Science.gov

Sample records for dominant electron trap

  1. High energy gain of trapped electrons in a tapered, diffraction-dominated inverse-free-electron laser.

    PubMed

    Musumeci, P; Tochitsky, S Ya; Boucher, S; Clayton, C E; Doyuran, A; England, R J; Joshi, C; Pellegrini, C; Ralph, J E; Rosenzweig, J B; Sung, C; Tolmachev, S; Travish, G; Varfolomeev, A A; Varfolomeev, A A; Yarovoi, T; Yoder, R B

    2005-04-22

    Energy gain of trapped electrons in excess of 20 MeV has been demonstrated in an inverse-free-electron-laser (IFEL) accelerator experiment. A 14.5 MeV electron beam is copropagated with a 400 GW CO2 laser beam in a 50 cm long undulator strongly tapered in period and field amplitude. The Rayleigh range of the laser, approximately 1.8 cm, is much shorter than the undulator length yielding a diffraction-dominated interaction. Experimental results on the dependence of the acceleration on injection energy, laser focus position, and laser power are discussed. Simulations, in good agreement with the experimental data, show that most of the energy gain occurs in the first half of the undulator at a gradient of 70 MeV/m and that the structure in the measured energy spectrum arises because of higher harmonic IFEL interaction in the second half of the undulator.

  2. Conversion process of the dominant electroluminescence mechanism in a molecularly doped organic light-emitting device with only electron trapping

    NASA Astrophysics Data System (ADS)

    Zhou, Liang; Zhang, Hongjie; Deng, Ruiping; Li, Zhefeng; Yu, Jiangbo; Guo, Zhiyong

    2007-09-01

    In this work, the detailed conversion process of the dominant electroluminescence (EL) mechanism in a device with Eu(TTA)3phen (TTA =thenoyltrifluoroacetone, phen =1,10-phenanthroline) doped CBP (4,4'-N,N'-dicarbazole-biphenyl) film as the emitting layer was investigated by analyzing the evolution of carrier distribution on dye and host molecules with increasing voltage. Firstly, it was confirmed that only electrons can be trapped in Eu(TTA)3phen doped CBP. As a result, holes and electrons would be situated on CBP and Eu(TTA)3phen molecules, respectively, and thus creates an unbalanced carrier distribution on both dye and host molecules. With the help of EL and photoluminescence spectra, the distribution of holes and electrons on both Eu(TTA)3phen and CBP molecules was demonstrated to change gradually with increasing voltage. Therefore, the dominant EL mechanism in this device changes gradually from carrier trapping at relatively low voltage to Förster energy transfer at relatively high voltage.

  3. Trapped-electron runaway effect

    NASA Astrophysics Data System (ADS)

    Nilsson, E.; Decker, J.; Fisch, N. J.; Peysson, Y.

    2015-08-01

    In a tokamak, trapped electrons subject to a strong electric field cannot run away immediately, because their parallel velocity does not increase over a bounce period. However, they do pinch toward the tokamak center. As they pinch toward the center, the trapping cone becomes more narrow, so eventually they can be detrapped and run away. When they run away, trapped electrons will have a very different signature from circulating electrons subject to the Dreicer mechanism. The characteristics of what are called trapped-electron runaways are identified and quantified, including their distinguishable perpendicular velocity spectrum and radial extent.

  4. Behavior of the 0. 82 eV and other dominant electron traps in organometallic vapor phase epitaxial Al/sub x/Ga/sub 1-x/As

    SciTech Connect

    Matsumoto, T.; Bhattacharya, P.K.; Ludowise, M.J.

    1982-10-01

    Thermal emission and capture properties of three dominant electron traps in organometallic vapor phase epitaxial Al/sub x/Ga/sub 1-x/As have been studied by transient capacitance measurements. The traps have activation energies ..delta..E/sub T/ = 0.82 +- 0.01, 0.62 +- 0.02, and 0.38 +- 0.02 eV, which remain invariant with x. The thermal capture cross section of the traps, however, decreases with increasing x. These results, together with the annealing behavior of the traps, add more evidence to the fact that the 0.82-eV trap, commonly known as the EL2 center, is related to a Ga vacancy. The 0.82- and 0.38-eV traps exhibit barriers to electron capture approx.0.06--0.08 eV and the concentration of the 0.62- and 0.38-eV traps increases with increasing x.

  5. Spin readout of trapped electron qubits

    NASA Astrophysics Data System (ADS)

    Peng, Pai; Matthiesen, Clemens; Häffner, Hartmut

    2017-01-01

    We propose a scheme to read out the spin of a single electron quantum bit in a surface Paul trap using oscillating magnetic-field gradients. The readout sequence is composed of cooling, driving, amplification, and detection of the electron's motion. We study the scheme in the presence of noise and trap anharmonicities at liquid-helium temperatures. An analysis of the four procedures shows short measurement times (25 μ s ) and high fidelities (99.7 % ) are achievable with realistic experimental parameters. Our scheme performs the function of fluorescence detection in ion trapping schemes, highlighting the potential to build all-electric quantum computers based on trapped electron-spin qubits.

  6. Electron trapping in polar-solvated zeolites.

    PubMed

    Ellison, Eric H

    2005-11-03

    Of current interest in our laboratory is the nature of photoinduced processes in the cavities of zeolites completely submerged in polar solvents, or polar-solvated zeolites (PSZ). The present study addresses the nature of electron trapping in PSZ with emphasis on the zeolites NaX and NaY. Free electrons were generated by two-photon, pulsed-laser excitation of either pyrene or naphthalene included in zeolite cavities. Trapped electrons were monitored by diffuse transmittance, transient absorption spectroscopy at visible wavelengths. In anhydrous alcohols, electron trapping by Na(4)(4+) ion clusters was observed in both NaX and NaY. The resulting trapped electrons decayed over the course of tens of milliseconds. No evidence for alcohol-solvated electrons was found. More varied results were observed in solvents containing water. In NaX submerged in CH(3)OH containing 5% or higher water, species having microsecond lifetimes characteristic of solvated electrons were observed. By contrast, a 2 h exposure of NaY to 95/5 CH(3)OH/H(2)O had no effect on electron trapping relative to anhydrous CH(3)OH. The difference between NaX and NaY was explained by how fast water migrates into the sodalite cage. Prolonged exposure to water at room temperature or exposure to water at elevated temperatures was necessary to place water in the sodalite cages of NaY and deactivate Na(4)(4+) as an electron trap. Additional studies in NaY revealed that solvent clusters eventually become lower energy traps than Na(4)(4+) as the water content in methanol increases. In acetonitrile-water mixtures, electron trapping by Na(4)(4+) was eliminated and no equivalent species characteristic of solvated electrons in methanol-water mixtures was observed. This result was explained by the formation of low energy solvated electrons which cannot be observed in the visible region of the spectrum. Measurements of the rate of O(2) quenching in anhydrous solvents revealed rate constants for the quenching of ion

  7. Nonlinear saturation of trapped electron modes via perpendicular particle diffusion.

    PubMed

    Merz, F; Jenko, F

    2008-01-25

    In magnetized fusion plasmas, trapped electron mode (TEM) turbulence constitutes, together with ion temperature gradient (ITG) turbulence, the dominant source of anomalous transport on ion scales. While ITG modes are known to saturate via nonlinear zonal flow generation, this mechanism is shown to be of little importance for TEM turbulence in the parameter regime explored here. Instead, a careful analysis of the statistical properties of the ExB nonlinearity in the context of gyrokinetic turbulence simulations reveals that perpendicular particle diffusion is the dominant saturation mechanism. These findings allow for the construction of a rather realistic quasilinear model of TEM induced transport.

  8. Electron beam ion source and electron beam ion trap (invited).

    PubMed

    Becker, Reinard; Kester, Oliver

    2010-02-01

    The electron beam ion source (EBIS) and its trap variant [electron beam ion trap (EBIT)] celebrated their 40th and 20th anniversary, respectively, at the EBIS/T Symposium 2007 in Heidelberg. These technologically challenging sources of highly charged ions have seen a broad development in many countries over the last decades. In contrast to most other ion sources the recipe of improvement was not "sorcery" but a clear understanding of the physical laws and obeying the technological constraints. This review will report important achievements of the past as well as promising developments in the future.

  9. Ultrafast electron trapping in ligand-exchanged quantum dot assemblies.

    PubMed

    Turk, Michael E; Vora, Patrick M; Fafarman, Aaron T; Diroll, Benjamin T; Murray, Christopher B; Kagan, Cherie R; Kikkawa, James M

    2015-02-24

    We use time-integrated and time-resolved photoluminescence and absorption to characterize the low-temperature optical properties of CdSe quantum dot solids after exchanging native aliphatic ligands for thiocyanate and subsequent thermal annealing. In contrast to trends established at room temperature, our data show that at low temperature the band-edge absorptive bleach is dominated by 1S3/2h hole occupation in the quantum dot interior. We find that our ligand treatments, which bring enhanced interparticle coupling, lead to faster surface state electron trapping, a greater proportion of surface-related photoluminescence, and decreased band-edge photoluminescence lifetimes.

  10. Energy Measurements of Trapped Electrons from a Plasma Wakefield Accelerator

    SciTech Connect

    Kirby, Neil; Berry, Melissa; Blumenfeld, Ian; Decker, Franz-Josef; Hogan, Mark J.; Ischebeck, Rasmus; Iverson, Richard; Siemann, Robert H.; Walz, Dieter; Auerbach, David; Clayton, Christopher E.; Huang, Chengkun; Johnson, Devon; Joshi, Chandrashekhar; Lu, Wei; Marsh, Kenneth A.; Mori, Warren B.; Zhou, Miaomiao; Katsouleas, Thomas; Muggli, Patric

    2006-11-27

    Recent electron beam driven plasma wakefield accelerator experiments carried out at SLAC indicate trapping of plasma electrons. More charge came out of than went into the plasma. Most of this extra charge had energies at or below the 10 MeV level. In addition, there were trapped electron streaks that extended from a few GeV to tens of GeV, and there were mono-energetic trapped electron bunches with tens of GeV in energy.

  11. Energy Measurements of Trapped Electrons from a Plasma Wakefield Accelerator

    SciTech Connect

    Kirby, Neal; Auerbach, David; Berry, Melissa; Blumenfeld, Ian; Clayton, Christopher E.; Decer, Franz-Josef; Hogan, Mark J.; Huang, Chengkun; Ischebeck, Rasmus; Iverson, Richard; Johnson, Devon; Joshi, Chadrashekhar; Katsouleas, Thomas; Lu, Wei; Marsh, Kenneth A.; Mori, Warren B.; Muggli, Patric; Oz, Erdem; Siemann, Robert H.; Walz, Dieter; Zhou, Miaomiao; /SLAC /UCLA /Southern California U.

    2007-01-03

    Recent electron beam driven plasma wakefield accelerator experiments carried out at SLAC indicate trapping of plasma electrons. More charge came out of than went into the plasma. Most of this extra charge had energies at or below the 10 MeV level. In addition, there were trapped electron streaks that extended from a few GeV to tens of GeV, and there were mono-energetic trapped electron bunches with tens of GeV in energy.

  12. The AE-8 trapped electron model environment

    NASA Technical Reports Server (NTRS)

    Vette, James I.

    1991-01-01

    The machine sensible version of the AE-8 electron model environment was completed in December 1983. It has been sent to users on the model environment distribution list and is made available to new users by the National Space Science Data Center (NSSDC). AE-8 is the last in a series of terrestrial trapped radiation models that includes eight proton and eight electron versions. With the exception of AE-8, all these models were documented in formal reports as well as being available in a machine sensible form. The purpose of this report is to complete the documentation, finally, for AE-8 so that users can understand its construction and see the comparison of the model with the new data used, as well as with the AE-4 model.

  13. New electron trap in p-type Czochralski silicon

    NASA Technical Reports Server (NTRS)

    Mao, B.-Y.; Lagowski, J.; Gatos, H. C.

    1984-01-01

    A new electron trap (acceptor level) was discovered in p-type Czochralski (CZ) silicon by current transient spectroscopy. The behavior of this trap was found to be similar to that of the oxygen thermal donors; thus, 450 C annealing increases the trap concentration while high-temperature annealing (1100-1200 C) leads to the virtual elimination of the trap. The new trap is not observed in either float-zone or n-type CZ silicon. Its energy level depends on the group III doping element in the sample. These findings suggest that the trap is related to oxygen, and probably to the acceptor impurity as well.

  14. Cyclotron Resonance of Electrons Trapped in a Microwave Cavity

    ERIC Educational Resources Information Center

    Elmore, W. C.

    1975-01-01

    Describes an experiment in which the free-electron cyclotron resonance of electrons trapped in a microwave cavity by a Penning trap is observed. The experiment constitutes an attractive alternative to one of the Gardner-Purcell variety. (Author/GS)

  15. Electronic Spectroscopy of Trapped PAH Photofragments

    NASA Astrophysics Data System (ADS)

    Joblin, Christine; Bonnamy, Anthony

    2016-06-01

    The PIRENEA set-up combines an ion cyclotron resonance cell mass spectrometer with cryogenic cooling in order to study the physical and chemical properties of polycyclic aromatic hydrocarbons (PAHs) of astrophysical interest. In space, PAHs are submitted to UV photons that lead to their dissociation. It is therefore of interest to study fragmentation pathways and search for species that might be good interstellar candidates because of their stability. Electronic spectroscopy can bring major insights into the structure of species formed by photofragmentation. This is also a way to identify new species in space as recently illustrated in the case of C60^+. In PIRENEA, the trapped ions are not cold enough, and thus we cannot use complexation with rare gas in order to record spectroscopy, as was nicely performed in the work by Campbell et al. on C60^+. We are therefore using the dissociation of the trapped ions themselves instead, which requires in general a multiple photon scheme. This leads to non-linear effects that affect the measured spectrum. We are working on improving this scheme in the specific case of the photofragment obtained by H-loss from 1-methylpyrene cation (CH_3-C16H9^+). A recent theoretical study has shown that a rearrangement can occur from 1-pyrenemethylium cation (CH_2-C16H9^+) to a system containing a seven membered ring (tropylium like pyrene system). This study also reports the calculated electronic spectra of both isomers, which are specific enough to distinguish them, and as a function of temperature. We will present experiments that have been performed to study the photophysics of these ions using the PIRENEA set-up and a two-laser scheme for the action spectroscopy. J. Montillaud, C. Joblin, D. Toublanc, Astron. & Astrophys. 552 (2013), id.A15 E.K. Campbell, M. Holz, D. Gerlich, and J.P. Maier, Nature 523 (2015), 322-323 F. Useli-Bacchitta, A. Bonnamy, G. Malloci, et al., Chem. Phys. 371 (2010), 16-23; J. Zhen, A. Bonnamy, G. Mulas, C

  16. Electronic circuit provides automatic level control for liquid nitrogen traps

    NASA Technical Reports Server (NTRS)

    Turvy, R. R.

    1968-01-01

    Electronic circuit, based on the principle of increased thermistor resistance corresponding to decreases in temperature provides an automatic level control for liquid nitrogen cold traps. The electronically controlled apparatus is practically service-free, requiring only occasional reliability checks.

  17. Electron Cloud Trapping in Recycler Combined Function Dipole Magnets

    SciTech Connect

    Antipov, Sergey A.; Nagaitsev, S.

    2016-10-04

    Electron cloud can lead to a fast instability in intense proton and positron beams in circular accelerators. In the Fermilab Recycler the electron cloud is confined within its combined function magnets. We show that the field of combined function magnets traps the electron cloud, present the results of analytical estimates of trapping, and compare them to numerical simulations of electron cloud formation. The electron cloud is located at the beam center and up to 1% of the particles can be trapped by the magnetic field. Since the process of electron cloud build-up is exponential, once trapped this amount of electrons significantly increases the density of the cloud on the next revolution. In a Recycler combined function dipole this multiturn accumulation allows the electron cloud reaching final intensities orders of magnitude greater than in a pure dipole. The multi-turn build-up can be stopped by injection of a clearing bunch of 1010 p at any position in the ring.

  18. TNF-receptor-associated periodic syndrome (TRAPS): an autosomal dominant multisystem disorder.

    PubMed

    Rezaei, Nima

    2006-11-01

    The TNF-receptor-associated periodic syndrome (TRAPS) is an autosomal dominant auto-inflammatory disorder, characterized by recurrent febrile attacks and localized inflammation. TRAPS is caused by mutations in the gene encoding the TNF Receptor Super Family 1A (TNFRSF1A) on chromosome 12p13. However, the incomplete penetrance and genetic heterogeneity have been reported in this syndrome. Although the ethnic diversity and clinical heterogeneity may propose the role of other genes in the pathogenesis of TRAPS, some low-penetrance TNFRSF1A variants contribute to atypical inflammatory responses in other autoimmune diseases. Furthermore, molecular studies on TRAPS and other auto-inflammatory disorders could be suggested to identify additional genes coding the molecules in the TNF signalling process.

  19. Properties of Trapped Electron Bunches in a Plasma Wakefield Accelerator

    SciTech Connect

    Kirby, Neil; /SLAC

    2009-10-30

    Plasma-based accelerators use the propagation of a drive bunch through plasma to create large electric fields. Recent plasma wakefield accelerator (PWFA) experiments, carried out at the Stanford Linear Accelerator Center (SLAC), successfully doubled the energy for some of the 42 GeV drive bunch electrons in less than a meter; this feat would have required 3 km in the SLAC linac. This dissertation covers one phenomenon associated with the PWFA, electron trapping. Recently it was shown that PWFAs, operated in the nonlinear bubble regime, can trap electrons that are released by ionization inside the plasma wake and accelerate them to high energies. These trapped electrons occupy and can degrade the accelerating portion of the plasma wake, so it is important to understand their origins and how to remove them. Here, the onset of electron trapping is connected to the drive bunch properties. Additionally, the trapped electron bunches are observed with normalized transverse emittance divided by peak current, {epsilon}{sub N,x}/I{sub t}, below the level of 0.2 {micro}m/kA. A theoretical model of the trapped electron emittance, developed here, indicates that the emittance scales inversely with the square root of the plasma density in the non-linear 'bubble' regime of the PWFA. This model and simulations indicate that the observed values of {epsilon}{sub N,x}/I{sub t} result from multi-GeV trapped electron bunches with emittances of a few {micro}m and multi-kA peak currents. These properties make the trapped electrons a possible particle source for next generation light sources. This dissertation is organized as follows. The first chapter is an overview of the PWFA, which includes a review of the accelerating and focusing fields and a survey of the remaining issues for a plasma-based particle collider. Then, the second chapter examines the physics of electron trapping in the PWFA. The third chapter uses theory and simulations to analyze the properties of the trapped electron

  20. Trapped electron cloud bolometer relying on frequency shift.

    PubMed Central

    Dehmelt, H

    1994-01-01

    An improved electron cloud bolometer is analyzed. In this device the cloud temperature is read out not via thermal noise induced by the electrons in a coupled LC circuit but via shift in their axial oscillation frequency in the Penning trap confining them. This shift occurs because as the electron cloud expands with increasing temperature, the average restoring force in the slightly anharmonic trap does change perceptibly. The scheme will be useful in exploring the microwave mode structure of the trap cavity and in locating magnetic field values for which the cavity-induced shift in the measured electron g factor disappears. PMID:11607480

  1. Trapped electron cloud bolometer relying on frequency shift.

    PubMed

    Dehmelt, H

    1994-07-05

    An improved electron cloud bolometer is analyzed. In this device the cloud temperature is read out not via thermal noise induced by the electrons in a coupled LC circuit but via shift in their axial oscillation frequency in the Penning trap confining them. This shift occurs because as the electron cloud expands with increasing temperature, the average restoring force in the slightly anharmonic trap does change perceptibly. The scheme will be useful in exploring the microwave mode structure of the trap cavity and in locating magnetic field values for which the cavity-induced shift in the measured electron g factor disappears.

  2. Collisionless microtearing modes in hot tokamaks: Effect of trapped electrons

    SciTech Connect

    Swamy, Aditya K.; Ganesh, R.; Brunner, S.; Vaclavik, J.; Villard, L.

    2015-07-15

    Collisionless microtearing modes have recently been found linearly unstable in sharp temperature gradient regions of large aspect ratio tokamaks. The magnetic drift resonance of passing electrons has been found to be sufficient to destabilise these modes above a threshold plasma β. A global gyrokinetic study, including both passing electrons as well as trapped electrons, shows that the non-adiabatic contribution of the trapped electrons provides a resonant destabilization, especially at large toroidal mode numbers, for a given aspect ratio. The global 2D mode structures show important changes to the destabilising electrostatic potential. The β threshold for the onset of the instability is found to be generally downshifted by the inclusion of trapped electrons. A scan in the aspect ratio of the tokamak configuration, from medium to large but finite values, clearly indicates a significant destabilizing contribution from trapped electrons at small aspect ratio, with a diminishing role at larger aspect ratios.

  3. Electrostatic ion beam trap for electron collision studies

    SciTech Connect

    Heber, O.; Witte, P.D.; Diner, A.; Bhushan, K.G.; Strasser, D.; Toker, Y.; Rappaport, M.L.; Ben-Itzhak, I.; Altstein, N.; Schwalm, D.; Wolf, A.; Zajfman, D.

    2005-01-01

    We describe a system combining an ion beam trap and a low energy electron target in which the interaction between electrons and vibrationally cold molecular ions and clusters can be studied. The entire system uses only electrostatic fields for both trapping and focusing, thus being able to store particles without a mass limit. Preliminary results for the electron impact neutralization of C{sub 2}{sup -} ions and aluminum clusters are presented.

  4. The electronic McPhail trap.

    PubMed

    Potamitis, Ilyas; Rigakis, Iraklis; Fysarakis, Konstantinos

    2014-11-25

    Certain insects affect cultivations in a detrimental way. A notable case is the olive fruit fly (Bactrocera oleae (Rossi)), that in Europe alone causes billions of euros in crop-loss/per year. Pests can be controlled with aerial and ground bait pesticide sprays, the efficiency of which depends on knowing the time and location of insect infestations as early as possible. The inspection of traps is currently carried out manually. Automatic monitoring traps can enhance efficient monitoring of flying pests by identifying and counting targeted pests as they enter the trap. This work deals with the hardware setup of an insect trap with an embedded optoelectronic sensor that automatically records insects as they fly in the trap. The sensor responsible for detecting the insect is an array of phototransistors receiving light from an infrared LED. The wing-beat recording is based on the interruption of the emitted light due to the partial occlusion from insect's wings as they fly in the trap. We show that the recordings are of high quality paving the way for automatic recognition and transmission of insect detections from the field to a smartphone. This work emphasizes the hardware implementation of the sensor and the detection/counting module giving all necessary implementation details needed to construct it.

  5. Unification of trap-limited electron transport in semiconducting polymers.

    PubMed

    Nicolai, H T; Kuik, M; Wetzelaer, G A H; de Boer, B; Campbell, C; Risko, C; Brédas, J L; Blom, P W M

    2012-10-01

    Electron transport in semiconducting polymers is usually inferior to hole transport, which is ascribed to charge trapping on isolated defect sites situated within the energy bandgap. However, a general understanding of the origin of these omnipresent charge traps, as well as their energetic position, distribution and concentration, is lacking. Here we investigate electron transport in a wide range of semiconducting polymers by current-voltage measurements of single-carrier devices. We observe for this materials class that electron transport is limited by traps that exhibit a gaussian energy distribution in the bandgap. Remarkably, the electron-trap distribution is identical for all polymers considered: the number of traps amounts to 3 × 10(23) traps per m(3) centred at an energy of ~3.6 eV below the vacuum level, with a typical distribution width of ~0.1 eV. This indicates that the electron traps have a common origin that, we suggest, is most likely related to hydrated oxygen complexes. A consequence of this finding is that the trap-limited electron current can be predicted for any polymer.

  6. Deep level transient spectroscopy study of electron traps in n-type GaAs after pulsed electron beam irradiation

    SciTech Connect

    Marrakchi, G.; Barbier, D.; Guillot, G.; Nouailhat, A.

    1987-10-01

    Electrical and deep level transient spectroscopy measurements on Schottky barriers were performed in order to characterize electrically active defects in n-type GaAs (Bridgman substrates or liquid-phase epitaxial layers) after pulsed electron beam annealing. Both surface damage and bulk defects were observed in the Bridgman substrates depending on the pulse energy density. No electron traps were detected in the liquid-phase epitaxial layers before and after annealing for an energy density of 0.4 J/cm/sup 2/. The existence of an interfacial insulating layer at the metal-semiconductor interface, associated with As out-diffusion during the pulsed electron irradiation, was revealed by the abnormally high values of the Schottky barrier diffusion potential. Moreover, two new electron traps with activation energy of 0.35 and 0.43 eV, called EP1 and EP2, were introduced in the Bridgman substrates after pulsed electron beam annealing. The presence of these traps, related to the As evaporation, was tentatively attributed to the decrease of the EL2 electron trap signal after 0.4-J/cm/sup 2/ annealing. It is proposed that these new defects states are due to the decomposition of the As/sub Ga/-As/sub i/ complex recently considered as the most probable defect configuration for the dominant EL2 electron trap usually detected in as-grown GaAs substrates.

  7. Threshold for electron trapping nonlinearity in Langmuir waves

    NASA Astrophysics Data System (ADS)

    Strozzi, D. J.; Williams, E. A.; Rose, H. A.; Hinkel, D. E.; Langdon, A. B.; Banks, J. W.

    2012-11-01

    We assess when electron trapping nonlinearity is expected to be important in Langmuir waves. The basic criterion is that the inverse of the detrapping rate νd of electrons in the trapping region of velocity space must exceed the bounce period of deeply trapped electrons, τB≡(ne/δn)1/22π /ωpe. A unitless figure of merit, the "bounce number" NB≡1/νdτB, encapsulates this condition and defines a trapping threshold amplitude for which NB=1. The detrapping rate is found for convective loss (transverse and longitudinal) out of a spatially finite Langmuir wave. Simulations of driven waves with a finite transverse profile, using the 2D-2V Vlasov code LOKI, show trapping nonlinearity increases continuously with NB for transverse loss, and is significant for NB≈1. The detrapping rate due to Coulomb collisions (both electron-electron and electron-ion) is also found, with pitch-angle scattering and parallel drag and diffusion treated in a unified manner. A simple way to combine convective and collisional detrapping is given. Application to underdense plasma conditions in inertial confinement fusion targets is presented. The results show that convective transverse loss is usually the most potent detrapping process in a single f/8 laser speckle. For typical plasma and laser conditions on the inner laser cones of the National Ignition Facility, local reflectivities ˜3% are estimated to produce significant trapping effects.

  8. Radiation-reaction trapping of electrons in extreme laser fields.

    PubMed

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

    2014-04-11

    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.

  9. Electron capture dissociation in a digital ion trap mass spectrometer.

    PubMed

    Ding, Li; Brancia, Francesco L

    2006-03-15

    Electron capture dissociation was implemented in a digital ion trap without using any magnetic field to focus the electrons. Since rectangular waveforms are employed in the DIT for both trapping and dipole excitation, electrons can be injected into the trap when the electric field is constant. Following deceleration, electrons reach the precursor ion cloud. The fragment ions produced by interactions with the electron beam are subsequently analyzed by resonant ejection. [Glu(1)]-Fibrinopeptide B and substance P were used to evaluate the performance of the current design. Fragmentation efficiency of 5.5% was observed for substance P peptide ions. Additionally, analysis of the monophosphorylated peptide FQ[pS]EEQQQTEDELQDK shows that in the resulting c- and z-type ions, the phosphate group is retained on the phophoserine residue, providing information on which amino acid residue the modification is located.

  10. Trapped Electron Mode Turbulence Driven Intrinsic Rotation in Tokamak Plasmas

    SciTech Connect

    Wang, W. X.; Hahm, T. S.; Ethier, S.; Zakharov, L. E.

    2011-02-07

    Recent progress from global gyrokinetic simulations in understanding the origin of intrinsic rotation in toroidal plasmas is reported with emphasis on electron thermal transport dominated regimes. The turbulence driven intrinsic torque associated with nonlinear residual stress generation by the fluctuation intensity and the intensity gradient in the presence of zonal flow shear induced asymmetry in the parallel wavenumber spectrum is shown to scale close to linearly with plasma gradients and the inverse of the plasma current. These results qualitatively reproduce empirical scalings of intrinsic rotation observed in various experiments. The origin of current scaling is found to be due to enhanced kll symmetry breaking induced by the increased radial variation of the safety factor as the current decreases. The physics origin for the linear dependence of intrinsic torque on pressure gradient is that both turbulence intensity and the zonal flow shear, which are two key ingredients for driving residual stress, increase with the strength of turbulence drive, which is R0/LTe and R0/Lne for the trapped electron mode. __________________________________________________

  11. Electron source for a mini ion trap mass spectrometer

    DOEpatents

    Dietrich, Daniel D.; Keville, Robert F.

    1995-01-01

    An ion trap which operates in the regime between research ion traps which can detect ions with a mass resolution of better than 1:10.sup.9 and commercial mass spectrometers requiring 10.sup.4 ions with resolutions of a few hundred. The power consumption is kept to a minimum by the use of permanent magnets and a novel electron gun design. By Fourier analyzing the ion cyclotron resonance signals induced in the trap electrodes, a complete mass spectra in a single combined structure can be detected. An attribute of the ion trap mass spectrometer is that overall system size is drastically reduced due to combining a unique electron source and mass analyzer/detector in a single device. This enables portable low power mass spectrometers for the detection of environmental pollutants or illicit substances, as well as sensors for on board diagnostics to monitor engine performance or for active feedback in any process involving exhausting waste products.

  12. Electron source for a mini ion trap mass spectrometer

    DOEpatents

    Dietrich, D.D.; Keville, R.F.

    1995-12-19

    An ion trap is described which operates in the regime between research ion traps which can detect ions with a mass resolution of better than 1:10{sup 9} and commercial mass spectrometers requiring 10{sup 4} ions with resolutions of a few hundred. The power consumption is kept to a minimum by the use of permanent magnets and a novel electron gun design. By Fourier analyzing the ion cyclotron resonance signals induced in the trap electrodes, a complete mass spectra in a single combined structure can be detected. An attribute of the ion trap mass spectrometer is that overall system size is drastically reduced due to combining a unique electron source and mass analyzer/detector in a single device. This enables portable low power mass spectrometers for the detection of environmental pollutants or illicit substances, as well as sensors for on board diagnostics to monitor engine performance or for active feedback in any process involving exhausting waste products. 10 figs.

  13. Threshold for electron trapping nonlinearity in Langmuir waves

    SciTech Connect

    Strozzi, D. J.; Williams, E. A.; Hinkel, D. E.; Langdon, A. B.; Banks, J. W.; Rose, H. A.

    2012-11-15

    We assess when electron trapping nonlinearity is expected to be important in Langmuir waves. The basic criterion is that the inverse of the detrapping rate {nu}{sub d} of electrons in the trapping region of velocity space must exceed the bounce period of deeply trapped electrons, {tau}{sub B}{identical_to}(n{sub e}/{delta}n){sup 1/2}2{pi}/{omega}{sub pe}. A unitless figure of merit, the 'bounce number'N{sub B}{identical_to}1/{nu}{sub d}{tau}{sub B}, encapsulates this condition and defines a trapping threshold amplitude for which N{sub B}=1. The detrapping rate is found for convective loss (transverse and longitudinal) out of a spatially finite Langmuir wave. Simulations of driven waves with a finite transverse profile, using the 2D-2V Vlasov code LOKI, show trapping nonlinearity increases continuously with N{sub B} for transverse loss, and is significant for N{sub B} Almost-Equal-To 1. The detrapping rate due to Coulomb collisions (both electron-electron and electron-ion) is also found, with pitch-angle scattering and parallel drag and diffusion treated in a unified manner. A simple way to combine convective and collisional detrapping is given. Application to underdense plasma conditions in inertial confinement fusion targets is presented. The results show that convective transverse loss is usually the most potent detrapping process in a single f/8 laser speckle. For typical plasma and laser conditions on the inner laser cones of the National Ignition Facility, local reflectivities {approx}3% are estimated to produce significant trapping effects.

  14. Electron and Hole Trapping in Polycrystalline Metal Oxide Materials

    SciTech Connect

    Mckenna, Keith P.; Shluger, Alexander L.

    2011-07-08

    Electron and hole trapping by grain boundaries and dislocations in polycrystalline materials is important for wide ranging technological applications such as solar cells, microelectronics, photo-catalysts and rechargeable batteries. In this article, we first give an overview of the computational and methodological challenges involved in modelling such effects. This is followed by a discussion of two recent studies we have made on electron/hole trapping in wide gap insulators. The results suggest that such effects can be important for many applications which we discuss. These computationally demanding calculations have made extensive use of both the HPCx and HECToR services.

  15. Electron trapping in rad-hard RCA IC's irradiated with electrons and gamma rays

    NASA Technical Reports Server (NTRS)

    Danchenko, V.; Brashears, S. S.; Fang, P. H.

    1984-01-01

    Enhanced electron trapping has been observed in n-channels of rad-hard CMOS devices due to electron and gamma-ray irradiation. Room-temperature annealing results in a positive shift in the threshold potential far beyond its initial value. The slope of the annealing curve immediately after irradiation was found to depend strongly on the gate bias applied during irradiation. Some dependence was also observed on the electron dose rate. No clear dependence on energy and shielding over a delidded device was observed. The threshold shift is probably due to electron trapping at the radiation-induced interface states and tunneling of electrons through the oxide-silicon energy barrier to fill the radiation-induced electron traps. A mathematical analysis, based on two parallel annealing kinetics, hole annealing and electron trapping, is applied to the data for various electron dose rates.

  16. ELECTRON TRAPPING IN WIGGLER AND QUADRUPOLE MAGNETS OF CESRTA

    SciTech Connect

    Wang, Lanfa; Huang, Xiaobiao; Pivi, Mauro; /SLAC

    2010-08-25

    The Cornell Electron Storage Ring (CESR) has been reconfigured as an ultra low emittance damping ring for use as a test accelerator (CesrTA) for International Linear Collider (ILC) damping ring R&D [1]. One of the primary goals of the CesrTA program is to investigate the interaction of the electron cloud with low emittance positron beam to explore methods to suppress the electron cloud, develop suitable advanced instrumentation required for these experimental studies and benchmark predictions by simulation codes. This paper reports the simulation of the electron-cloud formation in the wiggler and quadrupole magnets using the 3D code CLOUDLAND. We found that electrons can be trapped with long lifetime in a quadrupole magnet due to the mirror field trapping mechanism and photoelectrons produced in the wiggler zero field zone have long lifetime due to their complicated trajectory.

  17. Electron-Scattering Measurements using a Magneto-Optical Trap

    NASA Astrophysics Data System (ADS)

    Walker, Thad

    1996-05-01

    Optically trapped atoms are in many ways ideal replacements for atomic beams for scattering experiments. In a typical such experiment, a particle beam ejects atoms from the trap at a rate Γ=σ φ, where φ is the particle flux density and σ the scattering cross section. Γ is easily measured from trap decay transients. Since the trapped atoms have neV kinetic energies, the method is sensitive to extremely small momentum transfers. Since the beam flux is measured, the absolute target density is not required, removing an important source of error for most atomic beam experiments. At Wisconsin(Collaborators on this work have been R. S. Schappe, C.C. Lin, L. W. Anderson, P. Feng, and G. Piech. The research is supported by the NSF and the Packard Foundation.) we have integrated an electron beam with a magneto-optical trap and performed electron scattering experiments on Rb atoms in the range of 10-1000 eV. In the first experiment we measured total cross sections for scattering from the 5s state by lowering the capture velocity of the trap below the recoil velocity of the scattered atoms. In the second experiment we isolated the total ionization cross section by operating the trap such that virtually all elastically and inelastically scattered atoms were captured by the trap. These experimental results will test new theoretical methods for calculating total and ionization cross sections. Straightforward extensions of these methods should allow similar measurements using excited-state atoms (5p, 5d) as well. The techniques should also be readily adaptable to the important case of the metastable noble gases.

  18. New Frontiers In Trapped-Electron-Mode Turbulence

    NASA Astrophysics Data System (ADS)

    Pueschel, M. J.

    2016-10-01

    In tokamak core plasmas, trapped electron modes (TEMs) and their associated turbulence have long been identified as a central driving mechanism of heat and particle flux in electron-heated scenarios. Plasma parameters and magnetic geometries very different from such standard cases, however, can showcase new and important aspects of TEM turbulence; here, three examples are discussed. First, the outer radii of improved-confinement Madison Symmetric Torus reversed-field pinch discharges exhibit strong pressure gradients, which can overcome magnetic shear stabilization to drive TEM turbulence with exceptionally strong zonal flows. The resulting large Dimits shift collapses upon the inclusion of residual tearing fluctuations that short out the zonal flows to a significant degree. Second, on the low end of the magnetic shear spectrum, TEMs are seen in simulations of Helically Symmetric eXperiment stellarator plasmas. As before, zonal flows result from density gradient drive and affect turbulent saturation, despite indications that zonal flow shearing is insufficient, indicating catalyzed energy transfer to stable modes as the dominant process. The latter is furthermore supported by the nonlinear coalescence of a coherent structure comprised of stable eigenmode amplitudes. Third, the steep gradients in tokamak pedestal scenarios are able to bring about new excitation states whereby TEMs can take on tearing-parity structures, while remaining clearly distinct from microtearing modes. Such TEMs require a non-zero bounce average perturbation, which can be the result of spatial or temporal decorrelation as well as asymmetric magnetic geometries, all of which are more common in large-gradient regions in the plasma edge. An improved understanding of such highly excited TEMs may help understand pedestal microturbulence and predict H-mode performance in future reactors.

  19. Flavin Electron Shuttles Dominate Extracellular Electron Transfer by Shewanella oneidensis

    PubMed Central

    Kotloski, Nicholas J.; Gralnick, Jeffrey A.

    2013-01-01

    ABSTRACT Shewanella oneidensis strain MR-1 is widely studied for its ability to respire a diverse array of soluble and insoluble electron acceptors. The ability to breathe insoluble substrates is defined as extracellular electron transfer and can occur via direct contact or by electron shuttling in S. oneidensis. To determine the contribution of flavin electron shuttles in extracellular electron transfer, a transposon mutagenesis screen was performed with S. oneidensis to identify mutants unable to secrete flavins. A multidrug and toxin efflux transporter encoded by SO_0702 was identified and renamed bfe (bacterial flavin adenine dinucleotide [FAD] exporter) based on phenotypic characterization. Deletion of bfe resulted in a severe decrease in extracellular flavins, while overexpression of bfe increased the concentration of extracellular flavins. Strains lacking bfe had no defect in reduction of soluble Fe(III), but these strains were deficient in the rate of insoluble Fe(III) oxide reduction, which was alleviated by the addition of exogenous flavins. To test a different insoluble electron acceptor, graphite electrode bioreactors were set up to measure current produced by wild-type S. oneidensis and the Δbfe mutant. With the same concentration of supplemented flavins, the two strains produced similar amounts of current. However, when exogenous flavins were not supplemented to bioreactors, bfe mutant strains produced significantly less current than the wild type. We have demonstrated that flavin electron shuttling accounts for ~75% of extracellular electron transfer to insoluble substrates by S. oneidensis and have identified the first FAD transporter in bacteria. PMID:23322638

  20. A simple model for electron dissipation in trapped ion turbulence

    NASA Astrophysics Data System (ADS)

    Lesur, M.; Cartier-Michaud, T.; Drouot, T.; Diamond, P. H.; Kosuga, Y.; Réveillé, T.; Gravier, E.; Garbet, X.; Itoh, S.-I.; Itoh, K.

    2017-01-01

    Trapped ion resonance-driven turbulence is investigated in the presence of electron dissipation in a simplified tokamak geometry. A reduced gyrokinetic bounce-averaged model for trapped ions is adopted. Electron dissipation is modeled by a simple phase-shift δ between density and electric potential perturbations. The linear eigenfunction features a peak at the resonant energy, which becomes stronger with increasing electron dissipation. Accurately resolving this narrow peak in numerical simulation of the initial-value problem yields a stringent lower bound on the number of grid points in the energy space. Further, the radial particle flux is investigated in the presence of electron dissipation, including kinetic effects. When the density gradient is higher than the temperature gradient, and the phase-shift is finite but moderate ( δ≈0.02 ), the particle flux peaks at an order-of-magnitude above the gyro-Bohm estimate. Slight particle pinch is observed for δ<0.003 .

  1. Auroral Electrons Trapped and Lost: A Vlasov Simulation Study

    NASA Astrophysics Data System (ADS)

    Gunell, H.; Andersson, L.; De Keyser, J. M.; Mann, I.

    2014-12-01

    In the upward current region of the aurora, about two thirds of the total voltage between the auroral ionosphere and the equatorial magnetosphere can be concentrated in a stationary double layer at an altitude of about one earth radius, as Vlasov simulations of the plasma on a magnetic field line have shown (Gunell, et al., Ann. Geophys., 31, 1227-1240, 2013). We perform numerical experiments, changing the total voltage between the ionosphere and the equatorial magnetosphere during the course of the simulation. In the initial state, the total acceleration voltage is 3 kV and there is a double layer approximately 5000 km above the ionospheric end of the system. When the voltage is increased, electrons are trapped between the double layer and the magnetic mirror in a region of velocity space that initially was empty. When the voltage is decreased to its initial value these trapped electrons are released upwards. If the voltage is lowered first and then raised back to where it started, the newly trapped electrons remain trapped. As a consequence of the difference between the two cases, the electron pitch angle distribution, below the double layer, carries information about the recent history of the acceleration voltage. In both cases, most of the change in voltage, ΔV, is assumed by the double layer, in agreement with a study of Cluster data that could confine most of ΔV to altitudes below the spacecraft (Forsyth et al., JGR, 117, A12203, 2012). Hysteresis effects in the double layer position are seen in connection with the electron trapping. This work was supported by the Belgian Science Policy Office through the Solar-Terrestrial Centre of Excellence and by PRODEX/Cluster contract 13127/98/NL/VJ(IC)-PEA 90316.

  2. Use of Dominant-Negative/Substrate Trapping PTP Mutations to Search for PTP Interactors/Substrates.

    PubMed

    Radha, Vegesna

    2016-01-01

    Phosphorylation of proteins on tyrosine residues is the consequence of coordinated action of tyrosine kinases (TKs), and protein tyrosine phosphatases (PTPs). Together, they regulate intermolecular interactions, subcellular localization, and activity of a variety of proteins. The level of total protein-associated tyrosine phosphorylation in eukaryotic cells is only a small fraction of the total phosphorylation. PTPs, which have high specific activity compared to tyrosine kinases, play an important role in maintaining the tyrosine phosphorylation state of proteins and regulate signal transduction pathways and cellular responses. PTPs depend on specific invariant residues that enable binding to substrates phosphorylated at tyrosine and aid catalytic activity. Identification of PTP substrates has helped understand their role in distinct intracellular signaling pathways. Because of their high specific activity, the interaction between tyrosine phosphatases and their substrates is often very transient in the cellular context, and therefore identification of physiological substrates has been difficult. Single-site mutations in the enzymes stabilize interaction between the enzyme and its targets and have been used extensively to identify substrates. The mutations are either of the catalytic cysteine (Cys) residue or other invariant residues and have been classified as substrate-trapping mutants (STMs). These mutants often serve as dominant negatives that can inactivate effector functions of a specific PTP within cells. Considering their association with human disorders, inhibiting specific PTPs is important therapeutically. Since the catalytic domains are largely conserved, developing small-molecule inhibitors to a particular enzyme has proven difficult and therefore alternate strategies to block functions of individual enzymes are seriously being investigated. We provide a description of methods that will be useful to design strategies of using dominant-negative and

  3. Dynamics and reactivity of trapped electrons on supported ice crystallites.

    PubMed

    Stähler, Julia; Gahl, Cornelius; Wolf, Martin

    2012-01-17

    The solvation dynamics and reactivity of localized excess electrons in aqueous environments have attracted great attention in many areas of physics, chemistry, and biology. This manifold attraction results from the importance of water as a solvent in nature as well as from the key role of low-energy electrons in many chemical reactions. One prominent example is the electron-induced dissociation of chlorofluorocarbons (CFCs). Low-energy electrons are also critical in the radiation chemistry that occurs in nuclear reactors. Excess electrons in an aqueous environment are localized and stabilized by the local rearrangement of the surrounding water dipoles. Such solvated or hydrated electrons are known to play an important role in systems such as biochemical reactions and atmospheric chemistry. Despite numerous studies over many years, little is known about the microscopic details of these electron-induced chemical processes, and interest in the fundamental processes involved in the reactivity of trapped electrons continues. In this Account, we present a surface science study of the dynamics and reactivity of such localized low-energy electrons at D(2)O crystallites that are supported by a Ru(001) single crystal metal surface. This approach enables us to investigate the generation and relaxation dynamics as well as dissociative electron attachment (DEA) reaction of excess electrons under well-defined conditions. They are generated by photoexcitation in the metal template and transferred to trapping sites at the vacuum interface of crystalline D(2)O islands. In these traps, the electrons are effectively decoupled from the electronic states of the metal template, leading to extraordinarily long excited state lifetimes on the order of minutes. Using these long-lived, low-energy electrons, we study the DEA to CFCl(3) that is coadsorbed at very low concentrations (∼10(12) cm(-2)). Using rate equations and direct measurement of the change of surface dipole moment, we

  4. Natural variations in the geomagnetically trapped electron population

    NASA Technical Reports Server (NTRS)

    Vampola, A. L.

    1972-01-01

    Temporal variations in the trapped natural electron flux intensities and energy spectra are discussed and demonstrated using recent satellite data. These data are intended to acquaint the space systems engineer with the types of natural variations that may be encountered during a mission and to augment the models of the electron environment currently being used in space system design and orbit selection. An understanding of the temporal variations which may be encountered should prove helpful. Some of the variations demonstrated here which are not widely known include: (1) addition of very energetic electrons to the outer zone during moderate magnetic storms: (2) addition of energetic electrons to the inner zone during major magnetic storms; (3) inversions in the outer zone electron energy spectrum during the decay phase of a storm injection event and (4) occasional formation of multiple maxima in the flux vs altitude profile of moderately energetic electrons.

  5. PIC simulations of the trapped electron filamentation instability in finite-width electron plasma waves

    NASA Astrophysics Data System (ADS)

    Winjum, B. J.; Banks, J. W.; Berger, R. L.; Cohen, B. I.; Chapman, T.; Hittinger, J. A. F.; Rozmus, W.; Strozzi, D. J.; Brunner, S.

    2012-10-01

    We present results on the kinetic filamentation of finite-width nonlinear electron plasma waves (EPW). Using 2D simulations with the PIC code BEPS, we excite a traveling EPW with a Gaussian transverse profile and a wavenumber k0λDe= 1/3. The transverse wavenumber spectrum broadens during transverse EPW localization for small width (but sufficiently large amplitude) waves, while the spectrum narrows to a dominant k as the initial EPW width increases to the plane-wave limit. For large EPW widths, filaments can grow and destroy the wave coherence before transverse localization destroys the wave; the filaments in turn evolve individually as self-focusing EPWs. Additionally, a transverse electric field develops that affects trapped electrons, and a beam-like distribution of untrapped electrons develops between filaments and on the sides of a localizing EPW. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and funded by the Laboratory Research and Development Program at LLNL under project tracking code 12-ERD-061. Supported also under Grants DE-FG52-09NA29552 and NSF-Phy-0904039. Simulations were performed on UCLA's Hoffman2 and NERSC's Hopper.

  6. Spectroscopy of Argon Excited in an Electron Beam Ion Trap

    SciTech Connect

    Trabert, E

    2005-04-18

    Argon is one of the gases best investigated and most widely used in plasma discharge devices for a multitude of applications that range from wavelength reference standards to controlled fusion experiments. Reviewing atomic physics and spectroscopic problems in various ionization stages of Ar, the past use and future options of employing an electron beam ion trap (EBIT) for better and more complete Ar data in the x-ray, EUV and visible spectral ranges are discussed.

  7. Upgrade of the electron beam ion trap in Shanghai

    SciTech Connect

    Lu, D.; Yang, Y.; Xiao, J.; Shen, Y.; Fu, Y.; Wei, B.; Yao, K.; Hutton, R.; Zou, Y.

    2014-09-15

    Over the last few years the Shanghai electron beam ion trap (EBIT) has been successfully redesigned and rebuilt. The original machine, developed under collaboration with the Shanghai Institute of Applied Physics, first produced an electron beam in 2005. It could be tuned with electron energies between 1 and 130 keV and beam current up to 160 mA. After several years of operation, it was found that several modifications for improvements were necessary to reach the goals of better electron optics, higher photon detection, and ion injection efficiencies, and more economical running costs. The upgraded Shanghai-EBIT is made almost entirely from Ti instead of stainless steel and achieves a vacuum of less than 10{sup −10} Torr, which helps to minimize the loss of highly changed ions through charge exchange. Meanwhile, a more compact structure and efficient cryogenic system, and excellent optical alignment have been of satisfactory. The magnetic field in the central trap region can reach up till 4.8 T with a uniformity of 2.77 × 10{sup −4}. So far the upgraded Shanghai-EBIT has been operated up to an electron energy of 151 keV and a beam current of up to 218 mA, although promotion to even higher energy is still in progress. Radiation from ions as highly charged as Xe{sup 53+,} {sup 54+} has been produced and the characterization of current density is estimated from the measured electron beam width.

  8. Trapping of an electron in coupled quantum dots in graphene

    NASA Astrophysics Data System (ADS)

    Hewageegana, Prabath; Apalkov, Vadym

    2009-03-01

    Due to Klein’s tunneling the electronic states of a quantum dot in graphene have finite widths and an electron in quantum dot has a finite trapping time. This property introduces a special type of interdot coupling in a system of many quantum dots in graphene. The interdot coupling is realized not as a direct tunneling between quantum dots but as coupling through the continuum states of graphene. As a result the interdot coupling modifies both the positions and the widths of the energy levels of the quantum dot system. We study the system of quantum dots in graphene theoretically by analyzing the complex energy spectra of the quantum dot system. We show that in a double-dot system some energy levels become strongly localized with an infinite trapping time. Such strongly localized states are achieved only at one value of the interdot separation. We also study a periodic array of quantum dots in graphene within a tight-binding mode for a quantum dot system. The values of the hopping integrals in the tight-binding model are found from the expression for the energy spectra of the double quantum dot system. In the array of quantum dots the states with infinitely large trapping time are realized at all values of interdot separation smaller than some critical value. Such states have nonzero wave vectors.

  9. Solubility trapping in formation water as dominant CO(2) sink in natural gas fields.

    PubMed

    Gilfillan, Stuart M V; Lollar, Barbara Sherwood; Holland, Greg; Blagburn, Dave; Stevens, Scott; Schoell, Martin; Cassidy, Martin; Ding, Zhenju; Zhou, Zheng; Lacrampe-Couloume, Georges; Ballentine, Chris J

    2009-04-02

    Injecting CO(2) into deep geological strata is proposed as a safe and economically favourable means of storing CO(2) captured from industrial point sources. It is difficult, however, to assess the long-term consequences of CO(2) flooding in the subsurface from decadal observations of existing disposal sites. Both the site design and long-term safety modelling critically depend on how and where CO(2) will be stored in the site over its lifetime. Within a geological storage site, the injected CO(2) can dissolve in solution or precipitate as carbonate minerals. Here we identify and quantify the principal mechanism of CO(2) fluid phase removal in nine natural gas fields in North America, China and Europe, using noble gas and carbon isotope tracers. The natural gas fields investigated in our study are dominated by a CO(2) phase and provide a natural analogue for assessing the geological storage of anthropogenic CO(2) over millennial timescales. We find that in seven gas fields with siliciclastic or carbonate-dominated reservoir lithologies, dissolution in formation water at a pH of 5-5.8 is the sole major sink for CO(2). In two fields with siliciclastic reservoir lithologies, some CO(2) loss through precipitation as carbonate minerals cannot be ruled out, but can account for a maximum of 18 per cent of the loss of emplaced CO(2). In view of our findings that geological mineral fixation is a minor CO(2) trapping mechanism in natural gas fields, we suggest that long-term anthropogenic CO(2) storage models in similar geological systems should focus on the potential mobility of CO(2) dissolved in water.

  10. Phase space analysis for dynamics of three vortices of pure electron plasma trapped with Penning trap

    SciTech Connect

    Sanpei, Akio; Soga, Yukihiro; Ito, Kiyokazu; Himura, Haruhiko

    2015-06-29

    A trilinear phase space analysis is applied for dynamics of three electron clumps confined with a Penning-Malmberg trap. We show that the Aref’s concept of phase space describe the observed features of the dynamics of three point vortices qualitatively. In vacuum, phase point P moves to physical region boundary in phase space, i.e. triangular configuration cannot be kept. With the addition of a low level background vorticity distribution (BGVD), the excursion of the clumps is reduced and the distance between P and stable point does not extend in the phase space.

  11. Nonideal fishbone instability excited by trapped energetic electrons

    SciTech Connect

    Liu, Y.; Tang, C. J.; Wang, Z. T.; Long, Y. X.; Dong, J. Q.

    2013-03-15

    It is shown that trapped energetic electrons can resonate with the collisionless m = 1 nonideal kink mode, therefore exciting the nonideal e-fishbone, which would often lead to a drop in soft x-ray emissivity and frequency chirping. The theory predictions agree well with the experimental observations of e-fishbone on HL-2A. It is also found that the effects of MHD energy of background plasma might be the reason for the observed phenomena: frequency chirping up and down, and V-font-style sweeping.

  12. Nonideal fishbone instability excited by trapped energetic electrons

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Wang, Z. T.; Long, Y. X.; Dong, J. Q.; Tang, C. J.

    2013-03-01

    It is shown that trapped energetic electrons can resonate with the collisionless m = 1 nonideal kink mode, therefore exciting the nonideal e-fishbone, which would often lead to a drop in soft x-ray emissivity and frequency chirping. The theory predictions agree well with the experimental observations of e-fishbone on HL-2A. It is also found that the effects of MHD energy of background plasma might be the reason for the observed phenomena: frequency chirping up and down, and V-font-style sweeping.

  13. Intensity dependent waiting time for strong electron trapping events in speckle stimulated raman scatter

    SciTech Connect

    Rose, Harvey; Daughton, W; Yin, L

    2009-01-01

    The onset of Stimulated Raman scatter from an intense laser speckle is the simplest experimentally realizable laser-plasma-interaction environment. Despite this data and recent 3D particle simulations, the controlling mechanism at the onset of backscatter in the kinetic regime when strong electron trapping in the daughter Langmuir wave is a dominant nonlinearity is not understood. This paper explores the consequences of assuming that onset is controlled by large thermal fluctuations. A super exponential dependence of mean reflectivity on speckle intensity in the onset regime is predicted.

  14. Effect of electron shallow trap on breakdown performance of transformer oil-based nanofluids

    NASA Astrophysics Data System (ADS)

    Du, Yuefan; Lv, Yuzhen; Li, Chengrong; Chen, Mutian; Zhou, Jianquan; Li, Xiaoxin; Zhou, You; Tu, Youping

    2011-11-01

    Transformer oil-based nanofluids with TiO2 semiconductive nanoparticles exhibit substantially higher AC and positive impulse breakdown voltage levels than that of pure transformer oils. Thermally stimulated current method (TSC) and pulse electroacoustic technique (PEA) have been used to measure charge trap and transportation characteristics of pure oils and nanofluids. It is found that electron shallow trap density and charge decay rate are greatly increased in nanofluids, i.e., fast electrons may be converted to slow electrons by electron trapping and de-trapping in shallow traps of nanofluids, resulting in improved breakdown performance compared to that of pure oil.

  15. Optimum Electron Distributions for Space Charge Dominated Beams in Photoinjectors

    SciTech Connect

    Limborg-Deprey, C.; Bolton, P.R.; /SLAC

    2006-06-15

    The optimum photo-electron distribution from the cathode of an RF photoinjector producing a space charge dominated beam is a uniform distribution contained in an ellipsoid. For such a bunch distribution, the space charge forces are linear and the emittance growth induced by those forces is totally reversible and consequently can be compensated. With the appropriate tuning of the emittance compensation optics, the emittance, at the end of photoinjector beamline, for an ellipsoidal laser pulse, would only have two contributions, the cathode emittance and the RF emittance. For the peak currents of 50A and 100 A required from the SBand and L-Band RF gun photoinjectors discussed here, the RF emittance contribution is negligible. If such an ellipsoidal photo-electron distribution were available, the emittance at the end of the beamline could be reduced to the cathode emittance. Its value would be reduced by more than 40% from that obtained using cylindrical shape laser pulses. This potentially dramatic improvement warrants review of the challenges associated with the production of ellipsoidal photo-electrons. We assume the photo-electrons emission time to be short enough that the ellipsoidal electron pulse shape will come directly from the laser pulse. We shift the challenge to ellipsoidal laser pulse shaping. To expose limiting technical issues, we consider the generation of ellipsoidal laser pulse shape in terms of three different concepts.

  16. Trapped Energetic Electrons in the Magnetosphere of Ganymede

    NASA Technical Reports Server (NTRS)

    Eviatar, Aharon; Williams, Donald J.; Paranicas, Chris; McEntire, Richard W.; Mauk, Barry H.; Kivelson, Margaret G.

    2000-01-01

    On May 7, 1997, the Galileo orbiter flew through the magnetosphere of Ganymede and crossed flux tubes connected at both ends to the satellite. Energetic electrons, observed during this encounter by means of the Energetic Particle Detector on board Galileo, showed double loss cones and "butterfly" type pitch angle distributions, as has been noted in past publications. In addition, as the spacecraft flew toward Ganymede, both the shape and magnitude of the spectrum changed. The intensities decreased, with the greatest depletion observed at the lowest energies, and the monotonic slope characteristic of the Jovian environment was replaced by a rollover of the spectrum at the low-energy end. The spectra lead us to infer a strongly energy-dependent injection efficiency into the trapping region. As on previous encounters, the pitch angle distributions confirmed the position of the magnetopause as indicated by the magnetometer measurements, but the spectra remained Jovian until the trapping region was reached. Various physical mechanisms capable of generating the observed spectra and pitch angle distributions, including downstream reconnection insertion followed by magnetic gradient drift and absorption of the lowest-energy electrons by Ganymede and injection from Jovian flux tubes upstream are assessed.

  17. Ultrafast Electron Trapping in Ligand-Exchanged Quantum Dot Assemblies

    NASA Astrophysics Data System (ADS)

    Kikkawa, J. M.; Turk, M. E.; Vora, P. M.; Fafarman, A. T.; Diroll, B. T.; Murray, C. B.; Kagan, C. R.

    2015-03-01

    We use time-integrated and time-resolved photoluminescence and absorption to characterize the low-temperature (10 K) optical properties of CdSe quantum dot (QD) solids with different ligand and annealing preparation. Close-packed CdSe quantum dot solids are prepared with native aliphatic ligands and with thiocyanate with and without thermal annealing. Using sub-picosecond, broadband time-resolved photoluminescence and absorption, we find that ligand exchange increases the rate of carrier surface trapping. We further determine that holes within the QD core, rather than electrons, can bleach the band-edge transition in these samples at low temperature, a finding that comes as a surprise given what is known about the surface treatment in these QDs. We find that our ligand treatments lead to faster electron trapping to the quantum dot surface, a greater proportion of surface photoluminescence, and an increased rate of nonradiative decay due to enhanced interparticle coupling upon exchange and annealing. All aspects of this work supported by the U.S. Department of Energy Office of Basic Energy Sciences, Division of Materials Science and Engineering, under Award No. DE-SC0002158.

  18. Identification of trapped electron modes in frequency fluctuation spectra

    NASA Astrophysics Data System (ADS)

    Arnichand, H.; Citrin, J.; Hacquin, S.; Sabot, R.; Krämer-Flecken, A.; Garbet, X.; Bourdelle, C.; Bottereau, C.; Clairet, F.; Giacalone, J. C.; Guimarães-Filho, Z. O.; Guirlet, R.; Hornung, G.; Lebschy, A.; Lotte, P.; Maget, P.; Medvedeva, A.; Molina, D.; Nikolaeva, V.; Prisiazhniuk, D.; Tore Supra, the; the ASDEX Upgrade Teams

    2016-01-01

    Ion temperature gradient (ITG) and trapped electron modes (TEM) are two important micro-instabilities in the plasma core region of fusion devices (r/a≤slant 0.9 ). They usually coexist in the same range of spatial scale (around 0.1<{{k}\\bot}{ρi}<1 ), which makes their discrimination difficult. To investigate them, one can perform gyrokinetic simulations, transport analysis and phase velocity estimations. In Tore Supra, the identification of trapped electron modes (TEM) is made possible due to measured frequency fluctuation spectra. Indeed, turbulent spectra generally expected to be broad-band, can become narrow in case of TEM turbulence, inducing ‘quasi-coherent’ (QC) modes named QC-TEM. Therefore the analysis of frequency fluctuation spectra becomes a possible tool to differentiate TEM from ITG. We have found indications that the TEM can have a QC signature by comparing frequency fluctuation spectra from reflectometry measurements, gyrokinetic simulations and synthetic diagnostic results. Then the scope of the analysis of QC-TEM are discussed and an application is shown, namely transitions between TEM turbulence and MHD fluctuations.

  19. Gyroresonant interaction of energetic trapped electrons and protons

    NASA Astrophysics Data System (ADS)

    Villalon, Elena; Silevitch, Michael B.; Burke, William J.; Rothwell, Paul L.

    The present consideration of the theory of gyroresonant interactions of energetic trapped electrons and protons with ducted EM cyclotron waves in the earth's radiation zones derives a set of equations, based on the Fokker-Planck theory of pitch-angle diffusion, which describe the temporal evolution of the number of particles in the flux tube, and the energy density of waves, for (1) the interaction of Alfven waves with protons and (2) that of whistler waves with electrons. Attention is given to the reflection of the waves in the ionosphere. To dump the energetic particles from the radiation belts efficiently, the reflection coefficient must be close to unity to facilitate the growth of wave amplitudes; precipitating particle fluxes may then act as a positive feedback to raise the height-integrated conductivity of the ionosphere. This conductivity in turn enhances wave reflection.

  20. Discriminating the trapped electron modes contribution in density fluctuation spectra

    NASA Astrophysics Data System (ADS)

    Arnichand, H.; Sabot, R.; Hacquin, S.; Krämer-Flecken, A.; Bourdelle, C.; Citrin, J.; Garbet, X.; Giacalone, J. C.; Guirlet, R.; Hillesheim, J. C.; Meneses, L.

    2015-09-01

    Quasi-coherent (QC) modes have been reported for more than 10 years in reflectometry fluctuations spectra in the core region of fusion plasmas. They have characteristics in-between coherent and broadband fluctuations as they oscillate at a marked frequency but have a wide spectrum. This work presents further evidences of the link recently established between QC modes and the trapped electron modes (TEM) instabilities (Arnichand et al 2014 Nucl. Fusion 54 123017). In electron cyclotron resonance heated discharges of Tore Supra, an enhancement of QC modes amplitude is observed in a region where TEM cause impurity transport and turbulence. In JET Ohmic plasmas, QC modes disappear during density ramp-up and current ramp-down. This is reminiscent of Tore Supra and TEXTOR observations during transitions from the linear Ohmic confinement (LOC) to the saturated Ohmic confinement (SOC) regimes. Evidencing TEM activity then becomes experimentally possible via analysis of fluctuation spectra.

  1. Zonal flow generation from trapped electron mode turbulence

    NASA Astrophysics Data System (ADS)

    Wang, Lu; Hahm, T. S.

    2009-11-01

    Most existing zonal flow generation theory [1,2] has been developed with a usual assumption of qrρiθ<<1 (qr is the radial wave number of zonal flow, and ρiθ is the ion poloidal gyroradius). However, recent nonlinear gyrokinetic simulations of trapped electron mode (TEM) turbulence exhibit a relatively short radial scale of the zonal flows with qrρiθ˜1 [3,4,5]. This work reports an extension of zonal flow growth calculation to this short wavelength regime via the wave kinetics approach. A generalized expression for the polarization shielding for arbitrary radial wavelength [6] which extends the Rosenbluth-Hinton formula in the long wavelength limit [7] is applied. The electron nonlinearity effects on zonal flow are investigated by using GTC simulation. This work was supported by the China Scholarship Council (LW), U.S. DoE Contract No. DE--AC02--09CH11466 (TSH, LW), the U. S. DOE SciDAC center for Gyrokinetic Particle Simulation of Turbulent Transport in Burning Plasmas, and the U. S. DOE SciDAC-FSP Center for Plasma Edge Simulation (TSH). [1] P. H. Diamond et al., IAEA-CN-69/TH3/1 (1998). [2] L. Chen, Z. Lin, and R. White, Phys. Plasmas 7, 3129 (2000). [3] Z. Lin et al., IAEA-CN-138/TH/P2-8 (2006). [4] D. Ernst et al., Phys. Plasmas 16, 055906 (2009). [5] Y. Xiao and Z. Lin, ``Turbulent transport of trapped electron modes in collisionless plasmas'', submitted to Phys. Rev. Lett. (2009). [6] Lu Wang and T.S. Hahm, Phys. Plasmas 16, 062309 (2009). [7] M. N. Rosenbluth and F. L. Hinton, Phys. Rev. Lett. 80, 724 (1998).

  2. Radiation damping induced electron trapping and positron creation

    NASA Astrophysics Data System (ADS)

    Gu, Yanjun; Klimo, Ondrej; Weber, Stefan; Korn, Georg

    2016-10-01

    High power laser facilities with intensities up to 1022 W /cm2 have been realized and the forthcoming installations are expected to reach 10 22 - 24 W /cm2 or even higher. At these intensities, the radiation effects and quantum electrodynamics description come into play. The emitted photon momentum becomes comparable to the momentum of the emitting electrons. In this work, we propose a regime of electron self-injection and trapping in the ultra-high intensity laser-plasma interaction. The electrons accumulated at the head of the laser pulse are injected into the pulse centre due to the strong longitudinal electrostatic field created by the high density shell. These electrons, which experience a restoring force provided by the emitted photons, can be confined in the laser pulse for a long time. The corresponding photons are produced in the region where the laser field is strong. High energy and well collimated positron bunches are produced. This regime may be beneficial for the potential experiments to be carried out on large laser facilities such as ELI. This work was supported by the project ELI: Extreme Light Infrastructure (CZ.02.1.01/0.0/0.0/15_008/0000162) from European Regional Development.

  3. Momentum Transport in Electron-Dominated Spherical Torus Plasmas

    SciTech Connect

    Kaye, S. M.; Solomon, W.; Bell, R. E.; LeBlanc, B. P.; Levinton, F.; Menard, J.; Rewoldt, G.; Sabbagh, S.; Wang, W.; Yuh, H.

    2009-02-24

    The National Spherical Torus Experiment (NSTX) operates between 0.35 and 0.55 T, which, when coupled to up to 7 MW of neutral beam injection, leads to central rotation velocities in excess of 300 km/s and ExB shearing rates up to 1 MHz. This level of ExB shear can be up to a factor of five greater than typical linear growth rates of long-wavelength ion (e.g., ITG) modes, at least partially suppressing these instabilities. Evidence for this turbulence suppression is that the inferred diffusive ion thermal flux in NSTX H-modes is often at the neoclassical level, and thus these plasmas operate in an electron-dominated transport regime. Analysis of experiments using n=3 magnetic fields to change plasma rotation indicate that local rotation shear influences local transport coefficients, most notably the ion thermal diffusivity, in a manner consistent with suppression of the low-k turbulence by this rotation shear. The value of the effective momentum diffusivity, as inferred from steady-state momentum balance, is found to be larger than the neoclassical value. Results of perturbative experiments indicate inward pinch velocities up to 40 m/s and perturbative momentum diffusivities of up to 4 m2/s, which are larger by a factor of several than those values inferred from steady-state analysis. The inferred pinch velocity values are consistent with values based on theories in which low-k turbulence drives the inward momentum pinch. Thus, in Spherical Tori (STs), while the neoclassical ion energy transport effects can be relatively high and dominate the ion energy transport, the neoclassical momentum transport effects are near zero, meaning that transport of momentum is dominated by any low-k turbulence that exists.

  4. Deeply trapped electrons in imaging plates and their utilization for extending the dynamic range

    NASA Astrophysics Data System (ADS)

    Ohuchi, Hiroko; Kondo, Yasuhiro

    2010-09-01

    The absorption spectra of deep centers in an imaging plate (IP) made of BaFBr 0:85I 0:15:Eu 2+ have been studied in the ultraviolet region. Electrons trapped in deep centers are considered to be the cause of unerasable and reappearing latent images in IPs over-irradiated with X-rays. Deep centers showed a dominant peak at around 320 nm, followed by two small peaks at around 345 and 380 nm. By utilizing deeply trapped electrons, we have attempted to extend the dynamic range of an IP. The IP was irradiated by 150-kV X-rays with doses from 8.07 mGy to 80.7 Gy. Reading out the latent image by the stimulation of Eu 2+ luminescence with a 633-nm He-Ne laser light from a conventional Fuji reader showed a linear relationship with irradiated dose up to 0.8 Gy, but then becoming non-linear. After fully erasing with visible light, unerasable latent images were read out using 635-nm semi-conductor laser light combined with a photon-counting detection system. The dose-response curve so obtained gave a further two orders of magnitude extending the dynamic range up to 80.7 Gy. Comprehensive results indicate that electrons supplied from deep centers to the F centers provided the extended dynamic range after the F centers became saturated. Based on these facts, a model of the excitation of deeply trapped electrons and PSL processes is proposed.

  5. The Role of Electron Transport and Trapping in MOS Total-Dose Modeling

    SciTech Connect

    Fleetwood, D.M.; Winokur, P.S.; Riewe, L.C.; Flament, O.; Paillet, P.; Leray, J.L.

    1999-07-19

    Radiation-induced hole and electron transport and trapping are fundamental to MOS total-dose models. Here we separate the effects of electron-hole annihilation and electron trapping on the neutralization of radiation-induced charge during switched-bias irradiation for hard and soft oxides, via combined thermally stimulated current (TSC) and capacitance-voltage measurements. We also show that present total-dose models cannot account for the thermal stability of deeply trapped electrons near the Si/SiO{sub 2} interface, or the inability of electrons in deep or shallow traps to contribute to TSC at positive bias following (1) room-temperature, (2) high-temperature, or (3) switched-bias irradiation. These results require revisions of modeling parameters and boundary conditions for hole and electron transport in SiO{sub 2}. The nature of deep and shallow electron traps in the near-interfacial SiO{sub 2} is discussed.

