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Sample records for radiation fields encountered

  1. Strategies for Navigating Common Ethical Dilemmas Encountered by Operational Radiation Safety Professionals.

    PubMed

    Emery, Robert J; Rios, Janelle

    2016-02-01

    Because operational radiation safety professionals can encounter ethical dilemmas in the course of their work, codes of ethics and professional standards of conduct are maintained by the Health Physics Society (HPS) and the American Academy of Health Physics (AAHP). While these works provide valuable guidance, they do not operationalize the types of ethical dilemmas radiation safety practitioners might encounter. For example, consider the ethical conundrum of “dual loyalty,” defined as the situation in which an individual holds simultaneous obligations to two or more parties. In the case of radiation safety, practicing professionals hold obligations to the workers being protected and to the leaders of the organization. If these obligations are in conflict, serious difficulties can arise. The conundrum of dual loyalty is described and a strategy for reducing its effect is discussed. Two other common ethical issues; “confidentiality” and “organizational dissent” are similarly presented. A foundation from which to launch an ongoing dialogue about ethical issues within the radiation safety profession is also proposed. PMID:26710164

  2. Estimates of trapped radiation encountered on low-thrust trajectories through the Van Allen belts

    NASA Technical Reports Server (NTRS)

    Karp, I. M.

    1973-01-01

    Estimates were made of the number of trapped protons and electrons encountered by vehicles on low-thrust trajectories through the Van Allen belts. The estimates serve as a first step in assessing whether these radiations present a problem to on-board sensitive components and payload. The integrated proton spectra and electron spectra are presented for the case of a trajectory described by a vehicle with a constant-thrust acceleration A sub c equal to 0.001 meter/sq sec. This value of acceleration corresponds to a trip time of about 54 days from low earth orbit to synchronous orbit. It is shown that the time spent in the belts and hence the radiation encountered vary nearly inversely with the value of thrust acceleration. Thus, the integrated spectral values presented for the case of A sub c = 0.001 meter/sq sec can be generalized for any other value of thrust acceleration by multiplying them by the factor 0.001/A sub c.

  3. [Nonionizing radiation and electromagnetic fields].

    PubMed

    Bernhardt, J H

    1991-01-01

    Nonionising radiation comprises all kinds of radiation and fields of the electromagnetic spectrum where biological matter is not ionised, as well as mechanical waves such as infrasound and ultrasound. The electromagnetic spectrum is subdivided into individual sections and includes: Static and low-frequency electric and magnetic fields including technical applications of energy with mains frequency, radio frequency fields, microwaves and optic radiation (infrared, visible light, ultraviolet radiation including laser). The following categories of persons can be affected by emissions by non-ionising radiation: Persons in the environment and in the household, workers, patients undergoing medical diagnosis or treatment. If the radiation is sufficiently intense, or if the fields are of appropriate strength, a multitude of effects can occur (depending on the type of radiation), such as heat and stimulating or irritating action, inflammations of the skin or eyes, changes in the blood picture, burns or in some cases cancer as a late sequel. The ability of radiation to penetrate into the human body, as well as the types of interaction with biological tissue, with organs and organisms, differs significantly for the various kinds of nonionising radiation. The following aspects of nonionising radiation are discussed: protection of humans against excessive sunlight rays when sunbathing and when exposed to UV radiation (e.g. in solaria); health risks of radio and microwaves (safety of microwave cookers and mobile radio units); effects on human health by electric and magnetic fields in everyday life. PMID:1837859

  4. Gamma radiation field intensity meter

    DOEpatents

    Thacker, L.H.

    1994-08-16

    A gamma radiation intensity meter measures dose rate of a radiation field. The gamma radiation intensity meter includes a tritium battery emitting beta rays generating a current which is essentially constant. Dose rate is correlated to an amount of movement of an electroscope element charged by the tritium battery. Ionizing radiation decreases the voltage at the element and causes movement. A bleed resistor is coupled between the electroscope support element or electrode and the ionization chamber wall electrode. 4 figs.

  5. Gamma radiation field intensity meter

    DOEpatents

    Thacker, Louis H.

    1995-01-01

    A gamma radiation intensity meter measures dose rate of a radiation field. The gamma radiation intensity meter includes a tritium battery emitting beta rays generating a current which is essentially constant. Dose rate is correlated to an amount of movement of an electroscope element charged by the tritium battery. Ionizing radiation decreases the voltage at the element and causes movement. A bleed resistor is coupled between the electroscope support element or electrode and the ionization chamber wall electrode.

  6. Gamma radiation field intensity meter

    DOEpatents

    Thacker, Louis H.

    1994-01-01

    A gamma radiation intensity meter measures dose rate of a radiation field. The gamma radiation intensity meter includes a tritium battery emitting beta rays generating a current which is essentially constant. Dose rate is correlated to an amount of movement of an electroscope element charged by the tritium battery. Ionizing radiation decreases the voltage at the element and causes movement. A bleed resistor is coupled between the electroscope support element or electrode and the ionization chamber wall electrode.

  7. Gamma radiation field intensity meter

    DOEpatents

    Thacker, L.H.

    1995-10-17

    A gamma radiation intensity meter measures dose rate of a radiation field. The gamma radiation intensity meter includes a tritium battery emitting beta rays generating a current which is essentially constant. Dose rate is correlated to an amount of movement of an electroscope element charged by the tritium battery. Ionizing radiation decreases the voltage at the element and causes movement. A bleed resistor is coupled between the electroscope support element or electrode and the ionization chamber wall electrode. 4 figs.

  8. Development and Characterization of a High Throughput Screen to investigate the delayed Effects of Radiations Commonly Encountered in Space

    NASA Astrophysics Data System (ADS)

    Morgan, W. F.

    Astronauts based on the space station or on long-term space missions will be exposed to high Z radiations in the cosmic environment In order to evaluate the potentially deleterious effects of exposure to radiations commonly encountered in space we have developed and characterized a high throughput assay to detect mutation deletion events and or hyperrecombination in the progeny of exposed cells This assay is based on a plasmid vector containing a green fluorescence protein reporter construct We have shown that after stable transfection of the vector into human or hamster cells this construct can identify mutations specifically base changes and deletions as well as recombination events e g gene conversion or homologous recombination occurring as a result of exposure to ionizing radiation Our focus has been on those events occurring in the progeny of an irradiated cell that are potentially associated with radiation induced genomic instability rather than the more conventional assays that evaluate the direct immediate effects of radiation exposure Considerable time has been spent automating analysis of surviving colonies as a function of time after irradiation in order to determine when delayed instability is induced and the consequences of this delayed instability The assay is now automated permitting the evaluation of potentially rare events associated with low dose low dose rate radiations commonly encountered in space

  9. Numerical instabilities encountered in non-linear temperature analysis of radiation shield for SP-100 reactor

    NASA Astrophysics Data System (ADS)

    Barattino, William J.; El-Genk, Mohamed S.; McDaniel, Patrick J.

    The finite element method using Simplex elements and Newton-Raphson iteration has been shown to be quite accurate for solving nonlinear, nonhomogeneous, steady-state heat conduction problems, with radiative boundary conditions. However, at high values of internal heat generation, a bifurcation solution results in which the temperature at the radiative boundary oscillates between two values, neither of which is the exact solution. The introduction of a relaxation parameter in the radiative heat transfer coefficient was effective in eliminating the oscillatory behavior of the radiative surface temperature. A nodal decomposition was performed on the basic Newton-Raphson system of equations which led to a qualitative understanding of how the engineering parameters of the heat transfer-governing equation affected the oscillations. A method for determining the optimum relaxation parameter to ensure convergence and maximize the convergence rate was proposed.

  10. Binary-Encounter-Bethe ionisation cross sections for simulation of DNA damage by the direct effect of ionising radiation.

    PubMed

    Plante, I; Cucinotta, F A

    2015-09-01

    DNA damage is of crucial importance in the understanding of the effects of ionising radiation. To refine existing DNA damage models, an approach using the Binary-Encounter-Bethe (BEB) cross sections was developed. The differential cross sections for ionisation of the molecular orbitals of the DNA bases, sugars and phosphates are calculated using the electron binding energy, the mean kinetic energy and the occupancy number of each orbital as parameters. The resulting cross section has an analytic form which is quite convenient to use for Monte-Carlo codes that randomly sample the energy loss occurring during an ionisation event. We also describe an algorithm to simulate the interactions of electrons with DNA in the radiation transport code RITRACKS using the integrated BEB cross section for the bases, sugar and phosphates. PMID:25870431

  11. Notes from the Field: Injuries Associated with Bison Encounters - Yellowstone National Park, 2015.

    PubMed

    Cherry, Cara; Leong, Kirsten; Wallen, Rick; Buttke, Danielle

    2016-01-01

    Since 1980, bison have injured more pedestrian visitors to Yellowstone National Park (Yellowstone) than any other animal (1). After the occurrence of 33 bison-related injuries during 1983-1985 (range = 10-13/year), the park implemented successful outreach campaigns (1) to reduce the average number of injuries to 0.8/year (range = 0-2/year) during 2010-2014 (unpublished data, National Park Service, September 2015). During May-July 2015, five injuries associated with bison encounters occurred (Table). Case reports were reviewed to evaluate circumstances surrounding these injuries to inform prevention. PMID:27010506

  12. Calibration of TLD badges for photons of energy above 6 MeV and dosimetric intricacies in high energy gamma ray fields encountered in nuclear power plants.

    PubMed

    Pradhan, A S; Bakshi, A K

    2002-01-01

    CaSO4:Dy and LiF TLDs do not exhibit photon energy dependence beyond +/-55% for photons in the energy range from 1 MeV to about 7 MeV. However, when sandwiched between metal filters or used in TLD badge holders having metal filters, the response changes for irradiation from high energy photons as compared to that from 60Co gamma rays (generally used for reference calibrations). This effect is about the same for both the lower atomic number TLD (LiF) and higher atomic number TLD (CaSO4:Dy). For TLDs held on the surface of the phantom and irradiated in collimated photon beams, the response of TLDs without any filter or those under the open window of the TLD badge is considerably reduced due to insufficient build-up to high energy photons, whereas for uncollimated radiation fields from power reactors, an over-response is observed. It is observed that the use of inappropriate encapsulation of dosemeters would cause a significant error not only in the estimation of doses due to penetrating radiations but also in the estimation of beta doses in the mixed fields of beta radiation, high energy gamma rays and high energy electrons often encountered in the fields of pressurised heavy water reactors. PMID:12018745

  13. Relativistic theory for radiative forward electron emission in heavy ion-atom encounters

    NASA Astrophysics Data System (ADS)

    Jakubaßa-Amundsen, Doris; Müller, Robert; Surzhykov, Andrey; Yerokhin, Vladimir

    2014-12-01

    The forward electron emission with simultaneous photon production during the scattering of relativistic, highly stripped projectiles from light target atoms is calculated within the Dirac theory. The method of calculation is a simplification of the impulse approximation and is based on the relation of the cross section for radiative capture to continuum of loosely bound electrons to the frame-transformed electron bremsstrahlung cross section. It is demonstrated that such an approximation is well justified in a large region of energies and photon emission angles, with the exception of the extreme forward and backward emission and the soft-photon energy limit. The cusp spectrum and the corresponding angular distribution are compared to recent experimental data for the collision system 90.38 MeV/amu U88+ + N2.

  14. Identifying the Discomfort: An Examination of Ethical Issues Encountered by MSW Students during Field Placement

    ERIC Educational Resources Information Center

    Dodd, Sarah-Jane

    2007-01-01

    The purpose of this descriptive study was to determine which ethical issues graduate social work students experienced most frequently during their field placement, the resources students used to resolve these issues, and whether such resources were helpful. The results indicate that conflicts concerning beneficence versus agency policy and…

  15. Encounters with fierce dogs and itchy bedbugs: why my first field work failed.

    PubMed

    Svanberg, Ingvar

    2014-01-01

    This essay, which is the fifth in the series "Recollections, Reflections, and Revelations: Personal Experiences in Ethnobiology", is a personal reminiscence by the researcher on his first field experience in Turkey in the late 1970s, which was a failure from an ethnobiological point of view but a success for a social scientist pursuing Turkic studies. The author later returned to ethnobiology during subsequent fieldwork on the Faroes. PMID:24885471

  16. Encounters with fierce dogs and itchy bedbugs: why my first field work failed

    PubMed Central

    2014-01-01

    This essay, which is the fifth in the series “Recollections, Reflections, and Revelations: Personal Experiences in Ethnobiology”, is a personal reminiscence by the researcher on his first field experience in Turkey in the late 1970s, which was a failure from an ethnobiological point of view but a success for a social scientist pursuing Turkic studies. The author later returned to ethnobiology during subsequent fieldwork on the Faroes. PMID:24885471

  17. Modelling microscopic features of streamer encounters, electric fields, electron beams and X-ray bursts

    NASA Astrophysics Data System (ADS)

    Koehn, C.; Kochkin, P.; Ebert, U.

    2015-12-01

    Thunderstorms emit terrestrial gamma-ray flashes (TGFs), beams of photons with quantum energies ofup to 40 MeV. Likewise electric discharges in the laboratory, mimicing lightning on a small spatial andenergetic scale, emit X-rays whose energies are limited by the available potential difference betweenthe two electrodes. For a maximal available difference of 1 MV and a gap distance of 1 m between the twoelectrodes, we will present the energy and spatial distribution of generated X-rays.For that we have followed the motion of preaccelerated, monoenergetic and monodirectional electronbeams with energies between 100 keV and the maximal available energy of 1 MeV for different electricfield configurations using a particle Monte Carlo code. Omitting any field, we present the subsequent energy and spatial distribution of X-raysand analyse how the photon number depends on the initial electron energy. Fig. 1 shows the position and energy of photons generated by Bremsstrahlung after 0.3 ns by beams of 500 000 electrons with initial energies of 1 MeV moving in the zdirection in STP air. The electrons have generated electron avalanches and all have cooleddown and attached to oxygen after 0.3 ns. Every cross represents one photon projected onto the xz plane; the photon energies Eγ are color coded. We see that photons with energies of approx. 1 MeV can be produced and that the high-energy tail of X-rays is beamedtowards the direction of the initial electron beam whereas low-energy photons show a more isotropicbehaviour. Analysing the cross sections of photons interacting with air we conclude that photons travelseveral meters in air and can reach detectors several meters from the position of the discharge. Byestimating the electric field ahead of the discharge corona and by simulating the motion of electronbeams in these fields, we exclude that electrons travel as far as photons and disturb the measured X-raysignal.

  18. Radiation Q of dipole-generated fields

    NASA Astrophysics Data System (ADS)

    Grimes, Dale M.; Grimes, Craig A.

    1999-03-01

    The radiation Q of several dipole fields in free space are determined using the time-dependent Poynting theorem. Earlier works on this subject, recently summarized by McLean [1996], are based upon the complex Poynting theorem. It was previously shown [Grimes and Grimes, 1997] that the full complex Poynting theorem is correct only for single-mode radiation fields. The time-dependent theorem shows that three numbers are necessary to completely specify time-varying power, and complex numbers supply but two; the third piece of information, a phase, is discarded when complex notation is formed. Omissions inherent in the complex Poynting theorem affect the calculated value of standing energy about an antenna and hence the calculated value of Q. To avoid such omissions, we develop a method of determining Q based upon the time-dependent Poynting theorem that builds upon and extends our earlier work [Grimes and Grimes, 1997]. The purposes of this paper are to (1) provide a time domain basis for calculating Q in mixed modal radiation fields, (2) determine the Q of electric and magnetic dipoles, alone and in combination, and (3) demonstrate how source structure and relative phasing affect the physics of several combinations of electric and magnetic dipole radiation fields. The primary conclusion of this work is that the minimum possible Q of a radiation source established by Chu [1948] does not extend to properly mixed and phased multimodal radiation fields. A radiation source is presented for which, by our analysis, the radiation Q is zero.

  19. Evidence for the field line reconnection process in the particle and magnetic field measurements obtained during the Giotto-Halley encounter

    NASA Astrophysics Data System (ADS)

    Kirsch, E.; McKenna-Lawlor, S.; Daly, P.; Korth, A.; Neubauer, F. M.; O'Sullivan, D.; Thompson, A.; Wenzel, K.-P.

    1989-04-01

    Measurements of low and high energy particles, as well as the magnetic field obtained by three different instruments during the Giotto-Halley encounter on March 13, 14, 1986 are used to study the field-line merging process. Spikes of 5-15 min duration in the high energy particle flux which are superimposed on the general intensity time profile are correlated with minima in the low energy particle flux and time periods of oppositely directed magnetic field lines. Strong changes in the pitch angle distribution of energetic ions are observed simultaneously. The observations are considered as evidence for sporadic field line merging processes in the front side of Halley's cometosheath which can accelerate ions and electrons up to E of about 300 keV.

  20. Chemical Processes in Astrophysical Radiation Fields

    SciTech Connect

    Stancil, P.C.; Dalgarno, A.

    1997-12-31

    The effects of stimulated photon emission on chemical processes in a radiation field are considered and their influence on the chemistry of the early universe and other astrophysical environments is investigated. Spontaneous and stimulated radiative attachment rate coefficients for H(-), Li(-) and C(-) are presented.

  1. High Intensity Radiated Fields (HIRF) project plan

    NASA Astrophysics Data System (ADS)

    Glynn, Michael S.; Blair, Jerry T.; Hintze, M. Marx

    1991-09-01

    Addressed here is the Federal Aviation Administration's approach to High Intensity Radiated Fields (HIRF) affecting the aviation community. Near- and far-term tasks are described. Deliverables, program management, scheduling, and cost issues are discussed.

  2. Radiated fields from an electromagnetic pulse simulator

    NASA Astrophysics Data System (ADS)

    Pelletier, M.; Delisle, G. Y.; Kashyap, S.

    Simulators of electromagnetic pulses allow generation within a limited time of very high-intensity fields such as those produced in a nuclear explosion. These fields can be radiated out of the test zone at a lower but nevertheless significant level; if the intensity of these fields is sufficiently high, damage to humans and electronic equipment can result. An evaluation of the potential danger of these simulator emissions requires knowledge of the amplitude, duration, and the energy of the radiated impulses. A technique is presented for calculating the fields radiated by a parallel-plane electromagnetic pulse simulator. The same method can also be applied to a rhombic type simulator. Sample numerical results are presented along with the calculations of the energy and power density and a discussion of the formation of the field in the frequency domain.

  3. The NASA High Intensity Radiated Fields Laboratory

    NASA Technical Reports Server (NTRS)

    Williams, Reuben A.

    1997-01-01

    High Intensity Radiated Fields (HIRF) are the result of a multitude of intentional and nonintentional electromagnetic sources that currently exists in the world. Many of today's digital systems are susceptible to electronic upset if subjected to certain electromagnetic environments (EME). Modern aerospace designers and manufacturers increasingly rely on sophisticated digital electronic systems to provide critical flight control in both military, commercial, and general aviation aircraft. In an effort to understand and emulate the undesired environment that high energy RF provides modern electronics, the Electromagnetics Research Branch (ERB) of the Flight Electronics and Technology Division (FETD) conducts research on RF and microwave measurement methods related to the understanding of HIRF. In the High Intensity Radiated Fields Laboratory, the effects of high energy radiating electromagnetic fields on avionics and electronic systems are tested and studied.

  4. Radiation Entropy and Near-Field Thermophotovoltaics

    NASA Astrophysics Data System (ADS)

    Zhang, Zhuomin M.

    2008-08-01

    Radiation entropy was key to the original derivation of Planck's law of blackbody radiation, in 1900. This discovery opened the door to quantum mechanical theory and Planck was awarded the Nobel Prize in Physics in 1918. Thermal radiation plays an important role in incandescent lamps, solar energy utilization, temperature measurements, materials processing, remote sensing for astronomy and space exploration, combustion and furnace design, food processing, cryogenic engineering, as well as numerous agricultural, health, and military applications. While Planck's law has been fruitfully applied to a large number of engineering problems for over 100 years, questions have been raised about its limitation in micro/nano systems, especially at subwavelength distances or in the near field. When two objects are located closer than the characteristic wavelength, wave interference and photon tunneling occurs that can result in significant enhancement of the radiative transfer. Recent studies have shown that the near-field effects can realize emerging technologies, such as superlens, sub-wavelength light source, polariton-assisted nanolithography, thermophotovoltaic (TPV) systems, scanning tunneling thermal microscopy, etc. The concept of entropy has also been applied to explain laser cooling of solids as well as the second law efficiency of devices that utilize thermal radiation to produce electricity. However, little is known as regards the nature of entropy in near-field radiation. Some history and recent advances are reviewed in this presentation with a call for research of radiation entropy in the near field, due to the important applications in the optimization of thermophotovoltaic converters and in the design of practical systems that can harvest photon energies efficiently.

  5. Radiation Effects on Current Field Programmable Technologies

    NASA Technical Reports Server (NTRS)

    Katz, R.; LaBel, K.; Wang, J. J.; Cronquist, B.; Koga, R.; Penzin, S.; Swift, G.

    1997-01-01

    Manufacturers of field programmable gate arrays (FPGAS) take different technological and architectural approaches that directly affect radiation performance. Similar y technological and architectural features are used in related technologies such as programmable substrates and quick-turn application specific integrated circuits (ASICs). After analyzing current technologies and architectures and their radiation-effects implications, this paper includes extensive test data quantifying various devices total dose and single event susceptibilities, including performance degradation effects and temporary or permanent re-configuration faults. Test results will concentrate on recent technologies being used in space flight electronic systems and those being developed for use in the near term. This paper will provide the first extensive study of various configuration memories used in programmable devices. Radiation performance limits and their impacts will be discussed for each design. In addition, the interplay between device scaling, process, bias voltage, design, and architecture will be explored. Lastly, areas of ongoing research will be discussed.

  6. Radiative reactions in halo effective field theory

    NASA Astrophysics Data System (ADS)

    Rupak, Gautam

    2016-03-01

    In this article we review the recent progress in radiative reaction calculations in halo effective field theory. We look at radiative capture and breakup processes that involve a halo nucleus with a single valence neutron or proton. Looking at 7Li(n,γ) 8Li,14C(n,γ)15C and related reactions, the dominant source of theoretical uncertainty in s- and p-wave halo nuclei reaction calculations is quantified in a model-independent framework. The analysis for neutron halos is extended to proton halo systems. The effective field theory results quantify which observable parameters of the strong interaction at low energy need to be determined more precisely for accurate cross-section calculations.

  7. Radiative instabilities in sheared magnetic field

    NASA Technical Reports Server (NTRS)

    Drake, J. F.; Sparks, L.; Van Hoven, G.

    1988-01-01

    The structure and growth rate of the radiative instability in a sheared magnetic field B have been calculated analytically using the Braginskii fluid equations. In a shear layer, temperature and density perturbations are linked by the propagation of sound waves parallel to the local magnetic field. As a consequence, density clumping or condensation plays an important role in driving the instability. Parallel thermal conduction localizes the mode to a narrow layer where K(parallel) is small and stabilizes short wavelengths k larger-than(c) where k(c) depends on the local radiation and conduction rates. Thermal coupling to ions also limits the width of the unstable spectrum. It is shown that a broad spectrum of modes is typically unstable in tokamak edge plasmas and it is argued that this instability is sufficiently robust to drive the large-amplitude density fluctuations often measured there.

  8. Plasma wake field XUV radiation source

    DOEpatents

    Prono, Daniel S.; Jones, Michael E.

    1997-01-01

    A XUV radiation source uses an interaction of electron beam pulses with a gas to create a plasma radiator. A flowing gas system (10) defines a circulation loop (12) with a device (14), such as a high pressure pump or the like, for circulating the gas. A nozzle or jet (16) produces a sonic atmospheric pressure flow and increases the density of the gas for interacting with an electron beam. An electron beam is formed by a conventional radio frequency (rf) accelerator (26) and electron pulses are conventionally formed by a beam buncher (28). The rf energy is thus converted to electron beam energy, the beam energy is used to create and then thermalize an atmospheric density flowing gas to a fully ionized plasma by interaction of beam pulses with the plasma wake field, and the energetic plasma then loses energy by line radiation at XUV wavelengths Collection and focusing optics (18) are used to collect XUV radiation emitted as line radiation when the high energy density plasma loses energy that was transferred from the electron beam pulses to the plasma.

  9. Haemopoietic cell renewal in radiation fields.

    PubMed

    Fliedner, T M; Nothdurft, W; Tibken, B; Hofer, E; Weiss, M; Kindler, H

    1994-10-01

    Space flight activities are inevitably associated with a chronic exposure of astronauts to a complex mixture of ionising radiation. Although no acute radiation consequences are to be expected as a rule, the possibility of Solar Particle Events (SPE) associated with relatively high doses of radiation (1 or more Gray) cannot be excluded. It is the responsibility of physicians in charge of the health of astronauts to evaluate before, during and after space flight activities the functional status of haemopoietic cell renewal. Chronic low level exposure of dogs indicate that daily gamma-exposure doses below about 2 cGy are tolerated for several years as far as blood cell concentrations are concerned. However, the stem cell pool may be severely affected. The maintenance of sufficient blood cell counts is possible only through increased cell production to compensate for the radiation inflicted excess cell loss. This behaviour of haemopoietic cell renewal during chronic low level exposure can be simulated by bioengineering models of granulocytopoiesis. It is possible to define a "turbulence region" for cell loss rates, below which an prolonged adaptation to increased radiation fields can be expected to be tolerated. On the basis of these experimental results, it is recommended to develop new biological indicators to monitor haemopoietic cell renewal at the level of the stem cell pool using blood stem cells in addition to the determination of cytokine concentrations in the serum (and other novel approaches). To prepare for unexpected haemopoietic effects during prolonged space missions, research should be increased to modify the radiation sensitivity of haemopoietic stem cells (for instance by the application of certain regulatory molecules). In addition, a "blood stem cell bank" might be established for the autologous storage of stem cells and for use in space activities keeping them in a radiation protected container. PMID:11539991

  10. Haemopoietic cell renewal in radiation fields

    NASA Astrophysics Data System (ADS)

    Fliedner, T. M.; Nothdurft, W.; Tibken, B.; Hofer, E.; Weiss, M.; Kindler, H.

    1994-10-01

    Space flight activities are inevitably associated with a chronic exposure of astronauts to a complex mixture of ionising radiation. Although no acute radiation consequences are to be expected as a rule, the possibility of Solar Particle Events (SPE) associated with relatively high doses of radiation (1 or more Gray) cannot be excluded. It is the responsibility of physicians in charge of the health of astronauts to evaluate before, during and after space flight activities the functional status of haemopoietic cell renewal. Chronic low level exposure of dogs indicate that daily gamma-exposure doses below about 2 cGy are tolerated for several years as far as blood cell concentrations are concerned. However, the stem cell pool may be severely affected. The maintenance of sufficient blood cell counts is possible only through increased cell production to compensate for the radiation inflicted excess cell loss. This behaviour of haemopoietic cell renewal during chronic low level exposure can be simulated by bioengineering models of granulocytopoiesis. It is possible to define a ``turbulence region'' for cell loss rates, below which an prolonged adaptation to increased radiation fields can be expected to be tolerated. On the basis of these experimental results, it is recommended to develop new biological indicators to monitor haemopoietic cell renewal at the level of the stem cell pool using blood stem cells in addition to the determination of cytokine concentrations in the serum (and other novel approaches). To prepare for unexpected haemopoietic effects during prolonged space missions, research should be increased to modify the radiation sensitivity of haemopoietic stem cells (for instance by the application of certain regulatory molecules). In addition, a ``blood stem cell bank'' might be established for the autologous storage of stem cells and for use in space activities keeping them in a radiation protected container.

  11. Limited-field radiation for bifocal germinoma

    SciTech Connect

    Lafay-Cousin, Lucie . E-mail: lucie.lafay-cousin@sickkids.ca; Millar, Barbara-Ann; Mabbott, Donald; Spiegler, Brenda; Drake, Jim; Bartels, Ute; Huang, Annie; Bouffet, Eric

    2006-06-01

    Purpose: To report the incidence, characteristics, treatment, and outcomes of bifocal germinomas treated with chemotherapy followed by focal radiation. Methods and Materials: This was a retrospective review. Inclusion criteria included radiologic diagnosis of bifocal germinoma involving the pineal and neurohypophyseal region, no evidence of dissemination on spinal MRI, negative results from cerebrospinal fluid cytologic evaluation, and negative tumor markers. Results: Between 1995 and 2004, 6 patients (5 male, 1 female; median age, 12.8 years) fulfilled the inclusion criteria. All had symptoms of diabetes insipidus at presentation. On MRI, 4 patients had a pineal and suprasellar mass, and 2 had a pineal mass associated with abnormal neurohypophyseal enhancement. All patients received chemotherapy followed by limited-field radiation and achieved complete remission after chemotherapy. The radiation field involved the whole ventricular system (range, 2,400-4,000 cGy) with or without a boost to the primary lesions. All patients remain in complete remission at a median follow-up of 48.1 months (range, 9-73.4 months). Conclusions: This experience suggests that bifocal germinoma can be considered a locoregional rather than a metastatic disease. Chemotherapy and focal radiotherapy might be sufficient to provide excellent outcomes. Staging refinement with new diagnostic tools will likely increase the incidence of the entity.

  12. Radiative processes in external gravitational fields

    SciTech Connect

    Papini, Giorgio

    2010-07-15

    Kinematically forbidden processes may be allowed in the presence of external gravitational fields. These can be taken into account by introducing generalized particle momenta. The corresponding transition probabilities can then be calculated to all orders in the metric deviation from the field-free expressions by simply replacing the particle momenta with their generalized counterparts. The procedure applies to particles of any spin and to any gravitational fields. Transition probabilities, emission power, and spectra are, to leading order, linear in the metric deviation. It is also shown how a small dissipation term in the particle wave equations can trigger a strong backreaction that introduces resonances in the radiative process and deeply affects the resulting gravitational background.

  13. Virtual radiation fields for ALARA determination

    SciTech Connect

    Knight, T.W.

    1995-12-31

    As computing power has increased, so too has the ability to model and simulate complex systems and processes. In addition, virtual reality technology has made it possible to visualize and understand many complex scientific and engineering problems. For this reason, a virtual dosimetry program called Virtual Radiation Fields (VRF) is developed to model radiation dose rate and cumulative dose to a receptor operating in a virtual radiation environment. With the design and testing of many facilities and products taking place in the virtual world, this program facilitates the concurrent consideration of radiological concerns during the design process. Three-dimensional (3D) graphical presentation of the radiation environment is made possible through the use of IGRIP, a graphical modeling program developed by Deneb Robotics, Inc. The VRF simulation program was designed to model and display a virtual dosimeter. As a demonstration of the program`s capability, the Hanford tank, C-106, was modeled to predict radiation doses to robotic equipment used to remove radioactive waste from the tank. To validate VRF dose predictions, comparison was made with reported values for tank C-106, which showed agreement to within 0.5%. Graphical information is presented regarding the 3D dose rate variation inside the tank. Cumulative dose predictions were made for the cleanup operations of tank C-106. A four-dimensional dose rate map generated by VRF was used to model the dose rate not only in 3D space but also as a function of the amount of waste remaining in the tank. This allowed VRF to predict dose rate at any stage in the waste removal process for an accurate simulation of the radiological conditions throughout the tank cleanup procedure.

  14. Monte Carlo simulation of the radiation environment encountered by a biochip during a space mission to Mars.

    PubMed

    Le Postollec, A; Incerti, S; Dobrijevic, M; Desorgher, L; Santin, G; Moretto, P; Vandenabeele-Trambouze, O; Coussot, G; Dartnell, L; Nieminen, P

    2009-04-01

    Simulations with a Monte Carlo tool kit have been performed to determine the radiation environment a specific device, called a biochip, would face if it were placed into a rover bound to explore Mars' surface. A biochip is a miniaturized device that can be used to detect organic molecules in situ. Its specific detection part is constituted of proteins whose behavior under cosmic radiation is completely unknown and must be investigated to ensure a good functioning of the device under space conditions. The aim of this study is to define particle species and energy ranges that could be relevant to investigate during experiments on irradiation beam facilities. Several primary particles have been considered for galactic cosmic ray (GCR) and solar energetic particle (SEP) contributions. Ionizing doses accumulated in the biochip and differential fluxes of protons, alphas, neutrons, gammas, and electrons have been established for both the Earth-Mars transit and the journey at Mars' surface. Neutrons and gammas appear as dominant species on martian soil, whereas protons dominate during the interplanetary travel. Depending on solar event occurrence during the mission, an ionizing dose of around a few Grays (1 Gy = 100 rad) is expected. PMID:19368517

  15. Voyager: Neptune Encounter Highlights

    NASA Technical Reports Server (NTRS)

    1989-01-01

    Voyager encounter data are presented in computer animation (CA) and real (R) animation. The highlights include a view of 2 full rotations of Neptune. It shows spacecraft trajectory 'diving' over Neptune and intercepting Triton's orbit, depicting radiation and occulation zones. Also shown are a renegade orbit of Triton and Voyager's encounter with Neptune's Magnetopause. A model of the spacecraft's complex maneuvers during close encounters of Neptune and Triton is presented. A view from Earth of Neptune's occulation experiment is is shown as well as a recreation of Voyager's final pass. There is detail of Voyager's Image Compensation technique which produces Voyager images. Eighteen images were produced on June 22 - 23, 1989, from 57 million miles away. A 68 day sequence which provides a stroboscopic view - colorization approximates what is seen by the human eye. Real time images recorded live from Voyager on 8/24/89 are presented. Photoclinometry produced the topography of Triton. Three images are used to create a sequence of Neptune's rings. The globe of Neptune and 2 views of the south pole are shown as well as Neptune rotating. The rotation of a scooter is frozen in images showing differential motion. There is a view of rotation of the Great Dark Spot about its own axis. Photoclinometry provides a 3-dimensional perspective using a color mosaic of Triton images. The globe is used to indicate the orientation of Neptune's crescent. The east and west plumes on Triton are shown.

  16. A method for characterizing photon radiation fields

    SciTech Connect

    Whicker, J.J.; Hsu, H.H.; Hsieh, F.H.; Borak, T.B.

    1999-04-01

    Uncertainty in dosimetric and exposure rate measurements can increase in areas where multi-directional and low-energy photons (< 100 keV) exist because of variations in energy and angular measurement response. Also, accurate measurement of external exposures in spatially non-uniform fields may require multiple dosimetry. Therefore, knowledge of the photon fields in the workplace is required for full understanding of the accuracy of dosimeters and instruments, and for determining the need for multiple dosimeters. This project was designed to develop methods to characterize photon radiation fields in the workplace, and to test the methods in a plutonium facility. The photon field at selected work locations was characterized using TLDs and a collimated NaI(Tl) detector from which spatial variations in photon energy distributions were calculated from measured spectra. Laboratory results showed the accuracy and utility of the method. Field measurement results combined with observed work patterns suggested the following: (1) workers are exposed from all directions, but not isotropically, (2) photon energy distributions were directionally dependent, (3) stuffing nearby gloves into the glovebox reduced exposure rates significantly, (4) dosimeter placement on the front of the chest provided for a reasonable estimate of the average dose equivalent to workers` torsos, (5) justifiable conclusions regarding the need for multiple dosimetry can be made using this quantitative method, and (6) measurements of the exposure rates with ionization chambers pointed with open beta windows toward the glovebox provided the highest measured rates, although absolute accuracy of the field measurements still needs to be assessed.

  17. The Voyager 2 Neptune encounter

    SciTech Connect

    Tsurutani, B.T. )

    1989-10-01

    The findings made by the Voyager 2 Neptune encounter are reviewed. Data on the bowshock, magnetic field, magnetosphere, rings, plasma sheet, aurora, moons, and dust of Neptune are discussed. Findings made concerning Triton are summarized.

  18. AfricaArray International Geophysics Field School: Applications of Near Surface Geophysics to challenges encountered in mine planning

    NASA Astrophysics Data System (ADS)

    Webb, S. J.; Jones, M. Q.; Durrheim, R. J.; Nyblade, A.; Snyman, Q.

    2012-12-01

    Hard rock exploration and mining presents many opportunities for the effective use of near surface geophysics. For over 10 years the AfricaArray international geophysics field school has been hosted at a variety of mines in South Africa. While the main objective of the field school is practical training for the next generation of geophysicists, being hosted at a mine has allowed us to investigate applications of near surface geophysics in the early stages of mine planning and development as geophysics is often cheaper and faster than drilling. Several applications include: detailed delineation of dykes and stringer dykes, physical property measurements on drill core for modeling and marker horizons, determination of overburden thickness, locations of water and faults. Dolerite dykes are usually magnetic and are associated with loss of ground (i.e. where the dyke replaces the ore and thus reduces the amount of ore available) and safety/stability concerns. Thus the accurate mapping of dykes and narrow stringers that are associated with them are crucial to the safe planning of a mine. We have acquired several case studies where ground magnetic surveys have greatly improved on the resolution and detail of airborne magnetic surveys in regions of complicated dyke swarms. In many cases, thin stringer dykes of less than 5 cm have been detected. Physical property measurements of these dykes can be used to distinguish between different ages of dykes. It is important to accurately determine overburden thickness when planning an open pit mine as this directly affects the cost of development. Depending on the nature of the overburden, both refraction seismic and or DC resistivity can provide continuous profiling in the area of interest that fills in gaps between boreholes. DC resistivity is also effective for determining water associated with dykes and structures that may affect mine planning. The field school mainly addresses the training of a variety of students. The core

  19. Radiation burst from a single γ-photon field

    NASA Astrophysics Data System (ADS)

    Shakhmuratov, R. N.; Vagizov, F.; Kocharovskaya, O.

    2011-10-01

    The radiation burst from a single γ-photon field interacting with a dense resonant absorber is studied theoretically and experimentally. This effect was discovered for the fist time by P. Helisto [Phys. Rev. Lett. PRLTAO0031-900710.1103/PhysRevLett.66.203766, 2037 (1991)] and it was named the “gamma echo.” The echo is generated by a 180∘ phase shift of the incident radiation field, attained by an abrupt change of the position of the absorber with respect to the radiation source during the coherence time of the photon wave packet. Three distinguishing cases of the gamma echo are considered; i.e., the photon is in exact resonance with the absorber, close to resonance (on the slope of the absorption line), and far from resonance (on the far wings of the resonance line). In resonance the amplitude of the radiation burst is two times larger than the amplitude of the input radiation field just before its phase shift. This burst was explained by Helisto as a result of constructive interference of the coherently scattered field with the phase-shifted input field, both having almost the same amplitude. We found that out of resonance the scattered radiation field acquires an additional component with almost the same amplitude as the amplitude of the incident radiation field. The phase of the additional field depends on the optical thickness of the absorber and resonant detuning. Far from resonance this field interferes destructively with the phase-shifted incident radiation field and radiation quenching is observed. Close to resonance the three fields interfere constructively and the amplitude of the radiation burst is three times larger than the amplitude of the input radiation field.

  20. Radiation burst from a single {gamma}-photon field

    SciTech Connect

    Shakhmuratov, R. N.; Vagizov, F.; Kocharovskaya, O.

    2011-10-15

    The radiation burst from a single {gamma}-photon field interacting with a dense resonant absorber is studied theoretically and experimentally. This effect was discovered for the fist time by P. Helisto et al.[Phys. Rev. Lett. 66, 2037 (1991)] and it was named the ''gamma echo''. The echo is generated by a 180 Degree-Sign phase shift of the incident radiation field, attained by an abrupt change of the position of the absorber with respect to the radiation source during the coherence time of the photon wave packet. Three distinguishing cases of the gamma echo are considered; i.e., the photon is in exact resonance with the absorber, close to resonance (on the slope of the absorption line), and far from resonance (on the far wings of the resonance line). In resonance the amplitude of the radiation burst is two times larger than the amplitude of the input radiation field just before its phase shift. This burst was explained by Helisto et al. as a result of constructive interference of the coherently scattered field with the phase-shifted input field, both having almost the same amplitude. We found that out of resonance the scattered radiation field acquires an additional component with almost the same amplitude as the amplitude of the incident radiation field. The phase of the additional field depends on the optical thickness of the absorber and resonant detuning. Far from resonance this field interferes destructively with the phase-shifted incident radiation field and radiation quenching is observed. Close to resonance the three fields interfere constructively and the amplitude of the radiation burst is three times larger than the amplitude of the input radiation field.

  1. Reading the Other: Ethics of Encounter

    ERIC Educational Resources Information Center

    Allen, Sarah

    2008-01-01

    Most scholarly fields, at least in the humanities, have been asking the same questions about the politics of encounter for hundreds of years: Should we try to find a way to encounter an other without appropriating it, without imposing ourselves on it? Is encountering-without-appropriating even possible? These questions are profuse and taken up…

  2. Light-Cone Effect of Radiation Fields in Cosmological Radiative Transfer Simulations

    NASA Astrophysics Data System (ADS)

    Ahn, Kyungjin

    2015-02-01

    We present a novel method to implement time-delayed propagation of radiation fields in cosmo-logical radiative transfer simulations. Time-delayed propagation of radiation fields requires construction of retarded-time fields by tracking the location and lifetime of radiation sources along the corresponding light-cones. Cosmological radiative transfer simulations have, until now, ignored this "light-cone effect" or implemented ray-tracing methods that are computationally demanding. We show that radiative trans-fer calculation of the time-delayed fields can be easily achieved in numerical simulations when periodic boundary conditions are used, by calculating the time-discretized retarded-time Green's function using the Fast Fourier Transform (FFT) method and convolving it with the source distribution. We also present a direct application of this method to the long-range radiation field of Lyman-Werner band photons, which is important in the high-redshift astrophysics with first stars.

  3. Magnetic fields and nonthermal electromagnetic radiation of stars

    NASA Astrophysics Data System (ADS)

    Kryvdyk, Volodymyr

    2016-07-01

    The results of the astrophysical observations of the magnetic fields and the nonthermal electromagnetic radiation of stars and the mechanisms generation of the nonthermal electromagnetic radiation from the magnetized stars of different spectral classes on the different stages their evolution are present. Results of observations allow to calculate the plasma parameters and the magnetic fields in areas around magnetized stars where is generated given radiation and their change during stellar evolution.

  4. Radiation field associated with Hiroshima and Nagasaki

    SciTech Connect

    Loewe, W.E.

    1984-08-01

    Accuracy of dosimetric estimates can determine the value of the atomic bomb survivor experience in establishing radiation risks. The status of a major revision of this dosimetry, initiated in 1980, is assessed. 3 references, 6 figures.

  5. Influence of Hydroponically Grown Hoyt Soybeans and Radiation Encountered on Mars Missions on the Yield and Quality of Soymilk and Tofu

    NASA Technical Reports Server (NTRS)

    Wilson, Lester A.

    2005-01-01

    Soybeans were chosen for hmar and planetary missions due to their nutritive value and ability to produce oil and protein for further food applications. However, soybeans must be processed into foods prior to crew consumption. Wilson et al. (2003) raised questions about (1) the influence of radiation (on germination and functional properties) that the soybeans would be exposed to during bulk storage for a Mars mission, and (2) the impact of using hydroponically grown versus field grown soybeans on the yield and quality of soyfoods. The influence of radiation can be broken down into two components: (A) affect of surface pasteurization to ensure the astronauts safety from food-borne illnesses (a Hazard Analysis Critical Control Point), and (B) affect of the amount of radiation the soybeans receive during a Mars mission. Decreases in the amount of natural antioxidants and free radical formation and oxidation induced changes in the soybean (lipid, protein, etc.) will influence the nutritional value, texture, quality, and safety of soyfoods made from them. The objectives of this project are to (1) evaluate the influence of gamma and electron beam radiation on bulk soybeans (HACCP, CCP) on the microbial load, germination, ease of processing, and quality of soymilk and tofu; (2) provide scale up and mass balance data for Advanced Life Support subsystems including Biomass, Solid Waste Processing, and Water Recovery Systems; and (3) to compare Hoyt field grown to hydroponically grown Hoyt soybeans for soymilk and tofu production. The soybean cultivar Hoyt, a small standing, high protein cultivar that could grow hydroponically in the AIMS facility on Mars) was evaluated for the production of soymilk and tofu. The quality and yield of the soymilk and tofu from hydroponic Hoyt, was compared to Vinton 81 (a soyfood industry standard), field Hoyt, IA 2032LS (lipoxygenase-free), and Proto (high protein and antioxidant potential). Soymilk and tofu were produced using the Japanese

  6. LCLS Far-Field Spontaneous Radiation

    Energy Science and Technology Software Center (ESTSC)

    2004-04-16

    This application (FarFieldDisplay) is a tool for displaying and analyzing far-field spontaneous spectral flux data for the Linac Coherent Light Source (LCLS) Calculated by Roman Tatchyn (Stanford University). This tool allows the user to view sliced spatial and energy distributions of the fat-field photons selected for specific energies or positions transverse to the beam axis,

  7. Detection of alpha radiation in a beta radiation field

    DOEpatents

    Mohagheghi, Amir H.; Reese, Robert P.

    2001-01-01

    An apparatus and method for detecting alpha particles in the presence of high activities of beta particles utilizing an alpha spectrometer. The apparatus of the present invention utilizes a magnetic field applied around the sample in an alpha spectrometer to deflect the beta particles from the sample prior to reaching the detector, thus permitting detection of low concentrations of alpha particles. In the method of the invention, the strength of magnetic field required to adequately deflect the beta particles and permit alpha particle detection is given by an algorithm that controls the field strength as a function of sample beta energy and the distance of the sample to the detector.

  8. Near-field radiative thermal transport: From theory to experiment

    SciTech Connect

    Song, Bai Fiorino, Anthony; Meyhofer, Edgar; Reddy, Pramod

    2015-05-15

    Radiative thermal transport via the fluctuating electromagnetic near-field has recently attracted increasing attention due to its fundamental importance and its impact on a range of applications from data storage to thermal management and energy conversion. After a brief historical account of radiative thermal transport, we summarize the basics of fluctuational electrodynamics, a theoretical framework for the study of radiative heat transfer in terms of thermally excited propagating and evanescent electromagnetic waves. Various approaches to modeling near-field thermal transport are briefly discussed, together with key results and proposals for manipulation and utilization of radiative heat flow. Subsequently, we review the experimental advances in the characterization of both near-field heat flow and energy density. We conclude with remarks on the opportunities and challenges for future explorations of radiative heat transfer at the nanoscale.

  9. Scalar field radiation from dilatonic black holes

    NASA Astrophysics Data System (ADS)

    Gohar, H.; Saifullah, K.

    2012-12-01

    We study radiation of scalar particles from charged dilaton black holes. The Hamilton-Jacobi method has been used to work out the tunneling probability of outgoing particles from the event horizon of dilaton black holes. For this purpose we use WKB approximation to solve the charged Klein-Gordon equation. The procedure gives Hawking temperature for these black holes as well.

  10. Modern Radiation Therapy for Hodgkin Lymphoma: Field and Dose Guidelines From the International Lymphoma Radiation Oncology Group (ILROG)

    SciTech Connect

    Specht, Lena; Yahalom, Joachim; Illidge, Tim; Berthelsen, Anne Kiil; Constine, Louis S.; Eich, Hans Theodor; Girinsky, Theodore; Hoppe, Richard T.; Mauch, Peter; Mikhaeel, N. George; Ng, Andrea

    2014-07-15

    Radiation therapy (RT) is the most effective single modality for local control of Hodgkin lymphoma (HL) and an important component of therapy for many patients. These guidelines have been developed to address the use of RT in HL in the modern era of combined modality treatment. The role of reduced volumes and doses is addressed, integrating modern imaging with 3-dimensional (3D) planning and advanced techniques of treatment delivery. The previously applied extended field (EF) and original involved field (IF) techniques, which treated larger volumes based on nodal stations, have now been replaced by the use of limited volumes, based solely on detectable nodal (and extranodal extension) involvement at presentation, using contrast-enhanced computed tomography, positron emission tomography/computed tomography, magnetic resonance imaging, or a combination of these techniques. The International Commission on Radiation Units and Measurements concepts of gross tumor volume, clinical target volume, internal target volume, and planning target volume are used for defining the targeted volumes. Newer treatment techniques, including intensity modulated radiation therapy, breath-hold, image guided radiation therapy, and 4-dimensional imaging, should be implemented when their use is expected to decrease significantly the risk for normal tissue damage while still achieving the primary goal of local tumor control. The highly conformal involved node radiation therapy (INRT), recently introduced for patients for whom optimal imaging is available, is explained. A new concept, involved site radiation therapy (ISRT), is introduced as the standard conformal therapy for the scenario, commonly encountered, wherein optimal imaging is not available. There is increasing evidence that RT doses used in the past are higher than necessary for disease control in this era of combined modality therapy. The use of INRT and of lower doses in early-stage HL is supported by available data. Although the

  11. The Electromagnetic Dipole Radiation Field through the Hamiltonian Approach

    ERIC Educational Resources Information Center

    Likar, A.; Razpet, N.

    2009-01-01

    The dipole radiation from an oscillating charge is treated using the Hamiltonian approach to electrodynamics where the concept of cavity modes plays a central role. We show that the calculation of the radiation field can be obtained in a closed form within this approach by emphasizing the role of coherence between the cavity modes, which is…

  12. Radiation tolerant silicon nitride insulated gate field effect transistors

    NASA Technical Reports Server (NTRS)

    Newman, P. A.

    1969-01-01

    Metal-Insulated-Semiconductor Field Effect Transistor /MISFET/ device uses a silicon nitride passivation layer over a thin silicon oxide layer to enhance the radiation tolerance. It is useful in electronic systems exposed to space radiation environment or the effects of nuclear weapons.

  13. Radiative heat transfer in the extreme near field.

    PubMed

    Kim, Kyeongtae; Song, Bai; Fernández-Hurtado, Víctor; Lee, Woochul; Jeong, Wonho; Cui, Longji; Thompson, Dakotah; Feist, Johannes; Reid, M T Homer; García-Vidal, Francisco J; Cuevas, Juan Carlos; Meyhofer, Edgar; Reddy, Pramod

    2015-12-17

    Radiative transfer of energy at the nanometre length scale is of great importance to a variety of technologies including heat-assisted magnetic recording, near-field thermophotovoltaics and lithography. Although experimental advances have enabled elucidation of near-field radiative heat transfer in gaps as small as 20-30 nanometres (refs 4-6), quantitative analysis in the extreme near field (less than 10 nanometres) has been greatly limited by experimental challenges. Moreover, the results of pioneering measurements differed from theoretical predictions by orders of magnitude. Here we use custom-fabricated scanning probes with embedded thermocouples, in conjunction with new microdevices capable of periodic temperature modulation, to measure radiative heat transfer down to gaps as small as two nanometres. For our experiments we deposited suitably chosen metal or dielectric layers on the scanning probes and microdevices, enabling direct study of extreme near-field radiation between silica-silica, silicon nitride-silicon nitride and gold-gold surfaces to reveal marked, gap-size-dependent enhancements of radiative heat transfer. Furthermore, our state-of-the-art calculations of radiative heat transfer, performed within the theoretical framework of fluctuational electrodynamics, are in excellent agreement with our experimental results, providing unambiguous evidence that confirms the validity of this theory for modelling radiative heat transfer in gaps as small as a few nanometres. This work lays the foundations required for the rational design of novel technologies that leverage nanoscale radiative heat transfer. PMID:26641312

  14. School Facilities and Electric and Magnetic Field Radiation.

    ERIC Educational Resources Information Center

    Carr, Richard L.

    1990-01-01

    The possibility that electric and magnetic field radiation poses a health hazard should be recognized during the planning and designing of a school. A preconstruction assessment of possible exposure should be evaluated before the start of construction. (MLF)

  15. VOYAGER OBSERVATIONS OF THE DIFFUSE FAR-ULTRAVIOLET RADIATION FIELD

    SciTech Connect

    Murthy, Jayant; Henry, Richard Conn; Holberg, Jay B.

    2012-03-01

    The two Voyager spacecraft have completed their planetary exploration mission and are now probing the outer realms of the heliosphere. The Voyager ultraviolet spectrometers continued to operate well after the Voyager 2 Neptune encounter in 1989. We present a complete database of diffuse radiation observations made by both Voyagers: a total of 1943 spectra (500-1600 A) scattered throughout the sky. These include observations of dust-scattered starlight, emission lines from the hot interstellar medium, and a number of locations where no diffuse radiation was detected, with the very low upper limit of about 25 photons cm{sup -2} s{sup -1} sr{sup -1} A{sup -1}. Many of these observations were from late in the mission when there was significantly less contribution from interplanetary emission lines and thus less contamination of the interstellar signal.

  16. Reconstruction of radiating sound fields using minimum energy method.

    PubMed

    Bader, Rolf

    2010-01-01

    A method for reconstructing a pressure field at the surface of a radiating body or source is presented using recording data of a microphone array. The radiation is assumed to consist of many spherical radiators, as microphone positions are present in the array. These monopoles are weighted using a parameter alpha, which broadens or narrows the overall radiation directivity as an effective and highly intuitive parameter of the radiation characteristics. A radiation matrix is built out of these weighted monopole radiators, and for different assumed values of alpha, a linear equation solver reconstructs the pressure field at the body's surface. It appears that from these many arbitrary reconstructions, the correct one minimizes the reconstruction energy. The method is tested, localizing the radiation points of a Balinese suling flute, reconstructing complex radiation from a duff frame drum, and determining the radiation directivity for the first seven modes of an Usbek tambourine. Stability in terms of measurement noise is demonstrated for the plain method, and additional highly effective algorithm is added for a noise level up to 0 dB. The stability of alpha in terms of minimal reconstruction energy is shown over the whole range of possible values for alpha. Additionally, the treatment of unwanted room reflections is discussed, still leading to satisfactory results in many cases. PMID:20058977

  17. The Geomagnetic Field and Radiation in Near-Earth Orbits

    NASA Technical Reports Server (NTRS)

    Heirtzler, J. R.

    1999-01-01

    This report shows, in detail, how the geomagnetic field interacts with the particle flux of the radiation belts to create a hazard to spacecraft and humans in near-Earth orbit. It illustrates the geometry of the geomagnetic field lines, especially around the area where the field strength is anomalously low in the South Atlantic Ocean. It discusses how the field will probably change in the future and the consequences that may have on hazards in near space.

  18. Gravitational radiation from preheating with many fields

    SciTech Connect

    Jr, John T. Giblin; Price, Larry R.; Siemens, Xavier E-mail: larry@gravity.phys.uwm.edu

    2010-08-01

    Parametric resonances provide a mechanism by which particles can be created just after inflation. Thus far, attention has focused on a single or many inflaton fields coupled to a single scalar field. However, generically we expect the inflaton to couple to many other relativistic degrees of freedom present in the early universe. Using simulations in an expanding Friedmann-Lemaître-Robertson-Walker spacetime, in this paper we show how preheating is affected by the addition of multiple fields coupled to the inflaton. We focus our attention on gravitational wave production — an important potential observational signature of the preheating stage. We find that preheating and its gravitational wave signature is robust to the coupling of the inflaton to more matter fields.

  19. Multimodal far-field acoustic radiation pattern: An approximate equation

    NASA Technical Reports Server (NTRS)

    Rice, E. J.

    1977-01-01

    The far-field sound radiation theory for a circular duct was studied for both single mode and multimodal inputs. The investigation was intended to develop a method to determine the acoustic power produced by turbofans as a function of mode cut-off ratio. With reasonable simplifying assumptions the single mode radiation pattern was shown to be reducible to a function of mode cut-off ratio only. With modal cut-off ratio as the dominant variable, multimodal radiation patterns can be reduced to a simple explicit expression. This approximate expression provides excellent agreement with an exact calculation of the sound radiation pattern using equal acoustic power per mode.

  20. Theoretical investigation of non-equilibrium chemistry and optical radiation in hypersonic flow fields

    NASA Technical Reports Server (NTRS)

    Whiting, Ellis E.

    1990-01-01

    Future space vehicles returning from distant missions or high earth orbits may enter the upper regions of the atmosphere and use aerodynamic drag to reduce their velocity before they skip out of the atmosphere and enter low earth orbit. The Aeroassist Flight Experiment (AFE) is designed to explore the special problems encountered in such entries. A computer code was developed to calculate the radiative transport along line-or-sight in the general 3-D flow field about an arbitrary entry vehicle, if the temperatures and species concentrations along the line-of-sight are known. The radiative heating calculation at the stagnation point of the AFE vehicle along the entry trajectory was performed, including a detailed line-by-line accounting of the radiative transport in the vacuum ultraviolet (below 200 nm) by the atomic N and O lines. A method was developed for making measurements of the haze particles in the Titan atmosphere above 200 km altitude. Several other tasks of a continuing nature, to improve the technical ability to calculate the nonequilibrium gas dynamic flow field and radiative heating of entry vehicles, were completed or advanced.

  1. Radiation from Relativistic Shocks with Turbulent Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Nishkawa, K.; Medvedev, M.; Zhang, B.; Hardee, P.; Niemiec, J.; Mizuno, A.; Nordlund, A.; Frederiksen, J.; Sol, H.; Pohl, M.; Hartmann, D. H.; Oka, M.; Fishman, J.

    2009-01-01

    Recent PIC simulations of relativistic electron-positron (electron-ion) jets injected into a stationary medium show that particle acceleration occurs at shocked region. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the shock. The "jitter" radiation from deflected electrons in turbulent magnetic fields has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants. New recent calculation of spectra with various different Lorentz factors of jets (two electrons) and initial magnetic fields. New spectra based on small simulations will be presented.

  2. Electron trajectories in pulsed radiation fields

    SciTech Connect

    Einwohner, T.; Lippmann, B.A.

    1987-05-01

    The work reported here analyzes the dynamical behavior of an electron, initially at rest, when subjected to a radiation pulse of arbitrary, but integrable, shape. This is done by a general integration procedure that has been programmed in VAXIMA. Upon choosing a specific shape for the pulse, VAXIMA finds both the space-time trajectory and the four-momentum of the electron. These are obtained in analytic or numerical form - or both - at the choice of the user. Several examples of analytical and numerical solutions, for different pulse shapes, are given.

  3. [To encounter oneself, to encounter each other].

    PubMed

    Kogan, A A

    1982-06-01

    The purpose of this article is to elucidate the concept of encounter within the realm of psycotherapy, either individual or group, with its inter and intrapersonal connotations. Its importance is emphasized and means for its achievement are suggested. A double course is followed to attain this end: on the one hand, the tracing of the concept in the contemporary philosophic anthropology (the positions of M. Buber and of K. Jaspers are briefly examined) and in the views of several psychotherapists who have placed it as a significant issue in their treatments (the therapists considered are K. Binswanger, C. Rogers, J. L. Moreno and E. Pichon-Rivière), and on the other hand, some clinical means, and very special attitudes, are indicated as particularly favourable for the promotion of that enlargement of subjectivity leading to the encounter of one-self as well as the other person. Some fragments of sessions are presented demonstrating that in general the "how" of the attitude prevailing in the therapeutic relation is more effective than the "what" of the specific technical resources employed. However, some of these are commendable as a more direct way to bring about the experience of encounter. This leads me to psychodrama, with its techniques of the double, the inversion of roles, the mirror, and most of all with the general group sharing that closes the sessions, and to the gestalt methods, which involve in many instances physical contacts with other people, with the precise object of achieving a maximum insight, or, in the already classical expression, awareness, which is basically an encounter with oneself. Implicit in all the above considerations lies the conviction that man must share his existence with others not only for biological reasons; it is an indispensable requirement for his full development as an individual, a requirement for being himself. If one of the goals of psychological treatments is to promote personal growth and proximity to oneself, an

  4. Adaptive radiations: From field to genomic studies

    PubMed Central

    Hodges, Scott A.; Derieg, Nathan J.

    2009-01-01

    Adaptive radiations were central to Darwin's formation of his theory of natural selection, and today they are still the centerpiece for many studies of adaptation and speciation. Here, we review the advantages of adaptive radiations, especially recent ones, for detecting evolutionary trends and the genetic dissection of adaptive traits. We focus on Aquilegia as a primary example of these advantages and highlight progress in understanding the genetic basis of flower color. Phylogenetic analysis of Aquilegia indicates that flower color transitions proceed by changes in the types of anthocyanin pigments produced or their complete loss. Biochemical, crossing, and gene expression studies have provided a wealth of information about the genetic basis of these transitions in Aquilegia. To obtain both enzymatic and regulatory candidate genes for the entire flavonoid pathway, which produces anthocyanins, we used a combination of sequence searches of the Aquilegia Gene Index, phylogenetic analyses, and the isolation of novel sequences by using degenerate PCR and RACE. In total we identified 34 genes that are likely involved in the flavonoid pathway. A number of these genes appear to be single copy in Aquilegia and thus variation in their expression may have been key for floral color evolution. Future studies will be able to use these sequences along with next-generation sequencing technologies to follow expression and sequence variation at the population level. The genetic dissection of other adaptive traits in Aquilegia should also be possible soon as genomic resources such as whole-genome sequencing become available. PMID:19528644

  5. Fission Product Transmutation in Mixed Radiation Fields

    SciTech Connect

    Harmon, Frank; Burgett, Erick; Starovoitova, Valeriia; Tsveretkov, Pavel

    2015-01-15

    Work under this grant addressed a part of the challenge facing the closure of the nuclear fuel cycle; reducing the radiotoxicity of lived fission products (LLFP). It was based on the possibility that partitioning of isotopes and accelerator-based transmutation on particular LLFP combined with geological disposal may lead to an acceptable societal solution to the problem of management. The feasibility of using photonuclear processes based on the excitation of the giant dipole resonance (GDR) by bremsstrahlung radiation as a cost effective transmutation method was accessed. The nuclear reactions of interest: (γ,xn), (n,γ), (γ,p) can be induced by bremsstrahlung radiation produced by high power electron accelerators. The driver of these processes would be an accelerator that produces a high energy and high power electron beam of ~ 100 MeV. The major advantages of such accelerators for this purpose are that they are essentially available “off the shelf” and potentially would be of reasonable cost for this application. Methods were examined that used photo produced neutrons or the bremsstrahlung photons only, or use both photons and neutrons in combination for irradiations of selected LLFP. Extrapolating the results to plausible engineering scale transmuters it was found that the energy cost for 129I and 99Tc transmutation by these methods are about 2 and 4%, respectively, of the energy produced from 1000MWe.

