erosion and glow phenomena will be treated. In addition, projected experimental and theoretical studies of oxygen and nitrogen beam surface interactions on materials characteristic of spacecraft surfaces will be discussed.

Radiation effects in accelerator components

NASA Astrophysics Data System (ADS)

Borden, M. J.

1995-05-01

A review of basic radiation effects is presented. The fundamental definitions of radioactivity are given for alpha, beta, positron decay, gamma-ray emission and electron capture. The interaction of neutrons with material is covered including: absorption through radiative capture, neutron-proton interaction, alpha particle emission, neutron-multi-neutron reactions and fission. Basic equations defining inelastic and elastic scattering are presented with examples of neutron energy loss per collision for several elements. Photon interactions are considered for gamma-rays and x-rays. Photoelectric collisions, the Compton effect and pair production are reviewed. Electron-proton interactions are discussed with emphasis placed on defect production. Basic displacement damage mechanisms for photon and particle interaction are presented. Several examples of radiation effects to plastics, electronics and ceramics are presented. Extended references are given for each example.

Unified theory of quantized electrons, phonons, and photons out of equilibrium: A simplified ab initio approach based on the generalized Baym-Kadanoff ansatz

NASA Astrophysics Data System (ADS)

de Melo, Pedro Miguel M. C.; Marini, Andrea

2016-04-01

We present a full ab initio description of the coupled out-of-equilibrium dynamics of photons, phonons, and electrons. In the present approach, the quantized nature of the electromagnetic field as well as of the nuclear oscillations is fully taken into account. The result is a set of integrodifferential equations, written on the Keldysh contour, for the Green's functions of electrons, phonons, and photons where the different kinds of interactions are merged together. We then concentrate on the electronic dynamics in order to reduce the problem to a computationally feasible approach. By using the generalized Baym-Kadanoff ansatz and the completed collision approximation, we introduce a series of efficient but controllable approximations. In this way, we reduce all equations to a set of decoupled equations for the density matrix that describe all kinds of static and dynamical correlations. The final result is a coherent, general, and inclusive scheme to calculate several physical quantities: carrier dynamics, transient photoabsorption, and light emission, all of which include, at the same time, electron-electron, electron-phonon, and electron-photon interactions. We further discuss how all these observables can be easily calculated within the present scheme using a fully atomistic ab initio approach.

CEPXS

DOE Office of Scientific and Technical Information (OSTI.GOV)

2015-10-19

CEPXS is a multigroup-Legendre cross-section generating code. The cross sections produced by CEPXS enable coupled electron-photon transport calculations to be performed with multigroup radiation transport codes, e.g. MITS and SCEPTRE. CEPXS generates multigroup-Legendre cross sections for photons, electrons and positrons over the energy range from 100 MeV to 1.0 keV. The continuous slowing-down approximation is used for those electron interactions that result in small-energy losses. The extended transport correction is applied to the forward-peaked elastic scattering cross section for electrons. A standard multigroup-Legendre treatment is used for the other coupled electron-photon cross sections. CEPXS extracts electron cross-section information from themore » DATAPAC data set and photon cross-section information from Biggs-Lighthill data. The model that is used for ionization/relaxation in CEPXS is essentially the same as that employed in ITS.« less

Few-Photon Model of the Optical Emission of Semiconductor Quantum Dots

NASA Astrophysics Data System (ADS)

Richter, Marten; Carmele, Alexander; Sitek, Anna; Knorr, Andreas

2009-08-01

The Jaynes-Cummings model provides a well established theoretical framework for single electron two level systems in a radiation field. Similar exactly solvable models for semiconductor light emitters such as quantum dots dominated by many particle interactions are not known. We access these systems by a generalized cluster expansion, the photon-probability cluster expansion: a reliable approach for few-photon dynamics in many body electron systems. As a first application, we discuss vacuum Rabi oscillations and show that their amplitude determines the number of electrons in the quantum dot.

Directly tailoring photon-electron coupling for sensitive photoconductance

NASA Astrophysics Data System (ADS)

Huang, Zhiming; Zhou, Wei; Huang, Jingguo; Wu, Jing; Gao, Yanqing; Qu, Yue; Chu, Junhao

2016-03-01

The coupling between photons and electrons is at the heart of many fundamental phenomena in nature. Despite tremendous advances in controlling electrons by photons in engineered energy-band systems, control over their coupling is still widely lacking. Here we demonstrate an unprecedented ability to couple photon-electron interactions in real space, in which the incident electromagnetic wave directly tailors energy bands of solid to generate carriers for sensitive photoconductance. By spatially coherent manipulation of metal-wrapped material system through anti-symmetric electric field of the irradiated electromagnetic wave, electrons in the metals are injected and accumulated in the induced potential well (EIW) produced in the solid. Respective positive and negative electric conductances are easily observed in n-type and p-type semiconductors into which electrons flow down from the two metallic sides under light irradiation. The photoconductivity is further confirmed by sweeping the injected electrons out of the semiconductor before recombination applied by sufficiently strong electric fields. Our work opens up new perspectives for tailoring energy bands of solids and is especially relevant to develop high effective photon detection, spin injection, and energy harvesting in optoelectronics and electronics.

Neutron production in the interaction of 12 and 18 MeV electrons with a scattering foil inside a simple LINAC head.

PubMed

Soto-Bernal, Tzinnia Gabriela; Baltazar-Raigosa, Antonio; Medina-Castro, Diego; Vega-Carrillo, Hector Rene

2018-04-18

The characteristics of photons and neutrons produced during the interaction between a monoenergetic (12 and 18 MeV) electron beam and a tungsten scattering foil enclosed into a 10 cm-thick tungsten shell have been determined using Monte Carlo methods. This model was used aiming to represent a linac head working in electron-mode for cancer treatment. Photon and neutron spectra were determined around the scattering foil and to 50 and 100 cm below the electron source. Induced photons are mainly produced along the direction of the incoming electron beam. On the other hand, neutrons are produced in two sites, mainly in the inner surface of the linac head and in less extent in the scattering foil. The neutron spectra are evaporation neutrons which are emitted isotropically from the site where are produced leaking out from the linac head, reaching locations were the patient is allocated. Copyright © 2018 Elsevier Ltd. All rights reserved.

Handling Density Conversion in TPS.

PubMed

Isobe, Tomonori; Mori, Yutaro; Takei, Hideyuki; Sato, Eisuke; Tadano, Kiichi; Kobayashi, Daisuke; Tomita, Tetsuya; Sakae, Takeji

2016-01-01

Conversion from CT value to density is essential to a radiation treatment planning system. Generally CT value is converted to the electron density in photon therapy. In the energy range of therapeutic photon, interactions between photons and materials are dominated with Compton scattering which the cross-section depends on the electron density. The dose distribution is obtained by calculating TERMA and kernel using electron density where TERMA is the energy transferred from primary photons and kernel is a volume considering spread electrons. Recently, a new method was introduced which uses the physical density. This method is expected to be faster and more accurate than that using the electron density. As for particle therapy, dose can be calculated with CT-to-stopping power conversion since the stopping power depends on the electron density. CT-to-stopping power conversion table is also called as CT-to-water-equivalent range and is an essential concept for the particle therapy.

QED Based Calculation of the Fine Structure Constant

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lestone, John Paul

2016-10-13

Quantum electrodynamics is complex and its associated mathematics can appear overwhelming for those not trained in this field. Here, semi-classical approaches are used to obtain a more intuitive feel for what causes electrostatics, and the anomalous magnetic moment of the electron. These intuitive arguments lead to a possible answer to the question of the nature of charge. Virtual photons, with a reduced wavelength of λ, are assumed to interact with isolated electrons with a cross section of πλ 2. This interaction is assumed to generate time-reversed virtual photons that are capable of seeking out and interacting with other electrons. Thismore » exchange of virtual photons between particles is assumed to generate and define the strength of electromagnetism. With the inclusion of near-field effects the model presented here gives a fine structure constant of ~1/137 and an anomalous magnetic moment of the electron of ~0.00116. These calculations support the possibility that near-field corrections are the key to understanding the numerical value of the dimensionless fine structure constant.« less

Thermal conductivity and dielectric functions of alkali chloride XCl (X = Li, Na, K and Rb): a first-principles study

NASA Astrophysics Data System (ADS)

Xu, M.; Yang, J. Y.; Liu, L. H.

2016-07-01

The macroscopic physical properties of solids are fundamentally determined by the interactions among microscopic electrons, phonons and photons. In this work, the thermal conductivity and infrared-visible-ultraviolet dielectric functions of alkali chlorides and their temperature dependence are fully investigated at the atomic level, seeking to unveil the microscopic quantum interactions beneath the macroscopic properties. The microscopic phonon-phonon interaction dominates the thermal conductivity which can be investigated by the anharmonic lattice dynamics in combination with Peierls-Boltzmann transport equation. The photon-phonon and electron-photon interaction intrinsically induce the infrared and visible-ultraviolet dielectric functions, respectively, and such microscopic processes can be simulated by first-principles molecular dynamics without empirical parameters. The temperature influence on dielectric functions can be effectively included by choosing the thermally equilibrated configurations as the basic input to calculate the total dipole moment and electronic band structure. The overall agreement between first-principles simulations and literature experiments enables us to interpret the macroscopic thermal conductivity and dielectric functions of solids in a comprehensive way.

Overbias light emission due to higher-order quantum noise in a tunnel junction.

PubMed

Xu, F; Holmqvist, C; Belzig, W

2014-08-08

Understanding tunneling from an atomically sharp tip to a metallic surface requires us to account for interactions on a nanoscopic scale. Inelastic tunneling of electrons generates emission of photons, whose energies intuitively should be limited by the applied bias voltage. However, experiments [G. Schull et al., Phys. Rev. Lett. 102, 057401 (2009) indicate that more complex processes involving the interaction of electrons with plasmon polaritons lead to photon emission characterized by overbias energies. We propose a model of this observation in analogy to the dynamical Coulomb blockade, originally developed for treating the electronic environment in mesoscopic circuits. We explain the experimental finding quantitatively by the correlated tunneling of two electrons interacting with a LRC circuit modeling the local plasmon-polariton mode. To explain the overbias emission, the non-Gaussian statistics of the tunneling dynamics of the electrons is essential.

Two-Photon Study on the Electronic Interactions between the First Excited Singlet States in Carotenoid-Tetrapyrrole Dyads

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liao, Pen-Nan; Pillai, Smitha; Gust, Devens

Electronic interactions between the first excited states (S 1) of carotenoids (Car) of different conjugation lengths (8-11 double bonds) and phthalocyanines (Pc) in different Car-Pc dyad molecules were investigated by two-photon spectroscopy and compared with Car S 1-chlorophyll (Chl) interactions in photosynthetic light harvesting complexes (LHCs). The observation of Chl/Pc fluorescence after selective two-photon excitation of the Car S 1 state allowed sensitive monitoring of the flow of energy between Car S 1 and Pc or Chl. It is found that two-photon excitation excites to about 80% to 100% exclusively the carotenoid state Car S 1 and that only amore » small fraction of direct tetrapyrrole two-photon excitation occurs. Amide-linked Car-Pc dyads in tetrahydrofuran demonstrate a molecular gear shift mechanism in that effective Car S 1 → Pc energy transfer is observed in a dyad with 9 double bonds in the carotenoid, whereas in similar dyads with 11 double bonds in the carotenoid, the Pc fluorescence is strongly quenched by Pc → Car S 1 energy transfer. In phenylamino-linked Car-Pc dyads in toluene extremely large electronic interactions between the Car S 1 state and Pc were observed, particularly in the case of a dyad in which the carotenoid contained 10 double bonds. This observation together with previous findings in the same system provides strong evidence for excitonic Car S 1-Pc Q y interactions. Very similar results were observed with photosynthetic LHC II complexes in the past, supporting an important role of such interactions in photosynthetic down-regulation.« less

Phenomenology of ELDER dark matter

NASA Astrophysics Data System (ADS)

Kuflik, Eric; Perelstein, Maxim; Lorier, Nicolas Rey-Le; Tsai, Yu-Dai

2017-08-01

We explore the phenomenology of Elastically Decoupling Relic (ELDER) dark matter. ELDER is a thermal relic whose present density is determined primarily by the cross-section of its elastic scattering off Standard Model (SM) particles. Assuming that this scattering is mediated by a kinetically mixed dark photon, we argue that the ELDER scenario makes robust predictions for electron-recoil direct-detection experiments, as well as for dark photon searches. These predictions are independent of the details of interactions within the dark sector. Together with the closely related Strongly-Interacting Massive Particle (SIMP) scenario, the ELDER predictions provide a physically motivated, well-defined target region, which will be almost entirely accessible to the next generation of searches for sub-GeV dark matter and dark photons. We provide useful analytic approximations for various quantities of interest in the ELDER scenario, and discuss two simple renormalizable toy models which incorporate the required strong number-changing interactions among the ELDERs, as well as explicitly implement the coupling to electrons via the dark photon portal.

Superconducting fluctuations and characteristic time scales in amorphous WSi

NASA Astrophysics Data System (ADS)

Zhang, Xiaofu; Lita, Adriana E.; Sidorova, Mariia; Verma, Varun B.; Wang, Qiang; Nam, Sae Woo; Semenov, Alexei; Schilling, Andreas

2018-05-01

We study magnitudes and temperature dependencies of the electron-electron and electron-phonon interaction times which play the dominant role in the formation and relaxation of photon-induced hotspots in two-dimensional amorphous WSi films. The time constants are obtained through magnetoconductance measurements in a perpendicular magnetic field in the superconducting fluctuation regime and through time-resolved photoresponse to optical pulses. The excess magnetoconductivity is interpreted in terms of the weak-localization effect and superconducting fluctuations. Aslamazov-Larkin and Maki-Thompson superconducting fluctuations alone fail to reproduce the magnetic field dependence in the relatively high magnetic field range when the temperature is rather close to Tc because the suppression of the electronic density of states due to the formation of short-lifetime Cooper pairs needs to be considered. The time scale τi of inelastic scattering is ascribed to a combination of electron-electron (τe -e) and electron-phonon (τe -p h) interaction times, and a characteristic electron-fluctuation time (τe -f l) , which makes it possible to extract their magnitudes and temperature dependencies from the measured τi. The ratio of phonon-electron (τp h -e) and electron-phonon interaction times is obtained via measurements of the optical photoresponse of WSi microbridges. Relatively large τe -p h/τp h -e and τe -p h/τe -e ratios ensure that in WSi the photon energy is more efficiently confined in the electron subsystem than in other materials commonly used in the technology of superconducting nanowire single-photon detectors (SNSPDs). We discuss the impact of interaction times on the hotspot dynamics and compare relevant metrics of SNSPDs from different materials.

Unraveling the role of photons and electrons upon their chemical interaction with photoresist during EUV exposure

NASA Astrophysics Data System (ADS)

Pollentier, Ivan; Vesters, Yannick; Petersen, John S.; Vanelderen, Pieter; Rathore, Atish; de Simone, Danilo; Vandenberghe, Geert

2018-03-01

The interaction of 91.6 eV EUV photons with photoresist - in particular chemically amplified resist (CAR) - is different than exposure at 193 nm and 248 nm wavelengths. The latter is understood well and it is known that photons interact with electrons in the resist's molecular valence orbitals (for chemically amplified resist (CAR) the photon interacts with the photo acid generator (PAG), which leads to a deprotection reaction on a polymer after a thermal catalytic reaction during a post-exposure-bake.). At EUV however, more steps are involved in the radiolysis process between the absorption of the photon and the final chemical modification. These are related to the generation of primary electrons and their decay to lower energy secondary electrons, and most of this steps are not well understood. In this paper, the reaction products from EUV and low energy electron exposure are examined using Residual Gas Analysis (RGA), which measures and analyzes the outgassing products related to the ongoing reactions. This investigation is applied firstly on a model CAR where details of the resist chemical constituents were known prior to testing. The measurement not only resolved information on the expected acid related reactions from the PAG and protection groups, but also exhibited direct scission reactions of the polymer, where some of them lead to polymerization reactions. Moreover, the measurement quantifies the balance between the different ongoing reactions, which were confirmed by contrast curve measurements. Based on learnings on the model resist, applied the measurement technique to commercial resists, where actual resist chemistry composition is not known. Despite that, it was found that information could be deduced to distinguish between acid related ongoing reactions and direct scission of reaction on the base polymer and quantify their relation. Moreover, different generations of commercial resists based on similar chemistry platform were investigated, which revealed that improvements in printing performance could be explained by PAG reaction yield increase.

On thermalization of electron-positron-photon plasma

NASA Astrophysics Data System (ADS)

Siutsou, I. A.; Aksenov, A. G.; Vereshchagin, G. V.

2015-12-01

Recently a progress has been made in understanding thermalization mechanism of relativistic plasma starting from a non-equilibrium state. Relativistic Boltzmann equations were solved numerically for homogeneous isotropic plasma with collision integrals for two- and three-particle interactions calculated from the first principles by means of QED matrix elements. All particles were assumed to fulfill Boltzmann statistics. In this work we follow plasma thermalization by accounting for Bose enhancement and Pauli blocking in particle interactions. Our results show that particle in equilibrium reach Bose-Einstein distribution for photons, and Fermi-Dirac one for electrons, respectively.

Monte Carlo calculations of initial energies of electrons in water irradiated by photons with energies up to 1GeV.

PubMed

Todo, A S; Hiromoto, G; Turner, J E; Hamm, R N; Wright, H A

1982-12-01

Previous calculations of the initial energies of electrons produced in water irradiated by photons are extended to 1 GeV by including pair and triplet production. Calculations were performed with the Monte Carlo computer code PHOEL-3, which replaces the earlier code, PHOEL-2. Tables of initial electron energies are presented for single interactions of monoenergetic photons at a number of energies from 10 keV to 1 GeV. These tables can be used to compute kerma in water irradiated by photons with arbitrary energy spectra to 1 GeV. In addition, separate tables of Compton-and pair-electron spectra are given over this energy range. The code PHOEL-3 is available from the Radiation Shielding Information Center, Oak Ridge National Laboratory, Oak Ridge, TN 37830.

Ab Initio Optimized Effective Potentials for Real Molecules in Optical Cavities: Photon Contributions to the Molecular Ground State

PubMed Central

2018-01-01

We introduce a simple scheme to efficiently compute photon exchange-correlation contributions due to the coupling to transversal photons as formulated in the newly developed quantum-electrodynamical density-functional theory (QEDFT).1−5 Our construction employs the optimized-effective potential (OEP) approach by means of the Sternheimer equation to avoid the explicit calculation of unoccupied states. We demonstrate the efficiency of the scheme by applying it to an exactly solvable GaAs quantum ring model system, a single azulene molecule, and chains of sodium dimers, all located in optical cavities and described in full real space. While the first example is a two-dimensional system and allows to benchmark the employed approximations, the latter two examples demonstrate that the correlated electron-photon interaction appreciably distorts the ground-state electronic structure of a real molecule. By using this scheme, we not only construct typical electronic observables, such as the electronic ground-state density, but also illustrate how photon observables, such as the photon number, and mixed electron-photon observables, for example, electron–photon correlation functions, become accessible in a density-functional theory (DFT) framework. This work constitutes the first three-dimensional ab initio calculation within the new QEDFT formalism and thus opens up a new computational route for the ab initio study of correlated electron–photon systems in quantum cavities. PMID:29594185

Photon gating in four-dimensional ultrafast electron microscopy.

PubMed

Hassan, Mohammed T; Liu, Haihua; Baskin, John Spencer; Zewail, Ahmed H

2015-10-20

Ultrafast electron microscopy (UEM) is a pivotal tool for imaging of nanoscale structural dynamics with subparticle resolution on the time scale of atomic motion. Photon-induced near-field electron microscopy (PINEM), a key UEM technique, involves the detection of electrons that have gained energy from a femtosecond optical pulse via photon-electron coupling on nanostructures. PINEM has been applied in various fields of study, from materials science to biological imaging, exploiting the unique spatial, energy, and temporal characteristics of the PINEM electrons gained by interaction with a "single" light pulse. The further potential of photon-gated PINEM electrons in probing ultrafast dynamics of matter and the optical gating of electrons by invoking a "second" optical pulse has previously been proposed and examined theoretically in our group. Here, we experimentally demonstrate this photon-gating technique, and, through diffraction, visualize the phase transition dynamics in vanadium dioxide nanoparticles. With optical gating of PINEM electrons, imaging temporal resolution was improved by a factor of 3 or better, being limited only by the optical pulse widths. This work enables the combination of the high spatial resolution of electron microscopy and the ultrafast temporal response of the optical pulses, which provides a promising approach to attain the resolution of few femtoseconds and attoseconds in UEM.

Teaching Quantum Nonlocality

ERIC Educational Resources Information Center

Hobson, Art

2012-01-01

Nonlocality arises from the unified "all or nothing" interactions of a spatially extended field quantum such as a photon or an electron. In the double-slit experiment with light, for example, each photon comes through both slits and arrives at the viewing screen as an extended but unified energy bundle or "field quantum." When the photon interacts…

Spin-dependent heat and thermoelectric currents in a Rashba ring coupled to a photon cavity

NASA Astrophysics Data System (ADS)

Abdullah, Nzar Rauf; Tang, Chi-Shung; Manolescu, Andrei; Gudmundsson, Vidar

2018-01-01

Spin-dependent heat and thermoelectric currents in a quantum ring with Rashba spin-orbit interaction placed in a photon cavity are theoretically calculated. The quantum ring is coupled to two external leads with different temperatures. In a resonant regime, with the ring structure in resonance with the photon field, the heat and the thermoelectric currents can be controlled by the Rashba spin-orbit interaction. The heat current is suppressed in the presence of the photon field due to contribution of the two-electron and photon replica states to the transport while the thermoelectric current is not sensitive to changes in parameters of the photon field. Our study opens a possibility to use the proposed interferometric device as a tunable heat current generator in the cavity photon field.

Modulated phases of graphene quantum Hall polariton fluids

PubMed Central

Pellegrino, Francesco M. D.; Giovannetti, Vittorio; MacDonald, Allan H.; Polini, Marco

2016-01-01

There is a growing experimental interest in coupling cavity photons to the cyclotron resonance excitations of electron liquids in high-mobility semiconductor quantum wells or graphene sheets. These media offer unique platforms to carry out fundamental studies of exciton-polariton condensation and cavity quantum electrodynamics in a regime, in which electron–electron interactions are expected to play a pivotal role. Here, focusing on graphene, we present a theoretical study of the impact of electron–electron interactions on a quantum Hall polariton fluid, that is a fluid of magneto-excitons resonantly coupled to cavity photons. We show that electron–electron interactions are responsible for an instability of graphene integer quantum Hall polariton fluids towards a modulated phase. We demonstrate that this phase can be detected by measuring the collective excitation spectra, which is often at a characteristic wave vector of the order of the inverse magnetic length. PMID:27841346

Optical control of spin-dependent thermal transport in a quantum ring

NASA Astrophysics Data System (ADS)

Abdullah, Nzar Rauf

2018-05-01

We report on calculation of spin-dependent thermal transport through a quantum ring with the Rashba spin-orbit interaction. The quantum ring is connected to two electron reservoirs with different temperatures. Tuning the Rashba coupling constant, degenerate energy states are formed leading to a suppression of the heat and thermoelectric currents. In addition, the quantum ring is coupled to a photon cavity with a single photon mode and linearly polarized photon field. In a resonance regime, when the photon energy is approximately equal to the energy spacing between two lowest degenerate states of the ring, the polarized photon field can significantly control the heat and thermoelectric currents in the system. The roles of the number of photon initially in the cavity, and electron-photon coupling strength on spin-dependent heat and thermoelectric currents are presented.

MCNP6.1 simulations for low-energy atomic relaxation: Code-to-code comparison with GATEv7.2, PENELOPE2014, and EGSnrc

NASA Astrophysics Data System (ADS)

Jung, Seongmoon; Sung, Wonmo; Lee, Jaegi; Ye, Sung-Joon

2018-01-01

Emerging radiological applications of gold nanoparticles demand low-energy electron/photon transport calculations including details of an atomic relaxation process. Recently, MCNP® version 6.1 (MCNP6.1) has been released with extended cross-sections for low-energy electron/photon, subshell photoelectric cross-sections, and more detailed atomic relaxation data than the previous versions. With this new feature, the atomic relaxation process of MCNP6.1 has not been fully tested yet with its new physics library (eprdata12) that is based on the Evaluated Atomic Data Library (EADL). In this study, MCNP6.1 was compared with GATEv7.2, PENELOPE2014, and EGSnrc that have been often used to simulate low-energy atomic relaxation processes. The simulations were performed to acquire both photon and electron spectra produced by interactions of 15 keV electrons or photons with a 10-nm-thick gold nano-slab. The photon-induced fluorescence X-rays from MCNP6.1 fairly agreed with those from GATEv7.2 and PENELOPE2014, while the electron-induced fluorescence X-rays of the four codes showed more or less discrepancies. A coincidence was observed in the photon-induced Auger electrons simulated by MCNP6.1 and GATEv7.2. A recent release of MCNP6.1 with eprdata12 can be used to simulate the photon-induced atomic relaxation.

Microgap ultra-violet detector

DOEpatents

Wuest, Craig R.; Bionta, Richard M.

1994-01-01

A microgap ultra-violet detector of photons with wavelengths less than 400 run (4000 Angstroms) which comprises an anode and a cathode separated by a gas-filled gap and having an electric field placed across the gap. Either the anode or the cathode is semi-transparent to UV light. Upon a UV photon striking the cathode an electron is expelled and accelerated across the gap by the electric field causing interactions with other electrons to create an electron avalanche which contacts the anode. The electron avalanche is detected and converted to an output pulse.

Microgap ultra-violet detector

DOEpatents

Wuest, C.R.; Bionta, R.M.

1994-09-20

A microgap ultra-violet detector of photons with wavelengths less than 400 run (4,000 Angstroms) which comprises an anode and a cathode separated by a gas-filled gap and having an electric field placed across the gap is disclosed. Either the anode or the cathode is semi-transparent to UV light. Upon a UV photon striking the cathode an electron is expelled and accelerated across the gap by the electric field causing interactions with other electrons to create an electron avalanche which contacts the anode. The electron avalanche is detected and converted to an output pulse. 2 figs.

Short-pulse, high-energy radiation generation from laser-wakefield accelerated electron beams

NASA Astrophysics Data System (ADS)

Schumaker, Will

2013-10-01

Recent experimental results of laser wakefield acceleration (LWFA) of ~GeV electrons driven by the 200TW HERCULES and the 400TW ASTRA-GEMINI laser systems and their subsequent generation of photons, positrons, and neutrons are presented. In LWFA, high-intensity (I >1019 W /cm2), ultra-short (τL < 1 / (2 πωpe)) laser pulses drive highly nonlinear plasma waves which can trap ~ nC of electrons and accelerate them to ~GeV energies over ~cm lengths. These electron beams can then be converted by a high-Z target via bremsstrahlung into low-divergence (< 20 mrad) beams of high-energy (<600 MeV) photons and subsequently into positrons via the Bethe-Heitler process. By increasing the material thickness and Z, the resulting Ne+ /Ne- ratio can approach unity, resulting in a near neutral density plasma jet. These quasi-neutral beams are presumed to retain the short-pulse (τL < 40 fs) characteristic of the electron beam, resulting in a high peak density of ne- /e+ ~ 1016 cm-3 , making the source an excellent candidate for laboratory study of astrophysical leptonic jets. Alternatively, the electron beam can be interacted with a counter-propagating, ultra-high intensity (I >1021 W /cm2) laser pulse to undergo inverse Compton scattering and emit a high-peak brightness beam of high-energy photons. Preliminary results and experimental sensitivities of the electron-laser beam overlap are presented. The high-energy photon beams can be spectrally resolved using a forward Compton scattering spectrometer. Moreover, the photon flux can be characterized by a pixelated scintillator array and by nuclear activation and (γ,n) neutron measurements from the photons interacting with a secondary solid target. Monte-Carlo simulations were performed using FLUKA to support the yield estimates. This research was supported by DOE/NSF-PHY 0810979, NSF CAREER 1054164, DARPA AXiS N66001-11-1-4208, SF/DNDO F021166, and the Leverhulme Trust ECF-2011-383.

Search for Excited or Exotic Electron Production Using the Dielectron + Photon Signature at CDF in Run II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gerberich, Heather Kay

The author presents a search for excited or exotic electrons decaying to an electron and a photon with high transverse momentum. An oppositely charged electron is produced in association with the excited electron, yielding a final state dielectron + photon signature. The discovery of excited electrons would be a first indication of lepton compositeness. They use ~ 202 pb -1 of data collected in pmore » $$\\bar{p}$$ collisions at √s = 1.96 TeV with the Collider Detector at Fermilab during March 2001 through September 2003. The data are consistent with standard model expectations. Upper limits are set on the experimental cross-section σ($$\\bar{p}$$p → ee* → eeγ) at the 95% confidence level in a contact-interaction model and a gauge-mediated interaction model. Limits are also presented as exclusion regions in the parameter space of the excited electron mass (M e*) and the compositeness energy scale (Λ). In the contact-interaction model, for which there are no previously published limits, they find M e* < 906 GeV is excluded for M e* = Λ. In the gauge-mediated model, the exclusion region in the M e* versus the phenomenological coupling f/Λ parameter space is extended to M{sub e*} < 430 GeV for f/Λ ~ 10 -2 GeV -1. In comparison, other experiments have excluded M e* < 280 GeV for f/Λ ~ 10 -2 GeV -1.« less

Non-thermal damage to lead tungstate induced by intense short-wavelength laser radiation (Conference Presentation)

NASA Astrophysics Data System (ADS)

Vozda, Vojtech; Boháček, Pavel; Burian, Tomáš; Chalupský, Jaromir; Hájková, Vera; Juha, Libor; Vyšín, Ludek; Gaudin, Jérôme; Heimann, Philip A.; Hau-Riege, Stefan P.; Jurek, Marek; Klinger, Dorota; Krzywinski, Jacek; Messerschmidt, Marc; Moeller, Stefan P.; Nagler, Robert; Pelka, Jerzy B.; Rowen, Michael; Schlotter, William F.; Swiggers, Michele L.; Sinn, Harald; Sobierajski, Ryszard; Tiedtke, Kai; Toleikis, Sven; Tschentscher, Thomas; Turner, Joshua J.; Wabnitz, Hubertus; Nelson, Art J.; Kozlova, Maria V.; Vinko, Sam M.; Whitcher, Thomas; Dzelzainis, Thomas; Renner, Oldrich; Saksl, Karel; Fäustlin, Roland R.; Khorsand, Ali R.; Fajardo, Marta; Iwan, Bianca S.; Andreasson, Jakob; Hajdu, Janos; Timneanu, Nicusor; Wark, Justin S.; Riley, David; Lee, Richard W.; Nagasono, Mitsuru; Yabashi, Makina

2017-05-01

Interaction of short-wavelength free-electron laser (FEL) beams with matter is undoubtedly a subject to extensive investigation in last decade. During the interaction various exotic states of matter, such as warm dense matter, may exist for a split second. Prior to irreversible damage or ablative removal of the target material, complicated electronic processes at the atomic level occur. As energetic photons impact the target, electrons from inner atomic shells are almost instantly photo-ionized, which may, in some special cases, cause bond weakening, even breaking of the covalent bonds, subsequently result to so-called non-thermal melting. The subject of our research is ablative damage to lead tungstate (PbWO4) induced by focused short-wavelength FEL pulses at different photon energies. Post-mortem analysis of complex damage patterns using the Raman spectroscopy, atomic-force (AFM) and Nomarski (DIC) microscopy confirms an existence of non-thermal melting induced by high-energy photons in the ionic monocrystalline target. Results obtained at Linac Coherent Light Source (LCLS), Free-electron in Hamburg (FLASH), and SPring-8 Compact SASE Source (SCSS) are presented in this Paper.

Comparison of deep inelastic scattering with photoproduction interactions at HERA

NASA Astrophysics Data System (ADS)

Aid, S.; Andreev, V.; Andrieu, B.; Appuhn, R.-D.; Arpagaus, M.; Babaev, A.; Bähr, J.; Bán, J.; Ban, Y.; Baranov, P.; Barrelet, E.; Barschke, R.; Bartel, W.; Barth, M.; Bassler, U.; Beck, H. P.; Behrend, H.-J.; Belousov, A.; Berger, Ch.; Bernardi, G.; Bernet, R.; Bertrand-Coremans, G.; Besançon, M.; Beyer, R.; Biddulph, P.; Bispham, P.; Bizot, J. C.; Blobel, V.; Borras, K.; Botterweck, F.; Boudry, V.; Bourov, S.; Braemer, A.; Brasse, F.; Braunschweig, W.; Brisson, V.; Bruncko, D.; Brune, C.; Buchholz, R.; Büngener, L.; Bürger, J.; Büsser, F. W.; Buniatian, A.; Burke, S.; Burton, M. J.; Buschhorn, G.; Campbell, A. J.; Carli, T.; Charles, F.; Charlet, M.; Clarke, D.; Clegg, A. B.; Clerbaux, B.; Contreras, J. G.; Cormack, C.; Coughlan, J. A.; Courau, A.; Coutures, Ch.; Cozzika, G.; Criegee, L.; Cussans, D. G.; Cvach, J.; Dagoret, S.; Dainton, J. B.; Dau, W. D.; Daum, K.; David, M.; Davis, C. L.; Delcourt, B.; Del Buono, L.; De Roeck, A.; De Wolf, E. A.; Dixon, P.; Di Nezza, P.; Dollfus, C.; Dowell, J. D.; Dreis, H. B.; Droutskoi, A.; Duboc, J.; Düllmann, D.; Dünger, O.; Duhm, H.; Ebert, J.; Ebert, T. R.; Eckerlin, G.; Efremenko, V.; Egli, S.; Ehrlichmann, H.; Eichenberger, S.; Eichler, R.; Eisele, F.; Eisenhandler, E.; Ellison, R. J.; Elsen, E.; Erdmann, M.; Erdmann, W.; Evrard, E.; Favart, L.; Fedotov, A.; Feeken, D.; Felst, R.; Feltesse, J.; Ferencei, J.; Ferrarotto, F.; Flamm, K.; Fleischer, M.; Flieser, M.; Flügge, G.; Fomenko, A.; Fominykh, B.; Forbush, M.; Formánek, J.; Foster, J. M.; Franke, G.; Fretwurst, E.; Gabathuler, E.; Gabathuler, K.; Garvey, J.; Gayler, J.; Gebauer, M.; Gellrich, A.; Genzel, H.; Gerhards, R.; Glazov, A.; Goerlach, U.; Goerlich, L.; Gogitidze, N.; Goldberg, M.; Goldner, D.; Gonzalez-Pineiro, B.; Gorelov, I.; Goritchev, P.; Grab, C.; Grässler, H.; Grässler, R.; Greenshaw, T.; Griffiths, R.; Grindhammer, G.; Gruber, A.; Gruber, C.; Haack, J.; Haidt, D.; Hajduk, L.; Hamon, O.; Hampel, M.; Hapke, M.; Haynes, W. J.; Heatherington, J.; Heinzelmann, G.; Henderson, R. C. W.; Henschel, H.; Herynek, I.; Hess, M. F.; Hildesheim, W.; Hill, P.; Hiller, K. H.; Hilton, C. D.; Hladký, J.; Hoeger, K. C.; Höppner, M.; Horisberger, R.; Hudgson, V. L.; Huet, Ph.; Hütte, M.; Hufnagel, H.; Ibbotson, M.; Itterbeck, H.; Jabiol, M.-A.; Jacholkowska, A.; Jacobsson, C.; Jaffre, M.; Janoth, J.; Jansen, T.; Jönsson, L.; Johnson, D. P.; Johnson, L.; Jung, H.; Kalmus, P. I. P.; Kant, D.; Kaschowitz, R.; Kasselmann, P.; Kathage, U.; Katzy, J.; Kaufmann, H. H.; Kazarian, S.; Kenyon, I. R.; Kermiche, S.; Keuker, C.; Kiesling, C.; Klein, M.; Kleinwort, C.; Knies, G.; Ko, W.; Köhler, T.; Köhne, J. H.; Kolanoski, H.; Kole, F.; Kolya, S. D.; Korbel, V.; Korn, M.; Kostka, P.; Kotelnikov, S. K.; Krämerkämper, T.; Krasny, M. W.; Krehbiel, H.; Krücker, D.; Krüger, U.; Krüner-Marquis, U.; Küster, H.; Kuhlen, M.; Kurča, T.; Kurzhöfer, J.; Kuznik, B.; Lacour, D.; Laforge, B.; Lamarche, F.; Lander, R.; Landon, M. P. J.; Lange, W.; Lanius, P.; Laporte, J.-F.; Lebedev, A.; Lehner, F.; Leverenz, C.; Levonian, S.; Ley, Ch.; Lindström, G.; Link, J.; Linsel, F.; Lipinski, J.; List, B.; Lobo, G.; Loch, P.; Lohmander, H.; Lomas, J. W.; Lopez, G. C.; Lubimov, V.; Lüke, D.; Magnussen, N.; Malinovski, E.; Mani, S.; Maraček, R.; Marage, P.; Marks, J.; Marshall, R.; Martens, J.; Martin, G.; Martin, R.; Martyn, H.-U.; Martyniak, J.; Masson, S.; Mavroidis, T.; Maxfield, S. J.; McMahon, S. J.; Mehta, A.; Meier, K.; Mercer, D.; Merz, T.; Meyer, A.; Meyer, C. A.; Meyer, H.; Meyer, J.; Meyer, P.-O.; Migliori, A.; Mikocki, S.; Milstead, D.; Moreau, F.; Morris, J. V.; Mroczko, E.; Müller, G.; Müller, K.; Murín, P.; Nagovizin, V.; Nahnhauer, R.; Naroska, B.; Naumann, Th.; Newman, P. R.; Newton, D.; Neyret, D.; Nguyen, H. K.; Nicholls, T. C.; Niebergall, F.; Niebuhr, C.; Niedzballa, Ch.; Nisius, R.; Nowak, G.; Noyes, G. W.; Nyberg-Werther, M.; Oakden, M.; Oberlack, H.; Obrock, U.; Olsson, J. E.; Ozerov, D.; Palmen, P.; Panaro, E.; Panitch, A.; Pascaud, C.; Patel, G. D.; Pawletta, H.; Peppel, E.; Perez, E.; Phillips, J. P.; Pichler, Ch.; Pieuchot, A.; Pitzl, D.; Pope, G.; Prell, S.; Prosi, R.; Rabbertz, K.; Rädel, G.; Raupach, F.; Reimer, P.; Reinshagen, S.; Ribarics, P.; Rick, H.; Riech, V.; Riedlberger, J.; Riess, S.; Rietz, M.; Rizvi, E.; Robertson, S. M.; Robmann, P.; Roloff, H. E.; Roosen, R.; Rosenbauer, K.; Rostovtsev, A.; Rouse, F.; Royon, C.; Rüter, K.; Rusakov, S.; Rybicki, K.; Rylko, R.; Sahlmann, N.; Sankey, D. P. C.; Schacht, P.; Schiek, S.; Schleif, S.; Schleper, P.; von Schlippe, W.; Schmidt, D.; Schmidt, G.; Schöning, A.; Schröder, V.; Schuhmann, E.; Schwab, B.; Sciacca, G.; Sefkow, F.; Seidel, M.; Sell, R.; Semenov, A.; Shekelyan, V.; Sheviakov, I.; Shtarkov, L. N.; Siegmon, G.; Siewert, U.; Sirois, Y.; Skillicorn, I. O.; Smirnov, P.; Smith, J. R.; Solochenko, V.; Soloviev, Y.; Spiekermann, J.; Spielman, S.; Spitzer, H.; Starosta, R.; Steenbock, M.; Steffen, P.; Steinberg, R.; Stella, B.; Stephens, K.; Stier, J.; Stiewe, J.; Stößlein, U.; Stolze, K.; Strachota, J.; Straumann, U.; Struczinski, W.; Sutton, J. P.; Tapprogge, S.; Tchernyshov, V.; Theissen, J.; Thiebaux, C.; Thompson, G.; Truöl, P.; Turnau, J.; Tutas, J.; Uelkes, P.; Usik, A.; Valkár, S.; Valkárová, A.; Vallée, C.; Vandenplas, D.; Van Esch, P.; Van Mechelen, P.; Vartapetian, A.; Vazdik, Y.; Verrecchia, P.; Villet, G.; Wacker, K.; Wagener, A.; Wagener, M.; Walther, A.; Waugh, B.; Weber, G.; Weber, M.; Wegener, D.; Wegner, A.; Wellisch, H. P.; West, L. R.; Willard, S.; Winde, M.; Winter, G.-G.; Wittek, C.; Wright, A. E.; Wünsch, E.; Wulff, N.; Yiou, T. P.; Žáček, J.; Zarbock, D.; Zhang, Z.; Zhokin, A.; Zimmer, M.; Zimmermann, W.; Zomer, F.; Zsembery, J.; Zuber, K.; zurNedden, M.; H1 Collaboration

1995-02-01

Photon-proton ( γp) interactions with Q 2 < 10 -2 GeV 2 and deep-inelastic scattering ( γ ∗p ) interactions with photon virtualities Q 2 > 5 GeV 2 are studied at the high energy electron-proton collider HERA. The transverse energy flow and relative rates of large rapidity gap events are compared in the two event samples. The observed similarity between γp and γ ∗p interactions can be understood in a picture where the photon develops as a hadronic object. The transverse energy density measured in the central region of the collision, at η ∗ = 0 in the γ ∗p centre of mass frame, is compared with data from hadron-hadron interactions as function of the CMS energy of the collision.

Mechanisms of EUV exposure: electrons and holes

NASA Astrophysics Data System (ADS)

Narasimhan, Amrit; Grzeskowiak, Steven; Ackerman, Christian; Flynn, Tracy; Denbeaux, Greg; Brainard, Robert L.

2017-03-01

In extreme ultraviolet (EUV) lithography, 92 eV photons are used to expose photoresists. Current EUV photoresists are composed of photoacid generators (PAGs) in polymer matrices. Secondary electrons (2 - 80 eV) created in resists during EUV exposure play large role in acid-production. There are several proposed mechanisms for electron-resist interactions: internal excitation, electron trapping, and hole-initiated chemistry. Here, we will address two central questions in EUV resist research: (1) How many electrons are generated per EUV photon absorption? (2) By which mechanisms do these electrons interact and react with molecules in the resist? We will use this framework to evaluate the contributions of electron trapping and hole initiated chemistry to acid production in chemically amplified photoresists, with specific emphasis on the interdependence of these mechanisms. We will show measurements of acid yield from direct bulk electrolysis of PAGs and EUV exposures of PAGs in phenolic and nonphenolic polymers to narrow down the mechanistic possibilities in chemically amplified resists.

Direct Dark Matter Detection through the use of a Xenon Based TPC Detector

NASA Astrophysics Data System (ADS)

Daniel, Jonathan; Akerib, Daniel; LZ group at SLAC

2018-01-01

The vast majority of matter in the universe is unaccounted for. Only 15% of the universe's mass density is visible matter, while the other 85% is Dark Matter (DM). The Weakly Interacting Massive Particle (WIMP) is currently the frontrunner of the DM candidates. The Large Underground Xenon (LUX) and next generation LUX-ZEPLIN (LZ) experiments are designed to directly detect WIMPs. Both experiments are xenon-based Time Projection Chambers (TPC) used to observe possible WIMP interactions. These interactions produce photons and electrons with the photons being collected in a set of two photomultiplier tube (PMT) arrays and the electrons drifted upwards in the detector by a strong electric field to create a secondary production of photons in gaseous xenon. These two populations of photons are classified as S1 and S2 signals, respectively. Using these signals we reconstruct the energy and position of the interaction and in doing so we can eliminate background events that would otherwise “light up” the detector. My participation in the experiment, while at SLAC, was the creation of the grids that produce the large electric field, along with additional lab activities aimed at testing the grids. While at Stan State, I work on background modeling in order to distinguish a possible WIMP signal from ambient backgrounds.

Quantum optical signatures in strong-field laser physics: Infrared photon counting in high-order-harmonic generation.

PubMed

Gonoskov, I A; Tsatrafyllis, N; Kominis, I K; Tzallas, P

2016-09-07

We analytically describe the strong-field light-electron interaction using a quantized coherent laser state with arbitrary photon number. We obtain a light-electron wave function which is a closed-form solution of the time-dependent Schrödinger equation (TDSE). This wave function provides information about the quantum optical features of the interaction not accessible by semi-classical theories. With this approach we can reveal the quantum optical properties of high harmonic generation (HHG) process in gases by measuring the photon statistics of the transmitted infrared (IR) laser radiation. This work can lead to novel experiments in high-resolution spectroscopy in extreme-ultraviolet (XUV) and attosecond science without the need to measure the XUV light, while it can pave the way for the development of intense non-classical light sources.

Double photoionization of the Be isoelectronic sequence

NASA Astrophysics Data System (ADS)

Barmaki, S.; Albert, M. A.; Belliveau, J.; Laulan, S.

2018-05-01

We investigate the double photoionization (DPI) process along the Be isoelectronic sequence (Be‑Ne6+) by solving the time-dependent Schrödinger equation with a spectral method of configuration interaction type. The results that we obtain of the DPI cross sections are in a good agreement with other reported data. We also present the first results of double-to-single photoionization cross sections ratios for Be-like ions in support of possible photofragmentation experiments with x-ray free electron lasers. Finally, we probe the mutual interaction of the valence electrons at different photon energies and examine the subsequent redistribution of the excess photon energy among them.

Ionization of deep quantum wells: Optical trampoline effect

NASA Astrophysics Data System (ADS)

Perlin, E. Yu.; Levitskiĭ, R. S.

2007-02-01

A new mechanism of transitions of an electronic system from the ground state to states with excitation energies exceeding many times the energy of a light photon initiating the transitions has been considered. This mechanism is based on the so-called optical “trampoline” effect: one of the interacting electrons receives energy from another electron and, simultaneously absorbing a photon ħω, overcomes the energy gap significantly exceeding ħω. Ionization of deep quantum wells by low-frequency light of moderate intensity due to the optical trampoline effect was calculated.

Method and apparatus for detecting neutrons

DOEpatents

Perkins, R.W.; Reeder, P.L.; Wogman, N.A.; Warner, R.A.; Brite, D.W.; Richey, W.C.; Goldman, D.S.

1997-10-21

The instant invention is a method for making and using an apparatus for detecting neutrons. Scintillating optical fibers are fabricated by melting SiO{sub 2} with a thermal neutron capturing substance and a scintillating material in a reducing atmosphere. The melt is then drawn into fibers in an anoxic atmosphere. The fibers may then be coated and used directly in a neutron detection apparatus, or assembled into a geometrical array in a second, hydrogen-rich, scintillating material such as a polymer. Photons generated by interaction with thermal neutrons are trapped within the coated fibers and are directed to photoelectric converters. A measurable electronic signal is generated for each thermal neutron interaction within the fiber. These electronic signals are then manipulated, stored, and interpreted by normal methods to infer the quality and quantity of incident radiation. When the fibers are arranged in an array within a second scintillating material, photons generated by kinetic neutrons interacting with the second scintillating material and photons generated by thermal neutron capture within the fiber can both be directed to photoelectric converters. These electronic signals are then manipulated, stored, and interpreted by normal methods to infer the quality and quantity of incident radiation. 5 figs.

Method and apparatus for detecting neutrons

DOEpatents

Perkins, Richard W.; Reeder, Paul L.; Wogman, Ned A.; Warner, Ray A.; Brite, Daniel W.; Richey, Wayne C.; Goldman, Don S.

1997-01-01

The instant invention is a method for making and using an apparatus for detecting neutrons. Scintillating optical fibers are fabricated by melting SiO.sub.2 with a thermal neutron capturing substance and a scintillating material in a reducing atmosphere. The melt is then drawn into fibers in an anoxic atmosphere. The fibers may then be coated and used directly in a neutron detection apparatus, or assembled into a geometrical array in a second, hydrogen-rich, scintillating material such as a polymer. Photons generated by interaction with thermal neutrons are trapped within the coated fibers and are directed to photoelectric converters. A measurable electronic signal is generated for each thermal neutron interaction within the fiber. These electronic signals are then manipulated, stored, and interpreted by normal methods to infer the quality and quantity of incident radiation. When the fibers are arranged in an array within a second scintillating material, photons generated by kinetic neutrons interacting with the second scintillating material and photons generated by thermal neutron capture within the fiber can both be directed to photoelectric converters. These electronic signals are then manipulated, stored, and interpreted by normal methods to infer the quality and quantity of incident radiation.

Photon gating in four-dimensional ultrafast electron microscopy

PubMed Central

Hassan, Mohammed T.; Liu, Haihua; Baskin, John Spencer; Zewail, Ahmed H.

2015-01-01

Ultrafast electron microscopy (UEM) is a pivotal tool for imaging of nanoscale structural dynamics with subparticle resolution on the time scale of atomic motion. Photon-induced near-field electron microscopy (PINEM), a key UEM technique, involves the detection of electrons that have gained energy from a femtosecond optical pulse via photon–electron coupling on nanostructures. PINEM has been applied in various fields of study, from materials science to biological imaging, exploiting the unique spatial, energy, and temporal characteristics of the PINEM electrons gained by interaction with a “single” light pulse. The further potential of photon-gated PINEM electrons in probing ultrafast dynamics of matter and the optical gating of electrons by invoking a “second” optical pulse has previously been proposed and examined theoretically in our group. Here, we experimentally demonstrate this photon-gating technique, and, through diffraction, visualize the phase transition dynamics in vanadium dioxide nanoparticles. With optical gating of PINEM electrons, imaging temporal resolution was improved by a factor of 3 or better, being limited only by the optical pulse widths. This work enables the combination of the high spatial resolution of electron microscopy and the ultrafast temporal response of the optical pulses, which provides a promising approach to attain the resolution of few femtoseconds and attoseconds in UEM. PMID:26438835

Characteristics of a heavy water photoneutron source in boron neutron capture therapy

NASA Astrophysics Data System (ADS)

Danial, Salehi; Dariush, Sardari; M. Salehi, Jozani

2013-07-01

Bremsstrahlung photon beams produced by medical linear accelerators are currently the most commonly used method of radiation therapy for cancerous tumors. Photons with energies greater than 8-10 MeV potentially generate neutrons through photonuclear interactions in the accelerator's treatment head, patient's body, and treatment room ambient. Electrons impinging on a heavy target generate a cascade shower of bremsstrahlung photons, the energy spectrum of which shows an end point equal to the electron beam energy. By varying the target thickness, an optimum thickness exists for which, at the given electron energy, maximum photon flux is achievable. If a source of high-energy photons i.e. bremsstrahlung, is conveniently directed to a suitable D2O target, a novel approach for production of an acceptable flux of filterable photoneturons for boron neutron capture therapy (BNCT) application is possible. This study consists of two parts. 1. Comparison and assessment of deuterium photonuclear cross section data. 2. Evaluation of the heavy water photonuclear source.

Bright attosecond γ-ray pulses from nonlinear Compton scattering with laser-illuminated compound targets

NASA Astrophysics Data System (ADS)

Zhu, Xing-Long; Chen, Min; Yu, Tong-Pu; Weng, Su-Ming; Hu, Li-Xiang; McKenna, Paul; Sheng, Zheng-Ming

2018-04-01

Attosecond light sources have the potential to open up totally unexplored research avenues in ultrafast science. However, the photon energies achievable using existing generation schemes are limited to the keV range. Here, we propose and numerically demonstrate an all-optical mechanism for the generation of bright MeV attosecond γ-photon beams with desirable angular momentum. Using a circularly polarized Laguerre-Gaussian laser pulse focused onto a cone-foil target, dense attosecond bunches ( ≲ 170 as ) of electrons are produced. The electrons interact with the laser pulse which is reflected by a plasma mirror, producing ultra-brilliant (˜1023 photons/s/mm2/mrad2/0.1%BW) multi-MeV (Eγ,max > 30 MeV) isolated attosecond ( ≲ 260 as ) γ-ray pulse trains. Moreover, the angular momentum is transferred to γ-photon beams via nonlinear Compton scattering of ultra-intense tightly focused laser pulse by energetic electrons. Such a brilliant attosecond γ-photon source would provide the possibilities in attosecond nuclear science.

A space- and time-resolved single photon counting detector for fluorescence microscopy and spectroscopy

PubMed Central

Michalet, X.; Siegmund, O.H.W.; Vallerga, J.V.; Jelinsky, P.; Millaud, J.E.; Weiss, S.

2017-01-01

We have recently developed a wide-field photon-counting detector having high-temporal and high-spatial resolutions and capable of high-throughput (the H33D detector). Its design is based on a 25 mm diameter multi-alkali photocathode producing one photo electron per detected photon, which are then multiplied up to 107 times by a 3-microchannel plate stack. The resulting electron cloud is proximity focused on a cross delay line anode, which allows determining the incident photon position with high accuracy. The imaging and fluorescence lifetime measurement performances of the H33D detector installed on a standard epifluorescence microscope will be presented. We compare them to those of standard single-molecule detectors such as single-photon avalanche photodiode (SPAD) or electron-multiplying camera using model samples (fluorescent beads, quantum dots and live cells). Finally, we discuss the design and applications of future generation of H33D detectors for single-molecule imaging and high-throughput study of biomolecular interactions. PMID:29479130

Input-output theory for spin-photon coupling in Si double quantum dots

NASA Astrophysics Data System (ADS)

Benito, M.; Mi, X.; Taylor, J. M.; Petta, J. R.; Burkard, Guido

2017-12-01

The interaction of qubits via microwave frequency photons enables long-distance qubit-qubit coupling and facilitates the realization of a large-scale quantum processor. However, qubits based on electron spins in semiconductor quantum dots have proven challenging to couple to microwave photons. In this theoretical work we show that a sizable coupling for a single electron spin is possible via spin-charge hybridization using a magnetic field gradient in a silicon double quantum dot. Based on parameters already shown in recent experiments, we predict optimal working points to achieve a coherent spin-photon coupling, an essential ingredient for the generation of long-range entanglement. Furthermore, we employ input-output theory to identify observable signatures of spin-photon coupling in the cavity output field, which may provide guidance to the experimental search for strong coupling in such spin-photon systems and opens the way to cavity-based readout of the spin qubit.

Spectral and angular distribution of photons via radiative damping in extreme ultra-intense laser-plasma interaction

NASA Astrophysics Data System (ADS)

Pandit, Rishi; Sentoku, Yasuhiko

2012-10-01

Spectral and angular distribution of photons produced in the interaction of extremely intense laser (> 10^22,/cm^2) with dense plasma are studied with a help of a collisional particle-in-cell simulation, PICLS. In ultra-intense laser-plasma interaction, electrons are accelerated by the strong laser fields and emit γ-ray photons mainly via two processes, namely, Bremsstrahlung and radiative damping. We had developed numerical models of these processes in PICLS and study the spectrum and the angular distribution of γ-rays produced in the relativistic laser regime. Such relativistic γ-rays have wide range of frequencies and the angular distribution depends on the hot electron source. From the power loss calculation in PICLS we found that the Bremsstrahlung will get saturated at I > 10^22,/cm^2 while the radiative damping will continuously increase. Comparing the details of γ-rays from the Bremsstrahlung and the radiative damping in simulations, we will discuss the laser parameters and the target conditions (geometry and material) to distinguish the photons from each process and how to catch the signature of the radiative damping in future experiments.

Giant collimated gamma-ray flashes

NASA Astrophysics Data System (ADS)

Benedetti, Alberto; Tamburini, Matteo; Keitel, Christoph H.

2018-06-01

Bright sources of high-energy electromagnetic radiation are widely employed in fundamental research, industry and medicine1,2. This motivated the construction of Compton-based facilities planned to yield bright gamma-ray pulses with energies up to3 20 MeV. Here, we demonstrate a novel mechanism based on the strongly amplified synchrotron emission that occurs when a sufficiently dense ultra-relativistic electron beam interacts with a millimetre-thickness conductor. For electron beam densities exceeding approximately 3 × 1019 cm-3, electromagnetic instabilities occur, and the ultra-relativistic electrons travel through self-generated electromagnetic fields as large as 107-108 gauss. This results in the production of a collimated gamma-ray pulse with peak brilliance above 1025 photons s-1 mrad-2 mm-2 per 0.1% bandwidth, photon energies ranging from 200 keV to gigaelectronvolts and up to 60% electron-to-photon energy conversion efficiency. These findings pave the way to compact, high-repetition-rate (kilohertz) sources of short (≲30 fs), collimated (milliradian) and high-flux (>1012 photons s-1) gamma-ray pulses.

SU-F-T-370: A Fast Monte Carlo Dose Engine for Gamma Knife

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, T; Zhou, L; Li, Y

2016-06-15

Purpose: To develop a fast Monte Carlo dose calculation algorithm for Gamma Knife. Methods: To make the simulation more efficient, we implemented the track repeating technique on GPU. We first use EGSnrc to pre-calculate the photon and secondary electron tracks in water from two mono-energy photons of 60Co. The total photon mean free paths for different materials and energies are obtained from NIST. During simulation, each entire photon track was first loaded to shared memory for each block, the incident original photon was then splitted to Nthread sub-photons, each thread transport one sub-photon, the Russian roulette technique was applied formore » scattered and bremsstrahlung photons. The resultant electrons from photon interactions are simulated by repeating the recorded electron tracks. The electron step length is stretched/shrunk proportionally based on the local density and stopping power ratios of the local material. Energy deposition in a voxel is proportional to the fraction of the equivalent step length in that voxel. To evaluate its accuracy, dose deposition in a 300mm*300mm*300mm water phantom is calculated, and compared to EGSnrc results. Results: Both PDD and OAR showed great agreements (within 0.5%) between our dose engine result and the EGSnrc result. It only takes less than 1 min for every simulation, being reduced up to ∼40 times compared to EGSnrc simulations. Conclusion: We have successfully developed a fast Monte Carlo dose engine for Gamma Knife.« less

Strong coupling of a single electron in silicon to a microwave photon

NASA Astrophysics Data System (ADS)

Mi, Xiao; Cady, Jeffrey; Zajac, David; Petta, Jason

We demonstrate a hybrid circuit quantum electrodynamics (cQED) architecture in which a single electron in a Si/SiGe double quantum dot is dipole-coupled to the electric field of microwave photons in a superconducting cavity. Vacuum Rabi splitting is observed in the cavity transmission when the transition energy of the single-electron charge qubit matches that of a cavity photon, demonstrating that our device is in the strong coupling regime. The achievement of strong coupling is largely facilitated by an exceptionally low charge decoherence rate of 5 MHz and paves the way toward a wide range of cQED experiments with quantum dots, such as non-local qubit interactions, strong spin-cavity coupling and single photon generation . Research sponsored by ARO Grant No. W911NF-15-1-0149, the Gordon and Betty Moore Foundation's EPiQS Initiative through Grant GBMF4535, and the NSF (DMR-1409556 and DMR-1420541).

Steering attosecond electron wave packets with light.

PubMed

Kienberger, R; Hentschel, M; Uiberacker, M; Spielmann, Ch; Kitzler, M; Scrinzi, A; Wieland, M; Westerwalbesloh, Th; Kleineberg, U; Heinzmann, U; Drescher, M; Krausz, F

2002-08-16

Photoelectrons excited by extreme ultraviolet or x-ray photons in the presence of a strong laser field generally suffer a spread of their energies due to the absorption and emission of laser photons. We demonstrate that if the emitted electron wave packet is temporally confined to a small fraction of the oscillation period of the interacting light wave, its energy spectrum can be up- or downshifted by many times the laser photon energy without substantial broadening. The light wave can accelerate or decelerate the electron's drift velocity, i.e., steer the electron wave packet like a classical particle. This capability strictly relies on a sub-femtosecond duration of the ionizing x-ray pulse and on its timing to the phase of the light wave with a similar accuracy, offering a simple and potentially single-shot diagnostic tool for attosecond pump-probe spectroscopy.

The modified unified interaction model: incorporation of dose-dependent localised recombination.

PubMed

Lavon, A; Eliyahu, I; Oster, L; Horowitz, Y S

2015-02-01

The unified interaction model (UNIM) was developed to simulate thermoluminescence (TL) linear/supralinear dose-response and the dependence of the supralinearity on ionisation density, i.e. particle type and energy. Before the development of the UNIM, this behaviour had eluded all types of TL modelling including conduction band/valence band (CB/VB) kinetic models. The dependence of the supralinearity on photon energy was explained in the UNIM as due to the increasing role of geminate (localised recombination) with decreasing photon/electron energy. Recently, the Ben Gurion University group has incorporated the concept of trapping centre/luminescent centre (TC/LC) spatially correlated complexes and localised/delocalised recombination into the CB/VB kinetic modelling of the LiF:Mg,Ti system. Track structure considerations are used to describe the relative population of the TC/LC complexes by an electron-hole or by an electron-only as a function of both photon/electron energy and dose. The latter dependence was not included in the original UNIM formulation, a significant over-simplification that is herein corrected. The modified version, the M-UNIM, is then applied to the simulation of the linear/supralinear dose-response characteristics of composite peak 5 in the TL glow curve of LiF:Mg,Ti at two representative average photon/electron energies of 500 and 8 keV. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Perturbative calculation of two-photon double electron ionization of helium

NASA Astrophysics Data System (ADS)

Ivanov, I. A.; Kheifets, A. S.

2008-05-01

We report the total integrated cross-section (TICS) of two-photon double ionization of helium in the photon energy range from 40 to 54 eV. We compute the TICS in the lowest order perturbation theory (LOPT) using the length and Kramers-Henneberger gauges of the electromagnetic interaction. Our findings indicate that the LOPT gives results for the TICS in agreement with our earlier non-perturbative calculations.

Accelerator shield design of KIPT neutron source facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhong, Z.; Gohar, Y.

Argonne National Laboratory (ANL) of the United States and Kharkov Institute of Physics and Technology (KIPT) of Ukraine have been collaborating on the design development of a neutron source facility at KIPT utilizing an electron-accelerator-driven subcritical assembly. Electron beam power is 100 kW, using 100 MeV electrons. The facility is designed to perform basic and applied nuclear research, produce medical isotopes, and train young nuclear specialists. The biological shield of the accelerator building is designed to reduce the biological dose to less than 0.5-mrem/hr during operation. The main source of the biological dose is the photons and the neutrons generatedmore » by interactions of leaked electrons from the electron gun and accelerator sections with the surrounding concrete and accelerator materials. The Monte Carlo code MCNPX serves as the calculation tool for the shield design, due to its capability to transport electrons, photons, and neutrons coupled problems. The direct photon dose can be tallied by MCNPX calculation, starting with the leaked electrons. However, it is difficult to accurately tally the neutron dose directly from the leaked electrons. The neutron yield per electron from the interactions with the surrounding components is less than 0.01 neutron per electron. This causes difficulties for Monte Carlo analyses and consumes tremendous computation time for tallying with acceptable statistics the neutron dose outside the shield boundary. To avoid these difficulties, the SOURCE and TALLYX user subroutines of MCNPX were developed for the study. The generated neutrons are banked, together with all related parameters, for a subsequent MCNPX calculation to obtain the neutron and secondary photon doses. The weight windows variance reduction technique is utilized for both neutron and photon dose calculations. Two shielding materials, i.e., heavy concrete and ordinary concrete, were considered for the shield design. The main goal is to maintain the total dose outside the shield boundary at less than 0.5-mrem/hr. The shield configuration and parameters of the accelerator building have been determined and are presented in this paper. (authors)« less

Antenna-coupled photon emission from hexagonal boron nitride tunnel junctions.

PubMed

Parzefall, M; Bharadwaj, P; Jain, A; Taniguchi, T; Watanabe, K; Novotny, L

2015-12-01

The ultrafast conversion of electrical signals to optical signals at the nanoscale is of fundamental interest for data processing, telecommunication and optical interconnects. However, the modulation bandwidths of semiconductor light-emitting diodes are limited by the spontaneous recombination rate of electron-hole pairs, and the footprint of electrically driven ultrafast lasers is too large for practical on-chip integration. A metal-insulator-metal tunnel junction approaches the ultimate size limit of electronic devices and its operating speed is fundamentally limited only by the tunnelling time. Here, we study the conversion of electrons (localized in vertical gold-hexagonal boron nitride-gold tunnel junctions) to free-space photons, mediated by resonant slot antennas. Optical antennas efficiently bridge the size mismatch between nanoscale volumes and far-field radiation and strongly enhance the electron-photon conversion efficiency. We achieve polarized, directional and resonantly enhanced light emission from inelastic electron tunnelling and establish a novel platform for studying the interaction of electrons with strongly localized electromagnetic fields.

Electrically induced spontaneous emission in open electronic system

NASA Astrophysics Data System (ADS)

Wang, Rulin; Zhang, Yu; Yam, Chiyung; Computation Algorithms Division (CSRC) Team; Theoretical; Computational Chemistry (HKU) Collaboration

A quantum mechanical approach is formulated for simulation of electroluminescence process in open electronic system. Based on nonequilibrium Green's function quantum transport equations and combining with photon-electron interaction, this method is used to describe electrically induced spontaneous emission caused by electron-hole recombination. The accuracy and reliability of simulation depends critically on correct description of the electronic band structure and the electron occupancy in the system. In this work, instead of considering electron-hole recombination in discrete states in the previous work, we take continuous states into account to simulate the spontaneous emission in open electronic system, and discover that the polarization of emitted photon is closely related to its propagation direction. Numerical studies have been performed to silicon nanowire-based P-N junction with different bias voltage.

Amplification of light in one-dimensional vibrating metal photonic crystal

NASA Astrophysics Data System (ADS)

Ueta, Tsuyoshi

2012-04-01

Photon-phonon interaction on the analogy of electron-phonon interaction is considered in one-dimensional metal photonic crystal. When lattice vibration is artificially introduced to the photonic crystal, a governing equation of electromagnetic field is derived. A simple model is numerically analyzed, and the following novel phenomena are found out. The lattice vibration generates the light of frequency which added the integral multiple of the vibration frequency to that of the incident wave and also amplifies the incident wave resonantly. On a resonance, the amplification factor increases very rapidly with the number of layers. Resonance frequencies change with the phases of lattice vibration. The amplification phenomenon is analytically discussed for low frequency of the lattice vibration and is confirmed by numerical works.

A novel flurophore-cyano-carboxylic-Ag microhybrid: Enhanced two photon absorption for two-photon photothermal therapy of HeLa cancer cells by targeting mitochondria.

PubMed

Kong, Lin; Yang, Li; Xin, Chen-Qi; Zhu, Shu-Juan; Zhang, Hui-Hui; Zhang, Ming-Zhu; Yang, Jia-Xiang; Li, Lin; Zhou, Hong-Ping; Tian, Yu-Peng

2018-06-15

In this study, a novel two-photon photothermal therapy (TP-PTT) agent based on an organic-metal microhybrid with surface Plasmon resonance (SPR) enhanced two-photon absorption (TPA) characteristic was designed and synthesized using a fluorescent cyano-carboxylic derivative 2-cyano-3-(9-ethyl-9H-carbazol-3-yl) -acrylic acid (abbreviated as CECZA) and silver nanoparticles through self-assembly process induced by the interfacial coordination interactions between the O/N atom of CECZA and Ag + ion at the surface of Ag nanoparticles. The coordination interactions caused electron transfer from the Ag nanoparticles to CECZA molecules at the excited state, resulting in a decreased fluorescence quantum yield. The interfacial coordination interactions also enhanced the nonlinear optical properties, including 13 times increase in the TPA cross-section (δ). The decreased fluorescence quantum yield and increased two photon absorption caused by the SPR effect led excellent two-photon photothermal conversion, which was beneficial for the TP-PTT effect on HeLa cancer cells. Copyright © 2018 Elsevier B.V. All rights reserved.

One- and two-photon absorption spectra of the yellow fluorescent protein citrine: effects of intramolecular electron-vibrational coupling and intermolecular interactions

NASA Astrophysics Data System (ADS)

Chen, Fasheng; Zhao, Xinyi; Liang, WanZhen

2018-04-01

Both the vibrationally resolved and statistically averaged one-photon absorption (OPA) and two-photon absorption (TPA) spectra of the anionic form of chromophore (AC) in its micro-environment of yellow fluorescent protein (YFP) Citrine have been calculated. The result comparison has been made with those of the AC model compounds in vacuo and methanol solution, which allows us to allocate the individual contribution of the intramolecular electron-vibrational coupling, the electrostatic π-stacking interaction between Tyr203 and AC, and the interaction between AC and its micro-environment to the spectra. The results reveal that the non-Condon vibronic coupling effect is responsible for the blue shift of TPA absorption maximum compared with its OPA counterpart corresponding to S0 → S1, and that the π-stacking interaction between Tyr203 and AC alters the relative intensities of TPA maxima, which further enhances the higher-energy vibronic peaks and weakens the lowest-energy peak. The statically averaged OPA and TPA spectra calculated by quantum mechanics/molecular mechanics (QM/MM) methods based on Born-Oppenheimer molecular dynamics simulation largely deviate the experimental spectral lineshapes, which further verifies the significant contribution of non-Condon vibronic coupling effect on the spectra. The interaction of individual amino acid residue or water close to AC+Tyr203 has different effects on the spectra, which may increase/decrease the excitation energy depending on its position and electronic property.

A study of photon interaction in some hormones

NASA Astrophysics Data System (ADS)

Manjunatha, H. C.

2013-05-01

The effective atomic numbers (Z eff) and electron density (N el) of some hormones such as testosterone, methandienone, estradiol and rogesterone for total and partial photon interactions have been computed in the wide energy region 1 keV-100 GeV using an accurate database of photon-interaction cross sections and the WinXCom program. The computed Z eff and N el are compared with the values generated by XMuDat program. The computer tomography (CT) numbers and kerma values relative to air are also calculated and the computed data of CT numbers in the low-energy region help in visualizing the image of the biological samples and to obtain precise accuracy in treating the inhomogenity of them in medical radiology. In view of dosimetric interest, the photon absorbed dose rates of some commonly used gamma sources (Na-21, Cs-137, Mn-52, Co-60 and Na-22) are also estimated.

Experimental Verification of Predicted Oscillations near a Spin Resonance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kolanoski, Hermann; /Humboldt U., Berlin

2011-12-05

The E166 experiment at the Stanford Linear Accelerator Center (SLAC) has demonstrated a scheme for the production of polarized positrons which is suitable for implementation in a future Linear Collider. A multi-GeV electron beam passed through a helical undulator to generate multi-MeV, circularly polarized photons which were then converted in a thin target to produce positrons (and electrons) with longitudinal polarization above 80% at 6 MeV. The results are in agreement with GEANT4 simulations that include the dominant polarization-dependent interactions of electrons, positrons and photons in matter.