  6. Efficiently engineering pore-scale processes: The role of force dominance and topology during nonwetting phase trapping in porous media

    NASA Astrophysics Data System (ADS)

    Herring, Anna L.; Andersson, Linnéa; Schlüter, Steffen; Sheppard, Adrian; Wildenschild, Dorthe

    2015-05-01

    We investigate trapping of a nonwetting (NW) phase, air, within Bentheimer sandstone cores during drainage-imbibition flow experiments, as quantified on a three dimensional (3D) pore-scale basis via x-ray computed microtomography (X-ray CMT). The wetting (W) fluid in these experiments was deionized water doped with potassium iodide (1:6 by weight). We interpret these experiments based on the capillary-viscosity-gravity force dominance exhibited by the Bentheimer-air-brine system and compare to a wide range of previous drainage-imbibition experiments in different media and with different fluids. From this analysis, we conclude that viscous and capillary forces dominate in the Bentheimer-air-brine system as well as in the Bentheimer-supercritical CO2-brine system. In addition, we further develop the relationship between initial (post-drainage) NW phase connectivity and residual (post-imbibition) trapped NW phase saturation, while also taking into account initial NW phase saturation and imbibition capillary number. We quantify NW phase connectivity via a topological measure as well as by a statistical percolation metric. These metrics are evaluated for their utility and appropriateness in quantifying NW phase connectivity within porous media. Here, we find that there is a linear relationship between initial NW phase connectivity (as quantified by the normalized Euler number, χ ˆ) and capillary trapping efficiency; for a given imbibition capillary number, capillary trapping efficiency (residual NW phase saturation normalized by initial NW phase saturation) can decrease by up to 60% as initial NW phase connectivity increases from low connectivity (χ ˆ ≈ 0) to very high connectivity (χ ˆ ≈ 1). We propose that multiphase fluid-porous medium systems can be efficiently engineered to achieve a desired residual state (optimal NW phase saturation) by considering the dominant forces at play in the system along with the impacts of NW phase topology within the porous

  7. Kinetic Simulations of Electron Plasma Waves: trapped electron filamentation and sideband instabilities

    NASA Astrophysics Data System (ADS)

    Brunner, Stephan; Berger, R. L.; Banks, J. W.; Cohen, B. I.; Chapman, T.; Hittinger, J. A. F.; Rozmus, W.; Strozzi, D. J.; Winjum, B. J.; Valeo, E. J.

    2012-10-01

    Kinetic simulations of nonlinear electron plasma waves (EPW) are presented in 2D with the Vlasov code LOKI (2 space and 2 velocity dimensions; Banks et al., Phys. Plasmas 18, 052102 (2011)). Propagating EPWs are created with an external wave potential with uniform transverse amplitude. The evolution of the plasma wave field and its self-consistent quasi-steady distribution of trapped electrons is studied after the external drive is turned off. For finite-amplitude EPWs, the onset of the trapped-electron-induced filamentation instability (H. Rose, Phys. Plasmas 15, 042311 (2008)) and trapped electron sideband instability (S. Brunner and E. Valeo, PRL 93, 145003 (2004)) are studied as a function of wave amplitude and k0λDe, where k0 is the wavenumber of the external potential. We extend the theory of Kruer et al PRL 23, 1969 to 2D to find growth rates of both instabilities and compare these to the ones obtained from the simulations. In the nonlinear state, the distribution of resonant electrons is dramatically modified

  8. Stability of trapped charges in sapphires and alumina ceramics: Evaluation by secondary electron emission

    NASA Astrophysics Data System (ADS)

    Zarbout, K.; Si Ahmed, A.; Moya, G.; Bernardini, J.; Goeuriot, D.; Kallel, A.

    2008-03-01

    The stability of trapped charges in sapphires and alumina ceramics is characterized via an experimental parameter expressing the variation of the secondary electron emission yield between two electron injections performed in a scanning electron microscope. Two types of sapphires and polycrystalline alumina, which differ mainly by their impurity content, are investigated in the temperature range 300-663K. The stable trapping behavior in sapphires is attributed to trapping in different defects, whose nature depends on the purity level. In alumina ceramics, the ability to trap charges in a stable way is stronger in samples of high impurity content. In the low impurity samples, stable trapping is promoted when the grain diameter decreases, whereas the reverse is observed in high impurity materials. These behaviors can stem from a gettering effect occurring during sintering. The strong dependence of the variation of the secondary electron emission yield on the grain diameter and impurities enables a scaling of the stable trapping ability of alumina materials.

  9. X-ray spectroscopy of highly-ionized atoms in an electron beam ion trap (EBIT)

    SciTech Connect

    Marrs, R.E.; Bennett, C.; Chen, M.H.; Cowan, T.; Dietrich, D.; Henderson, J.R.; Knapp, D.A.; Levine, M.A.; Schneider, M.B.; Scofield, J.H.

    1988-01-01

    An Electron Beam Ion Trap at Lawrence Livermore National Laboratory is being used to produce and trap very-highly-charged-ions (q /le/ 70+) for x-ray spectroscopy measurements. Recent measurements of dielectronic recombination, electron impact excitation and transition energies are presented. 15 refs., 12 figs., 1 tab.

  10. Imaging electronic trap states in perovskite thin films with combined fluorescence and femtosecond transient absorption microscopy

    DOE PAGES

    Xiao, Kai; Ma, Ying -Zhong; Simpson, Mary Jane; ...

    2016-04-22

    Charge carrier trapping degrades the performance of organometallic halide perovskite solar cells. To characterize the locations of electronic trap states in a heterogeneous photoactive layer, a spatially resolved approach is essential. Here, we report a comparative study on methylammonium lead tri-iodide perovskite thin films subject to different thermal annealing times using a combined photoluminescence (PL) and femtosecond transient absorption microscopy (TAM) approach to spatially map trap states. This approach coregisters the initially populated electronic excited states with the regions that recombine radiatively. Although the TAM images are relatively homogeneous for both samples, the corresponding PL images are highly structured. Themore » remarkable variation in the PL intensities as compared to transient absorption signal amplitude suggests spatially dependent PL quantum efficiency, indicative of trapping events. Furthermore, detailed analysis enables identification of two trapping regimes: a densely packed trapping region and a sparse trapping area that appear as unique spatial features in scaled PL maps.« less

  11. Imaging electronic trap states in perovskite thin films with combined fluorescence and femtosecond transient absorption microscopy

    SciTech Connect

    Xiao, Kai; Ma, Ying -Zhong; Simpson, Mary Jane; Doughty, Benjamin; Yang, Bin

    2016-04-22

    Charge carrier trapping degrades the performance of organometallic halide perovskite solar cells. To characterize the locations of electronic trap states in a heterogeneous photoactive layer, a spatially resolved approach is essential. Here, we report a comparative study on methylammonium lead tri-iodide perovskite thin films subject to different thermal annealing times using a combined photoluminescence (PL) and femtosecond transient absorption microscopy (TAM) approach to spatially map trap states. This approach coregisters the initially populated electronic excited states with the regions that recombine radiatively. Although the TAM images are relatively homogeneous for both samples, the corresponding PL images are highly structured. The remarkable variation in the PL intensities as compared to transient absorption signal amplitude suggests spatially dependent PL quantum efficiency, indicative of trapping events. Furthermore, detailed analysis enables identification of two trapping regimes: a densely packed trapping region and a sparse trapping area that appear as unique spatial features in scaled PL maps.

  12. A review of pressure anisotropy caused by electron trapping in collisionless plasma, and its implications for magnetic reconnection

    NASA Astrophysics Data System (ADS)

    Egedal, Jan; Le, Ari; Daughton, William

    2013-06-01

    From spacecraft data, it is evident that electron pressure anisotropy develops in collisionless plasmas. This is in contrast to the results of theoretical investigations, which suggest this anisotropy should be limited. Common for such theoretical studies is that the effects of electron trapping are not included; simply speaking, electron trapping is a non-linear effect and is, therefore, eliminated when utilizing the standard methods for linearizing the underlying kinetic equations. Here, we review our recent work on the anisotropy that develops when retaining the effects of electron trapping. A general analytic model is derived for the electron guiding center distribution f¯(v∥,v⊥) of an expanding flux tube. The model is consistent with anisotropic distributions observed by spacecraft, and is applied as a fluid closure yielding anisotropic equations of state for the parallel and perpendicular components (relative to the local magnetic field direction) of the electron pressure. In the context of reconnection, the new closure accounts for the strong pressure anisotropy that develops in the reconnection regions. It is shown that for generic reconnection in a collisionless plasma nearly all thermal electrons are trapped, and dominate the properties of the electron fluid. A new numerical code is developed implementing the anisotropic closure within the standard two-fluid framework. The code accurately reproduces the detailed structure of the reconnection region observed in fully kinetic simulations. These results emphasize the important role of pressure anisotropy for the reconnection process. In particular, for reconnection geometries characterized by small values of the normalized upstream electron pressure, βe∞, the pressure anisotropy becomes large with p∥≫p⊥ and strong parallel electric fields develop in conjunction with this anisotropy. The parallel electric fields can be sustained over large spatial scales and, therefore, become important for

  13. A review of pressure anisotropy caused by electron trapping in collisionless plasma, and its implications for magnetic reconnection

    SciTech Connect

    Egedal, Jan; Le, Ari; Daughton, William

    2013-06-15

    From spacecraft data, it is evident that electron pressure anisotropy develops in collisionless plasmas. This is in contrast to the results of theoretical investigations, which suggest this anisotropy should be limited. Common for such theoretical studies is that the effects of electron trapping are not included; simply speaking, electron trapping is a non-linear effect and is, therefore, eliminated when utilizing the standard methods for linearizing the underlying kinetic equations. Here, we review our recent work on the anisotropy that develops when retaining the effects of electron trapping. A general analytic model is derived for the electron guiding center distribution f(v{sub ∥},v{sub ⊥}) of an expanding flux tube. The model is consistent with anisotropic distributions observed by spacecraft, and is applied as a fluid closure yielding anisotropic equations of state for the parallel and perpendicular components (relative to the local magnetic field direction) of the electron pressure. In the context of reconnection, the new closure accounts for the strong pressure anisotropy that develops in the reconnection regions. It is shown that for generic reconnection in a collisionless plasma nearly all thermal electrons are trapped, and dominate the properties of the electron fluid. A new numerical code is developed implementing the anisotropic closure within the standard two-fluid framework. The code accurately reproduces the detailed structure of the reconnection region observed in fully kinetic simulations. These results emphasize the important role of pressure anisotropy for the reconnection process. In particular, for reconnection geometries characterized by small values of the normalized upstream electron pressure, β{sub e∞}, the pressure anisotropy becomes large with p{sub ∥}≫p{sub ⊥} and strong parallel electric fields develop in conjunction with this anisotropy. The parallel electric fields can be sustained over large spatial scales and

  14. Trapped electron correction to beam driven current in general tokamak equilibria

    SciTech Connect

    Lin-Liu, Y.R.; Hinton, F.L.

    1997-11-01

    In the limit that the electron thermal velocity greatly exceeds the fast ion velocity for electrical currents driven by neutral beams, the trapped electron correction to the Ohkawa current and the electron density gradient contribution to bootstrap current are shown to share the same transport coefficient in the banana regime. Therefore, existing analytic expressions for the bootstrap coefficient valid for arbitrary aspect ratio tokamaks can also be used to calculate the trapped electron effect. {copyright} {ital 1997 American Institute of Physics.}

  15. Electron trapping optical data storage system and applications

    NASA Technical Reports Server (NTRS)

    Brower, Daniel; Earman, Allen; Chaffin, M. H.

    1993-01-01

    A new technology developed at Optex Corporation out-performs all other existing data storage technologies. The Electron Trapping Optical Memory (ETOM) media stores 14 gigabytes of uncompressed data on a single, double-sided 130 mm disk with a data transfer rate of up to 120 megabits per second. The disk is removable, compact, lightweight, environmentally stable, and robust. Since the Write/Read/Erase (W/R/E) processes are carried out photonically, no heating of the recording media is required. Therefore, the storage media suffers no deleterious effects from repeated W/R/E cycling. This rewritable data storage technology has been developed for use as a basis for numerous data storage products. Industries that can benefit from the ETOM data storage technologies include: satellite data and information systems, broadcasting, video distribution, image processing and enhancement, and telecommunications. Products developed for these industries are well suited for the demanding store-and-forward buffer systems, data storage, and digital video systems needed for these applications.

  16. A Landau fluid model for dissipative trapped electron modes

    SciTech Connect

    Hedrick, C.L.; Leboeuf, J.N.; Sidikman, K.L.

    1995-09-01

    A Landau fluid model for dissipative trapped electron modes is developed which focuses on an improved description of the ion dynamics. The model is simple enough to allow nonlinear calculations with many harmonics for the times necessary to reach saturation. The model is motivated by a discussion that starts with the gyro-kinetic equation and emphasizes the importance of simultaneously including particular features of magnetic drift resonance, shear, and Landau effects. To ensure that these features are simultaneously incorporated in a Landau fluid model with only two evolution equations, a new approach to determining the closure coefficients is employed. The effect of this technique is to reduce the matching of fluid and kinetic responses to a single variable, rather than two, and to allow focusing on essential features of the fluctuations in question, rather than features that are only important for other types of fluctuations. Radially resolved nonlinear calculations of this model, advanced in time to reach saturation, are presented to partially illustrate its intended use. These calculations have a large number of poloidal and toroidal harmonics to represent the nonlinear dynamics in a converged steady state which includes cascading of energy to both short and long wavelengths.

  17. Modeling of Trapped Electron Effects on Electron Cyclotron Current Drive for Recent DIII-D Experiments

    SciTech Connect

    Lin-Liu, Y.R.; Sauter, O.; Harvey, R.W.; Chan, V.S.; Luce, T.C.; Prater, R.

    1999-08-01

    Owing to its potential capability of generating localized non-inductive current, especially off-axis, Electron Cyclotron Current Drive (ECCD) is considered a leading candidate for current profile control in achieving Advanced Tokamak (AT) operation. In recent DIII-D proof-of-principle experiments [1], localized off-axis ECCD has been clearly demonstrated for first time. The measured current drive efficiency near the magnetic axis agrees well with predictions of the bounce-averaged Fokker-Planck theory [2,3]. However, the off-axis current drive efficiency was observed to exceed the theoretical results, which predict significant degradation of the current drive efficiency due to trapped electron effects. The theoretical calculations have been based on an assumption that the effective collision frequency is much smaller than the bounce frequency such that the trapped electrons are allowed to complete the banana orbit at all energies. The assumption might be justified in reactor-grade tokamak plasmas, in which the electron temperature is sufficiently high or the velocity of resonant electrons is much larger than the thermal velocity, so that the influence of collisionality on current drive efficiency can be neglected. For off-axis deposition in the present-day experiments, the effect of high density and low temperature is to reduce the current drive efficiency, but the increasing collisionality reduces the trapping of current-carrying electrons, leading to compensating increases in the current drive efficiency. In this work, we use the adjoint function formulation [4] to examine collisionality effects on the current drive efficiency.

  18. Development of diagnostic and manipulation systems for space-charge dominated electron beams and confined electron plasmas in ELTRAP

    NASA Astrophysics Data System (ADS)

    Romé, M.; Cavaliere, F.; Cavenago, M.; Ikram, M.; Maero, G.; Paroli, B.; Pozzoli, R.

    2013-03-01

    Modifications have been implemented in the Penning-Malmberg device ELTRAP aimed at performing studies on the dynamics of space-charge dominated nanosecond electron bunches traveling along the magnetic field. In particular, a Thomson backscattering apparatus has been developed where an infrared (IR) laser pulse collides with the bunched electron beam. The frequency-shifted backscattered radiation, acquired by means of a photomultiplier (PMT), can be exploited to evaluate information on energy, energy spread and density of the bunch. The achievable sensitivity of the diagnostics has been estimated, and valuable information on the main parameters affecting the signal-to-noise (S/N) ratio has been obtained [B. Paroli, F. Cavaliere, M. Cavenago, F. De Luca, M. Ikram, G. Maero, C. Marini, R. Pozzoli, and M. Romé, JINST 7, P01008 (2012)]. A series of upgrades are under way, aimed at increasing the S/N ratio through the use of a new laser for the electron source, the insertion of a stray light shield, and the optimization of the detection electronics. Moreover, electromagnetic simulations relevant to the design and implementation of a microwave heating system are presented. The generation of an electron plasma in ELTRAP by means of a low-power radio frequency (RF) drive in the MHz range applied on one of the trap electrodes and under ultra-high vacuum (UHV) conditions has previously been demonstrated [B. Paroli, F. De Luca, G. Maero, F. Pozzoli, and M. Romé, Plasma Sources Sci. Technol. 19, 045013 (2010)]. The new heating system will allow the extension of the RF studies to the GHz range and in particular the production of a more energetic electron plasma via cyclotron resonant excitation.

  19. Nonlinear acceleration of the electron inertia-dominated magnetohydrodynamic modes due to electron parallel compressibility

    SciTech Connect

    Matsumoto, Taro; Naitou, Hiroshi; Tokuda, Shinji; Kishimoto, Yasuaki

    2005-09-15

    The behavior of the collisionless magnetohydrodynamics modes is investigated by the gyrokinetic particle simulation in a cylindrical tokamak plasma in the parameter region where the effects of electron inertia and electron parallel compressibility are competitive for magnetic reconnection. Although the linear growth of the m=1 internal kink-tearing mode is dominated by the electron inertia, it is found that the growth rate can be nonlinearly accelerated due to the electron parallel compressibility proportional to the ion sound Larmor radius {rho}{sub s}. It is also found that, as decreasing the electron skin depth {delta}{sub e}, the maximum growth rate before the internal collapse saturates independently of the microscopic scales such as {delta}{sub e} and {rho}{sub s}. The acceleration of growth rate is also observed in the nonlinear phase of the m=2 double tearing mode.

  20. Electron spin resonance from NV centers in diamonds levitating in an ion trap

    NASA Astrophysics Data System (ADS)

    Delord, T.; Nicolas, L.; Schwab, L.; Hétet, G.

    2017-03-01

    We report observations of the electron spin resonance (ESR) of nitrogen vacancy centers in diamonds that are levitating in an ion trap. Using a needle Paul trap operating under ambient conditions, we demonstrate efficient microwave driving of the electronic spin and show that the spin properties of deposited diamond particles measured by the ESR are retained in the Paul trap. We also exploit the ESR signal to show angle stability of single trapped mono-crystals, a necessary step towards spin-controlled levitating macroscopic objects.

  1. Gyrokinetic studies of trapped electron mode turbulence in the Helically Symmetric eXperiment stellarator

    SciTech Connect

    Faber, B. J.; Pueschel, M. J.; Terry, P. W.; Proll, J. H. E.; Hegna, C. C.; Weir, G. M.; Likin, K. M.; Talmadge, J. N.

    2015-07-15

    Gyrokinetic simulations of plasma microturbulence in the Helically Symmetric eXperiment are presented. Using plasma profiles relevant to experimental operation, four dominant drift wave regimes are observed in the ion wavenumber range, which are identified as different flavors of density-gradient-driven trapped electron modes. For the most part, the heat transport exhibits properties associated with turbulence driven by these types of modes. Additionally, long-wavelength, radially localized, nonlinearly excited coherent structures near the resonant central flux surface, not predicted by linear simulations, can further enhance flux levels. Integrated heat fluxes are compatible with experimental observations in the corresponding density gradient range. Despite low shearing rates, zonal flows are observed to regulate turbulence but can be overwhelmed at higher density gradients by the long-wavelength coherent structures.

  2. 'Programming' Electron Beam Ion Traps To Produce Atomic Data Relevant To Plasma Physics

    SciTech Connect

    Currell, Fred; O'Rourke, Brian; Kavanagh, Anthony; Li Yueming; Nakamura, Nobuyuki; Ohtani, Shunsuke; Watanabe, Hirofumi

    2009-09-10

    After a brief review of the processes taking place in electron beam ions traps (EBITs), the means by which EBITs are used to make measurements of electron impact ionization cross-sections and dielectronic recombination resonance strengths are discussed. In particular, results from a study involving holmium ions extracted from an electron beam ion trap are used to illustrate a technique for studying dielectronic recombination in open-shell target ions.

  3. Electronic excitations and self-trapping of electrons and holes in CaSO4

    NASA Astrophysics Data System (ADS)

    Kudryavtseva, I.; Klopov, M.; Lushchik, A.; Lushchik, Ch; Maaroos, A.; Pishtshev, A.

    2014-04-01

    A first-principles study of the electronic properties of a CaSO4 anhydrite structural phase has been performed. A theoretical estimation for the fundamental band gap (p → s transitions) is Eg = 9.6 eV and a proper threshold for p → d transitions is Epd = 10.8 eV. These values agree with the data obtained for a set of CaSO4 doped with Gd3+, Dy3+, Tm3+ and Tb3+ ions using the methods of low-temperature highly sensitive luminescence and thermoactivation spectroscopy. The results are consistent with theoretical predictions of a possible low-temperature self-trapping of oxygen p-holes. The hopping diffusion of hole polarons starts above ˜40 K and is accompanied by a ˜50-60 K peak of thermally stimulated luminescence of RE3+ ions caused due to the recombination of hole polarons with the electrons localized at RE3+. There is no direct evidence of the self-trapping of heavy d-electrons, however, one can argue that their motion rather differs from that of conduction s-electrons.

  4. Ultralow-Power Electronic Trapping of Nanoparticles with Sub-10 nm Gold Nanogap Electrodes.

    PubMed

    Barik, Avijit; Chen, Xiaoshu; Oh, Sang-Hyun

    2016-10-12

    We demonstrate nanogap electrodes for rapid, parallel, and ultralow-power trapping of nanoparticles. Our device pushes the limit of dielectrophoresis by shrinking the separation between gold electrodes to sub-10 nm, thereby creating strong trapping forces at biases as low as the 100 mV ranges. Using high-throughput atomic layer lithography, we manufacture sub-10 nm gaps between 0.8 mm long gold electrodes and pattern them into individually addressable parallel electronic traps. Unlike pointlike junctions made by electron-beam lithography or larger micron-gap electrodes that are used for conventional dielectrophoresis, our sub-10 nm gold nanogap electrodes provide strong trapping forces over a mm-scale trapping zone. Importantly, our technology solves the key challenges associated with traditional dielectrophoresis experiments, such as high voltages that cause heat generation, bubble formation, and unwanted electrochemical reactions. The strongly enhanced fields around the nanogap induce particle-transport speed exceeding 10 μm/s and enable the trapping of 30 nm polystyrene nanoparticles using an ultralow bias of 200 mV. We also demonstrate rapid electronic trapping of quantum dots and nanodiamond particles on arrays of parallel traps. Our sub-10 nm gold nanogap electrodes can be combined with plasmonic sensors or nanophotonic circuitry, and their low-power electronic operation can potentially enable high-density integration on a chip as well as portable biosensing.

  5. Loading Detection and Number Estimation of an Electron Plasma in a Penning Trap

    NASA Astrophysics Data System (ADS)

    Satyajit, K. T.; Gupta, Anita; Joshi, Gopal; Mohan, Shyam; Rao, Pushpa; Ananthamurthy, Sharath

    2009-10-01

    A quadrupole Penning trap for spectroscopy and investigations of non-neutral plasmas was designed and built. In this work we provide details of the trap design and a discussion of a simple design and procedure for convenient electron loading from an aligned filament. Electrons from thermionic emission which form a low-energy diffuse beam are trapped in weak magnetic fields. They are detected through a non-destructive electronic detection scheme, the details of which are discussed. The detection signal is diminished when the electron beam energy is increased while the electron flux is kept constant. This is explained by considering the energy shift in the distribution function of electrons emitted from the filament and entering the trap. We present a calculation of the number of trapped electrons from the shape of the detection signal. This calculation, based on a model of a driven damped harmonic oscillator to describe the axial motion of the electrons, compares favourably with the numbers obtained by measurements of the space charge induced shift in the trap potential.

  6. Inducible Protein Traps with Dominant Phenotypes for Functional Analysis of the Drosophila Genome

    PubMed Central

    Singari, Swetha; Javeed, Naureen; Tardi, Nicholas J.; Marada, Suresh; Carlson, Jeff C.; Kirk, Steven; Thorn, Judith M.; Edwards, Kevin A.

    2014-01-01

    The Drosophila melanogaster genome has been extensively characterized, but there remains a pressing need to associate gene products with phenotypes, subcellular localizations, and interaction partners. A multifunctional, Minos transposon-based protein trapping system called Hostile takeover (Hto) was developed to facilitate in vivo analyses of endogenous genes, including live imaging, purification of protein complexes, and mutagenesis. The Hto transposon features a UAS enhancer with a basal promoter, followed by an artificial exon 1 and a standard 5′ splice site. Upon GAL4 induction, exon 1 can splice to the next exon downstream in the flanking genomic DNA, belonging to a random target gene. Exon 1 encodes a dual tag (FLAG epitope and mCherry red fluorescent protein), which becomes fused to the target protein. Hto was mobilized throughout the genome and then activated by eye-specific GAL4; an F1 screen for abnormal eye phenotypes was used to identify inserts that express disruptive fusion proteins. Approximately 1.7% of new inserts cause eye phenotypes. Of the first 23 verified target genes, 21 can be described as regulators of cell biology and development. Most are transcription factor genes, including AP-2, CG17181, cut, klu, mamo, Sox102F, and sv. Other target genes [l(1)G0232, nuf, pum, and Syt4] make cytoplasmic proteins, and these lines produce diverse fluorescence localization patterns. Hto permits the expression of stable carboxy-terminal subfragments of proteins, which are rarely tested in conventional genetic screens. Some of these may disrupt specific cell pathways, as exemplified by truncated forms of Mastermind and Nuf. PMID:24172131

  7. Electron Cloud Generation And Trapping in a Quadrupole Magnet at the Los Alamos PSR

    SciTech Connect

    Macek, R.J.; Browman, A.A.; Ledford, J.E.; Borden, M.J.; O'Hara, J.F.; McCrady, R.C.; Rybarcyk, L.J.; Spickermann, T.; Zaugg, T.J.; Pivi, M.T.F.; /SLAC

    2007-11-14

    A diagnostic to measure electron cloud formation and trapping in a quadrupole magnet has been developed, installed, and successfully tested at PSR. Beam studies with this diagnostic show that the electron flux striking the wall in the quadrupole is comparable to or larger than in an adjacent drift. In addition, the trapped electron signal, obtained using the sweeping feature of diagnostic, was larger than expected and decayed very slowly with an exponential time constant of 50 to 100 {micro}s. Experimental results were also obtained which suggest that a significant fraction of the electrons observed in the adjacent drift space were seeded by electrons ejected from the quadrupole.

  8. Electron trapping and acceleration by kinetic Alfven waves in the inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Artemyev, A. V.; Rankin, R.; Blanco, M.

    2015-12-01

    In this paper we study the interaction of kinetic Alfven waves generated near the equatorial plane of the magnetosphere with electrons having initial energies up to ˜100 eV. Wave-particle interactions are investigated using a theoretical model of trapping into an effective potential generated by the wave parallel electric field and the mirror force acting along geomagnetic field lines. It is demonstrated that waves with an effective potential amplitude on the order of ˜100-400 V and with perpendicular wavelengths on the order of the ion gyroradius can trap and efficiently accelerate electrons up to energies of several keV. Trapping acceleration corresponds to conservation of the electron magnetic moment and, thus, results in a significant decrease of the electron equatorial pitch angle with time. Analytical and numerical estimates of the maximum energy and probability of trapping are presented, and the application of the proposed model is discussed.

  9. IBS in a CAM-Dominated Electron Beam

    SciTech Connect

    Burov, A.; Nagaitsev, S.; Shemyakin, A.; Gusachenko, I.

    2006-03-20

    Electron cooling of the 8.9 GeV/c antiprotons in the Recycler ring requires high-quality dc electron beam with the current of several hundred mA and the kinetic energy of 4.3 MeV. That high electron current is attained through beam recirculation (charge recovery). The primary current path is from the magnetized cathode at high voltage terminal to the ground, where the electron beam interacts with the antiproton beam and cooling takes place, and then to the collector in the terminal. The energy distribution function of the electron beam at the collector determines the required collector energy acceptance. Multiple and single intra-beam scattering as well as the dissipation of density micro-fluctuations during the beam transport are studied as factors forming a core and tails of the electron energy distribution. For parameters of the Fermilab electron cooler, the single intra-beam scattering (Touschek effect) is found to be of the most importance.

  10. Self-generated zonal flows in the plasma turbulence driven by trapped-ion and trapped-electron instabilities

    NASA Astrophysics Data System (ADS)

    Drouot, T.; Gravier, E.; Reveille, T.; Collard, M.

    2015-10-01

    This paper presents a study of zonal flows generated by trapped-electron mode and trapped-ion mode micro turbulence as a function of two plasma parameters—banana width and electron temperature. For this purpose, a gyrokinetic code considering only trapped particles is used. First, an analytical equation giving the predicted level of zonal flows is derived from the quasi-neutrality equation of our model, as a function of the density fluctuation levels and the banana widths. Then, the influence of the banana width on the number of zonal flows occurring in the system is studied using the gyrokinetic code. Finally, the impact of the temperature ratio Te/Ti on the reduction of zonal flows is shown and a close link is highlighted between reduction and different gyro-and-bounce-average ion and electron density fluctuation levels. This reduction is found to be due to the amplitudes of gyro-and-bounce-average density perturbations ne and ni gradually becoming closer, which is in agreement with the analytical results given by the quasi-neutrality equation.

  11. Self-generated zonal flows in the plasma turbulence driven by trapped-ion and trapped-electron instabilities

    SciTech Connect

    Drouot, T.; Gravier, E.; Reveille, T.; Collard, M.

    2015-10-15

    This paper presents a study of zonal flows generated by trapped-electron mode and trapped-ion mode micro turbulence as a function of two plasma parameters—banana width and electron temperature. For this purpose, a gyrokinetic code considering only trapped particles is used. First, an analytical equation giving the predicted level of zonal flows is derived from the quasi-neutrality equation of our model, as a function of the density fluctuation levels and the banana widths. Then, the influence of the banana width on the number of zonal flows occurring in the system is studied using the gyrokinetic code. Finally, the impact of the temperature ratio T{sub e}/T{sub i} on the reduction of zonal flows is shown and a close link is highlighted between reduction and different gyro-and-bounce-average ion and electron density fluctuation levels. This reduction is found to be due to the amplitudes of gyro-and-bounce-average density perturbations n{sub e} and n{sub i} gradually becoming closer, which is in agreement with the analytical results given by the quasi-neutrality equation.

  12. Pumped helium system for cooling positron and electron traps to 1.2 K

    NASA Astrophysics Data System (ADS)

    Wrubel, J.; Gabrielse, G.; Kolthammer, W. S.; Larochelle, P.; McConnell, R.; Richerme, P.; Grzonka, D.; Oelert, W.; Sefzick, T.; Zielinski, M.; Borbely, J. S.; George, M. C.; Hessels, E. A.; Storry, C. H.; Weel, M.; Müllers, A.; Walz, J.; Speck, A.

    2011-06-01

    Extremely precise tests of fundamental particle symmetries should be possible via laser spectroscopy of trapped antihydrogen ( H¯) atoms. H¯ atoms that can be trapped must have an energy in temperature units that is below 0.5 K—the energy depth of the deepest magnetic traps that can currently be constructed with high currents and superconducting technology. The number of atoms in a Boltzmann distribution with energies lower than this trap depth depends sharply upon the temperature of the thermal distribution. For example, ten times more atoms with energies low enough to be trapped are in a thermal distribution at a temperature of 1.2 K than for a temperature of 4.2 K. To date, H¯ atoms have only been produced within traps whose electrode temperature is 4.2 K or higher. A lower temperature apparatus is desirable if usable numbers of atoms that can be trapped are to eventually be produced. This report is about the pumped helium apparatus that cooled the trap electrodes of an H¯ apparatus to 1.2 K for the first time. Significant apparatus challenges include the need to cool a 0.8 m stack of 37 trap electrodes separated by only a mm from the substantial mass of a 4.2 K Ioffe trap and the substantial mass of a 4.2 K solenoid. Access to the interior of the cold electrodes must be maintained for antiprotons, positrons, electrons and lasers.

  13. Emittance and Current of Electrons Trapped in a Plasma Wakefield Accelerator

    SciTech Connect

    Kirby, N.; Blumenfeld, I.; Decker, F. J.; Hogan, M. J.; Ischebeck, R.; Iverson, R. H.; Siemann, R. H.; Walz, D. R.; Clayton, C. E.; Huang, C.; Joshi, C.; Lu, W.; Marsh, K. A.; Mori, W. B.; Zhou, M.; Katsouleas, T.; Muggli, P.; Oz, E.; Martins, S.

    2009-01-22

    In recent experiments plasma electrons became trapped in a plasma wakefield accelerator (PWFA). The transverse size of these trapped electrons on a downstream diagnostic yields an upper limit measurement of transverse normalized emittance divided by peak current, {epsilon}{sub N,{sub x}}/I. The lowest upper limit for {epsilon}{sub N,{sub x}}/I measured in the experiment is 1.3{center_dot}10{sup -10} m/A.

  14. Charge Transfer Fluorescence and 34 nm Exciton Diffusion Length in Polymers with Electron Acceptor End Traps.

    PubMed

    Zaikowski, Lori; Mauro, Gina; Bird, Matthew; Karten, Brianne; Asaoka, Sadayuki; Wu, Qin; Cook, Andrew R; Miller, John R

    2015-06-18

    Photoexcitation of conjugated poly-2,7-(9,9-dihexylfluorene) polyfluorenes with naphthylimide (NI) and anthraquinone (AQ) electron-acceptor end traps produces excitons that form charge transfer states at the end traps. Intramolecular singlet exciton transport to end traps was examined by steady state fluorescence for polyfluorenes of 17-127 repeat units in chloroform, dimethylformamide (DMF), tetrahydrofuran (THF), and p-xylene. End traps capture excitons and form charge transfer (CT) states at all polymer lengths and in all solvents. The CT nature of the end-trapped states is confirmed by their fluorescence spectra, solvent and trap group dependence, and DFT descriptions. Quantum yields of CT fluorescence are as large as 46%. This strong CT emission is understood in terms of intensity borrowing. Energies of the CT states from onsets of the fluorescence spectra give the depths of the traps which vary with solvent polarity. For NI end traps, the trap depths are 0.06 (p-xylene), 0.13 (THF), and 0.19 eV (CHCl3). For AQ, CT fluorescence could be observed only in p-xylene where the trap depth is 0.27 eV. Quantum yields, emission energies, charge transfer energies, solvent reorganization, and vibrational energies were calculated. Fluorescence measurements on chains >100 repeat units indicate that end traps capture ∼50% of the excitons, and that the exciton diffusion length is LD = 34 nm, which is much larger than diffusion lengths reported in polymer films or than previously known for diffusion along isolated chains. The efficiency of exciton capture depends on chain length but not on trap depth, solvent polarity, or which trap group is present.

  15. Charge transfer fluorescence and 34 nm exciton diffusion length in polymers with electron acceptor end traps

    SciTech Connect

    Zaikowski, Lori; Mauro, Gina; Bird, Matthew; Karten, Brianne; Asaoka, Sadayuki; Wu, Qin; Cook, Andrew R.; Miller, John R.

    2014-12-22

    Photoexcitation of conjugated poly-2,7-(9,9-dihexylfluorene) polyfluorenes with naphthylimide (NI) and anthraquinone (AQ) electron-acceptor end traps produces excitons that form charge transfer states at the end traps. Intramolecular singlet exciton transport to end traps was examined by steady state fluorescence for polyfluorenes of 17 to 127 repeat units in chloroform, dimethylformamide (DMF), tetrahydrofuran (THF), and p-xylene. End traps capture excitons and form charge transfer (CT) states at all polymer lengths and in all solvents. The CT nature of the end-trapped states is confirmed by their fluorescence spectra, solvent and trap group dependence and DFT descriptions. Quantum yields of CT fluorescence are as large as 46%. This strong CT emission is understood in terms of intensity borrowing. Energies of the CT states from onsets of the fluorescence spectra give the depths of the traps which vary with solvent polarity. For NI end traps the trap depths are 0.06 (p-xylene), 0.13 (THF) and 0.19 eV (CHCl3). For AQ, CT fluorescence could be observed only in p-xylene where the trap depth is 0.27 eV. Quantum yields, emission energies, charge transfer energies, solvent reorganization and vibrational energies were calculated. Fluorescence measurements on chains >100 repeat units indicate that end traps capture ~50% of the excitons, and that the exciton diffusion length LD =34 nm, which is much larger than diffusion lengths reported in polymer films or than previously known for diffusion along isolated chains. As a result, the efficiency of exciton capture depends on chain length, but not on trap depth, solvent polarity or which trap group is present.

  16. Charge transfer fluorescence and 34 nm exciton diffusion length in polymers with electron acceptor end traps

    DOE PAGES

    Zaikowski, Lori; Mauro, Gina; Bird, Matthew; ...

    2014-12-22

    Photoexcitation of conjugated poly-2,7-(9,9-dihexylfluorene) polyfluorenes with naphthylimide (NI) and anthraquinone (AQ) electron-acceptor end traps produces excitons that form charge transfer states at the end traps. Intramolecular singlet exciton transport to end traps was examined by steady state fluorescence for polyfluorenes of 17 to 127 repeat units in chloroform, dimethylformamide (DMF), tetrahydrofuran (THF), and p-xylene. End traps capture excitons and form charge transfer (CT) states at all polymer lengths and in all solvents. The CT nature of the end-trapped states is confirmed by their fluorescence spectra, solvent and trap group dependence and DFT descriptions. Quantum yields of CT fluorescence are asmore » large as 46%. This strong CT emission is understood in terms of intensity borrowing. Energies of the CT states from onsets of the fluorescence spectra give the depths of the traps which vary with solvent polarity. For NI end traps the trap depths are 0.06 (p-xylene), 0.13 (THF) and 0.19 eV (CHCl3). For AQ, CT fluorescence could be observed only in p-xylene where the trap depth is 0.27 eV. Quantum yields, emission energies, charge transfer energies, solvent reorganization and vibrational energies were calculated. Fluorescence measurements on chains >100 repeat units indicate that end traps capture ~50% of the excitons, and that the exciton diffusion length LD =34 nm, which is much larger than diffusion lengths reported in polymer films or than previously known for diffusion along isolated chains. As a result, the efficiency of exciton capture depends on chain length, but not on trap depth, solvent polarity or which trap group is present.« less

  17. Phase-Space Density Analyses of the AE-8 Trapped Electron and the AP-8 Trapped Proton Model Environments

    SciTech Connect

    T.E. Cayton

    2005-08-12

    The AE-8 trapped electron and the AP-8 trapped proton models are used to examine the L-shell variation of phase-space densities for sets of transverse (or 1st) invariants, {mu}, and geometrical invariants, K (related to the first two adiabatic invariants). The motivation for this study is twofold: first, to discover the functional dependence of the phase-space density upon the invariants; and, second, to explore the global structure of the radiation belts within this context. Variation due to particle rest mass is considered as well. The overall goal of this work is to provide a framework for analyzing energetic particle data collected by instruments on Global Positioning System (GPS) spacecraft that fly through the most intense region of the radiation belt. For all considered values of {mu} and K, and for 3.5 R{sub E} < L < 6.5 R{sub E}, the AE-8 electron phase-space density increases with increasing L; this trend--the expected one for a population diffusing inward from an external source--continues to L = 7.5 R{sub E} for both small and large values of K but reverses slightly for intermediate values of K. The AP-8 proton phase-space density exhibits {mu}-dependent local minima around L = 5 R{sub E}. Both AE-8 and AP-8 exhibit critical or cutoff values for the invariants beyond which the flux and therefore the phase-space density vanish. For both electrons and protons, these cutoff values vary systematically with magnetic moment and L-shell and are smaller than those estimated for the atmospheric loss cone. For large magnetic moments, for both electrons and protons, the K-dependence of the phase-space density is exponential, with maxima at the magnetic equator (K = 0) and vanishing beyond a cutoff value, K{sub c}. Such features suggest that momentum-dependent trapping boundaries, perhaps drift-type loss cones, serve as boundary conditions for trapped electrons as well as trapped protons.

  18. Time evolution of secondary electron emission and trapped charge accumulation in polyimide film under various primary electron irradiation currents

    NASA Astrophysics Data System (ADS)

    Song, Bai-Peng; Zhou, Run-Dong; Su, Guo-Qiang; Mu, Hai-Bao; Zhang, Guan-Jun; Bu, Ren-An

    2016-12-01

    Time-resolved evolution of secondary electron emission and trapped charge accumulation in polyimide film is investigated during two interval electrons bombardment, derived from the measurement of displacement current and secondary current via a hemispherical detector with the shielded grid. Under various irradiation current, secondary electron yield (SEY σ) at a certain injected energy decreases exponentially from initial amplitude σ0 to self-consistent steady value σ∞ close to 0.93. The time constant τ of charging process is characterized as a function of incident current Ip, and the results indicate that the formula Ip × τ is fitted by a hyperbolical law. The influence of Ip on the amount of trapped charge is studied and no significant change in its saturation value is observed. The evolution of SEY σ and trapped charge is dependent on incident dose Qp but not the incident rate Ip. Furthermore, the trap density and capture cross section are discussed.

  19. Dominance of broken bonds and nonbonding electrons at the nanoscale.

    PubMed

    Sun, Chang Q

    2010-10-01

    Although they exist ubiquitously in human bodies and our surroundings, the impact of nonbonding lone electrons and lone electron pairs has long been underestimated. Recent progress demonstrates that: (i) in addition to the shorter and stronger bonds between under-coordinated atoms that initiate the size trends of the otherwise constant bulk properties when a substance turns into the nanoscale, the presence of lone electrons near to broken bonds generates fascinating phenomena that bulk materials do not demonstrate; (ii) the lone electron pairs and the lone pair-induced dipoles associated with C, N, O, and F tetrahedral coordination bonding form functional groups in biological, organic, and inorganic specimens. By taking examples of surface vacancy, atomic chain end and terrace edge states, catalytic enhancement, conducting-insulating transitions of metal clusters, defect magnetism, Coulomb repulsion at nanoscale contacts, Cu(3)C(2)H(2) and Cu(3)O(2) surface dipole formation, lone pair neutralized interface stress, etc, this article will focus on the development and applications of theory regarding the energetics and dynamics of nonbonding electrons, aiming to raise the awareness of their revolutionary impact to the society. Discussion will also extend to the prospective impacts of nonbonding electrons on mysteries such as catalytic enhancement and catalysts design, the density anomalies of ice and negative thermal expansion, high critical temperature superconductivity induced by B, C, N, O, and F, the molecular structures and functionalities of CF(4) in anti-coagulation of synthetic blood, NO signaling, and enzyme telomeres, etc. Meanwhile, an emphasis is placed on the necessity and effectiveness of understanding the properties of substances from the perspective of bond and nonbond formation, dissociation, relaxation and vibration, and the associated energetics and dynamics of charge repopulation, polarization, densification, and localization. Finding and grasping

  20. Emittance Measurements of Space Charge Dominated Electron Beam.

    DTIC Science & Technology

    2014-09-26

    AD-AI8 693 EMITTANE KASUREMNIS OF SPACE CHARG DOMINATED I/S ELECIRON BEAI) NAVAL SURFACE WEAPONS CENTER SILVER SPRING N, NASUNG El AL. 01 JUN 65 NSW...UNIT NUMBERS 10901 New Hampshire Avenue Silver Spring, Maryland 20903-5000 I. CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DATE 1 June 1985 13. NUMBER...by a plate with a pinhole of radius rp which travels on the -axis, This system is commonly 8 NSWC TR 85-244 designed as L > a (beam radius) >> d > rp

  1. Trapping of Electron Cloud LLC/Cesrta Quadrupole and Sextupole Magnets

    SciTech Connect

    Wang, L; Pivi, M.; /SLAC

    2011-08-18

    The Cornell Electron Storage Ring (CESR) has been reconfigured as an ultra low emittance damping ring for use as a test accelerator (CesrTA) for International Linear Collider (ILC) damping ring R&D [1]. One of the primary goals of the CesrTA program is to investigate the interaction of the electron cloud with low emittance positron beam to explore methods to suppress the electron cloud, develop suitable advanced instrumentation required for these experimental studies and benchmark predictions by simulation codes. This paper reports the simulation of the electron-cloud formation in CESRTA and ILC quadrupole and sextupole magnets using the 3D code CLOUDLAND. We found that electrons can be trapped with a long lifetime in a quadrupole and sextupole magnet due to the mirror field trapping mechanism. We study the effects of magnet strength, bunch current, ante-chamber effect, bunch spacing effect and secondary emission yield (SEY) in great detail. The development of an electron cloud in magnets is the main concern where a weak solenoid field is not effective. Quadrupole and sextupole magnets have mirror field configurations which may trap electrons by the mirror field trapping mechanism [2]. Fig.1 shows the orbit of a trapped electron in a quadrupole magnet. The electron makes gyration motion (called transverse motion) and also moves along the field line (called longitudinal motion). At the mirror point (middle of the field line), there is a maximum longitudinal energy and minimum transverse energy. When the electron moves away from the mirror point, its longitudinal energy reduces and the transverse energy increases as the magnetic field increases. If the magnetic field is strong enough, the longitudinal energy becomes zero at one point and then the electron is turned back by the strong field. Note that the electrons are trapped in the region near the middle of the field lines. Although all quadrupole and sextupole magnets can trap electrons in principle, the trapping

  2. Charge Breeding Techniques in an Electron Beam Ion Trap for High Precision Mass Spectrometry at TITAN

    NASA Astrophysics Data System (ADS)

    MacDonald, T. D.; Simon, M. C.; Bale, J. C.; Chowdhury, U.; Eibach, M.; Gallant, A. T.; Lennarz, A.; Simon, V. V.; Chaudhuri, A.; Grossheim, A.; Kwiatkowski, A. A.; Schultz, B. E.; Dilling, J.

    2012-10-01

    Penning trap mass spectrometry is the most accurate and precise method available for performing atomic mass measurements. TRIUMF's Ion Trap for Atomic and Nuclear science is currently the only facility to couple its Penning trap to a rare isotope facility and an electron beam ion trap (EBIT). The EBIT is a valuable tool for beam preparation: since the precision scales linearly with the charge state, it takes advantage of the precision gained by using highly charged ions. However, this precision gain is contingent on fast and efficient charge breeding. An optimization algorithm has been developed to identify the optimal conditions for running the EBIT. Taking only the mass number and half-life of the isotope of interest as inputs, the electron beam current density, charge breeding time, charge state, and electron beam energy are all specified to maximize this precision. An overview of the TITAN charge breeding program, and the results of charge breeding simulations will be presented.

  3. Electron capture dissociation in a branched radio-frequency ion trap.

    PubMed

    Baba, Takashi; Campbell, J Larry; Le Blanc, J C Yves; Hager, James W; Thomson, Bruce A

    2015-01-06

    We have developed a high-throughput electron capture dissociation (ECD) device coupled to a quadrupole time-of-flight mass spectrometer using novel branched radio frequency ion trap architecture. With this device, a low-energy electron beam can be injected orthogonally into the analytical ion beam with independent control of both the ion and electron beams. While ions and electrons can interact in a "flow-through" mode, we observed a large enhancement in ECD efficiency by introducing a short ion trapping period at the region of ion and electron beam intersection. This simultaneous trapping mode still provides up to five ECD spectra per second while operating in an information-dependent acquisition workflow. Coupled to liquid chromatography (LC), this LC-ECD workflow provides good sequence coverage for both trypsin and Lys C digests of bovine serum albumin, providing ECD spectra for doubly charged precursor ions with very good efficiency.

  4. Electron Fermi acceleration in collapsing magnetic traps: Computational and analytical models

    SciTech Connect

    Gisler, G. ); Lemons, D. )

    1990-09-01

    The authors consider the heating and acceleration of electrons trapped on magnetic field lines between approaching magnetic mirrors. Such a collapsing magnetic trap and consequent electron energization can occur whenever a curved (or straight) flux tube drifts into a relatively straight (or curved) perpendicular shock. The relativistic, three-dimensional, collisionless test particle simulations show that an initial thermal electron distribution is bulk heated while a few individual electrons are accelerated to many times their original energy before they escape the trap. Upstream field-aligned beams and downstream pancake distributions perpendicular to the field are predicted. In the appropriate limit the simulation results agree well with a nonrelativistic analytic model of the distribution of escaping electrons which is based on the first adiabatic invariant and energy conservation between collisions with the mirrors. Space science and astrophysical applications are discussed.

  5. Positron trapping at vacancies in electron-irradiated Si at low temperatures

    SciTech Connect

    Maekinen, J.; Corbel, C.; Hautojaervi, P.; Moser, P.; Pierre, F.

    1989-05-15

    Experimental results on positron trapping at vacancies in electron-irradiated silicon are presented. The positron lifetimes 273 +- 3 and 248 +- 2 ps in pure Si and heavily-phosphorus-doped Si ((P) = 10/sup 20/ cm/sup -3/) are assigned to a negative monovacancy V/sup -/ and a negative vacancy-phosphorus pair (V-P)/sup -/, respectively. In pure Si, positron trapping displays a strong negative temperature dependence, and the specific trapping rate reaches very large values (10/sup 17//sup --/10/sup 18/ s/sup -1/) at low temperatures. In Si:P the trapping rate is independent of temperature. These different temperature behaviors are attributed to different positron-trapping mechanisms, a cascade of one-phonon transitions in pure Si, and an Auger process in Si:P.

  6. Hot electron dominated rapid transverse ionization growth in liquid water.

    PubMed

    Brown, Michael S; Erickson, Thomas; Frische, Kyle; Roquemore, William M

    2011-06-20

    Pump/probe optical-transmission measurements are used to monitor in space and time the ionization of a liquid column of water following impact of an 800-nm, 45-fs pump pulse. The pump pulse strikes the 53-μm-diameter column normal to its axis with intensities up to 2 × 10(15) W/cm2. After the initial photoinization and for probe delay times < 500 fs, the neutral water surrounding the beam is rapidly ionized in the transverse direction, presumably by hot electrons with initial velocities of 0.55 times the speed of light (relativistic kinetic energy of ~100 keV). Such velocities are unusual for condensed-matter excitation at the stated laser intensities.

  7. Threshold for Trapping Positrons in the Wake Driven by a Ultra-relativistic Electron Bunch

    SciTech Connect

    Wang, X.; Muggli, P.; Katsouleas, T.; Ischebeck, R.; Hogan, M. J.; Joshi, C.; Mori, W. B.

    2009-01-22

    We have recently proposed a new concept for generating, injecting and accelerating positrons in a plasma using a double-pulse electron bunch. Monte Carlo simulations show that the number of the positrons produced in a foil target has an exponentially decay energy spectrum. The energy threshold for the trapping of these positrons in a ultra-relativistic electron wake is investigated numerically. For a typical 28.5 GeV electron drive bunch, the trapping threshold for the positrons is a few MeV, and therefore a majority of positrons generated in the foil target are focused and accelerated by the plasma wake.

  8. Effects of trapped electrons on ion reflection in an oblique shock wave

    SciTech Connect

    Toida, Mieko; Inagaki, Junya

    2015-06-15

    A magnetosonic shock wave propagating obliquely to an external magnetic field can trap electrons and accelerate them to ultrarelativistic energies. The trapped electrons excite two-dimensional (2D) electromagnetic fluctuations with finite wavenumbers along the shock front. We study effects of the trapped electrons on ion motions through the 2D fluctuations. It is analytically shown that the fraction of ions reflected from the shock front is enhanced by the 2D fluctuations. This is confirmed by 2D (two space coordinates and three velocities) relativistic, electromagnetic particle simulations with full ion and electron dynamics and calculation of test ions in the electromagnetic fields averaged along the shock front. A comparison between 2D and one-dimensional electromagnetic particle simulations is also shown.

  9. Design and Fabrication of Cryostat Interface and Electronics for High Performance Antimatter Trap (HI-PAT)

    NASA Technical Reports Server (NTRS)

    Smith, Gerald A.

    1999-01-01

    Included in Appendix I to this report is a complete set of design and assembly schematics for the high vacuum inner trap assembly, cryostat interfaces and electronic components for the MSFC HI-PAT. Also included in the final report are summaries of vacuum tests, and electronic tests performed upon completion of the assembly.

  10. Rapid increase in relativistic electron flux controlled by nonlinear phase trapping of whistler chorus elements

    NASA Astrophysics Data System (ADS)

    Saito, Shinji; Miyoshi, Yoshizumi; Seki, Kanako

    2016-07-01

    Wave-particle interactions with whistler chorus waves are believed to provide a primary acceleration for electrons in the outer radiation belt. Previous models for flux enhancement of the radiation belt have assumed the stochastic process as a diffusion manner of successive random-phase interactions, but physical mechanisms for the acceleration are not fully incorporated in these models because of the lack of a nonlinear scattering process. Here we report rapid increase in relativistic electron flux by using an innovative computer simulation model that incorporates not only diffusive process but also nonlinear scattering processes. The simulations show that three types of scattering simultaneously occur, which are diffusive, phase trapping, and phase bunching. It is found that the phase trapping is the most efficient mechanism to produce the MeV electrons rapidly in the scattering processes. The electrons are accelerated from 400 keV to over 1 MeV in time scale less than 60 s. On the other hand, as the phase trapping is suppressed by the breaking of relative phase angle between waves and gyrating electrons during the interaction, the increase of electron flux at MeV energy is clearly reduced. Our simulations conclude that the phase-trapping process causes a significant effect for the increase in relativistic electron flux and suggest that a quasi-linear diffusion model is not always valid to fully describe the relativistic electron acceleration.

  11. Location Of Hole And Electron Traps On Nanocrystalline Anatase TiO2

    SciTech Connect

    Mercado, Candy C.; Knorr, Fritz J.; McHale, Jeanne L.; Usmani, Shirin M.; Ichimura, Andrew S.; Saraf, Laxmikant V.

    2012-05-17

    The defect photoluminescence from TiO2 nanoparticles in the anatase phase is reported for nanosheets which expose predominantly (001) surfaces, and compared to that from conventional anatase nanoparticles which expose mostly (101) surfaces. Also reported is the weak defect photoluminescence of TiO2 nanotubes, which we find using electron back-scattered diffraction to consist of walls which expose (110) and (100) facets. The nanotubes exhibit photoluminescence that is blue-shifted and much weaker than that from conventional TiO2 nanoparticles. Despite the preponderance of (001) surfaces in the nanosheet samples, they exhibit photoluminescence similar to that of conventional nanoparticles. We assign the broad visible photoluminescence of anatase nanoparticles to two overlapping distributions: hole trap emission associated with oxygen vacancies on (101) exposed surfaces, which peaks in the green, and a broader emission extending into the red which results from electron traps on under-coordinated titanium atoms, which are prevalent on (001) facets. The results of this study suggest how morphology of TiO2 nanoparticles could be optimized to control the distribution and activity of surface traps. Our results also shed light on the mechanism by which the TiCl4 surface treatment heals traps on anatase and mixed-phase TiO2 films, and reveals distinct differences in the trap-state distributions of TiO2 nanoparticles and nanotubes. The molecular basis for electron and hole traps and their spatial separation on different facets is discussed.

  12. Complete erasing of ghost images on computed radiography plates and role of deeply trapped electrons

    NASA Astrophysics Data System (ADS)

    Ohuchi-Yoshida, Hiroko; Kondo, Yasuhiro

    2011-12-01

    Computed radiography (CR) plates made of europium-doped Ba(Sr)FBr(I) were simultaneously exposed to filtered ultraviolet light and visible light in order to erase ghost images, i.e., latent image that is unerasable with visible light (LIunVL) and reappearing one, which are particularly observed in plates irradiated with a high dose and/or cumulatively over-irradiated. CR samples showing LIunVLs were prepared by irradiating three different types of CR plates (Agfa ADC MD10, Kodak Directview Mammo EHRM2, and Fuji ST-VI) with 50 kV X-ray beams in the dose range 8.1 mGy-8.0 Gy. After the sixth round of simultaneous 6 h exposures to filtered ultraviolet light and visible light, all the LIunVLs in the three types of CR plates were erased to the same level as in an unirradiated plate and no latent images reappeared after storage at 0 °C for 14 days. With conventional exposure to visible light, LIunVLs consistently remained in all types of CR plates irradiated with higher doses of X-rays and latent images reappeared in the Agfa M10 plates after storage at 0 °C. Electrons trapped in deep centers cause LIunVLs and they can be erased by simultaneous exposures to filtered ultraviolet light and visible light. To study electrons in deep centers, the absorption spectra were examined in all types of irradiated CR plates by using polychromatic ultraviolet light from a deep-ultraviolet lamp. It was found that deep centers showed a dominant peak in the absorption spectra at around 324 nm for the Agfa M10 and Kodak EHRM2 plates, and at around 320 nm for the Fuji ST-VI plate, in each case followed by a few small peaks. The peak heights were dose-dependent for all types of CR samples, suggesting that the number of electrons trapped in deep centers increases with the irradiation dose.

  13. Trapped Electron Instability of Electron Plasma Waves: Vlasov simulations and theory

    NASA Astrophysics Data System (ADS)

    Berger, Richard; Chapman, Thomas; Brunner, Stephan

    2013-10-01

    The growth of sidebands of a large-amplitude electron plasma wave is studied with Vlasov simulations for a range of amplitudes (. 001 < eϕ0 /Te < 1) and wavenumbers (0 . 25 trapped electron. In 2D simulations, we find that the instability persists and co-exists with the filamentation instability. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and funded by the Laboratory Research and Development Program at LLNL under project tracking code 12-ERD.

  14. Probability of relativistic electron trapping by parallel and oblique whistler-mode waves in Earth's radiation belts

    SciTech Connect

    Artemyev, A. V. Vasiliev, A. A.; Neishtadt, A. I.; Mourenas, D.; Krasnoselskikh, V.

    2015-11-15

    We investigate electron trapping by high-amplitude whistler-mode waves propagating at small as well as large angles relative to geomagnetic field lines. The inhomogeneity of the background magnetic field can result in an effective acceleration of trapped particles. Here, we derive useful analytical expressions for the probability of electron trapping by both parallel and oblique waves, paving the way for a full analytical description of trapping effects on the particle distribution. Numerical integrations of particle trajectories allow to demonstrate the accuracy of the derived analytical estimates. For realistic wave amplitudes, the levels of probabilities of trapping are generally comparable for oblique and parallel waves, but they turn out to be most efficient over complementary energy ranges. Trapping acceleration of <100 keV electrons is mainly provided by oblique waves, while parallel waves are responsible for the trapping acceleration of >100 keV electrons.

  15. Role of trapped and nonthermal electron distributions in dust charging currents

    SciTech Connect

    Duha, S. S.

    2009-12-15

    The expressions for the dust charging current associated with plasma electrons, which follow either the trapped (vortexlike) distribution of Schamel [J. Plasma Phys. 13, 139 (1975)] or the nonthermal distribution of Cairns et al. [Geophys. Res. Lett. 22, 2709 (1995)], are derived. The effects of such trapped and nonthermal distributions of electrons on this dust charging current are then theoretically examined, and using current equations we derived dust grain charge. It is found that the dust charging currents are significantly modified by the population of the trapped and nonthermal electrons, and the dust grain charge is also modified. The implications of our results in the dust charging mechanism, which is the central point of the physics of dusty plasmas, are briefly discussed.

  16. Transverse Emittance and Current of Multi-GeV Trapped Electrons in a Plasma Wakefield Accelerator

    SciTech Connect

    Kirby, N.; Blumenfeld, I.; Clayton, C.E.; Decker, F.J.; Hogan, M.J.; Huang, C.; Ischebeck, R.; Iverson, R.H.; Joshi, C.; Katsouleas, T.; Lu, W.; Marsh, K.A.; Martins, S.F.; Mori, W.B.; Muggli, P.; Oz, E.; Siemann, R.H.; Walz, D.R.; Zhou, M.; /UCLA

    2009-10-17

    Multi-GeV trapped electron bunches in a plasma wakefield accelerator (PWFA) are observed with normalized transverse emittance divided by peak current, {epsilon}{sub N,x}/I{sub t}, below the level of 0.2 {micro}m/kA. A theoretical model of the trapped electron emittance, developed here, indicates that emittance scales inversely with the square root of the plasma density in the nonlinear 'bubble' regime of the PWFA. This model and simulations indicate that the observed values of {epsilon}{sub N,x}/I{sub t} result from multi-GeV trapped electron bunches with emittances of a few {micro}m and multi-kA peak currents.

  17. Dust Acoustic Solitary Waves in Dusty Plasma with Trapped Electrons Having Different Temperature Nonthermal Ions

    NASA Astrophysics Data System (ADS)

    Deka, Manoj Kr.

    2016-12-01

    In this report, a detailed investigation on the study of dust acoustics solitary waves solution with negatively dust charge fluctuation in dusty plasma corresponding to lower and higher temperature nonthermal ions with trapped electrons is presented. We consider temporal variation of dust charge as a source of dissipation term to derive the lower order modified Kadomtsev-Petviashvili equation by using the reductive perturbation technique. Solitary wave solution is obtained with the help of sech method in presence of trapped electrons and low (and high) temperature nonthermal ions. Both nonthermality of ions and trapped state of the electrons are found to have an imperative control on the nonlinear coefficient, dissipative coefficient as well as height of the wave potential.

  18. Hole and electron traps in the YAlO{sub 3} single crystal scintillator

    SciTech Connect

    Laguta, V. V.; Nikl, M.; Rosa, J.; Vedda, A.; Mihokova, E.; Blazek, K.

    2009-07-15

    The processes of hole and electron localization in YAlO{sub 3} single crystals were investigated by electron-spin resonance. It was found that holes created by UV or x-ray irradiation are trapped at regular oxygen ions forming two types of O{sup -} hole centers corresponding to hole localization at two inequivalent oxygen ions which are located in Y and Al planes, respectively. The hole can be either autolocalized or additionally stabilized by a defect in the neighborhood of the oxygen ion such as yttrium vacancy or an impurity ion at Y site. This leads to a variety of O{sup -} centers which differ both by thermal stability (from about 14 K up to room temperature) and spectral parameters. Electron-type trapping sites are assigned to Y{sub Al} antisite ions. After trapping an electron they become paramagnetic Y{sub Al}{sup 2+} centers. They are found in several configurations with thermal stability up to above 300 K that enables the radiative recombination of freed holes with such localized electrons and the appearance of thermoluminescence peaks. It is shown that the electron trapped around Y{sub Al} antisite ion is additionally stabilized either by an oxygen vacancy or by a defect at Y site. The yttrium antisite ions in the lattice were directly identified by {sup 89}Y nuclear magnetic resonance.

  19. Real-Space Mapping of Surface Trap States in CIGSe Nanocrystals Using 4D Electron Microscopy.

    PubMed

    Bose, Riya; Bera, Ashok; Parida, Manas R; Adhikari, Aniruddha; Shaheen, Basamat S; Alarousu, Erkki; Sun, Jingya; Wu, Tom; Bakr, Osman M; Mohammed, Omar F

    2016-07-13

    Surface trap states in copper indium gallium selenide semiconductor nanocrystals (NCs), which serve as undesirable channels for nonradiative carrier recombination, remain a great challenge impeding the development of solar and optoelectronics devices based on these NCs. In order to design efficient passivation techniques to minimize these trap states, a precise knowledge about the charge carrier dynamics on the NCs surface is essential. However, selective mapping of surface traps requires capabilities beyond the reach of conventional laser spectroscopy and static electron microscopy; it can only be accessed by using a one-of-a-kind, second-generation four-dimensional scanning ultrafast electron microscope (4D S-UEM) with subpicosecond temporal and nanometer spatial resolutions. Here, we precisely map the collective surface charge carrier dynamics of copper indium gallium selenide NCs as a function of the surface trap states before and after surface passivation in real space and time using S-UEM. The time-resolved snapshots clearly demonstrate that the density of the trap states is significantly reduced after zinc sulfide (ZnS) shelling. Furthermore, the removal of trap states and elongation of carrier lifetime are confirmed by the increased photocurrent of the self-biased photodetector fabricated using the shelled NCs.

  20. High resolution extreme ultraviolet spectrometer for an electron beam ion trap

    SciTech Connect

    Ohashi, Hayato; Yatsurugi, Junji; Nakamura, Nobuyuki; Sakaue, Hiroyuki A.

    2011-08-15

    An extreme ultraviolet spectrometer has been developed for spectroscopic studies of highly charged ions with an electron beam ion trap. It has a slit-less configuration with a spherical varied-line-spacing grating that provides a flat focal plane for grazing incidence light. Alternative use of two different gratings enables us to cover the wavelength range 1-25 nm. Test observations with the Tokyo electron beam ion trap demonstrate the high performance of the present spectrometer such as a resolving power of above 1000.

  1. Radio Frequency Generation of an Electron Plasma in a Malmberg-Penning Trap

    SciTech Connect

    Paroli, B.; De Luca, F.; Pozzoli, R.; Rome, M.; Maero, G.

    2010-06-16

    The generation of an electron plasma via low-power Radio Frequency (RF) excitation has been observed in the Malmberg-Penning trap ELTRAP under ultra-high vacuum conditions. The process is sensitive to the RF parameters as well as to the trapping length. The electron heating mechanism necessary to reach the ionization energy of the residual gas has been modeled with the use of a simple one-dimensional iterative map, whose properties show a behavior similar to that of the Fermi acceleration map.

  2. Mobility relaxation and electron trapping in a donor/acceptor copolymer

    NASA Astrophysics Data System (ADS)

    Schubert, Marcel; Preis, Eduard; Blakesley, James C.; Pingel, Patrick; Scherf, Ullrich; Neher, Dieter

    2013-01-01

    To address the nature of charge transport and the origin of severe (intrinsic) trapping in electron-transporting polymers, transient and steady-state charge transport measurements have been conducted on the prototype donor/acceptor copolymer poly[2,7-(9,9-dialkyl-fluorene)-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PFTBTT). A charge-generation layer technique is used to selectively address transport of the desired charge carrier type, to perform time-of-flight measurements on samples with <200 nm thickness, and to combine the time-of-flight and the photocharge extraction by linearly increasing voltage (photo-CELIV) techniques to investigate charge carrier dynamics over a wide time range. Significant trapping of free electrons is observed in the bulk of dioctyl-substituted PFTBTT (alt-PF8TBTT), introducing a strong relaxation of the charge carrier mobility with time. We used Monte-Carlo simulation to simulate the measured transient data and found that all measurements can be modeled with a single parameter set, with the charge transport behavior determined by multiple trapping and detrapping of electrons in an exponential trap distribution. The influence of the concomitant mobility relaxation on the transient photocurrent characteristics in photo-CELIV experiments is discussed and shown to explain subtle features that were seen in former publications but were not yet assigned to electron trapping. Comparable studies on PFTBTT copolymers with chemical modifications of the side chains and backbone suggest that the observed electron trapping is not caused by a distinct chemical species but rather is related to interchain interactions.

  3. All-optical control of electron trapping in plasma channels

    NASA Astrophysics Data System (ADS)

    Kalmykov, Serguei Y.; Shadwick, Bradley A.; Davoine, Xavier

    2013-10-01

    Generation of background-free, polychromatic electron beams using laser plasma acceleration in longitudinally uniform, mm-length dense plasma channels is demonstrated. Periodic self-injection and acceleration transfers up to 10 percents of the drive pulse energy to several 100-pC charge, GeV-scale-energy electron bunches, each having a few-percent energy spread. Negative chirp of the broad-bandwidth (up to 400 nm), few-Joule-energy driver reduces the nonlinear frequency red-shift, preventing rapid self-steepening of the pulse, whereas the channel suppresses diffraction of the pulse leading edge. The pulse thus remains uncompressed through electron dephasing, strongly reducing unwanted continuous injection. As a bonus, delayed self-compression of the driver extends the dephasing length, boosting electron energy to the GeV level. The number of the quasi-monoenergetic bunches, their charge, energy, and energy separation can be controlled by varying the channel radius and the acceleration length, whereas accumulation of the noise (viz. continuously injected charge) is prevented by the proper dispersion control via negative chirp of the pulse. These clean polychromatic beams can drive tunable, multi-color gamma-ray Compton sources. Supported by the U.S. DOE Grant DE-SC0008382, NSF Grant PHY-1104683, and DOD AFOSR Grant FA9550-11-1-0157. The CALDER-Circ simulations were performed using HPC resources of GENCI-CCRT and GENCI-CINES (grant 2013-057027).

  4. Hydride vapor phase GaN films with reduced density of residual electrons and deep traps

    SciTech Connect

    Polyakov, A. Y.; Smirnov, N. B.; Govorkov, A. V.; Yugova, T. G.; Cox, H.; Helava, H.; Makarov, Yu.; Usikov, A. S.

    2014-05-14

    Electrical properties and deep electron and hole traps spectra are compared for undoped n-GaN films grown by hydride vapor phase epitaxy (HVPE) in the regular process (standard HVPE samples) and in HVPE process optimized for decreasing the concentration of residual donor impurities (improved HVPE samples). It is shown that the residual donor density can be reduced by optimization from ∼10{sup 17} cm{sup −3} to (2–5) × 10{sup 14} cm{sup −3}. The density of deep hole traps and deep electron traps decreases with decreased donor density, so that the concentration of deep hole traps in the improved samples is reduced to ∼5 × 10{sup 13} cm{sup −3} versus 2.9 × 10{sup 16} cm{sup −3} in the standard samples, with a similar decrease in the electron traps concentration.

  5. Photoelectron emission as an alternative electron impact ionization source for ion trap mass spectrometry.

    PubMed

    Gamez, Gerardo; Zhu, Liang; Schmitz, Thomas A; Zenobi, Renato

    2008-09-01

    Electron impact ionization has several known advantages; however, heated filament electron sources have pressure limitations and their power consumption can be significant for certain applications, such as in field-portable instruments. Herein, we evaluate a VUV krypton lamp as an alternative source for ionization inside the ion trap of a mass spectrometer. The observed fragmentation patterns are more characteristic of electron impact ionization than photoionization. In addition, mass spectra of analytes with ionization potentials higher than the lamp's photon energy (10.6 eV) can be easily obtained. A photoelectron impact ionization mechanism is suggested by the observed data allowed by the work function of the ion trap electrodes (4.5 eV), which is well within the lamp's photon energy. In this case, the photoelectrons emitted at the surface of the ion trap end-cap electrode are accelerated by the applied rf field to the ring electrode. This allows the photoelectrons to gain sufficient energy to ionize compounds with high ionization potentials to yield mass spectra characteristic of electron impact. In this manner, electron impact ionization can be used in ion trap mass spectrometers at low powers and without the limitations imposed by elevated pressures on heated filaments.

  6. Direct probing of electron and hole trapping into nano-floating-gate in organic field-effect transistor nonvolatile memories

    SciTech Connect

    Cui, Ze-Qun; Wang, Shun; Chen, Jian-Mei; Gao, Xu; Dong, Bin E-mail: chilf@suda.edu.cn Chi, Li-Feng E-mail: chilf@suda.edu.cn Wang, Sui-Dong E-mail: chilf@suda.edu.cn

    2015-03-23

    Electron and hole trapping into the nano-floating-gate of a pentacene-based organic field-effect transistor nonvolatile memory is directly probed by Kelvin probe force microscopy. The probing is straightforward and non-destructive. The measured surface potential change can quantitatively profile the charge trapping, and the surface characterization results are in good accord with the corresponding device behavior. Both electrons and holes can be trapped into the nano-floating-gate, with a preference of electron trapping than hole trapping. The trapped charge quantity has an approximately linear relation with the programming/erasing gate bias, indicating that the charge trapping in the device is a field-controlled process.