  6. Adaptive radiations: from field to genomic studies.

    PubMed

    Hodges, Scott A; Derieg, Nathan J

    2009-06-16

    Adaptive radiations were central to Darwin's formation of his theory of natural selection, and today they are still the centerpiece for many studies of adaptation and speciation. Here, we review the advantages of adaptive radiations, especially recent ones, for detecting evolutionary trends and the genetic dissection of adaptive traits. We focus on Aquilegia as a primary example of these advantages and highlight progress in understanding the genetic basis of flower color. Phylogenetic analysis of Aquilegia indicates that flower color transitions proceed by changes in the types of anthocyanin pigments produced or their complete loss. Biochemical, crossing, and gene expression studies have provided a wealth of information about the genetic basis of these transitions in Aquilegia. To obtain both enzymatic and regulatory candidate genes for the entire flavonoid pathway, which produces anthocyanins, we used a combination of sequence searches of the Aquilegia Gene Index, phylogenetic analyses, and the isolation of novel sequences by using degenerate PCR and RACE. In total we identified 34 genes that are likely involved in the flavonoid pathway. A number of these genes appear to be single copy in Aquilegia and thus variation in their expression may have been key for floral color evolution. Future studies will be able to use these sequences along with next-generation sequencing technologies to follow expression and sequence variation at the population level. The genetic dissection of other adaptive traits in Aquilegia should also be possible soon as genomic resources such as whole-genome sequencing become available. PMID:19528644

  7. Mariner 10 mercury encounter.

    PubMed

    Dunne, J A

    1974-07-12

    Mariner 10's closet approach to Mercury on 29 March 1974 occurred on the dark side of the planet at a range of approximately 700 kilometers. The spacecraft trajectory passed through the shadows of both the sun and Earth. Experiments conducted included magnetic fields, plasma and charged particle studies of the solar wind interaction region, television photography, extreme ultraviolet spectroscopy of the atmosphere, the detection of infrared thermal radiation from the surface, and a dual-frequency radio occultation in search of an ionosphere. PMID:17810505

  8. Visual verification of linac light and radiation fields coincidence

    SciTech Connect

    Monti, Angelo F.; Frigerio, Milena; Frigerio, Giovanna

    2003-06-30

    X-ray and light field alignment evaluation is carried out during linac quality assurance programs. In this paper, we compare the size of the light field measured by a photodiode and by a more traditional visual observation with the size of the x-ray field. The comparison between actual light field size, measured with the photodiode, and light field size measured by human eye allow us to verify the reliability of human eye in the evaluation of this parameter. The visual field is always larger than real light field; however, it agrees better with the x-ray field. It matches the light field if we take into account the 25% ({+-} 1%) of the decrement line of the maximum central lightening; however, this method simulates better the actual field employed in radiation treatments.

  9. Active thermal extraction of near-field thermal radiation

    NASA Astrophysics Data System (ADS)

    Ding, D.; Kim, T.; Minnich, A. J.

    2016-02-01

    Radiative heat transport between materials supporting surface-phonon polaritons is greatly enhanced when the materials are placed at subwavelength separation as a result of the contribution of near-field surface modes. However, the enhancement is limited to small separations due to the evanescent decay of the surface waves. In this work, we propose and numerically demonstrate an active scheme to extract these modes to the far field. Our approach exploits the monochromatic nature of near-field thermal radiation to drive a transition in a laser gain medium, which, when coupled with external optical pumping, allows the resonant surface mode to be emitted into the far field. Our study demonstrates an approach to manipulate thermal radiation that could find applications in thermal management.

  10. Spontaneous Radiation Emission from Short, High Field Strength Insertion Devices

    SciTech Connect

    Geoffrey Krafft

    2005-09-15

    Since the earliest papers on undulaters were published, it has been known how to calculate the spontaneous emission spectrum from ''short'' undulaters when the magnetic field strength parameter is small compared to unity, or in ''single'' frequency sinusoidal undulaters where the magnetic field strength parameter is comparable to or larger than unity, but where the magnetic field amplitude is constant throughout the undulater. Fewer general results have been obtained in the case where the insertion device is both short, i.e., the magnetic field strength parameter changes appreciably throughout the insertion device, and the magnetic field strength is high enough that ponderomotive effects, radiation retardation, and harmonic generation are important physical phenomena. In this paper a general method is presented for calculating the radiation spectrum for short, high-field insertion devices. It is used to calculate the emission from some insertion device designs of recent interest.

  11. Field Testing of a Portable Radiation Detector and Mapping System

    SciTech Connect

    Hofstetter, K.J.; Hayes, D.W.; Eakle, R.F.

    1998-03-01

    Researchers at the Savannah River Site (SRS) have developed a man- portable radiation detector and mapping system (RADMAPS) which integrates the accumulation of radiation information with precise ground locations. RADMAPS provides field personnel with the ability to detect, locate, and characterize nuclear material at a site or facility by analyzing the gamma or neutron spectra and correlating them with position. the man-portable field unit records gamma or neutron count rate information and its location, along with date and time, using an embedded Global Positioning System (GPS). RADMAPS is an advancement in data fusion, integrating several off-the-shelf technologies with new computer software resulting in a system that is simple to deploy and provides information useful to field personnel in an easily understandable form. Decisions on subsequent actions can be made in the field to efficiently use available field resources. The technologies employed in this system include: recording GPS, radiation detection (typically scintillation detectors), pulse height analysis, analog-to-digital converters, removable solid-state (Flash or SRAM) memory cards, Geographic Information System (GIS) software and personal computers with CD-ROM supporting digital base maps. RADMAPS includes several field deployable data acquisition systems designed to simultaneously record radiation and geographic positions. This paper summarizes the capabilities of RADMAPS and some of the results of field tests performed with the system.

  12. An evaluation of RAMS radiation schemes by field measurements

    SciTech Connect

    Zhong, S; Doran, J C

    1994-02-01

    At present, two radiation schemes are used in RAMS: the Mahrer and Pielke (M-P) scheme and the Chen and Cotton (C-C) scheme. The M-P scheme requires little computational expense, but does not include the radiative effects of liquid water or ice; the C-C scheme accounts for the radiative effects of liquid water and ice but is fairly expensive computationally. For simulations with clouds, the C-C scheme is obviously a better choice, but for clear sky conditions, RAMS users face a decision regarding which radiation scheme to use. It has been noted that the choice of radiation scheme may result in significantly different results for the same case. To examine the differences in the radiative fluxes and the boundary-layer structure corresponding to the two radiation schemes in RAMS we have carried out a study where Rams was used to simulate the same case with two different radiation schemes. The modeled radiative fluxes by the two schemes were then compared with the field measurements. A description of the observations and the case study, a comparison and discussion of the results, and a summary and conclusions follow.

  13. Angry Birds Space Encounter

    NASA Video Gallery

    At NASA's Kennedy Space Center Visitor Complex in Florida, a grand opening celebration was held for the new Angry Birds Space Encounter, March 22. Finland-based Rovio Entertainment, the creator of ...

  14. [Encounters with strangers].

    PubMed

    Lindner, W V

    1990-01-01

    Beginning with three episodes about the encounter with the alien (from a working group, a therapeutic group and from the actual public discussion about aliens) it is pointed out, why the encounter with the alien is both, fascinating and frightening. From the psychoanalytic point of view this is explained with the concept of the representation of the alien, especially under the genetic, adaptive and topic aspects. Finally from the initial examples conclusions for counseling and psychotherapy are drawn. PMID:2399213

  15. Synchrotron radiation in strongly coupled conformal field theories

    SciTech Connect

    Athanasiou, Christiana; Chesler, Paul M.; Liu, Hong; Rajagopal, Krishna; Nickel, Dominik

    2010-06-15

    Using gauge/gravity duality, we compute the energy density and angular distribution of the power radiated by a quark undergoing circular motion in strongly coupled N=4 supersymmetric Yang-Mills theory. We compare the strong coupling results to those at weak coupling, finding them to be very similar. In both regimes, the angular distribution of the radiated power is in fact similar to that of synchrotron radiation produced by an electron in circular motion in classical electrodynamics: the quark emits radiation in a narrow beam along its velocity vector with a characteristic opening angle {alpha}{approx}1/{gamma}. To an observer far away from the quark, the emitted radiation appears as a short periodic burst, just like the light from a lighthouse does to a ship at sea. Our strong coupling results are valid for any strongly coupled conformal field theory with a dual classical gravity description.

  16. Community fear of nonionizing radiation: a field investigation

    SciTech Connect

    Daley, M.L.; Morton, W.E.; Chartier, V.; Zajac, H.; Benitez, H.

    1985-03-01

    Four children from the same school class developed cancer. Because of concern in the community, a field study designed to document levels of environmental, nonionizing radiation was undertaken. Two school sites were investigated, the one with the cluster of cases and the other without known cases of cancer. The measured values of nonionizing radiation at both sites were not different and were well below existing exposure standards.

  17. FLASH requirements for the high intensity radiated field electromagnetic environment

    NASA Astrophysics Data System (ADS)

    Murdock, John K.

    1995-05-01

    The worldwide proliferation of high intensity emitting sources and the more electric aircraft increase the intensity of the Electromagnetic Environment (EME) in which aircraft must operate. A FLASH program HIRF (High Intensity Radiated Field) EME requirement is derived to cover both commercial and military fixed and rotary wing aircraft. This requirement is derived from the radiated susceptibility requirement documents of both the FAA and U.S. military. Specific test data and analysis will show that we can meet this requirement.

  18. IAEA programme in the field of radiation technology

    NASA Astrophysics Data System (ADS)

    Chmielewski, Andrzej G.; Haji-Saeid, Mohammad

    2005-07-01

    Radiation technologies applying gamma sources and electron accelerators for material modification are well-established processes. There are over 160 gamma industrial irradiators and 1300 electron industrial accelerators in operation worldwide. A new advancement in the field of radiation sources engineering is the development of high power direct e-/X conversion sources based on electron accelerators. Technologies to be developed beside environmental applications could be nanomaterials, structure engineered materials (sorbents, composites, ordered polymers, etc.) and natural polymers' processing. New products based on radiation-processed polysaccharides have already been commercialised in many countries of the East Asia and Pacific Region, especially in those being rich in natural polymers. Very important and promising applications concern environmental protection-radiation technology, being a clean and environment friendly process, helps to curb pollutants' emission as well. Industrial plants for flue gas treatment have been constructed in Poland and China. The pilot plant in Bulgaria using this technology has just started its operation. The Polish plant is equipped with accelerators of over 1 MW power, a breakthrough in radiation technology application. The industrial plant for wastewater treatment is under development in Korea and a pilot plant for sewage sludge irradiation has been in operation in India for many years. Due to recent developments, the Agency has restructured its programme and organized a Technical Meeting (TM) on "Emerging Applications of Radiation Technology for the 21st Century" at its Headquarters in Vienna, Austria, in April 2003, to review the present situation and possible developments of radiation technology to contribute to a sustainable development. This meeting provided the basic input to launch others in the most important fields of radiation technology applications: "Advances in Radiation Chemistry of Polymers" (Notre Dame, USA

  19. Cosmological fluctuations of a random field and radiation fluid

    SciTech Connect

    Bastero-Gil, Mar; Berera, Arjun; Moss, Ian G.; Ramos, Rudnei O. E-mail: ab@ph.ed.ac.uk E-mail: rudnei@uerj.br

    2014-05-01

    A generalization of the random fluid hydrodynamic fluctuation theory due to Landau and Lifshitz is applied to describe cosmological fluctuations in systems with radiation and scalar fields. The viscous pressures, parametrized in terms of the bulk and shear viscosity coefficients, and the respective random fluctuations in the radiation fluid are combined with the stochastic and dissipative scalar evolution equation. This results in a complete set of equations describing the perturbations in both scalar and radiation fluids. These derived equations are then studied, as an example, in the context of warm inflation. Similar treatments can be done for other cosmological early universe scenarios involving thermal or statistical fluctuations.

  20. Polarization in cyclotron radiation in strong magnetic fields

    NASA Astrophysics Data System (ADS)

    Semionova, Luidmila; Leahy, Denis; Paez, Jorge

    2010-10-01

    We revisit the problem of radiative transitions of electrons in the presence of a strong magnetic field. We derive fully relativistic cyclotron transition rates for an arbitrary magnetic field, for any orientation of electron spin and for any polarization of the emitted radiation. Also, we obtain the transition rates for any value of the initial electron's parallel momentum. For very strong magnetic fields, transitions to the ground state predominate. Transition rates summed over the electron's spin orientation and for unpolarized radiation are also obtained, which confirm previous results by Latal. Transition widths are calculated for different electron spin orientations and different polarizations of radiation. We obtain general expressions for transition rates that reduce to the results for the non-relativistic case and for unpolarized radiation. Additionally we get, for the non-relativistic approximation, the transition rates for any polarization of radiation. As an application, the first five emission lines are evaluated and compared to the X-ray emitting neutron star V0332+53, which has multiple observable cyclotron lines, taking into account gravitational redshift. The most probable polarization is in(2).

  1. Topological magnetoelectric effects in microwave far-field radiation

    NASA Astrophysics Data System (ADS)

    Berezin, M.; Kamenetskii, E. O.; Shavit, R.

    2016-07-01

    Similar to electromagnetism, described by the Maxwell equations, the physics of magnetoelectric (ME) phenomena deals with the fundamental problem of the relationship between electric and magnetic fields. Despite a formal resemblance between the two notions, they concern effects of different natures. In general, ME-coupling effects manifest in numerous macroscopic phenomena in solids with space and time symmetry breakings. Recently, it was shown that the near fields in the proximity of a small ferrite particle with magnetic-dipolar-mode (MDM) oscillations have the space and time symmetry breakings and the topological properties of these fields are different from the topological properties of the free-space electromagnetic fields. Such MDM-originated fields—called magnetoelectric (ME) fields—carry both spin and orbital angular momenta. They are characterized by power-flow vortices and non-zero helicity. In this paper, we report on observation of the topological ME effects in far-field microwave radiation based on a small microwave antenna with a MDM ferrite resonator. We show that the microwave far-field radiation can be manifested with a torsion structure where an angle between the electric and magnetic field vectors varies. We discuss the question on observation of the regions of localized ME energy in far-field microwave radiation.

  2. Voyager 1: Encounter with Saturn

    NASA Technical Reports Server (NTRS)

    Panagakos, N.

    1980-01-01

    The history of the Voyager Project is reviewed as well as known facts about Saturn and its satellites. Important results of encounters with Jupiter are summarized. Scientific objectives of the flyby of Saturn involve the planet's atmosphere, rings, and magnetic field interactions with the solar wind and satellites. The search for additional satellites, and various aspects of Titan, Rhea, Dione, Mimas, Iapetus, Hyperion, and Enceladas are also of interest. The instruments developed to obtain these goals are described.

  3. Active Extraction of Near-field Thermal Radiation

    NASA Astrophysics Data System (ADS)

    Ding, Ding; Kim, Taeyong; Minnich, Austin

    Radiative heat transport between materials supporting surface-phonon polaritons is greatly enhanced when the materials are placed at sub-wavelength separation as a result of the contribution of near-field surface modes. However, the enhancement is limited to small separations due to the evanescent decay of the surface waves. In this work, we propose and numerically demonstrate an active radiative cooling (ARC) scheme to extract these modes to the far-field. Our approach exploits the monochromatic nature of near-field thermal radiation to drive a transition in a laser gain medium, which, when coupled with external optical pumping, allows the resonant surface mode to be emitted into the far-field. We also provide further insights into our ARC scheme by applying the theoretical framework used for laser cooling of solids (LCS) to ARC. We show that LCS and ARC can be described with the same mathematical formalism by replacing the electron-phonon coupling parameter in LCS with the electron-photon coupling parameter in ARC. Using this framework, we examine the predictions of the formalism for LCS and ARC using realistic parameters and find that ARC can achieve higher efficiency and extracted power over a wide range of conditions. Our study demonstrates a new approach to manipulate near-field thermal radiation for thermal management.

  4. Electrodynamics of Radiating Charges in a Gravitational Field

    NASA Astrophysics Data System (ADS)

    Grøn, Øyvind

    The electrodynamics of a radiating charge and its electromagnetic field based upon the Lorentz-Abraham-Dirac (LAD) equation are discussed both with reference to an inertial reference frame and a uniformly accelerated reference frame. It is demonstrated that energy and momentum are conserved during runaway motion of a radiating charge and during free fall of a charge in a field of gravity. This does not mean that runaway motion is really happening. It may be an unphysical solution of the LAD equation of motion of a radiating charge due to the unrealistic point particle model of the charge upon which it is based. However it demonstrates the consistency of classical electrodynamics, including the LAD equation which is deduced from Maxwell's equations and the principle of energy-momentum conservation applied to a radiating charge and its electromagnetic field. The decisive role of the Schott energy in this connection is made clear and an answer is given to the question: What sort of energy is the Schott energy and where is it found? It is the part of the electromagnetic field energy which is proportional to (minus) the scalar product of the velocity and acceleration of a moving accelerated charged particle. In the case of the electromagnetic field of a point charge it is localized at the particle. This energy is negative if the acceleration is in the same direction as the velocity and positive if it is in the opposite direction. During runaway motion the Schott energy becomes more and more negative and in the case of a charged particle with finite extension, it is localized in a region with increasing extension surrounding the particle. The Schott energy provides the radiated energy of a freely falling charge. Also it is pointed out that a proton and a neutron fall with the same acceleration in a uniform gravitational field, although the proton radiates and the neutron does not. It is made clear that the question as to whether or not a charge radiates has a reference

  5. The clinical encounter revisited.

    PubMed

    Schattner, Ami

    2014-04-01

    The patient-physician encounter is the pivotal starting point of any healthcare delivery, but it is subject to multiple process breakdowns and prevalent suboptimal performance. An overview of the techniques and components of a successful encounter valid for every setting and readily applicable is presented, stressing 7 rules: (1) ensuring optimal environment, tools, and teamwork; (2) viewing each encounter not only as a cognitive/biomedical challenge, but also as a personal one, and a learning opportunity; (3) adopting an attitude of curiosity, concentration, compassion, and commitment, and maintaining a systematic, orderly approach; (4) "simple is beautiful"-making the most of the basic clinical data and their many unique advantages; (5) minding "the silent dimension"-being attentive to the patient's identity and emotions; (6) following the "Holy Trinity" of gathering all information, consulting databases/colleagues, and tailoring gained knowledge to the individual patient; and (7) using the encounter as a "window of opportunity" to further the patient's health-not just the major problem, by addressing screening and prevention; promoting health literacy and shared decision-making; and establishing proper follow-up. Barriers to implementation identified can be overcome by continuous educational interventions. A high-quality encounter sets a virtuous cycle of patient-provider interaction and results in increasing satisfaction, adherence, and improved health outcomes. PMID:24333201

  6. Radiation-Reaction Trapping of Electrons in Extreme Laser Fields

    NASA Astrophysics Data System (ADS)

    Ji, L. L.; Pukhov, A.; Kostyukov, I. Yu.; Shen, B. F.; Akli, K.

    2014-04-01

    A radiation-reaction trapping (RRT) of electrons is revealed in the near-QED regime of laser-plasma interaction. Electrons quivering in laser pulse experience radiation reaction (RR) recoil force by radiating photons. When the laser field reaches the threshold, the RR force becomes significant enough to compensate for the expelling laser ponderomotive force. Then electrons are trapped inside the laser pulse instead of being scattered off transversely and form a dense plasma bunch. The mechanism is demonstrated both by full three-dimensional particle-in-cell simulations using the QED photonic approach and numerical test-particle modeling based on the classical Landau-Lifshitz formula of RR force. Furthermore, the proposed analysis shows that the threshold of laser field amplitude for RRT is approximately the cubic root of laser wavelength over classical electron radius. Because of the pinching effect of the trapped electron bunch, the required laser intensity for RRT can be further reduced.

  7. Far-field radiation from a cleaved cylindrical dielectric waveguide

    SciTech Connect

    Cerjan, C.

    1996-07-09

    Angular spread in the far-field radiation pattern of a cleaved dielectric waveguide is determined from the modal structure at the surface of the waveguide using the Smythe vector integral formulation. Essential features: First, a mode exists in the fiber that has no wavelength cutoff--the so-called HE{sub 11} mode. This mode arises when non-azimuthal angular dependence of the incoming radiation is present. Second, the energy flow from this hybrid mode fills the fiber face and is not annularly shaped as opposed to the symmetric TE and TM modes. Third, the HE{sub 11} mode is not polarization dependent in contrast to the TE and TM modes. Fourth, for small differences in the refractive indices between the core and cladding regions, only the HE{sub 11} mode will be supported until the next modes appear around 3.33{lambda}. At this point, three new modes can propagate and the model structure of the radiation becomes more complicated. Fifth, the far-field radiation pattern will have negligibly small angular dependence in the phases of the vector fields when only the lowest mode is present; the amplitude has an overall angular dependent form factor. Furthermore, when other modes are present (above 3.33{lambda}), the phase of the vector fields will acquire an angular dependence.

  8. Nanodosimetric Characterization of Mixed Radiation Fields: Status and Perspectives

    NASA Astrophysics Data System (ADS)

    Schulte, Reinhard; Bashkirov, Vladimir; Casiraghi, Margherita

    The nanodosimetric characterization of mixed radiation fields containing variable fluences of charged particles, neutrons, and photons with stochastic quantities related to the number of ionizations in biological targets of nanometric size is an active area of research and development. Applications include measurements in low-dose radiation environments, including outer space, for radiation protection as well as characterization of mixed radiation therapy fields present in particle therapy with protons, light ions, or neutrons. Approaches for the nanodosimetric characterization of mixed radiation fields should consist of balance of theoretical Monte Carlo simulations and experimental studies that can inform each other. The former should be carefully benchmarked with the latter, usually employing detectors filled with low-pressure gas in which nanodosimetric studies are possible. Research in experimental nanodosimetry has exploited the principle of low-pressure-gas scaling of mean interaction distances between energy transfer points up to a million-fold, thus allowing to collect single charges (ions or electrons) generated in cylindrical volumes equivalent to a short segment of DNA. When combined with arrival-time selection, position resolution of down to 5 nm, has been achieved for experimental track structure studies. The results of these experimental studies and Monte Carlo simulations using the Monte Carlo codes will be summarized. More recently, we have studied a new principle of 2D low-energy ion detection by impact ionization in a hole-pattern detector in combination with a low-pressure time projection chamber. First proof-of-principle and performance studies with this track-imaging detector and corresponding Monte Carlo simulations will be presented. The full potential of nanometric quantities in characterizing radiation quality for dosimetry of ionizing radiation is yet to be explored. The most significant signature of radiation quality may be the size and

  9. Understanding metropolitan patterns of daily encounters.

    PubMed

    Sun, Lijun; Axhausen, Kay W; Lee, Der-Horng; Huang, Xianfeng

    2013-08-20

    Understanding of the mechanisms driving our daily face-to-face encounters is still limited; the field lacks large-scale datasets describing both individual behaviors and their collective interactions. However, here, with the help of travel smart card data, we uncover such encounter mechanisms and structures by constructing a time-resolved in-vehicle social encounter network on public buses in a city (about 5 million residents). Using a population scale dataset, we find physical encounters display reproducible temporal patterns, indicating that repeated encounters are regular and identical. On an individual scale, we find that collective regularities dominate distinct encounters' bounded nature. An individual's encounter capability is rooted in his/her daily behavioral regularity, explaining the emergence of "familiar strangers" in daily life. Strikingly, we find individuals with repeated encounters are not grouped into small communities, but become strongly connected over time, resulting in a large, but imperceptible, small-world contact network or "structure of co-presence" across the whole metropolitan area. Revealing the encounter pattern and identifying this large-scale contact network are crucial to understanding the dynamics in patterns of social acquaintances, collective human behaviors, and--particularly--disclosing the impact of human behavior on various diffusion/spreading processes. PMID:23918373

  10. Simulation of the radiation fields from ionizing radiation sources inside the containment in an accident

    SciTech Connect

    Kalugin, M. A.

    2010-12-15

    In the present work, a set of codes used for simulations of the radiation fields from ionizing radiation sources inside the containment in an accident is described. A method of evaluating the gamma dose rate from a space and energy distributed source is given. The dose rate is calculated by means of the design point kernel method and using buildup factors. The code MCU-REA with the ORIMCU module is used for the burnup calculations.

  11. Galileo's Encounter with Amalthea

    NASA Astrophysics Data System (ADS)

    Johnson, T. V.; Anderson, J. D.

    2003-04-01

    Galileo's last science periapsis encounter with Jupiter before impact was on orbit 34. One of the main scientific goals of this encounter was a close, targeted flyby of the satellite Amalthea. Although two-way Doppler tracking was lost near closest approach, one-way data were obtained throughout the encounter. Together with solid two-way data before and after the encounter period, there is enough information to constrain the mass of the satellite. Together with previously determined shape and volume information these data yield a useful value for the density of this highly non-spherical moon. Preliminary analyses have been presented indicating a bulk density near 1 gm/cc, considerably lower than was expected from the satellite's dark albedo and anticipated rocky composition. Low-density rock or rock/ice mixtures combined with a high porosity, similar to that inferred from recent small asteroid data, are suggested as the most likely explanation. Refined estimates of mass and density as well as uncertainties will be presented and the implications for Amalthea's composition and porosity discussed.

  12. A Lakatosian Encounter

    ERIC Educational Resources Information Center

    Chick, Helen

    2010-01-01

    There is much to be learned and pondered by reading "Proofs and Refutations," by Imre Lakatos. It highlights the importance of mathematical definitions, and how definitions evolve to capture the essence of the object they are defining. It also provides an exhilarating encounter with the ups and downs of the mathematical reasoning process, where…

  13. Encountering an Alien Culture.

    ERIC Educational Resources Information Center

    Sproull, Lee S.; And Others

    1984-01-01

    Applies a cultural perspective to the problem of introducing novices to computing. Presents a model of initial socialization composed of reality shock, confusion, and attempts at control. Describes a survey of college students' first encounters with computers and suggests that the social contexts of introductory courses encourage feelings of…

  14. Electrical integrity of oxides in a radiation field

    SciTech Connect

    Zinkle, S.J.; Kinoshita, C.

    1996-04-01

    In the absence of an applied electric field, irradiation generally produces a decrease in the permanent (beam-off) electrical conductivity of ceramic insulators. However, in the past 6 years several research groups have reported a phenomenon known as radiation induced electrical degradation (RIED), which produces significant permanent increases in the electrical conductivity of ceramic insulators irradiated with an applied electric field. RIED has been reported to occur at temperatures between 420 and 800 K with applied electric fields as low as 20 V/mm.

  15. High field CdS detector for infrared radiation

    NASA Technical Reports Server (NTRS)

    Tyagi, R. C.; Robertson, J. B.; Boer, K. W.; Hadley, H. C., Jr. (Inventor)

    1974-01-01

    An infrared radiation detector including a cadmium sulfide platelet having a cathode formed on one of its ends and an anode formed on its other end is presented. The platelet is suitably doped such that stationary high-field domains are formed adjacent the cathode when based in the negative differential conductivity region. A negative potential is applied to the cathode such that a high-field domain is formed adjacent to the cathode. A potential measuring probe is located between the cathode and the anode at the edge of the high-field domain and means are provided for measuring the potential at the probe whereby this measurement is indicative of the infrared radiation striking the platelet.

  16. Genesis of quantization of matter and radiation field

    NASA Astrophysics Data System (ADS)

    de la Peña, Luis; Cetto, Ana María.

    2015-09-01

    Are we to accept quantization as a fundamental property of nature, the origin of which does not require or admit further investigation? To get an insight into this question we consider atomic systems as open systems, since they are by necessity in contact with the electromagnetic radiation field. This includes not only photonic radiation, but, more importantly for our purposes, the random zero-point or nonthermal radiation that pervades the Universe. The Heisenberg inequalities, atomic stability and the existence of discrete solutions are explained as a result of the permanent action of this field upon matter and the balance between mean absorbed and emitted powers in the equilibrium regime. A detailed study carried out along the years has led to the usual quantum-mechanical formalism as a powerful and revealing statistical description of the behavior of matter in the radiationless approximation, as well as to the radiative corrections of nonrelativistic QED. The theory presented gives thus a response to the question posed above, within a local, realist and objective framework: quantization appears as an emergent phenomenon due to the matter-field interaction.

  17. Quantum driven dissipative parametric oscillator in a blackbody radiation field

    SciTech Connect

    Pachón, Leonardo A.; Department of Chemistry and Center for Quantum Information and Quantum Control, Chemical Physics Theory Group, University of Toronto, Toronto, Ontario M5S 3H6 ; Brumer, Paul

    2014-01-15

    We consider the general open system problem of a charged quantum oscillator confined in a harmonic trap, whose frequency can be arbitrarily modulated in time, that interacts with both an incoherent quantized (blackbody) radiation field and with an arbitrary coherent laser field. We assume that the oscillator is initially in thermodynamic equilibrium with its environment, a non-factorized initial density matrix of the system and the environment, and that at t = 0 the modulation of the frequency, the coupling to the incoherent and the coherent radiation are switched on. The subsequent dynamics, induced by the presence of the blackbody radiation, the laser field, and the frequency modulation, is studied in the framework of the influence functional approach. This approach allows incorporating, in analytic closed formulae, the non-Markovian character of the oscillator-environment interaction at any temperature as well the non-Markovian character of the blackbody radiation and its zero-point fluctuations. Expressions for the time evolution of the covariance matrix elements of the quantum fluctuations and the reduced density-operator are obtained.

  18. A characteristic scale in radiation fields of fractal clouds

    SciTech Connect

    Wiscombe, W.; Cahalan, R.; Davis, A.; Marshak, A.

    1996-04-01

    The wavenumber spectrum of Landsat imagery for marine stratocumulus cloud shows a scale break when plotted on a double log plot. We offer an explanation of this scale break in terms of smoothing by horizontal radiative fluxes, which is parameterized and incorporated into an improved pixel approximation. We compute the radiation fields emerging from cloud models with horizontally variable optical depth fractal models. We use comparative spectral and multifractal analysis to qualify the validity of the independent pixel approximation at the largest scales and demonstrate it`s shortcomings on the smallest scales.

  19. Compliance with High-Intensity Radiated Fields Regulations - Emitter's Perspective

    NASA Technical Reports Server (NTRS)

    Statman, Joseph; Jamnejad, Vahraz; Nguyen, Lee

    2012-01-01

    NASA's Deep Space Network (DSN) uses high-power transmitters on its large antennas to communicate with spacecraft of NASA and its partner agencies. The prime reflectors of the DSN antennas are parabolic, at 34m and 70m in diameter. The DSN transmitters radiate Continuous Wave (CW) signals at 20 kW - 500 kW at X-band and S-band frequencies. The combination of antenna reflector size and high frequency results in a very narrow beam with extensive oscillating near-field pattern. Another unique feature of the DSN antennas is that they (and the radiated beam) move mostly at very slow sidereal rate, essentially identical in magnitude and at the opposite direction of Earth rotation.The DSN is in the process of revamping its documentation to provide analysis of the High Intensity Radiation Fields (HIRF) environment resulting from radio frequency radiation from DSN antennas for comparison to FAA regulations regarding certification of HIRF protection as outlined in the FAA regulations on HIRF protection for aircraft electrical and electronic systems (Title 14, Code of Federal Regulations (14 CFR) [section sign][section sign] 23.1308, 25.1317, 27.1317, and 29.1317).This paper presents work done at JPL, in consultation with the FAA. The work includes analysis of the radiated field structure created by the unique DSN emitters (combination of transmitters and antennas) and comparing it to the fields defined in the environments in the FAA regulations. The paper identifies areas that required special attention, including the implications of the very narrow beam of the DSN emitters and the sidereal rate motion. The paper derives the maximum emitter power allowed without mitigation and the mitigation zones, where required.Finally, the paper presents summary of the results of the analyses of the DSN emitters and the resulting DSN process documentation.

  20. High field magnetic resonance imaging-based gel dosimetry for small radiation fields

    NASA Astrophysics Data System (ADS)

    Ding, Xuanfeng

    Small megavoltage photon radiation fields (< 3cm diameter) are used in advanced radiation therapy techniques, such as intensity modulated radiotherapy, and stereotactic radiosurgery, as well as for cellular and preclinical radiobiology studies (very small fields, <1 mm diameter). Radiation dose characteristics for these small fields are difficult to determine in multiple dimensions because of steep dose gradients (30--40% per mm) and conditions of electronic disequilibrium. Conventional radiation dosimetry techniques have limitations for small fields because detector size may be large compared to radiation field size and/or dose acquisition may be restricted to one or two dimensions. Polymer gel dosimetry, is a three-dimensional (3D) dosimeter based on radiation-induced polymerization of tissue equivalent gelatin. Polymer gel dosimeters can be read using magnetic resonance imaging (MRI), which detects changes in relaxivity due to gel polymerization. Spatial resolution for dose readout is limited to 0.25--0.5mm pixel size because of available the magnetic field strengths (1.5T and 3T) and the stability of polymer gelatin at room temperature. A reliable glucose-based MAGIC (methacrylic and ascorbic acid in gelatine initiated by copper) gel dosimeter was formulated and evaluated for small field 3D dosimetry using 3T and 7T high field MRI for dose readout. The melting point of the original recipe MAGIC gel was increased by 4°C by adding 10% glucose to improve gel stability. Excellent spatial resolution of 79um (1.5 hr scan) and 39um (12 hr scan) was achieved using 7T MRI, proving gel stability for long scan times and high resolution 3D dosimetry.

  1. Encounters with Protostellar Disks

    NASA Astrophysics Data System (ADS)

    Heller, Clayton H.

    1992-12-01

    A numerical study of encounters between stars with circumstellar disks has bee completed. Cross sections and rates for disk tilt, disk disruption, and binary formation are estimated using a large data base of encounter simulations. The consequences of these results for star-forming regions and our solar system are discussed. A numerical code is developed which is capable of evolving a mixture of stars and gas in three dimensions. The algorithm is based on the method of smoothed-particle hydrodynamics combined with the heirarchical tree method of computing gravitational forces. The code is tested by simulating the collision between two sheets of gas and the radial pulsations of a polytropic gas sphere. A protostellar-disk model is developed based on simple assumptions. Test encounters are performed to determine the sensitivity of measured quantities on algorithm parameters, such as the gravitational tolerance and viscosity. It is shown that the solar system could have had an encounter shortly after its formation of sufficient strength to generate the observed obliquity yet retain enough mass and radial extent to form the planetary system. For the Orion B clusters as a whole, it is estimated that during a one-million-year period of time a few percent of the stars will experience an enoucnter that results in a disk tilt of 7 degrees or greater. For the central regions of NGC 2024 and the Trapezium cluster values of 24% and 39% are obtained, respectively. Encounters between equal-mass stars with periastra of 0.5, 1.0, 1.5, and 2.0 disk radii will retain on average about 15%, 40%, 55%, and 75% of the disk mass, respectively. For encounters that do not penetrate the disk a minimum of 15% of the mass is retained. Even in dense environments the characteristic lifetime of a disk due to disruptive encounters can be many millions of years. On average, an encounter that penetrates the disk will dissipate an amount of orbital energy equal to approximately 50% of the initial

  2. Mesoscopic near-field radiative heat transfer at low temperatures

    NASA Astrophysics Data System (ADS)

    Maasilta, Ilari; Geng, Zhuoran; Chaudhuri, Saumyadip; Koppinen, Panu

    2015-03-01

    Near-field radiative heat transfer has mostly been discussed at room temperatures and/or macroscopic scale geometries. Here, we discuss our recent theoretical and experimental advances in understanding near-field transfer at ultra-low temperatures below 1K. As the thermal wavelengths increase with lowering temperature, we show that with sensitive tunnel junction bolometers it is possible to study near-field transfer up to distances ~ 10 μm currently, even though the power levels are low. In addition, these type of experiments correspond to the extreme near-field limit, as the near-field region starts at ~ mm distances at 0.1 K, and could have theoretical power enhancement factors of the order of 1010. Preliminary results on heat transfer between two parallel metallic wires are presented. We also comment on possible areas were such heat transfer might be relevant, such as densely packed arrays of low-temperature detectors.

  3. First Investigation on the Radiation Field of the Spherical Hohlraum

    NASA Astrophysics Data System (ADS)

    Huo, Wen Yi; Li, Zhichao; Chen, Yao-Hua; Xie, Xuefei; Lan, Ke; Liu, Jie; Ren, Guoli; Li, Yongsheng; Liu, Yonggang; Jiang, Xiaohua; Yang, Dong; Li, Sanwei; Guo, Liang; Zhang, Huan; Hou, Lifei; Du, Huabing; Peng, Xiaoshi; Xu, Tao; Li, Chaoguang; Zhan, Xiayu; Yuan, Guanghui; Zhang, Haijun; Jiang, Baibin; Huang, Lizhen; Du, Kai; Zhao, Runchang; Li, Ping; Wang, Wei; Su, Jingqin; Ding, Yongkun; He, Xian-Tu; Zhang, Weiyan

    2016-07-01

    The first spherical hohlraum energetics experiment is accomplished on the SGIII-prototype laser facility. In the experiment, the radiation temperature is measured by using an array of flat-response x-ray detectors (FXRDs) through a laser entrance hole at four different angles. The radiation temperature and M -band fraction inside the hohlraum are determined by the shock wave technique. The experimental observations indicate that the radiation temperatures measured by the FXRDs depend on the observation angles and are related to the view field. According to the experimental results, the conversion efficiency of the vacuum spherical hohlraum is in the range from 60% to 80%. Although this conversion efficiency is less than the conversion efficiency of the near vacuum hohlraum on the National Ignition Facility, it is consistent with that of the cylindrical hohlraums used on the NOVA and the SGIII-prototype at the same energy scale.

  4. ICE encounter operations

    NASA Technical Reports Server (NTRS)

    Fanelli, N.; Morris, D.

    1986-01-01

    The operations encompassing the International Cometary Explorer's (ICE) encounter with the Comet Giacobini-Zinner on September 11, 1985 are documented. The ICE mission presented new challenges for the Deep Space Network (DSN) 64 meter subnetwork. Because of poor telemetry link margin predicted for Giacobini-Zinner (GZ) encounter, supplemental support by the Japanese Institute for Space and Astronautical Sciences 64-meter antenna at Usuda, Japan and the 305-meter Arecibo Radio Observatory in Puerto Rico was required. To improve the 64 meter subnetwork telemetry performance the following were also implemented: (1) Real time antenna array of 64 meter and 34 meter at a single complex and the required performance testing; and (2) Nonreal time antenna array of two complexes was implemented as a backup in the event of ground or spacecraft failure.

  5. Theoretical studies relating to the interaction of radiation with matter: Atomic collision processes occurring in the presence of radiation fields

    NASA Astrophysics Data System (ADS)

    1980-10-01

    Work is reported in the areas of: (1) collisionally-aided radiative excitation; (2) model potential calculations in atom-field-radiation systems; (3) coherence effects in radiative collisions; (4) two level atom radiation pulse; (5) resonance fluorescence in three level systems; (6) modulation spectroscopy; and (7) effects of collisions on atomic coherences.

  6. A Computational Model of Cellular Response to Modulated Radiation Fields

    SciTech Connect

    McMahon, Stephen J.; Butterworth, Karl T.; McGarry, Conor K.; Trainor, Colman; O'Sullivan, Joe M.; Hounsell, Alan R.; Prise, Kevin M.

    2012-09-01

    Purpose: To develop a model to describe the response of cell populations to spatially modulated radiation exposures of relevance to advanced radiotherapies. Materials and Methods: A Monte Carlo model of cellular radiation response was developed. This model incorporated damage from both direct radiation and intercellular communication including bystander signaling. The predictions of this model were compared to previously measured survival curves for a normal human fibroblast line (AGO1522) and prostate tumor cells (DU145) exposed to spatially modulated fields. Results: The model was found to be able to accurately reproduce cell survival both in populations which were directly exposed to radiation and those which were outside the primary treatment field. The model predicts that the bystander effect makes a significant contribution to cell killing even in uniformly irradiated cells. The bystander effect contribution varies strongly with dose, falling from a high of 80% at low doses to 25% and 50% at 4 Gy for AGO1522 and DU145 cells, respectively. This was verified using the inducible nitric oxide synthase inhibitor aminoguanidine to inhibit the bystander effect in cells exposed to different doses, which showed significantly larger reductions in cell killing at lower doses. Conclusions: The model presented in this work accurately reproduces cell survival following modulated radiation exposures, both in and out of the primary treatment field, by incorporating a bystander component. In addition, the model suggests that the bystander effect is responsible for a significant portion of cell killing in uniformly irradiated cells, 50% and 70% at doses of 2 Gy in AGO1522 and DU145 cells, respectively. This description is a significant departure from accepted radiobiological models and may have a significant impact on optimization of treatment planning approaches if proven to be applicable in vivo.

  7. Potential theoretic methods for far field sound radiation calculations

    NASA Technical Reports Server (NTRS)

    Hariharan, S. I.; Stenger, Edward J.; Scott, J. R.

    1995-01-01

    In the area of computational acoustics, procedures which accurately predict the far-field sound radiation are much sought after. A systematic development of such procedures are found in a sequence of papers by Atassi. The method presented here is an alternate approach to predicting far field sound based on simple layer potential theoretic methods. The main advantages of this method are: it requires only a simple free space Green's function, it can accommodate arbitrary shapes of Kirchoff surfaces, and is readily extendable to three-dimensional problems. Moreover, the procedure presented here, though tested for unsteady lifting airfoil problems, can easily be adapted to other areas of interest, such as jet noise radiation problems. Results are presented for lifting airfoil problems and comparisons are made with the results reported by Atassi. Direct comparisons are also made for the flat plate case.

  8. Analysis of the radiated information in spinning sound fields.

    PubMed

    Carley, Michael

    2010-10-01

    The information content of a spinning sound field is analyzed using a combination of exact and asymptotic results, in order to set limits on how accurately source identification can be carried out. Using a transformation of the circular source to an exactly equivalent set of line source modes, given by Chebyshev polynomials, it is found that the line source modes of order greater than the source wavenumber generate exponentially small fields. Asymptotic analysis shows that the remaining, lower order, modes radiate efficiently only into a region around the source plane, with this region shrinking as the mode order is increased. The results explain the ill-conditioning of source identification methods; the successful use of low order models in active noise control; and the low radiation efficiency of subsonic jets. PMID:20968340

  9. Modelling of radiation field around spent fuel container.

    PubMed

    Kryuchkov, E F; Opalovsky, V A; Tikhomirov, G V

    2005-01-01

    Operation of nuclear reactors leads to the production of spent nuclear fuel (SNF). There are two basic strategies of SNF management: ultimate disposal of SNF in geological formations and recycle or repeated utilisation of reprocessed SNF. In both options, there is an urgent necessity to study radiation properties of SNF. Information about SNF radiation properties is required at all stages of SNF management. In order to reach more effective utilisation of nuclear materials, new fuel cycles are under development based on uranium-plutonium, uranium-thorium and some other types of nuclear fuel. These promising types of nuclear fuel are characterised by quite different radiation properties at all the stages of nuclear fuel cycle (NFC) listed above. So, comparative analysis is required for radiation properties of different nuclear fuel types at different NFC stages. The results presented here were obtained from the numerical analysis of the radiation field around transport containers of different SNF types and in SNF storage. The calculations are carried out with the application of the computer code packages SCALE-4.3 and MCNP-4C. Comparison of the dose parameters obtained for different models of the transport container with experimental data allowed us to make certain conclusions about the errors of numerical results caused by the approximate geometrical description of the transport container. PMID:16604702

  10. Cosmological perturbations for an inflaton field coupled to radiation

    SciTech Connect

    Visinelli, Luca

    2015-01-01

    Within the framework of the interacting fluid formalism, we provide the numerical solution to the Boltzmann equation describing the evolution of an inflaton field coupled to radiation. We study the behavior of the system during the slow-roll regime, in the case in which an additional stochastic source term is included in the set of equations, and we recover the expression for the cosmological perturbations previously obtained in the Warm inflation scenarios.

  11. THE RADIATIVE TRANSFER OF SYNCHROTRON RADIATION THROUGH A COMPRESSED RANDOM MAGNETIC FIELD

    SciTech Connect

    Cawthorne, T. V.; Hughes, P. A.

    2013-07-01

    This paper examines the radiative transfer of synchrotron radiation in the presence of a magnetic field configuration resulting from the compression of a highly disordered magnetic field. It is shown that, provided Faraday rotation and circular polarization can be neglected, the radiative transfer equations for synchrotron radiation separate for this configuration, and the intensities and polarization values for sources that are uniform on large scales can be found straightforwardly in the case where opacity is significant. Although the emission and absorption coefficients must, in general, be obtained numerically, the process is much simpler than a full numerical solution to the transfer equations. Some illustrative results are given and an interesting effect, whereby the polarization increases while the magnetic field distribution becomes less strongly confined to the plane of compression, is discussed. The results are of importance for the interpretation of polarization near the edges of lobes in radio galaxies and of bright features in the parsec-scale jets of active galactic nuclei, where such magnetic field configurations are believed to exist.

  12. A sensitive near-field microscope for thermal radiation.

    PubMed

    Kajihara, Yusuke; Kosaka, Keishi; Komiyama, Susumu

    2010-03-01

    A scattering-type scanning near-field optical microscope in long-wavelength infrared (LWIR) region is developed by using an extremely sensitive detector, called the charge-sensitive infrared phototransistor. A tungsten probe attached to a quartz tuning fork is controlled in shear-force mode. Evanescent wave at a sample surface is periodically scattered by slowly (2 Hz) modulating the probe in the direction normal to the sample surface. Near-field microscopy of thermal LWIR radiation from room-temperature Au/GaAs gratings is demonstrated without using any external illumination or excitation. Achieved spatial resolution is better than 300 nm. PMID:20370184

  13. Radiation from electrons in graphene in strong electric field

    SciTech Connect

    Yokomizo, N.

    2014-12-15

    We study the interaction of electrons in graphene with the quantized electromagnetic field in the presence of an applied uniform electric field using the Dirac model of graphene. Electronic states are represented by exact solutions of the Dirac equation in the electric background, and amplitudes of first-order Feynman diagrams describing the interaction with the photon field are calculated for massive Dirac particles in both valleys. Photon emission probabilities from a single electron and from a many-electron system at the charge neutrality point are derived, including the angular and frequency dependence, and several limiting cases are analyzed. The pattern of photon emission at the Dirac point in a strong field is determined by an interplay between the nonperturbative creation of electron–hole pairs and spontaneous emission, allowing for the possibility of observing the Schwinger effect in measurements of the radiation emitted by pristine graphene under DC voltage.

  14. Assessment of occupational exposure to radiofrequency fields and radiation.

    PubMed

    Cooper, T G; Allen, S G; Blackwell, R P; Litchfield, I; Mann, S M; Pope, J M; van Tongeren, M J A

    2004-01-01

    The use of personal monitors for the assessment of exposure to radiofrequency fields and radiation in potential future epidemiological studies of occupationally exposed populations has been investigated. Data loggers have been developed for use with a commercially available personal monitor and these allowed personal exposure records consisting of time-tagged measurements of electric and magnetic field strength to be accrued over extended periods of the working day. The instrumentation was worn by workers carrying out tasks representative of some of their typical daily activities at a variety of radio sites. The results indicated significant differences in the exposures of workers in various RF environments. A number of measures of exposure have been examined with a view to assessing possible exposure metrics for epidemiological studies. There was generally a good correlation between a given measure of electric field strength and the same measure of magnetic field strength. PMID:15266067

  15. Conservation of ζ with radiative corrections from heavy field

    NASA Astrophysics Data System (ADS)

    Tanaka, Takahiro; Urakawa, Yuko

    2016-06-01

    In this paper, we address a possible impact of radiative corrections from a heavy scalar field χ on the curvature perturbation ζ. Integrating out χ, we derive the effective action for ζ, which includes the loop corrections of the heavy field χ. When the mass of χ is much larger than the Hubble scale H, the loop corrections of χ only yield a local contribution to the effective action and hence the effective action simply gives an action for ζ in a single field model, where, as is widely known, ζ is conserved in time after the Hubble crossing time. Meanwhile, when the mass of χ is comparable to H, the loop corrections of χ can give a non-local contribution to the effective action. Because of the non-local contribution from χ, in general, ζ may not be conserved, even if the classical background trajectory is determined only by the evolution of the inflaton. In this paper, we derive the condition that ζ is conserved in time in the presence of the radiative corrections from χ. Namely, we show that when the dilatation invariance, which is a part of the diffeomorphism invariance, is preserved at the quantum level, the loop corrections of the massive field χ do not disturb the constant evolution of ζ at super Hubble scales. In this discussion, we show the Ward-Takahashi identity for the dilatation invariance, which yields a consistency relation for the correlation functions of the massive field χ.

  16. HADRON ACCELERATORS: Study on CYCIAE-100 radiation field and residual radioactivity

    NASA Astrophysics Data System (ADS)

    Bi, Yuan-Jie; Zhang, Tian-Jue; Jia, Xian-Lu; Zhou, Zheng-He; Wang, Feng; Wei, Su-Min; Zhong, Jun-Qing; Tang, Chuan-Xiang

    2009-06-01

    The accelerators should be properly designed to make the radiation field produced by beam loss satisfy the dose limits. The radiation field for high intensity H- cyclotron includes prompt radiation and residual radiation field. The induced radioactivity in accelerator components is the dominant source of occupational radiation exposure if the accelerator is well shielded. The source of radiation is the beam loss when cyclotron is operating. In this paper, the radiation field for CYCIAE-100 is calculated using Monte Carlo method and the radioactive contamination near stripping foil is studied. A method to reduce the dose equivalent rate of maintenance staff is also given.

  17. CONCORD: comparison of cosmic radiation detectors in the radiation field at aviation altitudes

    NASA Astrophysics Data System (ADS)

    Meier, Matthias M.; Trompier, François; Ambrozova, Iva; Kubancak, Jan; Matthiä, Daniel; Ploc, Ondrej; Santen, Nicole; Wirtz, Michael

    2016-05-01

    Space weather can strongly affect the complex radiation field at aviation altitudes. The assessment of the corresponding radiation exposure of aircrew and passengers has been a challenging task as well as a legal obligation in the European Union for many years. The response of several radiation measuring instruments operated by different European research groups during joint measuring flights was investigated in the framework of the CONCORD (COmparisoN of COsmic Radiation Detectors) campaign in the radiation field at aviation altitudes. This cooperation offered the opportunity to measure under the same space weather conditions and contributed to an independent quality control among the participating groups. The CONCORD flight campaign was performed with the twin-jet research aircraft Dassault Falcon 20E operated by the flight facility Oberpfaffenhofen of the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt, DLR). Dose rates were measured at four positions in the atmosphere in European airspace for about one hour at each position in order to obtain acceptable counting statistics. The analysis of the space weather situation during the measuring flights demonstrates that short-term solar activity did not affect the results which show a very good agreement between the readings of the instruments of the different institutes.

  18. Verification of light & radiation field coincidence quality assurance for radiation therapy by using a-Se based DR system

    NASA Astrophysics Data System (ADS)

    Kim, Jin-Young; Park, Eun-Tae; Choi, Yun-Seon; Cho, Heung-Lae; Ahn, Ki-Jung; Park, Sung-Kwang; Kim, Ji-Na; Suh, Tae-Suk; Kim, Jin-Seon; Hong, Ju-Yeon; Park, Jeong-Eun; Kim, Kyo-Tae; Oh, Kyung-Min; Kim, Hyunjung; Jo, Sun-Mi; Oh, Won-Yong; Jin, Seong-Jin; Cho, Woong

    2015-04-01

    Currently, the American Association of Physicists in Medicine (AAPM) recommends measuring the surface field size once a week by using an analog film in order to verify light and radiation field coincidence in the Quality Assurance (QA) of radiotherapy. However, the use of the film does not allow for a quantitative method of evaluation, and measuring the light field with radiation field detectors in a 2D array is difficult. Therefore, we used an amorphous-Se (a-Se) digital radiation detection system to measure the light and radiation fields simultaneously for a quantitative QA system, and the feasibility of using such a system was confirmed by ensuring the coincidence of the light and the radiation field measurements. The characteristics of the analog film and the a-Se digital radiation detection system were compared by delivering to each doses of 100, 10 monitor units(MU) of radiation at a rate of 400 MU/min to a radiation field 100 × 100 mm2 in size from a 100 cm source-surface distance (SSD). A 0.5 mm to 0.6 mm difference was measured in the X-axis, and a 0.3 mm difference was measured in the Y-axis. The difference in the measurements of the coincidence of light and the radiation field was less than 0.3 mm, which is relatively insignificant. These results indicate that the use of an a-Se digital radiation detection system is adequate for quality assurance of radiotherapy using light and radiation field coincidence. In addition, the experiment is considered to have provided valuable results in that the a-Se based digital radiation detection system enables simple and accurate QA for clinical radiation therapy by assessing the coincidence in the alignment of the light and the radiation fields.

  19. Radial diffusion of radiation belt particles in nondipolar magnetic fields

    NASA Astrophysics Data System (ADS)

    Cunningham, Gregory S.

    2016-06-01

    The fact that charged particles trapped in Earth's magnetic field can be redistributed along their radial distance from Earth due to drift-resonant interactions with small-amplitude waves has been known since early in the space age. Early theoretical efforts assumed that a dipole background magnetic field was modified by a time-varying electromagnetic perturbation that changed the particle's distance from Earth while preserving the first two invariants of motion. The stochastic nature of the perturbation allowed the effect of the waves on the trapped particles to be represented by a Fokker-Planck equation, which updates the phase space density in time via radial diffusion with diffusion coefficients that depend on the wave characteristics. In this paper, we extend those early theoretical efforts to define radial diffusion coefficients in arbitrary static background fields and define a numerical scheme for their evaluation. The background fields we consider are allowed to have significant deviations from a dipole field. Radial diffusion coefficients are computed using the new scheme for one of the empirical magnetic field models (T89) developed by Tsyganenko and coauthors as the background on top of which the perturbations are added. The new diffusion coefficients are shown to be substantially larger than those computed with a dipole background field model, especially at large radial distances and during geomagnetically active times, and it is suggested that outward radial diffusion may be a more substantial loss process for trapped electrons in the outer radiation belt than previously believed.

  20. An automated system for gamma radiation field mapping

    NASA Astrophysics Data System (ADS)

    Gould, Robert; Tarpinian, James E.; Kenney, Edward S.

    1990-12-01

    Remote radiation survey equipment was sorely needed at Chernobyl but adequate systems did not exist. The current state of the art still consists of a survey meter mounted on a robotic carriage, which scans an area at many points on a grid. This process is both time consuming and somewhat inaccurate. The system we have developed will overcome these limitations, and would provide significant savings in man-hours and man-rem over manual survey techniques. The system we have developed consists of a collimated ionization chamber mounted in a scanning head. The measurement process is similar to that used in medical computed tomography (CT) imaging and consists of a series of collimator rotations and translations. The key to this work is the use of a collimator to provide position information with a position insensitive detector. In addition, an inverse filter image reconstruction technique has been used to reduce the distortion effects due to the scanner and scanning process in the resulting maps. This technique models the distortion as a linear, space invariant degrading function which is removed in a deconvolution process. We have constructed first- and second-generation prototype scanners, and developed software to produce three-dimensional radiation field "iso-dose" maps. The iso-dose maps will be superimposed on three-dimensional computer-aided design and drafting (CADD) drawings of the radiation area, aiding in the characterization of the source of radiation.

  1. An absorbed dose to water calorimeter for collimated radiation fields

    NASA Astrophysics Data System (ADS)

    Brede, H. J.; Hecker, O.; Hollnagel, R.

    2000-12-01

    A transportable calorimeter of compact design has been developed as a device for the absolute determination of the absorbed dose to water. The ease of operation of the calorimeter allows the application in clinical therapy beams of various energies, specifically for neutron, proton and heavy ion beams. The calorimeter requires collimated radiation fields with diameters lesser than 40 mm. The temperature rise caused by radiation is measured with a thermistor probe which is located in the centre of the calorimeter core. The calorimeter core consists of a cylindrical water-filled gilded aluminium can suspended by three thin nylon threads in a vacuum block in order to reduce the heat transfer by conduction. In addition, it operates at a temperature of 4°C, preventing heat transfer in water by convection. Heat transfer from the core to the surrounding by radiation is minimised by the use of two concentric temperature-controlled jackets, the inner jacket being operated at core temperature. A description of the mechanical and electrical design, of the construction and operation of the water calorimeter is given. In addition, calculations with a finite-element program code performed to determine correction factors for various radiation conditions are included.

  2. Radiation and near field in resistance-inductor circuit transients

    NASA Astrophysics Data System (ADS)

    Latypov, Damir; Bulmer, John

    2012-06-01

    A full wave solution to the classical problem of a transient response in an RL circuit is analyzed. We show that when radiation effects are rigorously taken into account, the response differs from a familiar exponential decay. The circuit behaves more like an RLC circuit and can exhibit an underdamped response. As a result of a two way energy transfer between the circuit and the near field in the underdamped regime, despite the radiation losses, current decay may be slower than predicted by the standard RL circuit model. During a transient, when retardation effects become important, inductance can no longer be defined as a coefficient of proportionality between the magnetic flux through the circuit and the current in the circuit. If rate of current decay is nearly constant, one can define a time-dependent generalized inductance which turns into conventional inductance after time D/c, where D is the diameter of the current loop. Connection of this generalized inductance with the radiation damping problem is discussed. The theory developed in this paper has been used to analyze ultra wide band radiation observed during a fast laser triggered superconducting to normal transition of a superconducting switch.

  3. Measurement of Radiation - Light Field Congruence using a Photodiode Array

    NASA Astrophysics Data System (ADS)

    Balderson, Michael J.

    Improved treatment techniques in radiation therapy provide incentive to reduce treatment margins, thereby increasing the necessity for more accurate geometrical setup of the linear accelerator and accompanying components. In this thesis, we describe the development of a novel device that enables precise and automated measurement of radiation-light field congruence of medical linear accelerators for the purpose of improving setup accuracy, and standardizing repeated quality control activities. The device consists of a silicon photodiode array, an evaluation board, a data acquisition card, and a laptop. Using the device, we show that the radiation-light field congruence for both 6 and 15 MV beams is within 2 mm on a Varian Clinac 21 EX medical linear accelerator. Because measurements are automated, ambiguities resulting from observer variability are removed, greatly improving the reproducibility of measurements over time and across observers. We expect the device to be useful in providing consistent measurements on linear accelerators used for stereotactic radiosurgery, during the commissioning of new linear accelerators, and as an alternative to film or other commercially available devices for performing monthly or annual quality control checks.

  4. Rings from Close Encounters

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-09-01

    Weve recently discovered narrow sets of rings around two minor planets orbiting in our solar system. How did these rings form? A new study shows that they could be a result of close encounters between the minor planets and giants like Jupiter or Neptune.Unexpected Ring SystemsPositions of the centaurs in our solar system (green). Giant planets (red), Jupiter trojans (grey), scattered disk objects (tan) and Kuiper belt objects (blue) are also shown. [WilyD]Centaurs are minor planets in our solar system that orbit between Jupiter and Neptune. These bodies of which there are roughly 44,000 with diameters larger than 1 km have dynamically unstable orbits that cross paths with those of one or more giant planets.Recent occultation observations of two centaurs, 10199 Chariklo and 2060 Chiron, revealed that these bodies both host narrow ring systems. Besides our four giant planets, Chariklo and Chiron are the only other bodies in the solar system known to have rings. But how did these rings form?Scientists have proposed several models, implicating collisions, disruption of a primordial satellite, or dusty outgassing. But a team of scientists led by Ryuki Hyodo (Paris Institute of Earth Physics, Kobe University) has recently proposed an alternative scenario: what if the rings were formed from partial disruption of the centaur itself, after it crossed just a little too close to a giant planet?Tidal Forces from a GiantHyodo and collaborators first used past studies of centaur orbits to estimate that roughly 10% of centaurs experience close encounters (passing within a distance of ~2x the planetary radius) with a giant planet during their million-year lifetime. The team then performed a series of simulations of close encounters between a giant planet and a differentiated centaur a body in which the rocky material has sunk to form a dense silicate core, surrounded by an icy mantle.Some snapshots of simulation outcomes (click for a closer look!) for different initial states of

  5. A field test of a simple stochastic radiative transfer model

    SciTech Connect

    Byrne, N.

    1995-09-01

    The problem of determining the effect of clouds on the radiative energy balance of the globe is of well-recognized importance. One can in principle solve the problem for any given configuration of clouds using numerical techniques. This knowledge is not useful however, because of the amount of input data and computer resources required. Besides, we need only the average of the resulting solution over the grid scale of a general circulation model (GCM). Therefore, we are interested in estimating the average of the solutions of such fine-grained problems using only coarse grained data, a science or art called stochastic radiation transfer. Results of the described field test indicate that the stochastic description is a somewhat better fit to the data than is a fractional cloud cover model, but more data are needed. 1 ref., 3 figs.

  6. Evaluation of neutron radiation field in carbon ion therapy

    NASA Astrophysics Data System (ADS)

    Xu, Jun-Kui; Su, You-Wu; Li, Wu-Yuan; Yan, Wei-Wei; Chen, Xi-Meng; Mao, Wang; Pang, Cheng-Guo

    2016-01-01

    Carbon ions have significant advantages in tumor therapy because of their physical and biological properties. In view of the radiation protection, the safety of patients is the most important issue in therapy processes. Therefore, the effects of the secondary particles produced by the carbon ions in the tumor therapy should be carefully considered, especially for the neutrons. In the present work, the neutron radiation field induced by carbon ions was evaluated by using the FLUKA code. The simulated results of neutron energy spectra and neutron dose was found to be in good agreement with the experiment data. In addition, energy deposition of carbon ions and neutrons in tissue-like media was studied, it is found that the secondary neutron energy deposition is not expected to exceed 1% of the carbon ion energy deposition in a typical treatment.

  7. Radiative corrections from heavy fast-roll fields during inflation

    SciTech Connect

    Jain, Rajeev Kumar; Sandora, McCullen; Sloth, Martin S.

    2015-06-09

    We investigate radiative corrections to the inflaton potential from heavy fields undergoing a fast-roll phase transition. We find that a logarithmic one-loop correction to the inflaton potential involving this field can induce a temporary running of the spectral index. The induced running can be a short burst of strong running, which may be related to the observed anomalies on large scales in the cosmic microwave spectrum, or extend over many e-folds, sustaining an effectively constant running to be searched for in the future. We implement this in a general class of models, where effects are mediated through a heavy messenger field sitting in its minimum. Interestingly, within the present framework it is a generic outcome that a large running implies a small field model with a vanishing tensor-to-scalar ratio, circumventing the normal expectation that small field models typically lead to an unobservably small running of the spectral index. An observable level of tensor modes can also be accommodated, but, surprisingly, this requires running to be induced by a curvaton. If upcoming observations are consistent with a small tensor-to-scalar ratio as predicted by small field models of inflation, then the present study serves as an explicit example contrary to the general expectation that the running will be unobservable.

  8. Operation Sun Beam, Shots Little Feller II and Small Boy. Project Officer's report - Project 7. 16. Airborne E-field radiation measurements of electromagnetic-pulse phenomena

    SciTech Connect

    Butler, K.L.

    1985-09-01

    Airborne measurements of the absolute vertical electric field (E-field) of the radiated electromagnetic pulse were attempted for Shots Little Feller II and Small Boy. Instrumentation included calibrated vertical whip antennas, wideband magnetic tape recorders, and photographs of oscilloscope traces. One instrumented aircraft participated in Little Feller II (C-131F); two aircraft participated in Small Boy (a C-131F and an A-3A). No detectable signals were recorded for either event. It is concluded that the vertical E-field intensities encountered were below the calibrated levels of the instrumentation or the method of instrumentation and calibration was inadequate for nonrepetitive pulse signals.