Simulating TGF and gamma ray emission above and within stormclouds due to the interaction of TeV cosmic ray shower electrons/positrons/photons with plausible electric field geometries generated in stormclouds.

NASA Astrophysics Data System (ADS)

Connell, P. H.

2017-12-01

The University of Valencia has developed a software simulator LEPTRACK to simulate lepton and photon scattering in any kind of media with a variable density, and permeated by electric/magnetic fields of any geometry, and which can handle an exponential runaway avalanche. Here we show results of simulating the interaction of electrons/positrons/photons in an incoming TeV cosmic ray shower with the kind of electric fields expected in a stormcloud after a CG discharge which removes much of the positive charge build up at the centre of the cloud. The point is to show not just a Relativistic Runaway Electron Avalanche (RREA) above the upper negative shielding layer at 12 km but other gamma ray emission due to electron/positron interaction in the remaining positive charge around 9km and the lower negative charge at 6km altitude. We present here images, lightcurves, altitude profiles, spectra and videos showing the different ionization, excitation and photon density fields produced, their time evolution, and how they depend critically on where the cosmic ray shower beam intercepts the electric field geometry. We also show a new effect of incoming positrons, which make up a significant fraction of the shower, where they appear to "orbit" within the high altitude negative shielding layer, and which has been conjectured to produce significant microwave emission, as well as a short range 511 keV annihilation line. The interesting question is if this conjectured emission can be observed and correlated with TGF orbital observations to prove that a TGF originates in the macro-fields of stormclouds or the micro-fields of light leaders and streamers where this "positron orbiting" is not likely to occur.

Studying electron-PAG interactions using electron-induced fluorescence

NASA Astrophysics Data System (ADS)

Narasimhan, Amrit; Grzeskowiak, Steven; Ostrander, Jonathan; Schad, Jonathon; Rebeyev, Eliran; Neisser, Mark; Ocola, Leonidas E.; Denbeaux, Gregory; Brainard, Robert L.

2016-03-01

In extreme ultraviolet (EUV) lithography, 92 eV photons are used to expose photoresists. Typical EUV resists are organic-based and chemically amplified using photoacid generators (PAGs). Upon exposure, PAGs produce acids which catalyze reactions that result in changes in solubility. In EUV lithography, photo- and secondary electrons (energies of 10- 80 eV) play a large role in PAG acid-production. Several mechanisms for electron-PAG interactions (e.g. electron trapping, and hole-initiated chemistry) have been proposed. The aim of this study is to explore another mechanism - internal excitation - in which a bound PAG electron can be excited by receiving energy from another energetic electron, causing a reaction that produces acid. This paper explores the mechanism of internal excitation through the analogous process of electron-induced fluorescence, in which an electron loses energy by transferring that energy to a molecule and that molecule emits a photon rather than decomposing. We will show and quantify electron-induced fluorescence of several fluorophores in polymer films to mimic resist materials, and use this information to refine our proposed mechanism. Relationships between the molecular structure of fluorophores and fluorescent quantum yield may aid in the development of novel PAGs for EUV lithography.

Michel electron reconstruction using cosmic-ray data from the MicroBooNE LArTPC

NASA Astrophysics Data System (ADS)

Acciarri, R.; Adams, C.; An, R.; Anthony, J.; Asaadi, J.; Auger, M.; Bagby, L.; Balasubramanian, S.; Baller, B.; Barnes, C.; Barr, G.; Bass, M.; Bay, F.; Bishai, M.; Blake, A.; Bolton, T.; Bugel, L.; Camilleri, L.; Caratelli, D.; Carls, B.; Castillo Fernandez, R.; Cavanna, F.; Chen, H.; Church, E.; Cianci, D.; Cohen, E.; Collin, G. H.; Conrad, J. M.; Convery, M.; Crespo-Anadón, J. I.; Del Tutto, M.; Devitt, D.; Dytman, S.; Eberly, B.; Ereditato, A.; Escudero Sanchez, L.; Esquivel, J.; Fleming, B. T.; Foreman, W.; Furmanski, A. P.; Garcia-Gamez, D.; Garvey, G. T.; Genty, V.; Goeldi, D.; Gollapinni, S.; Graf, N.; Gramellini, E.; Greenlee, H.; Grosso, R.; Guenette, R.; Hackenburg, A.; Hamilton, P.; Hen, O.; Hewes, J.; Hill, C.; Ho, J.; Horton-Smith, G.; Huang, E.-C.; James, C.; de Vries, J. Jan; Jen, C.-M.; Jiang, L.; Johnson, R. A.; Joshi, J.; Jostlein, H.; Kaleko, D.; Karagiorgi, G.; Ketchum, W.; Kirby, B.; Kirby, M.; Kobilarcik, T.; Kreslo, I.; Laube, A.; Li, Y.; Lister, A.; Littlejohn, B. R.; Lockwitz, S.; Lorca, D.; Louis, W. C.; Luethi, M.; Lundberg, B.; Luo, X.; Marchionni, A.; Mariani, C.; Marshall, J.; Martinez Caicedo, D. A.; Meddage, V.; Miceli, T.; Mills, G. B.; Moon, J.; Mooney, M.; Moore, C. D.; Mousseau, J.; Murrells, R.; Naples, D.; Nienaber, P.; Nowak, J.; Palamara, O.; Paolone, V.; Papavassiliou, V.; Pate, S. F.; Pavlovic, Z.; Piasetzky, E.; Porzio, D.; Pulliam, G.; Qian, X.; Raaf, J. L.; Rafique, A.; Rochester, L.; von Rohr, C. Rudolf; Russell, B.; Schmitz, D. W.; Schukraft, A.; Seligman, W.; Shaevitz, M. H.; Sinclair, J.; Snider, E. L.; Soderberg, M.; Söldner-Rembold, S.; Soleti, S. R.; Spentzouris, P.; Spitz, J.; St. John, J.; Strauss, T.; Sutton, K. A.; Szelc, A. M.; Tagg, N.; Terao, K.; Thomson, M.; Toups, M.; Tsai, Y.-T.; Tufanli, S.; Usher, T.; Van de Water, R. G.; Viren, B.; Weber, M.; Wickremasinghe, D. A.; Wolbers, S.; Wongjirad, T.; Woodruff, K.; Yang, T.; Yates, L.; Zeller, G. P.; Zennamo, J.; Zhang, C.

2017-09-01

The MicroBooNE liquid argon time projection chamber (LArTPC) has been taking data at Fermilab since 2015 collecting, in addition to neutrino beam, cosmic-ray muons. Results are presented on the reconstruction of Michel electrons produced by the decay at rest of cosmic-ray muons. Michel electrons are abundantly produced in the TPC, and given their well known energy spectrum can be used to study MicroBooNE's detector response to low-energy electrons (electrons with energies up to ~ 50 MeV). We describe the fully-automated algorithm developed to reconstruct Michel electrons, with which a sample of ~ 14,000 Michel electron candidates is obtained. Most of this article is dedicated to studying the impact of radiative photons produced by Michel electrons on the accuracy and resolution of their energy measurement. In this energy range, ionization and bremsstrahlung photon production contribute similarly to electron energy loss in argon, leading to a complex electron topology in the TPC. By profiling the performance of the reconstruction algorithm on simulation we show that the ability to identify and include energy deposited by radiative photons leads to a significant improvement in the energy measurement of low-energy electrons. The fractional energy resolution we measure improves from over 30% to ~ 20% when we attempt to include radiative photons in the reconstruction. These studies are relevant to a large number of analyses which aim to study neutrinos by measuring electrons produced by νe interactions over a broad energy range.

Effect of Electron Seeding on Experimentally Measured Multipactor Discharge Threshold

NASA Astrophysics Data System (ADS)

Noland, Jonathan; Graves, Timothy; Lemon, Colby; Looper, Mark; Farkas, Alex

2012-10-01

Multipactor is a vacuum phenomenon in which electrons, moving in resonance with an externally applied electric field, impact material surfaces. If the number of secondary electrons created per primary electron impact averages more than unity, the resonant interaction can lead to an electron avalanche. Multipactor is a generally undesirable phenomenon, as it can cause local heating, absorb power, or cause detuning of RF circuits. In order to increase the probability of multipactor initiation, test facilities often employ various seeding sources such as radioactive sources (Cesium 137, Strontium 90), electron guns, or photon sources. Even with these sources, the voltage for multipactor initiation is not certain as parameters such as material type, RF pulse length, and device wall thickness can all affect seed electron flux and energy in critical gap regions, and hence the measured voltage threshold. This study investigates the effects of seed electron source type (e.g., photons versus beta particles), material type, gap size, and RF pulse length variation on multipactor threshold. In addition to the experimental work, GEANT4 simulations will be used to estimate the production rate of low energy electrons (< 5 keV) by high energy electrons and photons. A comparison of the experimental fluxes to the typical energetic photon and particle fluxes experienced by spacecraft in various orbits will also be made. Initial results indicate that for a simple, parallel plate device made of aluminum, there is no threshold variation (with seed electrons versus with no seed electrons) under continuous-wave RF exposure.

Electron–Positron Pair Creation Close to a Black Hole Horizon: Redshifted Annihilation Line in the Emergent X-Ray Spectra of a Black Hole. I.

NASA Astrophysics Data System (ADS)

Laurent, Philippe; Titarchuk, Lev

2018-06-01

We consider a Compton cloud (CC) surrounding a black hole (BH) in an accreting BH system, where electrons propagate with thermal and bulk velocities. In that cloud, soft (disk) photons may be upscattered off these energetic electrons and attain energies of several MeV. They could then create pairs due to photon–photon interactions. In this paper, we study the formation of the 511 keV annihilation line due to this photon–photon interaction, which results in the creation of electron–positron pairs, followed by the annihilation of the created positrons with the CC electrons. The appropriate conditions for annihilation-line generation take place very close to a BH horizon within (103–104)m cm from it, where m is the BH hole mass in solar units. As a result, the created annihilation line should be seen by the Earth observer as a blackbody bump, or the so-called reflection bump at energies around (511/20) (20/z) keV, where z ∼ 20 is a typical gravitational redshift experienced by the created annihilation-line photons when they emerge. This transient feature should occur in any accreting BH system, either galactic or extragalactic. Observational evidences for this feature in several galactic BH systems is detailed in an accompanying paper. An extended hard tail of the spectrum up to 1 MeV may also be formed due to X-ray photons upscattering off created pairs.

Circuit quantum electrodynamics architecture for gate-defined quantum dots in silicon

NASA Astrophysics Data System (ADS)

Mi, X.; Cady, J. V.; Zajac, D. M.; Stehlik, J.; Edge, L. F.; Petta, J. R.

2017-01-01

We demonstrate a hybrid device architecture where the charge states in a double quantum dot (DQD) formed in a Si/SiGe heterostructure are read out using an on-chip superconducting microwave cavity. A quality factor Q = 5400 is achieved by selectively etching away regions of the quantum well and by reducing photon losses through low-pass filtering of the gate bias lines. Homodyne measurements of the cavity transmission reveal DQD charge stability diagrams and a charge-cavity coupling rate g c / 2 π = 23 MHz. These measurements indicate that electrons trapped in a Si DQD can be effectively coupled to microwave photons, potentially enabling coherent electron-photon interactions in silicon.

Implementation of Monte Carlo Dose calculation for CyberKnife treatment planning

NASA Astrophysics Data System (ADS)

Ma, C.-M.; Li, J. S.; Deng, J.; Fan, J.

2008-02-01

Accurate dose calculation is essential to advanced stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT) especially for treatment planning involving heterogeneous patient anatomy. This paper describes the implementation of a fast Monte Carlo dose calculation algorithm in SRS/SRT treatment planning for the CyberKnife® SRS/SRT system. A superposition Monte Carlo algorithm is developed for this application. Photon mean free paths and interaction types for different materials and energies as well as the tracks of secondary electrons are pre-simulated using the MCSIM system. Photon interaction forcing and splitting are applied to the source photons in the patient calculation and the pre-simulated electron tracks are repeated with proper corrections based on the tissue density and electron stopping powers. Electron energy is deposited along the tracks and accumulated in the simulation geometry. Scattered and bremsstrahlung photons are transported, after applying the Russian roulette technique, in the same way as the primary photons. Dose calculations are compared with full Monte Carlo simulations performed using EGS4/MCSIM and the CyberKnife treatment planning system (TPS) for lung, head & neck and liver treatments. Comparisons with full Monte Carlo simulations show excellent agreement (within 0.5%). More than 10% differences in the target dose are found between Monte Carlo simulations and the CyberKnife TPS for SRS/SRT lung treatment while negligible differences are shown in head and neck and liver for the cases investigated. The calculation time using our superposition Monte Carlo algorithm is reduced up to 62 times (46 times on average for 10 typical clinical cases) compared to full Monte Carlo simulations. SRS/SRT dose distributions calculated by simple dose algorithms may be significantly overestimated for small lung target volumes, which can be improved by accurate Monte Carlo dose calculations.

Partial cross sections of helium satellites at medium photon energies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wehlitz, R.; Sellin, I.A.; Hemmers, O.

1997-04-01

Still of current interest is the important role of single ionization with excitation compared to single ionization alone. The coupling between the electrons and the incoming photon is a single-particle operator. Thus, an excitation in addition to an ionization, leading to a so-called satellite line in a photoelectron spectrum, is entirely due to electron-electron interaction and probes the electron correlation in the ground and final state. Therefore the authors have undertaken the study of the intensity of helium satellites He{sup +}nl (n = 2 - 6) relative to the main photoline (n = 1) as a function of photon energymore » at photon energies well above threshold up to 900 eV. From these results they could calculate the partial cross-sections of the helium satellites. In order to test the consistency of their satellite-to-1s ratios with published double-to-single photoionization ratios, the authors calculated the double-to-single photoionization ratio from their measured ratios using the theoretical energy-distribution curves of Chang and Poe and Le Rouzo and Dal Cappello which proved to be valid for photon energies below 120 eV. These calculated double-to-single ionization ratios agree fairly well with recent ion measurements. In the lower photon energy range the authors ratios agree better with the ratios of Doerner et al. while for higher photon energies the agreement is better with the values of Levin et al.« less

STATISTICAL STUDY of HARD X-RAY SPECTRAL CHARACTERISTICS OF SOLAR FLARES

NASA Astrophysics Data System (ADS)

Alaoui, M.; Krucker, S.; Saint-Hilaire, P.; Lin, R. P.

2009-12-01

We investigate the spectral characteristics of 75 solar flares at the hard X-ray peak time observed by RHESSI (Ramaty High Energy Solar Spectroscopic Imager) in the energy range 12-150keV. At energies above 40keV, the Hard X-ray emission is mostly produced by bremsstrahlung of suprathermal electrons as they interact with the ambient plasma in the chromosphere. The observed photon spectra therefore provide diagnostics of electron acceleration processes in Solar flares. We will present statistical results of spectral fitting using two models: a broken power law plus a thermal component which is a direct fit of the photon spectrum and a thick target model plus a thermal component which is a fit of the photon spectra with assumptions on the electrons emitting bremsstrahlung in the thick target approximation.

Can There Be Massive Photons? A Pedagogical Glance at the Origin of Mass

ERIC Educational Resources Information Center

Robles, P.; Claro, F.

2012-01-01

Among the most startling experiences a student encounters is learning that, unlike electrons and other elementary particles, photons have no mass. Under certain circumstances, however, the light quantum behaves as if it did have a finite mass. Starting from Maxwell's equations, we discuss how this arises when light interacts with a charged plasma,…

Nonlinear Interaction of the Beat-Photon Beams with the Brain Neurocenters: Laser Neurophysics

NASA Astrophysics Data System (ADS)

Stefan, V. Alexander

2010-03-01

I propose a novel mechanism for laser-brain interaction: Nonlinear interaction of ultrashort pulses of beat-photon, (φ1-- φ2), or double-photon, (φ1+φ2), footnotetextMaria Goeppert-Mayer, "Uber Elementarakte mit zwei Quantenspr"ungen, Ann Phys 9, 273, 95. (1931). beams with the corrupted brain neurocenters, causing a particular neurological disease. The open-scull cerebral tissue can be irradiated with the beat-photon pulses in the range of several 100s fs, with the laser irradiances in the range of a few mW/cm^2, repetition rate of a few 100s Hz, and in the frequency range of 700-1300nm generated in the beat-wave driven free electron laser.footnotetextV. Alexander Stefan, The Interaction of Photon Beams with the DNA Molecules: Genomic Medical Physics. American Physical Society, 2009 APS March Meeting, March 16-20, 2009, abstract #K1.276; V. Stefan, B. I. Cohen, and C. Joshi, Nonlinear Mixing of Electromagnetic Waves in Plasmas Science 27 January 1989:Vol. 243. no. 4890, pp. 494 -- 500 (January 1989). This method may prove to be an effective mechanism in the treatment of neurological diseases: Parkinson's, Lou Gehrig's, and others.

Evidence for Secondary Emission as the Origin of Hard Spectra in TeV Blazars

NASA Astrophysics Data System (ADS)

Zheng, Y. G.; Kang, T.

2013-02-01

We develop a model for the possible origin of hard, very high energy (VHE) spectra from a distant blazar. In the model, both the primary photons produced in the source and secondary photons produced outside it contribute to the observed high-energy γ-ray emission. That is, the primary photons are produced through the synchrotron self-Compton process, and the secondary photons are produced through high-energy proton interactions with background photons along the line of sight. We apply the model to a characteristic case of VHE γ-ray emission in the distant blazar 1ES 1101-232. Assuming suitable electron and proton spectra, we obtain excellent fits to the observed spectra of this blazar. This indicated that the surprisingly low attenuation of the high-energy γ-rays, especially the shape of the VHE γ-ray tail of the observed spectra, can be explained by secondary γ-rays produced in interactions of cosmic-ray protons with background photons in intergalactic space.

A toy model to investigate the existence of excitons in the ground state of strongly-correlated semiconductor

NASA Astrophysics Data System (ADS)

Karima, H. R.; Majidi, M. A.

2018-04-01

Excitons, quasiparticles associated with bound states between an electron and a hole and are typically created when photons with a suitable energy are absorbed in a solid-state material. We propose to study a possible emergence of excitons, created not by photon absorption but the effect of strong electronic correlations. This study is motivated by a recent experimental study of a substrate material SrTiO3 (STO) that reveals strong exitonic signals in its optical conductivity. Here we conjecture that some excitons may already exist in the ground state as a result of the electronic correlations before the additional excitons being created later by photon absorption. To investigate the existence of excitons in the ground state, we propose to study a simple 4-energy-level model that mimics a situation in strongly-correlated semiconductors. The four levels are divided into two groups, lower and upper groups separated by an energy gap, Eg , mimicking the valence and the conduction bands, respectively. Further, we incorporate repulsive Coulomb interactions between the electrons. The model is then solved by exact diagonalization method. Our result shows that the toy model can demonstrate band gap widening or narrowing and the existence of exciton in the ground state depending on interaction parameter values.

Terahertz Light-Matter Interaction beyond Unity Coupling Strength.

PubMed

Bayer, Andreas; Pozimski, Marcel; Schambeck, Simon; Schuh, Dieter; Huber, Rupert; Bougeard, Dominique; Lange, Christoph

2017-10-11

Achieving control over light-matter interaction in custom-tailored nanostructures is at the core of modern quantum electrodynamics. In strongly and ultrastrongly coupled systems, the excitation is repeatedly exchanged between a resonator and an electronic transition at a rate known as the vacuum Rabi frequency Ω R . For Ω R approaching the resonance frequency ω c , novel quantum phenomena including squeezed states, Dicke superradiant phase transitions, the collapse of the Purcell effect, and a population of the ground state with virtual photon pairs are predicted. Yet, the experimental realization of optical systems with Ω R /ω c ≥ 1 has remained elusive. Here, we introduce a paradigm change in the design of light-matter coupling by treating the electronic and the photonic components of the system as an entity instead of optimizing them separately. Using the electronic excitation to not only boost the electronic polarization but furthermore tailor the shape of the vacuum mode, we push Ω R /ω c of cyclotron resonances ultrastrongly coupled to metamaterials far beyond unity. As one prominent illustration of the unfolding possibilities, we calculate a ground state population of 0.37 virtual photons for our best structure with Ω R /ω c = 1.43 and suggest a realistic experimental scenario for measuring vacuum radiation by cutting-edge terahertz quantum detection.

Phase Transitions of the Polariton Condensate in 2D Dirac Materials

NASA Astrophysics Data System (ADS)

Lee, Ki Hoon; Lee, Changhee; Min, Hongki; Chung, Suk Bum

2018-04-01

For the quantum well in an optical microcavity, the interplay of the Coulomb interaction and the electron-photon (e -ph) coupling can lead to the hybridizations of the exciton and the cavity photon known as polaritons, which can form the Bose-Einstein condensate above a threshold density. Additional physics due to the nontrivial Berry phase comes into play when the quantum well consists of the gapped two-dimensional Dirac material such as the transition metal dichalcogenide MoS2 or WSe2 . Specifically, in forming the polariton, the e -ph coupling from the optical selection rule due to the Berry phase can compete against the Coulomb electron-electron (e -e ) interaction. We find that this competition gives rise to a rich phase diagram for the polariton condensate involving both topological and symmetry breaking phase transitions, with the former giving rise to the quantum anomalous Hall and the quantum spin Hall phases.

Phase Transitions of the Polariton Condensate in 2D Dirac Materials.

PubMed

Lee, Ki Hoon; Lee, Changhee; Min, Hongki; Chung, Suk Bum

2018-04-13

For the quantum well in an optical microcavity, the interplay of the Coulomb interaction and the electron-photon (e-ph) coupling can lead to the hybridizations of the exciton and the cavity photon known as polaritons, which can form the Bose-Einstein condensate above a threshold density. Additional physics due to the nontrivial Berry phase comes into play when the quantum well consists of the gapped two-dimensional Dirac material such as the transition metal dichalcogenide MoS_{2} or WSe_{2}. Specifically, in forming the polariton, the e-ph coupling from the optical selection rule due to the Berry phase can compete against the Coulomb electron-electron (e-e) interaction. We find that this competition gives rise to a rich phase diagram for the polariton condensate involving both topological and symmetry breaking phase transitions, with the former giving rise to the quantum anomalous Hall and the quantum spin Hall phases.

Analytical response function for planar Ge detectors

NASA Astrophysics Data System (ADS)

García-Alvarez, Juan A.; Maidana, Nora L.; Vanin, Vito R.; Fernández-Varea, José M.

2016-04-01

We model the response function (RF) of planar HPGe x-ray spectrometers for photon energies between around 10 keV and 100 keV. The RF is based on the proposal of Seltzer [1981. Nucl. Instrum. Methods 188, 133-151] and takes into account the full-energy absorption in the Ge active volume, the escape of Ge Kα and Kβ x-rays and the escape of photons after one Compton interaction. The relativistic impulse approximation is employed instead of the Klein-Nishina formula to describe incoherent photon scattering in the Ge crystal. We also incorporate a simple model for the continuous component of the spectrum produced by the escape of photo-electrons from the active volume. In our calculations we include external interaction contributions to the RF: (i) the incoherent scattering effects caused by the detector's Be window and (ii) the spectrum produced by photo-electrons emitted in the Ge dead layer that reach the active volume. The analytical RF model is compared with pulse-height spectra simulated using the PENELOPE Monte Carlo code.

Calculation of absorption parameters for selected narcotic drugs in the energy range from 1 keV to 100 GeV

NASA Astrophysics Data System (ADS)

Akman, Ferdi; Kaçal, Mustafa Recep; Akdemir, Fatma; Araz, Aslı; Turhan, Mehmet Fatih; Durak, Rıdvan

2017-04-01

The total mass attenuation coefficients (μ/ρ), total molecular (σt,m), atomic (σt,a) and electronic (σt,e) cross sections, effective atomic numbers (Zeff) and electron density (NE) were computed in the wide energy region from 1 keV to 100 GeV for the selected narcotic drugs such as morphine, heroin, cocaine, ecstasy and cannabis. The changes of μ/ρ, σt,m, σt,a, σt,e, Zeff and NE with photon energy for total photon interaction shows the dominance of different interaction process in different energy regions. The variations of μ/ρ, σt,m, σt,a, σt,e, Zeff and NE depend on the atom number, photon energy and chemical composition of narcotic drugs. Also, these parameters change with number of elements, the range of atomic numbers in narcotic drugs and total molecular weight. These data can be useful in the field of forensic sciences and medical diagnostic.

Multi-photon ionization of atoms in intense short-wavelength radiation fields

NASA Astrophysics Data System (ADS)

Meyer, Michael

2015-05-01

The unprecedented characteristics of XUV and X-ray Free Electron Lasers (FELs) have stimulated numerous investigations focusing on the detailed understanding of fundamental photon-matter interactions in atoms and molecules. In particular, the high intensities (up to 106 W/cm2) giving rise to non-linear phenomena in the short wavelength regime. The basic phenomenology involves the production of highly charged ions via electron emission to which both sequential and direct multi-photon absorption processes contribute. The detailed investigation of the role and relative weight of these processes under different conditions (wavelength, pulse duration, intensity) is the key element for a comprehensive understanding of the ionization dynamics. Here the results of recent investigations are presented, performed at the FELs in Hamburg (FLASH) and Trieste (FERMI) on atomic systems with electronic structures of increasing complexity (Ar, Ne and Xe). Mainly, electron spectroscopy is used to obtain quantitative information about the relevance of various multi-photon ionization processes. For the case of Ar, a variety of processes including above threshold ionization (ATI) from 3p and 3s valence shells, direct 2p two-photon ionization and resonant 2p-4p two-photon excitations were observed and their role was quantitatively determined comparing the experimental ionization yields to ab-initio calculations of the cross sections for the multi-photon processes. Using Ar as a benchmark to prove the reliability of the combined experimental and theoretical approach, the more complex and intriguing case of Xe was studied. Especially, the analysis of the two-photon ATI from the Xe 4d shell reveals new insight into the character of the 4d giant resonance, which was unresolved in the linear one-photon regime. Finally, the influence of intense XUV radiation to the relaxation dynamics of the Ne 2s-3p resonance was investigated by angle-resolved electron spectroscopy, especially be observing the intensity dependent variation of the angular distribution patterns for the sequential ionization process.

X-ray two-photon absorption with high fluence XFEL pulses

DOE PAGES

Hoszowska, Joanna; Szlachetko, J.; Dousse, J. -Cl.; ...

2015-09-07

Here, we report on nonlinear interaction of solid Fe with intense femtosecond hard x-ray free-electron laser (XFEL) pulses. The experiment was performed at the CXI end-station of the Linac Coherent Light Source (LCLS) by means of high- resolution x-ray emission spectroscopy. The focused x-ray beam provided extreme fluence of ~10 5 photons/Å 2. Two-photon absorption leading to K-shell hollow atom formation and to single K-shell ionization of solid Fe was investigated.

Poem: A Fast Monte Carlo Code for the Calculation of X-Ray Transition Zone Dose and Current

DTIC Science & Technology

1975-01-15

stored on the photon interaction data tape. Following the photoelectric ionization the atom will relax emitting either a fluorescent photon or an Auger 50...shell fluorescence yield CL have been obtained from the Storm and Israel1 9 and 25 Bambynek, et al. compilations, with preference given to the...Bambynek compilation, and stored on the photon inter- action data tape. The mean M fluorescence yield wM is approximated by zero. The total electron source

Laser-Induced Linear-Field Particle Acceleration in Free Space.

PubMed

Wong, Liang Jie; Hong, Kyung-Han; Carbajo, Sergio; Fallahi, Arya; Piot, Philippe; Soljačić, Marin; Joannopoulos, John D; Kärtner, Franz X; Kaminer, Ido

2017-09-11

Linear-field particle acceleration in free space (which is distinct from geometries like the linac that requires components in the vicinity of the particle) has been studied for over 20 years, and its ability to eventually produce high-quality, high energy multi-particle bunches has remained a subject of great interest. Arguments can certainly be made that linear-field particle acceleration in free space is very doubtful given that first-order electron-photon interactions are forbidden in free space. Nevertheless, we chose to develop an accurate and truly predictive theoretical formalism to explore this remote possibility when intense, few-cycle electromagnetic pulses are used in a computational experiment. The formalism includes exact treatment of Maxwell's equations and exact treatment of the interaction among the multiple individual particles at near and far field. Several surprising results emerge. We find that electrons interacting with intense laser pulses in free space are capable of gaining substantial amounts of energy that scale linearly with the field amplitude. For example, 30 keV electrons (2.5% energy spread) are accelerated to 61 MeV (0.5% spread) and to 205 MeV (0.25% spread) using 250 mJ and 2.5 J lasers respectively. These findings carry important implications for our understanding of ultrafast electron-photon interactions in strong fields.

Evolution of the modern photon

NASA Astrophysics Data System (ADS)

Kidd, Richard; Ardini, James; Anton, Anatol

1989-01-01

The term ``photon'' represents at least four distinct models and carries different connotations for students and for practicing physicists. This reflects the long and complex historical evolution of the concept and its association with the largely misinterpreted principle of duality. The unsatisfactory nature of the corpuscular and wave packet models is discussed, and the pedagogical desirability urged of replacing them with a semiclassical approach in elementary presentations. Derivations of the photoelectric (PE) effect without photons are cited and a vector analysis is given, demonstrating that the PE effect cannot be considered as simply the interaction of a photon and electron.

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

PubMed

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.

Time-dependent current into and through multilevel parallel quantum dots in a photon cavity

NASA Astrophysics Data System (ADS)

Gudmundsson, Vidar; Abdullah, Nzar Rauf; Sitek, Anna; Goan, Hsi-Sheng; Tang, Chi-Shung; Manolescu, Andrei

2017-05-01

We analyze theoretically the charging current into, and the transport current through, a nanoscale two-dimensional electron system with two parallel quantum dots embedded in a short wire placed in a photon cavity. A plunger gate is used to place specific many-body states of the interacting system in the bias window defined by the external leads. We show how the transport phenomena active in the many-level complex central system strongly depend on the gate voltage. We identify a resonant transport through the central system as the two spin components of the one-electron ground state are in the bias window. This resonant transport through the lowest energy electron states seems to a large extent independent of the detuned photon field when judged from the transport current. This could be expected in the small bias regime, but an observation of the occupancy of the states of the system reveals that this picture is not entirely true. The current does not reflect slower photon-active internal transitions bringing the system into the steady state. The number of initially present photons determines when the system reaches the real steady state. With two-electron states in the bias window we observe a more complex situation with intermediate radiative and nonradiative relaxation channels leading to a steady state with a weak nonresonant current caused by inelastic tunneling through the two-electron ground state of the system. The presence of the radiative channels makes this phenomena dependent on the number of photons initially in the cavity.

The spectrum of darkonium in the Sun

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kouvaris, Chris; Langæble, Kasper; Nielsen, Niklas Grønlund

Dark matter that gets captured in the Sun may form positronium-like bound states if it self-interacts via light dark photons. In this case, dark matter can either annihilate to dark photons or recombine in bound states which subsequently also decay to dark photons. The fraction of the dark photons that leave the Sun without decaying to Standard Model particles have a characteristic energy spectrum which is a mixture of the direct annihilation process, the decays of ortho- and para- bound states and the recombination process. The ultimate decay of these dark photons to positron-electron pairs (via kinetic mixing) outside themore » Sun creates a distinct signal that can either identify or set strict constraints on dark photon models.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Müller, Alfred; Bernhardt, Dietrich; Borovik, Alexander

Single, double, and triple photoionization of Ne + ions by single photons have been investigated at the synchrotron radiation source PETRA III in Hamburg, Germany. Absolute cross-sections were measured by employing the photon-ion merged-beams technique. Photon energies were between about 840 and 930 eV, covering the range from the lowest-energy resonances associated with the excitation of one single K-shell electron up to double excitations involving one K- and one L-shell electron, well beyond the K-shell ionization threshold. Also, photoionization of neutral Ne was investigated just below the K edge. The chosen photon energy bandwidths were between 32 and 500 meV,more » facilitating the determination of natural line widths. The uncertainty of the energy scale is estimated to be 0.2 eV. For comparison with existing theoretical calculations, astrophysically relevant photoabsorption cross-sections were inferred by summing the measured partial ionization channels. Discussion of the observed resonances in the different final ionization channels reveals the presence of complex Auger-decay mechanisms. The ejection of three electrons from the lowest K-shell-excited Ne + (1s2s 2p 6 2S 1/2) level, for example, requires cooperative interaction of at least four electrons.« less

Spin-orbit interaction of light on the surface of atomically thin crystals

NASA Astrophysics Data System (ADS)

Zhou, Junxiao; Chen, Shizhen; Zhang, Wenshuai; Luo, Hailu; Wen, Shuangchun

2017-09-01

Two-dimensional (2D) atomic crystals have extraordinary electronic and photonic properties and hold great promise in the applications of photonic and optoelectronics. Here, we review some of our works about the spin-orbit interaction of light on the surface of 2D atomic crystals. First, we propose a general model to describe the spin-orbit interaction of light of the 2D free standing atomic crystal, and find that it is not necessary to involve the effective refractive index to describe the spin-orbit interaction. By developing the quantum weak measurements, we detect the spin-orbit interaction of light in 2D atomic crystals, which can act as a simple method for defining the layer numbers of graphene. Moreover, we find the transverse spin-dependent splitting in the photonic spin Hall effect exhibits a quantized behavior. Furthermore, the spin-orbit interaction of light for the case of air-topological insulator interface can be routed by adjusting the strength of the axion coupling. These basic finding may enhance the comprehension of the spin-orbit interaction, and find the important application in optoelectronic.

Can there be massive photons? A pedagogical glance at the origin of mass

NASA Astrophysics Data System (ADS)

Robles, P.; Claro, F.

2012-09-01

Among the most startling experiences a student encounters is learning that, unlike electrons and other elementary particles, photons have no mass. Under certain circumstances, however, the light quantum behaves as if it did have a finite mass. Starting from Maxwell's equations, we discuss how this arises when light interacts with a charged plasma, or travels along a waveguide. The motion of such photons is analysed using kinematic concepts of special relativity, and we show how a cutoff frequency for effective propagation appears. Seeing how an environment may yield an apparent dynamic mass to the photon paves the way for later understanding: might the Higgs boson field provide other particles, such as the electron, with a mass? This paper is addressed to mid-level physics students, teachers and lecturers, requiring only a knowledge of classical electromagnetic and special relativity theories.

Studies on effective atomic numbers for photon energy absorption and electron density of some narcotic drugs in the energy range 1 keV-20 MeV

NASA Astrophysics Data System (ADS)

Gounhalli, Shivraj G.; Shantappa, Anil; Hanagodimath, S. M.

2013-04-01

Effective atomic numbers for photon energy absorption ZPEA,eff, photon interaction ZPI,eff and for electron density Nel, have been calculated by a direct method in the photon-energy region from 1 keV to 20 MeV for narcotic drugs, such as Heroin (H), Cocaine (CO), Caffeine (CA), Tetrahydrocannabinol (THC), Cannabinol (CBD), Tetrahydrocannabivarin (THCV). The ZPEA,eff, ZPI,eff and Nel values have been found to change with energy and composition of the narcotic drugs. The energy dependence ZPEA,eff, ZPI,eff and Nel is shown graphically. The maximum difference between the values of ZPEA,eff, and ZPI,eff occurs at 30 keV and the significant difference of 2 to 33% for the energy region 5-100 keV for all drugs. The reason for these differences is discussed.

Resonance Search for a Heavy Photon in the 2015 Engineering Run Data of the Heavy Photon Search Experiment

NASA Astrophysics Data System (ADS)

Moreno, Omar; Heavy Photon Search Collaboration

2017-01-01

The Heavy Photon Search (HPS) experiment at Jefferson Lab is searching for a new U(1) vector boson (``heavy photon'',``dark photon'' or A') in the mass range of 20-500 MeV/c2. An A' in this mass range is theoretically favorable and may also mediate dark matter interactions. The A' couples to the ordinary photon through kinetic mixing, which induces their coupling to electric charge. Since heavy photons couple to electrons, they can be produced through a process analogous to bremsstrahlung, subsequently decaying to an e+e- , which can be observed as a narrow resonance above the dominant QED trident background. For suitably small couplings, heavy photons travel detectable distances before decaying, providing a second signature. Using the CEBAF electron beam at Jefferson Lab incident on a thin tungsten target, along with a compact, large acceptance forward spectrometer consisting of a silicon vertex tracker and lead tungstate electromagnetic calorimeter, HPS is accessing unexplored regions in the mass-coupling phase space. The HPS engineering run took place in spring of 2015 using a 1.056 GeV, 50 nA beam and collected 1165 nb-1 (7.29 mC) of data. This talk will present the results of a resonance search for a heavy photon using the engineering run data.

Study of Electromagnetic Interactions with the MicroBooNE Detector

NASA Astrophysics Data System (ADS)

Caratelli, David; MicroBooNE Collaboration

2017-01-01

MicroBooNE is an experiment which employs the Liquid Argon Time Projection Chamber (LArTPC) detector technology to study neutrinos produced with the Fermilab Booster Neutrino Beam. As for any accelerator-based detector interested in studying neutrino oscillations, it is essential to be able to identify and reconstruct the kinematic properties of electrons and photons produced in μν and νe interactions. We report current progress in reconstructing electron and photon electromagnetic (EM) showers using data from the MicroBooNE LArTPC. These studies cover EM showers in the tens to hundreds of MeV energy range; they lay the foundation for MicroBooNE's investigation of the excess of low-energy EM events reported by MiniBooNE, and are of interest to the wider LArTPC neutrino community.

Photonics for life.

PubMed

Cubeddu, Rinaldo; Bassi, Andrea; Comelli, Daniela; Cova, Sergio; Farina, Andrea; Ghioni, Massimo; Rech, Ivan; Pifferi, Antonio; Spinelli, Lorenzo; Taroni, Paola; Torricelli, Alessandro; Tosi, Alberto; Valentini, Gianluca; Zappa, Franco

2011-01-01

Light is strictly connected with life, and its presence is fundamental for any living environment. Thus, many biological mechanisms are related to light interaction or can be evaluated through processes involving energy exchange with photons. Optics has always been a precious tool to evaluate molecular and cellular mechanisms, but the discovery of lasers opened new pathways of interactions of light with biological matter, pushing an impressive development for both therapeutic and diagnostic applications in biomedicine. The use of light in different fields has become so widespread that the word photonics has been utilized to identify all the applications related to processes where the light is involved. The photonics area covers a wide range of wavelengths spanning from soft X-rays to mid-infrared and includes all devices related to photons as light sources, optical fibers and light guides, detectors, and all the related electronic equipment. The recent use of photons in the field of telecommunications has pushed the technology toward low-cost, compact, and efficient devices, making them available for many other applications, including those related to biology and medicine where these requirements are of particular relevance. Moreover, basic sciences such as physics, chemistry, mathematics, and electronics have recognized the interdisciplinary need of biomedical science and are translating the most advanced researches into these fields. The Politecnico school has pioneered many of them,and this article reviews the state of the art of biomedical research at the Politecnico in the field internationally known as biophotonics.

Strong constraints on sub-GeV dark sectors from SLAC beam dump E137.

PubMed

Batell, Brian; Essig, Rouven; Surujon, Ze'ev

2014-10-24

We present new constraints on sub-GeV dark matter and dark photons from the electron beam-dump experiment E137 conducted at SLAC in 1980-1982. Dark matter interacting with electrons (e.g., via a dark photon) could have been produced in the electron-target collisions and scattered off electrons in the E137 detector, producing the striking, zero-background signature of a high-energy electromagnetic shower that points back to the beam dump. E137 probes new and significant ranges of parameter space and constrains the well-motivated possibility that dark photons that decay to light dark-sector particles can explain the ∼3.6σ discrepancy between the measured and standard model value of the muon anomalous magnetic moment. It also restricts the parameter space in which the relic density of dark matter in these models is obtained from thermal freeze-out. E137 also convincingly demonstrates that (cosmic) backgrounds can be controlled and thus serves as a powerful proof of principle for future beam-dump searches for sub-GeV dark-sector particles scattering off electrons in the detector.

Final Report - Few-Body Studies Using Electromagnetic Interactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Norum, Blaine

The work discussed here is an extension of work previously funded by U.S. Department of Energy Grant DE-FG02-97ER41025. Measurements of charged pion photoproduction from deuterium using the Laser Electron Gamma Source (LEGS) at the Brookhaven National Laboratory previously made by us, as members of the LEGS Collaboration, resulted in the most interesting result of two decades of work. By measuring the production of a charged pion (π +) in coincidence with an emitted photon we observed structures in the residual two-nucleon system. These indicated the existence of rare, long-lived states not explicable by standard nuclear theory; they suggested a setmore » of configurations not explicable in terms of a nucleon-nucleon pair. The existence of such “exotic” structures has formed the foundation for most of the work that has ensued. Several measurements at various laboratories have supported, but not proved, the existence of these exotic states. The rarity of these states made their existence undetectable in most previous measurements. Only by observing characteristic signatures of such states (i.e., decay photons), by using very specific kinematics which isolate certain reaction products, or by measuring polarization-dependent observables. During the period of this grant we pursued and made progress on the development of experiments to be performed at the High Intensity Gamma Source (HIGS) of the Tri Universities Nuclear Laboratory (TUNL). Our understanding of photon- and electron-induced nuclear reactions depends on understanding of the basic electron and photon interaction. Recently, the issue of two-photon contributions has arisen in the context of deeply inelastic electron scattering. One way to address this is to measure asymmetries in the Bethe-Heitler ee process. We also made progress in developing the detectors required to measure these asymmetries at HIGS. During the last several years the apparent discrepancy between the size of the proton as measured using electrons and that as measured using muons has received a great deal of attention. Working with colleagues at the Jefferson Laboratory (JLAB) we showed that the apparent discrepancy was almost surely the result of mistakes in the statistical analysis of electron scattering data, that there is almost surely no discrepancy.« less

X-ray emission reduction and photon dose lowering by energy loss of fast electrons induced by return current during the interaction of a short-pulse high-intensity laser on a metal solid target

NASA Astrophysics Data System (ADS)

Compant La Fontaine, A.

2018-04-01

During the interaction of a short-pulse high-intensity laser with the preplasma produced by the pulse's pedestal in front of a high-Z metal solid target, high-energy electrons are produced, which in turn create an X-ray source by interacting with the atoms of the converter target. The current brought by the hot electrons is almost completely neutralized by a return current j → driven by the background electrons of the conductive target, and the force exerted on the hot electrons by the electric field E → which induces Ohmic heating j → .E → , produced by the background electrons, reduces the energy of the hot electrons and thus lowers the X-ray emission and photon dose. This effect is analyzed here by means of a simple 1-D temperature model which contains the most significant terms of the relativistic Fokker-Planck equation with electron multiple scattering, and the energy equations of ions, hot, and cold electrons are then solved numerically. This Ohmic heating energy loss fraction τOh is introduced as a corrective term in an improved photon dose model. For instance, for a ps laser pulse with 10 μm spot size, the dose obtained with a tantalum target is reduced by less than about 10% to 40% by the Ohmic heating, depending upon the plasma scale length, target thickness, laser parameters, and in particular its spot size. The laser and plasma parameters may be optimized to limit the effect of Ohmic heating, for instance at a small plasma scale length or small laser spot size. Conversely, others regimes not suitable for dose production are identified. For instance, the resistive heating is enhanced in a foam target or at a long plasma scale length and high laser spot size and intensity, as the mean emission angle θ0 of the incident hot electron bunch given by the ponderomotive force is small; thus, the dose produced by a laser interacting in a gas jet may be inhibited under these circumstances. The resistive heating may also be maximized in order to reduce the X-ray emission to lower the radiation level for instance in a safety radiological goal.

Magnetic field influences on the lateral dose response functions of photon-beam detectors: MC study of wall-less water-filled detectors with various densities.

PubMed

Looe, Hui Khee; Delfs, Björn; Poppinga, Daniela; Harder, Dietrich; Poppe, Björn

2017-06-21

The distortion of detector reading profiles across photon beams in the presence of magnetic fields is a developing subject of clinical photon-beam dosimetry. The underlying modification by the Lorentz force of a detector's lateral dose response function-the convolution kernel transforming the true cross-beam dose profile in water into the detector reading profile-is here studied for the first time. The three basic convolution kernels, the photon fluence response function, the dose deposition kernel, and the lateral dose response function, of wall-less cylindrical detectors filled with water of low, normal and enhanced density are shown by Monte Carlo simulation to be distorted in the prevailing direction of the Lorentz force. The asymmetric shape changes of these convolution kernels in a water medium and in magnetic fields of up to 1.5 T are confined to the lower millimetre range, and they depend on the photon beam quality, the magnetic flux density and the detector's density. The impact of this distortion on detector reading profiles is demonstrated using a narrow photon beam profile. For clinical applications it appears as favourable that the magnetic flux density dependent distortion of the lateral dose response function, as far as secondary electron transport is concerned, vanishes in the case of water-equivalent detectors of normal water density. By means of secondary electron history backtracing, the spatial distribution of the photon interactions giving rise either directly to secondary electrons or to scattered photons further downstream producing secondary electrons which contribute to the detector's signal, and their lateral shift due to the Lorentz force is elucidated. Electron history backtracing also serves to illustrate the correct treatment of the influences of the Lorentz force in the EGSnrc Monte Carlo code applied in this study.

Bright and dark singlet excitons via linear and two-photon spectroscopy in monolayer transition metal dichalcogenides

DOE PAGES

Berkelbach, Timothy C.; Hybertsen, Mark S.; Reichmann, David R.

2015-08-10

We discuss the linear and two-photon spectroscopic selection rules for spin-singlet excitons in monolayer transition-metal dichalcogenides. Our microscopic formalism combines a fully k-dependent few-orbital band structure with a many-body Bethe-Salpeter equation treatment of the electron-hole interaction, using a model dielectric function. We show analytically and numerically that the single-particle, valley-dependent selection rules are preserved in the presence of excitonic effects. Furthermore, we definitively demonstrate that the bright (one-photon allowed) excitons have s-type azimuthal symmetry and that dark p-type excitons can be probed via two-photon spectroscopy. Thus, the screened Coulomb interaction in these materials substantially deviates from the 1/ε₀r form; thismore » breaks the “accidental” angular momentum degeneracy in the exciton spectrum, such that the 2p exciton has a lower energy than the 2s exciton by at least 50 meV. We compare our calculated two-photon absorption spectra to recent experimental measurements.« less

Laser-Neuron Interaction with Femtosecond Beat-Modulated 800-1200 nm Photon Beams, as the Treatment of Brain Cancer Tissue. Laser Neurophysics

NASA Astrophysics Data System (ADS)

Stefan, V. Alexander

2011-03-01

I propose a novel mechanism for the brain cancer tissue treatment: nonlinear interaction of ultrashort pulses of beat-photon, (ω1 -- ω2) , or double-photon, (ω1 +ω2) , beams with the cancer tissue. The multiphoton scattering is described via photon diffusion equation. The open-scull cerebral tissue can be irradiated with the beat-modulated photon pulses with the laser irradiances in the range of a few mW/cm2 , and repetition rate of a few 100s Hz generated in the beat-wave driven free electron laser. V. Stefan, B. I. Cohen, and C. Joshi, Nonlinear Mixing of Electromagnetic Waves in PlasmasScience 27 January 1989: V. Alexander Stefan, Genomic Medical Physics: A New Physics in the Making, (S-U-Press, 2008).} This highly accurate cancer tissue ablation removal may prove to be an efficient method for the treatment of brain cancer. Work supported in part by Nikola Tesla Laboratories (Stefan University), La Jolla, CA.

Selective Optical Addressing of Nuclear Spins through Superhyperfine Interaction in Rare-Earth Doped Solids.

PubMed

Car, B; Veissier, L; Louchet-Chauvet, A; Le Gouët, J-L; Chanelière, T

2018-05-11

In Er^{3+}:Y_{2}SiO_{5}, we demonstrate the selective optical addressing of the ^{89}Y^{3+} nuclear spins through their superhyperfine coupling with the Er^{3+} electronic spins possessing large Landé g factors. We experimentally probe the electron-nuclear spin mixing with photon echo techniques and validate our model. The site-selective optical addressing of the Y^{3+} nuclear spins is designed by adjusting the magnetic field strength and orientation. This constitutes an important step towards the realization of long-lived solid-state qubits optically addressed by telecom photons.

Selective Optical Addressing of Nuclear Spins through Superhyperfine Interaction in Rare-Earth Doped Solids

NASA Astrophysics Data System (ADS)

Car, B.; Veissier, L.; Louchet-Chauvet, A.; Le Gouët, J.-L.; Chanelière, T.

2018-05-01

In Er3 +:Y2SiO5 , we demonstrate the selective optical addressing of the Y89 3 + nuclear spins through their superhyperfine coupling with the Er3 + electronic spins possessing large Landé g factors. We experimentally probe the electron-nuclear spin mixing with photon echo techniques and validate our model. The site-selective optical addressing of the Y3 + nuclear spins is designed by adjusting the magnetic field strength and orientation. This constitutes an important step towards the realization of long-lived solid-state qubits optically addressed by telecom photons.

Topological Phases of Sound and Light

NASA Astrophysics Data System (ADS)

Peano, V.; Brendel, C.; Schmidt, M.; Marquardt, F.

2015-07-01

Topological states of matter are particularly robust, since they exploit global features of a material's band structure. Topological states have already been observed for electrons, atoms, and photons. It is an outstanding challenge to create a Chern insulator of sound waves in the solid state. In this work, we propose an implementation based on cavity optomechanics in a photonic crystal. The topological properties of the sound waves can be wholly tuned in situ by adjusting the amplitude and frequency of a driving laser that controls the optomechanical interaction between light and sound. The resulting chiral, topologically protected phonon transport can be probed completely optically. Moreover, we identify a regime of strong mixing between photon and phonon excitations, which gives rise to a large set of different topological phases and offers an example of a Chern insulator produced from the interaction between two physically distinct particle species, photons and phonons.

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

PubMed Central

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

Astrophysical gamma-ray production by inverse Compton interactions of relativistic electrons

NASA Technical Reports Server (NTRS)

Schlickeiser, R.

1979-01-01

The inverse Compton scattering of background photon gases by relativistic electrons is a good candidate for the production of high-energy gamma rays in the diffuse interstellar medium as well as in discrete sources. By discussing the special case of the scattering of the diffuse starlight in the interstellar medium by cosmic ray electrons, we demonstrate that previous derivations of the gamma ray source function for this process on the basis of the Thomson limit of the Klein-Nishina cross section lead to incorrect values for gamma-ray energies above 100 MeV. It is shown that the Thomson limit is not applicable for the calculation of gamma-ray source functions in astrophysical circumstances in which target photons with energies greater than 1 eV are scattered by relativistic electrons.

Radiation transport in kinetic simulations and the influence of photoemission on electron current in self-sustaining discharges

DOE PAGES

Fierro, Andrew S.; Moore, Christopher Hudson; Scheiner, Brett; ...

2017-01-12

A kinetic description for electronic excitation of helium for principal quantum number nmore » $$\\leqslant $$ 4 has been included into a particle-in-cell (PIC) simulation utilizing direct simulation Monte Carlo (DSMC) for electron-neutral interactions. The excited electronic levels radiate state-dependent photons with wavelengths from the extreme ultraviolet (EUV) to visible regimes. Photon wavelengths are chosen according to a Voigt distribution accounting for the natural, pressure, and Doppler broadened linewidths. This method allows for reconstruction of the emission spectrum for a non-thermalized electron energy distribution function (EEDF) and investigation of high energy photon effects on surfaces, specifically photoemission. A parallel plate discharge with a fixed field (i.e. space charge neglected) is used to investigate the effects of including photoemission for a Townsend discharge. When operating at a voltage near the self-sustaining discharge threshold, it is observed that the electron current into the anode is higher when including photoemission from the cathode than without even when accounting for self-absorption from ground state atoms. As a result, the photocurrent has been observed to account for as much as 20% of the total current from the cathode under steady-state conditions.« less

Optically tunable spontaneous Raman fluorescence from a single self-assembled InGaAs quantum dot.

PubMed

Fernandez, G; Volz, T; Desbuquois, R; Badolato, A; Imamoglu, A

2009-08-21

We report the observation of all-optically tunable Raman fluorescence from a single quantum dot. The Raman photons are produced in an optically driven Lambda system defined by subjecting the single electron charged quantum dot to a magnetic field in Voigt geometry. Detuning the driving laser from resonance, we tune the frequency of the Raman photons by about 2.5 GHz. The number of scattered photons and the linewidth of the Raman photons are investigated as a function of detuning. The study presented here could form the basis of a new technique for investigating spin-bath interactions in the solid state.

Photons in dense nuclear matter: Random-phase approximation

NASA Astrophysics Data System (ADS)

Stetina, Stephan; Rrapaj, Ermal; Reddy, Sanjay

2018-04-01

We present a comprehensive and pedagogic discussion of the properties of photons in cold and dense nuclear matter based on the resummed one-loop photon self-energy. Correlations among electrons, muons, protons, and neutrons in β equilibrium that arise as a result of electromagnetic and strong interactions are consistently taken into account within the random phase approximation. Screening effects, damping, and collective excitations are systematically studied in a fully relativistic setup. Our study is relevant to the linear response theory of dense nuclear matter, calculations of transport properties of cold dense matter, and investigations of the production and propagation of hypothetical vector bosons such as the dark photons.

Optical pulse generation in a transistor laser via intra-cavity photon-assisted tunneling and excess base carrier redistribution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, M.; Iverson, E. W.; Wang, C. Y.

2015-11-02

For a direct-gap semiconductor (e.g., a p-n junction), photon-assisted tunneling is known to exhibit a high nonlinear absorption. In a transistor laser, as discussed here, the coherent photons generated at the quantum well interact with the collector junction field and “assist” electron tunneling from base to collector, thus resulting in the nonlinear modulation of the laser and the realization of optical pulse generation. 1 and 2 GHz optical pulses are demonstrated in the transistor laser using collector voltage control.

The ‘cutting away’ of potential secondary electron tracks explains the effects of beam size and detector wall density in small-field photon dosimetry

NASA Astrophysics Data System (ADS)

Khee Looe, Hui; Delfs, Björn; Poppinga, Daniela; Jiang, Ping; Harder, Dietrich; Poppe, Björn

2018-01-01

The well-known field-size dependent overresponse in small-field photon-beam dosimetry of solid-state detectors equipped with very thin sensitive volumes, such as the PTW microDiamond, cannot be caused by the photon and electron interactions within these sensitive layers because they are only a few micrometers thick. The alternative explanation is that their overresponse is caused by the combination of two effects, the modification of the secondary electron fluence profile (i) by a field size too small to warrant lateral secondary electron equilibrium and (ii) by the density-dependent electron ranges in the structural detector materials placed in front of or backing the sensitive layer. The present study aims at the numerical demonstration and visualization of this combined mechanism. The lateral fluence profiles of the secondary electrons hitting a 1 µm thick scoring layer were Monte-Carlo simulated by modelling their generation and transport in the upstream or downstream adjacent layers of thickness 0.6 mm and densities from 0.0012 to 3 g cm-3, whose atomic composition was constantly kept water-like. The scoring layer/adjacent layer sandwich was placed in an infinite water phantom irradiated by circular 60Co, 6 MV and 15 MV photon beams with diameters from 3 to 40 mm. The interpretation starts from the ideal case of lateral secondary electron equilibrium, where the Fano theorem excludes any density effect. If the field size is then reduced, electron tracks potentially originating from source points outside the field border will then be numerically ‘cut away’. This geometrical effect reduces the secondary electron fluence at the field center, but the magnitude of this reduction also varies with the density-dependent electron ranges in the adjacent layers. This combined mechanism, which strongly depends on the photon spectrum, explains the field size and material density effect on the response of detectors with very thin sensitive layers used in small-field photon-beam dosimetry.

Laser-Induced Linear-Field Particle Acceleration in Free Space

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wong, Liang Jie; Hong, Kyung -Han; Carbajo, Sergio

Linear-field particle acceleration in free space (which is distinct from geometries like the linac that requires components in the vicinity of the particle) has been studied for over 20 years, and its ability to eventually produce high-quality, high energy multi-particle bunches has remained a subject of great interest. Arguments can certainly be made that linear-field particle acceleration in free space is very doubtful given that first-order electron-photon interactions are forbidden in free space. Nevertheless, we chose to develop an accurate and truly predictive theoretical formalism to explore this remote possibility when intense, few-cycle electromagnetic pulses are used in a computationalmore » experiment. The formalism includes exact treatment of Maxwell’s equations and exact treatment of the interaction among the multiple individual particles at near and far field. Several surprising results emerge. We find that electrons interacting with intense laser pulses in free space are capable of gaining substantial amounts of energy that scale linearly with the feld amplitude. For example, 30keV electrons (2.5% energy spread) are accelerated to 61MeV (0.5% spread) and to 205MeV (0.25% spread) using 250 mJ and 2.5J lasers respectively. Furthermore, these findings carry important implications for our understanding of ultrafast electron-photon interactions in strong fields.« less

Laser-Induced Linear-Field Particle Acceleration in Free Space

DOE PAGES

Wong, Liang Jie; Hong, Kyung -Han; Carbajo, Sergio; ...

2017-09-11

Linear-field particle acceleration in free space (which is distinct from geometries like the linac that requires components in the vicinity of the particle) has been studied for over 20 years, and its ability to eventually produce high-quality, high energy multi-particle bunches has remained a subject of great interest. Arguments can certainly be made that linear-field particle acceleration in free space is very doubtful given that first-order electron-photon interactions are forbidden in free space. Nevertheless, we chose to develop an accurate and truly predictive theoretical formalism to explore this remote possibility when intense, few-cycle electromagnetic pulses are used in a computationalmore » experiment. The formalism includes exact treatment of Maxwell’s equations and exact treatment of the interaction among the multiple individual particles at near and far field. Several surprising results emerge. We find that electrons interacting with intense laser pulses in free space are capable of gaining substantial amounts of energy that scale linearly with the feld amplitude. For example, 30keV electrons (2.5% energy spread) are accelerated to 61MeV (0.5% spread) and to 205MeV (0.25% spread) using 250 mJ and 2.5J lasers respectively. Furthermore, these findings carry important implications for our understanding of ultrafast electron-photon interactions in strong fields.« less

Biophoton research in blood reveals its holistic properties.

PubMed

Voeikov, V L; Asfaramov, R; Bouravleva, E V; Novikov, C N; Vilenskaya, N D

2003-05-01

Monitoring of spontaneous and luminophore amplified photon emission (PE) from non-diluted human blood under resting conditions and artificially induced immune reaction revealed that blood is a continuous source of biophotons indicating that it persists in electronically excited state. This state is pumped through generation of electron excitation produced in reactive oxygen species (ROS) reactions. Excited state of blood and of neutrophil suspensions (primary sources of ROS in blood) is an oscillatory one suggesting of interaction between individual sources of electron excitation. Excited state of blood is extremely sensitive to the tiniest fluctuations of external photonic fields but resistant to temperature variations as reflected in hysteresis of PE in response to temperature variations. These data suggest that blood is a highly cooperative non-equilibrium and non-linear system, whose components unceasingly interact in time and space. At least in part this property is provided by the ability of blood to store energy of electron excitation that is produced in course of its own normal metabolism. From a practical point of view analysis of these qualities of blood may be a basement of new approach to diagnostic procedures.

Detection of pulsed bremsstrahlung-induced prompt neutron capture gamma rays with a HPGe detector

NASA Astrophysics Data System (ADS)

Jones, James L.

1997-02-01

The Idaho National Engineering Laboratory (INEL) is developing a novel photoneutron-based nondestructive evaluation technique which uses a pulsed, high-energy electron accelerator and gamma-ray spectrometry. Highly penetrating pulses of bremsstrahlung photons are produced by each pulse of electrons. Interrogating neutrons are generated by the bremsstrahlung photons interacting within a photoneutron source material. The interactions of the neutrons within a target result in the emission of elemental characteristic gamma-rays. Spectrometry is performed by analyzing the photoneutron-induced, prompt gama-rays acquired between accelerator pulses with a unique, high- purity germanium gamma-ray detection system using a modified transistor reset preamplifier. The detection system, the experimental configuration, and the accelerator operation used to characterize the detection systems performance are described. Using a 6.5-MeV electron accelerator and a beryllium metal photoneutron source, gamma-ray spectra were successfully acquired for Al, Cu, polyethylene, NaCl, and depleted uranium targets as soon as 30 microsecond(s) after each bremsstrahlung flash.

Effective atomic numbers and electron densities of bioactive glasses for photon interaction

NASA Astrophysics Data System (ADS)

Shantappa, Anil; Hanagodimath, S. M.

2015-08-01

This work was carried out to study the nature of mass attenuation coefficient of bioactive glasses for gamma rays. Bioactive glasses are a group of synthetic silica-based bioactive materials with unique bone bonding properties. In the present study, we have calculated the effective atomic number, electron density for photon interaction of some selected bioactive glasses viz., SiO2-Na2O, SiO2-Na2O-CaO and SiO2-Na2O-P2O5 in the energy range 1 keV to 100 MeV. We have also computed the single valued effective atomic number by using XMuDat program. It is observed that variation in effective atomic number (ZPI, eff) depends also upon the weight fractions of selected bioactive glasses and range of atomic numbers of the elements. The results shown here on effective atomic number, electron density will be more useful in the medical dosimetry for the calculation of absorbed dose and dose rate.

A glimpse of gluons through deeply virtual compton scattering on the proton

DOE Office of Scientific and Technical Information (OSTI.GOV)

Defurne, Maxime; Jimenez-Arguello, A. Marti; Ahmed, Z.

The proton is composed of quarks and gluons, bound by the most elusive mechanism of strong interaction called confinement. In this work, the dynamics of quarks and gluons are investigated using deeply virtual Compton scattering (DVCS): produced by a multi-GeV electron, a highly virtual photon scatters off the proton which subsequently radiates a high energy photon. Similarly to holography, measuring not only the magnitude but also the phase of the DVCS amplitude allows to perform 3D images of the internal structure of the proton. The phase is made accessible through the quantum-mechanical interference of DVCS with the Bethe-Heitler (BH) process,more » in which the final photon is emitted by the electron rather than the proton. Here, we report herein the first full determination of the BH-DVCS interference by exploiting the distinct energy dependences of the DVCS and BH amplitudes. In the high energy regime where the scattering process is expected to occur off a single quark in the proton, these accurate measurements show an intriguing sensitivity to gluons, the carriers of the strong interaction.« less

A glimpse of gluons through deeply virtual compton scattering on the proton

DOE PAGES

Defurne, Maxime; Jimenez-Arguello, A. Marti; Ahmed, Z.; ...

2017-11-10

The proton is composed of quarks and gluons, bound by the most elusive mechanism of strong interaction called confinement. In this work, the dynamics of quarks and gluons are investigated using deeply virtual Compton scattering (DVCS): produced by a multi-GeV electron, a highly virtual photon scatters off the proton which subsequently radiates a high energy photon. Similarly to holography, measuring not only the magnitude but also the phase of the DVCS amplitude allows to perform 3D images of the internal structure of the proton. The phase is made accessible through the quantum-mechanical interference of DVCS with the Bethe-Heitler (BH) process,more » in which the final photon is emitted by the electron rather than the proton. Here, we report herein the first full determination of the BH-DVCS interference by exploiting the distinct energy dependences of the DVCS and BH amplitudes. In the high energy regime where the scattering process is expected to occur off a single quark in the proton, these accurate measurements show an intriguing sensitivity to gluons, the carriers of the strong interaction.« less

Electron Accelerator Shielding Design of KIPT Neutron Source Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhong, Zhaopeng; Gohar, Yousry

The Argonne National Laboratory of the United States and the Kharkov Institute of Physics and Technology of the Ukraine have been collaborating on the design, development and construction of a neutron source facility at Kharkov Institute of Physics and Technology utilizing an electron-accelerator-driven subcritical assembly. The electron beam power is 100 kW using 100-MeV electrons. The facility was designed to perform basic and applied nuclear research, produce medical isotopes, and train nuclear specialists. The biological shield of the accelerator building was designed to reduce the biological dose to less than 5.0e-03 mSv/h during operation. The main source of the biologicalmore » dose for the accelerator building is the photons and neutrons generated from different interactions of leaked electrons from the electron gun and the accelerator sections with the surrounding components and materials. The Monte Carlo N-particle extended code (MCNPX) was used for the shielding calculations because of its capability to perform electron-, photon-, and neutron-coupled transport simulations. The photon dose was tallied using the MCNPX calculation, starting with the leaked electrons. However, it is difficult to accurately tally the neutron dose directly from the leaked electrons. The neutron yield per electron from the interactions with the surrounding components is very small, similar to 0.01 neutron for 100-MeV electron and even smaller for lower-energy electrons. This causes difficulties for the Monte Carlo analyses and consumes tremendous computation resources for tallying the neutron dose outside the shield boundary with an acceptable accuracy. To avoid these difficulties, the SOURCE and TALLYX user subroutines of MCNPX were utilized for this study. The generated neutrons were banked, together with all related parameters, for a subsequent MCNPX calculation to obtain the neutron dose. The weight windows variance reduction technique was also utilized for both neutron and photon dose calculations. Two shielding materials, heavy concrete and ordinary concrete, were considered for the shield design. The main goal is to maintain the total dose outside the shield boundary less than 5.0e-03 mSv/h during operation. The shield configuration and parameters of the accelerator building were determined and are presented in this paper. Copyright (C) 2016, Published by Elsevier Korea LLC on behalf of Korean Nuclear Society.« less

Radiative double electron capture in collisions of fully-stripped fluorine ions with thin carbon foils

NASA Astrophysics Data System (ADS)

Elkafrawy, Tamer Mohammad Samy

Radiative double electron capture (RDEC) is a one-step process in ion-atom collisions occurring when two target electrons are captured to a bound state of the projectile simultaneously with the emission of a single photon. The emitted photon has approximately double the energy of the photon emitted due to radiative electron capture (REC), which occurs when a target electron is captured to a projectile bound state with simultaneous emission of a photon. REC and RDEC can be treated as time-reversed photoionization (PI) and double photoionization (DPI), respectively, if loosely-bound target electrons are captured. This concept can be formulated with the principle of detailed balance, in which the processes of our interest can be described in terms of their time-reversed ones. Fully-stripped ions were used as projectiles in the performed RDEC experiments, providing a recipient system free of electron-related Coulomb fields. This allows the target electrons to be transferred without interaction with any of the projectile electrons, enabling accurate investigation of the electron-electron interaction in the vicinity of electromagnetic field. In this dissertation, RDEC was investigated during the collision of fully-stripped fluorine ions with a thin carbon foil and the results are compared with the recent experimental and theoretical studies. In the current work, x rays associated with projectile charge-changing by single and double electron capture and no charge change by F9+ ions were observed and compared with recent work for O8+ ions and with theory. Both the F 9+ and O8+ ions had energies in the ˜MeV/u range. REC, in turn, was investigated as a means to compare with the theoretical predictions of the RDEC/REC cross section ratio. The most significant background processes including various mechanisms of x-ray emission that may interfere with the energy region of interest are addressed in detail. This enables isolation of the contributions of REC and RDEC from the entire continuous spectrum of x-ray emission or at least ensures that the background processes have negligible contribution to the energy range of interest. Special emphasis is given to showing how the data analysis was carried out by the subtraction of the x rays due to contamination lines.

Relativistic many-body bound systems: electromagnetic properties. Monograph report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Danos, M.; Gillet, V.

1977-04-01

The formulae for the calculation of the electron scattering form factors, and of the static magnetic dipole and electric quadrupole moments, of relativistic many-body bound systems are derived. The framework, given in NBS Monograph 147, is relativistic quantum field theory in the Schrodinger picture; the physical particles, i.e., the solutions of the interacting fields, are given as linear combinations of the solutions of the free fields, called the parton fields. The parton--photon interaction is taken as given by minimal coupling. In addition, the contribution of the photon--vector meson vertex of the vector dominance model is derived.

Photon Interaction Parameters for Some Borate Glasses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mann, Nisha; Kaur, Updesh; Singh, Tejbir

2010-11-06

Some photon interaction parameters of dosimetric interest such as mass attenuation coefficients, effective atomic number, electron density and KERMA relative to air have been computed in the wide energy range from 1 keV to 100 GeV for some borate glasses viz. barium-lead borate, bismuth-borate, calcium-strontium borate, lead borate and zinc-borate glass. It has been observed that lead borate glass and barium-lead borate glass have maximum values of mass attenuation coefficient, effective atomic number and KERMA relative to air. Hence, these borate glasses are suitable as gamma ray shielding material, packing of radioactive sources etc.

Recent advances in organic one-dimensional composite materials: design, construction, and photonic elements for information processing.

PubMed

Yan, Yongli; Zhang, Chuang; Yao, Jiannian; Zhao, Yong Sheng

2013-07-19

Many recent activities in the use of one-dimensional nanostructures as photonic elements for optical information processing are explained by huge advantages that photonic circuits possess over traditional silicon-based electronic ones in bandwidth, heat dissipation, and resistance to electromagnetic wave interference. Organic materials are a promising candidate to support these optical-related applications, as they combine the properties of plastics with broad spectral tunability, high optical cross-section, easy fabrication, as well as low cost. Their outstanding compatibility allows organic composite structures which are made of two or more kinds of materials combined together, showing great superiority to single-component materials due to the introduced interactions among multiple constituents, such as energy transfer, electron transfer, exciton coupling, etc. The easy processability of organic 1D crystalline heterostructures enables a fine topological control of both composition and geometry, which offsets the intrinsic deficiencies of individual material. At the same time, the strong exciton-photon coupling and exciton-exciton interaction impart the excellent confinement of photons in organic microstructures, thus light can be manipulated according to our intention to realize specific functions. These collective properties indicate a potential utility of organic heterogeneous material for miniaturized photonic circuitry. Herein, focus is given on recent advances of 1D organic crystalline heterostructures, with special emphasis on the novel design, controllable construction, diverse performance, as well as wide applications in isolated photonic elements for integration. It is proposed that the highly coupled, hybrid optical networks would be an important material basis towards the creation of on-chip optical information processing. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Detective quantum efficiency of photon-counting x-ray detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tanguay, Jesse, E-mail: jessetan@mail.ubc.ca; Yun, Seungman; Kim, Ho Kyung

Purpose: Single-photon-counting (SPC) x-ray imaging has the potential to improve image quality and enable novel energy-dependent imaging methods. Similar to conventional detectors, optimizing image SPC quality will require systems that produce the highest possible detective quantum efficiency (DQE). This paper builds on the cascaded-systems analysis (CSA) framework to develop a comprehensive description of the DQE of SPC detectors that implement adaptive binning. Methods: The DQE of SPC systems can be described using the CSA approach by propagating the probability density function (PDF) of the number of image-forming quanta through simple quantum processes. New relationships are developed to describe PDF transfermore » through serial and parallel cascades to accommodate scatter reabsorption. Results are applied to hypothetical silicon and selenium-based flat-panel SPC detectors including the effects of reabsorption of characteristic/scatter photons from photoelectric and Compton interactions, stochastic conversion of x-ray energy to secondary quanta, depth-dependent charge collection, and electronic noise. Results are compared with a Monte Carlo study. Results: Depth-dependent collection efficiency can result in substantial broadening of photopeaks that in turn may result in reduced DQE at lower x-ray energies (20–45 keV). Double-counting interaction events caused by reabsorption of characteristic/scatter photons may result in falsely inflated image signal-to-noise ratio and potential overestimation of the DQE. Conclusions: The CSA approach is extended to describe signal and noise propagation through photoelectric and Compton interactions in SPC detectors, including the effects of escape and reabsorption of emission/scatter photons. High-performance SPC systems can be achieved but only for certain combinations of secondary conversion gain, depth-dependent collection efficiency, electronic noise, and reabsorption characteristics.« less

Detective quantum efficiency of photon-counting x-ray detectors.