  7. Density-Gradient-Driven trapped-electron-modes in improved-confinement RFP plasmas

    NASA Astrophysics Data System (ADS)

    Duff, James

    2016-10-01

    Short wavelength density fluctuations in improved-confinement MST plasmas exhibit multiple features characteristic of the trapped-electron-mode (TEM), strong evidence that drift wave turbulence emerges in RFP plasmas when transport associated with MHD tearing is reduced. Core transport in the RFP is normally governed by magnetic stochasticity stemming from long wavelength tearing modes that arise from current profile peaking. Using inductive control, the tearing modes are reduced and global confinement is increased to values expected for a comparable tokamak plasma. The improved confinement is associated with a large increase in the pressure gradient that can destabilize drift waves. The measured density fluctuations have frequencies >50 kHz, wavenumbers k_phi*rho_s<0.14, and propagate in the electron drift direction. Their spectral emergence coincides with a sharp decrease in fluctuations associated with global tearing modes. Their amplitude increases with the local density gradient, and they exhibit a density-gradient threshold at R/L_n 15, higher than in tokamak plasmas by R/a. the GENE code, modified for RFP equilibria, predicts the onset of microinstability for these strong-gradient plasma conditions. The density-gradient-driven TEM is the dominant instability in the region where the measured density fluctuations are largest, and the experimental threshold-gradient is close to the predicted critical gradient for linear stability. While nonlinear analysis shows a large Dimits shift associated with predicted strong zonal flows, the inclusion of residual magnetic fluctuations causes a collapse of the zonal flows and an increase in the predicted transport to a level close to the experimentally measured heat flux. Similar circumstances could occur in the edge region of tokamak plasmas when resonant magnetic perturbations are applied for the control of ELMs. Work supported by US DOE.

  8. Electron cyclotron resonance acceleration of electrons to relativistic energies by a microwave field in a mirror trap

    SciTech Connect

    Sergeichev, K. F.; Karfidov, D. M.; Lukina, N. A.

    2007-06-15

    Results are presented from experiments on the acceleration of electrons by a 2.45-GHz microwave field in an adiabatic mirror trap under electron cyclotron resonance conditions, the electric and wave vectors of the wave being orthogonal to the trap axis. At a microwave electric field of {>=}10 V/cm and air pressures of 10{sup -6}-10{sup -4} Torr (the experiments were also performed with helium and argon), a self-sustained discharge was initiated in which a fraction of plasma electrons were accelerated to energies of 0.3-0.5 MeV. After the onset of instability, the acceleration terminated; the plasma decayed; and the accelerated electrons escaped toward the chamber wall, causing the generation of X-ray emission. Estimates show that electrons can be accelerated to the above energies only in the regime of self-phased interaction with the microwave field, provided that the electrons with a relativistically increased mass penetrate into the region with a higher magnetic field. It is shown that the negative-mass instability also can contribute to electron acceleration. The dynamic friction of the fast electrons by neutral particles in the drift space between the resonance zones does not suppress electron acceleration, so the electrons pass into a runaway regime. Since the air molecules excited by relativistic runaway electrons radiate primarily in the red spectral region, this experiment can be considered as a model of high-altitude atmospheric discharges, known as 'red sprites.'.

  9. Electron trapping and acceleration by the plasma wakefield of a self-modulating proton beam

    SciTech Connect

    Lotov, K. V.; Sosedkin, A. P.; Petrenko, A. V.; Amorim, L. D.; Vieira, J.; Fonseca, R. A.; Silva, L. O.; Gschwendtner, E.; Muggli, P.

    2014-12-15

    It is shown that co-linear injection of electrons or positrons into the wakefield of the self-modulating particle beam is possible and ensures high energy gain. The witness beam must co-propagate with the tail part of the driver, since the plasma wave phase velocity there can exceed the light velocity, which is necessary for efficient acceleration. If the witness beam is many wakefield periods long, then the trapped charge is limited by beam loading effects. The initial trapping is better for positrons, but at the acceleration stage a considerable fraction of positrons is lost from the wave. For efficient trapping of electrons, the plasma boundary must be sharp, with the density transition region shorter than several centimeters. Positrons are not susceptible to the initial plasma density gradient.

  10. All electronic approach for high-throughput cell trapping and lysis with electrical impedance monitoring.

    PubMed

    Ameri, Shideh Kabiri; Singh, Pramod K; Dokmeci, Mehmet R; Khademhosseini, Ali; Xu, Qiaobing; Sonkusale, Sameer R

    2014-04-15

    We present a portable lab-on-chip device for high-throughput trapping and lysis of single cells with in-situ impedance monitoring in an all-electronic approach. The lab-on-chip device consists of microwell arrays between transparent conducting electrodes within a microfluidic channel to deliver and extract cells using alternating current (AC) dielectrophoresis. Cells are lysed with high efficiency using direct current (DC) electric fields between the electrodes. Results are presented for trapping and lysis of human red blood cells. Impedance spectroscopy is used to estimate the percentage of filled wells with cells and to monitor lysis. The results show impedance between electrodes decreases with increase in the percentage of filled wells with cells and drops to a minimum after lysis. Impedance monitoring provides a reasonably accurate measurement of cell trapping and lysis. Utilizing an all-electronic approach eliminates the need for bulky optical components and cameras for monitoring.

  11. Variation of deep electron traps created by. gamma. irradiation of GaAs

    SciTech Connect

    Hashizume, T. ); Hasegawa, H. )

    1990-11-01

    The effect of {gamma} irradiation on deep electron states in liquid encapsulated Czochralski (LEC) grown GaAs has been investigated by deep-level transient spectroscopy (DLTS) and photocapacitance measurements. With {gamma} rays of 2{times}10{sup 8} R, EL6 was reduced in concentration by a factor of 3--5, whereas EL3 was increased about one order of magnitude, as compared with those in as-grown material. In addition to {ital E} traps that were previously reported in electron-irradiated material, two new traps were observed near the surface region. From their concentration profiles and annealing behavior, the new traps were most likely created by the interaction of the primary irradiation-induced defects with the grown-in defects. In contrast to these results, neither the DLTS spectrum nor the metastable behavior of EL2 was affected by {gamma} irradiation.

  12. Free-electron maser with high-selectivity Bragg resonator using coupled propagating and trapped modes

    NASA Astrophysics Data System (ADS)

    Ginzburg, N. S.; Golubev, I. I.; Golubykh, S. M.; Zaslavskii, V. Yu.; Zotova, I. V.; Kaminsky, A. K.; Kozlov, A. P.; Malkin, A. M.; Peskov, N. Yu.; Perel'Shteĭn, É. A.; Sedykh, S. N.; Sergeev, A. S.

    2010-10-01

    A free-electron maser (FEM) with a double-mirror resonator involving a new modification of Bragg structures operating on coupled propagating and quasi-cutoff (trapped) modes has been studied. The presence of trapped waves in the feedback chain improves the selectivity of Bragg resonators and ensures stable single-mode generation regime at a considerable superdimensionality of the interaction space. The possibility of using the new feedback mechanism has been confirmed by experiments with a 30-GHz FEM pumped by the electron beam of LIU-3000 (JINR) linear induction accelerator, in which narrow-band generation was obtained at a power of ˜10 MW and a frequency close to the cutoff frequency of the trapped mode excited in the input Bragg reflector.

  13. Identification of electron and hole traps in KH{sub 2}PO{sub 4} crystals

    SciTech Connect

    Garces, N. Y.; Stevens, K. T.; Halliburton, L. E.; Demos, S. G.; Radousky, H. B.; Zaitseva, N. P.

    2001-01-01

    Electron paramagnetic resonance (EPR) has been used to characterize a hole trap and several electron traps in single crystals of potassium dihydrogen phosphate (KH{sub 2}PO{sub 4} or KDP). The paramagnetic charge states of these centers are produced by ionizing radiation (e.g., x rays or a 266 nm beam from a pulsed Nd:YAG laser) and are stable for days and even weeks at room temperature. One center consists of a hole trapped on an oxygen ion adjacent to a silicon impurity located on a phosphorus site. This defect has a small, but easily observed, hyperfine interaction with the adjacent substitutional proton. The other centers are formed when an electron is trapped at an oxygen vacancy. These latter defects are best described as (PO{sub 3}){sup 2-} molecular ions, where the primary phosphorus nucleus is responsible for a large hyperfine splitting (500--800 G in magnitude). Five EPR spectra representing variations of these oxygen vacancy centers are observed, with the differences being attributed to the relative position of a nearby cation vacancy, either a missing proton or potassium. An angular study of the EPR spectra, conducted at room temperature, provided principal values and principal directions for the g matrices and hyperfine matrices for the hole center and two of the electron centers.

  14. Predicting Stored Grain Insect Population Densities Using an Electronic Probe Trap

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Manual sampling of insects in stored grain is a laborious and time consuming process. Automation of grain sampling should help to increase the adoption of stored-grain integrated pest management. A new commercial electronic grain probe trap (OPI Insector™) has recently been marketed. We field tested...

  15. Kinetic Alfven Waves Carrying Intense Field Aligned Currents: Particle Trapping and Electron Acceleration

    NASA Astrophysics Data System (ADS)

    Rankin, R.; Artemyev, A.

    2015-12-01

    It is now common knowledge that dispersive scale Alfvén waves can drive parallel electron acceleration [Lotko et al., JGR, 1998; Samson et al., Ann. Geophys., 2003; Wygant et al., JGR, 2002] and transverse ion energization in the auroral zone and inner magnetosphere [Johnson and Cheng, JGR, 2001; Chaston et al., 2004]. In this paper we show that relatively low energy electrons (plasma sheet electrons with energies ranging up to ˜100 eV) can be accelerated very efficiently as they interact nonlinearly with kinetic Alfvén waves (KAWs) that carry intense field aligned currents from the equatorial plane toward the ionosphere in the inner magnetosphere. We propose a theoretical model describing electron trapping into an effective wave potential generated by parallel wave electric fields (with perpendicular wavelengths on the order of the ion gyro-radius) and the mirror force acting on electrons as they propagate along geomagnetic field lines. We demonstrate that waves with an electric potential amplitude between ~100 - 400 V can trap and accelerate electrons to energies approaching several keVs. Trapping acceleration corresponds to conservation of the electron magnetic moment and, thus, results in a significant decrease of the electron equatorial pitch-angle with time. Analytical and numerical estimates of the maximum energy and probability of trapping are presented. We discuss the application of the proposed model in light of recent observations of electromagnetic fluctuations in the inner magnetosphere that are present during periods of strong geomagnetic activity [Chaston et al., GRL, 2014; Califf et al., JGR, 2015].

  16. Fast Transverse Beam Instability Caused by Electron Cloud Trapped in Combined Function Magnets

    SciTech Connect

    Antipov, Sergey

    2017-01-01

    Electron cloud instabilities affect the performance of many circular high-intensity particle accelerators. They usually have a fast growth rate and might lead to an increase of the transverse emittance and beam loss. A peculiar example of such an instability is observed in the Fermilab Recycler proton storage ring. Although this instability might pose a challenge for future intensity upgrades, its nature had not been completely understood. The phenomena has been studied experimentally by comparing the dynamics of stable and unstable beam, numerically by simulating the build-up of the electron cloud and its interaction with the beam, and analytically by constructing a model of an electron cloud driven instability with the electrons trapped in combined function dipoles. Stabilization of the beam by a clearing bunch reveals that the instability is caused by the electron cloud, trapped in beam optics magnets. Measurements of microwave propagation confirm the presence of the cloud in the combined function dipoles. Numerical simulations show that up to 10$^{-2}$ of the particles can be trapped by their magnetic field. Since the process of electron cloud build-up is exponential, once trapped this amount of electrons significantly increases the density of the cloud on the next revolution. In a combined function dipole this multi-turn accumulation allows the electron cloud reaching final intensities orders of magnitude greater than in a pure dipole. The estimated fast instability growth rate of about 30 revolutions and low mode frequency of 0.4 MHz are consistent with experimental observations and agree with the simulations. The created instability model allows investigating the beam stability for the future intensity upgrades.

  17. METHOD AND APPARATUS FOR INJECTING AND TRAPPING ELECTRONS IN A MAGNETIC FIELD

    DOEpatents

    Christofilos, N.C.

    1962-05-29

    An apparatus is designed for the manipulation of electrons in an exially symmetric magnetic field region and may be employed to trap electrons in such a field by directing an electron beam into a gradientially intensified field region therein to form an annular electron moving axially in the field and along a decreasing field gradient. Dissipative loop circuits such as resistive loops are disposed along at least the decreasing field gradient so as to be inductively coupled to the electron bunch so as to extract energy of the electron bunch and provide a braking force effective to reduce the velocity of the bunch. Accordingly, the electron bunch upon entering a lower intensity magnetic field region is retained therein since the electrons no longer possess sufficient energy to escape. (AEC)

  18. Surface trap mediated electronic transport in biofunctionalized silicon nanowires

    NASA Astrophysics Data System (ADS)

    Puppo, F.; Traversa, F. L.; Di Ventra, M.; De Micheli, G.; Carrara, S.

    2016-08-01

    Silicon nanowires (SiNWs), fabricated via a top-down approach and then functionalized with biological probes, are used for electrically-based sensing of breast tumor markers. The SiNWs, featuring memristive-like behavior in bare conditions, show, in the presence of biomarkers, modified hysteresis and, more importantly, a voltage memory component, namely a voltage gap. The voltage gap is demonstrated to be a novel and powerful parameter of detection thanks to its high-resolution dependence on charges in proximity of the wire. This unique approach of sensing has never been studied and adopted before. Here, we propose a physical model of the surface electronic transport in Schottky barrier SiNW biosensors, aiming at reproducing and understanding the voltage gap based behavior. The implemented model describes well the experimental I-V characteristics of the device. It also links the modification of the voltage gap to the changing concentration of antigens by showing the decrease of this parameter in response to increasing concentrations of the molecules that are detected with femtomolar resolution in real human samples. Both experiments and simulations highlight the predominant role of the dynamic recombination of the nanowire surface states, with the incoming external charges from bio-species, in the appearance and modification of the voltage gap. Finally, thanks to its compactness, and strict correlation with the physics of the nanodevice, this model can be used to describe and predict the I-V characteristics in other nanostructured devices, for different than antibody-based sensing as well as electronic applications.

  19. Quasi-stationary Regime of Tubular Electron Beam Confinement in a Self-consistent Penning-Malmberg trap

    SciTech Connect

    Lapshin, V. I.; Tarasov, I. K.; Tkachenko, I. V.; Tkachenko, V. I.

    2006-01-15

    Results of investigations of collective trap formation for a tubular electron beam which propagates in the conducting cylinder with a longitudinal magnetic field are submitted. It is shown that collective trap forms due to the double potential sag occurrence. Long lived particles accumulation may be theoretically described in the terms of shearless electron tubular beam rotation.

  20. Electrostatic diagnostics of nanosecond pulsed electron beams in a Malmberg-Penning trap

    SciTech Connect

    Paroli, B.; Bettega, G.; Maero, G.; Rome, M.; Norgia, M.; Pesatori, A.; Svelto, C.

    2010-06-15

    A fast electrostatic diagnostic and analysis scheme on nanosecond pulsed beams in the keV energy range has been developed in the Malmberg-Penning trap ELTRAP. Low-noise electronics has been used for the detection of small induced current signals on the trap electrodes. A discrete wavelet-based procedure has been implemented for data postprocessing. The development of an effective electrostatic diagnostics together with proper data analysis techniques is of general interest in view of deducing the beam properties through comparison of the postprocessed data with the theoretically computed signal shape, which contains beam radius, length, and average density as fit parameters.

  1. Trapped electron effects on ICRF Current Drive Predictions in TFTR

    NASA Astrophysics Data System (ADS)

    Wright, John C.; Phillips, Cynthia K.; Bonoli, Paul T.

    1996-11-01

    Most 2D RF modeling codes use a parameterization^1 of current drive efficiencies to calculate fast wave driven currents. Because this parameterization is derived from a ray--tracing model, there are difficulties in applying it to a spectrum of waves. In addition, one cannot account for multiple resonances and coherency effects between the electrons and the waves. These difficulties may be avoided by a direct calculation of the quasilinear diffusion coefficient in an inhomogenous geometry coupled with a full wave code for the field polarizations. Current profiles are then calculated using the adjoint formulation^2, with the magnetic equilibrium specified consistently in both the adjoint routine and the full wave code. This approach has been implemented in the FISIC code^3. Results are benchmarked by comparing a power deposition calculation from conductivity to one from the quasilinear expression. It is shown that the two expressions agree. We quantify differences seen based upon aspect ratio and elongation. The largest discrepancies are seen in the regime of small aspect ratio, and little loss in accuracy for moderate aspect ratios ~>3. This work supported by DoE contract No. DE--AC02--76--CH03073. ^1 D. A. Ehst and C. F. F. Karney, Nucl. Fusion 31, 1933 (1991). ^2 C. F. F. Karney, Computer Physics Reports 4, 183 (1986). ^3 M. Brambilla and T. Krücken, Nucl. Fusion 28, 1813 (1988).

  2. Electron trap level of hydrogen incorporated nitrogen vacancies in silicon nitride

    SciTech Connect

    Sonoda, Ken'ichiro Tsukuda, Eiji; Tanizawa, Motoaki; Yamaguchi, Yasuo

    2015-03-14

    Hydrogen incorporation into nitrogen vacancies in silicon nitride and its effects on electron trap level are analyzed using simulation based on density functional theory with temperature- and pressure-dependent hydrogen chemical potential. If the silicon dangling bonds around a nitrogen vacancy are well separated each other, hydrogen incorporation is energetically stable up to 900 °C, which is in agreement with the experimentally observed desorption temperature. On the other hand, if the dangling bonds strongly interact, the incorporation is energetically unfavorable even at room temperature because of steric hindrance. An electron trap level caused by a nitrogen vacancy becomes shallow by the hydrogen incorporation. An electron is trapped in a deep level created by a silicon dangling bond before hydrogen incorporation, whereas it is trapped in a shallow level created by an anti-bonding state of a silicon-silicon bond after hydrogen incorporation. The simulation results qualitatively explain the experiment, in which reduced hydrogen content in silicon nitride shows superior charge retention characteristics.

  3. Unified Electromagnetic-Electronic Design of Light Trapping Silicon Solar Cells.

    PubMed

    Boroumand, Javaneh; Das, Sonali; Vázquez-Guardado, Abraham; Franklin, Daniel; Chanda, Debashis

    2016-08-08

    A three-dimensional unified electromagnetic-electronic model is developed in conjunction with a light trapping scheme in order to predict and maximize combined electron-photon harvesting in ultrathin crystalline silicon solar cells. The comparison between a bare and light trapping cell shows significant enhancement in photon absorption and electron collection. The model further demonstrates that in order to achieve high energy conversion efficiency, charge separation must be optimized through control of the doping profile and surface passivation. Despite having a larger number of surface defect states caused by the surface patterning in light trapping cells, we show that the higher charge carrier generation and collection in this design compensates the absorption and recombination losses and ultimately results in an increase in energy conversion efficiency. The fundamental physics behind this specific design approach is validated through its application to a 3 μm thick functional light trapping solar cell which shows 192% efficiency enhancement with respect to the bare cell of same thickness. Such a unified design approach will pave the path towards achieving the well-known Shockley-Queisser (SQ) limit for c-Si in thin-film (<30 μm) geometries.

  4. Nitrogen-related electron traps in Ga(As,N) layers (<=3% N)

    NASA Astrophysics Data System (ADS)

    Krispin, P.; Gambin, V.; Harris, J. S.; Ploog, K. H.

    2003-05-01

    Capacitance spectroscopy is used to examine the compositional dependence of deep levels in Si-doped Ga(As,N) layers grown on GaAs. We find two predominant electron traps at about 0.80 and 1.1 eV above the valence band edge EV, which do not depend on composition. For N contents above 0.1% N, the concentration of the acceptor-like gap level at EV+1.1 eV strongly increases and leads to a distinct reduction of the donor doping efficiency in Ga(As,N) layers. Based on theoretical prediction, this electron trap is tentatively associated with a split interstitial defect containing a nitrogen and an arsenic atom on the same As lattice site [(AsN)As]. The trap at EV+0.80 eV likely corresponds to nitrogen dimers, i.e., two N atoms on a single As site [(NN)As]. When approaching the critical layer thickness, this electron trap is increasingly generated during growth. The dimer defect can be removed by rapid thermal annealing at 720 °C after growth, in contrast to the stable bulk level at EV+1.1 eV. By the formation of both N-related defects, the tensile strain in Ga(As,N) is reduced.

  5. Unified Electromagnetic-Electronic Design of Light Trapping Silicon Solar Cells

    PubMed Central

    Boroumand, Javaneh; Das, Sonali; Vázquez-Guardado, Abraham; Franklin, Daniel; Chanda, Debashis

    2016-01-01

    A three-dimensional unified electromagnetic-electronic model is developed in conjunction with a light trapping scheme in order to predict and maximize combined electron-photon harvesting in ultrathin crystalline silicon solar cells. The comparison between a bare and light trapping cell shows significant enhancement in photon absorption and electron collection. The model further demonstrates that in order to achieve high energy conversion efficiency, charge separation must be optimized through control of the doping profile and surface passivation. Despite having a larger number of surface defect states caused by the surface patterning in light trapping cells, we show that the higher charge carrier generation and collection in this design compensates the absorption and recombination losses and ultimately results in an increase in energy conversion efficiency. The fundamental physics behind this specific design approach is validated through its application to a 3 μm thick functional light trapping solar cell which shows 192% efficiency enhancement with respect to the bare cell of same thickness. Such a unified design approach will pave the path towards achieving the well-known Shockley-Queisser (SQ) limit for c-Si in thin-film (<30 μm) geometries. PMID:27499446

  6. Unified Electromagnetic-Electronic Design of Light Trapping Silicon Solar Cells

    NASA Astrophysics Data System (ADS)

    Boroumand, Javaneh; Das, Sonali; Vázquez-Guardado, Abraham; Franklin, Daniel; Chanda, Debashis

    2016-08-01

    A three-dimensional unified electromagnetic-electronic model is developed in conjunction with a light trapping scheme in order to predict and maximize combined electron-photon harvesting in ultrathin crystalline silicon solar cells. The comparison between a bare and light trapping cell shows significant enhancement in photon absorption and electron collection. The model further demonstrates that in order to achieve high energy conversion efficiency, charge separation must be optimized through control of the doping profile and surface passivation. Despite having a larger number of surface defect states caused by the surface patterning in light trapping cells, we show that the higher charge carrier generation and collection in this design compensates the absorption and recombination losses and ultimately results in an increase in energy conversion efficiency. The fundamental physics behind this specific design approach is validated through its application to a 3 μm thick functional light trapping solar cell which shows 192% efficiency enhancement with respect to the bare cell of same thickness. Such a unified design approach will pave the path towards achieving the well-known Shockley-Queisser (SQ) limit for c-Si in thin-film (<30 μm) geometries.

  7. Klein tunnelling and electron trapping in nanometre-scale graphene quantum dots

    NASA Astrophysics Data System (ADS)

    Gutiérrez, Christopher; Brown, Lola; Kim, Cheol-Joo; Park, Jiwoong; Pasupathy, Abhay N.

    2016-11-01

    Relativistic fermions that are incident on a high potential barrier can pass through unimpeded, a striking phenomenon termed the `Klein paradox’ in quantum electrodynamics. Electrostatic potential barriers in graphene provide a solid-state analogue to realize this phenomenon. Here, we use scanning tunnelling microscopy to directly probe the transmission of electrons through sharp circular potential wells in graphene created by substrate engineering. We find that electrons in this geometry display quasi-bound states where the electron is trapped for a finite time before escaping via Klein tunnelling. We show that the continuum Dirac equation can be successfully used to model the energies and wavefunctions of these quasi-bound states down to atomic dimensions. We demonstrate that by tuning the geometry of the barrier it is possible to trap particular energies and angular momentum states with increased efficiency, showing that atomic-scale electrostatic potentials can be used to engineer quantum transport through graphene.

  8. Studying electrons on curved surfaces by trapping and manipulating multielectron bubbles in liquid helium.

    PubMed

    Vadakkumbatt, Vaisakh; Joseph, Emil; Pal, Anustuv; Ghosh, Ambarish

    2014-08-01

    Investigations of two-dimensional electron systems (2DES) have been achieved with two model experimental systems, covering two distinct, non-overlapping regimes of the 2DES phase diagram, namely the quantum liquid phase in semiconducting heterostructures and the classical phases observed in electrons confined above the surface of liquid helium. Multielectron bubbles in liquid helium offer an exciting possibility to bridge this gap in the phase diagram, as well as to study the properties of electrons on curved flexible surfaces. However, this approach has been limited because all experimental studies have so far been transient in nature. Here we demonstrate that it is possible to trap and manipulate multielectron bubbles in a conventional Paul trap for several hundreds of milliseconds, enabling reliable measurements of their physical properties and thereby gaining valuable insight to various aspects of curved 2DES that were previously unexplored.

  9. Atomic origin of high-temperature electron trapping in metal-oxide-semiconductor devices

    SciTech Connect

    Shen, Xiao; Dhar, Sarit; Pantelides, Sokrates T.

    2015-04-06

    MOSFETs based on wide-band-gap semiconductors are suitable for operation at high temperature, at which additional atomic-scale processes that are benign at lower temperatures can get activated, resulting in device degradation. Recently, significant enhancement of electron trapping was observed under positive bias in SiC MOSFETs at temperatures higher than 150 °C. Here, we report first-principles calculations showing that the enhanced electron trapping is associated with thermally activated capturing of a second electron by an oxygen vacancy in SiO{sub 2} by which the vacancy transforms into a structure that comprises one Si dangling bond and a bond between a five-fold and a four-fold Si atoms. The results suggest a key role of oxygen vacancies and their structural reconfigurations in the reliability of high-temperature MOS devices.

  10. High Energy Laboratory Astrophysics Experiments using electron beam ion traps and advanced light sources

    NASA Astrophysics Data System (ADS)

    Brown, Gregory V.; Beiersdorfer, Peter; Bernitt, Sven; Eberle, Sita; Hell, Natalie; Kilbourne, Caroline; Kelley, Rich; Leutenegger, Maurice; Porter, F. Scott; Rudolph, Jan; Steinbrugge, Rene; Traebert, Elmar; Crespo-Lopez-Urritia, Jose R.

    2015-08-01

    We have used the Lawrence Livermore National Laboratory's EBIT-I electron beam ion trap coupled with a NASA/GSFC microcalorimeter spectrometer instrument to systematically address problems found in the analysis of high resolution X-ray spectra from celestial sources, and to benchmark atomic physics codes employed by high resolution spectral modeling packages. Our results include laboratory measurements of transition energies, absolute and relative electron impact excitation cross sections, charge exchange cross sections, and dielectronic recombination resonance strengths. More recently, we have coupled to the Max-Plank Institute for Nuclear Physics-Heidelberg's FLASH-EBIT electron beam ion trap to third and fourth generation advanced light sources to measure photoexcitation and photoionization cross sections, as well as, natural line widths of X-ray transitions in highly charged iron ions. Selected results will be presented.

  11. Dynamic tunneling force microscopy for characterizing electronic trap states in non-conductive surfaces

    SciTech Connect

    Wang, R.; Williams, C. C.

    2015-09-15

    Dynamic tunneling force microscopy (DTFM) is a scanning probe technique for real space mapping and characterization of individual electronic trap states in non-conductive films with atomic scale spatial resolution. The method is based upon the quantum mechanical tunneling of a single electron back and forth between a metallic atomic force microscopy tip and individual trap states in completely non-conducting surface. This single electron shuttling is measured by detecting the electrostatic force induced on the probe tip at the shuttling frequency. In this paper, the physical basis for the DTFM method is unfolded through a physical model and a derivation of the dynamic tunneling signal as a function of several experimental parameters is shown. Experimental data are compared with the theoretical simulations, showing quantitative consistency and verifying the physical model used. The experimental system is described and representative imaging results are shown.

  12. Dynamic tunneling force microscopy for characterizing electronic trap states in non-conductive surfaces.

    PubMed

    Wang, R; Williams, C C

    2015-09-01

    Dynamic tunneling force microscopy (DTFM) is a scanning probe technique for real space mapping and characterization of individual electronic trap states in non-conductive films with atomic scale spatial resolution. The method is based upon the quantum mechanical tunneling of a single electron back and forth between a metallic atomic force microscopy tip and individual trap states in completely non-conducting surface. This single electron shuttling is measured by detecting the electrostatic force induced on the probe tip at the shuttling frequency. In this paper, the physical basis for the DTFM method is unfolded through a physical model and a derivation of the dynamic tunneling signal as a function of several experimental parameters is shown. Experimental data are compared with the theoretical simulations, showing quantitative consistency and verifying the physical model used. The experimental system is described and representative imaging results are shown.

  13. Dynamic tunneling force microscopy for characterizing electronic trap states in non-conductive surfaces

    NASA Astrophysics Data System (ADS)

    Wang, R.; Williams, C. C.

    2015-09-01

    Dynamic tunneling force microscopy (DTFM) is a scanning probe technique for real space mapping and characterization of individual electronic trap states in non-conductive films with atomic scale spatial resolution. The method is based upon the quantum mechanical tunneling of a single electron back and forth between a metallic atomic force microscopy tip and individual trap states in completely non-conducting surface. This single electron shuttling is measured by detecting the electrostatic force induced on the probe tip at the shuttling frequency. In this paper, the physical basis for the DTFM method is unfolded through a physical model and a derivation of the dynamic tunneling signal as a function of several experimental parameters is shown. Experimental data are compared with the theoretical simulations, showing quantitative consistency and verifying the physical model used. The experimental system is described and representative imaging results are shown.

  14. Stretchable carbon nanotube charge-trap floating-gate memory and logic devices for wearable electronics.

    PubMed

    Son, Donghee; Koo, Ja Hoon; Song, Jun-Kyul; Kim, Jaemin; Lee, Mincheol; Shim, Hyung Joon; Park, Minjoon; Lee, Minbaek; Kim, Ji Hoon; Kim, Dae-Hyeong

    2015-05-26

    Electronics for wearable applications require soft, flexible, and stretchable materials and designs to overcome the mechanical mismatch between the human body and devices. A key requirement for such wearable electronics is reliable operation with high performance and robustness during various deformations induced by motions. Here, we present materials and device design strategies for the core elements of wearable electronics, such as transistors, charge-trap floating-gate memory units, and various logic gates, with stretchable form factors. The use of semiconducting carbon nanotube networks designed for integration with charge traps and ultrathin dielectric layers meets the performance requirements as well as reliability, proven by detailed material and electrical characterizations using statistics. Serpentine interconnections and neutral mechanical plane layouts further enhance the deformability required for skin-based systems. Repetitive stretching tests and studies in mechanics corroborate the validity of the current approaches.

  15. Electron trapping and transport by supersonic solitons in one-dimensional systems

    NASA Technical Reports Server (NTRS)

    Zmuidzinas, J. S.

    1978-01-01

    A one-dimensional chain of ions or molecules and electrons described by a Froehlich-type Hamiltonian with quartic phonon anharmonicities is investigated. It is shown that the anharmonic lattice supports supersonic solitons which under favorable circumstances may trap electrons and transport them along the lattice. For a lattice constant/soliton spatial extent quotient of the order of 0.1, rough estimates give electron trapping energies in the meV range. They imply a useful temperature range, up to tens of degrees K, for observing the new effect. The activation energy of a lattice soliton is proportional to the molecular mass and is therefore quite high (about 1 eV) for typical quasi-one-dimensional organic systems.

  16. Nonlinear Upshift of Trapped Electron Mode Critical Density Gradient: Simulation and Experiment

    NASA Astrophysics Data System (ADS)

    Ernst, D. R.

    2012-10-01

    A new nonlinear critical density gradient for pure trapped electron mode (TEM) turbulence increases strongly with collisionality, saturating at several times the linear threshold. The nonlinear TEM threshold appears to limit the density gradient in new experiments subjecting Alcator C-Mod internal transport barriers to modulated radio-frequency heating. Gyrokinetic simulations show the nonlinear upshift of the TEM critical density gradient is associated with long-lived zonal flow dominated states [1]. This introduces a strong temperature dependence that allows external RF heating to control TEM turbulent transport. During pulsed on-axis heating of ITB discharges, core electron temperature modulations of 50% were produced. Bursts of line-integrated density fluctuations, observed on phase contrast imaging, closely follow modulations of core electron temperature inside the ITB foot. Multiple edge fluctuation measurements show the edge response to modulated heating is out of phase with the core response. A new limit cycle stability diagram shows the density gradient appears to be clamped during on-axis heating by the nonlinear TEM critical density gradient, rather than by the much lower linear threshold. Fluctuation wavelength spectra will be quantitatively compared with nonlinear TRINITY/GS2 gyrokinetic transport simulations, using an improved synthetic diagnostic. In related work, we are implementing the first gyrokinetic exact linearized Fokker Planck collision operator [2]. Initial results show short wavelength TEMs are fully stabilized by finite-gyroradius collisional effects for realistic collisionalities. The nonlinear TEM threshold and its collisionality dependence may impact predictions of density peaking based on quasilinear theory, which excludes zonal flows.[4pt] In collaboration with M. Churchill, A. Dominguez, C. L. Fiore, Y. Podpaly, M. L. Reinke, J. Rice, J. L. Terry, N. Tsujii, M. A. Barnes, I. Bespamyatnov, R. Granetz, M. Greenwald, A. Hubbard, J. W

  17. Electron microscopic time-lapse visualization of surface pore filtration on particulate matter trapping process.

    PubMed

    Sanui, Ryoko; Hanamura, Katsunori

    2016-09-01

    A scanning electron microscope (SEM) was used to dynamically visualize the particulate matter (PM) trapping process on diesel particulate filter (DPF) walls at a micro scale as 'time-lapse' images corresponding to the increase in pressure drop simultaneously measured through the DPF. This visualization and pressure drop measurement led to the conclusion that the PM trapping in surface pores was driven by PM bridging and stacking at constricted areas in porous channels. This caused a drastic increase in the pressure drop during PM accumulation at the beginning of the PM trapping process. The relationship between the porous structure of the DPF and the depth of the surface pore was investigated in terms of the porosity distribution and PM penetration depth near the wall surface with respect to depth. The pressure drop calculated with an assumed surface pore depth showed a good correspondence to the measured pressure drop.

  18. Electron Traps Detected in p-type GaAsN Using Deep Level Transient Spectroscopy

    SciTech Connect

    Johnston, S.; Kurtz, S.; Friedman, D.; Ptak, A.; Ahrenkiel, R.; Crandall, R.

    2005-01-01

    The GaAsN alloy can have a band gap as small as 1.0 eV when the nitrogen composition is about 2%. Indium can also be added to the alloy to increase lattice matching to GaAs and Ge. These properties are advantageous for developing a highly-efficient, multi-junction solar cell. However, poor GaAsN cell properties, such as low open-circuit voltage, have led to inadequate performance. Deep-level transient spectroscopy of p-type GaAsN has identified an electron trap having an activation energy near 0.2 eV and a trap density of at least 1016 cm-3. This trap level appears with the addition of small amounts of nitrogen to GaAs, which also corresponds to an increased drop in open-circuit voltage.

  19. Rare-earth neutral metal injection into an electron beam ion trap plasma

    SciTech Connect

    Magee, E. W. Beiersdorfer, P.; Brown, G. V.; Hell, N.

    2014-11-15

    We have designed and implemented a neutral metal vapor injector on the SuperEBIT high-energy electron beam ion trap at the Lawrence Livermore National Laboratory. A horizontally directed vapor of a europium metal is created using a thermal evaporation technique. The metal vapor is then spatially collimated prior to injection into the trap. The source's form and quantity constraints are significantly reduced making plasmas out of metal with vapor pressures ≤10{sup −7} Torr at ≥1000 °C more obtainable. A long pulsed or constant feed metal vapor injection method adds new flexibility by varying the timing of injection and rate of material being introduced into the trap.

  20. EBIT (Electron Beam Ion Trap), N-Division Experimental Physics. Annual report, 1994

    SciTech Connect

    Schneider, D.

    1995-10-01

    The experimental groups in the Electron Beam Ion Trap (EBIT) program continue to perform front-line research with trapped and extracted highly charged ions (HCI) in the areas of ion/surface interactions, atomic spectroscopy, electron-ion interaction and structure measurements, highly charged ion confinement, and EBIT development studies. The ion surface/interaction studies which were initiated five years ago have reached a stage where they an carry out routine investigations, as well as produce breakthrough results towards the development of novel nanotechnology. At EBIT and SuperEBIT studies of the x-ray emission from trapped ions continue to produce significant atomic structure data with high precision for few electron systems of high-Z ions. Furthermore, diagnostics development for magnetic and laser fusion, supporting research for the x-ray laser and weapons programs, and laboratory astrophysics experiments in support of NASA`s astrophysics program are a continuing effort. The two-electron contributions to the binding energy of helium like ions were measured for the first time. The results are significant because their precision is an order of magnitude better than those of competing measurements at accelerators, and the novel technique isolates the energy corrections that are the most interesting. The RETRAP project which was initiated three years ago has reached a stage where trapping, confining and electronic cooling of HCI ions up to Th{sup 80+} can be performed routinely. Measurements of the rates and cross sections for electron transfer from H{sub 2} performed to determine the lifetime of HCI up to Xe{sup q+} and Th{sup q+} (35 {le} q {le} 80) have been studied at mean energies estimated to be {approximately} 5 q eV. This combination of heavy ions with very high charges and very low energies is rare in nature, but may be encountered in planned fusion energy demonstration devices, in highly charged ion sources, or in certain astrophysical events.

  1. Quantum control of a trapped electron spin in a quantum dot using photon polarization.

    PubMed

    Dubin, François; Combescot, Monique; Brennen, Gavin K; Melet, Romain

    2008-11-21

    We present an original scheme to rotate at will one electron spin trapped in a quantum dot by just acting on pump-laser polarization: The quantum control is based on the virtual excitation of electron light-hole pairs with pi symmetry, as possibly done by using a single laser beam with a propagation axis slightly tilted with respect to a weak magnetic field. This allows us to fully control the effective axis of the electron spin rotation through the pump polarization. Our analysis shows that quantum dots with inverted valence states are ideal candidates for ultrafast, high-fidelity, all optical control.

  2. A study of inner zone electron data and their comparison with trapped radiation models

    NASA Technical Reports Server (NTRS)

    Teague, M. J.; Schofield, N. J.; Chan, K. W.; Vette, J. I.

    1979-01-01

    A summary and intercomparison of recent inner radiation zone electron data are presented. The morphology of the inner radiation zone is described and the data compared with the current generation of inner zone trapped electron models. An analytic representation of the inner zone equatorial pitch angle distribution is presented. This model was based upon data from eight satellites and was used to reduce all data to the form of equatorial flux. Although no Starfish-free high energy electron measurements were available from the inner portion of the inner radiation zone, it was found that the AE-6 model provided a good description of the present solar maximum environment.

  3. Laser-driven wavebreaking, electron trapping, and mono-energetic beam production

    NASA Astrophysics Data System (ADS)

    Esarey, Eric

    2006-10-01

    Recent breakthrough results reported in Nature demonstrate that laser-plasma accelerators can produce high quality (e.g., narrow energy spread) electron bunches at the 100 MeV level that may be useful for numerous applications. More recently, high quality electron beams at 1 GeV were produced in experiments at LBNL using 40 TW laser pulse interacting with a 3.3 cm plasma channel. In these experiments, the accelerated electrons were self-trapped from the background plasma, often attributed to the process of wavebreaking. Using a warm fluid model, a general analytic theory of wavebreaking has been developed that is valid for all regimes of interest, i.e., arbitrary temperature and phase velocity. This theory indicates that the maximum electric field obtainable by a relativistic plasma wave is lower that previously calculated. The relation between wavebreaking and particle trapping is discussed, and various quantities, such as the fraction of electrons trapped (i.e., the dark current), are calculated. A variety of methods for particle trapping relevant to present experiments, including 2D wavebreaking, density ramps, and laser injection, will be described. Limitations from dephasing and pump depletion will be summarized. Also presented will be 2D and 3D simulations modeling the production high quality electron beams from laser-plasma accelerators. C.G.R. Geddes et al., Nature 431, 538 (2004); S.P.D. Mangles et al., ibid., p. 535; J. Faure et al., ibid., p. 541. W.P. Leemans et al., submitted. C.B. Schroeder et al., Phys. Rev. E bf 72, 055401 (2005). C.B. Schroeder et al., Phys. Plasmas 13, 033103 (2006). G. Fubiani et al., Phys. Rev. E 73, 026402 (2006).

  4. Compact soft x-ray spectrometer for plasma diagnostics at the Heidelberg Electron Beam Ion Trap

    NASA Astrophysics Data System (ADS)

    Lapierre, A.; Crespo López-Urrutia, J. R.; Baumann, T. M.; Epp, S. W.; Gonchar, A.; González Martínez, A. J.; Liang, G.; Rohr, A.; Soria Orts, R.; Simon, M. C.; Tawara, H.; Versteegen, R.; Ullrich, J.

    2007-12-01

    A compact flat-field soft x-ray grazing-incidence grating spectrometer equipped with a cryogenically cooled back-illuminated charge-coupled device camera was built and implemented at the Heidelberg Electron Beam Ion Trap. The instrument spans the spectral region from 1to37nm using two different gratings. In slitless operation mode, it directly images a radiation source, in this case ions confined in an electron beam ion trap, with high efficiency and reaching hereby a resolving power of λ /Δλ≅130 at 2nm and of λ /Δλ≅600 at 28nm. Capable of automatized operation, its low noise and excellent stability make it an ideal instrument not only for spectroscopic diagnostics requiring wide spectral coverage but also for precision wavelength measurements.

  5. Demonstration of charge breeding in a compact room temperature electron beam ion trap

    SciTech Connect

    Vorobjev, G.; Sokolov, A.; Herfurth, F.; Kester, O.; Quint, W.; Stoehlker, Th.; Thorn, A.; Zschornack, G.

    2012-05-15

    For the first time, a small room-temperature electron beam ion trap (EBIT), operated with permanent magnets, was successfully used for charge breeding experiments. The relatively low magnetic field of this EBIT does not contribute to the capture of the ions; single-charged ions are only caught by the space charge potential of the electron beam. An over-barrier injection method was used to fill the EBIT's electrostatic trap with externally produced, single-charged potassium ions. Charge states as high as K{sup 19+} were reached after about a 3 s breeding time. The capture and breeding efficiencies up to 0.016(4)% for K{sup 17+} have been measured.

  6. The Role of Energy Partitioning on Electron-hole Recombination, Trapping and Detection in Silicon Detectors

    SciTech Connect

    Zhang, Yanwen; Weber, William J

    2010-01-01

    The dynamics of electron-hole (e-h) pair creation and transport in a semiconductor control the fundamental signal response for radiation detection. Extensive studies on silicon detectors have led to contradictory interpretations on the origins of the pulse height defect (PHD) and nonlinear response. In this study, recombination and trapping behaviors of a controlled number of electron-hole pairs produced within different volumes along the ion path are investigated, and the pulse height generated is analyzed in terms of energy partitioning. The results clearly demonstrate that a high recombination rate is not observed for heavy ions; moreover, significant trapping associated with the atomic defects produced by individual ions is responsible for the nonlinear response at low energies and PHD at high energies.

  7. Role of energy partitioning on electron-hole recombination, trapping, and detection in silicon detectors

    SciTech Connect

    Zhang Yanwen; Weber, William J.

    2010-08-15

    The dynamics of electron-hole pair creation and transport in a semiconductor control the fundamental signal response for radiation detection. Extensive studies on silicon detectors have led to contradictory interpretations on the origins of the pulse height defect (PHD) and nonlinear response. In this study, recombination and trapping behaviors of a controlled number of electron-hole pairs produced within different volumes along the ion path are investigated, and the pulse height generated is analyzed in terms of energy partitioning. The results clearly demonstrate that a high recombination rate is not observed for heavy ions; moreover, significant trapping associated with the atomic defects produced by individual ions is responsible for the nonlinear response at low energies and PHD at high energies.

  8. Electron trapping in evolving coronal structures during a large gradual hard X-ray/radio burst

    NASA Technical Reports Server (NTRS)

    Bruggmann, G.; Vilmer, N.; Klein, K.-L.; Kane, S. R.

    1994-01-01

    Gradual hard X-ray/radio bursts are characterized by their long duration, smooth time profile, time delays between peaks at different hard X-ray energies and microwaves, and radiation from extended sources in the low and middle corona. Their characteristic properties have been ascribed to the dynamic evolution of the accelerated electrons in coronal magnetic traps or to the separate acceleration of high-energy electrons in a 'second step' process. The information available so far was drawn from quality considerations of time profiles or even only from the common occurrence of emissions in different spectral ranges. This paper presents model computations of the temporal evolution of hard X-ray and microwave spectra, together with a qualitative discussion of radio lightcurves over a wide spectral range, and metric imaging observations. The basis hypothesis investigated is that the peculiar 'gradual' features can be related to the dynamical evolution of electrons injected over an extended time interval in a coronal trap, with electrons up to relativistic energies being injected simultaneously. The analyzed event (26 April. 1981) is particularly challenging to this hypothesis because of the long time delays between peaks at different X-ray energies and microwave frequencies. The observations are shown to be consistent with the hypothesis, provided that the electrons lose their energy by Coulomb collisions and possibly betatron deceleration. The access of the electrons to different coronal structures varies in the course of the event. The evolution and likely destabilization of part of the coronal plasma-magnetic field configuration is of crucial influence in determining the access to these structures and possibly the dynamical evolution of the trapped electrons through betatron deceleration in the late phase of the event.

  9. The Oxford electron-beam ion trap: A device for spectroscopy of highly charged ions

    NASA Astrophysics Data System (ADS)

    Silver, J. D.; Varney, A. J.; Margolis, H. S.; Baird, P. E. G.; Grant, I. P.; Groves, P. D.; Hallett, W. A.; Handford, A. T.; Hirst, P. J.; Holmes, A. R.; Howie, D. J. H.; Hunt, R. A.; Nobbs, K. A.; Roberts, M.; Studholme, W.; Wark, J. S.; Williams, M. T.; Levine, M. A.; Dietrich, D. D.; Graham, W. G.; Williams, I. D.; O'Neil, R.; Rose, S. J.

    1994-04-01

    An electron-beam ion trap (EBIT) has just been completed in the Clarendon Laboratory, Oxford. The design is similar to the devices installed at the Lawrence Livermore National Laboratory. It is intended that the Oxford EBIT will be used for x-ray and UV spectroscopy of hydrogenic and helium-like ions, laser resonance spectroscopy of hydrogenic ions and measurements of dielectronic recombination cross sections, in order to test current understanding of simple highly charged ions.

  10. Selective ECR heating of trapped/passing electrons in the W7-X stellarator

    SciTech Connect

    Marushchenko, N. B.; Erckmann, V.; Beidler, C. D.; Geiger, J.; Laqua, H. P.; Helander, P.; Maassberg, H.; Turkin, Y.

    2014-02-12

    Using specific features of the magnetic equilibrium in the W7-X stellarator, ECRH scenarios with X2 and X3 modes are discussed. The aim is to explore the possibility of selective heating of the different classes of electrons, passing and trapped, by different RF beams with different frequencies, which can be launched from ports located in different crosssections of the device. Perspectives for this kind of experiments in W7-X are estimated numerically by coupling transport and ray tracing codes.

  11. Multisectional linear ion trap and novel loading method for optical spectroscopy of electron and nuclear transitions.

    PubMed

    Sysoev, Alexey A; Troyan, Victor I; Borisyuk, Peter V; Krasavin, Andrey V; Vasiliev, Oleg S; Palchikov, Vitaly G; Avdeev, Ivan A; Chernyshev, Denis M; Poteshin, Sergey S

    2015-01-01

    There is a growing need for the development of atomic and nuclear frequency standards because of the important contribution of methods for precision time and frequency measurements to the development of fundamental science, technology, and the economy. It is also conditioned by their potential use in optical clocks and quantum logic applications. It is especially important to develop a universal method that could allow one to use ions of most elements effectively (including ones that are not easily evaporated) proposed for the above-mentioned applications. A linear quadrupole ion trap for the optical spectroscopy of electron and nuclear transitions has been developed and evaluated experimentally. An ion source construction is based on an ultra-high vacuum evaporator in which a metal sample is subjected to an electron beam of energy up to 1 keV, resulting in the appearance of gaseous atoms and ions of various charge state. The linear ion trap consists of five successive quadrupole sections including an entrance quadrupole section, quadrupole mass filter, quadrupole ion guide, ion-trap section, and exit quadrupole section. The same radiofrequency but a different direct current voltage feeds the quadrupole sections. The instrument allows the mass and energy selected trapping of ions from ion beams of various intensities and their localization in the area of laser irradiation. The preliminary results presented show that the proposed instrument and methods allow one to produce effectively up to triply charged thorium ions as well as to trap ions for future spectroscopic study. The instrument is proposed for future use in optical clocks and quantum logic application development.

  12. Electron correlation in the self-trapped hole and exciton in the NaCl crystal

    NASA Astrophysics Data System (ADS)

    Puchin, V. E.; Shluger, A. L.; Itoh, N.

    1995-09-01

    An ab initio embedded molecular cluster method was used to find equilibrium configurations of the self-trapped hole (VK center) and self-trapped exciton in the NaCl crystal. The results obtained in the Hartree-Fock approximation are compared with those using the Mo/ller-Plesset second-order perturbation theory (MP2) for the calculation of the electron correlation correction to the total energy. The excitation energies for the VK center and self-trapped exciton (STE) were calculated using the configuration interaction for single excitations (CIS) combined with the MP2 method. It is demonstrated that the Σ band of the optical absorption spectrum of the VK center consists of two bands. These correspond to the intramolecular electron transition in the Cl-2 molecular ion, and the ``host-to-molecule'' transition from the surrounding lattice anions. For the self-trapped exciton, it is found that the atomic structure of the ``off-center'' configuration of the ground state of the triplet STE is not strongly affected by taking account of the electron correlation. In particular, the off-center displacement of the center of mass of the hole component of the STE from the on-center configuration is less than half that corresonding to a pair of nearest F and H centers. The intramolecular distance in the hole component of the STE obtained in this calculation is much shorter than in previous calculations and close to that in the H center. Two Σ polarized transitions with the energies of 3.7 and 4.02 eV were found for the hole component of the ``off-center'' STE. The correlated treatment, in contrast with the Hartree-Fock and one-electron approximations, predicts the existence of the local minimum on the adiabatic potential surface which corresponds to the ``on-center'' STE configuration (electron trapped by the VK center). The calculated energy of optical absorption by the electron component of the triplet STE in this configuration is 0.6 eV and that of the hole component is

  13. EPR study of electron traps in x-ray-irradiated yttria-stabilized zirconia

    SciTech Connect

    Azzoni, C.B.; Paleari, A. )

    1989-10-01

    Single crystals of yttria-stabilized zirconia (12 mol % of Y{sub 2}O{sub 3}) have been x-ray irradiated at room temperature. The electron paramagnetic resonance spectrum of the filled electron traps is analyzed in terms of a single oxygen vacancy type of defect with its symmetry axis along the {l angle}111{r angle} direction. The angular dependence of the linewidth and the asymmetry of the line shape are attributed to the disordered rearrangements of the anion sublattice surrounding the oxygen vacancy. This affects the local crystal fields and the directions of the symmetry axis of the defects.

  14. Dynamic trapping of electrons in the porcupine ionospheric ion beam experiment

    NASA Astrophysics Data System (ADS)

    Bohm, M.; Brenning, N.; Faelthammar, C.-G.

    1992-12-01

    Electrons are needed to maintain quasineutrality in a case where positive ions are injected across the magnetic field into a limited volume in a magnetized plasma. In the absence of collisions, a positive potential builds up and traps the electrons which enter the region along the magnetic field. If the added density of ions exceeds the ambient density, large potential differences along the magnetic field can be maintained this way. The process explains several features of the Porcupine xenon beam injection experiment, where strong magnetic field aligned electric fields were measured in the vicinity of a xenon ion beam which was injected into the ambient ionosphere from a spinning sub payload.

  15. Nonthermally Dominated Electron Acceleration during Magnetic Reconnection in a Low-beta Plasma

    SciTech Connect

    Li, Xiaocan

    2015-07-21

    This work was motivated by electron acceleration during solar flares. After some introductory remarks on proposed particle acceleration mechanisms and questions needing answers, dynamic simulations and simulation results are presented including energy spectra and the formation of the power law distribution. In summary, magnetic reconnection is highly efficient at converting the free magnetic energy stored in a magnetic shear and accelerating electrons to nonthermal energies in low-β regime. The nonthermal electrons have a dominant fraction and form power-law energy spectra with spectral index p ~ 1 in low-β regime. Electrons are preferentially accelerated along the curvature drift direction along the electric field induced by the reconnection outflow. The results can be applied to explain the observations of electron acceleration during solar flares.

  16. Large dielectric constant, high acceptor density, and deep electron traps in perovskite solar cell material CsGeI3

    DOE PAGES

    Ming, Wenmei; Shi, Hongliang; Du, Mao-Hua

    2016-01-01

    Here we report that many metal halides that contain cations with the ns2 electronic configuration have recently been discovered as high-performance optoelectronic materials. In particular, solar cells based on lead halide perovskites have shown great promise as evidenced by the rapid increase of the power conversion efficiency. In this paper, we show density functional theory calculations of electronic structure and dielectric and defect properties of CsGeI3 (a lead-free halide perovskite material). The potential of CsGeI3 as a solar cell material is assessed based on its intrinsic properties. We find anomalously large Born effective charges and a large static dielectric constantmore » dominated by lattice polarization, which should reduce carrier scattering, trapping, and recombination by screening charged defects and impurities. Defect calculations show that CsGeI3 is a p-type semiconductor and its hole density can be modified by varying the chemical potentials of the constituent elements. Despite the reduction of long-range Coulomb attraction by strong screening, the iodine vacancy in CsGeI3 is found to be a deep electron trap due to the short-range potential, i.e., strong Ge–Ge covalent bonding, which should limit electron transport efficiency in p-type CsGeI3. This is in contrast to the shallow iodine vacancies found in several Pb and Sn halide perovskites (e.g., CH3NH3PbI3, CH3NH3SnI3, and CsSnI3). The low-hole-density CsGeI3 may be a useful solar absorber material but the presence of the low-energy deep iodine vacancy may significantly reduce the open circuit voltage of the solar cell. Still, on the other hand, CsGeI3 may be used as an efficient hole transport material in solar cells due to its small hole effective mass, the absence of low-energy deep hole traps, and the favorable band offset with solar absorber materials such as dye molecules and CH3NH3PbI3.« less

  17. Nonthermally dominated electron acceleration during magnetic reconnection in a low-β plasma

    DOE PAGES

    Li, Xiaocan; Guo, Fan; Li, Hui; ...

    2015-09-24

    By means of fully kinetic simulations, we investigate electron acceleration during magnetic reconnection in a nonrelativistic proton–electron plasma with conditions similar to solar corona and flares. We demonstrate that reconnection leads to a nonthermally dominated electron acceleration with a power-law energy distribution in the nonrelativistic low-β regime but not in the high-β regime, where β is the ratio of the plasma thermal pressure and the magnetic pressure. The accelerated electrons contain most of the dissipated magnetic energy in the low-β regime. A guiding-center current description is used to reveal the role of electron drift motions during the bulk nonthermal energization.more » We find that the main acceleration mechanism is a Fermi-type acceleration accomplished by the particle curvature drift motion along the electric field induced by the reconnection outflows. Although the acceleration mechanism is similar for different plasma β, low-β reconnection drives fast acceleration on Alfvénic timescales and develops power laws out of thermal distribution. Thus, the nonthermally dominated acceleration resulting from magnetic reconnection in low-β plasma may have strong implications for the highly efficient electron acceleration in solar flares and other astrophysical systems.« less

  18. Nonthermally dominated electron acceleration during magnetic reconnection in a low-β plasma

    SciTech Connect

    Li, Xiaocan; Guo, Fan; Li, Hui; Li, Gang

    2015-09-24

    By means of fully kinetic simulations, we investigate electron acceleration during magnetic reconnection in a nonrelativistic proton–electron plasma with conditions similar to solar corona and flares. We demonstrate that reconnection leads to a nonthermally dominated electron acceleration with a power-law energy distribution in the nonrelativistic low-β regime but not in the high-β regime, where β is the ratio of the plasma thermal pressure and the magnetic pressure. The accelerated electrons contain most of the dissipated magnetic energy in the low-β regime. A guiding-center current description is used to reveal the role of electron drift motions during the bulk nonthermal energization. We find that the main acceleration mechanism is a Fermi-type acceleration accomplished by the particle curvature drift motion along the electric field induced by the reconnection outflows. Although the acceleration mechanism is similar for different plasma β, low-β reconnection drives fast acceleration on Alfvénic timescales and develops power laws out of thermal distribution. Thus, the nonthermally dominated acceleration resulting from magnetic reconnection in low-β plasma may have strong implications for the highly efficient electron acceleration in solar flares and other astrophysical systems.

  19. NONTHERMALLY DOMINATED ELECTRON ACCELERATION DURING MAGNETIC RECONNECTION IN A LOW-β PLASMA

    SciTech Connect

    Li, Xiaocan; Li, Gang; Guo, Fan; Li, Hui

    2015-10-01

    By means of fully kinetic simulations, we investigate electron acceleration during magnetic reconnection in a nonrelativistic proton–electron plasma with conditions similar to solar corona and flares. We demonstrate that reconnection leads to a nonthermally dominated electron acceleration with a power-law energy distribution in the nonrelativistic low-β regime but not in the high-β regime, where β is the ratio of the plasma thermal pressure and the magnetic pressure. The accelerated electrons contain most of the dissipated magnetic energy in the low-β regime. A guiding-center current description is used to reveal the role of electron drift motions during the bulk nonthermal energization. We find that the main acceleration mechanism is a Fermi-type acceleration accomplished by the particle curvature drift motion along the electric field induced by the reconnection outflows. Although the acceleration mechanism is similar for different plasma β, low-β reconnection drives fast acceleration on Alfvénic timescales and develops power laws out of thermal distribution. The nonthermally dominated acceleration resulting from magnetic reconnection in low-β plasma may have strong implications for the  highly efficient electron acceleration in solar flares and other astrophysical systems.

  20. Impurity-trapped excitons and electron traps in CaF2:Yb2+ and SrF2:Yb2+ probed by transient photoluminescence enhancement

    NASA Astrophysics Data System (ADS)

    Senanayake, P. S.; Wells, J. P. R.; Reid, M. F.; Berden, G.; Meijerink, A.; Reeves, R. J.

    2013-01-01

    CaF$_2$:Yb$^{2+}$ and SrF$_2$:Yb$^{2+}$ crystals have been investigated by a two-color UV + IR transient photoluminescence enhancement technique. The enhancement gives information about both changes in internal energy levels of the excitons and liberation of electrons from traps in the crystals.

  1. Electron Trapping in the Penning Fusion Experiment - Ions (PFX-I)

    NASA Astrophysics Data System (ADS)

    Barnes, D. C.

    1999-11-01

    PFX-I is a table-top, magneto-electrostatic confinement device. Nonneutral confinement and spherical focussing combine to achieve fusion conditions. PFX-I began operation in late '98 as a follow-on to PFX.(T.B. Mitchell, M.M. Schauer, and D.C. Barnes, Phys. Rev. Lett. 78, 58 (1997).) (D.C. Barnes, T.B. Mitchell, and M.M. Schauer, Phys. Plasmas 4, 1745 (1997).) (M.M. Schauer, T.B. Mitchell, M.H. Holzscheiter, and D.C. Barnes, Rev. Sci. Instr. 68, 3340 (1997).) A Penning-type trap confines electrons. Electron space-charge field E confines and spherically focuses high-energy deuterium ions to produce neutrons. Design parameters are: 1 cm spherical radius, applied DC voltage V to 100 kV, steady (superconducting) magnetic field B to over 2 T. The spherical confinement region is axially separated from two end cathodes at -HV, one supplying electrons. We have applied voltages up to 75 kV to the trap, operated the electron gun to 40 kV, and the instrument rack to the full 100 kV. The physical basis and arrangement are briefly described. Initial operation is described. Electron inventory and lifetime t vs. V and B are measured by dumping the electron inventory to a MCP. Up to 3 x 10^8 electrons have been trapped, with t greater than 100 ms. Mechanical alignment may limit t. Results using an improved alignment design are contrasted with the earlier design. E is inferred from electron inventory. Also, an optical diagnostic directly measures E by Stark splitting at low neutral hydrogen pressure (10-5 to 10-8Torr). Light produced by impact excitation is brought out by a fiber to the entrance slit of a spectrometer. Expected splitting of the atomic hydrogen lines of 1 to several Angstroms is compared to initial observations. POPS, a high Q operating mode, has been proposed[4] and an electron configuration for supporting POPS in PFX-I has been described.[5] Plans for future testing of these theoretical predictions are described briefly. An RF system to provide the required 10

  2. Relativistic-Electron-Dominated Solar Flares Observed by Fermi/GBM

    NASA Astrophysics Data System (ADS)

    Shih, A. Y.; Schwartz, R. A.; Dennis, B. R.

    2013-12-01

    Up to tens of percent of the energy released in solar flares goes into accelerating electrons above ~10 keV and ions above ~1 MeV, and the impulsive heating of the ambient solar atmosphere by these particles is partially or wholly responsible for the production of hot flare plasmas (up to ~50 MK). Although flares can accelerate electrons to relativistic energies, in even large flares the typical falling power-law energy spectrum means that the plasma is primarily heated by the much larger number of low-energy electrons. However, there have been flares observed where the electron energy spectra have high low-energy cutoffs (well above ~100 keV), which significantly changes the electron energies responsible for heating and modifies the usual conception of energy transport in a flare. A systematic study of a range of relativistic-electron-dominated flares can improve our understanding of the relevant acceleration processes and how they may differ from those in "typical" flares. We search the Fermi/GBM data set for such flares based on the electron-associated X-ray/gamma-ray bremsstrahlung emission, making use of an improved background-subtraction approach to improve the ability to detect weaker flares. We present the fitted parameters for the relativistic-electron spectrum and their evolution over time, and compare against RHESSI observations and other instruments when available. We also discuss these events in the context of previously observed correlations between relativistic-electron acceleration and ion acceleration in flares.

  3. Excess electron trapping in duplex DNA: long range transfer via stacked adenines.

    PubMed

    Black, Paul J; Bernhard, William A

    2012-11-08

    An understanding of charge transfer (CT) in DNA lies at the root of assessing the risks and benefits of exposure to ionizing radiation. Energy deposition by high-energy photons and fast-charged particles creates holes and excess electrons (EEs) in DNA, and the subsequent reactions determine the complexity of DNA damage and ultimately the risk of disease. Further interest in CT comes from the possibility that hole transfer, excess electron transfer (EET), or both in DNA might be used to develop nanoscale circuits. To study EET in DNA, EPR spectroscopy was used to determine the distribution of EE trapping by oligodeoxynucleotides irradiated and observed at 4 K. Our results indicate that stretches of consecutive adenine bases on the same strand serve as an ideal conduit for intrastrand EET in duplex DNA at 4 K. Specifically, we show that A is an efficient trap for EE at 4 K if, and only if, the A strand of the duplex does not contain one of the other three bases. If there is a T, C, or G on the A strand, then trapping occurs at T or C instead of A. This holds true for stretches up to 32 A's. Whereas T competes effectively against A for the EE, it does not compete effectively against C. Long stretches of T pass the majority of EE to C. Our results show that AT stretches channel EE to cytosine, an end point with significance to both radiation damage and the photochemical repair of pyrimidine dimers.

  4. Distribution of electron traps in SiO2/HfO2 nMOSFET

    NASA Astrophysics Data System (ADS)

    Xiao-Hui, Hou; Xue-Feng, Zheng; Ao-Chen, Wang; Ying-Zhe, Wang; Hao-Yu, Wen; Zhi-Jing, Liu; Xiao-Wei, Li; Yin-He, Wu

    2016-05-01

    In this paper, the principle of discharge-based pulsed I-V technique is introduced. By using it, the energy and spatial distributions of electron traps within the 4-nm HfO2 layer have been extracted. Two peaks are observed, which are located at ΔE ˜ -1.0 eV and -1.43 eV, respectively. It is found that the former one is close to the SiO2/HfO2 interface and the latter one is close to the gate electrode. It is also observed that the maximum discharge time has little effect on the energy distribution. Finally, the impact of electrical stress on the HfO2 layer is also studied. During stress, no new electron traps and interface states are generated. Meanwhile, the electrical stress also has no impact on the energy and spatial distribution of as-grown traps. The results provide valuable information for theoretical modeling establishment, material assessment, and reliability improvement for advanced semiconductor devices. Project supported by the National Natural Science Foundation of China (Grant Nos. 61334002, 61106106, and 61474091), the New Experiment Development Funds for Xidian University, China (Grant No. SY1434), and the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry, China (Grant No. JY0600132501).

  5. Electron Cloud Generation and Trapping in a Quadrupole Magnet at the Los Alamos Proton Storage Ring

    SciTech Connect

    Macek, Robert J.; Browman, Andrew A.; Ledford, John E.; Borden, Michael J.; O'Hara, James F.; McCrady, Rodney C.; Rybarcyk, Lawrence J.; Spickermann, Thomas; Zaugg, Thomas J.; Pivi, Mauro T.F.; /SLAC

    2008-03-17

    Recent beam physics studies on the two-stream e-p instability at the LANL proton storage ring (PSR) have focused on the role of the electron cloud generated in quadrupole magnets where primary electrons, which seed beam-induced multipacting, are expected to be largest due to grazing angle losses from the beam halo. A new diagnostic to measure electron cloud formation and trapping in a quadrupole magnet has been developed, installed, and successfully tested at PSR. Beam studies using this diagnostic show that the 'prompt' electron flux striking the wall in a quadrupole is comparable to the prompt signal in the adjacent drift space. In addition, the 'swept' electron signal, obtained using the sweeping feature of the diagnostic after the beam was extracted from the ring, was larger than expected and decayed slowly with an exponential time constant of 50 to 100 {micro}s. Other measurements include the cumulative energy spectra of prompt electrons and the variation of both prompt and swept electron signals with beam intensity. Experimental results were also obtained which suggest that a good fraction of the electrons observed in the adjacent drift space for the typical beam conditions in the 2006 run cycle were seeded by electrons ejected from the quadrupole.

  6. Theory and experiments of electron-hole recombination at silicon/silicon dioxide interface traps and tunneling in thin oxide MOS transistors

    NASA Astrophysics Data System (ADS)

    Cai, Jin

    2000-10-01

    Surface recombination and channel have dominated the electrical characteristics, performance and reliability of p/n junction diodes and transistors. This dissertation uses a sensitive direct-current current voltage (DCIV) method to measure base terminal currents (IB) modulated by the gate bias (VGB) and forward p/n junction bias (VPN) in a MOS transistor (MOST). Base terminal currents originate from electron-hole recombination at Si/SiO2 interface traps. Fundamental theories which relate DCIV characteristics to device and material parameters are presented. Three theory-based applications are demonstrated on both the unstressed as well as hot-carrier-stressed MOSTs: (1) determination of interface trap density and energy levels, (2) spatial profile of interface traps in the drain/base junction-space-charge region and in the channel region, and (3) determination of gate oxide thickness and impurity doping concentrations. The results show that interface trap energy levels are discrete, which is consistent with those from silicon dangling bonds; in unstressed MOS transistors interface trap density in the channel region rises sharply toward source and drain, and after channel-hot-carrier stress, interface trap density increases mostly in the junction space-charge region. As the gate oxide thins below 3 nm, the gate oxide leakage current via quantum mechanical tunneling becomes significant. A gate oxide tunneling theory which refined the traditional WKB tunneling probability is developed for modeling tunneling currents at low electric fields through a trapezoidal SiO2 barrier. Correlation with experimental data on thin oxide MOSTs reveals two new results: (1) hole tunneling dominates over electron tunneling in p+gate p-channel MOSTs, and (2) the small gate/drain overlap region passes higher tunneling currents than the channel region under depletion to flatband gate voltages. The good theory-experimental correlation enables the extraction of impurity doping concentrations

  7. Effects of traps and polarization charges on device performance of AlGaN/GaN high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Hussein, A. SH.; Ghazai, Alaa J.; Salman, Emad A.; Hassan, Z.

    2013-11-01

    This paper presents the simulated electrical characteristics of AlGaN/GaN high electron mobility transistors (HEMTs) by using ISE TCAD software. The effects of interface traps, bulk traps and polarization charges are investigated. It was observed that the role and dynamic of traps affect the device performance which requires a precondition to calculate the DC characteristics that are in agreement with the experimental data. On the other hand, polarization charges lead to quantum confinement of the electrons in the channel and form two-dimensional electron gas. The electron quantization leads to increasing the drain current and shift in the threshold voltage. The device performance can be improved by optimizing the fixed interface charge and thus reducing the bulk traps to enhance the DC characteristics.

  8. Investigation of nonextensivity trapped electrons effect on the solitary ion-acoustic wave using fractional Schamel equation

    NASA Astrophysics Data System (ADS)

    Nazari-Golshan, A.

    2016-08-01

    Ion-acoustic (IA) solitary wave propagation is investigated by solving the fractional Schamel equation (FSE) in a homogenous system of unmagnetized plasma. This plasma consists of the nonextensive trapped electrons and cold fluid ions. The effects of the nonextensive q-parameter, electron trapping, and fractional parameter have been studied. The FSE is derived by using the semi-inverse and Agrawal's methods. The analytical results show that an increase in the amount of electron trapping and nonextensive q-parameter increases the soliton ion-acoustic amplitude in agreement with the previously obtained results. However, it is vice-versa for the fractional parameter. This feature leads to the fact that the fractional parameter may be used to increase the IA soliton amplitude instead of increasing electron trapping and nonextensive parameters.

  9. A high-current electron gun for the electron beam ion trap at the National Superconducting Cyclotron Laboratory

    SciTech Connect

    Schwarz, S. Baumann, T. M.; Kittimanapun, K.; Lapierre, A.; Snyder, A.

    2014-02-15

    The Electron Beam Ion Trap (EBIT) in NSCL’s reaccelerator ReA uses continuous ion injection and accumulation. In order to maximize capture efficiency and minimize breeding time into high charge states, the EBIT requires a high-current/high current-density electron beam. A new electron gun insert based on a concave Ba-dispenser cathode has been designed and built to increase the current transmitted through the EBIT’s superconducting magnet. With the new insert, stable EBIT operating conditions with 0.8 A of electron beam have been established. The design of the electron gun is presented together with calculated and measured perveance data. In order to assess the experimental compression of the electron beam, a pinhole CCD camera has been set up to measure the electron beam radius. The camera observes X-rays emitted from highly charged ions, excited by the electron beam. Initial tests with this camera setup will be presented. They indicate that a current density of 640 A/cm{sup 2} has been reached when the EBIT magnet was operated at 4 T.

  10. Trapped electron acceleration by a laser-driven relativistic plasma wave

    NASA Astrophysics Data System (ADS)

    Everett, M.; Lal, A.; Gordon, D.; Clayton, C. E.; Marsh, K. A.; Joshi, C.