  9. Suppression of sound radiation to far field of near-field acoustic communication system using evanescent sound field

    NASA Astrophysics Data System (ADS)

    Fujii, Ayaka; Wakatsuki, Naoto; Mizutani, Koichi

    2016-01-01

    A method of suppressing sound radiation to the far field of a near-field acoustic communication system using an evanescent sound field is proposed. The amplitude of the evanescent sound field generated from an infinite vibrating plate attenuates exponentially with increasing a distance from the surface of the vibrating plate. However, a discontinuity of the sound field exists at the edge of the finite vibrating plate in practice, which broadens the wavenumber spectrum. A sound wave radiates over the evanescent sound field because of broadening of the wavenumber spectrum. Therefore, we calculated the optimum distribution of the particle velocity on the vibrating plate to reduce the broadening of the wavenumber spectrum. We focused on a window function that is utilized in the field of signal analysis for reducing the broadening of the frequency spectrum. The optimization calculation is necessary for the design of window function suitable for suppressing sound radiation and securing a spatial area for data communication. In addition, a wide frequency bandwidth is required to increase the data transmission speed. Therefore, we investigated a suitable method for calculating the sound pressure level at the far field to confirm the variation of the distribution of sound pressure level determined on the basis of the window shape and frequency. The distribution of the sound pressure level at a finite distance was in good agreement with that obtained at an infinite far field under the condition generating the evanescent sound field. Consequently, the window function was optimized by the method used to calculate the distribution of the sound pressure level at an infinite far field using the wavenumber spectrum on the vibrating plate. According to the result of comparing the distributions of the sound pressure level in the cases with and without the window function, it was confirmed that the area whose sound pressure level was reduced from the maximum level to -50 dB was

  10. Intercomparison of radiation protection instrumentation in a pulsed neutron field

    NASA Astrophysics Data System (ADS)

    Caresana, M.; Denker, A.; Esposito, A.; Ferrarini, M.; Golnik, N.; Hohmann, E.; Leuschner, A.; Luszik-Bhadra, M.; Manessi, G.; Mayer, S.; Ott, K.; Röhrich, J.; Silari, M.; Trompier, F.; Volnhals, M.; Wielunski, M.

    2014-02-01

    In the framework of the EURADOS working group 11, an intercomparison of active neutron survey meters was performed in a pulsed neutron field (PNF). The aim of the exercise was to evaluate the performances of various neutron instruments, including commercially available rem-counters, personal dosemeters and instrument prototypes. The measurements took place at the cyclotron of the Helmholtz-Zentrum Berlin für Materialien und Energie GmbH. The cyclotron is routinely used for proton therapy of ocular tumours, but an experimental area is also available. For the therapy the machine accelerates protons to 68 MeV. The interaction of the proton beam with a thick tungsten target produces a neutron field with energy up to about 60 MeV. One interesting feature of the cyclotron is that the beam can be delivered in bursts, with the possibility to modify in a simple and flexible way the burst length and the ion current. Through this possibility one can obtain radiation bursts of variable duration and intensity. All instruments were placed in a reference position and irradiated with neutrons delivered in bursts of different intensity. The analysis of the instrument response as a function of the burst charge (the total electric charge of the protons in the burst shot onto the tungsten target) permitted to assess for each device the dose underestimation due to the time structure of the radiation field. The personal neutron dosemeters were exposed on a standard PMMA slab phantom and the response linearity was evaluated.

  11. Field Deployable Gamma Radiation Detectors for DHS Use

    SciTech Connect

    Sanjoy Mukhopadhyay

    2007-08-31

    Recently, the U.S. Department of Homeland Security (DHS) has integrated all nuclear detection research, development, testing, evaluation, acquisition, and operational support into a single office: the Domestic Nuclear Detection Office (DNDO). The DNDO has specific requirements set for all commercial and government off-the-shelf radiation detection equipment and data acquisition systems. This article would investigate several recent developments in field deployable gamma radiation detectors that are attempting to meet the DNDO specifications. Commercially available, transportable, handheld radio isotope identification devices (RIID) are inadequate for DHS’s requirements in terms of sensitivity, resolution, response time and reach back capability. The leading commercial vendor manufacturing handheld gamma spectrometer in the United States is Thermo Electron Corporation. Thermo Electron’s identiFINDER™, which primarily uses sodium iodide crystals (3.18-cm x 2.54-cm cylinders) as gamma detector, has a Full-Width-at-Half-Maximum energy resolution of 7 percent at 662 keV. Thermo Electron has just recently come up with a reach-back capability patented as RadReachBack™ that enables emergency personnel to obtain real-time technical analysis of radiation samples they find in the field. The current project has the goal to build a prototype handheld gamma spectrometer, equipped with a digital camera and an embedded cell phone to be used as an RIID with higher sensitivity (comparable to that of a 7.62-cm x 7.62-cm sodium iodide crystal at low gamma energy ranging from 30 keV to 3,000 keV), better resolution (< 3.0 percent at 662 keV), faster response time (able to detect the presence of gamma-emitting radio isotopes within 5 seconds of approach), which will make it useful as a field deployable tool. The handheld equipment continuously monitors the ambient gamma radiation and, if it comes across any radiation anomalies with higher than normal gamma gross counts, it sets

  12. Field Deployable Gamma Radiation Detectors for DHS Use

    SciTech Connect

    Sanjoy Mukhopadhyay

    2007-08-01

    Recently, the Department of Homeland Security (DHS) has integrated all nuclear detection research, development, testing, evaluation, acquisition, and operational support into a single office: the Domestic Nuclear Detection Office (DNDO). The DNDO has specific requirements set for all commercial off-the-shelf and government off-the-shelf radiation detection equipment and data acquisition systems. This article would investigate several recent developments in field deployable gamma radiation detectors that are attempting to meet the DNDO specifications. Commercially available, transportable, handheld radio isotope identification devices (RIID) are inadequate for DHS requirements in terms of sensitivity, resolution, response time, and reach-back capability. The leading commercial vendor manufacturing handheld gamma spectrometer in the United States is Thermo Electron Corporation. Thermo Electron's identiFINDER{trademark}, which primarily uses sodium iodide crystals (3.18 x 2.54cm cylinders) as gamma detectors, has a Full-Width-at-Half-Maximum energy resolution of 7 percent at 662 keV. Thermo Electron has just recently come up with a reach-back capability patented as RadReachBack{trademark} that enables emergency personnel to obtain real-time technical analysis of radiation samples they find in the field. The current project has the goal to build a prototype handheld gamma spectrometer, equipped with a digital camera and an embedded cell phone to be used as an RIID with higher sensitivity, better resolution, and faster response time (able to detect the presence of gamma-emitting radio isotopes within 5 seconds of approach), which will make it useful as a field deployable tool. The handheld equipment continuously monitors the ambient gamma radiation, and, if it comes across any radiation anomalies with higher than normal gamma gross counts, it sets an alarm condition. When a substantial alarm level is reached, the system automatically triggers the saving of relevant

  13. Graphene-based field effect transistors for radiation-induced field sensing

    NASA Astrophysics Data System (ADS)

    Di Gaspare, Alessandra; Valletta, Antonio; Fortunato, Guglielmo; Larciprete, Rosanna; Mariucci, Luigi; Notargiacomo, Andrea; Cimino, Roberto

    2016-07-01

    We propose the implementation of graphene-based field effect transistor (FET) as radiation sensor. In the proposed detector, graphene obtained via chemical vapor deposition is integrated into a Si-based field effect device as the gate readout electrode, able to sense any change in the field distribution induced by ionization in the underneath absorber, because of the strong variation in the graphene conductivity close to the charge neutrality point. Different 2-dimensional layered materials can be envisaged in this kind of device.

  14. Cosmic Radiation Fields: Sources in the early Universe

    NASA Astrophysics Data System (ADS)

    Raue, Martin; Kneiske, Tanja; Horns, Dieter; Elsaesser, Dominik; Hauschildt, Peter

    The workshop "Cosmic Radiation Fields - Sources in the Early Universe" (CRF 2010) focuses on the connection between the extragalactic infrared background and sources in the early universe, in particular stars powered by dark matter burning (Dark Stars; DS). The workshop covers the following topics: the cosmic infrared background, formation of early stars, dark stars, effect of dark matter in the early universe, dark matter halos, primordial star formation rate, and reionization. Further information can be found on the conference webpage: http://www.desy.de/crf2010/. Organizing committee: Tanja Kneiske, Martin Raue, Dominik Elsaesser, Alexander Gewering-Peine, Peter Hausschildt, Dieter Horns, and Andreas Maurer.

  15. Localisation of atomic populations in the optical radiation field

    SciTech Connect

    Efremova, E A; Gordeev, M Yu; Rozhdestvensky, Yu V

    2014-10-31

    The possibility of two-dimensional spatial localisation of atomic populations under the influence of the travelling wave fields in the tripod-configuration of quantum states is studied for the first time. Three travelling waves propagating in the same plane at an angle of 120° to each other form a system of standing waves under the influence of which atomic populations are localised. The size of the region of spatial localisation of the populations, in principle, can be hundredths of a wavelength of optical radiation. (quantum optics)

  16. Novel properties of the q-analogue quantized radiation field

    NASA Technical Reports Server (NTRS)

    Nelson, Charles A.

    1993-01-01

    The 'classical limit' of the q-analog quantized radiation field is studied paralleling conventional quantum optics analyses. The q-generalizations of the phase operator of Susskind and Glogower and that of Pegg and Barnett are constructed. Both generalizations and their associated number-phase uncertainty relations are manifestly q-independent in the n greater than g number basis. However, in the q-coherent state z greater than q basis, the variance of the generic electric field, (delta(E))(sup 2) is found to be increased by a factor lambda(z) where lambda(z) greater than 1 if q not equal to 1. At large amplitudes, the amplitude itself would be quantized if the available resolution of unity for the q-analog coherent states is accepted in the formulation. These consequences are remarkable versus the conventional q = 1 limit.

  17. Measurement of neutron and gamma radiation in a mixed field.

    PubMed

    Kronenberg, S; Bechtel, E; Brucker, G J

    1995-10-01

    This paper describes a study of dosimeters with a range of 0 to 0.2 mGy that were developed by the authors and built by the Federal Emergency Management Agency (FEMA). These instruments are a type of air-filled ion chamber that is self-reading by means of an internal carbon fiber electrometer. Two types of these dosimeters were constructed: one with an ion chamber wall made of a conductive hydrogenous material, and the other device made with a conductive wall lining of non-hydrogenous material. Both types of dosimeters have the same sensitivity for gamma radiation, but greatly different sensitivities for fast neutrons, thus making it possible to measure gamma radiation and neutron doses separately in a mixed radiation field. The results indicate that such pairs of dosimeters can be used for the first time to accurately monitor personnel for gamma ray and neutron doses in real time. Since the difference in neutron sensitivities is due to the properties of wall materials, periodic calibrations of the dosimeter system can be accomplished using only gamma rays after the material constants are measured. The absolute number of neutron induced transmutations in sulfur was required for this work. Methods and techniques which were applied to determine this quantity are described in the text. This approach was one of several dosimetric procedures utilized in this investigation. PMID:7558835

  18. Field test of a post-closure radiation monitor

    SciTech Connect

    Reed, S.E.; Christy, C.E.; Heath, R.E.

    1995-10-01

    The DOE is conducting remedial actions at many sites contaminated with radioactive materials. After closure of these sites, long-term subsurface monitoring is typically required by law. This monitoring is generally labor intensive and expensive using conventional sampling and analysis techniques. The U.S. Department of Energy`s Morgantown Energy Technology Center (METC) has contracted with Babcock and Wilcox to develop a Long-Term Post-Closure Radiation Monitoring System (LPRMS) to reduce these monitoring costs. The system designed in Phase I of this development program monitors gamma radiation using a subsurface cesium iodide scintillator coupled to above-ground detection electronics using optical waveguide. The radiation probe can be installed to depths up to 50 meters using cone penetrometer techniques, and requires no downhole electrical power. Multiplexing, data logging and analysis are performed at a central location. A prototype LPRMS probe was built, and B&W and FERMCO field tested this monitoring probe at the Fernald Environmental Management Project in the fall of 1994 with funding from the DOE`s Office of Technology Development (EM-50) through METC. The system was used measure soil and water with known uranium contamination levels, both in drums and in situ depths up to 3 meters. For comparison purposes measurements were also performed using a more conventional survey probe with a sodium iodide scintillator directly butt-coupled to detection electronics.

  19. Marriage Encounter: A Critical Appraisal.

    ERIC Educational Resources Information Center

    Doherty, William J; And Others

    1978-01-01

    This paper describes and evaluates the marriage encounter movement from theoretical and clinical perspectives. While aknowledging that the marriage encounter responds to a need among many couples for greater marital closeness, the authors raise concerns about potentially destructive and illusory effects of the marriage encounter experience.…

  20. Teacher Educators Using Encounter Stories

    ERIC Educational Resources Information Center

    Davis, Danné E.; Kellinger, Janna Jackson

    2014-01-01

    Many prospective teachers are unaware of the encounters that Black, heterosexual women or White lesbians face. Here, we present encounter stories--individual narratives of poignant encounters and interactions that we have experienced with people unlike us--to identify with and ultimately draw on their experiences. Subsequently, the narratives…

  1. Chemical composition of tropospheric air masses encountered during high altitude flights (>11.5 km) during the 2009 fall Operation Ice Bridge field campaign

    NASA Astrophysics Data System (ADS)

    Yang, Mei Ying Melissa; Vay, Stephanie A.; Stohl, Andreas; Choi, Yonghoon; Diskin, Glenn S.; Sachse, Glen W.; Blake, Donald R.

    2012-09-01

    As part of the 2009 Operation Ice Bridge campaign, the NASA DC-8 aircraft was used to fill the data-time gap in laser observation of the changes in ice sheets, glaciers and sea ice between ICESat-I (Ice, Cloud, and land Elevation Satellite) and ICESat-II. Complementing the cryospheric instrument payload were four in situ atmospheric sampling instruments integrated onboard to measure trace gas concentrations of CO2, CO, N2O, CH4, water vapor and various VOCs (Volatile Organic Compounds). This paper examines two plumes encountered at high altitude (12 km) during the campaign; one during a southbound transit flight (13°S) and the other at 86°S over Antarctica. The data presented are especially significant as the Southern Hemisphere is heavily under-sampled during the austral spring, with few if any high-resolution airborne observations of atmospheric gases made over Antarctica. Strong enhancements of CO, CH4, N2O, CHCl3, OCS, C2H6, C2H2 and C3H8 were observed in the two intercepted air masses that exhibited variations in VOC composition suggesting different sources. The transport model FLEXPART showed that the 13°S plume contained predominately biomass burning emissions originating from Southeast Asia and South Africa, while both anthropogenic and biomass burning emissions were observed at 86°S with South America and South Africa as indicated source regions. The data presented here show evidence that boundary layer pollution is transported from lower latitudes toward the upper troposphere above the South Pole, which may not have been observed in the past.

  2. Development of a Characterized Radiation Field for Evaluating Sensor Performance

    SciTech Connect

    Rogers, D.M.; Coggins, T.L.; Marsh, J.; Mann, St.D.; Waggoner, Ch.A.

    2008-07-01

    Numerous efforts are funded by US agencies (DOE, DoD, DHS) for development of novel radiation sensing and measurement systems. An effort has been undertaken to develop a flexible shielding system compatible with a variety of sources (beta, X-ray, gamma, and neutron) that can be highly characterized using conventional radiation detection and measurement systems. Sources available for use in this system include americium-beryllium (AmBe), plutonium-beryllium (PuBe), strontium-90 (Sr-90), californium-252 (Cf-252), krypton-85 (Kr-85), americium-241 (Am-241), and depleted uranium (DU). Shielding can be varied by utilization of materials that include lexan, water, oil, lead, and polyethylene. Arrangements and geometries of source(s) and shielding can produce symmetrical or asymmetrical radiation fields. The system has been developed to facilitate accurately repeatable configurations. Measurement positions are similarly capable of being accurately re-created. Stand-off measurement positions can be accurately re-established using differential global positioning system (GPS) navigation. Instruments used to characterize individual measurement locations include a variety of sodium iodide (NaI(Tl)) (3 x 3 inch, 4 x 4 x 16 inch, Fidler) and lithium iodide (LiI(Eu)) detectors (for use with multichannel analyzer software) and detectors for use with traditional hand held survey meters such as boron trifluoride (BF{sub 3}), helium-3 ({sup 3}He), and Geiger-Mueller (GM) tubes. Also available are Global Dosimetry thermoluminescent dosimeters (TLDs), CR39 neutron chips, and film badges. Data will be presented comparing measurement techniques with shielding/source configurations. The system is demonstrated to provide a highly functional process for comparison/characterization of various detector types relative to controllable radiation types and levels. Particular attention has been paid to use of neutron sources and measurements. (authors)

  3. Monte Carlo simulation of the operational quantities at the realistic mixed neutron-photon radiation fields CANEL and SIGMA.

    PubMed

    Lacoste, V; Gressier, V

    2007-01-01

    The Institute for Radiological Protection and Nuclear Safety owns two facilities producing realistic mixed neutron-photon radiation fields, CANEL, an accelerator driven moderator modular device, and SIGMA, a graphite moderated americium-beryllium assembly. These fields are representative of some of those encountered at nuclear workplaces, and the corresponding facilities are designed and used for calibration of various instruments, such as survey meters, personal dosimeters or spectrometric devices. In the framework of the European project EVIDOS, irradiations of personal dosimeters were performed at CANEL and SIGMA. Monte Carlo calculations were performed to estimate the reference values of the personal dose equivalent at both facilities. The Hp(10) values were calculated for three different angular positions, 0 degrees, 45 degrees and 75 degrees, of an ICRU phantom located at the position of irradiation. PMID:17578872

  4. Further progress in the characterisation of complex radiation fields.

    PubMed

    Spurny, Frantisek; Silari, Marco

    2008-01-01

    One of the topics which forms part of CONRAD project addresses the problems related to the dosimetry of complex-mixed radiation fields at workplaces. This topic was included in work package (WP) 6. WP 6 was established to co-ordinate research activities in two areas:the development of new techniques and the improvement of current techniques for characterisation of complex workplace fields (including high-energy fields and pulsed fields): measurement and calculation of particle energy and direction distributions (Subgroup A); and model improvements for dose assessment of solar particle events (Subgroup B). In both cases in order to aid the research, WP 6 increases the efficiency of resource utilisation, and facilitates the technology transfer to practical application and for the development of standards. This contribution presents a general overview of activities of SG A; specific results related to the benchmark experiment at GSI Darmstadt are presented separately, and will be published in other way. As far as the results acquired in the frame of the SG B activities, these are presented in the meeting held as part of EURADOS AM 2008. PMID:18718960

  5. Modulation and amplification of radiative far field heat transfer: Towards a simple radiative thermal transistor

    SciTech Connect

    Joulain, Karl; Ezzahri, Younès; Drevillon, Jérémie; Ben-Abdallah, Philippe

    2015-03-30

    We show in this article that phase change materials (PCM) exhibiting a phase transition between a dielectric state and a metallic state are good candidates to perform modulation as well as amplification of radiative thermal flux. We propose a simple situation in plane parallel geometry where a so-called radiative thermal transistor could be achieved. In this configuration, we put a PCM between two blackbodies at different temperatures. We show that the transistor effect can be achieved easily when this material has its critical temperature between the two blackbody temperatures. We also see that the more the material is reflective in the metallic state, the more switching effect is realized, whereas the more PCM transition is stiff in temperature, the more thermal amplification is high. We finally take the example of VO{sub 2} that exhibits an insulator-metallic transition at 68 °C. We show that a demonstrator of a radiative transistor could easily be achieved in view of the heat flux levels predicted. Far-field thermal radiation experiments are proposed to back the results presented.

  6. A simple method to quantify the coincidence between portal image graticules and radiation field centers or radiation isocenter

    SciTech Connect

    Du Weiliang; Yang, James; Luo Dershan; Martel, Mary

    2010-05-15

    Purpose: The aim of this study was to develop a computerized method to quantify the coincidence between portal image graticules and radiation field centers or radiation isocenter. Three types of graticules were included in this study: Megavoltage (MV) mechanical graticule, MV electronic portal imaging device digital graticule, and kilovoltage (kV) on-board imaging digital graticule. Methods: A metal ball bearing (BB) was imaged with MV and kV x-ray beams in a procedure similar to a Winston-Lutz test. The radiation fields, graticules, and BB were localized in eight portal images using Hough transform-based computer algorithms. The center of the BB served as a static reference point in the 3D space so that the distances between the graticule centers and the radiation field centers were calculated. The radiation isocenter was determined from the radiation field centers at different gantry angles. Results: Misalignments of MV and kV portal imaging graticules varied with the gantry or x-ray source angle as a result of mechanical imperfections of the linear accelerator and its imaging system. While the three graticules in this study were aligned to the radiation field centers and the radiation isocenter within 2.0 mm, misalignments of 1.5-2.0 mm were found at certain gantry angles. These misalignments were highly reproducible with the gantry rotation. Conclusions: A simple method was developed to quantify the alignments of portal image graticules directly against the radiation field centers or the radiation isocenter. The advantage of this method is that it does not require the BB to be placed exactly at the radiation isocenter through a precalibrated surrogating device such as room lasers or light field crosshairs. The present method is useful for radiation therapy modalities that require high-precision portal imaging such as image-guided stereotactic radiotherapy.

  7. Two encounters with the flank low-latitude boundary layer - Further evidence for closed field topology and investigation of the internal structure

    NASA Technical Reports Server (NTRS)

    Traver, D. P.; Mitchell, D. G.; Williams, D. J.; Frank, L. A.; Huang, C. Y.

    1991-01-01

    The structure of the flank low-latitude boundary layer (LLBL) is examined through differential energy spectra and particle angular anisotropies for traversals of the dawn flank (December 19, 1977) and dusk flank (July 7, 1978) during periods of predominantly northward magnetosheath field orientation. Spectra are presented that were obtained from combined ISEE 1 low-energy-proton and electron-differential-energy-analyzer and medium-energy-particle-instrument data extending over the 200-eV/q to 2-MeV energy range for the plasma sheet, stagnation region, outer LLBL, and magnetosheath regions. The stagnation region and the outer LLBL are each a mixture of plasma-sheet and magnetosheath populations, but the stagnation region contains a relatively higher fraction of plasma sheet particles, consistent with its placement earthward of the outer LLBL. Evidence for energization of thermal electrons appears during the dusk flank crossing. Bidirectional field-aligned ion distributions are observed with typically 5-to-1 enhancement of the flux along the magnetic field during certain portions of the dusk flank crossing.

  8. Measurement of the radiation field surrounding the Collider Detector at Fermilab

    SciTech Connect

    K. Kordas et al.

    2004-01-28

    We present here the first direct and detailed measurements of the spatial distribution of the ionizing radiation surrounding a hadron collider experiment. Using data from two different exposures we measure the effect of additional shielding on the radiation field around the Collider Detector at Fermilab (CDF). Employing a simple model we parameterize the ionizing radiation field surrounding the detector.

  9. Out-of-Field Cell Survival Following Exposure to Intensity-Modulated Radiation Fields

    SciTech Connect

    Butterworth, Karl T.; McGarry, Conor K.; Trainor, Colman; O'Sullivan, Joe M.; Hounsell, Alan R.; Prise, Kevin M.

    2011-04-01

    Purpose: To determine the in-field and out-of-field cell survival of cells irradiated with either primary field or scattered radiation in the presence and absence of intercellular communication. Methods and Materials: Cell survival was determined by clonogenic assay in human prostate cancer (DU145) and primary fibroblast (AGO1552) cells following exposure to different field configurations delivered using a 6-MV photon beam produced with a Varian linear accelerator. Results: Nonuniform dose distributions were delivered using a multileaf collimator (MLC) in which half of the cell population was shielded. Clonogenic survival in the shielded region was significantly lower than that predicted from the linear quadratic model. In both cell lines, the out-of-field responses appeared to saturate at 40%-50% survival at a scattered dose of 0.70 Gy in DU-145 cells and 0.24 Gy in AGO1522 cells. There was an approximately eightfold difference in the initial slopes of the out-of-field response compared with the {alpha}-component of the uniform field response. In contrast, cells in the exposed part of the field showed increased survival. These observations were abrogated by direct physical inhibition of cellular communication and by the addition of the inducible nitric oxide synthase inhibitor aminoguanidine known to inhibit intercellular bystander effects. Additional studies showed the proportion of cells irradiated and dose delivered to the shielded and exposed regions of the field to impact on response. Conclusions: These data demonstrate out-of-field effects as important determinants of cell survival following exposure to modulated irradiation fields with cellular communication between differentially irradiated cell populations playing an important role. Validation of these observations in additional cell models may facilitate the refinement of existing radiobiological models and the observations considered important determinants of cell survival.

  10. S-76 rotorcraft high intensity radiated fields. Test plan

    NASA Astrophysics Data System (ADS)

    Blair, Jerry T.; Brooks, Steve M.; Barnes, Ken A.

    1991-07-01

    Concern over the effects of High Intensity Radiated Fields (HIRF) on civil and military aircraft has increased over the past 10 years. The increase is due to several factors which affect the safe flight of all fixed-wing and rotorcraft. Previous flight-critical mechanical controls are being replaced by electronic computer-driven controls; manufacturers are increasing the use of composite materials in the fabrication of new aircraft; and frequency ranges and output power levels of commercial and military transmitters have significantly increased. While much HIRF susceptibility information has been collected, the data are proprietary and have not been released. To address the HIRF concerns and begin development of a releasable HIRF data base, the FAA Technical Center, has implemented a HIRF research program. As part of that program, a HIRF test was performed on a Sikorsky S-76 Helicopter. The purpose, approach, and initial findings of the S-76 HIRF test are addressed.

  11. Field test of a post-closure radiation monitor

    SciTech Connect

    Reed, S.; Christy, C.E.; Heath, R.E.

    1995-12-01

    The DOE is conducting remedial actions at many sites contaminated with radioactive materials. After closure of these sites, long-term subsurface monitoring is typically required by law. This monitoring is generally labor intensive and expensive using conventional sampling and analysis techniques. The U.S. Department of Energy`s Morgantown Energy Technology Center (METC) has contracted with Babcock and Wilcox to develop a Long-Term Post-Closure Radiation Monitoring System (LPRMS) to reduce these monitoring costs. A prototype LPRMS probe was built, and B&W and FERMCO field tested this monitoring probe at the Fernald Environmental Management Project in the fall of 1994 with funding from the DOE`s Office of Technology Development (EM-50) through METC. The system was used to measure soil and water with known uranium contamination levels, both in drums and in situ at depths up to 3 meters. For comparison purposes, measurements were also performed using a more conventional survey probe with a sodium iodide scintillator directly butt-coupled to detection electronics. This paper presents a description and the results of the field tests. The results were used to characterize the lower detection limits, precision and bias of the system, which allowed the DOE to judge the monitoring system`s ability to meet its long-term post-closure radiation monitoring needs. Based on the test results, the monitoring system has been redesigned for fabrication and testing in a potential Phase III of this program. If the DOE feels that this system can meet its needs and chooses to continue into Phase III of this program, this redesigned full scale prototype system will be built and tested for a period of approximately a year. Such a system can be used at a variety of radioactively contaminated sites.

  12. Close encounters with DNA

    PubMed Central

    Maffeo, C.; Yoo, J.; Comer, J.; Wells, D. B.; Luan, B.; Aksimentiev, A.

    2014-01-01

    Over the past ten years, the all-atom molecular dynamics method has grown in the scale of both systems and processes amenable to it and in its ability to make quantitative predictions about the behavior of experimental systems. The field of computational DNA research is no exception, witnessing a dramatic increase in the size of systems simulated with atomic resolution, the duration of individual simulations and the realism of the simulation outcomes. In this topical review, we describe the hallmark physical properties of DNA from the perspective of all-atom simulations. We demonstrate the amazing ability of such simulations to reveal the microscopic physical origins of experimentally observed phenomena and we review the frustrating limitations associated with imperfections of present atomic force fields and inadequate sampling. The review is focused on the following four physical properties of DNA: effective electric charge, response to an external mechanical force, interaction with other DNA molecules and behavior in an external electric field. PMID:25238560

  13. Universalist ethics in extraterrestrial encounter

    NASA Astrophysics Data System (ADS)

    Baum, Seth D.

    2010-02-01

    If humanity encounters an extraterrestrial civilization, or if two extraterrestrial civilizations encounter each other, then the outcome may depend not only on the civilizations' relative strength to destroy each other but also on what ethics are held by one or both civilizations. This paper explores outcomes of encounter scenarios in which one or both civilizations hold a universalist ethical framework. Several outcomes are possible in such scenarios, ranging from one civilization destroying the other to both civilizations racing to be the first to commit suicide. Thus, attention to the ethics of both humanity and extraterrestrials is warranted in human planning for such an encounter. Additionally, the possibility of such an encounter raises profound questions for contemporary human ethics, even if such an encounter never occurs.

  14. Magnetic field and radiative transfer modelling of a quiescent prominence

    NASA Astrophysics Data System (ADS)

    Gunár, S.; Schwartz, P.; Dudík, J.; Schmieder, B.; Heinzel, P.; Jurčák, J.

    2014-07-01

    Aims: The aim of this work is to analyse the multi-instrument observations of the June 22, 2010 prominence to study its structure in detail, including the prominence-corona transition region and the dark bubble located below the prominence body. Methods: We combined results of the 3D magnetic field modelling with 2D prominence fine structure radiative transfer models to fully exploit the available observations. Results: The 3D linear force-free field model with the unsheared bipole reproduces the morphology of the analysed prominence reasonably well, thus providing useful information about its magnetic field configuration and the location of the magnetic dips. The 2D models of the prominence fine structures provide a good representation of the local plasma configuration in the region dominated by the quasi-vertical threads. However, the low observed Lyman-α central intensities and the morphology of the analysed prominence suggest that its upper central part is not directly illuminated from the solar surface. Conclusions: This multi-disciplinary prominence study allows us to argue that a large part of the prominence-corona transition region plasma can be located inside the magnetic dips in small-scale features that surround the cool prominence material located in the dip centre. We also argue that the dark prominence bubbles can be formed because of perturbations of the prominence magnetic field by parasitic bipoles, causing them to be devoid of the magnetic dips. Magnetic dips, however, form thin layers that surround these bubbles, which might explain the occurrence of the cool prominence material in the lines of sight intersecting the prominence bubbles. Movie and Appendix A are available in electronic form at http://www.aanda.org

  15. Stream Lifetimes Against Planetary Encounters

    NASA Technical Reports Server (NTRS)

    Valsecchi, G. B.; Lega, E.; Froeschle, Cl.

    2011-01-01

    We study, both analytically and numerically, the perturbation induced by an encounter with a planet on a meteoroid stream. Our analytical tool is the extension of pik s theory of close encounters, that we apply to streams described by geocentric variables. The resulting formulae are used to compute the rate at which a stream is dispersed by planetary encounters into the sporadic background. We have verified the accuracy of the analytical model using a numerical test.

  16. S-76 high intensity radiated fields, volume 1

    NASA Astrophysics Data System (ADS)

    Blair, Jerry

    1993-10-01

    The Federal Aviation Administration (FAA) Technical Center sponsored a series of High Intensity Radiated Fields (HIRF) test on a Sikorsky S-76 rotorcraft. The project was conducted to evaluate the practicality of performing aircraft level HIRF tests, determine the effects of HIRF on a specific rotorcraft with the potential to obtain information on rotorcraft in general, and evaluate the effects of exposure to real world HIRF emitters. HIRF ground and flight tests were conducted to achieve the objective of the project. Site calibration (SCAL) measurements were made in the test area to determine the levels at which the S-76 would be irradiated when placed in the test area. Ground tests consisted of Low Level Swept Coupling (LLSC) and Low Level Swept Fields (LLSF) tests. The flight tests were flown directly into the main beam of a variety of pulsed and continuous wave (CW) transmitters including the Over the Horizon Back Scatter (OTHB), PAVE PAWS, ASR-9, FPS-65, and FPS-16 radars. Results of the S-76 tests added credibility to the existence of HIRF as a flight safety hazard. In the evaluation of the emitters, the flight tests showed repeatable instances where exposure resulted in instrumentation disruptions. It should be noted that all the observed disruptions were of a non-critical nature.

  17. S-76 high intensity radiated fields, volume 3

    NASA Astrophysics Data System (ADS)

    Blair, Jerry

    1993-10-01

    The Federal Aviation Administration (FAA) Technical Center sponsored a series of High Intensity Radiated Fields (HIRF) tests on a Sikorsky S-76 rotorcraft. The project was conducted to evaluate the practically of performing aircraft level HIRF tests, determine the effects of HIRF on a specific rotorcraft with the potential to obtain information on rotorcraft in general, and evaluate the effects of exposure to 'real world' HIRF emitters. HIRF ground and flight tests were conducted to achieve the objective of the project. Site calibration (SCAL) measurements were made in the test area to determine the levels at which the S-76 would be irradiated when placed in the test area. Ground tests consisted of Low Level Swept Coupling (LLSC) and Low Level Swept Fields (LLSF) tests. The flight tests were flown directly into the main beam of a variety of pulsed and continuous wave (CW) transmitters including the Over the Horizon Back Scatter (OTHB), PAVE PAWS, ASR-9, FPS-65, and FPS-16 radars. Results of the S-76 tests added credibility to the existence of HIRF as a flight safety hazard. In the evaluation of the emitters, the flight tests showed repeatable instances where exposure resulted in instrumentation disruptions. It should however be noted that all the observed disruptions were of a non-critical nature.

  18. S-76 high intensity radiated fields, volume 2

    NASA Astrophysics Data System (ADS)

    Blair, Jerry

    1993-10-01

    The Federal Aviation Administration (FAA) Technical Center sponsored a series of High Intensity Radiated Fields (HIRF) test on a Sikorsky S-76 rotorcraft. The project was conducted to evaluate the practically of performing aircraft level HIRF tests, determine the effects of HIRF on a specific rotorcraft with the potential to obtain information on rotorcraft in general, and evaluate the effects of exposure to real world HIRF emitters. HIRF ground and flight tests were conducted to achieve the objective of the project. Site calibration (SCAL) measurements were made in the test area to determine the levels at which the S-76 would be irradiated when placed in the test area. Ground tests consisted of Low Level Swept Coupling (LLSC) and Low Level Swept Fields (LLSF) tests. The flight tests were flown directly into the main beam of a variety of pulsed and continuous wave (CW) transmitters including the Over the Horizon Back Scatter (OTHB), PAVE PAWS, ASR-9, FPS-65, and FPS-16 radars. Results of the S-76 tests added credibility to the existence of HIRF as a flight safety hazard. In the evaluation of the emitters, the flight tests showed repeatable instances where exposure resulted in instrumentation disruptions. It should be noted that all the observed disruptions were of a non-critical nature.

  19. Linac head scatter factor for asymmetric radiation field

    NASA Astrophysics Data System (ADS)

    Soubra, Mazen Ahmed

    1997-11-01

    The head scatter factor, Sh is an important dosimetric quantity used in radiation therapy dose calculation. It is empirically determined and its field size dependence reflects changes in photon scatter from components in the linac treatment head. In this work a detailed study of the physical factors influencing the determination of Sh was performed with particular attention given to asymmetric field geometries. Ionization measurements for 6 and 18 MV photon beams were made to examine the factors which determine Sh. These include: phantom size and material, collimator backscatter, non-lateral electronic equilibrium (LEE) conditions, electron contamination, collimator-exchange, photon energy, flattening filter and off-axis distance (OAD). Results indicated that LEE is not required for Sh measurements if electron contamination is minimized. Brass caps or polystyrene miniphantoms can both be used in Sh measurements provided the phantom thickness is large enough to stop contaminant electrons. Backscatter radiation effects into the monitor chamber were found to be negligible for the Siemens linac. It was found that the presence and shape of the flattening filter had a significant effect on the empirically determined value of Sh was also shown to be a function of OAD, particularly for small fields. For fields larger than 12×12 cm2/ Sh was independent of OAD. A flattening filter mass model was introduced to explain qualitatively the above results. A detailed Monte Carlo simulation of the Siemens KD2 linac head in 6 MV mode was performed to investigate the sources of head scatter which contribute to the measured Sh. The simulated head components include the flattening filter, the electron beam stopper, the primary collimator, the photon monitor chamber and the secondary collimators. The simulations showed that the scatter from the head of the Siemens linac is a complex function of the head components. On the central axis the flattening filter played the dominant role in

  20. Simplified field-in-field technique for a large-scale implementation in breast radiation treatment

    SciTech Connect

    Fournier-Bidoz, Nathalie; Kirova, Youlia M.; Campana, Francois; Dendale, Remi; Fourquet, Alain

    2012-07-01

    We wanted to evaluate a simplified 'field-in-field' technique (SFF) that was implemented in our department of Radiation Oncology for breast treatment. This study evaluated 15 consecutive patients treated with a simplified field in field technique after breast-conserving surgery for early-stage breast cancer. Radiotherapy consisted of whole-breast irradiation to the total dose of 50 Gy in 25 fractions, and a boost of 16 Gy in 8 fractions to the tumor bed. We compared dosimetric outcomes of SFF to state-of-the-art electronic surface compensation (ESC) with dynamic leaves. An analysis of early skin toxicity of a population of 15 patients was performed. The median volume receiving at least 95% of the prescribed dose was 763 mL (range, 347-1472) for SFF vs. 779 mL (range, 349-1494) for ESC. The median residual 107% isodose was 0.1 mL (range, 0-63) for SFF and 1.9 mL (range, 0-57) for ESC. Monitor units were on average 25% higher in ESC plans compared with SFF. No patient treated with SFF had acute side effects superior to grade 1-NCI scale. SFF created homogenous 3D dose distributions equivalent to electronic surface compensation with dynamic leaves. It allowed the integration of a forward planned concomitant tumor bed boost as an additional multileaf collimator subfield of the tangential fields. Compared with electronic surface compensation with dynamic leaves, shorter treatment times allowed better radiation protection to the patient. Low-grade acute toxicity evaluated weekly during treatment and 2 months after treatment completion justified the pursuit of this technique for all breast patients in our department.

  1. Successful I.D. Encounters.

    ERIC Educational Resources Information Center

    Poorman, Margaret J.

    Instructional Development (I.D.) encounters are dependent for success on such variables as power, politics, promotion, and organizational placement. I.D. consultants must be aware of power bases or orientation of other personnel and clients, e.g., these four "power personalities" which affect their efforts in managing I.D. encounters: the gate…

  2. Pioneer 11 Encounter. [with Jupiter

    NASA Technical Reports Server (NTRS)

    1975-01-01

    Pioneer 11's encounter with Jupiter is discussed in detail. The scientific experiments carried out on the probe are described along with the instruments used. Tables are included which provide data on the times of experiments, encounters, and the distances from Jupiter. Educational study projects are also given.

  3. Measurements of Radiating Flow Fields in the Vacuum Ultraviolet

    NASA Astrophysics Data System (ADS)

    Sheikh, U. A.; Jacobs, C.; Laux, C. O.; Morgan, R. G.; McIntyre, T. J.

    The vacuum ultraviolet (VUV) region of the radiation spectrum spans from 100 nm to 200 nm and is responsible for 30-50 % of the radiative heat flux during peak heating for a lunar return trajectory [1].

  4. Electric-field correlation in quantum charged fluids coupled to the radiation field

    SciTech Connect

    Jancovici, B.

    2006-11-15

    In a recent paper [S. El Boustani, P. R. Buenzli, and P. A. Martin, Phys. Rev. E 73, 036113 (2006)] about quantum charges in equilibrium with radiation, among other things the asymptotic form of the electric-field correlation has been obtained by a microscopic calculation. It has been found that this correlation has a long-range algebraic decay of the form 1/r{sup 3} (except in the classical limit). The macroscopic approach, in the Course of Theoretical Physics of Landau and Lifshitz, gives no such decay. In this Brief Report we revisit and complete the macroscopic approach of Landau and Lifshitz and suggest that, perhaps, the use of a classical electromagnetic field by El Boustani et al. was not justified.

  5. Involved-Field Radiation Therapy for Locoregionally Recurrent Ovarian Cancer

    PubMed Central

    Brown, Aaron P.; Jhingran, Anuja; Klopp, Ann H.; Schmeler, Kathleen M.; Ramirez, Pedro T.; Eifel, Patricia J.

    2015-01-01

    Objective To evaluate the effectiveness of definitive involved-field radiation therapy (IFRT) for selected patients with locoregionally-recurrent ovarian cancer. Methods We retrospectively reviewed records of 102 epithelial ovarian cancer patients treated with definitive IFRT (≥45 Gy). IFRT was directed to localized nodal (49%) and extranodal (51%) recurrences. Results The median time from diagnosis to IFRT was 36 months (range, 1–311), and the median follow-up after IFRT was 37 months (range, 1–123). Patients received a median of three chemotherapy courses before IFRT (range, 0–9). Five-year overall (OS) and progression-free survival (PFS) rates after IFRT were 40% and 24% respectively; the 5-year in-field disease control rate was 71%. Thirty-five patients (35%) had no evidence of disease at a median of 38 months after IFRT (range, 7–122), including 25 continuously without disease for a median of 61 months (range, 17–122) and 10 with salvage treatment following disease recurrence, disease-free for a median of 39 months after salvage treatment (range, 7–92). Eight clear cell carcinoma patients had higher 5-year OS (88% versus 37%; p=0.05) and PFS (75% versus 20%; p=0.01) rates than other patients. Patients sensitive to initial platinum chemotherapy had a higher 5-year OS rate than platinum-resistant patients (43% versus 27%, p=0.03). Patients who required chemotherapy for recurrence after IFRT often benefitted from longer chemotherapy-free intervals after than before IFRT. Conclusions Definitive IFRT can yield excellent local control, protracted disease-free intervals, and even cures in carefully selected patients. RT should be considered a tool in the curative management of locoregionally-recurrent ovarian cancer. PMID:23648467

  6. Violin f-hole contribution to far-field radiation via patch near-field acoustical holography.

    PubMed

    Bissinger, George; Williams, Earl G; Valdivia, Nicolas

    2007-06-01

    The violin radiates either from dual ports (f-holes) or via surface motion of the corpus (top+ribs+back), with no clear delineation between these sources. Combining "patch" near-field acoustical holography over just the f-hole region of a violin with far-field radiativity measurements over a sphere, it was possible to separate f-hole from surface motion contributions to the total radiation of the corpus below 2.6 kHz. A0, the Helmholtz-like lowest cavity resonance, radiated essentially entirely through the f-holes as expected while A1, the first longitudinal cavity mode with a node at the f-holes, had no significant f-hole radiation. The observed A1 radiation comes from an indirect radiation mechanism, induced corpus motion approximately mirroring the cavity pressure profile seen for violinlike bowed string instruments across a wide range of sizes. The first estimates of the fraction of radiation from the f-holes F(f) indicate that some low frequency corpus modes thought to radiate only via surface motion (notably the first corpus bending modes) had significant radiation through the f-holes, in agreement with net volume changes estimated from experimental modal analysis. F(f) generally trended lower with increasing frequency, following corpus mobility decreases. The f-hole directivity (top/back radiativity ratio) was generally higher than whole-violin directivity. PMID:17552736

  7. Voyager encounters Saturn

    NASA Astrophysics Data System (ADS)

    1981-05-01

    Scientific discoveries and observations of the November 11-13, 1980 Voyager 1 Saturn flyby and the resulting theories are presented. The basic appearance of the Saturn atmosphere is similar to that of Jupiter, but its features are made less clear by a much thicker haze layer above the visible clouds. The greatest wind speeds (more than 1600 km per hour) occur at the equator. Temperatures near the cloud tops range from -305 to -294 F, with the coolest temperature near the center of the equatorial zone. Auroral emissions were observed near the poles, and auroral-type emissions in the ultraviolet were also seen near the illuminated limbs of the planet. Radio emissions indicate that the body of the planet and its magnetosphere rotate every 10 hours 39 minutes 26 seconds. A, B, and C rings were observed to consist of hundreds of ringlets, a few of which are elliptical in shape, and a further explanation of the D, E, and F rings is given. Each of the recently discovered moons was photographed, but only S-10 and S-11 had large enough diameters in the images to permit their shapes to be determined. Data on Saturn's inner and outer moons are presented, and special attention is given to Titan. Saturn's magnetosphere extends nearly a million miles inward from the planet toward the sun, and its charged particles are dragged along by the magnetic field and circle Saturn once every 10 hours 39 minutes.

  8. The use of computed radiography plates to determine light and radiation field coincidence

    SciTech Connect

    Kerns, James R.; Anand, Aman

    2013-11-15

    Purpose: Photo-stimulable phosphor computed radiography (CR) has characteristics that allow the output to be manipulated by both radiation and optical light. The authors have developed a method that uses these characteristics to carry out radiation field and light field coincidence quality assurance on linear accelerators.Methods: CR detectors from Kodak were used outside their cassettes to measure both radiation and light field edges from a Varian linear accelerator. The CR detector was first exposed to a radiation field and then to a slightly smaller light field. The light impinged on the detector's latent image, removing to an extent the portion exposed to the light field. The detector was then digitally scanned. A MATLAB-based algorithm was developed to automatically analyze the images and determine the edges of the light and radiation fields, the vector between the field centers, and the crosshair center. Radiographic film was also used as a control to confirm the radiation field size.Results: Analysis showed a high degree of repeatability with the proposed method. Results between the proposed method and radiographic film showed excellent agreement of the radiation field. The effect of varying monitor units and light exposure time was tested and found to be very small. Radiation and light field sizes were determined with an uncertainty of less than 1 mm, and light and crosshair centers were determined within 0.1 mm.Conclusions: A new method was developed to digitally determine the radiation and light field size using CR photo-stimulable phosphor plates. The method is quick and reproducible, allowing for the streamlined and robust assessment of light and radiation field coincidence, with no observer interpretation needed.

  9. The use of computed radiography plates to determine light and radiation field coincidence

    PubMed Central

    Kerns, James R.; Anand, Aman

    2013-01-01

    Purpose: Photo-stimulable phosphor computed radiography (CR) has characteristics that allow the output to be manipulated by both radiation and optical light. The authors have developed a method that uses these characteristics to carry out radiation field and light field coincidence quality assurance on linear accelerators. Methods: CR detectors from Kodak were used outside their cassettes to measure both radiation and light field edges from a Varian linear accelerator. The CR detector was first exposed to a radiation field and then to a slightly smaller light field. The light impinged on the detector's latent image, removing to an extent the portion exposed to the light field. The detector was then digitally scanned. A MATLAB-based algorithm was developed to automatically analyze the images and determine the edges of the light and radiation fields, the vector between the field centers, and the crosshair center. Radiographic film was also used as a control to confirm the radiation field size. Results: Analysis showed a high degree of repeatability with the proposed method. Results between the proposed method and radiographic film showed excellent agreement of the radiation field. The effect of varying monitor units and light exposure time was tested and found to be very small. Radiation and light field sizes were determined with an uncertainty of less than 1 mm, and light and crosshair centers were determined within 0.1 mm. Conclusions: A new method was developed to digitally determine the radiation and light field size using CR photo-stimulable phosphor plates. The method is quick and reproducible, allowing for the streamlined and robust assessment of light and radiation field coincidence, with no observer interpretation needed. PMID:24320415

  10. Reverberation Chamber Uniformity Validation and Radiated Susceptibility Test Procedures for the NASA High Intensity Radiated Fields Laboratory

    NASA Technical Reports Server (NTRS)

    Koppen, Sandra V.; Nguyen, Truong X.; Mielnik, John J.

    2010-01-01

    The NASA Langley Research Center's High Intensity Radiated Fields Laboratory has developed a capability based on the RTCA/DO-160F Section 20 guidelines for radiated electromagnetic susceptibility testing in reverberation chambers. Phase 1 of the test procedure utilizes mode-tuned stirrer techniques and E-field probe measurements to validate chamber uniformity, determines chamber loading effects, and defines a radiated susceptibility test process. The test procedure is segmented into numbered operations that are largely software controlled. This document is intended as a laboratory test reference and includes diagrams of test setups, equipment lists, as well as test results and analysis. Phase 2 of development is discussed.

  11. Characteristic of the radiation field in low Earth orbit and in deep space.

    PubMed

    Reitz, Guenther

    2008-01-01

    The radiation exposure in space by cosmic radiation can be reduced through careful mission planning and constructive measures as example the provision of a radiation shelter, but it cannot be completely avoided. The reason for that are the extreme high energies of particles in this field and the herewith connected high penetration depth in matter. For missions outside the magnetosphere ionizing radiation is recognized as the key factor through its impact on crew health and performance. In absence of sporadic solar particle events the radiation exposure in Low Earth orbit (LEO) inside Spacecraft is determined by the galactic cosmic radiation (protons and heavier ions) and by the protons inside the South Atlantic Anomaly (SAA), an area where the radiation belt comes closer to the earth surface due to a displacement of the magnetic dipole axes from the Earth's center. In addition there is an albedo source of neutrons produced as interaction products of the primary galactic particles with the atoms of the earth atmosphere. Outside the spacecraft the dose is dominated by the electrons of the horns of the radiation belt located at about 60" latitude in Polar Regions. The radiation field has spatial and temporal variations in dependence of the Earth magnetic field and the solar cycle. The complexity of the radiation field inside a spacecraft is further increased through the interaction of the high energy components with the spacecraft shielding material and with the body of the astronauts. In interplanetary missions the radiation belt will be crossed in a couple of minutes and therefore its contribution to their radiation exposure is quite small, but subsequently the protection by the Earth magnetic field is lost, leaving only shielding measures as exposure reduction means. The report intends to describe the radiation field in space, the interaction of the particles with the magnetic field and shielding material and give some numbers on the radiation exposure in low earth

  12. Galaxy Transformation from Flyby Encounters

    NASA Astrophysics Data System (ADS)

    Davis, Christina

    2016-05-01

    Galaxy flybys are transient encounters where two halos interpenetrate and later detach forever. Although these encounters are surprisingly common—even outnumbering galaxy mergers for massive halos at the present epoch—their dynamical effects have been largely ignored. Using idealized collisionless N-body simulations of flyby encounters, it has been shown that a galaxy flyby can excite a bar and spin up the halo. Here, we compare the structural properties of recent flybys to that of recent mergers and isolated systems within the Illustris Simulation.

  13. Magnetic field control of near-field radiative heat transfer and the realization of highly tunable hyperbolic thermal emitters

    NASA Astrophysics Data System (ADS)

    Moncada-Villa, E.; Fernández-Hurtado, V.; García-Vidal, F. J.; García-Martín, A.; Cuevas, J. C.

    2015-09-01

    We present a comprehensive theoretical study of the magnetic field dependence of the near-field radiative heat transfer (NFRHT) between two parallel plates. We show that when the plates are made of doped semiconductors, the near-field thermal radiation can be severely affected by the application of a static magnetic field. We find that irrespective of its direction, the presence of a magnetic field reduces the radiative heat conductance, and dramatic reductions up to 700% can be found with fields of about 6 T at room temperature. We show that this striking behavior is due to the fact that the magnetic field radically changes the nature of the NFRHT. The field not only affects the electromagnetic surface waves (both plasmons and phonon polaritons) that normally dominate the near-field radiation in doped semiconductors, but it also induces hyperbolic modes that progressively dominate the heat transfer as the field increases. In particular, we show that when the field is perpendicular to the plates, the semiconductors become ideal hyperbolic near-field emitters. More importantly, by changing the magnetic field, the system can be continuously tuned from a situation where the surface waves dominate the heat transfer to a situation where hyperbolic modes completely govern the near-field thermal radiation. We show that this high tunability can be achieved with accessible magnetic fields and very common materials like n -doped InSb or Si. Our study paves the way for an active control of NFRHT and it opens the possibility to study unique hyperbolic thermal emitters without the need to resort to complicated metamaterials.

  14. Feasibility of EBT Gafchromic films for comparison exercises among standard beta radiation fields.

    PubMed

    Benavente, J A; Meira-Belo, L C; Reynaldo, S R; da Silva, T A

    2012-12-01

    The feasibility of using radiochromic films to verify the metrological coherence among standard beta radiation fields was evaluated. Exercises were done between two Brazilian metrology laboratories in beta fields from (90)Sr/(90)Y, (85)Kr and (147)Pm radiation sources. Results showed that the radiochromic film was useful for field mapping aiming uniformity and alignment verification and it was not reliable for absorbed dose measurements only for (147)Pm beta field. PMID:22917942

  15. Non-thermal continuous and modulated electromagnetic radiation fields effects on sleep EEG of rats.

    PubMed

    Mohammed, Haitham S; Fahmy, Heba M; Radwan, Nasr M; Elsayed, Anwar A

    2013-03-01

    In the present study, the alteration in the sleep EEG in rats due to chronic exposure to low-level non-thermal electromagnetic radiation was investigated. Two types of radiation fields were used; 900 MHz unmodulated wave and 900 MHz modulated at 8 and 16 Hz waves. Animals has exposed to radiation fields for 1 month (1 h/day). EEG power spectral analyses of exposed and control animals during slow wave sleep (SWS) and rapid eye movement sleep (REM sleep) revealed that the REM sleep is more susceptible to modulated radiofrequency radiation fields (RFR) than the SWS. The latency of REM sleep increased due to radiation exposure indicating a change in the ultradian rhythm of normal sleep cycles. The cumulative and irreversible effect of radiation exposure was proposed and the interaction of the extremely low frequency radiation with the similar EEG frequencies was suggested. PMID:25685416

  16. Practical method for evaluating the sound field radiated from a waveguide.

    PubMed

    Feng, Xuelei; Shen, Yong; Chen, Simiao; Zhao, Ye

    2015-01-01

    This letter presents a simple and practical method for evaluating the sound field radiated from a waveguide. By using the proposed method, detailed information about the radiated sound field can be obtained by measuring the sound field in the mouth of the baffled waveguide. To examine this method's effectiveness, the radiated sound pressure distribution in space was first evaluated by using the proposed method, and then it was measured directly for comparison. Experiments using two different waveguides showed good agreement between the evaluated and the measured radiated sound pressure distributions. PMID:25618097

  17. Voyager Encounters Saturn: Scientific Highlights

    NASA Technical Reports Server (NTRS)

    1980-01-01

    Observations generated by Voyager 1's encounter with Saturn are disclosed. Atmospheric conditions, the rings, new moons and the five inner moons are described. Titan, Hyperion and Iapetus are discussed in detail, as is Saturn's magnetosphere.

  18. 14 CFR 29.1317 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false High-intensity Radiated Fields (HIRF) Protection. 29.1317 Section 29.1317 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Equipment General § 29.1317 High-intensity Radiated Fields...

  19. 14 CFR 25.1317 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false High-intensity Radiated Fields (HIRF) Protection. 25.1317 Section 25.1317 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Equipment General § 25.1317 High-intensity Radiated Fields...

  20. 14 CFR 27.1317 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false High-intensity Radiated Fields (HIRF) Protection. 27.1317 Section 27.1317 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL CATEGORY ROTORCRAFT Equipment General § 27.1317 High-intensity Radiated Fields...

  1. 47 CFR 2.1053 - Measurements required: Field strength of spurious radiation.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 1 2014-10-01 2014-10-01 false Measurements required: Field strength of spurious radiation. 2.1053 Section 2.1053 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL... Procedures Certification § 2.1053 Measurements required: Field strength of spurious radiation....

  2. 47 CFR 2.1053 - Measurements required: Field strength of spurious radiation.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 1 2010-10-01 2010-10-01 false Measurements required: Field strength of spurious radiation. 2.1053 Section 2.1053 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL... Procedures Certification § 2.1053 Measurements required: Field strength of spurious radiation....

  3. 47 CFR 2.1053 - Measurements required: Field strength of spurious radiation.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 1 2012-10-01 2012-10-01 false Measurements required: Field strength of spurious radiation. 2.1053 Section 2.1053 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL... Procedures Certification § 2.1053 Measurements required: Field strength of spurious radiation....

  4. 47 CFR 2.1053 - Measurements required: Field strength of spurious radiation.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 1 2011-10-01 2011-10-01 false Measurements required: Field strength of spurious radiation. 2.1053 Section 2.1053 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL... Procedures Certification § 2.1053 Measurements required: Field strength of spurious radiation....

  5. 47 CFR 2.1053 - Measurements required: Field strength of spurious radiation.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 1 2013-10-01 2013-10-01 false Measurements required: Field strength of spurious radiation. 2.1053 Section 2.1053 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL... Procedures Certification § 2.1053 Measurements required: Field strength of spurious radiation....

  6. 14 CFR 25.1317 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false High-intensity Radiated Fields (HIRF) Protection. 25.1317 Section 25.1317 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Equipment General § 25.1317 High-intensity Radiated Fields...

  7. 14 CFR 25.1317 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false High-intensity Radiated Fields (HIRF) Protection. 25.1317 Section 25.1317 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Equipment General § 25.1317 High-intensity Radiated Fields...

  8. 14 CFR 27.1317 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false High-intensity Radiated Fields (HIRF) Protection. 27.1317 Section 27.1317 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL CATEGORY ROTORCRAFT Equipment General § 27.1317 High-intensity Radiated Fields...

  9. 14 CFR 27.1317 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false High-intensity Radiated Fields (HIRF) Protection. 27.1317 Section 27.1317 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL CATEGORY ROTORCRAFT Equipment General § 27.1317 High-intensity Radiated Fields...

  10. 14 CFR 29.1317 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false High-intensity Radiated Fields (HIRF) Protection. 29.1317 Section 29.1317 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Equipment General § 29.1317 High-intensity Radiated Fields...

  11. 14 CFR 29.1317 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false High-intensity Radiated Fields (HIRF) Protection. 29.1317 Section 29.1317 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Equipment General § 29.1317 High-intensity Radiated Fields...

  12. 14 CFR 25.1317 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false High-intensity Radiated Fields (HIRF) Protection. 25.1317 Section 25.1317 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Equipment General § 25.1317 High-intensity Radiated Fields...

  13. 14 CFR 27.1317 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false High-intensity Radiated Fields (HIRF) Protection. 27.1317 Section 27.1317 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL CATEGORY ROTORCRAFT Equipment General § 27.1317 High-intensity Radiated Fields...

  14. 14 CFR 27.1317 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false High-intensity Radiated Fields (HIRF) Protection. 27.1317 Section 27.1317 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL CATEGORY ROTORCRAFT Equipment General § 27.1317 High-intensity Radiated Fields...

  15. 14 CFR 25.1317 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false High-intensity Radiated Fields (HIRF) Protection. 25.1317 Section 25.1317 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Equipment General § 25.1317 High-intensity Radiated Fields...

  16. 14 CFR 29.1317 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false High-intensity Radiated Fields (HIRF) Protection. 29.1317 Section 29.1317 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Equipment General § 29.1317 High-intensity Radiated Fields...

  17. 14 CFR 29.1317 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false High-intensity Radiated Fields (HIRF) Protection. 29.1317 Section 29.1317 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Equipment General § 29.1317 High-intensity Radiated Fields...

  18. Characteristics of block-periodic phased-array antennas with circular polarization of the radiated field

    NASA Astrophysics Data System (ADS)

    Likhoded, Iu. V.; Mironnikov, A. S.

    1990-02-01

    The paper presents results of a numerical investigation of the directivity characteristics of a block-periodic waveguide phased-array antenna with circular polarization of the radiated field. The advantages of this array from the viewpoint of maximining the ellipticity coefficent of the radiated field in the scanning sector are pointed out.

  19. Radiation dose optimized lateral expansion of the field of view in synchrotron radiation X-ray tomographic microscopy

    PubMed Central

    Haberthür, David; Hintermüller, Christoph; Marone, Federica; Schittny, Johannes C.; Stampanoni, Marco

    2010-01-01

    Volumetric data at micrometer level resolution can be acquired within a few minutes using synchrotron-radiation-based tomographic microscopy. The field of view along the rotation axis of the sample can easily be increased by stacking several tomograms, allowing the investigation of long and thin objects at high resolution. On the contrary, an extension of the field of view in the perpendicular direction is non-trivial. This paper presents an acquisition protocol which increases the field of view of the tomographic dataset perpendicular to its rotation axis. The acquisition protocol can be tuned as a function of the reconstruction quality and scanning time. Since the scanning time is proportional to the radiation dose imparted to the sample, this method can be used to increase the field of view of tomographic microscopy instruments while optimizing the radiation dose for radiation-sensitive samples and keeping the quality of the tomographic dataset on the required level. This approach, dubbed wide-field synchrotron radiation tomographic microscopy, can increase the lateral field of view up to five times. The method has been successfully applied for the three-dimensional imaging of entire rat lung acini with a diameter of 4.1 mm at a voxel size of 1.48 µm. PMID:20724780

  20. Comparative investigation of three dose rate meters for their viability in pulsed radiation fields.

    PubMed

    Gotz, M; Karsch, L; Pawelke, J

    2015-06-01

    Pulsed radiation fields, characterized by microsecond pulse duration and correspondingly high pulse dose rates, are increasingly used in therapeutic, diagnostic and research applications. Yet, dose rate meters which are used to monitor radiation protection areas or to inspect radiation shielding are mostly designed, characterized and tested for continuous fields and show severe deficiencies in highly pulsed fields. Despite general awareness of the problem, knowledge of the specific limitations of individual instruments is very limited, complicating reliable measurements. We present here the results of testing three commercial dose rate meters, the RamION ionization chamber, the LB 1236-H proportional counter and the 6150AD-b scintillation counter, for their response in pulsed radiation fields of varied pulse dose and duration. Of these three the RamION proved reliable, operating in a pulsed radiation field within its specifications, while the other two instruments were only able to measure very limited pulse doses and pulse dose rates reliably. PMID:25978117

  1. Estimating the Reliability of Electronic Parts in High Radiation Fields

    NASA Technical Reports Server (NTRS)

    Everline, Chester; Clark, Karla; Man, Guy; Rasmussen, Robert; Johnston, Allan; Kohlhase, Charles; Paulos, Todd

    2008-01-01

    Radiation effects on materials and electronic parts constrain the lifetime of flight systems visiting Europa. Understanding mission lifetime limits is critical to the design and planning of such a mission. Therefore, the operational aspects of radiation dose are a mission success issue. To predict and manage mission lifetime in a high radiation environment, system engineers need capable tools to trade radiation design choices against system design and reliability, and science achievements. Conventional tools and approaches provided past missions with conservative designs without the ability to predict their lifetime beyond the baseline mission.This paper describes a more systematic approach to understanding spacecraft design margin, allowing better prediction of spacecraft lifetime. This is possible because of newly available electronic parts radiation effects statistics and an enhanced spacecraft system reliability methodology. This new approach can be used in conjunction with traditional approaches for mission design. This paper describes the fundamentals of the new methodology.