PubMed

Tanguay, Jesse; Yun, Seungman; Kim, Ho Kyung; Cunningham, Ian A

2015-01-01

Single-photon-counting (SPC) x-ray imaging has the potential to improve image quality and enable novel energy-dependent imaging methods. Similar to conventional detectors, optimizing image SPC quality will require systems that produce the highest possible detective quantum efficiency (DQE). This paper builds on the cascaded-systems analysis (CSA) framework to develop a comprehensive description of the DQE of SPC detectors that implement adaptive binning. The DQE of SPC systems can be described using the CSA approach by propagating the probability density function (PDF) of the number of image-forming quanta through simple quantum processes. New relationships are developed to describe PDF transfer through serial and parallel cascades to accommodate scatter reabsorption. Results are applied to hypothetical silicon and selenium-based flat-panel SPC detectors including the effects of reabsorption of characteristic/scatter photons from photoelectric and Compton interactions, stochastic conversion of x-ray energy to secondary quanta, depth-dependent charge collection, and electronic noise. Results are compared with a Monte Carlo study. Depth-dependent collection efficiency can result in substantial broadening of photopeaks that in turn may result in reduced DQE at lower x-ray energies (20-45 keV). Double-counting interaction events caused by reabsorption of characteristic/scatter photons may result in falsely inflated image signal-to-noise ratio and potential overestimation of the DQE. The CSA approach is extended to describe signal and noise propagation through photoelectric and Compton interactions in SPC detectors, including the effects of escape and reabsorption of emission/scatter photons. High-performance SPC systems can be achieved but only for certain combinations of secondary conversion gain, depth-dependent collection efficiency, electronic noise, and reabsorption characteristics.

Neutrino-electron scattering: general constraints on Z ' and dark photon models

NASA Astrophysics Data System (ADS)

Lindner, Manfred; Queiroz, Farinaldo S.; Rodejohann, Werner; Xu, Xun-Jie

2018-05-01

We study the framework of U(1) X models with kinetic mixing and/or mass mixing terms. We give general and exact analytic formulas of fermion gauge interactions and the cross sections of neutrino-electron scattering in such models. Then we derive limits on a variety of U(1) X models that induce new physics contributions to neutrino-electron scattering, taking into account interference between the new physics and Standard Model contributions. Data from TEXONO, CHARM-II and GEMMA are analyzed and shown to be complementary to each other to provide the most restrictive bounds on masses of the new vector bosons. In particular, we demonstrate the validity of our results to dark photon-like as well as light Z ' models.

Manipulation of photons at the surface of three-dimensional photonic crystals.

PubMed

Ishizaki, Kenji; Noda, Susumu

2009-07-16

In three-dimensional (3D) photonic crystals, refractive-index variations with a periodicity comparable to the wavelength of the light passing through the crystal give rise to so-called photonic bandgaps, which are analogous to electronic bandgaps for electrons moving in the periodic electrostatic potential of a material's crystal structure. Such 3D photonic bandgap crystals are envisioned to become fundamental building blocks for the control and manipulation of photons in optical circuits. So far, such schemes have been pursued by embedding artificial defects and light emitters inside the crystals, making use of 3D bandgap directional effects. Here we show experimentally that photons can be controlled and manipulated even at the 'surface' of 3D photonic crystals, where 3D periodicity is terminated, establishing a new and versatile route for photon manipulation. By making use of an evanescent-mode coupling technique, we demonstrate that 3D photonic crystals possess two-dimensional surface states, and we map their band structure. We show that photons can be confined and propagate through these two-dimensional surface states, and we realize their localization at arbitrary surface points by designing artificial surface-defect structures through the formation of a surface-mode gap. Surprisingly, the quality factors of the surface-defect mode are the largest reported for 3D photonic crystal nanocavities (Q up to approximately 9,000). In addition to providing a new approach for photon manipulation by photonic crystals, our findings are relevant for the generation and control of plasmon-polaritons in metals and the related surface photon physics. The absorption-free nature of the 3D photonic crystal surface may enable new sensing applications and provide routes for the realization of efficient light-matter interactions.

Photoionization of Ne Atoms and Ne + Ions Near the K Edge: PrecisionSpectroscopy and Absolute Cross-sections

DOE PAGES

Müller, Alfred; Bernhardt, Dietrich; Borovik, Alexander; ...

2017-02-17

Single, double, and triple photoionization of Ne + ions by single photons have been investigated at the synchrotron radiation source PETRA III in Hamburg, Germany. Absolute cross-sections were measured by employing the photon-ion merged-beams technique. Photon energies were between about 840 and 930 eV, covering the range from the lowest-energy resonances associated with the excitation of one single K-shell electron up to double excitations involving one K- and one L-shell electron, well beyond the K-shell ionization threshold. Also, photoionization of neutral Ne was investigated just below the K edge. The chosen photon energy bandwidths were between 32 and 500 meV,more » facilitating the determination of natural line widths. The uncertainty of the energy scale is estimated to be 0.2 eV. For comparison with existing theoretical calculations, astrophysically relevant photoabsorption cross-sections were inferred by summing the measured partial ionization channels. Discussion of the observed resonances in the different final ionization channels reveals the presence of complex Auger-decay mechanisms. The ejection of three electrons from the lowest K-shell-excited Ne + (1s2s 2p 6 2S 1/2) level, for example, requires cooperative interaction of at least four electrons.« less

The water-water cycle as alternative photon and electron sinks.

PubMed

Asada, K

2000-10-29

The water-water cycle in chloroplasts is the photoreduction of dioxygen to water in photosystem I (PS I) by the electrons generated in photosystem II (PS II) from water. In the water-water cycle, the rate of photoreduction of dioxygen in PS I is several orders of magnitude lower than those of the disproportionation of superoxide catalysed by superoxide dismutase, the reduction of hydrogen peroxide to water catalysed by ascorbate peroxidase, and the reduction of the resulting oxidized forms of ascorbate by reduced ferredoxin or catalysed by either dehydroascorbate reductase or monodehydroascorbate reductase. The water-water cycle therefore effectively shortens the lifetimes of photoproduced superoxide and hydrogen peroxide to suppress the production of hydroxyl radicals, their interactions with the target molecules in chloroplasts, and resulting photoinhibition. When leaves are exposed to photon intensities of sunlight in excess of that required to support the fixation of CO2, the intersystem electron carriers are over-reduced, resulting in photoinhibition. Under such conditions, the water-water cycle not only scavenges active oxygens, but also safely dissipates excess photon energy and electrons, in addition to downregulation of PS II and photorespiration. The dual functions of the water-water cycle for protection from photoinhibition under photon excess stress are discussed, along with its functional evolution.

The response of a radiophotoluminescent glass dosimeter in megavoltage photon and electron beams.

PubMed

Araki, Fujio; Ohno, Takeshi

2014-12-01

This study investigated the response of a radiophotoluminescent glass dosimeter (RGD) in megavoltage photon and electron beams. The RGD response was compared with ion chamber measurements for 4-18 MV photons and 6-20 MeV electrons in plastic water phantoms. The response was also calculated via Monte Carlo (MC) simulations with EGSnrc/egs_chamber and Cavity user-codes, respectively. In addition, the response of the RGD cavity was analyzed as a function of field sizes and depths according to Burlin's general cavity theory. The perturbation correction factor, PQ, in the RGD cavity was also estimated from MC simulations for photon and electron beams. The calculated and measured RGD energy response at reference conditions with a 10 × 10 cm(2) field and 10 cm depth in photons was lower by up to 2.5% with increasing energy. The variation in RGD response in the field size range of 5 × 5 cm(2) to 20 × 20 cm(2) was 3.9% and 0.7%, at 10 cm depth for 4 and 18 MV, respectively. The depth dependence of the RGD response was constant within 1% for energies above 6 MV but it increased by 2.6% and 1.6% for a large (20 × 20 cm(2)) field at 4 and 6 MV, respectively. The dose contributions from photon interactions (1 - d) in the RGD cavity, according to Burlin's cavity theory, decreased with increasing energy and decreasing field size. The variation in (1 - d) between field sizes became larger with increasing depth for the lower energies of 4 and 6 MV. PQ for the RGD cavity was almost constant between 0.96 and 0.97 at 10 MV energies and above. Meanwhile, PQ depends strongly on field size and depth for 4 and 6 MV photons. In electron beams, the RGD response at a reference depth, dref, varied by less than 1% over the electron energy range but was on average 4% lower than the response for 6 MV photons. The RGD response for photon beams depends on both (1 - d) and perturbation effects in the RGD cavity. Therefore, it is difficult to predict the energy dependence of RGD response by Burlin's theory and it is recommended to directly measure RGD response or use the MC-calculated RGD response, regarding the practical use. The response for electron beams decreased rapidly at a depth beyond dref for lower mean electron energies <3 MeV and in contrast PQ increased.

Laser-Matter Interaction in Dielectrics: Insight from Picosecond-Pulsed Second-Harmonic Generation in Periodically Poled LiTaO3

NASA Astrophysics Data System (ADS)

Louchev, Oleg A.; Wada, Satoshi; Panchenko, Vladislav Ya.

2017-08-01

We develop a modified two-temperature (2T) model of laser-matter interaction in dielectrics based on experimental insight from picosecond-pulsed high-frequency temperature-controlled second-harmonic (515 nm) generation in periodically poled stoichiometric LiTaO3 crystal and required for computational treatment of short-pulsed nonlinear optics and materials processing applications. We show that the incorporation of an extended set of recombination-kinetics-related energy-release and heat-exchange processes following short-pulsed photoionization by two-photon absorption of the second harmonic allows accurate simulation of the electron-lattice relaxation dynamics and electron-lattice temperature evolution in LiTaO3 crystal in nonlinear laser-frequency conversion. Our experimentally confirmed model and detailed simulation study show that two-photon ionization with the recombination mechanism via ion-electron-lattice interaction followed by a direct transfer of the recombination energy to the lattice is the main laser-matter energy-transfer pathway responsible for the majority of the crystal lattice heating (approximately 90%) continuing for approximately 50 ps after laser-pulse termination and competing with effect of electron-phonon energy transfer from the free electrons. This time delay is due to a recombination bottleneck which hinders faster relaxation to thermal equilibrium in photoionized dielectric crystal. Generally, our study suggests that in dielectrics photoionized by short-pulsed radiation with intensity range used in nonlinear laser-frequency conversion, the electron-lattice relaxation period is defined by the recombination-stage bottleneck of a few tens of picoseconds and not by the time of the electron-phonon energy transfer. This modification of the 2T model can be applied to a broad range of processes involving laser-matter interactions in dielectrics and semiconductors for charge density reaching the range of 1021- 1022 cm-3 .

Simulations of bremsstrahlung emission in ultra-intense laser interactions with foil targets

NASA Astrophysics Data System (ADS)

Vyskočil, Jiří; Klimo, Ondřej; Weber, Stefan

2018-05-01

Bremsstrahlung emission from interactions of short ultra-intense laser pulses with solid foils is studied using particle-in-cell (PIC) simulations. A module for simulating bremsstrahlung has been implemented in the PIC loop to self-consistently account for the dynamics of the laser–plasma interaction, plasma expansion, and the emission of gamma ray photons. This module made it possible to study emission from thin targets, where refluxing of hot electrons plays an important role. It is shown that the angular distribution of the emitted photons exhibits a four-directional structure with the angle of emission decreasing with the increase of the width of the target. Additionally, a collimated forward flash consisting of high energy photons has been identified in thin targets. The conversion efficiency of the energy of the laser pulse to the energy of the gamma rays rises with both the driving pulse intensity, and the thickness of the target. The amount of gamma rays also increases with the atomic number of the target material, despite a lower absorption of the driving laser pulse. The angular spectrum of the emitted gamma rays is directly related to the increase of hot electron divergence during their refluxing and its measurement can be used in experiments to study this process.

Photoemission study of the electronic structure and charge density waves of Na₂Ti₂Sb₂O

DOE PAGES

Tan, S. Y.; Jiang, J.; Ye, Z. R.; ...

2015-04-30

The electronic structure of Na₂Ti₂Sb₂O single crystal is studied by photon energy and polarization dependent angle-resolved photoemission spectroscopy (ARPES). The obtained band structure and Fermi surface agree well with the band structure calculation of Na₂Ti₂Sb₂O in the non-magnetic state, which indicates that there is no magnetic order in Na₂Ti₂Sb₂O and the electronic correlation is weak. Polarization dependent ARPES results suggest the multi-band and multi-orbital nature of Na₂Ti₂Sb₂O. Photon energy dependent ARPES results suggest that the electronic structure of Na₂Ti₂Sb₂O is rather two-dimensional. Moreover, we find a density wave energy gap forms below the transition temperature and reaches 65 meV atmore » 7 K, indicating that Na₂Ti₂Sb₂O is likely a weakly correlated CDW material in the strong electron-phonon interaction regime. (author)« less

Laser Assisted Free-Free Transition in Electron - Atom Collision

NASA Technical Reports Server (NTRS)

Sinha, C.; Bhatia, A. K.

2011-01-01

Free-free transition is studied for electron-Hydrogen atom system in ground state at very low incident energies in presence of an external homogeneous, monochromatic and linearly polarized laser field. The incident electron is considered to be dressed by the laser in a non perturbative manner by choosing the Volkov solutions in both the channels. The space part of the scattering wave function for the electron is solved numerically by taking into account the effect of electron exchange, short range as well as of the long range interactions. Laser assisted differential as well as elastic total cross sections are calculated for single photon absorption/emission in the soft photon limit, the laser intensity being much less than the atomic field intensity. A strong suppression is noted in the laser assisted cross sections as compared to the field free situations. Significant difference is noted in the singlet and the triplet cross sections.

Flat-panel detector, CCD cameras, and electron-beam-tube-based video for use in portal imaging

NASA Astrophysics Data System (ADS)

Roehrig, Hans; Tang, Chuankun; Cheng, Chee-Way; Dallas, William J.

1998-07-01

This paper provides a comparison of some imaging parameters of four portal imaging systems at 6 MV: a flat panel detector, two CCD cameras and an electron beam tube based video camera. Measurements were made of signal and noise and consequently of signal-to-noise per pixel as a function of the exposure. All systems have a linear response with respect to exposure, and with the exception of the electron beam tube based video camera, the noise is proportional to the square-root of the exposure, indicating photon-noise limitation. The flat-panel detector has a signal-to-noise ratio, which is higher than that observed with both CCD-Cameras or with the electron beam tube based video camera. This is expected because most portal imaging systems using optical coupling with a lens exhibit severe quantum-sinks. The measurements of signal-and noise were complemented by images of a Las Vegas-type aluminum contrast detail phantom, located at the ISO-Center. These images were generated at an exposure of 1 MU. The flat-panel detector permits detection of Aluminum holes of 1.2 mm diameter and 1.6 mm depth, indicating the best signal-to-noise ratio. The CCD-cameras rank second and third in signal-to- noise ratio, permitting detection of Aluminum-holes of 1.2 mm diameter and 2.2 mm depth (CCD_1) and of 1.2 mm diameter and 3.2 mm depth (CCD_2) respectively, while the electron beam tube based video camera permits detection of only a hole of 1.2 mm diameter and 4.6 mm depth. Rank Order Filtering was applied to the raw images from the CCD-based systems in order to remove the direct hits. These are camera responses to scattered x-ray photons which interact directly with the CCD of the CCD-Camera and generate 'Salt and Pepper type noise,' which interferes severely with attempts to determine accurate estimates of the image noise. The paper also presents data on the metal-phosphor's photon gain (the number of light-photons per interacting x-ray photon).

Detection efficiency calculation for photons, electrons and positrons in a well detector. Part I: Analytical model

NASA Astrophysics Data System (ADS)

Pommé, S.

2009-06-01

An analytical model is presented to calculate the total detection efficiency of a well-type radiation detector for photons, electrons and positrons emitted from a radioactive source at an arbitrary position inside the well. The model is well suited to treat a typical set-up with a point source or cylindrical source and vial inside a NaI well detector, with or without lead shield surrounding it. It allows for fast absolute or relative total efficiency calibrations for a wide variety of geometrical configurations and also provides accurate input for the calculation of coincidence summing effects. Depending on its accuracy, it may even be applied in 4π-γ counting, a primary standardisation method for activity. Besides an accurate account of photon interactions, precautions are taken to simulate the special case of 511 keV annihilation quanta and to include realistic approximations for the range of (conversion) electrons and β -- and β +-particles.

The Lunar Regolith as a Remote Sensing Target for the Lunar Reconnaissance Orbiter (LRO)

NASA Technical Reports Server (NTRS)

Mendell, Wendell W.

2009-01-01

Of the 6 instruments and one technology demonstration aboard the LRO, only CRaTER does not measure some kind of interaction of particles with the lunar regolith. LEND detects neutron fluence that contains information about the number density of protons in the upper regolith. To infer the presence of protons, the PI must assume a model that characterizes the surface as a collection of atoms. Thus, LEND does not sense the regolith as a structure. LROC, LOLA, and LAMP sense reflected photons whose wavelength is much shorter than the median particle size in the regolith. The photons interact with electrons, either in atomic shells or in chemical bonds. These interactions occur within a nanometer or so of the surface of a particle. Thus, the particles are macroscopic objects and models of the reflection process invoke ray-tracing optics. DIVINER senses photons that have been emitted by surface particles through thermal phonon processes. The wavelengths detected by the instrument are of the same order as the median particle size, and the photons contain information on particle dimensions as well as the molecular bonds in the constituent compounds. The Mini-RF synthetic aperture radar generates and detects photons of a few centimeters wavelength that interact with the regolith as a dielectric, the dielectric properties of the particulate component being described through effective medium theory. However, the interaction with rocks (macroscopic objects of interest to geologists) can be characterized using Fresnel or Mie models of electromagnetic properties.

Track-average LET of secondary electrons generated in LiF:Mg,Ti and liquid water by 20-300 kV x-ray, 137Cs and 60Co beams.

PubMed

Cabrera-Santiago, A; Massillon-Jl, G

2016-11-21

Electrons generated in matter by photons could be a fundamental basis for an adequate analysis of radiation effects and damage. We have studied separately the 'primary electrons' generated directly by photons from the 'secondary electrons' (SE) produced by electron-electron interactions. In this work, track-average linear energy transfer, [Formula: see text], of SE in LiF:Mg,Ti and liquid water produced by twelve photon energy beams from 20 kV x-ray to 60 Co gamma rays have been investigated using the EGSnrc Monte Carlo Code. The exposure of LiF:Mg,Ti in different phantom materials has been considered. Depending on the photon energy, SE represent 40%-90% of the total electron fluence (TEF) between 1 keV and 10 keV, being higher when the photon energy increases. Independent of the medium, [Formula: see text] versus mean photon energy displays a local minimum at around 40 keV, followed by a local maximum at ~80 keV-100 keV. The [Formula: see text] of SE generated by the x-ray beams are of order of 11 keV µm -1 to 19 keV µm -1 in LiF:Mg,Ti and 5 keV µm -1 to 9 keV µm -1 in liquid water which represent 3-5 times those produced by 60 Co gamma rays in both media. These values were considerably greater than those of TEF, by factors of 3-8. Furthermore, [Formula: see text] of SE generated in liquid water by 20 kV-200 kV x-rays are similar to those of 76 MeV-120 MeV 3 He ions. Contrary to the TEF, where [Formula: see text] were independent of the phantom material, at low photon energies [Formula: see text] of SE was found to be sensitive to the surrounding medium showing higher values within the phantom than in air. This result, which agrees with published experimental results, implies the importance of the SE ionization density for an understanding of dosimeter response induced by photon beams.

Study of Electromagnetic Interactions in the MicroBooNE Liquid Argon Time Projection Chamber

NASA Astrophysics Data System (ADS)

Caratelli, David

This thesis presents results on the study of electromagnetic (EM) activity in the MicroBooNE Liquid Argon Time Projection Chamber (LArTPC) neutrino detector. The LArTPC detector technology provides bubble-chamber like information on neutrino interaction final states, necessary to perform precision measurements of neutrino oscillation parameters. Accelerator-based oscillation experiments heavily rely on the appearance channel numu → nu e to make such measurements. Identifying and reconstructing the energy of the outgoing electrons from such interactions is therefore crucial for their success. This work focuses on two sources of EM activity: Michel electrons in the 10-50 MeV energy range, and photons from pi 0 decay in the ˜30-300 MeV range. Studies of biases in the energy reconstruction measurement, and energy resolution are performed. The impact of shower topology at different energies is discussed, and the importance of thresholding and other reconstruction effects on producing an asymmetric and biased energy measurement are highlighted. This work further presents a study of the calorimetric separation of electrons and photons with a focus on the shower energy dependence of the separation power.

Study of Electromagnetic Interactions in the MicroBooNE Liquid Argon Time Projection Chamber

DOE Office of Scientific and Technical Information (OSTI.GOV)

Caratelli, David

This thesis presents results on the study of electromagnetic (EM) activity in the MicroBooNE Liquid Argon Time Projection Chamber (LArTPC) neutrino detector. The LArTPC detector technology provides bubble-chamber like information on neutrino interaction final states, necessary to perform precision measurements of neutrino oscillation parameters. Accelerator-based oscillation experiments heavily rely on the appearance channel ! e to make such measurements. Identifying and reconstructing the energy of the outgoing electrons from such interactions is therefore crucial for their success. This work focuses on two sources of EM activity: Michel electrons in the 10-50 MeV energy range, and photons from 0 decay inmore » the 30-300 MeV range. Studies of biases in the energy reconstruction measurement, and energy resolution are performed. The impact of shower topology at different energies is discussed, and the importance of thresholding and other reconstruction effects on producing an asymmetric and biased energy measurement are highlighted. This work further presents a study of the calorimetric separation of electrons and photons with a focus on the shower energy dependence of the separation power.« less

Means and method for calibrating a photon detector utilizing electron-photon coincidence

NASA Technical Reports Server (NTRS)

Srivastava, S. K. (Inventor)

1984-01-01

An arrangement for calibrating a photon detector particularly applicable for the ultraviolet and vacuum ultraviolet regions is based on electron photon coincidence utilizing crossed electron beam atom beam collisions. Atoms are excited by electrons which lose a known amount of energy and scatter with a known remaining energy, while the excited atoms emit photons of known radiation. Electrons of the known remaining energy are separated from other electrons and are counted. Photons emitted in a direction related to the particular direction of scattered electrons are detected to serve as a standard. Each of the electrons is used to initiate the measurements of a time interval which terminates with the arrival of a photon exciting the photon detector. Only the number of time intervals related to the coincidence correlation and of electrons scattered in the particular direction with the known remaining energy and photons of a particular radiation level emitted due to the collisions of such scattered electrons are counted. The detector calibration is related to the number of counted electrons and photons.

A Bulk Comptonization Model for the Prompt GRB Emission and its Relation to the Fermi GRB Spectra

NASA Technical Reports Server (NTRS)

Kazanas, Demosthenes

2010-01-01

We present a model in which the GRB prompt emission at E E(sub peak) is due to bulk Comptonization by the relativistic blast wave motion of either its own synchrotron photons of ambient photons of the stellar configuration that gave birth to the GRB. The bulk Comptonization process then induces the production of relativistic electrons of Lorentz factor equal to that of the blast wave through interactions with its ambient protons. The inverse compton emission of these electrons produces a power law component that extends to multi GeV energies in good agreement with the LAT GRB observations.

Polarization-dependent two-photon absorption for the determination of protein secondary structure: A theoretical study

NASA Astrophysics Data System (ADS)

Wanapun, Duangporn; Wampler, Ronald D.; Begue, Nathan J.; Simpson, Garth J.

2008-03-01

A new method for sensitive determination of protein secondary structure via multi-photon absorption is considered theoretically. Perturbation theory is developed to describe the polarization-dependent two-photon absorption (TPA) of α-helix and β-sheet protein secondary structures. The exciton coupling interactions responsible for relatively weak electronic circular dichroism in one-photon absorption are predicted to give rise to large changes in the TPA cross-section (>200%) for circular versus linear incident polarizations, defined as CLD. The CLD effect in TPA is electric dipole-allowed, which explains the much greater sensitivity. These predictions suggest TPA should be a viable means of sensitively probing protein secondary structure.

Multiple photon emission in heavy particle decays

NASA Technical Reports Server (NTRS)

Asakimori, K.; Burnett, T. H.; Cherry, M. L.; Christl, M. J.; Dake, S.; Derrickson, J. H.; Fountain, W. F.; Fuki, M.; Gregory, J. C.; Hayashi, T.

1994-01-01

Cosmic ray interactions, at energies above 1 TeV/nucleon, in emulsion chambers flown on high altitude balloons have yielded two events showing apparent decays of a heavy particle into one charged particle and four photons. The photons converted into electron pairs very close to the decay vertex. Attempts to explain this decay topology with known particle decays are presented. Unless both events represent a b yields u transition, which is statistically unlikely, then other known decay modes for charmed or bottom particles do not account satisfactorily for these observations. This could indicate, possibly, a new decay channel.

Projection-reduction method applied to deriving non-linear optical conductivity for an electron-impurity system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kang, Nam Lyong; Lee, Sang-Seok; Graduate School of Engineering, Tottori University, 4-101 Koyama-Minami, Tottori

2013-07-15

The projection-reduction method introduced by the present authors is known to give a validated theory for optical transitions in the systems of electrons interacting with phonons. In this work, using this method, we derive the linear and first order nonlinear optical conductivites for an electron-impurity system and examine whether the expressions faithfully satisfy the quantum mechanical philosophy, in the same way as for the electron-phonon systems. The result shows that the Fermi distribution function for electrons, energy denominators, and electron-impurity coupling factors are contained properly in organized manners along with absorption of photons for each electron transition process in themore » final expressions. Furthermore, the result is shown to be represented properly by schematic diagrams, as in the formulation of electron-phonon interaction. Therefore, in conclusion, we claim that this method can be applied in modeling optical transitions of electrons interacting with both impurities and phonons.« less

Implementation of controlled quantum teleportation with an arbitrator for secure quantum channels via quantum dots inside optical cavities.

PubMed

Heo, Jino; Hong, Chang-Ho; Kang, Min-Sung; Yang, Hyeon; Yang, Hyung-Jin; Hong, Jong-Phil; Choi, Seong-Gon

2017-11-02

We propose a controlled quantum teleportation scheme to teleport an unknown state based on the interactions between flying photons and quantum dots (QDs) confined within single- and double-sided cavities. In our scheme, users (Alice and Bob) can teleport the unknown state through a secure entanglement channel under the control and distribution of an arbitrator (Trent). For construction of the entanglement channel, Trent utilizes the interactions between two photons and the QD-cavity system, which consists of a charged QD (negatively charged exciton) inside a single-sided cavity. Subsequently, Alice can teleport the unknown state of the electron spin in a QD inside a double-sided cavity to Bob's electron spin in a QD inside a single-sided cavity assisted by the channel information from Trent. Furthermore, our scheme using QD-cavity systems is feasible with high fidelity, and can be experimentally realized with current technologies.

An alternative mechanism for spin-forbidden photo-ionization of diatomic molecules and its rotation-electronic selection rules

NASA Astrophysics Data System (ADS)

Chiu, Ying-Nan; Chiu, Lue-Yung Chow

1990-02-01

The spin-forbidden photo-ionization of diatomic molecules is proposed. Spin orbit interaction is invoked, resulting in the correction and mixing of the wave functions of different multiplicities. The rotation-electronic selection rules given by Dixit and McKoy (1986) for Hund's case a based on the conventional mechanism of electric dipole transition are rederived and expressed in a different format. This new format permits the generalization of the selection rules to other photoionization transitions caused by the magnetic dipole, the electric quadrupole, and the two- and three-photon operators. These selection rules, which are for transitions from one specific rotational level of a given Kronig reflection symmetry to another, will help understand rotational branching and the dynamics of interaction in the excited state. They will also help in the selective preparation of well-defined rovibronic states in resonant-enhanced multi-photon ionization processes.

Characterization of fast photoelectron packets in weak and strong laser fields in ultrafast electron microscopy.

PubMed

Plemmons, Dayne A; Tae Park, Sang; Zewail, Ahmed H; Flannigan, David J

2014-11-01

The development of ultrafast electron microscopy (UEM) and variants thereof (e.g., photon-induced near-field electron microscopy, PINEM) has made it possible to image atomic-scale dynamics on the femtosecond timescale. Accessing the femtosecond regime with UEM currently relies on the generation of photoelectrons with an ultrafast laser pulse and operation in a stroboscopic pump-probe fashion. With this approach, temporal resolution is limited mainly by the durations of the pump laser pulse and probe electron packet. The ability to accurately determine the duration of the electron packets, and thus the instrument response function, is critically important for interpretation of dynamics occurring near the temporal resolution limit, in addition to quantifying the effects of the imaging mode. Here, we describe a technique for in situ characterization of ultrashort electron packets that makes use of coupling with photons in the evanescent near-field of the specimen. We show that within the weakly-interacting (i.e., low laser fluence) regime, the zero-loss peak temporal cross-section is precisely the convolution of electron packet and photon pulse profiles. Beyond this regime, we outline the effects of non-linear processes and show that temporal cross-sections of high-order peaks explicitly reveal the electron packet profile, while use of the zero-loss peak becomes increasingly unreliable. Copyright © 2014 Elsevier B.V. All rights reserved.

Silicon photonics cloud (SiCloud)

NASA Astrophysics Data System (ADS)

DeVore, Peter T. S.; Jiang, Yunshan; Lynch, Michael; Miyatake, Taira; Carmona, Christopher; Chan, Andrew C.; Muniam, Kuhan; Jalali, Bahram

2015-02-01

We present SiCloud (Silicon Photonics Cloud), the first free, instructional web-based research and education tool for silicon photonics. SiCloud's vision is to provide a host of instructional and research web-based tools. Such interactive learning tools enhance traditional teaching methods by extending access to a very large audience, resulting in very high impact. Interactive tools engage the brain in a way different from merely reading, and so enhance and reinforce the learning experience. Understanding silicon photonics is challenging as the topic involves a wide range of disciplines, including material science, semiconductor physics, electronics and waveguide optics. This web-based calculator is an interactive analysis tool for optical properties of silicon and related material (SiO2, Si3N4, Al2O3, etc.). It is designed to be a one stop resource for students, researchers and design engineers. The first and most basic aspect of Silicon Photonics is the Material Parameters, which provides the foundation for the Device, Sub-System and System levels. SiCloud includes the common dielectrics and semiconductors for waveguide core, cladding, and photodetection, as well as metals for electrical contacts. SiCloud is a work in progress and its capability is being expanded. SiCloud is being developed at UCLA with funding from the National Science Foundation's Center for Integrated Access Networks (CIAN) Engineering Research Center.

Establishment of a Photon Data Section of the BNL National Nuclear Data Center: A preliminary proposal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hanson, A.L.; Pearlstein, S.

1992-05-01

It is proposed to establish a Photon Data Section (PDS) of the BNL National Nuclear Data Center (NNDC). This would be a total program encompassing both photon-atom and photon-nucleus interactions. By utilizing the existing NNDC data base management expertise and on-line access capabilities, the implementation of photon interaction data activities within the existing NNDC nuclear structure and nuclear-reaction activities can reestablish a viable photon interaction data program at minimum cost. By taking advantage of the on-line capabilities, the x-ray users' community will have access to a dynamic, state-of-the-art data base of interaction information. The proposed information base would include datamore » that presently are scattered throughout the literature usually in tabulated form. It is expected that the data bases would include at least the most precise data available in photoelectric cross sections, atomic form factors and incoherent scattering functions, anomalous scattering factors, oscillator strengths and oscillator densities, fluorescence yields, Auger electron yields, etc. It could also include information not presently available in tabulations or in existing data bases such as EXAFS (extended x-ray absorption fine structure) reference spectra, chemical bonding induced shifts in the photoelectric absorption edge, matrix corrections, x-ray Raman, and x-ray resonant Raman cross sections. The data base will also include the best estimates of the accuracy of the interaction data as it exists in the data base. It is proposed that the PDS would support computer programs written for calculating scattering cross sections for given solid angles, sample geometries, and polarization of incident x-rays, for calculating Compton profiles, and for analyzing data as in EXAFS and x-ray fluorescence.« less

Establishment of a Photon Data Section of the BNL National Nuclear Data Center: A preliminary proposal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hanson, A.L.; Pearlstein, S.

1992-05-01

It is proposed to establish a Photon Data Section (PDS) of the BNL National Nuclear Data Center (NNDC). This would be a total program encompassing both photon-atom and photon-nucleus interactions. By utilizing the existing NNDC data base management expertise and on-line access capabilities, the implementation of photon interaction data activities within the existing NNDC nuclear structure and nuclear-reaction activities can reestablish a viable photon interaction data program at minimum cost. By taking advantage of the on-line capabilities, the x-ray users` community will have access to a dynamic, state-of-the-art data base of interaction information. The proposed information base would include datamore » that presently are scattered throughout the literature usually in tabulated form. It is expected that the data bases would include at least the most precise data available in photoelectric cross sections, atomic form factors and incoherent scattering functions, anomalous scattering factors, oscillator strengths and oscillator densities, fluorescence yields, Auger electron yields, etc. It could also include information not presently available in tabulations or in existing data bases such as EXAFS (extended x-ray absorption fine structure) reference spectra, chemical bonding induced shifts in the photoelectric absorption edge, matrix corrections, x-ray Raman, and x-ray resonant Raman cross sections. The data base will also include the best estimates of the accuracy of the interaction data as it exists in the data base. It is proposed that the PDS would support computer programs written for calculating scattering cross sections for given solid angles, sample geometries, and polarization of incident x-rays, for calculating Compton profiles, and for analyzing data as in EXAFS and x-ray fluorescence.« less

Electron Solvation in Two Dimensions

NASA Astrophysics Data System (ADS)

Miller, A. D.; Bezel, I.; Gaffney, K. J.; Garrett-Roe, S.; Liu, S. H.; Szymanski, P.; Harris, C. B.

2002-08-01

Ultrafast two-photon photoemission has been used to study electron solvation at two-dimensional metal/polar-adsorbate interfaces. The molecular motion that causes the excess electron solvation is manifested as a dynamic shift in the electronic energy. Although the initially excited electron is delocalized in the plane of the interface, interactions with the adsorbate can lead to its localization. A method for determining the spatial extent of the localized electron in the plane of the interface has been developed. This spatial extent was measured to be on the order of a single adsorbate molecule.

ALPS: the Dark Matter Generator (coming in 2019)

NASA Astrophysics Data System (ADS)

Barke, Simon; Bush, Zachary; Baum, Claire; Hollis, Hal; Mueller, Guido; Tanner, David

2017-01-01

Very promising dark matter candidates are axion-like particles: sub-eV particles that are expected to (weakly) interact with photons in the presence of a static electric or magnetic field. This interaction can turn photons into axions and back into photons. Hence, in order to generate axions, we will set up a 100 meter long Fabry-Perot cavity that can hold a 150,000 watt laser field and have a 5.3 tesla magnetic field along the entire length. If the theory holds up, a fraction of the photons should transform into relativistic axions. These axions would then propagate through any optical barrier and enter a matched cavity that is situated within an identical magnetic field. Here, some of the axions should turn back into photons of equal energy. Thus these photons resonate in the otherwise empty cavity where they can be detected. It is unknown if axion-like particles exist in the targeted mass range. However, the ALPS detection principle is very convenient because we will know the exact energy of the regenerated photons beforehand thus making a detection much easier.The final stage of the ALPS experiment will be completed by 2019 at the German Electron Synchrotron (DESY) site in Hamburg, Germany. This work is supported by grants from the Heising-Simons Foundation and the National Science Foundation.

Spectroscopic signatures of localization with interacting photons in superconducting qubits

NASA Astrophysics Data System (ADS)

Roushan, P.; Neill, C.; Tangpanitanon, J.; Bastidas, V. M.; Megrant, A.; Barends, R.; Chen, Y.; Chen, Z.; Chiaro, B.; Dunsworth, A.; Fowler, A.; Foxen, B.; Giustina, M.; Jeffrey, E.; Kelly, J.; Lucero, E.; Mutus, J.; Neeley, M.; Quintana, C.; Sank, D.; Vainsencher, A.; Wenner, J.; White, T.; Neven, H.; Angelakis, D. G.; Martinis, J.

2017-12-01

Quantized eigenenergies and their associated wave functions provide extensive information for predicting the physics of quantum many-body systems. Using a chain of nine superconducting qubits, we implement a technique for resolving the energy levels of interacting photons. We benchmark this method by capturing the main features of the intricate energy spectrum predicted for two-dimensional electrons in a magnetic field—the Hofstadter butterfly. We introduce disorder to study the statistics of the energy levels of the system as it undergoes the transition from a thermalized to a localized phase. Our work introduces a many-body spectroscopy technique to study quantum phases of matter.

WE-E-18A-05: Bremsstrahlung of Laser-Plasma Interaction at KeV Temperature: Forward Dose and Attenuation Factors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saez-Beltran, M; Fernandez Gonzalez, F

2014-06-15

Purpose: To obtain an analytical empirical formula for the photon dose source term in forward direction from bremsstrahlung generated from laser-plasma accelerated electron beams in aluminum solid targets, with electron-plasma temperatures in the 10–100 keV energy range, and to calculate transmission factors for iron, aluminum, methacrylate, lead and concrete and air, materials most commonly found in vacuum chamber labs. Methods: Bremsstrahlung fluence is calculated from the convolution of thin-target bremsstrahlung spectrum for monoenergetic electrons and the relativistic Maxwell-Juettner energy distribution for the electron-plasma. Unattenuatted dose in tissue is calculated by integrating the photon spectrum with the mass-energy absorption coefficient. Formore » the attenuated dose, energy dependent absorption coefficient, build-up factors and finite shielding correction factors were also taken into account. For the source term we use a modified formula from Hayashi et al., and we fitted the proportionality constant from experiments with the aid of the previously calculated transmission factors. Results: The forward dose has a quadratic dependence on electron-plasma temperature: 1 joule of effective laser energy transferred to the electrons at 1 m in vacuum yields 0,72 Sv per MeV squared of electron-plasma temperature. Air strongly filters the softer part of the photon spectrum and reduce the dose to one tenth in the first centimeter. Exponential higher energy tail of maxwellian spectrum contributes mainly to the transmitted dose. Conclusion: A simple formula for forward photon dose from keV range temperature plasma is obtained, similar to those found in kilovoltage x-rays but with higher dose per dissipated electron energy, due to thin target and absence of filtration.« less

Probing the Early Universe with the SZ Effect

NASA Technical Reports Server (NTRS)

Joy, M. K.; Carlstrom, J. E.; Rose, M. Franklin (Technical Monitor)

2001-01-01

The Cosmic Microwave Background Radiation (CMBR) which we observe today is relic radiation which last interacted with matter more than 10 billion years ago, when the expanding universe cooled to the point that free electrons and ionized nuclei recombined to form atoms. Prior to recombination, scattering between photons and free electrons was a very frequent occurrence, and the distance light could penetrate was small; afterwards, with free electrons out of circulation, the universe became largely transparent to light. Thus, the CMBR photons we observe today give us a clear view of the state of the early universe. Measured deviations in the intensity of the CMBR trace the small perturbations in the primordial matter density, which have been amplified by gravitational forces to form the magnificent, complex structures which comprise the present-day universe.

Co-integrating plasmonics with Si3N4 photonics towards a generic CMOS compatible PIC platform for high-sensitivity multi-channel biosensors: the H2020 PlasmoFab approach (Conference Presentation)

NASA Astrophysics Data System (ADS)

Tsiokos, Dimitris M.; Dabos, George; Ketzaki, Dimitra; Weeber, Jean-Claude; Markey, Laurent; Dereux, Alain; Giesecke, Anna Lena; Porschatis, Caroline; Chmielak, Bartos; Wahlbrink, Thorsten; Rochracher, Karl; Pleros, Nikos

2017-05-01

Silicon photonics meet most fabrication requirements of standard CMOS process lines encompassing the photonics-electronics consolidation vision. Despite this remarkable progress, further miniaturization of PICs for common integration with electronics and for increasing PIC functional density is bounded by the inherent diffraction limit of light imposed by optical waveguides. Instead, Surface Plasmon Polariton (SPP) waveguides can guide light at sub-wavelength scales at the metal surface providing unique light-matter interaction properties, exploiting at the same time their metallic nature to naturally integrate with electronics in high-performance ASPICs. In this article, we demonstrate the main goals of the recently introduced H2020 project PlasmoFab towards addressing the ever increasing needs for low energy, small size and high performance mass manufactured PICs by developing a revolutionary yet CMOS-compatible fabrication platform for seamless co-integration of plasmonics with photonic and supporting electronic. We demonstrate recent advances on the hosting SiN photonic hosting platform reporting on low-loss passive SiN waveguide and Grating Coupler circuits for both the TM and TE polarization states. We also present experimental results of plasmonic gold thin-film and hybrid slot waveguide configurations that can allow for high-sensitivity sensing, providing also the ongoing activities towards replacing gold with Cu, Al or TiN metal in order to yield the same functionality over a CMOS metallic structure. Finally, the first experimental results on the co-integrated SiN+plasmonic platform are demonstrated, concluding to an initial theoretical performance analysis of the CMOS plasmo-photonic biosensor that has the potential to allow for sensitivities beyond 150000nm/RIU.

High Current Density Cathodes for Future Vacuum Electronics Applications

DTIC Science & Technology

2008-05-30

Tube - device for generating high levels of RF power DARPA Defense Advanced Research Agency PBG Photonic band gap W- Band 75-111 GHz dB Decibels GHz...Extended interaction klystron 1. Introduction All RF vacuum electron sources require a high quality electron beam for efficient operation. Research on...with long life. Pres- ently, only thermionic dispenser cathodes are practical for high power RF sources. Typical thermi- onic cathodes consists of a

Polaronic exciton behavior in gas-phase water

NASA Astrophysics Data System (ADS)

Udal'tsov, Alexander V.

2018-03-01

Features of the absorption spectrum of gas-phase water in the energy range 7-10 eV have been considered applying polaronic exciton theory. The interaction of the incident photon generating polaronic exciton in water is described taking into account angular momentum of the electron so that polaronic exciton radii have been estimated in dependence on spin-orbit coupling under proton sharing. The suggested approach admits an estimate of kinetic and rotation energies of the polaronic exciton. As a result sixteen steps of half Compton wavelength, λC/2 = h/(2mec) changing polaronic exciton radius were found consistent with local maxima and shoulders in the spectrum. Thus, the absorption of gas-phase water in the energy range 8.5-10 eV has been interpreted in terms of polaronic exciton rotation mainly coupled with the proton sharing. The incident photon interaction with water is also considered in terms of Compton interaction, when the rotation energy plays a role like the energy loss of the incident photon under Compton scattering. The found symmetry and the other evidence allowed to conclude about polaronic exciton migration under the interaction angle 90°.

Theory of even-parity states and two-photon spectra of conjugated polymers

NASA Astrophysics Data System (ADS)

McWilliams, P. C. M.; Hayden, G. W.; Soos, Z. G.

1991-04-01

The two-photon absorption (TPA) spectrum of interacting π electrons in conjugated polymers is shown to be qualitatively different from any single-particle description, including the Hartree-Fock limit. Alternating transfer integrals t(1+/-δ) along the backbone lead to a weak TPA below the one-photon gap Eg for arbitrarily weak correlations at δ=0, for intermediate correlations at δ=0.07 in polyenes, and for strong correlations at any δ<1. More intense TPA is derived from two-electron transfer across Eg; this even-parity state shifts from 2Eg in single-particle theory to Eg in the limit of strong correlations in Hubbard models and is around 1.5Eg for Pariser-Parr-Pople (PPP) parameters. The PPP model, which accounts for one- and two-photon excitations of finite polyenes, is extended to even-parity states in polydiacetylenes (PDA's), polyacetylene (PA), and polysilanes (PS's). Previous experimental data for PDA and PS support both the strong TPA above Eg and weak TPA slightly below Eg for δ=0.15 in PDA and above Eg for δ~0.3 in PS. The strong TPA expected around 1.5Eg in isolated PA strands shifts to ~Eg due to interchain π-electron dispersion forces. TPA intensities in correlated states are shown to reflect both ionicity and mean-square charge separation. The even-parity states of conjugated polymers, like those of polyenes, show qualitatively different features associated with electron-electron correlations.

Cascades from nu_E above 1020 eV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klein, Spencer R.

2004-12-21

At very high energies, the Landau-Pomeranchuk-Migdal effect reduces the cross sections for electron bremsstrahlung and photon e{sup +}e{sup -} pair production. The fractional electron energy loss and pair production cross sections drop as the energy increases. In contrast, the cross sections for photonuclear interactions grow with energy. In solids and liquids, at energies above 10{sup 20} eV, photonuclear reactions dominate, and showers that originate as photons or electrons quickly become hadronic showers. These electron-initiated hadronic showers are much shorter (due to the absence of the LPM effect), but wider than purely electromagnetic showers would be. This change in shape altersmore » the spectrum of the electromagnetic and acoustic radiation emitted from the shower. These alterations have important implications for existing and planned searches for radiation from u{sub e} induced showers above 10{sup 20} eV, and some existing limits should be reevaluated.« less

Photoionization and electron-impact ionization of Ar5+

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, J.C.; Lu, M.; Esteves, D.

2007-02-27

Absolute cross sections for photoionization andelectron-impact Photionization of Ar5+ have been measuredusing twodifferent interacting-beams setups. The spectra consist of measurementsof the yield of products dueto single ionization as a function ofelectron or photon energy. In addition, absolute photoionization andelectron-impact ionization cross sections were measured to normalize themeasured Ar6+ product-ion yield spectra. In the energy range from 90 to111 eV, both electron-impact ionization and photoionization of Ar5+aredominated by indirect 3s subshell excitation-autoionization. In theenergy range from 270 to 285 eV, resonances due to 2p-3dexcitation-autoionization are prominent in the photoionization spectrum.In the range from 225 to 335 eV, an enhancement due tomore » 2p-nl (n>2>excitations are evident in the electron-impactionization cross section.The electron and photon impact data show some features due to excitationof the same intermediate autoionizing states.« less

Observation of the Second Harmonic in Thomson Scattering from Relativistic Electrons

NASA Astrophysics Data System (ADS)

Babzien, Marcus; Ben-Zvi, Ilan; Kusche, Karl; Pavlishin, Igor V.; Pogorelsky, Igor V.; Siddons, David P.; Yakimenko, Vitaly; Cline, David; Zhou, Feng; Hirose, Tachishige; Kamiya, Yoshio; Kumita, Tetsuro; Omori, Tsunehiko; Urakawa, Junji; Yokoya, Kaoru

2006-02-01

A free relativistic electron in an electromagnetic field is a pure case of a light-matter interaction. In the laboratory environment, this interaction can be realized by colliding laser pulses with electron beams produced from particle accelerators. The process of single photon absorption and reemission by the electron, so-called linear Thomson scattering, results in radiation that is Doppler shifted into the x-ray and γ-ray regions. At elevated laser intensity, nonlinear effects should come into play when the transverse motion of the electrons induced by the laser beam is relativistic. In the present experiment, we achieved this condition and characterized the second harmonic of Thomson x-ray scattering using the counterpropagation of a 60 MeV electron beam and a subterawatt CO2 laser beam.

Observation of the second harmonic in Thomson scattering from relativistic electrons.

PubMed

Babzien, Marcus; Ben-Zvi, Ilan; Kusche, Karl; Pavlishin, Igor V; Pogorelsky, Igor V; Siddons, David P; Yakimenko, Vitaly; Cline, David; Zhou, Feng; Hirose, Tachishige; Kamiya, Yoshio; Kumita, Tetsuro; Omori, Tsunehiko; Urakawa, Junji; Yokoya, Kaoru

2006-02-10

A free relativistic electron in an electromagnetic field is a pure case of a light-matter interaction. In the laboratory environment, this interaction can be realized by colliding laser pulses with electron beams produced from particle accelerators. The process of single photon absorption and reemission by the electron, so-called linear Thomson scattering, results in radiation that is Doppler shifted into the x-ray and gamma-ray regions. At elevated laser intensity, nonlinear effects should come into play when the transverse motion of the electrons induced by the laser beam is relativistic. In the present experiment, we achieved this condition and characterized the second harmonic of Thomson x-ray scattering using the counterpropagation of a 60 MeV electron beam and a subterawatt CO2 laser beam.

A glimpse of gluons through deeply virtual compton scattering on the proton.

PubMed

Defurne, M; Jiménez-Argüello, A Martí; Ahmed, Z; Albataineh, H; Allada, K; Aniol, K A; Bellini, V; Benali, M; Boeglin, W; Bertin, P; Brossard, M; Camsonne, A; Canan, M; Chandavar, S; Chen, C; Chen, J-P; de Jager, C W; de Leo, R; Desnault, C; Deur, A; El Fassi, L; Ent, R; Flay, D; Friend, M; Fuchey, E; Frullani, S; Garibaldi, F; Gaskell, D; Giusa, A; Glamazdin, O; Golge, S; Gomez, J; Hansen, O; Higinbotham, D; Holmstrom, T; Horn, T; Huang, J; Huang, M; Hyde, C E; Iqbal, S; Itard, F; Kang, H; Kelleher, A; Keppel, C; Koirala, S; Korover, I; LeRose, J J; Lindgren, R; Long, E; Magne, M; Mammei, J; Margaziotis, D J; Markowitz, P; Mazouz, M; Meddi, F; Meekins, D; Michaels, R; Mihovilovic, M; Camacho, C Muñoz; Nadel-Turonski, P; Nuruzzaman, N; Paremuzyan, R; Puckett, A; Punjabi, V; Qiang, Y; Rakhman, A; Rashad, M N H; Riordan, S; Roche, J; Russo, G; Sabatié, F; Saenboonruang, K; Saha, A; Sawatzky, B; Selvy, L; Shahinyan, A; Sirca, S; Solvignon, P; Sperduto, M L; Subedi, R; Sulkosky, V; Sutera, C; Tobias, W A; Urciuoli, G M; Wang, D; Wojtsekhowski, B; Yao, H; Ye, Z; Zhan, X; Zhang, J; Zhao, B; Zhao, Z; Zheng, X; Zhu, P

2017-11-10

The internal structure of nucleons (protons and neutrons) remains one of the greatest outstanding problems in modern nuclear physics. By scattering high-energy electrons off a proton we are able to resolve its fundamental constituents and probe their momenta and positions. Here we investigate the dynamics of quarks and gluons inside nucleons using deeply virtual Compton scattering (DVCS)-a highly virtual photon scatters off the proton, which subsequently radiates a photon. DVCS interferes with the Bethe-Heitler (BH) process, where the photon is emitted by the electron rather than the proton. We report herein the full determination of the BH-DVCS interference by exploiting the distinct energy dependences of the DVCS and BH amplitudes. In the regime where the scattering is expected to occur off a single quark, measurements show an intriguing sensitivity to gluons, the carriers of the strong interaction.

Searching for a dark photon with DarkLight

NASA Astrophysics Data System (ADS)

Corliss, R.; DarkLight Collaboration

2017-09-01

Despite compelling astrophysical evidence for the existence of dark matter in the universe, we have yet to positively identify it in any terrestrial experiment. If such matter is indeed particle in nature, it may have a new interaction as well, carried by a dark counterpart to the photon. The DarkLight experiment proposes to search for such a beyond-the-standard-model dark photon through complete reconstruction of the final states of electron-proton collisions. In order to accomplish this, the experiment requires a moderate-density target and a very high intensity, low energy electron beam. I describe DarkLight's approach and focus on the implications this has for the design of the experiment, which centers on the use of an internal gas target in Jefferson Lab's Low Energy Recirculating Facility. I also discuss upcoming beam tests, where we will place our target and solenoidal magnet in the beam for the first time.

A non-invasive online photoionization spectrometer for FLASH2.

PubMed

Braune, Markus; Brenner, Günter; Dziarzhytski, Siarhei; Juranić, Pavle; Sorokin, Andrey; Tiedtke, Kai

2016-01-01

The stochastic nature of the self-amplified spontaneous emission (SASE) process of free-electron lasers (FELs) effects pulse-to-pulse fluctuations of the radiation properties, such as the photon energy, which are determinative for processes of photon-matter interactions. Hence, SASE FEL sources pose a great challenge for scientific investigations, since experimenters need to obtain precise real-time feedback of these properties for each individual photon bunch for interpretation of the experimental data. Furthermore, any device developed to deliver the according information should not significantly interfere with or degrade the FEL beam. Regarding the spectral properties, a device for online monitoring of FEL wavelengths has been developed for FLASH2, which is based on photoionization of gaseous targets and the measurements of the corresponding electron and ion time-of-flight spectra. This paper presents experimental studies and cross-calibration measurements demonstrating the viability of this online photoionization spectrometer.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Albert, F.; Hartemann, F. V.; Anderson, S. G.

Tunable, high precision gamma-ray sources are under development to enable nuclear photonics, an emerging field of research. This paper focuses on the technological and theoretical challenges related to precision Compton scattering gamma-ray sources. In this scheme, incident laser photons are scattered and Doppler upshifted by a high brightness electron beam to generate tunable and highly collimated gamma-ray pulses. The electron and laser beam parameters can be optimized to achieve the spectral brightness and narrow bandwidth required by nuclear photonics applications. A description of the design of the next generation precision gamma-ray source currently under construction at Lawrence Livermore National Laboratorymore » is presented, along with the underlying motivations. Within this context, high-gradient X-band technology, used in conjunction with fiber-based photocathode drive laser and diode pumped solid-state interaction laser technologies, will be shown to offer optimal performance for high gamma-ray spectral flux, narrow bandwidth applications.« less

Ultrasensitive hot-electron nanobolometers for terahertz astrophysics.

PubMed

Wei, Jian; Olaya, David; Karasik, Boris S; Pereverzev, Sergey V; Sergeev, Andrei V; Gershenson, Michael E

2008-08-01

The submillimetre or terahertz region of the electromagnetic spectrum contains approximately half of the total luminosity of the Universe and 98% of all the photons emitted since the Big Bang. This radiation is strongly absorbed in the Earth's atmosphere, so space-based terahertz telescopes are crucial for exploring the evolution of the Universe. Thermal emission from the primary mirrors in these telescopes can be reduced below the level of the cosmic background by active cooling, which expands the range of faint objects that can be observed. However, it will also be necessary to develop bolometers-devices for measuring the energy of electromagnetic radiation-with sensitivities that are at least two orders of magnitude better than the present state of the art. To achieve this sensitivity without sacrificing operating speed, two conditions are required. First, the bolometer should be exceptionally well thermally isolated from the environment; second, its heat capacity should be sufficiently small. Here we demonstrate that these goals can be achieved by building a superconducting hot-electron nanobolometer. Its design eliminates the energy exchange between hot electrons and the leads by blocking electron outdiffusion and photon emission. The thermal conductance between hot electrons and the thermal bath, controlled by electron-phonon interactions, becomes very small at low temperatures ( approximately 1 x 10-16 W K-1 at 40 mK). These devices, with a heat capacity of approximately 1 x 10-19 J K-1, are sufficiently sensitive to detect single terahertz photons in submillimetre astronomy and other applications based on quantum calorimetry and photon counting.

Chemical bonding in aqueous hexacyano cobaltate from photon- and electron-detection perspectives

PubMed Central

Lalithambika, Sreeju Sreekantan Nair; Atak, Kaan; Seidel, Robert; Neubauer, Antje; Brandenburg, Tim; Xiao, Jie; Winter, Bernd; Aziz, Emad F.

2017-01-01

The electronic structure of the [Co(CN)6]3− complex dissolved in water is studied using X-ray spectroscopy techniques. By combining electron and photon detection methods from the solutions ionized or excited by soft X-rays we experimentally identify chemical bonding between the metal center and the CN ligand. Non-resonant photoelectron spectroscopy provides solute electron binding energies, and nitrogen 1 s and cobalt 2p resonant core-level photoelectron spectroscopy identifies overlap between metal and ligand orbitals. By probing resonances we are able to qualitatively determine the ligand versus metal character of the respective occupied and non-occupied orbitals, purely by experiment. For the same excitations we also detect the emitted X-rays, yielding the complementary resonant inelastic X-ray scattering spectra. For a quantitative interpretation of the spectra, we perform theoretical electronic-structure calculations. The latter provide both orbital energies and orbital character which are found to be in good agreement with experimental energies and with experimentally inferred orbital mixing. We also report calculated X-ray absorption spectra, which in conjunction with our orbital-structure analysis, enables us to quantify various bonding interactions with a particular focus on the water-solvent – ligand interaction and the strength of π-backbonding between metal and ligand. PMID:28098216

Effective atomic numbers and electron densities of bioactive glasses for photon interaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shantappa, Anil, E-mail: anilmalipatil@yahoo.co.in; Hanagodimath, S. M., E-mail: smhmath@rediffmail.com

2015-08-28

This work was carried out to study the nature of mass attenuation coefficient of bioactive glasses for gamma rays. Bioactive glasses are a group of synthetic silica-based bioactive materials with unique bone bonding properties. In the present study, we have calculated the effective atomic number, electron density for photon interaction of some selected bioactive glasses viz., SiO{sub 2}-Na{sub 2}O, SiO{sub 2}-Na{sub 2}O-CaO and SiO{sub 2}-Na{sub 2}O-P{sub 2}O{sub 5} in the energy range 1 keV to 100 MeV. We have also computed the single valued effective atomic number by using XMuDat program. It is observed that variation in effective atomic number (Z{submore » PI,} {sub eff}) depends also upon the weight fractions of selected bioactive glasses and range of atomic numbers of the elements. The results shown here on effective atomic number, electron density will be more useful in the medical dosimetry for the calculation of absorbed dose and dose rate.« less

A neutron track etch detector for electron linear accelerators in radiotherapy

PubMed Central

Vukovic, Branko; Faj, Dario; Poje, Marina; Varga, Maja; Radolic, Vanja; Miklavcic, Igor; Ivkovic, Ana; Planinic, Josip

2010-01-01

Background Electron linear accelerators in medical radiotherapy have replaced cobalt and caesium sources of radiation. However, medical accelerators with photon energies over 10 MeV generate undesired fast neutron contamination in a therapeutic X-ray photon beam. Photons with energies above 10 MeV can interact with the atomic nucleus of a high-Z material, of which the target and the head of an accelerator consist, and lead to the neutron ejection. Results and conclusions. Our neutron dosimeter, composed of the LR-115 track etch detector and boron foil BN-1 converter, was calibrated on thermal neutrons generated in the nuclear reactor of the Josef Stefan Institute (Slovenia), and applied to dosimetry of undesirable neutrons in photon radiotherapy by the linear accelerator 15 MV Siemens Mevatron. Having considered a high dependence of a cross-section between neutron and boron on neutron energy, and broad neutron spectrum in a photon beam, as well as outside the entrance door to maze of the Mevatron, we developed a method for determining the effective neutron detector response. A neutron dose rate in the photon beam was measured to be 1.96 Sv/h. Outside the Mevatron room the neutron dose rate was 0.62 μSv/h. PACS: 87.52. Ga; 87.53.St; 29.40.Wk. PMID:22933893

Photonic Microresonators from Charge Transfer in Polymer Particles: Toward Enhanced and Tunable Two-Photon Emission.

PubMed

Vattikunta, Radhika; Venkatakrishnarao, Dasari; Sahoo, Chakradhar; Naraharisetty, Sri Ram Gopal; Narayana Rao, Desai; Müllen, Klaus; Chandrasekar, Rajadurai

2018-05-16

Novel photonic microresonators with enhanced nonlinear optical (NLO) intensity are fabricated from polymer particles. As an additional advantage, they offer band gap tunability from the visible to near-infrared regions. A special protocol including (i) copolymerization of 4-(1-pyrenyl)-styrene, styrene, and 1,4-divinylbenzene, (ii) extraction of a dispersible and partly dissolvable, lightly cross-linked polymer network (PN), and (iii) treatment of the blue-emitting PN with electron acceptor (A) molecules such as 1,2,4,5-tetracyanobenzene (TCNB) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) furnishes orange- and red-emitting D-A charge-transfer (CT) complexes with the pendant pyrene units. These complexes, here named PN-TCNB and PN-TCNQ, respectively, precipitate as microparticles upon the addition of water and subsequent ultrasonication. Upon electronic excitation, these spherical microparticles act as whispering-gallery-mode resonators by displaying optical resonances in the photoluminescence (PL) spectra because of light confinement. Further, the trapped incident light increases the light-matter interaction and thereby enhances the PL intensity, including the two-photon luminescence. The described protocol for polymer-based CT microresonators with tunable NLO emissions holds promise for a myriad of photonic applications.

Establishing nonlinearity thresholds with ultraintense X-ray pulses

NASA Astrophysics Data System (ADS)

Szlachetko, Jakub; Hoszowska, Joanna; Dousse, Jean-Claude; Nachtegaal, Maarten; Błachucki, Wojciech; Kayser, Yves; Sà, Jacinto; Messerschmidt, Marc; Boutet, Sebastien; Williams, Garth J.; David, Christian; Smolentsev, Grigory; van Bokhoven, Jeroen A.; Patterson, Bruce D.; Penfold, Thomas J.; Knopp, Gregor; Pajek, Marek; Abela, Rafael; Milne, Christopher J.

2016-09-01

X-ray techniques have evolved over decades to become highly refined tools for a broad range of investigations. Importantly, these approaches rely on X-ray measurements that depend linearly on the number of incident X-ray photons. The advent of X-ray free electron lasers (XFELs) is opening the ability to reach extremely high photon numbers within ultrashort X-ray pulse durations and is leading to a paradigm shift in our ability to explore nonlinear X-ray signals. However, the enormous increase in X-ray peak power is a double-edged sword with new and exciting methods being developed but at the same time well-established techniques proving unreliable. Consequently, accurate knowledge about the threshold for nonlinear X-ray signals is essential. Herein we report an X-ray spectroscopic study that reveals important details on the thresholds for nonlinear X-ray interactions. By varying both the incident X-ray intensity and photon energy, we establish the regimes at which the simplest nonlinear process, two-photon X-ray absorption (TPA), can be observed. From these measurements we can extract the probability of this process as a function of photon energy and confirm both the nature and sub-femtosecond lifetime of the virtual intermediate electronic state.

Treating electron transport in MCNP{sup trademark}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hughes, H.G.

1996-12-31

The transport of electrons and other charged particles is fundamentally different from that of neutrons and photons. A neutron, in aluminum slowing down from 0.5 MeV to 0.0625 MeV will have about 30 collisions; a photon will have fewer than ten. An electron with the same energy loss will undergo 10{sup 5} individual interactions. This great increase in computational complexity makes a single- collision Monte Carlo approach to electron transport unfeasible for many situations of practical interest. Considerable theoretical work has been done to develop a variety of analytic and semi-analytic multiple-scattering theories for the transport of charged particles. Themore » theories used in the algorithms in MCNP are the Goudsmit-Saunderson theory for angular deflections, the Landau an theory of energy-loss fluctuations, and the Blunck-Leisegang enhancements of the Landau theory. In order to follow an electron through a significant energy loss, it is necessary to break the electron`s path into many steps. These steps are chosen to be long enough to encompass many collisions (so that multiple-scattering theories are valid) but short enough that the mean energy loss in any one step is small (for the approximations in the multiple-scattering theories). The energy loss and angular deflection of the electron during each step can then be sampled from probability distributions based on the appropriate multiple- scattering theories. This subsumption of the effects of many individual collisions into single steps that are sampled probabilistically constitutes the ``condensed history`` Monte Carlo method. This method is exemplified in the ETRAN series of electron/photon transport codes. The ETRAN codes are also the basis for the Integrated TIGER Series, a system of general-purpose, application-oriented electron/photon transport codes. The electron physics in MCNP is similar to that of the Integrated TIGER Series.« less

Room temperature operation of electro-optical bistability in the edge-emitting tunneling-collector transistor laser

NASA Astrophysics Data System (ADS)

Feng, M.; Holonyak, N.; Wang, C. Y.

2017-09-01

Optical bistable devices are fundamental to digital photonics as building blocks of switches, logic gates, and memories in future computer systems. Here, we demonstrate both optical and electrical bistability and capability for switching in a single transistor operated at room temperature. The electro-optical hysteresis is explained by the interaction of electron-hole (e-h) generation and recombination dynamics with the cavity photon modulation in different switching paths. The switch-UP and switch-DOWN threshold voltages are determined by the rate difference of photon generation at the base quantum-well and the photon absorption via intra-cavity photon-assisted tunneling controlled by the collector voltage. Thus, the transistor laser electro-optical bistable switching is programmable with base current and collector voltage, and the basis for high speed optical logic processors.

Application of the N-quantum approximation to the proton radius problem

NASA Astrophysics Data System (ADS)

Cowen, Steven

This thesis is organized into three parts: 1. Introduction and bound state calculations of electronic and muonic hydrogen, 2. Bound states in motion, and 3.Treatment of soft photons. In the first part, we apply the N-Quantum Approximation (NQA) to electronic and muonic hydrogen and search for any new corrections to energy levels that could account for the 0.31 meV discrepancy of the proton radius problem. We derive a bound state equation and compare our numerical solutions and wave functions to those of the Dirac equation. We find NQA Lamb shift diagrams and calculate the associated energy shift contributions. We do not find any new corrections large enough to account for the discrepancy. In part 2, we discuss the effects of motion on bound states using the NQA. We find classical Lorentz contraction of the lowest order NQA wave function. Finally, in part 3, we develop a clothing transformation for interacting fields in order to produce the correct asymptotic limits. We find the clothing eliminates a trilinear interacting Hamiltonian term and produces a quadrilinear soft photon interaction term.

Spectrum and Angular Distribution of γ-rays from Radiative Damping in Extremely Relativistic Laser-Plasma Interaction

NASA Astrophysics Data System (ADS)

Pandit, Rishi; Sentoku, Yasuhiko

2013-10-01

Effects of the radiative damping in the interaction of extremely intense laser (> 1022 W/cm2) with dense plasma is studied via a relativistic collisional particle-in-cell simulation, PICLS. When the laser intensity is getting close to 1024 W/cm2, the effect of quantum electrodynamics (QED) appears. We had calculated γ-rays from the radiative damping processes based on the classical model [1], but had taken into account the QED effect [2] in the spectrum calculation. In ultra-intense laser-plasma interaction, electrons are accelerated by the strong laser fields and emit γ-ray photons mainly via two processes, namely, Bremsstrahlung and radiative damping. Such relativistic γ-ray has wide range of frequencies and the angular distribution depends on the hot electron source. Comparing the details of γ-rays from the Bremsstrahlung and the radiative damping in simulations, we will discuss the laser parameters and the target conditions (geometry and material) to distinguish the photons from each process and also the QED effect in the γ-rays spectrum at the extremely relativistic intensity. Supported by US DOE DE-SC0008827.

High power beta electron device - Beyond betavoltaics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ayers, William M.; Gentile, Charles A.

Developing watt level power sources with beta emitting radioisotopes has been limited by the inability to utilize high energy (> 100 KeV) beta emitters at high radioisotope loadings without damaging the energy conversion materials. A new type of beta electron power source is described that removes those restrictions. This approach contains the radioisotope in a beta transparent titanium tube and confines beta electrons emitted through the tube wall to spiral trajectories around the tube with an axial magnetic field. The confined beta electrons dissipate energy though multiple interactions with surrounding excimer precursor gas atoms to efficiently generate photons. Photovoltaic cellsmore » convert the photons to electrical power. Since the beta electrons dissipate energy in the excimer precursor gas, the device can be loaded with more than 10 13 Bq of radioisotope to generate 100 milliwatt to watt levels of electrical power without damaging the device materials or degrading its performance. Furthermore, the power source can use a variety of beta radioisotopes and scales by stacking the devices.« less

Photoemission study of the electronic structure and charge density waves of Na2Ti2Sb2O.

PubMed

Tan, S Y; Jiang, J; Ye, Z R; Niu, X H; Song, Y; Zhang, C L; Dai, P C; Xie, B P; Lai, X C; Feng, D L

2015-04-30

The electronic structure of Na2Ti2Sb2O single crystal is studied by photon energy and polarization dependent angle-resolved photoemission spectroscopy (ARPES). The obtained band structure and Fermi surface agree well with the band structure calculation of Na2Ti2Sb2O in the non-magnetic state, which indicates that there is no magnetic order in Na2Ti2Sb2O and the electronic correlation is weak. Polarization dependent ARPES results suggest the multi-band and multi-orbital nature of Na2Ti2Sb2O. Photon energy dependent ARPES results suggest that the electronic structure of Na2Ti2Sb2O is rather two-dimensional. Moreover, we find a density wave energy gap forms below the transition temperature and reaches 65 meV at 7 K, indicating that Na2Ti2Sb2O is likely a weakly correlated CDW material in the strong electron-phonon interaction regime.

High power beta electron device - Beyond betavoltaics

DOE PAGES

Ayers, William M.; Gentile, Charles A.