    1994-04-01

    THE aim of new approaches for high-energy particle acceleration1 is to push the acceleration rate beyond the limit (~100 MeV m-1) imposed by radio-frequency breakdown in conventional accelerators. Relativistic plasma waves, having phase velocities very close to the speed of light, have been proposed2-6 as a means of accelerating charged particles, and this has recently been demonstrated7,8. Here we show that the charged particles can be trapped by relativistic plasma waves-a necessary condition for obtaining the maximum amount of energy theoretically possible for such schemes. In our experiments, plasma waves are excited in a hydrogen plasma by beats induced by two collinear laser beams, the difference in whose frequencies matches the plasma frequency. Electrons with an energy of 2 MeV are injected into the excited plasma, and the energy spectrum of the exiting electrons is analysed. We detect electrons with velocities exceeding that of the plasma wave, demonstrating that some electrons are 'trapped' by the wave potential and therefore move synchronously with the plasma wave. We observe a maximum energy gain of 28 MeV, corresponding to an acceleration rate of about 2.8 GeV m-1.

  11. Predicting stored grain insect population densities using an electronic probe trap.

    PubMed

    Flinn, P W; Opit, G P; Throne, J E

    2009-08-01

    Manual sampling of insects in stored grain is a laborious and time-consuming process. Automation of grain sampling should help to increase the adoption of stored grain integrated pest management. A new commercial electronic grain probe trap (OPI Insector) has recently been marketed. We field tested OPI Insector electronic grain probes in two bins, each containing 32.6 tonnes of wheat, Triticum aestivum L., over a 2-yr period. We developed new statistical models to convert Insector catch into insects per kilogram. We compared grain sample estimates of insect density (insects per kilogram of wheat) taken near each Insector to the model-predicted insect density by using Insector counts. An existing expert system, Stored Grain Advisor Pro, was modified to automatically read the Insector database and use the appropriate model to estimate Cryptolestes ferrugineus (Stephens), Rhyzopertha dominica (F.), and Tribolium castaneum (Herbst) density from trap catch counts. Management decisions using Insector trap-catch estimates for insect density were similar to those made using grain sample estimates of insect density for most sampling dates. However, because of the similarity in size of R. dominica and T. castaneum, the software was unable to differentiate counts between these two species. In the central and southern portions of the United States, where both species frequently occur, it may be necessary to determine the proportion of each species present in the grain by manual inspection of trap catch. The combination of SGA Pro with the OPI Insector system should prove to be a useful tool for automatic monitoring of insect pests in stored grain.

  12. Electron dominated thermoelectric response in MNiSn (M: Ti, Zr, Hf) half-Heusler alloys.

    PubMed

    Gandi, Appala Naidu; Schwingenschlögl, Udo

    2016-05-18

    We solve the transport equations of the electrons and phonons to understand the thermoelectric behaviour of the technologically important half-Heusler alloys MNiSn (M: Ti, Zr, Hf). Doping is simulated within the rigid band approximation. We clarify the origin of the electron dominated thermoelectric response and determine the carrier concentrations with maximal figures of merit. The phonon mean free path is studied to calculate the grain size below which grain refinement methods can enforce ballistic heat conduction to enhance the figure of merit.

  13. Thermal and optical excitation of trapped electrons in high-density polyethylene (HDPE) studied through positron annihilation

    NASA Astrophysics Data System (ADS)

    Nahid, F.; Zhang, J. D.; Yu, T. F.; Ling, C. C.; Fung, S.; Beling, C. D.

    2011-04-01

    Positronium (Ps) formation in high-density polyethylene (HDPE) has been studied below the glass transition temperature. The formation probability increases with positron irradiation time due to an increasing number of inter-track trapped electrons becoming available for positron capture. The temperature variation of the saturated Ps level is discussed in different models. The quenching of trapped electrons by light has been studied and the optical de-trapping cross-section for different photon energies has been estimated over the visible region.

  14. Shaping of nested potentials for electron cooling of highly-charged ions in a cooler Penning trap

    NASA Astrophysics Data System (ADS)

    Paul, Stefan; Kootte, Brian; Lascar, Daniel; Gwinner, Gerald; Dilling, Jens; Titan Collaboration

    2016-09-01

    TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN) is dedicated to mass spectrometry and decay spectroscopy of short-lived radioactive nuclides in a series of ion traps including a precision Penning trap. In order to boost the achievable precision of mass measurements TITAN deploys an Electron Beam Ion Trap (EBIT) providing Highly-Charged Ions (HCI). However, the charge breeding process in the EBIT leads to an increase in the ion bunch's energy spread which is detrimental to the overall precision gain. To reduce this effect a new cylindrical Cooler PEnning Trap (CPET) is being commissioned to sympathetically cool the HCI via a simultaneously trapped electron plasma. Simultaneous trapping of ions and electrons requires a high level of control over the nested potential landscape and sophisticated switching schemes for the voltages on CPET's multiple ring electrodes. For this purpose, we are currently setting up a new experimental control system for multi-channel voltage switching. The control system employs a Raspberry Pi communicating with a digital-to-analog board via a serial peripheral interface. We report on the implementation of the voltage control system and its performance with respect to electron and ion manipulation in CPET. University of British Columbia, Vancouver, BC, Canada.

  15. Electron paramagnetic resonance studies of electron and hole traps related to optical damage in KTiOPO(4)

    NASA Astrophysics Data System (ADS)

    Setzler, Scott Douglas

    Electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) studies have been performed on flux-grown and hydrothermal-grown potassium titanyl phosphate (KTiOPOsb4, or KTP) crystals. Four radiation-induced tapped-electron centers have been identified and a complete angular dependence analysis has provided spin-Hamiltonian parameters for each center. Either near-band-edge laser light (355-nm third-harmonic output from a Nd:YAG laser) or 60-kV x-rays can be used to produce the defects. These electron traps are perturbed Tisp{3+} ions, where the perturbation acts to stabilize the electron. Hyperfine parameters have been used to deduce that protons (in the form of OH-ions) act to stabilize the electron in hydrothermal material, while the stabilization in flux material probably comes from divalent impurities and oxygen vacancies. The thermal stability of the centers varies from 150 K to 300 K. The principal g values have been used to confirm that the titanium centers have related optical absorption bands in the visible region. Preliminary transient absorption experiments have been developed to measure the lifetime of the induced absorption. It is postulated that these centers can be formed during normal device operation and are closely related to the "gray-track" effect. Additional analysis has also been performed on the previously identified radiation-induced trapped-hole center (Edwards et. al., Phys. Rev. B 48, 6884 (1993)). The g values and hyperfine parameters are revised though the defect model remains unchanged.

  16. Nonlinear density excitations in electron-positron-ion plasmas with trapping in a quantizing magnetic field

    NASA Astrophysics Data System (ADS)

    Iqbal, M. J.; Masood, W.; Shah, H. A.; Tsintsadze, N. L.

    2017-01-01

    In the present work, we have investigated the effect of trapping as a microscopic phenomenon on the formation of solitary structures in the presence of a quantizing magnetic field in an electron-positron-ion (e-p-i) plasma having degenerate electrons and positrons, whereas ions are taken to be classical and cold. We have found that positron concentration, quantizing magnetic field, and finite electron temperature effects not only affect the linear dispersion characteristics of the electrostatic waves under consideration but also have a significant bearing on the propagation of solitary structures in the nonlinear regime. Importantly, the system under consideration has been found to allow the formation of compressive solitary structures only. The work presented here may be beneficial to understand the propagation of nonlinear electrostatic structures in dense astrophysical environments and in intense-laser plasma interactions.

  17. Angular-momentum-dominated electron beams and flat-beam generation

    SciTech Connect

    Sun, Yin-e

    2005-06-01

    In the absence of external forces, if the dynamics within an electron beam is dominated by its angular momentum rather than other effects such as random thermal motion or self Coulomb-repulsive force (i.e., space-charge force), the beam is said to be angular-momentum-dominated. Such a beam can be directly applied to the field of electron-cooling of heavy ions; or it can be manipulated into an electron beam with large transverse emittance ratio, i.e., a flat beam. A flat beam is of interest for high-energy electron-positron colliders or accelerator-based light sources. An angular-momentum-dominated beam is generated at the Fermilab/NICADD photoinjector Laboratory (FNPL) and is accelerated to an energy of 16 MeV. The properties of such a beam is investigated systematically in experiment. The experimental results are in very good agreement with analytical expectations and simulation results. This lays a good foundation for the transformation of an angular-momentum-dominated beam into a flat beam. The round-to-flat beam transformer is composed of three skew quadrupoles. Based on a good knowledge of the angular-momentum-dominated beam, the quadrupoles are set to the proper strengths in order to apply a total torque which removes the angular momentum, resulting in a flat beam. For bunch charge around 0.5 nC, an emittance ratio of 100 ± 5 was measured, with the smaller normalized root-mean-square emittance around 0.4 mm-mrad. Effects limiting the flat-beam emittance ratio are investigated, such as the chromatic effects in the round-to-flat beam transformer, asymmetry in the initial angular-momentum-dominated beam, and space-charge effects. The most important limiting factor turns out to be the uncorrelated emittance growth caused by space charge when the beam energy is low, for example, in the rf gun area. As a result of such emittance growth prior to the round-to-flat beam transformer, the emittance ratio achievable in simulation decreases from orders of thousands to

  18. Collisionless reversed magnetic shear trapped electron instability and contribution of sidebands to anomalous transport

    NASA Astrophysics Data System (ADS)

    Rogister, André L.; Singh, Raghvendra

    2005-11-01

    By keeping account of the trapped electron ∇B and curvature drifts, it is found that the spatial decay of the collisionless electron drift wave is governed either by the trapped electron response or by the resonant interaction of ions with the sidebands of the primary oscillation. In the former case, pairs of spatially bounded unstable and damped solutions are obtained for negative magnetic shear (ŝ<0) if, as usual, LTe=1/∂rlnTe<0; there are no bounded solutions if ŝLTe<0. In the latter case, there is either a set of bounded damped solutions if ηi>0 or a set of bounded unstable solutions if ηi<0. The unstable modes have a radiating character and the growth rates are γ ˜(2n+1)√1+2q2 ∣ŝ∣∣LNωe*/qR∣ (n is the Hermite polynomial solution index, q the safety factor, ŝ the magnetic shear parameter, R the major radius, ωe* the electron diamagnetic frequency, LN=1/∂rlnNe, and ηi=LN/LTi).The sidebands are responsible for unusually large ratios Qe/TeΓe, where Qe and Γe are the anomalous electron energy flux and the particle flux. These results may explain the box-type Te profile observed in lower hybrid current drive reversed magnetic shear plasmas on the Japan Atomic Energy Research Institute Tokamak 60 Upgrade (JT-60U) [H. Ninomiya and the JT-60U Team, Phys. Fluids B 4, 2070 (1992)]. It is finally demonstrated that the ballooning hypothesis generally leads to conflicting requirements: it is thus hardly relevant for the electron drift branch! The "radiating" boundary condition that has formerly been imposed on the slab solution is finally discussed.

  19. Trapped electron plasma formation and equilibrium with a low-power radio-frequency drive

    SciTech Connect

    Romé, M.; Maero, G.; Paroli, B.; Pozzoli, R.; Chen, S.

    2015-06-29

    Penning-Malmberg traps confining electron plasmas usually rely on external sources like thermo- and photocathodes. It has been already demonstrated that electron plasmas of comparable densities can be produced by applying a radio-frequency (RF) power to any inner electrode of the trap. Such excitation may result in significant electron heating and ionization of the residual gas with the formation of a plasma column when the RF frequency is of the order or larger than the typical axial bounce frequencies of few-eV electrons, even at RF amplitude of few volts. While discharges are common in plasma generation at higher pressures and RF power, this mechanism is not yet well explored in our working conditions, namely ultra-high vacuum and very low RF power. This plasma production mechanism is very sensitive to the experimental conditions. Interesting phenomena can be observed: transition from a diffuse to a narrow-section, denser plasma column; presence of low-order diocotron modes in transient and steady-state plasmas; modulation of the m=1 diocotron mode and suppression of its instability despite the presence of positive ions and resistive loads. These observations are reported here, and possible explanations are discussed. In addition, a possible electron heating mechanism is investigated with a single-particle, one-dimensional model described by an area-preserving map where an electron bounces within a square potential well and the RF excitation is modelled by a time-oscillating square barrier. The low-energy part of the Poincaré plot includes both quasi-periodic and chaotic regions, where heating up to ionization energies is achievable. Results of a systematic analysis of the map extracting its chaotic properties and scaling laws as a function of the control parameters are reported.

  20. Trapped electron plasma formation and equilibrium with a low-power radio-frequency drive

    NASA Astrophysics Data System (ADS)

    Romé, M.; Chen, S.; Maero, G.; Paroli, B.; Pozzoli, R.

    2015-06-01

    Penning-Malmberg traps confining electron plasmas usually rely on external sources like thermo- and photocathodes. It has been already demonstrated that electron plasmas of comparable densities can be produced by applying a radio-frequency (RF) power to any inner electrode of the trap. Such excitation may result in significant electron heating and ionization of the residual gas with the formation of a plasma column when the RF frequency is of the order or larger than the typical axial bounce frequencies of few-eV electrons, even at RF amplitude of few volts. While discharges are common in plasma generation at higher pressures and RF power, this mechanism is not yet well explored in our working conditions, namely ultra-high vacuum and very low RF power. This plasma production mechanism is very sensitive to the experimental conditions. Interesting phenomena can be observed: transition from a diffuse to a narrow-section, denser plasma column; presence of low-order diocotron modes in transient and steady-state plasmas; modulation of the m=1 diocotron mode and suppression of its instability despite the presence of positive ions and resistive loads. These observations are reported here, and possible explanations are discussed. In addition, a possible electron heating mechanism is investigated with a single-particle, one-dimensional model described by an area-preserving map where an electron bounces within a square potential well and the RF excitation is modelled by a time-oscillating square barrier. The low-energy part of the Poincaré plot includes both quasi-periodic and chaotic regions, where heating up to ionization energies is achievable. Results of a systematic analysis of the map extracting its chaotic properties and scaling laws as a function of the control parameters are reported.

  1. Studies on the Enantioselective Iminium Ion Trapping of Radicals Triggered by an Electron-Relay Mechanism

    PubMed Central

    2017-01-01

    A combination of electrochemical, spectroscopic, computational, and kinetic studies has been used to elucidate the key mechanistic aspects of the previously reported enantioselective iminium ion trapping of photochemically generated carbon-centered radicals. The process, which provides a direct way to forge quaternary stereocenters with high fidelity, relies on the interplay of two distinct catalytic cycles: the aminocatalytic electron-relay system, which triggers the stereoselective radical trap upon iminium ion formation, and the photoredox cycle, which generates radicals under mild conditions. Critical to reaction development was the use of a chiral amine catalyst, bearing a redox-active carbazole unit, which could rapidly reduce the highly reactive and unstable intermediate generated upon radical interception. The carbazole unit, however, is also involved in another step of the electron-relay mechanism: the transiently generated carbazole radical cation acts as an oxidant to return the photocatalyst into the original state. By means of kinetic and spectroscopic studies, we have identified the last redox event as being the turnover-limiting step of the overall process. This mechanistic framework is corroborated by the linear correlation between the reaction rate and the reduction potential of the carbazole unit tethered to the aminocatalyst. The redox properties of the carbazole unit can thus be rationally tuned to improve catalytic activity. This knowledge may open a path for the mechanistically driven design of the next generation of electron-relay catalysts. PMID:28281754

  2. Electron and boson clusters in confined geometries: Symmetry breaking in quantum dots and harmonic traps

    PubMed Central

    Yannouleas, Constantine; Landman, Uzi

    2006-01-01

    We discuss the formation of crystalline electron clusters in semiconductor quantum dots and of crystalline patterns of neutral bosons in harmonic traps. In a first example, we use calculations for two electrons in an elliptic quantum dot to show that the electrons can localize and form a molecular dimer. The calculated singlet–triplet splitting (J) as a function of the magnetic field (B) agrees with cotunneling measurements with its behavior reflecting the effective dissociation of the dimer for large B. Knowledge of the dot shape and of J(B) allows determination of the degree of entanglement. In a second example, we study strongly repelling neutral bosons in two-dimensional harmonic traps. Going beyond the Gross–Pitaevskii (GP) mean-field approximation, we show that bosons can localize and form polygonal-ring-like crystalline patterns. The total energy of the crystalline phase saturates in contrast to the GP solution, and its spatial extent becomes smaller than that of the GP condensate. PMID:16740665

  3. Dissociative electron attachment in nanoscale ice films: Thickness and charge trapping effects

    SciTech Connect

    Simpson, W.C.; Orlando, T.M.

    1998-03-01

    The yield and kinetic energy (KE) distributions of D{sup {minus}} ions produced via dissociative electron attachment (DEA) resonances in nanoscale D{sub 2}O ice films are collected as a function of film thickness. The {sup 2}B{sub 1}, {sup 2}A{sub 1}, and {sup 2}B{sub 2} DEA resonances shift to higher energies and their D{sup {minus}} ion yields first increase and then decrease as the D{sub 2}O films thicken. The D{sup {minus}} KE distributions also shift to higher energy with increasing film thickness. We interpret the changes in the DEA yield and the D{sup {minus}} KE distributions in terms of modifications in the electronic and geometric structure of the surface of the film as it thickens. A small amount of charge build-up occurs following prolonged electron beam exposure at certain energies, which primarily affects the D{sup {minus}} KE distributions. Charge trapping measurements indicate that an enhancement in the trapping cross section occurs at energies near zero and between 6 and 10 eV. {copyright} {ital 1998 American Institute of Physics.}

  4. Enhanced stabilisation of trapped electron modes by collisional energy scattering in tokamaks

    SciTech Connect

    Manas, P.; Camenen, Y.; Benkadda, S.; Hornsby, W. A.; Peeters, A. G.

    2015-06-15

    The collisional stabilisation via energy scattering and pitch-angle scattering of micro-instabilities in tokamak plasmas is investigated by means of gyrokinetic simulations with a special emphasis on the often neglected energy scattering operator. It is shown that in the linear regime energy scattering has a negligible effect on Ion Temperature Gradient (ITG) modes but enhances the stabilisation of Trapped Electron Modes (TEM) in presence of nonzero ion temperature and density gradients. This stabilisation is sensitive to the model used for the energy restoring term in the collision operator. The contributions of parallel and drift motion to the total growth rate in velocity space are used to characterize the complex stabilisation mechanisms behind pitch-angle and energy scattering for a range of relevant parameters such as the magnetic shear, the collisionality, the logarithmic density gradient, and the logarithmic ion temperature gradient. It is shown that depending on these parameters, energy scattering stabilisation of TEM can be either due to a decrease of the contribution from drifting trapped electrons or to an increase of the contribution from the parallel motion of passing electrons. Finally, for a standard ITG/TEM case, the effect of energy scattering on the nonlinear heat and particle fluxes is investigated.

  5. Studies on the Enantioselective Iminium Ion Trapping of Radicals Triggered by an Electron-Relay Mechanism.

    PubMed

    Bahamonde, Ana; Murphy, John J; Savarese, Marika; Brémond, Éric; Cavalli, Andrea; Melchiorre, Paolo

    2017-03-29

    A combination of electrochemical, spectroscopic, computational, and kinetic studies has been used to elucidate the key mechanistic aspects of the previously reported enantioselective iminium ion trapping of photochemically generated carbon-centered radicals. The process, which provides a direct way to forge quaternary stereocenters with high fidelity, relies on the interplay of two distinct catalytic cycles: the aminocatalytic electron-relay system, which triggers the stereoselective radical trap upon iminium ion formation, and the photoredox cycle, which generates radicals under mild conditions. Critical to reaction development was the use of a chiral amine catalyst, bearing a redox-active carbazole unit, which could rapidly reduce the highly reactive and unstable intermediate generated upon radical interception. The carbazole unit, however, is also involved in another step of the electron-relay mechanism: the transiently generated carbazole radical cation acts as an oxidant to return the photocatalyst into the original state. By means of kinetic and spectroscopic studies, we have identified the last redox event as being the turnover-limiting step of the overall process. This mechanistic framework is corroborated by the linear correlation between the reaction rate and the reduction potential of the carbazole unit tethered to the aminocatalyst. The redox properties of the carbazole unit can thus be rationally tuned to improve catalytic activity. This knowledge may open a path for the mechanistically driven design of the next generation of electron-relay catalysts.

  6. Differential spectra and phase space densities of trapped electrons at Jupiter

    NASA Technical Reports Server (NTRS)

    Mcilwain, C. E.; Fillius, R. W.

    1975-01-01

    Using Pioneer 10 data, differential spectra and phase-space densities have been constructed for trapped electrons at Jupiter. These quantities should assist in calculating synchrotron radiation from these particles and in evaluating the diffusion mechanisms that accelerate the particles. Absorption by the moons Io and Europa is evident, and injection by Io is demonstrated by a density peak in phase space, which demands a local source. There is also a rapid decrease in density between the moons, which could call for either a local loss mechanism or nonlocal losses fed by diffusion.

  7. Finite Larmor radius effects on the coupled trapped electron and ion temperature gradient modes

    SciTech Connect

    Sandberg, I.; Isliker, H.; Pavlenko, V. P.

    2007-09-15

    The properties of the coupled trapped electron and toroidal ion temperature gradient modes are investigated using the standard reactive fluid model and taking rigorously into account the effects attributed to the ion polarization drift and to the drifts associated with the lowest-order finite ion Larmor radius effects. In the flat density regime, where the coupling between the modes is relatively weak, the properties of the unstable modes are slightly modified through these effects. For the peak density regions, where the coupling of the modes is rather strong, these second-order drifts determine the spectra of the unstable modes near the marginal conditions.

  8. Irreversible event-based model for thermal emission of electrons from isolated traps

    NASA Astrophysics Data System (ADS)

    Dimitrijev, Sima

    2009-05-01

    In spite of the irreversible nature of macroscopic processes, our understanding of the fundamental physical phenomena remains limited to reversible models (the Loschmidt's paradox). We propose a direct irreversible model for the probability per unit time that an electron will be emitted from an isolated trap. This resolves a number of problems, including (1) the dubious link between emission measurements and the parameters of the independent capture process and (2) the elusive meaning of the degeneracy factor in the equilibrium Fermi-Dirac distribution.

  9. Simultaneous confinement of low-energy electrons and positrons in a compact magnetic mirror trap

    NASA Astrophysics Data System (ADS)

    Higaki, H.; Kaga, C.; Fukushima, K.; Okamoto, H.; Nagata, Y.; Kanai, Y.; Yamazaki, Y.

    2017-02-01

    More than 107 electrons and 105 positrons with energy less than a few eV were confined simultaneously for the first time in a compact magnetic mirror trap with plugging potentials. The exponential decay time constant of the confined positrons exceeded 70 ms at the beginning of the simultaneous confinement. Particle simulations in the early stages of the mixing process were also conducted. The results obtained in the experiments and simulations suggested that an improved setup would make it possible to investigate the unexplored field of low-energy electron–positron plasmas experimentally.

  10. Electron and hole transport in a green-emitting alternating block copolymer: space-charge-limited conduction with traps

    NASA Astrophysics Data System (ADS)

    Ma, Dongge; Hümmelgen, I. A.; Hu, Bin; Karasz, F. E.

    1999-10-01

    The transport characteristics of electrons and holes in an alternating block copolymer, poly(1,8-octanedioxy-2,6-dimethoxy-1,4-phenylene-1,2-ethenylene-1,4- phenylene-1,2-ethenylene-1,4-phenylene-1,2-ethenylene-3,5-dimethoxy-1,4- phenylene), have been investigated by current-voltage measurements in metal/polymer/metal sandwich structures. Strong evidence that the hole current is space-charge limited with a single discrete set of shallow traps and the electron current is space-charge limited with an exponential distribution of traps was obtained. A hole trap density of ~1 × 1017 cm-3 and a hole trap energy of ~0.1 eV relative to the highest occupied molecular orbital level were determined. The characteristic energy of the trap distribution, ~0.05 eV, and the trap density <3.7 × 1017 cm-3 for electrons were also estimated. It was found that the hole current became trap-free, space-charge limited, when using Au, Pd or Ni (φAu≈ φPd≈ φNi Cu (≈ 4.65 eV) and φ Au. A hole mobility of ~10-6 cm2 V-1 s-1 in this copolymer was determined.

  11. Temperature dependence of photoluminescence spectra of bilayer two-dimensional electron gases in LaAlO{sub 3}/SrTiO{sub 3} superlattices: coexistence of Auger recombination and single-carrier trapping

    SciTech Connect

    Ma, H. J. Harsan Ariando; Venkatesan, T.; Wang, S. J.

    2015-06-15

    We report emerging photoluminescence (PL) of bilayer two-dimensional electron gases (2DEG) in LaAlO{sub 3}/SrTiO{sub 3} (LAO/STO) systems. A strong blue PL emerges in bilayer-2DEGs in LAO/STO/LAO/STO which doesn’t show in LAO/STO. PL band in bilayer-2DEGs includes both nearly temperature independent Auger recombination and temperature dependent free electron trapping while it crossovers from Auger recombination to single carrier trapping in LAO/STO. The PL signal of free electron trapping appears at high temperatures and it is much stronger than Auger recombination in the conducting channel in bilayer 2DEGs. This observation shows that high mobility carriers dominate the carrier dynamics in bilayer-2DEGs in LAO/STO superlattices.

  12. Impact of residual carbon impurities and gallium vacancies on trapping effects in AlGaN/GaN metal insulator semiconductor high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Huber, Martin; Silvestri, Marco; Knuuttila, Lauri; Pozzovivo, Gianmauro; Andreev, Andrei; Kadashchuk, Andrey; Bonanni, Alberta; Lundskog, Anders

    2015-07-01

    Effects of residual C impurities and Ga vacancies on the dynamic instabilities of AlN/AlGaN/GaN metal insulator semiconductor high electron mobility transistors are investigated. Secondary ion mass spectroscopy, positron annihilation spectroscopy, and steady state and time-resolved photoluminescence (PL) measurements have been performed in conjunction with electrical characterization and current transient analyses. The correlation between yellow luminescence (YL), C- and Ga vacancy concentrations is investigated. Time-resolved PL indicating the CN ON complex as the main source of the YL, while Ga vacancies or related complexes with C seem not to play a major role. The device dynamic performance is found to be significantly dependent on the C concentration close to the channel of the transistor. Additionally, the magnitude of the YL is found to be in agreement with the threshold voltage shift and with the on-resistance degradation. Trap analysis of the GaN buffer shows an apparent activation energy of ˜0.8 eV for all samples, pointing to a common dominating trapping process and that the growth parameters affect solely the density of trap centres. It is inferred that the trapping process is likely to be directly related to C based defects.

  13. Impact of residual carbon impurities and gallium vacancies on trapping effects in AlGaN/GaN metal insulator semiconductor high electron mobility transistors

    SciTech Connect

    Huber, Martin; Silvestri, Marco; Knuuttila, Lauri; Pozzovivo, Gianmauro; Andreev, Andrei; Lundskog, Anders; Kadashchuk, Andrey; Bonanni, Alberta

    2015-07-20

    Effects of residual C impurities and Ga vacancies on the dynamic instabilities of AlN/AlGaN/GaN metal insulator semiconductor high electron mobility transistors are investigated. Secondary ion mass spectroscopy, positron annihilation spectroscopy, and steady state and time-resolved photoluminescence (PL) measurements have been performed in conjunction with electrical characterization and current transient analyses. The correlation between yellow luminescence (YL), C- and Ga vacancy concentrations is investigated. Time-resolved PL indicating the C{sub N} O{sub N} complex as the main source of the YL, while Ga vacancies or related complexes with C seem not to play a major role. The device dynamic performance is found to be significantly dependent on the C concentration close to the channel of the transistor. Additionally, the magnitude of the YL is found to be in agreement with the threshold voltage shift and with the on-resistance degradation. Trap analysis of the GaN buffer shows an apparent activation energy of ∼0.8 eV for all samples, pointing to a common dominating trapping process and that the growth parameters affect solely the density of trap centres. It is inferred that the trapping process is likely to be directly related to C based defects.

  14. Laboratory Astrophysics at the LLNL Electron Beam Ion Traps: EBIT-I and EBIT-II

    NASA Technical Reports Server (NTRS)

    Brown, G. V.; Boyce, K. R.; Kelley, R. L.; Porter, F. S.; Stahle, C. K.; Szymkowiak, A. E.; Tillotson, W.; Beiersdorfer, P.; Chen, H.; May, M. J.

    2002-01-01

    In order to provide a complete, accurate set of atomic data for interpreting spectra provided by missions such as XMM-Newton, the Chandra X-Ray Observatory, and Astro-E2, we have harnessed the Lawrence Livermore National Laboratory's electron beam ion traps EBIT-I. EBIT-II, and Super-EBIT for laboratory astrophysics. In support of this work we have developed a number of unique techniques, including the ability to experimentally simulate a Maxwellian distribution of electron energies and measuring low-energy charge exchange cross sections using the magnetic trapping mode. We have also built and operated a full suite of spectrometers spanning the 1-7000 Angstrom wavelength band, the most recent being a spectrometer based on a spare Astro-E (6 x 6) microcalorimeter array. Results of our efforts include a complete list of wavelengths of the Fe L-shell transitions, measurements of absolute and relative cross sections for direct impact, dielectronic, and resonance excitation, and measurements of low energy charge transfer reactions. A brief overview of the LLNL ebit facility, its capabilities, and some results will be discussed.

  15. EBIT - Electronic Beam Ion Trap: N Divison experimental physics annual report 1995

    SciTech Connect

    Schneider, D.

    1996-10-01

    The multi-faceted research effort of the EBIT (Electron Beam Ion Trap) program in N-Division of the Physics and Space Technology Department at Lawrence Livermore National Laboratory (LLNL) continues to contribute significant results to the physical sciences from studies with low energy very highly charged heavy ions. The EBIT program attracts a number of collaborators from the US and abroad for the different projects. The collaborations are partly carried out through participating graduate students demonstrating the excellent educational capabilities at the LLNL EBIT facilities. Moreover, participants from Historically Black Colleges and Universities are engaged in the EBIT project. This report describes EBIT work for 1995 in atomic structure measurements and radiative transition probabilities, spectral diagnostics for laboratory and astrophysical plasmas, ion/surface interaction studies, electron-ion interactions studies, retrap and ion collisions, and instrumental development.

  16. Ion-acoustic solitary waves in a positron beam plasma with electron trapping and nonextensivity effects

    NASA Astrophysics Data System (ADS)

    Ali Shan, S.; -Ur-Rehman, Aman; Mushtaq, A.

    2017-03-01

    Ion-acoustic solitary waves (IASWs) are investigated in a plasma having a cold positron beam fluid, electrons following a vortex-like distribution with entropic index q, and dynamic ions. Using a standard procedure, a pseudo-potential energy equation is derived. The presence of nonextensive q - distributed trapped electrons and cold positron beam has been shown to influence the small amplitude soliton structure quite significantly. From the analysis of our results, it is shown that compressive IASWs are supported in this plasma model. As the real plasma situations are observed with plasma species having a relative flow, our present analysis should be beneficial for comprehending the electrostatic solitary structures observed in fusion plasma devices and positron winds observed in astrophysical plasmas.

  17. Electron beam ion trap bi-annual report 1996/1997

    SciTech Connect

    Schneider, D

    1999-01-05

    The research of the EBIT (Electron Beam Ion Trap) program in N Division of the Physics and Space Technology Directorate at LLNL continues to contribute significantly to the understanding of physical processes with low energy highly charged ions in atomic physics, plasma physics, and material science. Low-energy highly charged ions (up to U92+), provided by the EBIT facilities, provide a unique laboratory opportunity to study high field effects in atomic structures and dynamic interaction processes. The formation, existence, and structure of highly charged ions in astrophysical environments and laboratory plasmas make highly charged ions desirable for diagnosing various plasma conditions. The strong interaction of highly charged ions with matter and the response of solid surfaces make them a sensitive analysis tool and possibly a future capability for materials modifications at the atomic scale (nano technology). These physical applications require a good understanding and careful study of the dynamics of the interactions of the ions with complex systems. The EBIT group hosted an international conference and a workshop on trapped charged particles. The various talks and discussions showed that physics research with trapped charged particles is a very active and attractive area of innovative research, and provides a basis for research efforts in new areas. It also became obvious that the EBIT/RETRAP project has unique capabilities to perform important new experiments with trapped very highly charged ions at rest, which are complementary to and competitive with research at heavy ion storage rings and other trapping facilities planned or in operation in Europe, Japan, and the United States. Atomic structure research at EBIT provides ever better and more experimental complete benchmark data, supplying data needed to improve atomic theories. Research highlights through 1996 and 1997 include hyperfine structure measurements in H-like ions, QED studies, lifetime

  18. Trap-mediated electronic transport properties of gate-tunable pentacene/MoS2 p-n heterojunction diodes

    PubMed Central

    Kim, Jae-Keun; Cho, Kyungjune; Kim, Tae-Young; Pak, Jinsu; Jang, Jingon; Song, Younggul; Kim, Youngrok; Choi, Barbara Yuri; Chung, Seungjun; Hong, Woong-Ki; Lee, Takhee

    2016-01-01

    We investigated the trap-mediated electronic transport properties of pentacene/molybdenum disulphide (MoS2) p-n heterojunction devices. We observed that the hybrid p-n heterojunctions were gate-tunable and were strongly affected by trap-assisted tunnelling through the van der Waals gap at the heterojunction interfaces between MoS2 and pentacene. The pentacene/MoS2 p-n heterojunction diodes had gate-tunable high ideality factor, which resulted from trap-mediated conduction nature of devices. From the temperature-variable current-voltage measurement, a space-charge-limited conduction and a variable range hopping conduction at a low temperature were suggested as the gate-tunable charge transport characteristics of these hybrid p-n heterojunctions. Our study provides a better understanding of the trap-mediated electronic transport properties in organic/2-dimensional material hybrid heterojunction devices. PMID:27829663

  19. Trapping effects in irradiated and avalanche-injected MOS capacitors

    NASA Technical Reports Server (NTRS)

    Bakowski, M.; Cockrum, R. H.; Zamani, N.; Maserjian, J.; Viswanathan, C. R.

    1978-01-01

    The trapping parameters for holes, and for electrons in the presence of trapped holes, have been measured from a set of wafers with different oxide thickness processed under controlled conditions. The trap cross-sections and densities indicate at least three trap species, including an interfacial species, a dominant bulk species which is determined to tail off from the silicon interface, and a third, lower density bulk species that is distributed throughout the oxide.

  20. The ReA electron-beam ion trap charge breeder for reacceleration of rare isotopes

    NASA Astrophysics Data System (ADS)

    Lapierre, A.; Schwarz, S.; Kittimanapun, K.; Fogleman, J.; Krause, S.; Nash, S.; Rencsok, R.; Tobos, L.; Perdikakis, G.; Portillo, M.; Rodriguez, J. A.; Wittmer, W.; Wu, X.; Bollen, G.; Leitner, D.; Syphers, M.; ReA Team

    2013-04-01

    ReA is a post-accelerator at the National Superconducting Cyclotron Laboratory at Michigan State University. ReA is designed to reaccelerate rare isotopes to energies of a few MeV/u following production by projectile fragmentation and thermalization in a gas cell. The facility consists of four main components: an electron-beam ion trap (EBIT) charge breeder, an achromatic charge-over-mass (Q/A) separator, a radio-frequency quadrupole accelerator, and a superconducting radio-frequency linear accelerator. The EBIT charge breeder was specifically designed to efficiently capture continuous beams of singly charged ions injected at low energy (<60 keV), charge breed in less than 50 ms, and extract highly charged ions to the Q/A separator for charge-state selection and reacceleration through the accelerator structures. The use of highly charged ions to reach high beam energies is a key aspect that makes ReA a compact and cost-efficient post-accelerator. The EBIT is characterized by a high-current electron gun, a long multi-electrode trap structure and a dual magnet to provide both the high electron-beam current density necessary for fast charge breeding of short-lived isotopes as well as the high capture probability of injected beams. This paper presents an overview and the status of the ReA EBIT, which has extracted for reacceleration tests stable 20Ne8+ ion beams produced from injected gas and more recently 39K16+ beams by injecting stable 39,41K+ ions from an external ion source.

  1. Highly charged ion research at the Livermore electron beam ion traps

    SciTech Connect

    Beiersdorfer, P

    2004-01-04

    Spectroscopy performed with the three Livermore electron beam ion traps is reviewed, which is continuing and complementing the innumerable contributions to atomic physics provided over the years by heavy-ion accelerators. Numerous spectrometers were developed that cover the spectral bands from the visible to the hard x ray region. These enabled exhaustive line surveys useful for x-ray astrophysics and for systematic studies along iso-electronic sequences, such as the 4s-4p, 3s-3p, and 2s-2p transitions in ions of the Cu-I, Na-I, and Li-I sequences useful for studying QED and correlation effects as well as for precise determinations of atomic-nuclear interactions. They also enabled measurements of radiative transition probabilities of very long-lived (milli- and microseconds) and very short-live (femtosecond) levels. Because line excitation processes can be controlled by choice of the electron beam energy, the observed line intensities are used to infer cross sections for electron-impact excitation, dielectronic recombination, resonance excitation, and innershell ionization. These capabilities have recently been expanded to simulate x-ray emission from comets by charge exchange. Specific contributions to basic atomic physics, nuclear physics, and high-temperature diagnostics are illustrated.

  2. Optical control of electron trapping: Generation of comb-like electron beams for tunable, pulsed, multi-color radiation sources

    NASA Astrophysics Data System (ADS)

    Kalmykov, Serge

    2014-10-01

    All-optical control over the electron phase space in laser-plasma accelerators enables production of ``designer'' electron beams that can be optimized for specific applications. GeV-scale acceleration with sub-100 TW (rather than PW) laser pulses, at repetition rates orders-of-magnitude higher than permitted by existing PW facilities, in a few-mm (rather than cm) length plasmas, requires maintaining an accelerating gradient as high as 10 GV/cm. This, in turn, dictates acceleration in the blowout regime in a dense plasma (~1019 cm-3). These highly dispersive plasmas rapidly transform the drive pulse into a relativistic optical shock, causing the plasma wake bucket (electron density bubble) to constantly expand, trapping background electrons, greatly degrading beam quality. We show that these effects can be overcome using a high-bandwidth driver (over 1/2 the carrier frequency) with a negative frequency chirp. Temporally advancing higher frequencies (thus compensating for the plasma-induced nonlinear frequency red-shift) and propagating the pulse in a plasma channel (to suppress diffraction of its leading edge) delays pulse self-steepening through electron dephasing and extends the dephasing length. As a result, continuous injection is suppressed and electron energy is boosted to the GeV level. In addition, periodic self-injection in the channel produces a sequence of femtosecond-length, quasi-monoenergetic bunches. The number of these spectral components, their charge, energy, and energy separation can be controlled by varying the channel radius and length, whereas accumulation of the noise (viz. continuously injected charge) is prevented by the negative chirp of the driver. This level of control is hard to achieve with conventional accelerator techniques. It is demonstrated that these clean, polychromatic, comb-like beams can drive high-brightness, tunable, multi-color gamma-ray sources. Work is supported by the US DOE Grant DE-SC0008382 and NSF Grant PHY-1104683.

  3. Variability and spatial fine structure of precipitating and trapped medium-energy electron fluxes in the noon sector

    NASA Astrophysics Data System (ADS)

    Hargreaves, J. K.; Birch, M. J.; Evans, D. S.

    2014-02-01

    The relationships between the precipitating and trapped components of magnetospheric electron flux for energy ranges exceeding 30 and 100 keV have been investigated using data from polar orbiting satellites, the study being restricted to a limited geographic region at auroral latitudes in the noon sector. The electron flux of these energies is the cause of auroral radio absorption. The data are analyzed at two levels of detail. Variations between different passes are studied using their median values, and variations within passes are derived from individual data points at 2 s intervals, equivalent to about 10 km in distance. Several types of behavior are recognized. Basically, the ratio of precipitating to trapped flux at energies exceeding 30 keV varies in proportion to the trapped flux, though there is a limiting upper value where the two components are approximately equal. The precipitating flux never exceeds the trapped flux by any significant amount. These types appear to be consistent with weak and strong pitch angle scatterings, respectively. The precipitation at >100 keV varies somewhat with the >100 keV trapped flux but more strongly with the >30 keV component, consistent with scattering by chorus waves produced by electrons less energetic than those being scattered. Comparison between the two energy ranges shows that the precipitating component is always softer than the trapped. The detailed relationship between the precipitating and trapped components varies from pass to pass by an amount related to the east-west component of the interplanetary magnetic field. Superimposed on the above behavior are large reductions of precipitation, spatial rather than temporal in nature, during which the trapped flux remains virtually unchanged. These reductions appear to be due to structures some tens of kilometers across, perhaps related to "ducts" within the magnetosphere. Some theoretical considerations based on the Kennel and Petscheck theory of scattering are

  4. Electronic structure of the interstitial lithium-associated electron trap in crystalline quartz

    NASA Astrophysics Data System (ADS)

    Wilson, T. M.; Weil, J. A.; Rao, P. S.

    1986-10-01

    A new, paramagnetic (S=1/2) defect, designated the [SiO4/Li]0 center, consisting of an interstitial lithium "atom," recently has been observed by Jani, Halliburton, and Halperin

    [Phys. Rev. Lett. 56, 1392 (1986)]
    in irradiated α-quartz. A model for this defect has been developed utilizing ab initio self-consistent-field, electronic-structure calculations. In this model, the interstitial lithium nucleus lies on a crystal twofold axis passing through two adjacent silicon ions, and has a nearly neutral charge but very low spin density. The properties calculated using this model are consistent with all the available experimental information for this defect.

  5. Trapping the M sub 1 and M sub 2 substrates of bacteriorhodopsin for electron diffraction studies

    SciTech Connect

    Perkins, G.A.

    1992-05-01

    Visible and Fourier transform infrared (FTIR) absorption spectroscopies are used to observe protein conformational changes occuring during the bacteriorhodopsin photocycle. Spectroscopic measurements which define the conditions under which bacteriorhodopsin can be isolated and trapped in two distinct substates of the m intermediate of the photocycle, M{sub 1}, and M{sub 2}, are described. A protocol that can be used for high-resolution electron diffraction studies is presented that will trap glucose-embedded purple membrane in the M{sub 1}and M{sub 2} substates at greater than 90% concentration. It was discovered that glucose alone does not provide a fully hydrated environment for bacteriorhodopsin. Equilibration of glucose-embedded samples at high humidity can result in a physical state that is demonstrably closer to the native, fully hydrated state. An extension of the C-T Model of bacteriorhodopsin functionality (Fodor et al., 1988; Mathies et al., 1991) is proposed based on FTIR results and guided by published spectra from resonance Raman and FTIR work. 105 refs.

  6. X-ray and optical pulse interactions via electron trapping in GaAs

    NASA Astrophysics Data System (ADS)

    Durbin, Stephen; Liu, Shih-Chieh; Dichiara, Anthony; Henning, Robert

    2014-03-01

    A highly excited state of GaAs is created by the absorption of an extremely intense focused 80 ps pulse of hard x-rays at the Advanced Photon Source synchrotron. This state is probed by 2 ps laser pulses with photon energies near the semiconducting band gap, which has previously revealed x-ray induced optical transparency. Two unexpected results are found: x-ray induced luminescence is dramatically enhanced when a high intensity laser pulse precedes the x-ray pulse, and the decay of the induced transparency becomes much slower when the intensity of the subsequent probe laser is increased. Both results require that energy be stored in GaAs by the first pulse, and then released by the second pulse. We describe how this can be explained by electron trapping centers in GaAs with trapping lifetimes of a few nanoseconds. We compare these results with lifetime measurements of other excitations produced by ultrafast optical absorption. We also show how minor improvements in focusing will lead to single-pulse x-ray induced temperature jumps of thousands of Kelvin, allowing new x-ray excited dense matter states to be explored. Supported by DOE award DE-SC0004078. The Advanced Photon Source is supported by the U.S. DOE under Contract No. DE-AC02-06CH11357. BioCARS is supported by the NIGMS of the NIH under grant number R24GM111072.

  7. Implementation of electron-transfer dissociation on a hybrid linear ion trap-orbitrap mass spectrometer.

    PubMed

    McAlister, Graeme C; Phanstiel, Doug; Good, David M; Berggren, W Travis; Coon, Joshua J

    2007-05-15

    We describe the adaptation of a hybrid quadrupole linear ion trap-orbitrap mass spectrometer to accommodate electron-transfer ion/ion reactions (ETD) for peptide and protein characterization. The method utilizes pulsed, dual electrospray ion sources and requires minimal instrument modification. Switching between cation and reagent anion injection schemes is automated and accomplished within a few hundred milliseconds. Ion/ion reactions are conducted within the linear ion trap, after which the c- and z-type product ions are passed to the orbitrap for high-resolution m/z analysis. With this arrangement, mass accuracies are typically measured to within 2 ppm at a resolving power of approximately 60 000. Using large peptides and intact proteins, we demonstrate such capabilities will accelerate our ability to interrogate high-mass species. To illustrate compatibility with automated data-dependent analysis and subsequent data processing, we couple the technique with an online chromatographic separation of a yeast whole-cell lysate followed by peptide identification using ProSight PC. Fairly long pulsing times and relatively low ET efficiency, as compared to conventional ETD instrumentation, are the main drawbacks of this approach. Still, our results suggest that the implementation of ETD on sensitive, high-resolution, and high-mass accuracy hybrid instrumentation, such as the orbitrap, will substantially propel the emergent fields of middle- and top-down proteomics.

  8. Mapping of the photoinduced electron traps in TiO₂ by picosecond X-ray absorption spectroscopy.

    PubMed

    Rittmann-Frank, M Hannelore; Milne, Chris J; Rittmann, Jochen; Reinhard, Marco; Penfold, Thomas J; Chergui, Majed

    2014-06-02

    Titanium dioxide (TiO2) is the most popular material for applications in solar-energy conversion and photocatalysis, both of which rely on the creation, transport, and trapping of charges (holes and electrons). The nature and lifetime of electron traps at room temperature have so far not been elucidated. Herein, we use picosecond X-ray absorption spectroscopy at the Ti K-edge and the Ru L3-edge to address this issue for photoexcited bare and N719-dye-sensitized anatase and amorphous TiO2 nanoparticles. Our results show that 100 ps after photoexcitation, the electrons are trapped deep in the defect-rich surface shell in the case of anatase TiO2, whereas they are inside the bulk in the case of amorphous TiO2. In the case of dye-sensitized anatase or amorphous TiO2, the electrons are trapped at the outer surface. Only two traps were identified in all cases, with lifetimes in the range of nanoseconds to tens of nanoseconds.

  9. Skin dominance of the dielectric-electronic-phononic-photonic attribute of nanoscaled silicon

    NASA Astrophysics Data System (ADS)

    Pan, Likun; Xu, Shiqing; Liu, Xinjuan; Qin, Wei; Sun, Zhuo; Zheng, Weitao; Sun, Chang Q.

    2013-11-01

    Nanoscaled or porous silicon (p-Si) with and without surface passivation exhibits unusually tunable properties that its parent bulk does never show. Such property tunability amplifies the applicability of Si in the concurrent and upcoming technologies. However, consistent understanding of the fundamental nature of nanoscaled Si remains a high challenge. This article aims to address the recent progress in this regard with focus on reconciling the tunable dielectric, electronic, phononic, and photonic properties of p-Si in terms of skin dominance. We show that the skin-depth bond contraction, local quantum entrapment, and electron localization is responsible for the size-induced property tunability. The shorter and stronger bonds between undercoordinated skin atoms result in the local densification and quantum entrapment of the binding energy and the bonding electrons, which in turn polarizes the dangling bond electrons. Such local entrapment modifies the Hamiltonian and associated properties such as the band gap, core level shift, Stokes shift (electron-phonon interaction), phonon and dielectric relaxation. Therefore, given the known trend of one property change, one is expected to be able to predict the variation of the rest based on the notations of the bond order-length-strength correlation and local bond average approach (BOLS-LBA). Furthermore, skin bond reformation due to Al, Cu, and Ti metallization and O and F passivation adds another freedom to enhance or attenuate the size effect. The developed formulations, spectral analytical methods, and importantly, the established database and knowledge could be of use in engineering p-Si and beyond for desired functions.

  10. A Miniaturized Linear Wire Ion Trap with Electron Ionization and Single Photon Ionization Sources

    NASA Astrophysics Data System (ADS)

    Wu, Qinghao; Tian, Yuan; Li, Ailin; Andrews, Derek; Hawkins, Aaron R.; Austin, Daniel E.

    2017-01-01

    A linear wire ion trap (LWIT) with both electron ionization (EI) and single photon ionization (SPI) sources was built. The SPI was provided by a vacuum ultraviolet (VUV) lamp with the ability to softly ionize organic compounds. The VUV lamp was driven by a pulse amplifier, which was controlled by a pulse generator, to avoid the detection of photons during ion detection. Sample gas was introduced through a leak valve, and the pressure in the system is shown to affect the signal-to-noise ratio and resolving power. Under optimized conditions, the limit of detection (LOD) for benzene was 80 ppbv using SPI, better than the LOD using EI (137 ppbv). System performance was demonstrated by distinguishing compounds in different classes from gasoline.

  11. High precision high voltage divider and its application to electron beam ion traps

    SciTech Connect

    Chen, W. D.; Xiao, J.; Shen, Y.; Fu, Y. Q.; Meng, F. C.; Chen, C. Y.; Zou, Y.; Hutton, R.

    2008-12-15

    A high precision high voltage divider has been developed for the electron beam ion trap in Shanghai. The uncertainty caused by the temperature coefficient of resistance (TCR) and the voltage coefficient of resistance has been studied in detail and was minimized to the level of ppm (10{sup -6}) range. Once the TCR was matched between the resistors, the precision of the dividing ratio finally reached the ppm range also. We measured the delay of the divider caused by the capacitor introduced to minimize voltage ripple to be 2.35 ms. Finally we applied the divider to an experiment to measure resonant energies for some dielectronic recombination processes for highly charged xenon ions. The final energies include corrections for both space charge and fringe field effects are mostly under 0.03%.

  12. Trap density of GeNx/Ge interface fabricated by electron-cyclotron-resonance plasma nitridation

    NASA Astrophysics Data System (ADS)

    Fukuda, Yukio; Otani, Yohei; Toyota, Hiroshi; Ono, Toshiro

    2011-07-01

    We have investigated GeNx/Ge interface properties using Si3N4(7 nm)/GeNx(2 nm)/Ge metal-insulator-semiconductor structures fabricated by the plasma nitridation of Ge substrates using an electron-cyclotron-resonance-generated nitrogen plasma. The interface trap density (Dit) measured by the conductance method is found to be distributed symmetrically in the Ge band gap with a minimum Dit value lower than 3 × 1011 cm-2eV-1 near the midgap. This result may lead to the development of processes for the fabrication of p- and n-Ge Schottky-barrier (SB) source/drain metal-insulator-semiconductor field-effect transistors using chemically and thermally robust GeNx dielectrics as interlayers for SB source/drain contacts and high-κ gate dielectrics.

  13. Theory of Fine-scale Zonal Flow Generation From Trapped Electron Mode Turbulence

    SciTech Connect

    Lu Wang and T.S. Hahm

    2009-06-11

    Most existing zonal flow generation theory has been developed with a usual assumption of qrρθ¡ << 1 (qr is the radial wave number of zonal flow, and ρθ¡ is the ion poloidal gyrora- dius). However, recent nonlinear gyrokinetic simulations of trapped electron mode (TEM) turbulence exhibit a relatively short radial scale of the zonal flows with qrρθ¡ ~ 1 [Z. Lin et al., IAEA-CN/TH/P2-8 (2006); D. Ernst et al., Phys. Plasmas 16, 055906 (2009)]. This work reports an extension of zonal flow growth calculation to this short wavelength regime via the wave kinetics approach. A generalized expression for the polarization shielding for arbitrary radial wavelength [Lu Wang and T.S. Hahm, to appear in Phys. Plasmas (2009)] which extends the Rosenbluth-Hinton formula in the long wavelength limit is applied.

  14. Magnetic field extraction of trap-based electron beams using a high-permeability grid

    SciTech Connect

    Hurst, N. C.; Danielson, J. R.; Surko, C. M.

    2015-07-15

    A method to form high quality electrostatically guided lepton beams is explored. Test electron beams are extracted from tailored plasmas confined in a Penning-Malmberg trap. The particles are then extracted from the confining axial magnetic field by passing them through a high magnetic permeability grid with radial tines (a so-called “magnetic spider”). An Einzel lens is used to focus and analyze the beam properties. Numerical simulations are used to model non-adiabatic effects due to the spider, and the predictions are compared with the experimental results. Improvements in beam quality are discussed relative to the use of a hole in a high permeability shield (i.e., in lieu of the spider), and areas for further improvement are described.

  15. Externally induced metastability of an electron in a Penning trap: Analytical results

    NASA Astrophysics Data System (ADS)

    Brouard, S.; Plata, J.

    2001-12-01

    The effect of a driving field on the cyclotron mode of a relativistic electron in a Penning trap is studied analytically. The Hamiltonian dynamics of this driven nonlinear oscillator is analyzed by using linearization techniques and displaced squeezed-state formalism. With the approximate analytical expressions obtained for the eigenstates in this approach, a simplified treatment of the dissipative dynamics is carried out and some of the nontrivial features found in a recent numerical study [D. Enzer and G. Gabrielse, Phys. Rev. Lett. 78, 1211 (1997)] are unraveled. The emergence of different time scales and the generation of a metastable statistical mixture are understood in terms of the changes induced in the structure of the master equation by the nonuniform characteristics of the eigenstates; the partial revivals of specific coherent states are accounted for by the evolution of particular coherences. The control of these effects by a proper choice of the driving parameters is discussed.

  16. Hydrogen passivation of electron trap in amorphous In-Ga-Zn-O thin-film transistors

    NASA Astrophysics Data System (ADS)

    Hanyu, Yuichiro; Domen, Kay; Nomura, Kenji; Hiramatsu, Hidenori; Kumomi, Hideya; Hosono, Hideo; Kamiya, Toshio

    2013-11-01

    We report an experimental evidence that some hydrogens passivate electron traps in an amorphous oxide semiconductor, a-In-Ga-Zn-O (a-IGZO). The a-IGZO thin-film transistors (TFTs) annealed at 300 °C exhibit good operation characteristics; while those annealed at ≥400 °C show deteriorated ones. Thermal desorption spectra (TDS) of H2O indicate that this threshold annealing temperature corresponds to depletion of H2O desorption from the a-IGZO layer. Hydrogen re-doping by wet oxygen annealing recovers the good TFT characteristic. The hydrogens responsible for this passivation have specific binding energies corresponding to the desorption temperatures of 300-430 °C. A plausible structural model is suggested.

  17. Longitudinal Space Charge Effects in Bunched Electron Beams Travelling through a Malmberg-Penning Trap

    SciTech Connect

    Rome, M.; Cavaliere, F.; De Luca, F.; Pozzoli, R.; Cavenago, M.; Maero, G.; Paroli, B.

    2010-06-16

    Nanosecond pulsed electron beams in the 1-10 keV energy range have been characterized by means of an electrostatic diagnostic in the Malmberg-Penning trap ELTRAP. The beam length has been inferred through the numerical analysis of the signals measured across the overall load impedance of a planar charge collector. The presence of space charge effects leading to a longitudinal spread of the beam during its transport are evidenced at low injection energies. This feature has also been tested with the use of a one-dimensional fluid model and with two-dimensional, cylindrically-symmetric Particle-In-Cell simulations, whose results are compared to the experimental observations.

  18. Electromagnetic field generation in the downstream of electrostatic shocks due to electron trapping.

    PubMed

    Stockem, A; Grismayer, T; Fonseca, R A; Silva, L O

    2014-09-05

    A new magnetic field generation mechanism in electrostatic shocks is found, which can produce fields with magnetic energy density as high as 0.01 of the kinetic energy density of the flows on time scales ∼10(4)ωpe-1. Electron trapping during the shock formation process creates a strong temperature anisotropy in the distribution function, giving rise to the pure Weibel instability. The generated magnetic field is well confined to the downstream region of the electrostatic shock. The shock formation process is not modified, and the features of the shock front responsible for ion acceleration, which are currently probed in laser-plasma laboratory experiments, are maintained. However, such a strong magnetic field determines the particle trajectories downstream and has the potential to modify the signatures of the collisionless shock.

  19. Cascade emission in electron beam ion trap plasma of W25+ ion

    NASA Astrophysics Data System (ADS)

    Jonauskas, V.; Pütterich, T.; Kučas, S.; Masys, Š.; Kynienė, A.; Gaigalas, G.; Kisielius, R.; Radžiūtė, L.; Rynkun, P.; Merkelis, G.

    2015-07-01

    Spectra of the W25+ ion are studied using the collisional-radiative model (CRM) with an ensuing cascade emission. It is determined that the cascade emission boosts intensities only of a few lines in the 10-30 nm range. The cascade emission is responsible for the disappearance of structure of lines at about 6 nm in the electron beam ion trap plasma. Emission band at 4.5-5.3 nm is also affected by the cascade emission. The strongest lines in the CRM spectrum correspond to 4d9 4f4 → 4f3 transitions, while 4f2 5 d → 4f3 transitions arise after the cascade emission is taken into account.

  20. Infrared ion spectroscopy in a modified quadrupole ion trap mass spectrometer at the FELIX free electron laser laboratory

    NASA Astrophysics Data System (ADS)

    Martens, Jonathan; Berden, Giel; Gebhardt, Christoph R.; Oomens, Jos

    2016-10-01

    We report on modifications made to a Paul-type quadrupole ion trap mass spectrometer and discuss its application in infrared ion spectroscopy experiments. Main modifications involve optical access to the trapped ions and hardware and software coupling to a variety of infrared laser sources at the FELIX infrared free electron laser laboratory. In comparison to previously described infrared ion spectroscopy experiments at the FELIX laboratory, we find significant improvements in efficiency and sensitivity. Effects of the trapping conditions of the ions on the IR multiple photon dissociation spectra are explored. Enhanced photo-dissociation is found at lower pressures in the ion trap. Spectra obtained under reduced pressure conditions are found to more closely mimic those obtained in the high-vacuum conditions of an Fourier transform ion cyclotron resonance mass spectrometer. A gas-mixing system is described enabling the controlled addition of a secondary gas into helium buffer gas flowing into the trap and allows for ion/molecule reactions in the trap. The electron transfer dissociation (ETD) option of the mass spectrometer allows for IR structure characterization of ETD-generated peptide dissociation products.

  1. Electron traps as major recombination centers in n-GaN films grown by metalorganic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Lee, In-Hwan; Polyakov, Alexander Y.; Smirnov, Nikolai B.; Yakimov, Eugene B.; Tarelkin, Sergey A.; Turutin, Andery V.; Shemerov, Ivan V.; Pearton, Stephen J.

    2016-06-01

    For a group of n-GaN films grown by metalorganic chemical vapor deposition (MOCVD) using both straight MOCVD and epitaxial lateral overgrowth techniques (ELOG proper or pendeo overgrowth), the spectra of deep traps were measured by deep-level transient spectroscopy (DLTS) with electrical or optical injection (ODLTS). The results were compared with diffusion length measurement results obtained from electron-beam-induced current experiments. The results strongly indicate that deep electron traps near E c - 0.56 eV could be the major recombination centers determining the diffusion length values in pendeo samples.

  2. Dust-acoustic solitary waves in a magnetized dusty plasma with nonthermal electrons and trapped ions

    NASA Astrophysics Data System (ADS)

    Misra, A. P.; Wang, Yunliang

    2015-05-01

    The nonlinear propagation of electrostatic dust-acoustic (DA) waves in a magnetized dusty plasma consisting of negatively charged mobile dusts, nonthermal fast electrons and trapped ions with vortex-like distribution is studied. Using the reductive perturbation technique, a Korteweg-de Vries (KdV)-like equation is derived which governs the dynamics of the small-amplitude solitary waves in a magnetized dusty nonthermal plasma. It is found that due to the dust thermal pressure, there exists a critical value (βc) of the nonthermal parameter β (>1), denoting the percentage of energetic electrons, below which the DA solitary waves cease to propagate. The soliton solution (traveling wave) of the KdV-like equation is obtained, and is shown to be only of the rarefactive type. The properties of the solitons are analyzed numerically with the system parameters. It is also seen that the effect of the static magnetic field (which only modifies the soliton width) becomes significant when the dust gyrofrequency is smaller than one-tenth of the dust plasma frequency. Furthermore, the amplitude of the soliton is found to increase (decrease) when the ratio of the free to trapped ion temperatures (σ) is positive (negative). The effects of the system parameters including the obliqueness of propagation (lz) and σ on the dynamics of the DA solitons are also discussed numerically, and it is found that the soliton structures can withstand perturbations and turbulence during a considerable time. The results should be useful for understanding the nonlinear propagation of DA solitary waves in laboratory and space plasmas (e.g., Earth's magnetosphere, auroral region, heliospheric environments, etc.).

  3. Survival of bacterial isolates exposed to simulated Jovian trapped radiation belt electrons and solar wind protons

    NASA Technical Reports Server (NTRS)

    Taylor, D. M.; Hagen, C. A.; Renninger, G. M.; Simko, G. J.; Smith, C. D.; Yelinek, J. A.

    1972-01-01

    With missions to Jupiter, the spacecraft will be exposed for extended duration to solar wind radiation and the Jovian trapped radiation belt. This study is designed to determine the effect of these radiation environments on spacecraft bacterial isolates. The information can be used in the probability of contamination analysis for these missions. A bacterial subpopulation from Mariner Mars 1971 spacecraft (nine sporeforming and three nonsporeforming isolates) plus two comparative organisms, Staphylococcus epidermidis ATCC 17917 and a strain of Bacillus subtilis var. niger, were exposed to 2-, 12-, and 25-MeV electrons at different doses with simultaneous exposure to a vacuum of 0.0013 N/sqm at 20 and -20 C. The radioresistance of the subpopulation was dependent on the isolate, dose, and energy of electrons. Temperature affected the radioresistance of only the sporeforming isolates. Survival data indicated that spores were reduced approximately 1 log/1500 J/kg, while nonsporeforming isolates (micrococci) were reduced 1.5 to 2 logs/1500 J/kg with the exception of an apparent radioresistant isolate whose resistance approached that of the spores. The subpopulation was found to be less resistant to lower energy than to higher energy electrons.

  4. Trapped energetic electron driven modes with second stable regime in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    He, Hongda; Dong, J. Q.; Zhao, K.; He, Zhixiong; Zheng, G. Y.; Lu, Gaimin; Hao, G. Z.; Tao, Xie; Wang, L. F.

    2014-06-01

    Features of fishbone-like trapped energetic electrons driven modes (TEEMs), which are a particular manifestation of the fishbone gap modes, are investigated taking into account model radial profile and the pitch angle distribution of the energetic electrons (EEs). The TEEMs are found unstable only when the beta values of EEs βh (=pressure of the energetic electrons/pressure of magnetic field) are higher than certain critical values which are proportional to perturbed energy δW ̂c of background plasma and much lower than that for traditional fishbone modes. In addition, TEEMs become stable again and enter a second stable regime when βh values are higher than second critical values. Furthermore, the modes can only be excited in plasmas which are stable for MHD instabilities. The real frequency and growth rate of the modes are approximately linear and parabolic functions of βh, respectively. The real frequency is very low but not zero in the vicinity of lower beta region, whereas it is comparable to the toroidal precession frequency of the EEs in higher critical beta region. The numerical results show that the second stable regime is easy to form when q = 1 flux surface is close to the magnetic axis. Suitable density gradient of EEs and magnetic shear are other two necessary conditions for excitation of the TEEMs.

  5. Trapped energetic electron driven modes with second stable regime in tokamak plasmas

    SciTech Connect

    He, Hongda; He, Zhixiong; Zheng, G. Y.; Lu, Gaimin; Hao, G. Z.; Tao, Xie; Wang, L. F.; Dong, J. Q.; Zhao, K.

    2014-06-15

    Features of fishbone-like trapped energetic electrons driven modes (TEEMs), which are a particular manifestation of the fishbone gap modes, are investigated taking into account model radial profile and the pitch angle distribution of the energetic electrons (EEs). The TEEMs are found unstable only when the beta values of EEs β{sub h} (=pressure of the energetic electrons/pressure of magnetic field) are higher than certain critical values which are proportional to perturbed energy δW{sup ^}{sub c} of background plasma and much lower than that for traditional fishbone modes. In addition, TEEMs become stable again and enter a second stable regime when β{sub h} values are higher than second critical values. Furthermore, the modes can only be excited in plasmas which are stable for MHD instabilities. The real frequency and growth rate of the modes are approximately linear and parabolic functions of β{sub h}, respectively. The real frequency is very low but not zero in the vicinity of lower beta region, whereas it is comparable to the toroidal precession frequency of the EEs in higher critical beta region. The numerical results show that the second stable regime is easy to form when q = 1 flux surface is close to the magnetic axis. Suitable density gradient of EEs and magnetic shear are other two necessary conditions for excitation of the TEEMs.

  6. Characteristics of Jovian trapped electrons and protons for the region within 20 Jupiter radii and their interaction with Io

    NASA Technical Reports Server (NTRS)

    Simpson, J. A.; Hamilton, D. C.; Mckibben, R. B.; Mogro-Campero, A.; Pyle, K. R.; Tuzzolino, A. J.

    1975-01-01

    A brief summary is given of Pioneer 10 observations of trapped particles in the inner-core region (within 20 Jupiter radii) of the Jovian magnetosphere. The three sensor systems used to study trapped radiation in this region are described. Intensity profiles are plotted as a function of magnetic-shell parameter (L) for electrons with energies of at least 3 MeV, protons with energies of at least 35 MeV, and protons with energies between 0.5 and 1.8 MeV. The effect of trapped-particle absorption by Io is clearly seen in the intensity profiles of all the observed particle species, and evidence is presented for preferential absorption of small-pitch-angle particles by Io. Conclusive evidence is given for the fact that Jupiter's trapped radiation is maintained by the inward diffusion of particles across L shells.

  7. Magnetism induced by excess electrons trapped at diamagnetic edge-quantum well in multi-layer graphene

    SciTech Connect

    Zhang, Xi; Wang, Chao; Diao, Dongfeng; Sun, Chang Q

    2014-07-28

    In this paper, we clarified a robust mechanism of magnetism generated by excess electrons captured by edge-quantum well of diamagnetic armchair edges. Consistency between density functional theory calculations and electron cyclotron resonance experiments verified that: (1) Multi-layer armchair nanoribbons are stable with proper amounts of excess electrons which can provide net spin; (2) Since under-coordination induces lattice relaxation and potential well modulation, electrons tend to be trapped at edges; and (3) Neither large amount of excess electrons nor positive charges can induce magnetism. This work shed light on the development of graphene devices in its magnetic applications.

  8. Trapping in GaN-based metal-insulator-semiconductor transistors: Role of high drain bias and hot electrons

    SciTech Connect

    Meneghini, M. Bisi, D.; Meneghesso, G.; Zanoni, E.

    2014-04-07

    This paper describes an extensive analysis of the role of off-state and semi-on state bias in inducing the trapping in GaN-based power High Electron Mobility Transistors. The study is based on combined pulsed characterization and on-resistance transient measurements. We demonstrate that—by changing the quiescent bias point from the off-state to the semi-on state—it is possible to separately analyze two relevant trapping mechanisms: (i) the trapping of electrons in the gate-drain access region, activated by the exposure to high drain bias in the off-state; (ii) the trapping of hot-electrons within the AlGaN barrier or the gate insulator, which occurs when the devices are operated in the semi-on state. The dependence of these two mechanisms on the bias conditions and on temperature, and the properties (activation energy and cross section) of the related traps are described in the text.

  9. Influence of electron radiation and temperature on the cyclic, matrix dominated response of graphite-epoxy

    NASA Technical Reports Server (NTRS)

    Reed, Susan M.; Herakovich, Carl T.; Sykes, George F., Jr.

    1987-01-01

    The effects of electron radiation and elevated temperature on the matrix-dominated cyclic response of standard T300/934 and a chemically modified T300/934 graphite-epoxy are characterized. Both materials were subjected to 1.0 x 10 to the 10th rads of 1.0 MeV electron irradiation, under vacuum, to simulate 30 years in geosynchronous orbit. Cyclic tests were performed at room temperature and elevated temperature (121 C) on 4-ply unidirectional laminates to characterize the effects associated with irradiation and elevated temperature. Both materials exhibited energy dissipation in their response at elevated temperature. The irradiated modified material also exhibited energy dissipation at room temperature. The combination of elevated temperature and irradiation resulted in the most severe effects in the form of lower proportional limits, and greater energy dissipation. Dynamic-mechanical analysis demonstrated that the glass transition temperature, T(g), of the standard material was lowered 39 C by irradiation, wereas the T(g) of the modified material was lowered 28 C by irradiation. Thermomechanical analysis showed the occurrence of volatile products generated upon heating of the irradiated materials.

  10. Formation of Electron Distribution Function in ECR Discharge Sustained by Strong Microwave Emission in an Open Trap

    SciTech Connect

    Erukhimov, V.L.; Semenov, V.E.

    2005-03-15

    We consider a formation of Electron Distribution Function (EDF) in the Electron Cyclotron Resonance (ECR) discharge in an open trap. The ECR heating by strong microwaves, ionization, collisions and ambipolar losses are considered. The model is based on a system of two-dimensional Fokker-Plank equation for EDF. The stationary solution for EDF is investigated analytically. It consists of three groups of electrons: hot electrons with highly anisotropic velocity distribution that are heated in the ECR region, cold electrons with isotropic distribution that define the losses from the trap and warm electrons with considerably anisotropic distribution that are concentrated in the center of the trap and do not reach the ECR region. We build a qualitative model for the electron distribution function such that the original differential equation for EDF is transformed into two algebraic equations with two unknown parameters: neutral density and main plasma density. The latter can be solved analytically. The applicability of these results to a self-consistent model for ECR ion source is discussed. We show that the solution contradicts experimental results so that important effect is not taken into account in the model.

  11. Formation of Electron Distribution Function in ECR Discharge Sustained by Strong Microwave Emission in an Open Trap

    NASA Astrophysics Data System (ADS)

    Erukhimov, V. L.; Semenov, V. E.

    2005-03-01

    We consider a formation of Electron Distribution Function (EDF) in the Electron Cyclotron Resonance (ECR) discharge in an open trap. The ECR heating by strong microwaves, ionization, collisions and ambipolar losses are considered. The model is based on a system of two-dimensional Fokker-Plank equation for EDF. The stationary solution for EDF is investigated analytically. It consists of three groups of electrons: hot electrons with highly anisotropic velocity distribution that are heated in the ECR region, cold electrons with isotropic distribution that define the losses from the trap and warm electrons with considerably anisotropic distribution that are concentrated in the center of the trap and do not reach the ECR region. We build a qualitative model for the electron distribution function such that the original differential equation for EDF is transformed into two algebraic equations with two unknown parameters: neutral density and main plasma density. The latter can be solved analytically. The applicability of these results to a self-consistent model for ECR ion source is discussed. We show that the solution contradicts experimental results so that important effect is not taken into account in the model.

  12. Overview of the current spectroscopy effort on the Livermore electron beam ion traps

    SciTech Connect

    Beiersdorfer, P.; Lopez-Urrutia, J.C.; Brown, G.