  2. Characterisation of three high-energy photon and fast neutron reference radiation fields.

    PubMed

    Behrens, R; Röttger, S

    2008-01-01

    Three reference radiation fields for the purpose of radiation protection were characterised: (1) radiation field R-F, consisting of photons in the energy range of about 6 and 7 MeV and a small neutron contamination; (2) radiation field R-C, consisting of photons with energies of about 4.4 MeV and neutrons with energies up to 2.65 MeV; (3) radiation field R-CF, consisting of photons in the energy range of about 1 and 7 MeV and neutrons with energies about 1.5 MeV. The radiation fields R-F and R-C have previously been defined in the ISO standard 4037. Their neutron components, however, have never been described accurately in the past. The new radiation field R-CF is proposed for the first time. This radiation field can, e.g., be used to calibrate tissue-equivalent proportional counters instruments for measurements at flight altitudes. PMID:19131379

  3. ESTIMATING SOLAR RADIATION EXPOSURE IN WETLANDS USING RADIATION MODELS, FIELD DATA, AND GEOGRAPHIC INFORMATION SYSTEMS

    EPA Science Inventory

    This seminar will describe development of methods for the estimation of solar radiation doses in wetlands. The methodology presents a novel approach to incorporating aspects of solar radiation dosimetry that have historically received limited attention. These include effects of a...

  4. BINARY ASTEROID ENCOUNTERS WITH TERRESTRIAL PLANETS: TIMESCALES AND EFFECTS

    SciTech Connect

    Fang, Julia; Margot, Jean-Luc

    2012-01-15

    Many asteroids that make close encounters with terrestrial planets are in a binary configuration. Here, we calculate the relevant encounter timescales and investigate the effects of encounters on a binary's mutual orbit. We use a combination of analytical and numerical approaches with a wide range of initial conditions. Our test cases include generic binaries with close, moderate, and wide separations, as well as seven well-characterized near-Earth binaries. We find that close approaches (<10 Earth radii) occur for almost all binaries on 1-10 million year timescales. At such distances, our results suggest substantial modifications to a binary's semimajor axis, eccentricity, and inclination, which we quantify. Encounters within 30 Earth radii typically occur on sub-million year timescales and significantly affect the wider binaries. Important processes in the lives of near-Earth binaries, such as tidal and radiative evolution, can be altered or stopped by planetary encounters.

  5. Guest-Host Encounters in Diaspora-Heritage Tourism: The Taglit-Birthright Israel Mifgash (Encounter)

    ERIC Educational Resources Information Center

    Sasson, Theodore; Mittelberg, David; Hecht, Shahar; Saxe, Leonard

    2011-01-01

    More than 300,000 diaspora Jewish young adults and tens of thousands of their Israeli peers have participated in structured, cross-cultural encounters--"mifgashim"--in the context of an experiential education program known as Taglit-Birthright Israel. Drawing on field observations, interviews, and surveys, the formal and informal components of the…

  6. Graphene-assisted near-field radiative heat transfer between corrugated polar materials

    SciTech Connect

    Liu, X. L.; Zhang, Z. M.

    2014-06-23

    Graphene has attracted great attention in nanoelectronics, optics, and energy harvesting. Here, the near-field radiative heat transfer between graphene-covered corrugated silica is investigated based on the exact scattering theory. It is found that graphene can improve the radiative heat flux between silica gratings by more than one order of magnitude and alleviate the performance sensitivity to lateral shift. The underlying mechanism is mainly attributed to the improved photon tunneling of modes away from phonon resonances. Besides, coating with graphene leads to nonlocal radiative transfer that breaks Derjaguin's proximity approximation and enables corrugated silica to outperform bulk silica in near-field radiation.

  7. Predicting the Earth encounters of (99942) Apophis

    NASA Technical Reports Server (NTRS)

    Giorgini, Jon D.; Benner, Lance A. M.; Ostro, Steven J.; Nolan, Michael C.; Busch, Michael W.

    2007-01-01

    Arecibo delay-Doppler measurements of (99942) Apophis in 2005 and 2006 resulted in a five standard-deviation trajectory correction to the optically predicted close approach distance to Earth in 2029. The radar measurements reduced the volume of the statistical uncertainty region entering the encounter to 7.3% of the pre-radar solution, but increased the trajectory uncertainty growth rate across the encounter by 800% due to the closer predicted approach to the Earth. A small estimated Earth impact probability remained for 2036. With standard-deviation plane-of-sky position uncertainties for 2007-2010 already less than 0.2 arcsec, the best near-term ground-based optical astrometry can only weakly affect the trajectory estimate. While the potential for impact in 2036 will likely be excluded in 2013 (if not 2011) using ground-based optical measurements, approximations within the Standard Dynamical Model (SDM) used to estimate and predict the trajectory from the current era are sufficient to obscure the difference between a predicted impact and a miss in 2036 by altering the dynamics leading into the 2029 encounter. Normal impact probability assessments based on the SDM become problematic without knowledge of the object's physical properties; impact could be excluded while the actual dynamics still permit it. Calibrated position uncertainty intervals are developed to compensate for this by characterizing the minimum and maximum effect of physical parameters on the trajectory. Uncertainty in accelerations related to solar radiation can cause between 82 and 4720 Earth-radii of trajectory change relative to the SDM by 2036. If an actionable hazard exists, alteration by 2-10% of Apophis' total absorption of solar radiation in 2018 could be sufficient to produce a six standard-deviation trajectory change by 2036 given physical characterization; even a 0.5% change could produce a trajectory shift of one Earth-radius by 2036 for all possible spin-poles and likely masses

  8. Computation of radiative fields in opposed-flow flame spread in a microgravity environment

    NASA Astrophysics Data System (ADS)

    Villaraza, Jeanie Ray P.

    The purpose of this thesis is to perform radiation computations in opposed-flow flame spread in a microgravity environment. In this work, the flame spread simulations consider a thermally thin, PMMA fuel in a quiescent, microgravity environment or facing low opposed-flow velocities at ambient conditions of 1 atm and 50-50 volumetric mixture of oxygen and nitrogen. The flame spread model, which is a Computational Fluid Dynamics (CFD) model, is used for numerical simulations in combination with a radiation model. The CFD code is written in FORTRAN language, and a Matlab code is developed for plotting results. The temperature and species fields from CFD computations are used as inputs into the radiation model. Radiative quantities are calculated by using a global balance method along with the total transmittance non-homogeneous model. Radiation effect on thermocouple temperature measurement is investigated. Although this topic is well known, performing radiation correction calculations usually considers surface radiation only and not gas radiation. The inclusion of gas radiation is utilized in predicting the gas temperature that a thermocouple would measure. A narrow bed radiation model is used to determine the average incident radiative flux at a specified location from which a thermocouple temperature measurement is predicted. This study focuses on the quiescent microgravity environment only. The effect of parameters such as thermocouple surface emissivity and bead diameter are also studied. For the main part of this thesis, the effect of gas radiation on the mechanism of flame spread over a thermally thin, solid fuel in microgravity is investigated computationally. Generated radiative fields including thermal and species fields are utilized to investigate the nature of the influence of gas radiation on flame structure as well as its role in the mechanism of opposed-flow flame spread. The opposed-flow configuration considers low flow velocities including a quiescent

  9. Near-field radiative thermal control with graphene covered on different materials

    NASA Astrophysics Data System (ADS)

    Wang, Ao; Zheng, Zhiheng; Xuan, Yimin

    2016-09-01

    Based on the structure of double-layer parallel plates, this paper demonstrates that thermal radiation in near field is greatly enhanced due to near-field effects, exceeding Planck‧s blackbody radiation law. To study the effect of graphene on thermal radiation in near field, the authors add graphene layer into the structure and analyze the ability of graphene to control near-field thermal radiation with different materials. The result indicates that the graphene layer effectively suppresses the near-field thermal radiation between metal plates or polar-dielectric plates, having good ability of thermal insulation. But for doped-silicon plates, depending on the specific models, graphene has different control abilities, suppressing or enhancing, and the control abilities mainly depend on the material graphene is attached to. The authors also summarize some common rules about the different abilities of graphene to control the near-field thermal radiation. In consideration of the thickness of 0.34 nm of monolayer graphene, this paper points out that graphene plays a very important role in controlling the near-field thermal radiation.

  10. Considerations concerning the use of counting active personal dosimeters in pulsed fields of ionising radiation.

    PubMed

    Ambrosi, Peter; Borowski, Markus; Iwatschenko, Michael

    2010-06-01

    Active personal electronic dosimeters (APDs) exhibit limitations in pulsed radiation fields, which cannot be overcome without the use of new detection technology. As an interim solution, this paper proposes a method by which some conventional dosimeters can be operated in a way such that, based on the basic knowledge about the pulsed radiation field, any dosimetric failure of the dosimeter is signalised by the instrument itself. This method is not applicable to all combinations of APD and pulsed radiation field. The necessary requirements for the APD and for the parameters of the pulsed radiation field are given in the paper. Up to now, all such requirements for APDs have not been tested or verified in a type test. The suitability of the method is verified for the use of one APD used in two clinical pulsed fields. PMID:20083488

  11. Magnetic field effects on THz radiation from rectangular shape Bi2212 IJJ’s

    NASA Astrophysics Data System (ADS)

    Yamaki, Kazuhiro; Tsujimoto, Manabu; Yamamoto, Takashi; Minami, Hidetoshi; Kadowaki, Kazuo

    2010-12-01

    The effects of magnetic field on terahertz radiation emitted from the rectangular mesa of intrinsic Josephson junctions (IJJ’s) made of Bi2212 single crystals were studied up to 150 Oe. Strong suppression of the radiation power was observed when magnetic field was applied to the c-axis of the sample, while in the case of H//ab-plane, the radiation power showed a weak and broad peak in the weak field region (˜50 Oe), then it decreased and diminished around 150 Oe. These magnetic field effects are interpreted by the strong influence of magnetic field on the I-V curve, which set up the condition for the THz radiation.

  12. Scatter radiation intensities around full-field digital mammography units.

    PubMed

    Judge, M A; Keavey, E; Phelan, N

    2013-01-01

    The aim of this study was to investigate the scatter radiation intensity around digital mammography systems and apply these data to standard shielding calculations to reveal whether shielding design of existing breast screening rooms is adequate for the use of digital mammography systems. Three digital mammography systems from GE Healthcare, Hologic and Philips were employed in the study. A breast-equivalent phantom was imaged under clinical workload conditions and scatter radiation intensities around the digital mammography systems were measured for a range of angles in three planes using an ionisation chamber. The results were compared with those from previous studies of film-screen systems. It may be deduced from the results that scattering in the backward direction is significant for all three systems, while scattering in the forward direction can be significant for some planes around the GE and Hologic systems. Measurements at typical clinical settings on each system revealed the Philips system to have markedly lower scatter radiation intensities than the other systems. Substituting the measured scattered radiation intensity into shielding calculations yielded barrier requirements similar to those already in place at the screening centres operating these systems. Current radiation protection requirements based on film-screen technology remain sufficient when applied to rooms with digital mammography installations and no alteration is required to the structural shielding. PMID:23239693

  13. Reduction of the Background Magnetic Field Inhibits Ability of Drosophila melanogaster to Survive Ionizing Radiation

    PubMed Central

    Portelli, Lucas; Madapatha, Dinu; Martino, Carlos; Hernandez, Mark; Barnes, Frank

    2012-01-01

    The effects of exposure to an environment where the background magnetic field has been reduced were studied on wild-type Drosophila melanogaster by measuring its ability to survive a single exposure to ionizing radiation during its larval stage. The experimental design presented shows a timeframe, ionizing radiation dose and background magnetic field parameters that will cause a significant and reproducible reduction of survival on this insect model. These results suggest that background magnetic fields may play a fundamental role in the recovery or harm of a biological system that is exposed to single doses of ionizing radiation. PMID:22532126

  14. Voyager 1 encounters new region of space

    NASA Astrophysics Data System (ADS)

    Zielinski, Sarah

    2006-10-01

    Voyager 1, which left Earth in 1977 and is now about 10 billion miles away, has entered a region of space with strange anomalies, according to project scientist Ed Stone, former director of the Jet Propulsion Laboratory. The spacecraft has encountered magnetic potholes and bumps-areas where the magnetic field of the heliosheath either nearly vanishes or doubles, respectively. It also has encountered `anomalous cosmic rays' that are less energetic, and thus less dangerous, than galactic cosmic rays. In addition, the solar wind in the heliosheath has been slower than scientists had expected, only about 54,700 kilometers per hour compared with the predicted 322,000-483,000 kilometers per hour. Voyager 1 is expected to reach the edge of the heliosheath in about 10 years.

  15. Radiation fields from neutron generators shielded with different materials

    NASA Astrophysics Data System (ADS)

    Chichester, D. L.; Blackburn, B. W.

    2007-08-01

    As a general guide for assessing radiological conditions around a DT neutron generator numerical modeling has been performed to assess neutron and photon dose profiles for a variety of shield materials ranging from 1 to 100 cm thick. In agreement with accepted radiation safety practices high-Z materials such as bismuth and lead have been found to be ineffective biological shield materials, owing in part to the existence of (n,2n) reaction channels available with 14.1 MeV DT neutrons, while low-Z materials serve as effective shields for these sources. Composite materials such as a mixture of polyethylene and bismuth, or regular concrete, are ideal shield materials for neutron generator radiation because of their ability to attenuate internally generated photon radiation resulting from neutron scattering and capture within the shields themselves.

  16. Stability of a liquid-film space radiator with internal electrostatic fields

    SciTech Connect

    Bankoff, S.G.; Miksis, M.J.

    1992-04-01

    A new concept in light-weight space radiators has been introduced by Kim, Miksis and Bankoff, consisting of a pumped-loop membrane radiator in which leakage of coolant from a puncture, due to micrometeorite or space debris impact, is prevented by the application of an internal electrostatic field. For nuclear space power, the coolant is generally a liquid metal, such as lithium, flowing as a thin film along the interior walls of the hollow radiator. A lightweight fully-modular radiator design is proposed, which is calculated to weight less than 1 kg/m{sup 2}. The feature which makes this thin-membrane radiator practical is the internal electrostatic field system, which can stop radiator leaks from punctures, sudden accelerations or accidental tears.

  17. Raman distributed temperature measurement at CERN high energy accelerator mixed field radiation test facility (CHARM)

    NASA Astrophysics Data System (ADS)

    Toccafondo, Iacopo; Nannipieri, Tiziano; Signorini, Alessandro; Guillermain, Elisa; Kuhnhenn, Jochen; Brugger, Markus; Di Pasquale, Fabrizio

    2015-09-01

    In this paper we present a validation of distributed Raman temperature sensing (RDTS) at the CERN high energy accelerator mixed field radiation test facility (CHARM), newly developed in order to qualify electronics for the challenging radiation environment of accelerators and connected high energy physics experiments. By investigating the effect of wavelength dependent radiation induced absorption (RIA) on the Raman Stokes and anti-Stokes light components in radiation tolerant Ge-doped multi-mode (MM) graded-index optical fibers, we demonstrate that Raman DTS used in loop configuration is robust to harsh environments in which the fiber is exposed to a mixed radiation field. The temperature profiles measured on commercial Ge-doped optical fibers is fully reliable and therefore, can be used to correct the RIA temperature dependence in distributed radiation sensing systems based on P-doped optical fibers.

  18. Dialogic Encounters as Art Education

    ERIC Educational Resources Information Center

    Miles, Adetty Perez

    2010-01-01

    Although educators believe in the importance of dialogue and dialogic encounters, and often propose to engage their students in "discussion," dialogic communication is rarely used in the classroom. Rather than through relational and substantive conversation, most educational dialogue in public schools is limited to telling, asking one-way…

  19. A Lakatosian Encounter with Probability

    ERIC Educational Resources Information Center

    Chick, Helen

    2010-01-01

    There is much to be learned and pondered by reading "Proofs and Refutations" by Imre Lakatos (Lakatos, 1976). It highlights the importance of mathematical definitions, and how definitions evolve to capture the essence of the object they are defining. It also provides an exhilarating encounter with the ups and downs of the mathematical reasoning…

  20. Mixed-radiation-field dosimetry utilizing Nuclear Quadrupole Resonance

    SciTech Connect

    Hintenlang, D.E.; Jamil, K.; Iselin, L.H.

    1992-01-01

    Radiation effects on urea, thiourea, guanidine carbonate and guanine sulfate were evaluated for both photon and neutron irradiations. Hydration of these materials typically provides a greatly increased sensitivity to both forms of radiation exposure, although not all materials lend themselves to this treatment without changing the chemical structure of the compound. Urea was found to be the most stable hydrated compound and provides the best sensitivity for quantifying radiation effects using NQR techniques. Urea permits a straight-forward quantification of each of the important parameters of the observed NQR signal, the FID. Several advanced data analysis methods were developed to assist in quantifying NQR spectra, both from urea and materials having more complex molecular structures, such as thiourea and guanidine sulfate. Unfortunately, these analysis techniques are frequently quite time consuming for the complex NQR spectra that result from some of these materials. The simpler analysis afforded by urea has therefore made it the prime candidate for an NQR dosimetry material. The moderate sensitivity of hydrated urea to photon irradiation does not permit this material to achieve the levels of performance required for a personnel dosimeter. It does, however, demonstrate acceptable sensitivity over dose ranges where it could provide a good biological dosimeter for several areas of radiation processing. The demonstrated photon sensitivity could permit hydrated urea to be used in applications such as food irradiation dosimetry. This material also exhibits a good sensitivity to neutron irradiation. The precise correlation between neutron exposure and the parameters of the resulting NQR spectra are currently being developed.

  1. Evaluation of the impact of non-uniform neutron radiation fields on the dose received by glove box radiation workers

    NASA Astrophysics Data System (ADS)

    Crawford, Arthur Bryan

    The effort to estimate the radiation dose received by an occupationally exposed worker is a complex task. Regulatory guidance assumes that the stochastic risks from uniform and non-uniform whole-body irradiations are equal. An ideal uniform irradiation of the whole body would require a broad parallel radiation field of relatively high-energy radiation, which many occupationally exposed workers do not experience. In reality, workers are exposed to a non-uniform irradiation of the whole body such as a radiation field with one or more types of radiation, each with varying energies and/or fluence rates, incident on the worker. Most occupational radiation exposure at LANL is due to neutron radiation. Many of these exposures originate from activities performed in glove boxes with nuclear materials. A standard Los Alamos 2 x 2 x 2 glove box is modeled with the source material being clean weapons grade plutonium. Dosimeter tally planes were modeled to stimulate the various positions that a dosimeter can be worn. An anthropomorphic phantom was used to determine whole body dose. Various geometries of source position and phantom location were used to determine the effects of streaming on the radiation dose a worker may receive. Based on computational and experimental results, the effects of a non-uniform radiation field have on radiation dose received by a worker in a glove box environment are: (1) Dosimeter worn at chest level can overestimate the whole body dose between a factor of two to six depending on location of the phantom with the source material close to the front of the glove box, (2) Dosimeter should be worn at waist level instead of chest level to more accurately reflect the whole body dose received, (3) Dose can be significantly higher for specific locations of the worker relative to the position of the source, (4) On the average the testes contribute almost 44% of the whole body dose for a male, and (5) Appropriate design considerations such as more shielding

  2. Quantum radiation of Maxwell’s electromagnetic field in nonstationary Kerr-de Sitter black hole

    NASA Astrophysics Data System (ADS)

    Ibungochouba Singh, T.; Ablu Meitei, I.; Yugindro Singh, K.

    2016-03-01

    Quantum radiation properties of nonstationary Kerr-de Sitter (KdS) black hole is investigated using the method of generalized tortoise coordinate transformation. The locations of horizons and the temperature of the thermal radiation as well as the maximum energy of the nonthermal radiation are derived. It is found that the surface gravity and the Hawking temperature depend on both time and different angles. An extra coupling effect is obtained in the thermal radiation spectrum of Maxwell’s electromagnetic field equations which is absent in the thermal radiation spectrum of scalar particles. Further, the chemical potential derived from the thermal radiation spectrum of scalar particle has been found to be equal to the highest energy of the negative energy state of the scalar particle in the nonthermal radiation for KdS black hole. It is also shown that the generalized tortoise coordinate transformation produces a constant term in the expression of the surface gravity and Hawking temperature.

  3. Low-Cost Shielding to Minimize Radiation Errors of Temperature Sensors in the Field

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The importance of shielding temperature sensors from solar radiation is understood, but there is a lack of prescriptive advice for plant scientists to build inexpensive, effective shields for replicated field experiments. Using general physical principles that govern radiation shielding, a number of...

  4. Near-field imaging and nano-Fourier-transform infrared spectroscopy using broadband synchrotron radiation.

    PubMed

    Hermann, Peter; Hoehl, Arne; Patoka, Piotr; Huth, Florian; Rühl, Eckart; Ulm, Gerhard

    2013-02-11

    We demonstrate scanning near-field optical microscopy with a spatial resolution below 100 nm by using low intensity broadband synchrotron radiation in the IR regime. The use of such a broadband radiation source opens up the possibility to perform nano-Fourier-transform infrared spectroscopy over a wide spectral range. PMID:23481749

  5. Attenuation of VHE Gamma Rays by the Milky Way Interstellar Radiation Field

    SciTech Connect

    Moskalenko, Igor V.; Porter, Troy A.; Strong, Andrew W.; /Garching, Max Planck Inst., MPE

    2006-04-19

    The attenuation of very high energy gamma rays by pair production on the Galactic interstellar radiation field has long been thought of as negligible. However, a new calculation of the interstellar radiation field consistent with multi-wavelength observations by DIRBE and FIRAS indicates that the energy density of the Galactic interstellar radiation field is higher, particularly in the Galactic center, than previously thought. We have made a calculation of the attenuation of very high energy gamma rays in the Galaxy using this new interstellar radiation field which takes into account its nonuniform spatial and angular distributions. We find that the maximum attenuation occurs around 100 TeV at the level of about 25% for sources located at the Galactic center, and is important for both Galactic and extragalactic sources.

  6. The effects of emitter-tied field plates on lateral PNP ionizing radiation response

    SciTech Connect

    Barnaby, H.J.; Schrimpf, R.D.; Cirba, C.R.; Pease, R.L.; Fleetwood, D.M.; Kosier, S.L.

    1998-03-01

    Radiation response comparisons of lateral PNP bipolar technologies reveal that device hardening may be achieved by extending the emitter contact over the active base. The emitter-tied field plate suppresses recombination of carriers with interface traps.

  7. Time-dependent and radiation field effects on collisional-radiative simulations of radiative properties of blast waves launched in clusters of xenon

    NASA Astrophysics Data System (ADS)

    Rodriguez, R.; Espinosa, G.; Gil, J. M.; Rubiano, J. G.; Mendoza, M. A.; Martel, P.; Minguez, E.; Symes, D. R.; Hohenberger, M.; Smith, R. A.

    2015-12-01

    Radiative shock waves are ubiquitous throughout the universe and play a crucial role in the transport of energy into the interstellar medium. This fact has led to many efforts to scale the astrophysical phenomena to accessible conditions. In some laboratory experiments radiative blast waves are launched in clusters of gases by means of the direct deposition of the laser energy. In this work, by using a collisional-radiative model, we perform an analysis of the plasma level populations and radiative properties of a blast wave launched in a xenon cluster. In particular, for both the shocked and unshocked material, we study the influence of different effects such as LTE, steady-state or time-dependent NLTE simulations, plasma self-absorption or external radiation field in the determination of those properties and also in the diagnosis of the electron temperature of the blast wave.

  8. Heat flux splitter for near-field thermal radiation

    SciTech Connect

    Ben-Abdallah, P.; Belarouci, A.; Frechette, L.; Biehs, S.-A.

    2015-08-03

    We demonstrate the possibility to efficiently split the near-field heat flux exchanged between graphene nano-disks by tuning their doping. This result paves the way for the development of an active control of propagation directions for heat fluxes exchanged in the near field throughout integrated nanostructured networks.

  9. Radiative Neutron β-Decay in Effective Field Theory

    PubMed Central

    Gardner, Susan; Bernard, Véronique; Meißner, Ulf-G.; Zhang, Chi

    2005-01-01

    We consider radiative β-decay of the neutron in heavy baryon chiral perturbation theory. Nucleon-structure effects not encoded in the weak coupling constants gA and gV are determined at next-to-leading order in the chiral expansion, and enter at the O(0.5%)-level, making a sensitive test of the Dirac structure of the weak currents possible. PMID:27308159

  10. Strong-Field Perspective on High-Harmonic Radiation from Bulk Solids

    NASA Astrophysics Data System (ADS)

    Higuchi, Takuya; Stockman, Mark I.; Hommelhoff, Peter

    2014-11-01

    Mechanisms of high-harmonic generation from crystals are described by treating the electric field of a laser as a quasistatic strong field. Under the quasistatic electric field, electrons in periodic potentials form dressed states, known as Wannier-Stark states. The energy differences between the dressed states determine the frequencies of the radiation. The radiation yield is determined by the magnitudes of the interband and intraband current matrix elements between the dressed states. The generation of attosecond pulses from solids is predicted. Ramifications for strong-field physics are discussed.

  11. Analysis of the failures and corrective actions for the LHC cryogenics radiation tolerant electronics and its field instruments

    SciTech Connect

    Balle, Christoph; Casas, Juan; Vauthier, Nicolas

    2014-01-29

    The LHC cryogenic system radiation tolerant electronics and their associated field instruments have been in nominal conditions since before the commissioning of the first LHC beams in September 2008. This system is made of about 15’000 field instruments (thermometers, pressure sensors, liquid helium level gauges, electrical heaters and position switches), 7’500 electronic cards and 853 electronic crates. Since mid-2008 a software tool has been deployed, this allows an operator to report a problem and then lists the corrective actions. The tool is a great help in detecting recurrent problems that may be tackled by a hardware or software consolidation. The corrective actions range from simple resets, exchange of defective equipment, repair of electrical connectors, etc. However a recurrent problem that heals by itself is present on some channels. This type of fault is extremely difficult to diagnose and it appears as a temporary opening of an electrical circuit; its duration can range from a few minutes to several months. This paper presents the main type of problems encountered during the last four years, their evolution over time, the various hardware or software consolidations that have resulted and whether they have had an impact in the availability of the LHC beam.

  12. Axial acoustic radiation force on a sphere in Gaussian field

    SciTech Connect

    Wu, Rongrong; Liu, Xiaozhou Gong, Xiufen

    2015-10-28

    Based on the finite series method, the acoustical radiation force resulting from a Gaussian beam incident on a spherical object is investigated analytically. When the position of the particles deviating from the center of the beam, the Gaussian beam is expanded as a spherical function at the center of the particles and the expanded coefficients of the Gaussian beam is calculated. The analytical expression of the acoustic radiation force on spherical particles deviating from the Gaussian beam center is deduced. The acoustic radiation force affected by the acoustic frequency and the offset distance from the Gaussian beam center is investigated. Results have been presented for Gaussian beams with different wavelengths and it has been shown that the interaction of a Gaussian beam with a sphere can result in attractive axial force under specific operational conditions. Results indicate the capability of manipulating and separating spherical spheres based on their mechanical and acoustical properties, the results provided here may provide a theoretical basis for development of single-beam acoustical tweezers.

  13. Radiation Isotope Identification Device (RIIDs) Field Test and Evaluation Campaign

    SciTech Connect

    Christopher Hodge, Raymond Keegan

    2007-08-01

    Handheld, backpack, and mobile sensors are elements of the Global Nuclear Detection System for the interdiction and control of illicit radiological and nuclear materials. They are used by the U.S. Department of Homeland Security (DHS) and other government agencies and organizations in various roles for border protection, law enforcement, and nonproliferation monitoring. In order to systematically document the operational performance of the common commercial off-the-shelf portable radiation detection systems, the DHS Domestic Nuclear Detection Office conducted a test and evaluation campaign conducted at the Nevada Test Site from January 18 to February 27, 2006. Named 'Anole', it was the first test of its kind in terms of technical design and test complexities. The Anole test results offer users information for selecting appropriate mission-specific portable radiation detection systems. The campaign also offered manufacturers the opportunity to submit their equipment for independent operationally relevant testing to subsequently improve their detector performance. This paper will present the design, execution, and methodologies of the DHS Anole portable radiation detection system test campaign.

  14. ANOLE Portable Radiation Detection System Field Test and Evaluation Campaign

    SciTech Connect

    Chris A. Hodge

    2007-07-12

    Handheld, backpack, and mobile sensors are elements of the Global Nuclear Detection System for the interdiction and control of illicit radiological and nuclear materials. They are used by the U.S. Department of Homeland Security (DHS) and other government agencies and organizations in various roles for border protection, law enforcement, and nonproliferation monitoring. In order to systematically document the operational performance of the common commercial off-the-shelf portable radiation detection systems, the DHS Domestic Nuclear Detection Office conducted a test and evaluation campaign conducted at the Nevada Test Site from January 18 to February 27, 2006. Named “Anole,” it was the first test of its kind in terms of technical design and test complexities. The Anole test results offer users information for selecting appropriate mission-specific portable radiation detection systems. The campaign also offered manufacturers the opportunity to submit their equipment for independent operationally relevant testing to subsequently improve their detector performance. This paper will present the design, execution, and methodologies of the DHS Anole portable radiation detection system test campaign.

  15. Electric-field distribution near rectangular microstrip radiators for hyperthermia heating: theory versus experiment in water.

    PubMed

    Underwood, H R; Peterson, A F; Magin, R L

    1992-02-01

    A rectangular microstrip antenna radiator is investigated for its near-zone radiation characteristics in water. Calculations of a cavity model theory are compared with the electric-field measurements of a miniature nonperturbing diode-dipole E-field probe whose 3 mm tip was positioned by an automatic three-axis scanning system. These comparisons have implications for the use of microstrip antennas in a multielement microwave hyperthermia applicator. Half-wavelength rectangular microstrip patches were designed to radiate in water at 915 MHz. Both low (epsilon r = 10) and high (epsilon r = 85) dielectric constant substrates were tested. Normal and tangential components of the near-zone radiated electric field were discriminated by appropriate orientation of the E-field probe. Low normal to transverse electric-field ratios at 3.0 cm depth indicate that the radiators may be useful for hyperthermia heating with an intervening water bolus. Electric-field pattern addition from a three-element linear array of these elements in water indicates that phase and amplitude adjustment can achieve some limited control over the distribution of radiated power. PMID:1612617

  16. Electric-field distribution near rectangular microstrip radiators for hyperthermia heating: Theory versus experiment in water

    SciTech Connect

    Underwood, H.R. ); Peterson, A.F. ); Magin, R.L. )

    1992-02-01

    A rectangular microstrip antenna radiator is investigated for its near-zone radiation characteristics in water. Calculations of a cavity model theory are compared with the electric-field measurements of a miniature nonperturbing diode dipole E-field probe whose 3 mm tip was positioned by an automatic three-axis scanning system. These comparisons have implications for the use of microstrip antennas in a multielement microwave hyperthermia applicator. Half-wavelength rectangular microstrip patches were designed to radiate in water at 915 MHz. Both low ([epsilon][sub r] = 10) and high ([epsilon][sub r] = 85) dielectric constant substrates were tested. Normal and tangential components of the near-zone radiated electric field were discriminated by appropriate orientation of the E-field probe. Low normal to transverse electric-field ratios ar 3.0 cm depth indicate that the radiators may be useful for hyperthermia heating with an intervening water bolus. Electric-field pattern addition from a three-element linear array of these elements in water indicates that phase and amplitude adjustment can achieve some limited control over the distribution of radiated power.

  17. Effects of external radiation fields on line emission—application to star-forming regions

    SciTech Connect

    Chatzikos, Marios; Ferland, G. J.; Williams, R. J. R.; Porter, Ryan; Van Hoof, P. A. M.

    2013-12-20

    A variety of astronomical environments contain clouds irradiated by a combination of isotropic and beamed radiation fields. For example, molecular clouds may be irradiated by the isotropic cosmic microwave background, as well as by a nearby active galactic nucleus. These radiation fields excite atoms and molecules and produce emission in different ways. We revisit the escape probability theorem and derive a novel expression that accounts for the presence of external radiation fields. We show that when the field is isotropic the escape probability is reduced relative to that in the absence of external radiation. This is in agreement with previous results obtained under ad hoc assumptions or with the two-level system, but can be applied to complex many-level models of atoms or molecules. This treatment is in the development version of the spectral synthesis code CLOUDY. We examine the spectrum of a Spitzer cloud embedded in the local interstellar radiation field and show that about 60% of its emission lines are sensitive to background subtraction. We argue that this geometric approach could provide an additional tool toward understanding the complex radiation fields of starburst galaxies.

  18. Radiated electric field measurements in U.S. Army helicopters.

    PubMed

    Bruckart, J E

    1992-11-01

    Aircraft systems and medical devices generate electromagnetic fields. Electromagnetic interference (EMI) can cause faulty operation of aircraft systems or medical devices and endanger patients or aircraft crewmembers. A ground and inflight study was conducted to describe the electromagnetic fields in typical operations. Broadband isotropic field sensors measured electric fields from 5 kHz to 3 MHz, 3 to 500 MHz, and 0.5 MHz to 6 GHz. Fields were measured at 0.5 m space intervals in JOH-58A, JUH-1H, and JUH-60A helicopters with systems off, operating RPM, 5-ft hover, 50-ft hover, and cruise. Electric fields in the environment were homogeneous and less than 0.1 V/m. Fields in the helicopters increased during ascent, but remained less than 2 V/m except during radio transmissions. EMI effect of the Physio Control Lifepack 8 was demonstrated during FM radio transmission. The results are useful in evaluating electromagnetic emissions and predicting operations that may result in an inflight malfunction of a medical device or aircraft system. PMID:1445153

  19. Radiated electric field measurements in U.S. Army helicopters

    NASA Astrophysics Data System (ADS)

    Bruckart, James E.

    1992-11-01

    Aircraft systems and medical devices generate electromagnetic fields. EMI can cause faulty operation of aircraft systems or medical devices and endanger patients or aircraft crewmembers. A ground and inflight study was conducted to describe the electromagnetic fields in typical operations. Broadband isotropic field sensors measured electric fields from 5 kHz to 3 MHz, 3 to 500 MHz, and 0.5 MHz to 6 GHz. Fields were measured at 0.5 m space intervals in JOH-58A, JUH-1H, and JUH-60A helicopters with systems off, operating RPM, 5-ft hover, 50-ft hover, and cruise. Electric fields in the environment were homogeneous and less than 0.1 V/m. Fields in the helicopters increased during ascent, but remained less than 2 V/m except during radio transmissions. EMI effect of the Physio Control Lifepack 8 was demonstrated during FM radio transmission. The results are useful in evaluating electromagnetic emissions and predicting operations that may result in an inflight malfunction of a medical device or aircraft system.

  20. 3D Cloud Radiative Effects on Aerosol Optical Thickness Retrievals in Cumulus Cloud Fields in the Biomass Burning Region in Brazil

    NASA Technical Reports Server (NTRS)

    Wen, Guo-Yong; Marshak, Alexander; Cahalan, Robert F.

    2004-01-01

    Aerosol amount in clear regions of a cloudy atmosphere is a critical parameter in studying the interaction between aerosols and clouds. Since the global cloud cover is about 50%, cloudy scenes are often encountered in any satellite images. Aerosols are more or less transparent, while clouds are extremely reflective in the visible spectrum of solar radiation. The radiative transfer in clear-cloudy condition is highly three- dimensional (3D). This paper focuses on estimating the 3D effects on aerosol optical thickness retrievals using Monte Carlo simulations. An ASTER image of cumulus cloud fields in the biomass burning region in Brazil is simulated in this study. The MODIS products (i-e., cloud optical thickness, particle effective radius, cloud top pressure, surface reflectance, etc.) are used to construct the cloud property and surface reflectance fields. To estimate the cloud 3-D effects, we assume a plane-parallel stratification of aerosol properties in the 60 km x 60 km ASTER image. The simulated solar radiation at the top of the atmosphere is compared with plane-parallel calculations. Furthermore, the 3D cloud radiative effects on aerosol optical thickness retrieval are estimated.

  1. Imaging Surface Plasmons: From Leaky Waves to Far-Field Radiation

    NASA Astrophysics Data System (ADS)

    Drezet, Aurélien; Genet, Cyriaque

    2013-05-01

    We show that, contrary to the common wisdom, surface plasmon poles are not involved in the imaging process in leakage radiation microscopy. Identifying the leakage radiation modes directly from a transverse magnetic potential leads us to reconsider the surface plasmon field and unfold the nonplasmonic contribution to the image formation. While both contributions interfere in the imaging process, our analysis reveals that the reassessed plasmonic field embodies a pole mathematically similar to the usual surface plasmon pole. This removes a long-standing ambiguity associated with plasmonic signals in leakage radiation microscopy.

  2. Difficulties encountered removing locked plates

    PubMed Central

    Raja, S; Imbuldeniya, AM; S, Garg; Groom, G

    2012-01-01

    INTRODUCTION Locked plates are commonly used to obtain fixation in periarticular and comminuted fractures. Their use has also gained popularity in repairing fractures in osteoporotic bone. These plates provide stable fixation and promote biological healing. Over the last 3 years, we have used over 150 locked plates with varying success to fix periarticular fractures involving mainly the knee and ankle. In this study, we report our clinical experience and the difficulties encountered when removing locked plates in adult patients with a variety of indications including implant failure, infection, non-union and a palpable symptomatic implant. METHODS A retrospective analysis was performed of patients enrolled prospectively into a database. Included in the study were 36 consecutive adult patients who each underwent the procedure of locked plate removal in a single inner city level 1 trauma centre. Data collected included primary indication for fixation, indication for implant removal, time of the implant in situ, grade of operating surgeon and difficulties encountered during the procedure. RESULTS Implant removal was associated with a complication rate of 47%. The major problems encountered were difficulty in removing the locked screws and the implant itself. A total of ten cold welded screws were found in eight cases. Removal was facilitated by high speed metal cutting burrs and screw removal sets in all but one case, where a decision was made to leave the plate in situ. CONCLUSIONS The majority of studies investigating implant removal and problems encountered in doing so report a relatively high complication rate. With the advent of locking plates and their growing popularity, difficulties are now being seen intra-operatively when removing them. There is a paucity of data, however, specifically directed at locking plate removal. We recommend that surgeons should be aware of the potential complications while removing locked plates. Fluoroscopic control and all

  3. Supervision Challenges Encountered during Kenyan University Students' Practicum Attachment

    ERIC Educational Resources Information Center

    Kathuri-Ogola, Lucy; VanLeeuwen, Charlene; Kabaria-Muriithi, Joan; Weeks, Lori E.; Kieru, Jane; Ndayala, Phoebe

    2015-01-01

    There is little published research that examines the supervision experience of field attachment supervisors in Kenya. In this study, we identify the challenges encountered by field supervisors during student field attachments with community organizations. Fifteen organizations that had hosted third year students from the Department of Community…

  4. Testing of Performance of Optical Fibers Under Irradiation in Intense Radiation Fields, When Subjected to Very High Temperatures

    SciTech Connect

    Blue, Thomas; Windl, Wolfgang; Dickerson, Bryan

    2013-01-03

    The primary objective of this project is to measure and model the performance of optical fibers in intense radiation fields when subjected to very high temperatures. This research will pave the way for fiber optic and optically based sensors under conditions expected in future high-temperature gas-cooled reactors. Sensor life and signal-to-noise ratios are susceptible to attenuation of the light signal due to scattering and absorbance in the fibers. This project will provide an experimental and theoretical study of the darkening of optical fibers in high-radiation and high-temperature environments. Although optical fibers have been studied for moderate radiation fluence and flux levels, the results of irradiation at very high temperatures have not been published for extended in-core exposures. Several previous multi-scale modeling efforts have studied irradiation effects on the mechanical properties of materials. However, model-based prediction of irradiation-induced changes in silica's optical transport properties has only recently started to receive attention due to possible applications as optical transmission components in fusion reactors. Nearly all damage-modeling studies have been performed in the molecular-dynamics domain, limited to very short times and small systems. Extended-time modeling, however, is crucial to predicting the long-term effects of irradiation at high temperatures, since the experimental testing may not encompass the displacement rate that the fibers will encounter if they are deployed in the VHTR. The project team will pursue such extended-time modeling, including the effects of the ambient and recrystallization. The process will be based on kinetic MC modeling using the concept of amorphous material consisting of building blocks of defect-pairs or clusters, which has been successfully applied to kinetic modeling in amorphized and recrystallized silicon. Using this procedure, the team will model compensation for rate effects, and the

  5. Modeling of cloud liquid water structure and the associated radiation field

    SciTech Connect

    Wiscombe, W.

    1995-09-01

    A 0.5{degrees}C global warming should result from every 1% decrease in global albedo. It is therefore necessary to accurately quantify the cloud radiation interaction. Most radiation calculations are one-dimensional and attempt to deal with horizontal variability using a horizontally-averaged optical depth. This study presents detailed scale-by-scale statistical analysis of the cloud liquid water content (LWC) field. The aim is to use this information to provide radiation calculations with more adequate information about inhomogeneity in cloud fields. The radiation community needs to carefully specify the minimum requirements which GCMs must include in order to treat cloud-radiation interaction correctly. This may involve GCMs predicting not only mean cloud quantities but also cloud variability. 3 figs.

  6. On the parameterization of the biological effect in a mixed radiation field.

    PubMed

    Kraft, G; Scholz, M

    1994-10-01

    The exposure of astronauts and electronics to the cosmic radiation especially to the particle component pose a major risk to all space flights. Up to now it is not possible to quantify this risk within acceptable limits of accuracy. This uncertainty is not only caused by difficulties in the more or less exact prediction of the incidence of the cosmic radiation but depends also on the problem of the quantification of the radiation field and the correlation of the biological effect. Usually the biological action of a mixed radiation field is estimated as product of the measured dose with an average quality factor, the relative biological efficiency. Because of the large variation in energy and atomic number of the cosmic particles, average values of the quality factor are not precise for risk estimation. A more appropriate way to treat the biological effects of mixed radiation is the concept of particle fluence and action cross section. PMID:11540044

  7. Basic theory for polarized, astrophysical maser radiation in a magnetic field

    NASA Technical Reports Server (NTRS)

    Watson, William D.

    1994-01-01

    Fundamental alterations in the theory and resulting behavior of polarized, astrophysical maser radiation in the presence of a magnetic field have been asserted based on a calculation of instabilities in the radiative transfer. I reconsider the radiative transfer and find that the relevant instabilities do not occur. Calculational errors in the previous investigation are identified. In addition, such instabilities would have appeared -- but did not -- in the numerous numerical solutions to the same radiative transfer equations that have been presented in the literature. As a result, all modifications that have been presented in a recent series of papers (Elitzur 1991, 1993) to the theory for polarized maser radiation in the presence of a magnetic field are invalid. The basic theory is thus clarified.

  8. Escape of gravitational radiation from the field of massive bodies

    NASA Technical Reports Server (NTRS)

    Price, Richard H.; Pullin, Jorge; Kundu, Prasun K.

    1993-01-01

    We consider a compact source of gravitational waves of frequency omega in or near a massive spherically symmetric distribution of matter or a black hole. Recent calculations have led to apparently contradictory results for the influence of the massive body on the propagation of the waves. We show here that the results are in fact consistent and in agreement with the 'standard' viewpoint in which the high-frequency compact source produces the radiation as if in a flat background, and the background curvature affects the propagation of these waves.

  9. Synchro-curvature radiation of charged particles in the strong curved magnetic fields

    SciTech Connect

    Kelner, S. R.; Prosekin, A. Yu.; Aharonian, F. A. E-mail: Anton.Prosekin@mpi-hd.mpg.de

    2015-01-01

    It is generally believed that the radiation of relativistic particles in a curved magnetic field proceeds in either the synchrotron or the curvature radiation modes. In this paper we show that in strong curved magnetic fields a significant fraction of the energy of relativistic electrons can be radiated away in the intermediate, the so-called synchro-curvature regime. Because of the persistent change of the trajectory curvature, the radiation varies with the frequency of particle gyration. While this effect can be ignored in the synchrotron and curvature regimes, the variability plays a key role in the formation of the synchro-curvature radiation. Using the Hamiltonian formalism, we find that the particle trajectory has the form of a helix wound around the drift trajectory. This allows us to calculate analytically the intensity and energy distribution of prompt radiation in the general case of magnetic bremsstrahlung in the curved magnetic field. We show that the transition to the limit of the synchrotron and curvature radiation regimes is determined by the relation between the drift velocity and the component of the particle velocity perpendicular to the drift trajectory. The detailed numerical calculations, which take into account the energy losses of particles, confirm the principal conclusions based on the simplified analytical treatment of the problem, and allow us to analyze quantitatively the transition between different radiation regimes for a broad range of initial pitch angles. These calculations demonstrate that even very small pitch angles may lead to significant deviations from the spectrum of the standard curvature radiation when it is formally assumed that a charged particle moves strictly along the magnetic line. We argue that in the case of realization of specific configurations of the electric and magnetic fields, the gamma-ray emission of the pulsar magnetospheres can be dominated by the component radiated in the synchro-curvature regime.

  10. Exploring graphene field effect transistor devices to improve spectral resolution of semiconductor radiation detectors

    SciTech Connect

    Harrison, Richard Karl; Howell, Stephen Wayne; Martin, Jeffrey B.; Hamilton, Allister B.

    2013-12-01

    Graphene, a planar, atomically thin form of carbon, has unique electrical and material properties that could enable new high performance semiconductor devices. Graphene could be of specific interest in the development of room-temperature, high-resolution semiconductor radiation spectrometers. Incorporating graphene into a field-effect transistor architecture could provide an extremely high sensitivity readout mechanism for sensing charge carriers in a semiconductor detector, thus enabling the fabrication of a sensitive radiation sensor. In addition, the field effect transistor architecture allows us to sense only a single charge carrier type, such as electrons. This is an advantage for room-temperature semiconductor radiation detectors, which often suffer from significant hole trapping. Here we report on initial efforts towards device fabrication and proof-of-concept testing. This work investigates the use of graphene transferred onto silicon and silicon carbide, and the response of these fabricated graphene field effect transistor devices to stimuli such as light and alpha radiation.

  11. The perturbation correction factor of ionisation chambers in beta-radiation fields.

    PubMed

    Böhm, J

    1980-01-01

    In determining the absorbed dose in a solid medium by means of gas-filled ionisation chambers, the perturbation of the radiation field by the chamber needs to be taken into account. So far, an appropriate correction factor has neither been calculated nor measured for beta-radiation. This work describes its experimental determination for an extrapolation chamber and beta-radiation fields of 147Pm, 204Tl, and 90Sr + 90Y. The results show that the correction factor may be assumed to be the product of a shield factor and a scatter factor the magnitudes of which depend on the chamber geometry and the radiation field. The change of the perturbation correction factor with phantom depth is important for the measurement of depth dose curves. This is demonstrated by an example. PMID:7360793

  12. Field size effect of radiation quality in carbon therapy using passive method

    SciTech Connect

    Nose, H.; Kase, Y.; Matsufuji, N.; Kanai, T.

    2009-03-15

    The authors have investigated the dependency of radiation quality and absorbed dose on radiation field size in therapeutic carbon beams. The field size of the broad beam, formed using the passive technique, was controlled from 20 to 100 mm per side with a multileaf collimator. The absorbed dose and radiation quality on the beam center were evaluated at several depths in a water phantom using microdosimetric technique in experiments and Monte Carlo simulations. With an increase in the field size, the radiation quality was reduced, although the absorbed dose grew at the center of the field. This indicates that the dose and radiation quality at the center of the broad beam are influenced by particles from the off-center region via large-angle scattering and that such particles have relatively low radiation quality and mainly consist of fragment particles. Because such a tendency appeared to be more remarkable in the deeper region of the water phantom, it is likely that fragment particles that are born in a water phantom have a marked role in determining the field size effect.

  13. Radiation from Relativistic Jets in Turbulent Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.; Mizuno, Y.; Medvedev, M.; Zhang, B.; Hardee, P.; Niemiec, J.; Nordlund, A.; Frederiksen, J.; Mizuno, Y.; Sol, H.; Fishman, G. J.

    2008-01-01

    Using our new 3-D relativistic electromagnetic particle (REMP) code parallelized with MPI, we have investigated long-term particle acceleration associated with an relativistic electron-positron jet propagating in an unmagnetized ambient electron-positron plasma. The simulations have been performed using a much longer simulation system than our previous simulations in order to investigate the full nonlinear stage of the Weibel instability and its particle acceleration mechanism. Cold jet electrons are thermalized and ambient electrons are accelerated in the resulting shocks. The acceleration of ambient electrons leads to a maximum ambient electron density three times larger than the original value. Behind the bow shock in the jet shock strong electromagnetic fields are generated. These fields may lead to the afterglow emission. We have calculated the time evolution of the spectrum from two electrons propagating in a uniform parallel magnetic field to verify the technique.

  14. High field CdS detector for infrared radiation

    NASA Technical Reports Server (NTRS)

    Tyagi, R. C.; Boer, K. W.; Hadley, H. C.; Robertson, J. B.

    1972-01-01

    New and highly sensitive method of detecting infrared irradiation makes possible solid state infrared detector which is more sensitive near room temperature than usual photoconductive low band gap semiconductor devices. Reconfiguration of high field domains in cadmium sulphide crystals provides basis for discovery.

  15. BOBCAT Personal Radiation Detector Field Test and Evaluation Campaign

    SciTech Connect

    Chris Hodge

    2008-03-01

    Following the success of the Anole test of portable detection system, the U.S. Department of Homeland Security (DHS) Domestic Nuclear Detection Office organized a test and evaluation campaign for personal radiation detectors (PRDs), also known as “Pagers.” This test, “Bobcat,” was conducted from July 17 to August 8, 2006, at the Nevada Test Site. The Bobcat test was designed to evaluate the performance of PRDs under various operational scenarios, such as pedestrian surveying, mobile surveying, cargo container screening, and pedestrian chokepoint monitoring. Under these testing scenarios, many operational characteristics of the PRDs, such as gamma and neutron sensitivities, positive detection and false alarm rates, response delay times, minimum detectable activities, and source localization errors, were analyzed. This paper will present the design, execution, and methodologies used to test this equipment for the DHS.

  16. Personal Radiation Detector Field Test and Evaluation Campaign

    SciTech Connect

    Chris A. Hodge, Ding Yuan, Raymond P. Keegan, Michael A. Krstich

    2007-07-09

    Following the success of the Anole test of portable detection system, the U.S. Department of Homeland Security (DHS) Domestic Nuclear Detection Office organized a test and evaluation campaign for personal radiation detectors (PRDs), also known as 'Pagers'. This test, 'Bobcat', was conducted from July 17 to August 8, 2006, at the Nevada Test Site. The Bobcat test was designed to evaluate the performance of PRDs under various operational scenarios, such as pedestrian surveying, mobile surveying, cargo container screening, and pedestrian chokepoint monitoring. Under these testing scenarios, many operational characteristics of the PRDs, such as gamma and neutron sensitivities, positive detection and false alarm rates, response delay times, minimum detectable activities, and source localization errors, were analyzed. This paper will present the design, execution, and methodologies used to test this equipment for the DHS.

  17. Radiative signature of magnetic fields in internal shocks

    NASA Astrophysics Data System (ADS)

    Mimica, P.; Aloy, M. A.

    2012-04-01

    Common models of blazars and gamma-ray bursts assume that the plasma underlying the observed phenomenology is magnetized to some extent. Within this context, radiative signatures of dissipation of kinetic and conversion of magnetic energy in internal shocks of relativistic magnetized outflows are studied. We model internal shocks as being caused by collisions of homogeneous plasma shells. We compute the flow state after the shell interaction by solving Riemann problems at the contact surface between the colliding shells, and then compute the emission from the resulting shocks. Under the assumption of a constant flow luminosity, we find that there is a clear difference between the models where both shells are weakly magnetized (σ≲ 10-2) and those where, at least, one shell has σ≳ 10-2. We obtain that the radiative efficiency is largest for models in which, regardless of the ordering, one shell is weakly and the other strongly magnetized. Substantial differences between weakly and strongly magnetized shell collisions are observed in the inverse-Compton part of the spectrum, as well as in the optical, X-ray and 1-GeV light curves. We propose a way to distinguish observationally between weakly magnetized and strongly magnetized internal shocks by comparing the maximum frequency of the inverse-Compton part and synchrotron part of the spectrum to the ratio of the inverse-Compton to synchrotron fluence. Finally, our results suggest that low-frequency peaked blazars (LBL) may correspond to barely magnetized flows, while high-frequency peaked blazars (HBL) could correspond to moderately magnetized ones. Indeed, by comparing with actual blazar observations, we conclude that the magnetization of typical blazars is σ≲ 0.01 for the internal shock model to be valid in these sources.

  18. Near field thermal memory based on radiative phase bistability of VO2

    NASA Astrophysics Data System (ADS)

    Dyakov, S. A.; Dai, J.; Yan, M.; Qiu, M.

    2015-08-01

    We report the concept of a near-field memory device based on the radiative bistability effect in the system of two closely separated parallel plates of SiO2 and VO2 which exchange heat by thermal radiation in vacuum. We demonstrate that the VO2 plate, having metal-insulator transition at 340 K, has two thermodynamical steady-states. One can switch between the states using an external laser impulse. We show that due to near-field photon tunneling between the plates, the switching time is found to be only 5 ms which is several orders lower than in case of far field.

  19. Near Field Radiation Characteristics of Implantable Square Spiral Chip Inductor Antennas for Bio-Sensors

    NASA Technical Reports Server (NTRS)

    Nessel, James A.; Simons, Rainee N.; Miranda, Felix A.

    2007-01-01

    The near field radiation characteristics of implantable Square Spiral Chip Inductor Antennas (SSCIA) for Bio-Sensors have been measured. Our results indicate that the measured near field relative signal strength of these antennas agrees with simulated results and confirm that in the near field region the radiation field is fairly uniform in all directions. The effects of parameters such as ground-plane, number of turns and microstrip-gap width on the performance of the SSCIA are presented. Furthermore, the SSCIA antenna with serrated ground plane produce a broad radiation pattern, with a relative signal strength detectable at distances within the range of operation of hand-held devices for self-diagnosis.

  20. Simulation of Relativistic Shocks and Associated Radiation from Turbulent Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.; Mizuno, Y.; Niemiec, J.; Medvedev, M.; Zhang, B.; Hardee, P.; Frederiksen, J.; Sol, H.; Pohl, M.; Hartmann, D. H.; Fishman, G. J.

    2010-01-01

    Recent PIC simulations of relativistic electron-positron (electron-ion) jets injected into a stationary medium show that particle acceleration occurs at shocked regions. Simulations show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields and particle acceleration. These magnetic fields contribute to the electron's transverse deflection behind the shock. The jitter'' radiation from deflected electrons in turbulent magnetic fields has different properties than synchrotron radiation, which is calculated in a uniform magnetic field. This jitter radiation may be important for understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets in general, and supernova remnants. We will present detailed spectra for conditions relevant of various astrophysical sites of shock formation via the Weibel instability. In particular we will discuss the application to GRBs and SNRs

  1. A MEMS Device Capable of Measuring Near-Field Thermal Radiation between Membranes

    PubMed Central

    Feng, Chong; Tang, Zhenan; Yu, Jun; Sun, Changyu

    2013-01-01

    For sensors constructed by freestanding membranes, when the gap between a freestanding membrane and the substrate or between membranes is at micron scale, the effects of near-field radiative heat transfer on the sensors' thermal performance should be considered during sensor design. The radiative heat flux is transferred from a membrane to a plane or from a membrane to a membrane. In the current study of the near-field thermal radiation, the scanning probe technology has difficulty in making a membrane separated at micron scale parallel to a plane or another membrane. A novel MEMS (micro electromechanical system) device was developed by sacrificial layer technique in this work to realize a double parallel freestanding membrane structure. Each freestanding membrane has a platinum thin-film resistor and the distance between the two membranes is 1 μm. After evaluating the electrical and thermal characteristics of the lower freestanding membrane,experimental measurements of near-field radiative heat transfer between the lower membrane and the upper membrane were carried out by setting the lower membrane as a heat emitter and the upper membrane as a heat receiver. The near-field radiative heat transfer between the two membranes was validated by finding a larger-than-blackbody radiative heat transfer based on the experimental data. PMID:23385413

  2. Fan Noise Prediction System Development: Source/Radiation Field Coupling and Workstation Conversion for the Acoustic Radiation Code

    NASA Technical Reports Server (NTRS)

    Meyer, H. D.

    1993-01-01

    The Acoustic Radiation Code (ARC) is a finite element program used on the IBM mainframe to predict far-field acoustic radiation from a turbofan engine inlet. In this report, requirements for developers of internal aerodynamic codes regarding use of their program output an input for the ARC are discussed. More specifically, the particular input needed from the Bolt, Beranek and Newman/Pratt and Whitney (turbofan source noise generation) Code (BBN/PWC) is described. In a separate analysis, a method of coupling the source and radiation models, that recognizes waves crossing the interface in both directions, has been derived. A preliminary version of the coupled code has been developed and used for initial evaluation of coupling issues. Results thus far have shown that reflection from the inlet is sufficient to indicate that full coupling of the source and radiation fields is needed for accurate noise predictions ' Also, for this contract, the ARC has been modified for use on the Sun and Silicon Graphics Iris UNIX workstations. Changes and additions involved in this effort are described in an appendix.

  3. A terahertz confocal microscope for far-field thermal radiation detection and near-field sub-wavelength imaging

    NASA Astrophysics Data System (ADS)

    Weng, Qianchun; Yang, Le; Xu, Jie; Qian, Qingbai; Yu, Haochi; Zhang, Bo; An, Zhenghua; Zhu, Ziqiang; Lu, Wei

    2015-11-01

    We present a novel scattering-type scanning near-field optical microscope (s-SNOM) operating in the terahertz (THz) wavelength. A home-made ultra-high sensitive detector named charge sensitive infrared phototransistor (CSIP, detection wavelength ~15 μm) is equipped for spontaneous thermal radiation detection (external illumination should be avoided). Thermal emission from room-temperature objects is collected by a cassegrain objective lens placed above the sample, and focused to a pinhole (d=250 μm) which is kept in liquid-helium (LHe) temperature(4.2 K). With the background radiation from environment efficiently blocked by the low-temperature pinhole, the detector is only sensitive to the THz radiation from a small spot (~λ) on sample surface (the confocal point). As a result, thermal radiation spontaneously emitted by object itself is measured with an excellent spatial resolution of ~14 μm (diffraction-limit). For overcoming the diffraction limit by detecting the near-field evanescent waves, this THz microscope is combined with a home-built atomic-force microscope (AFM). With sharp AFM tip (<100 nm) scattering the evanescent waves with an improved tip-modulation method, we successfully obtained thermal near-field images with a spatial resolution of ~100 nm, which is already less than 1% of the detection wavelength (15 μm). This THz s-SNOM should be a powerful tool for various material research down to the nanometer scale.

  4. Modern Radiation Therapy for Extranodal Lymphomas: Field and Dose Guidelines From the International Lymphoma Radiation Oncology Group

    SciTech Connect

    Yahalom, Joachim; Illidge, Tim; Specht, Lena; Hoppe, Richard T.; Li, Ye-Xiong; Tsang, Richard; Wirth, Andrew

    2015-05-01

    Extranodal lymphomas (ENLs) comprise about a third of all non-Hodgkin lymphomas (NHL). Radiation therapy (RT) is frequently used as either primary therapy (particularly for indolent ENL), consolidation after systemic therapy, salvage treatment, or palliation. The wide range of presentations of ENL, involving any organ in the body and the spectrum of histological sub-types, poses a challenge both for routine clinical care and for the conduct of prospective and retrospective studies. This has led to uncertainty and lack of consistency in RT approaches between centers and clinicians. Thus far there is a lack of guidelines for the use of RT in the management of ENL. This report presents an effort by the International Lymphoma Radiation Oncology Group (ILROG) to harmonize and standardize the principles of treatment of ENL, and to address the technical challenges of simulation, volume definition and treatment planning for the most frequently involved organs. Specifically, detailed recommendations for RT volumes are provided. We have applied the same modern principles of involved site radiation therapy as previously developed and published as guidelines for Hodgkin lymphoma and nodal NHL. We have adopted RT volume definitions based on the International Commission on Radiation Units and Measurements (ICRU), as has been widely adopted by the field of radiation oncology for solid tumors. Organ-specific recommendations take into account histological subtype, anatomy, the treatment intent, and other treatment modalities that may be have been used before RT.

  5. Acoustic radiation torque on an irregularly shaped scatterer in an arbitrary sound field.

    PubMed

    Fan, Zongwei; Mei, Deqing; Yang, Keji; Chen, Zichen

    2008-11-01

    To eliminate the limitation of the conventional acoustic radiation torque theory, which is only applicable to a disklike scatterer in a plane sound field, a new theory is established to calculate the radiation torque on any irregularly shaped scatterer in any arbitrary sound field. First, with the aid of the conservation law of angular momentum, the acoustic radiation torque is expressed as the angular momentum flux through a spherical surface with the center at the scatterer's centroid. Second, the velocity potential of the scattered field is derived, taking into account the influences of the translational and rotational movements of the scatterer induced by the first order stress of the incident sound field. Finally, a general calculating formula of the acoustic radiation torque is achieved. For a disklike scatterer in a plane sound filed, results from the above formula are well identical with those conventional formulas. By studying the case of a semicircular cylinder scatterer in a standing-wave sound field, it is found that for an irregularly shaped scatterer its rotation velocity is normally nonzero and the radiation torque changes with the spatial attitude. PMID:19045760

  6. Field size dependent mapping of medical linear accelerator radiation leakage

    NASA Astrophysics Data System (ADS)

    Vũ Bezin, Jérémi; Veres, Attila; Lefkopoulos, Dimitri; Chavaudra, Jean; Deutsch, Eric; de Vathaire, Florent; Diallo, Ibrahima

    2015-03-01

    The purpose of this study was to investigate the suitability of a graphics library based model for the assessment of linear accelerator radiation leakage. Transmission through the shielding elements was evaluated using the build-up factor corrected exponential attenuation law and the contribution from the electron guide was estimated using the approximation of a linear isotropic radioactive source. Model parameters were estimated by a fitting series of thermoluminescent dosimeter leakage measurements, achieved up to 100 cm from the beam central axis along three directions. The distribution of leakage data at the patient plane reflected the architecture of the shielding elements. Thus, the maximum leakage dose was found under the collimator when only one jaw shielded the primary beam and was about 0.08% of the dose at isocentre. Overall, we observe that the main contributor to leakage dose according to our model was the electron beam guide. Concerning the discrepancies between the measurements used to calibrate the model and the calculations from the model, the average difference was about 7%. Finally, graphics library modelling is a readily and suitable way to estimate leakage dose distribution on a personal computer. Such data could be useful for dosimetric evaluations in late effect studies.

  7. Microwave radiation power of relativistic electron beam with virtual cathode in the external magnetic field

    NASA Astrophysics Data System (ADS)

    Kurkin, S. A.; Hramov, A. E.; Koronovskii, A. A.