2017-11-10

Developing watt level power sources with beta emitting radioisotopes has been limited by the inability to utilize high energy (> 100 KeV) beta emitters at high radioisotope loadings without damaging the energy conversion materials. A new type of beta electron power source is described that removes those restrictions. This approach contains the radioisotope in a beta transparent titanium tube and confines beta electrons emitted through the tube wall to spiral trajectories around the tube with an axial magnetic field. The confined beta electrons dissipate energy though multiple interactions with surrounding excimer precursor gas atoms to efficiently generate photons. Photovoltaic cellsmore » convert the photons to electrical power. Since the beta electrons dissipate energy in the excimer precursor gas, the device can be loaded with more than 10 13 Bq of radioisotope to generate 100 milliwatt to watt levels of electrical power without damaging the device materials or degrading its performance. Furthermore, the power source can use a variety of beta radioisotopes and scales by stacking the devices.« less

High power beta electron device - Beyond betavoltaics.

PubMed

Ayers, William M; Gentile, Charles A

2018-01-01

Developing watt level power sources with beta emitting radioisotopes has been limited by the inability to utilize high energy (> 100KeV) beta emitters at high radioisotope loadings without damaging the energy conversion materials. A new type of beta electron power source is described that removes those restrictions. The approach contains the radioisotope in a beta transparent titanium tube and confines beta electrons emitted through the tube wall to spiral trajectories around the tube with an axial magnetic field. The confined beta electrons dissipate energy though multiple interactions with surrounding excimer precursor gas atoms to efficiently generate photons. Photovoltaic cells convert the photons to electrical power. Since the beta electrons dissipate energy in the excimer precursor gas, the device can be loaded with more than 10 13 Bq of radioisotope to generate 100 milliwatt to watt levels of electrical power without damaging the device materials or degrading its performance. The power source can use a variety of beta radioisotopes and scales by stacking the devices. Copyright © 2017. Published by Elsevier Ltd.

MO-E-18C-04: Advanced Computer Simulation and Visualization Tools for Enhanced Understanding of Core Medical Physics Concepts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Naqvi, S

2014-06-15

Purpose: Most medical physics programs emphasize proficiency in routine clinical calculations and QA. The formulaic aspect of these calculations and prescriptive nature of measurement protocols obviate the need to frequently apply basic physical principles, which, therefore, gradually decay away from memory. E.g. few students appreciate the role of electron transport in photon dose, making it difficult to understand key concepts such as dose buildup, electronic disequilibrium effects and Bragg-Gray theory. These conceptual deficiencies manifest when the physicist encounters a new system, requiring knowledge beyond routine activities. Methods: Two interactive computer simulation tools are developed to facilitate deeper learning of physicalmore » principles. One is a Monte Carlo code written with a strong educational aspect. The code can “label” regions and interactions to highlight specific aspects of the physics, e.g., certain regions can be designated as “starters” or “crossers,” and any interaction type can be turned on and off. Full 3D tracks with specific portions highlighted further enhance the visualization of radiation transport problems. The second code calculates and displays trajectories of a collection electrons under arbitrary space/time dependent Lorentz force using relativistic kinematics. Results: Using the Monte Carlo code, the student can interactively study photon and electron transport through visualization of dose components, particle tracks, and interaction types. The code can, for instance, be used to study kerma-dose relationship, explore electronic disequilibrium near interfaces, or visualize kernels by using interaction forcing. The electromagnetic simulator enables the student to explore accelerating mechanisms and particle optics in devices such as cyclotrons and linacs. Conclusion: The proposed tools are designed to enhance understanding of abstract concepts by highlighting various aspects of the physics. The simulations serve as virtual experiments that give deeper and long lasting understanding of core principles. The student can then make sound judgements in novel situations encountered beyond routine clinical activities.« less

Gravitational waves from dark first order phase transitions and dark photons

NASA Astrophysics Data System (ADS)

Addazi, Andrea; Marcianò, Antonino

2018-01-01

Cold Dark Matter particles may interact with ordinary particles through a dark photon, which acquires a mass thanks to a spontaneous symmetry breaking mechanism. We discuss a dark photon model in which the scalar singlet associated to the spontaneous symmetry breaking has an effective potential that induces a first order phase transition in the early Universe. Such a scenario provides a rich phenomenology for electron-positron colliders and gravitational waves interferometers, and may be tested in several different channels. The hidden first order phase transition implies the emission of gravitational waves signals, which may constrain the dark photon’s space of parameters. Compared limits from electron-positron colliders, astrophysics, cosmology and future gravitational waves interferometers such as eLISA, U-DECIGO and BBO are discussed. This highly motivates a cross-checking strategy of data arising from experiments dedicated to gravitational waves, meson factories, the International Linear Collider (ILC), the Circular Electron Positron Collider (CEPC) and other underground direct detection experiments of cold dark matter candidates. Supported by the Shanghai Municipality (KBH1512299) and Fudan University (JJH1512105)

Photonic topological insulator with broken time-reversal symmetry

PubMed Central

He, Cheng; Sun, Xiao-Chen; Liu, Xiao-Ping; Lu, Ming-Hui; Chen, Yulin; Feng, Liang; Chen, Yan-Feng

2016-01-01

A topological insulator is a material with an insulating interior but time-reversal symmetry-protected conducting edge states. Since its prediction and discovery almost a decade ago, such a symmetry-protected topological phase has been explored beyond electronic systems in the realm of photonics. Electrons are spin-1/2 particles, whereas photons are spin-1 particles. The distinct spin difference between these two kinds of particles means that their corresponding symmetry is fundamentally different. It is well understood that an electronic topological insulator is protected by the electron’s spin-1/2 (fermionic) time-reversal symmetry Tf2=−1. However, the same protection does not exist under normal circumstances for a photonic topological insulator, due to photon’s spin-1 (bosonic) time-reversal symmetry Tb2=1. In this work, we report a design of photonic topological insulator using the Tellegen magnetoelectric coupling as the photonic pseudospin orbit interaction for left and right circularly polarized helical spin states. The Tellegen magnetoelectric coupling breaks bosonic time-reversal symmetry but instead gives rise to a conserved artificial fermionic-like-pseudo time-reversal symmetry, Tp (Tp2=−1), due to the electromagnetic duality. Surprisingly, we find that, in this system, the helical edge states are, in fact, protected by this fermionic-like pseudo time-reversal symmetry Tp rather than by the bosonic time-reversal symmetry Tb. This remarkable finding is expected to pave a new path to understanding the symmetry protection mechanism for topological phases of other fundamental particles and to searching for novel implementations for topological insulators. PMID:27092005

Tunable photonic cavity coupled to a voltage-biased double quantum dot system: Diagrammatic nonequilibrium Green's function approach

NASA Astrophysics Data System (ADS)

Agarwalla, Bijay Kumar; Kulkarni, Manas; Mukamel, Shaul; Segal, Dvira

2016-07-01

We investigate gain in microwave photonic cavities coupled to voltage-biased double quantum dot systems with an arbitrarily strong dot-lead coupling and with a Holstein-like light-matter interaction, by employing the diagrammatic Keldysh nonequilibrium Green's function approach. We compute out-of-equilibrium properties of the cavity: its transmission, phase response, mean photon number, power spectrum, and spectral function. We show that by the careful engineering of these hybrid light-matter systems, one can achieve a significant amplification of the optical signal with the voltage-biased electronic system serving as a gain medium. We also study the steady-state current across the device, identifying elastic and inelastic tunneling processes which involve the cavity mode. Our results show how recent advances in quantum electronics can be exploited to build hybrid light-matter systems that behave as microwave amplifiers and photon source devices. The diagrammatic Keldysh approach is primarily discussed for a cavity-coupled double quantum dot architecture, but it is generalizable to other hybrid light-matter systems.

Micro-/nanoscale multi-field coupling in nonlinear photonic devices

NASA Astrophysics Data System (ADS)

Yang, Qing; Wang, Yubo; Tang, Mingwei; Xu, Pengfei; Xu, Yingke; Liu, Xu

2017-08-01

The coupling of mechanics/electronics/photonics may improve the performance of nanophotonic devices not only in the linear region but also in the nonlinear region. This review letter mainly presents the recent advances on multi-field coupling in nonlinear photonic devices. The nonlinear piezoelectric effect and piezo-phototronic effects in quantum wells and fibers show that large second-order nonlinear susceptibilities can be achieved, and second harmonic generation and electro-optic modulation can be enhanced and modulated. Strain engineering can tune the lattice structures and induce second order susceptibilities in central symmetry semiconductors. By combining the absorption-based photoacoustic effect and intensity-dependent photobleaching effect, subdiffraction imaging can be achieved. This review will also discuss possible future applications of these novel effects and the perspective of their research. The review can help us develop a deeper knowledge of the substance of photon-electron-phonon interaction in a micro-/nano- system. Moreover, it can benefit the design of nonlinear optical sensors and imaging devices with a faster response rate, higher efficiency, more sensitivity and higher spatial resolution which could be applied in environmental detection, bio-sensors, medical imaging and so on.

Link between the photonic and electronic topological phases in artificial graphene

NASA Astrophysics Data System (ADS)

Lannebère, Sylvain; Silveirinha, Mário G.

2018-04-01

In recent years the study of topological phases of matter has emerged as a very exciting field of research, both in photonics and in electronics. However, up to now the electronic and photonic properties have been regarded as totally independent. Here we establish a link between the electronic and the photonic topological phases of the same material system and theoretically demonstrate that they are intimately related. We propose a realization of the Haldane model as a patterned two-dimensional electron gas and determine its optical response using the Kubo formula. It is shown that the electronic and photonic phase diagrams of the patterned electron gas are strictly related. In particular, the system has a trivial photonic topology when the inversion symmetry is the prevalent broken symmetry, whereas it has a nontrivial photonic topology for a dominant broken time-reversal symmetry, similar to the electronic case. To confirm these predictions, we numerically demonstrate the emergence of topologically protected unidirectional electromagnetic edge states at the interface with a trivial photonic material.

ABOUT the phenomenon produced by the successive jumps of the peripheric electrons, at the absorbtion of the intense photon beam by the metal

NASA Astrophysics Data System (ADS)

Isarie, Claudiu I.; Oprean, Constantin; Marginean, Ion; Nemes, Toderita; Isarie, Ilie V.; Bokor, Corina; Itu, Sorin

2011-03-01

When a photon beam is in impact with a metal, the peripheric electrons which belong to the bombarded material are made jumps, and in the same time, new photons are absorbed by electrons which had not time to come back to the fundamental levels. At a high level concentration of the radiant energy, a peripheral electron, could sequentially absorb more photons and could realize energetic jumps in succesive phase, equivalent with some photons of high energy which have wave-lenght smaller than the incidental photons. After some succesive photon absorbtion of the same electron, in the interval in which it is not activated by new photons, the electron comes back to the fundamental level and delivers the accumulated energy, in photons of higher energy, which have a lower energy than the incident beam. Comming back to the fundamental level, the electrons disturb the electronic cloud of the atom or ion they belong. After a huge number of such phenomenon the electronic cloud which is succesivelly disturbed, produces an oscillation which risez the temperature of the nucleus. The authors have studied the conditions which generated the rise of temperature and multiple radiations at the place where the photons bombard the metal.

Compensated gadolinium-loaded plastic scintillators for thermal neutron detection (and counting)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dumazert, Jonathan; Coulon, Romain; Bertrand, Guillaume H. V.

2015-07-01

Plastic scintillator loading with gadolinium-rich organometallic complexes shows a high potential for the deployment of efficient and cost-effective neutron detectors. Due to the low-energy photon and electron signature of thermal neutron capture by gadolinium-155 and gadolinium-157, alternative treatment to Pulse Shape Discrimination has to be proposed in order to display a trustable count rate. This paper discloses the principle of a compensation method applied to a two-scintillator system: a detection scintillator interacts with photon radiation and is loaded with gadolinium organometallic compound to become a thermal neutron absorber, while a non-gadolinium loaded compensation scintillator solely interacts with the photon partmore » of the incident radiation. Posterior to the nonlinear smoothing of the counting signals, a hypothesis test determines whether the resulting count rate after photon response compensation falls into statistical fluctuations or provides a robust image of a neutron activity. A laboratory prototype is tested under both photon and neutron irradiations, allowing us to investigate the performance of the overall compensation system in terms of neutron detection, especially with regards to a commercial helium-3 counter. The study reveals satisfactory results in terms of sensitivity and orientates future investigation toward promising axes. (authors)« less

Nonlinear silicon photonics

NASA Astrophysics Data System (ADS)

Borghi, M.; Castellan, C.; Signorini, S.; Trenti, A.; Pavesi, L.

2017-09-01

Silicon photonics is a technology based on fabricating integrated optical circuits by using the same paradigms as the dominant electronics industry. After twenty years of fervid development, silicon photonics is entering the market with low cost, high performance and mass-manufacturable optical devices. Until now, most silicon photonic devices have been based on linear optical effects, despite the many phenomenologies associated with nonlinear optics in both bulk materials and integrated waveguides. Silicon and silicon-based materials have strong optical nonlinearities which are enhanced in integrated devices by the small cross-section of the high-index contrast silicon waveguides or photonic crystals. Here the photons are made to strongly interact with the medium where they propagate. This is the central argument of nonlinear silicon photonics. It is the aim of this review to describe the state-of-the-art in the field. Starting from the basic nonlinearities in a silicon waveguide or in optical resonator geometries, many phenomena and applications are described—including frequency generation, frequency conversion, frequency-comb generation, supercontinuum generation, soliton formation, temporal imaging and time lensing, Raman lasing, and comb spectroscopy. Emerging quantum photonics applications, such as entangled photon sources, heralded single-photon sources and integrated quantum photonic circuits are also addressed at the end of this review.

The response of a radiophotoluminescent glass dosimeter in megavoltage photon and electron beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Araki, Fujio, E-mail: f-araki@kumamoto-u.ac.jp; Ohno, Takeshi

Purpose: This study investigated the response of a radiophotoluminescent glass dosimeter (RGD) in megavoltage photon and electron beams. Methods: The RGD response was compared with ion chamber measurements for 4–18 MV photons and 6–20 MeV electrons in plastic water phantoms. The response was also calculated via Monte Carlo (MC) simulations with EGSnrc/egs-chamber and Cavity user-codes, respectively. In addition, the response of the RGD cavity was analyzed as a function of field sizes and depths according to Burlin’s general cavity theory. The perturbation correction factor, P{sub Q}, in the RGD cavity was also estimated from MC simulations for photon and electronmore » beams. Results: The calculated and measured RGD energy response at reference conditions with a 10 × 10 cm{sup 2} field and 10 cm depth in photons was lower by up to 2.5% with increasing energy. The variation in RGD response in the field size range of 5 × 5 cm{sup 2} to 20 × 20 cm{sup 2} was 3.9% and 0.7%, at 10 cm depth for 4 and 18 MV, respectively. The depth dependence of the RGD response was constant within 1% for energies above 6 MV but it increased by 2.6% and 1.6% for a large (20 × 20 cm{sup 2}) field at 4 and 6 MV, respectively. The dose contributions from photon interactions (1 − d) in the RGD cavity, according to Burlin’s cavity theory, decreased with increasing energy and decreasing field size. The variation in (1 − d) between field sizes became larger with increasing depth for the lower energies of 4 and 6 MV. P{sub Q} for the RGD cavity was almost constant between 0.96 and 0.97 at 10 MV energies and above. Meanwhile, P{sub Q} depends strongly on field size and depth for 4 and 6 MV photons. In electron beams, the RGD response at a reference depth, d{sub ref}, varied by less than 1% over the electron energy range but was on average 4% lower than the response for 6 MV photons. Conclusions: The RGD response for photon beams depends on both (1 − d) and perturbation effects in the RGD cavity. Therefore, it is difficult to predict the energy dependence of RGD response by Burlin’s theory and it is recommended to directly measure RGD response or use the MC-calculated RGD response, regarding the practical use. The response for electron beams decreased rapidly at a depth beyond d{sub ref} for lower mean electron energies <3 MeV and in contrast P{sub Q} increased.« less

MCNP (Monte Carlo Neutron Photon) capabilities for nuclear well logging calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Forster, R.A.; Little, R.C.; Briesmeister, J.F.

The Los Alamos Radiation Transport Code System (LARTCS) consists of state-of-the-art Monte Carlo and discrete ordinates transport codes and data libraries. The general-purpose continuous-energy Monte Carlo code MCNP (Monte Carlo Neutron Photon), part of the LARTCS, provides a computational predictive capability for many applications of interest to the nuclear well logging community. The generalized three-dimensional geometry of MCNP is well suited for borehole-tool models. SABRINA, another component of the LARTCS, is a graphics code that can be used to interactively create a complex MCNP geometry. Users can define many source and tally characteristics with standard MCNP features. The time-dependent capabilitymore » of the code is essential when modeling pulsed sources. Problems with neutrons, photons, and electrons as either single particle or coupled particles can be calculated with MCNP. The physics of neutron and photon transport and interactions is modeled in detail using the latest available cross-section data. A rich collections of variance reduction features can greatly increase the efficiency of a calculation. MCNP is written in FORTRAN 77 and has been run on variety of computer systems from scientific workstations to supercomputers. The next production version of MCNP will include features such as continuous-energy electron transport and a multitasking option. Areas of ongoing research of interest to the well logging community include angle biasing, adaptive Monte Carlo, improved discrete ordinates capabilities, and discrete ordinates/Monte Carlo hybrid development. Los Alamos has requested approval by the Department of Energy to create a Radiation Transport Computational Facility under their User Facility Program to increase external interactions with industry, universities, and other government organizations. 21 refs.« less

Observation of redshifting and harmonic radiation in inverse Compton scattering

DOE PAGES

Sakai, Y.; Pogorelsky, I.; Williams, O.; ...

2015-06-17

Inverse Compton scattering of laser photons by ultrarelativistic electron beam provides polarized x- to γ-ray pulses due to the Doppler blueshifting. Nonlinear electrodynamics in the relativistically intense linearly polarized laser field changes the radiation kinetics established during the Compton interaction. These are due to the induced figure-8 motion, which introduces an overall redshift in the radiation spectrum, with the concomitant emission of higher order harmonics. To experimentally analyze the strong field physics associated with the nonlinear electron-laser interaction, clear modifications to the angular and wavelength distributions of x rays are observed. The relativistic photon wave field is provided by themore » ps CO 2 laser of peak normalized vector potential of 0.5L<0.7, which due to the quadratic dependence of the strength of nonlinear phenomena on aL permits sufficient effects not observed in past 2 nd harmonic study with a L ≈ 0.3 laser [M. Babzien et al., Phys. Rev. Lett. 96, 054802 (2006)]. The angular spectral characteristics are revealed using K-, L-edge, and high energy attenuation filters. The observation indicates existence of the electrons’ longitudinal motion through frequency redshifting understood as the mass shift effect. The 3 rd harmonic radiation has been observed containing on-axis x-ray component that is directly associated with the induced figure-8 motion. These are further supported by an initial evidence of off-axis 2 nd harmonic radiation produced in a circularly polarized laser wave field. Total x-ray photon number per pulse, scattered by 65 MeV electron beam of 0.3 nC, at the interaction point is measured to be approximately 10 9.« less

Hot-electron-based solar energy conversion with metal-semiconductor nanodiodes.

PubMed

Lee, Young Keun; Lee, Hyosun; Lee, Changhwan; Hwang, Euyheon; Park, Jeong Young

2016-06-29

Energy dissipation at metal surfaces or interfaces between a metal and a dielectric generally results from elementary excitations, including phonons and electronic excitation, once external energy is deposited to the surface/interface during exothermic chemical processes or an electromagnetic wave incident. In this paper, we outline recent research activities to develop energy conversion devices based on hot electrons. We found that photon energy can be directly converted to hot electrons and that hot electrons flow through the interface of metal-semiconductor nanodiodes where a Schottky barrier is formed and the energy barrier is much lower than the work function of the metal. The detection of hot electron flow can be successfully measured using the photocurrent; we measured the photoyield of photoemission with incident photons-to-current conversion efficiency (IPCE). We also show that surface plasmons (i.e. the collective oscillation of conduction band electrons induced by interaction with an electromagnetic field) are excited on a rough metal surface and subsequently decay into secondary electrons, which gives rise to enhancement of the IPCE. Furthermore, the unique optical behavior of surface plasmons can be coupled with dye molecules, suggesting the possibility for producing additional channels for hot electron generation.

Photon Counting Imaging with an Electron-Bombarded Pixel Image Sensor

PubMed Central

Hirvonen, Liisa M.; Suhling, Klaus

2016-01-01

Electron-bombarded pixel image sensors, where a single photoelectron is accelerated directly into a CCD or CMOS sensor, allow wide-field imaging at extremely low light levels as they are sensitive enough to detect single photons. This technology allows the detection of up to hundreds or thousands of photon events per frame, depending on the sensor size, and photon event centroiding can be employed to recover resolution lost in the detection process. Unlike photon events from electron-multiplying sensors, the photon events from electron-bombarded sensors have a narrow, acceleration-voltage-dependent pulse height distribution. Thus a gain voltage sweep during exposure in an electron-bombarded sensor could allow photon arrival time determination from the pulse height with sub-frame exposure time resolution. We give a brief overview of our work with electron-bombarded pixel image sensor technology and recent developments in this field for single photon counting imaging, and examples of some applications. PMID:27136556

Strong field QED in lepton colliders and electron/laser interactions

NASA Astrophysics Data System (ADS)

Hartin, Anthony

2018-05-01

The studies of strong field particle physics processes in electron/laser interactions and lepton collider interaction points (IPs) are reviewed. These processes are defined by the high intensity of the electromagnetic fields involved and the need to take them into account as fully as possible. Thus, the main theoretical framework considered is the Furry interaction picture within intense field quantum field theory. In this framework, the influence of a background electromagnetic field in the Lagrangian is calculated nonperturbatively, involving exact solutions for quantized charged particles in the background field. These “dressed” particles go on to interact perturbatively with other particles, enabling the background field to play both macroscopic and microscopic roles. Macroscopically, the background field starts to polarize the vacuum, in effect rendering it a dispersive medium. Particles encountering this dispersive vacuum obtain a lifetime, either radiating or decaying into pair particles at a rate dependent on the intensity of the background field. In fact, the intensity of the background field enters into the coupling constant of the strong field quantum electrodynamic Lagrangian, influencing all particle processes. A number of new phenomena occur. Particles gain an intensity-dependent rest mass shift that accounts for their presence in the dispersive vacuum. Multi-photon events involving more than one external field photon occur at each vertex. Higher order processes which exchange a virtual strong field particle resonate via the lifetimes of the unstable strong field states. Two main arenas of strong field physics are reviewed; those occurring in relativistic electron interactions with intense laser beams, and those occurring in the beam-beam physics at the interaction point of colliders. This review outlines the theory, describes its significant novel phenomenology and details the experimental schema required to detect strong field effects and the simulation programs required to model them.

Ultra-fast switching of light by absorption saturation in vacuum ultra-violet region.

PubMed

Yoneda, Hitoki; Inubushi, Yuichi; Tanaka, Toshihiro; Yamaguchi, Yuta; Sato, Fumiya; Morimoto, Shunsuke; Kumagai, Taisuke; Nagasono, Mitsuru; Higashiya, Atsushi; Yabashi, Makina; Ishikawa, Tetsuya; Ohashi, Haruhiko; Kimura, Hiroaki; Kitamura, Hikaru; Kodama, Ryosuke

2009-12-21

Advances in free electron lasers producing high energy photons [Nat. Photonics 2(9), 555-559 (2008)] are expected to open up a new science of nonlinear optics of high energy photons. Specifically, lasers of photon energy higher than the plasma frequency of a metal can show new interaction features because they can penetrate deeply into metals without strong reflection. Here we show the observation of ultra-fast switching of vacuum ultra-violet (VUV) light caused by saturable absorption of a solid metal target. A strong gating is observed at energy fluences above 6J/cm2 at wavelength of 51 nm with tin metal thin layers. The ratio of the transmission at high intensity to low intensity is typically greater than 100:1. This means we can design new nonlinear photonic devices such as auto-correlator and pulse slicer for the VUV region.

Selected bibliography on atomic collisions: Data collections, bibliographies, review articles, books, and papers of particular tutorial value

DOE Office of Scientific and Technical Information (OSTI.GOV)

McDaniel, E.W.; Flannery, M.R.; Thomas, E.W.

This bibliography deals mainly with binary and ternary collisions involving electrons, photons, and heavy particles (i.e., atoms, molecules, and ions). The energy range covered for each kind of collision is such that the interactions might be described as electronic, atomic, or chemical--higher-energy collisions involving nuclear forces are not treated. Also covered are particle and photon impact on surfaces, the passage of particles and radiation through bulk matter, and transport phenomena in gases. Practically all of the references cited are data compilations, other bibliographies, review articles, or books. The main objective is to provide easy access to atomic collision data, althoughmore » some references are included principally for their tutorial value.« less

Configuration-specific electronic structure of strongly interacting interfaces: TiOPc on Cu(110)

NASA Astrophysics Data System (ADS)

Maughan, Bret; Zahl, Percy; Sutter, Peter; Monti, Oliver L. A.

2017-12-01

We use low-temperature scanning tunneling microscopy in combination with angle-resolved ultraviolet and two-photon photoemission spectroscopy to investigate the interfacial electronic structure of titanyl phthalocyanine (TiOPc) on Cu(110). We show that the presence of two unique molecular adsorption configurations is crucial for a molecular-level analysis of the hybridized interfacial electronic structure. Specifically, thermally induced self-assembly exposes marked adsorbate-configuration-specific contributions to the interfacial electronic structure. The results of this work demonstrate an avenue towards understanding and controlling interfacial electronic structure in chemisorbed films even for the case of complex film structure.

Looking for polarization bremsstrahlung in the midst of inner-shell ionization: Analysis of the x-ray spectrum in electron interactions with thin-film targets

NASA Astrophysics Data System (ADS)

Quarles, C. A.; Portillo, S.

1999-06-01

Calculations of the total bremsstrahlung spectrum including polarization bremsstrahlung (PB) for high energy electrons on atoms have been made recently by A. V. Korol, A. G. Lyalin and A. V. Solovy'ov. This has motivated us to look for the PB effect for 25 and 50 keV electrons on a variety of thin-film targets including C, Al, Cu, Ag, Tb and Au. PB is predicted to be a significant increase in radiated photon intensity at energies below the target K and L absorption edges. A good model of the thick-target bremsstrahlung background due to electrons elastically scattered into the detector window and a good understanding of the Ge and Si(Li) detector response are crucial for interpretation of the data. We have used a geometry in which the detector-window background is significantly reduced from that in prior experiments. We have analyzed the photon spectra from above 4 keV to the kinematic endpoint. The data are very well fit by normal bremsstrahlung alone. No PB contribution is seen in the data. Finally, we conclude with an argument why, in fact, we should not expect any PB effect when charged particles interact with solid film targets.

Atomistic tight-binding theory of excitonic splitting energies in CdX(X = Se, S and Te)/ZnS core/shell nanocrystals

NASA Astrophysics Data System (ADS)

Sukkabot, Worasak; Pinsook, Udomsilp

2017-01-01

Using the atomistic tight-binding theory (TB) and a configuration interaction description (CI), we numerically compute the excitonic splitting of CdX(X = Se, S and Te)/ZnS core/shell nanocrystals with the objective to explain how types of the core materials and growth shell thickness can provide the detailed manipulation of the dark-dark (DD), dark-bright (DB) and bright-bright (BB) excitonic splitting, beneficial for the active application of quantum information. To analyze the splitting of the excitonic states, the optical band gaps, ground-state wave function overlaps and atomistic electron-hole interactions tend to be numerically demonstrated. Based on the atomistic computations, the single-particle and excitonic gaps are mainly reduced with the increasing ZnS shell thickness owing to the quantum confinement. In the range of the higher to lower energies, the order of the single-particle gaps is CdSe/ZnS, CdS/ZnS and CdTe/ZnS core/shell nanocrystals, while one of the excitonic gaps is CdS/ZnS, CdSe/ZnS and CdTe/ZnS core/shell nanocrystals because of the atomistic electron-hole interaction. The strongest electron-hole interactions are mainly observed in CdSe/ZnS core/shell nanocrystals. In addition, the computational results underline that the energies of the dark-dark (DD), dark-bright (DB) and bright-bright (BB) excitonic splitting are generally reduced with the increasing ZnS growth shell thickness as described by the trend of the electron-hole exchange interaction. The high-to-low splitting of the excitonic states is demonstrated in CdSe/ZnS, CdTe/ZnS and CdS/ZnS core/shell nanocrystals because of the fashion in the electron-hole exchange interaction and overlaps of the electron-hole wave functions. As the resulting calculations, it is expected that CdS/ZnS core/shell nanocrystals are the best candidates to be the source of entangled photons. Finally, the comprehensive information on the excitonic splitting can enable the use of suitable core/shell nanocrystals for the entangled photons in the application of quantum information.

Hydrodynamic and kinetic models for spin-1/2 electron-positron quantum plasmas: Annihilation interaction, helicity conservation, and wave dispersion in magnetized plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andreev, Pavel A., E-mail: andreevpa@physics.msu.ru

2015-06-15

We discuss the complete theory of spin-1/2 electron-positron quantum plasmas, when electrons and positrons move with velocities mach smaller than the speed of light. We derive a set of two fluid quantum hydrodynamic equations consisting of the continuity, Euler, spin (magnetic moment) evolution equations for each species. We explicitly include the Coulomb, spin-spin, Darwin and annihilation interactions. The annihilation interaction is the main topic of the paper. We consider the contribution of the annihilation interaction in the quantum hydrodynamic equations and in the spectrum of waves in magnetized electron-positron plasmas. We consider the propagation of waves parallel and perpendicular tomore » an external magnetic field. We also consider the oblique propagation of longitudinal waves. We derive the set of quantum kinetic equations for electron-positron plasmas with the Darwin and annihilation interactions. We apply the kinetic theory to the linear wave behavior in absence of external fields. We calculate the contribution of the Darwin and annihilation interactions in the Landau damping of the Langmuir waves. We should mention that the annihilation interaction does not change number of particles in the system. It does not related to annihilation itself, but it exists as a result of interaction of an electron-positron pair via conversion of the pair into virtual photon. A pair of the non-linear Schrodinger equations for the electron-positron plasmas including the Darwin and annihilation interactions is derived. Existence of the conserving helicity in electron-positron quantum plasmas of spinning particles with the Darwin and annihilation interactions is demonstrated. We show that the annihilation interaction plays an important role in the quantum electron-positron plasmas giving the contribution of the same magnitude as the spin-spin interaction.« less

Impact excitation and electron-hole multiplication in graphene and carbon nanotubes.

PubMed

Gabor, Nathaniel M

2013-06-18

In semiconductor photovoltaics, photoconversion efficiency is governed by a simple competition: the incident photon energy is either transferred to the crystal lattice (heat) or transferred to electrons. In conventional materials, energy loss to the lattice is more efficient than energy transferred to electrons, thus limiting the power conversion efficiency. Quantum electronic systems, such as quantum dots, nanowires, and two-dimensional electronic membranes, promise to tip the balance in this competition by simultaneously limiting energy transfer to the lattice and enhancing energy transfer to electrons. By exploring the optical, thermal, and electronic properties of quantum materials, we may perhaps find an ideal optoelectronic material that provides low cost fabrication, facile systems integration, and a means to surpass the standard limit for photoconversion efficiency. Nanoscale carbon materials, such as graphene and carbon nanotubes, provide ideal experimental quantum systems in which to explore optoelectronic behavior for applications in solar energy harvesting. Within essentially the same material, researchers can achieve a broad spectrum of energetic configurations, from a gapless semimetal to a large band-gap semiconducting nanowire. Owing to their nanoscale dimensions, graphene and carbon nanotubes exhibit electronic and optical properties that reflect strong electron-electron interactions. Such strong interactions may lead to exotic low-energy electron transport behavior and high-energy electron scattering processes such as impact excitation and the inverse process of Auger recombination. High-energy processes, which become very important under photoexcitation, may be particularly efficient in nanoscale carbon materials due to the relativistic-like, charged particle band structure and sensitivity to the dielectric environment. In addition, due to the covalently bonded carbon framework that makes up these materials, electron-phonon coupling is very weak. In carbon nanomaterials, strong electron-electron interactions combined with weak electron-phonon interactions results in excellent optical, thermal and electronic properties, the exploration of which promises to reveal fundamentally new physical processes and deliver advanced nanotechnologies. In this Account, we review the results of novel optoelectronic experiments that explore the intrinsic photoresponse of carbon nanomaterials integrated into nanoscale devices. By fabricating gate voltage-controlled photodetectors composed of atomically thin sheets of graphene and individual carbon nanotubes, we are able to fully explore electron transport in these systems under optical illumination. We find that strong electron-electron interactions play a key role in the intrinsic photoresponse of both materials, as evidenced by hot carrier transport in graphene and highly efficient multiple electron-hole pair generation in nanotubes. In both of these quantum systems, photoexcitation leads to high-energy electron-hole pairs that relax energy predominantly into the electronic system, rather than heating the lattice. Due to highly efficient energy transfer from photons into electrons, graphene and carbon nanotubes may be ideal materials for solar energy harvesting devices with efficiencies that could exceed the Shockley-Queisser limit.

Soft pair excitations and double-log divergences due to carrier interactions in graphene

NASA Astrophysics Data System (ADS)

Lewandowski, Cyprian; Levitov, L. S.

2018-03-01

Interactions between charge carriers in graphene lead to logarithmic renormalization of observables mimicking the behavior known in (3+1)-dimensional quantum electrodynamics (QED). Here we analyze soft electron-hole (e -h ) excitations generated as a result of fast charge dynamics, a direct analog of the signature QED effect—multiple soft photons produced by the QED vacuum shakeup. We show that such excitations are generated in photon absorption, when a photogenerated high-energy e -h pair cascades down in energy and gives rise to multiple soft e -h excitations. This fundamental process is manifested in a double-log divergence in the emission rate of soft pairs and a characteristic power-law divergence in their energy spectrum of the form 1/ω ln(ω/Δ ) . Strong carrier-carrier interactions make pair production a prominent pathway in the photoexcitation cascade.

Constructions of secure entanglement channels assisted by quantum dots inside single-sided optical cavities

NASA Astrophysics Data System (ADS)

Heo, Jino; Kang, Min-Sung; Hong, Chang-Ho; Choi, Seong-Gon; Hong, Jong-Phil

2017-08-01

We propose quantum information processing schemes to generate and swap entangled states based on the interactions between flying photons and quantum dots (QDs) confined within optical cavities for quantum communication. To produce and distribute entangled states (Bell and Greenberger-Horne-Zeilinger [GHZ] states) between the photonic qubits of flying photons of consumers (Alice and Bob) and electron-spin qubits of a provider (trust center, or TC), the TC employs the interactions of the QD-cavity system, which is composed of a charged QD (negatively charged exciton) inside a single-sided cavity. Subsequently, the TC constructs an entanglement channel (Bell state and 4-qubit GHZ state) to link one consumer with another through entanglement swapping, which can be realized to exploit a probe photon with interactions of the QD-cavity systems and single-qubit measurements without Bell state measurement, for quantum communication between consumers. Consequently, the TC, which has quantum nodes (QD-cavity systems), can accomplish constructing the entanglement channel (authenticated channel) between two separated consumers from the distributions of entangled states and entanglement swapping. Furthermore, our schemes using QD-cavity systems, which are feasible with a certain probability of success and high fidelity, can be experimentally implemented with technology currently in use.

From quantum to classical modeling of radiation reaction: A focus on stochasticity effects

NASA Astrophysics Data System (ADS)

Niel, F.; Riconda, C.; Amiranoff, F.; Duclous, R.; Grech, M.

2018-04-01

Radiation reaction in the interaction of ultrarelativistic electrons with a strong external electromagnetic field is investigated using a kinetic approach in the nonlinear moderately quantum regime. Three complementary descriptions are discussed considering arbitrary geometries of interaction: a deterministic one relying on the quantum-corrected radiation reaction force in the Landau and Lifschitz (LL) form, a linear Boltzmann equation for the electron distribution function, and a Fokker-Planck (FP) expansion in the limit where the emitted photon energies are small with respect to that of the emitting electrons. The latter description is equivalent to a stochastic differential equation where the effect of the radiation reaction appears in the form of the deterministic term corresponding to the quantum-corrected LL friction force, and by a diffusion term accounting for the stochastic nature of photon emission. By studying the evolution of the energy moments of the electron distribution function with the three models, we are able to show that all three descriptions provide similar predictions on the temporal evolution of the average energy of an electron population in various physical situations of interest, even for large values of the quantum parameter χ . The FP and full linear Boltzmann descriptions also allow us to correctly describe the evolution of the energy variance (second-order moment) of the distribution function, while higher-order moments are in general correctly captured with the full linear Boltzmann description only. A general criterion for the limit of validity of each description is proposed, as well as a numerical scheme for the inclusion of the FP description in particle-in-cell codes. This work, not limited to the configuration of a monoenergetic electron beam colliding with a laser pulse, allows further insight into the relative importance of various effects of radiation reaction and in particular of the discrete and stochastic nature of high-energy photon emission and its back-reaction in the deformation of the particle distribution function.

Dark Searches and γγ Physics at KLOE

NASA Astrophysics Data System (ADS)

Curciarello, Francesca

2017-04-01

The search for a dark sector mediated by a new gauge boson, the dark photon, is motivated by many astrophysical anomalies and by the g - 2 discrepancy. The KLOE experiment, operating at the e+e- DAΦNE collider in Frascati, searched for a visibly-decaying dark photon by investigating the ϕ-Dalitz decay into the η meson, the dark photon production from continuum, and the Higgsstrahlung process. The KLOE-2 run started in November 2014, after the upgrade of both, DAΦNE and the KLOE apparatus. In particular, two high electron and positron tagger stations were installed in the DAΦNE layout to study γγ interactions at 1 GeV. Progress status of the project is given.

Soft-photon emission effects and radiative corrections for electromagnetic processes at very high energies

NASA Technical Reports Server (NTRS)

Gould, R. J.

1979-01-01

Higher-order electromagnetic processes involving particles at ultrahigh energies are discussed, with particular attention given to Compton scattering with the emission of an additional photon (double Compton scattering). Double Compton scattering may have significance in the interaction of a high-energy electron with the cosmic blackbody photon gas. At high energies the cross section for double Compton scattering is large, though this effect is largely canceled by the effects of radiative corrections to ordinary Compton scattering. A similar cancellation takes place for radiative pair production and the associated radiative corrections to the radiationless process. This cancellation is related to the well-known cancellation of the infrared divergence in electrodynamics.

Magnetoresistance of non-180° domain wall in the presence of electron-photon interaction

NASA Astrophysics Data System (ADS)

Majidi, Roya

2013-04-01

In the present paper, influence of photon on resistance of non-180° domain wall in metallic magnetic nanowires has been studied using the semiclassical approach. The analysis has been based on the Boltzmann transport equation, within the relaxation time approximation. The one-dimensional Néel-type domain wall between two ferromagnetic domains with relative magnetization angle less than 180° is considered. By increasing this angle, the contribution of the domain wall in the resistivity of the nanowire becomes considerable. It is also found that the fundamental contribution of the domain wall in resistivity can be controlled by propagating photon. These results are valuable in designing spintronic devices based on magnetic nanowires.

Photon-induced tunability of the thermospin current in a Rashba ring

NASA Astrophysics Data System (ADS)

Abdullah, Nzar Rauf; Arnold, Thorsten; Tang, Chi-Shung; Manolescu, Andrei; Gudmundsson, Vidar

2018-04-01

The goal of this work is to show how the thermospin polarization current in a quantum ring changes in the presence of Rashba spin-orbit coupling and a quantized single photon mode of a cavity the ring is placed in. Employing the reduced density operator and a general master equation formalism, we find that both the Rashba interaction and the photon field can significantly modulate the spin polarization and the thermospin polarization current. Tuning the Rashba coupling constant, degenerate energy levels are formed corresponding to the Aharonov-Casher destructive phase interference in the quantum ring system. Our analysis indicates that the maximum spin polarization can be observed at the points of degenerate energy levels due to spin accumulation in the system without the photon field. The thermospin current is thus suppressed. In the presence of the cavity, the photon field leads to an additional kinetic momentum of the electron. As a result the spin polarization can be enhanced by the photon field.

Rotational symmetry breaking and topological phase transition in the exciton-polariton condensate of gapped 2D Dirac material

NASA Astrophysics Data System (ADS)

Lee, Ki Hoon; Lee, Changhee; Jeong, Jae-Seung; Min, Hongki; Chung, Suk Bum

For the quantum well in an optical microcavity, the interplay of the Coulomb interaction and the electron-photon coupling can lead to the emergence of bosonic quasiparticles consisting of the exciton and the cavity photon known as polariton, which can form the Bose-Einstein condensate above a threshold density. Additional physics due to the nontrivial Berry phase comes into play when the quantum well consists of the gapped Dirac material such as the transition metal dichalcogenide (TMD) MoS2 or WTe2. Specifically, in forming excitons, the electron-photon coupling from the optical selection rule due to the Berry phase competes against, rather than cooperates with, the Coulomb interaction. We find that this competition gives rise to the spontaneous breaking of the rotational symmetry in the polariton condensate and also drives topological phase transition, both novel features in polariton condensation. We also investigate the possible detection of this competition through photoluminescence. This work was supported in part by the Institute for Basic Science of Korea (IBS) under Grant IBS-R009-Y1 and by the National Research Foundation of Korea (NRF) under the Basic Science Research Program Grant No. 2015R1D1A1A01058071.

Influence of non-collisional laser heating on the electron dynamics in dielectric materials

NASA Astrophysics Data System (ADS)

Barilleau, L.; Duchateau, G.; Chimier, B.; Geoffroy, G.; Tikhonchuk, V.

2016-12-01

The electron dynamics in dielectric materials induced by intense femtosecond laser pulses is theoretically addressed. The laser driven temporal evolution of the energy distribution of electrons in the conduction band is described by a kinetic Boltzmann equation. In addition to the collisional processes for energy transfer such as electron-phonon-photon and electron-electron interactions, a non-collisional process for photon absorption in the conduction band is included. It relies on direct transitions between sub-bands of the conduction band through multiphoton absorption. This mechanism is shown to significantly contribute to the laser heating of conduction electrons for large enough laser intensities. It also increases the time required for the electron distribution to reach the equilibrium state as described by the Fermi-Dirac statistics. Quantitative results are provided for quartz irradiated by a femtosecond laser pulse with a wavelength of 800 nm and for intensities in the range of tens of TW cm-2, lower than the ablation threshold. The change in the energy deposition induced by this non-collisional heating process is expected to have a significant influence on the laser processing of dielectric materials.

Investigation of radiological properties of some shielding materials on charged and uncharged radiation interaction for neutron generator

NASA Astrophysics Data System (ADS)

Büyükyıldız, Mehmet

2017-04-01

Radiation interaction parameters such as total stopping power, projected range (longitudinal and lateral) straggling, mass attenuation coefficient, effective atomic number (Zeff) and electron density (Neff) of some shielding materials were investigated for photon and heavy charged particle interactions. The ranges, stragglings and mass attenuation coefficients were calculated for the high-density polyethylene(HDPE), borated polyethylene (BPE), brick (common silica), concrete (regular), wood, water, stainless steel (304), aluminum (alloy 6061-O), lead and bismuth using SRIM Monte Carlo software and WinXCom program. In addition, effective atomic numbers (Zeff) and electron densities (Neff) of HDPE, BPE, brick (common silica), concrete (regular), wood, water, stainless steel (304) and aluminum (alloy 6061-O) were calculated in the energy region 10 keV-100 MeV using mass stopping powers and mass attenuation coefficients. Two different methods namely direct and interpolation procedures were used to calculate Zeff for comparison and significant differences were determined between the methods. Variations of the ranges, longitudinal and lateral stragglings of water, concrete and stainless steel (304) were compared with each other in the continuous kinetic energy region and discussed with respect to their Zeffs. Moreover, energy absorption buildup factors (EABF) and exposure buildup factors (EBF) of the materials were determined for gamma rays as well and were compared with each other for different photon energies and different mfps in the photon energy region 0.015-15 MeV.

Ion/Neutral, Ion/Electron, Ion/Photon, and Ion/Ion Interactions in Tandem Mass Spectrometry: Do we need them all? Are they enough?

PubMed Central

McLuckey, Scott A.; Mentinova, Marija

2011-01-01

A range of strategies and tools has been developed to facilitate the determination of primary structures of analyte molecules of interest via tandem mass spectrometry (MS/MS). The two main factors that determine the primary structural information present in an MS/MS spectrum are the type of ion generated from the analyte molecule and the dissociation method. The ion-type subjected to dissociation is determined by the ionization method/conditions and ion transformation processes that might take place after initial gas-phase ion formation. Furthermore, the range of analyte-related ion types can be expanded via derivatization reactions prior to mass spectrometry. Dissociation methods include those that simply alter the population of internal states of the mass-selected ion (i.e., activation methods like collision-induced dissociation) as well as processes that rely on transformation of the ion-type prior to dissociation (e.g., electron capture dissociation). A variety of ionic interactions has been studied for the purpose of ion dissociation and ion transformation that include ion/neutral, ion/photon, ion/electron, and ion/ion interactions. A wide range of phenomena has been observed, many of which have been explored/developed as means for structural analysis. The techniques arising from these phenomena are discussed within the context of the elements of structure determination in tandem mass spectrometry, viz., ion-type definition and dissociation. Unique aspects of the various ion interactions are emphasized along with any barriers to widespread implementation. PMID:21472539

Determination of the Goos-Hanchen shift in dielectric waveguides via photo emission electron microscopy in the visible spectrum

DOE PAGES

Stenmark, Theodore; Word, R. C.; Konenkamp, R.

2016-02-16

Photoemission Electron Microscopy (PEEM) is a versatile tool that relies on the photoelectric effect to produce high-resolution images. Pulse lasers allow for multi-photon PEEM where multiple photons are required excite a single electron. This non-linear process can directly image the near field region of electromagnetic fields in materials. We use this ability here to analyze wave propagation in a linear dielectric waveguide with wavelengths of 410nm and 780nm. The propagation constant of the waveguide can be extracted from the interference pattern created by the coupled and incident light and shows distinct polarization dependence. Furthermore, the electromagnetic field interaction at themore » boundaries can then be deduced which is essential to understand power flow in wave guiding structures. These results match well with simulations using finite element techniques.« less

Establishing nonlinearity thresholds with ultraintense X-ray pulses

DOE PAGES

Szlachetko, Jakub; Hoszowska, Joanna; Dousse, Jean-Claude; ...

2016-09-13

X-ray techniques have evolved over decades to become highly refined tools for a broad range of investigations. Importantly, these approaches rely on X-ray measurements that depend linearly on the number of incident X-ray photons. The advent of X-ray free electron lasers (XFELs) is opening the ability to reach extremely high photon numbers within ultrashort X-ray pulse durations and is leading to a paradigm shift in our ability to explore nonlinear X-ray signals. However, the enormous increase in X-ray peak power is a double-edged sword with new and exciting methods being developed but at the same time well-established techniques proving unreliable.more » Consequently, accurate knowledge about the threshold for nonlinear X-ray signals is essential. Here in this paper we report an X-ray spectroscopic study that reveals important details on the thresholds for nonlinear X-ray interactions. By varying both the incident X-ray intensity and photon energy, we establish the regimes at which the simplest nonlinear process, two-photon X-ray absorption (TPA), can be observed. From these measurements we can extract the probability of this process as a function of photon energy and confirm both the nature and sub-femtosecond lifetime of the virtual intermediate electronic state.« less

Vanderbilt free-electron-laser project in biomedical and materials research. Annual report, 1 February 1987-31 January 1988

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haglund, R.F.; Tolk, N.H.

The Medical Free Electron Laser Program was awarded to develop, construct and operate a free-electron laser facility dedicated to biomedical and materials studies, with particular emphases on: fundamental studies of absorption and localization of electromagnetic energy on and near material surfaces, especially through electronic and other selective, non-statistical processes; non-thermal photon-materials interactions (e.g., electronic bond-breaking or vibrational energy transfer) in physical and biological materials as well as in long-wavelength biopolymer dynamics; development of FEL-based methods to study drug action and to characterize biomolecular properties and metabolic processes in biomembranes; clinical applications in otolaryngology, neurosurgery, ophthalmology and radiology stressing the usemore » of the laser for selective laser-tissue, laser-cellular and laser-molecule interactions in both therapeutic and diagnostic modalities.« less

Time-dependent Schrödinger equation for molecular core-hole dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Picón, A.

2017-02-01

X-ray spectroscopy is an important tool for the investigation of matter. X rays primarily interact with inner-shell electrons, creating core (inner-shell) holes that will decay on the time scale of attoseconds to a few femtoseconds through electron relaxations involving the emission of a photon or an electron. Furthermore, the advent of femtosecond x-ray pulses expands x-ray spectroscopy to the time domain and will eventually allow the control of core-hole population on time scales comparable to core-vacancy lifetimes. For both cases, a theoretical approach that accounts for the x-ray interaction while the electron relaxations occur is required. We describe a time-dependentmore » framework, based on solving the time-dependent Schrödinger equation, that is suitable for describing the induced electron and nuclear dynamics.« less

Photon Beaming in External Compton models

NASA Astrophysics Data System (ADS)

Hutter, Anne; Spanier, Felix

In attempt to model blazar emission spectra, External Compton models have been employed to fit the observed data. In these models photons from the accretion disk or the CMB are upscat-tered via the Compton effect by the electrons and contribute to the emission. In previous works the resulting scattered photon angular distribution has been calculated for ultrarelativistic elec-trons. This work aims to extend the result to the case of mildly relativistic electrons. Hence, the beaming pattern produced by a relativistic moving blob consisting of isotropic distributed electrons, which scatter photons of an isotropic external radiation is calculated numerically. The isotropic photon density distribution in the blob frame is Lorentz-transformed into the rest frame of the electron and results in an anisotropic distribution with a preferred direction where it is upscattered by the electrons. The photon density distribution is determined and transformed back into the blob frame. As the photons in the rest frame of the electrons are dis-tributed anisotropically the scattering does not reproduce this anisotropic distribution. When transforming back into the blob frame the resulting photon distribution won't be isotropic. Approximations have shown that the resulting photon distribution is boosted more strongly than a distribution assumed to be isotropic in the rest frame of the electrons. Hence, in order to obtain the beaming caused by external Compton it is of particular interest to derive a more exact approximation of the resulting photon angular distribution.

Extraction of highly charged ions from the Berlin Electron Beam Ion Trap for interactions with a gas target

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allen, F.I.; Biedermann, C.; Radtke, R.

2006-03-15

Highly charged ions are extracted from the Berlin Electron Beam Ion Trap for investigations of charge exchange with a gas target. The classical over-the-barrier model for slow highly charged ions describes this process, whereby one or more electrons are captured from the target into Rydberg states of the ion. The excited state relaxes via a radiative cascade of the electron to ground energy. The cascade spectra are characteristic of the capture state. We investigate x-ray photons emitted as a result of interactions between Ar{sup 17+} ions at energies {<=}5q keV with Ar atoms. Of particular interest is the velocity dependencemore » of the angular momentum capture state l{sub c}.« less

Recipe for Topological Polaritons

NASA Astrophysics Data System (ADS)

Karzig, Torsten; Bardyn, Charles-Edouard; Lindner, Netanel; Refael, Gil

2015-03-01

The interaction between light and matter can give rise to novel topological states. This principle was recently exemplified in Floquet topological insulators, where classical light was used to induce a topological electronic band structure. Here, in contrast, we show that mixing single photons with excitons can result in new topological polaritonic states -- or ``topolaritons''. Taken separately, the underlying photons and excitons are topologically trivial. Combined appropriately, however, they give rise to non-trivial polaritonic bands with chiral edge modes allowing for unidirectional polariton propagation. The main ingredient in our construction is an exciton-photon coupling with a phase that winds in momentum space. We demonstrate how this winding emerges from spin-orbit coupling in the electronic system and an applied Zeeman field. We discuss the requirements for obtaining a sizable topological gap in the polariton spectrum. Funded by the Institute for Quantum Information and Matter, the Bi-National Science Foundation and I-Core: the Israeli Excellence Center ``Circle of Light'', and Darpa under funding for FENA, and the Swiss National Science Foundation.

Stimulated Raman spectroscopy and nanoscopy of molecules using near field photon induced forces without resonant electronic enhancement gain

NASA Astrophysics Data System (ADS)

Tamma, Venkata Ananth; Huang, Fei; Nowak, Derek; Kumar Wickramasinghe, H.

2016-06-01

We report on stimulated Raman spectroscopy and nanoscopy of molecules, excited without resonant electronic enhancement gain, and recorded using near field photon induced forces. Photon-induced interaction forces between the sharp metal coated silicon tip of an Atomic Force Microscope (AFM) and a sample resulting from stimulated Raman excitation were detected. We controlled the tip to sample spacing using the higher order flexural eigenmodes of the AFM cantilever, enabling the tip to come very close to the sample. As a result, the detection sensitivity was increased compared with previous work on Raman force microscopy. Raman vibrational spectra of azobenzene thiol and l-phenylalanine were measured and found to agree well with published results. Near-field force detection eliminates the need for far-field optical spectrometer detection. Recorded images show spatial resolution far below the optical diffraction limit. Further optimization and use of ultrafast pulsed lasers could push the detection sensitivity towards the single molecule limit.

Stimulated Raman spectroscopy and nanoscopy of molecules using near field photon induced forces without resonant electronic enhancement gain

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tamma, Venkata Ananth; Huang, Fei; Kumar Wickramasinghe, H., E-mail: hkwick@uci.edu

We report on stimulated Raman spectroscopy and nanoscopy of molecules, excited without resonant electronic enhancement gain, and recorded using near field photon induced forces. Photon-induced interaction forces between the sharp metal coated silicon tip of an Atomic Force Microscope (AFM) and a sample resulting from stimulated Raman excitation were detected. We controlled the tip to sample spacing using the higher order flexural eigenmodes of the AFM cantilever, enabling the tip to come very close to the sample. As a result, the detection sensitivity was increased compared with previous work on Raman force microscopy. Raman vibrational spectra of azobenzene thiol andmore » l-phenylalanine were measured and found to agree well with published results. Near-field force detection eliminates the need for far-field optical spectrometer detection. Recorded images show spatial resolution far below the optical diffraction limit. Further optimization and use of ultrafast pulsed lasers could push the detection sensitivity towards the single molecule limit.« less

Construction of Nanowire Heterojunctions: Photonic Function-Oriented Nanoarchitectonics.

PubMed

Li, Yong Jun; Yan, Yongli; Zhao, Yong Sheng; Yao, Jiannian

2016-02-10

Nanophotonics has received broad research interest because it may provide an alternative opportunity to overcome the fundamental limitations of electronic circuits. So far, diverse photonic functions, such as light generation, modulation, and detection, have been realized based on various nano-materials. The exact structural features of these material systems, including geometric characteristics, surface morphology, and material composition, play a key role in determining the photonic functions. Therefore, rational designs and constructions of materials on both morphological and componential levels, namely nanoarchitectonics, are indispensable for any photonic device with specific functionalities. Recently, a series of nanowire heterojunctions (NWHJs), which are usually made from two or more kinds of material compositions, were constructed for novel photonic applications based on various interactions between different materials at the junctions, for instance, energy transfer, exciton-plasmon coupling, or photon-plasmon coupling. A summary of these works is necessary to get a more comprehensive understanding of the relationship between photonic functions and architectonics of NWHJs, which will be instructive for designing novel photonic devices towards integrated circuits. Here, photonic function oriented nanoarchitectonics based on recent breakthroughs in nanophotonic devices are discussed, with emphasis on the design mechanisms, fabrication strategies, and excellent performances. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Two-photon or higher-order absorbing optical materials and methods of use

NASA Technical Reports Server (NTRS)

Perry, Joseph (Inventor); Marder, Seth (Inventor)

2001-01-01

Compositions capable of simultaneous two-photon absorption and higher order absorptivities are disclosed. Many of these compositions are compounds satisfying the formulae D-.PI.-D, A-.PI.-A, D-A-D and A-D-A, wherein D is an electron donor group, A is an electron acceptor group and .PI. comprises a bridge of .pi.-conjugated bonds connecting the electron donor groups and electron acceptor groups. In A-D-A and D-A-D compounds, the .pi. bridge is substituted with electron donor groups and electron acceptor groups, respectively. Also disclosed are methods that generate an electronically excited state of a compound, including those satisfying one of these formulae. The electronically excited state is achieved in a method that includes irradiating the compound with light. Then, the compound is converted to a multi-photon electronically excited state upon simultaneous absorption of at least two photons of light. The sum of the energies of all of the absorbed photons is greater than or equal to the transition energy from a ground state of the compound to the multi-photon excited state. The energy of each absorbed photon is less than the transition energy between the ground state and the lowest single-photon excited state of the compound is less than the transition energy between the multi-photon excited state and the ground state.

Spin-photon interface and spin-controlled photon switching in a nanobeam waveguide

NASA Astrophysics Data System (ADS)

Javadi, Alisa; Ding, Dapeng; Appel, Martin Hayhurst; Mahmoodian, Sahand; Löbl, Matthias Christian; Söllner, Immo; Schott, Rüdiger; Papon, Camille; Pregnolato, Tommaso; Stobbe, Søren; Midolo, Leonardo; Schröder, Tim; Wieck, Andreas Dirk; Ludwig, Arne; Warburton, Richard John; Lodahl, Peter

2018-05-01

The spin of an electron is a promising memory state and qubit. Connecting spin states that are spatially far apart will enable quantum nodes and quantum networks based on the electron spin. Towards this goal, an integrated spin-photon interface would be a major leap forward as it combines the memory capability of a single spin with the efficient transfer of information by photons. Here, we demonstrate such an efficient and optically programmable interface between the spin of an electron in a quantum dot and photons in a nanophotonic waveguide. The spin can be deterministically prepared in the ground state with a fidelity of up to 96%. Subsequently, the system is used to implement a single-spin photonic switch, in which the spin state of the electron directs the flow of photons through the waveguide. The spin-photon interface may enable on-chip photon-photon gates, single-photon transistors and the efficient generation of a photonic cluster state.

Experimental verification of ‘waveguide’ plasmonics

NASA Astrophysics Data System (ADS)

Prudêncio, Filipa R.; Costa, Jorge R.; Fernandes, Carlos A.; Engheta, Nader; Silveirinha, Mário G.

2017-12-01

Surface plasmons polaritons are collective excitations of an electron gas that occur at an interface between negative-ɛ and positive-ɛ media. Here, we report the experimental observation of such surface waves using simple waveguide metamaterials filled only with available positive-ɛ media at microwave frequencies. In contrast to optical designs, in our setup the propagation length of the surface plasmons can be rather long as low loss conventional dielectrics are chosen to avoid typical losses from negative-ɛ media. Plasmonic phenomena have potential applications in enhancing light-matter interactions, implementing nanoscale photonic circuits and integrated photonics.

Influence of phonon reservoir on photon blockade in a driven quantum dot-cavity system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Bo; Li, Gao-xiang, E-mail: gaox@phy.ccnu.edu.cn; Zhu, Jia-pei, E-mail: fengxue0506@163.com

2016-03-14

We theoretically investigate the influence of the phonon bath on photon blockade in a simultaneously driven dot-cavity system. An optimal condition for avoiding two-photon excitation of a cavity field is put forward which can be achieved by modulating the phase difference and the strengths of the driving fields. The second-order correlation function and the mean photon number of the cavity field are discussed. In the absence of phonon effect, the strong photon blockade in a moderate quantum dot (QD)-cavity coupling regime occurs, which can be attributed to the destructive quantum interference arisen from different transition paths induced by simultaneously drivingmore » the dressed QD-cavity system. The participation of acoustic-phonon reservoir produces new transition channels for the QD-cavity system, which leads to the damage of destructive interference. As a result, the photon blockade effect is hindered when taking the electron-phonon interaction into account. It is also found that the temperature of the phonon reservoir is disadvantageous for the generation of photon blockade.« less

Combined photon-electron beams in the treatment of the supraclavicular lymph nodes in breast cancer: A novel technique that achieves adequate coverage while reducing lung dose

DOE Office of Scientific and Technical Information (OSTI.GOV)

Salem, Ahmed, E-mail: ahmed.salem@doctors.org.uk; Mohamad, Issa; Dayyat, Abdulmajeed

2015-10-01

Radiation pneumonitis is a well-documented side effect of radiation therapy for breast cancer. The purpose of this study was to compare combined photon-electron, photon-only, and electron-only plans in the radiation treatment of the supraclavicular lymph nodes. In total, 13 patients requiring chest wall and supraclavicular nodal irradiation were planned retrospectively using combined photon-electron, photon-only, and electron-only supraclavicular beams. A dose of 50 Gy over 25 fractions was prescribed. Chest wall irradiation parameters were fixed for all plans. The goal of this planning effort was to cover 95% of the supraclavicular clinical target volume (CTV) with 95% of the prescribed dosemore » and to minimize the volume receiving ≥ 105% of the dose. Comparative end points were supraclavicular CTV coverage (volume covered by the 95% isodose line), hotspot volume, maximum radiation dose, contralateral breast dose, mean total lung dose, total lung volume percentage receiving at least 20 Gy (V{sub 20} {sub Gy}), heart volume percentage receiving at least 25 Gy (V{sub 25} {sub Gy}). Electron and photon energies ranged from 8 to 18 MeV and 4 to 6 MV, respectively. The ratio of photon-to-electron fractions in combined beams ranged from 5:20 to 15:10. Supraclavicular nodal coverage was highest in photon-only (mean = 96.2 ± 3.5%) followed closely by combined photon-electron (mean = 94.2 ± 2.5%) and lowest in electron-only plans (mean = 81.7 ± 14.8%, p < 0.001). The volume of tissue receiving ≥ 105% of the prescription dose was higher in the electron-only (mean = 69.7 ± 56.1 cm{sup 3}) as opposed to combined photon-electron (mean = 50.8 ± 40.9 cm{sup 3}) and photon-only beams (mean = 32.2 ± 28.1 cm{sup 3}, p = 0.114). Heart V{sub 25} {sub Gy} was not statistically different among the plans (p = 0.999). Total lung V{sub 20} {sub Gy} was lowest in electron-only (mean = 10.9 ± 2.3%) followed by combined photon-electron (mean = 13.8 ± 2.3%) and highest in photon-only plans (mean = 16.2 ± 3%, p < 0.001). As expected, photon-only plans demonstrated the highest target coverage and total lung V{sub 20} {sub Gy}. The superiority of electron-only beams, in terms of decreasing lung dose, is set back by the dosimetric hotspots associated with such plans. Combined photon-electron treatment is a feasible technique for supraclavicular nodal irradiation and results in adequate target coverage, acceptable dosimetric hotspot volume, and slightly reduced lung dose.« less

Radiative Processes in Graphene and Similar Nanostructures in Strong Electric Fields

NASA Astrophysics Data System (ADS)

Gavrilov, S. P.; Gitman, D. M.

2017-03-01

Low-energy single-electron dynamics in graphene monolayers and similar nanostructures is described by the Dirac model, being a 2+1 dimensional version of massless QED with the speed of light replaced by the Fermi velocity vF ≃ c/300. Methods of strong-field QFT are relevant for the Dirac model, since any low-frequency electric field requires a nonperturbative treatment of massless carriers in the case it remains unchanged for a sufficiently long time interval. In this case, the effects of creation and annihilation of electron-hole pairs produced from vacuum by a slowly varying and small-gradient electric field are relevant, thereby substantially affecting the radiation pattern. For this reason, the standard QED text-book theory of photon emission cannot be of help. We construct the Fock-space representation of the Dirac model, which takes exact accounts of the effects of vacuum instability caused by external electric fields, and in which the interaction between electrons and photons is taken into account perturbatively, following the general theory (the generalized Furry representation). We consider the effective theory of photon emission in the first-order approximation and construct the corresponding total probabilities, taking into account the unitarity relation.

Is the GeV-TeV emission of PKS 0447-439 from the proton synchrotron radiation?

NASA Astrophysics Data System (ADS)

Gao, Quan-Gui; Lu, Fang-Wu; Ma, Ju; Ren, Ji-Yang; Li, Huai-Zhen

2018-06-01

We study the multi-wavelength emission features of PKS 0447-439 in the frame of the one-zone homogeneous lepto-hadronic model. In this model, we assumed that the steady power-laws with exponential cut-offs distributions of protons and electrons are injected into the source. The non-linear time-dependent kinematic equations, describing the evolution of protons, electrons and photons, are defined; these equations self-consistently involve synchrotron radiation of protons, photon-photon interaction, synchrotron radiation of electron/positron pairs, inverse Compton scattering and synchrotron self-absorption. The model is applied to reproduce the multi-wavelength spectrum of PKS 0447-439. Our results indicate that the spectral energy distribution (SED) of PKS 0447-439 can be reproduced well by the model. In particular, the GeV-TeV emission is produced by the synchrotron radiation of relativistic protons. The physically plausible solutions require the magnetic strength 10 G≲ B ≲ 100 G. We found that the observed spectrum of PKS 0447-439 can be reproduced well by the model whether z = 0.16 or z = 0.2, and the acceptable upper limit of redshift is z=0.343.

Quantitative Probes of Electron-Phonon Coupling in an Organic Charge-Transfer Material

NASA Astrophysics Data System (ADS)

Rury, Aaron; Sorenson, Shayne; Driscoll, Eric; Dawlaty, Jahan

While organic charge transfer (CT) materials may provide alternatives to inorganic materials in electronics and photonics applications, properties central to applications remain understudied in these organic materials. Specifically, electron-phonon coupling plays a pivotal role in electronic applications yet this coupling in CT materials remains difficult to directly characterize. To better understand the suitability of organic CT materials for electronic applications, we have devised an experimental technique that can directly assess electron-phonon coupling in a model organic CT material. Upon non-resonant interaction with an ultrafast laser pulse, we show that coherent excitation of Raman-active lattice vibrations of quinhydrone, a 1:1 co-crystal of the hydroquinone and p-benzoquinone, modulates the energies of electronic transitions probed by a white light pulse. Using a well-established theoretical framework of vibrational quantum beat spectra across the probe bandwidth, we quantitatively extract the parameters describing these electronic transitions to characterize electron-phonon coupling in this material. In conjunction with temperature-dependent resonance Raman measurements, we assess the hypothesis that several sharp transitions in the near-IR correspond to previously unknown excitonic states of this material. These results and their interpretation set the foundation for further elucidation of the one of the most important parameters in the application of organic charge-transfer materials to electronics and photonics.

Radiological and Environmental Research Division annual report, October 1978-September 1979. Part I. Fundamental molecular physics and chemistry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1979-01-01

Research on the chemical physics of atoms and molecules, especially their interaction with external agents such as photons and electrons is reported. Abstracts of seven individual items from the report were prepared separately for the data base. (GHT)

Physics of Nonmagnetic Relativistic Thermal Plasmas. Ph.D. Thesis - Calif. Univ., San Diego

NASA Technical Reports Server (NTRS)

Dermer, C. D.

1984-01-01

A detailed treatment of the kinematics of relativistic systems of particles and photons is presented. In the case of a relativistic Maxwell-Boltzmann distribution of particles, the reaction rate and luminosity are written as single integrals over the invariant cross section, and the production spectrum is written as a double integral over the cross section differential in the energy of the produced particles (or photons) in the center-of-momentum system of two colliding particles. The results are applied to the calculation of the annihilation spectrum of a thermal electron-positron plasma, confirming previous numerical and analytic results. Relativistic thermal electron-ion and electron-electron bremsstrahlung are calculated exactly to lowest order, and relativistic thermal electron-positron bremsstrahlung is calculated in an approximate fashion. An approximate treatment of relativistic Comptonization is developed. The question of thermalization of a relativistic plasma is considered. A formula for the energy loss or exchange rate from the interaction of two relativistic Maxwell-Boltzmann plasmas at different temperatures is derived. Application to a stable, uniform, nonmagnetic relativistic thermal plasma is made. Comparison is made with other studies.

Constraints on Dark Matter Interactions with Standard Model Particles from Cosmic Microwave Background Spectral Distortions.

PubMed

Ali-Haïmoud, Yacine; Chluba, Jens; Kamionkowski, Marc

2015-08-14

We propose a new method to constrain elastic scattering between dark matter (DM) and standard model particles in the early Universe. Direct or indirect thermal coupling of nonrelativistic DM with photons leads to a heat sink for the latter. This results in spectral distortions of the cosmic microwave background (CMB), the amplitude of which can be as large as a few times the DM-to-photon-number ratio. We compute CMB spectral distortions due to DM-proton, DM-electron, and DM-photon scattering for generic energy-dependent cross sections and DM mass m_{χ}≳1 keV. Using Far-Infrared Absolute Spectrophotometer measurements, we set constraints on the cross sections for m_{χ}≲0.1 MeV. In particular, for energy-independent scattering we obtain σ_{DM-proton}≲10^{-24} cm^{2} (keV/m_{χ})^{1/2}, σ_{DM-electron}≲10^{-27} cm^{2} (keV/m_{χ})^{1/2}, and σ_{DM-photon}≲10^{-39} cm^{2} (m_{χ}/keV). An experiment with the characteristics of the Primordial Inflation Explorer would extend the regime of sensitivity up to masses m_{χ}~1 GeV.

MaRIE X-Ray Free-Electron Laser Pre-Conceptual Design

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carlsten, Bruce E.; Barnes, Cris W.; Bishofberger, Kip A.

2011-01-01

The proposed Matter-Radiation Interactions in Extremes (MaRIE) facility at the Los Alamos National Laboratory will include a 50-keV X-Ray Free-Electron Laser (XFEL), a significant extension from planned and existing XFEL facilities. To prevent an unacceptably large energy spread arsing from energy diffusion, the electron beam energy should not exceed 20 GeV, which puts a significant constraint on the beam emittance. A 100-pC baseline design is presented along with advanced technology options to increase the photon flux and to decrease the spectral bandwidth through pre-bunching the electron beam.

SU-E-T-137: The Response of TLD-100 in Mixed Fields of Photons and Electrons.