    1995-06-29

    An overview is given of the current spectroscopic effort on the Livermore electron beam ion trap facilities. The effort focuses on four aspects: spectral line position, line intensity, temporal evolution, and line shape. Examples of line position measurements include studies of the K-shell transitions in heliumlike Kr{sup 34+} and the 2s-2p intrashell transitions in lithiumlike Th{sup 87+} and U{sup 89+}, which provide benchmark values for testing the theory of relativistic and quantum electrodynamical contributions in high-Z ions. Examples of line intensity measurements are provided by measurements of the electron-impact excitation and dielectronic recombination cross sections of heliumlike transition-metal ions Ti{sup 20+} through CO{sup 25+}. A discussion of radiative lifetime measurements of metastable levels in heliumlike ions is given to illustrate the time-resolved spectroscopy techniques in the microsecond range. The authors also present a measurement of the spectral lineshape that illustrates the very low ion temperatures that can be achieved in an EBIT.

  13. E-beam addressed Spatial Light Modulator employing electron trapping materials. Phase 1

    NASA Astrophysics Data System (ADS)

    Lu, Xiaojing; Yang, Xiangyang; Wrigley, Charles Y.; Bradley, Richard; Meszaros, Janos

    1995-03-01

    Spatial light modulators (SLM's) play a critically important role in optical signal processing and optical computing. A novel electron beam addressed emissive SLM which combines high performance polycrystalline electron trapping (ET) materials with an advanced field-emitter array is being developed. The proposed SLM combines high resolution (greater than 100 lplmm), high SBP (greater than 1000 x 1000), high frame rate (greater than or equal 1 KHz), high contrast ratio (greater than l03:l) and low drive voltage (less than 15 V) in a single device. The additional features of the proposed SLM are its wide variety of operation modes and electrical and optical dual-addressability. Such a SLM, if successfully developed, will surely have substantial impact on optical processing technology. During the Phase-1 efforts, a review of field emitter arrays has been done to show that it has the merits of electrical-addressability, high space-bandwidth product (SBP), low drive voltage compatible with IC driving circuitry, and high update speed. The device architecture has been investigated and the design of two prototype devices has been provided.

  14. Analysis of fishbone instability excited by trapped energetic electrons on HL-2A tokamak

    NASA Astrophysics Data System (ADS)

    He, Hongda; Dong, J. Q.; Zhao, K.; He, Zhixiong; Chen, W.; Jiang, H. B.

    2014-11-01

    A generalized dispersion relation for fishbone instability is obtained by considering Gaussian distributions of spatial density and pitch angle of energetic electrons (EEs). The fishbone modes excited by trapped EEs are analysed in detail based on the HL-2A tokamak electron cyclotron resonant heating (ECRH) experiment. Numerical results show that the calculated time evolution of the mode real frequency is in reasonable agreement with the observations in ECRH experiment. Density gradient of the EEs plays an important role in excitation of the modes via resonant interaction between the modes and EEs. The modes are excited at the positions of maximum EE density gradient. The frequency of the mode in the case of on-axis heating is higher than that in the case of off-axis heating. The background plasma tends to prohibit excitation of the fishbone instabilities. The numerical results show that there is a cut-off background plasma density (or background plasma-β) for the fishbone instabilities. In addition, the toroidal magnetic field Bt has to be higher than a critical value in order to excite the mode, and the real frequency of the modes decreases with increasing Bt.

  15. Oxidative reactions during early stages of beer brewing studied by electron spin resonance and spin trapping.

    PubMed

    Frederiksen, Anne M; Festersen, Rikke M; Andersen, Mogens L

    2008-09-24

    An electron spin resonance (ESR)-based method was used for evaluating the levels of radical formation during mashing and in sweet wort. The method included the addition of 5% (v/v) ethanol together with the spin trap alpha-4-pyridyl(1-oxide)- N- tert-butylnitrone (POBN) to wort, followed by monitoring the rate of formation of POBN spin adducts during aerobic heating of the wort. The presence of ethanol makes the spin trapping method more selective and sensitive for the detection of highly reactive radicals such as hydroxyl and alkoxyl radicals. Samples of wort that were collected during the early stages of the mashing process gave higher rates of spin adduct formation than wort samples collected during the later stages. The lower oxidative stability of the early wort samples was confirmed by measuring the rate of oxygen consumption during heating of the wort. The addition of Fe(II) to the wort samples increased the rate of spin adduct formation, whereas the addition of Fe(II) during the mashing had no effect on the oxidative stability of the wort samples. Analysis of the iron content in the sweet wort samples demonstrated that iron added during the mashing had no effect on the iron level in the wort. The moderate temperatures during the early steps of mashing allow the endogenous malt enzymes to be active. The potential antioxidative effects of different redox-active enzymes during mashing were tested by measuring the rate of spin adduct formation in samples of wort. Surprisingly, a high catalase dosage caused a significant, 20% reduction of the initial rate of radical formation, whereas superoxide dismutase had no effect on the oxidation rates. This suggests that hydrogen peroxide and superoxide are not the only intermediates that play a role in the oxidative reactions occurring during aerobic oxidation of sweet wort.

  16. Minority Carrier Electron Traps in CZTSSe Solar Cells Characterized by DLTS and DLOS

    SciTech Connect

    Kheraj, V.; Lund, E. A.; Caruso, A. E.; Al-Ajmi, K.; Pruzan, D.; Miskin, C.; Agrawal, R.; Beall, Carolyn; Repins, Ingrid; Scarpulla, M. A.

    2016-11-21

    We report observations of minority carrier interactions with deep levels in 6-8% efficient Cu2ZnSn(S, Se)4 (CZTSSe) devices using conventional and minority deep level transient spectroscopy (DLTS) and deep level optical spectroscopy (DLOS). Directly observing defect interactions with minority carriers is critical to understanding the recombination impact of deep levels. In devices with Cu2ZnSn(S, Se)4 nanoparticle ink absorber layers we identify a mid-gap state capturing and emitting minority electrons. It is 590+/-50 meV from the conduction band mobility edge, has a concentration near 1015/cm3, and has an apparent electron capture cross section ~10-14 cm2. We conclude that, while energetically positioned nearly-ideally to be a recombination center, these defects instead act as electron traps because of a smaller hole cross-section. In CZTSe devices produced using coevaporation, we used minority carrier DLTS on traditional samples as well as ones with transparent Ohmic back contacts. These experiments demonstrate methods for unambiguously probing minority carrier/defect interactions in solar cells in order to establish direct links between defect energy level observations and minority carrier lifetimes. Furthermore, we demonstrate the use of steady-state device simulation to aid in the interpretation of DLTS results e.g. to put bounds on the complimentary carrier cross section even in the absence its direct measurement. This combined experimental and theoretical approach establishes rigorous bounds on the impact on carrier lifetime and Voc of defects observed with DLTS as opposed to, for example, assuming that all deep states act as strong recombination centers.

  17. Unraveling the Electronic Heterogeneity of Charge Traps in Conjugated Polymers by Single-Molecule Spectroscopy.

    PubMed

    Adachi, Takuji; Vogelsang, Jan; Lupton, John M

    2014-02-06

    Charge trapping is taken for granted in modeling the characteristics of organic semiconductor devices, but very few techniques actually exist to spectroscopically pinpoint trap states. For example, trap levels are often assumed to be discrete in energy. Using the well-known keto defect in polyfluorene as a model, we demonstrate how single-molecule spectroscopy can directly track the formation of charge and exciton traps in conjugated polymers in real time, providing crucial information on the energetic distribution of trap sites relative to the polymer optical gap. Charge traps with universal spectral fingerprints scatter by almost 1 eV in depth, implying that substantial heterogeneity must be taken into account when modeling devices.

  18. Determination of the ReA Electron Beam Ion Trap electron beam radius and current density with an X-ray pinhole camera.

    PubMed

    Baumann, Thomas M; Lapierre, Alain; Kittimanapun, Kritsada; Schwarz, Stefan; Leitner, Daniela; Bollen, Georg

    2014-07-01

    The Electron Beam Ion Trap (EBIT) of the National Superconducting Cyclotron Laboratory at Michigan State University is used as a charge booster and injector for the currently commissioned rare isotope re-accelerator facility ReA. This EBIT charge breeder is equipped with a unique superconducting magnet configuration, a combination of a solenoid and a pair of Helmholtz coils, allowing for a direct observation of the ion cloud while maintaining the advantages of a long ion trapping region. The current density of its electron beam is a key factor for efficient capture and fast charge breeding of continuously injected, short-lived isotope beams. It depends on the radius of the magnetically compressed electron beam. This radius is measured by imaging the highly charged ion cloud trapped within the electron beam with a pinhole camera, which is sensitive to X-rays emitted by the ions with photon energies between 2 keV and 10 keV. The 80%-radius of a cylindrical 800 mA electron beam with an energy of 15 keV is determined to be r(80%) = (212 ± 19)μm in a 4 T magnetic field. From this, a current density of j = (454 ± 83)A/cm(2) is derived. These results are in good agreement with electron beam trajectory simulations performed with TriComp and serve as a test for future electron gun design developments.

  19. Determination of the ReA Electron Beam Ion Trap electron beam radius and current density with an X-ray pinhole camera

    SciTech Connect

    Baumann, Thomas M. Lapierre, Alain Kittimanapun, Kritsada; Schwarz, Stefan; Leitner, Daniela; Bollen, Georg

    2014-07-15

    The Electron Beam Ion Trap (EBIT) of the National Superconducting Cyclotron Laboratory at Michigan State University is used as a charge booster and injector for the currently commissioned rare isotope re-accelerator facility ReA. This EBIT charge breeder is equipped with a unique superconducting magnet configuration, a combination of a solenoid and a pair of Helmholtz coils, allowing for a direct observation of the ion cloud while maintaining the advantages of a long ion trapping region. The current density of its electron beam is a key factor for efficient capture and fast charge breeding of continuously injected, short-lived isotope beams. It depends on the radius of the magnetically compressed electron beam. This radius is measured by imaging the highly charged ion cloud trapped within the electron beam with a pinhole camera, which is sensitive to X-rays emitted by the ions with photon energies between 2 keV and 10 keV. The 80%-radius of a cylindrical 800 mA electron beam with an energy of 15 keV is determined to be r{sub 80%}=(212±19)μm in a 4 T magnetic field. From this, a current density of j = (454 ± 83)A/cm{sup 2} is derived. These results are in good agreement with electron beam trajectory simulations performed with TriComp and serve as a test for future electron gun design developments.

  20. Observation of electron trapping along scratches on SiO2 surface in mirror electron microscope images under ultraviolet light irradiation

    NASA Astrophysics Data System (ADS)

    Hasegawa, Masaki; Shimakura, Tomokazu

    2010-04-01

    Surface charge distribution change caused by electrons trapped at defects of a SiO2 surface has been observed by using a mirror electron microscope (MEM) under monochromatized ultraviolet (UV) light irradiation. Scratches on the SiO2 surface on a silicon wafer were formed by mechanically polishing to create spatially distributed defects on the SiO2 surface. Exposure of the SiO2 surface by UV light with energy above 4.25 eV, which is the threshold energy for internal photoemission from silicon to SiO2, produced significant change in the contrast in the MEM images. This contrast change is mainly due to negative charging by the photoexcited electrons trapped at the defects along the scratches. The negative charging changes the curvature of the electrostatic equipotential surface above the scratches from a concave shape to a convex shape; as a result, their contrast in the MEM image becomes reversed. The surface density of the trapped electrons at a typical scratch was roughly estimated to be 1010 cm-2. This result of analysis of the contrast change shows that the MEM can be used for spatially resolved and spectroscopic characterizations of defects relating charge trapping in insulator films in conjunction with a charge-injection technique such as UV irradiation.

  1. Hydrogen trapping in δ-Pu: insights from electronic structure calculations.

    PubMed

    Taylor, Christopher D; Hernandez, Sarah C; Francis, Michael F; Schwartz, Daniel S; Ray, Asok K

    2013-07-03

    Density functional theory calculations have been performed to provide details of the structural and charge-transfer details related to the solid solution of hydrogen in (δ)-plutonium. We follow the Flanagan model that outlines the process by which hydrogen interacts with a metal to produce hydride phases, via a sequence of surface, interstitial and defect-bound (trapped) states. Due to the complexities of the electronic structure in plutonium solid-state systems, we take the pragmatic approach of adopting the 'special quasirandom structure' to disperse the atomic magnetic moments. We find that this approach produces sound structural and thermodynamic properties in agreement with the available experimental data. In δ-Pu, hydrogen has an exothermic binding energy to all of the states relevant in the Flanagan model, and, furthermore, is anionic in all these states. The charge transfer is maximized (i.e. most negative for hydrogen) in the hydride phase. The pathway from surface to hydride is sequentially exothermic, in the order surface < interstitial < grain boundary < vacancy < hydride (hydride being the most exothermic state). Thus, we find that there is no intermediate state that involves an endothermic increase in energy, consistent with the general experimental observations that the hydriding reaction in plutonium metal can proceed with zero apparent activation barrier.

  2. Evidence for density-gradient-driven trapped-electron modes in improved confinement RFP plasmas

    NASA Astrophysics Data System (ADS)

    Duff, James; Chapman, Brett; Sarff, John; Terry, Paul; Williams, Zach; Ding, Weixing; Brower, David; Parke, Eli

    2015-11-01

    Density fluctuations in the large-density-gradient region of improved-confinement MST RFP plasmas exhibit features characteristic of the trapped-electron-mode (TEM), strong evidence that drift wave turbulence emerges in RFP plasmas when magnetic transport is reduced. In standard RFP plasmas, core transport is governed by magnetic stochasticity stemming from current-driven tearing modes. Using inductive control, these tearing modes are reduced, improving confinement. The improved confinement is associated with substantial increases in the density and temperature gradients, and we present evidence for the onset of drift wave instability. Density fluctuations are measured with a multi-chord, laser-based interferometer. These fluctuations have wavenumbers kϕ *ρs <0.14, frequencies characteristic of drift waves (>50 kHz), and are clearly distinct from residual global tearing modes. Their amplitudes increase with the local density gradient, and require a critical density gradient. Gyrokinetic analysis provides supporting evidence of microinstability in these plasmas, in which the density-gradient-driven TEM is most unstable. The experimental threshold gradient is close to the predicted critical gradient for linear stability. Work supported by DOE.

  3. Control of ion density distribution by magnetic traps for plasma electrons

    SciTech Connect

    Baranov, Oleg; Romanov, Maxim; Fang Jinghua; Cvelbar, Uros; Ostrikov, Kostya

    2012-10-01

    The effect of a magnetic field of two magnetic coils on the ion current density distribution in the setup for low-temperature plasma deposition is investigated. The substrate of 400 mm diameter is placed at a distance of 325 mm from the plasma duct exit, with the two magnetic coils mounted symmetrically under the substrate at a distance of 140 mm relative to the substrate centre. A planar probe is used to measure the ion current density distribution along the plasma flux cross-sections at distances of 150, 230, and 325 mm from the plasma duct exit. It is shown that the magnetic field strongly affects the ion current density distribution. Transparent plastic films are used to investigate qualitatively the ion density distribution profiles and the effect of the magnetic field. A theoretical model is developed to describe the interaction of the ion fluxes with the negative space charge regions associated with the magnetic trapping of the plasma electrons. Theoretical results are compared with the experimental measurements, and a reasonable agreement is demonstrated.

  4. The XRS microcalorimeter spectrometer at the Livermore Electron Beam Ion Trap

    SciTech Connect

    Porter, F S; Beiersdorfer, P; Boyce, K; Brown, G V; Chen, H; Gygax, J; Kahn, S M; Kelley, R; Kilbourne, C A; Magee, E; Thorn, D B

    2007-08-22

    NASA's X-ray Spectrometer (XRS) microcalorimeter instrument has been operating at the Electron Beam Ion Trap (EBIT) facility at Lawrence Livermore National Laboratory since July of 2000. The spectrometer is currently undergoing its third major upgrade to become an easy to use, extremely high performance instrument for a broad range of EBIT experiments. The spectrometer itself is broadband, capable of simultaneously operating from 0.1 to 12 keV and has been operated at up to 100 keV by manipulating its operating conditions. The spectral resolution closely follows the spaceflight version of the XRS, beginning at 10 eV FWHM at 6 keV in 2000, upgraded to 5.5 eV in 2003, and will hopefully be {approx}3.8 eV in the Fall of 2007. Here we review the operating principles of this unique instrument, the extraordinary science that has been performed at EBIT over the last 6 years, and prospects for future upgrades. Specifically we discuss upgrades to cover the high-energy band (to at least 100 keV) with a high quantum efficiency detector, and prospects for using a new superconducting detector to reach 0.8 eV resolution at 1 keV, and 2 eV at 6 keV with high counting rates.

  5. Hydrogen trapping in δ-Pu: insights from electronic structure calculations

    NASA Astrophysics Data System (ADS)

    Taylor, Christopher D.; Hernandez, Sarah C.; Francis, Michael F.; Schwartz, Daniel S.; Ray, Asok K.

    2013-07-01

    Density functional theory calculations have been performed to provide details of the structural and charge-transfer details related to the solid solution of hydrogen in (δ)-plutonium. We follow the Flanagan model that outlines the process by which hydrogen interacts with a metal to produce hydride phases, via a sequence of surface, interstitial and defect-bound (trapped) states. Due to the complexities of the electronic structure in plutonium solid-state systems, we take the pragmatic approach of adopting the ‘special quasirandom structure’ to disperse the atomic magnetic moments. We find that this approach produces sound structural and thermodynamic properties in agreement with the available experimental data. In δ-Pu, hydrogen has an exothermic binding energy to all of the states relevant in the Flanagan model, and, furthermore, is anionic in all these states. The charge transfer is maximized (i.e. most negative for hydrogen) in the hydride phase. The pathway from surface to hydride is sequentially exothermic, in the order surface < interstitial < grain boundary < vacancy < hydride (hydride being the most exothermic state). Thus, we find that there is no intermediate state that involves an endothermic increase in energy, consistent with the general experimental observations that the hydriding reaction in plutonium metal can proceed with zero apparent activation barrier.

  6. Magnetically induced electron shelving in a trapped Ca{sup +} ion

    SciTech Connect

    Crick, D. R.; Donnellan, S.; Segal, D. M.; Thompson, R. C.

    2010-05-15

    Atomic states are perturbed by externally applied magnetic fields (Zeeman effect). As well as the usual Zeeman splittings, the magnetic field leads to mixing of states with different values of the J quantum number. We report on the direct experimental measurement of this effect using the electron shelving technique (employed to great effect in single-ion spectroscopy and quantum-information processing). Specifically we observe shelving to the metastable (3p{sup 6}3d) {sup 2}D{sub 5/2} state in a single {sup 40}Ca{sup +} ion, via spontaneous decay on the strongly forbidden 4p {sup 2}P{sub 1/2{r_reversible}}3d {sup 2}D{sub 5/2} transition. The rate of this transition is shown to scale as the square of the magnetic-field strength. The scaling and magnitude of the effect is compared to the result derived from first-order perturbation theory. For applications in quantum-information processing the J-mixing effect causes a degradation of readout fidelity. We show that this degradation is at a tolerable level for Ca{sup +} and is much less problematic for other trapped ionic species.

  7. Development of a Magneto-Optical Trap System of Francium Atoms for the Electron Electric-Dipole-Moment Search

    NASA Astrophysics Data System (ADS)

    Harada, K.; Aoki, T.; Kato, K.; Kawamura, H.; Inoue, T.; Aoki, T.; Uchiyama, A.; Sakamoto, K.; Ito, S.; Itoh, M.; Hayamizu, T.; Hatakeyama, A.; Hatanaka, K.; Wakasa, T.; Sakemi, Y.

    2016-02-01

    The finite value of an electron electric dipole moment (eEDM) provides the direct evidence for the violation of time reversal symmetry. Fr atoms, whose enhancement factor is 895, trapped by laser cooling and trapping techniques are one of the strongest candidates for measuring the eEDM. We are constructing a beamline for measuring the eEDM using laser- cooled Fr atoms at the Cyclotron and Radioisotope Center. We have developed laser light sources including the frequency stabilization system and a magneto-optical trap system for Fr atoms. As the Fr production requires the cyclotron operation, we also use Rb atoms whose chemical properties are similar to those of the Fr atoms. Thus, the Rb beam is utilized for optimizing the operation parameters of the entire apparatus. We have also developed the laser light sources for Rb atoms and observed the beat signal for frequency stabilization of the source using the frequency offset locking method.

  8. Survival of bacterial isolates exposed to simulated Jovian trapped radiation belt electrons and solar wind protons

    NASA Technical Reports Server (NTRS)

    Taylor, D. M.; Hagen, C. A.; Renninger, G. M.; Simko, G. J.; Smith, C. D.; Yelinek, J. A.

    1973-01-01

    With missions to Jupiter, the spacecraft will be exposed for extended durations to solar wind radiation and the Jovian trapped radiation belt. This study is designed to determine the effect of these radiation environments on spacecraft bacterial isolates. The information can be used in the probability of contamination analysis for these missions. A bacterial subpopulation from Mariner Mars 1971 spacecraft (nine spore-forming and three non-spore-forming isolates) plus two comparative organisms, Staphylococcus epidermidis ATCC 17917 and a strain of Bacillus subtilis var. niger, were exposed to 2, 12, and 25 MeV electrons at different doses with simultaneous exposure to a vacuum of 1.3 x 10(-4) N m-2 at 20 and -20 degrees C. The radioresistance of the subpopulation was dependent on the isolate, dose and energy of electrons. Temperature affected the radioresistance of only the spore-forming isolates. Survival data indicated that spores were reduced approximately 1 log/1500 J kg-1 (10 J kg-1=1 krad), while non-spore-forming isolates (micrococci) were reduced 1.5-2 logs/1500 J kg-1 with the exception of an apparent radioresistant isolate whose resistance approached that of the spores. The subpopulation was found to be less resistant to lower energy than to higher energy electrons. The bacterial isolates were exposed to 3 keV protons under the same conditions as the electrons with a total fluence of 1.5 x 10(13) p cm-2 and a dose rate of 8.6 x 10(9) p cm-2 s-1. The results showed that only 20% of S. epidermidis and 45% of B. subtilis populations survived exposure to the 3 keV protons, while the mean survival of the spacecraft subpopulation was 45% with a range from 31.8% (non-spore-former) to 64.8% (non-spore-former). No significant difference existed between spore-forming and non-spore-forming isolates.

  9. Survival of bacterial isolates exposed to simulated Jovian trapped radiation belt electrons and solar wind protons.

    PubMed

    Taylor, D M; Hagen, C A; Renninger, G M; Simko, G J; Smith, C D; Yelinek, J A

    1973-01-01

    With missions to Jupiter, the spacecraft will be exposed for extended durations to solar wind radiation and the Jovian trapped radiation belt. This study is designed to determine the effect of these radiation environments on spacecraft bacterial isolates. The information can be used in the probability of contamination analysis for these missions. A bacterial subpopulation from Mariner Mars 1971 spacecraft (nine spore-forming and three non-spore-forming isolates) plus two comparative organisms, Staphylococcus epidermidis ATCC 17917 and a strain of Bacillus subtilis var. niger, were exposed to 2, 12, and 25 MeV electrons at different doses with simultaneous exposure to a vacuum of 1.3 x 10(-4) N m-2 at 20 and -20 degrees C. The radioresistance of the subpopulation was dependent on the isolate, dose and energy of electrons. Temperature affected the radioresistance of only the spore-forming isolates. Survival data indicated that spores were reduced approximately 1 log/1500 J kg-1 (10 J kg-1=1 krad), while non-spore-forming isolates (micrococci) were reduced 1.5-2 logs/1500 J kg-1 with the exception of an apparent radioresistant isolate whose resistance approached that of the spores. The subpopulation was found to be less resistant to lower energy than to higher energy electrons. The bacterial isolates were exposed to 3 keV protons under the same conditions as the electrons with a total fluence of 1.5 x 10(13) p cm-2 and a dose rate of 8.6 x 10(9) p cm-2 s-1. The results showed that only 20% of S. epidermidis and 45% of B. subtilis populations survived exposure to the 3 keV protons, while the mean survival of the spacecraft subpopulation was 45% with a range from 31.8% (non-spore-former) to 64.8% (non-spore-former). No significant difference existed between spore-forming and non-spore-forming isolates.

  10. Methodological considerations of electron spin resonance spin trapping techniques for measuring reactive oxygen species generated from metal oxide nanomaterials

    NASA Astrophysics Data System (ADS)

    Jeong, Min Sook; Yu, Kyeong-Nam; Chung, Hyun Hoon; Park, Soo Jin; Lee, Ah Young; Song, Mi Ryoung; Cho, Myung-Haing; Kim, Jun Sung

    2016-05-01

    Qualitative and quantitative analyses of reactive oxygen species (ROS) generated on the surfaces of nanomaterials are important for understanding their toxicity and toxic mechanisms, which are in turn beneficial for manufacturing more biocompatible nanomaterials in many industrial fields. Electron spin resonance (ESR) is a useful tool for detecting ROS formation. However, using this technique without first considering the physicochemical properties of nanomaterials and proper conditions of the spin trapping agent (such as incubation time) may lead to misinterpretation of the resulting data. In this report, we suggest methodological considerations for ESR as pertains to magnetism, sample preparation and proper incubation time with spin trapping agents. Based on our results, each spin trapping agent should be given the proper incubation time. For nanomaterials having magnetic properties, it is useful to remove these nanomaterials via centrifugation after reacting with spin trapping agents. Sonication for the purpose of sample dispersion and sample light exposure should be controlled during ESR in order to enhance the obtained ROS signal. This report will allow researchers to better design ESR spin trapping applications involving nanomaterials.

  11. Generation of high charge state metal ion beams by electron cyclotron resonance heating of vacuum arc plasma in cusp trap

    SciTech Connect

    Nikolaev, A. G.; Savkin, K. P.; Oks, E. M.; Vizir, A. V.; Yushkov, G. Yu.; Vodopyanov, A. V.; Izotov, I. V.; Mansfeld, D. A.

    2012-02-15

    A method for generating high charge state heavy metal ion beams based on high power microwave heating of vacuum arc plasma confined in a magnetic trap under electron cyclotron resonance conditions has been developed. A feature of the work described here is the use of a cusp magnetic field with inherent ''minimum-B'' structure as the confinement geometry, as opposed to a simple mirror device as we have reported on previously. The cusp configuration has been successfully used for microwave heating of gas discharge plasma and extraction from the plasma of highly charged, high current, gaseous ion beams. Now we use the trap for heavy metal ion beam generation. Two different approaches were used for injecting the vacuum arc metal plasma into the trap - axial injection from a miniature arc source located on-axis near the microwave window, and radial injection from sources mounted radially at the midplane of the trap. Here, we describe preliminary results of heating vacuum arc plasma in a cusp magnetic trap by pulsed (400 {mu}s) high power (up to 100 kW) microwave radiation at 37.5 GHz for the generation of highly charged heavy metal ion beams.

  12. Generation of high charge state metal ion beams by electron cyclotron resonance heating of vacuum arc plasma in cusp trap.

    PubMed

    Nikolaev, A G; Savkin, K P; Oks, E M; Vizir, A V; Yushkov, G Yu; Vodopyanov, A V; Izotov, I V; Mansfeld, D A

    2012-02-01

    A method for generating high charge state heavy metal ion beams based on high power microwave heating of vacuum arc plasma confined in a magnetic trap under electron cyclotron resonance conditions has been developed. A feature of the work described here is the use of a cusp magnetic field with inherent "minimum-B" structure as the confinement geometry, as opposed to a simple mirror device as we have reported on previously. The cusp configuration has been successfully used for microwave heating of gas discharge plasma and extraction from the plasma of highly charged, high current, gaseous ion beams. Now we use the trap for heavy metal ion beam generation. Two different approaches were used for injecting the vacuum arc metal plasma into the trap--axial injection from a miniature arc source located on-axis near the microwave window, and radial injection from sources mounted radially at the midplane of the trap. Here, we describe preliminary results of heating vacuum arc plasma in a cusp magnetic trap by pulsed (400 μs) high power (up to 100 kW) microwave radiation at 37.5 GHz for the generation of highly charged heavy metal ion beams.

  13. Electron spin resonance study of self-trapped holes in CdWO{sub 4} scintillator crystals

    SciTech Connect

    Laguta, V. V.; Nikl, M.; Rosa, J.; Grinyov, B. V.; Nagornaya, L. L.; Tupitsina, I. A.

    2008-11-15

    The self-trapping of holes at oxygen anions was studied by electron spin resonance in UV irradiated CdWO{sub 4} crystals. Analysis of superhyperfine interaction of the holes with {sup 183}W and {sup 111,113}Cd isotopes shows that the self-trapped hole is either delocalized in the space between two energetically equivalent nearest neighbor oxygen ions or tunnels between them. When the temperature increases above 40-50 K the self-trapped holes are thermally liberated and can be retrapped by oxygen ions perturbed by impurity ions. In case of the Nb{sup 5+} or Li{sup +} stabilizing impurities the O{sup -} centers are thermally stable up to 160-170 K. The study of kinetic characteristics of the self-trapped holes suggests that holes leave oxygen ions by thermally assisted tunneling mechanism via two slightly different channels. Corresponding ionization probabilities are defined by the Arrhenius law with an average thermal ionization energy E=90(5) meV. Calculated pre-exponential factors, about 10{sup 5} s{sup -1}, are small, which is consistent with the tunneling mechanism. Thermal stability and kinetic characteristics of the trapped holes are discussed in light of the scintillation and thermoluminescence characteristics of CdWO{sub 4}.

  14. Variation of carrier concentration and interface trap density in 8MeV electron irradiated c-Si solar cells

    SciTech Connect

    Bhat, Sathyanarayana Rao, Asha; Krishnan, Sheeja; Sanjeev, Ganesh; Suresh, E. P.

    2014-04-24

    The capacitance and conductance measurements were carried out for c-Si solar cells, irradiated with 8 MeV electrons with doses ranging from 5kGy – 100kGy in order to investigate the anomalous degradation of the cells in the radiation harsh environments. Capacitance – Voltage measurements indicate that there is a slight reduction in the carrier concentration upon electron irradiation due to the creation of radiation induced defects. The conductance measurement results reveal that the interface state densities and the trap time constant increases with electron dose due to displacement damages in c-Si solar cells.

  15. Micromachined Dust Traps

    NASA Technical Reports Server (NTRS)

    Bearman, Gregory H.; Bradley, James G.

    1993-01-01

    Micromachined traps devised to capture dust particles for analysis without contaminating them. Based on micromachined structures retaining particles, rather than adhesives or greases interfering with scanning-electron-microscope analysis or x-ray imaging. Unlike maze traps and traps enmeshing particles in steel wool or similar materials, micromachined traps do not obscure trapped particles. Internal geometries of traps range from simple cones to U-shapes, all formed by etching silicon.

  16. Covalent O-H bonds as electron traps in proton-rich rutile TiO2 nanoparticles.

    PubMed

    Zhang, Jing; Steigerwald, Michael; Brus, Louis; Friesner, Richard A

    2014-01-01

    The cation in the electrolyte of the dye-sensitized solar cell (DSSC) has a profound effect on electron trapping and transport behavior in TiO2 nanocrystalline film; this is one of the important factors that determines the overall efficiency of DSSCs. Here, we present a quantum mechanical investigation on the structures and energetics of proton-induced electron trap states and the thermodynamical barrier heights for the ambipolar diffusion of proton/electron pair using a large cluster model for the computations. Our calculations indicate that protons react with TiO2 to form covalent O-H bonds. This is in contrast to the reaction of Li(+) with TiO2, in which case the alkali metal is more accurately described as a simple coordinating cation. The covalent O-H bonding leads both to deeper electron trap states and to significantly higher barriers for the diffusion of carriers. These results are qualitatively consistent with experimental observations, and they extend our understanding of the cation effect in DSSCs at an atomic level of detail.

  17. Role of Density Gradient Driven Trapped Electron Modes in the H-Mode Inner Core with Electron Heating

    NASA Astrophysics Data System (ADS)

    Ernst, D.

    2015-11-01

    We present new experiments and nonlinear gyrokinetic simulations showing that density gradient driven TEM (DGTEM) turbulence dominates the inner core of H-Mode plasmas during strong electron heating. Thus α-heating may degrade inner core confinement in H-Mode plasmas with moderate density peaking. These DIII-D low torque quiescent H-mode experiments were designed to study DGTEM turbulence. Gyrokinetic simulations using GYRO (and GENE) closely match not only particle, energy, and momentum fluxes, but also density fluctuation spectra, with and without ECH. Adding 3.4 MW ECH doubles Te /Ti from 0.5 to 1.0, which halves the linear TEM critical density gradient, locally flattening the density profile. Density fluctuations from Doppler backscattering (DBS) intensify near ρ = 0.3 during ECH, displaying a band of coherent fluctuations with adjacent toroidal mode numbers. GYRO closely reproduces the DBS spectrum and its change in shape and intensity with ECH, identifying these as coherent TEMs. Prior to ECH, parallel flow shear lowers the effective nonlinear DGTEM critical density gradient 50%, but is negligible during ECH, when transport displays extreme stiffness in the density gradient. GS2 predictions show the DGTEM can be suppressed, to avoid degradation with electron heating, by broadening the current density profile to attain q0 >qmin > 1 . A related experiment in the same regime varied the electron temperature gradient in the outer half-radius (ρ ~ 0 . 65) using ECH, revealing spatially coherent 2D mode structures in the Te fluctuations measured by ECE imaging. Fourier analysis with modulated ECH finds a threshold in Te profile stiffness. Supported by the US DOE under DE-FC02-08ER54966 and DE-FC02-04ER54698.

  18. Detection of electron and hole traps in CdZnTe radiation detectors by thermoelectric emission spectroscopy and thermally stimulated conductivity

    SciTech Connect

    E. Y. Lee; B. A. Brunett; R. W. Olsen; J. M. Van Scyoc III; H. Hermon; R. B. James

    1998-06-18

    The electrical properties of CdZnTe radiation detectors are largely determined by electron and hole traps in this material. The traps, in addition to degrading the detector performance, can function as dopants and determine the resistivity of the material. Thermoelectric emission spectroscopy and thermally stimulated conductivity are used to detect these traps in a commercially available spectrometer-grade CdZnTe detector, and the electrical resistivity is measured as a function of temperature. A deep electron trap having an energy of 695 meV and cross section of 8 x 10{sup {minus}16}cm{sup 2} is detected and three hole traps having energies of 70 {+-} 20 meV, 105 {+-} 30 meV and 694 {+-} 162 meV are detected. A simple model based on these traps explains quantitatively all the data, including the electrical properties at room temperature and also their temperature dependence.

  19. Dissipative dust-acoustic shock waves in a varying charge electronegative magnetized dusty plasma with trapped electrons

    NASA Astrophysics Data System (ADS)

    Bacha, Mustapha; Tribeche, Mouloud

    2016-08-01

    The combined effects of an oblique magnetic field and electron trapping on dissipative dust-acoustic waves are examined in varying charge electronegative dusty plasmas with application to the Halley Comet plasma (˜104 km from the nucleus). A weakly nonlinear analysis is carried out to derive a modified Korteweg-de Vries-Burger-like equation. Making use of the equilibrium current balance equation, the physically admissible values of the electron trapping parameter are first constrained. We then show that the Burger dissipative term is solely due to the dust charge variation process. It is found that an increase of the magnetic field obliqueness or a decrease of its magnitude renders the shock structure more dispersive.

  20. Extended-range grazing-incidence spectrometer for high-resolution extreme ultraviolet measurements on an electron beam ion trap

    SciTech Connect

    Beiersdorfer, P.; Magee, E. W.; Brown, G. V.; Träbert, E.; Widmann, K.; Hell, N.

    2014-11-15

    A high-resolution grazing-incidence grating spectrometer has been implemented on the Livermore electron beam ion traps for performing very high-resolution measurements in the soft x-ray and extreme ultraviolet region spanning from below 10 Å to above 300 Å. The instrument operates without an entrance slit and focuses the light emitted by highly charged ions located in the roughly 50 μm wide electron beam onto a cryogenically cooled back-illuminated charge-coupled device detector. The measured line widths are below 0.025 Å above 100 Å, and the resolving power appears to be limited by the source size and Doppler broadening of the trapped ions. Comparisons with spectra obtained with existing grating spectrometers show an order of magnitude improvement in spectral resolution.

  1. Extended-range grazing-incidence spectrometer for high-resolution extreme ultraviolet measurements on an electron beam ion trap.

    PubMed

    Beiersdorfer, P; Magee, E W; Brown, G V; Hell, N; Träbert, E; Widmann, K

    2014-11-01

    A high-resolution grazing-incidence grating spectrometer has been implemented on the Livermore electron beam ion traps for performing very high-resolution measurements in the soft x-ray and extreme ultraviolet region spanning from below 10 Å to above 300 Å. The instrument operates without an entrance slit and focuses the light emitted by highly charged ions located in the roughly 50 μm wide electron beam onto a cryogenically cooled back-illuminated charge-coupled device detector. The measured line widths are below 0.025 Å above 100 Å, and the resolving power appears to be limited by the source size and Doppler broadening of the trapped ions. Comparisons with spectra obtained with existing grating spectrometers show an order of magnitude improvement in spectral resolution.

  2. Collision of ion acoustic solitary waves in a magnetized plasma: Effect of dust grains and trapped electrons

    NASA Astrophysics Data System (ADS)

    Malik, Hitendra K.; Kumar, Ravinder; Lonngren, Karl E.; Nishida, Yasushi

    2015-12-01

    The head-on collision of two ion acoustic solitary waves is investigated in a magnetized plasma containing trapped electrons and dust grains. For completeness, the fluctuations in dust grain charge are taken into account. By using the extended Poincaré-Lighthill-Kuo (PLK) perturbation method, an analytical expression is obtained for the phase shift that takes place due to the collision of the waves. How the phase shift behaves under the combined effect of trapped electrons and dust grains along with the finite temperature of ions is examined. A focus is given to uncover the situations of fluctuating charge and fixed charge on the dust grains in the plasma. Interestingly, the solitary waves acquire a larger phase shift and are delayed more in the case of dust grains having a fluctuating charge.

  3. Enhanced loss of magnetic-mirror-trapped fast electrons by a shear Alfvén wave

    SciTech Connect

    Wang, Y.; Gekelman, W.; Pribyl, P.; Papadopoulos, K.

    2014-05-15

    Laboratory observations of enhanced loss of magnetic mirror trapped fast electrons irradiated by a shear Alfvén Wave (SAW) are reported. The experiment is performed in the quiescent after-glow plasma in the Large Plasma Device [Gekelman et al., Rev. Sci. Instrum. 62(12), 2875–2883 (1991)]. A trapped energetic electron population (>100 keV) is generated in a magnetic mirror section (mirror ratio ≈ 2, length = 3.5 m) by an X-mode high power microwave pulse, and forms a hot electron ring due to the grad-B and curvature drift. SAWs of arbitrary polarization are launched externally by a Rotating Magnetic Field source (δB/B{sub 0} ≈ 0.1%, λ{sub ∥} ≈ 9 m). Irradiated by a right-handed circularly polarized SAW, the loss of electrons, in both the radial and the axial direction of the mirror field, is significantly enhanced and is modulated at f{sub Alfvén}. The periodical loss continues even after the termination of the SAW. Experimental observations suggest that a spatial distortion of the ring is formed in the SAW field and creates a collective mode of the hot electron population that degrades its confinement and leads to electron loss from the magnetic mirror. The results could have implications on techniques of radiation belt remediation.

  4. Formation of high-{beta} plasma and stable confinement of toroidal electron plasma in Ring Trap 1

    SciTech Connect

    Saitoh, H.; Yoshida, Z.; Morikawa, J.; Furukawa, M.; Yano, Y.; Kawai, Y.; Kobayashi, M.; Vogel, G.; Mikami, H.

    2011-05-15

    Formation of high-{beta} electron cyclotron resonance heating plasma and stable confinement of pure electron plasma have been realized in the Ring Trap 1 device, a magnetospheric configuration generated by a levitated dipole field magnet. The effects of coil levitation resulted in drastic improvements of the confinement properties, and the maximum local {beta} value has exceeded 70%. Hot electrons are major component of electron populations, and its particle confinement time is 0.5 s. Plasma has a peaked density profile in strong field region [H. Saitoh et al., 23rd IAEA Fusion Energy Conference EXC/9-4Rb (2010)]. In pure electron plasma experiment, inward particle diffusion is realized, and electrons are stably trapped for more than 300 s. When the plasma is in turbulent state during beam injection, plasma flow has a shear, which activates the diocotron (Kelvin-Helmholtz) instability. The canonical angular momentum of the particle is not conserved in this phase, realizing the radial diffusion of charged particles across closed magnetic surfaces. [Z. Yoshida et al., Phys Rev. Lett. 104, 235004 (2010); H. Saitoh et al., Phys. Plasmas 17, 112111 (2010).].

  5. Efficient production of high-energy nonthermal particles during magnetic reconnection in a magnetically dominated ion-electron plasma

    SciTech Connect

    Guo, Fan; Li, Xiaocan; Li, Hui; Daughton, William; Zhang, Bing; Lloyd-Ronning, Nicole; Liu, Yi-Hsin; Zhang, Haocheng; Deng, Wei

    2016-02-03

    Magnetic reconnection is a leading mechanism for dissipating magnetic energy and accelerating nonthermal particles in Poynting-flux-dominated flows. We investigate nonthermal particle acceleration during magnetic reconnection in a magnetically dominated ion–electron plasma using fully kinetic simulations. For an ion–electron plasma with a total magnetization of ${\\sigma }_{0}={B}^{2}/(4\\pi n({m}_{i}+{m}_{e}){c}^{2})$, the magnetization for each species is ${\\sigma }_{i}\\sim {\\sigma }_{0}$ and ${\\sigma }_{e}\\sim ({m}_{i}/{m}_{e}){\\sigma }_{0}$, respectively. We have studied the magnetically dominated regime by varying σe = 103–105 with initial ion and electron temperatures ${T}_{i}={T}_{e}=5-20{m}_{e}{c}^{2}$ and mass ratio ${m}_{i}/{m}_{e}=1-1836$. Our results demonstrate that reconnection quickly establishes power-law energy distributions for both electrons and ions within several (2–3) light-crossing times. For the cases with periodic boundary conditions, the power-law index is $1\\lt s\\lt 2$ for both electrons and ions. The hard spectra limit the power-law energies for electrons and ions to be ${\\gamma }_{{be}}\\sim {\\sigma }_{e}$ and ${\\gamma }_{{bi}}\\sim {\\sigma }_{i}$, respectively. The main acceleration mechanism is a Fermi-like acceleration through the drift motions of charged particles. When comparing the spectra for electrons and ions in momentum space, the spectral indices sp are identical as predicted in Fermi acceleration. We also find that the bulk flow can carry a significant amount of energy during the simulations. Finally, we discuss the implication of this study in the context of Poynting-flux dominated jets and pulsar winds, especially the applications for explaining nonthermal high-energy emissions.

  6. Efficient production of high-energy nonthermal particles during magnetic reconnection in a magnetically dominated ion-electron plasma

    DOE PAGES

    Guo, Fan; Li, Xiaocan; Li, Hui; ...

    2016-02-03

    Magnetic reconnection is a leading mechanism for dissipating magnetic energy and accelerating nonthermal particles in Poynting-flux-dominated flows. We investigate nonthermal particle acceleration during magnetic reconnection in a magnetically dominated ion–electron plasma using fully kinetic simulations. For an ion–electron plasma with a total magnetization ofmore » $${\\sigma }_{0}={B}^{2}/(4\\pi n({m}_{i}+{m}_{e}){c}^{2})$$, the magnetization for each species is $${\\sigma }_{i}\\sim {\\sigma }_{0}$$ and $${\\sigma }_{e}\\sim ({m}_{i}/{m}_{e}){\\sigma }_{0}$$, respectively. We have studied the magnetically dominated regime by varying σe = 103–105 with initial ion and electron temperatures $${T}_{i}={T}_{e}=5-20{m}_{e}{c}^{2}$$ and mass ratio $${m}_{i}/{m}_{e}=1-1836$$. Our results demonstrate that reconnection quickly establishes power-law energy distributions for both electrons and ions within several (2–3) light-crossing times. For the cases with periodic boundary conditions, the power-law index is $$1\\lt s\\lt 2$$ for both electrons and ions. The hard spectra limit the power-law energies for electrons and ions to be $${\\gamma }_{{be}}\\sim {\\sigma }_{e}$$ and $${\\gamma }_{{bi}}\\sim {\\sigma }_{i}$$, respectively. The main acceleration mechanism is a Fermi-like acceleration through the drift motions of charged particles. When comparing the spectra for electrons and ions in momentum space, the spectral indices sp are identical as predicted in Fermi acceleration. We also find that the bulk flow can carry a significant amount of energy during the simulations. Finally, we discuss the implication of this study in the context of Poynting-flux dominated jets and pulsar winds, especially the applications for explaining nonthermal high-energy emissions.« less

  7. Simulation studies for operating electron beam ion trap at very low energy for disentangling edge plasma spectra

    SciTech Connect

    Jin Xuelong; Fei Zejie; Xiao Jun; Lu Di; Hutton, Roger; Zou Yaming

    2012-07-15

    Electron beam ion traps (EBITs) are very useful tools for disentanglement studies of atomic processes in plasmas. In order to assist studies on edge plasma spectroscopic diagnostics, a very low energy EBIT, SH-PermEBIT, has been set up at the Shanghai EBIT lab. In this work, simulation studies for factors which hinder an EBIT to operate at very low electron energies were made based on the Tricomp (Field Precision) codes. Longitudinal, transversal, and total kinetic energy distributions were analyzed for all the electron trajectories. Influences from the electron current and electron energy on the energy depression caused by the space charge are discussed. The simulation results show that although the energy depression is most serious along the center of the electron beam, the electrons in the outer part of the beam are more likely to be lost when an EBIT is running at very low energy. Using the simulation results to guide us, we successfully managed to reach the minimum electron beam energy of 60 eV with a beam transmission above 57% for the SH-PermEBIT. Ar and W spectra were measured from the SH-PermEBIT at the apparent electron beam energies (read from the voltage difference between the electron gun cathode and the central drift tube) of 60 eV and 1200 eV, respectively. The spectra are shown in this paper.

  8. Phase-Space Density Analysis of the AE-8 Traped Electron and the AP-8 Trapped Proton Model Environments

    SciTech Connect

    Thomas E. Cayton

    2005-08-01

    The AE-8 trapped electron and the AP-8 trapped proton models are used to examine the L-shell variation of phase-space densities for sets of transverse (or 1st) invariants, {mu}, and geometrical invariants, K (related to the first two adiabatic invariants). The motivation for this study is twofold: first, to discover the functional dependence of the phase-space density upon the invariants; and, second, to explore the global structure of the radiation belts within this context. Variation due to particle rest mass is considered as well. The overall goal of this work is to provide a framework for analyzing energetic particle data collected by instruments on Global Positioning System (GPS) spacecraft that fly through the most intense region of the radiation belt. For all considered values of {mu} and K, and for 3.5 R{sub E} < L < 6.5 R{sub E}, the AE-8 electron phase-space density increases with increasing L; this trend--the expected one for a population diffusing inward from an external source--continues to L = 7.5 R{sub E} for both small and large values of K but reverses slightly for intermediate values of K. The AP-8 proton phase-space density exhibits {mu}-dependent local minima around L = 5 R{sub E}. Both AE-8 and AP-8 exhibit critical or cutoff values for the invariants beyond which the flux and therefore the phase-space density vanish. For both electrons and protons, these cutoff values vary systematically with magnetic moment and L-shell and are smaller than those estimated for the atmospheric loss cone. For large magnetic moments, for both electrons and protons, the K-dependence of the phase-space density is exponential, with maxima at the magnetic equator (K = 0) and vanishing beyond a cutoff value, K{sub c}. Such features suggest that momentum-dependent trapping boundaries, perhaps drift-type loss cones, serve as boundary conditions for trapped electrons as well as trapped protons.

  9. Target normal sheath acceleration of foil ions by laser-trapped hot electrons from a long subcritical-density preplasma

    SciTech Connect

    Luan, S. X.; Yu, Wei; Shen, B. F.; Xu, Z. Z.; Yu, M. Y.; Zhuo, H. B.; Xu, Han; Wong, A. Y.; Wang, J. W.

    2014-12-15

    In a long subcritical density plasma, an ultrashort ultraintense laser pulse can self-organize into a fast but sub-relativistic propagating structure consisting of the modulated laser light and a large number of trapped electrons from the plasma. Upon impact of the structure with a solid foil target placed in the latter, the remaining laser light is reflected, but the dense and hot trapped electrons pass through the foil, together with the impact-generated target-frontsurface electrons to form a dense hot electron cloud at the back of the target suitable for enhancing target normal sheath acceleration of the target-backsurface ions. The accelerated ions are well collimated and of high charge and energy densities, with peak energies a full order of magnitude higher than that from target normal sheath acceleration without the subcritical density plasma. In the latter case, the space-charge field accelerating the ions is limited since they are formed only by the target-frontsurface electrons during the very short instant of laser reflection.

  10. Large electronic sputtering yield of nanodimensional Au thin films: Dominant role of thermal conductivity and electron phonon coupling factor

    NASA Astrophysics Data System (ADS)

    Singh, Udai B.; Pannu, Compesh; Agarwal, Dinesh C.; Ojha, Sunil; Khan, Saif A.; Ghosh, Santanu; Avasthi, Devesh K.

    2017-03-01

    Detailed experiments and theoretical calculations on electronic sputtering of Au thin films (5-200 nm) on a quartz substrate are performed, revealing unusually large electronic sputtering, dependent on the thickness of the films. The dependence of electronic thermal conductivity (κe), electron-phonon coupling factor (g), and lattice thermal conductivity (κa) on the effective electron mean free path is taken into account in the thermal spike calculation for nanodimensional systems to elucidate the combined effect of the thickness and grain size on the electronic sputtering yield. The thermal spike simulation with refined parameters for nanodimensional systems gives a better explanation of the electronic sputtering process with a very good correlation between the experimental and theoretical yields than that of the thermal spike model with bulk parameters.

  11. Large dielectric constant, high acceptor density, and deep electron traps in perovskite solar cell material CsGeI3

    SciTech Connect

    Ming, Wenmei; Shi, Hongliang; Du, Mao-Hua

    2016-01-01

    Here we report that many metal halides that contain cations with the ns2 electronic configuration have recently been discovered as high-performance optoelectronic materials. In particular, solar cells based on lead halide perovskites have shown great promise as evidenced by the rapid increase of the power conversion efficiency. In this paper, we show density functional theory calculations of electronic structure and dielectric and defect properties of CsGeI3 (a lead-free halide perovskite material). The potential of CsGeI3 as a solar cell material is assessed based on its intrinsic properties. We find anomalously large Born effective charges and a large static dielectric constant dominated by lattice polarization, which should reduce carrier scattering, trapping, and recombination by screening charged defects and impurities. Defect calculations show that CsGeI3 is a p-type semiconductor and its hole density can be modified by varying the chemical potentials of the constituent elements. Despite the reduction of long-range Coulomb attraction by strong screening, the iodine vacancy in CsGeI3 is found to be a deep electron trap due to the short-range potential, i.e., strong Ge–Ge covalent bonding, which should limit electron transport efficiency in p-type CsGeI3. This is in contrast to the shallow iodine vacancies found in several Pb and Sn halide perovskites (e.g., CH3NH3PbI3, CH3NH3SnI3, and CsSnI3). The low-hole-density CsGeI3 may be a useful solar absorber material but the presence of the low-energy deep iodine vacancy may significantly reduce the open circuit voltage of the solar cell. Still, on the other hand, CsGeI3 may be used as an efficient hole transport material in solar cells due to its small hole effective mass, the absence of low-energy deep hole traps, and the favorable band offset with solar

  12. Isotope effects of trapped electron modes in the presence of impurities in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Shen, Yong; Dong, J. Q.; Sun, A. P.; Qu, H. P.; Lu, G. M.; He, Z. X.; He, H. D.; Wang, L. F.

    2016-04-01

    The trapped electron modes (TEMs) are numerically investigated in toroidal magnetized hydrogen, deuterium and tritium plasmas, taking into account the effects of impurity ions such as carbon, oxygen, helium, tungsten and others with positive and negative density gradients with the rigorous integral eigenmode equation. The effects of impurity ions on TEMs are investigated in detail. It is shown that impurity ions have substantially-destabilizing (stabilizing) effects on TEMs in isotope plasmas for {{L}ez}\\equiv {{L}ne}/{{L}nz}>0 (<0 ), opposite to the case of ion temperature gradient (ITG) driven modes. Detailed analyses of the isotope mass dependence for TEM turbulences in hydrogenic isotope plasmas with and without impurities are performed. The relations between the maximum growth rate of the TEMs with respect to the poloidal wave number and the ion mass number are given in the presence of the impurity ions. The results demonstrate that the maximum growth rates scale as {γ\\max}\\propto Mi-0.5 in pure hydrogenic plasmas. The scale depends on the sign of its density gradient and charge number when there is a second species of (impurity) ions. When impurity ions have density profiles peaking inwardly (i.e. {{L}ez}\\equiv {{L}ne}/{{L}nz}>0 ), the scaling also depends on ITG parameter {ηi} . The maximum growth rates scale as {γ\\max}\\propto M\\text{eff}-0.5 for the case without ITG ({ηi}=0 ) or the ITG parameter is positive ({ηi}>0 ) but the impurity ion charge number is low (Z≤slant 5.0 ). However, when {ηi}>0 and the impurity ion charge number is moderate (Z=6.0-8.0 ), the scaling law is found as {γ\\max}\\propto M\\text{eff}-1.0 . Here, Z is impurity ion charge number, and the effective mass number, {{M}\\text{eff}}=≤ft(1-{{f}z}\\right){{M}i}+{{f}z}{{M}z} , with {{M}i} and {{M}Z} being the mass numbers of the hydrogenic and impurity ions, respectively, and {{f}z}=Z{{n}0z}/{{n}0e} being the charge concentration of impurity ions. In addition, with regard

  13. The protons and electrons trapped in the Jovian dipole magnetic field region and their interaction with Io

    NASA Technical Reports Server (NTRS)

    Simpson, J. A.; Hamilton, D. C.; Mckibben, R. B.; Mogro-Campero, A.; Pyle, K. R.; Tuzzolino, A. J.

    1974-01-01

    Detailed analysis of electrons equal to or greater than 3 MeV and of protons 0.5 to 1.8 MeV and equal to or greater than 35 MeV for both the inbound and the outbound passes of the Pioneer 10 spacecraft. Conclusive evidence is obtained that the trapped radiation in Jupiter's inner magnetosphere is maintained and supplied by inward diffusion from the outer regions of the trapped radiation zone. It is shown that the time required for isotropization of an anisotropic flux by pitch angle scattering inside L approximately equal to 6 is long in comparison with the time required for particles to diffuse inward from L approximately equal to 6 to L approximately equal to 3, that the high-energy protons were not injected at high energies by the Crand (cosmic ray albedo neutron decay) process but were accelerated in the magnetosphere of Jupiter, and that the main conclusions of this analysis are unaffected by use of either the D sub 1 or the D sub 2 magnetic field models. Theoretical studies of the capture of trapped electrons and protons by Io have been carried out, and it is found that the probability of capture by Io depends strongly upon the particle species and kinetic energy.

  14. High-accuracy current generation in the nanoampere regime from a silicon single-trap electron pump

    PubMed Central

    Yamahata, Gento; Giblin, Stephen P.; Kataoka, Masaya; Karasawa, Takeshi; Fujiwara, Akira

    2017-01-01

    A gigahertz single-electron (SE) pump with a semiconductor charge island is promising for a future quantum current standard. However, high-accuracy current in the nanoampere regime is still difficult to achieve because the performance of SE pumps tends to degrade significantly at frequencies exceeding 1 GHz. Here, we demonstrate robust SE pumping via a single-trap level in silicon up to 7.4 GHz, at which the pumping current exceeds 1 nA. An accuracy test with an uncertainty of about one part per million (ppm) reveals that the pumping current deviates from the ideal value by only about 20 ppm at the flattest part of the current plateau. This value is two orders of magnitude better than the best one reported in the nanoampere regime. In addition, the pumping accuracy is almost unchanged up to 7.4 GHz, probably due to strong electron confinement in the trap. These results indicate that trap-mediated SE pumping is promising for achieving the practical operation of the quantum current standard. PMID:28322339

  15. High-accuracy current generation in the nanoampere regime from a silicon single-trap electron pump

    NASA Astrophysics Data System (ADS)

    Yamahata, Gento; Giblin, Stephen P.; Kataoka, Masaya; Karasawa, Takeshi; Fujiwara, Akira

    2017-03-01

    A gigahertz single-electron (SE) pump with a semiconductor charge island is promising for a future quantum current standard. However, high-accuracy current in the nanoampere regime is still difficult to achieve because the performance of SE pumps tends to degrade significantly at frequencies exceeding 1 GHz. Here, we demonstrate robust SE pumping via a single-trap level in silicon up to 7.4 GHz, at which the pumping current exceeds 1 nA. An accuracy test with an uncertainty of about one part per million (ppm) reveals that the pumping current deviates from the ideal value by only about 20 ppm at the flattest part of the current plateau. This value is two orders of magnitude better than the best one reported in the nanoampere regime. In addition, the pumping accuracy is almost unchanged up to 7.4 GHz, probably due to strong electron confinement in the trap. These results indicate that trap-mediated SE pumping is promising for achieving the practical operation of the quantum current standard.

  16. Superoxide Anion Radical Production in the Tardigrade Paramacrobiotus richtersi, the First Electron Paramagnetic Resonance Spin-Trapping Study.

    PubMed

    Savic, Aleksandar G; Guidetti, Roberto; Turi, Ana; Pavicevic, Aleksandra; Giovannini, Ilaria; Rebecchi, Lorena; Mojovic, Milos

    2015-01-01

    Anhydrobiosis is an adaptive strategy that allows withstanding almost complete body water loss. It has been developed independently by many organisms belonging to different evolutionary lines, including tardigrades. The loss of water during anhydrobiotic processes leads to oxidative stress. To date, the metabolism of free radicals in tardigrades remained unclear. We present a method for in vivo monitoring of free radical production in tardigrades, based on electron paramagnetic resonance and spin-trap DEPMPO, which provides simultaneous identification of various spin adducts (i.e., different types of free radicals). The spin trap can be easily absorbed in animals, and tardigrades stay alive during the measurements and during 24-h monitoring after the treatment. The results show that hydrated specimens of the tardigrade Paramacrobiotus richtersi produce the pure superoxide anion radical ((•)O2(-)). This is an unexpected result, as all previously examined animals and plants produce both superoxide anion radical and hydroxyl radical ((•)OH) or exclusively hydroxyl radical.

  17. Lifetime of the 1s2s 3S1 metastable level in He-like S14+ measured with an electron beam ion trap

    SciTech Connect

    L?pez-Urrutia, J C; Beiersdorfer, P; Widmann, K

    2006-03-16

    A precision measurement of the lifetime of the lowest exited level of the He-like S{sup 14+} ion carried out at the Livermore EBIT-II electron beam ion trap yielded a value of (703 {+-} 4) ns. Our method extends the range of lifetime measurements accessible with electron beam ion traps into the nanosecond region and improves the accuracy of currently available data for this level by an order of magnitude.

  18. Opto-Mechanical and Electronic Design of a Tunnel-Trap Si Radiometer.

    PubMed

    Eppeldauer, G P; Lynch, D C

    2000-01-01

    A transmission-type light-trap silicon radiometer has been developed to hold the NIST spectral power and irradiance responsivity scales between 406 nm and 920 nm. The device is built from replaceable input apertures and tightly packed different-size silicon photodiodes. The photodiodes are positioned in a triangular shape tunnel such that beam clipping is entirely eliminated within an 8 field-of-view (FOV). A light trap is attached to the output of the radiometer to collect the transmitted radiation and to minimize the effect of ambient light. The photodiodes, selected for equal shunt resistance, are connected in parallel. The capacitance and the resultant shunt resistance of the device were measured and frequency compensations were applied in the feedback network of the photocurrent-to-voltage converter to optimize signal-, voltage-, and loop-gain characteristics. The trap radiometer can measure either dc or ac optical radiation with high sensitivity. The noise-equivalent-power of the optimized device is 47 fW in dc mode and 5.2 fW at 10 Hz chopping. The relative deviation from the cosine responsivity in irradiance mode was measured to be equal to or less than 0.02 % within 5° FOV and 0.05 % at 8° FOV. The trap-radiometer can transfer irradiance responsivities with uncertainties comparable to those of primary standard radiometers. Illuminance and irradiance meters, holding the SI units (candela, color- and radiance-temperature), will be calibrated directly against the transfer standard trap-radiometer to obtain improved accuracy in the base-units.

  19. Oxygen trapped by rare earth tetrahedral clusters in Nd4FeOS6: Crystal structure, electronic structure, and magnetic properties

    DOE PAGES

    Lin, Qisheng; Taufour, Valentin; Zhang, Yuemei; ...

    2015-05-22

    Single crystals of Nd4FeOS6 were grown from an Fe-S eutectic solution. Single crystal X-ray diffraction analysis revealed a Nd4MnOSe6-type structure (P63mc, a = 9.2693(1) Å, c = 6.6650(1) Å, V = 495.94(1) Å3, Z = 2), featuring parallel chains of face-sharing [FeS6x1/2]4- trigonal antiprisms and interlinked [Nd4OS3]4+ cubane-like clusters. Oxygen atoms were found to be trapped by Nd4 clusters in the [Nd4OS3]4+ chains. Structural differences among Nd4MnOSe6-type Nd4FeOS6 and the related La3CuSiS7- and Pr8CoGa3-type structures have been described. Magnetic susceptibility measurements on Nd4FeOS6 suggested the dominance of antiferromagnetic interactions at low temperature, but no magnetic ordering down to 2 Kmore » was observed. Spin-polarized electronic structure calculations revealed magnetic frustration with dominant antiferromagnetic interactions.« less

  20. Stabilizing nuclear spins around semiconductor electrons via the interplay of optical coherent population trapping and dynamic nuclear polarization

    NASA Astrophysics Data System (ADS)

    Onur, A. R.; de Jong, J. P.; O'Shea, D.; Reuter, D.; Wieck, A. D.; van der Wal, C. H.

    2016-04-01

    We experimentally demonstrate how coherent population trapping (CPT) for donor-bound electron spins in GaAs results in autonomous feedback that prepares stabilized states for the spin polarization of nuclei around the electrons. CPT was realized by excitation with two lasers to a bound-exciton state. Transmission studies of the spectral CPT feature on an ensemble of electrons directly reveal the statistical distribution of prepared nuclear-spin states. Tuning the laser driving from blue to red detuned drives a transition from one to two stable states. Our results have importance for ongoing research on schemes for dynamic nuclear-spin polarization, the central spin problem, and control of spin coherence.

  1. X-ray Spectropolarimetry of high temperature and high density plasma supported by LLNL Electron Beam Ion Trap Experiments

    SciTech Connect

    Shlyaptseva, A S; Kantsyrev, V L; Ouart, N D; Fedin, D A; Neill, P; Harris, C; Hamasha, S M; Hansen, S B; Safronova, U I; Beiersdorfer, P; Petrashen, A G

    2004-03-15

    Plasma polarization spectroscopy work done by our group since the 3rd US-Japan PPS Workshop is overviewed. Theoretically, the polarization dependence on various electron distribution functions for He-like, Ne-like, and Ni-like x-ray transitions for a wide range of Z has been investigated. In particular, this study was focused on the polarization dependence for monoenergetic and steep electron distribution functions. The diagnostically important spectral lines and features of K-, L-, and M-shell ions were identified which can be used in x-ray spectropolarimetry of plasma. Importance of polarization-sensitive LLNL Electron Beam Ion Trap data is emphasized. The results of the UNR polarization-sensitive Ti and Mo x-pinch experiments are discussed.

  2. Stochastic dynamics of an electron in a Penning trap: Phase flips correlated with amplitude collapses and revivals

    NASA Astrophysics Data System (ADS)

    Brouard, S.; Plata, J.

    2011-06-01

    We study the effect of noise on the axial mode of an electron in a Penning trap under parametric-resonance conditions. Our approach, based on the application of averaging techniques to the description of the dynamics, provides an understanding of the random phase flips detected in recent experiments. The observed correlation between the phase jumps and the amplitude collapses is explained. Moreover, we discuss the actual relevance of noise color to the identified phase-switching mechanism. Our approach is then generalized to analyze the persistence of the stochastic phase flips in the dynamics of a cloud of N electrons. In particular, we characterize the detected scaling of the phase-jump rate with the number of electrons.

  3. Proposal for manipulating and detecting spin and orbital States of trapped electrons on helium using cavity quantum electrodynamics.

    PubMed

    Schuster, D I; Fragner, A; Dykman, M I; Lyon, S A; Schoelkopf, R J

    2010-07-23

    We propose a hybrid architecture in which an on-chip high finesse superconducting cavity is coupled to the lateral motion and spin state of a single electron trapped on the surface of superfluid helium. We estimate the motional coherence times to exceed 15  μs, while energy will be coherently exchanged with the cavity photons in less than 10 ns for charge states and faster than 1  μs for spin states, making the system attractive for quantum information processing and strong coupling cavity quantum electrodynamics experiments. The cavity is used for nondestructive readout and as a quantum bus mediating interactions between distant electrons or an electron and a superconducting qubit.

  4. Dynamic defect correlations dominate activated electronic transport in SrTiO3

    NASA Astrophysics Data System (ADS)

    Snijders, Paul C.; Şen, Cengiz; McConnell, Michael P.; Ma, Ying-Zhong; May, Andrew F.; Herklotz, Andreas; Wong, Anthony T.; Ward, T. Zac

    2016-07-01

    Strontium titanate (SrTiO3, STO) is a critically important material for the study of emergent electronic phases in complex oxides, as well as for the development of applications based on their heterostructures. Despite the large body of knowledge on STO, there are still many uncertainties regarding the role of defects in the properties of STO, including their influence on ferroelectricity in bulk STO and ferromagnetism in STO-based heterostructures. We present a detailed analysis of the decay of persistent photoconductivity in STO single crystals with defect concentrations that are relatively low but significantly affect their electronic properties. The results show that photo-activated electron transport cannot be described by a superposition of the properties due to independent point defects as current models suggest but is, instead, governed by defect complexes that interact through dynamic correlations. These results emphasize the importance of defect correlations for activated electronic transport properties of semiconducting and insulating perovskite oxides.

  5. Dynamic defect correlations dominate activated electronic transport in SrTiO3

    PubMed Central

    Snijders, Paul C.; Şen, Cengiz; McConnell, Michael P.; Ma, Ying-Zhong; May, Andrew F.; Herklotz, Andreas; Wong, Anthony T.; Ward, T. Zac

    2016-01-01

    Strontium titanate (SrTiO3, STO) is a critically important material for the study of emergent electronic phases in complex oxides, as well as for the development of applications based on their heterostructures. Despite the large body of knowledge on STO, there are still many uncertainties regarding the role of defects in the properties of STO, including their influence on ferroelectricity in bulk STO and ferromagnetism in STO-based heterostructures. We present a detailed analysis of the decay of persistent photoconductivity in STO single crystals with defect concentrations that are relatively low but significantly affect their electronic properties. The results show that photo-activated electron transport cannot be described by a superposition of the properties due to independent point defects as current models suggest but is, instead, governed by defect complexes that interact through dynamic correlations. These results emphasize the importance of defect correlations for activated electronic transport properties of semiconducting and insulating perovskite oxides. PMID:27443503

  6. Interaction quench in the Holstein model: Thermalization crossover from electron- to phonon-dominated relaxation

    NASA Astrophysics Data System (ADS)

    Murakami, Yuta; Werner, Philipp; Tsuji, Naoto; Aoki, Hideo

    2015-01-01

    We study the relaxation of the Holstein model after a sudden switch-on of the interaction by means of the nonequilibrium dynamical mean field theory, with the self-consistent Migdal approximation as an impurity solver. We show that there exists a qualitative change in the thermalization dynamics as the interaction is varied in the weak-coupling regime. On the weaker interaction side of this crossover, the phonon oscillations are damped more rapidly than the electron thermalization time scale, as determined from the relaxation of the electron momentum distribution function. On the stronger interaction side, the relaxation of the electrons becomes faster than the phonon damping. In this regime, despite long-lived phonon oscillations, a thermalized momentum distribution is realized temporarily. The origin of the "thermalization crossover" found here is traced back to different behaviors of the electron and phonon self-energies as a function of the electron-phonon coupling. In addition, the importance of the phonon dynamics is demonstrated by comparing the self-consistent Migdal results with those obtained with a simpler Hartree-Fock impurity solver that neglects the phonon self-energy. The latter scheme does not properly describe the evolution and thermalization of isolated electron-phonon systems.

  7. Light-trap design using multiple reflections and solid-angle attenuation - Application to a spaceborne electron spectrometer

    NASA Technical Reports Server (NTRS)

    Herrero, Federico A.

    1992-01-01

    The design and performance of a new light trap for a spaceborne electron spectrometer are described. The light trap has a measured photon-rejection ratio of 2 x 10 exp -11, allowing only one in 5 x 10 exp 10 incident photons to reach the sensitive area of the instrument. This rejection is more than sufficient because the ambient UV in earth orbit requires a rejection no better than 10 exp -8 to maintain the photon interference to less than 10 count/s. The light trap uses triple reflections to keep most of the light passing through the entrance slit away from the sensitive area of the spectrometer. It is shown that the average reflectance of all the internal surfaces must be less than 0.006, which is consistent with the data on the black coating applied to all surfaces. The analysis makes it possible to compare the photon contributions of each of the internal reflecting areas and to estimate the effective scattering width of the metallic electrode edge.

  8. A survey of trapped low energy electrons near the inner boundary of the inner radiation zone from the OSO-7

    NASA Technical Reports Server (NTRS)

    Neighbours, J. E.; Clark, G. W.

    1974-01-01

    Data from the MIT X-ray experiment on the OSO-7 satellite were used to delineate the regions in B-L and geographic spaces where trapped radiation was encountered. The results pertain specifically to electrons with energies in a range of 10 keV centered on 55 keV which were encountered in an orbit between altitudes of 330 and 570 km and latitudes of 33.3 degrees. A typical pitch angle distribution is fitted by a Gaussian with a FWHM of 28 degrees.

  9. Mode trap for absorbing transverse modes of an accelerated electron beam

    DOEpatents

    Chojnacki, E.P.

    1994-05-31

    A mode trap to trap and absorb transverse modes formed by a beam in a linear accelerator includes a waveguide having a multiplicity of electrically conductive (preferably copper) irises and rings, each iris and ring including an aperture, and the irises and rings being stacked in a side-by-side, alternating fashion such that the apertures of the irises and rings are concentrically aligned. An absorbing material layer such as a dielectric is embedded in each iris and ring, and this absorbing material layer encircles, but is circumferentially spaced from its respective aperture. Each iris and ring includes a plurality of circumferentially spaced slots around its aperture and extending radially out toward its absorbing material layer. 9 figs.

  10. Mode trap for absorbing transverse modes of an accelerated electron beam

    DOEpatents

    Chojnacki, Eric P.

    1994-01-01

    A mode trap to trap and absorb transverse modes formed by a beam in a linear accelerator includes a waveguide having a multiplicity of electrically conductive (preferably copper) irises and rings, each iris and ring including an aperture, and the irises and rings being stacked in a side-by-side, alternating fashion such that the apertures of the irises and rings are concentrically aligned. An absorbing material layer such as a dielectric is embedded in each iris and ring, and this absorbing material layer encircles, but is circumferentially spaced from its respective aperture. Each iris and ring includes a plurality of circumferentially spaced slots around its aperture and extending radially out toward its absorbing material layer.