    2013-07-01

    The study of the output power of the electromagnetic radiation of the relativistic electron beam (REB) with virtual cathode in the presence of external magnetic field has been found out. The typical dependencies of the output microwave power of the vircator versus external magnetic field have been analyzed by means of 3D electromagnetic simulation. It has been shown that the power of vircator demonstrates several maxima with external magnetic field growth. The characteristic features of the power behavior are determined by the conditions of the virtual cathode formation in the presence of the external transversal magnetic field and the REB self-magnetic fields.

  8. Microwave radiation power of relativistic electron beam with virtual cathode in the external magnetic field

    SciTech Connect

    Kurkin, S. A.; Hramov, A. E.; Koronovskii, A. A.; Saratov State Technical University, Politechnicheskaja 77, Saratov 410028

    2013-07-22

    The study of the output power of the electromagnetic radiation of the relativistic electron beam (REB) with virtual cathode in the presence of external magnetic field has been found out. The typical dependencies of the output microwave power of the vircator versus external magnetic field have been analyzed by means of 3D electromagnetic simulation. It has been shown that the power of vircator demonstrates several maxima with external magnetic field growth. The characteristic features of the power behavior are determined by the conditions of the virtual cathode formation in the presence of the external transversal magnetic field and the REB self-magnetic fields.

  9. A NUMERICAL TREATMENT OF ANISOTROPIC RADIATION FIELDS COUPLED WITH RELATIVISTIC RESISTIVE MAGNETOFLUIDS

    SciTech Connect

    Takahashi, Hiroyuki R.; Ohsuga, Ken

    2013-08-01

    We develop a numerical scheme for solving fully special relativistic, resistive radiation magnetohydrodynamics. Our code guarantees conservation of total mass, momentum, and energy. The radiation energy density and the radiation flux are consistently updated using the M-1 closure method, which can resolve an anisotropic radiation field, in contrast to the Eddington approximation, as well as the flux-limited diffusion approximation. For the resistive part, we adopt a simple form of Ohm's law. The advection terms are explicitly solved with an approximate Riemann solver, mainly the Harten-Lax-van Leer scheme; the HLLC and HLLD schemes are also solved for some tests. The source terms, which describe the gas-radiation interaction and the magnetic energy dissipation, are implicitly integrated, relaxing the Courant-Friedrichs-Lewy condition even in an optically thick regime or a large magnetic Reynolds number regime. Although we need to invert 4 Multiplication-Sign 4 matrices (for the gas-radiation interaction) and 3 Multiplication-Sign 3 matrices (for the magnetic energy dissipation) at each grid point for implicit integration, they are obtained analytically without preventing massive parallel computing. We show that our code gives reasonable outcomes in numerical tests for ideal magnetohydrodynamics, propagating radiation, and radiation hydrodynamics. We also applied our resistive code to the relativistic Petschek-type magnetic reconnection, revealing the reduction of the reconnection rate via radiation drag.

  10. A Numerical Treatment of Anisotropic Radiation Fields Coupled with Relativistic Resistive Magnetofluids

    NASA Astrophysics Data System (ADS)

    Takahashi, Hiroyuki R.; Ohsuga, Ken

    2013-08-01

    We develop a numerical scheme for solving fully special relativistic, resistive radiation magnetohydrodynamics. Our code guarantees conservation of total mass, momentum, and energy. The radiation energy density and the radiation flux are consistently updated using the M-1 closure method, which can resolve an anisotropic radiation field, in contrast to the Eddington approximation, as well as the flux-limited diffusion approximation. For the resistive part, we adopt a simple form of Ohm's law. The advection terms are explicitly solved with an approximate Riemann solver, mainly the Harten-Lax-van Leer scheme; the HLLC and HLLD schemes are also solved for some tests. The source terms, which describe the gas-radiation interaction and the magnetic energy dissipation, are implicitly integrated, relaxing the Courant-Friedrichs-Lewy condition even in an optically thick regime or a large magnetic Reynolds number regime. Although we need to invert 4 × 4 matrices (for the gas-radiation interaction) and 3 × 3 matrices (for the magnetic energy dissipation) at each grid point for implicit integration, they are obtained analytically without preventing massive parallel computing. We show that our code gives reasonable outcomes in numerical tests for ideal magnetohydrodynamics, propagating radiation, and radiation hydrodynamics. We also applied our resistive code to the relativistic Petschek-type magnetic reconnection, revealing the reduction of the reconnection rate via radiation drag.

  11. Pion production via proton synchrotron radiation in strong magnetic fields in relativistic field theory: Scaling relations and angular distributions

    NASA Astrophysics Data System (ADS)

    Maruyama, Tomoyuki; Cheoun, Myung-Ki; Kajino, Toshitaka; Mathews, Grant J.

    2016-06-01

    We study pion production by proton synchrotron radiation in the presence of a strong magnetic field when the Landau numbers of the initial and final protons are ni,f ∼104-105. We find in our relativistic field theory calculations that the pion decay width depends only on the field strength parameter which previously was only conjectured based upon semi-classical arguments. Moreover, we also find new results that the decay width satisfies a robust scaling relation, and that the polar angular distribution of emitted pion momenta is very narrow and can be easily obtained. This scaling implies that one can infer the decay width in more realistic magnetic fields of 1015 G, where ni,f ∼1012-1013, from the results for ni,f ∼104-105. The resultant pion intensity and angular distributions for realistic magnetic field strengths are presented and their physical implications discussed.

  12. Pion production via proton synchrotron radiation in strong magnetic fields in relativistic field theory: Scaling relations and angular distributions

    NASA Astrophysics Data System (ADS)

    Maruyama, Tomoyuki; Cheoun, Myung-Ki; Kajino, Toshitaka; Mathews, Grant J.

    2016-06-01

    We study pion production by proton synchrotron radiation in the presence of a strong magnetic field when the Landau numbers of the initial and final protons are ni,f ∼104-105. We find in our relativistic field theory calculations that the pion decay width depends only on the field strength parameter which previously was only conjectured based upon semi-classical arguments. Moreover, we also find new results that the decay width satisfies a robust scaling relation, and that the polar angular distribution of emitted pion momenta is very narrow and can be easily obtained. This scaling implies that one can infer the decay width in more realistic magnetic fields of 1015 G, where ni,f ∼1012-1013, from the results for ni,f ∼104-105. The resultant pion intensity and angular distributions for realistic magnetic field strengths are presented and their physical implications discussed.

  13. Numerical Simulation of a Convective Turbulence Encounter

    NASA Technical Reports Server (NTRS)

    Proctor, Fred H.; Hamilton, David W.; Bowles, Roland L.

    2002-01-01

    A numerical simulation of a convective turbulence event is investigated and compared with observational data. The numerical results show severe turbulence of similar scale and intensity to that encountered during the test flight. This turbulence is associated with buoyant plumes that penetrate the upper-level thunderstorm outflow. The simulated radar reflectivity compares well with that obtained from the aircraft's onboard radar. Resolved scales of motion as small as 50 m are needed in order to accurately diagnose aircraft normal load accelerations. Given this requirement, realistic turbulence fields may be created by merging subgrid-scales of turbulence to a convective-cloud simulation. A hazard algorithm for use with model data sets is demonstrated. The algorithm diagnoses the RMS normal loads from second moments of the vertical velocity field and is independent of aircraft motion.

  14. The response of the RO-2 survey meter to mixed radiation fields

    SciTech Connect

    Shonka, J.J. ); Tschaeche, A.N.; Tomblison, M.R.; Gibeault, G.L.; Moon, U.Y.; McCoy, G.C.; Schrader, B.J. )

    1989-12-01

    Reactor fuel reprocessing can sometimes result in radiation fields originating from nearly-pure Ru-106/Rh-106 (E{sub max} = 3.5 MeV), and field measurements are often made where beta-to-gamma ratios exceed 100-to-1. If the range of the high energy beta particles exceeds the density-thickness of the side wall and/or end window of the radiation detector, a significant fraction of the beta radiation can easily be interpreted as gamma radiation. The magnitude of the error increases as the beta-to-gamma radio increases. Calculations and measurements are presented which show the magnitude of the resulting errors. To address this problem, a modification kit was developed for the Eberline RO-2A which increased the density-thickness of both the sidewall and slide to 1040 mg/cm{sup 2}. In this paper experimental results showing the effectiveness of the modification are discussed.

  15. Technical Note: Response measurement for select radiation detectors in magnetic fields

    SciTech Connect

    Reynolds, M.; Fallone, B. G.; Rathee, S.

    2015-06-15

    Purpose: Dose response to applied magnetic fields for ion chambers and solid state detectors has been investigated previously for the anticipated use in linear accelerator–magnetic resonance devices. In this investigation, the authors present the measured response of selected radiation detectors when the magnetic field is applied in the same direction as the radiation beam, i.e., a longitudinal magnetic field, to verify previous simulation only data. Methods: The dose response of a PR06C ion chamber, PTW60003 diamond detector, and IBA PFD diode detector is measured in a longitudinal magnetic field. The detectors are irradiated with buildup caps and their long axes either parallel or perpendicular to the incident photon beam. In each case, the magnetic field dose response is reported as the ratio of detector signals with to that without an applied longitudinal magnetic field. The magnetic field dose response for each unique orientation as a function of magnetic field strength was then compared to the previous simulation only studies. Results: The measured dose response of each detector in longitudinal magnetic fields shows no discernable response up to near 0.21 T. This result was expected and matches the previously published simulation only results, showing no appreciable dose response with magnetic field. Conclusions: Low field longitudinal magnetic fields have been shown to have little or no effect on the dose response of the detectors investigated and further lend credibility to previous simulation only studies.

  16. Edge diffracted caustic fields. [spacecraft antenna radiation patterns

    NASA Technical Reports Server (NTRS)

    Burnside, W. D.; Peters, L., Jr.

    1974-01-01

    The fields near a caustic created by an edge diffraction process are computed using the equivalent current concept. These fields are shown to have the property commonly associated with ray optical analysis or the Geometrical Theory of Diffraction (GTD), e.g., a 90 deg phase shift as the ray passes through the caustic. The present effort is directed toward consideration of the caustic created by an edge diffraction process. Particular attention is focused on electromagnetic excitation. The acoustic excitation for the hard boundary condition is outlined in an appendix. In addition, goal is to establish the extent of the caustic region. This is of particular importance when a ray optical solution involves multiply-diffracted terms in that the minimum size of the body that can be analyzed may be restricted by the extent of the caustic, i.e., the 90 deg phase shift used in ray optical analysis may be introduced only if the caustic is contained on the surface being studied.

  17. NOTE: Intraoperative radiation therapy using a mobile electron linear accelerator: field matching for large-field electron irradiation

    NASA Astrophysics Data System (ADS)

    Beddar, A. S.; Briere, T. M.; Ouzidane, M.

    2006-09-01

    Intraoperative radiation therapy (IORT) consists of delivering a large, single-fraction dose of radiation to a surgically exposed tumour or tumour bed at the time of surgery. With the availability of a mobile linear accelerator in the OR, IORT procedures have become more feasible for medical centres and more accessible to cancer patients. Often the area requiring irradiation is larger than what the treatment applicators will allow, and therefore, two or more adjoining fields are used. Unfortunately, the divergence and scattering of the electron beams may cause significant dose variations in the region of the field junction. Furthermore, because IORT treatments are delivered in a large single fraction, the effects of underdosing or overdosing could be more critical when compared to fractionated external beam therapy. Proper matching of the fields is therefore an important technical aspect of treatment delivery. We have studied the matching region using the largest flat applicator available for three different possibilities: abutting the fields, leaving a small gap or creating an overlap. Measurements were done using film dosimetry for the available energies of 4, 6, 9 and 12 MeV. Our results show the presence of clinically significant cold spots for the low-energy beams when the fields are either gapped or abutted, suggesting that the fields should be overlapped. No fields should be gapped. The results suggest that an optimal dose distribution may be obtained by overlapping the fields at 4 and 6 MeV and simply abutting the fields at 9 and 12 MeV. However, due to uncertainties in the placement of lead shields during treatment delivery, one may wish to consider overlapping the higher energy fields as well.

  18. Dipole-fiber systems: radiation field patterns, effective magnetic dipoles, and induced cavity modes

    NASA Astrophysics Data System (ADS)

    Atakaramians, Shaghik; Miroshnichenko, Andrey E.; Shadrivov, Ilya V.; Monro, Tanya M.; Kivshar, Yuri S.; Afshar, Shahraam V.

    2015-12-01

    We study the radiation patterns produced by a dipole placed at the surface of a nanofiber and oriented perpendicular to it, either along the radial (r-oriented) or azimuthal (Φ-oriented) directions. We find that the dipole induces an effective circular cavity-like leaky mode in the nanofiber. The first radiation peak of the Φ-oriented dipole contributes only to TE radiation modes, while the radiation of the r-oriented dipole is composed of both TE and TM radiation modes, with relative contribution depending on the refractive index of the nanofiber. We reveal that the field pattern of the first resonance of a Φ-oriented dipole is associated with a magnetic dipole mode and strong magnetic response of an optical nanofiber.

  19. Momentum energy of the non-radiating electromagnetic field: open problems?

    NASA Astrophysics Data System (ADS)

    Kholmetskii, Alexander L.

    2006-06-01

    This paper inspects more closely the problem of the momentum and energy of a bound (non-radiative) electromagnetic (EM) field. It has been shown that for an isolating system of non-radiative non-relativistic mechanically free charged particles, a transformation of mechanical to EM momentum and vice versa occurs in accordance with the requirement \\skew3\\vec{P}_G =const, where \\skew3\\vec{P}_G = \\skew3\\vec{P}_M + \\sum\

  20. Strained silicon modulation field-effect transistor as a new sensor of terahertz radiation

    NASA Astrophysics Data System (ADS)

    Moubarak Meziani, Yahya; Garcia, Enrique; Velazquez, Enrique; Diez, Enrique; El Moutaouakil, Amine; Otsuji, Taiichi; Fobelets, K.

    2011-10-01

    In this paper, we report on room temperature detection of terahertz radiation from strained-Si modulation-doped field-effect transistors. A non-resonant signal was observed with a maximum around the threshold voltage. The signal was interpreted due to the plasma wave nonlinearities in the channel. The intensity of the signal increases for the higher applied drain-to-source current. We also observed a dependence of the signal on the polarization of the incoming radiations.

  1. Ultraviolet radiation penetrating vehicle glass: a field based comparative study

    NASA Astrophysics Data System (ADS)

    Kimlin, M. G.; Parisi, A. V.

    1999-04-01

    The solar UV transmitted through automobile glass was measured in the field in two cars using a spectroradiometer. The two cars were identical except that one of the cars had all of the windows (except the windshield) tinted. The measured spectral erythemal UV on a horizontal plane with the windows fully closed was reduced in the tinted car by a factor of 42 when compared with the erythemal UV measured in the untinted car. The ambient UVA irradiances at various locations within four different makes of car and a tractor were also measured with a broad band UVA hand-held meter. The average normalized daily UVA exposure (measured with a broad band UVA meter) was 1.3 times higher in a large family sedan when compared with that in a small hatchback and the UVA exposure in a car with tinted windows was 3.8 times less than in a similar untinted car.

  2. EPR dosimetry in a mixed neutron and gamma radiation field.

    PubMed

    Trompier, F; Fattibene, P; Tikunov, D; Bartolotta, A; Carosi, A; Doca, M C

    2004-01-01

    Suitability of Electron Paramagnetic Resonance (EPR) spectroscopy for criticality dosimetry was evaluated for tooth enamel, mannose and alanine pellets during the 'international intercomparison of criticality dosimetry techniques' at the SILENE reactor held in Valduc in June 2002, France. These three materials were irradiated in neutron and gamma-ray fields of various relative intensities and spectral distributions in order to evaluate their neutron sensitivity. The neutron response was found to be around 10% for tooth enamel, 45% for mannose and between 40 and 90% for alanine pellets according their type. According to the IAEA recommendations on the early estimate of criticality accident absorbed dose, analyzed results show the EPR potentiality and complementarity with regular criticality techniques. PMID:15353687

  3. Calculating far-field radiated sound pressure levels from NASTRAN output

    NASA Technical Reports Server (NTRS)

    Lipman, R. R.

    1986-01-01

    FAFRAP is a computer program which calculates far field radiated sound pressure levels from quantities computed by a NASTRAN direct frequency response analysis of an arbitrarily shaped structure. Fluid loading on the structure can be computed directly by NASTRAN or an added-mass approximation to fluid loading on the structure can be used. Output from FAFRAP includes tables of radiated sound pressure levels and several types of graphic output. FAFRAP results for monopole and dipole sources compare closely with an explicit calculation of the radiated sound pressure level for those sources.

  4. Particle beams in ultrastrong laser fields: direct laser acceleration and radiation reaction effects

    NASA Astrophysics Data System (ADS)

    Salamin, Yousef I.; Li, Jian-Xing; Hatsagortsyan, Karen Z.; Tamburini, Matteo; Di Piazza, Antonino; Keitel, Christoph H.

    2015-03-01

    Several aspects of the interaction of particle beams with ultrastrong laser fields are discussed. Firstly, we consider regimes when radiation reaction is not essential and it is demonstrated that employing chirped laser pulses, significant improvement of the direct acceleration of particles can be achieved. Results from single- and many-particle calculations of the particle acceleration, in vacuum, by plane-wave fields, as well as in tightly-focused laser beams, show that the mean energies and their spreads qualify them for important applications. Secondly, we investigate the effect of radiation reaction in electron-laser-beam interactions. Signatures of the quantum radiation reaction during the interaction of an electron bunch with a focused superstrong ultrashort laser pulse can be observed in a characteristic behavior of the spectral bandwidth, and the angular spread of the nonlinear Compton radiation on the laser pulse duration. Furthermore, it is shown that the radiation reaction effects can be employed to control the electron dynamics via the nonlinear interplay between the Lorentz and radiation reaction forces. In particular, it is shown that an ultrarelativistic electron bunch colliding head- on with a strong bichromatic laser pulse can be deflected in a controllable way, by changing either the relative phase or the relative amplitude between the two frequency components of the bichromatic field.

  5. TSUBASA (MDS-1) observations of energetic electrons and magnetic field variations in outer radiation belt

    NASA Astrophysics Data System (ADS)

    Nakamura, M.; Matsuoka, H.; Liu, H.; Koshiishi, H.; Koga, K.; Matsumoto, H.; Goka, T.

    2002-12-01

    We have investigated variations of energetic electrons (> 0.4 MeV) and magnetic field in the radiation belt obtained from the Standard DOse Monitor (SDOM) and the MAgnetoMeter (MAM) of the Space Environment Data Acquisition equipment (SEDA) onboard TSUBASA (the Mission Demonstration Test Satellite (MDS)-1) launched on February 4, 2002. Since TSUBASA is operated in the geostationary transfer orbit, it has provided rare opportunities of directly observing near-equatorial radiation belt plasma particles and magnetic field, having already included several large magnetic storms. The energetic electrons in the outer radiation belt are contributors to the total radiation dose deposited in lightly shielded spacecraft electronics for high altitude orbits and are known to have a drastic variability associated with geomagnetic storm and high speed solar wind streams. The abrupt energetic electron flux decreases in the outside of outer radiation belt show characteristic variations of in situ magnetic field. These observations have implications for the possible mechanisms of the depletion and the following recovery and/or buildup of energetic electrons in the outer radiation belt.

  6. Radiation magnetohydrodynamic simulation of plasma formed on a surface by a megagauss field

    NASA Astrophysics Data System (ADS)

    Esaulov, A. A.; Bauer, B. S.; Makhin, V.; Siemon, R. E.; Lindemuth, I. R.; Awe, T. J.; Reinovsky, R. E.; Struve, K. W.; Desjarlais, M. P.; Mehlhorn, T. A.

    2008-03-01

    Radiation magnetohydrodynamic modeling is used to study the plasma formed on the surface of a cylindrical metallic load, driven by megagauss magnetic field at the 1MA Zebra generator (University of Nevada, Reno). An ionized aluminum plasma is used to represent the “core-corona” behavior in which a heterogeneous Z -pinch consists of a hot low-density corona surrounding a dense low-temperature core. The radiation dynamics model included simultaneously a self-consistent treatment of both the opaque and transparent plasma regions in a corona. For the parameters of this experiment, the boundary of the opaque plasma region emits the major radiation power with Planckian black-body spectrum in the extreme ultraviolet corresponding to an equilibrium temperature of 16eV . The radiation heat transport significantly exceeds the electron and ion kinetic heat transport in the outer layers of the opaque plasma. Electromagnetic field energy is partly radiated (13%) and partly deposited into inner corona and core regions (87%). Surface temperature estimates are sensitive to the radiation effects, but the surface motion in response to pressure and magnetic forces is not. The general results of the present investigation are applicable to the liner compression experiments at multi-MA long-pulse current accelerators such as Atlas and Shiva Star. Also the radiation magnetohydrodynamic model discussed in the paper may be useful for understanding key effects of wire array implosion dynamics.

  7. Simulation studies of wide and medium field of view earth radiation data analysis

    NASA Technical Reports Server (NTRS)

    Green, R. N.

    1978-01-01

    A parameter estimation technique is presented to estimate the radiative flux distribution over the earth from radiometer measurements at satellite altitude. The technique analyzes measurements from a wide field of view (WFOV), horizon to horizon, nadir pointing sensor with a mathematical technique to derive the radiative flux estimates at the top of the atmosphere for resolution elements smaller than the sensor field of view. A computer simulation of the data analysis technique is presented for both earth-emitted and reflected radiation. Zonal resolutions are considered as well as the global integration of plane flux. An estimate of the equator-to-pole gradient is obtained from the zonal estimates. Sensitivity studies of the derived flux distribution to directional model errors are also presented. In addition to the WFOV results, medium field of view results are presented.

  8. Magnetic fields and radiative shocks in protogalaxies and the origin of globular clusters

    NASA Technical Reports Server (NTRS)

    Shapiro, Paul R.; Clocchiatti, Alejandro; Kang, Hyesung

    1992-01-01

    The paper examines the hypothesis that globular clusters formed from gravitational instability in dense sheets of gas produced behind radiative shocks inside protogalaxies, such as those produced by the collision of subgalactic mass fragments partaking of the virial motions within the protogalaxy, in order to determine the differences which result if a magnetic field is present in the preshock medium. The MHD conservation equations are solved along with rate equations for nonequilibrium ionization, recombination, molecular formation and dissociation, and the equations of radiative transfer for steady-state shocks of velocity 300 km/s in a gas of preshock densities of 0.1-1 cu cm, and magnetic field strengths of 0.1-6 micro-G. The magnetic field is found to limit the degree of postshock compression and, thereby, to reduce the level of external radiation flux required to suppress H2 formation and cooling.

  9. Influence of Preoperative Radiation Field on Postoperative Leak Rates in Esophageal Cancer Patients after Trimodality Therapy

    PubMed Central

    Juloori, Aditya; Tucker, Susan L.; Komaki, Ritsuko; Liao, Zhongxing; Correa, Arlene M.; Swisher, Stephen G.; Hofstetter, Wayne L.; Lin, Steven H.

    2014-01-01

    Introduction Postoperative morbidities, such as anastomotic leaks, are common after trimodality therapy (chemoradiation followed by surgery) for esophageal cancer. We investigated for factors associated with an increased incidence of anastomotic leaks. Methods Data from 285 esophageal cancer patients treated from 2000–2011 with trimodality therapy was analyzed. Anastomotic location relative to preoperative radiation field was assessed using postoperative computed tomographic imaging. Logistic regression was used to evaluate for factors associated with any or clinically relevant (CR) (≥ grade 2) leaks. Results Overall anastomotic leak rate was 11% (31/285), and CR leak rate was 6% (17/285). Multivariable analysis identified body mass index (BMI) (OR 1.09, 95%CI 1.00–1.17; OR 1.11, 95%CI 1.01–1.22), three-field surgery (OR 10.01, 95%CI 3.83–26.21; OR 4.83, 95%CI 1.39–16.71), and within radiation field (“in-field”) anastomosis (OR 5.37, 95%CI 2.21–13.04; OR 8.63, 95%CI 2.90–25.65) as independent predictors of both all grade and CR leaks, respectively. While patients with distal esophageal tumors and Ivor-Lewis surgery had the lowest incidence of all grade (6.5%) and CR leaks (4.2%), most of the leaks were associated with the anastomosis constructed within the field of radiation (in-field: 39% and 30% versus out-of-field: 2.6% and 1.0%, respectively, for total and CR leaks, p<0.0001, Fisher’s Exact test). Conclusions Esophagogastric anastomosis placed within the preoperative radiation field was a very strong predictor for anastomotic leaks in esophageal cancer patients treated with trimodality therapy, among other factors. Surgical planning should include a critical evaluation of the preoperative radiation fields to ensure proper anastomotic placement after chemoradiation therapy. PMID:24736077

  10. COMET ENCOUNTERS AND CARBON 14

    SciTech Connect

    Eichler, David; Mordecai, David

    2012-12-20

    The {sup 14}C production of shock-accelerated particles is calculated in terms of the total energy released in energetic particles. The recently reported 1.2% jump in the {sup 14}C content of the atmosphere in the year C.E. 775, it is found, would require {approx}> 10{sup 34} erg in energetic particles, less than first estimates but far more than any known solar flare on record. It is noted that the superflare from a large comet (comparable to C/Hale-Bopp) colliding with the sun could produce shock-accelerated GeV cosmic rays in the solar corona and/or solar wind, and possibly account for the C.E. 775 event. Several additional predictions of cometary encounters with the sun and other stars may be observable in the future.

  11. A field study of pollutant deposition in radiation fog

    SciTech Connect

    Waldman, J.M.; Jacob, D.J.; Munger, J.W.; Hoffman, M.R.

    1986-04-01

    Deposition during fog episodes can make a significant contribution to the overall flux of pollutants in certain ecosystems. Furthermore, when atmospheric stagnation prevents normal ventilation in a region, fog deposition may become the main route of pollutant removal. Fogs can consequently exert dominant control over pollutant levels in certain atmospheres. The southern San Joaquin Valley (SJV) of California is a region prone to wintertime episodes of atmospheric stagnation. These lead to elevated pollutant concentrations and/or dense, widespread fogs. Major oil-recovery operations plus widespread agricultural and livestock feeding activities are important sources of SO/sub 2/, NO/sub X/ and NH/sub 3/ in the valley. A multifaceted program of field monitoring was conducted in the SJV during the winter 1984-1985, focusing on aspects of pollutant scavenging and removal in the fog-laden atmosphere. Concentrations of major species were measured in gas, dry aerosol and fogwater phases. In addition, depositional fluxes were monitored by surrogate-surface methods. These measurements were employed to directly assess the magnitude of removal enhancement by fog.

  12. Transient quantum coherent response to a partially coherent radiation field

    SciTech Connect

    Sadeq, Zaheen S.; Brumer, Paul

    2014-02-21

    The response of an arbitrary closed quantum system to a partially coherent electric field is investigated, with a focus on the transient coherences in the system. As a model we examine, both perturbatively and numerically, the coherences induced in a three level V system. Both rapid turn-on and pulsed turn-on effects are investigated. The effect of a long and incoherent pulse is also considered, demonstrating that during the pulse the system shows a coherent response which reduces after the pulse is over. Both the pulsed scenario and the thermally broadened CW case approach a mixed state in the long time limit, with rates dictated by the adjacent level spacings and the coherence time of the light, and via a mechanism that is distinctly different from traditional decoherence. These two excitation scenarios are also explored for a minimal “toy” model of the electronic levels in pigment protein complex PC645 by both a collisionally broadened CW laser and by a noisy pulse, where unexpectedly long transient coherence times are observed and explained. The significance of environmentally induced decoherence is noted.

  13. Superkicks in hyperbolic encounters of binary black holes.

    PubMed

    Healy, James; Herrmann, Frank; Hinder, Ian; Shoemaker, Deirdre M; Laguna, Pablo; Matzner, Richard A

    2009-01-30

    Generic inspirals and mergers of binary black holes produce beamed emission of gravitational radiation that can lead to a gravitational recoil or kick of the final black hole. The kick velocity depends on the mass ratio and spins of the binary as well as on the dynamics of the binary configuration. Studies have focused so far on the most astrophysically relevant configuration of quasicircular inspirals, for which kicks as large as approximately 3300 km s;(-1) have been found. We present the first study of gravitational recoil in hyperbolic encounters. Contrary to quasicircular configurations, in which the beamed radiation tends to average during the inspiral, radiation from hyperbolic encounters is plunge dominated, resulting in an enhancement of preferential beaming. As a consequence, it is possible in highly relativistic scatterings to achieve kick velocities as large as 10 000 km s;(-1). PMID:19257409

  14. Output microwave radiation power of low-voltage vircator with external inhomogeneous magnetic field

    NASA Astrophysics Data System (ADS)

    Kurkin, S. A.; Koronovskii, A. A.; Hramov, A. E.

    2011-04-01

    Dependence of the power of a broadband microwave radiation generated by a low-voltage oscillator with virtual cathode (vircator) on the parameters of an external inhomogeneous magnetic field has been studied by numerical simulations using a two-dimensional model. It is established that there are optimum parameters of the generator (configuration of the external magnetic field, electron beam current) for which the output radiation power is maximum. A relationship between the optimum conditions of virtual cathode formation in the electron beam and the microwave generation regime is established.

  15. Preliminary science results of Voyager 1 Saturn encounter

    NASA Technical Reports Server (NTRS)

    Bane, D.

    1981-01-01

    Preliminary science results of the Voyager 1 encounter of the planet Saturn are reported. On August 22, 1980, the spacecraft was 109 million km (68 million mi) from Saturn. Closest approach to Saturn took place on November 12, at 3:46 p.m. (PDT), when the spacecraft passed 126,000 km (78,000 mi) from the cloud tops. Measurements of the atmosphere, wind speed, radiation, six surrounding rings, and the planet's old and newly found satellites were recorded. The encounter ended December 15, 1980. The spacecraft took more than 17,500 photographs of Saturn and its satellites.

  16. The mechanism of the effect of a plasma layer with negative permittivity on the antenna radiation field

    SciTech Connect

    Wang, Chunsheng Liu, Hui; Jiang, Binhao; Li, Xueai

    2015-06-15

    A model of a plasma–antenna system is developed to study the mechanism of the effect of the plasma layer on antenna radiation. Results show a plasma layer with negative permittivity is inductive, and thus affects the phase difference between electric and magnetic fields. In the near field of antenna radiation, a plasma layer with proper parameters can compensate the capacitivity of the vacuum and enhance the radiation power. In the far field of antenna radiation, the plasma layer with negative permittivity increases the inductivity of the vacuum and reduces the radiation power.

  17. SPARTA - Solver for Polarized Atmospheric Radiative Transfer Applications: Introduction and application to Saharan dust fields

    NASA Astrophysics Data System (ADS)

    Barlakas, Vasileios; Macke, Andreas; Wendisch, Manfred

    2016-07-01

    Non-spherical particles in the atmosphere absorb and scatter solar radiation. They change the polarization state of solar radiation depending on their shape, size, chemical composition and orientation. To quantify polarization effects, a new three-dimensional (3D) vector radiative transfer model, SPARTA (Solver for Polarized Atmospheric Radiative Transfer Applications) is introduced and validated against benchmark results. SPARTA employs the statistical forward Monte Carlo technique for efficient column-response pixel-based radiance calculations including polarization for 3D inhomogeneous cloudless and cloudy atmospheres. A sensitivity study has been carried out and exemplarily results are presented for two lidar-based mineral dust fields. The scattering and absorption properties of the dust particles have been computed for spheroids and irregular shaped particles. Polarized radiance fields in two-dimensional (2D) and one-dimensional (1D) inhomogeneous Saharan dust fields have been calculated at 532 nm wavelength. The domain-averaged results of the normalized reflected radiance are almost identical for the 1D and 2D modes. In the areas with large spatial gradient in optical thickness with expected significant horizontal photon transport, the radiance fields of the 2D mode differ by about ±12% for the first Stokes component (radiance, I) and ±8% for the second Stokes component (linear polarization, Q) from the fields of the 1D mode.

  18. Online virtual isocenter based radiation field targeting for high performance small animal microirradiation

    NASA Astrophysics Data System (ADS)

    Stewart, James M. P.; Ansell, Steve; Lindsay, Patricia E.; Jaffray, David A.

    2015-12-01

    Advances in precision microirradiators for small animal radiation oncology studies have provided the framework for novel translational radiobiological studies. Such systems target radiation fields at the scale required for small animal investigations, typically through a combination of on-board computed tomography image guidance and fixed, interchangeable collimators. Robust targeting accuracy of these radiation fields remains challenging, particularly at the millimetre scale field sizes achievable by the majority of microirradiators. Consistent and reproducible targeting accuracy is further hindered as collimators are removed and inserted during a typical experimental workflow. This investigation quantified this targeting uncertainty and developed an online method based on a virtual treatment isocenter to actively ensure high performance targeting accuracy for all radiation field sizes. The results indicated that the two-dimensional field placement uncertainty was as high as 1.16 mm at isocenter, with simulations suggesting this error could be reduced to 0.20 mm using the online correction method. End-to-end targeting analysis of a ball bearing target on radiochromic film sections showed an improved targeting accuracy with the three-dimensional vector targeting error across six different collimators reduced from 0.56+/- 0.05 mm (mean  ±  SD) to 0.05+/- 0.05 mm for an isotropic imaging voxel size of 0.1 mm.

  19. Online virtual isocenter based radiation field targeting for high performance small animal microirradiation.

    PubMed

    Stewart, James M P; Ansell, Steve; Lindsay, Patricia E; Jaffray, David A

    2015-12-01

    Advances in precision microirradiators for small animal radiation oncology studies have provided the framework for novel translational radiobiological studies. Such systems target radiation fields at the scale required for small animal investigations, typically through a combination of on-board computed tomography image guidance and fixed, interchangeable collimators. Robust targeting accuracy of these radiation fields remains challenging, particularly at the millimetre scale field sizes achievable by the majority of microirradiators. Consistent and reproducible targeting accuracy is further hindered as collimators are removed and inserted during a typical experimental workflow. This investigation quantified this targeting uncertainty and developed an online method based on a virtual treatment isocenter to actively ensure high performance targeting accuracy for all radiation field sizes. The results indicated that the two-dimensional field placement uncertainty was as high as 1.16 mm at isocenter, with simulations suggesting this error could be reduced to 0.20 mm using the online correction method. End-to-end targeting analysis of a ball bearing target on radiochromic film sections showed an improved targeting accuracy with the three-dimensional vector targeting error across six different collimators reduced from [Formula: see text] mm (mean  ±  SD) to [Formula: see text] mm for an isotropic imaging voxel size of 0.1 mm. PMID:26540304

  20. Near-field thermal radiation between homogeneous dual uniaxial electromagnetic metamaterials

    NASA Astrophysics Data System (ADS)

    Chang, Jui-Yung; Basu, Soumyadipta; Yang, Yue; Wang, Liping

    2016-06-01

    Recently, near-field thermal radiation has attracted much attention in several fields since it can exceed the Planck blackbody limit through the coupling of evanescent waves. In this work, near-field radiative heat transfer between two semi-infinite dual uniaxial electromagnetic metamaterials with two different material property sets is theoretically analyzed. The near-field radiative heat transfer is calculated using fluctuational electrodynamics incorporated with anisotropic wave optics. The underlying mechanisms, namely, magnetic hyperbolic mode, magnetic surface polariton, electrical hyperbolic mode, and electrical surface polariton, between two homogeneous dual uniaxial electromagnetic metamaterials are investigated by examining the transmission coefficient and the spectral heat flux. The effect of vacuum gap distance is also studied, which shows that the enhancement at smaller vacuum gap is mainly due to hyperbolic mode and surface plasmon polariton modes. In addition, the results show that the contribution of s-polarized waves is significant and should not be excluded due to the strong magnetic response regardless of vacuum gap distances. The fundamental understanding and insights obtained here will facilitate the finding and application of novel materials for near-field thermal radiation.

  1. Near- to far-field characteristics of acoustic radiation through plug flow jets.

    PubMed

    Gabard, G

    2008-11-01

    This paper reports a theoretical study of the radiation of sound through jet exhausts. It focuses on the transition from near field to far field by considering the features of the near-field solution and how these features translate to the far field. The main focus of this work is the importance in some cases of lateral waves radiating from the jet. While the presence of lateral waves has long been recognized, there has been no systematic investigation of the practical consequences of these waves in the prediction of sound propagation through round jets. The physical mechanisms involved in the generation of these waves are presented as well as the conditions under which they become significant. Another issue is the possibility of "channeled waves" inside the jet associated with strong sound radiation in the forward arc. This paper also discusses the validity of the far-field approximation when lateral waves are present. It is shown that the standard far-field approximation can be improved by adding correction terms that account for the presence of the lateral waves and channeled waves. The challenge posed to computational aeroacoustics by these near-field effects is also discussed. PMID:19045763

  2. On Whether Angular Momentum in Electric and Magnetic Fields Radiates to Infinity

    NASA Technical Reports Server (NTRS)

    Canning, Francis X.; Knudsen, Steven

    2006-01-01

    The Feynman Disk experiment and a related thought experiment with a static magnetic field and capacitor are studied. The mechanical torque integrated over time (angular impulse) is related to the angular momentum in the electric/magnetic field. This is not called an electromagnetic field since quasi-static as well as electromagnetic effects are included. The angular momentum in the electric/magnetic field is examined to determine its static and radiative components. This comparison was then examined to see if it clarified the Abraham-Minkowski paradox.

  3. Cosmic ray pressure driven magnetic field amplification: dimensional, radiative and field orientation effects

    NASA Astrophysics Data System (ADS)

    Downes, T. P.; Drury, L. O'C.

    2014-10-01

    Observations of non-thermal emission from several supernova remnants suggest that magnetic fields close to the blastwave are much stronger than would be naively expected from simple shock compression of the field permeating the interstellar medium (ISM). We investigate in some detail a simple model based on turbulence generation by cosmic ray pressure gradients. Previously, this model was investigated using 2D magnetohydrodynamic simulations. Motivated by the well-known qualitative differences between 2D and 3D turbulence, we further our investigations of this model using both 2D and 3D simulations to study the influence of the dimensionality of the simulations on the field amplification achieved. Further, since the model implies the formation of shocks which can, in principle, be efficiently cooled by collisional cooling, we include such cooling in our simulations to ascertain whether it could increase the field amplification achieved. Finally, we examine the influence of different orientations of the magnetic field with respect to the normal of the blastwave. We find that dimensionality has a slight influence on the overall amplification achieved, but a significant impact on the morphology of the amplified field. Collisional cooling has surprisingly little impact, primarily due to the short time which any element of the ISM resides in the precursor region for supernova blastwaves. Even allowing for a wide range of orientations of the magnetic field, we find that the magnetic field can be expected to be amplified by, on average, at least an order of magnitude in the precursors of supernova blastwaves.

  4. Radiation field screening in photoconductive antennae studied via pulsed terahertz emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Loata, Gabriel C.; Thomson, Mark D.; Löffler, Torsten; Roskos, Hartmut G.

    2007-12-01

    We report terahertz emission experiments on low-temperature-grown GaAs photoconductive antennae. Two field-screening effects determine the device response: space-charge screening on a long time scale and radiation field screening of the local electric field. This latter effect is the principal cause for saturation of terahertz emission observed when the emitters are driven hard with high-repetition-rate femtosecond laser pulses. We present an equivalent-circuit model consisting of three elements: a resistor with time-dependent conductance (photoswitch), a time-dependent voltage source (space-charge screening), and the antenna impedance (terahertz emission and radiation field screening). The simulations with this voltage divider reproduce the measured data well.

  5. Quasinormal modes, scattering, and Hawking radiation of Kerr-Newman black holes in a magnetic field

    SciTech Connect

    Kokkotas, K. D.; Konoplya, R. A.; Zhidenko, A.

    2011-01-15

    We perform a comprehensive analysis of the spectrum of proper oscillations (quasinormal modes), transmission/reflection coefficients, and Hawking radiation for a massive charged scalar field in the background of the Kerr-Newman black hole immersed in an asymptotically homogeneous magnetic field. There are two main effects: the Zeeman shift of the particle energy in the magnetic field and the difference of values of an electromagnetic potential between the horizon and infinity, i.e. the Faraday induction. We have shown that 'turning on' the magnetic field induces a stronger energy-emission rate and leads to 'recharging' of the black hole. Thus, a black hole immersed in a magnetic field evaporates much quicker, achieving thereby an extremal state in a shorter period of time. Quasinormal modes are moderately affected by the presence of a magnetic field which is assumed to be relatively small compared to the gravitational field of the black hole.

  6. Development of a cryogenic radiation detector for mapping radio frequency superconducting cavity field emissions

    SciTech Connect

    Danny Dotson; John Mammosser

    2005-05-01

    Field emissions in a super conducting helium cooled RF cavity and the production of radiation (mostly X-Rays) have been measured externally on cryomodules at Jefferson Lab since 1991. External measurements are limited to radiation energies above 100 keV due to shielding of the stainless steel cryogenic body. To measure the onset of and to map field emissions from a superconducting cavity requires the detecting instrument be inside the shield and within the liquid Helium. Two possible measurement systems are undergoing testing at JLab. A CsI detector array set on photodiodes and an X-Ray film camera with a fixed aperture. Several devices were tested in the cell with liquid Helium without success. The lone survivor, a CsI array, worked but saturated at high power levels due to backscatter. The array was encased in a lead shield with a slit opening set to measure the radiation emitted directly from the cell eliminating a large portion of the backscatter. This is a work in progress and te sting should be complete before the PAC 05. The second system being tested is passive. It is a shielded box with an aperture to expose radiation diagnostic film located inside to direct radiation from the cell. Developing a technique for mapping field emissions in cryogenic cells will assist scientists and engineers in pinpointing any surface imperfections for examination.

  7. Analytic theory for betatron radiation from relativistic electrons in ion plasma channels with magnetic field

    SciTech Connect

    Lee, H. C.; Jiang, T. F.

    2010-11-15

    We analytically solve the relativistic equation of motion for an electron in ion plasma channels and calculate the corresponding trajectory as well as the synchrotron radiation. The relativistic effect on a trajectory is strong, i.e., many high-order harmonic terms in the trajectory, when the ratio of the initial transverse velocity (v{sub x0}) to the longitudinal velocity (v{sub z0}) of the electron injected to ion plasma channels is high. Interestingly, these high-order harmonic terms result in a quite broad and intense radiation spectrum, especially at an oblique angle, in contrast to an earlier understanding. As the initial velocity ratio (v{sub x0}:v{sub z0}) decreases, the relativistic effect becomes weak; only the first and second harmonic terms remain in the transverse and longitudinal trajectories, respectively, which coincides with the result of Esarey et al. [Phys. Rev. E 65, 056505 (2002)]. Our formalism also allows the description of electron's trajectory in the presence of an applied magnetic field. Critical magnetic fields for cyclotron motions are figured out and compared with semiclassical results. The cyclotron motion leads to more high-order harmonic terms than the trajectory without magnetic fields and causes an immensely broad spectrum with vastly large radiation amplitude for high initial velocity ratios (v{sub x0}:v{sub z0}). The radiation from hard x-ray to gamma-ray regions can be generated with a broad radiation angle, thus available for applications.

  8. Brief encounters: Assembling cosmetic surgery tourism.

    PubMed

    Holliday, Ruth; Bell, David; Cheung, Olive; Jones, Meredith; Probyn, Elspeth

    2015-01-01

    This paper reports findings from a large-scale, multi-disciplinary, mixed methods project which explores empirically and theoretically the rapidly growing but poorly understood (and barely regulated) phenomenon of cosmetic surgery tourism (CST). We explore CST by drawing on theories of flows, networks and assemblages, aiming to produce a fuller and more nuanced account of - and accounting for - CST. This enables us to conceptualise CST as an interplay of places, people, things, ideas and practices. Through specific instances of assembling cosmetic surgery that we encountered in the field, and that we illustrate with material from interviews with patients, facilitators and surgeons, our analysis advances understandings and theorisations of medical mobilities, globalisation and assemblage thinking. PMID:24985788

  9. Spider behaviors include oral sexual encounters.

    PubMed

    Gregorič, Matjaž; Šuen, Klavdija; Cheng, Ren-Chung; Kralj-Fišer, Simona; Kuntner, Matjaž

    2016-01-01

    Several clades of spiders whose females evolved giant sizes are known for extreme sexual behaviors such as sexual cannibalism, opportunistic mating, mate-binding, genital mutilation, plugging, and emasculation. However, these behaviors have only been tested in a handful of size dimorphic spiders. Here, we bring another lineage into the picture by reporting on sexual behavior of Darwin's bark spider, Caerostris darwini. This sexually size dimorphic Madagascan species is known for extreme web gigantism and for producing the world's toughest biomaterial. Our field and laboratory study uncovers a rich sexual repertoire that predictably involves cannibalism, genital mutilation, male preference for teneral females, and emasculation. Surprisingly, C. darwini males engage in oral sexual encounters, rarely reported outside mammals. Irrespective of female's age or mating status males salivate onto female genitalia pre-, during, and post-copulation. While its adaptive significance is elusive, oral sexual contact in spiders may signal male quality or reduce sperm competition. PMID:27126507

  10. Spider behaviors include oral sexual encounters

    PubMed Central

    Gregorič, Matjaž; Šuen, Klavdija; Cheng, Ren-Chung; Kralj-Fišer, Simona; Kuntner, Matjaž

    2016-01-01

    Several clades of spiders whose females evolved giant sizes are known for extreme sexual behaviors such as sexual cannibalism, opportunistic mating, mate-binding, genital mutilation, plugging, and emasculation. However, these behaviors have only been tested in a handful of size dimorphic spiders. Here, we bring another lineage into the picture by reporting on sexual behavior of Darwin’s bark spider, Caerostris darwini. This sexually size dimorphic Madagascan species is known for extreme web gigantism and for producing the world’s toughest biomaterial. Our field and laboratory study uncovers a rich sexual repertoire that predictably involves cannibalism, genital mutilation, male preference for teneral females, and emasculation. Surprisingly, C. darwini males engage in oral sexual encounters, rarely reported outside mammals. Irrespective of female’s age or mating status males salivate onto female genitalia pre-, during, and post-copulation. While its adaptive significance is elusive, oral sexual contact in spiders may signal male quality or reduce sperm competition. PMID:27126507

  11. Consideration of the radiation dose delivered away from the treatment field to patients in radiotherapy

    PubMed Central

    Taylor, Michael L.; Kron, Tomas

    2011-01-01

    Radiation delivery to cancer patients for radiotherapy is invariably accompanied by unwanted radiation to other parts of the patient’s body. Traditionally, considerable effort has been made to calculate and measure the radiation dose to the target as well as to nearby critical structures. Only recently has attention been focused also on the relatively low doses that exist far from the primary radiation beams. In several clinical scenarios, such doses have been associated with cardiac toxicity as well as an increased risk of secondary cancer induction. Out-of-field dose is a result of leakage and scatter and generally difficult to predict accurately. The present review aims to present existing data, from measurements and calculations, and discuss its implications for radiotherapy. PMID:21731221

  12. Far-ultraviolet studies. II - Galactic-latitude dependence of the 1530 A interstellar radiation field

    NASA Technical Reports Server (NTRS)

    Henry, R. C.; Swandic, J. R.; Shulman, S. D.; Fritz, G.

    1977-01-01

    A 0.62-sq cm Geiger counter, sensitive between 1425 and 1640 A, was used to map the far-ultraviolet brightness of about half the sky, providing an experimental measurement of the far-ultraviolet interstellar radiation field. At 1530 A, the energy density is approximately 7.4 by 10 to the -17th power erg/cu cm per A. Comparison with integrations of star catalogs calibrated to the ultraviolet shows, as expected, that the bulk of the radiation comes directly from B- and A-type stars. The galactic-latitude dependence of the radiation is analyzed in an unsuccessful attempt to set limits on the absorbing and scattering properties of the interstellar grains in the far-ultraviolet. Excess radiation observed at the galactic pole is probably residual airglow from above the rocket altitude.

  13. Study of shockwave method for diagnosing the radiation fields of laser-driven gold hohlraums

    NASA Astrophysics Data System (ADS)

    Li, Yongsheng; Lan, Ke; Huo, Wenyi; Lai, Dongxian; Gao, Yaoming; Pei, Wenbing

    2013-11-01

    Besides the routinely used broad-band x-ray spectrometer (Dante or SXS), ablative shock-wave method is often used to diagnose the radiation fields of laser-driven Hohlraums. The x-ray ablation process of Aluminum and Titanium is studied numerically with a 1-D radiation hydrodynamic code RDMG [F. Tinggui et al., Chin. J. Comput. Phys. 16, 199 (1999)], based on which a new scaling relation of the equivalent radiation temperature with the ablative shock velocity in Aluminum plates is proposed, and a novel method is developed for determining simultaneously the radiation temperature and the M-band (2-4 keV) fraction in laser-driven gold Hohlraums.

  14. The NOAA-9 Earth Radiation Budget Experiment Wide Field-of-View Data Set

    NASA Technical Reports Server (NTRS)

    Bush, Kathryn A.; Smith, G. Louis; Young, David F.

    1999-01-01

    The Earth Radiation Budget Experiment (ERBE) consisted of wide field-of-view (WFOV) radiometers and scanning radiometers for measuring outgoing longwave radiation and solar radiation reflected from the Earth. These instruments were carried by the dedicated Earth Radiation Budget Satellite (ERBS) and by the NOAA-9 and -10 operational spacecraft. The WFOV radiometers provided data from which instantaneous fluxes at the top of the atmosphere (TOA) are computed by use of a numerical filter algorithm. Monthly mean fluxes over a 5-degree equal angle grid are computed from the instantaneous TOA fluxes. The WFOV radiometers aboard the NOAA-9 spacecraft operated from February 1985 through December 1992, at which time a failure of the shortwave radiometer ended the usable data after nearly 8 years. This paper examines the monthly mean products from that data set.

  15. Cirrus microphysics and radiative transfer: Cloud field study on October 28, 1986

    NASA Technical Reports Server (NTRS)

    Kinne, Stefan; Ackerman, Thomas P.; Heymsfield, Andrew J.; Valero, Francisco P. J.; Sassen, Kenneth; Spinhirne, James D.

    1990-01-01

    The radiative properties of cirrus clouds present one of the unresolved problems in weather and climate research. Uncertainties in ice particle amount and size and, also, the general inability to model the single scattering properties of their usually complex particle shapes, prevent accurate model predictions. For an improved understanding of cirrus radiative effects, field experiments, as those of the Cirrus IFO of FIRE, are necessary. Simultaneous measurements of radiative fluxes and cirrus microphysics at multiple cirrus cloud altitudes allows the pitting of calculated versus measured vertical flux profiles; with the potential to judge current cirrus cloud modeling. Most of the problems in this study are linked to the inhomogeneity of the cloud field. Thus, only studies on more homogeneous cirrus cloud cases promises a possibility to improve current cirrus parameterizations. Still, the current inability to detect small ice particles will remain as a considerable handicap.

  16. On the electromagnetic fields, Poynting vector, and peak power radiated by lightning return strokes

    NASA Technical Reports Server (NTRS)

    Krider, E. P.

    1992-01-01

    The initial radiation fields, Poynting vector, and total electromagnetic power that a vertical return stroke radiates into the upper half space have been computed when the speed of the stroke, nu, is a significant fraction of the speed of light, c, assuming that at large distances and early times the source is an infinitesimal dipole. The initial current is also assumed to satisfy the transmission-line model with a constant nu and to be perpendicular to an infinite, perfectly conducting ground. The effect of a large nu is to increase the radiation fields by a factor of (1-beta-sq cos-sq theta) exp -1, where beta = nu/c and theta is measured from the vertical, and the Poynting vector by a factor of (1-beta-sq cos-sq theta) exp -2.

  17. Design of organic scintillators for non-standard radiation field dosimetry: experimental setup.

    PubMed

    Norman H, Machado R; Maximiliano, Trujillo T; Javier E, García G; Diana C, Narvaez G; Paula A, Marín M; Róbinson A, Torres V

    2013-01-01

    This paper describes an experimental setup designed for sensing the luminescent light coming from an organic plastic scintillator stimulated with ionizing radiation. This device is intended to be a part of a complete dosimeter system for characterization of small radiation fields which is the project of the doctoral thesis of the medical physicist at the Radiation Oncology facility of Hospital San Vicente Fundación in conjunction with the Universidad de Antioquia of Medellín Colombia. Some preliminary results predict a good performance of the unit, but further studies must be conducted in order to have a completed evaluation of the system. This is the first step in the development of an accuracy tool for measurement of non-standard fields in the Radiotherapy or Radiosurgery processes. PMID:24110369

  18. GAMMA-RAY BURST PROMPT EMISSION: JITTER RADIATION IN STOCHASTIC MAGNETIC FIELD REVISITED

    SciTech Connect

    Mao, Jirong; Wang Jiancheng

    2011-04-10

    We revisit the radiation mechanism of relativistic electrons in the stochastic magnetic field and apply it to the high-energy emissions of gamma-ray bursts (GRBs). We confirm that jitter radiation is a possible explanation for GRB prompt emission in the condition of a large electron deflection angle. In the turbulent scenario, the radiative spectral property of GRB prompt emission is decided by the kinetic energy spectrum of turbulence. The intensity of the random and small-scale magnetic field is determined by the viscous scale of the turbulent eddy. The microphysical parameters {epsilon}{sub e} and {epsilon}{sub B} can be obtained. The acceleration and cooling timescales are estimated as well. Due to particle acceleration in magnetized filamentary turbulence, the maximum energy released from the relativistic electrons can reach a value of about 10{sup 14} eV. The GeV GRBs are possible sources of high-energy cosmic-ray.

  19. Star Formation in the Galaxy and the Fluctuating UV Radiation Field

    NASA Technical Reports Server (NTRS)

    Hollenbach, David; Parravano, A.; McKee, C.; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    We examine the formation of massive stars in the Galaxy, the resultant fluctuating UV radiation field, and the effect of this Field on the star-forming interstellar medium. Following previous researchers such as Habing (1968), we calculate the average interstellar radiation field at the Solar Circle of the Galaxy. However, our new calculations follow more closely the time dependence of the field at any point. We show that there is a significant difference between the mean field and the median field, and that there are substantial fluctuations of the field (on timescales of order 100 million years) at a given point. Far Ultraviolet Radiation (FUV, photon energies of 6 eV - 13.6 eV) has been recognized as the main source of heating of the neutral interstellar gas. Given the pressure of the interstellar medium (ISM) the FUV field determines whether the thermal balance of the neutral gas results in cold (T approximately 50 - 100 K) clouds (CNM), warm (T about 10,000 K) (WNM), for a combination of the two (the two phase ISM) We present results for the time history of the FUV field for points in the local ISM of the Milky Way Galaxy. The presence of this fluctuating heating rate converts CNM to WNM and vice versa. We show how to calculate the average fractions of the gas in the CNM and WNM when the interstellar gas is subject to this fluctuating FUV field. The knowledge of how these fractions depend on the gas properties (i.e. mean density and composition) and on the FUV-sources (i.e. the star formation rate, or the IMF, or the size distribution of associations) is a basic step in building any detailed model of the large scale behavior of the ISM and the mutual relation between the ISM and the SFR.

  20. Pioneer Saturn Encounter. [Pioneer 11 space probe

    NASA Technical Reports Server (NTRS)

    1979-01-01

    The Pioneer Saturn Spacecraft, which began its journey as Pioneer 11, provided the first close view of the rings of Saturn as well as its system of moons. Its payload of 11 operating instruments obtained or confirmed data about the mass, temperature, composition, radiation belts, and atmosphere of the planet and its larger satellite, Titan. It made photometric and polarization measurements of lapetus, Rhea, Dione, and Tethys, as well as discovered additional rings. Scientific highlights of the mission are summarized. Color imagery provided by the photopolarimeter is included along with illustrations of the planet's magnetic field and radiation belts.

  1. An analysis of the radiation field beneath a bank of tubular quartz lamps

    NASA Technical Reports Server (NTRS)

    Ash, Robert L.

    1972-01-01

    Equations governing the incident heat flux distribution beneath a lamp-reflector system were developed. Analysis of a particular radiant heating facility showed good agreement between theory and experiment when a lamp power loss correction was used. In addition, the theory was employed to estimate thermal disruption in the radiation field caused by a protruding probe.

  2. 14 CFR 23.1308 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false High-intensity Radiated Fields (HIRF) Protection. 23.1308 Section 23.1308 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES Equipment General §...

  3. 14 CFR 23.1308 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false High-intensity Radiated Fields (HIRF) Protection. 23.1308 Section 23.1308 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES Equipment General §...

  4. 14 CFR 23.1308 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false High-intensity Radiated Fields (HIRF) Protection. 23.1308 Section 23.1308 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES Equipment General §...

  5. 14 CFR 23.1308 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false High-intensity Radiated Fields (HIRF) Protection. 23.1308 Section 23.1308 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES Equipment General §...

  6. 14 CFR 23.1308 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false High-intensity Radiated Fields (HIRF) Protection. 23.1308 Section 23.1308 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES Equipment General §...

  7. EFFECTS OF UV-B RADIATION ON SOYBEAN YIELD AND SEED QUALITY: A 6-YEAR FIELD

    EPA Science Inventory

    Two soybean, [Glycine max (L.) Merr.] cultivars, Essex and Williams, were grown in the field for 6 consecutive seasons under ambient and supplemental levels of ultraviolet B radiation to determine the potential for alterations in yield or seed quality with a reduction in the stra...

  8. Icing Encounter Duration Sensitivity Study

    NASA Technical Reports Server (NTRS)

    Addy, Harold E., Jr.; Lee, Sam

    2011-01-01

    This paper describes a study performed to investigate how aerodynamic performance degradation progresses with time throughout an exposure to icing conditions. It is one of the first documented studies of the effects of ice contamination on aerodynamic performance at various points in time throughout an icing encounter. Both a 1.5 and 6 ft chord, two-dimensional, NACA-23012 airfoils were subjected to icing conditions in the NASA Icing Research Tunnel for varying lengths of time. At the end of each run, lift, drag, and pitching moment measurements were made. Measurements with the 1.5 ft chord model showed that maximum lift and pitching moment degraded more rapidly early in the exposure and degraded more slowly as time progressed. Drag for the 1.5 ft chord model degraded more linearly with time, although drag for very short exposure durations was slightly higher than expected. Only drag measurements were made with the 6 ft chord airfoil. Here, drag for the long exposures was higher than expected. Novel comparison of drag measurements versus an icing scaling parameter, accumulation parameter times collection efficiency was used to compare the data from the two different size model. The comparisons provided a means of assessing the level of fidelity needed for accurate icing simulation.

  9. Assessment of the ultraviolet radiation field in ocean waters from space-based measurements and full radiative-transfer calculations.

    PubMed

    Vasilkov, Alexander P; Herman, Jay R; Ahmad, Ziauddin; Kahru, Mati; Mitchell, B Greg

    2005-05-10

    Quantitative assessment of the UV effects on aquatic ecosystems requires an estimate of the in-water radiation field. Actual ocean UV reflectances are needed for improving the total ozone retrievals from the total ozone mapping spectrometer (TOMS) and the ozone monitoring instrument (OMI) flown on NASA's Aura satellite. The estimate of underwater UV radiation can be done on the basis of measurements from the TOMS/OMI and full models of radiative transfer (RT) in the atmosphere-ocean system. The Hydrolight code, modified for extension to the UV, is used for the generation of look-up tables for in-water irradiances. A look-up table for surface radiances generated with a full RT code is input for the Hydrolight simulations. A model of seawater inherent optical properties (IOPs) is an extension of the Case 1 water model to the UV. A new element of the IOP model is parameterization of particulate matter absorption based on recent in situ data. A chlorophyll product from ocean color sensors is input for the IOP model. Verification of the in-water computational scheme shows that the calculated diffuse attenuation coefficient Kd is in good agreement with the measured Kd. PMID:15943340

  10. Electric field detection of coherent synchrotron radiation in a storage ring generated using laser bunch slicing

    NASA Astrophysics Data System (ADS)

    Katayama, I.; Shimosato, H.; Bito, M.; Furusawa, K.; Adachi, M.; Shimada, M.; Zen, H.; Kimura, S.; Yamamoto, N.; Hosaka, M.; Katoh, M.; Ashida, M.

    2012-03-01

    The electric field of coherent synchrotron radiation (CSR) generated by laser bunch slicing in a storage ring has been detected by an electro-optic sampling method. The gate pulses for sampling are sent through a large-mode-area photonic-crystal fiber. The observed electric field profile of the CSR is in good agreement with the spectrum of the CSR observed using Fourier transform far-infrared spectrometry, indicating good phase stability in the CSR. The longitudinal density profiles of electrons modulated by laser pulses were evaluated from the electric field profile.

  11. Electric field detection of coherent synchrotron radiation in a storage ring generated using laser bunch slicing

    SciTech Connect

    Katayama, I.; Shimosato, H.; Bito, M.; Furusawa, K.; Adachi, M.; Zen, H.; Kimura, S.; Katoh, M.; Shimada, M.; Yamamoto, N.; Hosaka, M.; Ashida, M.

    2012-03-12

    The electric field of coherent synchrotron radiation (CSR) generated by laser bunch slicing in a storage ring has been detected by an electro-optic sampling method. The gate pulses for sampling are sent through a large-mode-area photonic-crystal fiber. The observed electric field profile of the CSR is in good agreement with the spectrum of the CSR observed using Fourier transform far-infrared spectrometry, indicating good phase stability in the CSR. The longitudinal density profiles of electrons modulated by laser pulses were evaluated from the electric field profile.

  12. Cosmic radiation and magnetic fields: Exposure assessment and health outcomes among airline flight crews

    NASA Astrophysics Data System (ADS)

    Nicholas, Joyce Shealy

    Airline flight crews are chronically exposed to cosmic radiation and to magnetic fields generated by the aircraft's electrical system. Potential disease risks have been identified in health studies among commercial flight crews outside of the United States and among military pilots within the United States. The objectives of this study were (1) to quantify exposure to both cosmic radiation and magnetic fields onboard aircraft, (2) to develop a methodology for estimating career cosmic radiation doses to individual crew members, and (3) to compare mortality among United States commercial pilots and navigators with that of all occupational groups. Cosmic radiation equivalent doses to bone marrow and skeletal tissue were calculated on a flight-by-flight basis. Flight-by-flight calculations were used to develop an estimation methodology for cumulative (career) cosmic radiation doses. Magnetic fields were measured directly onboard aircraft during flight. Health outcomes among United States commercial pilots and navigators were investigated using proportional mortality ratios, proportional cancer mortality ratios, and mortality odds ratios. Based on the sample used in this study, the cosmic radiation equivalent dose to bone marrow and skeletal tissue associated with air travel ranges from 30 to 570 microsieverts per 100 flight hours (not including ground time) depending on altitude, latitude, phase of solar cycle, and flight duration. Magnetic field exposure appears to be characterized by frequencies between 100 and 800 hertz and varies in strength depending on stages of flight, location within the aircraft, and aircraft type. Based on limited measurements, maximum field strengths may increase from 0.6 microtesla in economy class to 1.2 microtesla in first class, suggesting that cockpit exposures may be higher. Potential synergistic effects of cosmic radiation and magnetic fields may be associated with certain cancers found in excess among flight crews, in particular

  13. The influences of solar wind pressure and interplanetary magnetic field on global magnetic field and outer radiation belt electrons

    NASA Astrophysics Data System (ADS)

    Yu, J.; Li, L. Y.; Cao, J. B.; Reeves, G. D.; Baker, D. N.; Spence, H.