PubMed

Lawless, M; Junell, S; Hammer, C; DeWerd, L

2012-06-01

Thermoluminescent dosimeters are used routinely for dosimetric measurements of photon and electron fields. However, no work has been published characterizing TLDs for use in combined photon and electron fields. This work investigates the response of TLD-100 (LiF:Mg,Ti) in mixed fields of photon and electron beam qualities. TLDs were irradiated in a 6 MV photon beam, 6 MeV electron beam, and a NIST traceable cobalt-60 beam. TLDs were also irradiated in a mixed field of the electron and photon beams. All irradiations were normalized to absorbed dose to water as defined in the AAPM TG-51 report. The average response per dose (nC/Gy) for each linac beam quality was normalized to the average response per dose of the TLDs irradiated by the cobalt-60 standard.Irradiations were performed in a water tank and a Virtual Water™ phantom. Two TLD dose calibration curves for determining absorbed dose to water were generated using photon and electron field TLD response data. These individual beam quality dose calibration curves were applied to the TLDs irradiated in the mixed field. The TLD response in the mixed field was less sensitive than the response in the photon field and more sensitive than the response in the electron field. TLD determination of dose in the mixed field using the dose calibration curve generated by TLDs irradiated by photons resulted in an underestimation of the delivered dose, while the use of a dose calibration curve generated using electrons resulted in an overestimation of the delivered dose. The relative response of TLD-100 in mixed fields fell consistently between the photon nd electron relative responses. When using TLD-100 in mixed fields, the user must account for this intermediate response to avoid an over- or underestimation of the dose due to calibration in a single photon or electron field. © 2012 American Association of Physicists in Medicine.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barty, C J

A renaissance in nuclear physics is occurring around the world because of a new kind of incredibly bright, gamma-ray light source that can be created with short pulse lasers and energetic electron beams. These highly Mono-Energetic Gamma-ray (MEGa-ray) sources produce narrow, laser-like beams of incoherent, tunable gamma-rays and are enabling access and manipulation of the nucleus of the atom with photons or so called 'Nuclear Photonics'. Just as in the early days of the laser when photon manipulation of the valence electron structure of the atom became possible and enabling to new applications and science, nuclear photonics with laser-based gamma-raymore » sources promises both to open up wide areas of practical isotope-related, materials applications and to enable new discovery-class nuclear science. In the United States, the development of high brightness and high flux MEGa-ray sources is being actively pursued at the Lawrence Livermore National Laboratory in Livermore (LLNL), California near San Francisco. The LLNL work aims to create by 2013 a machine that will advance the state of the art with respect to source the peak brightness by 6 orders of magnitude. This machine will create beams of 1 to 2.3 MeV photons with color purity matching that of common lasers. In Europe a similar but higher photon energy gamma source has been included as part of the core capability that will be established at the Extreme Light Infrastructure Nuclear Physics (ELI-NP) facility in Magurele, Romania outside of Bucharest. This machine is expected to have an end point gamma energy in the range of 13 MeV. The machine will be co-located with two world-class, 10 Petawatt laser systems thus allowing combined intense-laser and gamma-ray interaction experiments. Such capability will be unique in the world. In this talk, Dr. Chris Barty from LLNL will review the state of the art with respect to MEGa-ray source design, construction and experiments and will describe both the ongoing projects around the world as well some of the exciting applications that these machines will enable. The optimized interaction of short-duration, pulsed lasers with relativistic electron beams (inverse laser-Compton scattering) is the key to unrivaled MeV-scale photon source monochromaticity, pulse brightness and flux. In the MeV spectral range, such Mono-Energetic Gamma-ray (MEGa-ray) sources can have many orders of magnitude higher peak brilliance than even the world's largest synchrotrons. They can efficiently perturb and excite the isotope-specific resonant structure of the nucleus in a manner similar to resonant laser excitation of the valence electron structure of the atom.« less

A new class of galactic discrete gamma ray sources: Chaotic winds of massive stars

NASA Technical Reports Server (NTRS)

Chen, Wan; White, Richard L.

1992-01-01

We propose a new class of galactic discrete gamma-ray sources, the chaotic, high mass-loss-rate winds from luminous early-type stars. Early-type stellar winds are highly unstable due to intrinsic line-driven instabilities, and so are permeated by numerous strong shocks. These shocks can accelerate a small fraction of thermal electrons and ions to relativistic energies via the first-order Fermi mechanism. A power-law-like photon spectrum extending from keV to above 10 MeV energies is produced by inverse Compton scattering of the extremely abundant stellar UV photons by the relativistic electrons. In addition, a typical pi(sup 0)-decay gamma-ray spectrum is generated by proton-ion interactions in the densest part of the winds.

MCNP capabilities for nuclear well logging calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Forster, R.A.; Little, R.C.; Briesmeister, J.F.

The Los Alamos Radiation Transport Code System (LARTCS) consists of state-of-the-art Monte Carlo and discrete ordinates transport codes and data libraries. This paper discusses how the general-purpose continuous-energy Monte Carlo code MCNP ({und M}onte {und C}arlo {und n}eutron {und p}hoton), part of the LARTCS, provides a computational predictive capability for many applications of interest to the nuclear well logging community. The generalized three-dimensional geometry of MCNP is well suited for borehole-tool models. SABRINA, another component of the LARTCS, is a graphics code that can be used to interactively create a complex MCNP geometry. Users can define many source and tallymore » characteristics with standard MCNP features. The time-dependent capability of the code is essential when modeling pulsed sources. Problems with neutrons, photons, and electrons as either single particle or coupled particles can be calculated with MCNP. The physics of neutron and photon transport and interactions is modeled in detail using the latest available cross-section data.« less

Interpreting anomalous electron pairs as new particle decays

NASA Astrophysics Data System (ADS)

Wilczynski, Henryk

1999-08-01

In heavy particle decays found in cosmic ray interactions recorded in the JACEE emulsion chambers, multiple electron pairs were previously reported. These pairs apparently originated from conversions of photons emitted in the decays. It is difficult to explain the overall properties of these decays in terms of known heavy particle decay modes. A recently published compilation of low-energy nuclear data suggests existence of excess electron pairs with invariant mass about 9 MeV/c2 , which may be explained by postulating a new neutral boson decaying into the electron pair. The feasibility of explaining the JACEE electron pairs with this hypothesis is presented.

Higher energy: is it necessary, is it worth the cost for radiation oncology?

PubMed

Das, I J; Kase, K R

1992-01-01

The physical characteristics of the interactions of megavoltage photons and electrons with matter provide distinct advantages, relative to low-energy (orthovoltage) x rays, that lead to better radiation dose distributions in patients. Use of these high-energy radiations has resulted in better patient care, which has been reflected in improved radiation treatment outcome in recent years. But, as the desire for higher energy radiation beams increases, it becomes important to determine whether the physical characteristics that make megavoltage beams beneficial continue to provide a net advantage. It is demonstrated that, in fact, there is an energy range from 4 to 15 MV for photons and 4 to 20 MeV for electrons that is optimally suited for the treatment of cancer in humans. Radiation beams that exceed these maximum energies were found to add no advantage. This is because the costs (price of unit, installation, maintenance, shielding for neutron and photons) are not justified by either improved physical characteristics of the radiation (penetration, skin sparing, dose distribution) or treatment outcome. In fact, for photon beams some physical characteristics result in less desirable dose distributions, less accurate dosimetry, and increased safety problems as the energy increases for example, increasingly diffuse beam edges, loss of electron equilibrium, uncertainty in dose perturbations at interfaces, increased neutron contamination, and potential for higher personnel dose. The special features that make electron beams useful at lower energies, for example, skin sparing and small penetration, are lost at high energies. These physical factors are analyzed together with the economic factors related to radiation therapy patient care using megavoltage beams.

Neutrino production in electromagnetic cascades: An extra component of cosmogenic neutrino at ultrahigh energies

NASA Astrophysics Data System (ADS)

Wang, Kai; Liu, Ruo-Yu; Li, Zhuo; Dai, Zi-Gao

2017-03-01

Muon pairs can be produced in the annihilation of ultrahigh energy (UHE, E ≳1 018 eV ) photons with low energy cosmic background radiation in the intergalactic space, giving birth to neutrinos. Although the branching ratio of muon pair production is low, products of other channels, which are mainly electron/positron pairs, will probably transfer most of their energies into the new generated UHE photon in the subsequent interaction with the cosmic background radiation via Compton scattering in deep Klein-Nishina regime. The regeneration of these new UHE photons then provides a second chance to produce the muon pairs, enhancing the neutrino flux. We investigate the neutrino production in the propagation of UHE photons in the intergalactic space at different redshifts, considering various competing processes such as pair production, double pair production for UHE photons, and triplet production and synchrotron radiation for UHE electrons. Following the analytic method raised by Gould and Rephaeli, we firstly study the electromagnetic cascade initiated by an UHE photon, with paying particular attention to the leading particle in the cascade process. Regarding the least energetic outgoing particles as energy loss, we obtain the effective penetration length of the leading particle, as well as energy loss rate including the neutrino emission rate in the cascade process. Finally, we find that an extra component of UHE neutrinos will arise from the propagation of UHE cosmic rays due to the generated UHE photons and electron/positrons. However, the flux of this component is quite small, with a flux of at most 10% of that of the conventional cosmogenic neutrino at a few EeV, in the absence of a strong intergalactic magnetic field and a strong cosmic radio background. The precise contribution of extra component depends on several factors, e.g., cosmic radio background, intergalactic magnetic field, and the spectrum of proton, which are discussed in this work.

Electron and photon identification in the D0 experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abazov, V. M.; Abbott, B.; Acharya, B. S.

2014-06-01

The electron and photon reconstruction and identification algorithms used by the D0 Collaboration at the Fermilab Tevatron collider are described. The determination of the electron energy scale and resolution is presented. Studies of the performance of the electron and photon reconstruction and identification are summarized.

Spontaneous emission from radiative chiral nematic liquid crystals at the photonic band-gap edge: an investigation into the role of the density of photon states near resonance.

PubMed

Mavrogordatos, Th K; Morris, S M; Wood, S M; Coles, H J; Wilkinson, T D

2013-06-01

In this article, we investigate the spontaneous emission properties of radiating molecules embedded in a chiral nematic liquid crystal, under the assumption that the electronic transition frequency is close to the photonic edge mode of the structure, i.e., at resonance. We take into account the transition broadening and the decay of electromagnetic field modes supported by the so-called "mirrorless"cavity. We employ the Jaynes-Cummings Hamiltonian to describe the electron interaction with the electromagnetic field, focusing on the mode with the diffracting polarization in the chiral nematic layer. As known in these structures, the density of photon states, calculated via the Wigner method, has distinct peaks on either side of the photonic band gap, which manifests itself as a considerable modification of the emission spectrum. We demonstrate that, near resonance, there are notable differences between the behavior of the density of states and the spontaneous emission profile of these structures. In addition, we examine in some detail the case of the logarithmic peak exhibited in the density of states in two-dimensional photonic structures and obtain analytic relations for the Lamb shift and the broadening of the atomic transition in the emission spectrum. The dynamical behavior of the atom-field system is described by a system of two first-order differential equations, solved using the Green's-function method and the Fourier transform. The emission spectra are then calculated and compared with experimental data.

On the origin of gamma-rays in Fermi blazars: beyondthe broad-line region

NASA Astrophysics Data System (ADS)

Costamante, L.; Cutini, S.; Tosti, G.; Antolini, E.; Tramacere, A.

2018-07-01

The gamma-ray emission in broad-line blazars is generally explained as inverse Compton (IC) radiation of relativistic electrons in the jet scattering optical-UV photons from the broad-line region (BLR), the so-called BLR external Compton (EC) scenario. We test this scenario on the Fermi gamma-ray spectra of 106 broad-line blazars detected with the highest significance or largest BLR, by looking for cut-off signatures at high energies compatible with γ-γ interactions with BLR photons. We do not find evidence for the expected BLR absorption. For 2/3 of the sources, we can exclude any significant absorption (τmax < 1), while for the remaining 1/3 the possible absorption is constrained to be 1.5-2 orders of magnitude lower than expected. This result holds also dividing the spectra in high- and low-flux states, and for powerful blazars with large BLR. Only 1 object out of 10 seems compatible with substantial attenuation (τmax > 5). We conclude that for 9 out of 10 objects, the jet does not interact with BLR photons. Gamma-rays seem either produced outside the BLR most of the time, or the BLR is ˜100 × larger than given by reverberation mapping. This means that (i) EC on BLR photons is disfavoured as the main gamma-ray mechanism, versus IC on IR photons from the torus or synchrotron self-Compton; (ii) the Fermi gamma-ray spectrum is mostly intrinsic, determined by the interaction of the particle distribution with the seed-photon spectrum; and (iii) without suppression by the BLR, broad-line blazars can become copious emitters above 100 GeV, as demonstrated by 3C 454.3. We expect the CTA sky to be much richer of broad-line blazars than previously thought.

On the origin of gamma rays in Fermi blazars: beyond the broad line region.

NASA Astrophysics Data System (ADS)

Costamante, L.; Cutini, S.; Tosti, G.; Antolini, E.; Tramacere, A.

2018-05-01

The gamma-ray emission in broad-line blazars is generally explained as inverse Compton (IC) radiation of relativistic electrons in the jet scattering optical-UV photons from the Broad Line Region (BLR), the so-called BLR External Compton scenario. We test this scenario on the Fermi gamma-ray spectra of 106 broad-line blazars detected with the highest significance or largest BLR, by looking for cut-off signatures at high energies compatible with γ-γ interactions with BLR photons. We do not find evidence for the expected BLR absorption. For 2/3 of the sources, we can exclude any significant absorption (τmax < 1), while for the remaining 1/3 the possible absorption is constrained to be 1.5-2 orders of magnitude lower than expected. This result holds also dividing the spectra in high and low-flux states, and for powerful blazars with large BLR. Only 1 object out of 10 seems compatible with substantial attenuation (τmax > 5). We conclude that for 9 out of 10 objects, the jet does not interact with BLR photons. Gamma-rays seem either produced outside the BLR most of the time, or the BLR is ˜100 × larger than given by reverberation mapping. This means that i) External Compton on BLR photons is disfavoured as the main gamma-ray mechanism, vs IC on IR photons from the torus or synchrotron self-Compton; ii) the Fermi gamma-ray spectrum is mostly intrinsic, determined by the interaction of the particle distribution with the seed-photons spectrum; iii) without suppression by the BLR, broad-line blazars can become copious emitters above 100 GeV, as demonstrated by 3C 454.3. We expect the CTA sky to be much richer of broad-line blazars than previously thought.

RELATIVISTIC THOMSON SCATTERING EXPERIMENT AT BNL - STATUS REPORT.

DOE Office of Scientific and Technical Information (OSTI.GOV)

POGORELSKY,I.V.; BEN ZVI,I.; KUSCHE,K.

2001-12-03

1.7 x 10{sup 8} x-ray photons per 3.5 ps pulse have been produced in Thomson scattering by focusing CO{sub 2} laser pulse on counter-propagating relativistic electron beam. We explore a possibility of further enhancement of process efficiency by propagating both beams in a plasma capillary. Conventional synchrotron light sources based on using giga-electron-volt electron synchrotron accelerators and magnetic wigglers generate x-ray radiation for versatile application in multi-disciplinary research. An intense laser beam causes relativistic electron oscillations similar to a wiggler. However, because the laser wavelength is thousand times shorter than a wiggler period, very moderate electron energy is needed tomore » produce hard x-rays via Thomson scattering. This allows using relatively compact mega-electron-volt linear accelerators instead of giga-electron-volt synchrotrons. Another important advantage of Thomson sources is a possibility to generate femtosecond x-ray pulses whereas conventional synchrotron sources have typically {approx}300 ps pulse duration. This promises to revolutionize x-ray research in chemistry, physics, and biology expanding it to ultra-fast processes. Thomson sources do not compete in repetition rate and average intensity with conventional light sources that operate at the megahertz frequency. However, Thomson sources have a potential to produce much higher photon numbers per pulse. This may allow developing a single shot exposure important for structural analysis of live biological objects. The BNL Thomson source is a user's experiment conducted at the Accelerator Test Facility since 1998 by an international collaboration in High Energy Physics. Since inception, the ATF source produces the record peak x-ray yield, intensity and brightness among other similar proof-of-principle demonstrations attempted elsewhere. Note that this result is achieved with a moderate laser power of 15 GW. A key to this achievement is in choosing right apparatus and efficient interaction geometry. We use a CO{sub 2} laser that delivers 10 times more photons per unit energy than the 1-{micro}m laser, a high-brightness linac, and the most energy-efficient backscattering interaction geometry. The purpose of this report is to give an update on new results obtained during this year and our near-term plans.« less

Controllable optical modulation of blue/green up-conversion fluorescence from Tm3+ (Er3+) single-doped glass ceramics upon two-step excitation of two-wavelengths

PubMed Central

Chen, Zhi; Kang, Shiliang; Zhang, Hang; Wang, Ting; Lv, Shichao; Chen, Qiuqun; Dong, Guoping; Qiu, Jianrong

2017-01-01

Optical modulation is a crucial operation in photonics for network data processing with the aim to overcome information bottleneck in terms of speed, energy consumption, dispersion and cross-talking from conventional electronic interconnection approach. However, due to the weak interactions between photons, a facile physical approach is required to efficiently manipulate photon-photon interactions. Herein, we demonstrate that transparent glass ceramics containing LaF3: Tm3+ (Er3+) nanocrystals can enable fast-slow optical modulation of blue/green up-conversion fluorescence upon two-step excitation of two-wavelengths at telecom windows (0.8–1.8 μm). We show an optical modulation of more than 1500% (800%) of the green (blue) up-conversion fluorescence intensity, and fast response of 280 μs (367 μs) as well as slow response of 5.82 ms (618 μs) in the green (blue) up-conversion fluorescence signal, respectively. The success of manipulating laser at telecom windows for fast-slow optical modulation from rear-earth single-doped glass ceramics may find application in all-optical fiber telecommunication areas. PMID:28368041

The Impact of Electromagnetic Cascades of Very-high Energy Gamma Rays on the Extragalactic Gamma-ray Background

NASA Technical Reports Server (NTRS)

Venters, Tonia

2012-01-01

As very high energy (VHE) photons propagate through the extragalactic background light (EBL), they interact with the soft photons of the EBL and initiate electromagnetic cascades of photons and electrons. The collective intensity of a cosmological population emitting at VHEs (such as blazars) will be attenuated at the highest energies through interactions with the EBL and enhanced at lower energies by the resulting cascade. As such, depending on the space density and spectra of the sources and the model of the EBL, cascade radiation can provide a significant contribution to the extragalactic gamma-ray background (EGB). Through deflections of the charged particles of the cascade, an intergalactic magnetic field (IGMF) may leave an imprint on the anisotropy properties of the EGB. The impact of a strong IGMF is to isotropize lower energy cascade photons, inducing a modulation in the anisotropy energy spectrum of the EGB. We discuss the implications of cascade radiation for the origins of the EGB and the nature of the IGMF, as well as insight that will be provided by data from the Fermi Large Area Telescope in the upcoming years.

Selective two-photon absorption in carbon dots: a piece of the photoluminescence emission puzzle.

PubMed

Santos, Carla I M; Mariz, Inês F A; Pinto, Sandra N; Gonçalves, Gil; Bdikin, Igor; Marques, Paula A A P; Neves, Maria Graça P M S; Martinho, José M G; Maçôas, Ermelinda M S

2018-06-22

Carbon nanodots (Cdots) are now emerging as promising nonlinear fluorophores for applications in biological environments. A thorough and systematic approach to the two-photon induced emission of Cdots that could provide design guidelines to control their nonlinear emission properties is still missing. In this work, we address the nonlinear optical spectroscopy of Cdots prepared by controlled chemical cutting of graphene oxide (GO). The two-photon absorption in the 700-1000 nm region and the corresponding emission spectrum are carefully investigated. The highest two-photon absorption cross-section estimated was 130 GM at 720 nm. This value is comparable with the one reported for graphene nanoribbons with push-pull architecture. The emission spectrum depends on the excitation mode. At the same excitation energy, nonlinear excitation results in excitation-wavelength independent emission, while upon linear excitation the emission is excitation-wavelength dependent. The biphotonic interaction seems to be selective towards sp2 clusters bearing electron donor and acceptor groups found in push-pull architectures. Both linear and nonlinear emission can be understood based on the existence of isolated sp2 clusters involved in π-π stacking interactions with clusters in adjacent layers.

Dosimetry of Al2O3 optically stimulated luminescent dosimeter at high energy photons and electrons

NASA Astrophysics Data System (ADS)

Yusof, M. F. Mohd; Joohari, N. A.; Abdullah, R.; Shukor, N. S. Abd; Kadir, A. B. Abd; Isa, N. Mohd

2018-01-01

The linearity of Al2O3 OSL dosimeters (OSLD) were evaluated for dosimetry works in clinical photons and electrons. The measurements were made at a reference depth of Zref according to IAEA TRS 398:2000 codes of practice at 6 and 10 MV photons and 6 and 9 MeV electrons. The measured dose was compared to the thermoluminescence dosimeters (TLD) and ionization chamber commonly used for dosimetry works for higher energy photons and electrons. The results showed that the measured dose in OSL dosimeters were in good agreement with the reported by the ionization chamber in both high energy photons and electrons. A reproducibility test also reported excellent consistency of readings with the OSL at similar energy levels. The overall results confirmed the suitability of OSL dosimeters for dosimetry works involving high energy photons and electrons in radiotherapy.

Study of photonuclear muon interactions at Baksan underground scintillation telescope

NASA Technical Reports Server (NTRS)

Bakatanov, V. N.; Chudakov, A. E.; Dadykin, V. L.; Novoseltsev, Y. F.; Achkasov, V. M.; Semenov, A. M.; Stenkin, Y. V.

1985-01-01

The method of pion-muon-electron decays recording was used to distinguish between purely electron-photon and hadronic cascades, induced by high energy muons underground. At energy approx. 1 Tev a ratio of the number of hadronic to electromagnetic cascades was found equal 0.11 + or - .03 in agreement with expectation. But, at an energy approx. 4 Tev a sharp increase of this ratio was indicated though not statistically sound (0.52 + or - .13).

Coherent Terahertz Radiation from Multiple Electron Beams Excitation within a Plasmonic Crystal-like structure.

PubMed

Zhang, Yaxin; Zhou, Yucong; Gang, Yin; Jiang, Guili; Yang, Ziqiang

2017-01-23

Coherent terahertz radiation from multiple electron beams excitation within a plasmonic crystal-like structure (a three-dimensional holes array) which is composed of multiple stacked layers with 3 × 3 subwavelength holes array has been proposed in this paper. It has been found that in the structure the electromagnetic fields in each hole can be coupled with one another to construct a composite mode with strong field intensity. Therefore, the multiple electron beams injection can excite and efficiently interact with such mode. Meanwhile, the coupling among the electron beams is taken place during the interaction so that a very strong coherent terahertz radiation with high electron conversion efficiency can be generated. Furthermore, due to the coupling, the starting current density of this mechanism is much lower than that of traditional electron beam-driven terahertz sources. This multi-beam radiation system may provide a favorable way to combine photonics structure with electronics excitation to generate middle, high power terahertz radiation.

Coherent Terahertz Radiation from Multiple Electron Beams Excitation within a Plasmonic Crystal-like structure

PubMed Central

Zhang, Yaxin; Zhou, Yucong; Gang, Yin; Jiang, Guili; Yang, Ziqiang

2017-01-01

Coherent terahertz radiation from multiple electron beams excitation within a plasmonic crystal-like structure (a three-dimensional holes array) which is composed of multiple stacked layers with 3 × 3 subwavelength holes array has been proposed in this paper. It has been found that in the structure the electromagnetic fields in each hole can be coupled with one another to construct a composite mode with strong field intensity. Therefore, the multiple electron beams injection can excite and efficiently interact with such mode. Meanwhile, the coupling among the electron beams is taken place during the interaction so that a very strong coherent terahertz radiation with high electron conversion efficiency can be generated. Furthermore, due to the coupling, the starting current density of this mechanism is much lower than that of traditional electron beam-driven terahertz sources. This multi-beam radiation system may provide a favorable way to combine photonics structure with electronics excitation to generate middle, high power terahertz radiation. PMID:28112234

Complete tomography of a high-fidelity solid-state entangled spin-photon qubit pair.

PubMed

De Greve, Kristiaan; McMahon, Peter L; Yu, Leo; Pelc, Jason S; Jones, Cody; Natarajan, Chandra M; Kim, Na Young; Abe, Eisuke; Maier, Sebastian; Schneider, Christian; Kamp, Martin; Höfling, Sven; Hadfield, Robert H; Forchel, Alfred; Fejer, M M; Yamamoto, Yoshihisa

2013-01-01

Entanglement between stationary quantum memories and photonic qubits is crucial for future quantum communication networks. Although high-fidelity spin-photon entanglement was demonstrated in well-isolated atomic and ionic systems, in the solid-state, where massively parallel, scalable networks are most realistically conceivable, entanglement fidelities are typically limited due to intrinsic environmental interactions. Distilling high-fidelity entangled pairs from lower-fidelity precursors can act as a remedy, but the required overhead scales unfavourably with the initial entanglement fidelity. With spin-photon entanglement as a crucial building block for entangling quantum network nodes, obtaining high-fidelity entangled pairs becomes imperative for practical realization of such networks. Here we report the first results of complete state tomography of a solid-state spin-photon-polarization-entangled qubit pair, using a single electron-charged indium arsenide quantum dot. We demonstrate record-high fidelity in the solid-state of well over 90%, and the first (99.9%-confidence) achievement of a fidelity that will unambiguously allow for entanglement distribution in solid-state quantum repeater networks.

Estimation and correction of produced light from prompt gamma photons on luminescence imaging of water for proton therapy dosimetry

NASA Astrophysics Data System (ADS)

Yabe, Takuya; Komori, Masataka; Toshito, Toshiyuki; Yamaguchi, Mitsutaka; Kawachi, Naoki; Yamamoto, Seiichi

2018-02-01

Although the luminescence images of water during proton-beam irradiation using a cooled charge-coupled device camera showed almost the same ranges of proton beams as those measured by an ionization chamber, the depth profiles showed lower Bragg peak intensities than those measured by an ionization chamber. In addition, a broad optical baseline signal was observed in depths that exceed the depth of the Bragg peak. We hypothesize that this broad baseline signal originates from the interaction of proton-induced prompt gamma photons with water. These prompt gamma photons interact with water to form high-energy Compton electrons, which may cause luminescence or Cherenkov emission from depths exceeding the location of the Bragg peak. To clarify this idea, we measured the luminescence images of water during the irradiations of protons in water with minimized parallax errors, and also simulated the produced light by the interactions of prompt gamma photons with water. We corrected the measured depth profiles of the luminescence images by subtracting the simulated distributions of the produced light by the interactions of prompt gamma photons in water. Corrections were also conducted using the estimated depth profiles of the light of the prompt gamma photons, as obtained from the off-beam areas of the luminescence images of water. With these corrections, we successfully obtained depth profiles that have almost identical distributions as the simulated dose distributions for protons. The percentage relative height of the Bragg peak with corrections to that of the simulation data increased to 94% from 80% without correction. Also, the percentage relative offset heights of the deeper part of the Bragg peak with corrections decreased to 0.2%-0.4% from 4% without correction. These results indicate that the luminescence imaging of water has potential for the dose distribution measurements for proton therapy dosimetry.

Single-chip microprocessor that communicates directly using light

NASA Astrophysics Data System (ADS)

Sun, Chen; Wade, Mark T.; Lee, Yunsup; Orcutt, Jason S.; Alloatti, Luca; Georgas, Michael S.; Waterman, Andrew S.; Shainline, Jeffrey M.; Avizienis, Rimas R.; Lin, Sen; Moss, Benjamin R.; Kumar, Rajesh; Pavanello, Fabio; Atabaki, Amir H.; Cook, Henry M.; Ou, Albert J.; Leu, Jonathan C.; Chen, Yu-Hsin; Asanović, Krste; Ram, Rajeev J.; Popović, Miloš A.; Stojanović, Vladimir M.

2015-12-01

Data transport across short electrical wires is limited by both bandwidth and power density, which creates a performance bottleneck for semiconductor microchips in modern computer systems—from mobile phones to large-scale data centres. These limitations can be overcome by using optical communications based on chip-scale electronic-photonic systems enabled by silicon-based nanophotonic devices8. However, combining electronics and photonics on the same chip has proved challenging, owing to microchip manufacturing conflicts between electronics and photonics. Consequently, current electronic-photonic chips are limited to niche manufacturing processes and include only a few optical devices alongside simple circuits. Here we report an electronic-photonic system on a single chip integrating over 70 million transistors and 850 photonic components that work together to provide logic, memory, and interconnect functions. This system is a realization of a microprocessor that uses on-chip photonic devices to directly communicate with other chips using light. To integrate electronics and photonics at the scale of a microprocessor chip, we adopt a ‘zero-change’ approach to the integration of photonics. Instead of developing a custom process to enable the fabrication of photonics, which would complicate or eliminate the possibility of integration with state-of-the-art transistors at large scale and at high yield, we design optical devices using a standard microelectronics foundry process that is used for modern microprocessors. This demonstration could represent the beginning of an era of chip-scale electronic-photonic systems with the potential to transform computing system architectures, enabling more powerful computers, from network infrastructure to data centres and supercomputers.

Single-chip microprocessor that communicates directly using light.

PubMed

Sun, Chen; Wade, Mark T; Lee, Yunsup; Orcutt, Jason S; Alloatti, Luca; Georgas, Michael S; Waterman, Andrew S; Shainline, Jeffrey M; Avizienis, Rimas R; Lin, Sen; Moss, Benjamin R; Kumar, Rajesh; Pavanello, Fabio; Atabaki, Amir H; Cook, Henry M; Ou, Albert J; Leu, Jonathan C; Chen, Yu-Hsin; Asanović, Krste; Ram, Rajeev J; Popović, Miloš A; Stojanović, Vladimir M

2015-12-24

Data transport across short electrical wires is limited by both bandwidth and power density, which creates a performance bottleneck for semiconductor microchips in modern computer systems--from mobile phones to large-scale data centres. These limitations can be overcome by using optical communications based on chip-scale electronic-photonic systems enabled by silicon-based nanophotonic devices. However, combining electronics and photonics on the same chip has proved challenging, owing to microchip manufacturing conflicts between electronics and photonics. Consequently, current electronic-photonic chips are limited to niche manufacturing processes and include only a few optical devices alongside simple circuits. Here we report an electronic-photonic system on a single chip integrating over 70 million transistors and 850 photonic components that work together to provide logic, memory, and interconnect functions. This system is a realization of a microprocessor that uses on-chip photonic devices to directly communicate with other chips using light. To integrate electronics and photonics at the scale of a microprocessor chip, we adopt a 'zero-change' approach to the integration of photonics. Instead of developing a custom process to enable the fabrication of photonics, which would complicate or eliminate the possibility of integration with state-of-the-art transistors at large scale and at high yield, we design optical devices using a standard microelectronics foundry process that is used for modern microprocessors. This demonstration could represent the beginning of an era of chip-scale electronic-photonic systems with the potential to transform computing system architectures, enabling more powerful computers, from network infrastructure to data centres and supercomputers.

Optimization of combined electron and photon beams for breast cancer

NASA Astrophysics Data System (ADS)

Xiong, W.; Li, J.; Chen, L.; Price, R. A.; Freedman, G.; Ding, M.; Qin, L.; Yang, J.; Ma, C.-M.

2004-05-01

Recently, intensity-modulated radiation therapy and modulated electron radiotherapy have gathered a growing interest for the treatment of breast and head and neck tumours. In this work, we carried out a study to combine electron and photon beams to achieve differential dose distributions for multiple target volumes simultaneously. A Monte Carlo based treatment planning system was investigated, which consists of a set of software tools to perform accurate dose calculation, treatment optimization, leaf sequencing and plan analysis. We compared breast treatment plans generated using this home-grown optimization and dose calculation software for different treatment techniques. Five different planning techniques have been developed for this study based on a standard photon beam whole breast treatment and an electron beam tumour bed cone down. Technique 1 includes two 6 MV tangential wedged photon beams followed by an anterior boost electron field. Technique 2 includes two 6 MV tangential intensity-modulated photon beams and the same boost electron field. Technique 3 optimizes two intensity-modulated photon beams based on a boost electron field. Technique 4 optimizes two intensity-modulated photon beams and the weight of the boost electron field. Technique 5 combines two intensity-modulated photon beams with an intensity-modulated electron field. Our results show that technique 2 can reduce hot spots both in the breast and the tumour bed compared to technique 1 (dose inhomogeneity is reduced from 34% to 28% for the target). Techniques 3, 4 and 5 can deliver a more homogeneous dose distribution to the target (with dose inhomogeneities for the target of 22%, 20% and 9%, respectively). In many cases techniques 3, 4 and 5 can reduce the dose to the lung and heart. It is concluded that combined photon and electron beam therapy may be advantageous for treating breast cancer compared to conventional treatment techniques using tangential wedged photon beams followed by a boost electron field.

Quantum entanglement between an optical photon and a solid-state spin qubit.

PubMed

Togan, E; Chu, Y; Trifonov, A S; Jiang, L; Maze, J; Childress, L; Dutt, M V G; Sørensen, A S; Hemmer, P R; Zibrov, A S; Lukin, M D

2010-08-05

Quantum entanglement is among the most fascinating aspects of quantum theory. Entangled optical photons are now widely used for fundamental tests of quantum mechanics and applications such as quantum cryptography. Several recent experiments demonstrated entanglement of optical photons with trapped ions, atoms and atomic ensembles, which are then used to connect remote long-term memory nodes in distributed quantum networks. Here we realize quantum entanglement between the polarization of a single optical photon and a solid-state qubit associated with the single electronic spin of a nitrogen vacancy centre in diamond. Our experimental entanglement verification uses the quantum eraser technique, and demonstrates that a high degree of control over interactions between a solid-state qubit and the quantum light field can be achieved. The reported entanglement source can be used in studies of fundamental quantum phenomena and provides a key building block for the solid-state realization of quantum optical networks.

Photon absorption potential coefficient as a tool for materials engineering

NASA Astrophysics Data System (ADS)

Akande, Raphael Oluwole; Oyewande, Emmanuel Oluwole

2016-09-01

Different atoms achieve ionizations at different energies. Therefore, atoms are characterized by different responses to photon absorption in this study. That means there exists a coefficient for their potential for photon absorption from a photon source. In this study, we consider the manner in which molecular constituents (atoms) absorb photon from a photon source. We observe that there seems to be a common pattern of variation in the absorption of photon among the electrons in all atoms on the periodic table. We assume that the electrons closest to the nucleus (En) and the electrons closest to the outside of the atom (Eo) do not have as much potential for photon absorption as the electrons at the middle of the atom (Em). The explanation we give to this effect is that the En electrons are embedded within the nuclear influence, and similarly, Eo electrons are embedded within the influence of energies outside the atom that there exists a low potential for photon absorption for them. Unlike En and Eo, Em electrons are conditioned, such that there is a quest for balance between being influenced either by the nuclear force or forces external to the atom. Therefore, there exists a higher potential for photon absorption for Em electrons than for En and Eo electrons. The results of our derivations and analysis always produce a bell-shaped curve, instead of an increasing curve as in the ionization energies, for all elements in the periodic table. We obtained a huge data of PAPC for each of the several materials considered. The point at which two or more PAPC values cross one another is termed to be a region of conflicting order of ionization, where all the atoms absorb equal portion of the photon source at the same time. At this point, a greater fraction of the photon source is pumped into the material which could lead to an explosive response from the material. In fact, an unimaginable and unreported phenomenon (in physics) could occur, when two or more PAPCs cross, and the material is able to absorb more than that the photon source could provide, at this point. These resulting effects might be of immense materials engineering applications.

X-ray Survey of Centaurus A.

PubMed

Byram, E T; Chubb, T A; Friedman, H

1970-07-24

An x-ray survey of Centaurus A has given marginal evidence of its x-ray flux. If taken as an upper limit on inverse Compton x-rays generated by scattering interactions between relativistic electrons and cosmological background photons, the observation implies an upper limit of close to 3 degrees K for the background radiation temperature.

Atomic and Nuclear Interactions of High Energy Photons and Electrons with Matter.

DTIC Science & Technology

1975-09-29

IJ / VIh /hh1 ij~ ~ 111/ ~ ~~~~ ‘a” • •- • ~~ iitjiJ ~t~I~I1 J(I’,n) 17iTI~f ( ~ ,2n)II ~~~~~ I . a p g ~ ~ p p0 . — T:I Shacklston (Sh?t) LI

3D Localized Trions in Monolayer WSe2 in a Charge Tunable van der Waals Heterostructure.

PubMed

Chakraborty, Chitraleema; Qiu, Liangyu; Konthasinghe, Kumarasiri; Mukherjee, Arunabh; Dhara, Sajal; Vamivakas, Nick

2018-05-09

Monolayer transition metal dichalcogenides (TMDCs) have recently emerged as a host material for localized optically active quantum emitters that generate single photons. (1-5) Here, we investigate fully localized excitons and trions from such TMDC quantum emitters embedded in a van der Waals heterostructure. We use direct electrostatic doping through the vertical heterostructure device assembly to generate quantum confined trions. Distinct spectral jumps as a function of applied voltage bias, and excitation power-dependent charging, demonstrate the observation of the two different excitonic complexes. We also observe a reduction of the intervalley electron-hole exchange interaction in the confined trion due to the addition of an extra electron, which is manifested by a decrease in its fine structure splitting. We further confirm this decrease of exchange interaction for the case of the charged states by a comparative study of the circular polarization resolved photoluminescence from individual excitonic states. The valley polarization selection rules inherited by the localized trions will provide a pathway toward realizing a localized spin-valley-photon interface.

Splitting of the neutral mechanical plane depends on the length of the multi-layer structure of flexible electronics.

PubMed

Li, Shuang; Su, Yewang; Li, Rui

2016-06-01

Multi-layer structures with soft (compliant) interlayers have been widely used in flexible electronics and photonics as an effective design for reducing interactions among the hard (stiff) layers and thus avoiding the premature failure of an entire device. The analytic model for bending of such a structure has not been well established due to its complex mechanical behaviour. Here, we present a rational analytic model, without any parameter fitting, to study the bending of a multi-layer structure on a cylinder, which is often regarded as an important approach to mechanical reliability testing of flexible electronics and photonics. For the first time, our model quantitatively reveals that, as the key for accurate strain control, the splitting of the neutral mechanical plane depends not only on the relative thickness of the middle layer, but also on the length-to-thickness ratio of the multi-layer structure. The model accurately captures the key quantities, including the axial strains in the top and bottom layers, the shear strain in the middle layer and the locations of the neutral mechanical planes of the top and bottom layers. The effects of the length of the multi-layer and the thickness of the middle layer are elaborated. This work is very useful for the design of multi-layer structure-based flexible electronics and photonics.

Splitting of the neutral mechanical plane depends on the length of the multi-layer structure of flexible electronics

PubMed Central

Li, Shuang; Li, Rui

2016-01-01

Multi-layer structures with soft (compliant) interlayers have been widely used in flexible electronics and photonics as an effective design for reducing interactions among the hard (stiff) layers and thus avoiding the premature failure of an entire device. The analytic model for bending of such a structure has not been well established due to its complex mechanical behaviour. Here, we present a rational analytic model, without any parameter fitting, to study the bending of a multi-layer structure on a cylinder, which is often regarded as an important approach to mechanical reliability testing of flexible electronics and photonics. For the first time, our model quantitatively reveals that, as the key for accurate strain control, the splitting of the neutral mechanical plane depends not only on the relative thickness of the middle layer, but also on the length-to-thickness ratio of the multi-layer structure. The model accurately captures the key quantities, including the axial strains in the top and bottom layers, the shear strain in the middle layer and the locations of the neutral mechanical planes of the top and bottom layers. The effects of the length of the multi-layer and the thickness of the middle layer are elaborated. This work is very useful for the design of multi-layer structure-based flexible electronics and photonics. PMID:27436977

Generation of Optical Vortices by Nonlinear Inverse Thomson Scattering at Arbitrary Angle Interactions

NASA Astrophysics Data System (ADS)

Taira, Yoshitaka; Katoh, Masahiro

2018-06-01

We theoretically verify that optical vortices carrying orbital angular momentum are generated in various astrophysical situations via nonlinear inverse Thomson scattering. Arbitrary angle collisions between relativistic electrons and circularly polarized strong electromagnetic waves are treated. We reveal that the higher harmonic components of scattered photons carry well-defined orbital angular momentum under a specific condition that the Lorentz factor of the electron is much larger than the field strength parameter of the electromagnetic wave. Our study indicates that optical vortices in a wide frequency range from radio waves to gamma-rays are naturally generated in environments where high-energy electrons interact with circularly polarized strong electromagnetic waves at various interaction angles. Optical vortices should be a new multi-messenger member carrying information concerning the physical circumstances of their sources, e.g., the magnetic and radiation fields. Moreover, their interactions with matter via their orbital angular momenta may play an important role in the evolution of matter in the universe.

Single-photon superradiance and cooperative Lamb shift in an optoelectronic device (Conference Presentation)

NASA Astrophysics Data System (ADS)

Sirtori, Carlo

2017-02-01

Superradiance is one of the many fascinating phenomena predicted by quantum electrodynamics that have first been experimentally demonstrated in atomic systems and more recently in condensed matter systems like quantum dots, superconducting q-bits, cyclotron transitions and plasma oscillations in quantum wells (QWs). It occurs when a dense collection of N identical two-level emitters are phased via the exchange of photons, giving rise to enhanced light-matter interaction, hence to a faster emission rate. Of great interest is the regime where the ensemble interacts with one photon only and therefore all of the atoms, but one, are in the ground state. In this case the quantum superposition of all possible configurations produces a symmetric state that decays radiatively with a rate N times larger than that of the individual oscillators. This phenomenon, called single photon superradiance, results from the exchange of real photons among the N emitters. Yet, to single photon superradiance is also associated another collective effect that renormalizes the emission frequency, known as cooperative Lamb shift. In this work, we show that single photon superradiance and cooperative Lamb shift can be engineered in a semiconductor device by coupling spatially separated plasma resonances arising from the collective motion of confined electrons in QWs. These resonances hold a giant dipole along the growth direction z and have no mutual Coulomb coupling. They thus behave as a collection of macro-atoms on different positions along the z axis. Our device is therefore a test bench to simulate the low excitation regime of quantum electrodynamics.

Two photon excitation of atomic oxygen

NASA Technical Reports Server (NTRS)

Pindzola, M. S.

1977-01-01

A standard perturbation expansion in the atom-radiation field interaction is used to calculate the two photon excitation cross section for 1s(2) 2s(2) 2p(4) p3 to 1s(2) 2s(2) 2p(3) (s4) 3p p3 transition in atomic oxygen. The summation over bound and continuum intermediate states is handled by solving the equivalent inhomogeneous differential equation. Exact summation results differ by a factor of 2 from a rough estimate obtained by limiting the intermediate state summation to one bound state. Higher order electron correlation effects are also examined.

Scaling EUV and X-ray Thomson sources to optical free-electron laser operation with traveling-wave Thomson scattering (Conference Presentation)

NASA Astrophysics Data System (ADS)

Steiniger, Klaus; Albach, Daniel; Debus, Alexander; Loeser, Markus; Pausch, Richard; Roeser, Fabian; Schramm, Ulrich; Siebold, Matthias; Bussmann, Michael

2017-05-01

Traveling-Wave Thomson-Scattering (TWTS) allows for the realization of optical free-electron lasers (OFELs) from the interaction of short, high-power laser pulses with brilliant relativistic electron bunches. The laser field provides the optical undulator which is traversed by the electrons. In order to achieve coherent amplification of radiation through electron microbunching the interaction between electrons and laser must be maintained over hundreds to thousands of undulator periods. Traveling-Wave Thomson-Scattering is the only scattering geometry so far allowing for the realization of optical undulators of this length which is at the same time scalable from extreme ultraviolet to X-ray photon energies. TWTS is also applicable for the realization of incoherent high peak brightness hard X-ray to gamma-ray sources which can provide orders of magnitude higher photon output than classic head-on Thomson sources. In contrast to head-on Thomson sources TWTS employs a side-scattering geometry where laser and electron propagation direction of motion enclose an angle. Tilting the laser pulse front with respect to the wave front by half of this interaction angle optimizes electron and laser pulse overlap. In the side-scattering geometry the tilt of the pulse-front compensates the spatial offset between electrons and laser pulse-front which would be present otherwise for an electron bunch far from the interaction point where it overlaps with the laser pulse center. Thus the laser pulse-front tilt ensures continuous overlap between laser pulse and electrons while these traverse the laser pulse cross-sectional area. This allows to control the interaction distance in TWTS by the laser pulse width rather than laser pulse duration as is the case for head-on Thomson scattering. Utilizing petawatt class laser pulses with millimeter to centimeter scale width allows for the realization of compact optical undulators with thousands of periods. When laser pulses for TWTS are prepared, care has to be taken of laser dispersion. Especially for scenarios featuring interaction angles of several ten to over one hundred degree the angular dispersion originating from laser pulse-front tilt can significantly prolong the pulse duration during the interaction which leads to a decrease in optical undulator amplitude and eventually terminates the interaction long before the target interaction distance is reached. In the talk it is shown how a pair of two gratings can be used to first generate the pulse-front tilt and second control and compensate dispersion during the interaction by utilizing the plane of optimum compression. Furthermore an experimental setup strategy is presented allowing for an interaction outside the laser pulse focus. This is a necessity for TWTS OFELs requiring focusing to reach optical undulator strengths on the order of unity since the centimeter scale laser pulse width at the interaction point result in turn in Rayleigh lengths on the order of one hundred meter and thus in laser focusing distances of several hundred meter. The talk shows how an out-of-focus interaction geometry utilizing strong focusing of the incident laser pulse needs to be designed in order to regain compactness by reducing the focusing distance by one to two orders of magnitude.

Response of TLD-100 in mixed fields of photons and electrons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lawless, Michael J.; Junell, Stephanie; Hammer, Cliff

Purpose: Thermoluminescent dosimeters (TLDs) are routinely used for dosimetric measurements of high energy photon and electron fields. However, TLD response in combined fields of photon and electron beam qualities has not been characterized. This work investigates the response of TLD-100 (LiF:Mg,Ti) to sequential irradiation by high-energy photon and electron beam qualities. Methods: TLDs were irradiated to a known dose by a linear accelerator with a 6 MV photon beam, a 6 MeV electron beam, and a NIST-traceable {sup 60}Co beam. TLDs were also irradiated in a mixed field of the 6 MeV electron beam and the 6 MV photon beam.more » The average TLD response per unit dose of the TLDs for each linac beam quality was normalized to the average response per unit dose of the TLDs irradiated by the {sup 60}Co beam. Irradiations were performed in water and in a Virtual Water Trade-Mark-Sign phantom. The 6 MV photon beam and 6 MeV electron beam were used to create dose calibration curves relating TLD response to absorbed dose to water, which were applied to the TLDs irradiated in the mixed field. Results: TLD relative response per unit dose in the mixed field was less sensitive than the relative response in the photon field and more sensitive than the relative response in the electron field. Application of the photon dose calibration curve to the TLDs irradiated in a mixed field resulted in an underestimation of the delivered dose, while application of the electron dose calibration curve resulted in an overestimation of the dose. Conclusions: The relative response of TLD-100 in mixed fields fell between the relative response in the photon-only and electron-only fields. TLD-100 dosimetry of mixed fields must account for this intermediate response to minimize the estimation errors associated with calibration factors obtained from a single beam quality.« less

Response of TLD-100 in mixed fields of photons and electrons.

PubMed

Lawless, Michael J; Junell, Stephanie; Hammer, Cliff; DeWerd, Larry A

2013-01-01

Thermoluminescent dosimeters (TLDs) are routinely used for dosimetric measurements of high energy photon and electron fields. However, TLD response in combined fields of photon and electron beam qualities has not been characterized. This work investigates the response of TLD-100 (LiF:Mg,Ti) to sequential irradiation by high-energy photon and electron beam qualities. TLDs were irradiated to a known dose by a linear accelerator with a 6 MV photon beam, a 6 MeV electron beam, and a NIST-traceable (60)Co beam. TLDs were also irradiated in a mixed field of the 6 MeV electron beam and the 6 MV photon beam. The average TLD response per unit dose of the TLDs for each linac beam quality was normalized to the average response per unit dose of the TLDs irradiated by the (60)Co beam. Irradiations were performed in water and in a Virtual Water™ phantom. The 6 MV photon beam and 6 MeV electron beam were used to create dose calibration curves relating TLD response to absorbed dose to water, which were applied to the TLDs irradiated in the mixed field. TLD relative response per unit dose in the mixed field was less sensitive than the relative response in the photon field and more sensitive than the relative response in the electron field. Application of the photon dose calibration curve to the TLDs irradiated in a mixed field resulted in an underestimation of the delivered dose, while application of the electron dose calibration curve resulted in an overestimation of the dose. The relative response of TLD-100 in mixed fields fell between the relative response in the photon-only and electron-only fields. TLD-100 dosimetry of mixed fields must account for this intermediate response to minimize the estimation errors associated with calibration factors obtained from a single beam quality.

Technical Note: Detective quantum efficiency simulation of a-Se imaging detectors using ARTEMIS.

PubMed

Fang, Yuan; Ito, Takaaki; Nariyuki, Fumito; Kuwabara, Takao; Badano, Aldo; Karim, Karim S

2017-08-01

This work studies the detective quantum efficiency (DQE) of a-Se-based solid state x-ray detectors for medical imaging applications using ARTEMIS, a Monte Carlo simulation tool for modeling x-ray photon, electron and charged carrier transport in semiconductors with the presence of applied electric field. ARTEMIS is used to model the signal formation process in a-Se. The simulation model includes x-ray photon and high-energy electron interactions, and detailed electron-hole pair transport with applied detector bias taking into account drift, diffusion, Coulomb interactions, recombination and trapping. For experimental validation, the DQE performance of prototype a-Se detectors is measured following IEC Testing Standard 62220-1-3. Comparison of simulated and experimental DQE results show reasonable agreement for RQA beam qualities. Experimental validation demonstrated within 5% percentage difference between simulation and experimental DQE results for spatial frequency above 0.25 cycles/mm using uniform applied electric field for RQA beam qualities (RQA5, RQA7 and RQA9). Results include two different prototype detectors with thicknesses of 240 μm and 1 mm. ARTEMIS can be used to model the DQE of a-Se detectors as a function of x-ray energy, detector thickness, and spatial frequency. The ARTEMIS model can be used to improve understanding of the physics of x-ray interactions in a-Se and in optimization studies for the development of novel medical imaging applications. © 2017 American Association of Physicists in Medicine.

Neon in ultrashort and intense x-rays from free electron lasers

NASA Astrophysics Data System (ADS)

Buth, Christian; Beerwerth, Randolf; Obaid, Razib; Berrah, Nora; Cederbaum, Lorenz S.; Fritzsche, Stephan

2018-03-01

We theoretically examine neon atoms in ultrashort and intense x-rays from free electron lasers and compare our results with data from experiments conducted at the Linac Coherent Light Source. For this purpose, we treat in detail the electronic structure in all possible nonrelativistic cationic configurations using a relativistic multiconfiguration approach. The interaction with the x-rays is described in rate-equation approximation. To understand the mechanisms of the interaction, a path analysis is devised which allows us to investigate what sequences of photoionization and decay processes lead to a specific configuration and with what probability. Thereby, we uncover a connection to the mathematics of graph theory and formal languages. In detail, we study the ion yields and find that plain rate equations do not provide a satisfactory description. We need to extend the rate equations for neon to incorporate double Auger decay of a K-shell vacancy and photoionization shake off for neutral neon. Shake off is included for valence and core ionization; the former has hitherto been overlooked but has important consequences for the ion yields from an x-ray energy below the core ionization threshold. Furthermore, we predict the photon yields from XUV and x-ray fluorescence these allow one insights into the configurations populated by the interaction with the x-rays. Finally, we discover that inaccuracies in those Auger decay widths employed in previous studies have only a minor influence on ion and photon yields.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bernstein, A. M., E-mail: bernstein@mit.edu

Small angle electron scattering with intense electron beams opens up the possibility of performing almost real photon induced reactions with thin, polarized hydrogen and few body targets, allowing for the detection of low energy charged particles. This promises to be much more effective than conventional photon tagging techniques. For photo-pion reactions some fundamental new possibilities include: tests of charge symmetry in the N-N system by measurement of the neutron-neutron scattering length a{sub nn} in the and ggrD → π{sup +}nn reaction; tests of isospin breaking due to the mass difference of the up and down quarks; measurements with polarized targetsmore » are sensitive to πN phase shifts and will test the validity of the Fermi-Watson (final state interaction) theorem. All of these experiments will test the accuracy and energy region of validity of chiral effective theories.« less

The estimation of occupational dose in 15 MV varian clinac iX room by Argon-41 as an activation product of photoneutron

NASA Astrophysics Data System (ADS)

Latifah, R.; Bunawas; Noor, J. A. E.

2018-03-01

Linear accelerator (linac) becomes the most commonly used treatment to damage and kill cancer cell. Photon and electron as the radiation beam are produced by accelerating electrons to very high energy. Neutrons are generated when incident high photon energy interacts with component of linac such as target, flattering filter and collimator via photoneutrons reaction. The neutrons can also produce activation of materials in treatment room to generate radioactive materials. We have estimated the concentration of Argon-41 as activated product from argon-40 in the linac room using foil activation. The results show that the Argon-41 concentration in linac room which is operated 15 MV for 1 treatment (1 minute) is 1440 Bq/m3. Accordingly that concentration, the occupational dose is 6.4 mSv per year.

Cherenkov imaging for Total Skin Electron Therapy (TSET)

NASA Astrophysics Data System (ADS)

Xie, Yunhe; Petroccia, Heather; Maity, Amit; Miao, Tianshun; Zhu, Yihua; Bruza, Petr; Pogue, Brian W.; Andreozzi, Jacqueline M.; Plastaras, John P.; Dong, Lei; Zhu, Timothy C.

2018-03-01

Total Skin Electron Therapy (TSET) utilizes high-energy electrons to treat cancers on the entire body surface. The otherwise invisible radiation beam can be observed via the optical Cherenkov photons emitted from interaction between the high-energy electron beam and tissue. Using a specialized camera-system, the Cherenkov emission can thus be used to evaluate the dose uniformity on the surface of the patient in real-time. Each patient was also monitored during TSET via in-vivo detectors (IVD) in nine locations. Patients undergoing TSET in various conditions (whole body and half body) were imaged and analyzed, and the viability of the system to provide clinical feedback was established.

Entropy production in photovoltaic-thermoelectric nanodevices from the non-equilibrium Green’s function formalism

NASA Astrophysics Data System (ADS)

Michelini, Fabienne; Crépieux, Adeline; Beltako, Katawoura

2017-05-01

We discuss some thermodynamic aspects of energy conversion in electronic nanosystems able to convert light energy into electrical or/and thermal energy using the non-equilibrium Green’s function formalism. In a first part, we derive the photon energy and particle currents inside a nanosystem interacting with light and in contact with two electron reservoirs at different temperatures. Energy conservation is verified, and radiation laws are discussed from electron non-equilibrium Green’s functions. We further use the photon currents to formulate the rate of entropy production for steady-state nanosystems, and we recast this rate in terms of efficiency for specific photovoltaic-thermoelectric nanodevices. In a second part, a quantum dot based nanojunction is closely examined using a two-level model. We show analytically that the rate of entropy production is always positive, but we find numerically that it can reach negative values when the derived particule and energy currents are empirically modified as it is usually done for modeling realistic photovoltaic systems.

Entropy production in photovoltaic-thermoelectric nanodevices from the non-equilibrium Green's function formalism.

PubMed

Michelini, Fabienne; Crépieux, Adeline; Beltako, Katawoura

2017-05-04

We discuss some thermodynamic aspects of energy conversion in electronic nanosystems able to convert light energy into electrical or/and thermal energy using the non-equilibrium Green's function formalism. In a first part, we derive the photon energy and particle currents inside a nanosystem interacting with light and in contact with two electron reservoirs at different temperatures. Energy conservation is verified, and radiation laws are discussed from electron non-equilibrium Green's functions. We further use the photon currents to formulate the rate of entropy production for steady-state nanosystems, and we recast this rate in terms of efficiency for specific photovoltaic-thermoelectric nanodevices. In a second part, a quantum dot based nanojunction is closely examined using a two-level model. We show analytically that the rate of entropy production is always positive, but we find numerically that it can reach negative values when the derived particule and energy currents are empirically modified as it is usually done for modeling realistic photovoltaic systems.

Neutrino Photoproduction on the Electron of a Hydrogen-Like Atom

NASA Astrophysics Data System (ADS)

Skobelev, V. V.

2017-10-01

The process of interaction of a photon with the bound electron of a hydrogen-like atom with creation of a neutrino pair γ +{(Ze)}^{\\ast \\ast}\\to \\overline{νν}+{(Ze)}^{\\ast } is considered here for the first time. This process can take place with and without a change in the energy of the pair relative to the energy of the "initial" photon due to atomic transitions. It is shown that in the case when the system of atoms is located in an equilibrium radiation field with temperature T << m e this process can be neglected in comparison with spontaneous emission of the hydrogen-like atom {(Ze)}^{\\ast}\\to (Ze)+ν\\overline{ν} , despite the smaller power of the expansion parameter ( Zα) < < 1, α = e 2/ ℏc ≈ 1/137 in the expressions for the cross sections and probabilities. Calculations have been performed for the first time using the density matrix, introduced in the previous paper, of the electron in the field of the nucleus in the leading approximation in (Zα).

Virtual photon structure functions and the parton content of the electron

DOE Office of Scientific and Technical Information (OSTI.GOV)

Drees, M.; Godbole, R.M.

1994-09-01

We point out that in processes involving the parton content of the photon the usual effective photon approximation should be modified. The reason is that the parton content of virtual photons is logarithmically suppressed compared to real photons. We describe this suppression using several simple, physically motivated [ital Ansa]$[ital uml---tze]. Although the parton content of the electron in general no longer factorizes into an electron flux function and a photon structure function, it can still be expressed as a single integral. Numerical examples are given for the [ital e][sup +][ital e][sup [minus

Radiative one- and two-electron transitions into the empty K shell of He-like ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kadrekar, Riddhi; Natarajan, L.

2011-12-15

The branching ratios between the single and double electron radiative transitions to empty K shell in He-like ions with 2s2p configuration are evaluated for 15 ions with 4{<=}Z{<=}26 using fully relativistic multiconfiguration Dirac-Fock wavefunctions in the active space approximation. The effects of configuration interaction and Breit contributions on the transition parameters have been analyzed in detail. Though the influence of Breit interaction on the electric dipole allowed one-electron radiative transitions is negligible, it substantially changes the spin-forbidden rates and the two-electron one-photon transition probabilities. Also, while the single electron transition rates are gauge independent, the correlated double-electron probabilities are foundmore » to be gauge sensitive. The probable uncertainties in the computed transition rates have been evaluated by considering the line strengths and the differences between the calculated and experimental transition energies as accuracy indicators. The present results are compared with other available experimental and theoretical data.« less

Probing Electron-Phonon Interaction through Two-Photon Interference in Resonantly Driven Semiconductor Quantum Dots

NASA Astrophysics Data System (ADS)

Reigue, Antoine; Iles-Smith, Jake; Lux, Fabian; Monniello, Léonard; Bernard, Mathieu; Margaillan, Florent; Lemaitre, Aristide; Martinez, Anthony; McCutcheon, Dara P. S.; Mørk, Jesper; Hostein, Richard; Voliotis, Valia

2017-06-01

We investigate the temperature dependence of photon coherence properties through two-photon interference (TPI) measurements from a single quantum dot (QD) under resonant excitation. We show that the loss of indistinguishability is related only to the electron-phonon coupling and is not affected by spectral diffusion. Through these measurements and a complementary microscopic theory, we identify two independent separate decoherence processes, both of which are associated with phonons. Below 10 K, we find that the relaxation of the vibrational lattice is the dominant contribution to the loss of TPI visibility. This process is non-Markovian in nature and corresponds to real phonon transitions resulting in a broad phonon sideband in the QD emission spectra. Above 10 K, virtual phonon transitions to higher lying excited states in the QD become the dominant dephasing mechanism, this leads to a broadening of the zero phonon line, and a corresponding rapid decay in the visibility. The microscopic theory we develop provides analytic expressions for the dephasing rates for both virtual phonon scattering and non-Markovian lattice relaxation.

Electrophilic dark matter with dark photon: From DAMPE to direct detection

NASA Astrophysics Data System (ADS)

Gu, Pei-Hong; He, Xiao-Gang

2018-03-01

The electron-positron excess reported by the DAMPE collaboration recently may be explained by an electrophilic dark matter (DM). A standard model singlet fermion may play the role of such a DM when it is stabilized by some symmetries, such as a dark U(1)X gauge symmetry, and dominantly annihilates into the electron-positron pairs through the exchange of a scalar mediator. The model, with appropriate Yukawa couplings, can well interpret the DAMPE excess. Naively one expects that in this type of models the DM-nucleon cross section should be small since there is no tree-level DM-quark interactions. We however find that at one-loop level, a testable DM-nucleon cross section can be induced for providing ways to test the electrophilic model. We also find that a U (1) kinetic mixing can generate a sizable DM-nucleon cross section although the U(1)X dark photon only has a negligible contribution to the DM annihilation. Depending on the signs of the mixing parameter, the dark photon can enhance/reduce the one-loop induced DM-nucleon cross section.

If EM waves don't interfere, what causes interferograms?

NASA Astrophysics Data System (ADS)

Wellard, Stanley J.

2012-10-01

Photonics engineers involved in designing and operating Fourier transform spectrometers (FTS) often rely on Maxwell's wave equations and time-frequency (distance-wavenumber) Fourier theory as models to understand and predict the conversion of optical energy to electrical signals in their instruments. Dr. Chandrasekhar Roychoudhuri and his colleagues, at last year's conference, presented three significant concepts that might completely change the way we comprehend the interaction of light and matter and the way interference information is generated. The first concept is his non-interaction of waves (NIW) formulation, which puts in place an optical wave description that more accurately describe the properties of the finite time and spatial signals of an optical system. The second is a new description for the cosmic EM environment that recognizes that space is really filled with the ether of classical electromagnetics. The third concept is a new metaphysics or metaphotonics that compares the photon as a particle in a void against the photon as a wave in a medium to see which best explain the twelve different aspects of light. Dr. Henry Lindner presents a compelling case that photons are waves in a medium and particles (electrons, protons, atoms) are wave-structures embedded in the new ether. Discussion of the three new principles is intended to increase the curiosity of photonics engineers to investigate these changes in the nature of light and matter.

Integrating two-photon microscopy and cryo-electron microscopy for studying the interaction of Cafeteria roenbergensis and CroV

NASA Astrophysics Data System (ADS)

Aghvami, Seyedmohammadali

Cafeteria roenbergensis (Cro) is a marine zooplankton; its voracious appetite plays a significant role in regulating bacteria populations. The giant virus that lives within Cro, known as Cafeteria roenbergensis virus (CroV), has an important effect on the mortality of Cro populations. Although viral infections are extremely abundant in oceans, the complete procedure of the infection is still unknown. We study the infection process of Cro by CroV to find out whether the initial contact is through phagocytosis or CroV penetrating the host cell membrane directly. Cro is a moving at speed in the range of 10-100 um/s, therefore, there are many difficulties and challenges for traditional imaging techniques to study this viral-host interaction. We apply two-photon fluorescence microscopy to image this infection process. The image is taken at video rate (30 frame/s), which makes us able to catch the moment of interaction. We are able to image host and virus simultaneously where CroV is stained by SYBR gold dye and Cro is excited through NADH autofluorescence. For further structural biology study, we will obtain atomic level resolution information of infection. After catching the initial moment of infection, we will freeze the sample instantly and image it with cryo-electron microscope .

The NOvA simulation chain

NASA Astrophysics Data System (ADS)

Aurisano, A.; Backhouse, C.; Hatcher, R.; Mayer, N.; Musser, J.; Patterson, R.; Schroeter, R.; Sousa, A.

2015-12-01

The NOνA experiment is a two-detector, long-baseline neutrino experiment operating in the recently upgraded NuMI muon neutrino beam. Simulating neutrino interactions and backgrounds requires many steps including: the simulation of the neutrino beam flux using FLUKA and the FLUGG interface; cosmic ray generation using CRY; neutrino interaction modeling using GENIE; and a simulation of the energy deposited in the detector using GEANT4. To shorten generation time, the modeling of detector-specific aspects, such as photon transport, detector and electronics noise, and readout electronics, employs custom, parameterized simulation applications. We will describe the NOνA simulation chain, and present details on the techniques used in modeling photon transport near the ends of cells, and in developing a novel data-driven noise simulation. Due to the high intensity of the NuMI beam, the Near Detector samples a high rate of muons originating in the surrounding rock. In addition, due to its location on the surface at Ash River, MN, the Far Detector collects a large rate (˜ 140 kHz) of cosmic muons. We will discuss the methods used in NOνA for overlaying rock muons and cosmic ray muons with simulated neutrino interactions and show how realistically the final simulation reproduces the preliminary NOνA data.

The NO vA simulation chain

DOE PAGES

Aurisano, A.; Backhouse, C.; Hatcher, R.; ...

2015-12-23

The NO vA experiment is a two-detector, long-baseline neutrino experiment operating in the recently upgraded NuMI muon neutrino beam. Simulating neutrino interactions and backgrounds requires many steps including: the simulation of the neutrino beam flux using FLUKA and the FLUGG interface, cosmic ray generation using CRY, neutrino interaction modeling using GENIE, and a simulation of the energy deposited in the detector using GEANT4. To shorten generation time, the modeling of detector-specific aspects, such as photon transport, detector and electronics noise, and readout electronics, employs custom, parameterized simulation applications. We will describe the NO vA simulation chain, and present details onmore » the techniques used in modeling photon transport near the ends of cells, and in developing a novel data-driven noise simulation. Due to the high intensity of the NuMI beam, the Near Detector samples a high rate of muons originating in the surrounding rock. In addition, due to its location on the surface at Ash River, MN, the Far Detector collects a large rate ((˜) 140 kHz) of cosmic muons. Furthermore, we will discuss the methods used in NO vA for overlaying rock muons and cosmic ray muons with simulated neutrino interactions and show how realistically the final simulation reproduces the preliminary NO vA data.« less

Simulations of ultrafast x-ray laser experiments

NASA Astrophysics Data System (ADS)

Fortmann-Grote, C.; Andreev, A. A.; Appel, K.; Branco, J.; Briggs, R.; Bussmann, M.; Buzmakov, A.; Garten, M.; Grund, A.; Huebl, A.; Jurek, Z.; Loh, N. D.; Nakatsutsumi, M.; Samoylova, L.; Santra, R.; Schneidmiller, E. A.; Sharma, A.; Steiniger, K.; Yakubov, S.; Yoon, C. H.; Yurkov, M. V.; Zastrau, U.; Ziaja-Motyka, B.; Mancuso, A. P.

2017-06-01

Simulations of experiments at modern light sources, such as optical laser laboratories, synchrotrons, and free electron lasers, become increasingly important for the successful preparation, execution, and analysis of these experiments investigating ever more complex physical systems, e.g. biomolecules, complex materials, and ultra-short lived states of matter at extreme conditions. We have implemented a platform for complete start-to-end simulations of various types of photon science experiments, tracking the radiation from the source through the beam transport optics to the sample or target under investigation, its interaction with and scattering from the sample, and registration in a photon detector. This tool allows researchers and facility operators to simulate their experiments and instruments under real life conditions, identify promising and unattainable regions of the parameter space and ultimately make better use of valuable beamtime. In this paper, we present an overview about status and future development of the simulation platform and discuss three applications: 1.) Single-particle imaging of biomolecules using x-ray free electron lasers and optimization of x-ray pulse properties, 2.) x-ray scattering diagnostics of hot dense plasmas in high power laser-matter interaction and identification of plasma instabilities, and 3.) x-ray absorption spectroscopy in warm dense matter created by high energy laser-matter interaction and pulse shape optimization for low-isentrope dynamic compression.

Observation of three-photon bound states in a quantum nonlinear medium

NASA Astrophysics Data System (ADS)

Liang, Qi-Yu; Venkatramani, Aditya V.; Cantu, Sergio H.; Nicholson, Travis L.; Gullans, Michael J.; Gorshkov, Alexey V.; Thompson, Jeff D.; Chin, Cheng; Lukin, Mikhail D.; Vuletić, Vladan

2018-02-01

Bound states of massive particles, such as nuclei, atoms, or molecules, constitute the bulk of the visible world around us. By contrast, photons typically only interact weakly. We report the observation of traveling three-photon bound states in a quantum nonlinear medium where the interactions between photons are mediated by atomic Rydberg states. Photon correlation and conditional phase measurements reveal the distinct bunching and phase features associated with three-photon and two-photon bound states. Such photonic trimers and dimers possess shape-preserving wave functions that depend on the constituent photon number. The observed bunching and strongly nonlinear optical phase are described by an effective field theory of Rydberg-induced photon-photon interactions. These observations demonstrate the ability to realize and control strongly interacting quantum many-body states of light.

Time-dependent many-body treatment of electron-boson dynamics: Application to plasmon-accompanied photoemission

NASA Astrophysics Data System (ADS)

Schüler, M.; Berakdar, J.; Pavlyukh, Y.

2016-02-01

Recent experiments access the time-resolved photoelectron signal originating from plasmon satellites in correlated materials and address their buildup and decay in real time. Motivated by these developments, we present the Kadanoff-Baym formalism for the nonequilibrium time evolution of interacting fermions and bosons. In contrast to the fermionic case, the bosons are described by second-order differential equations. Solution of the bosonic Kadanoff-Baym equations—which is the central ingredient of this work—requires substantial modification of the usual two-times electronic propagation scheme. The solution is quite general and can be applied to a number of problems, such as the interaction of electrons with quantized photons, phonons, and other bosonic excitations. Here the formalism is applied to the photoemission from a deep core hole accompanied by plasmon excitation. We compute the time-resolved photoelectron spectra and discuss the effects of intrinsic and extrinsic electron energy losses and their interference.