  11. Toward sub-Kelvin resistive cooling and non destructive detection of trapped non-neutral electron plasma

    NASA Astrophysics Data System (ADS)

    Di Domizio, S.; Krasnický, D.; Lagomarsino, V.; Testera, G.; Vaccarone, R.; Zavatarelli, S.

    2015-01-01

    A resonant circuit tuned to a particular frequency of the motion of charged particles stored in a Penning trap and connected to a low noise amplifier allows, at the same time, cooling and non destructive detection of the particles. Its use is widely diffused when single or few particles are stored near the centre of a hyperbolic Penning trap. We present a consistent model that predicts the shape of the induced signal when the tuned circuit is used to detect and cool the axial motion of a cold non neutral plasma stored in an open-ended cylindrical Penning trap. The model correctly accounts for the not negligible axial plasma size. We show that the power spectrum of the signal measured across the tuned circuit provides information about the particle number and insights about the plasma temperature. We report on the design of a HEMT-based cryogenic amplifier working at 14.4 MHz and 4.2 K and the results of the noise measurements. We have measured a drain current noise in the range from 6 to 17 pA/√Hz, which corresponds to an increase of the tuned circuit equivalent temperature of at maximum 0.35 K. The cryogenic amplifier has a very low power consumption from few tens to few hundreds of μW corresponding to a drain current in the range 100-800 μ A. An additional contribution due to the gate noise has been identified when the drain current is below 300 μA above that value an upper limit of the increase of the equivalent tuned circuit temperature due to this contribution of 0.02 K has been obtained. These features make the tuned circuit connected to this amplifier a promising device for detecting and cooling the axial motion of an electron plasma when the Penning trap is mounted inside a dilution refrigerator.

  12. Discharge parameters and dominant electron conductivity mechanism in a low-pressure planar magnetron discharge

    SciTech Connect

    Baranov, O.; Romanov, M.; Ostrikov, Kostya

    2009-06-15

    Parameters of a discharge sustained in a planar magnetron configuration with crossed electric and magnetic fields are studied experimentally and numerically. By comparing the data obtained in the experiment with the results of calculations made using the proposed theoretical model, conclusion was made about the leading role of the turbulence-driven Bohm electron conductivity in the low-pressure operation mode (up to 1 Pa) of the discharge in crossed electric and magnetic fields. A strong dependence of the width of the cathode sputter trench, associated with the ionization region of the magnetron discharge, on the discharge parameters was observed in the experiments. The experimental data were used as input parameters in the discharge model that describes the motion of secondary electrons across the magnetic field in the ionization region and takes into account the classical, near-wall, and Bohm mechanisms of electron conductivity.

  13. Emittance measurements of space-charge-dominated electron beam. Final report

    SciTech Connect

    Namkung, W.; Chojnacki, E.P.

    1985-06-01

    A diagnostic technique of the beam emittance is developed for electron beams with diverging envelopes under strong space-charge forces. Radial profiles of current density, local temperature, and divergence angle are measured by the slit-pinhole method for axisymmetric beams. The partical distribution function in transverse phase space is then constructed and the rms emittance is obtained by numerical integrations. A 5-kV, 200-mA, and 3-microsec electron beam is used in the comparison between theory and experiment on this diagnostic method.

  14. Overcoming Coulombic Traps: Geometry and Electronic Characterizations of Light-Induced Separated Spins at the Bulk Heterojunction Interface.

    PubMed

    Kobori, Yasuhiro; Miura, Taku

    2015-01-02

    Recent progress is overviewed on experimental elucidations of fundamental molecular functions of the light-energy conversions by the photoactive layers of the organic photovoltalic (OPV) cells by means of the time-resolved electron paramagnetic resonance spectroscopy. Positions and orientations of the unpaired electrons and electronic coupling matrix elements are clarified in photoinduced, primary charge-separated (CS) states. Connections between the molecular geometries and the electronic couplings have been characterized for the initial CS states to elucidate how the structure, orbital delocalization, and molecular libration play roles on exothermic carrier dissociation via a vibrationally relaxed charge-transfer complex with prevention of the energy-wasting charge recombination. Superior functions to biological molecules are presented for the efficient photocurrent generations induced by orbital delocalization and by shallow trap depths at polymer-stacking domains. The above structural and electronic characteristics of the primary electron-hole pairs are essential to evaluations, designs, and developments of the efficient solar cells using organic molecules.

  15. Dynamic defect correlations dominate activated electronic transport in SrTiO3

    DOE PAGES

    Snijders, Paul C.; Sen, Cengiz; McConnell, Michael P.; ...

    2016-07-22

    Strontium titanate (SrTiO3, STO) is a critically important material for the study of emergent electronic phases in complex oxides, as well as for the development of applications based on their heterostructures. Despite the large body of knowledge on STO, there are still many uncertainties regarding the role of defects in the properties of STO, including their influence on ferroelectricity in bulk STO and ferromagnetism in STO-based heterostructures. In this paper, we present a detailed analysis of the decay of persistent photoconductivity in STO single crystals with defect concentrations that are relatively low but significantly affect their electronic properties. The resultsmore » show that photo-activated electron transport cannot be described by a superposition of the properties due to independent point defects as current models suggest but is, instead, governed by defect complexes that interact through dynamic correlations. In conclusion, these results emphasize the importance of defect correlations for activated electronic transport properties of semiconducting and insulating perovskite oxides.« less

  16. Dynamic defect correlations dominate activated electronic transport in SrTiO3

    SciTech Connect

    Snijders, Paul C.; Sen, Cengiz; McConnell, Michael P.; Ma, Ying-Zhong; May, Andrew F.; Herklotz, Andreas; Wong, Anthony T.; Ward, Thomas Zac

    2016-07-22

    Strontium titanate (SrTiO3, STO) is a critically important material for the study of emergent electronic phases in complex oxides, as well as for the development of applications based on their heterostructures. Despite the large body of knowledge on STO, there are still many uncertainties regarding the role of defects in the properties of STO, including their influence on ferroelectricity in bulk STO and ferromagnetism in STO-based heterostructures. In this paper, we present a detailed analysis of the decay of persistent photoconductivity in STO single crystals with defect concentrations that are relatively low but significantly affect their electronic properties. The results show that photo-activated electron transport cannot be described by a superposition of the properties due to independent point defects as current models suggest but is, instead, governed by defect complexes that interact through dynamic correlations. In conclusion, these results emphasize the importance of defect correlations for activated electronic transport properties of semiconducting and insulating perovskite oxides.

  17. Multi-dimensional Vlasov Simulations and Modeling of Trapped-Electron Sideband and Filamentation Instabilities of Non-Linear Electron Plasma Waves

    NASA Astrophysics Data System (ADS)

    Berger, Richard

    2014-10-01

    Vlasov simulations of large amplitude electron plasma waves (EPWs), which play an essential role in laser-fusion relevant plasmas, have been carried out in 1D and 2D and compared with theoretical models. The electrons trapped in the wave troughs are shown to be well described by an ``adiabatic'' distribution with a corresponding frequency shift of the EPW. Trapped particles play an essential role in the mechanisms underlying sideband instabilities that may affect the EPW, in particular longitudinal instabilities of trapped particle instability (TPI) type, as well as transverse instabilities of kinetic filamentation type. A systematic study of the spectrum of linearly unstable modes in 1D and 2D systems, including their growth rates and wavevectors, has been completed by scanning the amplitude and wavenumber of the initial wave. Simulation results for the TPI are successfully compared with Kruer's reduced model and are also analyzed for the development of the ``negative mass instability''. In the non-linear phase, both the TPI and filamentation instabilities are shown to lead to a rapid loss of field energy and an associated increase in electron kinetic energy. Saturation of the instabilities is reached in conjunction with the development of significant regions in phase space where trajectories of particles, resonant with the initial wave, become chaotic. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and funded by the Laboratory Research and Development Program at LLNL under project tracking code 12-ERD.

  18. Endor Studies of Radiation-Produced Trapped Electrons and Radicals in Disordered Systems and Radical-Matrix Interactions in Polymers and on Surfaces.

    DTIC Science & Technology

    1982-04-30

    electron. 8 4. ENDOR and ELDOR of Paramagnetic Species in Disordered Matrices, L. Kevan and P.A. Narayana, Chapter IV, in Multiple Electron Resonance...electron-electron double resonance ( ELDOR ) to radicals trapped in disordered matrices such as glasses and polycrystals are dis- cussed. In...model is currently being developed which appears to give a more quantitative picture of the matrix ENDOR response. ELDOR has been used to evaluate the

  19. Synergistic Effects of Plasmonics and Electron Trapping in Graphene Short-Wave Infrared Photodetectors with Ultrahigh Responsivity.

    PubMed

    Chen, Zefeng; Li, Xinming; Wang, Jiaqi; Tao, Li; Long, Mingzhu; Liang, Shi-Jun; Ang, Lay Kee; Shu, Chester; Tsang, Hon Ki; Xu, Jian-Bin

    2017-01-24

    Graphene's unique electronic and optical properties have made it an attractive material for developing ultrafast short-wave infrared (SWIR) photodetectors. However, the performance of graphene SWIR photodetectors has been limited by the low optical absorption of graphene as well as the ultrashort lifetime of photoinduced carriers. Here, we present two mechanisms to overcome these two shortages and demonstrate a graphene-based SWIR photodetector with high responsivity and fast photoresponse. In particular, a vertical built-in field is employed in the graphene channel for trapping the photoinduced electrons and leaving holes in graphene, which results in prolonged photoinduced carrier lifetime. On the other hand, plasmonic effects were employed to realize photon trapping and enhance the light absorption of graphene. Thanks to the above two mechanisms, the responsivity of this proposed SWIR photodetector is up to a record of 83 A/W at a wavelength of 1.55 μm with a fast rising time of less than 600 ns. This device design concept addresses key challenges for high-performance graphene SWIR photodetectors and is promising for the development of mid/far-infrared optoelectronic applications.

  20. Imaging crystal spectrometer for high-resolution x-ray measurements on electron beam ion traps and tokamaks

    NASA Astrophysics Data System (ADS)

    Beiersdorfer, P.; Magee, E. W.; Hell, N.; Brown, G. V.

    2016-11-01

    We describe a crystal spectrometer implemented on the Livermore electron beam ion traps that employ two spherically bent quartz crystals and a cryogenically cooled back-illuminated charge-coupled device detector to measure x rays with a nominal resolving power of λ/Δλ ≥ 10 000. Its focusing properties allow us to record x rays either with the plane of dispersion perpendicular or parallel to the electron beam and, thus, to preferentially select one of the two linear x-ray polarization components. Moreover, by choice of dispersion plane and focussing conditions, we use the instrument either to image the distribution of the ions within the 2 cm long trap region, or to concentrate x rays of a given energy to a point on the detector, which optimizes the signal-to-noise ratio. We demonstrate the operation and utility of the new instrument by presenting spectra of Mo34+, which prepares the instrument for use as a core impurity diagnostic on the NSTX-U spherical torus and other magnetic fusion devices that employ molybdenum as plasma facing components.

  1. Imaging crystal spectrometer for high-resolution x-ray measurements on electron beam ion traps and tokamaks.

    PubMed

    Beiersdorfer, P; Magee, E W; Hell, N; Brown, G V

    2016-11-01

    We describe a crystal spectrometer implemented on the Livermore electron beam ion traps that employ two spherically bent quartz crystals and a cryogenically cooled back-illuminated charge-coupled device detector to measure x rays with a nominal resolving power of λ/Δλ ≥ 10 000. Its focusing properties allow us to record x rays either with the plane of dispersion perpendicular or parallel to the electron beam and, thus, to preferentially select one of the two linear x-ray polarization components. Moreover, by choice of dispersion plane and focussing conditions, we use the instrument either to image the distribution of the ions within the 2 cm long trap region, or to concentrate x rays of a given energy to a point on the detector, which optimizes the signal-to-noise ratio. We demonstrate the operation and utility of the new instrument by presenting spectra of Mo(34+), which prepares the instrument for use as a core impurity diagnostic on the NSTX-U spherical torus and other magnetic fusion devices that employ molybdenum as plasma facing components.

  2. Multiple trapping on a comb structure as a model of electron transport in disordered nanostructured semiconductors

    SciTech Connect

    Sibatov, R. T. Morozova, E. V.

    2015-05-15

    A model of dispersive transport in disordered nanostructured semiconductors has been proposed taking into account the percolation structure of a sample and joint action of several mechanisms. Topological and energy disorders have been simultaneously taken into account within the multiple trapping model on a comb structure modeling the percolation character of trajectories. The joint action of several mechanisms has been described within random walks with a mixture of waiting time distributions. Integral transport equations with fractional derivatives have been obtained for an arbitrary density of localized states. The kinetics of the transient current has been calculated within the proposed new model in order to analyze time-of-flight experiments for nanostructured semiconductors.

  3. Generation of Nonlinear Electric Field Bursts in the Outer Radiation Belt through Electrons Trapping by Oblique Whistler Waves

    NASA Astrophysics Data System (ADS)

    Agapitov, Oleksiy; Drake, James; Mozer, Forrest

    2016-04-01

    Huge numbers of different nonlinear structures (double layers, electron holes, non-linear whistlers, etc. referred to as Time Domain Structures - TDS) have been observed by the electric field experiment on board the Van Allen Probes. A large part of the observed non-linear structures are associated with whistler waves and some of them can be directly driven by whistlers. The parameters favorable for the generation of TDS were studied experimentally as well as making use of 2-D particle-in-cell (PIC) simulations for the system with inhomogeneous magnetic field. It is shown that an outward propagating front of whistlers and hot electrons amplifies oblique whistlers which collapse into regions of intense parallel electric field with properties consistent with recent observations of TDS from the Van Allen Probe satellites. Oblique whistlers seed the parallel electric fields that are driven by the beams. The resulting parallel electric fields trap and heat the precipitating electrons. These electrons drive spikes of intense parallel electric field with characteristics similar to the TDSs seen in the VAP data. The decoupling of the whistler wave and the nonlinear electrostatic component is shown in PIC simulation in the inhomogeneous magnetic field system. These effects are observed by the Van Allen Probes in the radiation belts. The precipitating hot electrons propagate away from the source region in intense bunches rather than as a smooth flux.

  4. Generation of Nonlinear Electric Field Bursts in the Outer Radiation Belt through Electrons Trapping by Oblique Whistler Waves

    NASA Astrophysics Data System (ADS)

    Agapitov, O. V.; Drake, J. F.; Mozer, F.

    2015-12-01

    Huge numbers of different nonlinear structures (double layers, electron holes, non-linear whistlers, etc. referred to as Time Domain Structures - TDS) have been observed by the electric field experiment on board the Van Allen Probes. A large part of the observed non-linear structures are associated with whistler waves and some of them can be directly driven by whistlers. The parameters favorable for the generation of TDS were studied experimentally as well as making use of 2-D particle-in-cell (PIC) simulations for the system with inhomogeneous magnetic field. It is shown that an outward propagating front of whistlers and hot electrons amplifies oblique whistlers which collapse into regions of intense parallel electric field with properties consistent with recent observations of TDS from the Van Allen Probe satellites. Oblique whistlers seed the parallel electric fields that are driven by the beams. The resulting parallel electric fields trap and heat the precipitating electrons. These electrons drive spikes of intense parallel electric field with characteristics similar to the TDSs seen in the VAP data. The decoupling of the whistler wave and the nonlinear electrostatic component is shown in PIC simulation in the inhomogeneous magnetic field system. These effects are observed by the Van Allen Probes in the radiation belts. The precipitating hot electrons propagate away from the source region in intense bunches rather than as a smooth flux.

  5. Light quasiparticles dominate electronic transport in molecular crystal field-effect transistors

    SciTech Connect

    Li, Z. Q.; Podzorov, V.; Sai, N.; Martin, Michael C.; Gershenson, M. E.; Di Ventra, M.; Basov, D. N.

    2007-03-01

    We report on an infrared spectroscopy study of mobile holes in the accumulation layer of organic field-effect transistors based on rubrene single crystals. Our data indicate that both transport and infrared properties of these transistors at room temperature are governed by light quasiparticles in molecular orbital bands with the effective masses m[small star, filled]comparable to free electron mass. Furthermore, the m[small star, filled]values inferred from our experiments are in agreement with those determined from band structure calculations. These findings reveal no evidence for prominent polaronic effects, which is at variance with the common beliefs of polaron formation in molecular solids.

  6. Electron and recoil ion momentum imaging with a magneto-optically trapped target

    SciTech Connect

    Hubele, R.; Schuricke, M.; Goullon, J.; Lindenblatt, H.; Ferreira, N.; Laforge, A.; Brühl, E.; Globig, D.; Misra, D.; Sell, M.; Song, Z.; Wang, X.; Zhang, S.; Jesus, V. L. B. de; Kelkar, A.; Schneider, K.; Schulz, M.; Fischer, D.

    2015-03-15

    A reaction microscope (ReMi) has been combined with a magneto-optical trap (MOT) for the kinematically complete investigation of atomic break-up processes. With the novel MOTReMi apparatus, the momentum vectors of the fragments of laser-cooled and state-prepared lithium atoms are measured in coincidence and over the full solid angle. The first successful implementation of a MOTReMi could be realized due to an optimized design of the present setup, a nonstandard operation of the MOT, and by employing a switching cycle with alternating measuring and trapping periods. The very low target temperature in the MOT (∼2 mK) allows for an excellent momentum resolution. Optical preparation of the target atoms in the excited Li 2{sup 2}P{sub 3/2} state was demonstrated providing an atomic polarization of close to 100%. While first experimental results were reported earlier, in this work, we focus on the technical description of the setup and its performance in commissioning experiments involving target ionization in 266 nm laser pulses and in collisions with projectile ions.

  7. Identification of electron and hole traps in lithium tetraborate (Li{sub 2}B{sub 4}O{sub 7}) crystals: Oxygen vacancies and lithium vacancies

    SciTech Connect

    Swinney, M. W.; McClory, J. W.; Petrosky, J. C.; Yang Shan; Brant, A. T.; Halliburton, L. E.; Adamiv, V. T.; Burak, Ya. V.; Dowben, P. A.

    2010-06-15

    Electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) are used to identify and characterize electrons trapped by oxygen vacancies and holes trapped by lithium vacancies in lithium tetraborate (Li{sub 2}B{sub 4}O{sub 7}) crystals. Our study includes a crystal with the natural abundances of {sup 10}B and {sup 11}B and a crystal highly enriched with {sup 10}B. The as-grown crystals contain isolated oxygen vacancies, lithium vacancies, and copper impurities, all in nonparamagnetic charge states. During an irradiation at 77 K with 60 kV x-rays, doubly ionized oxygen vacancies trap electrons while singly ionized lithium vacancies and monovalent copper impurities trap holes. The vacancies return to their preirradiation charge states when the temperature of the sample is increased to approximately 90 K. Hyperfine interactions with {sup 10}B and {sup 11}B nuclei, observed between 13 and 40 K in the radiation-induced EPR and ENDOR spectra, provide models for the two vacancy-related defects. The electron trapped by an oxygen vacancy is localized primarily on only one of the two neighboring boron ions while the hole stabilized by a lithium vacancy is localized on a neighboring oxygen ion with nearly equal interactions with the two boron ions adjacent to the oxygen ion.

  8. A kinetic study of solar wind electrons in the transition region from collision dominated to collisionless flow

    NASA Technical Reports Server (NTRS)

    Lie-Svendsen, O.; Leer, E.

    1995-01-01

    We have studied the evolution of the velocity distribution function of a test population of electrons in the solar corona and inner solar wind region, using a recently developed kinetic model. The model solves the time dependent, linear transport equation, with a Fokker-Planck collision operator to describe Coulomb collisions between the 'test population' and a thermal background of charged particles, using a finite differencing scheme. The model provides information on how non-Maxwellian features develop in the distribution function in the transition region from collision dominated to collisionless flow. By taking moments of the distribution the evolution of higher order moments, such as the heat flow, can be studied.

  9. Reduced model prediction of electron temperature profiles in microtearing-dominated National Spherical Torus eXperiment plasmas

    SciTech Connect

    Kaye, S. M. Guttenfelder, W.; Bell, R. E.; Gerhardt, S. P.; LeBlanc, B. P.; Maingi, R.

    2014-08-15

    A representative H-mode discharge from the National Spherical Torus eXperiment is studied in detail to utilize it as a basis for a time-evolving prediction of the electron temperature profile using an appropriate reduced transport model. The time evolution of characteristic plasma variables such as β{sub e}, ν{sub e}{sup ∗}, the MHD α parameter, and the gradient scale lengths of T{sub e}, T{sub i}, and n{sub e} were examined as a prelude to performing linear gyrokinetic calculations to determine the fastest growing micro instability at various times and locations throughout the discharge. The inferences from the parameter evolutions and the linear stability calculations were consistent. Early in the discharge, when β{sub e} and ν{sub e}{sup ∗} were relatively low, ballooning parity modes were dominant. As time progressed and both β{sub e} and ν{sub e}{sup ∗} increased, microtearing became the dominant low-k{sub θ} mode, especially in the outer half of the plasma. There are instances in time and radius, however, where other modes, at higher-k{sub θ}, may, in addition to microtearing, be important for driving electron transport. Given these results, the Rebut-Lallia-Watkins (RLW) electron thermal diffusivity model, which is based on microtearing-induced transport, was used to predict the time-evolving electron temperature across most of the profile. The results indicate that RLW does a good job of predicting T{sub e} for times and locations where microtearing was determined to be important, but not as well when microtearing was predicted to be stable or subdominant.

  10. Reduced model prediction of electron temperature profiles in microtearing-dominated National Spherical Torus eXperiment plasmas

    SciTech Connect

    Kaye, S. M.; Guttenfelder, W.; Bell, R. E.; Gerhardt, S. P.; LeBlanc, B. P.; Maingi, R.

    2014-08-01

    A representative H-mode discharge from the National Spherical Torus eXperiment is studied in detail to utilize it as a basis for a time-evolving prediction of the electron temperature profile using an appropriate reduced transport model. The time evolution of characteristic plasma variables such as βe, ν*e, the MHD α parameter, and the gradient scale lengths of Te, Ti, and ne were examined as a prelude to performing linear gyrokinetic calculations to determine the fastest growing micro instability at various times and locations throughout the discharge. The inferences from the parameter evolutions and the linear stability calculations were consistent. Early in the discharge, when βe and ν*e were relatively low, ballooning parity modes were dominant. As time progressed and both βe and ν*e increased, microtearing became the dominant low-κθ mode, especially in the outer half of the plasma. There are instances in time and radius, however, where other modes, at higher-κθ, may, in addition to microtearing, be important for driving electron transport. Given these results, the Rebut-Lallia-Watkins (RLW) electron thermal diffusivity model, which is based on microtearing-induced transport, was used to predict the time-evolving electron temperature across most of the profile. The results indicate that RLW does a good job of predicting Te for times and locations where microtearing was determined to be important, but not as well when microtearing was predicted to be stable or subdominant.

  11. Visualization of Neutrophil Extracellular Traps and Fibrin Meshwork in Human Fibrinopurulent Inflammatory Lesions: III. Correlative Light and Electron Microscopic Study

    PubMed Central

    Onouchi, Takanori; Shiogama, Kazuya; Mizutani, Yasuyoshi; Takaki, Takashi; Tsutsumi, Yutaka

    2016-01-01

    Neutrophil extracellular traps (NETs) released from dead neutrophils at the site of inflammation represent webs of neutrophilic DNA stretches dotted with granule-derived antimicrobial proteins, including lactoferrin, and play important roles in innate immunity against microbial infection. We have shown the coexistence of NETs and fibrin meshwork in varied fibrinopurulent inflammatory lesions at both light and electron microscopic levels. In the present study, correlative light and electron microscopy (CLEM) employing confocal laser scanning microscopy and scanning electron microscopy was performed to bridge light and electron microscopic images of NETs and fibrin fibrils in formalin-fixed, paraffin-embedded, autopsied lung sections of legionnaire’s pneumonia. Lactoferrin immunoreactivity and 4'-6-diamidino-2-phenylindole (DAPI) reactivity were used as markers of NETs, and fibrin was probed by fibrinogen gamma chain. Of note is that NETs light microscopically represented as lactoferrin and DAPI-colocalized dots, 2.5 μm in diameter. CLEM gave super-resolution images of NETs and fibrin fibrils: “Dotted” NETs were ultrastructurally composed of fine filaments and masses of 58 nm-sized globular materials. A fibrin fibril consisted of clusters of smooth-surfaced filaments. NETs filaments (26 nm in diameter) were significantly thinner than fibrin filaments (295 nm in diameter). Of note is that CLEM was applicable to formalin-fixed, paraffin-embedded sections of autopsy material. PMID:27917008

  12. Intense electron-beam transport in the ion-focused regime through the collision-dominated regime

    SciTech Connect

    Sanford, T.W.L.; Poukey, J.W.; Welch, D.R.; Mock, R.C.

    1993-12-31

    This paper reviews the transport of the 19-MeV, 700-kA, 25-ns Hermes-III electron beam in long gas cells filled with N{sub 2} gas spanning six decades in pressure from 10{sup 3} to {approximately}10{sup 3} Torr. We show through measurements and theoretical analyses that the beam has two windows of stable transport: a low-pressure window (between {approximately}1 and {approximately}100 mTorr) that is dominated by propagation in the semi-collisionless IFR (ion-focused regime), and a high-pressure window (between {approximately}1 and {approximately}100 Torr) that is dominated by propagation in the resistive CDR (collision-dominated regime). In the CDR, 79{plus_minus}1.5% of the beam energy is transported over 11 m at 20 Torr. In the IFR, we show that intense radiation fields with controllable rise times and pulse widths can be generated on axis at a bremsstrahlung target. In summary, the measurements and analyses presented here provide a quantitative description of the Hermes-III beam transport over six decades in pressure.

  13. Too Hot for Photon-Assisted Transport: Hot-Electrons Dominate Conductance Enhancement in Illuminated Single-Molecule Junctions.

    PubMed

    Fung, E-Dean; Adak, Olgun; Lovat, Giacomo; Scarabelli, Diego; Venkataraman, Latha

    2017-02-08

    We investigate light-induced conductance enhancement in single-molecule junctions via photon-assisted transport and hot-electron transport. Using 4,4'-bipyridine bound to Au electrodes as a prototypical single-molecule junction, we report a 20-40% enhancement in conductance under illumination with 980 nm wavelength radiation. We probe the effects of subtle changes in the transmission function on light-enhanced current and show that discrete variations in the binding geometry result in a 10% change in enhancement. Importantly, we prove theoretically that the steady-state behavior of photon-assisted transport and hot-electron transport is identical but that hot-electron transport is the dominant mechanism for optically induced conductance enhancement in single-molecule junctions when the wavelength used is absorbed by the electrodes and the hot-electron relaxation time is long. We confirm this experimentally by performing polarization-dependent conductance measurements of illuminated 4,4'-bipyridine junctions. Finally, we perform lock-in type measurements of optical current and conclude that currents due to laser-induced thermal expansion mask optical currents. This work provides a robust experimental framework for studying mechanisms of light-enhanced transport in single-molecule junctions and offers tools for tuning the performance of organic optoelectronic devices by analyzing detailed transport properties of the molecules involved.

  14. Trapping the M{sub 1} and M{sub 2} substrates of bacteriorhodopsin for electron diffraction studies

    SciTech Connect

    Perkins, G.A.

    1992-05-01

    Visible and Fourier transform infrared (FTIR) absorption spectroscopies are used to observe protein conformational changes occuring during the bacteriorhodopsin photocycle. Spectroscopic measurements which define the conditions under which bacteriorhodopsin can be isolated and trapped in two distinct substates of the m intermediate of the photocycle, M{sub 1}, and M{sub 2}, are described. A protocol that can be used for high-resolution electron diffraction studies is presented that will trap glucose-embedded purple membrane in the M{sub 1}and M{sub 2} substates at greater than 90% concentration. It was discovered that glucose alone does not provide a fully hydrated environment for bacteriorhodopsin. Equilibration of glucose-embedded samples at high humidity can result in a physical state that is demonstrably closer to the native, fully hydrated state. An extension of the C-T Model of bacteriorhodopsin functionality (Fodor et al., 1988; Mathies et al., 1991) is proposed based on FTIR results and guided by published spectra from resonance Raman and FTIR work. 105 refs.

  15. Laboratory Astrophysics Using a Microcalorimeter and Bragg Crystal Spectrometer on an Electron Beam Ion Trap

    NASA Technical Reports Server (NTRS)

    Brinton, John (Technical Monitor); Silver, Eric

    2005-01-01

    We completed modifications to the new microcalorimeter system dedicated for use on the EBIT at NIST, which included: 1) a redesign of the x-ray calibration source from a direct electron impact source to one that irradiates the microcalorimeter with fluorescent x-rays. The resulting calibration lines are free of bremsstrahlung background; 2) the microcalorimeter electronic circuit was significantly improved to ensure long-term stability for lengthy experimental runs

  16. Excess electron is trapped in a large single molecular cage C60F60.

    PubMed

    Wang, Yin-Feng; Li, Zhi-Ru; Wu, Di; Sun, Chia-Chung; Gu, Feng-Long

    2010-01-15

    A new kind of solvated electron systems, sphere-shaped e(-)@C60F60 (I(h)) and capsule-shaped e(-)@C60F60 (D6h), in contrast to the endohedral complex M@C60, is represented at the B3LYP/6-31G(d) + dBF (diffusive basis functions) density functional theory. It is proven, by examining the singly occupied molecular orbital (SOMO) and the spin density map of e(-)@C60F60, that the excess electron is indeed encapsulated inside the C60F60 cage. The shape of the electron cloud in SOMO matches with the shape of C60F60 cage. These cage-like single molecular solvated electrons have considerably large vertical electron detachment energies VDE of 4.95 (I(h)) and 4.67 eV (D6h) at B3LYP/6-31+G(3df) + dBF level compared to the VDE of 3.2 eV for an electron in bulk water (Coe et al., Int Rev Phys Chem 2001, 20, 33) and that of 3.66 eV for e(-)@C20F20 (Irikura, J Phys Chem A 2008, 112, 983), which shows their higher stability. The VDE of the sphere-shaped e(-)@C60F60 (I(h)) is greater than that of the capsule-shaped e(-)@C60F60 (D6h), indicating that the excess electron prefers to reside in the cage with the higher symmetry to form the more stable solvated electron. It is also noticed that the cage size [7.994 (I(h)), 5.714 and 9.978 A (D6h) in diameter] is much larger than that (2.826 A) of (H2O)20- dodecahedral cluster (Khan, Chem Phys Lett 2005, 401, 85).

  17. Universal logic gates for quantum-dot electron-spin qubits using trapped quantum-well exciton polaritons

    NASA Astrophysics Data System (ADS)

    Puri, Shruti; McMahon, Peter L.; Yamamoto, Yoshihisa

    2017-03-01

    In this paper we introduce and analyze a system design for quantum-dot-based qubits that simultaneously supports scalable one-qubit and two-qubit gates, and single-shot qubit measurement. All three key processes (one-qubit gates, two-qubit gates, and qubit measurement) rely on the interaction between the electron in each quantum dot and exciton polaritons formed in a quantum well situated near the quantum dots. A key feature of our proposed system is the use of polariton traps, which we show enhances the quantum-dot-quantum-well interaction by a factor of 10 and consequently results in 100 × faster two-qubit gates. We also introduce a one-qubit gate that is based on a combination of optical and microwave control, which is supported in the same device and system configuration as the other operations, in contrast to the conventional one-qubit gate that is based on all-optical control.

  18. Dual electrospray ion source for electron-transfer dissociation on a hybrid linear ion trap-orbitrap mass spectrometer.

    PubMed

    Williams, D Keith; McAlister, Graeme C; Good, David M; Coon, Joshua J; Muddiman, David C

    2007-10-15

    A dual electrospray ionization source (ESI) has been modified to simultaneously produce cations and anions, one from each emitter, for performing rapid electron-transfer dissociation (ETD) ion/ion reactions on a hybrid linear ion trap-orbitrap mass spectrometer. Unlike the pulsed dual ESI sources that were used to generate ETD reagent ions, this source separates the emitters in space, rather than time, by physically switching which one is in front of the atmospheric inlet. The new arrangement allows for substantially enhanced spray stability and decreased switching times (

  19. Oxygen trapped by rare earth tetrahedral clusters in Nd4FeOS6: Crystal structure, electronic structure, and magnetic properties

    SciTech Connect

    Lin, Qisheng; Taufour, Valentin; Zhang, Yuemei; Wood, Max; Drtina, Thomas; Bud’ko, Sergey L.; Canfield, Paul C.; Miller, Gordon J.

    2015-05-22

    Single crystals of Nd4FeOS6 were grown from an Fe-S eutectic solution. Single crystal X-ray diffraction analysis revealed a Nd4MnOSe6-type structure (P63mc, a = 9.2693(1) Å, c = 6.6650(1) Å, V = 495.94(1) Å3, Z = 2), featuring parallel chains of face-sharing [FeS6x1/2]4- trigonal antiprisms and interlinked [Nd4OS3]4+ cubane-like clusters. Oxygen atoms were found to be trapped by Nd4 clusters in the [Nd4OS3]4+ chains. Structural differences among Nd4MnOSe6-type Nd4FeOS6 and the related La3CuSiS7- and Pr8CoGa3-type structures have been described. Magnetic susceptibility measurements on Nd4FeOS6 suggested the dominance of antiferromagnetic interactions at low temperature, but no magnetic ordering down to 2 K was observed. Spin-polarized electronic structure calculations revealed magnetic frustration with dominant antiferromagnetic interactions.

  20. Study of the visible-excitation luminescence of NTA-TiO2(AB) with single-electron-trapped oxygen vacancies

    NASA Astrophysics Data System (ADS)

    Qian, L.; Jin, Z. S.; Zhang, J. W.; Huang, Y. B.; Zhang, Z. J.; Du, Z. L.

    2005-05-01

    A new kind of TiO2 (NTA-TiO2(AB)) with single-electron-trapped oxygen vacancies was prepared by the dehydration of nanotubed titanic acid under vacuum. Under visible-light excitation (λex=420 nm to 650 nm) NTA-TiO2(AB) showed a relatively intense emission, which red shifts with the increase of excitation wavelength. Analyzing the photoluminescence spectra, a sub-band induced by single-electron-trapped oxygen vacancies within Eg(NTA-TiO2(AB)) was obtained.

  1. Investigation of trap states under Schottky contact in GaN/AlGaN/AlN/GaN high electron mobility transistors

    SciTech Connect

    Ma, Xiao-Hua E-mail: yhao@xidian.edu.cn; Chen, Wei-Wei; Hou, Bin; Zhu, Jie-Jie; Zhang, Kai; Zhang, Jin-Cheng; Zheng, Xue-Feng; Hao, Yue E-mail: yhao@xidian.edu.cn

    2014-03-03

    Forward gate-bias stress experiments are performed to investigate the variation of trap states under Schottky contact in GaN-based high electron mobility transistors. Traps with activation energy E{sub T} ranging from 0.22 eV to 0.31 eV are detected at the gate-semiconductor interface by dynamic conductance technique. Trap density decreases prominently after stressing, particularly for traps with E{sub T} > 0.24 eV. X-ray photoelectron spectroscopy measurements reveal a weaker Ga-O peak on the stressed semiconductor surface. It is postulated that oxygen is stripped by Ni to form NiO upon electrical stress, contributing to the decrease in O{sub N} donor sates under the gate contact.

  2. BaGe6 and BaGe(6-x): incommensurately ordered vacancies as electron traps.

    PubMed

    Akselrud, Lev; Wosylus, Aron; Castillo, Rodrigo; Aydemir, Umut; Prots, Yurii; Schnelle, Walter; Grin, Yuri; Schwarz, Ulrich

    2014-12-15

    We report the high-pressure high-temperature synthesis of the germanium-based framework compounds BaGe6 (P = 15 GPa, T = 1073 K) and BaGe(6-x) (P = 10 GPa, T = 1073 K) which are metastable at ambient conditions. In BaGe(6-x), partial fragmentation of the BaGe6 network involves incommensurate modulations of both atomic positions and site occupancy. Bonding analysis in direct space reveals that the defect formation in BaGe(6-x) is associated with the establishment of free electron pairs around the defects. In accordance with the electron precise composition of BaGe(6-x) for x = 0.5, physical measurements evidence semiconducting electron transport properties which are combined with low thermal conductivity.

  3. Michelson-Morley analogue for electrons using trapped ions to test Lorentz symmetry

    NASA Astrophysics Data System (ADS)

    Pruttivarasin, T.; Ramm, M.; Porsev, S. G.; Tupitsyn, I. I.; Safronova, M. S.; Hohensee, M. A.; Häffner, H.

    2015-01-01

    All evidence so far suggests that the absolute spatial orientation of an experiment never affects its outcome. This is reflected in the standard model of particle physics by requiring all particles and fields to be invariant under Lorentz transformations. The best-known tests of this important cornerstone of physics are Michelson-Morley-type experiments verifying the isotropy of the speed of light. For matter, Hughes-Drever-type experiments test whether the kinetic energy of particles is independent of the direction of their velocity, that is, whether their dispersion relations are isotropic. To provide more guidance for physics beyond the standard model, refined experimental verifications of Lorentz symmetry are desirable. Here we search for violation of Lorentz symmetry for electrons by performing an electronic analogue of a Michelson-Morley experiment. We split an electron wave packet bound inside a calcium ion into two parts with different orientations and recombine them after a time evolution of 95 milliseconds. As the Earth rotates, the absolute spatial orientation of the two parts of the wave packet changes, and anisotropies in the electron dispersion will modify the phase of the interference signal. To remove noise, we prepare a pair of calcium ions in a superposition of two decoherence-free states, thereby rejecting magnetic field fluctuations common to both ions. After a 23-hour measurement, we find a limit of h × 11 millihertz (h is Planck's constant) on the energy variations, verifying the isotropy of the electron's dispersion relation at the level of one part in 1018, a 100-fold improvement on previous work. Alternatively, we can interpret our result as testing the rotational invariance of the Coulomb potential. Assuming that Lorentz symmetry holds for electrons and that the photon dispersion relation governs the Coulomb force, we obtain a fivefold-improved limit on anisotropies in the speed of light. Our result probes Lorentz symmetry violation at

  4. Michelson-Morley analogue for electrons using trapped ions to test Lorentz symmetry.

    PubMed

    Pruttivarasin, T; Ramm, M; Porsev, S G; Tupitsyn, I I; Safronova, M S; Hohensee, M A; Häffner, H

    2015-01-29

    All evidence so far suggests that the absolute spatial orientation of an experiment never affects its outcome. This is reflected in the standard model of particle physics by requiring all particles and fields to be invariant under Lorentz transformations. The best-known tests of this important cornerstone of physics are Michelson-Morley-type experiments verifying the isotropy of the speed of light. For matter, Hughes-Drever-type experiments test whether the kinetic energy of particles is independent of the direction of their velocity, that is, whether their dispersion relations are isotropic. To provide more guidance for physics beyond the standard model, refined experimental verifications of Lorentz symmetry are desirable. Here we search for violation of Lorentz symmetry for electrons by performing an electronic analogue of a Michelson-Morley experiment. We split an electron wave packet bound inside a calcium ion into two parts with different orientations and recombine them after a time evolution of 95 milliseconds. As the Earth rotates, the absolute spatial orientation of the two parts of the wave packet changes, and anisotropies in the electron dispersion will modify the phase of the interference signal. To remove noise, we prepare a pair of calcium ions in a superposition of two decoherence-free states, thereby rejecting magnetic field fluctuations common to both ions. After a 23-hour measurement, we find a limit of h × 11 millihertz (h is Planck's constant) on the energy variations, verifying the isotropy of the electron's dispersion relation at the level of one part in 10(18), a 100-fold improvement on previous work. Alternatively, we can interpret our result as testing the rotational invariance of the Coulomb potential. Assuming that Lorentz symmetry holds for electrons and that the photon dispersion relation governs the Coulomb force, we obtain a fivefold-improved limit on anisotropies in the speed of light. Our result probes Lorentz symmetry violation

  5. Determination of the parametric region in which runaway electron energy losses are dominated by bremsstrahlung radiation in tokamaks

    SciTech Connect

    Fernandez-Gomez, I.; Martin-Solis, J. R.; Sanchez, R.

    2007-07-15

    It has been recently argued that, at sufficiently large parallel electric fields, bremsstrahlung radiation can greatly reduce the maximum energy that runaway electrons can gain in tokamaks [M. Bakhtiari et al., Phys. Plasmas 12, 102503 (2005)]. In this contribution, the work of these authors is extended to show that the region where bremsstrahlung radiation dominate runaway energy losses is however more restricted than reported by them. Expressions will be provided for the limits of this region within the parameter space spanned by the background density and parallel electric field, as a function of the rest of the plasma parameters. It will be shown that the background density has to be above a certain critical value and that the parallel electric field must lie within a range of values, below and above which synchrotron radiation dominate the runaway energy losses. Finally, it will be demonstrated that typical disruption parameters lie within this region and, as a result, bremsstrahlung losses still play an important role in controlling the runaway energy.

  6. The Effects of Surface Reconstruction and Electron-Positron Correlation on the Annihilation Characteristics of Positrons Trapped at Semiconductor Surfaces

    SciTech Connect

    Fazleev, N. G.; Jung, E.; Weiss, A. H.

    2009-03-10

    Experimental positron annihilation induced Auger electron spectroscopy (PAES) data from Ge(100) and Ge(111) surfaces display several strong Auger peaks corresponding to M{sub 4,5}N{sub 1}N{sub 2,3}, M{sub 2,3}M{sub 4,5}M{sub 4,5}, M{sub 2,3}M{sub 4,5}V, and M{sub 1}M{sub 4,5}M{sub 4,5} Auger transitions. The integrated peak intensities of Auger transitions have been used to obtain experimental annihilation probabilities for the Ge 3d and 3p core electrons. The experimental data were analyzed by performing theoretical studies of the effects of surface reconstructions and electron-positron correlations on image potential induced surface states and annihilation characteristics of positrons trapped at the reconstructed Ge(100) and Ge(111) surfaces. Calculations of positron surface states and annihilation characteristics have been performed for Ge(100) surface with (2x1), (2x2), and (4x2) reconstructions, and for Ge(111) surface with c(2x8) reconstruction. Estimates of the positron binding energy and annihilation characteristics reveal their sensitivity to the specific atomic structure of the topmost layers of the semiconductor and to the approximations used to describe electron-positron correlations. The results of these theoretical studies are compared with the ones obtained for the reconstructed Si(100)-(2x1) and Si(111)-(7x7) surfaces.

  7. The study of X-ray M-shell spectra of W ions from the LLNL Electron Beam Ion Trap

    SciTech Connect

    Neill, P; Harris, C; Shlyaptseva, A S; Hamasha, S; Hansen, S; Beiersdorfer, P; Safronova, U I

    2003-11-24

    M-shell spectra of W ions have been produced at the Livermore EBIT-II electron beam ion trap at different energies of the electron beam. A survey has been performed for 2.4 keV, 2.8 keV, 3.6 keV and for steps in energy of 100 eV over the 3.9-4.6 keV energy range. The analysis of 11 W spectra has shown the presence of a wide variety of ionization stages from Se-like to Cr-like W; the appearances of these ionization stages correlate well with the energy of their production. The present paper focuses on the identification of 63 experimental features of W ions in a spectral region from 5 to 6 Angstrom using calculations with inclusion of all ionization stages matching this spectral region. The majority of lines in all spectra have been identified and assigned to the 4f {yields} 3d and 4d {yields} 3p transitions. This is the first work that lists a comprehensive identification of so many resolved spectral features of M-shell transitions in W ions recorded in such detail in the laboratory.

  8. Calibration of the OHREX high-resolution imaging crystal spectrometer at the Livermore electron beam ion traps

    NASA Astrophysics Data System (ADS)

    Hell, N.; Beiersdorfer, P.; Magee, E. W.; Brown, G. V.

    2016-11-01

    We report the calibration of the Orion High-Resolution X-ray (OHREX) imaging crystal spectrometer at the EBIT-I electron beam ion trap at Livermore. Two such instruments, dubbed OHREX-1 and OHREX-2, are fielded for plasma diagnostics at the Orion laser facility in the United Kingdom. The OHREX spectrometer can simultaneously house two spherically bent crystals with a radius of curvature of r = 67.2 cm. The focusing properties of the spectrometer allow both for larger distance to the source due to the increase in collected light and for observation of extended sources. OHREX is designed to cover a 2.5°-3° spectral range at Bragg angles around 51.3°. The typically high resolving powers at these large Bragg angles are ideally suited for line shape diagnostics. For instance, the nominal resolving power of the instrument (>10 000) is much higher than the effective resolving power associated with the Doppler broadening due to the temperature of the trapped ions in EBIT-I. The effective resolving power is only around 3000 at typical EBIT-I conditions, which nevertheless is sufficient to set up and test the instrument's spectral characteristics. We have calibrated the spectral range for a number of crystals using well known reference lines in the first and second order and derived the ion temperatures from these lines. We have also made use of the 50 μm size of the EBIT-I source width to characterize the spatial focusing of the spectrometer.

  9. Study of the conditions for trapping of a neutralized electron beam into a circular trajectory on reflection from a metallic surface

    SciTech Connect

    Veingardt, V.F.; Grigor'ev, V.P.; Presler, L.V.

    1982-07-01

    The conditions are investigated for trapping of a beam into a ring orbit on reflection from the metallic surface of the chamber in which the electron-ion ring is formed. Regions of values of the beam and chamber parameters are determined which correspond to capture of the beam into a circular orbit.

  10. Complete erasing of ghost images caused by deeply trapped electrons on computed radiography plates

    NASA Astrophysics Data System (ADS)

    Ohuchi, H.; Kondo, Y.

    2011-03-01

    The ghost images, i.e., latent image that is unerasable with visible light (LIunVL) and reappearing image appeared on computed radiography (CR) plates were completely erased by simultaneous exposing them to filtered ultraviolet light and visible light. Three different types of CR plates (Agfa, Kodak, and Fuji) were irradiated with 50 kV X-ray beams in the dose range 8.1 mGy to 8.0 Gy, and then conventionally erased for 2 h with visible light. The remaining LIunVL could be erased by repeating 6 h simultaneous exposures to filtered ultraviolet light and visible light. After the sixth round of exposure, all the LIunVL in the three types of CR plates were erased to the same level as in an unirradiated plate and no latent images reappeared after storage at 0°C for 14 days. The absorption spectra of deep centers were specified using polychromatic ultraviolet light from a deep-ultraviolet lamp. It was found that deep centers showed a dominant peak in the absorption spectra at around 324 nm for the Agfa and Kodak plates, and at around 320 nm for the Fuji plate, in each case followed by a few small peaks. After completely erasing CR plates, these peaks were no longer observed.

  11. Direct observation of 0.57 eV trap-related RF output power reduction in AlGaN/GaN high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Arehart, A. R.; Sasikumar, A.; Rajan, S.; Via, G. D.; Poling, B.; Winningham, B.; Heller, E. R.; Brown, D.; Pei, Y.; Recht, F.; Mishra, U. K.; Ringel, S. A.

    2013-02-01

    This paper reports direct evidence for trap-related RF output power loss in GaN high electron mobility transistors (HEMTs) grown by metal organic chemical vapor deposition (MOCVD) through increased concentration of a specific electron trap at EC-0.57 eV that is located in the drain access region, as a function of accelerated life testing (ALT). The trap is detected by constant drain current deep level transient spectroscopy (CID-DLTS) and the CID-DLTS thermal emission time constant precisely matches the measured drain lag. Both drain lag and CID-DLTS measurements show this state to already exist in pre-stressed devices, which coupled with its strong increase in concentration as a function of stress in the absence of significant increases in concentrations of other detected traps, imply its role in causing degradation, in particular knee walkout. This study reveals EC-0.57 eV trap concentration tracks degradation induced by ALT for MOCVD-grown HEMTs supplied by several commercial and university sources. The results suggest this defect has a common source and may be a key degradation pathway in AlGaN/GaN HEMTs and/or an indicator to predict device lifetime.

  12. Trap states in enhancement-mode double heterostructures AlGaN/GaN high electron mobility transistors with different GaN channel layer thicknesses

    SciTech Connect

    He, Yunlong; Wang, Chong Li, Xiangdong; Zhao, Shenglei; Mi, Minhan; Pei, Jiuqing; Zhang, Jincheng; Hao, Yue; Li, Peixian; Ma, Xiaohua

    2015-08-10

    This is the report on trap states in enhancement-mode AlGaN/GaN/AlGaN double heterostructures high electron mobility transistors by fluorine plasma treatment with different GaN channel layer thicknesses. Compared with the thick GaN channel layer sample, the thin one has smaller 2DEG concentration, lower electron mobility, lower saturation current, and lower peak transconductance, but it has a higher threshold voltage of 1.2 V. Deep level transient spectroscopy measurements are used to obtain the accurate capture cross section of trap states. By frequency dependent capacitance and conductance measurements, the trap state density of (1.98–2.56) × 10{sup 12 }cm{sup −2} eV{sup −1} is located at E{sub T} in a range of (0.37–0.44) eV in the thin sample, while the trap state density of (2.3–2.92) × 10{sup 12 }cm{sup −2} eV{sup −1} is located at E{sub T} in a range of (0.33–0.38) eV in the thick one. It indicates that the trap states in the thin sample are deeper than those in the thick one.

  13. Permanent magnet electron beam ion source/trap systems with bakeable magnets for improved operation conditions.

    PubMed

    Schmidt, M; Zschornack, G; Kentsch, U; Ritter, E

    2014-02-01

    The magnetic system of a Dresden electron beam ion source (EBIS) generating the necessary magnetic field with a new type of permanent magnet made of high energy density NdFeB-type material operable at temperatures above 100 °C has been investigated and tested. The employment of such kind of magnets provides simplified operation without the time-consuming installation and de-installation procedures of the magnets for the necessary baking of the ion source after commissioning and maintenance work. Furthermore, with the use of a new magnetization technique the geometrical filling factor of the magnetic Dresden EBIS design could be increased to a filling factor of 100% leading to an axial magnetic field strength of approximately 0.5 T exceeding the old design by 20%. Simulations using the finite element method software Field Precision and their results compared with measurements are presented as well. It could be shown that several baking cycles at temperatures higher than 100 °C did not change the magnetic properties of the setup.

  14. Permanent magnet electron beam ion source/trap systems with bakeable magnets for improved operation conditions

    SciTech Connect

    Schmidt, M.; Zschornack, G.; Kentsch, U.; Ritter, E.

    2014-02-15

    The magnetic system of a Dresden electron beam ion source (EBIS) generating the necessary magnetic field with a new type of permanent magnet made of high energy density NdFeB-type material operable at temperatures above 100 °C has been investigated and tested. The employment of such kind of magnets provides simplified operation without the time-consuming installation and de-installation procedures of the magnets for the necessary baking of the ion source after commissioning and maintenance work. Furthermore, with the use of a new magnetization technique the geometrical filling factor of the magnetic Dresden EBIS design could be increased to a filling factor of 100% leading to an axial magnetic field strength of approximately 0.5 T exceeding the old design by 20%. Simulations using the finite element method software Field Precision and their results compared with measurements are presented as well. It could be shown that several baking cycles at temperatures higher than 100 °C did not change the magnetic properties of the setup.

  15. Direct detection of a transport-blocking trap in a nanoscaled silicon single-electron transistor by radio-frequency reflectometry

    SciTech Connect

    Villis, B. J.; Sanquer, M.; Jehl, X.; Orlov, A. O.; Barraud, S.; Vinet, M.; Fay, P.; Snider, G.

    2014-06-09

    The continuous downscaling of transistors results in nanoscale devices which require fewer and fewer charged carriers for their operation. The ultimate charge controlled device, the single-electron transistor (SET), controls the transfer of individual electrons. It is also the most sensitive electrometer, and as a result the electron transport through it can be dramatically affected by nearby charges. Standard direct-current characterization techniques, however, are often unable to unambiguously detect and resolve the origin of the observed changes in SET behavior arising from changes in the charge state of a capacitively coupled trap. Using a radio-frequency (RF) reflectometry technique, we are able to unequivocally detect this process, in very close agreement with modeling of the trap's occupation probability.

  16. Microfabricated ion trap array

    DOEpatents

    Blain, Matthew G.; Fleming, James G.

    2006-12-26

    A microfabricated ion trap array, comprising a plurality of ion traps having an inner radius of order one micron, can be fabricated using surface micromachining techniques and materials known to the integrated circuits manufacturing and microelectromechanical systems industries. Micromachining methods enable batch fabrication, reduced manufacturing costs, dimensional and positional precision, and monolithic integration of massive arrays of ion traps with microscale ion generation and detection devices. Massive arraying enables the microscale ion traps to retain the resolution, sensitivity, and mass range advantages necessary for high chemical selectivity. The reduced electrode voltage enables integration of the microfabricated ion trap array with on-chip circuit-based rf operation and detection electronics (i.e., cell phone electronics). Therefore, the full performance advantages of the microfabricated ion trap array can be realized in truly field portable, handheld microanalysis systems.

  17. Measurement of the electron shake-off in the β-decay of laser-trapped 6He atoms

    NASA Astrophysics Data System (ADS)

    Hong, Ran; Bagdasarova, Yelena; Garcia, Alejandro; Storm, Derek; Sternberg, Matthew; Swanson, Erik; Wauters, Frederik; Zumwalt, David; Bailey, Kevin; Leredde, Arnaud; Mueller, Peter; O'Connor, Thomas; Flechard, Xavier; Liennard, Etienne; Knecht, Andreas; Naviliat-Cuncic, Oscar

    2016-03-01

    Electron shake-off is an important process in many high precision nuclear β-decay measurements searching for physics beyond the standard model. 6He being one of the lightest β-decaying isotopes, has a simple atomic structure. Thus, it is well suited for testing calculations of shake-off effects. Shake-off probabilities from the 23S1 and 23P2 initial states of laser trapped 6He matter for the on-going beta-neutrino correlation study at the University of Washington. These probabilities are obtained by analyzing the time-of-flight distribution of the recoil ions detected in coincidence with the beta particles. A β-neutrino correlation independent analysis approach was developed. The measured upper limit of the double shake-off probability is 2 ×10-4 at 90% confidence level. This result is ~100 times lower than the most recent calculation by Schulhoff and Drake. This work is supported by DOE, Office of Nuclear Physics, under Contract Nos. DE-AC02-06CH11357 and DE-FG02-97ER41020.

  18. Controllable Threshold Voltage in Organic Complementary Logic Circuits with an Electron-Trapping Polymer and Photoactive Gate Dielectric Layer.

    PubMed

    Dao, Toan Thanh; Sakai, Heisuke; Nguyen, Hai Thanh; Ohkubo, Kei; Fukuzumi, Shunichi; Murata, Hideyuki

    2016-07-20

    We present controllable and reliable complementary organic transistor circuits on a PET substrate using a photoactive dielectric layer of 6-[4'-(N,N-diphenylamino)phenyl]-3-ethoxycarbonylcoumarin (DPA-CM) doped into poly(methyl methacrylate) (PMMA) and an electron-trapping layer of poly(perfluoroalkenyl vinyl ether) (Cytop). Cu was used for a source/drain electrode in both the p-channel and n-channel transistors. The threshold voltage of the transistors and the inverting voltage of the circuits were reversibly controlled over a wide range under a program voltage of less than 10 V and under UV light irradiation. At a program voltage of -2 V, the inverting voltage of the circuits was tuned to be at nearly half of the supply voltage of the circuit. Consequently, an excellent balance between the high and low noise margins (NM) was produced (64% of NMH and 68% of NML), resulting in maximum noise immunity. Furthermore, the programmed circuits showed high stability, such as a retention time of over 10(5) s for the inverter switching voltage. Our findings bring about a flexible, simple way to obtain robust, high-performance organic circuits using a controllable complementary transistor inverter.

  19. Wide-band, high-resolution soft x-ray spectrometer for the Electron Beam Ion Trap

    SciTech Connect

    Brown, G.V.; Beiersdorfer, P.; Widmann, K.

    1999-01-01

    We have constructed two wide-band, high-resolution vacuum flat crystal spectrometers and implemented them on the Electron Beam Ion Trap located at the Lawrence Livermore National Laboratory. Working in unison, these spectrometers can measure an x-ray bandwidth {le}9 {Angstrom} in the soft x-ray region below 21 {Angstrom}. In order to achieve this large bandwidth each spectrometer houses either two 125 mm {times} 13 mm {times} 2 mm RAP (rubidium acid phthalate, 2d=26.121 {Angstrom}), two 114 mm {times} 13 mm {times} 2 mm TlAP (thallium acid phthalate, 2d=25.75 {Angstrom}) crystals, or some combination thereof, for dispersion and two position sensitive proportional counters for detection of x rays. The spectrometers are used to measure wavelengths and relative intensities of the L-shell line emission from FethinspXVII{endash}XXIV for comparison with spectra obtained from astrophysical and laboratory plasmas. The wide wavelength coverage attainable by these spectrometers makes it possible to measure all the L-shell emission from a given iron ion species simultaneously. {copyright} {ital 1999 American Institute of Physics.}

  20. Spectroscopic study of promethiumlike bismuth with an electron-beam ion trap: Search for alkali-metal-like resonance lines

    NASA Astrophysics Data System (ADS)

    Kobayashi, Yusuke; Kato, Daiji; Sakaue, Hiroyuki A.; Murakami, Izumi; Nakamura, Nobuyuki

    2014-01-01

    We experimentally settle the three-decades-old question of whether or not promethiumlike heavy ions have strong resonance lines in hot plasmas. In 1980, Curtis and Ellis [Phys. Rev. Lett. 45, 2099 (1980), 10.1103/PhysRevLett.45.2099] predicted that promethiumlike heavy ions should have an alkali-metal structure with a ground-state configuration of 4f145s, and should exhibit strong 5s-5p resonance lines in hot plasmas. However, after many experimental efforts, no clear indication of the predicted resonance lines was found. The work presented herein resolves this question by clearly showing that the predicted resonance lines for bismuth are negligibly weak because of the presence of the [4f135s2]7/2 metastable state, even though the ground-state configuration is 4f145s, as predicted. To obtain these results, we used an electron-beam ion trap that made it possible to exploit a fine-tuned charge-state distribution, and analyzed the experimental spectra with collisional-radiative model calculations.

  1. EFFECTIVENESS OF ELECTROSTATIC SHIELDING AND ELECTRONIC SUBTRACTION TO CORRECT FOR THE HOLE TRAPPING IN CDZNTE SEMICONDUCTOR DETECTORS.

    SciTech Connect

    BOLOTNIKOV,A.E.; CAMARDA, G.S.; HOSSAIN, A.; CUI, Y.; JAMES, R.B.

    2007-08-26

    CdZnTe (CZT) is a very promising material for nuclear-radiation detectors. CZT detectors operate at ambient temperatures and offer high detection efficiency and excellent energy resolution, placing them ahead of high-purity Ge for those applications where cryogenic cooling is problematic. The progress achieved in CZT detectors over the past decade is founded on the developments of robust detector designs and readout electronics, both of which helped to overcome the effects of carrier trapping. Because the holes have low mobility, only electrons can be used to generate signals in thick CZT detectors, so one must account for the variation of the output signal versus the locations of the interaction points. To obtain high spectral resolution, the detector's design should provide a means to eliminate this dependence throughout the entire volume of the device. In reality, the sensitive volume of any ionization detector invariably has two regions. In the first, adjacent to the collecting electrode, the amplitude of the output signal rapidly increases almost to its maximum as the interaction point is located farther from the anode; in the rest of the volume, the output signal remains nearly constant. Thus, the quality of CZT detector designs can be characterized based on the magnitude of the signals variations in the drift region and the ratio between the volumes of the driR and induction regions. The former determines the ''geometrical'' width of the photopeak i.e., the line width that affects the total energy resolution and is attributed to the device's geometry when all other factors are neglected. The latter determines the photopeak efficiency and the area under the continuum in the pulse-height spectra. In this work, we describe our findings from systematizing different designs of CZT detectors and evaluating their performance based on these two criteria.

  2. Electronic excited state transport and trapping in disordered systems: Picosecond fluorescence mixing, transient grating, and probe pulse experiments

    SciTech Connect

    Miller, R.J.D.; Pierre, M.; Fayer, M.D.

    1983-04-15

    A detailed experimental examination of the dynamics of energy transport and trapping in two component systems, using rhodamine 6G (R6G) as the donor and malachite green (MG) as the trap in both glycerol and ethanol solvents, is presented. The experiments were performed using fluorescence mixing and ground state recovery techniques providing temporal resolution of approx.50 ps. Samples ranging from high trap-low donor concentrations (the Foerster limit) to the opposite regime of high donor and low trap concentrations, were studied. These results were compared with no adjustable parameters to the recent theoretical work of Loring, Andersen, and Fayer (LAF). The excellent agreement between theory and experiment over the entire donor-trap concentration range confirms the theoretical results of LAF and yields a comprehensive description of excited-state dynamics in solution. A variety of dynamic properties are calculated using the LAF theory and the measured parameters associated with R6G-MG system.

  3. Annealing shallow Si/SiO2 interface traps in electron-beam irradiated high-mobility metal-oxide-silicon transistors

    NASA Astrophysics Data System (ADS)

    Kim, J.-S.; Tyryshkin, A. M.; Lyon, S. A.

    2017-03-01

    Electron-beam (e-beam) lithography is commonly used in fabricating metal-oxide-silicon (MOS) quantum devices but creates defects at the Si/SiO2 interface. Here, we show that a forming gas anneal is effective at removing shallow defects (≤4 meV below the conduction band edge) created by an e-beam exposure by measuring the density of shallow electron traps in two sets of high-mobility MOS field-effect transistors. One set was irradiated with an electron-beam (10 keV, 40 μC/cm2) and was subsequently annealed in forming gas while the other set remained unexposed. Low temperature (335 mK) transport measurements indicate that the forming gas anneal recovers the e-beam exposed sample's peak mobility (14 000 cm2/Vs) to within a factor of two of the unexposed sample's mobility (23 000 cm2/Vs). Using electron spin resonance (ESR) to measure the density of shallow traps, we find that the two sets of devices are nearly identical, indicating the forming gas anneal is sufficient to anneal out shallow defects generated by the e-beam exposure. Fitting the two sets of devices' transport data to a percolation transition model, we extract a T = 0 percolation threshold density in quantitative agreement with our lowest temperature ESR-measured trap densities.

  4. Temperature dependence of photoluminescence spectra of nondoped and electron-doped SrTiO3: crossover from auger recombination to single-carrier trapping.

    PubMed

    Yamada, Yasuhiro; Yasuda, Hideki; Tayagaki, Takeshi; Kanemitsu, Yoshihiko

    2009-06-19

    We report unusual photoluminescence (PL) behaviors in highly photoexcited SrTiO(3) crystals at low temperatures. The PL spectrum and dynamics show abrupt changes below 150 K in both nondoped and electron-doped SrTiO(3) samples. We clarified that the PL dynamics in both nondoped and electron-doped SrTiO(3) is well described by the same simple model involving single-carrier trapping, radiative bimolecular recombination, and nonradiative Auger recombination. The unusual temperature dependence of PL dynamics is caused by the crossover from Auger recombination at high temperatures to single-carrier trapping at low temperatures. We discuss the temperature-dependent PL dynamics in conjunction with the high carrier mobility of SrTiO(3) at low temperatures.

  5. Instability of Electrons Trapped by the Coronal Magnetic Field and Its Evidence in the Fine Structure (Zebra Pattern) of Solar Radio Spectra

    NASA Astrophysics Data System (ADS)

    Zlotnik, E. Y.

    2013-06-01

    Solar radio emission is a significant source of information regarding coronal plasma parameters and the processes occurring in the solar atmosphere. High resolution frequency, space, and time observations together with the developed theory make it possible to retrieve physical conditions in the radiation source and recognize the radiation mechanisms responsible for various kinds of solar radio emission. In particular, the high brightness temperature of many bursts testifies to coherent radiation mechanisms, that is, to plasma instabilities in the corona. As an example, the fine structure of solar radio spectra looking like a set of quasi-harmonic stripes of enhanced and lowered radiation, which is observed against the type IV continuum at the post-flare phase of activity, is considered. It is shown that such emission arises from a trap-like source filled with a weakly anisotropic equilibrium plasma and a small addition of electrons which have a shortage of small velocities perpendicular to the magnetic field. For many recorded events with the mentioned fine spectral structure the instability processes responsible for the observed features are recognized. Namely, the background type IV continuum is due to the loss-cone instability of hot non-equilibrium electrons, and the enhanced striped radiation results from the double-plasma-resonance effect in the regions where the plasma frequency f p coincides with the harmonics of electron gyrofrequency f B ; f p= sf B . Estimations of the electron number density and magnetic field in the coronal magnetic traps, as well as the electron number density and velocities of hot electrons necessary to excite the radiation with the observed fine structure, are given. It is also shown that in some cases several ensembles of non-equilibrium electrons can coexist in magnetic traps during solar flares and that its radio signature sensitively depends on the parameters of the distribution functions of the various ensembles.

  6. In situ radiolysis time-resolved ESR studies of spin trapping by DMPO: Re-evalution of hydroxyl radical and hydrated electron trapping rates and spin adduct yields

    SciTech Connect

    Madden, K.P.; Taniguchi, Hitoshi

    1996-05-02

    The second-order rate constants for the reaction of 5, 5-dimethyl-1-pyrroline N-oxide (DMPO) with radiolytically produced hydroxyl radicals and hydrated electrons have been measured in aqueous solution by direct observation of spin adduct initial yield using time-resolved electron spin resonance. The rate constants are 2.8 x 10{sup 9} mol{sup -1} dm{sup 3} S{sup -1} for the DMPO-hydroxyl radical reaction and 3.2 x 10{sup 9} mol{sup -1} dm{sup 3} s{sup -1} for the reaction of DMPO and hydrated electron, using sodium formate and chloroacetic acid as competitive scavengers of the hydroxyl radical and hydrated electron, respectively. The hydrated electron-DMPO competition study determined the fraction of DMPO-H produced directly from radiolytically produced hydrogen atoms as 0.082 of the total DMPO-H yield, indicating that approximately half of the hydrogen atoms react with DMPO to produce non-aminoxyl products. The fraction of the total hydroxyl radical yield leading to DMPO-OH spin adduct was determined to be 0.94, using the bleach of 2,2,6,6-tetramethylpiperidone-N-oxyl by carbon dioxide radical anion as a reference standard. 36 refs., 8 figs., 1 tab.

  7. Trapping in TITANs Cooler Penning Trap

    NASA Astrophysics Data System (ADS)

    Kootte, Brian; Lascar, Daniel; Paul, Stefan; Gwinner, Gerald; Dilling, Jens; Titan Collaboration

    2016-09-01

    Penning trap mass spectrometry provides an excellent means of determining the masses of nuclei to high precision. Highly Charged Ions (HCIs) have been successfully used at TRIUMFs Ion Trap for Atomic and Nuclear science (TITAN) to enhance the precision of mass measurements for short-lived species. The gain in precision can theoretically scale with the charge state of the ion, but recent measurements of beam properties have shown that the process of charge breeding ions to higher charge states increases the energy spread of the ion bunch sent to the Penning trap. This reduces the gain from using HCIs. In order to maximize the precision of mass measurements, we are currently performing offline commissioning of a Cooler PEnning Trap (CPET) with the purpose of sympathetically cooling HCI bunches to an energy of 1 eV/q using a plasma of electrons. This will require implementing a nested potential configuration to trap the ions and electrons in the same region so they can interact via coulomb scattering. Recent progress in testing the trapping of electrons and singly charged ions in CPET, leading towards the cooling of HCIs prior to mass measurements in TITANs will be discussed.

  8. Effect of OFF-state stress induced electric field on trapping in AlGaN/GaN high electron mobility transistors on Si (111)

    SciTech Connect

    Anand, M. J. E-mail: eging@ntu.edu.sg; Ng, G. I. E-mail: eging@ntu.edu.sg; Syamal, B.; Zhou, X.; Arulkumaran, S.; Manoj Kumar, C. M.; Ranjan, K.; Vicknesh, S.; Foo, S. C.

    2015-02-23

    The influence of electric field (EF) on the dynamic ON-resistance (dyn-R{sub DS[ON]}) and threshold-voltage shift (ΔV{sub th}) of AlGaN/GaN high electron mobility transistors on Si has been investigated using pulsed current-voltage (I{sub DS}-V{sub DS}) and drain current (I{sub D}) transients. Different EF was realized with devices of different gate-drain spacing (L{sub gd}) under the same OFF-state stress. Under high-EF (L{sub gd} = 2 μm), the devices exhibited higher dyn-R{sub DS[ON]} degradation but a small ΔV{sub th} (∼120 mV). However, at low-EF (L{sub gd} = 5 μm), smaller dyn-R{sub DS[ON]} degradation but a larger ΔV{sub th} (∼380 mV) was observed. Our analysis shows that under OFF-state stress, the gate electrons are injected and trapped in the AlGaN barrier by tunnelling-assisted Poole-Frenkel conduction mechanism. Under high-EF, trapping spreads towards the gate-drain access region of the AlGaN barrier causing dyn-R{sub DS[ON]} degradation, whereas under low-EF, trapping is mostly confined under the gate causing ΔV{sub th}. A trap with activation energy 0.33 eV was identified in the AlGaN barrier by I{sub D}-transient measurements. The influence of EF on trapping was also verified by Silvaco TCAD simulations.

  9. Linear and nonlinear coupling of electromagnetic and electrostatic fluctuations with one dimensional trapping of electrons using product bi (r,q) distribution

    NASA Astrophysics Data System (ADS)

    Aziz, Tahir; Masood, W.; Qureshi, M. N. S.; Shah, H. A.; Yoon, P. H.

    2016-06-01

    In the present paper, we have investigated the ramifications of adiabatic trapping of electrons using a bi product ( r , q ) distribution function on obliquely propagating Alfven waves in a low β plasma. In this regard, we have analyzed the linear and nonlinear dispersion characteristics of finite amplitude coupled kinetic Alfven-acoustic solitary waves using the two-potential theory and employing Sagdeev potential approach. We have deliberated upon the results of the present inquest and highlighted its importance by citing works that have reported the simultaneous presence of electromagnetic pulses and flat-topped distribution of electrons.