    2016-07-01

    Using the Van Allen Probe in situ measured magnetic field and electron data, we examine the solar wind dynamic pressure and interplanetary magnetic field (IMF) effects on global magnetic field and outer radiation belt relativistic electrons (≥1.8 MeV). The dynamic pressure enhancements (>2 nPa) cause the dayside magnetic field increase and the nightside magnetic field reduction, whereas the large southward IMFs (Bz-IMF < -2nT) mainly lead to the decrease of the nightside magnetic field. In the dayside increased magnetic field region (magnetic local time (MLT) ~ 06:00-18:00, and L > 4), the pitch angles of relativistic electrons are mainly pancake distributions with a flux peak around 90° (corresponding anisotropic index A > 0.1), and the higher-energy electrons have stronger pancake distributions (the larger A), suggesting that the compression-induced betatron accelerations enhance the dayside pancake distributions. However, in the nighttime decreased magnetic field region (MLT ~ 18:00-06:00, and L ≥ 5), the pitch angles of relativistic electrons become butterfly distributions with two flux peaks around 45° and 135° (A < 0). The spatial range of the nighttime butterfly distributions is almost independent of the relativistic electron energy, but it depends on the magnetic field day-night asymmetry and the interplanetary conditions. The dynamic pressure enhancements can make the nighttime butterfly distribution extend inward. The large southward IMFs can also lead to the azimuthal expansion of the nighttime butterfly distributions. These variations are consistent with the drift shell splitting and/or magnetopause shadowing effect.

  14. The influences of solar wind pressure and interplanetary magnetic field on global magnetic field and outer radiation belt electrons

    DOE PAGESBeta

    Yu, J.; Li, L. Y.; Cao, J. B.; Reeves, Geoffrey D.; Baker, D. N.; Spence, H.

    2016-07-22

    Using the Van Allen Probe in situ measured magnetic field and electron data, we examine the solar wind dynamic pressure and interplanetary magnetic field (IMF) effects on global magnetic field and outer radiation belt relativistic electrons (≥1.8 MeV). The dynamic pressure enhancements (>2 nPa) cause the dayside magnetic field increase and the nightside magnetic field reduction, whereas the large southward IMFs (Bz-IMF < –2nT) mainly lead to the decrease of the nightside magnetic field. In the dayside increased magnetic field region (magnetic local time (MLT) ~ 06:00–18:00, and L > 4), the pitch angles of relativistic electrons are mainly pancakemore » distributions with a flux peak around 90° (corresponding anisotropic index A > 0.1), and the higher-energy electrons have stronger pancake distributions (the larger A), suggesting that the compression-induced betatron accelerations enhance the dayside pancake distributions. However, in the nighttime decreased magnetic field region (MLT ~ 18:00–06:00, and L ≥ 5), the pitch angles of relativistic electrons become butterfly distributions with two flux peaks around 45° and 135° (A < 0). The spatial range of the nighttime butterfly distributions is almost independent of the relativistic electron energy, but it depends on the magnetic field day-night asymmetry and the interplanetary conditions. The dynamic pressure enhancements can make the nighttime butterfly distribution extend inward. The large southward IMFs can also lead to the azimuthal expansion of the nighttime butterfly distributions. As a result, these variations are consistent with the drift shell splitting and/or magnetopause shadowing effect.« less

  15. Coherence-polarization properties of fields radiated from transversely periodic electromagnetic sources

    NASA Astrophysics Data System (ADS)

    Santarsiero, M.; de Sande, J. C. G.; Piquero, G.; Gori, F.

    2013-05-01

    Planar electromagnetic sources characterized by a periodic variation of their beam coherence-polarization matrix are investigated, as far as the polarization features of the radiated fields are concerned, within the framework of the paraxial approximation. A propagation scheme based on plane-wave decomposition leads to a longitudinal periodicity of the polarization properties of the field, thus extending the Talbot effect to the case of partially coherent electromagnetic sources. The polarization features of beams radiated from sources of this type are illustrated by means of simple examples. In particular, it is shown that completely unpolarized sources with uniform intensity profiles can be easily realized, for which the propagated field becomes perfectly polarized across some transverse planes, and vice versa.

  16. Deconvolution of wide field-of-view radiometer measurements of earth-emitted radiation. I - Theory

    NASA Technical Reports Server (NTRS)

    Smith, G. L.; Green, R. N.

    1981-01-01

    The theory of deconvolution of wide field-of-view (WFOV) radiometer measurements of earth-emitted radiation provides a technique by which the resolution of such measurements can be enhanced to provide radiant exitance at the top of the atmosphere with a finer resolution than the field of view. An analytical solution for the earth-emitted radiant exitance in terms of WFOV radiometer measurements is derived for the nonaxisymmetric (or regional) case, in which the measurements and radiant exitance are considered to be functions of both latitude and longitude. This solution makes it possible to deconvolve a set of WFOV radiometer measurements of earth-emitted radiation and obtain information with a finer resolution than the instantaneous field of view of the instrument. It is shown that there are tradeoffs involved in the selection between WFOV and scanning radiometers.

  17. Terahertz radiation induced chaotic electron transport in semiconductor superlattices with a tilted magnetic field

    SciTech Connect

    Wang, C. Wang, F.; Cao, J. C.

    2014-09-01

    Chaotic electron transport in semiconductor superlattice induced by terahertz electric field that is superimposed on a dc electric field along the superlattice axis are studied using the semiclassical motion equations including the effect of dissipation. A magnetic field that is tilted relative to the superlattice axis is also applied to the system. Numerical simulation shows that electrons in superlattice miniband exhibit complicate nonlinear oscillating modes with the influence of terahertz radiation. Transitions between frequency-locking and chaos via pattern forming bifurcations are observed with the varying of terahertz amplitude. It is found that the chaotic regions gradually contract as the dissipation increases. We attribute the appearance of complicate nonlinear oscillation in superlattice to the interaction between terahertz radiation and internal cooperative oscillating mode relative to Bloch oscillation and cyclotron oscillation.

  18. Terahertz radiation induced chaotic electron transport in semiconductor superlattices with a tilted magnetic field.

    PubMed

    Wang, C; Wang, F; Cao, J C

    2014-09-01

    Chaotic electron transport in semiconductor superlattice induced by terahertz electric field that is superimposed on a dc electric field along the superlattice axis are studied using the semiclassical motion equations including the effect of dissipation. A magnetic field that is tilted relative to the superlattice axis is also applied to the system. Numerical simulation shows that electrons in superlattice miniband exhibit complicate nonlinear oscillating modes with the influence of terahertz radiation. Transitions between frequency-locking and chaos via pattern forming bifurcations are observed with the varying of terahertz amplitude. It is found that the chaotic regions gradually contract as the dissipation increases. We attribute the appearance of complicate nonlinear oscillation in superlattice to the interaction between terahertz radiation and internal cooperative oscillating mode relative to Bloch oscillation and cyclotron oscillation. PMID:25273189

  19. Improvement of terahertz field effect transistor detectors by substrate thinning and radiation losses reduction.

    PubMed

    Coquillat, Dominique; Marczewski, Jacek; Kopyt, Pawel; Dyakonova, Nina; Giffard, Benoit; Knap, Wojciech

    2016-01-11

    Phenomena of the radiation coupling to the field effect transistors based terahertz (THz) detectors are studied. We show that in the case of planar metal antennas a significant portion of incoming radiation, instead of being coupled to the transistors, is coupled to an antenna substrate leading to responsivity losses and/or cross-talk effects in the field effect based THz detector arrays. Experimental and theoretical investigations of the responsivity versus substrate thickness are performed. They clearly show how to minimize the losses by the detector/ array substrate thinning. In conclusion simple quantitative rules of losses minimization by choosing a proper substrate thickness of field effect transistor THz detectors are presented for common materials (Si, GaAs, InP, GaN) used in semiconductor technologies. PMID:26832258

  20. Electrically tunable near-field radiative heat transfer via ferroelectric materials

    SciTech Connect

    Huang, Yi; Boriskina, Svetlana V.; Chen, Gang

    2014-12-15

    We explore ways to actively control near-field radiative heat transfer between two surfaces that relies on electrical tuning of phonon modes of ferroelectric materials. Ferroelectrics are widely used for tunable electrical devices, such as capacitors and memory devices; however, their tunable properties have not yet been examined for heat transfer applications. We show via simulations that radiative heat transfer between two ferroelectric materials can be enhanced by over two orders of magnitude over the blackbody limit in the near field, and can be tuned as much as 16.5% by modulating the coupling between surface phonon polariton modes at the two surfaces via varying external electric fields. We then discuss how to maximize the modulation contrast for tunable thermal devices using the studied mechanism.

  1. Enhancement of near-field radiative heat transfer using polar dielectric thin films.

    PubMed

    Song, Bai; Ganjeh, Yashar; Sadat, Seid; Thompson, Dakotah; Fiorino, Anthony; Fernández-Hurtado, Víctor; Feist, Johannes; Garcia-Vidal, Francisco J; Cuevas, Juan Carlos; Reddy, Pramod; Meyhofer, Edgar

    2015-03-01

    Thermal radiative emission from a hot surface to a cold surface plays an important role in many applications, including energy conversion, thermal management, lithography, data storage and thermal microscopy. Recent studies on bulk materials have confirmed long-standing theoretical predictions indicating that when the gap between the surfaces is reduced to tens of nanometres, well below the peak wavelength of the blackbody emission spectrum, the radiative heat flux increases by orders of magnitude. However, despite recent attempts, whether such enhancements can be obtained in nanoscale dielectric films thinner than the penetration depth of thermal radiation, as suggested by theory, remains experimentally unknown. Here, using an experimental platform that comprises a heat-flow calorimeter with a resolution of about 100 pW (ref. 7), we experimentally demonstrate a dramatic increase in near-field radiative heat transfer, comparable to that obtained between bulk materials, even for very thin dielectric films (50-100 nm) when the spatial separation between the hot and cold surfaces is comparable to the film thickness. We explain these results by analysing the spectral characteristics and mode shapes of surface phonon polaritons, which dominate near-field radiative heat transport in polar dielectric thin films. PMID:25705866

  2. Gamma–Gamma Absorption in the Broad Line Region Radiation Fields of Gamma-Ray Blazars

    NASA Astrophysics Data System (ADS)

    Böttcher, Markus; Els, Paul

    2016-04-01

    The expected level of γγ absorption in the Broad Line Region (BLR) radiation field of γ-ray loud Flat Spectrum Radio Quasars (FSRQs) is evaluated as a function of the location of the γ-ray emission region. This is done self-consistently with parameters inferred from the shape of the spectral energy distribution (SED) in a single-zone leptonic EC-BLR model scenario. We take into account all geometrical effects both in the calculation of the γγ opacity and the normalization of the BLR radiation energy density. As specific examples, we study the FSRQs 3C279 and PKS 1510-089, keeping the BLR radiation energy density at the location of the emission region fixed at the values inferred from the SED. We confirm previous findings that the optical depth due to γγ absorption in the BLR radiation field exceeds unity for both 3C279 and PKS 1510-089 for locations of the γ-ray emission region inside the inner boundary of the BLR. It decreases monotonically, with distance from the central engine and drops below unity for locations within the BLR. For locations outside the BLR, the BLR radiation energy density required for the production of GeV γ-rays rapidly increases beyond observational constraints, thus making the EC-BLR mechanism implausible. Therefore, in order to avoid significant γγ absorption by the BLR radiation field, the γ-ray emission region must therefore be located near the outer boundary of the BLR.

  3. Rounded leaf end effect of multileaf collimator on penumbra width and radiation field offset: an analytical and numerical study

    PubMed Central

    Zhou, Dong; Zhang, Hui; Ye, Peiqing

    2015-01-01

    Background Penumbra characteristics play a significant role in dose delivery accuracy for radiation therapy. For treatment planning, penumbra width and radiation field offset strongly influence target dose conformity and organ at risk sparing. Methods In this study, we present an analytical and numerical approach for evaluation of the rounded leaf end effect on penumbra characteristics. Based on the rule of half-value layer, algorithms for leaf position calculation and radiation field offset correction were developed, which were advantageous particularly in dealing with large radius leaf end. Computer simulation was performed based on the Monte Carlo codes of EGSnrc/BEAMnrc, with groups of leaf end radii and source sizes. Data processing technique of curve fitting was employed for deriving penumbra width and radiation field offset. Results Results showed that penumbra width increased with source size. Penumbra width curves for large radius leaf end were U-shaped. This observation was probably related to the fact that radiation beams penetrated through the proximal and distal leaf sides. In contrast, source size had negligible impact on radiation field offset. Radiation field offsets were found to be constant both for analytical method and numerical simulation. However, the overall resulting values of radiation field offset obtained by analytical method were slightly smaller compared with Monte Carlo simulation. Conclusions The method we proposed could provide insight into the investigation of rounded leaf end effects on penumbra characteristics. Penumbra width and radiation field offset calibration should be carefully performed to commission multileaf collimator for intensity modulated radiotherapy. PMID:26401137

  4. Response of dosemeters in the radiation field generated by a TW-class laser system.

    PubMed

    Olšovcová, V; Klír, D; Krása, J; Krůs, M; Velyhan, A; Zelenka, Z; Rus, B

    2014-10-01

    State-of-the-art laser systems are able to generate ionising radiation of significantly high energies by focusing ultra-short and intense pulses onto targets. Thus, measures ensuring the radiation protection of both working personnel and the general public are required. However, commercially available dosemeters are primarily designed for measurement in continuous fields. Therefore, it is important to explore their response to very short pulses. In this study, the responses of dosemeters in a radiation field generated by iodine high-power and Ti:Sapphire laser systems are examined in proton and electron acceleration experiments. Within these experiments, electron bunches of femtosecond pulse duration and 100-MeV energy and proton bunches with sub-nanosecond pulse duration and energy of several megaelectronvolts were generated in single-shot regimes. Responses of typical detectors (TLD, films and electronic personal dosemeter) were analysed and compared. Further, a first attempt was carried out to characterise the radiation field generated by TW-class laser systems. PMID:24563524

  5. Estimation of the radiation field homogeneity in 60Co blood irradiator

    NASA Astrophysics Data System (ADS)

    Urban, Tomas

    2014-11-01

    The aim of this work is to estimate the homogeneity of the radiation field in various configurations and relative activities of the “disposed” but still relatively highly active (approximately thousands of Curies, i.e. tens of TBq) sources for their potential use in irradiation of blood (or blood derivatives). Small dose rate, which is already unusable/inappropriate for the teletherapy, may be still utilized by simultaneous use of multiple sources or reducing the distance to the irradiated object (blood unit). To estimate the homogeneity of the radiation field a modeling approach has been chosen in which Monte Carlo code MCNP has been employed. (In-) homogeneity of the radiation field has been estimated on the basis of isodoses in the water phantom and for various configurations and relative activities of the 60Co sources. The results of simulations are also discussed with regard to further optimization (homogeneity of the sample irradiation, costs, radiation protection of service staff, availability of a sufficient number of resources, etc.).

  6. EVOLUTION OF X-RAY AND FAR-ULTRAVIOLET DISK-DISPERSING RADIATION FIELDS

    SciTech Connect

    Ingleby, Laura; Calvet, Nuria; Miller, Jon; Bergin, Edwin; Hartmann, Lee; Hernandez, Jesus; Briceno, Cesar; Espaillat, Catherine E-mail: ncalvet@umich.edu E-mail: ebergin@umich.edu E-mail: jesush@cida.ve E-mail: cespaillat@cfa.harvard.edu

    2011-04-15

    We present new X-ray and far-ultraviolet (FUV) observations of T Tauri stars covering the age range 1-10 Myr. Our goals are to observationally constrain the intensity of radiation fields responsible for evaporating gas from the circumstellar disk and to assess the feasibility of current photoevaporation models, focusing on X-ray and UV radiation. We greatly increase the number of 7-10 Myr old T Tauri stars observed in X-rays by including observations of the well-populated 25 Ori aggregate in the Orion OB1a subassociation. With these new 7-10 Myr objects, we confirm that X-ray emission remains constant from 1 to 10 Myr. We also show, for the first time, observational evidence for the evolution of FUV radiation fields with a sample of 56 accreting and non-accreting young stars spanning 1 Myr to 1 Gyr. We find that the FUV emission decreases on timescales consistent with the decline of accretion in classical T Tauri stars until reaching the chromospheric level in weak T Tauri stars and debris disks. Overall, we find that the observed strength of high-energy radiation is consistent with that required by photoevaporation models to dissipate the disks in timescales of approximately 10 Myr. Finally, we find that the high-energy fields that affect gas evolution are not similarly affecting dust evolution; in particular, we find that disks with inner clearings, transitional disks, have similar levels of FUV emission as full disks.

  7. A new multistack radiation boundary condition for FDTD based on self-teleportation of fields

    SciTech Connect

    Diaz, Rodolfo E.; Scherbatko, Igor . E-mail: igor_s@asu.edu

    2005-02-10

    In [Electromagnetics 23 (2003) 187], a technique for injecting perfect plane waves into finite regions of space in FDTD was reported. The essence of the technique, called Field Teleportation, is to invoke the principle of equivalent sources using FDTDs discrete definition of the curl to copy any field propagating in one FDTD domain to a finite region of another domain. In this paper, we apply this technique of Field Teleportation to the original domain itself to create a transparent boundary across which any outward traveling FDTD field produces an exact negative copy of itself. When this copied field is teleported one cell ahead and one cell forward in time it causes significant self-cancelation of the original field. Illustrative experiments in two-dimensions show that a two-layer (10-cell thick) multi-stack Radiation Boundary Condition (RBC) with a simplest Huygens's termination readily yields reflection coefficients of the order of -80 dB up to grazing incidence for all the fields radiated by a harmonic point source ({lambda} = 30 cells) in free space located 20 cells away from the boundary. Similarly low levels of artificial reflection are demonstrated for a case in which the RBC cuts through five different magnetodielectric materials.

  8. Evaluating a radiation monitor for mixed-field environments based on SRAM technology

    NASA Astrophysics Data System (ADS)

    Tsiligiannis, G.; Dilillo, L.; Bosio, A.; Girard, P.; Pravossoudovitch, S.; Todri, A.; Virazel, A.; Mekki, J.; Brugger, M.; Wrobel, F.; Saigne, F.

    2014-05-01

    Instruments operating in particle accelerators and colliders are exposed to radiations that are composed of particles of different types and energies. Several of these instruments often embed devices that are not hardened against radiation effects. Thus, there is a strong need for monitoring the levels of radiation inside the mixed-field radiation areas, throughout different positions. Different metrics exist for measuring the radiation damage induced to electronic devices, such as the Total Ionizing Dose (TID), the Displacement Damage (DD) and of course the fluence of particles for estimating the error rates of the electronic devices among other applications. In this paper, we propose an SRAM based monitor, that is used to define the fluence of High Energy Hadrons (HEH) by detecting Single Event Upsets in the memory array. We evaluated the device by testing it inside the H4IRRAD area of CERN, a test area that reproduces the radiation conditions inside the Large Hadron Collider (LHC) tunnel and its shielded areas. By using stability estimation methods and presenting experimental data, we prove that this device is proper to be used for such a purpose.

  9. Strong Field-Induced Frequency Conversion of Laser Radiation in Plasma Plumes: Recent Achievements

    PubMed Central

    Ganeev, R. A.

    2013-01-01

    New findings in plasma harmonics studies using strong laser fields are reviewed. We discuss recent achievements in the growth of the efficiency of coherent extreme ultraviolet (XUV) radiation sources based on frequency conversion of the ultrashort pulses in the laser-produced plasmas, which allowed for the spectral and structural studies of matter through the high-order harmonic generation (HHG) spectroscopy. These studies showed that plasma HHG can open new opportunities in many unexpected areas of laser-matter interaction. Besides being considered as an alternative method for generation of coherent XUV radiation, it can be used as a powerful tool for various spectroscopic and analytical applications. PMID:23864818

  10. Development of Near-Field-Enhanced High-Fill-Factor MEMS Radiator with Shared Spring

    NASA Astrophysics Data System (ADS)

    Nakajima, H.; Oh, S.; Ueno, A.; Morimoto, K.; Suzuki, Y.

    2015-12-01

    For precise thermal control in satellites under varying internal heat dissipation and thermal boundary condition, we propose a high-fill factor MEMS radiator enhanced by the near-field effect. We have successfully fabricated a prototype with parylene shared springs and achieved a fill factor of as high as 89%. It is found that at the ON state, the diaphragm temperature is increased from 58.0 °C to 106.4 °C, showing 144% enhancement in the radiation heat flux.

  11. Development of a proposed international standard for certification of aircraft to High Intensity Radiated Fields (HIRF)

    NASA Technical Reports Server (NTRS)

    Sargent, Noel B.

    1993-01-01

    Avionic systems performing critical functions in modern aircraft are potentially susceptible to the hazards of electromagnetic radiation from ground and airborne transmitters. The Federal Aviation Administration (FAA) requested that the Society of Automotive Engineers (SAE) coordinate the development of procedures and guidance material which can be used during the aircraft certification process to ensure adequate protection against high intensity radiated fields (HIRF). This paper addresses both the technical challenge of drafting a certification procedure and guidance standard as well as the management process used by the SAE subcommittee AE4R to converge a diverse range of opinions by its international membership in the shortest possible time.

  12. VizieR Online Data Catalog: Radiation fields in star-forming galaxies (Popescu+, 2013)

    NASA Astrophysics Data System (ADS)

    Popescu, C. C.; Tuffs, R. J.

    2013-09-01

    Radiative transfer model calculations of energy density of radiation fields (RFs) are presented on a cylindrical grid (r,z). The radiation fields are given for different values of central face-on dust opacity in the B-band {tau}Bf, which is the only parameter of the model shaping the spatial variation of the RFs. Since the energy densities of the radiation fields are additive quantities, they scale with the spatially integrated luminosity density at a given wavelength. Therefore RFs are only calculated for a fixed reference luminosity density (see Section 3 of journal paper). The radiation fields are separately calculated for the disk, thin disk and bulge. For the bulge different values of the Sersic index are considered. In total calculations are for seven values of the central face-on dust opacity, taufB=0.1,0.3,0.5,1.0,2.0,4.0,8.0. Solutions for other values of taufB can be found by interpolation. Four values for the Sersic index of the bulge are considered, n=1,2,4,8. In total we have 7 (for taufB) x 6 (wavelengths) x 1 (disk) + 7 (for taufB) x 15 (wavelengths) x 1 ( thin disk) + 7 (for taufB) x 6 (wavelengths) x 4 (for Sersic indices of bulge) = 315 combinations. In our model we consider the wavelength range from 912 Angstroem to 5 micron, as listed in Table E.2 of Popescu et al. (2011, Cat. J/A+A/527/109). Thus, the library contains a total of 315 files with two-dimensional spatial grids of energy densities of the RFs, in files.tar file. (2 data files).

  13. Matching Intensity-Modulated Radiation Therapy to an Anterior Low Neck Field

    SciTech Connect

    Amdur, Robert J. Liu, Chihray; Li, Jonathan; Mendenhall, William; Hinerman, Russell

    2007-10-01

    When using intensity-modulated radiation therapy (IMRT) to treat head and neck cancer with the primary site above the level of the larynx, there are two basic options for the low neck lymphatics: to treat the entire neck with IMRT, or to match the IMRT plan to a conventional anterior 'low neck' field. In view of the potential advantages of using a conventional low neck field, it is important to look for ways to minimize or manage the problems of matching IMRT to a conventional radiotherapy field. Treating the low neck with a single anterior field and the standard larynx block decreases the dose to the larynx and often results in a superior IMRT plan at the primary site. The purpose of this article is to review the most applicable studies and to discuss our experience with implementing a technique that involves moving the position of the superior border of the low neck field several times during a single treatment fraction.

  14. Internal Electric Field Behavior of Cadmium Zinc Telluride Radiation Detectors Under High Carrier Injection

    SciTech Connect

    Yang, G.; Bolotnikov, A.E.; Camarda, G.S.; Cui, Y.; Hossain, A.; Kim, K.H.; Gul, R.; and James, R.B.

    2010-10-26

    The behavior of the internal electric-field of nuclear-radiation detectors substantially affects the detector's performance. We investigated the distribution of the internal field in cadmium zinc telluride (CZT) detectors under high carrier injection. We noted the build-up of a space charge region near the cathode that produces a built-in field opposing the applied field. Its presence entails the collapse of the electric field in the rest of detector, other than the portion near the cathode. Such a space-charge region originates from serious hole-trapping in CZT. The device's operating temperature greatly affects the width of the space-charge region. With increasing temperature from 5 C to 35 C, its width expanded from about 1/6 to 1/2 of the total depth of the detector.

  15. Thermal electron acceleration by electric field spikes in the outer radiation belt: Generation of field-aligned pitch angle distributions

    NASA Astrophysics Data System (ADS)

    Vasko, I. Y.; Agapitov, O. V.; Mozer, F. S.; Artemyev, A. V.

    2015-10-01

    Van Allen Probes observations in the outer radiation belt have demonstrated an abundance of electrostatic electron-acoustic double layers (DL). DLs are frequently accompanied by field-aligned (bidirectional) pitch angle distributions (PAD) of electrons with energies from hundred eVs up to several keV. We perform numerical simulations of the DL interaction with thermal electrons making use of the test particle approach. DL parameters assumed in the simulations are adopted from observations. We show that DLs accelerate thermal electrons parallel to the magnetic field via the electrostatic Fermi mechanism, i.e., due to reflections from DL potential humps. The electron energy gain is larger for larger DL scalar potential amplitudes and higher propagation velocities. In addition to the Fermi mechanism, electrons can be trapped by DLs in their generation region and accelerated due to transport to higher latitudes. Both mechanisms result in formation of field-aligned PADs for electrons with energies comparable to those found in observations. The Fermi mechanism provides field-aligned PADs for <1 keV electrons, while the trapping mechanism extends field-aligned PADs to higher-energy electrons. It is shown that the Fermi mechanism can result in scattering into the loss cone of up to several tenths of percent of electrons with flux peaking at energies up to several hundred eVs.

  16. Pion production via proton synchrotron radiation in strong magnetic fields in relativistic field theory: Scaling relations and angular distributions

    DOE PAGESBeta

    Maruyama, Tomoyuki; Cheoun, Myung-Ki; Kajino, Toshitaka; Mathews, Grant J.

    2016-03-26

    We study pion production by proton synchrotron radiation in the presence of a strong magnetic field when the Landau numbers of the initial and final protons are n(i, f) similar to 10(4)-10(5). We find in our relativistic field theory calculations that the pion decay width depends only on the field strength parameter which previously was only conjectured based upon semi-classical arguments. Moreover, we also find new results that the decay width satisfies a robust scaling relation, and that the polar angular distribution of emitted pion momenta is very narrow and can be easily obtained. This scaling implies that one canmore » infer the decay width in more realistic magnetic fields of 10(15) G, where n(i, f) similar to 10(12)-10(13), from the results for n(i, f) similar to 10(4)-10(5). The resultant pion intensity and angular distributions for realistic magnetic field strengths are presented and their physical implications discussed. (C) 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP(3).« less

  17. Characterisation of radiation field for irradiation of biological samples at nuclear reactor-comparison of twin detector and recombination methods.

    PubMed

    Golnik, N; Gryziński, M A; Kowalska, M; Meronka, K; Tulik, P

    2014-10-01

    Central Laboratory for Radiological Protection is involved in achieving scientific project on biological dosimetry. The project includes irradiation of blood samples in radiation fields of nuclear reactor. A simple facility for irradiation of biological samples has been prepared at horizontal channel of the nuclear reactor MARIA in NCBJ in Poland. The radiation field, composed mainly of gamma radiation and thermal neutrons, has been characterised in terms of tissue kerma using twin-detector technique and recombination chambers. PMID:24366246

  18. Tips for Novice Researchers: Operational Difficulties Encountered in Underdeveloped Countries.

    ERIC Educational Resources Information Center

    Belcher El-Nahhas, Susan M.

    This paper provides a general overview of the type of problems encountered in the field of research so that individuals who are contemplating conducting research in an underdeveloped country for the first time are better prepared, and hence, better able to complete their research. The paper recounts a female researcher's personal experiences in…

  19. Would Larger Radiation Fields Lead to a Faster Onset of Pain Relief in the Palliation of Bone Metastases?

    SciTech Connect

    Chow, Edward Makhani, Leila; Culleton, Shaelyn; Makhani, Nadiya; Davis, Lori; Campos, Sarah; Sinclair, Emily

    2009-08-01

    Purpose: Hemibody irradiation has been shown to relieve bony metastatic pain within 24-48 hours of treatment, whereas for local external beam radiation, onset of pain relief is 1-4 weeks after radiation. The primary objective of this study is to examine whether there is a relationship between the areas of radiation treatment and onset of pain relief. Methods and Materials: From Jan 1999 to Jan 2002, a total of 653 patients with symptomatic bone metastases were treated with external beam radiation. Pain scores and analgesic consumption were recorded at baseline and Weeks 1, 2, 4, 8, and 12. The areas of radiation treatment for all patients were calculated, then correlated with the response and analyzed in various ways. We first compared pain score alone with mean radiation field size. Second, we combined pain score and analgesic consumption. Last, we implemented the International Consensus end points for pain score and analgesic intake. Results: Assessment of 653 patients showed no significant correlation comparing pain scores alone with radiation field area, with the exception of Week 4 for partial responders. Again, no significant correlation was found when combining both analgesic intake and pain score against radiation field size. Even when implementing the International Consensus end point definitions for radiation response, the only significant correlation between radiation field size and response was observed in Week 2 for partial response. Conclusion: There was no statistical significance between mean areas of radiation treatment with the onset of pain relief.

  20. The electric field changes and UHF radiations caused by the triggered lightning in Japan

    NASA Technical Reports Server (NTRS)

    Kawasaki, Zen-Ichiro; Kanao, Tadashi; Matsuura, Kenji; Nakano, Minoru; Horii, Kenji; Nakamura, Koichi

    1991-01-01

    In the rocket triggered lightning experiment of fiscal 1989, researchers observed electromagnetic field changes and UHF electromagnetic radiation accompanying rocket triggered lightning. It was found that no rapid changes corresponding to the return stroke of natural lightning were observed in the electric field changes accompanying rocket triggered lightning. However, continuous currents were present. In the case of rocket triggered lightning to the tower, electromagnetic field changes corresponding to the initiation of triggered lightning showed a bipolar pulse of a relatively large amplitude. In contrast, the rocket triggered lightning to the ground did not have such a bipolar pulse. The UHF radiation accompanying the rocket triggered lightning preceded the waveform portions corresponding to the first changes in electromagnetic fields. The number of isolated pulses in the UHF radiation showed a correlation with the time duration from rocket launching up to triggered lightning. The time interval between consecutive isolated pulses tended to get shorter with the passage of time, just like the stepped leaders of natural lightning.

  1. Particle Acceleration and Radiation associated with Magnetic Field Generation from Relativistic Collisionless Shocks

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.; Hardee, P. E.; Richardson, G. A.; Preece, R. D.; Sol, H.; Fishman, G. J.

    2003-01-01

    Shock acceleration is an ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, two-streaming instability, and the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. Using a 3-D relativistic electromagnetic particle (REMP) code, we have investigated particle acceleration associated with a relativistic jet front propagating through an ambient plasma with and without initial magnetic fields. We find only small differences in the results between no ambient and weak ambient magnetic fields. Simulations show that the Weibel instability created in the collisionless shock front accelerates particles perpendicular and parallel to the jet propagation direction. While some Fermi acceleration may occur at the jet front, the majority of electron acceleration takes place behind the jet front and cannot be characterized as Fermi acceleration. The simulation results show that this instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields, which contribute to the electron s transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.

  2. Simulation of Relativistic Shocks and Associated Radiation from Turbulent Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.; Niemiec, J.; Medvedev, M.; Zhang, B.; Hardee, P.; Mizuno, Y.; Nordlund, A.; Frederiksen, J.; Sol, H.; Pohl, M.; Hartmann, D. H.; Fishman, J. F.

    2009-01-01

    Plasma instabilities excited in collisionless shocks are responsible for particle acceleration. We have investigated the particle acceleration and shock structure associated with an unmagnetized relativistic electron-positron jet propagating into an unmagnetized electron-positron plasma. Cold jet electrons are thermalized and slowed while the ambient electrons are swept up to create a partially developed hydrodynamic-like shock structure. In the leading shock, electron density increases by a factor of about 3.5 in the simulation frame. Strong electromagnetic fields are generated in the trailing shock and provide an emission site. These magnetic fields contribute to the electron's transverse deflection behind the shock. The jitter'' radiation from deflected electrons in turbulent magnetic fields has different properties than synchrotron radiation, which is calculated in a uniform magnetic field. This jitter radiation may be important for understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets in general, and supernova remnants. New spectra based on simulations will be presented.

  3. Multi-band near-field radiative heat transfer between two anisotropic fishnet metamaterials

    NASA Astrophysics Data System (ADS)

    Bai, Yang; Jiang, Yongyuan; Liu, Linhua

    2015-06-01

    We study the near-field radiative heat transfer between two metal-insulator-metal sandwiched-like fishnet metamaterials (FMMs) by fluctuation electrodynamics. Results show that multi-band heat flux between the fishnet metamaterials is achieved, which is attributed to the thermally excited surface modes within the FMM. Apart from the electric response mode of the near-field heat flux, magnetic modes are also existed, which are related with the excitations of the surface plasmon polaritons (SPPs) propagating on the outer surface of metal (external SPPs) and along the inner metal-dielectric interface (internal SPPs). Moreover, we show that the electromagnetic parameters of this anisotropic fishnet metamaterial depend on the angles θ of the incident light when heating the fishnet metamaterial, and thus the overall effect of the anisotropic FMM parameters is considered to predict the near-field radiative heat transfer. Different external-SPPs and internal-SPPs modes are excited at different frequencies which is attributed to the anisotropic electromagnetic response of FMM, which open new frequency channels of the near-field radiative heat transfer. This kind of anisotropic metamaterial should assist in thermal management in nanoscale.

  4. Simulation of Relativistic Shocks and Associated Radiation from Turbulent Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.; Niemiec, J.; Medvedev, M.; Zhang, B.; Hardee, P.; Nordlund, A.; Frederiksen, J.; Mizuno, Y.; Sol, H.; Pohl, M.; Hartmann, D. H.; Fishman, G. J.

    2011-01-01

    Using our new 3-D relativistic particle-in-cell (PIC) code, we investigated long-term particle acceleration associated with a relativistic electron-positron jet propagating in an unmagnetized ambient electron-positron plasma. The simulations were performed using a much longer simulation system than our previous simulations in order to investigate the full nonlinear stage of the Weibel instability and its particle acceleration mechanism. Cold jet electrons are thermalized and ambient electrons are accelerated in the resulting shocks. Acceleration of ambient electrons leads to a maximum ambient electron density three times larger than the original value as predicted by hydrodynamic compression. Behind the bow shock, in the jet shock, strong electromagnetic fields are generated. These fields may lead to time dependent afterglow emission. In order to go beyond the standard synchrotron model used in astrophysical objects we have used PIC simulations and calculated radiation based on first principles. We calculated radiation from electrons propagating in a uniform parallel magnetic field to verify the technique. We also used the technique to calculate emission from electrons based on simulations with a small system. We obtain spectra which are consistent with those generated from electrons propagating in turbulent magnetic fields. This turbulent magnetic field is similar to the magnetic field generated at an early nonlinear stage of the Weibel instability. A fully developed shock within a larger system may generate a jitter/synchrotron spectrum.

  5. Impact of an external radiation field on handheld XRF measurements for nuclear forensics applications

    SciTech Connect

    Steeb, Jennifer L.; Mertz, Carol J.; Finck, Martha R.; Engelstad, Gary; Carney, Kevin P.; Chamberlain, David B.

    2015-03-28

    X-ray fluorescence (XRF) is an attractive technique for nuclear forensics applications. We evaluated a handheld, portable XRF device by applying an external radiation field (10 mR/h to 17 R/h) using two types of radiography sources: a 60Co radiography camera to observe effects from high-energy gamma emissions and an 192Ir radiography camera to observe effects from several low-energy gamma (0.604, 0.468, and 0.317 MeV) and decay daughter x-ray emissions. External radiation tests proved that radiation, in general, has a significant effect on the dead time or background at dose rates over 1 R/hr for both the 192Ir and 60Co sources.

  6. Radiation hardening of MOS devices by boron. [for stabilizing gate threshold potential of field effect device

    NASA Technical Reports Server (NTRS)

    Danchenko, V. (Inventor)

    1974-01-01

    A technique is described for radiation hardening of MOS devices and specifically for stabilizing the gate threshold potential at room temperature of a radiation subjected MOS field-effect device with a semiconductor substrate, an insulating layer of oxide on the substrate, and a gate electrode disposed on the insulating layer. The boron is introduced within a layer of the oxide of about 100 A-300 A thickness immediately adjacent the semiconductor-insulator interface. The concentration of boron in the oxide layer is preferably maintained on the order of 10 to the 18th power atoms/cu cm. The technique serves to reduce and substantially annihilate radiation induced positive gate charge accumulations.

  7. Study of high speed complex number algorithms. [for determining antenna for field radiation patterns

    NASA Technical Reports Server (NTRS)

    Heisler, R.

    1981-01-01

    A method of evaluating the radiation integral on the curved surface of a reflecting antenna is presented. A three dimensional Fourier transform approach is used to generate a two dimensional radiation cross-section along a planer cut at any angle phi through the far field pattern. Salient to the method is an algorithm for evaluating a subset of the total three dimensional discrete Fourier transform results. The subset elements are selectively evaluated to yield data along a geometric plane of constant. The algorithm is extremely efficient so that computation of the induced surface currents via the physical optics approximation dominates the computer time required to compute a radiation pattern. Application to paraboloid reflectors with off-focus feeds in presented, but the method is easily extended to offset antenna systems and reflectors of arbitrary shapes. Numerical results were computed for both gain and phase and are compared with other published work.

  8. Radiation sensitivity of graphene field effect transistors and other thin film architectures

    NASA Astrophysics Data System (ADS)

    Cazalas, Edward

    An important contemporary motivation for advancing radiation detection science and technology is the need for interdiction of nuclear and radiological materials, which may be used to fabricate weapons of mass destruction. The detection of such materials by nuclear techniques relies on achieving high sensitivity and selectivity to X-rays, gamma-rays, and neutrons. To be attractive in field deployable instruments, it is desirable for detectors to be lightweight, inexpensive, operate at low voltage, and consume low power. To address the relatively low particle flux in most passive measurements for nuclear security applications, detectors scalable to large areas that can meet the high absolute detection efficiency requirements are needed. Graphene-based and thin-film-based radiation detectors represent attractive technologies that could meet the need for inexpensive, low-power, size-scalable detection architectures, which are sensitive to X-rays, gamma-rays, and neutrons. The utilization of graphene to detect ionizing radiation relies on the modulation of graphene charge carrier density by changes in local electric field, i.e. the field effect in graphene. Built on the principle of a conventional field effect transistor, the graphene-based field effect transistor (GFET) utilizes graphene as a channel and a semiconducting substrate as an absorber medium with which the ionizing radiation interacts. A radiation interaction event that deposits energy within the substrate creates electron-hole pairs, which modify the electric field and modulate graphene charge carrier density. A detection event in a GFET is therefore measured as a change in graphene resistance or current. Thin (micron-scale) films can also be utilized for radiation detection of thermal neutrons provided nuclides with high neutron absorption cross section are present with appreciable density. Detection in thin-film detectors could be realized through the collection of charge carriers generated within the

  9. Assessment of radiation-induced second cancer risks in proton therapy and IMRT for organs inside the primary radiation field

    NASA Astrophysics Data System (ADS)

    Paganetti, Harald; Athar, Basit S.; Moteabbed, Maryam; Adams, Judith A.; Schneider, Uwe; Yock, Torunn I.

    2012-10-01

    There is clinical evidence that second malignancies in radiation therapy occur mainly within the beam path, i.e. in the medium or high-dose region. The purpose of this study was to assess the risk for developing a radiation-induced tumor within the treated volume and to compare this risk for proton therapy and intensity-modulated photon therapy (IMRT). Instead of using data for specific patients we have created a representative scenario. Fully contoured age- and gender-specific whole body phantoms (4 year and 14 year old) were uploaded into a treatment planning system and tumor volumes were contoured based on patients treated for optic glioma and vertebral body Ewing's sarcoma. Treatment plans for IMRT and proton therapy treatments were generated. Lifetime attributable risks (LARs) for developing a second malignancy were calculated using a risk model considering cell kill, mutation, repopulation, as well as inhomogeneous organ doses. For standard fractionation schemes, the LAR for developing a second malignancy from radiation therapy alone was found to be up to 2.7% for a 4 year old optic glioma patient treated with IMRT considering a soft-tissue carcinoma risk model only. Sarcoma risks were found to be below 1% in all cases. For a 14 year old, risks were found to be about a factor of 2 lower. For Ewing's sarcoma cases the risks based on a sarcoma model were typically higher than the carcinoma risks, i.e. LAR up to 1.3% for soft-tissue sarcoma. In all cases, the risk from proton therapy turned out to be lower by at least a factor of 2 and up to a factor of 10. This is mainly due to lower total energy deposited in the patient when using proton beams. However, the comparison of a three-field and four-field proton plan also shows that the distribution of the dose, i.e. the particular treatment plan, plays a role. When using different fractionation schemes, the estimated risks roughly scale with the total dose difference in%. In conclusion, proton therapy can

  10. The outflows accelerated by the magnetic fields and radiation force of accretion disks

    SciTech Connect

    Cao, Xinwu

    2014-03-01

    The inner region of a luminous accretion disk is radiation-pressure-dominated. We estimate the surface temperature of a radiation-pressure-dominated accretion disk, Θ=c{sub s}{sup 2}/r{sup 2}Ω{sub K}{sup 2}≪(H/r){sup 2}, which is significantly lower than that of a gas-pressure-dominated disk, Θ ∼ (H/r){sup 2}. This means that the outflow can be launched magnetically from the photosphere of the radiation-pressure-dominated disk only if the effective potential barrier along the magnetic field line is extremely shallow or no potential barrier is present. For the latter case, the slow sonic point in the outflow will probably be in the disk, which leads to a slow circular dense flow above the disk. This implies that hot gas (probably in the corona) is necessary for launching an outflow from the radiation-pressure-dominated disk, which provides a natural explanation for the observational evidence that the relativistic jets are related to hot plasma in some X-ray binaries and active galactic nuclei. We investigate the outflows accelerated from the hot corona above the disk by the magnetic field and radiation force of the accretion disk. We find that with the help of the radiation force, the mass loss rate in the outflow is high, which leads to a slow outflow. This may be why the jets in radio-loud narrow-line Seyfert galaxies are in general mildly relativistic compared with those in blazars.

  11. Radiation field in a multilayered geophysical medium: Ice-water-aerosol-vegetation-soil (IWAVES) model

    NASA Astrophysics Data System (ADS)

    Iaquinta, Jean; Pinty, Bernard

    1997-06-01

    Multiangular data which will be available with the upcoming satellite platforms (EOS, ENVISAT, ADEOS) offer a great potential for monitoring land surfaces on the global scale to the extent that physically based models describing the transfer of radiation can be developed. The present study constitutes an additional step toward modeling this radiative transfer with in particular the physical processes involved at the boundary between land vegetated surfaces and the atmospheric layer above. Our primary objectives are to address issues related to the perturbation by an atmospheric layer of the solar radiance field incident on the top of the vegetation canopy and the interpretation of the radiance field emerging from the atmospheric layer when isotropic scattering from the surface is a priori assumed. Indeed, the application of an inappropriate model for the interpretation of remotely sensed data can produce inaccurate retrievals of both the surface and atmosphere characteristics. In the present study the radiation transport problem in this coupled system is solved analytically for uncollided and first collided radiation and uses a discrete ordinates method for multiple-scattered radiation. A sensitivity analysis of the multilayered ice-water-aerosol-vegetation-soil model is conducted in order to quantify the effects of atmospheric and surface perturbations within the whole system. The results are essentially reported in terms of bidirectional reflectance factors at visible and near-infrared wavelengths, which allows the use of very different radiative properties of the vegetation layer. The consequences of assumptions made on one or the other of these media are investigated through an inversion experiment.

  12. Fluctuation-Induced Interactions in external magnetic fields: Casimir force and Radiative Heat Transfer

    NASA Astrophysics Data System (ADS)

    Esquivel-Sirvent, Raul

    Thermally induced electromagnetic fields give rise to the Casimir force and the near field heat transfer between two bodies separated by a gap. These phenomena are described by Rytova's theory of fluctuating electromagnetic fields and both the Casimir force and the near field heat transfer depend on the local dielectric function of the bodies. In this work we present a theoretical calculation on the modulation of fluctuation-induced interactions in the presence of an external magnetic field. The system consists of two parallel plates separated by a gap d. Each plate is isotropic and has a local dielectric function. Applying an external magnetic field parallel to the plates, in the so called Voigt configuration, the plates become anisotropic. In particular, we consider plates of InSb. For the Casimir force the two plates are kept at the same temperature and the external field reduces the magnitude of the force. Similarly if the two plates are kept at different temperature the near field radiative heat transfer is modulated by the magnitude of the external magnetic field. The results are extended to semiconducting quantum wells. In both cases, the excitation of magnetoplasmons provides an explanation for the observed effect.

  13. Occupational radiation exposure history of Idaho Field Office Operations at the INEL

    SciTech Connect

    Horan, J.R.; Braun, J.B.

    1993-10-01

    An extensive review has been made of the occupational radiation exposure records of workers at the Idaho National Engineering Laboratory (INEL) over the period of 1951 through 1990. The focus has been on workers employed by contractors and employees of the Idaho Field Operations Office (ID) of the United States Department of Energy (USDOE) and does not include the Naval Reactors Facility (NRF), the Argonne National Laboratory (ANL), or other operations field offices at the INEL. The radiation protection guides have decreased from 15 rem/year to 5 rem/year in 1990 for whole body penetrating radiation exposure. During these 40 years of nuclear operations (in excess of 200,000 man-years of work), a total of twelve individuals involved in four accidents exceeded the annual guidelines for exposure; nine of these exposures were received during life saving efforts on January 3, 1961 following the SL-1 reactor accident which killed three military personnel. These exposures ranged from 8 to 27 rem. Only one individual has exceeded the annual whole body penetrating radiation protection guidelines in the last 29 years.

  14. On the relativistic classical motion of a radiating spinning particle in a magnetic field

    SciTech Connect

    Kar, Arnab; Rajeev, S.G.

    2011-04-15

    Research Highlights: > We propose classical equations of motion for a charged particle with magnetic moment. > We account for radiation reaction as well. > Unlike previous proposals we do not have runaway solutions. > We find that the particle loses energy even in a constant magnetic field for a particular spin-polarized state. - Abstract: We propose classical equations of motion for a charged particle with magnetic moment, taking radiation reaction into account. This generalizes the Landau-Lifshitz equations for the spinless case. In the special case of spin-polarized motion in a constant magnetic field (synchrotron motion) we verify that the particle does lose energy. Previous proposals did not predict dissipation of energy and also suffered from runaway solutions analogous to those of the Lorentz-Dirac equations of motion.

  15. Reverse electric field Monte Carlo simulation for vector radiative transfer in the atmosphere

    NASA Astrophysics Data System (ADS)

    Li, Xu-You; Sun, Bo; Yu, Ying-Ying

    2014-06-01

    In this paper, a reverse electric field Monte Carlo (REMC) method is proposed to study the vector radiation transfer in the atmosphere. The REMC is based on tracing the multiply scattered electric field to simulate the vector transmitted radiance. The reflected intensities with different total optical depth values are obtained, which accord well with the results in the previous research. Stokes vector and the degree of polarization are numerically investigated. The simulation result shows that when the solar zenith angle is determined, the zenith angle of detector has two points, of which the degree of polarization does not change with the ground albedo and the optical depth. The two points change regularly with the solar zenith angle. Moreover, our REMC method can be applied to the vector radiative transfer in the atmosphere—ocean system.

  16. Active Thermal Extraction and Temperature Sensing of Near-field Thermal Radiation

    PubMed Central

    Ding, D.; Kim, T.; Minnich, A. J.

    2016-01-01

    Recently, we proposed an active thermal extraction (ATX) scheme that enables thermally populated surface phonon polaritons to escape into the far-field. The concept is based on a fluorescence upconversion process that also occurs in laser cooling of solids (LCS). Here, we present a generalized analysis of our scheme using the theoretical framework for LCS. We show that both LCS and ATX can be described with the same mathematical formalism by replacing the electron-phonon coupling parameter in LCS with the electron-photon coupling parameter in ATX. Using this framework, we compare the ideal efficiency and power extracted for the two schemes and examine the parasitic loss mechanisms. This work advances the application of ATX to manipulate near-field thermal radiation for applications such as temperature sensing and active radiative cooling. PMID:27595609

  17. Evaluation of focal fields and radiation characteristics of a dual-offset reflector antenna

    NASA Astrophysics Data System (ADS)

    Bird, T. S.; Boomars, J. L.

    1980-08-01

    A receive-mode analysis of a dual-offset reflector antenna consisting of an offset paraboloid and an offset hyperboloid is presented. In this analysis the field scattered from the offset paraboloid is determined using a GTD formulation involving two edge points and a reflection point, if one exists. A method is described for deciding whether there is a reflection point from the gradient of the path length at the edge points. The focal-region fields and the radiation characteristics are computed by numerical integration of the physical optics current on the offset hyperboloid. An experimental antenna operating at 35 GHz is described. Results of measurements of radiation patterns and of the power coupled into a circular waveguide array feed are compared with theory. In each case reasonable agreement is achieved for copolarized directed components. However, the experimental antenna produced higher crosspolarization than expected.

  18. The importance of using mesh tallies as an aid for radiation field evaluations.

    SciTech Connect

    Bland, J. R.; Crawford, A. B.; Perry, R. T.

    2004-01-01

    The many possible combinations of sources and position of sources in a glove box can lead to many different radiation field patterns of exposure to a glove box operator. The areas where the higher doses occur results mainly from streaming out of glove box ports. Scenarios leading to large doses may be avoided to some extent by administrative controls and using shielding inside the glove box. However, to do so requires knowledge of the locations in which the higher doses occur. Mesh tallies are a means to determine, a priori, the radiation fields in a plane outside the glove box. This paper will provide examples of using the mesh tallies to potentially provide for improved dose estimations and improved glove box shielding. The methods used in the examples may be expanded to other situations.

  19. Active Thermal Extraction and Temperature Sensing of Near-field Thermal Radiation.

    PubMed

    Ding, D; Kim, T; Minnich, A J

    2016-01-01

    Recently, we proposed an active thermal extraction (ATX) scheme that enables thermally populated surface phonon polaritons to escape into the far-field. The concept is based on a fluorescence upconversion process that also occurs in laser cooling of solids (LCS). Here, we present a generalized analysis of our scheme using the theoretical framework for LCS. We show that both LCS and ATX can be described with the same mathematical formalism by replacing the electron-phonon coupling parameter in LCS with the electron-photon coupling parameter in ATX. Using this framework, we compare the ideal efficiency and power extracted for the two schemes and examine the parasitic loss mechanisms. This work advances the application of ATX to manipulate near-field thermal radiation for applications such as temperature sensing and active radiative cooling. PMID:27595609

  20. COMPLEX SCATTERED RADIATION FIELDS AND MULTIPLE MAGNETIC FIELDS IN THE PROTOSTELLAR CLUSTER IN NGC 2264

    SciTech Connect

    Kwon, Jungmi; Tamura, Motohide; Kandori, Ryo; Kusakabe, Nobuhiko; Hashimoto, Jun; Nakajima, Yasushi; Nakamura, Fumitaka; Nagayama, Takahiro; Nagata, Tetsuya; Hough, James H.; Werner, Michael W.; Teixeira, Paula S.

    2011-11-01

    Near-infrared imaging polarimetry in the J, H, and K{sub s} bands has been carried out for the protostellar cluster region around NGC 2264 IRS 2 in the Monoceros OB1 molecular cloud. Various infrared reflection nebula clusters (IRNCs) associated with NGC 2264 IRS 2 and the IRAS 12 S1 core, as well as local infrared reflection nebulae (IRNe), were detected. The illuminating sources of the IRNe were identified with known or new near- and mid-infrared sources. In addition, 314 point-like sources were detected in all three bands and their aperture polarimetry was studied. Using a color-color diagram, reddened field stars and diskless pre-main-sequence stars were selected to trace the magnetic field (MF) structure of the molecular cloud. The mean polarization position angle of the point-like sources is 81 Degree-Sign {+-} 29 Degree-Sign in the cluster core, and 58 Degree-Sign {+-} 24 Degree-Sign in the perimeter of the cluster core, which is interpreted as the projected direction on the sky of the MF in the observed region of the cloud. The Chandrasekhar-Fermi method gives a rough estimate of the MF strength to be about 100 {mu}G. A comparison with recent numerical simulations of the cluster formation implies that the cloud dynamics is controlled by the relatively strong MF. The local MF direction is well associated with that of CO outflow for IRAS 12 S1 and consistent with that inferred from submillimeter polarimetry. In contrast, the local MF direction runs roughly perpendicular to the Galactic MF direction.

  1. EM modeling of far-field radiation patterns for antennas on the GMA-TT UAV

    NASA Astrophysics Data System (ADS)

    Mackenzie, Anne I.

    2015-05-01

    To optimize communication with the Generic Modular Aircraft T-Tail (GMA-TT) unmanned aerial vehicle (UAV), electromagnetic (EM) simulations have been performed to predict the performance of two antenna types on the aircraft. Simulated far-field radiation patterns tell the amount of power radiated by the antennas and the aircraft together, taking into account blockage by the aircraft as well as radiation by conducting and dielectric portions of the aircraft. With a knowledge of the polarization and distance of the two communicating antennas, e.g. one on the UAV and one on the ground, and the transmitted signal strength, a calculation may be performed to find the strength of the signal travelling from one antenna to the other and to check that the transmitted signal meets the receiver system requirements for the designated range. In order to do this, the antenna frequency and polarization must be known for each antenna, in addition to its design and location. The permittivity, permeability, and geometry of the UAV components must also be known. The full-wave method of moments solution produces the appropriate dBi radiation pattern in which the received signal strength is calculated relative to that of an isotropic radiator.

  2. EM Modeling of Far-Field Radiation Patterns for Antennas on the GMA-TT UAV

    NASA Technical Reports Server (NTRS)

    Mackenzie, Anne I.

    2015-01-01

    To optimize communication with the Generic Modular Aircraft T-Tail (GMA-TT) unmanned aerial vehicle (UAV), electromagnetic (EM) simulations have been performed to predict the performance of two antenna types on the aircraft. Simulated far-field radiation patterns tell the amount of power radiated by the antennas and the aircraft together, taking into account blockage by the aircraft as well as radiation by conducting and dielectric portions of the aircraft. With a knowledge of the polarization and distance of the two communicating antennas, e.g. one on the UAV and one on the ground, and the transmitted signal strength, a calculation may be performed to find the strength of the signal travelling from one antenna to the other and to check that the transmitted signal meets the receiver system requirements for the designated range. In order to do this, the antenna frequency and polarization must be known for each antenna, in addition to its design and location. The permittivity, permeability, and geometry of the UAV components must also be known. The full-wave method of moments solution produces the appropriate dBi radiation pattern in which the received signal strength is calculated relative to that of an isotropic radiator.

  3. Durability and shielding performance of borated Ceramicrete coatings in beta and gamma radiation fields

    NASA Astrophysics Data System (ADS)

    Wagh, Arun S.; Sayenko, S. Yu.; Dovbnya, A. N.; Shkuropatenko, V. A.; Tarasov, R. V.; Rybka, A. V.; Zakharchenko, A. A.

    2015-07-01

    Ceramicrete™, a chemically bonded phosphate ceramic, was developed for nuclear waste immobilization and nuclear radiation shielding. Ceramicrete products are fabricated by an acid-base reaction between magnesium oxide and mono potassium phosphate. Fillers are used to impart desired properties to the product. Ceramicrete's tailored compositions have resulted in several commercial structural products, including corrosion- and fire-protection coatings. Their borated version, called Borobond™, has been studied for its neutron shielding capabilities and is being used in structures built for storage of nuclear materials. This investigation assesses the durability and shielding performance of borated Ceramicrete coatings when exposed to gamma and beta radiations to predict the composition needed for optimal shielding performance in a realistic nuclear radiation field. Investigations were conducted using experimental data coupled with predictive Monte Carlo computer model. The results show that it is possible to produce products for simultaneous shielding of all three types of nuclear radiations, viz., neutrons, gamma-, and beta-rays. Additionally, because sprayable Ceramicrete coatings exhibit excellent corrosion- and fire-protection characteristics on steel, this research also establishes an opportunity to produce thick coatings to enhance the shielding performance of corrosion and fire protection coatings for use in high radiation environment in nuclear industry.

  4. The Effects of Aerosol on Atmospheric UV Radiation: Measurements and Modeling from the MILAGRO Field Campaign

    NASA Astrophysics Data System (ADS)

    Madronich, S.; Hall, S.; Shetter, R.; Slusser, J.; Arnott, P.

    2007-05-01

    The MILAGRO field campaign took place in and near Mexico City 1-30 March 2006. A comprehensive data set was obtained on atmospheric chemical composition (gas and aerosol), aerosol microphysics, spectral radiation, and meteorology from surface-, aircraft-, and satellite-based instruments. For much of this time, the lower atmosphere was laden with large amounts of aerosols originating from urban and industrial sources, biomass fires, and wind-blown dust. Spectral radiation measurements are available from filter radiometers and spectroradiometers, and span ultraviolet (UV) wavelengths important to surface biota and tropospheric photochemistry. By combining the spectral radiation measurements, aerosol composition, optical, and microphysical measurements, and modeling, an assessment is now possible on how aerosols affect surface UV radiation (e.g. DNA damage, erythema, vitamin-D production) and vertical profiles of photolysis frequencies (e.g. JNO2, JO3(O1D), JCH2O, JHONO). Interactions between aerosol-scattered radiation and absorption by gaseous pollutants (esp. O3, SO2, and NO2) can also be evaluated. Implications for human health and photochemical oxidant formation will be discussed.

  5. On the space-time scales of the surface solar radiation field

    SciTech Connect

    Barnett, T.P.; Ritchie, J.; Foat, J.; Stokes, G.

    1998-01-01

    The characteristic space-time scales of surface solar radiation fields measured by the 111-instrument ME-SONET in Oklahoma are estimated after removal of the diurnal cycle. These estimates of {open_quotes}within-day{close_quotes} are used to deduce the representativeness of surface solar radiation measurements measurement site as a function of time-averaging interval. Nomograms of the relation between point measurements and area averages are given for different space-time-averaging intervals. Examples from the nomograms show, for instance, that under conditions of low mean radiation (cloudy days), the central site point measurements are representative of a spatial area the size of a T42 GCM grid box (280 km X 280 km) if one uses hourly averages and is willing to accept a correlation of 0.45 between area average and point measurement. The point data represent a 60 km X 60 km region at a 0.90 correlation level if a 5-min time average is used. The characteristic timescale for the within-day radiation variability was roughly 60 min. Estimates of scale lengths for days when the mean background radiation conditions are high are also given in the nomographs. 10 refs., 8 figs.

  6. On the Space-Time Scales of the Surface Solar Radiation Field.

    NASA Astrophysics Data System (ADS)

    Barnett, T. P.; Ritchie, J.; Foat, J.; Stokes, G.

    1998-01-01

    The characteristic space-time scales of surface solar radiation fields measured by the 111-instrument MESONET in Oklahoma are estimated after removal of the diurnal cycle. These estimates of `within-day' variability are used to deduce the representativeness of surface solar radiation measurements made at the central ARM measurement site as a function of time-averaging interval. Nomograms of the relation between point measurements and area averages are given for different space-time-averaging intervals. Examples from the nomograms show, for instance, that under conditions of low mean radiation (cloudy days), the central site point measurements are representative of a spatial area the size of a T42 GCM grid box (280 km × 280 km) if one uses hourly averages and is willing to accept a correlation of 0.45 between area average and point measurement. The point data represent a 60 km × 60 km region at a 0.90 correlation level if a 5-min time average is used. The characteristic timescale for the within-day radiation variability was roughly 60 min. Estimates of scale lengths for days when the mean background radiation conditions are high are also given in the nomographs.

  7. A space weather index for the radiation field at aviation altitudes

    NASA Astrophysics Data System (ADS)

    Meier, Matthias M.; Matthiä, Daniel

    2014-04-01

    The additional dose contribution to the radiation exposure at aviation altitudes during Solar Particle Events (SPEs) has been a matter of concern for many years. After the Halloween storms in 2003 several airlines began to implement mitigation measures such as rerouting and lowering flight altitudes in response to alerts on the NOAA S-scale regarding solar radiation storms. These alerts are based on the integral proton flux above 10 MeV measured aboard the corresponding GOES-satellite which is operated outside the Earth's atmosphere in a geosynchronous orbit. This integral proton flux has, however, been proved to be an insufficient parameter to apply to the radiation field at aviation altitudes without an accompanying analysis of the shape of the energy spectrum. Consequently, false alarms and corresponding disproportionate reactions ensued. Since mitigating measures can be quite cost-intensive, there has been a demand for appropriate space weather information among responsible airline managers for about a decade. Against this background, we propose the introduction of a new Space Weather index D, based on dose rates at aviation altitudes produced by solar protons during solar radiation storms, as the relevant parameter for the assessment of corresponding radiation exposure. The Space Weather index D is a natural number given by a graduated table of ranges of dose rates in ascending order which is derived by an equation depending on the dose rate of solar protons.

  8. Wind induced interior and far field radiated exterior noise from automobiles

    NASA Astrophysics Data System (ADS)

    Dobrzynski, W.

    Aerodynamically induced interior noise in passenger cars was investigated. Surface pressure and resulting interior noise were measured on a full-scale automobile in wind tunnel tests. Both quantities are interrelated theoretically; corresponding interior noise predictions are compared to measured data. Results show that high surface-pressure originating even from highly localized flow separations on the car-body tend to dominate interior noise. Far field noise radiation from exterior flow/car-body interaction is predicted and compared to measured data.

  9. Far-ultraviolet studies. VII - The spectrum and latitude dependence of the local interstellar radiation field

    NASA Technical Reports Server (NTRS)

    Henry, R. C.; Anderson, R. C.; Fastie, W. G.