New Insights into High-Tc Superconductivity from Angle-Resolved Photoemission at Low Photon Energies

NASA Astrophysics Data System (ADS)

Plumb, Nicholas Clark

Angle-resolved photoemission spectroscopy (ARPES) is one of the most direct and powerful probes for studying the physics of solids. ARPES takes a "snapshot" of electrons in momentum space (k-space) to reveal details of the dispersion relation E( k), as well as information about the lifetimes of interacting quasiparticles. From this we learn not only where the electrons live, but also, if we are crafty, what they are doing. Beginning with work by our group in 2006 using a 6-eV laser, ARPES experiments have begun to make use of a new, low photon energy regime (roughly hnu = 6--9 eV). These low photon energies give drastic improvements in momentum resolution, photoelectron escape depths, and overall spectral sharpness. This has led to several important new findings in the intensively-studied problem of high-temperature superconductivity. This thesis will focus on two of the latest results from our group using low-energy ARPES (LE-ARPES) to study the cuprate high-Tc superconductor Bi2Sr2CaCu2O8+delta (Bi2212). The first of these is an investigation into the nature of many-body interactions at a well-known energy scale (˜ 60--70 meV) where the dispersion shows a large bend, or "kink". Using LE-ARPES measurements, the k-dependence of this kink is investigated in unprecedented detail. An attempt is then made to map the feature's k evolution into the scattering q-space of boson dispersions. In our analysis, the q-dispersion of the kink bears more resemblance to dispersive spin excitations than phonons --- a surprising finding in light of previous evidence that the the kink originates from interactions with phonons. However, phonons cannot be ruled out, and the results may hint that both types of interactions contribute to the main nodal kink. A second result is the discovery of a new ultralow (< 10 meV) energy scale for electron interactions, corresponding to a distinct, smaller kink in the electron dispersion. The temperature and doping dependence of this feature show not only that it turns on near Tc --- signalling a possible relation to the mechanism of high-T c superconductivity --- but also that it leads to a subtle breakdown of the so-called "universal" Fermi velocity vF along nodes of the anisotropic superconducting gap. Moreover, vF is found to depend quite strongly on temperature, which may be an important factor in the physics of cuprates.

Development of a silicon microstrip detector with single photon sensitivity for fast dynamic diffraction experiments at a synchrotron radiation beam

NASA Astrophysics Data System (ADS)

Arakcheev, A.; Aulchenko, V.; Kudashkin, D.; Shekhtman, L.; Tolochko, B.; Zhulanov, V.

2017-06-01

Time-resolved experiments on the diffraction of synchrotron radiation (SR) from crystalline materials provide information on the evolution of a material structure after a heat, electron beam or plasma interaction with a sample under study. Changes in the material structure happen within a microsecond scale and a detector with corresponding parameters is needed. The SR channel 8 of the VEPP-4M storage ring provides radiation from the 7-pole wiggler that allows to reach several tens photons within one μs from a tungsten crystal for the most intensive diffraction peak. In order to perform experiments that allow to measure the evolution of tungsten crystalline structure under the impact of powerful laser beam, a new detector is developed, that can provide information about the distribution of a scattered SR flux in space and its evolution in time at a microsecond scale. The detector is based on the silicon p-in-n microstrip sensor with DC-coupled metal strips. The sensor contains 1024 30 mm long strips with a 50 μm pitch. 64 strips are bonded to the front-end electronics based on APC128 ASICs. The APC128 ASIC contains 128 channels that consist of a low noise integrator with 32 analogue memory cells each. The integrator equivalent noise charge is about 2000 electrons and thus the signal from individual photons with energy above 40 keV can be observed. The signal can be stored at the analogue memory with 10 MHz rate. The first measurements with the beam scattered from a tungsten crystal with energy near 60 keV demonstrated the capability of this prototype to observe the spatial distribution of the photon flux with the intensity from below one photon per channel up to 0~10 photons per channel with a frame rate from 10 kHz up to 1 MHz.

Stacking the Deck: Leveraging Surface Interactions to Tune Interfacial Electronic Structure

NASA Astrophysics Data System (ADS)

Maughan, Bret; Eads, Calley; Zahl, Percy; Sutter, Peter; Monti, Oliver

We present results from a series of experiments aimed at understanding and controlling molecular interactions in phthalocyanine (Pc) thin-films on Cu(110) to tailor the interfacial electronic structure. Using low-temperature scanning tunneling microscopy (LT-STM), we identify interactions that drive surface-molecule coupling, molecular self-assembly and thin-film order. We provide evidence that interactions with native Cu adatoms play a pivotal role in self-assembly of Pc systems, along with anisotropic nanoribbon growth dynamics, supported by an agent-based kinetic Monte Carlo (AB-KMC) simulation. We show further that self-assembled nanoribbon length can be controlled using surface diffusion barriers and that ordered 2D thin-film growth is promoted by diminishing surface-molecule interactions that otherwise dominate native Cu(110) interfaces. Altogether, this detailed structural understanding allows us to interpret interfacial electronic structure and dynamics, uncovered through ultraviolet (UPS) and two-photon photoemission (2PPE) spectroscopy experiments, in molecular configuration-specific detail. In all, our understanding of interfacial processes guides strategic modifications to both surface and molecule to harness interfacial interactions and thereby modify the collective electronic structure of the interface. NSF No. CHE-1213243 and No. CHE-1565497, Arizona TRIF, DOE/BNL Cntrct No. DE-SC0012704, and DOE No. DE-SC0016343.

Teaching Electron--Positron--Photon Interactions with Hands-on Feynman Diagrams

ERIC Educational Resources Information Center

Kontokostas, George; Kalkanis, George

2013-01-01

Feynman diagrams are introduced in many physics textbooks, such as those by Alonso and Finn and Serway, and their use in physics education has been discussed by various authors. They have an appealing simplicity and can give insight into events in the microworld. Yet students often do not understand their significance and often cannot combine the…

Investigation of the radiation background in the interaction region of the medium-energy electron relativisitic heavy ion collider (MeRHIC)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beebe-Wang,J.

There are three main sources of the radiation background in MeRHIC: forward synchrotron radiation generated upstream of the detector, the direct backward radiation caused by the photons hitting beampipe downstream of the detector, and the indirect secondary radiation caused by hard photons hitting vacuum systems, masks, collimators, absorbers or any other elements in the interaction region. In this paper, we first calculate the primary radiation distribution by employing electromagnetic theory. Then we obtain the direct backward scattering rate by applying the kinematic Born approximation deduced from scattering dynamics. The diffuse scattering cross section is calculated as a function of themore » surface properties of the MeRHIC vacuum system. Finally, the dominating physical processes and minimization of indirect secondary radiation is presented and discussed.« less

Cavity Born-Oppenheimer Approximation for Correlated Electron-Nuclear-Photon Systems.

PubMed

Flick, Johannes; Appel, Heiko; Ruggenthaler, Michael; Rubio, Angel

2017-04-11

In this work, we illustrate the recently introduced concept of the cavity Born-Oppenheimer approximation [ Flick et al. PNAS 2017 , 10.1073/pnas.1615509114 ] for correlated electron-nuclear-photon problems in detail. We demonstrate how an expansion in terms of conditional electronic and photon-nuclear wave functions accurately describes eigenstates of strongly correlated light-matter systems. For a GaAs quantum ring model in resonance with a photon mode we highlight how the ground-state electronic potential-energy surface changes the usual harmonic potential of the free photon mode to a dressed mode with a double-well structure. This change is accompanied by a splitting of the electronic ground-state density. For a model where the photon mode is in resonance with a vibrational transition, we observe in the excited-state electronic potential-energy surface a splitting from a single minimum to a double minimum. Furthermore, for a time-dependent setup, we show how the dynamics in correlated light-matter systems can be understood in terms of population transfer between potential energy surfaces. This work at the interface of quantum chemistry and quantum optics paves the way for the full ab initio description of matter-photon systems.

Compact quasi-monoenergetic photon sources from laser-plasma accelerators for nuclear detection and characterization

NASA Astrophysics Data System (ADS)

Geddes, Cameron G. R.; Rykovanov, Sergey; Matlis, Nicholas H.; Steinke, Sven; Vay, Jean-Luc; Esarey, Eric H.; Ludewigt, Bernhard; Nakamura, Kei; Quiter, Brian J.; Schroeder, Carl B.; Toth, Csaba; Leemans, Wim P.

2015-05-01

Near-monoenergetic photon sources at MeV energies offer improved sensitivity at greatly reduced dose for active interrogation, and new capabilities in treaty verification, nondestructive assay of spent nuclear fuel and emergency response. Thomson (also referred to as Compton) scattering sources are an established method to produce appropriate photon beams. Applications are however restricted by the size of the required high-energy electron linac, scattering (photon production) system, and shielding for disposal of the high energy electron beam. Laser-plasma accelerators (LPAs) produce GeV electron beams in centimeters, using the plasma wave driven by the radiation pressure of an intense laser. Recent LPA experiments are presented which have greatly improved beam quality and efficiency, rendering them appropriate for compact high-quality photon sources based on Thomson scattering. Designs for MeV photon sources utilizing the unique properties of LPAs are presented. It is shown that control of the scattering laser, including plasma guiding, can increase photon production efficiency. This reduces scattering laser size and/or electron beam current requirements to scale compatible with the LPA. Lastly, the plasma structure can decelerate the electron beam after photon production, reducing the size of shielding required for beam disposal. Together, these techniques provide a path to a compact photon source system.

Properties of the electron cloud in a high-energy positron and electron storage ring

DOE PAGES

Harkay, K. C.; Rosenberg, R. A.

2003-03-20

Low-energy, background electrons are ubiquitous in high-energy particle accelerators. Under certain conditions, interactions between this electron cloud and the high-energy beam can give rise to numerous effects that can seriously degrade the accelerator performance. These effects range from vacuum degradation to collective beam instabilities and emittance blowup. Although electron-cloud effects were first observed two decades ago in a few proton storage rings, they have in recent years been widely observed and intensely studied in positron and proton rings. Electron-cloud diagnostics developed at the Advanced Photon Source enabled for the first time detailed, direct characterization of the electron-cloud properties in amore » positron and electron storage ring. From in situ measurements of the electron flux and energy distribution at the vacuum chamber wall, electron-cloud production mechanisms and details of the beam-cloud interaction can be inferred. A significant longitudinal variation of the electron cloud is also observed, due primarily to geometrical details of the vacuum chamber. Furthermore, such experimental data can be used to provide realistic limits on key input parameters in modeling efforts, leading ultimately to greater confidence in predicting electron-cloud effects in future accelerators.« less

The Hadronic Origin of the Hard Gamma-Ray Spectrum from Blazar 1ES 1101-232

NASA Astrophysics Data System (ADS)

Cao, Gang; Wang, Jiancheng

2014-03-01

The very hard γ-ray spectrum from distant blazars challenges the traditional synchrotron self-Compton (SSC) model, which may indicate that there is a contribution from an additional high-energy component beyond the SSC emission. In this paper, we study the possible origin of the hard γ-ray spectrum from distant blazars. We develop a model to explain the hard γ-ray spectrum from blazar 1ES 1101-232. In the model, the optical and X-ray radiation would come from the synchrotron radiation of primary electrons and secondary pairs and the GeV emission would be produced by the SSC process, however, the hard γ-ray spectrum would originate from the decay of neutral pion produced through proton-photon interactions with the synchrotron radiation photons within the jet. Our model can explain the observed spectral energy distribution of 1ES 1101-232 well, especially the very hard γ-ray spectrum. However, our model requires a very large proton power to efficiently produce the γ-ray through proton-photon interactions.

New opportunities at the frontiers of spintronics

DOE PAGES

Hoffmann, Axel; Bader, Sam D.

2015-10-05

The field of spintronics, or magnetic electronics, is maturing and giving rise to new subfields. These new directions involve the study of collective spin excitations and couplings of the spin system to additional degrees of freedom of a material, as well as metastable phenomena due to perturbations that drive the system far from equilibrium. The interactions lead to possibilities for future applications within the realm of energy-efficient information technologies. Examples discussed herein include research opportunities associated with (i) various spin-orbit couplings, such as spin Hall effects, (ii) couplings to the thermal bath of a system, such as in spin Seebeckmore » effects, (iii) spin-spin couplings, such as via induced and interacting magnon excitations, and (iv) spin-photon couplings, such as in ultra-fast magnetization switching due to coherent photon pulses. These four basic frontier areas of research are giving rise to new applied disciplines known as spin-orbitronics, spin-caloritronics, magnonics, and spin-photonics, respectively. These topics are highlighted in order to stimulate interest in the new directions that spintronics research is taking, and to identify open issues to pursue.« less

Gamma ray pulsars. [electron-photon cascades

NASA Technical Reports Server (NTRS)

Oegelman, H.; Ayasli, S.; Hacinliyan, A.

1977-01-01

Data from the SAS-2 high-energy gamma-ray experiment reveal the existence of four pulsars emitting photons above 35 MeV. An attempt is made to explain the gamma-ray emission from these pulsars in terms of an electron-photon cascade that develops in the magnetosphere of the pulsar. Although there is very little material above the surface of the pulsar, the very intense magnetic fields (10 to the 12th power gauss) correspond to many radiation lengths which cause electrons to emit photons by magnetic bremsstrahlung and which cause these photons to pair-produce. The cascade develops until the mean photon energy drops below the pair-production threshold which is in the gamma-ray range; at this stage, the photons break out from the source.

Quantum dot single-photon switches of resonant tunneling current for discriminating-photon-number detection

PubMed Central

Weng, Qianchun; An, Zhenghua; Zhang, Bo; Chen, Pingping; Chen, Xiaoshuang; Zhu, Ziqiang; Lu, Wei

2015-01-01

Low-noise single-photon detectors that can resolve photon numbers are used to monitor the operation of quantum gates in linear-optical quantum computation. Exactly 0, 1 or 2 photons registered in a detector should be distinguished especially in long-distance quantum communication and quantum computation. Here we demonstrate a photon-number-resolving detector based on quantum dot coupled resonant tunneling diodes (QD-cRTD). Individual quantum-dots (QDs) coupled closely with adjacent quantum well (QW) of resonant tunneling diode operate as photon-gated switches- which turn on (off) the RTD tunneling current when they trap photon-generated holes (recombine with injected electrons). Proposed electron-injecting operation fills electrons into coupled QDs which turn “photon-switches” to “OFF” state and make the detector ready for multiple-photons detection. With proper decision regions defined, 1-photon and 2-photon states are resolved in 4.2 K with excellent propabilities of accuracy of 90% and 98% respectively. Further, by identifying step-like photon responses, the photon-number-resolving capability is sustained to 77 K, making the detector a promising candidate for advanced quantum information applications where photon-number-states should be accurately distinguished. PMID:25797442

Quantum dot single-photon switches of resonant tunneling current for discriminating-photon-number detection.

PubMed

Weng, Qianchun; An, Zhenghua; Zhang, Bo; Chen, Pingping; Chen, Xiaoshuang; Zhu, Ziqiang; Lu, Wei

2015-03-23

Low-noise single-photon detectors that can resolve photon numbers are used to monitor the operation of quantum gates in linear-optical quantum computation. Exactly 0, 1 or 2 photons registered in a detector should be distinguished especially in long-distance quantum communication and quantum computation. Here we demonstrate a photon-number-resolving detector based on quantum dot coupled resonant tunneling diodes (QD-cRTD). Individual quantum-dots (QDs) coupled closely with adjacent quantum well (QW) of resonant tunneling diode operate as photon-gated switches- which turn on (off) the RTD tunneling current when they trap photon-generated holes (recombine with injected electrons). Proposed electron-injecting operation fills electrons into coupled QDs which turn "photon-switches" to "OFF" state and make the detector ready for multiple-photons detection. With proper decision regions defined, 1-photon and 2-photon states are resolved in 4.2 K with excellent propabilities of accuracy of 90% and 98% respectively. Further, by identifying step-like photon responses, the photon-number-resolving capability is sustained to 77 K, making the detector a promising candidate for advanced quantum information applications where photon-number-states should be accurately distinguished.

Indirect dark matter signatures in the cosmic dark ages. II. Ionization, heating, and photon production from arbitrary energy injections

NASA Astrophysics Data System (ADS)

Slatyer, Tracy R.

2016-01-01

Any injection of electromagnetically interacting particles during the cosmic dark ages will lead to increased ionization, heating, production of Lyman-α photons and distortions to the energy spectrum of the cosmic microwave background, with potentially observable consequences. In this paper we describe numerical results for the low-energy electrons and photons produced by the cooling of particles injected at energies from keV to multi-TeV scales, at arbitrary injection redshifts (but focusing on the post-recombination epoch). We use these data, combined with existing calculations modeling the cooling of these low-energy particles, to estimate the resulting contributions to ionization, excitation and heating of the gas, and production of low-energy photons below the threshold for excitation and ionization. We compute corrected deposition-efficiency curves for annihilating dark matter, and demonstrate how to compute equivalent curves for arbitrary energy-injection histories. These calculations provide the necessary inputs for the limits on dark matter annihilation presented in the accompanying paper I, but also have potential applications in the context of dark matter decay or deexcitation, decay of other metastable species, or similar energy injections from new physics. We make our full results publicly available at http://nebel.rc.fas.harvard.edu/epsilon, to facilitate further independent studies. In particular, we provide the full low-energy electron and photon spectra, to allow matching onto more detailed codes that describe the cooling of such particles at low energies.

Gadolinium-loaded Plastic Scintillators for Thermal Neutron Detection using Compensation

NASA Astrophysics Data System (ADS)

Dumazert, Jonathan; Coulon, Romain; Hamel, Matthieu; Carrel, Frédérick; Sguerra, Fabien; Normand, Stéphane; Méchin, Laurence; Bertrand, Guillaume H. V.

2016-06-01

Plastic scintillator loading with gadolinium-rich organometallic complexes shows a high potential for the deployment of efficient and cost-effective neutron detectors. Due to the low-energy photon and electron signature of thermal neutron capture by Gd-155 and Gd-157, alternative treatment to pulse-shape discrimination has to be proposed in order to display a count rate. This paper discloses the principle of a compensation method applied to a two-scintillator system: a detection scintillator interacts with photon and fast neutron radiation and is loaded with gadolinium organometallic compound to become a thermal neutron absorber, while a not-gadolinium loaded compensation scintillator solely interacts with the fast neutron and photon part of incident radiation. After the nonlinear smoothing of the counting signals, a hypothesis test determines whether the resulting count rate post-background response compensation falls into statistical fluctuations or provides a robust indication of neutron activity. Laboratory samples are tested under both photon and neutron irradiations, allowing the authors to investigate the performance of the overall detection system in terms of sensitivity and detection limits, especially with regards to a similar-active volume He-3 based commercial counter. The study reveals satisfactory figures of merit in terms of sensitivity and directs future investigation toward promising paths.

Study of Charm and Beauty using electron-D{sup 0} azimuthal correlations in the STAR experiment at RHIC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kabana, Sonia

The energy loss of heavy quarks in the hot and dense matter created in high-energy nuclear collisions at RHIC, can be used to probe the properties of the medium. Both charm and beauty quarks contribute to the non-photonic electrons through their semi-leptonic decays. It is essential to determine experimentally the relative contributions of charm and beauty quarks to understand the observed suppression of non-photonic electrons at high p{sub T} in central Au+Au collisions. The azimuthal angular correlations of non-photonic electrons with hadrons as well as with the reconstructed D{sup 0} allow to disentangle the contributions of charm and beauty tomore » the electron spectrum. We discuss the STAR measurement of non-photonic electron-D{sup 0} and non-photonic electron-hadron azimuthal correlations in p+p collisions at 200 GeV and explore the consequences for the heavy flavour suppression in heavy ion collisions at RHIC.« less

Some preliminary calculations of whole atom Compton scattering of unpolarized photons

NASA Astrophysics Data System (ADS)

Bergstrom, P. M.; Surić, T.; Pisk, K.; Pratt, R. H.

1992-07-01

This paper represents a preliminary attempt to develop a practical prescription for calculating whole atom cross sections for the Compton scattering of unpolarized photons from the bound electrons of an atom for the entire spectrum of scattered photon energies. We initially study the scattering of 2.94 keV photons from carbon. We make use of our new second order S-matrix computer code in this case to verify that, when our recently developed criterion for the validity of the relativistic impulse approximation (which concerns the average momentum contributing to the photon spectrum ( pav)) is satisfied, the spectrum is adequately described by the impulse approximation. This criterion is generally satisfied in the peak intensity region for scattering by the outer shells, which dominate at these scattered photon energies. For soft scattered photons, however, the spectrum, dominated by K shell contributions, is given by terms corresponding to the contribution of the " p· A" term in the nonrelativistic interaction Hamiltonian, not included in the impulse approximation. Here, the spectrum is adequately reproduced by the K shell contribution. We then consider scattering of 17.4 keV photons from aluminum and 279.1 keV photons from lead. In these cases we use the S-matrix for the K shell and the impulse approximation for the outer shells, and find good agreement with experiment.

Ru sub 3 (CO) sub 12 and Mo (CO) sub 6 overlayers adsorbed on Ru(001) and Au/Ru and their interaction with electrons and photons: An infrared reflection--absorption study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malik, I.J.; Hrbek, J.

1991-05-01

We studied adsorbed Ru{sub 3}(CO){sub 12} and Mo (CO){sub 6} overlayers on Ru(001) and Au/Ru surfaces by infrared reflection--absorption spectroscopy (IRAS) and thermal desorption spectroscopy (TDS). We characterized the C--O stretching mode of both metal carbonyls (4 cm{sup {minus}1} FWHM) and a deformation mode of Mo (CO){sub 6} at 608 cm{sup {minus}1} with an unusually narrow FWHM of 1 cm{sup {minus}1}. Both IRAS and TDS data suggest adsorption and desorption of metal carbonyls as molecular species with a preferential orientation in the overlayers. We discuss annealing experiments of Ru{sub 3}(CO){sub 12}/Ru(001), the interaction of Ru{sub 3}(CO){sub 12} overlayers with electronsmore » of up to 100-eV energy, and the interaction of Mo (CO){sub 6} overlayers with 300-nm photons.« less

Plasmonic Landau damping in active environments

NASA Astrophysics Data System (ADS)

Thakkar, Niket; Montoni, Nicholas P.; Cherqui, Charles; Masiello, David J.

2018-03-01

Optical manipulation of charge on the nanoscale is of fundamental importance to an array of proposed technologies from selective photocatalysis to nanophotonics. Open plasmonic systems where collective electron oscillations release energy and charge to their environments offer a potential means to this end as plasmons can rapidly decay into energetic electron-hole pairs; however, isolating this decay from other plasmon-environment interactions remains a challenge. Here we present an analytic theory of noble-metal nanoparticles that quantitatively models plasmon decay into electron-hole pairs, demonstrates that this decay depends significantly on the nanoparticle's dielectric environment, and disentangles this effect from competing decay pathways. Using our approach to incorporate embedding material and substrate effects on plasmon-electron interaction, we show that predictions from the model agree with four separate experiments. Finally, examination of coupled nanoparticle-emitter systems further shows that the hybridized in-phase mode more efficiently decays to photons whereas the out-of-phase mode more efficiently decays to electron-hole pairs, offering a strategy to tailor open plasmonic systems for charge manipulation.

NREL Scientists Report First Solar Cell Producing More Electrons In

Science.gov Websites

Photocurrent Than Solar Photons Entering Cell | News | NREL NREL Scientists Report First Solar Cell Producing More Electrons In Photocurrent Than Solar Photons Entering Cell News Release: NREL Scientists Report First Solar Cell Producing More Electrons In Photocurrent Than Solar Photons Entering Cell

CAST constraints on the axion-electron coupling

DOE PAGES

None, None

2013-05-09

In non-hadronic axion models, which have a tree-level axion-electron interaction, the Sun produces a strong axion flux by bremsstrahlung, Compton scattering, and axio- recombination, the “BCA processes.” Based on a new calculation of this flux, including for the first time axio-recombination, we derive limits on the axion-electron Yukawa coupling g ae and axion-photon interaction strength g aγ using the CAST phase-I data (vacuum phase). For m a ≲ 10 meV/c 2 we find g aγ gae < 8.1 × 10–23 GeV–1 at 95% CL. We stress that a next-generation axion helioscope such as the proposed IAXO could push this sensitivitymore » into a range beyond stellar energy-loss limits and test the hypothesis that white-dwarf cooling is dominated by axion emission.« less

Multidimensional photoemission spectroscopy—the space-charge limit

NASA Astrophysics Data System (ADS)

Schönhense, B.; Medjanik, K.; Fedchenko, O.; Chernov, S.; Ellguth, M.; Vasilyev, D.; Oelsner, A.; Viefhaus, J.; Kutnyakhov, D.; Wurth, W.; Elmers, H. J.; Schönhense, G.

2018-03-01

Photoelectron spectroscopy, especially at pulsed sources, is ultimately limited by the Coulomb interaction in the electron cloud, changing energy and angular distribution of the photoelectrons. A detailed understanding of this phenomenon is crucial for future pump-probe photoemission studies at (x-ray) free electron lasers and high-harmonic photon sources. Measurements have been performed for Ir(111) at hν = 1000 eV with photon flux densities between ˜102 and 104 photons per pulse and μm2 (beamline P04/PETRA III, DESY Hamburg), revealing space-charge induced energy shifts of up to 10 eV. In order to correct the essential part of the energy shift and restore the electron distributions close to the Fermi energy, we developed a semi-analytical theory for the space-charge effect in cathode-lens instruments (momentum microscopes, photoemission electron microscopes). The theory predicts a Lorentzian profile of energy isosurfaces and allows us to quantify the charge cloud from measured energy profiles. The correction is essential for the determination of the Fermi surface, as we demonstrate by means of ‘k-space movies’ for the prototypical high-Z material tungsten. In an energy interval of about 1 eV below the Fermi edge, the bandstructure can be restored up to substantial shifts of ˜7 eV. Scattered photoelectrons strongly enhance the inelastic background in the region several eV below E F, proving that the majority of scattering events involves a slow electron. The correction yields a gain of two orders of magnitude in usable intensity compared with the uncorrected case (assuming a tolerable shift of 250 meV). The results are particularly important for future experiments at SASE-type free electron lasers, since the correction also works for strongly fluctuating (but known) pulse intensities.

Using an intense laser beam in interaction with muon/electron beam to probe the noncommutative QED

NASA Astrophysics Data System (ADS)

Tizchang, S.; Batebi, S.; Haghighat, M.; Mohammadi, R.

2017-02-01

It is known that the linearly polarized photons can partly transform to circularly polarized ones via forward Compton scattering in a background such as the external magnetic field or noncommutative space time. Based on this fact we explore the effects of the NC-background on the scattering of a linearly polarized laser beam from an intense beam of charged leptons. We show that for a muon/electron beam flux {overline{ɛ}}_{μ, e}˜ 1{0}^{12}/{10}^{10} TeV cm-2 sec-1 and a linearly polarized laser beam with energy k 0 ˜1 eV and average power {overline{P}}_{laser}˜eq 1{0}^3 KW, the generation rate of circularly polarized photons is about R V ˜ 104 /sec for noncommutative energy scale ΛNC ˜ 10 TeV. This is fairly large and can grow for more intense beams in near future.

A non-invasive online photoionization spectrometer for FLASH2

PubMed Central

Braune, Markus; Brenner, Günter; Dziarzhytski, Siarhei; Juranić, Pavle; Sorokin, Andrey; Tiedtke, Kai

2016-01-01

The stochastic nature of the self-amplified spontaneous emission (SASE) process of free-electron lasers (FELs) effects pulse-to-pulse fluctuations of the radiation properties, such as the photon energy, which are determinative for processes of photon–matter interactions. Hence, SASE FEL sources pose a great challenge for scientific investigations, since experimenters need to obtain precise real-time feedback of these properties for each individual photon bunch for interpretation of the experimental data. Furthermore, any device developed to deliver the according information should not significantly interfere with or degrade the FEL beam. Regarding the spectral properties, a device for online monitoring of FEL wavelengths has been developed for FLASH2, which is based on photoionization of gaseous targets and the measurements of the corresponding electron and ion time-of-flight spectra. This paper presents experimental studies and cross-calibration measurements demonstrating the viability of this online photoionization spectrometer. PMID:26698040

Correlated Light-Matter Interactions in Cavity QED

NASA Astrophysics Data System (ADS)

Flick, Johannes; Pellegrini, Camilla; Ruggenthaler, Michael; Appel, Heiko; Tokatly, Ilya; Rubio, Angel

2015-03-01

In the last decade, time-dependent density functional theory (TDDFT) has been successfully applied to a large variety of problems, such as calculations of absorption spectra, excitation energies, or dynamics in strong laser fields. Recently, we have generalized TDDFT to also describe electron-photon systems (QED-TDDFT). Here, matter and light are treated on an equal quantized footing. In this work, we present the first numerical calculations in the framework of QED-TDDFT. We show exact solutions for fully quantized prototype systems consisting of atoms or molecules placed in optical high-Q cavities and coupled to quantized electromagnetic modes. We focus on the electron-photon exchange-correlation (xc) contribution by calculating exact Kohn-Sham potentials using fixed-point inversions and present the performance of the first approximated xc-potential based on an optimized effective potential (OEP) approach. Max Planck Institute for the Structure and Dynamics of Matter, Hamburg, and Fritz-Haber-Institut der MPG, Berlin

Landau-Zener-Stückelberg-Majorana Interferometry of a Single Hole

NASA Astrophysics Data System (ADS)

Bogan, Alex; Studenikin, Sergei; Korkusinski, Marek; Gaudreau, Louis; Zawadzki, Piotr; Sachrajda, Andy S.; Tracy, Lisa; Reno, John; Hargett, Terry

2018-05-01

We perform Landau-Zener-Stückelberg-Majorana (LZSM) spectroscopy on a system with strong spin-orbit interaction (SOI), realized as a single hole confined in a gated double quantum dot. Analogous to electron systems, at a magnetic field B =0 and high modulation frequencies, we observe photon-assisted tunneling between dots, which smoothly evolves into the typical LZSM funnel-shaped interference pattern as the frequency is decreased. In contrast to electrons, the SOI enables an additional, efficient spin-flip interdot tunneling channel, introducing a distinct interference pattern at finite B . Magnetotransport spectra at low-frequency LZSM driving show the two channels to be equally coherent. High-frequency LZSM driving reveals complex photon-assisted tunneling pathways, both spin conserving and spin flip, which form closed loops at critical magnetic fields. In one such loop, an arbitrary hole spin state is inverted, opening the way toward its all-electrical manipulation.

Gamma ray interaction studies of organic nonlinear optical materials in the energy range 122 keV-1330 keV

NASA Astrophysics Data System (ADS)

Awasarmol, V. V.; Gaikwad, D. K.; Raut, S. D.; Pawar, P. P.

The mass attenuation coefficients (μm) for organic nonlinear optical materials measured at 122-1330 keV photon energies were investigated on the basis of mixture rule and compared with obtained values of WinXCOM program. It is observed that there is a good agreement between theoretical and experimental values of the samples. All samples were irradiated with six radioactive sources such as 57Co, 133Ba, 22Na, 137Cs, 54Mn and 60Co using transmission arrangement. Effective atomic and electron numbers or electron densities (Zeff and Neff), molar extinction coefficient (ε), mass energy absorption coefficient (μen/ρ) and effective atomic energy absorption cross section (σa,en) were determined experimentally and theoretically using the obtained μm values for investigated samples and graphs have been plotted. The graph shows that the variation of all samples decreases with increasing photon energy.

Quantum memory node based on a semiconductor double quantum dot in a laser-controlled optical resonator

NASA Astrophysics Data System (ADS)

Tsukanov, A. V.; Kateev, I. Yu

2017-08-01

The concept of a quantum node consisting of a memory qubit and a frequency convertor is proposed and analysed. The memory qubit is presented by a semiconductor four-level double quantum dot (DQD) placed in an optical microresonator (MR). The DQD contains an electron in the quantised part of the conduction band and the MR can be populated by a certain number of photons. The DQD and MR states are controlled be applying the laser and electrostatic fields. The difference between the telecommunication frequency of the photon (transport qubit) supplied to the system through a waveguide and the frequency of the electronic transition in the DQD is compensated for using an auxiliary element, i.e. a frequency convertor based on a single quantum dot (QD). This design allows the electron - photon state of the hybrid system to be controlled by an appropriate variation of the field parameters and the switching between resonance and nonresonance DQD and MR interaction regimes. As an example, a GaAs DQD placed in a microdisk MR is studied. A numerical technique for modelling an optical spectrum of a microdisk MR with an additional layer (AL) deposited on its surface is developed. Using this technique, the effect of the AL on the MR eigenmode properties is investigated and the possibility of tuning its frequency to the QD electronic transition frequency by depositing an AL on the disk surface is demonstrated.

Experimental characterization of an ultra-fast Thomson scattering x-ray source with three-dimensional time and frequency-domain analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuba, J; Slaughter, D R; Fittinghoff, D N

We present a detailed comparison of the measured characteristics of Thomson backscattered x-rays produced at the PLEIADES (Picosecond Laser-Electron Interaction for the Dynamic Evaluation of Structures) facility at Lawrence Livermore National Laboratory to predicted results from a newly developed, fully three-dimensional time and frequency-domain code. Based on the relativistic differential cross section, this code has the capability to calculate time and space dependent spectra of the x-ray photons produced from linear Thomson scattering for both bandwidth-limited and chirped incident laser pulses. Spectral broadening of the scattered x-ray pulse resulting from the incident laser bandwidth, perpendicular wave vector components in themore » laser focus, and the transverse and longitudinal phase space of the electron beam are included. Electron beam energy, energy spread, and transverse phase space measurements of the electron beam at the interaction point are presented, and the corresponding predicted x-ray characteristics are determined. In addition, time-integrated measurements of the x-rays produced from the interaction are presented, and shown to agree well with the simulations.« less

Temporal analysis of nonresonant two-photon coherent control involving bound and dissociative molecular states

DOE Office of Scientific and Technical Information (OSTI.GOV)

Su Jing; Chen Shaohao; Jaron-Becker, Agnieszka

We theoretically study the control of two-photon excitation to bound and dissociative states in a molecule induced by trains of laser pulses, which are equivalent to certain sets of spectral phase modulated pulses. To this end, we solve the time-dependent Schroedinger equation for the interaction of molecular model systems with an external intense laser field. Our numerical results for the temporal evolution of the population in the excited states show that, in the case of an excited dissociative state, control schemes, previously validated for the atomic case, fail due to the coupling of electronic and nuclear motion. In contrast, formore » excitation to bound states the two-photon excitation probability is controlled via the time delay and the carrier-envelope phase difference between two consecutive pulses in the train.« less

Detailed Investigations of Interactions between Ionizing Radiation and Neutral Gases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Landers, Allen L

We are investigating phenomena that stem from the many body dynamics associated with ionization of an atom or molecule by photon or charged particle. Our program is funded through the Department of Energy EPSCoR Laboratory Partnership Award in collaboration with Lawrence Berkeley National Laboratory. We are using variations on the well established COLTRIMS technique to measure ions and electrons ejected during these interactions. Photoionization measurements take place at the Advanced Light Source at LBNL as part of the ALS-COLTRIMS collaboration with the groups of Reinhard Dörner at Frankfurt and Ali Belkacem at LBNL. Additional experiments on charged particle impact aremore » conducted locally at Auburn University where we are studying the dissociative molecular dynamics following interactions with either ions or electrons over a velocity range of 1 to 12 atomic units.« less

Advances in graphene-based optoelectronics, plasmonics and photonics

NASA Astrophysics Data System (ADS)

Nguyen, Bich Ha; Hieu Nguyen, Van

2016-03-01

Since the early works on graphene it has been remarked that graphene is a marvelous electronic material. Soon after its discovery, graphene was efficiently utilized in the fabrication of optoelectronic, plasmonic and photonic devices, including graphene-based Schottky junction solar cells. The present work is a review of the progress in the experimental research on graphene-based optoelectronics, plasmonics and photonics, with the emphasis on recent advances. The main graphene-based optoelectronic devices presented in this review are photodetectors and modulators. In the area of graphene-based plasmonics, a review of the plasmonic nanostructures enhancing or tuning graphene-light interaction, as well as of graphene plasmons is presented. In the area of graphene-based photonics, we report progress on fabrication of different types of graphene quantum dots as well as functionalized graphene and graphene oxide, the research on the photoluminescence and fluorescence of graphene nanostructures as well as on the energy exchange between graphene and semiconductor quantum dots. In particular, the promising achievements of research on graphene-based Schottky junction solar cells is presented.

Photonic and Plasmonic Nanotweezing of Nano- and Microscale Particles.

PubMed

Conteduca, Donato; Dell'Olio, Francesco; Krauss, Thomas F; Ciminelli, Caterina

2017-03-01

The ability to manipulate and sense biological molecules is important in many life science domains, such as single-molecule biophysics, the development of new drugs and cancer detection. Although the manipulation of biological matter at the nanoscale continues to be a challenge, several types of nanotweezers based on different technologies have recently been demonstrated to address this challenge. In particular, photonic and plasmonic nanotweezers are attracting a strong research effort especially because they are efficient and stable, they offer fast response time, and avoid any direct physical contact with the target object to be trapped, thus preventing its disruption or damage. In this paper, we critically review photonic and plasmonic resonant technologies for biomolecule trapping, manipulation, and sensing at the nanoscale, with a special emphasis on hybrid photonic/plasmonic nanodevices allowing a very strong light-matter interaction. The state-of-the-art of competing technologies, e.g., electronic, magnetic, acoustic and carbon nanotube-based nanotweezers, and a description of their applications are also included.

Possibilities for Nuclear Photo-Science with Intense Lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barty, C J; Hartemann, F V; McNabb, D P

2006-06-26

The interaction of intense laser light with relativistic electrons can produce unique sources of high-energy x rays and gamma rays via Thomson scattering. ''Thomson-Radiated Extreme X-ray'' (T-REX) sources with peak photon brightness (photons per unit time per unit bandwidth per unit solid angle per unit area) that exceed that available from world's largest synchrotrons by more than 15 orders of magnitude are possible from optimally designed systems. Such sources offer the potential for development of ''nuclear photo-science'' applications in which the primary photon-atom interaction is with the nucleons and not the valence electrons. Applications include isotope-specific detection and imaging ofmore » materials, inverse density radiography, transmutation of nuclear waste and fundamental studies of nuclear structure. Because Thomson scattering cross sections are small, < 1 barn, the output from a T-REX source is optimized when the laser spot size and the electron spot size are minimized and when the electron and laser pulse durations are similar and short compared to the transit time through the focal region. The principle limitation to increased x-ray or gamma-ray brightness is ability to focus the electron beam. The effects of space charge on electron beam focus decrease approximately linearly with electron beam energy. For this reason, T-REX brightness increases rapidly as a function of the electron beam energy. As illustrated in Figure 1, above 100 keV these sources are unique in their ability to produce bright, narrow-beam, tunable, narrow-band gamma rays. New, intense, short-pulse, laser technologies for advanced T-REX sources are currently being developed at LLNL. The construction of a {approx}1 MeV-class machine with this technology is underway and will be used to excite nuclear resonance fluorescence in variety of materials. Nuclear resonance fluorescent spectra are unique signatures of each isotope and provide an ideal mechanism for identification of nuclear materials. With TREX it is possible to use NRF to provide high spatial resolution (micron scale) images of the isotopic distribution of all materials in a given object. Because of the high energy of the photons, imaging through dense and/or thick objects is possible. This technology will have applicability in many arenas including the survey of cargo for the presence of clandestine nuclear materials. It is also possible to address the more general radiographic challenge of imaging low-density objects that are shielded or placed behind high density objects. In this case, it is the NRF cross section and not the electron density of the material that provides contrast. Extensions of T-REX technology will be dependent upon the evolution of short pulse laser technology to high average powers. Concepts for sources that would produce 10's of kWs of gamma-rays by utilizing MW-class average-power, diode-pumped, short pulse lasers and energy recovery LINAC technology have been developed.« less

Thermo-optical interactions in a dye-microcavity photon Bose-Einstein condensate

NASA Astrophysics Data System (ADS)

Alaeian, Hadiseh; Schedensack, Mira; Bartels, Clara; Peterseim, Daniel; Weitz, Martin

2017-11-01

Superfluidity and Bose-Einstein condensation are usually considered as two closely related phenomena. Indeed, in most macroscopic quantum systems, like liquid helium, ultracold atomic Bose gases, and exciton-polaritons, condensation and superfluidity occur in parallel. In photon Bose-Einstein condensates realized in the dye microcavity system, thermalization does not occur by direct interaction of the condensate particles as in the above described systems, i.e. photon-photon interactions, but by absorption and re-emission processes on the dye molecules, which act as a heat reservoir. Currently, there is no experimental evidence for superfluidity in the dye microcavity system, though effective photon interactions have been observed from thermo-optic effects in the dye medium. In this work, we theoretically investigate the implications of effective thermo-optic photon interactions, a temporally delayed and spatially non-local effect, on the photon condensate, and derive the resulting Bogoliubov excitation spectrum. The calculations suggest a linear photon dispersion at low momenta, fulfilling the Landau’s criterion of superfluidity. We envision that the temporally delayed and long-range nature of the thermo-optic photon interaction offer perspectives for novel quantum fluid phenomena.

Engineering Photon-Photon Interactions within Rubidium-Filled Waveguides

NASA Astrophysics Data System (ADS)

Perrella, C.; Light, P. S.; Vahid, S. Afshar; Benabid, F.; Luiten, A. N.

2018-04-01

Strong photon-photon interactions are a required ingredient for deterministic two-photon optical quantum logic gates. Multiphoton transitions in dense atomic vapors have been shown to be a promising avenue for producing such interactions. The strength of a multiphoton interaction can be enhanced by conducting the interaction in highly confined geometries such as small-cross-section optical waveguides. We demonstrate, both experimentally and theoretically, that the strength of such interactions scale only with the optical mode diameter, d , not d2 as might be initially expected. This weakening of the interaction arises from atomic motion inside the waveguides. We create an interaction between two optical signals, at 780 and 776 nm, using the 5 S1 /2→5 D5 /2 two-photon transition in rubidium vapor within a range of hollow-core fibers with different core sizes. The interaction strength is characterized by observing the absorption and phase shift induced on the 780-nm beam, which is in close agreement with theoretical modeling that accounts for the atomic motion inside the fibers. These observations demonstrate that transit-time effects upon multiphoton transitions are of key importance when engineering photon-photon interactions within small-cross-section waveguides that might otherwise be thought to lead to enhanced optical nonlinearity through increased intensities.

Modulated method for efficient, narrow-bandwidth, laser Compton X-ray and gamma-ray sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barty, Christopher P. J.

A method of x-ray and gamma-ray generation via laser Compton scattering uses the interaction of a specially-formatted, highly modulated, long duration, laser pulse with a high-frequency train of high-brightness electron bunches to both create narrow bandwidth x-ray and gamma-ray sources and significantly increase the laser to Compton photon conversion efficiency.

Method for efficient, narrow-bandwidth, laser compton x-ray and gamma-ray sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barty, Christopher P. J.

A method of x-ray and gamma-ray generation via laser Compton scattering uses the interaction of a specially-formatted, highly modulated, long duration, laser pulse with a high-frequency train of high-brightness electron bunches to both create narrow bandwidth x-ray and gamma-ray sources and significantly increase the laser to Compton photon conversion efficiency.

Two-photon coincident emission from thick targets for 70-keV incident electrons

NASA Astrophysics Data System (ADS)

Liu, J.; Kahler, D. L.; Quarles, C. A.

1993-04-01

Two-photon coincidence yields have been measured in thick targets of C, Al, Ag, and Ta for 70 keV incident electrons and photons radiated at +/-45° to the incident beam. A theoretical model, which is more rigorous, has been developed to simulate the two-photon processes of coherent thick-target double bremsstrahlung (TTDB) and the incoherent emission of two single-bremsstrahlung (SBSB) photons in a thick-target environment. The model is based on an integration of the thin-target cross sections over the target thickness taking into account electron energy loss, electron backscattering, and photon attenuation. It predicts a yield that is much lower than that of the previous model. The prediction of the model fits the present experimental data well by adjusting the relative weight of the two competing processes, and we find that TTDB dominates at low Z and incoherent SBSB dominates at higher Z.

Enhancing a slow and weak optomechanical nonlinearity with delayed quantum feedback

NASA Astrophysics Data System (ADS)

Wang, Zhaoyou; Safavi-Naeini, Amir H.

2017-07-01

A central goal of quantum optics is to generate large interactions between single photons so that one photon can strongly modify the state of another one. In cavity optomechanics, photons interact with the motional degrees of freedom of an optical resonator, for example, by imparting radiation pressure forces on a movable mirror or sensing minute fluctuations in the position of the mirror. Here, we show that the optical nonlinearity arising from these effects, typically too small to operate on single photons, can be sufficiently enhanced with feedback to generate large interactions between single photons. We propose a protocol that allows photons propagating in a waveguide to interact with each other through multiple bounces off an optomechanical system. The protocol is analysed by evolving the full many-body quantum state of the waveguide-coupled system, illustrating that large photon-photon interactions mediated by mechanical motion may be within experimental reach.

Radiative corrections to elastic proton-electron scattering measured in coincidence

NASA Astrophysics Data System (ADS)

Gakh, G. I.; Konchatnij, M. I.; Merenkov, N. P.; Tomasi-Gustafsson, E.

2017-05-01

The differential cross section for elastic scattering of protons on electrons at rest is calculated, taking into account the QED radiative corrections to the leptonic part of interaction. These model-independent radiative corrections arise due to emission of the virtual and real soft and hard photons as well as to vacuum polarization. We analyze an experimental setup when both the final particles are recorded in coincidence and their energies are determined within some uncertainties. The kinematics, the cross section, and the radiative corrections are calculated and numerical results are presented.

Wavelength dependent photoelectron circular dichroism of limonene studied by femtosecond multiphoton laser ionization and electron-ion coincidence imaging

NASA Astrophysics Data System (ADS)

Rafiee Fanood, Mohammad M.; Janssen, Maurice H. M.; Powis, Ivan

2016-09-01

Enantiomers of the monoterpene limonene have been investigated by (2 + 1) resonance enhanced multiphoton ionization and photoelectron circular dichroism employing tuneable, circularly polarized femtosecond laser pulses. Electron imaging detection provides 3D momentum measurement while electron-ion coincidence detection can be used to mass-tag individual electrons. Additional filtering, by accepting only parent ion tagged electrons, can be then used to provide discrimination against higher energy dissociative ionization mechanisms where more than three photons are absorbed to better delineate the two photon resonant, one photon ionization pathway. The promotion of different vibrational levels and, tentatively, different electronic ion core configurations in the intermediate Rydberg states can be achieved with different laser excitation wavelengths (420 nm, 412 nm, and 392 nm), in turn producing different state distributions in the resulting cations. Strong chiral asymmetries in the lab frame photoelectron angular distributions are quantified, and a comparison made with a single photon (synchrotron radiation) measurement at an equivalent photon energy.

Electron heated target temperature measurements in petawatt laser experiments based on extreme ultraviolet imaging and spectroscopy.

PubMed

Ma, T; Beg, F N; MacPhee, A G; Chung, H-K; Key, M H; Mackinnon, A J; Patel, P K; Hatchett, S; Akli, K U; Stephens, R B; Chen, C D; Freeman, R R; Link, A; Offermann, D T; Ovchinnikov, V; Van Woerkom, L D

2008-10-01

Three independent methods (extreme ultraviolet spectroscopy, imaging at 68 and 256 eV) have been used to measure planar target rear surface plasma temperature due to heating by hot electrons. The hot electrons are produced by ultraintense laser-plasma interactions using the 150 J, 0.5 ps Titan laser. Soft x-ray spectroscopy in the 50-400 eV region and imaging at the 68 and 256 eV photon energies give a planar deuterated carbon target rear surface pre-expansion temperature in the 125-150 eV range, with the rear plasma plume averaging a temperature approximately 74 eV.

An evaluation of ionizing radiation emitted by high power microwave generators

NASA Astrophysics Data System (ADS)

Lovell, C. David; Bolch, W. Emmett

1992-02-01

Ionizing radiation emitted by electron-beam driven high power microwave (HPM) generators were measured in the near and far-field using lithium fluoride (LiF) thermoluminescent dosimeters (TLD's). Simplified photon energy spectra were determined by measuring radiation transmission, at electron beam energies of 300 to 650 keV, through various thicknesses of steel and lead attenuators. These data were used to calculate the effective energy of the x-rays produced by interactions between the electrons and the walls or other structures of the HPM generators. Operators were polled to determine locations of burn marks or other visible damage to locate potential ionizing radiation source regions.

Graphene-based terahertz photodetector by noise thermometry technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Ming-Jye, E-mail: mingjye@asiss.sinica.edu.tw; Institute of Physics, Academia Sinica, Taipei 11529, Taiwan; Wang, Ji-Wun

2014-01-20

We report the characteristics of graphene-based terahertz (THz) photodetector based on noise thermometry technique by measuring its noise power at frequency from 4 to 6 GHz. Hot electron system in graphene microbridge is generated after THz photon pumping and creates extra noise power. The equivalent noise temperature and electron temperature increase rapidly in low THz pumping regime and saturate gradually in high THz power regime which is attributed to a faster energy relaxation process involved by stronger electron-phonon interaction. Based on this detector, a conversion efficiency around 0.15 from THz power to noise power in 4–6 GHz span has been achieved.

Calibration of a time-resolved hard-x-ray detector using radioactive sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stoeckl, C., E-mail: csto@lle.rochester.edu; Theobald, W.; Regan, S. P.

A four-channel, time-resolved, hard x-ray detector (HXRD) has been operating at the Laboratory for Laser Energetics for more than a decade. The slope temperature of the hot-electron population in direct-drive inertial confinement fusion experiments is inferred by recording the hard x-ray radiation generated in the interaction of the electrons with the target. Measuring the energy deposited by hot electrons requires an absolute calibration of the hard x-ray detector. A novel method to obtain an absolute calibration of the HXRD using single photons from radioactive sources was developed, which uses a thermoelectrically cooled, low-noise, charge-sensitive amplifier.

Nonlinear two-dimensional terahertz photon echo and rotational spectroscopy in the gas phase.

PubMed

Lu, Jian; Zhang, Yaqing; Hwang, Harold Y; Ofori-Okai, Benjamin K; Fleischer, Sharly; Nelson, Keith A

2016-10-18

Ultrafast 2D spectroscopy uses correlated multiple light-matter interactions for retrieving dynamic features that may otherwise be hidden under the linear spectrum; its extension to the terahertz regime of the electromagnetic spectrum, where a rich variety of material degrees of freedom reside, remains an experimental challenge. We report a demonstration of ultrafast 2D terahertz spectroscopy of gas-phase molecular rotors at room temperature. Using time-delayed terahertz pulse pairs, we observe photon echoes and other nonlinear signals resulting from molecular dipole orientation induced by multiple terahertz field-dipole interactions. The nonlinear time domain orientation signals are mapped into the frequency domain in 2D rotational spectra that reveal J-state-resolved nonlinear rotational dynamics. The approach enables direct observation of correlated rotational transitions and may reveal rotational coupling and relaxation pathways in the ground electronic and vibrational state.

Diagnostics for the optimization of an 11 keV inverse Compton scattering x-ray source

NASA Astrophysics Data System (ADS)

Chauchat, A.-S.; Brasile, J.-P.; Le Flanchec, V.; Nègre, J.-P.; Binet, A.; Ortega, J.-M.

2013-04-01

In a scope of a collaboration between Thales Communications & Security and CEA DAM DIF, 11 keV Xrays were produced by inverse Compton scattering on the ELSA facility. In this type of experiment, X-ray observation lies in the use of accurate electron and laser beam interaction diagnostics and on fitted X-ray detectors. The low interaction probability between < 100 μm width, 12 ps [rms] length electron and photon pulses requires careful optimization of pulse spatial and temporal covering. Another issue was to observe 11 keV X-rays in the ambient radioactive noise of the linear accelerator. For that, we use a very sensitive detection scheme based on radio luminescent screens.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hartemann, F V; Albert, F; Anderson, S G

Nuclear photonics is an emerging field of research requiring new tools, including high spectral brightness, tunable gamma-ray sources; high photon energy, ultrahigh-resolution crystal spectrometers; and novel detectors. This presentation focuses on the precision linac technology required for Compton scattering gamma-ray light sources, and on the optimization of the laser and electron beam pulse format to achieve unprecedented spectral brightness. Within this context, high-gradient X-band technology will be shown to offer optimal performance in a compact package, when used in conjunction with the appropriate pulse format, and photocathode illumination and interaction laser technologies. The nascent field of nuclear photonics is enabledmore » by the recent maturation of new technologies, including high-gradient X-band electron acceleration, robust fiber laser systems, and hyper-dispersion CPA. Recent work has been performed at LLNL to demonstrate isotope-specific detection of shielded materials via NRF using a tunable, quasi-monochromatic Compton scattering gamma-ray source operating between 0.2 MeV and 0.9 MeV photon energy. This technique is called Fluorescence Imaging in the Nuclear Domain with Energetic Radiation (or FINDER). This work has, among other things, demonstrated the detection of {sup 7}Li shielded by Pb, utilizing gamma rays generated by a linac-driven, laser-based Compton scattering gamma-ray source developed at LLNL. Within this context, a new facility is currently under construction at LLNL, with the goal of generating tunable {gamma}-rays in the 0.5-2.5 MeV photon energy range, at a repetition rate of 120 Hz, and with a peak brightness in the 10{sup 20} photons/(s x mm{sup 2} x mrad{sup 2} x 0.1% bw).« less

VUV and soft x-ray ionization of a plant volatile: Vanillin (C{sub 8}H{sub 8}O{sub 3})

DOE Office of Scientific and Technical Information (OSTI.GOV)

Betancourt, A. Moreno; Moura, C. E. V. de; Rocha, A. B.

2016-03-21

Plant volatiles are emitted by plants in response to several forms of stress, including interaction with energetic photons. In the present work, we discuss the interaction of extreme UV and soft X-ray photons with a plant volatile, vanillin. The single and double (multiple) ionization of the vanillin molecule have been studied for the first time using time-of-flight mass spectrometry and VUV and soft X-ray photons (synchrotron radiation, at 12.0 eV, 21.2 eV, 130 eV, 310 eV, 531 eV, and 550 eV). At 12.0 and 21.2 eV, only singly charged species are observed and the parent ion, C{sub 8}H{sub 8}O{sub 3}{supmore » +}, is the dominant species. Energy differences for some selected fragments were calculated theoretically in this energy region. At 130 eV, direct double and triple ionization of the valence electrons may occur. The fragmentation increases and CHO{sup +} becomes one of the main cations in the mass spectrum. The molecular ion is still the dominant species, but other fragments, such as C{sub 6}H{sub 5}O{sup +}, begin to present similar intensities. At 310 eV, C 1s electrons may be ionized and Auger processes give rise to dissociative doubly ionized cations. Ionization around the O 1s edge has been studied both at the 531 eV resonance and above the ionization edge. Resonant and normal Auger processes play a significant role in each case and a large fragmentation of the molecule is observed at both photon energies, with intense fragments such as CHO{sup +} and CH{sub 3}{sup +} being clearly observed. A near edge X-ray absorption fine structure spectrum of the vanillin molecule was obtained around the O 1s ionization threshold. In addition, the fragmentation of vanillin has also been studied using a fast beam of electrons (800 eV), for the sake of comparison.« less

A gamma-ray burst with a high-energy spectral component inconsistent with the synchrotron shock model.

PubMed

González, M M; Dingus, B L; Kaneko, Y; Preece, R D; Dermer, C D; Briggs, M S

2003-08-14

Gamma-ray bursts are among the most powerful events in nature. These events release most of their energy as photons with energies in the range from 30 keV to a few MeV, with a smaller fraction of the energy radiated in radio, optical, and soft X-ray afterglows. The data are in general agreement with a relativistic shock model, where the prompt and afterglow emissions correspond to synchrotron radiation from shock-accelerated electrons. Here we report an observation of a high-energy (multi-MeV) spectral component in the burst of 17 October 1994 that is distinct from the previously observed lower-energy gamma-ray component. The flux of the high-energy component decays more slowly and its fluence is greater than the lower-energy component; it is described by a power law of differential photon number index approximately -1 up to about 200 MeV. This observation is difficult to explain with the standard synchrotron shock model, suggesting the presence of new phenomena such as a different non-thermal electron process, or the interaction of relativistic protons with photons at the source.

Study of photon emission by electron capture during solar nuclei acceleration. 3: Photon production evaluations

NASA Technical Reports Server (NTRS)

Perez-Peraza, J.; Alvarez, M.; Gallegos, A.

1985-01-01

Lower limits of photon fluxes were evaluated from electron capture during acceleration in solar flares, because the arbitrary q sub c asterisk assumed in this work evolves very slow with velocity, probably much more slowly than the physical actual situation: in fact, more emission is expected toward the IR region. Nevertheless the authors claim to show that the factibility of sounding acceleration processes, charge evolution processes and physical parameters of the source itself, by the observational analysis of this kind of emissions. For instance, it would be interesting to search observationally, for the predicted flux and energy drift of F sub e ions interacting with the atomic 0 and F sub e of the source matter, or, even more feasible for the X-ray lines at 4.2 keV and 2.624 + 0.003 KeV from Fe and S ions in ionized Fe at T = 10 to the 7th power K respectively, the 418 + or - 2 eV and 20 + or - 4 eV lines of Fe and S in ionized Fe at 5 x 10 to the 6th power K, which are predicted from Fermi acceleration.

Modification and benchmarking of MCNP for low-energy tungsten spectra.

PubMed

Mercier, J R; Kopp, D T; McDavid, W D; Dove, S B; Lancaster, J L; Tucker, D M

2000-12-01

The MCNP Monte Carlo radiation transport code was modified for diagnostic medical physics applications. In particular, the modified code was thoroughly benchmarked for the production of polychromatic tungsten x-ray spectra in the 30-150 kV range. Validating the modified code for coupled electron-photon transport with benchmark spectra was supplemented with independent electron-only and photon-only transport benchmarks. Major revisions to the code included the proper treatment of characteristic K x-ray production and scoring, new impact ionization cross sections, and new bremsstrahlung cross sections. Minor revisions included updated photon cross sections, electron-electron bremsstrahlung production, and K x-ray yield. The modified MCNP code is benchmarked to electron backscatter factors, x-ray spectra production, and primary and scatter photon transport.

Photoinduced Electron Transfer in the Strong Coupling Regime: Waveguide-Plasmon Polaritons.

PubMed

Zeng, Peng; Cadusch, Jasper; Chakraborty, Debadi; Smith, Trevor A; Roberts, Ann; Sader, John E; Davis, Timothy J; Gómez, Daniel E

2016-04-13

Reversible exchange of photons between a material and an optical cavity can lead to the formation of hybrid light-matter states where material properties such as the work function [ Hutchison et al. Adv. Mater. 2013 , 25 , 2481 - 2485 ], chemical reactivity [ Hutchison et al. Angew. Chem., Int. Ed. 2012 , 51 , 1592 - 1596 ], ultrafast energy relaxation [ Salomon et al. Angew. Chem., Int. Ed. 2009 , 48 , 8748 - 8751 ; Gomez et al. J. Phys. Chem. B 2013 , 117 , 4340 - 4346 ], and electrical conductivity [ Orgiu et al. Nat. Mater. 2015 , 14 , 1123 - 1129 ] of matter differ significantly to those of the same material in the absence of strong interactions with the electromagnetic fields. Here we show that strong light-matter coupling between confined photons on a semiconductor waveguide and localized plasmon resonances on metal nanowires modifies the efficiency of the photoinduced charge-transfer rate of plasmonic derived (hot) electrons into accepting states in the semiconductor material. Ultrafast spectroscopy measurements reveal a strong correlation between the amplitude of the transient signals, attributed to electrons residing in the semiconductor and the hybridization of waveguide and plasmon excitations.

Comparing gold nano-particle enhanced radiotherapy with protons, megavoltage photons and kilovoltage photons: a Monte Carlo simulation.

PubMed

Lin, Yuting; McMahon, Stephen J; Scarpelli, Matthew; Paganetti, Harald; Schuemann, Jan

2014-12-21

Gold nanoparticles (GNPs) have shown potential to be used as a radiosensitizer for radiation therapy. Despite extensive research activity to study GNP radiosensitization using photon beams, only a few studies have been carried out using proton beams. In this work Monte Carlo simulations were used to assess the dose enhancement of GNPs for proton therapy. The enhancement effect was compared between a clinical proton spectrum, a clinical 6 MV photon spectrum, and a kilovoltage photon source similar to those used in many radiobiology lab settings. We showed that the mechanism by which GNPs can lead to dose enhancements in radiation therapy differs when comparing photon and proton radiation. The GNP dose enhancement using protons can be up to 14 and is independent of proton energy, while the dose enhancement is highly dependent on the photon energy used. For the same amount of energy absorbed in the GNP, interactions with protons, kVp photons and MV photons produce similar doses within several nanometers of the GNP surface, and differences are below 15% for the first 10 nm. However, secondary electrons produced by kilovoltage photons have the longest range in water as compared to protons and MV photons, e.g. they cause a dose enhancement 20 times higher than the one caused by protons 10 μm away from the GNP surface. We conclude that GNPs have the potential to enhance radiation therapy depending on the type of radiation source. Proton therapy can be enhanced significantly only if the GNPs are in close proximity to the biological target.

STIC: Photonic Quantum Computation through Cavity Assisted Interaction

DTIC Science & Technology

2007-12-28

PRA ; available as quant-ph/06060791. Report for the grant “Photonic Quantum Computation through Cavity Assisted Interaction” from DTO Luming Duan...cavity •B. Wang, L.-M. Duan, PRA 72 (in press, 2005) Single-photon source Photonic Quantum Computation through Cavity-Assisted Interaction H. Jeff Kimble...interaction [Duan, Wang, Kimble, PRA 05] • “Investigate more efficient methods for combating noise in photonic quantum computation ” • Partial progress

Astronomy and Space Technologies, Photonics Applications and Web Engineering, Wilga, May 2012

NASA Astrophysics Data System (ADS)

Romaniuk, Ryszard S.

2012-05-01

This paper is the first part (out of five) of the research survey of WILGA Symposium work, May 2012 Edition, concerned with photonics and electronics applications in astronomy and space technologies. It presents a digest of chosen technical work results shown by young researchers from different technical universities from this country during the Jubilee XXXth SPIE-IEEE Wilga 2012, May Edition, symposium on Photonics and Web Engineering. Topical tracks of the symposium embraced, among others, nanomaterials and nanotechnologies for photonics, sensory and nonlinear optical fibers, object oriented design of hardware, photonic metrology, optoelectronics and photonics applications, photonics-electronics co-design, optoelectronic and electronic systems for astronomy and high energy physics experiments, JET tokamak and pi-of-the sky experiments development. The symposium is an annual summary in the development of numerable Ph.D. theses carried out in this country in the area of advanced electronic and photonic systems. It is also a great occasion for SPIE, IEEE, OSA and PSP students to meet together in a large group spanning the whole country with guests from this part of Europe. A digest of Wilga references is presented [1-275].

Dosimetric characteristics of a new unshielded silicon diode and its application in clinical photon and electron beams.

PubMed

Griessbach, Irmgard; Lapp, Markus; Bohsung, Jörg; Gademann, Günther; Harder, Dietrich

2005-12-01

Shielded p-silicon diodes, frequently applied in general photon-beam dosimetry, show certain imperfections when applied in the small photon fields occurring in stereotactic or intensity modulated radiotherapy (IMRT), in electron beams and in the buildup region of photon beam dose distributions. Using as a study object the shielded p-silicon diode PTW 60008, well known for its reliable performance in general photon dosimetry, we have identified these imperfections as effects of electron scattering at the metallic parts of the shielding. In order to overcome these difficulties a new, unshielded diode PTW 60012 has been designed and manufactured by PTW Freiburg. By comparison with reference detectors, such as thimble and plane-parallel ionization chambers and a diamond detector, we could show the absence of these imperfections. An excellent performance of the new unshielded diode for the special dosimetric tasks in small photon fields, electron beams and build-up regions of photon beams has been observed. The new diode also has an improved angular response. However, due to its over-response to low-energy scattered photons, its recommended range of use does not include output factor measurements in large photon fields, although this effect can be compensated by a thin auxiliary lead shield.

Modeling and experimental investigation of x-ray spectra from a liquid metal anode x-ray tube

NASA Astrophysics Data System (ADS)

David, Bernd R.; Thran, Axel; Eckart, Rainer

2004-11-01

This paper presents simulated and measured spectra of a novel type of x-ray tube. The bremsstrahlung generating principle of this tube is based on the interaction of high energetic electrons with a turbulently flowing liquid metal separated from the vacuum by a thin window. We simulated the interaction of 50-150 keV electrons with liquid metal targets composed of the elements Ga, In, Sn, as well as the solid elements C, W and Re used for the electron windows. We obtained x-ray spectra and energy loss curves for various liquid metal/window combinations and thicknesses of the window material. In terms of optimum heat transport a thin diamond window in combination with the liquid metal GaInSn is the best suited system. If photon flux is the optimization criteria, thin tungsten/rhenium windows cooled by GaInSn should be preferred.

Production and dosimetry of simultaneous therapeutic photons and electrons beam by linear accelerator: A Monte Carlo study

NASA Astrophysics Data System (ADS)

Khledi, Navid; Arbabi, Azim; Sardari, Dariush; Mohammadi, Mohammad; Ameri, Ahmad

2015-02-01

Depending on the location and depth of tumor, the electron or photon beams might be used for treatment. Electron beam have some advantages over photon beam for treatment of shallow tumors to spare the normal tissues beyond of the tumor. In the other hand, the photon beam are used for deep targets treatment. Both of these beams have some limitations, for example the dependency of penumbra with depth, and the lack of lateral equilibrium for small electron beam fields. In first, we simulated the conventional head configuration of Varian 2300 for 16 MeV electron, and the results approved by benchmarking the Percent Depth Dose (PDD) and profile of the simulation and measurement. In the next step, a perforated Lead (Pb) sheet with 1mm thickness placed at the top of the applicator holder tray. This layer producing bremsstrahlung x-ray and a part of the electrons passing through the holes, in result, we have a simultaneous mixed electron and photon beam. For making the irradiation field uniform, a layer of steel placed after the Pb layer. The simulation was performed for 10×10, and 4×4 cm2 field size. This study was showed the advantages of mixing the electron and photon beam by reduction of pure electron's penumbra dependency with the depth, especially for small fields, also decreasing of dramatic changes of PDD curve with irradiation field size.

Evaluation of Mineral Content and Photon Interaction Parameters of Dental Enamel After Phosphoric Acid and Er:YAG Laser Treatment.

PubMed

Simsek, Huseyin; Gurbuz, Taskın; Buyuk, Suleyman Kutalmış; Ozdemir, Yuksel

2017-05-01

The purpose of this study was to evaluate the effects of laser and acid etching on the mineral content and photon interaction parameters of dental enamel in human teeth. The composition of dental enamel may vary, especially at the surface, depending on the reactions that occur during dental treatment. Forty maxillary premolars were divided randomly into 2 groups of 20 teeth. In the first group, half of teeth crowns were etched by using 37% phosphoric acid; in the second group, half of teeth crowns were etched by using an erbium:yttrium-aluminum-garnet (Er:YAG) laser. The remaining half crowns in each group were used as untreated controls. We characterized the calcium (Ca), phosphorus (P), magnesium (Mg), sodium (Na), and potassium (K) contents in each specimen by using wavelength dispersive X-ray fluorescence spectrometry. The total atomic cross-section ([Formula: see text]), effective atomic number ([Formula: see text]), and electron density (N e ) of the tooth samples were determined at photon energies of 22.1, 25, 59.5, and 88 keV by using a narrow beam transmission method. Data were analyzed statistically by using the Mann-Whitney U test. The mineral contents after Er:YAG laser and phosphoric acid etching did not differ significantly (p > 0.05), and no significant variation in [Formula: see text], [Formula: see text], or N e was observed. Therefore, we conclude that the Er:YAG laser and phosphoric acid systems used in this study did not affect mineral composition or photon interaction parameters of dental enamel.

Single-chain behavior of poly(3-hexylthiophene)

NASA Astrophysics Data System (ADS)

Ivanov, Momchil; Gross, Jonathan; Janke, Wolfhard

2017-03-01

Poly(3-hexylthiophene) (P3HT) has been in the focus of recent studies due to its promising future use in organic photovoltaics, electronics and photonics. Recent publications investigate the melt behavior of P3HT, its interaction with other molecules, mainly various fullerene derivates, and isolated chains interacting with substrates. In this work we lay the focus on the single-chain properties of P3HT in vacuum. We compare structural properties obtained from simulations using two coarse-grained models and an atomistic model of the polymer for various chain lengths and temperatures.

SU-C-206-01: Impact of Charge Sharing Effect On Sub-Pitch Resolution for CZT-Based Photon Counting CT Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, X; Cheng, Z; Deen, J

Purposes: Photon counting CT is a new imaging technology that can provide tissue composition information such as calcium/iodine content quantification. Cadmium zinc telluride CZT is considered a good candidate the photon counting CT due to its relatively high atomic number and band gap. One potential challenge is the degradation of both spatial and energy resolution as the fine electrode pitch is deployed (<50 µm). We investigated the extent of charge sharing effect as functions of gap width, bias voltage and depth-of-interaction (DOI). Methods: The initial electron cloud size and diffusion process were modeled analytically. The valid range of charge sharingmore » effect refers to the range over which both signals of adjacent electrodes are above the triggering threshold (10% of the amplitude of 60keV X-ray photons). The intensity ratios of output in three regions (I1/I2/I3: left pixel, gap area and right pixel) were calculated. With Gaussian white noises modeled (a SNR of 5 based upon the preliminary experiments), the sub-pitch resolution as a function of the spatial position in-between two pixels was studied. Results: The valid range of charge sharing increases linearly with depth-of-interaction (DOI) but decreases with gap width and bias voltage. For a 1.5mm thickness CZT detector (pitch: 50µm, bias: 400 V), the range increase from ∼90µm up to ∼110µm. Such an increase can be attributed to a longer travel distance and the associated electron cloud broadening. The achievable sub-pitch resolution is in the range of ∼10–30µm. Conclusion: The preliminary results demonstrate that sub-pixel spatial resolution can be achieved using the ratio of amplitudes of two neighboring pixels. Such ratio may also be used to correct charge loss and help improve energy resolution of a CZT detector. The impact of characteristic X-rays hitting adjacent pixels (i.e., multiple interaction) on charge sharing is currently being investigated.« less

Plan of production of MeV laser electron photons at SPring-8

NASA Astrophysics Data System (ADS)

Arimoto, Y.; Ohkuma, H.; Suzuki, S.; Tamura, K.; Kumagai, N.; Okajima, S.; Fujiwara, M.