  10. Probing electrons in TiO2 polaronic trap states by IR-absorption: Evidence for the existence of hydrogenic states

    PubMed Central

    Sezen, Hikmet; Buchholz, Maria; Nefedov, Alexei; Natzeck, Carsten; Heissler, Stefan; Di Valentin, Cristiana; Wöll, Christof

    2014-01-01

    An important step in oxide photochemistry, the loading of electrons into shallow trap states, was studied using infrared (IR) spectroscopy on both, rutile TiO2 powders and single-crystal, r-TiO2(110) oriented samples. After UV-irradiation or n-doping by exposure to H-atoms broad IR absorption lines are observed for the powders at around 940 cm−1. For the single crystal substrates, the IR absorption bands arising from an excitation of the trapped electrons into higher-lying final states show additional features not observed in previous work. On the basis of our new, high-resolution data and theoretical studies on the polaron binding energy in rutile we propose that the trap states correspond to polarons and are thus intrinsic in nature. We assign the final states probed by the IR-experiments to hydrogenic states within the polaron potential. Implications of these observations for photochemistry on oxides will be briefly discussed. PMID:24448350

  11. Effect of electron trap states on spin-dependent transport characteristics in CoFe/MgO/n{sup +}-Si junctions investigated by Hanle effect measurements and inelastic electron tunneling spectroscopy

    SciTech Connect

    Inokuchi, Tomoaki Ishikawa, Mizue; Sugiyama, Hideyuki; Tanamoto, Tetsufumi; Saito, Yoshiaki

    2014-12-08

    Spin-dependent transport properties in CoFe/MgO/n{sup +}-Si junctions were investigated by Hanle effect measurements and inelastic electron tunneling (IET) spectroscopy. The CoFe/MgO/n{sup +}-Si junctions examined in this study exhibited two different Hanle curves. In the low bias region, broad Hanle signals were mainly observed; in the high bias region, narrow Hanle signals were mainly observed. The d{sup 2}I/dV{sup 2}-V curves (which correspond to IET spectra) contain several peaks originating from phonon modes and other peaks originating from electron trap states. At the bias voltage where electron trap states are observed, Δd{sup 2}I/dV{sup 2} depends on the magnetic field and the full width at half-maximum of the Δd{sup 2}I/dV{sup 2}–H curves corresponds to that of the broad Hanle signals. These results indicate that electron trap states are located in the low energy region and cause a decrease in spin lifetime.

  12. Spectra of W19 +-W32 + observed in the EUV region between 15 and 55 Å with an electron-beam ion trap

    NASA Astrophysics Data System (ADS)

    Sakaue, H. A.; Kato, D.; Yamamoto, N.; Nakamura, N.; Murakami, I.

    2015-07-01

    We present extreme ultraviolet spectra of highly charged tungsten ions (W19 +-W32 + ) in the wavelength range of 15 -55 Å obtained with a compact electron-beam ion trap (CoBIT) and a grazing-incidence spectrometer at the National Institute for Fusion Science. The electron energy dependence of the spectra was investigated for electron energies from 490 to 1320 eV . Identification of the observed lines was aided by collisional-radiative (CR) modeling of CoBIT plasma. Good quantitative agreement was obtained between the CR-modeling results and the experimental observations. The ion charge dependence of the 6 g -4 f ,5 g -4 f ,5 f -4 d ,5 p -4 d , and 4 f -4 d transition wavelengths were measured.

  13. Achieving High Current Density of Perovskite Solar Cells by Modulating the Dominated Facets of Room-Temperature DC Magnetron Sputtered TiO2 Electron Extraction Layer.

    PubMed

    Huang, Aibin; Lei, Lei; Zhu, Jingting; Yu, Yu; Liu, Yan; Yang, Songwang; Bao, Shanhu; Cao, Xun; Jin, Ping

    2017-01-25

    The short circuit current density of perovskite solar cell (PSC) was boosted by modulating the dominated plane facets of TiO2 electron transport layer (ETL). Under optimized condition, TiO2 with dominant {001} facets showed (i) low incident light loss, (ii) highly smooth surface and excellent wettability for precursor solution, (iii) efficient electron extraction, and (iv) high conductivity in perovskite photovoltaic application. A current density of 24.19 mA cm(-2) was achieved as a value near the maximum limit. The power conversion efficiency was improved to 17.25%, which was the record value of PSCs with DC magnetron sputtered carrier transport layer. What is more, the room-temperature process had a great significance for the cost reduction and flexible application of PSCs.

  14. Rotational and vibrational dynamics in the excited electronic state of deprotonated and protonated fluorescein studied by time-resolved photofragmentation in an ion trap

    PubMed Central

    Imanbaew, Dimitri; Gelin, Maxim F.; Riehn, Christoph

    2016-01-01

    Excited state dynamics of deprotonated and protonated fluorescein were investigated by polarization dependent femtosecond time-resolved pump-probe photofragmentation in a 3D ion trap. Transients of deprotonated fluorescein exhibit vibrational wavepacket dynamics with weak polarization dependence. Transients of protonated fluorescein show only effects of molecular alignment and rotational dephasing. The time resolved rotational anisotropy of protonated fluorescein is simulated by the calculated orientational correlation function. The observed differences between deprotonated and protonated fluorescein are ascribed to their different higher lying electronically excited states and corresponding structures. This is partially supported by time-dependent density functional theory calculations of the excited state structures. PMID:27376104

  15. Improved apparatus for trapped radical and other studies down to 1.5 K. [microwave cavity cryogenic equipment for electron paramagnetic resonance experiments

    NASA Technical Reports Server (NTRS)

    Woollam, J. A.; Sugawara, K.

    1978-01-01

    A Dewar system and associated equipment for electron paramagnetic resonance (EPR) studies of trapped free radicals and other optical or irradiation experiments are described. The apparatus is capable of reaching a temperature of 1.5 K and transporting on the order of 20 W per K temperature gradient; its principal advantages are for use at pumped cryogen temperatures and for experiments with large heat inputs. Two versions of the apparatus are discussed, one of which is designed for EPR in a rectangular cavity operating in a TE(102) mode and another in which EPR is performed in a cylindrical microwave cavity.

  16. Low-energy operation of the Livermore electron beam ion traps: Atomic spectroscopy of Si V, S VII, and Ar IX

    SciTech Connect

    Lepson, J K; Beiersdorfer, P

    2004-01-02

    As part of a project to compile a comprehensive catalog of astrophysically relevant emission lines, we used the low-energy capability of the Lawrence Livermore electron beam ion traps to extend the spectroscopy of neon-like ions and the neighboring charge states to silicon, sulfur, and argon. They present wavelength data of Si V and demonstrate the effect of collisional deexcitation of electric dipole forbidden lines on the 2-3 L-shell spectra of Si V, S VII, and Ar IX.

  17. The drift-diffusion interpretation of the electron current within the organic semiconductor characterized by the bulk single energy trap level

    NASA Astrophysics Data System (ADS)

    Cvikl, B.

    2010-01-01

    The closed solution for the internal electric field and the total charge density derived in the drift-diffusion approximation for the model of a single layer organic semiconductor structure characterized by the bulk shallow single trap-charge energy level is presented. The solutions for two examples of electric field boundary conditions are tested on room temperature current density-voltage data of the electron conducting aluminum/tris(8-hydroxyquinoline aluminum/calcium structure [W. Brütting et al., Synth. Met. 122, 99 (2001)] for which jexp∝Va3.4, within the interval of bias 0.4 V≤Va≤7. In each case investigated the apparent electron mobility determined at given bias is distributed within a given, finite interval of values. The bias dependence of the logarithm of their lower limit, i.e., their minimum values, is found to be in each case, to a good approximation, proportional to the square root of the applied electric field. On account of the bias dependence as incorporated in the minimum value of the apparent electron mobility the spatial distribution of the organic bulk electric field as well as the total charge density turn out to be bias independent. The first case investigated is based on the boundary condition of zero electric field at the electron injection interface. It is shown that for minimum valued apparent mobilities, the strong but finite accumulation of electrons close to the anode is obtained, which characterize the inverted space charge limited current (SCLC) effect. The second example refers to the internal electric field allowing for self-adjustment of its boundary values. The total electron charge density is than found typically to be of U shape, which may, depending on the parameters, peak at both or at either Alq3 boundary. It is this example in which the proper SCLC effect is consequently predicted. In each of the above two cases, the calculations predict the minimum values of the electron apparent mobility, which substantially

  18. Autosomal dominant

    MedlinePlus

    ... whether the trait is dominant or recessive. A single abnormal gene on one of the first 22 nonsex ( autosomal ) chromosomes from either parent can cause an autosomal disorder. Dominant inheritance means ...

  19. Numerical simulation of the effect of recombination centres and traps created by electron irradiation on the performance degradation of GaAs solar cells.

    PubMed

    Meftah, A F; Sengouga, N; Belghachi, A; Meftah, A M

    2009-05-27

    In this paper, we report a detailed numerical study of the electron irradiation effect on the photoelectrical parameters of a GaAs based p(+)-n-n(+) solar cell which operates under an AM0 solar spectrum. As a consequence of irradiation different types of defects are created in the semiconductor lattice. These defects introduce energy levels in the gap of the material. The majority of studies dealing with irradiation-induced degradation in solar cells relate it mainly to recombination centres, which are deep levels lying near the mid gap. In the present study, numerical simulation is used to demonstrate that the irradiation-induced degradation is not solely due to recombination centres. Other less deep levels, or traps, play a major role in this degradation. When only recombination centres are taken into account, the short circuit current density (J(sc)) is hardly affected while the other cell output parameters such as the open circuit voltage (V(oc)), the conversion efficiency (η) and the fill factor (FF) are strongly deteriorated. However, if less deep levels or traps are taken into account together with recombination centres, J(sc) becomes sensitive to electron irradiation and the other output parameter deteriorations become less sensitive.

  20. Sn vacancies in photorefractive Sn2P2S6 crystals: An electron paramagnetic resonance study of an optically active hole trap

    NASA Astrophysics Data System (ADS)

    Golden, E. M.; Basun, S. A.; Evans, D. R.; Grabar, A. A.; Stoika, I. M.; Giles, N. C.; Halliburton, L. E.

    2016-10-01

    Electron paramagnetic resonance (EPR) is used to identify the singly ionized charge state of the Sn vacancy ( VSn - ) in single crystals of Sn2P2S6 (often referred to as SPS). These vacancies, acting as a hole trap, are expected to be important participants in the photorefractive effect observed in undoped SPS crystals. In as-grown crystals, the Sn vacancies are doubly ionized ( VSn 2 - ) with no unpaired spins. They are then converted to a stable EPR-active state when an electron is removed (i.e., a hole is trapped) during an illumination below 100 K with 633 nm laser light. The resulting EPR spectrum has g-matrix principal values of 2.0079, 2.0231, and 1.9717. There are resolved hyperfine interactions with two P neighbors and one Sn neighbor. The isotropic portions of these hyperfine matrices are 167 and 79 MHz for the two 31P neighbors and 8504 MHz for the one Sn neighbor (this latter value is the average for 117Sn and 119Sn). These VSn - vacancies are shallow acceptors with the hole occupying a diffuse wave function that overlaps the neighboring Sn2+ ion and (P2S6)4- anionic unit. Using a general-order kinetics approach, an analysis of isothermal decay curves of the VSn - EPR spectrum in the 107-115 K region gives an activation energy of 283 meV.

  1. Different charging behaviors between electrons and holes in Si nanocrystals embedded in SiNx matrix by the influence of near-interface oxide traps

    NASA Astrophysics Data System (ADS)

    Zhong-Hui, Fang; Xiao-Fan, Jiang; Kun-Ji, Chen; Wang, Yue-Fei; Li, Wei; Xu, Jun

    2015-01-01

    Si-rich silicon nitride films are prepared by plasma-enhanced chemical vapor deposition method, followed by thermal annealing to form the Si nanocrystals (Si-NCs) embedded in SiNx floating gate MOS structures. The capacitance-voltage (C-V), current-voltage (I-V), and admittance-voltage (G-V) measurements are used to investigate the charging characteristics. It is found that the maximum flat band voltage shift (ΔVFB) due to full charged holes (˜ 6.2 V) is much larger than that due to full charged electrons (˜ 1 V). The charging displacement current peaks of electrons and holes can be also observed by the I-V measurements, respectively. From the G-V measurements we find that the hole injection is influenced by the oxide hole traps which are located near the SiO2/Si-substrate interface. Combining the results of C-V and G-V measurements, we find that the hole charging of the Si-NCs occurs via a two-step tunneling mechanism. The evolution of G-V peak originated from oxide traps exhibits the process of hole injection into these defects and transferring to the Si-NCs. Project supported by the National Basic Research Program of China (Grant No. 2010CB934402) and the National Natural Science Foundation of China (Grant No. 11374153).

  2. Analysis of the fine structure of Sn11 +-Sn14 + ions by optical spectroscopy in an electron-beam ion trap

    NASA Astrophysics Data System (ADS)

    Windberger, A.; Torretti, F.; Borschevsky, A.; Ryabtsev, A.; Dobrodey, S.; Bekker, H.; Eliav, E.; Kaldor, U.; Ubachs, W.; Hoekstra, R.; Crespo López-Urrutia, J. R.; Versolato, O. O.

    2016-07-01

    We experimentally re-evaluate the fine structure of Sn11 +-Sn14 + ions. These ions are essential in bright extreme-ultraviolet (EUV) plasma-light sources for next-generation nanolithography, but their complex electronic structure is an open challenge for both theory and experiment. We combine optical spectroscopy of magnetic dipole M 1 transitions, in a wavelength range covering 260 to 780 nm, with charge-state selective ionization in an electron beam ion trap. Our measurements confirm the predictive power of ab initio calculations based on Fock space coupled cluster theory. We validate our line identification using semiempirical cowan calculations with adjustable wave-function parameters. Available Ritz combinations further strengthen our analysis. Comparison with previous work suggests that line identifications in the EUV need to be revisited.

  3. COLD TRAPS

    DOEpatents

    Thompson, W.I.

    1958-09-30

    A cold trap is presented for removing a condensable component from a gas mixture by cooling. It consists of a shell, the exterior surface of which is chilled by a refrigerant, and conductive fins welded inside the shell to condense the gas, and distribute the condensate evenly throughout the length of the trap, so that the trap may function until it becomes completely filled with the condensed solid. The contents may then be removed as either a gas or as a liquid by heating the trap. This device has particuinr use as a means for removing uranium hexafluoride from the gaseous diffusion separation process during equipment breakdown and repair periods.

  4. Optical trapping

    PubMed Central

    Neuman, Keir C.; Block, Steven M.

    2006-01-01

    Since their invention just over 20 years ago, optical traps have emerged as a powerful tool with broad-reaching applications in biology and physics. Capabilities have evolved from simple manipulation to the application of calibrated forces on—and the measurement of nanometer-level displacements of—optically trapped objects. We review progress in the development of optical trapping apparatus, including instrument design considerations, position detection schemes and calibration techniques, with an emphasis on recent advances. We conclude with a brief summary of innovative optical trapping configurations and applications. PMID:16878180

  5. Quadrupole ion traps.

    PubMed

    March, Raymond E

    2009-01-01

    The extraordinary story of the three-dimensional radiofrequency quadrupole ion trap, accompanied by a seemingly unintelligible theoretical treatment, is told in some detail because of the quite considerable degree of commercial success that quadrupole technology has achieved. The quadrupole ion trap, often used in conjunction with a quadrupole mass filter, remained a laboratory curiosity until 1979 when, at the American Society for Mass Spectrometry Conference in Seattle, George Stafford, Jr., of Finnigan Corp., learned of the Masters' study of Allison Armitage of a combined quadrupole ion trap/quadrupole mass filter instrument for the observation of electron impact and chemical ionization mass spectra of simple compounds eluting from a gas chromatograph. Stafford developed subsequently the mass-selective axial instability method for obtaining mass spectra from the quadrupole ion trap alone and, in 1983, Finnigan Corp. announced the first commercial quadrupole ion trap instrument as a detector for a gas chromatograph. In 1987, confinement of ions generated externally to the ion trap was demonstrated and, soon after, the new technique of electrospray ionization was shown to be compatible with the ion trap.

  6. Microfabricated cylindrical ion trap

    DOEpatents

    Blain, Matthew G.

    2005-03-22

    A microscale cylindrical ion trap, having an inner radius of order one micron, can be fabricated using surface micromachining techniques and materials known to the integrated circuits manufacturing and microelectromechanical systems industries. Micromachining methods enable batch fabrication, reduced manufacturing costs, dimensional and positional precision, and monolithic integration of massive arrays of ion traps with microscale ion generation and detection devices. Massive arraying enables the microscale cylindrical ion trap to retain the resolution, sensitivity, and mass range advantages necessary for high chemical selectivity. The microscale CIT has a reduced ion mean free path, allowing operation at higher pressures with less expensive and less bulky vacuum pumping system, and with lower battery power than conventional- and miniature-sized ion traps. The reduced electrode voltage enables integration of the microscale cylindrical ion trap with on-chip integrated circuit-based rf operation and detection electronics (i.e., cell phone electronics). Therefore, the full performance advantages of microscale cylindrical ion traps can be realized in truly field portable, handheld microanalysis systems.

  7. Quadrupole Strong Focusing for Transport of Space-Charge Dominated Electron Beams in Traveling-Wave Tubes

    NASA Astrophysics Data System (ADS)

    Nichols, Kimberley E. L.

    Analysis of quadrupole focusing lattices for high-frequency TWT's is presented. This work is motivated by recent work performed at the Naval Research Laboratory (NRL) which demonstrated an advantageous case for strong focusing employing a Halbach quadrupole lattice. Using realistic Permanent Magnet Quadruple (PMQ) field cancellation, the advantage of using PMQ to transport higher current densities than Permanent Periodic Magnet (PPM) lattices disappears, while other advantages for employing quadrupole focusing remain. This dissertation gives a comprehensive analysis of the applicability of PMQ focusing in vacuum electronic devices.

  8. Switching Oxide Traps

    NASA Technical Reports Server (NTRS)

    Oldham, Timothy R.

    2003-01-01

    We consider radiation-induced charge trapping in SiO2 dielectric layers, primarily from the point of view of CMOS devices. However, SiO2 insulators are used in many other ways, and the same defects occur in other contexts. The key studies, which determined the nature of the oxide charge traps, were done primarily on gate oxides in CMOS devices, because that was the main radiation problem in CMOS at one time. There are two major reviews of radiation-induced oxide charge trapping already in the literature, which discuss the subject in far greater detail than is possible here. The first of these was by McLean et al. in 1989, and the second, ten years later, was intended as an update, because of additional, new work that had been reported. Basically, the picture that has emerged is that ionizing radiation creates electron-hole pairs in the oxide, and the electrons have much higher mobility than the holes. Therefore, the electrons are swept out of the oxide very rapidly by any field that is present, leaving behind any holes that escape the initial recombination process. These holes then undergo a polaron hopping transport toward the Si/SiO2 interface (under positive bias). Near the interface, some fraction of them fall into deep, relatively stable, long-lived hole traps. The nature and annealing behavior of these hole traps is the main focus of this paper.

  9. Information Dominance

    DTIC Science & Technology

    1997-11-01

    Information dominance may be defined as superiority in the generation, manipulation, and use of information sufficient to afford its possessors... information dominance at the strategic level: knowing oneself and one’s enemy; and, at best, inducing them to see things as one does.

  10. Electron thermalization and trapping rates in pure and doped alkali and alkaline-earth iodide crystals studied by picosecond optical absorption

    NASA Astrophysics Data System (ADS)

    Ucer, K. B.; Bizarri, G.; Burger, A.; Gektin, A.; Trefilova, L.; Williams, R. T.

    2014-04-01

    Although light continues to be emitted from insulating crystals used as scintillators over a period of nanoseconds to microseconds after stopping of an energetic particle, much of what determines the nonlinearity of response goes on in the first picoseconds. On this time scale, free carriers and excitons are at high density near the track core and thus are subject to nonlinear quenching. The hot (free) electrons eventually cool to low enough energy that trapping on holes, dopants, or defects can commence. In the track environment, spatial distributions of trapped carriers determined on the picosecond time scale can influence the proportionality between light yield and the initial particle energy throughout the whole light pulse. Picosecond spectroscopy of optical absorption induced by a short pulse of above-gap excitation provides a useful window on what occurs during the crucial early evolution of excited populations. The laser excitation can be tuned to excite carriers that are initially very hot (˜3 eV) relative to the band edges, or that are almost thermalized (˜0.1 eV excess energy) at the outset. Undoped and doped samples of NaI:Tl(0%, 0.1%), CsI:Tl(0%, 0.01%, 0.04%, 0.3%), and SrI2:Eu(0%, 0.2%, 0.5%, 3%) are studied in this work.

  11. Calculations of the Probability of Positron Trapping by a Vacancy in a Metal and the Estimation of the Vacancy Contribution to the Work Function of Electrons and Positrons

    NASA Astrophysics Data System (ADS)

    Babich, A. V.; Pogosov, V. V.; Reva, V. I.

    2016-03-01

    The probabilities of the localization of positrons in monovacancies of Al and Cu have been calculated as functions of the energy and temperature. The vacancy was simulated by a void with a radius equal to the radius of the Wigner—Seitz cell in the model of stable jellium. Using the Fermi—Dirac golden rule for transitions, the formula for the rate of positron trapping by a vacancy has been derived as the function of the positron energy. For the thermalized positrons, the rate of localization near the triple point proved to be, on the order of magnitude, close to the rate of annihilation. Within the framework of our previously proposed models, the contribution of vacancies to the work function of electrons and positrons has been demonstrated based on the example of Al. The physical situations where the vacancy effect can manifest have been considered.

  12. Giant piezoresistance of p-type nano-thick silicon induced by interface electron trapping instead of 2D quantum confinement.

    PubMed

    Yang, Yongliang; Li, Xinxin

    2011-01-07

    The p-type silicon giant piezoresistive coefficient is measured in top-down fabricated nano-thickness single-crystalline-silicon strain-gauge resistors with a macro-cantilever bending experiment. For relatively thicker samples, the variation of piezoresistive coefficient in terms of silicon thickness obeys the reported 2D quantum confinement effect. For ultra-thin samples, however, the variation deviates from the quantum-effect prediction but increases the value by at least one order of magnitude (compared to the conventional piezoresistance of bulk silicon) and the value can change its sign (e.g. from positive to negative). A stress-enhanced Si/SiO(2) interface electron-trapping effect model is proposed to explain the 'abnormal' giant piezoresistance that should be originated from the carrier-concentration change effect instead of the conventional equivalent mobility change effect for bulk silicon piezoresistors. An interface state modification experiment gives preliminary proof of our analysis.

  13. Color stabilization in white organic light emitting devices utilizing trapping layers inserted in both an electron transport layer and an emitting layer.

    PubMed

    Kwack, Byoung Chan; Lee, Kwang Seop; Choo, Dong Chul; Kim, Tae Whan; Seo, Ji Hyun; Kim, Young Kwan

    2008-10-01

    The electrical and the optical properties of white organic light emitting devices (OLEDs) utilizing trapping layers inserted into both an electron transport layer (ETL) and an emitting layer (EML) were investigated. The current density of OLEDs with an ETL containing a 5,6,11,12-tetraphenylnaphthacene (rubrene) layer was slightly smaller than those of other devices. The luminance-current density and luminance efficiency-current density of the OLEDs with rubrene layers embedded in only an ETL or an EML were similar to the blue reference device. While the electroluminescence (EL) spectrum for the OLEDs with a rubrene layer in the ETL in the low voltage range showed the white color, that with rubrene layers in both the EML and the ETL exhibited white color, regardless of the applied voltage. The Commission International de l'Eclairage coordinates of the white OLEDs became stabilized by inserting rubrene layers into both the EML and the ETL.

  14. Stability of an emittance-dominated sheet-electron beam in planar wiggler and periodic permanent magnet structures with natural focusing

    NASA Astrophysics Data System (ADS)

    Carlsten, B. E.; Earley, L. M.; Krawczyk, F. L.; Russell, S. J.; Potter, J. M.; Ferguson, P.; Humphries, S.

    2005-06-01

    A sheet-beam traveling-wave amplifier has been proposed as a high-power generator of rf from 95 to 300 GHz, using a microfabricated rf slow-wave structure [Carlsten et al., IEEE Trans. Plasma Sci. 33, 85 (2005), ITPSBD, 0093-3813, 10.1109/TPS.2004.841172], for emerging radar and communications applications. The planar geometry of microfabrication technologies matches well with the nearly planar geometry of a sheet beam, and the greater allowable beam current leads to high-peak power, high-average power, and wide bandwidths. Simulations of nominal designs using a vane-loaded waveguide as the slow-wave structure have indicated gains in excess of 1 dB/mm, with extraction efficiencies greater than 20% at 95 GHz with a 120-kV, 20-A electron beam. We have identified stable sheet-beam formation and transport as the key enabling technology for this type of device. In this paper, we describe sheet-beam transport, for both wiggler and periodic permanent magnet (PPM) magnetic field configurations, with natural (or single-plane) focusing. For emittance-dominated transport, the transverse equation of motion reduces to a Mathieu equation, and to a modified Mathieu equation for a space-charge dominated beam. The space-charge dominated beam has less beam envelope ripple than an emittance-dominated beam, but they have similar stability thresholds (defined by where the beam ripple continues to grow without bound along the transport line), consistent with the threshold predicted by the Mathieu equation. Design limits are derived for an emittance-dominated beam based on the Mathieu stability threshold. The increased beam envelope ripple for emittance-dominated transport may impact these design limits, for some transport requirements. The stability of transport in a wiggler field is additionally compromised by the beam’s increased transverse motion. Stable sheet-beam transport with natural focusing is shown to be achievable for a 120-kV, 20-A, elliptical beam with a cross section of

  15. Band offsets and trap-related electron transitions at interfaces of (100)InAs with atomic-layer deposited Al2O3

    NASA Astrophysics Data System (ADS)

    Chou, H.-Y.; O'Connor, E.; O'Mahony, A.; Povey, I. M.; Hurley, P. K.; Dong, Lin; Ye, P. D.; Afanas'ev, V. V.; Houssa, M.; Stesmans, A.

    2016-12-01

    Spectral analysis of optically excited currents in single-crystal (100)InAs/amorphous (a-)Al2O3/metal structures allows one to separate contributions stemming from the internal photoemission (IPE) of electrons into alumina and from the trapping-related displacement currents. IPE spectra suggest that the out-diffusion of In and, possibly, its incorporation in a-Al2O3 lead to the development of ≈0.4 eV wide conduction band (CB) tail states. The top of the InAs valence band is found at 3.45 ± 0.10 eV below the alumina CB bottom, i.e., at the same energy as at the GaAs/a-Al2O3 interface. This corresponds to the CB and the valence band offsets at the InAs/a-Al2O3 interface of 3.1 ± 0.1 eV and 2.5 ± 0.1 eV, respectively. However, atomic-layer deposition of alumina on InAs results in additional low-energy electron transitions with spectral thresholds in the range of 2.0-2.2 eV, which is close to the bandgap of AlAs. The latter suggests the interaction of As with Al, leading to an interlayer containing Al-As bonds providing a lower barrier for electron injection.

  16. Simulation of electron transmittance and tunnel current in n{sup +} Poly-Si/HfSiO{sub x}N/Trap/SiO{sub 2}/Si(100) capacitors using analytical and numerical approaches

    SciTech Connect

    Noor, Fatimah A. Iskandar, Ferry; Abdullah, Mikrajuddin; Khairurrijal

    2015-04-16

    In this paper, we discuss the electron transmittance and tunneling current in high-k-based-MOS capacitors with trapping charge by including the off-diagonal effective-mass tensor elements and the effect of coupling between transverse and longitudinal energies represented by an electron velocity in the gate. The HfSiO{sub x}N/SiO{sub 2} dual ultrathin layer is used as the gate oxide in an n{sup +} poly- Si/oxide/Si capacitor to replace SiO{sub 2}. The main problem of using HfSiO{sub x}N is the charge trapping formed at the HfSiO{sub x}N/SiO{sub 2} interface that can influence the performance of the device. Therefore, it is important to develop a model taking into account the presence of electron traps at the HfSiO{sub x}N/SiO{sub 2} interface in the electron transmittance and tunneling current. The transmittance and tunneling current in n{sup +} poly- Si/HfSiO{sub x}N/trap/SiO2/Si(100) capacitors are calculated by using Airy wavefunctions and a transfer matrix method (TMM) as analytical and numerical approaches, respectively. The transmittance and tunneling current obtained from the Airy wavefunction are compared to those computed by the TMM. The effects of the electron velocity on the transmittance and tunneling current are also discussed.

  17. Trapped antihydrogen

    NASA Astrophysics Data System (ADS)

    Butler, E.; Andresen, G. B.; Ashkezari, M. D.; Baquero-Ruiz, M.; Bertsche, W.; Bowe, P. D.; Cesar, C. L.; Chapman, S.; Charlton, M.; Deller, A.; Eriksson, S.; Fajans, J.; Friesen, T.; Fujiwara, M. C.; Gill, D. R.; Gutierrez, A.; Hangst, J. S.; Hardy, W. N.; Hayden, M. E.; Humphries, A. J.; Hydomako, R.; Jenkins, M. J.; Jonsell, S.; Jørgensen, L. V.; Kemp, S. L.; Kurchaninov, L.; Madsen, N.; Menary, S.; Nolan, P.; Olchanski, K.; Olin, A.; Povilus, A.; Pusa, P.; Rasmussen, C. Ø.; Robicheaux, F.; Sarid, E.; Seif el Nasr, S.; Silveira, D. M.; So, C.; Storey, J. W.; Thompson, R. I.; van der Werf, D. P.; Wurtele, J. S.; Yamazaki, Y.

    Precision spectroscopic comparison of hydrogen and antihydrogen holds the promise of a sensitive test of the Charge-Parity-Time theorem and matter-antimatter equivalence. The clearest path towards realising this goal is to hold a sample of antihydrogen in an atomic trap for interrogation by electromagnetic radiation. Achieving this poses a huge experimental challenge, as state-of-the-art magnetic-minimum atom traps have well depths of only ˜1 T (˜0.5 K for ground state antihydrogen atoms). The atoms annihilate on contact with matter and must be `born' inside the magnetic trap with low kinetic energies. At the ALPHA experiment, antihydrogen atoms are produced from antiprotons and positrons stored in the form of non-neutral plasmas, where the typical electrostatic potential energy per particle is on the order of electronvolts, more than 104 times the maximum trappable kinetic energy. In November 2010, ALPHA published the observation of 38 antiproton annihilations due to antihydrogen atoms that had been trapped for at least 172 ms and then released—the first instance of a purely antimatter atomic system confined for any length of time (Andresen et al., Nature 468:673, 2010). We present a description of the main components of the ALPHA traps and detectors that were key to realising this result. We discuss how the antihydrogen atoms were identified and how they were discriminated from the background processes. Since the results published in Andresen et al. (Nature 468:673, 2010), refinements in the antihydrogen production technique have allowed many more antihydrogen atoms to be trapped, and held for much longer times. We have identified antihydrogen atoms that have been trapped for at least 1,000 s in the apparatus (Andresen et al., Nature Physics 7:558, 2011). This is more than sufficient time to interrogate the atoms spectroscopically, as well as to ensure that they have relaxed to their ground state.

  18. Trapped antihydrogen

    NASA Astrophysics Data System (ADS)

    Butler, E.; Andresen, G. B.; Ashkezari, M. D.; Baquero-Ruiz, M.; Bertsche, W.; Bowe, P. D.; Cesar, C. L.; Chapman, S.; Charlton, M.; Deller, A.; Eriksson, S.; Fajans, J.; Friesen, T.; Fujiwara, M. C.; Gill, D. R.; Gutierrez, A.; Hangst, J. S.; Hardy, W. N.; Hayden, M. E.; Humphries, A. J.; Hydomako, R.; Jenkins, M. J.; Jonsell, S.; Jørgensen, L. V.; Kemp, S. L.; Kurchaninov, L.; Madsen, N.; Menary, S.; Nolan, P.; Olchanski, K.; Olin, A.; Povilus, A.; Pusa, P.; Rasmussen, C. Ø.; Robicheaux, F.; Sarid, E.; Seif el Nasr, S.; Silveira, D. M.; So, C.; Storey, J. W.; Thompson, R. I.; van der Werf, D. P.; Wurtele, J. S.; Yamazaki, Y.

    2012-12-01

    Precision spectroscopic comparison of hydrogen and antihydrogen holds the promise of a sensitive test of the Charge-Parity-Time theorem and matter-antimatter equivalence. The clearest path towards realising this goal is to hold a sample of antihydrogen in an atomic trap for interrogation by electromagnetic radiation. Achieving this poses a huge experimental challenge, as state-of-the-art magnetic-minimum atom traps have well depths of only ˜1 T (˜0.5 K for ground state antihydrogen atoms). The atoms annihilate on contact with matter and must be `born' inside the magnetic trap with low kinetic energies. At the ALPHA experiment, antihydrogen atoms are produced from antiprotons and positrons stored in the form of non-neutral plasmas, where the typical electrostatic potential energy per particle is on the order of electronvolts, more than 104 times the maximum trappable kinetic energy. In November 2010, ALPHA published the observation of 38 antiproton annihilations due to antihydrogen atoms that had been trapped for at least 172 ms and then released—the first instance of a purely antimatter atomic system confined for any length of time (Andresen et al., Nature 468:673, 2010). We present a description of the main components of the ALPHA traps and detectors that were key to realising this result. We discuss how the antihydrogen atoms were identified and how they were discriminated from the background processes. Since the results published in Andresen et al. (Nature 468:673, 2010), refinements in the antihydrogen production technique have allowed many more antihydrogen atoms to be trapped, and held for much longer times. We have identified antihydrogen atoms that have been trapped for at least 1,000 s in the apparatus (Andresen et al., Nature Physics 7:558, 2011). This is more than sufficient time to interrogate the atoms spectroscopically, as well as to ensure that they have relaxed to their ground state.

  19. Electron transfer kinetics in photosynthetic reaction centers embedded in trehalose glasses: trapping of conformational substates at room temperature.

    PubMed Central

    Palazzo, Gerardo; Mallardi, Antonia; Hochkoeppler, Alejandro; Cordone, Lorenzo; Venturoli, Giovanni

    2002-01-01

    We report on room temperature electron transfer in the reaction center (RC) complex purified from Rhodobacter sphaeroides. The protein was embedded in trehalose-water systems of different trehalose/water ratios. This enabled us to get new insights on the relationship between RC conformational dynamics and long-range electron transfer. In particular, we measured the kinetics of electron transfer from the primary reduced quinone acceptor (Q(A)(-)) to the primary photo oxidized donor (P(+)), by time-resolved absorption spectroscopy, as a function of the matrix composition. The composition was evaluated either by weighing (liquid samples) or by near infrared spectroscopy (highly viscous or solid glasses). Deconvolution of the observed, nonexponential kinetics required a continuous spectrum of rate constants. The average rate constant ( = 8.7 s(-1) in a 28% (w/w) trehalose solution) increases smoothly by increasing the trehalose/water ratio. In solid glasses, at trehalose/water ratios > or = 97%, an abrupt increase is observed ( = 26.6 s(-1) in the driest solid sample). A dramatic broadening of the rate distribution function parallels the above sudden increase. Both effects fully revert upon rehydration of the glass. We compared the kinetics observed at room temperature in extensively dried water-trehalose matrices with the ones measured in glycerol-water mixtures at cryogenic temperatures and conclude that, in solid trehalose-water glasses, the thermal fluctuations among conformational substates are inhibited. This was inferred from the large broadening of the rate constant distribution for electron transfer obtained in solid glasses, which was due to the free energy distribution barriers having become quasi static. Accordingly, the RC relaxation from dark-adapted to light-adapted conformation, which follows primary charge separation at room temperature, is progressively hindered over the time scale of P(+)Q(A)(-) charge recombination, upon decreasing the

  20. Role of chloride ion in hydroxyl radical production in photosystem II under heat stress: electron paramagnetic resonance spin-trapping study.

    PubMed

    Yadav, Deepak Kumar; Pospíšil, Pavel

    2012-06-01

    Hydroxyl radical (HO•) production in photosystem II (PSII) was studied by electron paramagnetic resonance (EPR) spin-trapping technique. It is demonstrated here that the exposure of PSII membranes to heat stress (40 °C) results in HO• formation, as monitored by the formation of EMPO-OH adduct EPR signal. The presence of different exogenous halides significantly suppressed the EMPO-OH adduct EPR signal in PSII membranes under heat stress. The addition of exogenous acetate and blocker of chloride channel suppressed the EMPO-OH adduct EPR signal, whereas the blocker of calcium channel did not affect the EMPO-OH adduct EPR signal. Heat-induced hydrogen peroxide (H₂O₂) production was studied by amplex red fluorescent assay. The presence of exogenous halides, acetate and chloride blocker showed the suppression of H₂O₂ production in PSII membranes under heat stress. Based on our results, it is proposed that the formation of HO• under heat stress is linked to uncontrolled accessibility of water to the water-splitting manganese complex caused by the release of chloride ion on the electron donor side of PSII. Uncontrolled water accessibility to the water-splitting manganese complex causes the formation of H₂O₂ due to improper water oxidation, which leads to the formation of HO• via the Fenton reaction under heat stress.

  1. Discrimination Method of the Volatiles from Fresh Mushrooms by an Electronic Nose Using a Trapping System and Statistical Standardization to Reduce Sensor Value Variation

    PubMed Central

    Fujioka, Kouki; Shimizu, Nobuo; Manome, Yoshinobu; Ikeda, Keiichi; Yamamoto, Kenji; Tomizawa, Yasuko

    2013-01-01

    Electronic noses have the benefit of obtaining smell information in a simple and objective manner, therefore, many applications have been developed for broad analysis areas such as food, drinks, cosmetics, medicine, and agriculture. However, measurement values from electronic noses have a tendency to vary under humidity or alcohol exposure conditions, since several types of sensors in the devices are affected by such variables. Consequently, we show three techniques for reducing the variation of sensor values: (1) using a trapping system to reduce the infering components; (2) performing statistical standardization (calculation of z-score); and (3) selecting suitable sensors. With these techniques, we discriminated the volatiles of four types of fresh mushrooms: golden needle (Flammulina velutipes), white mushroom (Agaricus bisporus), shiitake (Lentinus edodes), and eryngii (Pleurotus eryngii) among six fresh mushrooms (hen of the woods (Grifola frondosa), shimeji (Hypsizygus marmoreus) plus the above mushrooms). Additionally, we succeeded in discrimination of white mushroom, only comparing with artificial mushroom flavors, such as champignon flavor and truffle flavor. In conclusion, our techniques will expand the options to reduce variations in sensor values. PMID:24233028

  2. Laboratory astrophysics and atomic physics using the NASA/GSFC microcalorimeter spectrometers at the LLNL Electron Beam Ion Trap and Radiation Properties Facility

    SciTech Connect

    Brown, G; Beiersdorfer, P; Boyce, K; Chen, H; Gu, M F; Kahn, S; Kelley, R; Kilbourne, C; May, M; Porter, F S; Szymkowiak, A; Thorn, D; Widmann, K

    2005-08-18

    The 32 pixel laboratory microcalorimeter spectrometer built by the NASA/Goddard Space Flight Center is now an integral part of the spectroscopy suite used routinely by the electron beam ion trap and radiative properties group at the Lawrence Livermore National Laboratory. The second generation laboratory instrument, dubbed the XRS/EBIT, is nearly identical to the XRS instrument on the Suzaku X-ray Observatory, formerly Astro-E2. The detector array is from the same processed wafer and uses the same HgTe absorbers. it is being used to measure the photon emission from a variety of radiation sources. These include x-ray emission from laboratory simulated celestial sources, x-ray emission from highly charged ions of Au, and x-ray emission following charge exchange and radiative electron capture. The wide range of applications demonstrates the versatility of a high-resolution, high-efficiency low temperature detector that is able to collect data continually with minimal operator servicing.

  3. Improved understanding of the electronic and energetic landscapes of perovskite solar cells: high local charge carrier mobility, reduced recombination, and extremely shallow traps.

    PubMed

    Oga, Hikaru; Saeki, Akinori; Ogomi, Yuhei; Hayase, Shuzi; Seki, Shu

    2014-10-01

    The intriguing photoactive features of organic-inorganic hybrid perovskites have enabled the preparation of a new class of highly efficient solar cells. However, the fundamental properties, upon which the performance of these devices is based, are currently under-explored, making their elucidation a vital issue. Herein, we have investigated the local mobility, recombination, and energetic landscape of charge carriers in a prototype CH3NH3PbI3 perovskite (PVK) using a laser-flash time-resolved microwave conductivity (TRMC) technique. PVK was prepared on mesoporous TiO2 and Al2O3 by one or two-step sequential deposition. PVK on mesoporous TiO2 exhibited a charge carrier mobility of 20 cm(2) V(-1) s(-1), which was predominantly attributed to holes. PVK on mesoporous Al2O3, on the other hand, exhibited a 50% lower mobility, which was resolved into balanced contributions from both holes and electrons. A general correlation between crystal size and mobility was revealed irrespective of the fabrication process and underlying layer. Modulating the microwave frequency from 9 toward 23 GHz allowed us to determine the intrinsic mobilities of each PVK sample (60-75 cm(2) V(-1) s(-1)), which were mostly independent of the mesoporous scaffold. Kinetic and frequency analysis of the transient complex conductivity strongly support the superiority of the perovskite, based on a significant suppression of charge recombination, an extremely shallow trap depth (10 meV), and a low concentration of these trapped states (less than 10%). The transport mechanism was further investigated by examining the temperature dependence of the TRMC maxima. Our study provides a basis for understanding perovskite solar cell operation, while highlighting the importance of the mesoporous layer and the perovskite fabrication process.

  4. Trapping photon-dressed Dirac electrons in a quantum dot studied by coherent two dimensional photon echo spectroscopy

    PubMed Central

    Roslyak, O.; Gumbs, Godfrey; Mukamel, S.

    2012-01-01

    We study the localization of dressed Dirac electrons in a cylindrical quantum dot (QD) formed on monolayer and bilayer graphene by spatially different potential profiles. Short lived excitonic states which are too broad to be resolved in linear spectroscopy are revealed by cross peaks in the photon-echo nonlinear technique. Signatures of the dynamic gap in the two-dimensional spectra are discussed. The effect of the Coulomb induced exciton-exciton scattering and the formation of biexciton molecules are demonstrated. PMID:22612079

  5. Suitability of magnetic particle immunoassay for the analysis of PBDEs in Hawaiian freshwater fish and crabs in comparison with gas chromatography/electron capture detection-ion trap mass spectrometry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A gas chromatograph/electron capture detector-ion trap mass spectrometer (GC/ECD-ITMS) was used for the determination of polybrominated diphenyl ethers (PBDEs) in freshwater fish and crabs. The samples were also analyzed with an enzyme-linked immunosorbent assay (ELISA). GC/ECD-ITMS results showed...

  6. High-k shallow traps observed by charge pumping with varying discharging times

    SciTech Connect

    Ho, Szu-Han; Chen, Ching-En; Tseng, Tseung-Yuen; Chang, Ting-Chang; Lu, Ying-Hsin; Lo, Wen-Hung; Tsai, Jyun-Yu; Liu, Kuan-Ju; Wang, Bin-Wei; Cao, Xi-Xin; Chen, Hua-Mao; Cheng, Osbert; Huang, Cheng-Tung; Chen, Tsai-Fu

    2013-11-07

    In this paper, we investigate the influence of falling time and base level time on high-k bulk shallow traps measured by charge pumping technique in n-channel metal-oxide-semiconductor field-effect transistors with HfO{sub 2}/metal gate stacks. N{sub T}-V{sub high} {sub level} characteristic curves with different duty ratios indicate that the electron detrapping time dominates the value of N{sub T} for extra contribution of I{sub cp} traps. N{sub T} is the number of traps, and I{sub cp} is charge pumping current. By fitting discharge formula at different temperatures, the results show that extra contribution of I{sub cp} traps at high voltage are in fact high-k bulk shallow traps. This is also verified through a comparison of different interlayer thicknesses and different Ti{sub x}N{sub 1−x} metal gate concentrations. Next, N{sub T}-V{sub high} {sub level} characteristic curves with different falling times (t{sub falling} {sub time}) and base level times (t{sub base} {sub level}) show that extra contribution of I{sub cp} traps decrease with an increase in t{sub falling} {sub time}. By fitting discharge formula for different t{sub falling} {sub time}, the results show that electrons trapped in high-k bulk shallow traps first discharge to the channel and then to source and drain during t{sub falling} {sub time}. This current cannot be measured by the charge pumping technique. Subsequent measurements of N{sub T} by charge pumping technique at t{sub base} {sub level} reveal a remainder of electrons trapped in high-k bulk shallow traps.

  7. Nonadiabatic transitions in electrostatically trapped ammonia molecules

    SciTech Connect

    Kirste, Moritz; Schnell, Melanie; Meijer, Gerard; Sartakov, Boris G.

    2009-05-15

    Nonadiabatic transitions are known to be major loss channels for atoms in magnetic traps but have thus far not been experimentally reported upon for trapped molecules. We have observed and quantified losses due to nonadiabatic transitions for three isotopologues of ammonia in electrostatic traps by comparing the trapping times in traps with a zero and a nonzero electric field at the center. Nonadiabatic transitions are seen to dominate the overall loss rate even for the present samples that are at relatively high temperatures of 30 mK. It is anticipated that losses due to nonadiabatic transitions in electric fields are omnipresent in ongoing experiments on cold molecules.

  8. Simplified Quantum Logic with Trapped Ions

    DTIC Science & Technology

    2016-06-23

    PHYSICAL REVIEW A ATOMIC , MOLECULAR, AND OPTICAL PHYSICS THIRD SERIES, VOLUME 55, NUMBER 4 APRIL 1997Simplified quantum logic with trapped ions C...Received 17 December 1996! We describe a simplified scheme for quantum logic with a collection of laser-cooled trapped atomic ions. Building on the...in a system of laser-cooled trapped atomic ions. In the simplest form of the ion trap quantum computer, two internal electronic levels of each ion in

  9. Study of gate oxide traps in HfO2/AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors by use of ac transconductance method

    NASA Astrophysics Data System (ADS)

    Sun, X.; Saadat, O. I.; Chang-Liao, K. S.; Palacios, T.; Cui, S.; Ma, T. P.

    2013-03-01

    We introduce an ac-transconductance method to profile the gate oxide traps in a HfO2 gated AlGaN/GaN Metal-Oxide-Semiconductor High-Electron-Mobility Transistors (MOS-HEMTs) that can exchange carriers with metal gates, which in turn causes changes in analog and pulsed channel currents. The method extracts energy and spacial distributions of the oxide and interface traps under the gate from the frequency dependence of ac transconductance. We demonstrate the method using MOS-HEMTs with gate oxides that were annealed at different temperatures.

  10. Geomagnetically trapped anomalous cosmic rays

    SciTech Connect

    Selesnick, R.S.; Cummings, A.C.; Cummings, J.R.

    1995-06-01

    Since its launch in July 1992, the polar-orbiting satellite SAMPEX has been collecting data on geomagnetically trapped heavy ions, predominantly O, N, and Ne, at energies {ge}15 MeV/nucleon and in a narrow L shell range L = 2. Their location, elemental composition, energy spectra, pitch angle distribution, and time variations all support the theory that these particles originated as singly ionized interplanetary anomalous cosmic rays that were stripped of electrons in the Earth`s upper atmosphere and subsequently trapped. The O are observed primarily at pitch angles outside the atmospheric loss cones, consistent with a trapped population, and their distribution there is nearly isotropic. The abundances relative to O of the N, possible Ne, and especially C are lower than the corresponding interplanetary values, which may be indicative of the trapping efficiencies. The distributions of trapped N, O, and Ne in energy and L shell suggest that most of the ions observed at the SAMPEX altitude of {approximately}600 km are not fully stripped when initially trapped. A comparison of the trapped intensity with the much lower interplanetary intensity of anomalous cosmic rays provides model-dependent estimates of the product of the trapping probability and the average trapped particle lifetime against ionization losses in the residual atmosphere for particles that mirror near the SAMPEX altitude. 36 refs., 13 figs., 1 tab.

  11. The dominant factors affecting the memory characteristics of (Ta{sub 2}O{sub 5}){sub x}(Al{sub 2}O{sub 3}){sub 1−x} high-k charge-trapping devices

    SciTech Connect

    Gong, Changjie; Lan, Xuexin; Yin, Qiaonan; Ou, Xin; Liu, Jinqiu; Sun, Chong; Wang, Laiguo; Lu, Wei; Yin, Jiang Xu, Bo; Xia, Yidong; Liu, Zhiguo; Li, Aidong

    2014-09-22

    The prototypical charge-trapping memory devices with the structure p-Si/Al{sub 2}O{sub 3}/(Ta{sub 2}O{sub 5}){sub x}(Al{sub 2}O{sub 3}){sub 1−x}/Al{sub 2}O{sub 3}/Pt(x = 0.5, 0.3, and 0.1) were fabricated by using atomic layer deposition and RF magnetron sputtering techniques. A memory window of 7.39 V with a charge storage density of 1.97 × 10{sup 13 }cm{sup −2} at a gate voltage of ±11 V was obtained for the memory device with the composite charge trapping layer (Ta{sub 2}O{sub 5}){sub 0.5}(Al{sub 2}O{sub 3}){sub 0.5}. All memory devices show fast program/erase speed and excellent endurance and retention properties, although some differences in their memory performance exist, which was ascribed to the relative individual band alignments of the composite (Ta{sub 2}O{sub 5}){sub x}(Al{sub 2}O{sub 3}){sub 1−x} with Si.

  12. The wave magnetic field amplitude threshold for nonlinear trapping of energetic gyroresonant and Landau resonant electrons by nonducted VLF waves in the magnetosphere

    NASA Technical Reports Server (NTRS)

    Bell, T. F.

    1986-01-01

    A recently developed theory is used to calculate the wave magnetic field amplitude threshold, B-tau, necessary to allow the nonlinear trapping of energetic gyroresonant and Landau resonant electrons by VLF whistler mode waves in the magnetosphere propagating at an arbitrary angle, psi, with respect to the earth's magnetic field. A detailed raytracing study is carried out to establish the variation of psi with position along each magnetic shell in the range L = 2-5 and for frequencies 5-17.8 kHz. It is found that the minimum values of B-tau along each L shell generally occur at points of second-order resonance. In general, for nonducted fixed frequency signals there is only one point of second-order resonance on each L shell, and this is located within a few degrees of the magnetic equator. However, over a narrow range of L, there are as many as three points of second-order resonance and as many as three associated minima in B-tau. At least one of these points is located more than 10 deg from the magnetic equator.

  13. Trapping and dark current in plasma-based accelerators

    SciTech Connect

    Schroder, C.B.; Esarey, E.; Shadwick, B.A.; Leemans, W.P.

    2004-06-01

    The trapping of thermal electrons in a nonlinear plasma wave of arbitrary phase velocity is investigated. The threshold plasma wave amplitude for trapping plasma electrons is calculated, thereby determining the fraction trapped and the expected dark current in a plasma-based accelerator. It is shown that the presence of a laser field (e.g., trapping in the self-modulated regime of the laser wakefield accelerator) increases the trapping threshold. Implications for experimental and numerical laser-plasma studies are discussed.

  14. Mini ion trap mass spectrometer

    DOEpatents

    Dietrich, D.D.; Keville, R.F.

    1995-09-19

    An ion trap is described which operates in the regime between research ion traps which can detect ions with a mass resolution of better than 1:10{sup 9} and commercial mass spectrometers requiring 10{sup 4} ions with resolutions of a few hundred. The power consumption is kept to a minimum by the use of permanent magnets and a novel electron gun design. By Fourier analyzing the ion cyclotron resonance signals induced in the trap electrodes, a complete mass spectra in a single combined structure can be detected. An attribute of the ion trap mass spectrometer is that overall system size is drastically reduced due to combining a unique electron source and mass analyzer/detector in a single device. This enables portable low power mass spectrometers for the detection of environmental pollutants or illicit substances, as well as sensors for on board diagnostics to monitor engine performance or for active feedback in any process involving exhausting waste products. 10 figs.

  15. Mini ion trap mass spectrometer

    DOEpatents

    Dietrich, Daniel D.; Keville, Robert F.

    1995-01-01

    An ion trap which operates in the regime between research ion traps which can detect ions with a mass resolution of better than 1:10.sup.9 and commercial mass spectrometers requiring 10.sup.4 ions with resolutions of a few hundred. The power consumption is kept to a minimum by the use of permanent magnets and a novel electron gun design. By Fourier analyzing the ion cyclotron resonance signals induced in the trap electrodes, a complete mass spectra in a single combined structure can be detected. An attribute of the ion trap mass spectrometer is that overall system size is drastically reduced due to combining a unique electron source and mass analyzer/detector in a single device. This enables portable low power mass spectrometers for the detection of environmental pollutants or illicit substances, as well as sensors for on board diagnostics to monitor engine performance or for active feedback in any process involving exhausting waste products.

  16. Intrinsic charge trapping in organic and polymeric semiconductors: a physical chemistry perspective

    SciTech Connect

    Kaake, Loren; Barbara, Paul F.; Zhu, Xiaoyang

    2010-01-12

    We aim to understand the origins of intrinsic charge carrier traps in organic and polymeric semiconductor materials from a physical chemistry perspective. In crystalline organic semiconductors, we point out some of the inadequacies in the description of intrinsic charge traps using language and concepts developed for inorganic semiconductors. In π-conjugated polymeric semiconductors, we suggest the presence of a two-tier electronic energy landscape, a bimodal majority landscape due to two dominant structural motifs and a minority electronic energy landscape from intrinsic charged defects. The bimodal majority electronic energy landscape results from a combination of amorphous domains and microcrystalline or liquid-crystalline domains. The minority tier of the electronic density of states is comprised of deep Coulomb traps embedded in the majority electronic energy landscape. This minority electronic energy landscape may dominate transport properties at low charge carrier densities, such as those expected for organic photovoltaic devices, while the bimodal majority electronic energy landscape becomes significant at high carrier densities, that is, in organic field effect transistors.

  17. Compression of Antiproton Clouds for Antihydrogen Trapping

    SciTech Connect

    Andresen, G. B.; Bowe, P. D.; Hangst, J. S.; Bertsche, W.; Butler, E.; Charlton, M.; Jenkins, M. J.; Joergensen, L. V.; Madsen, N.; Werf, D. P. van der; Bray, C. C.; Chapman, S.; Fajans, J.; Povilus, A.; Wurtele, J. S.; Cesar, C. L.; Lambo, R.; Silveira, D. M.; Fujiwara, M. C.; Gill, D. R.

    2008-05-23

    Control of the radial profile of trapped antiproton clouds is critical to trapping antihydrogen. We report the first detailed measurements of the radial manipulation of antiproton clouds, including areal density compressions by factors as large as ten, by manipulating spatially overlapped electron plasmas. We show detailed measurements of the near-axis antiproton radial profile and its relation to that of the electron plasma.

  18. Solar trap

    SciTech Connect

    Lew, H.S.

    1988-02-09

    A solar trap for collecting solar energy at a concentrated level is described comprising: (a) a compound light funnel including a pair of light reflecting substantially planar members arranged into a trough having a substantially V-shaped cross section; (b) a two dimensional Fresnel lens cover covering the opening of the compound light funnel, the opening being the open diverging end of the substantially V-shaped cross section of the compound light funnel; (c) at least one conduit for carrying a heat transfer fluid disposed substantially adjacent and substantially parallel to the apex line of the compound light funnel.

  19. COLD TRAP

    DOEpatents

    Milleron, N.

    1963-03-12

    An improved linear-flow cold trap is designed for highvacuum applications such as mitigating back migration of diffusion pump oil moiecules. A central pot of liquid nitrogen is nested within and supported by a surrounding, vertical, helical coil of metai sheet, all enveloped by a larger, upright, cylindrical, vacuum vessel. The vertical interstices between successive turns of the coil afford lineal, axial, high-vacuum passages between open mouths at top and bottom of said vessel, while the coil, being cold by virtue of thermal contact of its innermost turn with the nitrogen pot, affords expansive proximate condensation surfaces. (AEC)

  20. VACUUM TRAP

    DOEpatents

    Gordon, H.S.

    1959-09-15

    An improved adsorption vacuum trap for use in vacuum systems was designed. The distinguishing feature is the placement of a plurality of torsionally deformed metallic fins within a vacuum jacket extending from the walls to the central axis so that substantially all gas molecules pass through the jacket will impinge upon the fin surfaces. T fins are heated by direct metallic conduction, thereby ol taining a uniform temperature at the adeorbing surfaces so that essentially all of the condensible impurities from the evacuating gas are removed from the vacuum system.

  1. Dispersive liquid-liquid microextraction for the determination of organochlorine pesticides residues in honey by gas chromatography-electron capture and ion trap mass spectrometric detection.

    PubMed

    Zacharis, Constantinos K; Rotsias, Ilias; Zachariadis, Petros G; Zotos, Anastasios

    2012-10-01

    A simple dispersive liquid-liquid microextraction (DLLME) protocol for the determination of 15 organochlorine pesticides residues in honey is proposed. The selected pesticides were separated using gas chromatography and detected by electron capture (ECD) or ion trap mass spectrometry (GC-IT/MS). Several parameters affecting the extraction efficiency namely type and volume of organic extraction solvent, type and volume of disperser solvent, sample pH, ionic strength, extraction time and centrifugation speed were systematically investigated. The final DLLME protocol involved the addition of 750 μL acetonitrile (disperser) and 50 μL chloroform (extraction solvent) into a 5 mL aqueous honey solution followed by centrifugation. The sedimented organic phase (chloroform) were analysed directly by GC-IT/MS or evaporated and reconstituted in acetonitrile prior to the GC-ECD analysis. The analytical performance of the GC-ECD and GC-IT/MS methods was compared and discussed. Under the selected experimental conditions, the enrichment factors varied between of 36 and 114. The limits of detection (LOD) were in the range of 0.02-0.15 μg L(-1) (0.4-3 ng g(-1)) for GC-ECD and 0.01-0.2 μg L(-1) (0.2-4 ng g(-1)) for GC-IT/MS which is adequate to verify compliance of products to legal tolerances. The proposed method was applied to the analysis of the selected organochlorine pesticides residues in various honey samples obtained from Greek region. Mean recoveries were ranged from 75% to 119% while the precision was better than 20% in both methodologies.

  2. Correlation of photoluminescence and deep trapping in metalorganic chemical vapor deposited Al/sub x/Ga/sub 1-x/As (0< or =x< or =0. 40)

    SciTech Connect

    Bhattacharya, P.K.; Subramanian, S.; Ludowise, M.J.

    1984-05-15

    Shallow and deep level photoluminescence (PL) in metalorganic chemical vapor deposition grown Al/sub x/Ga/sub 1-x/As (0< or =x< or =0.40) are studied. Two sets of samples grown under different conditions are compared. The growth conditions are chosen to produce a large density of deep levels in one case and to minimize the deep level density in the other case. The 0.82-eV EL2 electron trap and four other dominant electron traps with activation energies E/sub T/ ranging from 0.25 to 0.62 eV are identified. The concentrations of the four other traps are observed to increase with Al content in those samples grown under trap-producing conditions, and the traps are nearly absent in the other set of samples. The PL intensity is inversely proportional to trap concentrations. The trap densities are related to background contamination in the growth ambient, most likely H/sub 2/O and O/sub 2/, leading to the speculation that two traps with E/sub T/ = 0.35 eV and E/sub T/ = 0.25 eV involve Al and O complexes. Hole traps have also been observed but show no definite trends with x or the growth ambient. Radiative centers up to 400 meV deep exhibit more intense PL in samples grown under larger V/III ratios.

  3. The habitats exploited and the species trapped in a Caribbean island trap fishery

    USGS Publications Warehouse

    Garrison, V.H.; Rogers, C.S.; Beets, J.; Friedlander, A.M.

    2004-01-01

    We visually observed fish traps in situ to identify the habitats exploited by the U.S. Virgin Islands fishery and to document species composition and abundance in traps by habitat. Fishers set more traps in algal plains than in any other habitat around St. John. Coral reefs, traditionally targeted by fishers, accounted for only 16% of traps. Traps in algal plain contained the highest number of fishes per trap and the greatest numbers of preferred food species. Traps on coral reefs contained the most species, 41 of the 59 taxa observed in the study. Acanthurus coeruleus was the most abundant species and Acanthuridae the most abundant family observed in traps. Piscivore numbers were low and few serranids were observed. Traps in algal plain contained the most fishes as a result of: ecological changes such as shifts in habitat use, mobility of species and degradation of nearshore habitat (fishery independent); and, catchability of fishes and long-term heavy fishing pressure (fishery dependent). The low number of serranids per trap, dominance of the piscivore guild by a small benthic predator, Epinephelus guttatus, and dominance of trap contents overall by a small, fast-growing species of a lower trophic guild, Acanthurus coeruleus, all point to years of intense fishing pressure.

  4. Large spin relaxation rates in trapped submerged-shell atoms

    SciTech Connect

    Connolly, Colin B.; Au, Yat Shan; Doret, S. Charles; Doyle, John M.; Ketterle, Wolfgang

    2010-01-15

    Spin relaxation due to atom-atom collisions is measured for magnetically trapped erbium and thulium atoms at a temperature near 500 mK. The rate constants for Er-Er and Tm-Tm collisions are 3.0x10{sup -10} and 1.1x10{sup -10} cm{sup 3} s{sup -1}, respectively, 2-3 orders of magnitude larger than those observed for highly magnetic S-state atoms. This is strong evidence for an additional, dominant, spin relaxation mechanism, electronic interaction anisotropy, in collisions between these 'submerged-shell,' Lnot =0 atoms. These large spin relaxation rates imply that evaporative cooling of these atoms in a magnetic trap will be highly inefficient.

  5. Electrostatic trapping of metastable NH molecules

    SciTech Connect

    Hoekstra, Steven; Metsaelae, Markus; Zieger, Peter C.; Scharfenberg, Ludwig; Gilijamse, Joop J.; Meijer, Gerard; Meerakker, Sebastiaan Y. T. van de

    2007-12-15

    We report on the Stark deceleration and electrostatic trapping of {sup 14}NH (a{sup 1}{delta}) radicals. In the trap, the molecules are excited on the spin-forbidden A{sup 3}{pi}<-a{sup 1}{delta} transition and detected via their subsequent fluorescence to the X{sup 3}{sigma}{sup -} ground state. The 1/e trapping time is 1.4{+-}0.1 s, from which a lower limit of 2.7 s for the radiative lifetime of the a{sup 1}{delta}, v=0, J=2 state is deduced. The spectral profile of the molecules in the trapping field is measured to probe their spatial distribution. Electrostatic trapping of metastable NH followed by optical pumping of the trapped molecules to the electronic ground state is an important step toward accumulation of these radicals in a magnetic trap.

  6. Ion traps fabricated in a CMOS foundry

    SciTech Connect

    Mehta, K. K.; Ram, R. J.; Eltony, A. M.; Chuang, I. L.; Bruzewicz, C. D.; Sage, J. M. Chiaverini, J.

    2014-07-28

    We demonstrate trapping in a surface-electrode ion trap fabricated in a 90-nm CMOS (complementary metal-oxide-semiconductor) foundry process utilizing the top metal layer of the process for the trap electrodes. The process includes doped active regions and metal interconnect layers, allowing for co-fabrication of standard CMOS circuitry as well as devices for optical control and measurement. With one of the interconnect layers defining a ground plane between the trap electrode layer and the p-type doped silicon substrate, ion loading is robust and trapping is stable. We measure a motional heating rate comparable to those seen in surface-electrode traps of similar size. This demonstration of scalable quantum computing hardware utilizing a commercial CMOS process opens the door to integration and co-fabrication of electronics and photonics for large-scale quantum processing in trapped-ion arrays.

  7. Scalable Designs for Planar Ion Trap Arrays

    NASA Astrophysics Data System (ADS)

    Slusher, R. E.

    2007-03-01

    Recent progress in quantum operations with trapped ion qubits has been spectacular for qubit counts up to approximately ten ions. Two qubit quantum gates, quantum error correction, simple quantum algorithms and entanglement of up to 8 qubits have been demonstrated by groups including those at NIST, University of Michigan, University of Innsbruck and Oxford. Interesting problems in quantum information processing including quantum simulations of condensed matter systems and quantum repeaters for long distance quantum communication systems require hundreds or thousands of qubits. Initial designs for an ion trap ``Quantum CCD'' using spatially multiplexed planar ion traps as well as initial experiments using planar ion traps are promising routes to scaling up the number of trapped ions to more interesting levels. We describe designs for planar ion traps fabricated using silicon VLSI techniques. This approach allows the control voltages required for the moving and positioning the ions in the array to be connected vertically through the silicon substrate to underlying CMOS electronics. We have developed techniques that allow the ion trap structures to be fabricated monolithically on top of the CMOS electronics. The planar traps have much weaker trapping depths than the more conventional multi-level traps. However, the trap depths are still adequate for trapping hot ions from many ion sources. The planar traps also involve more complex configurations for laser cooling and micromotion control. Initial solutions to these problems will be presented. Laser access to the ions can be provided by laser beams grazing the trap surface or by using vertical slots through the trap chip. We will also discuss limits imposed by power dissipation and ion transport through trap junctions (e.g. crosses and Ys). We have fabricated these VLSI based traps in a number of configurations. Initial fabrication and packaging challenges will be discussed. D. Kielpinski, C. Monroe, and D.J. Wineland

  8. Trapping ions in a segmented ring trap

    NASA Astrophysics Data System (ADS)

    Tabakov, B. P.; Sterk, J. D.; Benito, F.; Haltli, R.; Tigges, C. P.; Stick, D.; Blain, M. G.; Moehring, D. L.

    2012-06-01

    We demonstrate robust trapping in an ion trap which has a ring shaped RF node. Ions are back-side loaded through a small 10 μm diameter loading hole and we have demonstrated thousands of complete circuits around the trap. Each circuit passes through 44 trapping zones; the trap has 89 independent DC control electrodes. Measurements of the tangential secular frequency indicate a weak dependence on the RF and the loading hole. The ion trap is fabricated using four metal layers, allowing for the inner islanded electrodes to be electrically routed underneath the trap with negligible effects on the trapped ions. [4pt] This work was supported by the Intelligence Advanced Research Projects Activity (IARPA). Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the US Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  9. Envelope equation for the linear and nonlinear propagation of an electron plasma wave, including the effects of Landau damping, trapping, plasma inhomogeneity, and the change in the state of wave

    NASA Astrophysics Data System (ADS)

    Bénisti, Didier

    2016-10-01

    This paper addresses the linear and nonlinear three-dimensional propagation of an electron wave in a collisionless plasma that may be inhomogeneous, nonstationary, anisotropic, and even weakly magnetized. The wave amplitude, together with any hydrodynamic quantity characterizing the plasma (density, temperature, etc.) is supposed to vary very little within one wavelength or one wave period. Hence, the geometrical optics limit is assumed, and the wave propagation is described by a first order differential equation. This equation explicitly accounts for three-dimensional effects, plasma inhomogeneity, Landau damping, and the collisionless dissipation and electron acceleration due to trapping. It is derived by mixing results obtained from a direct resolution of the Vlasov-Poisson system and from a variational formalism involving a nonlocal Lagrangian density. In a one-dimensional situation, abrupt transitions are predicted in the coefficients of the wave equation. They occur when the state of the electron plasma wave changes, from a linear wave to a wave with trapped electrons. In a three dimensional geometry, the transitions are smoother, especially as regards the nonlinear Landau damping rate, for which a very simple effective and accurate analytic expression is provided.

  10. Density of state determination of two types of intra-gap traps in dye-sensitized solar cells and its influence on device performance.

    PubMed

    Wang, Yi; Wu, Dapeng; Fu, Li-Min; Ai, Xi-Cheng; Xu, Dongsheng; Zhang, Jian-Ping

    2014-06-21

    The density of state (DOS) of intra-gap traps and the dynamics of electron transport of a dye-sensitized TiO2 solar cell were investigated by means of time-resolved charge extraction (TRCE). The intrinsic chemical capacitance of the TiO2 layer was separated from the parasitic capacitance of the FTO electrode, and was found to be dependent biexponentially on the photovoltage. It was shown that the shallow traps (>700 meV) differ from the deep ones (<350 meV) by the respective characteristic energy of 48 meV and 765 meV, and that the amount of shallow traps is more than an order of magnitude larger than that of the deep ones. Our results support the mechanism of shallow-trap dominant multiple-trap limited charge transport, and suggest a substantial margin for the short-circuit photocurrent density to reach its theoretical limit.

  11. Multi-ring trap as a reservoir of cooled antiprotons

    SciTech Connect

    Ichioka, T.; Yamazaki, Y.; Higaki, H.; Komaki, K.; Hori, M.; Oshima, N.; Mohri, A.; Kuroki, K.

    1999-12-10

    For the ASACUSA project, a new charged particle trap was designed and constructed. Like a Penning-Malmberg trap, static electric and static magnetic fields are used. Multi-ring electrode is exploited to generate a harmonic potential on the trap axis. It enables the confinement of a number of antiprotons and electrons for the electron cooling. Upon its design, plasma behavior of trapped particle clouds was taken into consideration. As the first step, trap performances have been checked with electrons. Current status are presented.

  12. Spectroscopy with trapped highly charged ions

    SciTech Connect

    Beiersdorfer, P

    2008-01-23

    We give an overview of atomic spectroscopy performed on electron beam ion traps at various locations throughout the world. Spectroscopy at these facilities contributes to various areas of science and engineering, including but not limited to basic atomic physics, astrophysics, extreme ultraviolet lithography, and the development of density and temperature diagnostics of fusion plasmas. These contributions are accomplished by generating, for example, spectral surveys, making precise radiative lifetime measurements, accounting for radiative power emitted in a given wavelength band, illucidating isotopic effects, and testing collisional-radiative models. While spectroscopy with electron beam ion traps had originally focused on the x-ray emission from highly charged ions interacting with the electron beam, the operating modes of such devices have expanded to study radiation in almost all wavelength bands from the visible to the hard x-ray region; and at several facilities the ions can be studied even in the absence of an electron beam. Photon emission after charge exchange or laser excitation has been observed, and the work is no longer restricted to highly charged ions. Much of the experimental capabilities are unique to electron beam ion traps, and the work performed with these devices cannot be undertaken elsewhere. However, in other areas the work on electron beam ion traps rivals the spectroscopy performed with conventional ion traps or heavy-ion storage rings. The examples we present highlight many of the capabilities of the existing electron beam ion traps and their contributions to physics.

  13. An analysis of point defects induced by In, Al, Ni, and Sn dopants in Bridgman-grown CdZnTe detectors and their influence on trapping of charge carriers

    NASA Astrophysics Data System (ADS)

    Gul, R.; Roy, U. N.; James, R. B.

    2017-03-01

    In this research, we studied point defects induced in Bridgman-grown CdZnTe detectors doped with Indium (In), Aluminium (Al), Nickel (Ni), and Tin (Sn). Point defects associated with different dopants were observed, and these defects were analyzed in detail for their contributions to electron/hole (e/h) trapping. We also explored the correlations between the nature and abundance of the point defects with their influence on the resistivity, electron mobility-lifetime (μτe) product, and electron trapping time. We used current-deep level transient spectroscopy to determine the energy, capture cross-section, and concentration of each trap. Furthermore, we used the data to determine the trapping and de-trapping times for the charge carriers. In In-doped CdZnTe detectors, uncompensated Cd vacancies (VCd-) were identified as a dominant trap. The VCd- were almost compensated in detectors doped with Al, Ni, and Sn, in addition to co-doping with In. Dominant traps related to the dopant were found at Ev + 0.36 eV and Ev + 1.1 eV, Ec + 76 meV and Ev + 0.61 eV, Ev + 36 meV and Ev + 0.86 eV, Ev + 0.52 eV and Ec + 0.83 eV in CZT:In, CZT:In + Al, CZT:In + Ni, and CZT:In + Sn, respectively. Results indicate that the addition of other dopants with In affects the type, nature, concentration (Nt), and capture cross-section (σ) and hence trapping (tt) and de-trapping (tdt) times. The dopant-induced traps, their corresponding concentrations, and charge capture cross-section play an important role in the performance of radiation detectors, especially for devices that rely solely on electron transport.