    1980-01-01

    A direct measurement has been made of the spectrum (1180-1680 A) and Gould-latitude dependence of the local interstellar radiation field, over about one-third of the sky. The result is corrected to give expected values for the entire sky. The average local 1180-1680 A energy density is 5.8 x 10 to the -17th ergs/cu cm A. The surface brightness falls off toward high latitudes much more steeply than published models predict.

  10. Intelligent monitor functional model with ionization chamber for mixed nuclear radiation field measurements

    SciTech Connect

    Valcov, N.; Purghel, L.; Celarel, A.

    1998-12-31

    By using the statistical discrimination technique, the components of an ionization current, due to a mixed radiation field, may be simultaneously measured. A functional model, including a series manufactured gamma-ray ratemeter was done, as an intermediate step in the design of specialized nuclear instrumentation, in order to check the concept of statistical discrimination method. The obtained results are in good agreement with the estimations of the statistical discrimination method.

  11. Application of the TLD albedo technique for monitoring and interpretation of neutron stray radiation fields

    NASA Astrophysics Data System (ADS)

    Piesch, E.; Burgkhardt, B.

    1980-09-01

    A single sphere albedo technique with TLD 600/TLD 700 detectors has been applied in neutron monitoring to calibrate albedo dosimeters and to interpret neutron stray radiation fields in terms of neutron dose equivalent separated for the energy groups below 0.4 eV, 0.4-10 keV and 10 keV-10 MeV, and Eeff for fast neutrons. The paper describes the technique for field and personnel monitoring under the aspect of an on-line computer program for data recording and processing.

  12. Characteristics of Neutron Fields for Radiation Protection and Other Applications at the Kinki University Reactor

    NASA Astrophysics Data System (ADS)

    Ogawa, Yoshihiro; Fujiwara, Tatsuya; Morishima, Hiroshige; Urabe, Itsumasa; Sagawa, Hiroyuki

    2003-06-01

    In order to get useful information about neutron energy spectrum and neutron dose, a versatile and accurate reactor model of the Kinki University Reactor (UTR-KINKI) was developed under the three-dimensional continuous-energy MCNP Monte Carlo code. The agreement between MCNP predictions and the experimentally determined values was very good. This paper describes characteristics of neutron fields at the Kinki University Reactor calculated with the present MCNP model of the UTR-KINKI. From the results obtained it was clear that these neutron fields are applicable to development and performance evaluation of personnel dosimeters and experimental studies on biological effects of low levels of radiation.

  13. Near-field thermal radiation between hyperbolic metamaterials: Graphite and carbon nanotubes

    SciTech Connect

    Liu, X. L.; Zhang, R. Z.; Zhang, Z. M.

    2013-11-18

    The near-field radiative heat transfer for two hyperbolic metamaterials, namely, graphite and vertically aligned carbon nanotubes (CNTs), is investigated. Graphite is a naturally existing uniaxial medium, while CNT arrays can be modeled as an effective anisotropic medium. Different hyperbolic modes can be separately supported by these materials in certain infrared regions, resulting in a strong enhancement in near-field heat transfer. It is predicted that the heat flux between two CNT arrays can exceed that between SiC plates at any vacuum gap distance and is about 10 times higher with a 10 nm gap.

  14. Magnetic Field Generation through Angular Momentum Exchange between Circularly Polarized Radiation and Charged Particles

    SciTech Connect

    G. Shvets; N.J. Fisch; J.-M. Rax

    2002-01-18

    The interaction between circularly polarized (CP) radiation and charged particles can lead to generation of magnetic field through an inverse Faraday effect. The spin of the circularly polarized electromagnetic wave can be converted into the angular momentum of the charged particles so long as there is dissipation. We demonstrate this by considering two mechanisms of angular momentum absorption relevant for laser-plasma interactions: electron-ion collisions and ionization. The precise dissipative mechanism, however, plays a role in determining the efficiency of the magnetic field generation.

  15. Radiative accretion shocks along nonuniform stellar magnetic fields in classical T Tauri stars

    NASA Astrophysics Data System (ADS)

    Orlando, S.; Bonito, R.; Argiroffi, C.; Reale, F.; Peres, G.; Miceli, M.; Matsakos, T.; Stehlé, C.; Ibgui, L.; de Sa, L.; Chièze, J. P.; Lanz, T.

    2013-11-01

    Context. According to the magnetospheric accretion model, hot spots form on the surface of classical T Tauri stars (CTTSs) in regions where accreting disk material impacts the stellar surface at supersonic velocity, generating a shock. Aims: We investigate the dynamics and stability of postshock plasma that streams along nonuniform stellar magnetic fields at the impact region of accretion columns. We study how the magnetic field configuration and strength determine the structure, geometry, and location of the shock-heated plasma. Methods: We model the impact of an accretion stream onto the chromosphere of a CTTS by 2D axisymmetric magnetohydrodynamic simulations. Our model considers the gravity, the radiative cooling, and the magnetic-field-oriented thermal conduction (including the effects of heat flux saturation). We explore different configurations and strengths of the magnetic field. Results: The structure, stability, and location of the shocked plasma strongly depend on the configuration and strength of the magnetic field. In the case of weak magnetic fields (plasma β ≳ 1 in the postshock region), a large component of B may develop perpendicular to the stream at the base of the accretion column, which limits the sinking of the shocked plasma into the chromosphere and perturbs the overstable shock oscillations induced by radiative cooling. An envelope of dense and cold chromospheric material may also develop around the shocked column. For strong magnetic fields (β < 1 in the postshock region close to the chromosphere), the field configuration determines the position of the shock and its stand-off height. If the field is strongly tapered close to the chromosphere, an oblique shock may form well above the stellar surface at the height where the plasma β ≈ 1. In general, we find that a nonuniform magnetic field makes the distribution of emission measure vs. temperature of the postshock plasma at T > 106 K lower than when there is uniform magnetic field

  16. High-resolution Ultraviolet Radiation Fields of Classical T Tauri Stars

    NASA Astrophysics Data System (ADS)

    France, Kevin; Schindhelm, Eric; Bergin, Edwin A.; Roueff, Evelyne; Abgrall, Hervé

    2014-04-01

    The far-ultraviolet (FUV; 912-1700 Å) radiation field from accreting central stars in classical T Tauri systems influences the disk chemistry during the period of giant planet formation. The FUV field may also play a critical role in determining the evolution of the inner disk (r < 10 AU), from a gas- and dust-rich primordial disk to a transitional system where the optically thick warm dust distribution has been depleted. Previous efforts to measure the true stellar+accretion-generated FUV luminosity (both hot gas emission lines and continua) have been complicated by a combination of low-sensitivity and/or low-spectral resolution and did not include the contribution from the bright Lyα emission line. In this work, we present a high-resolution spectroscopic study of the FUV radiation fields of 16 T Tauri stars whose dust disks display a range of evolutionary states. We include reconstructed Lyα line profiles and remove atomic and molecular disk emission (from H2 and CO fluorescence) to provide robust measurements of both the FUV continuum and hot gas lines (e.g., Lyα, N V, C IV, He II) for an appreciable sample of T Tauri stars for the first time. We find that the flux of the typical classical T Tauri star FUV radiation field at 1 AU from the central star is ~107 times the average interstellar radiation field. The Lyα emission line contributes an average of 88% of the total FUV flux, with the FUV continuum accounting for an average of 8%. Both the FUV continuum and Lyα flux are strongly correlated with C IV flux, suggesting that accretion processes dominate the production of both of these components. On average, only ~0.5% of the total FUV flux is emitted between the Lyman limit (912 Å) and the H2 (0-0) absorption band at 1110 Å. The total and component-level high-resolution radiation fields are made publicly available in machine-readable format. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space

  17. High-resolution ultraviolet radiation fields of classical T Tauri stars

    SciTech Connect

    France, Kevin; Schindhelm, Eric; Bergin, Edwin A.; Roueff, Evelyne; Abgrall, Hervé

    2014-04-01

    The far-ultraviolet (FUV; 912-1700 Å) radiation field from accreting central stars in classical T Tauri systems influences the disk chemistry during the period of giant planet formation. The FUV field may also play a critical role in determining the evolution of the inner disk (r < 10 AU), from a gas- and dust-rich primordial disk to a transitional system where the optically thick warm dust distribution has been depleted. Previous efforts to measure the true stellar+accretion-generated FUV luminosity (both hot gas emission lines and continua) have been complicated by a combination of low-sensitivity and/or low-spectral resolution and did not include the contribution from the bright Lyα emission line. In this work, we present a high-resolution spectroscopic study of the FUV radiation fields of 16 T Tauri stars whose dust disks display a range of evolutionary states. We include reconstructed Lyα line profiles and remove atomic and molecular disk emission (from H{sub 2} and CO fluorescence) to provide robust measurements of both the FUV continuum and hot gas lines (e.g., Lyα, N V, C IV, He II) for an appreciable sample of T Tauri stars for the first time. We find that the flux of the typical classical T Tauri star FUV radiation field at 1 AU from the central star is ∼10{sup 7} times the average interstellar radiation field. The Lyα emission line contributes an average of 88% of the total FUV flux, with the FUV continuum accounting for an average of 8%. Both the FUV continuum and Lyα flux are strongly correlated with C IV flux, suggesting that accretion processes dominate the production of both of these components. On average, only ∼0.5% of the total FUV flux is emitted between the Lyman limit (912 Å) and the H{sub 2} (0-0) absorption band at 1110 Å. The total and component-level high-resolution radiation fields are made publicly available in machine-readable format.

  18. Control of whistler radiation efficiency of a loop antenna by generation of ambient magnetic field irregularities

    SciTech Connect

    Gushchin, M. E.; Korobkov, S. V.; Kostrov, A. V.; Strikovsky, A. V.; Koldanov, V. A.; Zaboronkova, T. M.; Krafft, C.

    2008-05-15

    Electrodynamic means for the control of loop antenna radiation efficiency in plasma is proposed, which can be used in the whistler frequency band. The method is based on the generation, without perturbing the plasma density, of localized ambient magnetic field irregularities in the vicinity of the antenna. In order to produce such irregularities, it is suggested to feed the antenna with additional dc current along with the rf current. Experiments performed in a large laboratory magnetoplasma showed that the generation of localized magnetic field enhancements provides the possibility of increasing the amplitude of the whistlers emitted by the loop antenna. Moreover, experiments have shown that the amplification of the whistlers' signals from the receiving loop antenna fed with additional dc current is observed when a static magnetic field enhancement is generated in the vicinity of the receiver. The experimental data are in good agreement with the theoretical results obtained for comparatively weak ambient magnetic field perturbations.

  19. GENERATION OF SEED MAGNETIC FIELD AROUND FIRST STARS: EFFECTS OF RADIATION FORCE

    SciTech Connect

    Ando, Masashi; Doi, Kentaro; Susa, Hajime E-mail: mn921009@center.konan-u.ac.j

    2010-06-20

    We investigate seed magnetic field generation in the early universe by the radiation force of first stars. In a previous study with the steady assumption, large amplitudes ({approx}10{sup -15} G for first stars, {approx}10{sup -11} G for QSOs) are predicted. In this study, we formulate this issue in an unsteady framework. Then, we consider a specific model of magnetic field generation around a very massive first star. Consequently, we (1) find that the steady assumption is not valid in realistic situations and (2) obtain a much smaller magnetic field strength than that predicted by Langer et al. In addition, we find that the momentum transfer process during photoionization is more important than Thomson scattering. The resultant magnetic flux density around the first star is {approx_lt}10{sup -19} G. This seed magnetic field will not affect subsequent star formation in the neighborhood of first stars.

  20. Generation of Seed Magnetic Field Around First Stars: Effects of Radiation Force

    NASA Astrophysics Data System (ADS)

    Ando, Masashi; Doi, Kentaro; Susa, Hajime

    2010-06-01

    We investigate seed magnetic field generation in the early universe by the radiation force of first stars. In a previous study with the steady assumption, large amplitudes (~10-15 G for first stars, ~10-11 G for QSOs) are predicted. In this study, we formulate this issue in an unsteady framework. Then, we consider a specific model of magnetic field generation around a very massive first star. Consequently, we (1) find that the steady assumption is not valid in realistic situations and (2) obtain a much smaller magnetic field strength than that predicted by Langer et al. In addition, we find that the momentum transfer process during photoionization is more important than Thomson scattering. The resultant magnetic flux density around the first star is lsim10-19 G. This seed magnetic field will not affect subsequent star formation in the neighborhood of first stars.

  1. Increase in Phi X174 DNA radiation sensitivity due to electric fields

    SciTech Connect

    McCormack, Percival D.; Swenberg, Charles E.

    1985-01-01

    The object of this research was to establish whether or not orientation of DNA in electric fields would result in a significant increase in its sensitivity to damage by ionizing radiation. The application of an external electric field simultaneously with gamma irradiation to an aqueous suspension of Phi X 174 (in the RFI form) is shown to increase significantly the number of strand breaks. Tritiated DNA allowed the number of single-strand breaks to be estimated from changes in the scintillation of electrophoretic gel band associated with the fastest mobility moiety. At 400 V ( approx. 2400 V/cm) the corrected increase (corrected for phoresis of DNA on the stainless steel plates) in the G-value yield is 38%. The increase in damage with field strength appears to follow the increase in reduced dichroism. Dichroism results correspond at 400 V to approximately 10% of the maximum orientation. These results support the conjecture that this significant increase in DNA-radiation interaction with an electric field is due to field-induced conformation changes in the molecule. Keywords: Polyelectrolytes, Polynucleotides, Polypeptides, Birefringence, Dipole, and Moments.

  2. An improved method for the calculation of Near-Field Acoustic Radiation Modes

    NASA Astrophysics Data System (ADS)

    Liu, Zu-Bin; Maury, Cédric

    2016-02-01

    Sensing and controlling Acoustic Radiation Modes (ARMs) in the near-field of vibrating structures is of great interest for broadband noise reduction or enhancement, as ARMs are velocity distributions defined over a vibrating surface, that independently and optimally contribute to the acoustic power in the acoustic field. But present methods only provide far-field ARMs (FFARMs) that are inadequate for the acoustic near-field problem. The Near-Field Acoustic Radiation Modes (NFARMs) are firstly studied with an improved numerical method, the Pressure-Velocity method, which rely on the eigen decomposition of the acoustic transfers between the vibrating source and a conformal observation surface, including sound pressure and velocity transfer matrices. The active and reactive parts of the sound power are separated and lead to the active and reactive ARMs. NFARMs are studied for a 2D baffled beam and for a 3D baffled plate, and so as differences between the NFARMS and the classical FFARMs. Comparisons of the NFARMs are analyzed when varying frequency and observation distance to the source. It is found that the efficiencies and shapes of the optimal active ARMs are independent on the distance while that of the reactive ones are distinctly related on.

  3. Star Formation in the Galaxy and the Fluctuating UV Radiation Field

    NASA Technical Reports Server (NTRS)

    Hollenbach, David; Parravano, Antonio; McKee, Christopher H.; Fonda, Mark (Technical Monitor)

    2001-01-01

    We examine the formation of massive stars in the Galaxy, the resultant fluctuating UV radiation field, and the effect of this field on the star-forming interstellar medium (ISM). There are substantial fluctuations of the UV radiation field in space (scales of 100's of parsecs) and time (time-scales of order 100 million years) at the solar circle. The Far Ultraviolet (FUV) (6 eV< hv < 13.6 eV) field and the pressure determines whether the thermal balance of the neutral gas results in cold clouds or warm (T - 10(exp 4) neutral medium. We show how to calculate the average fractions of the gas in the cold and warm phases when the interstellar gas is subject to this fluctuating FUV field. The knowledge of how these fractions depend on the gas properties and on the FUV sources is a basic step in building a model of the large scale behavior of the ISM and the mutual relation between the ISM and the star formation rate. Application is made to observations of spiral galaxies which correlate the star formation rate per unit area with the surface density of the gas. We acknowledge support from the NASA Astrophysical Theory program.

  4. Star Formation In the Galaxy and the Fluctuating UV Radiation Field

    NASA Technical Reports Server (NTRS)

    Hollenbach, David; Parravano, Antonio; McKee, Christopher H.; DeVincenzi, D. (Technical Monitor)

    2002-01-01

    We examine the formation of massive stars in the Galaxy, the resultant fluctuating UV (ultraviolet) radiation field, and the effect of this field on the star-forming interstellar medium. There are substantial fluctuations of the UV radiation field in space (scales of 100's of parsecs) and time (time-scales of order 100 million years). The FUV (far ultraviolet) (6 eV less than hv less than 13.6 eV) field and the pressure determines whether the thermal balance of the neutral gas results in cold clouds or warm (T approx. 10(exp 4) K) neutral medium. We show how to calculate the average fractions of the gas in the cold and warm phases when the interstellar gas is subject to this fluctuating FUV field. The knowledge of how these fractions depend on the gas properties and on the FUV sources is a basic step in building a model of the large scale behavior of the ISM (interstellar medium) and the mutual relation between the ISM and the star formation rate.

  5. THz near-field imaging of biological tissues employing synchrotron radiation (Invited Paper)

    NASA Astrophysics Data System (ADS)

    Schade, Ulrich; Holldack, Karsten; Martin, Michael C.; Fried, Daniel

    2005-04-01

    Terahertz scanning near-field infrared microscopy (SNIM) below 1 THz is demonstrated. The near-field technique benefits from the broadband and highly brilliant coherent synchrotron radiation (CSR) from an electron storage ring and from a detection method based on locking on to the intrinsic time structure of the synchrotron radiation. The scanning microscope utilizes conical waveguides as near-field probes with apertures smaller than the wavelength. Different cone approaches have been investigated to obtain maximum transmittance. Together with a Martin-Puplett spectrometer the set-up enables spectroscopic mapping of the transmittance of samples well below the diffraction limit. Spatial resolution down to about λ/40 at 2 wavenumbers (0.06 THz) is derived from the transmittance spectra of the near-field probes. The potential of the technique is exemplified by imaging biological samples. Strongly absorbing living leaves have been imaged in transmittance with a spatial resolution of 130 μm at about 12 wavenumbers (0.36 THz). The THz near-field images reveal distinct structural differences of leaves from different plants investigated. The technique presented also allows spectral imaging of bulky organic tissues. Human teeth samples of various thicknesses have been imaged between 2 and 20 wavenumbers (between 0.06 and 0.6 THz). Regions of enamel and dentin within tooth samples are spatially and spectrally resolved, and buried caries lesions are imaged through both the outer enamel and into the underlying dentin.

  6. Near-field radiation between graphene-covered carbon nanotube arrays

    SciTech Connect

    Zhang, Richard Z.; Liu, Xianglei; Zhang, Zhuomin M.

    2015-05-15

    It has been shown that at small separation distances, thermal radiation between hyperbolic metamaterials is enhanced over blackbodies. This theoretical study considers near-field radiation when graphene is covered on the surfaces of two semi-infinite vertically aligned carbon nanotube (VACNT) arrays separated by a sub-micron vacuum gap. Doped graphene is found to improve photon tunneling in a broad hyperbolic frequency range, due to the interaction with graphene-graphene surface plasmon polaritons (SPP). In order to elucidate the SPP resonance between graphene on hyperbolic substrates, vacuum-suspended graphene sheets separated by similar gap distances are compared. Increasing the Fermi energy through doping shifts the spectral heat flux peak toward higher frequencies. Although the presence of graphene on VACNT does not offer huge near-field heat flux enhancement over uncovered VACNT, this study identifies conditions (i.e., gap distance and doping level) that best utilize graphene to augment near-field radiation. Through the investigation of spatial Poynting vectors, heavily doped graphene is found to increase penetration depths in hyperbolic modes and the result is sensitive to the frequency regime. This study may have an impact on designing carbon-based vacuum thermophotovoltaics and thermal switches.

  7. L1599B: Cloud Envelope and C+ Emission in a Region of Moderately Enhanced Radiation Field

    NASA Astrophysics Data System (ADS)

    Goldsmith, Paul F.; Pineda, Jorge L.; Langer, William D.; Liu, Tie; Requena-Torres, Miguel; Ricken, Oliver; Riquelme, Denise

    2016-06-01

    We study the effects of an asymmetric radiation field on the properties of a molecular cloud envelope. We employ observations of carbon monoxide (12CO and 13CO), atomic carbon, ionized carbon, and atomic hydrogen to analyze the chemical and physical properties of the core and envelope of L1599B, a molecular cloud forming a portion of the ring at ≃27 pc from the star Λ Ori. The O8 star provides an asymmetric radiation field that produces a moderate enhancement of the external radiation field. Observations of the [C ii] fine structure line with the GREAT instrument on SOFIA indicate a significant enhanced emission on the side of the cloud facing the star, while the [C i], 12CO and 13CO J = 1–0 and 2–1, and 12CO J = 3–2 data from the Purple Mountain Observatory and APEX telescopes suggest a relatively typical cloud interior. The atomic, ionic, and molecular line centroid velocities track each other very closely, and indicate that the cloud may be undergoing differential radial motion. The H i data from the Arecibo GALFA survey and the SOFIA/GREAT [C ii] data do not suggest any systematic motion of the halo gas, relative to the dense central portion of the cloud traced by 12CO and 13CO.

  8. Thermal management in MoS2 based integrated device using near-field radiation

    NASA Astrophysics Data System (ADS)

    Peng, Jiebin; Zhang, Gang; Li, Baowen

    2015-09-01

    Recently, wafer-scale growth of monolayer MoS2 films with spatial homogeneity is realized on SiO2 substrate. Together with the latest reported high mobility, MoS2 based integrated electronic devices are expected to be fabricated in the near future. Owing to the low lattice thermal conductivity in monolayer MoS2, and the increased transistor density accompanied with the increased power density, heat dissipation will become a crucial issue for these integrated devices. In this letter, using the formalism of fluctuation electrodynamics, we explored the near-field radiative heat transfer from a monolayer MoS2 to graphene. We demonstrate that in resonance, the maximum heat transfer via near-field radiation between MoS2 and graphene can be ten times higher than the in-plane lattice thermal conduction for MoS2 sheet. Therefore, an efficient thermal management strategy for MoS2 integrated device is proposed: Graphene sheet is brought into close proximity, 10-20 nm from MoS2 device; heat energy transfer from MoS2 to graphene via near-field radiation; this amount of heat energy then be conducted to contact due to ultra-high lattice thermal conductivity of graphene. Our work sheds light for developing cooling strategy for nano devices constructing with low thermal conductivity materials.

  9. Near-field radiation between graphene-covered carbon nanotube arrays

    NASA Astrophysics Data System (ADS)

    Zhang, Richard Z.; Liu, Xianglei; Zhang, Zhuomin M.

    2015-05-01

    It has been shown that at small separation distances, thermal radiation between hyperbolic metamaterials is enhanced over blackbodies. This theoretical study considers near-field radiation when graphene is covered on the surfaces of two semi-infinite vertically aligned carbon nanotube (VACNT) arrays separated by a sub-micron vacuum gap. Doped graphene is found to improve photon tunneling in a broad hyperbolic frequency range, due to the interaction with graphene-graphene surface plasmon polaritons (SPP). In order to elucidate the SPP resonance between graphene on hyperbolic substrates, vacuum-suspended graphene sheets separated by similar gap distances are compared. Increasing the Fermi energy through doping shifts the spectral heat flux peak toward higher frequencies. Although the presence of graphene on VACNT does not offer huge near-field heat flux enhancement over uncovered VACNT, this study identifies conditions (i.e., gap distance and doping level) that best utilize graphene to augment near-field radiation. Through the investigation of spatial Poynting vectors, heavily doped graphene is found to increase penetration depths in hyperbolic modes and the result is sensitive to the frequency regime. This study may have an impact on designing carbon-based vacuum thermophotovoltaics and thermal switches.

  10. Thermal management in MoS{sub 2} based integrated device using near-field radiation

    SciTech Connect

    Peng, Jiebin; Zhang, Gang; Li, Baowen

    2015-09-28

    Recently, wafer-scale growth of monolayer MoS{sub 2} films with spatial homogeneity is realized on SiO{sub 2} substrate. Together with the latest reported high mobility, MoS{sub 2} based integrated electronic devices are expected to be fabricated in the near future. Owing to the low lattice thermal conductivity in monolayer MoS{sub 2}, and the increased transistor density accompanied with the increased power density, heat dissipation will become a crucial issue for these integrated devices. In this letter, using the formalism of fluctuation electrodynamics, we explored the near-field radiative heat transfer from a monolayer MoS{sub 2} to graphene. We demonstrate that in resonance, the maximum heat transfer via near-field radiation between MoS{sub 2} and graphene can be ten times higher than the in-plane lattice thermal conduction for MoS{sub 2} sheet. Therefore, an efficient thermal management strategy for MoS{sub 2} integrated device is proposed: Graphene sheet is brought into close proximity, 10–20 nm from MoS{sub 2} device; heat energy transfer from MoS{sub 2} to graphene via near-field radiation; this amount of heat energy then be conducted to contact due to ultra-high lattice thermal conductivity of graphene. Our work sheds light for developing cooling strategy for nano devices constructing with low thermal conductivity materials.

  11. Close encounters between two nanoshells.

    PubMed

    Lassiter, J Britt; Aizpurua, Javier; Hernandez, Luis I; Brandl, Daniel W; Romero, Isabel; Lal, Surbhi; Hafner, Jason H; Nordlander, Peter; Halas, Naomi J

    2008-04-01

    Plasmonic nanoparticle pairs known as "dimers" embody a simple system for generating intense nanoscale fields for surface enhanced spectroscopies and for developing an understanding of coupled plasmons. Individual nanoshell dimers in directly adjacent pairs and touching geometries show dramatically different plasmonic properties. At close distances, hybridized plasmon modes appear whose energies depend extremely sensitively on the presence of a small number of molecules in the interparticle junction. When touching, a new plasmon mode arising from charge transfer oscillations emerges. The extreme modification of the overall optical response due to minute changes in very reduced volumes opens up new approaches for ultrasensitive molecular sensing and spectroscopy. PMID:18345644

  12. Study of magnetic field expansion using a plasma generator for space radiation active protection

    NASA Astrophysics Data System (ADS)

    Jia, Xiang-Hong; Jia, Shao-Xia; Xu, Feng; Bai, Yan-Qiang; Wan, Jun; Liu, Hong-Tao; Jiang, Rui; Ma, Hong-Bo; Wang, Shou-Guo

    2013-09-01

    There are many active protecting methods including Electrostatic Fields, Confined Magnetic Field, Unconfined Magnetic Field and Plasma Shielding etc. for defending the high-energy solar particle events (SPE) and Galactic Cosmic Rays (GCR) in deep space exploration. The concept of using cold plasma to expand a magnetic field is the best one of all possible methods so far. The magnetic field expansion caused by plasma can improve its protective efficiency of space particles. One kind of plasma generator has been developed and installed into the cylindrical permanent magnet in the eccentric. A plasma stream is produced using a helical-shaped antenna driven by a radio-frequency (RF) power supply of 13.56 MHz, which exits from both sides of the magnet and makes the magnetic field expand on one side. The discharging belts phenomenon is similar to the Earth's radiation belt, but the mechanism has yet to be understood. A magnetic probe is used to measure the magnetic field expansion distributions, and the results indicate that the magnetic field intensity increases under higher increments of the discharge power.

  13. Encounter with Jupiter. [Pioneer 10 space probe

    NASA Technical Reports Server (NTRS)

    1975-01-01

    Pioneer 10 space probe's encounter with the Jupiter is discussed in detail. Tables are presented which include data on the distances during the encounter, times of crossing satellite orbits, important events in the flight near Jupiter, and time of experiments. Educational study projects are also included.

  14. Encountering Death: Structured Activities for Death Awareness.

    ERIC Educational Resources Information Center

    Welch, Ira David; And Others

    This book is intended to be used as a supplement to standard textbooks on death and dying for college students. Chapter 1 "Encountering Death in the Self" builds the foundation for increased self-awareness for the study of death and dying. Chapter 2 "Encountering Death in the Family" provides activities which are appropriate for a wide variety of…

  15. Encountering! The Arts Part of Basic Education.

    ERIC Educational Resources Information Center

    Oklahoma State Dept. of Education, Oklahoma City. Curriculum Div.

    This publication contains an "Encountering Model" and model lessons for integrating arts experiences into the basic curriculum at the elementary and junior high school levels. The model uses a three-phase learning sequence in which each phase is labeled an "encounter." The first phase is "exploration," when students are provided with certain ideas…

  16. Marriage Encounter Casualties: A Preliminary Investigation.

    ERIC Educational Resources Information Center

    Doherty, William J.; Walker, Brian J.

    1982-01-01

    Investigated the relationship between participation in Marriage Encounter and subsequent marital or family distress. An analysis of 13 case reports suggested that Marriage Encounter weekends can cause marital or family deterioration through increased marital conflict, avoidance of constructive problem solving, or marital enmeshment at the expense…

  17. GLOBAL ELECTROMAGNETIC RADIATION POLLUTION: RISK ASSESSMENT FROM FIELD MEASUREMENTS AND ANIMAL EXPERIMENTS

    NASA Astrophysics Data System (ADS)

    Fragkopoulou, A. F.; Margaritis, L. H.

    2009-12-01

    The extended use of wireless technology throughout the globe in almost all developed and non-developed countries has forced a large number of scientists to get involved in the investigation of the effects. The major issue is that unlike other forms of radiation exposure, this “non-ionizing electromagnetic radiation” was not present throughout the evolution of life in earth and therefore there are no adaptive mechanisms evolved. All organisms are vulnerable to the possible effects of radiation depending on the actual exposure level. “Safety limits” on the power density have been proposed but ongoing research has shown that these limits are not really safe for humans, not mentioning the entire population of living creatures on earth. The so called “Electrosmog Pollution” originating from the numerous radio and TV stations, communication satellite emission, but most importantly from mobile phone mast antennas, are of major concern, because it is gradually increasing at exponential rate. Therefore the key question is, do living organisms react upon their exposure to fields of non ionizing electromagnetic radiation? To have this question answered extensive research is being performed in various laboratories. One approach of our research includes field measurements within houses and classrooms, since a considerable proportion of the population in each country is exposed to the radiation coming from the nearby mast stations, in order to make a risk assessment. The measurements showed that in many cases the actual radiation present was potentially harmful. In other words, although the measured values were below the national safety levels, nevertheless they were above the levels of other countries. Therefore it has been suggested that a new cellular network should be constructed in order to minimize radiation levels in living areas and schools. Our experimental work is focusing on the elucidation of the effects of non-ionizing EMFs on mice exposed to mobile

  18. [An encounter with extraterrestrial intelligence].

    PubMed

    Hisabayashi, Hisashi

    2003-12-01

    It is much easier to find extraterrestrial intelligence than to detect simple organisms living on other planets. However, it is hard to communicate with such intelligence without the mutual understanding of inter-stellar communication protocol. The radio SETI (The Search for Extra-Terrestrial Intelligence) was initiated with the pioneering work of F. Drake in 1960, one year after the historical SETI paper by Cocconi and Morrison. This talk explains that SETI evolves with two bases of science; the understanding of our universe and the development of technology. Since SETI has had strong connection with radio astronomy from its early beginning, the impacts of radio astronomical findings and technological breakthrough can be seen in many aspects of the SETI history. Topics of this talk include the detection of microwave 3 K background radiation in the universe. Interstellar atomic and molecular lines found in radio-wave spectra provide the evidence of pre-biotic chemical evolution in such region. Radio telescope imaging and spectral technique are closely associated with methodology of SETI. Topics of the talk extend to new Allen Telescope Array and projected Square Kilometer Array. Recent optical SETI and the discoveries of extra solar planets are also explained. In the end, the recent understanding of our universe is briefly introduced in terms of matter, dark matter and dark energy. Even our understanding of the universe has been evolutionarily revolved and accumulated after 1960, we must recognize that our universe is still poorly understood and that astronomy and SETI are required to proceed hand in hand. PMID:15136757

  19. An analysis of the radiation field characteristics for extremity dose assessment during maintenance periods at nuclear power plants in Korea.

    PubMed

    Kim, Hee Geun; Kong, Tae Young

    2012-12-01

    Workers who maintain the water chambers of steam generators during maintenance periods in nuclear power plants (NPPs) have a higher likelihood of high radiation exposure, even if they are exposed for a short period of time. In particular, it is expected that the hands of workers would receive the highest radiation exposure as a consequence of hand contact with radioactive materials. In this study, a characteristic analysis of inhomogeneous radiation fields for contact operations was conducted using thermoluminescent dosemeters for the whole body and extremities during maintenance periods at Korean NPPs. It was observed that inhomogeneous radiation fields for contact operations at NPPs were dominated by high-energy photons. PMID:22628525

  20. Lightning-channel morphology by return-stroke radiation field waveforms

    NASA Technical Reports Server (NTRS)

    Willett, J. C.; Le Vine, D. M.; Idone, V. P.

    1995-01-01

    Simultaneous video and wideband electric field recordings of 32 cloud-to-ground lightning flashes in Florida were analyzed to show the formation of new channels to ground can be detected by examination of the return-stroke radiation fields alone. The return-stroke E and dE/dt waveforms were subjectively classified according to their fine structure. Then the video images were examined field by field to identify each waveform with a visible channel to ground. Fifty-five correlated waveforms and channel images were obtained. Of these, all 34 first-stroke waveforms (multiple jagged E peaks, noisy dE/dt), 8 of which were not radiated by the chronologically first stroke in the flash, came from new channels to ground (not previously seen on video). All 18 subsequent-stroke waveforms (smoothly rounded E and quiet dE/dt after initial peak) were radiated by old channels (illuminated by a previous stroke). Two double-ground waveforms (two distinct first-return-stroke pulses separated by tens of microseconds or less) coincided with video fields showing two new channels. One `anomalous-stroke' waveform (beginning like a first stroke and ending like a subsequent) was produced by a new channel segment to ground branching off an old channel. This waveform classification depends on the presence or absence of high-frequency fine structure. Fourier analysis shows that first-stroke waveforms contain about 18 dB more spectral power in the frequency interval from 500 kHz to at least 7 MHz than subsequent-stroke waveforms for at least 13 microseconds after the main peak.

  1. Effect of organ size and position on out-of-field dose distributions during radiation therapy

    NASA Astrophysics Data System (ADS)

    Scarboro, Sarah B.; Stovall, Marilyn; White, Allen; Smith, Susan A.; Yaldo, Derek; Kry, Stephen F.; Howell, Rebecca M.

    2010-12-01

    Mantle field irradiation has historically been the standard radiation treatment for Hodgkin lymphoma. It involves treating large regions of the chest and neck with high doses of radiation (up to 30 Gy). Previous epidemiological studies on the incidence of second malignancies following radiation therapy for Hodgkin lymphoma have revealed an increased incidence of second tumors in various organs, including lung, breast, thyroid and digestive tract. Multiple other studies, including the Surveillance, Epidemiology and End Results, indicated an increased incidence in digestive tract including stomach cancers following mantle field radiotherapy. Assessment of stomach dose is challenging because the stomach is outside the treatment field but very near the treatment border where there are steep dose gradients. In addition, the stomach can vary greatly in size and position. We sought to evaluate the dosimetric impact of the size and variable position of the stomach relative to the field border for a typical Hodgkin lymphoma mantle field irradiation. The mean stomach dose was measured using thermoluminescent dosimetry for nine variations in stomach size and position. The mean doses to the nine stomach variations ranged from 0.43 to 0.83 Gy when 30 Gy was delivered to the treatment isocenter. Statistical analyses indicated that there were no significant differences in the mean stomach dose when the stomach was symmetrically expanded up to 3 cm or shifted laterally (medial, anterior or posterior shifts) by up to 3 cm. There was, however, a significant (P > 0.01) difference in the mean dose when the stomach was shifted superiorly or inferiorly by >=2.5 cm.

  2. Effect of organ size and position on out-of-field dose distributions during radiation therapy

    PubMed Central

    Scarboro, Sarah B; Stovall, Marilyn; White, Allen; Smith, Susan A; Yaldo, Derek; Kry, Stephen F; Howell, Rebecca M

    2011-01-01

    Mantle field irradiation has historically been the standard radiation treatment for Hodgkin lymphoma. It involves treating large regions of the chest and neck with high doses of radiation (up to 30 Gy). Previous epidemiological studies on the incidence of second malignancies following radiation therapy for Hodgkin lymphoma have revealed an increased incidence of second tumors in various organs, including lung, breast, thyroid and digestive tract. Multiple other studies, including the Surveillance, Epidemiology and End Results, indicated an increased incidence in digestive tract including stomach cancers following mantle field radiotherapy. Assessment of stomach dose is challenging because the stomach is outside the treatment field but very near the treatment border where there are steep dose gradients. In addition, the stomach can vary greatly in size and position. We sought to evaluate the dosimetric impact of the size and variable position of the stomach relative to the field border for a typical Hodgkin lymphoma mantle field irradiation. The mean stomach dose was measured using thermoluminescent dosimetry for nine variations in stomach size and position. The mean doses to the nine stomach variations ranged from 0.43 to 0.83 Gy when 30 Gy was delivered to the treatment isocenter. Statistical analyses indicated that there were no significant differences in the mean stomach dose when the stomach was symmetrically expanded up to 3 cm or shifted laterally (medial, anterior or posterior shifts) by up to 3 cm. There was, however, a significant (P > 0.01) difference in the mean dose when the stomach was shifted superiorly or inferiorly by ≥ 2.5 cm. PMID:21076195

  3. SU-E-T-368: Effect of a Strong Magnetic Field On Select Radiation Dosimeters

    SciTech Connect

    Mathis, M; Wen, Z; Tailor, R; Sawakuchi, G; Flint, D; Beddar, S; Ibbott, G

    2014-06-01

    Purpose: To determine the effect of a strong magnetic field on TLD-100, OSLD (Al{sub 2}O{sub 2}:C), and PRESAGE dosimetry devices. This study will help to determine which types of dosimeters can be used for quality assurance and in-vivo dosimetry measurements in a magnetic resonance imaginglinear accelerator (MRI-linac) system. Methods: The dosimeters were separated into two categories which were either exposed or not exposed to a strong magnetic field. In each category a set of dosimeters was irradiated with 0, 2, or 6 Gy. To expose the dosimeters to a magnetic field the samples in that category were place in a Bruker small animal magnetic resonance scanner at a field strength slightly greater than 2.5 T for at least 1 hour preirradiation and at least 1 hour post-irradiation. Irradiations were performed with a 6 MV x-ray beam from a Varian TrueBeam linac with 10×10 cm{sup 2} field at a 600 MU/min dose rate. The samples that received no radiation dose were used as control detectors. Results: The readouts of the dosimeters which were not exposed to a strong magnetic field were compared with the measurements of the dosimetry devices which were exposed to a magnetic field. No significant differences (less than 2% difference) in the performance of TLD, OSLD, or PRESAGE dosimeters due to exposure to a strong magnetic field were observed. Conclusion: Exposure to a strong magnetic field before and after irradiation does not appear to change the dosimetric properties of TLD, OSLD, or PRESAGE which indicates that these dosimeters have potential for use in quality assurance and in-vivo dosimetry in a MRI-linac. We plan to further test the effect of magnetic fields on these devices by irradiating them in the presence of a magnetic fields similar to those produced by a MRI-linac system. Elekta-MD Anderson Cancer Center Research Agreement.

  4. Role of the UV external radiation field on the presence of astrophysical ices in protostellars environments

    NASA Astrophysics Data System (ADS)

    Robson Monteiro Rocha, Will; Pilling, Sergio

    2016-07-01

    The astrophysical ices survival is directly related with the temperature and ionizing radiation field in protostellars environments such as disks and envelopes. Computational models has shown that pure volatile molecules like CO and CH _{4} should survive only inside densest regions of molecular clouds or protoplanetary disks On the other hand, solid molecules such as H _{2}O and CH _{3}OH can be placed around 5 - 10 AU from the central protostar. Unlike of the previous models, we investigate the role of the UV external radiation field on the presence of ices in disks and envelopes. Once that a star-forming region is composed by the formation of many protostars, the external radiation field should be an important component to understand the real localization of the ices along the sight line. To address this topic it was employed the radiative transfer code RADMC-3D based on the Monte Carlo method. The code was used to model the spectrum and the near-infrared image of Elias 29. The initial parameters of the disk and envelope was taken from our previous paper (Rocha & Pilling (2015), ApJ 803:18). The opacities of the ices were calculated from the complex refractive index obtained at laboratory experiments perfomed at Grand Accélerateur National d'Íons Lourds (GANIL), by using the NKABS code from Rocha & Pilling (2014), SAA 123:436. The partial conclusions that we have obtained shows that pure CO volatile molecule cannot be placed at disk or envelope of Elias 29, unlike shown in our paper about Elias 29. Once it was observed in Elias 29 spectrum obtained with Infrared Space Observatory (ISO) between 2.5 - 190 μm, this molecule should be placed in foreground molecular clouds or trapped in the water ice matrix. The next calculations will be able to show where are placed the ices such as CH _{3}OH and CH _{3}CHO observed in Elias 29 spectrum.

  5. Radiation field characterization and shielding studies for the ELI Beamlines facility

    NASA Astrophysics Data System (ADS)

    Ferrari, A.; Amato, E.; Margarone, D.; Cowan, T.; Korn, G.

    2013-05-01

    The ELI (Extreme Light Infrastructure) Beamlines facility in the Czech Republic, which is planned to complete the installation in 2015, is one of the four pillars of the ELI European project. Several laser beamlines with ultrahigh intensities and ultrashort pulses are foreseen, offering versatile radiation sources in an unprecedented energy range: laser-driven particle beams are expected to range between 1 and 50 GeV for electrons and from 100 MeV up to 3 GeV for protons. The number of particles delivered per laser shot is estimated to be 109-1010 for the electron beams and 1010-1012 for the proton beams. The high energy and current values of the produced particles, together with the potentiality to operate at 10 Hz laser repetition rate, require an accurate study of the primary and secondary radiation fields to optimize appropriate shielding solutions: this is a key issue to minimize prompt and residual doses in order to protect the personnel, reduce the radiation damage of electronic devices and avoid strong limitations in the operational time. A general shielding study for the 10 PW (0.016 Hz) and 2 PW (10 Hz) laser beamlines is presented here. Starting from analytical calculations, as well as from dedicated simulations, the main electron and proton fields produced in the laser-matter interaction have been described and used to characterize the "source terms" in full simulations with the Monte Carlo code FLUKA. The secondary radiation fields have been then analyzed to assess a proper shielding. The results of this study and the proposed solutions for the beam dumps of the high energy beamlines, together with a cross-check analysis performed with the Monte Carlo code GEANT4, are presented.

  6. Impact of fractionation on out-of-field survival and DNA damage responses following exposure to intensity modulated radiation fields

    NASA Astrophysics Data System (ADS)

    Ghita, Mihaela; Coffey, Caroline B.; Butterworth, Karl T.; McMahon, Stephen J.; Schettino, Giuseppe; Prise, Kevin M.

    2016-01-01

    To limit toxicity to normal tissues adjacent to the target tumour volume, radiotherapy is delivered using fractionated regimes whereby the total prescribed dose is given as a series of sequential smaller doses separated by specific time intervals. The impact of fractionation on out-of-field survival and DNA damage responses was determined in AGO-1522 primary human fibroblasts and MCF-7 breast tumour cells using uniform and modulated exposures delivered using a 225 kVp x-ray source. Responses to fractionated schedules (two equal fractions delivered with time intervals from 4 h to 48 h) were compared to those following acute exposures. Cell survival and DNA damage repair measurements indicate that cellular responses to fractionated non-uniform exposures differ from those seen in uniform exposures for the investigated cell lines. Specifically, there is a consistent lack of repair observed in the out-of-field populations during intervals between fractions, confirming the importance of cell signalling to out-of-field responses in a fractionated radiation schedule, and this needs to be confirmed for a wider range of cell lines and conditions.

  7. Analysis of the Radiated Field in an Electromagnetic Reverberation Chamber as an Upset-Inducing Stimulus for Digital Systems

    NASA Technical Reports Server (NTRS)

    Torres-Pomales, Wilfredo

    2012-01-01

    Preliminary data analysis for a physical fault injection experiment of a digital system exposed to High Intensity Radiated Fields (HIRF) in an electromagnetic reverberation chamber suggests a direct causal relation between the time profile of the field strength amplitude in the chamber and the severity of observed effects at the outputs of the radiated system. This report presents an analysis of the field strength modulation induced by the movement of the field stirrers in the reverberation chamber. The analysis is framed as a characterization of the discrete features of the field strength waveform responsible for the faults experienced by a radiated digital system. The results presented here will serve as a basis to refine the approach for a detailed analysis of HIRF-induced upsets observed during the radiation experiment. This work offers a novel perspective into the use of an electromagnetic reverberation chamber to generate upset-inducing stimuli for the study of fault effects in digital systems.

  8. Influence of induced axial magnetic field on plasma dynamics and radiative characteristics of Z pinches

    NASA Astrophysics Data System (ADS)

    Kantsyrev, V. L.; Esaulov, A. A.; Safronova, A. S.; Velikovich, A. L.; Rudakov, L. I.; Osborne, G. C.; Shrestha, I.; Weller, M. E.; Williamson, K. M.; Stafford, A.; Shlyaptseva, V. V.

    2011-10-01

    The influence of an induced axial magnetic field on plasma dynamics and radiative characteristics of Z pinches is investigated. An axial magnetic field was induced in a novel Z-pinch load: a double planar wire array with skewed wires (DPWAsk), which represents a planar wire array in an open magnetic configuration. The induced axial magnetic field suppressed magneto-Rayleigh-Taylor (MRT) instabilities (with m = 0 and m = 1 instability modes) in the Z-pinch plasma. The influence of the initial axial magnetic field on the structure of the plasma column at stagnation was manifested through the formation of a more uniform plasma column compared to a standard double planar wire array (DPWA) load [V. L. Kantsyrev , Phys. PlasmasPHPAEN1070-664X10.1063/1.2896577 15, 030704 (2008)]. The DPWAsk load is characterized by suppression of MRT instabilities and by the formation of the sub-keV radiation pulse that occurs before the main x-ray peak. Gradients in plasma parameters along the cathode-anode gap were observed and analyzed for DPWAsk loads made from low atomic number Z (Al) and mid-Z (brass) wires.

  9. Influence of induced axial magnetic field on plasma dynamics and radiative characteristics of Z pinches

    SciTech Connect

    Kantsyrev, V. L.; Esaulov, A. A.; Safronova, A. S.; Osborne, G. C.; Shrestha, I.; Weller, M. E.; Stafford, A.; Shlyaptseva, V. V.; Velikovich, A. L.; Rudakov, L. I.; Williamson, K. M.

    2011-10-15

    The influence of an induced axial magnetic field on plasma dynamics and radiative characteristics of Z pinches is investigated. An axial magnetic field was induced in a novel Z-pinch load: a double planar wire array with skewed wires (DPWAsk), which represents a planar wire array in an open magnetic configuration. The induced axial magnetic field suppressed magneto-Rayleigh-Taylor (MRT) instabilities (with m = 0 and m = 1 instability modes) in the Z-pinch plasma. The influence of the initial axial magnetic field on the structure of the plasma column at stagnation was manifested through the formation of a more uniform plasma column compared to a standard double planar wire array (DPWA) load [V. L. Kantsyrev et al., Phys. Plasmas 15, 030704 (2008)]. The DPWAsk load is characterized by suppression of MRT instabilities and by the formation of the sub-keV radiation pulse that occurs before the main x-ray peak. Gradients in plasma parameters along the cathode-anode gap were observed and analyzed for DPWAsk loads made from low atomic number Z (Al) and mid-Z (brass) wires.

  10. Magnetic field effects on the energy deposition spectra of MV photon radiation.

    PubMed

    Kirkby, C; Stanescu, T; Fallone, B G

    2009-01-21

    Several groups worldwide have proposed various concepts for improving megavoltage (MV) radiotherapy that involve irradiating patients in the presence of a magnetic field-either for image guidance in the case of hybrid radiotherapy-MRI machines or for purposes of introducing tighter control over dose distributions. The presence of a magnetic field alters the trajectory of charged particles between interactions with the medium and thus has the potential to alter energy deposition patterns within a sub-cellular target volume. In this work, we use the MC radiation transport code PENELOPE with appropriate algorithms invoked to incorporate magnetic field deflections to investigate electron energy fluence in the presence of a uniform magnetic field and the energy deposition spectra within a 10 microm water sphere as a function of magnetic field strength. The simulations suggest only very minor changes to the electron fluence even for extremely strong magnetic fields. Further, calculations of the dose-averaged lineal energy indicate that a magnetic field strength of at least 70 T is required before beam quality will change by more than 2%. PMID:19088391

  11. Cosmological consequences of classical flavor-space locked gauge field radiation

    NASA Astrophysics Data System (ADS)

    Bielefeld, Jannis; Caldwell, Robert R.

    2015-06-01

    We propose a classical SU(2) gauge field in a flavor-space locked configuration as a species of radiation in the early Universe and show that it would have a significant imprint on a primordial stochastic gravitational wave spectrum. In the flavor-space locked configuration, the electric and magnetic fields of each flavor are parallel and mutually orthogonal to other flavors, with isotropic and homogeneous stress energy. Due to the non-Abelian coupling, the gauge field breaks the symmetry between left- and right-circularly polarized gravitational waves. This broken chiral symmetry results in a unique signal: nonzero cross-correlation of the cosmic microwave background temperature and polarization, T B and E B , both of which should be zero in the standard, chiral symmetric case. We forecast the ability of current and future cosmic microwave background experiments to constrain this model. Furthermore, a wide range of behavior is shown to emerge, depending on the gauge field coupling, abundance, and allocation into electric and magnetic field energy density. The fluctuation power of primordial gravitational waves oscillates back and forth into fluctuations of the gauge field. In certain cases, the gravitational wave spectrum is shown to be suppressed or amplified by up to an order of magnitude depending on the initial conditions of the gauge field.

  12. Radiation-induced solidification of ionic liquid under extreme electric field

    NASA Astrophysics Data System (ADS)

    Terhune, Kurt J.; King, Lyon B.; He, Kai; Cumings, John

    2016-09-01

    An extreme electric field on the order of 1010 V m‑1 was applied to the free surface of an ionic liquid to cause electric-field-induced evaporation of molecular ions from the liquid. The point of ion emission was observed in situ using a TEM. The resulting electrospray emission process was observed to create nanoscale high-aspect-ratio dendritic features that were aligned with the direction of the electric field. Upon removal of the stressing field the features were seen to remain, indicating that the ionic liquid residue was solidified or gelled. Similar electrospray experiments performed in a field-emission scanning electron microscope revealed that the features are created when the high-energy electron beam damages the molecular structure of the ionic liquid. While the electric field does not play a direct role in the fluid modification, the electric stress was critical in detecting the liquid property change. It is only because the electric stress mechanically elongated the fluid during the electrospray process and these obviously non-liquid structures persisted when the field was removed that the damage was evident. This evidence of ionic liquid radiation damage may have significant bearing on electrospray devices where it is possible to produce high-energy secondary electrons through surface impacts of emitted ions downstream of the emitter. Any such impacts that are in close proximity could see reflected secondary electrons impact the emitter causing gelling of the ionic liquid.

  13. Radiation-induced solidification of ionic liquid under extreme electric field.

    PubMed

    Terhune, Kurt J; King, Lyon B; He, Kai; Cumings, John

    2016-09-16

    An extreme electric field on the order of 10(10) V m(-1) was applied to the free surface of an ionic liquid to cause electric-field-induced evaporation of molecular ions from the liquid. The point of ion emission was observed in situ using a TEM. The resulting electrospray emission process was observed to create nanoscale high-aspect-ratio dendritic features that were aligned with the direction of the electric field. Upon removal of the stressing field the features were seen to remain, indicating that the ionic liquid residue was solidified or gelled. Similar electrospray experiments performed in a field-emission scanning electron microscope revealed that the features are created when the high-energy electron beam damages the molecular structure of the ionic liquid. While the electric field does not play a direct role in the fluid modification, the electric stress was critical in detecting the liquid property change. It is only because the electric stress mechanically elongated the fluid during the electrospray process and these obviously non-liquid structures persisted when the field was removed that the damage was evident. This evidence of ionic liquid radiation damage may have significant bearing on electrospray devices where it is possible to produce high-energy secondary electrons through surface impacts of emitted ions downstream of the emitter. Any such impacts that are in close proximity could see reflected secondary electrons impact the emitter causing gelling of the ionic liquid. PMID:27487731

  14. Determination of High-Frequency Current Distribution Using EMTP-Based Transmission Line Models with Resulting Radiated Electromagnetic Fields

    SciTech Connect

    Mork, B; Nelson, R; Kirkendall, B; Stenvig, N

    2009-11-30

    Application of BPL technologies to existing overhead high-voltage power lines would benefit greatly from improved simulation tools capable of predicting performance - such as the electromagnetic fields radiated from such lines. Existing EMTP-based frequency-dependent line models are attractive since their parameters are derived from physical design dimensions which are easily obtained. However, to calculate the radiated electromagnetic fields, detailed current distributions need to be determined. This paper presents a method of using EMTP line models to determine the current distribution on the lines, as well as a technique for using these current distributions to determine the radiated electromagnetic fields.

  15. Comptonization in ultra-strong magnetic fields: numerical solution to the radiative transfer problem

    NASA Astrophysics Data System (ADS)

    Ceccobello, C.; Farinelli, R.; Titarchuk, L.

    2014-02-01

    Context. We consider the radiative transfer problem in a plane-parallel slab of thermal electrons in the presence of an ultra-strong magnetic field (B ≳ Bc ≈ 4.4 × 1013 G). Under these conditions, the magnetic field behaves like a birefringent medium for the propagating photons, and the electromagnetic radiation is split into two polarization modes, ordinary and extraordinary, that have different cross-sections. When the optical depth of the slab is large, the ordinary-mode photons are strongly Comptonized and the photon field is dominated by an isotropic component. Aims: The radiative transfer problem in strong magnetic fields presents many mathematical issues and analytical or numerical solutions can be obtained only under some given approximations. We investigate this problem both from the analytical and numerical point of view, provide a test of the previous analytical estimates, and extend these results with numerical techniques. Methods: We consider here the case of low temperature black-body photons propagating in a sub-relativistic temperature plasma, which allows us to deal with a semi-Fokker-Planck approximation of the radiative transfer equation. The problem can then be treated with the variable separation method, and we use a numerical technique to find solutions to the eigenvalue problem in the case of a singular kernel of the space operator. The singularity of the space kernel is the result of the strong angular dependence of the electron cross-section in the presence of a strong magnetic field. Results: We provide the numerical solution obtained for eigenvalues and eigenfunctions of the space operator, and the emerging Comptonization spectrum of the ordinary-mode photons for any eigenvalue of the space equation and for energies significantly lesser than the cyclotron energy, which is on the order of MeV for the intensity of the magnetic field here considered. Conclusions: We derived the specific intensity of the ordinary photons, under the

  16. Comptonization in Ultra-Strong Magnetic Fields: Numerical Solution to the Radiative Transfer Problem

    NASA Technical Reports Server (NTRS)

    Ceccobello, C.; Farinelli, R.; Titarchuk, L.

    2014-01-01

    We consider the radiative transfer problem in a plane-parallel slab of thermal electrons in the presence of an ultra-strong magnetic field (B approximately greater than B(sub c) approx. = 4.4 x 10(exp 13) G). Under these conditions, the magnetic field behaves like a birefringent medium for the propagating photons, and the electromagnetic radiation is split into two polarization modes, ordinary and extraordinary, that have different cross-sections. When the optical depth of the slab is large, the ordinary-mode photons are strongly Comptonized and the photon field is dominated by an isotropic component. Aims. The radiative transfer problem in strong magnetic fields presents many mathematical issues and analytical or numerical solutions can be obtained only under some given approximations. We investigate this problem both from the analytical and numerical point of view, provide a test of the previous analytical estimates, and extend these results with numerical techniques. Methods. We consider here the case of low temperature black-body photons propagating in a sub-relativistic temperature plasma, which allows us to deal with a semi-Fokker-Planck approximation of the radiative transfer equation. The problem can then be treated with the variable separation method, and we use a numerical technique to find solutions to the eigenvalue problem in the case of a singular kernel of the space operator. The singularity of the space kernel is the result of the strong angular dependence of the electron cross-section in the presence of a strong magnetic field. Results. We provide the numerical solution obtained for eigenvalues and eigenfunctions of the space operator, and the emerging Comptonization spectrum of the ordinary-mode photons for any eigenvalue of the space equation and for energies significantly lesser than the cyclotron energy, which is on the order of MeV for the intensity of the magnetic field here considered. Conclusions. We derived the specific intensity of the

  17. Exploring Near-Field Radiative Heat Transfer for Thermo-photovoltaic Applications

    NASA Astrophysics Data System (ADS)

    Ganjeh, Yashar; Song, Bai; Sadat, Seid; Thompson, Dakotah; Fiorino, Anthony; Reddy, Pramod; Meyhofer, Edgar

    2014-03-01

    Understanding near-field radiative heat transfer (NFRHT) is critical for developing efficient thermo-photovoltaic devices. Theoretical predictions suggest that when the spatial separation of two parallel planes at different temperatures is less than their Wien's thermal wavelength, thermal transport via radiation can be greatly enhanced. The radiative heat flow across nanoscale gaps is predicted to be orders-of-magnitude higher than that given by Stefan-Boltzmann law, due to contribution of evanescent waves. In order to test these predictions, a novel experimental platform was designed and built enabling parallelization of two planar surfaces (50 μm by 50 μm) with 500 microradian resolution in their relative orientation. This platform was used to probe NFRHT between two planes and also between a plane and a sphere. It was found that, when a 50 μm diameter silica sphere was approximately 20 nm away from a 50 by 50 μm2 silica plane, a significant increase in radiative heat transfer coefficient was observed. This increase is 3 orders of magnitude higher than the value predicted by the blackbody limit. Other setups, including Au spheres and planes, and the plane-plane geometries are currently being investigated. 1) Army Research office (W911NF-12-1-0612), 2) NSF Thermal Transport Prcesses (CBET 1235691), 3) Center for Solar and Thermal Energy conversion, funded by the US Department of Energy, Office of Science, Basic Energy Sciences under award no. DE-SC0000957.

  18. Radial vibration and ultrasonic field of a long tubular ultrasonic radiator.

    PubMed

    Shuyu, Lin; Zhiqiang, Fu; Xiaoli, Zhang; Yong, Wang; Jing, Hu

    2013-09-01

    The radial vibration of a metal long circular tube is studied analytically and its electro-mechanical equivalent circuit is obtained. Based on the equivalent circuit, the radial resonance frequency equation is derived. The theoretical relationship between the radial resonance frequency and the geometrical dimensions is studied. Finite element method is used to simulate the radial vibration and the radiated ultrasonic field and the results are compared with those from the analytical method. It is concluded that the radial resonance frequency for a solid metal rod is larger than that for a metal tube with the same outer radius. The radial resonance frequencies from the analytical method are in good agreement with those from the numerical method. Based on the acoustic field analysis, it is concluded that the long metal tube with small wall thickness is superior to that with large wall thickness in producing radial vibration and ultrasonic radiation. Therefore, it is expected to be used as an effective radial ultrasonic radiator in ultrasonic sewage treatment, ultrasonic antiscale and descaling and other ultrasonic liquid handling applications. PMID:23466008

  19. Internal Radiation Field in the Nonlinear Transfer Problem for a One-Dimensional Anisotropic Medium. II

    NASA Astrophysics Data System (ADS)

    Pikichyan, H. V.

    2016-06-01

    It is shown that for the nonlinear boundary value problem of determining the radiation field inside a one-dimensional anisotropic medium illuminated from outside at its boundaries on both sides, the formulas for adding layers in semilinear systems of differential equations for radiative transfer, invariant embedding, and total Ambartsumyan invariance can be used to reduce the equations for the problem to separable equations with initial conditions. The fields travelling to the left and right are thereby found independently of one another. In addition, when one of them has been determined, the other can be found directly using an explicit expression. A general equivalence property of operators with respect to a certain mathematical form, expression, or functional is formulated mathematically. New equations, referred to as kinetic equations of equivalency, are derived from the mutual equivalence of the differential operators of the Boltzmann kinetic equation (the equations of radiative transfer) and the functional equation of the Ambartsumian's complete invariance. Besides separability, these new equations also have the property of linearity. Formulas are also introduced for special problems of single sided illumination of a medium that in this case serve as supplementary information in the initial conditions for formulating Cauchy problems.

  20. Inverse method predicting spinning modes radiated by a ducted fan from free-field measurements.

    PubMed

    Lewy, Serge

    2005-02-01

    In the study the inverse problem of deducing the modal structure of the acoustic field generated by a ducted turbofan is addressed using conventional farfield directivity measurements. The final objective is to make input data available for predicting noise radiation in other configurations that would not have been tested. The present paper is devoted to the analytical part of that study. The proposed method is based on the equations governing ducted sound propagation and free-field radiation. It leads to fast computations checked on Rolls-Royce tests made in the framework of previous European projects. Results seem to be reliable although the system of equations to be solved is generally underdetermined (more propagating modes than acoustic measurements). A limited number of modes are thus selected according to any a priori knowledge of the sources. A first guess of the source amplitudes is obtained by adjusting the calculated maximum of radiation of each mode to the measured sound pressure level at the same angle. A least squares fitting gives the final solution. A simple correction can be made to take account of the mean flow velocity inside the nacelle which shifts the directivity patterns. It consists of modifying the actual frequency to keep the cut-off ratios unchanged. PMID:15759694

  1. Inverse method predicting spinning modes radiated by a ducted fan from free-field measurements

    NASA Astrophysics Data System (ADS)

    Lewy, Serge

    2005-02-01

    In the study the inverse problem of deducing the modal structure of the acoustic field generated by a ducted turbofan is addressed using conventional farfield directivity measurements. The final objective is to make input data available for predicting noise radiation in other configurations that would not have been tested. The present paper is devoted to the analytical part of that study. The proposed method is based on the equations governing ducted sound propagation and free-field radiation. It leads to fast computations checked on Rolls-Royce tests made in the framework of previous European projects. Results seem to be reliable although the system of equations to be solved is generally underdetermined (more propagating modes than acoustic measurements). A limited number of modes are thus selected according to any a priori knowledge of the sources. A first guess of the source amplitudes is obtained by adjusting the calculated maximum of radiation of each mode to the measured sound pressure level at the same angle. A least squares fitting gives the final solution. A simple correction can be made to take account of the mean flow velocity inside the nacelle which shifts the directivity patterns. It consists of modifying the actual frequency to keep the cut-off ratios unchanged. .