2001-10-01

MeV photons at SPring-8 are produced by backward Compton scattering (BCS) of far infrared (FIR) laser photons from a 8 GeV electron beam. The MeV photons are a powerful probe to study nuclear physics, astro-nuclear physics, nuclear engineering, condensed matter physics, etc. owing to their attractive properties such as small emittance, high intensity, high polarization, etc. The 10 MeV photons which can be produced by the BCS process between the 8 GeV electron of SPring-8 storage ring and FIR laser photons with a wavelength of ~100 μm have a great advantage. Since energy loss of the electron due to the BCS process is smaller than energy acceptance of the storage ring (±160 MeV), the stored electron beam is not lost. A stable CO_2-pumped FIR laser with the wavelength of ~100 μm is practically using as a probe of plasma diagnostics at a nuclear fusion reactor. Furthermore, since the laser has many oscillations in wide wavelength region, the BCS photons in wide range can be obtained. We plan to produce the MeV laser electron photons by the BCS at SPring-8. For these purpose, we are now developing a high power CO_2-pumped FIR laser. Up to now ~1.5 watts CW laser action at a wavelength of 118.8 μm has been achieved. In this meeting, we will present a current status of the FIR laser system, a plan of construction of the test beam-line for the production of MeV photons at SPring-8, and future plan of this project.

Wilga Photonics and Web Engineering 2011

NASA Astrophysics Data System (ADS)

Romaniuk, Ryszard S.

2011-10-01

The paper presents a digest of chosen technical work results shown by young researchers from different technical universities from this country during the SPIE-IEEE Wilga 2011 symposium on Photonics and Web Engineering. Topical tracks of the symposium embraced, among others, nanomaterials and nanotechnologies for photonics, sensory and nonlinear optical fibers, object oriented design of hardware, photonic metrology, optoelectronics and photonics applications, photonics-electronics co-design, optoelectronic and electronic systems for astronomy and high energy physics experiments, JET and pi-of-the sky experiments development. The symposium is an annual summary in the development of numerable Ph.D. theses carried out in this country in the area of advanced electronic and photonic systems. It is also a great occasion for SPIE, IEEE, OSA and PSP students to meet together in a large group spanning the whole country with guests from this part of Europe. A digest of Wilga references is presented [1-225].

WILGA Photonics and Web Engineering, January 2012

NASA Astrophysics Data System (ADS)

Romaniuk, Ryszard S.

2012-05-01

The paper presents a digest of chosen technical work results shown by young researchers from technical universities during the SPIE-IEEE Wilga January 2012 Symposium on Photonics and Web Engineering. Topical tracks of the symposium embraced, among others, new technologies for photonics, sensory and nonlinear optical fibers, object oriented design of hardware, photonic metrology, optoelectronics and photonics applications, photonics-electronics codesign, optoelectronic and electronic systems for astronomy and high energy physics experiments, JET and pi-of-the sky experiments development. The symposium held two times a year is a summary in the development of numerable Ph.D. theses carried out in this country in the area of advanced electronic and photonic systems. It is also a great occasion for SPIE, IEEE, OSA and PSP students to meet together in a large group spanning the whole country with guests from this part of Europe. A digest of chosen Wilga references is presented [1-268].

Photonics Applications and Web Engineering: WILGA 2017

NASA Astrophysics Data System (ADS)

Romaniuk, Ryszard S.

2017-08-01

XLth Wilga Summer 2017 Symposium on Photonics Applications and Web Engineering was held on 28 May-4 June 2017. The Symposium gathered over 350 participants, mainly young researchers active in optics, optoelectronics, photonics, modern optics, mechatronics, applied physics, electronics technologies and applications. There were presented around 300 oral and poster papers in a few main topical tracks, which are traditional for Wilga, including: bio-photonics, optical sensory networks, photonics-electronics-mechatronics co-design and integration, large functional system design and maintenance, Internet of Things, measurement systems for astronomy, high energy physics experiments, and other. The paper is a traditional introduction to the 2017 WILGA Summer Symposium Proceedings, and digests some of the Symposium chosen key presentations. This year Symposium was divided to the following topical sessions/conferences: Optics, Optoelectronics and Photonics, Computational and Artificial Intelligence, Biomedical Applications, Astronomical and High Energy Physics Experiments Applications, Material Research and Engineering, and Advanced Photonics and Electronics Applications in Research and Industry.

Brilliant petawatt gamma-ray pulse generation in quantum electrodynamic laser-plasma interaction

PubMed Central

Chang, H. X.; Qiao, B.; Huang, T. W.; Xu, Z.; Zhou, C. T.; Gu, Y. Q.; Yan, X. Q.; Zepf, M.; He, X. T.

2017-01-01

We show a new resonance acceleration scheme for generating ultradense relativistic electron bunches in helical motions and hence emitting brilliant vortical γ-ray pulses in the quantum electrodynamic (QED) regime of circularly-polarized (CP) laser-plasma interactions. Here the combined effects of the radiation reaction recoil force and the self-generated magnetic fields result in not only trapping of a great amount of electrons in laser-produced plasma channel, but also significant broadening of the resonance bandwidth between laser frequency and that of electron betatron oscillation in the channel, which eventually leads to formation of the ultradense electron bunch under resonant helical motion in CP laser fields. Three-dimensional PIC simulations show that a brilliant γ-ray pulse with unprecedented power of 6.7 PW and peak brightness of 1025 photons/s/mm2/mrad2/0.1% BW (at 15 MeV) is emitted at laser intensity of 1.9 × 1023 W/cm2. PMID:28338010

The design of the electron beam dump unit of Turkish Accelerator Center (TAC)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cite, L. H., E-mail: hcite@gantep.edu.tr; Yilmaz, M., E-mail: Mustafa.Yilmaz@gaziantep.edu.tr

The required simulations of the electron beam interactions for the design of electron beam dump unit for an accelerator which will operate to get two Infra-Red Free Electron Lasers (IR-FEL) covering the range of 3-250 microns is presented in this work. Simulations have been carried out to understand the interactions of a bulk of specially shaped of four different and widely used materials for the dump materials for a 77 pC, 40 MeV, 13 MHz repetition rate e-beam. In the simulation studies dump materials are chosen to absorb the 99% of the beam energy and to restrict the radio-isotope production in themore » bulk of the dump. A Lead shielding also designed around the dump core to prevent the leakage out of the all the emitted secondary radiations, e.g., neutrons, photons. The necessary dump material requirements, for the overall design considerations and the possible radiation originated effects on the dump unit, are discussed and presented.« less

Large thermoelectric power factor from crystal symmetry-protected non-bonding orbital in half-Heuslers.

PubMed

Zhou, Jiawei; Zhu, Hangtian; Liu, Te-Huan; Song, Qichen; He, Ran; Mao, Jun; Liu, Zihang; Ren, Wuyang; Liao, Bolin; Singh, David J; Ren, Zhifeng; Chen, Gang

2018-04-30

Modern society relies on high charge mobility for efficient energy production and fast information technologies. The power factor of a material-the combination of electrical conductivity and Seebeck coefficient-measures its ability to extract electrical power from temperature differences. Recent advancements in thermoelectric materials have achieved enhanced Seebeck coefficient by manipulating the electronic band structure. However, this approach generally applies at relatively low conductivities, preventing the realization of exceptionally high-power factors. In contrast, half-Heusler semiconductors have been shown to break through that barrier in a way that could not be explained. Here, we show that symmetry-protected orbital interactions can steer electron-acoustic phonon interactions towards high mobility. This high-mobility regime enables large power factors in half-Heuslers, well above the maximum measured values. We anticipate that our understanding will spark new routes to search for better thermoelectric materials, and to discover high electron mobility semiconductors for electronic and photonic applications.

Enhancing a slow and weak optomechanical nonlinearity with delayed quantum feedback

PubMed Central

Wang, Zhaoyou; Safavi-Naeini, Amir H.

2017-01-01

A central goal of quantum optics is to generate large interactions between single photons so that one photon can strongly modify the state of another one. In cavity optomechanics, photons interact with the motional degrees of freedom of an optical resonator, for example, by imparting radiation pressure forces on a movable mirror or sensing minute fluctuations in the position of the mirror. Here, we show that the optical nonlinearity arising from these effects, typically too small to operate on single photons, can be sufficiently enhanced with feedback to generate large interactions between single photons. We propose a protocol that allows photons propagating in a waveguide to interact with each other through multiple bounces off an optomechanical system. The protocol is analysed by evolving the full many-body quantum state of the waveguide-coupled system, illustrating that large photon–photon interactions mediated by mechanical motion may be within experimental reach. PMID:28677674

Photon emission from massive projectile impacts on solids.

PubMed

Fernandez-Lima, F A; Pinnick, V T; Della-Negra, S; Schweikert, E A

2011-01-01

First evidence of photon emission from individual impacts of massive gold projectiles on solids for a number of projectile-target combinations is reported. Photon emission from individual impacts of massive Au(n) (+q) (1 ≤ n ≤ 400; q = 1-4) projectiles with impact energies in the range of 28-136 keV occurs in less than 10 ns after the projectile impact. Experimental observations show an increase in the photon yield from individual impacts with the projectile size and velocity. Concurrently with the photon emission, electron emission from the impact area has been observed below the kinetic emission threshold and under unlikely conditions for potential electron emission. We interpret the puzzling electron emission and correlated luminescence observation as evidence of the electronic excitation resulting from the high-energy density deposited by massive cluster projectiles during the impact.

Photon emission from massive projectile impacts on solids

PubMed Central

Fernandez-Lima, F. A.; Pinnick, V. T.; Della-Negra, S.; Schweikert, E. A.

2011-01-01

First evidence of photon emission from individual impacts of massive gold projectiles on solids for a number of projectile-target combinations is reported. Photon emission from individual impacts of massive Aun+q (1 ≤ n ≤ 400; q = 1–4) projectiles with impact energies in the range of 28–136 keV occurs in less than 10 ns after the projectile impact. Experimental observations show an increase in the photon yield from individual impacts with the projectile size and velocity. Concurrently with the photon emission, electron emission from the impact area has been observed below the kinetic emission threshold and under unlikely conditions for potential electron emission. We interpret the puzzling electron emission and correlated luminescence observation as evidence of the electronic excitation resulting from the high-energy density deposited by massive cluster projectiles during the impact. PMID:21603128

A TLD-based few-channel spectrometer for mixed photon, electron, and ion fields with high fluence rates.

PubMed

Behrens, R; Ambrosi, P

2002-01-01

A few-channel spectrometer for mixed photon, electron and ion radiation fields has been developed. It consists of a front layer of an etched-track detector foil for detecting protons and ions, a stack of PMMA with thermoluminescent detectors at different depths for gaining spectral information about electrons, and a stack of metallic filters with increasing cut-off photon energies, interspersed with thermoluminescent detectors for gaining spectral information about photons. From the reading of the TL detectors the spectral fluence of the electrons (400 keV to 9 MeV) and photons (20 keV to 2 MeV) can be determined by an unfolding procedure. The spectrometer can be used in pulsed radiation fields with extremely high momentary values of the fluence rate. Design and calibration of the spectrometer are described.

QED: Experimental Evidence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lincoln, Don

The theory of quantum electrodynamics (QED) is perhaps the most precisely tested physics theory ever conceived. It describes the interaction of charged particles by emitting photons. The most precise prediction of this very precise theory is the magnetic strength of the electron, what physicists call the magnetic moment. Prediction and measurement agree to 12 digits of precision. In this video, Fermilab’s Dr. Don Lincoln talks about this amazing measurement.

Covariant relativistic hydrodynamics of multispecies plasma and generalized Ohm's law

NASA Astrophysics Data System (ADS)

Gedalin, Michael

1996-04-01

Fully covariant hydrodynamical equations for a multispecies relativistic plasma in an external electromagnetic field are derived. The derived multifluid description takes into account binary Coulomb collisions, annihilation, and interaction with the photon background in terms of the invariant collision cross sections. A generalized Ohm's law is derived in a manifestly covariant form. Particular attention is devoted to the relativistic electron-positron plasma.

SYNCHROTRON RADIATION, FREE ELECTRON LASER, APPLICATION OF NUCLEAR TECHNOLOGY, ETC.: Measurement of radiation dose at the north interaction point of BEPC II

NASA Astrophysics Data System (ADS)

Mo, Xiao-Hu; Zhang, Jian-Yong; Zhang, Tian-Bao; Zhang, Qing-Jiang; Achasov, Mikhail; Fu, Cheng-Dong; Muchnoi, Nikolay; Qin, Qing; Qu, Hua-Min; Wang, Yi-Fang; Wu, Jing-Min; Xu, Jin-Qiang; Yu, Bo-Xiang

2009-10-01

The technique details for measuring radiation dose are expounded. The results of gamma and neutron radiation levels are presented and the corresponding radiation shielding is discussed based on the simplified estimation. In addition, the photon radiation level move as background for future experiments is measured by a NaI(Tl) detector.

Theoretical study of the crystal-field energy levels and two-photon absorption intensities of Tb3+ in cubic host lattices.

PubMed

Duan, Chang-Kui; Tanner, Peter A

2011-03-17

Published two photon excitation (TPE) intensities for the cubic elpasolite systems Cs(2)NaTbX(6) (X = Cl, F) have been simulated by a calculation of two photon absorption (TPA) intensities which takes into account electric dipole transitions involving the detailed crystal-field structure of 4f(7)5d intermediate states, as well as the interactions of the 4f(7) core with the d-electron. The intensity calculation employed parameters from an energy level calculation which not only presented an accurate fit, but also yielded parameters consistent with those from other lanthanide ions. The calculated intensities were used to confirm or adjust the previous assignments of energy levels, resulting in some minor revisions. Generally, the TPA intensity simulations were in better agreement with experimental data for the fluoride, rather than the chloride, system and possible reasons for this are given.

Quantum State Transfer from a Single Photon to a Distant Quantum-Dot Electron Spin

NASA Astrophysics Data System (ADS)

He, Yu; He, Yu-Ming; Wei, Yu-Jia; Jiang, Xiao; Chen, Kai; Lu, Chao-Yang; Pan, Jian-Wei; Schneider, Christian; Kamp, Martin; Höfling, Sven

2017-08-01

Quantum state transfer from flying photons to stationary matter qubits is an important element in the realization of quantum networks. Self-assembled semiconductor quantum dots provide a promising solid-state platform hosting both single photon and spin, with an inherent light-matter interface. Here, we develop a method to coherently and actively control the single-photon frequency bins in superposition using electro-optic modulators, and measure the spin-photon entanglement with a fidelity of 0.796 ±0.020 . Further, by Greenberger-Horne-Zeilinger-type state projection on the frequency, path, and polarization degrees of freedom of a single photon, we demonstrate quantum state transfer from a single photon to a single electron spin confined in an InGaAs quantum dot, separated by 5 m. The quantum state mapping from the photon's polarization to the electron's spin is demonstrated along three different axes on the Bloch sphere, with an average fidelity of 78.5%.

Picosecond Acoustics in Single Quantum Wells of Cubic GaN /(Al ,Ga )N

NASA Astrophysics Data System (ADS)

Czerniuk, T.; Ehrlich, T.; Wecker, T.; As, D. J.; Yakovlev, D. R.; Akimov, A. V.; Bayer, M.

2017-01-01

A picosecond acoustic pulse is used to study the photoelastic interaction in single zinc-blende GaN /AlxGa1 -x N quantum wells. We use an optical time-resolved pump-probe setup and demonstrate that tuning the photon energy to the quantum well's lowest electron-hole transition makes the experiment sensitive to the quantum well only. Because of the small width, its temporal and spatial resolution allows us to track the few-picosecond-long transit of the acoustic pulse. We further deploy a model to analyze the unknown photoelastic coupling strength of the quantum well for different photon energies and find good agreement with the experiments.

Double photoionization of atoms

NASA Astrophysics Data System (ADS)

Wiedenhoeft, Marco

2003-10-01

Double photoionization studies of atoms and molecules are new state-of-the-art studies providing a deeper knowledge of multi-electron excitations. This type of work advances the understanding of many-body problems. Double photoionization of atoms is of great interest to learn about electron-electron correlation and relaxation effects in atoms and molecules. In order to study double photoionization processes, a new electron-electron coincidence apparatus was built to carry out the measurements. I will present the apparatus I built as well as the results of the measurement of the triply-differential-cross-section (TDCS) for the predicted interference and Post-Collision-Interaction (PCI) effects in the Xenon N5O2,3 O2,3 Auger decay after 4d5/2 photoionization. Furthermore I present measurements for direct double photoionization of Helium at various photon energies.

Optimization of Compton Source Performance through Electron Beam Shaping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malyzhenkov, Alexander; Yampolsky, Nikolai

2016-09-26

We investigate a novel scheme for significantly increasing the brightness of x-ray light sources based on inverse Compton scattering (ICS) - scattering laser pulses off relativistic electron beams. The brightness of ICS sources is limited by the electron beam quality since electrons traveling at different angles, and/or having different energies, produce photons with different energies. Therefore, the spectral brightness of the source is defined by the 6d electron phase space shape and size, as well as laser beam parameters. The peak brightness of the ICS source can be maximized then if the electron phase space is transformed in a waymore » so that all electrons scatter off the x-ray photons of same frequency in the same direction, arriving to the observer at the same time. We describe the x-ray photon beam quality through the Wigner function (6d photon phase space distribution) and derive it for the ICS source when the electron and laser rms matrices are arbitrary.« less

Electron Beam Production and Characterization for the PLEIADES Thomson X-ray Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, W J; Hartemann, F V; Tremaine, A M

2002-10-14

We report on the performance of an S-band RF photocathode electron gun and accelerator for operation with the PLEIADES Thomson x-ray source at LLNL. Simulations of beam production, transport, and focus are presented. It is shown that a 1 ps, 500 pC electron bunch with a normalized emittance of less than 5 {pi}mm-mrad can be delivered to the interaction point. Initial electron measurements are presented. Calculations of expected x-ray flux are also performed, demonstrating an expected peak spectral brightness of 10{sup 20} photons/s/mm{sup 2}/mrad{sup 2}/0.1% bandwidth. Effects of RF phase jitter are also presented, and planned phase measurements and controlmore » methods are discussed.« less

Electron spectra of xenon clusters irradiated with a laser-driven plasma soft-x-ray laser pulse

DOE Office of Scientific and Technical Information (OSTI.GOV)

Namba, S.; Takiyama, K.; Hasegawa, N.

Xenon clusters were irradiated with plasma soft-x-ray laser pulses (having a wavelength of 13.9 nm, time duration of 7 ps, and intensities of up to 10 GW/cm{sup 2}). The laser photon energy was high enough to photoionize 4d core electrons. The cross section is large due to a giant resonance. The interaction was investigated by measuring the electron energy spectra. The photoelectron spectra for small clusters indicate that the spectral width due to the 4d hole significantly broadens with increasing cluster size. For larger clusters, the electron energy spectra evolve into a Maxwell-Boltzmann distribution, as a strongly coupled cluster nanoplasmamore » is generated.« less

High resolution energy-angle correlation measurement of hard x rays from laser-Thomson backscattering.

PubMed

Jochmann, A; Irman, A; Bussmann, M; Couperus, J P; Cowan, T E; Debus, A D; Kuntzsch, M; Ledingham, K W D; Lehnert, U; Sauerbrey, R; Schlenvoigt, H P; Seipt, D; Stöhlker, Th; Thorn, D B; Trotsenko, S; Wagner, A; Schramm, U

2013-09-13

Thomson backscattering of intense laser pulses from relativistic electrons not only allows for the generation of bright x-ray pulses but also for the investigation of the complex particle dynamics at the interaction point. For this purpose a complete spectral characterization of a Thomson source powered by a compact linear electron accelerator is performed with unprecedented angular and energy resolution. A rigorous statistical analysis comparing experimental data to 3D simulations enables, e.g., the extraction of the angular distribution of electrons with 1.5% accuracy and, in total, provides predictive capability for the future high brightness hard x-ray source PHOENIX (photon electron collider for narrow bandwidth intense x rays) and potential gamma-ray sources.

Correlated electron-nuclear dynamics in above-threshold multiphoton ionization of asymmetric molecule.

PubMed

Wang, Zhuo; Li, Min; Zhou, Yueming; Lan, Pengfei; Lu, Peixiang

2017-02-20

The partition of the photon energy into the subsystems of molecules determines many photon-induced chemical and physical dynamics in laser-molecule interactions. The electron-nuclear energy sharing from multiphoton ionization of molecules has been used to uncover the correlated dynamics of the electron and fragments. However, most previous studies focus on symmetric molecules. Here we study the electron-nuclear energy sharing in strong-field photoionization of HeH 2+ by solving the one-dimensional time-dependent Schrödinger equation (TDSE). Compared with symmetric molecules, the joint electron-nuclear energy spectrum (JES) of HeH 2+ reveals an anomalous energy shift at certain nuclear energies, while it disappears at higher and lower nuclear energies. Through tracing the time evolution of the wavepacket of bound states, we identify that this energy shift originates from the joint effect of the Stark shift, associated with the permanent dipole, and the Autler-Townes effect due to the coupling of the 2pσ and 2sσ states in strong fields. The energy shift in the JES appears at certain nuclear distances only when both Stark effect and Autler-Townes effect play important roles. We further demonstrate that the electron-nuclei energy sharing can be controlled by varying laser intensity for asymmetric molecules, providing alternative approaches to manipulate photochemical reactions for more complex molecules.

Extraction of the photon beam asymmetry Sigma in pi 0 photoproduction off the proton using the CBELSA/TAPS experiment

NASA Astrophysics Data System (ADS)

Sparks, Nathan Andrew

The CBELSA/TAPS experiment at the electron accelerator ELSA, in Bonn, Germany, was used in order to study the photoproduction of neutral pions off the proton with a linearly polarized photon beam; Neutral pions were reconstructed through their dominant decay mode into two photons. The photons were detected in a barrel/forward electromagnetic calorimeter system which covered 99% of the 4pi solid angle. The Crystal Barrel CsI(Tl) calorimeter detected photons at polar angles from 30° to 168°, while TAPS, a BaF2 spectrometer, covered forward polar angles from 5.8° to 30° and served as a fast trigger; Both calorimeters had complete azimuthal angular coverage. Coherent bremsstrahlung of electrons in a diamond radiator was used to produce a linearly polarized beam of photons with a coherent peak at 1305 or 1610 MeV. The analysis of these two datasets allowed for the measurement of the photon beam asymmetry in the beam photon energy range of 920 to 1680 MeV. For the first time, these results cover the very forward polar angles of the neutral pion. The measurements are compared to the SAID, MAID, and BnGa models and to previous measurements. These new measurements of the photon beam asymmetry contribute to the ongoing experimentally-driven exploration of the N and Delta resonances. The study of strange baryons provides a link between the strong interaction physics of the excited nucleons and the heavy flavor baryons. The upcoming GlueX experiment at Jefferson Lab is expected to provide an opportunity to examine strange baryons in much greater detail than ever before. GEANT-based Monte Carlo simulations of Cascade baryons at the GlueX experiment were conducted in order to better understand the capabilities of this experiment. A proposal, "An initial study of mesons and baryons containing strange quarks with GlueX", was submitted to the 40th Jefferson Lab Program Advisory Committee (PAC), in part, supported by these Cascade baryon simulations. 200 days of additional beam time were approved, with the proposal receiving an A scientific rating.

Organic/hybrid thin films deposited by matrix-assisted pulsed laser evaporation (MAPLE)

NASA Astrophysics Data System (ADS)

Stiff-Roberts, Adrienne D.; Ge, Wangyao

2017-12-01

Some of the most exciting materials research in the 21st century attempts to resolve the challenge of simulating, synthesizing, and characterizing new materials with unique properties designed from first principles. Achievements in such development for organic and organic-inorganic hybrid materials make them important options for electronic and/or photonic devices because they can impart multi-functionality, flexibility, transparency, and sustainability to emerging systems, such as wearable electronics. Functional organic materials include small molecules, oligomers, and polymers, while hybrid materials include inorganic nanomaterials (such as zero-dimensional quantum dots, one-dimensional carbon nanotubes, or two-dimensional nanosheets) combined with organic matrices. A critically important step to implementing new electronic and photonic devices using such materials is the processing of thin films. While solution-based processing is the most common laboratory technique for organic and hybrid materials, vacuum-based deposition has been critical to the commercialization of organic light emitting diodes based on small molecules, for example. Therefore, it is desirable to explore vacuum-based deposition of organic and hybrid materials that include larger macromolecules, such as polymers. This review article motivates the need for physical vapor deposition of polymeric and hybrid thin films using matrix-assisted pulsed laser evaporation (MAPLE), which is a type of pulsed laser deposition. This review describes the development of variations in the MAPLE technique, discusses the current understanding of laser-target interactions and growth mechanisms for different MAPLE variations, surveys demonstrations of MAPLE-deposited organic and hybrid materials for electronic and photonic devices, and provides a future outlook for the technique.

The integration of improved Monte Carlo compton scattering algorithms into the Integrated TIGER Series.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Quirk, Thomas, J., IV

2004-08-01

The Integrated TIGER Series (ITS) is a software package that solves coupled electron-photon transport problems. ITS performs analog photon tracking for energies between 1 keV and 1 GeV. Unlike its deterministic counterpart, the Monte Carlo calculations of ITS do not require a memory-intensive meshing of phase space; however, its solutions carry statistical variations. Reducing these variations is heavily dependent on runtime. Monte Carlo simulations must therefore be both physically accurate and computationally efficient. Compton scattering is the dominant photon interaction above 100 keV and below 5-10 MeV, with higher cutoffs occurring in lighter atoms. In its current model of Comptonmore » scattering, ITS corrects the differential Klein-Nishina cross sections (which assumes a stationary, free electron) with the incoherent scattering function, a function dependent on both the momentum transfer and the atomic number of the scattering medium. While this technique accounts for binding effects on the scattering angle, it excludes the Doppler broadening the Compton line undergoes because of the momentum distribution in each bound state. To correct for these effects, Ribbefor's relativistic impulse approximation (IA) will be employed to create scattering cross section differential in both energy and angle for each element. Using the parameterizations suggested by Brusa et al., scattered photon energies and angle can be accurately sampled at a high efficiency with minimal physical data. Two-body kinematics then dictates the electron's scattered direction and energy. Finally, the atomic ionization is relaxed via Auger emission or fluorescence. Future work will extend these improvements in incoherent scattering to compounds and to adjoint calculations.« less

Photonic Integrated Circuits

NASA Technical Reports Server (NTRS)

Krainak, Michael; Merritt, Scott

2016-01-01

Integrated photonics generally is the integration of multiple lithographically defined photonic and electronic components and devices (e.g. lasers, detectors, waveguides passive structures, modulators, electronic control and optical interconnects) on a single platform with nanometer-scale feature sizes. The development of photonic integrated circuits permits size, weight, power and cost reductions for spacecraft microprocessors, optical communication, processor buses, advanced data processing, and integrated optic science instrument optical systems, subsystems and components. This is particularly critical for small spacecraft platforms. We will give an overview of some NASA applications for integrated photonics.

Photon Physics and Plasma Research, Photonics Applications and Web Engineering, Wilga, May 2012

NASA Astrophysics Data System (ADS)

Romaniuk, Ryszard S.

2012-05-01

This paper is the third part (out of five) of the research survey of WILGA Symposium work, May 2012 Edition, concerned with Photon Physics and Plasma Research. It presents a digest of chosen technical work results shown by young researchers from different technical universities from this country during the Jubilee XXXth SPIE-IEEE Wilga 2012, May Edition, symposium on Photonics and Web Engineering. Topical tracks of the symposium embraced, among others, nanomaterials and nanotechnologies for photonics, sensory and nonlinear optical fibers, object oriented design of hardware, photonic metrology, optoelectronics and photonics applications, photonics-electronics co-design, optoelectronic and electronic systems for astronomy and high energy physics experiments, JET tokamak and pi-of-the sky experiments development. The symposium is an annual summary in the development of numerable Ph.D. theses carried out in this country in the area of advanced electronic and photonic systems. It is also a great occasion for SPIE, IEEE, OSA and PSP students to meet together in a large group spanning the whole country with guests from this part of Europe. A digest of Wilga references is presented [1-270].

Electronic structure of Mo1-x Re x alloys studied through resonant photoemission spectroscopy

NASA Astrophysics Data System (ADS)

Sundar, Shyam; Banik, Soma; Sharath Chandra, L. S.; Chattopadhyay, M. K.; Ganguli, Tapas; Lodha, G. S.; Pandey, Sudhir K.; Phase, D. M.; Roy, S. B.

2016-08-01

We studied the electronic structure of Mo-rich Mo1-x Re x alloys (0≤slant x≤slant 0.4 ) using valence band photoemission spectroscopy in the photon energy range 23-70 eV and density of states calculations. Comparison of the photoemission spectra with the density of states calculations suggests that, with respect to the Fermi level E F, the d states lie mostly in the binding energy range 0 to  -6 eV, whereas s states lie in the binding energy range  -4 to  -10 eV. We observed two resonances in the photoemission spectra of each sample, one at about 35 eV photon energy and the other at about 45 eV photon energy. Our analysis suggests that the resonance at 35 eV photon energy is related to the Mo 4p-5s transition and the resonance at 45 eV photon energy is related to the contribution from both the Mo 4p-4d transition (threshold: 42 eV) and the Re 5p-5d transition (threshold: 46 eV). In the constant initial state plot, the resonance at 35 eV incident photon energy for binding energy features in the range E F (BE  =  0) to  -5 eV becomes progressively less prominent with increasing Re concentration x and vanishes for x  >  0.2. The difference plots obtained by subtracting the valence band photoemission spectrum of Mo from that of Mo1-x Re x alloys, measured at 47 eV photon energy, reveal that the Re d-like states appear near E F when Re is alloyed with Mo. These results indicate that interband s-d interaction, which is weak in Mo, increases with increasing x and influences the nature of the superconductivity in alloys with higher x.

The design and dosimetric evaluation of tannin-based Rhizophora spp. particleboards as phantoms for high energy photons and electrons

NASA Astrophysics Data System (ADS)

Yusof, M. F. Mohd; Abdullah, R.; Tajuddin, A. A.; Hashim, R.; Bauk, S.; Hamid, P. N. K. Abd

2018-01-01

A set of phantom with an external dimension of 30 cm x 30 cm was constructed from tannin-based Rhizophora spp. particleboards similar to the solid water phantoms. The dosimetric characteristics of the particleboard phantoms were evaluated at high energy photons and electrons by measuring the beam output at 6 MV photons and 6 MeV electrons based on the IAEA TRS 398:2000 protocol. The tissue-phantom ratio (TPR20,10) was measured at 6 and 10 MV photons. The beam output calibration of the particleboards was in good agreement to water and solid water phantoms at 6 MV photons with percentage difference of 1.7 and 6.2% respectively. The beam output calibration of the tannin-based Rhizophora spp. particleboards at 6 MeV electrons on the other hand were in excellent agreement to water with percentage difference of 0.3. The percentage depth dose of tannin-based Rhizophora spp. particleboards were in agreement to water and solid water within 4.5% when measured using ionization chamber and EBT2 film. The electron beam parameters of R50, R80 and R90 at 6 MeV electrons also were in good agreement to water and solid water phantoms. The overall results had indicated the suitability of tannin-based Rhizophora spp. particleboards as water substitute phantom materials for high energy photons and electrons.

Single-photon non-linear optics with a quantum dot in a waveguide

NASA Astrophysics Data System (ADS)

Javadi, A.; Söllner, I.; Arcari, M.; Hansen, S. Lindskov; Midolo, L.; Mahmoodian, S.; Kiršanskė, G.; Pregnolato, T.; Lee, E. H.; Song, J. D.; Stobbe, S.; Lodahl, P.

2015-10-01

Strong non-linear interactions between photons enable logic operations for both classical and quantum-information technology. Unfortunately, non-linear interactions are usually feeble and therefore all-optical logic gates tend to be inefficient. A quantum emitter deterministically coupled to a propagating mode fundamentally changes the situation, since each photon inevitably interacts with the emitter, and highly correlated many-photon states may be created. Here we show that a single quantum dot in a photonic-crystal waveguide can be used as a giant non-linearity sensitive at the single-photon level. The non-linear response is revealed from the intensity and quantum statistics of the scattered photons, and contains contributions from an entangled photon-photon bound state. The quantum non-linearity will find immediate applications for deterministic Bell-state measurements and single-photon transistors and paves the way to scalable waveguide-based photonic quantum-computing architectures.

Carbon Nanotube-Based Membrane for Light-Driven, Simultaneous Proton and Electron Transport

DOE PAGES

Pilgrim, Gregory A.; Amori, Amanda R.; Hou, Zhentao; ...

2016-12-07

Here we discuss the photon driven transport of protons and electrons over hundreds of microns through a membrane based on vertically aligned single walled carbon nanotubes (SWNTs). Electrons are photogenerated in colloidal CdSe quantum dots that have been noncovalently attached to the carbon nanotube membrane and can be delivered at potentials capable of reducing earth-abundant molecular catalysts that perform proton reduction. Proton transport is driven by the electron photocurrent and is shown to be faster through the SWNT based membrane than through the commercial polymer Nafion. Furthermore, the potential utility of SWNT membranes for solar water splitting applications is demonstratedmore » through their excellent proton and electron transport properties as well as their ability to interact with other components of water splitting systems, such as small molecule electron acceptors.« less

Evaluation of Al2O3:C optically stimulated luminescence (OSL) dosimeters for passive dosimetry of high-energy photon and electron beams in radiotherapy.

PubMed

Yukihara, E G; Mardirossian, G; Mirzasadeghi, M; Guduru, S; Ahmad, S

2008-01-01

This article investigates the performance of Al2O3: C optically stimulated luminescence dosimeters (OSLDs) for application in radiotherapy. Central-axis depth dose curves and optically stimulated luminescence (OSL) responses were obtained in a water phantom for 6 and 18 MV photons, and for 6, 9, 12, 16, and 20 MeV electron beams from a Varian 21EX linear accelerator. Single OSL measurements could be repeated with a precision of 0.7% (one standard deviation) and the differences between absorbed doses measured with OSLDs and an ionization chamber were within +/- 1% for photon beams. Similar results were obtained for electron beams in the low-gradient region after correction for a 1.9% photon-to-electron bias. The distance-to-agreement values were of the order of 0.5-1.0 mm for electrons in high dose gradient regions. Additional investigations also demonstrated that the OSL response dependence on dose rate, field size, and irradiation temperature is less than 1% in the conditions of the present study. Regarding the beam energy/quality dependence, the relative response of the OSLD for 18 MV was (0.51 +/- 0.48)% of the response for the 6 MV photon beam. The OSLD response for the electron beams relative to the 6 MV photon beam. The OSLD response for the electron beams relative to the 6 MV photon beam was in average 1.9% higher, but this result requires further confirmation. The relative response did not seem to vary with electron energy at dmax within the experimental uncertainties (0.5% in average) and, therefore, a fixed correction factor of 1.9% eliminated the energy dependence in our experimental conditions.

Evaluation of Al{sub 2}O{sub 3}:C optically stimulated luminescence (OSL) dosimeters for passive dosimetry of high-energy photon and electron beams in radiotherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yukihara, E. G.; Mardirossian, G.; Mirzasadeghi, M.

This article investigates the performance of Al{sub 2}O{sub 3}:C optically stimulated luminescence dosimeters (OSLDs) for application in radiotherapy. Central-axis depth dose curves and optically stimulated luminescence (OSL) responses were obtained in a water phantom for 6 and 18 MV photons, and for 6, 9, 12, 16, and 20 MeV electron beams from a Varian 21EX linear accelerator. Single OSL measurements could be repeated with a precision of 0.7% (one standard deviation) and the differences between absorbed doses measured with OSLDs and an ionization chamber were within {+-}1% for photon beams. Similar results were obtained for electron beams in the low-gradientmore » region after correction for a 1.9% photon-to-electron bias. The distance-to-agreement values were of the order of 0.5-1.0 mm for electrons in high dose gradient regions. Additional investigations also demonstrated that the OSL response dependence on dose rate, field size, and irradiation temperature is less than 1% in the conditions of the present study. Regarding the beam energy/quality dependence, the relative response of the OSLD for 18 MV was (0.51{+-}0.48)% of the response for the 6 MV photon beam. The OSLD response for the electron beams relative to the 6 MV photon beam. The OSLD response for the electron beams relative to the 6 MV photon beam was in average 1.9% higher, but this result requires further confirmation. The relative response did not seem to vary with electron energy at d{sub max} within the experimental uncertainties (0.5% in average) and, therefore, a fixed correction factor of 1.9% eliminated the energy dependence in our experimental conditions.« less

Spin-orbit qubit in a semiconductor nanowire.

PubMed

Nadj-Perge, S; Frolov, S M; Bakkers, E P A M; Kouwenhoven, L P

2010-12-23

Motion of electrons can influence their spins through a fundamental effect called spin-orbit interaction. This interaction provides a way to control spins electrically and thus lies at the foundation of spintronics. Even at the level of single electrons, the spin-orbit interaction has proven promising for coherent spin rotations. Here we implement a spin-orbit quantum bit (qubit) in an indium arsenide nanowire, where the spin-orbit interaction is so strong that spin and motion can no longer be separated. In this regime, we realize fast qubit rotations and universal single-qubit control using only electric fields; the qubits are hosted in single-electron quantum dots that are individually addressable. We enhance coherence by dynamically decoupling the qubits from the environment. Nanowires offer various advantages for quantum computing: they can serve as one-dimensional templates for scalable qubit registers, and it is possible to vary the material even during wire growth. Such flexibility can be used to design wires with suppressed decoherence and to push semiconductor qubit fidelities towards error correction levels. Furthermore, electrical dots can be integrated with optical dots in p-n junction nanowires. The coherence times achieved here are sufficient for the conversion of an electronic qubit into a photon, which can serve as a flying qubit for long-distance quantum communication.

Determining photon energy absorption parameters for different soil samples

PubMed Central

Kucuk, Nil; Tumsavas, Zeynal; Cakir, Merve

2013-01-01

The mass attenuation coefficients (μs) for five different soil samples were measured at 661.6, 1173.2 and 1332.5 keV photon energies. The soil samples were separately irradiated with 137Cs and 60Co (370 kBq) radioactive point gamma sources. The measurements were made by performing transmission experiments with a 2″ × 2″ NaI(Tl) scintillation detector, which had an energy resolution of 7% at 0.662 MeV for the gamma-rays from the decay of 137Cs. The effective atomic numbers (Zeff) and the effective electron densities (Neff) were determined experimentally and theoretically using the obtained μs values for the soil samples. Furthermore, the Zeff and Neff values of the soil samples were computed for the total photon interaction cross-sections using theoretical data over a wide energy region ranging from 1 keV to 15 MeV. The experimental values of the soils were found to be in good agreement with the theoretical values. Sandy loam and sandy clay loam soils demonstrated poor photon energy absorption characteristics. However, clay loam and clay soils had good photon energy absorption characteristics. PMID:23179375

Review of an initial experience with an experimental spectral photon-counting computed tomography system

NASA Astrophysics Data System (ADS)

Si-Mohamed, Salim; Bar-Ness, Daniel; Sigovan, Monica; Cormode, David P.; Coulon, Philippe; Coche, Emmanuel; Vlassenbroek, Alain; Normand, Gabrielle; Boussel, Loic; Douek, Philippe

2017-11-01

Spectral photon-counting CT (SPCCT) is an emerging X-ray imaging technology that extends the scope of available diagnostic imaging tools. The main advantage of photon-counting CT technology is better sampling of the spectral information from the transmitted spectrum in order to benefit from additional physical information being produced during matter interaction, including photo-electric and Compton effects, and the K-edge effect. The K-edge, which is specific for a given element, is the increase in X-ray absorption of the element above the binding energy between its inner electronic shell and the nucleus. Hence, the spectral information contributes to better characterization of tissues and materials of interest, explaining the excitement surrounding this area of X-ray imaging. Other improvements of SPCCT compared with conventional CT, such as higher spatial resolution, lower radiation exposure and lower noise are also expected to provide benefits for diagnostic imaging. In this review, we describe multi-energy CT imaging, from dual energy to photon counting technology, and our initial experience results using a clinical-scale spectral photon counting CT (SPCCT) prototype system in vitro and in vivo. In addition, possible clinical applications are introduced.

TH-CD-201-06: Experimental Characterization of Acoustic Signals Generated in Water Following Clinical Photon and Electron Beam Irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hickling, S; El Naqa, I

Purpose: Previous work has demonstrated the detectability of acoustic waves induced following the irradiation of high density metals with radiotherapy linac photon beams. This work demonstrates the ability to experimentally detect such acoustic signals following both photon and electron irradiation in a more radiotherapy relevant material. The relationship between induced acoustic signal properties in water and the deposited dose distribution is explored, and the feasibility of exploiting such signals for radiotherapy dosimetry is demonstrated. Methods: Acoustic waves were experimentally induced in a water tank via the thermoacoustic effect following a single pulse of photon or electron irradiation produced by amore » clinical linac. An immersion ultrasound transducer was used to detect these acoustic waves in water and signals were read out on an oscilloscope. Results: Peaks and troughs in the detected acoustic signals were found to correspond to the location of gradients in the deposited dose distribution following both photon and electron irradiation. Signal amplitude was linearly related to the dose per pulse deposited by photon or electron beams at the depth of detection. Flattening filter free beams induced large acoustic signals, and signal amplitude decreased with depth after the depth of maximum dose. Varying the field size resulted in a temporal shift of the acoustic signal peaks and a change in the detected signal frequency. Conclusion: Acoustic waves can be detected in a water tank following irradiation by linac photon and electron beams with basic electronics, and have characteristics related to the deposited dose distribution. The physical location of dose gradients and the amount of dose deposited can be inferred from the location and magnitude of acoustic signal peaks. Thus, the detection of induced acoustic waves could be applied to photon and electron water tank and in vivo dosimetry. This work was supported in part by CIHR grants MOP-114910 and MOP-136774. S.H. acknowledges support by the NSERC CREATE Medical Physics Research Training Network grant 432290.« less

Radiation dose enhancement in skin therapy with nanoparticle addition: A Monte Carlo study on kilovoltage photon and megavoltage electron beams

PubMed Central

Zheng, Xiao J; Chow, James C L

2017-01-01

AIM To investigated the dose enhancement due to the incorporation of nanoparticles in skin therapy using the kilovoltage (kV) photon and megavoltage (MV) electron beams. Monte Carlo simulations were used to predict the dose enhancement when different types and concentrations of nanoparticles were added to skin target layers of varying thickness. METHODS Clinical kV photon beams (105 and 220 kVp) and MV electron beams (4 and 6 MeV), produced by a Gulmay D3225 orthovoltage unit and a Varian 21 EX linear accelerator, were simulated using the EGSnrc Monte Carlo code. Doses at skin target layers with thicknesses ranging from 0.5 to 5 mm for the photon beams and 0.5 to 10 mm for the electron beams were determined. The skin target layer was added with the Au, Pt, I, Ag and Fe2O3 nanoparticles with concentrations ranging from 3 to 40 mg/mL. The dose enhancement ratio (DER), defined as the dose at the target layer with nanoparticle addition divided by the dose at the layer without nanoparticle addition, was calculated for each nanoparticle type, nanoparticle concentration and target layer thickness. RESULTS It was found that among all nanoparticles, Au had the highest DER (5.2-6.3) when irradiated with kV photon beams. Dependence of the DER on the target layer thickness was not significant for the 220 kVp photon beam but it was for 105 kVp beam for Au nanoparticle concentrations higher than 18 mg/mL. For other nanoparticles, the DER was dependent on the atomic number of the nanoparticle and energy spectrum of the photon beams. All nanoparticles showed an increase of DER with nanoparticle concentration during the photon beam irradiations regardless of thickness. For electron beams, the Au nanoparticles were found to have the highest DER (1.01-1.08) when the beam energy was equal to 4 MeV, but this was drastically lower than the DER values found using photon beams. The DER was also found affected by the depth of maximum dose of the electron beam and target thickness. For other nanoparticles with lower atomic number, DERs in the range of 0.99-1.02 were found using the 4 and 6 MeV electron beams. CONCLUSION In nanoparticle-enhanced skin therapy, Au nanoparticle addition can achieve the highest dose enhancement with 105 kVp photon beams. Electron beams, while popular for skin therapy, did not produce as high dose enhancements as kV photon beams. Additionally, the DER is dependent on nanoparticle type, nanoparticle concentration, skin target thickness and energies of the photon and electron beams. PMID:28298966

Advanced photonic, electronic, and web engineering systems: WILGA Symposium, January 2013

NASA Astrophysics Data System (ADS)

Romaniuk, Ryszard S.

2013-10-01

The cycle of WILGA Symposia [wilga.ise.pw.edu.pl] on Photonics and Web Engineering, Advanced Electronic Systems, under the auspices of SPIE, IEEE, KEiT PAN and WEiTI PW was initiated in 1998 by a Research Team PERG/ELHEP ISE PW. The WILGA conferences take place two times a year and the participants are young scientists from this country and abroad. This paper debates chosen topical tracks and some papers presented during the 31 WILGA Multi-Conference, which took place on 8-10 February 2013 at the Faculty of WEiTI PW. The January conference was attended by around 100 persons. Here we discuss closer the subjects of biomedical photonics, electronics and informatics, as well as chosen aspects of applications of advanced photonic, electronic circuits and systems. The 32 nd WILGA Symposium took place on 27 May - 02 June 2013 in WUT WILGA resort near Warsaw. These two editions of WILGA Conferences - January and May have generated more than 250 articles, from which around 100 were chosen by the Symposium and Conference Committees to be published in this volume of Proc.SPIE. WILGA Symposium papers are traditionally submitted via the WILGA web page [wilga.ise.pw.edu.pl] to the SPIE Proceedings publishing system [spie.org]. Email for the correspondence is: photonics@ise.pw.edu.pl. All Wilga papers are published in journals Elektronika, IJET-PAN and in Proc.SPIE. Topical tracks of the symposium usually embrace, among others, new technologies for photonics, sensory and nonlinear optical fibers, object oriented design of hardware, photonic metrology, optoelectronics and photonics applications, photonics-electronics co-design, optoelectronic and electronic systems for astronomy and high energy physics experiments, JET and pi-of-the sky experiments development. The symposium In its two editions a year is a summary of the development of numerable Ph.D. theses carried out in this country and this geographical region in the area of advanced electronic and photonic systems. It is also a great occasion for SPIE, IEEE, OSA and PSP members, young researchers and students to meet together in a large group spanning the whole country with guests from this part of Europe. A digest of chosen Wilga references is presented.

Quantum interference in plasmonic circuits.

PubMed

Heeres, Reinier W; Kouwenhoven, Leo P; Zwiller, Valery

2013-10-01

Surface plasmon polaritons (plasmons) are a combination of light and a collective oscillation of the free electron plasma at metal/dielectric interfaces. This interaction allows subwavelength confinement of light beyond the diffraction limit inherent to dielectric structures. As a result, the intensity of the electromagnetic field is enhanced, with the possibility to increase the strength of the optical interactions between waveguides, light sources and detectors. Plasmons maintain non-classical photon statistics and preserve entanglement upon transmission through thin, patterned metallic films or weakly confining waveguides. For quantum applications, it is essential that plasmons behave as indistinguishable quantum particles. Here we report on a quantum interference experiment in a nanoscale plasmonic circuit consisting of an on-chip plasmon beamsplitter with integrated superconducting single-photon detectors to allow efficient single plasmon detection. We demonstrate a quantum-mechanical interaction between pairs of indistinguishable surface plasmons by observing Hong-Ou-Mandel (HOM) interference, a hallmark non-classical interference effect that is the basis of linear optics-based quantum computation. Our work shows that it is feasible to shrink quantum optical experiments to the nanoscale and offers a promising route towards subwavelength quantum optical networks.

Photonic Crystal-Based High-Power Backward Wave Oscillator

DOE PAGES

Poole, Brian R.; Harris, John R.

2017-12-01

An electron beam traversing a slow wave structure can be used to either generate or amplify electromagnetic radiation through the interaction of the slow space charge wave on the beam with the slow wave structure modes. Here, a cylindrical waveguide with a periodic array of conducting loops is used for the slow wave structure. This paper considers operation as a backward wave oscillator. The dispersion properties of the structure are determined using a frequency-domain eigenmode solver. The interaction of the electron beam with the structure modes is investigated using a 2-D particle-in-cell (PIC) code. In conclusion, the operating frequency andmore » growth rate dependence on beam energy and beam current are investigated using the PIC code and compared with analytic and scaling estimates where possible.« less

Photonic Crystal-Based High-Power Backward Wave Oscillator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Poole, Brian R.; Harris, John R.

An electron beam traversing a slow wave structure can be used to either generate or amplify electromagnetic radiation through the interaction of the slow space charge wave on the beam with the slow wave structure modes. Here, a cylindrical waveguide with a periodic array of conducting loops is used for the slow wave structure. This paper considers operation as a backward wave oscillator. The dispersion properties of the structure are determined using a frequency-domain eigenmode solver. The interaction of the electron beam with the structure modes is investigated using a 2-D particle-in-cell (PIC) code. In conclusion, the operating frequency andmore » growth rate dependence on beam energy and beam current are investigated using the PIC code and compared with analytic and scaling estimates where possible.« less

Application of relativistic distorted-wave method to electron-impact excitation of highly charged Fe XXIV ion embedded in weakly coupled plasmas

NASA Astrophysics Data System (ADS)

Chen, Zhanbin

2018-05-01

The process of excitation of highly charged Fe XXIV ion embedded in weakly coupled plasmas by electron impact is studied, together with the subsequent radiative decay. For the target structure, the calculation is performed using the multiconfiguration Dirac-Hartree-Fock method incorporating the Debye-Hückel potential for the electron-nucleus interaction. Fine-structure levels of the 1s22p and 1s2s2p configurations and the transition properties among these levels are presented over a wide range of screening parameters. For the collision dynamics, the distorted-wave method in the relativistic frame is adopted to include the effect of plasma background, in which the interparticle interactions in the system are described by screened interactions of the Debye-Hückel type. The continuum wave function of the projectile electron is obtained by solving the modified Dirac equations. The influence of plasma strength on the cross section, the linear polarization, and the angular distribution of x-ray photon emission are investigated in detail. Comparison of the present results with experimental data and other theoretical predictions, when available, is made.

Design and construction of a high-energy photon polarimeter

NASA Astrophysics Data System (ADS)

Dugger, M.; Ritchie, B. G.; Sparks, N.; Moriya, K.; Tucker, R. J.; Lee, R. J.; Thorpe, B. N.; Hodges, T.; Barbosa, F. J.; Sandoval, N.; Jones, R. T.

2017-09-01

We report on the design and construction of a high-energy photon polarimeter for measuring the degree of polarization of a linearly-polarized photon beam. The photon polarimeter uses the process of pair production on an atomic electron (triplet production). The azimuthal distribution of scattered atomic electrons following triplet production yields information regarding the degree of linear polarization of the incident photon beam. The polarimeter, operated in conjunction with a pair spectrometer, uses a silicon strip detector to measure the recoil electron distribution resulting from triplet photoproduction in a beryllium target foil. The analyzing power ΣA for the device using a 75 μm beryllium converter foil is about 0.2, with a relative systematic uncertainty in ΣA of 1.5%.

Improving LHC searches for dark photons using lepton-jet substructure

NASA Astrophysics Data System (ADS)

Barello, G.; Chang, Spencer; Newby, Christopher A.; Ostdiek, Bryan

2017-03-01

Collider signals of dark photons are an exciting probe for new gauge forces and are characterized by events with boosted lepton jets. Existing techniques are efficient in searching for muonic lepton jets but due to substantial backgrounds have difficulty constraining lepton jets containing only electrons. This is unfortunate since upcoming intensity frontier experiments are sensitive to dark photon masses which only allow electron decays. Analyzing a recently proposed model of kinetic mixing, with new scalar particles decaying into dark photons, we find that existing techniques for electron jets can be substantially improved. We show that using lepton-jet-substructure variables, in association with a boosted decision tree, improves background rejection, significantly increasing the LHC's reach for dark photons in this region of parameter space.

Ion-induced electron emission microscopy

DOEpatents

Doyle, Barney L.; Vizkelethy, Gyorgy; Weller, Robert A.

2001-01-01

An ion beam analysis system that creates multidimensional maps of the effects of high energy ions from an unfocussed source upon a sample by correlating the exact entry point of an ion into a sample by projection imaging of the secondary electrons emitted at that point with a signal from a detector that measures the interaction of that ion within the sample. The emitted secondary electrons are collected in a strong electric field perpendicular to the sample surface and (optionally) projected and refocused by the electron lenses found in a photon emission electron microscope, amplified by microchannel plates and then their exact position is sensed by a very sensitive X Y position detector. Position signals from this secondary electron detector are then correlated in time with nuclear, atomic or electrical effects, including the malfunction of digital circuits, detected within the sample that were caused by the individual ion that created these secondary electrons in the fit place.

Chapter in book "Many Body Structure of Strongly Interacting Systems, Refereed and Selected Contributions from the Symposium '20 Years of Physics at the Mainz Microtron MAMI,'" Part I, Editors: Arenhövel, H.; Backe, H.; Drechsel, D.; Friedrich, J.; Kaiser, K.-H.; Walcher, Th., p.7-17 (contribution entitled Physics at the Thomas Jefferson National Accelerator Facility)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lawrence Cardman

2006-09-01

The Continuous Electron Accelerator Facility, CEBAF, located at the Thomas Jefferson National Accelerator Facility, is devoted to the investigation of the electromagnetic structure of mesons, nucleons, and nuclei using high energy, high duty-cycle electron and photon beams. Selected experimental results of particular interest to the MAMI community are presented.

Ultrafast Light Switching of Ferromagnetism in EuSe

NASA Astrophysics Data System (ADS)

Henriques, A. B.; Gratens, X.; Usachev, P. A.; Chitta, V. A.; Springholz, G.

2018-05-01

We demonstrate that light resonant with the band gap forces the antiferromagnetic semiconductor EuSe to enter ferromagnetic alignment in the picosecond timescale. A photon generates an electron-hole pair, whose electron forms a supergiant spin polaron of magnetic moment of nearly 6000 Bohr magnetons. By increasing the light intensity, the whole of the illuminated region can be fully magnetized. The key to the novel large photoinduced magnetization mechanism is the huge enhancement of the magnetic susceptibility when both antiferromagnetic and ferromagnetic interactions are present in the material and are of nearly equal magnitude, as is the case in EuSe.

The effect of energy spectrum change on DNA damage in and out of field in 10-MV clinical photon beams.

PubMed

Ezzati, A O; Xiao, Y; Sohrabpour, M; Studenski, M T

2015-01-01

The aim of this study was to quantify the DNA damage induced in a clinical megavoltage photon beam at various depths in and out of the field. MCNPX was used to simulate 10 × 10 and 20 × 20 cm(2) 10-MV photon beams from a clinical linear accelerator. Photon and electron spectra were collected in a water phantom at depths of 2.5, 12.5 and 22.5 cm on the central axis and at off-axis points out to 10 cm. These spectra were used as an input to a validated microdosimetric Monte Carlo code, MCDS, to calculate the RBE of induced DSB in DNA at points in and out of the primary radiation field at three depths. There was an observable difference in the energy spectra for photons and electrons for points in the primary radiation field and those points out of field. In the out-of-field region, the mean energy for the photon and electron spectra decreased by a factor of about six and three from the in-field mean energy, respectively. Despite the differences in spectra and mean energy, the change in RBE was <1 % from the in-field region to the out-of-field region at any depth. There was no significant change in RBE regardless of the location in the phantom. Although there are differences in both the photon and electron spectra, these changes do not correlate with a change in RBE in a clinical MV photon beam as the electron spectra are dominated by electrons with energies >20 keV.

Photo-excitation of electrons in cytochrome c oxidase as a theory of the mechanism of the increase of ATP production in mitochondria by laser therapy

NASA Astrophysics Data System (ADS)

Zielke, Andrzej

2014-02-01

The hypothesis explains the molecular basis for restoring mitochondrial function by laser therapy. It also explains how laser therapy reverses both excessive oxidation (lack of NADH/FADH2) and excessive reduction (lack of O2) states of cytochrome c oxidase complex. It is proposed that photons interact with heme molecules of cytochrome c oxidase. A molecule of heme contains a porphyrin ring and an atom of iron in the center. The iron atom (Fe) can switch oxidation states back and forth between ferrous (Fe2+) and ferric (Fe3+) by accepting or releasing an electron. The porphyrin ring is a complex aromatic molecule that has 26 pi electrons which are "delocalized", spinning in the carbon rings creating a resonating electromagnetic cloud. Photons with similar wavelengths are absorbed by the cloud increasing its energy. The energy is then passed on to the centrally located atom of iron existing in a reduced state (Fe2+). The electrons on the orbits of the iron atom accept this electromagnetic energy, and change orbitals to a higher energetic level. If the energy is sufficient, electrons leave the atom entirely. If this occurs, Fe2+ become oxidized to Fe3+ releasing electrons, thus restoring electron flow and the production of ATP. At the same time, electrons freed from complex IV may have sufficient energy to be picked by NAD+/FADH and re-enter the chain at the complex I or II amplifying the flow of electrons.

Laser opacity in underdense preplasma of solid targets due to quantum electrodynamics effects

NASA Astrophysics Data System (ADS)

Wang, W.-M.; Gibbon, P.; Sheng, Z.-M.; Li, Y.-T.; Zhang, J.

2017-07-01

We investigate how next-generation laser pulses at 10 -200 PW interact with a solid target in the presence of a relativistically underdense preplasma produced by amplified spontaneous emission (ASE). Laser hole boring and relativistic transparency are strongly restrained due to the generation of electron-positron pairs and γ -ray photons via quantum electrodynamics (QED) processes. A pair plasma with a density above the initial preplasma density is formed, counteracting the electron-free channel produced by hole boring. This pair-dominated plasma can block laser transport and trigger an avalanchelike QED cascade, efficiently transferring the laser energy to the photons. This renders a 1 -μ m scale-length, underdense preplasma completely opaque to laser pulses at this power level. The QED-induced opacity therefore sets much higher contrast requirements for such a pulse in solid-target experiments than expected by classical plasma physics. Our simulations show, for example, that proton acceleration from the rear of a solid with a preplasma would be strongly impaired.

Application of a Java-based, univel geometry, neutral particle Monte Carlo code to the searchlight problem

DOE Office of Scientific and Technical Information (OSTI.GOV)

Charles A. Wemple; Joshua J. Cogliati

2005-04-01

A univel geometry, neutral particle Monte Carlo transport code, written entirely in the Java programming language, is under development for medical radiotherapy applications. The code uses ENDF-VI based continuous energy cross section data in a flexible XML format. Full neutron-photon coupling, including detailed photon production and photonuclear reactions, is included. Charged particle equilibrium is assumed within the patient model so that detailed transport of electrons produced by photon interactions may be neglected. External beam and internal distributed source descriptions for mixed neutron-photon sources are allowed. Flux and dose tallies are performed on a univel basis. A four-tap, shift-register-sequence random numbermore » generator is used. Initial verification and validation testing of the basic neutron transport routines is underway. The searchlight problem was chosen as a suitable first application because of the simplicity of the physical model. Results show excellent agreement with analytic solutions. Computation times for similar numbers of histories are comparable to other neutron MC codes written in C and FORTRAN.« less

QED: Experimental Evidence

ScienceCinema

Lincoln, Don

2018-01-16

The theory of quantum electrodynamics (QED) is perhaps the most precisely tested physics theory ever conceived. It describes the interaction of charged particles by emitting photons. The most precise prediction of this very precise theory is the magnetic strength of the electron, what physicists call the magnetic moment. Prediction and measurement agree to 12 digits of precision. In this video, Fermilab’s Dr. Don Lincoln talks about this amazing measurement.

An Assessment of the Science and Technology Predictions in the Army’s STAR21 Report

DTIC Science & Technology

2008-07-01

electronics, optics, and photonics; aeromechanics; molecular genetics ; clinical medicine ; atmospheric sciences; and terrain sciences. Both the Navy and the...for medical diagnostics, functional materials, and manufacturing at the nano-scale. There were a few serious misses, such as significant developments...overstatement. The predictions for vaccines and medicines are right. The study did not mention the key interactions between biomolecules and their

Single photon radioluminescence. I. Theory and spectroscopic properties.

PubMed Central

Bicknese, S; Shahrokh, Z; Shohet, S B; Verkman, A S

1992-01-01

The excitation of a fluorescent molecule by a beta-decay electron (radioluminescence) depends upon the electron energy, the distance between radioactive 'donor' and fluorescent 'acceptor', and the excitation characteristics and solvent environment of the fluorophore. The theory for calculation of single photon radioluminescence (SPR) signals is developed here; in the accompanying paper, measurement methods and biological applications are presented. To calculate the three-dimensional spatial profile for electron energy deposition in an aqueous environment, a Monte Carlo calculation was performed incorporating theories of electron energy distributions, energy loss due to interactions with matter, and deflections in electron motion due to collisions. For low energy beta emitters, 50% of energy deposition occurs within 0.63 micron (3H, 18.5 keV), 22 microns (14C, 156 keV), 25 microns (35S, 167 keV), and 260 microns (36Cl, 712 keV) of the radioisotope. In close proximity to the beta emitter (100 nm, 3H; 10 microns, 14C) the probability for fluorophore excitation is approximately proportional to the inverse square of the distance between the beta emitter and fluorophore. To investigate the other factors that determine the probability for fluorophore excitation, SPR measurements were carried out in solutions containing 3H and a series of fluorophores in different solvents. In water, the probability of fluorescence excitation was nearly proportional to the integrated absorbance over a > 1,000-fold variation in absorbances. The probability of fluorescence excitation was enhanced up to 2,600-fold when the fluorophore was in a "scintillant" aromatic or hydrocarbon solvent. SPR emission spectra were similar to fluorescence emission spectra obtained with photon excitation. The single photon signal due to Bremsstrahlung increased with wavelength in agreement with theory. The distance dependence for the SPR signal predicted by the model was in good agreement with measurements in which a 14C donor was separated by known thicknesses of water from a fluorescently-coated coverglass. Quantitative predictions for radioluminescence signal as a function of donor-acceptor distance were developed for specific radioisotope-fluorophore geometries in biological samples. Images FIGURE 1 PMID:1477277

Front surface structured targets for enhancing laser-plasma interactions

NASA Astrophysics Data System (ADS)

Snyder, Joseph; George, Kevin; Ji, Liangliang; Yalamanchili, Sasir; Simonoff, Ethan; Cochran, Ginevra; Daskalova, Rebecca; Poole, Patrick; Willis, Christopher; Lewis, Nathan; Schumacher, Douglass

2016-10-01

We present recent progress made using front surface structured interfaces for enhancing ultrashort, relativistic laser-plasma interactions. Structured targets can increase laser absorption and enhance ion acceleration through a number of mechanisms such as direct laser acceleration and laser guiding. We detail experimental results obtained at the Scarlet laser facility on hollow, micron-scale plasma channels for enhancing electron acceleration. These targets show a greater than three times enhancement in the electron cutoff energy as well as an increased slope temperature for the electron distribution when compared to a flat interface. Using three-dimensional particle-in-cell (PIC) simulations, we have modeled the interaction to give insight into the physical processes responsible for the enhancement. Furthermore, we have used PIC simulations to design structures that are more advantageous for ion acceleration. Such targets necessitate advanced target fabrication methods and we describe techniques used to manufacture optimized structures, including vapor-liquid-solid growth, cryogenic etching, and 3D printing using two-photon-polymerization. This material is based upon work supported by the Air Force Office of Scientific Research under Award Number FA9550-14-1-0085.

Photonics applications and web engineering: WILGA Summer 2016

NASA Astrophysics Data System (ADS)

Romaniuk, Ryszard S.

2016-09-01

Wilga Summer 2016 Symposium on Photonics Applications and Web Engineering was held on 29 May - 06 June. The Symposium gathered over 350 participants, mainly young researchers active in optics, optoelectronics, photonics, electronics technologies and applications. There were presented around 300 presentations in a few main topical tracks including: bio-photonics, optical sensory networks, photonics-electronics-mechatronics co-design and integration, large functional system design and maintenance, Internet of Thins, and other. The paper is an introduction the 2016 WILGA Summer Symposium Proceedings, and digests some of the Symposium chosen key presentations.

Photonics applications and web engineering: WILGA Summer 2015

NASA Astrophysics Data System (ADS)

Romaniuk, Ryszard S.

2015-09-01

Wilga Summer 2015 Symposium on Photonics Applications and Web Engineering was held on 23-31 May. The Symposium gathered over 350 participants, mainly young researchers active in optics, optoelectronics, photonics, electronics technologies and applications. There were presented around 300 presentations in a few main topical tracks including: bio-photonics, optical sensory networks, photonics-electronics-mechatronics co-design and integration, large functional system design and maintenance, Internet of Thins, and other. The paper is an introduction the 2015 WILGA Summer Symposium Proceedings, and digests some of the Symposium chosen key presentations.

Theory of few photon dynamics in light emitting quantum dot devices

NASA Astrophysics Data System (ADS)

Carmele, Alexander; Richter, Marten; Sitek, Anna; Knorr, Andreas

2009-10-01

We present a modified cluster expansion to describe single-photon emitters in a semiconductor environment. We calculate microscopically to what extent semiconductor features in quantum dot-wetting layer systems alter the exciton and photon dynamics in comparison to the atom-like emission dynamics. We access these systems by the photon-probability-cluster-expansion: a reliable approach for few photon dynamics in many body electron systems. As a first application, we show that the amplitude of vacuum Rabi flops determines the number of electrons in the quantum dot.

PLEIADES: a picosecond Compton scattering x-ray source for advanced backlighting and time-resolved material studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gibson, D J; Anderson, S G; Barty, C P

2003-10-20

The PLEIADES (Picosecond Laser-Electron Inter-Action for the Dynamical Evaluation of Structures) facility has produced first light at 70 keV. This milestone offers a new opportunity to develop laser-driven, compact, tunable x-ray sources for critical applications such as diagnostics for the National Ignition Facility and time-resolved material studies. The electron beam was focused to 50 {micro}m rms, at 57 MeV, with 260 C of charge, a relative energy spread of 0.2%, and a normalized emittance of 5 mm mrad horizontally and 13 mm mrad vertically. The scattered 820-nm laser pulse had an energy of 180 mJ and a duration of 54more » fs. Initial x-rays were captured with a cooled charge-coupled device using a Cesium Iodide scintillator; the peak photon energy was approximately 78 keV, with a total x-ray flux of 1.3 x 10{sup 6} photons/shot, and the observed angular distribution found to agree very well with three-dimensional codes. Simple K-edge radiography of a tantalum foil showed good agreement with the theoretical divergence-angle dependence of the x-ray energy. Optimization of the x-ray dose is currently underway, with the goal of reaching 10{sup 8} photons per shot and a peak brightness approaching 10{sup 20} photons/mm{sup 2}/mrad{sup 2}/s/0.1%bandwidth.« less

SU-F-I-13: Correction Factor Computations for the NIST Ritz Free Air Chamber for Medium-Energy X Rays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bergstrom, P

Purpose: The National Institute of Standards and Technology (NIST) uses 3 free-air chambers to establish primary standards for radiation dosimetry at x-ray energies. For medium-energy × rays, the Ritz free-air chamber is the main measurement device. In order to convert the charge or current collected by the chamber to the radiation quantities air kerma or air kerma rate, a number of correction factors specific to the chamber must be applied. Methods: We used the Monte Carlo codes EGSnrc and PENELOPE. Results: Among these correction factors are the diaphragm correction (which accounts for interactions of photons from the x-ray source inmore » the beam-defining diaphragm of the chamber), the scatter correction (which accounts for the effects of photons scattered out of the primary beam), the electron-loss correction (which accounts for electrons that only partially expend their energy in the collection region), the fluorescence correction (which accounts for ionization due to reabsorption ffluorescence photons and the bremsstrahlung correction (which accounts for the reabsorption of bremsstrahlung photons). We have computed monoenergetic corrections for the NIST Ritz chamber for the 1 cm, 3 cm and 7 cm collection plates. Conclusion: We find good agreement with other’s results for the 7 cm plate. The data used to obtain these correction factors will be used to establish air kerma and it’s uncertainty in the standard NIST x-ray beams.« less

Probing topological protection using a designer surface plasmon structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Fei; Gao, Zhen; Shi, Xihang

Topological photonic states, inspired by robust chiral edge states in topological insulators, have recently been demonstrated in a few photonic systems, including an array of coupled on-chip ring resonators at communication wavelengths. However, the intrinsic difference between electrons and photons determines that the 'topological protection' in time-reversal-invariant photonic systems does not share the same robustness as its counterpart in electronic topological insulators. Here in a designer surface plasmon platform consisting of tunable metallic sub-wavelength structures, we construct photonic topological edge states and probe their robustness against a variety of defect classes, including some common time-reversal-invariant photonic defects that can breakmore » the topological protection, but do not exist in electronic topological insulators. Furthermore, this is also an experimental realization of anomalous Floquet topological edge states, whose topological phase cannot be predicted by the usual Chern number topological invariants.« less

Probing topological protection using a designer surface plasmon structure

DOE PAGES

Gao, Fei; Gao, Zhen; Shi, Xihang; ...

2016-05-20

Topological photonic states, inspired by robust chiral edge states in topological insulators, have recently been demonstrated in a few photonic systems, including an array of coupled on-chip ring resonators at communication wavelengths. However, the intrinsic difference between electrons and photons determines that the 'topological protection' in time-reversal-invariant photonic systems does not share the same robustness as its counterpart in electronic topological insulators. Here in a designer surface plasmon platform consisting of tunable metallic sub-wavelength structures, we construct photonic topological edge states and probe their robustness against a variety of defect classes, including some common time-reversal-invariant photonic defects that can breakmore » the topological protection, but do not exist in electronic topological insulators. Furthermore, this is also an experimental realization of anomalous Floquet topological edge states, whose topological phase cannot be predicted by the usual Chern number topological invariants.« less

Software-defined networking control plane for seamless integration of multiple silicon photonic switches in Datacom networks.

PubMed

Shen, Yiwen; Hattink, Maarten H N; Samadi, Payman; Cheng, Qixiang; Hu, Ziyiz; Gazman, Alexander; Bergman, Keren

2018-04-16

Silicon photonics based switches offer an effective option for the delivery of dynamic bandwidth for future large-scale Datacom systems while maintaining scalable energy efficiency. The integration of a silicon photonics-based optical switching fabric within electronic Datacom architectures requires novel network topologies and arbitration strategies to effectively manage the active elements in the network. We present a scalable software-defined networking control plane to integrate silicon photonic based switches with conventional Ethernet or InfiniBand networks. Our software-defined control plane manages both electronic packet switches and multiple silicon photonic switches for simultaneous packet and circuit switching. We built an experimental Dragonfly network testbed with 16 electronic packet switches and 2 silicon photonic switches to evaluate our control plane. Observed latencies occupied by each step of the switching procedure demonstrate a total of 344 µs control plane latency for data-center and high performance computing platforms.