  14. Effects of oxide thickness on charge trapping in metal-nitride-oxide- semiconductor structures

    NASA Astrophysics Data System (ADS)

    Kapoor, Vikram J.; Delatore, James P.

    1982-07-01

    Charge trapping in chemically vapor-deposited Si3N4 thin films of metal-nitride-oxide- semiconductor (MNOS) structures has been studied using the internal photoelectric-effect technique in combination with high-frequency capacitance-voltage measurements. The trapped charge density in the Si3N4 film was investigated as a function of the experimental parameters of the internal photoelectric-effect technique and the oxide thickness (300-20 Å) of the MNOS structure. The optimum trapped electron density in the Si3N4 film was measured to be 1.5×1018/ cm3 using 4.14-eV photon energy, 3.0-mW/cm2 light intensity, and -20-V applied gate voltage bias for the MNOS structures whose oxide thicknesses were greater than 70 Å. The photoinjection of holes from Si into Si3N4 was inhibited in thick-oxide (300-43 Å) MNOS structures due to the large barrier height at the Si-SiO2 interface. This eliminated simultaneous trapping of holes and electrons in the Si3N4 film. As the oxide thickness of the MNOS structure was reduced below the critical thickness of 43 Å, the photoinjection of holes from Si into Si3N4 was enhanced substantially with subsequent dominant hole trapping in the Si3N4 film.

  15. One-electron oxidation of DNA by ionizing radiation: competition between base-to-base hole-transfer and hole-trapping.

    PubMed

    Sharma, Kiran K K; Tyagi, Rahul; Purkayastha, Shubhadeep; Bernhard, William A

    2010-06-10

    The distance of hole migration through DNA determines the degree to which radiation-induced lesions are clustered. It is the degree of clustering that confers to ionizing radiation its high toxicity. The migration distance is governed by a competition between hole transfer and irreversible trapping reactions. An important type of trapping is reactions that lead to the formation of deoxyribose radicals, which are precursors to free base release (fbr). Using HPLC, fbr was measured in X-irradiated films of d(CGCGCGCGCG)(2) and d(CGCGAATTCGCG)(2) as well as three genomic DNAs: M. luteus, calf thymus, and C. perfringens. The level of DNA hydration was varied from Gamma = 2.5 to 22 mol waters/mol nucleotide. The chemical yields of each base, G(base), were measured and used to calculate the modification factor, M(base). This factor compensates for differences in the GC/AT ratio, providing a measure of the degree to which a given base influences its own release. In the DNA oligomers, M(Gua) > M(Cyt), a result ascribed to the previously observed end effect in short oligomers. In the highly polymerized genomic DNA, we found that M(Cyt) > M(Gua) and that M(Thy) is consistently the smallest of the M factors. For these same DNA films, the yields of total DNA trapped radicals, G(tot)(fr), were measured using EPR spectroscopy. The yield of deoxyribose radicals was calculated using G(dRib)(fr) = approximately 0.11 x G(tot)(fr). Comparing G(dRib)(fr) with total fbr, we found that only about half of the fbr is accounted for by deoxyribose radical intermediates. We conclude that for a hole on cytosine, Cyt(*+), base-to-base hole transfer competes with irreversible trapping by the deoxyribose. In the case of a hole on thymine, Thy(*+), base-to-base hole transfer competes with irreversible trapping by methyl deprotonation. Close proximity of Gua protects the deoxyribose of Cyt but sensitizes the deoxyribose of Thy.

  16. Charge Trapping Flash Memory With High-k Dielectrics

    NASA Astrophysics Data System (ADS)

    Eun, Dong Seog

    2011-12-01

    High capacity and affordable price of flash memory make portable electronic devices popular, which in turn stimulates the further scaling down effort of the flash memory cells. Indeed the flash memory cells have been scaling down aggressively and face several crucial challenges. As a result, the technology trend is shifting from the floating-gate cell to the charge-trap cell in order to overcome fatal interference problems between cells. There are critical problems in the charge-trap memory cell which will become main-stream in the near future. The first potential problem is related to the memory retention which is degraded by the charge leakage through thin tunnel dielectrics. The second is the reduction of charge-storage capacity in the scaled down SiN trapping layer. The third is the low operation-efficiency resulting from the methods used to solve the first two problems. Using high-k tunnel dielectrics can solve the first problem. The second problem can be overcome by adopting a high-k trapping dielectric. The dielectric constant of the blocking layer must be higher than those of the tunnel dielectric and the trapping dielectric in order to maintain operation efficiency. This dissertation study is focused on adopting high-k dielectrics in all three of the aforementioned layers for figure generations of flash memory technology. For the high-k tunnel dielectric, the MAD Si3N4 and the MAD Al2O3 are used to fabricate the MANNS structure and the MANAS structure. The MANNS structure has the advantage of reducing the erase voltage due to its low barrier height for holes. In addition, the retention characteristic of the MANAS structure is not sensitive to temperature. The reason is that the carrier transport in MAD Al2O3 is dominated by F-N tunneling, which is nearly independent of temperature. Adopting TiOx as the trapping dielectric forms the MATAS structure. Although the charge capacity of TiOx is not very high, the operating voltage can be reduced to less than 10V

  17. Trapping polar molecules in an ac trap

    SciTech Connect

    Bethlem, Hendrick L.; Veldhoven, Jacqueline van; Schnell, Melanie; Meijer, Gerard

    2006-12-15

    Polar molecules in high-field seeking states cannot be trapped in static traps as Maxwell's equations do not allow a maximum of the electric field in free space. It is possible to generate an electric field that has a saddle point by superposing an inhomogeneous electric field to an homogeneous electric field. In such a field, molecules are focused along one direction, while being defocused along the other. By reversing the direction of the inhomogeneous electric field the focusing and defocusing directions are reversed. When the fields are being switched back and forth at the appropriate rate, this leads to a net focusing force in all directions. We describe possible electrode geometries for creating the desired fields and discuss their merits. Trapping of {sup 15}ND{sub 3} ammonia molecules in a cylindrically symmetric ac trap is demonstrated. We present measurements of the spatial distribution of the trapped cloud as a function of the settings of the trap and compare these to both a simple model assuming a linear force and to full three-dimensional simulations of the experiment. With the optimal settings, molecules within a phase-space volume of 270 mm{sup 3} (m/s){sup 3} remain trapped. This corresponds to a trap depth of about 5 mK and a trap volume of about 20 mm{sup 3}.

  18. Microscale ion trap mass spectrometer

    DOEpatents

    Ramsey, J. Michael; Witten, William B.; Kornienko, Oleg

    2002-01-01

    An ion trap for mass spectrometric chemical analysis of ions is delineated. The ion trap includes a central electrode having an aperture; a pair of insulators, each having an aperture; a pair of end cap electrodes, each having an aperture; a first electronic signal source coupled to the central electrode; a second electronic signal source coupled to the end cap electrodes. The central electrode, insulators, and end cap electrodes are united in a sandwich construction where their respective apertures are coaxially aligned and symmetric about an axis to form a partially enclosed cavity having an effective radius r.sub.0 and an effective length 2z.sub.0, wherein r.sub.0 and/or z.sub.0 are less than 1.0 mm, and a ratio z.sub.0 /r.sub.0 is greater than 0.83.

  19. Trap assisted space charge conduction in p-NiO/n-ZnO heterojunction diode

    SciTech Connect

    Tyagi, Manisha; Tomar, Monika; Gupta, Vinay

    2015-06-15

    Highlights: • p-NiO/n-ZnO heterojunction diode with enhanced junction parameters has been prepared. • Temperature dependent I–V throw insight into the involved conduction mechanism. • SCLC with exponential trap distribution was found to be the dominant mechanism. • C–V measurement at different frequencies support the presence of traps. - Abstract: The development of short-wavelength p–n junction is essentially important for the realization of transparent electronics for next-generation optoelectronic devices. In the present work, a p–n heterojunction diode based on p-NiO/n-ZnO has been prepared under the optimised growth conditions exhibiting improved electrical and junction parameters. The fabricated heterojunction gives typical current–voltage (I–V) characteristics with good rectifying behaviour (rectification ratio ≈ 10{sup 4} at 2 V). The temperature dependent current–voltage characteristics of heterojunction diode have been studied and origin of conduction mechanism is identified. The space-charge limited conduction with exponential trap distribution having deep level trap is found to be the dominant conduction mechanism in the fabricated p–n heterojunction diode. The conduction and valence band discontinuities for NiO/ZnO heterostructure have been determined from the capacitance–voltage (C–V) measurements.

  20. EPR spin-trapping evidence for the direct, one-electron reduction of tert-butylhydroperoxide to the tert-butoxyl radical by copper(II): paradigm for a previously overlooked reaction in the initiation of lipid peroxidation.

    PubMed

    Jones, Clare M; Burkitt, Mark J

    2003-06-11

    Lipid peroxidation is often initiated using Cu(II) ions. It is widely assumed that Cu(II) oxidizes preformed lipid hydroperoxides to peroxyl radicals, which propagate oxidation of the parent fatty acid via hydrogen atom abstraction. However, the oxidation of alkyl hydroperoxides by Cu(II) is thermodynamically unfavorable. An alternative means by which Cu(II) ions could initiate lipid peroxidation is by their one-electron reduction of lipid hydroperoxides to alkoxyl radicals, which would be accompanied by the generation of Cu(III). We have investigated by EPR spectroscopy, in conjunction with the spin trap 5,5-dimethyl-1-pyrroline N-oxide, the reactions of various Cu(II) chelates with tert-butylhydroperoxide. Spectra contained signals from the tert-butoxyl, methyl, and methoxyl radical adducts. In many previous studies, the signal from the methoxyl adduct has been assigned incorrectly to the tert-butylperoxyl adduct, which is now known to be unstable, releasing the tert-butoxyl radical upon decomposition. This either is trapped by 5,5-dimethyl-1-pyrroline N-oxide or undergoes beta-scission to the methyl radical, which either is trapped or reacts with molecular oxygen to give, ultimately, the methoxyl radical adduct. By using metal chelates that are known to be specific in either their oxidation or reduction of tert-butylhydroperoxide (the Cu(II) complex of bathocuproine disulfonic acid and the Fe(II) complex of diethylenetriaminepentaacetic acid, respectively) for comparison, we have been able to deduce, from the relative concentrations of the three radical adducts, that the Cu(II) complexes tested each reduce tert-butylhydroperoxide directly to the tert-butoxyl radical. These findings suggest that a previously overlooked reaction, namely the direct reduction of preformed lipid hydroperoxides to alkoxyl radicals by Cu(II), may be responsible for the initiation of lipid peroxidation by Cu(II) ions.

  1. Electronic influence of β-diketonato-type ligands on the coordination of 1,5-cyclooctadiene to palladium(II) as defined by 'Venus fly trap' geometric parameters.

    PubMed

    Hill, Tania N; Roodt, Andreas; Steyl, Gideon

    2013-02-01

    A range of single-crystal structures of the type [Pd(cod)(LL'-Bid)]A, where LL'-Bid = acetylacetonato (acac), thenoyltrifluoroactetonato (thtfac) and hexafluoroacetylacetonato (hfacac), and A = tetrafluoroborate (BF(4)(-)) and hexafluorophosphate (PF(6)(-)), are reported. The complexes [Pd(cod)(acac)]PF(6) (I), [Pd(cod)(thtfac)]PF(6) (III), [Pd(cod)(thtfac)]BF(4) (IV) and [Pd(cod)(hfacac)]PF(6) (V) are isostructural in the monoclinic space group P2(1)/c. The influence of the variation of the β-diketonato-type ligands on the coordination geometry of cis,cis-1,5-cycloocta-1,5-diene (cod) was investigated and found that no significant changes to the Pd-C and C=C bond distances were observed. The `Venus fly trap' parameters vary by 7.8° for the 'jaw' angle (ψ), while the `bite' angle (χ) remains virtually constant.

  2. Sorption vacuum trap

    NASA Technical Reports Server (NTRS)

    Barrington, A. E.; Caruso, A. J.

    1970-01-01

    Modified sorption trap for use in high vacuum systems contains provisions for online regeneration of sorbent material. Trap is so constructed that it has a number of encapsulated resistance heaters and a valving and pumping device for removing gases from heated sorbing material. Excessive downtime is eliminated with this trap.

  3. Ion trap simulation tools.

    SciTech Connect

    Hamlet, Benjamin Roger

    2009-02-01

    Ion traps present a potential architecture for future quantum computers. These computers are of interest due to their increased power over classical computers stemming from the superposition of states and the resulting capability to simultaneously perform many computations. This paper describes a software application used to prepare and visualize simulations of trapping and maneuvering ions in ion traps.

  4. GAMMASPHERE: Correction technique for detector charge trapping

    SciTech Connect

    Goulding, F.S.; Landis, D.A.

    1993-11-01

    GAMMASPHERE uses 110 very large germanium detectors. Such detectors exhibit charge trapping effects on energy resolution initially due to a native electron trap that is present in virtually all germanium. Furthermore, radiation damage is a serious problem in GAMMASPHERE experiments, producing hole traps that degrade resolution and eventually require annealing to restore the original performance. The technique discussed here uses the current pulse shape from a detector to develop a parameter related to the radius of the largest interaction in the ``track`` of a gamma ray in the detector. Since the charge trapping loss in a signal can be related to the distance carriers travel, the ``radius`` parameter can be used by software to apply a trap correction to the signal.

  5. Promotion of atomic hydrogen recombination as an alternative to electron trapping for the role of metals in the photocatalytic production of H2.

    PubMed

    Joo, Ji Bong; Dillon, Robert; Lee, Ilkeun; Yin, Yadong; Bardeen, Christopher J; Zaera, Francisco

    2014-06-03

    The production of hydrogen from water with semiconductor photocatalysts can be promoted by adding small amounts of metals to their surfaces. The resulting enhancement in photocatalytic activity is commonly attributed to a fast transfer of the excited electrons generated by photon absorption from the semiconductor to the metal, a step that prevents deexcitation back to the ground electronic state. Here we provide experimental evidence that suggests an alternative pathway that does not involve electron transfer to the metal but requires it to act as a catalyst for the recombination of the hydrogen atoms made via the reduction of protons on the surface of the semiconductor instead.

  6. An in situ trap capacitance measurement and ion-trapping detection scheme for a Penning ion trap facility

    NASA Astrophysics Data System (ADS)

    Reza, Ashif; Banerjee, Kumardeb; Das, Parnika; Ray, Kalyankumar; Bandyopadhyay, Subhankar; Dam, Bivas

    2017-03-01

    This paper presents the design and implementation of an in situ measurement setup for the capacitance of a five electrode Penning ion trap (PIT) facility at room temperature. For implementing a high Q resonant circuit for the detection of trapped electrons/ions in a PIT, the value of the capacitance of the trap assembly is of prime importance. A tunable Colpitts oscillator followed by a unity gain buffer and a low pass filter is designed and successfully implemented for a two-fold purpose: in situ measurement of the trap capacitance when the electric and magnetic fields are turned off and also providing RF power at the desired frequency to the PIT for exciting the trapped ions and subsequent detection. The setup is tested for the in situ measurement of trap capacitance at room temperature and the results are found to comply with those obtained from measurements using a high Q parallel resonant circuit setup driven by a standard RF signal generator. The Colpitts oscillator is also tested successfully for supplying RF power to the high Q resonant circuit, which is required for the detection of trapped electrons/ions.

  7. A study of the dependence of electron-induced defects on the doping impurity density in n-type germanium by deep-level transient spectroscopy (DLTS)

    NASA Astrophysics Data System (ADS)

    Nyamhere, Cloud; Auret, F. D.; Das, A. G. M.; Chawanda, A.

    2007-12-01

    We have measured the electrical characteristics of electron irradiation-induced defects in n-type (1 1 0), (1 1 1) and (1 0 0) germanium doped with antimony (Sb) by deep-level transient spectroscopy (DLTS) and Laplace-DLTS. The following electron traps at 0.04, 0.15, 0.20, 0.21, 0.23, 0.31 and 0.38 eV below the conduction band were observed and two hole traps at 0.09 and 0.30 eV above the valence band were recorded in the low doping (10 14 cm -3) samples. In the higher doping (10 15 cm -3) samples, similar electron traps were observed but the electron trap at 0.04 eV below the conduction band and hole trap at 0.09 eV above the valence band was not observed. The electron trap at 0.38 eV is identified as the (V-Sb) --/- center and the hole trap at 0.30 eV assigned the (V-Sb) 0/- appeared in almost equal concentrations in the higher-doped samples but in the lowest-doped samples the hole trap (V-Sb) 0/- was more dominant. We have also presented the annealing behavior of these electron-induced defects.

  8. ELECTRON ACCELERATION BY CASCADING RECONNECTION IN THE SOLAR CORONA. I. MAGNETIC GRADIENT AND CURVATURE DRIFT EFFECTS

    SciTech Connect

    Zhou, X.; Büchner, J.; Bárta, M.; Gan, W.; Liu, S.

    2015-12-10

    We investigate the electron acceleration by magnetic gradient and curvature drift effects in cascading magnetic reconnection of a coronal current sheet via a test particle method in the framework of the guiding center approximation. After several Alfvén transit times, most of the electrons injected at the current sheet are still trapped in the magnetic islands. A small fraction of the injected electrons precipitate into the chromosphere. The acceleration of trapped electrons is dominated by the magnetic curvature drifts, which change the parallel momentum of the electron, and appears to be more efficient than the acceleration of precipitating electrons, which is dominated by the perpendicular momentum change caused by the magnetic gradient drifts. With the resulting trapped energetic electron distribution, the corresponding hard X-ray (HXR) radiation spectra are calculated using an optically thin Bremsstrahlung model. Trapped electrons may explain flare loop top HXR emission as well as the observed bright spots along current sheets trailing coronal mass ejections. The asymmetry of precipitating electrons with respect to the polarity inversion line may contribute to the observed asymmetry of footpoint emission.

  9. Entanglement generation in planar Penning traps

    SciTech Connect

    Martins, Ana M.; Mendonca, J. T.; Guerreiro, A.; Vieira, V. R.

    2010-07-15

    We investigate the generation of entanglement between the axial degrees of freedom of electrons confined in separated locations in planar Penning traps. We show that there are two different sources of entanglement: one is related with the mechanism of switching on and off the electrical coupling between the two electrons, and the other is due to the two-quanta-transition term of the coupling interaction. We show that the degree of entanglement can be controlled by adjusting the strength of the coupling between the traps and the time of interaction. We show that the coupled electrons behave as a temporal active interferometer.

  10. The complex mixed Wentzel–Kramers–Brillouin-full-wave approach and its application to the two dimensional mode structure analysis of ion temperature gradient/collisionless trapped electron mode drift waves

    SciTech Connect

    Lu, Z. X.

    2015-05-15

    The complex mixed Wentzel–Kramers–Brillouin (WKB)-full-wave approach is applied to the 2D mode structure analysis of ion temperature gradient/collisionless trapped electron mode drift waves in tokamak plasmas. The parallel mode structure is calculated with the full-wave approach, while the radial envelope is calculated with the complex WKB method. The tilting of the global mode structure along radius is demonstrated analytically. The effects of the phase and amplitude variation of the radial envelope on the parallel mode structure are included in terms of a complex radial wave vector in the parallel mode equation. It is shown that the radial equilibrium non-uniformity leads to the asymmetry of the parallel mode structure not only in configuration space but also in spectrum space. The mixed approach provides a practical way to analyze the asymmetric component of the global mode structure due to radial equilibrium non-uniformity.

  11. Trap-based Cluster Research and Cluster-based Investigations of Ion Storage at ClusterTrap

    SciTech Connect

    Schweikhard, Lutz; Breitenfeldt, Martin; Herlert, Alexander; Martinez, Franklin; Marx, Gerrit; Walsh, Noelle

    2006-10-18

    ClusterTrap is a setup devoted to the investigation of atomic clusters. The Penning trap allows various studies after preceding preparation steps. In particular, the clusters may be size selected and their charge state may be varied by electron impact ionization or electron attachment during storage. On the other hand the clusters can be used for extended studies of the properties of the Penning trap. Both aspects are described with recent examples.

  12. Atoms and plasmas in a high-magnetic-field trap

    SciTech Connect

    Raithel, G.; Knuffman, B.; Shah, M. H.; Hempel, C.; Paradis, E.; Mhaskar, R.; Zhang, X.; Choi, J.-H.; Povilus, A. P.; Guest, J. R.

    2008-08-08

    We investigate cold rubidium plasmas in a particle trap that has the unique capability to simultaneously laser-cool and trap neutral atoms as well as to confine plasmas in magnetic fields of about three Tesla. The atom trap is a high-field Ioffe-Pritchard laser trap, while the plasma trap is a Ioffe-Penning trap that traps electrons and ions in separate wells. The observed plasma dynamics is characterized by a breathing-mode oscillation of the positive (ionic) plasma component, which feeds back on the behavior of the negative (electron) component of the plasma. At higher densities, the observed oscillations become nonlinear. The electron component has been found to undergo rapid cooling. We further report on the recombination of magnetized plasmas into Rydberg atoms in transient traps and quasi-steady-state traps. In transient traps, large numbers of recombined Rydberg atoms in high-lying states are observed. In quasi-steady-state traps, the measured numbers of recombined atoms are lower and the binding energies higher.

  13. Determination of active oxide trap density and 1/f noise mechanism in RESURF LDMOS transistors

    NASA Astrophysics Data System (ADS)

    Çelik-Butler, Z.; Mahmud, M. I.; Hao, P.; Hou, F.; Amey, B. L.; Pendharkar, S.

    2015-09-01

    The physical origin of majority charge carrier fluctuations in the SiO2 interface of Si at accumulation has been investigated and analyzed for differently processed and voltage-rated reduced surface field (RESURF), lateral-double-diffused MOS (LDMOS) transistors. Surface carrier mobility fluctuation due to remote Coulomb scattering by the trapped charge in the gate oxide is identified as the dominant physical mechanism for LDMOS 1/f noise irrespective of process technologies. A significant contribution to the measured noise has been noted from the surface majority carrier mobility fluctuation due to trapped charge at the accumulation region of the extended drain region, dominant over other sources including the surface minority charge carrier fluctuations in the channel. Active oxide trap density was characterized spatially and for the first time up to ∼0.4 eV above the conduction band-edge of Si. The interface trap density in the unstressed devices (∼8 × 106 cm-2) increased more than an order of magnitude (∼1 × 108 cm-2) after the devices were stressed for 10,000 sec at their individual worst drain current and on-resistance degradation conditions. The extracted Si/SiO2 interface trap density above the silicon conduction band edge was found to be several orders of magnitude lower than that reported for silicon mid-gap energies, even after stressing. Since the traps near the quasi-Fermi level for electrons are active in trapping-detrapping, and the Fermi level is energetically positioned above the conduction band edge of Si in the investigated devices as compared to the previously reported observations, the lower trap density obtained here is an indication for reversal of the well-known exponential trap energy distribution beyond the conduction band-edge of Si. These findings shift the focus from the channel to the gate overlap section of the extended drain and the quality of the Si/SiO2 interface in that region.

  14. Stokes Trap: Multiplexed particle trapping and manipulation using fluidics

    NASA Astrophysics Data System (ADS)

    Shenoy, Anish; Schroeder, Charles

    We report the development of the Stokes Trap, which is a multiplexed microfluidic trap for control over an arbitrary number of small particles in a microfluidic device. Our work involves the design and implementation of ``smart'' flow-based devices by coupling feedback control with microfluidics, thereby enabling new routes for the fluidic-directed assembly of particles. Here, we discuss the development of a new method to achieve multiplexed microfluidic trapping of an arbitrary number of particles using the sole action of fluid flow. In particular, we use a Hele-Shaw microfluidic cell to generate hydrodynamic forces on particles in a viscous-dominated flow defined by the microdevice geometry and imposed peripheral flow rates. This platform allows for a high degree of flow control over individual particles and can be used for manufacturing novel particles for fundamental studies, using fluidic-directed assembly. From a broader perspective, our work provides a solid framework for guiding the design of next-generation, automated on-chip assays.

  15. Protoype Solid State Quantum Interface for Trapped Ions

    DTIC Science & Technology

    2014-11-07

    We study how to couple the motion of trapped ions to each other. For this we set up an ion trap apparatus with an electrically floating electrode...connecting two trapping sites. We find that we can trap ions nearby such an electrically floating electrode. At the same time, we develop a method to...coupling electrode amenable to Arion treatment. Finally, we develop a vision for QIP with electrons with the distinct advantages of avoiding laser technology and being inherently faster than trapped ions .

  16. Trap style influences wild pig behavior and trapping success

    USGS Publications Warehouse

    Williams, B.L.; Holtfreter, R.W.; Ditchkoff, S.S.; Grand, J.B.

    2011-01-01

    Despite the efforts of many natural resource professionals, wild pig (Sus scrofa) populations are expanding in many areas of the world. Although many creative techniques for controlling pig populations are being explored, trapping has been and still is themost commonly usedmethod of population control formany public and private land managers. We conducted an observational study to examine the efficiency of 2 frequently used trap styles: a small, portable box-style trap and a larger, semi-permanent, corral-style trap.We used game cameras to examine patterns of trap entry by wild pigs around each style of trap, and we conducted a trapping session to compare trapping success between trap styles. Adult female and juvenile wild pigs entered both styles of trap more readily than did adult males, and adult males seemed particularly averse to entering box traps. Less than 10% of adult male visits to box traps resulted in entries, easily the least percentage of any class at any style of trap. Adult females entered corral traps approximately 2.2 times more often per visit than box traps and re-entered corral traps >2 times more frequently. Juveniles entered and reentered both box and corral traps at similar rates. Overall (all-class) entry-per-visit rates at corral traps (0.71) were nearly double that of box traps (0.37). Subsequent trapping data supported these preliminary entry data; the capture rate for corral traps was >4 times that of box traps. Our data suggest that corral traps are temporally and economically superior to box traps with respect to efficiency; that is, corral traps effectively trap more pigs per trap night at a lower cost per pig than do box traps. ?? 2011 The Wildlife Society.

  17. Ecological and evolutionary traps

    USGS Publications Warehouse

    Schlaepfer, Martin A.; Runge, M.C.; Sherman, P.W.

    2002-01-01

    Organisms often rely on environmental cues to make behavioral and life-history decisions. However, in environments that have been altered suddenly by humans, formerly reliable cues might no longer be associated with adaptive outcomes. In such cases, organisms can become 'trapped' by their evolutionary responses to the cues and experience reduced survival or reproduction. Ecological traps occur when organisms make poor habitat choices based on cues that correlated formerly with habitat quality. Ecological traps are part of a broader phenomenon, evolutionary traps, involving a dissociation between cues that organisms use to make any behavioral or life-history decision and outcomes normally associated with that decision. A trap can lead to extinction if a population falls below a critical size threshold before adaptation to the novel environment occurs. Conservation and management protocols must be designed in light of, rather than in spite of, the behavioral mechanisms and evolutionary history of populations and species to avoid 'trapping' them.

  18. Neutral atom traps.

    SciTech Connect

    Pack, Michael Vern

    2008-12-01

    This report describes progress in designing a neutral atom trap capable of trapping sub millikelvin atom in a magnetic trap and shuttling the atoms across the atom chip from a collection area to an optical cavity. The numerical simulation and atom chip design are discussed. Also, discussed are preliminary calculations of quantum noise sources in Kerr nonlinear optics measurements based on electromagnetically induced transparency. These types of measurements may be important for quantum nondemolition measurements at the few photon limit.

  19. Evaluating steam trap performance

    SciTech Connect

    Fuller, N.Y.

    1985-08-08

    This paper presents a method for evaluating the performance level of steam traps by preparing an economic analysis of several types to determine the equivalent uniform annual cost. A series of tests on steam traps supplied by six manufacturers provided data for determining the relative efficiencies of each unit. The comparison was made using a program developed for the Texas Instruments T1-59 programmable calculator to evaluate overall steam trap economics.

  20. Trapped positrons observed by PAMELA experiment

    NASA Astrophysics Data System (ADS)

    Mikhailov, V. V.; Adriani, O.; Barbarino, G.; Bazilevskaya, G. A.; Bellotti, R.; Boezio, M.; Bogomolov, E. A.; Bongi, M.; Bonvicini, V.; Bottai, S.; Bruno, A.; Cafagna, F. S.; Campana, D.; Carbone, R.; Carlson, P.; Casolino, M.; Castellini, G.; Consiglio, L.; De Santis, C.; De Simone, N.; Di Felice, V.; Galper, A. M.; Karelin, A. V.; Koldashov, S. V.; Koldobsky, S.; Krutkov, S. Yu; Kvashnin, A. N.; Leonov, A. A.; Malakhov, V. V.; Marcelli, L.; Martucci, M.; Mayorov, A. G.; Menn, W.; Merge, M.; Mocchiutti, E.; Monaco, A.; Mori, N.; Munini, R.; Osteria, G.; Papini, P.; Palma, F.; Panico, B.; Pearce, M.; Picozza, P.; Ricci, M.; Ricciarini, S. B.; Sarkar, R.; Scotti, V.; Simon, M.; Sparvoli, R.; Spillantini, P.; Stozhkov, Yu I.; Vacchi, A.; Vannuccini, E.; Vasiliev, G. I.; Voronov, S. A.; Yurkin, Yu T.; Zampa, G.; Zampa, N.

    2016-02-01

    Measurements of electron and positron spatial distributions in energy range from 80 MeV to several GeV below the geomagnetic cutoff rigidity were carried out using the PAMELA magnetic spectrometer. The instrument is installed on board the Resurs-DK satellite which was launched June 15th 2006 on an elliptical orbit with the inclination 70 degrees and the altitude 350-600 km. The procedure of trajectories calculations in the geomagnetic filed gives a way to separate stably trapped and short lived albedo components produced in interactions of cosmic ray protons with the residual atmosphere. The work presents spatial distributions of trapped, quasitrapped and short-lived albedo electrons and positrons in the near Earth space. Electron to positron ratio points out on different production mechanism of trapped and quasitrapped particles.

  1. Multi-GeV electron beams from capillary discharge guided sub-petawatt class laser pulses in the self-trapping regime

    NASA Astrophysics Data System (ADS)

    Leemans, Wim

    2014-10-01

    Laser plasma accelerators (LPAs) can produce acceleration gradients on the order of tens to hundreds of GV/m, making them attractive as compact particle accelerators. During the past decade, quasi-monochromatic electron beams at the 1 GeV energy level have been produced using laser pulses at the 40-50 TW peak power level. With the availability of petawatt class lasers, beams up to 2 GeV have been produced from 7 cm long gas cells at UT Austin using 150 J laser pulses and at the 1 GeV level with tails extending to 3 GeV at the GIST facility in Korea. In this talk we present experimental results using the 1 Hz petawatt class BELLA laser at LBNL of the generation of multi-GeV electron beams with center energy up to 4.2 GeV, 6% rms energy spread, charge approximately 10 pC and an rms divergence around 0.3 mrad. The beams were produced from 9 cm long capillary discharge waveguide structure with a plasma density of ~ 7 ×1017cm-3 , powered by laser pulses with peak power up to 0.3 PW. Preformed plasma waveguides allow the use of lower laser power compared to unguided plasma structures to achieve the same beam energy. Detailed comparison between experiment and simulation indicates the importance of the near-field laser transverse mode quality on guiding and acceleration in the LPA. By tuning the plasma density, regimes were found where laser beams with a top hat near-field profile were guided well, and where high energy electron beams can be produced, with narrow divergence [ <0.8 mrad (FWHM)], and relatively small integrated energy spread (<10%). Provided that the slice energy spread and emittance are sufficiently low, electron beams with this energy could power x-ray free electron lasers. Future experiments will aim at increasing the beam energy to the 10 GeV level. Work supported by Office of Science, Office of HEP, US DOE Contract DE-AC02-05CH11231.

  2. Steam Trap Users’ Guide,

    DTIC Science & Technology

    1985-04-01

    traps do not work well in a system where the condensate can back against the operating mechanism of the trap and open it when there is no condensate flow ...a flow through the trap. h. Float and thermostatic traps are widely used in low pressure heating 0 systems . If they are properly installed below the... system or trap problem. * Blowdown strainer. SOUND CHECK HOT TRAPS: • Listen to trap operate. * Check for continuous flow : - low pitch condensate flow

  3. Lift enhancement by trapped vortex

    NASA Technical Reports Server (NTRS)

    Rossow, Vernon J.

    1992-01-01

    The viewgraphs and discussion of lift enhancement by trapped vortex are provided. Efforts are continuously being made to find simple ways to convert wings of aircraft from an efficient cruise configuration to one that develops the high lift needed during landing and takeoff. The high-lift configurations studied here consist of conventional airfoils with a trapped vortex over the upper surface. The vortex is trapped by one or two vertical fences that serve as barriers to the oncoming stream and as reflection planes for the vortex and the sink that form a separation bubble on top of the airfoil. Since the full three-dimensional unsteady flow problem over the wing of an aircraft is so complicated that it is hard to get an understanding of the principles that govern the vortex trapping process, the analysis is restricted here to the flow field illustrated in the first slide. It is assumed that the flow field between the two end plates approximates a streamwise strip of the flow over a wing. The flow between the endplates and about the airfoil consists of a spanwise vortex located between the suction orifices in the endplates. The spanwise fence or spoiler located near the nose of the airfoil serves to form a separated flow region and a shear layer. The vorticity in the shear layer is concentrated into the vortex by withdrawal of fluid at the suction orifices. As the strength of the vortex increases with time, it eventually dominates the flow in the separated region so that a shear or vertical layer is no longer shed from the tip of the fence. At that point, the vortex strength is fixed and its location is such that all of the velocity contributions at its center sum to zero thereby making it an equilibrium point for the vortex. The results of a theoretical analysis of such an idealized flow field are described.

  4. Al{sub 2}O{sub 3}/GeO{sub x}/Ge gate stacks with low interface trap density fabricated by electron cyclotron resonance plasma postoxidation

    SciTech Connect

    Zhang, R.; Iwasaki, T.; Taoka, N.; Takenaka, M.; Takagi, S.

    2011-03-14

    An electron cyclotron resonance (ECR) plasma postoxidation method has been employed for forming Al{sub 2}O{sub 3}/GeO{sub x}/Ge metal-oxide-semiconductor (MOS) structures. X-ray photoelectron spectroscopy and transmission electron microscope characterizations have revealed that a GeO{sub x} layer is formed beneath the Al{sub 2}O{sub 3} capping layer by exposing the Al{sub 2}O{sub 3}/Ge structures to ECR oxygen plasma. The interface trap density (D{sub it}) of Au/Al{sub 2}O{sub 3}/GeO{sub x}/Ge MOS capacitors is found to be significantly suppressed down to lower than 10{sup 11} cm{sup -2} eV{sup -1}. Especially, a plasma postoxidation time of as short as 10 s is sufficient to reduce D{sub it} with maintaining the equivalent oxide thickness (EOT). As a result, the minimum D{sub it} values and EOT of 5x10{sup 10} cm{sup -2} eV{sup -1} and 1.67 nm, and 6x10{sup 10} cm{sup -2} eV{sup -1} and 1.83 nm have been realized for Al{sub 2}O{sub 3}/GeO{sub x}/Ge MOS structures with p- and n-type substrates, respectively.

  5. Genetic studies: dominant lethal study, sex linked recessive lethal, ames mutagenicity, and heritable translocation test of thermal processed, frozen, electron irradiated, and gamma irradiated chicken. Final report Jun 76-Aug 83

    SciTech Connect

    Sullivan, D.; Lusskin, R.M.; Thomson, G.M.; Kuzdas, C.D.; Ronning, D.C.

    1983-01-01

    Four samples of chicken meat identified as the frozen control, thermally processed, gamma sterilized (5.9 Mrad), and electron sterilized (5.9 MeV), along with negative and positive controls, were evaluated for genetic activity. The samples were evaluated for ability to induce dominant lethal mutations in spermatid and spermatozoan stages of spermatogenesis in mice fed 35 percent chicken meat. The test meat samples were not observed to have an effect on the incidence of the dominant lethal mutations. However, the positive control failed to give a positive response. The meat samples were investigated for mutagenic activity employing Drosophila melanogaster in the sex linked recessive lethal test. The samples were determined to be nonmutagenic in this test and the positive control gave a significant response. Reduced production of offspring in cultures of Drosophila reared on gamma irradiated chicken which could not be overcome by the addition of vitamins was observed. Pre-incubation tests with and without added mutagens revealed that in no case was a positive result observed in the Ames test from chicken meat without an added mutagen. The manner in which chicken meat was processed had no effect upon the response to the Ames test. A heritable translocation test in mice failed to reveal any cytological evidence of translocation heterozygosity in any of the chicken-containing diets.

  6. Hot Carrier Trapping in High-Purity and Doped Germanium Crystals at Millikelvin Temperatures

    NASA Astrophysics Data System (ADS)

    Piro, M.-C.; Broniatowski, A.; Marnieros, S.; Dumoulin, L.; Olivieri, E.

    2014-09-01

    A new set of experimental data is presented for the mean drift lengths and the drift velocities of hot electrons and holes as a function of the electric field in ultra-pure and in lightly doped (n- and p-type) germanium single crystals at mK temperatures. Measurements are made in the field range between 0.1 and 15 V/cm, typical for the operation of cryogenic germanium detectors for dark matter search. The analysis of the experimental data strongly suggests that the dominant trapping centers are the dopant species in the neutral state.

  7. Optical trapping of nanoparticles.

    PubMed

    Bergeron, Jarrah; Zehtabi-Oskuie, Ana; Ghaffari, Saeedeh; Pang, Yuanjie; Gordon, Reuven

    2013-01-15

    Optical trapping is a technique for immobilizing and manipulating small objects in a gentle way using light, and it has been widely applied in trapping and manipulating small biological particles. Ashkin and co-workers first demonstrated optical tweezers using a single focused beam. The single beam trap can be described accurately using the perturbative gradient force formulation in the case of small Rayleigh regime particles. In the perturbative regime, the optical power required for trapping a particle scales as the inverse fourth power of the particle size. High optical powers can damage dielectric particles and cause heating. For instance, trapped latex spheres of 109 nm in diameter were destroyed by a 15 mW beam in 25 sec, which has serious implications for biological matter. A self-induced back-action (SIBA) optical trapping was proposed to trap 50 nm polystyrene spheres in the non-perturbative regime. In a non-perturbative regime, even a small particle with little permittivity contrast to the background can influence significantly the ambient electromagnetic field and induce a large optical force. As a particle enters an illuminated aperture, light transmission increases dramatically because of dielectric loading. If the particle attempts to leave the aperture, decreased transmission causes a change in momentum outwards from the hole and, by Newton's Third Law, results in a force on the particle inwards into the hole, trapping the particle. The light transmission can be monitored; hence, the trap can become a sensor. The SIBA trapping technique can be further improved by using a double-nanohole structure. The double-nanohole structure has been shown to give a strong local field enhancement. Between the two sharp tips of the double-nanohole, a small particle can cause a large change in optical transmission, thereby inducing a large optical force. As a result, smaller nanoparticles can be trapped, such as 12 nm silicate spheres and 3.4 nm hydrodynamic radius

  8. Nonlinear integrable ion traps

    SciTech Connect

    Nagaitsev, S.; Danilov, V.; /SNS Project, Oak Ridge

    2011-10-01

    Quadrupole ion traps can be transformed into nonlinear traps with integrable motion by adding special electrostatic potentials. This can be done with both stationary potentials (electrostatic plus a uniform magnetic field) and with time-dependent electric potentials. These potentials are chosen such that the single particle Hamilton-Jacobi equations of motion are separable in some coordinate systems. The electrostatic potentials have several free adjustable parameters allowing for a quadrupole trap to be transformed into, for example, a double-well or a toroidal-well system. The particle motion remains regular, non-chaotic, integrable in quadratures, and stable for a wide range of parameters. We present two examples of how to realize such a system in case of a time-independent (the Penning trap) as well as a time-dependent (the Paul trap) configuration.

  9. Highly-Charged Ions in Traps - Progress and Opportunities

    NASA Astrophysics Data System (ADS)

    Church, D. A.; Schneider, D.; Steiger, J.; Beck, B. R.; Holder, J. P.; Weinberg, G.; Gruber, L.; Moehs, D. P.; McDonald, J.

    Penning and Kingdon ion traps have been used to study low-energy multiply-charged ions with charge states up to 80+ during the last few years. The ions have been captured into the traps from beams of external multiply-charged ion sources, or have been produced inside the trap. Measurements of cross sections for electron capture from neutrals to ions and studies of relative double electron capture rates have been completed. The lifetimes of metastable levels of ions, precision spectroscopy on multiply-charged ions in traps, and cooling of trapped ions using lasers, ion-ion elastic collisions, and parallel-tuned circuits, are briefly reviewed. Prospects for the future of highly-charged ions in traps are also discussed.

  10. Investigation of the behaviour of electronic resistive switching memory based on MoSe2-doped ultralong Se microwires

    NASA Astrophysics Data System (ADS)

    Zhou, Guangdong; Sun, Bai; Yao, Yanqing; Zhang, Huihui; Zhou, Ankun; Alameh, Kamal; Ding, Baofu; Song, Qunliang

    2016-10-01

    MoSe2-doped ultralong Se microwires of length/diameter ratio in the order of ˜240 are synthesized by hydrothermal method. An electronic resistive switching memory (ERSM) device using a single MoSe2-doped ultralong Se microwire is attained. The ERSM exhibits stable resistance ratio of ˜102 for 5000 s, highly stable performance during 500 stressing cycles, and excellent immunity to the frequency of the driving voltage. By investigating the dynamic processes of trap filling, de-trapping, and free-charge migration, trap-controlled space-charge-limited current mechanism is found to dominate the observed ERSM behaviour.

  11. Traps in Al2O3 detected by tunneling

    NASA Technical Reports Server (NTRS)

    Skarlatos, Y.; Barker, R. C.; Yelon, A.

    1976-01-01

    A structure, quite different from inelastic tunneling peaks, has been observed in electron-tunneling spectra of MOM junctions. A capacitance peak is associated with this structure, which is attributed to traps in the oxide at energies smaller than those previously reported. The C-V characteristics calculated using a single-energy trap model agree with experimental results; however, no satisfactory explanation has yet been found to account for the strong temperature dependence of the trap energy levels.

  12. New evidence for geomagnetically trapped anomalous cosmic rays

    SciTech Connect

    Cummings, J.R.; Cummings, A.C.; Mewaldt, R.A.; Selesnick, R.S.; Stone, E.C. ); Rosenvinge, T.T. von )

    1993-09-15

    This article presents data from the SAMPEX satellite of trapped heavy ions in the ionosphere, with energies greater than 15 MeV/nucleon. The data shows trapped He, N, O, and Ne. These ions are thought to be of cosmic ray origin, and to have been trapped by the geomagnetic field due to the loss of electrons due to scattering events in the upper atmosphere.

  13. Gaining Cyber Dominance

    DTIC Science & Technology

    2015-01-01

    2014 Carnegie Mellon University Gaining Cyber Dominance Software Engineering Institute Carnegie Mellon University NETCOM G3/5/7 TREX January 2015...JAN 2015 2. REPORT TYPE N/A 3. DATES COVERED 4. TITLE AND SUBTITLE Gaining Cyber Dominance 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c...2014) 4 GCD Overview January 2015 © 2014 Carnegie Mellon University FY15 Initiatives Gaining Cyber Dominance Program • Army topology development

  14. Sampling Small Mammals in Southeastern Forests: The Importance of Trapping in Trees

    SciTech Connect

    Loeb, S.C.; Chapman, G.L.; Ridley, T.R.

    1999-01-01

    We investigated the effect of sampling methodology on the richness and abundance of small mammal communities in loblolly pine forests. Trapping in trees using Sherman live traps was included along with routine ground trapping using the same device. Estimates of species richness did not differ among samples in which tree traps were included or excluded. However, diversity indeces (Shannon-Wiener, Simpson, Shannon and Brillouin) were strongly effected. The indeces were significantly greater than if tree samples were included primarily the result of flying squirrel captures. Without tree traps, the results suggested that cotton mince dominated the community. We recommend that tree traps we included in sampling.

  15. Controlling the efficiency of trapping in treelike fractals.

    PubMed

    Wu, Bin; Zhang, Zhongzhi

    2013-07-14

    Efficiently controlling the trapping process, especially the trapping efficiency, is central in the study of trap problem in complex systems, since it is a fundamental mechanism for diverse other dynamic processes. Thus, it is of theoretical and practical significance to study the control technique for trapping problem. In this paper, we study the trapping problem in a family of proposed directed fractals with a deep trap at a central node. The directed fractals are a generalization of previous undirected fractals by introducing the directed edge weights dominated by a parameter. We characterize all the eigenvalues and their degeneracies for an associated matrix governing the trapping process. The eigenvalues are provided through an exact recursive relation deduced from the self-similar structure of the fractals. We also obtain the expressions for the smallest eigenvalue and the mean first-passage time (MFPT) as a measure of trapping efficiency, which is the expected time for the walker to first visit the trap. The MFPT is evaluated according to the proved fact that it is approximately equal to reciprocal of the smallest eigenvalue. We show that the MFPT is controlled by the weight parameter by modifying which the MFPT can scale superlinealy, linearly, or sublinearly with the system size. Thus, this work paves a way to delicately controlling the trapping process in the fractals.

  16. Stratigraphic traps 2

    SciTech Connect

    Not Available

    1991-01-01

    This volume contains studies of fields with traps that are mainly stratigraphic in nature. Structure plays a role in the traps of several fields, but overall, it is clear that the main trapping features with the group of fields in this volume are stratigraphic. The first six fields in this volume, Alabama Ferry, Rospo Mare, Walker Creek, Bindley, Lexington, and Newburg/South Westhope, have carbonate reservoirs. The latter two of these, Lexington and Newburg/South Westhope, also have sandstone reservoirs. The remaining fields, East Texas, East Clinton, Stockholm Southwest, Sorrento, Port Acres, and Lagoa Parda, have only sandstone reservoirs.

  17. Rapid and simple determination of acrylamide in conventional cereal-based foods and potato chips through conversion to 3-[bis(trifluoroethanoyl)amino]-3-oxopropyl trifluoroacetate by gas chromatography coupled with electron capture and ion trap mass spectrometry detectors.

    PubMed

    Russo, Mario Vincenzo; Avino, Pasquale; Centola, Angela; Notardonato, Ivan; Cinelli, Giuseppe

    2014-03-01

    A new, simple, rapid and fully validated method based on gas chromatography coupled with Electron capture and ion trap mass spectrometry detectors (GC-ECD and GC-IT/MS) is presented for quantitative analysis of acrylamide contaminant in conventional cereal-based foods and potato chips. Before analysis acrylamide was efficiently derivatized with trifluoroacetic anhydride, the effects of temperature, reaction time and catalyst on the acylation reaction were evaluated. Chromatographic analysis was performed on SE-54 capillary column; good retention and peak response of the acrylamide derivative achieved under the optimal conditions. The analytical method has been fully validated by assessment of the following parameters: LODs and LOQs (1 and 25ngg(-1) by GC-ECD and 2 and 36ngg(-1) by GC-IT/MS, with a Relative Standard Deviations <4 and <6, respectively), linearity (R(2) above 0.981 in the range 0.005-50μgg(-1)) and extraction recovery (ranging between 91% and 99%, RSD below 4.0, for acrylamide spiked at levels of 1, 20, 50 and 100ngg(-1)). Furthermore, the method proposed requires no clean-up step of the acrylamide derivative to be performed prior to injection. The developed method has been successfully applied to determine acrylamide in different commercial cereal-based foods (including French fries and potato chips).

  18. Genetic Dominance & Cellular Processes

    ERIC Educational Resources Information Center

    Seager, Robert D.

    2014-01-01

    In learning genetics, many students misunderstand and misinterpret what "dominance" means. Understanding is easier if students realize that dominance is not a mechanism, but rather a consequence of underlying cellular processes. For example, metabolic pathways are often little affected by changes in enzyme concentration. This means that…

  19. Innovation: the classic traps.

    PubMed

    Kanter, Rosabeth Moss

    2006-11-01

    Never a fad, but always in or out of fashion, innovation gets rediscovered as a growth enabler every half dozen years. Too often, though, grand declarations about innovation are followed by mediocre execution that produces anemic results, and innovation groups are quietly disbanded in cost-cutting drives. Each managerial generation embarks on the same enthusiastic quest for the next new thing. And each generation faces the same vexing challenges- most of which stem from the tensions between protecting existing revenue streams critical to current success and supporting new concepts that may be crucial to future success. In this article, Harvard Business School professor Rosabeth Moss Kanter reflects on the four major waves of innovation enthusiasm she's observed over the past 25 years. She describes the classic mistakes companies make in innovation strategy, process, structure, and skills assessment, illustrating her points with a plethora of real-world examples--including AT&T Worldnet, Timberland, and Ocean Spray. A typical strategic blunder is when managers set their hurdles too high or limit the scope of their innovation efforts. Quaker Oats, for instance, was so busy in the 1990s making minor tweaks to its product formulas that it missed larger opportunities in distribution. A common process mistake is when managers strangle innovation efforts with the same rigid planning, budgeting, and reviewing approaches they use in their existing businesses--thereby discouraging people from adapting as circumstances warrant. Companies must be careful how they structure fledgling entities alongside existing ones, Kanter says, to avoid a clash of cultures and agendas--which Arrow Electronics experienced in its attempts to create an online venture. Finally, companies commonly undervalue and underinvest in the human side of innovation--for instance, promoting individuals out of innovation teams long before their efforts can pay off. Kanter offers practical advice for avoiding

  20. Laboratory Measurements of the Relative Oscillator Strengths of the Fe XVII Lines 3C and 3D Using an X-ray Laser and an Electron Beam Ion Trap

    NASA Astrophysics Data System (ADS)

    Brown, Gregory V.; Hi-Light Collaboration

    2013-04-01

    X-ray emission from neon-like Fe XVII has been observed in a plethora of celestial sources including stellar atmospheres, galaxy clusters, elliptical galaxies, and supernova remnants. Two of the strongest lines emitted from Fe XVII are the 3d to 2p transitions located at 15.01 and 15.26 angstroms and known as 3C and 3D, respectively. Owing to their strength and presence over a large temperature range, diagnostics involving these lines are of high value. Unfortunately, even though many theoretical and experimental studies have been conducted on 3C and 3D, significant discrepancies among different theories, and between theory and both laboratory and observational measurements have been found. Many different theoretical approaches have been pursued in attempt to resolve the discrepancies, but none has provided a consistent solution (Brown & Beiersdorfer Physical Review Letters, 2012). As a result, the diagnostic utility of these lines has not been fully realized. In order to further probe the nature of these X-ray transitions, we have used the Linac Coherent Light Source X-ray free electron laser in conjunction with the portable FLASH-EBIT electron beam ion trap to photo-excite these lines and measure their relative oscillator strength, Ro. Our results, Ro = 2.61+/- 0.23 (Bernitt, et al. Nature 2012) differs by over 3σ from the best quantum mechanical calculations. We present an overview of these measurements and their implications, as well as a sampling of other photoabsorption measurements using the FLASH-EBIT at various third and fourth generation light sources. This work was performed under the auspices of the U.S. D.o.E. by under Contract DE-AC52-07NA27344 and supported by NASA grants to LLNL and GSFC.

  1. Trapping and Probing Antihydrogen

    SciTech Connect

    Wurtele, Jonathan

    2013-03-27

    Precision spectroscopy of antihydrogen is a promising path to sensitive tests of CPT symmetry. The most direct route to achieve this goal is to create and probe antihydrogen in a magnetic minimum trap. Antihydrogen has been synthesized and trapped for 1000s at CERN by the ALPHA Collaboration. Some of the challenges associated with achieving these milestones will be discussed, including mixing cryogenic positron and antiproton plasmas to synthesize antihydrogen with kinetic energy less than the trap potential of .5K. Recent experiments in which hyperfine transitions were resonantly induced with microwaves will be presented. The opportunity for gravitational measurements in traps based on detailed studies of antihydrogen dynamics will be described. The talk will conclude with a discussion future antihydrogen research that will use a new experimental apparatus, ALPHA-I.

  2. Versatile electrostatic trap

    SciTech Connect

    Veldhoven, Jacqueline van; Bethlem, Hendrick L.; Schnell, Melanie; Meijer, Gerard

    2006-06-15

    A four electrode electrostatic trap geometry is demonstrated that can be used to combine a dipole, quadrupole, and hexapole field. A cold packet of {sup 15}ND{sub 3} molecules is confined in both a purely quadrupolar and hexapolar trapping field and additionally, a dipole field is added to a hexapole field to create either a double-well or a donut-shaped trapping field. The profile of the {sup 15}ND{sub 3} packet in each of these four trapping potentials is measured, and the dependence of the well-separation and barrier height of the double-well and donut potential on the hexapole and dipole term are discussed.

  3. Steam trap monitor

    DOEpatents

    Ryan, M.J.

    1987-05-04

    A steam trap monitor positioned downstream of a steam trap in a closed steam system includes a first sensor (a hot finger) for measuring the energy of condensate and a second sensor (a cold finger) for measuring the total energy of condensate and steam in the line. The hot finger includes one or more thermocouples for detecting condensate level and energy, while the cold finger contains a liquid with a lower boiling temperature than that of water. Vapor pressure from the liquid is used to do work such as displacing a piston or bellow in providing an indication of total energy (steam + condensate) of the system. Processing means coupled to and responsive to outputs from the hot and cold fingers subtracts the former from the latter to provide an indication of the presence of steam downstream from the trap indicating that the steam trap is malfunctioning. 2 figs.

  4. Hybrid quantum systems with trapped charged particles

    NASA Astrophysics Data System (ADS)

    Kotler, Shlomi; Simmonds, Raymond W.; Leibfried, Dietrich; Wineland, David J.

    2017-02-01

    Trapped charged particles have been at the forefront of quantum information processing (QIP) for a few decades now, with deterministic two-qubit logic gates reaching record fidelities of 99.9 % and single-qubit operations of much higher fidelity. In a hybrid system involving trapped charges, quantum degrees of freedom of macroscopic objects such as bulk acoustic resonators, superconducting circuits, or nanomechanical membranes, couple to the trapped charges and ideally inherit the coherent properties of the charges. The hybrid system therefore implements a "quantum transducer," where the quantum reality (i.e., superpositions and entanglement) of small objects is extended to include the larger object. Although a hybrid quantum system with trapped charges could be valuable both for fundamental research and for QIP applications, no such system exists today. Here we study theoretically the possibilities of coupling the quantum-mechanical motion of a trapped charged particle (e.g., an ion or electron) to the quantum degrees of freedom of superconducting devices, nanomechanical resonators, and quartz bulk acoustic wave resonators. For each case, we estimate the coupling rate between the charged particle and its macroscopic counterpart and compare it to the decoherence rate, i.e., the rate at which quantum superposition decays. A hybrid system can only be considered quantum if the coupling rate significantly exceeds all decoherence rates. Our approach is to examine specific examples by using parameters that are experimentally attainable in the foreseeable future. We conclude that hybrid quantum systems involving a single atomic ion are unfavorable compared with the use of a single electron because the coupling rates between the ion and its counterpart are slower than the expected decoherence rates. A system based on trapped electrons, on the other hand, might have coupling rates that significantly exceed decoherence rates. Moreover, it might have appealing properties such

  5. Testing the Model of Oscillating Magnetic Traps

    NASA Astrophysics Data System (ADS)

    Szaforz, Ż.; Tomczak, M.

    2015-01-01

    The aim of this paper is to test the model of oscillating magnetic traps (the OMT model), proposed by Jakimiec and Tomczak ( Solar Phys. 261, 233, 2010). This model describes the process of excitation of quasi-periodic pulsations (QPPs) observed during solar flares. In the OMT model energetic electrons are accelerated within a triangular, cusp-like structure situated between the reconnection point and the top of a flare loop as seen in soft X-rays. We analyzed QPPs in hard X-ray light curves for 23 flares as observed by Yohkoh. Three independent methods were used. We also used hard X-ray images to localize magnetic traps and soft X-ray images to diagnose thermal plasmas inside the traps. We found that the majority of the observed pulsation periods correlates with the diameters of oscillating magnetic traps, as was predicted by the OMT model. We also found that the electron number density of plasma inside the magnetic traps in the time of pulsation disappearance is strongly connected with the pulsation period. We conclude that the observations are consistent with the predictions of the OMT model for the analyzed set of flares.

  6. Optical trapping of nanoshells

    NASA Astrophysics Data System (ADS)

    Hester, Brooke C.; Crawford, Alice; Kishore, Rani B.; Helmerson, Kristian; Halas, Naomi J.; Levin, Carly

    2007-09-01

    We investigate near-resonant trapping of Rayleigh particles in optical tweezers. Although optical forces due to a near-resonant laser beam have been extensively studied for atoms, the situation for larger particles is that the laser wavelength is far from any absorption resonance. Theory predicts, however, that the trapping force exerted on a Rayleigh particle is enhanced, and may be three to fifty times larger for frequencies near resonance than for frequencies far off resonance. The ability to selectively trap only particles with a given absorption peak may have many practical applications. In order to investigate near-resonant trapping we are using nanoshells, particles with a dielectric core and metallic coating that can exhibit plasmon resonances. The resonances of the nanoshells can be tuned by adjusting the ratio of the radius of the dielectric core, r I, to the overall radius, r II, which includes the thickness of the metallic coating. Our nanoshells, fabricated at Rice University, consist of a silica core with a gold coating. Using back focal plane detection, we measure the trap stiffness of a single focus optical trap (optical tweezers), from a diode laser at 853 nm for nanoshells with several different r I/r II ratios.

  7. Interface trap density and mobility extraction in InGaAs buried quantum well metal-oxide-semiconductor field-effect-transistors by gated Hall method

    SciTech Connect

    Chidambaram, Thenappan; Madisetti, Shailesh; Greene, Andrew; Yakimov, Michael; Tokranov, Vadim; Oktyabrsky, Serge; Veksler, Dmitry; Hill, Richard

    2014-03-31

    In this work, we are using a gated Hall method for measurement of free carrier density and electron mobility in buried InGaAs quantum well metal-oxide-semiconductor field-effect-transistor channels. At room temperature, mobility over 8000 cm{sup 2}/Vs is observed at ∼1.4 × 10{sup 12} cm{sup −2}. Temperature dependence of the electron mobility gives the evidence that remote Coulomb scattering dominates at electron density <2 × 10{sup 11} cm{sup −2}. Spectrum of the interface/border traps is quantified from comparison of Hall data with capacitance-voltage measurements or electrostatic modeling. Above the threshold voltage, gate control is strongly limited by fast traps that cannot be distinguished from free channel carriers just by capacitance-based methods and can be the reason for significant overestimation of channel density and underestimation of carrier mobility from transistor measurements.

  8. Electron Acceleration by Cascading Reconnection in the Solar Corona. II. Resistive Electric Field Effects

    NASA Astrophysics Data System (ADS)

    Zhou, X.; Büchner, J.; Bárta, M.; Gan, W.; Liu, S.

    2016-08-01

    We investigate electron acceleration by electric fields induced by cascading reconnections in current sheets trailing coronal mass ejections via a test particle approach in the framework of the guiding-center approximation. Although the resistive electric field is much weaker than the inductive electric field, the electron acceleration is still dominated by the former. Anomalous resistivity η is switched on only in regions where the current carrier’s drift velocity is large enough. As a consequence, electron acceleration is very sensitive to the spatial distribution of the resistive electric fields, and electrons accelerated in different segments of the current sheet have different characteristics. Due to the geometry of the 2.5-dimensional electromagnetic fields and strong resistive electric field accelerations, accelerated high-energy electrons can be trapped in the corona, precipitating into the chromosphere or escaping into interplanetary space. The trapped and precipitating electrons can reach a few MeV within 1 s and have a very hard energy distribution. Spatial structure of the acceleration sites may also introduce breaks in the electron energy distribution. Most of the interplanetary electrons reach hundreds of keV with a softer distribution. To compare with observations of solar flares and electrons in solar energetic particle events, we derive hard X-ray spectra produced by the trapped and precipitating electrons, fluxes of the precipitating and interplanetary electrons, and electron spatial distributions.

  9. Selective NO trapping in the pores of chain-type complex assemblies based on electronically activated paddlewheel-type [Ru2(II,II)]/[Rh2(II,II)] dimers.

    PubMed

    Kosaka, Wataru; Yamagishi, Kayo; Hori, Akihiro; Sato, Hiroshi; Matsuda, Ryotaro; Kitagawa, Susumu; Takata, Masaki; Miyasaka, Hitoshi

    2013-12-11

    The design of porous materials that undergo selective adsorption of a specific molecule is a critical issue in research on porous coordination polymers or metal-organic frameworks. For the purpose of the selective capture of molecules possessing an electron-acceptor character such as nitric oxide (NO), one-dimensional chain compounds possessing a high donor character have been synthesized using 4-chloroanisate-bridged paddlewheel-type dimetal(II, II) complexes with M = Ru and Rh and phenazine (phz) as the chain linker: [M2(4-Cl-2-OMePhCO2)4(phz)]·n(CH2Cl2) (M = Ru, 1; Rh, 2). These compounds are isostructural and are composed of chains with a [-{M2}-phz-] repeating unit and CH2Cl2 occupying the void space between the chains. Compounds 1 and 2 change to a new phase (1-dry and 2-dry) upon evacuating the crystallization solvent (CH2Cl2) and almost lose their pores in the drying process: no void space in 1-dry and 31.8 Å(3), corresponding to 2.9% of the cell volume, in 2-dry. Nevertheless, the compounds show a unique gas accommodation ability. Accompanied by a structural transformation (i.e., the first gate-opening) at low pressures of <10 kPa, both compounds show a typical physisorption isotherm for O2 (90 K) and CO2 (195 K), with the adsorption amount of ca. 2-4 gas molecules per [M2] unit. In addition, the adsorption isotherm for NO (121 K) involves the first gate-opening followed by a second gate-opening anomaly at NO pressures of ≈52 kPa for 1-dry and ≈21 kPa for 2-dry. At the first gate-opening, the absorbed amount of NO is ca. 4 molecules per [M2] unit, and then it reaches 8.4 and 6.3 for 1-dry and 2-dry, respectively, at 95 kPa. Only the isotherm for NO exhibits hysteresis in the desorption process, and some of the NO molecules are trapped in pores even after evacuating at 121 K, although it recovers to the original dried sample on heating to room temperature. The adsorbed NO molecules accrue a significant electron donation from the host framework even in

  10. Emulsion Polymerization of Butyl Acrylate: Spin Trapping and EPR Study

    NASA Technical Reports Server (NTRS)

    Kim, S.; Westmoreland, D.

    1994-01-01

    The propagating radical in the emulsion polymerization reaction of butyl acrylate was detected by Electron Paramagnetic Resonance spectroscopy using two spin trapping agents, 2-methyl-2nitrosopropane and alpha -N-tert-butylnitrone.

  11. Expansion Rate Measurements at Moderate Pressure of Nonneutral Electron Plasmas in the Electron Diffusion Gauge (EDG) Experiment

    SciTech Connect

    Morrison, Kyle A.; Davidson, Ronald C.; Paul, Stephen F.; Belli, Emily A.; and Chao, Edward H.

    2001-05-18

    Measurements of the expansion rate of pure-electron plasmas have been performed on the Electron Diffusion Gauge (EDG) device at background helium gas pressures in the 5 x 10(superscript -8) Torr to 1 x 10(superscript -5) Torr range, where plasma expansion due to electron-neutral collisions dominates over plasma expansion due to trap asymmetries. It is found that the expansion rate, defined as the time rate of change of the particles' mean-square radius, scales approximately linearly with pressure and inversely as the square of the magnetic field strength in this regime, in agreement with classical predictions.

  12. Instrumentation Upgrades to TITAN's Cooler Penning Trap

    NASA Astrophysics Data System (ADS)

    Lascar, Daniel; Titan Collaboration

    2016-09-01

    The use of Highly Charged Ions (HCIs) is critical to improving the precision of Penning trap mass measurements of nuclides with half-lives substantially less than 100 ms, but the process of charge breeding imparts an unacceptably high energy spread to the ion bunch sent to TITAN's precision Penning trap for mass measurement. TITAN's Cooler PEnning Trap (CPET) at TRIUMF in Vancouver, Canada was designed to cool HCIs with a plasma of simultaneously trapped electrons. CPET is currently undergoing commissioning offline at TRIUMF. In order to prepare CPET for full operation, several technical challenges associated with the use of electrons in a strong magnetic field had to be overcome. First among these was the detection of electrons outside of CPET. A novel, thin charge-collecting detector was successfully developed. Known as the mesh detector, it is charge-agnostic and can be made effectively transparent to allow for the passage of any charged particle at the user's request. The second challenge, moving CPET's electron source off the central beam axis was overcome by the creation of an electron source which would allow for electron injection into CPET and the passage of cooled ions out of CPET. CPET's 7 T solenoid generates a stray field far outside of the magnet's central bore that forced the design of a set of electron injection optics that bend, steer and focus the beam in three dimensions. Results from the successful installation of these upgrades as well as a report on future work will be discussed. This work was partially supported by NSERC, the CFI and the DFG.

  13. Identification of microscopic hole-trapping mechanisms in nitride semiconductors

    DOE PAGES

    John L. Lyons; Krishnaswamy, Karthik; Luke Gordon; ...

    2015-12-17

    Hole trapping has been observed in nitride heterostructure devices, where the Fermi level is in the vicinity of the valence-band maximum. Using hybrid density functional calculations, we examine microscopic mechanisms for hole trapping in GaN and AlN. In a defect-free material, hole trapping does not spontaneously occur, but trapping can occur in the vicinity of impurities, such as C-a common unintentional impurity in nitrides. As a result, using Schrodinger-Poisson simulations, we assess the effects of C-derived hole traps on N-face high-electron mobility transistors, which we find to be more detrimental than the previously proposed interface traps.

  14. TRAP/SEE Code Users Manual for Predicting Trapped Radiation Environments

    NASA Astrophysics Data System (ADS)

    Armstrong, T. W.; Colborn, B. L.

    2000-01-01

    TRAP/SEE is a PC-based computer code with a user-friendly interface which predicts the ionizing radiation exposure of spacecraft having orbits in the Earth's trapped radiation belts. The code incorporates the standard AP8 and AE8 trapped proton and electron models but also allows application of an improved database interpolation method. The code treats low-Earth as well as highly-elliptical Earth orbits, taking into account trajectory perturbations due to gravitational forces from the Moon and Sun, atmospheric drag, and solar radiation pressure. Orbit-average spectra, peak spectra per orbit, and instantaneous spectra at points along the orbit trajectory are calculated. Described in this report are the features, models, model limitations and uncertainties, input and output descriptions, and example calculations and applications for the TRAP/SEE code.

  15. A system for trapping barium ions in a microfabricated surface trap

    SciTech Connect

    Graham, R. D. Sakrejda, T.; Wright, J.; Zhou, Z.; Blinov, B. B.; Chen, S.-P.

    2014-05-15

    We have developed a vacuum chamber and control system for rapid testing of microfabricated surface ion traps. Our system is modular in design and is based on an in-vacuum printed circuit board with integrated filters. We have used this system to successfully trap and cool barium ions and have achieved ion ‘dark' lifetimes of 31.6 s ± 3.4 s with controlled shuttling of ions. We provide a detailed description of the ion trap system including the in-vacuum materials used, control electronics and neutral atom source. We discuss the challenges presented in achieving a system which can work reliably over two years of operations in which the trap under test was changed at least 10 times.

  16. Trap state spectroscopy studies and wettability modification of hydroxyapatite nanobioceramics

    NASA Astrophysics Data System (ADS)

    Aronov, Daniel; Rosenman, Gil

    2007-02-01

    Sintered hydroxyapatite coatings on titanium-based implants demonstrate beneficial biocompatibility and osteoconductivity. It has been shown that charged surface states and bulk traps located in the vicinity of the surface of the hydroxyapatite coatings strongly influence wettability properties of the hydroxyapatite and may modify biocompatibility of these nanostructured bioceramics. Combination of high-resolution electron state spectroscopy methods, thermostimulated exoelectron emission, and thermoluminescence methods, applied in this work, have allowed studying electron trap energy spectrum of the hydroxyapatite bioceramics.

  17. Charge Trapping in Photovoltaically Active Perovskites and Related Halogenoplumbate Compounds.

    PubMed

    Shkrob, Ilya A; Marin, Timothy W

    2014-04-03

    Halogenoplumbate perovskites (MeNH3PbX3, where X is I and/or Br) have emerged as promising solar panel materials. Their limiting photovoltaic efficiency depends on charge localization and trapping processes that are presently insufficiently understood. We demonstrate that in halogenoplumbate materials the holes are trapped by organic cations (that deprotonate from their oxidized state) and Pb(2+) cations (as Pb(3+) centers), whereas the electrons are trapped by several Pb(2+) cations, forming diamagnetic lead clusters that also serve as color centers. In some cases, paramagnetic variants of these clusters can be observed. We suggest that charge separation in the halogenoplumbates resembles latent image formation in silver halide photography. Electron and hole trapping by lead clusters in extended dislocations in the bulk may be responsible for accumulation of trapped charge observed in this photovoltaic material.

  18. Trapped Electron Model 2 (TEM-2)

    DTIC Science & Technology

    2010-04-25

    and deposit their charge internal to the spacecraft surface. If a large electrostatic potential builds up before the charge can dissipate, an ESD may...on timescales shorter than a day. This is largely a limitation of the observational sampling in Lm and aeq, which are tied to the orbital period of...when we combine the data from multiple sensors. This assumption has largely been proven true. For example, Figure 10 shows a spectral fit of CRRES

  19. SAMPEX measurements of heavy ions trapped in the magnetosphere

    SciTech Connect

    Cummings, J.R.; Cummings, A.C.; Mewaldt, R.A.; Selesnick, R.S.; Stone, E.C. ); Rosenvinge, T.T. von ); Blake, J.B. )

    1993-12-01

    New observations of >15 MeV/nuc trapped heavy ions with Z [ge] 2 have been made by the S AMPEX spacecraft in low polar orbit. The composition of these ions, which are located primarily around L = 2, is dominated by He, N, O, and Ne. The N, O, and Ne ions are apparently trapped anomalous cosmic rays,'' while the origin of the trapped He flux is presently uncertain. These ions can affect the rate of single-event upsets (SEUs) in spacecraft hardware.

  20. Acoustic bubble traps

    NASA Astrophysics Data System (ADS)

    Geisler, Reinhard; Kurz, Thomas; Lauterborn, Werner

    2000-07-01

    A small, oscillating bubble in a liquid can be trapped in the antinode of an acoustic standing wave field. Bubble stability is required for the study of single bubble sonoluminescence (SBSL). The properties of the acoustic resonator are essential for the stable trapping of sonoluminescing bubbles. Resonators can be chosen according to the intended application: size and geometry can be varied in a wide range. In this work, the acoustic responses of different resonators were measured by means of holographic interferometry, hydrophones and a laser vibrometer. Also, high-speed photography was used to observe the bubble dynamics. Several single, stable sonoluminescent bubbles were trapped simultaneously within an acoustic resonator in the pressure antinodes of a higher harmonic mode (few bubble sonoluminescence, FBSL).