  2. Near-field radiative heat transfer between parallel structures in the deep subwavelength regime.

    PubMed

    St-Gelais, Raphael; Zhu, Linxiao; Fan, Shanhui; Lipson, Michal

    2016-06-01

    Thermal radiation between parallel objects separated by deep subwavelength distances and subject to large thermal gradients (>100 K) can reach very high magnitudes, while being concentrated on a narrow frequency distribution. These unique characteristics could enable breakthrough technologies for thermal transport control and electricity generation (for example, by radiating heat exactly at the bandgap frequency of a photovoltaic cell). However, thermal transport in this regime has never been achieved experimentally due to the difficulty of maintaining large thermal gradients over nanometre-scale distances while avoiding other heat transfer mechanisms, namely conduction. Here, we show near-field radiative heat transfer between parallel SiC nanobeams in the deep subwavelength regime. The distance between the beams is controlled by a high-precision micro-electromechanical system (MEMS). We exploit the mechanical stability of nanobeams under high tensile stress to minimize thermal buckling effects, therefore keeping control of the nanometre-scale separation even at large thermal gradients. We achieve an enhancement of heat transfer of almost two orders of magnitude with respect to the far-field limit (corresponding to a 42 nm separation) and show that we can maintain a temperature gradient of 260 K between the cold and hot surfaces at ∼100 nm distance. PMID:26950243

  3. Shape-Independent Limits to Near-Field Radiative Heat Transfer.

    PubMed

    Miller, Owen D; Johnson, Steven G; Rodriguez, Alejandro W

    2015-11-13

    We derive shape-independent limits to the spectral radiative heat transfer rate between two closely spaced bodies, generalizing the concept of a blackbody to the case of near-field energy transfer. Through conservation of energy and reciprocity, we show that each body of susceptibility χ can emit and absorb radiation at enhanced rates bounded by |χ|(2)/Im χ, optimally mediated by near-field photon transfer proportional to 1/d(2) across a separation distance d. Dipole-dipole and dipole-plate structures approach restricted versions of the limit, but common large-area structures do not exhibit the material enhancement factor and thus fall short of the general limit. By contrast, we find that particle arrays interacting in an idealized Born approximation (i.e., neglecting multiple scattering) exhibit both enhancement factors, suggesting the possibility of orders-of-magnitude improvement beyond previous designs and the potential for radiative heat transfer to be comparable to conductive heat transfer through air at room temperature, and significantly greater at higher temperatures. PMID:26613444

  4. Near-field radiative heat transfer between parallel structures in the deep subwavelength regime

    NASA Astrophysics Data System (ADS)

    St-Gelais, Raphael; Zhu, Linxiao; Fan, Shanhui; Lipson, Michal

    2016-06-01

    Thermal radiation between parallel objects separated by deep subwavelength distances and subject to large thermal gradients (>100 K) can reach very high magnitudes, while being concentrated on a narrow frequency distribution. These unique characteristics could enable breakthrough technologies for thermal transport control and electricity generation (for example, by radiating heat exactly at the bandgap frequency of a photovoltaic cell). However, thermal transport in this regime has never been achieved experimentally due to the difficulty of maintaining large thermal gradients over nanometre-scale distances while avoiding other heat transfer mechanisms, namely conduction. Here, we show near-field radiative heat transfer between parallel SiC nanobeams in the deep subwavelength regime. The distance between the beams is controlled by a high-precision micro-electromechanical system (MEMS). We exploit the mechanical stability of nanobeams under high tensile stress to minimize thermal buckling effects, therefore keeping control of the nanometre-scale separation even at large thermal gradients. We achieve an enhancement of heat transfer of almost two orders of magnitude with respect to the far-field limit (corresponding to a 42 nm separation) and show that we can maintain a temperature gradient of 260 K between the cold and hot surfaces at ∼100 nm distance.

  5. Experimental determination of radiated internal wave power without pressure field data

    SciTech Connect

    Lee, Frank M.; Morrison, P. J.; Paoletti, M. S.; Swinney, Harry L.

    2014-04-15

    We present a method to determine, using only velocity field data, the time-averaged energy flux (J) and total radiated power P for two-dimensional internal gravity waves. Both (J) and P are determined from expressions involving only a scalar function, the stream function ψ. We test the method using data from a direct numerical simulation for tidal flow of a stratified fluid past a knife edge. The results for the radiated internal wave power given by the stream function method agree to within 0.5% with results obtained using pressure and velocity data from the numerical simulation. The results for the radiated power computed from the stream function agree well with power computed from the velocity and pressure if the starting point for the stream function computation is on a solid boundary, but if a boundary point is not available, care must be taken to choose an appropriate starting point. We also test the stream function method by applying it to laboratory data for tidal flow past a knife edge, and the results are found to agree with the direct numerical simulation. The supplementary material includes a Matlab code with a graphical user interface that can be used to compute the energy flux and power from two-dimensional velocity field data.

  6. Near-field radiative heat transfer between arbitrarily shaped objects and a surface

    NASA Astrophysics Data System (ADS)

    Edalatpour, Sheila; Francoeur, Mathieu

    2016-07-01

    A fluctuational electrodynamics-based formalism for calculating near-field radiative heat transfer between objects of arbitrary size and shape and an infinite surface is presented. The surface interactions are treated analytically via Sommerfeld's theory of electric dipole radiation above an infinite plane. The volume integral equation for the electric field is discretized using the thermal discrete dipole approximation (T-DDA). The framework is verified against exact results in the sphere-surface configuration and is applied to analyze near-field radiative heat transfer between a complex-shaped probe and an infinite plane, both made of silica. It is found that, when the probe tip size is approximately equal to or smaller than the gap d separating the probe and the surface, coupled localized surface phonon (LSPh)-surface phonon-polariton (SPhP) mediated heat transfer occurs. In this regime, the net spectral heat rate exhibits four resonant modes due to LSPhs along the minor axis of the probe, while the net total heat rate in the near field follows a d-0.3 power law. Conversely, when the probe tip size is much larger than the separation gap d , heat transfer is mediated by SPhPs, resulting in two resonant modes in the net spectral heat rate, corresponding to those of a single emitting silica surface, while the net total heat rate approaches a d-2 power law. It is also demonstrated that a complex-shaped probe can be approximated by a prolate spheroidal electric dipole when the thermal wavelength is larger than the major axis of the spheroidal dipole and when the separation gap d is much larger than the radius of curvature of the dipole tip facing the surface.

  7. Radiative corrections to the Casimir Pressure under the influence of temperature and external fields

    SciTech Connect

    Robaschik, D.; Scharonhorst, K.; Wieczorek, E.

    1987-03-01

    Generalizing the quantum field theory (QFT) with boundary conditions in covariant gauge to the case of finite temperature, we develop the quantum electrodynamics (QED) with boundary conditions in the Matsubara approach as well as in the thermofield formulation. We rederive the known results of the free-field theory for the pressure and the free energy of the Casimir problem. For infinitely thin plates we calculate the radiative corrections in second-order perturbation theory at finite temperature. Thereby it turns out that the calculation in of the vacuum energy at the vanishing temperature via the Z functional is much simplier than the calculation via the energy momentum tensor. This observation allows determination of the influence of static electromagnetic fields on the Casimir problem. copyright 1987 Academic Press, Inc.

  8. Nonadiabatic behavior of the polarization of electric-field-induced Lyman-. alpha. radiation

    SciTech Connect

    Plotzke, O.; Wille, U.; Hippler, R.; Lutz, H.O. Bereich Schwerionenphysik, Hahn-Meitner-Institut Berlin, Berlin )

    1990-12-10

    The linear polarization of Lyman-{alpha} radiation emitted when hydrogen atoms in the metastable 2{ital s}{sub 1/2} state traverse an external electric field is studied as a function of the effective rise time of the field for field strengths extending from very small values up to 6 keV/cm. With decreasing rise time, the measured polarization exhibits a transition from {ital adiabatic} to {ital sudden} behavior. The transition region is centered at a rise time which is approximately equal to the characteristic time associated with the 2{ital s}{sub 1/2-}2{ital p}{sub 1/2} Lamb splitting in the unperturbed hydrogen system. The experimental data are well described by the results of a time-dependent theory.

  9. Analysis of resonances in Moeller scattering in a laser field of relativistic radiation power

    SciTech Connect

    Panek, P.; Kaminski, J.Z.; Ehlotzky, F.

    2004-01-01

    Presently available laser sources can yield powers for which the ponderomotive energy U{sub p} of an electron can be equal to or even larger than the rest energy mc{sup 2} of an electron. Therefore it has become of interest to consider fundamental radiation-induced or assisted processes in such powerful laser fields. In the present work we consider laser-assisted electron-electron scattering in such a field, assuming that the laser beam has linear polarization. We investigate in detail the angular and polarization dependence of the differential cross sections of the laser-assisted nonlinear processes as a function of the order N of absorbed or emitted laser photons {omega}. The present work is a continuation of our previous analysis of Compton scattering and of Mott scattering in a linearly polarized laser field [Phys. Rev. A 65, 022712 (2002); 65, 033408 (2002)].

  10. Stability of a liquid-film space radiator with internal electrostatic fields. Progress report, October 1, 1991--September 30, 1992

    SciTech Connect

    Bankoff, S.G.; Miksis, M.J.

    1992-04-01

    A new concept in light-weight space radiators has been introduced by Kim, Miksis and Bankoff, consisting of a pumped-loop membrane radiator in which leakage of coolant from a puncture, due to micrometeorite or space debris impact, is prevented by the application of an internal electrostatic field. For nuclear space power, the coolant is generally a liquid metal, such as lithium, flowing as a thin film along the interior walls of the hollow radiator. A lightweight fully-modular radiator design is proposed, which is calculated to weight less than 1 kg/m{sup 2}. The feature which makes this thin-membrane radiator practical is the internal electrostatic field system, which can stop radiator leaks from punctures, sudden accelerations or accidental tears.

  11. Deriving Radiative Effects of Aerosol-Immersed Broken Cloud Fields from Multi-spectral Imagery

    NASA Astrophysics Data System (ADS)

    Schmidt, Sebastian

    2016-04-01

    Recently, significant progress has been made in the understanding of cloud inhomogeneity effects in shortwave passive remote sensing. Yet it has proven difficult to correct such effects on the pixel level using multi-spectral imagery alone, mainly because three-dimensional (3D) radiative transfer in cloud fields is a non-local phenomenon. As a result, estimates of irradiance - the fundamental climate variable - from space-or air-borne imagery continue to pose problems for complex cloud fields. The presence of aerosols in the vicinity of clouds exacerbates the prob- lem. I will show evidence from field experiments and 3D radiative transfer calculations that biases may exceed 40% at the pixel level at the MODIS spatial resolution, and that some of these effects "survive" spatial averaging. A new way to cope with this problem is the discovery that 3D effects manifest themselves as spectral perturba- tion in reflected radiances and in the associated irradiance fields throughout an inhomogeneous cloud domain. In parameterized form, these correlations between spatial cloud distribution and spectral signature can be used to de- rive first-order inhomogeneity corrections for irradiance fields - not on a pixel basis, but for populations of pixels within a cloud domain represented by probability density functions. I will present the first practical approach for using these new findings in a future proxy-3D algorithm for deriving irradiances below and above cloud-aerosol fields from multi-spectral imagers, and discuss the accuracy that can be expected from this simplified method to account for 3D effects in mixed aerosol-cloud scenes.

  12. ASRS Reports on Wake Vortex Encounters

    NASA Technical Reports Server (NTRS)

    Connell, Linda J.; Taube, Elisa Ann; Drew, Charles Robert; Barclay, Tommy Earl

    2010-01-01

    ASRS is conducting a structured callback research project of wake vortex incidents reported to the ASRS at all US airports, as well as wake encounters in the enroute environment. This study has three objectives: (1) Utilize the established ASRS supplemental data collection methodology and provide ongoing analysis of wake vortex encounter reports; (2) Document event dynamics and contributing factors underlying wake vortex encounter events; and (3) Support ongoing FAA efforts to address pre-emptive wake vortex risk reduction by utilizing ASRS reporting contributions.

  13. Chiral effective-field theory in the Delta(1232) region : II. radiative pion photoproduction

    SciTech Connect

    Vladimir Pascalutsa; Marc Vanderhaeghen

    2007-10-12

    We present a theoretical study of the radiative pion photoproduction on the nucleon ($\\gamma N \\rightarrow \\pi N \\gamma'$) in the $\\De$-resonance region, with the aim to determine the magnetic dipole moment (MDM) of the $\\Delta^+(1232)$. The study is done within the framework of chiral effective-field theory where the expansion is performed (to next-to-leading order) in the $\\delta$ power-counting scheme which is an extension of chiral perturbation theory to the $\\Delta$-resonance energy region. We present in detail the results for the absorptive part of the $\\Delta$ MDM, as well as a sensitivity study for the radiative pion photoproduction observables on the real part of the $\\Delta$ MDM. We find that an asymmetry for circular polarization of the photon beam may provide a model-independent way to measure the $\\Delta$ MDM.

  14. Shortwave surface radiation network for observing small-scale cloud inhomogeneity fields

    NASA Astrophysics Data System (ADS)

    Lakshmi Madhavan, Bomidi; Kalisch, John; Macke, Andreas

    2016-03-01

    As part of the High Definition Clouds and Precipitation for advancing Climate Prediction Observational Prototype Experiment (HOPE), a high-density network of 99 silicon photodiode pyranometers was set up around Jülich (10 km × 12 km area) from April to July 2013 to capture the small-scale variability of cloud-induced radiation fields at the surface. In this paper, we provide the details of this unique setup of the pyranometer network, data processing, quality control, and uncertainty assessment under variable conditions. Some exemplary days with clear, broken cloudy, and overcast skies were explored to assess the spatiotemporal observations from the network along with other collocated radiation and sky imager measurements available during the HOPE period.

  15. Dosimetry in steep dose-rate gradient radiation fields: A challenge in clinical applications

    SciTech Connect

    Massillon-JL, G.

    2010-12-07

    The fundamental goal of radiotherapy is to reduce the damage to normal tissue and optimize the dose to the tumor with an associated high probability of cure. Because of this, an accurate and precise knowledge of the radiation dose distribution delivered around the tumor volume during radiotherapy treatments such as stereotactic radiosurgery, intensity modulated radiotherapy or brachytherapy with low-energy X-ray and beta particle sources is of great importance. However, in each of these radiation fields, there exists a steep dose-rate gradient which makes it very difficult to perform accurate dose measurements. In this work, the physics phenomena involved in the energy absorption for each of these situations are discussed, and a brief revision of what the Medical Physics community is doing is presented.

  16. Dosimetry in steep dose-rate gradient radiation fields: A challenge in clinical applications

    NASA Astrophysics Data System (ADS)

    Massillon-JL, G.

    2010-12-01

    The fundamental goal of radiotherapy is to reduce the damage to normal tissue and optimize the dose to the tumor with an associated high probability of cure. Because of this, an accurate and precise knowledge of the radiation dose distribution delivered around the tumor volume during radiotherapy treatments such as stereotactic radiosurgery, intensity modulated radiotherapy or brachytherapy with low-energy X-ray and beta particle sources is of great importance. However, in each of these radiation fields, there exists a steep dose-rate gradient which makes it very difficult to perform accurate dose measurements. In this work, the physics phenomena involved in the energy absorption for each of these situations are discussed, and a brief revision of what the Medical Physics community is doing is presented.

  17. An optimal numerical filter for wide-field-of-view measurements of earth-emitted radiation

    NASA Technical Reports Server (NTRS)

    Smith, G. L.; House, F. B.

    1981-01-01

    A technique is described in which all data points along an arc of the orbit may be used in an optimal numerical filter for wide-field-of-view measurements of earth emitted radiation. The statistical filter design is derived whereby the filter is required to give a minimum variance estimate of the radiative exitance at discrete points along the ground track of the satellite. An equation for the optimal numerical filter is given by minimizing the estimate error variance equation with respect to the filter weights, resulting in a discrete form of the Wiener-Hopf equation. Finally, variances of the errors in the radiant exitance can be computed along the ground track and in the cross track directions.

  18. Upper limits to the interstellar radiation field between 775 and 1050 A

    NASA Technical Reports Server (NTRS)

    Paresce, F.; Bowyer, S.

    1976-01-01

    A 40-A resolution extreme-ultraviolet spectrometer, sensitive to radiation in the 775-1050 A band, was flown on a Black Brant VC rocket to measure the night sky brightness in this region of the electromagnetic spectrum. A weak signal above background was recorded in most channels as the spectrometer's field of view scanned the sky in the vicinity of the galactic plane from Monoceros to Andromeda. Because the earth's upper atmosphere may produce some radiation in this wavelength region, the possibility cannot be excluded that some or all of the observed signal is terrestrial in origin. However, observational upper limits can be established at the 95-per cent confidence level for the intensity of an extraterrestrial extreme ultraviolet background which ranges from 6 millionths erg/sq cm/s/sr/A at 1050 A to 4 ten-millionths erg/sq cm/s/sr/A at 775 A. These results are consistent with existing theoretical predictions.

  19. [Human behavior in the solar radiation field with reference to ultraviolet exposure].

    PubMed

    Schauberger, G; Keck, G; Cabaj, A

    1992-09-01

    There is a causal relation between solar ultraviolet radiation and skin cancer. For epidemiological investigations, quantification of the UV exposure is essential. To set up a risk assessment for the whole population, a representative survey was performed in Austria. The questionnaire refers to three sectors of everyday life: work, recreation and holidays; in addition the use of solaria is asked about for a further investigation. The UV exposure caused by humans' behaviour in the field of solar radiation was analysed from various demographic aspects. For some subpopulations the UV exposure sustained during work, recreation and holidays was compared. Groups with high occupational UV exposure show a weaker tendency to stay outdoors during leisure time and holidays than groups characterized by high UV exposure in their leisure time, who also prefer sun-intensive activities during holidays. PMID:1399598

  20. Shortwave surface radiation budget network for observing small-scale cloud inhomogeneity fields

    NASA Astrophysics Data System (ADS)

    Madhavan, B. L.; Kalisch, J.; Macke, A.

    2015-03-01

    As part of the High Definition Clouds and Precipitation for advancing Climate Prediction Observational Prototype Experiment (HOPE), a high spatial density network of 99 silicon photodiode pyranometers was set up around Jülich (10 km x 12 km area) from April to July 2013, to capture the variability in the radiation field at the surface induced by small-scale cloud inhomogeneity. Each of these autonomously operated pyranometer stations was equipped with weather sensors for simultaneous measurements of ambient air temperature and relative humidity. In this paper, we provide the details of this unique setup of the pyranometer network and the data analysis with initial quality screening procedure we adopted. We also present some exemplary cases consisting of the days with clear, broken cloudy and overcast skies to assess our spatio-temporal observations from the network, and validate their consistency with other collocated radiation measurements available during the HOPE period.

  1. Silicon field-effect transistors as radiation detectors for the Sub-THz range

    SciTech Connect

    But, D. B. Golenkov, O. G.; Sakhno, N. V.; Sizov, F. F.; Korinets, S. V.; Gumenjuk-Sichevska, J. V.; Reva, V. P.; Bunchuk, S. G.

    2012-05-15

    The nonresonance response of silicon metal-oxide-semiconductor field-effect transistors (Si-MOSFETs) with a long channel (1-20 {mu}m) to radiation in the frequency range 43-135 GHz is studied. The transistors are fabricated by the standard CMOS technology with 1-{mu}m design rules. The volt-watt sensitivity and the noise equivalent power (NEP) for such detectors are estimated with the calculated effective area of the detecting element taken into account. It is shown that such transistors can operate at room temperature as broadband direct detectors of sub-THz radiation. In the 4-5 mm range of wavelengths, the volt-watt sensitivity can be as high as tens of kV/W and the NEP can amount to 10{sup -11} - 10{sup -12}W/{radical}Hz . The parameters of detectors under study can be improved by the optimization of planar antennas.

  2. Formation of ultrashort pulses from quasimonochromatic XUV radiation via infrared-field-controlled forward scattering

    NASA Astrophysics Data System (ADS)

    Akhmedzhanov, T. R.; Antonov, V. A.; Kocharovskaya, Olga

    2016-08-01

    We suggest a highly efficient method of ultrashort pulse formation from resonant XUV radiation due to sub-laser-cycle modulation of the excited state of non-hydrogen-like atoms by a nonionizing IR laser field. This modulation results in formation of the Raman-Stokes and anti-Stokes sidebands in coherently forward-scattered radiation, which, in turn, leads to formation of short pulses, when the phases of the sidebands are matched. This method is a generalization of a recently suggested technique [V. A. Antonov et al., Phys. Rev. A 88, 053849 (2013), 10.1103/PhysRevA.88.053849] for a non-hydrogen-like medium. The possibility to form 2-fs XUV pulses in the gas of helium atoms and 990-as XUV pulses in the plasma of Li+ ions with efficiencies over 80% is shown.

  3. Influence of ambient meteorology on the accuracy of radiation measurements: insights from field and laboratory experiments

    NASA Astrophysics Data System (ADS)

    Oswald, Sandro M.; Pietsch, Helga; Baumgartner, Dietmar J.; Rieder, Harald E.

    2016-04-01

    A precise knowledge of the surface energy budget, which includes the solar and terrestrial radiation fluxes, is needed to accurately characterize the global energy balance which is largely determining Earth's climate. To this aim national and global monitoring networks for surface radiative fluxes have been established in recent decades. The most prominent among these networks is the so-called Baseline Surface Radiation Network (BSRN) operating under the auspices of the World Climate Research Programme (WCRP) (Ohmura et al., 1998). National monitoring networks such as the Austrian RADiation Monitoring Network (ARAD), which has been established in 2010 by a consortium of the Central Agency of Meteorology and Geodynamics (ZAMG), the University of Graz, the University of Innsbruck, and the University of Natural Resources and Applied Sciences, Vienna (BOKU), orient themselves on BSRN standards (McArthur, 2005). ARAD comprises to date five sites (Wien Hohe Warte, Graz/University, Innsbruck/University, Kanzelhöhe Observatory and Sonnblick (which is also a BSRN site)) and aims to provide long-term monitoring of radiation budget components at highest accuracy and to capture the spatial patterns of radiation climate in Austria (Olefs et al., 2015). Given the accuracy requirement for the local monitoring of radiative fluxes instrument offsets, triggered by meteorological factors and/or instrumentation, pose a major challenge in radiation monitoring. Within this study we investigate effects of ambient meteorology on the accuracy of radiation measurements performed with pyranometers contained in various heating/ventilation systems (HV-systems), all of which used in regular operation within the ARAD network. We focus particularly on instrument offsets observed following precipitation events. To quantify pyranometer responses to precipitation we performed a series of controlled laboratory experiments as well as targeted field campaigns in 2015 and 2016. Our results indicate

  4. Effects of laser radiation field on energies of hydrogen atom in plasmas

    NASA Astrophysics Data System (ADS)

    Bahar, M. K.

    2015-09-01

    In this study, for the first time, the Schrödinger equation with more general exponential cosine screened Coulomb (MGECSC) potential is solved numerically in the presence of laser radiation field within the Ehlotzky approximation using the asymptotic iteration method. The MGECSC potential includes four different potential forms in consideration of different sets of the parameters in the potential. By applying laser field, the total interaction potential of hydrogen atom embedded in plasmas converts to double well-type potential. The plasma screening effects under the influence of laser field as well as confinement effects of laser field on hydrogen atom in Debye and quantum plasmas are investigated by solving the Schrödinger equation with the laser-dressed MGECSC potential. It is resulted that since applying a monochromatic laser field on hydrogen atom embedded in a Debye and quantum plasma causes to shift in the profile of the total interaction potential, the confinement effects of laser field on hydrogen atom in plasmas modeled by the MGECSC potential change localizations of energy states.

  5. Pulsed currents carried by whistlers. IV. Electric fields and radiation excited by an electrode

    SciTech Connect

    Stenzel, R.L.; Urrutia, J.M.; Rousculp, C.L.

    1995-04-01

    Electromagnetic properties of current pulses carried by whistler wave packets are obtained from a basic laboratory experiment. While the magnetic field and current density are described in the preceding companion paper (Part III), the present analysis starts with the electric field. The inductive and space charge electric field contributions are separately calculated in Fourier space from the measured magnetic field and Ohm`s law along B{sub 0}. Inverse Fourier transformation yields the total electric field in space and time, separated into rotational and divergent contributions. The space-charge density in whistler wave packets is obtained. The cross-field tensor conductivity is determined. The frozen-in condition is nearly satisfied, {bold E}+{bold v}{sub {ital e}}{times}{bold B}{congruent}0. The dissipation is obtained from Poynting`s theorem. The waves are collisionally damped; Landau damping is negligible. A radiation resistance for the electrode is determined. Analogous to Poynting`s theorem, the transport of helicity is analyzed. Current helicity is generated by a flow of helicity between pulses traveling in opposite directions which carry opposite signs of helicity. Helicity is dissipated by collisions. These observations complete a detailed description of whistler/current pulses which can occur in various laboratory and space plasmas. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  6. Effects of laser radiation field on energies of hydrogen atom in plasmas

    SciTech Connect

    Bahar, M. K.

    2015-09-15

    In this study, for the first time, the Schrödinger equation with more general exponential cosine screened Coulomb (MGECSC) potential is solved numerically in the presence of laser radiation field within the Ehlotzky approximation using the asymptotic iteration method. The MGECSC potential includes four different potential forms in consideration of different sets of the parameters in the potential. By applying laser field, the total interaction potential of hydrogen atom embedded in plasmas converts to double well-type potential. The plasma screening effects under the influence of laser field as well as confinement effects of laser field on hydrogen atom in Debye and quantum plasmas are investigated by solving the Schrödinger equation with the laser-dressed MGECSC potential. It is resulted that since applying a monochromatic laser field on hydrogen atom embedded in a Debye and quantum plasma causes to shift in the profile of the total interaction potential, the confinement effects of laser field on hydrogen atom in plasmas modeled by the MGECSC potential change localizations of energy states.

  7. Evolution of a magnetic field in a differentially rotating radiative zone

    NASA Astrophysics Data System (ADS)

    Gaurat, M.; Jouve, L.; Lignières, F.; Gastine, T.

    2015-08-01

    Context. Recent spectropolarimetric surveys of main-sequence intermediate-mass stars have exhibited a dichotomy in the distribution of the observed magnetic field between the kG dipoles of Ap/Bp stars and the sub-Gauss magnetism of Vega and Sirius. Aims: We would like to test whether this dichotomy is linked to the stability versus instability of large-scale magnetic configurations in differentially rotating radiative zones. Methods: We computed the axisymmetric magnetic field obtained from the evolution of a dipolar field threading a differentially rotating shell. A full parameter study including various density profiles and initial and boundary conditions was performed with a 2D numerical code. We then focused on the ratio between the toroidal and poloidal components of the magnetic field and discuss the stability of the configurations dominated by the toroidal component using local stability criteria and insights from recent 3D numerical simulations. Results: The numerical results and a simple model show that the ratio between the toroidal and the poloidal magnetic fields is highest after an Alfvén crossing time of the initial poloidal field. For high density contrasts, this ratio converges towards an asymptotic value that can thus be extrapolated to realistic stellar cases. We then consider the stability of the magnetic configurations to non-axisymmetric perturbations and find that configurations dominated by the toroidal component are likely to be unstable if the shear strength is significantly higher than the poloidal Alfvén frequency. An expression for the critical poloidal field below which magnetic fields are likely to be unstable is found and is compared to the lower bound of Ap/Bp magnetic fields.

  8. PLANT PROTECTIVE RESPONSE TO ENHANCED UV-B RADIATION UNDER FIELD CONDITIONS: LEAF OPTICAL PROPERTIES AND PHOTOSYNTHESIS

    EPA Science Inventory

    Plants of Vicia faba were grown in the field during early to midsummer while receiving two levels of supplemental UV-B radiation. Light-saturated photosynthesis and stomatal diffusive conductance of intact leaves did not show any indications of UV-radiation damage. Supplemental U...

  9. Near-field sound radiation of fan tones from an installed turbofan aero-engine.

    PubMed

    McAlpine, Alan; Gaffney, James; Kingan, Michael J

    2015-09-01

    The development of a distributed source model to predict fan tone noise levels of an installed turbofan aero-engine is reported. The key objective is to examine a canonical problem: how to predict the pressure field due to a distributed source located near an infinite, rigid cylinder. This canonical problem is a simple representation of an installed turbofan, where the distributed source is based on the pressure pattern generated by a spinning duct mode, and the rigid cylinder represents an aircraft fuselage. The radiation of fan tones can be modelled in terms of spinning modes. In this analysis, based on duct modes, theoretical expressions for the near-field acoustic pressures on the cylinder, or at the same locations without the cylinder, have been formulated. Simulations of the near-field acoustic pressures are compared against measurements obtained from a fan rig test. Also, the installation effect is quantified by calculating the difference in the sound pressure levels with and without the adjacent cylindrical fuselage. Results are shown for the blade passing frequency fan tone radiated at a supersonic fan operating condition. PMID:26428770

  10. Radiation Therapy Field Extent for Adjuvant Treatment of Axillary Metastases From Malignant Melanoma

    SciTech Connect

    Beadle, Beth M.; Guadagnolo, B. Ashleigh Ballo, Matthew T.; Lee, Jeffrey E.; Gershenwald, Jeffrey E.; Cormier, Janice N.; Mansfield, Paul F.; Ross, Merrick I.; Zagars, Gunar K.

    2009-04-01

    Purpose: To compare treatment-related outcomes and toxicity for patients with axillary lymph node metastases from malignant melanoma treated with postoperative radiation therapy (RT) to either the axilla only or both the axilla and supraclavicular fossa (extended field [EF]). Methods and Materials: The medical records of 200 consecutive patients treated with postoperative RT for axillary lymph node metastases from malignant melanoma were retrospectively reviewed. All patients received postoperative hypofractionated RT for high-risk features; 95 patients (48%) received RT to the axilla only and 105 patients (52%) to the EF. Results: At a median follow-up of 59 months, 111 patients (56%) had sustained relapse, and 99 patients (50%) had died. The 5-year overall survival, disease-free survival, and distant metastasis-free survival rates were 51%, 43%, and 46%, respectively. The 5-year axillary control rate was 88%. There was no difference in axillary control rates on the basis of the treated field (89% for axilla only vs. 86% for EF; p = 0.4). Forty-seven patients (24%) developed treatment-related complications. On both univariate and multivariate analyses, only treatment with EF irradiation was significantly associated with increased treatment-related complications. Conclusions: Adjuvant hypofractionated RT to the axilla only for metastatic malignant melanoma with high-risk features is an effective method to control axillary disease. Limiting the radiation field to the axilla only produced equivalent axillary control rates to EF and resulted in lower treatment-related complication rates.

  11. The analysis of complex mixed-radiation fields using near real-time imaging.

    PubMed

    Beaumont, Jonathan; Mellor, Matthew P; Joyce, Malcolm J

    2014-10-01

    A new mixed-field imaging system has been constructed at Lancaster University using the principles of collimation and back projection to passively locate and assess sources of neutron and gamma-ray radiation. The system was set up at the University of Manchester where three radiation sources: (252)Cf, a lead-shielded (241)Am/Be and a (22)Na source were imaged. Real-time discrimination was used to find the respective components of the neutron and gamma-ray fields detected by a single EJ-301 liquid scintillator, allowing separate images of neutron and gamma-ray emitters to be formed. (252)Cf and (22)Na were successfully observed and located in the gamma-ray image; however, the (241)Am/Be was not seen owing to surrounding lead shielding. The (252)Cf and (241)Am/Be neutron sources were seen clearly in the neutron image, demonstrating the advantage of this mixed-field technique over a gamma-ray-only image where the (241)Am/Be source would have gone undetected. PMID:24782559

  12. Designing and Dosimetry of a Shield for Photon Fields of Radiation Therapy in Oral Cavity Cancer

    PubMed Central

    Jabbari, Keyvan; Senobari, Somayeh; Roayaei, Mahnaz; Rostampour, Masoumeh

    2015-01-01

    The cancer of oral cavity is related to lesions of mucous membrane of tongue and gum that can be treated with radiation therapy. A lateral photon field can be used to treat this kind of tumor, which has a side-effect on normal tissue in the opposite side of the oral cavity. In this study the dosimetric effect of the various shields in oral cavity is evaluated. In this study, a special phantom similar to the structure of oral cavity with capability of film dosimetry was designed and constructed. The various shield slabs were made of five materials: Lead, Plexiglas, Acrylic resin, Silicon and Plaster. For irradiation, Cobalt 60 (60Co) and 6 MV photon beams were used. The film dosimetry before and after the shield was performed using GAFCHROMIC EBT2 films. The film before the shield measures the magnitude of backscattering radiation from the shield. The prescribed dose was 150 cGy. Results showed that 3 cm of the lead in both energies had the maximum absorption of radiation. The absorbed dose to opposite side of shield for 6 MV photon beams and 60Co were 21 and 32 cGy, respectively. The minimum attenuation on radiation was observed in silicon shield for which the dose of opposite side were 116 and 147 cGy for 6 MV and 60Co respectively. The maximum backscattered dose was measured 177 cGy and 219 cGy using 3 cm thickness of lead, which was quite considerable. The minimum backscattering where for acrylic resin 101 and 118 cGy for 6 MV and cobalt. In this study, it was concluded that the amount of backscattering for 3 cm Lead shield is quite considerable and increases the dose significantly. A composite layer of shield with 1–2 cm lead and 1 cm acrylic resin can have the protective effect and low backscattering radiation at the same time. PMID:26120570

  13. Designing and Dosimetry of a Shield for Photon Fields of Radiation Therapy in Oral Cavity Cancer.

    PubMed

    Jabbari, Keyvan; Senobari, Somayeh; Roayaei, Mahnaz; Rostampour, Masoumeh

    2015-01-01

    The cancer of oral cavity is related to lesions of mucous membrane of tongue and gum that can be treated with radiation therapy. A lateral photon field can be used to treat this kind of tumor, which has a side-effect on normal tissue in the opposite side of the oral cavity. In this study the dosimetric effect of the various shields in oral cavity is evaluated. In this study, a special phantom similar to the structure of oral cavity with capability of film dosimetry was designed and constructed. The various shield slabs were made of five materials: Lead, Plexiglas, Acrylic resin, Silicon and Plaster. For irradiation, Cobalt 60 (60Co) and 6 MV photon beams were used. The film dosimetry before and after the shield was performed using GAFCHROMIC EBT2 films. The film before the shield measures the magnitude of backscattering radiation from the shield. The prescribed dose was 150 cGy. Results showed that 3 cm of the lead in both energies had the maximum absorption of radiation. The absorbed dose to opposite side of shield for 6 MV photon beams and 60Co were 21 and 32 cGy, respectively. The minimum attenuation on radiation was observed in silicon shield for which the dose of opposite side were 116 and 147 cGy for 6 MV and 60Co respectively. The maximum backscattered dose was measured 177 cGy and 219 cGy using 3 cm thickness of lead, which was quite considerable. The minimum backscattering where for acrylic resin 101 and 118 cGy for 6 MV and cobalt. In this study, it was concluded that the amount of backscattering for 3 cm Lead shield is quite considerable and increases the dose significantly. A composite layer of shield with 1-2 cm lead and 1 cm acrylic resin can have the protective effect and low backscattering radiation at the same time. PMID:26120570

  14. First-Year Principal Encounters Homophobia

    ERIC Educational Resources Information Center

    Retelle, Ellen

    2011-01-01

    A 1st-year principal encounters homonegativity and an ethical dilemma when she attempts to terminate a teacher because of the teacher's inadequate and ineffective teaching. The teacher responds by threatening to "out" Ms. L. to the parents.

  15. A CLOSER ENCOUNTER WITH MARS

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Taking advantage of Mars's closest approach to Earth in eight years, astronomers using NASA's Hubble Space Telescope have taken the space-based observatory's sharpest views yet of the Red Planet. NASA is releasing these images to commemorate the second anniversary of the Mars Pathfinder landing. The lander and its rover, Sojourner, touched down on the Red Planet's rolling hills on July 4, 1997, embarking on an historic three-month mission to gather information on the planet's atmosphere, climate, and geology. The telescope's Wide Field and Planetary Camera 2 snapped these images between April 27 and May 6, when Mars was 54 million miles (87 million kilometers) from Earth. From this distance the telescope could see Martian features as small as 12 miles (19 kilometers) wide. The telescope obtained four images, which, together, show the entire planet. Each view depicts the planet as it completes one quarter of its daily rotation. In these views the north polar cap is tilted toward the Earth and is visible prominently at the top of each picture. The images were taken in the middle of the Martian northern summer, when the polar cap had shrunk to its smallest size. During this season the Sun shines continuously on the polar cap. Previous telescopic and spacecraft observations have shown that this summertime 'residual' polar cap is composed of water ice, just like Earth's polar caps. These Hubble telescope snapshots reveal that substantial changes in the bright and dark markings on Mars have occurred in the 20 years since the NASA Viking spacecraft missions first mapped the planet. The Martian surface is dynamic and ever changing. Some regions that were dark 20 years ago are now bright red; some areas that were bright red are now dark. Winds move sand and dust from region to region, often in spectacular dust storms. Over long timescales many of the larger bright and dark markings remain stable, but smaller details come and go as they are covered and then uncovered by sand

  16. Mode Content Determination of Terahertz Corrugated Waveguides Using Experimentally Measured Radiated Field Patterns.

    PubMed

    Jawla, Sudheer K; Nanni, Emilio A; Shapiro, Michael A; Woskov, Paul P; Temkin, Richard J

    2012-06-01

    This work focuses on the accuracy of the mode content measurements in an overmoded corrugated waveguide using measured radiated field patterns. Experimental results were obtained at 250 GHz using a vector network analyzer with over 70 dB of dynamic range. The intensity and phase profiles of the fields radiated from the end of the 19 mm diameter helically tapped brass waveguide were measured on planes at 7, 10, and 13 cm from the waveguide end. The measured fields were back propagated to the waveguide aperture to provide three independent estimates of the field at the waveguide exit aperture. Projecting that field onto the modes of the guide determined the waveguide mode content. The three independent mode content estimates were found to agree with one another to an accuracy of better than ±0.3%. These direct determinations of the mode content were compared with indirect measurements using the experimentally measured amplitude in three planes, with the phase determined by a phase retrieval algorithm. The phase retrieval technique using the planes at 7, 10, and 13 cm yielded a mode content estimate in excellent agreement, within 0.3%, of the direct measurements. Phase retrieval results using planes at 10, 20, and 30 cm were less accurate due to truncation of the measurement in the transverse plane. The reported measurements benefited greatly from a precise mechanical alignment of the scanner with respect to the waveguide axis. These results will help to understand the accuracy of mode content measurements made directly in cold test and indirectly in hot test using the phase retrieval technique. PMID:25264391

  17. Mode Content Determination of Terahertz Corrugated Waveguides Using Experimentally Measured Radiated Field Patterns

    PubMed Central

    Jawla, Sudheer K.; Nanni, Emilio A.; Shapiro, Michael A.; Woskov, Paul P.; Temkin, Richard J.

    2012-01-01

    This work focuses on the accuracy of the mode content measurements in an overmoded corrugated waveguide using measured radiated field patterns. Experimental results were obtained at 250 GHz using a vector network analyzer with over 70 dB of dynamic range. The intensity and phase profiles of the fields radiated from the end of the 19 mm diameter helically tapped brass waveguide were measured on planes at 7, 10, and 13 cm from the waveguide end. The measured fields were back propagated to the waveguide aperture to provide three independent estimates of the field at the waveguide exit aperture. Projecting that field onto the modes of the guide determined the waveguide mode content. The three independent mode content estimates were found to agree with one another to an accuracy of better than ±0.3%. These direct determinations of the mode content were compared with indirect measurements using the experimentally measured amplitude in three planes, with the phase determined by a phase retrieval algorithm. The phase retrieval technique using the planes at 7, 10, and 13 cm yielded a mode content estimate in excellent agreement, within 0.3%, of the direct measurements. Phase retrieval results using planes at 10, 20, and 30 cm were less accurate due to truncation of the measurement in the transverse plane. The reported measurements benefited greatly from a precise mechanical alignment of the scanner with respect to the waveguide axis. These results will help to understand the accuracy of mode content measurements made directly in cold test and indirectly in hot test using the phase retrieval technique. PMID:25264391

  18. Newton’s second law, radiation reaction and type II Einstein-Maxwell fields

    NASA Astrophysics Data System (ADS)

    Newman, Ezra T.

    2011-12-01

    Considering perturbations of the Reissner-Nordström metric while keeping the perturbations in the class of type II Einstein-Maxwell metrics, we perform a spherical harmonic expansion of all the variables up to the quadrupole term. This leads to rather surprising results. Referring to the source of the metric as a type II particle (analogous to referring to a Schwarzschild-Reissner-Nordström or Kerr-Newman particle), we see immediately that the Bondi momentum of the particle takes the classical form of mass times velocity plus an electromagnetic radiation reaction term, while the Bondi mass loss equation becomes the classical gravitational and electromagnetic (electric and magnetic) dipole and quadrupole radiation. The Bondi momentum loss equation turns into Newton’s second law of motion containing the Abraham-Lorentz-Dirac radiation reaction force plus a momentum recoil (rocket) force, while the reality condition on the Bondi mass aspect yields the conservation of angular momentum. Two things must be pointed out: (1) these results, (equations of motion, etc) take place, not in the spacetime of the type II metric but in an auxiliary space referred to as {H}-space, whose physical meaning is rather obscure and (2) this analysis of the type II field equations is a very special case of a similar analysis of the general asymptotically flat Einstein-Maxwell equations. Although the final results are similar (though not the same), the analysis uses different equations (specifically, the type II field equations) and is vastly simpler than the general case. Without a great deal of the technical structures needed in the general case, one can see rather easily where the basic results reside in the type II field equations.

  19. Dose measurements in pulsed radiation fields with commercially available measuring components.

    PubMed

    Friedrich, Sabrina; Hupe, Oliver

    2016-03-01

    Dose measurements in pulsed radiation fields with dosemeters using the counting technique are known to be inappropriate. Therefore, there is a demand for a portable device able to measure the dose in pulsed radiation fields. As a detector, ionisation chambers seem to be a good alternative. In particular, using a secondary standard ionisation chamber in combination with a reliable charge-measuring system would be a good solution. The Physikalisch-Technische Bundesanstalt (PTB) uses secondary standard ionisation chambers in combination with PTB-made measuring electronics for dose measurements at its reference fields. However, for general use, this equipment is too complex. For measurements on-site, a mobile special electronic system [Hupe, O. and Ankerhold, U. Determination of ambient and personal dose equivalent for personnel and cargo security screening. Radiat. Prot. Dosim. 121: (4), 429-437 (2006)] has been used successfully. Still, for general use, there is a need for a much simpler but a just as good solution. A measuring instrument with very good energy dependence for H*(10) is the secondary standard ionisation chamber HS01. An easy-to-use and commercially available electrometer for measuring the generated charges is the UNIDOS by PTW Freiburg. Depending on the expected dose values, the ionisation chamber used can be selected. In addition, measurements have been performed by using commercially available area dosemeters, e.g. the Mini SmartION 2120S by Thermo Scientific, using an ionisation chamber and the Szintomat 6134 A/H by Automess, using a scintillation detector. PMID:26056377

  20. Pioneer to encounter Saturn on September 1

    NASA Technical Reports Server (NTRS)

    1979-01-01

    The encounter of the Pioneer 11 Spacecraft with Saturn, designed to provide information on the evolution of the Sun and its planets, is described. Photographs and measurements of Saturn, its rings, and several of its 10 satellites, including Titan, to be taken by Pioneer instruments, are emphasized. The encounter sequence and spacecraft trajectory are discussed. A description of Saturn and its atmosphere is included. Onboard instruments and experiments are also described.

  1. Spectral evolution of non-thermal electron distributions in intense radiation fields

    NASA Astrophysics Data System (ADS)

    Manolakou, K.; Horns, D.; Kirk, J. G.

    2007-11-01

    Context: Models of many astrophysical gamma-ray sources assume they contain a homogeneous distribution of electrons that are injected as a power law in energy and evolve by interacting with radiation fields, magnetic fields, and particles in the source and by escaping. This problem is particularly complicated if the radiation fields have higher energy density than the magnetic field and are sufficiently energetic that inverse Compton scattering is not limited to the Thomson regime. Aims: We present a simple, time-dependent, semi-analytical solution to the electron kinetic equation that treats both continuous and impulsive injection, cooling via synchrotron and inverse Compton radiation (taking Klein-Nishina effects into account), and energy-dependent particle escape. We used this solution to calculate the temporal evolution of the multi-wavelength spectrum of systems where energetic electrons cool in intense photon fields. Methods: The kinetic equation for an arbitrary, time-dependent source function is solved by the method of Laplace transformations. Using an approximate expression for the energy-loss rate that takes synchrotron and inverse Compton losses into account, including Klein-Nishina effects for scattering off an isotropic photon field with either a power-law or black-body distribution, we find explicit expressions for the cooling time and escape probability of individual electrons. This enables the full, time-dependent solution to be reduced to a single quadrature. From the electron distribution, we then construct the time-dependent, multi-wavelength emission spectrum. Results: We compare our solutions with several limiting cases and discuss the general appearance and temporal behaviour of spectral features (i.e., cooling breaks, bumps, etc.). As a specific example, we model the broad-band energy spectrum of the open stellar association Westerlund-2 at different times of its evolution, and compare it with observations. The model calculation matches the

  2. Application of the planar-scanning technique to the near-field dosimetry of millimeter-wave radiators.

    PubMed

    Zhao, Jianxun; Lu, Hongmin; Deng, Jun

    2015-02-01

    The planar-scanning technique was applied to the experimental measurement of the electric field and power flux density (PFD) in the exposure area close to the millimeter-wave (MMW) radiator. In the near-field region, the field and PFD were calculated from the plane-wave spectrum of the field sampled on a scan plane far from the radiator. The measurement resolution was improved by reducing the spatial interval between the field samples to a fraction of half the wavelength and implementing multiple iterations of the fast Fourier transform. With the reference to the results from the numerical calculation, an experimental evaluation of the planar-scanning measurement was made for a 50 GHz radiator. Placing the probe 1 to 3 wavelengths from the aperture of the radiator, the direct measurement gave the near-field data with significant differences from the numerical results. The planar-scanning measurement placed the probe 9 wavelengths away from the aperture and effectively reduced the maximum and averaged differences in the near-field data by 70.6% and 65.5%, respectively. Applied to the dosimetry of an open-ended waveguide and a choke ring antenna for 60 GHz exposure, the technique proved useful to the measurement of the PFD in the near-field exposure area of MMW radiators. PMID:25644219

  3. Photoinduced processes in solid polymer solutions of dyes in an interference field of laser radiation

    SciTech Connect

    Sizykh, A G; Tarakanova, E A

    1998-12-31

    An investigation was made of the relationships governing the photochemical mechanism of formation of light-induced gratings in solid polymer solutions of a dye with a high quantum yield of the triplet states. The combined analysis of the results of real and numerical experiments was made for a solution of eosin K in gelatin. The protonation rate constant of the dye was measured and the dependence of the diffraction efficiency on the duration of irradiation was explained taking diffusion of the dye into account. A method was proposed for determination of the duffusion coefficient in a spatially modified interference field of the laser radiation. The diffusion coefficients were found. (nonlinear optical phenomena)

  4. Photodissociation rates of OH, OD, and CN by the interstellar radiation field

    NASA Technical Reports Server (NTRS)

    Nee, J. B.; Lee, L. C.

    1985-01-01

    The photoabsorption cross sections for OH, OD, and CN in the vacuum ultraviolet region are measured. The cross sections for the hydroxyl radicals are of the order of 10 to the -17th sq cm, but the photoabsorption for CN is so low that only an upper limit of 2 x 10 to the -18th sq cm is obtained. The molecular photodissociative processes are discussed. The photodissociation cross sections are inferred from the photoabsorption cross sections. On the basis of the measured data, the photodissociation rates by the interstellar radiation field are computed and discussed.

  5. Photodissociation rates of OH, OD, and CN by the interstellar radiation field

    SciTech Connect

    Nee, J.B.; Lee, L.C.

    1985-04-01

    The photoabsorption cross sections for OH, OD, and CN in the vacuum ultraviolet region are measured. The cross sections for the hydroxyl radicals are of the order of 10/sup -17/ cm/sup -2/, but the photoabsorption for CN is so low that only an upper limit of 2 x 10/sup -18/ is obtained. The molecular photodissociative processes are discussed. The photodissociation cross sections are inferred from the photoabsorption cross sections. On the basis of the measured data, the photodissociation rates by the interstellar radiation field are computed and discussed.

  6. Impacts of cloud overlap assumptions on radiative budgets and heating fields in convective regions

    NASA Astrophysics Data System (ADS)

    Wang, XiaoCong; Liu, YiMin; Bao, Qing

    2016-01-01

    Impacts of cloud overlap assumptions on radiative budgets and heating fields are explored with the aid of a cloud-resolving model (CRM), which provided cloud geometry as well as cloud micro and macro properties. Large-scale forcing data to drive the CRM are from TRMM Kwajalein Experiment and the Global Atmospheric Research Program's Atlantic Tropical Experiment field campaigns during which abundant convective systems were observed. The investigated overlap assumptions include those that were traditional and widely used in the past and the one that was recently addressed by Hogan and Illingworth (2000), in which the vertically projected cloud fraction is expressed by a linear combination of maximum and random overlap, with the weighting coefficient depending on the so-called decorrelation length Lcf. Results show that both shortwave and longwave cloud radiative forcings (SWCF/LWCF) are significantly underestimated under maximum (MO) and maximum-random (MRO) overlap assumptions, whereas remarkably overestimated under the random overlap (RO) assumption in comparison with that using CRM inherent cloud geometry. These biases can reach as high as 100 Wm- 2 for SWCF and 60 Wm- 2 for LWCF. By its very nature, the general overlap (GenO) assumption exhibits an encouraging performance on both SWCF and LWCF simulations, with the biases almost reduced by 3-fold compared with traditional overlap assumptions. The superiority of GenO assumption is also manifested in the simulation of shortwave and longwave radiative heating fields, which are either significantly overestimated or underestimated under traditional overlap assumptions. The study also pointed out the deficiency of constant assumption on Lcf in GenO assumption. Further examinations indicate that the CRM diagnostic Lcf varies among different cloud types and tends to be stratified in the vertical. The new parameterization that takes into account variation of Lcf in the vertical well reproduces such a relationship and

  7. Measurement of the Radiation Field in Atlas with the Atlas-Mpx Detectors

    NASA Astrophysics Data System (ADS)

    Campbell, Michael; Heijne, Erik; Leroy, Claude; Martin, Jean-Pierre; Mornacchi, Giuseppe; Nessi, Marzio; Pospisil, Stanislav; Solc, Jaroslav; Soueid, Paul; Suk, Michal; Turecek, Daniel; Vykydal, Zdenek

    2012-08-01

    A network of 16 ATLAS-MPX (silicon pixelated) detectors has been installed by the ATLAS-MPX Collaboration at various positions within the ATLAS detector and its environment. The ATLAS-MPX detectors allow real-time measurements of spectral characteristics and composition of the radiation field inside and around the ATLAS detector during its operation. Results obtained with the ATLAS-MPX detectors are reported in this article. They include luminosity measurement obtained with van der Meer luminosity scans and measurement of induced radioactivity in between/after collision.

  8. Nonlinear polarization response of a gaseous medium in the regime of atom stabilization in a strong radiation field

    SciTech Connect

    Volkova, E. A.; Popov, A. M. Tikhonova, O. V.

    2013-03-15

    The nonlinear polarization response of a quantum system modeling a silver atom in the field of high-intensity radiation in the IR and UV spectral ranges has been studied by direct numerical integration of a nonstationary Schroedinger equation. The domains of applicability of perturbation theory and polarization expansion in powers of the field intensity are determined. The contribution of excited atoms and electrons in a continuum to the atomic polarization response at the field frequency, which arises due to the radiation-induced excitation and photoionization processes, is analyzed. Features of the nonlinear response to an external field under conditions of atom stabilization are considered.

  9. Experimental observation of further frequency upshift from dc to ac radiation converter with perpendicular dc magnetic field

    PubMed

    Higashiguchi; Yugami; Gao; Niiyama; Sasaki; Takahashi; Ito; Nishida

    2000-11-20

    A frequency upshift of a short microwave pulse is generated by the interaction between a relativistic underdense ionization front and a periodic electrostatic field with a perpendicular dc magnetic field. When the dc magnetic field is applied, further frequency upshift of 3 GHz is observed with respect to an unmagnetized case which has typically a GHz range. The radiation frequency depends on both the plasma density and the strength of the dc magnetic field, i.e., the plasma frequency and the cyclotron frequency. The frequency of the emitted radiation is in reasonable agreement with the theoretical values. PMID:11082591

  10. Encounters between binaries and neutron stars

    NASA Technical Reports Server (NTRS)

    Davies, M. B.; Benz, W.; Hills, J. G.

    1993-01-01

    We simulated encounters between a neutron star and primordial and tidal-capture binaries. In the case of encounters involving a tidal-capture binary, comprising a white dwarf and a main-sequence star, we find that most exchange encounters will produce a single merged object with the white dwarf and neutron star engulfed in a common envelope of gas donated by the main-sequence primary of the original binary. A small fraction of exchanges induce a merger of the white dwarf and main-sequence star, with this object being unbound to the neutron star, and the two objects having a large relative speed at infinity. For encounters involving a primordial binary, fewer encounters require the inclusion of hydrodynamical effects. Those involving collisions or close encounters tend to produce a binary comprised of the two merged stars (now forming one star) and the third star. The binaries produced typically have large enough separations to prevent the formation of a single merged object until subsequent stellar evolution of one of the components causes it to fill its Roche lobe. Clean exchanges produce binaries with large eccentricities; they are typically sufficiently wide to avoid circularization.

  11. Interaction of laser radiation with plasma under the MG external magnetic field

    NASA Astrophysics Data System (ADS)

    Ivanov, V. V.; Maximov, A. V.; Covington, A. M.; Wiewior, P. P.; Astanovitskiy, A. L.; Nalajala, V.; Chalyy, O.; Dmitriev, O.

    2015-11-01

    A strong magnetic field can dramatically change the properties of plasmas. Studies of plasmas in the magnetic field are important for basic physics, astrophysics, and controlled fusion. A series of shots was carried out at the 1 MA pulsed power generator coupled with a 50-TW laser. A 2-2.5 MG magnetic field was generated on the surface of the Al 1 mm rod load by 1 MA current. A sub-nanosecond laser pulse with intensity of 3x1015 W/cm2 was focused on the load surface. A collimated plasma jet 1-3 mm long was observed propagating back from the focal spot with a speed of 240 km/s. Another plasma jet was seen on the rear side of the rod load. Both jets on the front and rear sides were also seen in shots with the 0.8 mm Cu load. The front plasma jet may be linked to the ExB drift observed elsewhere at smaller B-fields. The enhanced temperature and keV x-ray radiation of laser plasma in the magnetic field were found with x-ray spectroscopy. Work was supported by the DOE grant DE-SC0008824 and DOE/NNSA UNR grant DE-FC52-06NA27616.

  12. Factors affecting the gamma response of TLD-700 chips in mixed-radiation fields

    SciTech Connect

    Swaja, R.E. ); Scofield, P.A. )

    1986-10-01

    To determine the causes of gamma dose equivalent overestimates observed during mixed-radiation field personnel dosimetry intercomparisons at Oak Ridge National Laboratory, a study was performed to evaluate the effects of phosphor neutron sensitivity, badge materials, and phantoms on the response of TLD-700 chips. The results of the study presented in this paper indicate that even if a phosphor with relatively low neutron sensitivity is used, significant gamma overestimates can occur in mixed fields due to the interaction of the phosphor and badge materials with neutrons. Low energy photons can also contribute to gamma dose equivalent overestimates due to the increased sensitivity of the TLD-700 phosphor to photons with energies below about 100 keV.

  13. Mirror effect induced by the dilaton field on the Hawking radiation

    SciTech Connect

    Maeda, Kengo; Okamura, Takashi

    2006-11-03

    A ''stringy particle'' action is naturally derived from Kaluza-Klein compactification of a test string action coupled to the dilaton field in a conformally invariant manner. According to the standard procedure, we perform the second quantization of the stringy particle. As an interesting application, we consider evaporation of a near-extremal dilatonic black hole by Hawking radiation via the stringy particles. We show that a mirror surface which reflects them is induced by the dilaton field outside the the horizon when the size of the black hole is comparable to the Planck scale. As a result, the energy flux does not propagate across the surface, and hence the evaporation of the dilatonic black hole stops just before the naked singularity at the extremal state appears even though the surface gravity is non-zero in the extremal limit.

  14. Polarized radiance fields under a dynamic ocean surface: a three-dimensional radiative transfer solution

    SciTech Connect

    You Yu; Zhai Pengwang; Kattawar, George W.; Yang Ping

    2009-06-01

    The hybrid matrix operator, Monte Carlo (HMOMC) method previously reported [Appl. Opt.47, 1063-1071 (2008)APOPAI0003-693510.1364/AO.47.001063] is improved by neglecting higher-order terms in the coupling of the matrix operators and by introducing a dual grid scheme. The computational efficiency for solving the vector radiative transfer equation in a full 3D coupled atmosphere-surface-ocean system is substantially improved, and, thus, large-scale simulations of the radiance distribution become feasible. The improved method is applied to the computation of the polarized radiance field under realistic surface waves simulated by the power spectral density method. To the authors' best knowledge, this is the first time that the polarized radiance field under a dynamic ocean surface and the underwater image of an object above such an ocean surface have been reported.

  15. Near-field radiative heat transfer between metamaterials coated with silicon carbide thin films

    SciTech Connect

    Basu, Soumyadipta Yang, Yue; Wang, Liping

    2015-01-19

    In this letter, we study the near-field radiative heat transfer between two metamaterial substrates coated with silicon carbide (SiC) thin films. It is known that metamaterials can enhance the near-field heat transfer over ordinary materials due to excitation of magnetic plasmons associated with s polarization, while strong surface phonon polariton exists for SiC. By careful tuning of the optical properties of metamaterial, it is possible to excite electrical and magnetic resonances for the metamaterial and surface phonon polaritons for SiC at different spectral regions, resulting in the enhanced heat transfer. The effect of the SiC film thickness at different vacuum gaps is investigated. Results obtained from this study will be beneficial for application of thin film coatings for energy harvesting.

  16. Thermal radiative near field transport between vanadium dioxide and silicon oxide across the metal insulator transition

    NASA Astrophysics Data System (ADS)

    Menges, F.; Dittberner, M.; Novotny, L.; Passarello, D.; Parkin, S. S. P.; Spieser, M.; Riel, H.; Gotsmann, B.

    2016-04-01

    The thermal radiative near field transport between vanadium dioxide and silicon oxide at submicron distances is expected to exhibit a strong dependence on the state of vanadium dioxide which undergoes a metal-insulator transition near room temperature. We report the measurement of near field thermal transport between a heated silicon oxide micro-sphere and a vanadium dioxide thin film on a titanium oxide (rutile) substrate. The temperatures of the 15 nm vanadium dioxide thin film varied to be below and above the metal-insulator-transition, and the sphere temperatures were varied in a range between 100 and 200 °C. The measurements were performed using a vacuum-based scanning thermal microscope with a cantilevered resistive thermal sensor. We observe a thermal conductivity per unit area between the sphere and the film with a distance dependence following a power law trend and a conductance contrast larger than 2 for the two different phase states of the film.

  17. Field transients of coherent terahertz synchrotron radiation accessed via time-resolving and correlation techniques

    NASA Astrophysics Data System (ADS)

    Pohl, A.; Semenov, A.; Hübers, H.-W.; Hoehl, A.; Ries, M.; Wüstefeld, G.; Ulm, G.; Ilin, K.; Thoma, P.; Siegel, M.

    2016-03-01

    Decaying oscillations of the electric field in repetitive pulses of coherent synchrotron radiation in the terahertz frequency range was evaluated by means of time-resolving and correlation techniques. Comparative analysis of real-time voltage transients of the electrical response and interferograms, which were obtained with an ultrafast zero-bias Schottky diode detector and a Martin-Puplett interferometer, delivers close values of the pulse duration. Consistent results were obtained via the correlation technique with a pair of Golay Cell detectors and a pair of resonant polarisation-sensitive superconducting detectors integrated on one chip. The duration of terahertz synchrotron pulses does not closely correlate with the duration of single-cycle electric field expected for the varying size of electron bunches. We largely attribute the difference to the charge density oscillations in electron bunches and to the low-frequency spectral cut-off imposed by both the synchrotron beamline and the coupling optics of our detectors.

  18. Generation of 1.5-kW, 1-THz coherent radiation from a gyrotron with a pulsed magnetic field.

    PubMed

    Glyavin, M Yu; Luchinin, A G; Golubiatnikov, G Yu

    2008-01-11

    To cover a so-called terahertz gap in available sources of coherent electromagnetic radiation, the gyrotron with a pulsed solenoid producing up to a 40 T magnetic field has been designed, manufactured, and tested. At a 38.5 T magnetic field, the gyrotron generated coherent radiation at 1.022 THz frequency in 50 musec pulses. The microwave power and energy per pulse were about 1.5 kW and 75 mJ, respectively. Details of the gyrotron design, manufacturing, operation and measurements of output radiation are given. PMID:18232780

  19. Generation of 1.5-kW, 1-THz Coherent Radiation from a Gyrotron with a Pulsed Magnetic Field

    SciTech Connect

    Glyavin, M. Yu.; Luchinin, A. G.; Golubiatnikov, G. Yu.

    2008-01-11

    To cover a so-called terahertz gap in available sources of coherent electromagnetic radiation, the gyrotron with a pulsed solenoid producing up to a 40 T magnetic field has been designed, manufactured, and tested. At a 38.5 T magnetic field, the gyrotron generated coherent radiation at 1.022 THz frequency in 50 {mu}sec pulses. The microwave power and energy per pulse were about 1.5 kW and 75 mJ, respectively. Details of the gyrotron design, manufacturing, operation and measurements of output radiation are given.

  20. Developmental effects of magnetic field (50 Hz) in combination with ionizing radiation and chemical teratogens.

    PubMed

    Pafková, H; Jerábek, J; Tejnorová, I; Bednár, V

    1996-11-01

    The influence of a 50 Hz magnetic field (MF) on avian and mammalian embryogenesis, the MF level and vector, as well as the effect of exposure to MF (50 Hz, 10 mT) in combination with X-rays has been recently reported [2,3]. No significant alterations of chick or rat embryogenesis were found after repeated exposures to 50 Hz MF at 10 mT or 6 microT or with different vectors. However, X-ray chick embryotoxicity was significantly affected by repeated exposures of developing organisms to MF. A strong dependence of effect on the type of interaction was revealed. A decrease of X-ray induced teratogenicity was observed when MF preceded X-ray exposure (indirect interaction), while MF exposure applied immediately after X-ray radiation (direct interaction) non-significantly potentiated adverse developmental effects of ionizing radiation. This study deals with the effects of MF in combination with insulin or tetracycline. Exposure of chick embryos to MF influenced the sensitivity of embryonic morphogenetic systems to the subsequently administered chemical teratogens, insulin and/or tetracycline. A protective effect of MF was detected similarly as in the case of indirect interaction with ionizing radiation. PMID:8920754