On The Detection Of Footprints From Strong Electron Acceleration In High-Intensity Laser Fields, Including The Unruh Effect

NASA Astrophysics Data System (ADS)

Thirolf, P. G.; Habs, D.; Homma, K.; Hörlein, R.; Karsch, S.; Krausz, F.; Maia, C.; Osterhoff, J.; Popp, A.; Schmid, K.; Schreiber, J.; Schützhold, R.; Tajima, T.; Veisz, L.; Wulz, J.; Yamazaki, T.

2010-04-01

The ultra-high fields of high-power short-pulse lasers are expected to contribute to understanding fundamental properties of the quantum vacuum and quantum theory in very strong fields. For example, the neutral QED vacuum breaks down at the Schwinger field strength of 1.3 1018V/m, where a virtual e+e- pair gains its rest mass energy over a Compton wavelength and materializes as a real pair. At such an ultra-high field strength, an electron experiences an acceleration of as = 2 1028 g and hence fundamental phenomena such as the long predicted Unruh effect start to play a role. The Unruh effect implies that the accelerated electron experiences the vacuum as a thermal bath with the Unruh temperature. In its accelerated frame the electron scatters photons off the thermal bath, corresponding to the emission of an entangled pair of photons in the laboratory frame. In upcoming experiments with intense accelerating fields, we will encounter a set of opportunities to experimentally study the radiation from electrons under extreme fields. Even before the Unruh radiation detection, we should run into the copious Larmor radiation. The detection of Larmor radiation and its characterization themselves have never been experimentally carried out to the best of our knowledge, and thus this amounts to a first serious study of physics at extreme acceleration. For example, we can study radiation damping effects like the Landau-Lifshitz radiation. Furthermore, the experiment should be able to confirm or disprove whether the Larmor and Landau-Lifshitz radiation components may be enhanced by a collective (N2) radiation, if a tightly clumped cluster of electrons is accelerated. The technique of laser driven dense electron sheet formation by irradiating a thin DLC foil target should provide such a coherent electron cluster with a very high density. If and when such mildly relativistic electron sheets are realized, a counterpropagating second laser can interact with them coherently. Under these conditions enhanced Larmor and Unruh radiation signals may be observed. Detection of the Unruh photons (together with its competing radiation components) is envisaged via Compton polarimetry in a novel highly granular 2D-segmented position-sensitive germanium detector.

Correlation of two-photon in vivo imaging and FIB/SEM microscopy

PubMed Central

Blazquez-Llorca, L; Hummel, E; Zimmerman, H; Zou, C; Burgold, S; Rietdorf, J; Herms, J

2015-01-01

Advances in the understanding of brain functions are closely linked to the technical developments in microscopy. In this study, we describe a correlative microscopy technique that offers a possibility of combining two-photon in vivo imaging with focus ion beam/scanning electron microscope (FIB/SEM) techniques. Long-term two-photon in vivo imaging allows the visualization of functional interactions within the brain of a living organism over the time, and therefore, is emerging as a new tool for studying the dynamics of neurodegenerative diseases, such as Alzheimer’s disease. However, light microscopy has important limitations in revealing alterations occurring at the synaptic level and when this is required, electron microscopy is mandatory. FIB/SEM microscopy is a novel tool for three-dimensional high-resolution reconstructions, since it acquires automated serial images at ultrastructural level. Using FIB/SEM imaging, we observed, at 10 nm isotropic resolution, the same dendrites that were imaged in vivo over 9 days. Thus, we analyzed their ultrastructure and monitored the dynamics of the neuropil around them. We found that stable spines (present during the 9 days of imaging) formed typical asymmetric contacts with axons, whereas transient spines (present only during one day of imaging) did not form a synaptic contact. Our data suggest that the morphological classification that was assigned to a dendritic spine according to the in vivo images did not fit with its ultrastructural morphology. The correlative technique described herein is likely to open opportunities for unravelling the earlier unrecognized complexity of the nervous system. Lay Description Neuroscience and the understanding of brain functions are closely linked to the technical advances in microscopy. In this study we performed a correlative microscopy technique that offers the possibility to combine 2 photon in vivo imaging and FIB/SEM microscopy. Long term 2 photon in vivo imaging allows the visualization of functional interactions within the brain of a living organism over the time, and therefore, is emerging as a new tool to study the dynamics of neurodegenerative diseases, such as Alzheimer’s disease. However, light microscopy has important limitations in revealing synapses that are the connections between neurons, and for this purpose, the electron microscopy is necessary. FIB/SEM microscopy is a novel tool for three-dimensional (3D) high resolution reconstructions since it acquires automated serial images at ultrastructural level. This correlative technique will open up new horizons and opportunities for unravelling the complexity of the nervous system. PMID:25786682

Qudit-Basis Universal Quantum Computation Using χ^{(2)} Interactions.

PubMed

Niu, Murphy Yuezhen; Chuang, Isaac L; Shapiro, Jeffrey H

2018-04-20

We prove that universal quantum computation can be realized-using only linear optics and χ^{(2)} (three-wave mixing) interactions-in any (n+1)-dimensional qudit basis of the n-pump-photon subspace. First, we exhibit a strictly universal gate set for the qubit basis in the one-pump-photon subspace. Next, we demonstrate qutrit-basis universality by proving that χ^{(2)} Hamiltonians and photon-number operators generate the full u(3) Lie algebra in the two-pump-photon subspace, and showing how the qutrit controlled-Z gate can be implemented with only linear optics and χ^{(2)} interactions. We then use proof by induction to obtain our general qudit result. Our induction proof relies on coherent photon injection or subtraction, a technique enabled by χ^{(2)} interaction between the encoding modes and ancillary modes. Finally, we show that coherent photon injection is more than a conceptual tool, in that it offers a route to preparing high-photon-number Fock states from single-photon Fock states.

Electron and photon energy calibration with the ATLAS detector using LHC Run 1 data

DOE PAGES

Aad, G.; Abbott, B.; Abdallah, J.; ...

2014-10-01

This paper presents the electron and photon energy calibration achieved with the ATLAS detector using about 25 fb -1 of LHC proton–proton collision data taken at centre-of-mass energies of √s=7 and 8 TeV. The reconstruction of electron and photon energies is optimised using multivariate algorithms. The response of the calorimeter layers is equalised in data and simulation, and the longitudinal profile of the electromagnetic showers is exploited to estimate the passive material in front of the calorimeter and reoptimise the detector simulation. After all corrections, the Z resonance is used to set the absolute energy scale. For electrons from Zmore » decays, the achieved calibration is typically accurate to 0.05 % in most of the detector acceptance, rising to 0.2 % in regions with large amounts of passive material. The remaining inaccuracy is less than 0.2–1 % for electrons with a transverse energy of 10 GeV, and is on average 0.3 % for photons. The detector resolution is determined with a relative inaccuracy of less than 10 % for electrons and photons up to 60 GeV transverse energy, rising to 40 % for transverse energies above 500 GeV.« less

SU-E-T-554: Comparison of Electron Disequilibrium Factor in External Photon Beams for Different Models of Linear Accelerators

DOE Office of Scientific and Technical Information (OSTI.GOV)

LIU, B; Zhu, T

Purpose: The dose in the buildup region of a photon beam is usually determined by the transport of the primary secondary electrons and the contaminating electrons from accelerator head. This can be quantified by the electron disequilibrium factor, E, defined as the ratio between total dose and equilibrium dose (proportional to total kerma), E = 1 in regions beyond buildup region. Ecan be different among accelerators of different models and/or manufactures of the same machine. This study compares E in photon beams from different machine models/ Methods: Photon beam data such as fractional depth dose curve (FDD) and phantom scattermore » factors as a function of field size and phantom depth were measured for different Linac machines. E was extrapolated from these fractional depth dose data while taking into account inverse-square law. The ranges of secondary electron were chosen as 3 and 6 cm for 6 and 15 MV photon beams, respectively. The field sizes range from 2x2 to 40x40 cm{sup 2}. Results: The comparison indicates the standard deviations of electron contamination among different machines are about 2.4 - 3.3% at 5 mm depth for 6 MV and 1.2 - 3.9% at 1 cm depth for 15 MV for the same field size. The corresponding maximum deviations are 3.0 - 4.6% and 2 - 4% for 6 and 15 MV, respectively. Both standard and maximum deviations are independent of field sizes in the buildup region for 6 MV photons, and slightly decreasing with increasing field size at depths up to 1 cm for 15 MV photons. Conclusion: The deviations of electron disequilibrium factor for all studied Linacs are less than 3% beyond the depth of 0.5 cm for the photon beams for the full range of field sizes (2-40 cm) so long as they are from the same manufacturer.« less

Photodissociation of HCN and HNC isomers in the 7-10 eV energy range

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chenel, Aurelie; Roncero, Octavio, E-mail: octavio.roncero@csic.es; Aguado, Alfredo

2016-04-14

The ultraviolet photoabsorption spectra of the HCN and HNC isomers have been simulated in the 7-10 eV photon energy range. For this purpose, the three-dimensional adiabatic potential energy surfaces of the 7 lowest electronic states, and the corresponding transition dipole moments, have been calculated, at multireference configuration interaction level. The spectra are calculated with a quantum wave packet method on these adiabatic potential energy surfaces. The spectra for the 3 lower excited states, the dissociative electronic states, correspond essentially to predissociation peaks, most of them through tunneling on the same adiabatic state. The 3 higher electronic states are bound, hereaftermore » electronic bound states, and their spectra consist of delta lines, in the adiabatic approximation. The radiative lifetime towards the ground electronic states of these bound states has been calculated, being longer than 10 ns in all cases, much longer that the characteristic predissociation lifetimes. The spectra of HCN is compared with the available experimental and previous theoretical simulations, while in the case of HNC there are no previous studies to our knowledge. The spectrum for HNC is considerably more intense than that of HCN in the 7-10 eV photon energy range, which points to a higher photodissociation rate for HNC, compared to HCN, in astrophysical environments illuminated by ultraviolet radiation.« less

Transverse Space-Charge Field-Induced Plasma Dynamics for Ultraintense Electron-Beam Characterization

NASA Astrophysics Data System (ADS)

Tarkeshian, R.; Vay, J. L.; Lehe, R.; Schroeder, C. B.; Esarey, E. H.; Feurer, T.; Leemans, W. P.

2018-04-01

Similarly to laser or x-ray beams, the interaction of sufficiently intense particle beams with neutral gases will result in the creation of plasma. In contrast to photon-based ionization, the strong unipolar field of a particle beam can generate a plasma where the electron population receives a large initial momentum kick and escapes, leaving behind unshielded ions. Measuring the properties of the ensuing Coulomb exploding ions—such as their kinetic energy distribution, yield, and spatial distribution—can provide information about the peak electric fields that are achieved in the electron beams. Particle-in-cell simulations and analytical models are presented for high-brightness electron beams of a few femtoseconds or even hundreds of attoseconds, and transverse beam sizes on the micron scale, as generated by today's free electron lasers. Different density regimes for the utilization as a potential diagnostics are explored, and the fundamental differences in plasma dynamical behavior for e-beam or photon-based ionization are highlighted. By measuring the dynamics of field-induced ions for different gas and beam densities, a lower bound on the beam charge density can be obtained in a single shot and in a noninvasive way. The exponential dependency of the ionization yield on the beam properties can provide unprecedented spatial and temporal resolution, at the submicrometer and subfemtosecond scales, respectively, offering a practical and powerful approach to characterizing beams from accelerators at the frontiers of performance.

Fabrication of 3-D Photonic Band Gap Crystals Via Colloidal Self-Assembly

NASA Technical Reports Server (NTRS)

Subramaniam, Girija; Blank, Shannon

2005-01-01

The behavior of photons in a Photonic Crystals, PCs, is like that of electrons in a semiconductor in that, it prohibits light propagation over a band of frequencies, called Photonic Band Gap, PBG. Photons cannot exist in these band gaps like the forbidden bands of electrons. Thus, PCs lend themselves as potential candidates for devices based on the gap phenomenon. The popular research on PCs stem from their ability to confine light with minimal losses. Large scale 3-D PCs with a PBG in the visible or near infra red region will make optical transistors and sharp bent optical fibers. Efforts are directed to use PCs for information processing and it is not long before we can have optical integrated circuits in the place of electronic ones.

Design and construction of a high-energy photon polarimeter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dugger, M.; Ritchie, B. G.; Sparks, N.

Here, we report on the design and construction of a high-energy photon polarimeter for measuring the degree of polarization of a linearly-polarized photon beam. The photon polarimeter uses the process of pair production on an atomic electron (triplet production). The azimuthal distribution of scattered atomic electrons following triplet production yields information regarding the degree of linear polarization of the incident photon beam. Furthermore, the polarimeter, operated in conjunction with a pair spectrometer, uses a silicon strip detector to measure the recoil electron distribution resulting from triplet photoproduction in a beryllium target foil. The analyzing power Σ A for the devicemore » using a 75 μm beryllium converter foil is about 0.2, with a relative systematic uncertainty in Σ A of 1.5%.« less

Design and construction of a high-energy photon polarimeter

DOE PAGES

Dugger, M.; Ritchie, B. G.; Sparks, N.; ...

2017-06-12

Here, we report on the design and construction of a high-energy photon polarimeter for measuring the degree of polarization of a linearly-polarized photon beam. The photon polarimeter uses the process of pair production on an atomic electron (triplet production). The azimuthal distribution of scattered atomic electrons following triplet production yields information regarding the degree of linear polarization of the incident photon beam. Furthermore, the polarimeter, operated in conjunction with a pair spectrometer, uses a silicon strip detector to measure the recoil electron distribution resulting from triplet photoproduction in a beryllium target foil. The analyzing power Σ A for the devicemore » using a 75 μm beryllium converter foil is about 0.2, with a relative systematic uncertainty in Σ A of 1.5%.« less

Multiple Exciton Generation in Semiconductor Nanostructures: DFT-based Computation

NASA Astrophysics Data System (ADS)

Mihaylov, Deyan; Kryjevski, Andrei; Kilin, Dmitri; Kilina, Svetlana; Vogel, Dayton

Multiple exciton generation (MEG) in nm-sized H-passivated Si nanowires (NWs), and quasi 2D nanofilms depends strongly on the degree of the core structural disorder as shown by the perturbation theory calculations based on the DFT simulations. In perturbation theory, we work to the 2nd order in the electron-photon coupling and in the (approximate) RPA-screened Coulomb interaction. We also include the effect of excitons for which we solve Bethe-Salpeter Equation. To describe MEG we calculate exciton-to-biexciton as well as biexciton-to-exciton rates and quantum efficiency (QE). We consider 3D arrays of Si29H36 quantum dots, NWs, and quasi 2D silicon nanofilms, all with both crystalline and amorphous core structures. Efficient MEG with QE of 1.3 up to 1.8 at the photon energy of about 3Egap is predicted in these nanoparticles except for the crystalline NW and film where QE ~=1. MEG in the amorphous nanoparticles is enhanced by the electron localization due to structural disorder. The exciton effects significantly red-shift QE vs. photon energy curves. Nm-sized a-Si NWs and films are predicted to have effective MEG within the solar spectrum range. Also, we find efficient MEG in the chiral single-wall Carbon nanotubes and in a perovskite nanostructure.

Collisional Lifetimes of Elementary Excitations in Two-Dimensional Systems in the Field of a Strong Electromagnetic Wave

NASA Astrophysics Data System (ADS)

Kovalev, V. M.

2018-04-01

A two-dimensional system with two nonequivalent valleys in the field of a strong circularly polarized electromagnetic wave is considered. It is assumed that the optical selection rules for a given polarization of light allow band-to-band transitions only in valleys of one, optically active, type (two-dimensional layer based on transition metal dichalcogenides, gapped graphene, etc.). This leads to the formation of photon-coupled electron-hole pairs, or an "optical insulator" state. It is assumed that the valleys of the second type (optically inactive) are populated with an equilibrium electron gas. The relaxation of elementary excitations in this hybrid system consisting of an electron gas and a gas of electron-hole pairs caused by the Coulomb interaction between the particles is investigated.

Strong spin-photon coupling in silicon

NASA Astrophysics Data System (ADS)

Samkharadze, N.; Zheng, G.; Kalhor, N.; Brousse, D.; Sammak, A.; Mendes, U. C.; Blais, A.; Scappucci, G.; Vandersypen, L. M. K.

2018-03-01

Long coherence times of single spins in silicon quantum dots make these systems highly attractive for quantum computation, but how to scale up spin qubit systems remains an open question. As a first step to address this issue, we demonstrate the strong coupling of a single electron spin and a single microwave photon. The electron spin is trapped in a silicon double quantum dot, and the microwave photon is stored in an on-chip high-impedance superconducting resonator. The electric field component of the cavity photon couples directly to the charge dipole of the electron in the double dot, and indirectly to the electron spin, through a strong local magnetic field gradient from a nearby micromagnet. Our results provide a route to realizing large networks of quantum dot–based spin qubit registers.

Quantum state detection and state preparation based on cavity-enhanced nonlinear interaction of atoms with single photon

NASA Astrophysics Data System (ADS)

Hosseini, Mahdi

Our ability to engineer quantum states of light and matter has significantly advanced over the past two decades, resulting in the production of both Gaussian and non-Gaussian optical states. The resulting tailored quantum states enable quantum technologies such as quantum optical communication, quantum sensing as well as quantum photonic computation. The strong nonlinear light-atom interaction is the key to deterministic quantum state preparation and quantum photonic processing. One route to enhancing the usually weak nonlinear light-atom interactions is to approach the regime of cavity quantum electrodynamics (cQED) interaction by means of high finesse optical resonators. I present results from the MIT experiment of large conditional cross-phase modulation between a signal photon, stored inside an atomic quantum memory, and a control photon that traverses a high-finesse optical cavity containing the atomic memory. I also present a scheme to probabilistically change the amplitude and phase of a signal photon qubit to, in principle, arbitrary values by postselection on a control photon that has interacted with that state. Notably, small changes of the control photon polarization measurement basis by few degrees can substantially change the amplitude and phase of the signal state. Finally, I present our ongoing effort at Purdue to realize similar peculiar quantum phenomena at the single photon level on chip scale photonic systems.

Emergence of electron coherence and two-color all-optical switching in MoS2 based on spatial self-phase modulation

PubMed Central

Wu, Yanling; Wu, Qiong; Sun, Fei; Cheng, Cai; Meng, Sheng; Zhao, Jimin

2015-01-01

Generating electron coherence in quantum materials is essential in optimal control of many-body interactions and correlations. In a multidomain system this signifies nonlocal coherence and emergence of collective phenomena, particularly in layered 2D quantum materials possessing novel electronic structures and high carrier mobilities. Here we report nonlocal ac electron coherence induced in dispersed MoS2 flake domains, using coherent spatial self-phase modulation (SSPM). The gap-dependent nonlinear dielectric susceptibility χ(3) measured is surprisingly large, where direct interband transition and two-photon SSPM are responsible for excitations above and below the bandgap, respectively. A wind-chime model is proposed to account for the emergence of the ac electron coherence. Furthermore, all-optical switching is achieved based on SSPM, especially with two-color intraband coherence, demonstrating that electron coherence generation is a ubiquitous property of layered quantum materials. PMID:26351696

Aqueous Exfoliation of Graphite into Graphene Assisted by Sulfonyl Graphene Quantum Dots for Photonic Crystal Applications.

PubMed

Zeng, Minxiang; Shah, Smit A; Huang, Dali; Parviz, Dorsa; Yu, Yi-Hsien; Wang, Xuezhen; Green, Micah J; Cheng, Zhengdong

2017-09-13

We investigate the π-π stacking of polyaromatic hydrocarbons (PAHs) with graphene surfaces, showing that such interactions are general across a wide range of PAH sizes and species, including graphene quantum dots. We synthesized a series of graphene quantum dots with sulfonyl, amino, and carboxylic functional groups and employed them to exfoliate and disperse pristine graphene in water. We observed that sulfonyl-functionalized graphene quantum dots were able to stabilize the highest concentration of graphene in comparison to other functional groups; this is consistent with prior findings by pyrene. The graphene nanosheets prepared showed excellent colloidal stability, indicating great potential for applications in electronics, solar cells, and photonic displays which was demonstrated in this work.

Radiative decays of massive relic particles and the submillimeter background

NASA Technical Reports Server (NTRS)

Field, George B.; Walker, Terry P.

1989-01-01

The interaction of the decay photons of an unstable relic particle species with the microwave background radiation is considered. The radiative decays of these particles delay recombination and serve as an energy source for the resultant plasma. Nonrelativistic Compton scattering by these electrons couples the decay photons to the microwave background, producing submillimeter distortions. If the decay products close the universe, they must decay with a radiative branching ratio larger than 2.5 x 10 to the -5th in order to produce recently observed excess submillimeter background radiation. To be consistent with measurements of the UV background, their mass m is much greater than 114 keV and their decay redshift z is much greater than 5200.

Topological Transport of Light and Sound

NASA Astrophysics Data System (ADS)

Brendel, Christian; Peano, Vittorio; Schmidt, Michael; Marquardt, Florian

Since they exploit global features of a material's band structure, topological states of matter are particularly robust. Having already been observed for electrons, atoms, and photons, it is an outstanding challenge to create a Chern insulator of sound waves in the solid state. In this work, we propose an implementation based on cavity optomechanics in a photonic crystal. We demonstrate the feasibility of our proposal by means of an effective lattice model as well as first principle simulations. The topological properties of the sound waves can be wholly tuned in situ by adjusting the amplitude and frequency of a driving laser that controls the optomechanical interaction between light and sound. The resulting chiral, topologically protected phonon transport can be probed completely optically.

Improvement of density resolution in short-pulse hard x-ray radiographic imaging using detector stacks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Borm, B.; Gärtner, F.; Khaghani, D.

2016-09-15

We demonstrate that stacking several imaging plates (IPs) constitutes an easy method to increase hard x-ray detection efficiency. Used to record x-ray radiographic images produced by an intense-laser driven hard x-ray backlighter source, the IP stacks resulted in a significant improvement of the radiograph density resolution. We attribute this to the higher quantum efficiency of the combined detectors, leading to a reduced photon noise. Electron-photon transport simulations of the interaction processes in the detector reproduce the observed contrast improvement. Increasing the detection efficiency to enhance radiographic imaging capabilities is equally effective as increasing the x-ray source yield, e.g., by amore » larger drive laser energy.« less

Prospects of direct search for dark photon and dark Higgs in SeaQuest/E1067 experiment at the Fermilab main injector

NASA Astrophysics Data System (ADS)

Liu, Ming Xiong

2017-03-01

In this review, we present the current status and prospects of the dark sector physics search program of the SeaQuest/E1067 fixed target dimuon experiment at Fermilab Main Injector. There has been tremendous excitement and progress in searching for new physics in the dark sector in recent years. Dark sector refers to a collection of currently unknown particles that do not directly couple with the Standard Model (SM) strong and electroweak (EW) interactions but assumed to carry gravitational force, thus could be candidates of the missing Dark Matter (DM). Such particles may interact with the SM particles through “portal” interactions. Two of the simple possibilities are being investigated in our initial search: (1) dark photon and (2) dark Higgs. They could be within immediate reach of current or near future experimental search. We show there is a unique opportunity today at Fermilab to directly search for these particles in a highly motivated but uncharted parameter space in high-energy proton-nucleus collisions in the beam-dump mode using the 120 GeV proton beam from the Main Injector. Our current search window covers the mass range 0.2-10 GeV/c2, and in the near future, by adding an electromagnetic calorimeter (EMCal) to the spectrometer, we can further explore the lower mass region down to about ˜1 MeV/c2 through the di-electron channel. If dark photons (and/or dark Higgs) were observed, they would revolutionize our understanding of the fundamental structures and interactions of our universe.

Studies of Interactions Between Nano-Objects and Polarized Light

NASA Astrophysics Data System (ADS)

Xie, Dan

Optical studies of nano-objects that have dimensions 10--1000 nm have become a flourishing field of research. This special dimension category, connecting the smaller (molecular) world and the larger (cellular) world, have enabled these nano-objects to be widely utilized as novel optical tools in many fields. In addition to the extensive applications of nano objects, increasing efforts are also being put to better understand their interactions with light at a fundamental level. The work presented in this dissertation is part of such efforts, in which I selected three types of nano-objects and studied their optical properties both in theory and experiment. Second-harmonic and sum-frequency generations are among the most well-known nonlinear optical processes. Dielectric nanocrystals that are SHG- and SFG-active are favored tools in bioimaging. For a nanocrystal, its SHG/SFG intensity depends on the geometry of the light-particle system, i.e., the relationship between the nanocrystal orientation and the laser polarization. Using BaTiO 3 nanocrystals as an example, I carried out an in-depth, theoretical investigation of such dependence. Particularly, I studied the possibility of selectively maximizing the contrast between light signals from two or more nanocrystals by manipulating laser polarization. I will present a discussion on how the capacity of this selective illumination depends on the relative orientation between the two nanocrystals and the polarization of the excitation field. The optical responses of non-spherical plasmonic particles, being dynamic and complex, are only partially understood. Gold nanorods (AuNRs) are one of the most popular members in this nanoparticle family. They can produce two-photon luminescence (TPL) and amplify molecular events occurring at their surface. Both phenomena are known to be associated with surface plasmon resonances (SPR) of AuNRs, but details of the mechanisms are yet to be understood and quantified. I constructed a two-photon laser-scanning microscopy system to study these phenomena at the single-particle level. In the experiment, I measured the polarization-dependent TPL emissions from single nanorods that are triggered by time-resolved two-photon excitations. The observation indicates that, different from what was generally believed, the TPL in AuNRs is resulted from two sequentially one-photon absorption process that are both coupled to the longitudinal SPR mode. The studies on the two-photon fluorescence in dyes conjugated with AuNRs confirmed the coherent nature of the two-photon absorption process and provided an estimate of the fluorescence enhancement due to the presence of AuNRs. Molecules with cross-conjugated structures have a special role in molecular electronics. Their inherent quantum interference property can be utilized to create molecular switches with excellent on/off ratio. When a molecular junction is exposed to light, photons may open extra pathways for electron tunneling, and thus modify the conduction properties of the junction. Such modification depends on the electronic structure of the molecule, as well as on the frequency, amplitude, and polarization of the driving field. In collaboration with my colleague, I simulated electron tunneling properties of junctions with cross-conjugated molecules and discussed their dependence on light properties. It is noteworthy that symmetry plays a major role in zero-bias tunneling: the molecule-field systems with general parity show distinct tunneling behaviors from their counterparts without general parity.

Measurements of Electrical and Electron Emission Properties of Highly Insulating Materials

NASA Technical Reports Server (NTRS)

Dennison, J. R.; Brunson, Jerilyn; Hoffman, Ryan; Abbott, Jonathon; Thomson, Clint; Sim, Alec

2005-01-01

Highly insulating materials often acquire significant charges when subjected to fluxes of electrons, ions, or photons. This charge can significantly modify the materials properties of the materials and have profound effects on the functionality of the materials in a variety of applications. These include charging of spacecraft materials due to interactions with the severe space environment, enhanced contamination due to charging in Lunar of Martian environments, high power arching of cables and sources, modification of tethers and ion thrusters for propulsion, and scanning electron microscopy, to name but a few examples. This paper describes new techniques and measurements of the electron emission properties and resistivity of highly insulating materials. Electron yields are a measure of the number of electrons emitted from a material per incident particle (electron, ion or photon). Electron yields depend on incident species, energy and angle, and on the material. They determine the net charge acquired by a material subject to a give incident flu. New pulsed-beam techniques will be described that allow accurate measurement of the yields for uncharged insulators and measurements of how the yields are modified as charge builds up in the insulator. A key parameter in modeling charge dissipation is the resistivity of insulating materials. This determines how charge will accumulate and redistribute across an insulator, as well as the time scale for charge transport and dissipation. Comparison of new long term constant-voltage methods and charge storage methods for measuring resistivity of highly insulating materials will be compared to more commonly used, but less accurate methods.

Nonequilibrium electron and lattice dynamics of strongly correlated Bi2Sr2CaCu2O8+δ single crystals

PubMed Central

Li, Renkai; Gu, Genda; Avigo, Isabella; Dürr, Hermann A.; Johnson, Peter D.; Wang, Xijie

2018-01-01

The interplay between the electronic and lattice degrees of freedom in nonequilibrium states of strongly correlated systems has been debated for decades. Although progress has been made in establishing a hierarchy of electronic interactions with the use of time-resolved techniques, the role of the phonons often remains in dispute, a situation highlighting the need for tools that directly probe the lattice. We present the first combined megaelectron volt ultrafast electron diffraction and time- and angle-resolved photoemission spectroscopy study of optimally doped Bi2Sr2CaCu2O8+δ. Quantitative analysis of the lattice and electron subsystems’ dynamics provides a unified picture of nonequilibrium electron-phonon interactions in the cuprates beyond the N-temperature model. The work provides new insights on the specific phonon branches involved in the nonequilibrium heat dissipation from the high-energy Cu–O bond stretching “hot” phonons to the lowest-energy acoustic phonons with correlated atomic motion along the <110> crystal directions and their characteristic time scales. It reveals a highly nonthermal phonon population during the first several picoseconds after the photoexcitation. The approach, taking advantage of the distinct nature of electrons and photons as probes, is applicable for studying energy relaxation in other strongly correlated electron systems. PMID:29719862

The LAMP instrument at the Linac Coherent Light Source free-electron laser

NASA Astrophysics Data System (ADS)

Osipov, Timur; Bostedt, Christoph; Castagna, J.-C.; Ferguson, Ken R.; Bucher, Maximilian; Montero, Sebastian C.; Swiggers, Michele L.; Obaid, Razib; Rolles, Daniel; Rudenko, Artem; Bozek, John D.; Berrah, Nora

2018-03-01

The Laser Applications in Materials Processing (LAMP) instrument is a new end-station for soft X-ray imaging, high-field physics, and ultrafast X-ray science experiments that is available to users at the Linac Coherent Light Source (LCLS) free-electron laser. While the instrument resides in the Atomic, Molecular and Optical science hutch, its components can be used at any LCLS beamline. The end-station has a modular design that provides high flexibility in order to meet user-defined experimental requirements and specifications. The ultra-high-vacuum environment supports different sample delivery systems, including pulsed and continuous atomic, molecular, and cluster jets; liquid and aerosols jets; and effusive metal vapor beams. It also houses movable, large-format, high-speed pnCCD X-ray detectors for detecting scattered and fluorescent photons. Multiple charged-particle spectrometer options are compatible with the LAMP chamber, including a double-sided spectrometer for simultaneous and even coincident measurements of electrons, ions, and photons produced by the interaction of the high-intensity X-ray beam with the various samples. Here we describe the design and capabilities of the spectrometers along with some general aspects of the LAMP chamber and show some results from the initial instrument commissioning.

Photonic Aharonov–Bohm effect in photon–phonon interactions

PubMed Central

Li, Enbang; Eggleton, Benjamin J.; Fang, Kejie; Fan, Shanhui

2014-01-01

The Aharonov–Bohm effect is one of the most intriguing phenomena in both classical and quantum physics, and associates with a number of important and fundamental issues in quantum mechanics. The Aharonov–Bohm effects of charged particles have been experimentally demonstrated and found applications in various fields. Recently, attention has also focused on the Aharonov–Bohm effect for neutral particles, such as photons. Here we propose to utilize the photon–phonon interactions to demonstrate that photonic Aharonov–Bohm effects do exist for photons. By introducing nonreciprocal phases for photons, we observe experimentally a gauge potential for photons in the visible range based on the photon–phonon interactions in acousto-optic crystals, and demonstrate the photonic Aharonov–Bohm effect. The results presented here point to new possibilities to control and manipulate photons by designing an effective gauge potential. PMID:24476790

Parallel and Multivalued Logic by the Two-Dimensional Photon-Echo Response of a Rhodamine–DNA Complex

PubMed Central

2015-01-01

Implementing parallel and multivalued logic operations at the molecular scale has the potential to improve the miniaturization and efficiency of a new generation of nanoscale computing devices. Two-dimensional photon-echo spectroscopy is capable of resolving dynamical pathways on electronic and vibrational molecular states. We experimentally demonstrate the implementation of molecular decision trees, logic operations where all possible values of inputs are processed in parallel and the outputs are read simultaneously, by probing the laser-induced dynamics of populations and coherences in a rhodamine dye mounted on a short DNA duplex. The inputs are provided by the bilinear interactions between the molecule and the laser pulses, and the output values are read from the two-dimensional molecular response at specific frequencies. Our results highlights how ultrafast dynamics between multiple molecular states induced by light–matter interactions can be used as an advantage for performing complex logic operations in parallel, operations that are faster than electrical switching. PMID:25984269

Photon echo spectroscopy reveals structure-dynamics relationships in carotenoids

NASA Astrophysics Data System (ADS)

Christensson, N.; Polivka, T.; Yartsev, A.; Pullerits, T.

2009-06-01

Based on simultaneous analysis of the frequency-resolved transient grating, peak shift, and echo width signals, we present a model for the third-order optical response of carotenoids including population dynamics and system-bath interactions. Our frequency-resolved photon echo experiments show that the model needs to incorporate the excited-state absorption from both the S2 and the S1 states. We apply our model to analyze the experimental results on astaxanthin and lycopene, aiming to elucidate the relation between structure and system-bath interactions. Our analysis allows us to relate structural motifs to changes in the energy-gap correlation functions. We find that the terminal rings of astaxanthin lead to increased coupling between slow molecular motions and the electronic transition. We also find evidence for stronger coupling to higher frequency overdamped modes in astaxanthin, pointing to the importance of the functional groups in providing coupling to fluctuations influencing the dynamics in the passage through the conical intersection governing the S2-S1 relaxation.

Consequences of Relativistic Neutron Outflow beyond the Accretion Disks of Active Galaxies

NASA Astrophysics Data System (ADS)

Ekejiuba, I. E.; Okeke, P. N.

1993-05-01

Three channels of relativistic electron injection in the jets of extragalactic radio sources (EGRSs) are discussed. With the assumption that an active galactic nucleus (AGN) is powered by a spinning supermassive black hole of mass ~ 10(8) M_⊙ which sits at the center of the nucleus and ingests matter and energy through an accretion disk, a model for extracting relativistic neutrons from the AGN is forged. In this model, the inelastic proton--proton and proton--photon interactions within the accretion disk, of relativistic protons with background thermal protons and photons, respectively, produce copious amounts of relativistic neutrons. These neutrons travel ballistically for ~ 10(3gamma_n ) seconds and escape from the disk before they decay. The secondary particles produced from the neutron decays then interact with the ambient magnetic field and/or other particles to produce the radio emissions observed in the jets of EGRSs. IEE acknowledges the support of the World Bank and the Federal University of Technology, Yola, Nigeria as well as the hospitality of Georgia State University.

Laser modified processes: bremsstrahlung and inelastic photon atom scattering

NASA Astrophysics Data System (ADS)

Budriga, Olimpia; Dondera, Mihai; Florescu, Viorica

2007-08-01

We consider the influence of a low-frequency monochromatic external electromagnetic field (the laser) on two basic atomic processes: electron Coulomb bremsstrahlung and inelastic photon scattering on an electron bound in the ground state of a hydrogenic atom. We briefly describe the approximations adopted and illustrate in figures how the laser parameters modify the shape of the differential cross-sections and extend the energy domain for emitted electrons, due to simultaneous absorption or emission of a large number (hundreds) of laser photons.

Deterministic photon-emitter coupling in chiral photonic circuits.

PubMed

Söllner, Immo; Mahmoodian, Sahand; Hansen, Sofie Lindskov; Midolo, Leonardo; Javadi, Alisa; Kiršanskė, Gabija; Pregnolato, Tommaso; El-Ella, Haitham; Lee, Eun Hye; Song, Jin Dong; Stobbe, Søren; Lodahl, Peter

2015-09-01

Engineering photon emission and scattering is central to modern photonics applications ranging from light harvesting to quantum-information processing. To this end, nanophotonic waveguides are well suited as they confine photons to a one-dimensional geometry and thereby increase the light-matter interaction. In a regular waveguide, a quantum emitter interacts equally with photons in either of the two propagation directions. This symmetry is violated in nanophotonic structures in which non-transversal local electric-field components imply that photon emission and scattering may become directional. Here we show that the helicity of the optical transition of a quantum emitter determines the direction of single-photon emission in a specially engineered photonic-crystal waveguide. We observe single-photon emission into the waveguide with a directionality that exceeds 90% under conditions in which practically all the emitted photons are coupled to the waveguide. The chiral light-matter interaction enables deterministic and highly directional photon emission for experimentally achievable on-chip non-reciprocal photonic elements. These may serve as key building blocks for single-photon optical diodes, transistors and deterministic quantum gates. Furthermore, chiral photonic circuits allow the dissipative preparation of entangled states of multiple emitters for experimentally achievable parameters, may lead to novel topological photon states and could be applied for directional steering of light.

Deterministic photon-emitter coupling in chiral photonic circuits

NASA Astrophysics Data System (ADS)

Söllner, Immo; Mahmoodian, Sahand; Hansen, Sofie Lindskov; Midolo, Leonardo; Javadi, Alisa; Kiršanskė, Gabija; Pregnolato, Tommaso; El-Ella, Haitham; Lee, Eun Hye; Song, Jin Dong; Stobbe, Søren; Lodahl, Peter

2015-09-01

Engineering photon emission and scattering is central to modern photonics applications ranging from light harvesting to quantum-information processing. To this end, nanophotonic waveguides are well suited as they confine photons to a one-dimensional geometry and thereby increase the light-matter interaction. In a regular waveguide, a quantum emitter interacts equally with photons in either of the two propagation directions. This symmetry is violated in nanophotonic structures in which non-transversal local electric-field components imply that photon emission and scattering may become directional. Here we show that the helicity of the optical transition of a quantum emitter determines the direction of single-photon emission in a specially engineered photonic-crystal waveguide. We observe single-photon emission into the waveguide with a directionality that exceeds 90% under conditions in which practically all the emitted photons are coupled to the waveguide. The chiral light-matter interaction enables deterministic and highly directional photon emission for experimentally achievable on-chip non-reciprocal photonic elements. These may serve as key building blocks for single-photon optical diodes, transistors and deterministic quantum gates. Furthermore, chiral photonic circuits allow the dissipative preparation of entangled states of multiple emitters for experimentally achievable parameters, may lead to novel topological photon states and could be applied for directional steering of light.

Access to long-term optical memories using photon echoes retrieved from electron spins in semiconductor quantum wells

NASA Astrophysics Data System (ADS)

Poltavtsev, S. V.; Langer, L.; Yugova, I. A.; Salewski, M.; Kapitonov, Y. V.; Yakovlev, D. R.; Karczewski, G.; Wojtowicz, T.; Akimov, I. A.; Bayer, M.

2016-10-01

We use spontaneous (two-pulse) and stimulated (three-pulse) photon echoes for studying the coherent evolution of optically excited ensemble of trions which are localized in semiconductor CdTe/CdMgTe quantum well. Application of transverse magnetic field leads to the Larmor precession of the resident electron spins, which shuffles optically induced polarization between optically accessible and inaccessible states. This results in several spectacular phenomena. First, magnetic field induces oscillations of spontaneous photon echo amplitude. Second, in three-pulse excitation scheme, the photon echo decay is extended by several orders of magnitude. In this study, short-lived optical excitation which is created by the first pulse is coherently transferred into a long-lived electron spin state using the second optical pulse. This coherent spin state of electron ensemble persists much longer than any optical excitation in the system, preserving information on initial optical field, which can be retrieved as a photon echo by means of third optical pulse.

Changing optical band structure with single photons

NASA Astrophysics Data System (ADS)

Albrecht, Andreas; Caneva, Tommaso; Chang, Darrick E.

2017-11-01

Achieving strong interactions between individual photons enables a wide variety of exciting possibilities in quantum information science and many-body physics. Cold atoms interfaced with nanophotonic structures have emerged as a platform to realize novel forms of nonlinear interactions. In particular, when atoms are coupled to a photonic crystal waveguide, long-range atomic interactions can arise that are mediated by localized atom-photon bound states. We theoretically show that in such a system, the absorption of a single photon can change the band structure for a subsequent photon. This occurs because the first photon affects the atoms in the chain in an alternating fashion, thus leading to an effective period doubling of the system and a new optical band structure for the composite atom-nanophotonic system. We demonstrate how this mechanism can be engineered to realize a single-photon switch, where the first incoming photon switches the system from being highly transmissive to highly reflective, and analyze how signatures can be observed via non-classical correlations of the outgoing photon field.

Many-Body Theory of Proton-Generated Point Defects for Losses of Electron Energy and Photons in Quantum Wells

NASA Astrophysics Data System (ADS)

Huang, Danhong; Iurov, Andrii; Gao, Fei; Gumbs, Godfrey; Cardimona, D. A.

2018-02-01

The effects of point defects on the loss of either energies of ballistic electron beams or incident photons are studied by using a many-body theory in a multi-quantum-well system. This theory includes the defect-induced vertex correction to a bare polarization function of electrons within the ladder approximation, and the intralayer and interlayer screening of defect-electron interactions is also taken into account in the random-phase approximation. The numerical results of defect effects on both energy-loss and optical-absorption spectra are presented and analyzed for various defect densities, numbers of quantum wells, and wave vectors. The diffusion-reaction equation is employed for calculating distributions of point defects in a layered structure. For completeness, the production rate for Frenkel-pair defects and their initial concentration are obtained based on atomic-level molecular-dynamics simulations. By combining the defect-effect, diffusion-reaction, and molecular-dynamics models with an available space-weather-forecast model, it will be possible in the future to enable specific designing for electronic and optoelectronic quantum devices that will be operated in space with radiation-hardening protection and, therefore, effectively extend the lifetime of these satellite onboard electronic and optoelectronic devices. Specifically, this theory can lead to a better characterization of quantum-well photodetectors not only for high quantum efficiency and low dark current density but also for radiation tolerance or mitigating the effects of the radiation.

A Monte Carlo method using octree structure in photon and electron transport

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ogawa, K.; Maeda, S.

Most of the early Monte Carlo calculations in medical physics were used to calculate absorbed dose distributions, and detector responses and efficiencies. Recently, data acquisition in Single Photon Emission CT (SPECT) has been simulated by a Monte Carlo method to evaluate scatter photons generated in a human body and a collimator. Monte Carlo simulations in SPECT data acquisition are generally based on the transport of photons only because the photons being simulated are low energy, and therefore the bremsstrahlung productions by the electrons generated are negligible. Since the transport calculation of photons without electrons is much simpler than that withmore » electrons, it is possible to accomplish the high-speed simulation in a simple object with one medium. Here, object description is important in performing the photon and/or electron transport using a Monte Carlo method efficiently. The authors propose a new description method using an octree representation of an object. Thus even if the boundaries of each medium are represented accurately, high-speed calculation of photon transport can be accomplished because the number of voxels is much fewer than that of the voxel-based approach which represents an object by a union of the voxels of the same size. This Monte Carlo code using the octree representation of an object first establishes the simulation geometry by reading octree string, which is produced by forming an octree structure from a set of serial sections for the object before the simulation; then it transports photons in the geometry. Using the code, if the user just prepares a set of serial sections for the object in which he or she wants to simulate photon trajectories, he or she can perform the simulation automatically using the suboptimal geometry simplified by the octree representation without forming the optimal geometry by handwriting.« less

An analytical method for computing voxel S values for electrons and photons.

PubMed

Amato, Ernesto; Minutoli, Fabio; Pacilio, Massimiliano; Campenni, Alfredo; Baldari, Sergio

2012-11-01

The use of voxel S values (VSVs) is perhaps the most common approach to radiation dosimetry for nonuniform distributions of activity within organs or tumors. However, VSVs are currently available only for a limited number of voxel sizes and radionuclides. The objective of this study was to develop a general method to evaluate them for any spectrum of electrons and photons in any cubic voxel dimension of practical interest for clinical dosimetry in targeted radionuclide therapy. The authors developed a Monte Carlo simulation in Geant4 in order to evaluate the energy deposited per disintegration (E(dep)) in a voxelized region of soft tissue from monoenergetic electrons (10-2000 keV) or photons (10-1000 keV) homogeneously distributed in the central voxel, considering voxel dimensions ranging from 3 mm to 10 mm. E(dep) was represented as a function of a dimensionless quantity termed the "normalized radius," R(n) = R∕l, where l is the voxel size and R is the distance from the origin. The authors introduced two parametric functions in order to fit the electron and photon results, and they interpolated the parameters to derive VSVs for any energy and voxel side within the ranges mentioned above. In order to validate the results, the authors determined VSV for two radionuclides ((131)I and (89)Sr) and two voxel dimensions and they compared them with reference data. A validation study in a simple sphere model, accounting for tissue inhomogeneities, is presented. The E(dep)(R(n)) for both monoenergetic electrons and photons exhibit a smooth variation with energy and voxel size, implying that VSVs for monoenergetic electrons or photons may be derived by interpolation over the range of energies and dimensions considered. By integration, S values for continuous emission spectra from β(-) decay may be derived as well. The approach allows the determination of VSVs for monoenergetic (Auger or conversion) electrons and (x-ray or gamma-ray) photons by means of two functions whose parameters can be interpolated from tabular data provided. Through integration, it is possible to generalize the method to any continuous (beta) spectrum, allowing to calculate VSVs for any electron and photon emitter in a voxelized structure.

Coupled-resonator waveguide perfect transport single-photon by interatomic dipole-dipole interaction

NASA Astrophysics Data System (ADS)

Yan, Guo-an; Lu, Hua; Qiao, Hao-xue; Chen, Ai-xi; Wu, Wan-qing

2018-06-01

We theoretically investigate single-photon coherent transport in a one-dimensional coupled-resonator waveguide coupled to two quantum emitters with dipole-dipole interactions. The numerical simulations demonstrate that the transmission spectrum of the photon depends on the two atoms dipole-dipole interactions and the photon-atom couplings. The dipole-dipole interactions may change the dip positions in the spectra and the coupling strength may broaden the frequency band width in the transmission spectrum. We further demonstrate that the typical transmission spectra split into two dips due to the dipole-dipole interactions. This phenomenon may be used to manufacture new quantum waveguide devices.

Electron Trajectory Reconstruction for Advanced Compton Imaging of Gamma Rays

NASA Astrophysics Data System (ADS)

Plimley, Brian Christopher

Gamma-ray imaging is useful for detecting, characterizing, and localizing sources in a variety of fields, including nuclear physics, security, nuclear accident response, nuclear medicine, and astronomy. Compton imaging in particular provides sensitivity to weak sources and good angular resolution in a large field of view. However, the photon origin in a single event sequence is normally only limited to the surface of a cone. If the initial direction of the Compton-scattered electron can be measured, the cone can be reduced to a cone segment with width depending on the uncertainty in the direction measurement, providing a corresponding increase in imaging sensitivity. Measurement of the electron's initial direction in an efficient detection material requires very fine position resolution due to the electron's short range and tortuous path. A thick (650 mum), fully-depleted charge-coupled device (CCD) developed for infrared astronomy has 10.5-mum position resolution in two dimensions, enabling the initial trajectory measurement of electrons of energy as low as 100 keV. This is the first time the initial trajectories of electrons of such low energies have been measured in a solid material. In this work, the CCD's efficacy as a gamma-ray detector is demonstrated experimentally, using a reconstruction algorithm to measure the initial electron direction from the CCD track image. In addition, models of fast electron interaction physics, charge transport and readout were used to generate modeled tracks with known initial direction. These modeled tracks allowed the development and refinement of the reconstruction algorithm. The angular sensitivity of the reconstruction algorithm is evaluated extensively with models for tracks below 480 keV, showing a FWHM as low as 20° in the pixel plane, and 30° RMS sensitivity to the magnitude of the out-of-plane angle. The measurement of the trajectories of electrons with energies as low as 100 keV have the potential to make electron track Compton imaging an effective means of reducing image background for photons of energy as low as 500 keV, or even less. The angular sensitivity of the reconstruction algorithm was also evaluated experimentally, by measuring electron tracks in the CCD in coincidence with the scattered photon in a germanium double-sided strip detector. By this method, electron tracks could be measured with the true initial direction known to within 3° FWHM, and the angular response of the algorithm compared to the known direction. The challenge of this experiment lay in the low geometric efficiency for photons scattering into the germanium, the poor time resolution in the current CCD implementation, and the resulting signal-to-background ratio of about 10--4 for photons scattered from the CCD into the germanium detector. Nonetheless, 87 events were measured in the FWHM of the total energy deposited and the angular resolution measure, with electron tracks between 160 keV and 360 keV in energy. The electron tracks from true coincident event sequences showed a FWHM in the pixel plane of 23°, and excellent agreement with the distribution calculated with models, with likelihood p-values of 0.44 and 0.73. Thus, the models used for the more thorough evaluation of angular sensitivities are shown to be consistent with the measured tracks from true coincident event sequences.

Gamma ray pulsars

NASA Technical Reports Server (NTRS)

Oegelman, H.; Ayasli, S.; Hacinliyan, A.

1976-01-01

Recent data from the high energy gamma ray experiment have revealed the existence of four pulsars emitting photons above 35 MeV. An attempt is made to explain the gamma ray emission from these pulsars in terms of an electron-photon cascade that develops in the magnetosphere of the pulsar. Although there is very little material above the surface of the pulsar, the very intense magnetic fields correspond to many radiation lengths which cause electrons to emit photons via magnetic bremsstrahlung and these photons to pair produce. The cascade develops until the mean photon energy drops below the pair production threshold which happens to be in the gamma ray range; at this stage the photons break out from the source.

Experimental Study of Electronic Quantum Interference, Photonic Crystal Cavity, Photonic Band Edge Effects for Optical Amplification

DTIC Science & Technology

2016-01-26

MONITOR’S REPORT Kirtland AFB, NM 87117-5776 NUMBER(S) AFRL -RV-PS-TR-2016-0003 12. DISTRIBUTION / AVAILABILITY STATEMENT Approved for public release...22060-6218 1 cy AFRL /RVIL Kirtland AFB, NM 87117-5776 2 cys Official Record Copy AFRL /RVSS/David Cardimona 1 cy 12 Approved for... AFRL -RV-PS- AFRL -RV-PS- TR-2016-0003 TR-2016-0003 EXPERIMENTAL STUDY OF ELECTRONIC QUANTUM INTERFERENCE, PHOTONIC CRYSTAL CAVITY, PHOTONIC BAND

K-edge energy-based calibration method for photon counting detectors

NASA Astrophysics Data System (ADS)

Ge, Yongshuai; Ji, Xu; Zhang, Ran; Li, Ke; Chen, Guang-Hong

2018-01-01

In recent years, potential applications of energy-resolved photon counting detectors (PCDs) in the x-ray medical imaging field have been actively investigated. Unlike conventional x-ray energy integration detectors, PCDs count the number of incident x-ray photons within certain energy windows. For PCDs, the interactions between x-ray photons and photoconductor generate electronic voltage pulse signals. The pulse height of each signal is proportional to the energy of the incident photons. By comparing the pulse height with the preset energy threshold values, x-ray photons with specific energies are recorded and sorted into different energy bins. To quantitatively understand the meaning of the energy threshold values, and thus to assign an absolute energy value to each energy bin, energy calibration is needed to establish the quantitative relationship between the threshold values and the corresponding effective photon energies. In practice, the energy calibration is not always easy, due to the lack of well-calibrated energy references for the working energy range of the PCDs. In this paper, a new method was developed to use the precise knowledge of the characteristic K-edge energy of materials to perform energy calibration. The proposed method was demonstrated using experimental data acquired from three K-edge materials (viz., iodine, gadolinium, and gold) on two different PCDs (Hydra and Flite, XCounter, Sweden). Finally, the proposed energy calibration method was further validated using a radioactive isotope (Am-241) with a known decay energy spectrum.

Asymmetric photon transport in organic semiconductor nanowires through electrically controlled exciton diffusion

PubMed Central

Cui, Qiu Hong; Peng, Qian; Luo, Yi; Jiang, Yuqian; Yan, Yongli; Wei, Cong; Shuai, Zhigang; Sun, Cheng; Yao, Jiannian; Zhao, Yong Sheng

2018-01-01

The ability to steer the flow of light toward desired propagation directions is critically important for the realization of key functionalities in optical communication and information processing. Although various schemes have been proposed for this purpose, the lack of capability to incorporate an external electric field to effectively tune the light propagation has severely limited the on-chip integration of photonics and electronics. Because of the noninteractive nature of photons, it is only possible to electrically control the flow of light by modifying the refractive index of materials through the electro-optic effect. However, the weak optical effects need to be strongly amplified for practical applications in high-density photonic integrations. We show a new strategy that takes advantage of the strong exciton-photon coupling in active waveguides to effectively manipulate photon transport by controlling the interaction between excitons and the external electric field. Single-crystal organic semiconductor nanowires were used to generate highly stable Frenkel exciton polaritons with strong binding and diffusion abilities. By making use of directional exciton diffusion in an external electric field, we have realized an electrically driven asymmetric photon transport and thus directional light propagation in a single nanowire. With this new concept, we constructed a dual-output single wire–based device to build an electrically controlled single-pole double-throw optical switch with fast temporal response and high switching frequency. Our findings may lead to the innovation of concepts and device architectures for optical information processing. PMID:29556529

Multiplicity of transmission coefficients in photonic crystal and split ring resonator waveguides with Kerr nonlinear impurities

NASA Astrophysics Data System (ADS)

Rai, Buddhi; McGurn, Arthur R.

2015-02-01

Photonic crystal and split ring resonator (SRR) metamaterial waveguides with Kerr nonlinear dielectric impurities are studied. The transmission coefficients for two guided modes of different frequencies scattering from the Kerr impurities are computed. The systems are shown to exhibit multiple transmission coefficient solutions arising from the Kerr nonlinearity. Multiple transmission coefficients occur when different input intensities into a waveguide result in the same transmitted output intensities past its nonlinear impurities. (In the case of a single incident guided mode the multiplicity of transmission coefficients is known as optical bistability.) The analytical conditions under which the transmission coefficients are single and multiple valued are determined, and specific examples of both single and multiple valued transmission coefficient scattering are presented. Both photonic crystal and split ring resonator systems are studied as the Kerr nonlinearity enters the photonic crystal and SRR systems in different ways. This allows for an interesting comparison of the differences in behaviors of these two types of system which are described by distinctly different mathematical structures. Both the photonic crystal and SRR models used in the calculations are based on a difference equation approach to the system dynamics. The difference equation approach has been extensively employed in previous papers to model the basic properties of these systems. The paper is a continuation of work on the optical bistability of single guided modes interacting with Kerr impurities in photonic crystals originally considered by McGurn [Chaos 13, 754 (2003), 10.1063/1.1568691] and work on the resonant scattering from Kerr impurities in photonic crystal waveguides considered by McGurn [J. Phys.: Condens. Matter 16, S5243 (2004), 10.1088/0953-8984/16/44/021]. It generalizes this work making the extension to the more complex interaction of two guided modes at different frequencies. It extends the two guided mode treatment by McGurn [Organ. Electron. 8, 227 (2007), 10.1016/j.orgel.2006.06.008] which was limited to a special case of one of the photonic crystal systems considered here.

Theory of plasmonic effects in nonlinear optics: the case of graphene

NASA Astrophysics Data System (ADS)

Rostami, Habib; Katsnelson, Mikhail I.; Polini, Marco; Mikhail I. Katsnelson Collaboration; Habib Rostami; Marco Polini Collaboration

The nonlinear optical properties of two-dimensional electronic systems are beginning to attract considerable interest both in the theoretical and experimental sectors. Recent experiments on the nonlinear optical properties of graphene reveal considerably strong third harmonic generation and four-wave mixing of this single-atomic-layer electronic system. We develop a large-N theory of electron-electron interaction corrections to multi-legged Feynman diagrams describing second- and third-order nonlinear response functions. Our theory is completely general and is useful to understand all second- and third-order nonlinear effects, including harmonic generation, wave mixing, and photon drag. We apply our theoretical framework to the case of graphene, by carrying out microscopic calculations of the second- and third-order nonlinear response functions of an interacting two-dimensional gas of massless Dirac fermions. We compare our results with recent measurements, where all-optical launching of graphene plasmons has been achieved. This work was supported by Fondazione Istituto Italiano di Tecnologia, the European Union's Horizon 2020 research and innovation programme under Grant agreement No. 696656 GrapheneCore, and the ERC Advanced Grant 338957 FEMTO/NANO (M.I.K.).

HIGH ENERGY, HIGH BRIGHTNESS X-RAYS PRODUCED BY COMPTON BACKSCATTERING AT THE LIVERMORE PLEIADES FACILITY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tremaine, A M; Anderson, S G; Betts, S

2005-05-19

PLEIADES (Picosecond Laser Electron Interaction for the Dynamic Evaluation of Structures) produces tunable 30-140 keV x-rays with 0.3-5 ps pulse lengths and up to 10{sup 7} photons/pulse by colliding a high brightness electron beam with a high power laser. The electron beam is created by an rf photo-injector system, accelerated by a 120 MeV linac, and focused to 20 {micro}m with novel permanent magnet quadrupoles. To produce Compton back scattered x-rays, the electron bunch is overlapped with a Ti:Sapphire laser that delivers 500 mJ, 100 fs, pulses to the interaction point. K-edge radiography at 115 keV on Uranium has verifiedmore » the angle correlated energy spectrum inherent in Compton scattering and high-energy tunability of the Livermore source. Current upgrades to the facility will allow laser pumping of targets synchronized to the x-ray source enabling dynamic diffraction and time-resolved studies of high Z materials. Near future plans include extending the radiation energies to >400 keV, allowing for nuclear fluorescence studies of materials.« less

Measurement of Nuclear Recoils in the CDMS II Dark Matter Search

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fallows, Scott Mathew

The Cryogenic Dark Matter Search (CDMS) experiment is designed to directly detect elastic scatters of weakly-interacting massive dark matter particles (WIMPs), on target nuclei in semiconductor crystals composed of Si and Ge. These scatters would occur very rarely, in an overwhelming background composed primarily of electron recoils from photons and electrons, as well as a smaller but non-negligible background of WIMP-like nuclear recoils from neutrons. The CDMS II generation of detectors simultaneously measure ionization and athermal phonon signals from each scatter, allowing discrimination against virtually all electron recoils in the detector bulk. Pulse-shape timing analysis allows discrimination against nearly allmore » remaining electron recoils taking place near detector surfaces. Along with carefully limited neutron backgrounds, this experimental program allowed for \\background- free" operation of CDMS II at Soudan, with less than one background event expected in each WIMP-search analysis. As a result, exclusionary upper-limits on WIMP-nucleon interaction cross section were placed over a wide range of candidate WIMP masses, ruling out large new regions of parameter space.« less

Polarized γ source based on Compton backscattering in a laser cavity

NASA Astrophysics Data System (ADS)

Yakimenko, V.; Pogorelsky, I. V.

2006-09-01

We propose a novel gamma source suitable for generating a polarized positron beam for the next generation of electron-positron colliders, such as the International Linear Collider (ILC), and the Compact Linear Collider (CLIC). This 30-MeV polarized gamma source is based on Compton scattering inside a picosecond CO2 laser cavity generated from electron bunches produced by a 4-GeV linac. We identified and experimentally verified the optimum conditions for obtaining at least one gamma photon per electron. After multiplication at several consecutive interaction points, the circularly polarized gamma rays are stopped on a target, thereby creating copious numbers of polarized positrons. We address the practicality of having an intracavity Compton-polarized positron source as the injector for these new colliders.

Zero-bias photocurrent in ferromagnetic topological insulator.

PubMed

Ogawa, N; Yoshimi, R; Yasuda, K; Tsukazaki, A; Kawasaki, M; Tokura, Y

2016-07-20

Magnetic interactions in topological insulators cause essential modifications in the originally mass-less surface states. They offer a mass gap at the Dirac point and/or largely deform the energy dispersion, providing a new path towards exotic physics and applications to realize dissipation-less electronics. The nonequilibrium electron dynamics at these modified Dirac states unveil additional functions, such as highly efficient photon to spin-current conversion. Here we demonstrate the generation of large zero-bias photocurrent in magnetic topological insulator thin films on mid-infrared photoexcitation, pointing to the controllable band asymmetry in the momentum space. The photocurrent spectra with a maximal response to the intra-Dirac-band excitations can be a sensitive measure for the correlation between Dirac electrons and magnetic moments.

Depth-of-interaction estimates in pixelated scintillator sensors using Monte Carlo techniques

NASA Astrophysics Data System (ADS)

Sharma, Diksha; Sze, Christina; Bhandari, Harish; Nagarkar, Vivek; Badano, Aldo

2017-01-01

Image quality in thick scintillator detectors can be improved by minimizing parallax errors through depth-of-interaction (DOI) estimation. A novel sensor for low-energy single photon imaging having a thick, transparent, crystalline pixelated micro-columnar CsI:Tl scintillator structure has been described, with possible future application in small-animal single photon emission computed tomography (SPECT) imaging when using thicker structures under development. In order to understand the fundamental limits of this new structure, we introduce cartesianDETECT2, an open-source optical transport package that uses Monte Carlo methods to obtain estimates of DOI for improving spatial resolution of nuclear imaging applications. Optical photon paths are calculated as a function of varying simulation parameters such as columnar surface roughness, bulk, and top-surface absorption. We use scanning electron microscope images to estimate appropriate surface roughness coefficients. Simulation results are analyzed to model and establish patterns between DOI and photon scattering. The effect of varying starting locations of optical photons on the spatial response is studied. Bulk and top-surface absorption fractions were varied to investigate their effect on spatial response as a function of DOI. We investigated the accuracy of our DOI estimation model for a particular screen with various training and testing sets, and for all cases the percent error between the estimated and actual DOI over the majority of the detector thickness was ±5% with a maximum error of up to ±10% at deeper DOIs. In addition, we found that cartesianDETECT2 is computationally five times more efficient than MANTIS. Findings indicate that DOI estimates can be extracted from a double-Gaussian model of the detector response. We observed that our model predicts DOI in pixelated scintillator detectors reasonably well.

AIE-doped poly(ionic liquid) photonic spheres: a single sphere-based customizable sensing platform for the discrimination of multi-analytes† †Electronic supplementary information (ESI) available: Synthesis and characterization of the AIE luminogen, experimental details, response profiles and results of the multivariate analysis. See DOI: 10.1039/c7sc02409f Click here for additional data file.

PubMed Central

Zhang, Wanlin; Gao, Ning; Cui, Jiecheng; Wang, Chen; Wang, Shiqiang; Zhang, Guanxin; Dong, Xiaobiao

2017-01-01

By simultaneously exploiting the unique properties of ionic liquids and aggregation-induced emission (AIE) luminogens, as well as photonic structures, a novel customizable sensing system for multi-analytes was developed based on a single AIE-doped poly(ionic liquid) photonic sphere. It was found that due to the extraordinary multiple intermolecular interactions involved in the ionic liquid units, one single sphere could differentially interact with broader classes of analytes, thus generating response patterns with remarkable diversity. Moreover, the optical properties of both the AIE luminogen and photonic structure integrated in the poly(ionic liquid) sphere provide multidimensional signal channels for transducing the involved recognition process in a complementary manner and the acquisition of abundant and sufficient sensing information could be easily achieved on only one sphere sensor element. More importantly, the sensing performance of our poly(ionic liquid) photonic sphere is designable and customizable through a simple ion-exchange reaction and target-oriented multi-analyte sensing can be conveniently realized using a selective receptor species, such as counterions, showing great flexibility and extendibility. The power of our single sphere-based customizable sensing system was exemplified by the successful on-demand detection and discrimination of four multi-analyte challenge systems: all 20 natural amino acids, nine important phosphate derivatives, ten metal ions and three pairs of enantiomers. To further demonstrate the potential of our spheres for real-life application, 20 amino acids in human urine and their 26 unprecedented complex mixtures were also discriminated between by the single sphere-based array. PMID:28989662

[Determination of absorbed dose to water for high energy photon and electron beams--comparison of different dosimetry protocols].

PubMed

Zakaria, Golam Abu; Schütte, Wilhelm

2003-01-01

The determination of absorbed dose to water for high-energy photon and electron beams is performed in Germany according to the dosimetry protocol DIN 6800-2 (1997). At an international level, the main protocols used are the AAPM dosimetry protocol TG-51 (1999) and the IAEA Code of Practice TRS-398 (2000). The present paper systematically compares these three dosimetry protocols, and identifies similarities and differences. The investigations were performed using 4 and 10 MV photon beams, as well as 6, 8, 9, 10, 12 and 14 MeV electron beams. Two cylindrical and two plane-parallel type chambers were used for measurements. In general, the discrepancies among the three protocols were 1.0% for photon beams and 1.6% for electron beams. Comparative measurements in the context of measurement technical control (MTK) with TLD showed a deviation of less than 1.3% between the measurements obtained according to protocols DIN 6800-2 and MTK (exceptions: 4 MV photons with 2.9% and 6 MeV electrons with 2.4%). While only cylindrical chambers were used for photon beams, measurements of electron beams were performed using both cylindrical and plane-parallel chambers (the latter used after a cross-calibration to a cylindrical chamber, as required by the respective dosimetry protocols). Notably, unlike recommended in the corresponding protocols, we found out that cylindrical chambers can be used also for energies from 6 to 10 MeV.

Development of Compton X-ray spectrometer for high energy resolution single-shot high-flux hard X-ray spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kojima, Sadaoki, E-mail: kojima-s@ile.osaka-u.ac.jp, E-mail: sfujioka@ile.osaka-u.ac.jp; Ikenouchi, Takahito; Arikawa, Yasunobu

Hard X-ray spectroscopy is an essential diagnostics used to understand physical processes that take place in high energy density plasmas produced by intense laser-plasma interactions. A bundle of hard X-ray detectors, of which the responses have different energy thresholds, is used as a conventional single-shot spectrometer for high-flux (>10{sup 13} photons/shot) hard X-rays. However, high energy resolution (Δhv/hv < 0.1) is not achievable with a differential energy threshold (DET) X-ray spectrometer because its energy resolution is limited by energy differences between the response thresholds. Experimental demonstration of a Compton X-ray spectrometer has already been performed for obtaining higher energy resolutionmore » than that of DET spectrometers. In this paper, we describe design details of the Compton X-ray spectrometer, especially dependence of energy resolution and absolute response on photon-electron converter design and its background reduction scheme, and also its application to the laser-plasma interaction experiment. The developed spectrometer was used for spectroscopy of bremsstrahlung X-rays generated by intense laser-plasma interactions using a 200 μm thickness SiO{sub 2} converter. The X-ray spectrum obtained with the Compton X-ray spectrometer is consistent with that obtained with a DET X-ray spectrometer, furthermore higher certainly of a spectral intensity is obtained with the Compton X-ray spectrometer than that with the DET X-ray spectrometer in the photon energy range above 5 MeV.« less

Generating photon pairs from a silicon microring resonator using an electronic step recovery diode for pump pulse generation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Savanier, Marc, E-mail: msavanier@eng.ucsd.edu; Mookherjea, Shayan, E-mail: smookherjea@eng.ucsd.edu

Generation of photon pairs from compact, manufacturable, and inexpensive silicon (Si) photonic devices at room temperature may help develop practical applications of quantum photonics. An important characteristic of photon-pair generation is the two-photon joint spectral intensity, which describes the frequency correlations of the photon pair. Recent attempts to generate a factorizable photon-pair state suitable for heralding have used short optical pump pulses from mode-locked lasers, which are much more expensive and bigger table-top or rack-sized instruments compared with the Si microchip used for generating photon pairs, and thus dominate the cost and inhibit the miniaturization of the source. Here, wemore » generate photon pairs from an Si microring resonator by using an electronic step-recovery diode to drive an electro-optic modulator which carves the pump light from a continuous-wave laser diode into pulses of the appropriate width, thus potentially eliminating the need for optical mode-locked lasers.« less

Generating photon pairs from a silicon microring resonator using an electronic step recovery diode for pump pulse generation

NASA Astrophysics Data System (ADS)

Savanier, Marc; Mookherjea, Shayan

2016-06-01

Generation of photon pairs from compact, manufacturable, and inexpensive silicon (Si) photonic devices at room temperature may help develop practical applications of quantum photonics. An important characteristic of photon-pair generation is the two-photon joint spectral intensity, which describes the frequency correlations of the photon pair. Recent attempts to generate a factorizable photon-pair state suitable for heralding have used short optical pump pulses from mode-locked lasers, which are much more expensive and bigger table-top or rack-sized instruments compared with the Si microchip used for generating photon pairs, and thus dominate the cost and inhibit the miniaturization of the source. Here, we generate photon pairs from an Si microring resonator by using an electronic step-recovery diode to drive an electro-optic modulator which carves the pump light from a continuous-wave laser diode into pulses of the appropriate width, thus potentially eliminating the need for optical mode-locked lasers.

Noncollinear wave mixing of attosecond XUV and few-cycle optical laser pulses in gas-phase atoms: Toward multidimensional spectroscopy involving XUV excitations

NASA Astrophysics Data System (ADS)

Cao, Wei; Warrick, Erika R.; Fidler, Ashley; Neumark, Daniel M.; Leone, Stephen R.

2016-11-01

Ultrafast nonlinear spectroscopy, which records transient wave-mixing signals in a medium, is a powerful tool to access microscopic information using light sources in the radio-frequency and optical regimes. The extension of this technique towards the extreme ultraviolet (XUV) or even x-ray regimes holds the promise to uncover rich structural or dynamical information with even higher spatial or temporal resolution. Here, we demonstrate noncollinear wave mixing between weak XUV attosecond pulses and a strong near-infrared (NIR) few-cycle laser pulse in gas phase atoms (one photon of XUV and two photons of NIR). In the noncollinear geometry the attosecond and either one or two NIR pulses interact with argon atoms. Nonlinear XUV signals are generated in a spatially resolved fashion as required by phase matching. Different transition pathways can be identified from these background-free nonlinear signals according to the specific phase-matching conditions. Time-resolved measurements of the spatially gated XUV signals reveal electronic coherences of Rydberg wave packets prepared by a single XUV photon or XUV-NIR two-photon excitation, depending on the applied pulse sequences. These measurements open possible applications of tabletop multidimensional spectroscopy to the study of dynamics associated with valence or core excitation with XUV photons.